Foundry parts containing fly ash modified liquid phenol-formaldehyde resin and method for producing the same

Abstract

This invention belongs to the field of modified phenolic resin technology, specifically relating to a casting containing fly ash modified liquid phenolic resin and its preparation method, comprising the following steps: preheating the mold to 100-130℃ and holding it at that temperature for 20-30 minutes; pouring in fly ash modified liquid phenolic resin and pre-curing it at 100-130℃ for 1-3 hours; and subjecting the pre-cured fly ash modified liquid phenolic resin to stepwise heating and pressurization curing to obtain the casting; wherein, the preparation method of the fly ash modified liquid phenolic resin comprises the following steps: S1, pretreating the fly ash by sequentially performing mechanical grinding, acid washing activation, drying and dehydration, and coupling agent modification to obtain modified fly ash; S2, heating the liquid phenolic resin to 50-80℃ to reduce the viscosity to 100-300 mPa·s, then adding the modified fly ash and dispersing it by high-speed stirring to obtain fly ash modified liquid phenolic resin.

Description

Technical Field

[0001] This invention belongs to the field of modified phenolic resin technology, specifically relating to a casting containing fly ash-modified liquid phenolic resin and its preparation method. Background Technology

[0002] Phenolic resin is a core thermosetting resin in industry, but when it cures in its liquid state, volatile substances such as formaldehyde and water escape and form bubbles, leading to an increase in porosity (usually >8%), which reduces the impact strength to ≤1.8KJ / m. 2 Wear rate ≥ 50×10 -2 This severely limits its application in fields with stringent performance requirements, such as wear-resistant coatings.

[0003] The existing improvement plan has two major bottlenecks: ① expensive filler modification: if rare earth oxides are used, the cost is 12,000 yuan / ton, and the porosity can only be reduced to 5%-6%, which is not commensurate with the cost and effect, and it is difficult to promote on a large scale; ② physical degassing process: such as vacuum degassing, is ineffective for thick-walled castings and extends the curing time to more than 15 hours, which greatly reduces production efficiency and is difficult to meet the needs of industrial production.

[0004] Therefore, overcoming the defect of low degassing efficiency in castings made from phenolic resin is a technical problem that urgently needs to be solved in this field.

[0005] It should be noted that the information disclosed in this background section is only for understanding the background technology of the present application concept, and therefore, the above description is not considered to constitute prior art information. Summary of the Invention

[0006] This disclosure provides at least one example of a casting containing fly ash-modified liquid phenolic resin and a method for preparing the same.

[0007] In a first aspect, embodiments of this disclosure provide a method for preparing a casting, comprising the following steps: preheating the mold to 100-130°C and holding it at that temperature for 20-30 minutes; pouring in fly ash-modified liquid phenolic resin and pre-curing it at 100-130°C for 1-3 hours; and subjecting the pre-cured fly ash-modified liquid phenolic resin to stepwise heating and pressurization curing to obtain a casting; wherein, the method for preparing the fly ash-modified liquid phenolic resin comprises the following steps: S1, pre-treating the fly ash by sequentially performing mechanical grinding, acid washing activation, drying and dehydration, and coupling agent modification to obtain modified fly ash; S2, ... Liquid phenolic resin is heated to 50–80°C to reduce its viscosity to 100–300 mPa·s. Modified fly ash is then added and dispersed by high-speed stirring to obtain fly ash-modified liquid phenolic resin. The stepped heating and pressurizing curing process includes: a first stage of heating at 100–110°C for 1.5–3 hours while maintaining a pressure of 5.0–5.5 MPa; a second stage of heating at 110–130°C for 1.5–3 hours while maintaining a pressure of 5.5–6.0 MPa; and a third stage of heating at 130–150°C for 1.5–3 hours while maintaining a pressure of 6.0–6.5 MPa.

