JPH10114371A - Oxygen-absorbing multi-layer plastic container excellent in preservability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the decrease of preservability of fragrance and flavour resulting from elution of an oxygen-absorbent or oxidized products thereof, and retain the preservability of the contents and fragrance and flavour for a long time. SOLUTION: Thermoplastic resin layers in which an oxygen-absorbent is not yet mixed, are laminated at both sides of a thermoplastic resin layer containing an oxygen-absorbent to constitute this container. In this case, the resin matrix of the thermoplastic resin layers containing an oxygen-absorbent is constituted of a blended substance of a plurality of substantially incompatible thermoplastic resins or elastomers, the incompatible thermoplastic resins or elastomers are unevenly distributed in the resin matrix.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer plastic container excellent in preservation of contents and flavor retention over a long period of time, and more particularly, to a multilayer plastic container using an oxygen absorbent. The present invention relates to a plastic multilayer container that suppresses a decrease in flavor retention due to dissolution of an agent or an oxidation product thereof and achieves long-term content storage stability and flavor retention.

[0002]

2. Description of the Related Art Conventionally, metal cans, glass bottles, various plastic containers, and the like have been used as packaging containers. However, plastic containers have been used for various purposes in terms of lightness, impact resistance, and cost. I have.

However, while oxygen permeation through the container wall is zero in metal cans and glass bottles, oxygen permeation through the container wall occurs in a non-negligible order in the case of plastic containers, and the storage of the contents is It is a problem in terms of gender.

In order to prevent this, in a plastic container, the container wall has a multilayer structure, and at least one of the layers is made of an oxygen-permeable resin such as an ethylene-vinyl alcohol copolymer. I have.

[0005] An oxygen absorber has been used for a long time to remove oxygen in a container. An example of applying the oxygen absorber to a container wall is disclosed in Japanese Patent Publication No. 62-1824. According to this method, a layer formed by mixing an oxygen absorbent containing a reducing substance as a main component in a resin having oxygen permeability and a layer having oxygen gas barrier properties are laminated to form a multilayer structure for packaging.

As an oxygen absorbent, iron-based ones have a high oxygen absorption rate and a large absorption capacity and are excellent in cost, but when iron and its compounds are eluted in the contents,
Even if the amount is very small, there is a problem that the flavor retention of the contents is impaired.

[0007] In order to prevent the elution of the iron-based oxygen absorber into the contents, for example, as described in Japanese Patent Application Laid-Open No. HEI 9 (1994) -1999, the inner and outer surfaces of a resin layer containing the iron-based oxygen absorber are mixed. Means for sandwiching a resin layer containing no oxygen absorbent to prevent exposure of the iron-based oxygen absorbent is also employed.

[0008]

However, simply sandwiching a thermoplastic resin layer not containing an oxygen absorbent on both sides of a thermoplastic resin blend layer containing an iron-based oxygen absorbent may cause the content of iron or its compound. It was found that it was insufficient to prevent elution into the substance.

That is, it is assumed that the iron-based oxygen absorbent in the blend layer is completely covered with the thermoplastic resin layer not containing the oxygen absorbent while the number of days elapsed since the production of the multilayer plastic container is small. However, when the storage period of the multilayer plastic container is prolonged, the iron-based oxygen absorbent particles may break through the thermoplastic resin coating layer and be exposed outside the coating layer. When such breakthrough occurs, the oxygen absorbent is eluted into the content, and the flavor is reduced by factors other than oxygen.

The present inventors have conducted intensive studies on the cause, and as a result, in the oxygen-absorbing multilayer plastic container that has been stored for a long period of time, the oxygen-absorbing agent is reacted with oxygen, such as an iron-based oxygen-absorbing plastic container. It has been found that particles of the oxidized product grow or increase in volume, and accordingly, the thermoplastic resin protective layer breaks through.

Accordingly, an object of the present invention is to eliminate the above-mentioned disadvantages in the conventional oxygen-absorbing multilayer plastic container,
It is an object of the present invention to provide an oxygen-absorbing multilayer plastic container capable of suppressing a decrease in flavor retention due to elution of an oxygen absorber or an oxidation product thereof and achieving long-term content preservation and flavor retention.

Another object of the present invention is to ensure that a thermoplastic resin coating layer provided on a blend of a thermoplastic resin and an oxygen absorbent is maintained in a completely coated state even during long-term storage. Another object of the present invention is to provide an oxygen-absorbing multilayer plastic container.

