XUCHUAN CHEMICAL(SUZHOU) CO., LTD
So far, in addition to the original glue, solvent-free polyurethane structural glue, reactive polyurethane hot melt adhesive and other foreign glue are basically available in China. Although China's polyurethane industry has a considerable scale, there is still a big gap compared with developed countries, mainly because the output is not large, and the technical level is still low. Polyurethane adhesives are widely used in various fields with their excellent properties, and have increasingly become an important synthetic material in human life.
Application of polyurethane adhesives
1. Polyurethane adhesive for automobile
The introduction of large amounts of lightweight metals, composites and plastics into new automotive structures has led to a growing demand for automotive adhesives and sealants. The most widely used polyurethane adhesives in automobiles mainly include one-component moisture-curing polyurethane sealants for windshields, structural adhesives for bonding glass fiber reinforced plastics and sheet molding composites, two-component polyurethane adhesives for interior parts and waterborne polyurethane adhesives. Automotive interior parts are also an area where the use of adhesives is growing rapidly. For a long time in the past, China's automobile manufacturing industry has been importing polyurethane windshield glue from abroad, and it was not until the "Eighth Five-Year Plan" period that the research and development of this glue was included in the national key scientific and technological research projects.
Waterborne polyurethane adhesives, which are widely used in automobiles, refer to adhesives formed by polyurethane dissolving in water or dispersed in water. Most waterborne polyurethanes are linear thermoplastic polyurethanes, because their coating film is not crosslinked, the molecular weight is low, so its water resistance, solvent resistance, film strength and other properties are still poor, must be modified to improve its performance. The automotive refinish varnish prepared by the hybrid and dispersions of polyester and acrylic acid with ureadione and isocyanurate does not require high-speed mixing equipment, is easy to mix together, and has good adhesion properties.
2. Polyurethane adhesive for wood
With the rapid reduction of forest resources worldwide and the implementation of China's natural forest resources protection projects, small wood panels require adhesive bonding strength and durability and weather resistance to be better than wood itself. The amount of adhesive has become a symbol to measure the level of technological development of the wood industry. In the past, most of the wood adhesives used by people were urea-formaldehyde resin, phenolic resin and melamine formaldehyde resin with formaldehyde as the main raw material, but due to the presence of free formaldehyde, the product will gradually emit formaldehyde gas to the surroundings during use, causing environmental pollution. The wood processing industry has begun to look at new environmentally friendly adhesives polyurethane adhesives in order to reduce environmental pollution.
One-component, moisture-curable polyurethane adhesives used in the woodworking industry are liquid and are used at room temperature. Usually it has high bonding strength, flexibility and water resistance, and can bond with many non-wood substrates (such as textile fibers, metals, plastics, rubber, etc.). One-component polyurethane adhesives have been tested to demonstrate better wet and dry strength than phenolic adhesives. Applying hydroxymethylresorcinol (HMR) coupling to the surface of the bonded substrate prior to bonding can improve the bond strength, and HMR can enhance the bond strength of all thermoset wood adhesives. When the wood surface is pre-coated with HMR coupling, the strength and durability of one-component polyurethane adhesives can meet most of the stringent testing requirements.
3. Polyurethane adhesive for shoes
China is a big shoe-making country, the development of shoe adhesives after three generations, with the improvement of global environmental awareness, and the intensification of the oil crisis, the fourth generation of environmentally friendly solvent-free and water-based shoe adhesives have emerged. In recent years, the preparation process of waterborne polyurethane has become increasingly mature. For the bonding of some low-polarity shoe materials such as SBS, the peeling strength of polyurethane adhesive does not meet the requirements. By adding tackifying resin, etc., to modify it, polyurethane shoe adhesives with high crystallinity, fast crystallization speed, high cohesive strength, and ideal peel strength can be developed.
4. Polyurethane adhesive for packaging
Flexible packaging, also known as soft cans, has surpassed rigid packaging such as plastics, glass bottles and cans with its unique comprehensive properties such as light weight and convenience, long shelf life, hygiene, easy storage and transportation, easy to disassemble, less garbage and good shelf effect. Due to its excellent performance, polyurethane adhesive can bond film materials of different properties together to obtain composite films for flexible packaging with various properties such as cold resistance, oil resistance, pharmaceutical resistance, transparency, and wear resistance. At present, in the domestic and foreign markets, polyurethane adhesive has become the main adhesive for composite film processing for flexible packaging. In the domestic adhesive market, in the manufacturing of composite films for packaging, the amount of polyurethane adhesive ranks second only to the footwear industry.
