Preparation method of bonding wax for precision investment casting

Abstract

The invention discloses a preparation method of bonding wax for precision investment casting, and relates to the technical field of bonding wax. The preparation method of the bonding wax for precision investment casting comprises the following steps: performing polymerization reaction on a mixed monomer compounded from alpha-pinene and styrene in a low-temperature environment under the action of an immobilized chloroaluminate ionic liquid catalyst to form a polymer skeleton with a regular main chain and uniform molecular weight distribution, and subsequently adding phenol for reaction to obtain the bonding wax for precision investment casting. A phenolic hydroxyl active group is further introduced, so that the interaction of the resin with a wax matrix and a casting base material is enhanced; under the segmented hydrogenation process, the bimetallic catalyst can perform saturation treatment on the main chain of the resin, so that unsaturated bonds are reduced, and the thermal stability and aging resistance of the resin are improved.

Description

Technical Field

[0001] This invention relates to the field of bonding wax technology, specifically a method for preparing bonding wax for investment casting. Background Technology

[0002] In aerospace, high-end equipment manufacturing, and other fields, investment casting has become one of the core manufacturing technologies due to its ability to achieve high-precision forming of complex structural parts. As a key material for wax pattern assembly and casting system fixation in investment casting, the performance of the bonding wax directly determines the casting accuracy, yield rate, and production stability.

[0003] In existing technologies, bonding waxes for investment casting often use paraffin wax or microcrystalline wax as the base, combined with general-purpose adhesives, stabilizers, and surfactants. However, these technologies suffer from the following core defects: First, insufficient bonding strength. Traditional adhesives (such as EVA and ordinary terpene resins) are prone to aging at high temperatures (above 80°C) or after long-term storage, leading to detachment of the wax mold joints and a casting scrap rate as high as 5%-8%. Second, poor thermal stability. Single antioxidants or heavy metal stabilizers are difficult to adapt to the full temperature range of "85°C melting - 120°C casting preheating," easily causing wax oxidation, discoloration, and brittleness, affecting subsequent shell preparation. Third, poor component compatibility. The limited selection of surfactants results in uneven dispersion of adhesives and stabilizers in the wax matrix, leading to localized bonding failure or difficulty in demolding.

[0004] To address these issues, the present invention provides a method for preparing a bonding wax for investment casting. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing a bonding wax for investment casting, thus solving the problems mentioned in the background section.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a bonding wax for investment casting, comprising the following preparation steps:

[0007] Step 1: Add 1kg of microcrystalline wax to 2kg of paraffin wax, heat to 85℃ and stir for 90min to melt. Add 220g of heat stabilizer and surfactant and mix. Continue stirring for 20min. Then add 40g of initiator and binder and disperse at 1000r / min for 30min.

[0008] Step 2: After cooling to 100℃, add 250g of stearic acid and continue stirring for 60 minutes;

[0009] Step 3: After granulation, the product is packaged and stored to obtain the bonding wax for investment casting.

[0010] Preferably, the heat stabilizer is prepared by compounding an antioxidant and a calcium-zinc composite stabilizer in a mass ratio of 5:4; wherein the antioxidant is prepared by compounding antioxidant 1010 and antioxidant 168 in a mass ratio of 5:4, and the calcium-zinc composite stabilizer is prepared by compounding calcium stearate and zinc stearate in a mass ratio of 3:2.

[0011] Preferably, the surfactant is prepared by compounding polyoxyethylene sorbitan monooleate, sodium dodecylbenzenesulfonate and γ-aminopropyltriethoxysilane in a mass ratio of 5:4:2.

[0012] Preferably, the initiator is prepared by compounding dicumyl peroxide and azobisisobutyronitrile in a mass ratio of 5:3.

[0013] Preferably, the adhesive is prepared by:

[0014] S1. Add a composite silane coupling agent to p-mentholane and stir the reaction at 50-70℃ for 20-40 min to obtain a functionalized solvent system.

