Alumina ceramic slurry for non-aqueous tape casting

Abstract

The invention discloses aluminum oxide ceramic slurry for non-aqueous tape casting, which comprises aluminum oxide ceramic powder and a binder, and the binder is solid acrylic resin with the weight-average molecular weight of 300,000-600,000 Da and the glass transition temperature of-20 DEG C to 20 DEG C. Experiments prove that the solid acrylic resin with specific molecular weight and glass transition temperature is selected as the binder for preparing the non-water-based tape-casting aluminum oxide ceramic slurry, so that the dosage of an additional small-molecular plasticizer can be reduced to below 1%; the problem of performance degradation of the green body belt caused by migration of the plasticizer is avoided from the source, the green body belt can show excellent storage stability and excellent processing performance, and the method has important significance and application value in the high-end application fields of electronic ceramics and the like with strict requirements.

Description

Technical Field

[0001] This invention relates to a ceramic slurry, specifically an alumina ceramic slurry for non-water-based casting, belonging to the field of ceramic materials technology. Background Technology

[0002] Alumina ceramics are widely used in integrated circuit substrates, LED heat dissipation substrates, solid electrolyte supports, and thin-film discrete components due to their excellent insulation, high thermal conductivity, chemical stability, and mechanical strength. With the development of devices towards thinner, multilayer, and higher reliability, the demand for ultrathin alumina ceramic green sheets and sintered bodies with a thickness of less than 50 μm is increasing. Non-aqueous casting has become the mainstream process for preparing ultrathin ceramic green sheets due to its good powder wettability, low drying stress, and ability to be continuously rolled.

[0003] Typical non-aqueous cast slurry mainly consists of alumina powder, organic solvent, PVB binder, plasticizer, and dispersant. Among them, the amount of plasticizer (most commonly phthalates such as DBP and DOP) usually reaches 30-50 wt% of the total organic phase, equivalent to 4-6 wt% of the total slurry. Its function is to lower the glass transition temperature, give the green tape flexibility, and meet the processing requirements of roll-to-roll winding, post-punching, drilling, and lamination.

[0004] However, high plasticizer content brings the following prominent problems:

[0005] ① Environmental and regulatory pressures: Phthalate has been listed as a substance of very high concern by the European Union, and emission limits are becoming increasingly stringent; high VOC content increases the cost of end-of-pipe treatment.

[0006] ② Delamination defects: Plasticizers have low molecular weight and narrow decomposition range. During the delamination stage, rapid volatilization / decomposition can easily lead to bulging, delamination, and cracking, resulting in a scrap rate that is often higher than 5%. At the same time, it is necessary to extend the delamination insulation platform and increase the nitrogen flow rate, which significantly increases energy consumption.

[0007] ③ Uneven sintering shrinkage: After the excessive plasticizer volatilizes, it leaves additional pores in the green body, resulting in a shrinkage difference of 0.5% to 0.8% in the planar direction, which is difficult to meet the requirements of shape and position accuracy for large-size (>150mm) ultra-thin substrates.

[0008] ④ Cost and Storage Tackiness: Plasticizers are 20-30% more expensive than PVB and are prone to surface migration, which can cause tackiness in the green strip and interlayer contamination, leading to a decrease in the yield of subsequent laminates.

[0009] To address the aforementioned shortcomings, existing technologies primarily focus on remedial measures such as optimizing the glue removal curve, multi-layer gradient heating, or adding external venting channels. However, these approaches fail to fundamentally reduce the total amount of organic matter in the system. Some studies have attempted to replace plasticizers with water-based casting, but due to issues such as high drying stress, powder hydrolysis, and difficulty in eliminating bubbles, stable roll formation at ultra-thin thicknesses of 50μm has not yet been achieved. Therefore, how to significantly reduce plasticizer usage while maintaining the flexibility and integrity of the green tape, while simultaneously ensuring compatibility with existing non-water-based casting equipment, has become a pressing technical challenge in this field. Summary of the Invention

[0010] In view of the above-mentioned problems and needs of the existing technology, the purpose of this invention is to provide an alumina ceramic slurry for non-water-based casting molding that can significantly reduce the amount of added plasticizer.

[0011] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows:

[0012] An alumina ceramic slurry for non-aqueous casting includes alumina ceramic powder and a binder, wherein the binder is a solid acrylic resin with a weight-average molecular weight (Mw) of 300,000 to 600,000 Da and a glass transition temperature (Tg) of -20°C to 20°C.

