JP5862886B2 - Method for producing organic solvent-dispersed silica sol - Google Patents

Description

  The present invention relates to a method for producing an organic solvent-dispersed silica sol in which silica particles are dispersed in an organic solvent.

  Organic solvent-dispersed silica sol, in which colloidal silica particles of 1000 nm or less, for example, are dispersed in an organic solvent, is added to resins, resin raw materials, and binders, and is used for coating and nanocomposite applications. It is widely used as a nanofiller that can improve its strength, hardness, heat resistance, insulation, and other properties. Such an organic solvent-dispersed silica sol is produced by first preparing an aqueous silica sol using water or an aqueous solvent containing water as a dispersion medium, and then replacing the dispersion medium of the aqueous silica sol with an organic solvent (patent) Literature 1 etc.). This method of solvent replacement takes time, and when replacing with a low boiling organic solvent, it is necessary to use a large amount of organic solvent for dehydration. Moreover, when replacing with a water-insoluble organic solvent, it is necessary to perform the replacement via a water-soluble solvent-dispersed sol, which is a laborious process. Therefore, the method for obtaining the organic solvent-dispersed silica sol by solvent replacement of the aqueous silica sol is time-consuming, and since a large amount of the organic solvent is used, the organic solvent-dispersed silica sol cannot be obtained at a low cost.

  Here, if a colloidal silica powder can be directly dispersed in an organic solvent, an organic solvent-dispersed silica sol can be obtained easily and inexpensively without using a large amount of organic solvent. Form aggregates, and some mechanical pulverization is required.

  When silica particles obtained by a vapor phase method in which silicon chloride is decomposed in gas are used as silica powder, it can be dispersed in a solvent by pulverization under relatively mild conditions such as an ultrasonic disperser. Since the viscosity is likely to increase during pulverization, it is difficult to disperse in an organic solvent at a high concentration, and it is difficult to obtain an organic solvent-dispersed silica sol containing high concentration silica particles.

  Therefore, in order to obtain an organic solvent-dispersed silica sol containing high-concentration silica particles, silica particles obtained by a precipitation method in which water glass (sodium silicate) is neutralized and precipitated are used as the silica particles. Silica particles easily settle in an organic solvent. Therefore, in order to disperse the silica particles obtained by the precipitation method in an organic solvent without being precipitated, it is desirable to use a pulverizer that pulverizes with high energy, such as pulverization using a pulverization medium. When pulverizing using, etc., the viscosity increases during pulverization, which makes it difficult to pulverize. In addition, when the organic solvent-dispersed silica sol obtained is allowed to stand, the silica particles aggregate to increase the viscosity, resulting in a problem of poor storage stability.

  A dispersion in which wet silica is dispersed in a polar solvent, the silica concentration in the dispersion is 22% by weight or more, and the average particle size of the silica particles is less than 0.5 μm, and the dispersion A wet silica dispersion having a pH of 3 to 5 is disclosed (see Patent Document 2). However, since Patent Document 2 regulates pH, it is a technique for silica sol using water as a solvent instead of an organic solvent, and does not disperse silica in an organic solvent. Also, treatment of precipitated silica or precipitated silica suspension comprising mixing or adding carboxylic acid to the filter cake produced from the silica precipitation reaction before or during the crushing process of the filter cake. A method is disclosed (see Patent Document 3). However, since the filter cake generated from the silica precipitation reaction is a lump of silica particles containing a large amount of water, Patent Document 3 is also a technique for silica sol using water as a solvent, and does not disperse silica particles in an organic solvent.

JP-A-9-208213 JP 2004-331479 A Special table 2008-542163 gazette

  An object of the present invention is to solve the above-mentioned problems of the prior art, and an organic solvent-dispersed silica sol having excellent storage stability can be obtained by a simple and inexpensive method in which an increase in viscosity during pulverization of silica particles is suppressed. An object of the present invention is to provide a method for producing an organic solvent-dispersed silica sol that can be produced.

  The method for producing an organic solvent-dispersed silica sol of the present invention that solves the above problems is characterized in that the raw material silica particles obtained by the precipitation method are pulverized in an organic solvent in the presence of a polyvalent carboxylic acid.

  In addition, it is preferable that the raw material silica particles obtained by the precipitation method are pulverized in an organic solvent in the presence of a polyvalent carboxylic acid, and then the metal salt of the polyvalent carboxylic acid generated by the pulverization is removed.

