A soap-free hybrid high-performance polymer film-forming emulsion and a method for preparing the same

Abstract

The present application relates to the field of soap-free high solid content film forming emulsion preparation technology, and particularly relates to a preparation method of silica-polymer microsphere emulsion. A small particle size, high solid content silica-polymer microsphere emulsion is prepared by Pickering emulsion polymerization. The preparation method comprises the following steps: S1, preparing a reaction solution: preparing a silica aqueous dispersion; S2, preparing an initiator solution; S3, slowly dropping the initiator solution and monomers into the reaction solution after temperature rising and nitrogen removal, and a small particle size silica-polymer microsphere film forming emulsion can be obtained after polymerization. The preparation method of the present application can control the morphology of the polymer microspheres and further control the particle size of the silica-polymer microspheres by controlling the dropping time of the monomers and the initiator without adding other substances; the method is simple. Due to the advantages of no surface activation, uniform doping of inorganic particles and small particle size, the film forming performance is good, and the method has great application value in the field of water-based anticorrosive coatings.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of soap-free high solid content film-forming emulsion preparation, and particularly relates to a preparation method of a silica-polymer microsphere emulsion. BACKGROUND

[0002] The silica-polymer microsphere is one kind of organic-inorganic hybrid microspheres, and has the advantages of good stability, multiple functions, and convenience for subsequent dispersion of inorganic particles in a polymer matrix. The silica is widely used as an inorganic phase of the organic-inorganic hybrid particle due to its excellent stability, low cost and good functionality.

[0003] At present, the methods for synthesizing the organic-inorganic hybrid particle include miniemulsion polymerization, seed emulsion polymerization and Pickering emulsion polymerization. The method for preparing the organic-inorganic hybrid particle by the miniemulsion polymerization is mainly to modify the inorganic particle to have good compatibility with the monomer, then to uniformly disperse the inorganic particle in the monomer, to ultrasonically emulsify to obtain monomer droplets containing the inorganic particle, and then to perform a polymerization reaction in the monomer droplets to coat the inorganic particle in the generated polymer microsphere. The method for seed emulsion polymerization is to modify the inorganic particle, then to slowly add the monomer to make the monomer slowly grow on the inorganic particle to obtain the organic-inorganic hybrid particle. However, both the methods have certain limitations, and a large amount of surfactant is needed to assist in the preparation process.

[0004] The inorganic particle has the ability to stabilize the oil droplets in water, i.e. Pickering stabilization, and then the Pickering emulsion polymerization using the inorganic particle as the stabilizer is developed. The first developed Pickering emulsion polymerization is to modify the inorganic particle such as silica, to copolymerize with the polymer monomer having opposite charges to the silica, and to use the cationic azo initiator to promote the adsorption of the silica to the generated latex particle. The subsequent research shows that when the relatively hydrophilic monomer MMA is used, the unmodified silica can be promoted to the surface of the latex particle by the Van der Waals force through using KPS as the initiator. However, the organic-inorganic hybrid particle prepared by the method has a large particle size, and it is difficult to achieve a high solid content. The defects of the large particle size and the difficulty to achieve the high solid content will limit the further application of the film-forming emulsion. SUMMARY

[0005] In order to solve the above problems, the present application provides a preparation method of a small particle size and high solid content Pickering emulsion, which can obtain the hybrid microsphere with a small particle size without adding the auxiliary copolymer monomer or the cationic azo initiator, and the monomer dropping time is used to control the morphology and particle size of the latex particle.

[0006] The first aspect of the present application provides a preparation method of a soap-free hybrid high-performance polymer film-forming emulsion, comprising the following steps:

[0007] S1, preparing a reaction solution: preparing a silica aqueous dispersion, adjusting the pH to between 3 and 6;

[0008] S2, preparing an initiator solution: dissolving an initiator in water to obtain an initiator solution;

[0009] S3, slowly adding the initiator solution and monomers into the reaction solution after heating and removing nitrogen, and obtaining a white emulsion after polymerization, which is a small-particle-size silica-polymer microsphere film-forming emulsion.

[0010] Further, in step S1, the reaction solution contains 25-88 parts by mass of solvent water and 1-10 parts by mass of silica.

[0011] Further, in step S3, the monomers are selected from one or a combination of more than two of methyl methacrylate and ethyl methacrylate;

[0012] In one embodiment, the monomers in step S3 are methyl methacrylate monomers, and the addition amount is 10-30% of the total mass of the solution;

[0013] In some embodiments of the present application, the initiator is selected from any one or a combination of more than two of potassium persulfate, ammonium persulfate, and azobis diisobutyl amide hydrochloride.

