Baypren 350-2

Chloroprene rubber adhesive is the largest and most widely used variety among rubber adhesives. It can be sorted into a few groups, like resin modified, filler, grafted, and latex types. Grafted chloroprene rubber adhesive, which is made mostly of chloroprene rubber and a grafted modifier, is known as easy to their usage, strong bonds, high initial adhesion, and many uses. As early as the 1950s, the shoemaking industry began to use chloroprene rubber adhesive. As shoemaking materials and styles change, standard chloroprene rubber adhesive may not be strong enough. This can cause the upper and sole of shoes, or composite soles, to separate. This issue harms shoe quality and limits growth in the adhesive shoe business. To solve this problem, we used a variety of graftable chloroprene rubbers at home and abroad as graft bodies and used MMA to study their grafting modification.   1 Grafting mechanism     2 Experimental part   2.1 Raw materials and polymerization formula   2.2 Polymerization Procedure Add CR to the solvent. Heat the solution to 50 °C and stir until the CR is completely dissolved. Raise the temperature to 80°C, and slowly add the MMA solution that contains BPO while stirring. Maintain the temperature and continue stirring until the viscosity reaches a suitable level (about 40 minutes). Immediately add hydroquinone to stop the reaction. Keep warm for 4 to 6 hours. After the reaction is complete, cool down to 40°C; add thickening resin, vulcanizing agent, antioxidant and filler, and finally keep warm for 2 to 3 hours, cool down to room temperature, and obtain the product. A small amount of toluene can be added to adjust the viscosity. The obtained graft copolymer (CR-MMA) is a brown-yellow transparent viscous liquid. The viscosity measures between 1000 and 1500 mPa·s. Solid content ranges from 15% to 25%, and the strength registers at 34 N/cm².   2.3 Product analysis 2.3.1 Determination of adhesive viscosity The viscosity value (mPa·s) was tested in a 25℃ constant temperature water bath using a rotary viscometer (Shanghai Optical Factory, NDI-1 type). 2.3.2 Determination of adhesive solid content The film after vacuum drying and constant weight of the adhesive was wrapped with filter paper and placed in a fat extractor. It was extracted with acetone in a 65℃ constant temperature water bath for 48 hours (to remove PMMA homopolymer in copolymerization). The solid content (W%) was calculated according to the following formula: W %=W2 / W1×100% Wherein, W1 is the mass of the grafted adhesive, and W2 is the mass of the film after vacuum drying and constant weight. 2.3.3 Determination of peel strength of artificial leather/artificial leather (PVC/PVC) bonded by adhesive The soft PVC sheet was wiped with acetone or butanone to remove the oil stains on the surface. The entire process was in accordance with GB7126-86.   3 Results and discussion   3.1 Solvent selection The solvent used in chloroprene rubber adhesive is very important. It affects the solubility of chloroprene rubber, the initial viscosity of the adhesive, stability, permeability to the adherend, bonding strength, flammability and toxicity, etc. Therefore, the selection of solvents should take into account many factors. Commonly used solvents include toluene, ethyl acetate, butanone, acetone, n-hexane, cyclohexane, solvent gasoline, etc. The test confirmed that when the solvent cannot dissolve chloroprene rubber alone, two or three solvents can be mixed in appropriate proportions to have good solubility, viscosity and low toxicity.     3.2 Effect of CR type and concentration on the performance of grafted products Different types of chloroprene rubber (CR) show differences in how quickly they form crystals and how deep their colors are. These factors can change how well the grafted materials initially stick together and how they look. Tests show that using Denka A120 Chloroprene rubber and Chloroprene Rubber SN-244X to graft chloroprene rubber results in good initial adhesion and color. The amount of CR does not change peel strength much, but it does affect how well copolymerization works. When the CR concentration is too high, that is, the viscosity is high, MMA is difficult to diffuse and has a strong tendency to self-polymerize. Maintaining the appropriate CR concentration is necessary; if it's too low, the MMA volume will be too small, which slows down the grafting copolymerization. CR concentration works best between 11% and 12%.   3.3 Effect of reaction time on the performance of grafted products Generally speaking, the longer the reaction time, the higher the grafting rate and viscosity value. At the beginning, the initial and final adhesion strengths increase with the extension of reaction time and the increase of viscosity. Extended reaction times coupled with high viscosity can actually reduce both initial and final adhesion. Experiments suggest reaction times should ideally fall between 3.0 and 5.0 hours.   3.4 Effect of reaction temperature on grafting reaction When the reaction temperature is lower than 70℃, the reaction is slow, which is due to the slow decomposition of BPO. Because BPO decomposes quickly above 90℃, leading to a rapid increase in viscosity and poorer processing, we set the reaction temperature between 80°C and 90℃.   4 Conclusion Our initial tests included scaled-up experiments and pilot production runs, which successfully yielded acceptable products. They were supplied to many leather shoe factories and achieved satisfactory results. The quality met the various standards required for shoemaking. CR-MMA grafted adhesive shows better peel strength on PVC artificial leather compared to regular CR adhesive used for boots.The addition of a small quantity of isocyanate (5-10%) can serve as a temporary curing agent. The -NCO group in the isocyanate then reacts with active hydrogen in the rubber, creating an amide bond. This reaction strengthens the rubber's internal structure, improving the overall bond strength.   Website: www.elephchem.com Whatsapp: (+)86 13851435272 E-mail: admin@elephchem.com