A calcium stearate emulsion and its preparation method and application

Abstract

The invention relates to the technical field of calcium stearate, and specifically discloses a calcium stearate emulsion, a preparation method thereof, and an application thereof. The invention comprises the following steps: heating stearic acid to a molten state, adding calcium hydroxide, stirring and mixing, then adding deionized water, a silica-based composite emulsifier, a defoaming agent, and a dispersant, stirring and mixing, and cooling to obtain a calcium stearate emulsion. The emulsion adopts water as a dispersion medium to prepare the emulsion, and is environmentally friendly. The silica-based composite emulsifier used in the emulsion has a stable structure and is amphiphilic. The hydrophobic portion can interact with calcium stearate particles, while the hydrophilic portion contacts the water phase, thereby forming a stable adsorption layer at the emulsion interface, which plays a role in emulsifying and stabilizing the emulsion. The prepared calcium stearate emulsion has excellent dispersibility and a stable emulsion morphology, and can be used as an auxiliary agent in rubber processing to improve the fluidity and processing performance of rubber, and enhance the physical properties and quality stability of rubber products.

Description

Technical Field

[0001] The present invention relates to the technical field of calcium stearate, in particular to a calcium stearate emulsion and a preparation method and application thereof. Background Art

[0002] Calcium stearate is a metallic soap compound formed by the coordination bond between stearic acid and calcium ions. Its molecular structure, characterized by amphiphilic properties, consists of a long hydrophobic carbon chain and a hydrophilic calcium ion end, giving it excellent lubricity, dispersibility, and thermal stability. However, calcium stearate itself is a water-insoluble metallic soap surfactant (HLB value approximately 5-8). Direct use of calcium stearate solid powder in polymer matrices such as rubber and plastics can lead to interfacial defects due to uneven dispersion. Furthermore, the powder can create dust, threatening production safety.

[0003] In industrial production, calcium stearate is commonly converted into a stable emulsion system with controllable particle size through water-based emulsification technology, thereby achieving hydrophilic modification of hydrophobic materials. Due to its water-based nature, low toxicity, and strong processing adaptability, calcium stearate emulsions are gradually replacing traditional powdered products as the mainstream form, with significant growth in demand in the rubber processing sector. In particular, in the production of rubber products such as tires, seals, rubber hoses, and conveyor belts, calcium stearate emulsions can serve as plasticizers, lubricants, dispersants, and fillers, improving the processing and physical and mechanical properties of rubber products, preventing rubber agglomeration, and extending the life of rubber products.

[0004] Chinese patent application CN118359848A discloses a method for preparing a calcium stearate emulsion, comprising the following steps: S1, dispersing stearic acid in water to form a first dispersion system; S2, adding calcium oxide to water to react and form a second dispersion system; S3, adding the second dispersion system to the first dispersion system in multiple batches, and adding a light stabilizer to the emulsion after the reaction is completed. The addition of the light stabilizer to the calcium stearate emulsion improves the light stability and extends its service life, but the particle size in the emulsion is large and the dispersion uniformity is poor. Chinese patent application CN109778592A discloses a water-soluble calcium stearate emulsion and its application. The emulsion uses a polyoxyethylene ether and sodium sulfonate compound, which has excellent emulsification, can enhance the dispersion of calcium stearate in water, increase the solid content, reduce the viscosity, and has good dispersibility, but the emulsion has poor thermal stability.

[0005] Therefore, it is of great significance to provide a calcium stearate emulsion with excellent dispersibility and stability by optimizing the emulsifier system, improving the dispersion process and enhancing functionality. Summary of the Invention

[0006] (1) Technical problems solved

[0007] In view of the deficiencies in the prior art, the present invention provides a calcium stearate emulsion and a preparation method and application thereof, which solve the problems of poor stability and poor dispersibility of calcium stearate emulsion and provide a calcium stearate emulsion with excellent thermal stability.

