JPH03378B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides novel polybasic carboxylic acid poly-
The present invention relates to N,N-hydroxyalkylamides, their preparation and their use as cell opening components in the production of high modulus polyurethane foams. Experience in the commercial production of highly elastic polyurethane foams has shown that, despite the high level of technological development, the products are still subject to risks regarding the quality of the foam. Among other things, the foam is susceptible to shrinkage resulting in an uneven distribution of its mechanical properties over the cross-section of the foam block due to skin compression. The entire surface of the foam is particularly seriously affected by this compaction phenomenon and therefore has no practical value. It is therefore an object of the present invention, by using poly-N,N-hydroxyalkylamides of polybasic carboxylic acids in the form-forming reaction, to combine with easier recovery, It is possible to produce highly elastic polyurethane foams which have open cells throughout and whose tendency to shrink is drastically reduced. At the same time, the foam produced in this way guarantees a high level of dimensional stability during further processing. Furthermore, the present invention provides a novel poly-N,N-hydroxyalkylamide of polybasic carboxylic acid and a method for producing the same. The use of poly-N,N-hydroxyalkylamides of polybasic aliphatic, cycloaliphatic and/or aromatic carboxylic acids in polyurethane foam formulations thus provides a very large number of open cells. It was surprising to find that, at the same time, the tendency to shrink was considerably reduced. By using the novel cell opener according to the invention, organometallic catalysts, especially organotin compounds, for the production of urethanes, without exhibiting significant shrinkage effects on the foam as observed in other cases, can be used.
For example, modified (branched) aromatic diisocyanates, such as tolylene diisocyanates, such as allophanate groups, biuret groups, isocyanurate groups, even in the presence of tin() carboxylates or dialkyltin() dicarboxylates, It was also surprising to find that tolylene diisocyanates containing carbodiimide groups, urethane groups and/or urea groups can be foamed. Highly open-celled, non-shrinkable foams are also obtained in these cases where tin catalysts are used, which is furthermore due to the additional possibilities provided by the metal catalyst, as reflected, for example, in its compression hardness. It also shows improved mechanical properties. The same problem has traditionally affected highly functionalized (branched) diphenylmethane polyisocyanate polymers when used in the manufacture of foams. Even in such cases, the compounds described in the claims of the present invention clearly act as cell openers. In the production of cold foam, shrinkage and pore size problems can be counteracted to some extent by the addition of stabilizers (see e.g. US Pat. No. 3,748,288, DE-A Nos. 2,210,721 and 2,454,049) This has been common practice in the past, although it has led to a regression in the mechanical properties of the foam, particularly its compressive hardness, and at the same time has shown the limitations of these methods. Although DE-A No. 2103730 discloses the production of open-cell foams by using polyalkylene polyamines in the form of miscible catalysts, as described in section 6, section 2 of that publication, , organotin catalysts cannot be used because they cause shrinkage. Not only can the level of mechanical properties be maintained by the method of the invention using polyhydroxyalkylamides of polybasic carboxylic acids as cell openers, but also through the possibilities offered by the invention using metal catalysts. While increasing the level, a high level of open cells and a large reduction in shrinkage can be obtained. The cell opening effect of the compound of the present invention can be clearly observed not only in the block form but also in the molded form. The effect, which is of great significance for the considerable increase in the safety level in the processing during foam production, cannot be explained by the crosslinking action of the compounds of the type according to the invention, as was indeed expected. The reason for this is that if compounds of the type according to the invention have a crosslinking effect, experience should show that significant shrinkage occurs due to excessive crosslinking when added in high concentrations. , in this case the result is the opposite. If present in excessive concentrations,
Compounds of the type according to the invention collapse in form as a result of an enhanced cell opening effect. GB 1032873 already shows poly-N,N-hydroxy-alkylamides of fatty acid polymers of the formula: In this formula R is a dimer, trimer or polymeric residue of a fatty acid containing 8 to 24 carbon atoms. These compounds were used with polyisocyanates to produce coatings. However, the compounds of the invention have a different composition and are used for an entirely different purpose, namely as cell openers in the production of polyurethane foams. The present invention therefore relates to poly-N,N-hydroxyalkylamides of polybasic aliphatic, cycloaliphatic and/or aromatic polycarboxylic acids having the following formula: In this formula, n is an integer from 2 to 6 and preferably from 2 to 4, and X is a single bond (n=
