A method for preparing a silica opening agent for optical films

Abstract

The present application belongs to the technical field of optical film opening agent, and particularly relates to a preparation method of silica opening agent for optical film, which comprises the following steps: S1, keeping the temperature of a reaction kettle A at 200-300 DEG C and the pressure at 0.3-1.0 Mpa, simultaneously injecting a water glass solution W1 and sulfuric acid F1 into the reaction kettle A, and keeping the pH at 0.5-2.0 to form a silica sol; S2, transferring the silica sol to a reaction kettle B, keeping the temperature at 15-25 DEG C, simultaneously emulsifying and dispersing, and adjusting the pH to 10-12, then simultaneously adding a water glass solution W2 and sulfuric acid F2 into the reaction kettle B, after the addition is completed, aging at 80-100 DEG C, adjusting the pH to 3.0-5.0, and forming a silica precipitate through aging; S3, washing the precipitate and then wet grinding; and S4, spray drying the slurry to obtain the silica. The silica prepared by the method has a large pore volume, a small particle size and a low conductivity, has good opening property and transparency in the field of optical film, and has been successfully applied in the field of optical film.

Description

Technical Field

[0001] This invention belongs to the field of optical thin film opening agent technology, and specifically relates to a method for preparing a silica opening agent for optical thin films. Background Technology

[0002] In recent years, with the rapid development of e-commerce, express delivery, and food delivery industries, online shopping has become the preferred choice. Plastic film, a common material in express delivery and food delivery, is widely used in food packaging, daily chemical product packaging, and pharmaceutical packaging due to its advantages such as good protection, strong elasticity, good barrier properties, low price, and ease of printing. However, with the gradual implementation of national plastic bans, many places have prohibited the use of ordinary plastics, which necessitates plastic films with better performance and lower hazards. Optical plastic films, due to their excellent optical properties and low pollution characteristics, can be applied in many fields, such as medicine, food, and electronic products. Therefore, optical plastic films have become a research hotspot for materials companies.

[0003] During the production of optical plastic films, the molecular chains between the two layers can easily interpenetrate due to curling and pressing, making them difficult to separate and resulting in significant waste. Therefore, opening agents are added during production to address this waste caused by the difficulty in opening. For plastic films used in the optical field, environmentally friendly silica opening agents are generally chosen. The opening agent works by being added to the plastic masterbatch as a stabilizing agent. It remains unaffected by high-temperature melting. Because of its rich porous structure, silica has a certain degree of adsorption, randomly adhering to the film surface and forming many uneven areas. This creates gaps between the upper and lower film layers, facilitating air entry, preventing a vacuum between the films, and making opening easier. Silica opening agents are widely used in the field of optical plastic films because they reduce the static friction coefficient between films without affecting their optical properties.

[0004] Chinese patent CN110229380A discloses a method for preparing a high-efficiency, high-transparency silica plastic film opening agent. The method involves mixing bottom water, water glass, and ammonium bicarbonate at 80–90°C and adjusting the pH to 10.0–11.0. Then, dilute sulfuric acid is added dropwise to acidify to 7.5–8.5. The sulfuric acid and water glass are then flowed co-currently at this pH for 20–40 minutes, followed by further acidification to 3.0–5.0. The mixture is then aged for 30 minutes to obtain the target slurry. This slurry is then washed, atomized, dried, and pulverized to obtain a particle size of 3–5 μm and a BET (specific surface area) of 250–300 m². 2 / g, oil absorption value 1.3~1.6cm 3 / g, a silica opening agent with a heating loss of 5%. The silica synthesized by this method carries the risk of filter clogging during film production. A high heating loss can affect dispersibility and also poses a risk of filter clogging. Furthermore, no performance testing information for the film after adding the opening agent is provided; therefore, it is impossible to determine whether it can be used for optical films. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method for preparing a silica opening agent for optical thin films. The silica prepared by this invention has large pore volume, small particle size, and low conductivity, exhibiting excellent opening and transparency in the field of optical thin films, and has been successfully applied in the field of optical thin films.