[0008] In one optional embodiment, the mechanical grinding, acid washing activation, drying and dehydration, and coupling agent modification specifically include: S11, mechanical grinding, grinding fly ash to a particle size of 5-50 μm; S12, acid washing activation, soaking the ground fly ash in 5wt% hydrochloric acid to remove surface impurities and activate surface hydroxyl groups; S13, drying and dehydration, drying at 100-130℃ to make the activated fly ash moisture content <0.5%; S14, adding 0.5%-2% of a coupling agent by mass to the dried fly ash, and stirring at high speed to obtain modified fly ash.

[0009] In one optional embodiment, the high-speed stirring method in S2 is a high-speed homogenizing emulsifier with a rotation speed of 5000-10000 rpm and a stirring time of 30-60 min.

[0010] In one optional embodiment, the high-speed stirring method in S2 is an oil bath or a heated stirrer with a temperature range of 90 to 120°C and an auxiliary speed of 300 to 800 rpm.

[0011] In one optional embodiment, the liquid phenolic resin has a solid content of 70±2% and a viscosity of 600~700mPa·s at 25°C.

[0012] In one optional embodiment, the fly ash has a particle size of 1-100 μm and comprises the following components by mass: 40-60 parts SiO2, 20-40 parts Al2O3, and 5-15 parts Fe2O3.

[0013] In one optional embodiment, the impact strength of the fly ash modified liquid phenolic resin is not less than 3.60 KJ / m. 2 The tensile strength is not less than 28.51 MPa.

[0014] Secondly, embodiments of this disclosure also provide a casting prepared using the method described above.

[0015] Thirdly, this disclosure also provides a fly ash modified liquid phenolic resin. The preparation method of the fly ash modified liquid phenolic resin includes the following steps: S1, pretreating fly ash by sequentially performing mechanical grinding, acid washing activation, drying and dehydration, and coupling agent modification to obtain modified fly ash; S2, heating the liquid phenolic resin to 50-80°C to reduce the viscosity to 100-300 mPa·s, then adding the modified fly ash and dispersing it by high-speed stirring to obtain the fly ash modified liquid phenolic resin.

[0016] Fourthly, embodiments of this disclosure also provide an application of fly ash modified liquid phenolic resin as described above in the fields of wear-resistant coatings, mechanical parts encapsulation, and mold materials.

[0017] The beneficial effects of this invention are that the casting containing fly ash modified liquid phenolic resin and its preparation method obtain a phenolic resin with modified fly ash that is not prone to agglomeration by multi-stage modification of fly ash combined with heating and high-speed dispersion of phenolic resin. The porous structure of fly ash can effectively capture volatile molecules, resulting in a porosity of less than 1% in the cured casting, which is far superior to rare earth modification and vacuum degassing processes, effectively omitting the degassing process step. At the same time, it is superior to existing phenolic resin modification schemes in terms of impact strength, tensile strength, wear resistance and cost.

[0018] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained through the structures particularly pointed out in the description and the drawings.

[0019] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 Impact castings made from modified phenolic resin (left) and ordinary phenolic resin (right) according to embodiments of this disclosure; Figure 2 Impact fracture morphology images of modified phenolic resin (left) and ordinary phenolic resin (right) provided in the embodiments of this disclosure; Figure 3 Tensile castings of modified phenolic resin (left) and ordinary phenolic resin (right) provided in embodiments of this disclosure; Figure 4 Tensile fracture morphology images of modified phenolic resin (left) and ordinary phenolic resin (right) provided in embodiments of this disclosure; Figure 5 This is a case study of a failed ordinary phenolic resin tensile casting provided in the embodiments of this disclosure. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] As used herein, the phrases “in one embodiment,” “according to one embodiment,” “in some embodiments,” etc., generally refer to the fact that a particular feature, structure, or characteristic following the phrase can be included in at least one embodiment of this disclosure. Therefore, a particular feature, structure, or characteristic can be included in more than one embodiment of this disclosure, such that these phrases do not necessarily refer to the same embodiment. As used herein, the terms “example,” “exemplary,” etc., are used to “serve as an example, instance, or illustration.” Any implementation, aspect, or design described herein as “example” or “exemplary” is not necessarily to be construed as preferred or superior to other implementations, aspects, or designs. Rather, the use of the terms “example,” “exemplary,” etc., is intended to present concepts in a specific manner.

