Packaging printing ink is ultimately a storage stability. The ink storage stability is in turn the result of the interaction between the components. For example, the polarity of the solvent is different, and the adsorption on the pigment surface of the active agent is also different. The order of the adsorption amount of octadecylamine in each component solvent is: toluene>dichloroethane>mixing Solvents. Most scientists in the scientific community believe that various solvents only affect physisorption without affecting chemisorption. At the same time, they believe that the competitive adsorption of binders and active agents on the surface of pigments has been proved to be correct. This shows that the competitive adsorption depends on the size of the binder, the active agent and the color, and the surface affinity of the filler. If the pigment or filler is hydrophilic, the more polar substance is selected for adsorption in the non-polar solvent. If it is hydrophobic, in the polar solvent, the more hydrophobic substance is selected for adsorption.
The physical adsorption of the surfactant does not affect the chemical adsorption of the polymer, because the physical adsorption of the surfactant on the surface of the pigment and the filler is not strong, and the solvent is easily extruded by the resin from the surface of the pigment. The chemisorption surfactant formed on the surface of the pigmented filler cannot be extruded from the pigment filler surface by the resin polymer. The greater the adsorption saturation of the surfactant in performance, the greater the resistance to polymer adsorption. On the other hand, if the disperse grinding time during ink production is slightly shorter, the ink will not be easily expelled from the pigment surface by the resin in the solvent during the manufacturing process or the ink storage, but other phenomena may still occur. , to be practiced.
The ultra-fine active calcium and alkyd resins in polar solvents can be adsorbed on the surface of iron blue and yellow chromium. This is because the pigment has two active centers on the surface, so it is slightly acidic active calcium and alkyd. The resin can still be adsorbed on the surface, but its hiding rate is low, so it also causes poor wetting and dispersing. When dispersed to 7.5 MM, the surface will have a floating color; when dispersed to 1 to 2 MM, it will disappear. Now. If a thinner is added during the printing process, the floating color reappears again. Must choose the appropriate dispersant, adding wetting dispersant not only can reduce the grinding time of the pigment and filler, but also can save energy without improving work efficiency.
In order to prevent the floating color of the ink, the wetting and dispersing agent is introduced into the packaging printing ink system. Its purpose is to:
(1) increase the gloss of the ink film, improve the leveling of the ink film, can greatly improve the fineness of the pigment packing, ensure the storage stability of the ink, prevent the generation of large flocculate particles, and improve the flatness of the printing ink film;
(2) Reduce the viscosity of the ink and improve the fluidity of the ink. Under the same conditions, the concentration of the pigment filler can be greatly increased, and its filling property can be increased to reduce the material cost;
(3) Improve the storage stability of packaging printing inks. The storage stability of packaging printing inks depends entirely on the dispersion quality of the pigments, poor dispersion and precipitation, resulting in a decrease in floating color, hair growth, coloring power, and secondary rheological changes, due to the resin (base) and solvent The proportion of resin dispersion is also closely related. When the resin can not achieve a good wetting and dispersing effect, it can only be assisted by the wetting dispersant. If used properly, all wetting and dispersing agents have this function. Such as domestically produced P-104S, lecithin, CP-88, TC series products, especially with coupling bridge TM-27, TM-200S and other pseudoplastic fluid packaging printing ink is very effective, the general amount of 0.13%;
(4) Improve the coloring power and hiding power of pigments. It is known that the degree of light scattering and the hiding power of pigments tend to have a maximum value with the change of the particle size, and it is preferable that the viscosity of the pigment is small in the printing ink. The simplest way to determine is:
A, take 0.1 grams of ink drops in the scraper fineness meter slot, holding the scraper 90 degrees, scraping from top to bottom quickly, if the ink is interrupted or interrupted, it proves that the coloring power reaches less than 100%, which means that the ink is suitable for printing Poor or poor, the printing on the machine is not the tail of printing and graphic arts, it is easy to appear patchy and so on.
