JPH01289886A - Adhesive for metal and bonded structure - Google Patents

Abstract

PURPOSE:To obtain the title adhesive which exhibits an excellent bonding strength under a highly dry condition and under sterilizing conditions in which heat and water act simultaneously by melt-kneading a highly crystalline polyamide with a lowly crystalline or amorphous copolyamide and an olefin copolymer in a specified ratio. CONSTITUTION:A crstalline polyamide (e.g., nylon 610) having 6.1-15 carbon atoms per amide group on the average is mixed with a lowly crystalline or amorphous copolyamide (e.g., nylon 6/610/12 copolymer) having 6.0-15 carbon atoms per amide group on the average in a weight ratio of 97:3-65:35. The obtained mixture is mixed with an olefin copolymer (e.g., a metal salt of an ethylene/acrylic acid copolymer) containing at least one kind of groups selected from among carboxylic acid, its salt, its anhydride, its amide and its ester bonded to a polymer chain in a concentration of 10-400mmol/100g polymer (in terms of =CO) in a weight ratio of 94:6-65:35, and the resulting mixture is melt-blended to obtain a blend.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a metal adhesive and a metal bonded structure using the same, and more specifically, the present invention relates to a metal adhesive and a metal adhesive structure using the same. This invention relates to adhesives for metals. The present invention also relates to a metal bonded structure having excellent adhesive strength under various environmental conditions, and particularly to a metal bonded structure useful for easy oven can lids.

(Prior Art) Polyamides have been known to be excellent thermal adhesives for metal materials. For example, crystalline nylon (Japanese Patent Publication No. 45-3235
9), copolymerized nylon (Special Publication No. 49-16790)
Blends of crystalline nylon and amorphous or low-crystalline nylon (Japanese Patent Publications No. 48-18096 and Japanese Patent Publication No. 50-37690) are known. Also,
Japanese Patent Publication No. 52-26897 describes a metal adhesive in which an ionomer is blended with one or more types of crystalline polyamide.

On the other hand, the easy-open M used for cans containing beverages such as cola, beer, and juice is equipped with an opening portion divided by scores (partial cutting lines), and the opening portion is A widely used method is to form a rivet, fix a tension tab with the rivet, and pull the tab so that the score is broken and the opening portion is removed.

However, with this easy-to-open lid, the inner coating of the lid is easily damaged due to harsh processing such as riveting.
For applications such as edible canning, in which corrosive contents are filled and harsh treatments such as heat sterilization are performed, satisfactory results in terms of corrosion resistance cannot be obtained. This tendency is particularly noticeable in easy-to-open preparations made of aluminum.

Furthermore, contents with a high salt concentration cause pitting corrosion, and there is a problem of contamination due to leakage of contents from through holes and sterilization.

To solve this problem, Japanese Patent Application Laid-Open No. 61-6044
Publication No. 7 proposes that an opening tab is adhesively fixed to an opening portion of a can lid defined by a score using a polyamide adhesive.

(Problems 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 opening piece (
Shearing of the score is initiated by pushing the tip of the tab) into the score, and then shearing across the entire score is performed by pulling the tab, but in this case, the adhesive area receives the force necessary to insert the score. The problem is that the adhesive acts as a component and is likely to cause damage to the bonded portion.

Additionally, the method of opening an easy-open lid varies depending on the purchaser of the can. A relatively large moment acts on the adhesion fulcrum between the cover and the lid, making it easy for the adhesion 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 strong, so even when the aforementioned easy-to-open lid is opened, there is almost no risk of the polyamide adhesive layer at the adhesive fulcrum or the joint between the adhesive layer and the paint film being destroyed. Instead, it is observed that peeling or destruction often occurs at the adhesive interface between the coating film and the metal material. 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.

It has been found that this metal-to-coating failure occurs significantly when the bonded structure is placed under extremely dry conditions, especially in winter. This is because polyamides are hygroscopic, and the elastic modulus changes considerably depending on the amount of moisture absorbed, and when dried and the amount of moisture absorbed is extremely small, the elastic modulus of the polyamide adhesive layer increases significantly. This seems to be caused by.

Therefore, an object of the present invention is to provide a polyamide-based metal adhesive that has significantly improved adhesive strength under highly dry conditions.

Another object of the present invention is to provide a polyamide metal adhesive that has excellent adhesive strength under highly dry conditions and maintains excellent adhesive strength even under sterilization conditions where heat and moisture act simultaneously. It is on offer.

