JPH09271374A - Can for canned food having improved flavor preservability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a can having improved flavor preservability by using a can drum or a can cap having a layer comprising a resin in which a hydrophobic zeolite having a specific molar ratio of SiO2 /Al2 O3 is dispersed into at least a part of the internal surface and seaming the drum or the cap. SOLUTION: The objective can for canned foods having excellent adsorbability and scavenging property of a flavor-inhibiting component such as dimethyl disulfide (DMS) and improved flavor preservability is obtained by using a layer composed of an internal covered film in which a hydrophobic zeolite having >=10 a molar ratio of SiO2 /Al2 O3 is dispersed into a resin such as a thermoplastic polyester resin or a polycarbonate resin having >=50 deg.C glass transition point in an amount of 1mg-10g per 1L of ingredients in at least a part of an internal surface of a can drum or a can cap, in a can for canned foods obtained by seaming the can drum and the can cap.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a can for cans having improved flavor retention, and more particularly to dimethyl disulfide (DM).
The present invention relates to a can for cans excellent in adsorption and trapping of flavor inhibiting components such as S). The present invention particularly relates to a can for can in which the flavor deterioration of the contents due to hot packs and hot benders is suppressed.

[0002]

2. Description of the Related Art Conventionally, it has been known that when canned foods, particularly fruit drinks, tea drinks and the like are stored under certain conditions, the quality of the contents and the flavor are deteriorated. For example, it is known that hot-packing tangerine juice causes odor, and that when tea tea beverages are kept at a high temperature in a bender, odor also occurs.

One of the causes of the deterioration of the contents and the deterioration of the flavor is a tendency of the total reduction of flavor components in the contents during storage, but a sulfur-containing compound accompanying the decomposition of the components in the contents, It is considered that the production of complex odors due to the production of nitrogen-containing compounds, carbonyl compounds, etc., and the production of sulfides and amines due to the mutual reaction between the content components and the metal of the body.

Conventionally, as a general measure taken to prevent the deterioration of the flavor of canned foods, Japanese Examined Patent Publication No. 32-3029.
As disclosed in Japanese Patent Publication No. 48-2782 and Japanese Patent Publication No. 48-2782, a coating material containing a reducing tin compound such as stannous oxide is applied to the inner surface of a can to prevent the deterioration of flavor due to dissolved oxygen. It is intended to suppress the oxidizing action by the reducing property of stannous ions.

Another proposed proposal is Japanese Patent Publication No. 58-1.
No. 029 discloses a coating material containing a specific amount ratio of an acrylic resin and an epoxy resin obtained by copolymerizing a higher alkyl acrylate or methacrylate, a lower alkyl acrylate or methacrylate, and an unsaturated carboxylic acid or an anhydride thereof. Is provided on at least a part of the inner surface of the can to absorb the off-flavor and off-flavor components.

[0006]

Among the conventional techniques, the method utilizing the reducing action of tin is quite effective in eliminating the influence of dissolved oxygen, but the flavor is lowered due to thermal decomposition of the contents. In terms of preventing the above, a satisfactory effect has not yet been observed, and it is not yet sufficient to prevent the accumulation of sulfur-containing compounds, nitrogen-containing compounds, carbonyl compounds and the like.

Moreover, the reducing tin compound contained in the can coating material exhibits a reducing property when it is eluted, while it is unfavorable for hygiene to elute a large amount of tin ion in the content. As the impact is expected,
It will be understood that there are certain restrictions on the flavor retention of the contents by the reduction method.

On the other hand, the latter proposal of adsorbing and capturing off-flavor and off-flavor components such as DMS on the coating film is unusual in its idea, but the adsorption capacity of the acrylic-epoxy resin is not sufficiently high. No, I am still unsatisfied with the obtained effect and its sustainability. Further, it may be a problem that the chemical properties and physical properties of the coating film itself are changed by adsorbing sulfur-containing compounds, nitrogen-containing compounds, carbonyl compounds and the like.

The present inventors selected a hydrophobic silica zeolite having a high silica content among various adsorbents, and provided a layer in which the hydrophobic zeolite was dispersed in a resin on the inner surface of a can. It has been found that it is extremely effective for adsorption and trapping of inhibitory components.

That is, the object of the present invention is to exhibit exceptionally high adsorption and trapping ability for flavor inhibiting components such as DMS,
Moreover, it is an object of the present invention to provide a can for cans in which this adsorption and trapping is performed without adversely affecting the characteristics of the resin.

