CN111299497A - Curing agent of precoated sand binder and preparation method thereof - Google Patents
Curing agent of precoated sand binder and preparation method thereof Download PDFInfo
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- CN111299497A CN111299497A CN202010250683.1A CN202010250683A CN111299497A CN 111299497 A CN111299497 A CN 111299497A CN 202010250683 A CN202010250683 A CN 202010250683A CN 111299497 A CN111299497 A CN 111299497A
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- curing agent
- precoated sand
- sand binder
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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
Abstract
The invention relates to the field of polymer chemistry, in particular to a curing agent of a precoated sand binder and a preparation method thereof. The curing strength of the product and the binder is remarkably improved, and in a performance test, the product and the casting binder are cured, and the tensile strength of the 8-shaped block is 3.6-4.0MPa, which is 3.1-3.5MPa higher than that of the traditional curing process.
Description
Technical Field
The invention relates to the field of polymer chemistry, in particular to a curing agent of a precoated sand binder and a preparation method thereof.
Background
The casting industry is an important basic industry of the manufacturing industry, the development condition of the casting industry is closely related to the global economic development, and the quality of casting quality directly influences the quality of mechanical products. With the development of industry and the progress of society, the requirements on the quality of castings and the casting industry are higher and higher. The precoated sand is a molding material for shell-type precision casting, has the characteristics of good storage property, high dimensional precision of produced castings, smooth surface and the like, and can be used for producing cast steel, cast iron, alloy castings and non-ferrous metal castings. The precoated sand is prepared by taking quartz sand as raw sand and adding a binder and a curing agent.
The curing agent of the traditional precoated sand binder is urotropine, gas is generated in the curing process, and in order to meet the strength requirement and prolong the heat-resisting time, the dosage of the binder is generally increased, and the addition of the urotropine is increased along with the dosage of the urotropine, so that the gas evolution of the product is increased, the porosity of a casting is increased, and the quality of the casting is influenced. Meanwhile, the national environmental protection requirements are increasingly strict, and a large gas generation amount pollutes the atmosphere and harms the health of workers.
Disclosure of Invention
The invention aims to provide a curing agent for a precoated sand binder instead of urotropine, which is liquid phenolic resin and solves the technical problems that urotropine is used as the curing agent, gas is generated in the curing process, the gas evolution is large, the porosity of a casting is high, and the quality of the casting is influenced, and simultaneously provides a preparation method of the curing agent.
In order to solve the technical problems, the invention adopts the following technical scheme:
the curing agent of the precoated sand binder is liquid phenolic resin, and the molecular weight of the liquid phenolic resin is 890-1100.
Preferably, the liquid phenolic resin is made from phenol, formaldehyde, a catalyst, an acid, ammonia and a solvent.
Preferably, the liquid phenolic resin is prepared from the following raw materials in parts by weight:
preferably, the catalyst is triethylamine and/or triethanolamine.
Preferably, the solvent is methanol and/or ethanol.
Preferably, the acid is formic acid and/or acetic acid.
The preparation method of the curing agent of the precoated sand binder comprises the following steps:
a) mixing phenol and formaldehyde solution, adding a catalyst, and heating for reaction to obtain a mixed solution I;
b) cooling the mixed solution I, adding acid, performing neutralization reaction, and performing vacuum dehydration to obtain a product I;
c) and adding a solvent and ammonia water into the product I, performing reflux reaction, sampling, measuring and cooling to obtain the curing agent of the precoated sand binder.
Preferably, in step a), the formaldehyde solution is 37 wt.% formaldehyde aqueous solution;
the heating reaction specifically comprises the following steps: the temperature is raised to 75 ℃ within 20min, and the temperature is kept for 6 h.
Preferably, in step b), the temperature is reduced to 40 ℃, the neutralization reaction is carried out until the pH value is 7-8, the vacuum degree of vacuum dehydration is-0.08 MPa, and the moisture content of the product I is less than 3.5 wt.%.
