Study on the Dispersity of Black Water-based Covering Ink WANG Dandan a, HUANG Beiqing b, WEI Xianfu c, LIU Jianghao d and LIU Shuang e

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1 Applied Mechanics and Materials Online: ISSN: , Vol. 262, pp doi: / Trans Tech Publications, Switzerland Study on the Dispersity of Black Water-based Covering Ink WANG Dandan a, HUANG Beiqing b, WEI Xianfu c, LIU Jianghao d and LIU Shuang e Beijing Institute of Graphic Communication, China a wangdandan8585@163.com, b huangpeiqing@bigc.edu.cn, c weixianfu@bigc.edu.cn, d liujianghao@bigc.edu.cn, e lizy @gmail.com Keywords: Water-based covering ink; Dispersity; Particle size Abstract. Dispersity is one of the most important factors that affect the covering property of ink. In order to obtain the black water-based ink with high covering property, study the dispersity of ink, by changing the variety of both pigments and resins, the ratio of pigment to resin, the variety and the content of dispersants to prepare based ink, by testing the diameter size to explore the factors that affect the dispersion of black water-based covering ink. It has been proved that the interaction between different pigments and resins is the key factor that influences the dispersion property of the black water-based covering ink. The dispersity property of the resin to pigment depends on a great extent on the ratio of pigment to resin. The result also proved that different kind of dispersants and content are also important factors that influence the dispersion property. Introduction The black water-based covering ink is a kind of ink that can protect the information under it from discovered, and has already been widely used in the printing of lottery-attached bills. Since the lottery-attached bills are all have certain or even more value, as a method of anti-counterfeiting, the covering ink s covering property becomes very important. Dispersity is one of the most important factors that affect the covering quality of water-based covering ink, the better dispersity, the better covering quality. In order to achieve the black water-based ink with high covering power, it s necessary to research the dispersity of ink. Experimental Section Materials. Pigments: carbon black M-L, carbon black H8, carbon black C500; Resin: acrylic resin AZR, HPD 96, HPD 96 MEA; Film-forming resin: BASF 2640; Solvent: deionized water; Dispersants:750,760; Defoamers:810. Instruments and Equipments. D2004W electric mixer (Shanghai sile instrument corporation), IGT-2S high speed mechanical stirrer (Shanghai sile instrument corporation), AR2000 rheometer(ta corporation of American), IGT-G1 ink printability Miriam(made in Holland), Microtrac S3500-laser particle size analyzer(made in America), X-528 densimeter(x-rite). Sample Preparation. Based ink preparation: Blend different pigments with resin, deionized water and other promoter, and predispersing 30min in D2004W electric mixer, then grinding 2h in IGT- 2S high speed mechanical stirrer. Based ink thinning: mix the based ink with film-forming resin and deionized water, and then stir 30min in D2004W electric mixer. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania State University, University Park, USA-10/05/16,00:25:50)

2 528 Advances in Printing and Packaging Technologies Performance Test. Dispersity test: Using deionized water as diluent, test 90% particle size with S3500-laser particle size analyzer.viscosity test:using AR2000 -rheometer to test the viscosity of ink,and recording the viscosity when the shear rate is s -1.Covering power test: Proofing with IGT- G1 ink printability miriam when the printing pressure is 75N and the anilox roller pressure is 250N,then test the density which can be used to stand for the covering power of ink. Results and Discussions Influence of Pigment and Resin on the Dispersity of Ink. With different diameter, aggregate state and different surface structure, the dispersity of pigment is also unlike. Besides, the interaction between pigment and resin is an important factor that effect the dispersity too, so it s necessary to research the influence of pigment and resin on the dispersity of ink.fixing the content of pigment and changing the variety of pigment, resin and pigment/resin ratio to prepare ink. Since the viscosity of based ink is too high when the pigment/resin ratio is smaller than 1.5, it s unnecessary to prepare ink, so in this experiment the pigment/resin ratio starts from 1.5. And test the 90% particle size of every ink, the result shows in Fig :1 2:1 2.5:1 3:1 3.5:1 pigment/resin ratio (a) C MEA AZR MEA AZR 1.5:1 2:1 2.5:1 3:1 3.5:1 pigment/resin ratio (b) CABOT M-L MEA AZR :1 2:1 2.5:1 3:1 3.5:1 pigment/resin ratio (c) H8 Fig.1 Influence of different pigment, resin and pigment/resin ratio on the dispersity of ink Fig.1 shows that different resin has different effect on pigment. Compared with the other two resin, the ink prepared with HPD 96 has smaller particle size. It mainly depends on the affinity between resin and the surface modifiers of pigment. With surface modification, every pigment has certain chemical structure. So the affinity between resin and the surface modifiers of pigment is unlike with the change of resin, whose surface structure is different from each other. This experiment shows that HPD96, which is a kind of ammonia solubility acrylic resin emulsion, has better affinity with the surface modifiers of pigment, and the wetting result is better, so is the dispersity of ink.

