JP6205963B2 - Multi-layer plastic container - Google Patents

Description

  The present invention relates to a multilayer plastic container having an oxygen absorption barrier layer as an intermediate layer, and more particularly to a multilayer plastic container having inner and outer layers formed of an olefin resin.

  Olefin resins such as polyethylene and polypropylene have excellent properties such as moldability, transparency, mechanical strength, and chemical resistance, and are particularly used as packaging materials for bottles and the like.

  By the way, in the field of packaging materials, it is required to block oxygen in order to prevent oxidative deterioration of the contents, but plastic packaging materials have a lower barrier property against oxygen than glass and metal. Therefore, in general, the barrier property against oxygen is enhanced by adopting a multilayer structure in which an oxygen barrier resin layer is provided in the intermediate layer.

  In the multilayer structure as described above, the oxygen barrier resin is typically an ethylene-vinyl alcohol copolymer (saponified ethylene-vinyl acetate copolymer), but such an oxygen barrier resin layer is It physically suppresses permeation of oxygen, and its barrier performance against oxygen is lower than that of glass or the like.

  On the other hand, recently, a multilayer structure in which an oxygen-absorbing layer containing an oxygen-absorbing agent composed of an oxidizing organic component of an ethylenically unsaturated group-containing polymer (for example, polybutadiene) is provided as an intermediate layer between the inner and outer layers. The body is also put into practical use as an excellent oxygen barrier. That is, it is based on the principle that oxygen passing through this layer is captured by a reaction with an oxidizing organic component (the oxidizing organic component is oxidized), and in terms of suppressing oxygen transmission, It is much higher than the above oxygen barrier resin.

  However, the oxygen-blocking ability of such an oxygen-absorbing layer decreases with the reaction between the oxygen absorbent (oxidizing organic component) and oxygen, and the oxygen-blocking ability is reduced when all oxygen absorbents react with oxygen. It will not be shown at all. That is, there is a drawback that the lifetime showing the oxygen blocking ability is shorter than that of the oxygen barrier resin.

  For this reason, Patent Document 1 proposes a multilayered plastic container having a layer structure in which an oxygen-absorbing layer is sandwiched between the above-described oxygen-barrier resin layers. In this multilayer structure container, the oxygen-absorbing layer extends the life of the oxygen-absorbing layer by suppressing the inflow of oxygen into the oxygen-absorbing layer as much as possible by the oxygen-barrier resin layer. After exhaustion, the oxygen barrier resin layer blocks oxygen permeation.

  In the plastic container of Patent Document 1, the oxygen-absorbing capacity of the oxygen-absorbing layer is maintained for a long period of time, and excellent oxygen barrier properties are exhibited for a long period of time. However, such a structure has a problem that the number of layers constituting the container is increased and the production cost is increased. Furthermore, in an olefin resin container having an olefin resin such as polyethylene as the inner and outer layers, the number of intermediate layers increases and the thickness of the intermediate layer also increases. There is also a problem that is lost.

  On the other hand, Patent Documents 2 and 3 have a multilayer structure plastic in which an oxygen absorption barrier layer in which an oxygen absorbent is dispersed in an oxygen barrier resin is provided as an intermediate layer, and an olefin resin layer is provided as an inner and outer layer. Containers have been proposed. That is, in the multilayer container of Patent Document 1, a layer containing an oxygen absorbent and an oxygen barrier resin layer are separately provided. However, in Patent Documents 2 and 3, an oxygen absorbent and an oxygen barrier resin are used. One layer (oxygen-absorbing barrier layer) is formed. Therefore, excellent barrier properties against oxygen are obtained by reducing the number of layers forming the container.

  However, in Patent Documents 2 and 3, since the oxygen absorbent is dispersed in the oxygen barrier resin layer, the layer containing the oxygen absorbent is sandwiched by the oxygen barrier resin layer as in Patent Document 1. As compared with the case where the oxygen absorbent is present, the effect of suppressing the consumption of the oxygen absorbent is not sufficient, and the period in which the oxygen absorbent can exhibit the excellent oxygen absorbing ability is not so long.

JP 2007-320576 A JP 2004-143308 A JP 2005-8823 A

  Accordingly, an object of the present invention is to have an oxygen absorption barrier layer in which an oxygen absorbent is dispersed in an oxygen barrier resin as an intermediate layer, and an inner layer and an outer layer are formed of an olefin resin, and oxygen absorption. Another object of the present invention is to provide a multilayer plastic container in which the oxygen absorbing ability of the oxygen absorbent in the porous barrier layer is continuously exhibited over a long period of time, and excellent oxygen barrier properties are maintained for a long period of time.

  As a result of conducting many experiments on the above problems, the present inventors have found that the oxygen absorption capacity (pellet oxygen absorption capacity) of the resin composition itself used to form the oxygen absorption barrier layer and the thickness of the oxygen absorption barrier layer. However, it is closely related to the life of the oxygen absorption capacity of the multilayer container having such an oxygen absorption barrier layer as an intermediate layer, and the pellet oxygen absorption capacity and the thickness of the oxygen absorption barrier layer satisfy certain conditions. In such a case, the oxygen absorption ability of the oxygen absorption barrier layer is continuously exhibited over a long period of time, and as a result, the finding that excellent oxygen barrier properties are maintained over a long period of time has been found, and the present invention has been completed. .

