Hydrophobic silicon dioxide powder as well as preparation method and application thereof

Abstract

The invention relates to hydrophobic silicon dioxide powder as well as a preparation method and application thereof. The hydrophobic silicon dioxide powder is composed of a sesame ball body composed of spherical silicon dioxide particles, fumed silica coating the surface of the sesame ball body and hydrophobic modified groups on the surface of the fumed silica. The preparation method comprises the following steps: dispersing fumed silica in silica sol, adding a hydrophobic modifier while stirring, heating, and drying to obtain hydrophobic silica powder. When the hydrophobic silicon dioxide powder is used for modifying the carbon powder, the fumed silica attached to the surface of the silica gel can improve the printing resolution, and the large particles of the silica gel can enable the carbon powder to have higher blackness. In addition, the fumed silica is attached to the surface of the silica colloid, so that the modification cost of the carbon powder can be reduced. And the modified carbon powder has better barrier property.

Description

Technical Field

[0001] The present invention relates to the technical field of new materials, and in particular to a hydrophobic silicon dioxide powder and a preparation method and application thereof. Background Art

[0002] In the electrophotographic development method, a high-quality image is obtained by developing an electrostatic latent image or by reverse development. The toner suitable for electrophotographic development is a mixture of a dye or pigment as a colorant, a charge control agent, a wax as a release agent, and a magnetic material in a thermoplastic resin as a binder, and then crushed and classified to make toner particles. In addition, in order to give the toner particles fluidity and improve cleaning performance, external additives composed of inorganic fine powders such as silica, titanium oxide or aluminum oxide are usually added to the toner particles. However, these inorganic fine powders are usually hydrophilic and may be affected by the surrounding environment (humidity) and change the fluidity of the toner. By treating the hydrophilic silica particles, the hydrophilicity of the silica particles can be reduced, thereby giving the particles various degrees of hydrophobicity.

[0003] With the emergence of printers with faster printing speeds and better printing quality, the requirements for toner, which is essential for printing, are getting higher and higher. For example, the emergence of magnetic printers requires toner to have excellent negative charge. The original toner showed problems of poor fluidity and dispersibility during the use of new printers. These problems led to uneven printing effects and the long-term printing could not be guaranteed. Using such toner for printing often causes damage to the precision parts inside the printer, thereby shortening the service life of the printer. This puts forward requirements for the research of toner modified compounds. Using hydrophobic silica to modify toner can perfectly solve the above problems.

[0004] Therefore, in order to solve the problems of poor dispersibility and fluidity of toner in the prior art printers, enhance the barrier property of toner during printing, and solve the problem of insufficient charge in toner, it is urgent to provide a new hydrophobic silica powder and a preparation method thereof. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a hydrophobic silica powder and its preparation method and application. The hydrophobic silica powder of the present invention is composed of sesame balls composed of spherical silica particles, fumed silica coated on the surface of the sesame balls, and hydrophobic modified groups on the surface of the fumed silica. The present invention obtains hydrophobic silica powder by dispersing fumed silica in silica sol, adding a hydrophobic modifier while stirring, heating and drying. The hydrophobic silica powder prepared by the present invention can be used in carbon powder addition, resin composite materials, 3D printing composite materials or metal composite materials.

[0006] The present invention is achieved through the following technical solutions:

[0007] The first object of the present invention is to provide a hydrophobic silica powder, wherein the hydrophobic silica powder is composed of sesame ball spheres composed of spherical silica particles, fumed silica coated on the surface of the sesame ball spheres, and hydrophobic modified groups on the surface of the fumed silica;

[0008] The spherical silica particles are derived from silica sol; and the hydrophobic modification groups are derived from a hydrophobic modification agent.

[0009] In one embodiment of the present invention, the surface hydrophobicity degree of the hydrophobic silica powder is above 50%.

[0010] In one embodiment of the present invention, the primary particle size of the spherical silica particles is 15 nm to 200 nm;

[0011] And / or, the primary particle size of the fumed silica is 3 nm to 10 nm.

