Modified silica sol binder as well as preparation method and application thereof

Abstract

The invention provides a modified silica sol binder and a preparation method and application thereof, and relates to the technical field of binders.The preparation method comprises the following steps that a silane coupling agent and silica sol are mixed to react, and silanized silica sol is obtained; and mixing a molecular sieve with the silanized silica sol to obtain the modified silica sol binder. The silane coupling agent has amphipathy and is well combined with the surfaces of silica sol particles through chemical bonds, the silica sol has amphipathy after the silane coupling agent is mixed with the silica sol, the coating performance of the silica sol on refractory powder can be improved, the wettability of slurry on a wax mold can be improved, the size deviation of a mold shell is reduced, and the flatness of a surface layer is improved; therefore, cracks are reduced; no heteroatom is introduced into the cage structure of the molecular sieve in the process of introducing an Al-O-Si bond, and the molecular sieve has abundant pore channels and can be well staggered with a silica sol network structure in the high-temperature sintering process, so that the bonding strength of the silica sol binder is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of adhesives, and particularly relates to a modified silica sol adhesive and a preparation method and application thereof. Background Art

[0002] Silica sol, a sol system composed of SiO2 colloidal particles dispersed in an aqueous solution, has been put into practical use as a binder for refractory castables. The nanometer-sized SiO2 particles in the silica sol transform into quartz-type SiO2 powder at high temperatures, filling the gaps between α-Al2O3 particles and forming a physical bond. This improves the sintering properties of the castable, promotes densification, and ultimately allows the ceramic material to cohere and bond. However, traditional silica sol, used as a binder for refractory materials, is prone to forming a mullite phase during the high-temperature sintering process of the mold shell. Upon cooling, the mullite phase shrinks in volume, leading to cracks on the mold shell surface.

[0003] By modifying silica sol, its bonding properties can be enhanced to offset the cracking stress caused by the mullite phase's volume reduction, thereby increasing its application value. Currently, common methods for modifying silica sol include organic-inorganic hybridization and nanocomposites. Organic-inorganic hybridization forms polymers with silica particles through hydrolysis and condensation reactions, strengthening the bond between the silica sol and the refractory material and improving the binder's water resistance and mechanical properties. Nanocomposites primarily utilize alkali metal salts, nanofibers, and other methods to modify the silica sol network structure, enhancing the slurry's ability to coat the refractory material and the high-temperature strength of the ceramic shell.

[0004] However, the existing silica sol modification methods have the following problems: (1) The degree of hybridization between the organic-inorganic phase and the silica sol is not ideal, which makes the silica sol particles easy to agglomerate. When used as a binder for casting ceramic shells, the wrapping of refractory materials is poor, resulting in insufficient bonding strength of the modified silica sol binder, which in turn leads to cracking of the shell surface and insufficient flexural strength; (2) Nanocomposite modified silica sol requires more control over the degree of surface modification. Excessive modification will cause poor stability of the silica sol, and large gel particles will agglomerate and precipitate. When used as a binder for casting ceramic shells, the uniformity of the silica sol wrapping of the refractory powder will decrease, uneven bonding will occur during sintering, and excessive local stress will lead to cracking of the shell and insufficient flexural strength. Summary of the Invention

[0005] Therefore, the present invention provides a modified silica sol binder and a preparation method and application thereof, which can solve the problem of insufficient bonding strength of the modified silica sol binder in the prior art.

[0006] In order to solve the above problems, the present invention provides a method for preparing a modified silica sol binder, comprising the following steps:

[0007] Step 1): mixing a silane coupling agent with silica sol to react to obtain silanized silica sol;

[0008] Step 2): mixing the molecular sieve with the silanized silica sol to obtain a modified silica sol binder.

[0009] Furthermore, in step 1), the density of the silica sol is 1.18 to 1.20 g / cm 3 and / or

[0010] The room temperature viscosity of the silica sol is ≤8 Pa·s; and / or

[0011] The particle size of the silica sol is 8 to 15 nm; and / or

[0012] The pH of the silica sol is 9.5-10.5.

[0013] Furthermore, in the step 1), the silane coupling agent is one of γ-aminopropyltriethoxysilane, γ-glycidyloxypropyltrimethoxysilane, and γ-(methacryloyloxy)propyltrimethoxysilane.

