JP6166440B2 - Aerogel and matting agent comprising said airgel - Google Patents

Description

  The present invention relates to an airgel that exhibits good matting properties when used as a matting agent, a matting agent comprising the aerogel, and a matting paint containing the matting agent.

  The airgel has a very small bulk density, a high porosity, and pores on the order of 10 to 100 nm. Because of these properties, aerogels are used in a wide range of applications such as heat insulating materials, matting agents, catalysts, and cosmetics.

  On the other hand, metal oxides, particularly silica, have been incorporated into paints in order to obtain a “matte” feel. A general matting effect is obtained by irregularly reflecting light by forming irregularities on the surface of the coating film. If this unevenness is shorter than the wavelength of visible light, the scattering effect is lost. Therefore, the unevenness needs to be larger than the wavelength of visible light. However, if the particle diameter of the additive particles is too large, the surface of the coating becomes rough and the smoothness deteriorates, and it tends to be difficult to obtain a smooth matte feeling.

  In addition, silica used as a matting agent is often hydrophilic silica from the viewpoint of cost. Hydrophilic silica has silanol groups present on the surface of silica particles, so it tends to agglomerate and tends to deteriorate the dispersibility when added to the paint, forming lumps on the paint surface and precipitating in the paint. Problems such as separation may occur.

  As means for solving these problems, silica having a hydrophobic property by modifying silanol groups on the surface of silica particles with a silane compound having an alkyl group has been provided (see Patent Documents 1 and 2).

Japanese Patent No. 4225466 Japanese Patent No. 4225467

  The techniques disclosed in Patent Documents 1 and 2 and the like are certainly excellent. However, there is a continuing demand for matting agents for higher matting effects that have both low glossiness and good smoothness on the coating surface as matting agent applications.

  Therefore, in order to obtain a lower glossiness and good smoothness, the present inventors paid attention to the reduction of grains that do not contribute to matting and the reduction of coarse grains that deteriorate the smoothness of the coating surface. Airgel having a diameter and particle size distribution was studied.

  As a result, in a specific hydrophobic airgel, those having a particle size distribution D10 / D90 of 0.3 to 0.5 have a lower glossiness even at the same D50 than those having a particle size distribution D10 / D90 of less than 0.3. It has been found that smoothness is also good.

That is, the present invention relates to the general formula (I)
R _n SiX _4-n
(However, R is a hydrocarbon group, X is an alkoxy group or halogen, and n is an integer of 1 to 3)
Or a structure represented by the general formula (II)
R ₃ SiNHSiR ₃
(However, R is the same as above)
An airgel hydrophobized with a surface treatment agent having a structure represented by:
D10 and D90 having a specific surface area by BET method of 400 to 1000 m ² / g, pore volume and pore radius peaks by BJH method of 3 to 8 mL / g and 10 to 40 nm, respectively, and measured by Coulter counter method Ratio (D10 / D90) is 0.
3 to 0.5 (however, D10 is 10% from the smaller particle size of the volume-based cumulative particle size distribution curve)
Represents the particle size of the frequency value, and D90 represents the particle size of the 90% frequency value)
Another invention is a matting agent characterized by comprising the aerogel.

  Since the airgel of the present invention has a sharp particle size distribution, there are few useless particles that do not contribute to matting, and therefore the matting effect can be obtained efficiently.

  In addition, since there are few coarse particles that deteriorate the smoothness of the coating film surface, the unevenness of the surface is relaxed and a smooth coating film surface can be obtained.

Laser microscope image of the coating surface of Example 1 Laser microscope image of coating surface of Comparative Example 7

  Hereinafter, the present invention will be described in more detail.

  The airgel of the present invention is hydrophobic. Here, “hydrophobic” means not dispersed in water. More specifically, it means that 1 g of the airgel of the present invention is placed in a container together with 100 g of ion-exchanged water, shaken or stirred for 10 seconds or more, and then left to stand to completely separate into an airgel phase and an aqueous phase.

Obtaining such hydrophobicity can be easily achieved by capping the surface OH group with a hydrophobic organic group such as a silylating agent, as will be described in detail in the column of the production method described later. Such silylating agents include those represented by the general formula (I)
R _n SiX _4-n
(However, R is a hydrocarbon group, X is an alkoxy group or halogen, and n is an integer of 1 to 3)
Or a structure represented by the general formula (II)
R ₃ SiNHSiR ₃
(However, R is the same as above)
A treating agent having a structure represented by

  In the present invention, “aerogel” means a solid material having a high porosity and a gas as a dispersion medium, and particularly means a solid material having a porosity of 60% or more. The porosity is a value that expresses the amount of gas contained in the apparent volume as a volume percentage.

  Regarding the particle size distribution of the airgel in the present invention, a container containing 0.005 g of an airgel sample added to 50 g of alcohol (for example, Solmix A-7) was placed in an ultrasonic cleaner and dispersed at 90 W for 3 minutes. The value measured by the Coulter counter method is shown. The dispersion time of 3 minutes was changed to 1, 3 and 5 minutes, and it was confirmed that the D50 value did not change by 0.1 μm or more and the D10 / D90 value did not change by 0.01 or more. The result was obtained. In other words, when the airgel is dispersed with an ultrasonic cleaner (used as a disperser), the particle size in a dispersed state in which the change in D50 measured in ± 2 minutes is less than 0.1 μm. .

