Mussel bionic composite adhesive and preparation method thereof

Abstract

The invention provides a mussel bionic composite adhesive and a preparation method thereof, and belongs to the technical field of high-performance adhesives. The composite material is prepared from 88 parts by mass of premixed mother liquor, 3-6 parts by mass of a silane coupling agent KH-560 and 4-8 parts by mass of nano-hydroxyapatite, 3, 4-dihydroxy phenyl methacrylamide is taken as an adhesion function core of the premixed mother liquor, is cooperated with 2-ethylhexyl acrylate and isobornyl methacrylate, and is compounded with a specific composite photoinitiator, an antioxidant 1010 and an ultraviolet absorbent 328. The preparation method comprises the following steps: preparing premixed mother liquor under the dark condition of 30 DEG C, primarily dispersing the premixed mother liquor, the silane coupling agent and the nano-hydroxyapatite under normal pressure, and performing vacuum stirring, dispersing and degassing under-0.05 to-0.08 MPa. The adhesive has excellent adhesion to inorganic base materials such as hydroxyapatite and natural stone, has compressive strength of more than or equal to 22MPa and high elongation at break of 35-55%, has outstanding weather resistance and stable performance after long-term ultraviolet aging, and is suitable for the fields of medical bone repair material fixation, stone adhesion, high-end composite material forming and the like.

Description

Technical Field

[0001] This invention belongs to the field of high-performance adhesive technology, and more specifically, relates to a mussel-inspired composite adhesive and its preparation method. Background Technology

[0002] Achieving strong, durable, and adaptable bonding of inorganic mineral materials such as stone, ceramics, and hydroxyapatite for bone repair has always been a technological challenge in various fields, including high-end building materials, cultural relic restoration, medical composite materials, and handicrafts manufacturing. Existing epoxy resin, acrylate, or polyurethane adhesives, which are widely used, generally have the following significant limitations: Firstly, the chemical affinity with the surface of inorganic substrates is insufficient, and the adhesion mainly relies on physical anchoring, resulting in limited interfacial bonding strength. Especially in humid environments or scenarios with large temperature differences, interfacial failure is very likely to occur, affecting the bonding stability. Secondly, it is difficult to balance mechanical properties. High-modulus adhesives are usually brittle and have poor impact resistance, while high-toughness adhesives have insufficient load-bearing capacity and cannot adapt to complex stress environments. Third, it has poor weather resistance. When exposed to ultraviolet light, oxygen and temperature and humidity cycles for a long time, it is prone to yellowing and powdering, and its mechanical properties will be significantly degraded, greatly shortening its service life. Fourth, most high-performance adhesives have complex components, require strict proportions during on-site mixing, have poor process stability, and are difficult to guarantee batch-to-batch consistency of product performance.

[0003] Inspired by the excellent adhesive properties of byssal proteins in marine mussels, biomimetic adhesives containing catechol groups have become a research hotspot in this field. 3,4-Dihydroxyphenylmethylacrylamide (DMA), as a typical representative of such biomimetic monomers, possesses excellent wet adhesion potential, but current technologies have significant limitations in its application. On the one hand, research has focused on the adhesion properties of DMA itself, or only copolymerized it with a single type of modified monomer, failing to systematically construct a synergistic system at the molecular design level that can simultaneously achieve strong interfacial adhesion, high bulk strength, good toughness and excellent long-term weather resistance. On the other hand, there is a lack of systematic integration of multifunctional additives (such as silane coupling agents with specific structures and nanoscale active fillers) optimized for the characteristics of inorganic substrates, and the preparation process is mostly limited to the simple mechanical mixing stage in the laboratory, which makes it difficult to ensure the high uniformity and low defect rate of the products, and seriously restricts their large-scale application in high-standard fields such as high-end building materials and medical bone repair. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a mussel-inspired composite adhesive and its preparation method, which solves the technical problems of insufficient adhesion, difficulty in balancing mechanical properties (rigidity and flexibility), poor long-term weather resistance, and poor batch stability of existing adhesives when bonding inorganic mineral substrates such as hydroxyapatite and natural stone.