[0024] In this document, exemplary embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. As used herein, expressions such as “at least one of…” modify the entire list of elements when following a list of elements, rather than individual elements in the list. For example, the expression “at least one of a, b, and c” should be understood to include only a, only b, only c, both a and b, both a and c, both b and c, or all of a, b, and c.

[0025] The terminology used herein is for the purpose of describing specific exemplary configurations only and is not intended to be limiting. As used herein, the singular articles “a,” “an,” and “the” may also be intended to include plural forms unless otherwise clearly stated herein. The terms “comprising,” “including,” and “having” are inclusive and thus specify the presence of features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein should not be construed as requiring them to be performed in the specific order discussed or shown, unless specifically identified as such. Additional or alternative steps may be employed.

[0026] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0027] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0028] This disclosure provides a method for preparing a casting, comprising the following steps: preheating the mold to 100-130°C and holding it at that temperature for 20-30 minutes; pouring in fly ash-modified liquid phenolic resin and pre-curing it at 100-130°C for 1-3 hours; and subjecting the pre-cured fly ash-modified liquid phenolic resin to stepwise heating and pressurization curing to obtain the casting; wherein, the preparation method of the fly ash-modified liquid phenolic resin comprises the following steps: S1, pre-treating the fly ash by sequentially performing mechanical grinding, acid washing activation, drying and dehydration, and coupling agent modification to obtain modified fly ash; S2, adding liquid... Phenolic resin is heated to 50–80°C to reduce its viscosity to 100–300 mPa·s. Modified fly ash is then added and dispersed by high-speed stirring to obtain fly ash-modified liquid phenolic resin. The stepwise heating and pressurizing curing includes: a first stage of heating at 100–110°C for 1.5–3 hours while maintaining a pressure of 5.0–5.5 MPa; a second stage of heating at 110–130°C for 1.5–3 hours while maintaining a pressure of 5.5–6.0 MPa; and a third stage of heating at 130–150°C for 1.5–3 hours while maintaining a pressure of 6.0–6.5 MPa.

[0029] Specifically, preheating can prevent uneven curing caused by excessive temperature difference between the resin and the mold.

[0030] Specifically, in the first stage, the active hydroxymethyl group (-CH2OH) undergoes a condensation reaction with the ortho / para hydrogen of the phenolic hydroxyl group to generate a methylene bond (-CH2-); at the same time, some hydroxymethyl groups will dehydrate to form a methylene ether bond (-CH2-O-CH2-).

[0031] Specifically, in the second stage, the initially generated methylene ether bonds (-CH2-O-CH2-) undergo a cleavage-rearrangement reaction above 130°C, decomposing into formaldehyde and hydroxymethyl groups. Subsequently, the formaldehyde participates in the synthesis of new methylene bonds, transforming the cross-linked network from one containing unstable ether bonds to one dominated by stable methylene bonds. Unreacted hydroxymethyl and phenolic hydroxyl active sites continue to react, increasing the degree of molecular chain branching and further increasing the system viscosity, transitioning from a viscous flow state to an elastic state.

[0032] Specifically, in the third stage, the remaining active sites (phenolic hydroxyl groups and a small amount of unreacted hydroxymethyl groups) will react completely, the crosslinking density will reach its peak, and a highly stable three-dimensional network structure will be formed. Continuous pressure can avoid bubbling caused by the volatilization of small molecules (water, formaldehyde), while ensuring a tighter bond at the resin interface and guaranteeing the system's density.

[0033] In some embodiments, specifically, the mechanical grinding, acid washing activation, drying and dehydration, and coupling agent modification specifically include: S11, mechanical grinding, grinding fly ash to a particle size of 5-50 μm; S12, acid washing activation, soaking the ground fly ash in 5wt% hydrochloric acid to remove surface impurities and activate surface hydroxyl groups; S13, drying and dehydration, drying at 100-130℃ to make the activated fly ash moisture content <0.5%; S14, adding 0.5%-2% of coupling agent by mass to the dried fly ash, and stirring at high speed to obtain modified fly ash.

