Title of Invention	A PROCESS FOR THE PREPARATION OF AN AQUEOUS COMPOSITION
Abstract	The invention relates to an aqueous coating composition comprising a mixture of 90 to 99 wt.% of a film forming binder composition comprising an alkali non-swellable core-shell addition polymer dispersion (I), and 1-10 wt.% of a rheology modifying addition polymer dispersion (II). It is required that the total amount of (meth)acrylic acid in 100 parts of the total addition polymer (I) is less than 1.75 wt.%. The aqueous coating composition of the present invention can be advantageously used as a base coat in a base coat/clear coat system. This use shows a decrease in strike-in effect compared to previous known base coat/clear systems.

Title of Invention

A PROCESS FOR THE PREPARATION OF AN AQUEOUS COMPOSITION

Abstract

The invention relates to an aqueous coating composition comprising a mixture of 90 to 99 wt.% of a film forming binder composition comprising an alkali non-swellable core-shell addition polymer dispersion (I), and 1-10 wt.% of a rheology modifying addition polymer dispersion (II). It is required that the total amount of (meth)acrylic acid in 100 parts of the total addition polymer (I) is less than 1.75 wt.%. The aqueous coating composition of the present invention can be advantageously used as a base coat in a base coat/clear coat system. This use shows a decrease in strike-in effect compared to previous known base coat/clear systems.

