MXPA99007758A - Mixture containing organic and / or inorganic acids and acids, and / or acid derivatives - Google Patents

Abstract

In a mixture containing: (i) at least one isocyanate, and (ii) at least one acid and / or at least one derivative that is not an anhydride acid, (ii) is present in an amount from 0.01 to 20% by weight, based on the weight of the mixture, and the acid groups or derivatives of the acid groups of (ii) are present in a molar excess on any of the amines present in the mixture.

Description

MIXTURE CONTAINING ORGANIC AND / OR INORGANIC ISOCYANATES AND ACIDS AND / OR ACID DERIVATIVES The present invention relates to mixtures containing: i) at least one isocyanate, and ii) at least one acid and / or at least one acid derivative that is not an acidic anhydride, preferably at least one carboxylic acid and / or carboxylic acid derivative which is not yet carboxylic anhydride, wherein (ii) is present in an amount from 0.01 to 20% by weight, based on the weight of the mixture, and the acid groups or the acid group derivatives of (ii) are present in a molar excess on any of the amines present in the mixture. The present invention also relates to the processes for producing the polyisocyanate polyaddition products by reaction of the isocyanates with compounds that are reactive to the isocyanates in the presence or absence of catalysts, blowing agents, additives and / or auxiliaries, to the polyisocyanate polyaddition products which can be produced in this way and the use of acids and / or acid derivatives which are not acidic anhydrides according to the present invention in the polyisocyanate polyaddition products.

The production of polyisocyanate polyaddition products by reacting polyisocyanates with compounds that are reactive to isocyanates, catalysts that accelerate the reaction of materials that are reactive to isocyanates with isocyanates and, if desired, blowing agents, additives and / or auxiliaries is generally known. Like other plastics, polyisocyanate polyaddition products are the subject of an aging process that generally give rise to a deterioration in the properties of use over time. The significant influences with aging are, for example, hydrolysis, photo-oxidation and thermo-oxidation that give rise to the breaking of the bonds of the polymer chains. In the case of polyisocyanate polyaddition products, for example polyurethanes, the action of moisture and even more the combination of humidity and temperature cause hydrolytic dissociation of urethane and urea bonds. DE-A 42 32 420 describes the use of α, β-unsaturated carboxylates, which are used in addition to the amines as catalysts to produce polyurethane foams which have a better resistance to compression and elongation at break. It is assumed that the olefinic double bonds of the carboxylate ester trap the amines by the addition in the double bond, US 4,255,526 describes the use of amino acids in the production of polyurethane foams to increase the stability to moisture and heat. The disadvantages of these known teachings are that the materials used are relatively expensive and are also, according to the prior art, oadded in the production of polyisocyanate polyaddition products. EP-A 711 799 describes the production of molded parts of polyurethane with a cell nucleus and a compacted surface area, which are produced in the presence of polymeric carboxylic acids or their derivatives, with the polymers added to the component that is reactive to the isocyanates. The object on which this document is based was the substitution of chlorofluorocarbons as blowing agents and the production of molded parts with an improved surface. The problem of aging processes in polyurethanes is not solved in this document. In order to produce polyurethane systems, catalysts are frequently used, for example organic amines which, in the production of polyurethane foams, preferably accelerate the blowing reaction, ie the reaction of the isocyanate groups with, for example, water to form carbon dioxide and also the crosslinking reaction of the alcoholic hydroxyl groups and the isocyanates to form urethane groups. To improve the flow and curing of reaction mixtures, it may be advantageous, particularly in the production of foamed polyurethanes, to use the amines in a form in which they have been blocked by self-formation with an organic acid, usually formic, acetic or ethylenoanic acid. The catalysts which have been thermally and reversibly blocked are decomposed during the polyisocyanate polyaddition reaction as a result of the heat of reaction, the catalytically active amines are free and the crosslinking or foaming reaction is carried out to an increased degree only after a sufficient cream time and time of raising the reaction mixture. Catalysts of this type are described in DE-A 28 12 256. A disadvantage of this use of delayed action catalysts is the fact that these catalysts are used in an equimolar ratio of the basic catalyst to the blocking acid and, after completing the catalysis, the catalyst is present in unblocked form in the polyisocyanate polyaddition product. It should also be noted that the catalysts are usually blocked by volatile acids and these vaporize the system at high processing temperatures and are then no longer available to block the catalyst. Furthermore, in most cases it is not possible to use only blocked catalysts because otherwise the reaction becomes slower, so that the total amount of the catalyst in the system will never be blocked and very large amounts of the free catalyst can be blocked. catalyze the unfolding of urethane. An object of the present invention is to develop a mixture which, in the polyaddition reaction of the polyisocyanate, originates into products having improved stability against aging processes, in particular against hydrolysis. Furthermore, an object of the invention is to find a stabilizer which makes it possible to suppress the hydrolysis of the polyether urethanes and thus also prevent the aromatic amines from being released. We have found that this objective is achieved by the mixtures described at the beginning, which are preferably used as compounds in the production of the polyisocyanate polyaddition products. Surprisingly it has been found that an amine catalyst present in the production of the polyisocyanate polyaddition products accelerates not only the polyaddition reaction, ie the formation of the urethane groups, but also, after the polyaddition reaction has occurred. , catalyzes the dissociation or unfolding of urethane bonds. This is particularly true when the polyaddition products are stored under conditions of humidity and heat and is made worse by the fact that, after the production of the polyisocyanate polyaddition products, the catalyst is no longer present in blocked form and, therefore, So, it is active. The dissociation of the urethane bond causes not only a deterioration in the properties of the polyisocyanate polyaddition products, but can also cause the formation of amines which are undesirable. The use according to the present invention of (ii) at least one acid and / or acid derivative other than an acidic anhydride results in the acids blocking any amine catalyst present in the products by, for example, protonation and, in this way, the reisolation of the urethane and / or urea bonds is avoided. Acids and / or acid derivatives or mixtures of the present invention are thus used in the polyisocyanate polyaddition products to stabilize the polyisocyanate polyaddition products, in particular polyurethanes, against the dissociation of urethane and urea bonds, by example by blocking the amine catalysts by protonation of the catalysts. It is possible to use the acids in the polyisocyanate polyaddition products to block the amino groups in the polyisocyanate polyaddition products.

