JPS6123109B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a coating layer obtained by applying paint many times for the purpose of aesthetics, corrosion prevention, etc. Paints are applied to prevent corrosion of metal materials and metal products, and to decorate wood and wooden products, but in this case, it is rarely applied in one coat, and it is best to apply multiple coats to create a multilayer coating. This is the normal method. For example, if we explain the painting process using steel as an example,
Various steps are taken: surface treatment → undercoat → intermediate coat → topcoat. In the above, the surface treatment is performed by a physical method such as blasting or sanding. Next, boil oil (vegetable polymerized oil), long oil phthalate resin varnish, epoxy resin varnish, urethane resin varnish, chloride rubber varnish, vinyl chloride resin varnish, etc., which are commonly used as undercoat paints, and anti-rust pigments,
A paint made by mixing other pigments and the like is applied. In the painting process, the type of intermediate coat and top coat after applying the base coat is naturally determined by the type of the base coat. In other words, when a so-called oil-based anti-rust paint using boiler oil, long-oil phthalic acid resin varnish, etc. as a color vehicle is used as an undercoat, the intermediate coat and topcoat should be of the same type as the undercoat, that is, boiler oil. , limited to those using long-oil phthalic acid resin varnish as a color vehicle. Paints using polymeric synthetic resin varnishes such as the above-mentioned epoxy resin varnishes, urethane resin varnishes, chlorinated rubber varnishes, and vinyl chloride resin varnishes as color vehicles are used as intermediate coats, and as top coats, oil-based anti-rust paints are used. It cannot be painted over. Because these synthetic resins have high molecular weights, mineral turbene,
It does not dissolve in aliphatic solvents with low solubility such as white kerosene, and therefore aromatic solvents such as xylene and toluene, ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, and acetone, butyl acetate, ethyl acetate, etc. It is necessary to use a solvent with strong dissolving power such as an ester solvent or a glycol solvent. The aromatic, ketone, ester,
Glycol-based solvents have a strong ability to dissolve organic substances. For example, if a paint containing these solvents is applied as an intermediate coat or top coat over a film of oil-based anti-corrosion paint, the film of the oil-based anti-corrosion paint will dissolve due to the solvent. This is because the steel is easily remelted, causing defects such as wrinkles and peeling from the steel surface. In recent years, epoxy resin paints, urethane resin paints, and
A process has been adopted in which chlorinated rubber paints, vinyl chloride resin paints, and the like are arbitrarily combined as paint systems to bring out the characteristics of each paint. By the way, these paints exhibit extremely good film performance when applied under completely controlled conditions, such as when the steel surface is extremely clean by blasting before painting, but they are susceptible to rust and other problems. The durability of the coating film coated with the remaining deposits was significantly poor. On the other hand, the above-mentioned oil-based anti-rust paints have been widely used for a long time because they do not require very strict surface treatment, have excellent corrosion resistance of the paint film, and are easy to apply. However, as mentioned above, there are restrictions on the types of intermediate coatings and top coatings, and they are limited to oil-based or phthalic acid resin-based coatings. In addition, the weather resistance and chemical resistance of this type of paint are not very good, and paint systems using these as intermediate and top coats have suffered from poor durability due to recent air pollution. The number of years tends to be shorter. Therefore, as a recent trend, there is a tendency to use epoxy resin paints and urethane resin paints, which have particularly excellent weather resistance and chemical resistance, as intermediate and top coats, but the types of anti-rust paints are determined for the reasons mentioned above. It will be done. Therefore, by taking advantage of the advantages of oil-based anti-rust paints,
Phenol-modified phthalate resin varnish and MIO pigment (Micaceous Iron Oxlde; A phenol-MIO paint containing a combination of (oblique iron oxide) is applied onto the oil-based anti-corrosion paint film, and the MIO paint is interposed in the paint film.