Full Text	The invention relates to an aqueous coating composition based on a mixture of a dispersion of an addition polymer and a iridology modifier. Preferably, this aqueous coating composition is mixed with a metallic pigment, such as aluminum, or a pigment, such as a metal oxide-coated mica, so that coatings with a metallic appearance may be obtained. In this way there is obtained a differential light reflection effect referred to as "flop". A problem with costing systems having a metallic appearance is to obtain a high flop as well as a high gloss. To obtain a high flop, the metallic pigment on application of the coating composition should be and remain well oriented. To obtain a high gloss, the metallic pigment-containing coating is provided with an undigested, so-called dear coat. This system is generally called a "base coat/clear coat" system. In actual practice, the base coat will be sprayed with the clear coat, without prior curing of the base coat ("wet-on-wet"). Since the clear coat usually contains organic solvents, steps should be taken to prevent disorientation of the metallic pigment in the base coat as a result of the base coat being weakened up by the organic solvents in the clear coat ("strike-in"). An aqueous base coat composition is known from EP-A-0 038 127, i.e., a crosslinked core-shell dispersion whereby the shell, when swollen, provides the desired archeological properties. The crosslinking reduces the strike-in. A disadvantage to this system, however, is that the coating composition will have poor film-funning properties, which may manifest itself in poor mechanical properties. Another aqueous base coat composition is known from EP-A-0 287 144, i.e., a swellabie non-crossing core-shell dispersion having an amount of (meth)acrylic acid in the shell of 10-60 mole%. Exemplified are sellable non-crossiinked core-shell dispersions having more than 2 wt.% (meth)acrylic acid in 100 parts of the addition polymer. Also in this embodiment a decrease in strike-in is boson/ed. Both systems disclosed in EP-A-0 038 127 and EP-A-0 287 144 contain in the shell a lot of carfaoxyiic groups, neutralized by an amine to provide the desired archeological properties. However, because of this large amount of salt groups, coatings based on these compositions especially when applied and cured at ambient temperature, show a poor water-resistance. The present invention now provides an aqueous coating composition which may be used as base coat in a base coat system, having good mechanical properties, a high flop, a high gloss, practically no strike-in, and a good water-resistance. Due to the fact that higher solid contents can be achieved with the aqueous coating composition of the present invention, a reduction in drying times and number of coats is obtained. In one or more of these properties the aqueous coating composition of the present invention shows improvement over those disclosed in EP-A-0 038 127 and EP-A-0 287 144. The aqueous coating composition according to the invention comprises a niixture of 90 to 99 wt.% of a filmfonning binder composition comprising an alkali non- swellable core-shell addition polymer dispersion (1), and 1-10 wt.% of a riieoiogy modifying addition polymer dispersion (II), the sum of the wt,% indicated for the fllmforming binder composition and dispersron (11) always being 100 wt.%, wherein the polymer dispersion (I) is prepared in two or more steps by emulsion polymerization, and obtained by copolymerization in a first step of (1) 60-95 parts by weight (calculated on 100 parts by weight of the total addition polymer (I)) of a monomer mixture A consisting of (i) 65-100 mole% of a mixture of (a) 10-98 mole% of a (cycio)alkyl (meth)acryiate of which the (cycle)aikyl group contains 4-12 carbon atoms, (b) 0-55 mole% styrene, (c) 2-15 mole% hydroxy alkyl (meth)acrylate, and (d) 0-20 mole% of a di(cyclo)alkyl maieate and/or fumarate of which the (cycio)alkyl groups contain 4-12 carbon atoms, the sum of the mole% indicated for the monomers (a), (b), (c), and (d) always being 100 mole%, and (ii) 0-35 mole% of a different copolymerizable monoethylenically unsaturated monomer, the sum of the mole% indicated for the components (i) and (ii) always being 100 moie%, and by copolymerization in a subsequent step of (2) 5-40 parts by weight (calculated on 100 parts by weight of the total addition polymer (I)) of a monomer mixture B consisting of (e) 1-10 mole% (meth)acrylic acid, (f) 2-20 mole% hydroxy alkyl (meth)acrylate, (g) 0-55 mole% styrene, and (h) 15-97 mole% of a different copolymerizable monoethylenically unsaturated monomer, the sum of the mole% indicated for the monomers (e), (f), (g), and (h) always being 100 mole%, with the carboxylic acid groups derived from the (meth)acrylic acid being at least partially neutralized. resulting in a non-crosslinked addition polymer I, whereby the total amount of (meth)acrylic acid in 100 parts of the total addition polymer (I) is less than 1.75 wt.%, and wherein the polymer dispersion (II) is prepared by emulsion polymerization, and obtained by copolymerization of (iii) 99.5-99.99 parts by weight (calculated on 100 parts by weight of the total addition polymer (II)) of a monomer mixture C consisting of (j) 10-80 wt.% (cyclo)alkyl(meth)acrylate, (k) 20-50 wt.% (meth)acrylic acid, (m) 0-20 wt.% hydroxyalkyi (meth)acrylate, and (n) 0-20 wt.% of a different copolymerizable monoethylenicaily unsaturated monomer, the sum of the wt.% indicated for the monomers 0"), (k), (m), and (n) always being 100 wt.%, and (iv) 0.01-0.5 parts by weight (calculated on 100 parts by weight of the total addition polymer (II)) of a compound having at least two unsaturated groups, with the carboxyiic acid groups derived from the (meth)acryiic acid being at least partially neutralized. Preferably, in the first step of the preparation of the polymer dispersion (I), a monomer mixture A is used, consisting of (i) 80-100 mole%, more prefen-ed 100 mole%, of a mixture of (a) 30-95 mole % of a (cyclo)alkyl (meth)acrylate of which the (cyclo)alkyl group contains 4-12 carbon atoms, (b) 0-50 moie % styrene, (c) 5-12 mole % hydroxy alkyl (meth)acrylate, and (d) 0-8 mole % of a di(cyclo)aikyl maleate and/or fumarate of which the (cyclo)alkyl groups contain 4-12 carbon atoms, and (ii) 0-20 mole %, more preferred 0 moie%, of a different copoiymerizable monoethylenicaiiy unsaturated monomer. As examples of (cyclo)alkyl (meth)acrylates suitable for use in monomer mixture A and having a (cycio)alkyl group with 4-12 carbon atoms may be mentioned: butyl acrylate, butyl methacryiate, 2-ethyihexyl acrylate, 2-ethylhexyl methacryiate, octyl acrylate, octyl methacryiate, isobornyl acrylate, isobomyl methacryiate, dodecyl acrylate, dodecyl methacryiate, cyclohexyl acrylate, cyclohexyl methacryiate, and mixtures thereof. Butyl acrylate, butyl methacryiate, and mixtures thereof are preferred. Examples of hydroxyalkyi (meth)acrylates are 2-hydroxyethyi acrylate, 2- hydroxyethyl methacryiate, 2-hydroxypropyi acrylate, 2-hydroxypropyl methacryiate, 4-hydroxybutyl acrylate, 6-hydroxyhexyl acrylate, p- hydroxycyclohexyi acrylate, p-hydroxycyclohexyl methacryiate, hydroxypolyethylene glycol (meth)acrylates, hydroxypolypropyiene glycol (meth)acrylates, and mixtures thereof. 2-Hydroxyethyl methacryiate is preferred. As examples of di(cyclo)alkyl maieates and/or fumarates with the (cyclo)alkyl groups having 4-12 carbon atoms suitable for use in monomer mixture A may be mentioned dibutyl maleate, dibutyl fumarate, 2-ethylhexyl maleate, 2-ethylhexyl fumarate, octyl maleate, isobornyl maleate, dodecyl maleate, cyclohexyl maleate, and mixtures thereof. As suitable copoiymerizable monoethylenicaiiy unsaturated monomers to be used in monomer nnixture A may be mentioned: alkyl (meth)acrylates having fewer than 4 carbon atoms in the alkyl group, such as methyl methacryiate, methyl acrylate, ethyl acrylate, ethyl methacryiate, propyl acrylate, propyl methacryiate, and isopropyl acrylate; alkyl maieates and fumarates having fewer than 4 carbon atoms in the alkyl groups, such as dimethyl maleate, diethyl maleate, diethyl fumarate, and dipropyl maleate; (meth)acrylates having ether groups such as 2-methoxyethyl methacrylate, 2-ethoxyethyl methacrylate, and 3-methoxypropyl acrylate; monovinyl aromatic hydrocarbons, such as vinyl toluene, a-methyl styrene, and vinyl naphthalene; acrylamide and methacrylamide; nitrites such as acrylonitriie and methacrylonitrile; N-alkyI (meth)acrylamide such as N-isopropyl acrylamide, N-isopropyl methacrylamide, N-t-butyl acrylamide, N-t-octyl acrylamide, N,N-dimethyl aminoethyl methacrylate, N,N-diethyl aminoethyl methacrylate; monomers such as vinyl chloride, vinyl acetate, vinyl propionate, and vinyl pyrrolidone, and monomers containing one or more urea or urethane groups, such as for instance the reaction product of 1 mole of isocyanato-ethyl methacrylate and 1 mole of butylamine, 1 mole of benzyiamine, 1 mole of butanol, 1 mole of 2-ethylhexanol, and 1 mole of methanol, respectively. Mixtures of these compounds may also be used. Preferably, in a second step of the preparation of the polymer dispersion (I), a monomer mixture B is used, consisting of (e) 5-8 moie% (meth)acrylic acid, (f) 5-12 mole% hydroxy alkyl (meth)acrylate, (g) 0-30 mole% styrene, and (h) 50-90 mole% of a different copolymerizable monoethylenically unsaturated monomer. » Examples of hydroxy alkyl (meth)acrylates have been mentioned above. 2-hydroxyethyl methacrylate is prefen-ed. Examples of copolymerizable monoethylenically unsaturated monomers which may be used in the monomer mixture B include the examples mentioned above for copolymerizable monoethylenically unsaturated monomers which may be used in the monomer mixture A. Also included are (cyclo)alkyl (meth)acrylates having a (cycle)allcyl group with 4-12 carbon atoms. Examples thereof are also mentioned above. Mixtures of these compounds may also be used. Preferably, the copolymerizable monoethylenicaily unsaturated monomers are selected firom methyl methacrylate, butyl acrylate, butyl methacrylate, and mixtures thereof. Preferably, polymer dispersion (I) is prepared by emulsion polymerization of (1) 70-90, preferably 75-85, parts by weight of monomer mixture A and (2) 10-30, preferably 15-25, parts by weight of monomer mixture B. Optionally, different monomer mixtures A and/or B may be used successively. Since the addition polymer (I) is non-crosslinked, the choice of the monomers in monomer mixtures A and B is such that the functional groups present other than the unsaturated bonds cannot react with each other at the reaction conditions for the preparation of the addition polymer. It is required that the total amount of (meth)acryiic acid in 100 parts of the total addition polymer (I) is less than 1.75 wt.%, preferably less than 1.5 wt.%, more preferably between 0.5-1.4 wt.%. In this manner, the polymer dispersion (I) is non-swellable. The acid value is 3 to 10 mg KOH/g, preferably 5 to 8 mg KOH/g. The addition polymer (I) has a Mn of from 50 000 to 2 000 000, preferably from 100 000 to 1 000 000. Preferably, monomer mixture C used in the preparation of the polymer dispersion (II) consists of (j) 50-70 wt.% (cyclo)alkyl (meth)acrylate, (k) 30-40 wt.% (meth)acrylic acid, (m) 0-5 wt.% hydroxyalkyi (meth)acrylate, and (n) 0-5 wt.% of a different copolymerizable monoethylenically unsaturated monomer. Preferably, the polymer dispersion (II) is prepared by emulsion polymerization of (iii) 99.85-99.95 parts by weight of monomer mixture C and (iv) 0.05-0.15 parts by weight of a compound having at least two unsaturated groups. Preferably, the (cyclo)alkyl (meth)acrylates in monomer mixture C have alkyl groups with 1-4 carbon atoms. Examples include methyl methacrylate, methyl acrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, n-butyl acrylate, n-butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, sec-butyl acrylate, sec-butyl methacrylate, t-butyl acrylate, t-butyi methacrylate, and mixtures thereof. Preferred are methyl acrylate, ethyl acrylate, and propyl acrylate. Examples of hydroxyalkyi (meth)acryldtes and copolymerizable monoethylenically unsaturated monomer to be used in monomer mixture C are given above for monomer mixtures A and B. Examples of the compound having at least two unsaturated groups include divinyl toluene, divinyl benzene, trivinyi benzene, divinyl naphthalene, ethylene glycol dj(meth)acrylate, trimethylene glycol di(meth)acrylate, 2-ethyl hexane-1,3-dimethacrylate, divinyl xylene, divinyl ethyl benzene, divinyl ether, divinyl sulfone, allyl ethers of polyhydric compounds, such as glycerol, pentaerythritoi, sorbitol, sucrose, and resorcinoi, allyl ethers of polyisocyanate compounds, such as triallyl Isocyanurate, divinyl ketone, divinyl sulfide, allyl (meth)acrylate, diallyl maleate, diallyl fumarate, diallyl phthalate, diallyl succinate, diallyl carbonate, diallyl malonate, diaiiyi oxalate, diailyl adipate, dialiyi sebacate, diallyl tartrate, diallyl silicate, triallyl citrate, triallyl phosphate, and N,N"-methylene di(meth)acrylamlde. Prefen-ed is a compound having at least two unsaturated groups of which at least one is an allylic group. More preferred are diallyl phthalate, allyl methacrylate, and triallyl isocyanurate. The addition polymer (II) has an acid value of 175 to 350 mg KOH/g, preferably 200 to 300 mg KOH/g, and a hydroxyl value of 0 to 150 mg KOH/g, preferably 0 to 100 mg KOH/g. By emulsion polymerization is meant here the polymerization of the monomer mixtures of ethylenically unsaturated monomers in water in the presence of a water-soluble or -insoluble initiator and 0.1-5 wt.%, preferably 0.3-2.5 wt.% (calculated on the total monomer mixture(s)) of an emulsifier. The polymer dispersion (I) may be prepared by emulsion polymerization as disclosed in EP-A-0 287 144. The polymer dispersion (II) may be prepared by emulsion polymerization as disclosed in GB 870 994. The emulsifiers of which use is preferably made in the emulsion polymerization are of an anionic and/or non-ionic nature. Examples of anionic emulsifiers include: potassium laurate, potassium stearate, potassium oleate, sodium decyl sulphate, sodium dodecyl sulphate, sodium dodecylberizene sulphonic acid, and sodium rosinate. Examples of non-ionic emulsifiers include: linear and branched alkyi and alkylaryl polyethylene glycol and polypropylene glycol ethers and thioethers, alkyl phenoxypoly(ethyleneoxy) ethanols such as the adduct of 1 mole of nonyl phenol and 3-12 moles of ethylene oxide; alkyl (ethyleneoxy) ethanols with 8-18 carbon atoms in the alkyl groups, such as the adduct of 1 mole dodecanol and 3-12 moles of ethylene oxide. Examples of emulsifiers comprising anionic and non-ionic groups are the ammonium or sodium"salt of the sulphate of alkyl phenoxypoiy(ethyleneoxy) ethanols, such as the adduct of 1 mole of nonyl phenol and 3-12 moles of ethylene oxide, and the ammonium or sodium salt of the sulphate of alkyl (ethyleneoxy) ethanols with 8-18 carbon atoms in the alkyl groups, such as the adduct of 1 mole C^j-u alcohol and 3-12 moles of ethylene oxide. Prefered is the ammonium or sodium sulphate salt of the adduct of 1 mole C12.14 alcohol and 3-12 moles of ethylene oxide. Also, in emulsion polymerization, the conventional radical initiators may be used in the usual amounts. Examples of suitable radical initiators include water-soluble initiators, such as ammonium persulphate, sodium persulphate, potassium persulphate, and t-butyl hydroperoxide, and water-insoluble initiators, such as bis(2-ethylhexyl) peroxydicarbonate, di-n-butyl peroxydicarbonate, t-butyl perpivalate, cumene hydroperoxide, dibenzoyi peroxide, dilauroyl peroxide, 2,2"-azobisisobutyronitrile, and 2,2"-azobis-2-methylbutyronitrile. As suitable reducing agents which may be used in combination with e.g. a hydroperoxide may be mentioned: ascorbic acid, sodium sulphoxylate formaldehyde, thiosulphates, bisulphates hydrosuiphates, water-soluble amines such as diethylene triamine, triethylene tetramine, tetraethylene pentamine, N,N"-dimethyl ethanol"amine, and N,N-diethyl ethanol amine, and reducing salts such as cobalt, iron, nickel, and copper sulphate. Optionally, a chain length regulator, for instance n-octyl mercaptan, dodecyl mercaptan, and 3-mercaptopropionic acid, may also be used. Copolymerization of the monomer mixtures generally is earned out at atmospheric pressure at a temperature of 40-100 °C, preferably 60 - 90 °C, in an atmosphere of an inert gas, such as nitrogen. Optionally, however, copolymerization may also be canied out at elevated pressure. The reaction conditions for monomer mixtures A and B should however be chosen in such manner that functional groups present in the monomer mixtures other than the unsaturated bonds cannot react with each other. According to the invention the carboxylic acid groups derived from the acrylic acid and/or methacrylic acid are at least 40-100% neutralized by the addition of a neutralizing agent. As suitable neutralizing agents for the carboxylic acid may be mentioned ammonia and amines such as N,N-dimethyl ethanol amine, N,N-diethyl ethanol amine, 2-{dimethyl)-amino-2-methyl-1-propanol, triethyi amine, and morpholine. It is preferred that the neutralizing of the carboxylic acid groups should be carried out after the polymerization. The coating composition according to the invention comprises preferably a mixture of 92-95 wt.