[0013]

According to the present invention, there is provided an oxygen-absorbing multilayer plastic container comprising, on both sides of an oxygen-absorbing thermoplastic resin layer, a thermoplastic resin layer containing no oxygen absorbing agent. The resin matrix of the oxygen absorbent-containing thermoplastic resin layer comprises a blend of a plurality of substantially incompatible thermoplastic resins or elastomers, and the incompatible thermoplastic resin or elastomer has a non-uniform distribution structure in the resin matrix. An oxygen-absorbing multilayer plastic container characterized by being present in the following manner is provided.

In the present invention: 1. the non-uniform distribution structure is a layered distribution structure; 2. One of the incompatible thermoplastic resins or elastomers is a propylene-based polymer and the other is an ethylene-based polymer; 3. The blend contains a propylene-based polymer and an ethylene-based polymer in a weight ratio of 100: 1 to 1: 1, especially 50: 1 to 3: 2. 4. the oxygen absorbent is an iron-based oxygen absorbent; It is preferable that the oxygen absorbent is blended in an amount of 1 to 50% by weight, particularly 10 to 40% by weight based on the blend.

[0015]

The oxygen-absorbing multi-layer plastic container to which the present invention is directed is formed by laminating a thermoplastic resin layer containing no oxygen absorbent on both sides of a thermoplastic resin layer containing an oxygen absorbent. The resin matrix of the absorbent-containing thermoplastic resin layer comprises a blend of a plurality of substantially incompatible thermoplastic resins or elastomers, wherein the incompatible thermoplastic resin or elastomer has a non-uniform distribution structure in the resin matrix, In particular, it is characterized by being present in a multilayer distribution structure, whereby the volume expansion of the particles due to the reaction between the oxygen absorbent and oxygen is absorbed in the oxygen absorbent-containing thermoplastic resin layer, and Destruction of the blended thermoplastic resin coating layer can be prevented.

The volume expansion of the particles due to the reaction between the oxygen absorbent and oxygen is very large. For example, when metal iron particles completely react with oxygen to form iron sesquioxide (Fe ₂ O ₃ ), the iron density becomes 7.86 g / cm ^3. , The density of iron sesquioxide is 5.1 g / cm ³ And the volume is about 2.2
Inflates to double. The resin matrix of the conventional oxygen absorbent-containing resin layer has a rigid structure,
The volume expansion of the dispersed particles composed of the oxygen absorbent or its oxidation product acts to cause these dispersed particles to protrude out of the resin matrix, that is, to penetrate the coating resin layer. In particular, the resin coating layer provided on the inner surface of the container is thinly provided so as to be able to effectively absorb the residual oxygen in the container. Elution occurs.

On the other hand, according to the present invention, the thermoplastic resin in which the oxygen absorbent is dispersed is formed from a blend of a plurality of substantially incompatible thermoplastic resins or elastomers. Or that the elastomer forms a non-uniform distribution structure in the matrix, in particular a multilayer distribution structure. That is, a blend of a plurality of substantially incompatible thermoplastic resins, when melt-molded, is a multilayer in which each component is distributed in layers, each layer overlaps in the thickness direction, and each layer extends in the plane direction. Take the distribution structure. In this matrix structure, when a particle composed of an oxygen absorbent or its oxidation reaction product undergoes volume expansion, separation at an interface of a non-uniform distribution structure, particularly a multilayer distribution structure, and formation of a minute space (gap) between the interfaces. Then, the volume expansion of the particles composed of the oxygen absorbent or its oxidation reaction product is absorbed by the minute space, and the destruction of the resin coating layer is prevented.

In the present invention, it is preferable that one of the above-mentioned incompatible thermoplastic resins and elastomers, in particular, the main component is a propylene polymer and the other (a small amount) is an ethylene polymer. This combination is a general-purpose resin, and gives a combination excellent in phase separation without adversely affecting the moldability and mechanical properties of the resin. Further, in this combination, since the ethylene polymer has a lower melting point than the propylene polymer, an advantage that a fine non-uniform distribution structure can be formed is also provided.

