Silica aerogel dispersion

Abstract

To provide an organic solvent dispersion of silica aerogel that is appropriate for uses including low-refractive-index coating films and offers superior dispersibility and resistance to sedimentation.SOLUTION: A silica aerogel dispersion of the present invention is a silica aerogel dispersion containing silica aerogel, a polymeric dispersant, and an organic solvent. The polymeric dispersant has an acid value and / or an amine value, wherein: i) when an amine value is present, the amine value is 5 mgKOH / g or more and 70 mgKOH / g or less; and ii) when an acid value is present, the acid value is 5 mgKOH / g or more and 150 mgKOH / g or less. The water content in the silica aerogel dispersion is 2.0 wt.% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a silica aerogel dispersion containing silica aerogel, a polymeric dispersant, and an organic solvent. [Background technology]

[0002] Silica aerogel is a porous material with many minute pores. It is considered useful as a functional material with excellent thermal insulation properties and unique optical and electrical properties. For example, electronic substrate materials utilizing the low dielectric constant of silica aerogel, heat insulating materials utilizing the high thermal insulation properties of silica aerogel, and light reflective materials utilizing the low refractive index of silica aerogel have been developed.

[0003] Most industrially produced silica aerogels are subjected to a surface hydrophobic treatment. Specifically, the hydrophobic treatment is performed by end-capping silanol groups present on the surface with a hydrophobic organic group such as a silylating agent. The "silica aerogel" in this invention also refers to silica aerogels having a porous structure whose surface has been hydrophobized by a chemical treatment. Furthermore, aerogel powders obtained by powdering silica aerogels are also subjected to a hydrophobic treatment.

[0004] Patent Document 1 discloses a composition comprising a) an aerogel component, b) a surfactant, and c) either an inorganic binder or an inorganic binder-containing formulation. The composition is in the form of a slurry and contains an aerogel component (a silylated hydrophobic aerogel or silica aerogel) and water with a high pH. The slurry composition forms a composite upon drying, becoming a coating or a self-supporting rigid composite.

[0005] Patent Document 2 discloses an aerogel powder dispersion containing aerogel powder, water, and a surfactant. In this dispersion, the water content in the dispersion medium can be increased to 50% by weight or more by using a surfactant having an alkylene oxide structure or a siloxane structure. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2012-525290 [Patent Document 2] Japanese Patent Application Laid-Open No. 2018-145331 Summary of the Invention [Problem to be solved by the invention]

[0007] When forming a low refractive index coating film that utilizes the low refractive index properties of silica aerogel on the surface of a substrate such as glass or a film, it is necessary to add a film-forming resin or binder to the dispersion. However, these film-forming resins and binders have low solubility in aqueous solvents, making them difficult to mix.

[0008] Furthermore, when forming a low refractive coating film on a glass or film surface, the silica aerogel dispersion must be applied to the substrate surface, and then the solvent must be removed. However, because aqueous solvents are less volatile than organic solvents, there is a problem in that the drying process takes a long time.

[0009] Furthermore, when commercially available silica aerogel is used, it is prone to sedimentation due to aggregation in the dispersion medium, and in some cases it is even impossible to prepare a dispersion.

[0010] An object of the present invention is to provide an organic solvent dispersion of silica aerogel that is excellent in dispersibility and non-sedimentation (sedimentation suppression) and is easy to handle. [Means for solving the problem]

[0011] The present inventors have conducted extensive research to solve the above problems and have found that when a polymeric dispersant having a specific acid value and / or amine value is used, an organic solvent dispersion of silica aerogel with excellent dispersibility of the silica aerogel can be prepared, thereby completing the present invention.

[0012] Specifically, the present invention provides: Silica aerogel, A polymeric dispersant; an organic solvent; A silica aerogel dispersion comprising: The polymeric dispersant has an acid value and / or an amine value, In the case where the polymer has an amine value, the amine value is 5 mgKOH / g or more and 70 mgKOH / g or less; In the case where the acid value is present, the acid value is 5 mgKOH / g or more and 150 mgKOH / g or less; The water content of the silica aerogel dispersion is 2.0 wt% or less. This relates to silica aerogel dispersions.

