DE19628145A1 - Production of microcellular polyurethane elastomers with good static and dynamic mechanical properties - Google Patents

Abstract

Production of microcellular polyurethane elastomers comprises reacting; (A) high molecular weight polyhydroxy compounds and optionally (B) low molecular weight chain extenders and/or crosslinkers with (C) 4,4</>-stilbene diisocyanate in presence or absence of (D) catalysts, foaming agents etc.

Description

The invention relates to a method for producing microcellular polyurethane elastomers.

The production of compact or cellular, e.g. B. microcellular PU elastomers has long been made of numerous patent and lite ratur publications known.

Their technical importance is based on the combination of high quality mechanical properties with the advantages of inexpensive Processing methods. By using different types chemical components in different proportions nissen can be processed thermoplastically or cross-linked, com compact or cellular PU elastomers can be made with regard to their processability and their mechanical properties differentiate differently. An overview of PU-Elasto mere, their properties and applications z. B. in plastic manual, Volume 7, Polyurethane, 1st edition 1966, published from Dr. R. Vieweg and Dr. A. Höchstler, 2nd edition, 1983 out given by Prof. Dr. G.W. Becker and Prof. Dr. D. Braun (Carl- Hanser-Verlag, Munich, Vienna).

Microcellular PU elastomers stand out in relation to the in analogous usable rubber types by their clearly better damping properties with excellent volume pressibility, so that they are components of vibration and shock-absorbing systems, especially in the automotive indu strie, find use. For the production of microcellular PU elastomers have become reaction products from 1,5-NDI and Poly (ethylene glycol adipate) with a molecular weight of 2000, which is in the form of an isocyanate prepolymer with an activator gene, aqueous solution of a fatty acid sulfonate for reaction be brought, proven. (Plastic manual, volume 7, polyure thane, 1st edition, pages 270 ff and E.C. Prolingheuer, J.J. Lindzey, H. Kleimann, Journal of Elastomers and Plastics, Vol. 21, 1981, pages 100-121).

Because such basic formulations contain microcellular PU elastomers very good damping characteristics and static and dynamic performance parameters are from the prior art only isolated efforts known for the good elastomer properties responsible 1.5-NDI, despite its more difficult Handling due to its high melting point, by lighter  to handle manageable and less expensive diisocyanates, because this results in significant mechanical property losses.

The object of the present invention was to provide a ver are ready to manufacture microcellular PU elastomers where the expensive 1,5-NDI is easier to handle and less expensive organic diisocyanates can be replaced. There at should the mechanical properties of the so produced PU elastomers are improved or at least such Essentially correspond to the 1.5 NDI basis. Regardless of the type of the higher molecular weight polyhydroxyl compound used should the microcellular PU elastomers compared to PU elastomers on 4,4′-MDI basis clearly improved static and mechani have characteristic values, in particular compression set, so that they are used to manufacture vibration and shock absorber systems can be used.

Surprisingly, it was found that using 4,4'-stilbene diisocyanate with microcellular polyurethane elastomers extraordinarily good mechanical properties can be obtained.

The invention thus relates to a method for the production of microcellular PU elastomers by the implementation of

• a) higher molecular weight polyhydroxyl compounds and optionally
• b) low molecular chain extension and / or crosslinking average with
• c) 4,4'-stilbene diisocyanate in the absence or in the presence of
• d) catalysts
• e) blowing agents and
• f) additives

According to the preferred method of production, the PU elastomers produced by the prepolymer process, wherein expediently from the higher molecular weight polyhydroxyl compound (a) and 4,4'-stilbene diisocyanate (c) and possibly never the molecular chain extender and / or crosslinking agent (b) a polyaddition containing urethane and isocyanate groups product is manufactured. Microcellular PU elastomers can be made from such prepolymers containing isocyanate groups by Um settlement with water or mixtures of water and optionally  low molecular chain extension and / or crosslinking agents (b) and / or higher molecular weight polyhydroxyl compounds (a) getting produced.

The invention also relates to isocyanate groups Prepolymers with an NCO content of 2 to 20 wt .-%, preferably example, 3.5 to 10 wt .-%, which are produced by reaction at least one higher molecular weight polyhydroxyl compound (a) or a mixture of (a) and a low molecular weight chain extenders and / or crosslinking agents (b) with 4,4'-stilbenes have diisocyanate (c) to a urethane and isocyanate groups the polyaddition product.

To the starting materials (a) to (f) for the production of the compact or preferably cellular, e.g. B. microcellular PU elastomers and the method according to the invention is to be carried out as follows:

