JPS62273846A - Fluorocarbon resin-coated aluminum material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention Industrial Application Field The present invention relates to a fluororesin-coated aluminum material, and particularly to an aluminum material with an improved surface treatment layer used for building materials, etc. Regarding.

Conventional technology Aluminum materials are used in various fields because they are less rusty and lighter than iron materials, but they are especially used in roofing materials,
It is often used as a building material such as interior and exterior wall materials and window sashes.

Aluminum new human resources used as such building materials are
If the usage conditions are severe, such as when the product is exposed to wind and rain for a long period of time, corrosion of the surface is inevitable, and surface anti-corrosion treatment is applied to prevent this, but even this is insufficient. Therefore, in order to further improve the surface corrosion resistance and improve the appearance, the surface is coated with a resin film and used.

For such resin films, fluororesin is used, which has excellent physical properties such as outdoor weather resistance, bending workability, chemical resistance, solvent resistance, abrasion resistance, water repellency, stain resistance, non-adhesion, and corrosion resistance. The use of a coating film is being practiced. Because fluororesin paints have such excellent physical properties, for example, organosol paints mainly made of vinylidene fluoride resin have a uniform coating film that is baked, but their softening point is as high as 170°C. The materials used to form the coating layer are aluminum plates, galvanized steel plates, and other metal plates that can withstand this, and these metal plates coated with a fluorine resin coating are widely used as long-term maintenance-free materials. be done.

This type of fluororesin coating is applied after surface anti-corrosion treatment as described above, but this surface anti-corrosion treatment is also carried out to improve the adhesion with the fluororesin coating; Methods of forming insoluble phosphates on aluminum plates and methods of forming chromates on aluminum plates have been used. Among these, the chromate treatment method has a strong coating film and contains hexavalent chromium, which has strong oxidizing power, so it promotes passivation of the aluminum plate surface and has a corrosion-preventing effect. It is preferable because it has a enhancing effect.

Conventionally, in order to treat such an aluminum plate with chromate, the aluminum plate is degreased, the surface is roughened, and then soaked in a chromate solution.
Dry and chromate the surface to form a chromate treatment layer. However, in the case of a structure in which a resin coating film is provided on a chromated aluminum plate, the thickness of the chromate layer is 30 arg/rd or less in terms of film amount, so the surface corrosion resistance of the aluminum plate is improved. Rather, it can be said that it is applied to improve the adhesion of the fluororesin paint film, and it is difficult to set the treatment conditions, making it difficult to reproduce the corrosion resistance performance of the treated film and the adhesion of the paint film. However, they also have the disadvantage that their performance deteriorates rapidly over time. Fluororesins, such as vinylidene fluoride resin, have poor adhesion to such chromate-treated layers, so epoxy resin primers are applied to the chromate-treated layer. It is common practice to apply fluororesin through a fluorine resin. This has been done for fluororesin-coated galvanized steel sheets for a long time, and now it is also done for aluminum sheets.

However, the normally used bisphenol type epoxy resin primer has many light-sensitive aromatic rings in its molecular structure, and has the disadvantage that it is particularly susceptible to decomposition and deterioration due to ultraviolet rays. For this reason, in the case of fluororesin coatings that generally require long-term weather resistance of 20 years or more, organic UV absorbers cannot avoid deterioration of their performance, so inorganic pigments are kneaded into the coating to avoid UV rays. There is no other way than to prevent the transmission of inorganic pigments, but the type and concentration of inorganic pigments used for this purpose in the coating film are regulated. It has been difficult to use coatings with colors that transmit ultraviolet rays.

In addition, in the case of a thin aluminum plate, the distortion does not become so large even if it is repeatedly heated and cooled, such as by applying epoxy resin paint and baking it, then applying fluororesin paint and baking it, etc. In the case of molded products such as wood, repeated heating and cooling associated with baking can cause significant distortion, which poses a problem in terms of dimensional stability, so it is preferable to omit at least one coated layer.

Problems to be Solved by the Invention As mentioned above, conventional fluororesin-coated aluminum materials require an epoxy resin primer when the aluminum material is treated with chromate to form a fluororesin coating film. However, this epoxy resin primer has problems with weather resistance, and the heating and cooling associated with baking causes distortion in the aluminum material.
Improvement was desired.

Means for Solving the Problems In order to solve the above problems, the present invention provides a chromate treatment layer on an aluminum material of 90-g in terms of metallic chromium.
/m2 or more, and a coating layer having a fluororesin layer containing fluororesin as a main component is provided on the chromate treatment layer. .