Another object of the present invention is to provide a can for cans, which can stably maintain the contents excellent in flavor property for a long period of time even when the contents are subjected to heat history. is there.

[0012]

According to the present invention, in a can for can made by winding a can body and a can lid, SiO ₂ / Al _{2 is formed on} at least a part of the inner surface of the can body or the can lid. There is provided a can for improved flavor retention, which is characterized in that a layer in which a hydrophobic zeolite having an O ₃ molar ratio of 10 or more is dispersed is formed.

In the can for canning of the present invention: 1. The hydrophobic zeolite is contained in the resin layer in an amount of 10 g to 1 mg per 1 L of the content product; The resin is a resin having a glass transition point of 50 ° C. or higher, particularly a thermoplastic polyester resin or a polycarbonate resin having a glass transition point of 50 ° C. or higher, and the zeolite-dispersed resin layer is provided in the form of an inner coating film. Or the resin has a glass transition point of 50.
2. It is a thermosetting resin having a temperature of ℃ or more and the zeolite-dispersed resin layer is provided in the form of an inner surface protective paint. It is preferable that the zeolite-dispersed resin layer is provided with a thickness of 1 to 200 μm.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Zeolite is well known as an adsorptive deodorant, but in the present invention, a hydrophobic zeolite having a SiO ₂ / Al ₂ O ₃ molar ratio of 10 or more is selected among the zeolites, Further, it is a remarkable feature that it is provided on the inner surface of the can as a layer dispersed in the resin.

The basic structure of the zeolite crystal is SiO ₄ and its substituted AlO ₄ tetrahedrons, each of which shares an apex oxygen atom with each other to form a three-dimensionally developed crystal structure. . As a result, zeolite crystals have very large cavities and channels that are not found in other minerals. The entrance diameter of these pores varies depending on the zeolite, but is usually 3 to 9 angstrom, and various molecules can be trapped inside the pores. Further, cations are present inside the crystal to supplement the negative charge of AlO ₄ . Polar molecules and polarizable molecules are selectively adsorbed by the influence of the electrostatic field formed by the cations.
The SiO ₂ / Al ₂ O ₃ molar ratio of A-type zeolite, X-type zeolite, etc., which are generally used as a general-purpose adsorbent, is as low as 2 to 5, and these zeolites selectively select water over organic compounds. Adsorb. Therefore, it is not suitable as an adsorbent for purifying flavor-inhibiting components.

Zeolite loses hydrophilicity at a SiO ₂ / AI ₂ O ₃ molar ratio of 10 or more and gradually becomes hydrophobic. Zeolites exhibiting hydrophobicity are useful as hydrophobic adsorbents for flavor-inhibiting components. In particular, even in a system in which water coexists, the adsorption capacity for organic flavor-inhibiting components is small and shows a constant adsorption performance, so that the performance does not deteriorate even inside the can for cans under high humidity conditions.

There are two possible causes for the offensive taste, offensive odor, etc., of the contents such as black tea and fruit juice, which are caused by the container and the deterioration of the food contents, and the former cause. As a so-called plastic odor that is peculiar to plastic, and that plastic easily adsorbs flavor components in contents,
Also, as the cause of the latter, due to the alteration of the contents itself,
In particular, there are substances due to the formation of sulfur-containing compounds, nitrogen-containing compounds, carbonyl compounds, etc., but these off-taste and off-flavor components are extremely difficult to remove.

The present inventors measured the adsorbability of various zeolites using dimethyl sulfide (DMS), which is a typical one of these off-taste and off-flavor components (see Table 1 in the examples described later). . As a result, although it was not possible to predict based on the findings so far, SiO ₂
It was found that only the hydrophobic zeolite having a molar ratio of / Al ₂ O ₃ of 10 or more shows a specifically high DMS adsorption property. That is, when the molar ratio of SiO ₂ / Al ₂ O ₃ is less than 10, the DMS adsorption rate is less than 10%, whereas when the molar ratio is 10 or more, the DMS adsorption rate is 85% or more. In particular, it reaches 95% or more.

The adsorption site in the hydrophobic zeolite of the organic compound is a pore in the crystal, but its surface is formed of oxygen atoms regardless of the crystal structure. Therefore, it is presumed that the specific adsorption of the off-flavor and off-flavor components to the hydrophobic zeolite may be due to the special pore structure.

When an adsorptive deodorant is used, it often happens that the odor is absorbed in advance and does not contribute much to the absorption of the odor in the state of the package, but the can for can of the present invention has a hydrophobic property. Since the zeolite is dispersed and contained in the resin, the adsorption activity of the hydrophobic zeolite is stably maintained, and the adsorption and trapping action of the flavor-inhibiting component in the canned state is continuously and stably performed.

