I. The development of ink and wash. The development of ink and wash has basically taken shape as early as the Qin Dynasty (see the materials reported in the excavated tomb of the Nanyue King), but it was not until the Wei and Jin dynasty that Wei Xun integrated different inks and inks on the market (liquid, solid) Only set. Most of them have been used as writing for nearly ten centuries, the purpose of which is to spread the different cultures and civilizations of mankind to different places and leave them to be read and passed on to future generations. Until the advent of movable type printing, it was not widely used. Immediately after, for a long time, oil-based printing inks made up the defects of poor ink gloss, difficult overprinting, slow drying, and instability, and occupied the printing market for nearly 500 years.
In the 1960s, various countries issued environmental protection laws and regulations, and formulated VOC emission standards. During this period, it was the heyday of plastic flexible packaging printing products. The most severe blow that ink and ink encounters is: poor gloss, difficult adhesion, slow drying, high cost, and narrow range of applicability ... Although ink companies in many countries or regions have made beneficial attempts, they have not changed. Under the premise of traditional packaging printing methods, few successful plastic ink printing.
Shenzhen Gukangli Chemical Co., Ltd. has used its leading position in the spray coating industry to intervene in the manufacture of packaging printing inks. It has been developed and applied on plastic flowers and then transferred to flexible packaging substrates for four years. Let the author see that ink and wash can also play an important role in the fields of flexible letterpress, gravure, foam plastic flexo and gravure, rotary screen printing, and color printing inkjet printing.
Second, the related issues of water and ink use 1. What are the applications of water-soluble plastic inks?
The full name of the water-soluble plastic ink's main resin is W-5 resin, which can be applied to plastic printing. According to the reflection of printing manufacturers in Guangdong, Zhejiang, Jiangsu, etc., it can also be applied to paper products.
2. How to adjust the film drying speed of printed graphic ink film using water-soluble plastic ink?
① If W-5 resin is used, the normal printing speed is 40 ~ 70m / min, and if W-5A resin is used, the printing speed is 70 ~ 180m / min. ② Water-soluble plastic inks are used to adjust the speed of resins in order to adapt to different printing speeds. However, due to the increase in pH in formula design, alcohol or tap water or cross-linking curing agents and driers are used to control the film drying speed of printing inks to adapt to the printing machine transfer speed. For example, under the same conditions and with the same amount of alcohol or water, the viscosity values are different. Generally, the speed of the former is only one-third of the latter (this is caused by the surface tension and pH of the former being different from the latter's surface tension and pH), but although the color is close when printing, the ink The transfer rate is affected by false thickness or excessive foaming. In this regard, we can add an appropriate amount of neutralizing agent when diluting: one is to control the stability of viscosity and color miscibility; the other is to control the drying time of graphic ink film for ink printing; the third is to control the clogging of the printing plate cells ( (That is, the resolubility of ink and wash). At the same time, the characteristics and characteristics of the ink cannot be ignored because the ink can be diluted with alcohol or water.
3. Should water-soluble plastic inks be shallow-printed and dried?
After the author tested the printing on the machines of Zhejiang Weihang, Dibang, New Oriental, Antai of Guangdong, Nanyang Yuhua of Henan Province, Xiangfan of Hubei Province and Shifang of Sichuan Province, they thought that the water-soluble plastic ink usually does not need a light version. And drying facilities, but remember that EDM on plastic surfaces is still required.
4. Can water-soluble plastic inks be produced as solid?
In this regard, the author has done experiments in Shijiazhuang City, Hebei Province, Beizhen City, Liaoning Province, Yancheng City, Jiangsu Province, Xiangfan City, Hubei Province, and Zhongshan City, Guangdong Province. In order to serve the packaging and printing industry, LX-2 resin was used in economic reform After adding properties, grafting, stirring, rolling, cooling, crushing and sieving, add it to the printing ink tank, add the appropriate amount of alcohol, water and neutralizer, and then print after rotating for 10-20 minutes.
