JPH10100338A - Multilayered sheet and container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a styrenic barrier sheet and a container excellent in transparency and having high rigidity and high impact resistance. SOLUTION: This multilayered sheet is constituted by providing an EVOH layer (C) composed of a transparent ethylene/vinyl alcohol copolymer resin between two layers each composed of a styrenic resin layer (A) composed of a styrenic resin containing a copolymer containing a styrenic unit (a), an acrylic ester unit or a methacrylic ester unit excepting methyl methacrylate (b) and a methyl methacrylate unit (c) as a continuous phase and a rubbery elastomer consisting of a vinyl aromatic hydrocarbon polymer block and a polymer block based on a conjugated diene as a dispersed phase through adhesive layers (B) composed of a transparent adhesive. The multilayerd sheet has a recessed part having an opening and an opening peripheral edge part for sealing a lid material in an annular shape and the seal surface in the peripheral edge part is composed of the styrenic resin layer (A).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to the field of transparency, barrier properties, and the like, which are suitably used in the field of packaging, especially for the production of transparent containers.
The present invention relates to a multilayer sheet excellent in rigidity and impact resistance and a container excellent in transparency, rigidity, impact resistance and barrier properties.

[0002]

2. Description of the Related Art With the recent improvement in the quality of life of consumers and the enforcement of the PL law, transparent high-rigidity and high-impact containers have been desired. That is, the transparency of the container is required for confirming whether the contents meet the requirements or whether there is any abnormality in the contents. High rigidity is required to protect the shape of the contents and to enhance the appearance of the package when displaying it. In addition, barrier properties and high impact resistance
It is required to protect contents and maintain commercial value.

In a conventional transparent polystyrene-based barrier sheet, a mixed resin of polystyrene and a styrene-conjugated diene copolymer or a styrene-conjugated diene copolymer mainly composed of styrene is used as a polystyrene resin. However, a transparent polystyrene sheet using such a polystyrene resin has a drawback that it is difficult to achieve both high rigidity and high impact resistance. As methods for achieving both high rigidity and high impact resistance, (1) a method of using a high-impact polystyrene resin composition having a large amount of a conjugated diene component and increasing the thickness of a sheet; ) There is a method of dividing the high-rigidity layer and the high-impact-resistant layer into a plurality of styrene resin layers, but each has a major drawback. That is, the method (1) has a drawback that the production cost of the sheet is high, and the method (2) requires a large number of layers to produce a barrier sheet or the like, making stable production difficult. However, there is also a problem that a large number of extruders are required and the cost is increased.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a styrene-based barrier sheet which is excellent in transparency, has high rigidity and high impact resistance and is inexpensive to manufacture, and has excellent transparency and high clarity. An object of the present invention is to provide a container having rigidity and high impact resistance.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted various studies to solve the above-mentioned problems. As a result, (a) a styrene-based unit, (b) an acrylate unit or a methacrylate unit other than methyl methacrylate unit And (c) a copolymer containing methyl methacrylate units as a continuous phase,
A styrene-based resin containing a rubber-like elastic body composed of a vinyl aromatic hydrocarbon polymer block and a polymer block mainly composed of a conjugated diene as a dispersed phase has excellent transparency, and has both high rigidity and high impact resistance. In addition, they have found that they have excellent moldability suitable for molding a barrier sheet having a multilayer structure, and have completed the present invention based on this finding.

That is, the present invention provides (a) a styrene unit,
(B) acrylate units or methacrylate units other than methyl methacrylate (hereinafter referred to as acrylate (methacrylic acid) ester units), and (c)
Styrene resin composed of a styrene resin composed of a copolymer containing methyl methacrylate units as a continuous phase, and a rubbery elastic body composed of a polymer block mainly composed of a vinyl aromatic hydrocarbon polymer block and a conjugated diene as a dispersed phase Between the two layers (A), there is an EVOH layer (C) made of a transparent ethylene vinyl alcohol copolymer resin via an adhesive layer (B) made of a transparent adhesive (A) /
An object of the present invention is to provide a multilayer sheet having a multilayer structure of (B) / (C) / (B) / (A).

The present invention further provides the above (A), (B) and (C)
(B) a concave portion having the multilayer structure of (A) and having an opening;
An object of the present invention is to provide a container having an opening peripheral portion for sealing a lid material in an annular shape, wherein the sealing surface at the peripheral portion is a styrene resin layer (A).