The diffusion of the amines of the polyisocyanate polyaddition products and the redissolving of the urethane linkage due, for example, to the amine catalysts present in the polyisocyanate polyaddition products can thus be reduced according to the present invention. Surprisingly it has been found that (ii) they are stable in admixture with the isocyanates at room temperature, ie, at 25 ° C, and the isocyanate groups do not react significantly, if at all, with (ii). Acids and / or acid derivatives that are not acidic anhydrides, used in accordance with the present invention, or mixtures according to the present invention, can be used in a preferred way to produce polyisocyanate polyaddition products according to the usual processes known by reacting the isocyanates with compounds that are reactive to the isocyanates, in the presence or absence of catalysts, blowing agents, additives and / or auxiliaries. The polyisocyanate polyaddition products which can be used by conventional methods using the mixtures of the present invention are, for example, compact or cellular polyurethane foams, for example microcellular, flexible, semi-rigid or rigid, thermoplastic polyurethanes or polyurethane elastomers. . The blends of the present invention are preferably used in processes for producing polyurethane elastomers or foamed polyisocyanate polyaddition products, in particular flexible polyurethane foams, by reacting isocyanates with compounds which are reactive to isocyanates in the presence, blowing agents, additives and / or auxiliaries. Examples of the isocyanates that can be used in the mixtures of the present invention are the compounds described below: suitable isocyanates are the organic aliphatic, cycloaliphatic, araliphatic and, preferably, aromatic isocyanates known per se, preferably isocyanates polyfunctional, particularly preferably diisocyanates. Specific examples are: alkylene diisocyanates having from 4 to 12 carbon atoms in the alkylene radical, for example, 1,2-dodecane diisocyanate, 1,4-2-ethyltetramethylene diisocyanate, 1,5-diisocyanate 2 - pentamethylene, 1,4-tetramethylene diisocyanate and preferably 1,6-hexamethylene diisocyanate; cycloaliphatic diisocyanates such as 1,3- and 1,4-cyclohexane diisocyanate and also any of these isomer mixtures, l-isocyanato-3, 3, 5-trimethyl-5-isocyanate methyl cyclohexane (isophorone diisocyanate) , 2,4- and 2,6-hexahydrotolylene diisocyanate and also the corresponding isomer mixtures, 4,4'-, 2,2'- and 2,4'-dicyclohexamethane diisocyanate and also the corresponding isomer mixtures, the aromatic diisocyanates and polyisocyanates such as 2,4- and 2,6-tolylene diisocyanate (TDI) and the corresponding isomer mixtures, 4,4'-, 2,4'- and 2,2'-diphenyl methane diisocyanate (MDI) ) and mixtures of corresponding isomers, 1, 5-naphthalene diisocyanate (MDI), mixtures of 4,4'- and 2,4'-diphenyl methane diisocyanates, mixtures of NDI and 4,4'- and / or 2 , 4'-diisocyanates of diphenyl methane, 3, 3'-dimethyl-4,4'-diisocyanate biphenyl (TODI) mixtures of TODI and 4,4'- and / or 2,4'-diphenyl methane diisocyanates, polyisocyanates of polyphenil polymethylene, mixtures of diphenyl methane 4,4'-, 2,4'- and 2,2'-diisocyanates and polyphenylenepolymethylene polyisocyanates (crude MDI) and mixtures of crude MDI and tolylene diisocyanates. It is also possible to use the organic diisocyanates and polyisocyanates individually or in the form of mixtures. Also, modified polyfunctional isocyanates are often used, that is, products that are obtained by chemical reaction of diisocyanates and / or organic polyisocyanates. Examples which may be mentioned are diisocyanates and / or polyisocyanates containing ester groups, urea, biuret, allophanate, carbodiimide, isocyanurate, uretdione, and / or urethane. Specific examples are: urethane groups containing organic polyisocyanates, preferably aromatic and having NCO contents from 33.6 to 15% by weight, preferably from 31 to 21% by weight, based on total weight, 4, 4 ' - modified diphenyl methane diisocyanate, mixtures of 4,4'- and 2,4'-modified diphenylmethane diisocyanate, modified NDI, modified TODI, crude MDI, modified and / or 2,4- or 2,6-tolylene diisocyanate . Examples of the dialkylene or polyoxyalkylene glycols which can be used for the modification, either individually or as mixtures, are: diethylene glycol, dipropylene glycol, polyoxyethylene, polyoxypropylene and polyoxypropylene polyoxyethylene glycols, triols and / or tetraols. Also suitable are the prepolymers containing NCO groups, with NCO contents from 25 to 3.5% by weight, preferably from 21 to 14% by weight, based on the total weight, and are prepared from, for example, polyols of polyester and / or preferably polyether polyols and 4,4'-diphenyl methane diisocyanate, mixtures of 2,4'- and 4,4'-diphenylmethane diisocyanate, NDI, TODI, mixtures of NDI and isomers of MDI, 2,4- and / or 2,6-tolylene diisocyanates or crude MDI. Other modified polyisocyanates which have been found useful are liquid polyisocyanates containing carbodiimide groups and / or isocyanurate rings and having NCO contents from 33.6 to 15% by weight, preferably from 31 to 21% by weight, based on the total weight , for example, those based on 4,4'-, 2,4'- and / or 2, 2 '- diphenylmethane diisocyanate, NDI, TODI and / or 2,4- and / or 2,6-tolylene diisocyanate . If desired, the modified polyisocyanates can be mixed with each other or with unmodified organic polyisocyanates such as 2,4'- and / or 4,4 '- diphenylmethane diisocyanate, NDI, TODI, crude MDI, 2,4- and or 2,6-tolylene diisocyanate. As isocyanates in the mixtures or processes of the present invention, preference is given to the use of 4,4'-2,4'-and / or 2, 2'-diphenylmethane-diisocyanate, 2,4- and / or 2,6- tolylene diisocyanate NDI, hexamethylene diisocyanate and / or isophorone diisocyanate. These isocyanates can be used as any of the mixtures or in modified form as already described. However, the principle is the effectiveness of (ii) regardless of the isocyanate used. As the compounds that are reactive to the isocyanates and usually with at least two reactive hydrogen atoms, usually hydroxyl and / or amino groups, advantageous use is made of those having a functionality from 2 to 8, preferably 2 to 6, and a molecular weight usually from 60 to 10,000. Examples of the isocyanate-reactive compounds which have been found useful are polyether polyamines and / or preferably polyols selected from the group consisting of polyether polyols, polyester polyols, polythioether polyols, polyester amides, hydroxyl-containing polyacetals and aliphatic polycarbonates. containing hydroxyl or mixtures of at least two of the mentioned polyols. Preference is given to the use of polyester polyols and / or polyether polyols which can be prepared by the known methods. The polyester polyols preferably have a functionality from 2 to 4, in particular from 2 to 3, and a molecular weight of, typically, from 500 to 3000, preferably from 1200 to 3000 and, in particular, from 1800 to 2500. Polyether polyols have a functionality preferably from 2 to 6 and usually with molecular weights from 500 to 8000. Other suitable polyether polyols are, for example, polyether polyols modified with polymer, preferably grafted polyether polyols. , in particular those based on styrene and / or acrylonitrile which can be prepared by in situ polymerization of acrylonitrile, styrenes or preferably mixtures of styrene and acrylonitrile. It is possible to use polyether polyols, just like polyester polyols, individually or in the form of mixtures. They can also be mixed with polyether polyols or polyester polyols grafted or with polyester amides containing hydroxyl, polyacetals, polycarbonates and / or polyether polyamines. As the polyol components use is made of high functionality polyols, in particular polyether polyols based on high functionality alcohols, sugar alcohols and / or saccharides as starter molecules for rigid polyurethane foams which may contain isocyanurate structures although the polyols of polyether and / or polyester polyols of functionality 2 and / or 3 based on glycerol and / or trimethylol propane and / or glycols as initiator molecules or alcohols which can be esterified, are used for flexible foams. The polyether polyols are prepared by means of known technology. The alkylene oxides suitable for preparing the polyols are, for example, tetrahydrofuran, 1,3-propylene oxide, 1,2- or 2,3-butylene oxide, styrene oxide and preferably ethylene oxide and 1-oxide. , 2-propylene. The alkylene oxides can be used individually, alternatively in succession or as mixtures. Preference is given to the use of alkylene oxide which gives rise to primary hydroxyl groups in the polyol. The polyols which are particularly preferably used are those which have been alkoxylated with ethylene oxide at the end of the alkoxylation and therefore have primary hydroxyl groups.

