Modified spherical silica containing blocked isocyanate groups and preparation method and application thereof

Abstract

The present application discloses a modified spherical silica containing blocked isocyanate groups and a preparation method and application thereof, belonging to the technical field of functional materials. The method comprises: spraying an isocyanate coupling agent on the surface of silica to obtain isocyanate-modified silica powder; dispersing the isocyanate-modified silica powder in a solvent, then adding an oxime blocking agent A solution and reacting at 100-140°C for 4-8 h, and cooling to 20-80°C after the reaction is completed; adding an oxime blocking agent B solution to the above-mentioned cooled reaction system and reacting at 20-80°C for 2-4 h; and after the reaction is completed, washing the precipitate multiple times, and then drying same to obtain the modified spherical silica containing blocked isocyanate groups. In the present application, a suitable blocking agent is used to block an isocyanate coupling agent so as to form a water-based blocked isocyanate, and the water-based blocked isocyanate is used as a modifier to modify spherical silica, thus effectively improving the stability of isocyanate groups.

Description

A modified spherical silica containing blocked isocyanate groups, its preparation method and application

[0001] This application claims priority to Chinese Patent Application No. CN202411528356.2, filed on October 30, 2024, entitled "A spherical silica modified with isocyanate group and a method for preparing the same", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of functional materials technology, specifically to a modified spherical silica containing blocked isocyanate groups, its preparation method, and its application. Background Technology

[0003] In the chemical industry, isocyanate groups are commonly used as modifiers or in the treatment of spherical silica. However, due to the high reactivity of isocyanate groups, they readily react with substances such as moisture, leading to their consumption and reducing the stability and durability of the modification effect. To facilitate the transportation and storage of isocyanates, industrially, isocyanate groups are protected with blocking agents to improve their stability. After blocking, the isocyanate groups react with the blocking agent at low temperatures to form stable compounds, and at high temperatures, the isocyanate groups can be regenerated, restoring the reactivity.

[0004] Given the high reactivity of the -NCO group, many compounds containing active hydrogen can react with isocyanates to form blocked isocyanates, such as phenols, alcohols, and oximes. CN113121791A discloses a low-temperature deblocking isocyanate curing agent and its preparation method. It uses organic and inorganic blocking agents to react with hexamethylene diisocyanate (HDI) to form a blocked isocyanate curing agent. The resulting isocyanate curing agent can be completely deblocked at a relatively low temperature of 70-85°C. However, the amount of bisulfite used is more than three times that of the isocyanate group, and improper post-deblocking handling can easily leave residues in the product, causing side effects. CN117567724A discloses a water-based blocked isocyanate crosslinking agent. It uses isocyanate compounds, hydrophilic diols, and fluorinated diols to obtain a nonionic water-based blocked isocyanate crosslinking agent. This crosslinking agent has excellent hydrophobicity, but its use is limited by the presence of environmentally unfriendly fluorine. Summary of the Invention

[0005] This application addresses the aforementioned technical problems by providing a modified spherical silica containing blocked isocyanate groups, its preparation method, and its application. The modified spherical silica containing blocked isocyanate groups provided by this application exhibits good stability and a long shelf life.

[0006] The objective of this application can be achieved through the following technical solutions:

[0007] A modified spherical silica containing blocked isocyanate groups, wherein the modified spherical silica containing blocked isocyanate groups has a carbon content of <0.65% after 0 days of storage and a carbon content of <0.62% and a moisture content of <0.028% after 6 months of storage.

[0008] Furthermore, the modified spherical silica containing blocked isocyanate groups has a carbon content of <0.65% after 0 days of storage and a carbon content of <0.62% and a moisture content of <0.027% after 6 months of storage.

[0009] Furthermore, the carbon content of the modified spherical silica containing blocked isocyanate groups after being stored for 6 months is 0.580–0.619%.

[0010] A method for preparing modified spherical silica containing blocked isocyanate groups, the method comprising the following steps:

[0011] An isocyanate coupling agent is sprayed onto the surface of silica powder with a moisture content of less than 0.03% to obtain isocyanate-modified silica powder; the isocyanate coupling agent is a methoxy isocyanate, an ethoxy isocyanate, a pyridyl isocyanate, or a benzene ring isocyanate.

[0012] The isocyanate-modified silica powder was dispersed in a solvent, and then an oxime blocking agent A solution was added and reacted at 100-140°C for 4-8 hours. After the reaction was completed, the temperature was cooled to 20-80°C.

[0013] An oxime blocking agent B solution was added to the cooled reaction system and reacted at 20–80°C for 2–4 hours. After the reaction was completed, the precipitate was washed several times and then dried at 35–45°C to obtain modified spherical silica containing blocked isocyanate groups.

