JPH05338639A - Odor adhesion preventive method for sealed packaging container - Google Patents

Abstract

PURPOSE:To improve the flavor retentivity by a method wherein for a sealed packaging container the inner surface of which is made of a waterproof thermoplastic resin layer, as the waterproof thermoplastic resin, a resin which is subjected to hydrophilic treatment is used so that the contact angle of water on the innermost surface becomes a specified value or less of the contact angle of water on an unprocessed surface. CONSTITUTION:At least the inner surface of the title sealed packaging container is made of a waterproof thermoplastic resin layer, and the innermost surface of the waterproof thermoplastic resin layer consisting the inner surface of this container is hydrophilicly processed so that the contact angle of water becomes 9/10 or less of that of an unprocessed surface. As the hydrophilic process means, e.g. plasma, corona discharge, glow discharge, fire flame chromic oxidation and ozone treatment, etc., can be applied. Even when the hydrophilic process layer is an ultra-thin layer, this layer forms not only a highly potential barrier to the adsorption or absorption of lipophilic substances, but also forms a multi- layer by the hydrophilic layer's adsorbing water molecules, and the multi-layer works as a barrier to the adsorption and/or absorption of lipophilic substances.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing odor from a hermetically-sealed packaging container, and more specifically, the contents of a container wall in a hermetically-sealed packaging container having an inner surface made of a thermoplastic resin layer. To prevent odor from

[0002]

2. Description of the Related Art Conventionally, so-called canned foods, bottled foods, etc. have been widely used as packaging containers for storing foods for a long period of time, but these containers are excellent in terms of storability of contents. In addition, the weight of the container itself is large, and there is a problem in terms of distribution, and it is difficult to dispose of the used container.

In order to solve this problem, molded articles such as plastics, particularly containers made of polyolefin or polystyrene resin, for example, plastic bottles, cups, etc., a plastic film, or a laminate of this film and an aluminum foil are used. Body containers have come into widespread use.

[0004]

[Problems to be Solved by the Invention]
Although it is lightweight, it has excellent impact resistance and the like, and has the advantage of being easy to dispose of. It also significantly suppresses gas permeation through the vessel wall by selecting and combining the materials used. Although it is possible, the drawback is that the flavor retention of the contents is still inferior to that of canned foods, glass bottles, and the like.

That is, plastics used as a material for the inner surface of a container that comes into contact with the contents such as foods from a hygienic point of view are lipophilic materials such as polyolefin, and flavor components contained in foods in trace amounts. As a result of the absorption and adsorption of the aroma components and the like on the inner surface layer of the container, the palatability of the food, that is, off-flavor, occurs. Another problem is that lipophilic natural pigments contained in foods are similarly absorbed and adsorbed, resulting in fading from the original color of foods.

Further, another drawback observed in the conventional plastic containers is that the inner surface layer of the container has an odorous component contained in the outside air at the stage before filling the contents such as manufacturing, transportation and storage of the plastic container, Adsorbs solvent contained in ink or paint, exhaust from baking oven or drying oven, exhaust from extruder, etc., and these adsorbed components migrate into the contents, and reduce flavor characteristics of the contents. That is.

Therefore, it is an object of the present invention that the inner surface layer is formed of a plastic material having excellent hygienic properties.
Aroma components contained in the contents, flavor components, adsorption of the dye or other useful trace components to the inner surface layer, suppress the absorption tendency, and also suppress the adsorption tendency of odorous components before filling the contents, As a result, it is an object of the present invention to provide a method for preventing the odor of a hermetically sealed packaging container, which can significantly improve the flavor retention of the in-package material.

Another object of the present invention is to provide a method for preventing odor from a hermetically sealed packaging container, which enables the above improvement by a simple means and without substantially impairing hygienic properties.

[0009]

According to the present invention, at the time of hermetic packaging using a container in which at least the inner surface is made of a water-resistant thermoplastic resin, the water-resistant thermoplastic resin is used as water on the innermost surface. Provided is a method for preventing odor from a hermetically sealed packaging container, which comprises using a hydrophilized material having a contact angle of 9/10 or less, particularly 7/10 or less of that of untreated water. ..