[0015] S2. Under nitrogen protection and stirring conditions, add the immobilized chloroaluminate ionic liquid catalyst to the functionalized solvent system and cool it to -30 to -15℃. Then, add the mixed monomers dropwise at a uniform rate. After the addition is complete, keep the reaction at this temperature for 6-10 hours. Then, add phenol and raise the temperature to 45-60℃ to continue the reaction for 1-3 hours.

[0016] S3. After the reaction is complete, the product obtained in S2 is washed with hot water and separated into liquids. The resulting oil layer is then subjected to vacuum distillation to obtain terpene phenol modified styrene resin.

[0017] S4. After pulverizing the terpene phenol-modified styrene resin, mix it with p-menthol and bimetallic hydrogenation catalyst, place it in a high-pressure reactor, and after the reaction is completed, cool down and depressurize, then filter to separate the catalyst.

[0018] S5. Add the capping agent to the filtrate of S4 and stir the mixture at 90-130℃ for 1-1.5 hours. After the reaction is complete, distill under reduced pressure to obtain the adhesive.

[0019] Preferably, in S1, the composite silane coupling agent is prepared by compounding γ-aminopropyltriethoxysilane and γ-(2,3-epoxypropoxy)propyltrimethoxysilane in a mass ratio of 1:(0.8-1.5).

[0020] Preferably, in S2, the mixed monomer is prepared by compounding α-pinene and styrene in a mass ratio of 1:(6-6.25).

[0021] Preferably, in S4, the bimetallic hydrogenation catalyst is selected from either a Pd-Ru / C catalyst or a Pt-Pd / C catalyst, wherein the total content of the active metal is 3-8%, and the molar ratio of the two metals is 1:(0.2-1).

[0022] Preferably, in step S4, after being placed in a high-pressure reactor, the mixture is first reacted at 140-180°C and 5-9 MPa hydrogen pressure for 1-3 hours, and then reacted at 190-230°C and 10-16 MPa hydrogen pressure for 2-4 hours.

[0023] Preferably, in step S5, the capping agent is selected from hydrogenated rosin or C12-C18 alkyl glycidyl ether.

[0024] Beneficial effects

[0025] This invention provides a method for preparing a binder wax for investment casting. Compared with the prior art, it has the following advantages:

[0026] (1) The method for preparing the bonding wax for investment casting involves the polymerization reaction of a mixed monomer composed of α-pinene and styrene under the action of a supported aluminochloride ionic liquid catalyst at low temperature to form a polymer skeleton with a regular main chain and uniform molecular weight distribution. Phenol is then added to further introduce phenolic hydroxyl active groups to enhance the interaction between the resin and the wax matrix (paraffin wax, microcrystalline wax) and the casting substrate. Under the segmented hydrogenation process, the bimetallic catalyst can saturate the resin main chain, reduce unsaturated bonds, and improve the thermal stability and aging resistance of the resin. Adding a capping agent to form a closed structure not only prevents resin degradation or excessive cross-linking at high temperatures, but also enhances the compatibility and dispersibility of the adhesive in the wax matrix, ensuring uniform and durable bonding. This fundamentally solves the problems of easy aging and bonding failure of traditional EVA and ordinary terpene resin adhesives. Furthermore, the initiator can efficiently decompose at 85°C to generate free radicals, triggering a moderate cross-linking reaction between the adhesive and wax matrix molecules to form a stable three-dimensional network structure. This further strengthens the bonding strength at the joints of the wax mold and avoids bonding failure caused by high temperatures or long-term storage.

