Silicon dioxide anti-blocking agent and preparation method thereof

Abstract

The invention discloses a silicon dioxide anti-blocking agent and a preparation method thereof, and relates to the technical field of chemical preparation. Comprising the following steps: taking a water glass solution and a dilute sulphuric acid solution as raw materials, and carrying out parallel flow mixing reaction to prepare silica gel; the method comprises the following steps: crushing silica gel, transferring the crushed silica gel into a reaction kettle, adding an aprotic organic solvent, adding a pH buffer solution and organic alkali into the reaction kettle to adjust the pH value of the solution, carrying out heating reflux to carry out an aging reaction, stopping heating after the reaction is completed, opening a filter valve, and filtering the liquid into an alkaline recovery tank; continuously adding an aprotic organic solvent and an organic acid acidification system into the reaction kettle to adjust the pH value of the solution, aging, opening a filter valve to filter the liquid into an acidic recovery tank, washing gel to be neutral, and filtering washing water into a water recovery tank; and adding high-purity water into the reaction kettle, homogenizing and emulsifying to prepare slurry, drying and crushing to obtain the silicon dioxide anti-blocking agent product. The preparation cost is reasonable, the treatment method is simple, and the obtained product is fine and smooth in hand feeling, high in transparency and high in yield.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical preparation, and in particular to a silicon dioxide opening agent and a preparation method thereof. Background Art

[0002] With the rapid development of the national economy, demand for polyethylene film for food production has grown rapidly. However, during the production and storage of polyethylene film, adhesion between film layers can easily occur due to heat or physical pressure. During subsequent production and use, adhesion between films can severely impact unwinding speeds and even prevent unwinding. The primary cause of plastic film adhesion is the presence of a large number of exposed molecular chains on the film surface after molding. When two films are closed, these macromolecular chains become entangled and adhere to each other, preventing them from opening. To address this issue, solid inert particles are often added during the production process as an opening agent. These particles form a large number of raised dots on the surface of the film or sheet, creating a "bridge" between the two layers. This prevents the two inner walls from clinging together and causing "sticking." Furthermore, this allows air to penetrate the gaps between the raised dots created by the opening agent, counteracting atmospheric pressure and effectively preventing adhesion between the films.

[0003] In the prior art, Chinese patent CN109705402A discloses a method for preparing an aerogel film opening agent. The method comprises adding sulfuric acid to form a gel and glue, raising the temperature to 70-90°C, adding sulfuric acid and water glass solution to maintain a pH value of 8-10, and adjusting the temperature to 85-95°C after the co-flow is completed. A silane coupling agent is then added, and the mixture is aged for 2-4 hours, and the pH value is adjusted to 2-4. After aging, the mixture is washed with 1-3% dilute sulfuric acid, and the filter cake is washed with ammonium salt solution and then washed with water. Finally, the mixture is dispersed in a disperser and an emulsifier, spray-dried, and pulverized to obtain a particle size of 3.3-3.5 μm. The product has been successfully used in plastic film systems, but feedback indicates that the bulk density is too high in polyethylene plastic films.

[0004] Chinese patent CN102532950B discloses a method for preparing a microparticle-type silica gel film opening agent. The method comprises adding a sodium silicate aqueous solution to a reactor, adding an inorganic acid solution to react at an initial reaction temperature, adjusting the pH value to a certain value, and continuing to add an inorganic acid solution to adjust the pH value to another value after gelation. The final product is obtained through post-processing steps such as aging, filtration, washing, drying, and crushing. After filtration, the filter cake is first washed with deionized water until the pH value is 6-7, and then a volatile weak acid is added to adjust the slurry pH value to 4-5. Then, 0.5% of a surface tension control agent is added thereto, stirred for 5-10 minutes, and then spray-dried to obtain a microparticle-type silica gel film opening agent. The opening agent prepared by this method has a relatively low bulk density, and the silica opening agent is not easily dispersed in polyethylene resin.

[0005] Chinese patent CN101280127B describes a method for preparing precipitated silica for use as an opening agent in plastic films. The method involves adding water to a reactor, adding the precipitated silica, and heating the reactor to 87°C. A small amount of sodium silicate aqueous solution is then added to adjust the pH of the reaction solution to 10.2. The remaining sodium silicate aqueous solution and dilute sulfuric acid are then added simultaneously to the reactor, maintaining the pH at 10.2. The temperature is maintained at 87°C for 85 minutes. Dilute sulfuric acid is then added to adjust the pH to 3.8. The product is then aged, washed, slurried, and spray-dried to obtain the finished product. This method, a precipitation method, results in significantly lower transparency than the gel method, affecting the transparency of the opening agent. Consequently, it can only be used in films with low transparency requirements and cannot be applied to food-grade polyethylene films, which require high transparency.

[0006] Therefore, those skilled in the art are committed to providing a silica opening agent and its preparation method with reasonable preparation cost, simple processing method, smooth product feel, high transparency, high yield, excellent transparency and easy processing performance in the production of food-grade high-transparency polyethylene plastic film. Summary of the Invention

[0007] The present invention provides a silicon dioxide opening agent and a preparation method thereof, aiming to solve the problems existing in the above-mentioned background technology.

[0008] In order to achieve the above technical objectives, the present invention mainly adopts the following technical solutions:

[0009] The present invention discloses a method for preparing a silicon dioxide opening agent, comprising the following steps:

[0010] (1) Using water glass solution and dilute sulfuric acid solution as raw materials, silica gel is prepared by parallel mixing reaction;

[0011] (2) crushing the silica gel and transferring it to a reactor, adding an aprotic organic solvent, adding a pH buffer solution and an organic base to the reactor to adjust the pH value of the solution, heating and refluxing to perform an aging reaction, and after the reaction is completed, stopping heating and opening the filter valve to filter the liquid into an alkaline recovery tank;

[0012] (3) Continue to add aprotic organic solvent and organic acid acidification system to the reactor to adjust the pH value of the solution, age it, open the filter valve to filter the liquid into the acid recovery tank, wash the gel to neutrality, and filter the washing water into the water recovery tank;

[0013] (4) High-purity water is then added to the reactor, homogenized and emulsified to prepare a slurry, which is then dried and crushed to obtain the silica opening agent product.

