JP2023049913A - Surface treatment agent, method for treating surface and method for forming coating film - Google Patents

Abstract

To provide a surface treatment agent that can readily perform surface treatment to a substrate such as a metal, a ceramic material or the like without the need of a large-scale facility and a plurality of treatment processes, and can improve adhesion between a substrate and a coating film formed on the substrate and including a silanol group, and to provide a method for treating a surface and a method for forming a coating film.SOLUTION: A surface treatment agent includes (A) a colloidal silica and (B) an organic solvent.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a surface treatment agent and a film forming method.

BACKGROUND ART Conventionally, before coating a base material such as a metal material or a ceramic material, the surface of the base material is subjected to a surface treatment for the purpose of imparting adhesion of a coating film to the base material, corrosion resistance, and the like.

For example, zinc, aluminum, magnesium, chromium, cobalt, nickel, iron, copper, tin, or alloys thereof, as surface treatment methods before painting, include alkali degreasing, phosphating, chromium Chemical conversion treatment, primer treatment with a silane coupling agent, hydrophilization treatment with a surfactant, and the like are performed. Alkali degreasing treatment, plasma treatment, and the like are performed as surface treatment methods for various ceramic materials such as glass and metal oxides before coating (for example, see Patent Documents 1 to 3).

However, when performing the above surface treatment, it is necessary to install a degreasing tank, a chemical conversion treatment tank, and a water washing treatment tank, as well as large-scale equipment such as wastewater treatment equipment and plasma treatment equipment. The problem is that it is difficult to introduce.

Further, when a film (coating film) is formed on the surface of an article by priming with a silane coupling agent, there is a problem that the adhesion of the film to the substrate is not sufficient depending on the type of film.

Furthermore, when the surface of the article is hydrophilized with a surfactant, there is a problem that the surfactant remaining on the surface of the article inhibits the adhesion between the substrate and the film (coating film).

Therefore, it is possible to easily perform surface treatment on substrates such as metal materials and ceramic materials without requiring large-scale equipment and multiple treatment steps. There is a demand for the development of a surface treatment agent and a surface treatment method that can improve the adhesion to the film to be formed.

Japanese Patent Application Laid-Open No. 2021-1390 Japanese Patent Application Laid-Open No. 2020-111765 Japanese Patent Laid-Open No. 2019-77898

The present invention can easily perform surface treatment on substrates such as metals and ceramic materials without requiring large-scale equipment and multiple processing steps, and It is an object of the present invention to provide a surface treatment agent, a surface treatment method, and a film forming method that can improve adhesion to a film having silanol groups formed on a surface.

As a result of intensive research, the present inventors have achieved the above object by a surface treatment agent containing (A) colloidal silica and (B) an organic solvent, a surface treatment method using the same, and a film formation method. We have found that it can be achieved, and have completed the present invention.

That is, the present invention relates to the following surface treatment agent, surface treatment method and film formation method.
1. A surface treatment agent containing (A) colloidal silica and (B) an organic solvent.
2. Item 2. The surface treatment agent according to item 1, wherein the colloidal silica is water-dispersed colloidal silica, and the concentration of the colloidal silica is 0.1 to 10% by mass based on 100% by mass of the surface treatment agent.
3. Item 3. The surface treatment agent according to Item 1 or 2, wherein the colloidal silica has an average particle size of 1 to 50 nm.
4. Item 4. The surface treatment agent according to any one of Items 1 to 3, wherein the organic solvent is a polar solvent.
5. Item 5. The surface treating agent according to any one of Items 1 to 4, wherein the organic solvent is at least one selected from the group consisting of alcohol solvents and glycol solvents.
6. A surface treatment method comprising the step i of wiping off the substrate surface with a surface treatment agent,
The surface treatment method, wherein the surface treatment agent contains (A) colloidal silica and (B) an organic solvent.
7. Prior to the step i, a peeling step of peeling off the protective film covering the substrate surface,
Item 7. The surface treatment method according to Item 6, wherein the step i is a step of removing the adhesive adhering to the substrate surface after the peeling step.
8. A film forming method for forming a film on a substrate surface,
(1) Step I of wiping the substrate surface with a surface treatment agent,
(2) Step II of applying a film-forming composition to the substrate surface to form a film-forming composition layer, and
(3) Heating the film-forming composition layer to form a film having silanol groups;
The surface treatment agent contains (A) colloidal silica and (B) an organic solvent.
Film forming method.

