JPH0661529B2 - How to make painted products - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a coated article, and relates to an improvement in the method of forming a coating film, and more specifically, to a metal coated with a silicon alkoxide-based inorganic coating material. The present invention relates to a method for manufacturing a base material.

[Prior Art] Coating (coating) on a metal is performed mainly for the purpose of surface protection (corrosion prevention, etc.) and appearance beautification (coloring, etc.). Until now, the mainstream of the paints used are organic paints having an organic resin as a main component for forming a coating film.

However, organic paints generally have poor weather resistance, and
Since it has a drawback that it is easily scratched due to its low hardness, it has not been possible to achieve the coating purpose of protecting the object to be coated in the long term.

On the other hand, recently, fluororesin-based paints have begun to be applied as paints having a high degree of weather resistance, which is not found in conventional organic paints, and having good heat resistance, cold resistance, water resistance, chemical resistance and the like. However, this fluororesin-based resin has a problem that it is expensive as a paint and, like conventional organic paints, it has a low coating hardness and is easily scratched.

[Problems to be Solved by the Invention]

Therefore, it was considered to apply an inorganic coating material, specifically, a silicon alkoxide-based inorganic coating material known as a hard coating material for plastics, to a metal substrate instead of the organic coating material. This silicon alkoxide-based inorganic coating material forms a coating film with high weather resistance and high hardness, and has been conventionally used mainly for protecting base materials made of plastic, wood, cement and the like. .

However, when the above-mentioned inorganic coating material is directly applied to the metal surface, there is a problem that the adhesion of the formed coating film is deteriorated particularly on a base material such as iron. It is considered that this is because one component of the silicon alkoxide-based inorganic coating material reacts with the metal base material to change the surface state of the metal or modify the coating material component. Furthermore, the curability of the coating material may change, and it may be difficult to obtain a coating film having sufficient performance, or the coating film may blister.

In view of the above circumstances, the present invention relates to a method for forming a coating film excellent in weather resistance, hardness, etc. on a metal substrate, particularly an iron substrate, and having good adhesion without peeling or the like for a long period of time. Specifically, it is an object to provide a method for forming the same coating film using a silicon alkoxide-based inorganic coating material.

[Means for Solving the Problems]

In order to solve the above-mentioned problems, the present invention provides, on a metal substrate, 20 to 200 parts by weight of (a) a silicon alkoxide represented by the general formula Si (OR ') ₄ as a SiO ₂ component and / or colloidal silica ( However, in the case of colloidal silica, the solid content) (a) As RSiO _3/2 component, the general formula RSi (O
R ′) ₃ silicon alkoxide represented by 80 to 10
0 parts by weight (c) As the RSiO component, the general formula R ₂ Si (OR ′) ₂
In coating and baking a silicon alkoxide-based inorganic coating consisting of 15 to 60 parts by weight of silicon alkoxide, the following two components (A), (B) and (A) are coated on the metal substrate in advance. The resin having a hydroxyl group in the side chain as the film-forming main element is any of an epoxy resin having a weight average molecular weight of 1000 or more and / or its hydride, an alkyd resin having an oil length of less than 50%, and / or an oil-free alkyd resin. One kind (B) amino resin and / or phenol resin as a curing agent, and a continuous coating film composed of a primer containing (A) :( B) in a weight ratio of 8: 2 to 6: 4. To do so.

[Action]

In the combination of the silicon alkoxide-based inorganic coating material and the primer having the above-mentioned specific composition, the continuous coating film of the primer is present between the metal substrate and the coating film of the silicon alkoxide-based inorganic coating material, and is a main element for forming the coating film of the primer. The hydroxyl group of the side chain of the resin plays a role of reacting and bonding with both the metal and the paint component, and adhering them in a bridging manner. Therefore, a coating film of an inorganic coating material having good adhesion to a metal substrate is formed, and peeling or the like does not occur for a long period of time.