The water-resistant thermoplastic resin on the inner surface of the container is preferably polyolefin, polystyrene resin, polyester resin or other water-insoluble polymer, and the hydrophilic treatment on the innermost surface is plasma treatment, corona treatment, It is preferable to perform glow discharge treatment, flame treatment, chromic acid oxidation treatment, or ozone treatment.

[0011]

The hermetically sealed container intended by the present invention has at least the inner surface made of a thermoplastic resin layer. The innermost surface of the thermoplastic resin layer constituting the inner surface of the container is the contact angle of water. It is a remarkable feature of the present invention that the odor is prevented by using hydrophilic treatment so that it becomes 9/10 or less, particularly 7/10 or less of that of the untreated product.

[0012] In the present specification, the odor is the tendency of an aroma component, a flavor component, a pigment or other useful trace components contained in the content to be adsorbed on or absorbed by the inner surface layer, and the odor before filling the content. It means the tendency of adsorption and absorption of odorous components to the inner surface layer.

Thermoplastic resins such as polyolefin and polystyrene have a low tendency for the resin components to migrate into the contents even when they are in contact with the contents for a long time, and are excellent in hygiene, but they are contained in the contents. There is a marked tendency to adsorb and absorb aroma components, flavor components, pigments, and other useful trace components. This is because the thermoplastic resin has a high affinity with these components, that is, a high lipophilicity.

The attached drawing "FIG. 1" shows various resins.
It shows the relationship between the contact angle of water and the distribution ratio of d-limonene. The contact angle of water increases as the lipophilicity of the resin surface increases. On the other hand, the distribution ratio (D.R.) is

[0015]

## EQU1 ## D. R. = W L / W P where W L is the amount of d-limonene contained in the water phase when d-limonene dispersed water is contacted with the resin surface, and W P is contained in the resin phase during the contact. Is the amount of d-limonene,

It is represented by From "Figure 1", the water contact angle and d
-There is a certain correlation with the limonene distribution ratio (D.R.), and this relation is expressed by the following equation when the water contact angle is θ _{H 20.}

[0017]

(. D.R) [number 2] log = 0.0805θ _{H 2 0} -
6.7884

It is represented by From this "Fig. 1", polyolefins such as polystyrene (PS), polypropylene (PP), and low-density polyethylene (LDPE) have a slightly low value for high-density polyethylene (HDPE), but other resins such as polyvinyl chloride. Water contact angle (θ _{H 2 0} ) compared to (PVC), paint for thermosetting cans (A, B, C), etc.
And the distribution ratio of d-limonene (D.
R. ) Is also large, it becomes clear.

From the above facts, it is understood that making the plastic surface hydrophilic can prevent the odor of the plastic container surface. The degree of hydrophilicity of the plastic surface is
Although it depends on the type of plastic, in the present invention, if the hydrophilic treatment is performed so as to be 9/10 or less based on the contact angle of water of untreated one, the durability of the effect will be improved. However, it was found that satisfactory results were obtained in terms of preventing odor.

In the present specification, the contact angle of water means a value obtained by the following measuring method. [Contact angle measurement method] A small droplet is created on a solid surface using a syringe, and the height h of this droplet and the radius x of the bottom circle are read using a microscope or a video camera.
I asked.

[0021]

(3) θ = 2 arctan (h / x)

Examples of the hydrophilic treatment means include plasma treatment, corona discharge treatment, glow discharge treatment, flame treatment,
Although chromic acid oxidation treatment, ozone treatment, etc. can be used, plasma treatment, particularly plasma treatment in the presence of a hydrophilic group-containing monomer, is excellent in terms of durability of effect and prevention of odor of contents. There is. On the other hand, the operation of hydrophilic treatment is easy,
The corona discharge treatment is superior in that the cost is low.

According to the present invention, when the innermost surface of the thermoplastic resin layer constituting the inner surface of the container is subjected to the hydrophilic treatment, even if the hydrophilic layer formed is an ultrathin layer limited to the very surface. ,
A remarkable and continuous odor preventing effect can be obtained. "FIG. 2" shows a high-density polyethylene container filled with model water containing 250 ppm of d-limonene and 0.3% of sugar ester as a content, and an untreated one and an acrylic acid graft plasma treatment were carried out. 3 is a plot of the relationship between the time and the amount of d-limonene remaining in the contents for each product. From this figure, in the case of the acrylic acid graft treatment, d
-It is clear that the adsorption of limonene is significantly suppressed. In addition, it is also clear that this graft-treated product continues to have an odor preventing effect for several weeks, which is the shelf life of the plastic container package.

