Silica aerogel dispersion, method for preparing the same, and use thereof

Abstract

The application discloses a kind of silica aerogel dispersions and its preparation method and application;According to mass fraction, 100 parts of silica aerogel dispersion, comprising the following components: 10-15 parts modified silica aerogel, 85-90 parts ethylene glycol;Wherein, modified silica aerogel is added to silane containing double bond after hydrolysis using silicon source, then polycondensation, aging, again with vinyl silicone oil, styrene, maleic anhydride reaction, by impurity removal, drying is obtained.The viscosity of the silica aerogel dispersion of the application is low, the solid content is high, the particle size is small, it is applied in polyester in-situ polymerization, the breaking strength and breaking elongation of the prepared polyester fiber do not change obviously, the heat preservation performance of fiber is good, and the washing fastness after the application of silica aerogel is high, and it is not easy to fall off.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of fine chemical technology, in particular to a silica aerogel dispersion, a preparation method thereof and application thereof in polyester in-situ polymerization. BACKGROUND

[0002] In China, synthetic fibers containing more than 85% of polyethylene terephthalate components are called polyester fibers, and the trade name is polyester. Polyester is a polymer obtained by polycondensation of polybasic acid and polyhydric alcohol. The direct esterification method and the ester exchange method are used in polyester synthesis process. The direct esterification method has the advantages of low raw material consumption and short reaction time, and becomes the main synthesis process. The main reaction process of the direct esterification method is as follows: first, esterification reaction of high-purity terephthalic acid and ethylene glycol to generate ester and water, and then polycondensation of the generated ester to obtain polyester and ethylene glycol, wherein the polycondensation includes pre-polycondensation and final polycondensation. In order to improve the performance of polyester fibers, special substances (such as silicon-containing substances) are often added to modify the polyester fibers to improve the functionality of the fibers. For example, a polymer fiber with improved dispersibility is disclosed in Chinese Patent No. CN106460239A, which contains 0.1-20% by weight of silicone and silicone polymer as a dispersion phase. The silicone polymer can be cyclic polysiloxane, linear polysiloxane, branched polysiloxane, cross-linked polysiloxane and the like. Japanese Patent No. JP2023001834A discloses a polyester resin composition, which can make polyester fibers or films achieve good haze by adding 0.1-20% by mass of silica particles. The average particle size of the silica used is less than 3.0 microns, and the maximum particle size is less than 10.0 microns.

[0003] Aerogel has a special three-dimensional network structure, and the pore size is smaller than the average free path of air molecules, which can block all channels of heat propagation: heat conduction, heat convection and heat radiation, so it has good thermal insulation effect. Silica aerogel is usually prepared by sol-gel method, and its forming mechanism can be briefly described as follows: the silicon source is hydrolyzed by acid catalysis, and silicon exists in the form of Si(OH)4 in the solution system; after complete hydrolysis, alkali solution is added to initiate small molecule polycondensation reaction, in which -OH between them is dehydrated and condensed to form Si-O-Si structure, and the solution changes from sol state to gel "jelly" state; then the three-dimensional network framework structure of silica aerogel molecules is stabilized by aging; finally, the solution in the pore structure of the aerogel skeleton is replaced by gas molecules by solvent replacement and drying process, forming high specific surface area, nanoporous silica aerogel.

[0004] Silica aerogel is a kind of aerogel material with low density, low thermal conductivity, high specific surface area and high adsorption. It has high purity and large surface activity, and has been applied in building insulation, industrial insulation, polymer materials, aerospace and daily chemical industry. In order to improve the thermal insulation and insulation performance of fibers, the Chinese patent with publication number CN103388193A discloses a preparation method of aerogel modified synthetic fiber, 1) aerogel powder and polymer resin are mixed, and the mass ratio of mixing is 1:20-35, and mixing and granulation are carried out in a mixer; 2) melt spinning of the master batch obtained by mixing and granulation to obtain synthetic fiber; the Chinese patent with publication number CN110305340A discloses a preparation method of aerogel composite plastic master batch: 1) mix aerogel slurry and water-based resin emulsion uniformly to obtain aerogel water-based resin mixed solution; 2) granulate and dry the aerogel water-based mixed solution by spray drying to obtain heat insulation functional master batch; 3) mix and granulate the resin master batch and the heat insulation functional master batch to obtain the aerogel composite plastic master batch.

