JPH0742450B2 - Adhesives and bonded structures for metals - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an adhesive for metals and a metal adhesive structure using the same, and more specifically, to an improved adhesive strength under high dry conditions. And an adhesive for metals. The present invention also relates to an adhesive adhesive structure having excellent adhesive strength under various environmental conditions, particularly a metal adhesive structure useful for an easy open can lid.

(Prior Art) It has been conventionally known that polyamides are excellent thermal adhesives for metal materials. For example, as an adhesive for metals such as cans, crystalline nylon (Japanese Patent Publication No. 45-32359), copolymer nylon (Japanese Patent Publication No. 49-16790), crystalline nylon and non-crystalline or low crystalline nylon. Blended with (Japanese Patent Publication No. 48-18096 and Japanese Patent Publication No. 50-37690)
Etc. are known. Further, Japanese Examined Patent Publication No. 52-26897 describes an adhesive for metals, which is a single or a mixture of two or more crystalline polyamides and an ionomer.

On the other hand, as an easily openable lid used for storing beverages such as cola, beer, juice, etc., an easy opening (easy open) lid is provided with an opening part defined by a score (partial cut line), and this opening part is It is widely used that a rivet is formed, a pull tab is fixed by the rivet, and the tab is pulled so that the score is broken and the opening portion is removed.

However, with this easy-open lid, the inner coating film of the can lid is easily damaged by severe processing such as rivet processing,
Satisfactory results in terms of corrosion resistance cannot be obtained at all in applications such as edible filling in which corrosive contents are filled and severe treatment such as heat sterilization is performed. This tendency is particularly remarkable in the openable can lid using aluminum.
Further, contents having a high salt concentration cause pitting corrosion, and there is a problem of leakage of the contents from the through holes and contamination due to sterilization.

As a solution to this problem, Japanese Patent Application Laid-Open No. 61-60447 proposes that an opening tab is bonded and fixed to the opening portion of the can lid defined by the score with a polyamide adhesive.

(Problems to be Solved by the Invention) In this type of easily-openable lid, by lifting the grasping portion of the opening piece upward, the adhesive portion serves as a fulcrum and the tip of the opening piece (tab) is pushed into the score. Shedding of the score initiates shearing of the score, and then pulling of the tab causes shearing of the entire score, but in this case, the force necessary for tearing the score acts on the adhesive as a moment, and The problem is that breakage easily occurs.

Also, the method of opening the easy-open lid varies depending on the purchaser of the can.For example, when pulling the tab without lifting the tab until it comes to a position almost perpendicular to the can lid, A relatively large moment acts on the adhesive fulcrum between the lid and the lid, and the adhesive fulcrum is easily broken. If the tab is not pulled properly in the direction of the tab, a moment still acts on the adhesive fulcrum, and the adhesive fulcrum is likely to break.

The polyamide-based adhesive has a large hydrogen bond between molecular chains, and has a cohesive breaking force particularly large among the divided polymers, and also for a protective coating film or the like applied for the purpose of protecting the metal material for the lid. Adhesion is also large, and therefore, even when the above-mentioned easy-open lid is opened, there is almost no possibility that the polyamide adhesive layer at the adhesion fulcrum or the joint between the adhesive layer and the coating film is destroyed, Instead, it is often observed that peeling or breakage occurs at the adhesion interface between the coating and the metal material. The cause is that the peeling force between the metal and the coating film is quite large,
Since almost no deformation (elongation) occurs between the two, it is presumed that stress concentration occurs in this portion, leading to fracture.

It has been observed that this metal-coating failure occurs significantly when the bonded structure is placed under very dry conditions, especially in the winter months. This is because polyamides are hygroscopic, and the elastic modulus changes considerably depending on the amount of moisture absorption,
It is considered that this is due to the fact that the elastic modulus of the polyamide adhesive layer becomes extremely high in the dried state where the moisture absorption amount is extremely small.

Accordingly, an object of the present invention is to provide a polyamide-based metal adhesive for which the adhesive strength under highly dry conditions is remarkably improved.

Another object of the present invention is to provide an adhesive for polyamide metal, which has excellent adhesive strength under high dry conditions and also maintains excellent adhesive force even under sterilization conditions in which heat and moisture simultaneously act. To provide.

Still another object of the present invention is to provide a metal-bonded structure which has excellent adhesive strength under various environmental conditions and is useful as an easy-open lid (easy-open lid).

(Means for Solving Problems) According to the present invention, (i) the average carbon number per amide group is 6.
1 to 15 crystalline polyamide, (ii) low crystalline to amorphous copolyamide having an average carbon number of 6.0 to 15 per amide group, and (iii) carboxylic acid bound to polymer chain, carboxylic acid At least one group of salt, carboxylic acid anhydride, carboxylic acid amide or carboxylic acid ester As an essential component, an olefin copolymer containing 10 to 400 mmol / 100 g of polymer is contained, and component (i) and component (ii) are contained in a weight ratio of 97: 3 to 65:35. An adhesive for metals is provided, which contains the total amount of components (i) and (ii) and component (iii) in a weight ratio of 94: 6 to 65:35.

According to the present invention, there is also provided a metal structure formed by joining primer-coated metal materials to each other with the above polyamide-based metal adhesive.

