Indian Patents
Title of Invention

"CORROSION-RESISTANT COATING COMPOSITION"
Abstract A coating composition containing (A) a hydroxyl group-containing coating film-forming resin, (E) a crosslinking agent, (C) an anticorrosion pigment mixture, and (D) phosphate or phosphate salt group-containing resin/ the anticorrosion pigment mixture (C) being an anticorrosion pigment mixture consisting of a combination of (1) a vanadium compound and (2) an ion-exchange silica, the vanadium compound (1) being 3 to 50 parts by weight, the ion-exchange silica (2) being 3 to 50 parts by weight/ phosphate or phosphate salt group-containing resin (D) being 1 to 30 parts by weight per 100 parts by weight of a total solid content of the resin (A) and the crosslinking agent (B) respectively.
Full Text SPECIFICATION Title: Corrosion-Resistant Coating Composition Field of the Invention:
The present invention relates to a chrome-free coating composition showing excellent corrosion resistance and a coated metal sheet by use of the coating composition, particularly to a coating composition effective on improving corrosion resistance of not only non-fabricated flat portion but also fabricated portion and edge face in the coated metal sheet even after degradation of the coating film made progress due to photodegradation and hydrolysis in outdoor environment and a coated metal sheet by use of the coating composition. Background of the Art:
A precoated metal sheet such as a precoated steel sheet coated by coil coating has widely been used in the art as housing-related goods, for example, building materials such as roofs, walls, shutters, garage and the like for an architectural structure, various kinds of household appliances, panel boards, refrigerator showcase, steel furniture, kitchen fitments, etc.
The housing-related goods are usually prepared from the precoated metal sheet, for example, by a process which comprises cutting a precoated steel sheet, followed by subjecting to fabrication such as press molding and joining. Consequently, the housing-related goods often have a metal-exposed portion as a cut surface and a crack-developed
portion due to press molding. Corrosion resistance of the metal-exposed portion and the crack-developed portion may be reduced compared with other portions. For the purpose of improving corrosion resistance, a primer coating film on the precoated steel sheet generally contains a chrome-based anticorrosion pigment.
However, the chrome-based anticorrosion pigment may contain or produce a hexavalent chrome showing excellent corrosion resistance, resulting in providing problems from the standpoints of health of human body and environmental protection.
Various kinds of chrome-free anticorrosion pigments such as zinc phosphate, aluminum tripolyphosphate, zinc molybdate and the like have been commercially available, and various kinds of primers containing combinations of chrome-free pigments have been proposed. For example, Patent Reference 1 discloses a coating composition prepared by adding an anticorrosion pigment mixture consisting of a combination of calcium silicate and phosphorus vanadate, or an anticorrosion pigment mixture consisting of a combination of calcium carbonate, calcium silicate, aluminum phosphate and phosphorus vanadate to a vehicle component consisting of epoxy resin and phenol resin. Further, Patent Reference 2 discloses a coating composition prepared by adding an anticorrosion pigment mixture consisting of a combination of dibasic magnesium phosphate and a calcined product of manganese oxide vanadium oxide, or consisting of a calcined
product of calcium phosphate and vanadium oxide to a polyester resin. However, a coating film formed from the coating compositions disclosed in Patent References 1 and 2 shows poor corrosion resistance, particularly unsatisfactory corrosion resistance in the fabricated portion and edge face portion compared with a coating composition prepared by use of a chrome based pigment, and further often shows poor chemical resistance such as alkali resistance and acid resistance and poor water resistance when a large amount of the anticorrosion pigment mixture is used. Accordingly, the anticorrosion pigment mixture disclosed in Patent References 1 and 2 is unsatisfactory to be replaced for the chrome based anticorrosion pigment in the preparation of the precoated metal sheet.
Patent Reference 3 discloses a coating composition prepared by adding, to a vehicle component containing an organic resin having hydroxyl or epoxy group, and a curing agent, a silica fine particle having an oil absorption of 30 to 200 ml/100 g and a pore volume of 0.05 to 1.2 ml/g and forming a cured coating film having a glass transition temperature in the range of 40 to 125°C. However, a coating film formed from the coating composition disclosed in Patent Reference 3 shows some corrosion resistance, but shows poor corrosion resistance and poor chemical resistance, particularly unsatisfactory corrosion resistance in the edge face portion compared with a coating composition prepared by use of a chrome based pigment.
Further, Patent Reference 4 discloses a corrosion-resistant coating composition containing (A) a hydroxyl group-containing coating film-forming resin, (B) a crosslinking agent, and (C) an anticorrosion pigment mixture consisting of a specified vanadium compound, a silica particle and a phosphate-based metal salt selected from phosphate-based calcium salt, phosphate-based zinc salt, phosphate-based aluminum salt, phosphate-based magnesium salt, etc., and showing good corrosion resistance.
However, the above coating composition is unsatisfactory in resistance to corrosion reaction after degradation of topcoat coating film due to outdoor exposure, that is, in durability of corrosion resistance, further improvements in corrosion resistance being demanded. Patent Reference 1: Japanese Patent Application Laid-open No. 61001/99.
Patent Reference 2: Japanese Patent Application Laid-open No. 199078/00.
Patent Reference 3: Japanese Patent Application Laid-Open No. 129163/00-
Patent Reference 4: Japanese Patent Application Laid-Open No. 222833/08. Summary of the Invention:
It is an object of the present invention to provide a chrome-free coating composition capable of forming a coating film showing excellent corrosion resistance in a fabricated portion and an edge face portion in addition to other non-
fabricated portions when used in a coated metal sheet even after degfadation of the coating film made progress due to photodegradation and hydrolysis in outdoor environment and a coated metal sheet by use of the coating composition.
The present inventors made intensive studies for the purpose of solving the above-mentioned problems in the prior art to find out that a coating composition prepared by adding an anticorrosion pigment mixture consisting of a specified vanadium compound and an ion-exchange silica, and at least one resin of a phosphate group-containing resin and phosphate salt group-containing resin in a predetermined amount respectively, to a mixture of a hydroxyl group-containing coating film-forming resin and a crosslinking agent can form a coating film showing excellent corrosion resistance in a fabricated portion and an edge face portion in addition to other non-fabricated flat portion when used in a coated metal sheet in outdoor environment, resulting in accomplishing the present invention.
That is, the present invention provides a coating composition containing (A) a phosphate group-free, hydroxyl group-containing coating film-forming resin, (B) a crosslinking agent, (C) an anticorrosion pigment mixture, and (D) at least one resin of a phosphate group-containing resin and phosphate salt group-containing resin [hereinafter referred to as a phosphate or phosphate salt group-containing resin (D)], the anticorrosion pigment mixture (C) being an anticorrosion pigment mixture consisting of a combination of
(1) at least one vanadium compound selected from vanadium pentoxide, calcium vanadate and ammonium metavanadate, and
(2) an ion-exchange silica, the vanadium compound (1) being in the range of 3 to 50 parts by weight, and the ion-exchange silica (2) being in the range of 3 to 50 parts by weight, a total amount of the phosphate group-containing resin and the phosphate salt group-containg resin in the phosphate or phosphate salt group-containing resin (D) being in the range of 1 to 30 parts by weight, and the anticorrosion pigment mixture (C) being in the range of 6 to 100 parts by weight respectively, per 100 parts by weight of a total solid content of the resin (A) and the crosslinking agent (B) respectively.
The present invention provides a coated metal sheet having a cured coating film formed from the above coating composition on the surface of a metal sheet subjected to an optional metal surface treating process.
The present invention provides a coated metal sheet having a multi-layer coating film consisting of a cured coating film formed from the above coating composition on the surface of a metal sheet subjected to an optional metal surface treating process, and a topcoating film formed on the cured coating film.
The present invention provides a coated metal sheet having a cured coating film formed from the above coating composition on a double-side of both surfaces of a metal sheet subjected to a optional metal surface treating process
respectively.
The present invention provides a coated metal sheet having a multi-layer coating film consisting of a cured coating film formed from the above coating composition on a double-side of both surfaces of a metal sheet subjected to an optional metal surface treating process respectively, and a topcoating film on at least one side of both cured coating films. Effect of the Invention;
The coating composition of the present invention provides such particular effects that the coating composition of the present invention does not contain a chrome-based anticorrosion pigment and is advantageous from the standpoints of environment and health, that the coating composition of the present invention can form a coating film showing excellent corrosion resistance in a fabricated portion and an edge face portion in addition to other non-fabricated flat portion when used in the coated metal sheet, being difficult to provide by a chrome-free anticorrosive coating composition, and that the phosphate or phosphate salt group-containing resin (D) contained in the coating composition of the present invention function as a strong adhesion-imparting component, and has excellent adhesion-imparting properties in acid-environment, resulting in improvements in corrosion resistance with time in outdoor environment in combination with the specified vanadium compound and ion-exchange silica as the anticorrosion pigment
mixture.
