Solvent free pressure sensitive adhesive for applying to substrates such as plastics and paper comprises silicone resin, silicone gum, a silicone diluent and a thermally activatable crosslinking and/or polymerization initiator

摘要

A pressure sensitive, solvent free, cationically hardenable adhesive composition. The composition comprises: (a) one or more silicone resins containing at least one unit of formula R1SiO1/2, one or more units of formula SiO4/2 and/or a trifunctional unit of formula R2SiO3/2, R1, R2 = monovalent alkyl or alkenyl or hydroxy. (b) one or more silicone gums with viscosity above 100000 mPa.s and functionalized at end of chain with one or more hydroxy, epoxy and/or vinyl groups, the ratio by weight of (b) to (a) being 0.01-100, (c)1-50 wt.% of a silicone diluent with viscosity below 100 mPa.s based on a silicone oligomer or polymer comprising one or more units of formula ZSiR0aO(3-a)2, a = 0, 1, 2; R0 = 1-6C alkyl, cycloalkyl, aryl, vinyl, hydrogen, alkoxy; Z = organic substituent comprising one or more reactive epoxy or alkenylether or oxetane and/or dioxolan functional groups , (d) a thermally activatable initiator (Am), based on an unsolvated or solvated boron derivative of Formula (I) (A)xB(R4)y, (I) R4 = 1-12C alkyl or alkenyl optionally substituted by an electroattractor element such as a halogen or group such as CF3 or NO2 or CN, 1-12C alkoxy optionally substituted by an electroattractor element such as a halogen or group such as CF3 or NO2 or CN,, phenyl substituted with an electroattractor element such as a halogen or group such as CF3 or NO2 or CN, aryl containing at least two aromatic centers optionally substituted by an electroattractor element such as a halogen or group such as CF3 or NO2 or CN, -C2H4- Si(Q)3; Q = 1-10C alkyl or alkoxy, less than 10Si siloxane oligomer where necessary substituted with B(R4)2; A = H, halogen, hydroxyl; x = 0, 1, 2; y = 1, 2, 3; x + y = 3; Two R4 may combine to form with the B to which they are attached a 5 - 10 atom saturated, unsaturated, bridged and/or aromatic cycle, possibly comprise one or more heteroatoms H, N or B and the B present in the cycle may be substituted with A or R4. Independent claims are included for : (1) a coating preferably a pressure sensitive adhesive coating obtained by use of the claimed composition; (2) a method of preparation of a solvent- free pressure sensitive adhesive coating by mixing the resin and gum in solution, the diluent and optionally the initiator, devolatilizing to eliminate the solvent, addition of the initiator if not previously added, spreading on a support and crosslinking and/or polymerization by thermal treatment.