Polystyrene-polyisoprene-polystyrene block copolymer latices and process for their preparation

摘要

Stable concentrated latices of block copolymers are made by taking a dilute latex of a block copolymer of the formula A-B-A, B-A-B or A-B in which each A is an independently selected non-elastomeric polymer block having an average molecular weight in the range of 2,000 to 100,000 and a glass transition temperature above 25 DEG C. and B is an elastomeric polymer block having an average molecular weight in the range of 25,000 to 1,000,000 and a glass transition temperature below 10 DEG C., the dilute having a polymer: water ratio between 1:10 and 1:50, and adding thereto a normally liquid aliphatic hydrocarbon and/or a solution of a diene rubber dissolved in an aliphatic hydrocarbon in an amount such that the weight ratio of liquid aliphatic hydrocarbon added, either as such or as contained in the rubber solution, is between 1:1 and 5:1, and leaving the dilute latex in intimate contact with the added aliphatic hydrocarbon for a period of at least 1/4 hour, removing the added aliphatic hydrocarbon and concentrating the latex to a polymer content of at least 25% by weight. The resulting latices may be used in the production of dipped goods and coated or foamed rubber articles. The examples describe emulsifying in water benzene solutions of styrene-isoprene and isoprene-styrene-isoprene block copolymers, removing the benzene to produce dilute polymer latices which are then contacted with heptane or isopentane, followed by the removal of the aliphatic hydrocarbons and concentration of the resulting latices.