Packaging printing and plastic ink selection and requirements

1) pH stable ink system. The ink must have a stable pH during the printing process and no need to detect or adjust the pH during printing.

2) The resin tends to solidify in the ink due to the volatilization of the amine, and even if it solidifies on the printing plate, the re-solubility of the ink becomes another requirement of the packaging printing factory.

5. Requirements for alcohol-soluble plastic gravure ink

Since water-based gravure printing inks are not yet fully capable of replacing toluene-based inks, and the cost is too high, packaging and printing companies hope that ink companies will soon develop alcohol-soluble gravure inks. The alcohol-soluble composite plastic gravure ink has low odor and benzene-free characteristics, which can effectively reduce the health damage of toluene-based ink and effectively solve the influence of residual solvents on the quality of packaged food.

The use cost of alcohol-soluble ink is 20% higher than that of common solvent-based inks. Therefore, the biggest requirement for alcohol-soluble inks is to reduce the cost, followed by the requirement of non-stickiness, good flexibility, resistance to oil, rubbing, and heat resistance. Well, the selected pigment must have a certain light resistance.

From the interviews, we learned that many packaging and printing companies in China have far higher requirements for the quality of ink and printed matter than existing national standards, and some have approached international standards. This undoubtedly raised new and higher requirements for ink manufacturers. We believe that under the current severe market competition, the printing industry and the ink manufacturing industry will strengthen exchanges and communication, and they will certainly achieve the goal of mutual benefit. Although packaging and printing companies have chosen the right ink, there are also many problems caused by the ink itself during the use of the ink. So, what are the higher requirements for packaging inks for packaging and printing plants?

Packaging Printing Factory Requirements for Inks

In order to optimize its own operating expenses, improve the stability of production, and meet the requirements of customers, packaging and printing plants increase the production efficiency, improve the production environment, and satisfy the customers' environmental requirements for packaging. The basic requirements of the factory for ink.

1. Reduce the use of cost

Reducing costs and maximizing profit are prerequisites for the survival and development of a company. Packaging and printing plants are no exception. Although ink accounts for only 15% of the printing cost (paper accounts for 45%), we understand that the printing factory has never given up its efforts to reduce the cost of ink. Packaging printers prefer ink suppliers to provide the best price/performance ratio to meet the requirements. Ink products.

1) Improve ink coloring

Several printing companies interviewed hoped that the ink production plant would improve the coloration of the ink, and hoped to print more jobs with a fixed amount of ink or use a minimum amount of ink for a fixed number of jobs to reduce printing costs. However, the amount of ink is closely related to the colorability of the ink. In the case of a certain amount of ink, the higher the ink colorability, the more jobs printed and the greater the profit.

2) Reduce the use of additives or use supporting additives

On the one hand, the printing industry hopes that the ink used can be directly used during printing, and no need to add or little additives, just use the solvent to adjust the viscosity of the ink. Adding auxiliaries will increase the printing cost, increase the preparation time before printing, waste labor, and will also affect the stability of ink properties, and will also cause troubles for post-press processing.

On the other hand, the additives are required to have a certain degree of specificity. The additives must be matched with the ink, the effect is obvious, and the use is convenient. For example, Huangshan Xinli Ink Chemical Plant has formulated the corresponding additives for the characteristics of printing products of Huangshan Yongxin Co., Ltd. Among them, the auxiliary agents B-0020 and B0142 can effectively solve the problem of knife wire contamination in high-speed printing, and add additive No. B0142. It can improve the antistatic property of the ink, and it does not affect the composite strength of the printed ink.

For some printing plants, there is also the problem that used ink needs to be stored for a short period of time. Many inks that have not been used up yet have added auxiliary agents can not be used substantially, resulting in waste. Therefore, the printing plant hopes to use the ink after it is stored for 1-2 months and can be used after simple processing to reduce the waste of ink and save the cost. This requires the ink manufacturer to solve the problem that ink cannot be used continuously after deployment. .

3) Improve the ink's adaptability to high-speed printing

At present, the speed of domestic gravure printing machines is generally around 150 meters/minute, and the increase in the speed of printing presses will reduce the printing plant's operating costs and increase efficiency. Therefore, the printing manufacturers hope to be able to adapt to the printing speed of 300 m / min or even higher printing speed of plastic gravure ink can be available soon.

2. Technical performance requirements

1) Requirements for ink hue

The packaging and printing factory hopes that the hue of the ink will be more stable because when printing large quantities of live parts, the ink must be continuously added. If the hue of the ink is unstable, the quality of the printed matter will be inconsistent.

2) Requirements for ink gloss

Good gloss inks look bright, but in actual printing production, printing companies often add some solvents to the ink to affect the gloss of printed materials in order to reduce the cost, and the humidity in the workshop can also affect the users. Therefore, users It is hoped that the ink will still maintain a high gloss and a certain degree of stability without being affected by external conditions.