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

(Means for Solving the Problems) According to the present invention, (i) a crystalline polyamide having an average carbon number of 6.1 to 15 per amide group; (ii) a crystalline polyamide having an average carbon number of 6.1 to 15 per amide group; .0 to 15, and (iii) a carboxylic acid, carboxylic acid salt, or carboxylic acid anhydride bonded to the polymer chain.
10 to 400 mmol/1 as at least one group of carboxylic acid amide or carboxylic acid ester =co group
It contains as an essential component an olefin copolymer at a concentration of 00 g polymer, contains component (i) and component (ii) in a weight ratio of 97:3 to 65:35, and contains component (i) and ( A metal adhesive is provided, characterized in that it contains a total amount of ti) and component (ii) in a weight ratio of 94:6 to 65:35.

According to the present invention, there is also provided a metal structure formed by bonding primer-coated metal materials together using the polyamide-based metal adhesive described above.

(Function) The metal adhesive of the present invention is made of (i) a crystalline polyamide having an average number of carbon atoms per amide group of 6.1 to 15, particularly 7.0 to 14.0; (ii) an average number of carbon atoms per amide group; A low-crystalline to amorphous copolyamide having 6.0 to 15 carbon atoms, especially 7.0 to 12 carbon atoms, and (i i i) carboxylic acid, carboxylic acid salt, carboxylic acid anhydride, carboxylic acid amide, or carboxylic acid A distinctive feature is that it contains three components of an olefin copolymer containing at least one group of esters as =CO group in a concentration of 10 to 400 mmol/100 g polymer, in particular 20 to 300 mmol/100 g polymer. It is.

In general, components (i) and (ii) are present in a compatible continuous phase, and component (fit) is present in the form of a dispersed particle phase dispersed within this continuous phase.

Component (i) is the main component of the adhesive, and has the high strength, high impact resistance, heat resistance, dimensional stability, and
In order to satisfy requirements such as water resistance, it is necessary to have high crystallinity. It is important for component (i) (the same applies to component (it)) that the average number of carbon atoms per amide group is within the above range; if this carbon number exceeds the above range, the heat resistance of the adhesive will deteriorate. The adhesive properties tend to be lower than those within the above range, and the cohesive force of the adhesive also tends to be lower than those within the above range. On the other hand, if the number of carbon atoms is smaller than the above range, the heat resistance of the adhesive will be lower than that of an adhesive within the above range, and the elastic modulus will be too high under high dry conditions, resulting in stress concentration on the bonding surface. This tends to occur, resulting in a significant decrease in adhesive strength.

Component (i) is a modifying component of the adhesive;
) It is important that the copolyamide is composed of a low crystallinity or amorphous copolyamide in order to prevent it from becoming highly elastic (rigid) under highly dry conditions and to promote fine particle dispersion of component (iii). It is. That is, in the present invention, a low-crystalline to amorphous copolyamide is compatible with a crystalline polyamide to form a continuous phase of the adhesive, and this continuous phase is compared to a case consisting of only a crystalline polyamide. As a result, the component (itl), i.e., the =CO group-containing olefin copolymer, is in a soft or plastic state even under highly dry conditions, and the continuous phase is more It has the effect of dispersing in the form of a fine dispersed phase, that is, a dispersed phase with a larger interfacial area.

Component (iii) is also an adhesive modifying component, but this olefin copolymer is not compatible with polyamides and exists in the form of a dispersed particle phase. It is important for this olefin copolymer to have the above-mentioned functional groups in terms of adhesion and dispersibility at the interface with the polyamide continuous phase, and in addition, carbonyl groups (=CO) based on these functional groups are important. It is also important to include the following in concentrations within the aforementioned ranges. That is, if the functional group concentration is lower than the above range, it will be difficult to finely disperse component (IIF) in the polyamide, and the adhesion to the polyamide continuous phase will also decrease. Cohesive force decreases, resulting in a decrease in adhesive strength. On the other hand, if the functional group concentration exceeds the above range, component (iii)
The heat resistance of the adhesive decreases, and troubles such as decomposition and foaming are likely to occur during the production of adhesive blends.

In the adhesive composition of the present invention, components (i) and (ii)
) is 97=3 to 65:35, especially 91:9 to 80
: It is also important that it is present in a weight ratio of 20. That is, if the amount of the low-crystalline to amorphous copolyamide (ii) is less than the above range, the above-mentioned effect of component (ii) will not be sufficiently exerted, and the adhesive strength under highly dry conditions will decrease. become. Moreover, if this amount exceeds the above range, the cohesive force of the adhesive itself will decrease, and the heat resistance and hot water resistance will also decrease.

