Preparation of neoprene graft adhesive

1 Introduction In recent years, the cold glue bonding method has been widely used in the interface and repair of nylon belts, canvas belts, and flame retardant belts. The PVC all-plastic or rubber-plastic fire-retardant whole-core conveyor belt is widely used in underground coal mine transportation. Because there is no suitable PVC cold glue adhesive, it is rarely repaired by cold glue method. Polymethyl methacrylate (PMMA) is grafted with neoprene rubber and neoprene grafting adhesive of anti-aging agent is added. The activation temperature is low. , Sticky to maintain a long time, wide adaptability. The grafted PMMA side chain is similar to the surface free energy of polyvinyl chloride (PVC), which improves the compatibility between the glue and the PVC and improves the bonding strength. In this paper, the reaction mechanism, preparation process and properties of the reaction were studied.

2 Reaction mechanism The graft copolymerization of rubber (R) and monomer (M) is based on the free radical chain reaction process. The initiator (B) decomposes to produce reactive radicals (I.): B→2I.I. Initiate the monomer formation. The monomer radical (M.): I.+M→M.+IM. Continue to attack other monomers. Monomeric growth chain radicals (P.): M.+M→PI attack rubber to form rubber backbone free radicals (R.): I.+R→R.+IP. Transfer to rubber (R.):P The .+R→R.+P monomer grows on R. to form a graft rubber (RP): M+R.→R-PR., P. Self-polymerization or copolymerization produces a chain termination reaction R.+P.→RP R.+R.→R-RP.+P.→PP

3 experiments
3.1 Raw materials chloroprene rubber (CR) A-90 methyl methacrylate (MMA) industrial grade solvent industrial grade initiator BPO chemical pure polymerization inhibitor HQ chemical pure antioxidant 264 industrial grade thickener industrial grade

3.2 Process After neoprene plasticization, immersed in the solvent to dissolve, until dissolved completely into a three-necked flask with a stirrer device, control the temperature 85 ~ 95 °C, add a certain amount of initiator BPO continue to stir 15 ~ 20min, MMA dissolved in residual BPO, added in 1h, graft copolymerization at 90 ± 5 °C, the reaction 1.5 ~ 2h, adding inhibitor HQ, anti-aging agent 264, and finally added tackifier, Stir evenly.

4 Product Performance Index Appearance: Brownish yellow translucent viscous liquid Viscosity: 1000～1500CP Solid content: 18%～20% Peel strength (PVC-PVC): ≥8.0(kg/2.5cm) Storage period: more than half year

5 Results and Discussion
5.1 Effect of Monomer Concentration In the grafting reaction system, the ratio of CR to MMA has a decisive influence on the grafting reaction and the properties of the adhesive. Experiments have shown that the best CR/MMA is 100/60.

5.2 Influence of initiator concentration The determination of the amount of initiator is the main factor controlling the polymerization rate. When other conditions are constant, the polymerization rate is proportional to the square root of the initiator concentration, the initiator concentration increases, the reaction speed increases, and the viscosity of the glue increases. However, when the amount is higher than 2.4%, the increase in the amount of initiator causes the molecular weight of the polymer to become smaller and the viscosity of the system to decrease.

5.3 Influence of Temperature The reaction temperature has a great influence on the grafting reaction. The reaction temperature is lower than 85°C. The initiation rate and the polymerization rate are very low. When the reaction temperature is higher than 95°C, the initiator is triggered too quickly, which may cause the explosion or polymerization. The premature decomposition of the agent ends, and the polymerization stops at the low conversion stage.

5.4 Effect on PVC leather material's adhesive force It can be seen from the grafting reaction mechanism that the graft polymerization reaction is complicated. The adhesive force of the glue liquid is not only related to the polymerization rate of the monomer, but also the grafting efficiency of the monomer. related. Experiments show that: the polymerization rate of the glue is about 40%, and the grafting efficiency is greater than 50%, the glue has good adhesion to the PVC leather material.

5.5 Ways to increase the grafting ratio of the polymerization reaction Based on the reaction mechanism, prior to feeding, CR is plasticized on the unequal speed roller to form a certain number of chain radical CR. This is undoubtedly necessary to improve the grafting rate. of. The optimal feeding time of monomer MMA is about 15-20 min after the initiator is added, and it is preferable to adopt continuous dropping method, which can effectively reduce the formation of homopolymer PMMA and increase the grafting rate.

6 Conclusion
CR-MMA grafting process is simple, strong adhesion, wide applicability, in particular to solve the problem of PVC bonding. It can be used as a surface protective layer to repair the wear-resisting PVC full-core conveyor belt, so that the PVC full plastic or rubber-plastic whole-core conveyor belt exposed by the wear of the adhesive layer can be used continuously to achieve the goal of saving money.