[0014] Furthermore, the step 1) is specifically as follows: stirring the silica sol, adding a silane coupling agent, and stirring for 10 to 15 minutes;

[0015] Preferably, the stirring speed is 180-200 rpm.

[0016] Furthermore, in the step 2), the molecular sieve is an H-β molecular sieve.

[0017] Furthermore, the step 2) specifically includes: adding the molecular sieve into the silanized silica sol and continuously stirring to complete dispersion.

[0018] On the other hand, the present invention provides a modified silica sol binder, wherein the raw materials of the modified silica sol binder include: silica sol, silane coupling agent, molecular sieve and water; wherein the silica sol includes sodium oxide;

[0019] The mass percentage of silicon dioxide in the raw materials is 29-31 wt%, the mass percentage of sodium oxide is less than or equal to 0.5 wt%, the mass percentage of the silane coupling agent is 0.1-0.2 wt%, and the mass percentage of the molecular sieve is 0.2-0.4 wt%.

[0020] In another aspect, the present invention provides a use of the modified silica sol binder, wherein the modified silica sol binder is used for casting a ceramic shell.

[0021] In another aspect, the present invention provides a method for casting a ceramic shell, comprising the following steps:

[0022] Step 1: Mixing the modified silica sol binder, defoaming agent, and wetting agent to obtain silica sol slurry;

[0023] Wherein, the modified silica sol binder is prepared by any of the preparation methods of the modified silica sol binder described above or by using the modified silica sol binder described above.

[0024] Step 2: Add EC95 powder to the silica sol slurry, add deionized water to adjust the viscosity, and obtain the surface slurry of the ceramic shell;

[0025] Step 3: Immerse the assembled wax mold module in the surface slurry, sand and dry the wax mold module to obtain a shell module;

[0026] Step 4: steam dewaxing the shell mold assembly to obtain a wet shell blank;

[0027] Step 5: sintering the wet shell to obtain a ceramic shell.

[0028] Compared with the prior art, the present invention has at least the following beneficial effects:

[0029] 1. In one aspect, the present invention provides a method for preparing a modified silica sol binder, comprising the following steps: mixing a silane coupling agent with silica sol to react to obtain a silanized silica sol; and mixing a molecular sieve with the silanized silica sol to obtain a modified silica sol binder. It should be noted that the organic-inorganic phase (silane coupling agent) used in the present invention is amphiphilic and has a hydrolyzable group. It is well bonded to the surface of the silica sol particles through chemical bonds. After mixing with the silica sol, the silica sol becomes amphiphilic, which can not only improve the coating of the silica sol on the refractory powder, but also improve the wettability of the slurry on the wax mold, reduce the size deviation of the shell, improve the surface flatness, and thus reduce the generation of cracks; the cage structure of the molecular sieve does not introduce any heteroatoms during the introduction of the Al-O-Si bond, and the molecular sieve has abundant pore channels, which can be well interlaced with the silica sol network structure during the high-temperature sintering process, thereby improving the bonding strength of the silica sol binder, thereby further improving the flexural strength of the shell itself, while avoiding the generation of cracks and improving the surface quality of the shell.

[0030] 2. In another aspect, the present invention provides a modified silica sol binder prepared by the above method. The raw materials for the modified silica sol binder include silica sol, a silane coupling agent, a molecular sieve, and water. The silica sol includes sodium oxide. The raw materials contain 29-31% by weight of silica, ≤0.5% by weight of sodium oxide, 0.1-0.2% by weight of the silane coupling agent, and 0.2-0.4% by weight of the molecular sieve. It should be noted that the silane coupling agent and the molecular sieve synergistically modify the silica sol, improving the hydrophilicity of the silica particles and enhancing the silica sol's ability to coat ceramic refractory powder, thereby enhancing the bond strength of the silica sol binder during sintering.

[0031] Furthermore, the modified silica sol binder has a high silica content, and mullite phase is generated during high-temperature sintering, which can provide strength support for the ceramic shell; the smaller silica particle size has a larger specific surface area, which is conducive to the combination of silane coupling agent with it, and is also conducive to uniform coating of refractory powder.