  And it is preferable that the said organic solvent is alcohol.

  Moreover, it is preferable to add an organosilicon compound.

  According to the present invention, the raw material silica particles obtained by the precipitation method are pulverized in the presence of polyvalent carboxylic acid in an organic solvent, whereby the organic solvent-dispersed silica sol in which the silica particles are dispersed in the organic solvent is pulverized. The increase in viscosity at the time is suppressed, and it can be produced by a simple and inexpensive method. The obtained organic solvent-dispersed silica sol has excellent storage stability.

  In the method for producing an organic solvent-dispersed silica sol of the present invention, the raw material silica particles obtained by the precipitation method are pulverized in an organic solvent in the presence of a polyvalent carboxylic acid.

  The raw material silica particles are silica particles obtained by a precipitation method, that is, silica particles obtained by a precipitation method in which water glass (sodium silicate) is neutralized with an acid or the like to precipitate silica particles. Here, the raw material silica particles to be pulverized in the present invention is not a filter cake that is a lump containing water as in Patent Document 3, but a dry powder, and therefore contains substantially no water. It is. Commercially available raw silica particles obtained by the precipitation method include SIPONAT, CARPLEX, manufactured by EVONIC, Tokusil manufactured by Tokuyama, Fine Seal, nip seal manufactured by Tosoh Silica, Hi-Sil manufactured by PPG, and the like. Moreover, in order to improve the affinity with the organic solvent, the surface of the silica particles obtained by the precipitation method contains an organic group such as methyl group, octyl group, methacryl group, phenyl group, amino group and silicon. Silica particles introduced with a silicon organic group and having a parent organic group may be used as raw material silica particles.

The particle diameter and specific surface area of the raw silica particles are not limited. For example, the specific surface area measured by a nitrogen adsorption method or Sears titration method (Anal. Chem. Vol. 28, No. 12, 1956) is 30 to 500 m ² / g. It is preferable that

  Alcohol is mentioned as an organic solvent. Specific examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol, 1-pentanol, 1-hexanol, 1-octanol, 2- Ethyl-1-hexanol, allyl alcohol, benzyl alcohol, cyclohexanol, 1,2-ethanediol, 1,2-propanediol, 2-methoxyethanol, 2-ethoxyethanol, 2-propoxyethanol, 2- (methoxyethoxy) Examples include ethanol, 1-methoxy-2-propanol, dipropylene glycol monomethyl ether, diacetone alcohol, ethyl carbitol, and butyl carbitol. One organic solvent may be used, or two or more organic solvents may be mixed and used.

  The polyvalent carboxylic acid is a carboxylic acid having two or more carboxyl groups in the molecule. The polyvalent carboxylic acid preferably has a first dissociation constant pKa of 3.5 or less, more preferably a first dissociation constant pKa of 3.0 or less. Specific examples of the polyvalent carboxylic acid include oxalic acid, tartaric acid, citric acid, oxaloacetic acid, phthalic acid, maleic acid, malonic acid, malic acid, and the like. One type of polyvalent carboxylic acid may be used, but two or more types may be present together. In addition, it is preferable to select a polyvalent carboxylic acid that is soluble in the organic solvent to be used.

  The ratio in which the polyvalent carboxylic acid is allowed to coexist in the organic solvent is not particularly limited. For example, it is preferably about 0.2 to 10% by mass, more preferably 0.5 to 5% by mass based on the solid content of the raw material silica particles. Preferably it is 1.0-5 mass%.

  Moreover, the ratio in which the polyvalent carboxylic acid is allowed to coexist in the organic solvent can also be controlled by the pH of the mixed solution prepared by mixing water having the same mass as the organic solvent-dispersed silica sol obtained by the production method of the present invention. Specifically, the mixed solution prepared by mixing the organic solvent-dispersed silica sol obtained by the production method of the present invention with the same mass of water has a polyvalent amount in the range of pH in the range of 2.0 to 5.0. It is preferable to coexist carboxylic acid. Here, in the method for producing the organic solvent-dispersed silica sol of the present invention, silica particles, that is, powdered silica is used, and there is no step of adding water, and water is not contained as a dispersion medium. The resulting organic solvent-dispersed silica sol is substantially free of water. Specifically, even if the organic solvent-dispersed silica sol obtained by the production method of the present invention contains water, it is only derived from water in the atmosphere on which silica particles are adsorbed. It is as follows. Therefore, the pH of the organic solvent-dispersed silica sol obtained by the production method of the present invention cannot be measured. Therefore, as described above, the pH of the mixed solution prepared by mixing the same mass of water or the like is obtained. In addition, the pH obtained by mixing the same mass of water or the like with the organic solvent-dispersed silica sol obtained by the production method of the present invention is naturally not the pH of the organic solvent-dispersed silica sol itself obtained by the production method of the present invention. .

  In the present invention, the raw material silica particles are pulverized in an organic solvent in the presence of such a polyvalent carboxylic acid. Specifically, after the polyvalent carboxylic acid is allowed to coexist in the organic solvent, that is, after the polyvalent carboxylic acid is added to the organic solvent, the raw material silica particles are pulverized. The raw material silica particles may be added to the organic solvent simultaneously with the polyvalent carboxylic acid, or the raw material silica particles and the polyvalent carboxylic acid may be added to the organic solvent in this order. Further, since the polyvalent carboxylic acid only needs to coexist during the pulverization of the raw material silica particles in the organic solvent, it is added during the pulverization, that is, the raw material silica particles are pulverized to some extent to form a slurry state. After that, polyvalent carboxylic acid may be added, and then the silica particles may be further pulverized.

  The method for pulverizing the raw silica particles is not particularly limited, but it is preferable to use a pulverizer that pulverizes with high energy, for example, a pulverizer using a pulverization medium such as a bead mill. Common grinding media can be used, and examples thereof include quartz glass beads, soda lime glass beads, low soda glass beads, zirconia beads, and alumina beads. Of these, silica-based glass beads are particularly preferable.

  In addition, the pulverization may be a batch type in which an organic solvent, polyvalent carboxylic acid, raw material silica particles, and if necessary, pulverization media are put into a container (pulverizer) and pulverized by rotating or the like, or continuous pulverization. If necessary, put grinding media into the machine and pass or circulate the silica slurry containing organic solvent, polyvalent carboxylic acid, raw silica particles, or continuous grinding machine, if necessary. Alternatively, the raw material silica particles may be added while the organic solvent and the polyvalent carboxylic acid are passed through, and the slurry formed of the organic solvent, the polyvalent carboxylic acid and the silica particles may be passed through or circulated.

  By coexisting polyvalent carboxylic acid during pulverization in this way, even if the raw silica particles obtained by the precipitation method are pulverized in an organic solvent, the increase in viscosity is suppressed, so the pulverization efficiency can be improved. An organic solvent-dispersed silica sol can be easily produced. For example, it is possible to suppress the increase in viscosity during pulverization to some extent by adding raw material silica particles over time, but in the present invention, the increase in viscosity is suppressed. Therefore, it is not necessary to add the raw material silica particles over time little by little. For example, the raw material silica particles can be pulverized even if the raw silica particles are added at once or the addition speed of the raw silica particles is increased, High grinding efficiency. The method for producing the organic solvent-dispersed silica sol of the present invention is a method in which silica powder is directly dispersed in an organic solvent by pulverizing the silica powder in an organic solvent without passing through a solvent containing water. The organic solvent-dispersed silica sol can be produced easily and inexpensively. Furthermore, the obtained organic solvent-dispersed silica sol has excellent storage stability. Therefore, the aggregation of silica particles can be suppressed even when left for a long time after production. The storage stability of the organic solvent-dispersed silica sol is confirmed by a method of confirming a change in physical property value by standing at room temperature for 3 to 12 months, or by confirming a physical property value after warming to about 50 ° C. and allowing to stand for about 1 month. It can be confirmed by a method of performing a heating acceleration test. In addition, since sol products composed of nanoparticles may be handled at room temperature or higher during transportation or storage, it is required to have storage stability that does not substantially change the physical property value even after a heating acceleration test. It has been. Further, since this organic solvent-dispersed silica sol has few aggregated particles, it becomes a filler such as a resin film excellent in transparency and a coating agent.

  In addition, when monovalent carboxylic acid or mineral acid is used instead of polyvalent carboxylic acid, as shown in a comparative example described later, an increase in viscosity at the time of pulverization of raw material silica particles is suppressed, and the resulting organic The effect of the present invention that the solvent-dispersed silica sol is excellent in storage stability cannot be exhibited.

