I. Main pollution factors in the printing industry We are in an era of increasingly harsh environmental climate. Humanity has also destroyed the harmony of nature's ecological environment while creating material civilization. The sandstorm in spring and the abnormal warmth in winter; the ozone layer is destroyed, the glacier area is reduced; the ocean is polluted, the soil is desertified, rivers are drying up, and resources are depleting. People no longer take a walk in the rain, because rain and acid rain fall from the sky; people no longer dance in the wind, because the wind is full of dust and sand.
The waste of most industrial chemicals is the main cause of air pollution, water pollution, and a large amount of hazardous waste. The various solvents in the printing industry are no exception and have a large or small adverse effect on people's health and the ecosystem around us.
In the face of the deteriorating environment, what can our printers do to improve the environment? The principle of environmental protection against pollution is the correct use of various chemicals. It is not only necessary to reduce waste at the source, but also to reduce the environmental impact of various chemicals in the production process. In printing companies, manuscripts, films, printing plates, inks, fountain solutions, and printer washing liquids constitute an integral part of the printing process and are an important factor in printing. Some of them constitute a part of the printed products, and some of them become solid, gaseous, liquid waste after they are used in the printing shop. We analyze them here so as to effectively control the pollution of various factors to the environment. First of all, we must look for ways to use safe products to reduce or avoid environmental pollution. At the same time, we must also find a reasonable way to use the chemicals that we have to use now, and control their dosage to reduce environmental pollution.
1. Film is currently the most used printing method is offset printing, and offset printing plate is mostly used for making plates (CTFilm) made PS version to print on the machine. The film is a photosensitive material containing silver ions, and the waste water in the fixing also contains silver ions, so it is polluted by the environment. Although there is a door to recover the waste fixer, it still has a destructive effect on the environment during the production process and the production process of the printed product.
There is now a "green film" - dry film (dry film imaging) process. The biggest advantage of dry film imaging is that it does not require the exposure and stencil process of traditional film, and it does not need a developer. Naturally, it also eliminates the related equipment and operating procedures. The most important thing is that it can be imaged without using any chemical agents. Extremely advantageous, called "green" imaging technology.
In addition to meeting the requirements of environmental protection printing companies, dry film imaging machines also provide great convenience to design companies and advertising media organizations that require direct indoor imaging because they can be directly connected to laser printers to form an office automation unit. Equipment.
Due to the fact that unlike traditional wet versions, dry imaging requires consideration of material purchase costs, and consideration of the use and maintenance of other equipment, it has advantages over conventional wet plate imaging in that it can increase production and reduce costs.
The principle of dry film imaging is the same as that of traditional wet film imaging. The only difference is that the required imaging laser energy is different and the dry film is relatively high. The optical imaging system of the dry plate imaging machine can be used without any changes, as long as a set of filters is added, it can be applied to the traditional wet plate imaging requirements.
The biggest feature of this film output system is its good quality, strong point-to-point and versatility, suitable for various platemaking equipment. In addition, the entire system does not need to add other equipment, spending less time and money. No chemicals are needed for use, and there is no feeling of discomfort when filming, imaging, or filming. In operation, they are stored, installed or used with other films like traditional films.
Because film has given us great environmental protection, cost, and technical troubles, people have long wanted to avoid them, so people are constantly studying the direct plate making process and the updated digital printing technology.
2. Ink printing ink includes the following three basic components;
(1) Coupler: It is a pigment of fine solid particles. The pigment has transparency, opacity, light tightness and chemical resistance.
(2) Linking material (carrier): It is composed of resin, dry vegetable oil, mineral oil, hydrocarbons, aromatics, olefins, paraffin hydrocarbons, etc. It is a liquid material. Its role is to carry pigment particles during the printing process, and after transfer to the paper or carrier material, play a link between the carrier material and the pigment particles. The link material has a "carry" function, which moves the paint to the paper and causes it to dry. In addition, the binder provides the abrasion resistance and reflection characteristics for the dried ink.
The resin binder in the dissolving ink uses organic solvents such as alcohols, esters, ketones, and benzenes. After the ink is transferred to the substrate (paper), the solvent evaporates into the environment or penetrates into the substrate. The ink dries with the volatilization of the solvent. Because it is an organic solvent, it usually has a relatively strong odor, it is polluted to the environment, and it is toxic to the human body. According to the relevant regulations of the country, the use of this type of ink should have certain environmental protection measures (strengthened exhaust, solvent recovery, etc.), and This ink has some fire hazards.
(3) Additives: including dispersant, desiccant, plastic materials, lubricants and some special chemical substances, whose role is to change the printability of the ink, such as: viscosity, viscosity, dryness, etc., or to achieve the required The print quality characteristics. In addition, the additives help to ignore the requirements of the specification characteristics of the wear resistance of the object.
Since inks contain harmful substances, the ink industry has always been changing inks. The following improvements have been made in the past 40 years:
1974: Removed lead in ink pigments;
In the late 1970s: the removal of cellosolve (ethyl glycol);
In the early 1980s: Removed toluene from food packaging instructions;
In the late 1980s: the related benzidine yellow pigment was removed;
In the early 1990s: the use of phthalic acid plasticizers was reduced.
Now people are working hard to change the composition of ink solvents and research more innovative inks to reduce environmental and human pollution. The environmental protection initiatives of the printing industry are also moving forward with social responsibility and the promotion of ISO14001.
Let's take a look at the development of the following inks.
