Title of Invention

METHOD FOR PRODUCING MICROCELLULAR POLYURETHANE ELASTOMERS

Abstract

The invention provides microceilular polyurethane elastomers preparable by reacting polyisocyanates with compounds having at least two hydrogen atoms reactive with isocyanate groups, which comprises a combination a) consisting of ai) an aromatic phosphite having a phosphorus content of from 9.00 to 11.00% by weight and aii) an amine compound, the molar ratio between ai) and aii) being from 0.005 to 4.0.

Full Text

METHOD FOR PRODUCING MICROCELLULAR POLYURETHANE ELASTOMERS Integral polyurethane foams, frequently referred to as microcellular polyurethane elastomers and also referred to hereinbelow as MPE, have been known for some time and are used, for example, to produce shoe soles. They are described, for example, in Kunststoffhandbuch [Plastics Handbook], Volume 7 "Polyurethanes", 3rd edition, page 376 ff. They are prepared by reacting polyisocyanates with compounds having at least two hydrogen atoms reactive with isocyanate groups. Compounds which are used in this context are frequently polyester alcohols. This affords materials having outstanding use properties such as high elasticity, high tensile strength and tear propagation strength or low attrition. At the same time, such systems can be processed with high process reliability. One disadvantage of microcellular polyurethane elastomers based on polyester alcohol consists in the low hydrolysis resistance of the materials. The low hydrplysis resistance is caused by the intrinsic propensity of the ester groups to be degraded hydrolytically. The cleavage of the ester groups causes a degradation in the molar mass of the polymer and leads to a worsening in the use properties which can lead in the extreme case to total material failure. There have therefore been numerous efforts in the past to increase the hydrolysis stability of such materials. One means of improving the hydrolysis stability of polyester alcohol-based microcellular polyurethane elastomers which has been proposed is the use of specific polyester alcohols. Mention should be made here by way of example of DE 3 144 968 in which polyester alcohols based on adipic acid, 1,4-butanediol, 1,6-hexanediol and neopentyl glycol are used. In addition, the substitution or partial substitution of the polyester alcohols for more hydrolysis-resistant polyether alcohols is described. Another means of improving the hydrolysis resistance is the use of particular additives which are usually used in amounts of less than 10% by weight. For instance, EP 965 582 describes the use of acid anhydrides, while DE 19 710 978 describes the use of a combination of lactones and carbodiimides. However, the solutions which can be taken from the prior art usually have disadvantages. In some cases, higher hydrolysis resistances are indeed achieved, but only inadequate use properties before aging are at the same time obtained. In addition, some solutions cannot be realised in practice owing to the higher feedstock costs. This can occur, for example, in the case of use of specific polyester alcohols or higher use amounts of particular additives. A further disadvantage of many solutions which can be taken from the prior art is the reduction in the storage stability of the components. In addition, many solutions have too low an effectiveness, especially when extremely high demands on the hydrolysis stability are required. The use of phosphites in microcellular polyurethane elastomers in general is known and is described, for example, in Kunststoffhandbuch, Volume 7 „Polyurethanes\ 3rd edition, page 120 ff. In this case, phosphites are used as antioxidant assistants. The combined use with typical representatives of antioxidants, such as sterically hindered phenols, leads to a synergistic action, associated with a considerable increase in the effectiveness of prevention of thermooxidation processes. JP 61128904 describes the use of 4-14% by weight of phosphite esters in microcellular polyurethane elastomers based on polyester alcohol. Phosphites based on phenol and long-chain alkyl radicals are used as yellowing inhibitors. The phosphites are used in the prepolymer. JP 63278962 describes UV-stable MPE based on polyester for shoe soles. Phosphites are used as antioxidant assistants together with sterically hindered phenols as an antioxidant. The proportion by weight is 1% by weight. JP 63305162 describes a UV stabilization package for polyester alcohol-based MPE. Here, triphenyl phosphite (TPP), inter alia, is mentioned as an antioxidant assistant in conjunction with sterically hindered phenols. The proportion by weight is 0.5% by weight. JP 05214240 describes UV protection for PU shoe soles which comprises, inter alia, thiophosphites in use amounts of approx. 