Study on the Problems of Foaming Ink During Screen Printing

[Abstract] The application scope and current status of foaming inks are introduced; the characteristics, composition, properties and mechanism of foaming inks; the screen printing process of foaming inks; and through specific experiments, foaming inks are used in the screen printing process. Some of the laws, such as the rules of the height of the foam, the rules of the discoloration of the foam printing, the rules of the ratio of the pigments of the foaming ink, etc., have been initially discussed, and some problems in the screen printing process of the foaming ink have been discussed. Inductive, summary, analysis and processing.

Keywords: foaming ink; pigments; screen printing; color

The foamed ink is printed on the textile, the pattern is uniform in the cell, the handle is comfortable and soft, and it has the characteristics of wear resistance, pressure resistance and soft color, and the resulting three-dimensional effect is out of reach of other inks. Products like artificial embroidery can replace the old embroidery process. Can be used for high-end cover decoration, trademarks, packaging and decoration. Through the comparison of specific experiments and experimental data, some laws of foam printing on textile printing and packaging products were discussed.

1 Theoretical basis

The microsphere foaming ink is a kind of emulsion ink. After the image formation, the ink layer is raised by heat treatment to form a three-dimensional pattern. In the printing and printing industry, water emulsion polymer can be used as the ink connecting material, the raw material source is abundant, the cost is low, and the coating operation is simple.

The main component of microsphere foaming ink is microspheres. The microspheres are hollow, microplastic spheres that are made of several different macromolecule polymer monomers that have a diameter of 5 to 80 μm and are internally filled with a low-boiling solvent by suspension polymerization. After the microspheres are heated, the low-boiling solvent in the sphere is heated and vaporized, and the gas expands to increase the volume of the microspheres to 10 to 30 times the original volume. The ink is printed on the substrate, and it needs to be dried to vaporize the solvent of the ink and then heated to 100-120° C. for several seconds to several tens of seconds. The ink layer expands and builds up into a foam to form a three-dimensional pattern. Drying method can be used at room temperature, natural drying or forced drying, drying temperature should not exceed 50 °C, foaming heat source is generally applied far-infrared radiation or hot roller rolling two kinds.

The main composition of microsphere foaming ink:

Acrylates and other resin copolymers 60%; microspheres 20%; urea 5%; color paste 10%; other components 5%.

2 Experiments

Through concrete experiments, through the collation, analysis, comparison, and synthesis of experimental data, various data such as the height, velvet degree, overprint, combination composition, and various changes in the pre-foaming and post-foaming of foamed ink blots were compared. Explore the regularity of foam printing.

2.1 Experiment content

1) Line and dot enlargement rate; 2) Change in spacing; 3) Relationship between foam height and ink layer thickness; 4) Change in color before and after foaming; 5) Change in flatness measurement of substrates before and after foaming; ) The effect of pigment ratio on foaming.

2.2 Experimental Materials

1) Printing materials: white paper, white cardboard, light blue polyester cloth, white lining cloth, white velvet cloth.

2) Printing and plate making materials: Foamed pulp (Model: HF-988, Zhejiang Jiangshan Printing Process Material Factory), Pigment (6201 Coating Color Red FFG 100%, Tianjin Dye Chemical No. 8 Plant), Photosensitive Adhesive (SD) -II Diazo Screen Printing Photosensitive Adhesive, Tianjin Jiayou Screen Printing Material Factory, Diazo Photosensitizer, Adhesive Mesh Adhesive (DEF-300 Adhesive), Water-resistant Sealing Adhesive (Zhejiang Jiangshan Chemical Coating Factory ).

2.3 Experimental Procedure

1) Design manuscripts: Originals were designed and their spacing was: 1.5mm, 2.0mm, 2.5mm, 3.0mm, 3.5mm lines.

2) Foaming ink: In accordance with the principle of saving, take a certain amount of foamed pulp, and formulate different proportions of foaming ink according to the ratio of foamed pulp: pigment; 3:1 and foamed pulp: pigment: 5:1.

3) Heating: Cut the naturally dried prints with scissors straight from the middle, take one of them to be placed on the table, another for comparison, and pull the cut print around Tight, to prevent over-contracted printing materials when foaming, and affect the overall effect of printed products. The foaming temperature should be controlled between 100 and 120°C. The printed material is heated for a few seconds. After the foamed ink is raised, the heating can be stopped. Then, the foamed prints are placed on a drying rack and, after cooling, ready for the next measurement.