[0012] In one embodiment of the present invention, the particle size of the hydrophobic silica powder is 1 μm to 10 μm;

[0013] And / or, the true density of the hydrophobic silica powder is less than 2.2 g / cm 3 .

[0014] In one embodiment of the present invention, the hydrophobic modifying group is selected from one or more of a straight-chain alkyl group, a nitrogen-containing straight-chain alkyl group, and a cyclic nitrogen-containing alkyl group;

[0015] And / or, based on carbon content, the hydrophobic modification group is >0.5wt%.

[0016] In one embodiment of the present invention, the fumed silica is selected from hydrophilic fumed silica and / or hydrophobic fumed silica.

[0017] The second object of the present invention is to provide a method for preparing the hydrophobic silica powder, comprising the following steps:

[0018] (1) preparing a silica sol containing spherical silica particles by a sol-gel method;

[0019] (2) Dispersing fumed silica in silica sol, adding a hydrophobic modifier while stirring, heating and drying to obtain hydrophobic silica powder.

[0020] In one embodiment of the present invention, in step (2), the mass of silicon dioxide in the silicon dioxide sol / the mass of the fumed silicon dioxide ≥ the specific surface area of ​​the fumed silicon dioxide / 8×the specific surface area of ​​silicon dioxide in the silicon dioxide sol; that is, M 溶胶中二氧化硅 / M 气相二氧化硅 ≥S 气相二氧化硅 / 8S 硅溶胶 ; Wherein, M refers to mass and S refers to specific surface area;

[0021] And / or, the specific surface area of ​​the fumed silica is ≥150m 2 / g; preferably 400m 2 / g;

[0022] And / or, the specific surface area of ​​silicon dioxide in the silicon dioxide sol is 101m 2 / g.

[0023] In one embodiment of the present invention, in step (2), the amount of the hydrophobic modifier added is 10%-100% of the total amount of the fumed silica and the silica in the silica sol;

[0024] And / or, the hydrophobic modifier is selected from one or more of disilazane compounds, monochlorosilane, monoalkoxysilane, monoacyloxysilane and silicone oil.

[0025] In one embodiment of the present invention, in step (2), the heating conditions are: temperature ≥ 25°C; time ≥ 15 min; preferably, heating at 80°C for 120 min.

[0026] In one embodiment of the present invention, in step (2), the drying is spray drying.

[0027] In one embodiment of the present invention, the preparation method of the hydrophobic silica powder of the present invention is specifically as follows:

[0028] S1: Preparation of silica sol by sol-gel method;

[0029] S2: attaching fumed silica to the surface of silica sol, and aging the silica sol to obtain a gel slurry before hydrophobic modification;

[0030] S3: using a hydrophobic modifier to perform surface hydrophobic modification on the gel slurry obtained in step S2;

[0031] S4: After modification, the water phase is separated and the hydrophobic silica powder is obtained after drying.

[0032] or,

[0033] S1: Preparation of silica sol by sol-gel method;

[0034] S2: attaching fumed silica to the surface of silica sol to form a sol slurry, and modifying the silica sol slurry with a hydrophobic modifier;

[0035] S3: The sol slurry is aged to obtain a gel;

[0036] S4: After the gel is dried, hydrophobic silica powder is obtained.

[0037] The third object of the present invention is to provide the use of the hydrophobic silica powder in carbon powder addition, resin composite materials, 3D printing composite materials and metal composite materials.

[0038] The above technical solution of the present invention has the following advantages compared with the prior art:

[0039] 1. Small-particle hydrophobic silica has a relatively high specific surface area, and when mixed with carbon powder particles, it has a better coating effect on the surface of carbon powder; while large-particle silica has a certain barrier effect between carbon powder particles due to its larger particle size, so that the particles can be better dispersed.

[0040] 2. Attach fumed silica to the surface of silica colloid and mix it with toner to increase the fluidity of toner and solve the problem of poor fluidity and low transfer rate of crushed toner during printing.

[0041] 3. The hydrophobic silica powder of the present invention is used to modify carbon powder. The fumed silica attached to the surface of the silica gel can improve the resolution of printing, while the large particles of the silica gel can make the carbon powder have a higher blackness.

