JPS6111339A - Multilayer plastic vessel - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an intermediate layer 1 of ethylene vinyl alcohol copolymer.
and an inner and outer layer of moisture-resistant thermoplastic resin. The present invention is an improvement that completely improves the shelf life of the container under high humidity conditions and improves its N resistance (to hot filling into trench containers and heat sterilization after light filling). 1'ru.

Ethylene-vinyl alcohol copolymer is one of the resins that has the best permeability to gases such as oxygen among various resins.Using this property, it is used in packaging for bottles, cups, etc. It is widely used in fields such as containers and films. This ethylene-vinyl alcohol copolymer is
It is sensitive to humidity, and has the disadvantage that under high humidity conditions such as 100% RH, the oxygen permeability coefficient becomes about an order of magnitude larger. In order to improve this shortcoming,
Ethylene-vinyl alcohol copolymer 'c-containing i Gas Barrier N has a laminated structure sandwiched between inner and outer surface layers of low water absorption resin such as polyethylene or polypropylene, and the effect of humidity on the ethylene-vinyl alcohol copolymer is reduced. Techniques for reducing intelligence are widely used.

In this laminated structure, even though direct contact between the ethylene-vinyl alcohol copolymer and water or moisture is avoided, there is a non-negligible effect of moisture permeating through the moisture-resistant resin layer, such as It is known that when heat sterilization is performed after filling the contents and sealing the seedlings for the purpose of improving the shelf life of the contents, gas barrier properties are significantly reduced.

In addition to the problems mentioned above, there are
'At, there is a problem of regrind (scrap) reuse. That is, when manufacturing packaging containers from this laminate, when blow molding bottles etc.
In addition, in the case of cup molding, glue ind (scraps) such as punching waste are inevitably produced by light, J, L-, and YI.
)+71]" is necessary from the source point of view.Nori Kushindo has low water absorption due to the laminated structure mentioned above. This blend consists of a blend that is produced by a prefecture, l.
lJ Moisture qc l) a +1 "1" and ethylene vinyl alcohol (2).However, due to this regrind re-origination month 1, the characteristics of the carved product were extremely poor. It was observed that the gas barrier properties; strength, elongation, mechanical properties, flavor characteristics and appearance characteristics of m11. Ta.

Accordingly, an object of the present invention is to provide a container in which the various drawbacks of the above-mentioned conventional multilayer plastic containers are improved.

Another object of the present invention is to provide a multilayer plastic container in which the adverse effects of moisture on the ethylene-vinyl alcohol copolymer-containing layer are eliminated not only during storage but also during heat sterilization and hot filling. be.

Still another object of the present invention is to treat regrind consisting of a blend of ethylene-vinyl alcohol copolymer and moisture-resistant resin, which is produced as a by-product during the production of multilayer plastic containers.
To provide a multilayer plastic container that can be reused in the manufacture of the container without deteriorating its mechanical properties.

This AI [K. 11. t'Lif, for packaging formed of a laminate of a gas barrier layer entirely containing an ethylene-vinyl alcohol copolymer and inner and outer bottom layers of a moisture-resistant thermoplastic resin sandwiched between the gas barrier layer. In the multilayer plastic container, an intervening layer is provided between the gas barrier layer and the moisture-resistant resin layer, in which cylindrical water-absorbing resin particles are dispersed in a special VC thermoformable resin medium capable of layer formation. A container is provided comprising:

According to the present invention, the layer-formable, particularly release-formable resin medium in which the tooth water-absorbing resin particles are woven is a blend of an ethylene vinyl alcohol copolymer and a moisture-resistant tJ.1 resin. A) Seven cold drinks are served, which is characterized by a certain amount of food.

This sixth specification will be explained below based on a specific example shown in the attached drawings.

In FIG. 1 showing an example of the cross-sectional structure of a multilayer plastic container for packaging according to the present invention, a container wall 1 of the container has a gas barrier layer 2 entirely containing an ethylene vinyl alcohol copolymer.
This gas barrier consists of an inner surface layer 6 and an outer surface layer 4 of moisture-resistant resin, which are sandwiched. According to the invention, between this gas barrier layer and the moisture-resistant resin layer 6, 4 there is provided an intervening layer 5 in which water-absorbing resin particles are dispersed in a layer-formable, in particular thermoformable, resin medium;
5' is provided.