In the case of 2, an n-functional C ₁ -C ₁₀ straight-chain or branched alkane group, preferably a C ₁ -C ₄ alkane group, optionally substituted by a hydroxyl group, a heteroatom in the ring or _C4 - _C6 cycloalkane groups optionally containing O, S or N- _CH3 as heteroatom groups,
represents an n-functional _C6 - _C20 -aryl group optionally substituted by one or more hydroxyl groups, A being a straight or branched _C2 -chain optionally containing a hydroxyl group;
C ₆ -alkylene group, preferably ethylene group, 1,
It represents a 2- or 1,3-propane group, and more preferably an ethylene group. More preferably, X is a single bond (n=2), a _{C1- C6} -alkylene group (n=2), a HC-group (n=3), a _H3CC -group (n=3), or a H3CC-group (n=3). C-group (n=3), and represents. X = only one bond mark, =(-CH ₂ )- _n , in this formula m=1 to 4 Particularly preferred are di-(hydroxyalkyl)-amides. The present invention also provides polycarboxylic acid alkyl esters or polycarboxylic acid aryl esters corresponding to the following formula at elevated temperatures (50 to 200°C and preferably 70 to 150°C). (In this formula X and n are as defined above and R is C ₁ -C ₁₀ - (preferably
_C1 - _C4 ) represents an alkyl group or an aryl group (preferably a phenyl group). ) NH(-A-OH) ₂ (in which A is as defined above) and the resolved hydroxyl compound ROH at normal and/or reduced pressure. The present invention relates to a process for producing poly-N,N-hydroxyalkylamides of polybasic polycarboxylic acids, which is characterized in that they are distilled off from the reaction mixture in the following steps. The present invention also includes at least 2 isocyanate-reactive hydrogen atoms and from 400 to 10,000 hydrogen atoms.
The polybasic carboxylic acid polybasic acid according to the invention having the formula -N,N-hydroxyalkylamide (in this formula X, A and n are as defined above) in the presence of a catalyst and optionally a foam stabilizer, water and/or an organic blowing agent, characterized by its use as a cell opener. , a compound containing at least two isocyanate-reactive groups and having a molecular weight of from 400 to 10,000 is added to a polyisocyanate and optionally a chain extender (chain-extender) having a molecular weight ranging from 18 to 400.
The present invention relates to a method of using the compounds of the present invention in producing open-celled polyurethane foams by reacting with a polyurethane foam (extending agent). The cell-opening compound of the present invention is a derivative of a polybasic carboxylic acid amide, in which the amide nitrogen atom of the polybasic carboxylic acid amide is perhydroxyalkylated, and corresponds to a novel compound. Particularly effective representatives of the class of compounds according to the invention are hydroxyaralkyl derivatives of the type containing a primary hydroxyl group, and compounds of the invention in which the hydroxyalkyl group is a hydroxyethyl group are even more effective. . These hydroxyethylamide derivatives can be used in moderate amounts (e.g. 0.5 to
2.5% by weight) exhibits a particularly strong cell-opening effect. Surprisingly, the effectiveness of amide derivatives is highly dependent on structure. For example, amides of carbonic acid, e.g. has no actual cell opening effect. The new compounds are preferably prepared by aminolysis of the corresponding alkyl or aryl esters with dialkanolamines at elevated temperatures, the reaction being accompanied by the release of the alcohol component of the ester. Suitable aminolysis methods are described, for example, in Houben-Weyl, Vol. 8, pp. 653 et seq. and Vol. XI, pp. 27, vol.
It is described in the specification of No. 1032873. To produce polyurethane foams using the polyhydroxyalkylamides of polybasic carboxylic acids for cell opening of the present invention, the following foam-forming starting materials are used. 1 Compounds containing at least two isocyanate-reactive hydrogen atoms and having a molecular weight generally from 400 to 10,000. In addition to compounds containing amino, thiol or carboxyl groups, compounds of this type are preferably compounds containing hydroxyl groups, in particular compounds containing 2 to 8 hydroxyl groups, in particular 800 to 6000 and preferably 1500 and 4,000, but are preferably known per se for the production of foamed and unfoamed polyurethanes and are described, for example, in DE-A 2 832 253, pages 11 to 18. polyesters, polyethers, polythioethers, polyacetals, polycarbonates and polyesteramides containing 2 to 4 hydroxyl groups. Addition of one or more alkylene oxides (ethylene oxide and especially propylene oxide) to di- or polyfunctional "starters", propylene glycol, glycerol, sorbitol, formose, triethanolamine, trimethylolpropane and diisocyanates and hydrazines and/or diamines and/or glycols or polymers and/or graft polymers,
Particular preference is given to using polyethers of the type which preferably contain polyaddition products of polymers and/or graft polymers of styrene and acrylonitrile in dispersed or dissolved form. 2 Compounds containing at least two isocyanate reactant hydrogen atoms and having a molecular weight of 18 to 399 are optionally used as starting materials. Furthermore, this compound is a compound containing a hydroxyl group and/or an amino group and/or a thiol group and/or a carboxyl group and/or a hydrazide group, preferably containing a hydroxyl group and/or an amino group, which acts as a chain extender or a crosslinking agent. It is a compound containing. These compounds generally contain 2 to 8, preferably 2 to 4, isocyanate-reactive hydrogen atoms. Examples of such compounds are DE-A No.