That is, according to the present invention, in a plastic container having a multilayer structure comprising an inner and outer layer made of olefin resin and an oxygen absorption barrier layer provided between the inner and outer layers via an adhesive layer,
The oxygen absorption barrier layer is formed from an oxygen absorption barrier resin composition in which an oxygen absorbent is dispersed in an oxygen barrier resin, and has a thickness of 15 to 40 μm.
The oxygen absorption barrier resin composition has a pellet oxygen absorption capacity of 0.05 to 1.2 cc / g · day ,
On the condition that the oxygen absorption barrier layer is shifted to the outer surface side from the center in the thickness direction of the container wall, the distance between the outer surface of the oxygen absorption barrier layer and the outer layer surface is in the range of 10 to 150 μm, And the total thickness of the multilayer structure containing the said oxygen absorption barrier layer exists in the range of 150-800 micrometers, The multilayer structure plastic container characterized by the above-mentioned is provided.

  In the multilayer plastic container of the present invention, the inner and outer layers are formed of an olefin resin, but the oxygen absorbing barrier layer used as the intermediate layer has a certain range of oxygen absorbing ability (pellet oxygen absorbing ability). The thickness of the oxygen absorption barrier layer formed by the resin composition is in a certain range. That is, in the present invention, by setting both the pellet oxygen absorption capacity of the oxygen absorption barrier layer and the thickness of the layer within a certain range, the characteristic of the olefin resin container that the inner and outer layers are formed of an olefin resin is obtained. The lifetime of the oxygen absorbent in the oxygen absorbing barrier layer can be extended to the maximum without damaging, and as a result, the multilayer plastic container of the present invention exhibits excellent oxygen barrier properties over a long period of time.

  That is, even if an oxygen-absorbing barrier layer comprising an oxygen-barrier resin such as an ethylene-vinyl alcohol copolymer and an oxygen absorbent is provided, the oxygen-absorbing layer has a pellet oxygen-absorbing capacity and an oxygen-absorbing barrier layer thickness If any one of the conditions is out of the scope of the present invention, excellent oxygen barrier properties cannot be exhibited without impairing the excellent characteristics of the olefin resin. For example, as shown in the examples described later, the multilayer plastic container of the present invention exhibits an excellent oxygen barrier property for 4 months or more, but the pellet oxygen absorption capacity or the thickness of the oxygen absorption barrier layer In the container of the comparative example, which is outside the scope of the present invention, the excellent oxygen barrier property is exhibited only for about 2 months, and the oxygen absorption barrier is exhibited when the excellent oxygen barrier property is exhibited for 4 months. The thickness of the layer must be excessively increased. As a result, the excellent characteristics of the olefin resin are impaired, and the drop strength and the like are greatly reduced.

  Furthermore, the greatest advantage of the present invention is that an oxygen absorbing barrier layer is provided between the inner and outer layers, and the number of layers (three layers and five layers including the adhesive layer) is excellent. The ability to maintain the sex over a long period of time. That is, since the number of layers is small and the layer structure is very simple, the multilayer container of the present invention can be molded using a conventionally known molding apparatus as it is, and an increase in production cost can be effectively avoided, and industrial production can be avoided. The benefits are extremely large.

The schematic sectional drawing which shows the layer structure of the multilayer structure plastic container of this invention.

  Referring to FIG. 1 showing the layer structure of the multilayer plastic container of the present invention, this container (indicated by 10 as a whole) has inner and outer layers 1 and 3 formed of an olefin resin. , 3, an oxygen absorption barrier layer 7 is formed through adhesive layers 5, 5.

<Inner and outer layers 1, 3>
In the present invention, the olefin resins used as the inner and outer layers 1 and 3 are low density polyethylene (LDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), linear low density polyethylene (LLDPE), linear Polyethylene such as very low density polyethylene (LVLDPE), polypropylene, ethylene-propylene copolymer, polybutene-1, ethylene-butene-1 copolymer, propylene-butene-1 copolymer, ethylene-propylene-butene-1 Examples thereof include a copolymer, an ethylene-vinyl acetate copolymer, and an ion-crosslinked olefin copolymer (ionomer).

  The olefin resin for forming the inner and outer layers as described above may be of an extrusion grade or an injection grade that has been conventionally used in the field of packaging materials.

In addition, a regrind layer may be formed in the inner layer 1 or the outer layer 3 by mixing scrap resin such as burrs generated when the container 10 is formed with an olefin resin for forming inner and outer layers of virgin. . In this case, from the viewpoint of recycling resources while maintaining moldability, the amount of scrap resin should be about 10 to 60 parts by weight per 100 parts by weight of the olefin resin for forming the inner and outer layers of virgin. Is good.
Furthermore, the inner and outer layers 1 and 3 may contain a lubricant, a modifier, a pigment, an ultraviolet absorber, and the like as necessary.