[0005] However, silica aerogel products have the disadvantages of low strength, poor toughness and easy breakage, which to some extent limit the practical application of the products. By modifying and improving the performance of silica aerogel, the flexibility and compatibility of the aerogel with the application system are improved. In order to improve the strength, the Chinese patent with publication number CN111592329A discloses a preparation method of modified silica aerogel and modified silica aerogel. The thiol modified fiber is used as a reinforcing material, and a carbon-carbon unsaturated double bond modifier is used for modification during the preparation of silica aerogel. The thiol and carbon-carbon unsaturated double bond undergo "thiol-ene" click chemistry reaction under ultraviolet light irradiation to obtain fiber reinforced silica aerogel.

[0006] To improve the compatibility of aerogels with the system, hydrophobic / hydrophilic modifications are performed on the aerogels. Modification methods for silica aerogels mainly include the co-precursor method and surface post-treatment method. The co-precursor method involves adding a surface modifier to a silicon source precursor, followed by subsequent reactions such as hydrolysis and polycondensation. The surface post-treatment method involves reacting the surface modifier with the hydroxyl groups on the surface of the silica wet gel after its formation. Chinese patent CN111592004A discloses a method for preparing silica aerogels and the silica aerogel itself. In the preparation process, a carbon-carbon unsaturated double bond modifier is used to modify the silica wet gel, giving it carbon-carbon unsaturated double bonds. The wet gel is then immersed in a solution of a multi-thiol aromatic compound to undergo a thiol-alkene click chemical reaction. The surface of the silica wet gel is coated with a layer of cross-linked aromatic compound, which effectively resists capillary shrinkage and collapse caused by solvent evaporation during atmospheric pressure drying, thus achieving atmospheric pressure drying. Chinese Patent CN105819457A discloses a method for preparing silica aerogel and its application. It employs an acid-base catalytic sol-gel two-step method to prepare a wet silica gel, followed by aging, a one-step solvent exchange-surface modification process, and finally, atmospheric pressure drying to prepare a silica aerogel with low density and high specific surface area. Specifically, the wet gel is immersed in a mixed solution of n-hexane and trimethylchlorosilane for solvent exchange and surface modification. Chinese Patent CN107572538A discloses a hydrophilic silica aerogel material and its preparation method. The method involves: 1) uniformly mixing a silicon source with water, an acidic catalyst, and a solvent to form a sol; 2) adding an alkaline catalyst to the sol and mixing and stirring to form a gel, followed by aging; 3) solvent exchange of the aged gel to obtain a displaced gel; and 4) freeze-drying the displaced gel to obtain the hydrophilic silica aerogel material.

[0007] Adding silica aerogel to in-situ polyester polymerization requires that the aerogel be uniformly dispersed in the polyester, have good compatibility with the polyester, have high strength, and not easily fall off during subsequent use. Existing modified silica aerogels cannot simultaneously meet the above requirements. Summary of the Invention

[0008] To solve the above technical problems, the present application aims to provide a silica aerogel dispersion and its preparation method and application; the modified silica aerogel in the present application contains both lipophilic groups and hydrophilic groups on its surface, the hydrophilic groups improve the dispersion performance in ethylene glycol, so that the silica aerogel dispersion does not appear phenomena such as sedimentation, agglomeration, and thickening during storage or transportation, the lipophilic groups can improve the compatibility of the silica aerogel with polymers in polyester polymerization, thereby enabling the silica aerogel to be uniformly dispersed in the polyester, and the silicon oil introduced in the modified silica aerogel has flexibility, which improves the mechanical strength of the silica aerogel and prevents it from falling off during use.

[0009] To achieve the above technical purposes and effects, the present application realizes the technical solutions as follows:

[0010] In one aspect, the present application provides a silica aerogel dispersion, which contains the following components in 100 parts of the silica aerogel dispersion by mass fraction: 10-15 parts of modified silica aerogel and 85-90 parts of ethylene glycol; wherein the modified silica aerogel is obtained by adding a silane containing double bonds to a silicon source after hydrolysis, followed by polycondensation, aging, and reaction with vinyl silicone oil, styrene, and maleic anhydride, and then removing impurities and drying.

[0011] Preferably, the silicon source is at least one of tetraethyl orthosilicate, methyl orthosilicate, tetramethoxysilane, and phenyltriethoxysilane.

