Study on Compound Film Adhesive for Food Flexible Packaging (2)

4 Solvent-Free Polyurethane Adhesives
The solvent-free composite process for manufacturing composite film packaging materials has become a well-known and mature application technology. The use of solvent-free adhesives for dry-repair, in addition to the advantages of using solvent-based adhesives for dry compounding, also has the following features: no organic solvents are used, the cost is reduced; there is no organic solvent volatilization on the environment; no solvents are required to volatilize the drying section, reducing the Energy consumption; Composite products have no residual solvent damage, and eliminate the solvent erosion of printing inks; No organic solvents, eliminating the composite substrate susceptible to solvent and high temperature drying damage, so that the composite membrane structure, good dimensional stability The equipment is simple and the floor space is small, saving investment.
For example, the solvent-free two-component polyester-castor oil polyurethane adhesive developed by China Aerospace Corporation 42 has selected polyester as the component of the solvent PU adhesive, and used low-cost and abundant sources of castor oil and toluene diisocyanate (TDI). ), 4,4'-Dibenzoyl diisocyanate polyaddition, the resulting isocyanate-terminated PU prepolymer as component B; the two components were mixed and made. This adhesive is characterized by: suitable viscosity, and can be adjusted by adjusting the polymer composition and molecular weight, and its storage of up to 1a above; high adhesion strength to various composite film materials, high temperature (130 × 8h); cost Low, broad application prospects in food packaging. 
2 Thermoplastic elastomer food bag adhesive 
Guangdong Chaoan County Process Chemical Co., Ltd. used SBS (styrene-butadiene-styrene block copolymer) thermoplastic elastomer, rosin, orange aromatic sugar and a variety of chemical raw materials to synthesize a new type of composite film adhesive. The main raw materials are SBS thermoplastic elastomers, rosin, phenol, formaldehyde, zinc oxide, glycerin, toluene, ethyl acetate, antifreeze, defoamer, T90 resin (a terpene resin). Its products are single-component packaging, easy to use, characterized by: 1 good performance, long service life. After bonding, boiled in 100 °C mixed water for 1 h without peeling; in the 0 °C environment does not harden, does not deink, does not affect the printing ink; 2 dry performance is good, the composite film is not heated, 24 hours after the complete Self-drying, high transparency, and suitable for various films; 3 non-toxic, no odor, no pollution, in line with food hygiene requirements, the preparation process does not produce harmful substances that pollute the environment.
3  Controllable and breathable packaging adhesives
A good gas barrier acrylic/chlorinated polyethylene latex or acrylic/chlorinated polyethylene/ethylene latex is mixed with a poorer gas barrier acrylic/ethylene adhesive, and then coated. When the fabric is covered with a very breathable film (such as a polyolefin), a composite film with controlled gas permeability can be obtained. Adjusting the ratio of the two adhesives can be used both as a food package that requires low air permeability and as a fruit and vegetable package that requires high air permeability.
It can be seen that adhesives for food flexible packaging films have attracted much attention, and new types have also been increasing. At present, almost all manufacturers still use solvent-based polyurethane adhesives, although their excellent performance is outstanding, but because of its toxicity, have adverse effects on human health and the environment, it can not meet people and social requirements. While other new types of adhesives can eliminate toxicity to a certain extent, their performance and cost are far inferior to solvent-based adhesives. Therefore, adhesives used for this purpose require the joint efforts of researchers to achieve their versatility and eliminate deficiencies.