The surface treatment agent of the present invention can easily perform surface treatment on substrates such as metals and ceramic materials without requiring large-scale equipment and multiple treatment steps. It is possible to improve adhesion with a film having a silanol group formed on the substrate. In addition, the surface treatment method of the present invention can easily perform surface treatment by wiping the substrate surface with a surface treatment agent, and the substrate and the film having a silanol group formed on the substrate. can improve the adhesion of. Furthermore, in the film forming method of the present invention, the substrate is surface-treated by the above-described surface treatment method to form a film having silanol groups. An excellent film can be formed.

1. Surface treatment agent The surface treatment agent of the present invention comprises (A) colloidal silica (hereinafter also referred to as "(A) component") and (B) organic solvent (hereinafter also referred to as "(B) component"). It is a surface treatment agent containing In the surface treatment agent of the present invention, since component (A) is dispersed in component (B), for example, the surface treatment agent of the present invention can be soaked in a waste cloth, a thick tissue, or the like and wiped off the substrate surface. The surface of the base material can be polished and degreased. In addition, the component (B) volatilizes on the surface of the substrate, and the component (A) having silanol groups on the surface can adhere to the surface of the substrate. Thereby, when a film having silanol groups is formed on the surface of the component (A) on the substrate, the adhesion of the film to the substrate can be improved. Therefore, by using the surface protective layer of the present invention, it is possible to easily perform surface treatment on substrates such as metals and ceramic materials without requiring large-scale equipment and multiple treatment steps. It is possible to improve the adhesion between the substrate and the film having a silanol group formed on the substrate.

The present invention will be described in detail below.

((A) colloidal silica)
Component (A) is not particularly limited, and water-dispersed colloidal silica, hydrophobic colloidal silica, organic solvent-dispersed colloidal silica, and the like can be used. Among these, water-dispersed colloidal silica is preferable because the number of silanol groups on the colloidal silica surface is excellent (large).

The water-dispersed colloidal silica is preferably a dispersion of silica having silicon dioxide as a basic unit in an aqueous solvent. The average particle size of such water-dispersed colloidal silica is preferably 1 to 400 nm, more preferably 1 to 100 nm, more preferably 1 to 50 nm, even more preferably 1 to 20 nm. When the lower limit of the average particle size is within the above range, the storage stability of the surface treatment agent is further improved. In addition, when the upper limit of the average particle size is within the above range, the transparency of the formed film is further improved, and the number of silanol groups on the surface of the colloidal silica particles is increased, resulting in electrostatic contact with the substrate. This action further improves the adhesion to the substrate surface.

Water-dispersed colloidal silica can be used in the form of an aqueous dispersion, in which case the aqueous dispersion may be either acidic or basic. When colloidal silica and a hydrophilic compound contained in the aqueous dispersion are immobilized via non-covalent bonds, the non-covalent bonds become stronger, so the pH of the aqueous dispersion is preferably 10 or less. preferable.

Among water-dispersed colloidal silica, commercially available products can be used as acidic colloidal silica using water as a dispersion medium. Such commercial products include, for example, Nissan Chemical Industries, Ltd. Snowtex (registered trademark)-OXS, Snowtex-OS, Snowtex-O, Snowtex-OL, Snowtex-OYL, Asahi Denka Kogyo ( Adelite (registered trademark) AT-20Q manufactured by Co., Ltd., Clevosol (registered trademark) 20H12 manufactured by Clariant Japan Co., Ltd., and Clevosol 30CAL25.

Among water-dispersed colloidal silicas, the basic colloidal silica using water as a dispersion medium is not particularly limited, and examples thereof include silica stabilized by the addition of alkali metal ions, ammonium ions, and amines. A commercial item can be used as such basic colloidal silica. Examples of such commercial products include, for example, Nissan Chemical Industries, Ltd. Snowtex-20, Snowtex-30, Snowtex-C, Snowtex-C30, Snowtex-CM40, Snowtex-N, Snowtex- N30, Snowtex-K, Snowtex-XL, Snowtex-YL, Snowtex-ZL, Snowtex PS-M, and Snowtex PS-L, Asahi Denka Kogyo Co., Ltd. Adelite AT-20, Adelite AT- 30, Adelite AT-20N, Adelite AT-30N, Adelite AT-20A, Adelite AT-30A, Adelite AT-40, and Adelite AT-50. Furthermore, Clariant Japan Co., Ltd. Clevosol 30R9, Clevosol 30R50, and Clevosol 50R50, etc., DuPont Co. Ludox (registered trademark) HS-40, Ludox HS-30, Ludox LS, Ludox SM-30, and the like.

