JPH0240268A - Production of coated metal product - Google Patents

Abstract

PURPOSE:To enhance the rust preventing effect of a coated metal product when the product is allowed to stand over a long period by directly coating the surface of a metal with a coating compsn. prepd. by blending a specified amt. of a specified solvent-soluble fluorine-contg. copolymer with specified amts. of a UV absorber and a curing agent and curing the compsn. CONSTITUTION:A paint compsn. is prepd. by blending 100 pts.wt. solventsoluble fluorine-contg. copolymer contg. >=10wt.% fluorine in the units of a fluoroolefin polymer and having curing reactive moieties with 1-40 pts.wt. UV absorber and 0-40 pts.wt. curing agent. The surface of a metal is directly coated with the coating compsn. and this compsn. is cured to produce a coated metal product. The curing reactive moieties of the fluorine-contg. copolymer are preferably hydroxyl, carboxylic acid, acid amido or amino groups. The UV absorber may be benzophenone or benzotriazole.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for manufacturing painted metal products.

[Prior Art] As a coating composition that provides a coating film with excellent weather resistance, a coating composition for coating containing a fluorine-containing copolymer as an essential component and having a solvent-soluble crosslinking site is known. For example, JP-A-57-34107, JP-A-58-13
No. 6662 and other publications describe a solvent-soluble fluorine-containing copolymer and a coating composition containing the fluorine-containing copolymer, which are essential components of a coating composition.

Coated plates with excellent weather resistance are produced by directly coating stainless steel plates, copper plates, aluminum plates, copper plates, and titanium steel plates with this coating composition. Furthermore, the above-mentioned coating compositions are often directly coated onto these steels, stainless steel, aluminum, copper, etc. because they have better adhesion than the general-purpose coating compositions that have been used up to now.

These have excellent weather resistance and long-lasting beauty compared to painted objects coated with other coating materials. These are used as both colored paints (enamels) and clear paint types.

However, especially when used in clear coatings, it has been found that rust may occur over time due to crevice corrosion due to long-term outdoor exposure or accelerated exposure.

[Problems to be solved by the invention] Conventionally, when a coating composition is applied directly to a base metal, there has been a problem that rust may occur on the base metal during outdoor exposure and accelerated exposure. .

The present invention uses a previously unknown method of incorporating a stabilizer into a coating composition, and aims to provide a technology that does not cause rusting for a long period of time even when used for metals during outdoor exposure and accelerated exposure.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems, and the fluorine content g based on the polymerized units of the fluoroolefin is 10% by weight or more, and the curing reactivity is low. A coating composition comprising 1 to 40 parts by weight of an ultraviolet absorber and 0 to 40 parts by weight of a curing agent per 100 parts by weight of a solvent-soluble fluorine-containing copolymer having moieties is applied directly to a metal surface and cured. The present invention provides a method for manufacturing a painted metal product characterized by:

In the present invention, the solvent-soluble fluorine-containing copolymer used is a solvent-soluble copolymer comprising a fluoroolefin and a comonomer copolymerizable with the fluoroolefin. Here, as the fluoroolefin, CCIF=CF,
ClICl=CF2CCl□=CF2. CCl=C
C1□, CCl=CC1□, CII□=CCIFCCCL
, = CCIF, etc., fluoroethylene, CF, CIC
F・CF2. CF*CC1=CFa, CFl]CF
=CFCI, CF2ClCClCF2゜CICC1=
(, PCl, CFCl, CF=CF, CF, CC
1=CCIFCF, CC1=CCL, CCIF2CF
=CC12,CC13CF:CF2゜CF,CICC1
= CCI□, CFCl, CCl=CC1□, CF
3CF=CIICI.

CCIF2CF=C1lC1, CF3CCI=CIIC
I, CllF2CC1=CC1aCFzCICII=
CCI2. CF2ClCC1=CIICI, C(:
l3CF=C1iCI.