〔Example〕

First, the primer used in the present invention will be described. As the resin having a hydroxyl group in the side chain, which is the main component for forming a coating film of (A), any one of the following epoxy resins and alkyd resins is used. Specifically, the weight average molecular weight (hereinafter referred to as “Mw”) is 100.
Zero or more epoxy resins and / or hydrides thereof can be used. Examples of the resin type include bisphenol A type, aliphatic type, and cycloaliphatic type, but are not limited thereto, and various types can be arbitrarily selected. For the molecular weight,
If the Mw is less than 10,000, the total amount of hydroxyl groups contained in the resin may be insufficient, and the adhesion with the inorganic coating material may deteriorate. Further, from the viewpoint of leveling property as a primer, Mw is suitably 10,000 or less.

In addition, an alkyd resin having an oil length of less than 50% or oil-free can be used. If the oil length exceeds this range, cracks tend to occur during the coating and baking of the inorganic paint.

As the curing agent for the primer component (B), an amino resin or a phenol resin such as a urea resin and a modified urea resin, a melamine resin and a modified melamine resin, and a benzoguanamine resin may be used alone or in combination of complex species. The more detailed type of each and the individual molecular structure are not particularly limited.

The mixing ratio of the resin of (A) and the curing agent of (B) is preferably set appropriately according to the types of both components used, the characteristics, the form of use, and the like. A): (B)
= 8: 2 to 6: 4. More preferably,
It is recommended that the ratio is 8: 2 to 7: 3. Same ratio =
If it exceeds 8: 2 and the amount of the resin component is large, the curing may be insufficient, and cracks may occur during the coating or baking of the inorganic coating material, or the adhesiveness to the substrate may deteriorate. On the other hand, if the above ratio deviates from 6: 4 and the amount of the curing agent component increases,
There is a tendency that the coating film becomes too hard and causes poor adhesion.

The primer according to the present invention, if necessary, further contains a solvent for the components (A) and (B) (for example, one that is usually used depending on the type of the resin (A) used; an epoxy resin paint). If so, an aromatic solvent such as toluene or xylene) may be added and appropriately diluted. Also, as other components, various kinds of usual colorants, fillers,
Surfactants, thickeners, ultraviolet absorbers, etc. may be added. Each of these is blended within the range of the amount that does not impair the effect of the present invention.

Next, the silicon alkoxide-based inorganic coating material of the present invention will be described. Silicon alkoxide is a monomer component of the paint, the general formula _{R n Si (OR ') 4} -n
[Wherein R and R'are alkyl groups having 1 to 4 carbon atoms, n
Is a compound represented by 0, 1 or 2], for example, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, etc., where n = 0 in the above formula, Methoxysilane, methyltriethoxysilane, and the like, and dimethyldimethoxysilane and the like can be given as n = 2. Moreover, colloidal silica and the like may be contained as other components. Further, R may be partly an epoxy group, an amino group or the like.

Regarding the composition of the silicon alkoxide component, the following compounding amounts are used. That is, (a) SiO ₂ component is a silicon alkoxide represented by the general formula Si (OR ′) ₄ and / or 20 to 200 parts by weight of colloidal silica (however, solid content in the case of colloidal silica) (b) RSiO _{As the 3/2} component, the general formula RSi (O
R ′) ₃ silicon alkoxide represented by 80 to 10
0 parts by weight (c) As the RSiO component, the general formula R ₂ Si (OR ′) ₂
It is suitable that the composition is composed of 15 to 60 parts by weight of each component represented by silicon alkoxide. If the value is out of the above range, the resulting coating film may be too hard, or may be too soft, and it may be difficult to obtain a predetermined film thickness.

Similar to the primer, various kinds of ordinary colorants, fillers, and the like may be added to the silicon compound, if necessary, in appropriate amounts.

