JPS6311982B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to adhesive structures, and more particularly to adhesive structures such as adhesive cans that have excellent adhesive strength at joints, particularly hot water resistant adhesive strength, retort resistant adhesive strength, and aged adhesive strength. 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 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, an adhesive primer such as epoxy-phenolic resin is applied to the metal material.
After baking, a method of thermally bonding with a thermoplastic resin adhesive via this adhesive primer layer is generally employed. However, known epoxy-phenol paints are still unsatisfactory for the purpose of increasing hot water resistant adhesive strength, retort sterilization resistance, and aged adhesive strength, and are relatively expensive. There is also the troublesome process of having to apply it in the form of a coating film on the metal material. Furthermore, since the above-mentioned paint must be applied in the form of an organic solvent solution, solvent costs and energy costs for baking are required, and since the release of organic solvents into the atmosphere is not allowed, after-sales care is required to prevent this. Pollution prevention facilities such as burners are required. Therefore, an object of the present invention is to provide a material that has not only excellent initial adhesive strength but also outstandingly excellent hot water resistant adhesive strength, retort sterilization resistance, and aged adhesive strength, so that it is possible to hot-fill the contents or An object of the present invention is to provide a connection structure such as an adhesive can that is useful for retort sterilization after filling. Another object of the present invention is to provide an adhesive structure having an extremely thin organic surface treatment layer instead of a conventional thermosetting resin primer, and bonding with a nylon adhesive through this surface treatment layer. It's about providing things. Still another object of the present invention is to provide a bonded structure that can be manufactured with fewer steps and at lower cost than conventional bonded structures. According to the present invention, in an adhesive structure formed by bonding metal materials via a polyamide adhesive, the metal materials have phenols having a hydroxymethyl group on the outermost surface of at least one of the metal materials to be bonded in a gas phase. There is provided an adhesive structure characterized in that it has a bonding thin layer formed by applying it to a metal material under heating, and is bonded via the thin layer with a polyamide adhesive. The present invention will be explained in detail below. In Fig. 1 showing an example of a side seam adhesive can,
This adhesive can 1 is made by rolling a metal material 2 into a cylindrical shape, overlapping both ends 3, 3, and joining this overlapping part with a molten nylon adhesive 4 to form a straight seam 5. It is formed. In FIG. 2, which shows an enlarged cross section of the joint 5, the metal material 2 is a steel plate substrate or an aluminum plate substrate 6 manufactured by cold rolling, for example, and a chromium-containing coating layer 7 provided on the substrate. and a bonding thin layer 8 of hydroxymethyl-substituted phenols provided on this chromium-containing coating layer. As described above, the adhesive structure of the present invention has a bonding thin layer 8 of hydroxymethyl-substituted phenols on the outermost surface of at least one of the metal materials to be bonded, and a polyamide-based A notable feature is that the bonding is performed using adhesive 4. Conventionally, most adhesive cans used for beverage cans, etc. are made of tain-free steel (TFS,
As already pointed out, an epoxy-phenol resin adhesive primer is applied to the surfaces to be joined of (electrolytic chromic acid treated steel sheets) and thermal bonding is carried out with a nylon adhesive through this primer layer. However, if such adhesive cans are hot filled with coffee beverages or fruit juice beverages, or if they are subjected to retort sterilization after filling, the adhesive strength will decrease, and even if this is not the case, the adhesive strength of the seams will deteriorate. It is observed that the strength decreases over time. When examining the decrease in adhesive strength due to hot water treatment of such seams and the decrease in adhesive strength over time, it is found that in both cases, the adhesive strength between the adhesive primer