[0034] In some embodiments, specifically, the high-speed stirring method in S2 is a high-speed homogenizing emulsifier with a rotation speed of 5000-10000 rpm and a stirring time of 30-60 min.

[0035] In some embodiments, specifically, the high-speed stirring method in S2 is an oil bath or a heated stirrer, with a temperature range of 90 to 120°C and an auxiliary speed of 300 to 800 rpm.

[0036] In some embodiments, specifically, the liquid phenolic resin has a solid content of 70±2% and a viscosity of 600~700mPa·s at 25°C.

[0037] In some embodiments, specifically, the fly ash has a particle size of 1-100 μm and comprises the following components by mass: 40-60 parts SiO2, 20-40 parts Al2O3, and 5-15 parts Fe2O3.

[0038] In some embodiments, specifically, the impact strength of the fly ash modified liquid phenolic resin is not less than 3.60 KJ / m. 2 The tensile strength is not less than 28.51 MPa.

[0039] This disclosure also provides a fly ash modified liquid phenolic resin, which is prepared using the method described above.

[0040] In some embodiments, specifically, the impact strength of the fly ash modified liquid phenolic resin is not less than 3.60 KJ / m. 2 The tensile strength is not less than 28.51 MPa.

[0041] This disclosure also provides a casting prepared using the method described above.

[0042] This disclosure also provides a fly ash modified liquid phenolic resin. The preparation method of the fly ash modified liquid phenolic resin includes the following steps: S1, pretreating fly ash by sequentially performing mechanical grinding, acid washing activation, drying and dehydration, and coupling agent modification to obtain modified fly ash; S2, heating the liquid phenolic resin to 50-80℃ to reduce the viscosity to 100-300 mPa·s, then adding the modified fly ash and dispersing it by high-speed stirring to obtain the fly ash modified liquid phenolic resin.

[0043] This disclosure also provides an application of fly ash modified liquid phenolic resin as described above in the fields of wear-resistant coatings, mechanical parts encapsulation, and mold materials.

[0044] The liquid phenolic resin used in the following examples is a commercially available thermosetting phenolic resin (PF-6560 type, solid content 70±2%, viscosity 600-700mPa·s / 25℃), and the fly ash is Grade II fly ash (particle size 5~50μm, SiO2 content 50wt%, Al2O3 content 40wt%, residual metal oxide content 10%).

[0045] The preparation of modified fly ash includes: S1, pretreatment of fly ash, which involves mechanical grinding, acid washing and activation, drying and dehydration, and coupling agent modification to obtain modified fly ash. Specifically, this includes: S11, mechanical grinding, grinding the fly ash to a particle size of 5-50 μm for 10-40 min; S12, acid washing and activation, immersing the ground fly ash in 5 wt% hydrochloric acid for 1-3 h to remove surface impurities and activate surface hydroxyl groups; S13, drying and dehydration, drying at 100-130℃ to ensure the activated fly ash has a moisture content of <0. 0.5%; S14, add 0.5% to 2% of coupling agent by mass to the dried fly ash, stir at high speed so that the contact angle between the modified fly ash and the phenolic resin is not higher than 30°, and stir for 5 to 30 minutes to obtain modified fly ash; S2, heat the liquid phenolic resin to 50 to 80°C to reduce the viscosity to 100 to 300 mPa·s, then add the modified fly ash to it, and stir through a high-speed homogenizing emulsifier at a speed of 5000 to 10000 rpm for 30 to 60 minutes to obtain fly ash modified liquid phenolic resin.