An example of the preparation of this silicon alkoxide-based inorganic coating material will be described below. First, the above-mentioned monomer components and the like are diluted with a solvent into a solution having an appropriate concentration, and a catalyst for hydrolysis and polycondensation of the monomer, water as a curing agent and the like are added thereto. Examples of the diluent solvent include lower alcohols such as methanol, ethanol, propanol, and isopropyl alcohol (IPA), diols such as ethylene glycol, and cellosolves such as ethylene glycol monomethyl ether.
Alternatively, a plurality of types are used together. Examples of the catalyst include various acidic catalysts (for example, inorganic acids such as hydrochloric acid, phosphoric acid and sulfuric acid and organic acids such as formic acid, acetic acid, oxalic acid and chloroacetic acid), aminosilane [for example, γ-aminopropyltriethoxysilane, N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, etc.], metal salts of the above inorganic or organic acids, quaternary ammonium salts or amine salts thereof, organotin compounds (for example, dibutyltin dilaurate, Diacetate, dioctate, etc.) and the like. These catalysts may be used alone or in combination of two or more, and are mixed within an appropriately set amount range.

By the reaction of the monomer-containing solution thus prepared, a siloxane prepolymer solution (X liquid) having an alkoxide group at its end is obtained, and at the time of use, at least a curing agent is added to the inorganic coating composition. Is prepared.
That is, the two-pack type may be used as described above, but it is also possible to use the one-pack type in which all components are mixed in advance and stored in one container. As the curing agent, catalyst, etc., which are further added at the time of use, the same ones as those added in the above-mentioned monomer stage can be applied, and these are added after being prepared into a solution having an appropriate concentration with the same diluting solvent as the above. May be.

The coating of the metal substrate with the primer and the silicon alkoxide-based inorganic coating material described above is performed, for example, as follows. First, dust, oil, oxide film, etc. on the surface of the metal serving as the base material are removed to sufficiently clean the surface. For example, general solvent degreasing using toluene, trichlorethylene (trade name Triclen), or the like, cleaning using a surfactant, or the like is performed. In addition, although iron is preferably used as the metal material, other materials such as tin and galvanized iron may be used without any particular limitation.

Then, a continuous coating film of the above primer is formed on the cleaned substrate. For painting method, spray painting,
Roll coating, flow coater coating, dip coating, etc. are not particularly limited. The thickness of the primer coating film is also not particularly limited, but it is preferable to obtain a dry film thickness of about 5 to 15 μm.

The conditions of drying and baking after coating the primer are not particularly limited, but it is preferable to set mild conditions so that the primer is not completely cured at this stage. This is because if the following silicon alkoxide-based inorganic paint is applied and baked before the primer layer (coating film) is completely cured, the effect in terms of long-term adhesion can be recognized. . Specifically, it is preferably carried out at room temperature to about 250 ° C., and if the temperature is higher than this, curing may proceed excessively to cause poor adhesion and deterioration of the primer coating film.
Depending on the type of primer used, the primer coating film may not be baked here, and the next infinite paint may be applied in a wet-on-wet manner.

Next, a silicon alkoxide-based inorganic coating material is applied on the primer coating film. The coating method and the like are not particularly limited as described above. The thickness of the coating film of the inorganic coating is, for example, 5 when it is used as a clear coating containing no pigment.
It is preferable to obtain a dry film thickness of about ˜15 μm, and when a pigment or the like is included, a dry film thickness of about 5 to 30 μm is obtained, but the present invention is not limited thereto. However, if it is less than 5 μm, it tends to be difficult to form a uniform coating film, and if it exceeds 30 μm, cracks tend to occur during baking. About baking, it is suitable to carry out at about 50-200 degreeC.

The above is one embodiment of the method for producing a coated product according to the present invention, but it goes without saying that the present invention is not limited to this. For example, on a coating film of silicon alkoxide-based inorganic paint, another type or the same type of inorganic paint is applied.
You may bake and form a multilayer coating film.

Next, more detailed examples of the present invention will be described together with comparative examples.

-Examples 1 to 3-Preparation of base material A metal plate of material SPCC-B (JIS G 3310) was solvent-degreased with trichlene and then air-dried. Then, it was dried at 80 ° C. for 1 hour and cooled to room temperature.

Coating of primer Epoxy resin as resin component (A), which is the main component for coating film formation (DIC4050 manufactured by Dainippon Ink and Chemicals, Inc .; Mw = 140)
0, epoxy equivalent 900-1000), butylated melamine resin as a curing agent (B) (DI manufactured by Dainippon Ink and Chemicals, Inc.)
CJ820) at the ratios shown in Table 1 (A),
(B) was mixed to prepare a primer.

