Study On The Formula Optimization Of Pigmental Gel Ink

Gel ink pen has become the most popular writing instruments in the word with its excellent writing performance. The yield scale of gel ink pen in China stands in the first all over the world, while, the high-end ink that used for filling gel ink pen still rely on foreign imports up to now, and there is a wide gap between the domestic gel ink and foreign advanced level. To realize the localization of gel ink is significant to our country from a big manufacturing nation to powerful nation.In this paper, the advantages of gel ink pen, the definition and development present situation at home and abroad of gel ink and gel ink pen, the composition of gel ink and the involved key technologies were reviewed. It pointed out that to optimize adding amount of the important components in gel ink was of great significance to gel ink research.Orthogonal test method was used to optimize the dosage of dispersant BYK-191, wetting agent 4187 and styrene acrylic resin M101, which were important components in gel ink. It turned out that, the paste with good stability and the pigment particles had minimum size change rate under the condition of room temperature storage, when the adding quantity of dispersant BYK-191, wetting agent 4187 and styrene acrylic resin M 101 reached 3.0 wt.%,3.5 wt.% and6.0 wt.%, respectively. But the optimum combination from the orthogonal test method affected the curing process of the ink and it did not seem conducive to build a good thixotropic system of ink. Therefore, it made little sense to optimize the formula of gel ink with orthogonal test method.The type and dosage of dispersant, resin, wetting agent and lubricant directly affect the dispersion and stability of pigment particles and the construction of thixotropic system in pigment gel ink system. The rheological behavior of pigment slurry with different amount of dispersant BYK-191, and gel ink with different quantities of styrene acrylic resin M 101, wetting agent 4187 and lubricant MOA-3P was investigated. The particle size of pigment, microscopic imaging, CMC (critical micelle concentration) were studied by laser particle analyzer, optical microscope and surface tensiometer. Besides, it was the first time to use rheometer to optimize the gel ink formula. It turned out that not only a well thixotropic system of gel ink but also the ultra-fine dispersion and long-term stability of pigment could be realized when the adding quantity of dispersant BYK-191, styrene acrylic resin M 101, wetting agent 4187 and lubricant MOA-3P reached 2.0 wt.%,4.0 wt.%,2.5 wt.% and 1.0 wt.%, respectively. The influence of thixotropy and stability of gel ink were investigated in a condition of adding individually and its compound with non-associative alkali swell-able emulsion thickener ASE 60 and hydrophobic alkali swell-able emulsion thickener ALCOGUARD 5800. Results indicated that, the gel ink with good liquidity when adding non-associative alkali swell-able emulsion thickener ASE 60 individually, and there was no supernatant and sedimentation after high-speed centrifugal. However, the gel ink had a poor thixotropy with thixotropic index less than 3.0; because of the bad matching performance between hydrophobic alkali swell-able emulsion thickener ALCOGUARD 5800 and gel ink system, the gel ink had clumps and bad liquidity and there was supernatant and sedimentation after high-speed centrifugal. However, it could get larger viscosity with a small amount of thickening agent ALCOGUARD 5800 and the thickening effect was good. Besides, the gel ink had a good thixotropy with thixotropic index more than 4.0; Gel ink with different mixed proportion of thickening agent had good liquidity and there was no supernatant and sedimentation after high-speed centrifugal. And the gel ink had a good thixotropy with thixotropic index greater than 3.0. The thickening agent compounded with 0.4 wt.% ALCOGUARD 5800 and 0.6 wt.% ASE 60 in gel ink, which viscosity was appropriate to satisfy the requirements of writing and fillingThe rheological property of gel ink is closely related to writing performance. The rheological property of gel ink was investigated by Brookfiled rotational rheometer, and the simulation of the rheological curve of gel ink samples with four kinds of constitutive equations of non-newtonian fluid was introduced. The results show that, Hersegel-Bulkley equation could fit rheological curve of gel ink perfectly. Further more, the writing performance of gel ink could be characterized with rheological parameters. Pseudoplasticity, yield value and area of thixotropic loop affected the gel ink writing performance, comprehensively. The gel ink with excellent writing performance had its relatively large yield stress, appropriate strong pseudo-plasticity and moderate area of thixotropic loop.