That is, the present invention provides a coating composition effective on improving corrosion resistance of not only non-fabricated flat portion but also fabricated portion and edge face in the coated metal sheet even after degradation of the coating film made progress due to photodegradation and hydrolysis in outdoor environment by function of phosphate or phosphate salt group-containing resin (D) to inhibit peeling of the coating film in an anode near the corrosion-progressive portion along with function as a strong adhession-imparting component in acid-environment, in addition to by function of the anticorrosion pigment mixture (C) component consisting of vanadium compound (1) and ion-exchange silica (2) to effectively coat an exposed surface of a substrate, and a coated metal sheet by use of the coating composition.
A coated metal sheet coated with a cured coating film formed from the coating composition of the present invention shows excellent corrosion resistance in non-fabricated flat portion, fabricated portion and edge face portion, and shows such corrosion resistance as to be the same or improved compared with a coated metal sheet coated with a cured coating film formed from a coating composition by use of a chromate based anticorrosion pigment.
A coated metal sheet prepared by being coated with a cured coating film formed from the coating composition of the present invention, followed by being coated with a topcoating
film formed onto the cured coating film shows excellent corrosion resistance in non-fabricated flat portion, fabricated portion and edge face portion. Coating of the coating composition of the present invention onto a metal sheet as a coating substrate, such as a galvanized steel sheet, or an aluminum-zinc alloy plated steel sheet makes it possible to obtain excellent corrosion resistance in the edge face portion and fabricated portion in addition to non-fabricated flat portion. Preferred Embodiments of the Invention:
The coating composition of the present invention contains a hydroxyl group containing coating film-forming resin (A), a crosslinking agent (B), an anticorrosion pigment mixture (C) and a phosphate or phosphate salt group-containing resin (D). Hydroxyl Group Containing Coating Film-Forming Resin (A)
The hydroxyl group-containing film-forming resin (A) in the coating composition of the present invention may include any hydroxyl group containing resin having film-forming properties and usually used in the field of the coating composition without particular limitations, and typically may include, for example, at least one hydroxyl group-containing resin selected from polyester resin, epoxy resin, acrylic resin, fluorocarbon resin, vinyl chloride resin and the like, preferably at least one organic resin selected from hydroxyl group containing polyester resin and hydroxyl group containing epoxy resin.
The hydroxyl group-containing polyester resin as the preferable organic resin may include an oil-free polyester resin, oil-modified alkyd resin, modified products thereof, for example, urethane-modified polyester resin, urethane-modified alkyd resin, epoxy-modified polyester resin and acrylic-modified polyester resin, and the like. The hydroxyl group-containing polyester resin may preferably have a number average molecular weight in the range of 1,500 to 35,000, preferably 2,000 to 25,000, a glass transition temperature (Tg) in the range of 10 to 100°C, preferably 20 to 80°C, and a hydroxyl value in the range of 2 to 100 mg KOH/g, preferably 5 to 80 mg KOH/g.
In the present specification, the number average molecular weight of the resin is a value calculated on the basis of molecular weight of a standard polystyrene from chromatogram measured by use of a gel permeation chromatograph (HLC8120GPC, trade name marketed by Tosoh Corporation). The above measurement was carried out under the following conditions, that is, 4 columns: TSK gel G-4000 HXL, TSK gel G-3000 HXL, TSK gel G-2500 HXL and TSK gel G-2000 HXL (Trade names marketed by Tosoh Corporation, respectively); mobile phase: tetrahydrofuran; measuring temperature: 40 °C, flow rate: 1 ml/min, sensor: RI. In the present specification, the glass transition temperature (Tg) of the resin is determined by the differential scanning calorimeter (DSC).
The oil-free polyester resin consists of an esterified
product between a polybasic acid component and a polyhydric alcohol component. The polybasic acid component may include, as the major component, for example, at least one dibasic acid selected from phthalic anhydride, isophthalic acid, terephthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, succinic acid, fumaric acid, adipic acid, sebacic acid and maleic anhydride, and lower alkyl esterified products thereof, and in addition to the above acids, may optionally include monobasic acid such as benzoic acid, crotonic acid, p-t-butyl benzoic acid and the like, trivalent or higher polybasic acid such as trimellitic anhydride, methylcyclohexene tricarboxylic acid, pyromelitic anhydride and the like, and the like. The polyhydric alcohol may include, as the major component, for example, dihydric alcohol such as ethylene glycol, diethylene glycol, propylene glycol, 1,4-butane diol, neopentyl glycol, 3-methylpentane diol, 1,4-hexane diol, 1,6-hexane diol and the like, and, in addition to the above dihydric alcohol, may optionally include trihydric or higher polyhydric alcohol such as glycerine, trimethylol ethane, trimethylol propane, pentaerythritol and the like. These polyhydric alcohols may be used alone or in combination. Esterification or ester exchange reaction between both components may be carried out by a process known per se. The acid component may be particularly preferable to include isophthalic acid, terephthalic acid, and lower alkyl esterified products thereof.
The alkyd resin may be prepared by reacting an oil fatty acid in addition to the acid component and alcohol component in the above oil-free polyester resin according to a process known per se. The oil fatty acid may include, for example, coconut oil fatty acid, soybean oil fatty acid, linseed oil fatty acid, sun-flower oil fatty acid, tall oil fatty acid, dehydrated castor oil fatty acid, tung oil fatty acid and the like. The alkyd resin preferably has an oil length in the range of 30% or less, particularly 5 to 20%.
The urethane-modified polyester resin may include ones prepared by reacting a polyisocyanate compound with the above oil-free polyester resin or with a low molecular weight oil-free polyester resin obtained by reacting the acid component and alcohol component used in the preparation of the above oil-free polyester resin, according to a process known per se. The urethane-modified alkyd resin may include ones prepared by reacting a polyisocyanate compound with the above alkyd resin or with a low molecular weight alkyd resin obtained by reacting respective components used in the preparation of the above alkyd resin according to a process known per se. The polyisocyanate compound used in the preparation of the urethane-modified polyester resin and urethane-modified alkyd resin may include hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-methylenebis (cyclohexyl isocyanate), 2,4,6-triisocyanatotoluene and the like. The urethane-modified resin may preferably include
ones having such a degree of modification that an amount of polyisocyanate compound forming the urethane-modified resin is in the range of 30% by weight or less based on the urethane-modified resin.
The epoxy-modified polyester resin may include reaction products by reactions such as addition, condensation and grafting between polyester resin and epoxy resin, for example, a reaction product of carboxyl group of a polyester resin prepared from respective components used in the preparation of the above polyester resin with an epoxy group-containing resin; a reaction product obtained by bonding hydroxyl group in the polyester resin to hydroxyl group in the epoxy resin through the polyisocyanate compound. A degree of modification in the epoxy-modified polyester resin is preferably such that an amount of the epoxy resin is in the range of 0.1 to 30% by weight based on the epoxy-modified polyester resin.
The acrylic-modified polyester resin may include a reaction product between a polyester resin prepared from respective components used in the preparation of the above polyester resin and an acrylic resin containing a group reactable with carboxyl group or hydroxyl group in the polyester resin prepared as above, for example, carboxyl group, hydroxyl group or epoxy group; and a reaction product prepared by grafting (meth)acrylic acid, (meth)acrylate and the like to polyester resin by use of a peroxide polymerization initiator. A degree of modification in the
acrylic-modified polyester resin is preferably such that an amount of the acrylic resin is in the range of 0.1 to 50% by weight based on the acrylic-modified polyester resin.
Of the above polyester resins, the oil-free polyester resin and epoxy-modified polyester resin are preferable from the standpoints of fabrication properties and corrosion resistance.
The epoxy resin preferable as the hydroxyl group containing coating film-forming resin may include bisphenol type epoxy resin, novolak type epoxy resin; and modified epoxy resins prepared by reacting various kinds of modifiers with epoxy group or hydroxyl group in the above epoxy resins. In the preparation of the modified epoxy resin, modification by use of the modifier may be carried out at any stage in the preparation of epoxy resin and at a final stage in the preparation of epoxy resin without particular limitations.
The bisphenol type epoxy resin may include, for example, a resin prepared by subjecting epichlorohydrin and bisphenol optionally in the presence of a catalyst such as an alkali catalyst to condensation reaction so as to have a high molecular weight; and a resin obtained by subjecting epichlorohydrin and bisphenol optionally in the presence of a catalyst such as an alkali catalyst to condensation reaction to form a low molecular weight epoxy resin, followed by subjecting the low molecular weight epoxy resin and bisphenol to polyaddition reaction.
The bisphenol may preferably include bis(4-
hydroxyphenyl)methane [bisphenol F] , 1,1-bis(4-hydroxyphenyl ethane, 2,2-bis(4-hydroxyphenyl)propane [bisphenol A], 2,2-bis(4-hydroxyphenyl)butane [bisphenol B], bis (4-hydroxyphenyl)-1,1-isobutane, bis(4-hydroxy-tert-butylphenyl)-2,2-propane, p-(4-hydroxyphenyl)phenol, oxybis(4-hydroxyphenyl), sulfonylbis(4-hydroxyphenyl), 4,4'-dihydroxybenzophenone, bis(2-hydroxynaphthy1)methane and the like. Of these, bisphenol A and bisphenol F are preferably used. The above bisphenols are used alone or in combination.
