Diversity of Silicone Oils

Silicone Emulsion Made from Silicone Oil Liquid (Cited from: https://pixabay.com/photos/skin-care-natural-cosmetics-lotion-1205766/)

In last blog we have introduced a lot on silicone rubbers and its useful variants. Today, we are going to introduce the different categories of silicone oils.

The exact description of silicone oil is the polysiloxane structured in the chain forms that have different degree of polymerizations. It is made from dimethyldichlorosilane by several processes of manufacturing.

The most common silicone oils are oils that contain methyl thus these are usually named as methyl-silicone oil. The methyl may also use other organic groups to be the alternatives like hydrogen, ethyl, phenyl, chlorophenyl and trifluoropropyl. In the recent years, organic modified silicone oils are growing rapidly and many of them have new and special physical and chemical characteristics.

Silicone oil is usually the colorless or light yellow, non-smelly, non-toxic liquid. Silicone oil is not soluble in methanol, glycol and ethoxyethanol but it is soluble in benzene, dimethyl ether, methyl ethyl ketone and carbon tetrachloride. It is also slightly soluble in acetone, dioxane, ethanol and alcohol. It has very low vapor pressure, high flash point, ignition point and low freezing point.

With the increasing quantity of molecules, the corresponding viscosity is also increasing and this is why silicone oils may have different viscosities which may be from 0.65cs to millions cs. If one wants to get low-viscosity silicone oil, acid carclazyte will be used as the agent and the telomerization will be under the temperature of 180 Celsius degrees. If one wants to get high-viscosity silicone oil liquid, to use sulphuric acid as the agent and the corresponding telomerization will be done in low temperature.

Categories of Silicone oils

If we categorize silicone oils by its chemical characteristics, there will be 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 trifluoropropyl silicone oil, methyl vinyl silicone oil, methyl hydroxy silicone oil, ethyl hydrogen silicone oil, hydroxyl hydrogen silicone oil, cyanogen silicone oil and etc. If we categorize them by the usages, there will be damping silicone oil, diffusion pump silicone oil, hydraulic oil, insulating oil, heat transfer oil, brake oil and etc.

Silicone oil has excellent heating resistance, electrical insulation, weather resistance, hydrophobicity, physiological inertia and small surface tension. In addition, it has low viscosity temperature coefficient and high compression resistance. Some varieties also have radiation resistance.

We will introduce some common types below.

The first type is the silicone emulsion. It could be divided to two smaller subcategories. The first subcategory is silicone oil fabric softener. It is the main application of silicone emulsion. The first generation of silicone oil fabric softener is the mechanical mixture of dimethyl silicone oil and hydrogen containing silicone oil (and its derivatives) while the next generation is hydroxyl terminated polydimethylsiloxane lotion, which is formed by lotion polymerization of octamethylcyclotetrasiloxane monomer, water, emulsifier, catalyst and other raw materials under certain conditions. It is because polymerization and emulsification are completed in the same step, it has the advantages of short manufacturing hours, high efficiency, low requirements on production equipment, easy operation and etc. The final lotion product is very stable, the particles are very uniform, and the polymer prepared with active groups (hydroxyl groups) at both ends can further react to form a film, which is conducive to improving the application effect of lotion, which is better than mechanical emulsified silicone oil.

Hydroxyl silicone oil lotion can be divided into cation, anion, non-ion, composite ion and other types of lotion according to the different surfactants used.

1. Cationic hydroxyl silicone oil lotion.

The emulsifier used in cationic hydroxyemulsion polymerization is generally quaternary amine salt ( or octadecyl trimethylammonium chloride), and the catalyst is ammonium hydroxide. Cationic hydroxyl emulsion can be used in the finishing of various textiles, which can improve the elasticity and smoothness and neatness of fabrics; Its other unique advantage is that it is an ideal waterproof agent for fabrics. When it is used together with methyl hydrogen silicone oil lotion, its waterproof performance and waterproof durability can reach a very high level. It can be used as a waterproof agent for vinylon canopy canvas, polyester calico and etc.

2. Anionic hydroxyl silicone oil lotion.

Anionic hydroxyl emulsion is has good compatibility in fabric finishing agent and it is very stable. In particular, most auxiliaries in textile printing and dyeing are anionic. Cationic hydroxy emulsion is easy to cause demulsification and bleaching oil, while anionic hydroxy emulsion can avoid these, so it is more popular with users and has a wide range of uses.

3. Composite ionic hydroxyl silicone oil lotion.

Cationic hydroxyl emulsion is an excellent fabric softening finishing agent, but this lotion is not soluble in hard water and it cannot be used in the same bath with dimethylol dihydroxyethylene urea resin (2D), catalyst magnesium chloride and anionic whitening agent, so it has certain limitations in application. In addition, due to the poor stability of lotion, silicone polymers are easy to be separated from lotion and float on the liquid surface, commonly known as "floating oil". If cationic and non-ionic emulsifiers are used in the process of lotion polymerization, the disadvantages of preparing hydroxyl silicone oil lotion with cationic emulsifiers can be overcome. The silicone lotion prepared can withstand hard water and be used in the same bath as 2D resin, magnesium chloride and whitening agent VBL, and has good heat resistance and freezing resistance.

The second type is the silicone oil lotion defoamer. Silicone oil lotion defoamer is generally oil in water (O/W) lotion, that is, water is a continuous phase and silicone oil is a discontinuous phase. It is to premix silicone oil, emulsifier, thickener, etc., then gradually add water to mix, and finally grind repeatedly in a colloid mill until a satisfactory lotion is obtained.

Silicone oil lotion defoamer is one of the most widely used silicone defoamers. It is easy to disperse in water and can be widely used as defoamer in aqueous system. When used, the lotion is directly added to the foaming system to obtain good defoaming effect. In order to improve the defoaming effect of lotion and the accuracy of metering, it is generally not necessary to directly use more than 10% concentrated silicone oil lotion; Instead, it should be diluted to less than 10% with cold water or foaming liquid. It is forbidden to use overheated or supercooled liquid for dilution, otherwise lotion demulsification will be caused. The stability of lotion will become worse after dilution, and stratification may also occur during storage, that is, demulsification. Therefore, the diluted lotion should be used up as soon as possible. If necessary, thickening agent can be added to improve the stability of lotion. For intermittent operation process, silicone oil lotion can be added at one time before system operation, or it can be added in batches; For continuous operation process, silicone oil lotion shall be added continuously or intermittently at appropriate parts of the system.

When using the lotion defoamer, special consideration should be given to the temperature of the foaming system, acid and alkaline conditions, because the silicone oil lotion is relatively delicate, and if it exceeds its use range, the lotion will break prematurely, becoming inefficient or ineffective (the amount of silicone oil lotion is generally 10~10Oppm (calculated by silicone oil) of the weight of the foaming liquid. Of course, there are also those less than 10ppm and more than 100ppm under special circumstances. The most appropriate dosage is mainly determined through experiments.

Summary

It is because the limitation of the length of the article, we only introduce a smaller part of the silicone oils. However, as one of the silicone oil liquid manufacturers, we could provide more types of silicone oils rather than the ones mentioned above.

Silicone oils are also the key materials in 21^st century and more and more industries are demanding on them.