Polyvinyl alcohol processing application and market prospect of
Polyvinyl alcohol processing application and market prospect of ( Liu Wan Chan, Kang Zhiyong, Bai Shengguo ) 0, preface In recent ten years, along with the food industry and agricultural and sideline products deep processing of rapid development, in quality, preservation, and flavor and extend the shelf life of high barrier packaging materials and barrier technology requirements increasingly improving, high barrier packaging materials and barrier technology gets increasingly the attention of people. According to the report, because produce decay or moth-eaten rat in third world countries, food, grain loss rate ranging from 30 to 50%, while the developed countries because of the importance of preservation, protection, storage technology and its development and application of materials, the loss rate in 2 - 3%. In many developing countries, fresh fruit and vegetables in storage and transportation process, due to the lack of appropriate preservation technology and materials, resulting in dry and decaying, the annual loss rate of more than 40%, some even higher amounts to 60 ~ 70%. Our country serves as commissariat, vegetable, food production big country, due to the lack of packaging or packaging, which stored improperly, the grain loss, high amount to 400 ~ 60000000000 kg / year, fruit and vegetable losses of about 75000000000 yuan / year, improper packing fruit decay loss is caused by one of the most important reasons. High barrier plastics packaging materials usually refers to gas, liquid permeable material with high damping materials, i.e., preventing oxygen intrusion to avoid commodity oxidation, preventing water or water vapor permeability to avoid commodity moisture mildew, or prevent fragrance, scent and carbon dioxide to escape, so as to avoid the goods lose their flavor or taste, metamorphic and so on. In fact, both having excellent gas barrier properties, and has good waterproof performance, single or single layer materials is difficult to achieve, should be generally adopted multivariate composite, composite, modification, alloying, vacuum deposition, plasma deposition and other methods to achieve. Therefore, vigorously develop the barrier material is the key to the development of composite thin films. The main high barrier materials with polyvinyl alcohol ( PVA ), ethylene vinyl alcohol copolymer ( EVOH ), polyvinylidene chloride ( PVDC ), PVA of solution, which can degrade performance, as environmentally friendly, high barrier materials with larger market application prospect. 1.PVA, EVOH, PVDC raw materials market and Application 1.1 PVDC PVDC is VDC ( vinylidene chloride ) monomer and a second monomer copolymer pan, typically contains 75% to 90% VDC. PVDC homopolymer has good crystallization, which contains 50% to 80% crystals, high crystallinity and high density decided PVDC copolymer on water vapor and air high barrier, oxygen permeability after PVA and EVOH. At present, the global PVDC resin, the annual output of about 130000 tons, of which 70% for extrusion film. The western developed countries PVDC mainly used for food, medicine and military packaging, but China's PVDC products are more than 90% for cigarettes, food, medicine packaging. China's current annual consumption of 15000 tons of PVDC resin, latex 1000 tons ( dry basis ), domestic PVDC latex for part of the total share of about 20%. PVDC composite film has 5500 tons / year production capacity, and the actual operating rate of about 40%. Domestic PVDC used as packaging materials, is usually associated with other plastic compound or as a coating layer is used, PVDC latex coating film forming process: Substrate unwinding -- pretreatment -- bottom coating -- IR and AIR -- IR -- drying intermediate coating and AIR drying -- surface coating -- IR and AIR -- winding drying China since eighty time introduce PVDC packaging, ninety time begin to have its own PVDC manufacturing industry and the corresponding processing industry. But due to raw materials and processing equipment to rely on imports, and the level of restrictions, PVDC production and application of slow development. Domestic PVDC production capacity of manufacturers mainly in Zhejiang of group company, Shanghai Tianyuan Chemical Plant, chemical plant in Jinxi, but because of the quality of products, technology and other issues have been discontinued or reach design capacity, crop only 3000 tons, to meet the market demand, mainly rely on imports. In recent years, along with the pharmaceutical packaging processes, PVDC usage continues to grow at high speed. 