Gravure ink technology for plastic flexible packaging

China's flexible packaging production began in the 1980s in the 20th century. After more than 20 years of development, the flexible packaging industry has reached a considerable scale and has a certain level of technology. To incomplete statistics in 2004, China has already owned more than 7O0 of imported production lines, and the number of small and medium-sized manufacturing enterprises with domestic equipment is not less than 80,000. The country consumes more than 4 million tons of plastic film substrate per year (excluding aluminum foil and other substrates), consumes 70,000 tons of plastic packaging ink, and 80,000 tons of adhesive. The plastic flexible packaging industry has become a rapidly growing packaging industry. Emerging industry. In the case of gravure inks for plastic flexible packaging, chlorinated polypropylene type OPP composite inks, polyamide type surface printing inks, and polyurethane type inks are mainly used. According to statistics from China Packaging News, among the 70,000 tons of plastic packaging ink required in 2004, the chlorinated polypropylene type accounted for approximately 55-60%, the polyamide type accounted for 25-30%, and the polyester polyurethane type. Accounting for lO-l5%, other types only 5%.

Plastic gravure ink is a mixture of dispersed liquids, the key to production is that the components can be fully mixed and dispersed evenly. The basic process of plastic ink includes:

l, connection material production

A variety of compatible resins are dissolved by a solvent and become a uniform viscosity liquid, and the equipment is mainly a reaction kettle and the like. At present, some well-known brand ink manufacturers in China can directly produce resins with different functions and combine them into their own unique connection materials, such as Tianjin Toyo, Hangzhou Hanghua, Zhejiang New Oriental and other ink manufacturers.

2, scattered, grinding

The color material, the binder, the solvent and the additive are mixed and dispersedly ground into a semi-finished product. 3, adjustment, finished product packaging

Through various control measures, various indicators are tested, and the finished product is obtained after stabilization. The ink production equipment has a great influence on the stability of the ink product quality. In particular, the quality of the grinding is directly related to the stability of the ink and the printability. Therefore, a good ink product must be based on an excellent formula, with advanced production technology and equipment.

Use of plastic ink

In addition to the above-mentioned classification methods, plastic gravure inks can be divided into table printing inks and compound inks in the manner of printing processing. At present, many domestic ink manufacturers can produce these two types of inks. So, from what aspects should we choose the ink we need? We must choose the printing substrate film, EI] ~ U conditions, product quality requirements, post-processing conditions, end-use to select the ink, while the choice of the overall performance of the plastic printing ink must Learn about the type of ink, dilution solvents, and conditions of use.

l、Function and characteristics of different types of ink (see Table 4 for details)

2, the use of ink viscosity

The viscosity of the ink has a direct influence on the quality of the printed product. The viscosity of the ink in the production is determined by the specific process parameters, and the viscosity is also the dilution solvent (purity, solvent formulation) used in the workshop's temperature, humidity, speed of the printing press, and ink concentration. ) and so on are all related. In order for the printing to proceed smoothly, we must control the viscosity of the ink.

If the viscosity of the ink is too high or too low, it will result in incomplete prints, texts, patterns, and dots. The viscosity of the ink will cause the product not to appear bright, fade, and the abrasion resistance and scratch strength will be weakened. The adhesion will not be sufficient and the color will fade. Such phenomena. Composite inks can cause incomplete layered dots and poor hiding power. After printing, the bottom of the film leaks with spots. In particular, when compounded with aluminum foil and aluminized film, the white dots are serious.

In the polyurethane ink composition, butanone is the main solvent of the ink. It is a fast volatile ink. If the volatilization rate of the ink and the solubility of the added solvent cannot be controlled, the polyurethane resin may precipitate, the pigment flocculates, and the ink precipitates, resulting in a series of failures such as no coloring, dirty printing, hair growth, and discoloration. In order to make the solvent volatilization and dissolution of the polyurethane ink in the printing process parallel, we must adjust the dilution solvent reasonably so that the ink is always in a good fluid state during printing.

Development of flexible packaging inks

China's plastic flexible packaging market, the vast majority of small and medium-sized enterprises, the production of technical products is not high, or similar products, so the competition is fierce, and finally often focus on the cost reduction, while ignoring the product's technical requirements and health Claim. The use of plastic ink in China has increased substantially, but it has not been correspondingly improved in terms of safety and health performance, there is a significant hysteresis, toluene and other aromatic solvents are still in use, chlorine-based inks account for 60% The above ink market.

Since China's accession to the WTO, the economic and trade trade between China and other countries has become even closer. The requirement of "internationalization" has greatly boosted the development of China's plastic ink industry in the direction of environmental protection, but there are quite a number of plastic flexible packaging companies and ink manufacturers that are passive. Accept the status, instead of consciously and actively pre-active. Domestic plastic packaging inks must be associated with safety and hygiene. As far as its solvent system is concerned, it is currently developing in the direction of benzene-free and alcohol-soluble products. In terms of alcohol-soluble ink technology, Shanghai Sikebai, Zhejiang New Oriental, and Shanghai DIC are leading companies. As far as its connection material technology is concerned, it is heading towards the development of polyester urethanes. Because of its low toxicity, polyester-polyurethane inks are suitable for the printing and dyeing of P-star and NY materials. The excellent properties such as high-temperature cooking resistance, freezing-resistance, and wear-resistance are favored by users and will gradually replace chlorinated polypropylene inks. New Oriental Ink's polyester inks currently account for more than 50% of the company's total ink production and become the company's core competitiveness products. In terms of its pigment system, plastic packaging inks will move toward the absence of heavy metal pigments. If the domestic pigment manufacturers cannot integrate with international manufacturers at this point, they will face the risk of being eliminated.

Since gravure printing technology entered China, it has been in a steady development trend and its development prospects are still very promising. This is different from other countries such as Europe and the United States. In China's food plastic flexible packaging, gravure printing has absolute advantages. In large-scale supermarkets, foods and daily-use packaging that are greeted with a wide range of eye-catching curtains are gravure products. However, in Western Europe, flexo printing accounts for more than 70% of food plastic packaging, and gravure food packaging bags continue to decrease. According to the current development trend of gravure printing in China, we have reason to believe that gravure printing will continue to remain the absolute leading position in the printing of plastic flexible packaging. Of course, plastic flexible packaging inks must move toward safety and hygiene. With China's accession to the WTO, packaging requirements will gradually be brought into line with international standards, and the country will gradually formulate more stringent standards. Manufacturers who supply raw materials for flexible packaging enterprises must plan ahead, adjust their technological orientation, and adapt to the needs of the development of the times before they can enter the market. Standing in an invincible position.

Author: Yu Yongyue

Reprinted from: China Packaging Industry