No. 2832253, pages 19 to 20. Examples here include water, hydrazine, 1,4-butanediol, trimethylolpropane, formitol mixtures or adipic dihydrazide. 3 For example, W. Siefken, Justus Liebigs
Aliphatic, cycloaliphatic, aromatic heterocyclic and especially aromatic polyisocyanates of the type described in Annalen der Chemie, No. 562, pages 75 to 136, such as those of the formula Q(NCO) _o. The corresponding polyisocyanate, in this formula n
is between 2 and 4, preferably 2, and Q
is an aliphatic hydrocarbon group containing 2 to 18, preferably 6 to 12 carbon atoms, 4 to 20
an alicyclic hydrocarbon radical containing 6 to 20 carbon atoms, preferably 6 to 13 carbon atoms; or an aromatic hydrocarbon radical containing 6 to 20 carbon atoms, preferably 6 to 13 carbon atoms; or 13
10 of DE-A No. 2832253.
Polyisocyanates of the type described on pages 1-11. Polyisocyanates readily obtainable on a commercial scale, such as 2,4- and/or 2,6-tolylene diisocyanate, and mixtures of these isomers (“TDI”),
Diphenylmethane diisocyanate (4,4'-
and/or 2,4'- and/or 2,
2′-isomer), polyphenylpolymethylene polyisocyanates (“crude MDI”) of the type obtained by condensation of aniline with formaldehyde and subsequent phosgenation and, for example, carbodiimide groups, urethane groups, allophanate groups, isocyanurate groups. , "modified polyisocyanates" containing urea groups and/or Biuret groups, more particularly 2,4- and/or 2,6-tolylene diisocyanates or 4,
Particular preference is given to using modified polyisocyanates of the type derived from 4'- and/or 2,4'-diphenylmethane diisocyanates. Auxiliaries and additives, such as volatile inorganic or organic compounds such as blowing agents, catalysts known per se, such as tertiary amines, tin() and tin() compounds, surface-active additives, such as emulsifiers and tin() compounds. Foaming agents, reaction inhibitors, compounds which react as acids, such as hydrochloric acid or organic acid halides, and foam regulators known per se, such as paraffins, aliphatic alcohols or dimethylpolysiloxanes, and pigments or dyes and Flame retardants known per se, as well as stabilizers against the effects of aging, light and weather, plasticizers and bacteriostatic and bacteriostatic compounds and fillers can optionally be used. These optional auxiliaries and additives are described in detail, for example, on pages 21 to 24 of DE-A 2732292. Further examples of auxiliaries and additives can be found in Vieweg and Hoechtlen,
Published by Carl-Hanser-Verlag, Munich 1966.
