Silicon dioxide aqueous phase dispersion as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of papermaking, and discloses a silicon dioxide aqueous phase dispersion as well as a preparation method and application thereof. The method comprises the following steps: 1) dispersing a silane coupling agent in water, and then adding absolute ethyl alcohol to obtain a silane coupling agent dispersion liquid; 2) adding silicon dioxide powder into the silane coupling agent dispersion liquid, and uniformly mixing to obtain a silicon dioxide water-phase dispersion liquid; and the silane coupling agent is one or more of 3-aminopropyl triethoxy silane, gamma-glycidyl ether oxypropyl methyl diethoxy silane and gamma-methacryloyloxy propyl trimethoxy silane. The invention further discloses a preparation method of the silane coupling agent. The method is simple, the particle size of particles in the prepared silicon dioxide aqueous phase dispersion is smaller, after the silicon dioxide aqueous phase dispersion is used for paper gluing, uniform distribution of gluing particles is better facilitated, the air permeability of paper is more effectively reduced, and the silicon dioxide aqueous phase dispersion has a good reinforcing effect on the paper and is suitable for large-scale industrial application.

Description

Technical Field

[0001] The present invention relates to the technical field of pulp and paper making, and specifically relates to a silica aqueous dispersion, a preparation method thereof and an application thereof. Background Art

[0002] Silica has a special structure, contains a large number of active hydroxyl groups on its surface, has a large specific surface area, and has a small size effect. However, the surface free energy of silica is relatively high, so it is very easy to agglomerate. This characteristic is not conducive to its uniform dispersion in various materials, and may thus have an adverse impact on the structure and properties of the materials, severely limiting its application potential in the field of composite materials. Therefore, it is necessary to perform surface physical or chemical modification on silica so that the groups react with the hydroxyl groups and unsaturated bonds on the silica surface, introducing various required active groups, thereby improving the performance of silica, reducing or eliminating the content of surface silanol groups, and enhancing the compatibility of silica in the aqueous phase.

[0003] Therefore, it is of great significance to develop a silica dispersion with high stability. Summary of the Invention

[0004] In order to overcome the shortcomings and deficiencies of the prior art, the purpose of the present invention is to provide a silica aqueous dispersion, a preparation method thereof and an application thereof.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A preparation method of a silica aqueous dispersion includes the following steps:

[0007] 1) Disperse a silane coupling agent in water, and then add absolute ethanol to obtain a silane coupling agent dispersion;

[0008] 2) Add silica powder to the silane coupling agent dispersion and mix evenly to obtain a silica aqueous dispersion.

[0009] The silane coupling agent is one or more of 3-aminopropyltriethoxysilane (APTES), γ-glycidoxypropylmethyldiethoxysilane, γ-methacryloxypropyltrimethoxysilane, including 3-aminopropyltriethoxysilane (APTES) and γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylmethyldiethoxysilane and γ-methacryloxypropyltrimethoxysilane, 3-aminopropyltriethoxysilane (APTES) and γ-methacryloxypropyltrimethoxysilane, etc.

[0010] The mass ratio of the silica powder to the silane coupling agent is 1:(0.005 - 0.04), preferably 1:(0.005 - 0.03).

[0011] The mass ratio of the silane coupling agent to water is 1:(70 - 600); the mass-volume ratio of the silane coupling agent to ethanol is 1 g:(3 - 16) mL. The dispersion time in step 1) is 3 min - 5 min.

[0012] The dispersion in step 1) is ultrasonic dispersion or stirring dispersion.

[0013] The mixing time in step 2) is 30 min - 40 min. The mixing rotation speed is 8000 - 12000. The mixing device used in step 2) is a tissue pulverizing and dispersing machine.

[0014] A silica aqueous dispersion is prepared by the above preparation method.

[0015] A sizing agent for paper surface contains the above silica aqueous dispersion.