[0012] Preferably, the silane containing double bonds is at least one of 3-(methacryloyloxy)propyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltrichlorosilane, vinyl dimethylchlorosilane, vinyl dimethylethoxysilane, vinyl methyl dichlorosilane, vinyl methyl dimethoxysilane, and vinyl methyl diethoxysilane.

[0013] Preferably, the vinyl silicone oil is a commercially available product, which is a polydimethylsiloxane with a vinyl group at the end of the molecular chain, and has a viscosity of 600 mPa·s.

[0014] Further, the preparation method of the modified silica aerogel is as follows:

[0015] 1) Mix the silicon source, ethanol, and water according to a certain mass ratio, add an acidic solution to adjust the pH value to 1-4, and hydrolyze at 20-80℃ for 0.1-10h; add a silane containing double bonds and react for 0.5-2h; add an alkaline solution to adjust the pH value to 6-7, and stand to obtain a wet gel by polycondensation; pour an ethanol solution into the wet gel and age for 12-24h, and replace the ethanol solution every 6h to obtain the aged gel;

[0016] 2) add vinyl silicone oil to the aged gel, add initiator, control the temperature at 70-90℃, react for 1-2h; then add styrene, maleic anhydride, initiator, react at 70-90℃ for 2-4h, cool, remove impurities, dry to obtain modified silica aerogel.

[0017] Further, in the preparation method of the modified silica aerogel, the mass ratio of the four of the silicon source, ethanol, water and double bond-containing silane in step 1) is (260-270):(100-400):(50-150):(20-50).

[0018] Further, in step 2) of the preparation method of the modified silica aerogel, 5-8 parts of vinyl silicone oil and 0.1-0.2 parts of initiator are first added to every 200 parts of the aged gel for reaction, and then 16-21 parts of styrene, 15-20 parts of maleic anhydride and 0.5-0.8 parts of initiator are added for reaction.

[0019] Preferably, the acidic solution in step 1) is at least one of hydrochloric acid, oxalic acid, sulfuric acid, acetic acid, nitric acid and citric acid; and the basic solution in step 1) is at least one of ammonia, sodium hydroxide and potassium hydroxide.

[0020] Preferably, the initiator in step 2) is at least one of dicumyl peroxide and azobisisobutyronitrile.

[0021] Another aspect of the present application provides a preparation method of a silica aerogel dispersion, which specifically comprises: mixing a certain amount of modified silica aerogel and ethylene glycol and uniformly dispersing them by mechanical stirring to obtain a silica aerogel dispersion.

[0022] The present application also provides an application of the silica aerogel dispersion in polyester in-situ polymerization. Specifically, the silica aerogel dispersion is added in the polyester polymerization process, and the addition timing can be in the esterification, pre-polycondensation and final polycondensation process or before the reaction. Since the silica aerogel dispersion of the present application is the dispersion of modified silica aerogel in ethylene glycol, and the ethylene glycol can be used as the raw material for polyester esterification, the silica aerogel dispersion is preferably added before the esterification reaction.

[0023] The present application further provides an aerogel polyester fiber, which is obtained by esterification, pre-polycondensation and final polycondensation of raw materials such as the silica aerogel dispersion, polyterephthalic acid, ethylene glycol and oxidizing agent, and then spinning.

[0024] The present application has the following beneficial effects:

[0025] The modified silica aerogel surface of the present application contains both lipophilic groups and hydrophilic groups, and the silica aerogel is easy to float on the dispersion liquid due to its low density, and is difficult to disperse, the hydrophilic groups introduced after modification improve the dispersion performance of the silica aerogel in ethylene glycol, so that the prepared silica aerogel dispersion does not appear phenomena such as sedimentation, agglomeration, and coarsening during storage or transportation, and the quality of the dispersion is improved; the lipophilic groups introduced can improve the compatibility of the silica aerogel with the polymer in polyester polymerization, and then the silica aerogel can be uniformly dispersed in the polyester; at the same time, the introduced silicone oil has flexibility, and improves the mechanical strength of the silica aerogel, and the silica aerogel is not easy to fall off during use.