[0014] In a preferred embodiment of the present invention, in step (1), the SiO2 concentration in the water glass solution is 15-20 wt%, the concentration of the dilute sulfuric acid solution is 10-20 wt%, and the volume ratio of the water glass solution to the dilute sulfuric acid solution is 3-1:1.

[0015] In a preferred embodiment of the present invention, in step (1), the flow rate of the water glass solution in the co-current mixing reaction is 1 to 2.0 m 3 / h, the flow rate of dilute sulfuric acid solution is 0.5~1.0m 3 / h;

[0016] Optionally, the flow rate of the water glass solution is 1.2 to 1.6 m 3 / h, the flow rate of dilute sulfuric acid solution is 0.6~0.8m 3 / h.

[0017] In a preferred embodiment of the present invention, in step (2), the silica gel is crushed into blocks with a diameter of 12-17 mm; the pH buffer solution is a buffer solution with a pH of 10, selected from any one of an ammonia-ammonium chloride buffer system, a carbonate buffer system, and a borate buffer system; and the organic base is one or more combinations of ammonia water, methylamine, ethylamine, propylamine, diethylamine, triethylamine, diisopropylethylamine (DIPEA), aniline, N-methylmorpholine, and imidazole.

[0018] Preferably, the carbonate buffer system is selected from the Na2CO3 / NaHCO3 system, and the borate buffer system is selected from the Na2B4O7 / H3BO3 system.

[0019] In a preferred embodiment of the present invention, in step (2), the amount of the pH buffer solution is 4-10% of the amount of the silica gel, optionally 5-8%; the pH value of the solution is adjusted to 9.5-10.5; the aging reaction temperature is 25-60°C, and the aging reaction time is 2-6 hours.

[0020] In a preferred embodiment of the present invention, in step (3), the organic acid is one or more combinations of formic acid, acetic acid, propionic acid, oxalic acid, succinic acid, citric acid, benzoic acid, tartaric acid, phenylacetic acid, phenylpropionic acid, salicylic acid, trichloroacetic acid, trifluoroacetic acid, perfluorobutyric acid, perfluorooctanoic acid, benzenesulfonic acid, p-toluenesulfonic acid, methanesulfonic acid, and trifluoromethanesulfonic acid; the pH value of the solution is adjusted to 3.0-4.0 and aged for 2 hours; neutral refers to pH = 6.8-7.2 and the conductivity is 10-50 μs / cm.

[0021] In a preferred embodiment of the present invention, in step (4), the amount of high-purity water added is 1.0 to 1.5 times the amount of silica gel; homogenization is carried out under homogenizer conditions, the D100 value of the prepared slurry particle size parameter is ≤200 μm, and drying is carried out by spray drying.

[0022] In a preferred embodiment of the present invention, the aprotic organic solvent is dichloromethane, chloroform, carbon tetrachloride, ethyl chloride, dichloroethane, trichloroethane, ethyl bromide, dibromoethane, ether, petroleum ether, propyl acetate, isopropyl ether, tert-butyl methyl acetate, n-hexane, cyclohexane, cyclopentane, benzene, toluene, o-xylene, p-xylene, dioxane, or a combination of one or more thereof.

[0023] The present invention also provides a silicon dioxide opening agent prepared by the method.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The present invention uses water glass and dilute sulfuric acid to react to prepare silica gel, which is then aged after being crushed. Acidification, aging and filtrate filtration are all carried out in the same reactor, which reduces the complexity of equipment use and operation, improves production efficiency, and has a high product yield.

[0026] (2) In the reaction step, aprotic organic solvent is used as the aging and acidification liquid phase carrier, which can be filtered and recycled through the filter in the filter valve. The operation is easy and simple, and energy saving and emission reduction are achieved.

[0027] (3) The present invention uses a pH=10 buffer solution combined with an organic base to adjust the pH to 9.5-10.5 for aging reaction. The pH can be precisely controlled and the operation is easy, which is friendly to large-scale production operations.

[0028] (4) The organic solvent and pH buffer used in the present invention as the aging system can make the aging temperature lower and the time shorter, and the entire reaction process is mild, effectively avoiding the impurity content of inorganic anions such as chlorine and sulfate in the product, and greatly improving the transparency and smoothness of the silica opening agent product.

[0029] (5) The silica gel is emulsified into a slurry evenly and finely under the action of the homogenizer, and the D100 value of its particle size parameter is ≤200μm. This can effectively prevent the spray drying from causing the silica particles to agglomerate too large, affecting the smoothness and dispersibility. DETAILED DESCRIPTION

[0030] The present invention will be further described below. The following examples are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0031] The following are the test methods and standards for the physical and chemical properties of the finished products of each embodiment:

[0032] (1) Specific surface area test: Fully automatic specific surface area and porosity analyzer: Micromeritics TriStar II plus 3.03;

[0033] (2) Average particle size: Laser particle size analyzer: Malvern 3000;

[0034] (3) Iron content test: o-phenanthroline spectrophotometry;

[0035] (4) Conductivity test: Leici DDS-11A;

[0036] (5) pH value test: Leici PHBJ-260;

[0037] (6) Oil absorption value: Knife picking method: the amount of dibutyl phthalate absorbed by 1.0g silica; refer to industry standard HG / T3072-2008;

[0038] (7) Bulk density test: Bulk density refers to the density obtained by dividing the mass of the powder by the volume V of the container occupied by the powder, also known as bulk density;

[0039] (8) Tensile strength and friction coefficient test: Paratronix ETT-A electronic tensile testing machine. According to GB / T1040.3-2006 "Determination of tensile properties of plastics Part 3: Test conditions for thin plastics and sheets".