[0014] The oxime blocking agent A is at least one of pyruvate oxime, glyoxylate oxime, and 2-oxocyclopentaacetic acid oxime; the oxime blocking agent B is at least one of acetaldehyde oxime, acetone oxime, butanone oxime, pentanone oxime, cyclopentanone oxime, and cyclohexanone oxime.

[0015] In the above preparation method, the silica powder with a moisture content of less than 0.03% is obtained by drying silica raw material in a roller furnace.

[0016] In the above preparation method, the mass ratio of the silica powder with a moisture content of less than 0.03% to the isocyanate coupling agent is 100:0.1-1.5.

[0017] In the above preparation method, the isocyanate coupling agent is at least one of 3-isocyanatopropyltrimethoxysilane, 2-isocyanatepyridine, isocyanatopropyltriethoxysilane, triphenylmethane triisocyanate, and 2-(trifluoromethoxy)phenyl isocyanate.

[0018] In the above preparation method, the molar ratio of the isocyanate coupling agent, oxime blocking agent A and oxime blocking agent B is 1:1 to 5:0.01 to 5.

[0019] In the above preparation method, the molar ratio of the isocyanate coupling agent, oxime blocking agent A and oxime blocking agent B is 1:1 to 5:0.01 to 1.

[0020] In the above preparation method, the oxime blocking agent A is two of pyruvate oxime, glyoxylate oxime and 2-oxocyclopentaacetic acid oxime, and the molar ratio of the two is 1-3:1-3.

[0021] In the above preparation method, the oxime blocking agent A is pyruvate oxime and 2-oxocyclopentaacetic acid oxime, or glyoxylate oxime and 2-oxocyclopentaacetic acid oxime.

[0022] In the above preparation method, the oxime blocking agent B is two of acetaldehyde oxime, acetone oxime, butanone oxime, pentanone oxime, cyclopentanone oxime, and cyclohexanone oxime, and the molar ratio of the two is 1-3:1-3.

[0023] In the above preparation method, the oxime blocking agent B is acetaldehyde oxime and acetone oxime, or acetone oxime and butanone oxime, or butanone oxime and cyclohexanone oxime, or butanone oxime and cyclopentanone oxime, or acetone oxime and pentanone oxime, or pentanone oxime and cyclohexanone oxime, or acetaldehyde oxime and pentanone oxime, or acetone oxime and cyclopentanone oxime, or acetone oxime and cyclohexanone oxime.

[0024] In the above preparation method, the solvent in the oxime blocking agent A solution is anhydrous toluene; the molar volume ratio of the oxime blocking agent A to anhydrous toluene is 0.1-0.3 mol: 50-150 mL.

[0025] In the above preparation method, the solvent in the oxime blocking agent B solution is anhydrous toluene; the molar volume ratio of the oxime blocking agent B to anhydrous toluene is 0.001-0.1 mol: 0.1-15 mL.

[0026] This application provides the application of modified spherical silica containing blocked isocyanate groups as described in the above technical solution, or the modified spherical silica containing blocked isocyanate groups obtained by the preparation method, in a packaging substrate.

[0027] In the technical solution of this application, the modified spherical silica containing blocked isocyanate groups or the modified spherical silica containing blocked isocyanate groups prepared by the preparation method has wide applications in many fields such as electronics and semiconductor industries, and is expected to play a corresponding role in coatings, adhesives, polymer materials, catalysis, drug loading or adsorption separation.

[0028] The concept of this application is as follows: Oxime blocking agents A (pyruvate oxime, glyoxylate oxime, 2-oxocyclopentaacetic acid oxime) contain emulsifying groups, forming polyurethane emulsions after isocyanate end-capping, but their deblocking temperature is high, making them unsuitable for use alone as blocking agents. While oxime blocking agents B (acetaldehyde oxime, acetone oxime, butanone oxime, pentanone oxime, cyclopentanone oxime, cyclohexanone oxime) have low deblocking temperatures and are easy to deblock, they lack emulsifying groups and hydrophilic properties, making it difficult to form emulsions and limiting their application range. Therefore, this application designs a combination of these two types of oxime compounds to fully utilize their respective characteristics, achieving both easy deblocking and emulsification.

[0029] Unreacted -NCO in the system and -NCO on the surface of the surface-treated spherical silica readily react with the material and water in the environment to generate a series of byproducts, affecting the application performance of the product.

[0030] 2R-NCO + H2O → RNHCONHR + CO2

[0031] -NCO groups can be blocked by blocking agents, rendering them inactive at room temperature. However, under certain temperatures and other conditions, the isocyanate groups in the blocked polyurethane can be regenerated, undergoing a cross-linking reaction to generate thermosetting polyurethane. Compared to alcohol, phenol, and caprolactam blocking agents, oxime blocking agents have lower deblocking temperatures and can undergo blocking reactions without catalysts. However, oximes are inherently easily hydrolyzed compounds, making them unsuitable for use in water-based coatings, and they are prone to yellowing during storage. This application combines several types of oxime compounds to fully utilize their respective characteristics, preparing a low-temperature deblocking waterborne blocked isocyanate. Using this waterborne blocked isocyanate, modified spherical silica with stable blocked isocyanate groups is obtained, exhibiting high coating efficiency. This avoids reactions with materials or moisture in the environment, preventing the generation of byproducts that could affect the viscosity and other application properties of the resin system during use, thus improving the modification effect and extending the product's shelf life.