4) Measurement of experimental data. Two kinds of printings before and after foaming were measured respectively. The measurement contents included the width of the interval between the prints before and after the foaming, the thickness of the ink before and after the foaming, and the change of the color of the ink before and after the foaming.

3 Analysis In this section, only the foaming effect on Polyestercloth was analyzed.

3.1 Variations in interval between before and after foaming of inks with different proportions
As can be clearly seen from Tables 1, 2, and 3, when the interval between the lines is 2.0 mm, the foaming effect is most pronounced when printing on Polyester Cloth.

3.2 Different thickness ratios of ink before and after foaming

From Table 4, it can be seen that when the ratios of different pigments are the same, they are on the polyester cloth, and the change rate of the thickness thereof is basically the trend that the less the pigment, the greater the change rate of its thickness.

3.3 Color change before and after foaming

X, Y, Z are the tristimulus values ​​of the object; L* represents the psychological brightness; a*, b* represents the mental chroma; △L* is the difference in lightness; △a*, △b* is the difference in chroma; x, y Is the chromaticity coordinates; and, ΔL*= L1*-L2*, Δa*= a1*-a2*, Δb*= b1*-b2*, ΔEab*=[(△L*)2+ ( △a*)2+(△b*)2]1/2

The results showed that when the foaming ink was printed on the polyester fabric, the color before and after the foaming had a great change. This is because the widest point of the designed line is still smaller than the color aperture of the colorimeter used, so for Poly-cloth, since the good fabric used is light blue, the surface of the foamed ink is As the concentration becomes lower, the influence of the substrate's background color on its surface color increases, resulting in a larger color difference before and after foaming.

4 Conclusion

In this experiment, the graphic text expansion effect and color change of foamed ink on Diliang cloth were qualitatively analyzed, and some common changes were also in other materials. The main conclusions of the experiment are summarized as follows:

When the interval between the lines is 2.0 mm, the foaming effect is most pronounced when printing on Polyester Cloth.

When the ratio of different pigments is the same, the same is true on the polyester cloth, and the change rate of its thickness is basically the trend that the less the pigment, the greater the change rate of its thickness.
When the foaming ink is printed on the polyester fabric, the color changes greatly before and after foaming. Chromatic aberration decreases as the proportion of pigment increases.

By analyzing the problems arising from the experimental process, the following improvements are proposed for the following experiments:

1) During the printing process, manual printing and automatic printing using a screen printing machine can be used to print foaming inks. It is advisable to use a printing and heating foaming line, if the conditions do not allow it to do so, it is also possible to place the printed matter on a drying rack to dry naturally after printing. The printed matter must be fully dried before being heated and foamed (it takes time for the ink to evaporate and dry). After printing, the prints cannot be stacked together in large numbers to prevent excessive damage to the foamed graphics. It is better to place the prints upright.
2) Printing materials on the printing materials (to give more slurry), foaming is also high. Method for increasing the amount of pulp fed to the fabric: using a low mesh screen; reducing the hardness of the scraper and changing the angle of the scraper to make it obtuse, rounded; increasing the thickness of the stock; improving the overprinting of the printed material and screen printing Suitability; for high foaming products can be used twice silk screen printing method, that is, the first printing and drying and then overprinting once.

3) The printed product is placed on the drying rack, the drying temperature can not be greater than 40 °C, it is best to dry naturally at room temperature, to prevent the resin in the printed material "rigid" and affect the foam height. When drying, the moisture in the printing material must be dry, otherwise it will affect the foaming height, and it can not foam at all.

4) After the foamed ink is heated, the foam volume expands by 53 to 125 times, and the color tone concentration becomes lighter. The coordination of color matching should be taken into account in the design.

5) Due to the increase in foam volume, the surface of large-area solid patterns can easily cause shrinkage, uneven foaming, and damage to the artistic effect. When designing, large-area patterns and on-site use 80% coarse dots or lines with fine spacing, Leave room for foaming.

6) The color of foam printing should not be dark, and it can be matched with ordinary printing. It is better to use common printing background color, dark color printing and large area printing. When formulating foaming inks, the ratio of pigment to foaming paste should first be considered.

7) Foam printing For the lines below 0.2mm and the effect of too detailed graphics and text is not good, it is best not to use all foaming ink printing, only for the part that needs to be emphasized, the other part is printed with ordinary ink, to improve the water For the adhesion of the emulsion ink, it is better not to color the bottom of the ink. The printing sequence is to arrange the foam printing at the end.

8) The surface of the ink layer after foaming is roughened, becomes opaque, and cannot be multicolored overprinted like a typical ink. Must use their own special color according to design requirements. (Text / Huang Ling Ge Tian Wei)