In order to produce thermoplastic polyurethanes preference is given to the use of polyols having a functionality of 2 to 2.2 and not a crosslinker. In addition, it is possible to use chain extenders and / or crosslinkers as compounds that are reactive to isocyanates. The addition of chain extenders, crosslinkers or, if desired, mixtures thereof can prove to be advantageous, for example, in modifying the mechanical properties of the polyisocyanate polyaddition products produced using these substances, for example, hardness. As chain extenders, and / or crosslinkers, use can be made of water, diols and / or triols having molecular weights from 60 to < 500, preferably from 60 to 300. Examples of suitable chain extenders / crosslinkers are aliphatic, cycloaliphatic and / or araliphatic diols having from 2 to 14, preferably from 4 to 10 carbon atoms, for example ethylene glycol , 1,3-propanediol, 1, 10-decanediol, o-, m-, p-dihydroxycyclohexane, diethylene glycol, dipropylene glycol and preferably 1,4-butanediol, 1,6-hexanediol and bis (2-hydroxyethyl) hydroquinone , triols such as 1,2,4-, 1,3,5-trihydroxycyclohexane, glycerol and trimethylol propane and low molecular weight hydroxyl containing polyalkylene oxides based on ethylene oxide and / or 1,2-propylene oxide and diols and / or triols as starter molecules.