• a) Suitable higher molecular weight polyhydroxyl compounds advantageously have a functionality of 3 or preferably 2 and a molecular weight of 500 to 6000, preferably from 800 to 3500 and in particular from 1000 to 3300 and advantageously consist of hydroxyl-containing poly mers, for. B. polyacetals, such as polyoxymethylenes and especially water-insoluble formals, e.g. B. Polybutanediol formal and Po lyhexanediol formal, polyoxyalkylene polyols, such as. B. polyoxy butylene glycols, polyoxybutylene polyoxyethylene glycols, poly oxybutylene polyoxypropylene glycols, polyoxybutylene polyoxypropylene polyoxyethylene glycols, polyoxy propylene polyols and polyoxypropylene polyoxyethylene polyols, and polyester polyols, e.g. B. polyester polyols from organic dicarboxylic acids and / or dicarboxylic acid derivatives and 2- to 3-valent alcohols and / or dialkylene glycols, from hydroxy carboxylic acids and lactones and polycarbonates containing hydroxyl groups.
  As a higher molecular weight polyhydroxyl compound have proven to be excellent and are therefore preferably used difunctional polyhydroxyl compounds with molecular weights from greater than 800 to 3500, preferably from 1000 to 3300 selected from the group of polyester polyols, hydroxyl-containing polycarbonates and polyoxybutylene glycols. The higher molecular weight polyhydroxyl compounds can be used individually or as mixtures.
  Suitable polyoxyalkylene polyols can be prepared by known processes, for example by anionic polymerization with alkali metal hydroxides, such as. As sodium or potassium hydroxide, or alkali alcoholates, such as. Example, sodium methylate, sodium or potassium ethylate or potassium isopropylate, as catalysts and with the addition of at least one starter molecule which contains 2 or 3, preferably 2 reactive hydrogen atoms bonded, or by cationic polymerization with Lewis acids, such as, for. B. antimony pentachloride, boron fluoride etherate or bleaching earth as catalysts from one or more alkylene oxides having 2 to 4 carbon atoms in the alkylene radical.
  Suitable alkylene oxides are, for example, 1,3-propylene oxide, 1,2-or. 2,3-butylene oxide, preferably ethylene oxide and 1,2-propylene oxide and in particular tetrahydrofuran. The alkylene oxides can be used individually, alternately in succession or as a mixture. Examples of suitable starter molecules are: water, organic dicarboxylic acids, such as succinic acid, adipic acid, phthalic acid and terephthalic acid, aliphatic and aromatic, N-mono- and N, N'-dialkyl-substituted diamines with 1 to 4 carbon atoms in the alkyl radical, such as mono - And dialkyl-substituted ethyl namin, 1,3-propylenediamine, 1,3- or 1,4-butylenediamine, 1,2-, 1,3-, 1,4-, 1,5-, and 1,6-hexamethylene diamine , Alkanolamines, such as. B. ethanolamine, N-methyl and N-ethyl-diethanolamine and trialkanolamines, such as. B. triethanolamine and ammonia. Before preferably used are bivalent and / or trivalent alcohol, z. B. alkanediols having 2 to 12 carbon atoms, preferably 2 to 4 carbon atoms, such as. B. ethanediol, 1,2-propanediol and 1,3, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, glycerol and trimethylolpropane and dialkylene glycols, such as, for. B. diethylene glycol and dipropylene glycol.
  Preferred polyoxyalkylene polyols used are polyoxybutylene glycols (polyoxytetramethylene glycols) with molecular weights from 500 to 3000, preferably from 650 to 2300.
  Polyhydroxyl compounds (a) which can preferably be used are furthermore polyester polyols which, for example, from alkane dicarboxylic acids having 2 to 12 carbon atoms, preferably alkane dicarboxylic acids having 4 to 6 carbon atoms and / or aromatic dicarboxylic acids and polyhydric alcohols, preferably alkane diols having 2 to 12 carbon atoms, preferably 2 to 6 carbon atoms and / or dialkylene glycols can be produced. Examples of suitable alkanedicarboxylic acids are: succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid and decanedicarboxylic acid. Suitable aromatic dicarboxylic acids are e.g. B. phthalic acid, isophthalic acid and terephthalic acid. The alkanedicarboxylic acids can be used either individually or in a mixture with one another. Instead of the free dicarboxylic acids, the corresponding dicarboxylic acid derivatives, such as. B. dicarboxylic acid mono- or diesters from Alko fetch with 1 to 4 carbon atoms or dicarboxylic acid anhydrides are used. Dicarboxylic acid mixtures of succinic, glutaric and adipic acid are preferably used in proportions of, for example, 20 to 35: 35 to 50: 20 to 32 parts by weight, and in particular adipic acid. Examples for dihydric and polyhydric alcohols, especially alkanediols or dialkylene glycols are: ethanediol, diethylene glycol, 1,2- or 1,3-propanediol, dipropylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6- Hexanediol, 1,10-decanediol, glycerin and trimethylolpropane. Ethanediol, diethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol or mixtures of at least two of the diols mentioned, in particular mixtures of 1,4-butanediol, 1,5-pentanediol and 1, are preferably used. 6-hexanediol. Polyester polyols from lactones, e.g. B. ε-caprolactone or hydroxycarboxylic acids, e.g. B. ω-hydroxycaproic acid.
  To prepare the polyester polyols, the aromatic and / or aliphatic dicarboxylic acids and preferably alkane dicarboxylic acids and / or derivatives and polyhydric alcohols can be catalyst-free or preferably in the presence of esterification catalysts, advantageously in an atmosphere of inert gases, such as, for. B. nitrogen, helium, argon and others in the melt at temperatures of 150 to 250 ° C, preferably 180 to 220 ° C, optionally under reduced pressure to the desired acid number, which is advantageously less than 10, preferably less than 2, polycondensed. According to a preferred embodiment, the esterification mixture is polycondensed at the above temperatures up to an acid number of 80 to 30, preferably 40 to 30, under normal pressure and then under a pressure of less than 500 mbar, preferably 50 to 150 mbar. Examples of suitable esterification catalysts are iron, cadmium, cobalt, lead, zinc, antimony, magnesium, titanium and tin catalysts in the form of metals, metal oxides or metal salts. The polycondensation can, however, also in the liquid phase in the presence of diluents and / or entraining agents, such as. B. benzene, toluene, xylene or chlorobenzene, for azeotropic distillation of the condensation water.