In the method for preventing odor of a packaging container of the present invention,
The reason why the hydrophilic treatment layer is an ultra-thin layer of the order of hundreds to thousands of angstroms or less, but a significant and sustained odor preventing effect is obtained is that this layer absorbs or absorbs lipophilic substances. Not only because it forms a barrier with a high potential, but this hydrophilic layer adsorbs water molecules to form multiple layers, and this multiple layer acts as a barrier against the adsorption or absorption of lipophilic substances. Probably because it is working. Further, in the graft plasma treatment, the hydrophilic group is present in the form of a chemically stable monomer, and this monomer is firmly graft-bonded to the main chain or side chain of the thermoplastic resin, And the graft bond of the hydrophilic monomer to the thermoplastic resin is selectively and intensively formed on the very surface of the resin to form a high potential barrier against adsorption or absorption of the lipophilic substance. Therefore, it is considered that more excellent effects can be obtained.

[0025]

Preferred Embodiment of the Invention

Thermoplastic Resin and Container The thermoplastic resin used in the container of the present invention has the lipophilicity described above, and specific examples thereof include low-, medium- or high-density polyethylene, linear low density polyethylene, and iso Tactic polypropylene, ethylene-propylene copolymer, polybutene-1, ethylene-butene-1 copolymer, propylene-butene-1 copolymer, ethylene-propylene-butene-1 copolymer, ethylene-vinyl acetate copolymer Examples thereof include olefin resins such as coalesced products, ion-crosslinked olefin copolymers (ionomers) and blends thereof, and further polystyrene, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene such as ABS resin. Examples thereof include resins.

Further, the inner surface of the container may be made of polyester resin, and as the polyester resin, polyester having ethylene terephthalate units as a main component is used. 80 mol% or more, especially 90 mol% of the acid component
A polyester in which the above is the terephthalic acid component and 80 mol% or more, particularly 90 mol% or more of the diol component is the ethylene glycol component is suitable. Polyethylene terephthalate is most preferred, but modified copolyesters within the scope of not losing the essence of polyethylene terephthalate can also be used, for example isophthalic acid, P-β-
Oxyethoxybenzoic acid, naphthalene 2,6-dicarboxylic acid, diphenoxyethane-4,4'-dicarboxylic acid,
Dicarboxylic acid components such as 5-sodium sulfoisophthalic acid, adipic acid, sebacic acid or their alkyl ester derivatives, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexylene glycol, cyclohexanedimethanol A copolyester containing a glycol component such as an ethylene oxide adduct of bisphenol A may also be used.

The above-mentioned thermoplastic resin is formed into a packaging container either alone or in combination with other container forming materials. Of course, the inner surface layer of this container must be formed of the above-mentioned thermoplastic resin. For example, the above resin is subjected to a T-die method or an inflation film forming method to form a packaging film or a container molding sheet. The thickness and processing method of the film may be ordinary ones. Moreover, a parison for blow molding is formed by extruding this resin through a circular die.
A bag-shaped or pouch-shaped container is obtained by bag-making the film, and a plastic container is formed by subjecting the sheet to vacuum forming, pressure forming, plug assist forming, or the like,
A bottle-shaped plastic container is formed by blow molding or stretch blow molding the parison.

In extrusion molding, the olefin resin layer or styrene resin layer is used as an inner layer or an inner or outer layer,
A multi-layer film or a multi-layer plastic container is formed by co-extruding a gas barrier resin known per se as an intermediate layer. As the gas barrier resin, an ethylene-vinyl alcohol copolymer, for example, an ethylene-vinyl acetate copolymer having an ethylene content of 20 to 60 mol%, particularly 25 to 50 mol%, and a saponification degree of 96 mol% are used.
Above, especially saponified copolymer obtained by saponification to be 99 mol% or more, and polyamides having 5 to 50, especially 6 to 20, amide groups per 100 carbon atoms For example, nylon 6, nylon 6,6, nylon 6 / 6,6 copolymer, metaxylylene adipamide, nylon 6,10, nylon 11, nylon 12,
Nylon 13 or the like is used.