Furthermore, it is important that in this composition the total amount of components (i) and (ii) and component (iii) are present in a weight ratio of 94:6 to 65:35, especially 91:9 to 80:20. It is. If the amount of component (iii) is less than the above range, the area of the interface of the dispersed particle phase of component (iii) will be insufficient, resulting in a decrease in adhesive strength under highly dry conditions. Moreover, if the amount exceeds the above range, a stable dispersed particle phase will not be formed, and the cohesive force of the adhesive itself will decrease.

As explained above, according to the present invention, the polyamide as the continuous phase in the adhesive is a low-crystalline to amorphous polyamide and is softened even under highly dry conditions, and the olefin copolymer phase as the dispersed phase has a surface area of The interface between these two phases becomes a releasable interface when a large peeling force is applied to the adhesive layer under highly dry conditions, and stress is dispersed in the adhesive layer. , it is possible to avoid stress concentration occurring only at the adhesive interface. This may explain the improved adhesive strength under highly dry conditions in the adhesives of the invention.

In the adhesive composition of the present invention, generally components (i i i)
is present as a dispersed particle phase with an average particle minor axis of 0.05 to 5 μm, particularly 0.1 to 3 μm.

(Preferred embodiments of the invention) (i) Crystalline polyamide In the present invention, the 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 first condition is to use a certain crystalline polyamide. This polyamide is a homopolyamide containing ω-aminocarboxylic acid and/or a diamine dicarboxylic acid salt as a starting monomer component, or a copolyamide within a range that does not substantially impair the crystallinity of this homopolyamide. It is. "Substantially no loss of crystallinity" means that the copolyamide exhibits a heat of crystal fusion that is 80% or more, particularly 90% or more, of the heat of crystal fusion of the homopolyamide that shares the main amide repeating unit with the copolyamide. .

Examples of suitable polyamides are listed in Table A below.

Table A The crystalline polyamide used in the present invention has a heat of fusion of 8 to 18 cal/g, particularly 9 to 1 cal/g, as measured by a differential scanning calorimeter.
Preferably, it is in the range of 6 cal/H.

The polyamide used in the present invention contains 100cc of 98% sulfuric acid.
Relative viscosity (ηre) measured at 20 °C at a concentration of 1 gram of
l ) is preferably in the range of 1.8 to 3.5. A polyamide whose specific viscosity value is smaller than the above range has poor mechanical properties and the strength of the joint portion is insufficient. Further, polyamides with specific viscosity values higher than the range of the present invention are not preferred because the melt viscosity of the adhesive becomes too high during melt bonding, and bonding requires a temperature considerably higher than the melting point.

(ii) Low-crystalline to amorphous copolyamide The low-crystalline to amorphous copolyamide used also has an average number of main chain carbon atoms per amide group of 6.0 to 15.0, particularly 7.0 to 15.0. 1
It is in the range of 4.0. The copolyamide may be comprised of more than one type of amide repeating unit as described in Table A above, or at least one type of amide repeating unit as described in Table A to the extent that the above restrictions are met; other amide repeating units, such as nylon 4, nylon 6, etc.
-aminocarboxylic acid units; and at least one other diamine/dicarboxylic acid amide unit, such as nylon 4,6, nylon 6.6, or an amide repeating unit from a dimer acid and a diamine.

The crystallinity of the copolyamide depends on the type, number and amount of amide repeat units incorporated into the polyamide.

In the copolyamide of the invention, the amount of one polyamide repeating unit is preferably 15% or more, especially 20% by weight, and the amount of the other amide repeating unit is also preferably 15% or more, especially 20% or more, Also, the types of amide repeating units contained in the copolyamide are 3 f! It is desirable that it be above the same level. Further, it is preferable that one of the amide repeating units in the copolyamide is the same amide repeating unit as 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 above-mentioned differential scanning calorimeter. The copolyamide used in the adhesive of the present invention has a heat of fusion of 60% or less, particularly 50% or less of the heat of fusion of the crystalline polyamide.

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

(i i i) Olefin copolymer 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. It is. 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.

i) Carboxylic acids or carboxylic acid anhydrides acrylic acid, methacrylic acid, fumaric acid, maleic anhydride, itaconic anhydride, crotonic acid, tetrahydrophthalic anhydride.

fi) Carboxylic acid amide Acrylamide, methacrylamide, maleimide.

1ii) Carboxylic acid esters Vinyl esters 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 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.

Polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-butene-1 copolymer, ethylene-
Main polymers such as vinyl acetate copolymer, maleic anhydride, acrylic acid, methacrylic acid, (meth)acrylate,
A copolymer made by grafting (meth)acrylamide, etc.

