Study on the hottest neoprene adhesive

Research on neoprene adhesive (Part 2)

3 grafting modification of neoprene

grafting modification of Cr, the side chain on the grafting can destroy the regularity of the molecular structure arrangement of Cr, make it difficult to crystallize, prevent low-temperature gel, and increase the cold resistance of the adhesive. Moreover, the viscosity of the grafting adhesive is maintained for a long time and the activation temperature is low, which is suitable for both automatic mass production and manual operation. Therefore, it has developed very rapidly in Asia Japan, Eastern Europe, Australia and Southeast Asia mainly use modified graft CR adhesive as shoe adhesive 95% of shoe factories in China use ordinary and grafted CR adhesive, most of which are ordinary CR adhesive. The amount of grafted CR adhesive is still very small, accounting for only about 10% of CR adhesive. 3.1 binary graft adhesive

Neoprene/methyl methacrylate binary graft adhesive (cr/mma) is the most common graft modified CR adhesive at present Solubility parameters of PMMA side chain and bonded material PVC δ Both are about 9.4, and their surface free energy is similar, both about 3.9n/m. 236 aluminum alloy curtain wall, so it is easy to form a compatible diffusion layer between them In terms of acid-base coordination principle, PMMA containing ester group - O - c=o is alkaline, while PVC is acidic due to the existence of Cl atom, which also promotes the affinity of modified CR adhesive to PVC material More importantly, homopolymer PMMA has good compatibility with plasticizers (esters) in soft PVC, thus solving the problem that plasticized PVC cannot be bonded for a long time At present, the research in this area is relatively mature

3.2 multicomponent graft adhesive

although cr/mma binary graft adhesive has significant advantages in bonding strength compared with ordinary CR adhesive, the adhesive film is relatively hard and brittle. In order to improve its hard brittleness, other acrylate monomers can be used instead of MMA or in combination with MMA Generally, the longer the carbon chain of the alkyl connected to the ester group in the side branch chain of PMMA, the lower the brittleness temperature. However, when the carbon chain of the alkyl group is too long (such as the number of carbon atoms is greater than 9), the crystallinity of the side chain will restrict the flow of the whole molecular chain, but reduce its softness and increase its brittleness temperature MMA can usually be partially replaced by n-butyl methacrylate (nBMA) or isobutyl methacrylate (IBMA)

in order to meet the needs of mechanized production of shoes, the adhesive must have the characteristics of short drying time, long holding time and high initial bonding strength. At the same time, in order to adapt to the bonding of various shoe materials and the requirements of light color, the development of multi-purpose multi-component Graft Adhesive Based on cr/mma binary graft adhesive is an important trend in the development of neoprene in China At present, the research and development of grafted CR adhesive are mostly to add the third polymerized vinyl monomer or the fourth polymerized monomer, or to add a certain amount of styrene butadiene rubber (SBS) while adding the third and fourth monomers for multi-component graft copolymerization

3.2.1 cr/mma2ba

due to the introduction of butyl acrylate monomer (BA), the grafting system has excellent adhesion to PVC, SBS and other difficult to stick materials, with large initial viscosity and high peel strength, which can be cold bonded and injection molded hot bonded

3.2.2 Cr/MMA AA

due to the introduction of monomer acrylic acid (AA) containing active groups, this adhesive can act directly with curing agent isocyanate (- nco-), shorten the drying and curing time in the bonding process, and has excellent bonding properties for a variety of materials

3.2.3 cr/mma2vac

the vinyl acetate (VAC) monomer introduced by this adhesive has low cost, good compatibility with PVC, good affinity with plasticizers and oils, and reduces the amount of MMA with high cost. It is used for the bonding of PVC, PU and other materials

3.2.4 cr-sbs/mma

grafting modification with MMA can improve the CR of the skeleton material（ δ 2 =9.0) and SBS（ δ 2 =8.5), which makes them become a homogeneous system under a certain proportion, and has become an ideal cold viscose for new shoe-making materials In addition, Cr and SBS were grafted and copolymerized with MMA respectively, and then mixed into adhesive

3.2.5 cr-nr/mma

this adhesive overcomes the shortcomings of cr/mma binary Graft Adhesive in terms of insufficient bonding strength between PVC and natural rubber (NR), and improves the bonding strength between pvc/nr on the premise of maintaining sufficient bonding strength between PVC and PVC

3.2.6 cr-sbs/mma2ba quaternary graft adhesive

this adhesive has a light color and is suitable for the bonding of a variety of shoe materials, especially SBS, thermoplastic rubber (TPR) and other materials. The peel strength is more than 70n/25mm. It was developed by Guangzhou Institute of chemistry

