MXPA99002176A - Carbodiimides and its preparation - Google Patents

Abstract

In carbodiimides containing carbodiimide structures and also urethane and / or urea structures and are solid at 25 ° C, the carbodiimide structures are attached to non-aromatic carbon atoms

Description

CARBODIIMIDES AND ITS PREPARATION The present invention relates to carbodirruids containing carbodiimide structures and also urethane and / or urea structures and are solids at 25 ° C, wherein the carbodiimide structures are attached to non-aromatic carbon atoms. The invention further relates to processes for preparing these carbodiimides and mixtures comprising these carbodi ies and compounds containing ester structures, preferably polyurethanes containing ester structures. Organic carbodiimides are known and are used, for example, as stabilizers against the hydrolytic degradation of compounds containing ester groups, for example polyaddition and polycondensation products such as polyurethanes. The carbodiimides can be prepared in general by known methods, for example, by allowing the catalysts to act on the monoisocyanates or polyisocyanates with elimination of carbon dioxide. Suitable catalysts are, for example, heterocyclic compounds containing bound phosphorus, metal carbonyls, phospholines, phospholenes and phospholipids and also their oxides and sulphides. Such carbodiimides, their preparation and their use as stabilizers against the hydrolytic cleavage of plastics based on polyester are described, for example, in DE-A 4 318 979, DE-A 4 442 724 and EP-A 460 481. DE-A 4 318 979 describes the use of 1,3 'bis (1-methyl-1-isocyanatoethyl) benzene to prepare carbodiimides and / or oligomeric polycarbodiimides having terminal isocyanate urea and / or urethane groups. The terminal isocyanate groups of the carbodiimides described herein are usually reacted with monoalcohols or monoamines. A disadvantage of these carbodiimides is the fact that these compounds are viscous liquids that hinder the process in the metering units that are customary in the plastics process industry and are designed for the handling of pulverulent or granulated solids. EP-A 460 481 describes monocarbodies or substituted oligomeric polycarbodiimides containing up to 4 carbodiimide groups, are prepared from substituted diisocyanates and release virtually non-toxic volatile substances originating from carbodiimides both used at elevated temperatures, for example under the customary conditions of process, or at room temperature. These carbodiimides have the considerable disadvantage that the carbodiimide group is directly attached to aromatic carbon atoms. The dissociation of the carbodiimide groups, for example under severe hydrolytic conditions, leads in this case to aromatic amines which present problems of toxicity. In addition, the carbodiimides described in EP-A-460 481 have a comparatively greater tendency to yellowness, which is undesirable in many applications. It is an object of the present invention to develop carbodiimides as stabilizers against the hydrolytic dissociation of polyester-based plastics, such carbodiimides, as solids, can be mixed more simply with plastics and have excellent properties as stabilizers. We have found that this objective is carried out by the carbodiimides defined in the beginning. The preparation of the carbodiimides of the present invention comprises essentially two reaction steps. First, (1) carbodiimide structures are produced by the generally known reaction of isocyanate groups with each other to remove carbon dioxide in the presence of customary catalysts that are known for this reaction and have been written before, and second (2) isocyanate groups are they react with compounds that are reactive to the isocyanates to form urethane and / or urea structures. These two essential steps of process (1) and (2) can be carried out in any order as long as the free isocyanate groups are present for the respective reaction.

