WO2023163169A1 - Silica sol concentration method using ultrafiltration - Google Patents

Silica sol concentration method using ultrafiltration Download PDF

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Publication number
WO2023163169A1
WO2023163169A1 PCT/JP2023/007039 JP2023007039W WO2023163169A1 WO 2023163169 A1 WO2023163169 A1 WO 2023163169A1 JP 2023007039 W JP2023007039 W JP 2023007039W WO 2023163169 A1 WO2023163169 A1 WO 2023163169A1
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Prior art keywords
silica sol
concentration
silica
requirement
sol
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PCT/JP2023/007039
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French (fr)
Japanese (ja)
Inventor
透 西村
滋 三井
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日産化学株式会社
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Publication of WO2023163169A1 publication Critical patent/WO2023163169A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/14—Ultrafiltration; Microfiltration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/14—Ultrafiltration; Microfiltration
    • B01D61/16—Feed pretreatment
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
    • C01B33/14—Colloidal silica, e.g. dispersions, gels, sols
    • C01B33/141—Preparation of hydrosols or aqueous dispersions
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
    • C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
    • C01B33/187—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by acidic treatment of silicates
    • C01B33/193—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by acidic treatment of silicates of aqueous solutions of silicates

Definitions

  • the present invention relates to a silica sol concentration method using an ultrafiltration method.
  • a sol in which colloidal silica particles are dispersed in an aqueous medium can be obtained by heating an aqueous silicic acid solution obtained by removing sodium ions from an aqueous sodium silicate solution as a raw material, or by hydrolyzing an alkoxysilane.
  • Silica sol immediately after production is generally a liquid with a low concentration of silica components, but it is commercialized by concentrating it.
  • concentration is performed by ultrafiltration or an evaporation method. In the method of concentrating the silica component in the silica sol by ultrafiltration, the concentration of the silica component in the silica sol is increased by removing water out of the system through an ultrafiltration membrane.
  • a concentration method by ultrafiltration for example, after heating a zirconium salt aqueous solution in the presence of urea to obtain a transparent zirconia sol, a chelating agent and a metal compound other than zirconium are blended, and the temperature is 80 ° C. or less.
  • a method of concentrating with an ultrafiltration membrane is disclosed (see Patent Document 1). Also, when producing a colloidal silica concentrate from a geothermal fluid containing silica, silica colloidal growth is initiated by cooling from the initial temperature to the nucleation temperature, and the fluid containing silica particles is subjected to ultrafiltration to obtain a silica concentrate.
  • a method is disclosed.
  • Ultrafiltration can be used to concentrate the silica particles in the silica sol, but when the filtrate is removed from the system, the ultrafiltration membrane has a high-concentration silica layer called a cake layer on the inner surface of the ultrafiltration membrane. Deposits of particles may form.
  • the coarse silica particles contained in the cake layer drop out into the silica sol when the silica sol is circulated in the ultrafiltration device to increase the concentration of silica particles, and are mixed into the final product (concentrated silica sol product).
  • concentration silica sol product Concentrated silica sol product
  • An object of the present invention is to provide a method for concentrating silica sol that can prevent
  • the present inventors found that the following requirement A and requirement B are satisfied in the concentration step of increasing the concentration of silica particles contained in the silica sol using an ultrafiltration device.
  • the flow velocity of the silica sol liquid near the ultrafiltration membrane By increasing the flow velocity of the silica sol liquid near the ultrafiltration membrane and creating a situation in which silica particles are less likely to aggregate, it is possible to prevent the formation of aggregated silica particles in the concentrated silica sol.
  • a method for concentrating silica sol was discovered, and the present invention was completed.
  • a first aspect of the present invention is a method for concentrating a sol (silica sol) in which silica particles are dispersed as dispersoid particles in a dispersion medium, wherein the concentration of silica particles contained in the silica sol is increased by an ultrafiltration device. It relates to a method for concentrating a silica sol, characterized in that the following requirements A and B are satisfied in the concentration process.
  • Requirement A The liquid temperature of the silica sol immediately before being injected into the ultrafiltration device must be in the range of 0 to 45°C.
  • Requirement B By circulating the silica sol through the ultrafiltration device, the concentration of silica particles contained in the silica sol after the concentration step should be higher than before the concentration step.
  • Requirement B includes further injecting silica sol into the ultrafiltration device during or after the concentration step of circulating silica sol in the ultrafiltration device, and the injected silica sol is concentrated It relates to the method for concentrating silica sol according to the first aspect, wherein the concentration is 0.1 to 30 times the concentration of silica particles contained in the silica sol before the step.
  • the liquid temperature of the silica sol immediately before being injected into the ultrafiltration device is adjusted to a range of 0 to 30 ° C. It relates to a method for concentrating the described silica sol.
  • the ultrafiltration device is further injected with silica sol having the same concentration as the silica sol before the concentration step, or the silica sol with a higher concentration than the silica sol before the concentration step is circulated through the ultrafiltration device.
  • the silica sol concentration method according to the second aspect is characterized in that the concentration of silica particles contained in the silica sol after the concentration step is higher than that before the concentration step.
  • the concentrated silica sol is directly passed through a pipe from the ultrafiltration device after the concentration step, and filled into a concentrated silica sol filling container under conditions where the concentration of silica particles decreases within 5% by mass.
  • the method for concentrating silica sol according to any one of the first to fourth aspects characterized by:
  • the concentration step is performed in a concentration ratio range of 2 to 30 in which the concentration of the silica particles after the concentration step is in the range of 2 to 30 with respect to the concentration of the silica particles before the concentration step. It relates to the silica sol concentration method according to any one of the 1st to 5th aspects.
  • the silica sol before being injected into the ultrafiltration device is a silica sol containing silica particles obtained by heating an aqueous silicic acid solution obtained by removing alkali metal ions from an aqueous alkali silicate solution. It relates to the method for concentrating silica sol according to any one of the first to sixth aspects, characterized by:
  • the method of the present invention prevents the formation of agglomerated silica particles in the concentrated silica sol in performing concentration for increasing the concentration of the silica component in the silica sol by ultrafiltration, while removing the silica sol.
  • concentration for increasing the concentration of the silica component in the silica sol by ultrafiltration, while removing the silica sol.
  • the effect of being able to concentrate is exhibited.
  • the present invention is a method for concentrating a sol (silica sol) dispersed in water using silica particles as dispersoid particles as a dispersion medium, comprising a concentration step of increasing the concentration of silica particles contained in the silica sol using an ultrafiltration device.
  • a silica sol concentration method characterized in that the following requirements A and B are satisfied in the concentration step.
  • Requirement A The liquid temperature of the silica sol immediately before injection into the ultrafiltration device should be in the range of 0 to 45°C, preferably 0 to 40°C, more preferably 0 to 35°C, and most preferably 0 to 30°C.
  • Requirement B By circulating the silica sol through the ultrafiltration device, the concentration of silica particles contained in the silica sol after the concentration step should be higher than before the concentration step.
  • the present invention will be described in detail below.
  • an ultrafiltration membrane for example, an ultrafiltration membrane (UF membrane) is formed into a tube, silica sol to be concentrated circulates inside the tube, and an aqueous medium is discharged outside the tube.
  • a silica sol having a structure in which the silica component of the silica sol is concentrated can be used.
  • the main component of the aqueous medium is water, cations and anions contained in the silica sol may be discharged at the same time.
  • a cross-flow system is preferable for the ultrafiltration membrane, and by forming a flow parallel to the surface of the ultrafiltration membrane, the phenomenon of suspended solids and colloidal silica particles in the silica sol being deposited on the surface of the ultrafiltration membrane is suppressed. while increasing the silica component concentration in the silica sol.
  • ultrafiltration membranes examples include polyethylene, polyethylene fluoride, polyvinylidene fluoride, polypropylene, cellulose acetate, polyacrylonitrile, polyimide, polysulfone, and polyethersulfone. Also, aluminum oxide, zirconium oxide, titanium oxide, stainless steel, glass, or the like can be used alone or in combination with the above materials for the film material.
  • the ultrafiltration membrane module for example, it is possible to use a casing housing method, in which a membrane element formed by integrating members such as an ultrafiltration membrane, its support, and a channel material is housed in a casing. Then, silica sol is forced into the casing by a pump to filter the aqueous medium and concentrate the colloidal silica component to obtain a concentrated silica sol product.
  • the molecular weight cutoff of the ultrafiltration membrane is, for example, the nominal pore diameter of the membrane is about 5 nm to 100 nm, the suitable particle diameter is, for example, 5 nm to 500 nm, and the molecular weight cut off is, for example, 50 k (5 10,000), 100k (100,000), 300k (300,000), and 500k (500,000) can be used.
  • the molecular weight cutoff is 50,000
  • the nominal pore size of the membrane is 5 nm and the suitable particle size is 15 to 30 nm.
  • the nominal pore size of the membrane is 10 nm and the suitable particle size is 30 to 90 nm.
  • the nominal pore size of the membrane is 35 nm and the suitable particle size is 90 to 200 nm.
  • the molecular weight cutoff is 1 million, the nominal pore size of the membrane is 100 nm and the suitable particle size is 300-600 nm.
  • Delivery of the silica sol to the UF device is, for example, 0.01 to 10 MPa, or 0.05 to 5.0 MPa, or 0.1 to 1.0 MPa. It can be performed at a pressure of 0 MPa, or 0.3 to 1.0 MPa.
  • the time required to concentrate the silica sol to obtain the desired silica concentration is about 0.1 to 50 hours.
  • Requirement A is based on the condition that the liquid temperature of the silica sol immediately before being injected into the ultrafiltration device is in the range of 0 to 45°C.
  • the liquid temperature of the silica sol is, for example, 0 to 45°C, 0 to 40°C, 0 to 35°C, or 0 to 30°C.
  • Requirement A is based on the condition that the liquid temperature of the silica sol immediately before being injected into the ultrafiltration device is in the range of 0 to 45 ° C. If the liquid temperature of the silica sol is higher than this temperature, it is cooled. Therefore, it is preferable to adjust the liquid temperature within this range.
  • For cooling it is preferable to deposit the ultrafiltration membrane module in a tank in which cooling water is circulated and cool the silica sol to a predetermined temperature.
  • the temperature immediately before injection into the ultrafiltration membrane module is 0 to 45°C, or 0 to 40°C, or 0 to 35°C. , or 0 to 30 ° C., or 0 to 25 ° C., or 0 to 15 ° C., and is again injected from the ultrafiltration membrane module through temperature adjustment (for example, cooling) to the above temperature range. preferably.
  • Requirement B is a condition that the concentration of silica particles contained in the silica sol after the concentration process is higher than before the concentration process by circulating the silica sol in the ultrafiltration device.
  • circulation means, for example, once recovering silica sol that has been injected into an ultrafiltration device and has undergone a concentration step, and then injecting it into the ultrafiltration device again.
  • concentration step means, for example, once recovering silica sol that has been injected into an ultrafiltration device and has undergone a concentration step, and then injecting it into the ultrafiltration device again.
  • forming is meant repeating the concentration step without recovering the silica sol, and is also meant to include combinations thereof.