layer and the metal material has weakened, and the adhesive strength has weakened in this area. It was found that destruction had occurred. According to the present invention, by providing a thin bonding layer of hydroxymethyl-substituted phenols on the outermost surface of the metal materials to be bonded, this thin bonding layer has strong adhesion and adhesion to the metal materials and nylon. This method takes advantage of the new knowledge that not only does it exhibit strong adhesion to metal materials, but it also shows strong adhesion to metal materials regardless of hot water treatment and subsequent aging. That is, in general, the tendency of the joint between the thermoplastic resin layer and the metal material to deteriorate over time can be evaluated by immersing the laminate in a dilute aqueous solution of citric acid at high temperature. The can body joint, which is made by applying a known epoxy-phenol resin primer to electrolytic chromic acid treated steel plate (tein-free steel) and thermally bonding it with nylon adhesive tape, initially weighs 6 to 7 kg/kg.
Even if it shows initial adhesive strength of about 5mm width,
In the above-mentioned aging adhesion deterioration acceleration test, it was observed that the adhesive strength decreased on the order of 1.1 to 1.3 kg/5 mm width after 96 hours of immersion. In contrast, according to the present invention, the heated TFS plate surface is
Can body seams treated with steam containing saligenin (o-oxybenzyl alcohol) to form a thin bonding layer and then similarly lap-bonded with nylon adhesive not only showed similar initial adhesive strength; The adhesive strength of 4.4 to 4.5 kg/5 mm width is maintained even after immersion in citric acid solution for 96 hours. It was found that this had an extremely significant effect on improving adhesive strength. It is also extremely important for the organic surface treatment agent used in the present invention to have both a nuclear-substituted hydroxymethyl group and a phenolic hydroxyl group in terms of initial adhesive strength, hot water resistance, and aging adhesive strength. For example, compounds having only phenolic hydroxyl groups, such as para-cresol and carbolic acid, are heated in a high-temperature gas phase.
When applied to metal surfaces, the initial adhesive strength of the resulting adhesive structure was found to be quite low; For the first time, a high initial adhesive strength and a high adhesive strength retention rate when immersed in hot water and further aged can be obtained. As described above, the organic treatment agent used in the present invention has both a phenolic hydroxyl group and a hydroxymethyl group, and is therefore highly effective in improving adhesive strength, particularly adhesive strength over time. In addition, this hydroxymethyl-substituted phenol forms a bonding thin layer on the outermost surface of the metal material to be bonded.
That is, the fact that it exists in the form of a chemically bonded thin layer also has an important meaning. That is, chemical bonding of hydroxymethyl-substituted phenols to metal materials is possible under specific conditions in which both are activated. For example, this can be achieved by applying hydroxymethyl-substituted phenols in the gas phase to the surface of a metal material maintained at a high temperature. For example, when hydroxymethyl-substituted phenols are applied to the surface of a metal material by means such as spray coating, or when the temperature of the metal material is low, it is difficult to form a chemical bond between the two, and the initial adhesive strength also decreases. This is only less than half of the present invention. Not only chromic acid-treated metal materials but also other metal materials have an oxolation structure with enzymes bonded to them and an oration structure with hydroxyl groups coordinated on their outer surfaces. Moreover, the formation of chemical bonds involves the phenolic hydroxyl group and hydroxymethyl (-
Considering that the presence of CH ₂ OH) group plays an important role, it is recognized that a hydrogen bond, coordinate bond, or covalent bond exists between the two. Furthermore, in the present invention, the hydroxymethyl-substituted phenols may be present in an order of magnitude thinner layer than in conventional primer coatings, generally with a thickness of 1 to 100 angstroms (Å), particularly 1 to 30 Å. This is a remarkable feature. Conventionally, the thickness of a resin layer applied in the form of a paint film is generally in the range of 1 to 100 microns, and reducing this thickness to less than 1 micron is technically difficult due to loss of continuity of the paint film. be. In contrast, in the present invention,
