Preparation method of ceramic core plasticizer for high-temperature alloy investment casting

Abstract

The invention discloses a preparation method of a ceramic core plasticizer for high-temperature alloy investment casting, and relates to the technical field of plasticizers, and the preparation method comprises the following preparation steps: step 1, adding microcrystalline wax into modified chlorinated paraffin, heating, stirring and melting, adding a heat stabilizer, mixing, continuously stirring, heating for reaction, adding polyethylene wax, and continuously stirring; 2, after cooling, adding stearic acid, and continuously stirring; and 3, granulating and packaging to obtain the special plasticizer for the ceramic core. According to the preparation method of the ceramic core plasticizer for high-temperature alloy investment casting, polar groups such as hydroxyl groups and ester groups are introduced to a chlorinated paraffin molecular chain, strong interaction is formed between the polar groups and hydroxyl groups on the surface of ceramic powder, and a uniform wax coating layer is formed on the surface of powder particles.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of plasticizers, in particular to a preparation method of a ceramic core plasticizer for high-temperature alloy investment casting. BACKGROUND

[0002] Precision casting is one of the important manufacturing methods for complex parts in modern industry. Among them, hollow castings with complex internal cavity structure need to use ceramic cores to ensure the shape and size of the internal cavity of the parts, and the main raw material of the ceramic core is a plasticizer. The application of the plasticizer can effectively ensure the size of the ceramic core and its collapse when it is removed.

[0003] As a key additive for the preparation of ceramic cores, the plasticizer needs to meet three core requirements: first, it gives the ceramic powder good plasticity to ensure that the core is formed without cracking and complete edges; second, it has excellent thermal stability and does not decompose or release harmful substances during the core mixing and heating (usually 80-130℃) and subsequent dewaxing and preheating (150-180℃) processes; third, it has high removal efficiency and no residue after sintering to avoid air holes in the core or component contamination of high-temperature alloys.

[0004] The ceramic core plasticizers commonly used in the current industry mostly use ordinary chlorinated paraffin or paraffin as the main component, and are matched with conventional calcium-zinc composite soap (such as calcium stearate-zinc stearate complex) as a thermal stabilizer, but there are many technical bottlenecks in actual application:

[0005] (1) The molecular structure of ordinary chlorinated paraffin is single, and it has poor compatibility with wax components such as microcrystalline wax and polyethylene wax. After mixing, it is easy to separate into layers, resulting in uneven green density of the core, and cracks are easily produced after sintering. The plasticizing effect of paraffin is weak due to the absence of polar groups, and the green strength of the core is generally less than 2MPa, which makes it easy to break during demolding and cannot meet the molding requirements of complex structure cores;

[0006] (2) The thermal stability efficiency of conventional calcium-zinc composite soap is low, and it is difficult to effectively inhibit the decomposition of chlorinated paraffin at a high temperature of 130℃ or above. Not only does it cause the quality loss rate of the plasticizer to exceed 4%, but it also releases free chlorine, which on the one hand causes micro-pores in the core, and on the other hand, chlorine elements easily penetrate into high-temperature alloys (such as GH4169), resulting in a decrease in alloy purity and affecting the mechanical properties of the castings;

[0007] Therefore, the present application provides a preparation method of a ceramic core plasticizer for high-temperature alloy investment casting. SUMMARY

[0008] In view of the deficiencies of the prior art, the present application provides a preparation method of a ceramic core plasticizer for high-temperature alloy investment casting, which solves the problems mentioned in the background.

[0009] In order to achieve the above object, the present application is implemented by the following technical scheme: a preparation method of a ceramic core plasticizer for high-temperature alloy investment casting, comprising the following preparation steps:

[0010] Step one, add microcrystalline wax to modified chlorinated paraffin, stir and melt under heating, then add heat stabilizer for mixing, continue to stir and react under heating, then add polyethylene wax for continuous stirring;

[0011] Step two, after cooling, add stearic acid and continue to stir;

[0012] Step three, after granulation, package, and the ceramic core special plasticizer is obtained;

[0013] In the step one, the preparation steps of the modified chlorinated paraffin include:

[0014] S1, mix methyltetrahydrofuran with chlorinated paraffin, add polyethylene glycol-400 while stirring, after complete dissolution, add thiosalicylic acid and cesium carbonate, react under heating in nitrogen atmosphere, then perform extraction and vacuum drying in sequence;

[0015] S2, add a tetrahydrofuran solution containing a buffer, then perform extraction and vacuum drying to obtain product one;

[0016] S3, add 1,2-dichloroethane, epoxy fatty acid methyl ester, tetrabutylammonium bromide and N,N-dimethylformamide to product one, continue to react under heating, then perform extraction and vacuum drying, and the modified chlorinated paraffin is obtained.

