FIELD: chemistry.
SUBSTANCE: composition contains (a) 100 pts.wt solid selectively hydrogenated block-copolymer, having general formula A-B-A, (A-B)nX, where n varies from 2 to 3, and (b) 5-250 pts.wt hydrogenated plastification modifier which contains at least one hydrogenated conjugated diene selected from isoprene, 1,3-butadiene and mixtures thereof. Before hydrogenating the block-copolymer, each block A is a monoalkenylarene polymer block and each block B is a conjugated diene block. Each block A has average molecular weight varying from 3000 to 60000, and each block B has average molecular weight varying from 30000 to 300000. The total amount of monoalkenylarene in the hydrogenated block-copolymer ranges from 20 to 80 wt %. The plastification modifier is characterised by content of vinly groups (V2) before hydrogenation such that the ratio V2/V1 lies between 0.8 and 1.2. The ratio (MW2)/(MW1) of the average molecular weight of said plastification modifier (MW2) to the average molecular weight of block B (MW1) ranges from 0.01 to 0.3, with minimum molecular weight (MW2) 2000 and maximum molecular weight (MW2) 13000. The plastification modifier is further characterised by a polydispersity index (PDI). If PDI of said plastification modifier lies between 1.0 and less than 1.5, then the average molecular weight of said plastification modifier lies between 2000 and 7000. If PDI lies between 1.57 and 1.7, then the average molecular weight lies between 6800 and 13000.
EFFECT: considerably high breaking stress and improved compressions set of block-copolymer compositions, which enables to obtain compositions with low volatility at given hardness, as well as improved organoleptic properties, improved fogging characteristics and low level of extraction.
24 cl, 14 tbl, 10 ex
