Application of the hottest adhesive in flexible pa

2022-08-05
  • Detail

Application of adhesives in flexible packaging industry I. application status of adhesives at present, common composite adhesives in flexible packaging industry mainly include solvent-free adhesives, water-based adhesives and solvent-based adhesives. Developed in Europe and America, they have developed the technology of mixing polyrotaxane into resin to improve its strength. Countries pay great attention to environmental protection, and solvent-free adhesives and water-based adhesives are mainly used in flexible packaging composite production. Most countries in Asia and Africa still focus on solvent based adhesives. For example, in Japan, where the flexible packaging industry is relatively developed, solvent based adhesives account for more than 90% of the market share

according to incomplete statistics, there are more than 6000 flexible packaging production enterprises in China, mainly concentrated in the Pearl River Delta, Yangtze River Delta and some areas of Hebei and Shandong provinces. In these areas, more than 95% of flexible packaging manufacturing enterprises use solvent-based adhesives, and less than 5% of enterprises use environmental friendly adhesives (solvent-free adhesives and water-based adhesives)

at present, there are nearly 400 manufacturers of adhesives for flexible packaging in China. It is estimated that the annual production of adhesives in China is about 60000 tons, of which solvent adhesives still occupy the main position. The well-known production enterprises include Zhongshan Kanghe, Zhejiang New Oriental, Shanghai lieyin, Beijing GAOMENG, Beijing Research Institute of chemical industry (Beihua Institute), Jiangsu Jintan, etc. In recent years, some famous foreign adhesive manufacturers have also increased their investment and development in the Chinese market, and have set up factories in China, such as Henkel, Mitsui Takeda, Rohm Haas, bright and other companies. The participation of international manufacturers has greatly improved the production level and production capacity of adhesives in the domestic market

II. Types and characteristics of adhesives

the three types of adhesives commonly used in the flexible packaging industry have their own characteristics and corresponding application fields. Their advantages and disadvantages are briefly analyzed and summarized below

1. Solvent based adhesives

solvent based adhesives for flexible packaging composite mainly include two-component polyester, two-component polyether, two-component polyurethane and alcohol soluble polyurethane

(1) advantages

① it is applicable to a wide range of substrates and has good adhesion to commonly used materials in flexible packaging composites

② good initial adhesion and high composite strength

③ the composite film has high transparency and good flexibility, meeting the requirements of post-processing process and product packaging

④ heat resistance, cold resistance, medium resistance and other properties are the best among all kinds of adhesives

⑤ it is safe, hygienic and odorless, and meets the requirements of FDA standards and the relevant provisions of VOC (organic volatile matter)

⑥ good operability, relatively low requirements for equipment and operators

(2) disadvantages

① volatile organic solvents are harmful to human body and cause certain pollution to the environment

② incomplete reaction of free TDI (toluene diisocyanate) in some ester soluble adhesives is harmful to human body

③ there is a small amount of solvent residue in the composite film, which may pollute the contents of the package

2. Water based adhesives

flexible packaging composite water-based adhesives mainly include water-based polyurethane adhesive and water-based acrylic adhesive

(1) advantages

① it does not pollute the environment and is conducive to environmental protection

② it can be used on medium and high-speed compound machines

③ there is no solvent residue and the transparency of the composite membrane is high

④ the composite strength of the aluminized film is good, and the aluminized layer will not be damaged or transferred

⑤ small amount of glue (as low as 1.6g/m2) and low comprehensive use cost

⑥ good adaptability to alcohol soluble ink

(2) disadvantages

① it is not suitable for heavy packaging and high-temperature cooking packaging

② the requirements for the surface properties of the film are relatively strict, and the surface tension is higher than 3.8 × N/m。

③ high energy consumption and low production efficiency require the composite equipment to have strong heating and ventilation capacity (the temperature should reach 60 ~ 100 ℃)

④ the composite strength decreases obviously with time

⑤ the composite equipment is seriously rusted

⑥ in case of composite aluminum coating, the aluminum coating is easy to be corroded

3. Solventless adhesives

solventless adhesives for flexible packaging composite mainly include single component, two-component, UV curing and EB curing

(1) advantages

① non toxic, environment-friendly, solvent-free volatilization, no environmental pollution, in line with FDA standards

