JP5346599B2 - Multilayer plastic container and container-filled acidic oil-in-water emulsified food using the container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To develop a multi-layer container, in particular, a squeezed bottle for use in mayonnaise and the like, which is capable of keeping permeation of oxygen at substantially zero for a long period of time. <P>SOLUTION: The multi-layer container comprises an inner layer and an outer layer both made of plastics resistant to moisture with an intermediate layer disposed in between the inner and outer layers, wherein the intermediate layer is constituted of at least 3 layers an inner side barrier layer and outside barrier layer both having gas barrier properties with an intervening layer estranging the inner and outer barrier layers, located within 10 to 40% range from the container's outside wall surface with respect to the total wall thickness of the container's gross wall surface while, in addition, the average wall thickness of the intervening layer at the container's body portion is set within a range of 1 to 20% with respect to the average wall thickness of the container's body portion, with the inner and outer barrier layers having oxygen absorbing resin being blended. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a squeezed multilayer container having a layer made of a gas barrier resin composition, and more particularly to a squeezed multilayer plastic container excellent in oxygen barrier property, interlayer adhesion, and squeeze property.

  Since the development of saponified ethylene-vinyl acetate copolymer (EVOH) with excellent gas (oxygen, carbon dioxide) barrier properties, EVOH has been developed as a substitute for glass, metal or conventional plastic materials. In the fields of cosmetics, industrial chemicals, etc., it is a resin that is widely used as a gas barrier material for packaging materials or containers for products that do not like oxygen. In particular, it is widely used as a container (squeeze bottle) for filling water-oil emulsion with viscosity like mayonnaise using its gas barrier property, and squeezing out at the time of use, but it completely blocks oxygen Rather, a slight oxygen permeation is inevitable.

  The EVOH has a hygroscopic property, and if it absorbs moisture, the gas barrier property is lowered. Therefore, is EVOH covered with a hydrophobic thermoplastic resin such as polyolefin resin or polyester resin? Or, it is usually used as a multilayer structure in which EVOH is an intermediate layer and thermoplastic resin is an inner layer and an outer layer. Further, for the purpose of preventing the deterioration of the gas barrier property of EVOH due to moisture from the contents filled in the container, the barrier layer made of EVOH is formed on the container outer peripheral surface side of the wall thickness center line having a low relative humidity. Has been proposed to provide a container with excellent gas barrier properties by arranging the inner layer at a position of 55 to 98% from the inside to the outside, thereby reducing the moisture permeability by making the inner layer relatively thick (for example, patents). References 1-3).

  However, by bringing the barrier layer made of EVOH closer to the outer layer, the deterioration of the oxygen barrier property of EVOH due to moisture absorption can be reduced, but EVOH itself has no action of absorbing oxygen, Inevitably, it has been proposed to add various oxygen-absorbing resins to the barrier layer in order to impart oxygen absorption performance to EVOH (see, for example, Patent Document 4).

  By using EVOH blended with an oxygen-absorbing resin within a predetermined range, oxygen entering from the outside of the container is blocked by the barrier layer made of EVOH and trapped in the barrier layer without being blocked. Absorbing and oxygen permeation into the container can be made substantially zero.

  On the other hand, in many oxygen-absorbing resins, moisture serves as a trigger for the expression of oxygen absorption performance, and the oxygen absorption rate of the oxygen-absorbing resin is improved in the presence of moisture. For this reason, from the viewpoint of preventing the deterioration of EVOH due to moisture absorption, if the barrier layer made of EVOH added with an oxygen-absorbing resin is simply brought to the outer layer side, the oxygen-absorbing performance of the oxygen-absorbing resin will not be sufficiently exerted. As a result, the amount of oxygen permeated to the water increases.

Japanese Patent No. 2864563 JP 2003-063542 A Japanese Patent Laying-Open No. 2005-066857 JP 2001-039475 A

  Accordingly, an object of the present invention is to develop a multilayer plastic container that can keep oxygen permeation into the container substantially zero over a long period of time. In particular, the content filled with a water-oil emulsion or the like can be squeezed out. The goal is to develop a squeeze bottle that is possible.