On the treated metal plate, apply the same primer with a coating thickness of 5 to 1
It was applied by spraying to have a thickness of 0 μm. After setting for 5 minutes, bake this at 100 ° C for 10 minutes,
After cooling to room temperature, a primer coating film was obtained.

Preparation of Inorganic Paint (C1) A composition comprising the following components: * OSCAL1432 manufactured by Catalysts & Chemicals Co., Ltd .; SiO ₂ content of 30% was prepared and used as a prepolymer solution (liquid Xa).
The composition of the above components is 30 ° C at 25 ° C and 500 rpm.
It was carried out with stirring for a minute.

The prepared Xa solution was stored in a sealed stopper at 25 ° C. for 1 week or more.

Thereafter, 7.5 parts of commercially available titanium oxide and 0.3 part of finely powdered silica (Aerosil R972 manufactured by Nippon Aerosil Co., Ltd.) were added to 100 parts by weight of the Xa solution (hereinafter simply referred to as “part”). Using a disper (disperser), glass beads were added to the inside of the container and dispersed at 2000 rpm for 15 minutes to obtain a liquid Xb.

The above Xb solution was stored in a tightly closed state at 25 ° C. for 3 days, and when used, 100 parts of the Xb solution was used with 27 parts of water and IPA2.
Add 7 parts and 2 parts of 1N hydrochloric acid, and at 25 ° C., 500
After stirring at rpm for 10 minutes, a silicon alkoxide-based inorganic coating C1 was obtained.

Application of inorganic paint On the above primer coating film, apply the above inorganic paint C1 to a film thickness of 1
It was applied by spraying to have a thickness of 0 to 20 μm. After setting for 5 minutes, this was baked at 150 ° C. for 30 minutes to obtain a test piece.

-Example 4--In addition to using the following C2 as an inorganic coating,
A test piece was prepared in the same manner as in Example 1 above.

Preparation of Inorganic Paint (C2) Composition comprising the following components: Was prepared in the same manner as the above Xa solution to obtain Xc solution.

The prepared Xc solution was stored in the same manner as the above Xa solution, and when used, 43 parts of water and IPA were added to 100 parts of the Xc solution.
43 parts was added and a silicon alkoxide-based inorganic coating material C2 was obtained in the same manner as in the above C1.

—Examples 5 and 6 — The same steps as in Examples 1 and 2 above were carried out, and the primer coating film ((A) and (B) was mixed on the metal substrate as shown in Table 1). And an inorganic coating C1 coating film was formed. However, the baking time of the inorganic paint C1 was set to 15 minutes.

After cooling this to room temperature, the inorganic coating material C2 was further applied onto the C1 coating film by spraying so as to have a film thickness of 5 to 10 μm. After setting for 5 minutes, baking was performed at 150 ° C. for 30 minutes to obtain a test piece.

-Example 7-Except for using epoxy resin (DIC7050 manufactured by Dainippon Ink and Chemicals, Inc .; Mw = 2900, epoxy equivalent 1750-2100) as the resin component (A) of the primer A test piece was prepared in the same manner.

-Examples 8 and 9-The above-mentioned Example 2 was repeated except that an alkyd resin having an oil length of 30% (DIC50-593-80 manufactured by Dainippon Ink and Chemicals, Inc.) was used as the resin component (A) of the primer. , 6 were prepared in the same manner as described above.

-Examples 10 to 12-Except for using an oil-free alkyd resin (DICM6003-60 manufactured by Dainippon Ink and Chemicals, Inc.) as the resin component (A) of the primer, Test pieces were prepared in the same manner.

-Comparative Example 1-A test piece was prepared in the same manner as in the above-described example except that the inorganic coating material C1 was directly coated on the metal plate without performing the primer coating.

-Comparative Example 2-A test piece was prepared in the same manner as in the above-mentioned example except that Tosprime D (trade name, manufactured by Toshiba Silicone Co., Ltd., silane type) was used as a primer. However, baking was not performed after applying the primer, and the coating was allowed to stand at room temperature for 30 minutes, and then the inorganic coating material C1 was applied.

