Silicon dioxide slurry for paper coating, preparation method of silicon dioxide slurry and coating paint

Abstract

The invention belongs to the technical field of preparation of slurry, and provides silicon dioxide slurry for paper coating, a preparation method of the silicon dioxide slurry and coating paint. The preparation method comprises the following steps: mixing quartz sand with a grinding aid, and carrying out dry grinding to obtain powder; mixing the powder, a wet grinding aid and water, and sequentially performing wet grinding and wet grading to obtain silicon dioxide slurry for paper coating; wherein the particle size of particles in the silicon dioxide slurry for paper coating is 0.1-45 [mu] m. According to the method, two grinding processes of dry grinding and wet grinding are combined, so that the service life of grinding equipment is prolonged, the dreg content in the silicon dioxide slurry is reduced, ultrafine grinding of silicon dioxide is realized, and the silicon dioxide with fine granularity, uniform particle size distribution and uniform particle size distribution is obtained. The silicon dioxide slurry has good dispersity and stability and can be suitable for paper coating.

Description

Technical Field

[0001] The invention relates to the technical field of slurry preparation, and in particular to a silicon dioxide slurry for paper coating, a preparation method thereof, and a coating paint. Background Art

[0002] As an important component of the earth's crust, silicon dioxide is widely distributed in nature, mainly in the form of amorphous silicon dioxide and crystalline silicon dioxide. Among them, the most common quartz is crystalline silicon dioxide, which is divided into three types: quartz, tridymite and cristobalite due to different crystal structures. Pure quartz appears as colorless crystals, while those large, transparent, prismatic quartz are called crystals, which are widely used in the decoration industry. Ordinary sand is a tiny quartz crystal, and its contribution to the field of human building materials is huge. When the sand is further ultra-fine and functionalized, it becomes an industrial raw material with multifunctional characteristics, which has a wide range of uses and covers many industries. Taking the refractory industry as an example, the application effect of silicon dioxide powder is significant. It can effectively reduce the water consumption of castables, improve the interaction between particles, and then reduce the viscosity of the material and improve its fluidity. In a high temperature environment, silicon dioxide powder will transform into a liquid phase, promote mass transfer and sintering process between particles, and significantly enhance the high temperature strength and thermal vibration resistance of refractory materials. In the semiconductor industry, silica slurry also plays an important role. It can be used in process links such as surface polishing, grinding and coating of semiconductor materials to achieve extremely high flatness and finish. In addition, in the electronics and semiconductor industries, spherical silica powder is widely used in the field of large-scale integrated circuit packaging due to its excellent physical and chemical properties. Not only that, spherical silica powder also shows great application potential in fields such as aviation, aerospace, and fine chemicals that have extremely high requirements for material performance.

[0003] In the papermaking industry, the application of silica materials is currently relatively limited. Its application form is mainly silica colloid, and most of it is concentrated in the wet end of papermaking. In this process, silica colloid can effectively improve the operating performance of high-speed paper machines and increase the retention rate of fillers. When silica powder is used in papermaking coatings, silica needs to be ultra-fine, but silica itself has high hardness. During the mechanical grinding process, it is more difficult to grind than other inorganic non-metallic minerals, and the degree of damage to the equipment is also greater. It will not only seriously shorten the service life of the equipment, but also introduce more slag into the product, making it impossible to use it in papermaking coatings.

[0004] Therefore, it is of great significance to develop a silica slurry for paper coating and a preparation method thereof that can reduce equipment wear and slag content. Summary of the invention

[0005] In view of this, the present invention provides a silica slurry for paper coating, a preparation method thereof and a coating coating to solve the problems that the existing grinding method is difficult to achieve ultrafine grinding of silica, causes great damage to the grinding equipment, and cannot prepare silica slurry suitable for paper coating.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] The present invention provides a method for preparing a silicon dioxide slurry for paper coating, comprising the following steps:

[0008] 1) Mixing quartz sand and a grinding aid, and performing dry grinding to obtain a powder;

[0009] 2) mixing the powder, the wet grinding aid and water, and sequentially performing wet grinding and wet classification to obtain a silica slurry for paper coating;

[0010] Wherein, the particle size of the particles in the silicon dioxide slurry for paper coating is 0.1 to 45 μm.

