A Process for the Preparation of Soft, Low-Shrinkage, Thermoplastic Polyurethane Elastomers Which Can Be Easily Released from the Mold

摘要

A process for preparation of thermoplastic workable polyurethane elastomers of Shore A hardness 45-65 by the steps: (A) reaction of specific polyester-polyols with one or more organic diisocyanates in molar ratio 1.1:1 to 1.9:1 to give an isocyanate terminated prepolymer, (B) mixing of the prepolymer from (A) with organic diisocyanates, and (C) reaction of the mixture obtained in (B) with one or more diol-chain lengtheners is new A process for preparation of workable thermoplastic polyurethane (TPU) elastomers of Shore A hardness 45-65 (measured by DIN 53 505), tensile strength greater than 12 Mpa (measured by ISO 37), shrinkage at most 3.5% (measured by DIN 16 770, part 3), and DMA-storage-tensile E modulus at -10degreesC of less than 20 Mpa in the presence of catalysts, where: (A) one or more linear hydroxy terminated polyols from the group: (a) polyester-polyols of number average mol. wt. 450-5000 obtained by reaction of a mixture of at least two different multihydric alcohols with one or more dicarboxylic acids with a maximum of 12C, (b) mixtures of at least two polyester-polyols of different number average mol. wt. of 400-5000, (c) mixtures of at least two polyether-polyols of different number average mol. wt. of 450-5000, (d) polyether-polyols of number average mol. wt. 450-5000 containing at least two different alkylene oxide units, (e) polyether-polyols from an alkylene oxide units of number average mol. wt. 450-1500, with one or more organic diisocyanates of molar NCO/OH ratio 1.2:1 to 1.9:1, preferably 1,1:1 to 1.7:1 is reacted to give an isocyanate-terminated prepolymer, (B) the prepolymer from stage (A) is mixed with a organic diisocyanates, and (C) the mixture obtained in (B) is reacted with one or more diol-chain lengtheners of mol. wt. 60-400, where the molar NCO/OH ratio of the components obtained in A, B, and C is 0.9:1 to 1.1:1, and the ratio of the OH groups of the polyols to the OH groups of chain lengthener is 0.3:1 to 2.0:1, preferably 0.4:1 to 1.5:1.