JPH0355308B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a metal bonded structure formed by bonding primer-coated metal materials to each other with a polyamide adhesive. The present invention relates to a durable adhesive structure. In particular, the present invention relates to an adhesive structure in which an opening tab for shearing the score of the can lid is fixed to the can lid via an adhesive. (Prior Art) Conventionally, easy-open lids used for cans containing beverages such as cola, beer, youth, etc. have been provided with opening portions demarcated by scores (partial cutting lines). Widely used devices include a rivet formed in the opening portion, a tension tab fixed by the rivet, and the score broken and the opening portion removed by pulling the tab. However, with this easy-to-open lid, the inner coating of the can lid is easily damaged due to harsh processing such as riveting. For applications involving severe treatment, satisfactory results in terms of corrosion resistance cannot be obtained. This tendency is particularly noticeable in easy-to-open can lids made of aluminum. Furthermore,
Contents with a high salt concentration cause pitting corrosion, and there is a problem of leakage of contents from through holes and contamination by bacteria. Japanese Utility Model Publication No. 51-524 proposes an easy-to-open can lid in which an opening piece is adhesively fixed to an opening section defined by scores. Polyamides are also known to be excellent hot melt adhesives for bonding metals together. (Problem to be Solved by the Invention) In this type of easy-to-open lid, by lifting the grip part of the opening piece upward, the adhesive part becomes a fulcrum and the tip of the opening piece (tab) is pushed into the score. Shearing of the score is started by pulling the tab, and shearing is performed across the entire score by pulling the tab, but in this case, the force necessary to tear the score acts as a moment on the adhesive part, The problem is that the parts are likely to break. Furthermore, the method of opening an easy-open lid varies depending on the purchaser of the can. For example, when pulling the tab without lifting it until it is at a position approximately perpendicular to the can lid, , a relatively large moment acts on the adhesive fulcrum between the tab and the lid, making it easy for the adhesive fulcrum to break. Furthermore, if the tab is not pulled correctly in the tab direction, a moment will still act on the adhesive fulcrum, making it easy for the adhesive fulcrum to break. Polyamide-based adhesives have large hydrogen bonds between molecular chains and particularly high cohesive failure force among component polymers, and are also highly resistant to protective coatings applied to protect the metal material for lids. The adhesion is also great,
Therefore, even when the above-mentioned easy-to-open lid is opened, there is almost no risk that the polyamide adhesive layer at the adhesive fulcrum or the joint between the adhesive layer and the paint film will be destroyed; It has been observed that peeling or destruction often occurs at the close contact interface with metal materials. The reason for this is thought to be that although the peeling force between the metal and the paint film is quite large, there is almost no deformation (elongation) between the two, so stress concentration occurs in this area, leading to fracture. be done. Therefore, the present invention provides a metal bonded structure in which primer-coated metal materials are bonded to each other with a polyamide adhesive, by allowing partial destruction of the adhesive layer to a certain extent, thereby improving the bond between the primer and the metal material. It is an object of the present invention to provide a bonded structure which prevents breakage and thereby prevents bond failure as a whole, in particular bond failure under conditions where a moment acts. (Means for Solving the Problems) The present invention provides a metal adhesive structure in which primer-coated metal materials are bonded to each other using a polyamide adhesive. A group consisting of a linear aliphatic polyamide having carbon numbers in the range of 6.1 to 15, and (B) a carboxylic acid, a carboxylic acid anhydride, a carboxylic acid salt, a carboxylic acid amide, and a carboxylic acid ester bonded to the polymer chain. At least one group selected from = CO group
and an olefin copolymer contained at a concentration of 10 to 400 mmol/100 g polymer in a weight ratio of A:B = 94:6 to 65:35, and the polyamide (A) is a continuous phase and the olefin copolymer is Using an adhesive layer in which (B) exists as a dispersed particle phase, and using an epoxy resin and a phenolic resin as a primer in a ratio of 95:5 to 95:5.
It is characterized by using a curable coating film containing a weight ratio of 30:70. (Function) In FIG. 1, which shows an enlarged cross-sectional structure of the adhesive structure of the present invention, this adhesive structure shows the above-mentioned adhesive fulcrum between the can lid and the opening tab in an enlarged manner. The outside is shown at the top and the inside of the can is shown at the bottom. An adhesive primer layer 2 is applied to the outer surface of the metal can lid 1.
However, the inner surfaces are each provided with a protective coating 3, while the inner surface of the metal opening tab 4 is also provided with an adhesive primer layer 5, and the outer surface is provided with a protective coating 6. The can lid 1 and the opening tab 4 have adhesive primer layers 2 and 5 applied to their surfaces.
They are joined by an adhesive layer 7 via. According to the present invention, the adhesive primer layers 2 and 5 are made of epoxy resin and phenolic resin in a ratio of 95:5.
A curable coating film containing a specific linear aliphatic polyamide and an olefin copolymer is used as the adhesive layer 7 in a weight ratio of 94:6 to 30:70.
A layer of a composition containing a weight ratio of 65:35 and in which the polyamide is the continuous phase and the olefin copolymer is the dispersed phase is used. Figure 2 of the attached drawings is an electron micrograph (10,000x magnification) showing the cross-sectional structure of the adhesive layer used in the present invention.
