JPH0471925B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to modified acrylic resin coated decorative stainless steel. More specifically, an acrylic ester or methacrylic ester is copolymerized with a vinyl group-containing alkoxysilane, a vinyl group-containing polysiloxane, and an acrylic ester or methacrylic ester having a hydroxyl group or an epoxy group as a modification monomer by copolymerization. The present invention relates to the steel material coated with a coating material containing the obtained modified acrylic resin as an active ingredient. Stainless steel materials, especially BA with mirror finish
(Bright Annealing), surface-conditioned stainless steel plates, steel strips, steel pipes, etc. that have been surface-conditioned by fabric polishing, hairline polishing, etc. are characterized by their durability and metallic luster, and are molded into automotive moldings, emblems, etc. Stainless steel foil is widely used for interior and exterior parts of automobiles, interior and exterior materials for building materials, furniture, home appliances, etc. However, even with such surface-conditioned stainless steel materials, the products related to the above-mentioned applications tend to rust or become dirty due to long-term use, and the color of the steel materials may differ from that of the stainless steel itself. There were problems such as limited colors and restrictions in terms of decoration. Stainless steel materials are sometimes painted with acrylic resin paint for decoration, rust prevention, and stain prevention purposes while taking advantage of the metallic luster of stainless steel. However, when transparency and high hardness are required for the paint film, flexibility and adhesion are sacrificed, and stainless steel materials with such a high hardness paint film are processed by press processing, roll processing, etc. Forming has the drawback that cracks occur in the coating film or the coating film peels off. Furthermore, such coatings have insufficient salt resistance, alkali resistance, and weather resistance, so the use of stainless steel materials with high hardness acrylic resin coatings is limited to indoor use where there is less ultraviolet rays. There is. In addition, regarding the coloring of the surface of stainless steel materials, there is a method in which an anodic oxide film with a thickness of 500 to 10,000 Å is formed on the surface of the material, and the surface is colored by the interference of natural light and reflected light (Note: Parakeet Color). There is. However, steel materials produced using this coloring method have the following drawbacks: ``The processed surface of the stainless steel material changes color, the color tone changes depending on the viewing direction or due to the adhesion of oil, etc., and the manufacturing cost due to processing technology. ``becomes higher.'' Therefore, this technology has only been applied to extremely limited applications. Therefore, it has been practically extremely difficult to color the stainless steel material with transparency while maintaining its metallic luster, and also to impart rust prevention properties to the surface. As a result of intensive research in order to solve the above-mentioned problems of the conventional technology related to stainless steel materials, the present inventors applied a coating material containing an acrylic resin modified with a specific silicone resin as an active ingredient to a stainless steel material and then baked it. It has been found that by attaching this material, a resin coating containing siloxane bonds can be obtained on the surface of the material. It has been discovered that this film does not have the above-mentioned disadvantages of conventional acrylic resin coatings, can be mixed with pigments that can be colored as desired, and does not have the above-mentioned disadvantages of anodized coatings. Thus, the present invention was completed. As is clear from the above description, an object of the present invention is to provide a modified acrylic resin coated decorative stainless steel with excellent colorability and durability. Other objectives will become apparent from the description below. The present invention has the following main configuration (1) and embodiment configurations (2) to (4). (1) 20 to 2% by weight of vinyl group-containing alkoxysilane, 20 to 0.01% by weight of vinyl group-containing polysiloxane, 20 to 5% by weight of acrylic acid ester or methacrylic acid ester having a hydroxyl group or epoxy group, and the number of carbon atoms in the ester group. 80 to 40% by weight of acrylic ester having 1 to 12 carbon atoms or methacrylic ester having ester group having 1 to 12 carbon atoms and 0.1% of organic acid having 3 or more carbon atoms
The active ingredient is a modified acrylic resin produced by radical copolymerization in the presence of ~5% by weight.
Modified acrylic resin painted decorative stainless steel with paint film baked at 100-350℃. (2) The stainless steel according to item (1) above, wherein the coating film has a thickness of 1 to 30 μm. (3) The stainless steel according to item (1) above, wherein the coating film contains a pigment having an average particle diameter of 2 μm or less. (4) The stainless steel according to item (1) above, which has a coating film that is rebaked at 100 to 300°C after deformation. The modified acrylic resin used in the present invention is
It is produced by copolymerizing the following monomers and/or the following monomers. Vinyl group-containing alkoxysilane Vinyl group-containing polysiloxane Containing hydroxyl group or epoxy group (a) Acrylic ester or (b) Methacrylic ester Acrylic ester Methacrylic ester However, in order to obtain the best physical properties of the coating film, it is necessary to There is a preferable range (% by weight) for the proportion of each compound used in the production of a copolymer. These ranges are 20 to 2% by weight (hereinafter simply expressed as %) for vinyl group-containing alkoxysilanes, 20 to 0.01% by weight for vinyl group-containing polysiloxanes, and 20 to 2% by weight for vinyl group-containing polysiloxanes. Acrylic acid ester or b.