(Function) The metal adhesive of the present invention comprises (i) a crystalline amide having an average carbon number per amide group of 6.1 to 15, particularly 7.0 to 14.0,
(Ii) Average carbon number per amide group is 6.0 to 15, especially 7.0
To 12 low crystalline to amorphous copolyamides, and (ii
i) at least one of carboxylic acid, carboxylic acid salt, carboxylic acid anhydride, carboxylic acid amide or carboxylic acid ester
Seed group As 10 to 400 mmol / 100 g polymer, especially 20 to 300
It is a remarkable feature that it contains three components of the olefin copolymer contained at a concentration of mmol / 100 g polymer.

Generally, components (i) and (ii) are compatible and are present in the form of a continuous phase, and component (iii) is present in the form of a dispersed particle phase dispersed in this continuous phase.

The component (i) is a component that constitutes the main component of the adhesive, and has high strength, high impact resistance, heat resistance, and dimensional stability required for the adhesive.
In order to satisfy the requirements such as water resistance, high crystallinity is required. For component (i) (similarly for component (ii)), it is important that the average number of carbon atoms per amide group is within the above range. If the number of carbon atoms exceeds the above range, the heat resistance of the adhesive will be low. The property is lower than that in the above range, and the cohesive force of the adhesive tends to be smaller than that in the above range. On the other hand, when the number of carbon atoms is smaller than the above range, the heat resistance of the adhesive becomes lower than that in the above range, and the elastic modulus becomes too high under high dry conditions, resulting in stress concentration on the adhesive surface. Is likely to occur,
This leads to a significant decrease in adhesive strength.

The component (ii) is a component for modifying the adhesive, prevents the component (i) from becoming highly elastic (stiffening) under high drying conditions, and promotes atomization and dispersion of the component (iii). Above all, it is important to be composed of a low crystalline to amorphous copolyamide. That is, in the present invention, the low crystalline or amorphous copolyamide is compatible with the crystalline polyamide to form the continuous phase of the adhesive, and this continuous phase is more than that composed of the crystalline polyamide alone. And becomes soft or plasticized even under high dry conditions, and the component (iii), that is, It has a function of dispersing the contained olefin copolymer in the form of a finer disperse phase, that is, a disperse phase having a larger interfacial area, as compared with the case where the continuous phase consists of the crystalline polyamide alone.

The component (iii) is also a component for modifying the adhesive, but this olefin copolymer is incompatible with polyamides and exists in the form of dispersed particles. It is important for the olefin copolymer to have the above-mentioned functional groups from the viewpoint of the adhesiveness and dispersibility at the interface with the polyamide continuous phase, and moreover, the carbonyl group based on these functional groups. Is also important in the concentration within the above range. That is, when the functional group concentration is lower than the above range, it becomes difficult to atomize and disperse the component (iii) in the polyamide, and the adhesiveness with the polyamide continuous phase also decreases, so that the adhesive coalesce The cohesive force is reduced and the adhesive strength is reduced. On the other hand, when the functional group concentration exceeds the above range,
The heat resistance of the component (iii) is lowered, and troubles due to decomposition, foaming, etc. are likely to occur during production of the adhesive blend.

In the adhesive composition of the present invention, the components (i) and (ii)
It is also important that and are present in a weight ratio of 97: 3 to 65:35, especially 91: 9 to 80:20. That is, when the amount of the low-crystalline or amorphous copolyamide (ii) is less than the above range, the above-mentioned action of the component (ii) is not sufficiently exerted, and the adhesive strength under the high dry condition is lowered. become. On the other hand, if this amount exceeds the above range, the cohesive force of the adhesive itself is lowered, and the heat resistance and hot water resistance are also lowered.

Further, in this composition, the total amount of components (i) and (ii) and component (iii) is 94: 6 to 65:35, especially 91: 9 to 80:20.
It is also important to be present in a weight ratio of When the amount of the component (iii) is less than the above range, the interfacial area of the dispersed particle phase of the component (iii) becomes insufficient, resulting in a decrease in adhesive strength under high dry conditions. On the other hand, when the amount is larger than the above range, a stable dispersed particle phase is not formed and the cohesive force of the adhesive itself is reduced.

As described above, according to the present invention, in the adhesive, the continuous phase polyamide is a low crystalline or amorphous polyamide and is softened even under high drying conditions, and the dispersion phase of the olefin copolymer phase is In a large state, they are atomized and dispersed, and the interface between these two phases becomes a peeling interface when a large peeling force acts on the adhesive layer under high dry conditions, and the stress is dispersed in the adhesive layer. , It is possible to avoid stress concentration only at the adhesive interface. Thus, the improvement of the adhesive strength under the high dry condition in the adhesive of the present invention can be explained.

In the adhesive composition of the present invention, the component (iii) is generally present in a dispersed particle phase having an average particle minor axis of 0.05 to 5 μm, particularly 0.1 to 3 μm.

(Preferred Embodiment of the Invention) Adhesive (i) Crystalline Polyamide In the present invention, the average number of main chain carbon atoms per amide group is
The first condition is to use a crystalline polyamide in the range of 6.1 to 15.0, particularly 7.0 to 14.0. This polyamide is a homopolyamide having ω-aminocarboxylic acid and / or diamine-dicarboxylic acid salt as a starting monomer component, or a copolyamide within a range that does not substantially impair the crystallinity of the homopolyamide. Is. The crystallinity is not substantially impaired, and this copolyamide has a crystal fusion heat of homopolyamide having a main amide repeating unit in common with this copolyamide.
It has a crystal fusion heat amount of 80% or more, particularly 90% or more.

