JP5110297B2 - Method for producing hydrophilic coating agent and article coated with the coating agent - Google Patents

Description

  The present invention relates to a method for producing a hydrophilic coating agent and an article having a coating surface excellent in hydrophilicity obtained by applying the obtained hydrophilic coating agent.

  Conventionally, many attempts have been made to prevent soiling of a base material by forming a hydrophilic film on the surface of the base material. For example, in a low-contamination paint used on the outer wall of a building, a partially hydrolyzed condensate of alkyl silicate is blended into the paint, applied to the outer wall surface, and dried to form a hydrophilic film. The hydrolyzed condensate component moves to the coating surface, the silicon concentration on the surface increases, and the alkoxy group of the partially hydrolyzed condensate is further hydrolyzed by rainfall to produce a hydrophilic silanol group, resulting in the outer wall surface There has been proposed a method in which familiarity between water and water is improved, and dirt adhering to each time it rains is washed away (Patent Document 1: JP-A-9-137120, Patent Document 2: JP-A-9-249732, etc.) reference).

  On the other hand, in place of the partial hydrolysis condensate of alkyl silicate, many attempts have been made to further improve the contamination resistance by using a fully hydrolyzed alkyl silicate condensate obtained by further hydrolysis, or by adding silica sol. (Patent Documents 3 to 8: JP 2007-245369 A, WO 99/52986 pamphlet, JP 2006-176635 A, JP 2000-119596 A, JP 2004-28784 A JP, 10-142161, A). However, although this attempt also has good initial stain resistance (hydrophilicity), the stain resistance (hydrophilicity) often deteriorates with time. Further, the storage stability of the coating liquid itself is not so good, and an improvement thereof has been desired.

JP-A-9-137120 JP-A-9-249732 JP 2007-245369 A International Publication No. 99/52986 Pamphlet JP 2006-176635 A JP 2000-119596 A JP 2004-287846 A JP-A-10-142161

  The present invention has been made in view of the above circumstances, and is capable of easily forming a hydrophilic coating film excellent in initial hydrophilicity and excellent in its sustainability. Further, the coating agent itself has good storage stability. It is an object of the present invention to provide an article coated with an excellent hydrophilic coating film by applying a coating method of the adhesive coating agent and the coating agent.

  As a result of intensive studies to achieve the above object, the present inventor has found that in the presence of a solid catalyst insoluble in the system in a solvent containing water in an amount such that the amount of water is 2 mol or more per 1 mol of silicate. Hydrolysis, then adding a metal oxide sol solution to the resulting silicate hydrolyzate solution, further hydrolyzing and condensing, it is easy to impart hydrophilicity from the beginning and further maintain the hydrophilicity. It was found that a hydrophilic coating agent excellent in the storage stability of the coating solution and having good storage stability was obtained, and the present invention was made.

Therefore, this invention provides the manufacturing method of the following hydrophilic coating agent, and the articles | goods which apply | coated this coating agent.
[Claim 1]
(1) (A) General formula: Si (OR ¹ ) ₄ (wherein R ¹ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms), an acidic solid insoluble in the system In the presence of a cation exchange resin catalyst, (A) hydrolysis is carried out in a solvent containing water in an amount of 4 to 40 mol with respect to 1 mol, and (2) the resulting silicate A method for producing a hydrophilic coating agent, comprising adding (B) a metal oxide sol solution to a hydrolyzate solution, followed by hydrolysis and condensation.
[ Claim 2 ]
The method for producing a hydrophilic coating agent according to claim 1, wherein the solvent comprises water or water of 50% by mass of the solvent composition and an organic solvent.
[Claim 3 ]
(B) The method for producing a hydrophilic coating agent according to claim 1, wherein the metal oxide sol of the metal oxide sol solution is a silica sol.
[ Claim 4 ]
The amount of the cation exchange resin used is 0.1 to 20% by mass relative to the total amount of the silica equivalent of the silicate (A) and the solid content of the metal oxide sol (B). The manufacturing method of the hydrophilic coating agent of any one of Claims 1.
[ Claim 5 ]
The amount of the metal oxide sol (B) is determined by the solid content mass of the metal oxide sol (B) / (silica equivalent mass of the silicate (A) + solid content mass of the metal oxide sol (B)). Is 0.1-0.95, The manufacturing method of the hydrophilic coating agent of any one of Claims 1-4.
[Claim 6 ]
The active ingredient concentration of the solid content derived from the silicate and the solid content derived from the metal oxide sol in the obtained hydrophilic coating agent is 0.1 to 30% by mass, the solvent is 99.9 to 70% by mass, the solvent is water and It consists of a hydrophilic solvent, The manufacturing method of the hydrophilic coating agent of any one of Claims 1-5 characterized by the above-mentioned.
[Claim 7 ]
An article excellent in surface hydrophilicity coated with a hydrophilic coating agent obtained by the production method according to any one of claims 1 to 6 .