Next, the present invention will be explained in detail.

The fluororesin-coated aluminum material of the present invention includes not only aluminum alone but also alloys containing 99% by weight or more of aluminum. A chromate-treated layer is formed on this aluminum material, and this chromate-treated layer is formed by immersing the aluminum material in a chromate solution, and its thickness is 90 mg/n1 in terms of metal chromium.
Do more than that. This can be achieved, for example, by immersion in a chromate treatment bath consisting of sodium chromate, sodium dichromate, carbonic acid, sodium fluoride, etc. for 2 to 10 minutes. This is the thickness of the chromate-treated layer when a chromate-treated layer is formed on conventional aluminum material, an epoxy resin primer is applied thereto, and a fluororesin coating is further applied in terms of metal chromium.
This is more than three times the rd.

A specific example of a chromate treatment bath is 5 g of chromic anhydride>
Sodium fluoride 4g, sodium dichromate 10g
, 6 g of nitric acid, and 75 g of water are also exemplified.

The reason why the chromate treatment layer can be thickened in this way is that aluminum material has excellent workability and it is difficult to apply excessive force to the surface coating layer, and the aluminum oxide formed on the surface This is thought to be because the chromate-treated layer and chromium oxide form a solid solution, which causes the chromate-treated layer to firmly adhere to the aluminum material surface, making it difficult for the chromate-treated layer to peel off. This allows a fluororesin coating to be directly formed without the need for a conventional epoxy resin primer. The effect of aluminum material is that galvanized steel sheets do not have sufficient workability, and the surface oxide does not form a solid solution with chromium oxide like aluminum oxide does, so epoxy This is a marked difference compared to those that require a resin primer.

In addition, in the present invention, a coating layer having a fluororesin layer mainly composed of a fluororesin is provided, but this fluororesin paint may be made of a so-called solvent-based dispersion organosol in which a fluororesin is dispersed in a solvent. is used, but is not limited to this.

Fluorocarbon resins used in these materials include tetrafluoroethylene (CI"a=CFz), chlorotrifluoroethylene (CF2=CFCj!), hexafluoropropylene (CF, -CF=CFY), trifluoroethylene ( CHF=CF2), vinyl fluoride (C11
2=CIIF) and vinylidene fluoride (CF2=C
All fluorine-containing polymers obtained by homopolymerization of fluorinated monomers such as Hz) or copolymerization with other monomers are included. Among these, examples include those in which the fluorine content in the resin is 20 to 6 (1% by weight); Examples include copolymers of vinylidene and acrylic (7/3 copolymerization ratio) (fluorine content in resin 50% by weight), polyvinyl fluoride, etc. Thermosetting fluororesins are also used. be done.

Other resins can also be used in combination with the above fluororesin,
These include thermoplastic resins such as acrylic resins, thermosetting acrylic resins, melamine resins, urea resins, and isocyanate compounds. Furthermore, one or more of each or both of a silane coupling agent and a titanate coupling agent is added at a rate of 0.00% per 100 parts by weight of the fluororesin.
It can also contain 1 to 10 parts by weight, and additives commonly used in paints, such as coloring pigments, extender pigments, plasticizers, organic solvents, surfactants, and antifoaming agents, may also be used alone or in combination of two or more. It can also be used in combination.

Examples of the thermoplastic acrylic resin include polymers of acrylic esters and methacrylic esters, or copolymers thereof. In this case, the ester groups include methyl, ethyl, propyl, butyl, isobutyl, n-
Examples include hexyl, lauryl, stearyl and the like. The copolymer may contain one or more of these ester groups.

Thermosetting acrylic resins contain functional groups (carboxyl groups, hydroxyl groups, amino groups,
methylol group, epoxy group, etc.), such as acrylic acid, methacrylic acid, acrylamide, methacrylamide, N-methylol acrylamide, allyl glycidyl ether, glycidyl methacrylate;
Examples include, but are not limited to, polymers obtained by copolymerizing two or more heptamers selected from the two groups of styrene, acrylic esters, and methacrylic esters.

The above-mentioned fluororesin paint may contain other resins, titanate coupling agents, or silane coupling agents in addition to the above-mentioned fluororesin as described above. When polyvinylidene fluoride resin is used, 10 to 10 parts of thermoplastic resin or thermosetting acrylic resin are added to 100 M parts of polyvinylidene fluoride resin.
It is preferable to add 0 parts by weight, preferably 60 parts by weight or more. At such a mixing ratio, the vinylidene fluoride resin or copolymer thereof in the dried coating film is 30% by weight, preferably 45% by weight.
It is preferable that it is contained in an amount of % by weight or more. Note that various plasticizers may be added to maintain appropriate fluidity of the coating material.