[0006] The primary objective of this invention is to provide a method for preparing a silica opening agent for optical thin films. To achieve this objective, the technical solution adopted by this invention is as follows:

[0007] A method for preparing a silica opening agent for optical thin films includes the following steps:

[0008] S1. Maintain the temperature of reactor A at 200-300℃ and the pressure at 0.3-1.0 MPa. Simultaneously inject water glass solution W1 and sulfuric acid F1 into reactor A, and maintain the pH at 0.5-2.0 to form silica sol.

[0009] S2. Transfer the silica sol obtained in step S1 to reactor B, maintain the temperature at 15-25℃, emulsify and disperse, and adjust the pH to alkaline. Then add water glass solution W2 and sulfuric acid F2 to reactor B at the same time. After the addition is complete, raise the temperature for aging, adjust the pH to acidic, and then age to form silica precipitate.

[0010] S3. Wash the silica precipitate obtained in step S2, and then perform wet grinding.

[0011] S4. Spray dry the slurry ground in step S3 to obtain the silica opening agent for optical thin films.

[0012] Preferably, the water glass solution W1 in step S1 has a modulus of 3.00 to 3.30, an iron content of less than 50 ppm, a silica concentration of 40 wt% to 50 wt%, and a sulfuric acid F1 concentration of 80 wt% to 98 wt%.

[0013] Preferably, in step S1, the pressure of the water glass W1 pipeline must be maintained at 0.1-0.5 MPa, the pressure of the sulfuric acid F1 pipeline must be maintained at 0.1-0.5 MPa, and the sulfuric acid and water glass pipelines are distributed on both sides of the reactor, with 100-150 fine holes in each type of pipeline.

[0014] Preferably, the amount of silica in the injected water glass W1 in step S1 accounts for 0.2 to 0.4% of the total mass of silica in the system.

[0015] Preferably, the modulus of the water glass solution W2 in step S2 is 3.00-3.30, the concentration of silica is 5wt%-10wt%, and the concentration of sulfuric acid F2 is 5wt%-10wt%.

[0016] Preferably, the emulsification speed in step S2 is 28,000 to 35,000 rpm, and the dispersion emulsification time is 30 to 60 minutes.

[0017] Preferably, in step S2, the pH is adjusted to an alkaline value of 10-12 and the pH is adjusted to an acidic value of 3.0-5.0.

[0018] Preferably, the aging temperature in step S2 is 80–100°C.

[0019] Preferably, the washing in step S3 refers to washing the filter cake using pure water at 40-70°C, an ammonium salt solution with a concentration of 0.10-0.50 wt%, and pure water at 40-70°C at a time interval of 1:2:3, for a washing time of 4-5 hours, with the pure water conductivity ≤5 μS / cm, and washing until the conductivity ≤50 μS / cm; the ammonium salt is one of ammonium carbonate, ammonium bicarbonate, ammonium sulfate, and ammonium bisulfate.

[0020] Preferably, the grinding flow rate of wet grinding in step S3 is 100-1000 L / h, and the particle size of silica after grinding is 500-1000 nm.

[0021] A second objective of this invention is to provide a silica opening agent for optical thin films prepared by the above method, wherein the silica has a particle size of 500–1000 nm, an oil absorption capacity of 1.50–2.00 g / g, and a bulk density of 0.15–0.18 g / cm³. 3 Iron content less than 50 ppm, electrical conductivity less than 100 μS / cm.

[0022] A third objective of this invention is to provide the application of the silica prepared above in the preparation of optical thin film opening agents. The silica synthesized in this application has a small, uniform, and fine particle size, exhibiting good dispersibility and transparency in the field of optical thin films.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] (1) The temperature of reactor A in this application is 200-300℃, the pressure is 0.3-1.0 MPa, the pH is 0.5-2, the concentration of water glass W1 is 40wt%-50wt%, and the concentration of sulfuric acid F1 is 80wt%-98wt%. The sulfuric acid and water glass pipes are distributed on both sides of the reactor, with 100-150 pores in each type of pipe. The high temperature and pressure ensure a vigorous and complete reaction between the high-concentration water glass and the high-concentration sulfuric acid. The structural design of distributing the sulfuric acid and water glass pipes on both sides of the reactor prevents the vigorous reaction of the high-concentration water glass and sulfuric acid from causing agglomeration. The pH of 0.5-2 ensures that the generated silica particles have a small primary particle size. This process design ensures that the generated silica particles have a small and uniform size, with a primary particle size of 50-100 nm.

