At present, the commonly used adhesives in the flexible packaging industry mainly include solvent-free adhesives, water-based adhesives and solvent-based adhesives. Developed countries in Europe and the United States attach great importance to environmental protection. Solvent-free adhesives and water-based adhesives are mainly used in the composite production of flexible packaging. Flexible packaging manufacturers in most Asian and African countries are still dominated by solvent-based adhesives. For example, Japan's solvent-based adhesives, which are relatively developed in the flexible packaging industry, account for more than 90% of the market share. Today, let Xiaobian take you to understand the flexible packaging printing products and introduce the technical characteristics.
According to statistics, there are more than 6,000 flexible packaging production enterprises in my country, mainly in the Pearl River Delta, Yangtze River Delta and parts of Hebei Province and Shandong Province. In these regions, more than 95% of flexible packaging manufacturers use solvent-based adhesives, and less than 5% of companies use environmentally friendly adhesives (solvent-free adhesives and water-based adhesives).
At present, there are nearly 400 manufacturers of adhesives for flexible packaging in my country. It is estimated that the current annual production of adhesives in China is about 60,000 tons, of which solvent-based adhesives still dominate. Well-known manufacturers include Zhongshan Kanghe, Zhejiang New Oriental, Shanghai Lieyin, Beijing Gaomeng, Beijing Chemical Industry Research Institute (Beijing Institute of Chemical Industry), Jiangsu Jintan, etc. In recent years, some famous foreign adhesive manufacturers have also increased their investment and development in the Chinese market, and have built factories in China, such as Henkel, Mitsui Takeda, Rohm and Haas, Bright and other companies, and the participation of international manufacturers. The production level and market capacity of adhesives in the international market have been greatly improved.
Types and characteristics of adhesives
The three types of adhesives commonly used in the flexible packaging industry have their own characteristics and corresponding fields. The following is a brief analysis and summary of their advantages and disadvantages.
01. Solvent-based adhesives
(1) Advantages
It is suitable for a wide range of substrates, and basically has good adhesion to the materials commonly used in flexible packaging composites.
Good initial adhesion and high composite strength.
The composite film has high transparency and good softness, and is required for post-composite processing and product packaging.
Heat resistance, cold resistance, medium resistance and other properties are the best among all kinds of adhesives.
Safe, hygienic, odorless, and complies with FDA standard requirements and VOC (organic volatile matter) regulations.
The operability is good, and the requirements for equipment and operators are relatively low.
(2) Disadvantages
Volatile organic solvents have certain harm to the human body and also cause certain pollution to the environment.
The incompletely reacted free TDI (toluene diisocyanate) in some ester-soluble adhesives is harmful to human body.
A small amount of solvent remains in the composite film, which may contaminate the contents of the package.
2. Water based adhesive
There are mainly two types of water-based adhesives for flexible packaging compounding: water-based polyvinyl ester adhesives and water-based acrylic adhesives.
(1) Advantages
Does not pollute the environment, is conducive to environmental protection.
It can be used on medium and high speed composite machines.
There is no solvent residue, and the transparency of the composite film is high.
The composite strength of the aluminized film is good, and it will not cause damage to the aluminized layer, nor will it cause the transfer of the aluminized layer.
The amount of glue applied is small (can be as low as 1.6g/㎡), and the comprehensive use cost is low.
It has good adaptability to alcohol-soluble ink.
(2) Disadvantages
Not suitable for heavy packaging and high temperature cooking packaging
The requirements for the surface properties of the film are relatively strict, and the surface tension requirements are higher than 3,8*10-2N/m.
The capacity consumption is large and the production efficiency is low. The composite equipment is required to have strong heating and ventilation capacity (the temperature should reach 60-100°C).
The phenomenon that the composite strength weakens with time is obvious.
The corrosion of composite equipment is more serious.
When composite aluminized film is used, the aluminized layer is easily corroded.
3. Solvent-free adhesive
There are mainly one-component, two-component, UV curing type and field curing type of solvent-free adhesives for flexible packaging.
(1) Advantages
Non-toxic, environmentally friendly, no solvent volatilization, no environmental pollution, compound FDA standards.
Safe operation, no need to take fire and explosion protection measures.
The amount of glue applied is small, the compounding process is simple, and the compounding speed can reach 200-300m/min.
The composite product has no solvent residue or migration problem, so it will not pollute the contents, and it is more suitable for food packaging.
The solid content can reach 100%, and the comprehensive use cost of users is low.
(2) Disadvantages
The investment of solvent-free composite equipment is large, and the coating system is relatively complicated, and a heating device is required.
The glue has high viscosity, and the storage time after compounding is short.
Low initial tack and long curing time.
The requirements for the precision of the tension system of the composite equipment are high, and the requirements for the operating level of the operators are also high.
The requirements for the flatness and thickness of the composite substrate are strict, and the surface tension of the film should be greater than 3,8*10-2N/m.
The phenomenon that the composite strength weakens with time is obvious.
Compound some packaging products with higher quality requirements. (pesticide bags, high temperature cooking, etc.), its performance and composite quality cannot reach the level of ester-soluble polyurethane adhesives.
The domestic adhesive market is stable and innovative
The overall situation of the domestic and external flexible packaging industry is that various adhesive products have their own markets, but the development direction is to use safe and environmentally friendly products to produce green packaging.
1. Coexistence of various adhesive products
(1) Solvent-based adhesives occupy an obvious dominant position in the domestic market by virtue of their excellent softness, low temperature resistance and cooking resistance, easy operation and wide adaptability, and other adhesives cannot be replaced temporarily.
(2) In practical applications, there are still some practical problems that cannot be solved temporarily for solvent-free adhesives, hot-melt adhesives and water-based adhesives.
The dry compounding equipment in the domestic flexible packaging industry is currently only suitable for solvent-based adhesives. If you want to replace the compounding equipment, you need to invest a lot of money, which will cause a lot of waste of resources;
Environmentally friendly adhesives have certain limitations in performance;
The extra heat consumption is also a waste of environmental resources, and it will also cause pollution to the environment.
(3) The flexible packaging industry has begun to pay attention to environmental protection. Only by completely changing the emission of harmful substances in raw and auxiliary materials such as adhesives, inks, solvents, and films, can the goal of environmentally friendly packaging be fundamentally achieved;
(4) The harm of solvents to the environment is still inconclusive. Internationally, Japan and European and American countries are still controversial on this issue, and some solvent-based adhesives have also passed FDA certification and VOC regulations.
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