JP2006182015A - Fluorine resin-coated aluminum material with excellent antifouling properties - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the antifouling property against oily contamination such as magic without impairing the properties required for a metal plate precoat material such as bending workability, etc., with excellent adhesion to a fluorine resin coating layer A resin-coated aluminum material is obtained.
SOLUTION: A fluororesin coating layer is composed of a fluororesin and a curing agent resin, and the mixing ratio is 30:70 to 85:15 by weight, and the curing agent resin is a mixture of an isocyanate resin and a melamine resin. The thickness is 19: 1 to 2: 1 by weight, and further contains 1 to 30 parts by weight of a hydrolyzable silane compound as an additive with respect to 100 parts by weight of a resin composed of a fluororesin and a curing agent. A fluorine resin-coated aluminum material having a fluorine resin coating layer of 5 to 30 μm.
[Selection] None

Description

  The present invention relates to a fluorine-based resin-coated aluminum material having excellent antifouling properties, moldability, and weather resistance, and is particularly suitable for outdoor building materials, civil engineering products, vehicles, electrical products, kitchen products, and the like.

  The aluminum material in the present invention includes not only a JIS 1000 series pure aluminum system but also an alloy system such as JIS 3000, 5000, 6000, and 7000 series.

  There are two types of materials used in this application: a post-coating material that paints the surface of a metal plate that has been molded into a predetermined shape in advance, and a pre-coating material that has a coating film provided on the surface of the metal plate in advance.

  Conventionally, post-coating materials have been the mainstream, but the production efficiency is low, the cost is high, and the biggest problem is that the user must provide a coating film after molding into a predetermined shape, and therefore a coating material containing a solvent It is easy to pollute the environment because it is released directly into the atmosphere. Accordingly, precoat materials that hardly cause environmental pollution have been developed and used mainly (for example, see Patent Document 1 and Patent Document 2).

Pre-coating materials generally employ a structure in which a chemical conversion film is provided on the surface of a metal plate and a resin coating layer is provided on the surface, and the user only needs to mold it into a predetermined shape before use. This is an environmentally friendly material.
JP 2000-212764 A JP 2003-060382 A JP 2003-293169 A

  The pre-coating material has an adhesive property that prevents the resin coating layer from being peeled off even during its molding, a bending property that can be easily molded into a predetermined shape, and contaminants are less likely to adhere during use. In addition to the antifouling property that is easy to fall off, there is also a need for weather resistance against an operating atmosphere that can withstand long-term use.

  However, the precoat material usually uses a reactive chemical film represented by a phosphoric acid chromate film as the chemical film, but this chemical film itself has excellent adhesion to the metal plate, but it has difficulty in weather resistance and bending workability. In addition, there is a problem that adhesion with a fluororesin excellent in antifouling property and weather resistance is not good, and peeling at the interface tends to occur.

  Patent Document 3 discloses at least one selected from the group consisting of an organic component composed of a water-soluble resin, chromate, a Zr compound, and a Ti compound in order to improve adhesion between both the aluminum plate and the fluororesin. It is disclosed that a composite chemical conversion film composed of an inorganic component is provided, and a baking film of a mixture of a solvent-soluble fluororesin and a curing agent is provided thereon. However, for the fluorine-based resin film shown in this patent document, when an isocyanate-based resin is used alone as a curing agent, bendability and carbon stain resistance are good, but it is weak against oily dirt such as magic, which will be described later. In the red magic resistance test, the red magic residue is generated. In addition, when melamine resin is used alone as a curing agent, the red magic stain resistance is good, but there is a disadvantage that the coating film cracks in the bending test, and both bendability and antifouling properties are contradictory. It was difficult to do.

  Therefore, the present invention is excellent in adhesion to the fluororesin coating layer with respect to the above-mentioned problems, and without impairing the properties required for the metal plate precoat material such as bending workability, and further oily contamination such as magic. An object of the present invention is to provide a fluorine-based resin-coated aluminum material with improved antifouling properties.

  In order to achieve the above object, the present invention provides a fluororesin-coated aluminum having a chemical conversion film formed on the surface and further having a fluororesin coating layer having a thickness of 5 to 30 μm thereon as shown in claim 1. The fluorine resin coating layer is made of a fluorine resin and a curing agent resin, and the mixing ratio is 30:70 to 85:15 by weight, and the curing resin is a mixture of an isocyanate resin and a melamine resin. The ratio is 19: 1 to 2: 1 by weight, and further contains 1 to 30 parts by weight of a hydrolyzable silane compound as an additive with respect to 100 parts by weight of a resin composed of a fluororesin and a curing agent. Is a fluorine-based resin-coated aluminum material excellent in antifouling properties.