Further, when molding the hydrophobic zeolite-containing resin composition, since it is heated to the molding temperature of the resin, there is an advantage that the adsorptivity is activated. Furthermore, since this hydrophobic zeolite is literally hydrophobic, it also provides the advantage that it can be easily compounded and dispersed in a resin.

In the can for cans, a resin coating is provided on the inner surface of the can body or the can lid in order to protect the metal substrate and prevent metal elution. In the present invention, the resin constituting the coating layer is made hydrophobic. By dispersing the water-soluble zeolite,
It is possible to effectively adsorb and capture the flavor-inhibiting component while protecting the inner surface of the can.

As the resin for dispersing the hydrophobic zeolite, any of thermoplastic resins and thermosetting resins which have been conventionally used for protective coating on the inner surface of a can can be used. However, the above-mentioned off-flavor due to resin adsorption of the flavor component is used. In order to prevent this, a resin having a glass transition point as high as possible is preferably used, and a resin having a glass transition point of 50 ° C. or higher is particularly suitable. The thermoplastic resin has a glass transition point of 50.
A thermoplastic polyester resin or a polycarbonate resin having a temperature of not less than 0 ° C is suitable, while a thermosetting resin having a glass transition point of not less than 50 ° C is suitable as the thermosetting resin.

[Hydrophobic Zeolite] The hydrophobic zeolite used in the present invention has a SiO ₂ / AI ₂ O ₃ molar ratio of 10: 1.
Or more, particularly 30 or more, most preferably 100 to 5000
It is good to be in the range. This hydrophobic zeolite is ZS
It is available as M-5 type zeolite, silicalite and the like. Further, although the effect is slightly inferior, it is possible to use Y-type zeolite in which the alumina content is reduced by the steaming treatment. The hydrophobic zeolite may contain an alkali metal component such as sodium in addition to the silica component and the alumina component, and may be a hydrogen-type zeolite in which the alkali metal component is replaced with hydrogen.

The BET specific surface area of hydrophobic zeolite such as ZSM-5 type zeolite is generally 200 to 700 m.
² / g, while the pore volume is 0.18-0.
It is preferably in the range of 6 cc / g. The average particle diameter is generally within the range of 1 to 10 μm.

The hydrophobic zeolite such as ZSM-5 type zeolite can be obtained by a method known per se, for example, a method of hydrothermally treating a silica source, an alumina source, an alkali metal component and water with a basic organic nitrogen compound as a template, It can be obtained by hydrothermal treatment of aqueous colloidal silica sol, alkali aluminate, and alkali hydroxide without using a template.

[Zeolite-Containing Resin Composition] As the resin to which the hydrophobic zeolite is added, any moldable thermoplastic resin or coatable thermosetting resin is used. Of course, since these resins are provided on the inner surface side of the can, they should be moisture resistant resins (low water absorption resins).
A resin having a water absorption rate measured at 0 of 0.5% or less, particularly 0.1% or less is preferable.

Suitable examples of thermoplastic resins include low-, medium- or high-density polyethylene, isotactic polypropylene, ethylene-propylene copolymers, polybutene-1, ethylene-butene-1 copolymers, propylene. -Butene-1 copolymer, ethylene-propylene-butene-1 copolymer, cyclic olefin-based copolymer, ethylene-vinyl acetate copolymer, ion-crosslinked olefin copolymer (ionomer) or blends thereof Styrene resins such as olefin resins, polystyrene, styrene-butadiene copolymers, styrene-isoprene copolymers and ABS resins, thermoplastic polyesters such as polyethylene terephthalate and polytetramethylene terephthalate, polycarbonates, polyphenylene oxide, polysulfone, etc. Hold Rukoto can.

Among these thermoplastic resins, thermoplastic polyesters and polycarbonates having a glass transition point of 50 ° C. or higher are suitable from the viewpoint of content resistance.

One type of polyester resin which is preferably used is a homopolyester or a copolyester derived from a dibasic acid mainly containing terephthalic acid and a diol mainly containing ethylene glycol. .

As dibasic acids other than terephthalic acid, isophthalic acid, P-β-oxyethoxybenzoic acid, naphthalene-2,6-dicarboxylic acid, diphenoxyethane-
4,4'-dicarboxylic acid, 5-sodium sulfoisophthalic acid, hexahydroterephthalic acid, adipic acid, sebacic acid and the like can be mentioned.