[0025] (2) The silica sol in reactor A is transferred to reactor B for emulsification. The emulsification speed of the emulsifier is 28,000 to 35,000 rpm. The emulsifier can fully disperse and emulsify the silica primary particles formed in reactor A to 10 to 50 nm, thereby preventing secondary agglomeration of the silica primary particles.

[0026] (3) The concentration of water glass solution W1 injected into reactor A in this application is 40wt% to 50wt%, and the concentration of sulfuric acid F1 is 80wt% to 98wt%. The concentration of W2 in reactor B is 5wt% to 10wt%, and the concentration of sulfuric acid F2 is 5wt% to 10wt%. Reactors A and B use water glass and sulfuric acid of different concentrations for the reaction. The difference is that high concentration of acid and alkali can quickly form primary silica particles and prevent the growth of primary silica particles, while low concentration of acid and alkali ensures uniform growth of primary silica particles and reduces the formation of primary silica particles.

[0027] (4) After washing, the present application performs wet grinding. The purpose of wet grinding is to reduce secondary silica particles and prevent the silica particles from agglomerating too much due to spray drying, so as to ensure that the particle size of the synthesized silica particles meets the expected requirements. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below with reference to embodiments and comparative examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; the materials and reagents used are commercially available unless otherwise specified. The water glass used in the experiments had a modulus of 3.00–3.30 and an iron content of less than 50 ppm.

[0030] Example 1

[0031] A method for preparing a silica opening agent for optical thin films includes the following steps:

[0032] Maintaining a temperature of 200℃ and a pressure of 1 MPa, simultaneously injecting 40 wt% silica water glass (pipe pressure 0.1 MPa) and 98 wt% sulfuric acid (pipe pressure 0.1 MPa) into reactor A (150 raw material injection holes distributed on both sides of the reactor) into reactor A. The effective silica content of the injected water glass accounts for 0.2% of the total silica mass of the system. The injection time is 20 minutes, and the pH value is maintained at 0.5. After the water glass injection is completed, the silica gel in reactor A is transferred to reactor B via pipeline, and the reactor is cooled to 15℃ using an ice machine. The stirring speed of the reactor is adjusted to 50 Hz, the emulsification speed to 35000 rpm, and dispersion and emulsification are carried out for 30 minutes. After dispersion and emulsification, 10 wt% water glass is added to adjust the pH to 10. After the temperature and pH of reactor B are reached, the reaction... Water glass with a silica concentration of 10 wt% and sulfuric acid with a concentration of 10 wt% were simultaneously added to reactor B, and the pH was maintained at 10. The co-flow time was 120 minutes. After the co-flow was completed, the temperature was raised to 100℃, and the reaction was aged for 120 minutes under this pH condition. After aging, sulfuric acid was added at this temperature to adjust the pH to 3.0, and the mixture was aged for 30 minutes. After aging, the mixture was pumped into a filter press frame for washing. The filter cake was washed in a sequence of 70℃ pure water: 0.50 wt% ammonium carbonate solution: 70℃ pure water with a time interval of 1:2:3, and the washing time was 4 hours. The washing was carried out until the conductivity was below 50 μS / cm. After washing, the mixture was ground for 30 minutes with a grinding speed of 1000 L / h. The particle size after grinding was 500-1000 nm. The resulting slurry was spray-dried to obtain silica for optical thin films.

[0033] Test methods and standards for the physicochemical properties of products:

[0034] (1) Iron content test: o-phenanthroline spectrophotometry;

[0035] (2) Average particle size: Laser particle size analyzer: Malvern 3000;

[0036] (3) Oil absorption value: knife method: the amount of dibutyl phthalate absorbed by 1g of silica; refer to industry standard HG / T3072-2008;

[0037] (4) Conductivity test: Leici DDS-11A;

[0038] (5) Bulk density test: Bulk density is the density obtained by dividing the mass of the powder by the volume V of the container occupied by the powder.

[0039] The physicochemical properties of the seven parallel products are shown in Table 1.