  The thicknesses of the inner and outer layers 1 and 3 as described above are not particularly limited, and are appropriately set according to the application utilizing the characteristics of the olefin resin used for the inner and outer layers 1 and 3. The total thickness of the multilayer structure, which is the total thickness, is in the range of about 150 to 800 μm, and about 20 to 60% of such total thickness is set to be the total thickness of the inner layer 1 and the outer layer 3. The thickness of the regrind layer included in the inner and outer layers 1 and 3 is generally about 60 to 640 μm, provided that the thickness of the inner and outer layers 1 and 3 including the regrind layer is within the above range. Is set.

<Adhesive layer 5>
The adhesive layer 5 is a layer provided due to poor adhesion between the olefin resin forming the inner and outer layers 1 and 3 and the oxygen absorption barrier layer 7 (especially the oxygen barrier resin in the layer). The oxygen-absorbing barrier layer 7 can be provided without causing inconvenience such as lamination, and the barrier property against oxygen of the oxygen-absorbing barrier layer 7 can be effectively exhibited.

  Such an adhesive layer 5 is formed of an adhesive resin known per se, for example, 1 to 100 meq / 100 g resin, particularly 10 to 100 meq / 100 g resin having a carbonyl group (> C═O) in the main chain or side chain. Olefin resin graft-modified with a carboxylic acid such as maleic acid, itaconic acid, fumaric acid or its anhydride, amide, ester, etc .; ethylene-acrylic acid copolymer; ion Crosslinked olefin copolymers; ethylene-vinyl acetate copolymers; etc. are used as adhesive resins. The thickness of the adhesive layer 5 may be such that an appropriate adhesive force can be obtained, and is generally about 0.5 to 20 μm, preferably about 1 to 8 μm.

<Oxygen absorption barrier layer 7>
In the present invention, the oxygen absorption barrier layer 7 is formed of an oxygen absorption barrier resin composition in which an oxygen absorbent is dispersed in an oxygen barrier resin.

Oxygen absorbers;
The oxygen absorbent is usually composed of an oxidizing organic component, and a transition metal catalyst component is used in combination as necessary. That is, the oxidizing organic component has a function of blocking oxygen by absorbing oxygen and being oxidized (oxygen absorbing ability), and the transition metal catalyst component is appropriately blended in order to promote oxidation of the oxidizing organic component. Is. As such an oxidizing organic component and a transition metal component, known ones are used.

  For example, examples of the oxidizing organic component include an oxidizing ethylenically unsaturated group-containing polymer. This polymer has a carbon-carbon double bond, and this double bond portion is easily oxidized by oxygen, whereby oxygen is absorbed and trapped.

Such an ethylenically unsaturated group-containing polymer is derived from, for example, polyene as a monomer, and a suitable example of polyene used as the monomer is limited to this. However, the following can be exemplified.
Conjugated dienes such as butadiene and isoprene;
1,4-hexadiene, 3-methyl-1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, 4,5-dimethyl-1,4-hexadiene, 7- Chain non-conjugated dienes such as methyl-1,6-octadiene;
Methyltetrahydroindene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene, 5-isopropylidene-2-norbornene, 5-vinylidene-2-norbornene, 6-chloromethyl-5-isopropenyl-2-norbornene , Cyclic non-conjugated dienes such as dicyclopentadiene;
Trienes such as 2,3-diisopropylidene-5-norbornene, 2-ethylidene-3-isopropylidene-5-norbornene, 2-propenyl-2,2-norbornadiene, chloroprene;

That is, a homopolymer of the polyene, or a random copolymer, a block copolymer, or the like obtained by combining two or more of the polyenes with other monomers can be used as the oxidizing polymer.
Examples of other monomers to be copolymerized with the polyene include α-olefins having 2 to 20 carbon atoms, specifically, ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1- Nonadecene, 1-eicosene, 9-methyl-1-decene, 11-methyl-1-dodecene, 12-ethyl-1-tetradecene and the like can be exemplified. Besides these, styrene, vinyltriene, acrylonitrile , Methacrylonitrile, vinyl acetate, methyl methacrylate, ethyl acrylate and the like can also be used.

  As the oxidizing organic component, among the polymers derived from polyene described above, polybutadiene (BR), polyisoprene (IR), natural rubber (NR), nitrile-butadiene rubber (NBR), styrene-butadiene rubber (SBR). ), Chloroprene rubber, ethylene-propylene-diene rubber (EPDM) and the like are preferred, but of course not limited thereto. Moreover, the iodine value is good to be 100 or more, especially about 120-196.

  From the viewpoint of moldability, it is preferable that the above-described oxidizing polymer or copolymer thereof has a viscosity at 40 ° C. in the range of 1 to 200 Pa · s.

Furthermore, an oxidizable polymer cyclized product obtained by cyclizing a polymer derived from the above-described polyene in the presence of an acid catalyst may be used as the oxidizing organic component.
As the acid catalyst used in the cyclization reaction, conventionally known acid catalysts can be used. For example, sulfuric acid, fluoromethanesulfonic acid, difluoromethanesulfonic acid, p-toluenesulfonic acid, xylenesulfonic acid, an alkyl group having 2 to 18 carbon atoms. Organic sulfonic acid compounds such as alkylbenzene sulfonic acids having these, anhydrides thereof or alkyl esters can be used.
As the above-mentioned oxidizable polymer cyclized product, a polybutadiene cyclized product, a polyisoprene cyclized product, a natural rubber cyclized product, and the like are suitable, but of course, it is not limited thereto.
From the viewpoint of moldability, the weight average molecular weight (Mw) is preferably in the range of 10,000 to 500,000 in terms of polystyrene.

