CN115784240A - Preparation method of non-spherical silica sol - Google Patents
Preparation method of non-spherical silica sol Download PDFInfo
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- CN115784240A CN115784240A CN202211657222.1A CN202211657222A CN115784240A CN 115784240 A CN115784240 A CN 115784240A CN 202211657222 A CN202211657222 A CN 202211657222A CN 115784240 A CN115784240 A CN 115784240A
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- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 title claims abstract description 100
- 238000002360 preparation method Methods 0.000 title claims abstract description 45
- 239000013078 crystal Substances 0.000 claims abstract description 79
- 239000000413 hydrolysate Substances 0.000 claims abstract description 79
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 47
- 238000000034 method Methods 0.000 claims abstract description 45
- 239000012452 mother liquor Substances 0.000 claims abstract description 40
- 238000002156 mixing Methods 0.000 claims abstract description 34
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 29
- 229920006318 anionic polymer Polymers 0.000 claims abstract description 21
- KPUWHANPEXNPJT-UHFFFAOYSA-N disiloxane Chemical class [SiH3]O[SiH3] KPUWHANPEXNPJT-UHFFFAOYSA-N 0.000 claims abstract description 15
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 14
- 235000012239 silicon dioxide Nutrition 0.000 claims abstract description 9
- 230000003301 hydrolyzing effect Effects 0.000 claims abstract description 5
- HZAXFHJVJLSVMW-UHFFFAOYSA-N 2-Aminoethan-1-ol Chemical compound NCCO HZAXFHJVJLSVMW-UHFFFAOYSA-N 0.000 claims description 26
- 239000000463 material Substances 0.000 claims description 17
- 229920002125 Sokalan® Polymers 0.000 claims description 16
- -1 amine compounds Chemical class 0.000 claims description 16
- 239000004584 polyacrylic acid Substances 0.000 claims description 16
- LFQCEHFDDXELDD-UHFFFAOYSA-N tetramethyl orthosilicate Chemical compound CO[Si](OC)(OC)OC LFQCEHFDDXELDD-UHFFFAOYSA-N 0.000 claims description 15
- 239000002904 solvent Substances 0.000 claims description 13
- 238000010438 heat treatment Methods 0.000 claims description 10
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 9
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 9
- 239000003960 organic solvent Substances 0.000 claims description 9
- 229920001577 copolymer Polymers 0.000 claims description 8
- 238000001914 filtration Methods 0.000 claims description 8
- 239000003054 catalyst Substances 0.000 claims description 7
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 claims description 6
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 6
- 150000008044 alkali metal hydroxides Chemical class 0.000 claims description 6
- 238000004519 manufacturing process Methods 0.000 claims description 6
- WGTYBPLFGIVFAS-UHFFFAOYSA-M tetramethylammonium hydroxide Chemical compound [OH-].C[N+](C)(C)C WGTYBPLFGIVFAS-UHFFFAOYSA-M 0.000 claims description 6
- NQOFYFRKWDXGJP-UHFFFAOYSA-N 1,1,2-trimethylguanidine Chemical compound CN=C(N)N(C)C NQOFYFRKWDXGJP-UHFFFAOYSA-N 0.000 claims description 5
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 claims description 5
- KYVBNYUBXIEUFW-UHFFFAOYSA-N 1,1,3,3-tetramethylguanidine Chemical compound CN(C)C(=N)N(C)C KYVBNYUBXIEUFW-UHFFFAOYSA-N 0.000 claims description 4
- VILCJCGEZXAXTO-UHFFFAOYSA-N 2,2,2-tetramine Chemical compound NCCNCCNCCN VILCJCGEZXAXTO-UHFFFAOYSA-N 0.000 claims description 4
- RPNUMPOLZDHAAY-UHFFFAOYSA-N Diethylenetriamine Chemical compound NCCNCCN RPNUMPOLZDHAAY-UHFFFAOYSA-N 0.000 claims description 4
- CHJJGSNFBQVOTG-UHFFFAOYSA-N N-methyl-guanidine Natural products CNC(N)=N CHJJGSNFBQVOTG-UHFFFAOYSA-N 0.000 claims description 4
- GSEJCLTVZPLZKY-UHFFFAOYSA-N Triethanolamine Chemical compound OCCN(CCO)CCO GSEJCLTVZPLZKY-UHFFFAOYSA-N 0.000 claims description 4
- ZRALSGWEFCBTJO-UHFFFAOYSA-N anhydrous guanidine Natural products NC(N)=N ZRALSGWEFCBTJO-UHFFFAOYSA-N 0.000 claims description 4
- STIAPHVBRDNOAJ-UHFFFAOYSA-N carbamimidoylazanium;carbonate Chemical compound NC(N)=N.NC(N)=N.OC(O)=O STIAPHVBRDNOAJ-UHFFFAOYSA-N 0.000 claims description 4
- ZBCBWPMODOFKDW-UHFFFAOYSA-N diethanolamine Chemical compound OCCNCCO ZBCBWPMODOFKDW-UHFFFAOYSA-N 0.000 claims description 4
- SWSQBOPZIKWTGO-UHFFFAOYSA-N dimethylaminoamidine Natural products CN(C)C(N)=N SWSQBOPZIKWTGO-UHFFFAOYSA-N 0.000 claims description 4
- 239000003002 pH adjusting agent Substances 0.000 claims description 4
- ZQZCOBSUOFHDEE-UHFFFAOYSA-N tetrapropyl silicate Chemical compound CCCO[Si](OCCC)(OCCC)OCCC ZQZCOBSUOFHDEE-UHFFFAOYSA-N 0.000 claims description 4
- MAGFQRLKWCCTQJ-UHFFFAOYSA-N 4-ethenylbenzenesulfonic acid Chemical compound OS(=O)(=O)C1=CC=C(C=C)C=C1 MAGFQRLKWCCTQJ-UHFFFAOYSA-N 0.000 claims description 3
- PIICEJLVQHRZGT-UHFFFAOYSA-N Ethylenediamine Chemical compound NCCN PIICEJLVQHRZGT-UHFFFAOYSA-N 0.000 claims description 3
- 230000007062 hydrolysis Effects 0.000 claims description 3
- 238000006460 hydrolysis reaction Methods 0.000 claims description 3
- 150000002357 guanidines Chemical class 0.000 claims description 2
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 2
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 2
- 238000006467 substitution reaction Methods 0.000 claims description 2
- 239000002245 particle Substances 0.000 abstract description 39
- 230000003321 amplification Effects 0.000 abstract description 7
- 230000000694 effects Effects 0.000 abstract description 7
- 238000003199 nucleic acid amplification method Methods 0.000 abstract description 7
- 238000005498 polishing Methods 0.000 abstract description 7
- 239000004065 semiconductor Substances 0.000 abstract description 7
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 abstract description 6