5. Is the water-based plastic ink printed on the flexible packaging printed on the surface or printed on the inside?
The ink is usually printed on the inside and the surface is good (because the gloss after the printing is slightly lower than that of traditional benzene or ketone ester solvent inks, and the dots on the light or high-profile parts will occasionally be powdered off after a certain period of time. drop). Polyester resins are usually introduced as auxiliary resins for W-5 resins in the Liyin ink system, especially the production cycle from printing to composite film is very stable. The graphic ink film printed by ink is physically closed to communicate with Oxygen in the air is isolated, so the chance of pulverization is small, even if it is oxidized, it will take a long time. However, as a surface printing ink, the printed image is not covered with a film, and its ink film is easily oxidized by oxygen in the air during processing and use, and gradually falls off. In order to solve these defects, Gu Kangli introduced thermal stabilizers into his ink system to stabilize water-based inks.
6. The development trend of water-soluble plastic inks The development of alcohol-soluble, alcohol-water, water-soluble, and water-based plastic printing inks has been booming. Inkjet printing and even electronic ink are also being developed. This is not only to meet the call of environmental protection, but also to extend the technology of tangible printing plates and ink tanks to plateless and ink tankless. This further reduces the environmental pollution caused by printing plates and ink tanks during color change and cleaning. This non-old-fashioned, unconventional ink painting and graphic reproduction technology has pushed today's ink painting technology to a new starting point.
7. What is the reason for the loss of water-soluble plastic ink dots, and how to remedy it?
In flexible packaging printing (either flexible letterpress or photogravure), the reasons for the loss of halftone dots are generally five cases: one is the printing speed is too slow or the heat blowing is too large; the second is the lack of toughener or slow-drying solvent in the ink system. . The third is that there are dust or dried ink residue in the network of printing plate and text; the fourth is that the viscosity is too high or the foam is too much; the fifth is that the ink has no viscoelasticity.
Gu Kangli usually adds alcohol ether or neutralizer, and uses TM-200S or special plate-washing agent containing ethanolamine. As long as the ink in the plate's cells is not completely dry, it can be cleaned with water or alcohol alone. The above second method can be directly added into the ink body, and the gloss of the ink can also be improved. Secondly, an appropriate amount of lithium salt is added to control the viscosity and especially fluidity of the ink to prevent the ink film from floating or flowing. And add defoamer to eliminate foam in the ink to prevent chemical pinholes in the ink film.
8. How to remedy the poor adhesion of water-soluble plastic ink?
If using water-soluble plastic ink produced with W-5 main resin, it is recommended to choose 1.5% ~ 3% of water-based auxiliary resin (PET). Conversely, W-5 can be used as an adhesion promoter for water-based PET inks. When printing, the plastic tension can be controlled between 38 ~ 42 dyne. K4206 curing agent can also be used as the adhesion promoter or catalyst for the ink. The above four methods are low in cost and easy to buy in Gu Kangli. In addition, after resolving the water-soluble plastic ink in the above four ways, the drying speed of the printing ink and the heat resistance of the printing ink film can be improved.
9. How to deal with skin crust on water-based plastic ink?
When W-5 resin is used as the ink connecting material, 1 ‰ of 3114 heat stabilizer can be added, and if the water-resistant PET resin used for cooking is used as the connecting material, 0.5% ~ 3% special ink dispersant L can be added. × 6000 is sufficient.
10. What is the light color and low transfer rate of water-soluble plastic ink after dilution?
This is because the pH decreases after dilution with water and alcohol. The reason is: a part of the neutralizer in the ink system is volatilized, but it may also be caused by the volatilization of alcohol solvents. Causes inaccurate ink transfer.
Suggestions: When diluting the ink, one is to add an appropriate amount of neutralizer, the other is to add 2% to 5% of the buffer; the third is to increase the amount of coupling aid. In short: it is necessary to control the pH of the ink at about 7.5 (When the pH is higher than 7.5, its amount can produce a peak after adding water-called the dilution peak, but when the neutralization added in the ink system It will also appear after the agent is reduced. When a certain proportion of water is added, its peak value often decreases with the addition of water, but this is only a temporary viscosity index. It does not ensure that the viscosity will not change after printing. The purpose of this repeated dilution is to control the printing viscosity of the ink, but the color of the uncertain diluent will gradually become lighter with its amount. When the acrylic monomer content in the auxiliary resin reaches At 30%, the phenomenon of dilution peaks does not appear repeatedly.