Examples of suitable polyamides are shown in Table A below.

The crystalline polyamide used in the present invention preferably has a heat of fusion measured by a differential scanning calorimeter in the range of 8 to 18 cal / g, particularly 9 to 16 cal / g.

The polyamide used in the present invention has a relative viscosity (ηrel) measured at 20 ° C. at a concentration of 1 gram in 100 cc of 98% sulfuric acid is 1.8.
It is preferably in the range of 3.5 to 3.5. Polyamides having a specific viscosity smaller than the above range have poor mechanical properties and insufficient joint strength. A polyamide having a specific viscosity higher than the range of the present invention is not preferable because the melt viscosity of the adhesive becomes too high at the time of melt bonding, and the bonding is required at a temperature considerably higher than the melting point.

(Ii) Low crystalline to amorphous copolyamide The low crystalline to amorphous copolyamide used also has amide group 1
Average main chain carbon number per piece is 6.0 to 15.0, especially 7.0 to 1
It is in the 4.0 range. This copolyamide may be composed of a plurality of amide repeating units described in Table A above, and at least one amide repeating unit described in Table A within a range satisfying the above-mentioned restrictions. Other amide repeating units other than ω-, such as nylon 4, nylon 6
Aminocarboxylic acid units and; nylon 4,6, nylon 6,6,
It may consist of dimer acid and at least one other diamine / dicarboxylic acid amide unit such as an amide repeating unit of diamine.

The crystallinity of the copolyamide depends on the type and number of amide repeat units incorporated into the polyamide and their amount.
In the copolyamide of the present invention, the amount of one polyamide repeating unit is 15% by weight or more, particularly 20% by weight, and the amount of the other amide repeating unit is also 15% by weight or more and particularly preferably 20% by weight or more, Further, the number of amide repeating units contained in the copolyamide is preferably 3 or more. Also,
One of the amide repeating units in the copolyamide is preferably an amide repeating unit common to the crystalline polyamide (i) from the viewpoint of compatibility.

The degree of crystallinity of the copolyamide is indicated by the heat of crystal fusion measured by the differential scanning calorimeter described above. The copolyamide used in the adhesive of the present invention has a heat of fusion of crystalline polyamide.
It has a heat of fusion of 60% or less, especially 50% or less.

The relative viscosity of this copolyamide should be in the same range as that of the crystalline polyamide.

(Iii) Olefin Copolymer The olefin copolymer used in the present invention contains a carboxylic acid, carboxylic acid anhydride, carboxylic acid salt, carboxylic acid amide or carboxylic acid ester group bonded to the polymer chain. . Such an olefin copolymer can be obtained by copolymerizing an ethylenically unsaturated monomer containing the above group with an olefin, or by modifying the polyolefin with a means such as graft polymerization or block copolymerization. To be

Suitable examples of the above-mentioned ethylenically unsaturated monomer containing a carboxylic acid derivative group are as follows.

i) Carboxylic acid or carboxylic acid anhydride Acrylic acid, methacrylic acid, fumaric acid, maleic anhydride, itaconic anhydride, crotonic acid, tetrahydrophthalic anhydride.

ii) Carboxylic acid amides acrylamide, methacrylamide, maleimide.

iii) Carboxylic acid esters Vinyl acetates such as vinyl acetate and vinyl propionate, ethyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, 3-hydroxypropyl (meth) acrylate, N-ethylaminoethyl (meth) (Meth) acrylates such as acrylates.

Suitable examples of olefin copolymers are:

Ethylene-based random copolymers such as ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer.

Ion cross-linking olefin copolymers such as ethylene or propylene with acrylic acid or methacrylic acid, if necessary, with these ester monomers, and alkali metal ions such as sodium and potassium, alkaline earth metals such as magnesium. A copolymer obtained by ionically crosslinking with ions, zinc ions, organic cations, and the like.

Main polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-butene-1 copolymer and ethylene-vinyl acetate copolymer are added to maleic anhydride, acrylic acid, methacrylic acid, (meth) acrylate, (meth) ) A copolymer obtained by grafting acrylamide or the like.

Of course, these copolymers are based on groups of carboxylic acids or their derivatives. At the above-mentioned concentration, that is, 10 to 400 per 100 grams of copolymer.
Should be included at a millimolar concentration. In the present invention,
Of course, the above copolymer may have the above concentration as a whole, for example, It may be a blend of two or more olefin copolymers having different concentrations or a blend of an unmodified olefin polymer and a modified olefin copolymer.

The olefin copolymer used should have a molecular weight sufficient to form a film and has a melting point of 40 to 20.
It is advantageous for the dispersion structure of the present invention that the melt flow rate (MI) is in the range of 0 ° C., particularly 60 to 180 ° C., and the melt flow rate (MI) is in the range of 0.5 to 300, particularly 0.7 to 150.