[0027] (2) The method for preparing the bonding wax for precision casting of investment casting uses a heat stabilizer composed of an antioxidant and a calcium-zinc composite stabilizer to form a synergistic system of "main antioxidant - auxiliary antioxidant - metal ion chelating agent". Among them, antioxidant 1010 can capture free radicals generated during the oxidation of wax and terminate the chain oxidation reaction. Antioxidant 168 can decompose the hydrogen peroxide generated by the oxidation reaction and convert it into stable alcohols or ketones, thus preventing the further decomposition of hydrogen peroxide to generate new free radicals. The two work together to significantly improve the antioxidant efficiency. Calcium stearate can react with acidic substances that may exist in the wax (such as a small amount of carboxylic acid generated during the processing) to neutralize acidic impurities and reduce the degradation effect of acidic substances on the molecular chain of wax. Zinc stearate can form a stable chelate with the metal ions generated during the oxidation of wax and inhibit the catalytic effect of metal ions on the oxidation reaction. Thus, in the full temperature casting range of 85-120℃, the wax can be effectively prevented from oxidizing, discoloring and becoming brittle.

[0028] (3) In the preparation method of the bonding wax for precision casting of investment mold, the three components of the surfactant play different interfacial functions and work synergistically: polyoxyethylene sorbitan monooleate is a nonionic surfactant. The polyoxyethylene segments in its molecule can form hydrophobic interactions with the wax matrix, while the fatty acid segments can form hydrogen bonds with polar components such as adhesives and stabilizers, thus acting as a bridge; sodium dodecylbenzenesulfonate is an anionic surfactant, which can improve the dispersibility of polar components in nonpolar wax matrix and reduce agglomeration through electrostatic interaction; γ-aminopropyltriethoxysilane is a silane surfactant. The amino groups in its molecule can react chemically with the phenolic hydroxyl groups in the adhesive and the carboxyl groups in the heat stabilizer to form chemical bonds. At the same time, after hydrolysis, the ethoxysilane groups can form siloxane bonds with the wax mold surface or shell material, further improving the compatibility and interfacial bonding force between the components. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and 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.

[0030] For details on the preparation method of the supported chloroaluminate ionic liquid catalyst, please refer to Chinese Patent A Short-Porous Mesoporous Silica Supported Chloroaluminate Ionic Liquid Catalyst and Its Preparation Method (Announcement No. CN110064432B, Announcement Date: 2022-04-26).

[0031] In this technical solution, the heat stabilizer is prepared by compounding an antioxidant and a calcium-zinc composite stabilizer in a mass ratio of 5:4; wherein, the antioxidant is prepared by compounding antioxidant 1010 and antioxidant 168 in a mass ratio of 5:4, and the calcium-zinc composite stabilizer is prepared by compounding calcium stearate and zinc stearate in a mass ratio of 3:2.

[0032] The surfactant is prepared by compounding polyoxyethylene sorbitan monooleate, sodium dodecylbenzenesulfonate and γ-aminopropyltriethoxysilane in a mass ratio of 5:4:2.

[0033] The initiator is prepared by compounding dicumyl peroxide and azobisisobutyronitrile in a mass ratio of 5:3.

[0034] Example 1

[0035] A method for preparing a bonding wax for investment casting includes the following preparation steps:

[0036] Step 1: Add 1kg of microcrystalline wax to 2kg of paraffin wax, heat to 85℃ and stir for 90min to melt. Add 220g of heat stabilizer and surfactant and mix. Continue stirring for 20min. Then add 40g of initiator and binder and disperse at 1000r / min for 30min.

[0037] The preparation method of the adhesive is as follows:

[0038] S1. Add 24g of composite silane coupling agent (γ-aminopropyltriethoxysilane and γ-(2,3-epoxypropoxy)propyltrimethoxysilane in a mass ratio of 1:0.8) to 800g of p-mentholane, stir and react at 50℃ for 20min to obtain a functionalized solvent system.

[0039] S2. Under nitrogen protection and stirring conditions, 20g of supported aluminochlorochlorohydrate ionic liquid catalyst was added to the functionalized solvent system and the temperature was lowered to -30℃. Then, 400g of mixed monomer (α-pinene and styrene were compounded in a mass ratio of 1:6) was added dropwise at a uniform rate. After the addition was completed, the reaction was kept at this temperature for 6h. Then, 30g of phenol was added and the temperature was raised to 45℃ to continue the reaction for 1h.