The colloidal silica may be used singly or in combination of two or more.

The concentration of component (A) is not particularly limited, and is preferably 0.05 to 70% by mass, more preferably 0.1 to 50% by mass, more preferably 0.2 to 20% by mass, based on 100% by mass of the surface treatment agent. Preferably, 0.5 to 10% by weight is particularly preferred. When the lower limit of the content of component (A) is within the above range, the adhesion between the substrate and the film having silanol groups formed on the substrate is further improved. When the upper limit of the content of component (A) is within the above range, the stability of the surface treatment agent is further improved, and excessive precipitation of colloidal silica on the substrate surface after surface treatment can be suppressed. Therefore, appearance defects can be further suppressed.

((B) organic solvent)
The component (B) is not particularly limited, and a polar solvent, a non-polar solvent, or the like can be used. Among these, a polar solvent is preferable from the viewpoint of excellent dispersion stability of colloidal silica particles.

Specific examples of component (B) include alcohol solvents, glycol solvents, glycol ether solvents, ester solvents, and the like. Among these, alcohol-based solvents, glycol-based solvents, and glycol ether-based solvents are preferable, and these polar solvents are more preferable in terms of more excellent dispersion stability of colloidal silica particles.

Examples of alcohol solvents include methanol, ethanol, isopropyl alcohol, normal propyl alcohol, tertiary butanol, secondary butyl alcohol, 1,3-butanediol, 1,4-butanediol, 2-ethylhexyl alcohol, isobutanol, benzyl Alcohol etc. are mentioned.

Examples of glycol-based solvents include ethylene glycol, propylene glycol, propylene glycol, diethylene glycol, triethylene glycol, and polyethylene glycol.

Glycol ether solvents include, for example, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether, ethylene glycol monotertiary butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, dipropylene glycol methyl ether, triethylene glycol monomethyl ether, 3-methoxy-3-methyl-1-butanol and the like.

Examples of ester solvents include methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, methoxybutyl acetate, amyl acetate, normal propyl acetate, isopropyl acetate, methyl lactate, ethyl lactate, butyl lactate and the like.

The above organic solvents may be used singly or in combination of two or more.

The concentration of component (B) is not particularly limited, and is preferably 0.1 to 99% by mass, more preferably 1 to 95% by mass, and even more preferably 10 to 90% by mass, based on 100% by mass of the surface treatment agent. When the lower limit of the content of the component (B) is within the above range, the stability of the surface treatment agent is further improved, and excessive deposition of colloidal silica on the substrate surface after surface treatment can be suppressed. Therefore, appearance defects can be further suppressed. When the upper limit of the content of component (B) is within the above range, the adhesion between the substrate and the film having silanol groups formed on the substrate is further improved.

(other ingredients)
The surface treatment agent of the present invention may contain other components in addition to the above components (A) and (B). Other components include aluminum-containing compounds, stabilizers, and the like.

Aluminum-containing compounds include alumina, sodium aluminate, and the like.

The content of the aluminum-containing compound is not particularly limited, and is preferably 10% by mass or less based on 100% by mass of the surface treating agent of the present invention. Moreover, the lower limit of the content is not particularly limited, and may be 0% by mass.

Examples of stabilizers include inorganic bases such as sodium hydroxide, potassium hydroxide, lithium hydroxide, and ammonia; organic acid salts such as tetramethylammonium;

The content of the stabilizer is not particularly limited, and is preferably 10% by mass or less based on 100% by mass of the surface treating agent of the present invention. Moreover, the lower limit of the content is not particularly limited, and may be 0% by mass.

(Method for producing surface treatment agent)
The method for producing the surface treatment agent is not particularly limited. A production method involving stirring is included.

The temperature of the surface treatment agent during stirring is not particularly limited, and the stirring may be performed at room temperature of about 0 to 50°C. The stirring time is not particularly limited as long as component (A) can be uniformly dispersed in component (B), and may be about 1 to 120 minutes.