[0013] When preparing a silica aerogel dispersion in an organic solvent, a specific polymeric dispersant is used as the dispersant. That is, when the polymeric dispersant has an amine value, the amine value can be 5 mgKOH / g or more and 70 mgKOH / g or less. When the polymeric dispersant has an acid value, the acid value can be 5 mgKOH / g or more and 150 mgKOH / g or less.

[0014] The polymeric dispersant is When the polymer dispersant has an amine value, the amine value is preferably 5 mgKOH / g or more and 60 mgKOH / g or less, and particularly preferably 5 mgKOH / g or more and 30 mgKOH / g or less. By using such a polymer dispersant, a silica aerogel dispersion can be obtained that exhibits little change in viscosity and excellent non-settling properties.

[0015] When preparing a coating film-forming composition for use in forming a coating film, such as a high visible light transmittance film or a low optical refractive index film, from the silica aerogel dispersion of the present invention, if the silica aerogel content in the silica aerogel dispersion is too low, a large amount of silica aerogel dispersion must be added during preparation of the coating composition, thereby increasing the coating film formation cost for purchasers of the silica aerogel dispersion. Therefore, the content of the silica aerogel in the silica aerogel dispersion is preferably 1 wt % or more, more preferably 3 wt % or more. However, if the content exceeds 15 wt %, the viscosity increases, which can lead to problems such as poor handleability. Therefore, the content of the silica aerogel in the silica aerogel dispersion is preferably 15 wt % or less.

[0016] The organic solvent is preferably at least one selected from the group consisting of methyl ethyl ketone, isopropyl alcohol, and propylene glycol monomethyl ether acetate.

[0017] The average particle size (volume moment average) of the silica aerogel in the silica aerogel dispersion is preferably 2000 nm or less, and more preferably 1000 nm or less.

[0018] The viscosity of the silica aerogel dispersion immediately after preparation is preferably 1000 mPa·s or less, and more preferably 600 mPa·s or less. [Effects of the Invention]

[0019] According to the present invention, it is possible to obtain an organic solvent dispersion of silica aerogel that is excellent in dispersibility and non-settling properties (settling suppression) and easy to handle. The silica aerogel dispersion obtained by the present invention is resistant to settling or sedimentation even after storage at room temperature for one week, so when preparing a coating-forming composition, the effort of re-stirring the silica aerogel dispersion with a mixer or the like can be eliminated. Furthermore, even when the silica aerogel dispersion is directly mixed with a film-forming resin or binder to prepare a coating-forming composition, the quality of the resulting coating-forming composition is uniform, and there is little variation in coating performance (coating amount, thickness) between coating areas. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an embodiment of the present invention will be described.

[0021] As described above, the silica aerogel dispersion of the present invention is Silica aerogel, A polymeric dispersant; an organic solvent; A silica aerogel dispersion comprising: The polymeric dispersant has an acid value and / or an amine value, In the case where the polymer has an amine value, the amine value is 5 mgKOH / g or more and 70 mgKOH / g or less; In the case where the acid value is present, the acid value is 5 mgKOH / g or more and 150 mgKOH / g or less; The silica aerogel dispersion is characterized in that the water content is 2.0% by weight or less.

[0022] The silica aerogel in the present invention is a low-density structure (dry gel) made of silica (SiO2), and is referred to as "aerogel" in IUPAC. Silica aerogel generally has the physical properties of low specific gravity, low thermal conductivity, transparency (visible light transmission), and a low optical refractive index. Examples of such silica aerogel include ENOVA® Aerogel Particles IC3110 (oxy-trimethylsilyl modified product) manufactured by CABOT Corporation and DOW CORNING® VM-2270 manufactured by DOW-CORNING.

[0023] Dispersants include polymeric dispersants and low-molecular-weight surfactant-based dispersants. The dispersant used in the present invention is a polymeric dispersant. It is believed that polymeric dispersants effectively adsorb to the hydrophobized surface of silica aerogel particles, disperse the silica aerogel particles through steric and electrostatic repulsion, and prevent reagglomeration of the silica aerogel particles. The polymeric dispersant used in the present invention may be a polymeric dispersant with a weight-average molecular weight of 5,000 or more and a specific acid value and / or amine value. Anionic, cationic, or amphoteric polymeric dispersants may be used.