  According to the present invention, it is possible to easily form a hydrophilic coating film excellent in initial hydrophilicity and excellent in its sustainability, and further to produce a hydrophilic coating agent having good storage stability of the coating agent itself. By applying the coating agent, an article coated with an excellent hydrophilic coating film can be obtained.

Method for producing a hydrophilic coating agent of the present invention, (1) (A) the general formula: Si (OR ¹⁾ ₄ (wherein, R ¹ represents a hydrogen atom or a carbon number of 1 to 4 alkyl group.) Is hydrolyzed in a solvent containing an amount of water such that the amount of water is 2 mol or more per 1 mol of (A) in the presence of a solid catalyst insoluble in the system, (2) The resulting silicate hydrolyzate solution is obtained by adding (B) a metal oxide sol solution, followed by hydrolysis and condensation.

In the production method of the present invention, the silicate of component (A) is represented by the general formula: Si (OR ¹ ) ₄ . In the above formula, R ¹ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and specific examples thereof include a hydrogen atom, a methyl group, an ethyl group, a propyl group, and a butyl group. Alkyl groups having a smaller number have a faster hydrolysis rate of the component (A) and tend to easily generate a silanol group. Therefore, a methyl group and an ethyl group are preferred.

  Such silicates of component (A) are generally commercially available as orthosilicates, and specific examples thereof include methyl orthosilicate, ethyl orthosilicate, and isopropyl orthosilicate, and these two or more types should be used in combination. However, as described above, since methyl silicate having an alkyl group having a small number of carbon atoms has a higher hydrolysis rate and tends to easily generate a silanol group, methyl orthosilicate, ethyl ortho It is preferably a silicate.

  In the production method of the present invention, 2 mol or more of water is first added to 1 mol of silicate (A). In this case, the number of moles of all alkoxy groups is 0.5 times or more. When the number of moles of water is 0.5 times, the hydrolysis rate corresponds to 100%. By adding more water and hydrolyzing, the proportion of silanol groups contributing to hydrophilicity is increased. be able to. Accordingly, the amount of water is 2 mol or more, preferably 2 to 100 mol, more preferably 4 to 40 mol, and particularly 6 to 20 mol relative to 1 mol of (A). When this amount is less than 2 mol, hydrophilicity does not appear from the beginning.

  In this case, the solvent may be only the above water, but other organic solvents may be used in combination. Alcohol-based, ketone-based and ester-based solvents are preferable, and alcohol-based solvents are particularly preferable. Of the alcohol solvents, a lower alcohol is particularly preferred. It does not specifically limit as a lower alcohol, For example, methyl alcohol, ethyl alcohol, i-propyl alcohol, n-propyl alcohol is mentioned, Preferably methyl alcohol and ethyl alcohol are mentioned.

  The amount of the organic solvent used in this case is preferably small because the organic solvent volatilizes and causes environmental problems, and is preferably 50% by mass or more, particularly 60% by mass or more of the solvent composition. In addition, it is possible to use a water-soluble organic solvent other than the alcohol solvent in combination as long as the object of the present invention is not impaired.

  The catalyst used at this time is not particularly limited as long as it is a solid catalyst insoluble in the system, but is preferably an acidic solid catalyst. By making the catalyst component insoluble in the system, the storage stability of the obtained hydrophilic coating agent is remarkably enhanced, and the hydrophilicity of the hydrophilic film obtained by applying the hydrophilic coating agent to the substrate is further increased. The sustainability of can be significantly improved. Here, the solid catalyst insoluble in the system used is particularly limited as long as the catalyst component is insoluble in any of silicate (A), metal oxide sol (B), water, reaction product and solvent. Is not to be done.

