One machine and its ink analysis (2)

Third, the ink production process

1, the flow chart

2. The key to oil phase processing is the dispersion and grinding of pigments. The pigment pores are filled with air and a very small amount of water. When the pigments are stirred in the binder, the binders enter the capillary pores from different directions and begin to wet and wrap the pigment particles, so the air begins to self-system at the same time. It is squeezed out, which is the initial wetting process. The mechanical power of the sand mill overcomes the cohesion of the pigment aggregates, allowing the pigment particles to be crushed into fine particles as much as possible and wetted and wrapped to complete the pigment particle-air phase to pigment particle-linkage process. The fineness of the oil phase is less than 10 μs. The general grinding machine is difficult to achieve. The equipment requirements are very strict. Because of the different structure and surface properties of various pigment particles, there is a very significant difference in the affinity of each component. This difference will cause the dispersed and various pigment particles to slowly and agglomerate, and settling occurs (oil phase The dispersant is effectively slowing the progress of the process.) However, this kind of aggregation system is loose and unstable. Under external forces and effects, it returns to its original dispersion effect. Therefore, after the completion of the oil phase processing, it should not be long stay. It is necessary to continue the next step as soon as possible.

3, water phase processing water phase production is very simple, confirm that all the components can be dissolved completely. The water phase should not be left for long. It should be used as soon as possible.

4. The principle and process of emulsification and emulsification are more complicated. The emulsion must have the following components: water, emulsifiers, initiators, and monomers. From the structural point of view, all the emulsifier molecules are composed of a polar hydrophilic group and a non-polar lipophilic group. The hydrophilic group extends the molecule to the aqueous phase, while the lipophilic group leaves the molecule. The aqueous phase extends to the oil phase. The selected emulsifier must be able to form micelles, dissolve monomers, and stabilize emulsion properties. In addition, it depends on the desired properties of the final product - molecular weight, mechanical and freeze-thaw stability, water sensitivity, corrosion resistance, gloss, and the like. The emulsification process is simply divided into three steps: the emulsion particle generation process; the emulsion particle growth process; and the emulsion particle reaction completion process. Throughout the process, emulsifiers play a decisive role and are one of the most critical components of the ink. After emulsification is complete, the emulsion particles can reach a particle size of 0.1 um. The emulsification process generates a large amount of heat. On the one hand, the process needs a certain temperature. On the other hand, it must be controlled at a certain temperature. If the temperature is too high, the chemical properties of the components of the ink system will produce qualitative changes, affecting the overall quality of the ink. . Under the action of high shear force, a large amount of bubbles are generated in the system, so the emulsification reaction process should be performed in a vacuum environment.

IV. Technical indicators of ink quality

The inspection index of the ink is viscosity, fineness, concentration, fluidity, environmental protection, drying, stability, fluidity, number of printed sheets, and print fastness. Among them, viscosity is the most important indicator.

(1) Viscosity Viscosity is a property of a fluid that resists flow. It is a measure of the relative motion of interfering molecules that occurs when fluid molecules attract one another, that is, the internal resistance of an object's flow. Test principle: The relationship between the flow resistance of the ink and the speed and gradient of the ink is measured with a rotational viscometer. Show it with PaS. Its level directly affects the quality of printed products. If it is too low, it will cause the printed products to be light in color and the dots will expand. The edges will be prone to defects such as burrs and inaccuracies. High, resulting in poor ink transfer, uneven ink, at the same time easy to paste and poor printability and other ills. The factors that affect the viscosity are temperature, thixotropy of ink and PH value. The viscosity can be measured with a rotational viscometer (eg NDJ-79) (different instruments can be used, the values ​​measured by different instruments are different). Ideal ink, Depot ink viscosity is generally in the 80000 ~ 10000CP (20 °C) or so; Ricoh / Gestetner ink viscosity is basically 50,000 ~ 70,000 CP (20 °C) or so, and good fluidity.

(2) Fineness is the degree of fineness and dispersion of the ink. Test principle: Determined by a scraper fineness meter, observe its particle concentration point, in micrometers. In general, the smaller the fineness is, the better the dispersibility of the colorant is, and the higher the degree of blackness and gloss is. The finer the fineness is, the lighter the color of the printed product is, and the coarser it is, which can easily cause blockage and blockage. At the same time reduce the life of the uniform ink roller.

(3) Fluidity The size of the ink is used to indicate the degree of thickness of the ink and is the inverse of the viscosity. Inspection principle: A certain volume of ink sample can be expanded to a cylinder diameter in a certain time under the specified pressure and shown in millimeters.