[0013] In one embodiment, the alumina ceramic slurry has the following composition and proportions:

[0014] 100 parts by weight of alumina ceramic powder;

[0015] 5-10 parts by weight of adhesive;

[0016] Plasticizer 0.2 to 1 part by weight;

[0017] Slurry dispersant: 0.2–1 parts by weight;

[0018] Slurry solvent: 40-75 parts by weight.

[0019] In one embodiment, the alumina ceramic slurry is prepared by: first adding the binder, plasticizer, slurry dispersant and slurry solvent in the specified proportions into a container, heating to 40℃~60℃, and then maintaining the temperature and stirring pneumatically until fully mixed and dissolved; then adding alumina ceramic powder and ball milling until uniformly dispersed to obtain the alumina ceramic slurry.

[0020] In one embodiment, the adhesive is obtained by copolymerizing a type A monomer and a type B monomer, wherein the type A monomer is selected from at least one of methacrylate monomers with a homopolymer glass transition temperature (Tg) greater than 100°C, and the type B monomer is selected from at least one of (meth)acrylate monomers with a homopolymer glass transition temperature (Tg) less than 30°C, and the mass ratio of the type A monomer to the type B monomer is 1:4 to 2:3.

[0021] In a preferred embodiment, the type A monomer is selected from at least one of methacrylate monomers whose homopolymer glass transition temperature (Tg) is between 100°C and 180°C.

[0022] In a further preferred embodiment, the type A monomer is selected from at least one of methyl methacrylate (MMA, Tg≈105℃), tert-butyl methacrylate (tBMA, Tg≈107℃), cyclohexyl methacrylate (CHMA, Tg≈110℃), 3,3,5-trimethylcyclohexyl methacrylate (TMCHMA, Tg≈127℃), and isobornyl methacrylate (IBOMA, Tg≈170℃).

[0023] In a preferred embodiment, the type B monomer is selected from at least one of (meth)acrylate monomers with a homopolymer glass transition temperature (Tg) between -100°C and 25°C.

[0024] In a further preferred embodiment, the type B monomer is selected from at least one of the following: n-butyl methacrylate (BMA, Tg≈20℃), isooctyl methacrylate (EHMA, Tg≈-10℃), lauryl methacrylate (LMA, Tg≈-65℃), methyl acrylate (MA, Tg≈0℃), ethyl acrylate (EA, Tg≈-21℃), n-butyl acrylate (BA, Tg≈-56℃), isobutyl acrylate (IBA, Tg≈-24℃), isooctyl acrylate (EHA, Tg≈-70℃), and octadecyl acrylate (SA, Tg≈-49℃).

[0025] A method for preparing the adhesive involves suspension polymerization, in which the type A monomer and type B monomer undergo free radical polymerization in the presence of a dispersant, an initiator, and a chain transfer agent.

[0026] One embodiment of the preparation method includes the following steps:

[0027] a) Add the A-type monomer, B-type monomer, initiator and chain transfer agent to a container in the specified proportions, and stir at room temperature until all components are completely dissolved to form a homogeneous oil phase;

[0028] b) Add the specified amount of dispersant and a certain volume of deionized water to the reaction vessel, controlling the volume ratio of the aqueous phase to the oil phase to be (2-4):1. Then, stir at a constant temperature in a water bath at 40-60℃ until the dispersant is completely dissolved to obtain the aqueous phase.

[0029] c) Add the oil phase prepared in step a) to the aqueous phase in step b), and stir at a constant temperature for 30 to 50 minutes under a constant temperature water bath at 40 to 60°C.

[0030] d) The polymerization reaction is carried out at a constant temperature of 65-95℃ for 2-4 hours, and then stirred at a constant temperature of 98-100℃ for 0.5-1.5 hours.

[0031] e) Stop heating. When the temperature in the reaction system cools naturally to below 60°C, stop stirring. Collect the solid product by static sedimentation and filtration. Then wash and dry the obtained solid product to obtain the binder.

[0032] In one embodiment, the initiator is selected from at least one of benzoyl peroxide, tert-butyl peroxide-2-ethylhexanoate, dilauroyl peroxide, and 1,1-bis(tert-amylperoxy)cyclohexane.

[0033] In a preferred embodiment, the amount of the initiator is 0.1% to 0.2% of the total mass of monomers of types A and B.