If the chain extenders, crosslinkers or mixtures thereof are used to produce the polyisocyanate polyaddition products these are advantageously used in an amount from 0 to 20% by weight, preferably from 2 to 8% by weight, based on in the weight of the compounds that are reactive to the isocyanates. The thermoplastic polyurethanes are preferably produced without using crosslinkers. As (ii), it is possible to use organic or inorganic acids and / or acid derivatives, for example, acid halides, or polyacids, preferably carboxylic acids, for example, aliphatic, cycloaliphatic, araliphatic and / or aromatic carboxylic acids usually have from 1 to 10, preferably 1 6 2 carboxyl groups. As carboxylic acids it is also possible to use co-lipids of acid and some alkenes. The compounds (ii) usually have a molecular weight of from 60 to 1,000,000. Examples that may be mentioned are: acetic acid, propionic acid, butyric acid, pentanoic acid, hexanoic acid, heptanic acid, octanoic acid, dimethylolpropionic acid, adipic acid, fumaric acid, mesaconic acid, methylenemalonic acid, trimellitic acid, acid 4, 4 '- (trimethylic anhydro-ethylene glycol), 4,4' - (2-acetyl-1,3-glycerol) bis anhydrous trimellitic acid, decandioic acid, dodecanedioic acid, azelaic acid, pimelic acid, brazilic acid, citraconic acid, itaconic acid, naphthalene-l, 8-dicarboxylic acid, naphthalene-1,2-dicarboxylic acid, chlordenedic acid, 1,2,3,6-tetrahydrophthalic acid, melphalanic acid, benzene-1,2,4-tetracarboxylic acid, acid benzene-1,2,3-tricarboxylic acid, benzoic acid, biphenyl-3, 3 ', 4,4'-tetracarboxylic acid, biphenyl-2, 2', 3, 3'-tetracarboxylic acid, naphthalene acid 2, 3, 6 , 7-tetracarboxylic acid, naphthalene-1,2,4,5-tetracarboxylic acid, acid Naphthalene 1, 4, 5, 8-tetracarboxylic acid, decahydronaphthalene-1,4,5,8-tetracarboxylic acid, 4,8-dimethyl-l, 2, 3, 5, 6, 7-hexahydronaphthalene-l, 2, 5 6-tetracarboxylic acid, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic acid, 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic acid, 2,3,6,7-teracloronaphthalene- 1, 4, 5, 8-tetracarboxylic acid, phenanthren-1,3,3,9,10-tetracarboxylic acid, perylene-3, 4, 9, 10-tetracarboxylic acid, bis (2,3-dicarboxyphenyl) methane, bis (3, 4-dicarboxyphenyl) methane, 1,1-bis (2,3-dicarboxyphenyl) ethane, 1,1-bis (3,4-dicarboxyphenyl) ethane, 2,2-bis (2,3-dicarboxyphenyl) propane, 2, 2-bis (3,4-dicarboxyphenyl) propane, bis (3,4-dicarboxyphenyl) sulfone, bis (3, -dicarboxyphenyl) ether, ethylene tetracarboxylic acid, butan-1,2,3,4-tetracarboxylic acid, cyclopentan-1,2,3,4-tetracarboxylic acid, pyrrolidin-2,3,4,5-tetracarboxylic acid, pyrazin-2, 3, 5, 6 acid -tetracarboxylic acid, melific acid, thiophene-2,3,4,5-tetracarboxylic acid, benzophenone-3, 3 ', 4,4'-tetracarboxylic acid, maleic acid, glutaric acid, pyromellic acid, phthalic acid, isophthalic acid and / or terephthalic acid, benzoic acid, phenylacetic acid, polyacrylic acid, polymethacrylic acid, cyclohexylalcanic acid, malonic acid, succinic acid, polymaleic acid, acids based on maleic acid addition products with styrene, dodecenyl succinic acid, acids based on acid maleic acid and alkylene, for example, N-octylene succinic acid,? -dodecylene succinic acid,? -dodecylene succinic acid and / or copolymers of acids and any of the other monomers, for example, isobutene and maleic acid, poly (ethylene-co-) (butyl acrylate) -co-acid-maleic and / or poly (styrene-co-maleic acid) As comonomers which are copolymerizable with unsaturated carboxylic acids or carboxylic anhydrides can be used, for example: olefins such as ethylene, propylene, α-butylene, isobutylene and diisobutylene, vinyl alkyl ethers such as vinyl methyl -, vinyl ethyl-, vinyl propyl-, vinyl isopropyl-, vinyl butyl, vinyl isobutyl-, and vinyl tert-butyl ethers, vinyl aromatics such as styrene and A-methylstyrene, furan and 2-methylfuran, diketene, derivatives of acrylic acid and methacrylic acid, for example, (meth) acrylamide, (meth) acrylonitrile, alkyl (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, (meth) isobutyl acrylate and tert-butyl (meth) acrylate, hydroxylalkyl (meth) acrylates such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate and (meth) acrylate of hydroxyisobutyl, vinyl carboxylates as format d vinyl acetate, vinyl butyrate and vinyl pivalate and other vinyl-containing monomers such as N-vinylpyrrolidone, N-vinylcaprolactam, N-vinylformamide, N-vinylacetamide, N-vinylmethylacetamide and N-vinylimidazole. Other suitable acids are organic poly acids containing the following structure unit: Where: n: is an integer from 2 to 2600, inclusive; X: is H or a straight or branched chain alkyl radical having from 1 to 6 carbon atoms, preferably H, methyl, ethyl; Y: it's H; is H or -COOY.