  In the present invention, “D10” represents a particle size of 10% of the volume-based cumulative particle size distribution curve counted from the smaller particle size in the particle size distribution measured by the Coulter counter method. The particle size is expressed in terms of%, and “D50” is a 50% value, which is a so-called median diameter.

  A larger D10 / D90 means that the airgel has a sharper particle size distribution. The airgel of the present invention has D10 / D90 of 0.3 or more. Therefore, it is possible to prevent the mixing of small grains that do not contribute to matting and large grains that impair the uniformity of the coating surface, and to obtain an efficient matting effect without waste. The upper limit of D10 / D90 is 0.5 or less from the viewpoint of availability.

  Further, by making D50 as fine as 2 to 5 μm, more preferably 2 to 4 μm, the smoothness of the coating film surface is improved and the gloss is effectively removed (that is, a smooth mat feeling). Can be granted.

  Generally, when the particle size is increased, the unevenness of the coating film surface becomes large and the matting effect is improved, but at the same time, the smoothness of the coating film surface is deteriorated. On the other hand, when the particle size is made smaller than the wavelength of visible light, the smoothness is improved, but the incident light is not irregularly reflected on the coating film surface, and the matting performance is deteriorated.

  In other words, the numerical data of the surface roughness representing the smoothness of the coating surface and the glossiness representing the matting effect depend on the particle size of the matting agent, and in addition to the general matte state, the coating surface is smooth. The above particle size is effective when a good mat feeling is also required.

The specific surface area according to the BET method of the airgel in the present invention is 400 m ² / g or more, preferably 500 m ² / g or more. Moreover, the specific surface area by BET method is 1000 m < ² > / g or less, Preferably it is 800 m < ² > / g or less. The larger the specific surface area, the smaller the primary particle diameter constituting the airgel, and it is possible to form the airgel skeleton structure in a smaller amount, which is preferable for improving the matte performance.

  The pore volume of the airgel in the present invention by the BJH method is 3 to 8 mL / g, preferably 4 to 8 mL / g, and more preferably 5 to 8 mL / g. In addition, when the pore volume is small, the number of particles per unit mass decreases, so it is desirable that the pore volume be large.

  The pore radius peak of the airgel in the present invention is in the range of 10 to 40 nm, more preferably 20 to 30 nm. In order to obtain an efficient matting effect, it is desirable to reduce the bulk density of the airgel and increase the number of particles per unit mass in the coating film. Therefore, it is preferable that the pore radius is large. In addition, it is preferable that the pore radius is small in that good transparency can be easily obtained.

  In the present invention, “specific surface area by BET method” means that the sample to be measured is dried at a temperature of 150 ° C. for 2 hours or more under a vacuum of 1 kPa or less, and then adsorbed only on the nitrogen adsorption side at the liquid nitrogen temperature. It means a value obtained by measuring an isotherm and analyzing the adsorption isotherm by the BET method. The pressure range used for the analysis in that case is the range of relative pressure 0.1-0.25.

  The “pore volume by the BJH method” refers to the adsorption isotherm obtained in the same manner as described above using the BJH method (Barrett, EP; Joyner, LG; Halenda, PP, J., etc.). Am. Chem. Soc. 73, 373 (1951)) means a pore volume derived from pores having a pore radius of 1 nm to 100 nm.

  “The peak of the pore radius by the BJH method” is the differential of the cumulative pore volume by the logarithm of the pore radius, obtained by analyzing the adsorption isotherm on the adsorption side obtained in the same manner as described above by the BJH method. In other words, the pore distribution curve (volume distribution curve) plotted with the pore radius on the horizontal axis represents the value of the pore radius at which the maximum peak is obtained.

  Although the manufacturing method of the hydrophobic airgel of this invention which has the above-mentioned physical property is not specifically limited, According to inventors' examination, it can manufacture with the following method.

  That is, the airgel as the matting agent of the present invention is produced by a normal pressure drying method in which a metal oxide sol is prepared, and the sol is gelled, aged, washed, solvent substituted, hydrophobized, and dried in order. can do.

Hereinafter, the case where the metal oxide is silica (SiO ₂ ) will be described in detail as an example.

Among the above steps, the silica (metal oxide) sol preparation step may be performed by appropriately selecting a known method. As raw materials for producing the silica sol, metal alkoxide, alkali metal silicate, and the like can be used. Specific examples of the metal alkoxide that can be used as the raw material of the airgel used in the matting agent of the present invention include tetramethoxysilane and tetraethoxysilane. Examples of the alkali metal silicate include potassium silicate and sodium silicate. The chemical formula is represented by the following formula 1.
m (M ₂ O) · n (SiO ₂ ) (Formula 1)
(In the formula, m and n represent a positive integer, and M represents an alkali metal atom.)
Among the raw materials for producing the silica sol, an alkali metal silicate can be preferably used from the viewpoint of inexpensiveness, and sodium silicate which is easily available is preferable.