Examples of diol components other than ethylene glycol include propylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexylene glycol, diethylene glycol, triethylene glycol, cyclohexanedimethanol, and bisphenol A ethylene oxide. Mention may be made of glycol components such as adducts.

It is particularly preferable that the acid content of the copolyester is composed of terephthalic acid and isophthalic acid from the viewpoint of processability and mechanical properties, and from the viewpoint of flavor retention.
As the acid component, a small amount of another dibasic acid component, for example, an amount of 1 mol% or less is allowed to be contained, but it prevents adsorption of the flavor component and suppresses elution of the polyester component. It is desirable that at least the polyester layer on the inner surface of the container does not contain an aliphatic dibasic acid. The polyester containing isophthalic acid as an acidic component is characterized by having a large barrier effect against various components, flavor components and corrosive components, and having a small adsorptivity.

The diol component of the copolyester is preferably one mainly composed of ethylene glycol.
It is preferable that 95 mol% or more, particularly 98 mol% or more of the diol component is composed of ethylene glycol from the viewpoint of molecular orientation, barrier properties against corrosive components and odor components, and the like.

The homopolyester or copolyester should have a molecular weight in the film forming range,
The intrinsic viscosity [η] measured using a phenol / tetrachloroethane mixed solvent as a solvent is 0.5 to 1.5,
Particularly, it is preferable that it is in the range of 0.6 to 1.5.

The polyester preferably used as the thermoplastic resin may be a homopolyester or a copolyester, or a blend of two or more of these.

Other types of suitable polyesters are polyethylene naphthalates, especially polyethylene-2,6-naphthalate or copolymerized polyesters based on ethylene naphthalate, such as polyethylene-2,6-naphthalate / terephthalate, polyethylene / butylene. −
Examples thereof include 2,6-naphthalate and polyethylene-2,6-naphthalate / isophthalate. As the copolymerization component other than ethylene naphthalate, those exemplified above are used. This ethylene-2,6-naphthalate polyester can also be used in the form of a blend with an ethylene terephthalate polyester.

Yet another suitable example is polyarylate. Polyarylate is defined as a polyester derived from a dihydric phenol and a dibasic acid, and as the dihydric phenol, as bisphenols, 2,
2'-bis (4-hydroxyphenyl) propane (bisphenol A), 2,2'-bis (4-hydroxyphenyl) butane (bisphenol B), 1,1'-bis (4-hydroxyphenyl) ethane, bis ( 4-hydroxyphenyl) methane (bisphenol F), 4-hydroxyphenyl ether, p- (4-hydroxy) phenol and the like are used, but bisphenol A and bisphenol B are preferable. As the dibasic acid, terephthalic acid, isophthalic acid, 2,2- (4-carboxyphenyl) propane, 4,4'-dicarboxydiphenyl ether, 4,4'-dicarboxybenzophenone and the like are used.

The polyarylate may be a homopolymer or a copolymer derived from the above monomer components.
Further, it may be a copolymer of an aliphatic glycol and an ester unit derived from a dibasic acid as long as the essence thereof is not impaired. These polyarylates are U-polymers or AX-series, UC, U-polymers from Unitika
Ardel D-100 from C, APE from Bayer,
Duech from Hoechst, Ar from DuPont
Ylon, available as NAP resin from Kanegafuchi Chemical Co., Ltd. These polyarylates can also be used in the form of blends with the above-mentioned polyesters.

Polycarbonate is preferably used as a resin having a low tendency to adsorb flavor components in the contents. Polycarbonate is a carbonic acid ester resin derived from a bicyclic dihydric phenol and phosgene, and is characterized by having a high glass transition point and heat resistance. Examples of the polycarbonate include bisphenols such as 2,2'-
Bis (4-hydroxyphenyl) propane (bisphenol A), 2,2'-bis (4-hydroxyphenyl)
Butane (bisphenol B), 1,1′-bis (4-hydroxyphenyl) ethane, bis (4-hydroxyphenyl) methane (bisphenol F), 1,1-bis (4
-Hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) cyclopentane, 1,1-
Polycarbonates derived from bis (4-hydroxyphenyl) -1-phenylmethane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,2-bis (4-hydroxyphenyl) ethane and the like are preferable. Is. These polycarbonates can also be used in the form of blends with polyesters.

In the present invention, hydrophobic zeolite is dispersed in the above thermoplastic resin and used as a resin composition in the form of an inner coating layer. The amount of hydrophobic zeolite to be blended must satisfy the above-mentioned coating amount per internal volume, but it is possible to blend the hydrophobic zeolite in an amount of 0.1 to 200 parts by weight per 100 parts by weight of the resin. It is preferable in terms of workability and coatability.