[0042] 4. Attaching fumed silica to the surface of silica colloid can reduce the modification cost of carbon powder. The modified carbon powder has better barrier properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0044] Figure 1 is a TEM image of the hydrophobic silica powder of the present invention. DETAILED DESCRIPTION

[0045] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0046] The invention provides a hydrophobic silicon dioxide powder. Under TEM, the powder is composed of spherical silicon dioxide particles with a primary particle size of 15nm to 200nm and silicon dioxide agglomerates with a primary particle size of 3nm to 10nm. The surface hydrophobicity is more than 50%, the hydrophobic angle is 90-150 degrees, the water content of the hydrophobic silicon dioxide powder is 0.1%-2%, and the number of silanol groups on the surface of the powder is 1-2 / nm. 2 .

[0047] Furthermore, the hydrophobic silicon dioxide powder has a particle size of 1 μm to 10

[0048] μm, true density <2.2g / cm 3 .

[0049] Furthermore, the surface of the hydrophobic silica powder contains one or more of a straight-chain alkyl group, a nitrogen-containing straight-chain alkyl group, and a cyclic nitrogen-containing alkyl group.

[0050] Furthermore, the modified groups on the surface of the hydrophobic silica have a carbon content of >0.5wt%,

[0051] Furthermore, the silicon dioxide agglomerates of 3 to 10 nm are fumed silicon dioxide.

[0052] Furthermore, the 15-200 nm spherical silica particles are sol-gel silica.

[0053] The present invention also provides a method for preparing the hydrophobic silicon dioxide powder:

[0054] S1: Preparation of silica sol by sol-gel method;

[0055] S2: attaching fumed silica to the surface of silica sol, and aging the silica sol to obtain a gel slurry before hydrophobic modification;

[0056] S3: using a hydrophobic modifier to perform surface hydrophobic modification on the gel slurry obtained in step S2;

[0057] S4: After modification, the aqueous phase is separated and dried to obtain the product.

[0058] or,

[0059] S1: Preparation of silica sol by sol-gel method;

[0060] S2: attaching fumed silica to the surface of silica sol to form a sol slurry, and modifying the silica sol slurry with a hydrophobic modifier;

[0061] S3: The sol slurry is aged to obtain a gel;

[0062] S4: The product is obtained after the gel is dried.

[0063] Furthermore, the hydrophobic silica powder has a sesame ball structure, including sesame ball spheres composed of spherical silica particles, sesame ball surface particles composed of silica agglomerates, and hydrophobic modified groups on the surface of the silica agglomerates.

[0064] Furthermore, the hydrophobic modifier is selected from one or more of disilazane compounds, monochlorosilane, monoalkoxysilane, monoacyloxysilane and silicone oil.

[0065] Further, the disilazane compound includes tetramethyldisilazane, tetramethyldivinyldisilazane, heptamethyldisilazane, hexaethyldisilazane, and hexamethyldisilazane; the monochlorosilane includes trimethylchlorosilane, triethylchlorosilane, etc.; the monoalkoxysilane includes dimethylmonochlorosilane, triisopropylchlorosilane, tert-butyldimethoxychlorosilane, n-dodecyldimethylchlorosilane, dimethyldichlorosilane, trimethylmethoxysilane, trimethylethoxysilane, etc.; the monoacyloxysilane includes monoaminosilanes such as trimethylsilyldimethylamine and trimethylsilyldiethylamine; trimethylacetoxysilane, etc.; the silicone oil includes one or more of methyl silicone oil, ethyl silicone oil, phenyl silicone oil, methyl hydrogen silicone oil, methylphenyl silicone oil, methylchlorophenyl silicone oil, methylethoxy silicone oil, methyltrifluoropropyl silicone oil, methylvinyl silicone oil, and methylhydroxy silicone oil.

[0066] The preparation method of the silica sol used in the embodiment of the present invention refers to the preparation method of the silica sol disclosed in patent CN112875710A. The silica sol in the present invention can also be silica sol obtained by other preparation methods or commercially available silica sol.