When an alkali metal silicate is used as a silica sol preparation raw material for an airgel used in the matting agent of the present invention, it is neutralized with a mineral acid such as hydrochloric acid or sulfuric acid, or the counter ion is H ^+. A silica sol can be produced by a method using a cation exchange resin (hereinafter referred to as “acid-type cation exchange resin”).

  Examples of the method for preparing the silica sol by neutralizing with the acid described above include a method of adding an alkali metal silicate solution with stirring to an acid solution, and a method of collision mixing in a pipe. . The amount of acid used is preferably 1.05 to 1.2 as the molar ratio of the alkali metal silicate salt to the alkali content. When the amount of acid is within this range, the pH of the produced silica sol is about 1 to 3.

  Moreover, the method for producing silica sol using the above acid type cation exchange resin can be performed by a known method, and the alkali metal silicate having an appropriate concentration in the packed bed filled with the acid type cation exchange resin. The acid type cation exchange resin is separated by adding the acid type cation exchange resin to the alkali metal silicate solution, mixing, removing the alkali metal, and then separating by filtration. This can be done. At that time, the amount of the acid-type cation exchange resin to be used must be equal to or greater than the amount capable of exchanging the alkali metal contained in the solution.

  A commercially available acid-type cation exchange resin can be used. For example, styrene-based, acryl-based, methacryl-based, etc., and those having a sulfonic acid group or a carbonyl group substituted as the ion-exchange group can be used. Among these, a so-called strong acid type cation exchange resin having a sulfonic acid group can be suitably used.

  In addition, after using said acid type cation exchange resin for replacement | exchange of an alkali metal, a reproduction | regeneration process can be performed by letting sulfuric acid and hydrochloric acid pass. The amount of acid used for regeneration is usually 2 to 10 times the exchange capacity of the ion exchange resin.

  The concentration of the silica sol produced by the above method is preferably about 50 to 150 g / L as the concentration of silica. By making it 50 g / L or more, the gelation time can be shortened moderately and efficiently produced, and since the silica content in the silica sol is large, the formation of the airgel skeleton structure is likely to be sufficient, and shrinkage occurs during drying. Since it does not easily occur, the pore volume tends to increase. Furthermore, there is a low possibility that the pores will be crushed by the external pressure when filled in a closed container or the like, and when stirring / mixing, a strong agglomerated structure is obtained, and the performance of the matting agent can be exhibited effectively.

  Moreover, by setting it as 150 g / L or less, since the density of an airgel becomes small and the number of silica particles contained per unit mass increases, it exists in the tendency for a favorable matting effect to be acquired.

  In order to produce the airgel of the present invention, following the preparation of the sol, ammonia water (for example, about 5%), caustic soda, alkali metal salt, etc. are added to the silica sol to adjust the pH to 3-6. Gelate. The gel is pulverized through a sieve having an appropriate opening while crushing the gel so that the gel has an appropriate particle size (for example, about 150 μm to 4 mm) to obtain an aqueous gel slurry having an appropriate particle size. If the pH is lower than 3, it takes time to gel and the efficiency is poor, and if the pH exceeds 6, it immediately gels and it becomes difficult to form a uniform gel. Furthermore, the primary particles are coalesced or grown, the primary particle diameter is increased, the specific surface area tends to be reduced, the fine aggregate structure is difficult to form, the pore volume is reduced, and the desired airgel tends not to be formed. .

  The time required for the gelation depends on the temperature and the concentration of the silica sol, but when the pH is 5.0, 50 ° C. and the silica concentration in the silica sol is 80 g / L, gelation occurs after several minutes.

  When producing the airgel of the present invention, following the above gelation, when the silica concentration is as low as 50 to 80 g / L or when the gelation pH is as low as 3 to 4, the silica skeleton structure strength of the gelled product In order to strengthen the strength, aging is preferably performed. The specific surface area of the airgel varies depending on the pH, temperature, and time during the aging. The higher the pH, the higher the temperature, the longer the time, the lower the specific surface area, but the airgel's skeletal structure becomes stronger, so it has the effect of suppressing drying shrinkage and increasing the pore volume, and also matte When used as an agent, since the pores can be kept intact, it is preferable to adjust the physical property balance and determine the conditions.

  The range of the aging temperature is preferably 30 to 80 ° C. If the ripening temperature is high outside this range, the amount of heat required to raise the temperature is large, and if the ripening temperature is low outside this range, the time required to obtain the aging effect is large. become longer. Moreover, as a range of said aging time, when pH to gelatinize is 3-4, about 5 to 24 hours are preferable. Moreover, when the pH to gelatinize is 4-6, about 0 to 24 hours immediately after gelatinization are preferable. When the aging time exceeds 24 hours, the primary particles of silica are coalesced or grown during aging, the primary particle size increases, the specific surface area decreases, the fine aggregate structure is difficult to form, and the pore volume decreases. Tend.

  The washing operation is an operation for removing the salt contained in the gel by washing the aqueous gel slurry with water. Therefore, this cleaning operation is not necessary when a sol is produced using an acid type cation exchange resin. In order to produce the airgel used for the matting agent of the present invention, this washing is preferably performed until the conductivity of the washing solution is 100 μS / cm or less. The washing operation can be performed by a known method. For example, a method of repeatedly adding a certain amount of water to the gel and draining the washing water after standing for a certain time, a method of allowing a certain amount of water to pass through the gel placed in the column, and the like can be mentioned. When washing with a column, it can be performed under a pressure of about 0.2 to 1.0 MPa for the purpose of increasing efficiency.