These copolymers should, of course, contain <=CO groups based on carboxylic acid or derivatives thereof in the concentrations mentioned above, ie from 10 to 400 mmol per ioo gram 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 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 40 to 200°C, especially 60 to 180°C, and a melt flow rate (MI) of 0.5. 300 to 300, especially 0
．． It is advantageous for the dispersion structure of the present invention to be within the range of 7 to 150.

(iv) Blends The above three components are melt-kneaded to form a blend.

The degree of kneading varies depending on the melting point and functional group concentration of the resin, and cannot be generally specified, but in general, the above components are dry blended and then kneaded using a metering type screw.
It is desirable to form it into a film. When using an extruder using a Dalmage type screw or a twin-screw extruder, it is preferable to shorten the kneading time to prevent mutual reaction between the two resins.

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. 20% by weight of the entire resin composition as long as it does not damage it
It can be added as an additive within a range not exceeding .

The adhesive structure of the present invention is particularly useful as an easy-to-open can lid.

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 inside of the can is shown facing down.

An adhesive primer layer 2 is provided on the outer surface of the metal can lid 1, and a protective coating 3 is provided on the inner surface, while an adhesive primer layer 5 is provided on the inner surface of the metal opening tab 4, and an adhesive primer layer 5 is provided on the outer surface. is provided with a protective coating 6. The can M1 and the opening tab 4 are bonded together by the aforementioned adhesive layer 7 via the adhesive primer layers 2 and 5 applied to their surfaces.

As shown in FIGS. 2 and 3, the lid 1 includes a circumferential groove 8 on the outer periphery and a panel 10 connected to the groove via an annular rim 9. A layer of sealing compound 11 is provided which is in sealing engagement with the flange (not shown) during double seaming. 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 is the panel portion 1
The panel portion 1 may substantially coincide with most of the panel portion 1.
A part of 0 may be an opening part.

As shown in the enlarged sectional view of FIG. 1, the score 12 is provided so as to reach the middle of the extra length material 1 in the thickness direction,
The mechanism described in detail below facilitates shearing when opening the package.

An opening tab 4 is provided in this opening portion 13 using a specific mechanism described below. This opening tab 4 has a score insertion tip 14 at one end, a grip part (ring) 15 at the other end, and a fulcrum part 1 located between these parts and joined to the lid.
6.

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 such that a connection 18 exists between the fulcrum portion 16 and the tip 14. It is formed by providing a tongue-like shape. The tearing tip 14 of the opening tab 4 has a score of 1 for the lid.
The opening portion 13 of the lid is thermally bonded to the opening portion 13 of the lid at the tongue-shaped fulcrum portion 16 so that the positions of the opening portion 2 and the opening portion 2 substantially coincide with each other.

In this can lid, when the ring 15 of the opening tab 4 is picked up with fingers and lifted upward, this force is transmitted as a downward force to the insertion tip 14 via the fulcrum part 16, and the score 12 is directed downward. At the same time as the insertion force is applied, a peeling force is applied to 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 blended adhesive as the adhesive layer 7, it is possible to withstand the above-mentioned peeling force under any environmental conditions. By then pulling the opening tab 4 at an angle of approximately 90 degrees with respect to the lid 1, the score 12 is sheared from the location where the cut was made.

Metal materials for the lid include light metal plates such as aluminum and various surface-treated steel plates such as zinc, tin, etc.
It is made of plated with chromium, aluminum, etc., or has a chemical conversion treatment film of chromic acid, phosphoric acid, etc. formed on the surface, and any metal material that has pressure deformation resistance and rigidity that can withstand seaming can be used. . The thickness of the material is generally 0.10 to 0.40 mm.

In particular, it is desirable that the thickness be within the range of 0.12 to 0.35 mm. In addition, the opening tab is made of various metal materials mentioned above,
In particular aluminum is used.

This lid material is made of metal materials that are difficult to rivet, such as chromate surface-treated steel sheets, especially electrolytic chromate-treated steel sheets, chromate-treated nickel-plated steel sheets, chromate-treated membranes,
It is suitably applied to tin alloy plated steel sheets, chromate treated ladle/nickel alloy plated steel sheets, chromate treated film/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 metal chromium layer is determined by the balance between corrosion resistance and workability, and the amount is 30 to 300 tng/m2. Especially 5
It is preferably in the range of 0 to 250 mg/m2. In addition, the thickness of the nonmetallic chromium layer is related to paint film adhesion and adhesive peel strength, and is expressed as the amount of chromium.
The range is preferably from 7 to 40 mg/m2, particularly from 7 to 30 rng/m.

