The Development of Modified Softening Agent

Many of the modified silicone softening agents developed in the late 1970s have been used in the finishing of fabrics and are currently being researched and developed at home and abroad. This kind of product is through the introduction of various active groups such as amino, epoxy, polyether, hydroxyl and other active groups on the side chain of siloxane, which greatly improves the hydrophilicity, washing resistance and shrink resistance of the fabric, and depends on different groups to give the fabric different styles. At present, the new products that are being researched and developed in competition at home and abroad are generally divided into three categories, reactive type, including modification of amino, epoxy, carboxyl, methacryl and fluoroalkyl group, non-reactive type, mainly simple modified polyether and mixed type, such as polyether amino and epoxy modification. Polyether modification is the most widely used in textile, while amino modification is more used in softeners. Most products are mixed modification, including a small amount of pure amino, epoxy group, carboxyl group and fluoroalkyl active group modification.

1. Amino modified silicone softening agent

The amino-modified silicone softening agent is a polysiloxane with amino groups on its side chains or end groups. The amino group can be primary, secondary, tertiary, or ammonium salt, and can also be aromatic ammonia. Its synthesis methods include bulk polymerization and emulsion polymerization. The elasticity of the fabric finished with amino-modified silicone softening agent is obviously improved, which has firm combination with the fiber. Its good washing resistance makes it soft, smooth, plump and elastic. At the same time, it greatly improves the mechanical properties of the fabric with a certain anti-wrinkle and shrink-proof effect. Among amino-modified silicone softening agent, silicones with aminoethyl and aminopropyl have the best effect.

Amino-modified silicone softening agent is easy to yellow under the influence of heat or ultraviolet rays, so it is not suitable for softening and finishing light-colored fabrics. At present, such softeners are still being improved, the methods of which include epoxidation, amidation or secondary amination, controlling the degree of modification or adopting mixed modification. It can also be made into a stable silicone microemulsion.

2. Epoxy modified silicone softening agent

According to the type of reaction, there are three main methods for epoxy modified silicone oil, hydrosilation addition reaction of hydrogen-containing silicone oil and terminal alkenyl epoxy compounds, octamethylcyclotetrasiloxane (D4), epoxy-containing substituted the polymerization reaction of cyclotetrasiloxane (D4) and other synthesis methods, such as the condensation reaction of α,ω-dihydroxy silicone oil and epichlorohydrin. Epoxy groups have high activity and can cross-link with the hydroxyl, amino, carboxyl and other groups on the fiber surface to form a stable chemical bond, so that the treated fabric has a durable finishing effect. The fabric treated with epoxy-modified silicone is highly non-yellowing and has good stability and softness, but its smoothness and water absorption are poor. Because epoxy itself has extremely high reactivity. Therefore, the water absorption of the fabric treated with epoxy-modified silicone can be improved by grafting a strong water-absorbing group to the end of the epoxy group.

3. Polyether modified silicone softening agent

The preparation of polyether modified silicone softener can be carried out according to the mechanism of hydrosilylation reaction, esterification reaction, Michael addition reaction, active hydrogen epoxy addition reaction, alcohol hydrogen condensation and siloxane hydrolysis condensation reaction. Because this type of polymer also has good adaptability, biocompatibility and low glass transition temperature, it has advantage that other surfactants cannot match. The introduction of water-soluble unsaturated polyether into the side chain of polysiloxane can change the hydrophobic silicone into hydrophilic silicone. The fabric finished with polyether modified silicone also has good stain resistance and antistatic properties, but its softness and washing resistance are poor. Because of its good compatibility with other finishing agents, it can also be used in the same bath with dyeing. Polyether-epoxy hybrid modified silicone combines the advantages of polyether and epoxy silicone, and at the same time makes up for their respective shortcomings as a multi-functional, multi-component silicone finishing agent with good comprehensive performance.

4. Other modified silicone softening agent

(1) Carboxy modified silicone softening agent

In the presence of platinum catalyst, the addition reaction of unsaturated fatty acid and Si-H bond in the organosilicon can obtain the carboxyl modified organosilicon. The carboxyl modified silicone softening agent has chemical reactivity and polarity. It can be used in the finishing of natural fibers, well combined, and can improve the antistatic and hygroscopic properties of chemical fibers. Used together with amino or epoxy-modified silicone, it can improve the soft touch, and is not easy to fall off during washing.

(2) Sulfhydryl modified silicone softening agent

Thiourea method or acetic acid method can be used to prepare sulfhydryl-modified silicone. When it is used on wool, the wool can have durable shrinkage resistance and lubricity.

(3) Alcohol modified organic silicon softening agent

Polar addition of unsaturated alcohol and Si-H bond in silicone oil, or the introduction of hydroxyl groups for reaction, can obtain alcohol-modified silicone. Such softeners can improve the dyeability, heat resistance and water resistance of fabrics.

(4) Ester-based modified silicone softening agent

The ester-based modified silicone softening agent is synthesized by emulsion polymerization using hydrogen-containing silicone oil and acrylic ester under the action of a water-soluble catalyst. The softener can make the fabric soft and smooth, with good elasticity, and is suitable for the soft finishing of blended fabrics of chemical fiber and cotton.