[Multilayer Structure of Container] The oxygen-absorbing multilayer plastic container of the present invention comprises an oxygen-absorbing thermoplastic resin layer and, on both sides, a thermoplastic resin layer containing no oxygen-absorbing agent. Any layer structure can be adopted as long as the resin matrix of the absorbent-containing thermoplastic resin layer is composed of a blend of a plurality of substantially incompatible thermoplastic resins or elastomers.

FIG. 1 shows an example of the multilayer structure of the container of the present invention.
In this case, the container wall 1 comprises an outer layer 2 of a moisture-resistant thermoplastic resin, an adhesive resin layer 3a, a first intermediate layer 4 made of a gas barrier resin, an adhesive resin layer 3b, and a resin composition containing an oxygen absorbent. A second intermediate layer 5 made of a material and an inner layer 6 of a moisture-resistant thermoplastic resin. The second intermediate layer comprises a thermoplastic resin layer containing an oxygen absorbent, and the thermoplastic resin comprises a plurality of substantially incompatible thermoplastic resins or elastomers. It should be noted that the second intermediate layer is provided inside the gas barrier resin layer 4.

In FIG. 2, which shows another example of the multilayer structure of the container of the present invention, the container wall 1 has a first layer made of an outer layer 2 of a moisture-resistant thermoplastic resin, an adhesive resin layer 3a, and a gas barrier resin. An intermediate layer 4, an adhesive resin layer 3b, a second intermediate layer 5 made of a resin composition containing an oxygen absorbent, a third intermediate layer 7 made of a resin composition containing an adsorbent deodorant, and moisture resistance. It comprises an inner layer 6 of a thermoplastic resin. The oxygen absorbent and the adsorptive deodorant are separately compounded in the second intermediate layer 5 and the third intermediate layer 7, respectively, and from the outside in order, the gas barrier resin layer 4, the oxygen absorbent layer 5, and the adsorbent. Deodorant layer 7
It will be understood that.

[Oxygen Absorbent] As the oxygen absorbent used in the present invention, any oxygen absorbent conventionally used for this type of application can be used, but generally, it is reducing and substantially insoluble in water. Suitable examples thereof include metal powders having a reducing property, such as reducing iron, reducing zinc, and reducing tin powder; low metal oxides such as ferrous oxide, iron sesquioxide, and further reducing powders. Metal compounds such as iron carbide, silicon iron, iron carbonyl, iron hydroxide; and the like, as the main component, may be used. Compounds, carbonates, sulfites, thiosulfates, tertiary phosphates, secondary phosphates, organic acid salts, halides and the like. Further, a high molecular compound having a polyhydric phenol in the skeleton, for example, a phenol-aldehyde resin containing a polyhydric phenol may be used. These oxygen absorbers generally have an average particle size of 100 μm or less, particularly preferably 50 μm or less. The present invention is particularly preferable in the case of an iron-based oxygen absorbent having a large oxygen absorption rate and capacity, because off-flavor can be effectively prevented.

The oxygen absorbent may be used in combination with a water absorbing agent. Examples of the water absorbing agent include deliquescent inorganic salts, deliquescent organic compounds, and superabsorbent resins. As inorganic salts such as sodium chloride, calcium chloride, zinc chloride, ammonium chloride, ammonium sulfate, sodium sulfate, magnesium sulfate, disodium hydrogen phosphate, sodium diphosphate, potassium carbonate, sodium nitrate; glucose, fructose, sweet pepper, Examples include gelatin, modified casein, modified starch, tragacanth gum, polyvinyl alcohol, CMC, organic compounds such as sodium polyacrylate, sodium alginate, and the like.

The water absorbing agent is preferably used in an amount of 0.1 to 10% by weight, particularly 1 to 5% by weight, based on the oxygen absorbing agent. The water absorbing agent can be used alone or in combination. For example, a combination of an inorganic salt and a polymer water absorbing agent can be used.

[Resin Matrix] As the resin matrix in which the oxygen absorbent is dispersed, a blend of a plurality of thermoplastic resins or elastomers which can be mutually dispersed under melting conditions but are substantially incompatible is used. You.

The thermoplastic resin includes an olefin resin, a thermoplastic polyester resin, a polyamide resin, an acrylic resin, a styrene resin, a vinyl resin, a polycarbonate resin, and the like. These resins can form a film. Should have sufficient molecular territory. The resins to be combined may be the same or different resins as long as the above conditions are satisfied.

