JPS6222668B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a technology for finding adhesive molecules that can firmly bond to metal surfaces and applying the adhesive molecules to metal surfaces.Compared to conventional so-called adhesive primers, this invention applies an extremely thin coating layer on the order of angstroms to metal surfaces. The present invention provides a method for forming a surface. It has been found that when a thermoplastic resin layer is coated on a metal surface treated with this adhesive molecule, it shows a revolutionary improvement not only in initial adhesiveness but also in adhesiveness over time, compared to conventional methods. The same effect can be obtained even when paints containing not only thermoplastic resins but also thermosetting resins are applied to the metal surface treated with these adhesive molecules and dried, and organic materials are applied to the metal surface, lamination, etc. When performing this, it is possible to maintain strong adhesion at the joint part, such as in the case of metal-to-metal joining. In general, there is a strong desire in various fields to form a strong thermal adhesive bond between a metal and a thermoplastic resin layer. For example, in the field of can manufacturing, it is widely practiced to form a can body by overlapping both end edges of a metal material for forming a can body with a thermoplastic adhesive such as polyamide and thermally bonding. When joining metal materials together using a thermoplastic adhesive, the adhesive strength between the surface of the metal material and the thermoplastic adhesive is not necessarily high even at the initial stage, and there is a tendency for the adhesive to deteriorate significantly over time. There is. To solve this problem, a method is generally adopted in which an adhesive primer such as epoxy-phenolic resin is applied to the metal material, baked, and then thermally bonded with a thermoplastic resin adhesive through this adhesive primer layer. There is. However, epoxy-phenol paints are relatively expensive and have a cumbersome process, as they must be applied in the form of a coating film onto a metal material. Furthermore, since the above paints must be applied in the form of an organic solvent solution, solvent costs and energy costs are required for baking, and since the release of organic solvents into the atmosphere is not allowed, afterburners are used to prevent this. Pollution prevention facilities such as these will be required. Such strong adhesion between thermoplastic resin and metal materials is also strongly desired for applications such as film laminated steel sheets that replace conventional coated steel sheets, and the above-mentioned drawbacks also occur in this case. It turns out. Therefore, an object of the present invention is to provide a surface treatment for a metal material that can improve the adhesion or adhesion between the metal material and a thermoplastic resin layer by applying extremely simple operations to the surface of the metal material. It is in providing the law. Another object of the present invention is to provide a method for surface treatment of metal materials, which can significantly improve the tendency of adhesive deterioration over time compared to the case where a conventional adhesive primer is applied to the surface of metal materials. Still another object of the present invention is to provide a treatment method that can improve the thermal adhesion of a thermoplastic resin layer to a metal material by forming a treatment layer that is extremely thin compared to conventional adhesive primers and with extremely simple operations. is to provide. According to the present invention, a method for surface treatment of a metal material is provided, which comprises applying a water-insoluble fatty acid in a gas phase to the surface of the metal material maintained at a high temperature. The invention will be explained in detail below. The processing agent used in the present invention is characterized in that it simultaneously contains a carboxyl group and a long-chain alkyl or alkylene group in its molecule, and has a combination of polarity and non-polarity. Therefore, when this water-insoluble fatty acid is applied in the form of steam to the surface of a high-temperature metal material, a remarkable improvement is brought about in the adhesive strength with the resin layer, especially the adhesive strength over time. Moreover, this improvement in adhesive strength results from the fact that the thickness of the vapor phase deposited layer (coating layer) is extremely thin, ranging from just a few angstroms (angstroms) to several hundred angstroms, which cannot be predicted from conventional adhesive primers or oiling layers. This is done in a timely manner. For example, a can body joint made by thermally bonding electrolytic chromic acid treated steel sheets (TFS) via a nylon adhesive has an initial adhesive strength of the order of 2.5 to 3.0 kg/cm, but after aging for more than 2 days. Later on, the bond strength decreases to the order of less than 0.5 Kg/cm. On the other hand, if TFS is heated and its surface is treated with oleic acid vapor to form a coating layer of about 20 Å, and then used as an adhesive can body in the same manner as above, the initial adhesive strength will be lower than that of the untreated one. The adhesive strength is improved by about 300% or more compared to the conventional adhesive, and the adhesive strength is maintained at 6 kg/cm or more even