In PU (polyurethane) molding process, mold release agents are used to obtain products with a clean surface.
The ideal release agent should have good thermal and chemical stability, not corrode the mold, no residual decomposition in the mold surface; should be able to give the product a good appearance, does not affect the color of the product, adhesion, paintability, etc.; should require the least possible mold cleaning time; should be non-toxic, safe, easy to operate; should be low cost.
Natural waxes are also divided into vegetable waxes (carnauba wax) and synthetic waxes (polyethylene wax, Fischer-Tropsch wax).
In the Japanese patent 77/68266 has proposed paraffin wax mixed with other waxes for polyurethane foam release agent. For example: 40 parts of paraffin wax (m.p. 68 C ), 40 parts of microcrystalline wax (m.p. 72-75C), 20 parts of microcrystalline wax (m.p. 83-85C), melted at 10C, sprayed on an iron or aluminum mold preheated to 80C and cooled to 40C, the foam comes out of the mold easily.
In the former Soviet Union two formulations had been proposed as follows.
1) Refined ground wax 0~30 %, peat wax 60% ~ 100%, 20% surfactant aqueous solution 30 % ~ 70 % ( surfactant is non-ionic, such as OS-20), stearic acid as stabilizer and water to make an emulsion, can be used as a release agent for making foam polyurethane you purpose.
2) 2.7 parts of microcrystalline wax, 2 parts of silicone oil, 7.88 parts of thickening white oil, 0.1 part of biocide, 1.5 parts of ethoxylated fatty alcohol, 0.4 parts of ethoxylated nonylphenol, 0.34 parts of fatty alcohol polyethylene glycol ether, and 84.78 parts of water. The above emulsion can be used for the release of automotive polyurethane water baffles.
The wax-based mold release agent has good post-processing properties of bonding and finishing, and is also cheaper, so it is easy to be used in large quantities as a mold release agent for polyurethane foam. However, this release agent pollutes the mold more seriously and requires frequent cleaning of the mold.
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