The primer coating film used in the present invention is used for the purpose of promoting adhesion and protecting the underlying metal, and may be of any type as long as it exhibits excellent adhesion and adhesion to the above-mentioned adhesive and underlying metal. No questions asked. However, the phenol resin and epoxy resin are generally 95=5 to 30:
It is preferable that the content is in a weight ratio of 70%. As the phenol 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 carbolic acid, difunctional phenols represented by p-cresol, polynuclear phenols represented by bisphenol A, etc. are used alone or in combination of two or more types. However,
Particularly suitable phenolic resins for the purposes of the present invention have the following formula 1:
Formula % In the formula, M2 is the number of moles of bifunctional monohydric phenol in 100 g of the total phenol components contained in the phenol aldehyde resin, M3 is the number of moles of trifunctional monohydric phenol in 100 g of the total phenol component M4 represents the number of moles of polycyclic dihydric phenol in 100 g of total phenolic components, and the functional index (1, F,) defined by is 1.5 to 2.5.
, especially in the range of 1.6 to 2.8. In addition, the number of methylol groups per phenol nucleus is 0 on average.
．． 05 to 0.40, particularly 0.07 to 0.30, and the number average molecular weight is generally 200 to 80.
0, particularly in the range of 230 to 600.

As an epoxy resin, the epoxy equivalent obtained by condensation of bisphenol A and epihalohydrin is 600 to 6.
000, especially epoxy resins within the range of 900 to 4000 are preferably used.

Epoxy resins and phenolic resins are used in the form of a mixture or in a precondensed form to paint metal materials, and after being applied to the metal materials, they are baked at 140 to 280 degrees Celsius for 1 to 20 minutes. It is best used for post-adhesion.

The thickness of the primer coating is not particularly limited as long as the above-mentioned purpose is achieved, but - for boat fishing, it is between 0.2 and 3.
The thickness is preferably 0 μm, particularly in the range of 1 to 20 μm.

When manufacturing easy-to-open adhesive can lids, first coat at least one side of the aforementioned metal material with a primer paint in an organic solvent solution.
It is applied in the form of an aqueous dispersion or solution by spray coating, roller coating, dip coating, electrostatic coating, electrophoretic coating, etc., 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 to a predetermined can lid size, press-molded into a can lid of a predetermined shape, and scored simultaneously or in a separate process. The score processing is such that the residual thickness b in the score part is 178 to 1/2 of the base plate thickness and the absolute thickness is in the range of 0.2 to 0.9 mm, especially 0.3 to 0.8 mm. It is desirable that

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 dried. and form 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 suitably in the range of 3 to 150 μm, particularly 10 to 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,
Then, it is cooled and solidified to complete the bonding of both. 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 canned food, it is desirable to provide the score close to the annular rim and over the entire circumference, as shown in the attached drawing, in a so-called full oven format. However, it can also be provided in any 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.

(Effects of the Invention) According to the present invention, an adhesive composition is prepared by blending three components of a highly crystalline polyamide, a low crystalline or amorphous copolyamide, and an olefin copolymer in a specific quantitative ratio. In the adhesive, the continuous phase polyamide is a low-crystalline to amorphous polyamide that is softened even under highly dry conditions, and the dispersed olefin copolymer phase is finely dispersed with a large surface area. The interface between these two phases becomes a releasable interface when a large peeling force is applied to the adhesive layer under highly dry conditions, and the stress is dispersed in the adhesive layer.
It was possible to prevent stress concentration from occurring only at the adhesive interface.

Therefore, using the adhesive of the present invention, it is possible to significantly improve adhesive strength under highly dry conditions, and by selecting and combining each component, it is also excellent even under sterilizing conditions where heat and moisture act simultaneously. We were able to provide an adhesive for metals that exhibits excellent adhesive strength even under various environmental conditions.

The following examples specifically explain the effects of the present invention. In each example, the following basic characteristics regarding adhesion (I) and adhesion with a lid as an application example (II) were evaluated for metal adhesive structures made of materials for each test number. did.

■, Adhesion test plate thickness 0.22+nm, amount of nonmetallic chromium on the surface 15mg/
epoxy on both sides of a regular tin-free steel (TFS) plate with a metal chromium content of 100 mg/m2.
A phenol-based paint (the weight ratio and composition of epoxy resin and phenol-based resin vary depending on each example as described later) was applied so that the thickness after baking was 5 μm.
Baking was carried out at .degree. C. for 10 minutes.

