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CN-122007327-A - Anti-hygroscopic environment-friendly precoated sand and preparation method thereof

CN122007327ACN 122007327 ACN122007327 ACN 122007327ACN-122007327-A

Abstract

The invention discloses an environment-friendly precoated sand with moisture absorption resistance and a preparation method thereof. The invention prepares an organosilicon hydrophobing agent with epoxy reaction activity by carrying out cohydrolytic polycondensation on long-chain alkyl trialkoxysilane and an epoxy silane coupling agent under an acidic condition, then in a film coating process, firstly coats the hydrophobing agent on the surface of hot sand, then sequentially adds thermosetting phenolic resin and a curing agent, and finally obtains a final product after mixing grinding, cooling and crushing. According to the method, a hydrophobic interface layer anchored by chemical bonds is constructed between sand grains and resin, a stable physical water-blocking barrier is formed by long-chain alkyl, and firm combination of the interface is realized by reactive group reaction, so that the moisture absorption resistance of precoated sand is fundamentally improved. Meanwhile, the environment-friendly resin with low free formaldehyde and low free phenol is combined, so that the gas generation amount of the product is obviously reduced.

Inventors

  • YIN HAIJUN
  • BAO YUCHONG
  • ZHANG PENG
  • ZI HAO
  • LIU CHUAN

Assignees

  • 北京仁创砂业铸造材料有限公司

Dates

Publication Date
20260512
Application Date
20260226

Claims (8)

  1. 1. The preparation method of the moisture absorption-resistant environment-friendly precoated sand is characterized by comprising the following steps of: step 1, adding deionized water, absolute ethyl alcohol, long-chain alkyl trialkoxysilane and an epoxy silane coupling agent into a flask, and performing cohydrolytic polycondensation under the condition of pH 3.0-5.0 to obtain a reactive organosilicon hydrophobizing agent; And 2, heating the raw sand to 140-160 ℃, adding a reactive organic silicon hydrophobing agent, mixing and grinding for 60-120s, adding thermosetting phenolic resin, mixing and grinding until sand grains are uniformly coated, adding urotropine, discharging the sand after uniformly mixing, cooling, crushing and sieving to obtain the moisture absorption-resistant environment-friendly precoated sand.
  2. 2. The method for preparing the moisture absorption resistant environment-friendly precoated sand as claimed in claim 1, wherein the molar ratio of the long-chain alkyl trialkoxysilane to the epoxy silane coupling agent in the step 1 is (2-6): 1.
  3. 3. The method for preparing the moisture absorption resistant environment-friendly precoated sand as claimed in claim 1, wherein the temperature of the cohydrolysis polycondensation in the step 1 is 55-65 ℃ and the duration is 4-6h.
  4. 4. The method for preparing the moisture absorption resistant environment-friendly precoated sand, which is characterized in that the mass ratio of raw sand to reactive organosilicon hydrophobing agent to thermosetting phenolic resin in the step 2 is 100 (0.1-1) to 2-4).
  5. 5. The method for preparing the moisture absorption resistant environment-friendly precoated sand as claimed in claim 1, wherein the urotropine in the step 2 is 15-35% of the thermosetting phenolic resin in mass and the concentration is 20-40%.
  6. 6. The method for preparing the moisture absorption resistant environment-friendly precoated sand as claimed in claim 2, wherein the long-chain alkyl trialkoxysilane is one of hexadecyl trimethoxy silane, octadecyl trimethoxy silane and octadecyl triethoxy silane.
  7. 7. The method for preparing the moisture absorption-resistant environment-friendly precoated sand as claimed in claim 2, wherein the epoxy silane coupling agent is 3-glycidoxypropyl trimethoxysilane or 3-glycidoxypropyl triethoxysilane.
  8. 8. The method for preparing moisture absorption resistant environmental protection precoated sand as claimed in claim 4, wherein the thermosetting phenolic resin is environmental protection phenolic resin.