  The inventors of the present invention conducted intensive research to solve the above-mentioned problems. As a result, at least the inner and outer barrier layers in which the oxygen-absorbing resin is blended with the gas barrier thermoplastic resin and the intervening layer separating the inner and outer barrier layers are included. An intermediate layer composed of three layers is located within a range of 10 to 40% from the outer wall surface of the container with respect to the total wall thickness of the container wall, and the average thickness of the intervening layer in the container body is the container body By making it within the range of 1 to 20% with respect to the average thickness of the oxygen, without increasing the thickness of the barrier layer and increasing the amount of use of the gas barrier thermoplastic resin or oxygen-absorbing resin composition, oxygen It has been found that the period of substantially zero transmission can be extended. The present invention has been made based on such findings.

That is, this invention provides the multilayer plastic container and multilayer squeeze container which consist of the following structures.
1) A multilayer plastic container comprising an inner layer and an outer layer made of a moisture-resistant resin, and an intermediate layer disposed between the inner layer and the outer layer, wherein the intermediate layer includes an inner barrier layer and an outer barrier layer having gas barrier properties. The inner and outer barrier layers are composed of at least three layers with the intervening layers spaced apart, and are located within a range of 10 to 40% from the outer wall surface of the container with respect to the total thickness of the container wall surface, and in the container body An average thickness of the intervening layer is in a range of 1 to 20% with respect to an average thickness of the container body, and the inner and outer barrier layers are blended with an oxygen-absorbing resin. container.
2) A multilayer plastic container in which the average thickness of the outer barrier layer is larger than the average thickness of the inner barrier layer.
3) The multilayer plastic container is a squeezed container, wherein the moisture-resistant resin constituting the inner layer and the outer layer is made of a polyethylene resin having a density of less than 0.935 g / cm ³ , and the average thickness of the outer layer in the container body is the container body A multilayer plastic container which is in the range of 10 to 25% with respect to the average thickness of the part.
4) A packaged acidic oil-in-water emulsified food filled in any of the above multilayer plastic containers.

  The multilayer plastic container of the present invention has an intermediate layer composed of at least three layers of an inner and outer barrier layer in which an oxygen-absorbing resin is blended with a gas barrier thermoplastic resin and an intervening layer separating the inner and outer barrier layers. It is located within the range of 10 to 40% from the outer wall surface of the container with respect to the total wall thickness, and the average thickness of the intervening layer in the container body is 1 to 20% with respect to the average wall thickness of the container body By making it within the range, the period during which oxygen permeation is substantially zero can be extended without increasing the thickness of the barrier layer and increasing the amount of the gas barrier thermoplastic resin or oxygen-absorbing resin used.

    Furthermore, by making the average thickness of the outer barrier layer larger than the average thickness of the inner barrier layer, the oxygen barrier property that blocks oxygen from the outside of the container is improved, and deterioration due to oxidation of the contents is suitably prevented. can do.

Furthermore, the moisture resistant resin constituting the inner and outer layers is a polyethylene resin having a density of less than 0.935 g / cm ³ , and the average thickness of the outer layer in the container body is 10 to 25% of the average thickness of the container body. By setting it within this range, it is possible to obtain a squeezed container that has suitable squeeze properties and does not cause delamination between the inner and outer layers and the middle during use.

An example of the layer structure of the multilayer plastic container of the present invention is shown, and is composed of five layers of inner layer / inner barrier layer / intervening layer / outer barrier layer / outer layer from the inside. It is an example of the multilayer plastic container of the present invention, and is a squeezed container in which a stopper is screwed into a mouth portion formed at the end of a neck portion whose diameter is reduced upward from the trunk portion.