[0027] Resins in which an oxygen absorbent is easily incorporated and oxygen is easily permeated are olefin resins. Examples of the olefin resins include low-density polyethylene, medium-density polyethylene, high-density polyethylene, homopolypropylene, and poly-1.
Α-olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene and 4-methyl-1-pentene in addition to olefin homopolymers such as -butene and poly-4-methyl-1-pentene Copolymers of olefins such as random or block copolymers, ethylene-vinyl acetate copolymers, ethylene- (meth) acrylate copolymers, ionomers (ion-crosslinked olefin copolymers), ethylene-vinyl alcohol Copolymer,
Copolymers mainly containing an olefin such as an ethylene / vinyl chloride copolymer and containing other monomers are exemplified.

Further, as the thermoplastic elastomer,
For example, ethylene-propylene rubber (EPR), ethylene-propylene-diene rubber (EPDM), thermoplastic elastomer such as styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, hydrogenated styrene-butadiene-styrene Block copolymer, hydrogenated styrene-isoprene-styrene block copolymer, hydrogenated butadiene-isoprene block copolymer, nitrile-butadiene rubber (NB
R), styrene-butadiene rubber (SBR), chloroprene rubber (CR), polybutadiene (BR), polyisoprene (IIB), butyl rubber, natural rubber, thermoplastic polyurethane, silicone rubber, acrylic rubber, and the like. Among them, hydrocarbon elastomers,
In particular, EPR and EPDM are preferred.

In the present invention, combinations of thermoplastic resins and elastomers which are incompatible with each other are not limited to these, but are, for example, propylene-based polymers / ethylene-based polymers, polyamide / olefin-based resins, polyamide / styrene-based resins. Resin, polyamide / ABS resin, polyethylene terephthalate / polybutylene terephthalate, polycarbonate / polystyrene resin, polyester resin / olefin resin, polycarbonate / polyester resin and the like.

A resin combination which is easy to disperse and thermoform the oxygen absorbent and is therefore particularly suitable for the purpose of the present invention is a combination of a crystalline propylene polymer and an ethylene polymer. As the crystalline propylene polymer, a random or block copolymer containing 1 to 20% by weight, especially 2 to 15% by weight of ethylene, in addition to homopolypropylene, is used. These polypropylenes may have an isotactic structure or a syndiotactic structure. Examples of the ethylene polymer include high density polyethylene (HDPE), medium density polyethylene (MDPE), and low density polyethylene (LDP).
E), linear low density polyethylene (LLDPE), ethylene and other olefins such as propylene, butene-
1, pentene-1, hexene-1, 4-methylpentene-1, octene-1, decene-1, etc., at least one copolymer, ethylene-vinyl acetate copolymer, ethylene-
An acrylate copolymer, an ionomer and the like can be mentioned.

The ratio of one resin to the other resin in the resin matrix can be varied over a wide range, but the weight ratio is 100: 1 to 1: 1, especially 50:
It is preferably in the range of 1 to 3: 2.

In the resin matrix used in the present invention, a compatibilizer can be blended in order to adjust the degree of dispersion between the resin and the elastomer. A compatibilizer enhances the interaction between different polymers,
A block copolymer or a graft copolymer having the same components as the polymers A and B to be blended; a block copolymer or a graft copolymer having a third component which is molecularly mixed with either one of the polymers A or B to be blended Coalescing; two types of graft copolymers that are compatible only with one of the polymers A and B to be blended;

Focusing on the function of the compatibilizer, there are two types, a non-reactive compatibilizer and a reactive compatibilizer.
Examples of the former include styrene-ethylene-butadiene block copolymer, polyethylene-polymethyl methacrylate block copolymer, polyethylene-polystyrene block copolymer, and the like.Examples of the latter include a maleic anhydride-modified olefin-based resin, Particularly, there are maleic anhydride-grafted polypropylene and polyethylene, styrene-maleic anhydride copolymer, ethylene-glycidyl methacrylate copolymer, ethylene-acrylate ester-maleic anhydride copolymer, styrene-glycidyl methacrylate copolymer and the like.

These compatibilizers can be present in the resin matrix in an amount of 1 to 20% by weight, especially 2 to 10% by weight.

