Waterborne polyurethane is two yuan colloidal system of polyurethane dissolved or dispersed in water to form, since the last century in 50s has been 60 years of history, waterborne polyurethane preparation technology has improved, waterborne polyurethane adhesive is a waterborne polyurethane as a main raw material for the production of environmental protection, high performance water adhesive. Polyurethane adhesive without solvent odor, non-toxic, no pollution, convenient operation, easy cleaning residue, high solid content, safe and convenient transportation. In recent years, with the increasingly stringent environmental concerns and other restrictions on volatile organic compounds and toxic substances, which uses water as medium high environmental protection, waterborne polyurethane adhesive low consumption has become more and more important, its applications are constantly expanding, will gradually replace the solvent based polyurethane adhesive to occupy the dominant position in the market.
One. waterborne polyurethane and waterborne polyurethane adhesive
Waterborne polyurethane refers to polyurethane dissolved in water or dispersed in water, according to appearance and particle size can be divided into 3 categories, namely polyurethane emulsion, polyurethane dispersion and polyurethane aqueous solution
Polyurethane emulsion: refers to polyurethane dispersion containing emulsifier dispersion. Through external emulsification method. The particle size of >0.1 m, the appearance of whitish.
Polyurethane dispersion: Polyurethane usually will not contain emulsifier dispersion called aqueous polyurethane dispersion, or polyurethane dispersion, the particle size of 0.001-0.1 m, the appearance of translucent, through emulsification or self emulsifying method. According to the introduction of polyurethane molecules in the hydrophilic group is different, can be divided for anionic, cationic and nonionic.
Aqueous polyurethane: refers to the solution of polyurethane molecules generated by dissolving in water and form. The particle size of <0.001 m, transparent appearance. But as the water resistance of the film is poor, and the process is complicated, the cost is higher, its application is restricted.
In practical application, waterborne polyurethane adhesive is mainly composed of aqueous polyurethane dispersion or emulsion with thickener, defoaming agent, wetting agent, curing agent and so on. The application of water solution in adhesive is very little
Two, the present situation and application of waterborne polyurethane adhesive
Foreign countries started to study on waterborne polyurethane adhesive in 1950s, until 80s in technical breakthrough, to market in 90s. China's research began in the early 1970s, but compared with the international standard, and is still in the development stage of development. With the rapid development of economy, the requirement of environmental protection is more and more high, many domestic units are actively the research and development of waterborne polyurethane, the waterborne polyurethane adhesive in China research and production units. There are hundreds of waterborne polyurethane adhesive with low temperature resistance, flexibility, good adhesive property, physical properties of rubber film can be wide regulating range in various laminate flocking, adhesive, adhesive, automotive interior material carpentry, pressure-sensitive adhesive, is widely used in shoes making.
Waterborne polyurethane adhesive used for general use, must be suitable for deployment, construction conditions and other factors. Base on aqueous polyurethane based added crosslinking agent, thickening agent, filler, plasticizer, pigment and other additives, other types of water-based resin and water. In order to obtain high water resistance. Heat resistance and adhesive strength, at present a lot of waterborne polyurethane has been popular with the crosslinking agent, the composition of the two component system, and the single component solvent based polyurethane adhesive (volatile) system is a bit similar. Sizing method and solvent type adhesive waterborne polyurethane adhesive is basically the same, such as hand brush, roller machine coating, spraying. When spraying, must pay attention to the emulsion particle size and viscosity can not be too big.
Third, the application of waterborne polyurethane adhesive in shoemaking field
1, the development process with the adhesive shoes
The modern shoemaking industry, the key parts of the sole and the upper of the vast majority of products in order to glue, beautiful light, comfortable and durable, reliable quality; and the production process is simple, can carry out automatic and continuous operation.
Adhesive for shoes is the 30 in twentieth Century 40s to start with, but because the bond strength is not high, can only help the real leather sole. Bond leather shoe adhesive era began in 50s after the rapid crystallization type chloroprene rubber adhesive technology makes the advent of shoe-making industry is developing rapidly.
General adhesive Neoprene is the first generation of products in Germany.1957 company launched Bayer fast crystallization type chloroprene rubber, due to the presence of highly polar chlorine atoms in the molecular structure has good adhesive properties of polar materials; and the rapid crystallization and improve the initial viscosity and the neoprene adhesive to a large number of applications, gradually become the dominant the adhesive of the footwear industry.
