Preparation And Study Of Carbon Black Dispersion For Gel Ink

Gel ink is one of ink that its apparent viscosity between oil ink and aqueous ink. It has bothlubrication of oil ink and fluency of aqueous Ink. Compared with dye ink, gel ink has manyexcellent properties, such as light permanency, waterproof, temperature-resistance, chemicalstability, writing convergence, permanent preservation and able meet the requirements of archivalrecords. China as a major country of gel pen producer and consumer, its output of gel pen accountmore than80percent of the world. Carbon black as a colorant in the ink, its dispersion stability inthe system is an important factor determining the performance of the ink. Carbon black can’tself-disperse in the water, easy to become gel, and extremely unstable in the production andstorage, due to the small primary particle size, large specific surface area, there is a strong forcebetween particles. At present, many domestic and foreign companies have developed aqueouscarbon black paste, but there are few suitable for gel ink. Even if universal paste also have someproblem. First, though the stability is good, but viscosity is too high, and the particle size can notmeet the requirements of gel ink; Second, smaller particle size paste, solid content is low; What’smore, the compatibility of paste is not well, which will break stability of system in the followingproducing process of ink.Firstly, a number of studies on improvement of the dispersion of carbon black in the waterincluding the dispersant dispersion, carbon black surface grafting dispersion and carbon blacksurface oxide modified were summarized in this paper. Carbon black surface grafting dispersionand carbon black surface oxide modified can get stable product because it modified from pigmentsurface. However, they are not suitable for gel ink paste preparation because of the complicatedpreparation process and high production costs. The method of dispersant dispersion is widely usedbecause of its low cost, simple processing and easy quality controlling of products.Secondly, considering the aspects of carbon black pigment’s physical and chemical properties,dispersant structure and grinding dispersion process, carbon black gel ink paste with the particlesize distribution (D50) in100~120nm, pigment content of30%and viscosity of350mpa.s was prepared. The research includes the following aspects:1) Three types of carbon black with different physical and chemical properties (FW200,Printex U, MA-100) were used as research subjects. By studying the wettability, viscosity andparticle size distribution, the results show that the carbon black MA-100is the most suitablepigment for producing gel ink pigment paste.2) Starting from the structure of the dispersant, three representative dispersants (smallmolecule anionic NNO, nonionic polymers PVP, polymer anionic SMA-NH4) were chosen bymeasuring the ζ potential, sedimentation rate and rheological properties of Carbon Black MA-100under different conditions. The impact of the structure of the dispersant on carbon black dispersionstability was studied. Results showed that the best performance of paste is at pH value of8and theSMA-NH4amount of4%.3) Starting from grinding mode, different grinding mode (basket grinder, high pressurehomogenizer, pin mill) and process parameters were chosen to explore the best preparationprocess of gel ink with carbon black paste. Results show that the combined process mode ofhigh-speed basket grinder-high pressure homogenizer-pin mill is the most effective. The pastewith particle size distribution (D50) of100~120nm can be gained at the following processparameters of pin mill: the size of zirconia bead stabilized with yttrium oxide is0.5mm, the speedof sand mill is1500rpm, the filling ratio is70%, grinding time is1h.Finally, gel ink was prepared from the carbon black paste and then was filled into gel pen.The gel pen was stored under normal temperature(25℃), high temperature(60℃) and lowtemperature(-20℃) for2month and was tested its writing performance regularly. The gel inkprepared with SMA-NH4showed good storage stability and writing properties.