% of a filmforming binder composition comprising an alkali non-swellable core-shell addition polymer dispersion (I), and 5-7.5 wt.% of a rtieology modifying addition polymer dispersion (II). The coating composition of the present invention consists essentially of water, being an aqueous coating composition. However, about 20 wt.% of liquid content of the coating composition may be an organic solvent. As suitable organic solvents may be mentioned such ether group-containing alcohols as hexylglycol, butoxyethanol, 1-methoxy-propapol-2, 1-ethoxy-propanol-2, 1-propoxy-propanol-2, 1-butoxy-propanol-2, and 1-isobutoxy-propanGl-2; alcohols, such as methanol, ethanol, propanol, butanol, pentanol, and hexanol; diols, such as ethylene glycol and diethylene glycol. The coating composition according to the present invention may be cured by physical drying. Alternatively, however, the coating compositions may be cured in the presence of a curing agent which reacts with hydroxyl and/or carboxyl groups. Examples of suitable curing agents include N-methylol and/or N-methyiol ether groups-containing aminoplastes obtained by reacting an aldehyde, for instance formaldehyde, with an amino or amido groups-containing compound such as melamine, such as Cymei 328, ex Cytec, urea, N,N"-ethylene urea, dicyanodiamide, and benzoguanamine. The resulting compounds are areferably wholly or partially etherified with alcohols having 1-6 carbon atoms, such as methanol, ethanol, n-propanol. isopropanol, n-butanol, isobutanol, amyl alcohol, hexanol, or mixtures thereof. Especially favourable results may be Dbtained when using a methylol melamine having 4-6 methyl groups per molecule of melamine, at least 3 methylol groups being etherified with butanol ar a butanol etherified condensation product of formaldehyde and N,N"-ethyiene diurea. Examples of other suitable curing agents include polyisocyanates or water-dispersible blocked polyisocyanate such as a methyl ethyl ketoxime-biocked, isocyanate group-containing adduct of a polyisocyanate to a hydroxycarboxylic acid, e.g. dimethylol propionic acid, and aliphatic or aromatic carbodiimides. In addition to the alkali non-swellable core-shell addition polymer dispersion (I), the fiimforming binder composition may also comprise water-dilutable materials such as alkyd resins, polyesters, polyurethanes, and mixtures thereof. Preferably, the water dilutable material is a" polyurethane. The filmfomning binder composition may comprise 0,1 to 100 wt.% of the alkali non-swellable core-shell addition polymer dispersion (I) and 99,9 to 0 wt.% of at least one water dilutable material, wherein the sum of the wt.% indicated for dispersion (1) and the water dilutable material(s) is always 100 wt.%. More preferably, the filmfomning binder composition may comprise 1 to 99 wt.% of the alkali non-swellable core-shell addition polymer dispersion (!) and 99 to 1 wt.% of at least one water dilutable material. Most preferably, the fiimforming binder composition may comprise 25 to 75 wt.% of the alkali non-swellable core-shell addition polymer dispersion (I) and 75 to 25 wt.% of at least one water dilutable material. In addition, the coating composition may contain the conventional additives and adjuvants, such as pigments, dispersing agents, dyes, and accelerators for the curing reaction. The applicable pigments may have an acid, a neutral or a basic character. Optionally, the pigments may be pre-treated to modify the properties. Examples of suitable pigments include metallic pigments such as aluminum and stainless steel; nacreous pigments, such as mica coated with a, metal oxide such as iron oxide and/or titanium dioxide; inorganic pigments, such as titanium dioxide, iron oxide, carbon black, silica, kaolin, talc, barium sulphate, lead silicate, strontium chromate, and chromium oxide; and organic pigments, such as phthalocyanine pigments. The solids content of the coating composition ranges from 5-60 wt.%, preferably from 10-40 wt.%. This depends on whether a metallic pigment is used or not. The presence of metallic pigments results in a lower solid content compared to the presence of non-metallic pigments. However, compared to conventional aqueous base coat systems, the solid content of the coating composition of the present invention is in both cases higher. Preferably, the coating composition according to the present invention is used as a base coat in a so-called base coat/clear coat system to provide a high gloss metallic appearance. To this end the coating composition according to the invention comprises so-called "non-leafing" aluminum paste or some other metallic pigment. Use of the coating compositions according to the invention as a base coat may prevent the base coat from being softened by the clear coat after being sprayed with it, so that the metallic effect will not be lost. The clear coat used in the base coat/clear coat system may for instance be a clear baking lacquer of a conventional polyacrylate/melamine composition. The clear coat may also be a two-component polyester or polyacrylate/polyisocyanate composition. The polyisocyanate may be for example the trimerof 1,6-hexamethylene diisocyanate. The coating composition according to the invention may be applied to a substrate in any desirable manner, such as by roller coating, spraying, brushing, sprinkling, flow coating, dipping, electrostatic spraying, or electrophoresis, preferably by spraying. Suitable substrates may be made of wood, metal, and synthetic material. Curing may be earned out at ambient temperature or, optionally, at elevated temperature to reduce the curing time. Optionally, the coating composition may be baked at higher temperatures in the range of, for instance, 60 to 160 "C, in a baking oven over a period of 10 to 60 minutes. The clear coat may be applied wet-on-wet on the base coat. Optionally, the base coat may be partially cured prior to the application of the clear coat. Also, the base coat may be fully cured prior to the application of the clear coat. The compositions are particulariy suitable in the preparation of coated metal > substrates, such as in the refinish industry, in particular the body shop, to repair automobiles and transportation vehicles and in finishing large transportation vehicles such as trains, trucks, buses, and aeroplanes. The compositions of the present invention may also be used in the first finishing of automobiles. The invention will be further described in the following examples, which must not be construed as limiting the scope of the present invention. EXAMPLES Test methods used in the examples are described below. The mean particle size of the dispersions was determined by dynamic light scattering, the dispersion being diluted with water to a solids content of about 0.1 wt.%. The viscosity was determined with a Braokfield viscometer. The solids content is detennined in accordance with ASTM method D 1644-59 with heating at 130 "C over a period of 30 minutes. The metallic-flake orientation can be measured by a spectrogoniometer. The intensity of the reflected light at angle p is measured for a given incident angle a. The so-called flop can be obtained by measurement of the intensity of the reflection (L-value) at two different angles. Flop=AL = L(p,)-L(P2) wherein L(Pi) = intensity of the reflected light at an angle of ± 110" •-(P2) - intensity of the reflected light at an angle of ± 25" A silver-shaded low solids metallic base coat /clear coat system exhibits a flop-value of approximately 55 to 75 depending on the metallic grade, when measured in this way. The humidity resistance can be judged visually by the presence of blisters after the test. The following compounds were used. Trigonox A-W70®, 70 wt.% t-butyl hydroperoxide in water, ex Akzo Nobel Chemicals Abex JKB®, ammonium sulphate of an ethoxylated alkyl alcohol, solids content of 29.3 wt.%, ex Rhone-Poulenc Perlankrol EP36®, sodium sulphate of the adduct of 1 mole dodecanol and 6 moles ethylene oxide, solid content of 29.2 wt.%, ex Ackros Rhodapex AB/20®, ammonium sulphate of the adduct of 1 mole Ci2.i4-alcohol and 9 moles ethylene oxide, solids content of 28.7 wt.%, ex Rhone-Poulenc Setal EPC 4673, polyesterpolyol, ex. Akzo Nobel Resins Cyme! 328®, melamine crosslinker, ex Cytec Preparation of alkali non-sweliable core-shell addition Dolvmer dispersions (\) Example 1 A: Preparation of copolymer A of monomer mixture A in step 1 A 2 I flask fitted with a stirrer, a thermometer, a reflux condenser and dropping funnels A and B was filled with: 435.0 g of demineralized water and 12.0 g of emulsifier Perlankrol EP36®. Dropping funnel A was filled with: 280.0 g of monomer mixture I (see Table I). Dropping funnel B was filled with a homogeneous mixture of: 140.0 g of demineralized water and 1.4 g of sodium persulphate. After deaeration, the contents of both the flask and the dropping funnels were brought under a nitrogen atmosphere, and the contents of the flask were heated to 80 "C. Next, the contents of dropping funnel B were introduced into the flask over a period of 3 minutes. After the contents of the flask were brought again to SO"C, the contents of dropping funnel A were introduced into the flask at a constant rate over a period of 2.5 hours, after which the contents of the flask were kept at 80°C for another 1.5 hours. B: Preparation of polvmer dispersion (\) in Step 2 Dropping funnel A was filled with 70.0 g of monomer mixture II (see Table I) and dropping funnel B was filled with a homogeneous mixture of: 35.0 g of demineralized water and 0.35 g of sodium persulphate. The contents of dropping funnel B were introduced into the flask, comprising copolymer A, over a period of 3 minutes. The contents of the flask were brought again to 80""C and the contents of dropping funnel A were introduced into the flask at a constant rate over a period of 1 hour, after which the contents of the flask were kept at SO"C for another 2 hours. The reaction was carried out under a nitrogen atmosphere. On conclusion of the reaction the contents of the flask were cooled to 70°C, after which there were added dropwise 41,3 g of a 10 .wt.% solution of N,N-dimethyl ethanol amine in water. Subsequently, the contents of the flask were cooled to ambient temperature and filtered over a 30pm filter cloth. The properties of the dispersion are given in Table II. Example 2 Example 1 was repeated except for the following: A: Preparation of copolymer A of monomer mixture A in step 1 Dropping funnel A was filled with 280.0 g of monomer mixture III (see Table I) Instead of monomer mixture I. B: Preparation of polvmer dispersion (\) in Step 2 Dropping funnel A was filled with 70.0 g of monomer mixture IV (see Table I) instead of II. After conclusion of the reaction were added 43.5 g of a 10 wt.% solution of N,N-dimethyl ethanol amine in water. The properties of the resulting dispersion are given In Table II. Example 3 A: Preparation of copolymer A of monomer mixture A in step 1 A 2 I flask fitted with a stin-er, a thermometer, a reflux condenser, and dropping funnels A and B was filled with: 339.0 g of demineraiized water, and 8.0 g of emulsifier Rhodapex AB/20®. Dropping funnel A was filled with: 378.7 g of a monomer pre-emulsion composed of 93.3 g of demineraiized water, 5.4 g of Rhodapex AB/20®, and 280.0 g of monomer mixture III (see Table I). Dropping funnel B was filled with a homogeneous mixture of: 140.0 g of demineraiized water and 1.4 g of ammonium persulphate. After deaeration, the contents of both the flask and the dropping funnels were brought under a nitrogen atmosphere, and the contents of the flask were heated to SOX, after which 5% of the contents of dropping funnel A were introduced into the flask over a period of 2 minutes. Next, the contents of the flask were heated to SCC and 30% of the contents of dropping funnel B were added to the contents of the flask. The contents of the flask were kept at dCC for 15 minutes, and subsequently the rest of the contents of the dropping funnels A and B were introduced into the flask at a constant rate over a period of 2.5 hours, after which the contents of the flask were kept at 80°C for another hour. B: Preparation of polymer dispersion (\) in Step 2 Dropping funnel A was filled with: 70.0 g of monomer mixture IV (see table I) and dropping funnel B was filled with a homogeneous mixture of: 35.0 g of demineralized water and 0.35 g of ammonium persulphate. The contents of both dropping funnels were introduced into the flask comprising copolymer A at a constant rate over a period of 1 hour, after which the contents of the flask were kept at SO"C for another hour. On conclusion of the reaction the contents of the flask were cooled to TO"C, after which there were added dropwise 43,5 g of a 10 wt.% solution of N,N-dimethyl ethanol amine in water. Subsequently, the contents of the flask were cooled to ambient temperature and filtered over a 30\|im filter cloth. The properties of the dispersion are given in Table II. Example 4 Example 3 was repeated except for the following: A: Preparation of copolymer A of monomer mixture A in step 1 The flask was filled with 338.0 g of demineralized water and 13,4 g of emulsifier Rhodapex AB/20®. B: Preparation of polymer dispersion (]) in Step 2 Dropping funnel A was filled with: 70.0 g of monomer mixture V (see Table 1) The properties of the dispersion are given in Table II. Example 5 Example 4 was repeated, except for the following: A: Preparation of copolymer A of monomer mixture A in step 1 The monomer pre-emuision was composed of 280.0 g of monomer mixture VI (see Table I) instead of monomer mixture III. The properties of the dispersion are given in Table II. Example 6 Example 4 was repeated, except for the following: B: Preparation of polymer dispersion (\) in Step 2 Dropping funnel A was filled with 70.0 g of monomer mixture VII (see Table I) instead of monomer mixture V. The properties of the dispersion are given in Table II. E; A: Preparation of copolymer A of monomer mixture A in steo 1 A 3 I flask fitted with a stirrer, a thermometer, a reflux condenser, and dropping funnels A and B was filled with: 621.1 g of demineraiized water, and 5.4 g of a 20 wt.