[0011] Preferably, the content of silicon dioxide in the quartz sand in step 1) is ≥99%, and the particle size is 150-200 mesh; the grinding aid is prepared from ethylene glycol, triethanolamine and titanate coupling agent.

[0012] Preferably, the mass ratio of the quartz sand to the grinding aid is 1:0.007-0.011; the mass ratio of the ethylene glycol, triethanolamine and titanate coupling agent is 1-2:1-2:2; and the particle size D50 of the powder is 9-10 μm.

[0013] Preferably, the dry grinding in step 1) is dry grinding by a horizontal ball mill; the grinding medium of the dry grinding is zirconia balls; the rotation speed of the horizontal ball mill is 26 to 31 r / min; the total addition amount of the grinding medium and quartz sand is 50 to 60% of the volume of the cylinder in the horizontal ball mill; the mass ratio of the grinding medium to quartz sand is 1:2 to 3.

[0014] Preferably, the wet grinding in step 2) is specifically as follows: firstly, the powder, part of the wet grinding aid and water are mixed to obtain a slurry, and then the slurry is wet-grinded while adding the remaining wet grinding aid; the mass ratio of the part of the wet grinding aid to the remaining wet grinding aid is 1:1.

[0015] Preferably, the mass ratio of the powder to the wet grinding aid is 1:0.007-0.011; and the solid content of the slurry is 65-73%.

[0016] Preferably, the wet grinding aid in step 2) is prepared from EP-44 water-based epoxy emulsion and a polymer; the mass ratio of the EP-44 water-based epoxy emulsion to the polymer is 0.8-1.2:1; and the polymer is sodium polyacrylate or polyethylene glycol.

[0017] Preferably, in the slurry after wet grinding in step 2), the content of particles with a particle size of ≤2 μm is ≥65%, and the content of particles with a particle size of ≤45 μm is 100%.

[0018] Preferably, the wet grinding in step 2) is performed by a vertical wet stirring ball mill; the power of the vertical wet stirring ball mill is 240-260kw.

[0019] Preferably, the wet classification in step 2) is performed by a hydrocyclone; the feed pressure of the hydrocyclone is 0.2-0.4 MPa.

[0020] The present invention also provides a silicon dioxide slurry for paper coating prepared by the method for preparing the silicon dioxide slurry for paper coating.

[0021] The present invention also provides a coating material, comprising the following components in percentage by mass:

[0022] 90-92% of silicon dioxide slurry for paper coating, 7.8-9.5% of Dow styrene-butadiene latex and 0.2-0.5% of sodium carboxymethyl cellulose; the silicon dioxide slurry for paper coating is the above-mentioned silicon dioxide slurry for paper coating.

[0023] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

[0024] The method for preparing the silica slurry for paper coating of the present invention combines the two grinding processes of dry grinding and wet grinding, prolongs the service life of the grinding equipment and reduces the slag content of the silica slurry product, and also realizes the ultra-fine grinding of silica to obtain the silica slurry suitable for paper coating. At the same time, the silica slurry prepared by the method of the present invention has fine particle size, uniform particle size distribution, good dispersibility and stability, and can improve the smoothness, glossiness and printability of the coated paper. DETAILED DESCRIPTION

[0025] The present invention provides a method for preparing a silicon dioxide slurry for paper coating, comprising the following steps:

[0026] 1) Mixing quartz sand and a grinding aid, and performing dry grinding to obtain a powder;

[0027] 2) mixing the powder, the wet grinding aid and water, and sequentially performing wet grinding and wet classification to obtain a silica slurry for paper coating;

[0028] The particle size of the particles in the silica slurry for paper coating is 0.1 to 45 μm, preferably 0.11 to 43 μm, more preferably 0.12 to 42 μm, and even more preferably 0.13 to 40 μm.

[0029] In the present invention, the content of silicon dioxide in the quartz sand in step 1) is ≥99%, and the particle size is 150-200 mesh, preferably 160-180 mesh, and more preferably 170 mesh; the grinding aid includes one or more of ethylene glycol, triethanolamine and titanate coupling agent.

[0030] In the present invention, the mass ratio of the quartz sand to the grinding aid is 1:0.007-0.011, preferably 1:0.0075-0.010, more preferably 1:0.008-0.0095, and more preferably 1:0.0085-0.009.

