JP2019019308A - Adhesive method of metal material using adhesive, and metal material conjugate - Google Patents

Abstract

To provide an adhesive method of a metal material having adhesiveness equal to or more than the case by treating with various acid solution without deteriorating appearance of a metal material surface, and further achieving excellent water resistant adhesiveness under a high temperature high humidity condition.SOLUTION: After forming a thin film having polyacrylic acid crosslinked by oxazoline and having weight average molecular weight of 5,000 to 450,000 on a surface of a metal material consisting of a stainless steel, a copper material, a steel material or an aluminum material appropriately, an adhesive is applied to a surface of the thin film, and preferably adhered to a metal to be adhered consisting of the stainless steel, the copper material, the steel material, or the aluminum material.SELECTED DRAWING: None

Description

  TECHNICAL FIELD The present invention relates to a method for bonding a metal material using an adhesive and a metal material joined body, and more specifically, using an adhesive for a metal material on which a thin film having water-soluble polyacrylic acid crosslinked with oxazoline is formed. And a metal material joined body in which the metal material is bonded with an adhesive.

  Metal materials such as steel, copper material, aluminum material, and stainless steel are widely used in various fields by taking advantage of the characteristics of these metals. Conventionally, welding of these metal materials has been mainly performed by welding, but in recent years, an adhesion method in which a metal material is bonded by applying an adhesive has attracted attention. However, in reality, the joining of metal materials by such an adhesion method has problems peculiar to each metal material.

  Specifically, steel materials are used as high-tensile materials for high-strength steel sheets in the field of automobiles, taking advantage of their excellent workability, strength, and surface appearance, and can be reduced in weight without reducing strength. Because it can be realized, it contributes greatly to resource and energy savings by improving fuel efficiency. On the other hand, steel materials are being considered for compounding with aluminum alloys and fiber reinforced plastics for further weight reduction. However, since welding is commonly used as a method for joining steel plates in the automobile assembly process, electrochemical corrosion due to contact with dissimilar metals may be a problem in welding joining with aluminum alloys. Welding joints cannot be applied to joints with reinforced plastics.

  Therefore, there is an increasing expectation for an adhesive method that is excellent in insulation at the joint and can be joined to fiber reinforced plastic. The production of a molded body by the bonding method eliminates the need for the sheet metal process found in the welding method and increases the stress distribution at the joints, which can improve reliability. However, when the bonded portion of the iron plate is exposed to a high-temperature and high-humidity atmosphere, water may enter the bonding interface to form a water-containing layer, resulting in a problem that the adhesive strength is greatly reduced in a short period of time.

  As a countermeasure against this decrease in adhesion, surface treatment for bonding iron (soft steel) by degreasing and subsequent etching has been proposed. For example, JIS-K6848-2 of Non-Patent Document 1 discloses an acid treatment that is immersed in a 60 ° C solution composed of 2 L of industrial methanol and 1 L of orthophosphoric acid for 10 minutes, washed with running water, removed with a nylon brush, and dried by heating. ing. In addition, a method has been attempted in which the steel surface is pre-coated with an organic thin film to improve adhesion. For example, Patent Document 1 discloses a technique for treating a metal plate with an aqueous primer containing an acidic phosphate ester and / or a salt thereof and water, and Patent Document 2 discloses that a metal surface is treated with a silane coupling agent. A technique for improving adhesion with a fluorine-based coating film by processing is disclosed.

  In a copper material, a lead frame material made of, for example, a copper alloy is used in the field of the electronic industry by taking advantage of its excellent workability, corrosion resistance, conductivity, and thermal conductivity. The lead frame material is subjected to a surface roughening treatment with a chemical to ensure adhesion with the mold resin. In the roughening treatment, the anchoring effect by the bite of the mold resin into the irregularities formed on the surface is the basis for improving the adhesion. However, since the copper surface is very easily oxidized, an oxide film grows after the surface roughening treatment, which may become a fragile layer and reduce adhesion.

  As a countermeasure against this decrease in the adhesive strength, it is proposed to activate the copper material with an acid in advance. For example, in JIS-K6848-2 of Non-Patent Document 2, etching treatment with an aqueous nitric acid solution, ferric chloride and nitric acid are proposed. Techniques for etching using a mixed aqueous solution and etching using an aqueous ammonium persulfate solution are disclosed. In addition, a method has been attempted in which a copper material is preliminarily coated with an organic thin film to improve adhesion. For example, Non-Patent Document 5 reports that the adhesion is improved when a copper plate is treated with an imidazolesilane compound aqueous solution.

  Aluminum materials such as pure aluminum and various aluminum alloys are used as, for example, building structural materials and machine parts by taking advantage of their excellent lightness, workability and surface appearance. When an aluminum material is used, it may be necessary to join the aluminum material to another material, and welding is often used as the joining method. However, in joining by welding, welding marks may remain on the surface of the welded aluminum material or welding distortion may occur.

  Therefore, as a joining method that replaces this welding joint, an adhesion method in which an aluminum material is joined using an adhesive has attracted attention. In the bonding method, welding marks as seen in the above-described welding method are not generated, and stress is not generated in the joint portion, so that the problem of distortion hardly occurs, so that sheet metal processing is not necessary. However, when aluminum materials are bonded and bonded, the water resistance of the bonding interface tends to be low, and when the bonded portion of the aluminum material is exposed to a high-temperature and high-humidity atmosphere, water enters the bonding interface and forms a moisture-containing layer. As a result, there has been a problem that the water-resistant adhesion is greatly lowered in a short period of time.

  As a countermeasure against this decrease in adhesive strength, pretreatment by surface treatment of an aluminum material effective in the bonding method has been studied. For example, Non-Patent Document 3 shows a test result of excellent high-temperature and high-humidity durability in epoxy adhesion of phosphoric acid anodizing treatment and sulfuric acid / bichromic acid aqueous solution treatment to aluminum. In addition, a method has been attempted in which an aluminum material is preliminarily coated with an organic thin film to improve adhesion. For example, Non-Patent Document 6 discloses a technique for improving adhesion with an epoxy by treating an aluminum material surface with a silane coupling agent.