A preformed water-resistant thermoplastic resin film or sheet and another resin film, a metal foil or sheet, or a combination thereof are used in a known method such as sandwich lamination, dry lamination or extrusion coating. By applying the means, a multilayer film or a laminate for forming a multilayer container can be obtained. The metal foil or sheet may be various surface-treated steel plates or foils or aluminum plates or foils.

According to the present invention, according to the present invention, the container or the container-forming inner surface member has a water contact angle of 9/10 or less, particularly 7 / The hydrophilic treatment is performed so that the ratio becomes 10 or less.

The hydrophilic treatment is not particularly limited as long as the contact angle of water is within the above range,
From the viewpoint of ease of treatment, plasma treatment, corona treatment, glow discharge treatment, flame treatment, chromic acid oxidation treatment, ozone treatment, etc. are suitable.

Although these treatments are publicly known as treatment means themselves, these treatment means themselves are performed as a pretreatment for painting or pre-adhesion of plastics. To be done for, and in that the processing surface itself is directly exposed in the content,
The purpose and composition are completely different. These processes will be described below.

The plasma treatment is a method of treating a container or an inner surface member for forming the container by a chemical reaction with plasma of the gas in a gas atmosphere having a low pressure. As the gas atmosphere, a gas atmosphere of about 0.1 to 1.0 Torr is generally used. As the processing gas, in addition to an inert gas such as oxygen or argon, a vapor of a polar group-containing monomer described later can be mentioned. The treatment time is only a few seconds to about 1 minute, and it is characterized by its great effect. In particular, a method of forming an ultrathin layer of a hydrophilic polymer by grafting by polar polymerization of a polar group-containing monomer In, the effect is outstanding and the sustainability is excellent.

In the present invention, the hydrophilic group-containing monomer for forming the ultrathin layer on the innermost surface of the packaging container can be graft-polymerized on the thermoplastic resin layer serving as a substrate, Any hydrophilic group-containing monomer capable of forming a stable ultra-thin layer is used. This hydrophilic group-containing monomer is
It has a polymerizable carbon-carbon double bond and a hydrophilic group such as an anionic, cationic, amphoteric or nonionic group, and has the formula:

[0035]

X- (Y) n In the formula, X is a hydrocarbon group containing an ethylenic double bond, for example, a vinyl group, a vinylidene group or a hydrocarbon group containing a vinylene group, and Y contains a hydrophilic group. Is a monovalent or divalent organic group, and n is a number of 1 or 2,

It is represented by Suitable examples of the hydrophilic group include a nonionic group such as a hydroxyl group, an ether group and an ester group;
As the anionic group, a carboxyl group (including an acid anhydride group), a sulfonic acid group, a phosphonic acid group, or a group of these salts, etc .; as a cationic group, primary, secondary or tertiary
Primary amino groups, quaternary ammonium groups, hydrazino groups, guanidino groups, etc .; amphoteric groups include betaine-type groups and the like.

Suitable examples of monomers are as follows: Hydroxyl group-containing monomer; Hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate and other hydroxy group-containing acrylic monomer ;, Monovalent unsaturation of allyl alcohol, crotyl alcohol, pentenol, hexenol, cyclohexenol Alcohol; pentadienol, hexadienol, propargyl alcohol, propene diol, butenediol, pentene diol,
Unsaturated glycols such as hexene diol, cyclohexene diol and hexadiene diol; and trivalent or higher polyunsaturated alcohols such as pentenetriol, hexentriol and cyclohexent riol; hydroxystyrene, dihydroxystyrene, hydroxycinnamic alcohol, dihydroxycinnamic alcohol Compounds containing an aromatic hydroxyl group such as.

Monomers containing ether groups; vinyl ether compounds such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether; ether derivatives of trimethoxypropenylbenzene and the above alcohols; unsaturated carboxylic acid esters or unsaturated of polyethylene glycol or polypropylene glycol. Alcohol ether etc.

