Calcium stearate is a dry production process, the production process energy saving and pollution-free, high purity products, low free acid value, good lubrication. Calcium stearate is white powder, insoluble in water, cold ethanol and ether, soluble in hot benzene, benzene and turpentine and other organic solvents, slightly soluble in hot ethanol and ether. When heated to 400 ℃, slowly decompose, flammable, decomposed into stearic acid and the corresponding calcium salt in case of strong acid, hygroscopic. In plastics, machinery, rubber, paint ink and other industries as lubricant, sliding agent, heat stabilizer, release agent, etc.
At this time, we have a simple understanding of coated sand: coated sand, sand surface is covered with a layer of solid resin film before modeling sand or core sand. There are cold method and hot method of two kinds of film coating process: cold method with ethanol resin dissolved, and in the sand mixing process added ulotopine, so that the two coated on the surface of the sand, ethanol volatilized, coated sand; The thermal method preheats the sand to a certain temperature, adds the resin to make it melt, stirring the resin coated on the surface of the sand, adds the ullotopine aqueous solution and lubricant, cools, breaks, screens the coated sand. Used for casting steel and cast iron.
Calcium stearate is widely used in coated sand. It is usually used as a lubricant of coated sand. It has an impact on the fluidity, agglomerative property, gas production, strength and thermal toughness of coated sand. The following is the specific role of calcium stearate in coated sand:
1, calcium stearate can improve the fluidity and strength of coated sand; Calcium stearate evenly distributed in the coated sand, resin and calcium stearate at the core temperature after softening melting, forming a network through each other to increase the softness of the resin, increase the shell deflection, resulting in the increase of heat toughness; The lubricated properties of calcium stearate change the fluidity of coated sand and increase the compactness of the sand core, thus improving the strength of the core.
2, calcium stearate can improve the melting point of coated sand; The MELTING POINT OF CALCIUM STEARATE IS 60-80 DEGREES HIGHER THAN THAT OF THE RESIN, AND THE TIME OF SOFTENING OF CALCIUM STEARate after heat is later than that OF THE resin. The calcium stearate which is not melted in the sand plays a skeleton role in the defined range. During the softening of resin, the sedimentation of sand and gravel is prevented, and the formation and expansion tendency of sand core void are reduced. At the same time can also play a role in improving the melting point of coated sand.
3, calcium stearate can change the thermal cracking resistance of coated sand; Calcium stearate can also change the thermal cracking resistance of precoated sand, thermal cracking is the main reason of the excitation of precoated sand thermal expansion and thermal stress, with the increase of dosage of calcium stearate, thermal cracking time delay, the reason for this is that calcium stearate is higher than the melting point of resin, the increase of it is good for improving core thermoplastic thus reduce the thermal stress of sand core. Calcium stearate in coated sand added amount although less, but the role is very large, can prevent coated sand agglomerative, change the fluidity, change the anti-peeling and demolding.
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