- 229910021645 metal ion Inorganic materials 0.000 abstract description 6
- 229910052710 silicon Inorganic materials 0.000 abstract description 6
- 239000010703 silicon Substances 0.000 abstract description 6
- 238000011031 large-scale manufacturing process Methods 0.000 abstract description 4
- 230000000052 comparative effect Effects 0.000 description 11
- 230000002572 peristaltic effect Effects 0.000 description 9
- 238000003756 stirring Methods 0.000 description 9
- 238000006243 chemical reaction Methods 0.000 description 8
- 239000011164 primary particle Substances 0.000 description 8
- 235000012431 wafers Nutrition 0.000 description 8
- OFOBLEOULBTSOW-UHFFFAOYSA-N Propanedioic acid Natural products OC(=O)CC(O)=O OFOBLEOULBTSOW-UHFFFAOYSA-N 0.000 description 7
- NIXOWILDQLNWCW-UHFFFAOYSA-N acrylic acid group Chemical group C(C=C)(=O)O NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 7
- 239000011976 maleic acid Substances 0.000 description 7
- 239000011163 secondary particle Substances 0.000 description 7
- VZCYOOQTPOCHFL-UHFFFAOYSA-N trans-butenedioic acid Natural products OC(=O)C=CC(O)=O VZCYOOQTPOCHFL-UHFFFAOYSA-N 0.000 description 7
- 229910021642 ultra pure water Inorganic materials 0.000 description 7
- 239000012498 ultrapure water Substances 0.000 description 7
- 241001089723 Metaphycus omega Species 0.000 description 6
- 238000001704 evaporation Methods 0.000 description 6
- 229910052751 metal Inorganic materials 0.000 description 6
- 239000002184 metal Substances 0.000 description 6
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 5
- 238000003917 TEM image Methods 0.000 description 5
- 239000012535 impurity Substances 0.000 description 5
- 238000004458 analytical method Methods 0.000 description 4
- 238000005303 weighing Methods 0.000 description 4
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 239000012798 spherical particle Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 229960001124 trientine Drugs 0.000 description 3
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 description 2
- 235000017060 Arachis glabrata Nutrition 0.000 description 2
- 241001553178 Arachis glabrata Species 0.000 description 2
- 235000010777 Arachis hypogaea Nutrition 0.000 description 2
- 235000018262 Arachis monticola Nutrition 0.000 description 2
- JPVYNHNXODAKFH-UHFFFAOYSA-N Cu2+ Chemical compound [Cu+2] JPVYNHNXODAKFH-UHFFFAOYSA-N 0.000 description 2
- 238000004220 aggregation Methods 0.000 description 2
- 230000002776 aggregation Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 229910001430 chromium ion Inorganic materials 0.000 description 2
- 239000000084 colloidal system Substances 0.000 description 2
- 229910001431 copper ion Inorganic materials 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 238000001879 gelation Methods 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 229910001453 nickel ion Inorganic materials 0.000 description 2
- 235000020232 peanut Nutrition 0.000 description 2
- 229910001414 potassium ion Inorganic materials 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 229910001415 sodium ion Inorganic materials 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 1
- VEQPNABPJHWNSG-UHFFFAOYSA-N Nickel(2+) Chemical compound [Ni+2] VEQPNABPJHWNSG-UHFFFAOYSA-N 0.000 description 1
- NPYPAHLBTDXSSS-UHFFFAOYSA-N Potassium ion Chemical compound [K+] NPYPAHLBTDXSSS-UHFFFAOYSA-N 0.000 description 1
- FKNQFGJONOIPTF-UHFFFAOYSA-N Sodium cation Chemical compound [Na+] FKNQFGJONOIPTF-UHFFFAOYSA-N 0.000 description 1
- LCKIEQZJEYYRIY-UHFFFAOYSA-N Titanium ion Chemical compound [Ti+4] LCKIEQZJEYYRIY-UHFFFAOYSA-N 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000004931 aggregating effect Effects 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 125000000129 anionic group Chemical group 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000007730 finishing process Methods 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 238000001095 inductively coupled plasma mass spectrometry Methods 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 239000011229 interlayer Substances 0.000 description 1
- 239000010410 layer Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 229920002521 macromolecule Polymers 0.000 description 1
- 238000000206 photolithography Methods 0.000 description 1
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- 238000003980 solgel method Methods 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
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Abstract
The invention relates to a preparation method of non-spherical silica sol, which comprises the following steps: (1) Mixing siloxane with water, and hydrolyzing to obtain hydrolysate; (2) Mixing the hydrolysate and the mother liquor, adding an anionic polymer into the system in the mixing process, and maintaining the pH value of the system to be more than or equal to 6 to obtain seed crystals; (3) And mixing the seed crystal with the hydrolysate to complete the growth of the seed crystal, thereby obtaining the non-spherical silica sol. The preparation method successfully synthesizes the non-spherical silica sol of peanut-shaped particles, wherein the mass content of silicon dioxide is high, the metal ion content is low, the non-spherical silica sol can be used for polishing a semiconductor large silicon wafer or a wafer, the preparation method is not limited to small-scale preparation in a laboratory, the particle size and the degree of association are only slightly changed after the process is amplified, the amplification effect is small, and the preparation method is suitable for large-scale production.
Description
Technical Field
The invention relates to the technical field of silica sol, in particular to a preparation method of non-spherical silica sol.