[0024] Specifically, polymeric dispersants include urethane-based dispersants such as polyurethane, polycarboxylic acid esters such as polyacrylate, unsaturated polyamides, polycarboxylic acids, polycarboxylic acid (partial) amine salts, polycarboxylic acid ammonium salts, polycarboxylic acid alkylamine salts, polysiloxanes, long-chain polyaminoamide phosphate salts, hydroxyl group-containing polycarboxylic acid esters and their modifications, amides formed by the reaction of poly(lower alkylene imines) with polyesters having free carboxyl groups or their salts, (meth)acrylic acid-styrene copolymers, (meth)acrylic acid-(meth)acrylic acid ester copolymers, styrene-maleic acid copolymers, polyesters, modified polyacrylates, ethylene oxide / propylene oxide adducts, phosphate esters, nitrogen-containing graft copolymers, nitrogen-containing acrylic block copolymers having functional groups in the side chains including tertiary amino groups, quaternary ammonium salts, nitrogen-containing heterocycles, and urethane-based polymeric dispersants. These polymeric dispersants can be used alone or in combination of two or more.

[0025] "Polymeric dispersants with an amine value" include polymeric dispersants that have only an amine value but no acid value, and polymeric dispersants that have both an amine value and an acid value. Similarly, "polymeric dispersants with an acid value" include polymeric dispersants that have only an acid value but no amine value, and polymeric dispersants that have both an acid value and an amine value.

[0026] The acid value refers to the acid value per 1 g of dispersant solid content and can be determined by potentiometric titration in accordance with JIS K 0070 (1992) (unit: mgKOH / g). The amine value refers to the amine value per 1 g of dispersant solid content and is determined by potentiometric titration using a 0.1 N hydrochloric acid aqueous solution and then converted to the potassium hydroxide equivalent (unit: mgKOH / g).

[0027] The organic solvent is not particularly limited, but can be appropriately selected depending on the type of resin or binder component used for film formation, and various organic solvents can be used, such as ketone-based, alcohol-based, ester-based, ether-based, amide-based, sulfoxide-based, aliphatic, aromatic, etc. From the viewpoint of ease of handling and film-forming properties, ketone-based, alcohol-based, or ester-based organic solvents are preferred, and one or more selected from the group consisting of methyl ethyl ketone (MEK), isopropyl alcohol (IPA), and propylene glycol monomethyl ether acetate (PMA) are particularly preferred.

[0028] The silica aerogel dispersion of the present invention uses an organic solvent as the solvent, and may contain no water at all, as long as the water content of the dispersion is 2.0 wt% or less. Because hydrophilic organic solvents such as lower alcohols themselves contain a small amount of water, even when water is not used as the solvent, it is ideal to measure the water content of the organic solvent and adjust the water content of the silica aerogel dispersion to 2.0 wt% or less, more preferably 1.8 wt% or less, and even more preferably 1.6 wt% or less.

[0029] <Production example of silica aerogel dispersion> As the silica aerogel, "IC3110" (manufactured by CABOT, ENOVA (registered trademark) Aerogel IC3110, particle size 0.1 to 0.7 mm) was used.

[0030] The following 12 types of polymeric dispersants were used. Note that the acid value or amine value of each is calculated based on 100% solids.

[0031] <Polymer-based dispersant with only acid value> (01) "BYK170" (BYK Japan Co., Ltd., Disperbyk®-170, solid content 30.00% by weight, acid value 11 mg KOH / g) (02) "BYK174" (BYK Japan Co., Ltd., Disperbyk-174, solid content 52.50% by weight, acid value 22 mg KOH / g) (03) "BYK118" (BYK Japan Co., Ltd., Disperbyk-118, solid content 80.00% by weight, acid value 36 mg KOH / g) (04) "MD1100" (Otsuka Chemical Co., Ltd., TERPLUS (registered trademark) MD1100, solid content 40.80 wt%, acid value 85 mg KOH / g) (05) "BYK102" (BYK Japan Co., Ltd., Disperbyk-102, solid content 99.00% by weight, acid value 101 mg KOH / g)

