CN112126032A - Preparation method of modified phenolic resin for precoated sand - Google Patents
Preparation method of modified phenolic resin for precoated sand Download PDFInfo
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- C08G14/00—Condensation polymers of aldehydes or ketones with two or more other monomers covered by at least two of the groups C08G8/00 - C08G12/00
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- 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
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Abstract
The invention discloses a method for modifying phenolic resin by using organically modified nano montmorillonite, which comprises the steps of uniformly mixing montmorillonite and water, adding the mixture into molten nylon 66, mixing for 1-2 hours at 270-280 ℃, extruding and granulating to obtain organically modified nano montmorillonite, and then adding the organically modified nano montmorillonite into the phenolic resin for modification; the invention adopts the organic modified nano-montmorillonite to modify the performance of the phenolic resin, the addition of the organic modified nano-montmorillonite can obviously improve the fluidity of the phenolic resin and reduce the softening point of the resin, and the organic modified nano-montmorillonite is used for manufacturing the precoated sand and can obviously improve the tensile strength and toughness of the precoated sand.
Description
Technical Field
The invention relates to the technical field of phenolic resin, in particular to a preparation method of modified phenolic resin for precoated sand.
Background
The phenolic resin is an organic polymer prepared by condensation polymerization reaction of classified compounds and aldehyde compounds, has excellent thermodynamic property and chemical stability, is widely applied to manufacturing engineering plastics, fire-proof materials, adhesives and the like, and has irreplaceable effect in modern industry.
However, a large amount of phenol and formaldehyde residues are inevitably generated in the production process of the phenolic resin, and the two organic compounds are important organic pollutants in China and have great threats to the ecological environment and human health. Therefore, the development of a novel phenolic resin preparation process for reducing the emission of phenol and formaldehyde is very important for the sustainable and harmonious development of national economy.
In addition, the phenolic resin is an excellent adhesive for producing the precoated sand, and the chemical stability, the thermodynamic property, the fluidity, the caking property and the like of the phenolic resin have great influence on the performance of the precoated sand. The precoated sand produced by using phenolic resin as a binder has the advantages of good binding property, no collapsibility, high temperature resistance, low cost and the like, so that the precoated sand is widely applied to cast iron. Nodular cast iron, non-ferrous metal castings, etc. However, the precoated sand produced by using the phenolic resin as a binder still has many problems in casting high-precision castings (such as castings for automobiles, precision scientific instruments and high-end equipment), and the strength and toughness of the precoated sand need to be further improved. Therefore, the environment-friendly process is adopted to produce the high-performance phenolic resin, and the significance of the phenolic resin for manufacturing the precoated sand material with high strength and toughness is great.
Disclosure of Invention
The invention aims to provide a preparation method of modified phenolic resin for precoated sand, aiming at improving the production process of phenolic resin, reducing environmental pollution, improving the performance of phenolic resin and manufacturing precoated sand with high strength and toughness.
In order to achieve the purpose, the invention is realized by the following technical scheme:
a preparation method of modified phenolic resin for precoated sand comprises the steps of adding organic modified nano montmorillonite into phenolic resin for modification;
the organic modified nano montmorillonite is prepared by the following steps:
uniformly mixing montmorillonite and water, adding the mixture into molten nylon 66, mixing for 1-2 hours at 270-280 ℃, and extruding and granulating to obtain organic modified nano montmorillonite;
wherein the mass ratio of nylon 66 to montmorillonite to water is 20-30: 2-5: 20 to 30.
Preferably, the mass ratio of the organic modified nano montmorillonite to the phenolic resin is 0.1-1.2: 100 to 150.
Preferably, a modified coupling agent is further added in the modification process, and the modified coupling agent is prepared from sodium hexametaphosphate, a silane coupling agent and aluminum chloride according to the mass ratio of 1-4: 20-30: 3 to 6.
Preferably, the mass ratio of the modified coupling agent to the phenolic resin is 0.3-1.2: 100 to 150.
Preferably, the phenolic resin is prepared according to the following steps:
sequentially adding phenol, formaldehyde and oxalic acid into a reaction kettle, heating to 80-85 ℃ under stirring, stopping heating, controlling the temperature to react for 2-4 hours under reflux, cooling to 40-50 ℃, adding an amine compound, stirring for reacting for 1-2 hours, distilling and dehydrating when the content of free phenol is measured to be less than 0.5%, starting vacuum when the temperature in the reaction kettle rises to 130-150 ℃, dehydrating for 0.5-1 hour, and closing the vacuum to obtain phenolic resin;
the amine compound is acetamide or/and hexamethylene diamine;
wherein the mass ratio of phenol to formaldehyde to oxalic acid to the amine compound is 80-90: 55-65: 5-15: 20 to 30.
