Styrene-butadiene copolymers, process for the preparation thereof and high cohesion adhesive compositions

Abstract

The present patent of invention application refers to styrene-butadiene copolymers (SBR) that are prepared using aqueous emulsion polymerization technology and are intended for the adhesive and sealing industry, being particularly useful in the preparation of contact adhesives and pressure-sensitive adhesives (PSA) and widely applicable in the footwear and furniture industries. The use of this kind of elastomer in processes for preparing adhesives, having an aqueous or solvent base, provides high cohesion to adhesive compositions without compromising or jeopardizing the adhesion. The present invention is also intended to protect the process for obtaining SBR copolymers, simultaneously comprising: aqueous emulsion polymerization at high temperatures, the use of a specific surfactant and the maintenance of the Mooney viscosity and the combined styrene content in the copolymer in high ranges. Another object of the present invention application is the protection of adhesive compositions that are obtained from SBR copolymers, either in solid or latex form.

1 - Styrene-butadiene copolymers (SBR) of high styrene concentration and high Mooney viscosity, characterized by comprising the product of the reaction of high temperature emulsion polymerization, in the presence of a resinous soap emulsifier, which remains incorporated in the copolymers in its acid form, said copolymers having Mooney viscosity between 85 and 150 and styrene content between 45 and 75%. 
     
     
         2 - Styrene-butadiene copolymers (SBR), according to  claim 1 , characterized by the fact that the polymerization temperature is between 40° C. and 65° C. 
     
     
         3 - Styrene-butadiene copolymers (SBR), according to  claim 2 , characterized by the fact that the polymerization temperature is preferably between 45° C. and 60° C. 
     
     
         4 - Styrene-butadiene copolymers (SBR), according to  claim 1  or  2 , characterized by the fact that the Mooney viscosity is preferably between 100 and 130. 
     
     
         5 - Styrene-butadiene copolymers (SBR), according to any of  claims 1  to  4 , characterized by the fact that the total solids content is in the range of 20 to 40%, when in latex phase. 
     
     
         6 - Styrene-butadiene copolymers (SBR), according to  claim 5 , characterized by the fact that the total solids content is preferably between 22 and 30%. 
     
     
         7 - Styrene-butadiene copolymers (SBR), according to  claim 1 ,  2  or  5 , characterized by the fact that the combined styrene content is preferably between 45 and 650. 
     
     
         8 - Styrene-butadiene copolymers (SBR), according to  claim 7 , characterized by the fact that the combined styrene content is more preferably between 50 and 600. 
     
     
         9 - Styrene-butadiene copolymers (SBR), according to any of  claims 1  to  8 , characterized by being applied in the bonding of substrates selected from PVC, thermoplastic rubbers (TR), leather, reconstituted leather, wood, foams, expanded polystyrene, rock wool, glass wool, galvanized substrates and concrete. 
     
     
         10 - Process for preparing styrene-butadiene copolymers (SBR) according to any of  claims 1  to  8 , characterized by the fact that the process for obtaining them comprises, simultaneously, aqueous emulsion polymerization at high temperatures, the use of a resinous soap as a surfactant and the maintenance of the Mooney viscosity and the styrene content in high levels. 
     
     
         11 - Process, according to  claim 10 , characterized by comprising the following steps:
 purging the reactor with gaseous nitrogen to completely remove oxygen from the medium, which would inhibit the process of initiation and spreading of the reaction;   adding a preheated emulsifier at temperatures in the range of 40° C.-60° C.;   adding monomers (styrene and butadiene) and the chain transfer agent;   adding a previously prepared free radical initiator solution;   polymerizing at temperatures in the range of 40° C. to 65° C. until an SBR copolymer latex is formed, the Mooney viscosity of which is controlled to be within the range of 85-150, and the total solids content is maintained in the range of 20-40%;   stopping polymerization, after 600-80% conversion of monomers, by adding a reaction shortstop;   removing unreacted butadiene and styrene monomers;   optionally, coagulating the latex by adding coagulants, such as aqueous solutions of inorganic salts and acids to the coagulation container; and,   washing and drying said SBR copolymer, which contains the surfactant, the resinous soap, incorporated in its acid form.   
     
     
         12 - Process, according to  claim 10 , characterized by the fact that the polymerization occurs at temperatures preferably ranging between 45° C. and 60° C., until an SBR copolymer latex is formed whose Mooney viscosity is controlled preferably in the range of 100-130 and the total solids content is maintained preferably in the range of 22 to 30%. 
     
     
         13 - Adhesive compositions, characterized by comprising between 8 and 200 of the styrene-butadiene copolymers as defined in  claims 1  to  8 , between 8 and 24% of the tackifier agent, between 0.5 and 1.5% of the protection agent and between 54 and 84% of solvents. 
     
     
         14 - Adhesive compositions, according to  claim 13 , characterized by comprising, preferably, between 12 and 16% of said styrene-butadiene copolymers. 
     
     
         15 - Adhesive compositions, according to  claim 13  or  14 , characterized by being applied in the bonding of substrates selected from PVC, thermoplastic rubbers (TR), leather, reconstituted leather, wood, foams, expanded polystyrene, rock wool, glass wool, galvanized substrates and concrete.