The amount is 20 to 5% by weight for methacrylic esters, and 80 to 40% by weight for acrylic esters or methacrylic esters. If the amount of any one or more of the compounds used is outside the above range, the physical properties of the coating film painted using the obtained modified acrylic resin will be lower than those of the present invention, or if the amount of the compound used is outside the above range. The same applies if the amount is greater than the above range, and if it is less than the above range, the basic physical properties of the acrylic resin coating will be lost. Specific examples of the vinyl group-containing alkoxysilane include methacryloxypropyltrimethoxysilane and vinyltrimethoxysilane. Specific examples of the vinyl group-containing polysiloxane include vinyl dimethyl polysiloxane at both ends (viscosity: 50 CP) and methacryl dimethyl polysiloxane at both ends (viscosity: 200 CP). The viscosity range of these polysiloxanes is preferably about 5 to 10,000 CP. Specific examples of the acrylic ester or methacrylic ester containing a hydroxyl group or an epoxy group include glycidyl methacrylate and 2-hydroxyethyl methacrylate. The ester group of the acrylic ester or methacrylic ester preferably has 1 to 12 carbon atoms, and specific examples thereof include ethyl acrylate, n-butyl acrylate, methyl methacrylate, butyl methacrylate, and lauryl methacrylate. It will be done. Two or more of the compounds and may be used in combination. In the copolymerization of the compound (monomer) of ~, preferably an organic acid having 3 or more carbon atoms is added to the polymerization mixture (note: the total amount of the compound used) of 0.1~
Use 5% by weight. In addition, as a polymerization catalyst, 0.1 to 2% by weight based on the total amount of all monomers, preferably 0.2 to
1% by weight of a radical initiator such as benzoyl peroxide is used. As for the polymerization method, either bulk polymerization performed without a solvent or solution polymerization performed in the presence of a solvent can be carried out. However, considering the steps to be carried out after completion of polymerization (note: formulation for coating), solution polymerization is most preferable. Polymerization conditions (temperature, time) are not limited and are controlled by the polymerization type, but are usually 60℃ to 150℃, 2
Or it will be finished in 10 hours. The method of supplying the monomers during polymerization varies depending on the heat removal type of the polymerization vessel and the presence or absence of a solvent or dispersion medium, but it is possible to supply each monomer individually or in a mixed manner to the polymerization vessel sequentially. good. The degree of polymerization of the modified acrylic resin used in the present invention is controlled by the type and amount of polymerization catalyst used relative to the amount of monomer, or by the addition of a chain transfer agent. However, in solution polymerization using an organic solvent, a certain proportion of the solvent is used with respect to the total amount of monomers, and after the polymerization is completed, the above-mentioned viscosity range is adjusted to be suitable for the production of coatings. Adjust the degree of polymerization. The preferred viscosity range is 100 to 2,000 CP (25°C), more preferably 200 to 1,000 CP (25°C), and the weight average molecular weight (based on styrene) is 5,000 to 100,000 in a xylene solvent with a polymer concentration of 40% by weight. The organic solvent used in solution polymerization may be any organic solvent as long as it has physical properties that do not interfere with subsequent preparation and baking steps, and examples include toluene, xylene, butanol, and ethyl cellosolve. By adding a curing accelerator to the coating material according to the present invention, baking curing conditions can be relaxed. As the curing accelerator, a curing catalyst used in the siloxane production reaction is preferably used,
The amount used is usually 0.05 to 1% by weight based on the resin content. Specific examples include bases, salts, or acids such as caustic potash, tetramethylammonium hydroxide, sodium acetate, phosphoric acid, and toluenesulfonic acid.