See also Kunststoffhandbuch, Volume 1, pp. 103-113. The polyhydroxyalkylamides for cell opening according to the invention are usually mixed with relatively high molecular weight polyol compounds, such as polyethers, in the indicated amounts; this mixture may also contain customary auxiliaries and additives. . However polyol or already pre-formed
It is also possible to add the cell-opening compounds of the invention together with water and other auxiliaries to the reaction mixture consisting of the NCO-prepolymer. Although the usage of the cell opener of the present invention is within the ranges already mentioned, continuous testing will maximize its use within that range. However, clearly excessive concentrations in the mixture to be foamed lead to collapse of the foam. The production of the foam is carried out in the usual manner with the aid of measuring devices and conveyors. The main field of application is the production of semi-elastic and elastic foams by block forming or the known laminator process. However, it is also possible to mold the foam in the form of a foam instead of in the free state, thereby making it possible to produce corresponding molded foams. In this case, foaming is preferably carried out in the absence of heat (cold-curing molded foam). In-mold forming may be carried out in such a way that the molded article has a dense skin and a foamed core, but it can also be carried out in such a way that the molded article has a foamed structure on its surface. To this end, the foamable reaction mixture is introduced into the mold in such an amount that the formed foam just fills the mold, or alternatively, the foamable reaction mixture is introduced into the mold in an amount larger than that required to fill the interior of the mold. is introduced into the type. Applications of the product obtained according to the invention include:
Examples include furniture upholstery materials, pine upholstery, automobile seats, armrests, sponges and architectural elements, as well as seat and instrument panel hem materials. (A) Production example of poly-(N,N-hydroxyalkyl)-carbonamide 1 210 g (2 mol) of diethanolamine are added in portions to 146 g (1 mol) of oxalic acid diethyl ester and the temperature is raised to 90° C. to distill off the ethanol almost quantitatively. By treatment in vacuum, 864 g (quantitative) of tetrahydroxyethyl oxalamide having a viscosity at 80° C. of 1100 cp and an OH number of 850 are obtained. Calculated value: C45.4 H7.57 N10.6 Measured value: C45.0 H7.0 N10.4 Example 2 This compound was prepared in the same manner as in Example 1, and 160 g (1
mol) of malonic acid diethyl ester and 210 g (2
mol) of diethanolamine. Yield: Tetrahydroxyethylmalonic acid amide
278g (quantitative), OH number 800. Calculated value: C47.5 H7.9 N9.9 Measured value: C47.3 H7.5 N9.7 Example 3 This compound was prepared in the same manner as in Example 1, and 174 g (1
mol) of adipic acid dimethyl ester and 210 g
(2 moles) of diethanolamine.
Yield: 320g of viscous, slowly crystallizing substance
(Quantitative), OH number 700. Calculated value: C52.5 H8.75 N8.75 Measured value: C52.0 H8.3 N8.4 Example 4 This compound was prepared in the same manner as in Example 1, and 258 g (1
mol) of decanedicarboxylic acid dimethyl ester and
Produced from 210 g (2 moles) of diethanolamine. Yield: 402 g of extremely viscous mass (quantitative). Calculated value: C59.5 H9.88 N6.95 Measured value: C58.3 H9.30 N6.45 Example 5 This compound was prepared in the same manner as in Example 1, and 107 g
(0.46 mol) of methanetricarboxylic acid triethyl ester and 145 g (1.38 mol) of diethanolamine. Yield: 189g (quantitative),
OH number 910. Calculated value: C52.0 H8.4 N11.4 Measured value: C51.5 H8.0 N11.2 Example 6 64.5g of this compound was prepared in the same manner as in Example 1.
(0.2 mol) of 3,3-bis-ethoxycarbonylglutaric acid diethyl ester and 84 g (0.8 mol)
of diethanolamine. Yield: 106 g of extremely viscous residue (quantitative), OH number 800. Calculated value: C47.7 H7.9 N10.0 Measured value: C47.0 H7.4 N 9.7 Example 7 75.5 g of this compound was prepared in the same manner as in Example 1.
(0.25 mol) of 1,2,3,4-cyclopentanetetracarboxylic acid methyl ester and 105 g (1 mol) of diethanolamine. Yield: octahydroxyethyl-1,2,3,4-
Cyclopentanetetracarboxylic acid amide 146g
(Quantitative), OH number: 750. Calculated value: C50.6 H7.6 N9.4 Measured value: C50.0 H7.1 N9.3 Example 8 This compound was prepared in the same manner as in Example 1, and 76 g (0.25
mol) of tetrahydrofuran-2,3,4,5-
Obtained from tetracarboxylic acid methyl ester and 105 g (1 mol) of diethanolamine. yield:
Octahydroxyethyl-tetrahydrofuran-
2,3,4,5-tetracarboxylic acid amide 149g
(Quantitative), OH number: 750. Calculated value: C48.4 H7.2 N9.4 Measured value: C48.2 H7.0 N9.2 Example 9 This compound was prepared in the same manner as in Example 1, and 117 g (0.5
mol) of citric acid trimethyl ester and 157.5g
(1.5 mol) of diethanolamine.
