Thermochromic Pigment is a kind of microcapsules pigment which the particles are globe, the average particle diameter is 3 to 7 microns.The particles be more fine, the luster of the ink and paint will gloss better.But on the other hand, the more fine particle, the higher surface energy, easy to occur multiple of paint get together.So in the process of making ink,should dispersed the microcapsule uniform in the ink and also to avoid the rupture of the microcapsule.
1 : Blender:
Should use the strong ability of shear tooth disc mixer.
The diameter of the toothed plate should be about a third of the diameter of the ink mixing barrel .The depth is 1/10 of the tooth disc diameter. And take turns bent upward and downward for 30 degrees.Tooth surface must be rounded, eliminate acute the Angle.The stirring speed must be properly when mixing the ink.If too low will be too hard to achieve the single particle dispersion.If too high, will cause the material friction heat and lead to broken the outer wall of microcapsule. and loss the discoloration performance .For example, if the toothed plat diameter is 100 mm, the mixing speed is 600 ~ 900 RPM, stirring time is 5 ~ 15 minutes.
2 : Modulation process:
First addes most of the solvent paint , make the surface of the paint fully wet by solvent.Then stir gently and adding the resin liquid (if the resin is solid, should dissolve it first).After the preliminary well stir, speed up , continuous mixing for 5 ~ 15 minutes.(note: if adding the Thermochromic Pigment directly into the high viscosity resin, will cqause couple of pigments be wrapped by resin package, even adding the solvent to dilution, also be difficult to make the paint form be single particle dispersion).
3. The modulation of offset printing Thermochromic Ink:
The characteristic of the offset printing of reversible Thermochromic pigment is the pigment particles diameter be finer (2 -- 4 microns), the color concentration increase for15-20%. So as to adapt the characteristics of the offset printing process ink layer is thinner. Compared with screen printing and gravure ink, the modulation of thermochromic offset printing ink is difficult, when modulation should pay attention to those point:
A: Thermochromic pigments (AO) the content in the ink should be 22to23%.If the content be too low, the color concentration of the printing products is low. On the contrary if the content is exorbitant, the performance of the ink will be not good, and hard to use.
B: The particles of the offset printing Thermochromic pigment be thinner, the surface energy will be higher, easy to stay in a globle. Wil be difficult to spread evenly. The method of high speed stirring dispersion to modulation intaglio printing, screen printing ink. Because of the offset printing ink viscosity is too high will cause the wall of Thermochromic pigment microcapsules be crack. Suggestions: after preliminary modulation,use three-roll machine to relax the grinding mouth (0.8 1.5 mm), lowspeed rolling, until the ink evenly. Remember: do not clamp grinding mouth and high-speed milling.
C: Need to adding the silica as 2to4% of the Thermochromic pigment into the formula (it required the grain diameter is 4 to 6 microns). Use this hard particles to undertake the pressure in the process of modulation of printing ink and under , to reduce the damage from external force to the Thermochromic pigments microcapsules.
4 :Water-based Thermochromic ink and PH value
Polychromatic Thermochromic pigment can be using to modulation waterbaesd Thermochromic ink.When the range of the PH value of the system is from 3 to 7.5 ,it have no effect to the performance of the Thermochromic pigments.