In the above formula for organic polyacids, n is preferably from 26 to 1000, particularly preferably from 60 to 400. The polyacids used in the mixtures are preferably acids, polymethacrylic acids, maleic acid polymers and / or copolymers prepared using at least two of the following acids: acrylic acid, methacrylic acid and maleic acid. The polyacids can, for example, be prepared by the generally known polymerization processes from the known starting materials, for example, acrylic acid and / or methacrylic acid and / or maleic acid. Adjacent to the structural unit which is present according to the invention, for example, at the ends of the polyacid, it is possible to use the customary structural units as they are formed, for example from the unsaturated carboxylic acids in an anionic or radical polymerization free, for example, as a result of the use of the initiator compound. The polyacids which are used according to the present invention preferably have at least one of the following structural units (i), (ii) and / or (iii), wherein the polyacids which are copolymers contain at least two different structural units from among the following structural units, they are also possible: where: n and Y are as defined. The indicated structural units can also be present in the polyacids according to the present invention in the form of blocks (block polymers) or they can be randomly distributed. For example, it is possible to use at least one polyacid of the following formula: where: n: is an integer from 2 to 2600, inclusive; X: is H or a straight or branched chain alkyl radical having from 1 to 6 carbon atoms, preferably H, methyl, ethyl; Y: it's H; Z: is H or -COOY.