% solution of sodium dodecylbenzene sulphonic acid solution in demineraiized water Dropping funnel A was filled with: 683.8 g of a pre-emulsion composed of 507.1 g of monomer mixture VIII (see Table I) 10.0 g of a 20 wt.% solution of sodium dodecylbenzene sulphonic acid in demineraiized water 166.7 g of demineraiized water Dropping funnel B was filled with 55.3 g of a homogeneous mixture of 53.3 g of demineraiized water 2.02 g of sodium persulphate After deaeration, the contents of both the flask and the dropping funnels were brought under a nitrogen atmosphere, and the contents of the flask were heated to 50°C. After 9.6 g of the contents of dropping funnel A were introduced into the flask In a period of 1 minute, the contents of the flask were heated to 83°C. Subsequently, 25% of the contents of dropping funnel B were introduced into the flask after which the contents of the flask were kept at 83""C for a period of 15 minutes. Subsequently, the rest of the contents of dropping funnel A and B were introduced into the flask at a constant rate over a period of 3 hours, after which the contents of the flask were kept at 83""C for another 30 minutes and subsequently diluted with 143.3 g of demineraiized water. B: Preparation of polvmer dispersion (\) in Step 2 Dropping funnel A was filled with 126.7 g of monomer mixture IX (see Table I) and dropping funnel B was filled with a homogeneous mixture of 33.3 g of deminerallzed water and 0.51 g of sodium persulphate. The contents of both dropping funnels were introduced into the flask comprising copolymer A at a constant rate over a period of 1 hour, after which the contents of the flask were kept at SO"C for another hour. On conclusion of the reaction the contents of the flask were cooled to ambient temperature and filtered over a 80\|im filter cloth, after which there were added dropwise 13.5 g of a 30 wt.% solution of N,N-dimethyl ethanol amine in deminerallzed water. The properties of the dispersion are given in Table II. S^ample 9 Example 7 was repeated except for the following: A: Preparation of copolymer A of monomer mixture A in step 1 The monomer pre-emulsion was composed of: 507.1 g of monomer mixture X instead of monomer mixture VIII. For dropping funnel B ammonium persulphate was used instead of sodium persulphate. B: Preparation of polymer dispersion (\) in Step 2 The monomer mixture was composed of: 126.7 g of monomer mixture XI instead of monomer mixture IX. On conclusion of the reaction the dispersion was neutralized with 11.7 g of a 30 wt.% solution of N,N-dimethyl ethanol amine in demineralized water instead of 13.5 g of this solution. The properties of the dispersion are given in Table II. Exampte 9 Example 8 was repeated except for the following A: Preparation of copolymer A of monomer mixture A in step 1 The flask was filled with 626.0 g demineralized water and 3.7 g of emulsifier Perlankrol EP36®. Dropping funnel A was filled with: 680.7 g of a pre-emulsion composed of 507.1 g of monomer mixture X (see Table I), 6.85 g of emulsifier Perlankrol EP36, and 166.7 g of demineralized water. B: Preparation of polvmer dispersion (\) in Step 2 On conclusion of the reaction the dispersion was neutralized with 12.8 g of a 30 wt.% solution of N,N-dimethyl ethanol amine in demineralized water instead of 11.7 g of this solution. The properties of the dispersion are given in Table II. The preparation of rheology modifving addition polymer dispersions (W) Example 1Q A 2 I flask fitted with a stirrer, a thermometer, a reflux condenser, and dropping funnels was filled with: 460.0 g of demineralized water and 2.64gofAbexJKB. Dropping funnel A was filled with: 422.0 g of a monomer pre-emulsion composed of: 150.0 g of demlneralized water, 12.0 gofAbexJKB®, and 260.0 g of monomer mixture XII (see Table I). Dropping funnel B was filled with a homogeneous mixture of 25.0 g of demlneralized water and 0.38 g of ammonium persulphate. Dropping funnel C was filled with a homogeneous mixture of 30.0 g of demlneralized water and 0.14 g of ammonium persulphate After deaeration, the contents of both the flask and the dropping funnels were brought under a nitrogen atmosphere and the contents of the flask were heated to SS"C, after which 20 g of the contents of dropping funnel A and the contents of dropping funnel B were introduced into the flask. The contents of the flask were kept at 85 "C for 15 minutes. Subsequently the rest of the contents of dropping funnel A and the contents of dropping funnel C were introduced into the flask at a constant rate over a period of 90 minutes. Dropping funnel A was rinsed then with 60 g. of demlneralized water and after this has been introduced into the flask, the contents of the flask were kept at SS"C for another 30 minutes. In the meantime dropping funnel D was filled with a homogeneous mixture of: 30.0 g of demlneralized water and 0.60 g Trigonox A-W70® and dropping funnel E was filled with a homogeneous mixture of: 30.0 g of demlneralized water and 0.25 g of sodium fonnaldehyde sulphoxylate. After the contents of the flask were cooled to 63 "C, the contents of dropping funnel D were introduced into the flask and after 10 minutes the contents of dropping funnel E were introduced into the flask at a constant rate over a period of 30 minutes. Subsequently, the contents of the flask were cooled to ambient temperature and filtered over a 30jim filter cloth. The properties of the dispersion are given in Table III. Example 11 Example 10 was repeated except for the following: Dropping funnel A was filled with 260.0 g of monomer mixture XIII (see Table I) instead of monomer mixture XII. The properties of the dispersion are given in Table III. Example 12 Example 10 was repeated except for the following: Dropping funnel A was filled with 260.0 g of monomer mixture XIV (see Table I) instead of monomer mixture XII. The properties of the dispersion are given in Table III. Example 13 Example 10 was repeated except for the following: The flask was now filled with 279.7 g of demlneralized water and I.OgofAbexJKB. The properties of the dispersion are given in Table III. Base coat compositions Examples 14-19 and Comparative Examples A and B Base coat compositions were prepared as follows. A mixture of 22 g of aluminum paste (65% solids in aliphatic/aromatic hydrocarbons, Aquavex Sparkle Silver E5000AR , ex Silberline) and 28 g butoxyethanol was added with stirring to a mixture of 190 g of a polymer dispersion (1) according to Examples 1-6 and 14 g of a polymer dispersion (II) according to Examples 10-12. The base coat compositions were brought to a pH of 7.5-8.0 by the addition of N,N-dimethyl ethanol amine and diluted with water to spraying viscosity (efflux time of 35 sec. in DIN-cup No. 4). The solids contents of all the base coat compositions were in the range of 14-16 wt.% . In an atmosphere having a relative humidity of ^5% the base coat compositions of the present invention were sprayed onto primer coated steel test panels in a film thickness of 10-25 ^m (in the dry state). Additionally, two test panels were prepared with a conventional low solids solvent home base coat based on an acrylic/melamine system (comparative example A) and the aqueous core/shell dispersion of Example 5 of EP-A-0 287 144 (comparative example B). After drying to mat at ambient temperature, the panels were tack free. Next, these test panels were partially covered up and the remaining part was repainted by spraying with a conventional clear coat, a two-component polyester/polyisocyanate coating composition, with the polyisocyanate being a trimer of 1,6-hexamethylene diisocyanate (in a film thickness of 50-60 \im in a dry state). After curing for one day at ambient temperature, the test panels 14-19 showed a metallic coat of high gloss. After one week at ambient temperature, the solvent- and water-resistance of the test panels 14-19 were excellent, comparable with test panels A and B. The flop of both the base coat and the base coat provided with clear coat was measured (see Table IV). The flop values of the base coats based on the coating compositions according to the invention are excellent, comparable with test panels A and B. The decrease of flop by the application of the clear coat (strike-in) is practically zero, so that the excellent flop is maintained. However, the flop values of the base coat/ clear coat of test panels A and B are significantly lower showing a considerable strike-in effect. Examples 20-22 and Comparative Example C Base coat compositions were prepared as follows. A mixture of 20 g of aluminum paste (65 wt.%, Aquavex Sparkle Silver E5000AR from Silberiine), 25.6 g of butoxyethanol, 30.2 g of SetalEPC 4673, 23.5 g of Cyme! 328 97.8 g of water, and 7.2 g of a 30 wt.% solution of N,N-dimethyl ethanol amine in water was added with stirring to a mixture of f33.3 g of a polymer dispersion (1) according to Examples 7-9 90.7 g of water, and 13.3 g of a polymer dispersion (II) according to Example 13. The base coat compositions were brought to a pH of 7.5-8.0 by addition of N,N-dimethyl ethanol amine and diluted with water to spraying viscosity (efflux time of 28 sec in DIN-cup No. 4). Solid content was 20 wt.%. The base coat compositions were sprayed onto steel test panels in a film thickness of 12-18 jim (in the dry state). After a flash-off period of 2 minutes at 23 "C and 8 minutes at 80 "C, the test panels were repainted with a conventional clearcoat, in a film thickness of 40-45 i^m in the dry state. The clearcoat was a so-called one component polyacrylate/aminoplaste coating composition. The aminoplaste is a polymeric melamine type resin. After curing for 24 minutes at 140 "C, a metallic coat of good appearance was obtained. The test panels were tested for their humidity resistance in comparison with a reference waterbome base coat (Example 5 of EP-A-0 287 144; Comparative Example C). The humidity resistance of the test panels 20 to 22 is excellent in comparison to the humidity resistance of test panel C. Table V gives the results of the test. WE CLAIM: 1. A process for the preparation of an aqueous coating composition comprising a mixture of 90 to 99 wt. % of a film forming binder composition comprising an alkali non-swellable core-shell addition polymer dispersion (I), and 1-10 wt % of a rheology modifying addition polymer dispersion (II), the sum of the wt. % indicated for the filmforming binder composition and dispersion (II) always being 100 wt. %, wherein the polymer dispersion (I) is prepared in two or more steps by emulsion polymerization, and obtained by copolymerization in a first step of (1) 60-95 parts by weight (calculated on 100 parts by weight of the total addition polymer (I)) of a monomer mixture A consisting of (i) 65-100 mole% of a mixture of (a) 10-98 mole % of a (cyclo)alkyl (meth)acrylate of which the (cyclo)alkyl group contains 4-12 carbon atoms, (b) 0-55 mole% styrene, (c) 2-15 mole % hydroxy alkyl (meth)acrylate, and (d) 0-20 mole% of a di(cyclo)alkyl maleate and/or fumigate of which the (cyclo)alkyl groups contain 4-12 carbon atoms, the sum of the mole % indicated for monomers (a), (b), (c), and (d) always being 100 mole %, and (ii) 0-35 mole % of a different copolymerizable monoethylenically unsaturated monomer, the sum of the mole % indicated for components (i) and (ii) always being 100 mole %, and by copolymerization in a subsequent step of (2) 5-40 parts by weight (calculated on 100 parts by weight of the total addition polymer (I)) of a monomer mixture B consisting of (e) 1-10 mole % (meth)acrylic acid, (f) 2-20 mole % hydroxy alkyl (meth)acrylate, (g) 0-55 mole % styrene, and (h) 15-97 mole % of a different copolymerizable monoethylenically unsaturated monomer, the sum of the mole % indicated for monomers (e), (f), (g), and (h) always being 100 mole %, with the carboxylic acid groups derived from the (meth )acrylic acid being at least partially neutralized, resulting in a non-crosslinked addition polymer 1. whereby the total amount of (meth)acrylic acid in 100 parts of the total addition polymer (I) is less than 1.75 wt.%, and wherein the polymer dispersion (II) is prepared by emulsion polymerization, and obtained by copolymerization of (iii) 99.5-99.99 parts by weight (calculated on 100 parts by weight of the total addition polymer (II)) of a monomer mixture C consisting of U) 10-80 wt. % (cyclo)alkyl (meth)acrylate, (k) 20-50 wt.% (meth)acrylic acid, (m) 0-20 wt. % hydroxyalkyl (meth)acrylate, and (n) 0-20 wt.% of a different copolymerizable monoethylenically unsaturated monomer, the sum of the wt.% indicated for monomers (j), (k), (m), and (n) always being 100 wt. %, and (iv) 0.01-0.5 parts by weight (calculated on 100 parts by weight of the total addition polymer (II)) of a compound having at least two unsaturated groups, with the carboxylic acid groups derived from the (meth)acrylic acid being at least partially neutralized. 2. The process according to claim 1, wherein the monomer mixture A consists of (i) 80-100 mole% of a mixture of (a) 30-95 mole % of a (cyclo)alkyl (meth)acrylate of which the (cyclo)alkyl group contains 4-12 carbon atoms, (b) 0- 50 mole % styrene, (c) 5-12 mole % hydroxy alkyl (meth)acrylate, and (d) 0-8 mole % of a di(cyclo)alkyl maleate and/or fumigate of which the (cyclo )alkyl groups contain 4-12 carbon atoms, and (ii)0-20 mole % of a different copolymerizable monoethylenically unsaturated monomer. 3. The process according to anyone of the preceding claims, wherein the monomer mixture B consists of (e) 5-8 mole % (meth)acrylic acid, (f) 5-12 mole % hydroxy alkyl (meth)acrylate, (g) 0-30 mole % styrene, and (h) 50-90 mole % of a different copolymerizable monoethylenically unsaturated monomer. 4. The process according to anyone of the preceding claims, wherein the total amount of (meth)acrylic acid in 100 parts of the total addition polymer (I) is between 0.5-1.4 wt.%. 5. The process according to anyone of the preceding claims, wherein the monomer mixture C consists of (}) 50-70 wt.% (cyclo)alkyl (meth)acrylate, (k) 30-40 wt.% (meth)acrylic acid, (m) 0-5 wt.% hydroxyalkyl (meth)acrylate, and (n) 0-5 wt. % of a different copolymerizable monoethylenically unsaturated monomer. 6. The process according to anyone of the preceding claims, wherein the polymer dispersion (II) is prepared by emulsion polymerization of (iii) 99.85-99.95 parts by weight of monomer mixture C and (iv) 0.05-0.15 parts by weight of a compound having at least two unsaturated groups. 7. The process according to anyone of the preceding claims, wherein the compound having at least two unsaturated groups has at least one allylic group. 8. The process according to claim 7, wherein the compound having at least two unsaturated groups is selected from diallyl phthalate, allyl methacrylate, and triallyl isocyanurate. 9. The process according to any of the preceding claims, wherein the filmforming binder composition comprises in addition to the alkali non-swellable core-shell addition polymer dispersion (I) at least one water-dilutable material. 10. The process according to claim 9, wherein the filmforming binder composition preferably comprise 0.1 to 99.9 wt.% of the alkali non-swellable core-shell addition polymer dispersion (I) and 99.9 to 0.1 wt.% of at least one water dilutable material, wherein tiles sum of the wt.% indicated for dispersion (I) and the water dilutable material(s) is always 100 wt.%. 11.The process according to claims 9 or 10, wherein the water dilutable material is selected from alkyd resins, polyesters, polyurethanes, and mixtures thereof. 12.The process according to 11, wherein" the water dilutable material is polyurethane. 13. A process for the preparation of a base coat composition comprising mixing an aqueous coating composition prepared by the process according to anyone of the preceding claims and non leafing aluminum paste or metallic pigment.