That is, the present invention provides layers 5, 5''e containing super water-absorbent resin particles between the moisture-resistant resin layers 6, 4 and the ethylene vinyl alcohol copolymer layer 2, thereby making it possible to prevent the p1 container from being stored during storage. Not only that, but also during heat sterilization and hot filling, the adverse effect of moisture on the ethylene-vinyl alcohol copolymer is prevented, and as a result, the deterioration of the gas barrier properties of the container is significantly suppressed. It is based on

A super absorbent resin is defined as a resin that is essentially water-insoluble and has a stopping power capable of absorbing water tens to hundreds of times its own weight. This super-absorbent resin generally has an ionizable mineral that contributes to water absorption and a loose network or crosslinked structure or gel-like structure that makes the resin water-insoluble.

Examples of the super absorbent resin include starch or cellulose-based graft derivatives such as acrylic acid (salt)-grafted starch, acrylonitrile-grafted hydrolyzate of starch, acrylic acid (salt)-grafted cellulose, and crosslinked polyacrylic e
(salts), especially copolymers of acrylic acid (salts) and polyfunctional monomers such as divinylbenzene or hydrophobic monomers such as 1m styrene and acrylic esters; copolymers of vinyl acetate and acrylic esters; Symphonic union of vinyl alcohol and acrylic acid (salt) blocks produced by chemical reaction; fully reacting polyvinyl alcohol with acid anhydrides such as maleic anhydride and phthalic anhydride, and simultaneously introducing tsylboxyl groups and crosslinking imitations into the side chains. Modified polyvinyl alcohol and the like are known. In these resins, the starch, cellulose, or polyhinyl alcohol component has the effect of cooling the polyacrylic acid component and keeping it in a gel state.

In this book, all of these water-absorbing resins are
Among them, crosslinked polyacrylic acid (Tan) is preferred, and this one is Aqua Keep 4S, Aqua Keep 1u.
It is commercially available from Tetsu Seikagaku Co., Ltd. under the trade name SH. Another suitable example is a vinyl alcohol acrylic acid (salt) block copolymer, Sumikagel 5 from Sumitomo Kaji Co., Ltd.
It is commercially available under the trade name S.

As is clear from the above-mentioned composition and structure, these water-absorbing resins themselves do not have thermoformability, but according to the present invention, they can be formed into microspherical particles or microflake particles. By dispersing it in a layer-formable, particularly thermoformable resin, it can be laminated, for example by coextrusion, which is a significant advantage of the present invention.

When used for this purpose, the superabsorbent resin used in the present invention exhibits aged characteristics that are not found in ordinary desiccants. That is, this water-absorbing resin has a characteristic that its saturated moisture absorption rate under high temperature or high humidity is significantly higher than that of the desiccant. For example, silica, which is a typical example of a desiccant,
Whereas the super absorbent resin used in the present invention exhibits a saturated moisture absorption rate of less than 40% at a temperature of 40°C (humidity 95% RH), it has a saturated moisture absorption rate of about 4 times that of about 160%. shows. This tendency becomes more pronounced as the temperature increases. Also,
Even when compared under high humidity conditions of 95 x RH (temperature 20°C), the saturated moisture absorption of silica is on the order of about 60%, whereas that of the super absorbent resin used in the present invention is on the order of about 10%.
At 0%, it is on the order of about three times as much.

However, the fact that this water-absorbent resin exhibits an extremely large saturated moisture absorption rate under high temperature and high humidity conditions is due to the fact that, apart from heat sterilization and hot light filling, the ethylene vinyl alcohol copolymer deteriorates its gas barrier properties. This means that protection from That is, in heat sterilization of sealed packages, 1.10Q to 150
℃ The temperature is 70 to 99℃, and the humidity inside the container is RHlo (J
%, the ethylene vinyl alcohol copolymer has a relationship between the surfaces and the humidity reached by passing through the moisture-resistant 4fJJ fat layer (moisture permeability increases in Gaochang).
This leads to a decrease in gas barrier properties. On the other hand, according to this book-j6jJJ, the highly water-absorbent resin interposed between the invasive scaly and the ethylene-vinyl alcohol 33X combined layer, or Since it exhibits a significantly large saturation absorption 4, most of the moisture that permeates through the moisture-resistant resin is captured by the highly water-absorbent resin, suppressing the deterioration of the gas barrier properties of the ethylene-vinyl alcohol copolymer. be.

