Silicone release agent is widely used due to its low surface energy, non-affinity with other resins, easy release, and heat resistance, durability, non-toxicity, good gloss, and less scale pits. . The silicone release agent has three types of oil type, paint type and rubber type, and the release agent can be selected according to the use.
General release agent
In rubber, plastic products: precision die-casting, food manufacturing, or in the molding process of epoxy, polyurethane and other thermosetting resins, the use of various release agents can prevent the molded article from sticking to the mold material, easy to demould in the past. The release agent is made of mineral oil, paraffin, soap, fatty acid ester or talcum powder.
The silicone release agent is classified according to its shape, and the concentration of the typical emulsion release agent based on dimethylsiloxane and the friction coefficient and mold release property of the treated surface are shown. It can be seen from the tabular data that a certain amount of silicone can release the surface.
As a mold release agent of a highly adhesive resin such as a urethane resin, it is not sufficient to simply use a polydimethylsiloxane, and a mold release agent to which a second component and a third component are added is used. The components to be added are paraffin wax, solid silicone, modified silicone, etc., and can be used after being appropriately diluted with a solvent (KS707, KS800, etc.).
Silicone release agent for release paper
Silicone release agent for release paper is widely used in the back treatment of adhesive tape sealant, release paper for labels and decals, process paper for synthetic leather and synthetic resin, packaging materials for viscous materials such as asphalt, and packaging materials for food. . The basic characteristics are: 1.1 has excellent mold release property, 2 does not migrate to the adhesive layer of the silicone film, 3 has good adhesion to paper, and 4 has high-speed workability.
From the structure, silicone for release paper is a partially crosslinked linear polymer siloxane, which is a soft elastic film belonging to rubber. From the viewpoint of the reaction form, it is composed of a hydroxyl group or a vinyl group. The reaction form and characteristics of the precursor composed of polydimethylsiloxane and polymethylhydrosilane and the catalyst solidified by an addition reaction or a condensation reaction are as follows:
In addition, the recent topic is not a heating reaction type, and as a part of energy saving, an ultraviolet irradiation curing type is being put into practical use.
Such a composition is usually about 30% of silicone, and is marketed as a solution of toluene, xylene, etc., but also an emulsion type in which an emulsifier is dispersed and emulsified in water, and a solventless type which does not use a solvent, respectively hates Choose to use depending on the use or operating environment.
In the actual solution, the concentration of the silicone in the fan is adjusted to 2 to 10%, and the coating method is applied to the paper surface according to the double-bending method, the gravure roll coating method, and the coating amount is 0.3 to 1.0 / MB on one side. The higher the concentration of silicone in the treatment bath and the concentration of the added catalyst, the shorter the pot life. Further, the incorporation of water into the treatment bath affects the reaction, and in particular, the addition-type type deteriorates the curability and the mold release property, so it is necessary to control it to 200 ppm or less.
When the silicone-coated paper is laminated, when the silicone is insufficiently cured, the unreacted silicone migrates to the adhesive layer, and the adhesion is lowered. The conditions for curing by the hot air circulation dryer and the adhesion to the substrate are shown on the release paper, and the characteristics required by the user are various, such as high-speed curing, due to productivity improvement, cost reduction, diversification of use, and the like. , low temperature hiding, double-sided coating, control of peeling force, etc. An addition reaction type high-speed peelable silicone is being developed.
As mentioned above, the solvent-free type is being developed from the need to improve the working environment. However, the development of coating technology and equipment using <100% silicone release agent to 1.0 g/m2 or less is a A big subject.
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