2. Surface treatment method The surface treatment method of the present invention is a surface treatment method having a step i of wiping the substrate surface with a surface treatment agent, wherein the surface treatment agent comprises (A) colloidal silica and (B) an organic solvent. It is a surface treatment method containing

According to the surface treatment method of the present invention, the substrate surface can be polished and degreased by wiping the substrate surface with the above-described surface treating agent of the present invention. In addition, the component (B) volatilizes on the surface of the substrate, and the component (A) having silanol groups on the surface can adhere to the surface of the substrate. Thereby, when a film having silanol groups is formed on the surface of the component (A) on the substrate, the adhesion of the film to the substrate can be improved. Therefore, by using the surface protective layer of the present invention, it is possible to easily perform surface treatment on substrates such as metals and ceramic materials without requiring large-scale equipment and multiple treatment steps. It is possible to improve the adhesion between the substrate and the film having a silanol group formed on the substrate.

(Step i)
Step i is a step of wiping the substrate surface with a surface treatment agent. The surface treating agent of the present invention described above may be used as the surface treating agent.

The base material is not particularly limited, and examples thereof include metal materials and ceramic materials.

Metal materials are not particularly limited, and examples thereof include zinc, aluminum, magnesium, chromium, cobalt, nickel, iron, copper, tin, and alloys thereof.

The ceramic material is not particularly limited, and examples thereof include glass, alumina, zirconia, titania, ferrite, and enamel.

The method of wiping the surface of the base material with the surface treatment agent is not particularly limited, and it can be wiped off by a known method. Such a method includes, for example, a method of wiping the substrate surface with a waste cloth, a thick tissue, a towel, or the like containing the surface treatment agent. The method of immersing the substrate in the surface treating agent and the method of spray coating the surface of the substrate with the surface treating agent are also included in the method of wiping the surface of the substrate.

By the above step i, the component (B) volatilizes on the surface of the base material, and the component (A) can adhere to the surface of the base material. The coating amount of component (A) on the substrate surface is not particularly limited, and is preferably 0.001 to 1.0 g/m ² , more preferably 0.005 to 0.5 g/m ² . When the lower limit of the coating amount is within the above range, the adhesion between the substrate and the film having silanol groups formed on the substrate is further improved. When the upper limit of the coating amount is within the above range, it is possible to further suppress poor appearance caused by deposition of excessive colloidal silica on the substrate surface after the surface treatment.

The temperature (air temperature) at which step i is performed is not particularly limited, and may be normal temperature. Specifically, the room temperature is preferably 0 to 50°C, more preferably 5 to 40°C.

By the process i described above, the substrate surface is wiped off with the surface treatment agent, and the surface treatment can be applied to the substrate surface.

(Peeling process)
The surface treatment method of the present invention may have a peeling step of peeling off the protective film covering the substrate surface before step i. The substrate is sometimes covered with a protective film made of resin or the like for the purpose of suppressing oxidation and contamination of the surface of the substrate. In such a case, the surface treatment method of the present invention preferably includes a peeling step of peeling off the protective film before step i.

The method of peeling off the protective film is not particularly limited, and the protective film may be pulled up from the edge of the protective film and peeled off from the base material by a conventionally known method.

After peeling off the protective film, the adhesive for coating with the protective film remains on the substrate surface. In this case, the step i is a step of removing the adhesive adhering to the substrate surface after the peeling step.

Through the peeling step described above, the protective film covering the substrate surface is peeled off.

3. Coating Forming Method The coating forming method of the present invention is a coating forming method for forming a coating on the surface of a substrate, comprising:
(1) Step I of wiping the substrate surface with a surface treatment agent,
(2) Step II of applying a film-forming composition to the substrate surface to form a film-forming composition layer, and
(3) Heating the film-forming composition layer to form a film having silanol groups;
The surface treatment agent contains (A) colloidal silica and (B) an organic solvent.
It is a film forming method.

Since the film forming method of the present invention includes the step I, the substrate is surface-treated to form a layer of colloidal silica having silanol groups, so the surface treatment can be easily performed. The film forming method of the present invention further comprises steps II and III, so that a film having silanol groups can be formed on the colloidal silica layer, and the adhesion between the colloidal silica layer and the film is improved. Since it is excellent, it is possible to form a film having excellent adhesion to the substrate surface.