Background
Silica sol is a colloidal substance obtained by dispersing silica particles in water or other solvents, and is widely used in industries such as papermaking, catalysts, casting, coating and the like. With the progress of high integration and high performance of semiconductor integrated circuits, in the manufacture of semiconductor integrated circuit devices, in order to prevent problems such as unevenness (height difference) on the surface of a layer exceeding the depth of focus of photolithography and failing to obtain sufficient resolution, an interlayer insulating film, a buried wiring, and the like are planarized using a Chemical Mechanical Polishing (hereinafter referred to as CMP) method.
CN102390838A discloses a preparation method of non-spherical silica sol, which comprises the following steps: (1) Preparing non-spherical silica sol crystal seed mother liquor with the particle size of 20-50 nm; (2) preparing water-soluble silica sol with alcohol less than 5 wt%. The silica sol with a non-spherical structure is directly prepared by adopting a sol-gel method and carrying out process control on the charging ratio, the material concentration, the pH value of a reaction solution and the reaction temperature in the reaction process. The method has the advantages of less side reaction, short growth period, simple process, and no need of adding additives and inorganic salts or carrying out surface modification and other processes. The prepared silica sol can be applied to grinding and polishing in the rough polishing process of CMP technology or used as a carrier required in the modification process of other particles, the proportion of spherical particles in the non-spherical silica sol is less than 5 percent, the particle size of the colloid is controllable between 20 and 100nm, and the evaporation dehydration process is used for controlling the SiO in the water-soluble silica sol 2 The content of (B) is 5-50 wt%.
CN103896287A discloses a non-spherical silica sol and a preparation method thereof. The non-spherical silica sol comprises a liquid medium and sol particles, wherein the sol particles are formed by aggregating 2-10 silica colloid particles.
In the prior art, high-purity silica sol is widely used in the polishing of silicon wafers and in the CMP step of semiconductor devices, and if metal impurities exist in the CMP finishing process, metal may diffuse into the silicon wafers or electronic devices to cause short circuits, so that the content of the metal impurities in the silica sol is strictly required.
In conclusion, it is important to develop a method for preparing a non-spherical silica sol having a low content of metal impurities, which can overcome the above-mentioned drawbacks.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a preparation method of non-spherical silica sol, the preparation method successfully synthesizes the non-spherical silica sol of peanut-shaped particles, wherein the mass content of silicon dioxide is high, the metal ion content is low, the preparation method can be used for polishing semiconductor large silicon wafers or wafers, the preparation method is not limited to small-scale preparation in a laboratory, the particle size and the association degree are only slightly changed after the process is amplified, the amplification effect is small, and the preparation method is suitable for large-scale production.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a preparation method of non-spherical silica sol, which comprises the following steps:
(1) Mixing siloxane with water, and hydrolyzing to obtain hydrolysate;
(2) Mixing the hydrolysate and the mother liquor, adding an anionic polymer into the system during the mixing process, and maintaining the pH of the system to be more than or equal to 6 (such as 6.5, 7, 7.5, 8 and the like, and further preferably 7-8.5) to obtain seed crystals;
(3) And mixing the seed crystal with the hydrolysate to complete seed crystal growth to obtain the non-spherical silica sol.
According to the method, in the process of preparing the seed crystal, the anionic polymer is added, molecules have a larger spatial structure, and after the anionic polymer is added into a reaction system, on one hand, the repulsive force among silica sol particles is improved, on the other hand, collision and contact among the silica sol particles are hindered through a steric hindrance effect, and finally, the non-spherical silica sol particles with a certain degree of association are obtained and are in a peanut shape. In addition, the pH of the system is maintained during the preparation of the seeds, since an increase in pH leads to a tendency of the particles to grow into spheres and a decrease in pH leads to a tendency of the particles to aggregate and even to gel.
In the invention, the hydrolysate prepared in the step (1) is used in the step (2) and the step (3), the ratio of siloxane to water of the hydrolysate in the step (2) and the step (3) can be the same or different, and the preparation of the hydrolysate in the step (1) is adjusted according to the requirements of the step (2) and the step (3).
In the present invention, the seed crystal used in the step (3) may be all or part of the seed crystal produced in the step (2), and may be produced as needed.
In the present invention, the water is preferably ultrapure water.
Further, the ultrapure water has a resistivity of not less than 10 M.OMEGA.cm, for example, 12 M.OMEGA.cm, 14 M.OMEGA.cm, 16 M.OMEGA.cm, 18 M.OMEGA.cm or the like, and more preferably not less than 18.2 M.OMEGA.cm.
Preferably, in step (1), the siloxane comprises any one of tetramethoxysilane, tetraethoxysilane or tetrapropoxysilane, or a combination of at least two thereof, wherein typical but non-limiting combinations include: combinations of tetramethoxysilane and tetraethoxysilane, tetraethoxysilane and tetrapropoxysilane, tetramethoxysilane, tetraethoxysilane and tetrapropoxysilane, and the like, with tetramethoxysilane being more preferred.
Preferably, the hydrolysis temperature is 2-30 ℃, such as 5 ℃, 10 ℃, 15 ℃, 20 ℃, 25 ℃, and more preferably 5-20 ℃.
Preferably, in step (2), the mother liquor comprises water, and optionally, the mother liquor further comprises a pH regulator.
Preferably, the pH adjuster comprises a basic catalyst.
Preferably, the basic catalyst comprises any one of or a combination of at least two of alkali metal hydroxide, ammonia, organic amine compounds or guanidine compounds, wherein typical but non-limiting combinations include: a combination of an alkali metal hydroxide and aqueous ammonia, a combination of aqueous ammonia, an organic amine compound and a guanidine compound, a combination of an alkali metal hydroxide, aqueous ammonia, an organic amine compound and a guanidine compound, and the like.
Preferably, the alkali metal hydroxide comprises potassium hydroxide and/or sodium hydroxide.