[0017] Preferably, in the step one, the addition amount of each substance is: modified chlorinated paraffin 2-2.5 kg, microcrystalline wax 0.2-0.3 kg, heat stabilizer 20-28 g, polyethylene wax 40-50 g, and stearic acid 250-280 g;

[0018] The heat stabilizer is a calcium-zinc composite heat stabilizer.

[0019] Preferably, in the preparation process of the modified chlorinated paraffin, chlorinated paraffin 100 g, methyltetrahydrofuran 150-200 mL, polyethylene glycol-400 2-5 g, thiosalicylic acid 12-15 g, cesium carbonate 18-22 g, tetrahydrofuran solution containing a buffer 100-150 mL, 1,2-dichloroethane 120-160 mL, epoxy fatty acid methyl ester 15-20 g, tetrabutylammonium bromide 1-3 g, and N,N-dimethylformamide 20-30 mL.

[0020] Preferably, in the S1, the buffer is a 0.1 mol / L potassium dihydrogen phosphate-potassium hydrogen phosphate buffer, and the pH value is 6.5-7.0.

[0021] Preferably, among S1, S2 and S3, extraction is carried out using an ethyl acetate-water two-phase extraction system, and 0.5% by mass of β-cyclodextrin is added to the water phase.

[0022] Preferably, the preparation method of the calcium-zinc composite heat stabilizer is as follows:

[0023] (1) Preparation of calcium salt component: alkylated citric acid is added dropwise into saturated calcium hydroxide solution until the pH value of the solution system is 10.5; after the reaction is completed, centrifugal drying is performed to obtain white solid powder, which is the calcium salt component;

[0024] (2) Preparation of zinc salt component: alkylated citric acid and zinc oxide powder are mixed, deionized water is added for dispersion, a catalyst is added, and under stirring, the water bath is heated to 60 DEG C for 66-72 h; after centrifugal drying, white solid powder is obtained, which is the zinc salt component;

[0025] (3) Preparation of composite heat stabilizer: the calcium salt component and the zinc salt component are uniformly mixed in a mass ratio of 1:0.8-1.5 to obtain the calcium-zinc composite heat stabilizer.

[0026] Preferably, in (1), the molar ratio of alkylated citric acid to saturated calcium hydroxide solution is 1.8-2.2:1.

[0027] Preferably, in (2), the molar ratio of alkylated citric acid to zinc oxide powder is 1:1.05; the catalyst is acetic acid, and the mass of the catalyst is 1% of the mass of alkylated citric acid; during the reaction, the catalyst is added once every 8 h to maintain the pH value of the solution system at 4.

[0028] Preferably, the preparation method of the alkylated citric acid is as follows: citric acid, acetic anhydride and acetic acid are blended, the mixed solution is stirred and heated for reaction, after the reaction is completed, the mixed solution is added dropwise into chloroform, stirring, suction filtration, washing with chloroform for 2-3 times, vacuum drying at 40 DEG C, then adding dodecanol, continuing to stir and heat for reaction, after the reaction is completed, adding petroleum ether, continuing to stir, then centrifugal drying at 60 DEG C, to obtain alkylated citric acid.

[0029] Preferably, the mass of each substance is as follows: citric acid 8-10 g, citric anhydride 8.5-9.56 g, acetic acid 5.4-6.25 g, and dodecanol 2.1-2.56 g.

[0030] Beneficial effects

[0031] The application provides a preparation method of a ceramic core plasticizer for high-temperature alloy investment casting.

[0032] (1), the preparation method of the ceramic core plasticizer for high-temperature alloy investment casting, by introducing hydroxyl, ester group and other polar groups on the molecular chain of chlorinated paraffin wax, forming strong interaction with the hydroxyl on the surface of ceramic powder (such as alumina, silicon oxide), forming a uniform wax coating on the surface of the powder particles; at the same time, the long chain alkyl of microcrystalline wax and polyethylene wax can form "lubricating bridge" between particles, reduce the friction between particles, and the two can make the powder plastic deformation easily during pressing, and the stress distribution is uniform, so as to improve the green strength and reduce the damage of demolding.