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The styrene resin forming the styrene resin layer (A) has a continuous phase of a copolymer containing a styrene unit, an acrylic acid (methacrylic acid) ester unit and a methyl methacrylate unit. A rubber-like elastic body composed of a hydrocarbon polymer block and a polymer block mainly composed of a conjugated diene is used as a dispersed phase. In the styrene resin, the methyl methacrylate unit has a function of imparting rigidity, and the acrylate unit and the rubber-like elastic body have a function of imparting impact resistance.

The styrene-based units in the copolymer forming the continuous phase include, for example, styrene units, vinyltoluene units, vinylxylene units, propenylbenzene units,
Examples thereof include an α-methylstyrene unit and a 2,6-dichlorostyrene unit, and a styrene unit is particularly preferable. Also,
Examples of the acrylic acid (methacrylic acid) ester units, for example, methyl acrylate units, acrylic acid C _1-8 alkyl, such as ethyl acrylate units, preferably methacrylic acid C _2-8 alkyl such as ethyl methacrylate, in particular methyl acrylate units preferable. In addition, this copolymer may contain only one kind of styrene-based unit and acrylic acid (methacrylic acid) ester unit, respectively, or may contain two or more kinds.

The proportion of styrene units in the copolymer forming the continuous phase is preferably from 10 to 80% by weight, and from 20 to 70% by weight.
% By weight is more preferable, and the ratio of acrylic acid (methacrylic acid) ester unit is preferably 0.2 to 30% by weight,
The content is more preferably 0.5 to 20% by weight, and the ratio of the methyl methacrylate unit is preferably 19.8 to 89.8% by weight, and more preferably 29.5 to 79.5% by weight.

As the rubber-like elastic material forming the dispersed phase,
There is no particular limitation as long as it is a rubber-like polymer having elasticity, comprising a polymer block of a vinyl aromatic hydrocarbon such as styrene and a polymer block mainly containing a conjugated diene such as butadiene, and usually contains a styrene unit. Amount is 5-30%
Styrene-butadiene copolymer, for example, SBR is preferably used.

The particle size of the dispersed phase comprising the rubber-like elastic material is preferably from 0.2 to 1 μm, more preferably from 0.3 to 0.5 μm. When the particle size of the dispersed phase is 0.
If it is less than 2 μm, the effect of improving impact resistance may be insufficient, and if it is more than 1 μm, the transparency of the styrene resin layer (A) may decrease.

The proportion of the copolymer forming the continuous phase in the styrene resin is preferably 70 to 99.5% by weight,
The content of the rubber-like elastic body forming the dispersed phase is preferably 0.5 to 30% by weight, more preferably 1 to 99% by weight.
20% by weight is more preferred. If the proportion of the dispersed phase composed of the rubber-like elastic material is less than 0.5% by weight, the impact resistance improvement item may be insufficient, and if it exceeds 30% by weight, the styrene-based resin layer (A) Transparency may decrease.

The styrene resin forming the styrene resin layer (A) has a melt index value (MI) of 2
It is preferably 10 to 10 g / 10 minutes.

When a container is formed by pressure molding or the like using the multilayer sheet of the present invention, the container may be whitened and the transparency may be reduced during deep drawing container formation. This is because the rubber-modified polystyrene component precipitates on the surface of the container due to the stretching of the styrene resin, and the surface becomes uneven. In order to prevent this, it is preferable to further include a terpene component in the styrene-based resin to suppress the movement of the rubber component and prevent precipitation on the container surface. Examples of the styrene resin containing a terpene component include those obtained by further adding a terpene resin to the above styrene resin.
When a terpene resin is further added to the styrene resin, the terpene resin is added in an amount of 0.00% by weight per 100 parts by weight of the styrene resin.
It is preferably from 1 to 5.0 parts by weight, and 0.002 to
3.0 parts by weight is more preferred.

As another means for preventing a decrease in the transparency of the container at the time of forming the deep drawing container, the surface of the multilayer sheet of the present invention does not contain a rubber component or contains a rubber component. However, there is a method in which the content is low and the resin component is covered with a transparent resin layer to suppress the precipitation of the rubber component. Examples of the resin that can be used for forming the transparent resin layer include general-purpose polystyrene (GPPS), a blend of general-purpose polystyrene and a styrene-butadiene copolymer, and a low-styrene-butadiene copolymer ratio. It is preferable to use a blend of a styrene-butadiene copolymer with a copolymer of styrene, acrylate and methyl methacrylate and a styrene-butadiene copolymer.