[0031] In the present invention, after obtaining the powder in step 1), a classification operation is also included; the classification operation is specifically to classify the powder using a classifier; the particle size D50 of the classified powder is 9 to 10 μm, preferably 9.2 to 9.8 μm, more preferably 9.3 to 9.6 μm, and more preferably 9.5 μm.

[0032] In the present invention, the rotation speed of the classifier is preferably 1200 to 1700 r / min, more preferably 1300 to 1600 r / min, and even more preferably 1500 r / min.

[0033] In the present invention, the grinding aid is prepared from ethylene glycol, triethanolamine and titanate coupling agent; the mass ratio of ethylene glycol, triethanolamine and titanate coupling agent is 1-2:1-2:2, preferably 1.2-1.8:1.2-1.8:2, further preferably 1.3-1.6:1.3-1.6:2, and more preferably 1.5:1.5:2.

[0034] In the present invention, the dry grinding in step 1) is dry grinding by a horizontal ball mill; the inner lining of the horizontal ball mill is ceramic; the grinding medium of the dry grinding is a zirconia ball; the rotation speed of the horizontal ball mill is 26-31 r / min, preferably 27-30 r / min, and more preferably 28-29 r / min; the total addition amount of the grinding medium and quartz sand is 50-60% of the volume of the cylinder in the horizontal ball mill, preferably 52-58%, further preferably 53-57%, and more preferably 55%; the mass ratio of the grinding medium to quartz sand is 1:2-3, preferably 1:2.2-2.8, further preferably 1:2.3-2.6, and more preferably 1:2.5.

[0035] In the present invention, the wet grinding in step 2) is specifically as follows: firstly, the powder, part of the wet grinding aid and water are mixed to obtain a slurry, and then the slurry is wet-grinded while adding the remaining wet grinding aid; the mass ratio of the part of the wet grinding aid to the remaining wet grinding aid is 1:1.

[0036] In the present invention, the mixing in step 2) is preferably: the powder obtained in step 1) is transported to a powder storage tank through an induced draft pipe, and then the powder in the powder storage tank, water and a part of the wet grinding aid are added to a slurry storage tank at the same time, and the slurry is prepared by stirring while adding the materials; wherein the discharge port of the powder storage tank is connected to the feed port of the slurry storage tank, and the slurry storage tank is also provided with a water inlet and an additive addition port.

[0037] In the present invention, the mass ratio of the powder to the wet grinding aid (the total amount of part of the wet grinding aid and the remaining wet grinding aid) is 1:0.007-0.011, preferably 1:0.0075-0.010, further preferably 1:0.008-0.0095, and more preferably 1:0.0085-0.009; the solid content of the slurry is 65-73%, preferably 68-72%, and more preferably 70%.

[0038] In the present invention, the wet grinding aid in step 2) is prepared from EP-44 water-based epoxy emulsion and a polymer; the mass ratio of the EP-44 water-based epoxy emulsion to the polymer is 0.8 to 1.2:1, preferably 0.9 to 1.1:1, and more preferably 1:1; the polymer is sodium polyacrylate or polyethylene glycol.

[0039] In the present invention, the wet grinding in step 2) is wet grinding by a vertical wet stirred ball mill; the model of the vertical wet stirred ball mill is preferably LJM-3600, and the cylinder volume is preferably 3600L; the lining of the vertical wet stirred ball mill is ceramic; the power of the vertical wet stirred ball mill is 240-260kw, preferably 242-258kw, further preferably 245-255kw, and more preferably 250kw.

[0040] In the present invention, the wet grinding in step 2) is preferably: the slurry in the slurry storage tank is transported to a vertical wet stirred ball mill for wet grinding, and then the remaining wet grinding aid is added to continue wet grinding; wherein the discharge port of the slurry storage tank is connected to the feed port of the vertical wet stirred ball mill; the remaining wet grinding aid is added within 2 minutes; the time for adding the remaining wet grinding aid is preferably after 20 to 25 minutes of wet grinding, more preferably after 22 to 24 minutes, and more preferably after 23 minutes.

[0041] In the present invention, the slurry obtained after the wet grinding preferably overflows from the upper discharge port of the vertical wet stirring ball mill, and the overflowed slurry is vibrated and sieved to remove coarse particles, and then collected in a slurry storage barrel.