  In stainless steel, it is used as, for example, building structural materials or machine parts, taking advantage of its excellent corrosion resistance and surface appearance. In this case, joining between stainless steels or between stainless steel and other materials is required. In many cases, conventional welding is used as the joining method. However, in joining by welding, welding marks may remain on the surface of the welded stainless steel plate or welding distortion may occur. In order to remove these welding traces and welding distortions, it takes a lot of time and labor to process the sheet metal, and this sheet metal processing has problems in the work environment such as noise generation, so avoid it from the operator. Has been. Furthermore, since welding requires skill, some operators may not have sufficient joint strength.

  Therefore, as a joining method that replaces this welding joint, an adhesion method in which stainless steel is joined using an adhesive is attracting attention. In the bonding method, no welding mark as seen in the above-described welding method is generated, and stress is not generated in the joint portion, so that the problem of distortion hardly occurs, and therefore, sheet metal processing becomes unnecessary. However, when stainless steel is bonded and bonded, the water resistance of the bonded interface tends to be low, and when the bonded portion of stainless steel is exposed to a high-temperature and high-humidity atmosphere, water enters the bonded interface and forms a moisture-containing layer. As a result, there has been a problem that the adhesive strength is greatly reduced in a short period of time.

  As a countermeasure against this decrease in adhesion, it has been proposed to activate stainless steel in advance with an acid. For example, JIS-K6848-2 of Non-Patent Document 4 describes the surface of stainless steel with a mixed aqueous solution of sulfuric acid and oxalic acid. Techniques for processing are disclosed. In addition, a method has been attempted in which stainless steel is preliminarily coated with an organic thin film to improve adhesion. For example, Non-Patent Document 7 reports that the water-resistant adhesion of an acrylic adhesive is improved by treating stainless steel with a primer composed of an aqueous polyacrylic acid solution.

JP-A-6-93211 Japanese Patent Publication No. 6-57872

JIS-K6848-2, 7.2.1.7 steel (mild steel) JIS-K6848-2, 7.2.1.4 Copper and copper alloys Hidetoshi Yamabe, “Surfaces and Interfaces of Metallic Materials in Structural Bonding”, Journal of Color Material Association, 1993, Vol. 66, pages 605-613 JIS-K6848-2, 7.2.1.8 steel (stainless steel) Network Polymer, 2000, 21, 169 pages K. Dusek (ed.), Advances in Polymer Science, Epoxy Resins and Composites 2, Springer-Verlag 1986, p. 51 Hidetoshi Yamabe, 3 others, “Study on Surface Modification of Stainless Steel (II)”, Color Material Association, 1996, Vol. 69, pp.158-166

  However, when the surface of the metal material is activated by the acid treatment disclosed in Non-Patent Documents 1 to 4, smut may occur on the surface of the metal material. This smut can be removed by treating the surface of the metal material again with a dichromic acid / sulfuric acid mixed aqueous solution, but this desmutting treatment discharges chromium-containing wastewater that is strictly regulated from an environmental point of view. Therefore, there is a problem that the processing is expensive. Although it is conceivable to perform smut removal with a metal brush instead of desmutting treatment, smut removal with a metal brush requires a great deal of labor.

  Moreover, the surface treatment using the phosphate ester disclosed in Patent Document 1 and the silane coupling agents disclosed in Patent Document 2 and Non-Patent Documents 5 to 6 improves the affinity of the metal material for the adhesive. Although it was confirmed, it was difficult to obtain water-resistant adhesion at high temperatures. Further, in the surface treatment using polyacrylic acid disclosed in Non-Patent Document 7, the polyacrylic acid itself is water-soluble, and there are free carboxyl groups that do not contribute to hydrogen bonding with the metal material surface. Under high-temperature and high-humidity conditions, the adhesive strength of the adhesive portion of the metal material is reduced, and it is not suitable for use in a structure that requires a stable adhesive force over a long period of time.

  The present invention has been made in view of the problems of such a conventional bonding method, and improves the adhesion of an organic thin film formed on the surface of a metal material by a very simple method. An object of the present invention is to provide a bonding method of a metal material that has an adhesive property equal to or better than that treated with various acid aqueous solutions without impairing the appearance of the surface, and further realizes excellent water-resistant adhesion under high temperature and high humidity conditions. It is said.

  In order to achieve the above object, the metal material bonding method according to the present invention includes forming a thin film having polyacrylic acid having a weight average molecular weight of 5,000 to 450,000 cross-linked with oxazoline on the surface of the metal material. The method is characterized in that an adhesive is applied to the surface of the thin film to adhere to the metal to be bonded.

  In the metal material joined body according to the present invention, a metal material having a thin film having a polyacrylic acid having a weight average molecular weight of 5,000 or more and 450,000 or less crosslinked with oxazoline on the surface, and a metal to be bonded are adhesives. It is characterized by being joined by.

  According to the present invention, utilizing a strong bonding force to the surface of a metal material of a thin film having a polyacrylic acid having a weight average molecular weight of 5,000 or more and 450,000 or less crosslinked with oxazoline and a barrier property against water, Since it is bonded to the metal to be bonded with a high shear bonding strength comparable to various acid treatments, the bonded portion has good water-resistant adhesion, and can maintain high bonding strength over a long period of time.

It is a longitudinal cross-sectional view of one specific example of the metal material joined body of this invention. It is a longitudinal cross-sectional view of the other specific example of the metal material conjugate | zygote of this invention.

  Hereinafter, an embodiment of a method for bonding a metal material of the present invention will be described. First, as the types of metal materials to which the bonding method of the metal material of the present invention can be applied, in steel materials (steel), general rolled steel materials (SS material) that are general rolled steel materials, rolled steel materials for welded structures ( In addition to carbon steel (SC material) such as SM steel) and rolled steel for building structures (SN material), it is applicable to a wide variety of steel materials such as chromium molybdenum steel (SCM material) and nickel chromium molybdenum steel (SNCM material). it can.

  The copper material can be suitably applied to any copper material mainly composed of copper such as pure copper or a copper alloy. Examples of pure copper include oxygen-free copper, tough pitch copper, and deoxidized copper. Examples of copper alloys include beryllium copper, titanium copper, zirconium copper, and copper-nickel alloys. The aluminum material can be applied to a wide variety of aluminum materials such as pure aluminum, Al—Cu alloy, Al—Mn alloy, Al—Si alloy, Al—Mg alloy.

