High-transparency ultrathin flaky zinc stearate and preparation method thereof

Abstract

The invention provides high-transparency ultrathin flaky zinc stearate and a preparation method of the high-transparency ultrathin flaky zinc stearate. Comprising the following raw materials in parts by weight: 65-70 parts of double carbon chain stearic acid, 24-28 parts of nano zinc oxide, 150-180 parts of an ethanol-propylene glycol mixed solvent, 2.0-3.0 parts of a composite guiding agent, 1.0-1.5 parts of a transparent stabilizer, 0.2-0.4 part of a pH buffering agent and 0.8-1.0 part of colloidal silicon dioxide. The composite guiding agent is composed of oleamide and sodium stearyl fumarate according to the mass ratio of (1.8-2.2): 1.0, the double-carbon-chain stearic acid is composed of octadecane saturated fatty acid and hexadecane saturated fatty acid according to the mass ratio of (6.5-7.5): (2.8-3.2), and the transparent stabilizer is composed of triethyl citrate and polyvinylpyrrolidone K30 according to the mass volume ratio g / mL of (1.9-2.1): 1.0. Through the synergistic effect of the double-carbon-chain stearic acid, the composite guiding agent and the transparent stabilizer, the performance of zinc stearate is remarkably optimized, and finally an ultrathin flaky product with high transparency, low defect and thermal stability is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of zinc stearate and its preparation, and specifically relates to a highly transparent ultra-thin flaky zinc stearate and its preparation method. Background Art

[0002] Zinc stearate is a salt compound formed by the combination of stearic acid and zinc ions, and its chemical structure endows it with unique physical and chemical properties. Under normal temperature and pressure, zinc stearate usually exists in the form of white fine powder. This powder has good lubricity, dispersibility and thermal stability, making it widely used in many industrial fields. In the plastic industry, zinc stearate, as a lubricant and mold release agent, can effectively reduce the friction during the plastic processing, improve the surface finish of the products, and at the same time help the products to be demolded smoothly, improving the production efficiency. In the rubber industry, it is used as a vulcanization activator and softening agent, which can improve the processing performance and vulcanization effect of rubber and enhance the physical properties of rubber products. In addition, zinc stearate is also used in industries such as coatings, inks, and cosmetics as a thickener, anti-settling agent or stabilizer to improve the stability and performance of products. However, the powder form of zinc stearate also faces some challenges in applications. Due to its fine particles, it is easy to fly in the air, causing environmental pollution and the risk of inhalation by operators. At the same time, the powder has poor fluidity and may agglomerate during storage and transportation, affecting its uniform dispersion and use effect. Summary of the Invention

[0003] In view of this, the present invention proposes a highly transparent ultra-thin flaky zinc stearate and its preparation method to solve the above problems.

[0004] The technical solution of the present invention is realized as follows:

[0005] A highly transparent ultra-thin flaky zinc stearate, comprising the following raw materials in parts by weight: 65 - 70 parts of double carbon chain stearic acid, 24 - 28 parts of nano zinc oxide, 150 - 180 parts of ethanol - propylene glycol mixed solvent, 2.0 - 3.0 parts of composite guiding agent, 1.0 - 1.5 parts of transparent stabilizer, 0.2 - 0.4 parts of pH buffer, 0.8 - 1.0 parts of colloidal silica, and the composite guiding agent is composed of oleic acid amide and sodium stearyl fumarate with a mass ratio of (1.8 - 2.2):1.0.

[0006] Further, the double carbon chain stearic acid is composed of octadecane saturated fatty acid and hexadecane saturated fatty acid with a mass ratio of (6.5 - 7.5):(2.8 - 3.2).

[0007] Further, the particle size of the nano zinc oxide is 40 - 80 nm.

[0008] Further, the volume ratio of ethanol to propylene glycol in the ethanol-propylene glycol mixed solvent is (3.5 - 4.5):(0.9 - 1.1).

[0009] Further, the transparent stabilizer is composed of triethyl citrate and polyvinylpyrrolidone K30 with a mass-to-volume ratio of g / mL of (1.9 - 2.1):1.0.

[0010] Further, the pH buffer is composed of triethanolamine and sodium dihydrogen phosphate with a mass-to-volume ratio of g / mL of (1.8 - 2.2):1.0.

[0011] Further, a preparation method of highly transparent ultra-thin flaky zinc stearate includes the following steps:

[0012] S1. Melt the double-chain stearic acid and then place it into a molecular distillation device for molecular distillation. Collect the fraction with an acid value of 195 - 205 mg KOH / g to obtain the eutectic stearic acid fraction.