In this photograph, the polyamide continuous phase appears black, and the olefin copolymer dispersed phase appears white. The present invention shows that by using an adhesive layer having a structure in which polyamide is a continuous phase and an olefin copolymer is a dispersed layer, peel failure between the primer coating and the metal material is suppressed in an adhesive peel test. This is based on the knowledge that the overall toughness against adhesive failure is improved. FIG. 3 of the attached drawings shows that the epoxy-phenol primer of Example 1, which will be described later, was used as the primer coating, and nylon 6, nylon 6,
10 used alone (sample A), nylon 6,
10 and ethylene vinyl acetate copolymer (copolymerization ratio 90/
10, MI5) at a weight ratio of 85:15,
A sample with a dispersed structure as shown in FIG. 2 (sample B), and a blend of nylon 6, 10 and the above ethylene vinyl acetate copolymer at the same weight ratio,
After forming an adhesive fulcrum for an easy-to-open lid using a material with a uniformly dispersed structure (sample C), a repair paint for the inside of the lid was applied and baked, and then hot water treatment equivalent to retort sterilization was performed assuming a real can. Above, the peeling force (Kg) in the 90 degree direction at a tensile speed of 200 mm/sec at the adhesive fulcrum.
It shows the results of calculating the amount of displacement (cm). In Figure 3, the final peeling force at the rise is related to the initial opening force, and the integral value of the curve is 90
This corresponds to the degree of peeling work. The following can be seen from the results shown in Figure 3. That is,
When nylon alone is used as the adhesive (sample A), the ultimate peeling force is extremely large, but it is clear that destruction occurs within a small amount of displacement. When we actually observed sample A, we found that the failure was dominant at the adhesive interface between the primer coating and the metal, and therefore in the case of sample A, the location where stress was concentrated was at the interface between the primer coating and the metal. This indicates that the adhesive fulcrum is still unsatisfactory in terms of toughness (90 degree peeling work). In addition, in the case of an adhesive layer (sample C) in which nylon and olefin copolymer are uniformly dispersed, although the amount of displacement is large, the ultimate peeling force is quite low, and it is easy to peel off the adhesive layer. It will be understood that destruction will occur. In contrast, when using an adhesive layer (Sample B) in which polyamide is a continuous phase and an olefin copolymer is a dispersed phase according to the present invention, the ultimate peel force can be maintained at a relatively high level. However, it is possible to take a large amount of displacement at this level, and the 90 degree peeling work, that is, the toughness of the adhesive fulcrum, can be
It can be seen that it is possible to take a larger value than . This seems to mean the following regarding the failure of the adhesive fulcrum. That is, the adhesive failure between the primer coating and the metal occurs at a force greater than the ultimate peeling force of sample A, but in the adhesive structure of the present invention, as shown by curve B in FIG. The action only partially destroys the polyamide continuous phase in the adhesive layer, prevents destruction between the primer coating and the metal, and reduces the amount of work required to destroy the adhesive layer. is getting larger, so
On the contrary, destruction of the adhesive fulcrum is prevented. In order to effectively utilize polyamide, which has a large cohesive force, as a stress carrier, a heterogeneous distribution structure as shown in Figure 2 is essential, and a uniformly distributed structure like Sample C will reduce the strength of the adhesive layer itself. will be invited. In the polyamide used in the present invention, the average number of carbon atoms in the main chain per amide group is related to the strength of hydrogen bonds between molecules, and the magnitude of cohesive force is also important for hardness or affinity for water. affect. If the average number of carbon atoms in the main chain per amide group is less than 6.1, the melting point will be too high and the possible bonding temperature will be too high, making the bonding operation difficult. Inconveniences such as scorching of the coating film occur, and it becomes difficult to control cooling after adhesion, which tends to make it difficult to control the degree of crystallinity, which will be described later. In addition, this polyamide is extremely sensitive to water, and its mechanical properties vary greatly depending on the moisture content, and furthermore, the moisture content tends to cause defects such as foaming in the bonded area. Furthermore, if the average number of carbon atoms in the main chain per amide group exceeds 15.0, the cohesive force of the polyamide itself tends to decrease, resulting in a decrease in heat resistance, which may occur during baking of correction paint on score areas or during retort sterilization. This results in a decrease in adhesion, and in severe cases, even displacement of the adhesion fulcrum. Furthermore, the adhesion to the primer coating also decreases. It is also important that the olefin copolymer used in the present invention has a carboxylic acid, carboxylic anhydride, carboxylate, carboxylic acid amide, or carboxylic ester group bonded to the polymer chain; Olefin copolymers that do not contain polyamides lack dispersibility in polyamides, and even if they are dispersed, bonding at grain boundaries is insufficient and the adhesive layer tends to become brittle. Also, = the concentration of these groups expressed on a CO group basis is 10 to 400 mmol/100g,
In particular, it is important that the concentration be within the range of 15 to 300 mmol/100g; if this concentration is lower than the above range, the above-mentioned disadvantages are likely to occur, and if it is higher than the above range, it is also important that It tends to be difficult to disperse and cause thermal decomposition and foaming during kneading. It is also important to use polyamide (A) and olefin copolymer (B) in a weight ratio of A:B = 94:6 to 65:35, especially 91:9 to 70:30, and the amount of olefin copolymer is less than the above range,
The same drawbacks as when polyamide is used alone appear, and when the amount exceeds the above range, the mechanical strength of the adhesive layer tends to decrease, as well as the adhesive strength with the primer layer. . In the adhesive layer used in the present invention, the median minor axis of the dispersed particle phase (olefin copolymer) is 0.05.