Examples of commercially available bisphenol type epoxy resin may include jER 828, 812, 815, 820, 834, 1001, 1004, 1007, 1009, 1010 (Trade names, all marketed by Japan Epoxy Resins Co. Ltd.); Araldite AER 6099 (Trade name, marketed by Asahi-Ciba Ltd.); Epomik R-309 (Trade name, marketed by Mitsui Chemicals), and the like.
Examples of novolak type epoxy resin usable as the epoxy resin may include various kinds of novolak type epoxy resins such as phenol novolak type epoxy resin, cresol novolak type epoxy resin, phenol glyoxalic type epoxy resin and the like.
The modified epoxy resin may include an epoxy ester resin obtained by reacting, for example, a drying oil fatty acid; an epoxy acrylate resin obtained by reacting a polymerizable unsaturated monomer component; and urethane-modified epoxy resin obtained by reacting an isocyanate compound with the bisphenol type epoxy resin or the novolak type epoxy resin respectively; an amine-modified epoxy resin
obtained by reacting an amine compound with the epoxy group in the bisphenol type epoxy resin, the novolak type epoxy resin or the above modified epoxy resins so as to introduce amino group or quaternary ammonium salt. Crosslinking Agent (B)
The crosslinking agent (B) is reacted with the hydroxyl group containing coating film-forming resin (A) to form a cured coating film, and may include ones capable of curing by reacting with the hydroxyl group containing coating film-forming resin (A), for example, by heating without particular limitations. Of these, an amino resin and an optionally blocked polyisocyanate compound are preferable. These crosslinking agents may be used alone or in combination.
The amino resin may include a methylol amino resin obtained by reaction of aldehyde with an amino component such as melamine, urea, benzoguanamine, acetoguanamine, stearoguanamine, spiroguanamine, dicyandiamide and the like. The aldehyde used in the above reaction may include formaldehyde, paraformaldehyde, acetoaldehyde, benzaldehyde and the like. The amino resin may also include ones obtained by etherifying the methylol amino resin with a suitable alcohol. Examples of the alcohol used in the etherification may include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, 2-ethyl butanol, 2-ethyl hexanol and the like.
The phenol resin used as the crosslinking agent is reacted and crosslinked with the hydroxyl group containing
coating film-forming resin (A), and may include, for example, a resol phenol resin prepared by heating and subjecting a phenol component and formaldehydes to condensation reaction in the presence of a reaction catalyst to introduce a methylol group, followed by alkyl etherifying at least part of the methylol group in the resulting methylol phenol resin with alcohol.
The phenol component used as a starting material in the preparation of the resol phenol resin may include a bifunctional phenol compound, trifunctional phenol compound and tetra or higher functional phenol compound.
The phenol compound may include, for example, bifunctional phenol compounds such as o-cresol, p-cresol, p-tert-butyl phenol, p-ethyl phenol, 2,3-xylenol, 2,5-xylenol and the like, trifunctional phenol compounds such as phenol, m-cresol, m-ethyl phenol, 3,5-xylenol, m-methoxyphenol and the like, tetra-functional phenol compounds such as bisphenol A, bisphenol F and the like, and the like. Of these, trifunctional or higher phenol compounds, particularly phenol and/or m-cresol are preferable for the purpose of improving scratch resistance. These phenol compounds are used alone or in combination.
The formaldehydes used in the preparation of the phenol resin may include formaldehyde, paraformaldehyde, trioxane, etc., and may be used alone or in combination.
The alcohol used in partly alkyl etherifying the methylol group in the methylol phenol resin may preferably
include monohydric alcohol having 1 to 8, preferably 1 to 4 carbon atoms, particularly methanol, ethanol, n-propanol, n-butanol, isobutanol, etc.
The phenol resin preferably include ones having 0.5 or more, preferably 0.6 to 3.0 on an average of alkoxymethyl group per one benzene ring from the standpoints of reactivity with the hydroxyl group containing coating film-forming resin (A) .
A non-blocked polyisocyanate compound in the optionally blocked polyisocyanate compound used in the crosslinking agent may include organic diisocyanate per se, for example, aliphatic diisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate and the like; alicyclic diisocyanates such as hydrogenated xylylene diisocyanate, isophorone diisocyanate and the like; and aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, 4,4'-diphenylmethane diisocyanate, crude MDI, and the like; adducts of these organic diisocyanates with polyhydric alcohol, low molecular weight polyester resin, water and the like; cyclic polymers between above organic diisocyanates; isocyanate'biuret, and the like.
The blocked polyisocyanate compound usable as the crosslinking agent is a compound prepared by blocking a free isocyanate group in the polyisocyanate compound with a blocking agent. The blocking agent used in blocking isocyanato group may include, for example, phenols such as phenol, cresol, xylenol and the like; lactams such as E -
caprolactam, δ-valerolactam, y-butylolactam, and the like; alcohols such as methanol, ethanol, n-, i- or t-butyl alcohol, ethylene glycol monomethylether, ethylene glycol monobutylether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, benzyl alcohol and the like; oximes such as formamidoxime, acetoaldoxime, acetoxime, methyl ethyl ketoxime, diacetylmonoxime, benzophenone oxime, cyclohexanone oxime and the like; and active methylene based ones such as dimethyl malonate, diethyl malonate, ethyl acetoacetate, acetyl acetone, and the like. Mixing of the polyisocyanate compound with the blocking agent makes it possible to easily block the free isocyanato group in the polyisocyanate compound.
A mixing amount of the hydroxyl group-containing coating film-forming resin (A) and the curing agent (B) is such that the hydroxyl group containing coating film-forming resin (A) is in the range of 55 to 95 parts by weight, preferably 60 to 95 parts by weight, and the crosslinking agent (B) is in the range of 5 to 45 parts by weight, preferably 5 to 40 parts by weight per 100 parts by weight of the total solid content of the components (A) and (B) from the standpoints of corrosion resistance, boiling water resistance, fabrication properties, curing properties, etc.
The curing catalyst may optionally be used for the purpose of promoting a curing reaction of the coating composition and may arbitrarily be selected and used depending on kinds of the curing agent to be used.
In the case where the crosslinking agent (B) is amino resin, particularly methyl etherified or methyl ether-butyl ether mixed etherified melamine resin, the curing catalyst preferably includes a sulfonic acid compound and an amine-neutrified product of the sulfonic acid compound. Typical examples of the sulfonic acid compound may include p-toluene sulfonic acid, dodecylbenzene sulfonic acid, dinonylnaphthalene sulfonic acid, dinonylnaphthalene disulfonic acid and the like. An amine used in the amine-neutralized product of the sulfonic acid compound may include a primary amine, secondary amine and tertiary amine. Of these, the amine-neutralized product of p-toluene sulfonic acid and/or amine-neutralized product of dodecylbenzene sulfonic acid are preferable from the standpoints of stability and reaction-promoting effect of the coating composition, resulting coating film properties and the like.
In the case where the crosslinking agent (B) is a phenol resin, the curing catalyst may include the sulfonic acid compound and the amine-neutralized product of the sulfonic acid compound.
In the case where the crosslinking agent (B) is the blocked polyisocyanate compound, a curing catalyst promoting dissociation of a blocking agent of the blocked polyisocyanate compound as the crosslinking agent is preferable. Examples of preferable curing catalysts may include organometal catalysts such as tin octylate, dibutyltin di(2-ethylhexanoate), dioctyltin di(2-
ethylhexanoate), dioctyltin diacetate, dioctyltin dilaurate, dibutyltin oxide, dioctyltin oxide, lead 2-ethylhexanoate and the like, and the like.
In the case where the crosslinking agent (B) is a combination of two or more crosslinking agents, the curing catalyst may include a combination of respective curing catalysts effective on respective crosslinking agents. Anticorrosion Pigment Mixture (C)
The anticorrosion pigment mixture (C) in the coating composition of the present invention is an anticorrosion pigment mixture consisting of (1) a vanadium compound and (2) an ion-exchange silica. Vanadium Compound (1)
The vanadium compound (1) may include at least one vanadium compound selected from vanadium pentoxide, calcium vanadate and ammonium metavanadate. The vanadium pentoxide, calcium vanadate and ammonium metavanadate show excellent eluation properties in water of a pentavalent vanadium ion, and the pentavalent vanadium ion emitted from the vanadium compound (1) is effective on improvement in corrosion resistance due to a reaction with a substrate metal, or a reaction with ions emitted from other anticorrosion pigment mixture. Ion-Exchange Silica (2)
The ion-exchange silica (2) is a silica fine particle obtained by introducing a cation such as calcium ion onto a fine, porous silica carrier by ion-exchange. The ion-exchange
silica may include, for example, calcium ion-exchange silica, magnesium ion-exchange silica, cobalt ion-exchange silica and the like.
The ion-exchange silica (2) may preferably include a silica fine powder having a mean particle size in the range of 0.5 to 15/µm, preferably 1 to 10µm, and an oil absorption in the range of 30 to 300 ml/100g, preferably 30 to 150 ml/100g.
Of the ion-exchange silica (2), calcium ion-exchange silica is preferable. Commercially available calcium ion-exchange silica may include, for example, SHIELDEX (trademark) C303, AC-3, and C-5, marketed by W.R. Grace & Co. respectively.