3 Applied Mechanics and Materials Vol From Fig.1, it can also see that the pigment/resin ratio has a great influence on the dispersity of ink. The dispersity becomes better with the increase of pigment/resin ratio, and when the pigment/resin ratio reaches a certain value, the dispersity gets the best state. This is because the process of disperse is actually the same as the process of flow, ink can get sufficient shear only when it in the best flow point, and also the dispersity will at the best state. When grinding, different pigment/resin ratio leads to different shear effect [1, 2]. So in order to obtain the ink with best dispersity, it should confirm the best pigment/resin ratio first, and then prepare ink[3]. Besides, it also can be seen from the Fig.1 that ink prepared with different pigment, the dispersity is different too. This is because the surface structure, particle size and aggregate state of pigment is different from each other, so the affinity to resin is dissimilar[4]. In this experiment, the ink prepared with C500 and HPD 96, and the pigment/resin ratio is 2:1 has the smallest particle size. This is because C500 has porosity surface structure, and resin can bled into pigment easily and then wet the pigment sufficiently. Influence of Pigment on the Covering Power of Ink. The variety of pigment is an important factor that influence the covering power of ink, in order to obtain high covering power ink, choosing HPD96 and mix with C500,Cabot M-L and H8, the pigment/resin ratio is 2:1,2.5:1 and 2:1 respectively, in which all of them at best dispersity state, to prepare based ink, thinning the based-ink to meet the requirement of viscosity in flexography.proofing and testing the density of each ink to represent the covering power, the result is shown in Fig.2: density C C+96 H8+96 pigment and resin Fig.2 Densities of ink prepared with different pigment :760=3:1 750:760=2:1 750:760=1:1 750:760=1:2 750:760=1:3 760 the variety of the dispersant Fig.3 Influence of the variety of the dispersants on dispersivity of ink As can be seen from Fig.2 that ink prepared with different pigment has diverse covering power. The ink prepared with Cabot M-L has the best covering power, but the covering power of the ink which prepared with C500 and has the best dispersity is not the best. So it can be included that the covering power is not always the best with the best dispersity, pigment is also an important factor. This is up to the property of absorb light of pigment. The property of absorb light of Cabot M-L is better than other pigments, so the better of covering power. Influence of Dispersants on the Dispersity of Ink Influence of the variety of dispersants on the dispersity of ink. Dispersant existing in ink is used to keep a good dispersity and stability of ink, the effect is always different with the change of dispersant, so the experiment gives a research towards the influence of the variety of dispersants on

4 530 Advances in Printing and Packaging Technologies the dispersity of ink. Fix the content of dispersant, changing the variety of it to prepare ink.the diameter shows in Fig.3. As can be seen from Fig.3 that the ink prepared with 750 has bigger particle size than the ink prepared with 760.This is because dispersant is used to decrease the surface tension of pigment, forming an ion layer on the surface of pigment, and to make sure ink with good dispersity as well as stability based on the theory of like charges repel[1].and 760 is a kind of dispersant that with high content of pigment affinity groups and surface-active substance, so it has better wetting effect on pigment. When ink prepared with the dispersant that made with 750:760 is 1:2, it has the smallest particle size,and also the best dispersity.this is because the combination of these two kinds of dispersants can promote the wetting effect each other, and as a result, ink can be dispersed better. Influence of the content of dispersant on the dispersity of ink. Different content of dispersant has dissimilar effect on the dispersity of ink, so it's necessary to research the influence of the content of dispersant on the dispersity of ink. Fix other components, using the dispersant made with 750:760 is 1:2 to prepare ink by changing the content of dispersant. The result is shown in Fig.4. Fig.4 shows that the same dispersant, with the increase of content, the dispersity of ink is enhanced. But when the content of dispersant reached 1%, the dispersity of ink will get worse with the increase of it. This is because different content of dispersant will form different ion layer in different concentration, when the dispersant has low content, the concentration of ion is also not big enough to obtain sufficient repulsion; when the content of dispersant is too high, the distant between two particle will become smaller, the potential will decrease correspondingly, so the repulsion potential will decrease too, and as a result, the repulsion decreases [1,5] % 1% 1.5% 2% 2.5% the content of dispersant Fig.4 Influence of the content of the dispersant on dispersivity of ink Conclusions 1) In order to obtain the ink with good dispersity,it's necessary to choose resin which can wet the pigment sufficiently. In this experiment, grinding resin HPD 96 can match all the three pigments, and obtain inks with smaller particle size, and better dispersity corresponding. Besides, ink prepared with proper pigment/resin ratio can have the best dispersity. At the same time, the dispersity of pigment is different because of the different surface structure. In this experiment, the ink prepared by C500 and HPD 96 and the pigment/resin ratio has the best dispersity.

5 Applied Mechanics and Materials Vol ) The variety and content of dispersant is also an important factor that influence the dispersity on ink, it should choose the dispersant which can decrease the surface tension of pigment as well as wetting the pigment sufficiently. And the proper content of dispersant could form effective ion layer to obtain enough repulsion, which is conductive to enhance the dispersity and the stability of ink. In this experiment, when using the dispersity made with 750:760 is 1:2, and the content is 1%, ink has the best disperse quality. 3) Apart from the dispersity of ink, the variety of pigment is also an important factor that influences the covering power of ink. In order to obtain black water-based ink with high covering quality, it needs to choose pigment with good covering power. In this experiment, the ink prepared by Cabot M-L has the best covering quality. Acknowledgements This work is supported by Beijing Municipal Education Commission, science & technology committee "Research on the key technology of Plastic water-based gravure ink industrialization (KM )" and Research base-science & technology innovation platform-the construction of laboratory of printing and packaging material. References [1] Xin Xiulan: Water-based Ink (Chemical Industry Press, Beijing 2004). [2] Li Rongxing: Ink (Printing Industry Press, Beijing 1986). [3] Huang Beiqing: Packaging Engineering Vol.28 (2007), p.66 [4] TuWeiping: Water-based paint (Chemical Industry Press, Beijing 2005) [5] Shen Zhong: Colloid and Surface Chemistry (Chemical Industry Press, Beijing 2004)

6 Advances in Printing and Packaging Technologies / Study on the Dispersity of Black Water-Based Covering Ink /