JP6911413B2 - Thermoformed container - Google Patents

Description

The present invention relates to a multi-layer container molded by thermoforming such as vacuum forming or pressure molding, and more specifically, molding having a layer made of a propylene-based polymer and a layer made of an ethylene-vinyl alcohol copolymer. The present invention relates to a thermoformed container having excellent properties and appearance characteristics.

Conventionally, a multilayer container having an inner / outer layer made of an olefin resin and an intermediate layer made of an ethylene-vinyl alcohol copolymer has been widely known.
Such a multilayer container is generally molded by direct blow molding, melt molding such as injection molding, or thermoforming such as vacuum forming or compressed air molding (Patent Document 1 and the like).
The multi-layer container by thermoforming has the advantages of excellent productivity, transparency and mechanical strength, while in thermoforming, the container is molded by reheating to a temperature equal to or higher than the melting point. In particular, it has been difficult to efficiently form a deep-drawn container having a large ratio (L / D) of height (L) to diameter (D).

In order to solve such a problem, (i) melt flow rate (MFR) (temperature 230 ° C., load 2.16 kg) is 0.2 to 1.5 g / 10 min, and (ii) differential scanning calorimetry (DSC). A deep drawing structure having a container depth / diameter ratio of 1 or more, which is formed by solid-phase pressure air molding using a polypropylene-based sheet made of a propylene-based resin composition having a melting peak temperature of 165 ° C. or higher as measured in 1. A thermoformed container characterized by having a container has been proposed (Patent Document 2).

Japanese Patent No. 4894066 Japanese Unexamined Patent Publication No. 2011-126544

However, even in the thermoformed container described in Patent Document 2, when the ethylene-vinyl alcohol copolymer is used as the intermediate layer, the ethylene-vinyl alcohol copolymer is different from the olefin resin constituting the inner and outer layers. Due to having different stretching characteristics, the intermediate layer made of an ethylene-vinyl alcohol copolymer may be cut or uneven in thickness, and the desired gas barrier property may not be obtained, and the appearance characteristics and molding may not be obtained. I was not completely satisfied with the sex.

Therefore, an object of the present invention is to sufficiently exhibit the excellent gas barrier property of the ethylene-vinyl alcohol copolymer in a thermoformed container having a layer made of a propylene-based polymer and a layer made of an ethylene-vinyl alcohol copolymer. It is an object of the present invention to provide a thermoformed container which is possible and has excellent appearance characteristics such as transparency and wall thickness distribution and moldability.

According to the present invention, it is composed of a propylene-based polymer containing homopolypropylene as a main component, which has an isotactic index of 93% or more and a melt flow rate of 0.3 g / 10 minutes or more and less than 1.0 g / 10 minutes. Provided is a multilayer container characterized by having at least a layer and a layer made of an ethylene-vinyl alcohol copolymer having two or more peak crystal melting temperatures.

In the thermoformed container of the present invention
1. 1. The layer made of ethylene-vinyl alcohol copolymer is made of a blend made by blending two or more kinds of ethylene-vinyl alcohol copolymers having different ethylene contents, and the crystal melting peak temperature is at least 180 ° C. or higher and 170 ° C. To have below
2. The layer made of the ethylene-vinyl alcohol copolymer comprises an ethylene-vinyl alcohol copolymer having an ethylene content of 20 to 35 mol% and an ethylene-vinyl alcohol copolymer having an ethylene content of 36 to 50 mol%. Blended in a blending ratio of 90: 10 to 50:50,
3. 3. The propylene-based polymer contains a crystal nucleating agent , and the crystal nucleating agent is an organic phosphate, which is contained in an amount of 0.01 to 5 parts by weight with respect to 100 parts by weight of the propylene-based polymer. What you are doing
4. The layer structure is, in order from the outside, a layer composed of the propylene-based polymer / a regrind layer / an adhesive resin layer / an ethylene vinyl alcohol copolymer intermediate layer / an oxygen absorbing layer / an ethylene-vinyl alcohol copolymer intermediate layer / an adhesive resin. A layer / an adsorbent-containing layer / an inner layer made of the propylene-based polymer.
5. The main component of the propylene-based polymer is homopolypropylene having a melt flow rate of 0.3 to 0.5 g / 10 minutes or less.
Is preferable.