[0008] (2) Technical solution

[0009] In order to achieve the above object, the present invention discloses a method for preparing a calcium stearate emulsion, comprising the following steps:

[0010] Step 1: Ultrasonic dispersion of nano-silica in an ethanol solution, uniform dispersion, and then adding γ-methacryloxypropyltrimethoxysilane, adjusting the pH to 4 with a hydrochloric acid solution, stirring and mixing, and reacting. After the reaction is completed, the solution is filtered, washed with anhydrous ethanol and deionized water, and vacuum dried at 60° C. for 12 hours to obtain modified silica;

[0011] Step 2: ultrasonically disperse the modified silica in N,N-dimethylformamide. After uniform dispersion, add butylated β-cyclodextrin, acrylic acid, 2-hydroxyethyl acrylate, maleic anhydride, polyethylene glycol and an initiator, stir and mix, and react. After the reaction is completed, cool, filter, wash with anhydrous ethanol, and dry at 60° C. for 6 hours to obtain a silica-based composite emulsifier;

[0012] Step 3: Heat stearic acid to a molten state, add calcium hydroxide, stir and mix, react, add deionized water after the reaction is completed, heat, add a silica-based composite emulsifier, a defoamer, and a dispersant, adjust the pH value to 8, stir and mix, mix evenly, and slowly cool to obtain a calcium stearate emulsion.

[0013] Preferably, the ethanol solution in step 1 is a 75% wt ethanol aqueous solution.

[0014] Preferably, in the step 1, the mass ratio of nano-silica, ethanol solution, and γ-methacryloxypropyltrimethoxysilane is 100:(3800-4500):(18-30).

[0015] Preferably, the reaction temperature in step 1 is 70-80° C., and the reaction time is 5-8 h.

[0016] Preferably, in the step 2, the mass ratio of modified silica, N,N-dimethylformamide, butylated acid monoesterified-β-cyclodextrin, acrylic acid, 2-hydroxyethyl acrylate, maleic anhydride, polyethylene glycol and initiator is (9-16):(750-950):(5-8):100:(35-48):(12-20):(7-10):(1-2).

[0017] The maleic acid monoesterified-β-cyclodextrin in step 2 is prepared according to the preparation method of maleic acid monoesterified-β-cyclodextrin in “Chen Pengfei, Song Hang, Li Fulin, Tang Mengyu, Zhou Lu, Preparation and performance study of magnetic nanoparticles modified with maleic acid monoesterified-β-cyclodextrin”.

[0018] Preferably, the reaction temperature in step 2 is 65-75° C., and the reaction time is 6-8 h.

[0019] Preferably, the initiator in step 2 is selected from any one of ammonium persulfate, potassium persulfate, and benzoyl peroxide.

[0020] Preferably, in step 3, the stearic acid is heated to 70-80° C. to melt.

[0021] Preferably, in step 3, the mass ratio of stearic acid, calcium hydroxide, deionized water, silica-based composite emulsifier, defoaming agent, and dispersant is (300-320):100:(2100-2400):(95-120):(0.5-1):(1-3).

[0022] Preferably, the reaction time in step 3 is 1.5-3 h, and the stirring speed during the reaction is 350-450 r / min.

[0023] Preferably, the temperature after heating in step 3 is 80-90° C., the stirring and mixing time is 1-2 h, and the stirring and mixing rate is 1800-2400 r / min.

[0024] Preferably, the defoaming agent in step three is a water-soluble silane defoaming agent.

[0025] Furthermore, the defoaming agent is polydimethylsiloxane.

[0026] The dispersant in step 3 includes any one of alkylphenol polyoxyethylene ether, lauryl alcohol polyoxyethylene ether, and sodium polyacrylate.

[0027] Preferably, the calcium stearate emulsion is prepared by the preparation method of the calcium stearate emulsion.

[0028] Preferably, the calcium stearate emulsion is used in rubber.

[0029] (3) Beneficial technical effects

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) In the present invention, γ-methacryloxypropyltrimethoxysilane is used to modify nano-silica, and alkenyl groups are introduced on the surface of the nano-silica to obtain modified silica. Modified silica, butenedioic acid monoesterified-β-cyclodextrin, acrylic acid, 2-hydroxyethyl acrylic acid, maleic anhydride, and polyethylene glycol are reacted with an initiator to generate free radicals, which trigger the monomers to undergo free radical polymerization to obtain a silica-based composite emulsifier. A large number of active groups are introduced during the reaction. Stearic acid is heated to a molten state and reacts with calcium hydroxide to produce calcium stearate. The silica-based composite emulsifier is used as an emulsifier, and a defoamer and a dispersant are added. The mixture is stirred and mixed in a deionized water solvent. After mixing evenly, the mixture is slowly cooled to obtain a calcium stearate emulsion.