Of course, the above composition used in the present invention includes a filler, a coloring agent, a heat resistance stabilizer, an antioxidant, an antiaging agent,
A known resin compounding agent such as an antistatic agent, a lubricant such as metal soap or wax, an antiblocking agent, a modifying resin or a rubber can be compounded according to a method known per se.

On the other hand, as the coating material for coating, a thermosetting resin coating material such as phenol-formaldehyde resin, furan-formaldehyde resin, xylene-formaldehyde resin, ketone-formaldehyde resin, urea-formaldehyde resin, melamine-formaldehyde resin, alkyd is used. Resin, unsaturated polyester resin, epoxy resin, bismaleimide resin, triallyl cyanurate resin, thermosetting acrylic resin, silicone resin, oily resin, or thermoplastic resin paint, for example, vinyl chloride-vinyl acetate copolymer, chloride Vinyl-maleic acid copolymer,
Examples thereof include vinyl chloride-maleic acid-vinyl acetate copolymers, acrylic polymers, saturated polyester resins and the like. These resin coatings may be used alone or in combination of two or more.

As a particularly suitable coating resin, an epoxy thermosetting coating material can be mentioned, and in particular, a composition containing an epoxy resin and a curing agent resin for the epoxy resin is used.

As the epoxy resin component, all the epoxy resin components conventionally used as the epoxy resin component in this type of coating material can be used without limitation. Among these, epihalohydrin and bisphenol A [2 are typical. ，
2'-bis (4-hydroxyphenyl) propane] average molecular weight 800-5500, produced by condensation with
Particularly desirable are 1400 to 5500 epoxy resins, which are preferably used for the purpose of the present invention. This epoxy resin has the following general formula In the formula, R is 2,2′-bis (4-hydroxyphenyl)
It is a condensation residue of propane, and n has an average molecular weight of 8
It is a number selected to be 00 to 5500. Is represented by Incidentally, the molecular weight of the above-mentioned epoxy resin is an average molecular weight, therefore, a relatively low degree of polymerization epoxy resin for paints, and a high molecular weight linear epoxy resin, that is, a phenoxy resin, the average molecular weight is within the above range. There is no problem in using them in combination.

As the curing agent resin component for the epoxy resin, any resin having a polar group having reactivity with an epoxy group such as a hydroxyl group, an amino group and a carboxyl group;
For example, one or a combination of two or more of a phenol-formaldehyde resin, a xylene-formaldehyde resin, a urea-formaldehyde resin, a melamine-formaldehyde resin, a melamine-formaldehyde resin, a polar group-containing vinyl resin, and a polar group-containing acrylic resin are used. Is done. Among these curing agent resins, it is desirable to use a phenol-formaldehyde resin, particularly a phenol-aldehyde resin component containing a polycyclic polyphenol, in terms of adhesion to a film, barrier properties against a corrosive component, and processing resistance. . Any phenol / aldehyde resin component may be used as long as it contains a polycyclic phenol in the resin skeleton.

The above coating composition can be used as an organic solvent type coating composition and also as an aqueous coating composition.
In the case of an organic solvent type paint, the solvent includes an aromatic solvent such as toluene and xylene, an alcohol solvent such as ethanol and butanol, a methyl ethyl ketone, a ketone solvent such as cyclohexanone, methyl cellosolve, a cellosolve solvent such as butyl cellosolve, and butyl acetate. One or two or more ester solvents such as

In the case of a water-based paint, in order to improve dispersion stability, a water-miscible organic solvent may be added, and a dispersant and a surfactant may be added. Also, in the case of epoxy-based water-based paint, acrylic resin is mixed or partially reacted,
It is desirable to neutralize this with ammonia or amines to impart self-emulsifying property.

When the coating resin composition is used, the resin concentration in the paint is suitably in the range of 1 to 60% by weight. Further, the hydrophobic zeolite is preferably added in an amount of 0.1 to 80% by weight based on the resin solid content. Needless to say, the coating composition may contain a modifier or a compounding agent known per se, for example, a modifier such as a fatty acid, a polymerized fatty acid, a rosin, a drying oil or a xylene resin by mixing or precondensation, and further vinyl acetal. A resin, a leveling agent such as silicone oil, a lubricant such as wax, a curing accelerator for phosphoric acid or a metal salt of naphthenic acid, and the like may be added.