Furthermore, as shown in claim 2, the thermosetting fluororesin coating layer is composed of a fluororesin and a curing agent resin, and the mixing ratio is 50:50 to 80:20 by weight. The ratio of the isocyanate resin and melamine resin is 14: 1 to 4: 1 by weight, and the crosslinking density is 4 × 10 ⁻⁴ mol / cc or more and 2 × 10 ⁻³ mol / cc or less. It is a characteristic fluorine-based resin-coated aluminum material.

  The fluororesin-coated precoated aluminum plate according to the present invention is excellent in weather resistance, bending workability and antifouling property, and is used industrially for outdoor building materials, civil engineering products, vehicles, electrical products, kitchen products, etc. It has a remarkable effect.

  The fluororesin-coated aluminum material according to the present invention will be described in detail.

  When forming the organic-inorganic composite chemical conversion film on the surface of the aluminum material, first, degreasing treatment is performed to clean the surface of the aluminum material. As the method, for example, a commercially available alkaline degreasing agent may be used by a normal method performed by a spray method, an immersion method or the like, and there is no particular limitation. Thereafter, washing with water is performed, and if necessary, pickling treatment for removing smut may be performed.

As the chemical film provided on the surface of the aluminum material, a chemical film having good adhesion between both the aluminum material and the fluororesin coating layer is used. Among them, an organic-inorganic composite type chemical conversion film is preferable. The reason for this is that the adhesion with the aluminum material, which is the same inorganic material, is enhanced by the action of the contained inorganic component, and the adhesion with the fluorine-based resin coating layer formed thereon by the action of the contained organic component. It is for improving. As a result, the occurrence of delamination between the films during processing such as bending is suppressed. In addition, it is more flexible than the inorganic component such as phosphate chromate film due to the organic component, so it absorbs the stress applied to this chemical film during processing, and the aluminum material and the fluororesin coating layer It plays the role of a buffering function and also maintains the adhesion between the aluminum material and the fluororesin film after processing.
Examples of the organic / inorganic composite chemical conversion film include a film formed with a treatment liquid containing an organic compound in chromate, zircon nonchromate, titanium nonchromate, or the like.

As the organic compound, polyacrylic acid, polyvinyl alcohol, cellulose hydroxy ether, ethylene maleic anhydride, polyvinyl pyrrolidine, polyvinyl methyl ether, or the like is used. More preferably, any one of a film made of chromium phosphate and a water-soluble acrylic resin, a film made of zirconium carbonate and a water-soluble acrylic resin, or a film made of titanic acid and a water-soluble phenol resin is used. Further, preferably 2 to 50 mg / ^{m 2} in metal weight basis containing its coating amount, 5 to 40 mg / ^{m 2} in weight metal Cr in coating and more preferably made of chromium phosphate and water-soluble acrylic resin, and zirconium carbonate A film made of a water-soluble acrylic resin has a metal Zr content of 3 to 20 mg / m ² , and a film made of titanic acid and a water-soluble phenol resin has a metal Ti content of 3 to 30 mg / m ² .

  When the coating amount is less than the above range, the adhesion and bendability are poor, and when it is large, the bendability is inferior, and the coating peels off due to cohesive failure of the organic-inorganic composite chemical coating itself.

  The organic-inorganic composite type chemical conversion film may be a known method such as a roll coating method, a dipping method, or a spray method, and the forming method is not particularly limited.

  For the above reasons, an organic-inorganic composite type conversion film is essential as a conversion film formed between the fluororesin film and the aluminum alloy. However, a reactive inorganic conversion film is formed between this conversion film and the aluminum material. A film may be formed as necessary.

As the inorganic chemical conversion film, any one of a phosphoric acid chromate film, a chromic acid chromate film, a zirconium phosphate film, and a titanium phosphate film is selected and used. Furthermore, the film amount of the inorganic chemical conversion film is preferably 100 mg / m ² or less in terms of the amount of metal contained, but more preferably, the inorganic chemical conversion film used is 5 to 50 mg / m in terms of metal Cr in the phosphate chromate film. ² below, 15~80mg / ^{m 2} in weight metal Cr in chromic acid chromate film, a metallic Zr amount of zirconium phosphate coating 3 to 20 mg / ^{m 2,} a metallic Ti amount of titanium phosphate coating 3 to 30 mg / a m ^2.
If the amount of the film is too much, the bendability is inferior, and the adhesion with the organic / inorganic composite type conversion film is also deteriorated.