Hereinafter, the present invention will be described in detail.
The inner barrier layer and the outer barrier layer constituting the intermediate layer have gas barrier properties, and a thermoplastic resin having a low oxygen permeability is used from the viewpoint of suitably blocking oxygen entering from the outside of the container. Preferably, the oxygen permeability at 30 ° C.-60% RH is 10 (cc · 20 μm / m ² · day · atm) or less, more preferably 1.0 (cc · 20 μm / m ² · day · atm) or less. Resin is used. The thermoplastic resin constituting the inner barrier layer and the outer barrier layer preferably has a melting point of 180 ° C. or higher, more preferably 185 ° C. or higher, and further preferably 190 ° C. or higher. As the thermoplastic resin, saponified ethylene-vinyl acetate copolymer (EVOH) or polyamide is preferably used, and EVOH is particularly preferable. Generally, ethylene-vinyl acetate copolymer having an ethylene content of 60 mol% or less is preferable. A saponified polymer having a saponification degree of 90% or more is used.

  The gas-barrier thermoplastic resin constituting the inner barrier layer and the outer barrier layer preferably contains an oxygen-absorbing resin in the range of 5 to 50 wt%, more preferably 5 to 15 wt%. As the oxygen-absorbing resin added to the inner barrier layer and the outer barrier layer of the present invention, a known oxygen-absorbing resin can be used. A thermoplastic resin having a carbon-carbon double bond, a polyolefin resin (particularly, Having a tertiary carbon atom in the main chain) or metaxylylene adipamide (MX-nylon), a reaction product of polyamide and polyamide-reactive oxidizable polydiene or oxidizable polyether, or a mixture thereof, etc. An oxidizing resin that is easily oxidized in the presence of an oxidation catalyst and reacts with oxygen in the air to develop oxygen absorption performance (oxygen scavenging function) can be suitably used.

  Furthermore, various known additives, colorants, heat and weathering agents, antistatic agents, oxidation catalysts, and the like can be blended as long as the characteristics are not impaired. In particular, from the viewpoint of improving the oxygen absorption performance of the oxygen-absorbing resin, a transition metal salt is added as an oxidation catalyst in a range of 5000 ppm or less in terms of metal atomic weight. Transition metal salts are inorganic salts, organic salts, or complex salts of transition metals such as cobalt, iron, nickel, and copper, titanium, chromium, manganese, ruthenium, and especially organic acid salts such as carboxylates and sulfonates. Specific examples thereof include acetate, stearate, propionate, hexanoate, octanoate, neodecanoate and the like.

  Furthermore, other thermoplastic resins such as an adhesive resin can be appropriately added as necessary to the gas barrier thermoplastic resin constituting the inner barrier layer and the outer barrier layer as long as the function is not lost. As the adhesive resin, an olefin copolymer having a carboxyl group is preferably used. Among them, an ethylene-acrylic acid copolymer, an ethylene-methacrylic acid copolymer, a maleic anhydride-modified polyethylene and the like are used as the polyolefin resin layer. Suitable for bonding. It is preferable that the amount of the adhesive resin added to the inner barrier layer and the outer barrier layer is 20 wt% or less as long as the gas barrier property is not lost.

In addition, a polyolefin-based resin is preferably used as the moisture-resistant resin constituting the inner layer and the outer layer, and other polyamide resins, polyester resins, and the like can also be used. Examples of polyolefin resins include low density polyethylene having a density of less than 0.935 g / cm ³ , linear low density polyethylene, ultra low density polyethylene, linear ultra low density polyethylene, polypropylene, ethylene-propylene copolymer, and mixtures thereof. For example, a known resin can be used as appropriate.

  Furthermore, from the viewpoint of simplifying the molding equipment, the resin constituting the intervening layer disposed between the inner barrier layer and the outer barrier layer may be the same resin as the moisture-resistant resin constituting the inner layer and the outer layer. Preferably, the inner and outer layers and the intervening layer are melt-kneaded by a single extruder and supplied to a multilayer head to be extruded as a multilayer structure.