The compound (s) (ii) can be used as acids, that is, in protonated form. As (ii) preference is given to the use of the following compounds: pyromellitic acid, succinic acid, maleic acid, polymaleic acid, glutaric acid, each of which may also contain different side groups, adipic acid, dimethylolpropionic acid, glutamic acid and / or malonic acid. In general, preference is given to the use of those acids that dissolve easily in (i). The compounds (ii) used according to the present invention may be present in the mixture at least partially in deprotonated form as a salt with the at least partially protonated amines that may be present; due to the molar excess of (ii), at least part of (ii) is present in free form. By means of a thermal treatment generally known in the production of the polyisocyanate polyaddition products or by means of the heat of reaction in this production process, at least part of the organic amines can be free and show their catalytic activity, but preferably they are blocked again by the acids after the catalysis. The amines that may be present in the mixtures are, for example, the following compounds. Organic amines for example triethylamine, triethylene diamine, tributylamine, dimethylbenzylamine, N, N, N ', N' -tetramethylethylenediamine, N, N, N ', N' -tetramethylbutanediamine, N, N, N ', N' -tetramethylhexan-1, 6-diamine, dimethylcyclohexylamine, pentamethyl dipropylenetriamine, pentamethyldiethylenetriamine, 3-methyl-6-dimethylamino-3-azapentol, dimethylaminopropylamine, 1,3-bis (dimethylamino) butane, bis (2-dimethylaminoethyl) ether, N-ethylmorpholine, N-methylmorpholine, N-cyclohexylmorpholine, 2-dimethylaminoethoxyethanol, dimethylethanolamine, tetramethylhexamethylenediamine, dimethylamino-N-methylethanolamine, N-methylimidazole, N-formyl-N, N '-di-ethylbutylenediamine, N-dimethylaminoethylmorpholine, 3,3'-bis (dimethylamino) di-N-propylamine and / or bis (2-piperazinesopropyl) ether, dimethylpiperazine, N, N'-bis (3-aminopropyl) ethylenediamine and / or tris (N, N-dimethylaminopropyl) -s-hexahydrotriazine, or mixtures containing at least two of the above-mentioned amines, also relatively high molecular weight tertiary amines being possible as described, example, in DE-A 28 12 256. The amines that may be present in the mixtures are preferably aliphatic and / or cycloaliphatic tertiary amines, particularly preferably triethylenediamine. The molar excess of the acid groups or the derivatives of the acid groups on any of the amines present in the mixtures of the present invention is preferably at least 2: 1, particularly preferably at least 10: 1, in particular at least 100. :1. Even after the reaction of some of the carboxylic acid groups (or derivatives of the carboxylic acid groups) of (ii) with the isocyanate groups of (i), the mixture according to the present invention preferably contains a molar excess of the acid groups (or derivatives of the acid groups) of (ii) on the amines that may be present. In addition to (i) and (ii), the mixtures may contain blowing agents, additives, auxiliaries and / or catalysts, for example, those which accelerate the reaction of the isocyanates with the compounds which are reactive to the isocyanates, for example the blowing reaction and / or crosslinking. As blowing agents it is possible to use, preferably, to produce foamed polyurethanes, the blowing agents generally known as materials having a boiling point at atmospheric pressure in the range from -40 ° C to 120 ° C, blowing agents gases and / or solids and / or water in customary quantities, for example carbon dioxide, alkanes and / or cycloalkanes such as isobutane, propane, N- or isobutane, N-pentane and cyclopentane, ethers such as diethyl ether, methyl isobutyl ether and dimethyl ether, nitrogen, oxygen, helium, argon, nitrous oxide, halogenated hydrocarbons and / or partially halogenated hydrocarbons such as trifluoromethane, monochlorotrifluoroethane, difluoroethane, pentafluoroethane, tetrafluoroethane or mixtures containing at least two of the blowing agents mentioned by way of example. Examples of auxiliaries and / or additives are active surface substances, foam stabilizers, cell regulators, fillers, dyes, pigments, flame retardants, hydrolysis inhibitors, fungistatic and bacteriostatic substances. Suitable catalysts are the generally known compounds, for example organic metal compounds, preferably organic tin compounds such as tin (II) salts of organic carboxylic acids, for example, tin (II) acetate, tin (II) octoate. , tin (II) ethylhexanoate and tin (II) laurate, and dialkyltin (IV) salts of organic carboxylic acids, for example dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate and dioctyltin diacetate. Other catalysts which can be used for this purpose are the customary organic amines, for example tritylamine, triethylene diamine, tributylamine, dimethylbenzylamine, N, N ', N' -tetramethylethylenediamine, N, N, N ', N' -tetramethylbutanediamine, N, N, N ', N' -tetramethylhexan-1,6-diamine, dimethylcyclohexylamine, pentamethyldipropylenetriamine, pentamethyldiethylenetriamine, 3-methyl-6-dimethylamino-3-azapentol, dimethylaminopropylamine, 1,3-bis (dimethylamino) butane, bis (2-) dimethylaminoethyl) ether, N-ethylmorpholine, N-methylmorpholine, N-cyclohexylmorpholine, 2-dimethylaminoethoxyethanol, dimethylethanolamine, tetramethylhexamethylenediamine, N-dimethylamino-methylethanolamine, N-methylimidazole, N-formyl-N, N'-dimetilbutilendiamina, N-dimetilaminoetilmorfolina, 3 , 3'-bis (dimethylamino) di-N-propylamine and / or bis (2-piperazinesopropyl) ether, dimethylpiperazine, N, N'-bis (3-aminopropyl) ethylenediamine and / or tris (N, N-dimethylaminopropyl) -s-hexahydrotriazine, or mixtures containing at least two of the amines mentioned above, with tertiary amines of molecular weight relatively high as described, for example, in DE-A 28 12 256 are also possible. The amines which may be present in the mixtures are preferably aliphatic and / or cycloaliphatic tertiary amines, particularly preferably triethylenediamine. The blends of the present invention are preferably used to produce polyisocyanate polyaddition products, for example, compact or cellular polyurethanes, for example microcellular, thermoplastic or crosslinked, rigid, semi-rigid or flexible, elastic or inelastic. The starting materials for producing the polyisocyanate polyaddition products have already been described by way of example. Organic polyisocyanates and compounds that are reactive to isocyanates and have molecular weights of from 60 to 10,000 g / mol are usually reacted in such amounts as the equivalence ratio of the NCO groups of the polyisocyanates to the sum of the atoms Hydrogen reactants of compounds that are reactive to isocyanates is 0.5-5: 1, preferably 0.9-3: 1 and in particular 0.95-2: 1. It can be advantageous if the polyurethanes contain at least some isocyanurate groups bound, in these cases, a ratio of the NCO groups of the polyisocyanates to the sum of the reactive hydrogen atoms of 1.5-60: 1, preferably 1.5-8, can be flexed. :1. The polyisocyanate polyaddition products can be produced, for example by the one-step process or by the known prepolymer process, for example using high pressure or low pressure technique in open or closed molds, reaction extruders or conveyor belt units. . It has been found advantageous to produce the polyisocyanate polyaddition products by the two-component method and combine the compounds that are reactive to the isocyanates and, if desired, the catalysts, blowing agents and / or auxiliaries and / or additives such as the component A and using the isocyanates and catalysts and / or blowing agents as component B. The component (ii), according to the present invention is added to the component B. In the process of the present invention for producing the polyisocyanate polyaddition products (ii) it is preferably used in an amount from 0.1 to 20% by weight, particularly preferably from 0.1 to 6% by weight, based on the weight of the sum of (ii) and the isocyanates used. The invention is illustrated by the following examples. Flexible polyurethane foams are produced using the following formulation where, in the individual examples, the carboxylic acids indicated in Table 1 are added to the isocyanate component (component B) before mixing with the polyol component (component A). By comparison, foams were produced without the addition of acids.