[0013] S2. Place the nano-zinc oxide into a fluidized bed and introduce nitrogen containing 0.8 - 1.2% KH550. React at 180 - 220 °C for 1.5 - 2.5 h to obtain activated nano-zinc oxide.

[0014] S3. Preheat the ethanol-propylene glycol mixed solvent. Under stirring conditions, add the eutectic stearic acid fraction and the composite guiding agent thereto for homogenization treatment. Then add 50% of the activated nano-zinc oxide at 49 - 51 °C, perform ultrasonic treatment for 40 - 50 min, synchronously add the transparent stabilizer dropwise at a dropping rate of 1.5 - 2.5 mL / min. Then add 30% of the activated nano-zinc oxide at 68 - 72 °C and stir magnetically for 50 - 70 min. Then add 20%, then add 20% of the activated nano-zinc oxide at 68 - 72 °C and stir magnetically for 25 - 35 min. Add the pH buffer and the transparent stabilizer, and cure at 59 - 61 °C for 75 - 105 min. Then add colloidal silica to obtain a reaction solution; Filter the reaction solution with a 0.1 - 0.2 μm fiber membrane and perform vacuum degassing treatment on the filtered reaction solution.

[0015] S4. Use a 0.1 M sodium hydroxide solution to ultrasonically clean an anodic aluminum oxide template with a pore size of 150 - 250 μm, then rinse it with deionized water until neutral, dry it and perform plasma treatment; Then inject the vacuum-degassed reaction solution into the treated anodic aluminum oxide template, and then keep the pressure at 10 - 15 MPa for 25 - 35 min to form a preformed sheet embryo.

[0016] S5. Dry the prefabricated sheet embryo at a temperature of 25 - 30 °C and a humidity of 70 - 80% for 5 - 7 h, and then dry it at a temperature of 35 - 40 °C and a humidity of 25 - 30% for 10 - 15 h to obtain a highly transparent ultra-thin flaky zinc stearate.

[0017] Further, in S1, the melting temperature is 75 - 85 °C, the molecular distillation temperature is 140 - 160 °C, and the distillation vacuum degree is 0.1 - 0.3 Pa.

[0018] Further, in S3, preheat to 63 - 68 °C, the stirring speed is 1500 - 2500 rpm, the homogenization treatment pressure is 150 - 200 MPa, the ultrasonic power during ultrasonic treatment is 180 - 220 W, the ultrasonic frequency is 30 - 50 kHz, the magnetic field strength during magnetic stirring is 0.4 - 0.6 T, the stirring speed is 40 - 60 rpm, the vacuum degassing vacuum degree is -0.08 to -0.10 MPa, and the vacuum degassing time is 8 - 12 min.

[0019] Further, in S4, the ultrasonic cleaning time is 10 - 15 min, the drying temperature is 110 - 130 °C, the drying time is 2 - 3 h, during ion treatment, use a mixed gas of argon and oxygen for plasma treatment at a power of 100 - 150 W for 4 - 6 min, and the volume ratio of argon to oxygen in the mixed gas of argon and oxygen is (3.5 - 4.5):1.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] The composite guiding agent in the present invention application forms micelles in the ethanol - propylene glycol mixed solvent, thereby coating and activating nano - zinc oxide, preventing its agglomeration, and making it evenly distributed. Oleic acid amide in the composite guiding agent can adsorb on the crystal plane of zinc stearate, inhibit the growth in the vertical direction, and promote the formation of a flaky structure, thereby regulating the crystal growth. Sodium stearyl fumarate in the composite guiding agent delays the crystal growth rate through the complexation of the carboxylate group with Zn 2+ to avoid grain coarsening caused by local supersaturation. The amide group of oleic acid amide forms hydrogen bonds with the carboxyl group of stearic acid, thereby increasing the solubility and reaction activity of stearic acid in the solvent, thereby increasing the reaction conversion rate, and thus reducing free acid. The oleic acid amide therein forms a monolayer on the surface of the zinc stearate sheet layer, thereby inhibiting the molecular chain movement at high temperature and enhancing the thermal stability.

