Silicone oil is a kind of polyorganosiloxane with different degree of polymerization chain structure. It is obtained by hydrolyzing dimethyldichlorosilane with water to obtain an initial polycondensation ring body. The ring body is cracked and rectified to obtain a low ring body. A mixture of different degrees of polymerization can be obtained by removing low boilers by distillation under reduced pressure.


The most commonly used silicone oil, all organic groups are methyl, called methyl silicone oil. The organic group can also use other organic groups to replace part of the methyl group to improve certain properties of the silicone oil and apply to various uses. Common other groups are hydrogen, ethyl, phenyl, chlorophenyl, trifluoropropyl and the like. In recent years, organo-modified silicone oil has developed rapidly, and many organo-modified silicone oils with special properties have appeared.


Silicone oil is generally colorless (or pale yellow), odorless, non-toxic, and non-volatile liquid. Silicone oil is insoluble in water, methanol, glycol and -ethoxyethanol, miscible with benzene, dimethyl ether, methyl ethyl ketone, carbon tetrachloride or kerosene, slightly soluble in acetone, dioxane, ethanol and alcohol . It has a small vapor pressure, high flash point and ignition point, and low freezing point. As the number of segments n is different, the molecular weight increases and the viscosity increases, so this silicone oil can have various viscosities, from 0.65 centistokes to millions of centistokes. If low-viscosity silicone oil is to be prepared, acid clay can be used as a catalyst for telomerization at a temperature of 180°C, or sulfuric acid is used as a catalyst for telomerization at low temperature to produce high-viscosity silicone oil or viscous material with alkaline catalyst.
02 Classification of silicone oil

Silicone oil is divided into methyl silicone oil, ethyl silicone oil, phenyl silicone oil, methyl hydrogen silicone oil, methyl phenyl silicone oil, methyl chlorophenyl silicone oil, methyl ethoxy silicone oil, methyl trifluoropropane according to chemical structure. Base silicone oil, methyl vinyl silicone oil, methyl hydroxy silicone oil, ethyl hydrogen-containing silicone oil, hydroxyl hydrogen-containing silicone oil, cyano-containing silicone oil, etc.; in terms of use, there are damping silicone oil, diffusion pump silicone oil, hydraulic oil, insulating oil, Heat transfer oil, brake oil, etc.


Silicone oil has excellent heat resistance, electrical insulation, weather resistance, hydrophobicity, physiological inertness and small surface tension, in addition to low viscosity temperature coefficient, high compression resistance) some varieties also have radiation resistance performance.
03 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.


2. 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.


The general silicone oil emulsion type defoamer is mostly oil-in-water type. According to the different types of silicone oil, silicone oil emulsion

defoamer has the following types:

1. Silicone oil emulsion based on dimethyl silicone oil

This type of defoamer is prepared from dimethyl silicone oil plus emulsifier and water, and can be widely used in fermentation, food, paper, fiber, pharmaceutical, synthetic resin and so on.
2. Silicone oil emulsion based on methyl ethoxy silicone oil

This type of defoamer is made of methyl ethoxy silicone oil and compounding agents.
3. Silicone oil emulsion based on ethyl silicone oil

Silicone defoamers are developing in the direction of silicone-polyether block copolymerization (or graft copolymerization). Since this type of defoamer has the characteristics of both silicone and polyether, the defoaming power is greatly improved; the silicone-polyether copolymerized defoamer can also be called a self-emulsifying silicone Block (or graft) a hydrophilic ethylene oxide chain or ethylene oxide propylene oxide chain in the silicone molecular chain, so that the hydrophobic siloxane part is combined with the hydrophilic polyether, such a molecule has a larger As a defoamer, it has a large spreading coefficient, can be evenly dispersed in the foaming medium, and has high defoaming effect. It is a new type of high-efficiency defoamer. This kind of self-emulsifying silicone oil without the use of emulsifiers, the defoaming effect is quite satisfactory for some systems, and it is especially suitable for those occasions where the use of general silicone oil emulsions is not suitable and the general silicone oil emulsions are incompetent.
04Points to note when silicone oil is softening

There are many varieties of silicone oil emulsion finishing agents, and the quality is uneven. There are cationic, anionic, non-ionic, etc., modified amino silicone oil and linear silicone oil and so on. Generally, the following points should be paid attention to when using silicone oil for soft finishing.


1. Control the dosage

Such as 20% solid content of amino silicone oil, the dosage of 1.5-3% (O.W.F) is enough, and increasing the dosage cannot increase the softness.


2. Fixed speed problem

When the factory is making some thin fabrics (such as chiffon, artificial silk, Bali yarn), the speed of setting is very fast, and sometimes it can reach a speed of 60 m/min. Due to the poor permeability of ordinary silicone oil, it is easy to cause the backflow of silicone oil on the roller. Sticky roll. When using, pay attention to changing the working fluid in the rolling groove and clean the rolls frequently.


3. Dip cylinder problem

When the factory is doing dipping and soft, ordinary silicone oil will stick to the cylinder wall. After a long time, some black oil spots will form on the cylinder wall, and it will form silicone oil spots on the cloth surface.


4. Cohesion problems

In fabrics containing short fibers (such as cotton, viscose, and velvet), some of the short fibers will inevitably fall off during the processing. Poly, as the finishing liquid goes up to the roller, it is bonded with the squeezed and demulsified silicone oil, and it is easy to form sticky roller or silicon spot. Do a good job of cleaning before driving, and clean up loose hair in time.


5. Hand feeling problem

Due to the increasing requirements for the feel of fabrics in the market, various fabrics need to show a variety of different styles due to different seasons and different customer requirements, such as those that require a smooth and drapey feel, those that are slippery and flexible, Fluffy and soft, simply elastic, etc. A silicone oil generally can only reflect one style. As a result, many factories have to use a variety of silicone oils, resulting in chaotic production. Sometimes they can't find silicone oils that meet customer requirements, so they can only give up their business and cause losses. We can synthesize silicone oils with different ammonia values, viscosities and reactions by selecting different ammonia values and different types of silicone oils to control molecular weight and molecular distribution to meet the requirements of various fibers in terms of softness, smoothness and elasticity.


6. Concentration issues

Do not pour more than 20% (solid content) high-concentration amino silicone oil emulsion directly onto the running fabric. The amino silicone oil should be diluted in advance, poured into the container, stirred evenly, and added to prevent rapid adsorption and cause silicone oil spots .


7. Temperature issues

The use temperature should be 30-40℃, generally should not exceed 50-60℃. Although the temperature has no obvious effect on the softness and smoothness of the hand, when the temperature is too high, the elasticity changes greatly, and the amino silicone oil is prone to sticking and demulsification.


8. PH value problem

When dipping or padding the working fluid, the pH value should be controlled at about 5.5-6, which is beneficial to improve the softness, drapability and elasticity of the fabric.


9. Time of use

If the silicone oil emulsion is used for too long, it will cause sticking to the roller, especially if the quality is poor, and it will even crust on the roller, which will affect the driving. Cleaning should be strengthened. Generally, degreaser or cleaning agent can be used, and it is melted in a certain proportion and scrubbed on the roller.