[0014] In some embodiments of the present application, the particle size of the latex particles in the film-forming emulsion is between 100 nm and 300 nm.

[0015] In some embodiments of the present application, the reaction temperature in step S3 is 50-80°C.

[0016] In some embodiments of the present application, in step S1, the addition amount of silica is 1%-10% of the total mass of water and silica;

[0017] In some embodiments of the present application, in step S3, the addition amount of monomers is 10-30% of the total mass of the emulsion;

[0018] In some embodiments of the present application, the addition amount of the initiator is 1%-3% of the total mass of the solution;

[0019] In some embodiments of the present application, the monomer dropwise addition time is between 0 min and 180 min;

[0020] In some embodiments of the present application, the initiator dropwise addition time is between 0 min and 180 min;

[0021] Further, the silica particle size in step S1 is 10-30 nm;

[0022] In some preferred embodiments, the silica is in the form of an aqueous dispersion;

[0023] In a preferred embodiment, the silica source is Ludox TM-40;

[0024] In one embodiment, the pH of the solution after adjustment by dilute hydrochloric acid is 3-6;

[0025] The second aspect of the present application provides a film-forming emulsion prepared by the method described above, and the solid content of the film-forming emulsion is 10%-40%.

[0026] In some embodiments of the present application, the preparation method comprises the following steps (S1 and S2); S1: adding silica and water in a reaction vessel, adjusting the pH by adding dilute hydrochloric acid, and purging the reaction vessel with nitrogen to remove residual oxygen. S2: heating the S1 system to 70°C, then adding methyl methacrylate monomer and initiator to the S1 system dropwise and reacting for 12 h; obtaining a polymer emulsion.

[0027] In some preferred embodiments, the monomer and the initiator are added synchronously.

[0028] Advantages: Compared with the prior art, the present application has at least the following characteristics and advantages:

[0029] The present application provides a method for preparing small-particle-size, high-solid-content silica-polymer microsphere emulsion by Pickering emulsion polymerization. The emulsion is prepared without adding surfactants, and without adding auxiliary comonomers or using cationic initiators, and a silica-polymer microsphere emulsion with small particle size and high solid content is obtained. The silica-polymer hybrid microspheres in the prepared film-forming emulsion have good uniformity; the particle size of the emulsion particles in the film-forming emulsion is between 100 nm and 300 nm, and the solid content can reach 40%;

[0030] The preparation method of the present application can control the morphology of the polymer microspheres by controlling the dropping time of the monomer and the initiator without adding any substances, thereby realizing the control of the particle size of the silica-polymer microspheres, and the method is simple.

[0031] Due to the absence of surfactants, uniform doping of inorganic particles, and small particle size, the film-forming performance is good and has great application value in the field of water-based anticorrosive coatings. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The scanning electron microscope characterization graph of the polymer microspheres in Example 1;

[0033] Figure 2 Scanning electron micrograph of polymer microspheres of Example 2;

[0034] Figure 3 Scanning electron micrograph of polymer microspheres of Example 3;

[0035] Figure 4 Scanning electron micrograph of polymer microspheres of Example 4;

[0036] Figure 5 Particle size distribution of polymer microspheres of Examples 1-4;

[0037] Figure 6 Scanning electron micrograph of polymer microspheres of Example 5;

[0038] Figure 7 Scanning electron micrograph of polymer microspheres of Example 6;

[0039] Figure 8 Digital photograph of film formation of Example 7;

[0040] Figure 9 Scanning electron micrograph of polymer microspheres of Comparative Example 1;

[0041] Figure 10 Digital photograph of film formation of Comparative Example 2;

[0042] Figure 11 Photograph of high solid emulsion prepared in Comparative Example 6. DETAILED DESCRIPTION

[0043] The present application will be further described with reference to the following drawings and examples. The examples described herein are intended to be illustrative of the application and are not intended to limit the scope of the application as described in the claims. Those skilled in the art will readily understand that the specific materials, conditions and results described in the examples are illustrative only and are not intended to limit the scope of the application as described in the claims.

[0044] Example 1: Preparation of a polymer emulsion

[0045] This example describes in detail a method for preparing a polymer microsphere emulsion.

[0046] The raw materials used were: methyl methacrylate (MMA), Ludox TM-40 (aqueous dispersion of silica), potassium persulfate (KPS), dilute hydrochloric acid, and water.

[0047] The specific preparation process was as follows:

[0048] 1. A three-necked flask was charged with 88 g of ultrapure water and 12 g of Ludox TM-40, and mixed uniformly at a stirring rate of 300 rpm. Dilute hydrochloric acid was added to adjust the pH to 5.5, and then nitrogen was bubbled for 30 min to remove oxygen. The temperature was raised to 70°C, and 10 g of monomer and 0.2 g of initiator KPS dissolved in 10 g of water were added directly and reacted for 12 h.

