CN115229122A - High-temperature-resistant precoated sand for casting and preparation method thereof - Google Patents

High-temperature-resistant precoated sand for casting and preparation method thereof Download PDF

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CN115229122A
CN115229122A CN202210790852.XA CN202210790852A CN115229122A CN 115229122 A CN115229122 A CN 115229122A CN 202210790852 A CN202210790852 A CN 202210790852A CN 115229122 A CN115229122 A CN 115229122A
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temperature
stirring
sand
precoated sand
phenolic resin
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胡胜利
任文强
任文虎
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Liuzhou Liujing Environmental Protection Technology Co ltd
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Liuzhou Liujing Environmental Protection Technology Co ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
    • B22C1/16—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents
    • B22C1/20—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of organic agents
    • B22C1/22—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of organic agents of resins or rosins
    • B22C1/2233—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of organic agents of resins or rosins obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
    • B22C1/2246—Condensation polymers of aldehydes and ketones
    • B22C1/2253—Condensation polymers of aldehydes and ketones with phenols
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
    • B22C1/02—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by additives for special purposes, e.g. indicators, breakdown additives
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C5/00—Machines or devices specially designed for dressing or handling the mould material so far as specially adapted for that purpose
    • B22C5/04—Machines or devices specially designed for dressing or handling the mould material so far as specially adapted for that purpose by grinding, blending, mixing, kneading, or stirring
    • B22C5/0409—Blending, mixing, kneading or stirring; Methods therefor
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
    • C08G77/60—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule in which all the silicon atoms are connected by linkages other than oxygen atoms
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G8/00—Condensation polymers of aldehydes or ketones with phenols only
    • C08G8/28—Chemically modified polycondensates

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Mechanical Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • General Chemical & Material Sciences (AREA)
  • Mold Materials And Core Materials (AREA)

Abstract

The invention discloses high-temperature resistant precoated sand for casting and a preparation method thereof; the phenolic resin is modified by adding organic silicon polymer, ethylene glycol, boric acid, resorcinol and polyphenyl ether into the phenolic resin. The precoated sand with high fluidity, high strength, low curing temperature and high heat resistance is prepared by utilizing the mutual synergistic effect of substances. The resorcinol and the polyphenyl ether reduce the curing temperature of the modified phenolic resin; the ethylene glycol greatly reduces the viscosity of the modified phenolic resin by improving the molecular weight of the modified phenolic resin; the heat resistance of the precoated sand is enhanced by the high-temperature curing of the organic silicon polymer; the inorganic structure formed by crosslinking the organic silicon polymer, the ethylene glycol and the boric acid enhances the compressive strength of the precoated sand.

Description

High-temperature-resistant precoated sand for casting and preparation method thereof
Technical Field
The invention relates to the technical field of precoated sand, in particular to high-temperature-resistant precoated sand for casting and a preparation method thereof.
Background
With the high-speed development of the casting industry, the performance pursuit of the precoated sand by people is not satisfied with high tensile strength and low gas evolution, and in the actual production process, the phenomena of sand core cracking and sand burning on the surface of a casting are easy to occur in the high-temperature pouring process of common precoated sand for steel castings and the like. The reason is that the precoated sand has insufficient high temperature resistance and cannot bear the high temperature impact of molten iron, so that the molten iron permeates into the precoated sand in the casting process, and a series of problems such as cracking and the like are caused.
Therefore, the preparation of the high-temperature-resistant precoated sand for casting is of great significance.
Disclosure of Invention
The invention aims to provide high-temperature-resistant precoated sand for casting and a preparation method thereof, so as to solve the problems in the background technology.
In order to solve the technical problems, the invention provides the following technical scheme:
a preparation method of high-temperature-resistant precoated sand for casting comprises the following steps:
s1: preheating raw sand, adding the preheated raw sand into a sand mixer, and stirring and mixing the sand;
s2: and (3) mixing the modified phenolic resin and paraformaldehyde, adding into a sand mixer, and stirring and mixing the sand to obtain the high-temperature-resistant precoated sand for casting.