[0040] Example 1

[0041] At room temperature, the water glass pump flow rate is adjusted to 1.2m 3 / h, the sulfuric acid pump flow rate is adjusted to 0.6m 3 / h, and simultaneously inject 0.4m3 of water glass with a silica concentration of 15wt% into the 1000L pool. 3 and 0.2m sulphuric acid solution with a concentration of 10wt% 3The addition time was 20 minutes, forming a silica gel liquid. After 24 hours of quiescence, the silica gel liquid gelled and produced acid water. After the acid water was discharged, the silica gel was manually scraped and broken into 15 mm blocks using a spatula. 35 kg of the silica gel blocks were weighed and transferred to a 100 L enameled reactor. 52.5 kg of dichloromethane and 1.75 kg of ammonia-ammonium chloride buffer were added. The pH of the system was adjusted to 10.0 ± 0.5 with triethylamine. The cooling reflux system was activated and the reactor was heated to 40°C for aging. After 5 hours of reaction, heating was stopped. The bottom filter valve was opened to transfer the aged reaction liquid to an alkali recovery tank. The silica gel blocks were sprayed with 5 kg of dichloromethane in small amounts multiple times, and the spray liquid was also transferred to the alkali recovery tank. The washing was completed. 52.5 kg of dichloromethane was added to the reactor and the pH of the system was adjusted to 3.0-4.0 with acetic acid. The reactor was then aged for another 2 hours. The bottom filter valve was opened to transfer the aged liquid to an acid recovery tank. The silica gel block was repeatedly spray-washed with 5 kg of dichloromethane in small amounts, and the spray solution was transferred to an acid recovery tank. Then, 35 kg of high-purity water was added to soak the silica gel block for 15 minutes. The bottom filter valve was opened to transfer the soaking water to the water recovery tank. The high-purity water soaking and washing process was repeated several times until the pH of the high-purity water measured after the final soaking reached 6.8-7.2 and the conductivity was ≤50 μs / cm. This completed the washing process. After opening the bottom filter valve to transfer the soaking water to the water recovery tank, 42 ​​kg of high-purity water was added to the reactor. The homogenizing pump was activated to emulsify the reactor contents to prepare a slurry. Samples were taken during the process and the particle size was measured using a particle size analyzer until the D100 value was ≤200 μm. The resulting slurry was spray-dried and then subjected to air flow milling to obtain a finished product with a particle size of 2.00-9.00 μm.

[0042] The following are the test results of the physicochemical properties of samples taken from three different positions of the finished product of Example 1, as shown in Table 1.

[0043] Table 1

[0044] serial number <![CDATA[Specific surface area m 2 / g]]> Average particle size μm Iron content ppm Conductivity μs / cm pH Oil absorption value g / g <![CDATA[Bulk density g / cm 3 > 1 443.82 5.105 46.1 38.9 6.81 1.46 0.2588 2 441.95 5.089 43.9 35.2 6.78 1.45 0.2527 3 445.38 5.209 45.1 36.6 6.62 1.45 0.2509 average 443.72 5.1343 45.03 36.9 6.737 1.453 0.2541

[0045] Example 2

[0046] At room temperature, the water glass pump flow rate is adjusted to 1.5m 3 / h, the sulfuric acid pump flow rate is adjusted to 0.7m 3 / h, and simultaneously inject 0.374m3 of water glass with a silica concentration of 18wt% into the 1000L pool. 3 and 0.175m of 15wt% sulfuric acid solution 3The addition time was 15 minutes, forming a silica gel liquid. After 24 hours of quiescence, the silica gel liquid gelled and produced acid water. After the acid water was discharged, the silica gel was manually scraped and broken into 15 mm blocks using a spatula. 30 kg of the silica gel blocks were weighed and transferred to a 100 L enameled reactor. 48 kg of chloroform and 1.95 kg of carbonate (Na2CO3 / NaHCO3) buffer solution were added. The pH of the system was adjusted to 10.0 ± 0.5 with aqueous ammonia. The cooling reflux system was activated and the reactor was heated to 35°C for aging. After 6 hours of reaction, heating was stopped. The bottom filter valve was opened to transfer the aging reaction liquid to an alkali recovery tank. The silica gel blocks were sprayed with 5 kg of chloroform in small amounts multiple times, and the spray liquid was also transferred to the alkali recovery tank. After washing, 48 kg of chloroform was added to the reactor, and the pH of the system was adjusted to 3.0-4.0 with p-toluenesulfonic acid. The reactor was then aged for another 2 hours. Open the bottom filter valve and transfer the aged liquid to the acid recovery tank. Use 5 kg of chloroform in small amounts and multiple sprays to rinse the silica gel block. This spray solution is also transferred to the acid recovery tank. Then, add 30 kg of high-purity water to soak the silica gel block for 15 minutes. Open the bottom filter valve and transfer the soaking water to the water recovery tank. Repeat the high-purity water soaking and washing process several times until the pH of the high-purity water after the final soaking reaches 6.8-7.2 and the conductivity is ≤50 μs / cm. This completes the washing process. Open the bottom filter valve and transfer the soaking water to the water recovery tank. Add another 36 kg of high-purity water to the reactor. Start the homogenizer pump to emulsify the reactor contents to prepare a slurry. Samples are taken during the process and the particle size is measured using a particle size analyzer until the D100 value is ≤200 μm. The resulting slurry is spray-dried and then air-jet milled to produce a finished product with a particle size of 2.00-9.00 μm.