Preferably, the organic amine compound includes any one of ethylene diamine, diethylene triamine, triethylene tetramine, ethanolamine, diethanolamine, triethanolamine, or tetramethyl ammonium hydroxide, or a combination of at least two thereof, wherein typical but non-limiting combinations include: combinations of ethylenediamine and diethylenetriamine, combinations of triethylenetetramine, ethanolamine, diethanolamine, and triethanolamine, combinations of diethylenetriamine, triethylenetetramine, ethanolamine, diethanolamine, triethanolamine, and tetramethylammonium hydroxide, and the like.
Preferably, the guanidine compound comprises any one of tetramethylguanidine, trimethylguanidine or guanidine carbonate or a combination of at least two thereof, wherein typical but non-limiting combinations include: combinations of tetramethylguanidine and trimethylguanidine, trimethylguanidine and guanidine carbonate, tetramethylguanidine, trimethylguanidine and guanidine carbonate, and the like.
Preferably, in the step (2), the mass ratio of the hydrolysate to the mother liquor is 1: (0.2-0.8), wherein 0.2-0.8 may be 0.3, 0.4, 0.5, 0.6, 0.7, etc., and more preferably 1: (0.3-0.7).
Preferably, in the step (2), the mass ratio of siloxane to water in the hydrolysate is (5-26): 100, wherein 5-26 can be 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, etc.
Preferably, the manner of mixing the hydrolysate and the mother liquor comprises adding the hydrolysate to the mother liquor.
Preferably, the flow rate of the hydrolysate added to the mother liquor is 0.5-10mL/min, such as 0.6mL/min, 0.7mL/min, 0.8mL/min, 0.6mL/min, 1mL/min, 1.2mL/min, 1.4mL/min, 2mL/min, 4mL/min, 6mL/min, 8mL/min, and the like.
Preferably, the time for adding the hydrolysate into the mother liquor is 4-50h, such as 5h, 10h, 20h, 30h, 40h and the like.
Preferably, the temperature of the system during the mixing process is 50 to 100 ℃, such as 60 ℃, 70 ℃, 80 ℃, 90 ℃ and the like, and more preferably 60 to 95 ℃.
Preferably, the anionic polymer comprises any one of, or a combination of at least two of, polyacrylic acid, poly (4-styrenesulfonic acid), or acrylic maleic acid copolymer, with typical but non-limiting combinations comprising: polyacrylic acid, poly (4-styrenesulfonic acid), and acrylic acid/maleic acid copolymer, and polyacrylic acid and/or acrylic acid/maleic acid copolymer are more preferable.
In the present invention, the reason why the anionic polymer is preferably polyacrylic acid and/or acrylic maleic acid copolymer is that: compared with other anionic polymers, polyacrylic acid and acrylic maleic acid copolymer have higher molecular weight, and generate anionic macromolecules after being dissolved in water.
Preferably, the number average molecular weight of the anionic polymer is 2000-80000g/mol, such as 2000g/mol, 4000g/mol, 6000g/mol, 8000g/mol, 10000g/mol, 20000g/mol, 60000g/mol, 80000g/mol, and the like.
In the present invention, the reason why the number average molecular weight of the anionic polymer is controlled in the above range is that: certain steric hindrance effect can be maintained; the higher number average molecular weight leads to the formation of spherical particles; lower number average molecular weight results in increased particle aggregation and even gelation.
Preferably, the anionic polymer is added in an amount of 50 to 1000ppm, such as 100ppm, 200ppm, 400ppm, 600ppm, 800ppm, etc., based on 100% by mass of the total siloxane employed to prepare the hydrolysate.
In the present invention, the reason why the amount of the anionic polymer to be added is controlled to be in the above range is: the method has good steric hindrance and electrostatic repulsion, and can well control the association degree of particles; the addition amount is too low, so that the aggregation degree of the particles is high and even gelation occurs; too high an amount may result in the formation of spherical particles.
Preferably, the anionic polymer is added into the system for 0-6h, such as 1h, 2h, 3h, 4h, 5h and the like, of the mixing of the hydrolysate and the mother liquor.
Preferably, the system pH is 6-8.5, such as 6.5, 7, 7.5, 8, etc., more preferably 7-8.5, during the mixing process, even more preferably the system pH is kept constant at 6-8.5 during the mixing process.
In the invention, in the mixing process, the pH value of the system is 6-8.5, because in a reaction system with the pH value of 6-8.5, the electrostatic repulsive force between silica sol particles is low, the particles tend to be aggregated together, so that the phenomenon that the particles are adhered together occurs, and the nonspherical silica sol is formed.
Preferably, the pH adjusting agent employed to maintain the pH of the system comprises a basic catalyst.
Preferably, in the step (3), the mass ratio of the hydrolysate to the seed crystals is 1: (0.125-0.875), wherein 0.125-0.875 may be 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, etc., and more preferably 1: (0.15-0.7).
Preferably, in the step (3), the mass ratio of siloxane to water in the hydrolysate is (11-44): 100, wherein 11-44 can be 15, 20, 25, 30, 35, 40, etc.
Preferably, the mixing comprises: the hydrolysate is added to seed crystals, which are optionally first mixed with water.
Preferably, when the seed crystal is mixed with water first, the mass ratio of the seed crystal to the water is 1: (1-3), wherein 1-3 can be 1.5, 2, 2.5, etc.
Preferably, the hydrolysate is added to the seed crystals at a flow rate of 0.5-10mL/min, such as 0.6mL/min, 0.7mL/min, 0.8mL/min, 0.6mL/min, 1mL/min, 1.2mL/min, 1.4mL/min, 2mL/min, 4mL/min, 6mL/min, 8mL/min, and the like.
Preferably, the time for adding the hydrolysate to the seed crystal is 4-50h, such as 5h, 10h, 20h, 30h, 40h and the like.
Preferably, the temperature of the system during the mixing process is 50 to 100 ℃, such as 60 ℃, 70 ℃, 80 ℃, 90 ℃ and the like, and more preferably 60 to 95 ℃.
Preferably, during said mixing, the system pH is maintained.
Preferably, the system pH is maintained to be the same as the system pH in step (2).
Preferably, after the seed crystal is grown, the obtained non-spherical silica sol is used as the seed crystal to continue the seed crystal growth.
Preferably, in the step (3), after the seed crystal growth is completed, concentration and solvent replacement are further included.