[Can body and can lid] As the metal base material forming the can body and the can lid, various surface-treated steel plates and light metal plates such as aluminum are used.

As the surface-treated steel sheet, a cold rolled steel sheet is annealed.
After that, 0.1 to 30% temper rolling or secondary cold rolling
Galvanized, tin plated, nickel plated, electrolytic black
One or two types of surface treatment such as mumic acid treatment and chromic acid treatment
What was performed above can be used. Suitable surface treatment
An example of a steel sheet is an electrolytic chromic acid treated steel sheet, and particularly 10
To 200 mg / m^Two 1 ~ 50mg with metallic chromium layer
/ M^Two With a chromium oxide layer (converted to metallic chromium)
This is a combination of coating adhesion and corrosion resistance.
It ’s excellent. Other examples of the surface-treated steel sheet include 0.5 to
11.2 g / m ^Two With a hard tin plate with the tin plating amount of
is there. This tin plate has a chromium content in terms of metal chromium.
1 to 30 mg / m^Two Chromic acid treatment or
It is desirable that chromic acid-phosphoric acid treatment is performed.

As still another example, an aluminum-coated steel sheet plated with aluminum, pressure-bonded with aluminum, or the like is used.

As the light metal plate, an aluminum alloy plate is used in addition to a so-called aluminum plate. An aluminum alloy plate excellent in corrosion resistance and workability has a Mn: 0.
2 to 1.5% by weight, Mg: 0.8 to 5% by weight, Z
n: 0.20 to 0.3% by weight, Cu: 0.15 to 0.45% by weight, and the balance is Al. It is desirable that these light metal plates have also been subjected to a chromic acid treatment or a chromic / phosphoric acid treatment such that the chromium amount becomes 20 to 300 mg / m ^{2 in} terms of chromium metal.

The thickness (tB) of the metal plate varies depending on whether it is a can body or a lid, and also varies depending on the type of metal, the use or size of the container, but generally 0.10 to 0. It is preferable to have a thickness of 60 mm. Among them, in the case of a surface-treated steel sheet, 0.10 to 0.4
The thickness is 0 mm, and in the case of a light metal plate, the thickness is preferably 0.15 to 0.50 mm.

The hydrophobic zeolite-containing resin composition can be provided to the can material at any stage for can manufacturing.

In the case of a thermoplastic resin composition containing a hydrophobic zeolite, this resin composition is previously formed into a film by a T-die method, an inflation film forming method or the like, and the obtained film is used for coating a metal. be able to. The film to be used may be either unoriented or biaxially oriented, but the biaxially oriented film is preferable from the viewpoint of content resistance. Instead of using a preformed film for coating, the hydrophobic zeolite-containing resin composition can be extruded through a die and extrusion-coated on a metal plate.

The resin layer used for lamination with a metal is a single layer,
That is, it may consist of a thermoplastic resin layer containing hydrophobic zeolite alone, or may be a multi-layer combined with another resin layer. For example, with respect to the resin layer containing hydrophobic zeolite, a resin layer not containing hydrophobic zeolite is laminated as the innermost layer, or a resin layer having excellent adhesiveness to metal is laminated as a layer facing the metal. be able to.

The laminate used for can making can be produced by heat-bonding the above-mentioned metal substrate and film, and can also be produced by extrusion coating a thermoplastic resin on the metal substrate. To enhance corrosion resistance and adhesion,
In the case of the laminating method, the adhesion primer can be applied in advance to the metal substrate or the thermoplastic resin film, and also in the case of the extrusion coating method, the adhesion primer can be applied in advance to the metal substrate. .

Although not generally required, when an adhesive primer is used, it is generally desirable to subject the surface of the film or the like to corona discharge treatment in order to enhance the adhesion to the adhesive primer on the film. It is desirable that the degree of the corona discharge treatment is such that the wetting tension is 44 dyne / cm or more.

In addition, it is also possible to subject the film to a known adhesion-improving surface treatment such as plasma treatment or flame treatment, or an adhesion-improving coating treatment such as urethane resin type or modified polyester resin type. .

The thermal bonding is carried out by heating the metal plates to be laminated to a predetermined temperature and press-bonding the film and the metal plates with a laminating roller or the like.
For 1), a temperature of Tm-50 ° C to Tm + 100 ° C, particularly Tm-50 ° C to Tm + 50 ° C is suitable. In the case of the extrusion coating method, instead of pulling out the polyester film from the supply roll, the molten polyester may be pulled out in a film form from the extrusion die and the same lamination may be performed by the laminating roll. In this extrusion coating method, the thermoplastic resin layer of the manufactured laminate is naturally in an unoriented state.