A test piece with a width of 5 mm and a length of 10 cm was cut out from this coated plate, each adhesive film with a width of 7 mm was sandwiched between the two test pieces, and then bonded using high frequency heating. The bonding temperature is the melting point of each adhesive + 30℃ for the entire bonding surface.
The aim was to achieve a temperature of Some of these adhesive pieces were baked in a 4-minute oven at -20°C, the melting point of each adhesive, in order to investigate the effect 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 heated at 116° C. for 90 minutes in a hot water treatment equivalent to retort sterilization, and a portion of the sample was placed in water at 90° C. for one week.

To evaluate the adhesion, five test pieces each were subjected to a Tl test after being heated in an oven at the initial stage of adhesion, after being retorted, and after being placed in hot water at 90°C. For the T-peel test, an Instron type tensile tester was used at a tensile speed of 200 m.
m/min at room temperature, and the arithmetic mean value of the average values of each measurement value was used as the result.

11.ii Adhesion test As a specific application example of the metal adhesive structure of the present invention, Fig. 4
．． The adhesive performance of an adhesive structure as shown in No. 5, in which an opening tab for shearing the score of the can lid is fixed to the can lid via an adhesive, was tested. The lid for this purpose was created as follows.

That is, the plate thickness is 0.20 mm, the amount of non-metallic chromium on the surface is 15 mg/m", and the amount of metallic chromium is 100 mg/m".
<7) Normal (7) Tin free steel (TFS
) The same epoxy/phenol paint as previously used in the test (2) was applied to both sides of the board so that the thickness after baking was 5 μm, and baking was performed at 210° C. for 10 minutes. This paint TF
The S plate was formed into a 211-diameter lid using a press, and then a sealing compound was applied to the curled portion by a conventional method and dried. Next, score processing was performed on the outer surface of the lid in a circular shape having a diameter of 58 mm so that the score residual thickness/thickness of the steel plate was 0.23. On the other hand, an aluminum coil with a thickness of 0.46 (#50
82) Apply epoxy phenol paint (
The weight ratio of epoxy resin and phenolaldehyde resin is 7.
5:25 (bisphenol A was used as a raw material for phenolaldehyde resin) and epoxy resin paint was coated on the opposite side so that the thickness after baking was 5 μm, and then slits were made to a width of 30 mm. On the contrary,
Thickness 45-50 consisting of the composition shown in each test number below
A microslit film with a diameter of 8 mm and a width of 8 mm was laminated by high-frequency induction heating and then press-molded into a tab having the shape shown in Figure 4.5. The tabs prepared in this manner were adhered onto the previously formed lids by heating at least 30° C. higher than the melting point of each adhesive using high-frequency heating so that the distance from the score to the adhesion fulcrum was 6 mm. In addition,
In this case, the width of the adhesive layer at the adhesive fulcrum is approximately 7 mm,
The area of the bonded portion was approximately 40 mm2.

Next, after adhering each tab, epoxy/phenol paint was applied to the score parts of the inner and outer surfaces of each lid, and after baking in an oven for 4 minutes at a temperature of -20°C, the melting point of each adhesive, the following process was performed. The peel strength and lid opening properties described in 1.2 were evaluated.

1. Peel Strength After adhering the tab under predetermined bonding conditions, the tab was baked in a predetermined oven and then subjected to retort sterilization equivalent to heat sterilization, and the peel strength of the lid was measured using the following method. In other words, after lifting the tab and performing the initial opening of the score part and raising the tab vertically to the lid panel surface, place the tab ring perpendicular to the lid panel surface so that the adhesive part is peeled at 90 degrees. A tensile test was conducted. The tensile test was carried out using an Instron type tensile tester at a tensile speed of 200 mm/min at room temperature to evaluate the initial strength and peeling work. Peeling work was determined by integrating the area within the peeling strength curve on the chart using an automatic integrator and converting the result to 1 cm' of adhesive area. Measurements were performed five times for each sample NO, and the arithmetic mean value of these measurements was taken as the measured value.

2. M opening property The opening property of the lid is: ■ Immediately after adhesion, ■ After applying correction paint to the score area on the inner and outer surfaces of the lid and performing the prescribed oven baking.
Furthermore, after double-sealing this lid onto a 211-diameter flange fake can, filling the contents with dressing tuna, and tightening the flat lid, retort sterilization was carried out at 116°C for 90 minutes. Humidity (RH) 60
%, 37°C, after 6 months (time course A) and ■RHIO%
20 panelists were asked to open 5 cans each at 37° C. and after 6 months (Time B), for a total of 100 cans. As a result, the number of cases where the tab could not be opened during opening due to detachment, and the number of cases in which the opening could not be opened at the initial stage among these opening failures are shown in parentheses.