[0049] After the reaction was completed, a polymer microsphere emulsion was obtained.

[0050] As shown in Figure 1 , the average particle size of the obtained polymer microspheres was about 250 nm.

[0051] Example 2: Preparation of a polymer emulsion (monomer dropwise addition time 30 min)

[0052] This example describes in detail a method for preparing a polymer microsphere emulsion.

[0053] The raw materials were as follows: methyl methacrylate (MMA), Ludox TM-40 (aqueous dispersion of silicon dioxide), potassium persulfate (KPS), dilute hydrochloric acid, and water.

[0054] The specific preparation process was as follows:

[0055] 1. A three-necked flask was charged with 88 g of ultrapure water and 12 g of Ludox TM-40, and mixed uniformly at a stirring rate of 300 rpm. Dilute hydrochloric acid was added to adjust the pH to 5.5, and then nitrogen was bubbled for 30 min to remove oxygen. The temperature was raised to 70°C, and 10 g of monomer and 0.2 g of initiator KPS dissolved in 10 g of water were added directly and reacted for 12 h.

[0056] After the reaction was completed, a polymer microsphere emulsion was obtained.

[0057] As shown in Figure 2 , the average particle size of the obtained polymer microspheres was about 220 nm.

[0058] Example 3: Preparation of a polymer emulsion (monomer dropwise addition time 60 min)

[0059] This example describes in detail a method for preparing a polymer microsphere emulsion.

[0060] The raw materials were as follows: methyl methacrylate (MMA), Ludox TM-40 (aqueous dispersion of silicon dioxide), potassium persulfate (KPS), dilute hydrochloric acid, and water.

[0061] The specific preparation process was as follows:

[0062] 1. A three-necked flask was charged with 88 g of ultrapure water, 12 g of Ludox TM-40, and stirred at a rate of 300 rpm to mix them uniformly. Dilute hydrochloric acid was added to adjust the pH to 5.5, and then nitrogen was bubbled for 30 min to remove oxygen. The temperature was raised to 70°C, and 10 g of monomer and 0.2 g of initiator KPS dissolved in 10 g of water were slowly added dropwise (the dropwise addition was completed in 60 min) to react for 12 h.

[0063] After the reaction was completed, a polymer microsphere emulsion was obtained.

[0064] As shown in Figure 3 , the average particle size of the obtained polymer microspheres was about 210 nm.

[0065] Example 4: Preparation of a polymer emulsion (monomer dropwise addition time 90 min)

[0066] This example describes in detail a method for preparing a polymer microsphere emulsion.

[0067] The raw materials were as follows: methyl methacrylate (MMA), Ludox TM-40 (aqueous dispersion of silicon dioxide), potassium persulfate (KPS), dilute hydrochloric acid, and water.

[0068] The specific preparation process was as follows:

[0069] 1. A three-necked flask was charged with 88 g of ultrapure water, 12 g of Ludox TM-40, and stirred at a rate of 300 rpm to mix them uniformly. Dilute hydrochloric acid was added to adjust the pH to 5.5, and then nitrogen was bubbled for 30 min to remove oxygen. The temperature was raised to 70°C, and 10 g of monomer and 0.2 g of initiator KPS dissolved in 10 g of water were slowly added dropwise (the dropwise addition was completed in 90 min) to react for 12 h.

[0070] After the reaction was completed, a polymer microsphere emulsion was obtained.

[0071] As shown in Figure 4 , the average particle size of the obtained polymer microspheres was about 120 nm.

[0072] As shown in Figure 5 , the effect of different monomer dropwise addition times on the particle size of the generated latex particles, as the monomer dropwise addition time was prolonged, the swelling effect of the monomer into the newly generated polymer core was continuously weakened, leading to a continuously decreasing particle size of the newly generated core.

[0073] Example 5: Preparation of a polymer emulsion (changing the mass ratio of silicon dioxide and monomer to 3:4)

[0074] This example describes in detail a method for preparing a polymer microsphere emulsion.

[0075] Methyl methacrylate (MMA), Ludox TM-40 (aqueous dispersion of silica), potassium persulfate (KPS), dilute hydrochloric acid, water.