[0042] In the present invention, the content of particles with a particle size of ≤2 μm in the slurry after wet grinding in step 2) is ≥65%, preferably 66-67%, and more preferably 68%; the content of particles with a particle size of ≤45 μm in the slurry after wet grinding is 100%.

[0043] In the present invention, the wet classification in step 2) is wet classification by a hydrocyclone; the inner lining of the hydrocyclone is ceramic; the feed pressure of the hydrocyclone is 0.2-0.4Mpa, preferably 0.25-0.38Mpa, further preferably 0.28-0.35Mpa, and more preferably 0.3Mpa.

[0044] In the present invention, the wet classification in step 2) is preferably: the slurry collected in the slurry storage barrel after wet grinding is conveyed to a hydrocyclone for wet classification; wherein, the hydrocyclone makes particles of different particle sizes in the slurry concentrated in different areas, and the slurry enters the feed port of the hydrocyclone tangentially, and by controlling the feed pressure, the slurry forms an inner and outer double spiral flow under the action of centrifugal force, and particles with a particle size less than 0.1 μm flow out from the overflow port along the inner spiral, and particles with a particle size greater than 0.1 μm are discharged from the underflow port along the outer spiral and stored in the finished slurry tank for preparing coating.

[0045] The present invention also provides a silicon dioxide slurry for paper coating prepared by the method for preparing the silicon dioxide slurry for paper coating.

[0046] The present invention also provides a coating material, comprising the following components in percentage by mass:

[0047] 90-92% of silicon dioxide slurry for paper coating, 7.8-9.5% of Dow styrene-butadiene latex and 0.2-0.5% of sodium carboxymethyl cellulose; the silicon dioxide slurry for paper coating is the above-mentioned silicon dioxide slurry for paper coating.

[0048] In the present invention, the silica slurry for paper coating is preferably 90.5-91.8%, more preferably 91.5%; the Dow styrene-butadiene latex is preferably 7.9-9.0%, more preferably 8%; the sodium carboxymethyl cellulose is preferably 0.25-0.4%, more preferably 0.3%.

[0049] In the present invention, the sodium carboxymethyl cellulose is a dispersant.

[0050] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0051] Example 1

[0052] 1. Select 150 mesh quartz sand with a silica content of 99.5% as raw material, transport it to a ceramic-lined horizontal ball mill, add zirconium oxide balls as grinding media, and a solvent prepared by ethylene glycol, triethanolamine and titanate coupling agent in a mass ratio of 1:1:1 as a grinding aid, and then control the speed of the horizontal ball mill to be 30r / min for dry grinding; wherein, the total volume of the zirconium oxide balls and the quartz sand accounts for 50% of the volume of the entire horizontal ball mill cavity, the mass ratio of the zirconium oxide balls and the quartz sand is 1:2, and the mass ratio of the quartz sand to the grinding aid is 1:0.008; then add the powder obtained by dry grinding into a classifier, and classify it at a speed of 1500r / min to obtain a powder with a particle size D50 of 9.5μm.

[0053] 2. Prepare wet grinding aid by mixing EP-44 water-based epoxy emulsion and sodium polyacrylate in a mass ratio of 1:1 for standby use; then transport the powder obtained in step 1 to a powder storage tank through an induced draft pipe, and then add the powder, water and part of the wet grinding aid in the powder storage tank to the slurry storage tank through the feed inlet, the water inlet and the additive addition port, respectively, while adding and stirring to prepare a slurry with a solid content of 70%; then transport the slurry with a solid content of 70% to a vertical wet stirring ball mill lined with ceramic (model LJM -3600, the cylinder volume is preferably 3600L) for wet grinding, and the remaining wet grinding aid is added after 23 minutes of wet grinding, and the remaining wet grinding aid is controlled to be added within 2 minutes, and the power of the vertical wet stirring ball mill is controlled to be 250kw for wet grinding, and then the slurry overflowing from the discharge port of the vertical wet stirring ball mill is collected and vibrated, sieved (sieve mesh number is 325 mesh) to remove coarse particles, and stored in a slurry storage barrel to obtain a slurry with a particle size of 2μm and a content of 66%. Among them, the mass ratio of the powder to the total wet grinding aid is 1:0.01, and the mass ratio of the part of the wet grinding aid added when preparing the slurry to the remaining wet grinding aid added during the wet grinding process is 1:1.

