Main uses of ethylene-vinyl acetate copolymer EVA

Ethylene-vinyl acetate copolymer is a copolymer of ethylene and vinyl acetate, and the content of vinyl acetate (VA) is generally 5% ~ 40%. Compared with polyethylene, EVA is widely used in foam shoes, functional shed films, packaging films, hot melt adhesives, wires and cables, toys and other fields because of the introduction of vinyl acetate monomer in the molecular chain, which reduces the high crystallinity and improves the flexibility, impact resistance, filler compatibility and heat sealing performance. Generally speaking, the properties of ethylene-vinyl acetate copolymer mainly depend on the content of vinyl acetate in the molecular chain. The market consumption of 200 1 ethylene-vinyl acetate copolymer is about 290 kt. With the development of China's footwear industry and the increase in the amount of functional films, the demand for ethylene-vinyl acetate copolymer in China will increase year by year. (1) Foamed shoe material is the most important application field of ethylene-vinyl acetate copolymer. In the ethylene-vinyl acetate copolymer used for shoe materials, the content of vinyl acetate is generally 15% ~ 22%. Ethylene-vinyl acetate copolymer * * * mixed foam products have the properties of softness, good elasticity and chemical corrosion resistance, and are widely used in the soles of middle and high-grade travel shoes, hiking shoes, slippers and sandals and interior materials. In addition, the material is also used in sound insulation board, gymnastics mat, sealing material and other fields. Shunde, Zhongshan in Guangdong, Jinjiang, Quanzhou in Fujian and Wenzhou in Zhejiang are the main production bases of China's footwear industry, which consume a lot of ethylene-vinyl acetate copolymer products every year. 1999 In the field of foamed shoe materials and shock absorption in China, the consumption of ethylene-vinyl acetate copolymer is about 150 kt. The main purpose of EVA film is to produce functional greenhouse film. Functional greenhouse film has high weatherability, anti-fog and heat preservation. Because polyethylene has no polarity, even if a certain amount of antifogging agent is added, its antifogging performance can only last about 2 months. The shed film made by adding a certain amount of ethylene-vinyl acetate copolymer not only has high light transmittance, but also greatly improves the anti-fog performance, which can generally exceed 4 months. In addition, EVA can also be used to produce packaging films, medical films, composite films and cast films. From 65438 to 0999, more than 50 enterprises in China used ethylene-vinyl acetate copolymer to process films. 1999, China * * * produced 800 kt of greenhouse film, including 220 kt of functional greenhouse film, and consumed about 30 kt of ethylene-vinyl acetate copolymer. In addition, in the field of packaging film and medical film, China * * consumed 37 kt in ethylene-vinyl acetate copolymer. (3) Wires and Cables With the continuous development of computer and network engineering, halogen-free flame-retardant cables and silane crosslinked cables are increasingly used for the safety of computer rooms. Ethylene-vinyl acetate copolymer is widely used in halogen-free flame retardant cables, semiconductor shielded cables and two-step silane crosslinked cables because of its good filler inclusiveness and crosslinking. In addition, ethylene-vinyl acetate copolymer is also used to manufacture some special cable sheaths. The vinyl acetate content of ethylene-vinyl acetate copolymer for wire and cable is generally 12% ~ 24%. From 65438 to 0999, the wire and cable industry consumed about 6000t EVA. (4) Toy ethylene-vinyl acetate copolymer is also widely used in toys, such as children's wheels and cushions. In recent years, China's toy processing industry has developed rapidly, and its production is mostly concentrated in Dongguan, Shenzhen, Shantou and other coastal areas, mainly for export and foreign processing. According to analysis, these manufacturers consume about 5,000 tons of ethylene-vinyl acetate copolymer every year, and the brands used are basically the same as the materials used in shoe materials. (5) Hot melt adhesive Hot melt adhesive with ethylene-vinyl acetate copolymer as the main component is very suitable for auto production line production because it contains no solvent, does not pollute the environment and has high safety. Therefore, it is widely used in wireless binding of books, edge sealing of furniture, assembly of automobiles and household appliances, shoemaking, carpet coating, metal anti-corrosion coating and so on. It can be used to make refrigerator pipes, gas pipes, civil plates, containers and daily necessities, as well as packaging films, gaskets and medical devices, and can also be used as hot melt adhesives and cable insulation layers. EVA emulsion is the abbreviation of vinyl acetate-ethylene emulsion, which is a polymer emulsion made by emulsion polymerization with ethylene and ethylene monomer as basic raw materials and other auxiliary materials. The copolymer of ethylene and vinyl acetate is the most important product in ethylene copolymer, which is generally referred to as EVA abroad. In China, according to the different vinyl acetate content, ethylene and vinyl acetate polymers are divided into ethylene-vinyl acetate copolymer, EVA rubber and