  To prepare the polyester polyols, the organic polycarboxylic acids and / or derivatives and polyhydric alcohols are advantageously polycondensed in a molar ratio of 1: 1 to 1.8, preferably 1: 1.05 to 1.2.
  As polyester polyols are preferably used poly (al kandioladipate) such. B. poly (ethanediol adipates), poly (1,4-butanediol adipates), poly (ethanediol-1,4-butanediol adipates), poly (1,6-hexanediol-neopentylglycol adipates) and poly (1,6-he xanediol-1,4 -butanediol adipates) and polycaprolactones.
  Suitable polyester polyols also include hydroxyl-containing polycarbonates. Such hydroxyl group-containing polycarbonates can be prepared, for example, by reacting the abovementioned alkanediols, in particular 1,4-butanediol and / or 1,6-hexanediol, and / or dialkylene glycols, such as, for. B. diethylene glycol, dipropylene glycol and dibutylene glycol, with dialkyl or diaryl carbonates, e.g. B. diphenyl carbonate, or phosgene.
  As polycarbonates containing hydroxyl groups, preference is given to using polyether polycarbonate diols which can be prepared by polycondensation of
  • a1) Polyoxybutylene glycol with a molecular weight of
    150 to 500 or from
  • a2) Mixtures that consist of
    • i) at least 10 mol%, preferably 50 to 95 mol% of a polyoxybutylene glycol with a molecular weight of 150 to 500 (a1) and
    • ii) less than 90 mol%, preferably 5 to 50 mol% of at least one of (a1) different polyoxyalkylene glycol having a molecular weight of 150 to 2000, at least one dialkylene glycol, at least one linear or branched alkane diol having 2 to 12 carbon atoms and at least a cyclic alkanediol with 5 to 15 carbon atoms or mixtures thereof with phosgene, diphenyl carbonate or dialkyl carbonates with C₁ to C₄ alkyl groups.
• b) In addition to the higher molecular weight polyhydroxyl compounds (a), low molecular weight difunctional chain extenders (b), low molecular weight, preferably tri- or tetrafunctional crosslinking agents (b) or mixtures of chain extensions can optionally be used to produce the compact or preferably cellular PU elastomers by the process according to the invention - And crosslinking agents are used.
  Such chain extenders and crosslinking agents (b) who used to modify the mechanical properties, in particular the hardness of the PU elastomers. Ge suitable chain extenders, such as. B. alkanediols, dialkylene glycols and polyoxyalkylene glycols and crosslinking agents, for. B. trihydric or tetravalent alcohols and oligomeric poly oxyalkylene polyols with a functionality of 3 to 4, usually sit molecular weights less than 800, preferably from 18 to 400 and in particular from 60 to 300. Alkanediols with 2 are preferably used as chain extenders to 12 carbon atoms, preferably 2.4 or 6 carbon atoms, such as. B. ethane, 1,3-propane, 1,5-pentane, 1,6-hexane, 1,7-heptane, 1,8-octane, 1,9, nonane, 1, 10 -Decanediol and especially 1,4-butanediol and dialkylene glycols with 4 to 8 carbon atoms, such as. B. diethylene glycol and dipropylene glycol and polyoxyalkylene glycols. However, Ge are also branched chain and / or unsaturated alkane diols with usually no more than 12 carbon atoms, such as. B. 1,2-propanediol, 2-methyl-, 2,2-dimethyl-propanediol-1,3, 2-butyl-2-ethylpropanediol-1,3, butene-2-diol-1,4 and butyne-2 -diol-1,4, diester of terephthalic acid with glycols having 2 to 4 carbon atoms, such as. B. terephthalic acid bis-ethylene glycol or 1,4-butanediol, hydroxyalkylene ether of hydroquinone or resorcinol, such as. B. 1,4-di- (p-hydroxy-ethyl) -hydroquinone or 1,3-di- (β-hydroxyethyl) - resorcinol, alkanolamines with 2 to 12 carbon atoms, such as. B. ethanolamine, 2-aminopropanol and 3-amino-2,2-dimethylpropanol, N-alkyldialkanolamines, such as. B. N-methyl and N-ethyl-diethanolamine, (cyclo) aliphatic diamines having 2 to 15 carbon atoms, such as. B. ethylene, 1,2-, 1,3-propylene, 1,4-butylene and 1,6-hexamethylene diamine, isophorone diamine, 1,4-cyclohexylene diamine and 4,4'-diamino -dicyclo hexylmethane, N-alkyl and N, N'-dialkyl-alkylenediamines such as. B. N-methylpropylenediamine and N, N'-dimethylethylene diamine and aromatic diamines, such as. B. methylene-bis (4-amino-3-ben methyl zoate), 1,2-bis (2-aminophenyl-thio) ethane, trimethylene glycol di-p-aminobenzoate, 2,4- and 2,6- Toluene diamine, 3,5-diethyl-2,4- and -2,6-toluenediamine, 4,4'-diamine-di-phenylmethane, 3,3'-dichloro-4,4'-diamino-diphenylme than and primary ortho-di-, tri- and / or tetraalkyl-substituted 4,4'-diamino-diphenylmethanes, such as. B. 3,3'-di- and 3,3 ', 5,5'-tetraisopropyl-4,4'-diamino-diphenylmethane.
  Examples of at least trifunctional crosslinking agents which are expediently used for the production of the PU cast elastomers are: trifunctional and tetrafunctional alcohols, such as. As glycerol, trimethylolpropane, pen taerythritol and trihydroxycyclohexane and tetrahydroxyalkylene diamine, such as. B. tetra (2-hydroxyethyl) ethylene diamine or tetra (2-hydroxypropyl) ethylene diamine and oligomeric poly oxyalkylene polyols with a functionality of 3 to 4.
  The chain extenders and crosslinking agents (b) suitable according to the invention can be used individually or in the form of mixtures. Mixtures of chain extenders and crosslinking agents can also be used.
  To adjust the hardness of the PU elastomers, the structural components (a) and (b) can be varied in relatively wide proportions, the hardness increasing with increasing content of difunctional chain extenders and at least trifunctional crosslinking agents in PU elastomers.