The cation such as calcium ion emitted from the ion-exchange silica has an electrochemical function and salts-forming function, and effectively functions to improve corrosion resistance. The silica fixed in the coating film effectively functions to peeling resistance of the coating film under corrosive atmosphere. Phosphate or Phosphate Salt Group-Containing Resin (D)
Of the phosphate or phosphate salt group-containing resin (D), the phosphate group-containing resin may include ones containing phosphate group [-OPO(OH) (OR1)] , wherein R1 represents hydrogen atom, phenyl group or alkyl group having 1 to 20 carbon atoms, particularly hydrogen atom and alkyl group having 1 to 20 carbon atoms, and may include ones compatible with hydroxyl group-containing coating film-
forming resin (A) and crosslinking agent (B), for example, phosphate group-containing acrylic resin, phosphate group-containing epoxy resin, phosphate group-containing polyester resin, etc.
The phosphate group-containing acrylic resin may be obtained by copolymerizing a phosphate group-containing unsaturated monomer and other polymerizable unsaturated monomer.
The phosphate group-containing unsaturated monomer may include, for example, (meth)acryloyloxyalkyl acid phosphate, wherein alkyl has 2 to 20 carbon atoms, acid phosphate such as (2-acryloyloxyethyl) acid phosphate, (2-methacryloyloxyethyl) acid phosphate, (2-acryloyloxypropyl) acid phosphate, (2-methacryloyloxypropyl) acid phosphate, 10-acryloyloxydecyl acid phosphate, 10-methacryloyloxydecyl acid phosphate and the like; an equimolar adduct of orthophosphoric acid or acid phosphate having 1 to 20 carbon atoms with an epoxy group-containing unsaturated monomer such as glycidyl (meth)acrylate and the like; Kayamer PM-2, Kayamer PM-21 (Trade names marketed by Nippon Kayaku Co., Ltd. respectively). Examples of the acid phosphate may include methyl acid phosphate, butyl acid phosphate, 2-ethylhexyl acid phosphate, isodecyl acid phosphate, lauryl acid phosphate, isotridecyl acid phosphate, oleyl acid phosphate, phenyl acid phosphate, and the like.
Other polymerizable unsaturated monomer copolymerized with phosphate group-containing unsaturated monomer and
constituting the phosphate group-containing acrylic resin may include, for example, hydroxy group-containing unsaturated monomer such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether, 2-hydroxyethyl alkyl ether and the like; acrylic acid, methacrylic acid; vinyl aromatic compounds such as styrene, α-methylstyrene, vinyl toluene, α-chlorostyrene and the like; alkyl ester having 1 to 24 carbon atoms for alkyl or cycloalkyl ester of acylic acid or methacrylic acid such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, (n-, i-, t-) butyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isobornyl (meth)acrylate and the like; vinyl acetate, vinyl chloride, vinyl ether, acrylonitrile, methacrylonitrile, and the like.
Hereinbefore, "(meth) acrylate" means "acrylate or methacrylate".
The phosphate group-containing acrylic resin may also be obtained by addition of a phosphate based compound to a copolymer resin of an epoxy group-containing unsaturated monomer such as glycidyl (meth)acrylate with the above other polymerizable unsaturated monomer. The phosphate based compound for addition may include, for example, orthophosphoric acid, acid phosphate and the like. The acid
phosphate may include above-exemplified acid phosphates.
The phosphate group-containing epoxy resin may be obtained by addition of a phosphate based compound to an epoxy resin. The epoxy resin for addition of the phosphate based compound may include, for example, bisphenol type epoxy resin, novolac type epoxy resin, and modified epoxy resins obtained by reacting various kinds of modifying agents with epoxy group or hydroxyl group in the above epoxy resins. The phosphate based compound for addition may include ones exemplified as the phosphate based compound for addition to the copolymer resin of epoxy group-containing with other polymerizable unsaturated monomer as explained in the above phosphate group-containing acrylic resin.
The phosphate group-containing polyester resin may be obtained, for example, by reacting a phosphate based compound with hydroxyl group in the polyester resin.
The phosphate based compound to be reacted may include ones exemplified as the phosphate based compound in the explanation of the phosphate group-containing acrylic resin.
Of phosphate or phosphate salt group-containing resin (D), the phosphate salt group-containing resin may be obtained by reacting the phosphate group in the phosphate group-containing resin with a metal compound to form a phosphate salt.
The metal compound to be reacted with the phosphate group may include, for example, calcium oxide, magnesium oxide, cobalt oxide, nickel oxide, zinc oxide, cerium oxide,
lanthanum oxide and the like.
The phosphate group or phosphate salt group in the phosphate or phosphate salt group-containing resin (D) effectively functions for improvements in adhesion-imparting properties and corrosion resistance.
From the standpoint of corrosion resistance, the coating composition of the present invention preferably contains the vanadium compound {1) in the range of 3 to 50, preferably 5 to 40 parts by weight, the ion-exchange silica (2) in the range of 3 to 50, preferably 3 to 30 parts by weight, the phosphate or phosphate salt group-containing resin (D) in the range of 1 to 30, preferably 1 to 20 parts by weight, and the anticorrosion pigment mixture (C) in the range of 6 to 100, preferably 10 to 60 parts by weight respectively, per 100 parts by weight of a total solid content of the resin (A) and the crosslinking agent (B) respectively.
According to the coating composition of the present invention, combination of respective specified amounts of the vanadium compound (1) and the ion-exchange silica (2) in the anticorrosion pigment mixture (C), and the phosphate or phosphate salt group-containing resin (D) makes it possible to synergistically improve corrosion resistance.
It is desirable from the standpoints of water solubility of the vanadium compound (1) and the ion-exchange silica (2), reactivity between an anticorrosion pigment-dissolved solution and a metal sheet, and corrosion
resistance that a filtrate prepared by adding a mixture of the vanadium compound (1) and the ion-exchange silica (2) constituting the anticorrosion pigment mixture (C) within the range of parts by weight per 100 parts by weight of the total solid content of the resin (A) and the crosslinking agent (B) as described below respectively to 10000 parts by weight of a 5 wt% aqueous sodium chloride solution at 25°C, followed by stirring for 6 hours, leaving at rest for 48 hours at 25°C, and filtering a resulting supernatant liquid, has a pH in the range of 3 to 8, preferably 5 to 8.
That is, the filtrate subjected to the pH measurement is a filtrate prepared by adding a mixture of the vanadium compound (1) in an amount of in the range of 3 to 50 parts by weight and the ion-exchange silica (2) in an amount of in the range of 3 to 50 parts by weight, per 100 parts by weight of the total solid content of the resin (A) and the crosslinking agent (B) respectively to 10000 parts by weight of a 5 wt% aqueous sodium chloride solution at 25°C, followed by dissolving, and filtering the resulting solution.
The coating composition of the present invention may optionally contain a color pigment, extender pigment, ultraviolet light absorber, ultraviolet stabilizer, organic solvent; additives such as anti-settling agent, anti-foaming agent, coating surface controlling agent and the like as known for use in the field of the coating composition in addition to the hydroxyl group-containing film-forming resin (A), the curing agent (B), the anticorrosion pigment mixture
(C), the phosphate or phosphate salt group-containing resin (D) and the optionally used curing catalyst.
The color pigment may include, for example, organic color pigments such as cyanine blue, cyanine green, organic red pigments such as azo pigment and quinacridone pigment and the like; inorganic color pigment titanium white, titanium yellow, red iron oxide, carbon black, various kinds of calcined pigments, of these titanium white is preferable.
The extender pigment may include, for example, talc, clay, mica, alumina, calcium carbonate, barium sulfate, and the like.
The ultraviolet light absorber may include, for example, ben20triazole derivatives such as 2-(2-hydroxy-3,5-di-t-amylphenyl)-2H-benzotriazole, isooctyl-3-(3-(2H-benzotriazole-2-yl)-5-t-butyl-4-hydroxyphenyl)propionate, 2-[2-hydroxy-3,5-di(1,1-dimethylbenzine)phenyl]-2H-benzotriazole, 2-[2-hydroxy-3-dimethylbenzyl-5-(1,1,3,3-tetramethylbutyl)phenyl]-2H-benzotriazole, a condensation product of methyl-3-[3-t-butyl-5-(2H-benzotriazole-2-yl)-4-hydroxyphenyl]propionate with polyethylene glycol 300, and the like; triazine derivatives such as 2-[4-(2-hydroxy-3-dodecyloxypropyl)-oxy]-2-hydroxyphenyl-4,6-bis(2,4-dimethylphenyl)-1,3,5-1,3,5-triazine and the like; oxalic anilide derivatives such as ethanediamide-N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)-(oxalic amide), ethanediamide-N-(2-ethoxyphenyl)-N'-(4-isododecylphenyl)-(oxalic amide) and the like.
The ultraviolet stabilizer may include, for example, a hindered amine-based compound, a hindered phenol based compound; CHIMASORB 944, TINUVIN 144, TINUVIN 2 92, TINUVIN 770, IRGANOX 1010, IRGANOX 1098 (Trade names, marketed by Ciba Specialty Chemicals K.K. respectively), and the like.
Addition of the ultraviolet light absorber and the ultraviolet stabilizer to the coating composition makes it possible to control degradation of the coating film surface by light, and, when the coating composition used as a primer coating composition, to control degradation of the primer coating film surface by the light reached the primer coating film surface through a topcoating film, resulting in preventing intercoat peeling between the primer coating film and the topcoating film due to degradation of the primer coating film surface, and in keeping excellent corrosion resistance.
The organic solvent used in the coating composition of the present invention may include ones optionally added for the purpose of improving coating properties of the coating composition of the present invention, ones capable of dissolving or dispersing the hydroxyl group-containing film-forming resin (A) and the crosslinking agent (B), and specifically, for example, hydrocarbon solvent such as toluene, xylene, high boiling point petroleum based hydrocarbon and the like, ketone solvent such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone and the like, ester solvent such as ethyl acetate, butyl acetate,
ethylene glycol monoethyl ether acetate, diethylene glycol monoethyl ether acetate and the like; alcohol solvent such as methanol, ethanol, isopropanol, butanol and the like; ether alcohol solvent such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether and the like, and the like. These solvents may be used alone or in combination.
The coating composition of the present invention is such that a glass transition temperature of a cured coating film obtained from the composition of the present invention is preferably in the range of 40 to 115°C, preferably 50 to 105°C, from the standpoints of corrosion resistance, acid resistance, fabrication properties and the like. In the present invention, the glass transition temperature of the coating film is a maximum temperature determined from a tan 5 change due to a temperature dispersion measurement at a frequency of 110 Hz by use of Dinamic Viscoelastomer Model Vibron DDV-II EA Type (Automatic Viscoelasticity Measuring Instrument, marketed by TOYO BALDWIN Co., Ltd.).
The coating film formed by coating the coating composition of the present invention onto a metal sheet shows excellent corrosion resistance.
This is firstly because a direct formation of a precipitating salt in place of a redox reaction between a metal ion formed by dissolution of a substrate metal due to chloride ion or the like under corrosion environment and pentavalent vanadium ion, i.e., vanadate ion such as VO3- or
VO43-, and an effective formation of a precipitating salt or compound due to a combination of cation and silicate ion. emitted by hydrolysis of the ion-exchange silica in corrosion environment with trivalent vanadium ion formed by redox reaction of pentavalent vanadium ion with the substrate metal ion and the substrate metal ion, results in that exposed surface of a substrate may effectively coated.
This is secondly because the ion-exchange silica strongly functions to control pH of a wet environment near corrosion environment at a weakly acidic value due to effect of weakly acidic functional group on its surface in addition to effect due to cation emitted in corrosion environment and promotes redox reaction between pentavalent vanadium ion and the substrate metal, and further the ion-exchange silica is fixed in the coating film and keeps pH-controlling power for progressive corrosion under corrosion environment over a long term, and keeps taking place hydrolysis sacrificially, emitting silicate ion under stronger progressive corrosion environment.
This is thirdly because in the case of a coated steel sheet, although a topcoat coating film may become hydrophilic due to degradation and various kinds of corrosion-promoting materials may penetrate from non-fabricated flat portion of the topcoat coating film, phosphate or phosphate salt group-containing resin (D) functions as a strong adhesion-imparting component in acid environment and has a function to inhibit peeling of the coating film in anode near the corrosion-
progressive portion, and can effectively neutralize hydroxyl group generated by reduction reaction of oxygen in cathode and can keep the resulting pH near neutrality.
The phosphate group and phosphate salt group of phosphate or phosphate salt group-containing resin (D) may provide an effect to keep pH of environment at weakly acidic value.
Combinations of the above various functions may accomplish excellent corrosion resisitance.
Combined use of vanadium compound (1) and ion-exchange silica (2) constituting anticorrosion pigment mixture (C), and phosphate or phosphate salt group-containing resin (D) makes it possible to effectively conquer respective poor properties in acid resistance, alkali resistance and water resistance of vanadium compound (1), ion-exchange silica (2) and phosphate or phosphate salt group-containing resin (D). Synergistic effects of respective functions of the anticorrosion pigment mixture (C) and phosphate or phosphate salt group-containing resin (D) result excellent corrosion resistance.
That is, the present invention provides a coating composition effective on improving corrosion resistance of not only non-fabricated flat portion but also fabricated portion and edge face in the coated metal sheet even after degradation of the coating film made progress due to photodegradation and hydrolysis in outdoor environment by function of phosphate or phosphate salt group-containing
resin (D) to inhibit peeling of the coating film in an anode near the corrosion-progressive protion along with function as a strong adhesion-imparting component in acid-environment, in addition to by function of the anticorrosion pigment mixture (C) component consisting of vanadium compound (1) and ion-exchange silica (2) to effectively coat an exposed surface of a substrate, and a coated metal sheet by use of the coating composition. Coated Metal Sheet
The coated metal sheet of the present invention has a coating film formed by coating the coating composition of the present inventxon onto a metal sheet as a substrate, followed by curing.
The metal sheet as the substrate may include cold-rolled steel sheet, hot dipped galvanized steel sheet, electroplated galvanized steel sheet, iron-zinc alloy plated steel sheet (galvanneal steel sheet), aluminum-zinc alloy plated steel sheet ("galvalume steel sheet" containing about 55% of aluminum in the alloy, "galfan" containing about 5% of aluminum in the alloy, etc.), nickel-zinc alloy plated steel sheet, stainless steel sheet, aluminum sheet, copper sheet, copper plated steel sheet, tin plated steel sheet, etc. These metal sheet may optionally be subjected to conventional metal surface treating process, for example, the phosphating process such as zinc phosphate-treating process, iron phosphate-treating process and the like, composite oxide film-treating process, chrome phosphate-treating process,
chromating process, etc.
The coating composition of the present invention may be coated onto the metal sheet by the conventional coating method such as roll coating method, curtain flow coating method, spray coating method, brushing method, dip coating method and the like. A film thickness of the coating film formed from the composition of the present invention may not particularly be limited, but is usually in the range of 2 to 10 urn, preferably 3 to 6 urn. Drying of the coating film may be carried out under suitable conditions depending on kind of the resin to be used, but in the case where a coating film formed by the coil coating method is continuously heat cured, the heat curing may be carried out, usually at a substrate maximum temperature of 160 to 250°C, preferably 180 to 230°C for 15 to 60 seconds. Heat curing in the batch-wise process may be carried out, usually at a surrounding temperature of 80 to 200°C for 10 to 30 minutes.
In the case where heating is unnecessary in the crosslinking reaction on forming a coating film, for example, in the case where a non-blocked polyisocyanate compound is used as the crosslinking agent (B), or in the case where a bisphenol type epoxy resin is used as the resin (A) and an amine compound is used as the crosslinking agent (B), drying may be carried out at room temperature to be cured according to the conventional process.
The coated metal sheet of the present invention may include ones having the coating film only formed from the
coating composition of the present invention on an optionally surface treated metal sheet, but may also include ones having a topcoating film on the above coating film. The topcoating film has a film thickness in the range of 8 to 30 urn, preferably 10 to 25 urn.
A topcoating composition forming the topcoating film may include conventionally available ones for use in the precoat metal sheet, for example, polyester resin based, alkyd resin based, silicone-modified polyester resin based, silicone-modified acrylic resin based, fluorocarbon resin based topcoating compositions. In the case where fabrication properties are of a great importance, use of a topcoating composition having good fabrication properties such as a polyester resin based topcoating composition for use in high fabrication makes it possible to obtain a coated metal plate having particularly good fabrication properties. The coated metal sheet having the above topcoating film in the present invention shows good film performances in corrosion resistance.
In the case where the galvanized steel sheet and aluminum-zinc alloy plated steel sheet, corrosion resistance in a non-fabricated flat portion has been improved to some extent, but corrosion resistance in a cut edge surface portion and fabricated portion have been unsatisfactory in the art. In contrast, coating of the coating composition of the present invention makes it possible to obtain excellent corrosion resistance in edge surface portion and fabricated
portion.
A coating film from the coating composition of the present invention may be formed on a double-side of the substrate, and optionally the topcoating film may be formed on the coating film from the coating composition of the present invention. Forming the coating film from the coating composition of the present invention on the double-side including the back side of the substrate makes it possible to obtain a coated metal sheet free of a chrome-based anticorrosion pigment and advantageous from the standpoints of environmental protection and health and showing excellent corrosion resistance. Example
The present invention is explained more specifically by reference to the following Preparation Examples and Examples. The present invention should not be limited to the following Examples. Hereinafter, "part" and "%" is represented by "part by weight" and "% by weight" respectively. Preparation Example 1
Preparation of resol phenol resin crosslinking agent solution;
A reactor was charged with 100 parts of bisphenol A, 178 parts of 37% aqueous formaldehyde solution and one part of sodium hydroxide, followed by reacting for 3 hours at 60°C, dehydrating at 50°C for one hour under vacuum, adding 100 parts of n-butanol and 3 parts of phosphoric acid, reacting at 110 to 120°C for 2 hours, filtering the resulting solution,
filtering off the resulting sodium phosphate to obtain resol phenol resin crosslinking agent solution Bl having a solid content of about 50%. The resin obtained as above had a number average molecular weight of 880, methylol group of 0.4 on an average and alkoxyraethyl group of 1.0 on an average per one benzene ring, respectively. Preparation Example 2 Preparation of back side-used coating composition:
A mixture of 200 parts of an epoxy resin solution prepared by dissolving 80 parts of jER 1009 (trade name, marketed by Japan Epoxy Resins Co., Ltd., bisphenol A type epoxy resin, hydroxyl group-containing resin) in 120 parts of a mixed solvent 1 [cyclohexanone/ethylene glycol monobutyl ether/Solvesso 150 (trade name, marketed by Esso Standard Oil Co., Ltd., high boiling point aromatic hydrocarbon based solvent) = 3/1/1 by weight ratio] with 40 parts of titanium white, 40 parts of baryta and a predetermined amount of a mixed solvent 2 [Solvesso 150 (trade name, marketed by Esso Standard Oil Co., Ltd., high boiling point aromatic hydrocarbon based solvent)/cyclohexanone = 1/1 by weight ratio] was subjected to pigment dispersion so that a grain, i.e., particle size of pigment coarse particle may be reduced to 20 urn or less, followed by adding 26.7 parts (20 parts as solid content) of Desmodur BL-3175 (trade name, marketed by Sumika Bayel Urethane Co., Ltd., methyl ethyl ketoxime-blocked RDI isocyanurate type polyisocyanate compound solution, solid content about 75%) and 2 parts of Takenate
TK-1 (trade name, marketed by Takeda Pharmaceutical Company
Limited, organotin based blocking agent-dissociation catalyst,
solid content about 10%), uniformly mixing, adding the mixed
solvent 2 and controlling viscosity at about 80 sec. (Ford
Cup #4/25°C) to obtain a back side-used coating composition.
Preparation of phosphate or phosphate salt group-containing
resin:
Preparation Example 3
Preparation of phosphate group-containing acrylic resin 1
A reactor was charged with 100 parts of butanol, followed by dropping a mixture of 50 parts of styrene, 35 parts of 2-ethylhexyl methacrylate, 15 parts of glycidyl methacrylate and 2.0 parts of 2, 2'-azobisisobutylonitrile over 3 hours, while keeping a reactor temperature at 110°C.
Thereafter, 0.5 part of 2,2'-azobisisobutylonitrile was added, followed by reacting at 110°C for 2 hours, keeping the reactor temperature at 80°C, slowly adding 12.2 parts of 85% orthophosphoric acid and 10.4 parts of butanol and reacting for one hour until turbidity of the resulting mixture in the reactor disappear to obtain a phosphate group-containing acrylic resin 1 solution having a solid content of 50%. Phosphate group-containing acrylic resin 1 as solid content had a resin acid value of 54 (0.096 equivalent/resin lOOg as phosphate group content). Preparation Example 4 Preparation of phosphate group-containing acrylic resin 2
A reactor was charged with 100 parts of butanol,
followed by dropping a mixture of 53 parts of styrene, 40 parts of 2-ethylhexyl methacrylate, 7 parts of glycidyl methacrylate and 2.0 parts of 2, 2'-azobisisobutylonitrile over 3 hours, while keeping a reactor temperature at 110°C.
Thereafter, 0.5 part of 2,2'-azobisisobutylonitrile was added, followed by reacting at H0°C for 2 hours, keeping the reactor temperature at 80°C, slowly adding 5.7 parts of 85% orthophosphoric acid and 4.9 parts of butanol and reacting for one hour until turbidity of the resulting mixture in the reactor disappear to obtain a phosphate group-containing acrylic resin 2 solution having a solid content of 50%. Phosphate group-containing acrylic resin 2 as solid content had a resin acid value of 26 (0.047 equivalent/resin lOOg as phosphate group content). Preparation Example 5 Preparation of phosphate group-containing acrylic resin 3
A reactor was charged with 100 parts of butanol, followed by dropping a mixture of 40 parts of styrene, 30 parts of 2-ethylhexyl methacrylate, 30 parts of glycidyl methacrylate and 2-0 parts of 2, 2'-azobisisobutylonitrile over 3 hours, while keeping a reactor temperature at 110°C.
Thereafter, 0.5 part of 2,2'-azobisisobutylonitrile was added, followed by reacting at 110°C for 2 hours, keeping the reactor temperature at 80°C, slowly adding 25 parts of 85% orthophosphoric acid and 17 parts of butanol and reacting for one hour until turbidity of the resulting mixture in the reactor disappear to obtain a phosphate group-containing
acrylic resin 3 solution having a solid content of 50%.
Phosphate group-containing acrylic resin 3 as solid content
had a resin acid value of 98 (0.17 equivalent/resin lOOg as
phosphate group content).
Preparation Example 6
Preparation of phosphate group-containing epoxy resin
A reactor was charged with 100 parts of cyclohexanone and 100 parts of jER 1007 (Trade name, marketed by Japan Epoxy Resins Co., Ltd., bisphenol type epoxy resin, hydroxy group-containing resin), followed by stirring and heating at 70 °C to dissolve the resin, adding 5.7 6 parts of 85 % orthophosphoric acid, reacting at 70°C for 2 hours, and adding 4 parts of cyclohexanone to obtain 50% phosphate group-containing epoxy resin solution. The phosphate group-containing resin as solid content had a resin acid value of 28 (0.05 equivalent / resin 100g as phosphate group content). Preparation Example 7 Preparation of phosphate salt group-containing acrylic resin
A strong glass vessel was charged with 100 parts (50 parts as solid content ) of 50% solid content acrylic resin 1 solution obtained in Preparation Example 3 and 5 parts of calcium oxide mashed in a mortar, followed by charging glass beads, carrying out dispersion with Skandex(Trade name, marketed by Mitsuwa-Tech Ltd., stirrer) until the resin solution becomes transparent, leaving to stant at room temperature for 48 hours, and removing the glass beads to obtain a phosphate salt group-containing acrylic resin
solution.
Preparation of ion exchange silica
Preparation Example 8
Preparation of magnesium ion-exchange silica
Into 10000 parts by weight of 5 wt% aqueous magnesium chloride solution was added 10 parts by weight of Sylysia 710 (Trade neme, marketed by Fuji Silysia Chemical Ltd., silica fine particle, oil absorption about 105 ml/100g), followed by mixing with agitation for 5 hours, filtering and removing a solid content, well washing the solid content with water, and drying to obtain magnesium ion-exchange silica. Preparation Example 9 Preparation of cobalt ion-exchange silica
Into 10000 parts by weight of 5 wt% aqueous cobalt chloride solution was added 10 parts by weight of Sylysia 710 (Trade neme, marketed by Fuji Silysia Chemical Ltd., silica fine particle, oil absorption about 105 ml/lOOg), followed by mixing with agitation for 5 hours, filtering and removing a solid content, well washing the solid content with water, and drying to obtain cobalt ion-exchange silica. Preparation of Anticorrosive Coating Composition: Example 1
A mixture of 220 parts of an epoxy resin solution prepared by dissolving 85 parts of jER 1009 (trade name, marketed by Japan Epoxy Resins Co., Ltd., bisphenol A type epoxy resin, hydroxyl group containing resin) in 135 parts of a mixed solvent 1 (cyclohexanone/ethylene glycol monobutyl
ether/Sorvesso 150 (trade name, marketed by Esso Standard Oil Co., Ltd., high boiling point aromatic hydrocarbon based solvent) = 3/1/1 by weight ratio] with 5 parts of vanadium pentoxide, 3 parts of Shieldex AC-3 (Trade name,•marketed by W.R.Grace & Co., calcium ion-exchange silica), 20 parts of titanium white, 20 parts of baryta and a predetermined amount of a mixed solvent 2 [Solvesso 150 (trade name, marketed by Esso Standard Oil Co., Ltd., high boiling point aromatic hydrocarbon based solvent)/cyclohexanone = 1/1 by weight ratio] was subjected to pigment dispersion so that a grain, i.e., particle size of pigment coarse particle may be reduced to 20 µm or less, followed by adding 20 parts (15 parts by solid content) of Desmodur BL-3175 (trade name, marketed by Sumika Bayer Urethane Co., Ltd., methyl ethyl ketoxime-blocked HDI isocyanurate type polyisocyanate compound solution, solid content about 75%, 4 parts (2 parts as solid content) of phosphate group-containing acrylic resin 1 solution obtained in Preparation Example 3, and 2 parts of Takenate TK-1 (trade name, marketed by Takeda Pharmaceutical Company Limited, organotin based blocking agent-dissociation catalyst, solid content about 10%), uniformly mixing, adding the mixed solvent 2 and controlling viscosity at about 80 sec (Ford Cup #4/25°C) to obtain an anticorrosive coating composition.