Full Text

The invention relates to an aqueous coating composition based on a mixture of a dispersion of an addition polymer and a iridology modifier. Preferably, this aqueous coating composition is mixed with a metallic pigment, such as aluminum, or a pigment, such as a metal oxide-coated mica, so that coatings with a metallic appearance may be obtained. In this way there is obtained a differential light reflection effect referred to as "flop". A problem with costing systems having a metallic appearance is to obtain a high flop as well as a high gloss.
To obtain a high flop, the metallic pigment on application of the coating composition should be and remain well oriented. To obtain a high gloss, the metallic pigment-containing coating is provided with an undigested, so-called dear coat. This system is generally called a "base coat/clear coat" system. In actual practice, the base coat will be sprayed with the clear coat, without prior curing of the base coat ("wet-on-wet"). Since the clear coat usually contains organic solvents, steps should be taken to prevent disorientation of the metallic pigment in the base coat as a result of the base coat being weakened up by the organic solvents in the clear coat ("strike-in").

An aqueous base coat composition is known from EP-A-0 038 127, i.e., a
crosslinked core-shell dispersion whereby the shell, when swollen, provides the
desired archeological properties. The crosslinking reduces the strike-in. A
disadvantage to this system, however, is that the coating composition will have
poor film-funning properties, which may manifest itself in poor mechanical
properties.

Another aqueous base coat composition is known from EP-A-0 287 144, i.e., a swellabie non-crossing core-shell dispersion having an amount of (meth)acrylic acid in the shell of 10-60 mole%. Exemplified are sellable non-crossiinked core-shell dispersions having more than 2 wt.% (meth)acrylic acid in 100 parts of the addition polymer. Also in this embodiment a decrease in strike-in is boson/ed.
Both systems disclosed in EP-A-0 038 127 and EP-A-0 287 144 contain in the shell a lot of carfaoxyiic groups, neutralized by an amine to provide the desired archeological properties. However, because of this large amount of salt groups, coatings based on these compositions especially when applied and cured at ambient temperature, show a poor water-resistance.
The present invention now provides an aqueous coating composition which may be used as base coat in a base coat system, having good mechanical properties, a high flop, a high gloss, practically no strike-in, and a good water-resistance. Due to the fact that higher solid contents can be achieved with the aqueous coating composition of the present invention, a reduction in drying times and number of coats is obtained. In one or more of these properties the aqueous coating composition of the present invention shows improvement over those disclosed in EP-A-0 038 127 and EP-A-0 287 144.
The aqueous coating composition according to the invention comprises a
niixture of
90 to 99 wt.% of a filmfonning binder composition comprising an alkali non-
swellable core-shell addition polymer dispersion (1), and
1-10 wt.% of a riieoiogy modifying addition polymer dispersion (II),
the sum of the wt,% indicated for the fllmforming binder composition and
dispersron (11) always being 100 wt.%,

wherein
the polymer dispersion (I) is prepared in two or more steps by emulsion
polymerization, and obtained by copolymerization in a first step of
(1) 60-95 parts by weight (calculated on 100 parts by weight of the total
addition polymer (I)) of a monomer mixture A consisting of
(i) 65-100 mole% of a mixture of
(a) 10-98 mole% of a (cycio)alkyl (meth)acryiate of which the (cycle)aikyl group contains 4-12 carbon atoms,
(b) 0-55 mole% styrene,
(c) 2-15 mole% hydroxy alkyl (meth)acrylate, and
(d) 0-20 mole% of a di(cyclo)alkyl maieate and/or fumarate of which the (cycio)alkyl groups contain 4-12 carbon atoms,
the sum of the mole% indicated for the monomers (a), (b), (c), and (d)
always being 100 mole%, and (ii) 0-35 mole% of a different copolymerizable monoethylenically
unsaturated monomer, the sum of the mole% indicated for the components (i) and (ii) always being 100 moie%, and by copolymerization in a subsequent step of
(2) 5-40 parts by weight (calculated on 100 parts by weight of the total addition
polymer (I)) of a monomer mixture B consisting of
(e) 1-10 mole% (meth)acrylic acid,
(f) 2-20 mole% hydroxy alkyl (meth)acrylate,
(g) 0-55 mole% styrene, and
(h) 15-97 mole% of a different copolymerizable monoethylenically unsaturated monomer,
the sum of the mole% indicated for the monomers (e), (f), (g), and (h)
always being 100 mole%, with the carboxylic acid groups derived from the (meth)acrylic acid being at least partially neutralized.

resulting in a non-crosslinked addition polymer I,
whereby the total amount of (meth)acrylic acid in 100 parts of the total addition
polymer (I) is less than 1.75 wt.%, and
wherein
the polymer dispersion (II) is prepared by emulsion polymerization, and
obtained by copolymerization of
(iii) 99.5-99.99 parts by weight (calculated on 100 parts by weight of the total
addition polymer (II)) of a monomer mixture C consisting of
(j) 10-80 wt.% (cyclo)alkyl(meth)acrylate,
(k) 20-50 wt.% (meth)acrylic acid,
(m) 0-20 wt.% hydroxyalkyi (meth)acrylate, and
(n) 0-20 wt.% of a different copolymerizable monoethylenicaily unsaturated monomer,
the sum of the wt.% indicated for the monomers 0"), (k), (m), and (n) always
being 100 wt.%, and (iv) 0.01-0.5 parts by weight (calculated on 100 parts by weight of the total
addition polymer (II)) of a compound having at least two unsaturated
groups, with the carboxyiic acid groups derived from the (meth)acryiic acid being at least partially neutralized.
Preferably, in the first step of the preparation of the polymer dispersion (I), a
monomer mixture A is used, consisting of
(i) 80-100 mole%, more prefen-ed 100 mole%, of a mixture of
(a) 30-95 mole % of a (cyclo)alkyl (meth)acrylate of which the (cyclo)alkyl group contains 4-12 carbon atoms,
(b) 0-50 moie % styrene,
(c) 5-12 mole % hydroxy alkyl (meth)acrylate, and
(d) 0-8 mole % of a di(cyclo)aikyl maleate and/or fumarate of which the (cyclo)alkyl groups contain 4-12 carbon atoms, and

(ii) 0-20 mole %, more preferred 0 moie%, of a different copoiymerizable monoethylenicaiiy unsaturated monomer.
As examples of (cyclo)alkyl (meth)acrylates suitable for use in monomer mixture A and having a (cycio)alkyl group with 4-12 carbon atoms may be mentioned: butyl acrylate, butyl methacryiate, 2-ethyihexyl acrylate, 2-ethylhexyl methacryiate, octyl acrylate, octyl methacryiate, isobornyl acrylate, isobomyl methacryiate, dodecyl acrylate, dodecyl methacryiate, cyclohexyl acrylate, cyclohexyl methacryiate, and mixtures thereof. Butyl acrylate, butyl methacryiate, and mixtures thereof are preferred.
Examples of hydroxyalkyi (meth)acrylates are 2-hydroxyethyi acrylate, 2-
hydroxyethyl methacryiate, 2-hydroxypropyi acrylate, 2-hydroxypropyl
methacryiate, 4-hydroxybutyl acrylate, 6-hydroxyhexyl acrylate, p-
hydroxycyclohexyi acrylate, p-hydroxycyclohexyl methacryiate,
hydroxypolyethylene glycol (meth)acrylates, hydroxypolypropyiene glycol (meth)acrylates, and mixtures thereof. 2-Hydroxyethyl methacryiate is preferred.
As examples of di(cyclo)alkyl maieates and/or fumarates with the (cyclo)alkyl groups having 4-12 carbon atoms suitable for use in monomer mixture A may be mentioned dibutyl maleate, dibutyl fumarate, 2-ethylhexyl maleate, 2-ethylhexyl fumarate, octyl maleate, isobornyl maleate, dodecyl maleate, cyclohexyl maleate, and mixtures thereof.
As suitable copoiymerizable monoethylenicaiiy unsaturated monomers to be used in monomer nnixture A may be mentioned: alkyl (meth)acrylates having fewer than 4 carbon atoms in the alkyl group, such as methyl methacryiate, methyl acrylate, ethyl acrylate, ethyl methacryiate, propyl acrylate, propyl methacryiate, and isopropyl acrylate; alkyl maieates and fumarates having

fewer than 4 carbon atoms in the alkyl groups, such as dimethyl maleate, diethyl maleate, diethyl fumarate, and dipropyl maleate; (meth)acrylates having ether groups such as 2-methoxyethyl methacrylate, 2-ethoxyethyl methacrylate, and 3-methoxypropyl acrylate; monovinyl aromatic hydrocarbons, such as vinyl toluene, a-methyl styrene, and vinyl naphthalene; acrylamide and methacrylamide; nitrites such as acrylonitriie and methacrylonitrile; N-alkyI (meth)acrylamide such as N-isopropyl acrylamide, N-isopropyl methacrylamide, N-t-butyl acrylamide, N-t-octyl acrylamide, N,N-dimethyl aminoethyl methacrylate, N,N-diethyl aminoethyl methacrylate; monomers such as vinyl chloride, vinyl acetate, vinyl propionate, and vinyl pyrrolidone, and monomers containing one or more urea or urethane groups, such as for instance the reaction product of 1 mole of isocyanato-ethyl methacrylate and 1 mole of butylamine, 1 mole of benzyiamine, 1 mole of butanol, 1 mole of 2-ethylhexanol, and 1 mole of methanol, respectively. Mixtures of these compounds may also be used.
Preferably, in a second step of the preparation of the polymer dispersion (I), a monomer mixture B is used, consisting of
(e) 5-8 moie% (meth)acrylic acid,
(f) 5-12 mole% hydroxy alkyl (meth)acrylate,
(g) 0-30 mole% styrene, and
(h) 50-90 mole% of a different copolymerizable monoethylenically unsaturated monomer.
»
Examples of hydroxy alkyl (meth)acrylates have been mentioned above. 2-hydroxyethyl methacrylate is prefen-ed.
Examples of copolymerizable monoethylenically unsaturated monomers which may be used in the monomer mixture B include the examples mentioned above for copolymerizable monoethylenically unsaturated monomers which may be

used in the monomer mixture A. Also included are (cyclo)alkyl (meth)acrylates having a (cycle)allcyl group with 4-12 carbon atoms. Examples thereof are also mentioned above. Mixtures of these compounds may also be used. Preferably, the copolymerizable monoethylenicaily unsaturated monomers are selected firom methyl methacrylate, butyl acrylate, butyl methacrylate, and mixtures thereof.
Preferably, polymer dispersion (I) is prepared by emulsion polymerization of
(1) 70-90, preferably 75-85, parts by weight of monomer mixture A and
(2) 10-30, preferably 15-25, parts by weight of monomer mixture B. Optionally, different monomer mixtures A and/or B may be used successively.
Since the addition polymer (I) is non-crosslinked, the choice of the monomers in monomer mixtures A and B is such that the functional groups present other than the unsaturated bonds cannot react with each other at the reaction conditions for the preparation of the addition polymer.
It is required that the total amount of (meth)acryiic acid in 100 parts of the total addition polymer (I) is less than 1.75 wt.%, preferably less than 1.5 wt.%, more preferably between 0.5-1.4 wt.%. In this manner, the polymer dispersion (I) is non-swellable. The acid value is 3 to 10 mg KOH/g, preferably 5 to 8 mg KOH/g.
The addition polymer (I) has a Mn of from 50 000 to 2 000 000, preferably from 100 000 to 1 000 000.
Preferably, monomer mixture C used in the preparation of the polymer
dispersion (II) consists of
(j) 50-70 wt.% (cyclo)alkyl (meth)acrylate,
(k) 30-40 wt.% (meth)acrylic acid,