However, from the viewpoint of chemical stability of the catalyst itself,
Organometallic compounds such as dibutyltin oxide or tetrabutyltin are preferably used. The organic solvent solution of the modified acrylic resin used in the present invention produced as described above is then mixed with dyes and pigments, ultraviolet absorbers, antioxidants, and other additives necessary for the coating. Regarding the dyes and pigments, if the weather resistance of the coating film is important, it is preferable to use pigments. In addition, if the transparency of the colored coating film is important by adding pigments, the pigment particles should be reduced to 2μ or less, preferably 1μ, using various paint shakers such as ball mills, centrimills, and sand grind mills.
It is ground into the following fine particles and used by dispersing it in a coating material. One of the characteristics of the coating material according to the present invention is that it has good pigment dispersibility. If transparency is not particularly required, general pigments can be used as they are dispersed in the coating material. Next, a manufacturing example of the coating material according to the present invention will be described. Coating material production example 1-1, 2 40 parts by weight of methyl methacrylate (shown in parts below), 10 parts of n-butyl methacrylate, 10 parts of ethyl acrylate (subtotal of 60 parts), and glycidyl methacrylate as a modification monomer. , 10 parts each of 2-hydroxyethyl methacrylate, double-terminated vinyl dimethyl polysiloxane (viscosity 50CP), and methacryloxypropyltrimethoxysilane, 0.5 part of acrylic acid, and 0.5 part of benzoyl peroxide were mixed to form monomers for polymerization. A mixed solution was prepared. This mixed solution was dropped into 150 parts of xylene kept at 100℃ to cause a copolymerization reaction, and the final solution viscosity was 340CP.
A silicone resin-modified acrylic resin solvent solution was obtained at (25°C) (note: resin concentration 40% by weight). To this solution, a mixed solvent of xylene-butanol (weight ratio 1:1) was added to make the resin content 30%, and then 0.5% by weight of ultraviolet absorber was added to the resin content, and the following two types were added. 2.5% by weight of each coloring pigment was added and mixed based on the resin content. That is, in coating production example 1-1, the particle size was 1μ.
The following transoxide reds [Dainichiseika Kagyo Kogyo Co., Ltd.]
In 1-2, 1.5% by weight of Cyan Blue 5050 (manufactured by Dainichiseika Kagyo Co., Ltd.) was used based on the resin content to obtain red and blue paints, respectively. Coating material production examples 2-1 and 2 In coating material production examples 1-1 and 2, 19 parts of lauryl methacrylate was used instead of ethyl acrylate as a comonomer, and methacrylate at both ends was used instead of vinyl dimethyl polysiloxane at both ends. A polymerization monomer mixture was prepared and a copolymerization reaction was carried out under the same conditions except that 1 part of dimethylpolysiloxane (viscosity 200CP) was used to obtain a silicone resin modified acrylic resin solvent solution with a solution viscosity of 600CP (25°C). Ta. A solvent, an ultraviolet absorber, and a pigment were added to this solution in the same manner as in Coating Material Production Examples 1-1 and 1-2 to obtain red and blue coating materials, respectively. The present invention relates to a stainless steel material having a cured film having a skeleton of siloxane bonds formed by applying a coating agent mainly composed of a silicone-modified acrylic resin to the surface of the stainless steel material and then heating and curing the coating material. The stainless steel used is not particularly limited in its composition or surface conditioning method. However, as will be described later, in order to ensure the adhesion of the coating film, it is preferable to wash and remove dirt such as oil and dust in advance. The modified acrylic resin coating according to the present invention can naturally be applied to materials such as steel or aluminum. However, the reason why the paint according to the present invention is limited to stainless steel materials is that general paints, including known acrylic resin paints, have all of the weather resistance, rust prevention, hardness, and adhesion properties of stainless steel materials. This is because there was nothing that was completely satisfying. Stainless steel products are generally surface-conditioned, and methods such as BA (Bright
Annealing), 2B (skin pass rolling after annealing and pickling), cloth polishing, and hairline polishing (HL). The stainless steel material used in the present invention does not necessarily require surface conditioning as described above. However, if contaminants such as oil or dust adhere to the surface of the steel material during preparation or storage before painting, it is preferable to perform degreasing cleaning (e.g. solvent cleaning with Triclean, etc.) or alkaline cleaning. . As a method for applying the modified acrylic resin coating according to the present invention, any of a roll coater method, a blade coater method, a gravure coater method, a beat coater method, a curtain flow coater method, a dip coating method, and a spray coating method are possible. The roll coater equipment is illustrated as follows. In the diagram, indicates a payoff reel, indicates a welding machine for coil connection, indicates an accumulator,
Pretreatment equipment for degreasing and cleaning, No. 1 roll coater, No. 2 roll coater, No. 1
The baking furnace is No. 2 baking furnace, the cooling device after painting and baking, and the coil winding machine after painting and baking are completed. This equipment is a device that continuously paints and bakes strip steel sheets, and is the No. 1 roll coater and the No. 1 roll coater.