  Depending on the desired hardness, the required amounts of the structural components (a) and (b) can be determined experimentally in a simple manner. 5 to 50% by weight of the chain extender and / or crosslinking agent (b) are advantageously used, based on the weight of the higher molecular weight polyhydroxyl compound (a), 30 to 50% by weight preferably being used to produce hard PU elastomers. % are used.
• c) To produce the microcellular polyethane elastomers, det, according to the invention, 4,4, -style diisocyanate (c) use.
  Preferred embodiments are those in which the 4,4'-stilbene diisocyanate (c) is used in the form of a prepolymer containing isocyanate groups. This can be produced, for example, by reacting 4,4'-stilbene diisocyanate with at least one high molecular weight polyhydroxyl compound (a) or a mixture of (a) and at least one low molecular weight chain extender and / or crosslinking agent (b).
  As already stated, mixtures of (a) and (b) can be used to prepare the prepolymers containing isocyanate groups. According to a preferred embodiment, however, the prepolymers containing isocyanate groups are prepared by reacting only higher molecular weight polyhydroxyl compounds (a) with 4,4'-style bendiisocyanate (c). Particularly suitable for this purpose are difunctional polyhydroxyl compounds with a molecular weight of 500 to 6000, preferably greater than 800 to 3500, in particular 1000 to 3300, which are selected from the group of polyester polyols, hydroxyl-containing polycarbonates and polyoxytetramethylene glycols.
  The isocyanate groups which can be used according to the invention advantageously have an isocyanate content of from 2 to 20% by weight, preferably from 3.5 to 10% by weight, based on their total weight.
  To prepare the prepolymers containing isocyanate groups, the higher molecular weight polyhydroxyl compounds (a) or mixtures of (a) and lower molecular chain extenders and / or crosslinking agents (b) with 4,4′-stilbene diisocyanate at temperatures from 80 to 160 ° C., preferably from 110 to 150 ° C are reacted.
  After the theoretically calculated isocyanate content has been reached, the reaction is terminated. This usually requires reaction times in the range from 15 to 200 minutes, preferably from 40 to 150 minutes.
  The prepolymers containing isocyanate groups can be prepared in the presence of catalysts. However, it is also possible to prepare the prepolymers containing isocyanate groups in the absence of catalysts and to lend them to the reaction mixture for producing the PU elastomers.
• d) Compounds are expediently used as catalysts (d) used the reaction of the hydroxyl groups Compounds of components (a) and optionally (b) with Accelerate 4,4'-stilbene diisocyanate (c). In consideration come organic metal compounds, preferably organic Tin compounds such as tin (II) salts of organic carbon acids, e.g. B. tin (II) acetate, tin (II) octoate,  Tin (II) ethylhexoate and tin (II) laurate and the dialkyl Tin (IV) salts of organic carboxylic acids, e.g. B. Dibutyl tin diacetate, dibutyltin dilaurate, dibutyltin maleate and Dioctyltin diacetate. The organic metal compounds who the alone or preferably in combination with strong basi used amines. For example Amidines such as 2,3-dimethyl-3,4,5,6-tetrahydropyrimidine, ter tertiary amines such as triethylamine, tributylamine, dimethylbenzyl amine, N-methyl, N-ethyl, N-cyclohexylmorpholine, N, N, N ', N'- Tetraalkylalkylenediamines, such as e.g. B. N, N, N ', N'-tetramethylethy lendiamine, N, N, N ', N'-tetramethylbutane diamine or hexane dia min, pentamethyl-diethylenetriamine, tetramethyl-diaminoethyl ether, bis (dimethylaminopropyl) urea, 1,4-dimethyl piperazine, 1,2-dimethylimidazole, 1-azabicyclo (3,3,0) octane and preferably 1,4-diazabicyclo (2,2,2) octane and alkanol amine compounds, such as triethanolamine, triisopropanolamine, N- Methyl and N-ethyldiethanolamine and dimethylethanolamine. 0.001 to 3% by weight, in particular, are preferably used the other 0.01 to 1 wt .-% catalyst or catalyst combination tion based on the weight of the structural components (a), (c) and optionally (b).
• e) In the absence of moisture and physically or chemically active blowing agents, compact PU elastomers, such as, for. B. PU-Gießela stomers are produced. However, the method is preferably used for the production of cellular, preferably microcellular PU elastomers. Water is used as blowing agent (s) for this purpose, which reacts with the organic polyisocyanates and preferably isocyanate group-containing prepolymers (a) in situ to form carbon dioxide and amino groups, which in turn react further with the isocyanate prepolymers to form urea groups and thereby as chain extenders Act.
  Since the structural components (a) and optionally (b) may have water due to the preparation and / or chemical composition, in some cases it is not necessary to separately add water to the structural components (a) and, if appropriate, (b) or the reaction mixture. However, if water has to be incorporated into the polyurethane formulation in order to achieve the desired density, this is usually in amounts of 0.001 to 3.0% by weight, preferably 0.01 to 2.0% by weight and in particular from 0.2 to 1.2% by weight, based on the weight of the structural components (a) to (c), is used.
  As blowing agent (s) instead of water or preferably in combination with water, low-boiling liquids which evaporate under the influence of the exothermic polyaddition reaction and advantageously have a boiling point under atmospheric pressure in the range from -40 to 120 ° C, preferably from 10 to Have 90 ° C, or gases are used as physical blowing agents or chemical blowing agents.
