High-strength phenolic resin for coated sand and method for preparing the same

Abstract

The application discloses a kind of high-strength phenolic resin for coated sand and a preparation method thereof, the preparation method comprises the following steps: S1, phenol and aldehyde are added to a reaction kettle, then an acidic catalyst is added, stirred, and a phenolic resin is prepared by reaction;S2, the phenolic resin prepared in step S1 is subjected to distillation treatment until the phenol content is less than 5.0wt%, then silicon powder is added, mixed, and discharged.The phenolic resin product obtained by the application can be mixed with silica sand and other materials to obtain a kind of coated sand.The phenolic resin of the application has the characteristics of low price and high strength.The coated sand produced by the phenolic resin of the application has the characteristics of high temperature resistance, low gas emission and low expansion.

Description

Technical Field

[0001] This invention belongs to the field of casting coated sand, specifically relating to a phenolic resin for high-strength coated sand and its preparation method. Background Technology

[0002] Coated sand is molding sand or core sand whose surface is coated with a solid resin film before molding. Currently, coated sand is mainly prepared using a thermal coating process, which involves heating the raw sand to a certain temperature, then mixing it with phenolic resin, hexamethylenetetramine aqueous solution, and calcium stearate, followed by stirring, cooling, crushing, and sieving.

[0003] In the existing technology, the coated sand prepared has disadvantages such as low high-temperature strength, short heat resistance time, and large high-temperature deformation during the shell core manufacturing process, which easily leads to a high scrap rate and cannot meet production needs. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a high-strength phenolic resin for coated sand and its preparation method. This phenolic resin binder has the characteristics of high strength and good heat resistance. Coated sand produced using the phenolic resin of this invention has the characteristics of high high-temperature performance, low gas evolution, low expansion rate, and oxidation resistance.

[0005] The technical solution of this invention is as follows:

[0006] This invention relates to a method for preparing a high-strength coated sand phenolic resin, comprising the following steps:

[0007] S1. Add phenol and aldehyde to the reaction vessel, then add an acidic catalyst, stir, and react to obtain phenolic resin;

[0008] S2. The phenolic resin obtained in step S1 is distilled until the phenol content is less than 5.0 wt%, and then silica powder is added and mixed well.

[0009] Preferably, in step S1, the mass ratio of phenol to aldehyde is 100:35-65; the reaction conditions are: heating to 80-100°C and maintaining for 1-8 hours.

[0010] Preferably, in step S1, the acidic catalyst is selected from one or more of hydrochloric acid, oxalic acid, phosphoric acid, sulfuric acid, diethyl sulfate, halosulfonic acid, benzenesulfonic acid, and their alkyl-substituted derivatives. In the preparation of phenolic resin, this invention uses an acidic catalyst to ensure that the obtained phenolic resin is a thermoplastic phenolic resin, providing sufficient reaction time to guarantee complete reaction of the aldehyde.

[0011] Preferably, in step S2, the distillation process is vacuum distillation. The distillation process removes excess phenol until the phenol content is below 5.0 wt%.

[0012] Preferably, in step S2, the mass of added silicon micropowder accounts for 1 to 30 wt% of the total weight.

[0013] Preferably, in step S2, the particle size of the silicon micropowder is 10-100 micrometers.

[0014] This invention also relates to a high-strength phenolic resin for coated sand, prepared using the above-described method. This phenolic resin is used as a binder in the preparation of coated sand, and is used together with silica sand, hexamethylenetetramine, and calcium stearate as raw materials to prepare the coated sand.

[0015] The beneficial effects of this invention are:

[0016] (1) The phenolic resin prepared by the present invention has the characteristics of high strength and good heat resistance as a binder. The coated sand produced by using the phenolic resin of the present invention has the characteristics of high high temperature performance, low gas generation, low expansion rate and oxidation resistance.

[0017] (2) The silicon micro powder used in this invention has a very fine particle size, which can reach 10-100 micrometers. Due to the fine particle size, adding it during the mixing process of coated sand will cause fine powder to fly around and be unevenly mixed. In this invention, silicon micro powder is first used to manufacture phenolic resin. Silicon micro powder and phenolic resin can be mixed very evenly. Then, when manufacturing coated sand, it will be evenly distributed and coated on the surface of the sand along with the resin, thereby improving the strength and heat resistance of the coated sand. Detailed Implementation

[0018] The present invention will now be described in detail with reference to specific embodiments. The description in this section is merely illustrative and explanatory, and should not be construed as limiting the scope of protection of the present invention.

[0019] Example 1

[0020] Phenol, formaldehyde, and oxalic acid were added to a reaction vessel at a mass ratio of 100:35:2. The mixture was heated and stirred to 100°C and kept at this temperature for 3 hours. The phenol was removed by vacuum distillation. Finally, 10 wt% of silica powder (with a particle size of 10 micrometers) was added and stirred evenly before being discharged.

[0021] Example 2

[0022] Phenol, formaldehyde, and sulfuric acid were added to a reaction vessel at a mass ratio of 100:50:1. The mixture was heated and stirred to 80°C and kept at this temperature for 2 hours. The phenol was removed by vacuum distillation. Finally, 20 wt% of silica powder (with a particle size of 20 micrometers) was added and stirred evenly before being discharged.

[0023] Example 3

[0024] Phenol, formaldehyde, and hydrochloric acid were added to the reaction vessel in a mass ratio of 100:65:1.5. The mixture was heated and stirred to 70°C and kept at this temperature for 3 hours. The phenol was removed by vacuum distillation. Finally, 30 wt% of silica powder (with a particle size of 44 micrometers) was added and stirred evenly before discharging.