[0016] The sizing agent for paper surface is prepared by compounding the prepared silica aqueous dispersion liquid with the sizing agent and coating it on the paper to obtain the paper with sizing agent on the surface. The proportion of silica content in the dispersion liquid in the compounded sizing agent is (25 - 35)%, and the sizing agent ratio is 10:3.3. The sizing agent is a silicone resin-based release agent.

[0017] The paper is used for preparing medical dialysis paper.

[0018] An application of the silica aqueous dispersion as described above in the field of pulp and paper making.

[0019] The beneficial effects of the present invention are as follows: The silica aqueous dispersion of the present invention has good dispersion stability. The paper coated with it has good air permeability, can be used for medical dialysis paper, and has a good strengthening effect on the paper, which is suitable for large-scale industrial application.

[0020] Specifically:

[0021] The present invention uses silane coupling agents (γ-glycidoxypropylmethyldiethoxysilane, γ-methacryloxypropyltrimethoxysilane) to surface-modify silica, so that the groups react with the hydroxyl groups and unsaturated bonds on the silica surface, introducing various required active groups, thereby improving the performance of silica, reducing or eliminating the content of surface silanol groups on it, and improving the compatibility of silica in the aqueous phase. Compared with the modification by KH550 (3-aminopropyltriethoxysilane (APTES)), the use of two silane coupling agents, γ-glycidoxypropylmethyldiethoxysilane and γ-methacryloxypropyltrimethoxysilane, also achieves good modification effects, exploring the diversity of silica surface modification methods and providing another idea for the preparation and application of silica aqueous dispersion. Detailed Embodiments

[0022] The present invention will be further described in detail below in conjunction with specific embodiments, but the implementation manners of the present invention are not limited thereto.

[0023] Example 1:

[0024] A preparation method of a silica aqueous dispersion comprises the following steps:

[0025] 1) Add 1 g of a silane coupling agent (3-aminopropyltriethoxysilane (APTES)) to 295 mL of deionized water, then add 4 mL of absolute ethanol, and then add it to a magnetic stirrer and run for 5 min to obtain a silane coupling agent dispersion;

[0026] 2) Add 100 g of micron-sized fumed silica powder to the dispersion obtained in step 1), place it in a tissue pulverizing and dispersing machine, and run at 10,000 rpm for 30 min to obtain a silica aqueous dispersion.

[0027] Example 2:

[0028] A preparation method of a silica aqueous dispersion comprises the following steps:

[0029] 1) Add 2 g of a silane coupling agent (3-aminopropyltriethoxysilane (APTES)) to 290 mL of deionized water, then add 8 mL of absolute ethanol, and then add it to a magnetic stirrer and run for 5 min to obtain a silane coupling agent dispersion;

[0030] 2) Add 100 g of micron-sized fumed silica powder to the dispersion obtained in step 1), place it in a tissue pulverizing and dispersing machine, and run at 10,000 rpm for 30 min to obtain a silica aqueous dispersion.

[0031] Example 3:

[0032] A preparation method of a silica aqueous dispersion comprises the following steps:

[0033] 1) Add 3 g of a silane coupling agent (3-aminopropyltriethoxysilane (APTES)) to 285 mL of deionized water, then add 12 mL of absolute ethanol, and then add it to a magnetic stirrer and run for 5 min to obtain a silane coupling agent dispersion;

[0034] 2) Add 100 g of micron-sized fumed silica powder to the dispersion obtained in step 1), place it in a tissue pulverizing and dispersing machine, and run at 10,000 rpm for 30 min to obtain a silica aqueous dispersion.

[0035] Example 4:

[0036] A preparation method of a silica aqueous dispersion comprises the following steps:

[0037] 1) Add 4 g of silane coupling agent (3-aminopropyltriethoxysilane (APTES)) to 280 mL of deionized water, then add 16 mL of absolute ethanol, and then add it to a magnetic stirrer and run for 5 min to obtain a silane coupling agent dispersion;

[0038] 2) Add 100 g of micron-sized fumed silica powder to the dispersion obtained in step 1), place it in a tissue pulverizer and disperser, and run at 10000 rpm for 30 min to obtain a silica aqueous dispersion.