—Comparative Example 3— As a comparative example with respect to the method for producing a coated article according to claim 2, M
Epoxy resin with w of 360 (manufactured by Dainippon Ink and Chemicals, Inc.)
DIC850; epoxy equivalent 182 to 194) was used as the resin component (A) of the primer, and other conditions were the same as in Example 1 to prepare test pieces.

—Comparative Example 4— As a comparative example to the method for producing a coated article according to claim 3, a test piece was produced as follows. As the component (A) of the primer, an alkyd resin having an oil length of 80% (DICJ571 manufactured by Dainippon Ink and Chemicals, Inc.) was used, where
A primer was prepared by adding wt% cobalt-based metal peroxide (dryer) as a curing agent component (B). This was similarly spray-coated on the substrate and then left at room temperature for 1 day, and the inorganic coating C1 coating film was formed in the same manner.

The following coating film performance tests were conducted on the test pieces of the examples and comparative examples obtained above.

(a) Initial peeling test-A cross-cut was put in a test piece and a cellotape peeling test was performed.

(b) Peeling test after cycle test: Hot water 60 ° C. × 2 hours → air drying 2 hours as one cycle, a cellotape peeling test after 10 cycles was performed.

(c) Weather resistance test-The state of the coating film after 5,000 hours was observed with a weather sunshine meter.

The above results are shown in Table 1.

As shown in Table 1, in an example in which a silicon alkoxide-based inorganic coating material was applied after forming a coating film of a primer having a resin having a hydroxyl group in a side chain as a coating film forming main element, the adhesiveness is very good. A coating film was obtained.

Comparative Example 3 is a comparative example with respect to the method for producing a coated article according to claim 2, in which an epoxy resin having a low molecular weight (Mw = less than 1000) is used as the component (A) of the primer, and therefore the adhesion of the coating film is improved. In this respect, the effect as seen in the examples was not obtained. Since cracks were found in this coating film at the initial stage, the subsequent test was not performed. Further, Comparative Example 4 is a comparative example to the method for producing a coated article according to claim 3, and since an alkyd resin having a long oil length (50% or more) is used as the component (A) of the primer, it is also an Example. Not so effective.

〔The invention's effect〕

According to the method for producing a coated article according to the present invention, it is possible to form a coating film excellent in weather resistance, hardness, etc. on a metal base material, particularly an iron base material, and having good adhesion without peeling or the like for a long period of time. Is possible. As the resin having a hydroxyl group in the side chain contained in the primer, an epoxy resin having a Mw of 1000 or more and / or a hydride thereof, or an alkyd resin having an oil length of less than 50% and / or an oil-free alkyd resin are used, the above-mentioned effect is obtained. It becomes even more prominent.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Minor Inoue Minato 1048 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works Ltd. (72) Yukio Shimada 1048 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works Ltd. (56) References JP-A-61-107981 (JP, A) JP-A-60-225672 (JP, A)

Claims (1)

[Claims] 1. On a metal substrate, 20 to 200 parts by weight of a silicon alkoxide represented by the general formula Si (OR ') ₄ and / or colloidal silica as a (A) SiO ₂ component (however, In the case of solid content) (a) As RSiO _3/2 component, the general formula RSi (O
R ′) ₃ silicon alkoxide represented by 80 to 10
0 parts by weight (c) As the RSiO component, the general formula R ₂ Si (OR ′) ₂
In coating and baking a silicon alkoxide-based inorganic coating consisting of 15 to 60 parts by weight of silicon alkoxide, the following two components (A), (B) and (A) are coated on the metal substrate in advance. As the resin having a hydroxyl group in the side chain as a film forming main element, any one of an epoxy resin having a weight average molecular weight of 1000 or more and / or its hydride, an alkyd resin having an oil length of less than 50% and / or an oil-free alkyd resin. One kind (B) amino resin and / or phenol resin as a curing agent, and a continuous coating film composed of a primer containing (A) :( B) in a weight ratio of 8: 2 to 6: 4. A method of manufacturing coated products characterized by the following.