I. Introduction and review With the continuous development of modern industry, the status of the printing industry in production and life is increasingly important. The degree of development of the printing industry is often one of the important signs of measuring the degree of industrialization and modernization of a country.
With the development of human industrialized tuxedos, people are improving their production and living conditions while also causing damage and pollution to the global environment on which we depend. Both developed and developing countries are threatened by environmental issues to varying degrees. The entire planet also faces various problems such as global warming, atmospheric ozone hole, water pollution and desertification. Therefore, solving various environmental problems is no longer an area, a country, or an industry. All countries in the world must act together to protect and protect our global village. Otherwise, humans will be destroyed by the pollution they cause.
It is based on this understanding of the importance and urgency of environmental protection. Western Europe, North America, and other developed countries have started environmental protection and environmental protection activities since the 1970s. Up to the national government, legislatures, medium to large, small and medium-sized enterprises, down to all homes, all participate in environmental protection activities to varying degrees. The government’s environmental protection and legislative departments quickly formulate various practical laws and implement them in phases. The industrial sector actively responded to the call of the environmental protection and legislative departments to formulate a phased compliance plan. In this context, the printing industry using solvent ink is also facing new options.
Many of the inks used in packaging, newspapers, and magazines at that time were based on aromatic compounds such as benzene, toluene, and xylene. After volatilization of such aromatic solvents, it not only causes air pollution, but it is also a carcinogen, which is harmful to the health of printing operators. There are usually two options for the use of such solvent inks: First, install a solvent recovery unit to recover the benzene solvent that has been volatilized during the printing process and then incinerate; the other method is to use a low level of environmental pollution. A little toxic solvent to replace the aromatic solvent. Although the former can recover most of the volatile solvents, it is still inevitable that part of the solvents will evaporate into the air during production, storage and use. Moreover, the recycling equipment used is expensive and the operating costs are not low. The latter method is to improve the production of ink in Western languages ​​and it is relatively easy to implement. It is also more popular with printing manufacturers. Alcoholic solvents were used earlier to replace benzene solvents. Usually ethanol, propanol, etc. People also call this ink an alcohol solvent ink. The use of alcohol-soluble ink to replace benzene solvent ink is a big improvement in terms of environmental protection. In the study of atmospheric pollution and protection, people have found that the generation and accumulation of greenhouse effect is largely due to the organic substances that are volatilized into the air. People named these substances organic volatiles. Obviously, although alcoholic solvents have very low pollution and toxicity, this type of lyophyll, like benzene-based solvents, also belongs to the category of organic volatiles. With the further increase in environmental protection requirements, the market's demand for non-organic solvent inks is growing.
In the United States, for example, the United States Environmental Protection Agency (EPA) has proposed restrictions on the content of organic volatile substances in inks and coatings. This restriction is getting stricter over time. In the late 1970s, with the development and commercialization of water-emulsion polymer emulsions, Europe and the United States successively produced industrial-scale water-based inks, or ink inks for short. From the angle of environmental protection trials, the production and application of this non-polluting, non-toxic new ink is a revolution in the ink manufacturing industry.
Second, the status of ink production and application After more than 20 years of improvement, improvement and development, ink production and application technology has greatly improved and developed, it gradually evolved from simple printing to high-quality multi-color printing and color printing. The development of high-line anilox rolls in recent years has put new demands on ink quality. This combination of high-line anilox rolls and high-quality inks has further improved the print quality of ink. This is not only reflected in the fact that more flexo printers use ink to replace solvent inks, and many prints previously printed by offset printing have gradually adopted flexo.
Take the United States as an example. With the improvement of environmental protection requirements, the practicalization and commercialization of ink-and-wash technology has driven printing companies from using solvent inks to using inks. Tables 1 and 2 list the comparative data of the United States in 1992 and 1993.
With the development of new materials and new technologies, the share of the ink-and-wash market has increased year by year, and the use of solvent inks has continued to decrease. This change is more evident in the flexographic packaging and printing industry.
In general, the ink used for flexographic printing is a low-viscosity ink with good fluidity. The main advantages of flexo printing are: wide use, convenient application, good printing quality and low cost. In general, the speed of multi-color printing can reach 130-200 m/min. It can also be folded, cut, and laminating.
The ink used for flexo printing is dried after printing by absorbing the solvent in the ink or volatilizing the solvent by the printing material. When printing, in order to improve efficiency, people want ink to dry faster. However, if the drying speed of the ink is too fast, the re-solubility is poor, and the ink on the printing surface will accumulate and produce a dirty version (also called paste) phenomenon. This requires a moderate balance of drying speed so that the ink printed on the substrate can be dried in a timely manner while the machine can be operated for a longer period of time without gluing. (To be continued)