  • circulating the silica sol in the ultrafiltration device can prevent the cake layer from falling off. That is, by circulating the silica sol having a low silica concentration, it is possible to prevent the cake layer from being dissolved in the low-concentration portion. Then, it is preferable to circulate a silica sol having a higher concentration than the silica sol before concentration.
  • silica sol can be further injected into the silica sol circulating in the ultrafiltration membrane module during or after the concentration process.
  • the injected silica sol preferably has a concentration of 0.1 to 30 times the concentration of silica particles contained in the silica sol before the concentration step.
  • silica sol is more concentrated than before the concentration step, but further injection of silica sol is preferably performed with silica sol having the same concentration as the silica sol before the concentration step. It is preferably carried out at a higher concentration than the silica sol before concentration.
  • the concentrated silica sol When the concentrated silica sol is taken out from the ultrafiltration device as a final product, if low-concentration silica sol or water is used as the carrying-out solvent, the concentration of the concentrated silica sol is temporarily lowered due to the carrying-out solvent, resulting in a cake layer. is dropped into the silica sol product by the transported solvent, which causes coarse particles. Therefore, the concentrated silica sol is packed (filled into a container filled with concentrated silica sol) as a concentrated silica sol product under the condition that the silica concentration decreases by 5% by mass or less upon completion of concentration through a direct pipe from the ultrafiltration device. preferably.
  • these operations are carried out through a pipe directly from the ultrafiltration device when the final product of silica sol is obtained, under the condition that the silica concentration decreases within 5% by mass when the concentration is completed, for example in the range of 0 to 5% by mass. It is desirable that the concentrated silica sol product be packed (filled in a container filled with concentrated silica sol) under the above conditions, preferably without causing a decrease in silica concentration.
  • the silica sol concentration step is preferably carried out in a concentration ratio range of 2 to 30 for the concentration of the silica particles after the concentration step to the concentration of the silica particles before the concentration step.
  • the silica sol concentration method of the present invention is characterized by little change in concentration of ionic components (cations and anions) contained in the silica sol before and after the concentration process.
  • cations e.g., cations containing potassium ions, typically potassium ions
  • anions e.g., anions containing sulfate ions, typically is a sulfate ion.
  • the ionic component imparts an electric charge to the surface of the silica particles in the silica sol and forms an appropriate repulsive force of the silica particles to prevent aggregation of the silica particles. can be done.
  • the presence of a large amount of ionic components also leads to agglomeration of silica particles.
  • the concentrations of cations and anions in these silica sols change little by ultrafiltration. For example, it is preferable to suppress changes in the concentration of cations and anions within 10 times the concentration (mass % concentration) in the silica sol before the concentration step. Formation of a cake layer can be suppressed by setting the concentrations of these ion components within the above range.
  • the process (requirement B) by injecting or circulating silica sol in the concentration process. That is, by further injecting silica sol into the silica sol during the circulating concentration step or after the concentration step (the concentration of silica particles contained in the silica sol to be further injected is the same as that of the silica particles contained in the silica sol before the concentration step
  • the concentration is 0.1 to 30 times the concentration of ), and the above range can be set by adjusting the circulation time of the silica sol.
  • Examples of the above cations include monovalent cations, and potassium ions or sodium ions are particularly preferable from the viewpoint of suppressing coarse particles.
  • Examples of the above anions include anions containing sulfate ions, and sulfate ions are particularly preferable from the viewpoint of suppressing coarse particles.
  • silica sol produced by the alkoxide method can also be used as the silica sol to be concentrated by the ultrafiltration device.
  • a silica sol containing can be preferably used.
  • JIS No. 3 sodium water glass was prepared as a raw water-soluble alkali metal silicate.
  • the main components of this water glass other than water were SiO 2 : 28.8% by weight and Na 2 O: 9.47% by weight.
  • 833 kg of the above water glass was diluted with 5167 kg of pure water to prepare 6000 kg of sodium silicate aqueous solution (a).
  • the sodium silicate aqueous solution (a) was passed through a column filled with a hydrogen-type strongly acidic cation exchange resin Amberlite IR-120B at a space velocity of 4.5 per hour to recover 5500 kg of an aqueous solution of active silicic acid. did.
  • Example 1 (Concentration of silica sol thin liquid)
  • the obtained silica sol thin liquid 1 was circulated through a polysulfone tubular ultrafiltration membrane (also referred to as a UF tube, inner diameter: 1/2 inch) having a molecular weight cutoff of 100,000, under a pressure of 0.25 MPa and a flow rate of 6.0.
  • a polysulfone tubular ultrafiltration membrane also referred to as a UF tube, inner diameter: 1/2 inch
  • the solution was concentrated to a silica concentration of about 40% by mass.
  • the silica concentration of the sample is diluted with pure water to 15.0% by mass, and the LPC value is measured using AccuSizer FX-nano manufactured by PSS Japan Co., Ltd. (trade name AccuSizer A9000, manufactured by Nihon Entegris LLC). It was measured. When the silica concentration of the sample was less than 15.0% by mass, it was measured as it was, and the measured value was converted to 15.0% by mass. About 1 g of a sample was precisely weighed, dried on a hot plate at 140° C., fired at 1000° C. for 0.5 hours, and the silica concentration was calculated from the fired residue.
  • Example 2 The silica sol obtained by the same operation as in Example 1 was circulated through a polysulfone tubular ultrafiltration membrane (inner diameter of 1/2 inch) having a molecular weight cut off of 100,000, and the pressure was 0.10 MPa and the flow rate was 8.8 L/ The mixture was concentrated at 30° C. for a minute to a silica concentration of about 40% by mass.
  • Example 3 The silica sol obtained by the same operation as in Example 1 was circulated through a polysulfone tubular ultrafiltration membrane (inner diameter of 1/2 inch) having a molecular weight cut off of 100,000, and the pressure was 0.05 MPa and the flow rate was 9.5 L/ The mixture was concentrated at 30° C. for a minute to a silica concentration of about 40% by mass.
  • Example 4 The silica sol obtained by the same operation as in Example 1 was circulated through a polysulfone tubular ultrafiltration membrane (inner diameter of 1/2 inch) having a molecular weight cut off of 500,000, and the pressure was 0.25 MPa and the flow rate was 6.9 L/ The mixture was concentrated at 30° C. for a minute to a silica concentration of about 40% by mass.
  • Example 5 The silica sol obtained by the same operation as in Example 1 was circulated through a polysulfone tubular ultrafiltration membrane (inner diameter of 1/2 inch) having a molecular weight cut off of 500,000, and the pressure was 0.10 MPa and the flow rate was 8.8 L/ The mixture was concentrated at 30° C. for a minute to a silica concentration of about 40% by mass.
  • Example 6 The silica sol obtained by the same operation as in Example 1 was circulated through a polysulfone tubular ultrafiltration membrane (inside diameter of 1/2 inch) having a cutoff molecular weight of 500,000, and the pressure was 0.05 MPa and the flow rate was 9.5 L/ The mixture was concentrated at 30° C. for a minute to a silica concentration of about 40% by mass.
  • Example 7 The silica sol obtained by the same operation as in Example 1 was circulated through a polysulfone tubular ultrafiltration membrane (inner diameter of 1/2 inch) having a molecular weight cut off of 100,000, and the pressure was 0.05 MPa and the flow rate was 9.5 L/ The mixture was concentrated at 15° C. to a silica concentration of about 40% by mass.
  • Table 1 shows the concentration of silica sol using a UF tube with an inner diameter of 1/2 inch, and the presence or absence of contamination of washing water after UF concentration (so-called operation of removing silica sol from the pipe by pushing water). Those that did not use washing water after UF concentration were indicated as (none), and those that used washing water after UF concentration were indicated as (yes).
  • Thin liquid 1 is a silica sol having a silica concentration of 3.2% by mass before UF concentration, and is a raw material for the following silica concentrates 1 to 13 obtained in Examples 1 to 8 and Comparative Examples 1 to 5.
  • Concentrated liquid 1 is a silica sol having a silica concentration of 36.0% by mass by UF concentration obtained in Example 1 (Example 1).
  • Concentrated liquid 2 is a silica sol having a silica concentration of 35.7% by mass obtained by UF concentration obtained in Example 2 (Example 2).
  • Concentrated liquid 3 is a silica sol having a silica concentration of 35.2% by mass by UF concentration obtained in Example 3 (Example 3).
  • Concentrated liquid 4 is the silica sol having a silica concentration of 38.4% by mass by UF concentration obtained in Example 4 (Example 4).
  • Concentrated liquid 5 is a silica sol having a silica concentration of 35.1% by mass by UF concentration obtained in Example 5 (Example 5).
  • Concentrated liquid 6 is the silica sol having a silica concentration of 36.9 mass % obtained by UF concentration obtained in Example 6 (Example 6).
  • Concentrated liquid 7 is the silica sol having a silica concentration of 38.6% by mass by UF concentration obtained in Example 7 (Example 7). (--) in Table 1 indicates that it was not implemented.
  • Table 2 shows the physical properties of the concentrated silica sol. SiO2 concentration (mass %), cation content (mass percent), anion content (mass percent) are indicated.
  • LPC in Table 2 indicates the number of coarse particles having a particle diameter of 0.48 ⁇ m or more.
  • (--) in Table 2 indicates unmeasured.
  • Example 3 and Example 7 When comparing Example 3 and Example 7 at the same cutoff molecular weight and the same pressure, the concentrated solution 7 of Example 7 with a UF treatment temperature of 15 ° C. was higher than the concentrated solution 3 of Example 3 with a UF treatment temperature of 30 ° C. It was confirmed that the numerical value of LPC decreased in . When comparing Examples 1 to 3 and Examples 4 to 6 at the same temperature and the same molecular weight cutoff, it was confirmed that the value of LPC increases as the UF treatment pressure increases.
  • Example 8 Silica sol obtained by the same operation as in Example 1 was filtered using a commercially available ultrafiltration device equipped with a polyvinylidene fluoride tubular ultrafiltration membrane (inner diameter of 1 inch) having a cutoff molecular weight of 100,000. It was concentrated to a SiO 2 concentration of about 40% by weight at 30° C. at 3 MPa and a flow rate of 420 L/min. There was no contamination of washing water after UF concentration (so-called operation of removing silica sol from pipes by pushing water).
  • Example 5 Silica sol obtained by the same operation as in Example 1 was filtered using a commercially available ultrafiltration device equipped with a polyvinylidene fluoride tubular ultrafiltration membrane (inner diameter of 1 inch) having a cutoff molecular weight of 100,000. Concentration was carried out at 50 to 70° C. to a SiO 2 concentration of about 40 mass % at 3 MPa and a flow rate of 420 L/min. The case where the washing water after UF concentration was mixed (the so-called operation of taking out the silica sol from the pipe by pushing water) and the case where it was not were also shown. The case where the washing water after UF concentration is mixed is the case where pure water is flowed into the UF tube and the concentrated solution is collected.
