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With the development of composite flexible packaging materials in China, polyurethane adhesive for composite has also gone through a history of more than 20 years. Since the mid-1970s, Shanghai first developed the extrusion coating and extrusion composite method to manufacture simple composite flexible packaging materials for food. In the late 1970s, it first developed the dry composite method to manufacture more high-grade composite flexible packaging materials for food, from general composite flexible packaging materials for simple food to plastic/plastic cooking bags that can withstand 121 ℃ high temperature cooking for 40 minutes and more advanced aluminum/plastic cooking bags. At the same time, dry composite adhesives are also developed synchronously

we know that the dry method should be used to make composite flexible packaging materials. In addition to various plastic films and aluminum foil substrates, adhesives should also be used. One component solvent-based pressure-sensitive adhesive made of butyl rubber was first used. It can be used to compound pet, Pt and PE films to make the simplest and most original composite flexible packaging materials, which can be used in the packaging of compressed biscuits, sweets and pickles. By the end of the 1970s, due to the need to develop cooking bags that could withstand 121 ℃ high temperature cooking for 40 minutes, it was obviously impossible for one component pressure-sensitive adhesive. Therefore, Shanghai was the first to develop two-component high-performance polyurethane adhesive. Of course, this kind of adhesive has been industrialized in China since the 1960s. However, because its performance does not meet the requirements of composite flexible packaging, it has some shortcomings, such as high boiling point of solvent, serious odor, too many residual monomers, unreliable sanitary performance, and too small initial adhesion. It can not be used in dry compounding to produce qualified food packaging materials. Therefore, it should aim at the level of the United States and Japan at that time, Redevelop and research the two-component polyurethane adhesive that meets the requirements of food hygiene and safety and can withstand cooking at 121 ℃ for 40 minutes. 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 been gradually reforming and opening up, the people's living standards have been significantly improved, the market economy has become increasingly active, the food industry has developed rapidly, the main and non-staple foods have become increasingly abundant, the demand for improving packaging has also risen, and the demand for composite flexible packaging materials is large. Therefore, Shanghai, Wuxi and Dalian first introduced relatively advanced production lines of composite flexible packaging materials from Japan, including multi-color combined gravure color printing machines Dry compounding machine, bag making machine, slitting machine and corresponding testing instruments have played a leading role in the development of modern composite flexible packaging industry in China. However, gravure ink, adhesive, 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, all parts of the country have made great efforts to develop flexible packaging, which has pointed out the direction for comprehensively promoting the adjustment of the national new material industrial structure and the transformation and upgrading of the manufacturing industry. The flexible packaging machinery production enterprises in Shanghai, Wuxi, Haining, Guangdong and other places have mushroomed rapidly, and the flexible packaging material production enterprises of composite color printing are also booming, As a result, the demand for imported gravure inks and dry-type composite adhesives has soared. In this situation, the production technology of polyurethane adhesive for food composite packaging materials in Shanghai has the soil for industrial production. Therefore, in 1984, China first established a food grade polyurethane adhesive production base with an annual output of 60 tons. With this model base, the packaging industry has seen the hope and Prospect of adhesive localization. In just two or three years, two or three places have successively built enterprises with an annual output of about 500 tons, officially launching the climax of adhesive localization. In the mid-1980s, Beijing Research Institute of chemical industry cooperated with German Henkel company to produce solvent based two-component polyurethane adhesive for dry compounding in China by using the technology provided by Henkel. However, there is no cooperation in the production technology of the curing agent. It should be imported from Germany and then used together with the domestic main agent after sub packaging. Later, through their own development and research, they mastered the production technology of the curing agent, and then they used the domestic curing agent to replace the imported products and use it together with the main agent produced in China

polyurethane adhesives produced by domestic technology in the 1980s, on the one hand, have few varieties, and are mostly used in low and medium-grade composite flexible packaging materials with low requirements. On the other hand, there are some defects in quality, such as too high viscosity of the glue liquid, poor frost resistance, and easy to freeze in winter. When using, it is necessary to heat it to 50 ~ 60 ℃ and melt it before pouring it out of the packaging barrel to prepare the operating solution. On the other hand, The adhesive film has few functions, the adhesive force is not very high, and the resistance to medium is very poor. Therefore, despite a large number of output and users, some large factories are willing to buy and use adhesives produced in Germany, Japan, the United States and France at a high price. Since the late 1980s, researchers in Shanghai have not only studied aliphatic high-temperature resistant cooking adhesive that meets the specifications of FDA and fills the gap in China, but also studied functional adhesives in order to solve the quality problems of Sichuan mustard and Zhejiang mustard soft packaging bags in China. It turned out that the opp/al/pe mustard packing bag made of domestic adhesive at that time was not resistant to acid, salty and spicy corrosion. After the packed mustard was soaked in 80 ~ 90 ℃ hot water for 10 minutes, the inner PE and Al had been automatically layered, resulting in the bag breaking and leakage of mustard before it was put on the market. The mustard production plant claimed against the packaging material plant. After about two years, Shanghai Shenhua Technology Co., Ltd. first introduced to the market in 1991 a special adhesive for aluminum foil, which is resistant to the corrosion of acid, spicy and salty media and can withstand 100 ℃ boiling. It was used by Zhejiang and Fuling color printing plants to make mustard bags, which solved the problem. In the next few years, as the adhesive was widely used, the number of complaints or claims from mustard mustard production plants to color printing packaging materials plants should be reduced year by year. By 1996, there was only one case. The original imagination did not account for 13.9%; The equipment with a journey of 500 ~ 900mm arrives. The adhesive produced by Shanghai technology also solves the quality problem that the aluminum layer needs to be transferred and the stripping force is zero after the aluminum coating is compounded. The composite fastness of vacuum aluminum coating such as m-pet and m-CPP can be improved from the original to more than 1n/15mm, and the best can reach 3 ~ 4n/15mm. The aluminum coating will not be 100% transferred. In more than ten years, it has been designated as aluminum coating The special adhesive for jelly cover and acid, salty and spicy resistant composite film is also designated as the adhesive for wine film composite by the soft wine bag composite manufacturer. Since the quality of this adhesive is reliable and stable, it has been exported to Singapore since the first half of the 1990s, becoming the first and only export product of domestic adhesive

