With the development of composite flexible packaging materials in China, the composite poly-alkaline adhesive has also passed the history of more than 20 years. Since the mid-1970s, Shanghai first developed the use of extrusion coating and extrusion compounding to make simple composite soft packaging materials for food. In the late 1970s, it first developed a dry composite method to make higher-grade products. Composite soft packaging materials for food, from composite soft packaging materials for general simple foods, to plastic/plastic retort pouches resistant to high temperature cooking at 121 °C for 40 minutes and more advanced aluminum/plastic retort pouches. At the same time, dry composite adhesives were also developed simultaneously.

　　　　　

We know that the dry method is used to make composite flexible packaging materials. In addition to various plastic film and aluminum foil substrates, adhesives are also used. The first to be used is a one-component solvent-based pressure-sensitive adhesive made of butyl rubber. It can be combined with PET, PT and PE to make the simplest and most original composite flexible packaging material. Compresses the packaging aspects of biscuits, candies and mustard. By the end of the 1970s, due to the development of a retort pouch resistant to 121 ° C for 40 minutes, the one-component pressure-sensitive adhesive was obviously not acceptable. Therefore, Shanghai first developed a two-component high-performance polyurethane adhesive. Of course, this kind of adhesive has already been industrialized in China in the 1960s, because its performance does not meet the requirements of composite flexible packaging, there are high boiling point of solvent, serious odor, too much residual monomer, and no hygienic performance. Reliable, too low initial adhesion, etc., can not be used in dry compounding to produce qualified food packaging materials, so the goal of the United States and Japan at that time, re-development research is in line with food hygiene and safety, can withstand 121 ° C40 Minute-cooked two-component polyurethane adhesive. After more than two years of research, it finally passed the appraisal of the State Science and Technology Commission and the Ministry of Light Industry in August 1981, and completed this task.

 

Since 1980, China has gradually reformed and opened up, the people's living standards have improved remarkably, the market economy has become increasingly active, the food industry has developed rapidly, the main and non-staple foods have become increasingly abundant, and the call for perfect packaging has also increased. The demand for composite flexible packaging materials is high. Therefore, Shanghai, Wuxi and Dalian first introduced a relatively advanced production line of composite flexible packaging materials from Japan, including multi-color combined gravure color printing machine, dry laminating machine, bag making machine, slitting machine and corresponding testing instruments. The development of China's modern composite flexible packaging industry has taken the lead. However, gravure inks, adhesives, PET, OPP, OPA, CPP, aluminum foil, etc. required for the production of composite flexible packaging materials must be imported.

 

In order to meet the needs of domestic composite flexible packaging production, since the first half of the 1980s, flexible packaging production equipment has been vigorously developed in various parts of the country. Soft packaging machinery manufacturers in Shanghai, Wuxi, Haining and Guangdong have mushroomed and developed rapidly. The production of color-printed flexible packaging materials has also flourished, resulting in a sharp increase in the demand for imported gravure inks and dry-type composite adhesives. In this situation, Shanghai has a production technology for polyurethane adhesives for food composite packaging materials, and there is soil for industrial production. Therefore, in 1984, the first production base of Chinese food grade polyurethane adhesive with an annual output of 60 tons was established. With this sample base, the packaging industry has seen the hope and prospects of localization of adhesives. In just two or three years, two or three places have successively built enterprises with an annual output of about 500 tons. The climax of localization of adhesives. In the mid-1980s, the Beijing Research Institute of Chemical Industry and the German company Henkel used the technology provided by Henkel to produce solvent-based two-component polyurethane adhesives for dry compounding in China. However, the production technology of the curing agent does not cooperate, and it must be imported from Germany, and then used in combination with the domestically produced main agent. Later, through his own research and development, he mastered the production technology of curing agent, and used the domestically produced curing agent to replace the imported product, which was used together with the main agent produced in China.

　　　

The polyurethane adhesives produced by the domestic technology in the 1980s are relatively rare on the one hand, and are mostly used in low-mid-range composite flexible packaging materials that are not required to be high. On the other hand, there are some defects in the quality, such as too high viscosity of the glue, antifreeze Poor sex, easy to freeze in winter, use it to warm to 50 ~ 60 ° C, let it melt, then can be poured out from the packaging barrel to prepare the operating solution, and on the other hand, the film does not have much function, bonding The force is not very high and the resistance to medium is very poor.