  Specific examples of such a solid catalyst include the following, but are not limited thereto.

Cation exchange resin : Amberlite 15, Amberlite 200C, Amberlist 15 (above, manufactured by Rohm and Haas), Purolite CT-175, CT-171, CT-169 (above, manufactured by Purolite), Dowex MWC-1-H, Dowex 88, Dowex HCR-W2 (above, manufactured by Dow Chemical Co., Ltd.), Levacit SPC-108, Levacit SPC-118 (above, manufactured by Bayer), Diaion RCP-150H (Mitsubishi Kasei) , Sumikaion KC-470, Duolite C26-C, Duolite C-433, Duolite-464 (above, manufactured by Sumitomo Chemical Co., Ltd.), Nafion-H (manufactured by DuPont), and the like.

Inorganic solids in which a group containing a proton acid group is bonded to the surface : Zr (O ₃ PCH ₂ CH ₂ SO ₃ H) ₂ , Th (O ₃ PCH ₂ CH ₂ COOH) ₂ or the like.

Clay minerals : acid clay, activated clay, montmorillonite, kaolinite, etc.

  Among these, activated clay is preferable from the viewpoint of price, cation exchange resin is preferable from the viewpoint of ease of handling, and cation exchange resin is particularly preferable.

  Although the usage-amount of the solid catalyst at this time is not specifically limited, It is 0.1-20 mass% with respect to the total amount of the silica conversion amount of a silicate (A), and the solid content of the metal oxide sol (B) mentioned later. Preferably there is. More preferably, it is 0.2-10 mass%. If this amount is less than 0.1% by mass, the hydrolysis of the silicate (A) and the condensation of the silicate (A) hydrolyzate with the metal oxide sol (B) may not be successful. Moreover, it is not preferable in terms of cost that this amount exceeds 20% by mass.

  In the production method of the present invention, the reaction temperature during hydrolysis of the silicate (A) is not particularly limited, but for example, the reaction temperature is preferably 10 to 60 ° C. The reaction time is not particularly limited, but is preferably about 1 to 6 hours.

  Subsequently, in the production method of the present invention, the metal oxide sol solution (B) is added to the hydrolyzate solution of the silicate (A) obtained by the hydrolysis reaction, and a hydrolysis condensation reaction is further performed. This metal oxide sol (B) contributes to improving the smoothness and crack resistance by increasing the effect of imparting hydrophilicity and increasing the hardness of the coating film formed on the substrate. Further, although the detailed mechanism is unknown, it seems that the hydrolyzed condensation of this metal oxide sol (B) is more effective in maintaining hydrophilicity than the hydrolyzate of silicate (A) alone. .

There is no particular limitation on the metal oxide sol (B), for example, CeO _2, SiO _{2 (silica), TiO 2, ZrO 2,} SnO 2, PZT, Y 2 O 3, TIO 2, In 2 O ₃ , ITO, α-AL ₂ O ₃ , HAP, Fe ₂ O ₃ , Fe ₃ O ₄ , ZnO, BaTiO ₃ , MgF ₂ , TiN, Sb ₂ O ₃ , CaF ₂ , CeO ₂ , CeF ₃ , Na ₃ Sols such as ALF ₆ , La ₂ O ₃ , LaF ₃ , PbF ₂ , NdF ₃ , Pr ₅ O ₁₁ , SiO, ThO ₂ , ThF ₄ and ZnS can be used. Silica sol, alumina sol, cerium oxide sol and the like are preferable. More preferred is silica sol.

  The silica sol is not particularly limited. For example, a water-dispersible or non-aqueous organic solvent-dispersible silica sol such as alcohol can be used. The water-dispersible silica sol is usually made from water glass, but can be easily obtained as a commercial product. The organic solvent-dispersible silica sol can be easily prepared by replacing the water of the water-dispersible silica sol with an organic solvent. Such an organic solvent-dispersible silica sol can be easily obtained as a commercial product in the same manner as the water-dispersible silica sol. In general, such a silica sol contains 20 to 50% by mass of silica as a solid content, and the amount of silica can be determined from this value.

