The copolymer of ethylene and vinyl acetate is the most important product in ethylene copolymer, which is generally referred to as EVA abroad. However, in China, according to the different vinyl acetate content, ethylene and vinyl acetate polymers are divided into ethylene-vinyl acetate copolymer, EVA rubber and VAE 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 VAE emulsion. The appearance of VAE emulsion is milky white or yellowish.
The study of ethylene-vinyl acetate copolymer abroad is relatively early. British Imperial Chemical Company issued the patent of high-pressure free radical polymerization of EVA*** polymer in 1938, and DuPont Company 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 Plant introduced the VAE emulsion device with an annual output of 15000 tons from the United States for the first time, 199 1 year, and Sichuan Vinylon Factory introduced the same VAE emulsion device from the United States again. Jiangxi Chemical Fiber Co., Ltd. has built a set of production line with an annual output of 1000 tons, but it has never entered substantive production.
VAE emulsion is mainly used in adhesives, coatings, cement modifiers and paper processing, and has many excellent properties.
VAE emulsion has permanent elasticity. VAE emulsion can be regarded as an internal plasticizing 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.
VAE emulsion has good acid and alkali resistance. VAE emulsion can maintain 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.
VAE emulsion can resist ultraviolet aging. Because VAE emulsion uses ethylene as the internal plasticizer of * * * polymer, VAE polymer has internal plasticity, and the plasticizer will not migrate, thus avoiding the aging of polymer performance. Therefore, VAE emulsion not only has good stability to ultraviolet rays, but also can maintain this characteristic after VAE emulsion is formed into a film.
VAE emulsion has good miscibility. VAE emulsion can be mixed with most additives, such as dispersant, wetting agent, antifreeze, defoamer, preservative and flame retardant, so it can meet various needs. VAE emulsion can be mixed with many pigments and fillers without coagulation. VAE emulsion can be directly mixed with many low-molecular and high-molecular water-soluble polymers, such as polyvinyl alcohol aqueous solution, polyethylene glycol aqueous solution, starch or modified starch gelatinization solution, sodium polyacrylate aqueous solution, polymaleic acid aqueous solution, polyoxyethylene aqueous solution, urea-formaldehyde aqueous solution, phenolic aldehyde aqueous solution, hydroxyethyl cellulose, carboxymethyl cellulose aqueous solution, etc. VAE emulsion can be directly mixed with many other polymer emulsions, such as polyvinyl acetate emulsion and polyacrylate emulsion. VAE emulsion can be directly mixed with aldehydes, esters, ketones, organic acids, polyols, higher alcohols, halogenated hydrocarbons and aromatic hydrocarbons, such as formaldehyde, glyoxal, dibutyl phthalate, dioctyl phthalate, acetic acid, carbon tetrachloride, chloroform, benzene, toluene, xylene, octanol, ethylene glycol, glycerol, ethyl acetate and butyl acetate.
VAE emulsion has good film-forming property. Emulsion adhesives can only form transparent films at a certain temperature, which is called the minimum film-forming temperature. The lowest film forming temperature of VAE is generally lower than 5℃, so it can form a good film, and the film has good barrier to water droplets.
VAE emulsion has good adhesion. Good adhesion to fiber, wood, paper, plastic film, aluminum foil, cement, ceramics and other products.
According to the water resistance of VAE emulsion polymer, it can be divided into general type and waterproof type. General product brand VAE polymer has good rigidity and high bonding strength, but poor water resistance. VAE polymer of waterproof product brand has good flexibility and water resistance, but its adhesive strength is low. According to the application performance of VAE, the composition of * * * polymer and the type of * * * third monomer, VAE emulsion can be divided into two categories: adhesives and textiles. Adhesive VAE is mostly used as general adhesive, and textile adhesive is mostly used as textile fiber adhesive, but there is no absolute boundary between them.
Because VAE emulsion has many excellent properties, it is widely used.
VAE emulsion is widely used as an adhesive for adhesives. VAE emulsion has good mechanical properties, small average particle size, good balance between creep resistance and heat sealing, good wet viscosity and fast curing speed. VAE emulsion has a wide range of adhesive properties, which can be used not only for wood, leather, fabric, paper, cement, concrete, aluminum foil, galvanized steel plate and other materials, but also as pressure sensitive adhesive and heat sealing adhesive, and has unique adhesive properties for some difficult-to-adhere materials such as polyethylene, polypropylene, polyvinyl chloride, polyester and other films.
VAE emulsion can be used as the base material of coatings. Coatings based on polyvinyl acetate emulsion, acrylic emulsion, VAE emulsion, styrene-butadiene emulsion, propylene emulsion, vinyl acetate emulsion, etc. Collectively referred to as latex paint. VAE latex paint can be used as interior and exterior wall coating, roof waterproof coating, fire retardant coating and antirust coating. The film of VAE latex paint has good foam resistance, aging resistance, difficult cracking, good adhesion to various substrates, safety, non-toxicity and convenient use. VAE latex paint can be coated not only on wood, masonry and concrete, but also on the surfaces of metal, glass, paper and fabric. It has a good affinity with paint and can be coated on each other's surfaces.
VAE 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 VAE emulsion is one of them. VAE emulsion is mainly used for paper impregnation, paper coating and pulp addition in papermaking process. 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. VAE emulsion can also be used for special paper processing, such as making disposable napkins, towels, diapers, sanitary napkins and so on.
VAE emulsion can be used as cement modifier, and cement is one of the most widely used materials in building 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, VAE emulsion and so on. Among them, VAE 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.
With the improvement of people's living standards and the enhancement of environmental awareness, VAE emulsion has attracted more and more attention from the market. Although the actual output of two sets of imported production facilities in China has been greatly improved after technical transformation, the annual total output of VAE emulsion in China is between 45,000 and 50,000 tons, but there is still a big gap compared with the actual demand, so it can only be supplemented by imports. Therefore, the market prospect of VAE emulsion is good.