after the above-mentioned period of time has passed. Generally, when considering the deterioration of adhesion over time between a metal material and its coating layer, it is necessary to consider not only the adhesiveness of the joint but also the water resistance factor. The exact reason why the surface treatment of the present invention provides a combination of high initial bond strength and resistance to adhesive deterioration over time is unclear, but the chemical bonding with the metal surface due to vapor deposition on the hot metal surface is unknown. It is thought that this may lead to bonding and improve these properties. The surface treatment agent used in the present invention is a water-insoluble fatty acid, and even if it is a carboxylic acid, an aromatic carboxylic acid or a water-soluble fatty acid has almost no effect on improving resin adhesion. In addition, this fatty acid
It must be able to generate steam at high temperatures and be able to deposit on hot metal surfaces. Suitable examples of this surface treatment agent include, but are not limited to, the following: Caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid , cerotic acid,
Saturated fatty acids such as heptacosanoic acid and montanic acid, or undecylenic acid, oleic acid, elaidic acid, centreic acid, erucic acid, brassic acid,
Unsaturated fatty acids such as linoleic acid, linolenic acid, arachidonic acid, and stearolic acid. These fatty acids can be used alone or in the form of a mixture of two or more. Suitable examples of mixed fatty acids are coconut oil fatty acids, palm oil fatty acids, soybean oil fatty acids, tallow fatty acids, and the like. These fatty acids are preferred in terms of surface treatment workability and surface treatment effects, especially fatty acids with 6 to 28 carbon atoms.
It is preferable to use a fatty acid having a number of 1 to 18, and unsaturated fatty acids such as oleic acid are particularly effective in enhancing adhesion. If the number of carbon atoms is less than the above range, there will be a greater tendency to dissolve in water, and the effect of surface treatment on improving adhesion will be small; on the other hand, if the number of carbon atoms is greater than the above range,
It tends to be difficult to generate steam effectively. The metal material used for the surface treatment of the present invention may consist of any metal material in the form of a foil or plate.
For example, light metal plates such as steel plates, soft iron plates, stainless steel, aluminum plates, steel plates, brass plates, etc., or tin, zinc, etc. on the surface of these metal plates.
Plated plates made of different metals such as copper, chromium, nickel, and aluminum, which are melt-plated or electroplated;
Further examples include chemically treated plates obtained by chemically treating or cathodic electrolytically treating the surfaces of these metal plates with chromic acid, phosphoric acid, or a combination thereof, and anodically treated plates of the above-mentioned metals. Of course, iron foil, steel foil, aluminum foil, copper foil, phosphoric acid and/or chromic acid treated metal foil, and iron foil, steel foil with tin, zinc, copper, etc.
Materials plated with chromium, nickel, etc. can also be used in the treatment of the present invention. In the present invention, as shown in the examples described below, it is particularly suitable to use a metal material obtained by chemically treating the surface with chromic acid or cathodic electrolytically treating the surface in order to improve initial adhesion and adhesiveness over time. In the present invention, it is also possible to apply water-insoluble fatty acids in the gas phase to the surface of the metal material maintained at a high temperature in order to improve the initial adhesive strength and adhesive strength over time with the thermoplastic resin layer. When fatty acids are applied to the surface of a metal material by means such as spray coating, the adhesive strength is only about half or less than when applied in the form of steam. Moreover, according to the present invention, by applying water-insoluble fatty acids in the form of steam to the surface of metal materials, the thickness of the coating film is orders of magnitude thinner than that of conventional coatings, that is, generally 1 to 1.
A significant advantage is that the adhesion enhancement effect can be obtained with a thickness of only 100 Angstroms (Å), especially 1 to 30 Angstroms (Å). still,
The thicknesses mentioned above are determined by Electron Spectroscopy for Chemical Analysis.
Spectroscopy For Chemical Analysis (hereinafter simply referred to as ESCA) is used to determine the intensity of the 1S photoelectron spectrum of carbon, which is a constituent element of the treated film on the surface of the treated metal. Make a relative comparison of
The film thickness was determined by x defined by the following formula. In addition, since there was an organic substance attached to the metal material in advance, a blank test was conducted and the thickness of the organic substance was subtracted, and the subtracted value was taken as the treated thickness. x=-λc _sio θ・ln(1- _Ic /I〓)( ^ρsc /ρ
_c ^{） _} _{_} ^_
0.0654mol/cm ³ θ; sinθ= due to photoelectron emission angle θ=90°