  The average particle size of the metal oxide sol is preferably 0.1 to 100 nm, more preferably 1 to 50 nm, and particularly preferably 5 to 20 nm. If the average particle size is too small, it may be difficult to obtain, and if it is too large, the transparency of the resulting film may be reduced.

  In the organic solvent-dispersible silica sol, the type of the organic solvent in which the silica sol is dispersed is not particularly limited. For example, lower aliphatic alcohols such as methanol, ethanol, isopropanol, n-butanol, and isobutanol; ethylene glycol, Examples include ethylene glycol derivatives such as ethylene glycol monobutyl ether and ethylene glycol monoethyl ether; diethylene glycol derivatives such as diethylene glycol and diethylene glycol monobutyl ether; and diacetone alcohol. One or two selected from the group consisting of these More than species can be used.

  The compounding amount of the metal oxide sol (B) is not particularly limited, but the solid content mass of the metal oxide sol (B) / (the silica equivalent mass of the silicate (A) + the solid content of the metal oxide sol (B). The value obtained by (partial mass) is preferably in the range of 0.1 to 0.95, and more preferably in the range of 0.2 to 0.7.

  In the present invention, the metal oxide sol (B) is added to the hydrolyzate solution of the silicate (A) and then further subjected to a hydrolytic condensation reaction. The reaction conditions are such that the hydrolytic condensation reaction proceeds sufficiently, For example, the reaction temperature can be 10 to 60 ° C., and the reaction time can be 1 to 8 hours.

  A hydrophilic coating agent is obtained by the above reaction. It is desirable from the viewpoint of storage stability that the active ingredient concentration of the solid content derived from the silicate and the solid content derived from the metal oxide sol in the manufactured hydrophilic coating agent is adjusted to 0.1 to 30% by mass. More preferably, it is 1.0-15 mass%. When this amount exceeds 30% by mass, the storage stability of the coating agent may deteriorate. Further, if the amount is less than 0.1% by mass, the amount of active ingredient is dilute, so that sufficient performance tends not to be obtained even when coating.

  The amount of the solvent at this time is 99.9 to 70% by mass. The solvent is preferably composed of water and a hydrophilic solvent. In particular, the coating may be carried out by changing the amount ratio of water and organic solvent depending on the substrate. In the case of an organic resin base material, if the amount of water is large, the coating agent may be repelled and coating may not be performed well.

The hydrophilic coating agent further includes, for example, a polyol, a curing catalyst, a filler, a photocatalyst, a colorant, a film forming aid, a coating aid, and an antioxidant for the purpose of modifying the surface of the substrate and improving the coating film function. You may contain additives, such as a material, a ultraviolet absorber, a electrically conductive agent, and an antistatic agent.
In particular, a polyol is preferable because it has a high effect of improving hydrophilicity and antifogging functions, and when the polyol is water-absorbing, the antifogging, drip-proof and dew condensation effects are dramatically improved. Although it does not specifically limit as this polyol, For example, polyethylene glycol, polypropylene glycol, polycarbonate polyol, polycaprolactone polyol, polyglycerin, polyvinyl alcohol, etc. can be used, but monolauric acid decaglyceryl, monostearic acid polyglyceryl is especially used. Water-absorbing polyols such as polyglyceryl decastearate and polyglyceryl dekaoleate are preferred.

  A synthetic resin may be added for the purpose of suppressing the generation of interference fringes of light, further improving the adhesion to the substrate, improving the viscosity for improving workability, ensuring the film thickness, and the like. Synthetic resins include, for example, water-soluble acrylic resins, polyacrylamide, polyvinyl alcohol, polyvinyl pyrrolidone, casein, cellulose derivatives, dextrins, and other water-soluble resins such as acrylic resins, polyurethane resins, and styrene-butadiene. Examples include water-insoluble resins such as copolymer resins, vinyl acetate resins, ethylene-vinyl acetate copolymer resins, silicone resins, polybutene resins, water-soluble resins as aqueous solutions, and water-insoluble resins. The aqueous emulsion is preferably added to the dispersion. Among them, polyvinyl alcohol, acrylic resins such as a copolymer of acrylic acid or a derivative thereof and styrene, an acrylic-modified urethane resin, and the like are preferable, and polyvinyl alcohol having a saponification degree of 99% or more is particularly preferable. Specific examples include polyvinyl alcohol “GOHSENOL N300” manufactured by Nippon Gosei Co., Ltd.