No. 1 with baking furnace and No. 2 with roll coater.
There are two baking furnaces, each of which is a pair, and so-called two coats and two bakes are possible. When the paint baking according to the present invention is performed using this equipment, the above-mentioned No. 2 roll coater is not particularly required. In other words, the strip-shaped stainless steel sheet supplied from the payoff reel is continuously connected to the welding machine and subjected to alkaline degreasing and cleaning before coating by the pretreatment device. After that, the No. 1 roll coater coats the object to the desired thickness, and it is baked in the No. 1 baking furnace and No. 2 baking furnace, and then cooled and cut into coils by a cutting machine. It is cut and rolled up. As for the baking conditions, that is, the heat curing conditions, the relationship between temperature and time is relative, and
It depends on the required performance of the coating film. However, a wide range of temperatures from 100 to 350°C and from 1 hour to 0.5 minutes is possible.
A preferred baking condition that is easier to carry out is a relatively short baking time of 1 to 10 minutes in an atmosphere in which the object to be coated is heated to 150 to 300°C. However, under conditions where the heating time becomes somewhat longer, e.g.
Heating at 250°C for 10 to 60 minutes can further improve the performance of the coating film according to the invention. The above fact also means that when mass-producing the painted steel strip etc. according to the present invention, it is possible to improve the performance of the coating film by rebaking after baking as described below. i.e. for example, first 250
By reheating the coated stainless steel material baked at 1 to 5 minutes at 220° C. for 20 minutes, it is possible to produce the steel material with improved performance without impairing mass productivity. The thickness of the coating film according to the present invention is preferably 1 to 1.
If it is less than 1μ, interference fringes will be seen on the film surface, which is unfavorable in terms of appearance, and if it exceeds 30μ, the performance as a coating will not improve, and conversely, when processing the stainless steel material for strength, it may cause peeling. There is a tendency that it becomes easier to do things. A characteristic effect of the present invention is that sufficient corrosion resistance can be exhibited even if the coating film is extremely thin. In other words, in the case of a coating film related to general paints, there are drawbacks such as the possibility of chipping of the coating film unless the thickness is considerably thicker, for example, 30μ or more, but in the case of the present invention, the coating film thickness is as described above. Even if the thickness is only a few microns, the performance as a coating film can be maintained. As detailed above, in the present invention, special organic and inorganic coatings are formed on the stainless steel surface, and compared to conventional acrylic resin coatings or anodic oxidation coatings, the products of the present invention have the following properties: It has the characteristics of (1) Excellent pigment dispersibility makes it easy to obtain transparency;
It has a glossy color similar to stainless steel. (2) Hard and scratch-resistant with a surface hardness of 2H or higher. (3) Excellent weather resistance. (4) Excellent adhesion. (5) Good corrosion resistance. (6) Good chemical resistance. (7) The coating will not peel off due to roll processing, press processing, etc. (8) The color tone does not change depending on the viewing direction. (9) Excellent fingerprint stain resistance and oil stain resistance. (10) Can be manufactured economically. Due to the above-mentioned features, the product of the present invention can significantly expand the degree of freedom in design regarding color specifications as a coating material compared to conventional products. Further, by being able to mold a stainless steel plate or coil after surface treatment, various effects such as labor saving, lower defective rate, and cost reduction are brought about in the final product. The present invention will be explained below with reference to Examples and Comparative Examples. Examples 1 to 7, Comparative Example 12 The coating material according to the present invention was baked on a stainless steel plate under the conditions listed in Table 1 below and the notes column of the same table, and the properties of the coating film were evaluated and compared.

[Table] As is clear from Table 1, interference fringes are seen when the film thickness is less than 1μ, and some peeling is observed in the Erichsen Cellotape peeling test at 24μ, so a film thickness of 1 to 30μ is appropriate. It was determined that Furthermore, it is clear that sufficient film performance can be obtained under short curing conditions such as 3 minutes at 220°C to 1 minute at 300°C. Examples 7 to 10, Comparative Examples 3 and 4 SUS 304 DF (Dull
Finish finish, matte skin) or HL (Hair Line)
Finishing) was used, and the baked film thickness of the coating material was varied, and the product was exposed to the atmosphere as it was or bent at 90°, and the presence or absence of rust was compared with a stainless steel substrate without the coating material applied. Test conditions and results are shown in Table 2.