Preferably, the means of concentrating comprises vacuum heating.
Preferably, the content of the organic solvent in the system after the solvent replacement is 200ppm or less, for example, 180ppm, 160ppm, 140ppm or the like.
In the present invention, the reason for the solvent replacement is to remove the solvent such as methanol generated in the hydrolysis of siloxane.
Preferably, the mass percentage of silica in the silica sol in the system after the solvent replacement is more than or equal to 20%, such as 25%, 30%, 35%, 40%, etc.
Preferably, the solvent displacement is followed by filtration.
Preferably, the filter element material adopted by the filtration comprises polytetrafluoroethylene.
Preferably, the filtration precision is 0.2-5 μm, such as 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, and the like.
As a preferable technical scheme, the preparation method comprises the following steps:
(1) Mixing siloxane with water, and hydrolyzing at 2-30 deg.C to obtain hydrolysate;
water is used as mother liquor, and optionally, a pH regulator is also included in the mother liquor;
(2) Continuously adding the hydrolysate into the mother liquor at the flow rate of 0.5-1.5mL/min for mixing for 4-50h, adding the anionic polymer into the system at the 0-6h of the hydrolysate addition, maintaining the pH value of the system to 6-8.5 and the temperature to be 50-100 ℃, and controlling the mass ratio of the hydrolysate to the mother liquor to be 1: (0.2-0.8) to obtain seed crystals;
(3) Continuously adding the hydrolysate into the seed crystal at the flow rate of 0.5-1.5mL/min for mixing for 4-50h, maintaining the pH of the system to 6-8.5 and the temperature to 50-100 ℃, and controlling the mass ratio of the hydrolysate to the seed crystal to be 1: (0.125-0.875) to complete the growth of seed crystals to obtain a non-spherical silica sol initial material;
optionally, before the hydrolysate is added into the seed crystal, the seed crystal is mixed with water to form a seed crystal solution;
(4) And (4) concentrating the initial material of the non-spherical silica sol obtained in the step (3) and carrying out solvent replacement until the content of the organic solvent in the system is less than or equal to 200ppm and the mass percent of the silicon dioxide in the silica sol is more than or equal to 20%, and optionally filtering to obtain the non-spherical silica sol.
Compared with the prior art, the invention has the following beneficial effects:
(1) The preparation method successfully synthesizes the non-spherical silica sol of peanut-shaped particles, wherein the mass content of silicon dioxide is high, the metal ion content is low, the non-spherical silica sol can be used for polishing a semiconductor large silicon wafer or a wafer, the preparation method is not limited to small-scale preparation in a laboratory, the particle size and the degree of association are only slightly changed after the process is amplified, the amplification effect is small, and the preparation method is suitable for large-scale production.
(2) The primary particle size of the seed crystal obtained by the preparation method is 15.7-18.8nm, the secondary particle size is 29.3-35nm, and the association degree is 1.8-1.92; the nonspherical silica sol prepared by the preparation method has the primary particle size of 41.4-66.6nm, the secondary particle size of 77.9-130nm and the association degree of 1.76-1.98; the mass fraction of silicon dioxide in the nonspherical silica sol obtained by the preparation method is more than 20%.
(3) The non-spherical silica sol obtained by the preparation method of the invention has the total content of metal ions of less than 1ppm, such as the content of sodium ions of less than 99ppb, the content of potassium ions of less than 87ppb, the content of chromium ions of less than 13ppb, the content of copper ions of less than 11ppb, the content of iron ions of less than 30ppb, the content of nickel ions of less than 28ppb and the content of titanium ions of less than 11 ppb.
Drawings
FIG. 1 is a transmission electron micrograph of a seed crystal according to example 1;
FIG. 2 is a transmission electron micrograph of a non-spherical silica sol according to example 1;
FIG. 3 is a transmission electron micrograph of a seed crystal according to example 6;
FIG. 4 is a transmission electron micrograph of the non-spherical silica sol described in comparative example 1.
Detailed Description
For the purpose of facilitating an understanding of the present invention, the following examples are set forth herein. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
In the present invention, purchase information of part of raw materials in each embodiment is as follows:
polyacrylic acid: number average molecular weight 2300g/mol, available from Dow chemical company;
acrylic maleic acid copolymer: number average molecular weight 3000g/mol, CAS number 29132-58-9, available from Shanghai Aladdin Biotechnology Ltd.
Example 1
The embodiment provides an aspherical silica sol, and a preparation method of the aspherical silica sol comprises the following steps:
(1) 524g of water is weighed in a beaker, 76g of tetramethoxysilane is added after the water temperature is controlled to be 12 ℃, and after stirring for 1.5h, the pH value is about 4.3, so as to obtain a first hydrolysate;
weighing 463.2g of water in a beaker, adding 136.8g of tetramethoxysilane after the water temperature is controlled to 12 ℃, and stirring for 2 hours to obtain a second hydrolysate;
adding 350g of water into a 1L-sized flask with a thermometer and a condenser, and heating to 80 ℃ to obtain a mother liquor;
(2) Adding the first hydrolysate into the mother liquor by using a peristaltic pump at the temperature of 80 ℃, wherein the feeding speed is 1.1mL/min, the pH of the system is maintained to be 8.0 by adding ethanolamine (10 mmol/L) in the early feeding period, 10mg of polyacrylic acid is added after feeding for 1h, the pH of the system is maintained to be 8.0 by adding ethanolamine in the later feeding process, and the mass ratio of the hydrolysate to the mother liquor is controlled to be 1:0.58, obtaining seed crystals;
(3) And (3) selecting 350g of seed crystals obtained in the step (2) and adding the seed crystals into a 1L flask with a thermometer and a condenser, adding a second hydrolysate into the seed crystals by using a peristaltic pump, wherein the feeding speed is 1.1mL/min, in the feeding process, the pH value of the system is maintained to be 8.0 by adding ethanolamine, and the mass ratio of the hydrolysate to the seed crystals is controlled to be 1:0.58, obtaining an initial material of the non-spherical silica sol after the feeding is finished;
(4) Heating and concentrating the non-spherical silica sol initial material under reduced pressure at the temperature of 100 ℃ under 10kPa, and concentrating the content of silicon dioxide to 20% to obtain concentrated silica sol; and adding ultrapure water while evaporating until the content of the organic solvent in the silica sol is reduced to be less than 100ppm, thereby obtaining the non-spherical silica sol.
