Application of Carbon Black Pigment in Synthetic Leather
The coloring of synthetic leather is generally divided into two types: dye coloring and pigment coloring.
The disadvantage of dye coloring is poor heat resistance and prone to color shifting (transfer or bleeding of dye in the surface layer).
The pigment is insoluble in the solvent, and it exists in the resin as dispersed particles. Compared with dyes, pigments have better color shift resistance, better heat resistance and light resistance.
Carbon black pigment is used for the coloring of black synthetic leather, and also for the coloring of brown or gray synthetic leather.
Generally, carbon black with a particle size of 10-50nm is used. The amount of carbon black in the resin is generally 2%-7%. If the amount added is too small, the coloring effect will not be good, and if it is too much, the mechanical properties of synthetic leather will be reduced.
When preparing black synthetic leather, in addition to the surface layer, the base should also be colored with carbon black pigment in order to obtain the desired blackness.
The initial coloring of synthetic leather is to mix pigments and plasticizers into a coloring masterbatch, and then mix it with resin. Due to the poor dispersion of carbon black in this method, the coloring effect is not good.
The current method is to add a wetting agent to carbon black pigment and resin, knead to form a colored resin coated with resin on the surface of carbon black particles, then add a solvent to dissolve the colored resin to make a good dispersion of Pigment carbon black, and then coat it on the base layer on the method.
For example, the coloring method of black polyurethane synthetic leather is to put 55 parts by volume of polyurethane, 45 parts by volume of carbon black pigment, 8 parts by volume of propanol, and 8 parts by volume of methyl isobutyl ketone in a rolling mixer and the rolling surface temperature is 100 Mix at ℃±7℃.
During the mixing process, the wetting agent gradually volatilizes, then cools and pulverizes into colored resin. The above-mentioned colored resin was dissolved with a mixed solvent of tetrahydrofuran and cyclohexanone at a ratio of 10: 1 to prepare a solution with a resin content of 20% by volume. Then, apply this solution on the base layer made of non-woven fibers with a thickness of 1.0mm. After passing through a water bath, the polyurethane is solidified into a fine porous body, and then dried with hot air at 120°C for 10 minutes. The black synthetic leather made by this method has good color tone and air permeability.