Examples 2-20, Comparative Examples 1-10, Reference Examples 1-2:
Example 1 was duplicated except that respective
hydroxyl group-containing resins, crosslinking agents, anticorrosion pigments and other pigments as shown in Table 1 were used. Reference Examples 1 and 2 represent conventional anticorrosive coating compositions containing a chrome-based anticorrosion pigment. In Table 1, amounts of respective hydroxyl group-containing resin, crosslinking agents, phosphate or phosphate salt group-containing resin and pigment components are represented by weight of solid content, provided with, Example 15 does not contain Takenate TK-1 (trade name as above defined), and Examples 16 and 19 contain one part of Nacure 5225 (trade name, marketed by US King Industries Ltd., amine-neutralized solution of dodecylbenzene sulfonic acid) in place of 2 parts of Takenate TK-1 respectively.
The pH of a filtrate, pH of an anticorrosion pigment-dissolved liquid, prepared by adding a total amount of respective anticorrosion pigments (C) and strontium chromate per 100 parts by weight of the total solid content of the hydroxyl group-containing resin and the crosslinking agent as the resin components to 10000 parts by weight of 5 wt% aqueous sodium chloride solution at 25 °C, followed by stirring for 6 hours, leaving at rest for 48 hours at 25°C, and filtering the resulting supernatant liquid, is represented in Table 1. For example, the pH of the anticorrosion pigment-dissolved liquid in Example 1 is a pH of a filtrate prepared by adding 5 parts by weight of vanadium pentoxide, and 3 parts by weight of Shieldex AC-3 to
10000 parts by weight of 5 wt% aqueous sodium chloride solution at 25°C, followed by dissolving under the above-mentioned conditions, and filtering the resulting supernatant
liquid.
Table 1 (1)

Table Removed
In Table 1, (Note 1) to (Note 7) are explained as
follows.
(Note 1) Epokey 837: trade name, marketed by Mitsui
Chemicals, Inc., urethane-modified epoxy resin, hydroxyl group-containing resin, primary hydroxyl value about 35, acid value about 0 (zero).
(Note 2) Vylon 2 96: trade name, marketed by Toyobo Co., Ltd., epoxy-modified polyester resin, hydroxyl group-containing resin, hydroxyl value 7, acid value 6.
(Note 3) Sumidur N3300: trade name, marketed by Sumika Bayer Urethane Co., Ltd., isocyanurate type polyisocyanate compound, solid content 100%.
(Note 4) Cymel 303: trade name, marketed by Ninon Cytec Industries Inc., methyl etherified melamine resin.
(Note 5) Shieldex C303: Trade name, marketed by w.R. Grace & Co., calcium ion-exchange silica.
(Note 6) Aerosil 200: Trade name, marketed by Nippon Aerosil Co., Ltd., silica fine particle, oil absortion about 280 ml/100g.
(Note 7) Sandvor 3058: trade name, marketed by Clariant Japan KK, hindered amine-based ultraviolet stabilizer.
Preparation of Coating Test Panel
Respective anticorrosive coating compositions obtained
in Examples 1-20, Comparative Examples 1-10 and Reference
Examples 1 and 2, and topcoating composition were coated on
respective substrates and cured according to the following
coating specifications 1-3 to obtain respective coating test
panels.
Coating Specification 1:
The back side-used coating composition obtained in Preparation Example 2 was coated onto a galvalume steel sheet subjected to a metal surface treating process, with sheet thickness of 0.35 mm, aluminum-zinc alloy plated steel sheet, aluminum content in the alloy about 55%, plated alloy amount of 150 g/m2, GL steel sheet as referred in Table 2, to be a dry film thickness of 8 urn by use of a bar coater, followed by curing at a maximum temperature of substrate of 180°C for 30 seconds to form a back side coating film, coating respective anticorrosive coating compositions obtained in the above-mentioned Examples onto a steel sheet on an opposite side to the back side with the back side coating film of the steel sheet to be a dry film thickness of 5 µm by use of a bar coater, followed by curing at a maximum temperature of substrate of 220°C for 40 seconds to obtain respective primer coating films, cooling, and coating KP Color 1580B40 (trade name, marketed by Kansai Paint Co., Ltd., polyester based topcoating composition, blue, glass transition temperature of cured coating film about 70°C) onto respective primer coating films to be a dry film thickness of about 15 µm by use of a bar coater, and curing at a maximum temperature of substrate of 220°C for 40 seconds to obtain respective coating test panels. Coating Specification 2:
The back side-used coating composition obtained in
Preparation Example 2 was coated onto a hot-dipped galvanized steel sheet subjected to a metal surface treating process, with sheet thickness of 0.35 mm, plated zinc amount of 250 g/m2, GI steel sheet as referred in Table 2, to be a dry film thickness of 8 µm by use of a bar coater, followed by curing at a maximum temperature of substrate of 180°C for 30 seconds to form a back side coating film, coating respective anticorrosive coating compositions obtained in the above-mentioned Examples onto a steel sheet on an opposite side to the back side with the back side coating film of the steel sheet to be a dry film thickness of 5 µm by use of a bar coater, followed by curing at a maximum temperature of substrate of 220 °C for 40 seconds to obtain respective primer coating films, cooling, and coating KP Color 1580B40 (trade name, marketed by Kansai Paint Co., Ltd., polyester based topcoating composition, blue, glass transition temperature of cured coating film about 70°C) onto respective primer coating films to be a dry film thickness of about 15 µm by use of a bar coater, and curing at a maximum temperature of substrate of 220°C for 40 seconds to obtain respective coating test panels. Coating Specification 3:
The anticorrosive coating composition obtained in Example 3 was coated onto the same galvalume steel sheet as used in the coating specification 1 to be a dry film thickness of 8 µm by use of a bar coater, followed by curing at a maximum temperature of substrate of 180 °C for 30 seconds
to form a back side coating film, coating respective anticorrosive coating compositions obtained in the above-mentioned Examples onto a steel sheet on an opposite side to the back side with the back side coating film of the steel sheet to be a dry film thickness of 5 urn by use of a bar coater, followed by curing at a maximum temperature of substrate of 220°C for 40 seconds to obtain respective primer coating films, cooling, and coating KP Color 1580B40 (trade name, marketed by Kansai Paint Co., Ltd., polyester based topcoatmg composition, blue, glass transition temperature of cured coating film about 70°C) onto respective primer coating films to be a dry film thickness of about 15 µm by use of a bar coater, and curing at a maximum temperature of substrate of 220°C for 40 seconds to obtain respective coating test panels. Coating Film Performance Test
Respective coating test panels obtained in the above Coating Specifications 1 to 3, using the anticorrosive coating compositions obtained by Examples 1-20, Comparative Examples 1-10 and Reference Examples 1-2 were subjected to the coating film performance test according to the following test methods. Test results are shown in Table 2. Test Methods
Boiling Water Resistance: Respective coating test panels cut to a size of 5 cm x 10 cm are dipped into a boiling water at about 100°C for 2 hours, followed by taking up to evaluate appearance of a coating film formed on the front surface of
the coating panel, and separately are subjected to the cross cut-tape method for evaluation. The cross cut-tape method is as defined in accordance with JIS K-5400 8.5.2 (1990). That is, an adhesive cellophane tape is adhered onto the front surface of respective coating test panels with a cut interval of 1 mm, and 100 squares, followed by strongly separating the tape to evaluate the coating film with squares as follows. ◎: No abnormalities such as development of blisters and
whitening on the coating film, remaining squares 100. O; No abnormalities such as development of blisters and
whitening on the coating film, remaining squares 91-99. : slight development of blisters or whitening on 
coating film, remaining squares 91-99, or No
abnormalities such as development of blisters and
whitening on the coating film, but remaining squares 71-
90. X: considerable or remarkable development of blisters on the
coating film, or remaining squares 70 or less. Alkaline Resistance:
A back side and cut surface of respective coating test panels cut to a size of 5 cm x 10 cm were sealed with an anticorrosive coating composition and a cross cut reaching the substrate was formed at the center on the front side of the surface of the coating panel. The resulting coating panel was dipped in a 5% aqueous sodium hydroxide solution at 40 °C for 48 hours, followed by taking up, washing and drying at room temperature to evaluate coating film appearance on
the front side of the surface of the coating film, and further an adhesive cellophane tape was adhered onto the cross cut portion, followed by strongly separating the tape to evaluate a separated width (one side) from the cross cut portion in the resulting coating film. ◎: No blisters developed, tape-separated width from the cut
portion, 1.5 mm or less. O: No blisters developed, tape-separated width from the cut
portion, more than 1.5 mm but 3 mm or less-: Slight development of blisters, tape-separated width from
the cut portion 3 mm or less, or no blisters developed,
cut tape separated width from the cut portion, more than
3 mm. X: Blisters developed, and tape-separated width from the cut
portion, more than 3 mm. Acid Resistance:
A back side and cut surface of respective coating test panels cut to a size of 5 cm x 10 cm were sealed with an anticorrosive coating composition and a cross cut reaching the substrate was formed at the center on the front side of the surface of the coating panel. The resulting coating panel was dipped in a 5% aqueous sulfuric acid solution at 40°C for 48 hours, followed by taking up, washing and drying at room temperature to evaluate coating film appearance on the front side of the surface of the coating film, and further an adhesive cellophane tape was adhered onto the cross cut portion, followed by strongly separating the tape
to evaluate a separated width (one side) from the cross cut
portion in the resulting coating film.