For example, the carbodiimides of the present invention can be obtained by converting diisocyanates whose isocyanate groups are not bonded to aromatic carbon atoms »in the presence of catalysts, with removal of carbon dioxide in carbodiimides and subsequently by reacting carbodiimide containing isocyanate groups with compounds containing at least two groups which are reactive to isocyanates to form substituted carbodiimides, for example, carbodiimides containing urethane and / or urea structures . The molar ratio of the NCO groups of the carbodiimide containing isocyanate groups to the groups that are reactive to the isocyanates is usually from 10: 1 to 0.2: 1, preferably from 5: 1 to 0.5: 1. As an alternative, the carbodiimides of the present invention can be obtained by reaction of diisocyanates >; whose isocyanate groups are not linked to the aromatic carbon atoms / with compounds containing at least two groups which are reactive to the isocyanates, wherein the ratio of the isocyanate groups used to the groups which are reactive to the isocyanates is from 100: 1 to 2: 1, preferably from 50.1 to 2: 1, and subsequently converting the reaction product containing isocyanate groups, in the presence of catalysts with carbon dioxide removal, into carbodiimides containing urethane and / or urea structures . In this process variant, up to 50% by weight, preferably up to 23% by weight, of the isocyanate groups of the diisocyanate reacted in the first step with the compounds which are reactive to the isocyanates, and then the free isocyanate groups are completely condensed or partially in the presence of catalysts with elimination of carbon dioxide to form carbodiimides and / or oligomeric polycarbodiimides. Preference is given to carrying out the reaction first to form the carbodiimides and subsequently reacting the carbodiimides containing isocyanate groups with the compounds which are reactive to the isocyanates. The process step (1) for preparing carbodiimides of the present invention by reaction of diisocyanates can be carried out at elevated temperatures, for example, from 50 to 200 ° C, preferably from 150 to 185 ° C, advantageously in the presence of catalysts with carbon dioxide removal. Suitable methods are described, for example, in GB-A-1 083 410, DE-B 1 130 594 (GB-A-851 936) and DE-A-11 56 401 (US-A-3 502 722). The catalysts which have been found to be most used are, for example, phosphorus compounds which are preferably selected from the group consisting of phospholenes, phospholene oxides, phospholines and phospholine oxides. When the reaction mixture obtained the desired content of NCO groups, corresponding to a condensation degree of preferably at least 4, the formation of polycarbodiimide is normally interrupted. For this purpose, the catalysts can be distilled under reduced pressure or deactivated by the addition of a deactivator such as phosphorus trichloride. The preparation of the polycarbodiimides can also be carried out in the presence or absence of solvents which are inert under the reaction conditions. A person skilled in the art can fix the degree of condensation in the customary manner by suitably selecting the reaction conditions, such as the reaction temperature, the type of catalyst and the amount of catalyst and also the reaction time. The course of the reaction can be followed more simply by determination of the NCO content. Other parameters such as viscosity increase, color enhancement or C02 release can also be used to monitor the progress of the reaction and to control the reaction. The diisocyanates that can be used to prepare the carbodiimides of the present invention are generally customary isocyanates whose isocyanate groups are not attached to aromatic carbon atoms, for example, hexamethylene diisocyanate, l-isocyanate-3, 3, 5-trimethyl-5 isocyanatomethylcycloexano (isophorone diisocyanate), di (cyclohexyl) methane diisocyanate, trimethylhexamethylene diisocyanate, dodecane diisocyanate, octane diisocyanate, and / or cyclohexane 1,4-diisocyanate. Preference is given to the use of 1,3-bis (1-methyl-1-isocyanatoethyl) enne, hereinafter also referred to as TMXDI, as diisocyanate. It is also possible to use mixtures of two or more of the aforementioned diisocyanates, in particular mixtures with 1,3-bis (1-methyl-1-is-cyanatoethyl) benzene. In this case, preferably at least 30 mol% of 1,3-bis (1-methyl-1-isocyanatoethyl) benzene is used. The carbodiimides of the present invention particularly preferably contain at least one of the following structural units representing the carbodiimide structure corresponding to the diisocyanate which is particularly