[0032] 3. In another aspect, the present invention provides a method for preparing the modified silica sol binder, comprising the following steps: mixing a silane coupling agent with silica sol to obtain a silanized silica sol; and mixing a molecular sieve with the silanized silica sol to obtain a modified silica sol binder. The organic-inorganic phase (silane coupling agent) employed in the present invention is amphiphilic and has hydrolyzable groups, which chemically bond well to the surface of the silica sol particles. The molecular sieve's cage structure is free of heteroatoms during the introduction of Al-O-Si bonds, and the molecular sieve has abundant pore channels, which allow for good interlacing with the silica sol network during high-temperature sintering, thereby enhancing the bonding strength of the silica sol binder. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. The drawings described below are merely exemplary. Those skilled in the art can, without inventive effort, derive other implementation drawings based on the provided drawings.

[0034] Figure 1 1 are macroscopic images of ceramic shells obtained in the embodiments and comparative examples of the present invention; wherein: (a) is comparative example 1, (b) is embodiment 1, (c) is comparative example 2, and (d) is comparative example 3;

[0035] Figure 2 3 is a comparison chart of the wet blank strength and high temperature strength test results of the ceramic shell obtained in the embodiment of the present invention and the comparative example. DETAILED DESCRIPTION

[0036] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. The drawings described below are merely exemplary. Those skilled in the art can, without inventive effort, derive other implementation drawings based on the provided drawings.

[0037] The present invention provides a method for preparing the modified silica sol binder, comprising the following steps:

[0038] Step 1): 100 ml of a 30-32 wt% SiO2 aqueous silica sol solution is placed in a beaker and stirred at a low speed of 180-200 rpm to maintain a stable liquid level. 0.1-0.2 wt% of a silane coupling agent is then added to the silica sol and stirred for 10-15 minutes to obtain a silanized silica sol.

[0039] The density of silica sol is 1.18~1.20g / cm 3 The room temperature viscosity of the silica sol is ≤8 Pa·s; the particle size of the silica sol is 8 to 15 nm; the silane coupling agent is one of γ-aminopropyltriethoxysilane (KH550), γ-glycidyloxypropyltrimethoxysilane (KH560), and γ-(methacryloyloxy)propyltrimethoxysilane (KH570).

[0040] Step 2): 0.2-0.4 wt% of H-β molecular sieve is added to the above silanized silica sol, and the mixture is continuously stirred to complete dispersion, thereby obtaining a modified silica sol binder.

[0041] Among them, the parameters of H-β molecular sieve are: high-silicon zeolite with a three-dimensional cross-structured twelve-membered ring channel, its skeleton structure is composed of two different but closely related symbiotic hybrid networks, the pore size is 0.6-0.7nm, and the specific surface area is greater than 500m 2 A large specific surface area is conducive to the complete contact between the molecular sieve and the silica sol, which will promote its dissolution. At the same time, a certain pore structure will also promote the contact between the interior of the molecular sieve and the silica sol.

[0042] On the other hand, the present invention provides a modified silica sol binder, wherein the raw materials of the modified silica sol binder include: silica sol, silane coupling agent, molecular sieve and water; wherein the silica sol includes sodium oxide;

[0043] The mass percentage of silicon dioxide in the raw materials is 29-31 wt%, the mass percentage of sodium oxide is less than or equal to 0.5 wt%, the mass percentage of the silane coupling agent is 0.1-0.2 wt%, and the mass percentage of the molecular sieve is 0.2-0.4 wt%.

[0044] In another aspect, the present invention provides an application of the modified silica sol binder, wherein the modified silica sol binder is used for casting ceramic shells.

[0045] In another aspect, the present invention provides a method for casting a ceramic shell, comprising the following steps:

[0046] Step 1: Add the modified silica sol binder into the mixing barrel, stir at a speed of 280-300 rpm, and then add the defoamer and wetting agent to obtain silica sol slurry;

[0047] The modified silica sol binder is prepared by using the modified silica sol binder described above or by using any of the preparation methods for the modified silica sol binder described above.

[0048] Step 2: Slowly add 320 mesh EC95 powder to the above silica sol slurry at a mass ratio of 1:3.5-4.2, continue stirring at a speed of 180-220 rpm for 48 hours to evenly disperse the EC95 powder in the silica sol binder, add deionized water to adjust the slurry viscosity to 30-34 Pa·s, and obtain the surface layer slurry of the ceramic shell for shell coating;

[0049] Step 3: Immerse the assembled wax model module in the surface slurry, apply the slurry evenly on the surface of the wax model module, and then sand and dry it. The surface layer, transition layer, and back layer are all coated with the surface slurry, sanded, and dried. Repeat this process several times before sealing.

