THERMOPLASTICALLY PROCESSABLE POLYURETHANES BASED ON SUCCINIC ACID(cas:110-15-6) PROPIONATES

THERMOPLASTICALLY PROCESSABLE POLYURETHANES BASED ON SUCCINIC ACID PROPIONATES. The present invention relates to a thermoplastically processable polyurethane elastomer having a hardness of 50 Shore A to 70 Shore D (ISO 868), which are obtained from reacting components comprising a) one or more linear polyester diols having a functionality from 1.8 to 2.2, wherein the one or more linear polyester diols comprise succinic acid(cas:110-15-6) 1,3-propionate and have an average molecular weight from 1,950 to 4,000 g/mol. b) one or more organic diisocyanates, and c) one or more diols having a molecular weight from 60 to 350 g/mol, wherein the components have a molar NCO:OH ratio of from 0.9:1 to 1.1:1.

Thermoplastic polyurethane elastomers (TPUs) have been known for a long time. They are of industrial importance due to the combination of high performance mechanical properties with the known advantages of inexpensive thermoplastic processability. A wide range of variation of the mechanical properties can be achieved by the use of different chemical builder components. An overview of TPUs, their properties and uses is given e.g. in Kunststoffe 68 (1978), pages 819 to 825 or Kautschuk, Gummi, Kunststoffe 35 (1982), pages 568 to 584.

TPUs are built up from linear polyols, usually polyester or polyether polyols, organic diisocyanates and short-chain diols (chain lengtheners). Catalysts can additionally be added to accelerate the formation reaction. To establish the properties, the builder components can be varied within relatively wide molar ratios. Molar ratios of polyols to chain lengtheners of from 1:1 to 1:12 have proved appropriate. This results in products in the range of from 50 Shore A to 75 Shore D.

A diversity of combinations of properties can be established in a controlled manner via the polyols, good mechanical values of course being particularly important for elastomers. The use of polyether polyols imparts particularly good hydrolysis properties to TPUs. If the intention is to have good mechanical properties, polyester polyols are advantageous.

Polyester polyols for TPUs are prepared, for example, from dicarboxylic acids having 2 to 12 carbon atoms, preferably 4 to 6 carbon atoms, and polyfunctional alcohols, such as glycols having 2 to 10 carbon atoms, polyester molecular weights of from 500 to 5,000 being employed as standard. As is described in EP 175 76 32 A2 also for TPUs from polyester polyols, TPUs which deliver particularly homogeneous shaped articles with a particularly good stability are obtained by means of a particular metering sequence of the monomers.

WO 2008/104541 A describes the reaction of succinic acid(cas:110-15-6), which is produced biologically from carbohydrates by fermentation, with at least difunctional alcohols to give polyester alcohols. Difunctional alcohols which are chosen are monoethylene glycol, diethylene glycol,. monopropylene glycol, dipropylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, glycerol, trimethylpropanediol, pentaerythritol and sorbitol. Polyester alcohols based on 1,3-propanediol are not mentioned and no restrictions or preferred ranges are mentioned for the molecular weight of the polyester alcohols. TPUs prepared from these polyester alcohols are also claimed. In the examples, polyesters of succinic acid, adipic acid and ethylene glycol and butanediol with molecular weights of approx. 1,900 are described and are reacted to give TPUs which have no particular properties and average mechanical values. No improvements of mechanical values are found and the tear propagation resistance is even slightly reduced.