[0033] (2), the preparation method of the ceramic core plasticizer for high-temperature alloy investment casting, the metal ions of calcium salt and zinc salt in calcium-zinc composite heat stabilizer can form stable ionic bond with Cl - , block "chain reaction" and inhibit the decomposition of chlorinated paraffin wax; the long chain alkyl of alkylated citric acid can enhance the compatibility of metal salt and modified chlorinated paraffin wax, avoid the agglomeration of heat stabilizer, ensure the uniform dispersion of Ca 2+ , Zn 2+ , improve the efficiency of chloride ion capture, and the metal ion and citrate form chelate, so that no free Cl - is released during decomposition, avoiding Cl - penetration into high-temperature alloy to ensure the purity of castings; at the same time, the alkylated citric acid metal salt of the heat stabilizer can be adsorbed on the surface of the modified chlorinated paraffin wax particles, forming "steric hindrance" to prevent the agglomeration of particles due to van der waals force, so there is no caking phenomenon during storage, prolonging the storage time. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The ceramic core fracture SEM provided by the present application is provided. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

[0036] In the preparation process of modified chlorinated paraffin wax, ethyl acetate-water two-phase extraction system is used for extraction, and 0.5% of β-cyclodextrin is added in the water phase; the vacuum drying temperature is 100℃, and the vacuum drying time is 2h.

[0037] Preparation method of alkylated citric acid: 10 g of citric acid, 9.56 g of acetic anhydride and 6.25 g of acetic acid are blended, the mixed solution is stirred and heated to 38-40℃ for 18 h, after the reaction is completed, the mixed solution is added dropwise into chloroform, stirred, suction filtered, washed 2-3 times with chloroform, vacuum dried at 40℃, then 2.56 g of dodecanol is added, continue to stir and heat to 90℃ for 2.5 h, after the reaction is completed, petroleum ether is added, continue to stir and centrifuge, dry at 60℃, then alkylated citric acid is obtained.

[0038] Example 1

[0039] A preparation method of a ceramic core plasticizer for high-temperature alloy investment casting, comprising the following preparation steps:

[0040] Step one, 0.2 kg of microcrystalline wax is added to 2 kg of modified chlorinated paraffin, heated to 85℃ and stirred for 1 h to melt, then 20 g of heat stabilizer is added and mixed, continue to stir for 20 min, heat to 130℃, then add 40 g of polyethylene wax, stir at a speed of 300 r / min for 1 h;

[0041] (1) Preparation of modified chlorinated paraffin: 150 mL of methyltetrahydrofuran is mixed with 100 g of chlorinated paraffin, 2 g of polyethylene glycol-400 is added while stirring until completely dissolved, then 12 g of thiosalicylic acid and 18 g of cesium carbonate are added, heated to 45℃ for 12 h under nitrogen atmosphere, then extracted and vacuum dried; 100 mL of tetrahydrofuran solution containing 0.1 mol / L of potassium dihydrogen phosphate-potassium hydrogen phosphate buffer (pH=6.5) is added, then extracted and vacuum dried to obtain product one; 120 mL of 1,2-dichloroethane, 15 g of epoxy fatty acid methyl ester, 1 g of tetrabutylammonium bromide and 20 mL of N,N-dimethylformamide are added to product one, heated to 55℃ for 3 h, then extracted and vacuum dried to obtain modified chlorinated paraffin;

[0042] (2) Preparation of calcium-zinc composite heat stabilizer: alkylated citric acid is added dropwise into saturated calcium hydroxide solution (molar ratio of 1.8:1), until the pH value of the solution system is 10.5, after the reaction is completed, centrifugal drying to obtain white solid powder, which is the calcium salt component; alkylated citric acid and zinc oxide powder (molar ratio of 1:1.05) are mixed, dispersed with deionized water, then 1% of acetic acid based on the mass of alkylated citric acid is added, stirred and heated to 60℃ for 66 h in water bath, wherein the catalyst is added every 8 h to maintain the pH value of the solution system at 4, then centrifugal drying to obtain white solid powder, which is the zinc salt component; the calcium salt component and the zinc salt component are mixed uniformly at a mass ratio of 1:0.8 to obtain calcium-zinc composite heat stabilizer;

[0043] Step two, after cooling to 100℃, add 265g stearic acid, continue stirring for 1h;

[0044] Step three, after granulation, package, which is a special plasticizer for ceramic core.

