Industry development trend of various substrates for pre-coating
The main raw materials for precoating film are BOPP film, EVA hot melt adhesive, BOPET film and LDPE hot melt adhesive. The current development status of the industry is as follows:
1. BOPP industry
BOPP film is made of polypropylene particles through co-extrusion and vertical and horizontal stretching, and is used as the base material in the production of BOPP precoating film. BOPP film is widely used because it is light, non-toxic, pollution-free, odor-free, stable in physical properties, good in mechanical strength and air tightness, high in transparency and gloss, good in printing performance, simple in production process, time-saving and labor-saving, low in pollution, and cheap in price.
China is the world's largest producer of BOPP, accounting for about 40%of the world's total production. According to the statistics of relevant departments, the total production of BOPP film in China reached 2. 3159 million tons/year in 2008. By 2013, the new production capacity was more than 2 million tons, which could fully meet the production needs of downstream industries. BOPP is a downstream product of oil production, which changes greatly affected by the price of crude oil.
2. Current situation of EVA industry
EVA is a solid soluble polymer composed of ethylene and vinyl acetate. The higher the content of the latter, the higher the transparency, flexibility and toughness of EVA, and the lower the melting point. According to the content of vinyl acetate, EVA can be divided into foaming grade, wire and cable grade, coating grade, hot-melt grade, etc. , which can be used in packaging, adhesives, printing, footwear and clothing. The coating grade is the most common type of pre-coating film production, which is compounded with the substrate to form a pre-coating film after heating and pressure. The production of such EVA is large in Canada, Germany, Japan, South Korea and other countries. There is no domestic production capacity. However, China Petroleum and Chemical Corporation has established a joint venture with DuPont in China to solve the long-term dependence on import of domestic pre-coated EVA. The price of EVA is affected by the price of crude oil.
3. Current situation of BOPET industry
BOPET film is made of polyester as raw material. It is a colorless, transparent and glossy film with good mechanical properties, high and low temperature resistance, chemical resistance, oil resistance, air tightness and fragrance retention. It is one of the substrates of the barrier precoating film. China is the second largest producer in the world, second only to the United States. The domestic supply of BOPET film is sufficient, and the price is also closely related to the price trend of crude oil.
4. Current situation of LDPE industry
LDPE is a thermoplastic formed by free polymerization of ethylene under high pressure. Its main uses are in the production of film products, agricultural films, packaging films and industrial films. In addition, LDPE is used as hot melt adhesive for BOPET precoating film in the precoating film manufacturing. LDPE has been used for a long time, so the current production process is very mature.
That is, the common point of blistering and film stripping of the film-coated products processed by the gluing wet composite process is that the film breaks away from the substrate of paper and printing, and damages the compactness and smoothness of the paper/plastic composite.
To improve the wear resistance of biaxially oriented polypropylene membrane (BOPP membrane), a novel polypropylene surface modification coating with good transparency and wear resistance was prepared by sol-gel method, using silane coupling agent (KH550), aluminum sec butanol (ASB) and ethyl orthosilicate (TEOS) as precursors, solid acid (p-toluene sulfonic acid) as catalyst
The printing and film are combined by professional laminating equipment to form a paper-plastic product. This technology is called lamination. The surface of the printed matter coated with film is brighter and smoother, the pattern is more bright, and the performance of wear resistance, folding resistance, tensile resistance, moisture resistance, chemical corrosion resistance and other properties are also enhanced. Even some apparent defects in the printing process can be largely compensated. Therefore, not only the service life is extended, but also the beauty of the product is greatly improved. Since the film coating technology was born in the 1950s, the film coating technology has experienced three important development stages:solvent-based coating technology, water-soluble coating technology, and precoating technology.
Precoating film refers to the process of laminating plastic film with paper print after pre-gluing and rewinding. The precoating film structure is composed of substrate and adhesive layer. According to different substrates, the precoating film can be divided into BOPP precoating film, BOPET precoating film and BOPA precoating film. The adhesive layer is mainly EVA hot melt adhesive and LDPE hot melt adhesive. Downstream mainly applies to the packaging of books, food, medicine, daily necessities and other products in the field of industrial printing, digital printing, card certification, anti-counterfeiting, commercial advertising and construction materials in the special products market in the field of commercial printing.