1 Development Trends of Offset Printing Inks There has been a long history of the use of offset printing inks. Recently, soybean oil inks have become popular in the industry due to the limitations of volatile organic emissions and their environmental suitability. Soybean oil inks are gradually replacing mineral oils that have been centered around condensing rotary offset color inks. Because soybean oil ink does not contain volatile organic compounds that pollute the atmosphere, it is odorless and non-toxic. Affected by the upsurge of environmental protection, it has revealed the potential of latecomers in printing, color printing, and other uses.
The advantage of making inks from soybean oil is because the transparency of soybean oil is high. Its color is superior to petroleum ink, which is very beneficial to newspaper colorization. Another feature of the soybean oil ink is that it has very little ink loss and is excellent in color rendering. The same amount of soybean oil ink can be printed 10% to 15% more than the conventional ink. At present, the popularization of soybean oil inks is fast, with Europe taking the lead, followed by Japan and South Korea, and 90% of U.S. newspapers are using soybean oil ink. However, soybean oil itself is a semi-dry oil, which has the disadvantage of being hard to dry. Printers only add additives if they want to speed up the drying process. Although this can make the ink dry faster, the stability of the ink will be reduced, making it easier. Affect the final quality of the print. Some companies use flaxseed oil, which is also a natural raw material. However, it is a dry oil that dries faster than soybean oil, and has a smooth and stable printing performance. The effect is better than that of soybean oil. In addition, ink manufacturers in Japan almost all began to use the ink solvent to remove the aromatic (less than 1%) AF solvent.
Offset printing ink is one of the raw materials for offset printing, and the development goal in the future is toward the development of multicolor, high speed, quick drying, no pollution, and low consumption development. In the world-wide wave of environmental protection, the development of web offset inks is to consider how to handle the recovery of volatile organic compounds (VOC), polycyclic aromatic solvents (PCA), heavy metals, and industrial wastes (such as recycled paper) in the future. Environmental issues such as burning and dioxins have become important research topics.
The advent of high-speed, multi-color, low-pollution, and high-efficiency printing equipment has prompted printers to continue to make new demands on ink manufacturers. According to statistics, in the ink production of more developed countries, offset printing ink products mainly include offset bright fast drying ink, non-heat solid offset rotary printing ink, press rotation ink, etc., followed by ultraviolet drying ink and infrared drying ink. Synthetic paper offset printing ink, iron printing ink, anhydrous printing ink and various special inks for offset printing.
2 Non-horizontal printing inks Without horizontal printing, after more than 20 years of development, it has now entered the third generation. It has been popularized in Europe and the United States, and has been introduced in China. Since it does not pollute the environment and has no pollution, it is highly valued by the industry. Just because of the need for special plates and special inks, it has only been delayed.
In the two problems of plate and ink, it is difficult to do with ink. In terms of the required quality of the ink, it is necessary to have anti-dirt properties, and for this reason, the solvent incorporated into the ink is the key. It is preferable to use an aromatic hydrocarbon-free solvent. In order to meet the requirements of high speed, low viscosity and high fluidity inks have to be developed. For this purpose, the resin molecules in the ink are complexed with one another. Increases cohesion, causes viscosity to decrease, and becomes low viscosity. In addition, improving the ink transferability is also very important, but it and the anti-dirt properties belong to the relationship between the two can not be balanced, how to make it balance, is the key to this ink design.
3 Development trend of water-based inks Since environmental-friendly water-based inks do not contain volatile organic solvents, they can not only reduce the residual toxicity of the print surface, make cleaning of printing equipment convenient, but also reduce the risk of fire and hidden dangers caused by static electricity and flammable solvents. Therefore, water-based ink is called a new type of "green" printing material. At present, the main application areas are flexographic printing and gravure printing, and most of the products of these two printing methods are packaging products, of which food packaging, tobacco and wine packaging, and children's toy packaging account for a considerable proportion. In the world's appeal for environmental protection, pollution-free, non-toxic and pollution-free ink and wash are getting more and more attention. In the United States, 95% of flexographic prints use ink and 80% of gravure prints use ink.
In recent years, China has also introduced many narrow-width flexographic printing production lines, and some of the equipment has been designated for printing with water and ink. In addition, some printing companies received printing orders for foreign packaging bags and other products, and they also specified that they should use water and ink for printing. There are also a few printing plants that use solvent-based inks to print and have been involved in fires. They are also deeply affected and they also want to search for non-flammable and non-explosive water-based inks. More printers want to influence and nurture users in the fields of food, beverages, medicine, daily chemicals, culture, and so on. They are also looking for non-toxic and harmless water-based inks.
However, water-based inks have the disadvantages of non-alkaline resistance, non-ethanol resistance, non-water resistance, slow drying, poor gloss, and easy to cause paper shrinkage. To overcome these disadvantages, some use flexographic UV inks, which not only increase printing The process has also increased the printing cost, and some have used high-priced imported high-grade water-based inks, which also increases the printing cost. All these have caused China's flexographic printing to be restricted, which has restricted the development of China's packaging and printing industry.
The good news is that our country has successfully developed environmentally-friendly high-precision water-based ink products that are non-toxic, non-irritating, non-corrosive, non-flammable, non-explosive, and use-safe. The product can be directly diluted with tap water or ethanol during use. It does not harm the environment and the human body. After printing, the dried product not only has no harmful residual substances, but is insoluble in water, ethanol and alkaline substances, and can completely replace the high-grade imported water. Ink has played an active role in promoting the domestic production of flexible printing in China.
At present, environmentally friendly offset printing inks are also increasingly drawing attention from print users at home and abroad.
3. Fountain solution Currently used on the offset printing press is the alcohol dampening system. Isopropyl alcohol (industrial alcohol, IPA) is one of the dampening solution additives. Compared to the traditional moist version, this kind of dampening
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