  This inorganic chemical conversion film may be formed by a method such as spraying or dipping, and is not particularly limited.

  The fluororesin coating layer is formed by mixing a solvent-soluble fluororesin obtained by copolymerizing a copolymerizable monomer such as fluoroolefin or vinyl ether and a curing agent, and further adding a solvent ( Aromatic hydrocarbons, alcohols, ethers, esters, ketones, etc.) are added to prepare a paint having a predetermined viscosity, and this paint is applied using a roll coater, blade coater, die coater, spray device, etc. It coats on the 2nd chemical conversion film, then, after giving the baking process at the highest reached plate temperature of 200-300 ° C, it dries and forms.

  The thickness of the fluororesin coating layer is 5 to 30 μm. If it is less than 5 μm, the coating film adhesion in the DEW cycle test described later is inferior, and if it exceeds 30 μm, the coating cost becomes high.

  The ratio of the fluororesin and the curing agent resin in the coating layer is 30:70 to 85:15 by weight ratio. If the ratio of the curing agent resin exceeds 70% by weight, the coating film becomes too hard and the bendability is inferior, and since the fluororesin content is small, the coating film adhesion in the DEW cycle test described later is inferior. On the other hand, if it is less than 15% by weight, the red magic stain resistance is inferior due to insufficient coating film hardness. For the same reason, the ratio of the fluororesin and the curing agent resin is preferably 50:50 to 80:20 by weight.

  As a hardening | curing agent resin used for formation of the said fluorine-type resin coating layer, what mixed the isocyanate resin and the melamine resin in the ratio of 19: 1 to 2: 1 by weight ratio is used. If the ratio of isocyanate resin to melamine resin is greater than 19: 1, the red magic stain resistance described later is poor. If it is less than 2: 1, the bendability is inferior. The isocyanate resin is not particularly limited, and examples thereof include polyisocyanate and those obtained by blocking the isocyanate group with caprolactam. As the melamine resin, melamine, benzoguanamine and the like can be used, and there is no particular limitation. For the same reason, it is preferable that the isocyanate resin and the melamine resin have a weight ratio of 14: 1 to 5: 1.

The crosslink density of the resin layer composed of the fluororesin and the curing agent resin is preferably 4 × 10 ⁻⁴ mol / cc or more and 2 × 10 ⁻³ mol / cc or less. When the crosslink density is less than 4 × 10 ⁻⁴ mol / cc, the coating film hardness is not sufficient, and the magic ink component enters in the red magic stain resistance test described later, leaving a mark of red magic. On the other hand, if it is larger than 2 × 10 ⁻³ mol / cc, the red magic stain resistance can be completely removed, but the coating film becomes too hard and the bendability is poor.

  In order to develop the crosslinking density, it is important to control the baking conditions. Normally, the baking conditions for pre-coated metal sheets are determined by the baking temperature (PMT: Peak Metal Temperature), and the baking time, but in order to change the baking time in an existing coating line, it is common to change the line speed. However, in particular, increasing the baking time decreases the line speed, which is not a preferable method from the viewpoint of productivity. Therefore, a method of controlling by the baking temperature (PMT) is adopted. Accordingly, the baking temperature (PMT) for expressing the crosslinking density is preferably 210 ° C. or higher and 250 ° C. or lower because the baking time of a general coating line is 30 seconds to 100 seconds. When the PMT is 200 ° C. or less, the crosslink density is small, so that red magic resistance and adhesion are poor. On the other hand, at 260 ° C. or higher, the crosslink density is too large and the bendability is poor.

In the fluororesin coating layer, a silane compound may be blended in order to further improve the antifouling property, and when a hydrolyzable silane compound such as alkoxysilane is added during the preparation of the fluororesin coating layer, The hydrophilicity of the resin film surface is improved, and the antifouling property of the resin-coated metal material is further improved including the antifouling property against rain streaks.
Examples of the alkoxysilane include tetramethoxysilane and tetraethoxysilane, but are not particularly limited.