(Process I)
Step I is a step of wiping the substrate surface with a surface treatment agent. Step I is the same step as step i in the surface treatment method of the present invention described above. Therefore, the surface of the substrate may be wiped off with the surface treatment agent according to the details described in step i above.

(Step II)
Step II is a step of applying a film-forming composition to the substrate surface to form a film-forming composition layer.

The film-forming composition is not particularly limited as long as it can form a film having silanol groups by heating in step III described later. Such film-forming compositions include, for example, film-forming compositions containing alkoxysilanes and/or silicic acid compounds, catalysts, water, and solvents.

The alkoxysilane is not particularly limited, for example, the formula: (R ¹ ) _m Si(OR ² ) _4-m (wherein R 1 is a functional group, ^{R 2 is} a lower alkyl group, m is 0 to 3 is an integer), and in the above chemical formula, functional groups include vinyl, 3-glycidoxypropyl, 3-glycidoxypropylmethyl, 2-(3,4-epoxycyclohexyl)ethyl, p-styryl , 3-methacryloxypropyl, 3-methacryloxypropylmethyl, 3-acryloxypropyl, 3-aminopropyl, N-2-(aminoethyl)-3-aminopropyl, N-2-(aminoethyl)-3- Aminopropylmethyl, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyl, N-(vinylbenzyl)-2-aminoethyl-3-aminopropyl , tris-(trimethoxysilylpropyl) isocyanurate, 3-ureidopropyl, 3-mercaptopropyl, 3-mercaptopropylmethyl, bis(triethoxysilylpropyl) tetrasulfide, 3-isocyanatopropyl, 3-propylsuccinic anhydride etc. can be exemplified.

Specific examples of the lower alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, sec-butyl, n-pentyl, 1-ethylpropyl, isopentyl and neopentyl. A linear or branched alkyl group having about 1 to 6 carbon atoms can be mentioned.

Specific examples of the alkoxysilane represented by the above chemical formula include Si(OCH ₃ ) ₄ , Si(OC ₂ H ₅ ) ₄ , CH ₃ Si(OCH ₃ ) ₃ , CH ₃ Si(OC ₂ H ₅ ) ₃ , _C2H5Si ( _OCH3 ) ₃ , _C2H5Si ( _{OC2H5 ) 4 , CHCH2Si} ( _OCH3 ) ₃ , _{CH2CHOCH2O ( CH2} ) _3Si ( _{CH3O ) 3} , _CH2C ( _CH3 )COO( _CH2 ) _3Si ( _OCH3 ) ₃ , _CH2CHCOO ( _CH2 ) _3Si ( _OCH3 ) ₃ , _NH2 ( _CH2 ) _3Si ( _OCH3 ) ₃ , _SH ( _CH2 ) _3Si ( _CH3 ) ₃ , NCO( _CH2 ) _3Si ( _C2H5O ) ₃ may be mentioned.

The above alkoxysilanes can be used by mixing with resins such as urethane resins, epoxy resins, acrylic resins, polyester resins, melamine resins and silicone resins. Silicone-modified resins of these resins may also be used, and among these, silicone-modified acrylic resins are preferred.

The above alkoxysilanes can be used singly or in combination of two or more.

The silicic acid compound is not particularly limited, and various known silicic acid compounds can be used. Specific examples of the silicate compound include lithium silicate, sodium silicate, potassium silicate, ammonium silicate, choline silicate, calcium silicate, magnesium silicate, hexafluorosilicic acid and the like.

The above silicic acid compounds can be used singly or in combination of two or more.

The film-forming composition preferably contains water and a catalyst. As a result, the alkoxysilyl groups are hydrolyzed, and a film having silanol groups can be formed by step III described later.

Acids, bases, organometallic compounds and the like can be used as catalysts.

Examples of the acid include hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, boric acid, formic acid, acetic acid, citric acid, oxalic acid and the like.

Examples of the base include potassium hydroxide, sodium hydroxide, ammonia, monoethylamine, diethylamine, triethylamine and the like.

As the organometallic compound, for example, a water-soluble organometallic chelate compound containing titanium, zirconium, aluminum, tin or the like as a metal component, a metal alkoxide, or the like can be used.