Preferably, the amine compound is acetamide and hexamethylenediamine according to a mass ratio of 2-5: 1.
A preferred method of preparation comprises the steps of:
adding phenol, formaldehyde and oxalic acid into a reaction kettle in sequence, heating to 85 ℃ under stirring, stopping heating, controlling the temperature to react for 2-4 hours under reflux, cooling to 45-50 ℃, adding an amine compound, stirring and reacting for 1-2 hours, distilling and dehydrating when the content of free phenol is measured to be less than 0.5%, starting vacuum when the temperature in the reaction kettle rises to 140-150 ℃, dehydrating for 0.5-1 hour, and closing the vacuum to obtain a reaction solution for later use;
the amine compound is prepared from acetamide and hexamethylene diamine according to a mass ratio of 4: 1, obtaining;
wherein the mass ratio of phenol to formaldehyde to oxalic acid to the amine compound is 80-90: 55-65: 5-15: 20-30;
uniformly mixing montmorillonite and water, adding the mixture into molten nylon 66, mixing for 1-2 hours at 275-280 ℃, and extruding and granulating to obtain organic modified nano montmorillonite for later use;
wherein the mass ratio of nylon 66 to montmorillonite to water is 25: 4: 25;
adding a modified coupling agent and the organic modified nano-montmorillonite obtained in the step II into the reaction kettle in the step I, stirring and reacting for 1-2 hours at 130-150 ℃, cooling and discharging to obtain modified phenolic resin for precoated sand;
the modified coupling agent is prepared from sodium hexametaphosphate, a silane coupling agent and aluminum chloride according to the mass ratio of 1-4: 20-30: 3-6;
wherein the mass ratio of phenol, modifier and the organic modified nano montmorillonite obtained in the step II is 80-90: 0.5-1: 0.1 to 1.
Preferably, the modified coupling agent is prepared from sodium hexametaphosphate, a silane coupling agent and aluminum chloride according to a mass ratio of 2: 25: 5.
Preferably, the mass ratio of the phenol to the formaldehyde to the oxalic acid to the amine compound is 85: 60: 10: 25.
preferably, the mass ratio of the phenol, the modifier and the organic modified nano montmorillonite obtained in the step II is 85: 0.6: 0.8.
compared with the prior art, the invention has the following advantages:
the invention adopts the organic modified nano-montmorillonite to modify the performance of the phenolic resin, the addition of the organic modified nano-montmorillonite can obviously improve the fluidity of the phenolic resin and reduce the softening point of the resin, and the organic modified nano-montmorillonite is used for manufacturing the precoated sand and can obviously improve the tensile strength and toughness of the precoated sand.
The invention adopts the composition of acetamide or/and hexamethylene diamine as the amine compound, the modified phenolic resin can be condensed with unreacted aldehyde group in the phenolic resin, and can improve the mechanical property of the phenolic resin, in addition, the amine compound can react with unreacted formaldehyde in a reaction system, the emission of formaldehyde is reduced, the environmental pollution is reduced, the amine organic matter can be condensed with unreacted aldehyde group in the phenolic resin, the softening point is improved, the fluidity is reduced, the mechanical property of the phenolic resin is improved, the cold/heat resistance strength of the phenolic resin can be greatly improved in the process of preparing precoated sand by the phenolic resin, and the heat resistance time of the phenolic resin is prolonged.
The modified coupling agent can uniformly disperse the silane coupling agent in the phenolic resin, improve the adhesion between the surface of the special sand grains and the resin, enable the resin to be more firmly attached to the surface of the sand grains and fully exert the bonding efficiency of the phenolic resin; and the high temperature resistance time is prolonged, and the high temperature resistance performance is improved.
Detailed Description
The invention aims to provide a preparation method of modified phenolic resin for precoated sand, which is realized by the following technical scheme:
a preparation method of modified phenolic resin for precoated sand comprises the steps of adding organic modified nano montmorillonite into phenolic resin for modification;
the organic modified nano montmorillonite is prepared by the following steps:
uniformly mixing montmorillonite and water, adding the mixture into molten nylon 66, mixing for 1-2 hours at 270-280 ℃, and extruding and granulating to obtain organic modified nano montmorillonite;
wherein the mass ratio of nylon 66 to montmorillonite to water is 20-30: 2-5: 20 to 30.