(Iv) Blend The above three components are melt-kneaded to form a blend. The degree of kneading varies depending on the melting point of the resin and the concentration of the functional group and cannot be specified unconditionally, but it is generally desirable to dry-blend the above components and then knead using a metering screw to form a film. In an extruder or a twin-screw extruder using a dullage type screw, it is preferable to shorten the kneading time to prevent the mutual reaction of both resins.

This adhesive includes an antioxidant, a heat stabilizer, an ultraviolet absorber, a viscosity modifier, a plasticizer, a core material, inorganic fine particles, a filler,
20% by weight of the total resin composition unless the adhesive properties of organic lubricants, pigments, synthetic rubber latex particles, etc. are significantly impaired.
It can be added as an additive within the range not exceeding.

Adhesive Structure The adhesive structure of the present invention is particularly useful as an easily-openable can lid.

In FIG. 1 showing an enlarged cross-sectional structure of the adhesive structure of the present invention, this adhesive structure is an enlarged view of the above-mentioned adhesive fulcrum between the can lid and the opening tab, and the outside of the can is turned up, The inside of the can is shown as the bottom.

An adhesive primer layer 2 is provided on the outer surface of the metal can lid 1, and a protective coating film 3 is provided on the inner surface thereof, while the adhesive primer layer 5 is also provided on the inner surface side of the metal opening tab 4, and the outer surface is also provided. Is provided with a protective coating film 6. The can lid 1 and the opening tab 4 are joined by the above-mentioned adhesive layer 7 via the adhesive primer layers 2 and 5 provided on their surfaces.

As shown in FIGS. 2 and 3, this lid member 1 is provided with a circumferential groove portion 8 on the outer periphery and a panel portion 10 connected to the groove portion through an annular rim portion 9, and the groove portion 8 has a can body. A sealing compound layer 11 is provided which is sealingly engaged with a flange (not shown) for double winding. Inside the annular rim 9 there is a portion 13 to be opened which is delimited by a score 12. The opening portion 13 may substantially coincide with most of the panel portion 10, or a part of the panel portion 10 may be the opening portion. As shown in the enlarged cross-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 at the time of opening by the mechanism described in detail below.

The opening tab 4 is provided on the opening portion 13 by a specific mechanism described below. The unsealing tab 4 has a score tearing tip 14 at one end, a grip portion (ring) 15 at the other end, and a fulcrum portion 16 located between them and joined to the lid. In this embodiment, the fulcrum portion 16 has a tab between the tip 14 and the ring 15 and a notch 17 that is substantially U-shaped in shape.
Is formed so that a connecting portion 18 is present between the fulcrum portion 16 and the tip 14 and has a tongue shape. The tearing tip 14 of the unsealing tab 4 has a tongue-shaped fulcrum portion 16 and the opening portion 13 of the lid body and the above-mentioned polyamide adhesive so that the position of the tearing tip 14 substantially coincides with the score 12 of the lid pair. Thermal bonding is performed via the agent layer 7.

In this can lid, 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 cleaving tip 14 via the fulcrum portion 16, and the score is scored.
At the same time that a downward crushing force is applied to 12, a peeling force (moment) acts on the adhesive layer 7 between the fulcrum portion 16 and the opening portion 13. According to the present invention, by using the above-mentioned specific blend adhesive as the adhesive layer 7, it is possible to endure the above-mentioned peeling force under any environmental condition. Then, by pulling the opening tab 4 at an angle of about 90 degrees with respect to the lid 1, a score is obtained.
12 is sheared from the scored position.

Examples of the metal material for the lid include light metal plates such as aluminum and various surface-treated steel plates, such as zinc and tin on the surface of steel plates.
An arbitrary metal material is used which is plated with chromium, aluminum or the like or has a chemical conversion treatment film such as chromic acid or phosphoric acid formed on the surface thereof, and which has pressure deformation and rigidity enough to withstand winding. . Material thickness is generally 0.10 to 0.
It is desirable that it is in the range of 40 mm, particularly 0.12 to 0.35 mm. The opening tab is made of the above-mentioned various metal materials, especially aluminum.

This lid material is a metal material that is difficult to rivet, for example, chromate surface-treated steel sheet, particularly electrolytic chromic acid-treated steel sheet, chromate-treated nickel-plated steel sheet, chromate-treated iron,
Suitable for tin alloy plated steel sheet, chromate treated tin / nickel alloy plated steel sheet, chromate treated iron / tin / nickel alloy plated steel sheet, chromate treated aluminum plated steel sheet.

Electrolytic chromic acid treated steel sheet consists of a layer of metallic chrome on a cold rolled sheet steel substrate and a layer of non-metallic chrome thereon. The thickness of the metal chromium layer is determined by the balance between corrosion resistance and workability, and the amount thereof is preferably in the range of 30 to 300 mg / m ² , particularly 50 to 250 mg / m ² . The thickness of the non-metallic chrome layer is related to coating film adhesion and peel strength,
4 to 40 mg / m ² , especially 7 to 30 m
It is desirable to be in the range of g / m ² .