[0047] The following are the test results of the physicochemical properties of samples taken from three different positions of the finished product of Example 2, as shown in Table 2.

[0048] Table 2

[0049] serial number <![CDATA[Specific surface area m 2 / g]]> Average particle size μm Iron content ppm Conductivity μs / cm pH Oil absorption value g / g <![CDATA[Bulk density g / cm 3 > 1 472.15 5.222 43.8 25.6 6.83 1.41 0.2573 2 465.38 5.291 45.6 27.1 6.78 1.39 0.2561 3 458.96 5.316 47.3 26.2 6.82 1.36 0.2602 average 465.497 5.2763 45.567 26.3 6.81 1.3867 0.2579

[0050] Example 3

[0051] At room temperature, the water glass pump flow rate is adjusted to 1.6m 3 / h, the sulfuric acid pump flow rate is adjusted to 0.8m 3 / h, and simultaneously inject 0.4m3 of water glass with a silica concentration of 19wt% into the 1000L pool. 3 and 0.2m sulphuric acid solution with a concentration of 18wt% 3The addition time was 15 minutes, forming a silica gel liquid. After 24 hours of quiescence, the silica gel liquid gelled and produced acid water. After the acid water was discharged, the silica gel was manually scraped and broken into 15 mm blocks using a spatula. 40 kg of the silica gel blocks were weighed and transferred to a 100 L enameled reactor. 56 kg of petroleum ether and 2 kg of borate (Na2B4O7 / H3BO3) buffer solution were added. The pH of the system was adjusted to 10.0 ± 0.5 with aniline. The cooling reflux system was activated and the reactor was heated to 50°C for aging. After 3 hours of reaction, heating was stopped. The bottom filter valve was opened to transfer the aging reaction liquid to an alkali recovery tank. The silica gel blocks were sprayed with 6 kg of petroleum ether in small amounts multiple times, and the spray liquid was also transferred to the alkali recovery tank. After washing, 56 kg of petroleum ether was added to the reactor and the pH of the system was adjusted to 3.0-4.0 with oxalic acid. The reactor was then aged for another 2 hours. The bottom filter valve was opened to transfer the aged liquid to an acid recovery tank. The silica gel block was spray-washed with 6 kg of petroleum ether in small amounts multiple times, and the spray solution was transferred to the acid recovery tank. Then, 40 kg of high-purity water was added to soak the silica gel block for 15 minutes. The bottom filter valve was opened to transfer the soaking water to the water recovery tank. The high-purity water soaking and washing process was repeated several times until the high-purity water of the final soaking showed a pH of 6.8-7.2 and a conductivity of ≤50 μs / cm. This completed the washing process. After opening the bottom filter valve to transfer the soaking water to the water recovery tank, 56 kg of high-purity water was added to the reactor. The homogenizing pump was activated to emulsify the reactor contents to prepare a slurry. Samples were taken during the process and the particle size was measured using a particle size analyzer until the D100 value was ≤200 μm. The resulting slurry was spray-dried and then subjected to air flow milling to obtain a finished product with a particle size of 2.00-9.00 μm.

[0052] Table 3 shows the test results of the physicochemical properties of samples taken from three different locations on the finished product of Example 3.

[0053] Table 3

[0054] serial number <![CDATA[Specific surface area m 2 / g]]> Average particle size μm Iron content ppm Conductivity μs / cm pH Oil absorption value g / g <![CDATA[Bulk density g / cm 3 > 1 462.36 5.096 39.2 32.5 6.59 1.39 0.2468 2 461.89 5.179 37.4 33.4 6.63 1.42 0.2448 3 468.27 5.146 37.9 35.7 6.56 1.43 0.2472 average 464.17 5.14 38.17 33.87 6.593 1.413 0.2463

[0055] Example 4

[0056] At room temperature, the water glass pump flow rate is adjusted to 1.8m 3 / h, the sulfuric acid pump flow rate is adjusted to 0.8m 3 / h, and simultaneously inject 0.45m3 of water glass with a silica concentration of 18wt% into the 1000L pool. 3 and 0.2m sulphuric acid solution with a concentration of 20wt% 3The addition time was 15 minutes, forming a silica gel liquid. After 24 hours of quiescence, the silica gel liquid gelled and produced acid water. After the acid water was discharged, the silica gel was manually scraped and broken into 15 mm blocks using a spatula. 38 kg of the silica gel blocks were weighed and transferred to a 100 L enameled reactor. 53.2 kg of toluene and 2.28 kg of ammonia-ammonium chloride buffer solution were added. The pH of the system was adjusted to 10.0 ± 0.5 with N-methylmorpholine. The cooling reflux system was activated and the reactor was heated to 60°C for aging. After 4 hours of reaction, heating was stopped. The bottom filter valve was opened to transfer the aged reaction liquid to the alkali recovery tank. The silica gel blocks were sprayed with 6 kg of toluene in small amounts multiple times, and the spray liquid was also transferred to the alkali recovery tank. The washing was completed. 53.2 kg of toluene was added to the reactor and the pH of the system was adjusted to 3.0-4.0 with trifluoroacetic acid. The aging continued for 2 hours. The bottom filter valve was opened to transfer the aged liquid to the acid recovery tank. The silica gel block was repeatedly spray-washed with 6 kg of toluene in small amounts, and the spray solution was transferred to the acid recovery tank. Then, 35 kg of high-purity water was added to soak the silica gel block for 15 minutes. The bottom filter valve was opened to transfer the soaking water to the water recovery tank. The high-purity water soaking and washing process was repeated several times until the pH of the high-purity water after the final soaking reached 6.8-7.2 and the conductivity was ≤50 μs / cm. This completed the washing process. After opening the bottom filter valve to transfer the soaking water to the water recovery tank, 49 kg of high-purity water was added to the reactor. The homogenizing pump was activated to emulsify the reactor contents to prepare a slurry. Samples were taken during the process and the particle size was measured using a particle size analyzer until the D100 value was ≤200 μm. The resulting slurry was spray-dried and then subjected to air flow milling to obtain a finished product with a particle size of 2.00-9.00 μm.