[0022] In the transparent stabilizer of the present invention application, the three ester groups of triethyl citrate form a five - membered ring chelate with Zn 2+ through the lone pair electrons of oxygen atoms, effectively shielding Zn 2+Its catalytic activity inhibits side reactions and plays a role in chelating and passivating metal ions. Triethyl citrate can also adsorb on the crystal plane of zinc stearate crystals, induce self-repair of defect sites through intermolecular van der Waals forces, and reduce grain boundary light scattering. The transesterification of triethyl citrate can also react with stearic acid through transesterification, thereby converting free stearic acid into macromolecular esters and reducing the content of free acid. The amide group of polyvinylpyrrolidone K30 in the transparent stabilizer forms a hydrogen bond network with the carboxyl group of stearic acid, preventing free acid molecules from migrating to the surface and precipitating, and further reducing the content of free acid. In addition, the tertiary amine structure of polyvinylpyrrolidone K30 can capture free radicals generated by thermal decomposition and inhibit chain degradation reactions, thereby reducing the heating loss.

[0023] When the double carbon chain stearic acid of the present invention application is a eutectic mixture formed by mixing hexadecane saturated fatty acid and octadecane saturated fatty acid in a specific ratio, the viscosity of the system is reduced, thereby promoting the orderly arrangement of zinc stearate molecules and forming a eutectic system. In the eutectic system, the short chain of hexadecane saturated fatty acid inserts into the gap of the long chain of octadecane saturated fatty acid, weakening the intermolecular force in the vertical direction and inducing two-dimensional sheet growth. In addition, the eutectic structure can also hinder the escape of small molecules, thereby reducing the heating loss. The double carbon chain stearic acid acts together through the triple mechanisms of eutectic effect-chain length synergy-thermal stabilization, and is an indispensable core component for high-transparency and low-defect sheet products. Detailed implementation mode

[0024] To better understand the technical content of the present invention, specific examples are provided below to further illustrate the present invention.

[0025] The experimental methods used in the embodiments of the present invention are all conventional methods unless otherwise specified.

[0026] The materials, reagents, etc. used in the embodiments of the present invention can be obtained from commercial channels unless otherwise specified.

[0027] Example 1

[0028] A highly transparent ultra-thin flaky zinc stearate, comprising the following raw materials in parts by weight: 65 parts of double carbon chain stearic acid, 24 parts of nano zinc oxide, 150 parts of ethanol-propylene glycol mixed solvent, 2.0 parts of composite guiding agent, 1.0 part of transparent stabilizer, 0.2 part of pH buffer, and 0.8 part of colloidal silica. Among them, the composite guiding agent is composed of oleic acid amide and sodium stearyl fumarate with a mass ratio of 1.8:1.0, the double carbon chain stearic acid is composed of octadecane saturated fatty acid and hexadecane saturated fatty acid with a mass ratio of 6.5:2.8, the particle size of the nano zinc oxide is 40 nm, the volume ratio of ethanol to propylene glycol in the ethanol-propylene glycol mixed solvent is 3.5:0.9, the transparent stabilizer is composed of triethyl citrate and polyvinylpyrrolidone K30 with a mass-volume ratio (g / mL) of 1.9:1.0, and the pH buffer is composed of triethanolamine and sodium dihydrogen phosphate with a mass-volume ratio (g / mL) of 1.8:1.0.

[0029] Example 2

[0030] A highly transparent ultra-thin flaky zinc stearate, comprising the following raw materials in parts by weight: 70 parts of double carbon chain stearic acid, 28 parts of nano zinc oxide, 1180 parts of ethanol-propylene glycol mixed solvent, 3.0 parts of composite guiding agent, 1.5 parts of transparent stabilizer, 00.4 part of pH buffer, and 01.0 part of colloidal silica. Among them, the composite guiding agent is composed of oleic acid amide and sodium stearyl fumarate with a mass ratio of 2.2:1.0, the double carbon chain stearic acid is composed of octadecane saturated fatty acid and hexadecane saturated fatty acid with a mass ratio of 7.5:3.2, the particle size of the nano zinc oxide is 80 nm, the volume ratio of ethanol to propylene glycol in the ethanol-propylene glycol mixed solvent is 4.5:1.1, the transparent stabilizer is composed of triethyl citrate and polyvinylpyrrolidone K30 with a mass-volume ratio (g / mL) of 2.1:1.0, and the pH buffer is composed of triethanolamine and sodium dihydrogen phosphate with a mass-volume ratio (g / mL) of 2.2:1.0.