  The stainless steel can be applied to stainless steels having various compositions as defined in JIS, in which iron is the main component and chromium or nickel is added. Among them, it can be suitably applied to austenitic stainless steel (chromium nickel system), ferritic stainless steel (chromium system), and martensitic stainless steel (chromium system).

  As for the shape of these metal materials to be bonded, the shape of the other portions is not particularly limited as long as the bonding surface with the metal to be bonded is a flat shape, but it is plate-shaped. A flat plate shape is preferable. There is no particular limitation on the material of the metal to be bonded to the metal material, but it is preferably one of the above metal materials, and the same kind of metal material can maximize the effects of the present invention. Since it can be made to exhibit, it is more preferable.

  The method for adhering a metal material according to the embodiment of the present invention includes a polymer having an oxazoline group on the surface of the metal material (hereinafter also referred to as an oxazoline-containing polymer) and a polyacrylic acid having a weight average molecular weight of 5,000 to 450,000. A thin film of an aqueous solution containing the mixture is formed, and then the thin film is heated to evaporate water and crosslink free carboxyl groups contained in polyacrylic acid with oxazoline groups, and then an adhesive is applied to the surface of the thin film. It is applied and bonded to the metal to be bonded.

  As a result, it is made of a steel material, a copper material, an aluminum material, or stainless steel on which a thin film 2 having polyacrylic acid crosslinked with oxazoline as shown in FIG. 1 (hereinafter also referred to as an oxazoline-crosslinked polyacrylic acid thin film) is formed. A bonded body in which the metal material 1 and the metal 4 to be bonded are bonded to each other with the adhesive 3 can be manufactured. The form of the joined body is not limited to this. For example, as shown in FIG. 2, the oxazoline crosslinked polyacrylic acid thin film 2 may be formed on the surface of the metal 4 to be bonded. In this case, the adherend metal 4 is preferably made of a steel material, a copper material, an aluminum material, or stainless steel, and more preferably the same material as the metal material 1.

  In order to form a thin film of an aqueous solution containing a mixture of polyacrylic acid and an oxazoline-containing polymer on the surface of the metal material 1 or the surface of the adherend metal 4, the metal material 1 or the adherend is added to the aqueous solution containing the mixture. It may be applied by dipping the metal 4, or may be applied by spraying an aqueous solution containing the mixture onto the surface of the metal material 1 or the metal 4 to be bonded, or using a roll coater or a brush. .

  A polyacrylic acid used in the above mixture has a weight average molecular weight of 5,000 to 450,000. When the weight average molecular weight of polyacrylic acid is less than 5,000, the proportion of polyacrylic acid adsorbed on the surface of the metal material is increased due to molecular motion, and the formation of a uniform thin film Becomes difficult. Moreover, when the weight average molecular weight of polyacrylic acid exceeds 450,000, the water solubility that is characteristic of polyacrylic acid is lowered, and aggregates are likely to be deposited, and a uniform thin film is formed on the surface of the metal material. Becomes difficult.

  In order to form a more uniform thin film on the surface of the metal material, the concentration of polyacrylic acid in the aqueous solution containing the above mixture is preferably 0.1% by mass or more and 2.0% by mass or less, and 0.2% by mass. % To 2.0% by mass is more preferable. If this concentration is less than 0.1% by mass, it will be difficult to uniformly apply polyacrylic acid to the surface of the metal material. Conversely, if this concentration exceeds 2.0% by mass, it will be in the oxazoline-crosslinked polyacrylic acid thin film. There is a possibility that a free carboxyl group is present in each other, and the hydrogen bond between these carboxyl groups is easily dissociated by water, and the adhesiveness may be lowered.

  On the other hand, the polymer having oxazoline used in the above mixture is used in a state of being dispersed or dissolved in water together with the above polyacrylic acid. Therefore, an emulsion type or a water-soluble type can be used. Among these types, the water-soluble type is preferable to the emulsion type. The reason is that in the case of the emulsion type, the oxazoline group inside the emulsion hardly contributes to crosslinking by reaction with a carboxyl group. On the other hand, since the water-soluble type is easily dissolved in an aqueous solution, it can be sufficiently brought into contact with the carboxyl group of polyacrylic acid that is also dissolved in the aqueous solution, and as a result, crosslinking by amide esterification can be easily performed. it can.

  In the preparation of the aqueous solution containing the above mixture, it is preferable to blend more than 30 parts by mass and 100 parts by mass or less of an oxazoline-containing polymer with respect to 100 parts by mass of polyacrylic acid, and 50 parts by mass or more and less than 100 parts by mass of oxazoline-containing It is more preferable to blend a polymer. If the amount of the oxazoline-containing polymer is 30 parts by mass or less, the free carboxyl group contained in the polyacrylic acid may not be sufficiently cross-linked. Conversely, if the amount exceeds 100 parts by mass, the water-resistant adhesive property of the joint may be lowered. is there. The oxazoline-containing polymer is preferably added to an aqueous solution of polyacrylic acid immediately before use. The reason for this is that after mixing, the amide esterification reaction between the oxazoline group and the carboxyl group of polyacrylic acid proceeds with time, and the viscosity of the mixture increases or gelation occurs, resulting in a thin film of uniform aqueous solution. It is because it becomes difficult to form.

  Therefore, after mixing the polyacrylic acid and the oxazoline-containing polymer, the aqueous solution containing the obtained mixture is preferably applied immediately to the surface of the metal material by a known method such as dipping, spraying, or roll coater. After coating, heat treatment is performed at a temperature of 120 ° C. or higher. Thereby, the amide esterification reaction of an oxazoline group and a carboxyl group contained in polyacrylic acid can be advanced in a short time. If moisture is contained in the thin film having polyacrylic acid crosslinked with oxazoline, the residual moisture plasticizes the adhesive interface between the adhesive and the thin film having polyacrylic acid crosslinked with oxazoline, and adheres. Therefore, the above heat treatment is also aimed at evaporating moisture. Moreover, although the upper limit of heat processing temperature does not have limitation in particular, Generally 250 degrees C or less is preferable.