[0026] The silica aerogel dispersion of the present application has low viscosity, high solid content, and small particle size, and when applied to in-situ polymerization of polyester, the breaking strength and breaking elongation of the prepared polyester fiber do not change obviously, the heat preservation performance of the fiber is good, and the silica aerogel after application has high washing fastness and is not easy to fall off. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The nitrogen adsorption-desorption curve (a) and the pore size distribution graph (b) of the modified silica aerogel A1 prepared in Example 1 of the present application. Figure 1 Figure 1

[0028] Figure 2 The SEM graph of the modified silica aerogel A1 prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0029] The technical solutions in the present application will be described clearly and completely below in combination with specific embodiments, obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0030] The present application provides a silica aerogel dispersion, according to mass fraction, 10-15 parts of modified silica aerogel and 85-90 parts of ethylene glycol are contained in 100 parts of the silica aerogel dispersion; wherein the modified silica aerogel is obtained by hydrolysis of a silicon source, then adding a silane containing double bonds, followed by polycondensation, aging, and then reacting with vinyl silicone oil, styrene, and maleic anhydride, and then removing impurities and drying.

[0031] Preferably, the silicon source is at least one of tetraethyl orthosilicate, methyl orthosilicate, tetramethoxysilane, and phenyltriethoxysilane.

[0032] ​​The double bond-containing silane is preferably at least one of 3-(methacryloyloxy)propyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltrichlorosilane, vinyl dimethylchlorosilane, vinyl dimethylethoxysilane, vinyl methyl dichlorosilane, vinyl methyl dimethoxysilane, and vinyl methyl diethoxysilane.

[0033] The vinyl silicone oil is a commercially available product, which is a polydimethylsiloxane having a vinyl group at the end of a molecular chain, and has a viscosity of 600 mPa·s.

[0034] The preparation method of the modified silica aerogel is as follows:

[0035] 1) A silicon source, ethanol, and water are mixed in a certain mass ratio, an acidic solution is added dropwise to adjust the pH value to 1-4, and a hydrolysis reaction is performed at 20-80℃ for 0.1-10h; a double bond-containing silane is added, and a reaction is performed for 0.5-2h; an alkaline solution is added dropwise to adjust the pH value to 6-7, and a wet gel is obtained by standing and condensation; an ethanol solution is poured into the wet gel, and the gel is aged for 12-24h, and the ethanol solution is replaced every 6h to obtain an aged gel; in step 1), the mass ratio of the silicon source, ethanol, water, and double bond-containing silane is (260-270):(100-400):(50-150):(20-50).

[0036] 2) Vinyl silicone oil is added to the aged gel, an initiator is added, and a reaction is performed at a temperature of 70-90℃ for 1-2h; then styrene, maleic anhydride, and an initiator are added, and a reaction is performed at a temperature of 70-90℃ for 2-4h, and the modified silica aerogel is obtained by cooling, impurity removal, and drying. In step 2), 5-8 parts of vinyl silicone oil and 0.1-0.2 parts of an initiator are first added to 200 parts of the aged gel for reaction, and then 16-21 parts of styrene, 15-20 parts of maleic anhydride, and 0.5-0.8 parts of an initiator are added for reaction.

[0037] The acidic solution in step 1) is at least one of hydrochloric acid, oxalic acid, sulfuric acid, acetic acid, nitric acid, and citric acid; and the alkaline solution in step (1) is at least one of ammonia, sodium hydroxide, and potassium hydroxide.

[0038] The initiator in step 2) is at least one of dicumyl peroxide and azobisisobutyronitrile.

[0039] The preparation method of the silica aerogel dispersion is as follows: a certain amount of modified silica aerogel and ethylene glycol are mixed and uniformly dispersed by mechanical stirring to obtain a silica aerogel dispersion.

[0040] This invention also provides the application of this silica aerogel dispersion in in-situ polyester polymerization. Specifically, the silica aerogel dispersion is added during the polyester polymerization process, either during esterification, pre-condensation, final condensation, or before the reaction. Since the silica aerogel dispersion of this invention is a modified silica aerogel dispersed in ethylene glycol, and ethylene glycol can be used as a raw material for polyester esterification, the silica aerogel dispersion is preferably added before the esterification reaction.

[0041] The present invention further provides an aerogel polyester fiber, which is obtained by esterification, pre-condensation and final condensation of raw materials such as silica aerogel dispersion, polyethylene terephthalic acid, ethylene glycol and oxidant to obtain polyester melt, and then spinning it.

[0042] The present invention will be further described in detail below through specific embodiments.