In addition, the above fluororesin paint can be partially dissolved in a solvent or mixed with the above acrylic resin, etc., but it is generally supplied as a solvent-type dispersion organosol paint, and in this case, When adding a solvent, this solvent composition determines the coating suitability, dispersion of the fluororesin,
The viscosity and flow characteristics of the paint, the storage stability of the paint (the property that the resin particles are stably dispersed in the dispersion medium and do not aggregate), which shows the long-term shelf life of the paint, and the film-forming ability, which shows the film-forming performance. It has a big impact. Generally, a solvent having a polar group such as a ketone or ester solvent and an aromatic hydrocarbon solvent are used in combination.

In addition, as for the coloring agent that can be added to the above-mentioned fluororesin paint, any pigment can be used, but in order to take advantage of the properties of fluororesin such as heat resistance, chemical resistance, and outdoor weather resistance, it is necessary to use these pigments. It is preferable to use a pigment having the same characteristics as the above, and when using it, for example, 5 to 240 parts by weight can be added to 100 parts by weight of polyvinylidene fluoride. Metal powders such as aluminum powder and copper powder can also be used. When this metal powder is used, it is preferable to apply a top coat to prevent its oxidation.

When providing a top coat layer, all of the above-mentioned fluororesin paints except for colorants can be used. At this time, waxes, olefin-based synthetic resins, ultraviolet inhibitors, silicone-based repelling agents, etc. can also be included.

For paints that require top coats, roll coating, curtain coating, spray coating, etc. are used.

To form the fluororesin-coated aluminum material of the present invention, each of the above-mentioned paints is applied, and each is held and baked at a temperature exceeding the melting point of the vinylidene fluoride resin or its copolymer until a sufficient film is formed. .

When the coating film of the fluororesin layer is baked in this way, the fluororesin in the coating film is melted or swollen by the dimethyl phthalate, etc. contained therein, and as a result, the particles of the fluororesin fuse and become uniform. On the other hand, dimethyl phthalate evaporates and disappears from the paint film. When a uniform fluororesin coating Wj or film is formed in this manner, the features of the fluororesin such as water repellency, corrosion resistance, weather resistance, non-adhesiveness, and stain resistance are utilized. As a result, the corrosion resistance of the oxide film formed on the surface of this base material is maintained for a long time by blocking chemical substances and moisture contained in the atmosphere in which the aluminum material with the fluororesin coating is used. At the same time, the adhesive base of the fluorocarbon resin coating is maintained firmly, so its function can be maintained for a long time.In this way, the two act synergistically, and the effects of these alone are added to In addition, it is possible to exhibit remarkable effects that are more than expected.

Effects of the Invention As explained above, the present invention provides aluminum material with 90%
Since we formed a chromate-treated layer of tmg/rrr or higher, and directly provided a coating layer with a fluororesin layer containing fluororesin as its main component, we no longer needed a conventional epoxy resin primer. Epoxy resin primers, such as fluororesin-coated aluminum materials, are degraded by ultraviolet rays, resulting in a decrease in durability.To avoid this, using pigments that absorb ultraviolet rays in fluororesin paints has affected the type and amount of the pigments mixed. There are no restrictions that prevent us from painting in vivid colors or translucent colors that are close to the original colors, and we can provide long-term maintenance-free building materials that take advantage of the features of this fluororesin coating. In addition, since no epoxy resin primer is provided in this way, the workability of the fluororesin coating film is not limited by the less flexible epoxy primer, which is the case with conventional methods, and the primer application This process can be omitted, so productivity can be improved, and the baking of this primer can also reduce the occurrence of distortion in the aluminum material of molded products such as sashes due to heating and cooling associated with the baking process. In addition to the advantage of not providing an epoxy resin primer in this way, the chromate treatment layer also has good adhesion to the aluminum material, which improves its durability as a base material, thus improving the durability of the substrate. ! The durability of the film is also improved, and the durability of the entire film can also be significantly improved. This makes it possible to provide an innovative material that has a much longer service life as a building material than conventional materials.For example, it can extend the maintenance-free period of high-rise buildings, further increasing its effectiveness, and meeting recent demands. can be met.

Example The present invention will be explained in detail below using examples.