  • a commercially available ultrafiltration device equipped with a polyvinylidene fluoride tubular ultrafiltration membrane (inner diameter of 1 inch) having a cutoff molecular weight of 100,000. Concentration was carried out at 50 to 70° C. to a SiO 2 concentration of about 40 mass
  • Concentrated liquid 8 is the silica sol having a silica concentration of 39.0% by mass by UF concentration obtained in Example 8 (Example 8).
  • Concentrated liquid 9 is the silica sol having a silica concentration of 36.6 mass % obtained by UF concentration obtained in Comparative Example 1 (Comparative Example 1).
  • Concentrated liquid 10 is the silica sol having a silica concentration of 43.4% by mass by UF concentration obtained in Comparative Example 2 (Comparative Example 2).
  • Concentrated liquid 11 is the silica sol having a silica concentration of 40.0% by mass by UF concentration obtained in Comparative Example 3 (Comparative Example 3).
  • Concentrated liquid 12 is silica sol having a silica concentration of 40.6% by mass obtained by UF concentration obtained in Comparative Example 4 (Comparative Example 4).
  • Concentrated liquid 13 is the silica sol having a silica concentration of 44.3% by mass by UF concentration obtained in Comparative Example 5 (Comparative Example 5). (--) in Table 3 indicates that it was not implemented.
  • Table 4 shows the physical properties of the concentrated silica sol. SiO2 concentration (mass %), cation content (mass percent), anion content (mass percent) are indicated. LPC in Table 4 indicates the number of coarse particles having a particle diameter of 0.48 ⁇ m or more.
  • Example 8 and Comparative Examples 1 and 3 In comparison with the same cutoff molecular weight, the same pressure, and no mixing of washing water after UF, by comparison of Example 8 and Comparative Examples 1 and 3, the value of LPC increases as the UF treatment temperature rises. was confirmed. In comparison with the same cutoff molecular weight, the same pressure, and the same UF treatment temperature, Example 8 and Comparative Example 5 were compared in the case where washing water was not mixed after UF and when washing water was mixed after UF. Also, from the comparison between Comparative Examples 1 and 2 and the comparison between Comparative Examples 3 and 4, the LPC increased significantly due to the mixing of washing water after UF. Mixing of washing water after UF means an operation of pouring pure water into the UF tube and recovering the concentrate, but the concentration of silica in the concentrate is greatly reduced locally.
  • Circulating the silica sol in the device or injecting silica sol further into the ultrafiltration device is related to the fact that the concentration of silica particles contained in the silica sol after the concentration step is higher than before the concentration step.) Suppresses the contamination of LPC (coarse particles) generated in the silica sol concentration step. We were able to.
  • the silica sol concentration method of the present invention it is possible to prevent the formation of agglomerated silica particles in the concentrated silica sol when concentration is performed to increase the concentration of silica components in the silica sol by ultrafiltration. Therefore, the method is useful for producing silica sol used for polishing silicon wafers for semiconductors and devices, for example, because it can suppress inclusion of LPC (coarse particles) into the silica sol.

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  • Engineering & Computer Science (AREA)
  • Water Supply & Treatment (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
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Abstract

[Problem] To provide a silica sol concentration method with which it is possible, when carrying out concentration by means of ultra filtration in order to increase the concentration of a silica component in a silica sol, to prevent the formation of aggregated silica particles in the concentrated silica sol. [Solution] A concentration method for a sol (silica sol) in which silica particles are dispersed in a dispersion medium as dispersoid particles, said silica sol concentration method being characterized by including a concentration step for increasing the concentration of the silica particles contained in the silica sol using an ultrafiltration device, and by requirement A and requirement B being satisfied during the concentration step. Requirement A: The solution temperature of the silica sol immediately before being poured into the ultrafiltration device being in the range from 0-45°C. Requirement B: The concentration of the silica particles contained in the silica sol after the concentration step being increased relative to before the concentration step as a result of allowing the silica sol to circulate in the ultrafiltration device.

Description

限外ろ過法によるシリカゾルの濃縮方法Method for concentrating silica sol by ultrafiltration
　本発明は限外ろ過法を利用したシリカゾルの濃縮方法に関する。 The present invention relates to a silica sol concentration method using an ultrafiltration method.
　コロイド状シリカ粒子が水性媒体に分散したゾル（シリカゾル）は、原料となるケイ酸ナトリウム水溶液からナトリウムイオンを取り除いたケイ酸水溶液を加熱することや、アルコキシシランを加水分解して得られるケイ酸水溶液を加熱することで製造することができる。製造直後のシリカゾルはシリカ成分が低濃度の液体であることが一般的であるが、それを濃縮することで製品化される。
　シリカ成分を濃縮する方法としては、限外ろ過や蒸発法により濃縮が行われている。限外ろ過によってシリカゾル中のシリカ成分を濃縮する方法は、限外ろ過膜を通じて水が系外に除去されることでシリカゾル中のシリカ成分の濃度が上昇するものである。
　限外ろ過による濃縮方法としては、例えば、ジルコニウム塩水溶液を尿素の存在下に加熱して透明性ジルコニアゾルを得た後、キレート化剤及びジルコニウム以外の金属化合物を配合し、８０℃以下の温度で限外ろ過膜により濃縮する方法（特許文献１参照）が開示されている。
　また、シリカを含む地熱流体からコロイダルシリカ濃縮物を生成させる際に、初期温度から核形成温度まで冷却しシリカコロイド成長を開始し、シリカ粒子を有する流体を限外ろ過によりシリカの濃縮物を得る方法（特許文献２参照）が開示されている。 A sol in which colloidal silica particles are dispersed in an aqueous medium (silica sol) can be obtained by heating an aqueous silicic acid solution obtained by removing sodium ions from an aqueous sodium silicate solution as a raw material, or by hydrolyzing an alkoxysilane. can be produced by heating Silica sol immediately after production is generally a liquid with a low concentration of silica components, but it is commercialized by concentrating it.
As a method for concentrating the silica component, concentration is performed by ultrafiltration or an evaporation method. In the method of concentrating the silica component in the silica sol by ultrafiltration, the concentration of the silica component in the silica sol is increased by removing water out of the system through an ultrafiltration membrane.
As a concentration method by ultrafiltration, for example, after heating a zirconium salt aqueous solution in the presence of urea to obtain a transparent zirconia sol, a chelating agent and a metal compound other than zirconium are blended, and the temperature is 80 ° C. or less. A method of concentrating with an ultrafiltration membrane is disclosed (see Patent Document 1).
Also, when producing a colloidal silica concentrate from a geothermal fluid containing silica, silica colloidal growth is initiated by cooling from the initial temperature to the nucleation temperature, and the fluid containing silica particles is subjected to ultrafiltration to obtain a silica concentrate. A method (see Patent Document 2) is disclosed.
国際公開第９０／０９３５０号WO 90/09350 特表２０１８－５２４２５６号公報Japanese Patent Publication No. 2018-524256
　シリカゾル中のシリカ粒子の濃縮には限外ろ過法を用いることができるが、限外ろ過膜にはろ過液が系外に除かれる際に限外ろ過膜の内面にケーキ層と呼ばれる高濃度シリカ粒子の堆積物が形成されることがある。該ケーキ層に含まれるシリカ粗大粒子はシリカゾルを限外ろ過装置内で循環させてシリカ粒子の濃度を上昇させてゆく時に、シリカゾル中に脱落し、最終製品（濃縮されたシリカゾル製品）に混入し、その結果、それら製品を使用する場面で支障をきたす虞がある。例えば、該シリカゾル製品を研磨用途に適用する時に、粗大粒子は研磨面に傷を生じさせシリコンウエハーやデバイスに欠陥を生じる可能性がある。これらの粗大粒子が発生した場合に、後からフィルターで除去することも考えられるが、フィルターの目詰まりが生じるために効率的ではない。
　したがって、限外ろ過装置の限外ろ過膜内面に形成されるケーキ層からのシリカ粗大粒子の混入を抑制しつつシリカゾルのシリカ濃度を上昇させる方法が求められている。 Ultrafiltration can be used to concentrate the silica particles in the silica sol, but when the filtrate is removed from the system, the ultrafiltration membrane has a high-concentration silica layer called a cake layer on the inner surface of the ultrafiltration membrane. Deposits of particles may form. The coarse silica particles contained in the cake layer drop out into the silica sol when the silica sol is circulated in the ultrafiltration device to increase the concentration of silica particles, and are mixed into the final product (concentrated silica sol product). As a result, there is a possibility that problems will occur when using these products. For example, when the silica sol product is used for polishing, coarse particles may scratch the polished surface and cause defects in silicon wafers and devices. When these coarse particles are generated, it may be possible to remove them later with a filter, but this is not efficient because the filter clogs.
Therefore, there is a demand for a method for increasing the silica concentration of silica sol while suppressing the inclusion of coarse silica particles from the cake layer formed on the inner surface of the ultrafiltration membrane of the ultrafiltration device.
　本発明は上記に鑑みてなされたもので、シリカゾル中のシリカ成分の濃度を高めるための濃縮を限外ろ過法で行う上で、濃縮されたシリカゾル中に、凝集したシリカ粒子が形成されることを防ぐことができるシリカゾルの濃縮方法を提供することを目的とする。 The present invention has been made in view of the above. An object of the present invention is to provide a method for concentrating silica sol that can prevent
　本発明者らは、上記の課題解決を目標に鋭意検討した結果、シリカゾル中に含まれるシリカ粒子の濃度を限外ろ過装置により上昇させる濃縮工程において、下記の要件Ａ及び要件Ｂが満たされることを条件に、限外ろ過膜付近のシリカゾルの液体の流速を高めシリカ粒子が凝集しにくい状況を作ることによって、濃縮されたシリカゾル中に、凝集したシリカ粒子が形成されることを防ぐことができるシリカゾルの濃縮方法を見出し、本発明を完成した。 As a result of intensive studies aimed at solving the above problems, the present inventors found that the following requirement A and requirement B are satisfied in the concentration step of increasing the concentration of silica particles contained in the silica sol using an ultrafiltration device. By increasing the flow velocity of the silica sol liquid near the ultrafiltration membrane and creating a situation in which silica particles are less likely to aggregate, it is possible to prevent the formation of aggregated silica particles in the concentrated silica sol. A method for concentrating silica sol was discovered, and the present invention was completed.