In the thermoformed container of the present invention, the drawdown during thermoforming is effective by forming the inner and outer layers from a propylene-based polymer containing a highly crystalline homopolypropylene having an isotactic index of 93% or more as a main component. In addition to improving moldability, it is possible to impart excellent transparency. Further, since it has high crystallinity, its mechanical strength is improved and its impact resistance is excellent.
Further, by having the ethylene-vinyl alcohol copolymer used (hereinafter, sometimes simply referred to as "EVOH") have two or more crystal melting peak temperatures, the stretching characteristics of EVOH are improved without impairing the gas barrier property. As a result, it becomes possible to effectively prevent the occurrence of breakage of the intermediate layer made of EVOH, uneven thickness, and the like, and it becomes possible to exhibit the gas barrier property inherent in EVOH.
The thermoformed container of the present invention is excellent in transparency and has a uniform wall thickness distribution by being manufactured by compressed air molding, and EVOH has excellent thickness without breakage or uneven thickness of the layer made of EVOH. It can be seen that the container has sufficient gas barrier properties and also has excellent mechanical strength (impact resistance).
Further, since the thermoformed container of the present invention has excellent stretchability of the layer made of EVOH, L / D ((D) diameter, (L) height) is in the range of 0.1 to 5, and is highly advanced. Even if the container is stretched to a high profile, it is molded with good moldability without uneven stretching, and the EVOH layer is continuously formed to have a uniform thickness, and has excellent appearance characteristics and gas barrier properties.

It is a figure which shows an example of the thermoforming container multilayer structure of this invention. It is a figure which shows another example of the multilayer structure of the thermoformed container of this invention. It is a figure which shows another example of the multilayer structure of the thermoformed container of this invention. It is a figure which shows another example of the multilayer structure of the thermoformed container of this invention.

The thermoformed container of the present invention has a layer made of a propylene-based polymer containing homopolypropylene having an isotactic index of 93% or more as a main component, and an ethylene-vinyl alcohol co-weight having two or more crystal melting peak temperatures. It is an important feature to have at least a layer of coalescence.

(Propylene polymer)
In the present invention, the propylene-based polymer is mainly composed of homopolypropylene having an isotactic index of 93% or more, particularly 96 to 99% high crystallinity, that is, 90% by weight or more, particularly 100% by weight in the propylene-based polymer. It is preferable that it is contained in an amount of%.
The isotactic index is an isotactic fraction in pentad units in a polypropylene molecular chain measured using a nuclear magnetic resonance spectrum (13C-NMR) of isotope carbon, and is defined in the present invention. By having the isotopic index of homopolypropylene constituting the propylene-based polymer in the above range, drawdown during thermoforming is effectively prevented, moldability is improved, and the wall thickness distribution is uniform and transparent. It is possible to provide a container that is high in appearance and has excellent impact resistance.

In the present invention, as another propylene-based polymer that can be contained in the propylene-based polymer, a propylene / α-olefin random copolymer can be exemplified. Examples of the α-olefin in such a propylene / α-olefin random copolymer include ethylene, butene-1, penten-1, hexene-1, octene-1, 4-methylpentene-1, and the like, and in particular, propylene. Can be preferably contained in a proportion of 80% by weight or more, particularly 95 to 99% by weight, and the residual structural unit is an α-olefin, particularly a propylene / ethylene random copolymer composed of ethylene.

In the present invention, homopolypropylene, which is the main component of the propylene-based polymer, has a melt flow rate (JIS K7210 compliant: hereinafter referred to as "MFR", which is a value measured at 230 ° C.) of 0.3 to 3.0 g. A homopolypropylene in the range of / 10 min, particularly 0.3 to 1.0 g / 10 min is preferable from the viewpoint of impact resistance. When the MFR is larger than the above range, the impact resistance of the thermoformed container may be inferior to that when the MFR is in the above range, while when the MFR is too low, the fluidity is inferior and molding is performed. The sex may be impaired.