First, the surface treatment shown in the following example is performed to prepare a primer paint and a vinylidene fluoride paint having the following formulation.

Surface treatment example I JIS A 1100
5 to degreasing agent (consisting of borate, phosphoric acid, surfactant)
After soaking for 1 minute to degrease, further immersing for 1 minute in a 20% caustic soda solution for etching, and washing with dilute nitric acid.
Dip in Bonderite 713 (Nippon Parkara 2.5) for 30 seconds and dry. The thickness of the treatment layer is 30 lI in terms of chromium.
g/cd.

Surface Treatment Example 2 An aluminum plate according to JIS A 1100 It is immersed in the Bonderite 713 treatment agent for 3 minutes and dried. The thickness of the treated layer was 100 mg/td in terms of chromium.

Formulation example 1 (primer paint) Epoxy resin (40% non-volatile content toluene solution) 51.
0 (Epicoat 1009: manufactured by Shell Chemical Co.) Titanium white (Tai Pure R960: manufactured by DuPont > 1
2.0 Strontium chromate 2
．． Knead 0 or more. To this, melamine resin (60% non-volatile content xylene solution) 8.0 (
Super Beckamin L105: Dainippon Ink & Chemicals ■
Cellosolve Acetate 7.0 Cyclohexanone 1O10 Toluene 5.0 Methyl Ethyl Ketone 5.0 or more are stirred to make a 100 (parts by weight) paint.

Formulation example 2 (vinylidene fluoride paint (enamel)) Titanium white 10.0 (Typure R960 + manufactured by DuPont) NiO-SbO-T
iO based fired pigment 2.0 (Golden Yellow I28: Chef Art) FeO-CrO-
ZnO-based fired pigment 1.0 (Mahogany Brown I 12: Chef Art) Acrylic resin (
Non-volatile content 40% toluene solution) 25.0 (Paraloid B44: Rohm & Haas Co., Ltd.) is kneaded.

Vinylidene fluoride resin 23.0
(Liner 500: manufactured by Benwalt) Dimethyl phthalate 2.0 Isophorone
7.0 Cellosolve Acetate 10.0 Diacetone Alcohol 7.0 Xylene
Stir 13.0 or higher to 1
100 (wall) paint.

Formulation example 3 (vinylidene fluoride paint (metallic enamel) acrylic resin (40% non-volatile content toluene solution) 2
7.0 (Paraloidro 44: manufactured by Rohm & Haas) Vinylidene fluoride resin 32.0 (Liner 500: manufactured by Pennwalt) Dimethyl phthalate
3.0 isophorone
6.0 Cellosolve Acetate 6.0 Diacetone Alcohol 11.0 Xylene
15.0 aluminum paste (75% non-volatile content) 9.0 (Miragrow 1000: Toyo Aluminum) or more is stirred to make a 100 (parts by weight) paint.

Formulation example 4 (vinylidene fluoride paint (top coat paint)
) Acrylic resin (40% non-volatile content toluene solution) 31.
0 (Paraloid B44: manufactured by Rohm & Haas) Vinylidene fluoride resin 32.0 (Kaichi 500 = manufactured by Pennwalt) Dimethyl phthalate
4.0 Isophorone
7.0 Cellosolve Acetate
9.0 diacetone alcohol
13.0 xylene
4.0 or more is stirred to make a 100 (parts by weight) paint.

Example 1 The vinylidene fluoride paint (enamel) of Formulation Example 2 was applied by spraying to an aluminum plate treated according to Surface Treatment Example 2, and baked at 250° C. for 15 minutes to form a coating film with a thickness of 25 μm. These are summarized in Table 1.

Example 2 A fluororesin-coated aluminum plate using a combination of the enamel and top coat of Formulation Example 4 was obtained by processing according to the conditions shown in Table 1 in the same manner as in Example 1.

Comparative Examples 1 to 3 According to Example 1 according to the conditions shown in Table 1, a thin surface treatment layer, a primer combined with this, and a top coat applied in combination with the fluorine layer corresponding to the above example were prepared. A resin-coated aluminum plate was obtained.

The following tests were conducted on the above-mentioned fluorine resin-coated aluminum plate, and the results shown in Table 2 were obtained.

Test items and test method Pencil hardness According to JISDO202, the painted surface of the test piece is rubbed with a pencil whose tip has been ground flat. At this time, the pencil should be at a 45° angle with the painted surface, and the writing pressure should be as high as possible without crushing the lead.