  Thus, when the raw material silica particles obtained by the precipitation method are pulverized in an organic solvent coexisting with a polyvalent carboxylic acid, an increase in viscosity during pulverization of the raw silica particles is suppressed, and the obtained organic solvent-dispersed silica sol The reason why is excellent in storage stability is unknown in detail, but is presumed as follows. When metal ions (for example, Na, Ca, Zr, Al, etc.) are generated from the pulverization media or the pulverization container due to collisions between the pulverization media, silica particles, or the pulverization container, which occur during pulverization, the generated metal ions are nuclei. As a result, the silica particles are aggregated to increase the viscosity. In particular, in the pulverization of silica particles in an organic solvent, an increase in viscosity is more likely to occur than in the pulverization of silica particles in water. However, in the present invention, the metal ions generated by this pulverization are combined with the coexisting polyvalent carboxylic acid to form a polyvalent carboxylic acid metal salt. And since this metal salt of polyvalent carboxylic acid has low solubility in an organic solvent, it precipitates as a salt and does not become a nucleus of aggregation of silica particles. Therefore, in the present invention, an increase in viscosity during pulverization of silica particles is suppressed. In addition, the metal ion which can become a nucleus of aggregation of a silica particle arises also from the raw material silica particle obtained by the sedimentation method.

  Here, if a pulverizer that pulverizes with high energy, such as a high-speed rotating bead mill, is used as a pulverizer for pulverizing the raw material silica particles, the pulverization efficiency is better than that of a mild type pulverizer such as a ball mill. The increase in viscosity is particularly likely to occur due to the large amount of metal ions from the grinding media and the grinding vessel that are generated by collisions between the grinding media and the silica particles and the grinding vessel. In addition, bead mills, which are continuous grinders, often use a centrifugal separator to separate slurry and beads, so they are more susceptible to increased viscosity compared to batch grinders, and even with a small increase in viscosity. Separation cannot be performed and operation cannot be continued. In the present invention, not only a batch type pulverizer but also a continuous pulverizer such as a bead mill can be used to suitably suppress an increase in viscosity, and pulverization is easy.

  The organic solvent-dispersed silica sol obtained by the production method of the present invention is a silica particle dispersion in a sol state in which pulverized silica particles are dispersed in an organic solvent. And it contains the pulverized silica particles, polyvalent carboxylic acid, organic solvent, and metal salt of polyvalent carboxylic acid generated by pulverization.

  Moreover, the particle diameter of the pulverized silica particles contained in the organic solvent-dispersed silica sol produced by the production method of the present invention is, for example, a dispersed particle diameter (light intensity average diameter) by a dynamic light scattering method of 10 to 250 nm. can do.

  Further, in the production method of the present invention, since an increase in viscosity during pulverization is suppressed, high-concentration raw material silica particles can be added to the pulverizer, and the solid content concentration of the obtained organic solvent-dispersed silica sol (ie, silica particles) The concentration can be as high as 5 to 50% by mass.

  Moreover, it is preferable to remove part or all of the metal salt of the polyvalent carboxylic acid generated and precipitated by pulverization after the pulverization step. In addition, after the pulverization step and after standing, the metal salt of the polyvalent carboxylic acid may be removed.

  Examples of the method for removing the metal salt of the polyvalent carboxylic acid include filtration, centrifugation, and a method of allowing the metal salt of the polyvalent carboxylic acid to settle and allowing the decantation to be performed.

  Furthermore, you may have the process of adding an organosilicon compound. By adding the organosilicon compound, the affinity between the silica particles of the obtained organic solvent-dispersed silica sol and the resin can be improved. By improving the affinity between the silica particles and the resin, the transparency of the coating agent obtained by mixing the organic solvent-dispersed silica sol with the resin can be increased.