Another advantage of the superabsorbent resin used in the present invention is that it has a high water-retaining property, and the pressure dependence of this water-retaining property is also very small. That is, even in a structure in which superabsorbent resin particles are dispersed in a layer-formable resin medium, particularly for thermoforming, the hygroscopicity and water retention are low, and the particles retain a large amount of water. It has the advantage that moisture is gradually released even when the air is wet.

In the present invention, the amount of superabsorbent resin contained in the layer-formable, particularly thermoformable, resin medium is such that the layer formation, especially thermoforming such as melt extrusion, is possible while still allowing satisfactory moisture barrier. stipulated in For this purpose, it is desirable to contain 40 to 2% by weight, particularly 35 to 5% by weight of the superabsorbent resin, based on the weight of the entire intervening layer. The particle size of the super absorbent resin particles is 2000 microns or less, especially 100 microns or less.
It is desirable that it be in the range of 0 microns or less.

As a thermoformable resin medium for dispersing super absorbent resin,
Any thermoplastic resin that can be thermoformed can be used. In general, an adhesive resin is used to bond the moisture-resistant resin layer and the ethylene vinyl alcohol copolymer, and a resin blend is used for the above-mentioned regrind (qλ1). These intervening layers are made to have water-absorbing properties.This will be described later.

Ethylene-vinyl alcohol copolymer 1. -'cha,
An ethylene-vinyl acetate copolymer having an amount of 20 to 60 mol%, particularly 25 to 50 mol%, is saponified to a degree of saponification of 96 mol% or more, particularly 99 mol% or more. The resulting saponified copolymer is used extensively. This saponified ethylene vinyl alcohol copolymer is
Form a film! There should be enough molecules per tM to give a phenol:water ratio of 8.
Measured at 60°C in a mixed solvent of 5:15 o, o 1ti
It is desirable to have a viscosity of J/9 or more, particularly 0°05d13/g or more.

Kame 11 wet resin (low water absorption resin) is AS'l'
If the water absorption rate measured with MD570 is 0.5% or less, especially 0.
Up to 1% of thermoplastic resins are used, such as low-1 medium- or high-density polyethylene, intact polypropylene, ethylene-propylene copolymers, polybutene-1, ethylene-butene-1 Copolymer, propylene-buty7-1 copolymer, ethylene-propylene-butene-1 copolymer, ethylene-vinyl acetate copolymer, ionically crosslinked olefin copolymer (ionomer)
Alternatively, olefin resins such as blends thereof can be used, and thermoplastic polyesters such as polyethylene terephthalate and polytetramethylene terephthalate and polycarbonates can also be used.

In some cases, sufficient adhesiveness cannot be obtained between the ethylene vinyl alcohol copolymer and the moisture-resistant thermoplastic resin during lamination, but in this case, an adhesive resin is interposed between the two.

Such adhesive resins include carbonyl (-C-) groups based on carboxylic acids, carboxylic anhydrides, carboxylic acid salts, carboxylic acid amides, carboxylic acid esters, etc. in the main chain or side chain, and 1 to 700 mI 1 valent (?F1.
11q)/100fj resin, especially 1fj to 5
00mgq/100. ! Examples include thermoplastic resins containing a concentration of i' resin. Adhesive resin y14 hit 1
1 is ethylene-acrylic acid co-1 (combination, ionically crosslinked olefin resin body, maleic anhydride gshift polyethylene, maleic anhydride grafted polypropylene, acrylic acid kraft polyolefin, ethylene-vinyl acetate co-1)
It is one type or a combination of two or more types of coalescence, copolymerized polyester, copolymerized polyamide, etc. These A resins are useful for lamination by simultaneous (ψ deposition or sandwich lamination, etc.). A thermosetting adhesive resin such as incyanate yarn or epoxy yarn is also used.

In one embodiment of the present invention, as shown in FIG. 1, a super absorbent resin is dispersed in these adhesive resins and an intervening layer 5.5
′ also serves as an adhesive layer.

In another preferred embodiment of the present invention, during the manufacture of containers, regrind is produced as a by-product, that is, ethylene-vinyl alcohol copolymer (EVQH) and low water absorption thermoplastic resin (LMI
A super absorbent resin is added to the blend with l). As already pointed out, when a blend of EVOH and LMR, especially regrind, is reused, various physical properties deteriorate significantly. The inventors of the present invention have obtained the knowledge of a method as a result of extensive research into this cause. That is, EVOH has a water absorbency of p1. Therefore, since the blend, especially the regrind made of this blend, is necessarily placed in the atmosphere, it absorbs water to a certain extent.