[0032] <Polymer-based dispersant with only an amine value> (06) "BYK167" (BYK Japan Co., Ltd., Disperbyk-167, solid content 52.00 wt%, amine value 13 mg KOH / g) (07) "BYK108" (BYK Japan Co., Ltd., Disperbyk-108, solid content 97.00 wt%, amine value 71 mg KOH / g) (08) "BYK-109" (BYK Japan Co., Ltd., Disperbyk-109, solid content 99.50% by weight, amine value 140 mg KOH / g)

[0033] <Polymer dispersant with acid value and amine value> (09) "PB821F" (Ajinomoto Fine-Techno Co., Inc., Ajisper (registered trademark) PB821F, solid content 100.00% by weight, acid value 17 mg KOH / g, amine value 10 mg KOH / g) (10) "BYK101N" (BYK Japan Co., Ltd., Disperbyk-101N, solid content 52.00 wt%, acid value 28 mg KOH / g, amine value 24 mg KOH / g) (11) “BYK142” (BYK Japan Co., Ltd., Disperbyk-142, solid content 60.00 wt%, acid value 46 mg KOH / g, amine value 43 mg KOH / g) (12) “BYK140” (BYK Japan Co., Ltd., Disperbyk-140, solid content 52.00 wt%, acid value 73 mg KOH / g, amine value 76 mg KOH / g)

[0034] The following three types of organic solvents were used: The water content of each organic solvent was measured by volumetric titration using a Karl Fischer moisture meter MKV-710 manufactured by Kyoto Electronics Manufacturing Co., Ltd. MEK (methyl ethyl ketone, measured water content 0.06% by weight) IPA (isopropyl alcohol, measured water content 0.75% by weight) PMA (propylene glycol monomethyl ether acetate, measured water content 0.04% by weight)

[0035] [Example 1] 5.00 parts by weight of silica aerogel, 0.50 parts by weight of BYK170 (solids equivalent) as a polymeric dispersant, and MEK as an organic solvent were placed in a polyethylene container. The amount of solvent was adjusted so that the total weight of "silica aerogel + polymeric dispersant + solvent" was 100.00 parts by weight. 200.00 parts by weight of zirconia beads (φ0.8 mm) were placed in the container, and the mixture was dispersed for 60 minutes using a paint shaker manufactured by Asada Iron Works Co., Ltd. to obtain the silica aerogel dispersion of Example 1 (5.0 wt% silica aerogel, 0.5 wt% dispersant concentration).

[0036] [Example 2] A silica aerogel dispersion of Example 2 was obtained in the same manner as in Example 1, except that BYK174 was used instead of BYK170.

[0037] [Example 3] A silica aerogel dispersion of Example 3 was obtained in the same manner as in Example 1, except that BYK118 was used instead of BYK170.

[0038] [Example 4] A silica aerogel dispersion of Example 4 was obtained in the same manner as in Example 1, except that MD1100 was used instead of BYK170.

[0039] [Example 5] A silica aerogel dispersion of Example 5 was obtained in the same manner as in Example 1, except that BYK102 was used instead of BYK170.

[0040] [Example 6] A silica aerogel dispersion of Example 6 was obtained in the same manner as in Example 1, except that BYK167 was used instead of BYK170.

[0041] [Example 7] A silica aerogel dispersion of Example 7 was obtained in the same manner as in Example 1, except that PB821F was used instead of BYK170.

[0042] [Example 8] A silica aerogel dispersion of Example 8 was obtained in the same manner as in Example 1, except that BYK101N was used instead of BYK170.

[0043] [Example 9] A silica aerogel dispersion of Example 9 was obtained in the same manner as in Example 1, except that BYK142 was used instead of BYK170.

[0044] [Example 10] A silica aerogel dispersion of Example 10 (measured water content: 0.83 wt %) was obtained in the same manner as in Example 4, except that IPA was used instead of MEK.

[0045] [Example 11] A silica aerogel dispersion of Example 11 was obtained in the same manner as in Example 6, except that IPA was used instead of MEK.