② the operation is safe, and no fire and explosion-proof measures are required

③ small amount of glue, simple compounding process, and compounding speed up to 200 ~ 300m/min

④ save energy. After gluing, there is no need to heat and dry in the drying channel, and the energy consumption will not be increased due to waste gas incineration or recycling

⑤ there is no solvent residue or migration problem in the composite products, so it will not pollute the contents, which is more suitable for food packaging

⑥ the solid content can reach 100%, and the comprehensive use cost of users is low

(2) disadvantages

① the investment in solvent-free compounding equipment is large, the coating system is complex, and heating devices are required

② the glue solution has high viscosity and short storage time after mixing

③ low initial adhesion and long curing time

④ it has high requirements for the accuracy of the tension system of the composite equipment and the operation level of the operators

⑤ the flatness and thickness of the composite substrate are strictly required, and the surface tension of the film should be greater than 3.8 × N/m。

⑥ the composite strength decreases obviously with time

⑦ when compounding some packaging products with high quality requirements (pesticide bags, high-temperature cooking bags, etc.), their performance and compounding quality can not reach the level of ester soluble polyurethane adhesive

III. innovation in the domestic adhesive market

the overall situation of the domestic and foreign flexible packaging industry is that various adhesive products have their own markets, but the development direction is to adopt 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 with their excellent softness, low temperature resistance, cooking resistance, ease of operation and wide adaptability. Other adhesives cannot be replaced for the time being

(2) in practical application, there are still some practical problems that can not be solved temporarily for solvent-free adhesives, hot-melt adhesives and water-based adhesives. ① At present, the dry compounding equipment in the domestic flexible packaging industry is only applicable to 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; ② Environmental friendly adhesives have some limitations in performance; ③ The extra heat energy consumed is also a waste of environmental resources, and will also cause pollution to the environment

(3) the flexible packaging industry has begun to pay attention to environmental protection. Only by thoroughly changing the emission of harmful substances in raw and auxiliary materials such as adhesives, inks, solvents, films, etc., can the goal of environmental protection packaging be fundamentally realized

(4) the harm of solvents to the environment has not been determined yet. Internationally, Japan, Europe and the United States still have disputes on this issue, and some solvent based adhesives have also passed the FDA certification and VOC regulations

2. Environmental friendly adhesive is the development direction

it is undeniable that the development of domestic adhesive market towards environmental friendly direction is an inevitable trend. In 2004, water-based adhesive manufacturers seized the opportunity of rising prices in the international oil market and made great progress in the environment-friendly adhesive market. However, only one component water-based adhesive was mainly used for light-weight packaging with simple composite structure. Solvent free adhesives have not made much progress due to the influence of equipment and other factors in 2004

however, we should also see that solvent based adhesives will still be the mainstream products in the domestic market for a long time in the future, and will be improved in terms of environmental protection: first, develop some transitional and solvent based adhesives, such as low solvent residue adhesives, aliphatic polyurethane adhesives, alcohol soluble adhesives, etc; The second is to develop solvent-free composite equipment with low cost and simple operation

some domestic adhesive manufacturers pay close attention to the research and development of environmental friendly adhesives and carry out relevant technical reserve work. As long as the domestic market is mature, they can produce them at any time to meet the needs of customers. For example, Zhongshan Kanghe Chemical Co., Ltd. developed two-component solvent-free adhesives kh-fs762/kh-1762 as early as 2003, and independently developed kh-wb607 (for paper/plastic compounding) and kh-wb608 (for plastic/plastic compounding) single component aqueous adhesives in 2004. At the same time, Kanghe chemical also launched kh-ls800/3800 ultra-low solvent residual polyurethane adhesive to meet the environmental protection requirements of domestic flexible packaging manufacturers and end users at this stage. In addition, Kanghe chemical is actively cooperating with machinery and equipment manufacturers, and is committed to the application research of solvent-free adhesive on ordinary dry laminating machine, and has made breakthrough progress

with the development of technology, it is believed that domestic environmental friendly adhesives will make greater progress in the future and play a positive role in promoting environmental protection

this article is from the Internet. The copyright belongs to the original author. It is only for everyone to share and learn. If the author thinks that four Nobel Prize winners are involved in infringement, please contact us. We will delete it immediately after verification

Copyright © 2011 JIN SHI