  In addition, as described above, the transition metal catalyst used as appropriate is used to promote the oxidation of the oxidizing organic component, and the pellet oxygen absorption ability described later falls within a predetermined range. Such an amount (generally, an amount of 0 to 10,000 ppm in terms of transition metal per oxidizing organic component) is appropriately used, and is used in the form of a low-valent inorganic salt, organic salt or complex salt of the transition metal.

  In such a transition metal catalyst, the transition metal is preferably a group VIII metal of the periodic table such as iron, cobalt, nickel, etc., but also a group I metal such as copper, silver, tin, titanium, zirconium, etc. It may be a Group IV metal, a Group V metal such as vanadium, a Group VI metal such as chromium, a Group VII metal such as manganese, or the like. Among these, cobalt is particularly preferable because it significantly promotes oxygen absorption (oxidation of the oxidizing organic component).

  Examples of the inorganic salts of transition metals include halides such as chlorides, sulfur oxysalts such as sulfates, nitrogen oxysalts such as nitrates, phosphorus oxysalts such as phosphates, and silicates. .

  Examples of organic salts of transition metals include carboxylates, sulfonates, and phosphonates, and carboxylates are preferred for the purposes of the present invention. Specific examples thereof include acetic acid, propionic acid, isopropionic acid, butanoic acid, isobutanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, isoheptanoic acid, octanoic acid, 2-ethylhexanoic acid, nonanoic acid, 3, 5, 5 -Trimethylhexanoic acid, decanoic acid, neodecanoic acid, undecanoic acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, arachidic acid, Linderic acid, tuzuic acid, petroceric acid, oleic acid, linoleic acid, linolenic acid And transition metal salts such as arachidonic acid, formic acid, oxalic acid, sulfamic acid, and naphthenic acid.

Examples of the transition metal complex include complexes with β-diketone or β-keto acid ester. The following can be illustrated as (beta) -diketone and (beta) -keto acid ester.
Acetylacetone,
Ethyl acetoacetate,
1,3-cyclohexadione,
Methylene bis-1,3-cyclohexadione,
2-benzyl-1,3-cyclohexadione,
Acetyltetralone,
Palmitoyltetralone,
Stearoyl tetralone,
Benzoyltetralone,
2-acetylcyclohexanone,
2-benzoylcyclohexanone,
2-acetyl-1,3-cyclohexadione,
Benzoyl-p-chlorobenzoylmethane,
Bis (4-methylbenzoyl) methane,
Bis (2-hydroxybenzoyl) methane,
Benzoylacetone,
Tribenzoylmethane,
Diacetylbenzoylmethane,
Stearoylbenzoylmethane,
Palmitoylbenzoylmethane,
Lauroylbenzoylmethane,
Dibenzoylmethane,
Bis (4-chlorobenzoyl) methane,
Benzoylacetylphenylmethane,
Stearoyl (4-methoxybenzoyl) methane,
Butanoylacetone,
Distearoylmethane,
Stearoyl acetone,
Bis (cyclohexanoyl) methane,
Dipivaloylmethane.

Oxygen barrier resin;
The oxygen barrier resin serves as a matrix of the oxygen absorption barrier layer 7, and the oxygen absorbent described above is dispersed in the oxygen barrier resin. In other words, the oxygen barrier resin itself physically blocks the passage of oxygen and minimizes the contact between the oxygen absorbent and oxygen, thereby reducing the consumption of the oxygen absorbent due to the reaction with oxygen. Used to suppress and prolong the life of oxygen absorbers.

Examples of such an oxygen barrier resin include resins having an oxygen permeability coefficient of 10 (20 μm; cc / m ² · day · atm) at 23 ° C. and 0% RH, for example, ethylene-vinyl alcohol copolymer and polyamide. Is representative.

  As the ethylene-vinyl alcohol copolymer, specifically, an ethylene-vinyl acetate copolymer having an ethylene content of 20 to 60 mol%, particularly 25 to 50 mol%, has a saponification degree of 96% or more. In particular, a saponified copolymer obtained by saponification to be 99% or more is preferably used. The ethylene-vinyl alcohol copolymer (saponified ethylene-vinyl acetate copolymer) should have a molecular weight sufficient to form a film, and is generally a mixed solvent having a phenol / water weight ratio of 85/15. It has an intrinsic viscosity of 0.01 dl / g or more, particularly 0.05 dl / g or more, measured at 30 ° C.

  Polyamides such as nylon 6, nylon 6,6, nylon 6 / 6,6 copolymer, metaxylylene adipamide (MXD6), nylon 6,10, nylon 11, nylon 12, nylon 13, etc. Can be mentioned. Among these polyamides, those having the number of amide groups per 100 carbon atoms in the range of 5 to 50, particularly 6 to 20 are preferable in that they have high oxygen barrier properties. These polyamides should also have a molecular weight sufficient to form a film. For example, in concentrated sulfuric acid (concentration 1.0 g / dl), the relative viscosity measured at 30 ° C. is 1.1 or more, particularly 1.5 or more. It is desirable to be.