Preferably, in step c), the ammonia is 27 wt.% ammonia solution, and the curing time of the product II is 40-60 s.
The curing agent of the precoated sand binder is a special thermosetting phenolic resin with the molecular weight of more than 890, which is far higher than that of the general thermosetting phenolic resin. In the step a) of the preparation method, a large amount of active hydroxymethyl is generated due to strong basicity of organic amine such as triethylamine and the like, so that the reactivity of the product prepared by the method is guaranteed, the product is neutralized and dehydrated and then adjusted to be neutral, a large amount of solvent, methanol or ethanol solvent is added to dissolve phenolic resin in the product, and the phenolic resin plays a role in inhibiting polymerization, in the step c), the material is kept at pH 6-8 to continue reflux reaction, and a large amount of macromolecular products are generated due to the special catalysis mechanism of ammonia water, so that the crosslinking strength after curing is greatly improved. The liquid phenolic resin curing agent prepared by the method can replace urotropine, and in the sand mixing process, the liquid phenolic resin curing agent reacts with the casting binder thermoplastic phenolic resin, and a large amount of hydroxymethyl reacts with benzene ring vacancies of the thermoplastic phenolic resin to be fully crosslinked to form a body structure, and finally the body structure is cured.
Compared with the prior art, the invention has the following beneficial effects:
1) the adhesive has no ammonia gas generated in the curing process, the gas evolution is less, the quality of the precoated sand is improved, the working condition of workers is improved, and the environment is protected.
2) The curing strength of the product and the binder is remarkably improved, and in a performance test, the product and the casting binder are cured, and the tensile strength of the 8-shaped block is 3.6-4.0MPa, which is 3.1-3.5MPa higher than that of the traditional curing process.
Detailed Description
The invention is illustrated in detail below with reference to examples, in which it is noted that: unless specifically stated otherwise, the steps and values set forth in these examples do not limit the scope of the invention.
Example 1
a) Mixing 100g of phenol and 80g of formaldehyde solution in a three-necked bottle, adding 2g of triethylamine, heating to 75 ℃ within 20min, and keeping the temperature for 6h until the solution is turbid and has no water solubility to obtain a mixed solution I;
b) cooling the mixed solution I to 40 ℃ by using a cold water bath, adding 1g of formic acid with the pH value of 7, starting vacuum and negative pressure of 0.08MPa for dehydration, slowly heating to 58 ℃, sampling, and cooling to 30 ℃ when the water content is measured to be 2 wt.% to obtain a product I;
c) and adding 10g of ammonia water and 100g of methanol into the product I, heating for 20min, heating for refluxing, sampling after 5h, measuring the curing time for 55s, cooling to 30 ℃, and discharging to obtain liquid phenolic resin, namely the curing agent of the precoated sand binder.
Example 2
a) Mixing 100g of phenol and 140g of formaldehyde solution in a three-necked bottle, adding 8g of triethylamine, heating to 75 ℃ within 20min, and keeping the temperature for 5h until the solution is turbid and has no water solubility to obtain a mixed solution I;
b) cooling the mixed solution to 40 ℃ by using a cold water bath, adding 4g of formic acid with the pH value of 7, starting vacuum and negative pressure of 0.08MPa for dehydration, slowly heating to 57 ℃, sampling, and cooling to 40 ℃ when the water content is measured to be 2 wt.% to obtain a product I;
c) adding 15g of ammonia water and 100g of methanol into the product I, heating for 20min to 72 ℃, carrying out reflux reaction, sampling after 5h, measuring the curing time for 43s, cooling to 30 ℃, and discharging to obtain liquid phenolic resin, namely the curing agent of the precoated sand binder.