preferably used: For example, the carbodiimides of the present invention can have the following structure: where R can be identical or different, for example the radicals -NHCONHR1 or -NHCOOR1, where R 1 and R 2 are derivatives of the compounds that are reactive to the isocyanates and are described by the example below and can bind the structure shown for other carbodiimide structures, and n is, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, where n can be a whole number as indicated, or As a statistical average, it can be a fraction. The carbodiimides of the present invention which are solid at 25 ° C are thus, preferably derived from 1,3-bis (1-methyl-1-isocyanatoethyl) benzene (TMXDI). The isocyanate-reactive compounds containing at least two groups which are reactive to the isocyanates and can be used to prepare the carbodiimides of the present invention are generally customary substances which form urethane and / or urea groups by reaction with isocyanates. For example, it is possible to use aromatic, aliphatic and / or araliphatic compounds having from 2 to 20 carbon atoms and containing hydroxyl and / or amine groups as groups that are reactive to the isocyanates. As compounds containing at least two groups that are reactive to the isocyanates, preference is given to the use of organic compounds containing at least two hydroxyl groups, containing at least two amine groups and / or at least one hydroxyl group and at least one amine group. For example, it is possible to use: aromatic, araliphatic, and / or aliphatic polyols having from 2 to 20 carbon atoms, preferably those having primary hydroxyl groups. Specific examples are: 1,2-ethanediol, 1,3-propanediol, 1,2-propanediol, 1,4-2,4- and / or 2,3-butanediol, 1,5-pentanediol, 1, 6 hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,1-decanediol, neopentyl glycol, 2-methylpropan-1, 3-diol, 2- and 3-methylpentan-1, 5-diol, the isomers of bis (hydroxymethyl or -ethyl) benzene, hydroxy alkyl ethers of dihydroxybenzenes, trimethylolpropane, glycerol, pentaerythritol, and / or sugars having, for example, 4, 5 or 6 hydroxyl groups. Other compounds which can be used as compounds containing at least two hydroxyl groups are polyester alcohols and polyether alcohols as are suitable, for example, for the preparation of polyurethanes. Such macrools are described, for example, in 'Kunststoffhandbuch, vol. 7: Polyurethane. "Particularly suitable macrools are those which have also been used to form the polymer to be protected against hydrolysis.As a consequence, the macrools which are particularly useful for the protection of polyesters against hydrolysis are those which represent a part of the structure of the polyester Specific mention may be made of polyethylene terephthalates and polybutylene oligoesteric terephthalates These oligomers may be obtained from ethanediol or butanediol and terephthalic acid or lower esters of terephthalic acid by generally known condensation reactions or even by glycolytic degradation of commercial high molecular weight terephthalate esters The oligomers have a molecular weight Mn of from about 260 to 10,000 g / mol, preferably from 260 to 5000 g / mol, particularly preferably from 350 to 2000 g / mol. The amines used are amines that contain n at least two primary and / or secondary amine groups. Examples which may be mentioned are: amines having a molecular weight of from 32 to 500 g / mol, preferably from 60 to 300 g / mol, and containing at least two primary amino groups, at least two secondary or one primary and one secondary. Examples are diamines such as diaminoethane, diaminopropane, diaminobutane, diaminopentane, diaminohexane, piperazine, 2,5-dimethylpiperazine, 1-amino-3, 3, 5-trimethyl-5-aminomethylcyclohexane (isophoronediamine, IPDA),, -dia inodicyclohexylmethane, 1,4-diaocyclohexane, aminoethylethanolamine, hydrazine, hydrazine hydrate and / or triamines such as dimethiientriamine, and / or 1,8-diamino-4-aminomethyloctane. In addition, it is possible to use amines which are derived from the mentioned amines by one or more of the primary groups being substituted by other substituents as alkyl groups to form secondary amino groups. In addition, it is also possible to use compounds containing at least one hydroxyl group and at least one amine group, for example, ethanolamine, propanolamine, isopropanolamine, aminoethylethanolamine or N-alkylamine derivatives thereof. Preference is given to using linear alcohols, amines or aminoalcohols, particularly preferably those having an even number of carbon atoms. Also preferred are alcohols, amines or amino alcohols having cyclic structural elements.