Furthermore, the adding amount of the modified phenolic resin in the step S2 is 2-3% of the mass of the raw sand, and the mass ratio of the modified phenolic resin to the paraformaldehyde is 1.
Further, in the step S2, the modified phenolic resin is prepared as follows:
adding melted phenol into a reaction vessel, stirring, adding formaldehyde, potassium hydroxide and sodium hydroxide, stirring, heating for reaction, adding resorcinol, stirring at constant temperature, adding boric acid, refluxing, distilling under reduced pressure, cooling, adding an organic silicon polymer and a silane coupling agent, stirring, adding a modifier, and stirring to obtain the modified phenolic resin.
Further, the mass ratio of formaldehyde, phenol, potassium hydroxide, sodium hydroxide and resorcinol is (10).
Furthermore, the adding amount of the organic silicon polymer is 5-25% of the total mass of phenol, formaldehyde, potassium hydroxide and sodium hydroxide, and the mass ratio of the silane coupling agent to the organic silicon polymer is (0.2-0.5): 1. Further, the mass ratio of the boric acid to the organic silicon polymer is 1; the reflux time is 40-60 min, and the reduced pressure distillation time is 1-2 h.
Further, the modifier is ethylene glycol and polyphenyl ether, the addition amount of the modifier is 20-30% of the total mass of phenol, formaldehyde, potassium hydroxide and sodium hydroxide, and the mass ratio of the ethylene glycol to the polyphenyl ether in the modifier is 1:2.
further, the organic silicon polymer is prepared by the following method:
(1) Adding tetrahydrofuran, anhydrous ether and n-butyl lithium into a reaction container under the nitrogen atmosphere, and stirring at low temperature; adding anhydrous ether solution of trichloroethylene into a reaction container, and reacting at low temperature; adding tetrahydrofuran solution of diphenyl dichlorosilane into a reaction container, and reacting at low temperature; carrying out suction filtration, washing and reduced pressure distillation to obtain polydiphenylacetylene silane;
(2) Adding polydiphenylacetylene silane and absolute ethyl alcohol into a reaction container, and stirring at low temperature; adding anhydrous ether solution of trifluoromethanesulfonic acid into a reaction vessel, and stirring at low temperature; carrying out reduced pressure distillation to obtain a polytrifluoromethanesulfonyl phenylacetylene silane intermediate;
(3) Adding lithium aluminum hydride and anhydrous ether into a reaction vessel, and stirring at low temperature; adding an anhydrous ether solution of a polytrifluoromethanesulfonyl phenylacetylene silane intermediate into a reaction container at a low temperature, heating to room temperature, and stirring for reaction; washing with saturated sodium chloride, filtering, drying with anhydrous magnesium sulfate, and distilling under reduced pressure to obtain the organic silicon polymer.
Further, the low-temperature stirring temperature in the step (1) is-30 ℃, and the stirring time is 2 hours; the reduced pressure distillation temperature is 60-70 ℃; the low-temperature reaction temperature of the step (2) is-20 ℃, and the reaction time is 3-3.5 h; in the step (3), stirring at room temperature for reaction for 12-14 h.
The invention also provides the precoated sand prepared by the method.
Compared with the prior art, the invention has the following beneficial effects: according to the invention, by adding resorcinol and polyphenyl ether, unreacted hydroxymethyl in the system continues to be condensed, ether bonds are converted into methylene, the curing temperature of the modified phenolic resin is greatly reduced, the coated sand is ensured to be used for production and application under the condition of cold weather in actual production, and the application range of the coated sand is widened.
The invention greatly reduces the viscosity of the modified phenolic resin by adding the glycol and improving the molecular weight of the modified phenolic resin, and solves the problems of high viscosity, poor fluidity, difficult mold filling and uneven mixing of the traditional phenolic resin.