[0057] The following are the test results of the physicochemical properties of samples taken from three different positions of the finished product of Example 4, as shown in Table 4.

[0058] Table 4

[0059] serial number <![CDATA[Specific surface area m 2 / g]]> Average particle size μm Iron content ppm Conductivity μs / cm pH Oil absorption value g / g <![CDATA[Bulk density g / cm 3 > 1 439.21 5.075 28.9 31.7 6.49 1.51 0.2282 2 441.75 5.108 30.5 31.1 6.44 1.49 0.2273 3 440.58 5.047 27.5 30.5 6.36 1.53 0.2299 average 440.51 5.077 28.97 31.1 6.43 1.51 0.2285

[0060] Example 5

[0061] At room temperature, the water glass pump flow rate was adjusted to 2.0 m 3 / h, the sulfuric acid pump flow rate is adjusted to 0.7m 3 / h, and simultaneously inject 0.5m3 of water glass with a silica concentration of 15wt% into the 1000L pool. 3 and 0.175m of 20wt% sulfuric acid solution 3The addition time was 15 minutes, forming a silica gel liquid. After 24 hours of quiescence, the silica gel liquid gelled and produced acid water. After the acid water was discharged, the silica gel was manually scraped and broken into 15 mm blocks using a spatula. 40 kg of the silica gel blocks were weighed and transferred to a 100 L enameled reactor. 56 kg of dioxane and 3.2 kg of ammonia-ammonium chloride buffer solution were added. The pH of the system was adjusted to 10.0 ± 0.5 with imidazole. The cooling reflux system was activated and the reactor was heated to 40°C for aging. After 6 hours of reaction, heating was stopped. The bottom filter valve was opened to transfer the aged reaction liquid to the alkali recovery tank. The silica gel blocks were sprayed with 6 kg of dioxane in small amounts multiple times, and the spray liquid was also transferred to the alkali recovery tank. Washing was completed. 56 kg of dioxane was added to the reactor and the pH of the system was adjusted to 3.0-4.0 with benzoic acid. The reactor was then aged for another 2 hours. The bottom filter valve was opened to transfer the aged liquid to the acid recovery tank. The silica gel block was repeatedly spray-washed with 6 kg of dioxane in small amounts, and the spray solution was transferred to an acid recovery tank. Then, 40 kg of high-purity water was added to soak the silica gel block for 15 minutes. The bottom filter valve was opened to transfer the soaking water to the water recovery tank. The high-purity water soaking and washing process was repeated several times until the pH of the high-purity water measured for the final soaking reached 6.8-7.2 and the conductivity ≤50 μs / cm. This completed the washing process. After opening the bottom filter valve to transfer the soaking water to the water recovery tank, 60 kg of high-purity water was added to the reactor. The homogenizing pump was activated to emulsify the reactor contents to prepare a slurry. Samples were taken during the process and the particle size was measured using a particle size analyzer until the D100 value was ≤200 μm. The resulting slurry was spray-dried and then subjected to air flow milling to obtain a finished product with a particle size of 2.00-9.00 μm.

[0062] Table 5 shows the test results of the physicochemical properties of samples taken from three different locations on the finished product of Example 5.

[0063] Table 5

[0064] serial number <![CDATA[Specific surface area m 2 / g]]> Average particle size μm Iron content ppm Conductivity μs / cm pH Oil absorption value g / g <![CDATA[Bulk density g / cm 3 > 1 455.15 5.279 32.4 31.8 6.71 1.35 0.2352 2 451.89 5.316 31.8 32.5 6.63 1.31 0.2311 3 468.51 5.303 34.1 34.1 6.66 1.29 0.2272 average 458.52 5.299 32.77 32.8 6.67 1.317 0.2312

[0065] Example 6

[0066] At room temperature, the water glass pump flow rate is adjusted to 1.5m 3 / h, the sulfuric acid pump flow rate is adjusted to 0.6m 3 / h, and simultaneously inject 0.5m3 of water glass with a silica concentration of 18wt% into the 1000L pool. 3 and 0.2m sulphuric acid solution with a concentration of 18wt% 3The addition time was 20 minutes, forming a silica gel liquid. After 24 hours of quiescence, the silica gel liquid gelled and produced acid water. After the acid water was discharged, the silica gel was manually scraped and broken into 15 mm blocks using a spatula. 35 kg of the silica gel blocks were weighed and transferred to a 100 L enameled reactor. 49 kg of cyclohexane and 2.1 kg of ammonia-ammonium chloride buffer solution were added. The pH of the system was adjusted to 10.0 ± 0.5 with triethylamine. The cooling reflux system was activated and the reactor was heated to 60°C for aging. After 4 hours of reaction, heating was stopped. The bottom filter valve was opened to transfer the aged reaction liquid to the alkali recovery tank. The silica gel blocks were sprayed with 5 kg of cyclohexane in small amounts multiple times, and the spray liquid was also transferred to the alkali recovery tank. Washing was completed. 49 kg of cyclohexane was added to the reactor and the pH of the system was adjusted to 3.0-4.0 with acetic acid. The reactor was then aged for another 2 hours. The bottom filter valve was opened to transfer the aged liquid to the acid recovery tank. The silica gel block was spray-washed with 5 kg of cyclohexane in small amounts multiple times, and the spray solution was transferred to the acid recovery tank. Then, 35 kg of high-purity water was added to soak the silica gel block for 15 minutes. The bottom filter valve was opened to transfer the soaking water to the water recovery tank. The high-purity water soaking and washing process was repeated several times until the high-purity water of the final soaking showed a pH of 6.8-7.2 and a conductivity of ≤50 μs / cm. This completed the washing process. After opening the bottom filter valve to transfer the soaking water to the water recovery tank, 46 kg of high-purity water was added to the reactor. The homogenizing pump was activated to emulsify the reactor contents to prepare a slurry. Samples were taken during the process and the particle size was measured using a particle size analyzer until the D100 value was ≤200 μm. The resulting slurry was spray-dried and then subjected to air flow milling to obtain a finished product with a particle size of 2.00-9.00 μm.