  Examples of such organosilicon compounds include methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, trimethylethoxysilane, trimethylpropoxysilane, phenyldimethylmethoxysilane, chloropropyldimethylmethoxysilane, phenyltrimethoxysilane, methyltrimethoxysilane. Ethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, decyltrimethoxysilane, trifluoropropyltrimethoxysilane, vinyl Trimethoxysilane, vinyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxy Lopyltrimethoxysilane, 3-glycidoxypropylmethylditriethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxy Silane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2 -(Aminoethyl) -3-aminopropylmethyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane Lan, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, 3-chloropropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, Alkoxysilanes such as 3-mercaptopropyltrimethoxysilane, bis (triethoxysilylpropyl) tetrasulfide, 3-isocyanatopropyltriethoxysilane, hexamethyldisiloxane, 1,3-dibutyltetramethyldisiloxane, 1,3- Examples include diphenyltetramethyldisiloxane, 1,3-divinyltetramethyldisiloxane, hexaethyldisiloxane, and 3-glycidoxypropylpentamethyldisiloxane. When such an organosilicon compound is added, for example, the content may be about 1 to 20% by mass with respect to the solid content of the silica particles contained in the obtained organic solvent-dispersed silica sol.

  The organic solvent-dispersed silica sol of the present invention may contain various surfactants, silane coupling agents, alkoxysilanes, and the like.

  In addition, the addition time of other additives, such as an organosilicon compound, is not specifically limited, It can add before a grinding | pulverization or in the middle of a grinding | pulverization.

  The organic solvent-dispersed silica sol obtained by the production method of the present invention can be used, for example, for coating or nanocomposite by adding it to a resin, a resin raw material, or a binder.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to the examples.
[Example 1]
In a plastic container having a capacity of 500 ml and a diameter of 70 mm, 41.3 g of silica powder a obtained by the precipitation method described in Table 1 as raw silica particles, 2-propanol (hereinafter also referred to as IPA) (reagent grade 1) 148. 1 g, L (+)-tartaric acid (reagent special grade) 0.80 g, 180 g of soda lime glass beads having a diameter of 1 to 1.5 mm as grinding media, and grinding for 72 hours at 130 rpm, the beads are filtered and dispersed in IPA A silica sol (organic solvent-dispersed silica sol) was obtained. The physical properties of the silica powder used are shown in Table 1, and the blending ratio of silica sol is shown in Table 2-1.

In Table 1, the solid content was determined by baking silica powder at 800 ° C. for 30 minutes. The specific surface area was determined by the Sears titration method described below. First, 1.50 g of silica powder as a solid content was collected in a 200 ml beaker, about 100 ml of pure water was added to form a slurry, and then 30 g of NaCl was added and dissolved. Next, 1N-HCl was added to adjust the pH of the slurry to about 3, and then pure water was added until the slurry became 150 ml. The slurry was subjected to pH titration with 0.1N NaOH at 25 ° C., and the volume V (ml) of the 0.1N NaOH solution necessary for raising the pH from 4.00 to 9.00 was measured. The specific surface area was determined by the following Sears formula (1).
Specific surface area (m ² / g) = 32 × V (ml) −25 (1)

  The average particle diameter of the silica powder was the median diameter measured with a laser diffraction particle size distribution analyzer SALD-7000 manufactured by Shimadzu Corporation. The dispersion medium was determined using pure water, and the refractive index of the particles was determined using 1.45-0.10i. The pH of the silica powder was measured for a slurry prepared by adding 9.0 times pure water to the silica powder on a mass basis.

  The obtained IPA-dispersed silica sol had a solid content of 20.0% obtained by baking at 800 ° C. for 30 minutes, a moisture content of 1.6% by Karl Fischer titration, and a viscosity at 20 ° C. measured by a B-type viscometer of 13 The dispersion particle diameter (light intensity average diameter) by dynamic light scattering method was 187 nm. In addition, the dispersed particle diameter by the dynamic light scattering method is an average particle diameter (Z-Average) measured by Zetasizer Nano manufactured by Malvern Instruments after diluting silica sol 100 times on a volume basis with the same solvent as the dispersion medium. Further, when a solution prepared by adding water to the obtained IPA-dispersed silica sol so that the mass ratio was IPA-dispersed silica sol: water = 1: 1 was measured with a pH meter, the pH was 3.5. .

  In order to confirm the storage stability of the IPA-dispersed silica sol, a heating acceleration test was performed in which the IPA-dispersed silica sol was sealed in a glass bottle and allowed to stand at 50 ° C. for 28 days. As a result, the IPA-dispersed silica sol after standing at 50 ° C. for 28 days showed no sedimentation, increased viscosity, or increased dispersed particle size. Table 2-1 shows the viscosity and dispersed particle size of the IPA-dispersed silica sol after standing at 50 ° C. for 28 days.