[0054] 3. The slurry prepared in step 2 is conveyed to a ceramic-lined hydrocyclone at a feed pressure of 0.3 MPa for wet classification, and ultrafine powder less than 0.1 μm is separated and removed to obtain a silicon dioxide slurry 1 with a narrow particle size distribution.

[0055] Example 2

[0056] 1. Select 200 mesh quartz sand with a silica content of 99.5% as raw material, transport it to a ceramic-lined horizontal ball mill, add zirconium oxide balls as grinding media, and a solvent prepared by ethylene glycol, triethanolamine and titanate coupling agent in a mass ratio of 0.7:0.7:1 as a grinding aid, then control the speed of the horizontal ball mill to be 30r / min for dry grinding; wherein, the total volume of the zirconium oxide balls and the quartz sand accounts for 50% of the volume of the entire horizontal ball mill cavity, the mass ratio of the zirconium oxide balls to the quartz sand is 1:2.5, and the mass ratio of the quartz sand to the grinding aid is 1:0.01; then add the powder obtained by dry grinding into a classifier, and classify it at a speed of 1550r / min to obtain a powder with a particle size D50 of 9.5μm.

[0057] 2. Prepare wet grinding aid by mixing EP-44 water-based epoxy emulsion and polyethylene glycol in a mass ratio of 1:1 for standby use; then transport the powder obtained in step 1 to the powder storage tank through the induced draft pipe, and then add the powder, water and part of the wet grinding aid in the powder storage tank to the slurry storage tank through the feed inlet, the water inlet and the additive addition port, respectively, and stir while adding to prepare a slurry with a solid content of 70%; then transport the slurry with a solid content of 70% to a vertical wet stirred ball mill lined with ceramic (model LJM- 3600, the cylinder volume is preferably 3600L) for wet grinding, and the remaining wet grinding aid is added after 25 minutes of wet grinding, and the remaining wet grinding aid is controlled to be added within 2 minutes. At the same time, the power of the vertical wet stirring ball mill is controlled to be 260kw for wet grinding, and then the slurry overflowing from the discharge port of the vertical wet stirring ball mill is collected and vibrated, sieved (sieve mesh number is 325 mesh) to remove coarse particles, and stored in a slurry storage barrel to obtain a slurry with a particle size of 2μm and a content of 68%. Among them, the mass ratio of the powder to the total wet grinding aid is 1:0.01, and the mass ratio of the part of the wet grinding aid added when preparing the slurry to the remaining wet grinding aid added during the wet grinding process is 1:1.

[0058] 3. The slurry prepared in step 2 is conveyed to a ceramic-lined hydrocyclone at a feed pressure of 0.3 MPa for wet classification, and ultrafine powder less than 0.1 μm is separated and removed to obtain silica slurry 2 with a narrow particle size distribution.

[0059] Comparative Example 1

[0060] 1. Select 200 mesh quartz sand with a silica content of 99.4% as raw material, transport it to a ceramic-lined horizontal ball mill, add zirconium oxide balls as grinding media, and a solvent prepared by ethylene glycol, triethanolamine and titanate coupling agent in a mass ratio of 1:1:1 as a grinding aid, and then control the speed of the horizontal ball mill to 28r / min for dry grinding; wherein, the total volume of the zirconium oxide balls and the quartz sand accounts for 50% of the volume of the entire horizontal ball mill cavity, the mass ratio of the zirconium oxide balls and the quartz sand is 1:2, and the mass ratio of the quartz sand to the grinding aid is 1:0.008; then add the powder obtained by dry grinding into a classifier, and classify it at a speed of 1500r / min to obtain a powder with a particle size D50 of 10μm.