It may be advantageous to use monofunctional compounds in addition to the aforementioned compounds which are reactive to the isocyanates and contain at least two functional groups for regulating the molecular weight of the dicarbodiimides of the present invention, particularly if the diisocyanates are converted to carbodiimides in a first step and the reaction of the carbodiimides containing isocyanate groups with the compounds which are reactive to the isocyanates is carried out subsequently. As monofunctional compounds that are reactive to isocyanates, it is possible to use, for example, amines and preferably alcohols. Suitable amines, for example, primary or preferably secondary amines, advantageously have from 1 to 12 carbon atoms, preferably from 2 to 8 carbon atoms. Examples which may be mentioned are methylamine, ethylamine, propylamine, butylamine, benzylamine, hexylamine, 2-ethylhexylamine, octylamine, decylamine, diethylamine, dipropylamine, dibutylamine, methylbutylamine, ethylbutylamine and ethylhexylamine and also cyclohexylamine and benzylamine. However, preference is given to using alcohols, for example, primary or secondary alcohols having from 1 to 18 carbon atoms, preferably from 2 to 8 carbon atoms, to block the isocyanate groups. Examples of the primary or secondary alcohols are: methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, n-pentanol, industrial mixtures of pentanol, n-hexanol, industrial mixtures of hexanol, 2-ethylhexanol, octanol, 2-ethylctanol, decanol and dodecanol and also cyclohexanol and benzyl alcohol. The carbodiimides of the present invention are solids at room temperature, ie at 25 ° C, preferably at 30 ° C, particularly preferably at 40 ° C, particularly at 50 ° C, and a pressure of 1013 mbar. As a result, the carbodiimides have the advantage that they can be granulated or ground using known methods and can be used as solids in customary equipment in the plastics process industry. This use of solids in customary equipment is significantly easier to handle than the use of liquids. The carbodiimides of the present invention preferably contain at least four carbodiimide structures, preferably more than four carbodiimide structures, and the average degree of condensation (numerical average), i.e. the average number of carbodiimide structures in the carbodiimides of the present invention is, particularly preferably from 4.1 to 20, in particular from 5 to 15. In addition, the compounds of the present invention contain urethane and / or urea structures which are formed by reaction of isocyanate groups of the diisocyanates used in the preparation with compounds which are reactive to isocyanates, for example, compounds containing hydroxyls and / or amines. The carbodiimide structures of the compounds of the present invention are bonded to non-aromatic carbon atoms. This offers the significant advantage that no aromatic amine is released with the dissociation of the carbodiimides and the carbodiimides of the present invention, therefore, they present considerably lower toxicity problems than the carbodiimides described, for example, in EP-A 460 481. In the reaction with the carboxylic acids and / or carboxyl-containing compounds, the carbodiimides and oligomeric polycarbodiimides of the present invention form, in the case of the carbodiimides based on TMXDI, araliphatic isocyanates having a lower reactivity than the aromatic isocyanates. The araliphatic isocyanates formed, therefore, have influence on, for example, the rate of a polyaddition reaction to form urethanes. As a result, the molecular weights of the polyurethanes formed and thus their mechanical properties are constant and very reproducible. The carbodiimides of the present invention have isocyanate urea and / or urethane groups - preferably spherically hindered, bonded to non-aromatic carbon, show high resistance to hydrolysis and stability to light that is at least comparable with the aromatic carbodiimides and aromatic polycarbodiimides used industrially and can, in compliance with professional hygiene rules be incorporated without problems into the products of polycondensation and polyaddition containing ester groups. A further advantage is the large number of effective carbodiimide groups, based on the molecular weight of the carbodiimides. The carbodiimides have good compatibility with the polyaddition and polycondensation products containing ester groups, in particular with the polyester urethane rubbers, and are also easily miscible in homogeneous form with these materials in the molten state. The oligomeric monocarbodiimides and / or polycarbodiimides of the present invention are very suitable as acceptors for carboxyl compounds and therefore are preferably used as stabilizers against hydrolytic degradation of compounds containing ester groups, for example, polymers containing ester groups , for example polycondensation products such as thermoplastic polyesters, for example polyethylene and polybutylene terephthalates, polyether esters and polyester esters, polyamides, polyester amides, polycaprolactones and also unsaturated polyester resins and, for example, block copolymers of polyethylene terephthalate or polybutylene , polycaprolactone and polyaddition products, for example, polyurethanes, polyureas and polyurethane-polyurea elastomers, containing ester groups. These compounds containing ester groups are generally known. Its initial materials, preparation processes, structures and properties are widely described in the standard literature. Due to their good solubility in the formative components for preparing the polyurethanes and their good compatibility with the formed polyurethanes, the (poly) carbodiimides of the present invention are particularly suitable as stabilizers against the hydrolytic degradation of polyurethanes, preferably compact polyurethane elastomers. or cell phones, and in particular thermoplastic polyurethanes. If the carbodiimides of the present invention have terminal isocyanate groups, for example, when a carbodiimide containing isocyanate groups is used and that it has a deficiency of groups that are reactive to the isocyanates, the carbodiimides can be used in the preparation of polyaddition products by reaction of isocyanates with compounds that are reactive to the isocyanates. The concentration of the carbodiimides of the present invention in the polycondensation or polyaddition products containing ester groups to be stabilized is from 0.05 to 10% by weight, preferably from 0.1 to 5% by weight, based on the total weight of the mix. In particular cases, depending on the hydrolytic stresses to which the plastic is exposed, the concentration can also be high. The carbodiimides which can be used according to the present invention can be introduced into the products containing ester groups to be stabilized by different methods. For example, the carbodiimides of the present invention can be mixed with one of the formative components to prepare the polyaddition products, for example the polyisocyanates and / or polyhydroxyl compounds to prepare polyurethanes, or the carbodiimides can be added to the reaction mixture for prepare the polyurethanes. According to another variant of the process, the carbodiimides of the present invention can be incorporated entirely in the melt of the polyaddition or polycondensation products which reacted completely. However, it is also possible to cover the polyaddition or polycondensation products granulated with the carbodiimides of the present invention or to mix them with the pulverized carbodiimides of the present invention., granulated, or in the form of beads and introduce them into the plastic melt in a subsequent production of molded parts by melt extrusion. To prepare polyurethane casting or casting elastomers and polyester-based TPU, the carboxyl-containing polyester polyols are, in a preferred embodiment, first treated with the carbodiimides of the present invention to reduce the acid content and then they are, with or without adding more amounts of carbodiimides, which are reacted with polyisocyanates, if desired in the presence of auxiliaries or additional additives. In addition, the carbodiimides of the present invention can be introduced into the polyurethane via the isocyanate component. However, it is particularly advantageous to introduce the carbodiimides of the present invention into the polymer containing ester groups during custom manufacturing. In addition to their effectiveness as stabilizers against hydrolytic degradation of polyaddition and polycondensation products containing ester groups or to deacidify polyesterols which can be used to prepare polyester-containing plastics, in particular polyurethane rubbers, carbodiimides are also suitable, example, for the termination of esterification reactions in the preparation of polyesters when the desired degree of polycondensation has been reached.