Carboxyl group-containing monomer; acrylic acid,
Unsaturated monobasic carboxylic acids such as methacrylic acid, crotonic acid, isocrotonic acid propiolic acid cinnamic acid, itaconic acid,
Unsaturated dibasic carboxylic acids such as citraconic acid, fumaric acid, maleic acid, maleic anhydride, carboxycinnamic acid;
And unsaturated polybasic carboxylic acids such as aconitic acid and vinyl trimellitic acid.

Sulfonic acid group-containing monomer; sulfonic acids such as vinylbenzenesulfonic acid, divinylbenzenesulfonic acid and vinylsulfonic acid and salts thereof.

Monomers containing phosphonic acid groups; vinylbenzene phosphonic acid and the like.

Amino group- and ammonium group-containing monomer;
Aminoethyl (meth) acrylate, aminopropyl (meth) acrylate, N-aminoethyl-aminoethyl (meth) acrylate and the like.

Among these, the carboxyl group-containing monomer is particularly preferable for the purpose of the present invention because it is easy to graft and has an excellent odor preventing effect. Suitable monomers are acrylic acid, methacrylic acid, maleic anhydride. Further, if desired, a plurality of types of monomers may be used in combination, and a crosslinkable monomer such as divinylbenzene may be used in combination in order to enhance the durability of the graft polymerization layer.

The method of graft-polymerizing the hydrophilic group-containing monomer onto the innermost surface of the packaging container of the present invention or onto the material to be the innermost surface of the packaging container is not limited to the plasma polymerization method, but is a radiation polymerization method. , An ultraviolet polymerization method or the like can be used, and in any of these cases, it is a remarkable feature that an ultrathin layer of the graft polymer is formed. Graft polymerization is
The process proceeds via the polymer radicals formed in the polymer chains that form the innermost surface of the container, but first the polymer radicals are generated, then the monomer is introduced and polymerization is performed, and the post-polymerization method There is a simultaneous polymerization method in which the monomers are polymerized at the same time as the formation, and any of them is used for this purpose. Further, there are a gas phase polymerization method in which a monomer and a resin surface layer are brought into contact with each other in a gas phase, and a liquid phase method in which a monomer is brought into contact with a liquid layer, both of which are used for the purpose of the present invention. The gas phase method is advantageous in that it has no steps and is easy to process. In the present invention, since the formation of the graft layer may be an ultrathin layer, it is an advantage of the present invention that a packaging container having a sufficient odor preventing effect can be produced even by a gas phase method.

In the case of the plasma treatment method, there are glow discharge or high frequency corona discharge treatment depending on the means for generating plasma, and for activation of the surface, high temperature plasma is formed by using arc discharge or the like to form a jet. Plasma jet treatment to treat the resin surface with plasma, plasma contact treatment (CASING treatment) using excited inert gas (A, He, N ₂ ) in plasma, ions to accelerate ions or cluster ions to hit the resin surface Beam processing or the like is used. Also, as the simultaneous polymerization method, a method of forming a graft polymerized film by directly converting the monomer into plasma and forming a graft polymerized film on the resin surface, or a method of putting the monomer in a carrier gas in a plasma state and exciting it to form a graft polymerized film To be done.

The plasma treatment may be carried out by filling a container or a container forming material such as a film or a laminated body in a pressure resistant container (pressure reducing device). In the case of a film or a laminate, if these are filled in the form of a roll, and the treatment is performed while rewinding and winding, a considerably large amount of treatment can be performed in one operation.

In the case of the radiation polymerization method, a monomer adsorption layer or a thin coating layer is formed on the resin surface, and an electron beam, X-
There is used a method of irradiating ionizing radiation such as rays or γ-rays, or a post-polymerization method in which the resin surface is first irradiated with radiation and then brought into contact with a gas phase or liquid phase monomer. In the latter post-polymerization method, irradiation is carried out in a vacuum or an inert atmosphere to utilize the trapped polymer radicals, or irradiation is carried out in the air to once form a peroxide, and the peroxide is decomposed. A method of carrying out polymerization or the like is adopted. The radiation polymerization treatment is suitable for continuous treatment. For example, the polymerization treatment can be performed by using an electro curtain or the like while moving the container by placing it on a carrier device or continuously flowing the material.