[0039] Example 5:

[0040] A method for preparing a silica aqueous dispersion, comprising the following steps:

[0041] 1) Add 0.5 g of silane coupling agent (γ-glycidoxypropylmethyldiethoxysilane) to 297.5 mL of deionized water, then add 2 mL of absolute ethanol, and then add it to a magnetic stirrer and run for 5 min to obtain a silane coupling agent dispersion;

[0042] 2) Add 100 g of micron-sized fumed silica powder to the dispersion obtained in step 1), place it in a tissue pulverizer and disperser, and run at 10000 rpm for 30 min to obtain a silica aqueous dispersion.

[0043] Example 6:

[0044] A method for preparing a silica aqueous dispersion, comprising the following steps:

[0045] 1) Add 1 g of silane coupling agent (γ-glycidoxypropylmethyldiethoxysilane) to 295 mL of deionized water, then add 4 mL of absolute ethanol, and then add it to a magnetic stirrer and run for 5 min to obtain a silane coupling agent dispersion;

[0046] 2) Add 100 g of micron-sized fumed silica powder to the dispersion obtained in step 1), place it in a tissue pulverizer and disperser, and run at 10000 rpm for 30 min to obtain a silica aqueous dispersion.

[0047] Example 7:

[0048] A method for preparing a silica aqueous dispersion, comprising the following steps:

[0049] 1) Add 1.5 g of silane coupling agent (γ-glycidoxypropylmethyldiethoxysilane) to 292.5 mL of deionized water, then add 6 mL of absolute ethanol, and then add it to a magnetic stirrer and run for 5 min to obtain a silane coupling agent dispersion;

[0050] 2) Add 100 g of micron-sized fumed silica powder to the dispersion obtained in step 1, place it in a tissue grinder and disperser, and run it at 10,000 rpm for 30 min to obtain a silica aqueous dispersion.

[0051] Example 8:

[0052] A method for preparing a silica aqueous dispersion, comprising the following steps:

[0053] 1) Add 2 g of a silane coupling agent (γ-glycidoxypropylmethyldiethoxysilane) to 290 mL of deionized water, then add 8 mL of absolute ethanol, and then add it to a magnetic stirrer and run for 5 min to obtain a silane coupling agent dispersion;

[0054] 2) Add 100 g of micron-sized fumed silica powder to the dispersion obtained in step 1), place it in a tissue grinder and disperser, and run it at 10,000 rpm for 30 min to obtain a silica aqueous dispersion.

[0055] Example 9:

[0056] A method for preparing a silica aqueous dispersion, comprising the following steps:

[0057] 1) Add 0.5 g of a silane coupling agent (γ-methacryloxypropyltrimethoxysilane) to 290 mL of deionized water, then add 8 mL of absolute ethanol, and then add it to a magnetic stirrer and run for 5 min to obtain a silane coupling agent dispersion;

[0058] 2) Add 100 g of micron-sized fumed silica powder to the dispersion obtained in step 1), place it in a tissue grinder and disperser, and run it at 10,000 rpm for 30 min to obtain a silica aqueous dispersion.

[0059] Example 10:

[0060] A method for preparing a silica aqueous dispersion, comprising the following steps:

[0061] 1) Add 1 g of a silane coupling agent (γ-methacryloxypropyltrimethoxysilane) to 290 mL of deionized water, then add 8 mL of absolute ethanol, and then add it to a magnetic stirrer and run for 5 min to obtain a silane coupling agent dispersion;

[0062] 2) Add 100 g of micron-sized fumed silica powder to the dispersion obtained in step 1), place it in a tissue grinder and disperser, and run it at 10,000 rpm for 30 min to obtain a silica aqueous dispersion.

