Application of PES hot melt glue

Polyurethane adhesive for automobiles
The introduction of a large amount of lightweight metals, composite materials, and plastics into new automotive structures has led to a continuous growth in automotive adhesives and sealants. The most widely used polyurethane adhesives in automobiles are single component moisture cured polyurethane sealants for windshield assembly; Structural adhesives for bonding glass fiber reinforced plastics and sheet molded composite materials, two-component polyurethane adhesives for interior components, and water-based polyurethane adhesives. Automotive interior parts are also an area of increasing adhesive usage. For a considerable period of time in the past, China’s automobile manufacturing industry has been importing polyurethane windshield adhesive from abroad. It was not until the “Eighth Five Year Plan” period that the development of this adhesive was included in the national key scientific and technological research and development project. The water-based polyurethane adhesive widely used in automobiles refers to the adhesive formed by dissolving or dispersing polyurethane in water. Most water-based polyurethanes are linear thermoplastic polyurethanes. Due to the lack of cross-linking in their coatings and low molecular weight, their water resistance, solvent resistance, and film strength are still poor. Therefore, they must be modified to improve their performance. The automotive repair varnish prepared by blending polyester and acrylic acid with urea diketone and isocyanurate does not require high-speed stirring equipment, is easy to mix together, and has good adhesion properties.

Polyurethane adhesive for wood
With the rapid reduction of global forest resources and the implementation of China’s natural forest resource protection project, the adhesive bonding strength and durability weather resistance of small wood splicing boards are required to be superior to the wood itself. The amount of adhesive used has become a symbol for measuring the level of technological development in the wood industry. In the past, the wood adhesives used by people were mainly urea formaldehyde resin, phenolic resin, and melamine formaldehyde resin made from formaldehyde as the main raw material. However, due to the presence of free formaldehyde, the products gradually emit formaldehyde gas to the surrounding area during use, causing environmental pollution. The wood processing industry has begun to turn its attention to the new environmentally friendly adhesive polyurethane glue in order to reduce environmental pollution. The single component moisture cured polyurethane adhesive used in the woodworking industry is liquid and can be used at room temperature. Usually, it has high adhesive strength, good flexibility and water resistance, and can bond with many non wood substrates such as textile fibers, metals, plastics, rubber, etc. The dry and wet strength of single component polyurethane adhesive in testing is better than that of phenolic adhesive. Before bonding, applying hydroxymethylresorcinol (HMR) coupling agent on the surface of the bonding substrate can improve the bonding strength, and HMR can enhance the bonding strength of all thermosetting wood adhesives. When HMR coupling agent is pre coated on the surface of wood, the strength and durability of single component polyurethane adhesive can meet most strict testing requirements.

Polyurethane adhesive for shoes
China is a major shoe manufacturing country, and the development of shoe adhesives has gone through three generations. With the increasing global environmental awareness and the worsening oil crisis, the fourth generation of environmentally friendly solvent-free and water-based shoe adhesives has emerged. The preparation process of waterborne polyurethane has become increasingly mature. For the bonding of some low polarity shoe materials such as SBS, the peel strength of polyurethane adhesive cannot meet the requirements. By adding thickening resins and other modifications, polyurethane shoe adhesives with high crystallinity, fast crystallization rate, high cohesive strength, and ideal peel strength can be developed.

Polyurethane adhesive for packaging
Soft packaging, also known as soft cans, has surpassed hard packaging such as plastic, glass bottles, and cans due to its unique comprehensive properties of lightweight and convenient, long shelf life, hygiene, easy storage and transportation, easy disassembly, low waste volume, and good shelving effect. Polyurethane adhesive, due to its excellent properties, can bond different types of film materials together to obtain composite films for flexible packaging with various properties such as cold resistance, oil resistance, drug resistance, transparency, and wear resistance. Polyurethane adhesive has become the main adhesive for processing composite films for flexible packaging in both domestic and international markets. In the domestic adhesive market, polyurethane adhesive ranks second only to the footwear industry in terms of usage in the packaging composite film manufacturing industry. There are various types of polyurethane adhesives used for packaging, such as water-based polyurethane adhesives, hot melt polyurethane adhesives, solvent based polyurethane adhesives, and solvent-free polyurethane adhesives. The commonly used polyurethane hot melt adhesives can be divided into two categories: (1) thermoplastic polyurethane elastomer hot melt adhesives and (2) reactive hot melt adhesives. The main disadvantage of thermoplastic hot melt adhesive is its high viscosity, which has a significant 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. It 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 wide range of performance adjustment of polyurethane, and has excellent adhesion performance to multiple substrates. In addition, in terms of water-based polyurethane adhesive for packaging, the use of emulsifiers or the introduction of hydrophilic ionic groups in the molecule reduces its water resistance, and research on improving its water resistance has become a hot topic. At the same time, due to the large heat capacity of water, how to increase its solid content to improve its drying speed is also one of the urgent problems to be solved.