  The liquids suitable as blowing agents of the above-mentioned type and gases can, for. B. selected from the group of alkanes such. B. propane, n- and iso-butane, n- and iso-pen tan and preferably the technical pentane mixtures, cycloalkanes and cycloalkenes such as. B. cyclobutane, cyclopentene, cyclohexene and preferably cyclopentane and / or cyclohexane, dialkyl ethers, such as. B. dimethyl ether, methyl ethyl ether or diethyl ether, tert-butyl methyl ether, cycloalkylene ether, such as. B. furan, ketones, such as. B. acetone, methyl ethyl ketone, acetals and / or ketals, such as. B. formaldehyde dimethyl acetal, 1,3-dioxolane and acetone dimethyl acetal, carboxylic acid esters, such as. B. ethyl acetate, methyl formate and ethylene acrylic acid tert-butyl ester, tertiary alcohols, such as. B. tertiary butanol, fluoroalkanes, which are broken down in the troposphere and are half harmless to the ozone layer, such as. B. trifluoromethane, difluoromethane, difluoroethane, tetrafluoroethane and He xafluoroethane, chloroalkanes, such as. B. 2-chloropropane, and gases such as. B. nitrogen, carbon monoxide and noble gases such. B. He lium, neon and krypton and analog water-chemical blowing agents such as carboxylic acids, such as. B. formic acid, acetic acid and propionic acid.
  Of the liquids suitable as blowing agents (e) and inert with respect to NCO groups, alkanes with 4 to 8 C atoms, cycloalkanes with 4 to 6 C atoms or mixtures with a boiling point of -40 ° C. to 50 ° C. under atmospheres are preferred pressure from alkanes and cycloalkanes used. In particular, C₅- (cyclo) alkanes such as. B. n-pentane, isopentanes and cyclopentane and their technical mixtures.
  Also suitable as blowing agents are salts which decompose thermally, such as. B. ammonium bicarbonate, ammonium carba mat and / or ammonium salts of organic carboxylic acids, such as. B. the monoammonium salts of malonic acid, boric acid, formic acid or acetic acid.
  The most appropriate amount of solid propellants, LOW-end liquids and gases, each individually or in the form of mixtures, e.g. B. can be used as liquid or gas mixtures or as gas-liquid mixtures depends on the density that you want to achieve and the amount of water used. The required quantities can easily be determined by simple manual tests. Satisfactory results usually provide amounts of solids from 0.5 to 35 parts by weight, preferably from 2 to 15 parts by weight, liquid amounts from 1 to 30 parts by weight, preferably from 3 to 18 parts by weight and / or gas amounts of 0.01 to 80 parts by weight, preferably from 10 to 35 parts by weight, each based on the weight of the components (a), (c) and optionally (b). The gas load with z. B. air, carbon dioxide, nitrogen and / or helium can take place both via the higher molecular chain extenders and / or crosslinking agents (b) and via the polyisocyanates (c) or via (a) and (c) and optionally (b). Perfluorochlorohydrocarbons are not used as blowing agents, as has already been stated.
• f) If appropriate, additives (f) can also be incorporated into the reaction mixture for producing the compact and preferably cellular PU elastomers. Examples include surface-active substances, foam stabilizers, cell regulators, fillers, flame retardants, nucleating agents, antioxidants, stabilizers, lubricants and mold release agents, dyes and pigments.
  As surface-active substances such. B. compounds into consideration, which serve to support the homogenization of the starting materials and, if appropriate, are also suitable for regulating the cell structure. Emulsifiers, such as. B. the sodium salts of castor oil sulfates or of fatty acids and salts of fatty acids with amines, for. B. oleic acid diethylamine, stearic acid diethanolamine, ricinoleic acid diethanolamine, salts of sulfonic acids, for. B. alkali metal or ammonium salts of dodecylbenzene or dinaphthylmethane disulfonic acid and ricinoleic acid foam stabilizers, such as siloxane-oxalkylene copolymers and other organopolysiloxanes, oxyethylated alkylphenols, oxyethylated fatty alcohols, paraffin oils, castor oil or ricinoleic acid esters, paraffin oil, paraffin oil, turkish rotine oil ester, Fatty alcohols and dimethylpolysiloxanes. To improve the emulsifying effect, the cell structure and / or their stabilization, oligomeric polyacrylates with polyoxyalkylene and fluoroalkane radicals are also suitable as side groups. The surface-active substances are usually used in amounts of 0.01 to 5 parts by weight, based on 100 parts by weight of the higher molecular weight polyhydroxyl compounds (a).
  Fillers, in particular reinforcing fillers, are the conventional organic and inorganic fillers, reinforcing agents and weighting agents known per se. The individual examples include: organic fillers such as silicate minerals, example layered silicates such as antigorite, serpentine, hornblende, amphibole, chrisotile, talc, metal oxides such as kaolin, aluminum oxides, aluminum silicate, titanium oxides and iron oxides, metal salts such as chalk, heavy spar and inorganic pigments , such as cadmium sulfide, zinc sulfide and glass particles. Suitable organic fillers are, for example; Carbon black, melamine, expanded graphite, rosin, cyclopentadienyl resins and graft polymers.
  The reinforcing fillers used are preferably fibers, for example carbon fibers or in particular glass fibers, especially when high heat resistance or very high rigidity is required, the fibers being able to be equipped with adhesion promoters and / or sizes. Suitable glass fibers, e.g. B. also in the form of glass fabrics, mats, nonwovens and / or preferably glass silk rovings or cut glass silk from low-alkali E-glasses with a diameter of 5 to 200 μm, preferably 6 to 15 μm, are used after their incorporation in the molding compositions generally an average fiber length of 0.05 to 1 mm, preferably from 0.1 to 0.5 mm.
  The inorganic and organic fillers can be used individually or as mixtures and are usually the reaction mixture in amounts of 0.5 to 50 wt .-%, preferably 1 to 30 wt .-%, based on the weight of the structural components (a ) to (c).