[0061] 2. Polyethylene glycol is selected as a wet grinding aid, and the powder obtained in step 1 is conveyed to a powder storage tank through an induced draft pipe, and then the powder, water and part of the wet grinding aid in the powder storage tank are added to the slurry storage tank through the feed inlet, the water inlet and the additive addition port, respectively, and stirred while adding to prepare a slurry with a solid content of 70%; then the slurry with a solid content of 70% is conveyed to a vertical wet stirred ball mill lined with ceramic (model LJM-3600, the cylinder volume is preferably 360 0L), and the remaining wet grinding aid was added after 23 minutes of wet grinding, and the remaining wet grinding aid was controlled to be added within 2 minutes. At the same time, the power of the vertical wet stirring ball mill was controlled to be 250kw for wet grinding, and then the slurry overflowing from the discharge port of the vertical wet stirring ball mill was collected and vibrated, sieved (sieve mesh number was 325 meshes) to remove coarse particles, and stored in a slurry storage barrel to obtain a silicon dioxide slurry 3 with a particle size of 2μm and a content of 66%. Among them, the mass ratio of the powder to the total wet grinding aid is 1:0.01, and the mass ratio of the part of the wet grinding aid added when preparing the slurry to the remaining wet grinding aid added during the wet grinding process is 1:1.

[0062] Comparative Example 2

[0063] 1. Select 200 mesh quartz sand with a silica content of 99.4% as raw material, transport it to a ceramic-lined horizontal ball mill, add zirconium oxide balls as grinding media, and a solvent prepared by ethylene glycol, triethanolamine and titanate coupling agent in a mass ratio of 1:1:1 as a grinding aid, and then control the speed of the horizontal ball mill to be 28r / min for dry grinding; wherein, the total volume of the zirconium oxide balls and the quartz sand accounts for 50% of the volume of the entire horizontal ball mill cavity, the mass ratio of the zirconium oxide balls to the quartz sand is 1:2.5, and the mass ratio of the quartz sand to the grinding aid is 1:0.008; then add the powder obtained by dry grinding into a classifier, and classify it at a speed of 1600r / min to obtain a powder with a particle size D50 of 10μm.

[0064] 2. Prepare wet grinding aid by mixing EP-44 water-based epoxy emulsion and sodium polyacrylate in a mass ratio of 1:1 for standby use; then transport the powder obtained in step 1 to a powder storage tank through an induced draft pipe, and then add the powder, water and part of the wet grinding aid in the powder storage tank to the slurry storage tank through the feed inlet, the water inlet and the additive addition port, respectively, while adding and stirring to prepare a slurry with a solid content of 70%; then transport the slurry with a solid content of 70% to a vertical wet stirring ball mill lined with ceramic (model LJM-36 00, the cylinder volume is preferably 3600L) for wet grinding, and the remaining wet grinding aid is added after 23 minutes of wet grinding, and the remaining wet grinding aid is controlled to be added within 2 minutes. At the same time, the power of the vertical wet stirring ball mill is controlled to be 250kw for wet grinding, and then the slurry overflowing from the discharge port of the vertical wet stirring ball mill is collected and vibrated, sieved (sieve mesh number is 325 mesh) to remove coarse particles, and stored in a slurry storage barrel to obtain a silicon dioxide slurry 4 with a particle size of 2μm and a content of 66%. Among them, the mass ratio of the powder to the total wet grinding aid is 1:0.01, and the mass ratio of the part of the wet grinding aid added when preparing the slurry to the remaining wet grinding aid added during the wet grinding process is 1:1.

[0065] The viscosity and zate potential of the silicon dioxide slurries prepared in Examples 1 to 2 and Comparative Examples 1 to 2 were tested according to the testing standards of GB / T9269-1988 and GB / T24993-2010, respectively.

[0066] In addition, the silica slurries prepared in Examples 1-2 and Comparative Examples 1-2 were mixed and prepared into coatings according to the following coating formula: 91.5% silica slurry, 8% Dow styrene butadiene latex, and 0.5% sodium carboxymethyl cellulose. Then, the above four coatings were respectively used to prepare coated paper by air knife coating. The smoothness and glossiness of the four coated papers were tested according to the test standards of GB / T456-2002 and GB / T 8941-2007. The test results are shown in Table 1.