  Moreover, in order to improve wettability, you may add a commercially available leveling agent, a surface tension reducing agent, etc. Examples include ordinary polyether compounds and polyether-modified silicones.

  By applying the hydrophilic coating agent to a substrate and drying, a surface excellent in hydrophilicity is obtained. In this case, the contact angle of water is preferably 40 ° or less, more preferably 30 ° or less. . The hydrophilic coating agent of the present invention has a hydrophilic sustainability such that the contact angle of water is 40 ° or less even after one month at 60 ° C. even if the coating film is subjected to a deterioration promotion test by heat. It is.

  When applying the hydrophilic coating agent of this invention, a base material can use various base materials regardless of inorganic and organic, and it is not specifically limited. For example, it can be used for metal base materials, glass base materials, enamel base materials, water glass decorative boards, inorganic building materials made of inorganic cured bodies, inorganic base materials such as ceramics, and organic base materials such as polycarbonate resins, acrylic resins, and PET resins. .

Furthermore, at least one layer of an inorganic coating film, at least one layer of an organic coating film, and a coated substrate having the inorganic coating film and the organic coating film can also be used on the surface of these substrates.
Although it does not specifically limit as an inorganic substance coating film which comprises the said coating base material, For example, the cured coating film of the coating agent containing inorganic resins, such as a silicone resin type and a polysilazane type, is mentioned. In addition, the organic coating film constituting the coating substrate is not particularly limited, but for example, acrylic, polyester, epoxy, urethane, acrylic silicone, chlorinated rubber, phenol, melamine, fluorine Examples thereof include a cured coating film of a coating agent containing an organic resin such as.

  The method for applying the hydrophilic coating agent of the present invention to a substrate is not particularly limited. For example, various usual coating methods such as spray coating, brush coating, dipping (also referred to as dipping or dip coating), roll coating, flow coating, curtain coating, knife coating, spin coating, and bar coating can be appropriately selected. . Among the examples described above, spray coating, flow coating, brush coating, a method of spreading an absorbent by impregnating with a liquid, etc. are preferable because they can be applied in a complicated shape and a large area.

  The thickness of the hydrophilic coating agent coating film formed on the surface of the substrate is not particularly limited. The thickness is generally about 0.03 to 10 μm, but if it is a thick film, a problem may occur in crack resistance depending on the base material, and in that case, 0.05 to 1 μm. Preferably, the thickness is 0.1 to 0.7 μm.

  In addition, what is necessary is just to use a well-known method about the hardening method of the hydrophilic coating agent coating film apply | coated to the base material, and there is no limitation in particular. Further, the temperature at the time of curing is not particularly limited, and a wide temperature range from normal temperature to heating temperature can be taken depending on the desired cured coating film performance and the presence or absence of the use of a curing catalyst.

  The use of such a coated article of the present invention is not particularly limited. For example, construction-related members, painted steel sheets for construction, automobile bodies, railway bodies, aircraft, ships, architectural glass, displays, clears. Examples include cases, doors, carports, switchboards, road peripheral members (for example, soundproof walls, tunnel interior plates, guardrails), advertising towers, mirrors, and organic resin films.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example. In addition, in the following example,% shows the mass%.

[Example 1]
In a 1 liter four-necked flask equipped with a dropping tube with a straight tube, a serpentine condenser and a thermometer, 152 g (1.0 mol) of normal methyl silicate, 0.3 g of ion exchange resin solid catalyst Purolite CT-169 and ion exchange water 304 g was added and nitrogen was passed through the system at a very small flow rate while stirring. The solution was allowed to stir in this state. After 30 minutes, the internal temperature rose to 36 ° C., and the heterogeneous solution became a homogeneous solution. The mixture was further stirred for 1.5 hours from this state to allow hydrolysis to proceed.
Thereafter, 200 g of methanol-dispersed silica sol (solid content concentration 30%, average particle size 10 to 20 nm) (silica solid content 60 g) was added from a dropping pipe with a straight pipe, and further reacted at a liquid temperature of 20 ° C. for 3 hours. The reaction solution was filtered through a filter paper to remove the solid catalyst, and 604 g of a pale white transparent solution was obtained. The solid content concentration of this product was 21.9%. This was diluted with isopropyl alcohol to a solid content concentration of 3% to obtain hydrophilic coating agent 1. When this coating agent solution was hermetically stored in a high-density polyethylene wide-mouth bottle at room temperature, the viscosity of the solution did not change even after 3 months.

