Solution of Discoloration in Gold Silver Ink Printing

Understanding of thixotropy of ink.Solution of Discoloration in Gold Silver Ink Printing

       In the production process practice, we found that the general ink has a certain thixotropy, which is mainly manifested in that the ink becomes thin after stirring and friction, so as to increase the fluidity, and after it is left for a period of time, the ink will return to the original thicker state. For example, the ink with high viscosity will have a certain fluidity when its solidification state is damaged under the stirring of external force. Solution of Discoloration in Gold Silver Ink Printing

       In the static state, the solidification state increases gradually with the increase of time. When it is restarted, it will affect the normal flow of ink in the ink bucket, and even fail to transfer. On the other hand, the temperature of the ink on the ink bucket and cot of the printing machine increases after rotating friction, so the fluidity and ductility also increase. Solution of Discoloration in Gold Silver Ink Printing

       Until it is transferred to the printing sheet, due to the disappearance of external force, its fluidity and ductility decrease, and then change from thin to thick, so as to ensure the clarity of printing ink. Influence of Ink Thixotropy on Printing Quality

        In addition, when the temperature is low, the ink appears thick; On the contrary, the ink becomes thinner and the fluidity increases. Solution of Discoloration in Gold Silver Ink Printing

      When the machine is shut down for a long time, the ink in the ink bucket will gradually return to its original state from thin to thick. These are normal phenomena of ink thixotropy.Solution of Discoloration in Gold Silver Ink Printing

       Generally, in the printing process, the vast majority of ink will become thin from thick, which is caused by temperature changes, such as machine temperature rise, ink roller temperature rise, printing plate temperature rise, etc. When the ink has certain thixotropy, it is conducive to the smooth and uniform transmission and printing of the ink.Influence of Ink Thixotropy on Printing Quality

       In addition to the above factors, the thixotropy of ink is mainly determined by the composition characteristics of ink. For example, the thixotropy of ink made of pigment with strong surface adsorption is large; The pigment in the ink is needle and plate-shaped, and the thixotropy of particles is greater than that of spherical particles; Influence of Ink Thixotropy on Printing Quality

       If the amount of pigment is large, its thixotropy is also large, which is due to the flocculation caused by the attraction of pigment molecules to each other; If the wettability of pigment and binder is poor, the thixotropy of ink is large; Influence of Ink Thixotropy on Printing Quality

       The resin molecule ratio is large, and the thixotropy of ink is also large. In addition, the thixotropy of pigment ink is relatively large because of too much pigment content and poor pigment quality, such as poor wettability and low relative density. This problem also occurs when there is too little binder in the ink and the viscosity is too small.Influence of Ink Thixotropy on Printing Quality

Influence of ink thixotropy on printing quality 

        It can be said that ink thixotropy discomfort has a great impact on printing quality. In production practice, we found that during the printing process, especially when the temperature is low and the machine speed is slow, the ink in the ink bucket often has the phenomena of unsmooth transportation and abnormal ink supply.Solution of Discoloration in Gold Silver Ink Printing

       Resulting in the increasingly light ink color of the printed products, affecting the stability of the printing ink color, which is the main manifestation of the poor thixotropy of the oil and ink. In this regard, we should pay attention to often stirring the ink in the ink bucket to maintain continuous and uniform fluidity and ensure the ink quality of the product.Solution of Discoloration in Gold Silver Ink Printing

         Some inks have high viscosity before thixotropy due to excessive thixotropy during transmission, which is easy to cause ink blocking and plate pasting during printing. Therefore, some printing machines are equipped with agitators in the ink bucket to stir the ink to make it “thixotropic” to improve the flow condition of the ink and reduce the viscosity of the ink, so as to prevent the phenomenon of ink blocking and pasting. Solution of Discoloration in Gold Silver Ink Printing

         If the thixotropy of the ink is too large, the ink in the printing process becomes thinner and thinner, and the ink color of the printed matter becomes lighter and lighter, which can hardly be adjusted, this ink is not suitable for printing full-size printed matter on the spot. Attention should be paid to this problem during printing.Solution of Discoloration in Gold Silver Ink Printing

Technological measures for controlling ink thixotropy

        Printing requires proper thixotropy of ink. Too large or too small thixotropy of ink will have an adverse impact on printing. The thixotropy of ink is mainly determined by its material characteristics, but as mentioned above, printing conditions will also affect the thixotropy of ink to a certain extent. Influence of Ink Thixotropy on Printing Quality

      Therefore, when the inherent thixotropy of ink cannot realize normal printing, corresponding control can be carried out through process and technical measures. Solution of Discoloration in Gold Silver Ink Printing

       For example, during printing, the appropriate ink fluidity can be adjusted according to the characteristics of the printing machine and the temperature. When the printing speed is low and the temperature is low, because the thixotropy of the ink is small and its fluidity is small, it is not conducive to uniform ink transmission and inking. At this time, the ink can be thinned appropriately to meet the requirements of the printing process.Solution of Discoloration in Gold Silver Ink Printing

          In order to prevent the adverse effects of excessive “thixotropy” of ink on printing, it is necessary to control the printing process conditions to control the thixotropy of ink within the scope of printing suitability. First, try to print in a constant temperature and humidity environment and install air conditioning equipment in the production workshop. Solution of Discoloration in Gold Silver Ink Printing

          If the conditions are limited, when the climate is dry and windy, the doors and windows of the workshop can be closed to prevent the ink from thickening and sticking; Second, when the thixotropy of the ink itself is too large, the printing speed should be controlled within the lowest range as far as possible, so as to reduce the increase of the ink temperature due to the large friction coefficient of the machine, so as to dilute the ink; Solution of Discoloration in Gold Silver Ink Printing

         Third, under the condition of not affecting the uniform layout and sufficient inking, the number of inking rollers on the machine should be reduced as far as possible to reduce the friction coefficient during printing; Fourth, adjust the position of ink roller and water roller on the machine to prevent ink thinning due to abnormal temperature rise caused by too tight contact between ink roller and ink roller, between ink roller and plate, or between water roller and plate; Solution of Discoloration in Gold Silver Ink Printing

         Fifth, control the rotation stroke of the ink bucket roller. If the rotation stroke of the ink bucket roller is large, the temperature rise is high, and the ink is easy to become thin.Influence of Ink Thixotropy on Printing Quality

       Therefore, when the printing speed is high, the rotation stroke of the ink bucket roller should be reduced as much as possible, and the gap between the ink bucket steel sheet and the ink bucket roller should be appropriately increased to meet the printing ink supply requirements; Solution of Discoloration in Gold Silver Ink Printing

          Sixth, when the relief plate (including flexo) printing layout is large, the printing speed should be controlled lower to reduce friction and temperature rise; seventh, the printing ink should be reasonably selected.Influence of Ink Thixotropy on Printing Quality

       The thixotropy of the printing screen plate is required to be slightly larger, while the thixotropy of the printing ink of the large-area field plate should be slightly smaller, so as to better improve the printing quality.Solution of Discoloration in Gold Silver Ink Printing

        To sum up, ink thixotropy has a certain impact on printing, and there are many factors affecting ink thixotropy. Therefore, it is of great significance to correctly understand the thixotropy of ink and its related factors, take corresponding process and technical measures for appropriate control during printing, and keep the ink in a relatively stable state in the printing process, so as to effectively avoid the disadvantages of printing quality, and improve the printing efficiency and product printing quality.Solution of Discoloration in Gold Silver Ink Printing