1.2 EVOH EVOH ethylene vinyl alcohol copolymer, usually for 20% ~ 40% ratio of ethylene, 60% ~ 80% ethylene vinyl alcohol, combined with polyvinyl alcohol gas barrier property and processability characteristics of polyethylene. EVOH as a barrier material mainly used for composite barrier layer, for a large number of spices, fruit juice, tomato sauce, meat, cheese and fruit packing box, plastic bottles or fresh-keeping film for packaging food processing industry; oil food, agricultural chemicals and organic solvent; as electronic products packaging. The United States is the biggest EVOH consumer market, accounting for about 46% of the world total consumption, followed by Europe ( 30%), Japan ( 21%), Asia Pacific region accounts for only 3%. The expected global EVOH demand in the next two or three years the growth rate will reach 12 ~ 15%, to 2010 growth rate will be in 10 ~ 12%. Demand growth basically comes from the aspects of food packaging, accounting for about 80% of the total EVOH demand. In addition, from the fuel tank of automobile demand accounts for about 10 ~ 15% of total demand. Due to environmental regulations on passive emission requirements of increasingly stringent, the demand will grow rapidly. At present, the United States has 65 ~ 70% cars using co-extrusion EVOH fuel tank, is expected in 2006 will be increased to 90%. Currently only two company production of EVOH resin -- Japan coke beautiful company and Japanese chemical company, product grades Eval and Soarnol respectively. Originating in the United States and Europe have established branch offices, respectively, is an American EVALCA company and EVAL company in europe. The United States of America Noltex LLC company is Japan Synthetic Chemistry and Mitsubishi Chemical joint ventures, including synthetic chemical companies accounted for 79% of the shares. Dupont, American Quantum company and Solvay company of Italy EVOH production device are discontinued. Table - 12001 world EVOH resin production capacity as shown in the table: Countries and regions the company site production capacity / KT A-1 remarks The United States at the beginning of 412003 to 48 kt / a expansion EVALCA Pasadena, TX 23 Noltex LLC La Porte, TX 18 Western Europe 12 EVAL Belgium Antwerp 122003 capacity expansion to 24 kt / A Chemical synthesis of British construction of Saltend 15 kt / a ( 2003 ) Japan 20 Kuraray Okayama 10 Synthetic chemistry Island 10 The global total of 73125 kt / a ( 2003) According to relevant statistics, currently the world's ethylene vinyl alcohol copolymer ( EVOH ) demand is a two digit growth, such as the annual growth rate of 13% to 14%. In recent years, EVOH huge market potential for international EVOH device construction is also very active. The world's largest producer of EVOH Japan coke beautiful company in 2004 will be located in the Belgian Antwerp new plant capacity doubled, to 24000 tons / year, amplification of the coke beautiful company world EVOH capacity to 57000 tons / year. The company will invest $150000000 in the United States, Saydee, the EVOH production capacity from the current 24000 tons / year increased to 47000 tons / year, is planned for completion in 2006. Originating in Japan Okayama has 10000 tons / year EVOH device. The device after capacity expansion will enable the company to global EVOH capacity of over 80000 tons per year. The company also plans in 2008 ~ 2009 in Europe and new production line. In the EVOH market, coke beautiful rival Japan Synthetic Chemistry, synthetic chemistry company EVOH has a capacity of 45000 tons / year, including Hull 's 15000 tons / year of device. Production of our country EVOH is blank, all dependent on imported. 1.3 PVA China's PVA industry development is rapidder, from 1965 to 1995 the first production plant was built to production capacity and actual output already jumped house world first place, more than 1/3 of global output. According to the 2004" China Chemical Information" magazine ( forty-third ) report, 2003 domestic PVA production capacity of 440000 tons, the actual output of 43.16 reached 10000 tons. Table - 22003 PVA market dynamic unit: million tons Manufacturers PVA production method 1 of Shanghai Petrochemical Company Limited 3.6 ethylene method 2 organic chemical plant in Beijing 3.6 oil ethylene method Sichuan Vinylon factory 3 Vigny 5 gas acetylene 4 Fujian chemical fiber textile group limited company 2.5 of law of calcium carbide acetylene 5 Hunan Xiangwei Company Limited of the 3 law of calcium carbide acetylene 6 Jiangxi chemical fiber company 2.8 of law of calcium carbide acetylene 7 Guangxi Vigny Lun group limited liability company 2.5 of law of calcium carbide acetylene 8 Shanxi 7.5 three-dimensional group company calcium carbide acetylene method 9 Anhui wanwei company group 2.5 of law of calcium carbide acetylene 10 Lanzhou Vigny Lun 2.5 of law of calcium carbide acetylene factory 11 Yunnan Yunwei Company Limited 2.5 calcium carbide acetylene