1%. JP 2003147057 describes the use of polycarbonate diols in shoe systems. In the example, it is mentioned that approx. 2% by weight of TPP is added to the prepolymer. The documents JP 61128904, JP 63278962 and JP 05214240 describe, in general terms, the use of phosphites in polyester-based MPE as antioxidant assistants. The documents JP 63278962 and JP 63305162 mention that aromatic phosphites, inter alia, may be used as an antioxidant in the isocyanate-reactive component. The document JP 2003147057 describes the use of aromatic phosphites in microcellular polyurethane elastomers based on polyether carbonate alcohols. It is an object of the present invention to provide a hydrolysis inhibitor for polyester alcohol-based MPE, which enables high effectiveness at low use amount and guarantees high efficacy irrespective of the polyester alcohol used. This object is achieved by the use of a specific hydrolysis inhibitor a) consisting of a combination of ai) an aromatic phosphite having a phosphorus content of from 9.00 to 11.00% by weight, preferably from 9.90 to 10.10% by weight and in particular from 9.95 to 10.05% by weight and aii) an amine compound, for example triethylenediamine, the molar ratio between ai) and aii) being preferably from 0.005 to 4.0, more preferably from 0.1 to 3.0 and in particular from 0.5 to 2.0..Preference is given to using component ai) in the isocyanate-containing component (B component) and aii) in the isocyanate-reactive component (A component). The invention accordingly provides MPEs preparable by reacting polyisocyanates with compounds having at least two hydrogen atoms reactive with isocyanate groups, which comprises a combination a) consisting of ai) an aromatic phosphite having a phosphorus content of from 9.00 to 11.00% by weight and aii) an amine compound, the molar ratio between ai) and aii) being from 0.005 to 4.0. The invention further provides a process for preparing MPE by reacting polyisocyanates with compounds having at least two hydrogen atoms reactive with isocyanate groups, which comprises carrying out the reaction in the presence of a) which is a combination consisting of ai) an aromatic phosphite having a phosphorus content of from 9.00 to 11.00% by weight and aii) an amine compound, the molar ratio between ai) and aii) being from 0.005 to 4.0. The invention also provides for the use of a combination of ai) an aromatic phosphite having a phosphorus content of from 9.00 to 11.00% by weight and aii) an amine compound as a hydrolysis inhibitor for MPE. The invention also provides shoe soles comprising the inventive microcellular polyurethane elastomers. The molar ratio between ai) and aii) is preferably from 0.1 to 3.0 and in particular from 0.5 to 2.0. The phosphorus content of component ai) is preferably from 9.90 to 10.10% by weight and in particular from 9.95 to 10.05% by weight. The component ai) used is preferably triphenyl phosphite (TPP). The amine compounds aii) used may be primary, secondary and preferably tertiary amines. They are preferably amines which are typically used as catalysts for the preparation of polyurethanes. The amine compounds are preferably tertiary amines selected from the group comprising thethylamine, triethylenediamine, tributylamine, dimethylbenzylamine, N,N,N',fsmetramethylethylenediamine, N,N,N\N^etramethyIbutanediamine, N,N,N\N'-tetramethylhexane-1,6-diamine, dimethylcyclohexylamine, pentamethyldipropylenetriamine, pentamethyldiethylenetriamine, 3-methyl-6-dimethylamino-3-azapentol, dimethylaminopropylamine, 1,3-bisdimethylaminobutane, bis(2-dimethyiaminoethyl) ether, N-ethylmorpholine, N-methylmorpholine, N-cyclohexylmorpholine, 2-dimethylaminoethoxyethanol, dimethylethanolamine, tetramethylhexamethylenediamine, dimethylamino-N-methylethanolamine, N-methylimidazole, N-(3-aminopropyl)imidazole, N-(3-aminopropyl)-2-methylimidazole, 1- (2-hydroxyethyl)imidazole, N-formyl-N,N'-dimethylbutylenediamine, N-dimethylaminoethylmorpholine, 3,3'-bis-dimethylaminodi-n-propylamine and/or 2,2'-dipiparazinediisopropyl ether, dimethylpiperazine, N,N'-bis(3-aminopropyl)ethylenediamine and/or tris(N,N-dimethylaminopropyl)-s-hexahydrotriazine, or mixtures comprising at least two of the amines mentioned, although it is also possible to use higher molecular weight tertiary amines as described, for example, in DE-A 28 12 256. Particular preference is given to using triethylenediamine. In most cases, the amount of tertiary amines used as a catalyst is sufficient, in combination with the aromatic phosphites ai), to achieve the required stabilizing action. However, it is also possible, when catalysts other than aminic catalysts are used or when smaller amounts of aminic catalysts than are required for sufficient stabilization are used, to use additional amines. These will then not be the tertiary amines