Examples 750 parts by weight (3.1 mol) of 1,3-bis (1-methyl-1-iso-cyanatoethyl) benzene with a UCO content of 34.4% by weight heated in the absence of solvent at 180 ° C in the presence of 1.5 parts by weight, based on the 1-methyl-2-phospholene 1-oxide isocyanate and condensed at this temperature with moderate evolution of carbon dioxide. After the NCO content of the reaction mixture reached 11.2% by weight, the catalyst that had been added and the residues of 1, 3-bis (1-methyl-1-methyl-isocyanatoethyl) benzene that did not react were distilled at 180 °. C at a pressure of 1 mbar. This gave 570 parts by weight of a carbodiimide mixture with an NCO content of 7.79% by weight, a content of -N = C = 0- groups of 15.2% by weight (calculated), a melting point of less than 30 °. C and an iodine color number of about 5 to 7, measured according to DIN 6162. The structure of the mixture of monocarbodiimides and oligomeric polycarbodiimides containing groups. Isocyanate was confirmed by IR spectrum and gel atographic analysis. This mixture of carbodiimides hereafter will be referred to as carbodiimide 1.

Examples 1 to 12 500 g of this carbodiimide mixture 1 were reacted at 140 ° C in a flask with stirring with the alcohols indicated in Table 1 until the indicated NCO content was reached. The molar ratio given in Table 1 is the molar ratio of isocyanate: diols: monools in the initial reaction mixture.

Table 1 HQEE: Hydroquinone bis (2-hydroxyethyl) ether CHDM: cyclohexane-1,4-dimethanol HMBA: 1,4-Di- (hydroxymethyl) benzene Examples 13 to 20 500 g of the carbodiimide mixture 1 were reacted at 140 ° C in a flask with stirring with the amines and, in some cases, alcohols indicated in Table 2 until the indicated NCO content was reached. The molar ratio given in Table 2 is the molar ratio of isocyanate: diamines: alcohols in the initial reaction mixture.

Table 2 Table 2 (continued) Isophorone diamine: l-amino-3, 3, 5-trimethyl-5-aminomethylcyclohexane. All the carbodiimides prepared in Examples 1 to 20 have iodine color numbers less than 8, generally less than 5. The carbodiimides can be easily processed by grinding in a cross-hammer mill to give free flowing fine powders that do not tend to Harden. The pulverized carbodiimides were stored at 35 ° C for 14 days in an oven. After that time, they were still free flowing; any small piece easily crushed.