Further, conventionally known resin additives such as heat stabilizers, antioxidants, lubricants, inorganic fillers, colorants and the like can be added to the propylene-based polymer according to a conventionally known formulation, and in particular, propylene. In order to further enhance the crystallinity of the system polymer and further improve the moldability and transparency, it is preferable to add a crystal nucleating agent. Since the melting point is raised by adding the crystal nucleating agent, the drawdown during molding is reduced, and the container wall thickness distribution can be secured. In addition, since the crystallization temperature also rises, the container can be taken out at a high temperature during molding, and the molding cycle is improved.
The crystal nucleating agent is not compatible with propylene-based polymers and is not limited to metal salts of organic carboxylic acids such as benzoic acid, malonic acid and succinic acid, such as lithium salt, sodium salt and potassium. Conventionally known crystal nucleating agents such as organic nucleating agents such as salts, magnesium salts, calcium salts and organic phosphate ester salts, and inorganic nucleating agents such as talc, myoban, silica, titanium oxide and calcium oxide can be exemplified. However, organic phosphates can be particularly preferably used.
The crystal nucleating agent is added in an amount of 0.001 to 5 parts by weight, particularly 0.01 to 0.5 parts by weight and 0.1 to 0.5 parts by weight, based on 100 parts by weight of the propylene polymer. It is desirable to be there. If the amount of the crystal nucleating agent is smaller than the above range, the crystallinity cannot be sufficiently increased, while if it is more than the above range, the moldability may be impaired.

(Ethylene-vinyl alcohol copolymer)
In the present invention, the layer made of an ethylene-vinyl alcohol copolymer has two or more crystal melting peak temperatures, whereby, as described above, the stretching characteristics are improved without impairing the excellent gas barrier property. Will be possible.
Such a layer made of EVOH is preferably formed from a blend made by blending two or more kinds of ethylene-vinyl alcohol copolymers having different crystal melting peak temperatures, and in particular, the crystal melting peak temperature is high. It is desirable to blend at least two types of EVOH having a crystal melting peak temperature of 180 ° C. or higher and EVOH having a crystal melting peak temperature of 170 ° C. or lower.
Examples of EVOH having a crystal melting peak temperature of 180 ° C. or higher include EVOH having an ethylene content in the range of 20 to 35 mol%, particularly 25 to 30 mol%, while when the crystal melting peak temperature is 170 ° C. or lower. As a certain EVOH, an EVOH having an ethylene content in the range of 36 to 50 mol%, particularly 40 to 45 mol% can be exemplified.
Generally, in EVOH, the higher the ethylene content, the better the stretching property while lowering the gas barrier property, and the lower the ethylene content, the poorer the stretching property but the better the gas barrier property. In the present invention, by blending at least two types of EVOH having an ethylene content in the above range, a layer made of EVOH having excellent gas barrier properties can be formed as a continuous layer having a uniform thickness and without breaks. Therefore, it is surely exhibited without impairing the excellent gas barrier property inherent in EVOH.

In the layer made of the ethylene-vinyl alcohol copolymer, the ethylene-vinyl alcohol copolymer having an ethylene content of 20 to 35 mol% and the ethylene vinyl alcohol copolymer having an ethylene content of 36 to 50 mol% are 90: It is preferable that the mixture is blended in a blending ratio (weight ratio) of 10 to 50:50, particularly 80:20 to 60:40. As a result, the above-mentioned gas barrier properties and stretching properties are provided in a well-balanced manner, and as a result, the excellent gas barrier properties of EVOH can be maximized.
This ethylene-vinyl alcohol copolymer should have a molecular weight sufficient to form a film and is generally 0 as measured at 30 ° C. in a mixed solvent with a weight ratio of [phenol / water] of 85/15. It is desirable to have an intrinsic viscosity of 0.01 dl / g or more, particularly 0.05 dl / g or more.

(Multi-layer structure)
The multilayer container of the present invention has an essential structure of the above-mentioned layer made of a propylene polymer and a layer made of an ethylene-vinyl alcohol copolymer, and is a thermoformed container made of these two layers. However, preferably, it has a basic structure in which the inner layer and outer layer made of the above-mentioned propylene polymer and the gas barrier layer made of EVOH are intermediate layers, and further, an oxygen absorbing layer, an adhesive layer, and a regrind layer. , It is preferable to contain other conventionally known layers such as an adsorbent-containing layer. The following layer structures can be exemplified, but not limited to this.
FIG. 1 is a diagram showing an example of the multi-layer structure of the thermoformed container of the present invention. In this example, the outer layer 1 and the outer layer 1 made of a propylene-based polymer containing homopolypropylene having an isotactic index of 93% or more as a main component and A gas barrier layer made of EVOH having two or more crystal fusion heat peak temperatures is formed as an intermediate layer together with the inner layer 2, and the outer layer 1 / outer layer side adhesive layer 3a / gas barrier layer 4 / inner layer side is formed in this order from the outer layer side. It has a layer structure of an adhesive layer 3b / an inner layer 2.