Yield: Hexahydroxyethyl citrate amide
220g (quantitative), OH number: 860. Calculated value: C47.6 H7.7 N9.3 Measured value: C4.71 H7.2 N9.1 Example 10 This compound was prepared in the same manner as in Example 1, and 89 g (0.5
mol) of tartaric acid dimethyl ester and 105 g (1 mol) of diethanolamine. yield:
Tetrahydroxyethyltartaramide 160g (quantitative), OH number: 1040. Calculated value: C44.4 H7.5 N8.6 Measured value: C44.0 H7.2 N8.3 Example 11 This compound was prepared in the same manner as in Example 1, and 266 g (2
1 mole) of diisopropanolamine and 146 g (1 mole) of diisopropanolamine
mol) of oxalic acid diethyl ester. Yield: Tetra-(2-hydroxypropyl)-
Oxalic acid amide 320g (quantitative). Calculated value: C52.5 H8.75 N8.75 Measured value: C51.0 H8.4 N8.3 Example 12 This compound was prepared in the same manner as in Example 1, and 133 g (1
mol) of bis-(3-hydroxypropyl)-amine and 73 g (0.5 mol) of oxalic acid diethyl ester. Yield: 160 g (quantitative) of tetra-(3-hydroxypropyl)-oxalamide. Calculated value: C52.5 H8.75 N8.75 Measured value: C51.3 H8.3 N8.6 Example 12a The methanol is gradually distilled off from 210 g (2 mol) of diethanolamine and 194 g (1 mol) of dimethyl terephthalate to form a clear solution. Finally, pour this solution into a high vacuum at 120°C or more.
When treated at 140° C., a very viscous reaction product is formed quantitatively, which crystallizes on long standing. It dissolves smoothly in water and has an OH number of 656. Calculated value: C56.5 H7.06 N8.24 Measured value: C55.9 H6.90 N8.10 Example 12b Gradual distillation of methanol from 252 g (1 mol) of trimesic acid trimethyl ester and 315 g (3 mol) of diethanolamine produces a clear viscous solution. A high vacuum is then applied at 120 to 140° C. and a reaction product which solidifies into a glass is obtained quantitatively. It dissolves smoothly in water. Calculated value: C53.5 H7.0 N8.9 Measured value: C52.8 H6.8 N8.7 Example 12c Pyromellitic acid tetramethyl ester 310g (1
When methanol is distilled off from 420 g (4 moles) of diethanolamine and diethanolamine, a clear viscous solution gradually forms. Finally, the remaining solvent is distilled off at 130-140° C. in a high vacuum until a very viscous reaction product which solidifies into a glass is obtained. It dissolves smoothly in water and has 745 OH
have a number. Calculated value: C51.7 H6.97 N9.3 Measured value: C50.3 H6.80 N9.2 Example 12d When methanol is distilled off from 360 g (1 mol) of 1,4,5,8-naphthalenetetracarboxylic acid tetramethyl ester and 420 g (4 mol) of diethanolamine, a clear viscous solution is gradually formed,
Finally, volatile substances are distilled off from this at 140° C. in a high vacuum. A highly viscous reaction product which solidifies into a glass is obtained in quantitative yields. It dissolves smoothly in water and has an OH number of 685. Calculated value: C55.2 H6.75 N8.6 Measured value: C54.3 H6.55 N8.4 (B) Example of use of polyhydroxyalkylamides as “cell openers” in polyurethane foam formulations 13 UBT type continuous formula In a block forming reactor, 100 parts by weight of poly(oxyethylene-oxypropylene)-triol starting from trimethylol-propane having an average molecular weight of 6000 and an OH number of 28; water 3.0 parts by weight; triethylenediamine 0.2 parts by weight. 3.6 parts by weight of diisopropanolamine; 1.5 parts by weight of triethanolamine; 2.0 parts by weight of trichlorethyl phosphate; 0.3 parts by weight of a chlorine-containing polysiloxane foam stabilizer; 0.1 part by weight of tin dioctoate; and tetra-
(Hydroxyethyl)-oxalamide (see Example 1) 1.2 parts by weight of tolylene diisocyanate 58.3 to allophanate with an NCO content of 40.5%
React with parts by weight. An open-celled, non-shrinkable, highly elastic foam is produced. Comparative Example 13a For comparison, the foam described in Example 13 was prepared without the addition of tetrahydroxyethyl oxalamide. The resulting foam has closed cells,
Shows considerable shrinkage upon cooling. Comparative Example 13b For further comparison, without adding tetrahydroxyethylamine oxyalate and tin dioctoate,
The foam described in Example 13 was manufactured. The highly elastic foam thus produced showed only slight surface shrinkage phenomena, but its tensile and elongation at break properties were considerably inferior to those of Example 13. The mechanical properties of the foams produced by Example 13 and Comparative Example 13b are compared in Table 1 below.