[0040] S3. After the reaction is complete, the product obtained in S2 is washed with hot water and separated into liquids. The resulting oil layer is then subjected to vacuum distillation to obtain terpene phenol modified styrene resin.

[0041] S4. After pulverizing the terpene phenol modified styrene resin, mix it with 400g of p-menthane and 8.2g of Pd-Ru / C catalyst (total active metal content is 3%, and the molar ratio of the two metals is 1:0.2), place it in a high-pressure reactor, react it at 140℃ and 5MPa hydrogen pressure for 1h, and then react it at 190℃ and 10MPa hydrogen pressure for 2h. After the reaction is completed, cool down and depressurize, and filter to separate the catalyst.

[0042] S5. Add 4g of hydrogenated rosin to the filtrate of S4, stir and react at 90℃ for 1h. After the reaction is completed, distill under reduced pressure to obtain the binder.

[0043] Step 2: After cooling to 100℃, add 250g of stearic acid and continue stirring for 60 minutes;

[0044] Step 3: After granulation, the product is packaged and stored to obtain the bonding wax for investment casting.

[0045] Example 2

[0046] A method for preparing a bonding wax for investment casting includes the following preparation steps:

[0047] Step 1: Add 1kg of microcrystalline wax to 2kg of paraffin wax, heat to 85℃ and stir for 90min to melt. Add 220g of heat stabilizer and surfactant and mix. Continue stirring for 20min. Then add 40g of initiator and binder and disperse at 1000r / min for 30min.

[0048] The preparation method of the adhesive is as follows:

[0049] S1. Add 27g of composite silane coupling agent (γ-aminopropyltriethoxysilane and γ-(2,3-epoxypropoxy)propyltrimethoxysilane in a mass ratio of 1:1) to 900g of p-mentholane, stir and react at 60℃ for 30min to obtain a functionalized solvent system.

[0050] S2. Under nitrogen protection and stirring conditions, 22g of supported aluminochlorochlorohydrate ionic liquid catalyst was added to the functionalized solvent system and the temperature was lowered to -20℃. Then, 425g of mixed monomer (α-pinene and styrene were compounded at a mass ratio of 1:6.1) was added dropwise at a uniform rate. After the addition was completed, the reaction was kept at this temperature for 8h. Then, 32g of phenol was added and the temperature was raised to 50℃ to continue the reaction for 2h.

[0051] S3. After the reaction is complete, the product obtained in S2 is washed with hot water and separated into liquids. The resulting oil layer is then subjected to vacuum distillation to obtain terpene phenol modified styrene resin.

[0052] S4. After pulverizing the terpene phenol modified styrene resin, mix it with 425g of p-menthane and 10g of Pd-Ru / C catalyst (total active metal content is 5%, and the molar ratio of the two metals is 1:0.6), place it in a high-pressure reactor, react it at 160℃ and 7MPa hydrogen pressure for 2h, and then react it at 210℃ and 13MPa hydrogen pressure for 3h. After the reaction is completed, cool down and depressurize, and filter to separate the catalyst.

[0053] S5. Add 4.8g of hydrogenated rosin to the filtrate of S4, stir and react at 100℃ for 1.2h. After the reaction is completed, the binder is obtained by vacuum distillation.

[0054] Step 2: After cooling to 100℃, add 250g of stearic acid and continue stirring for 60 minutes;

[0055] Step 3: After granulation, the product is packaged and stored to obtain the bonding wax for investment casting.

[0056] Example 3

[0057] A method for preparing a bonding wax for investment casting includes the following preparation steps:

[0058] Step 1: Add 1kg of microcrystalline wax to 2kg of paraffin wax, heat to 85℃ and stir for 90min to melt. Add 220g of heat stabilizer and surfactant and mix. Continue stirring for 20min. Then add 40g of initiator and binder and disperse at 1000r / min for 30min.