(m) 0-5 wt.% hydroxyalkyi (meth)acrylate, and
(n) 0-5 wt.% of a different copolymerizable monoethylenically unsaturated monomer.
Preferably, the polymer dispersion (II) is prepared by emulsion polymerization of
(iii) 99.85-99.95 parts by weight of monomer mixture C and (iv) 0.05-0.15 parts by weight of a compound having at least two unsaturated groups.
Preferably, the (cyclo)alkyl (meth)acrylates in monomer mixture C have alkyl groups with 1-4 carbon atoms. Examples include methyl methacrylate, methyl acrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, n-butyl acrylate, n-butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, sec-butyl acrylate, sec-butyl methacrylate, t-butyl acrylate, t-butyi methacrylate, and mixtures thereof. Preferred are methyl acrylate, ethyl acrylate, and propyl acrylate.
Examples of hydroxyalkyi (meth)acryldtes and copolymerizable monoethylenically unsaturated monomer to be used in monomer mixture C are given above for monomer mixtures A and B.
Examples of the compound having at least two unsaturated groups include divinyl toluene, divinyl benzene, trivinyi benzene, divinyl naphthalene, ethylene glycol dj(meth)acrylate, trimethylene glycol di(meth)acrylate, 2-ethyl hexane-1,3-dimethacrylate, divinyl xylene, divinyl ethyl benzene, divinyl ether, divinyl sulfone, allyl ethers of polyhydric compounds, such as glycerol, pentaerythritoi, sorbitol, sucrose, and resorcinoi, allyl ethers of polyisocyanate compounds, such as triallyl Isocyanurate, divinyl ketone, divinyl sulfide, allyl (meth)acrylate, diallyl maleate, diallyl fumarate, diallyl phthalate, diallyl succinate, diallyl

carbonate, diallyl malonate, diaiiyi oxalate, diailyl adipate, dialiyi sebacate, diallyl tartrate, diallyl silicate, triallyl citrate, triallyl phosphate, and N,N"-methylene di(meth)acrylamlde. Prefen-ed is a compound having at least two unsaturated groups of which at least one is an allylic group. More preferred are diallyl phthalate, allyl methacrylate, and triallyl isocyanurate.
The addition polymer (II) has an acid value of 175 to 350 mg KOH/g, preferably 200 to 300 mg KOH/g, and a hydroxyl value of 0 to 150 mg KOH/g, preferably 0 to 100 mg KOH/g.
By emulsion polymerization is meant here the polymerization of the monomer mixtures of ethylenically unsaturated monomers in water in the presence of a water-soluble or -insoluble initiator and 0.1-5 wt.%, preferably 0.3-2.5 wt.% (calculated on the total monomer mixture(s)) of an emulsifier. The polymer dispersion (I) may be prepared by emulsion polymerization as disclosed in EP-A-0 287 144. The polymer dispersion (II) may be prepared by emulsion polymerization as disclosed in GB 870 994.
The emulsifiers of which use is preferably made in the emulsion polymerization are of an anionic and/or non-ionic nature. Examples of anionic emulsifiers include: potassium laurate, potassium stearate, potassium oleate, sodium decyl sulphate, sodium dodecyl sulphate, sodium dodecylberizene sulphonic acid, and sodium rosinate. Examples of non-ionic emulsifiers include: linear and branched alkyi and alkylaryl polyethylene glycol and polypropylene glycol ethers and thioethers, alkyl phenoxypoly(ethyleneoxy) ethanols such as the adduct of 1 mole of nonyl phenol and 3-12 moles of ethylene oxide; alkyl (ethyleneoxy) ethanols with 8-18 carbon atoms in the alkyl groups, such as the adduct of 1 mole dodecanol and 3-12 moles of ethylene oxide. Examples of emulsifiers comprising anionic and non-ionic groups are the ammonium or sodium"salt of the sulphate of alkyl phenoxypoiy(ethyleneoxy) ethanols, such as

the adduct of 1 mole of nonyl phenol and 3-12 moles of ethylene oxide, and the ammonium or sodium salt of the sulphate of alkyl (ethyleneoxy) ethanols with 8-18 carbon atoms in the alkyl groups, such as the adduct of 1 mole C^j-u alcohol and 3-12 moles of ethylene oxide. Prefered is the ammonium or sodium sulphate salt of the adduct of 1 mole C12.14 alcohol and 3-12 moles of ethylene oxide.
Also, in emulsion polymerization, the conventional radical initiators may be used in the usual amounts. Examples of suitable radical initiators include water-soluble initiators, such as ammonium persulphate, sodium persulphate, potassium persulphate, and t-butyl hydroperoxide, and water-insoluble initiators, such as bis(2-ethylhexyl) peroxydicarbonate, di-n-butyl peroxydicarbonate, t-butyl perpivalate, cumene hydroperoxide, dibenzoyi peroxide, dilauroyl peroxide, 2,2"-azobisisobutyronitrile, and 2,2"-azobis-2-methylbutyronitrile. As suitable reducing agents which may be used in combination with e.g. a hydroperoxide may be mentioned: ascorbic acid, sodium sulphoxylate formaldehyde, thiosulphates, bisulphates hydrosuiphates, water-soluble amines such as diethylene triamine, triethylene tetramine, tetraethylene pentamine, N,N"-dimethyl ethanol"amine, and N,N-diethyl ethanol amine, and reducing salts such as cobalt, iron, nickel, and copper sulphate. Optionally, a chain length regulator, for instance n-octyl mercaptan, dodecyl mercaptan, and 3-mercaptopropionic acid, may also be used.
Copolymerization of the monomer mixtures generally is earned out at atmospheric pressure at a temperature of 40-100 °C, preferably 60 - 90 °C, in an atmosphere of an inert gas, such as nitrogen. Optionally, however, copolymerization may also be canied out at elevated pressure. The reaction conditions for monomer mixtures A and B should however be chosen in such manner that functional groups present in the monomer mixtures other than the unsaturated bonds cannot react with each other.

According to the invention the carboxylic acid groups derived from the acrylic acid and/or methacrylic acid are at least 40-100% neutralized by the addition of a neutralizing agent. As suitable neutralizing agents for the carboxylic acid may be mentioned ammonia and amines such as N,N-dimethyl ethanol amine, N,N-diethyl ethanol amine, 2-{dimethyl)-amino-2-methyl-1-propanol, triethyi amine, and morpholine. It is preferred that the neutralizing of the carboxylic acid groups should be carried out after the polymerization.
The coating composition according to the invention comprises preferably a mixture of 92-95 wt.% of a filmforming binder composition comprising an alkali non-swellable core-shell addition polymer dispersion (I), and 5-7.5 wt.% of a rtieology modifying addition polymer dispersion (II).
The coating composition of the present invention consists essentially of water, being an aqueous coating composition. However, about 20 wt.% of liquid content of the coating composition may be an organic solvent. As suitable organic solvents may be mentioned such ether group-containing alcohols as hexylglycol, butoxyethanol, 1-methoxy-propapol-2, 1-ethoxy-propanol-2, 1-propoxy-propanol-2, 1-butoxy-propanol-2, and 1-isobutoxy-propanGl-2; alcohols, such as methanol, ethanol, propanol, butanol, pentanol, and hexanol; diols, such as ethylene glycol and diethylene glycol.
The coating composition according to the present invention may be cured by physical drying. Alternatively, however, the coating compositions may be cured in the presence of a curing agent which reacts with hydroxyl and/or carboxyl groups.
Examples of suitable curing agents include N-methylol and/or N-methyiol ether groups-containing aminoplastes obtained by reacting an aldehyde, for instance

formaldehyde, with an amino or amido groups-containing compound such as melamine, such as Cymei 328, ex Cytec, urea, N,N"-ethylene urea, dicyanodiamide, and benzoguanamine. The resulting compounds are areferably wholly or partially etherified with alcohols having 1-6 carbon atoms, such as methanol, ethanol, n-propanol. isopropanol, n-butanol, isobutanol, amyl alcohol, hexanol, or mixtures thereof. Especially favourable results may be Dbtained when using a methylol melamine having 4-6 methyl groups per molecule of melamine, at least 3 methylol groups being etherified with butanol ar a butanol etherified condensation product of formaldehyde and N,N"-ethyiene diurea. Examples of other suitable curing agents include polyisocyanates or water-dispersible blocked polyisocyanate such as a methyl ethyl ketoxime-biocked, isocyanate group-containing adduct of a polyisocyanate to a hydroxycarboxylic acid, e.g. dimethylol propionic acid, and aliphatic or aromatic carbodiimides.
In addition to the alkali non-swellable core-shell addition polymer dispersion (I), the fiimforming binder composition may also comprise water-dilutable materials such as alkyd resins, polyesters, polyurethanes, and mixtures thereof. Preferably, the water dilutable material is a" polyurethane. The filmfomning binder composition may comprise 0,1 to 100 wt.% of the alkali non-swellable core-shell addition polymer dispersion (I) and 99,9 to 0 wt.% of at least one water dilutable material, wherein the sum of the wt.% indicated for dispersion (1) and the water dilutable material(s) is always 100 wt.%. More preferably, the filmfomning binder composition may comprise 1 to 99 wt.% of the alkali non-swellable core-shell addition polymer dispersion (!) and 99 to 1 wt.% of at least one water dilutable material. Most preferably, the fiimforming binder composition may comprise 25 to 75 wt.% of the alkali non-swellable core-shell addition polymer dispersion (I) and 75 to 25 wt.% of at least one water dilutable material.

In addition, the coating composition may contain the conventional additives and adjuvants, such as pigments, dispersing agents, dyes, and accelerators for the curing reaction. The applicable pigments may have an acid, a neutral or a basic character. Optionally, the pigments may be pre-treated to modify the properties. Examples of suitable pigments include metallic pigments such as aluminum and stainless steel; nacreous pigments, such as mica coated with a, metal oxide such as iron oxide and/or titanium dioxide; inorganic pigments, such as titanium dioxide, iron oxide, carbon black, silica, kaolin, talc, barium sulphate, lead silicate, strontium chromate, and chromium oxide; and organic pigments, such as phthalocyanine pigments.
The solids content of the coating composition ranges from 5-60 wt.%, preferably from 10-40 wt.%. This depends on whether a metallic pigment is used or not. The presence of metallic pigments results in a lower solid content compared to the presence of non-metallic pigments. However, compared to conventional aqueous base coat systems, the solid content of the coating composition of the present invention is in both cases higher.
Preferably, the coating composition according to the present invention is used as a base coat in a so-called base coat/clear coat system to provide a high gloss metallic appearance. To this end the coating composition according to the invention comprises so-called "non-leafing" aluminum paste or some other metallic pigment. Use of the coating compositions according to the invention as a base coat may prevent the base coat from being softened by the clear coat after being sprayed with it, so that the metallic effect will not be lost.
The clear coat used in the base coat/clear coat system may for instance be a clear baking lacquer of a conventional polyacrylate/melamine composition. The clear coat may also be a two-component polyester or

polyacrylate/polyisocyanate composition. The polyisocyanate may be for example the trimerof 1,6-hexamethylene diisocyanate.
The coating composition according to the invention may be applied to a substrate in any desirable manner, such as by roller coating, spraying, brushing, sprinkling, flow coating, dipping, electrostatic spraying, or electrophoresis, preferably by spraying.
Suitable substrates may be made of wood, metal, and synthetic material. Curing may be earned out at ambient temperature or, optionally, at elevated temperature to reduce the curing time. Optionally, the coating composition may be baked at higher temperatures in the range of, for instance, 60 to 160 "C, in a baking oven over a period of 10 to 60 minutes. The clear coat may be applied wet-on-wet on the base coat. Optionally, the base coat may be partially cured prior to the application of the clear coat. Also, the base coat may be fully cured prior to the application of the clear coat.
The compositions are particulariy suitable in the preparation of coated metal
>
substrates, such as in the refinish industry, in particular the body shop, to repair automobiles and transportation vehicles and in finishing large transportation vehicles such as trains, trucks, buses, and aeroplanes. The compositions of the present invention may also be used in the first finishing of automobiles.
The invention will be further described in the following examples, which must not be construed as limiting the scope of the present invention.

