1. Applications and prospects of sublimation transfer paper

They can be widely used in the mass production of textiles such as T-shirts, curtains, bedding, etc. They can also be used in the mass production of ceramics, metals, home accessories and other items, and also be used to make personalized and commemorative products. Among them, textiles are the main application areas, as shown in Figure 1.

Figure 1 Thermal sublimation transfer process and application

With the rapid development of various industries in China, especially the future development trend of the clothing industry that promoted the development of sublimation transfer paper. The output of sublimation transfer paper in China in the past 10 years is shown in Figure 2.

Figure 2  Variation of thermal transfer paper output in China during 2011-2021

2. Sublimation heat transfer paper

Sublimation transfer paper generally consists of three parts: sublimation transfer paper base paper, pre-coating layer and transfer layer, as shown in Figure 3.

In order to make high-quality printing and transfer effects, the sublimation transfer base paper is generally required to have less filler, high whiteness, smoothness of about 30s, good uniformity, appropriate tightness, and low air permeability; in order to prevent paper breakage, base paper also needs to have high tensile index, tear index and heat resistance.

Figure 3  Structure of thermal sublimation transfer paper

2.1 Pre-coating layer

Pre-coating i.e surface sizing of pulp, which has many advantages: it will not affect other processes of papermaking; it has no effect on hydrogen bonds between fibers; it has high utilization rate and produces less waste water; it improves the surface strength of paper and reduces lint and powder problem; it can brighten the dispersed dye after transfer and improve the transfer performance. Research has found that the best formula for pre-coating sublimation transfer base paper is: the ratio of light calcium carbonate to china clay is 7:3, the amount of adhesive is 20 parts, the ratio of PVA to latex is 7:3, and the amount of water-repellent agent for 1 serving.

2.2 Coating layer

Coating layer i.e the transfer layer, its main function is to provide excellent ink absorption while preventing sublimation ink from being excessively absorbed into the paper fibers, controlling the dot increase of the ink, and forming high-quality images, text and other information. The coating used is mainly composed of glue Composed of adhesives, pigments and functional additives.

(1) Adhesive

When formulating the coating chemicals, the main function of the adhesive is to bond the pigments to each other, to bond the pigments to the base paper, and to fill the gaps between the pigments, as shown in Figure 4. An ideal adhesive must have stable chemical and physical properties, good bonding ability and water retention, be easily soluble in water, have good compatibility with other paint components, and be non-toxic and odorless.

1- Base paper

2- Pigment particles

3- Adhesive binds the pigment particles to the base paper

4- Adhesives bind pigment particles to each other

5- Adhesive fills the gaps between particles

Figure 4 Action of adhesive

Currently, commonly used adhesives include starch, polyvinyl alcohol (PVA, PVOH), styrene-butadiene latex (SB latex), soy protein, sodium carboxymethylcellulose (CMC), etc. Studies have shown that sublimation transfer paper coated with low alcoholysis degree PVA has higher dye outline definition and does not cause ink accumulation or color bleeding.

When very low molecular weight CMC is used as a dispersant, the gloss of the coating can be greatly improved. Improve the drying rate of the coating and obtain good transfer effects.

(2) Pigments

Pigments are generally the most commonly used component in coatings. The ideal pigment must have good chemical stability, high refractive index, high dispersion, low density, good fluidity in aqueous suspension, and good effect on other coating components. Compatibility and other properties. Pigments are divided into main pigments, special pigments and auxiliary pigments according to the actual dosage. The auxiliary pigments generally do not exceed 10%. When coating, the appropriate pigment or pigments should be selected according to the required performance or comprehensive performance. Currently, commonly used pigments include calcium carbonate, kaolin, talc, and titanium dioxide.

As the dosage of modified nano-TiO2 increases in the range of 0 to 10%, the whiteness, gloss, ink absorbency and surface strength of coated paper also continue to improve.

Clay and GCC (Ground Calcium Carbonate) increase the paper's resistance to high temperatures and pressures; the use of plastic pigments increases the optical density of the paper's secondary printing. Silica has the best drying and absorption performance for ink; the printing accuracy is highest after coating with porcelain clay; in single-color coated paper, the calcium carbonate group has the best coloring ability; when silica is combined with talc, calcium carbonate and silk When marble is compounded, its printing performance is better than that of single-pigment silica-coated paper.

(3) Functional additives

In order to improve the performance of the coating, ensure the quality of the coating and reduce the impact of other factors on the coated paper, one or several additives are often added when preparing the coating. Usually the amount of these additives is very small, usually 1%. ~2% or less. According to the functions of these additives, they can be divided into dispersants, defoaming agents, water retaining agents and rheology regulators, water repellents, bactericides, etc.

Polycarboxylic acid dispersants have better dispersion effects on inorganic pigments; phosphoric acid/phosphate ester functional dispersants have better dispersion effects on organic pigments.

Polymer dispersants for water-based paints are pointed out that they have a considerable effect on the wettability and stability of pigments.

Coating paper with NFC or NFC/chitosan nanoparticles (CHNP) improves the paper's tensile strength properties and reduces porosity and water absorption.

Thiocyanate nanocellulose has excellent thickening and rheology properties due to its highly charged surface and strong interactions with pigments and immobilized water molecules. Microfibers and nanocellulose are used as rheology-modifying additives in pigmented coating formulations to improve the strength properties of paper surfaces.

The sublimation transfer paper produced by our company's coating equipment of Qingdao JIERUIXIN Machinery and Technology CO.,Ltd, has a transfer rate of more than 96% and can be applied to chemical fiber items or textile products with a cotton content of less than 30%. Welcome to inquire about equipment solutions and chemical preparation supply or purchase paper.