Grafted chloroprene rubber and solvent based polyurethane adhesive is the second generation.20 century 70s developed cr-g-pmma, namely using methyl methacrylate grafted to the molecular chain of chloroprene rubber, can ease the migration of plasticizer PVC material, so as to improve footwear adhesive and durable fastness. The introduction of other acrylic monomer and polymer polybasic graft copolymerization, the properties of the grafted chloroprene rubber can meet the requirements of shoemaking.
Modification of the methacrylic acid "three benzene" general chloroprene rubber, modified chloroprene rubber and polyurethane adhesive is widely used. The third generation of products which not only has the polyurethane adhesive chloroprene rubber adhesive and excellent elasticity, flexibility and resistance significantly more than the latter, and has excellent water resistance. Oil resistant plasticizer and heat resistant properties, the developed countries in Europe and America in twentieth Century 80 to 90s, gradually make its shoe adhesive conversion from neoprene to polyurethane.
Waterborne polyurethane adhesive is the fourth generation of products, is currently the most advanced products. With the global awareness of environmental protection, and increasing the oil crisis, countries began to control the number of shoe factories, oily adhesive gradually transforms to the traditional water-based adhesives, prompted the fourth generation of environmentally friendly non solvent and water-based adhesives for shoes to emerge and gradually the occupation of the market.
2, the current situation of adhesive for shoes in China
China's shoe-making industry in the earliest use, use wet starch glue the largest, mainly used in shoes shoes lining on the bottom of.60 in the early 1980s began using chloroprene rubber and Graft Chloroprene rubber shoes; the middle of 80s has achieved rapid development of adhesives, modified neoprene, polyurethane adhesive provides good bonded to the bonding soles and uppers. At present, there is production of adhesive for shoes manufacturers more than 200 nationwide, including more than 100 distribution in the coastal areas, is generally accompanied by the base shoe factories.
Guangdong province is China's largest production base of the footwear, shoe adhesive factory is the largest, a total of more than 70, the scale above the level of more than 30, mostly foreign-funded enterprises, in which about half of these adhesive factory (the production of export products and export shoe matching). Fujian Province, Zhejiang Province, the about 40 of production shoe adhesive enterprises. In Jiangsu Province, Shandong Province, Tianjin City, the adhesive for shoes production more than 10 enterprises.
Since the reform and opening up, Chinese footwear industry rapid development, output in 2007 was about 10000000000, 2013 production reached about 20000000000 pairs. The existing domestic shoe-making enterprises are about more than 20 thousand, produced more than 80% footwear adhesive shoes (including shoes, travel shoes, sport shoes, casual shoes and shoes are needed, the basic use of solvent based adhesive) adhesive. With the glue was about 600 thousand tons (nonvolatiles <20% mass fraction).
At present. The outer end of the adhesive, whether at home or abroad, basically is to solvent based polyurethane and neoprene. For high shoe occasions, can use chloroprene latex. The waterborne polyurethane adhesive is water-based adhesive in one of the most important, with its excellent adhesion, outstanding oil resistance, impact resistance, abrasion resistance, low temperature resistance and other characteristics, has been developed rapidly in recent years. A few years ago, some foreign shoe factory in China has been using waterborne polyurethane adhesive, the main raw material of water-based polyurethane adhesive basically for imported products (such as Germany's Bayer OispercollU54, is based on amino sulfonic acid as hydrophilic monomer using acetone, preparation of high solid aqueous polyurethane emulsion), and is mainly used for the production of 4 brand-name shoes from China's export to foreign countries (Nike, Adidas) and OEM orders, the annual consumption of Waterborne Polyurethane Ester gum more than 20 thousand tons; domestic adhesive manufacturers more influential Nanguang resin, Dadong resin, Nanpao resins, these manufacturers mainly produce adhesives, despite water-based adhesive products and has been pushed to the market, mainly to meet the market demand, but also not vigorously promote its application. The domestic shoe brands only Kangnai, Hongxing Erke, double star, red dragonfly, few manufacturers began to use part of the waterborne polyurethane adhesive from before and after 2005.
Dongguan Haiya resin Co. Ltd. as a generalization of a waterborne polyurethane adhesive, was established in 2011, is specialized in environmental protection, promotion of high performance waterborne polyurethane resin adhesive, has launched a series of waterborne polyurethane adhesive products, shoe only aqueous polyurethane adhesives have 5 varieties, curing agent the product is currently in. Lining, double star, ABC (children's), Decathlon and other well-known brands in Fujian and Quanzhou, Putian, Shandong, Gaomi, Yinan and other places many OEM factory application, its excellent hydrolysis resistance, heat resistance, waterborne polyurethane adhesive without yellowing and good initial tack and high peeling strength are better than imported and the existing domestic manufacturers, in the international advanced level.