[0067] The fumed silica is combined with the silica sol (the order of adding the fumed silica, the organic solvent, and the silica sol is not particularly limited).

[0068] The amount of gas phase dioxide and silica sol added is S 气相二氧化硅 With S 硅溶胶 The ratio of M 溶胶中二氧化硅 / M 气相二氧化硅 The ratio (M refers to mass) must be greater than or equal to S 气相二氧化硅 / 8S 硅溶胶 If too much fumed silica is added, there will be no abundant grafting space on the surface of silica in the silica sol, resulting in the existence of fumed silica in a monomer state, and a hydrophobically modified sol slurry is obtained. After aging, a gel is obtained. After drying and grinding, the hydrophobic silica powder is obtained.

[0069] The hydrophobic modification in the present invention can also be carried out after gelation, and the hydrophobic silica powder can be obtained after drying and grinding.

[0070] The present invention also provides the powder for use in carbon powder addition, resin composite materials, 3D printing composite materials, and metal composite materials.

[0071] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods, and the materials, reagents, etc. used are all available from commercial sources unless otherwise specified.

[0072] The hydrophilic fumed silica in the embodiment of the present invention was purchased from Hubei Huifu Nanomaterial Co., Ltd., with the product number HL-380; the hydrophobic silica was purchased from Hubei Huifu Nanomaterial Co., Ltd., with the product number HL612;

[0073] The CAS number of tetramethoxysilane is 681-84-5; the CAS number of octyltriethoxysilane is 2943-75-1; the CAS number of hexamethyldisilazane is 999-97-3.

[0074] Example 1

[0075] This embodiment provides a method for preparing hydrophobic silica powder, and the specific steps are as follows:

[0076] (1) Preparation of silica sol: 2320 g of anhydrous methanol, 267.5 g of pure water, and 98 g of 25% aqueous ammonia were added to a 10 L flask equipped with a stirrer and a condenser. A mixture of 187 g of tetramethoxysilane with a molecular formula of Si(OCH3)4 and 18.7 g of methanol was added to the above methanol solution at 35°C for 40 min to obtain a mixed solution A containing a silica seed core with a solid content of 2.5% and a primary particle size of 13 nm.

[0077] The temperature of the mixed solution A was maintained at 35°C for 120 minutes; a mixed solution B of 1730 g of tetramethoxysilane with the molecular formula Si(OCH3)4 and 173 g of methanol was added to the mixed solution A, and at this stage a mixed solution C containing 1.8 g of glacial acetic acid, 112 g of 25% ammonia water and 344 g of pure water was added.

[0078] The methanol in the reaction solution was replaced with water and the acetate ions were removed by a hydroxide anion exchange resin, and then concentrated to obtain 3800 g of silica sol with a mass concentration of 20%. The specific surface area of ​​the obtained silica sol was 101 m 2 / g.

[0079] (2) Add 755.3 g of silica with a specific surface area of ​​400 m 2 / g of hydrophilic fumed silica, and then 1512g of water was added to dilute it to a solid content of 25%, and then 453.18g of hexamethyldisilazane (HMDS) was added and stirred. After 120 minutes, the temperature was raised from room temperature to 80°C, and then heated at 80°C for 120 minutes. The reaction mixture was then spray-dried at a temperature of 150°C to provide hydrophobic silica particles as a dry powder. The TEM image of the hydrophobic silica particles prepared in this example is shown in FIG. Figure 1 shown.

[0080] Example 2

[0081] This embodiment provides a method for preparing hydrophobic silica powder, which is similar to that of embodiment 1, except that:

[0082] In step (2), the amount of hydrophilic fumed silica added is 377.7 g; the amount of hexamethyldisilazane (HMDS) added is 339.9 g.

[0083] Example 3

[0084] This embodiment provides a method for preparing hydrophobic silica powder, which is similar to that of embodiment 1, except that:

[0085] In step (2), the amount of hydrophilic fumed silica added is 1510.6 g; the amount of hexamethyldisilazane (HMDS) added is 679.77 g.