[Example 2]
The reaction and operation were performed in the same manner as in Example 1 except that 76 g of normal methyl silicate and 152 g of ion-exchanged water were used in Example 1, to obtain 285 g of a pale white transparent solution. The solid content concentration of this product was 25.9%. This was diluted with isopropyl alcohol to a solid content concentration of 3% to obtain hydrophilic coating agent 2. When this coating agent solution was hermetically stored in a high-density polyethylene wide-mouth bottle at room temperature, the viscosity of the solution did not change even after 3 months.

[Example 3]
The reaction and operation were carried out in the same manner as in Example 1 except that 100 g of the methanol-dispersed silica sol of Example 1 was obtained to obtain 503 g of a pale white transparent solution. The solid content concentration of this product was 16.8%. This was diluted with isopropyl alcohol to a solid content concentration of 3% to obtain hydrophilic coating agent 3. When this coating agent solution was hermetically stored in a high-density polyethylene wide-mouth bottle at room temperature, the viscosity of the solution did not change even after 3 months.

[Example 4]
Except that the methanol-dispersed silica sol of Example 1 was changed to 300 g of water-dispersed silica sol (silica solid content concentration 20%, average particle size 10 to 20 nm), the reaction and operation were performed in the same manner as in Example 1 to obtain 732 g of a pale blue-white transparent solution. Obtained. The solid content concentration of this product was 16.3%. This was diluted with isopropyl alcohol to a solid content concentration of 3% to obtain hydrophilic coating agent 4. When this coating agent solution was hermetically stored in a high-density polyethylene wide-mouth bottle at room temperature, the viscosity of the solution did not change even after 3 months.

[Example 5]
The reaction and operation were carried out in the same manner as in Example 1 except that the methanol-dispersed silica sol of Example 1 was changed to 300 g of water-dispersed alumina sol (alumina solid content concentration 20%) to obtain 721 g of a white translucent solution. The solid content concentration of this product was 16.6%. This was diluted with isopropyl alcohol to a solid content concentration of 3% to obtain hydrophilic coating agent 5. When this coating agent solution was hermetically stored in a high-density polyethylene wide-mouth bottle at room temperature, the viscosity of the solution did not change even after 3 months.

[Example 6]
The reaction and operation were performed in the same manner as in Example 1 except that the methanol-dispersed silica sol of Example 1 was changed to 600 g of water-dispersed cerium oxide sol (cerium oxide solid content concentration 10%) to obtain 1006 g of a yellow translucent solution. The solid content concentration of this product was 11.9%. This was diluted with isopropyl alcohol to a solid content concentration of 3% to obtain hydrophilic coating agent 6. When this coating agent solution was hermetically stored in a high-density polyethylene wide-mouth bottle at room temperature, the viscosity of the solution did not change even after 3 months.

[Comparative Example 1]
In a 1 liter four-necked flask equipped with a dropping tube with a straight tube, a serpentine condenser and a thermometer, 152 g (1.0 mol) of normal methyl silicate, 0.3 g of ion exchange resin solid catalyst Purolite CT-169 and ion exchange water 304 g was added and nitrogen was passed through the system at a very small flow rate while stirring. The solution was allowed to stir in this state. After 30 minutes, the internal temperature rose to 35 ° C., and the heterogeneous solution became a homogeneous solution. The mixture was further stirred for 1.5 hours from this state to allow hydrolysis to proceed.
Here, the solution was once filtered to remove the solid catalyst in the system. To this solution, 200 g of methanol-dispersed silica sol (solid content concentration 30%, average particle size 10 to 20 nm) (silica solid content 60 g) was simply mixed. 650 g of a pale white transparent solution was obtained. The solid content concentration of this product was 18.4%. This was diluted with isopropyl alcohol to a solid content concentration of 3% to obtain hydrophilic coating agent 7. When this coating agent solution was hermetically stored at room temperature in a high-density polyethylene wide-mouth bottle, it gelled when one month had passed.