(4) Permeation Drying Speed: The ability of the ink to penetrate and dry on paper. Principle of inspection: At a certain time, the ink is scraped on the newsprint paper and the air news paper is rubbed under a certain pressure until the time when the empty newsprint is no longer dyed by friction. There are two kinds of initial drying and thorough drying. Drying refers to the drying time of the ink on the machine roller and the substrate. The drying mode of the ink in the integrated machine is penetration and absorption. Once the ink film is thoroughly dried, it becomes water. Reconstituted again. The ink of the general machine is slow and dry at the beginning of drying, and such ink is preferably used. That is, the ink does not dry on the printing plate and the ink roller, and is quickly dried on the printing substrate. This contradiction is handled well and balances the relationship between the two. This involves the professional skills of the formulator. Drying too quickly, the ink is easy to block version, dirty version, the edges of the printed product prone to burrs, the level of overprinting easy to appear when throwing dots, making overprinting is not allowed, the pattern level fuzzy and other ills. If it is too slow, the paper is apt to change, the printed matter is easy to be dirty, the printed materials are blurred, and adhesion is prone to occur. Quick-drying, number of prints, and print fastness are judged by trial printing one or several inks on a printer, usually according to the standard test version carried by the printer itself. Printed parts require clear and unclear handwriting. The back is not dirty, and the writing cannot be erased. The number of printed sheets is close to the original ink.

(5) Permeability After the ink sample is at a certain pressure and for a certain period of time, it is shown based on the change of the scratching of the ink and the number of penetrating dye filter papers. (6) Stability The ink was subjected to freezing and heating tests for a certain period of time to observe whether the ink had a gelation condition and an anti-roughening phenomenon. The stability was judged by the cold and heat experiments and the drop of ink on the paper. The ink was alternately placed in a hot and cold environment of -20-60°C, and then the viscosity of the ink was measured at room temperature to see if the water was out, whether it was thinning, whether it was softened or not. Whether or not to slag. Pick a little ink on copy paper or stencil paper. The shape is pagoda shape. After a certain period of time, observe the penetration of the oil ring, whether the oil ring is colored, the size of the oil ring is moderate, and whether the ink cracks, slag, surface knots Skin hardening, darkening, dark and other undesirable phenomena. The good quality ink basically sees only one oil ring, and the rest remains as it was.

(7) Bleeding After the ink has been placed on the filter paper for a certain period of time, it is observed whether or not the filter paper absorbs the bleeding oil from the oil ring, so as to check the bleeding condition of the ink.

(8) The concentration is the darkness and saturation of the ink color. The DFH-80 photoelectric meter was used to measure the ratio of absorbed and reflected light measured on the test surface under constant light irradiation to express the ink concentration.

(9) Drying Exposure was placed in an incubator at 80°C for three weeks to observe the presence or absence of drying.

(10) Number of prints The ability of a certain amount of ink to print in the standard text version.

(11) Printing fastness The ability to resist rubber bands after 24 hours of printing.

Fifth, ink quality identification method

(1) The naked eye: no crater, smooth and shiny, fine ink, uniform color, good gloss.
(2) smell smell: odorless or slightly scented.
(3) Combustion: Dip a small amount of ink on the copy paper and ignite. Observe that the flame is stable, and there is no sound or spatter.
(4) Viscosity denaturation: appropriate viscosity, the change of viscosity of the ink with temperature is small.
(5) Fineness: 8um or less.
(6) Oil ring: transparent, without any color.
(7) Concentration: High, soft color.
(8) Drying mechanism: The machine is not dry, moisturizing; dry fast after printing. Can be printed on both sides instantly without back sticking.
(9) Stability: No separation of oil and water and no water at high and low temperatures. Long shelf life.
(10) Printing: The text lines are delicate and clear, without diffusion; the image has a good sense of layering;
(11) Environmental protection: Neutral or near neutral, will not corrode rollers; No aromatic solvents.

Sixth, summary

The ink of the all-in-one requires outer thick inner pine, the ink surface looks thick, the ink does not flow in the printing cylinder, does not leak, does not overflow the ink, does not throw the ink. The interior of the ink is loose, and the ink is easily suctioned from the packaging container. The ink is evenly coated on the roller, and is easy to pass through the wax paper plate, and the printed writing is clear. Domestic inks are very close to the original ink quality, and some of the properties even exceed the original ink. The common problem of domestic ink is: the quality is unstable, the raw materials may be very good, the next batch is not necessarily very good, and the use of inexpensive raw materials. On the one hand, this is caused by the relatively low industrial base of domestic raw material producers. Domestic companies are most eager to reduce the cost of raw materials; on the other hand, domestic ink manufacturers have reduced costs and pursued high profits. At present, the quality of imported inks on the market is stable and the prices are high; domestic brands of ink are everywhere, shoddy, prices are different, quality is uneven, good or bad is poor, and stability is poor. With the exchange of information and the development of the logistics industry, the ink market for all-in-one printers will be transparent. As a manufacturer, reasonable prices and stable quality are the prerequisites for survival and development.

Author/Mou Zhishan