  In addition to the layers constituting the multilayer plastic container, it is possible to add layers made of resins having different functions as appropriate. For example, a layer made of recycled resin can be added between the inner layer or the outer layer and the intermediate layer from the viewpoint of recyclability. It is important from the viewpoint of effective use of resources as well as reduction of manufacturing costs to grind scrap resin generated during molding and use it as a recycled resin.

  The multilayer plastic container in the present invention is formed by direct blow molding. In addition, as a multilayer plastic container formed by blow molding, a layer structure comprising five layers of inner layer / inner barrier layer / intervening layer / outer barrier layer / outer layer from the inner layer side is particularly suitable.

  As the layer structure of the multilayer plastic container according to the present invention, the intermediate layer is disposed between the inner layer and the outer layer so that the intermediate layer is located within a range of 10 to 40% from the container outer wall surface of the container wall surface. Is done. Here, the average thickness is a value obtained by arithmetically averaging the thicknesses at the five points of each layer measured by enlarging the cross section of the container wall surface, which is cut out from approximately the center in the vertical direction of the container body, 300 times with a CCD camera. The intermediate layer is composed of an intervening layer disposed between the inner barrier layer, the outer barrier layer, and the inner and outer barrier layers to separate the inner barrier layer and the outer barrier layer, and the average thickness of the intervening layer in the container body is It exists in the range of 1-20% with respect to the average thickness of a container trunk | drum. Thereby, without lowering the oxygen absorption rate of the oxygen-absorbing resin composition, it is possible to prevent a decrease in barrier properties due to moisture absorption, and it is possible to prevent permeation of oxygen into the container over a long period of time. Although the details of the mechanism by which the oxygen barrier property is remarkably improved by the above configuration are unclear, the barrier layer containing the oxygen-absorbing resin is separated into the inner barrier layer and the outer barrier layer, so that the oxygen barrier of the barrier layer due to moisture absorption. The function of the inner barrier layer and the outer barrier layer is separated from the contradictory properties of lowering the property and improving the oxygen absorption rate, thereby improving the oxygen barrier performance.

  In other words, while the inner barrier layer absorbs a relatively large amount of moisture permeating from the inside of the container and the oxygen barrier property is lowered, the absorbed moisture is triggered to improve the oxygen absorption rate, and the inner barrier layer allows moisture to be absorbed. This is presumably due to the fact that moisture does not reach the outer barrier layer and high oxygen barrier properties can be maintained. When the barrier layer is not separated as the inner and outer barrier layers, there is no boundary surface due to the intervening layer, so moisture from the inside of the container is dispersed in the barrier layer, and the oxygen barrier property of the entire barrier layer is lowered, and enters from the outside of the container. The oxygen absorption performance of the oxygen-absorbing resin is deactivated at an early stage due to the oxygen that is generated, and oxygen permeates into the container within a short period of time. Moreover, the said effect is exhibited more notably by making the average thickness of an outer barrier layer larger than the average thickness of an inner barrier layer.

The composition ratio of the thickness of each layer of the inner layer, the outer layer and the intermediate layer to the average thickness of the container body is 10 to 25%, preferably 15 to 20% for the outer layer, 5 to 30% for the intermediate layer, and 60 to 85% for the inner layer. A range is preferable. That is, the intermediate layer located between the inner layer and the outer layer and located on the container outer peripheral surface side with respect to the wall thickness center line is 10 to 40% from the outer wall surface of the container when the average wall thickness of the container body is 100%, preferably It is located within the range of 15-30.
Next, the present invention will be described in more detail by way of examples.

A blow molded multilayer plastic container in which each layer was formed in the thickness composition ratio described in each example and comparative example was molded, and the oxygen barrier performance of this multilayer plastic container was evaluated by the following measurement method and standard. The multi-layer plastic container is a squeeze container capable of extruding the contents, and has a mouth portion and a mouth portion formed at an end portion of the neck portion whose diameter is reduced upward from the body portion. A plug is screwed into the part.
(Test methods and evaluation criteria)
A special solution in which the content changes from white to blue when oxygen enters the container was filled and sealed, and stored in an unhumidified environment (dry) at 35 ° C. to confirm the timing of oxygen permeation.