[Resin Composition Containing Oxygen Absorbent] In the present invention, the oxygen absorbent is preferably used in a concentration of 1 to 100 parts by weight per 100 parts by weight of the resin matrix. When the content of the oxygen absorbent is lower than the above range, it is difficult to suppress the oxygen concentration in the container to a concentration or less suitable for the growth of microorganisms. In this respect, there is no particular effect, and it is rather disadvantageous in terms of molding workability and price.

The mixture of the oxygen absorbent and the resin matrix may be a so-called dry blend or a melt blend.
In addition, in order to disperse the oxygen absorbent well, a resin composition (master batch) containing the oxygen absorbent at a high concentration can be produced, and this master batch can be blended with the resin matrix.

[Thermoplastic Resin] In the present invention, as the thermoplastic resin layer provided on both sides of the oxygen-absorbing agent-containing resin layer, a moisture-resistant resin (low water-absorbing resin), particularly ASTM D570
Thermoplastic resins having a water absorption of not more than 0.5%, particularly not more than 0.1%, measured in the above, are suitable. Typical examples are low-, medium-
Alternatively, high-density polyethylene, isotactic polypropylene, ethylene-propylene copolymer, polybutene-1, ethylene-butene-1 copolymer, propylene-butene-1 copolymer, ethylene-propylene-butene-1 copolymer And olefin resins such as ethylene-vinyl acetate copolymers, ion-crosslinked olefin copolymers (ionomers), and blends thereof, and further include polystyrene, styrene-butadiene copolymer, and styrene-isoprene copolymer. It is also possible to use a styrene resin such as coalesced or ABS resin, a thermoplastic polyester such as polyethylene phthalate or polytetramethylene terephthalate, or a polycarbonate. Of these,
From the viewpoint of hygiene, olefin-based resins are preferred, and from the viewpoint of heat resistance, propylene-based resins are preferred.

[Gas Barrier Resin] As the gas barrier resin optionally used in the container of the present invention, a thermoplastic resin having a low oxygen permeability coefficient and thermoformable is used. The most suitable example of the gas barrier resin is 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%. A saponified copolymer obtained by saponifying a polymer so as to have a saponification degree of 96 mol% or more, particularly 99 mol% or more is used. The saponified ethylene-vinyl alcohol copolymer should have a molecular weight sufficient to form a film and generally has a phenol: water weight ratio of 8%.
It is desirable to have a viscosity of at least 0.01 dL / g, particularly at least 0.05 dL / g, measured at 30 ° C. in a 5:15 mixed solvent.

Other examples of the gas barrier resin having the above-mentioned properties include polyamides having 5 to 50, especially 6 to 20, amide groups per 100 carbon atoms; 6, nylon 6,6, nylon 6 / 6,6 copolymer, metaxylylene adipamide, nylon 6,10, nylon 11, nylon 12, nylon 13, and the like. These polyamides should also have a molecular weight sufficient to form a film, and
It is desirable that the relative viscosity (ηrel) measured at a concentration of 1.0 g / dL and a temperature of 30 ° C. is 1.1 or more, particularly 1.5 or more. In addition, as shown in FIG. 1, these gas barrier resins can be provided so as to be adjacent to the resin layer containing the oxygen absorbent.

[Adhesive Resin] As in the case of an ethylene-vinyl alcohol copolymer, sufficient adhesiveness may not be obtained between the used gas barrier resin and the moisture-resistant thermoplastic resin during lamination. However, in this case, an adhesive resin layer is interposed between the two.

Examples of such an adhesive resin include carboxylic acid, carboxylic anhydride, and carboxylic acid. In the main chain or side chain, from 1 to 700 milliequivalent (meq) / 100 g resin, especially from 10 to 500 meq / 10
A thermoplastic resin contained at a concentration of 0 g resin is exemplified.
Suitable examples of the adhesive resin include ethylene-acrylic acid copolymer, ion-crosslinked olefin copolymer, maleic anhydride-grafted polyethylene, maleic anhydride-grafted polypropylene, acrylic acid-grafted polyolefin, ethylene-vinyl acetate copolymer, copolymer One or a combination of two or more such as a polymerized polyester and a copolymerized polyamide. These resins are useful for lamination by coextrusion or sandwich lamination. In addition, a thermosetting adhesive resin such as an isocyanate-based or epoxy-based resin is used for bonding and laminating the gas barrier resin film and the moisture-resistant resin film formed in advance.