For the purpose of the present invention, it is desirable that the thickness be between 10μ and 0.5μ and 8μ. Since the adhesive layer used in the present invention has the above-mentioned dispersed structure,
Since the contact interface between the olefin copolymer phase and the polyamide phase is extremely large, the strain that tends to remain in the adhesive layer during the bonding cycle of hot melting and cooling solidification is easily alleviated at the contact interface between the two phases. As a result, a bonded structure with no deterioration in adhesive strength over time can be obtained. The primer coating film having the above composition used in the present invention is:
It has particularly excellent adhesion to metals, and
It exhibits excellent adhesion to the polyamide-olefin copolymer blend layer described above, and is also excellent in imparting corrosion resistance to metals. If the epoxy resin component exceeds the above range, interfacial peeling with the adhesive will easily occur, while if the phenolic resin component exceeds the above range, interfacial peeling with the metal will tend to occur, and the primer coating will become brittle. There are also trends. (Operations and Effects of the Invention) According to the present invention, when bonding primer-coated metal materials using a polyamide adhesive, stress concentration occurs at the adhesion interface between the primer coating film and the metal material, and this portion is prevented from being destroyed. It is possible to prevent this and increase the toughness of the entire joint against adhesive failure. By applying this adhesive structure to the contact fulcrum between the can lid and the opening tab, an adhesive fulcrum with excellent peeling resistance is provided even when a moment is applied, and the lid material is connected to the can body. Although it is made of a rigid metal material used for fastening and fixing, it effectively prevents the joint fulcrum from breaking when unsealing, achieving the advantage that the unsealing operation can be performed stably even after a long period of time. . (Description of Preferred Embodiments of the Invention) Lid Structure As shown in FIGS. 1, 4 and 5, the easy-to-open can lid of the present invention is made of a rigid metal material 1 provided with a primer coating 2. This lid member 1 includes a circumferential groove 8 on the outer periphery and a panel portion 10 connected to the groove through an annular rim portion 9. A layer 11 of sealing compound is provided which sealingly engages upon tightening. Inside the annular rim portion 9 there is a portion 13 to be opened, which is defined by a score 12 . This opening portion 13 may substantially coincide with most of the panel portion 10, or a portion of the panel portion 10 may be the opening portion. As shown in the enlarged sectional view of FIG. 1, the score 12 is provided so as to reach the middle of the metal material 1 in the thickness direction, and is easily sheared when the package is opened by a mechanism described in detail below. According to the invention, this opening portion 13 is also provided with an opening tab 4 in a particular arrangement as described below. This opening tab 4 has a score tearing tip 14 at one end, a gripping part (ring) 15 at the other end, and a fulcrum part 16 located between these parts and joined to the lid. In this embodiment, the fulcrum portion 16 has a generally U-shaped cut 17 in the tab between the tip 14 and the ring 15.
A connecting portion 18 is provided between the tip 6 and the tip 14, and is formed into a tongue shape. The pushing tip 14 of the opening tab 4 presses the opening portion 1 of the lid at the tongue-shaped fulcrum portion 16 so that its position almost matches the score 12 of the lid.
3 and is thermally bonded via a polyamide adhesive layer 7. In the can lid of the present invention, when the ring 15 of the opening tab 4 is picked up with a finger and lifted upward, this force is transmitted as a downward force to the tearing tip 14 via the fulcrum portion 16, At the same time as a downward tearing force is applied to the score 12, a peeling force (moment) is applied to the adhesive layer 7 between the fulcrum part 16 and the opening part 13. According to the invention, adhesive layer 7
By using the specific polyamide-olefin copolymer blend adhesive mentioned above, it is made to be able to withstand the above-mentioned peeling force. Next, place this opening tab 4 approximately against the lid 1.
By pulling at a 90 degree angle, the score 12 is sheared away from the score. Metal materials Metal materials for the lid include light metal plates such as aluminum, various surface-treated steel plates, such as steel plates plated with zinc, tin, chromium, aluminum, etc., and plated with chromic acid, phosphoric acid, etc. on the surface. It is made of a material on which a chemical conversion treatment film is formed, and any metal material having pressure deformation resistance and rigidity that can withstand seaming can be used. The thickness of the material is generally 0.10 to 0.40mm,
In particular, it is desirable that the thickness be in the range of 0.12 to 0.35 mm. Further, the opening tab is also made of the various metal materials mentioned above, especially aluminum. The lid material of the present invention can be made of metal materials that are difficult to rivet, such as chromate surface-treated steel sheets, especially electrolytic chromic acid treated steel sheets, chromate-treated nickel-plated steel sheets, chromate-treated iron, tin alloy-plated steel sheets, chromate-treated tin/nickel. It is suitably applied to alloy-plated steel sheets, chromate-treated iron/tin/nickel alloy-plated steel sheets, and chromate-treated aluminum-plated steel sheets. Electrochromic acid treated steel sheets consist of a metallic chromium layer on a cold rolled steel substrate and a non-metallic chromium layer thereon. The thickness of the metallic chromium layer is determined by the balance between corrosion resistance and workability, and the amount is between 30 and 300 mm.