3) Requirements for ink viscosity

The printing factory hopes that the thick ink viscosity will be appropriately increased so that more solvents can be added to reduce the cost when used. The viscosity of the ink can be controlled at 30 to 60 seconds (painted No. 4 cup, the same below). For high-speed gravure, the viscosity of the original ink needs to be less than 40 seconds and the viscosity after dilution is 12 to 15 seconds. For medium-speed printing, the viscosity of the original ink is controlled at 40 to 50 seconds, and the viscosity after dilution is 16 to 18 seconds.

4) Requirements for ink fineness

Packaging printing is developing toward refinement, and printing equipment is becoming more and more sophisticated. The fineness of ink is required to be controlled below 15μm. The ink is too thick not only to hurt the printing plate, but also it is easy to produce quality problems such as knife lines.

5) Requirements for ink adhesion strength

Some special colors of ink have poor adhesion strength. Some large-scale ink manufacturers' products, especially gold, silver ink and white ink, will still cause ink-disappearance during printing and post-press processing. White ink is also prone to poor adhesion. Many of the packaging products are decorated and decorated with large color blocks. Therefore, discoloration has a direct impact on the quality of packaging prints.

6) Requirements for ink anti-blocking

Due to the high temperature in the workshop and the high humidity in the printing plants located in the south, there are often print adhesion problems. However, the adhesion of printed matter is also related to the ink itself. Because the ink contains an oxidation promoter, it can easily cause adhesion of the printing ink layer. This made the southern printing company have more specific requirements on the anti-blocking properties of the ink.

3. Environmental protection requirements

Many packaging printers use toluene to adjust the viscosity of ink in order to reduce costs. The consequences are not only the residual solvents that affect the safety of the printed matter, but also the main cause of the solvent contamination of the gravure printed plastic flexible packaging. The discharge of solvent-laden waste gas from the gravure exhaust gas discharge system causes environmental pollution. Toxic gases such as toluene can also affect the health of workers. Therefore, the problem of contamination of gravure ink by plastic gravure printing is a perennial problem in the gravure printing industry.

In recent years, due to increasing environmental protection in the society, the state has formulated some relevant environmental protection laws and regulations. The printing factories pay more and more attention to the health of workers, which increases the printing industry's demand for various environmental protection inks. . For example, high-concentration low-viscosity inks, benzene-free alcohol-soluble inks, and water-soluble plastic gravure inks that are suitable for shallow gravure printing are the development direction of plastic gravure inks.

4. Requirements for water-based ink

Water-based gravure inks have the advantages of reducing atmospheric pollution, facilitating safe production, and reducing potential safety hazards. From the perspective of print quality, due to the slower rate of evaporation of water-based inks, high-light parts are better inked. However, the currently used inks still do not meet the solvent-based gravure ink standards in terms of printing performance and print quality. The main reason is that the surface tension of water is relatively high, reaching 7.2×10-2N/m, which makes it difficult for the ink to wet with the printing material, and the drying is slow and the printing ink color is not bright enough. Therefore, the water-based gravure printing ink is still not popular in the country. Therefore, there is a need for technical improvements in inks and resins to improve their drying and film forming properties.

The basic requirements for the performance of ink and wash ink users are:

1) pH stable ink system. The ink must have a stable pH during the printing process and no need to detect or adjust the pH during printing.

2) The resin tends to solidify in the ink due to the volatilization of the amine, and even if it solidifies on the printing plate, the re-solubility of the ink becomes another requirement of the packaging printing factory.

5. Requirements for alcohol-soluble plastic gravure ink

Since water-based gravure printing inks are not yet fully capable of replacing toluene-based inks, and the cost is too high, packaging and printing companies hope that ink companies will soon develop alcohol-soluble gravure inks. The alcohol-soluble composite plastic gravure ink has low odor and benzene-free characteristics, which can effectively reduce the health damage of toluene-based ink and effectively solve the influence of residual solvents on the quality of packaged food.

The use cost of alcohol-soluble ink is 20% higher than that of common solvent-based inks. Therefore, the biggest requirement for alcohol-soluble inks is to reduce the cost, followed by the requirement of non-stickiness, good flexibility, resistance to oil, rubbing, and heat resistance. Well, the selected pigment must have a certain light resistance.

From the interviews, we learned that many packaging and printing companies in China have far higher requirements for the quality of ink and printed matter than existing national standards, and some have approached international standards. This undoubtedly raised new and higher requirements for ink manufacturers. We believe that under the current severe market competition, the printing industry and the ink manufacturing industry will strengthen exchanges and communication, and they will certainly achieve the goal of mutual benefit. (divid)

Reprinted from: Printing Technology