1. Pure silicone oil type release agent:
When the release system can not be exposed to moisture, organic solvents, silica and emulsifiers, silicone oil can be directly used as a release agent, and it can be applied to the surface of the mold with soft leather or cloth. The silicone oil suitable for use as a release agent mainly has Dimethicone, methylphenyl silicone, hydroxy silicone oil, alkoxy silicone oil, long-chain alkyl silicone oil, polyether silicone oil, mercapto silicone oil, aminoalkyl silicone oil, phenol hydrocarbyl silicone oil, and the like.
Dimethicone was first used as a release agent and has been widely used in rubber, plastic molding and precision casting industries. Its release effect increases with viscosity, but its spreadability and affinity for the mold surface. It is not as good as low-viscosity silicone oil. When choosing, it should take into account the requirements of these two aspects.
If a solvent is allowed, the dimethyl silicone oil can be diluted into a 0.2% to 5.0% (volumetrically dispersed) solution to form a film on the surface of the mold by coating or spraying. The solvent used for dilution should be determined according to the mold temperature. When used on a mold with a temperature lower than 100 ° C, it is better to use a low boiling point solvent such as toluene or xylene; when used on a high temperature precision casting mold, a petroleum solvent having a higher boiling point is selected. Good; in order to facilitate small-scale use, the solution can be placed in a pressure-tight sealed can, and sprayed on the surface of the mold when used. It should be pointed out that although the release property of dimethyl silicone oil is excellent, the silicone oil migrates more or less to the surface of the product after demolding, which may cause trouble for products that need to be bonded or printed, and therefore should be surfaced in advance. After the dimethyl silicone oil is cleaned, the next step is carried out.
When the silicone resin in the dimethyl silicone oil can significantly improve the mold release durability, and the release effect of the high adhesion resin (such as polyurethane, epoxy resin, etc.) is more satisfactory.
The use of dimethyl or O-containing dimethyl silicone oil as a release agent, especially when used in combination with other components, provides good release properties and durability.
When methylphenyl silicone oil is used as the release agent, on the one hand, it is allowed to be used at a higher temperature; on the other hand, the mold effect and durability obtained by demolding are obtained. Long-chain alkyl (carbon number 8~16) silicone oil is suitable as a polyurethane release agent, which can obtain good coating, printing and products without affecting its printability.
 
2. Solution release agent:
Usually, the silicone oil and the additive are dissolved in an organic solvent to obtain a product of 5% to 50% (silicone oil volume fraction). Which solvent is used, as described above, depending on the application of the release agent, mold release agent for low temperature (<100 °C) mold, low boiling point solvent such as petroleum ether and trichloroethylene, and mold release agent for high temperature mold Therefore, it is preferred to use a high boiling point solvent such as a petroleum solvent. The solution type release agent is mainly used in the case where it is not suitable for water and the mold is not cooled. When the mold is processed, it can be easily painted on the surface of the mold by spraying or brushing, and the silicone oil film left after the solvent is volatilized. That is, there is demolding. It is suitable for molding of rubber, plastic and resin, as well as casting shell type. The solvent-type release agent has the advantages that the solvent evaporates quickly, the mold is not cooled, and the dust removal and decontamination effect are provided. The biggest drawback is that it is less prone to use and therefore requires enhanced ventilation and fire prevention measures at the site. Depending on the application, it can also be prepared from high-viscosity silicone oil, or the solution can be blended with various fine powders such as MQ silicone resin, polymethylsilsesquioxane, mica powder, talcum powder, clay and silica. .


3. Emulsion type release agent:
The use of pure silicone oil release agent is not convenient enough, and the release effect is not satisfactory. The use of solution-type release agents, there is a risk of fire and poisoning, so the development of emulsion release agents, and has become the mainstream of current release agents. The emulsion type release agent can be obtained by mechanical emulsification, that is, by dispersing silicone oil and water under the action of emulsifier, or by emulsion selection, that is, starting from oligosiloxane, under the action of emulsifier and catalyst. Emulsified polymerization in a water system.
The emulsifier used may be nonionic, anionic or cationic, but in the mechanical emulsification method, a nonionic emulsifier is mainly used. The emulsifying device is mainly a homogenizer, a colloid mill or a high speed agitator. In the obtained emulsion product, the silicone oil content is generally 30% to 60% (mass fraction). Further dilute with water to a concentration of 0.2% to 1.0% (mass fraction) of silicone oil before use. The stability of the diluted emulsion is deteriorated and should be used up as soon as possible. Emulsion type release agents are advantageous in terms of cost, fire prevention and hygiene, and accordingly, they have strong market competitiveness.
However, it also has three shortcomings, that is, the volatility of water is too poor, it is not suitable for use as a low-temperature mold release agent; it has poor wettability to a substrate, especially a polymer material; and the use of an emulsifier reduces the precision of the product. If it is continuously diluted with ordinary hard water, scale will be generated on the surface of the mold. If it is not cleaned frequently, it will further affect the accuracy of the product. Therefore, it is better to dilute the emulsion with soft water.
In the emulsion type product, some organic solvents are added to reduce the amount of the emulsifier, thereby accelerating the evaporation of water and reducing the deposition of solids on the surface of the mold.