Application of hot melt adhesive coating technology
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First. Introduction
Hot melt adhesive coating is a green coating coating technology. At present, although the development history of domestic hot melt adhesive coating process has been more than ten years, the manufacturing technology of hot melt adhesive coating machine is still in the immature stage in China, and many hot melt adhesive coatings produced by printing and packaging machinery manufacturers. Machine, its main quality problems have not been well resolved.
Hot melt adhesive, as its name suggests, is a glue that is heated and then melted and coated to bond various materials together. Compared with other adhesives, hot melt adhesives have the following characteristics: 100% solid composition, solvent and water-free components; thermoplasticity, which can be repeatedly heated and cooled and solidified. This process is reversible, chemical physics of hot melt adhesives. The nature does not change as a result; the hot melt adhesive must be applied while it is heated to a molten state; the hot melt adhesive is solidified by cooling to produce adhesion.
Since its inception, hot melt adhesives have been widely used in food packaging, bookbinding, disposable hygiene products, furniture industry, label industry and other fields due to their high bonding strength and fast curing speed.
Second, the new technology and development trend of the hot melt adhesive industry
1. Low temperature hot melt adhesive
Low-temperature hot-melt adhesives have broken through the limits of the use of conventional hot melt adhesives. Its normal operating temperature is only 110 ° C ~ 130 ° C, low temperature hot melt adhesive is 30 ° C lower than the traditional hot melt adhesive. Compared with traditional hot melt adhesives, low temperature hot melt adhesives have significantly lower viscosity values, ensuring that the coating process requirements are met under low temperature operating conditions.
The direct benefit of low temperature hot melt adhesives is the savings in electricity and machine maintenance. A large number of practical applications show that the same hot melt machine, using low temperature hot melt adhesive can save customers about 15% of the electricity bill. However, since the low-temperature hot-melt adhesive has almost no aging phenomenon such as skinning and carbon deposition at its normal operating temperature of 110 ° C to 130 ° C, the maintenance cost of the machine is greatly reduced. More importantly, low temperature hot melt adhesive will not burn PE film.
2. Hydrophilic hot melt adhesive
Conventional hot melt adhesives are generally hydrophobic, and hydrophilic hot melt adhesives are made hydrophilic by special formulations. Each application of hydrophilic hot melt adhesives can give higher added value to the products and produce products. In the current highly competitive market, manufacturers effectively differentiate their products and ultimately win consumers.
3. Other new technologies for hot melt adhesives
In addition to the above aspects, the new technology of hot melt adhesives include: oil-resistant hot melt adhesive; hot melt adhesive suitable for high frequency spraying; high wet strength hot melt adhesive; degradable hot melt adhesive and so on.
Third, the classification of melt coating technology
1. Scrape system
In the coating process, the glue is often uneven, which requires a certain scraping mechanism to evenly scrape the glue. The scraping mechanism mainly includes a stainless steel scraper, a comma scraper, a scraping bar, a wire scraper, an air jet scraper, and the like.
2. Texture coating
This coating apparatus mainly uses a textured coating roll for sizing coating. The coating is uniform and the coating amount is relatively accurate. However, once the type of the coated anilox roller and the glue are fixed, it is difficult to adjust the coating amount, which is also the main reason for the limited application of the textured coating roller.
3. Calender coating
This method applies a rubber or the like to a surface of a paper or a textile substrate by a calender, and has a film calendering coating and a powder calendering coating. In the former, the coating plastic is formed into a film, and then heated and melted and bonded to the surface of the substrate by a calender roll; the latter is sprayed on the surface of the substrate by a powdered resin, and then heated and melted and bonded together by a calender roll.
4. Spray system
This coating equipment mainly heats and melts the solid type glue, and then sprays the glue directly onto the substrate through a coating die by a hydraulic device.
Fourth, no scratch coating technology
In 2007, in response to market demand, the research and development of hot melt adhesive coating equipment technology for film materials began. A new scratch-free hot melt adhesive coating head is available, which has the following features:
"No scratch" effect, especially suitable for coating and compounding of PET, PVC, OPP and other materials; minimum weight: up to 15g/m2, running speed up to 180m/min; high degree of automation, using PLC control, multiple functions and The operation is integrated in the human-machine interface to ensure that the operator can easily control the device.
The successful development of this equipment has filled the gap in China's technology in this area and is the first in China. It solves the situation that hot melt adhesive coating and UV curing hot melt adhesive coating of PET, PVC, OPP and other materials rely on imported equipment, saving a lot of capital investment for the upgrading of products in the industry.
In recent years, foreign countries have successively developed a new generation of environmentally friendly new products such as biodegradable and water-dispersible hot melt adhesives. Because this modified rubber is different from traditional thermosetting and solvent-based adhesives, it does not contain any solvent and does not pollute the environment due to solvent evaporation. Therefore, new environmentally-friendly hot melt adhesives are attracting more and more people in the industry. It is valued and favored by the market.