[0034] In one embodiment, the chain transfer agent is selected from at least one of n-dodecyl mercaptan, tert-dodecyl mercaptan, n-octyl mercaptan, and isooctyl mercaptopropionate.

[0035] In a preferred embodiment, the amount of chain transfer agent is 0.1% to 0.5% of the total mass of monomers of types A and B.

[0036] In one embodiment, the dispersant is selected from at least one of polyvinyl alcohol, hydroxyethyl cellulose, sodium polyacrylate, and polyvinylpyrrolidone.

[0037] In a preferred embodiment, the amount of the dispersant is 0.05% to 0.2% of the total mass of monomers A and B.

[0038] In one embodiment, in step e), the drying refers to drying by blowing air at 35°C to 45°C.

[0039] In one embodiment, the plasticizer is selected from at least one of dibutyl phthalate, dioctyl phthalate, triethylene glycol diisooctyl ester, and polyvinyl alcohol.

[0040] In one embodiment, the slurry dispersant is selected from at least one of trioleic acid glyceride, tributyl phosphate, and oleic acid.

[0041] In one embodiment, the slurry solvent is selected from at least one of toluene, butyl acetate, butanone, and ethyl acetate.

[0042] Compared with the prior art, the present invention has the following significant advantages:

[0043] 1) By selecting a solid acrylic resin with a specific molecular weight and glass transition temperature as the binder for formulating non-aqueous cast alumina ceramic slurry, this invention not only reduces the amount of added small molecule plasticizer to below 1%, thus avoiding the problem of green belt performance degradation caused by plasticizer migration, but also demonstrates through experiments that the mechanical properties (elastic modulus) of green belts using the binder of this invention remain almost unchanged after being stored at 40°C for one month, exhibiting excellent storage stability.

[0044] 2) This invention creatively combines the characteristics of high molecular weight (300,000 to 600,000 Da) and low glass transition temperature (-20°C to 20°C) into a single polymer, thereby achieving a perfect balance between strength and flexibility in the binder. This results in green strips that are easy to bend and process, and have a smooth, flat cut surface without roughness or cracks, exhibiting excellent performance.

[0045] 3) Since this invention significantly reduces the variable component of plasticizer, it has important significance and application value for high-end application fields such as electronic ceramics with stringent requirements.

[0046] 4) Since the residual carbon rate of the binder used in this invention after calcination is less than 0.3%, it will not affect the sintering density of the ceramic substrate, thus ensuring the high purity and high performance of the final ceramic product. Detailed Implementation

[0047] The technical solution of the present invention will be further described in detail and completely below with reference to the embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the manufacturer.

[0048] The performance testing methods for the adhesives in the following examples and comparative examples are as follows:

[0049] Weight-average molecular weight (Mw): Determined by gel permeation chromatography (GPC), using polystyrene (PS) of different molecular weights as standard, tetrahydrofuran as mobile phase, flow rate set at 1 mL / min, and differential refractive index detector (RI detector). The sample was dissolved in tetrahydrofuran before injection.

[0050] Glass transition temperature (Tg): Determined by differential scanning calorimetry (DSC), that is, about 0.15 g of resin sample was weighed and placed in an aluminum crucible, and two scans were performed at a heating rate of 10℃ / min. The midpoint value of the second scan curve was taken as the Tg value of the sample.

[0051] Resin calcination carbon residue rate: The resin sample is accurately weighed in a crucible, placed in a muffle furnace, and calcined at 400℃ for 5 hours. After cooling, it is weighed again, and the percentage of the mass of the residual solid to the mass of the original sample is calculated.

[0052] Examples 1-4: Preparation of the adhesive described in this invention

[0053] General preparation steps:

[0054] a) Take a clean 1500 mL beaker and add type A monomer, type B monomer, initiator and chain transfer agent according to the ratio (see Table 1 for the types and amounts used in each example). Stir at room temperature until all components are completely dissolved to form a homogeneous oil phase.

[0055] b) Take a clean 5000 mL three-necked flask, add the specified amount of dispersant (the types and amounts used in each embodiment are detailed in Table 1) and a certain volume of deionized water (the volume ratio of the aqueous phase to the oil phase in each embodiment is detailed in Table 1), and then stir at a constant temperature of 50°C in a water bath until the dispersant is completely dissolved to obtain the aqueous phase.