[0032] During the modification of spherical silica powder, isocyanate groups are prone to absorbing water. Therefore, a blocking agent is used to block the isocyanate groups to obtain modified spherical silica containing blocked isocyanate groups. This modified spherical silica with blocked isocyanate groups exhibits good stability during storage and use. Unmodified spherical silica, if left for an extended period, is prone to reaction between the isocyanate groups and moisture in the air or raw materials, resulting in a significant decrease in carbon content and ultimately, failure.

[0033] To overcome some of the shortcomings of blocked isocyanates in related technologies, a blocked isocyanate with a low deblocking temperature and emulsifying groups is needed. This application combines several types of oxime compounds to give full play to their respective characteristics and prepares a low-temperature deblocking aqueous blocked isocyanate. The aqueous blocked isocyanate is then used to modify spherical silica, which not only extends the shelf life of the product but also broadens its application in the electronics industry.

[0034] The beneficial effects of this application are:

[0035] By using a suitable blocking agent to seal isocyanate coupling agents to form water-based blocked isocyanates, and then using these water-based blocked isocyanates as modifiers to modify spherical silica, the stability of the isocyanate groups can be effectively improved. The blocking agent can seal the -NCO groups in the isocyanate-modified spherical silica, preventing them from reacting with moisture and other substances and being consumed. This reduces the requirements for the production environment, enhances product stability, extends shelf life, and reduces storage and transportation costs. It is expected to play a corresponding role in the fields of fine chemicals, coatings, adhesives, and polymer materials. Detailed Implementation

[0036] Carbon content was detected using an Inductar CS cube carbon-sulfur analyzer (Germany). The carbon and sulfur in the sample were inductively combusted at high temperature to generate carbon dioxide and sulfur dioxide gases. The concentration of these gases was then detected using an infrared detector to calculate the carbon content (specifically, the mass content of carbon mentioned in this application). Moisture content was detected using a Guanya SFY-118 moisture analyzer. The sample was dried to constant weight at a certain temperature, and the moisture content was calculated based on the decrease in mass of the sample (specifically, the mass content of moisture mentioned in this application). Infrared spectroscopy was performed using a Fourier transform infrared spectrometer. Since all chemical bonds in a molecule have specific vibrational frequencies that can match the wavelength of infrared light, molecules absorb specific frequencies of infrared light, thus generating peaks for detection.

[0037] The method for detecting the unblocking temperature is as follows: since isocyanate reacts with water to generate CO2, the lowest temperature at which modified spherical silica treated with the sealing agent is heated on a moist molecular sieve and CO2 is evaporated is considered to be the unblocking temperature of the sealed isocyanate.

[0038] The present application will be further described below with reference to embodiments, but the scope of protection of the present application is not limited thereto:

[0039] Example 1

[0040] Step 1: The silica raw material is dried in a roller furnace, and the moisture content of the dried silica powder is 0.023%.

[0041] Step 2: Put 240g of dried silica powder into a high-speed mixer, spray 2.4g of 3-isocyanate-propyltrimethoxysilane (0.01mol) onto the surface of the dried silica powder for modification, and then sieve to remove abnormal particles to obtain isocyanate-modified silica powder.

[0042] Step 3: Disperse the isocyanate-modified silica powder in 960 mL of anhydrous toluene and add it to a three-necked flask. Use a constant pressure dropping funnel to slowly add a mixed solution of 0.018 mol of oxime blocking agent A (pyruvate oxime) and 9.0 mL of anhydrous toluene to the three-necked flask. Keep stirring at 110°C for 6 hours and cool to 30°C.

[0043] Step 4: Using a constant pressure dropping funnel, slowly add a mixture of 0.002 mol of acetaldehyde oxime and acetone oxime in a molar ratio of 1:1 and 1 mL of anhydrous toluene into a three-necked flask, and stir at 30°C for 4 hours.

[0044] Step 5: After the reaction is complete, add a large amount of deionized water to a three-necked round-bottom flask and allow it to stand in an ice bath to precipitate. Filter the solid and wash it several times with deionized water. Place the solid in a vacuum drying oven and dry it at 40°C to constant weight. The disappearance of the -NCO infrared absorption peak indicates that modified spherical silica containing blocked isocyanate groups has been prepared.

[0045] The unsealing temperature of the modified spherical silica containing blocked isocyanate groups obtained in step 5 was determined.