method 12 Guizhou crystal organic chemical group of the 1.6 law of calcium carbide acetylene 13 Shijiazhuang Chemical Fiber Company Limited of the 1 Law of calcium carbide acetylene 14 Siping joint chemical plant in the 2 law of calcium carbide acetylene A total of 42.6 Source: 2005 June online collection of Statistics Table 3 - PVA consumption. A 2002 2003. Consumption ( million tons ) ratio ( % ) consumption ( million tons ) ratio ( % ) The total consumption of 31.1100 43.1100 Fiber with 10 32.15 12 27.84 Non fiber use 21.1 67.85 31.1 72.16 Textile size 7.2 34.12 10.8 34.73 Coatings, adhesives 4.9 23.22 7.3 23.47 Paper 2 9.48 2.8 9 Fine chemical industry 2 9.48 3.21029 The other 5 23.70 7 22.51 Sources: the November 8, 2004" China Chemical Information" magazine ( issue forty-third) Table 3 shows our country coating and adhesive consumption PVA accounted for 60 of the total consumption of ~ 70%, for processing a film is almost blank. Along with the PVA thermoplastic processing technology research and development and PVA has high barrier property and environment friendly, Bound for PVA new application areas open up broad prospects. Table 4 several resin film barrier property Thin films of PVA EVOH PVDC PAN PA HDPE Permeability of g / 24h.m2. 25mm thick ( 30 degrees 90%RH ) more than 50 of 15 ~ 801.55 ~ 4.65 and 77.5370 ~ 4004.7 ~ 10 Oxygen permeability of ml / 24h.m2 thick 25mm ( 23 degrees 0%RH ) < 0.2 ( humidity is high Through increasing the amount of ) 0.4 ~ 57.7 ~ 26.5 and 12.540510 ~ 3875 Oil resistance not radiopaque good not radiopaque. ( excerpt from Zhou Xiangxing." Plastic packaging materials forming and process color printing", China material press, first edition in 1997, 430 - 431 ) PVA film as packaging materials with excellent performance: 1 excellent transparency and gloss; 2 not dust, non-static, good printing adaptability; 3 higher tensile strength and elongation, good abrasion resistance; 4 under low humidity, excellent gas barrier properties and the retention of aroma, oxygen barrier performance is even better than that of EVOH and PVDC; 5 and EVOH, moisture permeability and large, sensitive to water; 6 good metal plating, thermal adhesive; 7 excellent resistance to oil resistance, radiation, and can be used for resisting radiation food packaging; 8 easy to dissolve in water, in water can be hydrolyzed, biodegradation, hydrolysis, degradation and burning of the final product of CO2 and H2O, which belongs to the internationally recognized environmental friendly materials. The main is the lack of moisture permeability, but as a composite film barrier layer can be completely overcome. PVDC is the earliest development of barrier material, but because the molecular chain unit containing two chlorine atoms, garbage incineration to generate a large number of HCL gas, environmental pollution and other reasons, by consumers against, Europe and the United States and Taiwan and other areas have started to use EVOH. Therefore, the rate of development of PVDC and the application prospect is better than PVA and EVOH. The EVOH and PVA properties to PVA, is actually the chemical copolymerization modified varieties, but EVOH is totally dependent on imported raw materials, high price of 80000 yuan / or so tons. PVA film with excellent oxygen barrier performance and environment friendly performance, by consumers, and domestic raw material is rich, the new processing technology of polyvinyl alcohol thermoplastic processing by more and more people's attention, and included in the plastic packaging materials in China" fifteen" development plan. In short, PVDC, EVOH, PVA oxygen barrier performance, retention of aroma and good comprehensive performance, in the packaging field of constant pursuit of performance, reduce the cost and pay attention to the development trend of environmental protection, the development and application prospects of PVDC than PVA and EVOH value, PVA, EVOH moisture resistance as well as three raw material homebred change and processing technologies need to be further solved. 2.PVA processing technology PVA is a polyhydroxy polymer, is characterized by good compactness, high crystallinity, but due to the high melting point, and the decomposition temperature of close, great processing difficulty. Preparation of PVA film, there are generally two kinds of ways: sol coating method or cast ( wet ) and blown film extrusion method ( dry ). 