[0005] A mussel-inspired composite adhesive is composed of the following components in parts by weight: 88 parts of premixed mother liquor, 6 parts of silane coupling agent KH-5603-, and 4-8 parts of nano-hydroxyapatite. The premixed mother liquor is composed of the following components in parts by weight: 40 parts of 3,4-dihydroxyphenylmethacrylamide, 25 parts of isooctyl acrylate, 30 parts of isobornyl methacrylate, 1-2 parts of composite photoinitiator, 0.5-1 part of antioxidant, and 0.5-1 part of ultraviolet absorber. The composite photoinitiator is a mixture of 2-hydroxy-2-methyl-1-phenyl-1-propanone and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide in a mass ratio of 1:1; The antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; The ultraviolet absorber is 2-(2'-hydroxy-3',5'-di-tert-pentylphenyl)benzotriazole.

[0006] Preferably, the particle size of the nano-hydroxyapatite is 50-80 nm.

[0007] A premixed mother liquor for a mussel biomimetic composite adhesive is composed of the following components in parts by weight: 40 parts of 3,4-dihydroxyphenylmethacrylamide, 25 parts of isooctyl acrylate, 30 parts of isobornyl methacrylate, 1-2 parts of composite photoinitiator, 0.5-1 parts of antioxidant, and 0.5-1 parts of ultraviolet absorber.

[0008] A method for preparing the mussel-inspired biomimetic composite adhesive includes the following steps: (1) Preparation of premixed mother liquor: Under light-protected conditions, the formula amounts of 3,4-dihydroxyphenylmethacrylamide, isooctyl acrylate, isobornyl methacrylate, antioxidant and ultraviolet absorber are mixed and stirred, and the formula amount of composite photoinitiator is added and stirred to obtain premixed mother liquor; (2) Preparation of finished product: Take 88 parts by mass of the premixed mother liquor, add 6 parts by mass of silane coupling agent KH-5603- and 4-8 parts by mass of nano hydroxyapatite, first stir and disperse under normal pressure, then continue to stir and disperse under vacuum and degas to obtain the finished product.

[0009] Preferably, the vacuum degree of the stirring and dispersion under vacuum conditions in step (2) is -0.05MPa to -0.08MPa, and the stirring time is 10-15 minutes.

[0010] Preferably, the stirring and dispersion at normal pressure in step (2) is performed at a speed of 1200-1500 r / min for 10-15 minutes.

[0011] Preferably, the mixing and stirring in step (1) is carried out at 30°C, and the total stirring time is 25-35 minutes.

[0012] Compared with the prior art, the present invention has the following beneficial effects: This innovative approach combines the biomimetic adhesion mechanism of DMA with the chemical coupling effect of the silane coupling agent KH-560. The catechol group in the DMA molecule can mimic mussel foot silk protein, forming strong interactions such as multiple hydrogen bonds, coordination bonds, and π-π stacking with hydroxyl groups and metal ions on the surface of inorganic substrates. The siloxane group of KH-560 can be hydrolyzed and bind to the surface of inorganic substrates, while the unsaturated double bond at the other end participates in copolymerization, forming a strong chemical "bridge" between the organic adhesive and the inorganic substrate. Under the synergistic effect of the dual mechanisms, the adhesive exhibits strong interfacial bonding force to inorganic substrates such as hydroxyapatite, natural jade, and ceramics, with a tensile shear strength significantly higher than that of conventional adhesives.

[0013] Through the scientific synergistic design of rigid and flexible monomers, a mechanical property that combines rigidity and flexibility is achieved. The bicyclic rigid structure of isobornyl methacrylate acts as a rigid crosslinking point in the polymer network, significantly improving the bulk modulus and compressive strength of the adhesive (≥22MPa, up to 26.5MPa under preferred conditions); the long-chain alkyl structure of isooctyl acrylate introduces flexible segments, effectively improving the elongation at break (35%-55%) and low-temperature impact resistance of the cured material, relieving internal stress, and enabling the adhesive to adapt to complex stress environments.

[0014] Leveraging its unique monomer structure and precisely formulated anti-aging system, the product possesses excellent resistance to thermo-oxidative and photo-aging. Antioxidant 1010 effectively quenches free radicals, while UV absorber 328 efficiently absorbs ultraviolet light. Together, they synergistically inhibit the oxidative degradation of polymer chains under heat, oxygen, and light radiation at the source. After rigorous accelerated aging tests (such as 500 hours of UVB-313 lamp irradiation at 60°C), the product exhibits no yellowing or chalking, and retains over 93% of its core mechanical properties, meeting the stringent durability requirements for long-term outdoor use and high-end applications.

[0015] By employing premixed mother liquor technology, the core components are prepared under strictly controlled temperature (30℃) and light-protected conditions, ensuring the precision and stability of the component ratios. The final product preparation process incorporates a vacuum dispersion process, which not only promotes the uniform dispersion of nano-hydroxyapatite and avoids agglomeration defects, but also effectively removes air bubbles introduced during stirring, resulting in a dense and homogeneous adhesive product. This process significantly improves the batch-to-batch consistency and reliability of the product, laying a solid foundation for its application in high-standard fields such as medical bone repair and cultural relic restoration. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the preparation process of the present invention. Detailed Implementation

[0017] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0018] The technical solution of the present invention is illustrated in detail through multiple specific embodiments, covering the defined component ratio range and process parameter range, and the product efficacy is verified through performance testing. In all embodiments, unless otherwise stated, the raw materials used are commercially available industrial-grade or reagent-grade products, and their purity meets the following requirements: 3,4-Dihydroxyphenylmethacrylamide (DMA) purity ≥98%, isooctyl acrylate purity ≥99%, isobornyl methacrylate purity ≥98%, silane coupling agent KH-560 purity ≥97%, nano-hydroxyapatite purity ≥99%; All “number of parts” refer to mass parts, and the test methods are all performed in accordance with national standards or industry-standard methods.

[0019] Experimental equipment and instruments:

[0020] Raw material pretreatment: Nano hydroxyapatite: Before use, place it in a vacuum drying oven at 80°C for 4 hours to remove adsorbed moisture. After cooling to room temperature, seal it for later use to ensure that the particle size is maintained at 50~80nm (verified by a laser particle size analyzer).

[0021] Silane coupling agent KH-560: Shake well before use to avoid separation, and store in a sealed container at room temperature.

[0022] Composite photoinitiator: Weigh 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173) and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (819) precisely at a mass ratio of 1:1, mix thoroughly, and store away from light. Specific implementation examples: Example 1: General-purpose mussel biomimetic composite adhesive (intermediate formulation) Raw material ratio:

[0024] 2. Preparation steps: (1) Preparation of premixed mother liquor: Adjust the temperature of the constant temperature and light-proof stirring vessel to 30°C, ensure the stirring paddle is clean and dry, and close the light-transmitting window to meet the light-proof conditions.

[0025] Add 40 parts DMA, 25 parts isooctyl acrylate, 30 parts isobornyl methacrylate, 0.6 parts antioxidant 1010, and 0.6 parts UV absorber 328 to the mixing vessel in sequence. Start the stirring and set the speed to 900 r / min. Stir for 18 minutes until the material forms a uniform and transparent liquid (without visible particles or stratification).

[0026] Add 1.6 parts of composite photoinitiator, maintain 30°C and light-protected conditions, and continue stirring at 900 r / min for 12 minutes to ensure that the photoinitiator is completely dissolved and dispersed.

[0027] Stop stirring, transfer the resulting premixed mother liquor into a brown sealed container, store it away from light for later use, and observe its appearance to ensure it is uniform and transparent, without any sediment or bubbles.

[0028] (2) Preparation of finished adhesive product: Take 88 parts of the above premixed mother liquor, add 5 parts of silane coupling agent KH-560 and 6 parts of pretreated nano hydroxyapatite, pour into the mixing tank of a vacuum planetary mixer, seal the mixing tank and turn off the light transmission device.

[0029] First, under normal pressure, set the rotation speed to 1400 r / min and stir for 12 minutes to initially disperse the silane coupling agent and nano hydroxyapatite in the premixed mother liquor. During this period, observe the material status every 3 minutes to ensure that there is no agglomeration or clumping.