[0046] Example 2

[0047] Step 1: The silica raw material is dried in a roller furnace, and the moisture content of the dried silica powder is 0.028%.

[0048] Step 2: Put 240g of dried silica powder into a high-speed mixer, spray 2.4g of 3-isocyanate-propyltrimethoxysilane (0.01mol) onto the surface of the dried silica powder for modification, and then sieve to remove abnormal particles to obtain isocyanate-modified silica powder.

[0049] Step 3: Disperse the isocyanate-modified silica powder in 960 mL of anhydrous toluene and add it to a three-necked flask. Using a constant pressure dropping funnel, slowly add a mixed solution of 0.0194 mol of oxime blocking agent A (a 1:1 molar ratio of pyruvate oxime and 2-oxocyclopentaacetic acid oxime) and 9.7 mL of anhydrous toluene to the three-necked flask. Keep stirring at 120°C for 6.5 h and cool to 50°C.

[0050] Step 4: Using a constant pressure dropping funnel, slowly add a mixture of 0.006 mol of acetone oxime and methyl ethyl ketone oxime in a molar ratio of 1:1 and 3 mL of anhydrous toluene into a three-necked flask, and stir at 25°C for 4 hours.

[0051] Step 5: After the reaction is complete, add a large amount of deionized water to a three-necked round-bottom flask and allow it to stand in an ice bath to precipitate. Filter the solid and wash it several times with deionized water. Place the solid in a vacuum drying oven and dry it at 40°C to constant weight. The disappearance of the -NCO infrared absorption peak indicates that modified spherical silica containing blocked isocyanate groups has been prepared.

[0052] The unsealing temperature of the modified spherical silica containing blocked isocyanate groups obtained in step 5 was determined.

[0053] Example 3

[0054] Step 1: The silica raw material is dried in a roller furnace, and the moisture content of the dried silica powder is 0.024%.

[0055] Step 2: Put 240g of dried silica powder into a high-speed mixer, spray 2.4g of 3-isocyanate-propyltrimethoxysilane (0.01mol) onto the surface of the dried silica powder for modification, and then sieve to remove abnormal particles to obtain isocyanate-modified silica powder.

[0056] Step 3: Disperse the isocyanate-modified silica powder in 960 mL of anhydrous toluene into a three-necked flask. Slowly add the mixture of 0.019 mol glyoxylate oxime and 9.5 mL of anhydrous toluene into the three-necked flask using a constant pressure dropping funnel. Stir at 130°C for 7 hours and then cool to 50°C.

[0057] Step 4: Using a constant pressure dropping funnel, slowly add 0.001 mol of blocking agent B (a mixture of butanone oxime and cyclohexanone oxime in a molar ratio of 1:1) and 0.5 mL of anhydrous toluene into a three-necked flask, and stir at 70°C for 4 hours.

[0058] Step 5: After the reaction is complete, add a large amount of deionized water to a three-necked round-bottom flask and allow it to stand in an ice bath to precipitate. Filter the solid and wash it several times with deionized water. Place the solid in a vacuum drying oven at 40°C and dry it until the -NCO infrared absorption peak disappears at constant weight, thus preparing modified spherical silica containing blocked isocyanate groups.

[0059] The unsealing temperature of the modified spherical silica containing blocked isocyanate groups obtained in step 5 was determined.

[0060] Example 4

[0061] Step 1: The silica raw material is dried in a roller furnace, and the moisture content of the dried silica powder is 0.025%.

[0062] Step 2: Put 240g of dried silica powder into a high-speed mixer, spray 2.4g of 3-isocyanate-propyltrimethoxysilane (0.01mol) onto the surface of the dried silica powder for modification, and then sieve to remove abnormal particles to obtain isocyanate-modified silica powder.

[0063] Step 3: Disperse the isocyanate-modified silica powder in 960 mL of anhydrous toluene and add it to a three-necked flask. Using a constant pressure dropping funnel, slowly add a mixed solution of 0.0186 mol of oxime blocking agent A (glyoxylate oxime and 2-oxocyclopentaacetic acid oxime in a molar ratio of 1:1) and 9.3 mL of anhydrous toluene to the three-necked flask. Keep stirring at 110 °C for 8 h and cool to 80 °C.

[0064] Step 4: Using a constant pressure dropping funnel, slowly add 0.0014 mol of blocking agent B (a mixture of butanone oxime and cyclopentanone oxime in a molar ratio of 1:1) and 0.7 mL of anhydrous toluene into a three-necked flask, and stir at 50°C for 4 hours.

[0065] Step 5: After the reaction is complete, add a large amount of deionized water to a three-necked round-bottom flask and allow it to stand in an ice bath to precipitate. Filter the solid and wash it several times with deionized water. Place the solid in a vacuum drying oven at 40°C and dry it until the -NCO infrared absorption peak disappears at constant weight, thus preparing modified spherical silica containing blocked isocyanate groups.