　すなわち、本発明は第１観点として、分散質粒子としてシリカ粒子を分散媒に分散したゾル（シリカゾル）の濃縮方法であって、該シリカゾル中に含まれるシリカ粒子の濃度を限外ろ過装置により上昇させる濃縮工程を含み、該濃縮工程において下記要件Ａ及び要件Ｂが満たされることを特徴とする、シリカゾルの濃縮方法に関する。
要件Ａ：限外ろ過装置に注入する直前のシリカゾルの液温が０乃至４５℃の範囲であること。
要件Ｂ：限外ろ過装置でシリカゾルを循環させることによって、濃縮工程後には該シリカゾル中に含まれるシリカ粒子の濃度が濃縮工程前より上昇していること。
　第２観点として、前記要件Ｂにおいて、限外ろ過装置でシリカゾルを循環させる濃縮工程中、又は濃縮工程後に、限外ろ過装置にシリカゾルをさらに注入することを含み、さらに注入されるシリカゾルが、濃縮工程前のシリカゾル中に含まれるシリカ粒子の濃度の０．１～３０倍の濃度であることを特徴とする、第１観点に記載のシリカゾルの濃縮方法に関する。
　第３観点として、前記要件Ａにおいて、限外ろ過装置に注入する直前のシリカゾルの液温が、０乃至３０℃の範囲に調整されていることを特徴とする、第１観点又は第２観点に記載のシリカゾルの濃縮方法に関する。
　第４観点として、前記要件Ｂにおいて、限外ろ過装置に濃縮工程前のシリカゾルと同じ濃度のシリカゾルをさらに注入すること、又は限外ろ過装置で濃縮工程前のシリカゾルより高い濃度のシリカゾルを循環させることによって、濃縮工程後には該シリカゾル中に含まれるシリカ粒子の濃度が濃縮工程前より上昇していることを特徴とする、第２観点に記載のシリカゾルの濃縮方法に関する。
　第５観点として、前記要件Ｂにおいて、濃縮されたシリカゾルは濃縮工程後に限外ろ過装置から直接配管を通じて、シリカ粒子の濃度の低下が５質量％以内となる条件で濃縮シリカゾル充填容器に充填されることを特徴とする、第１観点乃至第４観点の何れか一つに記載のシリカゾルの濃縮方法に関する。
　第６観点として、前記要件Ｂにおいて、濃縮工程後のシリカ粒子の濃度が濃縮工程前のシリカ粒子の濃度に対して濃度比２乃至３０の範囲で濃縮工程が行われることを特徴とする、第１観点乃至第５観点の何れか一つに記載のシリカゾルの濃縮方法に関する。
　第７観点として、限外ろ過装置に注入する前のシリカゾルが、ケイ酸アルカリ水溶液からアルカリ金属イオンを除去して得られたケイ酸水溶液を加熱して得られたシリカ粒子を含むシリカゾルであることを特徴とする、第１観点乃至第６観点の何れか一つに記載のシリカゾルの濃縮方法に関する。 That is, a first aspect of the present invention is a method for concentrating a sol (silica sol) in which silica particles are dispersed as dispersoid particles in a dispersion medium, wherein the concentration of silica particles contained in the silica sol is increased by an ultrafiltration device. It relates to a method for concentrating a silica sol, characterized in that the following requirements A and B are satisfied in the concentration process.
Requirement A: The liquid temperature of the silica sol immediately before being injected into the ultrafiltration device must be in the range of 0 to 45°C.
Requirement B: By circulating the silica sol through the ultrafiltration device, the concentration of silica particles contained in the silica sol after the concentration step should be higher than before the concentration step.
As a second aspect, Requirement B includes further injecting silica sol into the ultrafiltration device during or after the concentration step of circulating silica sol in the ultrafiltration device, and the injected silica sol is concentrated It relates to the method for concentrating silica sol according to the first aspect, wherein the concentration is 0.1 to 30 times the concentration of silica particles contained in the silica sol before the step.
As a third aspect, in the first aspect or the second aspect, in the requirement A, the liquid temperature of the silica sol immediately before being injected into the ultrafiltration device is adjusted to a range of 0 to 30 ° C. It relates to a method for concentrating the described silica sol.
As a fourth aspect, in the requirement B, the ultrafiltration device is further injected with silica sol having the same concentration as the silica sol before the concentration step, or the silica sol with a higher concentration than the silica sol before the concentration step is circulated through the ultrafiltration device. Thus, the silica sol concentration method according to the second aspect is characterized in that the concentration of silica particles contained in the silica sol after the concentration step is higher than that before the concentration step.
As a fifth aspect, in Requirement B, the concentrated silica sol is directly passed through a pipe from the ultrafiltration device after the concentration step, and filled into a concentrated silica sol filling container under conditions where the concentration of silica particles decreases within 5% by mass. The method for concentrating silica sol according to any one of the first to fourth aspects, characterized by:
As a sixth aspect, in the requirement B, the concentration step is performed in a concentration ratio range of 2 to 30 in which the concentration of the silica particles after the concentration step is in the range of 2 to 30 with respect to the concentration of the silica particles before the concentration step. It relates to the silica sol concentration method according to any one of the 1st to 5th aspects.
As a seventh aspect, the silica sol before being injected into the ultrafiltration device is a silica sol containing silica particles obtained by heating an aqueous silicic acid solution obtained by removing alkali metal ions from an aqueous alkali silicate solution. It relates to the method for concentrating silica sol according to any one of the first to sixth aspects, characterized by:
　本発明の方法は、シリカゾル中のシリカ成分の濃度を高めるための濃縮を限外ろ過法で行う上で、濃縮されたシリカゾル中に、凝集したシリカ粒子が形成されることを防ぎつつ、シリカゾルを濃縮することができるという効果を奏する。 The method of the present invention prevents the formation of agglomerated silica particles in the concentrated silica sol in performing concentration for increasing the concentration of the silica component in the silica sol by ultrafiltration, while removing the silica sol. The effect of being able to concentrate is exhibited.
　本発明は分散質粒子としてシリカ粒子を分散媒として水に分散したゾル（シリカゾル）の濃縮方法であって、該シリカゾル中に含まれるシリカ粒子の濃度を限外ろ過装置により上昇させる濃縮工程を含み、該濃縮工程において下記要件Ａ及び要件Ｂが満たされることを特徴とする、シリカゾルの濃縮方法に関する。
要件Ａ：限外ろ過装置に注入する直前のシリカゾルの液温が０乃至４５℃、好ましくは０乃至４０℃、更に好ましくは０乃至３５℃、最も好ましくは０乃至３０℃の範囲であること。
要件Ｂ：限外ろ過装置でシリカゾルを循環させることによって、濃縮工程後には該シリカゾル中に含まれるシリカ粒子の濃度が濃縮工程前より上昇していること。
　以下、本発明を詳細に説明する。 The present invention is a method for concentrating a sol (silica sol) dispersed in water using silica particles as dispersoid particles as a dispersion medium, comprising a concentration step of increasing the concentration of silica particles contained in the silica sol using an ultrafiltration device. , relates to a silica sol concentration method, characterized in that the following requirements A and B are satisfied in the concentration step.
Requirement A: The liquid temperature of the silica sol immediately before injection into the ultrafiltration device should be in the range of 0 to 45°C, preferably 0 to 40°C, more preferably 0 to 35°C, and most preferably 0 to 30°C.
Requirement B: By circulating the silica sol through the ultrafiltration device, the concentration of silica particles contained in the silica sol after the concentration step should be higher than before the concentration step.
The present invention will be described in detail below.
　本発明において用いられる限外ろ過装置としては、例えば、限外ろ過膜（ＵＦ膜）をチューブ状に成型し、そのチューブの内側を濃縮すべきシリカゾルが循環し、チューブの外側に水性媒体が排出されシリカゾルのシリカ成分が濃縮される構造を備えるものを用いることができる。上記水性媒体の主成分は水であるが、シリカゾル中に含まれる陽イオン、陰イオンが同時に排出されても良い。限外ろ過膜はクロスフロー方式が好ましく、限外ろ過膜面に対して平行な流れを形成することでシリカゾル中の懸濁物質やコロイド状シリカ粒子が限外ろ過膜面に堆積する現象を抑制しながらシリカゾル中のシリカ成分濃度を上昇させることができる。 As an ultrafiltration device used in the present invention, for example, an ultrafiltration membrane (UF membrane) is formed into a tube, silica sol to be concentrated circulates inside the tube, and an aqueous medium is discharged outside the tube. A silica sol having a structure in which the silica component of the silica sol is concentrated can be used. Although the main component of the aqueous medium is water, cations and anions contained in the silica sol may be discharged at the same time. A cross-flow system is preferable for the ultrafiltration membrane, and by forming a flow parallel to the surface of the ultrafiltration membrane, the phenomenon of suspended solids and colloidal silica particles in the silica sol being deposited on the surface of the ultrafiltration membrane is suppressed. while increasing the silica component concentration in the silica sol.
　限外ろ過膜の材質としては、例えば、ポリエチレン、ポリフッ化エチレン、ポリフッ化ビニリデン、ポリプロピレン、酢酸セルロース、ポリアクリロニトリル、ポリイミド、ポリスルホン、ポリエーテルスルホン等を挙げることができる。また、膜材料に酸化アルミニウム、酸化ジルコニウム、酸化チタン、ステンレス、ガラス等を単独で又は上記材質と共に使用することができる。限外ろ過膜モジュールとしては、例えば、ケーシング収納方式を用いることが可能であり、限外ろ過膜とその支持体及び流路材料などの部材を一体化して膜エレメントとしたものをケーシングに収納して、ポンプでケーシング内にシリカゾルを圧入することで水性媒体のろ過を行い、コロイド状のシリカ成分を濃縮し、濃縮されたシリカゾル製品を得ることができる。 Examples of materials for ultrafiltration membranes include polyethylene, polyethylene fluoride, polyvinylidene fluoride, polypropylene, cellulose acetate, polyacrylonitrile, polyimide, polysulfone, and polyethersulfone. Also, aluminum oxide, zirconium oxide, titanium oxide, stainless steel, glass, or the like can be used alone or in combination with the above materials for the film material. As the ultrafiltration membrane module, for example, it is possible to use a casing housing method, in which a membrane element formed by integrating members such as an ultrafiltration membrane, its support, and a channel material is housed in a casing. Then, silica sol is forced into the casing by a pump to filter the aqueous medium and concentrate the colloidal silica component to obtain a concentrated silica sol product.
　上記限外ろ過膜の分画分子量は、例えば、膜の公称孔径が５ｎｍ～１００ｎｍ程度であり、適合粒子径としては、例えば、５ｎｍ～５００ｎｍであり、分画分子量としては、例えば、５０ｋ（５万）、１００ｋ（１０万）、３００ｋ（３０万）、５００ｋ（５０万）のものを用いることができる。例えば、分画分子量、膜の公称孔径、及び適合粒子径の間には一例ではあるが以下の関係があるが、これらの関係に制約されるものではない。
　例えば、分画分子量５万である場合は膜の公称孔径５ｎｍであって適合粒子径は１５～３０ｎｍである。分画分子量１０万である場合は膜の公称孔径１０ｎｍであって適合粒子径は３０～９０ｎｍである。分画分子量３０万である場合は膜の公称孔径３５ｎｍであって適合粒子径は９０～２００ｎｍである。分画分子量１００万である場合は膜の公称孔径１００ｎｍであって適合粒子径は３００～６００ｎｍである。 The molecular weight cutoff of the ultrafiltration membrane is, for example, the nominal pore diameter of the membrane is about 5 nm to 100 nm, the suitable particle diameter is, for example, 5 nm to 500 nm, and the molecular weight cut off is, for example, 50 k (5 10,000), 100k (100,000), 300k (300,000), and 500k (500,000) can be used. For example, there is the following relationship between the molecular weight cutoff, the nominal pore size of the membrane, and the compatible particle size, although the relationship is not limited to these relationships.