[0063] Example 11:

[0064] A preparation method of a silica aqueous dispersion, comprising the following steps:

[0065] 1) Add 1.5 g of a silane coupling agent (γ-methacryloxypropyltrimethoxysilane) to 290 mL of deionized water, then add 8 mL of absolute ethanol, and then add it to a magnetic stirrer and run for 5 min to obtain a silane coupling agent dispersion;

[0066] 2) Add 100 g of micron-sized fumed silica powder to the dispersion obtained in step 1), place it in a tissue pulverizing and dispersing machine, and run at 10000 rpm for 30 min to obtain a silica aqueous dispersion.

[0067] Example 12:

[0068] A preparation method of a silica aqueous dispersion, comprising the following steps:

[0069] 1) Add 2 g of a silane coupling agent (γ-methacryloxypropyltrimethoxysilane) to 290 mL of deionized water, then add 8 mL of absolute ethanol, and then add it to a magnetic stirrer and run for 5 min to obtain a silane coupling agent dispersion;

[0070] 2) Add 100 g of micron-sized fumed silica powder to the dispersion obtained in step 1), place it in a tissue pulverizing and dispersing machine, and run at 10000 rpm for 30 min to obtain a silica aqueous dispersion.

[0071] Performance test:

[0072] The performance test results of the silica aqueous dispersions of Examples 1 to 4 and 5 to 12 are shown in Tables 1 and 2.

[0073] Table 1 Performance test results of the silica aqueous dispersions of Examples 1 to 4

[0074]

[0075] Table 2 Performance test results of the silica aqueous dispersions of Examples 5 to 12

[0076]

[0077] Note:

[0078] Volume average diameter: Take a small amount of the prepared silica aqueous dispersion, place it in an oven, dry it into powder, take a certain amount of the powder to prepare a 3% solution in a test tube, ultrasonically treat it for 10 min, and use a laser particle size analyzer to detect the particle size and light shielding rate of the modified silica.

[0079] Paper air permeability: Cut a white paper of 14.8 cm × 22 cm, dry it in an oven at 85 °C, use an air permeability tester to detect the air permeability of the paper's glue side and printing side respectively. Then, respectively compound the prepared silica aqueous dispersion with the release glue and the surface glue, coat the release glue and the surface glue on the 14.8 cm × 22 cm white paper in sequence, dry in the air for 5 min, and then dry it in an oven at 85 °C. After drying, use the air permeability tester to detect the air permeability of both sides of the paper again.

[0080] Tensile strength: Refer to "GB / T 453 Determination of Tensile Strength of Paper and Board (Constant Rate of Loading Method)" to test the tensile strength of the sample paper, and convert the tensile strength into the tensile index.

[0081] Smoothness: Refer to "GB / T 456-2002 Determination of Smoothness of Paper and Board" to test the smoothness of the sample paper.

[0082] Blank control: Silica without modification or paper coated with unmodified silica compound.

[0083] As can be seen from Tables 1 and 2:

[0084] 1) The volume average diameter of the modified silica prepared in Examples 1-4 is 20.02 um - 26.65 um, which is significantly lower than the volume average diameter of 30.09 um of the unmodified silica. KH550 (3-aminopropyltriethoxysilane (APTES)) used in Examples 1-4 is used to modify silica, and the average particle size of the prepared modified silica aqueous dispersion decreases. When the dosage of the silane coupling agent increases, it has a certain effect on reducing the particle size of silica, which is beneficial to the dispersion of silica in water.

[0085] 2) The volume average diameter of the modified silica prepared in Examples 5-12 is 25.20 um - 28.83 um, which is significantly lower than the volume average diameter of 30.09 um of the unmodified silica. Two silane coupling agents (γ-glycidoxypropylmethyldiethoxysilane, γ-methacryloxypropyltrimethoxysilane) used in Examples 5-12 are used to modify silica. When the dosage of the silane coupling agent increases, it has a certain effect on reducing the particle size of silica, which is beneficial to the dispersion of silica in water.