EXAMPLES
Test methods used in the examples are described below.
The mean particle size of the dispersions was determined by dynamic light scattering, the dispersion being diluted with water to a solids content of about 0.1 wt.%.
The viscosity was determined with a Braokfield viscometer.
The solids content is detennined in accordance with ASTM method D 1644-59 with heating at 130 "C over a period of 30 minutes.
The metallic-flake orientation can be measured by a spectrogoniometer. The intensity of the reflected light at angle p is measured for a given incident angle a. The so-called flop can be obtained by measurement of the intensity of the reflection (L-value) at two different angles.
Flop=AL = L(p,)-L(P2)
wherein
L(Pi) = intensity of the reflected light at an angle of ± 110"
•-(P2) - intensity of the reflected light at an angle of ± 25" A silver-shaded low solids metallic base coat /clear coat system exhibits a flop-value of approximately 55 to 75 depending on the metallic grade, when measured in this way.
The humidity resistance can be judged visually by the presence of blisters after the test.
The following compounds were used.

Trigonox A-W70®, 70 wt.% t-butyl hydroperoxide in water, ex Akzo Nobel
Chemicals
Abex JKB®, ammonium sulphate of an ethoxylated alkyl alcohol, solids content
of 29.3 wt.%, ex Rhone-Poulenc
Perlankrol EP36®, sodium sulphate of the adduct of 1 mole dodecanol and 6
moles ethylene oxide, solid content of 29.2 wt.%, ex Ackros
Rhodapex AB/20®, ammonium sulphate of the adduct of 1 mole Ci2.i4-alcohol
and 9 moles ethylene oxide, solids content of 28.7 wt.%, ex Rhone-Poulenc
Setal EPC 4673, polyesterpolyol, ex. Akzo Nobel Resins
Cyme! 328®, melamine crosslinker, ex Cytec
Preparation of alkali non-sweliable core-shell addition Dolvmer dispersions (\)
Example 1
A: Preparation of copolymer A of monomer mixture A in step 1
A 2 I flask fitted with a stirrer, a thermometer, a reflux condenser and dropping
funnels A and B was filled with:
435.0 g of demineralized water and 12.0 g of emulsifier Perlankrol EP36®. Dropping funnel A was filled with:
280.0 g of monomer mixture I (see Table I). Dropping funnel B was filled with a homogeneous mixture of:
140.0 g of demineralized water and 1.4 g of sodium persulphate.
After deaeration, the contents of both the flask and the dropping funnels were brought under a nitrogen atmosphere, and the contents of the flask were heated to 80 "C. Next, the contents of dropping funnel B were introduced into the flask over a period of 3 minutes.

After the contents of the flask were brought again to SO"C, the contents of dropping funnel A were introduced into the flask at a constant rate over a period of 2.5 hours, after which the contents of the flask were kept at 80°C for another 1.5 hours.
B: Preparation of polvmer dispersion (\) in Step 2 Dropping funnel A was filled with
70.0 g of monomer mixture II (see Table I) and dropping funnel B was filled with a homogeneous mixture of:
35.0 g of demineralized water and 0.35 g of sodium persulphate.
The contents of dropping funnel B were introduced into the flask, comprising copolymer A, over a period of 3 minutes. The contents of the flask were brought again to 80""C and the contents of dropping funnel A were introduced into the flask at a constant rate over a period of 1 hour, after which the contents of the flask were kept at SO"C for another 2 hours. The reaction was carried out under a nitrogen atmosphere.
On conclusion of the reaction the contents of the flask were cooled to 70°C, after which there were added dropwise 41,3 g of a 10 .wt.% solution of N,N-dimethyl ethanol amine in water. Subsequently, the contents of the flask were cooled to ambient temperature and filtered over a 30pm filter cloth. The properties of the dispersion are given in Table II.

Example 2
Example 1 was repeated except for the following:
A: Preparation of copolymer A of monomer mixture A in step 1
Dropping funnel A was filled with 280.0 g of monomer mixture III (see Table I)
Instead of monomer mixture I.
B: Preparation of polvmer dispersion (\) in Step 2
Dropping funnel A was filled with 70.0 g of monomer mixture IV (see Table I)
instead of II.
After conclusion of the reaction were added 43.5 g of a 10 wt.% solution of N,N-dimethyl ethanol amine in water. The properties of the resulting dispersion are given In Table II.
Example 3
A: Preparation of copolymer A of monomer mixture A in step 1
A 2 I flask fitted with a stin-er, a thermometer, a reflux condenser, and dropping
funnels A and B was filled with:
339.0 g of demineraiized water, and 8.0 g of emulsifier Rhodapex AB/20®. Dropping funnel A was filled with:
378.7 g of a monomer pre-emulsion composed of 93.3 g of demineraiized water, 5.4 g of Rhodapex AB/20®, and 280.0 g of monomer mixture III (see Table I). Dropping funnel B was filled with a homogeneous mixture of: 140.0 g of demineraiized water and 1.4 g of ammonium persulphate.

After deaeration, the contents of both the flask and the dropping funnels were brought under a nitrogen atmosphere, and the contents of the flask were heated to SOX, after which 5% of the contents of dropping funnel A were introduced into the flask over a period of 2 minutes.
Next, the contents of the flask were heated to SCC and 30% of the contents of dropping funnel B were added to the contents of the flask. The contents of the flask were kept at dCC for 15 minutes, and subsequently the rest of the contents of the dropping funnels A and B were introduced into the flask at a constant rate over a period of 2.5 hours, after which the contents of the flask were kept at 80°C for another hour.
B: Preparation of polymer dispersion (\) in Step 2 Dropping funnel A was filled with:
70.0 g of monomer mixture IV (see table I) and dropping funnel B was filled with a homogeneous mixture of: 35.0 g of demineralized water and 0.35 g of ammonium persulphate.
The contents of both dropping funnels were introduced into the flask comprising copolymer A at a constant rate over a period of 1 hour, after which the contents of the flask were kept at SO"C for another hour.
On conclusion of the reaction the contents of the flask were cooled to TO"C, after which there were added dropwise 43,5 g of a 10 wt.% solution of N,N-dimethyl ethanol amine in water. Subsequently, the contents of the flask were cooled to ambient temperature and filtered over a 30|im filter cloth. The properties of the dispersion are given in Table II.

Example 4
Example 3 was repeated except for the following:
A: Preparation of copolymer A of monomer mixture A in step 1
The flask was filled with
338.0 g of demineralized water and 13,4 g of emulsifier Rhodapex AB/20®.
B: Preparation of polymer dispersion (]) in Step 2 Dropping funnel A was filled with:
70.0 g of monomer mixture V (see Table 1) The properties of the dispersion are given in Table II.
Example 5
Example 4 was repeated, except for the following:
A: Preparation of copolymer A of monomer mixture A in step 1
The monomer pre-emuision was composed of 280.0 g of monomer mixture VI
(see Table I) instead of monomer mixture III.
The properties of the dispersion are given in Table II.
Example 6
Example 4 was repeated, except for the following:
B: Preparation of polymer dispersion (\) in Step 2
Dropping funnel A was filled with 70.0 g of monomer mixture VII (see Table I)
instead of monomer mixture V.
The properties of the dispersion are given in Table II.

E; A: Preparation of copolymer A of monomer mixture A in steo 1
A 3 I flask fitted with a stirrer, a thermometer, a reflux condenser, and dropping
funnels A and B was filled with:
621.1 g of demineraiized water, and 5.4 g of a 20 wt.% solution of sodium dodecylbenzene sulphonic acid solution in demineraiized water Dropping funnel A was filled with:
683.8 g of a pre-emulsion composed of
507.1 g of monomer mixture VIII (see Table I) 10.0 g of a 20 wt.% solution of sodium dodecylbenzene sulphonic acid in demineraiized water
166.7 g of demineraiized water Dropping funnel B was filled with 55.3 g of a homogeneous mixture of 53.3 g of demineraiized water 2.02 g of sodium persulphate
After deaeration, the contents of both the flask and the dropping funnels were brought under a nitrogen atmosphere, and the contents of the flask were heated to 50°C. After 9.6 g of the contents of dropping funnel A were introduced into the flask In a period of 1 minute, the contents of the flask were heated to 83°C. Subsequently, 25% of the contents of dropping funnel B were introduced into the flask after which the contents of the flask were kept at 83""C for a period of 15 minutes. Subsequently, the rest of the contents of dropping funnel A and B were introduced into the flask at a constant rate over a period of 3 hours, after which the contents of the flask were kept at 83""C for another 30 minutes and subsequently diluted with 143.3 g of demineraiized water.

B: Preparation of polvmer dispersion (\) in Step 2 Dropping funnel A was filled with
126.7 g of monomer mixture IX (see Table I) and dropping funnel B was filled with a homogeneous mixture of 33.3 g of deminerallzed water and 0.51 g of sodium persulphate.
The contents of both dropping funnels were introduced into the flask comprising copolymer A at a constant rate over a period of 1 hour, after which the contents of the flask were kept at SO"C for another hour.
On conclusion of the reaction the contents of the flask were cooled to ambient temperature and filtered over a 80|im filter cloth, after which there were added dropwise 13.5 g of a 30 wt.% solution of N,N-dimethyl ethanol amine in deminerallzed water. The properties of the dispersion are given in Table II.
S^ample 9
Example 7 was repeated except for the following:
A: Preparation of copolymer A of monomer mixture A in step 1
The monomer pre-emulsion was composed of:
507.1 g of monomer mixture X instead of monomer mixture VIII. For dropping funnel B ammonium persulphate was used instead of sodium persulphate.
B: Preparation of polymer dispersion (\) in Step 2 The monomer mixture was composed of:
126.7 g of monomer mixture XI instead of monomer mixture IX.

On conclusion of the reaction the dispersion was neutralized with 11.7 g of a 30 wt.% solution of N,N-dimethyl ethanol amine in demineralized water instead of 13.5 g of this solution. The properties of the dispersion are given in Table II.
Exampte 9
Example 8 was repeated except for the following
A: Preparation of copolymer A of monomer mixture A in step 1
The flask was filled with
626.0 g demineralized water and 3.7 g of emulsifier Perlankrol EP36®. Dropping funnel A was filled with:
680.7 g of a pre-emulsion composed of
507.1 g of monomer mixture X (see Table I), 6.85 g of emulsifier Perlankrol EP36*, and 166.7 g of demineralized water.
B: Preparation of polvmer dispersion (\) in Step 2
On conclusion of the reaction the dispersion was neutralized with 12.8 g of a 30 wt.% solution of N,N-dimethyl ethanol amine in demineralized water instead of 11.7 g of this solution. The properties of the dispersion are given in Table II.
The preparation of rheology modifving addition polymer dispersions (W)
Example 1Q
A 2 I flask fitted with a stirrer, a thermometer, a reflux condenser, and dropping
funnels was filled with:
460.0 g of demineralized water and 2.64gofAbexJKB*.

Dropping funnel A was filled with:
422.0 g of a monomer pre-emulsion composed of: 150.0 g of demlneralized water, 12.0 gofAbexJKB®, and 260.0 g of monomer mixture XII (see Table I). Dropping funnel B was filled with a homogeneous mixture of 25.0 g of demlneralized water and 0.38 g of ammonium persulphate. Dropping funnel C was filled with a homogeneous mixture of 30.0 g of demlneralized water and 0.14 g of ammonium persulphate
After deaeration, the contents of both the flask and the dropping funnels were brought under a nitrogen atmosphere and the contents of the flask were heated to SS"C, after which 20 g of the contents of dropping funnel A and the contents of dropping funnel B were introduced into the flask. The contents of the flask were kept at 85 "C for 15 minutes.
Subsequently the rest of the contents of dropping funnel A and the contents of dropping funnel C were introduced into the flask at a constant rate over a period of 90 minutes. Dropping funnel A was rinsed then with 60 g. of demlneralized water and after this has been introduced into the flask, the contents of the flask were kept at SS"C for another 30 minutes.
In the meantime dropping funnel D was filled with a homogeneous mixture of: 30.0 g of demlneralized water and 0.60 g Trigonox A-W70® and dropping funnel E was filled with a homogeneous mixture of: 30.0 g of demlneralized water and 0.25 g of sodium fonnaldehyde sulphoxylate.