Also in the case of the ultraviolet polymerization method, the simultaneous irradiation polymerization method and the pre-irradiation and post-polymerization method are used as in the radiation polymerization method. A combination of relatively long wavelength ultraviolet light and a photoinitiator may be used to generate the polymer radicals, or short wavelength ultraviolet light such as 253.7 nm or 184.9.
nm UV light may be used to effect the generation of polymer radicals without the use of photoinitiators. The ultraviolet polymerization method can also be carried out according to the radiation polymerization method.

In the present invention, when a graft-polymerized layer of a monomer having a hydrophilic group is formed, this layer is an ultrathin layer extremely limited to the inner surface of the resin, and the thickness of the hydrophilic group-containing layer is Although not particularly critical, it is usually 10 ⁻³ μm to 1
The thickness is about 0 μm. For the purpose of preventing odor, it is not necessary to make the film thickness of the thin layer so thick, but if it is too thick, there is a disadvantage that the flexibility and toughness of the hydrophilic base layer are impaired.
The hydrophilic group concentration of the innermost surface ultrathin layer is in the range of 0.1 to 25 mmol / 100 g of resin, preferably 0.2 to 10 mmol / 100 g. When the hydrophilic group concentration of the surface layer is lower than the above lower limit, odor cannot be sufficiently prevented and the effect of the present invention cannot be exhibited. On the other hand, even if the hydrophilic group concentration is higher than the above upper limit, the odor preventing effect is hardly changed, and rather the flexibility and toughness of the thin film layer are lost, which is not preferable. In the present invention, the thickness and hydrophilic group concentration of the hydrophilic group-containing ultrathin layer can be determined by a method known per se. For example, the concentration of hydrophilic groups can be measured by reflection infrared absorption spectrum (FTIR), and the chemical composition and thickness can be measured by X-ray photoelectron spectrum (ESCA).

In the present invention, since the grafting of the hydrophilic group-containing monomer may be performed by forming an ultrathin layer, plasma,
Irradiation with radiation, ultraviolet rays, etc. is sufficient even with an extremely small dose, and generally, an energy of about 5 to 500 jewels per unit area (1 dm ² ) is sufficient. Further, a short polymerization time of about 2 to 120 seconds is sufficient.

In the case of the gas phase polymerization method, the post-treatment after the polymerization treatment is not particularly required, and at most exhausting treatment and spraying with clean air are sufficient. Further, in the liquid phase polymerization method, it is sufficient to carry out simple water washing treatment and steam washing treatment. Other significant advantages of the surface graft polymerization method of the present invention are:
The surface of the packaging container is sterilized at the same time, therefore
The container after the grafting process can be used as an aseptic filling container (aseptic sterilization container) without any special sterilization treatment.

The corona treatment is a treatment method suitable for treatment of film or laminate, and a gap is formed between the electrode and the film or sheet supporting roll, and a high voltage is applied between the two to make a gap between them. Is a method of chemically modifying the resin surface by this discharge. It is considered that the carbonyl group (= CO) generated on the resin surface effectively acts on the hydrophilicity. The applied voltage should be as high as possible within the range where the resin layer does not cause discharge breakdown.
Minus corona is effective. Although this treatment method is easy to operate and easy to treat, it is generally effective for products with a short shelf life, although the effect is generally not persistent.

The flame (flame) treatment is a chemical treatment utilizing an oxidative flame, and using a special burner or nozzle,
Hydrophilic treatment is performed by applying an oxidizing flame of a gas containing excess air to the surface of the material for a short time. The temperature of the oxidizing flame is generally in the range of about 1000 to 2500 ° C., and the contact time is around 10 seconds. This method requires cooling from the back side, and the problem of thermal deformation must be taken into consideration.

The chromic acid oxidation treatment is a wet treatment method in which a sulfuric acid-chromic acid mixture is brought into contact with a material or a container to form a hydrophilic group such as a carbonyl group on the surface thereof. A typical composition is concentrated sulfuric acid 35 to 99.
Parts, potassium dichromate 1 to 15 parts and water 0 to 50
It is composed of parts (total of 100 parts). This method is effective, but has the drawback that it requires washing and drying.