With an extremely thin thickness of only 10 Å, the above-mentioned various adhesive strengths are significantly improved, and according to the present invention, significant advantages are also achieved in terms of adhesive pretreatment agents, processing operation costs, etc. It will be understood that The thickness mentioned above is determined by Electron Spectroscopy for Chemical Analysis.
Analysis (hereinafter sometimes simply referred to as ESCA)
By determining the intensity of the 1S photoelectron spectrum of carbon, which is a constituent element of the treatment film on the surface of the treated metal, and making a relative comparison with a standard sample made by vapor-depositing carbon, x is defined by the following formula. was determined and used as the film thickness. In addition, since there are organic substances attached to the metal material in advance, a blank test is performed.
The thickness of the organic matter was subtracted, and the subtracted value was taken as the treated thickness. x=-λcsinθ・ln(1- _Ic ^{/ Is} / _{c )}・( ^{ρsc /} _{ρc ) c} ; Carbon atom concentration of deposited carbon 0.1875 mol/cm ³ ρ _c ; Carbon atom concentration of sample (organic compound)
0.0645 mol/cm ³ θ; Emission angle of photoelectrons θ = 90°, so Sin θ = 1 λ _c ; Average escape depth of photoelectrons λ _c = 18.1 Å The metal material used for the adhesive structure of the present invention is a foil or a plate. It may be made of any metal material in the form of. For example, light metal plates such as steel plates, soft iron plates, stainless steel plates, aluminum plates, copper 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, aluminum, etc. are melt plated or electrolytically plated, and the surfaces of these metal plates are chemically treated or cathodic electrolytically treated with chromic acid, phosphoric acid, or a combination thereof. The resulting chemical conversion treated plate or anodized plate of the above-mentioned metal can be mentioned. Of course, iron foil, steel foil, aluminum foil, copper foil, phosphoric acid and/or chromic acid treated metal foil, tin foil or iron foil, steel foil plated with tin, zinc, copper, chromium, nickel, etc. are also available. It can be used in the treatment of the present invention. A preferred metal material is one having a chromium-containing coating layer of 6 to 360 mg/m ² , especially 10 to 250 mg/m ² in terms of chromium, on the rolled metal material, and the most preferred material is a cold rolled steel plate. above, from 0 to 300 mg/ ^m2 ,
In particular, a ^metallic chromium layer ^of 10 to 200 mg/m ² and a nonmetallic chromium compound (chromium oxide and/or hydrated chromium oxide (material) layer. The thickness of the metal material is preferably in the range of 0.01 to 0.50mm, and within this range, in the case of metal adhesive cans,
Preferably, the thickness is within the range of 0.10 to 0.30 mm. The surface treatment agent used in the present invention has at least one phenolic hydroxyl group and at least one hydroxymethyl group, and any compound can be used as long as it can be used for treatment in a gas phase at high temperatures. be able to. Suitable examples of this surface treatment agent include, but are not limited to, the following: general formula In the formula, R is a hydrogen atom, an alkyl group, a hydroxyl group, or a phenyl group, and n is an integer from 1 to 3,
m is an integer from 1 to 3, and the sum of n+m is 5
Hydroxymethyl-substituted phenols not exceeding . In the above formula, the hydroxymethyl group is preferably bonded to the ortho or para position with respect to the phenolic hydroxyl group. For example, saligenin, o
-Hydroxymethyl-p-cresol, p-hydroxymethyl-o-cresol, o-hydroxymethyl-p-t-butylphenol, o-hydroxymethyl-p-phenol, di(o-hydroxymethyl)-p-cresol, Mono- or dimethylol compounds of 2,4-dihydroxymethyl-o-cresol, 2,4-dimethyl-6-hydroxymethylphenol, resorcinol, catechol or hydroquinone. general formula In the formula, R ₂ represents a direct bond or a divalent bridging group, each of n' and m' is an integer up to 2 including zero, and the sum of n'+m' is an integer of 1 or more. , ring A
and B may be substituted with an alkyl group or a halogen atom, a hydroxymethyl-substituted dinuclear phenol represented by: In the above formula (2), suitable examples of the bridging group _R2 are a methylene group, a methyleneoxymethylene group ( _-CH2 -O- _CH2- ), an ethylidene group, a 2,2-
Propylidene group