11. When water-soluble plastic inks are overprinted (colored), occasional blank spots or sheet-like overprinting may not occur. What is the reason for this?
This is because the ink is not slightly reconstituted. The author recommends that flexible packaging printing operators use Gu Kangli's inks to first print the next color before the ink is completely dry; second, to add polyols and alcohol ethers or non-volatile neutralizing agents.
12. What is the proper resin for water-soluble plastic ink system?
According to the author's understanding, a low-viscosity water-soluble resin with a hydrogen bond value close to that of non-polar plastic is selected.
13. How to control the color and hue of water-soluble plastic ink?
The color and hue of water-soluble plastic inks are firstly the selection of suitable pigments and dyes. The second is the control of pH, as well as the control of technical indicators such as fineness. Because pH directly affects the transfer of water, affects printability, affects color strength, and affects drying. In order to maintain the stability of printing, we must first control the pH value. In order to ensure the stability of the pH value, in order to balance the number of steels (HLB) of the emulsifier in the system-hydrophilic and lipophilic balance, an appropriate amount of polymer electrolyte is necessary. . In order to control the odor of the neutralizer, AMP-95 can be used as a neutralizer for the resin in the ink. In order to ensure the stability of color and hue, the raw materials are selected by the manufacturer, model, and batch number (at least every manufacturer or batch number is changed, because its tinting power and color depth are changed) and can be carried out in batches after testing, testing, trial, and testing. The production of ink colors.
14. Why control the pH of water-soluble plastic inks?
Because there are millions of molecules in the water-soluble plastic ink system wandering in water, without the role of a neutralizing agent, the ink cannot be stable at normal temperature, followed by the foam defoamer in the ink has a relationship with the pH value. Because the mechanism works by replacing the elastic surface film with a brittle close-packed film. Therefore, the purpose of controlling the pH value is to ensure the stability of the water-soluble plastic ink during storage or use.
15. What are the main problems affecting the quality of water-soluble plastic inks?
① Drying speed; ② Printing pressure; ③ Ink viscosity; ④ pH value; ⑤ Cooking and sun exposure; ⑥ The depth of the printing plate mesh, or the amount of ink residue remaining in the ink transfer screen roller; the mutual solubility and slightly redissolvability of ink; printing Speed; ⑨ environment temperature and humidity; ⑩ whether the substrate is properly handled and other ten factors can not be ignored.
16. What are the manufacturing processes of water-soluble plastic inks?
Formulation design— → Resin, colorant selection and dosage of additives— → Pre-dispersion— → Auxiliary resin and water supplementation— → Grinding— → Fineness and viscosity detection— → pH adjustment— → Filter packaging— → Warehouse stand-by.
17. What is the purpose of choosing water-soluble plastic ink surface and back printing pigments?
Among the hundreds of types of colors and dyes, it is usually better to use alkaline colorants that are both alcohol-soluble and water-soluble! This is deliberately proposed to ensure the stable low viscosity, high color depth, and light and cooking resistance of packaging printing ink. Under normal circumstances, the lightfast and permanent color and dye can meet this requirement. Secondly, in the past decades, the author has designed, designed, researched and developed water-soluble plastic inks for PE, PP, PET, PVC and other printing materials, as well as the application of flexible packaging printing manufacturers. This ink is in contrast to traditional gravure, silk screen, and flexible printing. The price of ink materials for plastic and plastic foam gravure printing, and the results of cost accounting, concluded that as long as we can find out how to use and master technical skills from this article, especially the practical skills of packaging printing users, its various ink Technical indicators (such as: viscosity, color, fineness, pH value, gloss, fluidity, fluidity, adhesion fastness, etc.) can completely achieve the same price and quality requirements as traditional inks.
18. Exemplify the feasibility of the formula III. Concluding remarks The shortcomings of poor ink gloss, difficult overprinting, and slow drying have become a thing of the past. It has become possible to change the traditional packaging printing method and use mature ink products to manufacture environmentally friendly packaging and printing products.