[0045] Example 2

[0046] A method for preparing a ceramic core plasticizer for high-temperature alloy investment casting, comprising the following preparation steps:

[0047] Step one, add 0.25kg microcrystalline wax to 2.2kg modified chlorinated paraffin, heat to 85℃ and stir for 1h to melt, then add 24g heat stabilizer and mix, continue to stir for 20min, heat to 130℃ and add 45g polyethylene wax, stir at a rate of 300r / min for 1h;

[0048] (1) Preparation of modified chlorinated paraffin: mix 180mL methyltetrahydrofuran with 100g chlorinated paraffin, add 3.5g polyethylene glycol-400 while stirring until completely dissolved, then add 14g thiosalicylic acid and 20g cesium carbonate, heat to 50℃ for 12h under nitrogen atmosphere, then extract and vacuum dry; add 125mL tetrahydrofuran solution containing 0.1mol / L potassium dihydrogen phosphate-potassium hydrogen phosphate buffer (pH=6.8), then extract and vacuum dry to obtain product one; add 140mL 1,2-dichloroethane, 18g epoxy fatty acid methyl ester, 2g tetrabutylammonium bromide and 25mL N,N-dimethylformamide to product one, heat to 58℃ for 3h, then extract and vacuum dry to obtain modified chlorinated paraffin;

[0049] (2) Preparation of calcium-zinc composite heat stabilizer: add alkylated citric acid dropwise to saturated calcium hydroxide solution (molar ratio of 2:1), until the pH value of the solution system is 10.5, after the reaction is completed, centrifugal drying to obtain white solid powder, which is the calcium salt component; mix alkylated citric acid with zinc oxide powder (molar ratio of 1:1.05), disperse with deionized water, add 1% of the mass of alkylated citric acid of acetic acid, under stirring conditions, heat to 60℃ for 69h in water bath, wherein, every 8h, add a catalyst to maintain the pH value of the solution system at 4, centrifugal drying to obtain white solid powder, which is the zinc salt component; mix the calcium salt component and the zinc salt component uniformly according to the mass ratio of 1:1.2, to obtain calcium-zinc composite heat stabilizer;

[0050] Step two, after cooling to 100℃, add 265g stearic acid, continue stirring for 1h;

[0051] Step three, after granulation, package, which is a special plasticizer for ceramic core.

[0052] Example 3

[0053] A preparation method of a ceramic core plasticizer for superalloy investment casting, comprising the following preparation steps:

[0054] Step one, add 0.3 kg of microcrystalline wax to 2.5 kg of modified chlorinated paraffin, heat to 85℃ and stir for 1h to melt, then add 28g heat stabilizer and continue to stir for 20min, heat to 130℃ and then add 50g polyethylene wax, stir at a rate of 300r / min for 1h;

[0055] (1) Preparation of modified chlorinated paraffin: mix 200mL methyltetrahydrofuran with 100g chlorinated paraffin, add 5g polyethylene glycol-400 while stirring until completely dissolved, then add 15g thiosalicylic acid and 22g cesium carbonate, heat to 55℃ under nitrogen atmosphere for 12h, then extract and vacuum dry; add 150mL tetrahydrofuran solution containing 0.1mol / L potassium dihydrogen phosphate-potassium hydrogen phosphate buffer (pH=7.0), then extract and vacuum dry to obtain product one; add 160mL 1,2-dichloroethane, 20g epoxy fatty acid methyl ester, 3g tetrabutylammonium bromide and 30mL N,N-dimethylformamide to product one, heat to 60℃ for 3h, then extract and vacuum dry to obtain the modified chlorinated paraffin;

[0056] (2) Preparation of calcium-zinc composite heat stabilizer: add alkylated citric acid dropwise to a saturated calcium hydroxide solution (molar ratio of 2.2:1) until the pH value of the solution system is 10.5, after the reaction is completed, centrifugal drying to obtain white solid powder, which is the calcium salt component; mix alkylated citric acid with zinc oxide powder (molar ratio of 1:1.05), disperse with deionized water, add 1% of the mass of alkylated citric acid of acetic acid, under stirring conditions, heat to 60℃ in water bath for 72h, wherein the catalyst is added every 8h to maintain the pH value of the solution system at 4, centrifugal drying to obtain white solid powder, which is the zinc salt component; mix the calcium salt component and the zinc salt component uniformly according to the mass ratio of 1:1.5 to obtain the calcium-zinc composite heat stabilizer;

[0057] Step two, after cooling to 100℃, add 280g stearic acid and continue to stir for 1h;

[0058] Step three, after granulation, package to obtain the special plasticizer for ceramic core.

