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Development Trend of Solventless Laminating Adhesive
Time: 2013-05-08 Source: Frontier of Packaging Read: 13208 times
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Wenzhou Junchuan Machinery Equipment Co., Ltd.

At present, the compounding of domestic food flexible packaging enterprises is mainly dry compounding. However, with the rapid development of the economy and the gradual maturity of various conditions, domestic solvent-free composite and solvent-free polyurethane adhesives face unprecedented opportunities. In particular, the new national standard GB / T 10004-2008 "Packaging plastic composite film, bag dry lamination, extrusion lamination" was introduced and implemented on August 1, 2009 (total solvent residues ≤ 5mg / m2, Benzene solvents must not be detected), more and more flexible packaging companies have begun to focus on solvent-free compounding, and some flexible packaging companies have begun to introduce solvent-free compounding production lines. With the successful use of these imported solvent-free composite production lines in flexible packaging enterprises, it is not only hygienic and environmentally friendly, but also brings real economic benefits to the enterprise, which has led more flexible packaging enterprises to start choosing solvent-free composite production lines. With the rapid increase of solvent-free composite production lines, the solvent-free composite process is rapidly developing in China.
A few years ago, only Shanghai Kangda Chemical New Materials Co., Ltd., a domestic non-solvent laminating adhesive manufacturer, competed with foreign companies such as Henkel, Boss, Cromogenia-units, SA, etc., and now other domestic manufacturers of flexible packaging adhesives also Started research and development of solvent-free polyurethane adhesives for flexible packaging. However, at present, the solvent-free adhesives in the domestic market are mainly general-purpose products, and almost no other high-end products have been seen. With the popularization and application of solvent-free composite technology, solvent-free laminating adhesives also need to develop to more targeted high-end products.
The development trend of solvent-free adhesives for plastic flexible packaging mainly includes general-purpose solvent-free laminating adhesives, high-temperature cooking-resistant solvent-free laminating adhesives, medium-resistant solvent-free laminating adhesives, single-component solvent-free laminating adhesives, and UV curing Several types of solvent-free laminating adhesive.
I. General-purpose solvent-free laminating adhesive
There is no doubt that general-purpose solvent-free laminating adhesives are the main adhesives used in solvent-free lamination. In particular, the solvent-free compounding process is just in its infancy, and flexible packaging manufacturers have just introduced a solvent-free compounding production line, and they are still familiar with the entire compounding process. They have just started with the simplest and universal materials, and are gradually familiar with the solvent-free compounding process. After they have fully grasped the main points of the solvent-free compounding process, they will safely use solvent-free compounding in high-end products.
General-purpose solvent-free laminating adhesive, as the first solvent-free adhesive used by flexible packaging manufacturers at the beginning of contacting the solvent-free composite process, must meet the following requirements:
1.Easy operation process
The general-purpose solvent-free laminating adhesive must be convenient to operate first, including its two-component viscosity and mixing viscosity at normal temperature, and sufficient operating time. Many flexible packaging manufacturers have adopted manual mixing when they first introduced the solvent-free composite production line. If the viscosity of the solvent-free adhesive itself is large, it is not conducive to the uniform mixing of the adhesive, and it is easy to cause large errors in the proportion of the two components during operation, resulting in compound The product has poor local peel strength or stickiness. If you use a rubber blender, the initial viscosity is not high. It is necessary to have enough operating time, which is very necessary for manual mixing and mixing machine mixing, the first reel, the second reel and the rewinding of the reel during the compounding process, and the emergency situation during the compounding process. It takes a certain amount of time. If the operation time is too short, the viscosity of the adhesive will rise too quickly, which will affect the product quality. In severe cases, it will damage the solvent-free composite equipment. Generally, the operation time of the solvent-free adhesive is not less than 30min.
2. Wide applicability
One of the most prominent advantages of solvent-free compounding is that it is highly efficient and has a fast compounding speed, which requires that the applicability of solvent-free adhesives must be wide. The wide variety of products is one of the most prominent features of flexible packaging products. Flexible packaging manufacturers often receive different orders and compound different products. If each product requires a different type of adhesive, then only cleaning solvent-free composite equipment is required for flexible packaging manufacturers. That is a big burden. The cleaning of the solvent-free compounding machine generally takes 1 to 2 hours. It may take longer for workers who have just come into contact with the solvent-free compounding process. If a glue mixer is used to mix the glue, the cleaning of the glue mixer is more troublesome and may require more cleaning. One shift is used for cleaning, which makes it difficult to reflect the advantages of solvent-free compounding and high efficiency.
Therefore, for solvent-free adhesives, it is necessary to be able to use the composite of most common flexible packaging materials , including transparent materials, printing materials, and aluminized materials. Solvent-free adhesives can be divided into general-purpose products and some high-end products (such as whether they are resistant to cooking, pesticides, and other highly corrosive media). It should not be further classified in general-purpose products (such as instant noodles and transparent materials) Too fine distinction), otherwise it will cause unnecessary trouble to the users of flexible packaging during use.