3, environmental protection, fire fighting pressure and application prospect of waterborne polyurethane adhesive in shoemaking industry
China has become the world's largest footwear producing countries, export and consumption country. In the use of adhesive was 600 thousand tons, more than 90% solvent based adhesive, this adhesive contains a large amount of toluene, xylene, acetone, methyl ethyl ketone, ethyl acetate, alkanes and other organic solvents, with the amount of glue 80% by weight or more. These organic solvents have some toxicity, some inferior adhesive even with benzene to produce more toxic. In addition, the adhesive, footwear industry is also widely used in the cleaning agent, processing agent and polishing agent, is widely used in organic solvents in these raw materials.
Use a large amount of organic solvent resulted in direct contact with occupation disease, emissions in the atmosphere of the organic solvent in the role of ultraviolet light, which can generate ozone and photochemical reaction, aldehydes and other two pollutants. In addition, volatile organic compounds, flammable and explosive, related products for transportation, storage and use of fire. Put forward higher requirements of explosion-proof. In recent years, China's Guangdong, Fujian, Zhejiang and other shoe-making events occurred on the concentration of poisoning, fire, fully reflects the shoemaking industry of environmental protection, fire protection problems need to be solved fundamentally.
So the world has promulgated a number of related VOC (VOC is the floorboard of volatile organic compounds) regulations and laws. In shoemaking industry, in accordance with the provisions of the EU directive rule 1999/13/EG to October 31, 2005, each pair of shoes the VOC limit is 37.5g, in October 31, 2007, VOC 25g. for Nike, Adidas and other first-line brand sports shoes. The VOC is more demanding, at present, each pair of shoes VOC is lower than 25g, but they still take a variety of techniques and methods to make every pair of shoes VOC lower, zero VOC is the ultimate goal.
At present, Europe and the United States by environmental regulations are quite strict, water-based rubber shoes become a common standard in Europe and the United States Shoe field. But the standard of our country is relatively backward, most shoe enterprises still get into the habit of using very large harm oily rubber shoes. The Copenhagen climate conference, China began to introduce restrictions on oily rubber shoes the regulations and measures. In 12th Five-Year planning also clearly put forward the development planning of road water shoe adhesive. Affected by this, some of the strength of the shoe enterprises have begun to consciously choose water-based rubber shoes instead of oily rubber shoes. Shoe of Guangdong Province issued a local shoe industry standard DB44/817-2010< emission standard of volatile organic compounds. The release of 2010-10-22, 2010-11-01 implementation; Fujian provincial Environmental Protection Bureau formulated and issued the "Fujian provincial environmental protection product technical conditions - shoe adhesive on environment; the State Environmental Protection Administration Mark product standard: 2003 promulgated a mandatory national standard "shoes and bags with adhesive (GB19340-2003) >; < - > product certification technical requirements for environmental labeling adhesive (HBC18-2003); <2013 in the first batch of national standards and revision plan notification on the announcement, notice the national standards committee will develop" existing footwear and footwear components the determination of the limited material > phthalate two formic acid ester, "the national standard of organic tin limited material footwear and footwear components in the determination of >.
However, in China's footwear industry, in addition to a number of international brands of shoes processing factory, part of the foreign trade order and a handful of domestic shoe brand, can be said that there is no one to calculate and control the emissions per unit of VOC, a conservative estimate of each pair of shoes VOC at about 100g. From the entire industry, in 2013 there were more than 500 thousand tons of organic solvent is discharged directly into the atmosphere.
Water-based adhesive is the development direction of the footwear industry, the use of aqueous polyurethane adhesives for shoes both from the green barriers to international trade, or the creation of a harmonious society, care for employees, environmental protection standpoint, are of great significance. Green manufacturing is represent the general trend we advocate shoe enterprises, more to join the green environmental protection ranks, caring society, caring for the environment, more calls for the government to enact policies prohibiting "three benzene" adhesive, restrict the use of solvent based adhesive support, help using waterborne polyurethane adhesive. Hope that environmental protection water-based adhesives used in the promotion of Chinese shoe into the fast lane, as the "national ecological beauty, China" China dream "provides a piece of blue sky.