  The content of the silane compound is preferably 1 to 30 parts by weight and more preferably 4 to 30 parts by weight with respect to 100 parts by weight of the resin including the fluororesin and the curing agent. If it exceeds 30 parts by weight, paintability deteriorates, adhesion and bendability deteriorate.

  Furthermore, an antifoaming agent, a leveling agent, a catalyst, a wax and the like may be contained as long as the performance of the fluororesin-coated aluminum material of the present invention is not impaired.

  Since the fluorine-based resin used in the present invention has a high carbon-fluorine bond energy and is not easily decomposed by light energy, it has high weather resistance. Therefore, the fluorine-based resin coating layer does not contain a color pigment or dye in the coating layer. When a colorless and transparent resin is used, it can be used as a clear pre-coated metal plate, and when a colored pigment or dye is included, it can also be used as a colored resin-coated aluminum material.

  The type of aluminum material can be applied to any aluminum alloy other than pure aluminum, and the shape is not limited to coil shape, cut plate shape, etc., but from the standpoint of productivity, cost, and uniformity of performance It is preferable to coat the coil. In the case of using a plate, the thickness is not limited, but those having a thickness of about 0.1 to 2.5 mm are used in consideration of molding processability and shape retention.

  Hereinafter, the present invention will be described in detail with reference to examples. In addition, this invention is not limited to a following example, unless the range of a claim is exceeded.

(Invention Examples 1 to 16)
An aluminum alloy plate (A5052-H32, plate thickness: 1.0 mm) is degreased by a spray method with a commercially available alkaline degreasing agent, washed with water, dried, and then coated with an organic-inorganic composite chemical conversion film shown in Table 2 with a roll coater. After heating and drying (PMT 100 ° C.), the coating containing the resin components shown in Table 3 is applied on the surface with a roll coater, baking and drying (PMT 230 ° C. × 70 seconds), and the resin coating shown in Table 4 is applied. A specimen of an aluminum alloy plate was obtained.

(Invention Examples 17 to 40, Comparative Examples 1 to 10)
An aluminum alloy plate (A5052-H32, plate thickness: 1.0 mm) is degreased by spraying with a commercially available alkaline degreasing agent, washed with water, then provided with an inorganic chemical conversion film shown in Table 1 by spraying, washed with water and dried. Then, the organic-inorganic composite chemical conversion film shown in Table 2 was applied by a roll coater and then dried by heating (PMT 100 ° C.), and the coating containing the resin component shown in Table 3 was applied on the surface with a roll coater, followed by baking. Drying (PMT 230 ° C. × 70 seconds) yielded test materials for resin-coated aluminum alloy plates shown in Table 4.

  Tables 1, 2, 3, and 4 show the types of the inorganic chemical conversion film, the organic-inorganic composite chemical conversion film, and the fluorine resin, respectively.

  The following tests were performed using the obtained specimens.

(1) Adhesiveness The surface of the resin coating layer was cross-cut and a decycle test according to JIS Z 9117 7.5 was performed for 1000 hours, and then a tape peel test was performed to observe whether the film was peeled off. The case where there was no peeling of the film was evaluated as “◎”, and the case where peeling occurred was evaluated as “x”. In addition, the test conditions were set to one cycle of darkness for 60 minutes after irradiation for 120 minutes, and cooling water was sprayed to the back surface of the test piece for the first 30 minutes in the darkness of 60 minutes.

(2) Bendability In accordance with the bending test described in JIS H4001, after performing 3T and 4T tests with bending radii 3 and 4 times the thickness of the specimen, tape peeling test was performed on the bent part, and the film and coating layer The peeling state of was observed. No peeling at 3T was evaluated as “◎”, 4T without peeling was evaluated as “◯”, and 4T was evaluated as “×”.

(3) Antifouling property a An aqueous solution in which 5% by weight of carbon black was suspended was spray-coated on the surface of the carbon-fouling-resistant resin coating layer, and then dried in a thermostatic bath at 60 ° C for 1 hour. Subsequently, the surface state after carbon black adhering to the film surface in running water was wiped with gauze and dried was observed. The case where it could be removed cleanly was evaluated as “◎”, the case where it remained a little, “Δ”, and the case where it was hardly removed was evaluated as “x”.
b Resistance to Red Magic Contamination Red magic adhered to a frame of 3 cm × 5 cm in size, allowed to stand at room temperature for 24 hours and dried, then the surface was wiped with ethanol and the appearance was visually evaluated according to the following criteria.
(Evaluation criteria)
◎ ... Red magic can be completely removed ○ ... Red magic can be almost removed (very slightly tinted)
△ ... Weak traces left ... ... Almost no removal c Outdoor exposure test An outdoor exposure test was conducted for 12 months, and the presence or absence of rain streak was visually evaluated.
(Evaluation criteria)
◎ ... No rain streak ○: There is almost no rain streak × ... With rain streak stains For each of the above test results, a score of ○ or higher was accepted.