[0067] Table 6 shows the test results of the physicochemical properties of samples taken from three different locations of the finished product of Example 6.

[0068] Table 6

[0069] serial number <![CDATA[Specific surface area m 2 / g]]> Average particle size μm Iron content ppm Conductivity μs / cm pH Oil absorption value g / g <![CDATA[Bulk density g / cm 3 > 1 418.36 5.192 35.6 31.7 6.81 1.61 0.2182 2 423.03 5.205 38.7 31.1 6.74 1.59 0.2173 3 421.54 5.274 37.1 30.5 6.86 1.57 0.2199 average 420.98 5.224 37.13 31.1 6.803 1.59 0.2187

[0070] Comparative Example 1

[0071] At room temperature, 30 L of waterglass with a 15 wt% silica concentration and 13.5 L of a 10 wt% sulfuric acid solution were simultaneously added to a 100 L reactor with a paddle operated. The addition time was 30 minutes to form a silica gel solution. Stirring was stopped for 4 hours. After the silica gel formed a gel, the mixer was turned on. The gel fragmented under the stirring action of the paddles, forming irregular, irregular gel blocks of varying sizes. 5% potassium hydroxide solution was added to the system to adjust the pH to 10.0. The reactor was heated to 80°C for aging, and heating was stopped after 12 hours. The bottom filter valve was opened to transfer the aging reaction liquid to an alkali recovery tank. The lumps of silica gel were rinsed with 10 kg of purified water in small, repeated sprays. The rinse liquid was also transferred to the alkali recovery tank. After washing, 5% hydrochloric acid was added to the reactor to adjust the pH to 3.0-5.0, and aging continued for 1 hour. Open the bottom filter valve and transfer the aged liquid to the acid recovery tank. Use 10 kg of purified water in small amounts and multiple sprays to rinse the silica gel block. This spray solution is also transferred to the acid recovery tank. Then, add 45 kg of high-purity water to soak the silica gel block for 15 minutes. Open the bottom filter valve and transfer the soaking water to the water recovery tank. Repeat the high-purity water soaking and washing process several times until the pH of the high-purity water after the final soaking reaches 6.8-7.2 and the conductivity is ≤50 μs / cm. This completes the washing process. Open the bottom filter valve and transfer the soaking water to the water recovery tank. Add 61 kg of high-purity water to the reactor again. Start the homogenizer pump to emulsify the reactor contents to prepare a slurry. Samples are taken during the process and the particle size is measured using a particle size analyzer until the D100 value is ≤200 μm. The resulting slurry is spray-dried and air-jet milled to produce a finished product with a particle size of 2.00-9.00 μm.

[0072] The following are the physical and chemical properties test results of samples taken from three different positions of the finished product of this comparative example 1, as shown in Table 7.

[0073] Table 7

[0074] serial number <![CDATA[Specific surface area m 2 / g]]> Average particle size μm Iron content ppm Conductivity μs / cm pH Oil absorption value g / g <![CDATA[Bulk density g / cm 3 > 1 593.12 5.018 85.3 101.4 6.24 0.96 0.2971 2 581.57 5.092 82.7 105.1 6.15 0.94 0.2963 3 585.82 5.103 84.9 106.9 6.29 0.91 0.2986 average 586.837 5.071 84.3 104.47 6.227 0.937 0.2973

[0075] Comparative Example 2

[0076] At room temperature, 28 L of waterglass with an 18 wt% silica concentration and 12 L of 12 wt% sulfuric acid solution were simultaneously added to a 100 L reactor with a paddle operated. The addition time was 20 minutes to form a silica gel solution. Stirring was stopped for 4 hours. After the silica gel formed a gel, the mixer was turned on. The gel then broke apart under the stirring action of the paddles, forming irregular, irregular gel blocks of varying sizes. 10% ammonium bicarbonate solution was added to the system to adjust the pH to 10. The reactor was heated to 60°C for aging, and heating was stopped after 24 hours. The bottom filter valve was opened to transfer the aging reaction liquid to an alkali recovery tank. The silica gel blocks were rinsed with 8 kg of purified water in small, repeated sprays. The rinse liquid was also transferred to the alkali recovery tank. 4% hydrochloric acid was added to the reactor to adjust the pH to 3.0-4.0, and aging continued for 1 hour. Open the bottom filter valve and transfer the aged liquid to the acid recovery tank. Use 8 kg of purified water in small, repeated sprays to rinse the silica gel block. This spray solution is also transferred to the acid recovery tank. Then, add 40 kg of high-purity water to soak the silica gel block for 15 minutes. Open the bottom filter valve and transfer the soaking water to the water recovery tank. Repeat the high-purity water soaking and washing process several times until the pH of the high-purity water measured after the final soaking reaches 6.8-7.2 and the conductivity is ≤50 μs / cm. This completes the washing process. Open the bottom filter valve and transfer the soaking water to the water recovery tank. Add 56 kg of high-purity water to the reactor again. Start the homogenizer pump to emulsify the reactor contents to prepare a slurry. Samples are taken during the process and the particle size is measured using a particle size analyzer until the D100 value is ≤200 μm. The resulting slurry is spray-dried and air-jet milled to produce a finished product with a particle size of 2.00-9.00 μm.

