Ink thixotropy is one of the properties of printing process, which has a great impact on the quality of printing products.Influence of Ink Thixotropy on Printing
Thixotropy refers to the phenomenon that the ink becomes thinner or thicker and the fluidity changes under the action and influence of external forces and external environmental factors. For the printing process, stable product printing quality requires that the ink should maintain appropriate and stable fluidity. Influence of Ink Thixotropy on Printing
However, due to the inherent factors of ink itself and printing conditions, the ink will inevitably appear “thixotropy” in the printing process, which affects the stability of product quality. Therefore, we should correctly understand the thixotropy of ink, take some measures to overcome and make up from the process and technology, and reduce the thixotropy degree in ink printing, so as to better ensure the printing quality of products.Influence of Ink Thixotropy on 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. Influence of Ink Thixotropy on Printing
For example, the ink with high viscosity will have a certain fluidity when its solidification state is damaged under the stirring of external force. In the static state, the solidification state increases gradually with the increase of time. Influence of Ink Thixotropy on Printing
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. Influence of Ink Thixotropy on 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. In addition, when the temperature is low, the ink appears thick; Influence of Ink Thixotropy on Printing
On the contrary, the ink becomes thinner and the fluidity increases. 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.Influence of Ink Thixotropy on 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
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
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; The resin molecule ratio is large, and the thixotropy of ink is also large. Influence of Ink Thixotropy on Printing
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
It can be said that the thixotropy of ink has a great impact on the 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, 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.Influence of Ink Thixotropy on 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.
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.Influence of Ink Thixotropy on Printing