The ozone treatment is a method of treating a container or a container forming material in an ozone atmosphere. In recent years, improvements in the ozone generator have made it possible to produce ozone-containing gas or ozone water having a considerably high concentration. By using these, a hydrophilic group such as a carbonyl group can be effectively produced within a short time. In the case of ozone-containing gas, a concentration of about 2 to 2 × 10 ⁵ PPM is effective, while in the case of ozone water, a concentration of about 2 to 70 PPM is effective. An ultraviolet ray treatment using a single wavelength ultraviolet ray having a wavelength of 253.7 nm or 184.9 nm has the same effect as the ozone treatment. These ultraviolet rays actually generate ozone in the air and also have a large degree of chemical activation.

The glow discharge treatment has been explained in detail in the plasma treatment, but there is also a means of utilizing the sputtering by the cathode constituent material knocked out by the impact of the positive ions generated by the low pressure glow discharge.

According to the present invention, although the inner surface layer is formed of a plastic material having excellent hygienic properties, the aroma component, flavor component, pigment or other useful trace amount contained in the content can be obtained by simple means. It is possible to suppress the adsorption and absorption tendency of the components to the inner surface layer, and also suppress the adsorption tendency of the odorous component before filling the contents, and as a result, it is possible to remarkably improve the flavor retention of the substance inside the package. Become.

In the present invention, any means known per se can be used for filling and sterilizing the contents in the container. For example, an aseptic filling method, in which a container that has been sterilized in advance is sterilized by high-temperature short-time heat sterilization by heat exchange treatment and then rapidly cooled, is used in a sterile atmosphere, is advantageously used in terms of flavor retention. To be done. Of course, when the container has sufficient heat resistance, a hot filling method, a pasteurization method, a retort sterilization method, or the like is used.

[0059]

The present invention will be described in more detail by the following examples.

Example 1 A HDPE / aluminum foil / PET multilayer film was prepared by using a high-density polyethylene (HDPE) having a contact angle to water of 90 ° with a urethane-based adhesive to prepare HDP.
The discharge voltage was 300 V on the E side and the treatment time was 28 sec. Corona discharge treatment was not performed, and the contact angle with water was 45 °. Using this material, a heat-sealed bag (150 × 110 mm) whose inner surface side is a corona-treated HDPE surface was prepared. Into this bag, 200 ml of a model liquid in which 250 ppm of d-limonene was dispersed in a 0.03% sugar ester aqueous solution was filled, and hermetically sealed so that no air remained. It was stored at 25 ° C, and the distribution ratio was measured at regular intervals.

[0061]

[Equation 5]

The same experiment was conducted using a bag having no inner corona treatment as a control product. The results are shown in Table 1.

[0063]

[Table 1]

As is clear from the results, the corona-treated film has a smaller distribution ratio and less odor of the film.

Example 2 An organic coated steel sheet was obtained by thermally laminating a biaxially stretched polyethylene terephthalate film having a thickness of 25 μm on both sides of an electrolytic chromic acid treated steel sheet having a thickness of 0.15 mm and immediately cooling with water. At the final stage of this coating process, one surface of the coated steel sheet was subjected to a corona discharge treatment with a discharge voltage of 300 V and a treatment time of 2.4 sec. The water contact angle of the film before corona treatment is 80 °, and the contact angle after treatment is 53 °.
Met. Palm oil was thinly applied to this coated metal plate, and a can body was prepared by a two-step drawing method so that the corona-treated surface was on the inside. Further, trimming and flanging were performed on the edge portion of the opening to prepare a squeezed can having a diameter of 65 mm and a height of 37 mm. This can was filled with a model solution containing the following fragrance components, and was wound and sealed by a usual method. 37
The adsorption rate of the film when stored at 8 ° C. for 8 weeks was measured. The same test was performed using a can body molded without corona treatment as a control product. The results are shown in Table 2.

Aroma-containing model liquid: sugar ester 0.
01%, ethanol 1% Aqueous solution containing the following aroma components of 10 ppm each. Aroma compounds: octanal, d-limonene, p-cymene, r-terpinene, pinene, α-terpineol, linalool.

