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.

1 . A method of bonding rubber to a metal substrate, the method comprising:
 applying a silane solution comprising a substantially hydrolyzed bis amino-silane, a substantially hydrolyzed bis sulfur-containing silane, and a nanosize particulate material to at least a portion of a surface of the metal substrate;   drying the silane solution on the metal substrate to form a coating having a thickness in the range from about 0.1 μm to about 1 μm thereon; and   applying an uncured, sulfur curable rubber onto the surface of the metal substrate having the coating thereon and sulfur curing the rubber to bond the rubber to the coated metal substrate.   
   
   
       2 . The method of  claim 1  further comprising, prior to applying the solution:
 mixing a bis amino-silane and a bis sulfur-containing silane separately with an aqueous-based medium to substantially hydrolyze the bis amino-silane and the bis sulfur-containing silane; and   mixing the hydrolyzed bis amino-silane, the hydrolyzed bis sulfur-containing silane, and the nanosize particulate material together to form the solution to be applied to the metal substrate.   
   
   
       3 . The method of  claim 2  wherein the aqueous-based medium comprises water and alcohol. 
   
   
       4 . The method of  claim 2  wherein the bis amino-silane is a compound of the general formula I
   (R 1 O) 3 —Si—R 2 —X—R 2 —Si—(OR 1 ) 3      
     wherein:
 each R 1 , independently, is selected from the group consisting of a C 1 -C 20  alkyl and C 2 -C 20  acyl; 
 each R 2 , independently, is selected from the group consisting of a substituted or unsubstituted aliphatic and aromatic group; 
 X is selected from the group consisting of 
 
     
       
         
         
             
             
         
       
     
     wherein each R 3 , independently, is selected from the group consisting of hydrogen, substituted or unsubstituted, straight, branched or cyclic C 1 -C 20  alkyl, alkenyl, and alkynyl groups and substituted or unsubstituted C 3 -C 20  aryl and alkylaryl groups; and
 R 4  is selected from the group consisting of hydrogen, substituted or unsubstituted, straight, branched or cyclic C 1 -C 20  alkyl, alkenyl, and alkynyl groups and substituted or unsubstituted C 3 -C 20  aryl and alkylaryl groups. 
 
   
   
       5 . The method of  claim 2  wherein the bis amino silane is selected from the group consisting of bis(trimethoxysilylpropyl)ethylene diamine, bis(trimethoxysilylpropyl) amine, and combinations thereof. 
   
   
       6 . The method of  claim 2  wherein the bis sulfur-containing silane is a compound of the general formula II 
     
       
         
         
             
             
         
       
     
     wherein:
 each R 1 , independently, is selected from the group consisting of substituted or unsubstituted, straight, branched or cyclic C 1 -C 20  alkyl, alkenyl, alkynyl, and acetyl groups and substituted or unsubstituted C 3 -C 20  aryl and alkylaryl groups; 
 Z is -Q-S x -Q, wherein each Q, independently, is an aliphatic or aromatic group; and 
 x is an integer from 2-10. 
 
   
   
       7 . The method of  claim 2  wherein the bis sulfur-containing silane is selected from the group consisting of bis(triethoxysilylpropyl) disulfide, bis(triethoxysilylpropyl) tetrasulfide, and a combination thereof. 
   
   
       8 . The method of  claim 1  wherein the solution comprises a ratio of the hydrolyzed bis amino-silane to the hydrolyzed bis sulfur-containing silane in a range from about 1:4 to about 4:1 by volume. 
   
   
       9 . The method of  claim 1  wherein the solution comprises a ratio of the hydrolyzed bis amino-silane to the hydrolyzed bis sulfur-containing silane of about 1:1 by volume. 
   
   
       10 . The method of  claim 1  wherein applying the solution to the metal substrate comprises dipping the metal substrate in the solution. 
   
   
       11 . The method of  claim 1  wherein the nanosize particulate material is selected from the group consisting of silica, zinc oxide, and combinations thereof. 
   
   
       12 . The method of  claim 1  wherein the nanosize particulate material has an average particle size of about 0.1 μm or less. 
   
   
       13 . The method of  claim 1  wherein the nanosize particulate material is silica and in a concentration range from about 10 ppm to about 1% by weight of the solution. 
   
   
       14 . The method of  claim 1  wherein the nanosize particulate material is silica and in a concentration range from about 50 ppm to about 1000 ppm of the solution. 
   
   
       15 . The method of  claim 1  wherein drying comprises heating the silane solution on the metal substrate to a temperature of at least about 60° C. 
   
   
       16 . The method of  claim 1  wherein the coating formed has a thickness in the range from about 0.2 μm to about 0.6 μm. 
   
   
       17 . The method of  claim 1  wherein curing comprises applying heat and pressure to the rubber and coated metal substrate to form a bond therebetween. 
   
   
       18 . The method of  claim 1  wherein the sulfur curable rubber is selected from the group consisting of natural rubber, synthetic rubber, and combinations thereof. 
   
   
       19 . A bonded tire cord prepared by the method of  claim 1 . 
   
   
       20 . A method of bonding rubber to a metal substrate, the method comprising:
 mixing bis amino-silane and a bis sulfur-containing silane separately with an aqueous-based medium to substantially hydrolyze the bis amino-silane and the bis sulfur-containing silane;   mixing the hydrolyzed bis amino-silane, the hydrolyzed bis sulfur-containing silane, and a nanosize particulate material having an average particle size of about 0.1 μm or less, together to form a silane solution comprising a ratio of the hydrolyzed bis amino-silane to the hydrolyzed bis sulfur-containing silane in a range from about 1:4 to about 4:1 by volume,   applying the solution to at least a portion of a surface of the metal substrate in an amount sufficient to form a coating to a thickness in the range from about 0.1 μm to about 1 μm; and   drying the solution on the metal substrate to form the coating thereon;   applying an uncured, sulfur curable rubber onto the surface of the metal substrate having the solution applied thereon; and   sulfur curing the rubber with heat and pressure to bond the rubber to the metal substrate.   
   
   
       21 . A tire cord comprising sulfur curable rubber, a metal substrate, and an adhesive film therebetween bonding the rubber to the metal substrate, the adhesive film formed from a dried solution comprising a substantially hydrolyzed bis amino-silane, a substantially hydrolyzed bis sulfur-containing silane, and a nanosize particulate material and having a thickness in the range from about 0.1 μm to about 1 μm. 
   
   
       22 . The tire cord of  claim 21  wherein the rubber is selected from the group consisting of natural rubber, sulfur-cured rubber, peroxide-cured rubber, EPDM, NBR, SBR, and combinations thereof. 
   
   
       23 . The tire cord of  claim 21  wherein the substrate comprises a metal selected from the group consisting of zinc, steel, stainless steel, titanium, nickel, brass, copper, tin, aluminum, cobalt, alloys thereof, and combinations thereof. 
   
   
       24 . The tire cord of  claim 21  wherein the bis amino-silane is a compound of the general formula I
   (R 1 O) 3 —Si—R 2 —X—R 2 —Si—(OR 1 ) 3      
     wherein:
 each R 1 , independently, is selected from the group consisting of a C 1 -C 20  alkyl and C 2 -C 20     —   acyl; 
 each R 2 , independently, is selected from the group consisting of a substituted or unsubstituted aliphatic and aromatic group; 
 X is selected from the group consisting of 
 
     
       
         
         
             
             
         
       
     
     wherein each R 3 , independently, is selected from the group consisting of hydrogen, substituted or unsubstituted, straight, branched or cyclic C 1 -C 20  alkyl, alkenyl, and alkynyl groups and substituted or unsubstituted C 3 -C 20  aryl and alkylaryl groups; and
 R 4  is selected from the group consisting of hydrogen, substituted or unsubstituted, straight, branched or cyclic C 1 -C 20  alkyl, alkenyl, and alkynyl groups and substituted or unsubstituted C 3 -C 20  aryl and alkylaryl groups. 
 
   
   
       25 . The tire cord of  claim 21  wherein the bis sulfur-containing silane is a compound of the general formula II 
     
       
         
         
             
             
         
       
     
     wherein:
 each R 1 , independently, is selected from the group consisting of substituted or unsubstituted, straight, branched or cyclic C 1 -C 20  alkyl, alkenyl, alkynyl, and acetyl groups and substituted or unsubstituted C 3 -C 20  aryl and alkylaryl groups; 
 Z is -Q-S x -Q, wherein each Q, independently, is an aliphatic or aromatic group; and 
 x is an integer from 2-10. 
 
   
   
       26 . The tire cord of  claim 21  wherein the nanosize particulate material is selected from the group consisting of silica, zinc oxide, and combinations thereof.