In melt extrusion of a blend of Shikamo, ethylene-vinyl alcohol copolymer and low water absorption resin, unlike the case of single extrusion of ethylene-vinyl alcohol copolymer, the ethylene-vinyl alcohol copolymer in the blend is placed under very special conditions. That is, in the molten resin stream of this blend, the copolymer takes the form of being dispersed in a sea-island shape in the connecting rods in a low water absorption resin such as polyolefin, or as a main polymer. As the Genmeisha and others have already proposed,
It has a structure in which electricity is distributed in a thin molten form, and the water in the blend is adsorbed by the ethylene-vinyl alcohol co-AI combination with the above distribution of 4'+9, and it is surrounded by a hydrophobic wood 1iW medium. The current situation is that Furthermore, even though ethylene-vinyl alcohol copolymer can be melt-molded, it is easily susceptible to thermal deterioration compared to other resins such as polyolef 17.
Blends that have gone through a blending process such as pelletizing, lrt
In regrinding, which has a history of melt molding once every year, thermal deterioration of the resin has already progressed. However, when heat is applied to this ethylene-vinyl alcohol copolymer which tends to undergo thermal deterioration in the presence of water, the thermal deterioration of the resin is accelerated and reversed. In other words, when remelting an ethylene vinyl alcohol copolymer that has a history of melting,
It was discovered that water molecules act as a catalyst for thermal deterioration. Moreover, when melting the blend, the water-containing ethylene-vinyl alcohol copolymer is exposed to the melting temperature in the form of fine particles or layers confined by the hydrophobic resin, so the copolymer appears to be , under conditions such as autoclave treatment, all effects of heat occur, resulting in gelling, rubberization, foaming, etc., resulting in a decrease in gas barrier properties; a decrease in strength, elongation, and impact resistance;
Problems such as flavor deterioration due to the gradient of resin decomposition products and poor appearance due to coloring, foaming, etc. occur.

In the present invention, as already mentioned, the super absorbent resin has a large saturated moisture absorbing lid at high temperatures, and by blending this resin into the blend, the troubles 1 and 5'lf can be eliminated. The glue grind of a blend containing an ethylene-vinyl alcohol copolymer, which has been difficult to use in the past, can now be reused for molding into containers, films, and sheets.

In the blend used in the present invention, the ethylene-vinyl alcohol copolymer (I!j'VO1i) and the low water absorption thermoplastic IJP9: and the tsukure (LMR) may be present in any ratio, but generally The color is EVOIi: LMnot'= 1: 3 to ILl [JO: 1 especially 1: 2 to 500:
It is preferable that it exists in a lij-Rj ratio of 1. During regrind that occurs as a by-product during molding, EvoH:r,M)<=1:2000 to 1;6j-1
j, oxidation, j, j: of the low water absorption resin is considerably excessive compared to EVOIi.

Have you tried this blend before? Thermoplastic resins other than those shown may be contained. For example, since ethylene-vinyl alcohol copolymer and low water absorption resin do not generally have thermal bonding properties, it is necessary to mix adhesive resin in one or both of the layers, or Adhesive resin) ¥1 is provided between the horizontal fat layers.

These adhesive resins are naturally regrind blends'
It will also get mixed into the snout. 1. If the blend t1 is coextruded with a different low water absorption resin and/or ethylene vinyl alcohol copolymer, the entire adhesive resin may be mixed into the blend.

These carbonyl-containing thermoplastic resins generally have a total amount of EVOH and LMR of 100 to 200 o per part i,
Oi heavy parts are present, especially in amounts of 100 to 0.1 parts by weight.

These blends containing super absorbent resin are
The layer configuration shown in Figure 1, that is, the layer configuration that also serves as an adhesive layer, can be used, or as shown in Figure 2, a separate adhesive resin FVI6.6't- is provided and these adhesives It is also possible to provide a water-absorbing resin combination blend layer 5.5' between the resin 6.6' and the moisture-resistant resin layer 6.4.

Of course, the present invention is not limited to these embodiments, and a super absorbent resin may be blended with the moisture-resistant resin or ethylene-vinyl alcohol copolymer exemplified above and used as an intervening layer.

The container of the present invention can be manufactured by a method known per se, except for the layered structure described above.

