What are the processes, difficulties and solutions for paint dyeing?

Paint dyeing is a special dyeing method that uses a binder to fix water-insoluble pigments on fabrics.

Process flow

Includes coating working solution preparation, fabric padding, pre-baking, baking, and finally obtaining the finished product. Working solution preparation The coating dyeing working solution contains components such as pigments, adhesives, cross-linking agents, anti-migration agents, and softeners. Pigments are generally inorganic or organic pigments, and commonly used ones are titanium dioxide, carbon black, etc.; adhesives are mostly high molecular compounds such as polyacrylic acid, which can make the pigment firmly attached to the fabric; cross-linking agents can improve the fastness and stability of the coating; anti-migration agents can prevent the pigment from migrating during the drying process; softeners are used to improve the feel of dyed fabrics.

Dip dyeing method

1. Fabric pretreatment: Use cationic modifiers to treat fabrics, such as using quaternary ammonium salt compounds to treat cotton fabrics at a certain temperature and time to make their surfaces positively charged so as to better adsorb negatively charged paint molecules.

2. Paint dip dyeing: Put the pretreated fabric into the dip dyeing solution containing paint, auxiliaries, etc., dip dye at room temperature for a period of time, and then heat up to continue dip dyeing, such as dip dyeing at room temperature for 20-35 minutes, and then heat up to 65-75℃ for dip dyeing for 10-30 minutes.

3. Adhesive dyeing: Add adhesive for dyeing to improve the fastness of the paint on the fabric. Commonly used adhesives include polyacrylic acid adhesives, etc.

4. Dehydration: Use centrifugal dehydration and other methods to remove moisture from the fabric. The dehydration time is generally 5-10 minutes.

5. Drying: Dry at 50-70℃ for 20-40 minutes to dry the fabric and fix the paint and adhesive.

Pad dyeing method

1. Coating working liquid configuration: Mix the coating, adhesive, cross-linking agent, anti-migration agent, softener, etc. in a certain proportion to prepare the coating working liquid.

2. Fabric padding: Pass the fabric through the padding equipment to make the fabric evenly dipped in the coating working liquid. The padding rate is generally controlled at about 65%-70%, and the padding temperature is preferably room temperature.

3. Pre-baking: Use non-contact drying methods such as infrared to pre-bake to remove part of the moisture in the fabric and prevent the coating from migrating during subsequent processing.

4. Baking: According to different fiber materials and adhesives, choose the appropriate baking temperature and time. For example, polyester/cotton fabrics can be baked at 180-195℃ to make the adhesive fully react, solidify the coating, and improve the color fastness.

Process advantages

Wide application range: There is no restriction on fiber types, and it can be used for dyeing various fibers such as cotton, linen, wool, silk, chemical fiber and their blended fabrics.

Short process flow: Compared with the traditional dyeing process, paint dyeing does not require complex processes such as washing, reduction oxidation, soaping, etc., which can greatly shorten the processing flow and improve production efficiency.

Energy saving and emission reduction: The whole process no longer requires washing, which can save a lot of water resources, and also reduce the discharge of sewage, energy consumption and environmental pollution.

Intuitive color matching: There is no color development process in the dyeing process, the color matching is intuitive, the color imitation is easy, the color light control is accurate, and the color difference is small.

Process Disadvantages

Poor hand feel: The paint particles are bonded to the fabric surface by adhesives, so the dyed fabric does not feel as soft as the dyed fabric, especially when dyed in dark colors, the problem of hard and rough hand feel is more obvious. Poor friction fastness: Its friction fastness is not very good, especially the wet friction fastness is poor, and it is easy to fade during use and washing. Color restriction: It is generally only suitable for processing varieties with not too dark colors. For some particularly bright colors, such as phthalocyanine, scarlet, purple, etc., it is difficult to achieve the ideal color requirements by dyeing with paint.

Difficulties and solutions for paint dyeing

Poor dyeing uniformity

Difficulty: Paint particles tend to aggregate, resulting in uneven distribution on the fabric, resulting in color spots, color spots and other problems.

Solution: A suitable dispersant can be added to make the paint particles evenly dispersed in the dye solution. For example, an anionic dispersant can be used, which can adsorb on the surface of the paint particles, making them carry the same charge, repel each other and avoid aggregation. At the same time, strengthening stirring during the dyeing process can also help keep the paint evenly dispersed.

Low dyeing fastness Difficulty

The coating and fabric are mainly bonded by physical adsorption or with the help of adhesives, and the bonding force is relatively weak, so the rubbing fastness and washing fastness may be poor. Solution: Choose an adhesive with excellent performance, such as self-crosslinking acrylic adhesive, which can undergo a cross-linking reaction under certain conditions to form a stronger film and better fix the coating on the fabric. In addition, proper post-treatment after dyeing, such as high-temperature baking, can promote the full reaction of the adhesive and improve the fastness.

Insufficient color brightness and depth Difficulty: 

Compared with traditional dyeing, paint dyeing is difficult to achieve high color depth and brightness.

Solution: Choose high-quality paint. Some nano-scale paint particles have small particle size and narrow distribution, and have better light scattering and absorption properties, which can obtain brighter colors. You can also increase the color depth by increasing the amount of paint, but be careful not to use too much, which will cause problems such as dyeing uniformity. At the same time, reasonable control of dyeing process parameters, such as increasing dyeing temperature, can improve the color to a certain extent.

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