HK1062024B - Polyurethane elastomers with improved hydrolysis stability - Google Patents

Description

Polyurethane elastomers with improved hydrolytic stability

The invention relates to polyurethane elastomers (PUR elastomers) with improved hydrolytic stability, which are produced using polyester polyols, and to a method for the production thereof.

Semi-rigid, elastic polyurethane moldings which are compact or cellular, i.e. slightly foamed, are frequently synthesized on the basis of polyester-polyurethane materials. In order to improve the durability of such materials in moist environments, i.e.under conditions leading to hydrolysis, EP-A982336 teaches the addition of acids or acid derivatives to the isocyanate component in order to block the amino groups and optionally amine catalysts contained therein in the polyisocyanate polyaddition products by protonation and thereby prevent any further cleavage of the urethane bonds (urethaning). For this purpose, the acid or acid derivative is used in molar excess with respect to the amine contained in the mixture. For the same purpose, DE-OS 19838167 proposes the addition of anhydrides.

It has now been found that particularly hydrolytically stable polyester-polyurethanes are obtained if substoichiometric amounts of esters of mono-or polycarboxylic acids are added to the polyurethane formulation, which have a pK value of the (first) dissociation constant of from 0.5 to 4, preferably from 1 to 3.

The invention relates to

a) Di-and/or polyisocyanates with

b) At least one polyester polyol having an OH number of from 20 to 280, preferably from 28 to 150, and a functionality of from 1 to 3, preferably from 1.8 to 2.4,

c) optionally further polyether polyols or polyetherester polyols having an OH number of from 10 to 149 and a functionality of from 2 to 8,

d) optionally low molecular weight chain extenders and/or crosslinkers having an OH number of 150-1870

e) An amine catalyst, and a catalyst component,

f) esters of mono-or polycarboxylic acids having a pK value of the (first) dissociation constant of from 0.5 to 4, preferably from 1 to 3,

g) optionally a blowing agent, and

h) optional additives

A polyurethane elastomer obtained by reaction in the presence of a catalyst, wherein the ratio of the number of esters in component f) to the number of amino groups in component e) is at most 1.0, preferably 0.5 to 0.8.

The PUR elastomers are preferably prepared by the prepolymer process, it being advantageous to prepare polyaddition adducts containing isocyanate groups in a first step from at least part of the polyester polyols b) or mixtures thereof with the polyol component c) and at least one di-or polyisocyanate a). In a second step, compact PUR elastomers are prepared from these prepolymers containing isocyanate groups by reaction with low molecular weight chain extenders and/or crosslinkers d) and/or with the remainder of the polyol component b) or c) or mixtures thereof. If water or other blowing agents or mixtures thereof are also used in the second step, microcellular PUR elastomers can be prepared.

Suitable starting components a) for the process according to the invention are aliphatic, cycloaliphatic, araliphatic, aromatic and heterocyclic polyisocyanates, which are described, for example, by W.Siefken in Justus Liebigs Annalen der Chemie, 562, pages 75 to 136; such as those of the formula

Q(NCO)_nWherein n ═ 2 to 4, preferably 2, and Q denotes aliphatic hydrocarbon radicals having 2 to 18, preferably 6 to 10C atoms, cycloaliphatic hydrocarbon radicals having 4 to 15, preferably 5 to 10C atoms, aromatic hydrocarbon radicals having 6 to 15, preferably 6 to 13C atoms, or araliphatic hydrocarbon radicals having 8 to 15, preferably 8 to 13C atoms, such as ethylene diisocyanate, 1, 4-tetramethylene diisocyanate, 1, 6-Hexamethylene Diisocyanate (HDI), 1, 12-dodecane diisocyanate, cyclobutane-1, 3-diisocyanate, cyclohexane-1, 3-and-1, 4-diisocyanate and any mixtures of these isomers, 1-isocyanato-3, 5-trimethyl-5-isocyanatomethyl-cyclohexane, 2, 4-and 2, 6-hexahydrotolylene (toluylene) diisocyanate and any mixtures of these isomers, hexahydro-1, 3-and 1, 4-phenylene diisocyanate, perhydro-2, 4 ' -and 4, 4 ' -diphenylmethane diisocyanate, 1, 3-and 1, 4-phenylene diisocyanate, 1, 4-Durene Diisocyanate (DDI), 4 ' -1, 2-diphenylethylene diisocyanate, 3 ' -dimethyl-4, 4 ' -biphenylene diisocyanate (TODI), 2, 4-and 2, 6-Tolylene Diisocyanate (TDI) and any mixtures of these isomers, Diphenylmethane-2, 4 '-and/or-4, 4' -diisocyanate (MDI), or naphthylene-1, 5-diisocyanate (NDI).