[0077] The following are the physical and chemical properties test results of samples taken from three different positions of the finished product of this comparative example 2, as shown in Table 8.

[0078] Table 8

[0079] serial number <![CDATA[Specific surface area m 2 / g]]> Average particle size μm Iron content ppm Conductivity μs / cm pH Oil absorption value g / g <![CDATA[Bulk density g / cm 3 > 1 581.57 5.031 78.4 126.8 6.08 0.89 0.2896 2 580.42 5.068 74.9 124.7 6.13 0.84 0.2889 3 579.87 5.094 76.1 125.1 6.20 0.88 0.2891 average 580.62 5.0643 76.47 125.53 6.137 0.87 0.2892

[0080] Comparative Example 3

[0081] At room temperature, 32 L of waterglass with a 16 wt% silica concentration and 12 L of 12 wt% sulfuric acid solution were simultaneously injected into a 100 L reactor with a paddle operated. The addition time was 20 minutes to form a silica gel solution. Stirring was stopped for 4 hours. After the silica gel formed a gel, the mixer was activated. The gel fragmented under the stirring action of the paddles, forming irregular, irregular gel blocks of varying sizes. 5% ammonium carbonate solution was added to the system to adjust the pH to 10. The reactor was heated to 80°C for aging, and heating was stopped after 8 hours. The bottom filter valve was opened to transfer the aging reaction liquid to an alkali recovery tank. The silica gel blocks were rinsed with 8 kg of purified water in small, repeated sprays. The rinse liquid was also transferred to the alkali recovery tank. After washing, 5% sulfuric acid was added to the reactor to adjust the pH to 3.0-4.0, and aging continued for 4 hours. Open the bottom filter valve to transfer the aged liquid to the acid recovery tank. Use 8 kg of purified water in small, repeated sprays to rinse the silica gel block. This spray solution is also transferred to the acid recovery tank. Then, add 45 kg of high-purity water to soak the silica gel block for 15 minutes. Open the bottom filter valve to transfer the soaking water to the water recovery tank. Repeat the high-purity water soaking and washing process several times until the pH of the high-purity water measured after the final soaking reaches 6.8-7.2 and the conductivity is ≤50 μs / cm. This completes the washing process. Open the bottom filter valve to transfer the soaking water to the water recovery tank, and then add 62 kg of high-purity water to the reactor. Start the homogenizer pump to emulsify the reactor contents to prepare a slurry. Samples are taken during the process and the particle size is measured using a particle size analyzer until the D100 value is ≤200 μm. The resulting slurry is spray-dried and air-jet milled to produce a finished product with a particle size of 2.00-9.00 μm.

[0082] The following are the test results of the physicochemical properties of samples taken from three different positions of the finished product of this comparative example 3, as shown in Table 9.

[0083] Table 9

[0084] serial number <![CDATA[Specific surface area m 2 / g]]> Average particle size μm Iron content ppm Conductivity μs / cm pH Oil absorption value g / g <![CDATA[Bulk density g / cm 3 > 1 576.13 5.015 67.5 123.2 6.23 0.86 0.2956 2 574.91 5.029 64.7 125.5 6.18 0.87 0.2973 3 578.15 5.034 66.2 121.9 6.24 0.87 0.2949 average 576.4 5.026 66.13 123.53 6.217 0.867 0.29593

[0085] Application performance testing

[0086] The performance of the silica opening agents prepared in Examples 1-4 of the present invention was compared with that of the silica opening agents prepared in Comparative Examples 1-3 and similar products at home and abroad. Application performance test method: The polyethylene masterbatch and the opening agent were mixed in a mass ratio of 94:6, and the opening masterbatch was made in a parallel co-rotating twin-screw extruder. Then, the opening masterbatch: polyethylene masterbatch was mixed in a weight ratio of 5:95, and a polyethylene film was formed in a film blowing machine, and the film application performance test was performed. The physical and chemical indicators and application performance test results of the silica opening agent are shown in Table 10, where each data is the average value of the measured data for 3 parallel products.

[0087] Table 10: Comparison of physical and chemical indicators and application performance of silica anti-blocking agents with those at home and abroad

[0088] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 GRACE35S Domestic anti-blocking agent <![CDATA[Specific surface area m 2 / g]]> 443.72 465.497 464.17 440.51 586.837 580.62 576.4 354 265 Average particle size μm 5.1343 5.2763 5.14 5.077 5.071 5.0643 5.026 3.46 3.56 Iron content ppm 45.03 45.567 38.17 28.97 84.3 76.47 66.13 67 71 Oil absorption value g / g 1.453 1.3867 1.413 1.51 0.937 0.87 0.867 1.73 1.7 <![CDATA[Bulk density g / cm 3 > 0.2541 0.2579 0.2463 0.2285 0.2973 0.2892 0.29593 0.265 0.3002 Tensile strength MPa 14.3 14.8 15.2 15.0 12.5 12.9 13.2 14.4 13.5 Masterbatch color White White White White yellow light yellow yellow White light yellow Openness Easy to uncover Easy to uncover Easy to uncover Easy to uncover Not easy to uncover Not easy to uncover Easier to uncover Easy to uncover Easy to uncover

