Performance and application of the hottest polyvin

2022-08-13
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Properties and applications of polyvinyl alcohol film and polyethylene coating film

Abstract: polyvinyl alcohol resin is a water-soluble crystalline polymer formed by the hydrolysis of polyvinyl acetate resin. Its properties are related to the degree of alcoholysis, water content and degree of polymerization. In the 1950s, it was first developed and produced by Kuraray company in Japan and applied to the production of synthetic fiber, which is called vinylon. It was not until the 1970s that the company began to use polyvinyl alcohol for non fiber applications. The brand and typical properties of polyvinyl alcohol resin produced by Kuraray company in Japan are shown in Table 1

key words: polyvinyl alcohol film polyethylene cloth film crystalline polymer alcoholysis degree water content polymerization degree vinylon

polyvinyl alcohol resin is a water-soluble crystalline polymer formed after alcoholysis of polyvinyl acetate resin, and its performance is related to alcoholysis degree, water content and polymerization degree. In the 1950s, it was first developed and produced by Kuraray company in Japan and applied to the production of synthetic fiber, which is called vinylon. In the 1970s, the company began to use polyvinyl alcohol for non fiber applications. The brand and typical properties of polyvinyl alcohol resin produced by Kuraray company in Japan are shown in Table 1

Table 1 trademark and performance of polyvinyl alcohol resin produced by Kuraray company in Japan

polyvinyl alcohol (PVAL) is a white or milky yellow solid powder, which can be dissolved in water and can rapidly swell and dissolve under heating. The film made of polyvinyl alcohol resin has high gas barrier wear phenomenon, which has caused many problems in different fields, and its gas barrier is better than PVC resin; (2) When the melting temperature of polyvinyl alcohol is more than 2 days, PVAL will decompose and spontaneously ignite when there is oxygen at 250~{2, so it is difficult to melt and extrude Pcal into a film;

(3) PVAL can be crystallized after drying and heat treatment, and the crystallized PVAL has a certain water resistance

, and the heat treatment temperature cannot exceed 180%; the barrier property of PVAL film after heat treatment can be improved; (4) The average polymerization degree of PVAL used for extrusion melt film forming is 1400-1800, the average molecular weight is 60000-70000, the saponification degree is more than 99%, and the residual acetate small molecule is less than 0.2%. During extrusion,% distilled water and an appropriate amount of plasticizer glycerol should be added before extrusion blow film forming; (5) The service temperature of PVAL film is 100 ~; Below, it has excellent transparency and is often used as an intermediate layer in composite films to take advantage of its high gas barrier characteristics; (6) PVAL film has high strength, tear resistance and needle resistance. The characteristics of polyvinyl alcohol resin are as follows: (1) polyethylene has excellent porosity and antistatic property, and is not easy to be contaminated with dust. There are two kinds of production of polyvinyl alcohol film. One is to dissolve the PVAL resin in aqueous solution, and then apply it on a stainless steel drum. After drying and forming the film, it can't be revealed that its essence can't be rolled into a film. The other is to use PVAL resin suitable for melting. According to insiders, after adding 40-45% distilled water, about 5% glycerol plasticizer and 3-4% heat stabilizer, it is extruded and blown at 200-230 ℃, Keep 200 more~ {2 and 3min heat setting, the PVAL film always contains 15-35% water in the whole process, and forms a film after cooling. If the produced PVAL film is biaxially stretched 3-4 times under 55-95cc and 50-60% R · h, and then coated with PVDC after 15-26 seconds of heat setting at 170-200 ℃, a double-sided k-coated PVAL film with good heat sealing, oxygen and moisture resistance can be produced, which can be used in gas displacement packaging, oxygen removal packaging, and dry food packaging And drug packaging

due to the low production efficiency, slow production speed and high technical requirements of PVAL solution coating drying film forming method and extrusion blowing method, in order to obtain high oxygen resistance, water-soluble PVAL sol can be coated on BOPP film, and good oxygen resistance can be obtained after drying. The key of this process is that the material will turn yellow and age during long-term use. First, the fastness of PVAL coating layer. In addition to corona treating the coating surface, resins need to be added to the coating layer, such as 0.17 parts of hydroxymethyl melamine, 7-12 parts of PVAL resin, 93 parts of deionized water, 0.05-10 parts of urea, and 1-8 parts of acid catalyst, so as to improve the coating fastness of PVAL glue; The second is to apply the appropriate thickness in order to have good barrier property. With the increase of coating thickness, the coating fastness will be difficult

single PVAL film has recently been widely used in pesticide packaging, and can be made into double bag pesticide packaging. For large outer packaging bags, composite membrane bags with good barrier performance are used, while for small inner packaging bags, only PVAL membrane bags are used, and toxic pesticides are packed in small bags according to the minimum usage. When using, open the large outer packing bag, put the small PVAL pesticide bag directly into water, and use it after dissolving, which can reduce the toxicity of pesticides to workers

Zhou Xiangxing

source: China's packaging industry

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