The nano montmorillonite modified by the nylon 66 is of a sheet structure, is easier to intercalate into the thermoplastic phenolic resin, improves the mechanical property of the phenolic resin, improves the fluidity of the resin, reduces the softening point of the phenolic resin and improves the film coating property of the phenolic resin.
Preferably, the mass ratio of the organic modified nano montmorillonite to the phenolic resin is 0.1-1.2: 100 to 150.
Preferably, a modified coupling agent is further added in the modification process, and the modified coupling agent is prepared from sodium hexametaphosphate, a silane coupling agent and aluminum chloride according to the mass ratio of 1-4: 20-30: 3-6; the silane coupling agent is preferably a silane coupling agent containing amino, and because the precoated sand subjected to surface treatment by the silane coupling agent containing amino has higher strength, the resin and special sand grains can be converted from adhesive fracture into cohesive fracture in a discontinuous fracture mode, so that the silane coupling agent can be uniformly dispersed in the phenolic resin, the adhesion between the surface of the special sand grains and the resin is improved, the resin is more firmly adhered to the surface of the sand grains, and the adhesion efficiency of the phenolic resin is fully exerted; the high temperature resistance time is prolonged, and the high temperature resistance performance is improved;
the silane coupling agent can be selected from gamma-aminopropyltrimethoxysilane, gamma-aminopropyltriethoxysilane, N-beta (aminoethyl) -gamma-aminopropyltrimethoxysilane, N-beta (aminoethyl) -gamma-aminopropyltriethoxysilane, phenylaminomethyl triethoxysilane, phenylaminomethyl trimethoxysilane and the like;
preferably, the mass ratio of the modified coupling agent to the phenolic resin is 0.3-1.2: 100 to 150.
Preferably, the phenolic resin is prepared according to the following steps:
sequentially adding phenol, formaldehyde and oxalic acid into a reaction kettle, heating to 80-85 ℃ under stirring, stopping heating, controlling the temperature to react for 2-4 hours under reflux, cooling to 40-50 ℃, adding an amine compound, stirring for reacting for 1-2 hours, distilling and dehydrating when the content of free phenol is measured to be less than 0.5%, starting vacuum when the temperature in the reaction kettle rises to 130-150 ℃, dehydrating for 0.5-1 hour, and closing the vacuum to obtain phenolic resin;
the amine compound is acetamide or/and hexamethylene diamine;
wherein the mass ratio of phenol to formaldehyde to oxalic acid to the amine compound is 80-90: 55-65: 5-15: 20 to 30.
Preferably, the amine compound is acetamide and hexamethylenediamine according to a mass ratio of 2-5: 1.
The addition of the amine organic matter can be condensed with unreacted aldehyde groups in the phenolic resin, so that the softening point of the phenolic resin is improved, and the fluidity of the phenolic resin is reduced, so that the mechanical property of the phenolic resin is improved, the cold/heat resistance strength of the phenolic resin can be greatly improved in the process of preparing precoated sand by using the phenolic resin, and the heat resistance time of the phenolic resin is prolonged;
a preferred method of preparation comprises the steps of:
adding phenol, formaldehyde and oxalic acid into a reaction kettle in sequence, heating to 85 ℃ under stirring, stopping heating, controlling the temperature to react for 2-4 hours under reflux, cooling to 45-50 ℃, adding an amine compound, stirring and reacting for 1-2 hours, distilling and dehydrating when the content of free phenol is measured to be less than 0.5%, starting vacuum when the temperature in the reaction kettle rises to 140-150 ℃, dehydrating for 0.5-1 hour, and closing the vacuum to obtain a reaction solution for later use;
the amine compound is acetamide or/and hexamethylene diamine;
wherein the mass ratio of phenol to formaldehyde to oxalic acid to the amine compound is 80-90: 55-65: 5-15: 20-30;
uniformly mixing montmorillonite and water, adding the mixture into molten nylon 66, mixing for 1-2 hours at 270-280 ℃, and extruding and granulating to obtain organic modified nano montmorillonite for later use;
wherein the mass ratio of nylon 66 to montmorillonite to water is 20-30: 2-3: 20-30;
adding a modified coupling agent and the organic modified nano-montmorillonite obtained in the step II into the reaction kettle in the step I, stirring and reacting for 1-2 hours at 130-150 ℃, cooling and discharging to obtain amine modified phenolic resin for precoated sand;
the modified coupling agent is prepared from sodium hexametaphosphate, a silane coupling agent and aluminum chloride according to the mass ratio of 1-4: 20-30: 3-6;
wherein the mass ratio of phenol, modifier and the organic modified nano montmorillonite obtained in the step II is 80-90: 0.5-1: 0.1 to 1.