[Laminated Structure] The oxygen-absorbing agent-containing resin layer is generally 10 to 200 μm, particularly 20 to 150 μm, although it varies depending on the amount of oxygen allowed in the container and the shape of the container.
It is desirable to have a thickness of m.

On the other hand, the moisture-resistant resin layer provided on both sides of the oxygen-absorbing agent-containing resin layer is generally 20 to 300 μm, particularly 50 to 150 μm, and 0.1 to 30 times the thickness of the intermediate layer, particularly 0.5 to 300 μm. It is preferable to have ten times the thickness. In addition, the thickness of the inner layer and the outer layer may be equal, and one of the inner layer and the outer layer may be configured to be thicker than the other layer. Further, the thickness of the gas barrier resin layer is generally 5 to 100 μm, particularly 10 to 50 μm.
It is preferable to have a thickness of m.

[Production Method] The container of the present invention can be produced by a method known per se except for the above-mentioned layer constitution.

At the time of multilayer simultaneous extrusion, after melt-kneading with an extruder corresponding to each resin layer, the resin layer is extruded into a predetermined shape through a multilayer multiple die such as a T-die, a circular die and the like.
Further, after melt-kneading with an injection machine corresponding to each resin layer, co-injection or successive injection is performed into an injection mold to produce a multilayer container or a preform for the container. Further, a lamination method such as dry lamination, sandwich lamination, and extrusion coating may be employed.

The molded article may take the form of a film, a sheet, a parison or pipe for forming a bottle or tube, a preform for forming a bottle or tube, and the like. Parison,
The formation of a bottle from a pipe or a preform is easily performed by pinching off the extrudate with a pair of split molds and blowing a fluid into the extrudate. Further, after cooling the pipe or the preform, the pipe or the preform is heated to a stretching temperature, stretched in an axial direction, and blow-stretched in a circumferential direction by a fluid pressure to obtain a stretch blow bottle or the like.

Further, the film or sheet is vacuum formed,
By applying means such as pressure forming, overhang forming, plug assist forming, etc., a cup-shaped or tray-shaped packaging container can be obtained. Furthermore, in the case of a multilayer film, it can be stacked or folded in a bag shape and the periphery thereof can be heat-sealed to form a bag-like container.

[Use] The plastic multilayer container of the present invention is useful as a sealed packaging container for heating the contents by hot water sterilization, hot filling, retort sterilization, etc., and after opening the sealed contents, a microwave oven. It is useful as a packaging container for cooking by microwave heating and the like.

In a normal state, it is the gas barrier resin layer that is useful for preventing oxygen permeation, that is, for shutting off oxygen. However, under conditions where moisture and heat act simultaneously, such as heat sterilization, the intermediate resin layer is used. The oxygen absorbent existing in the container effectively serves to block oxygen, and the function is effectively shared depending on the state in which the container is placed. That is, under the condition where moisture and heat act simultaneously, the permeation of moisture occurs significantly through the moisture-resistant resin layer, and the gas barrier resin lowers the original oxygen barrier performance due to its moisture absorption and further rise in temperature. However, the moisture absorbed and the heat given activate the oxygen absorbent, the oxygen is effectively captured by the oxygen absorbent, and as a result, the permeation of oxygen during heat sterilization is also suppressed. Because

According to the present invention, the thermoplastic resin in which the oxygen absorbent is dispersed is formed from a blend of a plurality of substantially incompatible thermoplastic resins or elastomers, and the incompatible thermoplastic resin or elastomer is formed. The matrix is formed so as to form a non-uniform distribution structure, particularly a multilayer distribution structure, in the matrix structure. Therefore, when the volume expansion of the particles composed of the oxygen absorbent or its oxidation reaction product occurs, the non-uniform distribution structure is formed. In particular, separation at the interface of the multilayer distribution structure and generation of a minute space (gap) between the interfaces occur, and the volume expansion of particles composed of the oxygen absorbent or its oxidation reaction product is absorbed by the minute space. And the destruction of the resin coating layer is prevented.