  By bonding an adhesive to the surface of the thin film having polyacrylic acid crosslinked with oxazoline and bonding it to the metal to be bonded, bonding with extremely high adhesive strength becomes possible. The reason why such a high adhesive strength can be obtained is that polyacrylic acid tends to be strongly adsorbed on the surface of the adhesive surface of the metal material by the carboxyl group contained in the structure. That is, in the steel material, the surface of the steel material is generally covered with an iron oxide film, and the outermost surface is a hydroxyl layer such as an Fe—OH type hydrated by moisture in the atmosphere. Therefore, the carboxyl group of polyacrylic acid forms a carbanion by hydrogen bonding with the outermost hydroxyl group and further donating protons to the hydroxyl layer. It is considered that a strong bond derived from the acid-base interaction is formed between the protonated hydroxyl group on the outermost surface.

  In the copper material, the surface of the copper material is generally covered with a copper oxide film, and the outermost surface is a hydroxyl layer such as a Cu—OH type hydrated by moisture in the atmosphere. Therefore, the carboxyl group of polyacrylic acid forms a carbanion by hydrogen bonding with the outermost hydroxyl group and further donating protons to the hydroxyl layer. It is considered that a strong bond derived from the acid-base interaction is formed between the protonated hydroxyl group on the outermost surface.

  In the aluminum material, the surface of the aluminum material is generally covered with an aluminum oxide film, and the outermost surface is a hydroxyl layer such as an Al—OH type hydrated by moisture in the atmosphere. Therefore, the carboxyl group of polyacrylic acid forms a carbanion by hydrogen bonding with the outermost hydroxyl group and further donating protons to the hydroxyl layer. It is considered that a strong bond derived from the acid-base interaction is formed between the protonated hydroxyl group on the outermost surface.

  In stainless steel, the surface of stainless steel is generally covered with a chromium oxide film, and the outermost surface is a hydroxyl layer such as a Cr—OH type hydrated by moisture in the atmosphere. Therefore, the carboxyl group of polyacrylic acid forms a carbanion by hydrogen bonding with the outermost hydroxyl group and further donating protons to the hydroxyl layer. It is considered that a strong bond derived from the acid-base interaction is formed between the protonated hydroxyl group on the outermost surface.

  However, not all of the carboxyl groups of the polyacrylic acid are bonded to the hydroxyl layer on the surface of the metal material, and free carboxyl groups are present. This free carboxyl group exists in the thin film in a free state like a dimer. The free carboxyl group present in such a dimer-like form is water-soluble and, for example, hydrates during a high-temperature and high-humidity test and causes the water-resistant adhesion of the thin film to decrease. Therefore, by adding an oxazoline-containing polymer to polyacrylic acid, an amide esterification reaction between the oxazoline group and the above free carboxyl group is caused. As a result, since crosslinking occurs and hydration is suppressed, the water-resistant adhesion of the thin film is improved. Note that the strong adhesion of the thin film having polyacrylic acid crosslinked with oxazoline is more prominent by performing cleaning treatment such as degreasing and pickling on the surface of the metal material prior to the formation of the thin film. It will be a thing.

  By applying an appropriate adhesive to the metal material whose adhesion is improved as described above, it can be bonded to the metal to be bonded. The metal material joined body obtained in this way has an extremely high shear adhesive strength and a bonded portion with little deterioration due to moisture absorption, and becomes a strong joined body.

  The adhesive to be used is not particularly limited as long as it is capable of forming a hydrogen bond with the acrylic part of polyacrylic acid, that is, an adhesive having compatibility with acrylic. For example, an acrylic radical polymerization adhesive, and further an epoxy Adhesives such as polyurethane, polyester and the like, and acrylic radical polymerization adhesives are particularly preferable. A cyanoacrylate-based adhesive is not preferred because the polymerization reaction is inhibited by the acidity of polyacrylic acid and may cause curing failure. In addition, since the low-polarity silicone adhesive has a low affinity with the thin film, the effect is hardly obtained.

  In the metal material joining method according to the embodiment of the present invention, as described above, a thin film having polyacrylic acid cross-linked with an oxazoline group is formed on the surface of the metal material, thereby providing a strong adhesive force and water barrier property. And is obtained. Thereby, high adhesive strength comparable to various acid treatments can be maintained over a long period of time. In addition, according to the bonding method of the embodiment of the present invention, for example, when a metal material is assembled as a building structure used outdoors, no harmful substances are generated, and the work environment is not deteriorated, and simple construction is performed. A structure excellent in strength can be obtained by the method. Therefore, it has an industrially remarkable effect. Next, the present invention will be described in more detail with reference to examples and comparative examples.

[Example 1]
A plurality of test pieces having a width of 25 mm and a length of 100 mm were cut out from a 2B finish of an austenitic stainless steel plate SUS304 having a plate thickness of 1.0 mm as a base material, and these test pieces were degreased by being immersed in acetone for 3 minutes at room temperature. It was immersed in a 10% aqueous hydrochloric acid solution at room temperature for 3 minutes, pickled, and washed with distilled water. In this way, all the test pieces were pretreated.

  Next, polyacrylic acid having a weight average molecular weight of 90,000 and EPOCROSS WS-300 manufactured by Nippon Shokubai Co., Ltd. are prepared as an oxazoline-containing polymer, and the blending ratio of the oxazoline-containing polymer to 100 parts by mass of polyacrylic acid is 0 parts by mass. (That is, without adding an oxazoline-containing polymer), four types of aqueous solutions of 50 parts by mass, 75 parts by mass, and 100 parts by mass were prepared. Each of these four types of aqueous solutions was subdivided into three, and distilled water was added so that the polyacrylic acid concentrations were 0.20% by mass, 1.0% by mass, and 2.0% by mass, respectively.

  In this way, 12 types of aqueous solutions having different polymer concentrations were prepared. Each of these 12 types of aqueous solutions was immersed in 4 pieces of the above-mentioned pretreated test pieces for 1 minute to apply the aqueous solution to the surface, followed by heat treatment for 5 minutes at an atmospheric temperature of 120 ° C. After the heat treatment, these 12 types of test pieces were cooled to room temperature, and 12 types of test pieces (48 pieces in total) having different types of thin films were produced. For each of the above 12 types of test pieces, 4 types of test pieces having no thin film that had been subjected only to the pre-treatment described above were added. The second generation acrylic adhesive SGA (Hardlock C355), which is an acrylic radical polymerization adhesive manufactured by Denki Kagaku Kogyo Co., Ltd., was applied as an adhesive and bonded together with a wrap width of 12.5 mm. The bonded part was completely cured by holding at room temperature for 7 days.

