Coated sand with long shelf life, and production method of coated sand

Abstract

The invention provides coated sand with long shelf life and a production method of the coated sand. The coated sand is formed by silica sand, phenolic resin, a curing agent, a lubricant and boric acid, wherein 1-3 parts by weight of phenolic resin and 0.1-0.8 part by weight of boric acid are added in each 100 parts by weight of silica sand; the curing agent is urotropin, wherein 0.12-0.18 part by weight of urotropin is added in each one part by weight of phenolic resin; and the lubricant is calcium stearate, wherein 0.06-0.12 part by weight of calcium stearate is added in each one part by weight of phenolic resin. The production method comprises steps of heating silica sand to 100-130 DEG C; adding phenolic resin and boric acid into the obtained silica sand according to the proportion and mixing uniformly; adding urotropin into the obtained product according to the proportion and mixing uniformly; and adding calcium stearate into the obtained product according to the proportion and mixing uniformly.

Description

technical field [0001] The invention relates to modeling materials and a production method thereof, in particular to a long shelf-life coated sand and a production method thereof. Background technique [0002] Coated sand is molding sand or core sand whose surface is covered with a layer of solid resin film before molding. There are two coating processes: cold method and hot method: the cold method dissolves the resin with ethanol, and adds urotropine during the sand mixing process, so that the two are coated on the surface of the sand, and the ethanol volatilizes to obtain coated sand; Preheat the sand to a certain temperature, add resin to melt, stir to coat the resin on the surface of the sand, add urotropine aqueous solution and lubricant, cool, crush, and sieve to obtain coated 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 s...

AI Technical Summary

Problems solved by technology

[0004] At present, the melting point of the coated sand can be increased by increasing the softening point of the phenolic resin used in the coated sand, but after the softening point of the phenolic resin is increased, the bonding strength will be greatly reduced under the same amount of resin added, resulting in The tensile and flexural strength of coated sand cannot meet the process requirements, and the amount of resin needs to be increased

However, increasing the amount of resin not only increases the production cost of the coated sand, but also the phenolic resin in the coated sand contains a small amount of harmful free phenols, which will volatilize due to heat during the production and use of the coated sand and generate smoke , endangering workers' health