used as catalysts in the process, in order to rule out disruptions in the catalysis. Preference is given to using the hydrolysis inhibitor a) in an amount of from 0.0001 to 3% by weight, from 0.0005 to 2% by weight and from 0.001 to 1.6% by weight, based on the weight of the MPE. As for the starting materials used to prepare the inventive MPE, the following should be stated specifically. The polyisocyanates used in the process according to the invention include the aliphatic, cycloaliphatic and aromatic isocyanates known from the prior art and any mixtures thereof. Examples are diphenylmethane 4,4'-diisocyanate, the mixtures of monomeric diphenylmethane diisocyanates and homologs of diphenylmethane diisocyanate having a higher number of rings (polymeric MDI), tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), tolylene diisocyanate (TDI) or mixtures thereof. Preference is given to using 4,4'-MDI and/or HDI. The 4,4'-MDI used with particular preference may comprise small amounts, up to about 10% by weight, of allophanate-or uretonimine-modified polyisocyanates. It is also possible to use small amounts of polyphenylenepolymethylene polyisocyanate (crude MDI) in addition. The total amount of these high-functionality polyisocyanates should not exceed 5% by weight of the isocyanate used. In -addition, the 4,4'-MDI may comprise small amounts, preferably a maximum of 10% by weight, of 2,4'-MDL The polyisocyanates may also be used in the form of polyisocyanate prepolymers. These prepolymers are known in the prior art. They are prepared in a manner known per se, by reacting above-described polyisocyanates, for example at temperatures of about 80°C, with compounds which have hydrogen atoms reactive toward isocyanates and are described below to give the prepolymer. The poiyoi-polyisocyanate ratio is generally selected in such a way that the NCO content of the prepolymer is from 8 to 25% by weight, preferably from 10 to 22% by weight, more preferably from 13 to 20% by weight. The compounds having hydrogen atoms reactive toward isocyanates which are used are, as described, polyester alcohols. The polyester alcohols are prepared generally by condensation of polyfunctional alcohols, preferably diols, having from 2 to 12 carbon atoms, preferably from 2 to 6 carbon atoms, with polyfunctional carboxylic acids having from 2 to 12 carbon atoms, for example succinic acid, glutaric acid, adipic acid, phthalic acid, isophthalic acid and/or terephthalic acid and mixtures thereof. Examples of suitable di- and polyhydric alcohols are ethylene glycol, diethylene glycol, 1,4-butanediol, 1,5-pentanediol and/or 1,6-hexanediol and mixtures thereof. The polyester alcohols may also be branched. The branched polyester alcohols preferably have a functionality of from more than 2 to 3, in particular of from 2.2 to 2.8. In addition, the branched polyester alcohols preferably have a number-average molecular weight of from 500 to 5000 g/mol, more preferably of from 2000 to 3000 g/mol. In general, the polyester alcohols used for the process according to the invention have an average theoretical functionality of from 2 to 4, preferably of from more than 2 to less than 3, and the above-specified number-average molecular weights. The polyester alcohols may in principle also be used in a mixture with polyether alcohols. However, since such mixtures frequently have an insufficient phase stability, the use of such mixtures is not preferred. The compounds having two active hydrogen atoms also include the chain extenders which are used if appropriate. Suitable chain extenders are known in the prior art. Preference is given to using 2-functional alcohols having molecular weights below 400 g/mol, in particular in the range from 60 to 150 g/mol. Examples are ethylene glycol, 1,3-propanediol, diethylene glycol, butanediol-1,4, glycerol or trimethylolpropane, and mixtures thereof. Preference is given to using ethylene glycol. ■ The chain extender, when used, is used typically in an amount of from 1 to 15% by weight, preferably of from 3 to 12% by weight, more preferably of from 4 to 10%. by weight, based on the total weight of the compounds having two hydrogen atoms reactive with isocyanate groups. The polyisocyanates are reacted with the compounds having two active hydrogen atoms typically in the presence of blowing agents. The blowing agents used may be commonly known chemically or physically active compounds. The chemically active blowing agent may preferably be water. Examples of physical blowing agents are inert (cyclo)aliphatic hydrocarbons having from 4 to 8 carbon atoms which evaporate under the conditions of polyurethane formation. The amount of the blowing agents used depends upon the desired density of the foams. The polyisocyanates are reacted with the compounds having two active hydrogen atoms, if appropriate, in the presence of catalysts and of assistants and/or additives, for example cell regulators, mold-release agents, pigments, reinforcing agents such as glass fibers, surface-active compounds and/or stabilizers against oxidative, thermal or microbial degradation or aging. The catalysts used for the preparation of the inventive microcellular polyurethane elastomers may be the customary and known polyurethane formulation catalysts, for example organic metal compounds such as tin diacetate, tin dioctoate, dibutyltin dilaurate and/or strongly basic amines such as diazabicyclooctane, bis(N,N-dimethylaminoethyl) £ther or the abovementioned amines. The catalysts are used preferably in an amount of from 0.01 to 10% by weight, preferably from 0.02 to 5% by weight, based on the reaction mixture. As described above, preference is given to using amines, especially tertiary amines, as catalysts. The amines may, as described above, be used individually or as any mixtures with one another. These simultaneously act as component aii) in the microcellular polyurethane elastomers. To this end, preference is given to using only the amines mentioned in the amounts required for efficacy as a stabilizer. If this is not sufficient for the catalytic efficacy, the tertiary amines may be used in combination with other catalysts. The organic amines which can be used are the tertiary amines known from the prior art. Useful tertiary amines include, for example, organic amines such as triethylamine, triethylenediamine, tributylamine, dimethylbenzylamine, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetramethylbutanediamine, N,N,N\N'-tetramethylhexane-1,6-diamine, dimethylcyclohexylamine, pentamethyldipropylenetriamine, pentamethyldiethylenetriamine, 3-methyl-6-dimethylamino-3-azapentol, dimethylaminopropylamine, 1,3-bisdimethylaminobutane, bis(2-dimethylaminoethyl) ether, N-ethylmorpholine, N-methylmorpholine, N-cyclohexylmorpholine, 2-dimethylaminoethoxyethanol, dimethylethanolamine, tetramethylhexamethylenediamine, dimethylamino-N-methylethanolamine, N-methylimidazole, N-(3-aminopropyl)imidazole, N-(3-aminopropyl)-2-methylimidazole, 1- (2-hydroxyethyl)imidazole, N-formyl-N,N'-dimethylbutylenediamine, N-dimethylaminoethylmorpholine, 3,3'-bis-dimethylaminodi-n-propyiamine and/or 2,2'-dipiparazinediisopropyl ether, dimethylpiperazine, N,N'-bis(3-aminopropyi)ethylenediamine and/or tris(N,N-dimethylaminopropyl)-s-hexahydrotriazine, or mixtures comprising at least two of the amines mentioned, although higher molecular weight tertiary amines, as described, for example, in DE 28 12 256, are also possible. Particular preference is given to using triethylenediamine. The catalysts which can be used in a mixture with the tertiary amines are, as described above, mainly organic metal compounds, in particular tin compounds, such as tin diacetate, tin dioctoate, dibutyltin dilaurate and/or bismuth compounds. The catalysts are preferably mixed with the compounds having at least two hydrogen atoms reactive with isocyanate groups. It is in principle also possible to mix at least the organic metal compounds with the polyisocyanates. In general, the polyisocyanates are referred to as the isocyanate component and the compounds having at least two hydrogen atoms reactive with isocyanate groups, which are usually used in a mixture with the catalysts, and if appropriate the blowing agents and the additives, are referred to as the poiyol component. To produce polyurethane foams, the isocyanate component and the poiyol component are usually reacted in such amounts that the equivalence ratio of NCO groups to the sum of the reactive hydrogen atoms is from 1:0.8 to 1:1.25, preferably from 1:0.9 to 1:1.15. In this context, a ratio of 1:1 corresponds to an NCO index of 100. The reaction to give the microcellular polyurethane elastomer is preferably carried out in molds with compression. The molds consist preferably of metal, for example steel or aluminum, or else of plastic, for example epoxy resin. The starting components are mixed at temperatures of from 15 to 90°C, preferably from 20 to 35°C, and introduced into the preferably closed mold, if appropriate under elevated pressure. The mixing may be effected in the course of introduction through high- or low-pressure mixer heads known in the prior art. The temperature of the mold is generally between 20 and 90°C, preferably between 30 and 60°C. The amount of the reaction mixture introduced into the mold is such that the resulting moldings have a density of from 250 to 600 g/l or of from 800 to 1200 g/l, preferably of from 400 to 600 g/i or of from 820 to 1050 g/l. The degrees of compaction of the resulting microcellular polyurethane elastomers are between 1.1 and 8.5, preferably between 1.2 and 5, more preferably between 1.5 and 4. The inventive microcellular polyurethane elastomers may be used for steering wheels, safety clothing and preferably for shoe soles. The invention will be illustrated in detail by the examples which follow. Comparative Examples C1 to C3 and Examples 1 to 4 100 parts by weight of the polyol component and the parts by weight, specified in Table 1, of the isocyanate component were mixed intensively at 23°C and the mixture was introduced into a plaque-shaped aluminum mold which had been heated to 50°C and had the dimensions 20cm x 20cm x 1cm in such an amount that, after it had been foamed and allowed to cure in the closed mold, a plaque of microcellular polyurethane elastomer having an overall density of 550 g/l resulted. After storage for 24 h, dumbell test specimens were punched out of the thus produced elastomer plaques using a stamp. Before the start of the aging experiments, the starting values of tensile strength was determined to DIN 53543. The test specimens were then subjected to an aging test at 70°C under water to DIN 53543. The samples were taken after 14 days. The results are compiled in Table 2. After 2 weeks of hydrolysis aging, the residual tensile strength and elongation of samples 1-4 is distinctly higher than that of comparative samples C1-C3. Feedstocks used: PESOL 1: Polyester alcohol made from adipic acid, 1,4-butanediol and ethylene glycol (Lupraphen® 8108) from Elastogran GmbH, OHN=56 mg KOH/g, functionality=2 Amine catalyst: 33% by weight solution of triethylenediamine in ethylene glycol (Lupragen® N 202) from BASF AG Cell stabilizer: Dabco® DC 193 from Air Products Isocyanate prepolymer: prepolymer based on 4,4'-MDI and PESOL1, NCOcontent=17.4% Hydrolysis inhibitor ai): Triphenyl phosphite Hydrolysis inhibitor aii): Triethylenediamine What is claimed is: 1. A process for preparing microcellular polyurethane elastomers by reacting polyisocyanates with compounds having at least two hydrogen atoms reactive with isocyanate groups, which comprises carrying out the reaction in the presence of a hydrolysis inhibitor a) which is a combination consisting of ai) an aromatic phosphite having a phosphorus content of from 9.00 to 11.00% by weight and aii) an amine compound, the molar ratio between ai) and aii) being from 0.005 to 4.0 and the aromatic phosphite ai) being added to the polyisocyanates and the amine compound aii) being added to the compounds having at least two hydrogen atoms reactive with isocyanate groups.. 2. The process according to claim 1, wherein the molar ratio between ai) and aii) is from 0.1 to 3.0. 3. The process according to claim 1, wherein the molar ratio between ai) and aii) is from 0.5 to 2.0. 4. The process according to claim 1, wherein the aromatic phosphite has a phosphorus content of from 9.90 to 10.10% by weight. 5. The process according to claim 1, wherein the aromatic phosphite has a phosphorus content of from 9.95 to 10.05% by weight. 6. The process according to claim 1, wherein the aromatic phosphite is triphenyl phosphite. 7. The process according to claim 1, wherein the amines aii) used are tertiary amines. 8. The process according to claim 1, wherein the tertiary amines are selected from the group comprising triethylamine, triethylenediamine, tributylamine, dimethylbenzylamine, N.N.N'.N'-tetramethylethylenediamine, N,N,N\N'-tetramethylbutanediamine, NXN\N'-tetramethylhexane-1,6HJiamine, dimethylcyclohexylamine, pentamethyldipropylenetriamine, pentamethyldiethylenetriamine, 3-methyl-6-dimethylamino-3-azapentol, dimethylaminopropylamine, 1,3-bisdimethylaminobutane, bis(2-dimethyl-aminoethyl) ether, N-ethylmorpholine, N-methylmorpholine, N-cyclohexyl-morpholine, 2-dimethylaminoethoxyethanol, dimethylethanolamine, tetramethylhexamethylenediamine, dimethylamino-N-methylethanolamine, N-methylimidazole, N-(3-aminopropyl)imidazole, N-(3-aminopropyl)-2-methylimidazole, 1-(2-hydroxyethyI)imidazole, N-formyl-N.N'- dimethylbutylenediamine, N-dimethylaminoethylmorpholine, 3,3'-bis-dimethylaminodi-n-propylamine and/or 2,2'-dipiparezinediisopropyl ether, dimethylpiparezine, N,N'-bis(3-aminopropyl)ethylenediamine and/or tris(N,N-dimethylaminopropyl)-s-hexahydrotriazine, or mixtures comprising at least two of the amines mentioned. 9. The process according to claim 1, wherein the tertiary amine is triethylenediamine. 10. A microcellular polyurethane elastomer obtainable according to any of claims 1 to 9. 11. The use of microcellular polyurethane elastomers according to claim 10 for producing shoe soles. 12. The use of ai) an aromatic phosphite having a phosphorus content of from 9.00 to 11.00% by weight and aii) an amine compound as a hydrolysis inhibitor for microcellular polyurethane elastomers. 13. A shoe sole comprising microcellular polyurethane elastomers according to claim 10.

Documents:

3139 CHENP 2007 Petition for POR.pdf

3139-CHENP-2007 AMENDED CLAIMS 27-01-2015.pdf

3139-CHENP-2007 AMENDED PAGES OF SPECIFICATION 27-01-2015.pdf

3139-CHENP-2007 CORRESPONDENCE OTHERS 22-04-2014.pdf

3139-CHENP-2007 CORRESPONDENCE OTHERS 24-11-2014.pdf

3139-CHENP-2007 CORRESPONDENCE OTHERS 17-04-2013.pdf

3139-CHENP-2007 CORRESPONDENCE OTHERS 18-11-2013.pdf

3139-CHENP-2007 CORRESPONDENCE OTHERS 27-06-2014.pdf

3139-CHENP-2007 EXAMINATION REPORT REPLY RECEIVED 27-01-2015.pdf

3139-CHENP-2007 FORM-3 24-11-2014.pdf

3139-CHENP-2007 FORM-3 18-11-2013.pdf

3139-CHENP-2007 FORM-3 27-06-2014.pdf

3139-CHENP-2007 FORM-3 17-04-2013.pdf

3139-CHENP-2007 POWER OF ATTORNEY 27-01-2015.pdf

3139-CHENP-2007 FORM-1 27-01-2015.pdf

3139-chenp-2007-abstract.pdf

3139-chenp-2007-claims.pdf

3139-chenp-2007-correspondnece-others.pdf

3139-chenp-2007-description(complete).pdf

3139-chenp-2007-form 1.pdf

3139-chenp-2007-form 3.pdf

3139-chenp-2007-form 5.pdf

3139-chenp-2007-pct.pdf