[0031] Example 3

[0032] A highly transparent ultra-thin flaky zinc stearate, comprising the following raw materials in parts by weight: 68 parts of double-chain stearic acid, 26 parts of nano-zinc oxide, 165 parts of ethanol-propylene glycol mixed solvent, 2.5 parts of composite guiding agent, 1.2 parts of transparent stabilizer, 0.3 parts of pH buffer, and 0.9 parts of colloidal silica. Among them, the composite guiding agent is composed of oleic acid amide and sodium stearyl fumarate with a mass ratio of 2.0:1.0, the double-chain stearic acid is composed of octadecane saturated fatty acid and hexadecane saturated fatty acid with a mass ratio of 7.0:3.0, the particle size of the nano-zinc oxide is 60 nm, the volume ratio of ethanol to propylene glycol in the ethanol-propylene glycol mixed solvent is 4.0:1.0, the transparent stabilizer is composed of triethyl citrate and polyvinylpyrrolidone K30 with a mass-volume ratio (g / mL) of 2.0:1.0, and the pH buffer is composed of triethanolamine and sodium dihydrogen phosphate with a mass-volume ratio (g / mL) of 2.0:1.0.

[0033] The highly transparent ultra-thin flaky zinc stearate described in the above Examples 1-3 is prepared by the following method, which specifically includes the following steps:

[0034] S1. Melt the double-chain stearic acid at 80 °C and then place it into a molecular distillation device. Perform molecular distillation under the conditions of a temperature of 150 °C and a distillation vacuum degree of 0.2 Pa, and collect the fraction with an acid value of 200 mg KOH / g to obtain the eutectic stearic acid fraction.

[0035] S2. Place the nano-zinc oxide into a fluidized bed and introduce nitrogen containing 1.0% KH550, and react at 200 °C for 2.0 h to obtain activated nano-zinc oxide.

[0036] S3. Preheat the ethanol-propylene glycol mixed solvent to 65 °C, add the eutectic stearic acid fraction and the composite guiding agent thereto under the stirring condition of 2000 rpm, perform homogenization treatment under a pressure of 175 MPa, then add 50% of the activated nano-zinc oxide at 50 °C, perform ultrasonic treatment for 45 min under the conditions of an ultrasonic power of 200 W and an ultrasonic frequency of 40 kHz, synchronously dropwise add the transparent stabilizer at a dropping rate of 2.0 mL / min, then add 30% of the activated nano-zinc oxide at 70 °C, perform magnetic stirring for 60 min under the conditions of a magnetic field intensity of 0.5 T and a stirring speed of 50 rpm, then add 20%, then add 20% of the activated nano-zinc oxide at 70 °C, perform magnetic stirring for 30 min under the conditions of a magnetic field intensity of 0.5 T and a stirring speed of 50 rpm, add the pH buffer and the transparent stabilizer, and cure at 60 °C for 90 min, then add colloidal silica to obtain a reaction solution; filter the reaction solution with a 0.1 μm fiber membrane, and perform vacuum defoaming treatment on the filtered reaction solution for 10 min, and the vacuum degree of vacuum defoaming is -0.09 MPa.

[0037] S4. Use a 0.1 M sodium hydroxide solution to ultrasonically clean an anodic aluminum oxide template with a pore size of 200 μm for 12 min, then rinse it with deionized water until neutral, dry it at 120 °C for 2.5 h and perform plasma treatment. Use a mixed gas of argon and oxygen for plasma treatment at a power of 125 W for 5 min, and the volume ratio of argon to oxygen in the mixed gas of argon and oxygen is 4.0:1. Then inject the reaction solution after vacuum degassing treatment into the treated anodic aluminum oxide template, and then keep the pressure at 12.5 MPa for 30 min to form a preform embryo.

[0038] S5. Dry the preform embryo at a temperature of 27.5 °C and a humidity of 75% for 6 h, and then dry it at a temperature of 37.5 °C and a humidity of 27.5% for 12.5 h to obtain a highly transparent ultra-thin flaky zinc stearate.

[0039] Example 4

[0040] Compared with Example 3, Example 4 is different in that a highly transparent ultra-thin flaky zinc stearate in Example 4 is prepared by the following method, which specifically includes the following steps:

[0041] S1. Melt the double-chain stearic acid at 75 °C and then place it into a molecular distillation device. Perform molecular distillation at a temperature of 140 °C and a distillation vacuum of 0.1 Pa, and collect the fraction with an acid value of 195 mg KOH / g to obtain a eutectic stearic acid fraction.

[0042] S2. Place the nano-zinc oxide into a fluidized bed and introduce nitrogen containing 0.8% KH550, and react at 180 °C for 2.5 h to obtain activated nano-zinc oxide.