1 λc: Average escape depth of photoelectrons λc = 18.1 Å Maintaining the surface of the metal material at a high temperature is also important in terms of adhesive strength, and if this temperature is too low, the thermoplastic resin may The adhesion force is significantly lower than that in the case of the present invention. In the present invention, the surface of the metal material is heated to a temperature of 150°C or higher, particularly a temperature of 180 to 300°C, most preferably
It is preferable to maintain the temperature at 200 to 250°C and perform the treatment with water-insoluble fatty acids. If this temperature is lower than the above range, the degree of improvement in adhesion will be lower than if it is within the above range. The specific temperature conditions used vary depending on the type of water-insoluble fatty acid, and it is better to use a higher temperature for saturated fatty acids with a large number of carbon atoms. Various means can be used to apply fatty acids in a gas phase to the surface of a metal material. In the simplest method, fatty acids are placed in a hot atmosphere to generate a vapor of the compound, and the metal material is exposed to the atmosphere filled with this vapor. Of course, fatty acids can be used alone or in combination of two or more, and this compound may be supplied to the above-mentioned high-temperature atmosphere in the form of a lump, that is, in an undiluted state,
Further, it may be supplied in a diluted state such as a solution, emulsion, or suspension using water or an organic solvent. Furthermore, it may be supported on a carrier such as an inorganic pigment, filler, various gel particles, glass beads, etc., and supplied to the atmosphere in a state in which the surface area is increased. In short, it should be understood that in the present invention, any shape and composition can be used as long as it can generate fatty acid vapor. For example, as an example, a paint solution applied to one side of a metal plate or metal foil contains fatty acids, and a large number of these single-sided coated metal plates are placed side by side at small intervals in a high-temperature atmosphere. By doing so, it becomes possible to treat the surface of the metal material opposite to the coating surface with fatty acid vapor. This process can be carried out either batchwise or continuously. For example, a coiled or sheet-shaped metal foil or metal plate can be continuously fed into a tunnel-type heat treatment furnace and treated with steam, or a certain amount of metal material can be introduced into the treatment furnace. Alternatively, the treatment can be performed by sealing the treatment furnace and then filling the treatment furnace with steam. In any of these cases, hot air containing fatty acid vapor is prepared inside or outside the processing furnace,
Steam treatment may be performed by circulating this hot air into the treatment furnace. The time required for gas phase treatment with fatty acids is
Although it varies depending on the concentration and temperature of the vapor in the gas phase, it is sufficient that the time is sufficient to form a coating layer of the thickness described above, and any time can be taken depending on the processing temperature and vapor concentration conditions. I can do it. The thickness of this coating layer is extremely thin, and on the other hand, there is no particular advantage in forming a coating layer thicker than the above-mentioned range, so there is no particular advantage in making this treatment time longer than 10 minutes. , which is economically disadvantageous. In the surface treatment method of the present invention, on the surface of a metal material,
It is particularly advantageously used for adhesion or promotion of adhesion of many thermoplastic resins, such as polyamides, polyesters, acid-modified polyolefins, acrylic resins, vinyl resins, polycarbonates, etc. Note that the surface of the metal material mentioned above is usually oiled with various oils such as dioctyl sebacate and cottonseed oil. The surface treatment of the present invention may be performed on a metal material provided with such an oil layer, or may be performed on a material from which the oil layer has been removed by degreasing treatment. The invention is illustrated by the following example. Example 1 Commercially available stain-free steel with a plate thickness of 0.17 mm DR-8 (high top manufactured by Toyo Kohan Co., Ltd., metal chromium content
105mg/dm ² , chromium oxide amount 14mg/dm ² )
Oleic acid was applied to this surface in a gas phase using the method described below. That is, in the bottom of a cylindrical lidded container with a diameter of approximately 150 mm and a height of approximately 150 mm, approximately 1 g of oleic acid and a small piece of stain-free steel supported using a glass holder to prevent simultaneous contact were placed and the lid was placed. After that, put the entire metal container into an electric oven.
Heating was performed at 210°C for 10 minutes. Thereafter, the metal container was taken out of the oven and after cooling, a small piece of this stain-free steel was taken out and the coating film thickness was measured. On the other hand, two 5 mm x 70 mm samples were cut out from this small piece, and polyamide adhesive (manufactured by Toray Industries, Ltd., 80 μm thick) was cut out.
The samples were then heat-pressed together with a nylon 12 film) sandwiched between them. This adhesive sample was immersed in a 0.4% citric acid aqueous solution at 90°C, and after a suitable number of days had passed, it was taken out and the T-shaped peel strength was measured to examine the state of deterioration of the adhesive. The results are shown in Table 1.