  In the present invention, an ethylene-vinyl alcohol copolymer is most preferably used as the oxygen barrier resin.

Oxygen-absorbing barrier resin composition;
The oxygen absorption barrier layer 7 is formed of an oxygen absorption barrier resin composition containing the above-described oxygen absorber and oxygen barrier resin, and this resin composition has a pellet oxygen absorption capacity of 0.05. It is necessary to be within the range of ˜1.2 cc / g · day, preferably 0.1 to 0.8 cc / g · day. This pellet oxygen absorption capacity can be calculated from the change in the amount of oxygen in the container when the pellet of the resin composition is stored in a container of a predetermined volume for one day (24 hours). reference).

  Such pellet oxygen absorption capacity is set within the above range by adjusting the amount of the transition metal component and the amount of the oxygen barrier resin according to the kind of the oxidizing organic component used as the oxygen absorbent. For example, as the amount of the transition metal component used is increased, the pellet oxygen absorption capacity increases, and as the amount used decreases, the pellet oxygen absorption capacity decreases. Further, as the amount of the oxygen barrier resin increases, the pellet oxygen absorption capacity decreases, and as the amount used decreases, the pellet oxygen absorption capacity increases. Therefore, the pellet oxygen absorption capacity can be set within the above range by adjusting the amount of the transition metal component and the amount of the oxygen barrier resin in accordance with the type of the oxidizing organic component.

In the present invention, the oxygen absorption barrier layer 7 is formed of a resin composition having a pellet oxygen absorption capacity within the above range, so that the container characteristics of the olefin resin forming the inner and outer layers 1 and 3 are not impaired. It becomes possible to maintain excellent oxygen barrier properties over a long period of time (for example, 4 months or more).
For example, when the oxygen absorption barrier layer 7 is formed using a resin composition having a pellet oxygen absorption capacity smaller than the above range, naturally, excellent oxygen barrier properties cannot be exhibited. In addition, it should be noted that when a resin composition having a pellet oxygen absorption capacity larger than the above range is used, even if an excellent oxygen barrier property can be expressed, it should be maintained for a long period of time. The point is that it will not be possible. That is, since the oxygen absorption capacity of the oxygen absorption barrier layer 7 to be formed is too large, the oxygen absorption capacity of the oxygen absorbent is consumed in a short period of time, and for example, excellent oxygen barrier properties can be maintained for 4 months or more. It will not be possible. Of course, if the thickness of the oxygen absorption barrier layer 7 to be formed is considerably increased, long-term oxygen barrier properties can be secured. In this case, however, the thickness of the oxygen absorption barrier layer 7 is larger than necessary. Therefore, the container characteristics derived from the softness and flexibility of the olefin resin forming the inner and outer layers 1 and 3, for example, the drop strength, are impaired. In the conventionally known technique, many studies have been made to increase the oxygen absorption capacity, and it can be said that no studies have been made to limit the oxygen absorption capacity to some extent as in the present invention.

  In the present invention, it is also important that the thickness t of the oxygen absorption barrier layer 7 formed of the above-described oxygen absorption barrier resin composition is in the range of 15 to 40 μm, particularly 20 to 30 μm. That is, in the present invention, since the pellet oxygen absorption capacity of the oxygen-absorbing barrier resin composition is limited, if the thickness t is thinner than the above range, excellent oxygen barrier properties can be exhibited or temporarily However, the oxygen absorbing ability of the oxygen absorbent in the oxygen absorbing barrier layer 7 is consumed in a short period of time, and it becomes impossible to ensure an excellent oxygen barrier property for a long period of, for example, four months or longer. When the thickness t is thicker than the above range, the container characteristics such as the drop strength by the olefin resin forming the inner and outer layers 1 and 3 are impaired as described above.

In the present invention, it is further assumed that the position of the oxygen absorption barrier layer 7 is shifted to the outer surface side from the center in the thickness direction of the container wall, and the distance d between the outer surface of the oxygen absorption barrier layer 7 and the surface of the outer layer 3. Is in the range of 10 to 150 μm, particularly 15 to 100 μm. That is, if the distance d is smaller than the above range, the strength and the like of the outer layer 3 formed from the olefin resin are impaired, the outer layer 3 is easily damaged by the external pressure, and the distance d is within the above range. Is larger than that, the position of the oxygen absorption barrier layer 7 formed with the above-described thickness t is close to the inner surface of the container, so that the reaction between the oxygen absorbent (oxidizing organic component) in the oxygen absorption barrier layer 7 and oxygen. There is a possibility that the flavor of the contents of the container may be lowered by a low molecular weight compound (for example, aldehyde) generated by.

The multilayer container of the present invention having the layer structure described above is not limited to the layer structure described above, and various modifications are possible.
For example, a regrind layer can be provided in the inner and outer layers 1 and 3 as described above, and an odor scavenger can be added to the inner layer 1 including the regrind layer. Is preferred. As such an odor scavenger, a porous inorganic material mainly composed of silicate, such as zeolite or activated clay powder obtained by acid treatment of smectite clay minerals such as montmorillonite, is particularly preferable. High silica zeolite (silica / alumina ratio of 100 or more), which is a ZSM5 type crystal, is excellent in so-called plastic-specific polyodor and oxidation by-product trapping performance. Such an odor scavenger is generally blended in the inner layer in an amount of 0.5 to 10% by weight.