Example 2
The embodiment provides an aspherical silica sol, and a preparation method of the aspherical silica sol comprises the following steps:
(1) 524g of water is weighed in a beaker, 76g of tetramethoxysilane is added after the water temperature is controlled to be 12 ℃, and after stirring for 1.5h, the pH value is about 4.3, so as to obtain a first hydrolysate;
weighing 463.2g of water in a beaker, adding 136.8g of tetramethoxysilane after the water temperature is controlled to 12 ℃, and stirring for 2 hours to obtain a second hydrolysate;
adding 350g of water into a 1L flask with a thermometer and a condenser, and heating to 80 ℃ to obtain mother liquor;
(2) Adding the first hydrolysate into the mother liquor by using a peristaltic pump at the temperature of 80 ℃, wherein the feeding speed is 1.1mL/min, the pH value of the system is maintained to be 8.0 by adding ammonia water (10 mmol/L) in the early stage of feeding, 10mg of polyacrylic acid is added after feeding for 1h, the pH value of the system is maintained to be 8.0 by adding ammonia water in the feeding process, and the mass ratio of the hydrolysate to the mother liquor is controlled to be 1:0.58, obtaining seed crystals;
(3) And (3) adding 350g of the seed crystals obtained in the step (2) into a 1L flask with a thermometer and a condenser, adding a second hydrolysate into the seed crystals by using a peristaltic pump, wherein the feeding speed is 1.1mL/min, the pH of the system is maintained to be 8.0 by adding ammonia water in the feeding process, and the mass ratio of the hydrolysate to the seed crystals is controlled to be 1:0.58, obtaining an initial material of the non-spherical silica sol after the feeding is finished;
(4) Carrying out reduced pressure heating concentration on the non-spherical silica sol initial material at the temperature of 100 ℃ under 10kPa to obtain concentrated silica sol after concentration to 20%; and adding ultrapure water while evaporating until the content of the organic solvent in the silica sol is reduced to be less than 100ppm, thereby obtaining the non-spherical silica sol.
Example 3
The embodiment provides an aspherical silica sol, and a preparation method of the aspherical silica sol comprises the following steps:
(1) 1389.6g of water is weighed in a beaker, 410.4g of tetramethoxysilane is added after the water temperature is controlled to 12 ℃, and hydrolysate is obtained after stirring for 2 hours;
(2) Taking the initial nonspherical silica sol prepared in the step (3) in the example 2 as the seed crystal in the example, specifically, adding 350g of the initial nonspherical silica sol into a 2L flask with a thermometer and a condenser, heating to 80 ℃, and taking the initial nonspherical silica sol as the seed crystal;
(3) Adding the hydrolysate into the seed crystal by a peristaltic pump at the temperature of 80 ℃, wherein the feeding speed is 1.1mL/min, the pH value of the system is maintained to be 8.0 by adding ammonia water (10 mmol/L) in the feeding process, and the mass ratio of the hydrolysate to the seed crystal is controlled to be 1:0.19, obtaining an initial material of the non-spherical silica sol after the feeding is finished;
(4) Carrying out reduced pressure heating concentration on the non-spherical silica sol initial material at the temperature of 100 ℃ under 10kPa to obtain concentrated silica sol after concentration to 20%; and adding ultrapure water while evaporating until the content of the organic solvent in the silica sol is reduced to be less than 100ppm, thereby obtaining the non-spherical silica sol.
Example 4
The embodiment provides an aspherical silica sol, and a preparation method of the aspherical silica sol comprises the following steps:
(1) Weighing 2620g of water in a beaker, adding 380g of tetramethoxysilane after the water temperature is controlled to be 12 ℃, stirring for 1.5h, and obtaining a first hydrolysate with the pH value of about 4.3;
2316g of water is weighed in a beaker, 684g of tetramethoxysilane is added after the water temperature is controlled to be 12 ℃, and after stirring is carried out for 2 hours, a second hydrolysate is obtained;
1650g of water is added into a 5L flask with a thermometer and a condenser and heated to 80 ℃ to obtain mother liquor;
(2) Adding the first hydrolysate into the mother liquor by using a peristaltic pump at the temperature of 80 ℃, wherein the feeding speed is 5.5mL/min, the pH of the system is maintained to be 8.0 by adding ethanolamine (10 mmol/L) in the early feeding period, 50mg of polyacrylic acid is added after feeding for 1h, the pH of the system is maintained to be 8.0 by adding ethanolamine in the later feeding process, and the mass ratio of the hydrolysate to the mother liquor is controlled to be 1:0.58, obtaining seed crystals;
(3) And (3) selecting 1650g of seed crystals obtained in the step (2), adding the seed crystals into a 5L flask with a thermometer and a condenser tube, adding a second hydrolysate into the seed crystals by using a peristaltic pump, wherein the feeding speed is 5.5mL/min, in the feeding process, adding ethanolamine to maintain the pH of the system to be 8.0, and controlling the mass ratio of the hydrolysate to the seed crystals to be 1:0.58, obtaining an initial material of the non-spherical silica sol after the feeding is finished;
(4) Carrying out reduced pressure heating concentration on the non-spherical silica sol initial material at the temperature of 100 ℃ under 10kPa to obtain concentrated silica sol after concentration to 20%; and adding ultrapure water while evaporating until the content of the organic solvent in the silica sol is reduced to be less than 100ppm, thereby obtaining the non-spherical silica sol.