Further, in the embodiment shown in FIG. 2, in the embodiment shown in FIG. 1, two gas barrier layers made of EVOH are formed, and an oxygen absorbing layer is formed between them. Outer layer 1 / outer layer side adhesive layer 3a / gas barrier It is composed of a layer 4a / an oxygen absorbing layer 5 / a gas barrier layer 4b / an inner layer side adhesive layer 3b / an inner layer 2, and the gas barrier property is further enhanced by capturing the permeated oxygen with the oxygen absorbing layer.
Further, in the embodiment shown in FIG. 3, in the embodiment shown in FIG. 2, a regrind layer 6 made of a regrind resin generated during container molding is formed between the outer layer 1 and the outer layer side adhesive layer 3a. It is composed of an outer layer 1 / a regrind layer 6 / an outer layer side adhesive layer 3a / a gas barrier layer 4a / an oxygen absorbing layer 5 / a gas barrier layer 4b / an inner layer side adhesive layer 3b / an inner layer 2.
Furthermore, FIG. 4 shows an embodiment in which an adsorbent-containing layer 7 containing an adsorbent such as zeolite is formed between the inner layer side adhesive layer 3b and the inner layer 2 in the embodiment shown in FIG. 3, and the outer layer 1 / regrind It is composed of layer 6 / outer layer side adhesive layer 3a / gas barrier layer 4a / oxygen absorbing layer 5 / gas barrier layer 4b / inner layer side adhesive layer 3b / adsorbent-containing layer 7 / inner layer 2, and an adsorbent such as zeolite is placed on the inner layer side. By forming the adsorbent-containing layer 7 to be contained, the flavor property of the content can be improved.

In the thermoformed container of the present invention, the layer thickness of each layer is 280 to 380 μm, particularly 310 to 380 μm, in the body portion which is the thinnest part of the container, the thickness of the layer made of the propylene polymer (each of the inner layer and the outer layer) is 280 to 380 μm. It is preferably in the range of 340 μm, and the thickness of the layer made of EVOH is preferably in the range of 20 to 80 μm, particularly 40 to 60 μm. When a plurality of layers made of EVOH are formed, it is preferable that the total thickness of the plurality of layers is within the above range.
The thickness of the other layer formed in the mature molding container of the present invention is not limited to this, but the oxygen absorbing layer is preferably in the range of 10 to 60 μm, particularly 20 to 40 μm. When the regrind layer is provided, it is preferably formed in the range of 50 to 350 μm. Further, when the adsorbent-containing layer is provided, it is preferably formed in the range of 10 to 100 μm. As a result, gas barrier properties and oxygen absorption properties can be sufficiently exhibited without impairing impact resistance and moldability, and flavor properties can also be improved.

[Gas barrier layer]
In the thermoformed container of the present invention, the gas barrier layer is essential to have a layer made of the above-mentioned ethylene-vinyl alcohol copolymer, but it does not exclude the formation of a layer made of another gas barrier resin.
Examples of gas barrier resins other than the ethylene-vinyl alcohol copolymer include nylon 6, nylon 6.6, nylon 6/6 and 6 copolymers, metaxylylene diadipamide (MXD6), and nylon 6. 10, Nylon 11, Nylon 12, Nylon 13, and other polyamides 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.
When polyamide is used as the matrix resin of the oxygen-absorbing resin composition, a polyamide resin having a terminal amino group concentration of 40 eq / 10 ⁶ g or more is desirable because there is no oxidative deterioration during oxygen absorption.

