Patent ID: 6794477
Filing Date: 2004-09-21
Classification: B32B,C08F,Y10T

Abstract:
A silane-modified polyvinyl acetal, prepared by copolymerizing a) a comonomer mixture comprising at least one vinyl ester of an optionally branched alkylcarboxylic acid having from 1 to 15 carbon atoms, and optionally, one or more comonomers comprising (meth)acrylate(s) of alcohols having from 1 to 15 carbon atoms, olefms, dienes, vinylaromatics, or vinyl halides, with b) from 0.02 to 20.0% by weight of one or more of ethylenically unsaturated, hydrolyzable silicon compounds or hydrolyzable mercaptosilanes, to form a vinyl ester copolymer, wherein the silane compounds b) comprise ethylenically unsaturated silicon compounds of the formula R1SiRa(OR2)b, where R is a C1-C3-alkyl radical, a C1-C3-alkoxy radical, or halogen, R1 is CH2&boxH;CR3â€”(CH2)0-1 or CH2&boxH;CR3CO2(CH2)1-3, R2 is an optionally branched, optionally substituted alkyl radical having from 1 to 12 carbon atoms, or an acyl radical having from 2 to 12 carbon atoms, where the carbon atoms of R2 may be interrupted by an ether group, R3 is H or CH3, a is an integer from 0 to 2, b is an integer from 1 to 3, and the sum of a and b is 3, and wherein the hydrolyzable mercaptans comprise mercaptosilanes of the formula HSâ€”(CR42)1-3â€”SiR53, where R4 are identical or different and are H or a C1-C6-alkyl group, R5 are identical or different and are a C1-C6--alkyl group or a C1-C6-alkoxy group, and at least one of the radicals R5 is an alkoxy group;hydrolyzing the vinyl ester copolymer to contain 50 mol % or more of vinyl alcohol units; and acetalizing the vinyl alcohol units with one or more aliphatic or aromatic aldehydes having from 1 to 15 carbon atoms, wherein from 5 to 50% by weight of a mixture of comonomers a) and silane comonomers b), based on the total weight of the comonomers a) and b), is used as an initial charge, and the remainder of said mixture is metered in during the polymerization, such that the ratio between the comonomers a) and the silane comonomers b) remains constant throughout the polymerization.