Experimental Study on Preparation of Offset Printing Transfer Printing Ink

The characteristics and application of a gas phase transfer printing

Gas-phase transfer printing is to make disperse dyes into color inks and print them onto transfer papers to become transfer printing papers. During fabric printing, transfer printing papers and fabrics are pressed together and heated to complete the printing process. The gas phase transfer printing process consists of the following three parts:

1) The disperse dyes in the ink are heated to sublimate into a gas state;

2) The amorphous fiber area is heated and softened;

3) The gaseous disperse dye diffuses into the amorphous region of the fiber to color the fiber.

Compared with the traditional fabric printing process, the fabric gas phase transfer printing has the following advantages:

1) The post-processing process such as waterless washing and drying in the printing process avoids the pollution problem of dyes contaminating water sources. It is a new water-saving and environmentally friendly textile printing and dyeing process;

2) The fabric surface has no residual dyes, so the fabrics have high rubbing fastness and soaping fastness;

3) Printing pattern accuracy is higher than other printing methods, close to the paper printing precision, can print very fine patterns;

4) Can be printed on fabrics with greater flexibility;

5) Less equipment investment and simple production process.

Due to the above advantages, the gas phase transfer printing fabric has been stable for a long period of time with a yield of about 5% of the output of printed fabrics since its inception. In recent years, transfer printing fabrics have also been used more and more in advertising and decorative textiles. The production of fabrics has been greatly improved.

At present, the domestic transfer paper used for fabric transfer printing is mainly produced by the printing and dyeing factories themselves, and many of them are printed using self-made water-based transfer printing inks and solvent-type gravure transfer printing inks. Due to the lack of professional ink production equipment and technology, ink performance is poor and it is difficult to print high-quality transfer printing paper. In addition, the water-based ink has low content of disperse dyes, slow drying speed, large deformation of printed paper, and difficulty in printing fine patterns. The transfer paper printed with solvent-type gravure transfer printing ink is less deformed, and the drying speed is faster, so it can print relatively fine patterns. However, due to the high cost of gravure plate making and the long plate-making period, it is only suitable for high-volume production. Not applicable to small batches and multiple varieties of personalized products. In addition, the solvent-based gravure ink contains a large amount of solvent, and the volatilization of the solvent in the printing may cause environmental pollution.

Relatively speaking, offset printing is a printing method with high printing quality, low cost, fast printing speed, small environmental pollution, and high production flexibility. Offset printing technology has been used abroad to print transfer printing paper; although domestic manufacturers use offset transfer Printing inks are used for printing transfer papers, but because offset inks depend on imports, printing costs are higher. Therefore, the development of offset transfer printing ink with good overall performance and lower price is the key to the technology of printing transfer paper using the offset printing process. The following will introduce the formulation and development process of offset printing inks, and analyze the effects of various components of the ink on ink properties and disperse dye transfer properties.

Preparation of two offset ink transfer printing inks

1. Experiment

1) Raw materials

The experimental materials used to formulate offset printing inks for transfer printing include: substrates, dyes, ink binders, desiccants, and water repellents.

1 Substrate: Plain Polyester Silk

2 Dyestuffs: The dyes used in the preparation of offset printing inks are disperse dyes: 2BLN, 3B, RGFL original dyes.

3Binder: bisphenol resin, p-tert-butylphenol resin, nonylphenol resin, octylphenol resin, polyphenol resin, mineral oil, soybean oil alkyd resin.

4 desiccant.

5 anti-water additives.

2) Experimental equipment and test equipment

Three-roll mill, flatbed stamping machine, type 721 spectrophotometer

3) Test methods

1 dye transfer rate test

Extract the dye on 2cm×2cm printing paper with 22.5ml DMF and 2.5ml hydrochloric acid (1mol/L) solution. Determine the optical density A of the extract at λmax of type 721 spectrophotometer. Calculate dye transfer rate according to formula 1 .

2 Determination of ink transfer rate

0.1 g of ink was weighed and applied on a printability tester rubber roller. After 1 minute of uniform ink, a sample was printed on the precisely weighed transfer paper, and the ink transfer rate was calculated according to the following formula.