B, take 0.1 grams of ink droplets on the 65 × 195MM blueprint base paper above, holding the blade 25 degrees, quickly scraped from top to bottom (as soon as possible), if the sun surface pattern paint pigment saturation is not achieved, then prove it The coloring power fails to meet the printing requirements, that is, the printability is poor, and it is easy to float the color;
(5) It can prevent floating color, sagging and sinking effects. The use of a controlled flocculating wetting and dispersing agent can prevent the floating color, hair growth, and stability of the multi-color or inter-color ink;
(6) Improve the physical properties of the ink film. After more than 10 years of practice, the best pigment dispersion can increase the absorption and reflection ability of the ultraviolet ray, increase the weatherability and chemical resistance of the pigment, thus improving the physicochemical properties of the ink film;
(7) Change the rheology of packaging printing inks. Practice has shown that the use of different wetting and dispersing agents can sometimes result in packaging printing inks with similar low-viscosity dispersions to Newtonian fluids. The pigment particles can be dispersed close to the primary particle state (thinning the thickness of the printing ink film). A stable and ideal dispersion system. For example, in the ink where the high pigment ratio is higher than that of the ink and the easy to form the thixotropic structure, the viscosity is lowered, the flow is improved, and the leveling property with high gloss is ensured, but some wetting and dispersing agents make the dispersion system have pseudoplastic viscosity. And thixotropic viscosity, the ink system formed a structural viscosity, the ink system will be in a stable state, this anti-precipitation, anti-sag, anti-floating color hair flower is due to the control of the flocculation effect of dispersant pigment packing to be stable;
(8) Save time and energy. The addition of a wetting and dispersing agent to reduce the grinding time of the pigment filler also saves energy and greatly increases the productivity of the work.
Contrary to the eight effects already mentioned, if used improperly, the resin binder will penetrate the paper (even through the back), leaving the pigment alone on the surface and losing the gloss of the ink film.
In the molecule, the size of the anionic and cationic organic groups is basically the same as an electrically neutral surfactant, which not only has good miscibility with all solvent-based printing ink systems, but also has no side-effect wetting and dispersing agent. In addition, there is also an ultradispersed polymeric dispersant (a part of which is a polymer chain with a strong affinity for the solvent, and one part is an anchor group having a strong affinity with the surface of the particles, that is, an anchor group and a particle surface in the dispersion. Polymerization, like an iron anchor, is firmly attached to the surface of the particles, and the dispersed portion thereof is stretched in a solvent to form an anchor adsorption layer.
Although the wetting and dispersing agent can form a thick adsorption layer and generate external force to make the pigment dispersion system in a stable state, there are also individual particles that can cause co-flocculation between the pigment particles and prevent the over-flocculation of a single pigment, thereby preventing the floating color from blooming. effect. According to the experience of Hangzhou Yuhang Dibang Fine Chemical Factory and Yangzhou City Zhonglida Ink Co., Ltd., the author tried to remedy the printing process, and the dosage should be increased by 10 times or more.
In addition to the above-described wetting and dispersing agents that enable the pigments to be controlled in a stable state of dispersion or dispersion, the following emphasis is placed on the effect of leveling agents on repelling floating flowers.
According to Nabed's eddy current theory, the purpose of adding a leveling agent is to reduce the surface tension of the ink, prevent the smoky flow of the packaging printing ink, and make the surface smooth and flat to achieve a uniform color.
Among the additives for many leveling agents, silicone oils, silicone resins, acrylic copolymers, and the like are generally used. We have known in practice that silicone oil can not solve the problem of flowering of pigments. It can only change the hair color into floating color to form a uniform hue and a uniform hue surface. It can not solve the separation and flocculation of pigments.
Silicone oil and organic matter in the printing ink are not miscible at the interface between the air and the ink film, so that the surface tension is decreased, the surface is expanded, a monolayer is formed, the radius of curvature becomes large, and it can be expanded to the entire surface, so it can be formed better. The smooth surface condition prevents eddy currents - the ink film surface forms a smooth mirror-like ink layer.
The role of polyacrylate leveling agents is roughly the same as for silicones, but the active groups, thermal stability, and amounts of silicone polymers should be noted. Some will cause reprintability obstacles, and secondly, excessive use often results in poor compatibility with the resin in the ink system, resulting in dry skin and shrinkage defects.
The three thixotropic tackifiers in the ink system also make the packaging printing ink structurally viscous, improving the rheology of the printing ink. The increase in the viscosity of the ink tends to decrease the settling rate of the pigment in the system and prevent the separation of the pigment, thereby achieving the purpose of eliminating floating color and hair growth. However, this kind of additives can not be used for all packaging printing inks. For example, it is not appropriate to use a pump to recycle ink, especially printing ink products, because the addition of a thickener will directly affect the leveling of the ink after printing. The dosage should be determined after trial printing (or using color wheel before printing), otherwise it will cause ink flocculation.
Thickeners and thixotropic agents are widely used in packaging printing inks because such additives can cause the ink system to produce a structural viscosity that changes the rheology of the ink and controls the movement of the pigment.
In addition, the surface of the pigment filler is pre-stressed or modified in advance, which is also a common method for preventing floating of flowers, and the amount thereof is small.