For example, when the molecular weight cutoff is 50,000, the nominal pore size of the membrane is 5 nm and the suitable particle size is 15 to 30 nm. When the molecular weight cutoff is 100,000, the nominal pore size of the membrane is 10 nm and the suitable particle size is 30 to 90 nm. When the molecular weight cutoff is 300,000, the nominal pore size of the membrane is 35 nm and the suitable particle size is 90 to 200 nm. When the molecular weight cutoff is 1 million, the nominal pore size of the membrane is 100 nm and the suitable particle size is 300-600 nm.
　シリカゾルのＵＦ装置への送液（本明細書では、注入、注液又は圧入とも称する。）は、例えば、０．０１～１０ＭＰａ、又は０．０５～５．０ＭＰａ、又は０．１～１．０ＭＰａ、又は０．３～１．０ＭＰａの圧力で行うことができる。 Delivery of the silica sol to the UF device (herein also referred to as injection, injection or injection) is, for example, 0.01 to 10 MPa, or 0.05 to 5.0 MPa, or 0.1 to 1.0 MPa. It can be performed at a pressure of 0 MPa, or 0.3 to 1.0 MPa.
　また、所望のシリカ濃度を得るためのシリカゾルの濃縮に要する時間は０．１～５０時間程度である。 In addition, the time required to concentrate the silica sol to obtain the desired silica concentration is about 0.1 to 50 hours.
　要件Ａは、限外ろ過装置に注入する直前のシリカゾルの液温が０乃至４５℃の範囲であることを条件とするものである。シリカゾルの液温は、例えば、０～４５℃、又は０～４０℃、又は０～３５℃、又は０～３０℃である。シリカゾルを０～４５℃、又は０～４０℃、又は０～３５℃、又は０～３０℃という低温で限外ろ過装置に通液することにより、シリカ粒子のシラノール基の重縮合が進行し、シリカ粒子同士の凝集を避けることができる。 Requirement A is based on the condition that the liquid temperature of the silica sol immediately before being injected into the ultrafiltration device is in the range of 0 to 45°C. The liquid temperature of the silica sol is, for example, 0 to 45°C, 0 to 40°C, 0 to 35°C, or 0 to 30°C. By passing the silica sol through an ultrafiltration device at a low temperature of 0 to 45°C, 0 to 40°C, 0 to 35°C, or 0 to 30°C, the polycondensation of the silanol groups of the silica particles proceeds. Aggregation of silica particles can be avoided.
　要件Ａは、限外ろ過装置に注入する直前のシリカゾルの液温が０乃至４５℃の範囲であることを条件とするものであるが、該シリカゾルの液温がこの温度より高い場合は冷却することで液温をこの範囲に調整することが好ましい。冷却には冷却水を循環させたタンクに限外ろ過膜モジュールを沈積し、シリカゾルを所定の温度まで冷却することが好ましい。本発明において濃縮過程のシリカゾルを限外ろ過膜モジュールに循環する方法を行う場合に、限外ろ過膜モジュールに注入する直前の温度が０～４５℃、又は０～４０℃、又は０～３５℃、又は０～３０℃、又は０～２５℃、又は０～１５℃であり、限外ろ過膜モジュールから再度、上述温度範囲への温度調整（例えば冷却）を経て限外ろ過膜モジュールに注入されることが好ましい。 Requirement A is based on the condition that the liquid temperature of the silica sol immediately before being injected into the ultrafiltration device is in the range of 0 to 45 ° C. If the liquid temperature of the silica sol is higher than this temperature, it is cooled. Therefore, it is preferable to adjust the liquid temperature within this range. For cooling, it is preferable to deposit the ultrafiltration membrane module in a tank in which cooling water is circulated and cool the silica sol to a predetermined temperature. In the present invention, when the silica sol in the concentration process is circulated through the ultrafiltration membrane module, the temperature immediately before injection into the ultrafiltration membrane module is 0 to 45°C, or 0 to 40°C, or 0 to 35°C. , or 0 to 30 ° C., or 0 to 25 ° C., or 0 to 15 ° C., and is again injected from the ultrafiltration membrane module through temperature adjustment (for example, cooling) to the above temperature range. preferably.
　要件Ｂは、限外ろ過装置でシリカゾルを循環させることによって、濃縮工程後には該シリカゾル中に含まれるシリカ粒子の濃度が濃縮工程前より上昇していることを条件とするものである。 Requirement B is a condition that the concentration of silica particles contained in the silica sol after the concentration process is higher than before the concentration process by circulating the silica sol in the ultrafiltration device.
　本明細書において「循環」は、例えば、限外ろ過装置に注入されて濃縮工程を経たシリカゾルを一旦回収し、再び限外ろ過装置に注入することや、例えば、限外ろ過装置に循環路を形成することで該シリカゾルを回収することなく濃縮工程を繰り返すことを意味し、さらにこれらの組み合わせを包含することも意味する。 As used herein, "circulation" means, for example, once recovering silica sol that has been injected into an ultrafiltration device and has undergone a concentration step, and then injecting it into the ultrafiltration device again. By forming is meant repeating the concentration step without recovering the silica sol, and is also meant to include combinations thereof.
　要件Ｂにおいて、限外ろ過装置でシリカゾルを循環させることによって、ケーキ層の脱落を抑制することができる。即ち、低濃度のシリカ濃度のシリカゾルを循環させることによってケーキ層が低濃度部分に溶け混むことを防ぐことができる。そして、濃縮前のシリカゾルより高い濃度のシリカゾルの循環によって行われることが好ましい。 In Requirement B, circulating the silica sol in the ultrafiltration device can prevent the cake layer from falling off. That is, by circulating the silica sol having a low silica concentration, it is possible to prevent the cake layer from being dissolved in the low-concentration portion. Then, it is preferable to circulate a silica sol having a higher concentration than the silica sol before concentration.
　要件Ｂにおいて、限外ろ過膜モジュール内を循環している濃縮工程中又は濃縮工程後のシリカゾルに、シリカゾルをさらに注入することもできる。さらに注入されるシリカゾルは、濃縮工程前のシリカゾル中に含まれるシリカ粒子の濃度の０．１～３０倍の濃度であることが好ましい。シリカゾルをさらに注入することによって、ケーキ層が低濃度部分に溶け混むことをより防ぐことができる。さらに、その濃度範囲で循環してもよい。最終的に濃縮工程終了時に濃縮工程前より濃縮されるものであるが、シリカゾルのさらなる注入は、濃縮工程前のシリカゾルと同じ濃度のシリカゾルで行われることが好ましく、さらに、そのシリカゾルの循環は、濃縮前のシリカゾルより高い濃度で行われることが好ましい。 In Requirement B, silica sol can be further injected into the silica sol circulating in the ultrafiltration membrane module during or after the concentration process. Further, the injected silica sol preferably has a concentration of 0.1 to 30 times the concentration of silica particles contained in the silica sol before the concentration step. By further injecting silica sol, it is possible to further prevent the cake layer from dissolving into the low-concentration portion. Further, it may be cycled within that concentration range. Finally, at the end of the concentration step, the silica sol is more concentrated than before the concentration step, but further injection of silica sol is preferably performed with silica sol having the same concentration as the silica sol before the concentration step. It is preferably carried out at a higher concentration than the silica sol before concentration.
　そして、濃縮されたシリカゾルは最終製品として限外ろ過装置から取り出される時に、搬出溶媒として低濃度のシリカゾルや水を用いて装置から取り出される場合、搬出溶媒による一時的な濃度低下を生じ、ケーキ層が搬出溶媒によってシリカゾル製品中に脱落し、それが粗大粒子の原因になる。従って、濃縮されたシリカゾルは濃縮完了時に限外ろ過装置から直接配管を通じて、濃縮完了時のシリカ濃度の低下が５質量％以内となる条件で濃縮シリカゾル製品としてパッキング（濃縮シリカゾル充填容器に充填）されることが好ましい。 When the concentrated silica sol is taken out from the ultrafiltration device as a final product, if low-concentration silica sol or water is used as the carrying-out solvent, the concentration of the concentrated silica sol is temporarily lowered due to the carrying-out solvent, resulting in a cake layer. is dropped into the silica sol product by the transported solvent, which causes coarse particles. Therefore, the concentrated silica sol is packed (filled into a container filled with concentrated silica sol) as a concentrated silica sol product under the condition that the silica concentration decreases by 5% by mass or less upon completion of concentration through a direct pipe from the ultrafiltration device. preferably.
　また、これらの操作はシリカゾル最終製品を得る時に濃縮完了時に限外ろ過装置から直接配管を通じて、濃縮完了時のシリカ濃度の低下が５質量％以内となる条件で、例えば０～５質量％の範囲内となる条件で、好ましくはシリカ濃度低下を生じずに濃縮シリカゾル製品としてパッキング（濃縮シリカゾル充填容器に充填）されることが望ましい。 In addition, these operations are carried out through a pipe directly from the ultrafiltration device when the final product of silica sol is obtained, under the condition that the silica concentration decreases within 5% by mass when the concentration is completed, for example in the range of 0 to 5% by mass. It is desirable that the concentrated silica sol product be packed (filled in a container filled with concentrated silica sol) under the above conditions, preferably without causing a decrease in silica concentration.
　本発明では濃縮工程後のシリカ粒子の濃度が濃縮工程前のシリカ粒子の濃度に対して濃度比２乃至３０の範囲でシリカゾルの濃縮工程が行われることが好ましい。 In the present invention, the silica sol concentration step is preferably carried out in a concentration ratio range of 2 to 30 for the concentration of the silica particles after the concentration step to the concentration of the silica particles before the concentration step.
　また本発明のシリカゾルの濃縮方法は、濃縮工程の前後におけるシリカゾル中に含まれるイオン成分（陽イオンや陰イオンの）濃度変化が少ないことを特徴とする。 In addition, the silica sol concentration method of the present invention is characterized by little change in concentration of ionic components (cations and anions) contained in the silica sol before and after the concentration process.
　本発明では限外ろ過の過程で陽イオン（例えばカリウムイオンを含む陽イオンであり、典型的にはカリウムイオンである。）と、陰イオン（例えば硫酸イオンを含む陰イオンであり、典型的には硫酸イオンである。）が水と共に系外に除去されるが、イオン成分はシリカゾル中のシリカ粒子表面に電荷を与え、適度なシリカ粒子の反発力を形成してシリカ粒子の凝集を防ぐことができる。一方、イオン成分が多量に存在してもシリカ粒子同士の凝集につながる。これらのシリカゾル中の陽イオンと陰イオンの濃度は限外ろ過によってその変化が少ないことが好ましい。例えば、陽イオンと陰イオンの濃度変化はそれぞれ濃縮工程前のシリカゾル中の濃度（質量％濃度）の１０倍以内に抑えることが好ましい。
　これらのイオン成分の濃度を上記範囲内に設定することでケーキ層の生成を抑制することができる。 In the present invention, in the process of ultrafiltration, cations (e.g., cations containing potassium ions, typically potassium ions) and anions (e.g., anions containing sulfate ions, typically is a sulfate ion.) is removed out of the system together with water, but the ionic component imparts an electric charge to the surface of the silica particles in the silica sol and forms an appropriate repulsive force of the silica particles to prevent aggregation of the silica particles. can be done. On the other hand, the presence of a large amount of ionic components also leads to agglomeration of silica particles. It is preferable that the concentrations of cations and anions in these silica sols change little by ultrafiltration. For example, it is preferable to suppress changes in the concentration of cations and anions within 10 times the concentration (mass % concentration) in the silica sol before the concentration step.