[0030] Start the vacuum system and slowly evacuate to -0.06MPa. Maintain this vacuum level and continue stirring at 1400r / min for 12 minutes. Monitor the vacuum level in real time during the process and adjust it promptly if fluctuations occur to ensure effective removal of air bubbles from the material.

[0031] After mixing, slowly release the vacuum (to prevent air from entering quickly and causing secondary bubbles), open the mixing tank, and take out the finished adhesive. It should be a uniform, viscous liquid with no bubbles or obvious particle agglomeration.

[0032] (3) Curing treatment: The finished adhesive is evenly applied to the bonding surface of the standard test substrate (marble block: 100mm×25mm×25mm; hydroxyapatite board: 50mm×50mm×5mm), with the coating thickness controlled at 0.2~0.3mm. The substrate is then aligned and a pressure of 0.5MPa is applied to fix it.

[0033] Place it in a UV curing machine and set the irradiation power to 1000mW / cm². 2 Irradiation time is 2 minutes to complete the initial curing; then the bonded sample is placed in a 60℃ constant temperature oven for post-curing for 2 hours, and then taken out and cooled to room temperature for use.

[0034] 3. Performance Testing: The cured adhesive shall be tested for performance according to the following standards; The results are shown in the table below:

[0035] Example 2: High-strength, weather-resistant mussel-inspired biomimetic composite adhesive (upper limit ratio) Raw material ratio:

[0036] 2. Preparation steps: (1) Preparation of premixed mother liquor: Adjust the temperature of the constant temperature and light-proof stirring vessel to 30℃. Under light-proof conditions, add 40 parts DMA, 25 parts isooctyl acrylate, 30 parts isobornyl methacrylate, 0.9 parts antioxidant 1010, and 0.9 parts UV absorber 328 in sequence. Set the speed to 1000r / min and stir for 20 minutes until the material is completely homogeneous and transparent.

[0037] Add 1.0 part of composite photoinitiator, keep at 30°C and protected from light, and continue stirring at 1000 r / min for 15 minutes to ensure uniform dispersion of the photoinitiator, and obtain a premixed mother liquor, which is then sealed and stored in the dark.

[0038] (2) Preparation of finished adhesive product: Take 88 parts of premixed mother liquor, add 6 parts of KH-560 and 8 parts of pretreated nano hydroxyapatite, and put them into a vacuum planetary mixer.

[0039] Under normal pressure and in the dark, stir at 1500 r / min for 15 minutes to perform preliminary dispersion.

[0040] Evacuate to -0.07MPa and maintain this vacuum level. Continue stirring at 1500r / min for 15 minutes to degas and promote uniform dispersion of the nanofiller. After releasing the vacuum, take out the finished product, which is a viscous and homogeneous liquid without bubbles or agglomeration.

[0041] (3) Curing treatment: Curing conditions as in Example 1: UV irradiation (1000mW / cm²) 2 (2 min) + 60℃ and then cure for 2 hours.

[0042] 3. Performance Testing: In addition to standard performance testing, accelerated UV aging tests were conducted (UVB-313 lamp, irradiation at 60℃ for 500 hours). The performance changes before and after aging were tested, and the results are shown in the table below:

[0043] Example 3: Economical mussel-inspired biomimetic composite adhesive (lower limit ratio) Raw material ratio:

[0044] 2. Preparation steps: (1) Preparation of premixed mother liquor: At 30°C and in the dark, add 40 parts DMA, 25 parts isooctyl acrylate, 30 parts isobornyl methacrylate, 0.5 parts antioxidant 1010, and 0.5 parts UV absorber 328 to a mixing tank, set the speed to 800 r / min, and stir for 15 minutes until the material is homogeneous.

[0045] Add 2.0 parts of composite photoinitiator, keep the same conditions, and continue stirring at 800 r / min for 10 minutes to obtain a premixed mother liquor, which is then sealed and stored away from light.

[0046] (2) Preparation of finished adhesive product: Take 88 parts of premixed mother liquor, add 3 parts of KH-560 and 4 parts of pretreated nano hydroxyapatite, and put them into a vacuum planetary mixer.

[0047] Under normal pressure and in the dark, stir at 1200 r / min for 10 minutes to achieve initial dispersion.

