Performance of ink adjuvants and methods of use thereof
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With the development of technology and technology, oil-based inks have been gradually eliminated, and many new inks have been continuously developed. However, resin-based inks (referring to inks made of resin as the main binder) are still the most used inks in offset printing. Variety. In the process of using ink, it is often necessary to adjust the printing suitability of the ink according to the characteristics of the printing, the working environment and the production process, so it is necessary for the printer to understand the performance of the ink adjuvant. In the following, the author briefly introduces the functions and methods of several ink adjuvants commonly used in the work and some problems that should be paid attention to during use, for reference by peers.
First, the viscosity and fluidity modifiers are many types, the role is to adjust the fluidity and viscosity of the ink, mainly including varnish and debonding agent. Traditional varnishes mainly include seven varieties of oil No. 0 (ie, oil outside the number) to No. 6 oil. The viscosity is the largest with zero oil, and the oil is reduced in turn, but some are not commonly used. Of course, there are other varieties of varnish.
The main introductions are as follows:
1. No. 6 oil It is one of the traditional commonly used ink adjuvants. It is mainly used to increase the fluidity of the ink, and at the same time it can reduce the viscosity of the ink. The dosage of the resin type is generally less than 5%. The addition will reduce the dryness and gloss of the ink. 2. No. 0 varnish (also known as external oil) The most viscous oil in varnish, almost no fluidity, is a transparent elastic fluid with a higher viscosity. It is mainly used to increase the viscosity of the ink, reduce the degree of emulsification, adjust the viscosity of the ink before and after the color set, so that the viscosity of the first printed ink is slightly larger, and the transferability of the ink is improved. The dosage is generally below 5%, so as not to affect the drying property. 3. Resin varnish is more viscous than No. 6 oil and is used to adjust the fluidity of the ink, but it does not affect the viscosity of the ink. The dosage is generally around 3%. The addition of the varnish does not affect the gloss and adhesion fastness of the ink, and has little effect on the dryness. 4. Diluent Viscosity is smaller than that of No. 6 oil, which can increase the fluidity of the ink and lower the viscosity, and has the characteristics of less dosage but obvious effect. The dosage is generally below 3%, and the gloss and dryness of the ink are not substantially affected after the addition. 5. High-boiling kerosene (aviation kerosene) has a boiling point of 250-290 ° C. It is an excellent ink adjuvant. It has good miscibility with ink and can be directly used in inks to reduce the viscosity of the ink and increase the flow to a certain extent. Sex, also has the characteristics of less effect and less effect. The dosage is generally from 1% to 2% to meet the requirements, and of course, it can be increased or decreased as appropriate. It does not affect the gloss and adhesion of the ink after the addition, and has little effect on the drying property. 6 . The detackifier (also known as detackifier) is a paste and is one of the traditional ink adjuvants. It has the effect of reducing the viscosity of the ink but does not substantially increase the fluidity, and can be used together with the resin varnish, the sixth oil, or the like, or can be used alone. The amount is generally less than 5%, and too much is likely to cause dirty plates and reduce the gloss, dryness and adhesion of the ink. Printings that require film coating should be strictly controlled, otherwise it will cause defects such as blistering and poor adhesion. 7. Ink improver (also known as ink additive) is a new type of ink adjuvant. It has very good miscibility with the ink and will not dilute the ink when added to the ink. It can reduce the viscosity of the ink and increase the fluidity. The dosage is usually between 3% and 8%, and can be increased or decreased as appropriate. Under normal circumstances, it will not affect the drying of the ink, but excessive will reduce the gloss and adhesion of the ink.