5. Polyurethane adhesive for construction
   Polyurethane adhesives not only have the advantages of being non-toxic, pollution-free, and easy to use, but also have unparalleled advantages compared to other adhesives, such as excellent low temperature resistance, solvent resistance, aging resistance, ozone resistance, and bacterial resistance. They play an important role in the application of building paving materials. Widely used in elastic rubber floor mats, hard rubber floor tiles, and plastic track sports fields. The new two-component polyurethane adhesive breaks through the contradiction between shear strength and peel strength of traditional adhesives, enabling both to achieve high usage strength simultaneously. It demonstrates excellent performance in the bonding of steel plates for construction, with strong adhesion and less deformation. Moreover, the curing speed can be adjusted at room temperature, making the polyurethane adhesive easy to use and widely applicable. Polyurethane adhesive is widely used in the bonding of PVC materials in construction, sandwich panel production, and building waterproof coatings.
6. Polyurethane adhesive for ink
   Water based ink is listed as the preferred environmentally friendly printing option. Room temperature cross-linked waterborne polyurethane adhesive can be used to produce one component polyurethane water-based ink suitable for gravure printing. This water-based ink has high gloss and water resistance, strong adhesion, adjustable dryness, bright colors, clear layers, non-toxic and non flammable properties, weather resistance, and easy viscosity control. Compared with other water-based inks, it has a wide range of adaptability to various substrate materials. As the binder of water-based ink, polyurethane polypropylene ester combines the properties of polyurethane adhesive and polyacrylate in the drying process of ink film prints. The modified lotion also has good adhesion fastness to the film.
   The base films used in the color printing industry mainly include polyester film, nylon film, polypropylene film, polyethylene film, etc. The key to choosing ink is that it has good adhesion to all of these base films. A new type of polyurethane adhesive can be prepared by reacting vinyl chloride hydroxyethyl acrylate copolymer containing hydroxyl groups with large molecule diols, small molecule chain extenders, and toluene diisocyanate, which can effectively improve the quality of color printing ink.
7. Polyurethane adhesive for book binding
   In the past 20 years, the application of hot melt adhesive in book binding has experienced rapid development. The main reason is the astonishing growth in the production of low-priced paperback books, accompanied by the emergence of wireless binding technology. Due to the excellent adhesion and elasticity of EVA hot melt adhesive, the vast majority of book binding hot melt adhesive used in the domestic market is EVA type hot melt adhesive. However, EVA hot melt adhesive is expensive and has disadvantages such as memory retention. Polyurethane hot melt adhesive can compensate for the above defects. The production process of this adhesive is simple, the cost is low, the elasticity and toughness of the adhesive are good, the bonding strength is high, the adhesive can be repeatedly melted and used, the product utilization rate is high, and it has a broader application prospect.
8. Application in railway construction
   The adhesive used for ballastless track laying (the development direction of high-speed rail engineering technology) will mainly be domestic polyurethane adhesive products. A convex abutment will be embedded every 5 meters for the single track, and about 17.8kg of polyurethane adhesive needs to be poured on both sides of each abutment. The construction of double track ballastless track requires more than 7 tons of polyurethane sealing adhesive per kilometer. In addition to railway laying, the production of high-speed trains also greatly increases the demand for the use of polyurethane adhesives. Polyurethane plays various essential roles on vehicles, such as glass bonding, floor bonding, joint filling, sealing and waterproofing. On vehicles, based on the CRH3 of the moving train set, a single carriage uses about 84.07L of polyurethane adhesive, which is equivalent to 109.3Kg. It is mainly used for bonding and sealing of car window glass and sealing of some filling parts.
9. Other
   Polyurethane adhesive plays an increasingly important role in the bonding of aerospace equipment, cultural relic protection and restoration, military industry, stationery products, medical and health care, etc. due to its excellent bonding properties.
   Polyurethane adhesive is widely used in various fields due to its excellent performance, and has gradually become an important synthetic material in human life. The global polyurethane adhesive industry is developing towards adapting to environmental protection, safety and hygiene, and resource recycling. The Chinese polyurethane adhesive industry has also shown rapid growth momentum, and significant progress has been made in technological development. With the gradual expansion of polyurethane applications and the continuous enhancement of human environmental awareness. Polyurethane adhesives will play an increasingly important role.