A method of arranging pigments in a flat multi-layered manner and thus preventing the diffusion of solvents onto the surface of the oil-based anti-corrosion paint due to the shielding effect of the MIO pigment layer even if a strong solvent-containing paint is applied over the film. However, it is currently used as a standard method. However, this method is not perfect; for example, if the dissolving power of the solvent contained in the top coat applied to the phenol-MIO paint film is too strong, the phenol-modified phthalate resin may be re-dissolved, or The MIO pigment layer is not necessarily arranged in a uniform flat multilayered layer in the coating film, and has many pinholes in the coating film, so it has drawbacks such as the inability to completely prevent penetration and diffusion of the solvent. Therefore, in order to apply a strong solvent-containing paint over a paint film with poor solvent resistance, such as an oil-based anti-rust paint film, a film that is insoluble in the solvent and has few pinholes is interposed. It is sufficient to completely prevent the solvent in the paint from penetrating and diffusing into the undercoat layer. The present inventor has arrived at the present invention as a result of extensive research into this method. That is, the present invention relates to a coating layer formed by interposing at least one coating layer mainly composed of water-soluble or water-dispersible polyvinyl alcohol resin between two or more coating layers. The water-soluble or water-dispersible polyvinyl alcohol resin used in the present invention is one that can be dissolved or dispersed in cold water or hot water, but from the viewpoint of the moisture absorption resistance of the coating and the working viscosity, the saponification degree is 96 mol%. As mentioned above, those having an average molecular weight of 1500 or less and having hot water solubility are more preferable. For example Solsiden
DF-107, DF-108, DF-605N, DF-690, DF
-690N, DF-402, Denkapol K-20, K-
17, K-05, B-17R, W-24, B-24, B-
20, B-05, B-03 (all trade names manufactured by Denki Kagaku Kogyo), HiSelon H, HiSelon S, Gohsenol NH-20, NH-18, GH-17, GH-05 (all trade names made by Nippon Gosei Kagaku Kogyo) ), Kuraray Poval PVA
-105, PVA-107, PVA-110, PVA-204,
Commercially available resins such as PVA-205, PVA-210, and PVA-217 (all Kuraray product names) can be used. In the present invention, the intermediate coating material is mainly composed of the water-soluble or water-dispersible polyvinyl alcohol resin, but if necessary, coloring pigments such as carbon black, iron oxide, titanium oxide, zinc chromate, strontium, etc. Anticorrosive pigments such as chromate, aluminum phosphate, zinc phosphate, red lead, lead cyanamide, extender pigments such as talc, barium sulfate, calcium carbonate, etc. may be mixed and used in the form of a coating composition. In addition, additives such as surface conditioners, antifoaming agents, anti-settling agents, anti-sag agents, stabilizers, surfactants, chelate compounds, silane coupling agents, etc., which are commonly used as raw materials for paints, are included. Can also be used as an additive. Furthermore, a small amount of water-soluble or water-dispersible resin other than polyvinyl alcohol resin may be used in combination without impairing the object of the present invention. The method for obtaining the coating layer of the present invention is to apply a specific polyvinyl alcohol resin aqueous solution or aqueous dispersion on the dry undercoat layer in the previous step of overcoating the strong solvent-containing paint in the process of applying multiple coats.
Spray, brush, etc. to a dry film thickness of about 5 to 30 microns.