[Formula] Oxygen atom (-O-), Sulfur atom (-S-), sulfonyl group

[Formula] Imino group (-NH-), etc. In addition, hydroxymethyl derivatives of naphthols, such as 2-hydroxymethyl-1-naphthol and 2,4-dihydroxymethyl-1-naphthol, can also be used. Of course, methylolated products of trinuclear phenols can also be used for the purpose of the present invention, but as the number of benzene rings in the phenols used increases, the amount of vapor generated becomes smaller compared to that at the same temperature. It is desirable to use the compounds described above. Particularly suitable hydroxymethyl-substituted phenols for the purposes of the present invention are 124 to 320, especially 124 to 260
A mononuclear substance having a molecular weight of Dinuclear phenol is preferred in terms of adhesion and surface treatment workability. In forming the bonded thin layer of phenols, as described above, the aforementioned phenols are applied in the gas phase to the metal material maintained at a high temperature. In the present invention, it is preferable to maintain the surface of the metal material at a temperature of 150°C or higher, particularly at a temperature of 180 to 300°C, most preferably at a temperature of 200 to 250°C, and perform the treatment with hydroxymethyl-substituted phenols. good. 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 to be used differ depending on the type of hydroxymethyl-substituted phenol, and it is preferable to use a higher temperature for high molecular weight phenols. Various means can be used to apply hydroxymethyl-substituted phenols to the surface of a metal material in a gas phase. The simplest method involves placing hydroxymethyl-substituted phenols in a hot atmosphere to generate a vapor of the compound, and exposing the metal material to the atmosphere filled with this vapor. Of course, hydroxymethyl-substituted phenols can be used alone or in combination of two or more kinds, 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, or it can be supplied with water, an organic solvent, etc. It may be supplied in a diluted state such as a solution, emulsion, or suspension. 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, hydroxymethyl-substituted phenols of any shape and composition can be used as long as they can generate vapor. For example, a coating solution applied to one side of a metal plate or metal foil contains hydroxymethyl-substituted phenols, and this single-sided coated metal plate is placed in a high temperature atmosphere in large numbers at small intervals. By arranging them side by side, it becomes possible to treat the surface of the metal material opposite to the coating surface with the vapor of the hydroxymethyl-substituted phenols. This process can be carried out 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 may be performed by sealing the treatment furnace and then filling the treatment furnace with steam. In any of these cases, hot air containing steam of hydroxymethyl-substituted phenols is adjusted inside or outside the processing furnace, and this hot air is circulated within the processing furnace to perform treatment with steam. good. The time required for treatment in the gas phase with hydroxymethyl-substituted phenols varies depending on the concentration and temperature of the vapor in the gas phase, but as long as it is enough time to form a coating layer with the thickness described above. Generally, any time can be taken depending on the processing temperature and vapor concentration conditions. 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. ,
Economically, it is even more disadvantageous. In the case of an adhesive can, the metal material thus treated is formed into a cylindrical shape by any means, and its opposite edges are bonded with a hot melt adhesive known per se, such as a polyamide adhesive. Joins side seams such as wrap seams, lock seals or wrap and lock seams. As such polyamide adhesive, 1 in 98% concentrated sulfuric acid is used.
Relative viscosity (ηrel) when measured at g/100c.c. concentration
Linear homopolyamides, copolyamides, modified polyamides, or polymer blends of two or more of these are used in which the polyamide is in the range of 1.5 or more, especially 1.8 or more. Suitable examples of this are polyhexamethylene adipamide, polyhexamethylene sebamide, polyhexamethylene dodecamide, polydodecamethylene dodecamide, 6-amino-caproic acid polymers, 11-amino-undecanoic acid polymers, Homopolyamides such as 12-amino-lauric acid polymers; copolyamides consisting of a combination of two or more constituent monomers of the above homopolyamides, that is, dicarboxylic acid-diamine salts or ω-aminocarboxylic acids, or homopolyamides thereof; It is made by modifying polyamide or copolyamide with polymerized fatty acids, etc. Furthermore, adhesives such as polyester adhesives and modified polyolefin adhesives can also be used. For example, various means can be employed to interpose the polyamide adhesive between the edges of the can body material to be joined. For example, a pre-formed tape-shaped polyamide adhesive is applied to both end edges of the can body material to be joined, or a tape-shaped polyamide adhesive in a molten state is applied by melt extrusion. Instead of applying the polyamide adhesive in the form of a tape, it can be applied in the form of a powder or solution to the parts of the metal materials to be joined. The thickness of the layer of polyamide adhesive applied to the parts to be joined is
There is no particular restriction as long as the treated film on the metal material and the polyamide adhesive are in uniform and close contact, but it is generally preferred that the thickness be in the range of 0.01 to 0.2 mm. The polyamide adhesive may be applied in advance to one or both of the edges of the can body materials to be bonded prior to bonding, or may be placed between both edges of the metal material during bonding. To join both ends of the can body material, the polyamide adhesive located between the opposing ends of the can body material formed into a cylindrical shape is melted, and then both end edges of the can body material are crimped together while cooling. This is done by solidifying the polyamide adhesive. The can body formed by such side lap bonding is then subjected to can making processes known per se, such as notching, flange processing, can lid seaming, etc., to form the final can. The manufacturing method of the above adhesive can is described in the Japan Adhesive Association Journal No.
11, No. 2, pp. 26-31 (1975). Of course, the adhesive structure of the present invention can be used not only for the above-mentioned adhesive can, but also for various purposes such as joining a can and a lid, and joining any plurality of metal parts, to obtain remarkable effects. It is something. Incidentally, the surface of a metal material, particularly a metal material having a chromium-containing coating layer, is often subjected to an oiling treatment with various oils such as dioctyl phthalate and cottonseed oil. In the present invention, the layer treated with hydroxymethyl-substituted phenols may be formed on this oil layer, or may be directly formed on the metal material from which the oil layer has been removed by degreasing. The invention is illustrated by the following example. Example 1 and Comparative Example 1 A plate thickness of 0.17 having a surface with a metallic chromium content of 112 mg/m ² and a non-metallic chromium content of 14 mg/m ² in terms of chromium.
mm of tene-free steel (Toyo Kotetsu's Hight R○), its surface contains phenol, p-cresol, bisphenol A, saligenin, p-cresol dimethylol (mononuclear substance), 1,1'-dihydroxy-2 ,2'-dihydroxymethyl-4,
Each purification reagent (each with a purity of 99% or more) of 4'-dimethyl-diphenylmethane (dinuclear substance) was applied using the following method. (b) The reagent was dissolved in chloroform and applied to a dry film of approximately 1 μm in thickness on protein-free steel, followed by drying at 100°C for 10 minutes. (b) It was applied in the same manner as above and dried at 200°C for 10 minutes. C. In a metal container with a lid of approximately 150 mm in diameter and approximately 150 mm in height, place approximately 1 g of reagent at the bottom and a small piece of tain-free steel supported using a glass holder so that they do not come into contact with each other, and then cover the container with a lid. After that, it was heated at 200℃ for 10 minutes. Thereafter, the sample was cut into 5 mm width pieces, and a polyamide adhesive (80 μm thick nylon 12 film manufactured by Toray Industries, Ltd.) was sandwiched between the plates with the coated sides facing inside, and thermocompression bonding was performed at 200°C for 1 minute to form a T shape. The mold peel strength was measured. The results are shown in Table 1.