For multilayer simultaneous extrusion, the mixture is melt-kneaded using an extruder compatible with Tani Resin Jso, and then extruded into a predetermined shape through a multilayer die such as a T-die or a circular die. Furthermore, lamination methods such as dry lamination, sandwich lamination, and extrusion coating may also be employed. The molded product is a film,
It can be shaped like a sheet, a parison or pipe for forming bottles or tubes, a preform for forming bottles or tubes, etc. Formation of bottles from parisons, pipes or preforms is easily accomplished by pinching off the extrudate with a pair of splitters and blowing fluid into the interior. Further, after the pipe or preform is cooled, it is heated to a stretching temperature, stretched in the axial direction, and braised in the circumferential direction using fluid pressure, thereby obtaining a stretched blow bottle or the like.

In addition, packaging containers in the form of a cup, a tray, etc. can be obtained by subjecting the material to film or sheet forming, vacuum forming, pressure forming, stretch forming, plug assist forming, and the like.

Furthermore, in the case of multilayer films, they are stacked in a bag shape, folded, and heat sealed around the periphery to form a bag-like packaging container (pouch).

Hon f! A will be explained using the following example.

Example 1 Polypropylene (Mitsubishi Noblen BC-80゜3iI Yuka) was used as the inner and outer layers, ethylene-vinyl alcohol copolymer (Everlu F1 Kuraray) was used as the middle layer, and acid-modified polypropylene (Modic, P- 500F, Mitsubishi Yuka) as the adhesive layer for the inner, outer and intermediate layers, and the layer composition ratio is outer layer:adhesive layer:intermediate layer:adhesive layer:inner layer = io: 0
．． An elliptical bottle having a symmetrical five-layer laminated structure of 5:1:0.5:10 was molded. The average wall thickness of the bottle was approximately 600μ, and the internal volume was 280Ω. The inner and outer layers have a diameter of 65W and an extruder with a metering fine screw with a L/D of 22. The middle layer has a diameter of 40111XL/D.
iE20 (h output s similar to Q, adhesion Mlk! iE diameter; A1
Extrusion was carried out using a similar extruder of 32 m, L/DmZ20 at a die temperature of 190°C.

In addition to the above adhesive, polyacrylic rR-based super absorbent resin (
Aqua Keep 10SH, Seitetsu Kagaku Kogyo Co., Ltd.) were tri-blended at various ratios in a Hen-El mixer, thoroughly dried, and then molded into the same bottles as described above.

Similarly, the above-mentioned super absorbent resin used had a mesh size of 150 mesh or less.

After the resulting bottle was retorted at 120°C for 30 minutes, the oxygen permeability of the bottle was measured by the following method.

Put a small amount of distilled water in the bottle, and while keeping the inside of the bottle at t-100')6RH, replace the bottle with nitrogen gas in a complete vacuum, and then seal it with a heat seal lid containing aluminum foil, which practically does not allow oxygen to pass through. Then, a rubber for gas chromatography inlet was attached to the lid using silicone thread adhesive.

The bottle was stored for one week in a constant temperature and humidity chamber at 67°C and 6oXRH, and then the rI that permeated into the bottle! The concentration of the element in the bottle was determined using a gas chromatograph, and according to the following formula, the concentration in the bottle was 1 [Jo
The oxygen gas permeability (Qot) at 67° C. was calculated at XRH and 6oXRH outside the bottle. The results are the average values of N=5 pieces.

Here, m: Amount of nitrogen gas filled into the bottle (gIt) t: Storage period in a constant temperature and humidity chamber [d x] Ct: Oxygen concentration in the bottle after 8 hours CVol"X] A:
Effective different area of bottle [Inertia 2] op: IIIK gas partial pressure (= 0.209) C
atm] Same, for comparison, a bottle that is not retorted.

0! was also measured. The results are shown below.

From the above, it has been found that as the superabsorbent resin content increases, the influence of retort treatment is reduced, and furthermore, the oxygen barrier properties are improved even without retort treatment.

However, when the superabsorbent resin content was 40% by weight, the adhesive function deteriorated, and in some cases, delamination occurred in a drop test from a height of 1 after retorting. When the superabsorbent resin content was 35% by weight or less, no delamination occurred in the drop test.

Furthermore, at 50% by weight, most of the samples showed delamination in the drop test.

Example Z In the same manner as in Example 1, a cage-sized super absorbent resin was triblended with the adhesive at a ratio of 20% by weight, and a similar bottle was molded. Immediately after retorting at 120° C. for 30 minutes, the container was filled with water and the mouth was sealed with an aluminum foil seal lid, followed by a drop test of 10 times onto a concrete surface from a height of 1 rn. There were 6 bottles each tested. The results are shown below.