[0048] Evacuate to -0.05MPa, maintain this vacuum level, and continue stirring at 1200r / min for 10 minutes. After degassing, remove the finished product.

[0049] (3) Curing treatment: Curing conditions as in Example 1: UV irradiation (1000mW / cm²) 2 (2 min) + 60℃ and then cure for 2 hours.

[0050] Performance testing:

[0051] Comparison of Examples: 1. The impact of component ratio on performance: Dosage of silane coupling agent KH-560: As the amount of KH-560 increased from 3 parts to 6 parts (Example 3 → Example 1 → Example 2), the tensile shear strength gradually increased (2.8MPa → 3.6MPa → 4.2MPa). This is because the chemical "bridging" effect formed by KH-560 between the organic adhesive and the inorganic substrate is enhanced, and the interfacial bonding force is improved.

[0052] The amount of nano hydroxyapatite used increased from 4 parts to 8 parts. The compressive strength increased from 22.1 MPa to 26.5 MPa, while the elongation at break decreased from 55% to 46%. This indicates that nano hydroxyapatite can enhance the strength of the system as a rigid filler, but excessive amounts will reduce flexibility. The amount used needs to be balanced to take into account both rigidity and flexibility.

[0053] Antioxidants and UV absorbers: With increased dosage (0.5 parts → 0.6 parts → 0.9 parts), the performance retention rate after aging improved (yellowing index 1.5 in Example 3 → yellowing index 1.2 in Example 2), verifying their synergistic anti-aging effect.

[0054] 2. The impact of process parameters on product quality: Stirring speed: In the preparation of premixed mother liquor, a stirring speed of 800~1000 r / min can achieve uniform mixing of components. The higher the speed (such as 1000 r / min), the shorter the mixing time can be, but it is necessary to avoid excessive speed causing the material to heat up.

[0055] Vacuum degree and stirring time: The vacuum degree is increased from -0.05MPa to -0.07MPa, resulting in better degassing, reduced bubble content in the adhesive, and improved compressive strength; a vacuum stirring time of 10~15 minutes is sufficient, but too long will increase energy consumption, while too short will result in incomplete degassing.

[0056] 3. Product suitability verification: Example 1 (General Type): With balanced overall performance, it is suitable for common scenarios such as stone bonding and handicraft manufacturing. It has a tensile shear strength of 3.6MPa and an elongation at break of 52%, and can adapt to daily stress and temperature and humidity changes.

[0057] Example 2 (High Strength and Weather Resistance): Compressive strength ≥26MPa, performance retention rate after aging ≥93%, suitable for high-end outdoor building materials, cultural relic restoration and other scenarios with stringent requirements for strength and weather resistance.

[0058] Example 3 (Economy): The performance meets the basic bonding requirements, the cost is low, and it is suitable for mass production scenarios with moderate performance requirements (such as ordinary ceramic bonding).

[0059] Precautions: All raw materials must be stored away from light, especially DMA and composite photoinitiators, to prevent premature polymerization.

[0060] The temperature must be strictly controlled during the preparation process (premixed mother liquor preparation 30℃). Too high a temperature may cause the photoinitiator to decompose and the monomer to self-polymerize.

[0061] Before using a vacuum planetary mixer, check its sealing performance to ensure that the vacuum level can be stably maintained at -0.05 to -0.08 MPa.

[0062] Cured adhesive samples should be stored in a dry environment to avoid moisture affecting performance test results.

[0063] The specific embodiments of the present invention cover all defined component ratio ranges (3-6 parts of silane coupling agent, 4-8 parts of nano hydroxyapatite, 1-2 parts of composite photoinitiator, etc.) and process parameter ranges (stirring speed, vacuum degree, time, etc.). The feasibility and stability of the technical solution have been verified through different embodiments. The product performance meets the preset requirements and is suitable for inorganic substrate bonding needs in different scenarios.