mg/m ² , preferably in the range of 50 to 250 mg/m ² . The thickness of the nonmetallic chromium layer is related to paint film adhesion and adhesive peel strength, and is preferably in the range of 4 to 40 mg/m ² , particularly 7 to 30 mg/m ² in terms of chromium content. . Primer The primer coating film used in the present invention is used for the purpose of promoting adhesion and protecting the underlying metal, and contains a phenol resin and an epoxy resin in the above-mentioned quantitative ratio. As the phenolic resin, a resol type phenolic resin obtained by condensing various phenols and formaldehyde in the presence of a basic catalyst is used. Examples of phenols include trifunctional phenols typified by carbolic acid, difunctional phenols typified by p-cresol, and polynuclear phenols typified by bisphenol A, either singly or in combination of two or more. The phenolic resin used, but particularly suitable for the purposes of the present invention, has the following formula: IF = 2M ₂ + 3M ₃ + 4M ₄ , where M ₂ is the difunctional _M3 is the number of moles of trifunctional monovalent phenol in 100g of total phenol components, and _M4 is the number of moles of polycyclic divalent phenol in 100g of total phenol components. The sensory index (IF) is in the range of 1.5 to 2.5, particularly 1.6 to 2.8. Also, the average number of methylol groups per phenol nucleus is
The number average molecular weight is generally in the range of 200 to 800, especially in the range of 0.05 to 0.40, especially 0.07 to 0.30.
A value in the range of 230 to 600 is desirable. As the epoxy resin, an epoxy resin obtained by condensing bisphenol A and epihalohydrin and having an epoxy equivalent in the range of 600 to 6,000, particularly 900 to 4,000 is preferably used. Epoxy resins and phenolic resins are used in the coating of metal materials in the form of a mixture or precondensed form, and after being applied to the metal materials, the temperature is 140 to 280℃.
It is best to use it for bonding after baking it for 1 to 20 minutes. The thickness of the primer coating is not particularly limited as long as the above-mentioned purpose is achieved, but it is generally desirable to have a thickness in the range of 0.2 to 30 μm, particularly 1 to 20 μm. Adhesive In the present invention, the first condition is to use a polyamide whose average main chain carbon number per amide group is in the range of 6.1 to 15.0, particularly 7.0 to 14.0. The polyamide may be a homopolyamide, a copolyamide or a blend thereof, whose starting monomer components are ω-aminocarboxylic acid and/or diamine dicarboxylic acid salt. Examples of suitable polyamides are listed in Table A below. Of course, in the case of copolyamide or blend polyamide compositions, it is perfectly acceptable to contain ω-aminocaproic acid units, hexamethylene adipamide units, etc., provided that the entire composition satisfies the above-mentioned restrictions. . The polyamide used in the present invention is 98% sulfuric acid 100%
Preferably, the specific viscosity (ηγ), measured at 20° C. at a concentration of 1 gram in cc, is in the range of 1.8 to 3.5. A polyamide having a specific viscosity value smaller than the above range has poor mechanical properties and does not have sufficient strength at the bonded portion. Furthermore, with polyamides whose specific viscosity is higher than the range of the present invention, the melt viscosity of the adhesive becomes too high during melt bonding, and bonding is required at a temperature considerably higher than the melting point.
Undesirable.

[Table] The olefin copolymer used in the present invention contains a carboxylic acid, carboxylic anhydride, carboxylate, carboxylic amide, or carboxylic ester group bonded to the polymer chain. Such olefin copolymers can be obtained by copolymerizing ethylenically unsaturated monomers containing the above groups with olefins, or by modifying polyolefins by means such as graft polymerization or block copolymerization. It will be done. Suitable examples of the carboxylic acid derivative group-containing ethylenically unsaturated monomers mentioned above are as follows. ) Carboxylic acids or carboxylic acid anhydrides, acrylic acid, methacrylic acid, fumaric acid, maleic anhydride, itaconic anhydride, crotonic acid, tetrahydrophthalic anhydride. ) Carboxylic acid amides acrylamide, methacrylamide, maleimide. ) Carboxylic acid esters Vinyl esters such as vinyl acetate and vinyl propionate. (Meth)acrylates such as ethyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, 3-hydroxypropyl (meth)acrylate, and N-ethylaminoethyl (meth)acrylate. Suitable examples of olefin copolymers are as follows. Ethylene random copolymers such as ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, and ethylene-ethyl acrylate copolymer. Ionically crosslinked olefin copolymers, such as ethylene or propylene and acrylic acid or methacrylic acid, are copolymerized with these ester monomers if necessary, and alkali metal ions such as sodium and potassium, alkaline earth metal ions such as magnesium, etc. A copolymer formed by ionic crosslinking with , zinc ions, organic cations, etc. Maleic anhydride, acrylic acid, methacrylic acid, (meth) acrylate, (meth) ) A copolymer made by grafting acrylamide, etc. Of course, these copolymers are based on carboxylic acid or its derivative groups =CO groups at the aforementioned concentration,
That is, it should be present in a concentration of 10 to 400 mmol per 100 grams of copolymer. In the present invention, the above-mentioned copolymer need only have the above-mentioned concentration as a whole. For example, even if it is a blend of two or more olefin copolymers having different =CO group concentrations, an unmodified olefin polymer and a modified olefin copolymer may be used. It may also be a blend with a copolymer. The olefin copolymer used should have a molecular weight sufficient to form a film, a melting point in the range of 40 to 200°C, especially 60 to 180°C, and a melt flow rate (MI) of 0.5 to 180°C.