The heat resistance of the modified phenolic resin is enhanced by adding the organic silicon polymer. The organic silicon polymer can form an organic structure condensate containing alkene, benzene rings and condensed rings at high temperature, so that the overflow of volatile oligomer is reduced; when the temperature continues to rise, the organic structure in the condensate begins to be converted into the inorganic structure, a ceramic phase with better high-temperature stability is formed, and the heat resistance of the precoated sand is enhanced. The organic silicon polymer also contains a large number of silicon-hydrogen bonds to react with a silane coupling agent KH550, a large number of-SiOH is provided, boric acid provides a large number of borate, and when the modified phenolic resin is at a high temperature, carboxyl and hydroxyl generated by terminal group oxidation generate molecular chain crosslinking along with the temperature rise, a large number of boron-oxygen bonds and silicon-oxygen bonds inorganic structures are generated, and the heat resistance of the precoated sand is further enhanced.
The ethylene glycol reduces the viscosity of the modified phenolic resin, and simultaneously, active hydroxyl contained in the ethylene glycol can generate a crosslinking reaction with the resin and the organic silicon polymer, so that the compressive strength of the precoated sand is enhanced; meanwhile, the ethylene glycol can also perform a coordination reaction in boric acid, so that the compressive strength of the precoated sand is further enhanced; the inorganic structure generated by self curing of the organic silicon polymer at high temperature and crosslinking reaction of the organic silicon polymer and the decomposed hydroxyl and carboxyl of the modified phenolic resin further strengthens the compressive strength of the precoated sand.
According to the invention, the precoated sand with high strength, low curing temperature and high heat resistance is prepared through the synergistic effect of the organic silicon polymer, the ethylene glycol, the boric acid, the resorcinol and the polyphenyl ether in the modified phenolic resin.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The silicone polymers in the following examples were prepared as follows:
adding 10mL of tetrahydrofuran, 10mL of anhydrous ether and 40mmol of n-butyllithium into a reaction vessel under the nitrogen atmosphere, and stirring for 2h at the low temperature of-30 ℃; mixing 13.5mmol of trichloroethylene with 10mL of anhydrous ether, adding into a reaction vessel, and reacting for 2 hours at the low temperature of-30 ℃; mixing 10mL of tetrahydrofuran and 13.5mmol of diphenyldichlorosilane, adding the mixture into a reaction vessel, and reacting for 2 hours at the low temperature of-30 ℃; performing suction filtration, washing to be neutral, and performing reduced pressure distillation at 60 ℃ until the solvent is evaporated to obtain polydiphenylacetylene silane;
adding 3g of polydiphenylacetylene silane and 10mL of absolute ethyl alcohol into a reaction container, and stirring for 2 hours at the low temperature of-30 ℃; mixing 13.5mmol of trifluoromethanesulfonic acid with 50mL of anhydrous ether, quickly dropping the mixture into a reaction vessel, and stirring the mixture for 3 hours at the low temperature of-20 ℃; carrying out reduced pressure distillation at 60 ℃ until the solvent is evaporated to obtain a poly (trifluoromethanesulfonic acid group) phenylacetylene silane intermediate;
adding 6.5mmol of lithium aluminum hydride and 60mL of anhydrous ether into a reaction vessel, and stirring for 2h at the low temperature of-30 ℃; mixing the poly (trifluoromethanesulfonic) phenylacetylene silane intermediate with 30mL of anhydrous ether, adding the mixture into a reaction container at a low temperature, heating to room temperature after dropwise addition, and stirring for reaction for 12 hours; washing with saturated sodium chloride, filtering, drying with anhydrous magnesium sulfate, and distilling under reduced pressure to remove solvent to obtain organosilicon polymer.
The silane coupling agent in the following examples is KH550.