[0086] Example 4

[0087] This embodiment provides a method for preparing hydrophobic silica powder, which is similar to that of embodiment 1, except that:

[0088] Step (2) is: add 755.3 g of silica with a specific surface area of ​​400 m 2 / g of hydrophobic fumed silica, 200g of methanol was added to dilute to a solid content of 25%, 453.18g of hexamethyldisilazane (HMDS) was added and stirred, and the temperature was raised from room temperature to 80°C over 120 minutes, and then heated at 80°C for 120 minutes. The reaction mixture was then spray-dried at a temperature of 150°C to provide hydrophobic silica particles as a dry powder.

[0089] Example 5

[0090] This embodiment provides a method for preparing hydrophobic silica powder, which is similar to that of embodiment 1, except that:

[0091] In step (2), hexamethyldisilazane (HMDS) is replaced by octyltriethoxysilane.

[0092] Example 6

[0093] This embodiment provides a method for preparing hydrophobic silica powder, and the specific steps are as follows:

[0094] (1) Preparation of silica sol: 2320 g of anhydrous methanol, 267.5 g of pure water, and 143 g of 25% aqueous ammonia were added to a 10 L flask equipped with a stirrer and a condenser. A mixture of 230 g of tetramethoxysilane with a molecular formula of Si(OCH3)4 and 18.7 g of methanol was added to the above methanol solution at 35°C for 40 min to obtain a mixed solution A containing a silica seed core with a solid content of 2.5% and a primary particle size of 13 nm.

[0095] The temperature of the mixed solution A was maintained at 35°C for 120 minutes; a mixed solution B of 1840 g of tetramethoxysilane with the molecular formula Si(OCH3)4 and 173 g of methanol was added to the mixed solution A, and at this stage a mixed solution C containing 1.8 g of glacial acetic acid, 112 g of 25% ammonia water and 344 g of pure water was added.

[0096] The methanol in the reaction solution was replaced with water and the acetate ions were removed by a hydroxide anion exchange resin, and then concentrated to obtain 3800 g of silica sol with a mass concentration of 20%. The specific surface area of ​​the obtained silica sol was 50 m 2 / g.

[0097] (2) Add 377.7 g of silica with a specific surface area of ​​400 m 2 / g of hydrophilic fumed silica, 1512g of water was added to dilute to 25% solid content, 339.9g of hexamethyldisilazane (HMDS) was added and stirred, and the temperature was raised from room temperature to 80°C over 120 minutes, and then heated at 80°C for 120 minutes. The reaction mixture was then spray-dried at 150°C to provide hydrophobic silica particles as dry powder. .

[0098] Comparative Example 1

[0099] The preparation method of the hydrophobic silica powder provided in this comparative example is similar to that in Example 1, except that:

[0100] In step (2), the amount of hydrophilic fumed silica added is 3776.5 g; the amount of hexamethyldisilazane (HMDS) added is 1359.54 g.

[0101] Comparative Example 2

[0102] The preparation method of the hydrophobic silicon dioxide powder provided in this comparative example is similar to that of Example 6, except that:

[0103] In step (2), the amount of hydrophilic fumed silica added is 3776.5 g; the amount of hexamethyldisilazane (HMDS) added is 1359.54 g.

[0104] Comparative Example 3

[0105] The preparation method of the hydrophobic silicon dioxide powder provided in this comparative example is similar to that of Example 4, except that:

[0106] Step (2) is: add 3776.5 g of silica with a specific surface area of ​​400 m 2 / g of hydrophobic fumed silica, 755g of methanol was added to dilute to a solid content of 25%, 1359.54g of hexamethyldisilazane (HMDS) was added and stirred, and the temperature was raised from room temperature to 80°C over 120 minutes, and then heated at 80°C for 120 minutes. The reaction mixture was then spray-dried at a temperature of 150°C to provide hydrophobic silica particles as a dry powder.