  Suitable flame retardants are, for example, tricresyl phosphate, tris (2-chloroethyl) phosphate, tris (2-chloropropyl) phosphate, tris (1,3-dichloropropyl) phosphate, tris (2,3-dibromopropyl) phosphate and tetrakis - (2-chloroethyl) ethylene diphosphate.
  In addition to the halogen-substituted phosphates already mentioned, inorganic flame retardants such as red phosphorus, aluminum oxide hydrate, antimony trioxide, arsenic trioxide, ammonium polyphosphate and calcium sulfate or cyanuric acid derivatives, such as. B. melamine or mixtures of at least two flame retardants, such as. B. ammonium polyphosphates and melamine and optionally starch and / or expandable graphite for flame retarding the PU elastomers produced according to the invention can be used. In general, it has proven expedient to use 5 to 50 parts by weight, preferably 5 to 25 parts by weight of the flame retardants or mixtures mentioned for 100 parts by weight of the structural components (a) to (c) .
  As nucleating agents such. B. talc, calcium fluoride, sodium phenylphosphinate, aluminum oxide and finely divided poly tetrafluoroethylene in amounts up to 5 wt .-%, based on the total weight of the components (a) to (c), are used.
  Suitable oxidation retarders and heat stabilizers that can be added to the PU elastomers according to the invention are, for example, halides of metals of group I of the periodic system, e.g. B. sodium, potassium, lithium halides, optionally in combination with copper (I) halides, for. B. chlorides, bromides or iodides, sterically hindered phenols, hydroquinones and substituted connec tions of these groups and mixtures thereof, which are preferably used in a concentration of up to 1% by weight, based on the weight of the structural components (a) to (c) will.
  Examples of UV stabilizers are various substituted resorcinols, salicylates, benzotriazoles and benzophenones as well as sterically hindered amines, which are generally present in amounts of up to 2.0% by weight, based on the weight of the components (a) to (c). , are used.
  Lubricants and mold release agents, which are generally also added in amounts of up to 1% by weight, based on the weight of the structural components (a) to (c), are stearic acids, stearyl alcohol, stearic acid esters and amides and also Fatty acid esters of pentaerythritol.
  Organic dyes such as nigrosine, pigments, e.g. As titanium dioxide, cadmium sulfide, cadmium sulfide selenide, Phtha locyanine, ultramarine blue or carbon black can be added.
  More detailed information on the other customary auxiliaries and additives mentioned above can be found in the specialist literature, for example the monograph by JH Saunders and KC Frisch "High Polymers", Volume XVI, Polyurethanes, Parts 1 and 2, published by Interscience Publishers 1962 and 1964, or in the plastics manual, Polyurethane, Volume VII, Carl Hanser Verlag, Munich, Vienna, 1st, 2nd and 3rd editions, 1966, 1983 and 1993.
  To produce the compact or preferably cellular PU elastomers, in the presence or absence of catalysts (d), physically active blowing agents (e) and additives (f), the higher molecular weight polyhydroxyl compounds (a), optionally low molecular weight chains, can be extended and / or Crosslinking agents (b) and, if appropriate, the chemically active blowing agents, preferably the isocyanate group-containing prepolymers from (a), (b) and (c) or preferably from (a) and (c) and chain extenders and / or crosslinking agents (b), mixtures of Aliquots (a) and (b), mixtures of aliquots (a), (b) and water or preferably mixtures of (b) and water or water are reacted in amounts such that the equivalence ratio of NCO groups of the polyisocyanates ( c) or prepolymers containing isocyanate groups to the sum of the reactive hydrogens of components (a) and optionally (b) and optionally the chemically active blowing agents is 0.8 to 1.2: 1, preferably 0.95 to 1.15: 1 and in particular 1.00 to 1.05: 1.
  The compact or preferably cellular PU elastomers can be according to the methods described in the literature, such as. B. the one shot or preferably prepolymer process, using known mixing devices.
  To produce the compact PU elastomers, the starting components, in the absence of blowing agents (e), are usually mixed homogeneously at a temperature of 80 to 160 ° C., preferably 110 to 150 ° C., and the reaction mixture is introduced into an open, optionally tempered mold and let it harden. To form cellular PU elastomers, the structural components can be mixed in the same way in the presence of a blowing agent, preferably water, and filled into the mold, which may be tempered. After filling, the mold is closed and the reaction mixture with compression, for. B. with a degree of compaction from 1.1 to 8, preferably from 1.2 to 6 and in particular from 2 to 4 foam to form bodies. As soon as the moldings have sufficient strength, they are removed from the mold. The demolding times depend, among other things, on the mold temperature, geometry and the reactivity of the reaction mixture and are usually in a range from 10 to 180 minutes.
  The microcellular PU elastomers show excellent static and dynamic characteristics. Due to their specific damping characteristics and long-term use properties, they are used in particular in vibration and shock absorber systems.
  The compact PU elastomers produced by the process according to the invention have a density without filler of 1.0 to 1.4 g / cm³, preferably from 1.1 to 1.25 g / cm³, products containing fillers usually having a density greater than Have 1.2 g / cm³. The cellular PU elastomers show densities from 0.2 to 1.1 g / cm³, preferably from 0.35 to 0.80 g / cm³.
  The PU elastomers produced by the process are used for the production of moldings, transportation sector. The cellular PU elastomers are particularly suitable for the production of damping and spring elements such. B. for means of transport, preferably motor vehicles, buffers and cover layers.