Example 1 As an adhesive film, nylon 610 (concentrated sulfuric acid 1% relative viscosity 2.7) was used as the crystalline polyamide component, and nylon 6/66/610/12 copolymer (relative viscosity 2.8) was used as the low crystalline polyamide component. , Ionomer resin (ethylene acrylic acid copolymer metal salt, -C=O group concentration 155 millimorph 100 g polymer, M
I = 0.7) to prepare compositions having the composition blend ratios (wt%) shown in Table 1. During film formation, resin chips of all the components were dry blended in advance, and each was kneaded and formed into a film using an extruder equipped with a metering type screw.

The dispersion structure of the cross section 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. Regarding the dispersion structure in the table below, OinA is a structure in which a granular phase of polyolefin is dispersed in a continuous nylon resin phase, A is a homogeneous structure with almost no dispersion structure recognized, and 0andA is a structure in which both a polyolefin phase and a nylon resin phase are dispersed. This indicates that the structure is continuous and the presence of the granular polyolefin phase 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, and according to the method described above. A test was conducted after obtaining a painted board for adhesion testing and a painted board for the lid.

Table 1 summarizes the evaluation results, and according to this,
In cases where the polyamide component is composed only of crystalline polyamide resin (No. 1-1, 2), the polyolefin resin phase has poor dispersibility, the particle size distribution is wide, and many particles of 3 μ or more are observed, and the adhesiveness is also poor. Reflecting this, there is a large variation in strength, and the average value shows a decreasing trend, and in terms of lid adhesion, there are cases where it becomes impossible to open, especially when stored in a dry atmosphere. did. On the other hand, when the proportion of the low-crystalline polyamide resin component in the polyamide component exceeds a certain level, the adhesive strength, especially in terms of heat resistance and hot water resistance, tends to decrease significantly, and the performance of the crystalline polyamide resin, which is the main component, decreases. This will cause damage and make it difficult to open the lid.

Example 2 Nylon 61 as a crystalline polyamide resin component of adhesive
0 (concentrated sulfuric acid 1%, relative viscosity 2.7), nylon 6/66/610 copolymer (concentrated sulfuric acid 1%, relative viscosity 2.7),
2.9) were fixed so that the ratio of both was approximately 85:15, and films with different contents of ionomer resin (same as that used in Example 1) as the polyolefin resin component were prepared as shown in Table 2.・Created with blend ratio.

The dispersion structure changes when the content of ionomer resin is low (No.
, 2-1.2) The granular dispersion structure was unclear and showed a homogeneous structure, and when the -Banko abundance was high (No, 2-8) the polyolefin phase also showed a tendency to become a continuous phase.

In evaluating the performance of these adhesives, the weight ratio of epoxy resin and phenol formaldehyde resin was 80:20 as a primer. Tests were conducted according to the method described above using a phenol formaldehyde resin made from bisphenol A and m-cresol.

The evaluation results are shown in Table 2. When the content of the ionomer resin is low, there is a strong tendency for adhesive failure to occur as a cohesive failure of the primer coating or at the interface of the metal material, and there is a tendency for the adhesiveness to decrease. In addition, in terms of lid adhesion, breakage is likely to occur between the tab metal material and the primer, making it impossible to open the lid. This tendency was particularly noticeable when the actual cans were stored under dry conditions in the actual can tests.

On the other hand, when the content of the ionomer resin increases, the polyolefin resin phase also takes on a continuous phase dispersed structure, which weakens the inherent adhesiveness of the polyamide resin and reduces the initial adhesive strength and especially the adhesive strength after oven heating. This resulted in a decrease in adhesion due to a decrease in the heat resistance or hot water resistance of the adhesive itself, and the opening ability of the lid was also significantly impaired.

Example 3 For adhesive compositions in which the crystalline polyamide resin component and the low-crystalline to non-grade polyamide resin component have different average primary mirror carbon numbers per unit amide group, the polyolefin component maleic anhydride-modified polypropylene (-C = O group concentration 230 mmol/100 g polymer, MI-3,5)
, and their blend ratio was fixed at 80:10:10, and the relationship between the average main chain carbon number per unit amide group and adhesiveness was investigated. The adhesive film was formed in the same manner as in Example 1 using the component chips shown in Table 3.

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 0-cresol as raw materials, and coated plates according to the method described above. was created 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 peeling between the primer and the plate was particularly dominant. Even if the lid opened to some extent initially, the tab often came off when the score part was sheared, making it impossible to open the lid (NO, 3-1).

In addition, even when nylon 66 is copolymerized with nylon 6, although the adhesion property improves slightly, no improvement effect is observed, and the adhesion property between the primer and the plate tends to decrease due to oven heating or retort treatment, etc. The opening of the lid is also insufficient (No. 3-2).