  In this way, two joined samples of Samples 1 to 13 were prepared. And the initial shearing adhesive strength was measured based on JIS-K6850 with respect to one of the two joined bodies of each sample. In addition, the remaining one joined body of each sample was immersed in boiling water for 7 days in order to evaluate the water-resistant adhesion of the bonded portion, then cooled to room temperature and promptly compliant with JIS-K5850. The shear bond strength was measured. These measurement results are shown in the following Table 1 together with the concentration of polyacrylic acid and oxazoline-containing polymer in the aqueous solution used for forming the thin film and the blending ratio thereof (that is, the value of parts by mass of the oxazoline-containing polymer with respect to 100 parts by mass of polyacrylic acid). Show.

  From Table 1 above, it can be seen that the water-resistant adhesion is greatly improved by forming a thin film having a polyacrylic acid having a weight average molecular weight of 90,000 crosslinked by an oxazoline group. This is presumably because polyacrylic acid was strongly adsorbed on the surface of the stainless steel plate and free carboxyl groups were cross-linked by oxazoline groups to suppress hydration. Moreover, it turns out that 50 mass parts or more and 100 mass parts or less are preferable with respect to 100 mass parts of polyacrylic acid. In addition, in the case of 100 parts by mass of the oxazoline-containing polymer with respect to 100 parts by mass of the polyacrylic acid, the effect of water-resistant adhesion is maintained, but it is slightly lowered because the oxazoline group that does not contribute to crosslinking becomes excessive. This is presumed to remain unreacted. Moreover, when a thin film was formed with an aqueous solution of only polyacrylic acid without adding an oxazoline-containing polymer, the test pieces were all decomposed in the water-resistant adhesion test.

[Comparative Example 1]
For comparison, 12 test pieces made of 2B-finished SUS304 stainless steel plate were pretreated in the same manner as in Example 1, and then divided into 3 groups of 4 sheets, each of which was processed by 3 types of conventional processing methods. In the same manner as in Example 1, two bonded samples of Samples 14 to 16 were prepared by bonding with an adhesive. That is, sample 14 was dipped with a phosphate ester primer and then adhered with an adhesive, and sample 15 was a 1% aqueous solution of γ-glycidoxypropyltrimethoxysilane (product number KBM403) manufactured by Shin-Etsu Chemical Co., Ltd. After the silane coupling treatment was performed by using the dipping method, the sample was dipped in a mixed aqueous solution (60 ° C.) of 10 parts by mass of sulfuric acid and 10 parts by mass of oxalic acid. The mixture was treated with a chromic acid mixture, washed with water, and then adhered with an adhesive. For the joined bodies of Samples 14 to 16, the initial shear adhesive strength and water-resistant adhesiveness of the bonded portion were evaluated in the same manner as in Example 1. The results are shown in Table 2 below.

  As can be seen by comparing Table 2 and Table 1 showing the result of bonding with an adhesive after processing a stainless steel plate by a conventional processing method, the initial shear strength was high, but water-resistant bonding It can be seen that the test pieces are all decomposed in the property test, and the water-resistant adhesion can be remarkably improved by forming a thin film having polyacrylic acid crosslinked with oxazoline.

[Example 2]
In the case of Sample 11 of Example 1 except that polyacrylic acid having a weight average molecular weight of 1,500, 5,000, 18,000, 450,000, 600,000 was used instead of the weight average molecular weight of 90,000, respectively. In the same manner, joined bodies of Samples 17 to 21 were produced. Further, a joined body of Sample 22 was prepared in the same manner as Sample 11 of Example 1 except that polyacrylic acid having a weight average molecular weight of 450,000 was used and no oxazoline-containing polymer was added. The joints of these samples 17 to 22 were evaluated in the same manner as in Example 1 for the initial shear adhesive strength and water-resistant adhesiveness of the connecting portion. The measurement results are shown in Table 3 below.

  From Table 3 above, excellent water-resistant adhesiveness can be obtained by bonding with an adhesive via a thin film obtained by crosslinking polyacrylic acid having a weight average molecular weight of 5,000 or more and 450,000 or less with oxazoline. I understand that. In contrast, polyacrylic acid having a weight average molecular weight of 600,000 was insoluble in water, and polyacrylic acid having a weight average molecular weight of 1,500 was inferior in water-resistant adhesion. Even when the weight average molecular weight of the polyacrylic acid is 450,000, as in the case of the weight average molecular weight of Example 1 being 90,000, the test piece is decomposed and adhered in the water-resistant adhesion evaluation unless crosslinking with oxazoline is performed. It was confirmed that the power could not be maintained.

[Example 3]
Ferritic stainless steel plate SUS405 is used instead of austenitic stainless steel plate SUS304 as a base material, and polyacrylic acid having a weight average molecular weight of 5,000 is used instead of weight average molecular weight 90,000 as an aqueous solution for immersion. Four kinds of aqueous solutions having 30 parts by mass, 50 parts by mass, 75 parts by mass, and 100 parts by mass of the oxazoline-containing polymer with respect to 100 parts by mass of the acid are prepared, and distilled water is added to adjust the concentration of polyacrylic acid. Except that all were adjusted to 0.10% by mass, joined bodies of Samples 23 to 26 were produced in the same manner as in Example 1 above.

  Similarly, a ferritic stainless steel plate SUS405 is used as a base material and polyacrylic acid having a weight average molecular weight of 5,000 is used as an aqueous solution for immersion, and the blending ratio of an oxazoline-containing polymer with respect to 100 parts by mass of the polyacrylic acid. Prepare 5 types of aqueous solutions of 30 parts by weight, 50 parts by weight, 60 parts by weight, 75 parts by weight, and 100 parts by weight, and add distilled water to make the concentration of polyacrylic acid 2.0% by weight. Except as described above, joined bodies of Samples 27 to 31 were produced in the same manner as in Example 1 above.