Second, the drier is used for the adjustment of the drying of the ink. There are two main types: 1. White dry oil is a mixed desiccant that promotes the simultaneous drying of the inner layer and surface of the ink. It can be used alone or in combination with red dry oil. It has strong drying performance and can improve the gloss of the printing to a certain extent. The dosage is preferably 5% or less, and the maximum is not more than 10%. Excessive addition will cause adverse effects such as dry, dirty, dry rubber roller, etc. In case of such failure, the amount of white dry oil (less than 3%) may be reduced as appropriate, and a small amount of red dry oil (about 0.5%) is added. solve. It should be noted that the white dry oil contains heavy metal lead which is harmful to the human body, so it cannot be used for printing printed food packaging and other sanitary requirements. If such a print can be changed to red dry oil or mixed desiccant. 2. The red dry oil has the characteristics of less dosage and obvious effect, which can quickly dry the conjunctiva on the surface of the ink, and can improve the gloss of the printed matter.
Usually used in combination with white dry oil, sometimes it can be used alone. The dosage is generally about 1%, and the excess is easy to produce the phenomenon of “dry rubber roller”. In the case of "dry overprinting" (ie wet-drying printing), the first two colors cannot be used or used as little as possible to avoid crystallization of the ink layer. In addition, although the red dry oil is dark red or purple, it is generally transparent and does not affect the color tone of the ink. Even light inks such as yellow and white are usually used. 3. Mixed Desiccant In addition to the above two desiccants, another new advanced drier is a product recently developed by ink manufacturers and is a mixed desiccant. It has the characteristics of promoting the ink to be comprehensive and quick drying from the inside and the inside of the table, and can improve the gloss of the printing and the adhesion fastness of the ink to a certain extent. Because it does not contain heavy metals that are harmful to the human body, it can be used as an alternative to white dry oil for printing printed products such as food packaging. It can be used alone or in combination with white dry oil if it is not hygienic. When used alone, the dosage is generally controlled below 2%. In addition, the mixed desiccant itself is dark red or purplish red, but since it is transparent and used in a small amount, it generally does not affect the color tone of the ink as with the red dry oil.
3. Dilution agent (dilute ink) Auxiliary agent used to formulate light-colored inks, mainly including white ink and eliminator. 1. White ink is a kind of dilute agent commonly used in blending light-colored inks. The light-colored inks blended with it have good hiding power, and the ink is white and thick and has a strong powdery texture, which has unmatched effects of other thinners. However, because the white ink pigment ratio is large and the particles are coarse, the printability is not ideal, and sometimes the ink transfer and transfer failure are prone to failure, and the adhesion of the ink is relatively low. Prints that require filming sometimes have the drawback of not sticking well. To avoid such failures, use a light varnish or a varnish. For prints that must use white ink as a thinner, it is recommended to choose a better quality white ink, or use both white ink and bright light paste, so as to maintain the unique quality of the white ink, and improve the printing suitability of the ink and improve the ink. The gloss and adhesion of the print. 2 . The lightening agent (also known as the lightening agent) is a transparent thinning agent which has good miscibility with the ink. It is only used to add color to the ink without affecting the color tone of the original ink. The lower grade of the decontaminant has a slightly poorer drying and glossiness, and the desiccant should be added as needed. Higher grades of fumigant have the characteristics of high gloss, good printability and moderate dryness, usually without the use of desiccant. It is generally used alone or in combination with white ink. 3. Brightening paste is an excellent ink thinner. In addition to the same advantages as the lightening agent, it also has higher transparency and gloss, better printability and dryness. In addition to being used as a thinner, it can sometimes be used as a glazing on the surface of a print, which has good gloss but is not high in abrasion resistance.
4. Offset varnish is a type of printing varnish that can be applied directly to the surface of the print using a printing press. It has excellent transparency, gloss and abrasion resistance, water resistance and solvent resistance. It is mainly used for glazing on the surface of printed materials, and sometimes it can also be used as a thinner. The diluted ink has high gloss and abrasion resistance and good printability. However, the varnish will reduce the service life of the ink roller and the blanket, so it should be avoided as a thinner as much as possible, and it is better to use the gloss paste. Offset varnishes are classified into bright and matt types, and should be distinguished when used.
The above is only a part of the ink adjuvant, and there are also anti-drying agents, anti-adhesive agents, anti-friction agents, etc., which will not be repeated here.