A further preferred preparation method comprises the following steps:
adding phenol, formaldehyde and oxalic acid into a reaction kettle in sequence, heating to 85 ℃ under stirring, stopping heating, controlling the temperature to react for 2-4 hours under reflux, cooling to 45-50 ℃, adding an amine compound, stirring and reacting for 1-2 hours, distilling and dehydrating when the content of free phenol is measured to be less than 0.5%, starting vacuum when the temperature in the reaction kettle rises to 140-150 ℃, dehydrating for 0.5-1 hour, and closing the vacuum to obtain a reaction solution for later use;
the amine compound is prepared from acetamide and hexamethylene diamine according to a mass ratio of 4: 1, obtaining;
wherein the mass ratio of phenol to formaldehyde to oxalic acid to the amine compound is 80-90: 55-65: 5-15: 20-30;
uniformly mixing montmorillonite and water, adding the mixture into molten nylon 66, mixing for 1-2 hours at 275-280 ℃, and extruding and granulating to obtain organic modified nano montmorillonite for later use;
wherein the mass ratio of nylon 66 to montmorillonite to water is 25: 4: 25;
adding a modified coupling agent and the organic modified nano-montmorillonite obtained in the step II into the reaction kettle in the step I, stirring and reacting for 1-2 hours at 130-150 ℃, cooling and discharging to obtain modified phenolic resin for precoated sand;
the modified coupling agent is prepared from sodium hexametaphosphate, a silane coupling agent and aluminum chloride according to the mass ratio of 1-4: 20-30: 3-6;
wherein the mass ratio of phenol, modifier and the organic modified nano montmorillonite obtained in the step II is 80-90: 0.5-1: 0.1 to 1.
Preferably, the modified coupling agent is prepared from sodium hexametaphosphate, a silane coupling agent and aluminum chloride according to a mass ratio of 2: 25: 5.
Preferably, the mass ratio of the phenol to the formaldehyde to the oxalic acid to the amine compound is 85: 60: 10: 25.
preferably, the mass ratio of the phenol, the modifier and the organic modified nano montmorillonite obtained in the step II is 85: 0.6: 0.8.
according to the production method, the organic modified nano montmorillonite is adopted to modify the performance of the phenolic resin, the addition of the organic modified nano montmorillonite can obviously improve the fluidity of the phenolic resin and reduce the softening point of the resin, the organic modified nano montmorillonite is used for manufacturing the precoated sand, the tensile strength and the toughness of the precoated sand can be obviously improved, the productivity of the phenolic resin for the precoated sand can be expanded to 4-10 times of the original productivity, for example, a 10-square reaction kettle can be adopted for reaction, a 40-100-square reaction kettle can be adopted for production, and the production capacity and the production efficiency are greatly improved.
The invention is further described with reference to specific examples.
Example 1
A preparation method of modified phenolic resin for precoated sand comprises the following steps:
adding 400kg of phenol, 275kg of formaldehyde and 25kg of oxalic acid into a reaction kettle in sequence, heating to 85 ℃ under stirring, stopping heating, controlling the temperature to react for 2 hours under reflux, cooling to 45 ℃, adding 100kg of amine compound, stirring for reaction for 1 hour, distilling and dehydrating when the content of free phenol is less than 0.5 percent, and opening vacuum, dehydrating for 0.5 hour and closing the vacuum when the temperature in the reaction kettle is raised to 140 ℃ to obtain a reaction solution for later use;
the amine compound is acetamide;
uniformly mixing montmorillonite and water, adding the mixture into nylon 66 in a molten state, mixing for 1 hour at 270 ℃, and extruding and granulating to obtain organic modified nano montmorillonite for later use;
wherein the mass ratio of nylon 66 to montmorillonite to water is 20: 2: 20;
adding 2.5kg of modified coupling agent and 0.5kg of the organic modified nano-montmorillonite obtained in the second step into the reaction kettle in the first step, stirring and reacting for 1 hour at the temperature of 130 ℃, cooling and discharging to obtain amine modified phenolic resin for precoated sand;
the modified coupling agent is prepared from sodium hexametaphosphate, a silane coupling agent and aluminum chloride according to the mass ratio of 1: 20: 3, and (3).