[Examples 2 to 5]
The same operation as in Example 1 was performed except that the types (Table 1) and blending ratios of silica powder, the types and blending ratios of polyvalent carboxylic acids, and the blending ratios of organic solvents were as shown in Table 2-1. Thus, an organic solvent-dispersed silica sol was obtained, and physical properties were measured and a heating acceleration test was performed.

[Comparative Examples 1-2]
The same operation as in Example 1 was performed except that the polyvalent carboxylic acid was not added, and the type and blending ratio of the silica powder and the blending ratio of the organic solvent were as shown in Table 2-2. A solvent-dispersed silica sol was obtained, and physical properties were measured and a heating acceleration test was performed. The results are shown in Table 2-2.

[Comparative Example 3]
Example 1 except that 1.5 g of 10% nitric acid was added instead of the polyvalent carboxylic acid, and the type and blending ratio of the silica powder and the blending ratio of the organic solvent were as shown in Table 2-2. The same operation was performed to obtain an organic solvent-dispersed silica sol, and physical properties were measured and a heating acceleration test was performed. The results are shown in Table 2-2.

[Comparative Example 4]
As in Example 1, except that 0.61 g of glycolic acid was added instead of the polyvalent carboxylic acid, and the kind and blending ratio of silica powder and blending ratio of the organic solvent were as shown in Table 2-2. Thus, an organic solvent-dispersed silica sol was obtained, and physical properties were measured and a heating acceleration test was performed. The results are shown in Table 2-2.

Example 6
A bead mill with a slurry tank (Apex Mill 015 manufactured by Kotobuki Industries Co., Ltd., 150 ml capacity) is filled with 100 ml of 0.2 mm soda lime beads, and a solution of 8.4 g of tartaric acid dissolved in 1545 g of 2-propanol is prepared. While circulating the crusher (bead mill) at a peripheral speed of 6 m / s, 445 g of silica powder b was added little by little over 15 minutes. After completion of the addition, the peripheral speed was increased to 8 m / s, and circulation pulverization was performed for 8 hours to obtain the IPA-dispersed silica sol of Example 6-1. 800 g of the IPA-dispersed silica sol of Example 6-1 was transferred to a transparent 1 L plastic container and allowed to stand at room temperature (23 ° C.) for 7 days. After standing, a small amount of white precipitate was formed at the bottom of the container. The upper sol was recovered by decantation, that is, the precipitate generated by standing the IPA-dispersed silica sol of Example 6-1 was removed. The recovered sol weighed 795 g, and was used as the IPA-dispersed silica sol of Example 6-2.

  With respect to the IPA-dispersed silica sol of Example 6-1 and the IPA-dispersed silica sol of Example 6-2, physical property measurements and warming acceleration tests were performed in the same manner as in Example 1, respectively. The results are shown in Table 2-1.

  Further, 10 g of IPA was added to the remainder of the sol collected by decantation, that is, a plastic container having a white precipitate, and 15 g of the white precipitate was recovered as a slurry. This white precipitate slurry contains silica sol remaining inside the plastic container. About this white precipitate slurry, the recovered amount (mass), solid content, anion and metal impurities were determined. Moreover, about the IPA dispersion | distribution silica sol of Example 6-2, the collection amount, solid content, an anion, and the metal impurity were calculated | required. The solid content was obtained by baking a white precipitate slurry or the IPA-dispersed silica sol of Example 6-2 at 800 ° C. for 30 minutes, and the anions and metal impurities were mass% based on the solid content. The results are shown in Table 3.

Example 7
A bead mill with the same slurry tank as in Example 6 was filled with 100 ml of 0.2 mm diameter soda lime beads, and a solution of 8.4 g of tartaric acid dissolved in 1528 g of 2-propanol was charged. While circulating at / s, 443 g of silica powder b was added in small portions over 15 minutes, followed by 20 g of methyltrimethoxysilane. After completion of the addition, the peripheral speed was increased to 8 m / s, and cyclic grinding was performed for 8 hours. The obtained sol was allowed to stand at room temperature for 7 days, and the generated trace amount of precipitate was removed by decantation to obtain an IPA-dispersed silica sol (organic solvent-dispersed silica sol).