300, particularly within the range of 0.7 to 150, is advantageous for forming the dispersed structure of the present invention. In order to achieve the dispersed structure measured in the present invention, it is essential to use the polyamide and olefin copolymer in the above-mentioned ratio, but this alone is not sufficient, and the degree of melt-kneading of both resins is also essential. need to be adjusted. The degree of kneading varies depending on the melting point and sensory concentration of the resins, and cannot be absolutely defined, but it is generally desirable to dry blend the two resins, then knead them using a metal ring type screw, and form them into a film. In an extruder using a Dalmage type screw or a twin-screw extruder, the dispersion of both resins becomes homogeneous unless the kneading time is extremely shortened.
The dispersed structure of the present invention is difficult to obtain. This adhesive contains antioxidants, heat stabilizers, ultraviolet absorbers, viscosity modifiers, plasticizers, core materials, inorganic fine particles, fillers, organic lubricants, pigments, synthetic rubber latex particles, etc. to significantly improve its adhesive performance. As long as it doesn't hurt
It can be added as an additive in an amount not exceeding 20% by weight of the entire resin composition. Manufacturing method In manufacturing the easy-open can lid of the present invention, first, at least one side of the metal material described above is coated with a primer paint in the form of an organic solvent solution, an aqueous dispersion, or an aqueous solution, by spray paint or roller coating. , dip painting,
It is applied by means such as electrostatic coating or electrophoretic coating, and a coating film is formed by drying or baking. In this case, it is also possible to laminate a thermoplastic resin film on the side different from the side on which the adhesive fulcrum is formed using an adhesive, if necessary. This painted or painted laminate plate is punched out to a predetermined can lid size, press-molded into a can lid of a predetermined shape, and scored at the same time or in a separate process. In score processing, the residual thickness in the score part is 1/8 to 1/2 of the base plate thickness, and the absolute thickness is 0.2 to 0.9 mm, especially 0.3 to 0.8 mm.
It is desirable that the range also be within the range. Prior to or after this scoring process, a sealing compound composition made of a synthetic rubber latex such as styrene-butadiene rubber latex, a tackifier, and a filler is applied to the circumferential groove of the can lid, and then dried. Make it a compound layer. A layer of the above-mentioned blend adhesive is provided on the fulcrum portion of a separately manufactured opening tab, or a layer of the blend adhesive is provided on the portion of the can lid where the opening tab is to be provided. Of course, it is also possible to do both. The adhesive layer can be formed by any method other than applying an adhesive film cut to a predetermined size, such as applying the adhesive in the form of powder, melt, suspension, or solution. can.
The thickness of the adhesive resin is 3 to 150μm, especially 10 to 150μm.
A suitable range is 100 μm. Next, the opening tab is positioned on the can lid, and the thermoplastic resin located between the fulcrum part of the tab and the can lid is melted and then cooled and solidified to complete adhesion between the two. In addition, prior to this, the vicinity of the score may be lined with a resin such as rubber or plastisol in order to prevent injuries when the lid is opened. In the case of edible cans, it is preferable that the score be provided close to the annular rim and over the entire circumference, as shown in the attached drawing, in a so-called full open format. It is also possible to provide a portion of the can lid with an arbitrary shape such as a raindrop shape or a semicircular shape. In addition, in order to repair damage to the covering material during scoring on the inner surface of the lid, paint is further applied and baked as necessary. The adhesive structure of the present invention is most effective as an adhesive fulcrum for the above-mentioned easy-to-open lid, but this advantage can be applied to other adhesive applications, for example, when a force with a complex directional component such as a peeling force is applied to the adhesive surface. It should be understood that the same effect can be achieved even when used for bonding between metal materials. The following examples specifically explain the effects of the present invention. In each example, the following basic characteristics regarding adhesion () and adhesion with a lid as an application example () were evaluated for the metal adhesive structure composed of the materials of each test number. . Adhesion test Plate thickness 0.22mm, amount of non-metallic chromium on the surface 15mg/
^m2 , normal stain-free steel (TFS)
Epoxy/phenol paint (the weight ratio and composition of epoxy resin and phenol resin are slightly different in each example as described later) was applied to both sides of the board so that the thickness after baking was 5 μm. ℃
Baking was carried out for 10 minutes. A test piece with a width of 5 mm and a length of 10 cm was cut out from this painted board, each adhesive film with a width of 7 mm was sandwiched between the two test pieces, and then bonded using high frequency heating. The adhesion temperature was set so that the entire adhesive surface reached a temperature that was 30°C above the melting point of each adhesive. Some of these adhesive pieces were heated in an oven for 4 minutes at 20°C below the melting point of each adhesive in order to examine the effects of post-heating applied during baking and curing of paint when repairing damage to the score processed area on lids, etc. A portion of the sample was treated with hot water equivalent to retort sterilization at 116°C for 90 minutes, and a portion of the sample was placed in water at 90°C for one week. To evaluate the adhesion, a T-peel test was conducted on five test pieces each after heating in an oven at the initial stage of adhesion, after retorting, and after aging in hot water at 90°C. For the T-peel test, an Instron type tensile testing machine was used to measure at room temperature at a tensile speed of 200 mm/min, and the results were calculated as the arithmetic mean of the average values of each measured value. Lid Adhesion Test As a specific application example of the metal adhesive structure of the present invention, as shown in Figures 4 and 5, an opening tab for shearing the score of the can lid is fixed to the can lid via adhesive. The adhesive performance of the adhesive structure was tested. The lid for this purpose was created as follows. In other words, the plate thickness is 0.20 mm, the amount of non-metallic chromium on the surface is 15 mg/m ² , and the amount of metallic chromium is 100 mg/m ²
The same epoxy used in the previous test was applied to both sides of a regular stain-free steel (TFS) plate.