[Comparative Example 2]
In a 1-liter four-necked flask equipped with a dropping tube with a straight tube, a serpentine condenser and a thermometer, 152 g (1.0 mol) of normal methyl silicate, 0.3 g of ion-exchange resin solid catalyst Purolite CT-169, ion-exchanged water 27 g and 277 g of methanol were added, and nitrogen was passed through the system at a very small flow rate while stirring. In this state, the solution was stirred at room temperature for 2 hours to allow hydrolysis to proceed. Thereafter, 200 g of methanol-dispersed silica sol (solid content concentration 30%, average particle size 10 to 20 nm) (silica solid content 60 g) was added from a dropping tube with a straight tube, and further reacted at a liquid temperature of 20 ° C. for 3 hours. The reaction solution was filtered through a filter paper to remove the solid catalyst, thereby obtaining 623 g of a pale white transparent solution. The solid content concentration of this product was 19.2%. This was diluted with isopropyl alcohol to a solid content concentration of 3% to obtain hydrophilic coating agent 8. When this coating agent solution was hermetically stored in a high-density polyethylene wide-mouth bottle at room temperature, the viscosity of the solution did not change even after 1 month.

[Comparative Example 3]
To a 1 liter four-necked flask equipped with a dropping tube with a straight tube, a serpentine condenser and a thermometer, 152 g (1.0 mol) of normal methyl silicate and 304 g of 0.05N hydrochloric acid water were added, and the system was stirred. Nitrogen was passed at a very small flow rate. When the solution was stirred in this state, the internal temperature immediately increased to 42 ° C., and the heterogeneous solution became a homogeneous solution. From this state, the mixture was further stirred for 2 hours to allow hydrolysis to proceed. Thereafter, 200 g of methanol-dispersed silica sol (solid content concentration of 30%, average particle size of 10 to 20 nm) (silica solid content of 60 g) is added from a dropping pipe with a straight pipe, and further reacted at a liquid temperature of 20 ° C. for 3 hours, 631 g of a clear solution was obtained. The solid content concentration of this product was 21.9%. This was diluted with isopropyl alcohol to a solid content concentration of 3% to obtain hydrophilic coating agent 9. When this coating agent solution was stored tightly in a high-density polyethylene wide-mouth bottle at room temperature, it gelled when 2 weeks passed.

[Comparative Example 4]
76 g (0.5 mol) of normal methyl silicate and 424 g of 0.4% ammonia water were added to a 1 liter four-necked flask equipped with a dropping tube with a straight tube, a serpentine condenser and a thermometer, and the system was stirred while stirring. Nitrogen was passed at a very small flow rate. When the solution was stirred in this state, the internal temperature immediately increased to 37 ° C., and the heterogeneous solution became a homogeneous solution. From this state, the mixture was further stirred for 2 hours to allow hydrolysis to proceed. Thereafter, 150 g of water-dispersed basic silica sol (solid content concentration 20%) (silica solid content 30 g) was added from a dropping tube with a straight pipe, and further reacted at a liquid temperature of 20 ° C. for 3 hours to obtain 649 g of a blue-white transparent solution. Obtained. The solid content concentration of this product was 9.9%. This was diluted with isopropyl alcohol to a solid content concentration of 3% to obtain hydrophilic coating agent 10. When this coating agent solution was stored tightly in a high-density polyethylene wide-mouth bottle at room temperature, it gelled when 2 weeks passed.

[Comparative Example 5]
To a 1 liter four-necked flask equipped with a dropping tube with a straight tube, a serpentine condenser and a thermometer, 152 g (1.0 mol) of normal methyl silicate and 304 g of 0.05N hydrochloric acid water were added, and the system was stirred. Nitrogen was passed at a very small flow rate. When the solution was stirred in this state, the internal temperature immediately increased to 42 ° C., and the heterogeneous solution became a homogeneous solution. From this state, the mixture was further stirred for 2 hours to allow hydrolysis to proceed. 453 g of a colorless transparent solution was obtained. The solid content concentration of this product was 13.2%. This was diluted with isopropyl alcohol to a solid content concentration of 3% to obtain hydrophilic coating agent 11. When this coating agent solution was stored tightly in a high-density polyethylene wide-mouth bottle at room temperature, it gelled when 2 weeks passed.