[0043] S3. Preheat the ethanol-propylene glycol mixed solvent to 63 °C, add the eutectic stearic acid fraction and the composite guiding agent thereto under stirring at 1500 rpm, perform homogenization treatment under a pressure of 150 MPa, then add 50% of the activated nano-zinc oxide at 49 °C, perform ultrasonic treatment for 50 min under an ultrasonic power of 180 W and an ultrasonic frequency of 30 kHz, synchronously dropwise add the transparent stabilizer at a dropping rate of 1.5 mL / min, then add 30% of the activated nano-zinc oxide at 68 °C, perform magnetic stirring for 70 min under a magnetic field strength of 0.4 T and a stirring speed of 40 rpm, then add 20%, then add 20% of the activated nano-zinc oxide at 68 °C, perform magnetic stirring for 25 min under a magnetic field strength of 0.4 T and a stirring speed of 40 rpm, add a pH buffer and a transparent stabilizer, and cure at 59 °C for 105 min, then add colloidal silica to obtain a reaction solution; filter the reaction solution with a 0.1 μm fiber membrane and perform vacuum degassing treatment on the filtered reaction solution for 12 min, and the vacuum degree of vacuum degassing is -0.10 MPa.

[0044] S4. Use a 0.1 M sodium hydroxide solution to ultrasonically clean an anodic aluminum oxide template with a pore size of 150 μm for 10 min, then rinse it with deionized water until neutral, dry it at 110 °C for 3 h, and perform plasma treatment. Use a mixed gas of argon and oxygen to perform plasma treatment at a power of 100 W for 6 min, and the volume ratio of argon to oxygen in the mixed gas of argon and oxygen is 3.5:1. Then inject the reaction solution after vacuum degassing treatment into the treated anodic aluminum oxide template, and then maintain the pressure at 10 MPa for 35 min to form a preform.

[0045] S5. Dry the preform at a temperature of 25 °C and a humidity of 70% for 7 h, and then dry it at a temperature of 35 °C and a humidity of 25% for 15 h to obtain a highly transparent ultra-thin flaky zinc stearate.

[0046] Example 5

[0047] Compared with Example 3, Example 5 is different in that a highly transparent ultra-thin flaky zinc stearate in Example 5 is prepared by the following method, which specifically includes the following steps:

[0048] S1. Melt the double-chain stearic acid at 85 °C and then place it into a molecular distillation device. Perform molecular distillation at a temperature of 160 °C and a distillation vacuum of 0.5 Pa, and collect the fraction with an acid value of 205 mg KOH / g to obtain a eutectic stearic acid fraction.

[0049] S2. Place the nano-zinc oxide into a fluidized bed and introduce nitrogen containing 1.2% KH550, and react at 220 °C for 1.5 h to obtain activated nano-zinc oxide.

[0050] S3. Preheat the ethanol - propylene glycol mixed solvent to 68°C. Add the eutectic stearic acid fraction and the composite guiding agent thereto under the stirring condition of 2500 rpm, and conduct homogenization treatment under a pressure of 200 MPa. Subsequently, add 50% activated nano - zinc oxide under the condition of 51°C, and perform ultrasonic treatment for 40 min under the conditions of an ultrasonic power of 220 W and an ultrasonic frequency of 50 kHz. Synchronously drop - add the transparent stabilizer at a dropping rate of 2.5 mL / min. Subsequently, add 30% activated nano - zinc oxide at 72°C, and perform magnetic stirring for 50 min under the conditions of a magnetic field strength of 0.6 T and a stirring speed of 60 rpm. Subsequently, add 20%, and then add 20% activated nano - zinc oxide at 72°C, and perform magnetic stirring for 25 min under the conditions of a magnetic field strength of 0.6 T and a stirring speed of 60 rpm. Add the pH buffer and the transparent stabilizer, and cure at 61°C for 75 min. Subsequently, add colloidal silica to obtain the reaction solution; filter the reaction solution with a 0.2 - μm fiber membrane, and perform vacuum degassing treatment on the filtered reaction solution for 8 min, and the vacuum degree of vacuum degassing is - 0.10 MPa.

[0051] S4. Use a 0.1 M sodium hydroxide solution to ultrasonically clean the anodic aluminum oxide template with a pore size of 250 μm for 15 min, then rinse it with deionized water until neutral, dry it at 130°C for 2 h and perform plasma treatment. Use a mixed gas of argon and oxygen to perform plasma treatment at a power of 100 W for 4 min, and the volume ratio of argon to oxygen in the mixed gas of argon and oxygen is 4.5:1. Subsequently, inject the reaction solution after vacuum degassing treatment into the treated anodic aluminum oxide template, and then keep the pressure at 15 MPa for 25 min to form a pre - fabricated sheet embryo.

[0052] S5. Dry the pre - fabricated sheet embryo at a temperature of 30°C and a humidity of 80% for 5 h, and then dry it at a temperature of 40°C and a humidity of 30% for 10 h to obtain a highly transparent ultra - thin sheet - shaped zinc stearate.