CCl5CF=CIICl, CIIBrCF=CC
Fluoroprohenes such as 1, CF, CC1/CFCF
,, CF2・CFCF2CCIF2゜CF, CF2C
Examples include fluoroolefins having 4 or more carbon atoms such as F=CCI□. Among these, chlortrifluoroethylene is preferably employed from the viewpoint of polymerizability and safety.

Further, as the copolymer, an ethylenically unsaturated compound copolymerizable with a fluoroolefin or the like is employed. Examples of such ethylenically unsaturated compounds include olefins, vinyl ethers, vinyl esters, allyl ethers, allyl esters, and organic compounds containing an acroyl group or a methacroyl group.

In particular, it has excellent copolymerizability with fluoroolefins. From the viewpoint of excellent solvent solubility, vinyl ethers, vinyl esters, and allyl ethers are preferably those having a linear monobranched or alicyclic alkyl group having about 1 to IO carbon atoms.

Further, the fluoroolefins and the comonomers copolymerizable with the fluoroolefins may be used alone, or two or more types of compounds may be copolymerized.

In addition, the solvent-soluble fluorine-containing copolymer has a fluorine content of 10
It is preferable that it is at least M% by weight.

If the fluorine content is too low, sufficient weather resistance cannot be obtained, which is not preferable. Preferably the fluoroolefin is 30
It is a fluorine-containing copolymer copolymerized at a ratio of ~70 mol%. If the copolymerization ratio of fluoroolefin is too high, the solubility in the solvent will be poor, and if it is too low, the weather resistance will be deteriorated, which is not preferable.

Further, the fluorine-containing resin copolymer has a curing site, and by curing it using a curing agent, the solvent resistance, acid resistance, alkali resistance, etc. of the coating are further improved, which is preferable.

Examples of such curing reactive sites include active hydrogen-containing groups such as hydroxyl groups, carboxylic acid groups, acid amide groups, and amino groups, epoxy groups, unsaturated groups, and active halogen-containing groups. Among these, active hydrogen-containing groups are preferred from the standpoint of excellent reactivity with isocyanate curing agents, aminoblast curing agents, etc. that are commonly used as curing agents, and hydroxyl groups are particularly preferred. A method for introducing such a curing reactive site is to copolymerize a monomer having a curing reactive site such as hydroxyalkyl vinyl ether, hydroxyalkyl allyl ether, hydroxyalkyl vinyl ester, glycidyl vinyl ether, acrylic acid, methacrylic acid, allyl vinyl ether, etc. Methods include adding acid anhydride, isocyanate alkyl (meth)acrylate, etc. to a fluorine-containing copolymer through a polymer reaction, hydrolyzing the ester bonds of the polymer, and converting them into carboxylic acid groups or hydroxyl groups. Adopted.

Further, it is preferable that the solvent-soluble fluorine-containing copolymer has an intrinsic viscosity in the range of 0.01 to 4.0 Odl/g as measured in tetrahydrofuran because it has excellent coating properties and physical properties of the coating film.

In the present invention, the ultraviolet absorber is blended in an amount of ~40 parts per 1,130 parts by weight of the solvent-soluble fluorine-containing copolymer. If the amount of the ultraviolet absorber is less than the above, the effect of preventing rusting will be small, and if it is too large, it may cause myblade on the coating film, which is not preferable.

The ultraviolet absorber blended into this coating composition is 62.4-dihydroxybenzophenone, such as benzophenone type, benzotriazole type, phenyl salicylate type, Q organic oxide type, etc.

2, -2'-4-4'-tetrahydroxybenzophenone, 2-hydroxy-4-ctoxybenzophenone, 2-hydroxy-4-tridecyloxybenzophenone, 2 (2'-hydroxyl 4'-octoxyphenyl) Examples include benzotriazole, P-sheepylphenyl salicylate, particulate titanium oxide, and particulate pigment. In addition, by using a UV absorber with a crosslinking part that can react with the curing agent, the UV absorber is fixed in the coating film formation network, resulting in a more durable coating composition that does not migrate or elute over a long period of time. It is also possible to form a substance, and such ultraviolet absorbers include 2-
Hydroxy-4-hydroxyethoxybenzophenone:
Examples include 2-hydroxy 4-(2'-hydroxy)propoxybenzophenone.