[0059] The preparation method of the adhesive is as follows:

[0060] S1. Add 30g of composite silane coupling agent (γ-aminopropyltriethoxysilane and γ-(2,3-epoxypropoxy)propyltrimethoxysilane in a mass ratio of 1:1.5) to 1000g of p-mentholane, stir and react at 70℃ for 40min to obtain a functionalized solvent system.

[0061] S2. Under nitrogen protection and stirring conditions, 25g of immobilized aluminochlorochlorohydrate ionic liquid catalyst was added to the functionalized solvent system and the temperature was lowered to -15℃. Then, 450g of mixed monomer (α-pinene and styrene were compounded at a mass ratio of 1:6.25) was added dropwise at a uniform rate. After the addition was completed, the reaction was kept at this temperature for 10h. Then, 35g of phenol was added and the temperature was raised to 60℃ to continue the reaction for 3h.

[0062] S3. After the reaction is complete, the product obtained in S2 is washed with hot water and separated into liquids. The resulting oil layer is then subjected to vacuum distillation to obtain terpene phenol modified styrene resin.

[0063] S4. After pulverizing the terpene phenol modified styrene resin, mix it with 450g of p-menthol and 11.25g of Pt-Pd / C catalyst (total active metal content is 8%, and the molar ratio of the two metals is 1:1), place it in a high-pressure reactor, react it at 180℃ and 9MPa hydrogen pressure for 3h, and then react it at 230℃ and 16MPa hydrogen pressure for 4h. After the reaction is completed, cool down and depressurize, and filter to separate the catalyst.

[0064] S5. Add 5.6g of C18 alkyl glycidyl ether to the filtrate of S4, stir and react at 130℃ for 1.5h. After the reaction is completed, the adhesive is obtained by vacuum distillation.

[0065] Step 2: After cooling to 100℃, add 250g of stearic acid and continue stirring for 60 minutes;

[0066] Step 3: After granulation, the product is packaged and stored to obtain the bonding wax for investment casting.

[0067] Comparative Example 1

[0068] Compared with Example 1, the difference is that the adhesive is replaced with terpene resin; everything else remains the same.

[0069] Comparative Example 2

[0070] Compared with Example 1, the difference is that the heat stabilizer is replaced with a calcium-zinc composite stabilizer; the rest remains the same.

[0071] Comparative Example 3

[0072] Compared with Example 1, the difference is that the surfactant is replaced with polyoxyethylene sorbitan monooleate; the rest remains the same.

[0073] Bond strength test: A universal testing machine (model CMT5105) was used to conduct tensile tests at room temperature (25℃) and high temperature (80℃, temperature controlled by constant temperature chamber) at a tensile rate of 5 mm / min; the results are shown in Table 1.

[0074] Thermal stability test: A thermogravimetric analyzer (model TGA / DSC3+) was used under a nitrogen atmosphere (flow rate 50 mL / min) and a heating rate of 10 °C / min. The test range was room temperature to 200 °C. The mass loss rate at 120 °C and 150 °C was recorded. The results are shown in Table 1.

[0075] Table 1

[0076]

[0077] Long-term storage stability: The samples were sealed in aluminum-plastic composite bags and stored in a constant temperature and humidity chamber (model HWS-250) at 25℃ and 60% relative humidity for 6 months. The appearance was observed monthly, and the bonding strength at room temperature was tested after 6 months. The results are shown in Table 2.

[0078] Table 2

[0079]

[0080] Furthermore, any content not described in detail in this specification is existing technology known to those skilled in the art.