[Table] Compression hardness

Claims (1)

[Scope of Claims] 1. A polybasic aliphatic, alicyclic and/or aromatic polycarboxylic acid corresponding to the following formula:
N,N-hydroxyalkylamide, In this formula, n is an integer from 2 to 6, and
is a single bond (if n=2), an n-functional C ₁ -C ₁₀ straight-chain or branched alkane group optionally substituted with a hydroxyl group, optionally a heteroatom or a heteroatom in the ring. _C4 - _C6 cycloalkane radicals containing O, S or N- _CH3 as radicals, n-functional _C6 - _C20 aryl radicals optionally substituted with one or more hydroxyl groups; where A is a straight or branched _C2 - _C6 alkylene group optionally containing a hydroxyl group. 2 X is a single bond (n=2), _C1 - _C6 alkylene group (n=2), HC- group (n=3), _H3C・C- group (n=3), HO-C- group (n=3), and 2. A compound according to claim 1, wherein n is an integer from 2 to 4 and A is an ethylene group or a 1,3-trimethylene group. 3 formulas (In this formula, n is an integer from 2 to ₆ , _and an alkane group, optionally O, S or N- as a heteroatom or group of heteroatoms in the ring;
represents a C ₄ -C ₆ cycloalkane group containing CH ₃ , an n-functional C ₆ -C ₂₀ aryl group optionally substituted with one or more hydroxyl groups;
is a straight or branched chain C ₂ − that optionally contains a hydroxyl group.
In the method for producing poly-N,N-hydroxyalkylamides of polybasic aliphatic, alicyclic and/or aromatic polycarboxylic acids corresponding to _C6 alkylene groups, , polycarboxylic acid alkyl ester or polycarboxylic acid aryl ester corresponding to the following formula is used. HN(-A-OH) ₂ (in these formulas, X, A and n are as defined above, and R is a C ₁ -C ₁₀ alkyl group or aryl group) and the split hydroxyl compound ROH is distilled off from the reaction mixture under normal pressure and/or reduced pressure. 4. Polyisocyanate and a compound containing at least two isocyanate-reactive hydrogen atoms and having a molecular weight of 400 to 10,000 in the presence of a catalyst and optionally a foam stabilizer, water and/or an organic blowing agent. Optionally, between 18 and
Based on mixtures containing compounds containing at least two isocyanate-reactive hydrogen atoms and having a molecular weight between 400 and 10,000 for the production of open-cell polyurethane foams by reaction with chain extenders having a molecular weight in the range of 400. as
In an amount of 0.1 to 10% by weight, the formula (In this formula, n is an integer from 2 to ₆ , _and an alkane group, optionally O, S or N- as a heteroatom or group of heteroatoms in the ring;
represents a C ₄ -C ₆ cycloalkane group containing CH ₃ , an n-functional C ₆ -C ₂₀ aryl group optionally substituted with one or more hydroxyl groups;
is a straight or branched chain C ₂ − that optionally contains a hydroxyl group.
A method of using a poly-N,N-hydroxyalkylamide of a polybasic aliphatic, alicyclic and/or aromatic polycarboxylic acid corresponding to _C6 alkylene group as a cell opening component. 5 The polyisocyanate is a modified branched aromatic diisocyanate containing an allophanate group, a biuret group, an isocyanurate group, a carbodiimide group, a urethane group and/or a urea group, the catalyst is an organometallic catalyst, and A is -CH ₂ −
_CH2- and/or _-CH2 - _CH2 - _CH2- groups, and the amount of cell opening component used is
5. A process according to claim 4, in an amount of 0.5 to 7.5% by weight, based on the mixture comprising a compound containing at least two isocyanate-reactive hydrogen atoms and having a molecular weight of 400 to 10,000. 6 The polyisocyanate is a modified branched tolylene diisocyanate containing allophanate groups, biuret groups, isocyanurate groups, urethane groups and/or urea groups, and the catalyst is tin() carboxylate or dialkyltin() dicarboxylate. and A is −CH ₂ −
CH ₂ - group and the amount of cell opening component used is 0.5 based on a mixture containing a compound containing at least two isocyanate-reactive hydrogen atoms and having a molecular weight of 400 to 10,000.
5. The method according to claim 4, wherein the amount is between 2.5% and 2.5% by weight.