[0050] Step 4: steam dewaxing the shell mold to obtain a wet shell blank;

[0051] Step 5: After the wet mold shell is fired, a ceramic mold shell is obtained.

[0052] The present invention is further described below with reference to specific examples and comparative examples.

[0053] Example 1

[0054] This embodiment provides a method for preparing a modified silica sol binder, comprising the following steps:

[0055] Step 1): 100 ml of a 32 wt% SiO2 aqueous silica sol solution was placed in a beaker and stirred at a low speed of 200 rpm to maintain a stable liquid level. 0.15 wt% KH550 (γ-aminopropyltriethoxysilane) was then added to the silica sol and stirred for 15 minutes to obtain a silanized silica sol.

[0056] Among them, the density of silica sol is 1.20g / cm 3 ; The room temperature viscosity of the silica sol is ≤8 Pa·s; the pH of the silica sol is 10.5; the particle size of the silica sol is 8 to 15 nm.

[0057] Step 2): 0.35 wt% of H-β molecular sieve is added to the above-mentioned silanized silica sol, and the mixture is continuously stirred to complete dispersion to obtain a modified silica sol binder; wherein the pore size of the H-β molecular sieve is 0.6 to 0.7 nm, and the specific surface area is greater than 500 m 2 / g.

[0058] The modified silica sol binder obtained above is used for casting a ceramic shell, comprising the following steps:

[0059] Step 1: Add the modified silica sol binder into the mixing barrel, stir at a speed of 280 rpm, and then add the defoamer and wetting agent to obtain silica sol slurry.

[0060] Step 2: Slowly add 320 mesh EC95 powder to the above silica sol slurry at a ratio of 1:3.7, continue stirring at 200 rpm for 48 hours to evenly disperse the EC95 powder in the silica sol binder, add deionized water to adjust the slurry viscosity to 33 Pa·s, and obtain the surface layer slurry of the ceramic shell for shell coating;

[0061] Step 3: Immerse the assembled wax model module in the surface slurry, apply the slurry evenly on the surface of the wax model module, and then sand and dry it. The surface layer, transition layer, and back layer are all coated with the surface slurry, sanded, and dried. Repeat this process several times before sealing.

[0062] Step 4: steam dewaxing the shell mold to obtain a wet shell blank;

[0063] Step 5: After the wet mold shell is fired, a ceramic mold shell is obtained.

[0064] Example 2

[0065] This embodiment provides a method for preparing a modified silica sol binder, comprising the following steps:

[0066] Step 1): 100 ml of a 32 wt% SiO2 aqueous silica sol solution was placed in a beaker and stirred at a low speed of 200 rpm to maintain a stable liquid level. 0.15 wt% KH560 (γ-glycidyloxypropyltrimethoxysilane) was then added to the silica sol and stirred for 15 minutes to obtain a silanized silica sol.

[0067] Among them, the density of silica sol is 1.20g / cm 3 ; The room temperature viscosity of the silica sol is ≤8 Pa·s; the pH of the silica sol is 10.5; the particle size of the silica sol is 8 to 15 nm.

[0068] Step 2): 0.35 wt% of H-β molecular sieve is added to the above-mentioned silanized silica sol, and the mixture is continuously stirred to complete dispersion to obtain a modified silica sol binder; wherein the pore size of the H-β molecular sieve is 0.6 to 0.7 nm, and the specific surface area is greater than 500 m 2 / g.

[0069] The modified silica sol binder obtained above is used for casting a ceramic shell, comprising the following steps:

[0070] Step 1: Add the modified silica sol binder into the mixing barrel, stir at a speed of 300 rpm, and then add the defoaming agent and wetting agent to obtain silica sol slurry.

[0071] Step 2: Slowly add 320 mesh EC95 powder to the above silica sol slurry at a ratio of 1:3.7, continue stirring at 200 rpm for 48 hours to evenly disperse the EC95 powder in the silica sol binder, add deionized water to adjust the slurry viscosity to 33 Pa·s, and obtain the surface layer slurry of the ceramic shell for shell coating;

[0072] Step 3: Immerse the assembled wax model module in the surface slurry, apply the slurry evenly on the surface of the wax model module, and then sand and dry it. The surface layer, transition layer, and back layer are all coated with the surface slurry, sanded, and dried. Repeat this process several times before sealing.

[0073] Step 4: steam dewaxing the shell mold to obtain a wet shell blank;

[0074] Step 5: After the wet mold shell is fired, a ceramic mold shell is obtained.