The adhesive primer optionally provided between the film and the metal material exhibits excellent adhesion to both the metal material and the film. A typical example of a primer coating having excellent adhesion and corrosion resistance is a phenol epoxy-based coating composed of a resol-type phenol aldehyde resin derived from various phenols and formaldehyde, and a bisphenol-type epoxy resin. Particularly, the phenol resin and the epoxy resin are 50:50 to 5: 9.
It is a coating material containing 5 weight ratio, particularly 40:60 to 10:90 weight ratio. The adhesive primer layer is generally 0.0
The thickness is preferably 1 to 10 μm. The adhesive primer layer may be previously provided on the metal material or may be previously provided on the film.

The thickness of the zeolite-containing resin layer should be determined in consideration of the processability of the can, the corrosion resistance, the flavor retention, etc., and is generally preferably in the range of 1 to 200 μm.

In the laminate used in the present invention, the above-mentioned zeolite-containing film layer is provided on the inner surface of the can, but the outer surface of the can has the same kind as the inner surface. A film not containing zeolite may be provided, or a can coating material known per se may be provided.

This coating material can be applied by any means such as dip coating, roller coating, spray coating, brush coating, electrostatic coating, electrodeposition coating, wire coating, flow coating, doctor coating, can material, can body, It can be applied to a can lid or can. The paint thickness is generally 1 to 2 on a dry matter basis.
It can be in the range of 00 microns, especially 5 to 40 microns.

The baking conditions of the coating material differ depending on the composition of the coating material, etc., but generally speaking, within the temperature range of 150 to 300 ° C. and the baking time period of 15 to 1200 seconds, the extraction resistance and hot water resistance are different. It suffices to select the conditions under which sufficient curing is achieved.

The metal body or the coated metal material is molded into a can body or a can lid by a means known per se. That is, the can for canning of the present invention may be a two-piece can or a three-piece can, and in the former case, it is wound between the seamless can and the can lid, and in the latter case, it is wound between the side seam can and the top and bottom can lid. .

In the case of a seamless can, the coated metal plate is subjected to deep drawing, thinning deep drawing, or ironing so that the hydrophobic zeolite-containing resin layer is on the inner surface side of the can to form a seamless can. . This is subjected to flange processing, neck-in processing, etc. to obtain the final can body. Of course, the inner surface of the can may be uncoated and subjected to squeezing or squeezing-ironing, and the hydrophobic zeolite-containing paint may be applied to the inner surface of the molded can body and baked.

In the case of a side seam can, the coated metal plate is formed into a tubular shape so that the hydrophobic zeolite-containing resin layer is on the inner surface side of the can, and both sides are soldered, welded, joined by an adhesive, etc. Join with to make a can body. This is subjected to flange processing, neck-in processing, bead processing, etc. to obtain the final can body.

In the case of a can lid, the coated metal material is punched out and press-molded so that the hydrophobic zeolite-containing resin layer is on the inner surface side of the can, or further score processing, button molding,
Attach the tabs, etc. to form a can lid or an easy open can lid. Of course, the order may be reversed, and the zeolite-containing paint may be applied to the molded can lid and baked.

[Usage] The canned can of the present invention is a food product in which flavor retention is a problem when it is canned, for example, favorite beverages such as black tea, green tea, oolong tea, coffee; orange juice, lemon juice, plum juice, It is useful as a can for storing fruit juice drinks such as apple juice and grapefruit juice or drinks containing fruit juice; vegetable juices such as tomato juice.

[0072]

The present invention will be further described with reference to the following examples.