Examples 21 to 41 Using a solid-fed, double-helix extruder, the carbodiimides of the present invention of Examples 1 to 20 were incorporated in a concentration of 0.65% by weight, based on the weight of TPU, into a "thermoplastic" polyurethane ( TPU) that was obtained by reaction of 440 g (1.76 mol) of 4, '-diphenylmethane-diisocyanate 1000 g (0.5 myrtle) of polyadipate of 1,4-butanediol-l, 6-hexanediol 113 g (1.26 mol) of 1 , 4-butanediol The carbodiimide-containing granules were injection molded to give the test samples.The tensile strength and the elongation at break of the test samples were measured in accordance with DIN 53 504 both immediately after they had been manufactured and after storage for 21 days at 80 ° C in water The carbodiimides used and the mechanical properties measured are summarized in Table 3.

Table 3 Example 42 616 g (0.947 mol) of a PET oligomer, obtained from dimethyl terephthalate and 1,2-ethanediol by transesterification and with an OH number of 172, and 500 g (0.464 mol) of the polycarbodiimide 1 were reacted 200 ° C in a shake flask until an NCO content was reached < 0.3% by weight. The product had a glass transition temperature of 45 ° C.

Example 43 Example 1 was repeated using 454 g of the oligo-PET. The product had a glass transition temperature of 57 ° C.

Example 44 Example 1 was repeated using 404 g of oligo-PET. The product had a vitreous transition of 57 ° C.

Example 45 495 g (0.932 mol) of PBT oligomer obtained from dimethyl terephthalate and 1,4-butanediol by transesterification and with an OH number of 211, and 500 g (0.464 mol) of a polycarbodiimide having an NCO content of 7.79% by weight and prepared according to DE-A 4 318 979 were reacted at 200 ° C in a flask with stirring until an NCO content of << 0.3% by weight.

EXAMPLE 46 Example 4 was repeated using 273 g of oligo-PBT.

Example 47 Example 4 was repeated using 330 g of oligo-PBT.

Claims (13)

1. A carbodiimide containing carbodiimide structures and also urethane and / or urea structures and is solid at 25 ° C, wherein the carbodiimide structures are attached to non-aromatic carbon atoms.

2. The carbodiimide as claimed in claim 1 contains at least 4 carbodiimide structures.

3. The carbodiimide as recited in claim 1, which is derived from 1,3-bis (1-methyl-1-isocyanatoethyl) benzene.

4. A process for preparing carbodiimides containing carbodiimide structures and also urethane and / or urea structures and are solid at room temperature, which consists in converting the diisocyanates whose isocyanate groups are not bound to aromatic carbon atoms, in the presence of catalysts with removing carbon dioxide in carbodiimides and subsequently reacting the carbodiimide containing isocyanate groups with compounds containing at least two groups that are reactive to the isocyanates.

5. A process for preparing carbodiides containing carbodiimide structures and also urethane and / or urea structures and are solid at room temperature, which comprises reacting diisocyanates whose isocyanate groups are not bonded to aromatic carbon atoms with compounds containing at least two groups which are reactive to the isocyanates, wherein the ratio of the isocyanate groups to the groups which are isocyanate-related reactants is at least 2: 1, and subsequently convert the reaction product containing isocyanate groups in the presence of catalysts with elimination of carbon dioxide in carbodiimides. The process as recited in claims 4 or 5, wherein the compounds containing at least two groups that are reactive to the isocyanates are organic compounds containing at least two hydroxyl groups, containing at least two amine groups and / or containing at least one hydroxyl group and at least one amine group. The process as recited in claim 4 or 5, wherein the carbodiimides contain at least four carbodiimide structures. 8. The process as recited in claim 4 or 5, wherein 1,3-bis (1-methyl-1-isocyanatoethyl) benzene is used as the diisocyanate. 9. A carbodiimide which is solid at room temperature and is obtained by a process as recited in claim 4 or 5. 10. A mixture comprising the compounds containing ester and carbodiimide structures as mentioned in claim 1 or 9. 11. The mixture comprising carbodiimides as claimed in claim 1 or 9 and at least one compound selected from the group consisting of: polyurethanes containing ester structures, polycondensation products such as thermoplastic polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyether esters, polyester esters, polyesteramides, polycaprolactones, unsaturated polyester resins and polyamides. The mixture as recited in claim 10 or 11 containing carbodiimide as claimed in claim 1 or 9 in an amount from 0.05 to 10% by weight, based on the total weight of the mixture. 13. The use of carbodiimides as claimed in claim 1 or 9 as stabilizers against the hydrolytic degradation of compounds containing ester groups.