[0040] Table 1

[0041]

[0042] Example 2

[0043] A method for preparing a silica opening agent for optical thin films includes the following steps:

[0044] Maintaining a temperature of 300℃ and a pressure of 0.3 MPa, simultaneously injecting 50 wt% silica water glass (at a pipeline pressure of 0.5 MPa) and 98 wt% sulfuric acid (at a pipeline pressure of 0.5 MPa) into reactor A, which has 100 raw material injection holes distributed on both sides of the reactor, into reactor A. The effective silica content of the injected water glass accounts for 0.4% of the total silica mass of the system. The injection time is 10 minutes, and the pH value is maintained at 2.0. After the water glass injection is completed, the silica gel in reactor A is transferred to reactor B through pipeline, and the reactor is cooled to 25℃ using an ice machine. The stirring speed of the reactor is adjusted to 50 Hz, the emulsification speed to 28000 rpm, and the dispersion and emulsification is carried out for 60 minutes. After dispersion and emulsification, 5 wt% water glass is added to adjust the pH to 12. After the temperature and pH of reactor B are reached, the... Water glass with a silica concentration of 5 wt% and sulfuric acid with a concentration of 5 wt% were simultaneously added to reactor B, and the pH was maintained at 12. The co-flow time was 90 minutes. After co-flow, the temperature was raised to 80°C, and the reaction was aged for 90 minutes under this pH condition. After aging, sulfuric acid was added at this temperature to adjust the pH to 5.0, and the mixture was aged for 60 minutes. After aging, the mixture was pumped into a filter press frame for water washing. The filter cake was washed in a sequence of 70°C pure water: 0.10 wt% ammonium bicarbonate solution: 70°C pure water with a time interval of 1:2:3, and the washing time was 4 hours. The water was washed until the conductivity was below 50 μS / cm. After washing, the mixture was ground for 30 minutes with a grinding speed of 1000 L / h. The particle size after grinding was 500-1000 nm. The resulting slurry was spray-dried to obtain silica for optical thin films.

[0045] The physicochemical properties of the seven parallel products are shown in Table 2.

[0046] Table 2

[0047]

[0048]

[0049] Example 3

[0050] A method for preparing a silica opening agent for optical thin films includes the following steps:

[0051] Maintaining a temperature of 300℃ and a pressure of 0.7 MPa, simultaneously injecting water glass (40 wt% silica, 0.5 MPa pressure) and sulfuric acid (80 wt% sulfuric acid, 0.5 MPa pressure) into reactor A (130 raw material injection holes distributed on both sides of the reactor) into reactor A. The effective silica content of the injected water glass accounts for 0.2% of the total silica mass in the system. The injection time is 10 minutes, and the pH value is maintained at 2. After the water glass injection is completed, the silica gel in reactor A is transferred to reactor B via pipeline. The reactor is then cooled to 20℃ using an ice machine, and the stirring speed of the reactor is adjusted to 50 Hz, the emulsification speed to 28000 rpm, and the dispersion and emulsification is carried out for 60 minutes. After dispersion and emulsification, 8 wt% water glass is added to adjust the pH to 12. After the temperature and pH of reactor B are reached, the reaction... Water glass with a silica concentration of 8 wt% and sulfuric acid with a concentration of 8 wt% were simultaneously added to reactor B, and the pH was maintained at 12. The co-flow time was 120 minutes. After the co-flow was completed, the temperature was raised to 100℃, and the reaction was aged for 120 minutes under this pH condition. After aging, sulfuric acid was added at this temperature to adjust the pH to 5.0, and the mixture was aged for 60 minutes. After aging, the mixture was pumped into a filter press frame for washing. The filter cake was washed in a sequence of 60℃ pure water: 0.10 wt% ammonium sulfate solution: 60℃ pure water with a time interval of 1:2:3, and the washing time was 5 hours. The washing was continued until the conductivity was below 50 μS / cm. After washing, the mixture was ground for 60 minutes with a grinding speed of 500 L / h. The particle size after grinding was 500-1000 nm. The resulting slurry was spray-dried to obtain silica for optical thin films.

[0052] The physicochemical properties of the seven parallel products are shown in Table 3.

