Basic knowledge of paint dyeing

Paint dyeing is to make the paint into a dispersion liquid, and make the fabric or yarn evenly carry the liquid through padding or dipping. With the help of the adhesive, a transparent and tough resin film is formed on the fabric or yarn, so that the paint is mechanically fixed to the fiber.

1. Structure and properties of paint:

The paint is a uniform dispersion system made by mixing and grinding organic or inorganic pigments and a certain proportion of glycerin, chlorpyrifos O, emulsifier and water. The solid content of the slurry is generally around 14% to 40%, and the fineness is mostly between 0.5 and 2μm. If the particles are too small, the brightness of the paint will be reduced, and excessive grinding of inorganic pigments and metal powders will make them lose their luster. If the particles are too large, the color will darken, the coloring rate will decrease, and the brushing and abrasion fastness will be poor. The paint that has been ground to a certain fineness has a tendency to condense during storage, so it is generally necessary to add protective colloids such as emulsifiers or cyclohexanone to the paint. 

Pigments used for coatings should have high stability to light, heat and climate, be resistant to acid, alkali, oxidants and commonly used chemicals, and have good sublimation fastness and smoke fading fastness; coatings should have a certain relative density and dispersibility. If the relative density is too large or too small or the dispersion is poor, it is easy to cause the coating to float or sink in the color paste; it should have a high color yield and covering power, so that a small amount of coating can print a darker color, and the pattern printed on the dark ground color will not cause a color mixing effect with the ground color.

Coatings are usually classified according to their different chemical characteristics, that is, chemical classification, and can be divided into two categories: inorganic pigments and metal powders, organic pigments and fluorescent coatings. Inorganic pigments include white titanium dioxide and black carbon black, such as coating black FBRN; metal powders are mostly copper-zinc alloy powders and aluminum powders with a certain degree of fineness. Organic pigments are azo dyes, metal complex dyes, phthalocyanine dyes and vat dyes that do not have water-soluble groups in their molecular structures. Generally speaking, dark red, blue, sauce and yellow paints are azo dyes, bright blue and bright green paints are phthalocyanine dyes, and golden yellow and lotus-colored paints are vat dyes; fluorescent paints are special varieties of organic paints. The occurrence of fluorescence is mainly due to the presence of fluorescent groups in the dye molecules and the conjugated system. They can absorb shorter wavelengths of visible light and reflect longer wavelengths of light. They absorb the energy of incident light and convert part of the energy into light energy, thereby increasing the amount of reflected light, significantly improving its brightness and intensity, and generating fluorescence.

2. Characteristics of paint dyeing:

The paint dyeing process has the following characteristics:

1. The variety is highly adaptable and is suitable for dyeing various fiber products such as cotton, linen, viscose, silk, wool, polyester, and brocade.

2. The process flow is short, the equipment is simple, the process is simple, the energy consumption is low, and it is conducive to reducing production costs. 

3. There is no color development process, the color matching is intuitive, and the color imitation is easy.

4. The sewage discharge is small, which can meet the requirements of "green" production.

5. The paint has a stable hue, strong hiding power, and is not easy to produce dyeing defects.

6. The paint color spectrum is complete, and the dyeing fastness of each color is good, especially for light colors. It can also produce special varieties that general dyes cannot produce, which is conducive to increasing the added value of products.

However, paint dyeing also has shortcomings, such as mechanical fixation determines that its friction fastness and rubbing fastness are not high, especially for medium and dark products; the fabric feels hard after dyeing, and the water absorption will also be affected to a certain extent.

3. Paint impregnation principle:

Paint impregnation can be applied to garments, fabrics and yarn dyeing. In cotton garment dyeing, combined with the trendy technology of imitation denim, the paint impregnation method is widely used.

Paint has no affinity for fibers, so it cannot rely on mechanical rolling to evenly distribute the paint on fiber products like padding. The mechanism of paint impregnation is to give the paint dispersion a strong negative charge through special additive treatment, and the fabric is treated with another special treatment to make it positively charged, that is, cationic modification treatment, and then the paint is adsorbed on the fiber product through impregnation. Since the adsorption binding force is relatively weak, it is necessary to use the effect of adhesives to ensure the fastness of the paint on the fabric. Cationic modifiers for fibers generally contain cationic amino groups, especially quaternary ammonium salts. On the one hand, they must be firmly bonded to the fiber, and on the other hand, they must make the fiber positively charged, which is actually very similar to the reaction of reactive dyes. Cationic modifiers can be divided into two types: low molecular weight and high molecular weight compounds. Low molecular weight compounds are mainly reactive, and are divided into two types: monofunctional and multifunctional. High molecular weight compounds are divided into two types: reactive and adsorbent.

If you want to know more about dyeing solutions, please contact: info@tiankunchemical.com