2.1 domestic sol casting coating method Home to the Zhuzhou Institute of Technology in Hunan and Guangdong Zhaoqing Fang Xing packing material limited company as the representative of the sol casting coating method. The method is to prepare a PVA solid content is 18% - 20% water sol, and then cast coating to mirror stainless steel belt, drying the film strip from the strip, and then into the drying chamber to provide moisture to dry, edge cutting, rolling process and the finished film, PVA film performance is shown in Figure 1 and table - 5. Table 5 - coating method the main physical properties of PVA thin films The performance of the unit data Elongation % Tensile strength of M PA 30 ~ 47 Heat sealing strength of N / 15mm 5 ~ 12 The tear strength of KN / M 150 ~ 200 This method requires high purity of materials, impurities which makes films, the blowhole defects such as trachoma, therefore, the PVA sol water must be filtered, impurity or dissolved solids removal. The legal system is the key to control membrane gelatinize and drying temperature and air flow rate, the temperature is too high or hot air amount is too large, will make the film become hard and fever, effect, too difficult to remove moisture, reduce membrane efficiency. 2.2 foreign blown film extrusion method ( wet ) The production of PVA membrane is another method of extrusion blow molding method, currently only found in foreign countries. The patent describes a wet extrusion blown formula, in PVA, adding proper amount of water, plasticizers, lubricants, wetting agent and the bonding agent, using special structure having dissolved, mixing and degassing apparatus of extrusion molding or blow molding film. Optional plasticizer are generally two glycol, dipropylene glycol dinitrate ( sugar ), alcohol, glycerin, glycol and other water soluble compound and other additives, kind and amount of plasticizer on the properties of PVA film has a great influence. The United States of America 's Air Product & Chemical company at a low degree of polymerization of PVA resin developed the brand "Vinex" products, at the same time it has the water-soluble, thermoplastic processing property and biodegradability. " Vinex" through extrusion molding, blow molding, coextruded, spinning, processing packaging films for food products, agricultural water soluble film, containers and disposable consumer goods, its waste in the damp soil by the microorganism phagocytosis and degradation of water and carbon dioxide, the company has built an annual output of 84000 tons of plant, product price about $2.5 / lb. In addition, the Japanese chemical industry company production of " Ecomate Ax" varieties of polyvinyl alcohol resin, the method of PVA was modified into a thermoplastic, molecular structure, its melting point is reduced to 200 to 210 DEG C, the decomposition temperature rises to 240 C ( PVA melting and decomposition temperature of about 230 DEG C to, so it can not be hot forming processing), Ecomate Ax in 214 ~ 230 DEG C for extrusion molding, blow molding, injection molding, made of transparent, water soluble, resistance are very advantageous, for composite forming films, containers and packaging materials. From at present domestic PVA film enterprises to understand, they from the United States, Japan imported PVA membrane is mainly ( wet ) casting products. 2.3 dry film blowing method The two PVA filming process, foreign to the wet extrusion ( CAST ) method is simple, practical, high production efficiency, good stability, but wet extrusion of high energy consumption, equipment structure with special requirements. While domestic sol casting coating method of complex process, long process, high energy consumption, low production efficiency, high product cost. In recent years, light industrial plastics processing and Application Research Institute on PVA plastics was studied, succeeded in finding the temperature can reduce PVA plasticizing plasticization modifying agent, with a slightly improved extrusion machine can carry out the PVA granulation, achieved with the ordinary extruding machine dry film blowing, can obtain the superior performance of the PVA film ( main properties in Table 6 ). Table 6 dry extrusion blow molding ( PVA membrane without treatment ) performance (23 degrees C, RH50%, ) According to a number of single Longitudinal to transverse to the Tensile strength of Mpa 41.7 ~ 54, 39.4 ~ 77.1 % elongation of 340 ~ 380160 ~ 200 Angle tear strength of KN / m 109.1 ~ 151.4, 52.1 ~ 84.9 O2 transmittance coefficient Cm3.cm / cm2.s.cmHg 1.63 ~ 1.97 x 10-13 By the national plastic products quality supervision and inspection center test Granulation and blown film temperature control at 200 degrees Celsius, the thin film thickness can be up to 0.006 ~ 0.008mm, 0.03 ~ 0.06mm in the general control. If the film after appropriate treatment, can slow down the film in water dissolving speed, improve the moisture barrier, oxygen barrier properties and the corresponding mechanical properties. PVA dry film blowing, and has the advantages of simple process, high production efficiency, low cost, will be the development direction of PVA film processing.