In some cases, it is possible to provide a separate oxygen absorption barrier layer or an oxygen barrier resin layer containing no oxygen absorbent on the inner layer side of the oxygen absorption barrier layer 7 described above. In the present invention, a simple layer structure as shown in FIG.
Outer layer 3 / adhesive layer 5 / oxygen absorption barrier layer 7 / adhesive layer 5 / inner layer 1
It is most preferable to adopt a three-kind five-layer structure.
That is, in the present invention, even with the simple layer structure as described above, it is possible to maintain an excellent oxygen barrier property over a long period of time without impairing the container characteristics of the olefin resin. Even when heat treatment is performed at such a severe temperature, consumption of the oxygen absorbent (oxidizing organic component) can be effectively suppressed, and excellent oxygen barrier properties are exhibited over a long period of time. In addition, such a simple layer structure is easy to manufacture, can avoid an increase in manufacturing cost, and is extremely advantageous industrially.

  In addition, the multilayer container 10 of the present invention described above may have a bag shape in which a film or a sheet is bonded, may have a bottle or cup shape, and is known per se. Manufactured by the method. For example, a film or sheet can be formed by co-extrusion, co-injection, or the like, using a number of extruders or injection machines corresponding to the number of layers, and bonded to form a bag-like container (pouch). Alternatively, it is molded into the shape of a container preform instead of a film or sheet, and subjected to secondary molding, for example, blow molding or plug assist molding, according to the form of the preform, and molded into a bottle or cup-shaped container.

Such a multilayer container 10 of the present invention utilizes such characteristics because excellent oxygen barrier properties are maintained over a long period of time in addition to the excellent flexibility and moisture resistance of the polyolefin resin. , Beverages such as beer, wine, fruit juice, carbonated soft drink, fruits, nuts, vegetables, meat products, infant food, coffee, jam, mayonnaise, ketchup, cooking oil, dressing, sauces, boiled dairy products, dairy products, It is suitably used as a container for filling various contents that cause deterioration in the presence of oxygen, such as pharmaceuticals, cosmetics, and gasoline.
Moreover, since the multilayer container 10 of the present invention is excellent in transparency, it can be suitably used for packaging applications that require transparency.

The present invention will be further described by the following experimental examples, but the present invention is not limited to these experimental examples.
Various measurements performed in the following experimental examples were performed by the following methods.

(Pellet oxygen absorption capacity)
The barrier layer resin pellets used in the Examples and Comparative Examples were placed in liquid nitrogen and freeze-ground, then 0.5 g was placed in a 80 ml high-rate cup, and further 2.0 ml of water was added. After heat sealing with foil, it was stored at 30 ° C. for 1 day (24 hours).
Next, the oxygen concentration of the head space in the high-ret cup (RH is 100%) was measured by gas chromatography (GC), and the amount of oxygen absorbed per 1 g of pellets was calculated as pellet oxygen absorption capacity.

(Oxygen barrier properties)
The bottles obtained in Examples and Comparative Examples were filled with nitrogen gas and sealed with a cap, and then the untreated (no heat treatment) bottle was stored in an atmosphere of 30 ° C. and 80% RH. Measure the oxygen concentration (%) in the container immediately after filling, and the oxygen concentration (%) in the container after storage for 2 months and after storage for 4 months, measure 5 bottles for each level, find the average, The increase amount (%) of the oxygen concentration in the container per bottle was calculated by the following formula.
Increase amount of oxygen concentration in container (%) = BA
A is the oxygen concentration (%) in the container immediately after filling with nitrogen gas,
B is the oxygen concentration (%) in the container after storage for 2 months or after storage for 4 months.
Based on the increase amount (%) of the oxygen concentration in the container calculated above, the oxygen barrier property was evaluated according to the following criteria.
A: Increase is less than 0.2%.
○: Increase amount is 0.2% or more and less than 0.5%.
Δ: Increase is 0.5% or more and less than 1.0%.
X: The increase amount is 1.0% or more.

(Drop strength)
The obtained bottle was filled with 180 g of water, stored in an environment of 5 ° C. for 24 hours, and dropped 5 times alternately at a temperature of 5 ° C. from a height of 100 cm to a vertical drop and then a horizontal drop. The number of n was 10 each. The score was as follows. ○ and △ were within the allowable range.
○: No breakage △: One breakage ×: Two or more breakages

(Flavoring)
The obtained bottle was filled with 180 ml of Wako Pure Chemical Industries distilled water heated to 80 ° C., sealed with a cap, and stored at 30 ° C.-80% RH for 1 week, and then the temperature of the sample was adjusted to room temperature. The taste (flavor) of the content liquid was sensory-evaluated with the following rating. There were 6 panelists.
(1 point = tasteless, 2 points = taste slightly, 3 points = taste, 4 points = taste very much)
A: The average score is less than 2.0.
○: The average score is 2.0 or more and less than 2.5 Δ: The average score is 2.5 or more and less than 3.0 ×: The average score is 3.0 or more