[Table] *1 This is an example of the present invention.
Example 2 Using the same protein-free steel in Example 1 and using the dimethylolated p-cresol in Example 1, the heating temperature was changed using the method (c) in Example 1, and after each treatment for 10 minutes, T The shape peel strength was determined. Similarly, the thickness of the treated film can be changed by increasing or decreasing the amount of reagents put into the metal container with a lid, or by performing multiple treatments.
The shape peel strength was measured. The results are shown in Tables 2 and 3.

【table】

[Table] Example 3 and Comparative Example 2 A 0.20 mm thick 0.20 mm stainless steel plate with a surface containing 110 mg/m ² of metallic chromium and 15 mg/m ² of non-metallic chromium in terms of chromium (Toyo Kohan High Top R○) This was cut into a size that could be used to manufacture a 250 ml can body, and then subjected to the following treatment. B. In a container made of a thin iron plate large enough to accommodate the above blanks, support the five blanks using a glass holder so that they do not come into contact with each other, and at the same time place a dimethylol compound of p-cresol (a mononuclear compound, Add 1 g of molecular weight 168) and heat at 200℃ for 10
Heating was performed for 1 minute. At that time, the thickness of the organic film deposited on the surface of the stain-free steel was in the range of 16 ű2 Å. (b) Apply epoxy phenol paint with good adhesion (patent pending, described in Japanese Patent Application No. 55-69012 (Japanese Patent Publication No. 61-20433)) on the front and back sides of the blank to a thickness of 5 μm to the stain-free steel. The first coated surface was baked at 185°C for 10 minutes, and the second coated side was baked at 210°C for 10 minutes to create a double-sided coated board. The opposing short sides of the rectangular blanks treated by methods A and B were glued together with an adhesive margin of 5 mm. At this time, use Toray nylon 12 as adhesive, width 5 mm.
A thickness of 40 μm was used, and the ends were bonded together using a heat fusion method. Cut out the side seam adhesive part from this can body,
T-peel measurements were performed. Furthermore, the bonded area was maintained at 90°C in a 0.4% citric acid solution to examine the state of deterioration in adhesive strength. In addition, after tightening the bottom of the can body and filling it with coffee at 95℃ using a known method, tightening the can lid and heat sterilizing each 10 sample cans at 135℃, while changing the heating time. The rupture (damage) of the bonded area was investigated. These results are shown in Tables 4 and 5.