After the contents of the flask were cooled to 63 "C, the contents of dropping funnel D were introduced into the flask and after 10 minutes the contents of dropping funnel E were introduced into the flask at a constant rate over a period of 30 minutes. Subsequently, the contents of the flask were cooled to ambient temperature and filtered over a 30jim filter cloth. The properties of the dispersion are given in Table III.
Example 11
Example 10 was repeated except for the following:
Dropping funnel A was filled with 260.0 g of monomer mixture XIII (see Table I)
instead of monomer mixture XII.
The properties of the dispersion are given in Table III.
Example 12
Example 10 was repeated except for the following:
Dropping funnel A was filled with 260.0 g of monomer mixture XIV (see Table I)
instead of monomer mixture XII.
The properties of the dispersion are given in Table III.
Example 13
Example 10 was repeated except for the following:
The flask was now filled with
279.7 g of demlneralized water and I.OgofAbexJKB*. The properties of the dispersion are given in Table III.

Base coat compositions
Examples 14-19 and Comparative Examples A and B Base coat compositions were prepared as follows.
A mixture of
22 g of aluminum paste (65% solids in aliphatic/aromatic hydrocarbons, Aquavex Sparkle Silver E5000AR , ex Silberline) and
28 g butoxyethanol was added with stirring to a mixture of
190 g of a polymer dispersion (1) according to Examples 1-6 and 14 g of a polymer dispersion (II) according to Examples 10-12.
The base coat compositions were brought to a pH of 7.5-8.0 by the addition of N,N-dimethyl ethanol amine and diluted with water to spraying viscosity (efflux time of 35 sec. in DIN-cup No. 4). The solids contents of all the base coat compositions were in the range of 14-16 wt.% .
In an atmosphere having a relative humidity of ^5% the base coat compositions of the present invention were sprayed onto primer coated steel test panels in a film thickness of 10-25 ^m (in the dry state). Additionally, two test panels were prepared with a conventional low solids solvent home base coat based on an acrylic/melamine system (comparative example A) and the aqueous core/shell dispersion of Example 5 of EP-A-0 287 144 (comparative example B).
After drying to mat at ambient temperature, the panels were tack free. Next, these test panels were partially covered up and the remaining part was repainted by spraying with a conventional clear coat, a two-component polyester/polyisocyanate coating composition, with the polyisocyanate being a

trimer of 1,6-hexamethylene diisocyanate (in a film thickness of 50-60 \im in a dry state).
After curing for one day at ambient temperature, the test panels 14-19 showed a metallic coat of high gloss. After one week at ambient temperature, the solvent- and water-resistance of the test panels 14-19 were excellent, comparable with test panels A and B.
The flop of both the base coat and the base coat provided with clear coat was measured (see Table IV). The flop values of the base coats based on the coating compositions according to the invention are excellent, comparable with test panels A and B. The decrease of flop by the application of the clear coat (strike-in) is practically zero, so that the excellent flop is maintained. However, the flop values of the base coat/ clear coat of test panels A and B are significantly lower showing a considerable strike-in effect.
Examples 20-22 and Comparative Example C Base coat compositions were prepared as follows.
A mixture of
20 g of aluminum paste (65 wt.%, Aquavex Sparkle Silver E5000AR from
Silberiine),
25.6 g of butoxyethanol,
30.2 g of SetalEPC 4673,
23.5 g of Cyme! 328*
97.8 g of water, and
7.2 g of a 30 wt.% solution of N,N-dimethyl ethanol amine in water was added with stirring to a mixture of
f33.3 g of a polymer dispersion (1) according to Examples 7-9

90.7 g of water, and
13.3 g of a polymer dispersion (II) according to Example 13.
The base coat compositions were brought to a pH of 7.5-8.0 by addition of N,N-dimethyl ethanol amine and diluted with water to spraying viscosity (efflux time of 28 sec in DIN-cup No. 4). Solid content was 20 wt.%.
The base coat compositions were sprayed onto steel test panels in a film thickness of 12-18 jim (in the dry state). After a flash-off period of 2 minutes at 23 "C and 8 minutes at 80 "C, the test panels were repainted with a conventional clearcoat, in a film thickness of 40-45 i^m in the dry state.
The clearcoat was a so-called one component polyacrylate/aminoplaste coating composition. The aminoplaste is a polymeric melamine type resin. After curing for 24 minutes at 140 "C, a metallic coat of good appearance was obtained.
The test panels were tested for their humidity resistance in comparison with a reference waterbome base coat (Example 5 of EP-A-0 287 144; Comparative Example C). The humidity resistance of the test panels 20 to 22 is excellent in comparison to the humidity resistance of test panel C. Table V gives the results of the test.

WE CLAIM:
1. A process for the preparation of an aqueous coating composition comprising a mixture of 90 to 99 wt. % of a film forming binder composition comprising an alkali non-swellable core-shell addition polymer dispersion (I), and 1-10 wt % of a rheology modifying addition polymer dispersion (II), the sum of the wt. % indicated for the filmforming binder composition and dispersion (II) always being 100 wt. %, wherein the polymer dispersion (I) is prepared in two or more steps by emulsion polymerization, and obtained by copolymerization in a first step of (1) 60-95 parts by weight (calculated on 100 parts by weight of the total addition polymer (I)) of a monomer mixture A consisting of (i) 65-100 mole% of a mixture of (a) 10-98 mole % of a (cyclo)alkyl (meth)acrylate of which the (cyclo)alkyl group contains 4-12 carbon atoms, (b) 0-55 mole% styrene, (c) 2-15 mole % hydroxy alkyl (meth)acrylate, and (d) 0-20 mole% of a di(cyclo)alkyl maleate and/or fumigate of which the (cyclo)alkyl groups contain 4-12 carbon atoms, the sum of the mole % indicated for monomers (a), (b), (c), and (d) always being 100 mole %, and (ii) 0-35 mole % of a different copolymerizable monoethylenically unsaturated monomer, the sum of the mole % indicated for components (i) and (ii) always being 100 mole %, and by copolymerization in a subsequent step of (2) 5-40 parts by weight (calculated on 100 parts by weight of the total addition polymer (I)) of a monomer mixture B consisting of (e) 1-10 mole % (meth)acrylic acid, (f) 2-20 mole % hydroxy alkyl (meth)acrylate, (g) 0-55 mole % styrene, and (h) 15-97 mole % of a different copolymerizable monoethylenically unsaturated monomer, the sum of the mole % indicated for monomers (e), (f), (g), and (h) always being 100 mole %, with the carboxylic acid groups derived from the (meth )acrylic acid being at least partially neutralized, resulting in a non-crosslinked addition polymer

1. whereby the total amount of (meth)acrylic acid in 100 parts of the total addition
polymer (I) is less than 1.75 wt.%, and wherein the polymer dispersion (II) is
prepared by emulsion polymerization, and obtained by copolymerization of (iii)
99.5-99.99 parts by weight (calculated on 100 parts by weight of the total addition
polymer (II)) of a monomer mixture C consisting of U) 10-80 wt. % (cyclo)alkyl
(meth)acrylate, (k) 20-50 wt.% (meth)acrylic acid, (m) 0-20 wt. % hydroxyalkyl
(meth)acrylate, and (n) 0-20 wt.% of a different copolymerizable
monoethylenically unsaturated monomer, the sum of the wt.% indicated for
monomers (j), (k), (m), and (n) always being 100 wt. %, and (iv) 0.01-0.5 parts by
weight (calculated on 100 parts by weight of the total addition polymer (II)) of a
compound having at least two unsaturated groups, with the carboxylic acid groups
derived from the (meth)acrylic acid being at least partially neutralized.
2. The process according to claim 1, wherein the monomer mixture A consists of
(i) 80-100 mole% of a mixture of (a) 30-95 mole % of a (cyclo)alkyl
(meth)acrylate of which the (cyclo)alkyl group contains 4-12 carbon atoms, (b) 0-
50 mole % styrene, (c) 5-12 mole % hydroxy alkyl (meth)acrylate, and (d) 0-8
mole % of a di(cyclo)alkyl maleate and/or fumigate of which the (cyclo )alkyl
groups contain 4-12 carbon atoms, and (ii)0-20 mole % of a different
copolymerizable monoethylenically unsaturated monomer.
3. The process according to anyone of the preceding claims, wherein the monomer
mixture B consists of (e) 5-8 mole % (meth)acrylic acid, (f) 5-12 mole % hydroxy
alkyl (meth)acrylate, (g) 0-30 mole % styrene, and (h) 50-90 mole % of a different
copolymerizable monoethylenically unsaturated monomer.

4. The process according to anyone of the preceding claims, wherein the total amount of (meth)acrylic acid in 100 parts of the total addition polymer (I) is between 0.5-1.4 wt.%.
5. The process according to anyone of the preceding claims, wherein the monomer mixture C consists of (}) 50-70 wt.% (cyclo)alkyl (meth)acrylate, (k) 30-40 wt.% (meth)acrylic acid, (m) 0-5 wt.% hydroxyalkyl (meth)acrylate, and (n) 0-5 wt. % of a different copolymerizable monoethylenically unsaturated monomer.
6. The process according to anyone of the preceding claims, wherein the polymer dispersion (II) is prepared by emulsion polymerization of (iii) 99.85-99.95 parts by weight of monomer mixture C and (iv) 0.05-0.15 parts by weight of a compound having at least two unsaturated groups.
7. The process according to anyone of the preceding claims, wherein the
compound having at least two unsaturated groups has at least one allylic group.
8. The process according to claim 7, wherein the compound having at least two unsaturated groups is selected from diallyl phthalate, allyl methacrylate, and triallyl isocyanurate.
9. The process according to any of the preceding claims, wherein the filmforming binder composition comprises in addition to the alkali non-swellable core-shell addition polymer dispersion (I) at least one water-dilutable material.
10. The process according to claim 9, wherein the filmforming binder composition
preferably comprise 0.1 to 99.9 wt.% of the alkali non-swellable core-shell
addition polymer dispersion (I) and 99.9 to 0.1 wt.% of at least one water dilutable

material, wherein tiles sum of the wt.% indicated for dispersion (I) and the water dilutable material(s) is always 100 wt.%.
11.The process according to claims 9 or 10, wherein the water dilutable material is selected from alkyd resins, polyesters, polyurethanes, and mixtures thereof.
12.The process according to 11, wherein" the water dilutable material is polyurethane.
13. A process for the preparation of a base coat composition comprising mixing an aqueous coating composition prepared by the process according to anyone of the preceding claims and non leafing aluminum paste or metallic pigment.

Documents:

in-pct-2000-870-che abstract.pdf

in-pct-2000-870-che claims-duplicate.pdf

in-pct-2000-870-che claims.pdf

in-pct-2000-870-che correspondence-others.pdf

in-pct-2000-870-che correspondence-po.pdf

in-pct-2000-870-che description (complete)-duplicate.pdf

in-pct-2000-870-che description (complete).pdf

in-pct-2000-870-che form-1.pdf

in-pct-2000-870-che form-19.pdf

in-pct-2000-870-che form-3.pdf

in-pct-2000-870-che form-5.pdf

in-pct-2000-870-che pct.pdf

in-pct-2000-870-che petition.pdf

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Patent Number

217025

Indian Patent Application Number

IN/PCT/2000/870/CHE

PG Journal Number

21/2008

Publication Date

23-May-2008

Grant Date

24-Mar-2008

Date of Filing

21-Dec-2000

Name of Patentee

AKZO NOBEL N.V

Applicant Address

Velperweg 76, NL-6824 BM Arnhem,

Inventors:

#	Inventor's Name	Inventor's Address
1	BUTER, Roelof	Surinkhof 1, NL-6952 HT Dieren,
2	ROELOFS, Andreas, Henricus, Johannes	Cadier en Keerpad 16, NL-6845 HV Arnhem,

PCT International Classification Number

C07D 26/18

PCT International Application Number

PCT/EP99/04340

PCT International Filing date

1999-06-22

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	98111529.8	1998-06-23	EUROPEAN UNION