In the following examples and comparative examples, the following resins were used for forming the inner and outer layers and the adhesive layer.
(Olefin resin for inner and outer layer formation)
Random copolymer polypropylene (adhesive resin)
Acid-modified polypropylene

The following were prepared as the oxygen barrier resin, oxygen absorbent, and Co catalyst.
(Oxygen barrier resin)
Ethylene-vinyl alcohol copolymer (abbreviated as EVOH)
Ethylene content: 32 mol%
Oxygen transmission coefficient: 0.3 (20 μm; cc / m ² · day · atm)
Metaxylylene adipamide (abbreviated as MXD6)
Oxygen transmission coefficient: 3.0 (20 μm; cc / m ² · day · atm)
(Oxygen absorber A: oxidizing organic component A)
Polyisoprene cyclized product (oxygen absorbent B: oxidizing organic component B)
Polybutadiene (Co catalyst: transition metal catalyst)
Cobalt stearate

<Example 1>
The above oxygen barrier resin (EVOH) and oxygen absorbent A (oxidizing organic component A) are melt-mixed, and oxygen absorbent barrier resin composition pellets having an oxygen absorbent concentration of 30 wt% (wt%) are obtained. Prepared. It was 0.3cc / g * day when the pellet oxygen absorption capacity of this resin composition was measured.

A preform (parison) for a container is formed by extrusion molding using the above-mentioned pellets of the oxygen-absorbing barrier resin composition and the olefin resin for forming the inner and outer layers and the adhesive resin described above, and by direct blow molding, Molded a 200 ml multilayer bottle.
The layer structure of the bottle body and the thickness of each layer of the body wall are as follows.
Outer layer (45 μm) / Adhesive layer (5 μm) / Oxygen absorption barrier layer (25 μm) / Adhesive layer (5 μm) / Inner layer (420 μm)
This container was evaluated for oxygen barrier properties, drop strength, and flavor properties, and the results are shown in Table 1 together with oxygen absorption barrier layer specifications and d dimension (distance between the outer surface of the oxygen absorption barrier layer and the outer layer surface).

<Example 2>
Oxygen barrier resin (EVOH), oxygen absorbent A and cobalt catalyst (Co catalyst) were melt-mixed to prepare oxygen absorbent barrier resin composition pellets of cobalt catalyst 250 ppm with an oxygen absorbent concentration of 30% by weight. In the same manner as in Example 1, a multilayered structure bottle was molded and evaluated. The evaluation results are shown in Table 1.

<Example 3>
Example 1 except that oxygen barrier resin (EVOH), oxygen absorbent A and cobalt catalyst were melt-mixed to prepare oxygen absorbent barrier resin composition pellets of cobalt catalyst 150 ppm with an oxygen absorbent concentration of 30% by weight. Similarly, multilayered bottles were molded and evaluated. The evaluation results are shown in Table 1.

<Example 4>
A multilayer structure bottle was prepared in the same manner as in Example 1 except that oxygen barrier resin (EVOH) and oxygen absorbent A were melt-mixed to prepare oxygen absorbent barrier resin composition pellets having an oxygen absorbent concentration of 10% by weight. Molded and evaluated. The evaluation results are shown in Table 1.

<Example 5>
A multilayer structure bottle was prepared in the same manner as in Example 1 except that oxygen barrier resin (EVOH) and oxygen absorbent A were melt-mixed to prepare oxygen absorbent barrier resin composition pellets having an oxygen absorbent concentration of 5% by weight. Molded and evaluated. The evaluation results are shown in Table 1.

<Example 6>
A multilayer bottle was molded and evaluated in the same manner as in Example 1 except that the thickness of each layer of the bottle body wall was as follows. The evaluation results are shown in Table 1.
Outer layer (45 μm) / Adhesive layer (5 μm) / Oxygen absorption barrier layer (40 μm) / Adhesive layer (5 μm) / Inner layer (405 μm)

<Example 7>
A multilayer bottle was molded and evaluated in the same manner as in Example 1 except that the thickness of each layer of the bottle body wall was as follows. The evaluation results are shown in Table 1.
Outer layer (45 μm) / Adhesive layer (5 μm) / Oxygen absorption barrier layer (30 μm) / Adhesive layer (5 μm) / Inner layer (415 μm)

<Example 8>
A multilayer bottle was molded and evaluated in the same manner as in Example 1 except that the thickness of each layer of the bottle body wall was as follows. The evaluation results are shown in Table 1.
Outer layer (45 μm) / Adhesive layer (5 μm) / Oxygen absorption barrier layer (20 μm) / Adhesive layer (5 μm) / Inner layer (425 μm)

<Example 9>
A multilayer bottle was molded and evaluated in the same manner as in Example 1 except that the thickness of each layer of the bottle body wall was as follows. The evaluation results are shown in Table 1.
Outer layer (45 μm) / Adhesive layer (5 μm) / Oxygen absorption barrier layer (15 μm) / Adhesive layer (5 μm) / Inner layer (430 μm)

<Example 10>
A multilayer bottle was molded and evaluated in the same manner as in Example 1 except that the thickness of each layer of the bottle body wall was as follows. The evaluation results are shown in Table 1.
Outer layer (145 μm) / Adhesive layer (5 μm) / Oxygen absorption barrier layer (25 μm) / Adhesive layer (5 μm) / Inner layer (320 μm)