Example 2
A preparation method of modified phenolic resin for precoated sand comprises the following steps:
adding 450kg of phenol, 325kg of formaldehyde and 75kg of oxalic acid into a reaction kettle in sequence, heating to 85 ℃ under stirring, stopping heating, controlling the temperature to react for 4 hours under reflux, cooling to 50 ℃, adding 150kg of amine compound, stirring for reaction for 2 hours, distilling and dehydrating when the content of free phenol is less than 0.5 percent, and opening vacuum, dehydrating for 1 hour and closing the vacuum when the temperature in the reaction kettle is raised to 150 ℃ to obtain reaction liquid for later use;
the amine compound is hexamethylene diamine;
uniformly mixing montmorillonite and water, adding the mixture into molten nylon 66, mixing for 2 hours at 280 ℃, and extruding and granulating to obtain organic modified nano montmorillonite for later use;
wherein the mass ratio of nylon 66 to montmorillonite to water is 6: 1: 6;
adding 5kg of modified coupling agent and 5kg of the organic modified nano montmorillonite obtained in the step II into the reaction kettle in the step I, stirring and reacting for 2 hours at the temperature of 150 ℃, cooling and discharging to obtain amine modified phenolic resin for precoated sand;
the modified coupling agent is prepared from sodium hexametaphosphate, a silane coupling agent and aluminum chloride according to a mass ratio of 4: 30: 6.
Example 3
A preparation method of modified phenolic resin for precoated sand comprises the following steps:
adding 410kg of phenol, 300kg of formaldehyde and 40kg of oxalic acid into a reaction kettle in sequence, heating to 85 ℃ under stirring, stopping heating, controlling the temperature to react for 3 hours under reflux, cooling to 46 ℃, adding 140kg of amine compound, stirring for reaction for 1.5 hours, distilling and dehydrating when the content of free phenol is less than 0.5 percent, starting vacuum when the temperature in the reaction kettle is increased to 148 ℃, dehydrating for 40 minutes, and closing the vacuum to obtain a reaction solution for later use;
the amine compound is prepared from acetamide and hexamethylene diamine according to a mass ratio of 2: 1, preparing a composition;
uniformly mixing montmorillonite and water, adding the mixture into molten nylon 66, mixing for 1.5 hours at 274 ℃, and extruding and granulating to obtain organic modified nano montmorillonite for later use;
wherein the mass ratio of nylon 66 to montmorillonite to water is 22: 2.2: 28;
adding 3kg of modified coupling agent and 2kg of the organic modified nano montmorillonite obtained in the second step into the reaction kettle in the first step, stirring and reacting for 1-2 hours at 145 ℃, cooling and discharging to obtain amine modified phenolic resin for precoated sand;
the modified coupling agent is prepared from sodium hexametaphosphate, a silane coupling agent and aluminum chloride according to the mass ratio of 3: 22: 4.
Example 4
A preparation method of modified phenolic resin for precoated sand comprises the following steps:
firstly, adding 425kg of phenol, 300kg of formaldehyde and 50kg of oxalic acid into a reaction kettle in sequence, heating to 85 ℃ under stirring, stopping heating, controlling the temperature to react for 3 hours under reflux, cooling to 48 ℃, adding 125kg of amine compound, stirring for reaction for 1.5 hours, distilling and dehydrating when the content of free phenol is less than 0.5 percent, starting vacuum when the temperature in the reaction kettle is raised to 145 ℃, dehydrating for 45 minutes, and closing the vacuum to obtain a reaction solution for later use;
the amine compound is prepared from acetamide and hexamethylene diamine according to a mass ratio of 4: 1, preparing a composition;
uniformly mixing montmorillonite and water, adding the mixture into molten nylon 66, mixing for 1.5 hours at 275 ℃, and extruding and granulating to obtain organic modified nano montmorillonite for later use;
wherein the mass ratio of nylon 66 to montmorillonite to water is 25: 4: 25;
adding 3kg of modified coupling agent and 4kg of the organic modified nano montmorillonite obtained in the step II into the reaction kettle in the step I, stirring and reacting for 1.5 hours at the temperature of 140 ℃, cooling and discharging to obtain amine modified phenolic resin for precoated sand;
the modified coupling agent is prepared from sodium hexametaphosphate, a silane coupling agent and aluminum chloride according to the mass ratio of 2: 25: 5, preparing a composition;
the silane coupling agent is gamma-aminopropyl triethoxysilane.