[Oxygen absorbing layer]
In the thermoformed container of the present invention, the oxygen-absorbing layer uses the above-mentioned propylene polymer, gas barrier resin, regrind resin and the like as a matrix resin, and at least an oxidizing organic component and a transition metal catalyst (oxidation catalyst) as described above. It can consist of a resin composition which is contained in a matrix resin.
(I) Oxidizing Organic Component Examples of the oxidizing organic component include an ethylene-based unsaturated group-containing polymer. This polymer has a carbon-carbon double bond, and α-methylene adjacent to the double bond portion and particularly the double bond portion is easily oxidized by oxygen, whereby oxygen is trapped.
Such an ethylene-based unsaturated group-containing polymer is derived from, for example, a polyene as a monomer, and is a homopolymer of the polyene, or a random combination of two or more of the above polyenes or a combination with another monomer. A polymer, a block copolymer, or the like can be used as the oxidizing polymer.
Among the polymers derived from polyene, polybutadiene (BR), polyisoprene (IR), natural rubber, nitrile-butadiene rubber (NBR), styrene-butadiene rubber (SBR), chloroprene rubber, ethylene-propylene-diene rubber (EPDM) ) Etc. are preferable, but of course, the present invention is not limited to these.

In addition to the above-mentioned ethylene-based unsaturated group-containing polymer, a polymer that is easily oxidized by itself, for example, polypropylene, an ethylene / propylene copolymer, or a polymethoxide having a terminal amino group concentration of less than ^{40 eq / 10 6 g.} Range adipamide and the like can also be used as an oxidizing organic component.
From the viewpoint of moldability and the like, the viscosity of the above-mentioned oxidizing polymer and its copolymer at 40 ° C. is preferably in the range of 1 to 200 Pa · s.
These polyene-based polymers are preferably acid-modified polyene polymers into which a carboxylic acid group, a carboxylic acid anhydride group, and a hydroxyl group have been introduced.
The oxidizing organic component composed of these oxidizing polymers or copolymers thereof is preferably contained in the oxygen absorbing resin in a proportion of 0.01 to 10% by weight.

(Ii) Transition metal-based catalyst As the transition metal-based catalyst, group VIII metals of the periodic table such as iron, cobalt, and nickel are suitable, but other group I metals such as copper and silver, tin, titanium, etc. It may be a Group IV metal such as zirconium, a Group V metal such as vanadium, a Group VI metal such as chromium, a Group VII metal such as manganese, or the like.
Transition metal catalysts are generally used in the form of low valence inorganic salts, organic salts or complex salts of the transition metals. Examples of the inorganic salt include halides such as chlorides, sulfur oxy salts such as sulfates, nitrogen oxyate salts such as nitrates, phosphor oxy salts such as phosphates, and silicates. Examples of the organic salt include carboxylate, sulfonate, phosphonate and the like. Examples of the transition metal complex include a complex with a β-diketone or a β-keto acid ester.
The transition metal catalyst is preferably in the range of 100 to 3000 ppm as the concentration of the transition metal atom (based on the weight concentration) in the oxygen-absorbing resin.

[Adhesive layer]
In the thermoformed container of the present invention, an adhesive layer can be formed between the layers as needed.
As the adhesive resin used for the adhesive layer, a carbonyl (-CO-) group based on a carboxylic acid, a carboxylic acid anhydride, a carboxylic acid salt, a carboxylic acid amide, a carboxylic acid ester, etc. is used as a main chain or a side chain from 1 to 700. Examples thereof include thermoplastic resins contained in a concentration of milliequylene (meq) / 100 g resin, particularly 10 to 500 (meq) / 100 g resin.
Suitable examples of adhesive resins are ethylene-acrylic acid copolymers, ion-crosslinked olefin copolymers, maleic anhydride-grafted polyethylene, maleic anhydride-modified polypropylene, maleic anhydride-grafted polypropylene, acrylic acid-grafted polyoleffin, ethylene. Examples thereof include those formed from a blend of a vinyl acetate copolymer, an ethylene-vinyl alcohol copolymer and a maleic anhydride-modified olefin resin, and in particular, maleic anhydride-modified polypropylene and maleic anhydride-modified polypropylene. Can be preferably used. The adhesive resin may be used alone or in combination of two or more, or may be blended with a polyolefin-based resin.

[Adsorbent-containing layer]
In the thermoformed container of the present invention, the adsorbent-containing layer formed as necessary is preferably located on the inner layer side of the oxygen absorbing layer, whereby the by-products generated by the oxygen absorption reaction can be placed in the container. It is possible to suppress migration and improve the flavor of the contents.
The adsorbent is preferably blended with a propylene polymer or a regrind resin.
As the adsorbent, a conventionally known adsorbent can be used, but an active clay obtained by acid-treating a porous inorganic substance containing a silicate as a main component, for example, a zeolite or a smectite clay mineral such as montmorillonite. Powder is suitable, and in particular, high silica zeolite (silica / alumina ratio of 100 or more), which is a Na-type ZSM5 zeolite, is excellent in the function of capturing the polyodor peculiar to plastics and the above-mentioned oxidative decomposition products. It is suitable.
Generally, such an adsorbent is preferably blended in an adsorbent-containing layer in an amount of 0.5 to 10% by weight.

