Adhesion promoting additives and low temperature curing organosiloxane compositions containing same
AssigneeDow Corning Corporation
InventorCarl J. Bilgrien
Life of this patent
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Abstract
Adhesion promoting additives for organosiloxane compositions that cure by a platinum-catalyzed hydrosilation reaction are reaction products of (1) an ethylenically unsaturated ether of a polyfunctional alcohol and (2) at least one silicon compound selected from the group consisting of (i) epoxy-substituted organosilicon compounds containing at least one hydrolyzable group per molecule and (ii) tetraalkyl orthosilicates, also referred to tetraalkoxysilanes, where the reaction is conducted in the presence of a suitable catalyst such as an organotitanium compound. The additive optionally includes a chelated organoaluminum compound.
Claims16
An adhesion-promoting additive for curable organosiloxane compositions, said additive comprising the reaction product of
- (1) a partial ether derived from an ethylenically unsaturated alcohol and a polyhydric alcohol, and
- (2) at least one organosilicon compound containing at least one epoxide group and at least one silicon-bonded hydrolyzable group, and
- (3) at least one tetraalkyl orthosilicate;
- wherein said reaction product is prepared in the presence of a catalytically effective amount of an organotitanium compound.
A curable organosiloxane composition exhibiting adhesion to both organic and inorganic substrates following curing at temperatures below 100.degree. C., said composition comprising
- (A) a polyorganosiloxane containing at least two alkenyl radicals per molecule,
- (B) an amount sufficient to cure said composition of an organohydrogensiloxane containing at least two silicon-bonded hydrogen atoms per molecule, where the sum of the alkenyl radicals per molecule of (A) and the silicon-bonded hydrogen atoms per molecule of (B) is greater than 4,
- (C) an amount sufficient to promote curing of said composition of a hydrosilation catalyst selected from the group consisting of metals from the platinum group of the periodic table and compounds of said metals, and
- (D) an amount sufficient to achieve adhesion to substrates in contact with said composition during curing at temperatures below 100.degree. C. of an adhesion promoting additive comprising the reaction product of
- (1) at least one partial ether derived from an ethylenically unsaturated alcohol and a polyhydric alcohol,
- (2) at least one organosilicon compound containing at least one epoxide group and at least one silicon-bonded hydrolyzable group, and
- (3) at least one tetraalkyl orthosilicate, wherein said reaction product is prepared in the presence of a catalytically effective amount of an organotitanium compound.
A method for bonding two substrates, the method comprising the sequential steps of
- (I) applying to a surface of one of said substrates a curable organosiloxane composition comprising
- (A) a polyorganosiloxane containing at least two alkenyl radicals per molecule,
- (B) an amount sufficient to cure said composition of an organohydrogensiloxane containing at least two silicon-bonded hydrogen atoms per molecule, where the some of the alkenyl radicals per molecule of (A) and the silicon-bonded hydrogen atoms per molecule of (B) is greater than 4,
- (C) an amount sufficient to promote curing of said composition of a hydrosilation catalyst selected from the group consisting of metals from the platinum group of the periodic table and compounds of said metals, and
- (D) an amount sufficient to achieve adhesion to substrates in contact with said composition during curing at temperatures below 100.degree. C. of an adhesion promoting additive comprising the reaction product of
- (1) at least one partial ether derived from an ethylenically unsaturated alcohol and a polyhydric alcohol,
- (2) at one organosilicon compound containing at least one epoxide group and at least one silicon-bonded hydrolyzable group, and
- (3) at least one tetraalkyl orthosilicate, wherein said reaction product is prepared in the presence of a catalytically effective amount of an organotitanium compound;
- (II) placing the surface coated with said composition in contact with a surface of a second substrate and
- (III) curing said organosiloxane composition.
A method according to claim 21 where the terminal carbon atoms of said ethylenically unsaturated alcohol are unsaturated;
- said polyhydric alcohol contains from 2 to 10 carbon atoms;
- said organosilicon compound corresponds to the formula R.sup.1 SiR.sup.2.sub.m R.sup.3.sub.(3-m), where R.sup.1 represents an epoxyalkyl radical or an epoxy-substituted cycloalkyl radical, R.sup.2 represents an alkyl radical, R.sup.3 represents a hydrolyzable group and m is 0 or 1, said tetraalkyl orthosilicate is selected from the group consisting of tetramethyl orthosilicate, tetraethyl orthosilicate and tetra-npropyl orthosilicate;
- said polyorganosiloxane is a polydiorganosiloxane corresponding to the formula ##STR3## where each R.sup.8 is individually selected from monovalent hydrocarbon radicals and monovalent halohydrocarbon radicals, R.sup.9 represents an alkenyl radical, and n represents a degree of polymerization equivalent to a viscosity of at:
- least:
- 0.1 Pa.s and said hydrosilation catalyst is a platinum compound and is present at a concentration equivalent to from 0.1 to 500 parts by weight of platinum per million parts, based on the combined weight of said polyorganosiloxane and said organohydrogensiloxane, and said composition is cured at a temperature of from 25.degree. to 70.degree. C.
Dependencies are inferred from the claim text.