Research and Application of Benzene-free Solvents and Inks in Food Packaging Printing (I)

I. Prospects of the printing industry
In recent years, with the rapid development of social economy and people’s increasing demands for quality of life, the domestic market for the development of plastic flexible packaging has been particularly fast. In the past, some manufacturers of non-flexible packaging products began to turn to the production of plastic flexible packaging, food, and detergents. The requirements for form and quality of packaging such as cosmetic products have undergone great changes. Plastic gravure printing is the main method for printing plastic films today. The use of gravure printed plastic film prints, bright color, clear and crisp, moderate contrast, vivid image, strong sense of three-dimensional, product specifications, and other advantages. It is difficult to achieve other printing methods, due to the unparalleled effect of China's flexible packaging and printing, especially in the field of food packaging and printing, gravure printing has taken a dominant position.

Indeed, the development of gravure printing today is inseparable from the joint efforts of many related industries. Such as equipment manufacturing, ink manufacturing, solvent, plate making new technology applications and the implementation of new processes in the printing industry, etc., all contribute to the prosperity and development of gravure. With the development of social economy, under the joint efforts of various related industries, China's "first-rate products, second-rate packaging," this situation is changing. However, more and more companies attach great importance to the safety of their products' packaging and packaging in the context of increasing attention to product brand awareness. In particular, food companies pay special attention to the hygiene and safety of their products' packaging. At the same time, the state has also mentioned the major issues of national economy and people's livelihood for food hygiene and safety issues. Food packaging has been included in one of the six categories of national quality supervision.

At present, in the field of paper gravure printing, water-based inks have been basically used, and most of the water-soluble inks are used in the field of decoration (such as wood-grain paper printing); however, due to the special nature of the material in the gravure printing of food soft packaging, , And the special requirements of food packaging, together with the ink in the manufacture of technical difficulties still to be solved, making the food packaging in gravure printing mainly used ink or solvent-based ink. The material suitable for gravure printing is very wide, among them are commonly used: PVDC, PET, IPE, NY, CPP, OPP, BOPP, composite film, and other films with the same characteristics as the above materials, these materials are basically safe to use. And health requirements. However, most of the inks suitable for gravure printing of food packaging contain a large amount of volatile solvents, and these volatile solvents account for almost 30%-50% of the gravure ink composition, and the most reaches 60%-70%.

Among them, benzene, toluene, xylene and other aromatic hydrocarbon volatile solvents as the main raw material, these raw materials are toxic and not conducive to environmental protection, health and safety, how to solve food packaging in the printing of health, and safety issues have become food Cross-industry issues such as industry, printing industry, and ink manufacturing.

Second, the development of low toxicity solvent research process and results

As we all know, benzene is a colorless liquid with a special aromatic odor that is volatile, flammable, explosive, and highly toxic. Therefore, toluene and xylene are generally used instead of pure benzene in ink printing as a solvent or diluent for various offset printing inks. However, toluene and xylene are toxic substances.

When people inhale higher concentrations of toluene or xylene in a short period of time, central nervous system anesthesia may occur, lightness may cause dizziness, headache, nausea, chest tightness, fatigue, and confusion; severe coma and even respiratory and circulatory failure Death; If a long-term exposure to a certain concentration of toluene, xylene gas, will cause chronic poisoning directly lead to leukemia, so the benzene series has been identified as a strong carcinogen by the World Health Organization. At the same time, if the residues of benzene series and other harmful substances in the printed packaging are too large, it will directly cause serious damage to the packaged food caused by serious pollution. How to better and more effective solve the impact of toxic and hazardous substances and benzene residues in printed matter on food has become a pressing issue for the printing industry.

In view of this, Foshan Baojule Chemical Technology Co., Ltd. started its exploration in this area as early as 1996. In the same year, Baojule Company formally established the “No Benzene Chemicals Chemical Research Center”, and together with several domestic universities The school's chemical experts and professors form an expert group and specialize in systematic research on scientific theories and practical applications of chemical solvents without benzene series chemicals. After more than two years of hard work in 1998, we first successfully developed the "Geometric Solvent Digital Model Geometry Substitution Method" to lay the theoretical foundation for the development of benzene-free solvents. Under the guidance of this basic theory, we officially launched the food packaging. Solvents for inks for gravure printing inks and special diluents for inks "Research on the practical application of benzene-free alternatives to benzene-containing materials."

First of all, we analyze and study the printing substrates and inks used by current printing companies. After a lot of investigations, the substrates currently available on the market for gravure printing are usually: PVDC, PET, IPE, NY, CPP, OPP, BOPP is particularly commonly used for PET, BOPP. At the same time, we found that the dozens of printing production companies actually printed the actual operation process and found that the reason for the large excess of benzene series in food packaging printing materials was that the diluent used in the ink was mostly butyl, ethyl, and dibutyl. Ketone, isopropanol, toluene or xylene, and the amount of toluene or xylene used exceeds 50%, plus the addition of toluene or xylene in the production process of the original ink leads to a high level of benzene content in the entire printing machine. However, the residual benzene content of the printed matter is very large. After the above investigation, for this purpose, we set a clear research goal: a new type of benzene-based ink mixed solvent, must adapt to the speed of various printing presses, and the structure of the drying system; widely adapt to various printing materials The characteristics, as well as the indoor temperature and relative humidity of the production site, as well as the effective dissolving power of the ink should be relatively high, and the proper dry speed and other aspects should be fully considered. At the same time, a new type of benzene-free ink mixture solvent and ink thinner, the selected organic solvent should have good dissolving power, free of any mechanical impurities and free acid, alkali and moisture; the new solvent can not corrode the printing plate. New solvents cannot react chemically with the constituents of the ink; new solvents must be low-toxic, micro-toxic, non-toxic, and have wide applicability to all types of inks.

In the investigation of the production process of the company, we found that gravure printing in food packaging has a relatively high requirement for ink, and ink and solvent are also one of the necessary materials for printing. Improving the transfer of ink is the key to controlling the quality of printed matter. However, due to the difference in printing materials and printing methods, the ink transfer rate is different, and the ink transfer rate determines the pros and cons of the printed product. Therefore, there are specific requirements for the composition, fixation and drying of plastic gravure printing inks. Different printing materials and different inks and different solvents have different special effects.

First of all, we studied the composition and characteristics of packaged intaglio printing inks, and at the same time conducted a detailed analysis of the various factors that affect the printing quality of printing inks. This is a new type of non-toxic and low-toxicity solvent in printing adaptability. Laid a good foundation.

We all know that inks consist of pigments, binders, additives, and solvents. According to a certain ratio of mixing, grinding, bar system made. In the printing, the binder is used as a carrier to transfer the solid pigment from the ink tank to the plastic.

among them:

1. Pigments are divided into inorganic pigments and organic pigments (mainly used for color adjustment).

2, link material: refers to the ink in the dispersion medium, is the carrier of pigment particles. The printing adaptability of inks is very close to that of the linking materials. The components of the linking materials are relatively complex. There are mainly oil type linking materials and resin type linking materials. The linking materials of the plastic gravure inks are mainly resin linking materials: generally, polyamide resins. Class, nitrocellulose, acrylic resins.

3. Solvents: Solvents for plastic gravure inks are an important part of plastic gravure inks and are indispensable materials for plastic film adhesives. It has the ability of dissolving substances and self volatilization, and its solvency and volatilization rate are important factors that determine the drying condition of the plastic gravure ink ink layer and affect the printing quality. Therefore, the choice of solvent is a prerequisite for ensuring the quality of the ink.