  In order to produce the airgel of the present invention, solvent substitution is performed. This solvent replacement replaces the water used for preparing the gel with a solvent having a small surface tension so that the drying shrinkage does not occur when the gel obtained by the above method is dried. Since it is difficult to directly replace water with a solvent having a low surface tension, this solvent replacement is usually performed in two stages. The selection criteria for the solvent used in the first stage include good miscibility with water and the solvent used for the second stage solvent substitution.

  For the first-stage solvent replacement, a so-called hydrophilic organic solvent that can be mixed with water such as methanol, ethanol, isopropyl alcohol, and acetone at an arbitrary ratio can be used, and preferably methanol or ethanol is used. be able to. The selection criteria for the solvent used in the second stage include that it does not react with the treatment agent used in the subsequent hydrophobization treatment and that the surface tension is small so as not to cause drying shrinkage. As the solvent used in the second stage, hexane, dichloromethane, methyl ethyl ketone, heptane, or the like can be used, and hexane can be preferably used. Of course, if necessary, further solvent substitution may be performed between the first-stage solvent substitution and the second-stage solvent substitution.

  The first-stage solvent replacement can be performed by a known method. For example, a method of repeatedly adding a certain amount of solvent to the gel and leaving it for a certain time and then removing the solvent, a method of allowing a certain amount of solvent to pass through the gel placed in the column, etc. In order to save the solvent used for substitution, a method using a column is preferred. Moreover, when replacing by a column, it can carry out under the pressurization of about 0.2-1 Mpa for the purpose of raising efficiency.

  The amount of the solvent used for the solvent replacement is preferably an amount that can sufficiently replace the moisture in the gel. The water content in the gel after substitution is preferably 10% or less with respect to the silica content. When the method is employed with the above-mentioned column, the solvent can be used in an amount 5 to 10 times the gel volume.

  The second-stage solvent replacement can be performed in the same manner as the first-stage solvent replacement, and can be performed in an amount that can sufficiently replace the solvent used in the first stage. When the column method is employed, 5 to 10 times as much solvent as the gel volume can be used.

  The solvent used for the above substitution is preferably collected and reused after purification of the distillation column in order to save the cost of the solvent.

The airgel used for the matting agent of the present invention is subjected to a hydrophobization treatment after the above solvent replacement. As the treating agent used for the hydrophobizing treatment, the general formula (I)
R _n SiX _4-n
(However, R is a hydrocarbon group, X is an alkoxy group or halogen, and n is an integer of 1 to 3)
Or a structure represented by the general formula (II)
R ₃ SiNHSiR ₃
(However, R is the same as above)
Is preferably used. Preferred are trimethylchlorosilane, dimethyldichlorosilane (hereinafter referred to as DMDCS), monomethyltrichlorosilane (hereinafter referred to as MTS), and hexamethyldisilazane.

  The amount of the treatment agent used in the above hydrophobization treatment depends on the kind of the treatment agent. For example, when DMDCS is used as the treatment agent, it is 50 to 150 parts by mass with respect to 100 parts by mass of silica. is there. When the amount of the DMDCS treatment agent is less than 50 parts by mass, drying shrinkage occurs during solvent drying in the subsequent step, and the target pore volume cannot be obtained, or the aerogel has the target pore volume. However, the repulsion between the particles (spring back effect) is reduced and the pores are crushed when an external force is applied. More preferably, it is 80-130 mass parts.

  The conditions for the above-described hydrophobizing treatment can be performed by adding a certain amount of solvent to the liquid containing the gel after the solvent substitution treatment, adding a hydrophobizing agent, and reacting for a certain time. When DMDCS is used as the hydrophobizing agent and the treatment temperature is 50 ° C., the treatment can be performed by holding for about 12 hours or more.

  In order to obtain the airgel of the present invention, after the hydrophobization treatment, it is filtered off, the unreacted treatment agent is washed with a solvent, and then dried. The drying temperature is preferably not less than the boiling point of the solvent and not more than the decomposition temperature of the surface treatment agent, and the pressure is preferably normal or reduced.

  The airgel in the present invention can be obtained by pulverizing the lump-shaped dry airgel obtained as described above by a known method.

  However, since airgel having a sharp particle size distribution is difficult to obtain by wet pulverization, dry pulverization is preferably performed. The mechanism of these causes is not clear, but in wet grinding, the grinding energy applied to each particle is too large, or it is difficult to uniformly apply energy to the particles, so the proportion of small particles significantly below the average particle size increases, conversely It is considered that an airgel having a sharp particle size distribution is difficult to obtain due to an increase in the proportion of coarse particles having a large particle size that remain without being pulverized, or both phenomena. Therefore, dry pulverization is preferably performed to obtain the airgel of the present invention.

  In addition, a method of applying a strong force for a relatively short time, such as a jet mill, can obtain a sharper particle size distribution than a method of continuously applying a strong force for a relatively long time, such as a ball mill. This is preferable in that it is difficult to destroy the fine structure, and thus it is difficult to reduce the specific surface area and pore volume, and to prevent the generation of small particles that do not contribute to matting.