[0032] (2) The modification of nano-silica in the present invention can effectively avoid the agglomeration of nano-silica and can utilize its steric hindrance effect to prevent particle aggregation. The cavity structure of monoesterified β-cyclodextrin with butenedioic acid has excellent inclusion properties, and the surface contains active groups, which can effectively enhance the interaction between the emulsifier and calcium stearate and other components, and improve the stability and dispersibility of the emulsion. Acrylic acid and its ester monomers in the composite emulsifier have a good balance of hydrophilicity and lipophilicity, which helps to disperse and stabilize the emulsifier in stearic acid and water. Maleic anhydride can further enhance the reactivity and cross-linking ability of the emulsifier, forming an emulsifier molecule with a hydrophilic-lipophilic balance. Polyethylene glycol can enhance the flexibility and stability of the emulsifier molecule through its long chain structure, thereby improving the fluidity and wettability of the emulsion and promoting the dispersion performance of other components.

[0033] (3) The silica-based composite emulsifier prepared in the present invention has a stable structure and is amphiphilic, containing both hydrophilic and hydrophobic segments. The hydrophobic portion can interact with the calcium stearate particles, while the hydrophilic portion contacts the aqueous phase, thereby forming a stable adsorption layer at the emulsion interface, which plays a role in emulsifying and stabilizing the emulsion. The emulsifier can be evenly dispersed in the emulsion, and further, it also helps the calcium stearate particles to be evenly dispersed in the aqueous phase, forming a stable interfacial film in the calcium stearate emulsion system, and preventing the aggregation and sedimentation of the emulsion particles. The modified silica, as an inorganic skeleton, can retard the thermal motion of the polymer chain, and the anhydride group of maleic anhydride forms a coordination bond with calcium stearate to enhance thermal stability. The inorganic-organic composite emulsification system can effectively enhance the heat resistance and mechanical strength of the emulsion. The composite emulsifier contains a large number of active functional groups, which can interact with the calcium stearate particles and the aqueous phase, adsorb on the surface of the calcium stearate particles, form a charged layer or a spatial steric hindrance layer, reduce the mutual attraction between the particles, and prevent the particles from agglomerating, so that the emulsion has good dispersibility, ensure the uniform particle size of the calcium stearate particles in the emulsion, improve the adhesion and adhesion of the emulsion, improve the product quality, and make the emulsion less likely to stratify and demulsify during storage and use. The various components in the composite emulsifier work synergistically to reduce interfacial tension, improve the stability of the emulsion, and improve the stability of the emulsion.

[0034] (4) The present invention uses water as a dispersion medium to prepare the emulsion, which reduces the use of organic solvents, is environmentally friendly, and meets environmental protection requirements. The prepared calcium stearate emulsion has a stable emulsion morphology and contains active groups. When applied to rubber, it can be evenly dispersed in the rubber matrix and used as a lubricant, release agent, and stabilizer in rubber processing. It reduces the friction between rubber molecules, improves the fluidity and processing performance of rubber, improves the surface finish and demoulding efficiency of rubber products, and improves the physical properties and quality stability of rubber products. DETAILED DESCRIPTION

[0035] To facilitate understanding of the present invention, the present invention will be described in more detail below. Preferred embodiments of the present invention are provided below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure of the present invention.