Comparative examples 1 to 4
The preparation processes of the embodiments 1 to 4 are respectively adopted in sequence, and the difference is that the step of adding the organic modified nano montmorillonite is eliminated. The modified phenolic resins for the precoated sand of examples 1 to 4 and the phenolic resins of comparative examples 1 to 4 were tested, the softening point was tested by the ring-and-ball method, and the fluidity was tested by the inclined plate method, and the results are shown in table 1.
TABLE 1 modified phenolic resins for precoated sand of examples 1 to 4 and phenolic resins of comparative examples 1 to 4
| Softening point/. degree.C | Fluidity (mm) | Molecular weight (Mn) | Molecular weight distribution | |
| Example 1 | 90 | 55 | 754 | 1.2 |
| Example 2 | 95 | 61 | 740 | 0.8 |
| Example 3 | 92 | 59 | 749 | 1.1 |
| Example 4 | 93 | 60 | 746 | 1.0 |
| Comparative example 1 | 92 | 53 | 752 | 1.2 |
| Comparative example 2 | 98 | 58 | 742 | 0.8 |
| Comparative example 3 | 95 | 56 | 747 | 1.1 |
| Comparative example 4 | 96 | 57 | 748 | 1.0 |
As can be seen from the data in Table 1, the adding step of the organic modified nano montmorillonite has little influence on the molecular weight and the molecular weight distribution of the phenolic resin, but the softening point of the phenolic resin can be reduced by 2-3 ℃, and the fluidity is improved by 2-3 mm, so that the phenolic resin is not easy to agglomerate and easily coated when the coated sand is prepared, and the obtained coated sand has good fluidity and strong moisture resistance.
The coated sand prepared from the phenolic resin for the coated sand obtained in the examples 1 to 4 and the phenolic resin for the coated sand obtained in the comparative examples 1 to 4 was tested, wherein the coated sand prepared by the following steps:
heating 150kg of 70-140-mesh Dalin sand to 120-130 ℃, putting the Dalin sand into a precoated sand mixer, adding 3kg of phenolic resin, coating for 60s, then adding 0.25kg of urotropine and 0.65kg of water, mixing for 20s, cooling, crushing, discharging sand, performing performance test, and using a detection instrument: SAT-B type precoated sand electric heating sample preparation machine, SWY type hydraulic strength testing machine, SGQW-1 type precoated sand high-temperature performance tester.
The heat-resisting time detection method comprises the following steps: placing the precoated sand on a concave bracket, placing the concave bracket in a high-temperature furnace at 1000 ℃, and detecting the collapse time of the precoated sand
The results are shown in Table 2.
Table 2 table of results of performance test of precoated sand
In the process of preparing the precoated sand, the addition of the existing urotropine is generally about 10 percent, but the addition of the urotropine in the application is less, so that the prepared precoated sand has low gas evolution, smooth casting surface and high dimensional accuracy. The results in table 2 show that the phenolic resin for precoated sand of the present invention greatly improves the hot tensile strength and the cold tensile strength thereof, greatly increases the heat-resistant time of the precoated sand, and improves the high temperature resistance of the precoated sand, due to the addition of the organic modified nano montmorillonite in the preparation process.
Since the performance of the phenolic resin for precoated sand prepared in example 4 is optimal, the following comparative examples are all the parameters of example 4 are adjusted, comparative example 5 removes the step of adding the amine organic matter, and comparative example 6 removes sodium hexametaphosphate and aluminum chloride in the modified coupling agent, and only the step of adding the silane coupling agent is reserved. The results of the tests on the precoated sand obtained in comparative examples 5 to 6 using the phenol resin are shown in table 3. The precoated sand was prepared by the same method as described above, and the performance of the precoated sand was measured, and the results are shown in table 4.