Among the above organometallic compounds, the organotitanium compounds include titanium alkoxide compounds such as tetraisopropyl titanate, tetra-normal butyl titanate, butyl titanate dimer, tetra-tert-butyl titanate, and tetraoctyl titanate; titanium diisopropoxybisacetylacetonate; Titanium tetraacetylacetonate, titanium dioctyloxybisethylacetoacetonate, titanium octylene glycolate, titanium diisopropoxybisethylacetylacetonate, titanium lactate, titanium lactate ammonium salt, titanium diisopropoxybistriethanolamine, etc. Examples include titanium chelate compounds. Examples of organic zirconium compounds include zirconium alkoxide compounds such as normal propyl zirconate and normal butyl zirconate; zirconium tetraacetylacetonate, zirconium tributoxymonoacetylacetonate, zirconium dibutoxybisethylacetoacetate, zirconium tributoxymonostearate and the like. and zirconium chelate compounds. Examples of organic aluminum compounds include aluminum alkoxide compounds such as aluminum isopropylate, monobutoxyaluminum diisopropylate, and aluminum butyrate; Examples include aluminum chelate compounds such as acetylacetonate bisethylacetoacetate.

The above catalysts can be used singly or in combination of two or more.

The content of the catalyst is not particularly limited, and the film-forming composition is taken as 100% by mass. .

The content of water is generally about 0.1 to 50% by mass based on 100% by mass of the film-forming composition.

The solvent is not particularly limited as long as the alkoxysilyl group can cause hydrolysis and polycondensation reaction in an organic solvent. A ketone-based solvent or the like can be used.

The content of the solvent is not particularly limited as long as it can dissolve the above components, and may be about 1 to 95% by mass based on 100% by mass of the film-forming composition.

The method of applying the film-forming composition to the substrate surface is not particularly limited, and may be applied by known coating methods such as dip coating, spray coating, roll coating, spin coating, bar coating, and the like.

The coating amount of the film-forming composition layer in step II is not particularly limited, and is preferably 10-1000 g/m ² , more preferably 50-500 g/m ² .

(Step III)
Step III is a step of heating the film-forming composition layer to form a film having silanol groups. By heating the film-forming composition layer in step III, the solvent in the film-forming composition can be volatilized and a film having silanol groups can be formed.

The heating method is not particularly limited as long as the solvent in the film-forming composition layer formed in step II can be volatilized and a film having silanol groups can be formed. The composition layer can be heated by a method such as placing the substrate together in a constant temperature bath or placing the substrate together in a dryer.

The heating temperature is preferably 20° C. or higher, more preferably 60° C. or higher. Moreover, the heating temperature is preferably 300° C. or lower, more preferably 250° C. or lower.

The heating time is not particularly limited, and is preferably 3 minutes or longer, more preferably 5 minutes or longer. Also, the heating time is preferably 120 minutes or less, more preferably 60 minutes or less.

The thickness of the film formed in step III is not particularly limited, and is preferably 50 μm or less, more preferably 30 μm or less. Moreover, the thickness of the film is preferably 0.1 μm or more, more preferably 0.5 μm or more. When the upper limit of the thickness of the coating is within the above range, the coating is transparent, and together with this, it is possible to impart more excellent anticorrosive properties to the substrate and to suppress deterioration of the appearance of the substrate. When the lower limit of the thickness of the coating is within the above range, it is possible to impart superior rust prevention to the substrate.

Through Step III described above, the film-forming composition layer is heated to form a film having silanol groups.

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples. However, the present invention is not limited to the examples.

(Preparation of surface treatment agent)
Example 1
Colloidal silica having an average particle size of 10 nm (trade name Snowtex ST-O manufactured by Nissan Chemical Industries, Ltd.) was prepared. The colloidal silica was added to ethanol as an organic solvent and stirred to prepare a surface treatment agent. The content of colloidal silica in the surface treatment agent was 10% by mass with the surface treatment agent being 100% by mass.

(surface treatment)
As a substrate, an aluminum substrate (No. 1050 aluminum plate: 50 mm×100 mm) was prepared. Next, a waste cloth was impregnated with a surface treatment agent, and the waste cloth was reciprocated twice on the surface of the base material to wipe off the surface of the base material. The coating amount of colloidal silica on the substrate surface was 0.2 g/m ² .

Separately, a film-forming composition was prepared by dissolving a silicone-modified acrylic resin in propylene glycol monomethyl ether as a solvent. The content of the silicone-modified acrylic resin in the film-forming composition was 30% by mass.

