I. Use of pigment:
Our products can be directly used to prepare printing inks (screen printing, offset printing, gravure printing and flexography), coatings and for injection/extrusion. Second, the choice of solvent:
Temperature-sensitive color-changing powder has good tolerance to gasoline, kerosene, mineral oil, benzene, toluene, xylene, cyclohexanone, benzyl alcohol, turpentine, DBP/DOP plasticizer and aqueous solution with PH=2-7.5, and its color-changing performance will not be affected basically after soaking for 2 months at room temperature. When butyl acetate is used as solvent, its storage life is shorter than that of the above solvents. Low-boiling solvents such as methanol, ethanol, acetone, propanol, isopropanol, DMF, butanone, butanol and ethyl acetate will affect the color-changing performance of the pigment and reduce its color concentration within a few days (solvents above C6 have little effect on the pigment). Therefore, the following measures should be taken in ink mixing and printing:
(1) Use alcohol solvents as little as possible or not, and replace them with other solvents. For example, cyclohexanone can be used instead of butanol. (2) When solvent such as propanol must be used for ink mixing, the ink should be prepared as needed to avoid storage.
Because the temperature-sensitive color-changing powder is easily dispersed in the resin solution, all the ink sets except the temperature-sensitive color-changing powder can be well distributed. Before printing, a specified amount of temperature-sensitive color-changing powder can be added, and then it can be added into Mo Dou to start printing. It is also possible to prepare inks (including color-changing pigments) other than propanol, isopropanol, butanol, etc., add a specified amount of the above solvent just before use, and start printing after stirring evenly. Be careful not to mix too much ink at a time, and do not store it as you use it.
Third, ink mixing process:
Thermochromic powder is a kind of microencapsulated pigment with spherical particles, and its particle diameter is 3~9 microns. The finer the pigment particles, the better the gloss of the prepared ink or coating. On the other hand, the finer the particles are, the higher their surface energy is, and it is easy for multiple pigment particles to gather together. Therefore, it is very important to try to eliminate particle aggregation in the preparation process and make the pigment form a single particle dispersion state in ink or coating.
(1) Agitator:
A toothed disc agitator with strong shearing ability should be used. The diameter of the toothed plate is about 1/3 of the diameter of the ink mixing barrel, and the height of the tooth is 1/10 of the diameter of the toothed plate, and it is bent upward and downward by 30 degrees in turn. The tooth surface must be rounded to eliminate acute angles. The stirring speed should be appropriate. Too low, it is difficult to achieve single particle dispersion; If it is too high, the material will be heated and the surface protective layer of microcapsule pigment will be destroyed, resulting in the loss of color change performance. For example, when the diameter of the toothed disc is 100mm, the stirring speed is 800-1300rpm and the stirring time is 5-15min.
(2) modulation process:
First, mix the solvent with the resin (if the viscosity of the resin is high, half of the resin can be added first), then slowly add the temperature-change pigment while stirring, and then continuously stir for 5-15 minutes, and finally add the remaining resin or other components and stir evenly. If the prepared ink is scraped and pressed through a 250-mesh screen with a rubber plate, the aggregation of pigment particles can be completely eliminated and the ink body can be more uniform.
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