[0051]

The present invention will be further described with reference to the following examples. [Example 1] As an inner layer and an outer layer, a propylene-ethylene block copolymer manufactured by Mitsubishi Chemical Corporation (grade name: E
C9J), as the first intermediate layer, an ethylene-vinyl alcohol copolymer manufactured by Kuraray Co., Ltd. (grade name: EP-
T101A), as the resin composition of the second intermediate layer, the resin matrix is a propylene-ethylene random copolymer (grade name: EX8, manufactured by Mitsubishi Chemical Corporation) of 25 parts by weight per 100 parts by weight of Mitsui Petrochemical ( Co., Ltd. ethylene-α olefin copolymer (grade name: Tuffmer P-
0680) comprising a blended resin and containing 37 parts by weight of an iron-based oxygen scavenger per 100 parts by weight of the matrix.
The co-extrusion is carried out so that an adhesive resin layer is formed between the vinyl alcohol copolymer and the layer adjacent thereto.
A seed 6-layer multilayer sheet was formed. FIG. 1 shows the layer configuration, and Table 1 shows the thickness configuration. In addition, 1 is used for the polypropylene resin of the inner layer.
2% by weight and 6% by weight of titanium oxide were blended into the outer layer of the polypropylene resin layer to hide the black color of the iron-based oxygen scavenger. The above multilayer sheet was vacuum-formed into a container having an inner volume of 110 mL and a surface area of 120 cm ² using a vacuum forming machine manufactured by Yamazaki Mold Co., Ltd. After adding 5 mL of water to the container, the container was sealed, and a storage test was performed for 6 months in a constant temperature and humidity chamber at a temperature of 30 ° C. and a relative humidity of 80% RH to oxidize the iron-based oxygen absorber in the container wall. . As a result of observing the cross section of the container wall after storage with a scanning electron microscope (JSM-6300F, manufactured by JEOL Ltd.), a large number of fine peelings between the interfaces occurred in the second intermediate layer cross section. In addition, the appearance characteristics of the container were evaluated by having 10 panelists evaluate the unevenness of the inner surface of the container after the storage test. The evaluation criteria were graded from 1 (impossible) to 5 (excellent), and the average was shown in Table 2.
And three or more were regarded as good appearance characteristics. Table 2 shows the results. Even after storage for 6 months, the inner surface of the container was smooth and maintained good appearance characteristics.

Example 2 As a resin composition of the second intermediate layer, a resin matrix was a propylene-ethylene random copolymer (grade name: EX manufactured by Mitsubishi Chemical Corporation).
8) The resin matrix 100 is a resin blended with 25 parts by weight of low-density polyethylene (grade name: HE30) manufactured by Mitsubishi Chemical Corporation per 100 parts by weight.
Except that the composition was changed to a composition containing 37 parts by weight of an iron-based oxygen scavenger per part by weight, a multilayer sheet was formed, a container was formed, a storage test, a container wall cross-section was observed, and the appearance characteristics of the container were changed in exactly the same manner as in Example 1. An evaluation was performed. As a result of observing the cross section of the container wall, a large number of minute peelings occurred between the interfaces in the second intermediate layer cross section as in Example 1. Table 2 shows the results of the appearance characteristics. Even after storage for 6 months, the inner surface of the container was smooth and maintained good appearance characteristics.

Example 3 As a resin composition of the second intermediate layer, a resin matrix was a propylene-ethylene random copolymer (grade name: EX manufactured by Mitsubishi Chemical Corporation).
8) 25 parts by weight of ethylene-vinyl acetate copolymer manufactured by Mitsubishi Chemical Corporation (grade name: LV4
Multilayer sheet molding and container molding were carried out in exactly the same manner as in Example 1 except that the composition was changed to a composition comprising a resin blended with (20) and 37 parts by weight of an iron-based oxygen scavenger per 100 parts by weight of the resin matrix. , A storage test, observation of a container wall cross section, and evaluation of appearance characteristics of the container. As a result of observing the cross section of the container wall, a large number of minute peelings occurred between the interfaces in the second intermediate layer cross section as in Example 1. Table 2 shows the results of the appearance characteristics. Even after storage for 6 months, the inner surface of the container maintained good appearance characteristics.

Example 4 As a resin composition for the second intermediate layer, a resin matrix was a propylene-ethylene random copolymer (grade name: EX manufactured by Mitsubishi Chemical Corporation).
8) A resin blended with 25 parts by weight of ionomer (grade name: Himilan 1707) manufactured by Du Pont-Mitsui Polychemicals Co., Ltd. per 100 parts by weight, and 37 parts by weight of iron-based desorber per 100 parts by weight of the resin matrix. Except that the composition was changed to a composition containing an oxygen agent, a multilayer sheet was formed, a container was formed, a storage test was performed in exactly the same manner as in Example 1.
The container wall cross section was observed and the appearance characteristics of the container were evaluated. As a result of observing the cross section of the container wall, a large number of minute peelings occurred between the interfaces in the second intermediate layer cross section as in Example 1.
Table 2 shows the results of the appearance characteristics. Even after storage for 6 months, the inner surface of the container maintained good appearance characteristics.