(Manufacturing method of container)
The mature molded container of the present invention can be produced by conventionally known vacuum forming or compressed air forming, and further by a thermoforming method plug-assisted thereto, and is particularly produced by compressed air forming heated to a temperature equal to or lower than the melting point of a propylene polymer. It is preferable to have.
That is, a multilayer film, a multilayer sheet, or a multilayer precursor is produced by an extrusion coating method, sandwich lamination, or dry lamination of a preformed film, and the multilayer sheet or the like is produced by the thermoforming method of a cup, a tray, or the like. It can be molded into a multi-layer container with a shape.
The thickness of the multilayer sheet used for compressed air molding or the like is preferably in the range of 250 to 4000 μm, particularly 800 to 2000 μm, and L / D (diameter (D) and height (L)) is 0 from the multilayer sheet. It is particularly preferable to mold into a container in the range of 1 to 5, especially 0.2 to 1.5.
As criteria for determining that the container is a compressed air-formed container, methods such as shrinkage before and after retort treatment, observation by polarized light irradiation, and X-ray diffraction are used. Since it is manufactured by compressed air molding, it is stretch-oriented, so that a container having excellent transparency and mechanical strength can be obtained.

The present invention will be further described with reference to the following examples and comparative examples, but the present invention is not limited to these examples.
Various measurements and evaluations in Examples and Comparative Examples were carried out by the following methods.

(1) Isotactic index (I.I.)
The isotactic index of the propylene-based polymer was calculated as an isotactic fraction in pentad units from nuclear magnetic resonance spectrum (13C-NMR) measurements using isotope carbon. The 13C-NMR measurement was carried out using a nuclear magnetic resonance apparatus (manufactured by JEOL Ltd.) while heating at 135 ° C. From the obtained chart, 21 for the sum of the peak heights of 21.82, 21.57, 21.31, 21.03, 20.82, 20.64, 20.29, 20.17, 19.88 ppm. The ratio of peak heights of .82 ppm was calculated to determine the isotactic index.
(2) Melt flow rate (MFR)
The MFR of each material was measured according to JIS K7210 using a melt indexer (manufactured by Toyo Seiki Seisakusho Co., Ltd.). The measurement temperatures were 210 ° C. and 230 ° C., and a load of 2160 g was applied to perform the measurement.
(3) Moldability (drawdown resistance, container wall thickness distribution)
When compressed air molding is performed, the state where the drawdown is small and the wall thickness distribution of the container can be secured is "○", and the state where the drawdown is large and the wall thickness distribution of the container cannot be secured or bursts is "x". I evaluated it.
(4) Appearance With respect to the appearance of the prepared container, the presence or absence of uneven stretching of EVOH was visually judged. The state in which the stretching unevenness did not occur on the side surface of the body of the container was evaluated as “◯”, and the state in which the stretching unevenness occurred was evaluated as “x”.
(5) Oxygen barrier property The prepared container is filled with 1 g of pure water, sealed with an aluminum foil laminated film in a nitrogen-substituted glove box, and then shower-type isobaric retort treatment is performed under sterilization conditions of 121 ° C. and 30 minutes. rice field. After the retort treatment, it was stored in an environment of 30 ° C. and 80% RH, and the oxygen concentration in the container after 2 weeks was measured by a gas chromatograph. If the oxygen concentration in the container at this time is 1% or more, there is a tendency that the quality of the contents may deteriorate. Therefore, the barrier property of the container of less than 1% is marked with "○", and the barrier property of the container of 1% or more Was evaluated as "x".