Furthermore, when pulverizing using a jet mill to obtain an airgel having a particle size distribution in the range specified in the present invention, the pulverization conditions in the jet mill include powder in an inert gas such as compressed air or N _2. The body concentration is preferably 10 g / m ³ or more and 220 g / m ³ or less, preferably 15 g / m ³ or more and 190 g / m ³ or less, more preferably 15 g / m ³ or more and 30 g / m ³ or less. By setting the powder concentration, the powder concentration in the pulverizing chamber of the jet mill is increased and the pulverizing ability is improved. However, the pulverizing force applied to the individual particles is dispersed even if the powder concentration is excessively increased. Body concentration is preferred.

  Furthermore, when it is difficult to obtain the supply amount, an airgel having a particle size distribution in the range defined in the present invention can be obtained by pulverizing the material once pulverized several times.

  Since the airgel of the present invention has a structure with a dense network, it is presumed that it does not take pulverization energy and is not easily pulverized compared to hydrophilic wet silica generally used for adding paints. The

  As described above, the strength of the network structure of the airgel tends to be difficult to pulverize because the higher the pH during gel aging, the longer the aging time, and the higher the aging temperature, the stronger. Therefore, in order to obtain the airgel of the present invention, there is a tendency that the necessity of increasing the pulverization pressure / air volume or subjecting it to multiple pulverizations is high.

  In other words, the airgel of the present invention is less likely to be pulverized by this method of applying a strong force for a relatively short time, so that waste particles that do not contribute to matting are less likely to be generated by the pulverization process, and at the same time, the coating surface Coarse powder that deteriorates the smoothness of the material has good characteristics in two points that it is preferentially crushed.

  By such pulverization, pulverization is preferably performed until D50 becomes 2 to 5 μm.

  Of course, the above-described production method is an example, and the airgel of the present invention is not limited to the one obtained by the production method described above, and other known pulverization, pulverization, classification, etc. are appropriately selected and carried out. It may be manufactured.

  Due to its sharp particle size distribution, the airgel of the present invention can obtain good matting properties and surface smoothness when used as a matting agent as described above.

  When used as a matting agent, the airgel of the present invention is usually used after being dispersed in an organic resin.

  In the matte paint containing the matting agent and the organic resin in the present invention, any organic resin can be used. For example, according to the type of resin, conventional oil paints, nitrocellulose paints, alkyd resin paints, amino alkyd paints, vinyl resin paints, acrylic resin paints, epoxy resin paints, polyester resin paints, chlorinated rubber paints, etc. In addition to known paints, rosin, ester gum, pentaresin, coumarone / indene resin, phenolic resin, modified phenolic resin, maleic resin, alkyd resin, amino resin, vinyl resin, petroleum resin, epoxy resin Polyester resins, styrene resins, acrylic resins, silicone resins, rubber-based resins, chlorinated resins, urethane resins, polyamide resins, polyimide resins, fluorine resins, natural or synthetic lacquers, etc. Contains one or more Paint and the like. Moreover, the coating material to be used may be an arbitrary one such as a solvent-based coating material, an ultraviolet curable coating material, or a powder coating material, depending on how it is used.

  Examples of the organic solvent for the solvent-type paint include aromatic hydrocarbon solvents such as toluene and xylene; aliphatic hydrocarbon solvents such as n-heptane, n-hexane and isopar; alicyclic hydrocarbon solvents such as cyclohexane Ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; alcohol solvents such as ethanol, propanol, butanol and diacetone alcohol; ether solvents such as tetrahydrofuran and dioxane; cellosolv solvents such as ethyl cellosolve and butyl cellosolve; One type or two or more types of ester solvents such as ethyl acetate and butyl acetate; aprotic polar solvents such as dimethylformamide, dimethylacetamide and dimethylsulfoxide can be used.

  As the ultraviolet (UV) curable paint, a high solid resin such as UV curable acrylic resin, epoxy resin, vinyl urethane resin, acrylic urethane resin, polyester resin, or the like is used alone or in combination of two or more.

  Examples of powder coatings include polyamide resins, polyester resins, acrylic resins, olefin resins, cellulose derivatives, polyethers, vinyl chloride resins, and other thermoplastic resins, as well as epoxy resins, epoxy / novolak resins, isocyanates, or epoxy curable polyester resins. It is done.

  Although the addition amount in the resin of the matting agent in this invention can be added in arbitrary ratios, 1-90 mass parts with respect to 100 mass parts of organic resins, Preferably, 3-80 mass parts is suitable. Thereby, a high matte effect can be provided to the coating film surface with a small amount of blending. At the same time, it is presumed that the scratch resistance of the coating surface is also improved.

  EXAMPLES Hereinafter, examples will be shown to specifically describe the present invention, but the present invention is not limited to only these examples. In the following, the BET specific surface area, the pore volume by the BJH method, and the pore distribution by the BJH method were measured by BELSORP-max manufactured by Nippon Bell Co., Ltd.