[0053] Table 3

[0054]

[0055]

[0056] Example 4

[0057] A method for preparing a silica opening agent for optical thin films includes the following steps:

[0058] Maintaining a temperature of 200℃ and a pressure of 0.3 MPa, simultaneously injecting 40 wt% silica water glass (at a pipeline pressure of 0.5 MPa) and 90 wt% sulfuric acid (at a pipeline pressure of 0.5 MPa) into reactor A, which has 120 raw material injection holes distributed on both sides of the reactor, into reactor A. The effective silica content of the injected water glass accounts for 0.2% of the total silica mass in the system. The injection time is 10 minutes, and the pH value is maintained at 1. After the water glass injection is completed, the silica gel in reactor A is transferred to reactor B through pipeline, and the reactor is cooled to 15℃ using an ice machine. The stirring speed of the reactor is adjusted to 50 Hz, the emulsification speed is 28000 rpm, and dispersion and emulsification are carried out for 45 minutes. After dispersion and emulsification, 10 wt% water glass is added to adjust the pH to 10. After the temperature and pH of reactor B are reached, the reaction is then... Water glass with a silica concentration of 10 wt% and sulfuric acid with a concentration of 10 wt% were simultaneously added to reactor B, and the pH was maintained at 10. The co-flow time was 90 minutes. After the co-flow was completed, the temperature was raised to 80°C, and the reaction was aged for 120 minutes under this pH condition. After aging, sulfuric acid was added at this temperature to adjust the pH to 5.0, and the mixture was aged for 30 minutes. After aging, the mixture was pumped into a filter press frame for washing. The filter cake was washed in a sequence of 40°C pure water: 0.10 wt% ammonium bisulfate solution: 40°C pure water with a time interval of 1:2:3, and the washing time was 5 hours. The washing was continued until the conductivity was below 50 μS / cm. After washing, the mixture was ground for 30 minutes at a grinding speed of 1000 L / h. The particle size after grinding was 500–1000 nm. The resulting slurry was spray-dried to obtain silica for optical thin films.

[0059] The physicochemical properties of the seven parallel products are shown in Table 4.

[0060] Table 4

[0061]

[0062]

[0063] Example 5

[0064] A method for preparing a silica opening agent for optical thin films includes the following steps:

[0065] Maintaining a temperature of 250℃ and a pressure of 1 MPa, simultaneously injecting 45 wt% silica water glass (at a pipeline pressure of 0.3 MPa) and 85 wt% sulfuric acid (at a pipeline pressure of 0.3 MPa) into reactor A, which has 140 raw material injection holes distributed on both sides of the reactor, into reactor A. The effective silica content of the injected water glass accounts for 0.3% of the total silica mass in the system. The injection time is 20 minutes, and the pH value is maintained at 2. After the water glass injection is completed, the silica gel in reactor A is transferred to reactor B via pipeline, and the reactor is cooled to 25℃ using an ice machine. The stirring speed of the reactor is adjusted to 50 Hz, the emulsification speed to 30,000 rpm, and the dispersion and emulsification is carried out for 45 minutes. After dispersion and emulsification, 8 wt% water glass is added to adjust the pH to 10. After the temperature and pH of reactor B are reached, the reactor is then... In step B, water glass with a silica concentration of 8 wt% and sulfuric acid with a concentration of 8 wt% are added simultaneously, maintaining the pH at 10 and the co-flow time at 100 minutes. After co-flow, the temperature is raised to 100°C, and the reaction is aged for 120 minutes under this pH condition. After aging, sulfuric acid is added at this temperature to adjust the pH to 4.0, and the mixture is aged for 60 minutes. After aging, the mixture is pumped into a filter press frame for washing. The filter cake is washed in a sequence of 50°C pure water: 0.30 wt% ammonium carbonate solution: 50°C pure water with a time interval of 1:2:3, for a total washing time of 4 hours, until the conductivity is below 50 μS / cm. After washing, the mixture is ground for 45 minutes at a grinding speed of 1000 L / h, resulting in a particle size of 500–1000 nm. The resulting slurry is then spray-dried to obtain silica for optical thin films.

[0066] The physicochemical properties of the seven parallel products are shown in Table 5.