[0053] Comparative Example 1

[0054] This comparative example is compared with Example 3. The difference is that the raw materials do not contain the composite guiding agent.

[0055] Comparative Example 2

[0056] This comparative example is compared with Example 3. The difference is that the composite guiding agent is only oleic acid amide.

[0057] Comparative Example 3

[0058] This comparative example is compared with Example 3. The difference is that the raw materials do not contain the transparent stabilizer.

[0059] Comparative Example 4

[0060] This comparative example is compared with Example 3. The difference is that a single saturated fatty acid with 18 carbon atoms is used instead of double-chain stearic acid.

[0061] Comparative Example 5

[0062] This comparative example is compared with Example 3. The difference is that during the preparation of highly transparent ultra-thin flake zinc stearate, ultrasonic treatment is not performed in step S3.

[0063] Comparative Example 6

[0064] This comparative example is compared with Example 3. The difference is that the zinc stearate in this comparative example is commercially available ultra-thin flake zinc stearate.

[0065] Light transmittance detection

[0066] Referring to the standard of GB / T 2410-2008 "Determination of Light Transmittance and Haze of Transparent Plastics", the light transmittance of the ultra-thin flake zinc stearate of Examples 1-5 and Comparative Examples 1-6 was detected using a UV-visible spectrophotometer. Each was detected 5 times, and the average value was recorded in Table 1.

[0067] Performance detection

[0068] Referring to the technical requirements and corresponding test methods of type I zinc stearate in the standard of HG / T3667-2012 "Zinc Stearate", the zinc content, free acid, and heating loss were detected. The ultra-thin flake zinc stearate of Examples 1-5 and Comparative Examples 1-6 was detected respectively. Each was detected 5 times, and the average value was recorded in Table 1.

[0069] Table 1

[0070]

[0071]

[0072] As can be seen from Table 1, the ultra-thin flake zinc stearate prepared in Examples 1-5 has the advantages of high transparency, high zinc content, low free acid, and low heating loss. Among them, Example 3 has better effects.

[0073] By comparing Example 3 with Comparative Examples 1-2, the composite guiding agent in Example 3 forms micelles in the ethanol-propylene glycol mixed solvent, thereby coating and activating the nano-zinc oxide, preventing its agglomeration, and making it evenly distributed. Oleic acid amide in the composite guiding agent can adsorb on the crystal plane of zinc stearate, inhibit the growth in the vertical direction, and promote the formation of flake structure, thereby regulating the growth of crystals. This directional growth reduces grain boundaries and lattice defects, thereby reducing light scattering. Sodium stearyl fumarate in the composite guiding agent binds to Zn through the carboxylate group 2+The complexing effect delays the crystal growth rate and avoids grain coarsening caused by local supersaturation. Through the combined action of oleic acid amide and sodium stearyl fumarate, the prepared zinc stearate has a high light transmittance. The amide group of oleic acid amide forms a hydrogen bond with the carboxylic acid group of stearic acid, thereby increasing the solubility and reaction activity of stearic acid in the solvent, thus increasing the reaction conversion rate and reducing the free acid. The oleic acid amide therein forms a monolayer on the surface of the zinc stearate lamella, thereby inhibiting the molecular chain movement at high temperature and enhancing the thermal stability, so the heating loss is reduced. Therefore, the composite guiding agent realizes the synergistic effects of improving light transmittance, reducing free acid and optimizing heating loss through the trinity of crystal engineering - interface regulation - thermal stabilization. The absence of sodium stearyl fumarate will lead to 2+ a decrease in the complexing ability, resulting in incomplete local reactions. In addition, without the hydrogen bond network of the carboxylate group of sodium stearyl fumarate and stearic acid, free acid is more likely to precipitate. The introduction of sodium stearyl fumarate makes up for the deficiencies of oleic acid amide in 2+ complexing and thermal stability, and neither of them can be absent.