with the increasing application of composite flexible packaging materials, they are not only used in the packaging of food and drugs, but also in the packaging of daily necessities, cosmetics, washing products, sanitary products, pesticides and some chemicals, so the functional requirements are more urgent. For this reason, Shanghai lieyin Chemical Co., Ltd., founded by Shanghai Shenhua Technology Co., Ltd., has improved the quality of adhesive on the original basis since the beginning of 1997, making the function of special adhesive for aluminum foil more comprehensive and the application field further expanded. Finally, in the middle of 1998, the concept of functional adhesive was put forward for the first time, and the functional adhesive products were introduced to the market at the same time. Some of this series of functional adhesives have the functions of resisting acid, alkali, spicy, salty and oil, while others have the functions of resisting benzene, toluene and xylene with the increasing proportion of plastic packaging in the packaging industry, ester, hydrocarbon, wine, surfactant, DMF organic solvent mixture with content less than 20% and pesticides, and some are suitable for plastics/plastics cooked at 128 ℃ for a long time (even 120 minutes) Use of aluminum/plastic composites. Among the functional products, the company has ly-50a/ly-50ah, ly-9850r/ly-9875r, ly-50vr/ly-50vrh, ly-9850/ly-9850h and other models

since the industrial production in the mid-1980s, the adhesives for composite flexible packaging in China have grown from scratch. There are about 300 production enterprises from a few to the present. The varieties range from single to multiple, the quality ranges from medium to low-grade to high-grade, and the types range from ordinary to functional and then to special. It can be said that there are some adhesives in the world in China, including ordinary adhesive, functional adhesive, plastic/plastic, aluminum/plastic, low-temperature resistant adhesive High temperature resistant adhesive, aromatic adhesive and aliphatic adhesive, including food packaging adhesive, pesticide and chemical packaging adhesive, solvent-based adhesive, solvent-free adhesive, non flame retardant adhesive and flame-retardant adhesive

as mentioned earlier, at present, nearly 300 enterprises in China are producing adhesives for composite flexible packaging, and the equipment capacity has reached 100000 tons per year, far exceeding the market demand of 30000 to 40000 tons. However, due to the different technical levels and development and research capabilities of various enterprises, the quality of products is uneven, and the adaptability of products is also different. Therefore, there is still a large gap between the adhesive products of some manufacturers and the imported or domestic famous brand products. In order to arouse everyone's attention and promote the healthy development of adhesives, the author here talks about three issues

first, the product quality of some enterprises is not stable enough and fluctuates greatly. a. Most of these enterprises have been established in the past three to five years. Their foundation is too shallow, their technical skills are not strong, and their personnel quality is not high. In particular, the first-line production personnel are not rich in experience, and their quality control methods are not smart and stable

therefore, the author believes that "the more you know, the better you can do". At present, some domestic enterprises obtain the production technology of adhesives by improper means, or secretly buy processes and formulas, or secretly recruit personnel and hire consultants, but they do not fundamentally master the comprehensive technology. They only get some surface parts, and have not mastered the key core content, so the products have shortcomings. Although they also pat their chest and say: "my product quality is consistent with ×× The brand is the same, and the price is cheap, so you can use it with confidence ". However, after real comparison and strict testing, you will find that it will take time to truly achieve superior quality and long-term stability. There is another problem, that is, as users, we should learn a lesson, do not pursue too much cheapness, and when selecting any raw and auxiliary materials, we should put quality first and price second. No quality, no quantity, no output, no cost and benefit! Just think, how to estimate the loss of using inferior adhesives and making scrapped products? Therefore, the author believes that all enterprises producing adhesives should work hard to refine their basic skills, strengthen technical training, strictly control and supervise quality, improve product quality, and do not easily launch uncertain "new products"

second, adhesive manufacturers should follow the principle of "seeking truth from facts, honesty and credibility", oppose and stop the exaggerated and impetuous unscientific mentality, and do not practice fraud, shoddy, and mislead consumption. In the previous two or three years of investigation, it was found that the solid content of the adhesive was low and the packaging weight was short, which caused the user

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