[0067]

[Table 2]

From this result, although the adsorption amount may be slightly increased depending on the compound by the corona treatment, the total adsorption amount can be suppressed to 1/2 or less.

Example 3 The laminated film of Example 1 was subjected to glow discharge treatment under a reduced pressure of 1 Torr in an atmosphere of 100 Torr for 30 seconds, and then a certain amount of acrylic acid was poured into the HDPE surface while maintaining the reduced pressure. The group was grafted. The contact angle of HDPE before treatment with water was 91 °, and the contact angle after grafting with acrylic acid was 33 °. A bag was made using the multilayer film before and after this treatment so that the inner surface side became HDPE, and 200 ml of a 0.03% sugar ester aqueous solution containing 250 ppm of d-limonene was filled and sealed. The amount transferred into the film and the amount remaining in the liquid were measured at regular intervals. The results are shown in Table 3.

[0070]

[Table 3] It clearly shows the treatment effect.

Example 4 Polystyrene resin / adhesive / aluminum foil / adhesive / PET
A multilayer film consisting of 20 under a reduced pressure of 0.5 Torr.
Glow discharge was performed at 0 mA for 30 seconds. The contact angle of polystyrene with water before glow discharge is 96 °,
It was 43 ° after discharge. The test was conducted using the same contents as in Example 3. As a result, the same effect as in Example 3 was recognized.

[0072]

According to the present invention, the thermoplastic resin which constitutes at least the inner surface of the container and which is exposed to the contents, is graft-polymerized in the form of an ultra-thin layer of, for example, a hydrophilic group-containing monomer. By hydrophilizing by means such as, the inner surface layer is formed of a plastic material having excellent hygienic properties, while aroma components, flavor components, pigments or other useful trace components contained in the content It is possible to suppress the adsorption and absorption tendency to the inner surface layer, and to suppress the adsorption tendency of the odorous component before filling the contents, and as a result, it is possible to remarkably improve the flavor retention of the contents in the package. ..

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a contact angle of water and a distribution ratio of d-limonene for various resins.

FIG. 2 shows a high density polyethylene container filled with model water containing 250 ppm of d-limonene and 0.3% of sugar ester, which is untreated,
(Acrylic acid graft treatment) FIG. 7 is a diagram plotting the relationship between the time and the amount of d-limonene remaining in the contents of the plasma-treated one.

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Claims (8)

[Claims] 1. At the time of hermetically packaging using a container in which at least the inner surface is made of a water-resistant thermoplastic resin, the water-resistant thermoplastic resin has a contact angle of water on the innermost surface which is untreated. A method for preventing odor from a hermetically sealed packaging container, which comprises using a material that has been subjected to a hydrophilic treatment so as to have a corner of 9/10 or less. 2. The odor preventing method for a hermetically sealed container according to claim 1, wherein the water resistant thermoplastic resin on the inner surface is polyolefin, polystyrene resin, polyester resin or other water insoluble polymer. 3. The odor preventing method for a hermetically sealed container according to claim 2, wherein the polyolefin is a polymer of polyethylene, polypropylene, polybutene-1, polymethylpentene-1, or a copolymer containing them as a main component. 4. The method for preventing odor from a hermetically sealed container according to claim 2, wherein the polyester resin is a copolymer of a dihydric alcohol, a dibasic acid and an esterified product thereof. 5. The polystyrene resin is a copolymer with polystyrene or an olefin monomer.
A method for preventing odor from a sealed container as described. 6. The odor preventing method for a hermetically sealed container according to claim 1, wherein the hydrophilic treatment of the innermost surface is performed by plasma treatment, corona treatment, glow discharge treatment, flame treatment, chromic acid oxidation treatment or ozone treatment. 7. The method for preventing odor from a hermetically sealed container according to claim 6, wherein the glow discharge treatment is performed by a grafting treatment using a hydrophilic group-containing monomer. 8. The hydrophilic group is selected from the group consisting of a hydroxyl group; an ether group; an amino group; a carbonyl group derived from a carboxylic acid or salt, its anhydride, ester or amide; and a sulfonic acid or its salt group. The method for preventing odor from a hermetically sealed container according to claim 7, wherein the method is at least one group.