[0074] By comparing Example 3 with Comparative Example 3, the three ester groups of triethyl citrate in the transparent stabilizer of Example 3 form a five-membered ring chelate with Zn 2+ through the lone pair electrons of oxygen atoms, effectively shielding the catalytic activity of Zn 2+ and inhibiting side reactions, playing the role of chelating and passivating metal ions. Triethyl citrate can also adsorb on the crystal plane of zinc stearate crystals, inducing self-repair of defect sites through intermolecular van der Waals forces and reducing light scattering at grain boundaries. The transesterification of triethyl citrate can also react with stearic acid through transesterification, thereby converting free stearic acid into macromolecular esters and reducing the free acid content. The amide group of polyvinylpyrrolidone K30 in the transparent stabilizer forms a hydrogen bond network with the carboxylic acid group of stearic acid, preventing free acid molecules from migrating to the surface and precipitating, and further reducing the free acid content. In addition, the tertiary amine structure of polyvinylpyrrolidone K30 can capture free radicals generated by thermal decomposition and inhibit chain degradation reactions, thus reducing the heating loss. Therefore, the transparent stabilizer synergistically acts through the triple mechanisms of chelation - repair - immobilization to precisely regulate the crystal growth environment at the molecular level, thereby obtaining high-transparency and low-defect zinc stearate flake products.

[0075] By comparing Example 3 with Comparative Example 4, when the double-chain stearic acid in Example 3 is a eutectic mixture formed by mixing saturated fatty acids with 16 carbon atoms and saturated fatty acids with 18 carbon atoms in a specific ratio, the viscosity of the system is reduced, thereby promoting the orderly arrangement of zinc stearate molecules and forming a eutectic system. In the eutectic system, the short chains of saturated fatty acids with 16 carbon atoms are inserted into the gaps between the long chains of saturated fatty acids with 18 carbon atoms, weakening the intermolecular forces in the vertical direction and inducing two-dimensional sheet growth. In addition, the eutectic structure can also prevent small molecules from escaping, thereby reducing the loss on heating. The double-chain stearic acid acts through the combined action of the eutectic effect-chain length synergy-thermal stabilization triple mechanism and is an essential core component for high-transparency and low-defect sheet products. Single saturated fatty acids with 18 carbon atoms cannot form a eutectic mixture, and the melt viscosity is high, resulting in disordered arrangement of zinc stearate molecules and reduced crystal plane orientation degree. Moreover, the long-chain molecules of saturated fatty acids with 18 carbon atoms are closely arranged, which may hinder the diffusion of Zn 2+ to the carboxylic acid group, resulting in incomplete local reactions. Therefore, compared with single saturated fatty acids with 18 carbon atoms, the double-chain stearic acid has a better effect.

[0076] By comparing Example 3 with Comparative Example 5, in Example 3, through ultrasonic treatment, the cavitation bubbles generated by ultrasound release local high temperature and high pressure instantaneously during collapse, forming strong microjets and shear forces, effectively breaking and activating the nano-zinc oxide aggregates and reducing scattering. In addition, the mechanical vibration of ultrasound induces the orientation of zinc stearate molecules along the crystal plane, reducing the grain boundary density. Moreover, ultrasound can also promote the uniform mixing of reactants, forming a dense and uniform crystal structure. In addition, the microjets generated by ultrasonic cavitation accelerate the mass transfer of Zn 2+ and stearic acid, thereby improving the conversion rate. The local high temperature generated by the ultrasonic cavitation effect can also promote the deprotonation of the carboxylic acid groups of stearic acid molecules, reducing the reaction activation energy. In addition, the locally high temperature induced by ultrasound promotes lattice reorganization. Through the triple mechanism of cavitation effect-micro-mixing enhancement-crystal reconstruction, ultrasonic treatment significantly improves the light transmittance of zinc stearate, reduces the free acid, and reduces the loss on heating.

[0077] By comparing Examples 1-5 with Comparative Example 6, it can be seen that the ultra-thin sheet zinc stearate prepared in this invention application has higher transparency, lower free acid content, and lower loss on heating compared with commercially available products. It can be seen that the ultra-thin sheet zinc stearate prepared in this invention application has comprehensive performance advantages.

[0078] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A highly transparent ultra-thin flaky zinc stearate, characterized in that, It includes the following raw materials in parts by weight: 65 - 70 parts of double carbon chain stearic acid, 24 - 28 parts of nano zinc oxide, 150 - 180 parts of ethanol - propylene glycol mixed solvent, 2.0 - 3.0 parts of composite guiding agent, 1.0 - 1.5 parts of transparent stabilizer, 0.2 - 0.4 parts of pH buffer, 0.8 - 1.0 parts of colloidal silica. The composite guiding agent is composed of oleic acid amide and sodium stearyl fumarate with a mass ratio of (1.8 - 2.2):1.

0.

2. The zinc stearate in the form of a highly transparent and ultra-thin sheet as described in claim 1, wherein The double carbon chain stearic acid is composed of octadecanoic saturated fatty acid and hexadecanoic saturated fatty acid with a mass ratio of (6.5 - 7.5):(2.8 - 3.2).