Next, a silicone-modified acrylic resin was applied onto the substrate at a coating amount of 200 g/m ² to form a film-forming composition layer.

The substrate on which the film-forming composition layer was formed was heated in a constant temperature bath at 80° C. for 30 minutes to form a film having silanol groups. The thickness of the film was 10 μm.

Examples 2-4
A surface treatment agent was prepared in the same manner as in Example 1 except that the average particle size and content of colloidal silica in the surface treatment agent were changed as shown in Table 1, and the surface of the substrate was subjected to surface treatment. A film having silanol groups was formed.

Comparative example 1
A film having silanol groups was formed on the surface of the substrate in the same manner as in Example 1, except that the surface treatment was not performed.

Comparative example 2
Alkaline degreasing treatment was performed instead of surface treatment with a surface treatment agent. Specifically, a degreasing bath containing a 1% sodium hydroxide aqueous solution was prepared, and the substrate was immersed in the degreasing bath under conditions of 50° C. and 5 minutes. Other than that, in the same manner as in Example 1, a film having silanol groups was formed on the surface of the substrate.

The substrates on which the films having silanol groups were formed in the above examples and comparative examples were evaluated as follows.

Corrosion resistance evaluation (alkali immersion)
A 2% sodium hydroxide aqueous solution was prepared as an alkaline bath for evaluating corrosion resistance to alkali. The substrates of Examples and Comparative Examples having films having silanol groups formed thereon were immersed in an alkaline bath at 25° C. for 10 hours. The film-formed surface of the substrate was visually observed and evaluated.

(acid immersion)
10% sulfuric acid was prepared as an acidic bath for evaluating corrosion resistance to acid. The substrates of Examples and Comparative Examples having films having silanol groups formed thereon were immersed in an acid bath at 25° C. for 10 hours. The film-formed surface of the substrate was visually observed and evaluated.

Table 1 shows the results.

As is clear from the above results, the rust prevention of the coating film is improved by surface-treating the substrate using a surface-treating agent containing (A) colloidal silica and (B) an organic solvent. I found out. As a result, by using the surface treatment agent of the present invention, the substrate can be easily surface treated without requiring large-scale equipment and multiple treatment steps. It was found that the adhesiveness to the film having silanol groups formed on the substrate can be improved.

On the other hand, in Comparative Example 1 in which the surface treatment using the surface treatment agent of the present invention was not performed, the rust prevention of the substrate was reduced, and the substrate and the silanol formed on the substrate It was found that the adhesiveness to the coating having a group was low.

In addition, in Comparative Example 2 in which alkaline degreasing treatment was performed as the surface treatment of the base material, rust prevention and adhesion equivalent to those of Example 1 were exhibited, but degreasing bath equipment and wastewater treatment equipment were required. It took a long time and could not be easily surface-treated.

Claims (8)

A surface treatment agent containing (A) colloidal silica and (B) an organic solvent. 2. The surface treatment agent according to claim 1, wherein the colloidal silica is water-dispersed colloidal silica, and the concentration of the colloidal silica is 0.1 to 10% by mass based on 100% by mass of the surface treatment agent. 3. The surface treatment agent according to claim 1, wherein the colloidal silica has an average particle size of 1 to 50 nm. The surface treatment agent according to any one of claims 1 to 3, wherein the organic solvent is a polar solvent. The surface treatment agent according to any one of claims 1 to 4, wherein the organic solvent is at least one selected from the group consisting of alcohol solvents and glycol solvents. A surface treatment method comprising the step i of wiping off the substrate surface with a surface treatment agent,
The surface treatment method, wherein the surface treatment agent contains (A) colloidal silica and (B) an organic solvent. Prior to the step i, a peeling step of peeling off the protective film covering the substrate surface,
7. The surface treatment method according to claim 6, wherein said step i is a step of removing the adhesive adhering to the substrate surface after said peeling step. A film forming method for forming a film on a substrate surface,
(1) Step I of wiping the substrate surface with a surface treatment agent,
(2) Step II of applying a film-forming composition to the substrate surface to form a film-forming composition layer, and
(3) Heating the film-forming composition layer to form a film having silanol groups;
The surface treatment agent contains (A) colloidal silica and (B) an organic solvent.
Film forming method.