[Comparative Example 6]
76 g (0.5 mol) of normal methyl silicate and 424 g of 0.4% ammonia water were added to a 1 liter four-necked flask equipped with a dropping tube with a straight tube, a serpentine condenser and a thermometer, and the system was stirred while stirring. Nitrogen was passed at a very small flow rate. When the solution was stirred in this state, the internal temperature immediately increased to 37 ° C., and the heterogeneous solution became a homogeneous solution. From this state, the mixture was further stirred for 2 hours to allow hydrolysis to proceed. 497 g of a colorless transparent solution was obtained. The solid content concentration of this product was 6.0%. This was diluted with isopropyl alcohol to a solid content concentration of 3% to obtain hydrophilic coating agent 12. When this coating agent solution was stored tightly in a high-density polyethylene wide-mouth bottle at room temperature, it gelled when 2 weeks passed.

  Using the hydrophilic coating agents of the above Examples and Comparative Examples, a coating film was formed by the following forming method, and adhesion, surface hydrophilicity, and storage stability of the paint were evaluated by the following evaluation methods.

(Formation method of coating film)
A slide glass washed with ion-exchanged water and acetone was used as a substrate, and the hydrophilic coating agent was applied by a dip method (10-second immersion, lifting speed 85 mm / min). The cure was dried at room temperature for 1 hour, followed by curing at 80 ° C. for 30 minutes to form a hydrophilic film.

(Evaluation method)
(1) Adhesion:
The adhesion of the coating film obtained above was evaluated by a boiling test described in JIS-K5400.

(2) Surface hydrophilicity (measurement of contact angle with water):
Contact angle meter manufactured by Kyowa Interface Science Co., Ltd .: measured by CA-X150 type. The contact angle was measured by dropping 0.2 cc of distilled water on the surface of the coating film formed above and then observing with a magnifying camera. The smaller the contact angle, the higher the hydrophilicity. The measurement was carried out to evaluate the sustainability of the hydrophilic film by measuring two points immediately after the coating film formation (initial stage) and after the deterioration acceleration test (left in a 60 ° C. dryer for one month).

(3) Storage stability of paint:
The prepared hydrophilic coating agent was stored at 25 ° C., and a coating film was periodically formed to evaluate whether hydrophilicity was developed (determination of hydrophilicity: the contact angle with water immediately after the coating film formation was 30 °. Below). The number of storage days when the hydrophilic coating agent during storage was no longer hydrophilic was examined.
Table 1 shows the evaluation results of (1) to (3).

Claims (7)

(1) (A) General formula: Si (OR ¹ ) ₄ (wherein R ¹ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms), an acidic solid insoluble in the system In the presence of a cation exchange resin as a catalyst, hydrolysis is performed in a solvent containing water in an amount of 4 to 40 mol per 1 mol of (A), and (2) the resulting silicate is then obtained. A method for producing a hydrophilic coating agent, comprising adding (B) a metal oxide sol solution to a hydrolyzate solution, followed by hydrolysis and condensation. The method for producing a hydrophilic coating agent according to claim 1, wherein the solvent comprises water or water of 50% by mass of the solvent composition and an organic solvent.   (B) The method for producing a hydrophilic coating agent according to claim 1, wherein the metal oxide sol of the metal oxide sol solution is a silica sol. The amount of the cation exchange resin used is 0.1 to 20% by mass relative to the total amount of the silica equivalent of the silicate (A) and the solid content of the metal oxide sol (B). The manufacturing method of the hydrophilic coating agent of any one of Claims 1. The amount of the metal oxide sol (B) is determined by the solid content mass of the metal oxide sol (B) / (silica equivalent mass of the silicate (A) + solid content mass of the metal oxide sol (B)). Is 0.1-0.95, The manufacturing method of the hydrophilic coating agent of any one of Claims 1-4. The active ingredient concentration of the solid content derived from the silicate and the solid content derived from the metal oxide sol in the obtained hydrophilic coating agent is 0.1 to 30% by mass, the solvent is 99.9 to 70% by mass, the solvent is water and It consists of a hydrophilic solvent, The manufacturing method of the hydrophilic coating agent of any one of Claims 1-5 characterized by the above-mentioned. An article excellent in surface hydrophilicity coated with a hydrophilic coating agent obtained by the production method according to any one of claims 1 to 6 .