Formation of a cake layer can be suppressed by setting the concentrations of these ion components within the above range.
　これら範囲に設定するには、濃縮工程でのシリカゾルの注入又は循環によるプロセス（要件Ｂ）で調整することができる。即ち、循環している濃縮工程中、又は濃縮工程後のシリカゾルにさらにシリカゾルを注入すること（さらに注入されるシリカゾル中に含まれるシリカ粒子の濃度は、濃縮工程前のシリカゾル中に含まれるシリカ粒子の濃度の０．１～３０倍の濃度である。）や、シリカゾルの循環時間を調整することで上記範囲に設定することが可能である。 To set these ranges, it is possible to adjust the process (requirement B) by injecting or circulating silica sol in the concentration process. That is, by further injecting silica sol into the silica sol during the circulating concentration step or after the concentration step (the concentration of silica particles contained in the silica sol to be further injected is the same as that of the silica particles contained in the silica sol before the concentration step The concentration is 0.1 to 30 times the concentration of ), and the above range can be set by adjusting the circulation time of the silica sol.
　上記陽イオンとしては、例えば、１価の陽イオンが挙げられ、粗大粒子の抑制という観点から特にカリウムイオン又はナトリウムイオンが好ましい。 Examples of the above cations include monovalent cations, and potassium ions or sodium ions are particularly preferable from the viewpoint of suppressing coarse particles.
　上記陰イオンとしては、例えば、硫酸イオンを含む陰イオンが挙げられ、粗大粒子の抑制という観点から特に硫酸イオンが好ましい。 Examples of the above anions include anions containing sulfate ions, and sulfate ions are particularly preferable from the viewpoint of suppressing coarse particles.
　本発明では限外ろ過装置で濃縮するシリカゾルとしては、アルコキシド法によるシリカゾルも使用できるが、ケイ酸アルカリ水溶液からアルカリ金属イオンを除去して得られたケイ酸水溶液を加熱して得られたシリカ粒子を含むシリカゾルが好適に使用できる。 In the present invention, silica sol produced by the alkoxide method can also be used as the silica sol to be concentrated by the ultrafiltration device. A silica sol containing can be preferably used.
（活性珪酸の製造）
　原料の水溶性アルカリ金属珪酸塩として、ＪＩＳ３号のナトリウム水ガラスを用意した。この水ガラスの水以外の主な成分は、ＳｉＯ２：２８．８重量％、Ｎａ２Ｏ：９．４７質量％であった。上記水ガラス８３３ｋｇを純水５１６７ｋｇで希釈し、珪酸ナトリウム水溶液（ａ）６０００ｋｇを調製した。次いで、上記珪酸ナトリウム水溶液（ａ）を、水素型強酸性陽イオン交換樹脂アンバーライトＩＲ－１２０Ｂを充填したカラムに１時間当たりの空間速度４．５で通液し、活性珪酸の水溶液５５００ｋｇを回収した。
（シリカゾル薄液の製造) 
　攪拌機と加熱装置が具備されたＳＵＳ製耐圧反応槽に、活性珪酸の水溶液（ＳｉＯ２分として３．２質量％）、１０質量％の水酸化カリウム水溶液、及び純水を仕込んで、ｐＨを１１．１に調整し、反応液温を１１０～１３０℃まで昇温した。反応液温が１１０～１３０℃に達した後、反応液温を１１０～１３０℃に保ったまま、反応液のｐＨが１１．２に達するまで、活性珪酸の水溶液を連続的に供給した。引続き、得られた反応液を１１０～１３０℃に保ちながら２時間加熱を続けた後、室温まで冷却し、シリカゾル（薄液１）を得た。 (Production of activated silicic acid)
JIS No. 3 sodium water glass was prepared as a raw water-soluble alkali metal silicate. The main components of this water glass other than water were SiO 2 : 28.8% by weight and Na 2 O: 9.47% by weight. 833 kg of the above water glass was diluted with 5167 kg of pure water to prepare 6000 kg of sodium silicate aqueous solution (a). Next, the sodium silicate aqueous solution (a) was passed through a column filled with a hydrogen-type strongly acidic cation exchange resin Amberlite IR-120B at a space velocity of 4.5 per hour to recover 5500 kg of an aqueous solution of active silicic acid. did.
(Production of silica sol thin liquid)
An aqueous solution of active silicic acid (3.2% by mass as SiO2 ), a 10% by mass potassium hydroxide aqueous solution, and pure water were charged into a SUS pressure-resistant reactor equipped with a stirrer and a heating device, and the pH was adjusted to 11. .1, and the temperature of the reaction solution was raised to 110-130°C. After the reaction liquid temperature reached 110 to 130°C, an aqueous solution of activated silicic acid was continuously supplied while the reaction liquid temperature was maintained at 110 to 130°C until the pH of the reaction liquid reached 11.2. Subsequently, the obtained reaction liquid was kept at 110 to 130° C. and heated for 2 hours, and then cooled to room temperature to obtain silica sol (thin liquid 1).
（実施例１）
（シリカゾル薄液の濃縮）
　得られたシリカゾル薄液１を、分画分子量１０万のポリスルホン製の管状限外ろ過膜（ＵＦチューブとも称する。内径：１/２インチ）に循環通液し、圧力０．２５ＭＰａ、流量６．９Ｌ／分、液温３０℃で、シリカ濃度４０質量％程度まで濃縮した。
（ＬＰＣ（粗大粒子数）の測定方法）
　ＬＰＣの測定は、サンプルのシリカ濃度を純水で１５．０質量％に希釈し、株式会社ピーエスエスジャパン製ＡｃｃｕＳｉｚｅｒ ＦＸ－ｎａｎｏ（日本インテグリス合同会社製、商品名ＡｃｃｕＳｉｚｅｒ Ａ９０００）にて、ＬＰＣ値を測定した。サンプルのシリカ濃度が１５．０質量％未満の場合は、そのまま測定し、測定値を１５．０質量％に換算した。
　シリカ濃度の測定は、サンプル約１ｇを精秤し、１４０℃のホットプレート上で乾燥させ、１０００℃で０．５時間焼成し、焼成残分から、シリカ濃度を算出した。
（遊離イオン量の測定方法）
　１５．０質量％のＳｉＯ２に希釈したサンプルを密閉容器に入れ、全凍結させ、解凍した後、孔径０．４５ｕｍのクロマトディスクでろ過した。そのろ液中のイオン濃度が検量線の濃度範囲になるように、純水で希釈し、イオンクロマト分析装置にて、陽イオン量と陰イオン量を定量した。 (Example 1)
(Concentration of silica sol thin liquid)
The obtained silica sol thin liquid 1 was circulated through a polysulfone tubular ultrafiltration membrane (also referred to as a UF tube, inner diameter: 1/2 inch) having a molecular weight cutoff of 100,000, under a pressure of 0.25 MPa and a flow rate of 6.0. At 9 L/min and a liquid temperature of 30° C., the solution was concentrated to a silica concentration of about 40% by mass.
(Method for measuring LPC (number of coarse particles))
For LPC measurement, the silica concentration of the sample is diluted with pure water to 15.0% by mass, and the LPC value is measured using AccuSizer FX-nano manufactured by PSS Japan Co., Ltd. (trade name AccuSizer A9000, manufactured by Nihon Entegris LLC). It was measured. When the silica concentration of the sample was less than 15.0% by mass, it was measured as it was, and the measured value was converted to 15.0% by mass.
About 1 g of a sample was precisely weighed, dried on a hot plate at 140° C., fired at 1000° C. for 0.5 hours, and the silica concentration was calculated from the fired residue.
(Method for measuring the amount of free ions)
A sample diluted to 15.0% by mass of SiO 2 was placed in a sealed container, completely frozen, thawed, and then filtered through a chromatodisc with a pore size of 0.45 um. The filtrate was diluted with pure water so that the ion concentration in the filtrate fell within the concentration range of the calibration curve, and the amount of cations and anions was quantified using an ion chromatography analyzer.
（実施例２）
　実施例１と同じ操作で得られたシリカゾルを、分画分子量１０万のポリスルホン製の管状限外ろ過膜（内径１/２インチ）に循環通液し、圧力０．１０ＭＰａ、流量８．８Ｌ／分、３０℃で、シリカ濃度４０質量％程度まで濃縮した。 (Example 2)
The silica sol obtained by the same operation as in Example 1 was circulated through a polysulfone tubular ultrafiltration membrane (inner diameter of 1/2 inch) having a molecular weight cut off of 100,000, and the pressure was 0.10 MPa and the flow rate was 8.8 L/ The mixture was concentrated at 30° C. for a minute to a silica concentration of about 40% by mass.
（実施例３）
　実施例１と同じ操作で得られたシリカゾルを、分画分子量１０万のポリスルホン製の管状限外ろ過膜（内径１/２インチ）に循環通液し、圧力０．０５ＭＰａ、流量９．５Ｌ／分、３０℃で、シリカ濃度４０質量％程度まで濃縮した。 (Example 3)
The silica sol obtained by the same operation as in Example 1 was circulated through a polysulfone tubular ultrafiltration membrane (inner diameter of 1/2 inch) having a molecular weight cut off of 100,000, and the pressure was 0.05 MPa and the flow rate was 9.5 L/ The mixture was concentrated at 30° C. for a minute to a silica concentration of about 40% by mass.
（実施例４）
　実施例１と同じ操作で得られたシリカゾルを、分画分子量５０万のポリスルホン製の管状限外ろ過膜（内径１/２インチ）に循環通液し、圧力０．２５ＭＰａ、流量６．９Ｌ／分、３０℃で、シリカ濃度４０質量％程度まで濃縮した。 (Example 4)
The silica sol obtained by the same operation as in Example 1 was circulated through a polysulfone tubular ultrafiltration membrane (inner diameter of 1/2 inch) having a molecular weight cut off of 500,000, and the pressure was 0.25 MPa and the flow rate was 6.9 L/ The mixture was concentrated at 30° C. for a minute to a silica concentration of about 40% by mass.
（実施例５）
　実施例１と同じ操作で得られたシリカゾルを、分画分子量５０万のポリスルホン製の管状限外ろ過膜（内径１/２インチ）に循環通液し、圧力０．１０ＭＰａ、流量８．８Ｌ／分、３０℃で、シリカ濃度４０質量％程度まで濃縮した。 (Example 5)
The silica sol obtained by the same operation as in Example 1 was circulated through a polysulfone tubular ultrafiltration membrane (inner diameter of 1/2 inch) having a molecular weight cut off of 500,000, and the pressure was 0.10 MPa and the flow rate was 8.8 L/ The mixture was concentrated at 30° C. for a minute to a silica concentration of about 40% by mass.