[0056] c) Add the oil phase prepared in step a) to the aqueous phase in step b), and then stir at a constant temperature for 40 minutes in a water bath at 50°C.

[0057] d) The polymerization reaction was carried out in a constant temperature water bath at 65-95°C for 2-4 hours (the polymerization temperature and polymerization reaction time of each embodiment are detailed in Table 1), and then stirred in a constant temperature water bath at 99°C for 1 hour.

[0058] e) Stop heating. When the temperature in the reaction system cools naturally to below 60°C, stop stirring. Collect the solid product by allowing it to settle and filter. Then wash the obtained solid product five times with deionized water. Finally, place the washed product in a 40°C forced-air oven and dry it to constant weight to obtain the binder described in this invention.

[0059] Table 1. Composition, formulation, main process parameters, and properties of the resulting acrylic resins in each embodiment.

[0060]

[0061] Comparative Examples 1-6: Preparation of Comparative Acrylic Resins

[0062] The only difference between Comparative Example 1 and Example 1 is that the amount of chain transfer agent is increased so that the molecular weight of the resulting acrylic resin is less than the molecular weight range of the adhesive described in this invention, as detailed in Table 2.

[0063] The only difference between Comparative Example 2 and Example 1 is that the amount of chain transfer agent and initiator is reduced at the same time, so that the molecular weight of the resulting acrylic resin is greater than the molecular weight range of the adhesive described in this invention, as shown in Table 2.

[0064] The only difference between Comparative Example 3 and Example 1 is that the ratio of type B monomers was changed so that the Tg of the resulting acrylic resin was lower than the Tg range of the adhesive described in this invention, as detailed in Table 2.

[0065] The only difference between Comparative Example 4 and Example 1 is that the ratio of type A monomers to type B monomers is changed so that the Tg of the resulting acrylic resin is higher than the Tg range of the adhesive described in this invention, as shown in Table 2.

[0066] The only difference between Comparative Example 5 and Example 1 is that the ratio of type A monomer to type B monomer is changed so that the mass ratio of type A monomer to type B monomer is less than the range of 1:4 to 2:3 described in this invention, as shown in Table 2.

[0067] The only difference between Comparative Example 6 and Example 1 is that the ratio of type A monomer to type B monomer is changed so that the mass ratio of type A monomer to type B monomer is greater than the range of 1:4 to 2:3 described in this invention, as shown in Table 2.

[0068] Table 2 shows the composition, main process parameters, and properties of the resulting acrylic resins for each comparative example.

[0069]

[0070] Application Examples 1-4

[0071] Add 5-10 parts by weight of binder (the specific types and amounts of each embodiment are detailed in Table 3), 0.2-1 parts by weight of plasticizer (the specific types and amounts of each embodiment are detailed in Table 3), 0.2-1 parts by weight of slurry dispersant (the specific types and amounts of each embodiment are detailed in Table 3), and 40-75 parts by weight of slurry solvent (the specific types and amounts of each embodiment are detailed in Table 3) to a container, heat to 50°C, and then keep warm and pneumatically stir until fully mixed and dissolved (about 24 hours); then add 100 parts by weight of alumina ceramic powder, and ball mill until uniformly dispersed (about 20 hours) to obtain an alumina ceramic slurry for non-aqueous casting molding.

[0072] Using a casting apparatus, the alumina ceramic slurry prepared for each application example was used to prepare film strips with a thickness of approximately 50 micrometers. After drying, the elastic modulus of the obtained film strips at 22°C and 50°C was measured using the vibration pulse excitation method according to ASTM E1876-2007 standard. The measurement results are detailed in Table 4.

[0073] Application Comparative Examples 1-6

[0074] The same ceramic slurry formulation and preparation process as Application Example 1 were used, except that the binder in Application Example 1 was replaced with the acrylic resin prepared in Comparative Examples 1 to 6. All other contents were the same as described in Application Example 1.

[0075] The alumina ceramic slurries prepared according to the comparative proportions for each application were respectively prepared into films with a thickness of approximately 50 micrometers. After drying, the elastic modulus of the obtained films at 22℃ and 50℃ were measured respectively. The measurement results are shown in Table 4.

[0076] Application Comparative Example 7

[0077] The only difference between this application comparison example and application comparison example 4 is that the amount of plasticizer is increased from 0.2% to 5%. All other contents are the same as application comparison example 4.