That's all, 9 meshes (eyes open, 1.981 iot)
It has been found that the following superabsorbent resins are desirable.

Example S Polypropylene (Mitsubishi Noblen MA-6, Mitsubishi Yuka)
are the innermost and outermost layers, ethylene-vinyl alcohol co-electric 8 body (Everloo F1 Kuraray) 'Jk intermediate layer, this molded product glue grind is the inner and outer layer, acid-modified polypropylene (Modic, P-600F, Mitsubishi Oil) ) inside,
The layer composition ratio of the adhesive layer between the outer layer and the intermediate layer, innermost layer: inner layer: adhesive layer: intermediate layer 2 adhesive layers: outer layer: outermost layer - 20:25
:3:4:3:25:20. Thick? A 0.8M sheet was created.

The temperature of the extruder head was 200°C for polypropylene, 175°C for regrind, 210°C for acid-modified polypropylene, and 200°C for ethylene vinyl alcohol co-electrolyte.

The above regrind was performed under the conditions of 20℃ and 65XRH.
This was left to stand for 0 days, and the super absorbent resin of Example 1 was tri-blended in various ratios for 15 minutes using a Henschel type mixer, and all multilayer sheets were prepared in the same manner.

The entire situation during sheet extrusion was observed, and the results are shown below.

That is, it has been found that by completely mixing the super absorbent resin into the regrind, the water content of ethylene vinyl alcohol in the regrind can be reduced and deterioration can also be prevented.

Next, the above E and C containing super absorbent resin.

Sheets D and E were regrinded and heated in the same manner at 20°C, 6
After standing at 5XRH for 20 days, all of these were similarly extruded to form multilayer sheets. The results are shown below.

In other words, even if the superabsorbent resin is included in the regrind and the superabsorbent resin absorbs some moisture, foaming and yellowing hardly occur, and the water absorption ability of the superabsorbent resin or the moisture retention method is turned out to be very good.

Example 4 Stretched polypropylene film (thickness 2 μm, Torefan BO East) All outer layers, ethylene vinyl alcohol copolymer film (thickness 17 μm, EVAL F1 Kuraray) All middle layers, Unstretched polypropylene film (thickness 50 μm, Torefan NO, Higashi) All inner layers, Toluene: Ethyl acetate =
Urethane adhesive (AD503) dissolved in a ratio of 50:50
, curing agent CAT-10, Toyo Morton) to prepare a multilayer film. Further, 60% of the superabsorbent resin described in Example 1 having a mesh size of 400 or less was mixed in the above adhesive solution as a solid content, and cured in the same manner to prepare a multilayer film.

After making a bag for each multilayer film, immediately after retorting at 120° C. for 60 minutes, a small amount of distilled water was put into the bag, the air was replaced with nitrogen, and the opening was heat-sealed and sealed.

A rubber for gas chromatography inlet was attached to the bag with silicone adhesive, and the bag was stored in a constant temperature and humidity chamber at 60°C and 60 According to the formula described in Example 1, the oxygen gas permeability at 60°C and 60XRH (
QO2) was calculated.

The results are the average values of N=6 pieces. For comparison, Qo2 was also measured for bags that were not subjected to retort treatment.

It has been found that bags containing superabsorbent resin have improved gas barrier properties even under normal storage conditions, but that performance is maintained even after retort treatment.

Comparative Example 1 In Example 1, silica gel was used as a substitute for the super absorbent resin, and the oxygen permeability of a molded bottle after retort was measured in the same manner. The results are shown below.

Comparison with the results of Example 1 shows that the superabsorbent resin is significantly more effective than silica gel.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing one aspect of the cross-sectional structure of the plastic container of the present invention, and FIG. 2 is a diagram showing another aspect of the cross-sectional structure of the plastic container of the present invention. Reference number 1 is the container wall, 2 is the gas barrier layer, 6 is the inner surface layer, 4 is the outer surface layer, 5 and 5' are the intervening layers, and 6.6' is the adhesive resin layer.

Claims (1)

[Claims] (1) A packaging multilayer formed of a laminate of a gas barrier layer containing an ethylene-vinyl alcohol copolymer and inner and outer surface layers of moisture-resistant thermoplastic resin sandwiching the gas barrier layer. The plastic container is characterized in that a valve layer is provided between the gas barrier layer and the moisture-resistant resin layer, in which highly water-absorbent resin particles are dispersed in a layer-formable, particularly thermoformable, resin medium. container.