[0066] The unsealing temperature of the modified spherical silica containing blocked isocyanate groups obtained in step 5 was determined.

[0067] Example 5

[0068] Step 1: The silica raw material is dried in a roller furnace, and the moisture content of the dried silica powder is 0.027%.

[0069] Step 2: Put 240g of dried silica powder into a high-speed mixer, spray 2.4g of 3-isocyanate-propyltrimethoxysilane (TMXDI) onto the surface of the dried silica powder for modification, and then sieve to remove abnormal particles to obtain isocyanate-modified silica powder.

[0070] Step 3: Disperse the isocyanate-modified silica powder in 960 mL of anhydrous toluene and add it to a three-necked flask. Use a constant pressure dropping funnel to slowly add a mixed solution of 0.0186 mol 2-oxocyclopentaacetic acid oxime and 9.3 mL of anhydrous toluene to the three-necked flask. Keep stirring at 120°C for 7 h and cool to 80°C.

[0071] Step 4: Using a constant pressure dropping funnel, slowly add 0.0014 mol of blocking agent B (acetone oxime and pentoone oxime in a molar ratio of 1:1) and 0.7 mL of anhydrous toluene into a three-necked flask, and stir at 80°C for 4 hours.

[0072] Step 5: After the reaction is complete, add a large amount of deionized water to a three-necked round-bottom flask and allow it to stand in an ice bath to precipitate. Filter the solid and wash it several times with deionized water. Place the solid in a vacuum drying oven at 40°C and dry it until the -NCO infrared absorption peak disappears at constant weight, thus preparing modified spherical silica containing blocked isocyanate groups.

[0073] The unsealing temperature of the modified spherical silica containing blocked isocyanate groups obtained in step 5 was determined.

[0074] Example 6

[0075] Step 1: The silica raw material is dried in a roller furnace, and the moisture content of the dried silica powder is 0.022%.

[0076] Step 2: Put 240g of dried silica powder into a high-speed mixer, spray 2.4g of 2-isocyanate pyridine (0.02mol) onto the surface of the dried silica powder for modification, and then sieve to remove abnormal particles to obtain isocyanate-modified silica powder.

[0077] Step 3: Disperse the isocyanate-modified silica powder in 960 mL of anhydrous toluene into a three-necked flask. Slowly add the mixture of 0.019 mol pyruvate oxime and 9.5 mL anhydrous toluene into the three-necked flask using a constant pressure dropping funnel. Stir at 130°C for 6.5 h and then cool to 70°C.

[0078] Step 4: Using a constant pressure dropping funnel, slowly add 0.001 mol of blocking agent B (a mixture of pentanone oxime and cyclohexanone oxime in a molar ratio of 1:1) and 0.5 mL of anhydrous toluene into a three-necked flask, and stir at 70°C for 4 hours.

[0079] Step 5: After the reaction is complete, add a large amount of deionized water to a three-necked round-bottom flask and allow it to stand in an ice bath to precipitate. Filter the solid and wash it several times with deionized water. Place the solid in a vacuum drying oven at 40°C and dry it until the -NCO infrared absorption peak disappears at constant weight, thus preparing modified spherical silica containing blocked isocyanate groups.

[0080] The unsealing temperature of the modified spherical silica containing blocked isocyanate groups obtained in step 5 was determined.

[0081] Example 7

[0082] Step 1: The silica raw material is dried in a roller furnace, and the moisture content of the dried silica powder is 0.023%.

[0083] Step 2: Put 240g of dried silica powder into a high-speed mixer, spray 2.4g of isocyanate propyltriethoxysilane (0.01mol) onto the surface of the dried silica powder for modification, and then sieve to remove abnormal particles to obtain isocyanate-modified silica powder.

[0084] Step 3: Disperse the isocyanate-modified silica powder in 960 mL of anhydrous toluene and add it to a three-necked flask. Using a constant pressure dropping funnel, slowly add a mixed solution of 0.0194 mol of oxime blocking agent A (a 1:1 molar ratio of pyruvate oxime and 2-oxocyclopentaacetic acid oxime) and 9.7 mL of anhydrous toluene to the three-necked flask. Keep stirring at 110 °C for 6.5 h and cool to 50 °C.

[0085] Step 4: Using a constant pressure dropping funnel, slowly add 0.0006 mol of blocking agent B (acetaldehyde oxime and pentanone oxime in a molar ratio of 1:1) and 0.3 mL of anhydrous toluene into a three-necked flask, and stir at 50°C for 4 hours.

[0086] Step 5: After the reaction is complete, add a large amount of deionized water to a three-necked round-bottom flask and allow it to stand in an ice bath to precipitate. Filter the solid and wash it several times with deionized water. Place the solid in a vacuum drying oven at 40°C and dry it until the -NCO infrared absorption peak disappears at constant weight, thus preparing modified spherical silica containing blocked isocyanate groups.