[0046] [Example 12] A silica aerogel dispersion of Example 12 was obtained in the same manner as in Example 7, except that IPA was used instead of MEK.

[0047] [Example 13] A silica aerogel dispersion of Example 13 (measured water content: 1.52 wt%) was obtained in the same manner as in Example 10, except that IPA, an organic solvent, was used as the solvent, and 1.00 parts by weight of water was used. The amount of solvent represents the total amount of organic solvent and water, and was adjusted so that the total amount of "silica aerogel + polymer dispersant + solvent" was 100.00 parts by weight.

[0048] [Example 14] A silica aerogel dispersion of Example 14 was obtained in the same manner as in Example 4, except that PMA was used instead of MEK.

[0049] [Example 15] A silica aerogel dispersion of Example 15 was obtained in the same manner as in Example 7, except that PMA was used instead of MEK.

[0050] [Comparative Example 1] 5.00 parts by weight of silica aerogel and MEK as an organic solvent were placed in a polyethylene container. The amount of solvent was adjusted so that the "silica aerogel + solvent" ratio was 100.00 parts by weight. The zirconia beads used in Examples 1 to 15 were not used, and dispersion treatment was carried out for 60 minutes using a paint shaker manufactured by Asada Iron Works Co., Ltd. to obtain the silica aerogel dispersion of Comparative Example 1 (5.0% by weight of silica aerogel, 0% by weight of dispersant concentration, no dispersant contained).

[0051] Comparative Example 2 A silica aerogel dispersion of Comparative Example 2 was obtained in the same manner as in Comparative Example 1, except that the zirconia beads used in Examples 1 to 15 were used for the dispersion treatment.

[0052] Comparative Example 3 A silica aerogel dispersion of Comparative Example 3 was obtained in the same manner as in Example 1, except that BYK108 was used instead of BYK170.

[0053] Comparative Example 4 A silica aerogel dispersion of Comparative Example 4 was obtained in the same manner as in Example 1, except that BYK109 was used instead of BYK170.

[0054] Comparative Example 5 A silica aerogel dispersion of Comparative Example 5 was obtained in the same manner as in Example 1, except that BYK140 was used instead of BYK170.

[0055] Comparative Example 6 A silica aerogel dispersion of Comparative Example 6 (measured water content: 2.16 wt%) was obtained in the same manner as in Example 10, except that 2.00 parts by weight of water was used in addition to the organic solvent IPA. The amount of solvent represents the total amount of organic solvent and water, and was adjusted so that the total amount of "silica aerogel + polymer dispersant + solvent" was 100.00 parts by weight.

[0056] Comparative Example 7 A silica aerogel dispersion of Comparative Example 7 (measured water content: 3.38 wt%) was obtained in the same manner as in Example 10, except that IPA, an organic solvent, was used as the solvent, and 3.00 parts by weight of water was used. The amount of solvent represents the total amount of organic solvent and water, and was adjusted so that the total amount of "silica aerogel + polymer dispersant + solvent" was 100.00 parts by weight.

[0057] The compositions of the silica aerogel dispersions of Examples 1 to 15 and Comparative Examples 1 to 7 are shown in Tables 1 to 3.

[0058] [Table 1]

[0059] [Table 2]

[0060] [Table 3]

[0061] <Physical properties of silica aerogel dispersion> The silica aerogel dispersions of Examples 1 to 15 and Comparative Examples 1 to 7 were measured for the average particle size, viscosity, and non-settling property of the silica aerogel.

[0062] (Method for measuring average particle size) The average particle size (volume moment average, unit: nm) of the silica aerogel dispersion was measured by laser diffraction using a Malvern Panalytical Mastersizer 3000. The average particle size was measured twice: immediately after the silica aerogel dispersion was prepared and after it had been stored at room temperature for one week.

[0063] (Viscosity measurement method) The viscosity (unit: mPa s) of the silica aerogel dispersion was measured immediately after preparation and after one week of storage at room temperature using a TV-22 E-type viscometer manufactured by Toki Sangyo Co., Ltd. The viscosity change rate [%] was calculated using Equation 1.