【table】

[Table] Example 4 and Comparative Example ³ Two types of samples were prepared in exactly the same manner as in Experimental Example 3 using 5052 material (manufactured by Sumitomo Light Metal Co., Ltd.) with a plate thickness of 0.30 mm and a surface chromium content of 15 mg/m2. A cylindrical body for a can body was prepared, the side seam adhesive part thereof was cut out, and the T-shaped peel strength was measured. Furthermore, the same adhesive part was soaked in a 0.4% citric acid aqueous solution for 90 minutes.
The adhesive was maintained at ℃ and the deterioration of adhesive strength was examined. The results are shown in Table 6.

[Table] Example 5 and Comparative Example 4 A low carbon steel plate with a thickness of 0.22 mm was degreased and pickled, then washed with water,
It was immersed in 3% chromic anhydride at 25°C for 5 seconds, washed with water, and dried. The surface of this board was coated with saligenin in a vapor phase using the method of Example 1. The film thickness was 29.7 Å. This sample and a sample that had not been vapor-phase coated with saligenin were thermally bonded using the same adhesive as in Example 1, and then held at 90°C in a 0.4% citric acid solution to deteriorate the adhesive strength over time. I checked the condition. Table 7 shows the measurement results of the T-shaped peel strength.

[Table] Example 6 and Comparative Example 5 A Nippon Steel chromic acid-treated nickel-plated steel plate (trade name Canwell) with a thickness of 0.24 mm was used, and saligenin was applied to the surface in a vapor phase using the method of Example 1. Ta. The film thickness was 10.7 Å. This sample and a sample that had not been vapor-phase coated with saligenin were thermally bonded using the same adhesive as in Example 1, and then held at 90°C in a 0.4% citric acid solution to evaluate the adhesive strength over time. The state of deterioration was investigated. Table 8 shows the measurement results of the T-shaped peel strength.

【table】 [Brief explanation of the drawing]

FIG. 1 is a perspective view of the adhesive can of the present invention;
The figure is an enlarged sectional view of the seam of the adhesive can of FIG. 1. Reference number 1 is the adhesive can, 2 is the metal material, 3 is both ends, 4 is the nylon adhesive, 5 is the seam, 6 is the metal substrate, 7 is the chromium-containing coating, and 8 is the treated layer with hydroxymethyl-substituted phenols. are shown respectively.

Claims (1)

[Scope of Claims] 1. In an adhesive structure formed by bonding metal materials via a polyamide adhesive, at least one outermost surface of the metal materials to be bonded contains a phenol having a hydroxymethyl group. 1. An adhesive structure characterized in that it has a bonding thin layer formed by applying a phase to a metal material under heating, and is bonded with a polyamide adhesive via the thin layer. 2. The adhesive structure according to claim 1, wherein the bonded thin layer of phenols has a thickness of 1 to 100 angstroms. 3. The bonded structure according to claim 1, wherein the metal material is a cold rolled steel plate having a chromium-containing coating layer. 4 The hydroxymethyl-substituted phenols are
The adhesive structure according to claim 1, which has a molecular weight of 124 to 320. 5 The hydroxymethyl-substituted phenols have the general formula In the formula, R is a hydrogen atom, an alkyl group, a hydroxyl group, or a phenyl group, and n is an integer of 1 to 3,
m is an integer from 1 to 3, and the sum of n+m is 5
The adhesive structure according to claim 1, wherein the adhesive structure does not exceed . 6 The hydroxymethyl-substituted phenols have the general formula In the formula, R ₂ represents a direct bond or a divalent bridging group, each of n' and m' is an integer up to 2 including zero, and the sum of n'+m' is an integer of 1 or more. , ring A
The adhesive structure according to claim 1, wherein and B are hydroxymethyl-substituted dinuclear phenols represented by the following, which may be substituted with an alkyl group.