The main raw material (PVA) for the production of water-soluble membranes

u003cpu003eIntroduction to the main raw material (PVA) for the production of water-soluble membranesu003c/pu003eu003cbr /u003eu003c/pu003eBackground introduction: The article 'Uses of PVA Water-soluble Membrane' gives a detailed introduction to PVA water-soluble membranes, here is a brief introduction The main raw material for the production of PVA water-soluble film-polyvinyl alcohol. PVA (PVOH) is a special high molecular polymer, which can be water-soluble, and can also be called water-soluble 'plastic'. PVA itself has excellent solvent resistance, gas barrier properties, light transmittance and antistatic properties. PVA water-soluble film products are green and environmentally friendly materials, and are recognized by the national environmental protection departments in Europe, America, Japan and other countries. Third-party test results show that PVA consumes much less oxygen (BOD) than starch. Biological tests have shown that PVA is non-toxic and can prevent the growth and reproduction of microorganisms, and has no effect on solid waste treatment and environmental sanitation; PVA can almost completely decompose, especially after PVA enters the soil, it can also improve the soil. China is the largest producer of polyvinyl alcohol. Domestic manufacturers of water-soluble film products use the most raw materials PVA1788 or PVA1799. The production process is basically a belt alcoholysis process. The quality of products from various manufacturers is uneven. China’s PVA water-soluble film also has 20 For several years, foreign products have been catching up. Several well-known film manufacturers use imported materials to produce fast-dissolving water-soluble films, most of which are Kuraray. The main problems in the use of PVA film □ The leakage of the water-soluble film of PVA used for laundry beads is the most complained problem; some manufacturers solve the problem of leakage by adding additives, and the water solubility of the packaging film becomes poor, and the customer insoluble after use It will stick to clothes. *The tensile strength, tear strength, and experience of PVA film used for general packaging are still different from those of ordinary plastics. *Shopping bags made of all-polyvinyl alcohol are not water resistant. Once they leak or rain, customers will feel bad when using them. Many additives are added to lower the melting point, thereby reducing its biodegradability. u003cbr /u003ePVA film manufacturing method and raw material selection: using special film-making equipment, using the water solubility of PVA to prepare 10%-30% PVA aqueous solution. This method is the basic method for the production of water-soluble membranes abroad, and different modified PVA raw materials are selected mainly for different temperature requirements. In terms of film making, domestic manufacturers mainly use non-modified films such as PVA1799\PVA2488\PVA0588. In order to make up for the shortcomings of film materials, manufacturers mainly use domestic polyvinyl alcohol as the main raw material and add a variety of additives, such as surfactants. , Plasticizers, anti-sticking agents, etc., as well as compound starch, etc., to improve performance, adjust the formula, so that the PVA film has a greater improvement in performance and appearance. Improve the effect, but these are contrary to the basic requirements for the development of green and fast water-soluble PVA water-soluble film. It is difficult to cause environmental problems when controlling the appropriate dosage. If a large amount of chemical additives enter the environment, the damage to the environment is no less than that of ordinary plastics. . The film made in this way will lose transparency. When the cost is acceptable, the use of imported PVA raw materials becomes the first choice to produce PVA fast-dissolving membranes. Film production with ordinary film-making equipment. This method requires pre-preparation of blown film grade PVA pellets and pre-preparation of PVA pellets to meet the processing conditions. It is a composite formula. The main direction of the prefabrication process is to reduce the melting point, improve the plasticizing performance, and improve the film strength and tensile properties. At this stage, although this method of film production cannot fully reach the level of the aqueous solution method, it has a good prospect in terms of production efficiency. On a global scale, we see that almost all manufacturers that produce high-quality PVA water-soluble films are PVA producers, such as Kuraray, Mitsubishi Chemical (Nippon Synthetic Chemical Company), Sekisui, etc., while MONOSOL in the US Its unique manufacturing advantages have included PVA in the bag, and the US MONOSOL company basically produces and sells itself because of its best water-soluble film manufacturer, the US MONOSOL company, and there is no way to talk about export. Some foreign-transported varieties belong to early raw materials, which are eliminated by their own use. From a technical point of view, the selection principles for the production of water-soluble membrane-grade PVA are: 1. Existing market information and manufacturing experience show that only chemically modified PVA can be used to make high-quality detergent bead film from PVA. . Theoretically, PVA that can be filmed can be divided into anionic modified PVA, cationic modified PVA and non-ionic modified PVA, all of which are chemically modified, which can change the crystallinity, melting point and film-forming properties of PVA. The common physical modification methods on the market can also be used to make blown film grade and injection grade PVA. It mainly depends on adding materials to reduce the melting temperature of PVA and improve its processing performance. The disadvantage is that adding additives will affect the performance of the PVA film itself. To prepare PVA film, PVA with high purity, low ash content and low VOC is required as raw material. The water-soluble film prepared from anionic modified PVA has good alkali resistance and good compatibility with corn starch. If the pH value of the laundry liquid is too alkaline, it will have little effect on the water-soluble film. Non-ionic modified PVA can be made into a very soft film. The film made of completely alcoholysis polyvinyl alcohol is hardly soluble in water or soluble in hot water. Films prepared from partially alcoholylated polyvinyl alcohol dissolve faster in water. A film made of water-resistant polyvinyl alcohol can be made into a film with high temperature resistance and water resistance. Choose chemically modified PVA as the main raw material. The fewer types of additives, the better the effect of PVA water-soluble film for food packaging. The types and grades of additives must be strictly restricted and must be approved by the national regulatory authority. u003c/pu003eu003cpu003eu003c/pu003e