3.The ripening temperature and time are appropriate
The late curing temperature of solvent-free adhesives is generally controlled at 40 ℃ ~ 50 ℃, which is not much different from the dry compound curing temperature. The curing time should be controlled at about one day. Excessively long curing time not only increases energy consumption, but also affects composite flexible packaging materials. The post-processing steps are carried out normally.
4. Good stability The solvent-free adhesive for food flexible packaging is just in its infancy. It must have good stability and stand the test of the market. It can be said that product stability and reliability are the lifeblood of enterprises to survive and develop.
Second, high temperature cooking solvent-free laminating adhesive
High temperature resistant cooking bag refers to a composite film bag made of PET, PA, Al, CPP and other film materials compounded with cooking resistant adhesive for packaging food, medical appliances, etc., and can withstand high temperature steam sterilization , Also known as soft-cookable package or soft can. Flexible packaging food is suitable for people's daily life due to its light weight, convenience, long freshness period, hygiene, easy storage, and easy disassembly.
The cooking bag is divided into three levels according to the disinfection level:
(1) 121 ℃ medium temperature cooking bag: most foods need to be cooked at 121 ℃ for 40min. Special foods, such as beef, need to be sterilized at 121 ℃ for 60min. Aquatic products and soy products, generally 121 ℃ for 20min are sufficient;
(2) Aseptic packaging can be achieved by steaming at 135 ° C for a maximum of 20 minutes;
(3) 145 ℃ super high temperature cooking, usually 2 ~ 3min, maximum 3 ~ 5min, is enough to destroy the most heat-resistant harmful bacteria (Spore botulinum).
So far, general-purpose solvent-free laminating adhesives (ie, below 100 ° C, boiling and sterilizing) have been applied in the domestic market, while solvent-free two-component polyurethane resistant cooking adhesives at home and abroad, especially resistant to 135 ° C There are very few high-temperature cooking laminating products. In order to completely replace the traditional dry compounding process with solvent-free compounding, it is essential to develop a solvent-resistant solvent-free adhesive.
Third, medium-resistant solvent-free laminating adhesive
With the increasing application scope of composite flexible packaging materials, it is not only used in the packaging of food and drugs, but also in the packaging of daily necessities, cosmetics, washing supplies, sanitary products, pesticides and certain chemicals, so the functional requirements Even more urgent. Research and development with anti-acid, alkali, spicy, salty, oil functions, and with benzene, toluene, xylene, esters, hydrocarbons, alcohol, surfactants, less than 20% DMF organic solvent mixtures, pesticides and other corrosion Functional solvent-free adhesive is also a trend for the development of solvent-free in the future. The fully cured composite film should be able to package liquid pesticides containing toluene, xylene, a small amount of DMF, alcohols, esters, and hydrocarbon mixed solvents.
Four, one-component solvent-free laminating adhesive
The main advantages of single-component solvent-free adhesives are that they are more convenient to use, do not require on-site batching, can be applied at higher temperatures, have a longer pot life, and have higher initial adhesion than two-component solvent-free adhesives. The requirements are lower. The disadvantage is that it depends on the water vapor in the air to solidify and is greatly affected by the environment (if necessary, the air must be humidified to ensure that the colloid is fully matured); carbon dioxide is generated during the maturation process. If it can not be eliminated in time, it is easy to produce bubbles in the product.
The future development direction of single-component solvent-free laminating adhesive is mainly applied to paper-plastic composite products, because paper is easy to absorb glue during paper-plastic composite process. If a general-purpose solvent-free adhesive is used, it will cause serious problems due to its low viscosity. Adhesive affects the quality and appearance of composite products. The single-component solvent-free laminating adhesive is coated at high temperature, and the temperature decreases after compounding, and the viscosity of the adhesive increases rapidly, which can solve this problem well.
Five, UV-curable solvent-free laminating adhesive
In addition to the characteristics of fast curing speed, transparent product, high bonding strength, and good flexibility of the finished adhesive, UV-curable solvent-free laminating adhesive also has no solvent, no toxicity, no corrosion, energy saving, and environmental protection. Features will be a new generation of environmentally friendly products that will partially replace traditional solventless laminating adhesives in the future. UV curing adhesive can be used in the rapid production of laminated plastic / plastic, plastic / paper, plastic / metal film and other products. It has the characteristics of simple production and high efficiency, and is very suitable for the rapid lamination production process of high-speed production lines. The ultimate trend in solvent development.
6. Conclusion
With its unique advantages and the guidance of relevant domestic laws and regulations, the solvent-free composite process will definitely become the development trend of domestic flexible packaging enterprises and will gradually replace the traditional dry composite process. The solvent-free adhesive should also gradually develop from the original single general-purpose solvent-free laminating adhesive to high-end products. In addition to general-purpose solvent-free laminating adhesives, high-temperature-resistant cooking, aluminum foil-specific, and single-component solvent-free laminating adhesives are currently used in the flexible packaging compound market. There are already domestic companies developing and researching it, I believe it will accelerate the promotion and development of solvent-free composite technology in China.

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