[Table] * A sample in which the same operations as in the example were carried out without using oleic acid. All of the following examples are the same. 2 Commercially available plate thickness 0.30 mm 5052 material (commercially available material for can lids,
Allozin 401-45 treatment, surface chromium amount 18mg/d
m ² ), and the same treatments and measurements as in Example 1 were performed to obtain the results shown in Table 2.

[Table] Example 3 Same as Example 1, but instead of oleic acid, caproic acid, caprylic acid, capric acid, stearic acid, arachidic acid, undecylenic acid, linoleic acid,
A similar sample was prepared using arachidonic acid and the T-shaped peel strength was measured. The results are shown in Table-3.

[Table] Example 4 Same as Example 1, except that the thickness of the commercially available plate material
0.30mm2052 material (commercially available can lid material, Alodine 401
-45 treatment, a surface chromium content of 18 mg/dm ² ), and using caproic acid, caprylic acid, and capric acid instead of oleic acid to prepare samples and measure the T-shaped peel strength. The results are shown in Table 4.

[Table] Example 5 The same method as Example 1 was used, but the amount of oleic acid added to the bottom of the metal container for vapor phase coating was increased or decreased, and the coating thickness was adjusted by repeating the application. Instead, a sample was prepared and the adhesive strength was measured by T-shaped peel strength. Table the results.
5.

[Table] Example 6 Samples were prepared in the same manner as in Example 1 by changing the temperature of the vapor phase coating, and the adhesive strength was measured by T-peel strength. The results are shown in Table 6.

【table】

Claims (1)

[Scope of Claims] 1. A method for surface treatment of a metal material, which comprises applying a water-insoluble fatty acid in a gas phase to the surface of the metal material maintained at a high temperature. 2. The method according to claim 1, wherein the surface of the metal material is maintained at a temperature of 150° C. or higher and the fatty acid is allowed to act on it. 3. The method according to claim 1, wherein the fatty acid is a fatty acid having 6 to 28 carbon atoms. 4. The method according to claim 1, wherein the fatty acid is an unsaturated fatty acid having 11 to 20 carbon atoms. 5. The method according to claim 1, wherein the treatment with the fatty acid is carried out so that the thickness of the treated coating layer formed is 1 to 100 angstroms. 6. The method according to claim 1, wherein the treatment is carried out by introducing a metal material into a heat treatment furnace and exposing the metal material to a high-temperature atmosphere containing vapor of fatty acids. 7. The method according to claim 1, wherein the metal material is a metal material obtained by chemically treating the surface with chromic acid or cathodic electrolysis treatment.