Example 1
S1: preheating 1000g of raw sand, adding the preheated raw sand into a sand mixer, and mixing the sand;
s2: adding 5g of phenol into a reaction vessel after melting, stirring, adding 10g of formaldehyde, 5g of potassium hydroxide and 1g of sodium hydroxide, heating to 70 ℃, stirring for reaction for 2 hours, adding 2.5g of resorcinol, stirring at a constant temperature of 70 ℃ for 2 hours, adding 1.05g of boric acid, refluxing for 60 minutes, distilling under reduced pressure for 2 hours, cooling, adding 1.05g of organic silicon polymer and 0.21g of silane coupling agent KH550, stirring, adding 1.4g of ethylene glycol and 2.8g of polyphenyl ether, and stirring to obtain a modified phenolic resin;
s3: and (3) mixing 20g of modified phenolic resin and 20g of paraformaldehyde, adding into a sand mixer, and mixing to obtain the high-temperature-resistant precoated sand for casting.
And (3) testing: the precoated sand is punched three times on a SAC hammering type sampling machine to prepare a sample with the thickness of 50mm multiplied by 50mm, and then the sample with the thickness of 0.7-0.8 m is used 2 Blowing in CO at a flow rate 2 And hardening to obtain a precoated sand sample.
Thermogravimetric analysis and compressive strength tests were performed, as shown in the following table.
Example 2
S1: preheating 1000g of raw sand, adding the preheated raw sand into a sand mixer, and mixing the sand;
s2: adding 5g of phenol into a reaction vessel after melting, stirring, adding 10g of formaldehyde, 5g of potassium hydroxide and 1g of sodium hydroxide, heating to 70 ℃, stirring for reaction for 2 hours, adding 2.7g of resorcinol, stirring at a constant temperature of 70 ℃ for 2 hours, adding 1.05g of boric acid, refluxing for 60 minutes, distilling under reduced pressure for 2 hours, cooling, adding 1.05g of an organic silicon polymer and 0.42g of a silane coupling agent KH550, stirring, adding 1.4g of ethylene glycol and 2.8g of polyphenyl ether, and stirring to obtain a modified phenolic resin;
s3: and (3) mixing 20g of modified phenolic resin and 20g of paraformaldehyde, adding into a sand mixer, and mixing to obtain the high-temperature-resistant precoated sand for casting.
And (3) testing: the precoated sand is punched three times on a SAC hammering type sampling machine to prepare a sample with the thickness of 50mm multiplied by 50mm, and then the sample with the thickness of 0.7-0.8 m is used 2 Blowing in CO at a flow rate 2 And hardening to obtain a precoated sand sample.
Thermogravimetric analysis and compressive strength tests were performed, as shown in the following table.
Example 3
S1: preheating 1000g of raw sand, adding the preheated raw sand into a sand mixer, and mixing the sand;
s2: adding 5g of phenol into a reaction vessel after melting, stirring, adding 10g of formaldehyde, 5g of potassium hydroxide and 1g of sodium hydroxide, heating to 70 ℃, stirring for reaction for 2 hours, adding 3g of resorcinol, stirring at a constant temperature of 70 ℃ for 2 hours, adding 1.05g of boric acid, refluxing for 60min, distilling under reduced pressure for 2 hours, cooling, adding 1.05g of an organic silicon polymer and 0.525g of a silane coupling agent KH550, stirring, adding 1.4g of ethylene glycol and 2.8g of polyphenyl ether, and stirring to obtain a modified phenolic resin;
s3: and (3) mixing 20g of modified phenolic resin and 20g of paraformaldehyde, adding into a sand mixer, and mixing to obtain the high-temperature-resistant precoated sand for casting.
And (3) testing: the precoated sand is punched three times on a SAC hammering type sampling machine to prepare a sample with the thickness of 50mm multiplied by 50mm, and then the sample with the thickness of 0.7-0.8 m is used 2 Blowing in CO at a flow rate 2 And hardening to obtain a precoated sand sample.
Thermogravimetric analysis and compressive strength tests were performed, as shown in the following table.
Example 4
S1: preheating 1000g of raw sand, adding the preheated raw sand into a sand mixer, and mixing the sand;
s2: adding 5g of phenol into a reaction vessel after melting, stirring, adding 10g of formaldehyde, 5g of potassium hydroxide and 1g of sodium hydroxide, heating to 70 ℃, stirring for reaction for 2 hours, adding 2.5g of resorcinol, stirring at a constant temperature of 70 ℃ for 2 hours, adding 3.15g of boric acid, refluxing for 60 minutes, distilling under reduced pressure for 2 hours, cooling, adding 3.15g of organic silicon polymer and 1.575g of silane coupling agent KH550, stirring, adding 1.4g of ethylene glycol and 2.8g of polyphenyl ether, and stirring to obtain modified phenolic resin;
s3: and (3) mixing 20g of modified phenolic resin and 20g of paraformaldehyde, adding into a sand mixer, and mixing to obtain the high-temperature-resistant precoated sand for casting.
And (3) testing: the precoated sand is punched three times on a SAC hammering type sample making machine to prepare a sample of 50mm multiplied by 50mm, and then the sample is punched by 0.7-0.8 m 2 Blowing in CO at a flow rate 2 And hardening to obtain a precoated sand sample.
Thermogravimetric analysis and compressive strength tests were performed, as shown in the following table.
Example 5
S1: preheating 1000g of raw sand, adding the preheated raw sand into a sand mixer, and mixing the sand;
s2: adding 5g of phenol into a reaction vessel after melting, stirring, adding 10g of formaldehyde, 5g of potassium hydroxide and 1g of sodium hydroxide, heating to 70 ℃, stirring for reaction for 2 hours, adding 3g of resorcinol, stirring at a constant temperature of 70 ℃ for 2 hours, adding 5.25g of boric acid, refluxing for 60min, distilling under reduced pressure for 2 hours, cooling, adding 5.25g of an organic silicon polymer and 2.625g of a silane coupling agent KH550, stirring, adding 1.4g of ethylene glycol and 2.8g of polyphenyl ether, and stirring to obtain a modified phenolic resin;
s3: and (3) mixing 20g of modified phenolic resin and 20g of paraformaldehyde, adding into a sand mixer, and mixing to obtain the high-temperature-resistant precoated sand for casting.
And (3) testing: the precoated sand is punched three times on a SAC hammering type sample making machine to prepare a sample of 50mm multiplied by 50mm, and then the sample is punched by 0.7-0.8 m 2 Blowing in CO at a flow rate 2 And hardening to obtain a precoated sand sample.
Thermogravimetric analysis and compressive strength tests were performed, as shown in the following table.
Example 6
S1: preheating 1000g of raw sand, adding the preheated raw sand into a sand mixer, and mixing the sand;
s2: melting 5g of phenol, adding the phenol into a reaction vessel, stirring, adding 10g of formaldehyde, 5g of potassium hydroxide and 1g of sodium hydroxide, heating to 70 ℃, stirring for reacting for 2 hours, adding 2.5g of resorcinol, stirring at constant temperature of 70 ℃ for 2 hours, adding 5.25g of boric acid, refluxing for 60 minutes, distilling under reduced pressure for 2 hours, cooling, adding 5.25g of organic silicon polymer and 2.625g of silane coupling agent KH550, stirring, adding 2.1g of ethylene glycol and 4.2g of polyphenyl ether, and stirring to obtain a modified phenolic resin;
s3: and mixing 30g of modified phenolic resin and 30g of paraformaldehyde, adding into a sand mixer, and mixing to obtain the high-temperature-resistant precoated sand for casting.
And (3) testing: the precoated sand is punched three times on a SAC hammering type sampling machine to prepare a sample with the thickness of 50mm multiplied by 50mm, and then the sample with the thickness of 0.7-0.8 m is used 2 Blowing in CO at a flow rate 2 And hardening to obtain a precoated sand sample.
Thermogravimetric analysis and compressive strength tests were performed, as shown in the following table.
Comparative example 1 (Silicone modifier is phenyl trimethoxysilane)
S1: preheating 1000g of raw sand, adding the preheated raw sand into a sand mixer, and mixing the sand;
s2: adding 5g of phenol into a reaction vessel after melting, stirring, adding 10g of formaldehyde, 5g of potassium hydroxide and 1g of sodium hydroxide, heating to 70 ℃, stirring for reacting for 2 hours, adding 2.5g of resorcinol, stirring at a constant temperature of 70 ℃ for 2 hours, adding 1.05g of boric acid, refluxing for 60 minutes, distilling under reduced pressure for 2 hours, cooling, adding 1.05g of phenyltrimethoxysilane and 0.21g of silane coupling agent KH550, stirring, adding 1.4g of ethylene glycol and 2.8g of polyphenyl ether, and stirring to obtain a modified phenolic resin;
s3: and (3) mixing 20g of modified phenolic resin and 20g of paraformaldehyde, adding into a sand mixer, and mixing to obtain the high-temperature-resistant precoated sand for casting.
And (3) testing: the precoated sand is punched three times on a SAC hammering type sampling machine to prepare a sample with the thickness of 50mm multiplied by 50mm, and then the sample with the thickness of 0.7-0.8 m is used 2 Blowing CO at a flow rate of 2 And hardening to obtain a precoated sand sample.
Thermogravimetric analysis and compressive strength tests were performed, as shown in the following table.
Comparative example 2 (without addition of Resorcinol)
S1: preheating 1000g of raw sand, adding the preheated raw sand into a sand mixer, and mixing the sand;
s2: adding 5g of phenol into a reaction vessel after melting, stirring, adding 10g of formaldehyde, 5g of potassium hydroxide and 1g of sodium hydroxide, heating to 70 ℃, stirring for reaction for 2 hours, adding 1.05g of boric acid, refluxing for 60 minutes, distilling under reduced pressure for 2 hours, cooling, adding 1.05g of organic silicon polymer and 0.21g of silane coupling agent KH550, stirring, adding 1.4g of ethylene glycol and 2.8g of polyphenyl ether, and stirring to obtain modified phenolic resin;
s3: and (3) mixing 20g of modified phenolic resin and 20g of paraformaldehyde, adding into a sand mixer, and mixing to obtain the high-temperature-resistant precoated sand for casting.
And (3) testing: the precoated sand is punched three times on a SAC hammering type sample making machine to prepare a sample of 50mm multiplied by 50mm, and then the sample is punched by 0.7-0.8 m 2 Blowing CO at a flow rate of 2 And hardening to obtain a precoated sand sample.
Thermogravimetric analysis and compressive strength tests were performed, as shown in the following table.
Comparative example 3 (triethylene glycol and polyphenylene oxide as modifiers)
S1: preheating 1000g of raw sand, adding the preheated raw sand into a sand mixer, and mixing the sand;
s2: melting 5g of phenol, adding the phenol into a reaction vessel, stirring, adding 10g of formaldehyde, 5g of potassium hydroxide and 1g of sodium hydroxide, heating to 70 ℃, stirring for reacting for 2 hours, adding 2.5g of resorcinol, stirring at constant temperature of 70 ℃ for 2 hours, adding 1.05g of boric acid, refluxing for 60 minutes, distilling under reduced pressure for 2 hours, cooling, adding 1.05g of organic silicon polymer and 0.21g of silane coupling agent KH550, stirring, adding 1.4g of triethylene glycol and 2.8g of polyphenyl ether, and stirring to obtain a modified phenolic resin;
s3: and (3) mixing 20g of modified phenolic resin and 20g of paraformaldehyde, adding into a sand mixer, and mixing to obtain the high-temperature-resistant precoated sand for casting.
And (3) testing: the precoated sand is punched three times on a SAC hammering type sample making machine to prepare a sample of 50mm multiplied by 50mm, and then the sample is punched by 0.7-0.8 m 2 Blowing CO at a flow rate of 2 And hardening to obtain a precoated sand sample.
Thermogravimetric analysis and compressive strength tests were performed, as shown in the following table.
Comparative example 4 (silane coupling agent KH 570)
S1: preheating 1000g of raw sand, adding the preheated raw sand into a sand mixer, and mixing the sand;
s2: melting 5g of phenol, adding the phenol into a reaction vessel, stirring, adding 10g of formaldehyde, 5g of potassium hydroxide and 1g of sodium hydroxide, heating to 70 ℃, stirring for reacting for 2 hours, adding 2.5g of resorcinol, stirring at constant temperature of 70 ℃ for 2 hours, adding 1.05g of boric acid, refluxing for 60 minutes, distilling under reduced pressure for 2 hours, cooling, adding 1.05g of organic silicon polymer and 0.21g of silane coupling agent KH570, stirring, adding 1.4g of ethylene glycol and 2.8g of polyphenyl ether, and stirring to obtain a modified phenolic resin;
s3: and (3) mixing 20g of modified phenolic resin and 20g of paraformaldehyde, adding into a sand mixer, and mixing to obtain the high-temperature-resistant precoated sand for casting.
And (3) testing: the precoated sand is punched three times on a SAC hammering type sampling machine to prepare a sample with the thickness of 50mm multiplied by 50mm, and then the sample with the thickness of 0.7-0.8 m is used 2 Blowing in CO at a flow rate 2 The mixture is hardened and cured,and obtaining a precoated sand sample.
Thermogravimetric analysis and compressive strength tests were performed, as shown in the following table.
Precoated sand sample test
Initial decomposition temperature/. Degree.C Compressive strength/MPa
Example 1 470 2.8
Example 2 492 2.9
Example 3 512 2.9
Example 4 523 3.2
Example 5 535 3.5
Example 6 545 3.7
Comparative example 1 432 2.5
Comparative example 2 411 2.4
Comparative example 3 398 2.2
Comparative example 4 452 2.6
And (4) conclusion: examples 1 to 6 show that when the mass ratio of formaldehyde, phenol, potassium hydroxide, sodium hydroxide, and resorcinol is 10.
In comparative example 1, phenyl trimethoxysilane which is an organosilicon modifier is used for replacing an organosilicon polymer, so that the heat resistance and compressive strength of the prepared precoated sand are reduced, the phenyl trimethoxysilane can not be cured to form an organic structure cured product containing alkene, benzene rings and condensed rings, and can not be converted into an inorganic structure, so that a ceramic phase with better high-temperature stability is formed.
In the comparative example 2, resorcinol is not added into the modified phenolic resin, so that the heat resistance and the compressive strength of the prepared precoated sand are reduced, the curing temperature of the precoated sand can be reduced by adding resorcinol, and the phenolic resin can be subjected to condensation reaction better, so that unreacted groups are reduced in the curing process of the precoated sand.
In comparative example 3, triethylene glycol was used instead of ethylene glycol, resulting in too low viscosity of the resulting precoated sand and a decrease in heat resistance and compressive strength.
In comparative example 4, the substitution of KH570 for KH550 resulted in a decrease in heat resistance of the coated sand, because KH570 was not catalyzed by an amine and could not be dehydrogenated to produce — SiOH and to produce a siloxane bond inorganic structure.
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. A preparation method of high-temperature-resistant precoated sand for casting is characterized by comprising the following steps: the method comprises the following steps:
s1: preheating raw sand, adding the preheated raw sand into a sand mixer, and stirring and mixing the sand;
s2: and mixing the modified phenolic resin and paraformaldehyde, adding into a sand mixer, and stirring and mixing to obtain the high-temperature-resistant precoated sand for casting.
2. The preparation method of the high-temperature-resistant precoated sand for casting according to claim 1, characterized by comprising the following steps: in the step S2, the addition amount of the modified phenolic resin is 2-3% of the mass of the raw sand, and the mass ratio of the modified phenolic resin to the paraformaldehyde is 1.
3. The preparation method of the high-temperature-resistant precoated sand for casting according to claim 1, characterized by comprising the following steps: in step S2, the modified phenolic resin is prepared as follows:
adding melted phenol into a reaction vessel, stirring, adding formaldehyde, potassium hydroxide and sodium hydroxide, stirring, heating for reaction, adding resorcinol, stirring at constant temperature, adding boric acid, refluxing, distilling under reduced pressure, cooling, adding an organic silicon polymer and a silane coupling agent, stirring, adding a modifier, and stirring to obtain the modified phenolic resin.
4. The preparation method of the high-temperature-resistant precoated sand for casting according to claim 3, characterized by comprising the following steps: the mass ratio of formaldehyde, phenol, potassium hydroxide, sodium hydroxide and resorcinol is (10).
5. The preparation method of the high-temperature-resistant precoated sand for casting according to claim 3, characterized by comprising the following steps: the addition amount of the organic silicon polymer is 5 to 25 percent of the total mass of the phenol, the formaldehyde, the potassium hydroxide and the sodium hydroxide, and the mass ratio of the silane coupling agent to the organic silicon polymer is (0.2 to 0.5): 1.
6. The preparation method of the high-temperature-resistant precoated sand for casting according to claim 3, characterized by comprising the following steps: the mass ratio of the boric acid to the organic silicon polymer is 1; the reflux time is 40-60 min, and the reduced pressure distillation time is 1-2 h.
7. The preparation method of the high-temperature-resistant precoated sand for casting according to claim 3, characterized by comprising the following steps: the modifier is ethylene glycol and polyphenyl ether, the addition amount of the modifier is 20-30% of the total mass of phenol, formaldehyde, potassium hydroxide and sodium hydroxide, and the mass ratio of the ethylene glycol to the polyphenyl ether in the modifier is 1:2.
8. the preparation method of the high-temperature-resistant precoated sand for casting according to claim 3, characterized by comprising the following steps: the silicone polymer was prepared as follows:
(1) Adding tetrahydrofuran, anhydrous ether and n-butyllithium into a reaction container under the nitrogen atmosphere, and stirring at low temperature; adding anhydrous ether solution of trichloroethylene into a reaction container, and reacting at low temperature; adding tetrahydrofuran solution of diphenyl dichlorosilane into a reaction container, and reacting at low temperature; carrying out suction filtration, washing and reduced pressure distillation to obtain polydiphenylacetylene silane;
(2) Adding polydiphenylacetylene silane and absolute ethyl alcohol into a reaction container, and stirring at low temperature; adding anhydrous ether solution of trifluoromethanesulfonic acid into a reaction vessel, and stirring at low temperature; carrying out reduced pressure distillation to obtain a polytrifluoromethanesulfonyl phenylacetylene silane intermediate;
(3) Adding lithium aluminum hydride and anhydrous ether into a reaction vessel, and stirring at low temperature; adding an anhydrous ether solution of a polytrifluoromethanesulfonyl phenylacetylene silane intermediate into a reaction container at a low temperature, heating to room temperature, and stirring for reaction; washing with saturated sodium chloride, filtering, drying with anhydrous magnesium sulfate, and distilling under reduced pressure to obtain the organic silicon polymer.
9. The preparation method of the high-temperature-resistant precoated sand for casting according to claim 8, characterized by comprising the following steps: the low-temperature stirring temperature in the step (1) is-30 ℃, and the stirring time is 2 hours; the reduced pressure distillation temperature is 60-70 ℃; the low-temperature reaction temperature in the step (2) is-20 ℃, and the reaction time is 3-3.5 h; in the step (3), stirring at room temperature for reaction for 12-14 h.
10. The precoated sand obtained by the method for preparing high-temperature-resistant precoated sand for casting according to any one of claims 1 to 9.
CN202210790852.XA 2022-07-05 2022-07-05 High-temperature-resistant precoated sand for casting and preparation method thereof Pending CN115229122A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117181990A (en) * 2023-10-07 2023-12-08 胜利油田金岛实业有限责任公司 High-temperature-resistant precoated sand and preparation method thereof

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117181990A (en) * 2023-10-07 2023-12-08 胜利油田金岛实业有限责任公司 High-temperature-resistant precoated sand and preparation method thereof
CN117181990B (en) * 2023-10-07 2024-03-19 胜利油田金岛实业有限责任公司 High-temperature-resistant precoated sand and preparation method thereof

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