[0078] The alumina ceramic slurry prepared according to the application ratio was used to prepare a film strip with a thickness of about 50 micrometers. After drying, the elastic modulus of the obtained film strip was measured at 22℃ and 50℃, respectively. The measurement results are shown in Table 4.

[0079] Storage stability test of the film strips: Each prepared film strip was stored in a 40℃ oven for 1 month, then taken out and cooled to room temperature. The elastic modulus of each film strip at 22℃ and 50℃ was then retested. The test results are shown in Table 4.

[0080] Table 3. Ceramic slurry formulations for application examples 1-4

[0081]

[0082] Table 4 Elastic modulus of each sample film strip

[0083]

[0084] Membrane tape appearance evaluation:

[0085] Membrane tape processing: The membrane tape was stacked into 30 layers using a laminator, and then pressed together using a warm isostatic press. The cut surface was observed after cutting. The appearance of the membrane tape was observed in its initial state, after being stored at 40℃ for one month, and after processing and cutting. Detailed results are shown in Table 5.

[0086] Table 5. Appearance and processing performance of the membrane tape

[0087]

[0088] Note: The acceptable range of elastic modulus for alumina cast film at 22℃ is 250–350 MPa, and the acceptable range of elastic modulus at 50℃ is 42–58 MPa.

[0089] Combining the results shown in Tables 4 and 5, it can be seen that:

[0090] ① By applying the binders of Examples 1 to 4 of this invention, the amount of external small molecule plasticizer in the alumina ceramic slurry can be less than 1%. This not only ensures that the initial elastic modulus of the prepared alumina cast film meets the requirements, but also that its elastic modulus hardly changes after being stored at 40°C for one month, demonstrating excellent storage stability. Furthermore, the film has a good appearance, excellent processing performance, and a smooth cut surface. This indicates that the binder used in this invention can achieve a balance between strength and flexibility, producing unexpected technical effects.

[0091] ② Under the same ceramic slurry formulation and preparation process, the alumina cast film obtained by using acrylic resin (although Tg meets the requirements, Mw is too low) as a binder in Comparative Example 1 has insufficient strength (elastic modulus is below the acceptable range), resulting in rough cut surfaces and poor processing performance; the alumina cast film obtained by using acrylic resin (although Tg meets the requirements, Mw is too high) as a binder in Comparative Example 2 is too rigid (elastic modulus is above the acceptable range), and after the film is made, there are unqualified phenomena such as surface roughness, cracks and bubbles, so it cannot be used; thus, it can be proved that limiting the molecular weight range of the binder in this invention to 300,000 to 60 Da is one of the key contributions to obtaining the beneficial effects of this invention.

[0092] ③ Under the same conditions of ceramic slurry formulation and preparation process, the alumina cast film obtained by using acrylic resin (although Mw meets the requirements, Tg is too low) as a binder in Comparative Example 3 is too soft and lacks strength, resulting in rough cut surfaces and poor processing performance; the alumina cast film obtained by using acrylic resin (although Mw meets the requirements, Tg is too high) as a binder in Comparative Example 4 is too brittle and hard, and after the film is made, there are unqualified phenomena such as rough surface, cracks and bubbles, so it cannot be used; thus, it can be proved that limiting the Tg range of the binder described in this invention to -20℃ to 20℃ is one of the key contributions to obtaining the beneficial effects of this invention.

[0093] ④ Under the same conditions of ceramic slurry formulation and preparation process, the alumina cast film obtained by using acrylic resins in Comparative Examples 5 and 6 (although Mw and Tg are numerically qualified, the ratio of type A monomers to type B monomers is inappropriate) as binders still failed to achieve the optimal microstructure, resulting in substandard mechanical properties (elastic modulus too low or too high) and poor processing performance (rough cut surface or cracks). This highlights that limiting the mass ratio of the two types of monomers (1:4 to 2:3) of the binder described in this invention is one of the key contributions to obtaining the beneficial effects of this invention.

[0094] ⑤ Under the same conditions, by increasing the amount of plasticizer (from 0.2% to 5%), although the initial elastic modulus of the obtained alumina cast film tape can be made to meet the requirements (see Application Comparative Example 4 and Application Comparative Example 7), after one month of storage at 40°C, its elastic modulus increases sharply by as much as 23.5% (see Application Comparative Example 7), which is seriously exceeding the standard. This is direct evidence that plasticizer migration causes the film tape to become hard and brittle.