A phenol-based paint was applied so that the thickness after baking was 5 μm, and baking was performed at 210°C for 10 minutes.
This painted TFS plate was formed into a lid for diameter 211 using a press, and then a sealing compound was applied to the curled portion by a conventional method and dried. Next, a score was processed on the outer surface of the lid in a circular shape with a diameter of 58 mm so that the score residual thickness/thickness of the steel plate was 0.23.
On the other hand, epoxyphenol paint was applied to the adhesive side of the 0.46-thick aluminum coil (#5082) material (the weight ratio of epoxy resin and phenol aldehyde resin was 75:25, and bisphenols A were used as the raw material for the phenol aldehyde resin. ) on the opposite side with epoxy area paint so that the thickness after baking is 5 μm, and then the width is 30 mm.
I slit it. In contrast, each of the following tests
Made of the composition shown in No., thickness 45-50μm, width 8
After laminating microslit films of mm in diameter by high-frequency induction heating, they were press-molded into tabs having the shapes shown in Figures 4 and 5. The distance from the score to the adhesive fulcrum is 6 mm for the tab created in this way.
The melting point of each adhesive is at least 30° below the melting point of each adhesive by high-frequency heating.
It was bonded by heating to a high temperature. In this case, the width of the adhesive layer at the adhesive fulcrum portion was approximately 7 mm, and the area of the adhesive portion was approximately 40 mm ² . Next, after adhering each tab, epoxy/phenol paint was applied to the score parts of the inner and outer surfaces of the lid, and then the melting point of each adhesive was applied at a temperature of -20°C for 4 hours.
After baking in the oven for a few minutes, follow steps 1 and 2 below.
The peel strength and lid opening properties were evaluated as described in . 1. Peel strength After the tabs were adhered under predetermined adhesive conditions, baked in a predetermined oven, and further subjected to retort sterilization equivalent to heat sterilization, the peel strength of the lid was measured by the following method. In other words, when the tab is lifted and the initial opening of the score section is performed, and the tab is raised vertically to the lid panel surface, the adhesive part will be peeled at 90 degrees when the tab ring is perpendicular to the lid panel surface. A tensile test was conducted as follows. For the tensile test, an Instron type tensile tester was used, and the tensile speed was 200 mm/min.
Measurements were carried out at room temperature, and the breaking strength was evaluated by peeling work. Peeling work was determined by integrating the area within the peel strength curve on the chart using an automatic integrator and converting the result to 1 cm ² of bonded area. Each sample No.
Measurements were carried out five times, and the arithmetic mean value of these measurements was taken as the measured value. 2. Lid opening performance The opening performance of the lid is determined immediately after adhesion, after applying correction paint to the scored parts of the internal and external surfaces of the lid, and after performing the prescribed oven baking process, and after double-sealing the lid to the 211-diameter flange can body. 116 after filling with dressing tuna and tightening the flat lid.
When retort sterilization was carried out for 90 minutes at ℃, 20 panelists were asked to open 5 cans each immediately after retorting and after 6 months at 37℃, for a total of 100 cans. As a result, the number of cans that could not be opened because the tab came off during opening, and the number of cans that could not be opened initially among these opening failures are shown in the box. Example 1 Adhesive films having the compositions and blend ratios shown in Table 1 were prepared. During film formation,
In No. 1-1 and 1-3, the resin chips of both components were dry blended in advance, and in No. 1-4, the resin chips of both components were kneaded into pellets using a twin-screw extruder, and then each was made into a metal ring mold. The mixture was kneaded and made into a film using an extruder equipped with a screw. In addition, in No. 1-5, the melt-kneading temperature was lowered by 20℃ than the standard temperature above, but the discharge speed was also 100%.