The pencil hardness of the painted surface is defined as the hardest pencil that does not scratch the painted surface.

Coin Scratch Apply an unused 10 yen coin to the painted surface of the test piece at a 45° angle and rub the painted surface with the maximum force that will not damage the underlying metal. At that time, if the base metal is not visible at all, ◎, if the entire surface is peeled off, ×, and in between, O1△ according to the degree of peeling.
And so.

Ml! Rub A gauze sufficiently impregnated with methyl ethyl ketone (Mt!K) is wrapped around the index finger, and a load of 15 kg is applied to the tip of the finger, and the coated surface of the test piece is rubbed. It is indicated by the number of times the rubbing is repeated until the underlying metal is exposed.

Stripped Cellotape Peeling According to JISDO 202, 100 strips (10 x 10
)make. A cellophane tape having a width of 12 squares in accordance with JIS Z1522 is completely adhered to the goblets, and immediately the cellophane tape is held perpendicular to the coating surface and pulled off momentarily, and the number of goblets remaining without being peeled off is counted.

Bending process A painted aluminum plate with a thickness of 2.0 mm has a radius of curvature of 2.0 mm on the painted surface.
Bend it to 180'' so that it becomes 180'' so that the radius of curvature becomes 4.0*■ before OT.

This process is called 2T processing. That is, the former is a test piece with the painted plate folded in half, and the latter is a 2.0
This corresponds to the state in which two coated test specimens are sandwiched and folded in half. A cellophane tape with a width of 12 cranes according to JIS Z1522 is completely adhered to the processed part and immediately and momentarily pulled off. A case where there was no peeling at all was rated as ◎, a case where the entire surface was peeled was rated as ×, and a value in between was rated as 0 or △ depending on the degree of peeling.

Boiling test According to JISI [5400], the test piece is kept in boiling water for 8 hours. Immediately after taking out the test piece, the presence of blisters on the surface is determined and the cellophane tape is removed. Regarding the determination of blisters, those that do not have any blisters at all are ◎
, Blisters covering 10% or more of the total area were rated as x. The method and evaluation of grain peeling are the same as above.

Cath Test According to JISDO 201, the test piece is held in a mist of 5% saline and cupric chloride acetic acid solution for 500 hours, and no damage is observed on the flat surface. % or more was rated as ×, and those in between were rated as ○ and △ depending on the degree. ◎ if there is no damage at all in the cant part, 0 if the damage is less than 2N on one wheel in the cant, △ if there is 2 to 51 layers.
Items that exceeded the above were marked as ×.

Salt water spray test According to JIS Z2351, the test piece was placed in salt water mist for 3 minutes.
It was held for 000 hours. The evaluation items and criteria are the same as for the CASS test.

Due cycle test according to JISA1415, light source closed 750V, 6
0A (7) Arrange the test pieces in a due cycle tester equipped with a carbon arc lamp, and set the relative humidity to 50% light at 1
One cycle was defined as one hour of darkness at a relative humidity of 95%, and 250 cycles, ie, 500 hours, were performed. After 500 hours had elapsed, the test piece was subjected to a cellophane tape peeling test.

A 15 W germicidal lamp was used as the ultraviolet ray irradiation test light source, and the test piece was placed at a distance of 25 mm from the light source and held for 500 hours.

Thereafter, a strip tape peel test was conducted.

Chemical resistance test specimens were tested with 5% NaOH, 5% HC1, and 5% HCOO, respectively.
The sample was kept immersed in H for 10 days. After taking it out, it was washed with water and immediately evaluated. If no <tii is seen on the coating, mark it as ◎, and if blisters occur over the entire surface, mark it as ×.
The intermediate value was defined as 01Δ depending on the degree.

From the above test results, Comparative Example 1 with a thin chromate treatment layer
Comparative Examples 2 and 3, in which an epoxy primer was provided on this thin chromate treatment layer and a fluororesin coating was provided on top of this, had poor processability and poor weather resistance (due cycle test). , ultraviolet irradiation test) are also found to be poor. In comparison, Examples 1 and 2 are both good.

(Margins below this page) Table 1 Notes] Note that #f1. ICIB indicates 1 coat, 1 bake (1 coat applied).

Table 2 Examination - Section

Claims (1)

[Claims] (1) A chromate-treated layer is formed on aluminum material at a concentration of 90 mg/m^2 or more in terms of metal chromium, and a coating layer having a fluororesin layer containing fluororesin as a main component is formed on the chromate-treated layer. A fluororesin-coated aluminum material characterized by the following: