Adhesive System For The Direct Bonding Of A Cured Polyurethane To Crude Rubber

Abstract

Adhesive composition usable in particular as an adhesion primer, based on a polyisocyanate compound and a polyester or vinyl ester resin comprising (in particular hydroxyl) functional groups which are reactive towards isocyanate groups of said polyisocyanate, the total number of said isocyanate groups being in excess relative to the total number of said functional groups of the polyester or vinyl ester resin. The polyisocyanate compound is preferably a diisocyanate, the resin is preferably an epoxy vinyl ester resin, in particular novolac- and/or bisphenol-based. Said composition is usable, as an adhesion primer, in combination with a secondary adhesion layer preferably based on a polyvinylpyridine/stirene/butadiene elastomer and a polyester or vinyl ester resin. Use of such an adhesive system for bonding a cured polyurethane to an uncured diene elastomer composition, in particular in the manufacture of rubber articles consisting of ground contact systems for motor vehicles, in particular pneumatic or non-pneumatic tires.

1 . An adhesive composition, usable in particular as an adhesion primer for bonding a polymerised polyurethane to an uncured diene elastomer composition, characterised in that said adhesive composition comprises a polyisocyanate compound and a polyester or vinyl ester resin comprising functional groups which are reactive towards the isocyanate groups of said polyisocyanate compound, the total number of these isocyanate groups being in excess relative to the total number of said functional groups of the polyester or vinyl ester resin.  
   
   
       2 . A composition according to  claim 1 , the polyisocyanate compound being selected within the group consisting of diisocyanates, triisocyanates and mixtures of such compounds.  
   
   
       3 . A composition according to  claim 2 , the polyisocyanate compound being a diisocyanate.  
   
   
       4 . A composition according to  claim 3 , the diisocyanate compound being selected within the group consisting of diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI) and mixtures of these compounds.  
   
   
       5 . A composition according to  claim 4 , the diisocyanate compound being TDI.  
   
   
       6 . A composition according to  claim 1 , the functional groups of the polyester or vinyl ester resin being selected within hydroxyl groups, carboxyl groups, thiol groups, amine groups —NH, —NH 2  and —NHR, amide groups —CONH 2  and —CONHR, thioamide groups —CSNH 2  and CSNHR, sulfonic groups —SO 2 OH, and mixtures of such functional groups (R being any monovalent hydrocarbon radical).  
   
   
       7 . A composition according to  claim 6 , the functional groups of the polyester or vinyl ester resin being hydroxyl groups.  
   
   
       8 . A composition according to  claim 1 , the resin being a vinyl ester resin.  
   
   
       9 . A composition according to  claim 8 , the vinyl ester resin being an epoxy vinyl ester resin.  
   
   
       10 . A composition according to  claim 9 , the epoxy vinyl ester resin being a novolac- and/or bisphenol-based resin.  
   
   
       11 . A composition according to  claim 1 , furthermore comprising a solvent for the resin.  
   
   
       12 . A composition according to  claim 11 , the solvent for the resin being stirene.  
   
   
       13 . A composition according to  claim 12 , the stirene content being between 5% and 15% (% by total weight of the resin and its associated solvent).  
   
   
       14 . A composition according to  claim 1 , wherein there are at least twice as many isocyanate groups as functional groups of the polyester or vinyl ester resin.  
   
   
       15 . A composition according to  claim 14 , the functional groups of the resin being hydroxyl groups.  
   
   
       16 . A composition according to  claim 14 , the excess of isocyanate groups relative to the functional groups of the resin being greater than 3.  
   
   
       17 . A composition according to  claim 1 , the weight ratio of polyisocyanate to resin when dry being between 0.5(M/174)(2/N) and 2.0(M/174)(2/N), M being the molar mass and N the number of —NCO groups per mole of the polyisocyanate compound.  
   
   
       18 . A composition according to  claim 17 , the weight ratio of polyisocyanate to resin when dry being between 1.0(M/174)(2/N) and 1.8(M/174)(2/N).  
   
   
       19 . A composition according to  claim 1 , furthermore comprising, as chain extender, a low molecular weight diene elastomer.  
   
   
       20 . A composition according to  claim 19 , the chain extender having a weight average molecular weight (Mw) of between 2000 and 4000 g/mol.  
   
   
       21 . A composition according to  claim 19 , the chain extender being a polybutadiene.  
   
   
       22 . A composition according to  claim 1 , the chain extender being a diene elastomer functionalised at the chain ends with vinyl ester or polyester.  
   
   
       23 . A composition according to  claim 1 , the weight ratio of chain extender to resin when dry being between 0 and 1.5, preferably between 0.8 and 1.4.  
   
   
       24 . (canceled)  
   
   
       25 . A pre-adherised polyurethane, covered with an adhesive composition according to  claim 1 .  
   
   
       26 . An adhesive system usable for bonding a cured polyurethane to an uncured diene elastomer composition, comprising as adhesion primer an adhesive composition according to  claim 1  and a secondary adhesion layer for diene elastomer, capable of bonding to the vinyl ester or polyester resin of the adhesion primer.  
   