Example 5
The embodiment provides an aspherical silica sol, and a preparation method of the aspherical silica sol comprises the following steps:
(1) 524g of water is weighed in a beaker, 76g of tetramethoxysilane is added after the water temperature is controlled to be 12 ℃, and after stirring for 1.5h, the pH value is about 4.3, so as to obtain a first hydrolysate;
weighing 463.2g of water in a beaker, adding 132.8g of tetramethoxysilane after the water temperature is controlled to 12 ℃, and stirring for 2 hours to obtain a second hydrolysate;
350g of water and 3g of ethanolamine (10 mmol/L) were added to a 1L-sized flask having a thermometer and a condenser, and heated to 80 ℃ to obtain a mother liquor;
(2) Adding the first hydrolysate into the mother liquor by using a peristaltic pump, wherein the feeding speed is 1.8mL/min, in the early stage of feeding, adding ethanolamine to maintain the pH of the system to be 8.0, adding 10mg of polyacrylic acid after feeding for 1h, in the feeding process, adding ammonia water to maintain the pH of the system to be 8.0, controlling the temperature of the system to be 80 ℃, and controlling the mass ratio of the hydrolysate to the mother liquor to be 1:0.58, obtaining seed crystals;
(3) And (3) adding 350g of the seed crystals obtained in the step (2) into a 1L flask with a thermometer and a condenser, adding a second hydrolysate into the seed crystals by using a peristaltic pump, wherein the feeding speed is 1.8mL/min, the pH of the system is maintained to be 8.0 by adding ethanolamine in the feeding process, and the mass ratio of the hydrolysate to the seed crystals is controlled to be 1:0.58, obtaining an initial material of the non-spherical silica sol after the feeding is finished;
(4) Carrying out reduced pressure heating concentration on the non-spherical silica sol initial material at the temperature of 100 ℃ under 10kPa to obtain concentrated silica sol after concentration to 20%; and adding ultrapure water while evaporating until the content of the organic solvent in the silica sol is reduced to be less than 100ppm, thereby obtaining the non-spherical silica sol.
Example 6
This comparative example is different from example 1 in that the addition amount of polyacrylic acid at the time of seed crystal preparation was 100mg, and the rest is the same as example 1.
Example 7
This example is different from example 1 in that polyacrylic acid was replaced with an acrylic maleic acid copolymer of equal mass, and the rest was the same as example 1.
Comparative example 1
This comparative example differs from example 1 in that no polyacrylic acid was added during seed preparation, and the rest was the same as example 1.
Comparative example 2
This comparative example differs from example 1 in that the reaction system gelled during the feed process, in the case of seed preparation, after addition of polyacrylic acid, without maintaining the pH of the system, as in example 1.
Performance testing
The following tests were carried out on the seed crystals and the nonspherical silica sol obtained by the production methods described in examples 1 to 7 and comparative example 1 (the reaction system in comparative example 2 gelled during the feeding, and the results are not shown):
(1) And (3) morphology characterization: and observing the shapes of the seed crystal and the non-spherical silica sol by adopting a transmission electron microscope.
(2) Primary particle size and secondary particle size:
the secondary particle size of the silica sol colloidal particles is measured by a Malvern particle sizer Zetasizer Nano ZS90, and the primary particle size is measured by a BET specific surface area measuring method to obtain a specific surface area S bet Primary particle diameter is 2727/S bet . The degree of association is the ratio of the secondary particle size to the primary particle size.
(3) Metal impurities: the metal impurities in the non-spherical silica sol were tested by Agilent 7900 ICP-MS.
The test results are summarized in tables 1-2 and FIGS. 1-4.
TABLE 1
As can be seen from the analysis of the data in Table 1, in examples 1 to 7 (except example 6), the seed crystal obtained by the preparation method of the present invention has a primary particle size of 15.7 to 18.8nm, a secondary particle size of 29.3 to 35nm, and an association degree of 1.8 to 1.92; the nonspherical silica sol prepared by the preparation method has the primary particle size of 41.4-66.6nm, the secondary particle size of 77.9-130nm and the association degree of 1.76-1.98; in addition, according to the implementation process, the mass fraction of the silicon dioxide of the non-spherical silica sol obtained by the preparation method is more than 20 percent; the preparation method successfully synthesizes the non-spherical silica sol of peanut-shaped particles, wherein the mass content of the silica is high, and the silica can be used for polishing large semiconductor silicon wafers or wafers.
Analysis of comparative example 1 and example 1 shows that, in comparative example 1, no anionic polymer is added in the reaction process, the seed crystal particle size is polydisperse and is in a multi-association shape, the adhesion among particles is serious, silica sol particles with uniform particle size distribution cannot be obtained, the particle size distribution of the obtained sample particles is wide, and the adhesion among particles is serious.
As is clear from the analysis of example 6 and example 1, in example 6, the amount of the anionic polymer added is relatively high, and the seed particles obtained are mostly spherical.
FIGS. 1, 2, 3 and 4 show TEM images of the seed crystals or silica sols obtained in examples 1 and 6 according to the invention and comparative example 1. As can be seen from the figure, the particles in example 1 are mostly associated with each other, and have a peanut shape. Whereas the particles of example 6 are mostly spherical.
As can be seen from example 4, after the amplification of example 1, the particle size and the degree of association are only slightly changed, and the amplification effect is small, so that the preparation method is proved to be not limited to small-scale preparation in a laboratory, the particle size and the degree of association are only slightly changed after the process amplification, the amplification effect is small, and the preparation method is suitable for large-scale production. Therefore, the degree of association of the silica sol prepared by the method is controllable, and the association of the prepared silica sol particles can be well controlled by adding polyacrylic acid.
TABLE 2
As can be seen from the analysis of the data in Table 2, the nonspherical silica sol obtained by the production method of the present invention has a low metal ion content, a total metal ion content of less than 1ppm, for example, a sodium ion content of 99ppb or less, a potassium ion content of 87ppb or less, a chromium ion content of 13ppb or less, a copper ion content of 11ppb or less, an iron ion content of 30ppb or less, a nickel ion content of 28ppb or less, and a titanium ion content of 11ppb or less.