TABLE 3 phenolic resin Performance results of example 4 and comparative examples 5-6
| Softening point/. degree.C | Fluidity (mm) | Molecular weight (Mn) | Molecular weight distribution | |
| Example 4 | 93 | 60 | 746 | 1.0 |
| Comparative example 5 | 91 | 63 | 740 | 1.0 |
| Comparative example 6 | 92 | 61 | 741 | 1.0 |
Table 4 table of performance results of precoated sand prepared from the phenolic resins of example 4 and comparative examples 5 to 6
As can be seen from the results in tables 3 and 4, the addition of the amine organic compound can condense with unreacted aldehyde groups in the phenolic resin, thereby improving the softening point and reducing the fluidity thereof, so as to improve the mechanical properties of the phenolic resin, greatly improve the cold/heat resistance strength of the phenolic resin during the preparation of the precoated sand, and increase the heat resistance time thereof; the design of the modified coupling agent can enable the silane coupling agent to be better dispersed in the phenolic resin, the bonding performance of the silane coupling agent is effectively improved, the modified coupling agent can enable the phenolic resin to be more firmly attached to the surface of sand grains in the process of preparing the precoated sand, the bonding efficiency of the phenolic resin is fully exerted, and the high-temperature resistant time of the phenolic resin is prolonged.
Comparative example 7
A preparation method of modified phenolic resin for precoated sand comprises the following steps:
adding 42.5kg of phenol, 30kg of formaldehyde and 5kg of oxalic acid into a reaction kettle in sequence, heating to 85 ℃ under stirring, stopping heating, controlling the temperature to react for 3 hours under reflux, cooling to 48 ℃, adding 12.5kg of amine compound, stirring and reacting for 1.5 hours, distilling and dehydrating when the content of free phenol is less than 0.5%, starting vacuum when the temperature in the reaction kettle is raised to 145 ℃, dehydrating for 45 minutes, and closing the vacuum to obtain a reaction solution for later use;
the amine compound is prepared from acetamide and hexamethylene diamine according to a mass ratio of 4: 1, preparing a composition;
adding 0.3kg of modified coupling agent into the reaction kettle in the step I, stirring and reacting for 4 hours at the temperature of 140 ℃, then sampling, measuring the polymerization rate to 65-70 s, cooling and discharging to obtain amine modified phenolic resin for precoated sand;
the modified coupling agent is prepared from sodium hexametaphosphate, a silane coupling agent and aluminum chloride according to the mass ratio of 2: 25: 5, preparing a composition;
the silane coupling agent is gamma-aminopropyl triethoxysilane.
Comparative example 8
A preparation method of modified phenolic resin for precoated sand comprises the following steps:
firstly, adding 425kg of phenol, 300kg of formaldehyde and 50kg of oxalic acid into a reaction kettle in sequence, heating to 85 ℃ under stirring, stopping heating, controlling the temperature to react for 3 hours under reflux, cooling to 48 ℃, adding 125kg of amine compound, stirring for reaction for 1.5 hours, distilling and dehydrating when the content of free phenol is less than 0.5 percent, starting vacuum when the temperature in the reaction kettle is raised to 145 ℃, dehydrating for 45 minutes, and closing the vacuum to obtain a reaction solution for later use;
the amine compound is prepared from acetamide and hexamethylene diamine according to a mass ratio of 4: 1, preparing a composition;
adding 3kg of modified coupling agent into the reaction kettle in the step I, stirring and reacting for 5 hours at the temperature of 140 ℃, cooling and discharging to obtain amine modified phenolic resin for precoated sand, wherein the sampling and polymerization rate can not reach below 100s all the time;
the modified coupling agent is prepared from sodium hexametaphosphate, a silane coupling agent and aluminum chloride according to the mass ratio of 2: 25: 5, preparing a composition;
the silane coupling agent is gamma-aminopropyl triethoxysilane.
It can be seen from comparative examples 7 and 8 that the polymerization rate can be barely required after stirring reaction for 4 hours in comparative example 7 due to the small amount of the added substances, while the polymerization rate can not be always required after 10 times of the enlarged production in comparative example 8, and it can be seen that the organically modified nano-montmorillonite (the mass ratio of nylon 66, montmorillonite and water is 25: 4: 25) of the invention has very important significance for enlarging the productivity.
Claims (10)
1. A preparation method of modified phenolic resin for precoated sand is characterized by comprising the following steps: adding the organic modified nano montmorillonite into phenolic resin for modification;
the organic modified nano montmorillonite is prepared by the following steps:
uniformly mixing montmorillonite and water, adding the mixture into molten nylon 66, mixing for 1-2 hours at 270-280 ℃, and extruding and granulating to obtain organic modified nano montmorillonite;
wherein the mass ratio of nylon 66 to montmorillonite to water is 20-30: 2-5: 20 to 30.