[Comparative Example 1] As the resin composition of the second intermediate layer, 37 parts by weight of an iron-based resin per 100 parts by weight of a propylene-ethylene random copolymer (grade name: EX8) manufactured by Mitsubishi Chemical Corporation was used. A multilayer sheet was formed, a container was formed, a storage test, a container wall cross-section was observed, and the appearance characteristics of the container were evaluated in exactly the same manner as in Example 1 except that the composition was changed to a composition containing an oxygen agent. As a result of observation of the cross section of the container wall, the oxygen absorbent expanded in the cross section of the second intermediate layer, and as a result, irregularities were generated on the container surface. Further, as shown in Table 2, the appearance characteristics were also reduced.

[0056]

[Table 1]

[0057]

[Table 2]

[0058]

According to the present invention, the thermoplastic resin in which the oxygen absorbent is dispersed is formed from a blend of a plurality of substantially incompatible thermoplastic resins or elastomers. Since the elastomer forms a non-uniform distribution structure in the matrix, particularly a multi-layer distribution structure, when the volume expansion of the particles composed of the oxygen absorbent or its oxidation reaction product occurs, the non-uniform distribution structure is generated. Separation occurs at the interface of the structure, particularly the multilayer distribution structure, and a minute space (gap) is generated between the interfaces, and the volume expansion of the particles made of the oxygen absorbent or its oxidation reaction product is absorbed by the minute space. As a result, the destruction of the resin coating layer is prevented. Thus, according to the present invention, the drawbacks of the conventional oxygen-absorbing multilayer plastic container are solved, the decrease in flavor retention due to the dissolution of the oxygen absorber or its oxidation product is suppressed, and the content preservation for a long time is prevented. And flavor retention.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a multilayer structure of a container of the present invention.

FIG. 2 is a sectional view showing another example of the multilayer structure of the container of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Container wall 2 Outer layer of moisture resistant thermoplastic resin 3a, 3b Adhesive resin layer 4 First intermediate layer composed of gas barrier resin 5 Second intermediate layer composed of resin composition containing oxygen absorbent 6 Moisture resistance Inner layer of plastic resin 7 Third intermediate layer composed of resin composition containing adsorbent deodorant

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masato Kogure 2-206, Nishitobe-cho, Nishi-ku, Yokohama-shi, Kanagawa Prefecture (72) Inventor Masayasu Koyama 1-2-7 Kotsubo, Zushi-shi, Kanagawa Prefecture (72) Inventor Toshio Gorita 503 Lions Mansion Taimachi 11-26 Daimachi, Kanagawa-ku, Yokohama-shi, Kanagawa

Claims (6)

[Claims] 1. An oxygen-absorbing multilayer plastic container comprising a thermoplastic resin layer containing no oxygen-absorbing agent on both sides of an oxygen-absorbing-agent-containing thermoplastic resin layer. The matrix comprises a blend of a plurality of substantially incompatible thermoplastic resins or elastomers, wherein the incompatible thermoplastic resins or elastomers are present in the resin matrix in a non-uniform distribution structure. Oxygen-absorbing multilayer plastic container. 2. The oxygen-absorbing multilayer plastic container according to claim 1, wherein the non-uniform distribution structure is a multilayer distribution structure. 3. The oxygen-absorbing multilayer plastic container according to claim 1, wherein one of the incompatible thermoplastic resins and elastomers is a propylene-based polymer and the other is an ethylene-based polymer. 4. The blend according to claim 1, wherein the blend comprises a propylene polymer and an ethylene polymer in a weight ratio of 100: 1 to 1: 1. 2. The oxygen-absorbing multilayer plastic container according to item 1. 5. The oxygen-absorbing multilayer plastic container according to claim 1, wherein the oxygen-absorbing agent is an iron-based oxygen-absorbing agent. 6. The oxygen-absorbing multilayer plastic container according to claim 1, wherein an oxygen-absorbing agent is blended in an amount of 1 to 50% by weight based on the blend.