What is Silicone Emulsion

Silicone emulsion is a form of silicone oil, which will be introduced from the following two aspects: silicone oil fabric softening and finishing agent and silicone oil emulsion type defoamer.

Silicone oil fabric softener

Silicone emulsion is mainly used as a softening and finishing agent for silicone oil fabrics.

The first generation of silicone fabric finishes is a mechanical mixture of dimethyl silicone oil and hydrogen-containing silicone oil (and its derivatives); the second generation of silicone fabric finishes is a hydroxyl terminated polydimethylsiloxane emulsion, It is formed by emulsion polymerization of octamethylcyclotetrasiloxane monomer, water, emulsifier, catalyst and other raw materials under certain conditions. Since the polymerization and emulsification are completed in one step, it has the advantages of short working time, high work efficiency, simple equipment, convenient operation, etc., and the obtained emulsion is very stable, the particles are very uniform, and the obtained polymer has active groups (hydroxyl groups at both ends) ) can be further reacted to form a film, which is beneficial to improve the application effect of the emulsion, which is inferior to the mechanical emulsification of silicone oil.

Hydroxy silicone oil emulsion can be divided into cationic, anionic, nonionic, composite ionic and other types of emulsions according to the different surfactants used.

1. Cationic hydroxyl silicone oil emulsion

The emulsifiers used in cationic hydroxy emulsion polymerization are generally quaternary ammonium salts (octadecyl trimethyl ammonium chloride reported in foreign literature), and the catalyst is ammonium hydroxide. Cationic hydroxy emulsion can be used in the post-finishing of various textiles, and has the properties of improving fabric hand, elasticity, smoothness and stiffness of fabrics; its other unique advantage is that it is an ideal waterproofing agent for fabrics, and it can be used together with methyl hydrogen silicone oil emulsion. , Waterproof performance and waterproof durability can reach a very high level, can be used as a waterproofing agent for vinylon canopy canvas, a waterproofing agent for polyester card cloth, etc.

2. Anionic hydroxy silicone oil emulsion

Anionic hydroxy emulsion is characterized by good compatibility in fabric finishing agents, and the emulsion is very stable. In particular, most of the auxiliaries in textile printing and dyeing are anionic. If cationic hydroxyemulsion is used, it is easy to cause demulsification and oil leaching. Anionic hydroxyemulsion can avoid this drawback, so it is more popular with users and has a wide range of uses.

3. Complex ionic hydroxyl silicone oil emulsion

Although cationic hydroxy emulsion is an excellent fabric softening and finishing agent, this emulsion is not resistant to hard water and cannot be bathed with dimethylol dihydroxyethylene urea resin (2D) resin, catalyst magnesium chloride and anionic brightener use, so there are certain limitations in use. In addition, due to the poor stability of the emulsion, the silicone polymer is easily separated from the emulsion and floats on the liquid surface, commonly known as "floating oil". If the cationic and nonionic emulsifiers are used for compounding in the emulsion polymerization process, the shortcomings of the cationic emulsifiers in the preparation of hydroxy silicone oil emulsions can be overcome. Brightener VBL is equivalent to bath use and has good heat resistance and freezing resistance.

4. Nonionic Hydroxy Silicone Oil Emulsion

Non-ionic hydroxy milk has stronger adaptability and better stability than isolated hydroxy milk, so many countries have vigorously researched non-ionic hydroxy milk.

5. Silicone Finishes with Other Active Groups

In order to meet the needs of advanced finishing of various fabrics, improve the anti-oil, anti-static and hydrophilic properties of silicone-finished fabrics, and make chemical fiber fabrics have many advantages of natural fabrics, silicone workers have studied the introduction of other Reactive groups such as amino group, amide group, ester group, cyano group, carboxyl group, epoxy group, etc. The introduction of these groups makes organosilicon fabric finishing agents have special effects. For example, the introduction of amino groups into silicone molecules is suitable for shrinkage-resistant and soft finishing of wool fabrics; the introduction of amide groups is suitable for antifouling finishing, and the softness is greatly improved: introduction The cyano group has good oil resistance, and the copolymer of polyoxyethylene ether and organosilicon has a good antistatic effect; the organofluorine-modified organosilicon has many advantages such as oil repellency, antifouling, antistatic, and water repellency.

Silicone oil emulsion type defoamer

Silicone oil emulsion type defoamer is generally an oil-in-water (O/W) emulsion, that is, water is the continuous phase, and silicone oil is the discontinuous phase. It is to pre-mix silicone oil, emulsifier and thickener, and then gradually add water to mix, and finally grind repeatedly in a colloid mill until the desired emulsion is obtained.

Silicone oil emulsion defoamer is the most widely used and the largest amount of defoamer among silicone defoamers. It is characterized by being easy to disperse in the water system and can be widely used as a defoamer in the water system. When in use, the emulsion can be directly added to the foaming system to obtain a good defoaming effect. In order to improve the defoaming effect of the emulsion and the accuracy of the measurement, it is generally not necessary to directly use the concentrated silicone oil emulsion of more than 10%: instead, it should be diluted to below 10% with cold water or directly with a foaming liquid. It is contraindicated to use hot or cold liquid to dilute, otherwise it will cause the emulsion to break. After the emulsion is diluted, the stability will become poor, and the phenomenon of delamination (bleaching) may also occur during storage, that is, demulsification. Therefore, the diluted lotion should be used up as soon as possible. If desired, thickeners can be added to improve the stability of the emulsion. For batch operation, the silicone oil emulsion can be added at one time before the system runs, or it can be added in batches; for continuous operation, the silicone oil emulsion should be added continuously or intermittently at appropriate parts of the system.

When using an emulsion type defoamer, special consideration should be given to the temperature of the foaming system and conditions such as acid and alkalinity, because the silicone oil emulsion is squeamish, and if it exceeds its use range, the emulsion will break prematurely and become inefficient or ineffective. (The dosage of silicone oil emulsion is generally 10-100ppm of the weight of the foaming liquid (calculated by silicone oil). Of course, under special circumstances, there are also less than 10ppm and more than 100ppm. The optimum dosage is mainly determined by experiments.