The primer coating film used in the present invention is used for the purpose of promoting adhesion and protecting the underlying metal, and is of any kind as long as it exhibits excellent adhesion and adhesiveness to the above-mentioned adhesive and underlying metal. It doesn't matter. However, it is generally preferred to contain the phenolic resin and the epoxy resin in a weight ratio of 95: 5 to 30:70. As a phenolic resin,
A resol type phenol aldehyde resin obtained by condensing various phenols and formaldehyde in the presence of a basic catalyst is used. As phenols, trifunctional phenols represented by carboxylic acid,
Bifunctional phenols typified by p-cresol,
Polynuclear phenols typified by bisphenol A are used alone or in combination of two or more, and a phenol resin particularly suitable for the purpose of the present invention is represented by the following formula IF = 2M ₂ + 3M ₃ + 4M _{4 2} is the number of moles of the bifunctional monohydric phenol in 100 g of the total phenol component contained in the phenol aldehyde resin, M ₃ is the number of moles of the functional monohydric phenol in 100 g of the total phenol component, M ₄ is the total phenol The number of moles of polycyclic dihydric phenol in 100 g of each component is 1.5 to 2.5, especially 1.6.
The range is from 2.8 to 2.8. The average number of methylol groups per phenol nucleus is 0.05 to 0.40,
In particular, it is desirable that the number average molecular weight is in the range of 0.07 to 0.30 and the number average molecular weight thereof is generally in the range of 200 to 800, especially 230 to 600.

The epoxy resin has an epoxy equivalent of 600 to 600 obtained by condensation of bisphenol A and epihalohydrin.
Epoxy resins in the range 0, especially in the range 900 to 4000 are preferably used.

Epoxy resin and phenol resin are used in the coating of metal materials in the form of a mixture or in the form of pre-condensation, and after being applied to the metal material, it is baked under the baking conditions of 140 to 280 ° C for 1 to 20 minutes. Good for post-bonding.

The thickness of the primer coating film is not particularly limited as long as the above-mentioned object is achieved, but generally speaking, it is 0.2 to 30 μm.
m, particularly preferably in the range of 1 to 20 μm.

At the time of manufacturing the easily-openable adhesive can lid, first, on at least one surface of the metal material described above, a primer coating solution in an organic solvent,
It is applied in the form of an aqueous dispersion or an aqueous solution by means of spray coating, roller coating, dip coating, electrostatic coating, electrophoretic coating, etc., and the coating film is formed by drying or baking. In this case, it is also possible to laminate a thermoplastic resin film on the surface side different from the side on which the adhesion fulcrum is formed with an adhesive if necessary.

This coated or coated laminated plate is punched into a predetermined can lid size and press-molded to form a can lid having a predetermined shape, and at the same time or in another step, score processing is performed. Score processing, the residual thickness in the score part is 1/8 to 1/2 of the bare plate thickness and the absolute thickness is 0.2 to 0.9 mm, especially
It is desirable that the range is 0.3 to 0.8 mm.

Prior to or after this score processing, the circumferential groove of the can lid is coated with a sealing compound composition from a synthetic rubber latex such as styrene-butadiene rubber latex, a tackifier and a filler, and dried. It will be the compound layer.

A layer of the blend-based adhesive described above is provided on the fulcrum portion of the separately manufactured opening tab, or a layer of the blend-based adhesive is provided on the portion of the can lid where the opening tab is to be provided. Of course, both of these can be done. The adhesive layer can be formed by any method such as applying the adhesive in the form of powder, melt, suspension or solution, in addition to applying the adhesive film cut into a predetermined size. it can. The thickness of the adhesive resin is 3 to 150 μm, especially 10 to 100 μm
It is suitable to be in the range.

Then, the opening tab is positioned on the can lid, and the thermoplastic resin located between the fulcrum portion of the tab and the can lid is melted,
It is then allowed to cool and solidify to complete both bonds. Prior to this, there is a case where a rubber-based resin or a resin such as plastisol is lined in the vicinity of the score portion in order to prevent injury or the like when the lid is opened.

In the case of edible canned food, it is desirable that the score is provided in the so-called full-open form near the annular rim, as shown in the attached drawing, but if desired, a part of the can lid may be used. In addition, it can be provided as an arbitrary shape such as a raindrop type or a semicircular type. Further, in order to repair damage to the covering material during score processing 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 of the above-mentioned easy-open lid, but this advantage is that other adhesive applications, for example, force of a complicated directional component such as peeling force with respect to an adhesive surface, It should be understood that the same effect can be obtained when used for joining between additional metal materials.

(Effect of the Invention) According to the present invention, three components of a highly crystalline polyamide, a low crystalline or amorphous copolyamide, and an olefin copolymer are blended in a specific amount ratio to form an adhesive composition. , In the adhesive, the continuous phase polyamide is a low crystalline or amorphous polyamide and is softened even under high dry conditions,
Moreover, the olefin copolymer phase, which is the dispersed phase, is finely dispersed in a state of a large surface area, and the interface between these two phases is a releasable interface when a large peeling force acts on the adhesive layer under high dry conditions. Thus, it was possible to prevent the stress from being dispersed in the adhesive layer and causing stress concentration only at the adhesive interface.

Therefore, using the adhesive of the present invention, it is possible to significantly improve the adhesive strength under high dry conditions, and also excellent under sterilization conditions in which heat and water act simultaneously by the selection and combination of each component. It was possible to provide an adhesive for metals that exhibits excellent adhesive strength even under various environmental conditions, such as good adhesive strength.