Further, mention may be made, for example, of triphenylmethane-4, 4', 4 "-triisocyanate, Polyphenyl-polymethylene polyisocyanates (Polyphenyl-polymethylene-polyisocynate), such as those obtained by aniline-formaldehyde condensation and subsequent phosgenation, and such as those described in GB-PS 874430 and GB-PS 848671, such as m-and p-isocyanatophenylsulfonyl isocyanates according to US-PS 3454606, perchlorinated aryl polyisocyanates, such as those described in US-PS 3277138, polyisocyanates containing carbodiimide groups, such as those described in US-PS 3152162 and DE-OS 2504400, 2537685 and 2552350, norbornane (norbomane) diisocyanates according to US-PS 3492301, polyisocyanates containing allophanate groups, such as those described in GB-PS 994890, BE-PS 761626 and NL-A7102524, polyisocyanates containing isocyanurate groups, such as those described in US-PS 30019731, DE-PS 1022789, 1222067 and 1027394 and DE-OS 1929034 and 2004048, polyisocyanates containing urethane (urethane) groups, such as those described in BE-PS 752261 or US-PS 3394164 and 3644457, polyisocyanates containing acetylated urea groups according to DE-PS 1230778, polyisocyanates containing biuret groups, such as those described in US-PS 3124605, 3201372 and 3124605 and GB-PS 889050, polyisocyanates prepared by telomerization, such as those described in US-PS 3654106, polyisocyanates containing ester groups, such as those described in GB-PS 965474 and 1072956, US-PS 3567763 and DE-PS 1231688, Reaction products of the above-mentioned isocyanates with acetals according to DE-PS 1072385 and polymeric polyisocyanates containing fatty acid esters according to U.S. Pat. No. 3, 3455883.

It is also possible to use the distillation residues obtained in the isocyanate industry, which contain isocyanate groups, optionally dissolved in one or more of the polyisocyanates mentioned. Furthermore, any mixtures of the above polyisocyanates may be used.

Polyisocyanates which are preferably used are those which are readily accessible industrially, for example 2, 4-and 2, 6-tolylene diisocyanate and any mixtures of these isomers ("TDI"), 4 '-diphenylmethane diisocyanate, 2' -diphenylmethane diisocyanate and polyphenylpolymethylene polyisocyanates, for example those obtained by aniline-formaldehyde condensation and subsequent phosgenation ("crude MDI") and polyisocyanates containing carbodiimide groups, Uretonimin groups, urethane groups, allophanate groups, isocyanurate groups, urea groups or biuret groups ("modified polyisocyanates"), in particular those prepared from 2, 4-and/or 2, 6-tolylene diisocyanate or from 4, modified polyisocyanates derived from 4 '-and/or 2, 4' -diphenylmethane diisocyanate. Mixtures of naphthylene-1, 5-diisocyanate and the abovementioned polyisocyanates are also suitable.

However, it is particularly preferred in the process of the invention to use prepolymers containing isocyanate groups, which are polyaddition products containing urethane groups and isocyanate groups, formed by reacting at least a partial amount of polyester polyol b) or a mixture of at least a partial amount of polyester polyol b), polyol component c) and/or chain extenders and/or crosslinkers d) with at least one aromatic diisocyanate from the group consisting of TDI, MDI, TODI, DIBDI, NDI, DDI, preferably with 4, 4' -MDI and/or 2, 4-TDI and/or 1, 5-NDI, with an NCO content of 10 to 27% by weight, preferably 12 to 25% by weight.

As mentioned above, mixtures of b), c) and d) can be used for preparing prepolymers containing isocyanate groups. According to a preferred embodiment, however, the prepolymer containing isocyanate groups is prepared without chain extenders or crosslinkers d).

The prepolymer containing isocyanate groups may be prepared in the presence of a catalyst. However, it is also possible to prepare prepolymers containing isocyanate groups in the absence of catalysts and to add the catalysts to the reaction mixture only during the preparation of the PUR elastomers.