  The obtained IPA-dispersed silica sol was measured in the same manner as in Example 1. As a result, the solid content was 20.0%, the moisture was 1.6%, the viscosity was 11.7 mPa · s, the pH was 3.6, and the dispersed particle size was 155 nm. there were. In addition, the IPA-dispersed silica sol after the IPA-dispersed silica sol was sealed in a glass bottle did not show sedimentation, increased viscosity, or increased dispersed particle size. Table 2-1 shows the viscosity and dispersed particle size of the IPA-dispersed silica sol after standing at 50 ° C. for 28 days.

[Comparative Example 5]
The same bead mill with slurry tank as in Example 6 was filled with 100 ml of 0.2 mm soda lime beads, charged with 1553 g of 2-propanol, and the pulverizer (bead mill) was circulated at a peripheral speed of 6 m / s, while silica. 445 g of powder b was added in small portions over 20 minutes. After the addition was completed, the peripheral speed was increased to 8 m / s and circulation pulverization was started. After a few minutes, the viscosity increased remarkably and the liquid could not be fed, so the operation was stopped.

[Comparative Example 6]
The same bead mill with slurry tank as in Example 6 was filled with 100 ml of 0.2 mm soda lime beads, charged with 1536 g of 2-propanol, and the pulverizer (bead mill) was circulated at a peripheral speed of 6 m / s, while silica. 443 g of powder b was added in small portions over 45 minutes. Subsequently, 20 g of methyltrimethoxysilane was added. After completion of the addition, the peripheral speed was increased to 8 m / s and circulation pulverization was performed for 15 hours to obtain an IPA-dispersed silica sol (organic solvent-dispersed silica sol). The obtained IPA-dispersed silica sol was measured by the same method as in Example 1. The solid content was 20.0%, the moisture was 1.6%, the viscosity was 20.0 mPa · s, the pH was 7.1, and the dispersed particle size was 160 nm. It was. When this IPA-dispersed silica sol was sealed in a glass bottle and allowed to stand at 50 ° C., the viscosity increased and gelled after 2 weeks.

Example 8
A bead mill with the same slurry tank as in Example 6 was filled with 100 ml of 0.2 mm diameter soda lime beads, and a solution of 8.4 g of tartaric acid dissolved in 1520 g of 1-methoxy-2-propanol (hereinafter also referred to as PGM). 443g of silica powder b was added while charging and circulating the grinder (bead mill) at a peripheral speed of 6m / s, and then 30g of 3-methacryloxypropyltrimethoxysilane was added. After completion of the addition, the peripheral speed was increased to 8 m / s and circulation pulverization was performed for 8 hours to obtain a sol. This sol was allowed to stand at room temperature for 5 days, and a small amount of the resulting precipitate was removed by suction filtration with a Buchner funnel set with 1 μm glass fiber filter paper (Advantech GA-100), and PGM-dispersed silica sol (organic solvent dispersed) Silica sol) was obtained.

  The obtained PGM-dispersed silica sol was measured in the same manner as in Example 1. The solid content was 20.0%, the moisture was 1.6%, the viscosity was 12.0 mPa · s, the pH was 3.7, and the dispersed particle size was 153 nm. It was. When this PGM-dispersed silica sol was allowed to stand at 50 ° C. for 28 days and then reanalyzed, the viscosity was 12.4 mPa · s and the dispersed particle size was 155 nm. In addition, pH measured the pH of the solution which added the same mass water and the same mass methanol as the PGM dispersion | distribution silica sol with the pH meter.

  As a result, Examples 1 to 8 in which the raw material silica particles were pulverized in an organic solvent in which a polycarboxylic acid coexists had a small increase in viscosity during pulverization and could be easily pulverized. On the other hand, the comparative example which grind | pulverized in the organic solvent which does not coexist polyvalent carboxylic acid, specifically, the comparative example 1 and 2 which grind | pulverized in the organic solvent which does not coexist an acid, and grind | pulverized in the organic solvent which coexisted nitric acid In Comparative Example 3 and Comparative Example 4 pulverized in an organic solvent coexisting with a monovalent carboxylic acid, the viscosity increased significantly during pulverization, and pulverization was difficult.