The following examples specifically explain the effects of the present invention. In each of the examples, the following basic characteristics (I) regarding the adhesiveness and the adhesiveness (II) with the lid as the application example are shown for the metal adhesive structure composed of the material for each test No. evaluated.

I. Adhesiveness test Epoxy / phenolic paint (with epoxy resin) on both sides of a normal TEIN FREE steel (TFS) plate with a plate thickness of 0.22 mm, surface non-metallic chromium amount of 15 mg / m ² and metallic chromium amount of 100 mg / m ^2. The weight ratio, composition, etc. of the phenolic resin are slightly different in each example as described later) so that the thickness after baking becomes 5 μm, and baking is performed at 210 ° C. for 10 minutes. A test piece having a width of 5 mm and a length of 10 cm was cut out from this coated plate, and each adhesive film having a width of 7 mm was sandwiched between the two test pieces and bonded by using high frequency heating. The target of the adhesion temperature was the melting point of each adhesive plus 30 ° C on the entire adhesion surface. About a part of this adhesive piece, melting point of each adhesive is -20 ° C, oven for 4 minutes in order to investigate the effect of post-heating applied when baking and curing the paint when repairing damage to the score processing part with a lid etc. Heating, part 11
Hot water treatment equivalent to retort sterilization for 90 minutes at 6 ℃
It was aged for 1 week in water at 0 ° C.

As an evaluation of the adhesiveness, a T-peel test was carried out on each of the five test pieces after heating in the initial oven for adhesion, after retort and after aging in 90 ° C. hot water. For the T-peel test, an Instron type tensile tester was used and the pulling speed was 200 mm / min.
The measurement was carried out at room temperature, and the arithmetic mean value of the average values of the respective measurement values was taken as the result.

II. Lid Adhesion Test As a specific application example of the metal adhesive structure of the present invention, FIG.
The adhesive performance was tested on an adhesive structure, as shown in 5, in which an opening tab for shearing the can lid score is fixed to the can lid via an adhesive. The lid for this was made as follows. That is, the same epoxy-phenol used in the test I above was applied to both sides of a normal tin-free steel (TFS) plate having a plate thickness of 0.20 mm, a nonmetal chromium amount of 15 mg / m ^{2 on} the surface, and a metal chromium amount of 100 mg / m ^2. The system paint was applied so that the thickness after baking would be 5 μm, and baking was performed at 210 ° C. for 10 minutes. This coated TFS plate was molded into a 211 diameter lid using a press, and then a curling portion was coated with a sealing compound by a conventional method and dried. Next, the outer surface of the lid was scored into a circular shape having a diameter of 58 mm so that the score remaining thickness / steel plate thickness was 0.23. On the other hand, a 0.46 thick aluminum coil (# 508
2) Epoxy phenolic paint (weight ratio of epoxy resin and phenol aldehyde resin is 75: 2 on the adhesive side of the material)
In step 5, bisphenol A was used as the raw material of the phenol aldehyde resin), and the epoxyurea-based paint was coil-coated on the opposite side so that the thickness after baking was 5 μm, and then slit to a width of 30 mm. On the other hand, a micro slit film having a thickness of 45 to 50 μm and a width of 8 mm and having a composition shown in each of the following test Nos was laminated by high frequency induction heating, and then press-formed into a tab having a shape shown in FIGS. . The tabs created in this way were placed on the previously molded lid so that the distance from the score to the adhesive fulcrum was 6 mm, and also by high-frequency heating, at least 30 ° C above the melting point of each adhesive.
Heated high and glued. In this case, the width of the adhesive layer at the adhesive fulcrum portion was about 7 mm, and the area of the adhesive portion was about 40 mm ² .

Then, after applying the epoxy / phenolic paint to the inner and outer surface score portions of the lids after the tabs are adhered, the adhesives are subjected to oven baking for 4 minutes at a temperature of -20 ° C, and then the following 1, The peeling strength and lid opening property described in 2 were evaluated.

1. Peeling strength After the tabs were bonded under predetermined bonding conditions, they were baked in a predetermined oven and further subjected to retort sterilization equivalent to heat sterilization, and the peeling strength of this lid was measured by the following method. In other words, for the tab that was lifted up and the initial opening of the score part was performed and the tab was raised to the direction perpendicular to the lid panel surface, the tab ring should be perpendicular to the lid panel surface, and the adhesive part should be 90 ° peel. A tensile test was performed. For the tensile test, an Instron type tensile tester was used, and the tensile strength was 200 mm / min and the measurement was carried out at room temperature to evaluate the initial strength and the peeling work. For the peeling work, the area in the peeling strength curve on the chart is integrated by an automatic integrator, and then the adhesion area is 1 cm ^2.
It was calculated in terms of hits. Each sample No. was measured 5 times, and the arithmetic mean value thereof was used as the measured value.

2. Lid opening property The opening property of the lid is as follows immediately after bonding, after applying the correction paint to the inner and outer score parts of the lid and performing the predetermined oven baking,
Furthermore, after double-tightening this lid to the 211 diameter flange can body, filling dressing tuna as the contents and tightening the flat lid, and performing retort sterilization at 116 ° C for 90 minutes, immediately after the retort, the relative humidity ( RH) 60%, 37 ℃,
After 6 months (aging A), 10% RH, 37 ° C., and 6 months (aging B), 20 panelists were allowed to open 5 cans each, and a total of 100 cans were opened. As a result, the number of cans that could not be opened, such as the tab coming off during opening, and the number of cans that could not be opened initially in the brackets are shown.

