PVA film manufacturing
PVA is only can be bacteria as carbon source and energy use vinyl polymer, under the action of bacteria and enzymes, 46 days 75% biodegradable, belongs to a kind of biodegradable polymer materials, can be made of non-oil route for mass production, the price is low, the oil resistance, solvent resistance and gas barrier performance is outstanding, has unique advantages in terms of food, medicine packaging. Based on the application of PVA solution method, through stretch film preparation of thin film materials, but the dissolved solution processing molding experience and drying process, and there are complex process, high cost and low production faults, it is difficult to the preparation of thick wall, shape of complex products, at the same time, also can't with other materials for composite membrane preparation multi-layer co-extrusion blow molding.
(1) the copolymerization modification, through copolymerization or macromolecular reaction in the main chain or side of the base forces is introduced in the weaker units, less PVA molecules and molecular inter-atomic forces, in lower melting point; Japanese cola li company can be thermoplastic processed PVA was synthesized, the PVA of alpha olefin containing carbon atom number less than 4 units and/or vinyl ether, melting point is 160-230 ℃; Japan synthetic chemical companies to develop AXPVA copolymer film, its processing performance, in 200-210 ℃, melting point processing temperature at 210-230 ℃.
(2) the blending modification, by joining with hydroxyl groups in PVA can generate hydrogen bonding of polymer, PVA molecular inter-atomic forces, lower melting point or raise the thermal decomposition temperature, such as sugar derivatives, collagen hydrolysate etc. Nishino will Poly real sugar derivatives (GEMA) and PVA blend, raise the thermal decomposition temperature, when the addition amount is to 25 wt %, the mixture of thermal decomposition temperature of 326 ℃. Italian Montedison group Novamont company development and production of the most successful PVA/starch composites "MaterBi" brand, composed of modified starch and modified PVA blend interpenetrating polymer network structure plastic alloy, excellent processability, secondary workability, mechanical properties and biodegradability. The company has developed the extrusion molding with slice, blown film, stretch film, injection molding products, hollow container, toys and other products.
(3) after the modification reaction, based on the modification of hydroxy, PVA molecular chain can reduce the neat degree of PVA and improve the thermal stability of the unit structure, improve the performance of thermoplastic processing on the PVA. Nishimura, studies have shown that alkyl boric acid complex compound can effectively reduce the melting temperature and decomposition temperature of PVA, realize the melt spinning.
(4) plasticizing modification, this method is simple, efficient, domestic and foreign research on plasticizing is more, such as Japanese cola company, Japan synthetic chemical company, the United States dupont, sichuan vinylon factory, sichuan university, Beijing university of chemical industry and business university, south China university of technology, Beijing, and other units with water, inorganic salt, glycerin, polyol and its oligomers, caprolactam, alcohol amine (single or composite plasticizing modifier, reduce the melting point of PVA, improve processing flow