EVA emulsion. Products with vinyl acetate content less than 40% are ethylene-vinyl acetate copolymers; Products with vinyl acetate content of 40% ~ 70% have great elasticity; With elastic properties, people sometimes refer to ethylene-vinyl acetate copolymer in this range as EVA rubber; The content of vinyl acetate in the range of 70% ~ 95% is usually in emulsion state, which is called EVA emulsion. The appearance of EVA emulsion is milky white or yellowish. The study of ethylene-vinyl acetate copolymer abroad is relatively early. In 1938, British Imperial Chemical issued the patent of high-pressure free radical polymerization of EVA*** polymer, and DuPont of the United States realized industrialization in 1960. China began to develop ethylene-vinyl acetate copolymer in the 1960s, and successfully put it into trial production in the mid-1970s. 1988, Beijing Organic Chemical Company introduced the EVA emulsion device with an annual output of 15000 tons from the United States for the first time, 199 1 year, and Sichuan Vinylon introduced the same EVA emulsion device from the United States again. In 2007, Guangxi Guangwei Chemical imported an EVA plant with an annual output of 50,000 tons from the United States. In 2009, it expanded and produced two sets of EVA plants with an annual output of 25,000 tons, which have been put into production. Jiangxi Chemical Fiber has built a production line with an annual output of 1 10,000 tons, but it has never entered substantive production. EVA emulsion is mainly used in adhesives, coatings, cement modifiers and paper processing, and has many excellent properties. EVA emulsion has permanent flexibility. EVA emulsion can be regarded as the internal plasticization product of polyvinyl acetate emulsion. Because it introduces ethylene molecular chain into polyvinyl acetate molecule, the acetyl group is discontinuous, the freedom of rotation of polymer chain is increased, the space obstacle is small, the polymer main chain becomes soft, and plasticizer migration does not occur, thus ensuring the permanent softness of the product. EVA emulsion has good acid and alkali resistance. EVA emulsion can keep stable performance in the presence of weak acid and weak base, so it will not demulsify when mixed with weak acid and weak base, and the product has a wide application range. EVA emulsion can resist ultraviolet aging. Because EVA emulsion uses ethylene as the internal plasticizer of * * * polymer, EVA polymer has internal plasticity, and the plasticizer will not migrate, thus avoiding the aging of polymer performance. Therefore, not only EVA emulsion has good stability to ultraviolet rays, but also EVA emulsion can maintain this characteristic after film formation. EVA emulsion can be used as the base material of coatings. Coatings based on polyvinyl acetate emulsion, acrylic emulsion, EVA emulsion, styrene-butadiene emulsion, propylene emulsion, vinyl acetate emulsion, etc. Collectively referred to as latex paint. EVA latex paint can be used as interior and exterior wall coating, roof waterproof coating, fire retardant coating and antirust coating. EVA latex paint film has good foaming resistance and aging resistance, is not easy to crack, has good adhesion to various substrates, is safe and nontoxic, and is convenient to use. EVA latex paint can be coated not only on wood, brick and concrete, but also on metal, glass, paper, fabric and other surfaces. It has a good affinity with paint and can be coated on each other's surfaces. EVA product EVA emulsion can be used for paper processing. With the development of synthetic polymer technology, many polymer substances play a great role in paper processing, especially some synthetic polymer emulsions have more advantages in paper processing, and EVA emulsion is one of them. EVA emulsion is mainly used for paper impregnation, paper coating and pulp addition in papermaking. Its characteristic is that it can polish all kinds of paper, increase its dry and wet strength, toughness and gloss, improve color stability, reduce ink printing consumption and improve paper grade. As a pulp additive, it can be made into various non-asbestos gaskets. EVA emulsion can also be used for special paper processing, such as making disposable napkins, towels, diapers, sanitary napkins and so on. EVA emulsion can be used as cement modifier, and cement is one of the most widely used materials in construction engineering. However, simple cement products have the disadvantages of easy cracking and poor water resistance, impact resistance and acid resistance, which affect the practical effect of cement to some extent. Since the 1920s, people have been devoted to the study of cement modification. With the deepening of research, it is found that many synthetic emulsions have good effects on cement modification, such as polyvinyl acetate emulsion, acrylic emulsion, styrene-butadiene emulsion, EVA emulsion and so on. Among them, EVA emulsion is widely used in civil engineering as a new material because of its good water resistance, acid and alkali resistance, weather resistance and lower price than similar products. In recent years, for the sake of environmental protection, EVA redispersible emulsion powder has gradually appeared in the market, and gradually replaced the position of EVA emulsion in cement modifier, becoming the main product of main cement modifier.