[0059] Comparative Example 1

[0060] The difference from Example 1 is that the modified chlorinated paraffin in Example 1 is replaced by chlorinated paraffin; the rest remains unchanged.

[0061] Comparative Example 2

[0062] The difference from Example 1 is that the modified chlorinated paraffin in Example 1 is replaced by paraffin; the rest remains unchanged.

[0063] Comparative Example 3

[0064] The difference from Example 1 is that the calcium-zinc composite heat stabilizer in Example 1 is replaced by calcium-zinc composite soap; the rest remains unchanged.

[0065] The calcium-zinc composite soap is compounded by calcium stearate and zinc stearate in a mass ratio of 2:1.

[0066] Performance test:

[0067] (1) Heat stability test: test according to GB / T 29613.2-2014, record the mass loss rate (decomposition product volatilization caused) and initial decomposition temperature (temperature when mass loss is 5%) in the range of 100-200℃; the results are shown in Table 1.

[0068] (2) Storage stability test: test according to GB / T 7304-2014, record the acid value change after 30 days of storage (acid value increase <0.5mg KOH / g is qualified); the results are shown in Table 1.

[0069] (3) Formability test: test the green strength of the dewaxed core according to GB / T 6569-2006; the results are shown in Table 1.

[0070] (4) High temperature sintering performance test: place the dewaxed core in a high temperature sintering furnace, heat to 1600℃, keep for 3h, cool with the furnace, test according to GB / T 25995-2010, record the high temperature bending strength; the results are shown in Table 1.

[0071] Table 1

[0072] Mass loss rate / % Initial decomposition temperature / °C Acid value / mg KOH / g Green strength / MPa High temperature flexural strength / MPa Example 1 2.1 165 0.21 2.8 15.8 Example 2 1.8 172 0.18 3.1 16.5 Example 3 2.0 168 0.23 2.9 16.1 Comparative Example 1 4.5 142 0.45 2.0 12.3 Comparative Example 2 3.8 135 0.62 1.4 9.8 Comparative Example 3 3.2 150 0.58 2.3 13.5

[0073] From Figure 1 It can be seen that the modified chlorinated paraffin in Examples 1-3 and Comparative Example 2 decomposes completely, volatilizes smoothly, has no stress concentration, the heat stabilizer has no residue, and does not hinder particle sintering, so the ceramic core has uniform pores; the ordinary chlorinated paraffin used in Comparative Example 1 has a fast decomposition rate, and the gas impact produces large pores and cracks; the calcium-zinc composite soap (calcium stearate) in Comparative Example 3 carbonizes at high temperature, forms carbide residues, and the residual substances occupy space to form irregular pores.

[0074] Meanwhile, the contents not described in detail in the specification all belong to the existing technology known to those skilled in the art.

[0075] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting; it is not intended to exclude myriad other embodiments of the present application that other inventors can develop based on the same general inventive concepts embodied by the described embodiments. That is, although the present application is described in terms of particular embodiments and illustrative figures, it should be apparent that the scope of the present application is not limited to these specific embodiments.

[0076] While the embodiments of the application have been shown and described herein, it will be understood by those skilled in the art that many changes, modifications, substitutions and alterations to these embodiments can be made without departing from the principles and spirits of the application, and it is intended that the scope of the application be limited solely by the scope of the appended claims and the equivalents thereof.