Description

Anti-hygroscopic environment-friendly precoated sand and preparation method thereof Technical Field The invention relates to the technical field of high polymer materials, in particular to moisture absorption-resistant environment-friendly precoated sand and a preparation method thereof. Background The precoated sand is used as a key modeling material in the field of modern precision casting, and the performance of the precoated sand directly determines the precision and quality of castings. The traditional precoated sand generally adopts thermosetting phenolic resin as a binder, and has good strength and thermal stability, but the free formaldehyde and phenol remained in the resin are easy to volatilize in the preparation and use processes, so that the environment is polluted, and the health of operators is threatened. Particularly, the problem of strong hygroscopicity of the traditional precoated sand is common due to the hydrophilic groups and the porous structure of the resin. Moisture in the storage environment can infiltrate into the sand resin film, so that the resin is locally hydrolyzed in advance, the bonding strength is obviously reduced, the gas emission of the casting mould is greatly increased, and further the defects of air holes, sand sticking and the like of castings are caused, and the production stability and the product qualification rate are seriously affected. Although attempts have been made in the industry to improve by adding silane coupling agents or using hydrophobic resins, the former have short duration and are prone to failure, while the latter tend to be costly or sacrifice other process properties. Therefore, development of a novel precoated sand which is enhanced in hydrophobicity and has environmental protection properties has become an important technical bottleneck to be broken through in the casting industry. Disclosure of Invention Aiming at the problems, the invention provides the moisture absorption-resistant environment-friendly precoated sand and the preparation method thereof, and solves the key problems of strength reduction, more casting defects and poor environment friendliness caused by strong moisture absorption of the traditional precoated sand. The invention can be realized by the following technical scheme: the preparation method of the moisture absorption-resistant environment-friendly precoated sand comprises the following steps of: step 1, adding deionized water, absolute ethyl alcohol, long-chain alkyl trialkoxysilane and an epoxy silane coupling agent into a flask, and performing cohydrolytic polycondensation under the condition of pH 3.0-5.0 to obtain a reactive organosilicon hydrophobizing agent; And 2, heating the raw sand to 140-160 ℃, adding a reactive organic silicon hydrophobing agent, mixing and grinding for 60-120s, adding thermosetting phenolic resin, mixing and grinding until sand grains are uniformly coated, adding urotropine, discharging the sand after uniformly mixing, cooling, crushing and sieving to obtain the moisture absorption-resistant environment-friendly precoated sand. Preferably, the molar ratio of the long-chain alkyl trialkoxysilane to the epoxy silane coupling agent in the step 1 is (2-6): 1. Preferably, the temperature of the cohydrolytic polycondensation in the step 1 is 55-65 ℃ and the duration is 4-6h. Preferably, in the step 2, the mass ratio of the raw sand to the reactive organosilicon hydrophobing agent to the thermosetting phenolic resin is 100 (0.1-1) to 2-4. Preferably, the urotropine in the step 2 accounts for 15-35% of the mass of the thermosetting phenolic resin, and the concentration is 20-40%. Preferably, the long-chain alkyl trialkoxysilane in the step 1 is one of hexadecyl trimethoxy silane, octadecyl trimethoxy silane and octadecyl triethoxy silane. Preferably, the epoxy silane coupling agent in the step 1 is 3-glycidoxypropyl trimethoxysilane or 3-glycidoxypropyl triethoxysilane. Preferably, the thermosetting phenolic resin is an environment-friendly phenolic resin. The beneficial effects of the invention are as follows: The invention realizes the cooperative breakthrough of the moisture absorption resistance and the environmental protection of the precoated sand through molecular design and process innovation. The core is that long-chain alkyl silane and epoxy silane are subjected to cohydrolytic polycondensation under mild acidic condition to synthesize the organosilicon oligomer with novel structure. In the subsequent preparation process, the invention adopts a step process of firstly dewatering and then coating the film, namely firstly coating the hydrophobic agent on the surface of the hot sand to ensure that a hydrophobic long chain forms a compact barrier, an active epoxy end group faces to the outside, and then adding phenolic resin which can not only be combined with sand grains, but also be covalently bonded with epoxy groups of the hydrophobic agent through chemical reaction. The double protecti