[0067] Table 5

[0068]

[0069]

[0070] Example 6

[0071] A method for preparing a silica opening agent for optical thin films includes the following steps:

[0072] Maintaining a temperature of 200℃ and a pressure of 0.3 MPa, simultaneously injecting 50 wt% silica water glass (at a pipeline pressure of 0.2 MPa) and 80 wt% sulfuric acid (at a pipeline pressure of 0.3 MPa) into reactor A, which has 150 raw material injection holes distributed on both sides of the reactor, into reactor A. The effective silica content of the injected water glass accounts for 0.4% of the total silica mass in the system. The injection time is 20 minutes, and the pH value is maintained at 1. After the water glass injection is completed, the silica gel in reactor A is transferred to reactor B through pipeline, and the reactor is cooled to 15℃ using an ice machine. The stirring speed of the reactor is adjusted to 50 Hz, the emulsification speed to 30,000 rpm, and the dispersion and emulsification is carried out for 60 minutes. After dispersion and emulsification, 5 wt% water glass is added to adjust the pH to 12. After the temperature and pH of reactor B are reached, the reactor is then... In step B, water glass with a silica concentration of 10 wt% and sulfuric acid with a concentration of 10 wt% are added simultaneously, maintaining the pH at 12 and the co-flow time at 90 minutes. After co-flow, the temperature is raised to 90°C, and the reaction is aged for 120 minutes under this pH condition. After aging, sulfuric acid is added at this temperature to adjust the pH to 4.0, and the mixture is aged for 45 minutes. After aging, the mixture is pumped into a filter press frame for washing. The filter cake is washed in a sequence of 60°C pure water: 0.20 wt% ammonium bicarbonate solution: 60°C pure water with a time interval of 1:2:3, for a total washing time of 5 hours, until the conductivity is below 50 μS / cm. After washing, the mixture is ground for 60 minutes at a grinding speed of 1000 L / h, resulting in a particle size of 500–1000 nm. The resulting slurry is then spray-dried to obtain silica for optical thin films.

[0073] The physicochemical properties of the seven parallel products are shown in Table 6.

[0074] Table 6

[0075]

[0076] Comparative Example 1

[0077] The difference from Example 1 is that no emulsification operation is performed in reactor B, and no emulsifier is used to emulsify the primary silica particles. All other operations are the same as in Example 1.

[0078] The testing methods and standards for the physical and chemical properties of the products are the same as in Example 1. The physical and chemical properties of the seven parallel products are shown in Table 7.

[0079] Table 7

[0080]

[0081] Comparative Example 2

[0082] The difference from Example 1 is that the temperature of reactor A is raised to 350°C and the pressure is raised to 2 MPa, while other operations are the same as in Example 1.

[0083] The testing methods and standards for the physical and chemical properties of the products are the same as in Example 1. The physical and chemical properties of the seven parallel products are shown in Table 8.

[0084] Table 8

[0085]

[0086] Comparative Example 3

[0087] The difference from Example 1 is that the temperature of reactor A is 150°C and the pressure is 0.2 MPa. Other operations are the same as in Example 1.

[0088] The testing methods and standards for the physical and chemical properties of the products are the same as in Example 1. The physical and chemical properties of the seven parallel products are shown in Table 9.

[0089] Table 9

[0090]

[0091] Comparative Example 4

[0092] The difference from Example 1 is that after washing, the resulting slurry is spray-dried instead of wet grinding, while other operations are the same as in Example 1.

[0093] The testing methods and standards for the physical and chemical properties of the products are the same as in Example 1. The physical and chemical properties of the seven parallel products are shown in Table 10.

[0094] Table 10

[0095]

[0096] Comparative Example 5

[0097] The difference from Example 1 is that after washing, wet grinding is not performed, the resulting slurry is spray-dried, and finally air jet milling is performed. Other operations are the same as in Example 1.

[0098] The testing methods and standards for the physical and chemical properties of the products are the same as in Example 1. The physical and chemical properties of the seven parallel products are shown in Table 11.

[0099] Table 11

[0100]

[0101]

[0102] Comparative Example 6

[0103] The difference from Example 1 is that after the temperature and pH of reactor B are reached, water glass with a silica concentration of 15 wt% and sulfuric acid with a concentration of 12 wt% are added to reactor B simultaneously. Other operations are the same as in Example 1.