(Invention Examples 47 to 56)
An aluminum alloy plate (A5052-H32, plate thickness: 1.0 mm) is degreased by spraying with a commercially available alkaline degreasing agent, washed with water, provided with an inorganic chemical conversion coating by spraying, washed with water and dried with a roll coater. An organic-inorganic composite chemical conversion coating was provided, and a coating material containing the resin component shown in Table 3 was applied on the surface thereof using a roll coater, and baked and dried to obtain a test material for a resin-coated aluminum alloy plate shown in Table 7. .

  The test similar to Example 1 was done using the obtained test material.

The crosslink density shown in Table 7 was measured by the following method. That is, a coating film (free film) having a width of 10 mm and a length of 40 mm was measured with a leo vibron at a heating rate of 2 ° C./min and a frequency of 11 Hz, and calculated using the following rubber elasticity formula.
n = E '/ 3RT
n: crosslink density (mol / cc), E ′: equilibrium storage elastic modulus (dyne / cm ² ),
R: gas constant (8.314 × 10 ⁷ erg.deg / mol),
T: Absolute temperature at equilibrium storage modulus (° K)

The results are shown in Table 4, Table 5, Table 6, and Table 7.
As apparent from Table 4, Table 5, Table 6, and Table 7, No. 1-No. The 50 fluororesin-coated aluminum alloy plate has excellent adhesion, bendability, and antifouling properties.
In addition, No. 2 corresponding to the invention example of claim 2. 48, 50, 51, 52, 54, and 55 are particularly excellent in red magic resistance and bendability.
On the other hand, Comparative Example No. No. 1 was inferior in adhesion and bendability because there was no chemical conversion film.
Comparative Example No. in which the coating amount of the inorganic chemical conversion coating or the coating amount of the organic-inorganic composite conversion coating is too large. 2 and no. No. 3 had poor bendability.
Comparative Example No. in which the film thickness of the fluororesin coating layer is too thin. No. 4 had poor adhesion.
Comparative Example No. 5 and no. No. 6 was inferior in antifouling property (red magic stain resistance) because the proportion of the melamine resin in the curing agent resin was small and the crosslinking density was too low.
Comparative Example No. No. 7 had poor adhesion and bendability because the fluororesin content in the fluororesin coating layer was too low.
Comparative Example No. No. 8 had inferior red magic stain resistance because the content of the curing agent resin in the fluororesin coating layer was too low.
Comparative Example No. No. 9 was inferior in antifouling property (outdoor exposure test) because no silane compound was added.
Comparative Example No. No. 10 had poor bendability because the proportion of the melamine resin in the curing agent resin was too large.
Comparative Example No. No. 11 was inferior in adhesion and bendability because the amount of silane compound added was too large.

Claims (2)

In a fluorine resin-coated aluminum material having a chemical conversion film formed on the surface and further having a fluorine resin coating layer having a thickness of 5 to 30 μm thereon, the fluorine resin coating layer is composed of a fluorine resin and a curing agent resin. The mixing ratio is 30:70 to 85:15 by weight, the curing agent resin is a mixture of isocyanate resin and melamine resin, the ratio is 19: 1 to 2: 1 by weight, and water is added as an additive. 1 to 30 parts by weight of a decomposable silane compound with respect to 100 parts by weight of a resin composed of a fluorine resin and a curing agent. The thermosetting fluororesin coating layer is composed of a fluororesin and a curing agent resin, and the mixing ratio is 50:50 to 80:20 by weight, and the curing resin is a mixture of an isocyanate resin and a melamine resin. 2. The prevention according to claim 1, wherein the ratio is 14: 1 to 4: 1 by weight, and the crosslinking density is 4 × 10 ⁻⁴ mol / cc or more and 2 × 10 ⁻³ mol / cc or less. Fluorine resin-coated aluminum material with excellent soiling properties.