Suitable polyester polyols b) can be prepared, for example, from organic dicarboxylic acids having from 2 to 12 carbon atoms, preferably aliphatic dicarboxylic acids having from 4 to 6 carbon atoms, and polyols, preferably diols, having from 2 to 12 carbon atoms, preferably from 2 to 6 carbon atoms. Examples of suitable dicarboxylic acids include: succinic acid, malonic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid and terephthalic acid. These dicarboxylic acids can be used either individually or in the form of mixtures with one another. Instead of the free dicarboxylic acids, it is also possible to use the corresponding dicarboxylic acid derivatives, for example mono-and/or diesters of dicarboxylic acids with alcohols having 1 to 4 carbon atoms or dicarboxylic anhydrides. Preference is given to using dicarboxylic acid mixtures comprising succinic acid, glutaric acid and adipic acid in proportions of, for example, 20 to 35/35 to 50/20 parts by weight, in particular adipic acid. Examples of di-and polyhydric alcohols include ethylene glycol, diethylene glycol, 1, 2-and 1, 3-propanediol, dipropylene glycol, methyl-1, 3-propanediol, 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, neopentyl glycol, 1, 10-decanediol, glycerol, trimethylolpropane and pentaerythritol. Preference is given to using 1, 2-ethanediol, diethylene glycol, 1, 4-butanediol, 1, 6-hexanediol, glycerol, trimethylolpropane or mixtures of at least two of the abovementioned diols, in particular mixtures comprising ethanediol, 1, 4-butanediol and 1, 6-hexanediol, glycerol and/or trimethylolpropane. In addition, polyester polyols from lactones, such as epsilon-caprolactone, or hydroxycarboxylic acids, such as o-hydroxycaproic acid and glycolic acid, can be used.

For the preparation of the polyester polyols, the condensation of organic polycarboxylic acids, such as aromatic and preferably aliphatic polycarboxylic acids and/or derivatives thereof, with polyols, in the absence or presence of an esterification catalyst, advantageously in an inert atmosphere, such as nitrogen, carbon monoxide, helium, argon, in solution and also in the melt, at from 150-.

According to a preferred preparation method, the esterification mixture is polycondensed at the above-mentioned temperatures and atmospheric pressure until the acid number is from 80 to 30, preferably from 40 to 30, and then at less than 500mbar, preferably from 10 to 150 mbar. Examples of suitable esterification catalysts are iron, cobalt, lead, zinc, antimony, magnesium, titanium and tin in the form of metals, metal oxides or metal salts. However, the polycondensation can also be carried out in the liquid phase in the presence of diluents and/or entrainers for the azeotropic distillation of the water of condensation, for example benzene, toluene, xylene or chlorobenzene.

For the preparation of the polyester polyols, the organic polycarboxylic acids and/or derivatives thereof are polycondensed with the polyols, advantageously in a molar ratio of 1: 1 to 1.8, preferably 1: 1.05 to 1.2. The polyester polyols obtained preferably have a functionality of from 1 to 3, in particular from 1.8 to 2.4, and a number average molecular weight of 400-.

Furthermore, polycarbonates containing hydroxyl groups can be mentioned as suitable polyester polyols. Suitable polycarbonates containing hydroxyl groups include those known in the art, for example those which can be prepared by reacting diols, such as 1, 2-propanediol, 1, 3-propanediol, 1, 4-butanediol, 1, 6-hexanediol, diethylene glycol, triethylene glycol (trioxythenylglykol) and/or tetraethylene glycol, with dialkyl or diaryl carbonates, for example diphenyl carbonate or phosgene.

In the preparation of the elastomers of the invention, preference is given to using difunctional polyester polyols having a number average molecular weight of 500-.

Polyether polyols and polyether ester polyols c) are optionally used for preparing the elastomers according to the invention. Polyether polyols can be prepared in a known manner, for example by anionic polymerization of alkylene oxides in the presence of alkali metal hydroxides or alkali metal alkoxides as catalysts and addition of at least one starter molecule containing from 2 to 3 bonded reactive hydrogen atoms, or by cationic polymerization of alkylene oxides in the presence of Lewis acids, for example antimony pentachloride or boron fluoride etherate. Suitable alkylene oxides have 2 to 4 carbon atoms in the alkylene radical, examples including tetrahydrofuran, 1, 2-propylene oxide and 1, 2-or 2, 3-butylene oxide. Preference is given to using ethylene oxide and/or 1, 2-propylene oxide. The alkylene oxides can be used individually, alternately one after the other or as mixtures. Preferably, a mixture of 1, 2-propylene oxide and ethylene oxide is used, wherein the amount of ethylene oxide is 10-50%, as an ethylene oxide cap ("EO cap"), so that the resulting polyol contains more than 70% primary terminal OH. Suitable starter molecules include water or di-and triols such as ethylene glycol, 1, 2-and 1, 3-propanediol, diethylene glycol, dipropylene glycol, 1, 4-ethanediol, glycerol, trimethylolpropane, and the like. Suitable polyether polyols have a functionality of from 2 to 8, preferably from 2 to 6, particularly preferably from 2 to 4, and a number average molecular weight of from 500-. Preferably, a poly (oxypropylene-oxyethylene) polyol is used.

Other suitable polyether polyols include polymer-modified polyether polyols, preferably graft polyether polyols, in particular those based on styrene and/or acrylonitrile, which have been prepared by in situ polymerization of acrylonitrile, styrene or preferably mixtures of styrene and acrylonitrile, for example in a weight ratio of from 90: 10 to 10: 90, preferably from 70: 30 to 30: 70, in the abovementioned polyether polyols, and polyether polyol dispersions, which as disperse phase frequently contain from 1 to 50% by weight, preferably from 2 to 25% by weight, of, for example, inorganic fillers, polyureas, polyhydrazides, polyurethanes containing tertiary amino groups in combination and/or melamines.

In order to improve the compatibility of the polyester polyols of b) and the polyether polyols of c), polyetherester polyols may also be added. These polyetherester polyols are obtained by propoxylation or ethoxylation of polyester polyols, preferably polyester polyols having a functionality of from 1 to 3, in particular from 1.8 to 2.4, and a number average molecular weight of from 400-3500 and preferably 800-3500.

For the preparation of the PUR elastomers according to the invention, it is also possible to use low molecular weight difunctional chain extenders, tri-or tetrafunctional crosslinkers or mixtures of chain extenders and crosslinkers as component d).

Such chain extenders and crosslinkers d) are used to improve the mechanical properties, in particular the hardness of the PUR elastomers. Suitable chain extenders, such as alkanediols, dialkylene diols and polyalkylene polyols, and crosslinking agents, such as tri-or tetrahydric alcohols and oligomeric polyalkylene polyols having a functionality of from 3 to 4, often have a molecular weight of < 800, preferably from 18 to 400, in particular from 60 to 300. As chain extenders there are preferably used alkanediols having 2 to 12, preferably 2, 4 or 6, carbon atoms, such as ethylene glycol, 1, 6-hexanediol, 1, 7-heptanediol, 1, 8-octanediol, 1, 9-nonanediol, 1, 10-decanediol and in particular 1, 4-butanediol and dialkylene glycols having 4 to 8 carbon atoms, such as diethylene glycol and dipropylene glycol and polyoxyalkylene glycols. Also suitable are branched and/or unsaturated alkanediols having usually not more than 12 carbon atoms, for example 1, 2-propanediol, 2-methyl-1, 3-propanediol, 2-dimethyl-1, 3-propanediol, 2-butyl-2-ethyl-1, 3-propanediol, 2-butene-1, 4-diol and 2-butyne-1, 4-diol, diesters of terephthalic acid with diols having 2 to 4 carbon atoms, for example terephthalic acid-di-ethylene glycol or terephthalic acid-di-1, 4-butanediol, hydroxyalkylene ethers of hydroquinone or resorcinol, for example 1, 4-di- (. beta. -hydroxyethyl) -hydroquinone or 1, 3- (. beta. -hydroxyethyl) -resorcinol, alkanolamines having 2-12 carbon atoms, such as ethanolamine, 2-aminopropanol and 3-amino-2, 2-dimethylpropanol; n-alkyldialkanolamines, such as N-methyl-and N-ethyl-diethanolamine, (cyclo) aliphatic diamines having from 2 to 15 carbon atoms, such as 1, 2-ethylenediamine, 1, 3-propylenediamine, 1, 4-butylenediamine and 1, 6-hexamethylenediamine, isophoronediamine, 1, 4-cyclohexanediamine and 4, 4' -diaminodicyclohexylmethane; n-alkyl-, N, N ' -dialkyl-substituted and aromatic diamines which may also be substituted by alkyl on aryl and have 1 to 20, preferably 1 to 4, carbon atoms in the N-alkyl radical, for example N, N, N ' diethyl-, N, N ' -di-sec-pentyl-, N, N ' -di-sec-hexyl-, N, N ' -di-sec-decyl-and N, N, N ' dicyclohexyl-, (p-or m-) phenylenediamine, N, N ' -dimethyl-, N, N ' -diethyl-, N, N ' -diisopropyl-, N, N ' -di-sec-butyl-, N, N ' -dicyclohexyl-, -4, 4 ' -diamino-diphenylmethane, N, N ' -di-butyl-methyl-, N, N ' -dicyclohexyl-, 4, N ' -diamino-diphenylmethane, N, N '-di-sec-butylbenzidine, methylene-bis (4-amino-3-benzoic acid methyl ester), 2, 4-chloro-4, 4' -diamino-diphenylmethane and 2, 4-and 2, 6-methylenephenylenediamine.

The compounds of component d) can be used in the form of mixtures or individually. Mixtures of chain extenders and crosslinkers may also be used.

In order to adjust the hardness of the PUR elastomers, the proportions of the amounts of the building components b), c) and d) can be varied within a relatively wide range, for which hardness increases with increasing content of component d) in the reaction mixture.

The required amounts of the building components b), c) and d) can be determined in a simple manner by experiment in order to achieve the desired hardness of the material. It is advantageous to use from 1 to 50 parts by weight, preferably from 3 to 20 parts by weight, of chain extenders and/or crosslinkers d), based on 100 parts by weight of high molecular weight compounds b) and c).

Amine catalysts known to the person skilled in the art can be used as component e), for example tertiary amines, such as triethylamine, tributylamine, N-methylmorpholine, N-ethyl-morpholine, N, N, N ', N ' -tetramethyl-ethylenediamine, pentamethyldiethylenetriamine and its higher analogues (DE-OS 2624527 and 2624528), 1, 4-diaza-bicyclo- [2, 2, 2] -octane, N-methyl-N ' -dimethylaminoethyl-piperazine, bis- (dimethylaminoalkyl) -piperazine, N, N-dimethylbenzylamine, N, N-dimethylcyclohexylamine, N, N-diethylbenzylamine, di- (N, N-diethylaminoethyl) adipate, N, N, n ', N' -tetramethyl-1, 3-butanediamine, N-dimethyl- β -phenylethylamine, bis- (dimethyl-aminopropyl) -urea, 1, 2-dimethylimidazole, 2-methylimidazole, mono-and bicyclic amidines, di- (dialkylamino) -alkyl ethers and tertiary amines having an amide group, preferably a carboxamide group (according to DE-OS 2523633 and 2732292). Suitable catalysts also include Mannich bases known in the art, which are derived from secondary amines, such as dimethylamine, and an aldehyde, preferably formaldehyde, or a ketone, such as acetone, methyl ethyl ketone or cyclohexanone, and a phenol, such as phenol, nonylphenol or bisphenol. Examples of tertiary amines comprising hydrogen atoms which are reactive toward isocyanate groups as catalysts are triethanolamine, triisopropanolamine, N-methyl-diethanolamine, N-ethyl-diethanolamine, N-dimethylethanolamine, their reaction products with alkylene oxides, such as propylene oxide and/or ethylene oxide, and also secondary-tertiary amines according to DE-OS 2732292. Furthermore, silamines containing carbon-silicon bonds can be used as catalysts, such as those described in US-PS 3620984, such as 2, 2, 4-trimethyl-2-silamorpholine (silamorphin) and 1, 3-diethyl-aminomethyl-tetramethyldisiloxane. Bases containing nitrogen atoms, such as tetraalkylammonium hydroxides, hexahydrotriazines, can also be used. The reaction between NCO groups and Zerewitinoff-active hydrogen atoms is also greatly accelerated by lactams and azalactams. According to the invention, organometallic compounds, in particular organotin compounds, can be used simultaneously as further catalysts. Preferred organotin compounds, in addition to sulfur-containing compounds, such as, for example, di-n-octyltin mercaptide, are tin (II) salts of carboxylic acids, such as, for example, tin (II) acetate, tin (II) octanoate, tin (II) ethylhexanoate and tin (II) laurate, and also tin (IV) compounds, such as, for example, dibutyltin oxide, dibutyltin dichloride, dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate or dioctyltin diacetate.

The catalysts or catalyst combinations are generally used in amounts of about 0.001 to 10% by weight, in particular 0.01 to 1% by weight, based on the total amount of compounds having at least two hydrogen atoms reactive toward isocyanates.

Esters of mono-or polycarboxylic acids are used as component f). The (first) dissociation constants pK of these carboxylic acids, measured in aqueous solution, are generally in the range from 0.5 to 4, preferably from 1 to 3. Suitable as acid components are, for example, alkyl monocarboxylic acids, such as formic acid, aryl monocarboxylic acids, such as α -naphthoic acid, alkyl polycarboxylic acids, such as oxalic acid, malonic acid, maleic acid, fumaric acid and citric acid, and aryl polycarboxylic acids, such as isomers and alkyl-substituted derivatives of phthalic acid, 1, 2, 4-trimellitic acid and 1, 2, 4, 5-pyromellitic acid, isomers of naphthalenedicarboxylic acid, and cyclic diesters of α -hydroxycarboxylic acids, such as mandelic acid or lactic acid. Preference is given to using saturated or unsaturated C₂-C₄-an alkyl polycarboxylic acid; particular preference is given to using oxalic acid. Suitable alcohol components include aliphatic mono-and polyhydric alcohols, such as methanol, ethanol, propanol, isopropanol, ethylene glycol, 1, 2-and 1, 3-propanediol, isomers of butanol, 2-butene-1, 4-diol, 2-butyne-1, 4-diol, neopentyl glycol, glycerol, trimethylolpropane and pentaerythritol. Examples of suitable aryl alcohols include phenol and its alkyl-substituted derivatives, naphthol and its alkyl-substituted derivatives, hydroquinone, resorcinol, trihydroxybenzene and all polyether and polyether ester polyols mentioned under c). Aliphatic monoalcohols, in particular methanol, ethanol, n-or isopropanol, or n-, iso-or tert-butanol, are preferred.