   
       27 . An adhesive system according to  claim 26 , the secondary adhesion layer being based on a diene elastomer and an additional compound capable of bonding to the vinyl ester or polyester resin of the adhesion primer.  
   
   
       28 . An adhesive system according to  claim 27 , the diene elastomer of the secondary adhesion layer being a polyvinylpyridine/stirene/butadiene elastomer (abbreviated to “p-VSBR”).  
   
   
       29 . An adhesive system according to  claim 27 , the additional compound of the secondary adhesion layer capable of bonding to the vinyl ester or polyester resin of the adhesion primer being a vinyl ester or polyester resin.  
   
   
       30 . An adhesive system according to  claim 29 , the resin of the secondary adhesion layer being a vinyl ester resin, preferably an epoxy vinyl ester resin.  
   
   
       31 .- 32 . (canceled)  
   
   
       33 . A process for adhering a cured polyurethane to an uncured diene elastomer composition, characterised in that it comprises the following steps: 
 applying an adhesive composition according to  claim 1 , as adhesion primer, onto the prepolymerised polyurethane;    polymerising the adhesion primer and the polyurethane thus covered with its primer;    then applying onto the thus pre-adherised polyurethane the secondary adhesion layer for diene elastomer capable of bonding to the vinyl ester or polyester resin of the adhesion primer;    bringing the uncured diene elastomer composition into contact with the polyurethane thus adherised;    curing the assembly, preferably under pressure.    
   
   
       34 . A process according to  claim 33 , the secondary adhesion layer being based on a diene elastomer and an additional compound capable of bonding to the vinyl ester or polyester resin of the adhesion primer.  
   
   
       35 . A process according to  claim 34 , the diene elastomer of the secondary adhesion layer being a polyvinylpyridine/stirene/butadiene elastomer (abbreviated to “p-VSBR”).  
   
   
       36 . A process according to  claim 34 , the additional compound of the secondary adhesion layer capable of bonding to the vinyl ester or polyester resin of the adhesion primer being a vinyl ester or polyester resin, preferably a vinyl ester resin.  
   
   
       37 . A process according to  claim 36 , the resin of the secondary adhesion layer being an epoxy vinyl ester resin, preferably a novolac- and/or bisphenol-based epoxy vinyl ester resin.  
   
   
       38 . A process according to  claim 33 , the step of applying the adhesion primer being preceded by a prior step of mechanical and/or chemical activation of the surface of the polyurethane.  
   
   
       39 . A process according to  claim 33 , the polymerisation step of the adhesion primer on the polyurethane being performed at a temperature of between 90° C. and 120° C., preferably under pressure.  
   
   
       40 . A process according to  claim 39 , the duration of the adhesion primer polymerisation step being between 10 and 20 hours.  
   
   
       41 . A process according to  claim 35 , the amount of p-VSBR in the secondary adhesion layer being between 10% and 40% (% by weight of secondary adhesion layer when dry).  
   
   
       42 . A process according to  claim 36 , the amount of resin in the secondary adhesion layer being between 40% and 80% (% by weight of secondary adhesion layer when dry).  
   
   
       43 . A process according to  claim 36 , the secondary adhesion layer furthermore comprising, as solvent for the resin, between 0% and 40% of stirene (% by weight of the ready-to-use secondary adhesion layer).  
   
   
       44 . A process according to  claim 33 , the secondary adhesion layer furthermore comprising a polymerisation accelerator and polymerisation activator.  
   
   
       45 . A process according to  claim 33 , the secondary adhesion layer furthermore comprising a crosslinking system, preferably based on sulfur and sulfenamide accelerator.  
   
   
       46 . A process according to  claim 33 , the secondary adhesion layer furthermore comprising a reinforcing filler, preferably selected within the group consisting of carbon black and silica.  
   
   
       47 . A composite comprising at least a first polyurethane part integral with a second diene rubber part by means of an adhesive interphase, characterised in that said adhesive interphase is based on at least one polyisocyanate compound, a polyester or vinyl ester resin comprising functional groups which are reactive towards isocyanate groups of said polyurethane, and a secondary adhesion layer for diene elastomer capable of bonding to the vinyl ester or polyester resin.  
   
   
       48 . A composite according to  claim 47 , the secondary adhesion layer being based on a diene elastomer and an additional compound capable of bonding to the vinyl ester or polyester resin of the adhesion primer.  
   
   
       49 . A composite according to  claim 48 , the diene elastomer of the secondary adhesion layer being a polyvinylpyridine/stirene/butadiene elastomer (abbreviated to “p-VSBR”).  
   
   
       50 . A composite according to  claim 48 , the additional compound of the secondary adhesion layer capable of bonding to the vinyl ester or polyester resin of the adhesion primer consisting of a vinyl ester or polyester resin.  
   
   
       51 . A composite according to  claim 47 , the adhesive interphase being based on at least one polyisocyanate compound, an epoxy vinyl ester resin and a p-VSBR elastomer.  
   
   
       52 .- 53 . (canceled)  
   
   
       54 . A rubber article comprising a composite according to  claim 47 .  
   
   
       55 . An article according to  claim 54 , consisting of a motor vehicle ground contact system.  
   
   
       56 . An article according to  claim 55 , consisting of a pneumatic tire or a non-pneumatic tire.