[0087] The unsealing temperature of the modified spherical silica containing blocked isocyanate groups obtained in step 5 was determined.

[0088] Example 8

[0089] Step 1: The silica raw material is dried in a roller furnace, and the moisture content of the dried silica powder is 0.025%.

[0090] Step 2: Put 240g of dried silica powder into a high-speed mixer, spray 2.4g of triphenylmethane triisocyanate (0.007mol) onto the surface of the dried silica powder for modification, and then sieve to remove abnormal particles to obtain isocyanate-modified silica powder.

[0091] Step 3: Disperse the isocyanate-modified silica powder in 960 mL of anhydrous toluene into a three-necked flask. Slowly add a mixture of 0.018 mol glyoxylate oxime and 9 mL of anhydrous toluene into the three-necked flask using a constant pressure dropping funnel. Stir at 120°C for 8 hours and then cool to 30°C.

[0092] Step 4: Using a constant pressure dropping funnel, slowly add 0.002 mol of blocking agent B (acetaldehyde oxime and cyclopentanone oxime in a molar ratio of 1:1) and 1 mL of anhydrous toluene into a three-necked flask, and stir at 30°C for 4 hours.

[0093] Step 5: After the reaction is complete, add a large amount of deionized water to a three-necked round-bottom flask and allow it to stand in an ice bath to precipitate. Filter the solid and wash it several times with deionized water. Place the solid in a vacuum drying oven at 40°C and dry it until the -NCO infrared absorption peak disappears at constant weight, thus preparing modified spherical silica containing blocked isocyanate groups.

[0094] The unsealing temperature of the modified spherical silica containing blocked isocyanate groups obtained in step 5 was determined.

[0095] Example 9

[0096] Step 1: The silica raw material is dried in a roller furnace, and the moisture content of the dried silica powder is 0.027%.

[0097] Step 2: Put 240g of dried silica powder into a high-speed mixer, spray 2.4g of 2-(trifluoromethoxy)phenyl isocyanate (0.01mol) onto the surface of the dried silica powder for modification, and then sieve to remove abnormal particles to obtain isocyanate-modified silica powder.

[0098] Step 3: Disperse the isocyanate-modified silica powder in 960 mL of anhydrous toluene and add it to a three-necked flask. Using a constant pressure dropping funnel, slowly add a mixed solution of 0.0186 mol of oxime blocking agent A (glyoxylate oxime and 2-oxocyclopentaacetic acid oxime in a molar ratio of 1:1) and 9.3 mL of anhydrous toluene to the three-necked flask. Keep stirring at 130°C for 8 hours and cool to 80°C.

[0099] Step 4: Using a constant pressure dropping funnel, slowly add 0.0014 mol of blocking agent B (acetone oxime and cyclohexanone oxime in a molar ratio of 1:1) and 0.7 mL of anhydrous toluene into a three-necked flask, and stir at 80°C for 4 hours.

[0100] Step 5: After the reaction is complete, add a large amount of deionized water to a three-necked round-bottom flask and allow it to stand in an ice bath to precipitate. Filter the solid and wash it several times with deionized water. Place the solid in a vacuum drying oven at 40°C and dry it until the -NCO infrared absorption peak disappears at constant weight, thus preparing modified spherical silica containing blocked isocyanate groups.

[0101] The unsealing temperature of the modified spherical silica containing blocked isocyanate groups obtained in step 5 was determined.

[0102] The processing method described in the above embodiments can effectively seal the active groups of spherical silica treated with isocyanate modifiers, preventing them from reacting with substances such as moisture and being consumed, thereby improving the stability of spherical silica treated with isocyanate modifiers.

[0103] Comparative Example 1

[0104] Step 1: The silica raw material is dried in a roller furnace, and the moisture content of the dried silica powder is 0.025%.

[0105] Step 2: 240g of dried silica powder was put into a high-speed mixer. 2.4g of triphenylmethane triisocyanate (0.007mol) was sprayed onto the surface of the dried silica powder for modification. Then, the powder was sieved to remove abnormal particles and obtain silica powder modified with isocyanate. The -NCO infrared absorption peak was detected.

[0106] Comparative Example 2

[0107] Step 1: The silica raw material is dried in a roller furnace, and the moisture content of the dried silica powder is 0.026%.

[0108] Step 2: Put 240g of dried silica powder into a high-speed mixer, spray 2.4g of 3-isocyanate-propyltrimethoxysilane (TMXDI) onto the surface of the dried silica powder for modification, and then sieve to remove abnormal particles to obtain isocyanate-modified silica powder.

[0109] Step 3: Disperse the isocyanate-modified silica powder in 960 mL of anhydrous toluene into a three-necked flask. Slowly add a mixture of 0.02 mol pyruvate oxime and 10 mL anhydrous toluene into the three-necked flask using a constant pressure dropping funnel. Stir at 110 °C for 6 h.