There are many types of polyurethane adhesives for packaging, such as water-based polyurethane adhesives, hot-melt polyurethane adhesives, solvent-based polyurethane adhesives, solvent-free polyurethane adhesives. Among them, the commonly used polyurethane hot melt adhesive can be divided into two categories, one is thermoplastic polyurethane elastomer hot melt adhesive, and the other is reactive hot melt adhesive. The main disadvantage of thermoplastic hot melt adhesives is their high viscosity, so they have a greater impact on the apparent quality of coating. Reactive polyurethane hot melt adhesive is a new type of adhesive developed on the basis of traditional hot melt adhesive, which not only has the characteristics of good initial adhesion and excellent post-curing performance of traditional hot melt adhesive, but also has the advantages of variable composition structure and large performance adjustment range of polyurethane, and has excellent bonding performance for a variety of substrates.
In addition, in terms of waterborne polyurethane adhesives for packaging, due to the use of emulsifiers or the introduction of hydrophilic ionic groups in molecules, their water resistance has decreased, and in recent years, research on improving their water resistance has become a hot spot. At the same time, due to the large heat capacity of water, how to increase its solid content and improve its drying speed is also one of the urgent problems to be solved.
5. Polyurethane adhesive for construction
In addition to the advantages of non-toxic, non-polluting, easy to use, polyurethane adhesive also has the advantages of other adhesives incomparable, that is, excellent low temperature resistance, solvent resistance, aging resistance, ozone resistance and bacterial resistance, and plays an important role in the application of building paving materials. Widely used in elastic rubber floor mats, hard rubber floor tiles and laying plastic track sports fields.
The new two-component polyurethane adhesive breaks through the contradiction between the shear strength and peeling strength of the traditional adhesive, can make the two achieve higher use strength at the same time, reflects excellent performance in the bonding of building steel plates, the bonding is firm and not easy to deform, and the room temperature can be adjusted curing speed, making the polyurethane adhesive convenient and easy to use and widely used. Polyurethane adhesives are widely used in the bonding of PVC materials for construction, sandwich panel production and architectural waterproofing coatings.
6. Polyurethane adhesive for ink
Water-based inks are listed as the first choice for environmentally friendly printing. Room temperature crosslinking waterborne polyurethane adhesive can be prepared suitable for gravure printing one-component polyurethane water-based ink, the water-based ink high gloss water resistance, strong adhesion, dry adjustable, bright color, clear layer, non-toxic and non-combustible, weather resistance, viscosity and easy control, compared with other water-based inks, a wide range of adaptability to a variety of substrate materials.
Polyurethane-polyacrylate as a water-based ink binder, in the ink film printing process, the properties of polyurethane adhesive and polyacrylate are integrated, and the emulsion obtained by the modification also has good adhesion fastness to the film.
The base film used in the color printing industry mainly includes polyester film, nylon film, polypropylene film, polyethylene film and other several, Tianjiang Chemical experts remind that the key to choosing ink is that it should have good adhesion to these base films. Luoyang Tianjiang Chemical New Materials Co., Ltd. uses a new polyurethane adhesive prepared by the joint reaction of vinyl chloride-hydroxyethyl acrylate copolymer containing hydroxyl groups and macromolecular dialcohols, small molecule chain extenders and toluene diisocyanate, which can effectively improve the quality of color printing inks.
7. Polyurethane adhesive for book binding
In the past 20 years, the application of hot melt adhesives in book binding has developed rapidly. The reason is mainly that the production of low-cost paperback books has grown amazingly, and at the same time the wireless binding process has been produced, because EVA hot melt adhesive has good adhesion and elasticity, most of the book binding hot melt adhesives currently used in the domestic market are EVA type hot melt adhesives. However, EVA type hot melt adhesive is expensive, and EVA type hot melt adhesive has disadvantages such as memory. Polyurethane hot melt adhesive can make up for the above defects, the adhesive production process is simple, low cost, adhesive elasticity, toughness is good, high bonding strength, adhesive can be repeatedly melted and used, high product utilization, with broader application prospects.
8. Others
Due to its excellent bonding characteristics, polyurethane adhesives play an increasingly important role in the bonding of aerospace equipment, cultural relics protection and restoration, military industry, stationery, medical and health care.
With the gradual expansion of the use of polyurethane and the continuous enhancement of human environmental awareness, at present, the world's polyurethane adhesive industry is developing in the direction of environmental protection, safety and health, and resource recycling. China's polyurethane adhesive industry has also shown a rapid growth momentum, and technology development has also made great progress.
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