Film formation was carried out under fast conditions. The dispersed structure of the cross sections of these films was observed using a transmission electron microscope using an ultrathin section method. Here, phosphotungstic acid staining was also used in order to more clearly capture the dispersed structure. In the distribution structure in the table,
OinA has a structure in which a granular phase of polyolefin is dispersed in a continuous nylon resin phase, A has a homogeneous structure with almost no dispersed structure, and Oand A has a granular polyolefin phase in which both the polyolefin phase and the nylon resin phase are continuous phases. This indicates a structure in which the existence of phases is unclear. In evaluating the performance of these adhesives, we used a primer with a weight ratio of epoxy resin and phenol formaldehyde resin of 85:15, and a phenol formaldehyde resin made from bisphenol A and p-cresol as raw materials, using the method described above. A test was conducted after obtaining a painted board for adhesion testing and a painted board for the lid. The evaluation results are summarized in Table 1, and according to this, when the adhesive is made only of nylon resin, even if good initial strength or good strength is obtained after heating in an oven, the adhesive strength after retorting or aging in hot water The strength decreased significantly (No. 1-2, 1-3),
A similar decrease in strength is also noticeable even when polyolefin is contained but without a dispersed structure (No. 1
-4) Furthermore, when the dispersed structure of the polyolefin phase was disordered and did not have a granular dispersed structure, the strength generally showed a tendency to be low. These differences in adhesion correspond well to the peel strength and opening properties of the lid, with Nos. 1-2 and 1-4 having poor opening in the actual can test, and Nos. 1-5 having poor adhesion. Opening defects occurred even in the initial stage, and the difference in performance from No. 1-1 of the present invention was obvious.

[Table] Example 2 Nylon as polyamide resin component of adhesive
610, ionomer resin (ethylene acrylic acid copolymer metal salt, -
C=O group concentration 155 mmol/100g polymer, MI=
0.7) and the blend ratio shown in Table 2, a film was prepared in the same manner as in Example 1, No. 1-1. Regarding the dispersion structure, when the content of ionomer resin is low (No. 2-1), the granular dispersion structure is unclear and shows a homogeneous structure, while when the content is high (No. 2-8, 2-
9) The polyolefin phase also showed a tendency to become a continuous phase. In evaluating the performance of these adhesives, we used a primer with a weight ratio of epoxy resin and phenol formaldehyde resin of 80:20, and a phenol formaldehyde resin made from bisphenol A and m-cresol as raw materials, using the method described above. Therefore, a test was conducted. The evaluation results are listed in Table 2, and when the content of the ionomer resin is low, the tendency is similar to that of the case of only nylon resin in Example 1, and the adhesion after retorting or aging in hot water is still poor. insufficient;
Even in actual can tests with lids, opening defects may occur. On the other hand, when the content of ionomer resin increases, the initial adhesive strength and especially the adhesive strength after oven heating tend to decrease, resulting in a decrease in adhesiveness due to a decrease in the heat resistance or hot water resistance of the adhesive itself. As a result, the ability to open the lid was also significantly impaired.

[Table] Example 3 For adhesive compositions in which the average main chain carbon number per unit amide group of the polyamide resin component was different, maleic anhydride-modified polypropylene (-C=O group concentration 230 mmol/100
g polymer, MI=3.5) and its blend ratio is 80:
After fixing the number of carbon atoms to 20, the relationship between the average number of main chain carbon atoms per unit amide group and adhesiveness was investigated. The adhesive film was formed using the component chips shown in Table 3 in the same manner as in Example 1, No. 1-1. In each case, the dispersed structure was such that a granular phase of polyolefin resin was dispersed in a continuous phase of polyamide resin. In evaluating the performance of these adhesives, we used a primer with a weight ratio of epoxy resin and phenol formaldehyde resin of 75:25, and a phenol formaldehyde resin made from bisphenol A and o-cresol as raw materials, and according to the method described above. A painted board was prepared and tested. The evaluation results are shown in Table 3. When using nylon 6, which has an average main chain carbon number of 6 per unit amide group, only low adhesive strength was obtained, and interfacial delamination between the primer plate and the primer plate was particularly dominant. Even if the lid opened to some extent initially, there were many cases where the tab came off when the score part was sheared and the lid could not be opened (No. 3-1). In addition, even when nylon 6 is copolymerized with nylon 6, adhesion improves slightly, but no improvement effect is observed, and adhesion between the primer and the plate tends to decrease due to oven heating or retort treatment. The opening of the lid is also insufficient (No. 3-
1). On the other hand, the average number of main chain carbons per unit amide group is
When using a blend of nylon 12, which is 16.5 or higher than 15, and dimer acid-based polyamide, the adhesive itself has insufficient heat resistance and hot water resistance, resulting in a decrease in adhesive properties during oven heating, retort processing, etc. As a result, a sufficiently high initial peel strength could not be obtained in the lid, which tended to make initial opening extremely difficult (No. 3-8).