The applicant states that the present invention is illustrated by the above examples to show the detailed method of the present invention, but the present invention is not limited to the above detailed method, that is, it does not mean that the present invention must rely on the above detailed method to be carried out. It should be understood by those skilled in the art that any modifications of the present invention, equivalent substitutions of the raw materials of the product of the present invention, and the addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (10)
1. A preparation method of non-spherical silica sol is characterized by comprising the following steps:
(1) Mixing siloxane with water, and hydrolyzing to obtain hydrolysate;
(2) Mixing the hydrolysate and the mother liquor, adding an anionic polymer into the system in the mixing process, and maintaining the pH value of the system to be more than or equal to 6 to obtain seed crystals;
(3) And mixing the seed crystal with the hydrolysate to complete the growth of the seed crystal, thereby obtaining the non-spherical silica sol.
2. The production method according to claim 1, wherein in the step (1), the siloxane includes any one of tetramethoxysilane, tetraethoxysilane or tetrapropoxysilane or a combination of at least two thereof, and further preferably tetramethoxysilane;
preferably, the temperature of the hydrolysis is 2-30 ℃.
3. The method according to claim 1 or 2, wherein in step (2), the mother liquor comprises water, and optionally, the mother liquor further comprises a pH regulator;
preferably, the pH adjuster comprises a basic catalyst;
preferably, the basic catalyst comprises any one or a combination of at least two of alkali metal hydroxide, ammonia water, organic amine compounds or guanidine compounds;
preferably, the alkali metal hydroxide comprises potassium hydroxide and/or sodium hydroxide;
preferably, the organic amine compound includes any one of ethylenediamine, diethylenetriamine, triethylenetetramine, ethanolamine, diethanolamine, triethanolamine or tetramethylammonium hydroxide or a combination of at least two thereof;
preferably, the guanidine compound comprises any one of tetramethylguanidine, trimethylguanidine or guanidine carbonate or a combination of at least two of them.
4. The preparation method according to any one of claims 1 to 3, wherein in the step (2), the mass ratio of the hydrolysate to the mother liquor is 1: (0.2-0.8);
preferably, in the step (2), the mass ratio of siloxane to water in the hydrolysate is (5-26): 100, respectively;
preferably, the mixing of the hydrolysate and the mother liquor comprises adding the hydrolysate to the mother liquor;
preferably, the flow rate of adding the hydrolysate into the mother liquor is 0.5-10mL/min;
preferably, the time for adding the hydrolysate into the mother liquor is 4-50h;
preferably, the temperature of the system during the mixing process is 50-100 ℃.
5. The method according to any one of claims 1 to 4, wherein the anionic polymer comprises any one of polyacrylic acid, poly (4-styrenesulfonic acid), or acrylic acid-maleic acid copolymer, or a combination of at least two thereof;
preferably, the number average molecular weight of the anionic polymer is from 2000 to 80000g/mol;
preferably, the anionic polymer is added in an amount of 50-1000ppm based on 100% by mass of the total siloxane used for preparing the hydrolysate;
preferably, the time for adding the anionic polymer into the system is 0-6h after the hydrolysate and the mother liquor are mixed.
6. The method according to any one of claims 1 to 5, wherein during the mixing, the pH of the system is 6 to 8.5;
preferably, the pH adjusting agent employed to maintain the pH of the system comprises a basic catalyst.
7. The method according to any one of claims 1 to 6, wherein in the step (3), the mass ratio of the hydrolysate to the seed crystals is 1: (0.125-0.875);
preferably, in the step (3), the mass ratio of siloxane to water in the hydrolysate is (11-44): 100, respectively;
preferably, the mixing comprises: adding the hydrolysate into seed crystals, and optionally mixing the seed crystals with water;
preferably, when the seed crystal is mixed with water first, the mass ratio of the seed crystal to the water is 1: (1-3);
preferably, the flow rate of the hydrolysate added into the seed crystal is 0.5-10mL/min;
preferably, the time for adding the hydrolysate into the seed crystal is 4-50h;
preferably, the temperature of the system is 50-100 ℃ in the mixing process;
preferably, during the mixing, the system pH is maintained;
preferably, the system pH is maintained to be the same as the system pH in step (2);
preferably, after the seed crystal is grown, the obtained non-spherical silica sol is used as the seed crystal to continue the seed crystal growth.
8. The production method according to any one of claims 1 to 7, wherein in the step (3), after the completion of the seed crystal growth, concentration and solvent replacement are further included;
preferably, the means of concentrating comprises vacuum heating;
preferably, after the solvent replacement, the content of the organic solvent in the system is less than or equal to 200ppm;
preferably, after the solvent replacement, the mass percentage of the silicon dioxide in the silica sol in the system is more than or equal to 20%.
9. The method according to claim 8, wherein the solvent substitution further comprises filtration;
preferably, the filter element material adopted by the filtration comprises polytetrafluoroethylene;
preferably, the filtration precision is 0.2-5 μm.
10. The production method according to any one of claims 1 to 9, characterized by comprising the steps of:
(1) Mixing siloxane with water, and hydrolyzing at 2-30 deg.C to obtain hydrolysate;
water is used as mother liquor, and optionally, the mother liquor also comprises a pH regulator;
(2) Continuously adding the hydrolysate into the mother liquor at the flow rate of 0.5-1.5mL/min for mixing for 4-50h, adding the anionic polymer into the system at the 0-6h of the hydrolysate addition, maintaining the pH value of the system to 6-8.5 and the temperature to be 50-100 ℃, and controlling the mass ratio of the hydrolysate to the mother liquor to be 1: (0.2-0.8) to obtain seed crystals;
(3) Continuously adding the hydrolysate into the seed crystal at the flow rate of 0.5-1.5mL/min for mixing for 4-50h, maintaining the pH of the system to 6-8.5 and the temperature to 50-100 ℃, and controlling the mass ratio of the hydrolysate to the seed crystal to be 1: (0.125-0.875) to complete the growth of seed crystals to obtain a non-spherical silica sol initial material;
optionally, before the hydrolysate is added into the seed crystal, the seed crystal is mixed with water to form a seed crystal solution;
(4) And (4) concentrating the initial material of the non-spherical silica sol obtained in the step (3) and carrying out solvent replacement until the content of the organic solvent in the system is less than or equal to 200ppm and the mass percent of the silicon dioxide in the silica sol is more than or equal to 20%, and optionally filtering to obtain the non-spherical silica sol.
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