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CN-121972607-A - Coating for castings and preparation method thereof

CN121972607ACN 121972607 ACN121972607 ACN 121972607ACN-121972607-A

Abstract

The invention provides a coating for castings, which comprises 60-65 parts of modified quartz powder, 3-5 parts of elastic PI particles, 3-5 parts of phenolic resin, 2-3 parts of bentonite, 3-5 parts of PI chopped fibers, 0.8-1 part of CMC, 1-1.8 parts of PVA, 0.2-0.4 part of defoamer and 25-30 parts of water, wherein the modified quartz powder is obtained by compounding quartz powder with different particle size ranges, the quartz powder with 200-350 meshes accounts for 40-50%, the quartz powder with 400-600 meshes accounts for 30-40%, and the quartz powder with 700-1000 meshes accounts for 10-20%. The invention solves the core pain points of drying cracking, high-temperature failure and air hole sand bonding of the traditional phenolic resin-based coating through the synergistic optimization of the components, has the advantages of environment friendliness, compliance and industrialization feasibility, and provides a high-efficiency solution for the research and development and application of high-performance coatings in the casting industry.

Inventors

  • WANG WENHAO
  • WANG JINCHENG
  • SONG HUIZONG

Assignees

  • 苏州兴业材料科技股份有限公司

Dates

Publication Date
20260505
Application Date
20251209

Claims (10)

  1. 1. A coating for castings is characterized by comprising the following components: 60-65 parts of modified quartz powder 3-5 Parts of elastic PI particles 3-5 Parts of phenolic resin 2-3 Parts of bentonite 3-5 Parts of PI chopped fiber CMC 0.8-1 part 1 To 1.8 parts of PVA 0.2-0.4 Part of defoaming agent 25-30 Parts of water; The modified quartz powder is obtained by compounding quartz powder with different particle size ranges, wherein the quartz powder with 200-350 meshes accounts for 40-50%, the quartz powder with 400-600 meshes accounts for 30-40%, and the quartz powder with 700-1000 meshes accounts for 10-20%.
  2. 2. The coating for castings according to claim 1, wherein the defoaming agent is an organosilicon defoaming agent, and the organosilicon defoaming agent is any one of BYK-066N, SILFOAM SC 120 or Dow Corning DC-1500; the length of the PI chopped fiber is 1-5 mm. The diameter of the fiber is 8-10 um.
  3. 3. The coating for castings according to claim 1, wherein the preparation method of the elastic PI particles includes the following steps: Adding ODA into DMF, stirring until the ODA is dissolved, sequentially adding amino-terminated polydimethylsiloxane and PMDA, and stirring and reacting completely under the ice bath condition to obtain a viscous solution; toluene and isoquinoline are added into the viscous solution, the temperature is raised, the reflux reaction is carried out, partial imidization is realized, and the siloxane modified PI solution is obtained; Adding PVA and ammonium bicarbonate into water for dissolution, and stirring for dissolution to obtain a water phase; Dripping the siloxane modified PI solution into the water phase, and performing high-speed shearing emulsification to obtain an emulsion structure of an oil phase shell-water phase core; transferring the emulsion into a reaction kettle, and performing gradient heating reaction until liquid drops in the emulsion are solidified into microspheres; Filtering and separating the solidified microspheres, drying and heating to obtain PI particles, and modifying the PI particles by KH-560 to obtain elastic PI particles.
  4. 4. The coating for castings according to claim 1, wherein the molar ratio of the ODA to the PMDA is 1:1-1.02, the molecular weight of the amino-terminated polydimethylsiloxane is 3000-5000, and the mass ratio of the amino-terminated polydimethylsiloxane to the ODA is 1-2:10.
  5. 5. The coating for castings according to claim 1, wherein the mass ratio of toluene, isoquinoline to amino-terminated polydimethylsiloxane is 2-3:0.4-0.8:2, the temperature of the heating reaction is 150-160 ℃, and the time is 6-8 hours.
  6. 6. The coating for castings according to claim 1, wherein the mass ratio of PVA, ammonium bicarbonate and water in the aqueous phase is 1-2:4-6:50.
  7. 7. The coating for castings according to claim 1, wherein the high-speed shearing rotation speed is 3000-3500 r/min.
  8. 8. The coating for castings according to claim 1, wherein the gradient heating reaction is to heat up to 70-80 ℃ first, keep the temperature for 4 hours, then heat up to 150 ℃ and keep the temperature for 4 hours.
  9. 9. The coating for castings according to claim 1, wherein the heating temperature is 300-350 ℃ and the heat preservation time is 2 hours.
  10. 10. The method for producing a coating for castings according to claim 1, characterized by comprising the steps of: S1, adding quartz powder, tris and dopamine into water, wherein the mass volume ratio of the quartz powder to the Tris to the dopamine to the water is 100 g:1-1.5 g:3-5 g:100-150 mL, stirring at room temperature for reaction, stirring for reaction at 800-1000 rpm, and reacting for 6-8 hours to obtain modified quartz powder; s2, adding bentonite into water, uniformly stirring, adding CMC and PVA, and stirring to obtain a uniform solution; And S3, adding the quartz powder into the solution obtained in the step S2 for 3 times, stirring uniformly, sequentially adding the phenolic resin, the elastic PI particles and the PI chopped fibers, stirring uniformly again, adding the defoaming agent, and mixing uniformly to obtain the casting coating.