  In addition, regarding the particle size distribution, the sample was added to Solmix A-7 (standard composition: ethanol 85.5%, propyl alcohol 9.6%, methanol 4.9%, water 0.2%) manufactured by Nippon Alcohol Sales Co., Ltd. Was added for 3 minutes with an ultrasonic cleaner B1510J-MT manufactured by Nippon Emerson Co., Ltd., and was used with a multisizer III manufactured by Beckman Coulter Co., Ltd. with an aperture tube of 50 μm. Regarding the dispersion time, it was confirmed that the D50 values did not change by 0.1 μm or more when the dispersion time was 1, 3, and 5 minutes.

  Moreover, in order to confirm the matting effect of a coating film, it confirmed by the method according to JISZ8741. Specifically, a glass plate having a refractive index of 1.567 was coated with a doctor blade (coating thickness: 3 MIL, manufactured by Kamishima Seisakusho Co., Ltd.) using a gloss meter (manufactured by NIPPON DENSHOKU, Gloss Meter). UG2000), and the glossiness (gloss value) at an incident angle of 60 degrees was evaluated. Further, smoothness was evaluated with a laser microscope (manufactured by Olympus Corporation, LEXT OLS4000) using an arithmetic average surface roughness (hereinafter referred to as Ra) defined in JIS B0601.

Example 1
No. 3 sodium silicate (JIS K1408) was diluted until the SiO ₂ concentration became 16.5 g / 100 mL, and this sodium silicate and sulfuric acid (9.5 g / 100 mL) were mixed and reacted at room temperature to obtain silica sol (SiO ₂ concentration 8%, pH 2) 1000 ml. To the silica sol, No. 3 sodium silicate diluted to a SiO ₂ concentration of 8% was added to obtain a pH of 5.8, followed by aging in a water bath at 40 ° C. for 90 minutes. Thereafter, the crushed gel was passed through a 2 mm net into a liquid column, and water was passed to a conductivity of 100 μS or less to wash the gel. Then, in a liquid flow column, the water concentration was replaced with ethanol to 0.2 wt% or less, and further, the ethanol concentration was replaced with toluene to 0.1 wt% or less.

  The obtained gel using toluene as a dispersion medium was placed in a 2000 ml glass container, 60 g of DMDCS was added, and the mixture was stirred at 60 ° C. for 6 hours. After the reaction, the gel was separated by suction filtration and dried at 120 ° C. under normal pressure and nitrogen atmosphere for 12 hours to obtain a crude airgel.

  The hydrophobicity of the crude airgel thus obtained was confirmed by placing 1 g of the airgel in a beaker of 100 mL of water, stirring for several tens of seconds, and then allowing it to stand to completely separate into an airgel phase and an aqueous phase.

The crude airgel was pulverized with a jet mill (manufactured by Seishin Enterprise Co., Ltd., STJ-100). At this time, the feed pressure and the mill pressure were both 0.1 MPa and 0.2 m ³ / min of compressed air, the feed rate of the bulk was 35 g / min, and 187 g / m ³ per unit air volume. An airgel (hereinafter, aerogel 1-A) having 12.6 μm and D10 / D90 of 0.21 was obtained.

The airgel 1-A was ground again with a jet mill. At this time, the feed pressure and the mill pressure were both 0.5 MPa and 0.9 m ³ / min of compressed air, the feed rate of the bulk was 24 g / min, and the unit air volume was 26 g / m ^3. An airgel (hereinafter aerogel 1-B) having 2.8 μm, D10 / D90 of 0.33, a specific surface area of 687 m ² / g, a pore volume of 5.29 mL / g and a pore radius peak of 29.5 nm was obtained. .

  Aerogel 1-B was added as a matting agent at a ratio of 3 parts by mass of matting agent to 100 parts by mass of urethane paint (RETAN PG80III, 388-026, manufactured by Kansai Paint Co., Ltd.).

  Thereafter, the mixture was stirred with a stirrer at 1000 rpm for 5 minutes, and then defoamed with a defoamer (IWAKI KM Shaker, Iwaki Sangyo, V-SX, 150 SPM) for 2 hours to obtain a matte paint.

  Thereafter, a matte paint was applied on the glass plate with an applicator (PI-1210 FILM COATER, manufactured by Tester Sangyo Co., Ltd.) and a doctor blade, dried at 20 ° C. for 20 minutes, and then dried at 60 ° C. for 20 minutes. .

  When the coating film thus obtained was evaluated, it had a gloss value of 14 and a Ra of 0.40 μm.

Example 2
The aging temperature at the time of aging of the silica gel was changed to 60 ° C., and a crude airgel was prepared in the same manner as in Example 1, but the specific surface area was 507 m ² / g, the pore volume was 5.14 mL / g, the pores A crude airgel having a radius peak of 25.5 nm was obtained.

  As a result of pulverizing the crude airgel by the same method as the pulverization of 1-A in Example 1, an aerogel having D50 of 12.6 μm and D10 / D90 of 0.21 (hereinafter referred to as “Aerogel 2-A”) was obtained.

The airgel 2-A is the same jet mill as in Example 1, the feed pressure and the mill pressure are both 0.64 MPa, compressed air of 1.2 m ³ / min, the supply amount of the original is 24 g / min, the unit air volume As a result of carrying out at 20 g / m ³ per unit, an airgel having D50 of 2.2 μm and D10 / D90 of 0.35 was obtained.

  When this airgel was evaluated in the same manner as in Example 1, the gloss value was 16 and Ra was 0.30 μm.

