Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Patent
1997-05-19
1999-05-25
Housel, James C.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
524588, 524611, 524841, 524843, 525475, 525505, 525502, C08J 910, C08L 6100, C08L 8300, C08F28300
Patent
active
059070153
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to aqueous formulations that are useful for bonding elastomers to various inorganic substrates such as metals, ceramics, and glass. More specifically, the invention relates to novel aqueous adhesive compositions based on the combination of amino- and alkenyl-functional silanes which compositions are water-dilutable, do not require the presence of an organic solvent to form a stable and workable adhesive solution and are useful for bonding a variety of different elastomers.
BACKGROUND OF THE INVENTION
Numerous silane adhesive compositions have previously been developed for the purpose of bonding elastomeric materials, particularly silicone elastomer-based materials. Many of these silane adhesive compositions rely on various organo-functional silane compositions as the active bonding agent. Due to the highly organic nature of the organo-functional silane compounds, traditional silane adhesive compositions have relied on organic solvents in order to form a stable and workable solution. While some traditional silane adhesive compositions contain water in addition to an organic solvent, the organic solvent is required in order to form a stable composition.
One example of an organic solvent-based silane adhesive composition is described in U.S. Pat. No. 3,022,196 as being a mixture of an unsaturated silane and an aminoalkyl silane. For utilization as an adhesive, the mixture is prepared as a solution in the presence of a water-miscible organic solvent. The adhesive composition may also contain a small amount of water in addition to the water-miscible organic solvent; however, the water-miscible organic solvent in such case predominates.
Another example of an organic solvent-based silane adhesive composition is described in U.S. Pat. No. 4,618,389 as being a mixture of an alkenyltrihydrocarbonoxy silane, a water-miscible solvent, and water.
In light of the continuing effort to eliminate volatile organic solvents from all chemical formulations for environmental purposes, a need presently exists for an aqueous silane adhesive composition which is largely free of any volatile organic solvent and which is stable and dilutable with water.
SUMMARY OF THE INVENTION
The present invention relates to an aqueous adhesive composition comprising an amino silane, an alkenyl-functional silane hydrolysate and water, having a slightly acid pH between 7 and 4, wherein the alkenyl-functional silane moiety is present in an amount from about 40 to about 70 mol % based on the total mols of silane and wherein the alkenyl-functional silane hydrolysate is formed in situ in the presence of said amino silane.
It has been unexpectedly discovered that the hydrolysis of a normally water-immiscible alkenyl-functional silane in the presence of the amino silane in the stated proportions and in essentially aqueous solution at the mildly acid conditions recited results in a stable aqueous solution which can be diluted further with water to form an unusually stable aqueous solution which, upon drying, possesses a marked ability for bonding various and different elastomeric polymers to substrates. Without being bound by any theory, it is presently believed that the amino silane under the stated conditions complexes or otherwise stabilizes the hydrolyzed alkenyl silane to prevent the latter from gelling or from precipitating from solution even upon further dilution with water. While an alcohol is formed as a reaction product during hydrolysis, its presence is incidental and is not required--in fact it can be removed by stripping--to provide a stable, water-dilutable solution.
DETAILED DESCRIPTION OF THE INVENTION
The amino silanes used in accordance with the present invention can be represented by the following formula: ##STR1## wherein X is an aminoalkyl group NH.sub.2 R-- where R is an alkyl or alkyl amino alkyl group containing from 2 to about 10 carbon atoms, and R.sub.1, 2.sub.2, and R.sub.3 are the same or different alkyl or alkoxyalkyl groups having from about 1 to about 5 carbon a
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Housel James C.
Lord Corporation
Rupert Wayne W.
Swartz Rodney P.
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