Third, concluding remarks Do not worry about and complain that China's packaging and printing of science and technology can not reach or exceed the quality of international packaging and printing, the only key is that China's packaging and printing industry must have a high degree of interest in science and technology. As long as we can accumulate knowledge in practice, we will surely walk ahead of the international industry; as long as we can communicate regularly in process technology, our scientific packaging and printing theory will certainly continue to innovate; as long as all of our colleagues can be courageous "Wolf" dance, we will be able to dominate the market economy competition!
The physical adsorption of the surfactant does not affect the chemical adsorption of the polymer, because the physical adsorption of the surfactant on the surface of the pigment and the filler is not strong, and the solvent is easily extruded by the resin from the surface of the pigment. The chemisorption surfactant formed on the surface of the pigmented filler cannot be extruded from the pigment filler surface by the resin polymer. The greater the adsorption saturation of the surfactant in performance, the greater the resistance to polymer adsorption. On the other hand, if the disperse grinding time during ink production is slightly shorter, the ink will not be easily expelled from the pigment surface by the resin in the solvent during the manufacturing process or the ink storage, but other phenomena may still occur. , to be practiced.
The ultra-fine active calcium and alkyd resins in polar solvents can be adsorbed on the surface of iron blue and yellow chromium. This is because the pigment has two active centers on the surface, so it is slightly acidic active calcium and alkyd. The resin can still be adsorbed on the surface, but its hiding rate is low, so it also causes poor wetting and dispersing. When dispersed to 7.5 MM, the surface will have a floating color; when dispersed to 1 to 2 MM, it will disappear. Now. If a thinner is added during the printing process, the floating color reappears again. Must choose the appropriate dispersant, adding wetting dispersant not only can reduce the grinding time of the pigment and filler, but also can save energy without improving work efficiency.
In order to prevent the floating color of the ink, the wetting and dispersing agent is introduced into the packaging printing ink system. Its purpose is to:
(1) increase the gloss of the ink film, improve the leveling of the ink film, can greatly improve the fineness of the pigment packing, ensure the storage stability of the ink, prevent the generation of large flocculate particles, and improve the flatness of the printing ink film;
(2) Reduce the viscosity of the ink and improve the fluidity of the ink. Under the same conditions, the concentration of the pigment filler can be greatly increased, and its filling property can be increased to reduce the material cost;
(3) Improve the storage stability of packaging printing inks. The storage stability of packaging printing inks depends entirely on the dispersion quality of the pigments, poor dispersion and precipitation, resulting in a decrease in floating color, hair growth, coloring power, and secondary rheological changes, due to the resin (base) and solvent The proportion of resin dispersion is also closely related. When the resin can not achieve a good wetting and dispersing effect, it can only be assisted by the wetting dispersant. If used properly, all wetting and dispersing agents have this function. Such as domestically produced P-104S, lecithin, CP-88, TC series products, especially with coupling bridge TM-27, TM-200S and other pseudoplastic fluid packaging printing ink is very effective, the general amount of 0.13%;
(4) Improve the coloring power and hiding power of pigments. It is known that the degree of light scattering and the hiding power of pigments tend to have a maximum value with the change of the particle size, and it is preferable that the viscosity of the pigment is small in the printing ink. The simplest way to determine is:
A, take 0.1 grams of ink drops in the scraper fineness meter slot, holding the scraper 90 degrees, scraping from top to bottom quickly, if the ink is interrupted or interrupted, it proves that the coloring power reaches less than 100%, which means that the ink is suitable for printing Poor or poor, the printing on the machine is not the tail of printing and graphic arts, it is easy to appear patchy and so on.
B, take 0.1 grams of ink droplets on the 65 × 195MM blueprint base paper above, holding the blade 25 degrees, quickly scraped from top to bottom (as soon as possible), if the sun surface pattern paint pigment saturation is not achieved, then prove it The coloring power fails to meet the printing requirements, that is, the printability is poor, and it is easy to float the color;
(5) It can prevent floating color, sagging and sinking effects. The use of a controlled flocculating wetting and dispersing agent can prevent the floating color, hair growth, and stability of the multi-color or inter-color ink;
(6) Improve the physical properties of the ink film. After more than 10 years of practice, the best pigment dispersion can increase the absorption and reflection ability of the ultraviolet ray, increase the weatherability and chemical resistance of the pigment, thus improving the physicochemical properties of the ink film;
(7) Change the rheology of packaging printing inks. Practice has shown that the use of different wetting and dispersing agents can sometimes result in packaging printing inks with similar low-viscosity dispersions to Newtonian fluids. The pigment particles can be dispersed close to the primary particle state (thinning the thickness of the printing ink film). A stable and ideal dispersion system. For example, in the ink where the high pigment ratio is higher than that of the ink and the easy to form the thixotropic structure, the viscosity is lowered, the flow is improved, and the leveling property with high gloss is ensured, but some wetting and dispersing agents make the dispersion system have pseudoplastic viscosity. And thixotropic viscosity, the ink system formed a structural viscosity, the ink system will be in a stable state, this anti-precipitation, anti-sag, anti-floating color hair flower is due to the control of the flocculation effect of dispersant pigment packing to be stable;
(8) Save time and energy. The addition of a wetting and dispersing agent to reduce the grinding time of the pigment filler also saves energy and greatly increases the productivity of the work.
