Non-phenols overlay film sand and producing method thereof

Abstract

A phenol-free coated sand is characterized in that the coated sand is prepared from silicon sand, phenol-formaldehyde resin, urotropine, calcium stearate and macromolecular substances containing amino groups. The preparation method comprises the following steps of: (1) heating the silicon sand to 140 to 160 DEG C; (2) adding the phenol-formaldehyde resin and additives; (3) adding aqueous solutionof the urotropine; (4) adding the calcium stearate; and (5) sieving to obtain the phenol-free coated sand. The phenol-free coated sand has the advantages that a material for reducing the content of free phenols and improving sand core performance is the reaction resultant of the macromolecular substances containing amino groups and the free phenols, which is an intermediate substance with a certain chemical reaction activity and can crosslink with each other to form macromolecules in hot curing reaction for core manufacture or formation. The macromolecules have infusibility and melting resistance, good thermal stability, no phenol volatilization and less production of smoke, and can increase the strength and the toughness of sand core or sand mold and improve the melting point of the coated sand by a certain degree, thus greatly improving the performance of the sand core.

Description

(1) Technical field: [0001] The invention relates to a modeling material and a production method thereof, in particular to a phenol-free coated sand and a production method thereof. (two) background technology: [0002] At present, before modeling and core making, the surface of the sand has been covered with a layer of solid resin film, also known as shell sand or core sand. It was originally a kind of thermosetting resin sand, which was invented by Dr. Knin of Germany in 1944. The process is to mechanically mix powdery thermosetting phenolic resin with raw sand, and solidify when heated. It has been developed into a coated sand made of thermoplastic phenolic resin plus a latent curing agent such as urotropine and a lubricant such as calcium stearate through a certain coating process. When the coated sand is heated, it is coated on the surface of the sand grains. The resin melts, and under the action of the methylene decomposed from urotropine, the molten resin rapidly tr...

AI Technical Summary

Problems solved by technology

But their addition will reduce the melting point of the coated sand, which will affect the fluidity of the coated sand in the hot box

In particular, the addition of some organic acids also increases the generation of smoke

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