The objective and practical requirements are also increasingly diversified and rigorous. As a result, the adhesives used in composite materials are no longer limited to ordinary properties such as room temperature use and moisture and temperature resistance, but also satisfy special conditions and special conditions of use. Performance requirements. Specifically, it includes corrosion resistance to chemical media, high versatility, high transparency, good temperature resistance, and fast curing. Here are some brief descriptions of their characteristics and applications.
First, anti-chemical media erosion adhesive
Chemical media are diverse. In foods there are salty, sour, spicy, spices, alcohol, water, grains, carbon dioxide, oils, proteins, etc.; in addition to water, there are flavors, spices, polyols, pigments, emulsifiers, surface Active agents, various additives, etc. Chemicals include solvents, pesticides, acids, alkalis, and salts.
These chemical substances have different characteristics but one thing in common is the corrosion and destruction of the adhesive layer of the composite material, which can cause separation, rupture and failure of the composite packaging bag. This requires the adhesive to have a good chemical resistance to aggressiveness, that is, the glue can maintain a good adhesive force in the case of resisting the above chemical medium, and ensure sufficient peeling degree.
The adhesive is resistant to acids, salt and salt because it contains a small amount of urethane and carboxylic acid esters, as well as a small amount of activity on the aluminum foil surface. Elements react chemically to produce specific chemical bonds that allow the adhesive and aluminum foil to chemically react to form a strong bond.
Ordinary adhesives work with van der Waals force, double-elastic force, dipole moment force, or dispersive force. These adhesives need chemical bond strength, which is much stronger than simple adhesion. , better withstand the erosion of various media. Therefore, the mustard bags made with it have better quality.
Second, the versatility of the adhesive
The versatility is strong, that is, the adhesive is required to have good adaptability, and can be used for the composite of aluminized film and aluminum foil in addition to the common ordinary optical film such as CPP, OPP, PE, PET, and nylon. In addition, it is also required that the adhesive be used on a low speed machine; it can also be used for high speed recombination.
Compared with ordinary adhesives, this kind of adhesives introduce functional genes into the molecules; they change the structure of the molecular chain, and they have the same urethane and carboxylate structure as ordinary polyurethanes. The aluminum metal surface active element reacts chemically; chemical bonds are formed in the chemical bond, so that a relatively firm bond is formed between the adhesive layer and the aluminum layer. This combination is like a tight bond between the adhesive layer and the aluminum layer. The bonding force of the bridges and ordinary adhesives mainly comes from intermolecular cohesion; it includes van der Waals forces, dipole distance forces, dispersive forces, etc. These forces are weak relative to chemical bond forces. Therefore, this new functional adhesive can provide much stronger composite fastness than ordinary adhesives, and is fully qualified for the composite of aluminum foil, aluminized film and other various substrates.
Third, high transparency adhesive
With the continuous improvement of product quality and to meet the needs of export, transparency has gradually become an important indicator of customer requirements. Especially in food and clothing, there are many applications for high-transparency packaging, and there are many factors that affect the transparency of composite packaging products. In addition to plastic substrates, the main causes related to the adhesive itself are insufficient adhesive fluidity. Poor flatness, resulting in the glue on the surface of the substrate can not be well wet, the formation of water marks traces affect the transparency of the product.
By controlling the molecular weight, we keep the length of the molecular chain in a suitable range. Due to the high content and low viscosity; good fluidity, this greatly improves the transparency of the product. In addition, through the adjustment of production raw materials and processes, the amount of side impurities introduced into the colored impurities is controlled, and the transparency of the product is further improved.
Fourth, fast curing adhesive
After the general two-component adhesive is well compounded, it should be placed in an environment of about 50° C. for 24-48 hours or more in order to fully cure the adhesive layer; only then can the next process be performed. This brings with it a problem: aging takes too much time and production efficiency is low, so customers have come up with the possibility of supplying a fast curing adhesive. (to be continued)
