Patent EA-001373-B1 (EA)
Title: Microcellular urea-containing polyurethane elestomer
Inventor: KRECH RUDIGER
IPC: C08G18/76
Filed: 1996-12-16
Abstract: 1. A microcellular polyurethane elastomer containing urea groups, based on  a) an isocyanate component consisting essentially of diphenylmethane 4,4'-diisocyanate together with  b) at least one oligomeric polyhydroxyl compound having a number average molar mass of from 1000 to 5000 g/mol and a functionality of from 1.7 to 3,  c) if desired, low molecular weight chain extenders and/or crosslinkers and  d) blowing agents and also  e) catalysts and, if desired,  f) auxiliaries and/or additives, which has a urea content of from 14 to 18% by weight, defined as the amount in percent of urea of the empirical formula C14H12ON2 formed from diphenylmethane diisocyanate, based on the total amount of the elastomer after urea formation, and has, after heating at from 100 to 120 degree C for from 8 to 24 hours, a melting range of from 130 degree C as the minimum lower limit to 230 degree C as the minimum upper limit, measured by differential scanning calorimetry (DSC) at a heating rate of 20 degree C/min, which melting range can be set by adding acid reagents in an amount of from 0.01 to 5% by weight, based on the weight of the components a), b), e) and, if used, c). 2. A microcellular polyurethane elastomer containing urea groups as claimed in claim 1, having a physicochemical structure which, in the gel permeation chromatogram (GPC) of a solution of the microcellular polyurethane elastomer prepared at 90 degree C in N,N-dimethylformamide containing 1% of di-n-butylamine measured against polymethyl methacrylate (PMMA) as standard displays a signal occurring in addition to the low molecular weight main signal and comprising one or more peaks at an  (apparent) molar mass of greater than 250,000 g/mol which becomes smaller or disappears on addition of lithium chloride to this solution. 3. A process for preparing a microcellular polyurethane elastomer containing urea groups as claimed in claim 1 by reacting  a) an isocyanate component essentially comprising diphenylmethane 4,4'-diisocyanate with  b) at least one oligomeric polyhydroxyl compound having a number-average molar mass of from 1000 to 5000 g/mol and a functionality of from 1.7 to 3,  c) if desired, low molecular weight chain extenders and/or crosslinkers and  d) blowing agents and also  e) catalysts and, if desired,  f) auxiliaries and/or additives in closed molds, wherein acid reagents are added in an amount of from 0.01 to 5% by weight, based on the weight of the components a), b), e) and, if used, c), and the microcellular polyurethane elastomer containing urea groups is heated at from 100 to 120 degree C for from 8 to 24 hours. 4. A process as claimed in claim 3, wherein the acid reagents are used in an amount of from 0.05 to 2% by weight, based on the weight of the components a), b), e) and, if used, c). 5. A process as claimed in claim 3 or 4, wherein a salt of monoethanolamine and n-alkylbenzenesulfonic acid having alkyl radicals of from C9H19 to C15H31 is used. 6. A process as claimed in any of claims 3 to 5, wherein the heating of the moldings for from 8 to 24 hours at from 100 to 120 degree C begins after removal from the mold, during storage at room temperature, within a period of 2 hours. 7. A process as claimed in any of claims 3 to 6, wherein the components a), d), e) and, if used, f) contain from 0.05 to 5% by weight of urea groups. 8. A process as claimed in any of claims 3 to 7, wherein the oligomeric polyhydroxyl compounds having a number average molar mass of from 1000 to 5000 g/mol of component b) have a functionality of 2. 9. Use of the microcellular polyurethane elastomers containing urea groups as claimed in claim 1 for producing damping elements.