The amount of component f) used in the preparation of the elastomers of the invention is such that the ratio of the number of amino groups contained in catalyst component e) to the number of ester groups contained in component f) is at most 1.0. Preferably 0.5-0.8.

The process according to the invention makes it possible to prepare compact PUR elastomers, such as PUR cast elastomers, in the absence of moisture and of physical or chemical blowing agents.

To prepare cellular, preferably microcellular, PUR elastomers, water is preferably used as blowing agent g), the latter being reacted in situ with the organic polyisocyanate a) or with the prepolymer containing isocyanate groups under formation of carbon dioxide and amino groups which themselves continue to react with other isocyanate groups to form urea groups and act therein as chain extenders.

If water has to be added to the polyurethane formulation in order to adjust the desired density, the amount of water added is generally from 0.001 to 3.0% by weight, preferably from 0.01 to 2.0% by weight, in particular from 0.05 to 0.5% by weight, based on the weight of the building components a), b) and optionally c) and d).

It is also possible to use gases or volatile inorganic or organic substances, which vaporize under the action of the exothermic polyaddition reaction and advantageously have a boiling point of from-40 to 120 ℃, preferably from 10 to 90 ℃ at normal pressure, as physical blowing agents, instead of or preferably in combination with water as blowing agents g). Examples of suitable organic blowing agents include acetone, ethyl acetate, halogen-substituted alkanes or perhalogenated alkanes such as (R134a, R141b, R65mfc, R245fa) and butane, pentane, cyclopentane, hexane, cyclohexane, heptane or diethyl ether. Examples of inorganic blowing agents include air, CO₂And N₂And O. Foaming can also be achieved by adding compounds which decompose at temperatures above room temperature into gases, for example nitrogen and/or carbon dioxide, for example azo compounds, such as azodicarbonamide or azoisobutyronitrile, or salts, for example ammonium hydrogen carbonate, ammonium carbamate or ammonium salts of organic carboxylic acids, for example monoammonium salts of malonic acid, boric acid, formic acid or acetic acid. Examples of other blowing agents and details of blowing agent applications are described in "Kunststoff-Handbuch", volume VII, Carl-H, of R.Vieweg and A.H * chtlen (eds.), "volume VIIanser-Verlag, Munich, 3 rd edition, 1993, pages 115-715.

The advantageous amounts of solid blowing agent, low-boiling liquid or gas, which can be used in each case individually or in mixtures, for example as liquid mixture or gas mixture or as gas-liquid mixture, depend on the density to be achieved and the amount of water added. The required amount can be easily determined by experiment. Satisfactory results are frequently achieved by adding from 0.5 to 35% by weight, preferably from 2 to 15% by weight, of solids, from 0.5 to 30% by weight, preferably from 0.8 to 18% by weight, of liquids and/or from 0.01 to 80% by weight, preferably from 10 to 50% by weight, of gases, in each case based on the weight of the building components a), b), c) and optionally d). Gases, for example air, carbon dioxide, nitrogen and/or helium, can be passed in with the high molecular weight polyhydroxyl compounds b) and c), with the low molecular weight chain extenders and/or crosslinkers d), with the polyisocyanates a) or with a) and b) and optionally c) and d).

Optionally, additives h) can be added to the reaction mixture in order to prepare compact and porous PUR elastomers. Mention may be made, for example, of surface-active additives, such as emulsifiers, foam stabilizers, cell regulators, flame retardants, nucleating agents, antioxidants, stabilizers, lubricating and mold-release agents, colorants, dispersants and pigments. Examples of emulsifiers include castor oil sulphonic acid sodium salt or salts of fatty acids with amines, for example oleic acid and diethylamine or stearic acid with diethanolamine. It is also possible to use sulfonic acids, for example dodecylbenzenedisulfonic acid or dinaphthylmethanedisulfonic acid, or fatty acids, for example ricinoleic acid, or alkali metal or ammonium salts of polymerized fatty acids, as surface-active additives. Preferred foam stabilizers are polyether siloxanes, in particular their water-soluble representatives. These compounds are generally obtained by linking a copolymer of ethylene oxide and propylene oxide to a polydimethylsiloxane radical. Foam stabilizers of this type are described, for example, in U.S. Pat. Nos. 3, 2834748, 2917480 and 3629308. Of particular interest are polysiloxane-polyoxyalkylene copolymers which are polybranched by allophanate according to DE-OS 2558523. Also suitable are other organopolysiloxanes, ethoxylated alkylphenols, ethoxylated fatty alcohols, paraffin oils, castor oil or ricinoleic acid esters, turkey red oil, peanut oil, and pore regulators such as paraffins, fatty alcohols and polydimethylsiloxanes. In addition, oligomeric polyacrylates having polyalkylene oxides and fluoroalkyl groups as side groups are suitable for improving the emulsifying effect, the dispersion of the fillers, the pore structure and/or for stabilizing them. These surface-active substances are generally used in amounts of from 0.01 to 5 parts by weight, based on 100 parts by weight of the high molecular weight polyhydroxyl compounds b) and c). Reaction retarders, pigments or colorants and flame retardants known in the art, and stabilizers against aging, atmospheric agents, plasticizers and substances with a fungistatic or bacteriostatic action may also be added.