[0104] The testing methods and standards for the physical and chemical properties of the products are the same as in Example 1. The physical and chemical properties of the seven parallel products are shown in Table 12.

[0105] Table 12

[0106]

[0107] Results Analysis

[0108] The test data from the above six embodiments show that the physical properties of the products produced according to the technical solution of the present invention are basically similar, indicating that the technical solution is stable in production.

[0109] Comparative Example 1 shows that without emulsification in reactor B, and without using an emulsifier to emulsify the primary silica particles, the product's oil absorption value decreases, the bulk density increases significantly, the silica particle size increases, and the conductivity also improves. If the primary silica particles are not emulsified, they will agglomerate. During silica growth, certain primary particles will also be generated. The growth and agglomeration of primary and secondary particles cause some silica particles to increase significantly in size. After aging, the silica particles are of uneven size, the oil absorption value decreases, the bulk density increases, and the porosity decreases. Under the same washing conditions, the conductivity of silica will also increase.

[0110] As can be seen from Comparative Example 2, the reaction is more vigorous when the temperature and pressure are increased, resulting in a product with a higher oil absorption value, lower bulk density, and a richer silica network structure. Due to the rapid formation of the network structure, the network structure is unstable, resulting in a large fluctuation in bulk density and excessive lightness. The viscosity in the PET system is also high, making it prone to clogging the network.

[0111] Comparative Example 3 shows that lowering the temperature and pressure results in a lower oil absorption value and a higher bulk density for silica products. Under low pressure and low temperature conditions, high-concentration water glass and sulfuric acid react rapidly, forming instantaneous agglomerates. Under these conditions, the agglomerates cannot be broken up, and the water glass and sulfuric acid cannot react sufficiently in time, resulting in insufficient richness of the silica network structure and an excessive number of large particles.

[0112] Comparative Example 4 shows that skipping wet milling results in a lower oil absorption value, higher bulk density, and larger particle size. This is because wet milling aims to reduce the growth of secondary silica particles, preventing excessive agglomeration of silica particles during spray drying, thus ensuring that the synthesized silica particles meet the desired particle size. Conversely, skipping wet milling slightly reduces the oil absorption value and increases the bulk density.

[0113] Comparative Example 5 shows that even without wet grinding, air jet milling after drying still results in a silica particle size of around 2200 nm, which is higher than the expected particle size of 1000 nm. The bulk density and oil absorption value also fail to meet the specifications of the example. The main reason is that silica formed in a dry milling environment will generate a large amount of electrostatic attraction and van der Waals forces after air jet milling. The electrostatic attraction and van der Waals forces between silica particles are much greater than the pressure of air jet milling, making it difficult for silica particles to reach the expected size of less than 1000 nm through air jet milling. As a result, the particles cannot meet the expected specifications, and the bulk density also increases accordingly.

[0114] Comparative Example 6 shows that adding water glass with a silica concentration of 15 wt% and sulfuric acid with a concentration of 12 wt% to reactor B, both at higher concentrations than in the previous embodiment, slightly decreases the oil absorption value, increases electrical conductivity, and increases particle size. This is because low-concentration acids and alkalis ensure uniform growth of primary silica particles, reducing the formation of primary silica particles. Increasing the concentration leads to increased agglomeration of silica particles, thereby reducing electrical conductivity and increasing packing density to some extent. The particle size also increases, but the increase is not significant.

[0115] Application performance testing

[0116] The performance of three silica sol-gel products (1-3, 4-3, 6-3) and comparative examples (2-5, 4-5, 6-5) produced by this invention as plastic film opening agents was compared with that of Tosoh K200. Polyethylene terephthalate (PET), silica, dispersant (ethylene glycol), antioxidant (commercially available antioxidant 1010), and antistatic agent (sold by Dinghai Plastic Chemical Co., Ltd.) were melt-mixed in a ratio of 93.5:0.5:3:2:1 to form an opening masterbatch. This masterbatch was then melt-mixed using a twin-screw extruder and subjected to longitudinal stretching, transverse stretching, and heat setting to obtain a 3 μm PET film. The film's application performance was then tested. The physicochemical properties and application test results are shown in Table 13.

