Introduction to anti-fouling and easy-to-decontaminate finishing agents and finishing processes

Anti-fouling and easy-to-remove finishing are textiles that not only have good anti-fouling effects in the atmosphere, but also need to be easy to remove stains once they are contaminated. The fabric must be both anti-fouling and easy to remove dirt. It must have high wettability in the liquid medium and low interfacial energy in the air medium. Not wetted by common oily dirt.

After finishing, the critical surface tension of textiles is lower than water-based stains and oil-based stains. This is the reason why finished textiles can repel water and stains in the atmosphere. However, compared with unfinished textiles during washing, treated textiles tend to absorb dirt in the washing liquid, which is the reason for the above phenomenon. It can be explained by the changes in critical surface tension of cotton fabrics finished with different types of finishing agents in water and atmosphere, as shown in Table 1.

Table 1 Critical surface tension of cotton fabrics treated with different finishing agents

Fabric	Critical surface tension (mN/m)
Fabric	In the atmosphere	in the water
Unfinished cotton fabric	＞72	<28
Silicone finishing agent for finishing cotton fabrics	38~45	＞50
Organic fluorine finishing agent for finishing cotton fabrics	24~25	9~15
Polyacrylic acid type easy stain remover for finishing cotton fabrics	＞72	4.5~9.3

As can be seen from Table 1, the critical surface tension of cotton fabrics treated with organic fluorine finishing agents in the atmosphere is much lower than that of unfinished cotton fabrics, so they have excellent water and oil repellency. However, in water, the critical surface tension of unfinished cotton fabrics is only 2.8 mN/m, while the critical surface tension of cotton fabrics treated with organic fluorine finishing agents is greater than 9 mN/m. This is why ordinary cotton fabrics are easy to remove oil stains. However, cotton fabrics treated with organic fluorine finishing agents are not easy to clean after being stained with oil. Therefore, anti-fouling and easy-to-remove finishing should meet three conditions at the same time: ① Cover the fiber surface with a thin film to reduce the unevenness of the fiber surface; ② Reduce the surface energy of the fiber and inhibit the spontaneous spreading of oily dirt on the fabric surface ;③Is to improve the hydrophilicity of the fiber surface.

The application of mixed block copolymers containing fluorine-containing segments with low surface energy and hydrophilic polyoxyethylene segments can achieve two opposite effects at the same time. Using fluorine-containing segments with low surface energy and hydrophilic polyoxyethylene segments The mixed block copolymer of water-based polyoxyethylene segments can achieve two opposite effects at the same time.

Hybrid fluoroblock copolymers are oleophobic in air and hydrophilic in water. This dual functional effect is caused by the different orientations of the oleophobic and hydrophilic segments in air and water. In the air, the polyoxyethylene segments are in a curled state, and the oil-repellent fluorine-containing segments are densely arranged on the surface of the textile to form a surface with low surface energy and have oil-repellent properties. In water, polyoxyethylene generates hydration and stretches, and is oriented and arranged on the surface of the fabric. It gives the fiber surface hydrophilicity through changes in interfacial tension, making the fiber easy to decontaminate and prevent wet re-contamination. During the drying process, the hydrophilic segments are dehydrated and the fluorine-containing segments reoccupy their main interfaces. Using hydrophilic fluorine-containing block copolymer easy-to-contaminate finishing agent together with appropriate cross-linking agents can improve dry anti-fouling properties and give fabrics better easy-to-contaminate properties.

Hydrophilic fluorine-containing block copolymer is used in the anti-fouling and easy-decontamination finishing process of polyester-cotton blended fabrics. The process flow is: two-dip and two-padding → drying → baking (160℃, 3min) → soaping → washing → drying . Padding liquid: 2.5% to 3% hydrophilic fluorine-containing antifouling and easy-to-remove finishing agent, 1% to 1.2% magnesium chloride, 8% to 10% DMDHEU (45%), add water to 100%.