Example 3
a) Mixing 100g of phenol and 80g of formaldehyde in a three-necked bottle, adding 2g of triethylamine, heating to 75 ℃ within 20min, and keeping the temperature for 6h until the solution is turbid and has no water solubility to obtain a mixed solution I;
b) cooling the mixed solution to 40 ℃ by using a cold water bath, adding 1g of formic acid with the pH value of 7, starting vacuum and negative pressure of 0.08MPa for dehydration, slowly heating to 58 ℃ for sampling, and cooling to 40 ℃ when the water content is measured to be 2 wt.% to obtain a product I;
c) and adding 10g of ammonia water and 100g of ethanol into the product I, heating for 20min to 74 ℃, carrying out reflux reaction, sampling after 5h, measuring the curing time for 58s, cooling to 30 ℃, and discharging to obtain liquid phenolic resin, namely the curing agent of the precoated sand binder.
Example 4
a) Mixing 100g of phenol and 140g of formaldehyde in a three-necked bottle, adding 8g of triethylamine, heating to 75 ℃ within 20min, and keeping the temperature for 5h until the solution is turbid and has no water solubility to obtain a mixed solution I;
b) cooling the mixed solution to 40 ℃ by using a cold water bath, adding 4g of formic acid with the pH value of 7, starting vacuum and negative pressure of 0.08MPa for dehydration, slowly heating to 60 ℃, sampling, and cooling to 40 ℃ when the water content is measured to be 2 wt.% to obtain a product I;
c) adding 15g of ammonia water and 100g of ethanol into the product I, heating for 20min to 72 ℃, carrying out reflux reaction, sampling after 5h, measuring the curing time for 45s, cooling to 30 ℃, and discharging to obtain liquid phenolic resin, namely the curing agent of the precoated sand binder.
Example 5
a) Mixing 100g of phenol and 140g of formaldehyde in a three-necked bottle, adding 10g of triethylamine, heating to 75 ℃ within 20min, and keeping the temperature for 6h until the solution is turbid and has no water solubility to obtain a mixed solution I;
b) cooling the mixed solution to 40 ℃ by using a cold water bath, adding 11g of acetic acid with the pH value of 7, starting vacuum and negative pressure of 0.08MPa for dehydration, slowly heating to 61 ℃, sampling, and cooling to 40 ℃ when the water content is measured to be 2 wt.% to obtain a product I;
c) and adding 10g of ammonia water and 100g of methanol into the product I, heating for 20min to 72 ℃, carrying out reflux reaction, sampling after 5h, measuring the curing time for 40s, cooling to 30 ℃, and discharging to obtain liquid phenolic resin, namely the curing agent of the precoated sand binder.
Example 6
a) Mixing 100g of phenol and 80g of formaldehyde in a three-necked bottle, adding 8g of triethanolamine, heating to 75 ℃ within 20min, and keeping the temperature for 8h until the solution is turbid and has no water solubility to obtain a mixed solution I; .
b) Cooling the mixed solution to 40 ℃ by using a cold water bath, adding 2g of formic acid with the pH value of 7, starting vacuum and negative pressure of 0.08MPa for dehydration, slowly heating to 59 ℃, sampling, and cooling to 40 ℃ when the measured water content is 2 wt.% to obtain a product I;
c) adding 15g of ammonia water and 100g of methanol into the product I, heating for 20min to 73 ℃, carrying out reflux reaction, sampling after 5h, measuring the curing time for 60s, cooling to 30 ℃, and discharging to obtain liquid phenolic resin, namely the curing agent of the precoated sand binder.
The curing agent of the precoated sand binder synthesized above was used to make a precoated sand strength application test, and the results and molecular weight are shown in table 1.
Comparative example 1 is a conventional urotropin aqueous solution
The application test of the coated sand tensile strength comprises the following steps: heating the sand to 120 ℃, adding the binder and the calcium stearate, stirring for 150s, adding the curing agent, fully stirring for 80s, unloading, sieving with a 40-mesh experimental sieve, curing with a lower die at 235 ℃ for 150s, taking out a sample block, cooling to room temperature, and measuring the strength by using a strength tester.