[0095] As can be seen from the above, by selecting a solid acrylic resin with a specific molecular weight and glass transition temperature as the binder for formulating non-aqueous cast alumina ceramic slurry, this invention not only reduces the amount of added small molecule plasticizer to below 1%, thus avoiding the problem of performance degradation of green belt caused by plasticizer migration, but also demonstrates through experiments that the binder of this invention can enable the green belt to exhibit excellent storage stability and superior processing performance, which is of great significance and application value for high-end application fields such as electronic ceramics with stringent requirements.

[0096] Finally, it should be noted that the above are only some preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention shall fall within the scope of protection of the present invention.

Claims

1. An alumina ceramic slurry for non-aqueous casting, comprising alumina ceramic powder and a binder, characterized in that: the binder is a solid acrylic resin with a weight-average molecular weight (Mw) of 300,000 to 600,000 Da and a glass transition temperature (Tg) of -20°C to 20°C.

2. The alumina ceramic slurry according to claim 1, characterized in that, The alumina ceramic slurry has the following composition and proportions: 100 parts by weight of alumina ceramic powder; 5-10 parts by weight of adhesive; Plasticizer 0.2 to 1 part by weight; Slurry dispersant: 0.2–1 parts by weight; Slurry solvent: 40-75 parts by weight.

3. The alumina ceramic slurry according to claim 1 or 2, characterized in that: The adhesive is obtained by copolymerizing type A monomers and type B monomers. Type A monomers are selected from at least one of methacrylate monomers with a glass transition temperature (Tg) of greater than 100°C for homopolymers, and type B monomers are selected from at least one of (meth)acrylate monomers with a glass transition temperature (Tg) of less than 30°C for homopolymers. The mass ratio of type A monomers to type B monomers is 1:4 to 2:

3.

4. The alumina ceramic slurry according to claim 3, characterized in that: The type A monomer is selected from at least one of methacrylate monomers whose homopolymer glass transition temperature (Tg) is between 100℃ and 180℃, and the type B monomer is selected from at least one of (meth)acrylate monomers whose homopolymer glass transition temperature (Tg) is between -100℃ and 25℃.

5. The alumina ceramic slurry according to claim 4, characterized in that: The monomers of type A are selected from at least one of methyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, 3,3,5-trimethylcyclohexyl methacrylate, and isobornyl methacrylate. The monomers of type B are selected from at least one of n-butyl methacrylate, isooctyl methacrylate, lauryl methacrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, isooctyl acrylate, and octadecyl acrylate.

6. The alumina ceramic slurry according to claim 1 or 2, characterized in that: The binder is prepared by suspension polymerization, in which the type A monomers and type B monomers undergo free radical polymerization in the presence of a dispersant, initiator and chain transfer agent.

7. The alumina ceramic slurry according to claim 6, characterized in that, The preparation method includes the following steps: a) Add the A-type monomer, B-type monomer, initiator and chain transfer agent to a container in the specified proportions, and stir at room temperature until all components are completely dissolved to form a homogeneous oil phase; b) Add the specified amount of dispersant and a certain volume of deionized water to the reaction vessel, controlling the volume ratio of the aqueous phase to the oil phase to be (2-4):

1. Then, stir at a constant temperature in a water bath at 40-60℃ until the dispersant is completely dissolved to obtain the aqueous phase. c) Add the oil phase prepared in step a) to the aqueous phase in step b), and stir at a constant temperature for 30 to 50 minutes under a constant temperature water bath at 40 to 60°C. d) The polymerization reaction is carried out at a constant temperature of 65-95℃ for 2-4 hours, and then stirred at a constant temperature of 98-100℃ for 0.5-1.5 hours. e) Stop heating. When the temperature in the reaction system cools naturally to below 60°C, stop stirring. Collect the solid product by static sedimentation and filtration. Then wash and dry the obtained solid product to obtain the binder.

8. The alumina ceramic slurry according to claim 2, characterized in that: The plasticizer is selected from at least one of dibutyl phthalate, dioctyl phthalate, triethylene glycol diisooctyl ester, and polyvinyl alcohol.

9. The alumina ceramic slurry according to claim 2, characterized in that: The slurry dispersant is selected from at least one of trioleic acid glyceride, tributyl phosphate, and oleic acid.

10. The alumina ceramic slurry according to claim 2, characterized in that: The slurry solvent is selected from at least one of toluene, butyl acetate, butanone, and ethyl acetate.

Images