[0075] Example 3

[0076] This embodiment provides a method for preparing a modified silica sol binder, comprising the following steps:

[0077] Step 1): 100 ml of a 32 wt% SiO2 aqueous silica sol solution was placed in a beaker and stirred at a low speed of 200 rpm to maintain a stable liquid level. 0.15 wt% KH570 (γ-(methacryloyloxy)propyltrimethoxysilane) was then added to the silica sol and stirred for 15 minutes to obtain a silanized silica sol.

[0078] Among them, the density of silica sol is 1.20g / cm 3 ; The room temperature viscosity of the silica sol is ≤8 Pa·s; the pH of the silica sol is 10.5; the particle size of the silica sol is 8 to 15 nm.

[0079] Step 2): 0.35 wt% of H-β molecular sieve is added to the above-mentioned silanized silica sol, and the mixture is continuously stirred to complete dispersion to obtain a modified silica sol binder; wherein the pore size of the H-β molecular sieve is 0.6 to 0.7 nm, and the specific surface area is greater than 500 m 2 / g.

[0080] The modified silica sol binder obtained above is used for casting a ceramic shell, comprising the following steps:

[0081] Step 1: Add the modified silica sol binder into the mixing barrel, stir at a speed of 300 rpm, and then add the defoaming agent and wetting agent to obtain silica sol slurry.

[0082] Step 2: Slowly add 320 mesh EC95 powder to the above silica sol slurry at a ratio of 1:3.7, continue stirring at 200 rpm for 48 hours to evenly disperse the EC95 powder in the silica sol binder, add deionized water to adjust the slurry viscosity to 33 Pa·s, and obtain the surface layer slurry of the ceramic shell for shell coating;

[0083] Step 3: Immerse the assembled wax model module in the surface slurry, apply the slurry evenly on the surface of the wax model module, and then sand and dry it. The surface layer, transition layer, and back layer are all coated with the surface slurry, sanded, and dried. Repeat this process several times before sealing.

[0084] Step 4: steam dewaxing the shell mold to obtain a wet shell blank;

[0085] Step 5: After the wet mold shell is fired, a ceramic mold shell is obtained.

[0086] Comparative Example 1

[0087] This comparative example provides a method for casting a ceramic shell, comprising the following steps:

[0088] Step 1: Add the silica sol binder into the mixing barrel, stir at a speed of 300 rpm, and then add the defoamer and wetting agent to obtain silica sol slurry;

[0089] Step 2: Slowly add 320 mesh EC95 powder to the above silica sol slurry at a ratio of 1:3.7, continue stirring at 200 rpm for 48 hours to evenly disperse the EC95 powder in the silica sol binder, add deionized water to adjust the slurry viscosity to 33 Pa·s, and obtain the surface layer slurry of the ceramic shell for shell coating;

[0090] Step 3: Immerse the assembled wax model module in the surface slurry, apply the slurry evenly on the surface of the wax model module, and then sand and dry it. The surface layer, transition layer, and back layer are all coated with the surface slurry, sanded, and dried. Repeat this process several times before sealing.

[0091] Step 4: steam dewaxing the shell mold to obtain a wet shell blank;

[0092] Step 5: After the wet mold shell is fired, a ceramic mold shell is obtained.

[0093] The ceramic shell obtained in this comparative example forms cracks. This is because during high-temperature sintering, silica sol easily reacts with the alumina component in the refractory powder to form a mullite phase. After cooling, the generated mullite phase shrinks in volume. When the bonding strength is insufficient, the stress generated by the volume reduction can cause cracks.

[0094] Comparative Example 2

[0095] This comparative example provides a method for preparing a modified silica sol binder, comprising the following steps:

[0096] 100 ml of a 32 wt% SiO2 aqueous silica sol solution was placed in a beaker and stirred at a low speed of 200 rpm to maintain a stable liquid level. 0.15 wt% KH550 (γ-aminopropyltriethoxysilane) was then added to the silica sol and stirred for 15 minutes to obtain a silanized silica sol.

[0097] Among them, the density of silica sol is 1.20g / cm 3 ; The room temperature viscosity of the silica sol is ≤8 Pa·s; the pH of the silica sol is 10.5; the particle size of the silica sol is 8 to 15 nm.