3. A highly transparent and ultra-thin flaky zinc stearate as described in claim 1, characterized in that, The particle size of the nano zinc oxide is 40 - 80 nm.

4. A highly transparent and ultra-thin flaky zinc stearate according to claim 1, characterized in that, In the ethanol - propylene glycol mixed solvent, the volume ratio of ethanol to propylene glycol is (3.5 - 4.5):(0.9 - 1.1).

5. A highly transparent and ultra-thin flaky zinc stearate as claimed in claim 1, wherein, The transparent stabilizer is composed of triethyl citrate and polyvinylpyrrolidone K30 with a mass - to - volume ratio of g / mL of (1.9 - 2.1):1.

0.

6. The zinc stearate in the form of a highly transparent ultra-thin sheet as described in claim 1, wherein, The pH buffer is composed of triethanolamine and sodium dihydrogen phosphate with a mass - to - volume ratio of g / mL of (1.8 - 2.2):1.

0.

7. The preparation method of a highly transparent and ultra-thin flaky zinc stearate according to any one of claims 1-6, characterized in that, It includes the following steps: S1. Melt the double carbon chain stearic acid and then place it into a molecular distillation device for molecular distillation. Collect the fraction with an acid value of 195 - 205 mg KOH / g to obtain a eutectic stearic acid fraction. S2. Place the nano zinc oxide into a fluidized bed and introduce nitrogen containing 0.8 - 1.2% KH550. React at 180 - 220 °C for 1.5 - 2.5 h to obtain activated nano zinc oxide. S3. Preheat the ethanol - propylene glycol mixed solvent. Under stirring conditions, add the eutectic stearic acid fraction and the composite guiding agent to it for homogenization treatment. Then add 50% of the activated nano zinc oxide at 49 - 51 °C, perform ultrasonic treatment for 40 - 50 min, synchronously drop the transparent stabilizer at a dropping rate of 1.5 - 2.5 mL / min. Then add 30% of the activated nano zinc oxide at 68 - 72 °C and stir magnetically for 50 - 70 min. Then add 20%, then add 20% of the activated nano zinc oxide at 68 - 72 °C and stir magnetically for 25 - 35 min. Add the pH buffer and the transparent stabilizer, cure at 59 - 61 °C for 75 - 105 min, and then add colloidal silica to obtain a reaction solution. Filter the reaction solution with a 0.1 - 0.2 μm fiber membrane and perform vacuum degassing treatment on the filtered reaction solution. S4. Use a 0.1 M sodium hydroxide solution to ultrasonically clean anodic aluminum oxide templates with a pore size of 150 - 250 μm, then rinse with deionized water until neutral, dry and perform plasma treatment. Then inject the reaction solution after vacuum degassing treatment into the treated anodic aluminum oxide template, and then keep the pressure at 10 - 15 MPa for 25 - 35 min to form a prefabricated sheet embryo. S5. Dry the prefabricated sheet embryo at a temperature of 25 - 30°C and a humidity of 70 - 80% for 5 - 7 h, and then dry it at a temperature of 35 - 40°C and a humidity of 25 - 30% for 10 - 15 h to obtain a highly transparent ultra-thin sheet-like zinc stearate.

8. The preparation method of a highly transparent ultra-thin flaky zinc stearate according to claim 7, characterized in that, In the S1, the melting temperature is 75 - 85°C, the molecular distillation temperature is 140 - 160°C, and the distillation vacuum degree is 0.1 - 0.3 Pa.

9. The preparation method of a highly transparent and ultra-thin flaky zinc stearate according to claim 7, characterized in that, In the S3, preheat to 63 - 68°C, the stirring speed is 1500 - 2500 rpm, the homogenization treatment pressure is 150 - 200 MPa, the ultrasonic power during ultrasonic treatment is 180 - 220 W, the ultrasonic frequency is 30 - 50 kHz, the magnetic field strength during magnetic stirring is 0.4 - 0.6 T, the stirring speed is 40 - 60 rpm, the vacuum degree for vacuum degassing is -0.08 to -0.10 MPa, and the vacuum degassing time is 8 - 12 min.

10. The preparation method of a highly transparent and ultrathin flaky zinc stearate according to claim 7, characterized in that, In the S4, the ultrasonic cleaning time is 10 - 15 min, the drying temperature is 110 - 130°C, the drying time is 2 - 3 h, during ion treatment, use a mixed gas of argon and oxygen for plasma treatment at a power of 100 - 150 W for 4 - 6 min, and the volume ratio of argon to oxygen in the mixed gas of argon and oxygen is (3.5 - 4.5):1.

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