Contrary to the eight effects already mentioned, if used improperly, the resin binder will penetrate the paper (even through the back), leaving the pigment alone on the surface and losing the gloss of the ink film.
In the molecule, the size of the anionic and cationic organic groups is basically the same as an electrically neutral surfactant, which not only has good miscibility with all solvent-based printing ink systems, but also has no side-effect wetting and dispersing agent. In addition, there is also an ultradispersed polymeric dispersant (a part of which is a polymer chain with a strong affinity for the solvent, and one part is an anchor group having a strong affinity with the surface of the particles, that is, an anchor group and a particle surface in the dispersion. Polymerization, like an iron anchor, is firmly attached to the surface of the particles, and the dispersed portion thereof is stretched in a solvent to form an anchor adsorption layer.
Although the wetting and dispersing agent can form a thick adsorption layer and generate external force to make the pigment dispersion system in a stable state, there are also individual particles that can cause co-flocculation between the pigment particles and prevent the over-flocculation of a single pigment, thereby preventing the floating color from blooming. effect. According to the experience of Hangzhou Yuhang Dibang Fine Chemical Factory and Yangzhou City Zhonglida Ink Co., Ltd., the author tried to remedy the printing process, and the dosage should be increased by 10 times or more.
In addition to the above-described wetting and dispersing agents that enable the pigments to be controlled in a stable state of dispersion or dispersion, the following emphasis is placed on the effect of leveling agents on repelling floating flowers.
According to Nabed's eddy current theory, the purpose of adding a leveling agent is to reduce the surface tension of the ink, prevent the smoky flow of the packaging printing ink, and make the surface smooth and flat to achieve a uniform color.
Among the additives for many leveling agents, silicone oils, silicone resins, acrylic copolymers, and the like are generally used. We have known in practice that silicone oil can not solve the problem of flowering of pigments. It can only change the hair color into floating color to form a uniform hue and a uniform hue surface. It can not solve the separation and flocculation of pigments.
Silicone oil and organic matter in the printing ink are not miscible at the interface between the air and the ink film, so that the surface tension is decreased, the surface is expanded, a monolayer is formed, the radius of curvature becomes large, and it can be expanded to the entire surface, so it can be formed better. The smooth surface condition prevents eddy currents - the ink film surface forms a smooth mirror-like ink layer.
The role of polyacrylate leveling agents is roughly the same as for silicones, but the active groups, thermal stability, and amounts of silicone polymers should be noted. Some will cause reprintability obstacles, and secondly, excessive use often results in poor compatibility with the resin in the ink system, resulting in dry skin and shrinkage defects.
The three thixotropic tackifiers in the ink system also make the packaging printing ink structurally viscous, improving the rheology of the printing ink. The increase in the viscosity of the ink tends to decrease the settling rate of the pigment in the system and prevent the separation of the pigment, thereby achieving the purpose of eliminating floating color and hair growth. However, this kind of additives can not be used for all packaging printing inks. For example, it is not appropriate to use a pump to recycle ink, especially printing ink products, because the addition of a thickener will directly affect the leveling of the ink after printing. The dosage should be determined after trial printing (or using color wheel before printing), otherwise it will cause ink flocculation.
Thickeners and thixotropic agents are widely used in packaging printing inks because such additives can cause the ink system to produce a structural viscosity that changes the rheology of the ink and controls the movement of the pigment.
In addition, the surface of the pigment filler is pre-stressed or modified in advance, which is also a common method for preventing floating of flowers, and the amount thereof is small.
Third, concluding remarks Do not worry about and complain that China's packaging and printing of science and technology can not reach or exceed the quality of international packaging and printing, the only key is that China's packaging and printing industry must have a high degree of interest in science and technology. As long as we can accumulate knowledge in practice, we will surely walk ahead of the international industry; as long as we can communicate regularly in process technology, our scientific packaging and printing theory will certainly continue to innovate; as long as all of our colleagues can be courageous "Wolf" dance, we will be able to dominate the market economy competition!
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