[0098] The modified silica sol binder obtained above is used for casting a ceramic shell, comprising the following steps:

[0099] Step 1: Add the modified silica sol binder into the mixing barrel, stir at a speed of 300 rpm, and then add the defoamer and wetting agent to obtain silica sol slurry;

[0100] The modified silica sol binder is prepared by using the modified silica sol binder described above or by using any of the preparation methods for the modified silica sol binder described above.

[0101] Step 2: Slowly add 320 mesh EC95 powder to the above silica sol slurry at a ratio of 1:3.7, continue stirring at 200 rpm for 48 hours to evenly disperse the EC95 powder in the silica sol binder, add deionized water to adjust the slurry viscosity to 33 Pa·s, and obtain the surface layer slurry of the ceramic shell for shell coating;

[0102] Step 3: Immerse the assembled wax model module in the surface slurry, apply the slurry evenly on the surface of the wax model module, and then sand and dry it. The surface layer, transition layer, and back layer are all coated with the surface slurry, sanded, and dried. Repeat this process several times before sealing.

[0103] Step 4: steam dewaxing the shell mold to obtain a wet shell blank;

[0104] Step 5: After the wet mold shell is fired, a ceramic mold shell is obtained.

[0105] When the modified silica sol of this comparative example is applied to the ceramic shell, the wettability of the slurry on the wax mold is improved, so the surface cracks of the ceramic shell prepared by it are improved. However, the bonding strength of the silica sol is insufficient, resulting in some cracks on the surface, such as Figure 1 As shown in (c), the strength and surface quality of the ceramic shell obtained are improved compared with the original ceramic shell, but the modification effect is slightly worse than the synergistic modification effect of silane coupling agent KH550 and H-β molecular sieve.

[0106] Comparative Example 3

[0107] This comparative example provides a method for preparing a modified silica sol binder, comprising the following steps:

[0108] 0.35 wt% of H-β molecular sieve was added to the silica sol, and the mixture was continuously stirred to complete dispersion, thereby obtaining a modified silica sol binder.

[0109] Among them, the pore size of H-β molecular sieve is 0.6~0.7nm, and the specific surface area is greater than 500m 2 / g.

[0110] Among them, the density of silica sol is 1.20g / cm 3 ; The room temperature viscosity of the silica sol is ≤8 Pa·s; the pH of the silica sol is 9.5-10.5; the particle size of the silica sol is 8-15 nm.

[0111] The modified silica sol binder obtained above is used for casting a ceramic shell, comprising the following steps:

[0112] Step 1: Add the modified silica sol binder into the mixing barrel, stir at a speed of 300 rpm, and then add the defoamer and wetting agent to obtain silica sol slurry;

[0113] The modified silica sol binder is prepared by using the modified silica sol binder described above or by using any of the preparation methods for the modified silica sol binder described above.

[0114] Step 2: Slowly add 320 mesh EC95 powder to the above silica sol slurry at a ratio of 1:3.7, continue stirring at 200 rpm for 48 hours to evenly disperse the EC95 powder in the silica sol binder, add deionized water to adjust the slurry viscosity to 33 Pa·s, and obtain the surface layer slurry of the ceramic shell for shell coating;

[0115] Step 3: Immerse the assembled wax model module in the surface slurry, apply the slurry evenly on the surface of the wax model module, and then sand and dry it. The surface layer, transition layer, and back layer are all coated with the surface slurry, sanded, and dried. Repeat this process several times before sealing.

[0116] Step 4: steam dewaxing the shell mold to obtain a wet shell blank;

[0117] Step 5: After the wet mold shell is fired, a ceramic mold shell is obtained.

[0118] The modified silica sol in this comparative example introduced an Al-O-Si structure, which improved bonding strength and reduced cracking in the resulting ceramic shell. However, the slurry prepared by coating the refractory powder with hydrophilic silica sol exhibited poor wetting properties with the wax mold. As a result, while the strength and surface quality of the resulting ceramic shell improved compared to the original, the modification effect was slightly inferior to the synergistic modification achieved by combining the silane coupling agent KH550 with H-β molecular sieve.