Examples Comparative Example I a) Preparation of a prepolymer having an isocyanate group based on 1.5 NDI

1000 parts by weight (0.5 mol) of a poly (ethanediol (0.5 mol) -1.4- butanediol (0.5 mol) adipate (1 mol)) with an average mentally determined hydroxyl number) were heated to 140 ° C. and at this temperature with 240 parts by weight (1.14 mol) fixed 1,5-NDI with intensive stirring and to the reak tion brought.

A prepolymer with an NCO content of 4.32% by weight and a viscosity at 90 ° C of 2800 mPas (ge measure with a rotary viscometer from Haake  which also the viscosities of the following comparative examples and examples are measured).

b) Production of cellular molded parts

Crosslinker component that consisted of
20.7 parts by weight of 2,2 ', 6,6'-tetraisopropyldiphenyl-carbodiimide
2.9 parts by weight of a mixture of ethoxylated oleic and ricinoleic acid with an average of 9 oxyethylene units
3.8 parts by weight of the monoethanolamine salt of n-alkylbenzenesulfonic acid with C₉ to C₁₅ alkyl radicals
36.3 parts by weight sodium salt of sulfated castor oil
36.3 parts by weight of water and
0.03 part by weight of a mixture
30 wt .-% pentamethyl-diethylenetriamine and
70% by weight of N-methyl-N '- (dimethylaminomethyl) piperazine.

100 parts by weight of the isocyanate prepolymer heated to 90 ° C. res, prepared according to Comparative Example Ia, were with 2.4 Parts by weight of the crosslinker component in about 8 seconds stirred vigorously. The reaction mixture was then opened Lockable, metallic mold at 80 ° C filled, the mold closed and the reaction let the mixture harden. After 25 minutes the micro cellular moldings demolded and for thermal post-curing annealed at 110 ° C for 16 hours.

Comparative Example II a) Preparation of a prepolymer containing isocyanate groups on a 4,4′-MDI basis

A mixture of 1000 parts by weight of that in Comparative Example 1 described poly (ethanediol-1,4-butanediol adipate) and 3 parts by weight of trimethylolpropane was analogous to the information from Comparative Example II with 380 parts by weight (1.52 mol) at 50 ° C. tempered 4,4'-MDI implemented.  

A prepolymer with an NCO content of 5.80 was obtained % By weight and a viscosity at 90 ° C of 1750 mPas (measured with a rotary viscometer).

b) Production of cellular molded parts

From 100 parts by weight of the prepolymer according to the comparative example IIa and 3.1 parts by weight of the crosslinking component according to Ver same example Ib were analogous to the information in the comparison example I made molded body.

Comparative Example III a) Preparation of a prepolymer containing isocyanate groups based on TODI

The procedure was analogous to that of Comparative Example Ia, however used 290 parts by weight (1,097 mol) 3,3'-dimethyl-4,4'-biphenyl diisocyanate (tolidinediiso cyanate (TODI)).

A prepolymer with an NCO content of 3.76 was obtained % By weight and a viscosity at 90 ° C of 5100 mPas (measured with a rotary viscometer).

b) Production of cellular molded parts

From 100 parts by weight of the prepolymer according to the comparative example IIIa and 2.07 parts by weight of the crosslinking component according to Ver same example Ib were analogous to the information in the comparison example I molded body made only after a shape tool life of 40 minutes demolded and for thermal post-processing curing at 110 ° C for 16 hours.

example 1 a) Preparation of a prepolymer containing isocyanate groups based on 4,4'-stilbene diisocyanate

1000 parts by weight (0.5 mol) of a poly (ethanediol (0.5 mol) - 1,4-butanediol (0.5 mol) adipate (1 mol) with a through average molecular weight of 2000 (calculated from the experimentally determined hydroxyl number) were at 140 ° C warms and at this temperature with 340 parts by weight (1.30 mol) solid 4,4'-stilbene diisocyanate with intensive Stirring added and brought to reaction.  