  Further, similarly, ferritic stainless steel plate SUS405 is used as a base material, and polyacrylic acid having a weight average molecular weight of 450,000 is used in place of the weight average molecular weight 90,000 as an aqueous solution for immersion, and 100 parts by mass of the polyacrylic acid 5 types of aqueous solutions of 30 parts by weight, 50 parts by weight, 60 parts by weight, 75 parts by weight, and 100 parts by weight of the oxazoline-containing polymer are prepared, and distilled water is added to adjust the concentration of polyacrylic acid. Except that all were adjusted to 0.10% by mass, joined bodies of Samples 32-36 were produced in the same manner as in Example 1 above.

  Similarly, ferritic stainless steel plate SUS405 is used as a base material and polyacrylic acid having a weight average molecular weight of 450,000 is used as an aqueous solution for immersion, and the blending ratio of the oxazoline-containing polymer with respect to 100 parts by mass of the polyacrylic acid. Example 3 except that three types of aqueous solutions of 50 parts by mass, 75 parts by mass, and 100 parts by mass were prepared and distilled water was added so that the concentration of polyacrylic acid was 2.0% by mass. In the same manner as in Example 1, joined bodies of Samples 37 to 39 were produced. The joints of these samples 23 to 39 were evaluated in the same manner as in Example 1 for the initial shear adhesive strength and water-resistant adhesiveness of the connecting portion. The measurement results are shown in Table 4 below.

  From Table 4 above, even in the case of ferritic stainless steel sheet SUS405, bonding with an adhesive via a thin film obtained by crosslinking polyacrylic acid having a weight average molecular weight of 5,000 or more and 450,000 or less with oxazoline. Thus, it can be seen that excellent water-resistant adhesiveness can be obtained similarly to the austenitic stainless steel plate SUS304.

[Example 4]
A martensitic stainless steel plate SUS403 is used instead of the austenitic stainless steel plate SUS304 as a base material, and a polyacrylic acid having a weight average molecular weight of 5,000 is used instead of a weight average molecular weight of 90,000 as its aqueous solution. Four kinds of aqueous solutions having 30 parts by mass, 50 parts by mass, 75 parts by mass, and 100 parts by mass of the oxazoline-containing polymer with respect to 100 parts by mass of acrylic acid are prepared, and distilled water is added to the concentration of polyacrylic acid. Were joined in the same manner as in Example 1 except that 0.10% by mass was used.

  Similarly, a martensitic stainless steel plate SUS403 is used as a base material, and polyacrylic acid having a weight average molecular weight of 5,000 is used as an aqueous solution for immersion, and an oxazoline-containing polymer is blended with respect to 100 parts by mass of the polyacrylic acid. Five types of aqueous solutions having a proportion of 30 parts by mass, 50 parts by mass, 60 parts by mass, 75 parts by mass, and 100 parts by mass are prepared, and distilled water is added to make the concentration of polyacrylic acid 2.0% by mass. Except for this, a joined body of Samples 44 to 48 was produced in the same manner as in Example 1 above.

  Further, similarly, a martensitic stainless steel plate SUS403 is used as a base material, and polyacrylic acid having a weight average molecular weight of 450,000 is used instead of a weight average molecular weight of 90,000 as an aqueous solution for immersion. 5 parts of the aqueous solution containing 30 parts by mass, 50 parts by mass, 60 parts by mass, 75 parts by mass, and 100 parts by mass of the oxazoline-containing polymer with respect to parts, and adding distilled water to the concentration of polyacrylic acid The samples 49 to 53 were joined in the same manner as in Example 1 except that the amount of each of the samples was 0.10% by mass.

  Similarly, martensitic stainless steel plate SUS403 is used as a base material, and polyacrylic acid having a weight average molecular weight of 450,000 is used as an aqueous solution for immersion, and blending of an oxazoline-containing polymer with respect to 100 parts by mass of the polyacrylic acid. The above implementation was performed except that three types of aqueous solutions having a proportion of 50 parts by mass, 75 parts by mass, and 100 parts by mass were prepared, and distilled water was added so that the concentration of polyacrylic acid was 2.0% by mass. In the same manner as in Example 1, joined bodies of Samples 54 to 56 were produced. The initial shear adhesive strength and water-resistant adhesiveness of the connection portion were evaluated in the same manner as in Example 1 for the joined bodies of Samples 40 to 56. The measurement results are shown in Table 5 below.

  From Table 5 above, even in the case of martensitic stainless steel sheet SUS403, bonding is performed with an adhesive via a thin film obtained by crosslinking polyacrylic acid having a weight average molecular weight of 5,000 or more and 450,000 or less with oxazoline. By this, it turns out that the water-resistant adhesiveness outstanding similarly to the austenitic stainless steel plate SUS304 is obtained.

[Example 5]
A joined body of Samples 1F1 to 13F1 was prepared in the same manner as in Example 1 except that a cold-rolled steel plate (SPCC material) was used instead of the austenitic stainless steel plate SUS304 as a base material, and the connection was made in the same manner as in Example 1. The initial shear adhesive strength and water-resistant adhesion of the parts were evaluated. The measurement results are shown in Table 6 below. In addition, each sample of this Example 5 formed the thin film on the same conditions as the sample of Example 1 which has the sample number which excluded F1 from the number.

  From Table 6 above, it can be seen that also in the cold-rolled steel sheet, the water-resistant adhesion is greatly improved by forming a thin film having a polyacrylic acid having a weight average molecular weight of 90,000 crosslinked by an oxazoline group. Moreover, it turns out that 50 mass parts or more and 100 mass parts or less are preferable with respect to 100 mass parts of polyacrylic acid.

[Example 6]
A joined body of samples 17F1 to 22F1 was prepared in the same manner as in Example 2 except that a cold-rolled steel plate (SPCC material) was used in place of the austenitic stainless steel plate SUS304 as a base material, and the connection was made in the same manner as in Example 2. The initial shear adhesive strength and water-resistant adhesion of the parts were evaluated. The measurement results are shown in Table 7 below. In addition, each sample of this Example 6 formed the thin film on the same conditions as the sample of Example 2 which has the sample number which excluded F1 from the number.