◎: No blisters developed, tape-separated width from the cut
portion, 1.5 mm or less. O: No blisters developed, tape-separated width from the cut
portion, more than 1.5 mm but 3 mm or less. : Slight development of blisters, tape-separated width from
the cut portion 3 mm or less, or no blisters developed,
cut tape separated width from the cut portion, more than
3 mm. X: Blisters developed, and tape-separated width from the cut
portion, more than 3 mm. Anti-Scratch Property: At room temperature of 20°C, by use of a coin-scratch hardness tester (marketed by Jido-ka Giken Kogyo K.K.), an edge of a ten yen copper coin was kept at an angle of 45° on a coating film on the side of the surface of the respective coating test panels, followed by pulling the ten yen copper coin at a speed of 10 mm/sec, about 30 mm, while pressing under a load of 3 kg, forming mars on the coating film, and evaluating a degree of the mar as follows. ◎: Substrate metal is not exposed in the mar portion. O: Substrate metal is slightly exposed in the mar portion. : Substrate metal is considerably exposed in the mar
portion. X: Almost no coating film remains and the substrate metal is
clearly exposed in the mar portion. Composite Corrosion resistance Test:
Respective coating test panels used in composite corrosion resistance test were prepared as follows. Respective coating test panels cut to a size of 7 cm X15 cm were subjected to 500 hours accelerated weather resistance test by use of exenon lamp accelerated weather resistance tester.
The resulting coating test panels were cut at 5 mm from respective edges of the long sides by use of a shearing machine so that a burr in an edge portion of a long side of respective coating test panels faces the front side of the surface on the right side to the coating film on the side of the surface, and faces the back side on the left side to the coating film on the side of the surface. Thereafter, a cross cut reaching the substrate with an included angle 30° and a line width of 0.5 mm was formed by use of a back of a cutter knife at the center on the side of the surface of respective coating test panels followed by sealing an upper end edge portion of the coating panel with an anticorrosive coating composition, and subjecting the upper end portion to 3T folding fabrication, that is, a fabrication comprising folding the coating panel with the front side of the surface of the coating panel outside, putting 3 sheets having the same thickness as the coating panel inside the folded coating panel, and folding the resulting coating panel at an angle of 180° by use of a vise to obtain respective test panels.
The resulting test panels were subjected to cyclic corrosion test in accordance with JISK-5621(1990) comprising
200 cycles of 1200 hours in total by cycling one cycle consisting of the following successive steps: 5% salt spray test at 30°C for 0.5 hour, a test in a moisture resistance tester under RH 95% or higher at 30°C for 1.5 hours, drying at 50°C for 2 hours, and drying at 30°C for 2 hours. The resulting coating panel was subjected to evaluation of conditions in a non-fabricated flat portion, an edge portion, cross cut portion and 3T folding-fabricated portion respectively.
3T fabricated portion: Evaluation was made on a total length of a rust portion and development of red rust in the 3T fabricated portion. ◎: No white rust developed, or white rust developed, less
than 5 mm. O: White rust developed, more than 5mm but less than 20 mm. : White rust 20 mm or more, but less than 40 mm. X: White rust 40 mm or more, or red rust developed. Edge portion: An average value of an edge creep width of both left and right long sides was determined and examined development of red rust to evaluate as follows. ◎: Less than 5 mm, and no red rust developed. O: 5 mm or more, but less than 10 mm, and no red rust
developed. : 10 mm or more, but less than 20 mm, and no red rust
developed. X: 20 mm or more, or red rust developed. Cross cut portion: Corrosion conditions in the cross cut
portion were evaluated based on a degree of a white rust-developed length in a substrate metal exposed portion with a cut width of 0.5 mm, and an average value of a left and right blister width of both sides in the cut portion, and development of red rust as follows. ◎: Degree of white rust-developed length in the substrate
metal exposed portion is less than 50%, and the blister
width is less than 3 mm. O: Degree of white rust-developed length is 50% or more, and
the blister width is less than 3 mm, or degree of white
rust-developed length is less than 50%, and the blister
width is 3 mm or more, but less than 5 mm. : Degree of white rust-developed length is 50% or more, and
the blister width is 5 mm or more, but less than 10 mm. X: Degree of white rust-developed width is 50% or more, and
the blister width is 10 mm or more, or red rust developed. Non-fabricated flat portion:
Discontinuous and sporadic blisters developed at a portion separated from edge of continuous corrosion portion in non-fabricated flat portion were evaluated as follows. ◎: No blisters developed. O: blister diameter: about less than 2mm, number of
blisters: less than 10. : blister diameter: about 2 mm or more, and number of
blisters: less than 10, or blister diamerter: less than 2
mm, and number of blisters: 10 or more. X: blister diameter: about 2 mm or more, and number of
blisters: 10 or more.

Table 2 (1)
Table Removed







What is claimed is:
1. A coating composition containing (A) a phosphate group-free,
hydroxyl group-containing coating film-forming resin, (B) a
crosslinking agent, (D) at least one resin of a phosphate group-containing resin and phosphate salt group-containing resin, the anticorrosion pigment mixture (C) being an anticorrosion pigment mixture consisting of a combination of (1) at least one vanadium compound selected from vanadium pentoxide, calcium vanadate and ammonium metavanadate, and (2) an ion-exchange silica, the vanadium compound (1) being in the range of 3 to 50 parts by weight, and the ion-exchange silica (2) being in the range of 3 to 50 parts by weight, a total amount of the phosphate group-containing resin and the phosphate salt group-containing resin in the phosphate or phosphate salt group-containing resin (D) being in the range of 1 to 30 parts by weight, and the anticorrosion pigment mixture (C) being in the range of 6 to 100 parts by weight respectively, per 100 parts by weight of a total solid content of the resin (A) and the crosslinking agent (B) respectively.
2. A coating composition as claimed in claim 1, wherein the hydroxyl group-containing coating film-forming resin (A) is at least one selected from a hydroxyl group-containing epoxy resin and hydroxyl group-containing polyester resin.
3. A coating composition as claimed in claim 1, wherein the crosslinking agent (B) is at least one crosslinking agent selected from an amino resin, a phenol resin and optionally-
blocked polyisocyanate compound.
4. A coating composition as claimed in claim 1, wherein the ion-exchange silica (2) is at least one selected from calcium ion-exchange silica, magnesium ion-exchange silica and cobalt ion-exchange silica.
5. A coating composition as claimed in claim 1, wherein the coating composition further contains at least one pigment component selected from an anticorrosive pigment other than the anticorrosion pigment mixture (C), titanium dioxide pigment and an extender pigment in addition to the anticorrosion pigment mixture (C).
6. A coating composition as claimed in claim 1, wherein the coating composition further contains at least one selected from an ultraviolet light absorber and an ultraviolet stabilizer.
7. A coating composition as claimed in claim 1, wherein the coating composition is such that a filtrate prepared by adding a mixture of the vanadium compound (1), and the ion-exchange silica (2) constituting the anticorrosion pigment mixture (C) within the range of parts by weight per 100 parts by weight of the total solid content of the resin (A) and the crosslinking agent (B) as claimed in claim 1 respectively to 10000 parts by weight of a 5 wt% aqueous sodium chloride solution at 25°C, followed by stirring for 6 hours, leaving at rest for 48 hours at 25°C, and filtering a resulting supernatant liquid,' has a pH in the range of 3 to 8.
8. A coated metal sheet having a cured coating film formed from the coating composition as claimed in claim 1 on the
surface of a metal sheet subjected to an optional metal surface treating process.
9. A coated metal sheet having a multi-layer coating film consisting of a cured coating film formed from the coating composition as claimed in claim 1 on the surface of a metal sheet subjected to an optional metal surface treating process, and a topcoating film formed on the cured coating film.
10. A coated metal sheet having a cured coating film formed from the coating composition as claimed in claim 1 on a double-side of both surfaces of a metal sheet subjected to an optional metal surface treating process respectively.
11. A coated metal sheet having a multi-layer coating film consisting of a cured coating film formed from the coating composition as claimed in claim 1 on a double-side of both surfaces of a metal sheet subjected to an optional metal surface treating process respectively, and a topcoating film formed on at least one side of both cured coating films.
12. A coating composition containing a phosphate group-free, substantially as herein described with reference to accompanying drawings and example.

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Patent Number 268247
Indian Patent Application Number 1678/DEL/2010
PG Journal Number 35/2015
Publication Date 28-Aug-2015
Grant Date 24-Aug-2015
Date of Filing 19-Jul-2010
Name of Patentee KANSAI PAINT CO., LTD.
Applicant Address 33-1, KANZAKI-CHO, AMAGASAKI-SHI, HYOGO-KEN 661-0964 JAPAN.
Inventors:
# Inventor's Name Inventor's Address
1 HIDEKI MATSUDA C/O, KANSAI PAINT CO., LTD., 17-1, HIGASHIYAWATA 4-CHOME, HIRATSUKA-SHI, KANAGAWA-KEN, 254-0016 JAPAN
PCT International Classification Number C08L
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 09/182218 2009-08-05 Japan