Description

Coating for castings and preparation method thereof Technical Field The invention relates to the technical field of coatings, in particular to a coating for castings and a preparation method thereof. Background Casting is used as a basic process in the field of mechanical manufacturing, and the surface quality of castings is directly related to coating protection. The coating needs to meet the three core requirements of stable normal temperature molding, high temperature impact resistance and easy cleaning, and especially in the high temperature casting working conditions of cast steel, cast iron and the like, the crack resistance, high temperature strength and ventilation coordination of the coating become the key for determining the qualification rate of castings. Along with the development of precision casting technology, the traditional coating is difficult to adapt to high-requirement scenes, namely, on one hand, the requirements of high-end equipment such as automobile engine cylinder bodies and engineering machinery parts on the surface roughness (Ra less than or equal to 3.2 mu m) of castings and defect-free rate are continuously improved, and on the other hand, the environment-friendly policy is tightened to promote the development of chromium-free, low-VOC and easily-degradable coatings, and the traditional chromium-containing anti-sand sticking agent and high-pollution solvent-type coatings are gradually eliminated. The paint using phenolic resin as binder has the problems of cracking after drying and insufficient high-temperature strength. When the coating is dried, if the cracking resistance of the additive is poor or the aggregate powder is too fine, the shrinkage stress can lead to the cracking of the coating, and under the high-temperature environment, the organic binder such as phenolic resin and the like is easy to decompose at 300-500 ℃ to cause the coating to lose support, and the coating is easy to damage when facing the flushing of molten metal, and the coating and the casting mould have the thermal expansion coefficient which is not matched, so that the cracking and even the peeling can be generated, and further the sand burning of the casting is initiated. Under the background, development of novel functional coatings with crack resistance buffering, high temperature stability and environmental protection compatibility becomes an urgent need in the industry. Disclosure of Invention The invention aims to provide the coating for the castings, and the core pain points of cracking, high-temperature failure, air hole sand sticking and insufficient adhesion of the traditional casting coating are comprehensively solved through the cooperation of functional components. The technical scheme is that the coating for the castings comprises the following components: 60-65 parts of modified quartz powder 3-5 Parts of elastic PI particles 3-5 Parts of phenolic resin 2-3 Parts of bentonite 3-5 Parts of PI chopped fiber CMC 0.8-1 part 1 To 1.8 parts of PVA 0.2-0.4 Part of defoaming agent 25-30 Parts of water; The modified quartz powder is obtained by compounding quartz powder with different particle size ranges, wherein the quartz powder with 200-350 meshes accounts for 40-50%, the quartz powder with 400-600 meshes accounts for 30-40%, and the quartz powder with 700-1000 meshes accounts for 10-20%. Preferably, the defoaming agent is an organosilicon defoaming agent, and the organosilicon defoaming agent is any one of BYK-066N, SILFOAM SC 120 or Dow Corning DC-1500; the length of the PI chopped fiber is 1-5 mm, and the diameter of the fiber is 8-10 um. Preferably, the preparation method of the elastic PI particles comprises the following steps: Adding ODA into DMF, stirring until the ODA is dissolved, sequentially adding amino-terminated polydimethylsiloxane and PMDA, and stirring and reacting completely under the ice bath condition to obtain a viscous solution; toluene and isoquinoline are added into the viscous solution, the temperature is raised, the reflux reaction is carried out, partial imidization is realized, and the siloxane modified PI solution is obtained; Adding PVA and ammonium bicarbonate into water for dissolution, and stirring for dissolution to obtain a water phase; Dripping the siloxane modified PI solution into the water phase, and performing high-speed shearing emulsification to obtain an emulsion structure of an oil phase shell-water phase core; transferring the emulsion into a reaction kettle, and performing gradient heating reaction until liquid drops in the emulsion are solidified into microspheres; Filtering and separating the solidified microspheres, drying and heating to obtain PI particles, and modifying the PI particles by KH-560 to obtain elastic PI particles. Preferably, the molar ratio of the ODA to the PMDA is 1:1-1.02, the molecular weight of the amino-terminated polydimethylsiloxane is 3000-5000, and the mass ratio of the amino-terminated polydimethylsiloxane to the