[0025] Comparative Example 1

[0026] Phenol, formaldehyde, and hydrochloric acid were added to a reaction vessel in a mass ratio of 100:65:1.5. The mixture was heated and stirred to 70°C and kept at this temperature for 3 hours. The phenol was removed by vacuum distillation, and the product was discharged to obtain ordinary phenolic resin.

[0027] Comparative Example 2

[0028] Phenol, formaldehyde, and hydrochloric acid were added to a reaction vessel at a mass ratio of 100:65:1.5, heated and stirred to 70°C, and kept at this temperature for 3 hours. The phenol was then removed by vacuum distillation, and the resulting material was ordinary phenolic resin. Then, during the preparation of the coated sand, silica powder (with a particle size of 44 micrometers) was added as an additive, and the mixture was thoroughly mixed to obtain the coated sand.

[0029] Comparative Example 3

[0030] Phenol, formaldehyde, and hydrochloric acid were added to the reaction vessel in a mass ratio of 100:65:1.5. The mixture was heated and stirred to 70°C and kept at this temperature for 3 hours. The phenol was removed by vacuum distillation. Finally, 30 wt% of alumina powder (with a particle size of 44 micrometers) was added and stirred evenly before being discharged.

[0031] Comparative Example 4

[0032] Phenol, formaldehyde, and hydrochloric acid were added to the reaction vessel in a mass ratio of 100:65:1.5. The mixture was heated and stirred to 70°C and kept at this temperature for 3 hours. The phenol was removed by vacuum distillation. Finally, ceramic powder (with a particle size of 44 micrometers) accounting for 30 wt% of the total mass was added and stirred evenly before being discharged.

[0033] The phenolic resin-coated sands prepared in Examples 1-3 and Comparative Examples 1-4, as shown in Table 1, have the following mass fractions of main components. The prepared coated sands were pressed into cylinders with a diameter of Φ12mm × 20mm using a sample preparation machine. High-temperature compressive strength, high-temperature heat resistance time, high-temperature expansion rate, and gas evolution were tested according to "JB / T13037-2017 Test Method for High-Temperature Performance of Coated Sand". The comparative experimental results are shown in Table 2.

[0034] Table 1 Composition of Coated Sand

[0035]

[0036] Table 2 Comparative test results of coated sand with different additives

[0037]

[0038]

[0039] As can be seen from Examples 1-3 and Comparative Example 1 in Table 1, the only difference between the above-mentioned coated sands is the binder; the other components and contents are the same. Comparative testing was conducted on these four groups of coated sands, and the results are listed in Table 2. The results in Table 2 show that, under the same manufacturing conditions, the coated sand produced by this invention has significantly improved performance compared to the coated sand produced by ordinary phenolic resin in Comparative Example 1, exhibiting higher high-temperature compressive strength and higher high-temperature heat resistance time; and lower gas evolution and higher high-temperature expansion rate.

[0040] As can be seen from Example 3 and Comparative Example 2 in Table 1, the coated sand produced by adding silica powder to phenolic resin in this invention is significantly better than the coated sand obtained by directly adding silica powder during the production of coated sand in Comparative Example 2. The results of the comparative tests are listed in Table 2. Table 2 shows that the coated sand produced by this invention has significantly improved performance, exhibiting higher high-temperature compressive strength and higher high-temperature heat resistance time; lower gas evolution and lower high-temperature expansion rate.

[0041] As can be seen from Table 1, Examples 3 and 4 differ only in the use of silica powder, alumina powder, and ceramic powder; all other components and their contents are the same. Comparative testing was conducted on these three groups of coated sand, and the results are listed in Table 2. Table 2 shows that, under the same manufacturing conditions, the coated sand produced by this invention exhibits significantly improved performance compared to the coated sand produced using alumina powder and ceramic powder in Comparative Examples 3 and 4. It possesses higher high-temperature compressive strength and higher high-temperature heat resistance time, as well as lower gas evolution and higher high-temperature expansion rate.

[0042] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a high-strength coated sand phenolic resin, characterized in that, Includes the following steps: S1. Add phenol and aldehyde to the reaction vessel, then add an acidic catalyst, stir, and react to obtain phenolic resin; S2. The phenolic resin obtained in step S1 is distilled until the phenol content is less than 5.0 wt%, then silica powder is added and mixed well; wherein the particle size of the silica powder is 10-100 micrometers, and the mass of the silica powder added accounts for 1-30 wt% of the total weight; The phenolic resin is used as a binder in the preparation of coated sand, and is used together with silica sand, hexamethylenetetramine, and calcium stearate as raw materials to prepare coated sand.

2. The preparation method according to claim 1, characterized in that, In step S1, the mass ratio of phenol to aldehyde is 100:35-65; the reaction conditions are: heating to 80-100℃ and maintaining for 1-8 hours.

3. The preparation method according to claim 1, characterized in that, In step S1, the acidic catalyst is selected from one or more of hydrochloric acid, oxalic acid, phosphoric acid, sulfuric acid, diethyl sulfate, halosulfonic acid and benzenesulfonic acid and their alkyl-substituted derivatives.

4. The preparation method according to claim 1, characterized in that, In step S2, the distillation process is vacuum distillation.

5. A phenolic resin for high-strength coated sand, characterized in that, It is prepared by the preparation method according to any one of claims 1-4.

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