[0046] Example 1: Preparation of fly ash modified resin impact test specimens Preparation of modified resin: Take 100 parts of liquid phenolic resin, heat to 60℃, and reduce the viscosity to 300 mPa·s; gradually add 5 parts of pretreated fly ash, and stir for 45 minutes using a high-speed disperser (8000 rpm) to obtain a uniform modified resin. Curing and Molding: The modified resin is poured into a preheated mold (110℃, 30min) and cured according to the following stepped curing regime: 110℃ / 2h (5.0MPa), 130℃ / 2h (5.5MPa), 150℃ / 2h (6.0MPa). After crosslinking and curing, the resin is demolded to obtain the modified resin impact test specimen, such as... Figure 1 As shown on the left, the appearance is uniformly dark gray with no visible pores; Performance testing: Tested according to GB / T 2567-2008 Test methods for the properties of resin castings, the impact strength is 3.60 KJ / m²; the fracture morphology is as follows. Figure 2 As shown on the left (SEM, 500×), the fracture surface is rough, exhibiting ductile tearing characteristics, with no obvious pores and low porosity.

[0047] Example 2: Preparation of tensile specimens of fly ash modified resin Preparation of modified resin: Same as in Example 1, take 100 parts of liquid phenolic resin and 5 parts of pretreated fly ash to prepare modified resin; Curing and molding: The modified resin was poured into a preheated mold (110℃, 30 min), and the curing process was the same as in Example 1. After demolding, a modified resin tensile specimen was obtained, such as... Figure 3 As shown on the left; Performance testing: Tested according to GB / T 2567-2008 Test methods for properties of resin castings, the tensile strength was 28.51 MPa; the fracture morphology is as follows. Figure 4 As shown on the left (SEM, 1200×), the fracture surface exhibits a fibrous and stepped structure with no macroscopic pores and a tight interface.

[0048] Comparative Example 1: Preparation of ordinary resin impact test specimens Ordinary resin treatment: Take 100 parts of liquid phenolic resin, heat to 60℃, and treat with vacuum degassing process for 45 minutes; Curing and Molding: Ordinary resin was poured into a preheated mold (110℃, 30 min), and the curing process was the same as in Example 1. After demolding, the ordinary resin impact sample was obtained. Due to too many air bubbles, relevant tests could not be performed. Figure 5 As shown on the left.

[0049] Comparative Example 2: Preparation of ordinary resin tensile specimens Ordinary resin treatment: Same as Comparative Example 1, take 100 parts of liquid phenolic resin and degas under vacuum for 45 minutes; Curing and molding: Ordinary resin was poured into a preheated mold (110℃, 30 min), and the curing process was the same as in Example 1. After demolding, the ordinary resin tensile specimens were obtained. However, due to too many air bubbles, relevant tests could not be performed (e.g., Figure 5 (As shown on the right).

[0050] Comparative Example 3: Preparation of pure phenolic resin impact test specimens Ordinary resin treatment: Same as Comparative Example 1, take 100 parts of liquid phenolic resin and degas under vacuum for 45 minutes; Curing and Molding: Ordinary resin is poured into a preheated mold (120℃, 30 min) and cured according to the following stepped curing regime: 120℃ / 3h (5.5MPa), 150℃ / 3h (6.0MPa), 170℃ / 3h (6.5MPa). After demolding, ordinary resin impact test specimens are obtained, such as... Figure 1 As shown on the right, a large number of pores can be seen on the surface of the sample; Performance testing: Tested according to GB / T 2567-2008 Test methods for the properties of resin castings, the impact strength is 1.73 KJ / m²; the fracture morphology is as follows. Figure 2 As shown on the right, the fracture surface is flat and smooth, exhibiting brittle fracture characteristics, with a large number of round or elliptical pores and a relatively high porosity.

[0051] Comparative Example 4: Preparation of tensile specimens from pure phenolic resin Ordinary resin treatment: Same as Comparative Example 1, take 100 parts of liquid phenolic resin and degas under vacuum for 45 minutes; Curing and molding: Ordinary resin was poured into a preheated mold (120°C, 30 min), and the curing regime was the same as that of Comparative Example 3. After demolding, ordinary resin tensile specimens were obtained (e.g., Figure 3 As shown on the right, the specimen thickness is 4mm, some air bubbles can be expelled, and there are no obvious pores on the surface. Performance testing: Tested according to GB / T 2567-2008 Test methods for properties of resin castings, the tensile strength was 12 MPa; the fracture morphology is as follows. Figure 4 As shown on the right, the fracture surface is flat and smooth, without any toughness characteristics.