[0043] Preparation of modified silica aerogel

[0044] Example 1

[0045] 264 parts of tetraethyl orthosilicate, 150 parts of ethanol, and 100 parts of water were mixed, and 1 mol / L hydrochloric acid was added dropwise to adjust the pH to 2.0. The mixture was hydrolyzed at 60°C for 0.5 h. 30 parts by mass of 3-(methacryloyloxy)propyltrimethoxysilane were added, and the mixture was reacted for 1 h. 1 mol / L dilute ammonia was added dropwise to adjust the pH to 6.5, and the mixture was allowed to stand for condensation to obtain a wet gel. An ethanol solution was poured into the wet gel and aged for 18 h, with the ethanol solution being replaced every 6 h, to obtain the aged gel.

[0046] Six parts by weight of vinyl silicone oil were added to 200 parts by weight of aged gel, along with 0.15 parts by weight of benzoyl peroxide. The reaction was carried out at 80°C for 1.5 hours. Then, 18 parts by weight of styrene, 16 parts by weight of maleic anhydride, and 0.6 parts by weight of benzoyl peroxide were added. The reaction was carried out at 80°C for 3 hours. After cooling, impurity removal, and drying, modified silica aerogel A1 was obtained.

[0047] Figure 1 Nitrogen adsorption-desorption curves of modified silica aerogel A1 ( Figure 1 (a) and aperture distribution map ( Figure 1 (b) The specific surface area of ​​BET was calculated to be 852.69 m². 2 / g, the average pore size of BJH desorption is 4.95nm, and the pore structure is a mesoporous distribution close to micropores. Figure 2 The image shows a SEM image of modified silica aerogel A1. The aerogel exhibits a loose and porous structure with pore sizes mostly below 10 nm, consistent with the results of nitrogen adsorption-desorption.

[0048] Example 2

[0049] Mix 264 parts of tetraethyl orthosilicate, 400 parts of ethanol and 50 parts of water, drop 0.5 mol / L hydrochloric acid to adjust pH value to 1.0, hydrolysis reaction at 80℃ for 0.1 h; add 50 parts of 3-(methacryloyloxy) propyl trimethoxysilane, reaction for 2 h; drop 0.5 mol / L dilute ammonia water to adjust pH value to 6.5, and get wet gel by standing and condensation; pour ethanol solution into the wet gel to age for 24 h, and change the ethanol solution every 6 h to get aged gel.

[0050] Add 8 parts of vinyl silicone oil to 200 parts of the aged gel, add 0.2 parts of dicumyl peroxide, control the temperature at 90℃ for reaction for 1 h; then add 21 parts of styrene, 20 parts of maleic anhydride and 0.8 parts of dicumyl peroxide, reaction at 90℃ for 4 h, cool, remove impurities and dry to obtain modified silica aerogel A2.

[0051] Example 3

[0052] Mix 264 parts of tetraethyl orthosilicate, 100 parts of ethanol and 150 parts of water, drop 0.1 mol / L hydrochloric acid to adjust pH value to 4.0, hydrolysis reaction at 20℃ for 10 h; add 20 parts of 3-(methacryloyloxy) propyl trimethoxysilane, reaction for 0.5 h; drop 0.1 mol / L dilute ammonia water to adjust pH value to 6.5, and get wet gel by standing and condensation; pour ethanol solution into the wet gel to age for 12 h, and change the ethanol solution every 6 h to get aged gel.

[0053] Add 5 parts of vinyl silicone oil to 200 parts of the aged gel, add 0.1 parts of azobisisobutyronitrile, control the temperature at 70℃ for reaction for 2 h; then add 16 parts of styrene, 15 parts of maleic anhydride and 0.5 parts of azobisisobutyronitrile, reaction at 70℃ for 2 h, cool, remove impurities and dry to obtain modified silica aerogel A3.

[0054] Comparative Example 1

[0055] Mix 264 parts of tetraethyl orthosilicate, 150 parts of ethanol and 100 parts of water, drop 1 mol / L hydrochloric acid to adjust pH value to 2.0, hydrolysis reaction at 60℃ for 0.5 h; drop 1 mol / L dilute ammonia water to adjust pH value to 6.5, and get wet gel by standing and condensation; pour ethanol solution into the wet gel to age for 18 h, and change the ethanol solution every 6 h to get aged gel, and dry to obtain silica aerogel B1.