[0064]

number

[0065] (Method for evaluating non-settling properties) First, the solid content [%] of the silica aerogel dispersion was measured immediately after preparation. Next, the silica aerogel dispersion was dispensed into a Labvida Scientific screw tube (LVH004, capacity 15 mL) to a height of 10 cm from the bottom of the container. After leaving the dispensed silica aerogel dispersion at room temperature for one week, 2 cm of liquid was removed from the liquid surface, and approximately 1 mL was dispensed from the top of the remaining silica aerogel dispersion and weighed to four decimal places (unit: g) to measure the solid content [%] of the top portion.

[0066] Further liquid was removed so that the liquid level was 2 cm from the bottom, and approximately 1 mL of the silica aerogel dispersion at the bottom was also taken and weighed to four decimal places (unit: g) to measure the solid content [%] at the bottom. Using the obtained solid content at the top and bottom, the rate of change between the solid content at the top and bottom was calculated using Equation 2 to evaluate the non-settling property.

[0067]

number

[0068] The evaluation criteria are as follows, with evaluations of "good" and "fair" indicating practical use. ○: The change rate [%] between the solid content of the upper part and the solid content of the lower part is less than 1.0 [%] △: The percentage change between the solid content of the upper part and the solid content of the lower part is 1.0% or more and less than 20.0% ×: The change rate [%] between the solid content of the upper part and the solid content of the lower part is 20.0 [%] or more

[0069] The solid content [%] of the silica aerogel dispersion was measured by placing approximately 1 mL of the dispersion in a pre-weighed aluminum cup, leaving it in a thermostatic bath maintained at 130°C for 1 hour, and then measuring the weight (weight before heating and weight after heating) to four decimal places (unit: g) and calculating using Equation 3.

[0070]

number

[0071] <Method for producing coating film using silica aerogel dispersion> MD1100 was added to the silica aerogel dispersions of Examples 1 to 15 and Comparative Examples 1 to 7 so that the silica aerogel content and other resin components were 70:30, and the mixture was stirred and mixed to prepare a coating film-forming composition. Each coating film-forming composition was spin-coated onto a substrate using an Opticoat MS-A150 manufactured by Mikasa Co., Ltd. The resulting mixture was dried at 90°C for 2.5 minutes using a hot air dryer to produce a coating film. The coating film thickness was adjusted to approximately 1 μm by adjusting the rotation speed during spin coating.

[0072] <Physical properties of coating film> The haze value, total light transmittance, and refractive index of the prepared coating film were measured. When measuring the haze value and total light transmittance, alkali-free glass (manufactured by Optoscience Co., Ltd.) was used as the substrate. When measuring the refractive index, a silicon wafer (4PN-MONITOR manufactured by Seiren KST Co., Ltd.) was used as the substrate.

[0073] (Haze value and total light transmittance) The total light transmittance (%TT) and haze value of each coating film were measured using an NDH4000 (D65 light source) manufactured by Nippon Denshoku Co., Ltd. Here, the haze value means "the value obtained by dividing the diffuse reflectance by the total light transmittance and multiplying the result by 100," and is an index that indicates the degree of cloudiness of a substrate such as glass or plastic.

[0074] (refractive index) The refractive index of each coating film was measured by optical interferometry using F20-EXR manufactured by FILMETRICS.

[0075] The average particle size, viscosity, viscosity change rate, and non-settling evaluation of the silica aerogel particles of the silica aerogel dispersions of Examples 1 to 15 and Comparative Examples 1 to 7 are shown in Tables 4 to 6. The haze value, total light transmittance, and refractive index of the coating films prepared using the silica aerogel dispersions of Examples 1 to 15 are also shown in Tables 4 and 5. In Tables 4 to 6, the symbol "-" indicates that the value could not be measured or calculated.