[0052] Specifically, the porosity in Example 1 and Comparative Example 3 was qualitatively determined through fracture morphology analysis. In further quantitative analysis, the density of the ordinary phenolic resin in Comparative Example 3 was 1.2652 g / cm³. 3 The density of the modified phenolic resin in Example 1 is 1.3506 g / cm³. 3 According to the calculation, the porosity of the modified phenolic resin in Example 1 is less than 1%.

[0053] Comparative test of wear resistance Reciprocating friction tests were conducted on ordinary phenolic resin and modified phenolic resin. Test conditions: load 30 N, test duration 15 min, grinding ball diameter 6 mm (GCr15 steel ball), 3 samples per group. Results are as follows: Table 1 compares the performance of ordinary phenolic resin and modified phenolic resin.

[0054] As shown in Table 1, the modified resin maintained a relatively stable coefficient of friction, but the wear rate decreased by 96.3%, the wear life was extended by ≥275%, and the wear resistance was significantly improved.

[0055] Specifically, fly ash-modified phenolic resin castings exhibit lower temperature, pressure, and time requirements during the curing process compared to pure phenolic resin. This is primarily due to the unique role of fly ash as a filler and modifier. Through the capillary adsorption of the porous structure of fly ash, volatile molecules such as formaldehyde and water vapor generated during curing can be effectively captured, reducing the resin porosity to below 1%, with no visible pores. This is far superior to the 5%-6% porosity of rare earth-modified resins and the 3%-4% porosity of vacuum degassing, and the vacuum degassing process is ineffective on thick-walled parts, completely resolving the bubble defects in liquid phenolic resin curing. Fly ash is an industrial byproduct, mainly composed of silica, alumina, and small amounts of metal oxides. These components can synergistically interact with phenolic resin, promoting the cross-linking reaction. Through modification, the gelation kinetics of the composite material are accelerated, forming a more stable network structure, thereby optimizing the overall curing process. This modification not only improves the mechanical properties and thermal stability of the material but also reduces energy consumption and production cycle, making it more advantageous in casting applications.

[0056] Regarding temperature, the maximum reaction temperature of fly ash-modified phenolic resin is also lower than that of pure phenolic resin. This is because the inorganic components in fly ash establish strong interfacial bonds between the organic phenolic polymer and the inorganic network, causing the microstructure to shift from an open-cell structure to a closed-cell structure. This structural modulation accelerates the gelation process, reduces the activation energy requirement, and thus allows the curing reaction to be completed at a lower temperature, avoiding the problems of excessively rapid hardening or uneven resin development that may be caused by high temperatures.

[0057] Regarding curing time, the modified material exhibits faster gelation dynamics and a significantly shorter overall curing cycle. This is attributed to the catalyst-like effect of fly ash, whose oxide components promote resin cross-linking and reduce the reaction duration. Compared to pure phenolic resin, which requires a longer heating period to ensure full polymerization, the modified material achieves a similar degree of curing in a shorter time while simultaneously increasing its strength.

[0058] Phenolic resins produce byproducts such as water vapor during curing. Applying pressure helps to remove these volatiles, reducing porosity in the composite material and forming a denser structure. Due to its high porosity, fly ash provides numerous adsorption sites, giving it high surface activity. Furthermore, unburned carbon residue enhances its gas adsorption capacity. Therefore, fly ash can effectively capture and immobilize volatile small molecules in the system, inhibiting their aggregation and escape into bubbles during the curing heating stage. This allows for a reduction in pressure requirements during curing, achieving effective molding and curing at lower pressures. This not only simplifies the process but also reduces equipment requirements.

