Application of alcohol-soluble two-component polyurethane adhesive in composite film

Summary: The alcohol-soluble two-component polyurethane adhesive is a new type of adhesive product for composite films developed independently by the company in recent years. It has prominent characteristics such as good adaptability to alcohol-soluble ink, low residual solvent in laminating products, good resistance to lubricants, normal temperature curing, insensitivity to humidity, and favorable environmental protection. The development of the alcohol-soluble two-component polyurethane adhesive and the future development trend were proposed in conjunction with the research progress of this unit.

Keywords: alcohol-soluble polyurethane adhesive two-component

I. Preface [1, 2]

Alcohol-soluble two-component polyurethane adhesive is a new type of adhesive that has appeared in the domestic composite film market in recent years. Its main features are:

1. Good compatibility with alcohol-soluble ink;
2. The residual solvent of composite membrane products is low;
3, the performance of the anti-slip agent is good, and the increase of the friction coefficient after compounding is small. For films with high lubricating agent content, the adhesive strength decreases after compounding;
4, without heating aging, reduce energy consumption;
5. Alcohol solvents are cheaper than ethyl acetate, which reduces the cost of use;
6, does not contain free isocyanate units, improve the operating environment;
7, is not sensitive to humidity, improve the stability and adaptability of the adhesive;

Alcohol-soluble two-component polyurethane adhesives can be used for composite bonding of Plastic Film/plastic film, plastic film/aluminum film, paper/plastic film and many other material structures. Now domestic manufacturers mostly use it for light food packaging. Due to the fierce competition in the social and economic market in China, alcohol-soluble two-component polyurethane adhesives have gradually gained market attention due to their application characteristics, energy consumption, and environmental protection.

Second, product overview [1,2]

The alcohol-soluble two-component polyurethane adhesive is an environment-friendly composite film adhesive material, which can be widely used in the compounding and bonding processes of plastic film, aluminized film, paper and other film laminates, and is mainly used in the food composite film packaging industry. Excellent machine operability, and good spreadability on a variety of materials. Can be used for polyethylene, polypropylene, aluminized film, polyester, nylon and other film materials bonding and compounding.

Currently, smoothing agents are used in many PE films to satisfy the processability of composite films and the openness of finished products. After undergoing multiple processes such as compounding and printing, the lubricant is often eroded to reduce slippage or even lose smoothness. Alcohol-soluble two-component polyurethane adhesives have been specially designed to maintain high smoothness of the film and minimize loss of the slip agent. It is worth mentioning that when the composite film is used, the increase in temperature will increase the mobility of the slip agent in the film, and the slip agent must be on the surface of the film to function. The increase in mobility will make the lubricant no longer stay. On the surface layer of the film, it migrates to the adhesive layer, which will increase the friction coefficient and decrease the adhesive strength. Therefore, the film should maintain the minimum temperature at which the solvent can be completely removed during the drying of the sizing.

Alcohol-soluble two-component polyurethane adhesives require the addition of a curing agent during use. The proportion of the two components can be adjusted within a certain range. The stability of the two components is good, and they are not deteriorated by the influence of the humidity in the air, and can be stored for a long time without changing the adhesive properties of the adhesive. Compared with general polyurethane adhesives, alcohol-soluble two-component polyurethane adhesives can be cured at room temperature, have a better initial adhesion, and the later adhesive strength is higher.

Alcohol-soluble two-component polyurethane adhesives can be mixed with various solvents including methanol, n-propanol, isopropanol, and other solvents in addition to being diluted with ethanol, and can be protected from environmental high humidity. It is also possible to adjust the addition ratio of different solvents according to the compounding requirements to adapt to the composite film composite. It is worth noting that ketones or ketone-containing solvents are considered as impurities in alcohol sols because ketones such as MEK, etc., can cause off-flavors to remain in the composite film. Therefore, ketones or ketone-containing solvents cannot be used for composite food packaging.