Example 3
The airgel 1-B obtained in Example 1 was further supplied with compressed air of 0.5 MPa and 0.9 m ³ / min for both feed pressure and mill pressure, the feed rate of the bulk was 20 g / min, and 21 g per unit air volume. / ^{m 3} with a result of performing, D50 is 2.5 [mu] m, D10 / D90 was obtained airgel 0.36. An airgel having a smaller D50 and a larger D10 / D90 as compared with Example 1 was obtained.

  When this airgel was evaluated in the same manner as in Example 1, the gloss value was 15 and the Ra was 0.38 μm.

Example 4
The airgel obtained in Example 3 was further supplied with both feed pressure and mill pressure of 0.5 MPa, compressed air of 0.9 m3 / min, the feed rate of the bulk was 18 g / min, and 19 g / m ³ per unit air volume. As a result, an airgel having D50 of 2.2 μm and D10 / D90 of 0.37 was obtained.

  An airgel having a smaller D50 and a larger D10 / D90 as compared with Example 3 was obtained.

  When this airgel was evaluated in the same manner as in Example 1, the gloss value was 17 and Ra was 0.31 μm.

Example 5
A rough airgel was produced in the same procedure as in Example 1 except that monomethyltrichlorosilane (hereinafter referred to as MTS) was used instead of DMDCS and the addition amount was 7 g with respect to 100 mL of the gel.

The airgel thus obtained had a specific surface area of 737 m ² / g, a pore volume of 4.09 mL / g, and a pore radius peak of 25.5 nm.

  The airgel was pulverized in the same manner as in Example 4 to obtain an airgel having a D50 of 2.3 μm and a D10 / D90 of 0.39.

  When this airgel was evaluated in the same manner as in Example 1, the gloss value was 22 and the Ra was 0.24 μm.

Example 6
When the crude airgel was produced in the same procedure as in Example 1 except that the aging time during silica gel aging was extended to 120 minutes, the specific surface area was 667 m ² / g, the pore volume was 4.38 mL / g, An airgel having a pore radius peak of 27.4 nm was obtained.

The airgel obtained in this way was the same jet mill as in Example 1, both feed pressure and mill pressure were 0.6 MPa, compressed air of 1.1 m ³ / min, and the feed rate of the bulk was 17 g / min, unit As a result of grinding twice at 15 g / m ³ per air volume, an airgel having D50 of 2.8 μm and D10 / D90 of 0.33 was obtained.

  When the airgel was evaluated in the same manner as in Example 1, the gloss value was 16 and Ra was 0.41 μm.

Example 7
The aging time at the time of aging of silica gel was shortened to 30 minutes, and other conditions were the same as in Example 1, and a crude airgel was prepared. The specific surface area was 790 m ² / g, the pore volume was 5.81 mL / g, The airgel having a pore radius peak of 22.1 nm was obtained.

  The airgel thus obtained was pulverized in the same procedure as in Example 6. As a result, an airgel having a D50 of 2.9 μm and a D10 / D90 of 0.33 was obtained.

  When this airgel was evaluated in the same manner as in Example 1, the gloss value was 12 and the Ra was 0.48 μm.

Example 8
When the aging time at the time of aging of the silica gel was shortened to 60 minutes and the other conditions were the same as in Example 1, a crude airgel was prepared. The specific surface area was 815 m ² / g, the pore volume was 5.19 mL / g, An airgel having a pore radius peak of 29.5 nm (hereinafter referred to as “Aerogel 8-A”) was obtained.

The airgel thus obtained was pulverized in the same procedure as in Example 6 except that the feed rate of the bulk was changed to 18 g / min and 16 g / m ³ per unit air volume. As a result, D50 was 2.6 μm, D10 / An airgel having a D90 of 0.37 was obtained.

  When this airgel was evaluated in the same manner as in Example 1, the gloss value was 13 and the Ra was 0.40 μm.

Example 9
The airgel 8-A was fed by the same jet mill as in Example 1, using both feed pressure and mill pressure of 0.35 MPa, compressed air of 0.7 m ³ / g, and the feed rate of the bulk was 18 g / min per unit air volume of 27 g. As a result of grinding once at / m ³ , an airgel having a D50 of 3.9 μm and a D10 / D90 of 0.30 was obtained.

  When this airgel was evaluated in the same manner as in Example 1, the gloss value was 12 and Ra was 0.65 μm.

Comparative Example 1
When airgel 2-A produced in Example 2 was classified using a classifier (manufactured by Eurus Techno Co., Ltd., Microcut 400H type) instead of pulverizing again with a jet mill, D50 was 2.7 μm and D10 / D90. An aerogel of 0.23 was obtained. According to the above procedure, an airgel having D50 equivalent to that of Example 1 but small D10 / D90 was obtained.

  When this airgel was evaluated in the same manner as in Example 1, the gloss value was 22 and the Ra was 0.54 μm.