  From Table 7 above, even in the cold-rolled steel sheet, it is excellent by bonding with an adhesive via a thin film obtained by crosslinking polyacrylic acid having a weight average molecular weight of 5,000 or more and 450,000 or less with oxazoline. It can be seen that water-resistant adhesion is obtained.

[Example 7]
A joined body of Samples 1F2 to 13F2 was prepared in the same manner as in Example 1 except that a general structural rolled steel plate SS material (SS330) was used in place of the austenitic stainless steel plate SUS304 as a base material. The initial shear adhesive strength and water-resistant adhesion of the connection part were evaluated. The measurement results are shown in Table 8 below. In addition, each sample of this Example 7 formed the thin film on the same conditions as the sample of Example 1 which has the sample number which excluded F2 from the number.

  From Table 8 above, it can be seen that even in the general structural rolled steel sheet, the water-resistant adhesion is greatly improved by forming a thin film having a polyacrylic acid having a weight average molecular weight of 90,000 crosslinked by an oxazoline group. . Moreover, it turns out that 50 mass parts or more and 100 mass parts or less are preferable with respect to 100 mass parts of polyacrylic acid.

[Example 8]
Samples 17F2 to 20F2 and 22F2 were produced in the same manner as in Example 2 except that a general structural rolled steel plate SS material (SS330) was used instead of the austenitic stainless steel plate SUS304 as a base material. In the same manner as in Example 2, the initial shear adhesive strength and water-resistant adhesiveness of the connection part were evaluated. The measurement results are shown in Table 9 below. In addition, each sample of Example 8 formed the thin film on the same conditions as the sample of Example 2 which has the sample number which excluded F2 from the number.

  From Table 9 above, also in the general structural rolled steel sheet, by bonding with an adhesive through a thin film obtained by crosslinking polyacrylic acid having a weight average molecular weight of 5,000 or more and 450,000 or less with oxazoline, It can be seen that excellent water-resistant adhesion can be obtained.

[Example 9]
Except that a copper plate (2600 copper alloy) was used in place of the austenitic stainless steel plate SUS304 as a base material, a joined body of Samples 1C1 to 13C1 was prepared in the same manner as in Example 1 above, Initial shear bond strength and water-resistant adhesion were evaluated. The measurement results are shown in Table 10 below. In addition, each sample of this Example 9 formed the thin film on the same conditions as the sample of Example 1 which has the sample number which excluded C1 from the number.

  From Table 10 above, it can be seen that also in the 2600 copper alloy, the water-resistant adhesiveness is greatly improved by forming a thin film having polyacrylic acid having a weight average molecular weight of 90,000 crosslinked by an oxazoline group. Moreover, it turns out that 50 mass parts or more and 100 mass parts or less are preferable with respect to 100 mass parts of polyacrylic acid.

[Example 10]
A joined body of Samples 17C1 to 22C1 was prepared in the same manner as in Example 2 except that a copper plate (2600 copper alloy) was used instead of the austenitic stainless steel plate SUS304 as a base material. Initial shear bond strength and water-resistant adhesion were evaluated. The measurement results are shown in Table 11 below. In addition, each sample of this Example 10 formed the thin film on the same conditions as the sample of Example 2 which has the sample number which excluded C1 from the number.

  From Table 11 above, the 2600 copper alloy was also excellent by bonding with an adhesive via a thin film obtained by crosslinking polyacrylic acid having a weight average molecular weight of 5,000 to 450,000 with oxazoline. It can be seen that water-resistant adhesion is obtained.

[Example 11]
A joined body of Samples 23C2 to 39C2 was prepared in the same manner as in Example 3 except that pure copper was used instead of the ferritic stainless steel plate SUS405 as a base material. The water-resistant adhesion was evaluated. The measurement results are shown in Table 12 below. In addition, each sample of this Example 11 formed the thin film on the same conditions as the sample of Example 3 which has the sample number which excluded C2 from the number.

  From Table 12 above, even in pure copper, excellent water-resistant adhesion can be achieved by bonding with an adhesive via a thin film obtained by crosslinking polyacrylic acid having a weight average molecular weight of 5,000 to 450,000 with oxazoline. It turns out that sex is obtained.

[Example 12]
A joined body of Samples 1A1 to 13A1 was prepared in the same manner as in Example 1 except that an A2024-T3 aluminum alloy plate was used instead of the austenitic stainless steel plate SUS304 as a base material. Initial shear bond strength and water-resistant adhesion were evaluated. The measurement results are shown in Table 13 below. In addition, each sample of this Example 12 formed the thin film on the same conditions as the sample of Example 1 which has the sample number which excluded A1 from the number.

  From Table 13 above, it can be seen that the A2024-T3 aluminum alloy plate also has a particularly improved water-resistant adhesion by forming a thin film having a polyacrylic acid having a weight average molecular weight of 90,000 crosslinked by an oxazoline group. I understand. Moreover, it turns out that 50 mass parts or more and 100 mass parts or less are preferable with respect to 100 mass parts of polyacrylic acid.

[Example 13]
A joined body of Samples 17A1 to 22A1 was prepared in the same manner as in Example 2 except that an A2024-T3 aluminum alloy plate was used instead of the austenitic stainless steel plate SUS304 as a base material. Initial shear bond strength and water-resistant adhesion were evaluated. The measurement results are shown in Table 14 below. In addition, each sample of this Example 13 formed the thin film on the same conditions as the sample of Example 2 which has the sample number which excluded A1 from the number.

  From Table 14 above, also in the A2024-T3 aluminum alloy plate, by bonding with an adhesive via a thin film obtained by crosslinking polyacrylic acid having a weight average molecular weight of 5,000 or more and 450,000 or less with oxazoline It can be seen that excellent water-resistant adhesion can be obtained.

[Example 14]
A joined body of Samples 23A2 to 39A2 was prepared in the same manner as in Example 3 except that pure aluminum (A1050-H18) was used instead of the ferritic stainless steel plate SUS405 as the base material. The initial shear adhesive strength and water-resistant adhesive property of were evaluated. The measurement results are shown in Table 15 below. In addition, each sample of this Example 14 formed the thin film on the same conditions as the sample of Example 3 which has the sample number which excluded A2 from the number.

