Glue the green direction
Time：2013-08-28 14:37:12 Hits：1597
As China's industrial and agricultural production and export trade development, accelerate the pace of people's lives, improve the level of consumption, travel, tourism increasing food consumption concepts and methods are changed accordingly. Composite bag of food (also known as soft canned food) is its lightweight, convenient, long shelf life, health, easy storage and transportation, easy to disassemble, garbage less good effect and shelves, etc., adapted to the people's daily needs, increasingly people of all ages.
Food package bag is different characteristics adhesive composite film with a dedicated sealing system to overcome the defects inherent single film. To ensure the films from the food content of erosion and ensuring preservation shielding effect, often with PE, PET, PP, NY aluminum film and plastic film or aluminum foil. Such composite film is widely used beverage, pharmaceutical, electronics, pesticides and cosmetics packaging of goods, to become an integral part of modern industrial compound bag.
Package bag with adhesive
To meet the requirements of food packaging bags, special adhesives play a crucial role. It must meet a variety of materials, adhesion, resistance to various food seasoning, fatty acids, fats and proteins, corrosion medium, high transparency, heat resistance, food processing, pressurized retort sterilization temperature (100 ~ 135 ℃) and the moment when the bag sealing temperature (220 ℃), curing speed and the sound requirements. If used in cooking bag making, the above properties are indispensable; if used for general food bag making, performance requirements can be relaxed.
Excellent overall performance polyurethane adhesive compound bag with adhesive to become preferred varieties, domestic and foreign more than 90% of the food composite bags are used to it. According to the data, in 2001 the European polyurethane adhesive for composite film is about 37,650 tons, accounting for almost the total amount of a polyurethane adhesive / 4. Japan 2000 polyurethane adhesive for composite films was 28,098 tons, accounting for the total amount of polyurethane adhesives half. Composite film of polyurethane adhesives for annual consumption of about 30,000 to 40,000 tons, of which about 10% were resistant to cooking adhesive. According to another report, from 2001 to 2002, as the international market downturn, adhesives and sealants manufacturers are in trouble edges, but the U.S. market for food and pharmaceutical packaging composite film adhesives sales always maintained an upward trend, the Asian market is continued strong growth. Expected over the next five years, the global food composite film bag with adhesive average annual growth will be 4%, China will be 15% to 20%.
Status of package bag with adhesive
Since the 1980s, China has imported and self designed and installed dry composite film production line with 300 to 500, which also will be used in the production of polyurethane adhesives rapid development, sales gratifying. Basically they are two-component solution based systems to meet domestic universal composite film production needs. High-performance varieties such as resistance to 121 ℃ or 135 ℃ cooking aluminum / plastic composite film of polyurethane adhesives used in the production a few years ago to rely on imports, Japan, Germany, the United States and other countries adhesive suppliers have to seize the Chinese market, with sales of high prices such products. In recent years, some domestic enterprises and research institutions actively involved in human and material resources of the successful development of a number of varieties resistant to cooking polyurethane adhesive, made gratifying achievements. Liming Chemical Institute RP-05 resistant to cooking food with adhesive composite film is one of a kind. This class polyurethane adhesive can be high temperature, anti-food types of spices, fats and oils erosion produced by domestic and foreign more than dry compound machine machine test, the resulting PET / Al / CPP composite film appearance of three bright, flat, no tunnel, pattern, bubbles and white and so on. Composite bags were loaded by beef, chicken wings and other things actual retort sterilization, are zero rupture. This shows that the developed resistant cooking bag with polyurethane adhesive performance meets resistant cooking bag composite process requirements, with the corresponding import product performance considerably.
The development of environmentally friendly adhesives
Despite the use of the composite film adhesive made no retort pouch samples tested small molecule precipitates; press GB/T9683-88 required testing, in line with food hygiene standards; curing agent-NCO content of less than 0.5%, but also meet the requirements.
But it remains a two-component solvent-based polyurethane adhesives, needs to environmentally friendly adhesives transition. Abroad are actively developing solvent-free and water-based polyurethane adhesive composite film, particularly the former is more active. DuPont, Henkel, Rohm & Haas, BASF, Dainippon Ink and Chemicals and other companies existing products, but most of the general-purpose.
1 solvent-free polyurethane adhesive
Environmental awareness encourage people to actively develop solvent-free polyurethane adhesive, which is normally provided by a relatively low molecular weight polyols and polyisocyanates or polyisocyanate prepolymer and polyol or polyamine comprising two-component adhesive. Adhesives used in such composite films starting in 1974 in Germany, Japan, the introduction of such technology in 1977, to 1997 has built dozens of solvent-free laminating film production line, in Europe and more than 50 per cent of such adhesives for dry composite film industry, has grown to the 4th generation technology. Some high-performance varieties not only good tack, also applies to aluminum foil bonded, the company has successfully developed a high-temperature cooking of special structure of the polyurethane adhesive.