On the other hand, 1 with an average main chain carbon number of 15 or more per amide group
When using a blend of 6.5 nylon 12 and dimer acid polyamide as a component, the adhesive itself has insufficient heat resistance and hot water resistance, resulting in a noticeable decrease in adhesive properties during oven heating, retort processing, etc. In addition, due to the decrease in cohesive force of the adhesive itself, it was not possible to obtain a sufficiently high initial peel strength in the lid, so it tended to be extremely difficult to initially open the lid ( No. 3-8
).

Example 4 In the adhesive composition, nylon 12 was used as the crystalline polyamide resin component, nylon 6/66/12 copolymer was used as the low crystalline polyamide resin component, and various types with different carbonyl group concentrations were used as the polyolefin resin component. The relationship between the carbonyl group concentration and the dispersion structure of polyolefin resin, and the relationship between this and adhesiveness were investigated. N.

4-2 to 4-4, the original resin of 4-1 with a different grafting rate with maleic anhydride, No. 4-5
In Examples 4-9 to 4-9, metal salt resins of ethylene-methacrylic acid copolymers with different copolymerization ratios were used as polyolefin resin components. In addition, in No4-1 to 4-4, MI=
M I =0.7 for 30-80 and N04-5-4-9
2.5 was used. An adhesive film was obtained from these resins in the same manner as in Example 1 at a blend ratio of 75:10:15.

Except for Nos. 4-9, in which a homogeneous structure was dominant, the polyolefin resin phase generally showed a structure dispersed in the polyamide resin phase, but carbonyl groups? When using low-density polyethylene with JHt almost equal to zero (No. 4-1)
In order to obtain a good granular dispersion structure with almost no blocking, the blocking of the polyolefin phase is significant.
It has been found that the polyolefin resin needs to have a certain concentration or more of carbonyl groups. In addition, when the carbonyl group concentration of polyolefin resin becomes extremely high, it tends to form a homogeneous phase with polyamide resin, and foaming due to resin decomposition increases during film formation, resulting in decreased film formability (No.
4-9).

In evaluating the performance of these adhesives, the weight ratio of epoxy resin and phenol formaldehyde resin was 80:20 as a primer. A painted board was created by using p-cresol as the phenol formaldehyde resin and using a 0.35-thick phosphoric acid chromate treated aluminum board (5082 material) as the board material, unlike the method described above. A test was conducted.

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. In addition, regarding the opening property of the lid, initial opening becomes difficult due to the reduced draw strength, and there is a tendency for the tab to become misaligned and to come off frequently. On the other hand, when the carbonyl group concentration of the polyolefin resin increased and a homogeneous phase was formed with the polyamide resin, the hot water resistance of the adhesive tended to decrease.

[Brief explanation of the drawing]

FIG. 1 is an enlarged view of the adhesion fulcrum between the can lid and the opening tab in an easy-open can lid for a rolled can as the metal adhesive structure of the present invention, and FIG. FIG. 3 is a top view of an easy-to-open can lid that is an example of a structure; FIG. 3 is a cross-sectional view of the can lid taken along line A-A'' in FIG. 2;

Claims (6)

[Claims] (1) (i) Average number of carbon atoms per amide group is 6.1 to 1
5, (ii) a low-crystalline to amorphous copolyamide with an average number of carbon atoms per amide group of 6.0 to 15, and (iii) a carboxylic acid or a carboxylic acid bonded to the polymer chain. 10 with at least one group of salt, carboxylic acid anhydride, carboxylic acid amide, or carboxylic acid ester as =CO group
It contains as an essential component an olefin copolymer in a concentration of 400 mmol to 400 mmol/100 g of polymer, contains component (i) and component (ii) in a weight ratio of 97:3 to 65:35, and contains component (
The total amount of i) and (ii) and component (iii) is 94:
A metal adhesive characterized in that the adhesive is contained in a weight ratio of 6 to 65:35. (2) Components (i) and (ii) are continuous phases and component (i)
An adhesive according to claim 1, wherein ii) is present in a dispersed particle phase. (3) Component (iii) has an average particle minor axis of 0.05 to 5
3. Adhesive according to claim 2, present as a micrometer dispersed particle phase. 4. The adhesive of claim 1, wherein the low-crystalline to amorphous copolyamide (ii) is a copolyamide containing a common amide repeating unit with the crystalline polyamide (i). (5) A metal adhesive structure formed by bonding primer-coated metal materials to each other using the metal adhesive according to claim 1. (6) The metal adhesive structure according to claim 5, wherein one of the primer-coated metal materials is a can lid and the other is an opening tab.