Component A: 97 parts by weight of a polyether polyol with a hydroxyl number of 28 mg KOH / g, an average functionality of 2.3 and prepared using a ratio of ethylene oxide to propylene oxide of 14:86, 3 parts by weight of a polyether polyol with a hydroxyl number of 42 mg KOH / g, an average functionality of 2.3 and prepared using a ratio of ethylene oxide to propylene oxide of 30:70, 3. 31 parts by weight of water, 0. 8 parts by weight of aminopropylimidazole, 0. 6 parts by weight of dimethylaminodiglycol, and 0. 5 parts by weight of a stabilizer (Tegostab® B 8631, Goldschmidt) Component B: Mixture of a polymeric MDI (50% weight ratio) and a bifunctional MDI mixture (weight ratio (50%) with an NCO content of 32.7%.

Table 1 The flexible foams are produced by mixing 750 g of component A at room temperature in a 5 liter cuvette at a rate of 100 with 393 g of component B using a stirrer, emptying the foaming mixture when the cream time has been reached in a aluminum mold with dimensions of 40 x 40 x 10 cm and heated to 53 ° C, closing the mold and removing the flexible foam from the mold after reaching the time of gel formation. The mechanical properties of the polyurethane foams produced according to the present invention were examined immediately after production and also after storage for 3 days at 90 ° C and 90% relative atmospheric humidity and compared with flexible foams which had been produced using the indicated A and B components without the addition of the compounds as shown in Table 1. The excellent properties, in particular the significantly increased stability of the foams produced according to the present invention can be seen in Table 2.

Table 2 sa: without storage, ca: with storage. DC: mechanical compression deformation, reported in [%], measured in accordance with DIN 53572 RR: rebound resilience reported in [%], measured according to DIN 53573.

Compressive strength: reported in [KPa], measured in accordance with DIN 53577 at 40% compression.

Tensile strength: reported in [KPa], measured in accordance with DIN 53571. Elongation: reported in [%], measured in accordance with DIN 53571.

Claims (5)

1. RE I VIND I CAC I ONE S A mixture consisting of: (i) at least one isocyanate, and (ii) at least one acid and / or at least one acid derivative other than an acid anhydride wherein: (ii) is present in an amount from 0.01 to 20% by weight, based on the weight of the mixture, and the acid groups or derivatives of the acid groups of (ii) are present in a molar excess on any of the amines present in the mixture. The mixture as mentioned in claim 1, wherein (ii) is present in an amount from 0.1 to 6% by weight, based on the weight of the mixture. 3 . The mixture as mentioned in claim 1, wherein (ii) consists of pyromellitic acid, succinic acid, maleic acid, polymaleic acid, glutaric acid, each of which may also contain some side groups, adipic acid, dimethylolpropionic acid, glutamic acid and / or malonic acid. Four . A process for producing polyisocyanate polyaddition products by reacting the isocyanates with the compounds that are reactive to the isocyanates, in the presence or absence of catalysts, blowing agents, additives and / or auxiliaries, wherein the reaction is carried out in the presence of mixtures as mentioned in claim 1. A process for the production of polyisocyanate polyaddition products foamed by reacting the isocyanates with compounds that are reactive to the isocyanates, in the presence of catalysts, blowing agents, additives and / or auxiliaries, wherein the reaction is carried out in the presence of the mixtures as recited in claim 1. A polyisocyanate polyaddition products which can be obtained by a process as mentioned in claim 4 or 5. The use of acids and / or derivatives acids that are not acid anhydrides in the polyisocyanate polyaddition products to stabilize the products of polyisocyanate polyaddition the dissociation of urethane and urea bonds.