The gas forming amount measuring method comprises the following steps: 1 plus or minus 0.001g of sand ground from a fracture of the strength sample is weighed and placed in a porcelain boat. The porcelain boat containing the precoated sand sample is sent to a red hot part of a quartz tube of the gas evolution tester, the tube orifice is quickly sealed by a plug, meanwhile, a recording part of the gas evolution tester starts to work, and the gas evolution of the sample can be directly read from the recording paper after 3 min.
TABLE 1
The liquid phenolic curing agent prepared by the method has a larger molecular weight than that of the conventional thermosetting phenolic resin, and simultaneously, the strength of the curing casting adhesive replacing urotropine is also improved, and the gas evolution is obviously reduced.
The curing strength of the product and the binder is remarkably improved, and in a performance test, the product and the casting binder are cured, and the tensile strength of the 8-shaped block is 3.6-4.0MPa, which is 3.1-3.5MPa higher than that of the traditional curing process.
Claims (10)
1. The curing agent of the precoated sand binder is characterized in that the curing agent is liquid phenolic resin, and the molecular weight of the liquid phenolic resin is 890-1100.
2. The curing agent for precoated sand binder according to claim 1, wherein the liquid phenolic resin is made of phenol, formaldehyde, a catalyst, an acid, ammonia water and a solvent.
3. The curing agent for the precoated sand binder according to claim 2, which is prepared from the following raw materials in parts by weight:
4. the curing agent for precoated sand binder according to claim 2 or 3, wherein the catalyst is triethylamine and/or triethanolamine.
5. The curing agent for precoated sand binder according to claim 2 or 3, wherein the solvent is methanol and/or ethanol.
6. The curing agent for precoated sand binder according to claim 2 or 3, wherein the acid is formic acid and/or acetic acid.
7. The preparation method of the curing agent of the precoated sand binder is characterized by comprising the following steps:
a) mixing phenol and formaldehyde solution, adding a catalyst, and heating for reaction to obtain a mixed solution I;
b) cooling the mixed solution I, adding acid, performing neutralization reaction, and performing vacuum dehydration to obtain a product I;
c) and adding a solvent and ammonia water into the product I, performing reflux reaction, sampling, measuring and cooling to obtain the curing agent of the precoated sand binder.
8. The method for preparing a curing agent for precoated sand binder according to claim 7,
in step a), the formaldehyde solution is 37 wt.% formaldehyde aqueous solution;
the heating reaction specifically comprises the following steps: the temperature is raised to 75 ℃ within 20min, and the temperature is kept for 6 h.
9. The method for preparing a curing agent for precoated sand binder according to claim 7,
in the step b), the temperature is reduced to 40 ℃, the neutralization reaction is carried out until the pH value is 7-8, the vacuum degree of vacuum dehydration is-0.08 MPa, and the moisture content of the product I is less than 3.5 wt.%.
10. The method for preparing the curing agent for precoated sand binder according to claim 7, wherein the ammonia water in step c) is 27 wt.% ammonia water solution, and the curing time is 40-60 s.
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| CN202010250683.1A CN111299497A (en) | 2020-04-01 | 2020-04-01 | Curing agent of precoated sand binder and preparation method thereof |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111909334A (en) * | 2020-07-22 | 2020-11-10 | 山东宇世巨化工有限公司 | Preparation method of low-expansion resin curing agent and low-expansion resin curing agent |
| CN111909333A (en) * | 2020-07-22 | 2020-11-10 | 山东宇世巨化工有限公司 | Preparation method of low-ammonia resin curing agent and low-ammonia resin curing agent |
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| CN111909333A (en) * | 2020-07-22 | 2020-11-10 | 山东宇世巨化工有限公司 | Preparation method of low-ammonia resin curing agent and low-ammonia resin curing agent |
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Application publication date: 20200619 |