[0059] In summary, the casting containing fly ash modified liquid phenolic resin and its preparation method, through multi-stage modification of fly ash combined with heating to reduce viscosity and high-speed dispersion of phenolic resin, obtains a phenolic resin with modified fly ash that is not prone to agglomeration. The porous structure of fly ash can effectively capture volatile molecules, resulting in a porosity of less than 1% in the cured casting, which is far superior to rare earth modification and vacuum degassing processes, effectively omitting the degassing process step. At the same time, it is superior to existing phenolic resin modification schemes in terms of impact strength, tensile strength, wear resistance, and cost.

[0060] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for preparing a casting, characterized in that, Includes the following steps: Preheat the mold to 100-130℃ and keep it warm for 20-30 minutes; Pour in fly ash-modified liquid phenolic resin and pre-cur at 100–130°C for 1–3 hours; Pre-cured fly ash modified liquid phenolic resin is cured by step heating and pressurization to obtain castings; The preparation method of the fly ash modified liquid phenolic resin includes the following steps: S1, the fly ash is pretreated by mechanical grinding, acid washing and activation, drying and dehydration and coupling agent modification in sequence to obtain modified fly ash; S2, the liquid phenolic resin is heated to 50-80℃ to reduce the viscosity to 100-300mPa·s, and then modified fly ash is added to it and dispersed by high-speed stirring to obtain fly ash modified liquid phenolic resin. The stepped temperature and pressure curing includes: In the first stage, heat at 100–110℃ for 1.5–3 hours while maintaining a pressure of 5.0–5.5 MPa; In the second stage, heat at 110–130℃ for 1.5–3 hours while maintaining a pressure of 5.5–6.0 MPa; In the third stage, heat at 130–150℃ for 1.5–3 hours while maintaining a pressure of 6.0–6.5 MPa.

2. The preparation method according to claim 1, characterized in that, The mechanical grinding, acid washing and activation, drying and dehydration, and coupling agent modification specifically include: S11, mechanical grinding, grinding fly ash to a particle size of 5-50μm; S12, acid washing and activation, involves soaking the ground fly ash in 5wt% hydrochloric acid to remove surface impurities and activate surface hydroxyl groups. S13, dried and dehydrated at 100-130℃, so that the activated fly ash has a moisture content of <0.5%; S14, modified fly ash is obtained by adding 0.5% to 2% of a coupling agent by mass to dried fly ash and stirring at high speed.

3. The preparation method according to claim 1, characterized in that, The high-speed stirring method in S2 is a high-speed homogenizing emulsifier with a speed of 5000-10000 rpm and a stirring time of 30-60 min.

4. The preparation method according to claim 1, characterized in that, The high-speed stirring method in S2 is an oil bath or a heated stirrer, with a temperature range of 90 to 120°C and an auxiliary speed of 300 to 800 rpm.

5. The preparation method according to claim 1, characterized in that, The liquid phenolic resin has a solid content of 70±2% and a viscosity of 600~700mPa·s at 25℃.

6. The preparation method according to claim 1, characterized in that, The fly ash has a particle size of 1–100 μm and comprises the following components by mass: 40-60 parts SiO2, 20-40 parts Al2O3, 5-15 parts Fe2O3.

7. The preparation method according to claim 1, characterized in that, The impact strength of the fly ash modified liquid phenolic resin is not less than 3.60 KJ / m. 2 The tensile strength is not less than 28.51 MPa.

8. A casting, characterized in that, It is prepared by the method described in any one of claims 1-8.

9. A fly ash modified liquid phenolic resin, characterized in that, The preparation method of the fly ash modified liquid phenolic resin includes the following steps: S1, the fly ash is pretreated by mechanical grinding, acid washing and activation, drying and dehydration and coupling agent modification in sequence to obtain modified fly ash; S2, the liquid phenolic resin is heated to 50-80℃ to reduce the viscosity to 100-300mPa·s, and then modified fly ash is added to it and dispersed by high-speed stirring to obtain fly ash modified liquid phenolic resin.

10. The application of fly ash modified liquid phenolic resin as described in claim 9 in the fields of wear-resistant coatings, mechanical parts encapsulation, and mold materials.

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