【table】

[Table] From Table 2, the product of the present invention does not rust even under atmospheric exposure conditions where the base material rusts, and the coating film according to the present invention:
It is clear that the rust prevention function is not lost even after 90° bending. Examples 11 to 15, Comparative Example 5 SUS 430 BA (thickness 0.5
mm), and the coating material obtained in Coating Material Production Example 2-1 was used to observe the bending workability depending on the curing conditions of the coating material and the film thickness of the coating film according to the present invention. Table 3 shows the firing conditions and the presence or absence of abnormalities in the R portion of the fired coating film.

[Table] From Table 3, the coating film of the product of the present invention has a bending angle of 180°.
It is generally good for roller bending, but the heating time for baking is preferably at least 10 minutes at 200℃, at least 3 minutes at 250℃, and at least 2 minutes at 300℃. However, since some interference colors were observed after firing at 300° C. for 8 minutes, it is desirable that the firing time be 8 minutes or less. Examples 16 to 19, Comparative Examples 6 and 7 SUS 430 BA or SUS 304 as base material
Performance of the obtained coated board by baking with HL and using coating material production example 1-1 or 1-2 or commercially available acrylic resin or Incocolor with varying curing conditions and film thickness. was evaluated on the following items. The coating conditions and results are shown in Table 4. The evaluation method was based on the following three-stage method. That is, ○: No abnormality of the coating film such as peeling, staining, cracking etc. △: Slight abnormality is observed ×: Obviously abnormality is observed Rust prevention: Artificial seawater spray (20℃, 1 2), followed by infrared lamp drying, and the subsequent appearance was evaluated. Moldability: 90° bending and 180° bending were performed at R=2t, and the cellophane tape peeling test was performed on the bent portions, and the appearance thereafter was evaluated. Chemical resistance: It was immersed in a mixed solution of 28% HCI and 3% H ₂ O ₂ water for 30 seconds, and its appearance was evaluated thereafter. Salt water resistance: 144 in 3% NaCI aqueous solution kept at 50℃
After soaking for a time, washing with water and drying, a cellophane tape peeling test was conducted to evaluate the subsequent appearance. Alkali resistance: The product was immersed in a 0.5% NaOH aqueous solution kept at 50°C for 144 hours, and its appearance was evaluated. Coin scratch resistance: The surface of the painted board was scratched with a 10 yen coin, and depending on the scratches, it was graded A (good).
Ratings were ranked in 4 grades: ~D (bad). Trichloroethane resistance: A cotton cloth was impregnated with trichloroethane, and the surface of the painted board was rubbed a predetermined number of times, and the appearance thereafter was evaluated. Weather resistance: A test was conducted in accordance with the accelerated weather resistance test of JISK5400, and the appearance and reflectance (Q = 60°) were measured.

【table】 [Brief explanation of the drawing]

The figure shows roll coater equipment as an example of coating equipment used in the method of the present invention. In the figure, ...payoff reel, ...welding machine, ...accumulator, ...pretreatment device, ...No.1 roll coater, ...No.2 roll coater, ...No.1 baking furnace, ...No. .2 Baking furnace, ...cooling device, ...cutting machine, ...coil winding machine, ...material to be coated (stainless steel coil).

Claims (1)

[Scope of Claims] 1 20 to 2% by weight of a vinyl group-containing alkoxysilane, 20 to 0.01% by weight of a vinyl group-containing polysiloxane, 20 to 20% by weight of an acrylic ester or methacrylic ester having a hydroxyl group or an epoxy group.
5% by weight and 80-40% by weight of an acrylic ester with an ester group having 1 to 12 carbon atoms or a methacrylic ester with an ester group having 1 to 12 carbon atoms, and 0.1 to 5% by weight of an organic acid having 3 or more carbon atoms. Modified acrylic resin-coated decorative stainless steel with a coating film baked at 100 to 350°C, whose active ingredient is modified acrylic resin produced by radical copolymerization in the presence of. 2. The stainless steel according to claim 1, wherein the coating film has a thickness of 1 to 30 μm. 3. The stainless steel according to claim 1, wherein the coating film contains a pigment having an average particle diameter of 2 μm or less. 4. The stainless steel according to claim 1, which has a coating film that is rebaked at 100 to 300°C after deformation.