2. The preparation method of the modified phenolic resin for precoated sand according to claim 1, characterized by comprising the following steps: the mass ratio of the organic modified nano montmorillonite to the phenolic resin is 0.1-1.2: 100 to 150.
3. The preparation method of the modified phenolic resin for precoated sand according to claim 1, characterized by comprising the following steps: and a modified coupling agent is also added in the modification process, wherein the modified coupling agent is prepared from sodium hexametaphosphate, a silane coupling agent and aluminum chloride according to the mass ratio of 1-4: 20-30: 3 to 6.
4. The preparation method of the modified phenolic resin for precoated sand according to claim 3, characterized by comprising the following steps: the mass ratio of the modified coupling agent to the phenolic resin is 0.3-1.2: 100 to 150.
5. The preparation method of the modified phenolic resin for precoated sand according to claim 1, characterized by comprising the following steps: the phenolic resin is prepared according to the following steps:
sequentially adding phenol, formaldehyde and oxalic acid into a reaction kettle, heating to 80-85 ℃ under stirring, stopping heating, controlling the temperature to react for 2-4 hours under reflux, cooling to 40-50 ℃, adding an amine compound, stirring for reacting for 1-2 hours, distilling and dehydrating when the content of free phenol is less than 0.5%, starting vacuum when the temperature in the reaction kettle is raised to 130-150 ℃, dehydrating for 0.5-1 hour, and closing the vacuum to obtain phenolic resin;
the amine compound is acetamide or/and hexamethylene diamine;
wherein the mass ratio of phenol to formaldehyde to oxalic acid to the amine compound is 80-90: 55-65: 5-15: 20 to 30.
6. The preparation method of the modified phenolic resin for precoated sand according to claim 5, characterized by comprising the following steps: the amine compound is prepared from acetamide and hexamethylene diamine according to a mass ratio of (2-5): 1.
7. The preparation method of the modified phenolic resin for precoated sand according to claim 5, characterized by comprising the following steps: the method comprises the following steps:
adding phenol, formaldehyde and oxalic acid into a reaction kettle in sequence, heating to 85 ℃ under stirring, stopping heating, controlling the temperature to react for 2-4 hours under reflux, cooling to 45-50 ℃, adding an amine compound, stirring and reacting for 1-2 hours, distilling and dehydrating when the content of free phenol is less than 0.5%, starting vacuum when the temperature in the reaction kettle is raised to 140-150 ℃, dehydrating for 0.5-1 hour, and closing the vacuum to obtain a reaction solution for later use;
the amine compound is prepared from acetamide and hexamethylene diamine according to a mass ratio of 4: 1, obtaining;
wherein the mass ratio of phenol to formaldehyde to oxalic acid to the amine compound is 80-90: 55-65: 5-15: 20-30;
uniformly mixing montmorillonite and water, adding the mixture into molten nylon 66, mixing for 1-2 hours at 275-280 ℃, and extruding and granulating to obtain organic modified nano montmorillonite for later use;
wherein the mass ratio of nylon 66 to montmorillonite to water is 25: 4: 25;
adding a modified coupling agent and the organic modified nano-montmorillonite obtained in the step II into the reaction kettle in the step I, stirring and reacting for 1-2 hours at 130-150 ℃, cooling and discharging to obtain modified phenolic resin for precoated sand;
the modified coupling agent is prepared from sodium hexametaphosphate, a silane coupling agent and aluminum chloride according to the mass ratio of 1-4: 20-30: 3-6;
wherein the mass ratio of phenol, modifier and the organic modified nano montmorillonite obtained in the step II is 80-90: 0.5-1: 0.1 to 1.
8. The method for preparing the modified phenolic resin for precoated sand according to claim 7, characterized by comprising the following steps: the modified coupling agent is prepared from sodium hexametaphosphate, a silane coupling agent and aluminum chloride according to the mass ratio of 2: 25: 5.
9. The method for preparing the modified phenolic resin for precoated sand according to claim 7, characterized by comprising the following steps: wherein the mass ratio of phenol, formaldehyde, oxalic acid and amine compounds is 85: 60: 10: 25.
10. the method for preparing the modified phenolic resin for precoated sand according to claim 7, characterized by comprising the following steps: the mass ratio of phenol, modifier and the organic modified nano montmorillonite obtained in the step II is 85: 0.6: 0.8.
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| CN117736004A (en) * | 2024-02-20 | 2024-03-22 | 宜兴市恒祥耐火材料有限公司 | Thermal shock resistant refractory casting material and preparation method thereof |
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