Further examples of surface-active additives and foam stabilizers and also cell regulators, reaction retarders, stabilizers, flame retardants, plasticizers, colorants and fillers and substances which inhibit fungi or bacteria and the use and action of these additives, which are optionally applied simultaneously according to the invention, are described in "Kunststoff-Handbuch" from R.Vieweg and A.Hochtlen, Vol.VII, Carl-Hanser-Verlag, Munich, 3 rd edition, 1993, page 118-124.

To prepare the PUR elastomers according to the invention, the components are reacted in such amounts that they are reacted. The equivalent ratio of NCO groups of the polyisocyanate a) to the sum of the hydrogens reactive with isocyanate groups in components b), c), d) and the chemical blowing agents which may be used is from 0.8: 1 to 1.2: 1, preferably from 0.95: 1 to 1.15: 1, in particular from 1.00: 1 to 1.05: 1.

The PUR materials of the invention can be prepared by processes described in the literature, for example by the "one-pot" process or the prepolymer process, with the aid of mixing devices known to those skilled in the art. Preferably according to the prepolymer method.

In one embodiment of the preparation of the PUR materials according to the invention, the starting components are homogeneously mixed in the absence of blowing agent g), generally at a temperature of from 20 to 80 ℃ and preferably from 25 to 60 ℃, and the reaction mixture is introduced into an optionally heated open mold and allowed to harden. In a further variant of the preparation of the PUR elastomers according to the invention, the building components are mixed in the same way in the presence of a blowing agent g), preferably water, and introduced into an optionally heated mold. After the addition, the mold is closed and the reaction mixture is foamed to form a shaped body, which is carried out under dense conditions, for example with a density (ratio of the density of the shaped body to the density of the free foam) of from 1.05 to 8, preferably from 1.1 to 6, in particular from 1.2 to 4. Once the shaped body has sufficient strength, it is demolded. The demolding time depends in particular on the temperature and geometry of the mold and the reactivity of the reaction mixture and is generally from 2 to 15 minutes.

The density of the compact PUR elastomers according to the invention is from 0.8 to 1.4g/cm, depending mainly on the filler content and type³Preferably 1.0 to 1.25g/cm³. The porous PUR elastomers according to the invention have a density of from 0.2 to 1.4g/cm³Preferably 0.30 to 0.8g/cm³。

Polyurethane plastics of this type are particularly valuable raw materials for industrial components which are often exposed to the atmosphere and moisture, such as roller (Rollen) elements and elastic elements or for building one or more layers of shoe soles.

Examples

To prepare polyurethane test bodies, the a-and B-components were mixed at 45 ℃ in a low-pressure foaming apparatus (NDI) in a weight ratio (MV) of 100: 60 of a-and B-components at 45 ℃, the mixture was cast into an aluminum clip mold (Klappform) heated to 50 ℃ (200 x 140 x 5mm in size), the mold was closed and the elastomer was demolded after 3 minutes.

The thus-obtained elastic flat plate press-formed shoulder bar (type I bar: [ ISO 37 type I Standard ]) was used as a test body with a press tool after 24 hours of storage. Before the aging test was started, the initial values of the tensile strengths of the three test bodies were determined in accordance with the above criteria. The aging test was then carried out at 70 ℃ and 100% relative humidity. Samples were removed at regular intervals of 2-5 days, for which three test bodies were removed from the sample chamber each time, reconditioned at 25 ℃ for 24 hours and then tested for tensile strength according to din 53504. The results are shown in Table 2.