[0056] Comparative Example 2

[0057] Mix 264 parts of tetraethyl orthosilicate, 150 parts of ethanol and 100 parts of water, add 1 mol / L hydrochloric acid dropwise to adjust the pH value to 2.0, and hydrolyze at 60°C for 0.5 h; add 30 parts of 3-(methacryloyloxy) propyl trimethoxysilane, and react for 1 h; add 1 mol / L dilute ammonia water dropwise to adjust the pH value to 6.5, and stand to condense to obtain a wet gel; pour an ethanol solution into the wet gel to age for 18 h, replace the ethanol solution every 6 h, obtain an aged gel, and dry to obtain silica aerogel B2.

[0058] Comparative Example 3

[0059] Mix 264 parts of tetraethyl orthosilicate, 150 parts of ethanol and 100 parts of water, add 1 mol / L hydrochloric acid dropwise to adjust the pH value to 2.0, and hydrolyze at 60°C for 0.5 h; add 30 parts of 3-(methacryloyloxy) propyl trimethoxysilane, and react for 1 h; add 1 mol / L dilute ammonia water dropwise to adjust the pH value to 6.5, and stand to condense to obtain a wet gel; pour an ethanol solution into the wet gel to age for 18 h, replace the ethanol solution every 6 h, obtain an aged gel, and dry to obtain silica aerogel B2.

[0060] Add 6 parts of vinyl silicone oil to 200 parts of the aged gel, add 0.15 parts of dicumyl peroxide, control the temperature to 80°C, react for 1.5 h, cool, remove impurities, and dry to obtain silica aerogel B3.

[0061] Comparative Example 4

[0062] Mix 264 parts of tetraethyl orthosilicate, 150 parts of ethanol and 100 parts of water, add 1 mol / L hydrochloric acid dropwise to adjust the pH value to 2.0, and hydrolyze at 60°C for 0.5 h; add 30 parts of 3-(methacryloyloxy) propyl trimethoxysilane, and react for 1 h; add 1 mol / L dilute ammonia water dropwise to adjust the pH value to 6.5, and stand to condense to obtain a wet gel; pour an ethanol solution into the wet gel to age for 18 h, replace the ethanol solution every 6 h, obtain an aged gel, and dry to obtain silica aerogel B2.

[0063] Add 20 parts of vinyl silicone oil to 200 parts of the aged gel, add 0.15 parts of dicumyl peroxide, control the temperature to 80°C, react for 1.5 h; then add 18 parts of styrene, 16 parts of maleic anhydride and 0.6 parts of dicumyl peroxide, and react at 80°C for 3 h; cool, remove impurities, and dry to obtain silica aerogel B4.

[0064] Preparation and testing of silica aerogel dispersion

[0065] The silica aerogel prepared in Examples 1-3 and Comparative Examples 1-4 was dispersed uniformly with ethylene glycol in a mass ratio shown in Table 1 by mechanical stirring to obtain silica aerogel dispersions 1-9.

[0066] Table 1. Mass ratio of components of silica aerogel dispersion

[0067]

[0068]

[0069] The silica aerogel dispersions 1-8 were tested for viscosity and particle size, and the test data are shown in Table 2. The slurry obtained from the silica aerogel dispersion 9 was paste-like and had poor flowability, so no relevant tests were performed.

[0070] Table 2. Test results of properties of silica aerogel dispersion

[0071]

[0072] As shown in Table 2, the silica aerogel dispersions 1-3 and 8 had a smaller particle size D90 and lower viscosity, and the particle size and viscosity changed little after 30 days of storage. The silica aerogel dispersions 4-7 had a larger particle size D90 and higher viscosity, and the particle size and viscosity changed greatly after 30 days of storage.

[0073] Preparation and performance testing of polyester fibers

[0074] The silica aerogel dispersions 1-8 were added to a polyester reaction vessel (the mass of silica aerogel in the silica aerogel dispersion accounted for 1% of the total mass of terephthalic acid and ethylene glycol, the molar ratio of terephthalic acid to ethylene glycol was 1:1.2, and the mass of the catalyst tetrabutyl titanate accounted for 0.2% of the mass of terephthalic acid), and esterification (reaction temperature 265°C, reaction pressure 150 kPa), pre-polycondensation (reaction temperature 260°C, reaction pressure 3 kPa), and final polycondensation (reaction temperature 265°C, reaction pressure 100 Pa) were performed to obtain a polyester melt. Spinning was performed at a temperature of 255°C and a winding speed of 4500 m / min to obtain polyester fibers.