[Example 1]
Using the resins described in the following a) and b), a five-layer blow molded multilayer plastic container composed of inner layer / inner barrier layer / intervening layer / outer barrier layer / outer layer was produced from the inside.
A) Inner layer, outer layer and intervening layer: low density polyethylene resin having a density of 0.920 g / cm ³ .
B) Inner barrier layer and outer barrier layer: 10 wt% of an adhesive resin was added to a thermoplastic resin in which an oxygen-absorbing resin was blended with an ethylene-vinyl acetate copolymer.
The thickness composition ratio of each layer was 71: 1: 5: 3: 20 (%) from the inner layer, and the intermediate layer was located within a range of 20 to 29% of the outer wall surface of the container. The inner volume of the multilayer plastic container was 200 cc, and the average film thickness of the container body was 400 μm. Furthermore, it was confirmed that there was substantially no oxygen permeation for 15 weeks under the condition of 35 ° C.-dry. The squeeze property was suitable for use.

[Example 2]
A multilayer plastic container was produced in accordance with the method described in Example 1, except that the thickness composition ratio of each layer was 71: 2: 5: 2: 20 (%) from the inner layer.
Further, it was confirmed that there was substantially no oxygen permeation for 12 weeks under the condition of 35 ° C.-dry, but a slight permeation of oxygen was observed thereafter.

[Example 3]
A multilayer plastic container was produced in accordance with the method described in Example 1, except that the thickness composition ratio of each layer was 64: 1: 12: 3: 20 (%) from the inner layer.
Further, it was confirmed that there was substantially no oxygen permeation for 8 weeks under the condition of 35 ° C.-dry, but a slight permeation of oxygen was observed thereafter.

[ Comparative Example 1 ]
Mayonnaise (acid oil-in-water emulsified food) in the multilayer plastic container obtained in Example 1
The product was packed and sealed, and an acidic oil-in-water emulsified food was obtained. Condition 35
After storing for 15 weeks under the condition of ° C.-dry, the flavor was confirmed by sampling the mayonnaise near the container wall, but no change was confirmed compared to before storage. Moreover, when extruding mayonnaise, the squeeze property was good and the amount dispensed was constant throughout.

[Comparative Example 2 ]
The inner layer and the outer layer are the resin a) used in Example 1 and the barrier layer is the resin b) used in Example 1. From the inner layer side, three layers of blow-molded layers consisting of the inner layer / barrier layer / outer layer A plastic container was prepared.
The thickness composition ratio of each layer is 76: 4: 20 (%) from the inner layer, and the intermediate layer is 2 on the outer wall surface of the container.
It was located within the range of 0-24%. The inner volume of the multilayer plastic container was 200 cc, and the average film thickness of the container body was 400 μm. Further, it was confirmed that there was substantially no oxygen permeation for 7 weeks under the condition of 35 ° C.-dry, but a slight permeation of oxygen was observed thereafter.

[Comparative Example 3 ]
Example 1 except that the thickness composition ratio of each layer was 52: 2: 18: 2: 26 (%) from the inner layer.
A multilayer plastic container was produced according to the method described in 1. above. The intermediate layer is 26-4 on the outer wall of the container
It was located within the range of 8%.
In addition, it was confirmed that there was substantially no oxygen permeation for 6 weeks at 35 ° C.-dry condition.
Thereafter, permeation of oxygen was observed.

[Comparative Example 4 ]
Mayonnaise which is an acidic oil-in-water emulsified food in a multilayer container prepared according to the method described in Example 1 except that the thickness composition ratio of each layer is 75: 2: 12: 2: 9 (%) from the inner layer Filled and tightly sealed (manufactured by QP Corporation), a container-packed acidic oil-in-water emulsified food was obtained.
Moreover, when the body or neck wall of this multilayer container was pressed and the mayonnaise was pushed out, delamination was observed.