A prepolymer with an NCO content of 4.28 was obtained Wt .-% and a viscosity of 11000 (measured with a Rotational viscometer).

b) Production of cellular moldings

100 parts by weight of the isocyanate prepoly heated to 90 ° C. mers, produced according to Example Ia, was under intensive Stir with 2.44 parts by weight of the crosslinking component, here represents according to comparative example Ib, mixed.

After a stirring time of about 8 seconds, the reaction mixture into a lockable metal that is tempered to 80 ° C filled mold, the mold locked sen and let the reaction mixture harden. After 30 mi The mold life was removed from the microcellular molded body forms and for thermal post-curing at 110 ° C for 16 hours long annealed.

Example 2 a) Preparation of a prepolymer containing isocyanate groups on a 4.4 ′ stilbene diisocyanate base

1000 parts by weight (0.5 mol) of a poly (ethanediol (0.5 mol) - 1,4-butanediol (0.5 mol) adipate (1 mol)) with a through average molecular weight of 2000 (calculated from the experimentally determined hydroxyl number) were at 140 ° C warms and at this temperature with 382 parts by weight (1.46 mol) solid 4,4'-stilbene diisocyanate with intensive Stirring added and brought to reaction.

A prepolymer with an NCO content of 5.40 was obtained % By weight and a viscosity of 5500 mPas (measured with a Rotational viscometer).

b) Production of cellular moldings

100 parts by weight of the isocyanate prepoly heated to 90 ° C. mers, prepared according to Example 2a, were under intensive Stir with 3.08 parts by weight of the crosslinker component represents according to comparative example Ib, mixed.

After a stirring time of about 8 seconds, the reaction mixture into a lockable metal that is tempered to 80 ° C filled mold, the mold locked sen and let the reaction mixture harden. After 30 mi  The mold life was removed from the microcellular molded body forms and for thermal post-curing at 110 ° C for 16 hours long annealed.

table

Static and dynamic mechanical properties of the cellular PUR elastomers according to Comparative Examples I to III and Examples 1 and 2

Process for the production of microcellular polyurethane elastomers and suitable isocyanate prepolymers.

Claims (11)

1. Process for the preparation of microcellular polyurethane elastomers by reacting

• a) High molecular weight polyhydroxyl compounds and if appropriate
• b) low molecular chain extenders and / or crosslinking agents
• c) 4,4'-stilbene diisocyanate in the absence or preferably the presence of
• d) catalysts
• e) blowing agents and
• f) additives

2. The method according to claim 1, characterized in that the higher molecular weight polyhydroxyl compounds a functionality from 2 to 3 and a molecular weight from 500 to 6000 be to sit. 3. The method according to claim 1, characterized in that the higher molecular weight polyhydroxyl compounds are difunctional, have a molecular weight of 800 to 3500 and selected are from the group of polyester polyols, hydroxyl groups containing polycarbonates and polyoxybutylene glycols. 4. The method according to any one of claims 1 to 3, characterized records that the chain extender is a molecular own weight up to 800 and are selected from the group the alkanediols, dialkylene glycols and polyoxyalkylene glycols and the crosslinking agents have a molecular weight of up to 800 be sit and are selected from the group of 3 or 4 people term alcohols and oligomeric polyoxyalkylene polyols with a Functionality from 3 to 4.   5. The method according to any one of claims 1 to 3, characterized in that

• a) a prepolymer with an NCO content of 2 to 20 wt .-% is prepared in a first reaction step from 4,4'-stilbene diiso cyanate and higher molecular weight polyhydroxyl compounds and optionally a low molecular chain extender and / or crosslinking agent
• b) the prepolymer obtained is reacted in a second reaction step with water or a mixture of water and low molecular weight chain extender and / or crosslinking agent.

6. The method according to any one of claims 1 to 3, characterized in that

• a) in a first reaction step from 4,4'-stilbene diiso cyanate and part of the higher molecular weight polyhydroxyl compound and optionally a low molecular weight chain extender and / or crosslinking agent a prepolymer is prepared and
• b) the prepolymer obtained is reacted in a second reaction step with a mixture of the rest of the higher molecular weight polyhydroxyl compound, water and optionally a chain extender and / or crosslinking agent.

7. The method according to claim 1, characterized in that the Ratio of the NCO group of component (c) to the Zerewiti noff active hydrogen atoms of components (a), (b) and (e) is 0.8 to 1.3. 8. The method according to claim 1, characterized in that the amount of water used up to 5% by weight based on the total weight of components (a), (c) and optionally (b) be wearing. 9. The method according to any one of claims 1 to 8, characterized records that per 1 mole of higher molecular weight polyhydroxyl compound 0 to 0.3 mol chain extension and / or crosslinking means are used.   10. The method according to any one of claims 1 to 9, characterized records that the blowing agent (e) is selected from the Group of the alkanes with 4 to 8 C atoms and the cycloalkanes with 4 to 6 carbon atoms. 11. The method according to any one of claims 1 to 10, characterized records that the microcellular polyurethane elastomers Have densities of 250 to 800 g / l.