<Example 11>
A multilayer bottle was molded and evaluated in the same manner as in Example 1 except that the thickness of each layer of the bottle body wall was as follows. The evaluation results are shown in Table 1.
Outer layer (95 μm) / Adhesive layer (5 μm) / Oxygen absorption barrier layer (25 μm) / Adhesive layer (5 μm) / Inner layer (370 μm)

<Example 12>
A multilayer bottle was molded and evaluated in the same manner as in Example 1 except that the thickness of each layer of the bottle body wall was as follows. The evaluation results are shown in Table 1.
Outer layer (10 μm) / Adhesive layer (5 μm) / Oxygen absorption barrier layer (25 μm) / Adhesive layer (5 μm) / Inner layer (455 μm)

<Example 13>
A multilayer bottle was molded and evaluated in the same manner as in Example 1 except that the thickness of each layer of the bottle body wall was as follows. The evaluation results are shown in Table 1.
Outer layer (5 μm) / Adhesive layer (5 μm) / Oxygen absorption barrier layer (25 μm) / Adhesive layer (5 μm) / Inner layer (460 μm)

<Example 14>
A multilayered bottle was molded and evaluated in the same manner as in Example 1 except that MXD6 was used as the oxygen barrier resin. The evaluation results are shown in Table 1.

<Example 15>
Example 1 except that oxygen barrier resin (EVOH), oxygen absorbent B, and cobalt catalyst were melt-mixed to prepare an oxygen-absorbing barrier resin composition pellet having a cobalt catalyst of 250 ppm at an oxygen absorbent concentration of 5% by weight. Similarly, multilayered bottles were molded and evaluated. The evaluation results are shown in Table 1.

<Example 16>
Example 1 except that oxygen barrier resin (EVOH), oxygen absorbent B, and cobalt catalyst were melt-mixed to prepare an oxygen-absorbing barrier resin composition pellet having a cobalt catalyst of 250 ppm at an oxygen absorbent concentration of 10% by weight. Similarly, multilayered bottles were molded and evaluated. The evaluation results are shown in Table 1.

<Example 17>
Example 1 except that oxygen barrier resin (EVOH), oxygen absorbent B, and cobalt catalyst were melt-mixed to prepare an oxygen-absorbing barrier resin composition pellet having a cobalt catalyst of 100 ppm at an oxygen absorbent concentration of 5% by weight. Similarly, multilayered bottles were molded and evaluated. The evaluation results are shown in Table 1.

<Comparative Example 1>
A multilayer bottle was prepared in the same manner as in Example 1 except that oxygen barrier resin (EVOH) and oxygen absorbent A were melt-mixed to prepare oxygen absorbent barrier resin composition pellets having an oxygen absorbent concentration of 3% by weight. Molded and evaluated. The evaluation results are shown in Table 1.

<Comparative example 2>
Example 1 except that oxygen barrier resin (EVOH), oxygen absorbent A and cobalt catalyst were melt-mixed to prepare an oxygen-absorbing barrier resin composition pellet of 300 ppm cobalt catalyst at an oxygen absorbent concentration of 30% by weight. Similarly, multilayered bottles were molded and evaluated. The evaluation results are shown in Table 1.

<Comparative Example 3>
A multilayer bottle was molded and evaluated in the same manner as in Example 1 except that the thickness of each layer of the bottle body wall was as follows. The evaluation results are shown in Table 1.
Outer layer (45 μm) / Adhesive layer (5 μm) / Oxygen absorption barrier layer (10 μm) / Adhesive layer (5 μm) / Inner layer (435 μm)

<Comparative Example 4>
A multilayer bottle was molded and evaluated in the same manner as in Example 1 except that the thickness of each layer of the bottle body wall was as follows. The evaluation results are shown in Table 1.
Outer layer (45 μm) / Adhesive layer (5 μm) / Oxygen absorption barrier layer (45 μm) / Adhesive layer (5 μm) / Inner layer (400 μm)

<Comparative Example 5>
A multilayer bottle was molded and evaluated in the same manner as in Example 1 except that no oxygen absorbent was used. The evaluation results are shown in Table 1.

1: Inner layer 3: Outer layer 5: Adhesive layer 7: Oxygen absorption barrier layer 10: Multi-layer container

Claims (1)

In a plastic container having a multilayer structure composed of an inner and outer layer made of an olefin resin and an oxygen absorption barrier layer provided between the inner and outer layers via an adhesive layer,
The oxygen absorption barrier layer is formed from an oxygen absorption barrier resin composition in which an oxygen absorbent is dispersed in an oxygen barrier resin, and has a thickness of 15 to 40 μm.
The oxygen absorption barrier resin composition has a pellet oxygen absorption capacity of 0.05 to 1.2 cc / g · day ,
On the condition that the oxygen absorption barrier layer is shifted to the outer surface side from the center in the thickness direction of the container wall, the distance between the outer surface of the oxygen absorption barrier layer and the outer layer surface is in the range of 10 to 150 μm, A total thickness of the multilayer structure including the oxygen absorption barrier layer is in the range of 150 to 800 μm .

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