[0064] This mussel-inspired composite adhesive is named Beiliansu, meaning "mussel-inspired, strong bonding, and excellent quality." This name aligns with the product's core R&D concept of relying on the biomimetic adhesion mechanism of mussel byssal proteins, highlights its strong bonding characteristics to inorganic substrates and its superior product quality, and facilitates market recognition, promotion, and application of the product. This adhesive has been validated through practical applications in medical bone repair material fixation, natural stone bonding, and high-end composite material molding, demonstrating excellent performance. It is easy to use during construction, requires no complex on-site mixing, and exhibits excellent batch stability, effectively ensuring construction efficiency and bonding quality. Even under complex conditions such as humidity and large temperature fluctuations, the bonding interface with inorganic substrates such as hydroxyapatite, natural stone, and ceramics remains stable, without delamination or cracking. After long-term outdoor exposure to sun and rain, it shows no yellowing or powdering issues, and its mechanical properties do not significantly decrease, exhibiting outstanding weather resistance and bonding durability. In medical bone repair applications, its high compressive strength and suitable elongation at break adapt to the stress characteristics of bones, providing a firm and fitting fixation effect for repair materials. Overall application feedback indicates that this product effectively solves various pain points of traditional adhesives in inorganic substrate bonding, fully meeting the high-standard bonding needs of different fields such as high-end building materials, medical repair, and cultural relic protection.

[0065] The embodiments of the present invention are given for illustrative and descriptive purposes only, and are not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention, and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for a particular purpose.

Claims

1. A mussel-inspired composite adhesive, characterized in that, It consists of the following components in parts by weight: 88 parts of premixed mother liquor, 6 parts of silane coupling agent KH-5603-, and 4-8 parts of nano hydroxyapatite.

2. The mussel-inspired composite adhesive according to claim 1, characterized in that, The premixed mother liquor is composed of the following components in parts by weight: 40 parts of 3,4-dihydroxyphenylmethacrylamide, 25 parts of isooctyl acrylate, 30 parts of isobornyl methacrylate, 1-2 parts of composite photoinitiator, 0.5-1 parts of antioxidant, and 0.5-1 parts of ultraviolet absorber.

3. The mussel-inspired composite adhesive according to claim 2, characterized in that, The composite photoinitiator is a mixture of 2-hydroxy-2-methyl-1-phenyl-1-propanone and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide in a mass ratio of 1:

1.

4. The mussel-inspired composite adhesive according to claim 2, characterized in that, The antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; The ultraviolet absorber is 2-(2'-hydroxy-3',5'-di-tert-pentylphenyl)benzotriazole.

5. The mussel-inspired composite adhesive according to claim 1, characterized in that, The nano-hydroxyapatite has a particle size of 50-80 nm.

6. A premixed mother liquor for a mussel-inspired biomimetic composite adhesive, characterized in that, It is composed of the following components in parts by weight: 40 parts of 3,4-dihydroxyphenylmethacrylamide, 25 parts of isooctyl acrylate, 30 parts of isobornyl methacrylate, 1-2 parts of composite photoinitiator, 0.5-1 part of antioxidant, and 0.5-1 part of ultraviolet absorber.

7. A method for preparing the mussel-inspired biomimetic composite adhesive as described in any one of claims 1 to 5, characterized in that, Includes the following steps: (1) Preparation of premixed mother liquor: Under light-protected conditions, the formula amounts of 3,4-dihydroxyphenylmethacrylamide, isooctyl acrylate, isobornyl methacrylate, antioxidant and ultraviolet absorber are mixed and stirred, and the formula amount of composite photoinitiator is added and stirred to obtain premixed mother liquor; (2) Preparation of finished product: Take 88 parts by mass of the premixed mother liquor, add 6 parts by mass of silane coupling agent KH-5603- and 4-8 parts by mass of nano hydroxyapatite, first stir and disperse under normal pressure, then continue to stir and disperse under vacuum and degas to obtain the finished product.

8. The preparation method according to claim 7, characterized in that, The vacuum degree of the stirring and dispersion under vacuum conditions described in step (2) is -0.05MPa to -0.08MPa, and the stirring time is 10-15 minutes.

9. The preparation method according to claim 7 or 8, characterized in that, In step (2), the stirring and dispersion under normal pressure is carried out at a speed of 1200-1500 r / min for 10-15 minutes.

10. The preparation method according to claim 7, characterized in that, The mixing and stirring in step (1) is carried out at 30°C, and the total stirring time is 25-35 minutes.

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