  From Table 15 above, pure aluminum (A1050-H18) is bonded with an adhesive via a thin film obtained by crosslinking polyacrylic acid having a weight average molecular weight of 5,000 or more and 450,000 or less with oxazoline. Thus, it can be seen that excellent water-resistant adhesion can be obtained.

[Example 15]
A joined body of Samples 23A3 to 39A3 was prepared in the same manner as in Example 3 except that an Al—Mn alloy (A3003-H18) was used instead of the ferritic stainless steel plate SUS405 as a base material, and the same as in Example 3. The initial shear adhesive strength and water-resistant adhesion of the connection part were evaluated. The measurement results are shown in Table 16 below. In addition, each sample of this Example 14 formed the thin film on the same conditions as the sample of Example 3 which has the sample number which excluded A3 from the number.

  From Table 16 above, even in the Al-Mn alloy (A3003-H18), the adhesive is used through a thin film obtained by crosslinking polyacrylic acid having a weight average molecular weight of 5,000 or more and 450,000 or less with oxazoline. It turns out that the outstanding water-resistant adhesiveness is acquired by joining.

[Example 16]
A joined body of Samples 23A4 to 39A4 was prepared in the same manner as in Example 3 except that an Al—Mg alloy (A5052-H38) was used instead of the ferritic stainless steel plate SUS405 as a base material, and the same as in Example 3. The initial shear adhesive strength and water-resistant adhesion of the connection part were evaluated. The measurement results are shown in Table 17 below. In addition, each sample of this Example 14 formed the thin film on the same conditions as the sample of Example 3 which has the sample number which excluded A4 from the number.

  From Table 17 above, in the Al-Mg alloy (A5052-H38), an adhesive is used via a thin film obtained by crosslinking polyacrylic acid having a weight average molecular weight of 5,000 to 450,000 with oxazoline. It turns out that the outstanding water-resistant adhesiveness is acquired by joining.

[Example 17]
A joined body of Samples 23A5 to 39A5 was prepared in the same manner as in Example 3 except that an Al—Si based alloy (A4032-T6) was used instead of the ferritic stainless steel plate SUS405 as a base material, and the same as in Example 3. The initial shear adhesive strength and water-resistant adhesion of the connection part were evaluated. The measurement results are shown in Table 18 below. In addition, each sample of this Example 14 formed the thin film on the same conditions as the sample of Example 3 which has the sample number which excluded A5 from the number.

  From Table 18 above, even in the Al—Si based alloy (A4032-T6), an adhesive is used via a thin film obtained by crosslinking polyacrylic acid having a weight average molecular weight of 5,000 or more and 450,000 or less with oxazoline. It turns out that the outstanding water-resistant adhesiveness is acquired by joining.

1 Metal Material 2 Oxazoline Crosslinked Polyacrylic Acid Thin Film 3 Adhesive 4 Adhered Metal

Claims (18)

  A thin film containing polyacrylic acid having a weight average molecular weight of 5,000 to 450,000 cross-linked with oxazoline is formed on the surface of the metal material, and then an adhesive is applied to the surface of the thin film to adhere to the adherend metal. It features and bonding method of metal material.   The method for adhering a metal material according to claim 1, wherein the metal material is stainless steel, copper material, steel material, or aluminum material.   The method for bonding a metal material according to claim 1 or 2, wherein the metal to be bonded is stainless steel, copper material, steel material, or aluminum material.   The method for adhering a metal material according to claim 2 or 3, wherein the stainless steel is one selected from the group consisting of austenitic stainless steel, ferritic stainless steel, and martensitic stainless steel.   The method for adhering a metal material according to claim 2 or 3, wherein the copper material is pure copper or a copper alloy.   The aluminum material is one kind selected from the group consisting of pure aluminum, Al-Cu alloy, Al-Mn alloy, Al-Si alloy, and Al-Mg alloy. Or the adhesion method of the metal material of 3.   The thin film is obtained by applying an aqueous solution containing a mixture of polyacrylic acid having a weight average molecular weight of 5,000 or more and 450,000 or less and an oxazoline-containing polymer, and then heat-treating at a temperature of 120 ° C. or more. The method for adhering a metal material according to any one of claims 1 to 6.   The aqueous solution contains 0.1% by mass or more and 2.0% by mass or less of the polyacrylic acid and contains 30 parts by mass or more and 100 parts by mass or less of an oxazoline-containing polymer with respect to 100 parts by mass of the polyacrylic acid. The method for adhering a metal material according to claim 7,   The method for adhering a metal material according to any one of claims 1 to 8, wherein the adhesive is a radical polymerization adhesive.   A metal material comprising: a metal material having a thin film having a polyacrylic acid having a weight average molecular weight of 5,000 to 450,000 cross-linked with oxazoline on the surface; and a metal to be bonded, bonded with an adhesive. Joined body.   The metal material joined body according to claim 10, wherein the metal material is stainless steel, copper material, steel material, or aluminum material.   The metal material joined body according to claim 10 or 11, wherein the adherend metal is stainless steel, copper material, steel material, or aluminum material.   The metal material joined body according to claim 10 or 11, wherein the stainless steel is one selected from the group consisting of austenitic stainless steel, ferritic stainless steel, and martensitic stainless steel.   The metal material joined body according to claim 10 or 11, wherein the copper material is pure copper or a copper alloy.   The aluminum material is one selected from the group consisting of pure aluminum, an Al-Cu alloy, an Al-Mn alloy, an Al-Si alloy, and an Al-Mg alloy. Or the metal material joined body according to 11.   The thin film is obtained by applying an aqueous solution containing a mixture of polyacrylic acid having a weight average molecular weight of 5,000 or more and 450,000 or less and an oxazoline-containing polymer, and then heat-treating at a temperature of 120 ° C. or more. The metal material joined body according to any one of claims 10 to 15.   The aqueous solution contains 0.1% by mass or more and 2.0% by mass or less of the polyacrylic acid and contains 30 parts by mass or more and 100 parts by mass or less of an oxazoline-containing polymer with respect to 100 parts by mass of the polyacrylic acid. The metal material joined body according to claim 16, characterized in that it is characterized in that:   The metal material joined body according to any one of claims 10 to 17, wherein the adhesive is a radical polymerization type adhesive.

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