1. Field of the Invention
This invention relates to a novel class of organosilicon compounds. This invention also relates to organosiloxane compositions that cure by a platinum group metal catalyzed hydrosilation reaction and contain these compound as adhesion promoting additives. The compounds are particularly useful for achieving adhesion to a variety of substrates at curing temperatures below about 100.degree. C.
2. Background Information
One type of curable organosiloxane composition comprises an organopolysiloxane containing ethylenically unsaturated organic groups and an organosilicon compound containing silicon-bonded hydrogen atoms, curable in the presence of a catalyst which comprises a group VIII metal or a compound or complex thereof. Usually, the catalyst is a compound or complex of platinum. Unfortunately, the adhesion of these type of compositions is generally poor, limiting their usefulness in many applications.
Several methods are known to improve the adhesion of organosiloxane compositions, however most generally have limitations. For example, primers can be used to improve the adhesion, but their use requires a separate processing step which increases process time and cost. Additionally, the primer usually requires a heat-activated cure to be effective. Adhesion additives, which are added directly to the composition to promote adhesion, have therefore received considerable attention.
Useful adhesion additives typically contain at least two functional groups. U.S. Pat. No. 3,772,026 and U.S. Pat. No. 3,873,334 teach acyloxy functional silanes which additionally contain silicon bonded hydrogen atoms or alkenyl radicals, respectively. Although the acyloxy functionality is very reactive, it liberates corrosive acetic acid upon reaction with hydroxyl groups present at the surface of the substrate or with upon contact with water.
U.S. Pat. No. 4,196,273 teaches use of unsaturated alkoxysilanes as adhesion additives, however, adhesion is not demonstrated at temperatures below 100.degree. C. and only adhesion to glass is demonstrated at 100.degree. C. U.S. Pat. No. 4,329,273 teaches use of partially hydrolyzed alkoxysilanes containing ethylenically unsaturated groups bonded to the silicon atom. While satisfactory curing of these compositions containing these adhesion additives was demonstrated at 100.degree. C., the compositions did not cure at ambient laboratory temperatures.
U.S. Pat. No. 4,082,726 teaches using organosilicon compounds containing epoxy functional dialkoxysilyl groups and at least one alkenyl group or silicon-bonded hydrogen atom as adhesion additives. The exemplified compositions are cured at temperatures between 100.degree.-200.degree.C.
U.S. Pat. No. 4,087,585 teaches physical blends of epoxy functional alkoxysilanes with silanol functional fluids containing alkenyl functionality. Cure was obtained at elevated temperatures. Multifunctional organosilanes containing ethylenic unsaturation, epoxy functionality, and alkoxy functionality are taught in U.S. Pat. No. 4,732,932. U.S. Pat. No. 5,106,933 teaches use of mixtures of alkoxysilanes.
U.S. Pat. No. 4,659,851, U.S. Pat. No. 4,719,262, and U.S. Pat. No. 4,906,686 teach reaction products of 1) unsaturated alcohols and ethers derived from these alcohols and 2) alkoxysilanes. A shortcoming of these reaction products is that the resultant Sew-O-C bond between the unsaturated alcohol and alkoxysilane would be susceptible to hydrolysis to the extent that the adhesion may be decreased upon exposure to moisture.
Organosilicon compounds obtained from the reaction of polyhydric alcohols with compounds containing silicon-bonded hydrolyzable groups are known in the art. U.S. Pat. No. 2,349,338 teaches silicic acid esters of monohydric and polyhydric alcohols, including various glycol and glycerol silicate ester derivatives, are useful as corrosion prevention additives for heat transfer liquids. The corrosion prevention is afforded by the hydrolysis product of these compounds.
U.S. Pat. No. 2,776,307 claims silicon-containing esters of the type (R.sup.1 O).sub.3 Si(XR.sup.2).sub.n OSi(OR.sup.3).sub.3, where X can be oxygen, and n has a value of 2, 3, or 4. The compounds are said to be useful as hydraulic fluids and other lubricant purposes.
U.S. Pat. No. 3,992,429 teaches novel alkoxysilane cluster compounds containing sterically hindered alkyl groups to improve hydrolytic stability. Intended uses include heat transfer fluids, hydraulic fluids, brake fluids, transmission fluids, and the like.
U.S. Pat. No. 2,630,446 teaches polymeric silicates prepared from tetraalkyl orthosilicates and polyhydric alcohols. The silicates are intended for use as plasticizers, lubricants, and hydraulic fluid additives.
U.S. Pat. No. 4,072,655 teaches reaction products of polyhydric alcohols and silanes containing from 1 to 4 hydrolyzable groups per molecule. The reaction products are used as non-slump additives for moisture curable organosiloxane compositions.
The preparation of alkoxysilanes from glycols and glycol monoethers is taught by H. G. Emblem and K. Hargreaves in the Journal of Inorganic Nuclear Chemistry, Vol. 30 (3), p. 721, 1968).
The preparation of esters derived from tetraalkyl orthosilicates and polyhydroxy alcohols by a transesterification reaction is described in British Patent No. 450,875.
U.S. Pat. No. 3,029,269 teaches compounds of the type (RO).sub.3 SiOCR'.sub.2 (CH.sub.2).sub.n CR'.sub.2 -OSi(OR).sub.3, where n is 0-16 and R' is H or a lower aliphatic radical, and R is a saturated aliphatic radical of 1-16 carbons. The compounds are suggested as lubricants and hydraulic fluids and in general show low pour point, good viscosity and viscosity index properties as well as hydrolytic stability.
Finally, Applicants' copending application Ser. No. 08/240,598 filed on May 10, 1944, U.S. Pat. No. 5,424,384 describes adhesion promoting additives for curable organosiloxane compositions that are reaction products of a polyhydric saturated alcohol with a silane or bis-silylalkane. The organosilicon reactant contains at least three alkoxy or enoloxy groups on each silicon atom.
One objective of this invention is to provide a class of novel organosiloxanes that are particularly useful as adhesion promoting additives in organosiloxane compositions, particularly those that cure by a platinum group metal catalyzed hydrosilation reaction at temperatures below about 100.degree.C.