Example 1 As an adhesive film, nylon 610 (concentrated sulfuric acid 1% relative viscosity 2.7) as a crystalline polyamide component and nylon 6 ・ 66 ・ 610 ・ 12 copolymer as a low crystalline polyamide component (
2.8), an ionomer resin as a polyolefin resin component (ethylene acrylic acid copolymer metal salt, A polymer having a composition blend ratio (wt%) shown in Table 1 was prepared using a concentration of 155 mmol / 100 g polymer, MI = 0.7). During film formation, resin chips of all components were dry-blended in advance, and each was kneaded into a film by an extruder equipped with a metering screw.

The dispersed structure of these film cross sections was observed with a transmission electron microscope by the ultrathin section method. Here, a phosphotungstic acid dyeing method was also used in order to capture a clearer dispersed structure. In the dispersion structure shown in the table below, OinA is a structure in which a polyolefin particulate phase is dispersed in a nylon resin continuous phase, A is a homogeneous structure in which almost no dispersion structure is recognized, and OandA is a polyolefin phase and a nylon resin phase. This indicates that the structure is continuous and the presence of the polyolefin granular phase is unclear.

In evaluating the performance of these adhesives, a weight ratio of epoxy resin to phenol formaldehyde resin of 85:15 was used as the primer, and bisphenol A and p-cresol were used as the phenol formaldehyde resin as raw materials. The test was carried out after obtaining a coated plate for adhesion test and a coated plate for lid.

The evaluation results are summarized in Table 1. According to this,
When the polyamide component is composed only of crystalline polyamide resin (No. 1-1, 2), the dispersion of the polyolefin resin phase is poor, the particle size distribution is wide, and there are many particles with a size of 3μ or more, and the adhesiveness is also high. Reflecting this, there is a large variation in strength, showing a tendency to decrease as an average value, and with respect to the adhesiveness of the lid, it may be impossible to open because of the openability, especially when stored in a dry atmosphere. did. On the other hand, when the ratio of the low crystalline polyamide resin component to the polyamide component is a certain level or more, the adhesive strength, particularly the heat resistance, the tendency of a decrease in hot water resistance becomes remarkable, and the performance of the crystalline polyamide resin as the main component is improved. It will be damaged and the opening of the lid will be difficult.

Example 2 Nylon 610 as a crystalline polyamide resin component of an adhesive
(Concentrated sulfur flow 1%, relative viscosity 2.7), Nylon 6.66.610 copolymer (2.9) as a low crystalline polyamide component was fixed so that the ratio of both was about 85:15, and a polyolefin resin Films having different ionomer resin contents (the same as those used in Example 1) as components were prepared with the compositions and blending ratios shown in Table 2.

The dispersion structure has a low ionomer resin content (No. 2
-1,2) The powdery dispersion structure was unclear and showed a homogeneous structure, while when the content was high (No. 2-8), the polyolefin phase also tended to be structurally phased.

In evaluating the performance of these adhesives, a weight ratio of epoxy resin to phenol formaldehyde resin of 80:20 was used as a primer, and bisphenol A and m-cresol were used as raw materials of phenol formaldehyde resin. Was done.

The evaluation results are shown in Table 2. When the content of the ionomer resin is low, the adhesive failure tends to be the cohesive failure of the primer coating film or the metal material interface, and the adhesiveness tends to decrease. In addition, even in the lid adhesive, breakage easily occurs between the tab metal material and the primer, and some of the lid adhesive cannot be opened. This tendency was particularly remarkable when the cans were stored under dry conditions in the can test.

On the other hand, if the content of the ionomer resin becomes high, the polyolefin resin phase will also take a continuous phase dispersed structure, the original adhesiveness of the polyamide resin will be weakened, and the initial adhesive strength and especially the adhesive strength after heating in an oven will decrease. The adhesive property deteriorated due to the decrease in heat resistance or hot water resistance of the adhesive itself, and thus the opening property of the lid was significantly impaired.

Example 3 Among the adhesive compositions, those having different average main chain carbon number per unit amide group of the crystalline polyamide resin component and the low crystalline to amorphous polyamide resin component, the maleic anhydride-modified polyfluoropyrene of the polyolefin component was used. The concentration of 230 mmol / 100 g polymer, MI = 3.5), and their blend ratio were fixed at 80:10:10, and the relationship between the average number of main chain carbon atoms per amide group and the adhesiveness was examined.
The adhesive film was formed by using the component chips shown in Table 3 and in the same manner as in Example 1.

In each case, the dispersed structure was a structure in which the granular phase of the polyolefin resin was dispersed in the continuous phase of the polyamide resin.

In evaluating the performance of these adhesives, a weight ratio of epoxy resin and phenol formaldehyde resin of 75:25 was used as a primer, and bisphenol A and o-cresol were used as phenol formaldehyde resins as raw materials. Was prepared and tested.