[0076] The detailed preparation process is as follows:

[0077] 1, a three-necked flask was added 88 g of ultrapure water, 18.75 g of Ludox TM-40, and stirred at a speed of 300 rpm to mix them evenly. Dilute hydrochloric acid was added to adjust the pH to 5.5, then nitrogen was passed for 30 min to remove oxygen, and then the temperature was raised to 70°C. 10 g of monomer and 0.2 g of initiator KPS dissolved in 10 g of water were slowly added (60 min for addition) and reacted for 12 h.

[0078] After the reaction was completed, a polymer microsphere emulsion was obtained.

[0079] As shown in Figure 6 , the obtained polymer microspheres have silica on their surface, but the silica tends to aggregate by itself, because the probability of collision between high-concentration silica increases, and they are more likely to aggregate before coagulating with the latex particles to form nuclei.

[0080] This example describes in detail a method for preparing a polymer microsphere emulsion in S1.

[0081] Methyl methacrylate (MMA), Ludox TM-40 (aqueous dispersion of silica), potassium persulfate (KPS), dilute hydrochloric acid, water.

[0082] The detailed preparation process is as follows:

[0083] 1, a three-necked flask was added 88 g of ultrapure water, 18.75 g of Ludox TM-40, and stirred at a speed of 300 rpm to mix them evenly. Dilute hydrochloric acid was added to adjust the pH to 5.5, then nitrogen was passed for 30 min to remove oxygen, and then the temperature was raised to 70°C. 10 g of monomer and 0.2 g of initiator KPS dissolved in 10 g of water were slowly added (60 min for addition) and reacted for 12 h.

[0084] After the reaction was completed, a polymer microsphere emulsion was obtained.

[0085] As shown in Figure 7 , the obtained polymer microspheres have silica on their surface, but the silica tends to aggregate by itself, because the probability of collision between high-concentration silica increases, and they are more likely to aggregate before coagulating with the latex particles to form nuclei.

[0086] Example 6: Preparation of a high-solid polymer emulsion

[0087] This embodiment describes in detail a method for preparing a high solid content polymer microsphere emulsion.

[0088] The raw materials are as follows: methyl methacrylate (MMA), Ludox TM-40 (aqueous silica dispersion), potassium persulfate (KPS), dilute hydrochloric acid, and water.

[0089] The specific preparation process is as follows:

[0090] 1. A three-necked flask is added with 20 g of ultrapure water and 25 g of Ludox TM-40, which are mixed uniformly at a stirring rate of 300 rpm. Dilute hydrochloric acid is added to adjust the pH to 5.5, and then nitrogen is passed for 30 min to remove oxygen. The temperature is raised to 70°C, and 20 g of monomers and 0.2 g of initiator KPS dissolved in 10 g of water are slowly added dropwise (60 min for dropwise addition). The reaction is carried out for 12 h.

[0091] After the reaction is completed, a polymer microsphere emulsion is obtained.

[0092] The solid content of the emulsion can be determined by the mass of the remaining solids m (SiO2) + m (M) = 30 g.

[0093] The mass of the system is 75 g, and the solid content is 30 / 75 = 40%.

[0094] The prepared high solid content emulsion is as shown in Figure 11 .

[0095] Example 7: Preparation of a polymer emulsion and its use for film formation

[0096] The raw materials are as follows: methyl methacrylate (MMA), n-butyl acrylate (BA), Ludox TM-40 (aqueous silica dispersion), potassium persulfate (KPS), dilute hydrochloric acid, and water.

[0097] The specific preparation process is as follows:

[0098] 1. A three-necked flask is added with 20 g of ultrapure water and 25 g of Ludox TM-40, which are mixed uniformly at a stirring rate of 300 rpm. Dilute hydrochloric acid is added to adjust the pH to 5.5, and then nitrogen is passed for 30 min to remove oxygen. The temperature is raised to 70°C, and 20 g of monomers and 0.2 g of initiator KPS dissolved in 10 g of water are slowly added dropwise (60 min for dropwise addition). The reaction is carried out for 12 h.

[0099] After the reaction is completed, a polymer microsphere emulsion is obtained.

[0100] After the reaction is completed, a polymer microsphere emulsion is obtained, ammonia is added to adjust the pH to about 8-9, and then the emulsion is poured into a polytetrafluoroethylene mold to form a film at 70°C for 24 h.

[0101] As Figure 8As shown, the emulsion exhibits good film-forming properties and high film transmittance.

[0102] Comparative Example 1: Preparation of polymer emulsion (using styrene as monomer)

[0103] The raw materials are as follows: styrene (St), Ludox TM-40 (silica aqueous dispersion), potassium persulfate (KPS), dilute hydrochloric acid, and water.

[0104] The specific preparation process is as follows:

[0105] 1. Add 88g of ultrapure water and 12g of Ludox TM-40 to a three-necked flask and stir at 300rpm until homogeneous. Adjust the pH to 5.5 with dilute hydrochloric acid, then purge with nitrogen for 30min to remove oxygen. Heat to 70℃ and slowly add 10g of monomer and 0.2g of initiator KPS dissolved in 10g of water (addition completed over 60min). React for 12h.

[0106] After the reaction was completed, a polymer microsphere emulsion was obtained.

[0107] like Figure 9 As shown, there is no obvious silica loading on the surface of the obtained polymer microspheres because the styrene monomer is relatively hydrophobic and cannot cause silica to be spontaneously adsorbed onto the surface of the latex particles.

[0108] Comparative Example 2: Preparation of polymer emulsion (silica directly blended with polymer emulsion)

[0109] The raw materials are as follows: styrene (St), Ludox TM-40 (silica aqueous dispersion), potassium persulfate (KPS), dilute hydrochloric acid, water, and sodium dodecyl sulfate (SDS).

[0110] The specific preparation process is as follows:

[0111] 1. Add 88g of ultrapure water and 0.1g of SDS to a three-necked flask and stir at 300rpm until homogeneous. Adjust the pH to 5.5 with dilute hydrochloric acid, then purge with nitrogen for 30min to remove oxygen. Heat to 70℃, add 10g of monomer and 0.2g of initiator KPS dissolved in 10g of water, and react for 12h.

[0112] After the reaction was completed, the polymer microsphere emulsion was mixed with 12g of Ludox TM-40 silica aqueous dispersion.

[0113] like Figure 10 As shown, the polymer film obtained by direct blending has whitish areas, indicating that the direct incorporation of silica cannot be uniformly dispersed in the emulsion.

[0114] The present application is a method for preparing small-particle-size and high-solid-content silica-polymer microsphere emulsion by Pickering emulsion polymerization. The silica-polymer microsphere emulsion with small particle size and high solid content can be obtained without adding surfactant, without adding auxiliary comonomer or using cationic initiator. The silica-polymer hybrid microspheres in the film-forming emulsion have good uniformity; the particle size of the latex particles in the film-forming emulsion is between 100 nm and 300 nm, and the solid content can reach 40%; the film-forming performance is excellent. The preparation method of the present application can control the morphology of the polymer microspheres and then control the particle size of the silica-polymer microspheres by controlling the dropping time of the monomer and the initiator without adding any substance, and the method is simple.

[0115] It should be understood that the above detailed examples of the present disclosure are only for illustration or explanation of the principles of the present disclosure, but not to limit the present application. It should be noted that any modifications, equivalent substitutions and improvements within the spirit and principles of the present disclosure should be included in the protection scope of the present application.

Claims

1. A process for the preparation of a soap-free hybrid high performance polymer film forming emulsion characterized in that, The method comprises the following steps: S1, preparing a reaction solution: preparing a water dispersion of silica, adjusting the pH to 3-6; S2, preparing an initiator solution: dissolving an initiator in water to obtain an initiator solution; S3, slowly adding the initiator solution and monomers into the reaction solution after heating and removing nitrogen, and obtaining a white emulsion after polymerization, which is a film-forming emulsion of small-particle-size silica-polymer microspheres; The monomer addition time is 30 min-90 min; The initiator addition time is 30 min-90 min; The particle size of the latex particles in the film-forming emulsion is 100 nm-220 nm.

2. The method for preparing a soap-free hybrid high performance polymer film forming emulsion according to claim 1, characterized in that, In step S1, the reaction solution contains 25-88 parts of solvent water and 1-10 parts of silica by mass fraction.

3. The method according to claim 1, wherein the method is characterized by, In step S3, the monomers are selected from one or a combination of more than two of methyl methacrylate and ethyl methacrylate.

4. The method according to claim 1, wherein the method is characterized by, The initiator is selected from one or a combination of potassium persulfate, ammonium persulfate, and azobisdimethylamid hydrochloride.

5. The method of claim 1, wherein the method is characterized by, The reaction temperature in step S3 is 50-80℃.

6. The method of claim 1, wherein the method is characterized by, In step S1, the amount of silica added is 1%-10% of the total mass of water and silica; In step S3, the amount of monomers added is 10%-30% of the total mass of the emulsion.

7. The method according to claim 1, wherein the method is characterized by, The amount of initiator added is 1%-3% of the total mass of the initiator solution.

8. The method of claim 1, wherein the method is characterized by, In step S1, the particle size of the silica is 10-30 nm.

9. The film-forming emulsion produced by the method of any one of claims 1-8, characterized by, The solid content of the film-forming emulsion is 10%-40%.

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