Examples 1 to 5

Component A

100 parts of a mixture of:

80.7% by weight of 1, 4-butanediol-ethanediol polyadipate (ratio 14.1: 20.5: 65.4),

having a number average molecular weight of 2000g/mol

4.7% by weight trimethylolpropane-ethylene glycol polyadipate (ratio 3.2: 41.1: 55.7),

having a number average molecular weight of 2400g/mol

0.3% by weight of triethanolamine

5.0% by weight ethylene glycol

0.1% by weight of water

0.9 wt.% amine catalyst diaza-bicyclo- [2.2.2] -octane

8.3% by weight of antistatic agent, mold release agent and emulsifier

B component

60 parts of a prepolymer having an NCO content of 19% obtained by reacting:

56% by weight of 4, 4' -MDI

6% by weight of carbodiimide-modified MDI having 29.8% by weight of NCO,

functionality 2.1 (Desmodur)^*CD，Bayer AG)

38% by weight of ethylene glycol-diethylene glycol polyadipate (ratio 14.3: 24.4: 61.3),

has a number average molecular weight of 2000 g/mol.

In each case to the B component was added the amount of carboxylic acid ester shown in Table 1

TABLE 1

Examples	Compound of B	Parts by weight	Ratio of ester group (oxalate) to amino group (catalyst)
				1	Oxalic acid diethyl ester	0.6	0.5∶1
2	Oxalic acid diethyl ester	1.2	1.0∶1
				3 comparison	Oxalic acid diethyl ester	1.7	1.5∶1
4 comparison	Oxalic acid diethyl ester	2.3	2.0∶1
				5 comparison	Oxalic acid diethyl ester	2.9	2.5∶1

TABLE 2

Examples	Residual tensile strength expressed as a percentage of the initial tensile strength after aging for said day at 70 ℃ and 100% relative humidity
						Sky	0	3	6	9	13
Without additives	100.0	60.1	27.1	10.1	0.0
						1	100.0	107.6	87.1	62.4	27.1
2	100.0	84.8	67.1	61.0	22.6
						3 comparison	100.0	80.9	46.3	28.4	9.9
4 comparison	100.0	97.6	49.4	25.9	8.8
						5 comparison	100.0	84.7	43.9	16.6	6.4

Claims (8)

1. A polyurethane elastomer comprising

a) At least one selected from the group consisting of diisocyanates and polyisocyanates;

b) at least one polyester polyol having an OH number of 20 to 280 and a functionality of 1.8 to 2.4, and optionally

c) At least one member selected from the group consisting of polyether polyols and polyether ester polyols having an OH number of 10 to 149 and a functionality of 2 to 8, and

d) optionally at least one member selected from the group consisting of (i) chain extenders having a molecular weight of less than 800, and (ii) crosslinking agents having an OH number of 150-1870,

in that

e) At least one kind of amine catalyst is used,

f) at least one selected from the group consisting of (i) esters of monocarboxylic acids, and (ii) esters of polycarboxylic acids having a dissociation constant or first dissociation constant pK value of 0.5 to 4, said esters of polycarboxylic acids (ii) containing a polycarboxylic acid residue selected from the group consisting of oxalic acid, malonic acid, maleic acid, fumaric acid, citric acid, phthalic acid, 1, 2, 4-trimellitic acid, 1, 2, 4, 5-pyromellitic acid, and said esters of polycarboxylic acids (ii) containing at least one alcohol residue selected from the group consisting of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol and phenol,

g) optionally a blowing agent, and

h) optionally at least one additive selected from the group consisting of emulsifiers, foam stabilizers, cell regulators, flame retardants, nucleating agents, antioxidants, lubricants, mold release agents, colorants, dispersants, pigments, reaction retarders, anti-aging stabilizers, plasticizers, fungistats and antibacterial agents, in the presence of a reaction product, wherein the ratio of the number of ester groups in component f) to the number of amino groups in component e) is at most 1.0.

2. The polyurethane elastomer according to claim 1, wherein component a) is the prepolymer reaction product of 4, 4' -diphenylmethane diisocyanate and a polyester polyol.

3. A molded body comprising the polyurethane elastomer of claim 1.

4. Use of the polyurethane elastomer according to claim 1 for the production of moulded bodies selected from the group consisting of rollers, elastic elements and shoe soles.

5. The polyurethane elastomer of claim 1, wherein the ester (i) of a monocarboxylic acid comprises the residue of a monocarboxylic acid selected from the group consisting of formic acid and α -naphthoic acid, and the ester (i) of a monocarboxylic acid comprises the residue of an alcohol selected from the group consisting of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t-butanol and phenol.

6. The polyurethane elastomer of claim 1, wherein the ester (i) of a monocarboxylic acid comprises at least one alcohol residue selected from the group consisting of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol and tert-butanol.

7. The polyurethane elastomer of claim 6, wherein the polycarboxylic acid of said ester of a polycarboxylic acid (ii) is oxalic acid.

8. The polyurethane elastomer according to claim 1, wherein the ratio of the number of esters in component f) to the number of amino groups in component e) is from 0.5 to 0.8.