The evaluation results are shown in Table 3. When nylon 6 having an average main chain carbon number of 6 per unit amide group is used, only low adhesive strength is obtained, and interfacial peeling between the primer plate and the primer plate is predominant. In many cases, the opening of the lid could not be opened due to the detachment of the tab in the sheared portion of the score even if the initial opening was made to some extent (No. 3-1). In addition, even when the nylon 6 and nylon 66 are copolymerized, the adhesiveness is slightly improved, but the effect of the improvement is not recognized, and the adhesiveness between the primer and the plate tends to decrease due to oven heating or retort treatment. And the opening of the lid is insufficient (No. 3-2).

On the other hand, the average main chain carbon number per unit amide group is 16.5 with 15 or more.
When using a blend of nylon 12 and dimer acid-based polyamide as a component, the heat resistance of the adhesive itself is insufficient and the hot water resistance is insufficient, so that the decrease in adhesiveness due to oven heating or retort treatment is significant, Further, due to the decrease in the cohesive force of the adhesive itself, it was not possible to obtain a sufficiently high initial strength in peeling strength, so that there was a tendency that initial opening at the time of opening became extremely difficult (No. 3). -8).

Example 4 Nylon 12 as a crystalline polyamide resin component and nylon 6 as a low crystalline polyamide resin component in the adhesive composition
・ 66 ・ 12 copolymer is used, and various kinds of polyolefin resin components with different carbonyl group concentrations are used.
The relationship between the carbonyl group concentration of the polyolefin resin and the dispersion structure and the relationship between it and the adhesiveness were investigated. No4
In -2-4-4, 4-1 is the one in which the graft ratio by the maleic anhydride is changed for the raw resin, No4-5-4
In No. 9, a metal salt resin of ethylene-methacryl terpolymer having a changed copolymerization ratio was used as a polyolefin resin component. In addition, in No4-1 to 4-4, MI = 30 to 80, N
For o4-5 to 4-9, those with MI = 0.7 to 2.5 were used. An adhesive film was obtained from these resins by a method similar to Example 1 with a blend ratio of 75:10:15.

No. 4-9 showed a structure in which the polyolefin resin phase was dispersed in the polyamide resin phase, except that the homogeneous structure was predominant. However, when low density polyethylene with a carbonyl group concentration of almost zero was used ( In No. 4-1), it was found that the polyolefin resin had to have a certain concentration or more of carbonyl groups in order to obtain a good granular dispersion structure with almost no blocking of the polyolefin phase and almost no blocking. Further, when the carbonyl group concentration of the polyolefin resin becomes extremely high, it tends to form a homogeneous phase with the polyamide resin, and the foaming due to the decomposition of the resin during film formation increases, resulting in a decrease in film formability (No4-9). .

In evaluating the performance of these adhesives, the weight ratio of epoxy resin and phenol formaldehyde resin was 80:20 as a primer, and p was the phenol formaldehyde resin.
-Using cresol as a raw material, and using a phosphoric acid chromic acid-treated aluminum plate (5082 material) having a plate thickness of 0.35 as the plate material, a coated plate was prepared and tested.

The evaluation results are shown in Table 4, and the difference in the dispersion structure of the polyolefin resin phase is reflected in the adhesiveness as it is, and when the degree of blocking of the polyolefin resin is large, the cohesive force of the adhesive film is lowered, so that high adhesive strength is obtained. With respect to the opening property of the lid, the initial opening becomes difficult because the peeling strength is lowered, and the displacement of the tab and the tab removal tend to occur frequently. On the other hand, when the carbonyl group concentration of the polyolefin resin becomes high and a uniform phase with the polyamide resin is formed, the hot water resistance of adhesion tends to decrease.

[Brief description of drawings]

FIG. 1 is an enlarged view of an adhesion fulcrum between a can lid and an opening tab in an easily openable can lid for a winding can as a metal adhesion structure of the present invention, and FIG. 2 is a metal adhesion of the present invention. FIG. 3 is a top view of an easily openable can lid that is an example of a structure, and FIG. 3 is a cross-sectional view of the can lid of FIG. 2 taken along the line AA ′.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display area C08L 23:08) (C08L 77/00 23:26)

Claims (6)

[Claims] 1. A crystalline polyamide having (i) an average carbon number of 6.1 to 15 per amide group, and (ii) a low crystalline or amorphous copolyamide having an average carbon number of 6.0 to 15 per amide group. And (iii) at least one group of carboxylic acid, carboxylic acid salt, carboxylic acid anhydride, carboxylic acid amide or carboxylic acid ester bonded to the polymer chain An olefin copolymer containing 10 to 400 millimoles / 100 g of polymer as a base, is contained as an essential component, and component (i) and component (ii) are contained.
And a total amount of component (i) and component (ii) and component (iii) at a weight ratio of 94: 6 to 65:35. Adhesive for metal. 2. The adhesive according to claim 1, wherein (i) and component (ii) are in a continuous phase and component (iii) is in a dispersed particle phase. 3. The component (iii) has an average particle minor axis of 0.05 to 5 μm.
The adhesive according to claim 2, which is present as a dispersed particle phase of m. 4. The adhesive according to claim 1, wherein the low crystalline to amorphous copolyamide (ii) is a copolyamide containing an amide repeating unit common to the crystalline polyamide (i). 5. A metal-bonded structure obtained by bonding primer-coated metal materials together with the metal adhesive according to claim 1. 6. The metal-bonded structure according to claim 5, wherein one of the primer-coated metal materials is a can lid and the other is an opening tab.