（実施例６）
　実施例１と同じ操作で得られたシリカゾルを、分画分子量５０万のポリスサルホン製の管状限外ろ過膜（内径１/２インチ）に循環通液し、圧力０．０５ＭＰａ、流量９．５Ｌ／分、３０℃で、シリカ濃度４０質量％程度まで濃縮した。 (Example 6)
The silica sol obtained by the same operation as in Example 1 was circulated through a polysulfone tubular ultrafiltration membrane (inside diameter of 1/2 inch) having a cutoff molecular weight of 500,000, and the pressure was 0.05 MPa and the flow rate was 9.5 L/ The mixture was concentrated at 30° C. for a minute to a silica concentration of about 40% by mass.
（実施例７）
　実施例１と同じ操作で得られたシリカゾルを、分画分子量１０万のポリスルホン製の管状限外ろ過膜（内径１/２インチ）に循環通液し、圧力０．０５ＭＰａ、流量９．５Ｌ／分、１５℃で、シリカ濃度４０質量％程度まで濃縮した。 (Example 7)
The silica sol obtained by the same operation as in Example 1 was circulated through a polysulfone tubular ultrafiltration membrane (inner diameter of 1/2 inch) having a molecular weight cut off of 100,000, and the pressure was 0.05 MPa and the flow rate was 9.5 L/ The mixture was concentrated at 15° C. to a silica concentration of about 40% by mass.
　表１は内径１／２インチのＵＦチューブを用いてシリカゾルの濃縮を行い、ＵＦ濃縮後の水洗水の混入（いわゆる水押しによる配管からのシリカゾルの取り出し操作）の有無を記載した。ＵＦ濃縮後の水洗水を使用しないものは（なし）、ＵＦ濃縮後の水洗水を使用したものは（あり）と記載した。
　薄液１はＵＦ濃縮する前のシリカ濃度３．２質量％のシリカゾルであり、実施例１～実施例８及び比較例１～５で得られる下記シリカ濃縮液１～１３の原料である。
　濃縮液１は実施例１で得られたＵＦ濃縮によるシリカ濃度３６．０質量％のシリカゾルである（実施例１）。
　濃縮液２は実施例２で得られたＵＦ濃縮によるシリカ濃度３５．７質量％のシリカゾルである（実施例２）。
　濃縮液３は実施例３で得られたＵＦ濃縮によるシリカ濃度３５．２質量％のシリカゾルである（実施例３）。
　濃縮液４は実施例４で得られたＵＦ濃縮によるシリカ濃度３８．４質量％のシリカゾルである（実施例４）。
　濃縮液５は実施例５で得られたＵＦ濃縮によるシリカ濃度３５．１質量％のシリカゾルである（実施例５）。
　濃縮液６は実施例６で得られたＵＦ濃縮によるシリカ濃度３６．９質量％のシリカゾルである（実施例６）。
　濃縮液７は実施例７で得られたＵＦ濃縮によるシリカ濃度３８．６質量％のシリカゾルである（実施例７）。
　表１中の（－－）は実施されていないことを示した。 Table 1 shows the concentration of silica sol using a UF tube with an inner diameter of 1/2 inch, and the presence or absence of contamination of washing water after UF concentration (so-called operation of removing silica sol from the pipe by pushing water). Those that did not use washing water after UF concentration were indicated as (none), and those that used washing water after UF concentration were indicated as (yes).
Thin liquid 1 is a silica sol having a silica concentration of 3.2% by mass before UF concentration, and is a raw material for the following silica concentrates 1 to 13 obtained in Examples 1 to 8 and Comparative Examples 1 to 5.
Concentrated liquid 1 is a silica sol having a silica concentration of 36.0% by mass by UF concentration obtained in Example 1 (Example 1).
Concentrated liquid 2 is a silica sol having a silica concentration of 35.7% by mass obtained by UF concentration obtained in Example 2 (Example 2).
Concentrated liquid 3 is a silica sol having a silica concentration of 35.2% by mass by UF concentration obtained in Example 3 (Example 3).
Concentrated liquid 4 is the silica sol having a silica concentration of 38.4% by mass by UF concentration obtained in Example 4 (Example 4).
Concentrated liquid 5 is a silica sol having a silica concentration of 35.1% by mass by UF concentration obtained in Example 5 (Example 5).
Concentrated liquid 6 is the silica sol having a silica concentration of 36.9 mass % obtained by UF concentration obtained in Example 6 (Example 6).
Concentrated liquid 7 is the silica sol having a silica concentration of 38.6% by mass by UF concentration obtained in Example 7 (Example 7).
(--) in Table 1 indicates that it was not implemented.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　表２は濃縮されたシリカゾルの物性を示した。ＳｉＯ２濃度（質量％）、陽イオン量（質量％）、陰イオン量（質量％）を示した。表２中のＬＰＣは粒子径０．４８μｍ以上の粗大粒子の数を示した。表２中の（――）は未測定であることを示した。 Table 2 shows the physical properties of the concentrated silica sol. SiO2 concentration (mass %), cation content (mass percent), anion content (mass percent) are indicated. LPC in Table 2 indicates the number of coarse particles having a particle diameter of 0.48 μm or more. (--) in Table 2 indicates unmeasured.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　同一分画分子量と同一圧力で実施例３と実施例７を対比したときに、ＵＦ処理温度が３０℃の実施例３の濃縮液３よりＵＦ処理温度が１５℃の実施例７の濃縮液７においてＬＰＣの数値が低下していることが確認された。
　同一温度と同一分画分子量で実施例１～実施例３、実施例４～実施例６をそれぞれ対比したときに、ＵＦ処理圧力が上昇することでＬＰＣの値も上昇することが確認された。 When comparing Example 3 and Example 7 at the same cutoff molecular weight and the same pressure, the concentrated solution 7 of Example 7 with a UF treatment temperature of 15 ° C. was higher than the concentrated solution 3 of Example 3 with a UF treatment temperature of 30 ° C. It was confirmed that the numerical value of LPC decreased in .
When comparing Examples 1 to 3 and Examples 4 to 6 at the same temperature and the same molecular weight cutoff, it was confirmed that the value of LPC increases as the UF treatment pressure increases.
（実施例８）
　実施例１と同じ操作で得られたシリカゾルを、分画分子量１０万のポリフッ化ビニリデン製の管状限外ろ過膜（内径１インチ）が装着された市販の限外ろ過装置を用いて、圧力０．３ＭＰａ、流速４２０Ｌ／分により、３０℃でＳｉＯ２濃度４０質量％程度まで濃縮した。ＵＦ濃縮後の水洗水の混入（いわゆる水押しによる配管からのシリカゾルの取り出し操作）はなかった。 (Example 8)
Silica sol obtained by the same operation as in Example 1 was filtered using a commercially available ultrafiltration device equipped with a polyvinylidene fluoride tubular ultrafiltration membrane (inner diameter of 1 inch) having a cutoff molecular weight of 100,000. It was concentrated to a SiO 2 concentration of about 40% by weight at 30° C. at 3 MPa and a flow rate of 420 L/min. There was no contamination of washing water after UF concentration (so-called operation of removing silica sol from pipes by pushing water).
（比較例１～比較例５）
　実施例１と同じ操作で得られたシリカゾルを、分画分子量１０万のポリフッ化ビニリデン製の管状限外ろ過膜（内径１インチ）が装着された市販の限外ろ過装置を用いて、圧力０．３ＭＰａ、流速４２０Ｌ／分により、５０～７０℃でＳｉＯ２濃度４０質量％程度まで濃縮した。ＵＦ濃縮後の水洗水の混入（いわゆる水押しによる配管からのシリカゾルの取り出し操作）が行われた場合と、行われない場合を併記した。ＵＦ濃縮後の水洗水の混入が行われる場合とは、ＵＦチューブ内に純水を流し濃縮液を回収する場合であるが、この操作により濃縮液のシリカ濃度が局所的に大きく低下するものである。
濃縮液８は実施例８で得られたＵＦ濃縮によるシリカ濃度３９．０質量％のシリカゾルである（実施例８）。
濃縮液９は比較例１で得られたＵＦ濃縮によるシリカ濃度３６．６質量％のシリカゾルである（比較例１）。
濃縮液１０は比較例２で得られたＵＦ濃縮によるシリカ濃度４３．４質量％のシリカゾルである（比較例２）。
濃縮液１１は比較例３で得られたＵＦ濃縮によるシリカ濃度４０．０質量％のシリカゾルである（比較例３）。
濃縮液１２は比較例４で得られたＵＦ濃縮によるシリカ濃度４０．６質量％のシリカゾルである（比較例４）。
濃縮液１３は比較例５で得られたＵＦ濃縮によるシリカ濃度４４．３質量％のシリカゾルである（比較例５）。
表３中の（－－）は実施されていないことを示した。 (Comparative Examples 1 to 5)
Silica sol obtained by the same operation as in Example 1 was filtered using a commercially available ultrafiltration device equipped with a polyvinylidene fluoride tubular ultrafiltration membrane (inner diameter of 1 inch) having a cutoff molecular weight of 100,000. Concentration was carried out at 50 to 70° C. to a SiO 2 concentration of about 40 mass % at 3 MPa and a flow rate of 420 L/min. The case where the washing water after UF concentration was mixed (the so-called operation of taking out the silica sol from the pipe by pushing water) and the case where it was not were also shown. The case where the washing water after UF concentration is mixed is the case where pure water is flowed into the UF tube and the concentrated solution is collected. This operation locally greatly reduces the silica concentration of the concentrated solution. be.
Concentrated liquid 8 is the silica sol having a silica concentration of 39.0% by mass by UF concentration obtained in Example 8 (Example 8).
Concentrated liquid 9 is the silica sol having a silica concentration of 36.6 mass % obtained by UF concentration obtained in Comparative Example 1 (Comparative Example 1).
Concentrated liquid 10 is the silica sol having a silica concentration of 43.4% by mass by UF concentration obtained in Comparative Example 2 (Comparative Example 2).
Concentrated liquid 11 is the silica sol having a silica concentration of 40.0% by mass by UF concentration obtained in Comparative Example 3 (Comparative Example 3).
Concentrated liquid 12 is silica sol having a silica concentration of 40.6% by mass obtained by UF concentration obtained in Comparative Example 4 (Comparative Example 4).
Concentrated liquid 13 is the silica sol having a silica concentration of 44.3% by mass by UF concentration obtained in Comparative Example 5 (Comparative Example 5).
(--) in Table 3 indicates that it was not implemented.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　表４は濃縮されたシリカゾルの物性を示した。ＳｉＯ２濃度（質量％）、陽イオン量（質量％）、陰イオン量（質量％）を示した。表４中のＬＰＣは粒子径０．４８μｍ以上の粗大粒子の数を示した。
Figure JPOXMLDOC01-appb-T000004
 Table 4 shows the physical properties of the concentrated silica sol. SiO2 concentration (mass %), cation content (mass percent), anion content (mass percent) are indicated. LPC in Table 4 indicates the number of coarse particles having a particle diameter of 0.48 μm or more.
