Chloroprene rubber (CR) contains unsaturated double bonds in its main chain. Under the action of a free radical initiator, MMA monomers undergo graft copolymerization with CR via chain transfer reaction, forming a graft copolymer mixture.
A typical preparation process is as follows: Chloroprene rubber is dissolved in a mixed solvent and heated to approximately 85°C. Under stirring and nitrogen protection, an MMA solution containing the initiator benzoyl peroxide (BPO) is slowly added dropwise. After reacting for 3.5 to 4.0 hours, the mixture is cooled and discharged.
Key process parameters include reaction temperature, initiator dosage, monomer ratio, feeding method, reaction atmosphere, and CR concentration. A suitable reaction temperature is approximately 85°C. The amount of initiator BPO should be controlled at approximately 1.0% of the CR mass. The amount of MMA added should be approximately 60% of the CR, i.e., a CR to MMA mass ratio of approximately 1:0.6. A batch-feeding method using a slow, drip-feeding technique to add a BPO-dissolved MMA solution resulted in an adhesive with good grafting rate and bonding properties. The polymerization reaction should be carried out under nitrogen protection. The concentration of CR in the solvent before the grafting reaction should ideally be around 13%.
Based on the above conditions, the optimized process is as follows: reaction temperature around 85℃, BPO addition amount of 1.0% of CR mass, CR to MMA mass ratio of 1:0.5–0.9, CR concentration around 13%, batch-feeding method, and reaction under nitrogen protection. The grafted adhesive prepared using this process has a monomer grafting rate greater than 21%, moderate viscosity, and high adhesive strength.
In addition, a ternary grafted adhesive of chloroprene rubber/styrene-butadiene-styrene copolymer (SBS)/methyl methacrylate (MMA) also exists. Studies have shown that when CR is 100g, SBS is 20g, MMA is 60g-70g, and initiator BPO is 1.2g, and the reaction is carried out at 85℃-88℃ for 4.5 hours, an adhesive with high peel strength and satisfactory water resistance can be obtained, thus improving the adhesion performance of SBS materials.