[0081] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0082] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a bonding wax for investment casting, characterized in that, The preparation steps include the following: Step 1: Add 1kg of microcrystalline wax to 2kg of paraffin wax, heat to 85℃ and stir for 90min to melt. Add 220g of heat stabilizer and surfactant and mix. Continue stirring for 20min. Then add 40g of initiator and binder and disperse at 1000r / min for 30min. Step 2: After cooling to 100℃, add 250g of stearic acid and continue stirring for 60 minutes; Step 3: After granulation, the product is packaged and stored to obtain the bonding wax for investment casting.

2. The method for preparing a bonding wax for investment casting according to claim 1, characterized in that: The heat stabilizer is prepared by compounding an antioxidant and a calcium-zinc composite stabilizer in a mass ratio of 5:4; wherein the antioxidant is prepared by compounding antioxidant 1010 and antioxidant 168 in a mass ratio of 5:4, and the calcium-zinc composite stabilizer is prepared by compounding calcium stearate and zinc stearate in a mass ratio of 3:

2.

3. The method for preparing a bonding wax for investment casting according to claim 1, characterized in that: The surfactant is prepared by compounding polyoxyethylene sorbitan monooleate, sodium dodecylbenzenesulfonate and γ-aminopropyltriethoxysilane in a mass ratio of 5:4:

2.

4. The method for preparing a bonding wax for investment casting according to claim 1, characterized in that: The initiator is prepared by compounding dicumyl peroxide and azobisisobutyronitrile in a mass ratio of 5:

3.

5. The method for preparing a bonding wax for investment casting according to claim 1, characterized in that: The adhesive is prepared by: S1. Add a composite silane coupling agent to p-mentholane and stir the reaction at 50-70℃ for 20-40 min to obtain a functionalized solvent system. S2. Under nitrogen protection and stirring conditions, add the immobilized chloroaluminate ionic liquid catalyst to the functionalized solvent system and cool it to -30 to -15℃. Then, add the mixed monomers dropwise at a uniform rate. After the addition is complete, keep the reaction at this temperature for 6-10 hours. Then, add phenol and raise the temperature to 45-60℃ to continue the reaction for 1-3 hours. S3. After the reaction is complete, the product obtained in S2 is washed with hot water and separated into liquids. The resulting oil layer is then subjected to vacuum distillation to obtain terpene phenol modified styrene resin. S4. After pulverizing the terpene phenol-modified styrene resin, mix it with p-menthol and bimetallic hydrogenation catalyst, place it in a high-pressure reactor, and after the reaction is completed, cool down and depressurize, then filter to separate the catalyst. S5. Add the capping agent to the filtrate of S4 and stir the mixture at 90-130℃ for 1-1.5 hours. After the reaction is complete, distill under reduced pressure to obtain the adhesive.

6. The method for preparing a bonding wax for investment casting according to claim 5, characterized in that: In S1, the composite silane coupling agent is prepared by compounding γ-aminopropyltriethoxysilane and γ-(2,3-epoxypropoxy)propyltrimethoxysilane in a mass ratio of 1:(0.8-1.5).

7. The method for preparing a bonding wax for investment casting according to claim 5, characterized in that: In S2, the mixed monomer is prepared by compounding α-pinene and styrene in a mass ratio of 1:(6-6.25).

8. The method for preparing a bonding wax for investment casting according to claim 5, characterized in that: In S4, the bimetallic hydrogenation catalyst is selected from either a Pd-Ru / C catalyst or a Pt-Pd / C catalyst, wherein the total content of the active metal is 3-8%, and the molar ratio of the two metals is 1:(0.2-1).

9. The method for preparing a bonding wax for investment casting according to claim 5, characterized in that: In step S4, after being placed in a high-pressure reactor, the mixture is first reacted at 140-180℃ and 5-9MPa hydrogen pressure for 1-3 hours, and then reacted at 190-230℃ and 10-16MPa hydrogen pressure for 2-4 hours.

10. A method for preparing a bonding wax for investment casting according to claim 5, characterized in that: In S5, the capping agent is selected from hydrogenated rosin or C12-C18 alkyl glycidyl ether.

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