[Comparative Example 5 ]
A multilayer plastic container was produced in accordance with the method described in Example 1 except that the thickness composition ratio of each layer was changed from the inner layer to 60: 1: 22: 3: 14 (%). The intermediate layer is 14-40 on the outer wall of the container
%.
In addition, it was confirmed that there was substantially no oxygen permeation for 7 weeks under the condition of 35 ° C.-dry.
Thereafter, permeation of oxygen was observed.

  The layer configuration and oxygen permeation test results of the multilayer plastic containers prepared in the examples and comparative examples are summarized in Table 1 below.

The following was clarified from the results of the above test measurement.
1) An intermediate layer composed of at least three layers of an inner barrier layer and an outer barrier layer having gas barrier properties mixed with an oxygen-absorbing resin, and an intervening layer separating the inner and outer barrier layers is a thickness center line of the container body When the average thickness of the container body is 100% on the outer peripheral surface side of the container, the average thickness of the intermediate layer in the container body is located within the range of 10 to 40% from the outer wall surface of the container. Is within the range of 1 to 20% with respect to the average thickness of the container body, high oxygen barrier properties can be obtained, and oxygen permeation can be substantially zero for two months or more.

  2) By making the average thickness of the outer barrier layer larger than the average thickness of the inner barrier layer, the oxygen barrier property for blocking oxygen from the outside of the container is improved.

  3) In a container having squeeze properties, the average thickness of the outer layer in the body portion is within the range of 10 to 25% with respect to the average thickness of the container body portion. In this case, it is possible to obtain a squeezed container in which delamination between the inner and outer layers and the intermediate layer does not occur.

  As described above in detail, the present invention is composed of at least three layers of an inner barrier layer and an outer barrier layer having gas barrier properties blended with an oxygen-absorbing resin composition, and an intervening layer separating the inner and outer barrier layers. By locating the intermediate layer on the outer peripheral surface side of the container relative to the thickness center line of the container body, the storage period of the contents can be extended over a long period of time with substantially no oxygen permeation. Oxygen-barrier multilayer containers are useful as packaging containers for foods, beverages, cosmetics, industrial chemicals, etc., especially seasonings that can be used for a relatively long period of time by opening and closing the lid, especially mayonnaise, sauces, ketchup It is useful as a squeeze container suitable for applications such as dressing and cooking oil.

Claims (3)

A multilayer plastic container comprising an inner layer and an outer layer made of a moisture-resistant resin, and an intermediate layer disposed between the inner layer and the outer layer, the intermediate layer comprising an inner barrier layer and an outer barrier layer having gas barrier properties; The inner and outer barrier layers are composed of at least three layers with an intervening layer spaced apart, and are located within a range of 10 to 30 % from the outer wall surface of the container with respect to the total thickness of the container wall surface, and The average thickness of the intervening layer is 5% or less with respect to the average thickness of the container body, and the average thickness of the inner barrier layer and the outer barrier layer in the container body is equal to the average thickness of the container body. And the total thickness of the inner barrier layer and the outer barrier layer in the container body is 4% or less of the average thickness of the container body, and the outer barrier layer Average meat There smaller than the average thickness of the intervening layer, wherein the average thickness of the outer barrier layer above the average thickness of the inner barrier layer, the inner and outer barrier layer, characterized in that the oxygen-absorbing resin is blended Multi-layer plastic container. The multilayer plastic container is a squeezed container, and the moisture-resistant resin constituting the inner layer and the outer layer is made of polyethylene resin having a density of less than 0.935 g / cm ³ , and the average thickness of the outer layer in the container body is the container body multilayer plastic container of claim 1 Symbol mounting, characterized in that for an average thickness in the range of 10% to 25%. A containerized acidic oil-in-water emulsified food filled in the multilayer plastic container according to claim 1 or 2 .