[0107] Performance Testing

[0108] The hydrophobicity, carbon content and fluidity of the hydrophobic silica powder prepared in the above examples and comparative examples were tested. The specific methods and results are as follows:

[0109] (1) Hydrophobicity:

[0110] 0.2 g of the sample was weighed with a balance and dispersed in a 500 mL beaker containing 50 mL of pure water. Anhydrous methanol was added dropwise while stirring with a magnetic stirrer. The degree of hydrophobization was calculated from the amount of methanol X (mL) added until the powder sample was completely dispersed.

[0111] Hydrophobicity: X / (X+50)*100;

[0112] Wherein, X: is the volume of anhydrous methanol added; 50: is the volume of pure water added;

[0113] The arithmetic mean of the parallel determination results was taken as the determination result, and the absolute difference of the parallel determination results was no more than 1%.

[0114] (2) Carbon content: tested with a carbon-sulfur analyzer;

[0115] (3) Fluidity: Mix hydrophobic silica and carbon powder in a certain ratio, then pass through a test funnel and measure the flow time to determine the fluidity.

[0116] Table 1

[0117]

[0118]

[0119] It can be seen from Table 1 that the proportion of gas silicon added in the comparative example exceeds the previous constraint of "the amount of gas phase dioxide and silica sol added, according to S 气相二氧化硅 With S 硅溶胶 The ratio of M 溶胶中二氧化硅 / M 气相二氧化硅 The ratio (M refers to mass) must be greater than or equal to S 气相二氧化硅 / 8S 硅溶胶 "If too much fumed silica is added, there will be no abundant grafting space on the surface of silica in the silica sol, causing the fumed silica to exist in a monomer state. Excessive fumed silica monomers will affect the fluidity of the powder.

[0120] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A hydrophobic silicon dioxide powder, characterized in that The hydrophobic silicon dioxide powder is composed of sesame ball bodies composed of spherical silicon dioxide particles, fumed silicon dioxide coated on the surface of the sesame ball bodies, and hydrophobic modified groups on the surface of the fumed silicon dioxide.

2. The hydrophobic silicon dioxide powder according to claim 1, characterized in that The primary particle size of the spherical silica particles is 15nm to 200nm; And / or, the primary particle size of the fumed silica is 3 nm to 10 nm.

3. The hydrophobic silicon dioxide powder according to claim 1, characterized in that The particle size of the hydrophobic silica powder is 1 μm to 10 μm; And / or, the true density of the hydrophobic silica powder is less than 2.2 g / cm 3 .

4. The hydrophobic silicon dioxide powder according to claim 1, characterized in that The hydrophobic modifying group is selected from one or more of a straight-chain alkyl group, a nitrogen-containing straight-chain alkyl group and a cyclic nitrogen-containing alkyl group.

5. The hydrophobic silicon dioxide powder according to claim 1, characterized in that The fumed silica is selected from hydrophilic fumed silica and / or hydrophobic fumed silica.

6. The method for preparing the hydrophobic silicon dioxide powder according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) preparing silica sol; (2) Dispersing fumed silica in silica sol, adding a hydrophobic modifier while stirring, heating and drying to obtain hydrophobic silica powder.

7. The preparation method according to claim 6, characterized in that: In step (2), the mass of silicon dioxide in the silicon dioxide sol / the mass of the fumed silicon dioxide ≥ the specific surface area of ​​the fumed silicon dioxide / 8×the specific surface area of ​​silicon dioxide in the silicon dioxide sol; And / or, the specific surface area of ​​the fumed silica is ≥150m 2 / g.

8. The preparation method according to claim 6, characterized in that: In step (2), the amount of the hydrophobic modifier added is 10% to 100% of the total amount of the fumed silica and the silica sol; And / or, the hydrophobic modifier is selected from one or more of disilazane compounds, monochlorosilane, monoalkoxysilane, monoacyloxysilane and silicone oil.

9. The preparation method according to claim 6, characterized in that: In step (2), the fumed silica is selected from hydrophilic fumed silica and / or hydrophobic fumed silica.

10. Use of the hydrophobic silica powder according to any one of claims 1 to 5 in carbon powder addition, resin composite materials, 3D printing composite materials or metal composite materials.

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