[0067] Table 1

[0068] Test items Example 1 Example 2 Comparative Example 1 Comparative Example 2 Viscosity / mPa.s 172.3 173.4 203.5 189.6 zate potential / mv -42 -40 -33 -39 Paper smoothness / S 87 86 73 76 Glossiness of paper / % 12 12 10 11

[0069] As can be seen from Table 1, the silica slurry in Examples 1 to 2 has a lower viscosity due to wet classification and the use of composite grinding aids, which can be more convenient for coating construction, reduce the construction difficulty, and improve the efficiency and quality of coating. At the same time, the zate potential of the silica slurry prepared by the method described in the present invention is electronegative. For the slurry, the more negative the potential, the better the dispersibility of the slurry. Therefore, the silica slurry in Examples 1 to 2 of the present invention has better dispersibility and can maintain a stable dispersion state. In addition, it can be seen from the above data that the paper coated with the silica slurry of Examples 1 to 2 has better smoothness and glossiness than Comparative Examples 1 to 2. This is mainly because the silica slurry prepared by the method described in the present invention has a finer particle size, a more uniform particle size distribution, and better dispersibility and stability, thereby significantly improving the smoothness and glossiness of the coated paper. In summary, the silica slurry prepared by the method of the present invention is more suitable for paper coating, which solves the problem that the existing grinding method is difficult to achieve ultrafine grinding of silica, causes great damage to the grinding equipment, and cannot prepare silica slurry suitable for paper coating.

[0070] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a silicon dioxide slurry for paper coating, characterized in that: The steps include: 1) Mixing quartz sand and a grinding aid, and performing dry grinding to obtain a powder; 2) mixing the powder, the wet grinding aid and water, and sequentially performing wet grinding and wet classification to obtain a silica slurry for paper coating; Wherein, the particle size of the particles in the silicon dioxide slurry for paper coating is 0.1 to 45 μm.

2. The method for preparing a silicon dioxide slurry for paper coating according to claim 1, characterized in that: The content of silicon dioxide in the quartz sand in step 1) is ≥99%, and the particle size is 150-200 mesh; The grinding aid is prepared from ethylene glycol, triethanolamine and a titanate coupling agent.

3. The method for preparing a silicon dioxide slurry for paper coating according to claim 2, characterized in that: The mass ratio of the quartz sand to the grinding aid is 1:0.007-0.011; The mass ratio of ethylene glycol, triethanolamine and titanate coupling agent is 1-2:1-2:2; The particle size D50 of the powder is 9-10 μm.

4. The method for preparing a silica slurry for paper coating according to any one of claims 1 to 3, characterized in that: The dry grinding in step 1) is performed by a horizontal ball mill; The grinding medium of the dry grinding is zirconium oxide balls; The rotation speed of the horizontal ball mill is 26-31 r / min; The total amount of the grinding media and quartz sand added is 50-60% of the volume of the cylinder in the horizontal ball mill; The mass ratio of the grinding medium to the quartz sand is 1:2-3.

5. The method for preparing a silicon dioxide slurry for paper coating according to claim 4, characterized in that: The wet grinding in step 2) is specifically as follows: firstly, the powder, part of the wet grinding aid and water are mixed to obtain a slurry, and then the slurry is wet-grinded while adding the remaining wet grinding aid; The mass ratio of the part of the wet grinding aid to the remaining wet grinding aid is 1:

1.

6. The method for preparing a silicon dioxide slurry for paper coating according to claim 5, characterized in that: The mass ratio of the powder to the wet grinding aid is 1:0.007-0.011; The solid content of the slurry is 65-73%.

7. The method for preparing a silicon dioxide slurry for paper coating according to claim 6, characterized in that: The wet grinding aid in step 2) is prepared by mixing EP-44 waterborne epoxy emulsion with a polymer; The mass ratio of the EP-44 waterborne epoxy emulsion to the polymer is 0.8 to 1.2:1; The polymer is sodium polyacrylate or polyethylene glycol; In the slurry after wet grinding in step 2), the content of particles with a particle size of ≤2 μm is ≥65%, and the content of particles with a particle size of ≤45 μm is 100%; The wet grinding in step 2) is performed by a vertical wet stirring ball mill; The power of the vertical wet stirring ball mill is 240-260kw.

8. The method for preparing a silicon dioxide slurry for paper coating according to claim 7, characterized in that: The wet classification in step 2) is performed by a hydrocyclone; The feed pressure of the hydrocyclone is 0.2-0.4Mpa.

9. The silica slurry for paper coating prepared by the method for preparing the silica slurry for paper coating according to any one of claims 1 to 8.

10. A coating material, characterized in that: The composition includes the following mass percentages: Silica slurry for paper coating 90-92%, Dow styrene-butadiene latex 7.8-9.5%, sodium carboxymethyl cellulose 0.2-0.5%; The silica slurry for paper coating is the silica slurry for paper coating as claimed in claim 9.