Polyurethane ink connecting material has the advantages of simple use, stable performance, strong adhesion, excellent gloss, and good heat resistance, and can be suitable for various printing methods, especially for screen printing, plastic packaging and composite film. In recent years, there have been many research and production units in China that are engaged in the research of polyurethane ink binders and have achieved good results. For example, 121Â°C and 135Â°C resistant cooking inks have been put into production and widely promoted in the market. However, there is a certain gap between the comprehensive performance of the product and imported products. To improve the overall performance of the product and develop multi-functional products is the focus of research on polyurethane binder inks in China.
With the rapid economic growth, domestic plastic printing inks, food packaging printing inks, etc. have shown an upward trend, but related polyurethane ink connecting material products have not been developed and produced in time. In food packaging, such as milk bags, the material is BOPP and other low-polarity materials, but also need to resist boiling, sun, etc., so the application requirements of the binder is higher. Especially for ink binder solvents, since many European companies in Europe and America have stipulated that all packaging materials must not contain aromatic hydrocarbons in their internal control quality standards, China has begun to prohibit the use of food printing inks from the perspective of environmental protection and the safety of users. Aromatic hydrocarbons are toxic solvents. To meet this requirement, benzene-free inks have emerged. This kind of ink is theoretically free of aromatic hydrocarbon solvents, but due to the storage, transportation of raw materials, manufacturing process and the use process will be more or less mixed with a small amount of aromatic hydrocarbon solvents, so the "no benzene" It should be understood that the aromatic hydrocarbon content in the system is â‰¤1.
Due to the rapid development of the national ink industry, polyurethane ink connecting materials will develop rapidly in the future with its unique performance advantages. At the same time, due to the increasing awareness of environmental protection, the original benzene polyurethane ink connecting materials have superior performance, but due to its toxicity. It is also destined to be eliminated. The development of benzene-free polyurethane inks will be an inevitable trend.
In particular, it should be pointed out that due to the increasingly stringent national requirements for environmental protection, benzene-solvent-based ink products that are widely used today have a large amount of toxic solvents that evaporate during use and have a small amount of residues, which pollutes the environment. It also harmed the physical and mental health of workers, especially in the soft packaging of benzene on the production of bags have been continuously exposed, known as "poison bag." Now the country has explicitly banned the use of ink containing toluene in the food flexible packaging industry should be Sichuan, benzene-free inks, water-based inks, alcohol-soluble inks have been greatly developed. Water-based gravure inks have attracted attention as an alternative to toluene-based inks, but there has been a lot of resistance to water-based inks in packaging film printing. The reason is mainly due to the fact that the printing suitability and the printing quality site cannot reach the standard of the solvent type ink because the tension of the water is too high and the wettability on the surface of the film substrate is poor. If you want to get the printing quality of solvent-based inks, in addition to the technical improvements needed for water-based inks, the printing equipment and printing roller pages need to be changed. For these reasons, the ink industry has focused its attention on the development of ketone solvents, alcohol ester solvents, and alcohol-soluble inks.
Second, polyurethane connection material properties and use
1. Main product models and physical properties
2. Product Features
(1) Excellent adhesion and good connectivity;
(2) good film formation and solvent release;
(3) Good compatibility with solvents such as ester alcohols;
(4) Good resistance to yellowing, hydrolysis, and media resistance;
(5) Good dispersibility, wetting, and leveling properties. The gravure ink configured to have good printability.
3. Product use
(1) Dissolution and Dilution: The main solvent of the resin is mainly organic solvents such as butanone, ethyl acetate and isopropyl alcohol. At the same time according to different needs, in the ink to add a good amount of solubility, moderate volatility medium boiling point solvent. For organic solvents such as methyl isobutyl ketone, n-butyl acetate, n-propyl acetate, n-propyl alcohol, and propylene glycol methyl ether, the solvent solubility parameters and volatilization rate of the ink system are appropriately adjusted to further improve the ink system. Adhesion, color development, so that the preparation of the ink to achieve the best printability.
(2) The product has good compatibility with various resins (chlorinated vinegar resin, PVB resin, aldehyde and ketone resin, nitrocellulose, and other resins and cellulose, etc.) all show good compatibility. In order to improve the overall performance of the ink, the above-mentioned resins and fiber cords are often used in conjunction with PU resins in ink formulation and serve as pigment polishing media. It is recommended that detailed material testing be performed before use to ensure that the resin or cellulose has good solubility in the ink solvent, and that the resin and the resin have better compatibility between the resin and the cellulose.
(3) In order to improve the smoothness of the ink system, a certain amount of polyethylene wax (wax powder or wax liquid) is often added to the ink.
(4) Polyurethane resin is a polar material, in order to improve the adhesion of ink to PP, PE and other non-polar substrates, it is necessary to add an appropriate amount of PP or PE adhesion promoter.
(5) When the printed product is used for cooking, an appropriate amount of hardener may be added to improve the adhesion and heat resistance of the ink.
Third, the conclusion
Ketone-soluble, alcohol-alcohol-soluble, alcohol-soluble ink can effectively solve the health damage caused by toluene-based ink and solvent residues affect the quality of packaged food. In Europe and the United States, this has become a trend. Some countries in Asia have already begun to replace the toluene-soluble ink. In recent years, due to the introduction of mandatory policies, benzene ink connecting materials will be gradually introduced to the historical stage. It can be predicted that in the near future, benzene-free solvent-based polyurethane inks will occupy a major share of the Chinese food and pharmaceutical packaging ink market.
Reprinted from: China Packaging Network Information Center
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