EVA foam is a foam made of foamed plastic particles. Foam is divided into PU foam, antistatic foam, conductive foam, EPE, antistatic EPE, PORON, Cr, EVA, bridging PE, SBR, EPDM, etc. EVA plastics and resins are characterized by outstanding softness, rubber like elasticity, good flexibility at - 50 ℃, good transparency and appearance gloss, outstanding chemical stability, good anti-aging and ozone resistance, and non-toxic. It has good mixing property with filler, good coloring and molding processability.
EVA resin is widely used. In general, EVA with vinyl acetate content of less than 5% mainly produces films, wires and cables, LDPE modifiers, adhesives, etc; EVA products with vinyl acetate content of 5% ~ 10% are elastic films; EVA with vinyl acetate content of 20 ~ 28% is mainly used for hot melt adhesives and coating products; The content of vinyl acetate is 5% ~ 45%, and the main products are films (including agricultural films) and sheets, injection molding, molding products, foaming products, hot-melt adhesives, etc. For example:
(1) Film, sheet and laminated products: with sealing, adhesion, softness, strong resistance and tightness, suitable elastic packaging film, heat shrinkable film, agricultural film, food packaging film, laminated film can be used as the intermediate layer of polyolefin laminated film.
(2) General articles: it has the advantages of flexibility, resistance to environmental stress cracking, and good weather resistance. Suitable industrial materials include power wire insulation bags, household appliance accessories, window sealing materials, etc.
(3) Daily groceries include sporting goods, toys, cushions, belts, sealed container covers, EVA rubber football, etc.
(4) Car accessories include shock absorbers, mudguards, interior and exterior decoration accessories, etc.
(5) Foaming products: pressure foaming includes foam plastic slippers, sandals, building materials, etc. Injection foaming has various industrial parts, women's soles, hot-melt adhesives and so on.
Molding process of ethylene vinyl acetate copolymer
EVA can be used for injection molding, extrusion, blow molding, calendering, rotomolding, vacuum thermoforming, foaming, coating, heat sealing, welding and other molding processes.
EVA resin is an ethylene vinyl acetate copolymer, and the content of vinyl acetate (VA) is generally 5% ~ 40%. Compared with polyethylene, EVA is widely used in the fields of foamed shoes, functional shed films, packaging films, hot melt adhesives, electric cables and toys because it introduces vinyl acetate monomer into the molecular chain and then reduces the high crystallinity, which improves the flexibility, impact resistance, filler compatibility and heat sealing function. Generally speaking, the function of EVA resin mainly depends on the content of vinyl acetate in the molecular chain. In 2001, the market consumption of EVA resin in China was about 290 KT. With the development of China's shoemaking industry and the increase of the amount of functional shed film, China's demand for EVA resin will increase year by year.
(1) Foamed shoe material
Shoe material is the most important application category of EVA resin in China. In the EVA resin used for shoes, the content of vinyl acetate is generally 15% ~ 22%. Because EVA resin blended foamed products have soft, good elasticity, chemical corrosion resistance and other functions, they are widely used in the soles and interior decoration of middle and high-end travel shoes, mountaineering shoes, slippers and sandals. In addition, this information is also used in the fields of soundproof panels, gymnastic mats and sealing materials. Shunde and Zhongshan in Guangdong, Jinjiang, Quanzhou in Fujian and Wenzhou in Zhejiang are the primary production bases of China's footwear industry, which consume a large amount of EVA resin products every year. In 1999, China consumed about 150 KT of EVA resin in the field of foamed shoe materials and shock absorption.
(2) Film
The primary use of EVA film is to produce functional greenhouse film. The functional shed film has high weather resistance, fog drop prevention and heat preservation functions. Because polyethylene has no polarity, even if a certain amount of anti fog drop agent is added, its fog drop prevention function can only be maintained for about 2 months; The shed film made by adding a certain amount of EVA resin not only has a higher transmittance, but also has a greater progress in the anti fog function, which can generally exceed 4 months. In addition, EVA can also be used to produce packaging film, medical film, laminated film, casting film, etc.
In 1999, there were more than 50 enterprises using EVA resin to process films in China. In 1999, China produced a total of 800 kt of shed film, among which 220 KT of functional shed film consumed about 30 kt of EVA resin. In addition, in the fields of packaging film and medical film, China consumed 37 KT of EVA resin in the field of film.
(3) Wire and cable
With the continuous development of computer and network engineering, people are increasingly using halogen-free flame-retardant cables and silane crosslinked cables out of consideration for the safety of computer rooms. EVA resin is widely used in halogen-free flame-retardant cables, semiconductor shielded cables and two-step silane crosslinked cables because of its excellent filler inclusiveness and crosslinkability. EVA resin is also used to make sheaths for some special cables. The content of EVA resin used in wires and cables is generally 12% ~ 24%. In 1999, the wire and cable industry consumed about 6000 tons of EVA.
(4) Toys
EVA resin is also widely used in toys, such as children's wheels and cushions. In recent years, China's toy processing industry has developed rapidly. Most of its products are concentrated in Dongguan, Shenzhen, Shantou and other places along the coast, mainly for export and foreign processing. According to the analysis, these manufacturers consume about 5000 tons of EVA resin every year, and the trademarks used are basically the same as those used for shoes.
(5) Hot melt adhesive
The hot melt adhesive with EVA resin as the main component is very suitable for automatic assembly line production because it does not contain solvent, does not pollute the environment and has high safety. Therefore, it is widely used in book wireless binding, furniture edge banding, car and household appliance installation, shoemaking, carpet coating and metal anti-corrosion coating.
The hot melt adhesive mainly uses the kind with vinyl acetate content of 25% ~ 40%. Although there are products with this trademark in China, they have not been produced for a long time, so all of them are occupied by imported materials. In 1999, it was estimated that 17 KT of EVA resin was consumed in the hot melt adhesive category in China.
(6) Other
EVA resin is also widely used in ink, bags, wine bottle covers and other fields. It is estimated that the consumption of EVA resin in these areas is not less than 15 kt.
Cutting such products requires a high-power laser first. The em150w laser tube with high stability and power is used for cutting. The spot is thin and the cutting is perfect. For products with large cutting thickness, focus lenses with large focal length must be selected. The perpendicularity of the cut is good, and the blowing is as big as that. At least 750W fans are used for smoke extraction. Water coolers are also very important. If you want to work for a long time continuously, automatic cooling water coolers are essential. If the size of the product to be cut is small, you can choose a double headed laser cutting machine, which is equivalent to the output of two machines. The specific parameters shall be subject to the specific equipment parameters of the company.