Claims

1. A method for preparing a ceramic core plasticizer for high temperature alloy investment casting, characterized by, The preparation steps include the following steps: Step one, add microcrystalline wax to modified chlorinated paraffin, melt by stirring and heating, then add heat stabilizer and mix, continue to stir and heat to react, then add polyethylene wax and continue to stir; Step two, after cooling, add stearic acid and continue to stir; Step three, after granulation, package, and the special plasticizer for ceramic core is obtained; In the step one, the preparation steps of the modified chlorinated paraffin include: S1, mix methyltetrahydrofuran with chlorinated paraffin, add polyethylene glycol-400 while stirring, after complete dissolution, add thiosalicylic acid and cesium carbonate, heat under nitrogen atmosphere, then carry out extraction and vacuum drying in sequence; S2, add tetrahydrofuran solution containing buffer, then carry out extraction and vacuum drying to obtain product one; S3, add 1,2-dichloroethane, epoxy fatty acid methyl ester, tetrabutylammonium bromide and N,N-dimethylformamide to product one, continue to heat to react, then carry out extraction and vacuum drying to obtain the modified chlorinated paraffin.

2. The method for preparing a ceramic core plasticizer for high-temperature alloy investment casting according to claim 1, characterized in that: In the step one, the adding amount of each substance is: modified chlorinated paraffin 2-2.5 kg, microcrystalline wax 0.2-0.3 kg, heat stabilizer 20-28 g, polyethylene wax 40-50 g, and stearic acid 250-280 g. The heat stabilizer is calcium-zinc composite heat stabilizer.

3. The method of claim 1, wherein the method is characterized by: In the preparation process of the modified chlorinated paraffin, chlorinated paraffin 100 g, methyltetrahydrofuran 150-200 mL, polyethylene glycol-400 2-5 g, thiosalicylic acid 12-15 g, cesium carbonate 18-22 g, tetrahydrofuran solution containing buffer 100-150 mL, 1,2-dichloroethane 120-160 mL, epoxy fatty acid methyl ester 15-20 g, tetrabutylammonium bromide 1-3 g, and N,N-dimethylformamide 20-30 mL.

4. The method of claim 1, wherein the method is characterized by: In the S1, the buffer is 0.1 mol / L potassium dihydrogen phosphate-potassium hydrogen phosphate buffer, and the pH value is 6.5-7.

0.

5. The method for preparing a ceramic core plasticizer for high-temperature alloy investment casting according to claim 1, characterized in that: In the S1, S2 and S3, extraction is carried out by using ethyl acetate-water two-phase extraction system, and 0.5% mass fraction of β-cyclodextrin is added in the water phase.

6. The method of claim 2, wherein the method is characterized by: The preparation method of the calcium-zinc composite heat stabilizer is: (1) calcium salt component preparation: drop alkylated citric acid into saturated calcium hydroxide solution until the pH value of the solution system is 10.5, after the reaction is completed, centrifugal drying is carried out to obtain white solid powder, which is the calcium salt component; (2) zinc salt component preparation: mix alkylated citric acid with zinc oxide powder, disperse by adding deionized water, add catalyst, and after water bath heating to 60℃ for 66-72 h under stirring condition, centrifugal drying is carried out to obtain white solid powder, which is the zinc salt component; (3) composite heat stabilizer preparation: mix the calcium salt component and the zinc salt component uniformly according to the mass ratio of 1:0.8-1.5 to obtain the calcium-zinc composite heat stabilizer.

7. A method of preparing a ceramic core make for investment casting of superalloys according to claim 6, characterized in that: In the (1), the molar ratio of alkylated citric acid to saturated calcium hydroxide solution is 1.8-2.2:

1.

8. The method of claim 6, wherein the method is characterized by: In the (2), the molar ratio of the alkylated citric acid to the zinc oxide powder is 1:1.05; the catalyst is acetic acid, and the mass of the catalyst is 1% of the mass of the alkylated citric acid; and during the reaction, the catalyst is added once every 8 hours to maintain the pH value of the solution system at 4.

9. The method of claim 6, wherein the method is characterized by: The preparation method of the alkylated citric acid comprises the following steps: blending citric acid, acetic anhydride and acetic acid, stirring and heating the mixed solution to react, adding the mixed solution into chloroform after the reaction is completed, stirring, suction filtration, washing the alkylated citric acid with chloroform for 2-3 times, vacuum drying at 40℃, adding dodecanol, continuing to stir and heat to react, adding petroleum ether after the reaction is completed, continuing to stir, centrifuging, and drying at 60℃ to obtain the alkylated citric acid.

10. A method of preparing a ceramic core make for investment casting of superalloys according to claim 9, characterized in that: The mass of each substance is as follows: citric acid 8-10g, acetic anhydride 8.5-9.56g, acetic acid 5.4-6.25g, and dodecanol 2.1-2.56g.

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