[0110] Step 4: After the reaction is complete, add a large amount of deionized water to a three-necked round-bottom flask and allow it to stand in an ice bath to precipitate. Filter the solid and wash it several times with deionized water. Place the solid in a vacuum drying oven at 40°C and dry it until the -NCO infrared absorption peak disappears at constant weight, thus preparing modified spherical silica containing blocked isocyanate groups.

[0111] The unsealing temperature of the modified spherical silica containing blocked isocyanate groups obtained in step 4 was determined.

[0112] Comparative Example 3

[0113] Step 1: The silica raw material is dried in a roller furnace, and the moisture content of the dried silica powder is 0.028%.

[0114] Step 2: Put 240g of dried silica powder into a high-speed mixer, spray 2.4g of 3-isocyanate-propyltrimethoxysilane (TMXDI) onto the surface of the dried silica powder for modification, and then sieve to remove abnormal particles to obtain isocyanate-modified silica powder.

[0115] Step 3: Disperse the isocyanate-modified silica powder in 960 mL of anhydrous toluene and add it to a three-necked flask. Using a constant pressure dropping funnel, slowly add 0.02 mol of a mixture of acetone oxime and butanone oxime in a molar ratio of 1:1 and 10 mL of anhydrous toluene into the three-necked flask, and stir at 25°C for 4 h.

[0116] Step 4: After the reaction is complete, add a large amount of deionized water to a three-necked round-bottom flask and allow it to stand in an ice bath to precipitate. Filter the solid and wash it several times with deionized water. Place the solid in a vacuum drying oven at 40°C and dry it until the -NCO infrared absorption peak disappears at constant weight, thus preparing modified spherical silica containing blocked isocyanate groups.

[0117] The unsealing temperature of the modified spherical silica containing blocked isocyanate groups obtained in step 4 was determined.

[0118] Comparative Example 4

[0119] Other conditions are the same as in Example 1, except for step 4. The conditions for step 4 in Comparative Example 4 are as follows:

[0120] Step 4: Using a constant pressure dropping funnel, slowly add a mixture of 0.002 mol of acetaldehyde oxime and 1 mL of anhydrous toluene into a three-necked flask, and stir at 30°C for 4 hours.

[0121] Comparative Example 5

[0122] Other conditions are the same as in Example 1, except for step 4. The conditions for step 4 in Comparative Example 5 are as follows:

[0123] Step 4: Using a constant pressure dropping funnel, slowly add a mixture of 0.002 mol of acetone oxime and 1 mL of anhydrous toluene into a three-necked flask, and stir at 30°C for 4 hours.

[0124] The carbon content of the products prepared in Examples 1-9 and Comparative Examples 1-5 was tested after being left in an environment with uncontrolled temperature and humidity for 6 months, and the results were compared with the data before the storage. At the same time, the moisture content was tested after 6 months of storage.

[0125] Table 1. Test results of the products prepared in Examples 1-9 and Comparative Examples 1-5 before and after 6 months of storage.

[0126] Table 2 Unsealing temperatures of the products prepared in Examples 1-9 and Comparative Examples 1-5

[0127] As can be seen from Table 1, compared with other schemes, Example 3 showed the least change in carbon content after 6 months of storage compared with 0 days of storage, and the lowest moisture content, indicating that its modified product was the most stable.

[0128] Based on the data from Comparative Examples 1-5 in Tables 1 and 2, it can be seen that using only pyruvate oxime, glyoxylate oxime, and 2-oxocyclopentaacetic acid oxime containing emulsifying groups results in high deblocking temperatures, making them unsuitable as blocking agents alone. Furthermore, using acetaldehyde oxime, acetone oxime, butanone oxime, pentanone oxime, cyclopentanone oxime, and cyclohexanone oxime alone results in poor stability of the modified spherical silica, making them unsuitable as blocking agents alone.

[0129] According to the data from Examples 1-9, by combining two types of oxime blocking agents and adjusting the preparation process parameters, the unblocking temperature of the blocked isocyanate can be effectively reduced, and the stability of the modified spherical silica can be significantly improved. Among them, the blocking agent in Example 3 has the best blocking and modification effect.

[0130] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A modified spherical silica containing blocked isocyanate groups, characterized in that, The modified spherical silica containing blocked isocyanate groups has a carbon content of <0.65% after 0 days of storage and a carbon content of <0.62% and a moisture content of <0.028% after 6 months of storage.

2. The modified spherical silica containing blocked isocyanate groups according to claim 1, characterized in that, The modified spherical silica containing blocked isocyanate groups has a carbon content of <0.65% after 0 days of storage and a carbon content of <0.62% and a moisture content of <0.027% after 6 months of storage.

3. The modified spherical silica containing blocked isocyanate groups according to claim 1 or 2, characterized in that, The carbon content of the modified spherical silica containing blocked isocyanate groups after 6 months of storage is 0.580–0.619%.

4. A method for preparing modified spherical silica containing blocked isocyanate groups as described in any one of claims 1 to 3, characterized in that, The preparation method includes the following steps: An isocyanate coupling agent is sprayed onto the surface of silica powder with a moisture content of less than 0.03% to obtain isocyanate-modified silica powder; the isocyanate coupling agent is a methoxy isocyanate, an ethoxy isocyanate, a pyridyl isocyanate, or a benzene ring isocyanate. The isocyanate-modified silica powder was dispersed in a solvent, and then an oxime blocking agent A solution was added and reacted at 100-140°C for 4-8 hours. After the reaction was completed, the temperature was cooled to 20-80°C. An oxime blocking agent B solution was added to the cooled reaction system and reacted at 20–80°C for 2–4 hours. After the reaction was completed, the precipitate was washed several times and then dried at 35–45°C to obtain modified spherical silica containing blocked isocyanate groups. The oxime blocking agent A is at least one of pyruvate oxime, glyoxylate oxime, and 2-oxocyclopentaacetic acid oxime; the oxime blocking agent B is at least one of acetaldehyde oxime, acetone oxime, butanone oxime, pentanone oxime, cyclopentanone oxime, and cyclohexanone oxime.

5. The preparation method according to claim 4, characterized in that, The silica powder with a moisture content of less than 0.03% is obtained by drying silica raw materials in a roller furnace.

6. The preparation method according to claim 4, characterized in that, The mass ratio of the silica powder with a moisture content of less than 0.03% to the isocyanate coupling agent is 100:0.1 to 1.

5.

7. The preparation method according to claim 4 or 6, characterized in that, The isocyanate coupling agent is at least one of 3-isocyanatopropyltrimethoxysilane, 2-isocyanatepyridine, isocyanatopropyltriethoxysilane, triphenylmethane triisocyanate, and 2-(trifluoromethoxy)phenyl isocyanate.

8. The preparation method according to claim 4, characterized in that, The molar ratio of the isocyanate coupling agent, oxime blocking agent A, and oxime blocking agent B is 1:1 to 5:0.01 to 5.

9. The preparation method according to claim 8, characterized in that, The molar ratio of the isocyanate coupling agent, oxime blocking agent A, and oxime blocking agent B is 1:1 to 5:0.01 to 1.

10. The preparation method according to claim 4, characterized in that, The oxime blocking agent A is two of pyruvate oxime, glyoxylate oxime, and 2-oxocyclopentaacetic acid oxime, and the molar ratio of the two is 1-3:1-3.

11. The preparation method according to claim 10, characterized in that, The oxime blocking agent A is pyruvate oxime and 2-oxocyclopentaacetic acid oxime, or glyoxylate oxime and 2-oxocyclopentaacetic acid oxime.

12. The preparation method according to claim 4, characterized in that, The oxime-type blocking agent B is two of the following: acetaldehyde oxime, acetone oxime, butanone oxime, pentanone oxime, cyclopentanone oxime, and cyclohexanone oxime, and the molar ratio of the two is 1-3:1-3.

13. The preparation method according to claim 12, characterized in that, The oxime-type blocking agent B is acetaldehyde oxime and acetone oxime, or acetone oxime and butanone oxime, or butanone oxime and cyclohexanone oxime, or butanone oxime and cyclopentanone oxime, or acetone oxime and pentanone oxime, or pentanone oxime and cyclohexanone oxime, or acetaldehyde oxime and pentanone oxime, or acetone oxime and cyclopentanone oxime, or acetone oxime and cyclohexanone oxime.

14. The preparation method according to claim 4, characterized in that, The solvent in the oxime blocking agent A solution is anhydrous toluene; the molar volume ratio of the oxime blocking agent A to anhydrous toluene is 0.01–0.3 mol: 50–150 mL.

15. The preparation method according to claim 4, characterized in that, The solvent in the oxime blocking agent B solution is anhydrous toluene; the molar volume ratio of the oxime blocking agent B to anhydrous toluene is 0.001–0.1 mol: 0.1–15 mL.

16. The preparation method according to claim 4, characterized in that, The drying process is carried out in a vacuum drying oven.

17. The application of the modified spherical silica containing blocked isocyanate groups as described in any one of claims 1 to 3, or the modified spherical silica containing blocked isocyanate groups obtained by the preparation method described in any one of claims 4 to 16, in an encapsulation substrate.

18. The use of the modified spherical silica containing blocked isocyanate groups as described in any one of claims 1 to 3, or the modified spherical silica containing blocked isocyanate groups obtained by the preparation method described in any one of claims 4 to 16, in coatings, adhesives, polymer materials, catalysis, drug loading, or adsorption separation.

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