The materials used in the examples are as follows, and the catalog values and actual measurement data are described.
Propylene polymer A: Isotactic index 98.3%, MFR = 0.5 g / 10 min (230 ° C, load 2160 g)
Propylene polymer B: Isotactic index 98.2%, MFR = 3.5 g / 10 min (230 ° C, load 2160 g)
Propylene polymer C: Isotactic index 92.4%, MFR = 0.5 g / 10 min (230 ° C, load 2160 g)
EVOH (1): Ethylene content is 27 mol%, melting point is 191 ° C, MFR = 4.0 g / 10 min (210 ° C, load 2160 g).
EVOH (2): Ethylene content is 44 mol%, melting point is 165 ° C, MFR = 3.3 g / 10 min (210 ° C, load 2160 g).
AD: Maleic acid-modified resin, MFR = 2.0 g / 10 min (230 ° C, load 2160 g)

(Example 1)
Using a coextrusion multilayer sheet molding machine, a layer made of propylene polymer A / adhesive resin (AD) layer / ethylene-vinyl alcohol copolymer (EVOH) layer / AD layer / layer made of propylene polymer A A multilayer sheet having a structure was produced. For the layer made of the propylene-based polymer A, 0.2 parts by weight of a crystal nucleating agent (organic phosphate) was added to 100 parts by weight of the propylene-based polymer A. The EVOH layer was a blend of EVOH (1) and EVOH (2) in a blending ratio of 80:20. Subsequently, the recovered product obtained by crushing the multilayer sheet and the propylene-based polymer A were mixed at a weight ratio of 50:50, and 3 parts by weight of a compatibilizer was added to 100 parts by weight of the mixture and mixed. Was used as a ligrin (Reg), and further sheet molding was performed. As the prepared sheet, a sheet (Structure 1) of a layer made of a propylene-based polymer A / a Reg layer / an AD layer / an EVOH layer / an AD layer / a Reg layer / a layer made of a propylene-based polymer A was prepared.
Subsequently, the produced multilayer sheet was heated below the melting point of the propylene polymer with a far-infrared heater, and a container having a drawing ratio of 0.5 and an internal capacity of 110 ml was produced using a plug-assisted compressed air molding machine.
Table 1 shows the results of various evaluations.

(Example 2)
A multilayer sheet and a container were prepared in the same manner as in Example 1 except that the propylene-based polymer B was used instead of the propylene-based polymer A. Table 1 shows the results of various evaluations. The reason why the mechanical strength is inferior to that of Example 1 is that the propylene-based polymer B has a high MFR and a large amount of low molecular weight components.

(Example 3)
A multilayer sheet having a layer composed of a propylene-based polymer A / AD layer / EVOH layer / oxygen absorption (Sc) layer / EVOH layer / AD layer / adsorbent-containing layer / propylene-based polymer A was prepared. The Sc layer contained the above-mentioned two-kind mixed EVOH as a main component, an oxidizing organic component, and a transition metal catalyst. The adsorbent-containing layer contained a synthetic zeolite in the polypropylene-based polymer A. Subsequently, using regrind (Reg) in the same manner as in Example 1, a layer composed of the propylene-based polymer A / Reg layer / AD layer / EVOH layer / Sc layer / EVOH layer / AD layer / adsorbent-containing layer / A container was prepared in the same manner as in Example 1 except that a multilayer sheet (Structure 2) having a layer structure made of propylene-based polymer A was prepared.
Table 1 shows the results of various evaluations.

(Example 4)
A multilayer sheet and a container were prepared in the same manner as in Example 1 except that the crystal nucleating agent was not added to the layer made of the propylene-based polymer A. Table 1 shows the results of various evaluations. The reason why the wall thickness distribution of the container could not be secured is that the melting point of the layer made of the propylene-based polymer A was lower and the drawdown was larger than in Example 1. Further, as compared with Example 1, the crystallization temperature of the layer made of the propylene-based polymer A is lower, so that the molding cycle is also inferior.

(Example 5)
The multilayer sheet and the container were produced in the same manner as in Example 1 except that the heating temperature of the multilayer sheet was set to be equal to or higher than the melting point of the propylene polymer and a plug-assisted vacuum compressed air molding machine was used. Table 1 shows the results of various evaluations. The reason why the mechanical strength is inferior to that of Example 1 is that the drawing orientation is not applied in the vacuum compressed air molding in which the propylene-based polymer is molded at a temperature equal to or higher than the melting point.

(Comparative Example 1)
A container was prepared in the same manner as in Example 1 except that the EVOH layer was used as a single layer of EVOH (1). Table 1 shows the results of various evaluations. Since EVOH (1) has a low ethylene content and inferior stretchability, it is considered that stretching unevenness occurred in the container body.