Example 1 A hydrophobic zeolite having a SiO ₂ / Al ₂ O ₃ content of 100 and a particle size of 3 μ was dispersed in 20 wt% PET resin to a thickness of 100 μ.
Was produced. Epoxy primer is applied to one side of a 0.2 mm thick tin-free steel plate, and this film is heat laminated at 240 ° C, and 15 is applied to the other side.
The PET film of μ was similarly heat laminated. Using this laminated plate, a can lid having a diameter of 4 cm (area: 12.6 cm ² ) was molded so that the zeolite-containing PET was on the inner surface.
Using this laminated plate, a can body having a content volume of 267 ml was formed by DI molding from a blank of 16 cm in diameter so that the zeolite-containing PET was on the inner surface. This empty can was filled with 250 ml of black tea at 95 ° C., the lid made previously was wrapped and sealed, sterilized at 115 ° C. for 20 minutes, and then stored at 55 ° C. for 10 days assuming heating sale in a vending machine. The amount of zeolite added is 0.6 g / liter of the content product.
Then, the concentration of dimethyl sulfide in the head space of the can was measured by gas chromatography with a flame photometric detector (FPD-
When measured by GC), dimethyl sulfide (DMS) was 0.1 ppm. The total DMS amount in black tea and in the gas phase, which was obtained from a calibration curve in a gas-liquid equilibrium state at 55 ° C. prepared in advance, corresponds to 0.5 μg. Also, cut out the lid and
When heated to ℃ and measured the volatile components by FPD-GC, the total amount of DMS in the lid and the can body was 25 μg. Therefore, 98% of DMS was adsorbed on the PET film containing zeolite. Canned black tea made in the same way at 55 ℃ 1
After storage for 0 days, a flavor test was conducted, and when opening the can, no potato odor was felt and the taste was good.

Comparative Example 1 Instead of 100 μPET containing zeolite of Example 1, 1
The same test was conducted except that a can body and a can lid were made using 00 μPET film. The DMS concentration in the headspace is 4.85 ppm, and the DMS amount in the content liquid and the gas phase is 24.2.
The amount adsorbed on the can body and the lid was 1.25 μg. The adsorption rate was 4.5%. Similarly, when a flavor test was conducted, a remarkable potato odor was felt when opening the can.

Examples 2 to 4 Comparative Examples 2 to 4 Instead of the zeolite used in Example 1, SiO ₂ / A
Similar tests were conducted using various zeolites having different l ₂ O ₃ . Table 1 shows the obtained results.

Example 5 Si was added to 100 parts of resin in an epoxyphenol coating.
O ₂ / Al ₂ O ₃ is 1800, specific surface area is 400 m ² / g
20 parts by weight of H-ZSM zeolite having a particle size of 5 μm was added.
This is 4cm in diameter, 5.25cm in inner diameter, and 13.2c in height.
m of the molded TFS DI can was spray-painted on the can body and the can lid. The can body and lid were baked in an oven at 250 ° C. for 10 minutes. A total of 0.5 g of coating film was formed on the can body and the can lid. 50 ml of mandarin orange juice was hot-packed at 95 ° C. in this can, the lid was closed, and stored at 25 ° C. for 3 months. The DMS concentration in the headspace was measured by FPD-GC. The amount of DMS remaining in the internal article was determined by a calibration curve for determining the total concentration in the liquid phase and in the gas phase from the DMS concentration in the headspace prepared in advance. As a result, DMS was not detected. The amount of zeolite added is 0.4 g
/ Content 1L. A canned tangerine juice prepared in the same manner was stored at 25 ° C. for 3 months and then subjected to a flavor test.

Comparative Examples 5-6 Examples 7-8 Similar tests were carried out in Example 5 except that the amount of zeolite added was changed. Table 2 shows the obtained results.

[0078]

[Table 1]

[0079]

[Table 2]

[0080]

EFFECTS OF THE INVENTION According to the present invention, a hydrophobic zeolite having a SiO ₂ / Al ₂ O ₃ molar ratio of 10 or more is provided as a layer in which at least a part of the inner surface of a can for can is dispersed in a resin. As a result, it was possible to obtain the adsorption characteristics of the offensive taste and offensive odor components.

Claims (6)

[Claims] 1. A can for can made by winding a can body and a can lid, wherein at least a part of an inner surface of the can body or the can lid has a SiO ₂ / Al ₂ O ₃ molar ratio of 10 or more. A can for improving flavor retention, which is characterized in that a layer in which a crystalline zeolite is dispersed in a resin is formed. 2. The can for cans according to claim 1, wherein the hydrophobic zeolite is contained in the resin layer in an amount of 10 g to 1 mg per 1 L of the content product. 3. The can for cans according to claim 1, wherein the resin has a glass transition point of 50 ° C. or higher. 4. The can for cans according to claim 1, wherein the resin is a thermoplastic polyester resin or a polycarbonate resin having a glass transition point of 50 ° C. or higher, and the zeolite-dispersed resin layer is provided in the form of an inner surface coating film. . 5. The can for cans according to claim 1, wherein the resin is a thermosetting resin having a glass transition point of 50 ° C. or higher, and the zeolite-dispersed resin layer is provided in the form of an inner surface protective paint. 6. The zeolite-dispersed resin layer is 1 to 20.
The can for canning according to claim 1, wherein the can is provided with a thickness of 0 μm.