Of solvent-free laminating film production line also has dozens. Beijing Chemical Engineering Institute in 1984 from the German company Henkel introduced solvent-free polyurethane adhesive production technology, available dry composite film production use. At that time, only one because solvent laminating machine, it is not long formal production. Driven by environmental regulations, in 1990, the country also have introduced the corresponding composite production line. But there are some technical problems, lack of capacity utilization.
I believe that the development of solvent-free laminating adhesives adhesives application development is undoubtedly one direction, but there are also many problems. Summed up in the following points:
(A) the amount of glue, though small (only 1.5g/m2), but its price is too high, ordinary glue about 65 yuan / kg, high production costs.
(2) In order to improve the wettability of the film adhesive, the adhesive has a low viscosity required, the result is a low initial cohesion, adhesion is not high, the curing speed is not fast enough, affects the composite production efficiency. This is attributed to the master agent is a polyester polyurethane or a relatively low molecular weight, the general control 3000-4000. If increasing molecular weight, the viscosity is too high, not the composite film, uniform coating, which greatly affect the quality of the composite membrane. Viscosity generally be controlled at 2000 ~ 3000mPa.s. By raising the temperature of the coating and compound (> 40 ℃), to reduce the viscosity, but should be considered a polyisocyanate curing agent security.
(2) water-based adhesives
Water-based adhesives are another environmentally friendly adhesives. Abroad have developed water-based acrylic adhesive, mostly to do with the isocyanate curing agent (made with isocyanate curing agent is considered to be polyurethane adhesive category). In North America because of its abundant raw materials, cheap, high solid content, low viscosity, has succeeded in composite films account for a large share of the market. But so far, the film - film composite water-based acrylic adhesives are still some problems, such as:
(A) technical performance in general, especially in the printed film can only be used on low-end products. Due to water-based acrylate adhesive universal print film in the peel strength of the composite is low, of course, vary depending on the printing ink peel strength category. Food packaging film of printing ink to nitrocellulose used more, unfortunately it with the general water-based acrylate adhesive is compatible composite film is easy to peel, the strength of only (0.1 ~ 0.5) N/15mm. In solvent-based and solvent-free polyurethane adhesive of this phenomenon does not occur, because when these two adhesive composite film after moving to the ink layer, you can still act as an adhesive ink, printing ink layer produces cohesion.
(2) poor response, the film is relatively high molecular weight and low gloss, drying energy consumption, the composite membrane will produce bubbles.
Hydrogen and good crosslinking density of the composite to obtain excellent adhesion of the two key elements.
As the chemical nature of the decision, an aqueous acrylate having no hydrogen bonding strength, so most of crosslinking acrylate adhesive is low. However, one-component acrylic adhesive typically has a high solid content, high shear strength, high mechanical resistance and a long pot life flow, which is the reach of the other water-based adhesives. An aqueous acrylate adhesive to improve the adhesion while maintain its excellent properties, Rohm & Haas company has developed a new two-component acrylic / urethane hybrid thereof. Since the system molecule interpenetrating network structure is formed, the reaction urethane crosslinking points, and compared to a single component acrylic adhesive also has superior cohesive strength, peel strength, moisture resistance, heat resistance and other properties of contents ; and waterborne polyurethane adhesive compared to its bonding properties comparable or better. This superior performance, combined with low prices, so that the composite film packaging applications in the food has a strong competitive edge.
China also has used in the production of composite films acrylate adhesive, but the performance in general. Must be the main agent of the chemical structure of the process of refining.
Polyurethane composite film can also be used a compound, in order to improve their performance, both in development and application of domestic water-dispersible polyisocyanate technology.
3 other environmentally friendly adhesives
Other composite films are environmentally friendly adhesives: UV curing and electron beam curing type, moisture curing polyurethane hot melt adhesive and alcohol-soluble adhesive. Alcohol polyurethane adhesives which have been in Europe Techtronic Industries (Shenzhen) Co., Ltd., organization of production, it is a plastic film / aluminized specific.
Our universal solvent-based polyurethane adhesive composite film has a lot of production, resistance 120 ~ 135 ℃ cooking composite bag with high performance solvent-based polyurethane adhesives have been developed successfully. Environmentally friendly adhesives, such as alcohol-aluminized composite polyurethane adhesives, polyurethane adhesives and solvent-based adhesives are produced. However, because of the price, or problems or because of quality problems, has not as solvent-based adhesives that are widely used. In the future need to actively organize forces to start from the chemical structure of the resin itself, meet the various requirements of developing environmentally friendly composite film adhesive.