3.2.7 cr2sbs/mma2aa quaternary graft adhesive

due to the introduction of active monomer AA, the adhesive provides a direct cross-linking point, which shortens the drying and curing time during bonding, and improves the initial adhesion. For some difficult to stick materials such as SBS, TPR, etc., it can be directly coated without first using surface treatment agent, simplifying the production process Its peel strength is 30 ~ 40n/cm

3.2.8 cr/hccp2mma

on the basis of cr/mma binary graft adhesive, the introduction of high chloride polymer (HCCP) components such as polyvinyl chloride (PVC), chlorinated polyethylene (CPE), chlorinated rubber (CLR) and chlorinated polyvinyl chloride (CPVC) has also achieved good results. At present, researchers engaged in this work mainly include Ma Xingfa of Shandong Institute of non metallic materials and he Jinliang, Wang LIA, etc. of Hubei Institute of chemistry

research shows that the introduction of HCCP has significantly improved the performance of CR adhesive, especially for the bonding of PVC materials. The adhesion of PVC synthetic leather, leather, cloth, foaming materials (EVA, PVC) and vulcanized rubber is also higher than that of cr/mma binary graft adhesive. Therefore, the development prospect is good, but there are few visible studies at present, Most of the reported studies introduced the influence of the addition of a small amount (the weight ratio is generally no more than 10%) of the third component of HCCP

Gong Chunhong and others selected chlorinated polyvinyl chloride (C system display calibration zero point pvcj2700, cpvcn2500), chlorinated polyethylene (CPE), vinyl chloride 2 vinyl acetate copolymer (CEVA) and other perchloride polymers (HCCP) for experiments. Through the preparation and in-depth research of hccp/CR series ternary graft adhesives with different proportions, they characterized them by modern analytical means such as electron microscopy, infrared spectroscopy, differential thermal analyzer, etc, The viscosity, peel strength, water resistance, aging resistance and durability of the product were tested The results show that a large amount of HCCP can be introduced to replace Cr (hccp:cr 7:13), and the properties of the ternary graft adhesive obtained are significantly improved than those of cr/mma binary graft adhesive. However, due to the plastic nature of HCCP itself, the addition amount should not be too large Considering the production and use performance, hccp/CR below 7/13 can meet the requirements of adhesive For domestic HCCP (CPVC), due to its low price, it can also reduce the cost of adhesive; For imported HCCP (CPE, CEVA), due to its small molecular weight, the viscosity of the adhesive can be changed as required without changing the adhesive and without adding other materials such as the volatile content and monomer conversion rate of non-metallic, metallic or organic materials to the pure resin, so as to meet the requirements of different operations. For example, the spraying operation requires a lower viscosity, while the higher viscosity is used for brushing operation

4 conclusion

(1) because the preparation process of ordinary CR adhesive is relatively simple, the cost is low, and its performance can meet the general use requirements, it still has a large market at present, and most of the domestic shoe industry now adopts this adhesive

(2) as the main modified variety of ordinary CR adhesive, the development of grafted CR adhesive has expanded the application range of CR adhesive, improved the bonding performance of CR adhesive pig iron market price stabilizer, and with the competition of market product quality, it has a great trend to replace ordinary CR adhesive. At present, there are many researches in this field, but most of them are in the development stage, and the practical application of grafted adhesive is less

(3) although the performance of grafted CR adhesive is good, when the system is complex, there will be some side effects, such as glue layering, short shelf life, unstable performance, and so on. Some glue viscosities are too high, causing some trouble for construction In addition, there are too many components in the system and strict requirements on the production conditions of the glue solution, such as the proportion of raw materials, reaction time and temperature, stirring speed, the addition order of raw materials, etc., which bring considerable difficulties to the actual operation Therefore, these factors need to be considered in the development of grafted CR adhesive, especially multicomponent graft adhesive

(4) the solvent used in the solvent based CR adhesive system is mainly "triphenyl" solvent, which is because this kind of solvent (benzene, toluene, xylene) has good solubility to Cr, low price and fast drying speed, but the fatal disadvantage is that it is toxic. From the perspective of environmental protection, the selection of new non-toxic or low toxic solvents to replace benzene solvents and the development of water-based CR adhesives have attracted more and more attention The main problem is that the price of solvents (ketones) is expensive, and the solubility is not very ideal, while the drying speed of water-based CR adhesive still needs to be greatly improved

author/Gong Chunhong, Lu Guangyong

(11 school of chemistry and chemical engineering, Henan University, Kaifeng, Henan 475001; 21 Department of chemistry, South China Normal University, Guangzhou, Guangdong 510631)