Silane Compositions and Methods for Bonding Rubber to Metals

Abstract

Compositions and methods for treating metal substrates and / or bonding metal substrates to polymeric materials, such as rubber, are provided. The compositions include at least one substantially hydrolyzed amino silane and at least one substantially hydrolyzed sulfur-containing silane. Optionally, the compositions include a nano-size particulate material. The compositions provide coatings on metal substrates for protecting the metal from corrosion and for adhering rubber-like polymeric compositions to the metal with polymer-to-metal vulcanization conditions less dependent on the coating thickness, and with use of less coating materials.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation of U.S. application Ser. No. 10 / 681,422, filed Oct. 8, 2003 (pending), the disclosure of which is hereby incorporated by reference herein.BACKGROUND OF THE INVENTION[0002]I. Field of the Invention[0003]The present invention relates to silane coatings for treating metals. More particularly, the present invention provides organofunctional silane coatings which improve the adhesion of rubber and other polymeric materials to a metal substrate.[0004]II. Description of the Prior Art[0005]Rubber to metal bonded components find two major areas of application which may be classified as tire and non-tire applications. In tires, traditionally brass is used as a thin coating over a steel cord for imparting adhesion to natural rubber compounds. Non-tire applications include components, such as vibration dampers on motor and engine mounts, and applications in the medical, appliance, and other industries, where basic f...

AI Technical Summary

Benefits of technology

The present invention provides improved silane compositions and methods for coating metal substrates and bonding polymeric materials to metal surfaces with minimal use of silane materials. The silane compositions include at least one substantially hydrolyzed aminosilane and at least one substantially hydrolyzed sulfur-containing silane. The use of nano-sized particulate material, such as silica, zinc oxide, or a combination thereof, can further improve rubber-to-metal bonding. The solution applied to the metal substrate should have a concentration ratio of aminosilane to sulfur-containing silane ranging from about 4:1 to about 1:4. The coated metal substrate should have a thickness of about 1 μm or less. The invention is useful for protecting metal substrates from damage and for adhesion of polymeric materials to metal surfaces.

Problems solved by technology

For example, while certain silanes may provide improved adhesion between the metal substrate and a peroxide-cured rubber, these same silanes will often not provide the same results for sulfur-cured rubber.

However, formulations of such silane solutions require flammable organic solvents for dissolution, leading to more viscous solutions and thicker final coatings.

Such coatings are difficult to apply, cure, and control, particularly for coating uniformity, and need to be dried, prior to bonding to the rubber, at elevated temperatures, such as about 160° C. which pose additional hazards from flammable solvents.

Such coatings are not very amenable to industrial applications, and tire-cord applications in particular, where efficiency in time and cost is important to the success of the products.

Further, it has been difficult to bond rubbers to metal substrates utilizing various silanes and combinations thereof, and especially in those instances in which the adhesively-bound surfaces are subjected to fuels, oils, and / or other organic solvents, as the silanes may react therewith and / or dissolve therein to weaken or degrade the adhesive bond.

However, solvent-based adhesives are flammable, and hence hazardous, generate high levels of volatile organic compounds and vapors, and pose environmental disposal problems.

These disadvantages render these systems less useful in industrial applications.

Although the performance of the rubber-to-metal bond is adequate for most applications, inclusion of such promoters presents drawbacks.

For example, cobalt salts are expensive and pose availability problems.

Further, cobalt has been found to affect the rubber properties upon aging, and in particular, cobalt causes accelerated degradation of the rubber.

Rubber to metal bonded applications in tires have further drawbacks.

Additionally, brass is prone to galvanic erosion in conjunction with the underlying steel, and furthermore, the brass composition typically requires a copper content of about 63-68% which imposes restrictions on the rubber composition.

These limitations further require consideration when selecting an appropriate adhesive and / or bonding method for bonding rubber, or other tire materials, to the metal tire cord.

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