The use of ethanol as a solvent has several outstanding advantages. First, its low price can greatly reduce the cost of use; second, it can optimize the working environment to reduce the damage to the operators. Due to the use of ethanol as a solvent for the two-component soluble polyurethane adhesives, high temperature storage should be avoided, especially in direct sunlight.

Third, the research results of this unit

Alcohol-soluble polyurethane adhesives have been successfully developed and applied in foreign countries in the 1980s, while development and research work in China is currently in its infancy. Our company has used its own years of research and development experience and technical strength in polyurethane adhesives, continuous technological breakthroughs, after years of hard work, it finally opened up the technical line and got the target product. The brand name of the alcohol-soluble two-component polyurethane adhesive researched and manufactured by our company is UF2870/UF9985E, and the corresponding indicators are shown in Table 1. Diluted to a solid content of 30 to 35% during compound processing can be used, dry coating weight can be selected between 2-3.5g/m2. After being compounded, the film products are cured at room temperature, and can be cut and bagged in 48 hours, and the maximum strength can be achieved within 5 to 7 days. UF2870 adhesives can be used to compound BOPP/CPP, BOPP/PE, and other plastic/plastic films. The initial peel strength can reach 2 to 3 newtons/15 mm, and the final peel strength can reach 4 to 5 newtons/15 mm; for BOPP/ The compounding of plastic film/plastic aluminum film, such as aluminized film, printing film/aluminum film, etc., can also reach 2 Newtons/15 mm or more, and the final peeling strength can reach 3 Newtons/15 mm or more, which can meet relevant requirements. Refer to Figure 1.

Fourth, the significance of the development of this product [3]

At present, with the rapid development of China's economy and the continuous improvement of the quality of life of the people, the environmental protection issues of the composite film packaging industry are increasingly receiving increasing attention. The market needs more environmentally friendly composite adhesives, and alcohol-soluble polyurethane adhesives are environmentally friendly products that meet this need.

In recent years, polyurethane adhesives at home and abroad, like the entire adhesives and coatings industries, have been characterized by developments in environmental protection, industrial hygiene, resources, and other policies and regulations. They have adjusted the industrial structure and strive to reduce the proportion of organic solvent-based products. Advanced countries have established environmental protection laws and regulations that require the development of non-hazardous adhesives to minimize the use of solvents and the toxicity of solvents. However, solvent-based adhesives have their own unique features and cannot be replaced on certain occasions, so they cannot be completely cancelled in a short time. . The solution is to use a low-toxic solvent, increase the solid content of the working fluid and closed ventilation operations, and use solvent recovery devices. In recent years, Europe has proposed the concept of "green" solvents, that is, those that are not toxic, and some even biodegradable, and thus have been removed from the list of toxic release materials (TRI) and organic volatiles (VOC), such as ethanol, etc. Polyurethane adhesives using these solvents have less environmental pressure.

Many cities in China are now increasingly focusing on environmental issues and are increasingly concerned about the pollution of the composite film industry. Many complex manufacturers are eager to find less-contaminated adhesives for production, thereby reducing the environmental pressure. Although the development of adhesives is ultimately going to be solventless, because solventless adhesives require specialized solventless laminators and large investment in equipment, it is unlikely that the mainland will be widely promoted in the country. Therefore, alcohol-based polyurethane adhesives can still be marketed. On the mainstream products.

The use of alcohol-soluble two-component polyurethane adhesives to remove the environmental advantages, the other main feature is that it can reduce the cost of use. Because the current ethanol price in the domestic market is lower than the price of ethyl acetate, and the adhesive can be cured at normal temperature, reducing energy consumption, which are conducive to reducing costs.

The introduction and marketing of our alcohol-soluble two-component polyurethane adhesives has only just begun, and practical application experience is still relatively small, but we believe that with the cooperation and assistance of a large number of manufacturers, alcohol-soluble two-component polyurethane adhesives will surely be used in the composite film industry. It has been widely used. The composite film industry has entered a new stage of development.

From: (Beijing Institute of Chemical Industry Branch)