[0117] Table 13: Comparison of Physicochemical Properties and Application Performance of Opening Agents with Domestic and Foreign Standards

[0118]

[0119] A comparison of the physicochemical properties and application performance of the three samples in Examples 1-3, 4-3, and 6-3, the three samples in Comparative Examples 2-5, 4-5, and 6-5, and the Tosoh K200 product shows that the opening agent synthesized by this method has relatively close physicochemical properties to foreign opening agents, lower particle size, and application performance that is basically close to Tosoh K200. The product has better transparency and clarity.

[0120] The physicochemical indicators in the above six embodiments are only a portion of the embodiments, and only three embodiments and three comparative examples were selected for application performance testing and comparison with foreign competing products. However, it cannot be concluded that the specific implementation of this invention is limited to these examples and these application tests. Clearly, the above embodiments of this invention are merely examples to clearly illustrate the technical solution of this invention, and are not intended to limit the specific implementation of this invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the claims of this invention should be included within the scope of protection of the claims of this invention.

Claims

1. A method for preparing a silica opening agent for optical thin films, characterized in that, Includes the following steps: S1. Maintain the temperature of reactor A at 200~300℃ and the pressure at 0.3~1.0 MPa. Simultaneously inject water glass solution W1 and sulfuric acid F1 into reactor A, and maintain the pH at 0.5~2.0 to form silica sol. S2. Transfer the silica sol obtained in step S1 to reactor B, keep the temperature at 15~25℃, emulsify and disperse at the same time, and adjust the pH to alkaline. Then add water glass solution W2 and sulfuric acid F2 to reactor B at the same time. After the addition is complete, raise the temperature for aging, adjust the pH to acidic, and then age to form silica precipitate. S3. Wash the silica precipitate obtained in step S2, and then perform wet grinding. S4. Spray dry the slurry ground in step S3 to obtain the final product; The water glass solution W1 in step S1 has a modulus of 3.00~3.30, an iron content of less than 50 ppm, a silica concentration of 40 wt%~50 wt%, and a sulfuric acid F1 concentration of 80 wt%~98 wt%. In step S1, the pressure of the water glass W1 pipeline is maintained at 0.1~0.5 MPa, and the pressure of the sulfuric acid F1 pipeline is maintained at 0.1~0.5 MPa. The sulfuric acid and water glass pipelines are distributed on both sides of the reactor, and the number of fine holes in the two types of pipelines is 100~150. The water glass solution W2 in step S2 has a modulus of 3.00-3.30, a silica concentration of 5wt%~10wt%, and a sulfuric acid F2 concentration of 5wt%~10wt%.

2. The preparation method according to claim 1, characterized in that, The silica mass of the water glass W1 mentioned in step S1 accounts for 0.2 to 0.4% of the total silica mass of the system.

3. The preparation method according to claim 1, characterized in that, The emulsification speed in step S2 is 28,000 to 35,000 rpm, and the dispersion emulsification takes 30 to 60 minutes.

4. The preparation method according to claim 1, characterized in that, In step S2, the pH is adjusted to an alkaline value of 10-12, and the pH is adjusted to an acidic value of 3.0-5.

0.

5. The preparation method according to claim 1, characterized in that, The grinding flow rate of wet grinding in step S3 is 100~1000L / h, and the particle size of silica after grinding is 500~1000nm.

6. The preparation method according to claim 1, characterized in that, The washing described in step S3 refers to washing the filter cake using pure water at 40~70℃, an ammonium salt solution with a concentration of 0.10~0.50wt%, and pure water at 40~70℃ in a washing sequence with time intervals of 1:2:

3. The washing time is 4~5 hours, the conductivity of the pure water is ≤5us / cm, and the washing continues until the conductivity is ≤50us / cm. The ammonium salt is one of ammonium carbonate, ammonium bicarbonate, ammonium sulfate, and ammonium bisulfate.

7. The silica opening agent for optical thin films prepared by the method according to any one of claims 1-6, characterized in that, The silica has a particle size of 500-1000 nm, an oil absorption capacity of 1.50-2.00 g / g, and a bulk density of 0.15-0.18 g / cm³. 3 Iron content less than 50 ppm, electrical conductivity less than 100 μS / cm.

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