[0076] [Table 4]

[0077] [Table 5]

[0078] [Table 6]

[0079] The silica aerogel dispersion of Comparative Example 1 showed a large amount of sedimentation even immediately after preparation, and the silica aerogel particles and the solvent were separated. This made it impossible to measure the average particle size and viscosity immediately after preparation, and the non-sedimentation evaluation was also poor. The silica aerogel dispersion of Comparative Example 2 was measurable in terms of average particle size and viscosity immediately after preparation, but after one week of storage at room temperature, a large amount of sedimentation was observed, and the silica aerogel particles and the solvent were separated. This made it impossible to measure the average particle size and viscosity after storage, and the non-sedimentation evaluation was poor. The silica aerogel dispersions of Comparative Examples 3 to 5 showed a viscosity change rate of more than 20%. The silica aerogel dispersions of Comparative Examples 6 and 7 were measurable in terms of average particle size immediately after preparation, but gelation prevented viscosity measurement. Therefore, the silica aerogel dispersions of Comparative Examples 1 to 7 were deemed to lack practical applicability as organic solvent dispersions of silica aerogel for applications such as low refractive index coatings.

[0080] On the other hand, the silica aerogel dispersions of Examples 1 to 15 did not gel, and the average particle size immediately after preparation and after one week of storage at room temperature was 2000 nm or less. Furthermore, the viscosity of the silica aerogel dispersions of Examples 1 to 15 immediately after preparation and after one week of storage at room temperature was 1000 mPa s or less, and the non-sedimentation evaluation was "△" or "○".

[0081] The silica aerogel dispersions of Examples 1 to 15 each contain a polymer dispersant having an acid value and / or an amine value, (1) A polymeric dispersant having an amine value, if any, of 5 mg KOH / g or more and 70 mg KOH / g or less; or (2) If it has an acid value, it is a polymeric dispersant having an acid value of 5 mgKOH / g or more and 150 mgKOH / g or less.

[0082] It was confirmed that the use of such a polymeric dispersant makes it possible to obtain an organic solvent dispersion of silica aerogel with excellent dispersion stability, in which the average particle size of the silica aerogel is 2000 nm or less and the viscosity change rate is less than ±10%.

[0083] In particular, when the polymeric dispersant has an amine value of 5 mgKOH / g or more and 30 mgKOH / g or less, the non-settling property of the silica aerogel dispersion was evaluated as "Good," and it was confirmed that more preferable physical properties were obtained as a silica aerogel dispersion.

[0084] From Examples 10 and 13 and Comparative Examples 6 and 7, it was also confirmed that when the water content of the silica aerogel dispersion is 2.0 wt % or less, more preferably 1.8 wt % or less, and even more preferably 1.6 wt % or less, a silica aerogel dispersion can be obtained that is not affected by water, has little change in viscosity, and is excellent in non-sedimentation.

[0085] Furthermore, coating films could be produced using any of the silica aerogel dispersions of Examples 1 to 15. When the physical properties of these coating films were measured, all of the coating films had a total light transmittance of 90% or more, a refractive index of 1.21 or less, and a haze value of 25.0 or less, confirming that they could be used as coating films. [Industrial Applicability]

[0086] The silica aerogel dispersion of the present invention is suitable for forming films with high visible light transmittance, low optical refractive index, and low thermal conductivity (high heat insulation) films, and is useful in the field of coatings, etc.

Claims

1. Silica aerogel, A polymeric dispersant; an organic solvent; A silica aerogel dispersion comprising: The polymeric dispersant has an acid value and / or an amine value, In the case where the polymer has an amine value, the amine value is 5 mgKOH / g or more and 70 mgKOH / g or less, In the case where the acid value is present, the acid value is 5 mgKOH / g or more and 150 mgKOH / g or less, The water content of the silica aerogel dispersion is 2.0 wt% or less. Silica aerogel dispersion.

2. The polymeric dispersant is When the amine value is present, the amine value is 5 mgKOH / g or more and 30 mgKOH / g or less. The silica aerogel dispersion according to claim 1.

3. The content of the silica aerogel is 1% by weight or more and 15% by weight or less. The silica aerogel dispersion according to claim 1.

4. The organic solvent is at least one selected from the group consisting of methyl ethyl ketone, isopropyl alcohol, and propylene glycol monomethyl ether acetate. The silica aerogel dispersion according to claim 1.

5. The average particle size of the silica aerogel in the silica aerogel dispersion is 2000 nm or less. The silica aerogel dispersion according to claim 1.

6. The viscosity immediately after preparation is 1000 mPa s or less. The silica aerogel dispersion according to any one of claims 1 to 5.

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