[0089] From the comparative analysis of the physical and chemical indicators and application performance of Examples 1, 2, 3, and 4 with Comparative Examples 1, 2, and 3, it can be seen that the opening performance of Comparative Examples 1, 2, and 3 is worse than that of the samples of Examples 1, 2, 3, and 4, and the tensile strength is also worse than that of the samples of Examples 1, 2, 3, and 4. Since the examples are all subjected to gel crushing treatment, the uniformity of the silica particles is high, which improves the aging effect and avoids the situation where large pieces of gel are not aged properly. The product quality is stable, thereby improving the product opening effect and tensile strength; the opening performance of Comparative Examples 1, 2, and 3 is worse than that of the samples of Examples 1, 2, 3, and 4. In Examples 1, 2, 3, and 4, a pH buffer is added to lock the aging system and stabilize it at 10.0±0.5. The stable pH is conducive to the stable reaction of the system. It avoids the unstable pH leading to unstable product quality. Thus, the product quality is stabilized and the opening effect and tensile strength of the product are improved. The opening agent product synthesized by the present invention improves the quality of the product through a comprehensive synthesis method such as fixed pH aging and pore expansion, using aprotic organic solvent as an aging and acidification liquid phase carrier, and homogenizer emulsification. Compared with the foreign Grace35S opening agent product and the commonly used domestic opening agent products, the opening agents of Examples 1, 2, and 3 synthesized by the method of the present invention have physical and chemical indicators and application performances similar to those of foreign opening agents, have good tensile strength and opening performance, and the color and appearance of the product are not much different from those of foreign products.

[0090] 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 technical principles 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 opening agent, characterized in that: The following steps are involved: (1) Using water glass solution and dilute sulfuric acid solution as raw materials, silica gel is prepared by parallel mixing reaction; (2) crushing the silica gel and transferring it to a reactor, adding an aprotic organic solvent, adding a pH buffer solution and an organic base to the reactor to adjust the pH value of the solution, heating and refluxing to perform an aging reaction, and after the reaction is completed, stopping heating and opening the filter valve to filter the liquid into an alkaline recovery tank; (3) Continue to add aprotic organic solvent and organic acid acidification system to the reactor to adjust the pH value of the solution, age it, open the filter valve to filter the liquid into the acid recovery tank, wash the gel to neutrality, and filter the washing water into the water recovery tank; (4) High-purity water is then added to the reactor, homogenized and emulsified to prepare a slurry, which is then dried and crushed to obtain the silica opening agent product.

2. The preparation method of the silicon dioxide opening agent according to claim 1, wherein In step (1), the SiO2 concentration in the water glass solution is 15-20wt%, the concentration of the dilute sulfuric acid solution is 10-20wt%, and the volume ratio of the water glass solution to the dilute sulfuric acid solution is 3-1:

1.

3. The preparation method of the silicon dioxide opening agent according to claim 1, wherein In step (1), the flow rate of the water glass solution in the co-current mixing reaction is 1 to 2.0 m 3 / h, the flow rate of dilute sulfuric acid solution is 0.5~1.0m 3 / h; Optionally, the flow rate of the water glass solution is 1.2 to 1.6 m 3 / h, the flow rate of dilute sulfuric acid solution is 0.6~0.8m 3 / h.

4. The preparation method of the silicon dioxide opening agent according to claim 1, wherein In step (2), the silica gel is crushed into blocks with a diameter of 12-17 mm; the pH buffer solution is a buffer solution with a pH of 10, selected from any one of an ammonia-ammonium chloride buffer system, a carbonate buffer system, and a borate buffer system; and the organic base is one or more combinations of ammonia water, methylamine, ethylamine, propylamine, diethylamine, triethylamine, diisopropylethylamine (DIPEA), aniline, N-methylmorpholine, and imidazole.

5. The preparation method of the silicon dioxide opening agent according to claim 4, wherein The carbonate buffer system is selected from the Na2CO3 / NaHCO3 system, and the borate buffer system is selected from the Na2B4O7 / H3BO3 system.

6. The preparation method of the silicon dioxide opening agent according to claim 1, wherein In step (2), the amount of the pH buffer solution is 4-10% of the amount of the silica gel, and optionally 5-8%; the pH value of the solution is adjusted to 9.5-10.5; the aging reaction temperature is 25-60°C, and the aging reaction time is 2-6 hours.

7. The preparation method of the silicon dioxide opening agent according to claim 1, wherein In step (3), the organic acid is one or more combinations of formic acid, acetic acid, propionic acid, oxalic acid, succinic acid, citric acid, benzoic acid, tartaric acid, phenylacetic acid, phenylpropionic acid, salicylic acid, trichloroacetic acid, trifluoroacetic acid, perfluorobutyric acid, perfluorooctanoic acid, benzenesulfonic acid, p-toluenesulfonic acid, methanesulfonic acid, and trifluoromethanesulfonic acid; the pH value of the solution is adjusted to 3.0-4.0 and aged for 2 hours; neutral refers to pH = 6.8-7.2 and the conductivity is 10-50 μs / cm.

8. The preparation method of the silicon dioxide opening agent according to claim 1, wherein In step (4), the amount of high-purity water added is 1.0 to 1.5 times the amount of silica gel; homogenization is carried out under homogenizer conditions, the D100 value of the prepared slurry particle size parameter is ≤200 μm, and drying is carried out by spray drying.

9. The method for preparing a silicon dioxide opening agent according to claim 1, wherein The aprotic organic solvent is one or more of dichloromethane, chloroform, carbon tetrachloride, ethyl chloride, dichloroethane, trichloroethane, ethyl bromide, dibromoethane, ethyl ether, petroleum ether, propyl alcohol, isopropyl ether, tert-butyl methyl alcohol, n-hexane, cyclohexane, cyclopentane, benzene, toluene, o-xylene, p-xylene, dioxane, or a combination thereof.

10. A silicon dioxide opening agent prepared by the method according to any one of claims 1 to 9.