Rotary screen printing is inseparable from the application of sodium alginate paste.

　　The sodium alginate paste is perfectly applied to rotary screen printing, which can produce patterns with many colors, rich colors, full layers and lively patterns, especially large patterns, and obtain excellent printing results. However, rotary screen printing requires high performance of the original paste, such as dilution resistance, temperature resistance and non-delamination.

　　(1) Excellent rheology. Rotary screen printing requires that the color paste can be easily scraped out of the mesh, but also keep a smooth outline and a uniform surface, so the original paste should have excellent rheology and good thixotropy.

　　The definition of pattern outline is not only related to the rheological properties of the original paste, but also often related to the wandering properties of the original paste itself. In rotary screen printing, especially when printing hydrophobic fibers, because most of the color paste passing through the mesh is piled on the surface of the fabric, the paste with good fluidity, high content and low viscosity should be selected, otherwise it will wander due to the wandering nature of the paste, which will affect the definition of the pattern.

　　(2) Permeability of the original paste. For rotary screen printing, the permeability of the original paste is also an important criterion for selecting the original paste. Because the color paste is piled up on the surface of the fabric through the mesh during printing, it is not like roller printing, which is pressed back and forth by the extrusion of the cylinder or flat screen printing, so that the color paste enters the gap of the fabric. Therefore, the original paste with strong permeability is easy to obtain uniform surface effect and full color, but when the permeability is too good, it will reduce the surface color gain, so the original paste with moderate permeability should be selected.

　　(3) The water holding capacity of the original paste. When the hydrophobic synthetic fiber is printed by rotary screen printing, the original paste with poor water holding capacity will have serious infiltration phenomenon, and the solid content should be increased.

　　(4) Spinnability of the original paste. The original paste with excellent spinnability has strong adhesion to the fabric, which is more important in rotary screen printing of synthetic fiber fabrics [1]. Hydrophobic synthetic fiber has a smooth surface and poor adhesion. If the conjunctival adhesion of the original paste is not good, it will often peel off, stain and pollute each other, so it is also one of the important performance criteria for selecting the original paste in rotary screen printing.

　　Printing paste is an important part of printing color paste. Controlling the rheology and permeability of printing color paste is one of the important factors that determine the printing quality, which determines the printing performance, the surface color supply of dyes, the smoothness of pattern outline and so on.

　　Sodium alginate paste is the most widely used printing paste at present. Because of its limitations in rheology and permeability, it is not effective in fine printing and large-area printing. In addition, in recent years, the price of sodium alginate has increased, leading to an increase in printing costs. Therefore, the industry is also looking for substitutes for sodium alginate, and the main research is synthetic thickener and modified cellulose paste. Although these two kinds of pastes are superior to sodium alginate in some single properties, they still have insurmountable shortcomings. For example, highly substituted CMC/SA composite paste, SA/NDY composite paste, etc., combine all kinds of pastes with excellent single performance and show excellent comprehensive performance. Through the chemical compatibility, rheology and other performance characteristics of composite paste, the apparent color yield and permeability of printed fabric are improved, which is one of the research directions of printing paste at present.

　　Thickener FS-80E has excellent characteristics such as high paste forming rate and good rheology, but it has poor spinnability and will be contaminated in practice, which will affect its wide use. In this experiment, thickener FS-80E and sodium alginate were mixed to study the performance and printing effect of composite pastes with different mixing ratios, and the influence of color paste performance on pattern clarity was analyzed from the perspectives of viscosity, water holding capacity, storage, rheology, debinding rate and pattern clarity, so as to obtain a composite paste with good printing effect and low cost.
　

　　1 test

　　1.1 Materials, reagents and instruments and equipment

　　Material T65/C35 plain cloth

　　Reagent sodium alginate (Rizhao, Shandong) and thickener FS-80E (Dandong Star)

　　Disperse and reduce dyes

　　Instruments: RION viscometer VT-04F, computer spectrocolorimeter PRO (USA), STORK rotary screen printing machine, LMH688Y-180 curing machine, YLM481-180 steamer, Z(B) O1B disc sampler.

　　1.2 Preparation of original paste and color paste

　　Preparation of original paste: sodium alginate and thickener FS-80E were mixed with water to form a 6% original paste, which was stirred into a uniform paste and allowed to stand for 4 hours to fully expand, to prepare the original paste [2]. The two kinds of raw pastes were compounded in different proportions to obtain a composite raw paste.

　　Preparation of color paste: 3% dye and 60% composite original paste, add water to 100%, and beat evenly with a high-speed mixer for later use.

　　1.3 printing process

　　Sizing → Rotary screen printing → Drying (100-105℃ for 3min) → Baking (185-190℃, 2.5min) → High-speed steaming (105℃, relative humidity 80%, 30s) → Soaking → Drying.