4) Screening of raw materials

1 selection of disperse dyes

Disperse dyes are the main dyestuffs used for conventional dyeing of polyester fabrics. Commercially available disperse dyes contain a large amount of additives. These disperse dyes have high fineness (domestic disperse dyes have a particle size of less than 2 μm and imported disperse dyes have a particle size of less than 1 μm. ). However, due to the large amount of hydrophilic additives contained therein, they have poor compatibility with offset ink resin binders, and the resulting inks have unsatisfactory performance. In addition, the presence of a large number of additives not only reduces the content of active ingredients in the disperse dyes, increases the cost of the ink, but also has an adverse effect on the transferability of the disperse dyes.

Due to the transfer printing process, the disperse dyes for transfer printing should begin to sublime at 150°C, have excellent sublimation dyeing properties at 190-200°C, and generally have a molecular weight below 350. On the basis of meeting the above requirements, we chose the low-temperature tricolor 2BLN, 3B, and RGFL dyes for experiments.

2 resin choice

Rosin-modified phenolic resin has good compatibility with disperse dyes. We tested and screened the bisphenol resin, p-tert-butylphenol resin, nonylphenol resin, octylphenol resin and polyphenol resin. The effect of the resin on the transfer ink performance is shown in Table 1 and Table 2.

2. Results and discussion

1) Effect of Resin on Ink Properties

The performance of the ink depends mainly on the compatibility of the resin and the dye. The ink transfer rate is the most important indicator of the ink performance. Among the five rosin-modified phenolic resins used in the experiment, the disperse dye content in the inks formulated with tert-butyl phenol resin and quinone disperse dyes 3B and 2BLN can reach 40%, while the inks formulated with other resins and 3B and 2BLN are used. The highest content of disperse dyes can only reach 22% to 27%, indicating that tert-butyl phenol resin has good compatibility with quinone disperse dyes. Table 1 shows the transfer rate of the ink with the dye content of 20%. Among them, the transfer rates of tert-butylphenol resin and 3B and 2BLN inks can reach 76% and 74%. This is due to the fact that the tert-butyl phenol resin and the dye are comparable. Good wettability, the ink can be better transferred to the paper when printing.

It can be seen from Table 2 that the transfer paper printed with tert-butyl phenol resin-anthraquinone disperse dye ink has higher disperse dye transfer rate, which is due to the better wettability of tert-butyl phenol resin and terpenoid disperse dyes. The dye is evenly dispersed in the continuous phase of the resin composition. After the printing, the resin forms a resin film with excellent sealing property on the surface of the paper. When the resin film is transferred, the diffusion of the gaseous dye into the paper is hindered. Therefore, the transfer paper has a relatively high Dye transfer rate.

The content of dyes in inks formulated with bisphenol resin and RGFL is up to 48%. This is because the structure of bisphenol resin is similar to the structure of azo dyes, making the resin and dyes have better compatibility. The ink has better ink and dye transfer properties.

2) Effect of disperse dye fineness on ink performance

The original dye of disperse dyes is generally more than 100 μm in size, and it needs to be ground to less than 5 μm in order to meet the printing needs. Because the selected resin system has good compatibility with disperse dyes, proper main and auxiliary resins are selected and the dye can be ground to 5 μm or less by tri-roller grinding.

When the dispersion dye has a fineness of 1 to 5 μm, although the ink has a good printing adaptability, the disperse dye has a low transferability. Table 3 shows the relationship between the fineness of disperse dyes and the disperse dye transfer rate.

When the disperse dye particle size is less than 1 μm, the disperse dye transfer rate reaches more than 70%. Therefore, the disperse dye should be grinded to 1 μm or less when making ink.

3. Conclusion

1) Tert-butyl phenol resin and terpenoid disperse dyes 3B and 2BLN have good wettability, and bisphenol resin and azo disperse dye RGFL have good wettability.

2) The inks made of tert-butyl phenol resin, bisphenol resin and 3B, 2BLN and RGFL have good ink properties, and the disperse dye transfer rate can reach over 70% after printing.

3) The fineness of disperse dyes has a great influence on the dye transfer rate. When the particle size is less than 1 μm, the disperse dye transfer rate can reach more than 70%.


(Author: Tianjin University of Technology Institute of Materials and Chemical Deng Xinhua

Tianjin Yunxing Ink Co., Ltd. Du Zhongjiang)

Source: "Printing Technology - Equipment and Special Printing"