[0119] Figure 1 The following is a macroscopic view of the ceramic shells obtained in the embodiment of the present invention and the comparative example. It can be seen that the surface of the ceramic shell obtained in the embodiment of the present invention is smooth and free of cracks, while the surface of the ceramic shell obtained in comparative example 1 is obviously cracked, and the ceramic shells obtained in comparative examples 2 and 3 have cracks. Therefore, the ceramic shell obtained in the embodiment of the present invention has better strength. Strength test results are shown in Figure 2. Figure 2 As shown, it can be seen that when no silane coupling agent and H-β molecular sieve are added (Comparative Example 1), the wet blank strength and sintered strength of the ceramic shell are 8.77 MPa and 9.74 MPa, respectively; when only the silane coupling agent is added (Comparative Example 2), the wet blank strength and sintered strength of the ceramic shell are 8.61 MPa and 10.90 MPa, respectively; when only the H-β molecular sieve is added (Comparative Example 3), the wet blank strength and sintered strength of the ceramic shell are 10.339 MPa and 11.81 MPa, respectively; while the wet blank strength and sintered strength of the ceramic shell with the addition of silane coupling agent KH550 (γ-aminopropyltriethoxysilane) (Example 1) and H-β molecular sieve are increased to 8.99 MPa and 13.82 MPa, respectively.

[0120] Therefore, the present invention adds aluminum-based nano-metal organic frameworks as a reinforcing phase to the silica sol, which can improve the dispersion state of the silica sol and enhance the stability of the silica sol. The modified silica sol is applied to the casting of alumina-based ceramic shells, thereby solving the problem of crack resistance of the castings and improving the yield of the castings, while meeting the requirements of simple operation, strong adjustability, and green environmental protection.

[0121] It is easy for those skilled in the art to understand that, under the premise of no conflict, the advantageous technical features of the above-mentioned methods can be freely combined and superimposed.

[0122] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention. The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and variations without departing from the technical principles of the present invention, and such improvements and variations shall also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a modified silica sol binder, characterized in that: The following steps are involved: Step 1): mixing a silane coupling agent with silica sol to react to obtain silanized silica sol; Step 2): mixing the molecular sieve with the silanized silica sol to obtain a modified silica sol binder.

2. The method for preparing the modified silica sol binder according to claim 1, wherein: In said step 1): The density of the silica sol is 1.18-1.20 g / cm 3 and / or The room temperature viscosity of the silica sol is ≤8 Pa·s; and / or The particle size of the silica sol is 8 to 15 nm; and / or The pH of the silica sol is 9.5-10.

5.

3. The method for preparing the modified silica sol binder according to claim 1, wherein: In said step 1): The silane coupling agent is one of γ-aminopropyltriethoxysilane, γ-glycidyloxypropyltrimethoxysilane and γ-(methacryloyloxy)propyltrimethoxysilane.

4. The method for preparing the modified silica sol binder according to any one of claims 1 to 3, characterized in that: The step 1) is specifically as follows: Stirring the silica sol, adding a silane coupling agent, and stirring for 10 to 15 minutes; Preferably, the stirring speed is 180-200 rpm.

5. The method for preparing the modified silica sol binder according to claim 1, wherein: In the step 2): The molecular sieve is H-β type molecular sieve.

6. The method for preparing the modified silica sol binder according to claim 1, wherein: The step 2) is specifically as follows: The molecular sieve is added to the silanized silica sol and stirred continuously to complete dispersion.

7. A modified silica sol binder, characterized in that: The raw materials of the modified silica sol binder include: silica sol, silane coupling agent, molecular sieve and water; wherein, the silica sol includes sodium oxide; The mass percentage of silicon dioxide in the raw materials is 29-31 wt%, the mass percentage of sodium oxide is less than or equal to 0.5 wt%, the mass percentage of the silane coupling agent is 0.1-0.2 wt%, and the mass percentage of the molecular sieve is 0.2-0.4 wt%.

8. The use of the modified silica sol binder according to claim 6, characterized in that: The modified silica sol binder is used for casting ceramic shells.

9. A method for casting a ceramic shell, characterized in that: The following steps are involved: Step 1: Mixing the modified silica sol binder, defoaming agent, and wetting agent to obtain silica sol slurry; Wherein, the modified silica sol binder is prepared by the preparation method of the modified silica sol binder according to any one of claims 1 to 6 or the modified silica sol binder according to claim 7; Step 2: Add EC95 powder to the silica sol slurry, add deionized water to adjust the viscosity, and obtain the surface slurry of the ceramic shell; Step 3: Immerse the assembled wax mold module in the surface slurry, sand and dry the wax mold module to obtain a shell module; Step 4: steam dewaxing the shell mold assembly to obtain a wet shell blank; Step 5: sintering the wet shell to obtain a ceramic shell.

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