Comparative Example 2
The surface of Tokuyama Co., Ltd. Fine Seal E-50 was treated with silicone oil to produce hydrophobic silica. The silica thus obtained had a specific surface area of 160 m ² / g, a pore volume of 1.30 mL / g, and no pore radius peak was observed. This hydrophobic silica was pulverized once at a feed pressure and a mill pressure of 0.4 MPa, compressed air of 0.8 m ³ / min, the feed rate of the bulk was 24 g / min, and 32 g / m 3 per unit air volume. A hydrophobic silica having a D50 of 2.3 μm and a D10 / D90 of 0.34 was obtained.

  When this hydrophobic silica was evaluated in the same manner as in Example 1, the gloss value was 58 and Ra was 0.19 μm.

Comparative Example 3
The airgel 1-A of Example 1 is the same jet mill as that of Example 1. The feed pressure and the mill pressure are both 0.4 MPa and 0.8 m ³ / min of compressed air. As a result of grinding once at 35 g / m ³ per unit air volume for min, an airgel having a D50 of 3.2 μm and a D10 / D90 of 0.28 was obtained.

  When this airgel was evaluated in the same manner as in Example 1, the gloss value was 12 and Ra was 0.70 μm.

Comparative Example 4
In the jet mill using the airgel 8-A of Example 8 in Example 1, the feed pressure and the mill pressure are both 0.3 MPa and 0.6 m ³ / g of compressed air, and the supply amount of the raw material is 18 g / As a result of pulverization at 32 g / m ³ per unit air volume, an airgel having a D50 of 5.5 μm and a D10 / D90 of 0.24 was obtained.

  When this airgel was evaluated in the same manner as in Example 1, the gloss value was 12 and the Ra was 1.33 μm.

Comparative Example 5
The pH at the time of gelation was changed to 5.5, and the other conditions were the same as in Example 1 to produce a crude aerogel. The specific surface area was 783 m ² / g, and the pore volume was 5.76 mL / g. An airgel having a pore radius peak of 22.1 nm was obtained.

The airgel thus obtained was a jet mill different from Example 1 (CO-JETSYSTEMα-mkIII, manufactured by Seishin Enterprise Co., Ltd.), both feed pressure and mill pressure were 0.6 MPa, using compressed air of 0.3 m ³ / min, As a result of pulverization at a feed rate of 1 g / min and 3 g / m ³ per unit air volume, an airgel having a D50 of 8.1 μm and a D10 / D90 of 0.15 was obtained.

  When this airgel was evaluated in the same manner as in Example 1, the gloss value was 16 and Ra was 4.37 μm.

Comparative Example 6
50 g of the airgel 1-A produced in Example 1 was dispersed and mixed in 5000 mL of toluene to prepare a slurry. The slurry was pulverized at 140 MPa using a wet atomizer (Utimaizer System, manufactured by Sugino Machine Co., Ltd.) and dried at 120 ° C. for 12 hours. As a result, D50 was 2.5 μm and D10 / D90 was 0.25 aerogel. Got.

  When this airgel was evaluated in the same manner as in Example 1, the gloss value was 16 and the Ra was 1.53 μm.

Comparative Example 7
The air pressure was changed to 100 MPa and the other conditions were the same as in Comparative Example 6. As a result, an airgel with D50 of 2.9 μm and D10 / D90 of 0.25 was obtained.

  When this airgel was evaluated in the same manner as in Example 1, the gloss value was 26 and the Ra was 1.61 μm.

Comparative Example 8
5 g of the airgel 8-A of Example 8 is put into a ball mill (ZR-P pot mill Type: A-5, manufactured by Nippon Chemical Ceramics Co., Ltd.), and alumina spheres having a diameter of 15 mm are about 17% of the mill container. It was thrown up.

Then, as a result of grinding for 1 hour at 85 rpm, the specific surface area and pore volume decreased, the specific surface area was 670 m ² / g, the pore volume was 1.08 mL / g, and the peak of the pore radius Was not seen, and an airgel having D50 of 5.6 μm and D10 / D90 of 0.12 was obtained.

  When this airgel was evaluated in the same manner as in Example 1, the gloss value was 85.

  Table 1 below shows the airgel production conditions, and Table 2 summarizes the results obtained.

Claims (6)

Formula (I)
R _n SiX _4-n
(However, R is a hydrocarbon group, X is an alkoxy group or halogen, and n is an integer of 1 to 3)
Or a structure represented by the general formula (II)
R ₃ SiNHSiR ₃
(However, R is the same as above)
An airgel hydrophobized with a treating agent having a structure represented by:
D10 and D90 having a specific surface area by BET method of 400 to 1000 m ² / g, pore volume and pore radius peaks by BJH method of 3 to 8 mL / g and 10 to 40 nm, respectively, and measured by Coulter counter method The ratio (D10 / D90) is 0.3 to 0.5 (where D10 represents a particle size having a frequency of 10% from the smaller particle size of the volume-based cumulative particle size distribution curve, and D90 is 90% of the same). Represents the particle size of the frequency value)
The airgel characterized by being.   The airgel according to claim 1, wherein the surface treatment agent has a structure represented by the general formula (I).   The airgel according to claim 2, wherein the surface treatment agent having a structure represented by the general formula (I) is dimethyldichlorosilane.   D50 is 2-5 micrometers, The airgel as described in any one of Claims 1-3.   A matting agent comprising the airgel according to any one of claims 1 to 4.   A matting paint comprising the matting agent according to claim 5 and an organic resin.

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