It may be applied by a conventional method such as using a roller, left at room temperature, forced heating, etc. to sufficiently scatter the water contained in the film, and then optionally coated with an organic solvent-containing paint. Furthermore, the number of polyvinyl alcohol resin layers in the multilayer coating layer does not need to be limited to one layer. That is, it is also possible to form a coating layer and a plurality of layers in the form of a sandwich, if necessary. In the above description, the case where a strong solvent-containing paint is coated over an oil-based rust preventive paint film has been explained as an example, but the present invention is not limited to oil-based rust preventive paint films. For example, it can be used to prevent tar from bleeding onto the top coat when a different type of top coat is applied by interposing it on a tar epoxy resin paint film, and it can also be used to color or coat bituminous films such as coal tar and asphalt. It can also be used as an intermediate layer when recoating paint to prevent deterioration. Furthermore, the method of the present invention is not limited to new overcoat layers. For example, when repainting a structure or the like, the intended purpose of the present invention can be achieved by interposing it between an old paint film and a new paint film. In this way, the coating layer obtained by the method of the present invention can be used in any combination, and has excellent solvent resistance such as oil-based anti-rust paints and phthalic acid resin-based anti-rust paints, which is impossible with known methods. Its industrial value is extremely high in that it has become possible to recoat an inferior coating film with a top coat containing a strong solvent such as an epoxy resin paint or a urethane resin paint. The present invention (particularly specific effects) will be explained below with reference to Examples. In addition, "part" or "%" in Examples and Comparative Examples indicates "part by weight" or "% by weight." First, various compositions used in Examples and Comparative Examples were kneaded in the following formulations by a conventional method. (1) Anti-rust paint A Boil oil 15.5 parts Red lead No. 1 78.0 15% lead naphthenate dryer 1.0 5% manganese naphthenate dryer 0.3 5% cobalt naphthenate dryer 0.2 Mineral turpentine 5.0 Total 100.0 (2) Anti-rust paint B Boil oil 31.5 parts Lead cyanamide 13.5 Iron oxide 10.0 Calcium carbonate 39.0 15% lead naphthenate dryer 1.0 5% manganese naphthenate dryer 0.3 5% cobalt naphthenate dryer 0.2 Mineral turpentine 4.5 Total 100.0 (3) Rust preventive paint C Long oil phthalate Acid resin varnish 20.0 parts (trade name Betsukosol P-470 manufactured by Dainippon Ink and Chemicals) Red lead No. 1 70.0 15% lead naphthenate dryer 1.0 5% manganese naphthenate dryer 0.3 5% cobalt naphthenate dryer 0.2 Mineral turpentine 8.5 total 100.0 (4) Epoxy resin paint A (mixing ratio; main agent: curing agent = 85 parts: 15 parts) (main agent) Epicoat 1001 (trade name manufactured by Ciel Chemical)
25.0 parts Iron oxide 10.0 Talc 30.0 Xylene 5.0 Methyl isobutyl ketone 20.0 Ethyl cellosolve 10.0 Total 100.0 (Curing agent) Tomide 410 (Product name manufactured by Fuji Kasei Industries)
80.0 parts Isobutanol 20.0 Total 100.0 (5) Urethane resin paint A (mixing ratio; main agent: curing agent = 85 parts: 15 parts) (main agent) Epicoat 1004 (trade name manufactured by Ciel Chemical)
12.0 parts Burnock DE140-70 (trade name manufactured by Dainippon Ink Industries) 10.0 Precipitated barium sulfate 30.0 Iron oxide 20.0 Methyl isobutyl ketone 10.0 Butyl acetate 10.0 Cellosolve acetate 8.0 Total 100.0 (Curing agent) Desmodyur N-75 (Bayer) product name)
80.0 parts Methyl isobutyl ketone 20.0 Total 100.0 (6) Tar epoxy resin paint A (mixing ratio; main ingredient:
Curing agent = 85 parts: 15 parts) (Main agent) Epicoat 1001 25.0 parts Coal tar pitch 20.0 Talc 20.0 Xylene 20.0 Methyl isobutyl ketone 5.0 Ethyl cellosolve 10.0 Total 100.0 (Curing agent) Sanmide X-2700 (trade name manufactured by Sanwa Chemical Industry) )
60.0 parts Isobutanol 20.0 Butyl acetate 20.0 Total 100.0 (7) Polyvinyl alcohol resin composition A Denkapol K-05 (trade name manufactured by Denki Kagaku Kogyo)
10.0 parts Talc 10.0 Water 80.0 Total 100.0 (8) Polyvinyl alcohol resin composition B Kuraray Poval PVA-107 (product name manufactured by Kuraray)
12.0 parts Water 88.0 Total 100.0 (9) Polyvinyl alcohol resin composition C Denkapol B-05 (trade name manufactured by Denki Kagaku Kogyo)
12.0 parts Iron oxide 5.0 Precipitated barium sulfate 5 Water 78.0 Total 100.0 Example 1 A dry film thickness of 35 microns of one coat of rust preventive paint A was applied to a cold-rolled steel plate that had been polished with #240 abrasive paper and degreased with solvent. Spray it twice at 24-hour intervals to ensure that it is dry, and let it dry indoors at 20℃ and 75%RH each time. 24 hours after the completion of the second coating, polyvinyl alcohol resin composition A was coated to a dry film thickness of 20 microns and left under the above conditions for 24 hours to allow water to scatter. Next, epoxy resin paint A was applied over and over to a dry film thickness of 100 microns, dried in a room at 20° C. and 75% RH for 7 days, and used as the sample material of Example 1 in a comparative test. Example 2 A sample material was prepared in the same manner as in Example 1 except that the epoxy resin paint A in Example 1 was replaced with urethane resin paint A, and was subjected to a comparative test. Example 3 A sample material was prepared in the same manner as in Example 1 except that epoxy resin paint A in Example 1 was replaced with tar epoxy resin paint A, and was subjected to a comparative test. Example 4 A cold-rolled steel plate that had been polished with #240 abrasive paper and desolvented was coated with anti-rust paint B twice at 24-hour intervals so that the dry film thickness of one coat was 35 microns.