Figure JPOXMLDOC01-appb-T000004
　同一分画分子量と同一圧力とＵＦ後の水洗水混入が行われない場合による対比では、実施例８と比較例１と比較例３の対比により、ＵＦ処理温度の上昇によりＬＰＣの数値も上昇することが確認された。
　同一分画分子量と同一圧力と同一ＵＦ処理温度による対比では、ＵＦ後の水洗水混入が行われない場合とＵＦ後の水洗水混入が行われた場合では、実施例８と比較例５の対比や、比較例１と比較例２の対比、比較例３と比較例４の対比から、ＵＦ後の水洗水混入によりＬＰＣが大きく上昇した。ＵＦ後の水洗水混入とはＵＦチューブ内に純水を流し濃縮液を回収する操作を意味するが、濃縮液のシリカ濃度が局所的に大きく低下するものである。この操作によりＵＦ膜内面のケーキ層がシリカ濃縮液中への脱落し、ＬＰＣが上昇したものと考えられる。
　表１と表２の結果、表３と表４の結果を対比すると、ＵＦチューブの内径を大きくして、圧力を高くした表３と表４においては処理液の流速が表１と表２の結果よりも高く、シリカ粒子の体積層がＵＦ膜上に形成されにくいためＬＰＣの数値が低いと考えられる。
　表１から表４の結果から、ＵＦ処理温度を本発明の範囲に設定することと、ＵＦ後の水洗水混入を行わないこと（即ち、一連のシリカ粒子の濃度を上昇させる操作が限外ろ過装置でシリカゾルを循環させることや限外ろ過装置にさらにシリカゾルを注入すること（さらに注入されるシリカゾルが、濃縮工程前のシリカゾル中に含まれるシリカ粒子の濃度の０．１～３０倍の濃度である。）によって濃縮工程後には該シリカゾル中に含まれるシリカ粒子の濃度が濃縮工程前より上昇していることに関連する。）によってシリカゾルの濃縮工程で発生するＬＰＣ（粗大粒子）の混入を抑制することができた。 In comparison with the same cutoff molecular weight, the same pressure, and no mixing of washing water after UF, by comparison of Example 8 and Comparative Examples 1 and 3, the value of LPC increases as the UF treatment temperature rises. was confirmed.
In comparison with the same cutoff molecular weight, the same pressure, and the same UF treatment temperature, Example 8 and Comparative Example 5 were compared in the case where washing water was not mixed after UF and when washing water was mixed after UF. Also, from the comparison between Comparative Examples 1 and 2 and the comparison between Comparative Examples 3 and 4, the LPC increased significantly due to the mixing of washing water after UF. Mixing of washing water after UF means an operation of pouring pure water into the UF tube and recovering the concentrate, but the concentration of silica in the concentrate is greatly reduced locally. It is believed that this operation caused the cake layer on the inner surface of the UF membrane to fall off into the silica concentrate, resulting in an increase in LPC.
Comparing the results in Tables 1 and 2 with the results in Tables 3 and 4, it can be seen that in Tables 3 and 4, in which the inner diameter of the UF tube is increased and the pressure is increased, the flow rate of the treatment liquid is the same as in Tables 1 and 2. It is considered that the LPC value is low because it is difficult to form a layer of silica particles on the UF membrane.
From the results in Tables 1 to 4, setting the UF treatment temperature within the range of the present invention and not mixing water for washing after UF (that is, the operation of increasing the concentration of a series of silica particles is the only way to perform ultrafiltration). Circulating the silica sol in the device or injecting silica sol further into the ultrafiltration device (the silica sol to be further injected has a concentration of 0.1 to 30 times the concentration of silica particles contained in the silica sol before the concentration step ) is related to the fact that the concentration of silica particles contained in the silica sol after the concentration step is higher than before the concentration step.) Suppresses the contamination of LPC (coarse particles) generated in the silica sol concentration step. We were able to.
　本発明のシリカゾルの濃縮方法では、限外ろ過によりシリカゾル中のシリカ成分の濃度を高める濃縮を行う際に、濃縮されたシリカゾル中に凝集したシリカ粒子が形成されることを防ぐことができる。したがって、例えば半導体用シリコンウエハーやデバイスの研磨に用いられるシリカゾルを製造する上で、前記方法は、ＬＰＣ（粗大粒子）の該シリカゾル中への混入を抑制できるため有用である。
  In the silica sol concentration method of the present invention, it is possible to prevent the formation of agglomerated silica particles in the concentrated silica sol when concentration is performed to increase the concentration of silica components in the silica sol by ultrafiltration. Therefore, the method is useful for producing silica sol used for polishing silicon wafers for semiconductors and devices, for example, because it can suppress inclusion of LPC (coarse particles) into the silica sol.

Claims (7)

  1. 　分散質粒子としてシリカ粒子を分散媒に分散したゾル（シリカゾル）の濃縮方法であって、該シリカゾル中に含まれるシリカ粒子の濃度を限外ろ過装置により上昇させる濃縮工程を含み、該濃縮工程において下記要件Ａ及び要件Ｂが満たされることを特徴とする、シリカゾルの濃縮方法。
    要件Ａ：限外ろ過装置に注入する直前のシリカゾルの液温が０乃至４５℃の範囲であること。
    要件Ｂ：限外ろ過装置でシリカゾルを循環させることによって、濃縮工程後には該シリカゾル中に含まれるシリカ粒子の濃度が濃縮工程前より上昇していること。     A method for concentrating a sol (silica sol) in which silica particles are dispersed in a dispersion medium as dispersoid particles, comprising a concentration step of increasing the concentration of silica particles contained in the silica sol by an ultrafiltration device, wherein A method for concentrating a silica sol, characterized in that the following requirement A and requirement B are satisfied.
    Requirement A: The liquid temperature of the silica sol immediately before being injected into the ultrafiltration device must be in the range of 0 to 45°C.
    Requirement B: By circulating the silica sol through the ultrafiltration device, the concentration of silica particles contained in the silica sol after the concentration step should be higher than before the concentration step.
  2. 　前記要件Ｂにおいて、限外ろ過装置でシリカゾルを循環させる濃縮工程中に、限外ろ過装置にシリカゾルをさらに注入することを含み、さらに注入されるシリカゾルが、濃縮工程前のシリカゾル中に含まれるシリカ粒子の濃度の０．１～３０倍の濃度であることを特徴とする、請求項１に記載のシリカゾルの濃縮方法。 Requirement B includes further injecting silica sol into the ultrafiltration device during the concentration step of circulating the silica sol in the ultrafiltration device, and the injected silica sol is silica contained in the silica sol before the concentration step. 2. The method for concentrating silica sol according to claim 1, wherein the concentration is 0.1 to 30 times the concentration of the particles.
  3. 　前記要件Ａにおいて、限外ろ過装置に注入する直前のシリカゾルの液温が、０乃至３０℃の範囲に調整されていることを特徴とする、請求項１又は請求項２に記載のシリカゾルの濃縮方法。 3. The concentration of silica sol according to claim 1 or 2, wherein in the requirement A, the liquid temperature of the silica sol immediately before being injected into the ultrafiltration device is adjusted to a range of 0 to 30 ° C. Method.
  4. 　前記要件Ｂにおいて、限外ろ過装置に濃縮工程前のシリカゾルと同じ濃度のシリカゾルをさらに注入すること、又は限外ろ過装置で濃縮工程前のシリカゾルより高い濃度のシリカゾルを循環させることによって、濃縮工程後には該シリカゾル中に含まれるシリカ粒子の濃度が濃縮工程前より上昇していることを特徴とする、請求項２に記載のシリカゾルの濃縮方法。 In the requirement B, the concentration step is performed by further injecting silica sol having the same concentration as the silica sol before the concentration step into the ultrafiltration device, or by circulating silica sol with a higher concentration than the silica sol before the concentration step in the ultrafiltration device. 3. The method for concentrating a silica sol according to claim 2, wherein the concentration of silica particles contained in the silica sol afterward is higher than before the concentration step.
  5. 　前記要件Ｂにおいて、濃縮されたシリカゾルは濃縮工程後に限外ろ過装置から直接配管を通じて、シリカ粒子の濃度の低下が５質量％以内となる条件で濃縮シリカゾル充填容器に充填されることを特徴とする、請求項１乃至請求項４の何れか１項に記載のシリカゾルの濃縮方法。 In Requirement B, the concentrated silica sol is filled into the concentrated silica sol filling container through a pipe directly from the ultrafiltration device after the concentration step under the condition that the concentration of silica particles decreases within 5% by mass. The method for concentrating silica sol according to any one of claims 1 to 4.
  6. 　前記要件Ｂにおいて、濃縮工程後のシリカ粒子の濃度が濃縮工程前のシリカ粒子の濃度に対して濃度比２乃至３０の範囲で濃縮工程が行われることを特徴とする、請求項１乃至請求項５の何れか１項に記載のシリカゾルの濃縮方法。 Claims 1 to 30, wherein in the requirement B, the concentration of silica particles after the concentration step is performed in a concentration ratio range of 2 to 30 with respect to the concentration of silica particles before the concentration step. 6. The method for concentrating silica sol according to any one of 5.
  7. 　限外ろ過装置に注入する前のシリカゾルが、ケイ酸アルカリ水溶液からアルカリ金属イオンを除去して得られたケイ酸水溶液を加熱して得られたシリカ粒子を含むシリカゾルであることを特徴とする、請求項１乃至請求項６の何れか１項に記載のシリカゾルの濃縮方法。 The silica sol before being injected into the ultrafiltration device is a silica sol containing silica particles obtained by heating an aqueous silicic acid solution obtained by removing alkali metal ions from an aqueous alkali silicate solution. The method for concentrating silica sol according to any one of claims 1 to 6.
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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0648719A (en) * 1992-05-15 1994-02-22 Bayer Ag Method for production and concentration of silica sol
JP2002075929A (en) * 2000-08-24 2002-03-15 Nippon Chem Ind Co Ltd Method for regenerating polishing spent liquid
WO2014188934A1 (en) * 2013-05-20 2014-11-27 日産化学工業株式会社 Silica sol and silica-containing epoxy resin composition
JP2017071527A (en) * 2015-10-06 2017-04-13 日揮触媒化成株式会社 Method for producing silica using geothermal brine
JP2018524256A (en) * 2015-06-19 2018-08-30 ジーイーオーフォーティー リミテッド Method for producing silica concentrate

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0648719A (en) * 1992-05-15 1994-02-22 Bayer Ag Method for production and concentration of silica sol
JP2002075929A (en) * 2000-08-24 2002-03-15 Nippon Chem Ind Co Ltd Method for regenerating polishing spent liquid
WO2014188934A1 (en) * 2013-05-20 2014-11-27 日産化学工業株式会社 Silica sol and silica-containing epoxy resin composition
JP2018524256A (en) * 2015-06-19 2018-08-30 ジーイーオーフォーティー リミテッド Method for producing silica concentrate
JP2017071527A (en) * 2015-10-06 2017-04-13 日揮触媒化成株式会社 Method for producing silica using geothermal brine

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