(Comparative Example 2)
A container was prepared in the same manner as in Example 1 except that the EVOH layer was used as a single layer of EVOH (2). Table 1 shows the results of various evaluations. Since EVOH (2) has a high ethylene content, it has excellent stretchability, but lacks barrier properties.

(Comparative Example 3)
A container was prepared in the same manner as in Example 1 except that the propylene-based polymer C was used instead of the propylene-based polymer A. Table 1 shows the results of various evaluations. The reason why the drawdown is so large that molding is not possible is that the isotactic index of the propylene-based polymer C is low.

(Comparative Example 4)
A container was prepared in the same manner as in Example 1 except that propylene-based polymer C was used instead of propylene-based polymer A and EVOH (1) was used as a single layer in the EVOH layer. Table 1 shows the results of various evaluations. The reason why the drawdown is so large that molding is not possible is that the isotactic index of the propylene-based polymer C is low. Further, since EVOH (1) has a low ethylene content and inferior stretchability, it is considered that stretching unevenness occurred in the container body.

The thermoformed container of the present invention has excellent gas barrier properties, does not cause uneven stretching, has excellent transparency, and has excellent appearance characteristics. It also has excellent impact resistance. Further, by providing an oxygen absorption layer, excellent oxygen barrier properties can be exhibited, and by providing an adsorbent-containing layer, deterioration of the flavor of the contents due to oxidative decomposition products accompanying the oxygen absorption reaction can be effectively prevented. It can be effectively used as a container for storing various contents such as various beverages and foods, especially contents given to heat sterilization such as retort sterilization.
Specific contents that can be stored include, but are not limited to, beverages such as beer, wine, fruit juice, and carbonated soft drinks, fruits, nuts, vegetables, meat products, infant foods, coffee, jams, mayonnaise, etc. Suitable for ketchup, cooking oil, dressings, sauces, boiled foods, dairy products, processed fish products, baby foods, pet foods, etc., as well as various contents such as pharmaceuticals, cosmetics, gasoline, etc. that deteriorate due to the presence of oxygen. Can be used.

1 outer, 2 inner layer 3 adhesive layer, 4 a gas barrier layer, 5 an oxygen-absorbing layer, 6 regrind layer, 7 adsorption agent-containing layer.

Claims (6)

A layer made of a propylene-based polymer containing homopolypropylene as a main component and two or more having an isotactic index of 93% or more and a melt flow rate of 0.3 g / 10 minutes or more and less than 1.0 g / 10 minutes. A multilayer container comprising at least a layer made of an ethylene-vinyl alcohol copolymer having a crystal melting peak temperature of. The layer made of ethylene-vinyl alcohol copolymer is made of a blend made by blending two or more kinds of ethylene-vinyl alcohol copolymers having different ethylene contents, and the crystal melting peak temperature is at least 180 ° C. or higher and 170 ° C. The thermoformed container according to claim 1, which has the following. The layer made of the ethylene-vinyl alcohol copolymer consists of an ethylene-vinyl alcohol copolymer having an ethylene content of 20 to 35 mol% and an ethylene vinyl alcohol copolymer having an ethylene content of 36 to 50 mol%. The thermoformed container according to claim 1 or 2, which is made by blending in a blending ratio of 10: 10 to 50:50. The propylene-based polymer contains a crystal nucleating agent , and the crystal nucleating agent is an organic phosphate, which is contained in an amount of 0.01 to 5 parts by weight with respect to 100 parts by weight of the propylene-based polymer. The thermoformed container according to any one of claims 1 to 3. The layer structure is, in order from the outside, a layer composed of the propylene-based polymer / a regrind layer / an adhesive resin layer / an ethylene-vinyl alcohol copolymer intermediate layer / an oxygen absorbing layer / an ethylene-vinyl alcohol copolymer intermediate layer / adhesive. The thermoformed container according to any one of claims 1 to 4, which is a resin layer / an adsorbent-containing layer / an inner layer made of a propylene-based polymer. The thermoformed container according to any one of claims 1 to 5, wherein the propylene-based polymer contains homopolypropylene having a melt flow rate of 0.3 to 0.5 g / 10 minutes or less as a main component.

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