[0075] The polyester fibers 1-8 and a commercially available polyester fiber 9 (no silica aerogel dispersion was added during polymerization) were tested for breaking strength, breaking elongation, room temperature thermal conductivity, and room temperature thermal conductivity after 50 times of washing, and the test results are shown in Table 3.

[0076] Table 3. Test results of properties of polyester fibers

[0077]

[0078] As shown in Table 3, the tensile breaking strength and tensile breaking elongation of the polyester fibers No. 1-3 and No. 8 are similar to those of the commercially available polyester fibers, which indicates that the modified silicon dioxide aerogel has little effect on the mechanical properties of the polyester fibers; the thermal conductivity of the polyester fibers No. 1-3 and No. 8 is low, and the fibers have good heat preservation performance; and the room temperature thermal conductivity of the fibers changes little after washing for 50 times, which indicates that the modified silicon dioxide aerogel has good washing resistance.

[0079] The above examples are only used to illustrate the technical solutions of the present application but not limit the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently without departing from the purpose and scope of the present application, and all of them should be covered in the scope of the claims of the present application.

Claims

1. A silica aerogel dispersion characterized in that: Each 100 parts of the silica aerogel dispersion contains the following components by mass fraction: 10-15 parts of modified silica aerogel, 85-90 parts of ethylene glycol; wherein the modified silica aerogel is obtained by adding a silane containing double bonds after hydrolysis of a silicon source, then performing polycondensation and aging, and then reacting with vinyl silicone oil, styrene and maleic anhydride, and finally removing impurities and drying; The preparation method of the modified silica aerogel is as follows: 1) A silicon source, ethanol and water are mixed in a certain mass ratio, an acidic solution is added dropwise to adjust the pH value to 1-4, and a hydrolysis reaction is performed at 20-80℃ for 0.1-10h; a silane containing double bonds is added and reacted for 0.5-2h; an alkaline solution is added dropwise to adjust the pH value to 6-7, and a wet gel is obtained by standing and polycondensation; an ethanol solution is poured into the wet gel and aged for 12-24h, and the ethanol solution is replaced every 6h to obtain an aged gel; 2) The vinyl silicone oil is added to the aged gel, an initiator is added, the temperature is controlled at 70-90℃, and the reaction is performed for 1-2h; then styrene, maleic anhydride and an initiator are added, and the reaction is performed at 70-90℃ for 2-4h, and then the modified silica aerogel is obtained by cooling, removing impurities and drying.

2. A silica aerogel dispersion according to claim 1, characterized in that, The silicon source is at least one of tetraethyl orthosilicate, methyl orthosilicate, tetramethoxysilane and phenyltriethoxysilane.

3. The silica aerogel dispersion of claim 1, wherein, The silane containing double bonds is at least one of 3-(methacryloyloxy)propyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltrichlorosilane, vinyl dimethylchlorosilane, vinyl dimethylethoxysilane, vinyl methyl dichlorosilane, vinyl methyl dimethoxysilane and vinyl methyl diethoxysilane.

4. The silica aerogel dispersion of claim 1, wherein, In the preparation method of the modified silica aerogel, the mass ratio of the silicon source, ethanol, water and silane containing double bonds in step 1) is (260-270):(100-400):(50-150):(20-50).

5. The silica aerogel dispersion of claim 1, wherein, In step 2) of the preparation method of the modified silica aerogel, 5-8 parts of vinyl silicone oil and 0.1-0.2 parts of an initiator are first added to every 200 parts of the aged gel for reaction, and then 16-21 parts of styrene, 15-20 parts of maleic anhydride and 0.5-0.8 parts of an initiator are added for reaction.

6. The silica aerogel dispersion of claim 1, wherein, The acidic solution in step 1) is at least one of hydrochloric acid, oxalic acid, sulfuric acid, acetic acid, nitric acid and citric acid; and the alkaline solution in step 1) is at least one of ammonia, sodium hydroxide and potassium hydroxide.

7. The silica aerogel dispersion of claim 1, wherein, The initiator in step 2) is at least one of dicumyl peroxide and azobisisobutyronitrile.

8. A process for the preparation of a silica aerogel dispersion according to any one of claims 1 to 7, characterized in that: A certain mass of the modified silica aerogel and ethylene glycol are mixed and uniformly dispersed by mechanical stirring to obtain a silica aerogel dispersion.

9. Use of the silica aerogel dispersion of any one of claims 1-7 in in-situ polymerization of polyester.

Images