【table】

[Table] Example 4 Nylon 12 was used as the polyamide resin component in the adhesive composition, and those with different carbonyl group concentrations were used as the polyolefin resin components, and the relationship between the carbonyl group concentration of the polyolefin resin and the dispersion structure and its adhesion We examined the relationship with gender. Nos. 4-2 to 4-4 are the original resins of 4-1 with different grafting ratios with maleic anhydride, and Nos. 4-5 to 4-9 are ethylene-based resins with different copolymerization ratios. A metal salt resin of methacrylic acid copolymer was used as a polyolefin resin component. In addition, for No. 4-1 to 4-4, MI = 30 to 80,
In Nos. 4-5 to 4-9, those with MI in the range of 0.7 to 2.5 were used. From these resins, the blend ratio is 85:15
An adhesive film was obtained in the same manner as in Example 1, No. 1-1. Except for No. 4-9, where a homogeneous structure was predominant, the polyolefin resin phase generally showed a structure dispersed in the polyamide resin phase, but low-density polyethylene with a carbonyl group concentration of almost zero was used. In case (No. 4-1), the blocking of the polyolefin phase is significant, and in order to obtain a good granular dispersion structure with almost no blocking, it is necessary for the polyolefin resin to have a certain concentration or more of carbonyl groups. There was found. Furthermore, when the carbonyl group concentration of the polyolefin resin becomes extremely high, it tends to form a homogeneous phase with the polyamide resin, and foaming due to the decomposition of the resin increases during film formation, resulting in a decrease in film formability (No. 4- 9). In evaluating the performance of these adhesives, we used a primer with a weight ratio of epoxy resin and phenol formaldehyde resin of 80:20, a phenol formaldehyde resin made from p-cresol, and a plate material different from the method described above. 0.35 thick phosphoric acid chromate treated aluminum plate (5082
A coated board was prepared using the material) and tested. The evaluation results are listed in Table 4, and the difference in the dispersion structure of the polyolefin resin phase is directly reflected in the adhesiveness, and when the degree of blocking of the polyolefin resin is large, the cohesive force of the adhesive film decreases, resulting in high adhesive strength. As for the opening properties of the lid, initial opening becomes difficult due to a decrease in peel strength, and tabs tend to shift in position and come off frequently. On the other hand, when the carbonyl group concentration of the polyolefin resin increases and a homogeneous phase is formed with the polyamide resin, the hot water resistance of the adhesive tends to decrease.

【table】

[Table] ** Polyolefin phase partially blocked *** Phase structure partially unclear Example 5 Nylon 610 and ethylene vinyl acetate copolymer (copolymerization ratio 95/5, MI = 21) 85:
A film consisting of 15 blend compositions and produced in the same manner as in the previous examples was used. This adhesive film had a typical polyolefin granular dispersion structure. As primers, primers were used in which the weight ratios of epoxy resin and phenol formaldehyde resin were varied as shown in Table 5. Here, a phenolaldehyde resin made from bisphenol A and p-cresol was used, and in Nos. 5-1 and 5-2, which had a low content of phenolaldehyde resin, phosphoric acid was used as a curing accelerator for the entire paint. 3 PHR was added to the solid content. Using these paints, predetermined coated plates for adhesion testing and coated plates for lids were obtained, and then tests were conducted. As shown in the evaluation results in Table 5, it can be seen that the content of epoxy and phenol in the primer has a significant effect on adhesiveness. In other words, if the epoxy content is high, even if high strength is achieved at the initial stage of adhesion or after heat treatment, the adhesion between the primer and the metal material surface will be significantly reduced when placed in a retort or hot water. Even when this was used as an adhesive structure for a lid, the openings often became defective due to the decrease in adhesion during heat sterilization. On the other hand, as the phenol ratio in the primer increases, that is, the content of phenolaldehyde resin, it becomes difficult to obtain high adhesive strength.
The ability to open the lid was significantly reduced.

【table】 [Brief explanation of drawings]

FIG. 1 is an enlarged view of the adhesion fulcrum between the can lid and the opening tab in an easy-to-open can lid for a rolled-up can as the metal adhesive structure of the present invention, and FIG. FIG. 3 is a diagram showing a cross-sectional view of the agent layer;
The figure shows the adhesive fulcrum when using typical adhesives.
FIG. 4 is a graph plotting the relationship between the peeling force in the 90-degree direction and the amount of displacement; FIG. The figure is a sectional view taken along line A-A' of the can lid in FIG. 4.

Claims (1)

[Scope of Claims] 1. A metal adhesive structure formed by bonding primer-coated metal materials to each other with a polyamide adhesive, wherein the adhesive has (A) an average number of carbon atoms in the main chain per amide group of 6.1 to 6.1. (B) a carboxylic acid, carboxylic anhydride, carboxylic acid salt, carboxylic acid amide bonded to the polymer chain;
and an olefin copolymer containing at least one group selected from the group consisting of carboxylic acid esters as a =CO group at a concentration of 10 to 400 mmol/100 g of polymer, A:B = 94:6 to 65. :35 and in which polyamide (A) exists as a continuous phase and olefin copolymer (B) as a dispersed particle phase, and the primer mixes epoxy resin and phenolic resin in a ratio of 95:5 to 95:5. A metal adhesive structure characterized by being a curable coating film containing a 30:70 weight ratio.