  Further, in Comparative Example 5 using a continuous pulverizer, the viscosity increased and liquid feeding could not be performed, and pulverization could not be performed. Moreover, in Comparative Example 6 in which the addition of silica powder was performed over time little by little, liquid feeding could not be performed unlike Comparative Example 5, but in comparison with Examples 6 to 8, The increase in viscosity was large. In Comparative Example 5, it took time to add and pulverize the silica powder, and the pulverization efficiency was poor. In Comparative Examples 1 to 6, the viscosity once increased significantly during pulverization, and then the viscosity decreased.

  Moreover, in Examples 1-8, sedimentation, increase in viscosity, and increase in dispersed particle size were not observed even after standing for 28 days, but Comparative Examples 1-5 were pulverized in an organic solvent in which no polyvalent carboxylic acid was allowed to coexist. Then, after standing, the viscosity was remarkably increased due to the aggregation of the silica particles, and the storage stability was poor.

  Further, as shown in Table 3, when compared with the generated white precipitate and the IPA-dispersed silica sol of Example 6-2, the white precipitate contains tartaric acid, which is a polyvalent carboxylic acid, pulverization media, The salt of polyvalent carboxylic acid which is a compound with the metal (Na, Ca, Mg) generated from the pulverization container was included, and in particular, tartaric acid and sodium were included at a particularly high concentration.

[Test Example 1]
The IPA dispersion prepared in Example 6-1, Example 6-2, and Example 7 with respect to 100 parts by mass of pentaerythritol triacrylate (KAYARAD PET3A manufactured by Nippon Kayaku Co., Ltd.), which is a UV (ultraviolet) curable resin. Silica sol was mixed in an amount of 25 parts by mass or 50 parts by mass as silica solid content, and further 5 parts by mass of a polymerization initiator (Irgacure 184) was mixed. The obtained mixture was applied to a PET (polyethylene terephthalate) film (Toyobo Cosmo Shine A4100, 125 μm) with wire bar # 9 (WET film thickness 20.6 μm). This was dried on a hot plate at 50 ° C. for 10 minutes and then cured by irradiation with UV. The total light transmittance and haze of the obtained film were measured with TOKYO DENSHOKU, SPECTRAL HAZE METER, TC-H3DPK-MKII. Moreover, the pencil hardness of the obtained film was measured. The results are shown in Table 4.

[Test Example 2]
Resin solid content 100 in a solution obtained by dissolving 70 parts by mass of UA-306H (Kyoeisha Chemical Co., Ltd., pentaerythritol triacrylate hexamethylene diisocyanate, urethane-modified acrylic resin), which is a UV curable resin, in 30 parts by mass of methyl ethyl ketone (MEK). 25 parts by mass or 50 parts by mass of the IPA-dispersed silica sol prepared in Example 6-2 and Example 7 as silica solids is mixed with 5 parts by mass of the polymerization initiator (Irgacure 184). Mixed. The obtained mixture was applied to a PET (polyethylene terephthalate) film (Toyobo Cosmo Shine A4100, 125 μm) with wire bar # 9 (WET film thickness 20.6 μm). This was dried on a hot plate at 50 ° C. for 10 minutes and then cured by irradiation with UV. The total light transmittance and haze of the obtained film were measured with TOKYO DENSHOKU, SPECTRAL HAZE METER, TC-H3DPK-MKII. Moreover, the pencil hardness of the obtained film was measured. The results are shown in Table 5.

  As shown in Tables 4 and 5, the organic solvent-dispersed silica sol of the present invention had high transparency even when any of the Examples was used. In addition, all of the examples had sufficient hardness as a hard coat agent such as a film. In addition, when the organic solvent-dispersed silica sol of Comparative Examples 1 to 5 pulverized without coexisting polyvalent carboxylic acid instead of the organic solvent-dispersed silica sol of Example is used, the organic solvent-dispersed silica sol of Comparative Examples 1 to 5 is silica particles. Aggregates, and a product having high transparency cannot be obtained as in the case of using the organic solvent-dispersed silica sol of the above example.

Claims (3)

The raw material silica particles obtained in precipitation, in an organic solvent, the presence of polycarboxylic acid, after grinding, you and removing the metal salt of the polycarboxylic acid produced by the pulverization manufacturing method of organic solvent-dispersed silica sol. The method for producing an organic solvent-dispersed silica sol according to claim 1, wherein the organic solvent is an alcohol. An organic silicon compound is added, The method for producing an organic solvent-dispersed silica sol according to claim 1 or 2 .