[0036] Example 1

[0037] A method for preparing a calcium stearate emulsion comprises the following steps:

[0038] (1) Ultrasonic dispersion of nano-silica in a 75% wt ethanol aqueous solution was performed, and after uniform dispersion, γ-methacryloxypropyltrimethoxysilane was added, wherein the mass ratio of nano-silica, ethanol solution, and γ-methacryloxypropyltrimethoxysilane was 100:3800:18, and the pH was adjusted to 4 using a hydrochloric acid solution. The mixture was stirred and reacted at a temperature of 70° C. and a reaction time of 8 h. After the reaction was completed, the mixture was filtered, washed with anhydrous ethanol and deionized water, and vacuum dried at 60° C. for 12 h to obtain modified silica;

[0039] (2) ultrasonically dispersing the modified silica into N,N-dimethylformamide, and after uniform dispersion, adding butenedioic acid monoesterified-β-cyclodextrin, acrylic acid, 2-hydroxyethyl acrylic acid, maleic anhydride, polyethylene glycol and initiator ammonium persulfate, wherein the mass ratio of the modified silica, N,N-dimethylformamide, butenedioic acid monoesterified-β-cyclodextrin, acrylic acid, 2-hydroxyethyl acrylic acid, maleic anhydride, polyethylene glycol and initiator ammonium persulfate is 9:750:5:100:35:12:7:1, stirring and mixing, reacting, the reaction temperature is 65°C, the reaction time is 8h, and after the reaction is completed, cooling, filtering, washing with anhydrous ethanol, and drying at 60°C for 6h to obtain a silica-based composite emulsifier;

[0040] (3) Stearic acid was heated to a molten state at 70°C, calcium hydroxide was added and stirred at a speed of 350 r / min, and a reaction took place for 1.5 h. After the reaction was completed, deionized water was added, the temperature was raised to 80°C, and a silica-based composite emulsifier, a defoaming agent polydimethylsiloxane, and a dispersant sodium polyacrylate were added, wherein the mass ratio of stearic acid, calcium hydroxide, deionized water, silica-based composite emulsifier, defoaming agent polydimethylsiloxane, and dispersant sodium polyacrylate was 300:100:2100:95:0.5:1, the pH value was adjusted to 8, the mixture was stirred for 1 h, and the stirring rate was 1800 r / min. After mixing evenly, the mixture was slowly cooled to obtain a calcium stearate emulsion.

[0041] Example 2

[0042] A method for preparing a calcium stearate emulsion comprises the following steps:

[0043] (1) Ultrasonic dispersion of nano-silica in a 75% wt ethanol aqueous solution, uniform dispersion, and then adding γ-methacryloxypropyltrimethoxysilane, the mass ratio of nano-silica, ethanol solution, and γ-methacryloxypropyltrimethoxysilane being 100:4200:25, adjusting the pH to 4 with hydrochloric acid solution, stirring and mixing, reacting at a temperature of 75° C. and a reaction time of 6 h. After the reaction is completed, the mixture is filtered, washed with anhydrous ethanol and deionized water, and vacuum dried at 60° C. for 12 h to obtain modified silica;

[0044] (2) ultrasonically dispersing the modified silica into N,N-dimethylformamide, and after uniform dispersion, adding butenedioic acid monoesterified-β-cyclodextrin, acrylic acid, 2-hydroxyethyl acrylic acid, maleic anhydride, polyethylene glycol and initiator ammonium persulfate, wherein the mass ratio of the modified silica, N,N-dimethylformamide, butenedioic acid monoesterified-β-cyclodextrin, acrylic acid, 2-hydroxyethyl acrylic acid, maleic anhydride, polyethylene glycol and initiator ammonium persulfate is 12:850:6:100:40:15:8:1.5, stirring and mixing, reacting, the reaction temperature is 70°C, the reaction time is 7h, and after the reaction is completed, cooling, filtering, washing with anhydrous ethanol, and drying at 60°C for 6h to obtain a silica-based composite emulsifier;

[0045] (3) Stearic acid was heated to a molten state at 75°C, calcium hydroxide was added and stirred at a speed of 400 r / min, and a reaction took place for 2 h. After the reaction was completed, deionized water was added, the temperature was raised to 85°C, and a silica-based composite emulsifier, a defoaming agent polydimethylsiloxane, and a dispersant sodium polyacrylate were added, wherein the mass ratio of stearic acid, calcium hydroxide, deionized water, silica-based composite emulsifier, defoaming agent polydimethylsiloxane, and dispersant sodium polyacrylate was 310:100:2200:100:0.6:1.5, the pH value was adjusted to 8, and the mixture was stirred for 1.5 h at a speed of 2000 r / min. After mixing evenly, the mixture was slowly cooled to obtain a calcium stearate emulsion.

[0046] Example 3

[0047] A method for preparing a calcium stearate emulsion comprises the following steps:

[0048] (1) Ultrasonic dispersion of nano-silica in a 75% wt ethanol aqueous solution, uniform dispersion, and then adding γ-methacryloxypropyltrimethoxysilane, the mass ratio of nano-silica, ethanol solution, and γ-methacryloxypropyltrimethoxysilane being 100:4200:25, adjusting the pH to 4 with hydrochloric acid solution, stirring and mixing, reacting at a temperature of 75° C. and a reaction time of 6 h. After the reaction is completed, the mixture is filtered, washed with anhydrous ethanol and deionized water, and vacuum dried at 60° C. for 12 h to obtain modified silica;

[0049] (2) ultrasonically dispersing the modified silica into N,N-dimethylformamide, and after uniform dispersion, adding butenedioic acid monoesterified-β-cyclodextrin, acrylic acid, 2-hydroxyethyl acrylic acid, maleic anhydride, polyethylene glycol and initiator ammonium persulfate, wherein the mass ratio of the modified silica, N,N-dimethylformamide, butenedioic acid monoesterified-β-cyclodextrin, acrylic acid, 2-hydroxyethyl acrylic acid, maleic anhydride, polyethylene glycol and initiator ammonium persulfate is 15:850:7:100:45:18:9:1.8, stirring and mixing, reacting, the reaction temperature is 70°C, the reaction time is 7h, and after the reaction is completed, cooling, filtering, washing with anhydrous ethanol, and drying at 60°C for 6h to obtain a silica-based composite emulsifier;

[0050] (3) Stearic acid was heated to a molten state at 75°C, calcium hydroxide was added and stirred at a speed of 400 r / min, and a reaction took place for 2 h. After the reaction was completed, deionized water was added, the temperature was raised to 85°C, and a silica-based composite emulsifier, a defoaming agent polydimethylsiloxane, and a dispersant sodium polyacrylate were added, wherein the mass ratio of stearic acid, calcium hydroxide, deionized water, silica-based composite emulsifier, defoaming agent polydimethylsiloxane, and dispersant sodium polyacrylate was 310:100:2200:112:0.6:1.5, the pH value was adjusted to 8, and the mixture was stirred for 1.5 h at a speed of 2000 r / min. After mixing evenly, the mixture was slowly cooled to obtain a calcium stearate emulsion.

[0051] Example 4

[0052] A method for preparing a calcium stearate emulsion comprises the following steps:

[0053] (1) Ultrasonic dispersion of nano-silica in a 75% wt ethanol aqueous solution, uniform dispersion, and then adding γ-methacryloxypropyltrimethoxysilane, the mass ratio of nano-silica, ethanol solution, and γ-methacryloxypropyltrimethoxysilane being 100:4500:30, adjusting the pH to 4 with hydrochloric acid solution, stirring and mixing, reacting at a temperature of 80° C. and a reaction time of 8 h. After the reaction is completed, the mixture is filtered, washed with anhydrous ethanol and deionized water, and vacuum dried at 60° C. for 12 h to obtain modified silica;

[0054] (2) ultrasonically dispersing the modified silica into N,N-dimethylformamide, and after uniform dispersion, adding butenedioic acid monoesterified-β-cyclodextrin, acrylic acid, 2-hydroxyethyl acrylic acid, maleic anhydride, polyethylene glycol and initiator ammonium persulfate, wherein the mass ratio of the modified silica, N,N-dimethylformamide, butenedioic acid monoesterified-β-cyclodextrin, acrylic acid, 2-hydroxyethyl acrylic acid, maleic anhydride, polyethylene glycol and initiator ammonium persulfate is 16:950:8:100:48:20:10:2, stirring and mixing, reacting, the reaction temperature is 75°C, the reaction time is 6h, and after the reaction is completed, cooling, filtering, washing with anhydrous ethanol, and drying at 60°C for 6h to obtain a silica-based composite emulsifier;

[0055] (3) Stearic acid is heated to a molten state at 80°C, calcium hydroxide is added and stirred and mixed at a speed of 450 r / min, and a reaction occurs for 3 hours. After the reaction is completed, deionized water is added, the temperature is raised to 90°C, and a silica-based composite emulsifier, a defoaming agent polydimethylsiloxane, and a dispersant sodium polyacrylate are added, wherein the mass ratio of stearic acid, calcium hydroxide, deionized water, silica-based composite emulsifier, defoaming agent polydimethylsiloxane, and dispersant sodium polyacrylate is 320:100:2400:120:1:3, the pH value is adjusted to 8, and the mixture is stirred and mixed for 2 hours at a speed of 2400 r / min. After mixing evenly, the mixture is slowly cooled to obtain a calcium stearate emulsion.

[0056] Comparative Example 1

[0057] A method for preparing a calcium stearate emulsion comprises the following steps:

[0058] (1) N,N-dimethylformamide, butylated acid monoesterified-β-cyclodextrin, acrylic acid, 2-hydroxyethyl acrylic acid, maleic anhydride, polyethylene glycol and initiator ammonium persulfate in a mass ratio of 850:7:100:45:18:9:1.8 were stirred and mixed to react at a temperature of 70°C for 7 hours. After the reaction was completed, the mixture was cooled, filtered, washed with anhydrous ethanol, and dried at 60°C for 6 hours to obtain a composite emulsifier;

[0059] (2) Stearic acid is heated to a molten state at 75°C, calcium hydroxide is added and stirred and mixed at a speed of 400 r / min, and a reaction is carried out for 2 hours. After the reaction is completed, deionized water is added, the temperature is raised to 85°C, and nano-silica, a composite emulsifier, a defoaming agent polydimethylsiloxane, and a dispersant sodium polyacrylate are added, wherein the mass ratio of stearic acid, calcium hydroxide, deionized water, nano-silica, a composite emulsifier, a defoaming agent polydimethylsiloxane, and a dispersant sodium polyacrylate is 310:100:2200:8:104:0.6:1.5, the pH value is adjusted to 8, and the mixture is stirred and mixed for 1.5 hours at a speed of 2000 r / min. After mixing evenly, the mixture is slowly cooled to obtain a calcium stearate emulsion.

[0060] Comparative Example 2

[0061] A method for preparing a calcium stearate emulsion comprises the following steps:

[0062] (1) Ultrasonic dispersion of nano-silica in a 75% wt ethanol aqueous solution, uniform dispersion, and then adding γ-methacryloxypropyltrimethoxysilane, the mass ratio of nano-silica, ethanol solution, and γ-methacryloxypropyltrimethoxysilane being 100:4200:25, adjusting the pH to 4 with hydrochloric acid solution, stirring and mixing, reacting at a temperature of 75° C. and a reaction time of 6 h. After the reaction is completed, the mixture is filtered, washed with anhydrous ethanol and deionized water, and vacuum dried at 60° C. for 12 h to obtain modified silica;

[0063] (2) ultrasonically dispersing the modified silica into N,N-dimethylformamide, and after uniform dispersion, adding acrylic acid, 2-hydroxyethyl acrylate, maleic anhydride, polyethylene glycol and initiator ammonium persulfate, wherein the mass ratio of the modified silica, N,N-dimethylformamide, acrylic acid, 2-hydroxyethyl acrylate, maleic anhydride, polyethylene glycol and initiator ammonium persulfate is 15:850:100:45:18:9:1.8, stirring and mixing, reacting, the reaction temperature is 70°C, the reaction time is 7h, and after the reaction is completed, cooling, filtering, washing with anhydrous ethanol, and drying at 60°C for 6h to obtain a silica-based composite emulsifier;

[0064] (3) Stearic acid is heated to a molten state at 75°C, calcium hydroxide is added and stirred and mixed at a speed of 400 r / min, and a reaction is carried out for 2 hours. After the reaction is completed, deionized water is added, the temperature is raised to 85°C, and a silica-based composite emulsifier, β-cyclodextrin, defoaming agent polydimethylsiloxane, and dispersant sodium polyacrylate are added, wherein the mass ratio of stearic acid, calcium hydroxide, deionized water, silica-based composite emulsifier, β-cyclodextrin, defoaming agent polydimethylsiloxane, and dispersant sodium polyacrylate is 310:100:2200:4:108:0.6:1.5, the pH value is adjusted to 8, and the mixture is stirred and mixed for 1.5 hours at a speed of 2000 r / min. After mixing evenly, the mixture is slowly cooled to obtain a calcium stearate emulsion.

[0065] Comparative Example 3

[0066] A method for preparing a calcium stearate emulsion comprises the following steps:

[0067] (1) N,N-dimethylformamide, acrylic acid, 2-hydroxyethyl acrylate, maleic anhydride, polyethylene glycol and initiator ammonium persulfate in a mass ratio of 850:100:45:18:9:1.8 were stirred and mixed to react at a temperature of 70°C for 7 hours. After the reaction was completed, the mixture was cooled, filtered, washed with anhydrous ethanol, and dried at 60°C for 6 hours to obtain a composite emulsifier;

[0068] (2) Stearic acid is heated to a molten state at 75°C, calcium hydroxide is added and stirred and mixed at a speed of 400 r / min, and a reaction is carried out for 2 hours. After the reaction is completed, deionized water is added, the temperature is raised to 85°C, and nano-silica, β-cyclodextrin, a composite emulsifier, a defoaming agent polydimethylsiloxane, and a dispersant sodium polyacrylate are added, wherein the mass ratio of stearic acid, calcium hydroxide, deionized water, nano-silica, β-cyclodextrin, a composite emulsifier, a defoaming agent polydimethylsiloxane, and a dispersant sodium polyacrylate is 310:100:2200:8:4:100:0.6:1.5, the pH value is adjusted to 8, and the mixture is stirred and mixed for 1.5 hours at a speed of 2000 r / min. After mixing evenly, the mixture is slowly cooled to obtain a calcium stearate emulsion.

[0069] Nano-silica used in the examples and comparative examples of the present invention was purchased from Jiangsu Lianyungang Pengrui Chemical Co., Ltd., with a particle size of 15 nm; polyethylene glycol was polyethylene glycol 6000, purchased from Sinopharm Chemical Reagent Co., Ltd.; other raw materials and reagents not specified were commercially available.

[0070] The calcium stearate emulsions prepared in Examples 1-4 and Comparative Examples 1-3 were subjected to relevant performance tests, as follows:

[0071] (1) Dispersibility test: 1 mL of the emulsion was diluted with deionized water to a transmittance of 80%. After ultrasonic dispersion for 5 min, the test was performed. The particle size distribution of the emulsion was measured using a BT-9300Z laser particle size distribution analyzer. The refractive index of the calcium stearate particles was 1.45, the refractive index of deionized water was 1.33, the absorptivity was 0.01, the test range was 0.01-3500 μm, the circulating pump speed was 2000-2500 rpm, and the measurement was repeated 3 times. The average particle size and distribution were calculated.

[0072] (2) Stability test

[0073] 1) Centrifugal stability: Place the calcium stearate emulsion in a centrifuge at 4000 rpm for 15 min. The stability of the emulsion is determined by the stratification effect. The worse the stratification effect, the better the emulsion stability.

[0074] Storage stability: Store in a constant temperature incubator at 25°C, relative humidity 60%, protected from light for 30 days. Calculate the delamination rate and sedimentation amount. The delamination rate is calculated as delamination rate (%) = (H1 / H0) × 100%, where the height of the supernatant (H1) is divided by the total height (H0). The sedimentation amount is the mass of the sediment at the bottom of the bottle after pouring the emulsion, divided by the mass of the original emulsion.

[0075] (3) Thermal stability test: The sample was freeze-dried at -50 °C, ground, and 10 mg of the sample was weighed for thermogravimetric analysis. The test was conducted in a nitrogen atmosphere at a heating rate of 10 °C / min. The decomposition temperature (T d );

[0076] The test results are shown in Table 1:

[0077] Table 1

[0078]

[0079]

[0080] According to the test results of Table 1, it can be seen that the synergistic effect of modified silica of Examples 1-4 and monoesterified butylated β-cyclodextrin in the present invention effectively suppresses agglomeration, and the corresponding calcium stearate emulsion has excellent performance, excellent dispersibility, and good stability. In Comparative Example 1, nano silicon dioxide is not modified and is directly added to the emulsion, resulting in poor interfacial compatibility and easy agglomeration, which causes the overall stability of the emulsion to decrease and the overall performance to deteriorate. In Comparative Example 2, β-cyclodextrin is not modified, the inclusion capacity of β-cyclodextrin decreases, the thermal stability of the emulsion decreases, and the dispersibility is greatly reduced. In Comparative Example 3, the emulsifying effect is poor, nano silicon dioxide is easy to agglomerate, and β-cyclodextrin is not modified either, and the overall performance is greatly reduced, with poor dispersibility, and both stability and heat resistance are greatly reduced.

[0081] Although the embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present invention, and that all equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A method for preparing a calcium stearate emulsion, characterized in that: The steps include: Step 1: Ultrasonic dispersion of nano-silica in an ethanol solution, uniform dispersion, and then adding γ-methacryloxypropyltrimethoxysilane, adjusting the pH to 4, stirring and mixing, reacting, and after the reaction is completed, filtering, washing, and vacuum drying at 60° C. for 12 hours to obtain modified silica; Step 2: ultrasonically disperse the modified silica in N,N-dimethylformamide. After uniform dispersion, add butylated β-cyclodextrin, acrylic acid, 2-hydroxyethyl acrylate, maleic anhydride, polyethylene glycol, and an initiator, stir and mix, react, and after the reaction is completed, cool, filter, wash, and dry at 60° C. for 6 hours to obtain a silica-based composite emulsifier. Step 3: Heat stearic acid to a molten state, add calcium hydroxide, stir and mix, react, add deionized water after the reaction is completed, heat, add a silica-based composite emulsifier, a defoamer, and a dispersant, adjust the pH value to 8, stir and mix, mix evenly, and slowly cool to obtain a calcium stearate emulsion; In the step 2, the mass ratio of modified silica, N,N-dimethylformamide, maleic acid monoesterified-β-cyclodextrin, acrylic acid, 2-hydroxyethyl acrylate, maleic anhydride, polyethylene glycol and initiator is (9-16): (750-950): (5-8): 100: (35-48): (12-20): (7-10): (1-2); In the step 3, the mass ratio of stearic acid, calcium hydroxide, deionized water, silica-based composite emulsifier, defoaming agent, and dispersant is (300-320):100:(2100-2400):(95-120):(0.5-1):(1-3).

2. The method for preparing a calcium stearate emulsion according to claim 1, wherein: The reaction temperature in step 2 is 65-75° C., and the reaction time is 6-8 h.

3. The preparation method of a calcium stearate emulsion according to claim 1, wherein: In the step 2, the initiator is selected from any one of ammonium persulfate, potassium persulfate, and benzoyl peroxide.

4. The method for preparing a calcium stearate emulsion according to claim 1, wherein: The reaction time in step 3 is 1.5-3 hours, and the stirring speed during the reaction is 350-450 r / min.

5. The method for preparing a calcium stearate emulsion according to claim 1, wherein: The temperature after heating in the step 3 is 80-90° C., the stirring and mixing time is 1-2 hours, and the stirring and mixing rate is 1800-2400 r / min.

6. The method for preparing a calcium stearate emulsion according to claim 1, wherein: The defoaming agent in step 3 is a water-soluble silane defoaming agent; The dispersant in step 3 includes any one of alkylphenol polyoxyethylene ether, lauryl alcohol polyoxyethylene ether, and sodium polyacrylate.

7. A calcium stearate emulsion prepared by the preparation method of the calcium stearate emulsion according to any one of claims 1 to 6.

8. Use of the calcium stearate emulsion as claimed in claim 7 in rubber.

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