Dry indoors at 20℃ and 75%RH. 24 hours after the completion of the second coating, apply polyvinyl alcohol resin composition B to a dry film thickness of 15 microns and leave it under the above conditions for 24 hours to allow water to scatter.Next, apply epoxy resin paint A to a dry film thickness of 100 microns. Recoat the paint to make it micron, 20℃, 75%RH.
It was dried in a room for 7 days and used as a test material in Example 4. Example 5 A sample material was prepared in the same manner as in Example 4 except that the epoxy resin paint A in Example 4 was replaced with urethane resin paint A, and was subjected to a comparative test. Example 6 A sample material was prepared in the same manner as in Example 4, except that epoxy resin paint A was replaced with tar epoxy resin paint A, and was subjected to a comparative test. Example 7 A cold-rolled steel plate that had been polished with #240 abrasive paper and degreased with solvent was coated with anti-rust paint C twice at 24-hour intervals so that the dry film thickness of one coat was 35 microns.
Dry indoors at 20℃ and 75%RH. 24 hours after the completion of the second coating, apply polyvinyl alcohol resin composition C to a dry film thickness of 20 microns, and leave it for 24 hours under the above conditions to scatter water. Next, apply epoxy resin paint A to a dry film thickness of 20 microns. Reapply paint to 100 microns and heat at 20℃, 75%
It was dried in a RH room for 7 days and used as a test material in Example 7. Example 8 A sample material was prepared in the same manner as in Example 7 except that epoxy resin paint A was replaced with urethane resin paint A, and was subjected to a comparative test. Example 9 A sample material was prepared in the same manner as in Example 7 except that epoxy resin paint A was replaced with tar epoxy resin paint A, and was subjected to a comparative test. Comparative Example 1 Comparative Example 1 was prepared in Example 1 without applying polyvinyl alcohol resin composition A. Comparative Example 2 Comparative Example 2 was prepared in Example 2 without applying polyvinyl alcohol resin composition A. Comparative Example 3 Comparative Example 3 was prepared in Example 3 without applying polyvinyl alcohol resin composition A. Comparative Example 4 Comparative Example 4 was prepared in Example 4 without applying polyvinyl alcohol resin composition B. Comparative Example 5 Comparative Example 5 was prepared in Example 5 without applying polyvinyl alcohol resin composition B. Comparative Example 6 Comparative Example 6 was prepared in Example 6 without applying polyvinyl allure resin composition B. Comparative Example 7 Comparative Example 7 was prepared in Example 7 without applying polyvinyl alcohol resin composition C. Comparative Example 8 Comparative Example 8 was prepared in Example 8 without applying polyvinyl alcohol resin composition C. Comparative Example 9 Comparative Example 9 was prepared in Example 9 without applying polyvinyl alcohol resin composition C. Examples 1 to 9 and Comparative Examples 1 to 9 thus obtained
The test results of No. 9 are shown in Table 1.

[Table] This was done with a skirt.
As is clear from the above test results, the present invention
Synthetic resin paints such as epoxy resin paints and urethane resin paints can be applied over the oil-based anti-rust paint film to form a paint layer, which was previously considered impossible, which further improves the performance of the paint film. do.

Claims (1)

[Claims] 1. A coating layer in which at least one coating layer made of a water-soluble or water-dispersible polyvinyl alcohol resin is interposed between two or more coating layers.