[0086] 3) After coating with the silica aqueous dispersion prepared in Examples 1-4, the air permeability of the paper decreases. Among them, the decrease value of the air permeability of the glue side of the paper is 190 ml·min-1 - 203 ml·min-1, and the decrease value of the air permeability of the printing side is 182 ml·min-1 - 200 ml·min-1. The decrease values of the air permeability are all higher than those of the blank control paper.

[0087] 4) After coating with the silica aqueous dispersion prepared in Examples 5-12, the air permeability of the paper decreased. Among them, the decrease in air permeability of the sizing surface of the paper was 178 ml·min-1 to 201 ml·min-1, and the decrease in air permeability of the printing surface was 176 ml·min-1 to 199 ml·min-1. The decrease in air permeability was higher than that of the blank control paper. This indicates that the fine particles of the modified silica dispersion are more evenly distributed, effectively reducing the porosity of the paper.

[0088] 5) The tensile strength of the paper after coating with the silica aqueous dispersion prepared in Examples 5-12 was 81.52 to 91.72 ml·min -1 which was significantly higher than 60.54 ml·min of the unmodified coated paper -1 , indicating that coating with the silica aqueous dispersion prepared in Examples 5-12 has a good strengthening effect on the paper.

[0089] 6) The smoothness of the paper after coating with the silica aqueous dispersion prepared in Examples 5-12 was 6.1 to 6.5 s, lower than 7.2 s of the blank control paper. This shows that after coating with the silica aqueous dispersion prepared in Examples 5-12, the paper surface is smoother, reducing fiber burrs and the risk of particle shedding.

[0090] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A method for preparing an aqueous dispersion of silica, characterized in that: It includes the following steps: 1) Disperse the silane coupling agent in water, and then add absolute ethanol to obtain a silane coupling agent dispersion; 2) Add the silicon dioxide powder into the silane coupling agent dispersion and mix evenly to obtain a silicon dioxide aqueous dispersion; The silane coupling agent is one or more of 3-aminopropyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and γ-methacryloxypropyltrimethoxysilane; The mass ratio of the silicon dioxide powder to the silane coupling agent is 1:(0.005 - 0.04).

2. The preparation method of the silica aqueous dispersion according to claim 1, characterized in that: The silane coupling agent is one or more of γ-glycidoxypropylmethyldiethoxysilane and γ-methacryloxypropyltrimethoxysilane.

3. The method for preparing the silicon dioxide aqueous dispersion according to claim 1, wherein: The mass ratio of the silane coupling agent to water is 1:(70 - 600); the mass-volume ratio of the silane coupling agent to ethanol is 1 g:(3 - 16) mL.

4. The preparation method of the silica aqueous dispersion according to claim 1, wherein: The dispersion time in step 1) is 3 min to 5 min; The dispersion in step 1) is ultrasonic dispersion or stirring dispersion; The mixing time in step 2) is 30 min to 40 min; the mixing speed is 8000 - 12000.

5. A silicon dioxide aqueous dispersion obtained by the preparation method according to any one of claims 1 to 4.

6. Use of the silica aqueous dispersion according to claim 5, characterized in that: The silicon dioxide aqueous dispersion is used for preparing paper with sizing on the surface.

7. A piece of paper with glue applied on its surface, characterized in that: It is to compound the silicon dioxide aqueous dispersion obtained by the preparation method according to any one of claims 1 to 4 with sizing, coat it on the paper to obtain paper with sizing on the surface.

8. The paper with glue coating on the surface according to claim 7, characterized in that: After compounding, the mass percentage of silicon dioxide in the dispersion in the sizing is (25 - 35)%; the sizing is a silicone-based release agent.

9. The application of the paper with glue coating on the surface according to claim 7, characterized in that: The paper is used for preparing medical dialysis paper.

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