As the curing agent, a compound that reacts with the curable reaction site of the above-mentioned solvent-soluble fluorine-containing copolymer and/or the crosslinked portion of the ultraviolet absorber to give a good cured product is used, and is usually used in the paint field. Hardening agents can be used.

Examples include polyisocyanate curing agents, metal alkoxides, aminoplus 8, and the like. As the polyincyanate curing agent, polyisocyanate compounds such as hexamethylene diisocyanate, polymers thereof, and blocked isocyanate compounds in which isocyanate groups are blocked with a blocking agent such as phenol are used. Particularly preferred are non-yellowing types.

Melamine resin is also used as aminoblast.

Guanamine resin, urea resin, etc. are used.

In particular, among melamine resins, melamine that has been at least partially etherified with one or more lower alcohols such as methanol, ethanol, propatool, and butanol is preferably employed.

Examples of metal alkoxides include aluminum propoxide, titanium butoxide, zirconium butoxide,
Silane alkoxide etc. are used.

It goes without saying that common additives for paints such as antifoaming agents, leveling agents, and solvents can also be added. Furthermore, a synthetic resin such as acrylic resin may be mixed.

In the method of the present invention, the paint as described above is applied directly to a metal surface. The painting method is roll coat.

Any coating method such as spray coating, dip coating, etc. may be used.

Furthermore, the method of the present invention is particularly useful for application to easily corroded substrates such as iron, stainless steel, aluminum, copper, ditan, tone, and brass.

[Example] Examples ■ to 6. Comparative Example 1゜ Using fluorine-containing copolymers a and ~a6 having the copolymer compositions (wt%) shown in Table 1, a coating composition was prepared at the blending ratio (heavy portion) shown in Table 2. I got it. This coating composition was directly applied onto the substrate shown in Table 2 using a film applicator to a dry film thickness of 25μ, and then cured under the curing conditions shown in Table 2 to obtain a test piece. Ta. Table 3 shows the results of weathering tests performed on each test piece.

Table 1 all shows the chemical reaction of succinic acid to produce HB V E of 0.
5% was acid-denatured.

CTFE: chlorotrifluoroethylene CHV E dichlorohexyl vinyl ether EV E: ethyl vinyl ether HBVE dihydroxybityl vinyl ether G V E nigericidyl vinyl ether EVE
S: Ethyl vinyl ester V-130 is manufactured by Kyodo Pharmacy Co., Ltd.: 2-Hydroxy-4-octoxybenzophenone titabine P is manufactured by Nihon Cibagaggi Co., Ltd.: 2-(2'-Hydroxy-4'-octoxyphenyl)benzotriazole T -42 is manufactured by Adeka Argus = 2-hydroxy-41
2'-Hydroxy)-ethoxybenzophenone C-EH is manufactured by Nippon Polyurethane Co., Ltd. Hexamethylene isocyanate cyclic trimer Cymel 303 is manufactured by Mitsui Toatsu Chemical Co., Ltd. Hexamethoxymethylol melamine Aluminum base material is Bonderite treated No. 3 In each test in the table, those with rust are ×, those without are O
And so.

[Effects of the Invention] The coated metal products obtained by the method of the present invention have a much better rust-preventing effect on the base material than conventional products coated directly on metal. This difference is especially noticeable when clear coating is applied.

SUS304 is stainless steel.

Claims (1)

[Claims] (1) 1 to 40 parts by weight of an ultraviolet absorber per 100 parts by weight of a solvent-soluble fluorine-containing copolymer having a curing reactive site and having a fluorine content of 10% by weight or more based on the polymerized units of the fluoroolefin; A method for producing a coated metal product, which comprises directly coating a metal surface with a coating composition containing 0 to 40 parts by weight of a curing agent and curing the coating composition.