The transparent adhesive for forming the adhesive layer (B) is usually a transparent ethylene propylene rubber adhesive or an ethylene-vinyl acetate copolymer (EVA) adhesive excellent in adhesion to polystyrene. An adhesive or the like is preferably used. The adhesive has an adhesive strength of 2.0 kg / 2 between the adhesive (B) and the polystyrene resin layer (A).
It is preferable to use one having a thickness of 5 mm or more.

Examples of the ethylene-propylene rubber-based adhesive include, for example, ethylene-propylene rubber having a molecular weight distribution ( _Mw / _Mn ) of 1.0 to 10 (ethylene content of 55 to 7).
5% by weight) and an adhesive such as a terpene resin. For example, ethylene-propylene rubber is 30 to
50% by weight, preferably 35 to 45% by weight;
Those containing 0 to 40% by weight, preferably 25 to 35% by weight, and 10 to 50% by weight, preferably 20 to 40% by weight of additives such as wax, plasticizer and filler are suitable.

As the ethylene-vinyl acetate copolymer adhesive, an ethylene-vinyl acetate copolymer (having a vinyl acetate content of 30 to 50% by weight, preferably 35% by weight) is used.
30 to 50% by weight, preferably 35 to 4% by weight.
5% by weight, 20-40% by weight of adhesive, preferably 25%
It is suitable that the composition contains 10 to 50% by weight, preferably 20 to 40% by weight of additives such as wax, plasticizer, and filler.

The adhesive forming the adhesive layer (B) preferably has a melt index of usually 1 to 10 g / 10 min, more preferably 2 to 6 g / 10 min.

The EVOH layer (C) is a layer for imparting gas barrier properties to the multilayer sheet of the present invention, and is made of a transparent ethylene-vinyl alcohol copolymer resin. The ethylene content of the ethylene-vinyl alcohol copolymer resin is preferably 29 to 47 mol%. The ethylene-vinyl alcohol copolymer resin generally preferably has a melt index value of 1 to 10 g / 10 minutes.

In the multilayer sheet of the present invention, the thickness of one styrene resin layer (A) is preferably from 50 to 1000 μm, more preferably from 100 to 700 μm. The thickness of one adhesive layer (B) is preferably from 5 to 50 μm, more preferably from 10 to 30 μm. The thickness of the EVOH layer (C) is preferably from 5 to 300 μm, more preferably from 10 to 200 μm. Further, (A) / (B) / (C) / (B) /
(A) The thickness of the multilayer sheet having the configuration is 0.1 to 2.0 mm.
And more preferably 0.3 to 1.5.
mm.

In the present invention, the melt index (MI) of the polystyrene resin is measured at a test temperature of 200 ° C. and 5 kgf in accordance with JIS K7210.
The melt index (MI) of other resins is based on JIS
It is measured under the conditions of a test temperature of 190 ° C. and a test load of 2.16 kgf in accordance with K 7199.

The multilayer sheet of the present invention can be obtained by coextrusion or lamination using the resin material forming each of the above layers. Examples of the coextrusion molding method include a polystyrene resin layer (A), an adhesive layer (B), and an EVOH.
Each material of the layer (C) is melt-extruded using a different extruder, and is laminated by a feed block and formed into a film by a flat die, or a film is formed in a die by using a multilayer die. Method.

As the laminating process, for example, methods such as extrusion lamination, hot melt lamination, dry lamination, and wet lamination can be used. For forming the multilayer sheet of the present invention, usually,
A co-extrusion laminating method of co-extruding an adhesive and a barrier resin, EVOH, and laminating this with a polystyrene resin layer (A) is preferably used.

FIG. 1 shows the present invention comprising five layers of a styrene resin layer (A) / adhesive layer (B) / EVOH layer (C) / adhesive layer (B) / styrene resin layer (A). Although the layer structure of the multilayer sheet is shown, the multilayer sheet of the present invention is not limited to these. For example, a styrene resin layer (A)
May have a transparent resin layer for suppressing precipitation of the rubber component, a polyethylene layer for retaining oil resistance, PET (polyethylene terephthalate) or PETG for retaining fragrance. (Trade name, non-crystalline PET resin manufactured by Kodak Corporation), and may have a polycarbonate layer for improving heat resistance.

The container of the present invention is characterized in that the above (A) / (B) /
It has a multilayer structure of (C) / (B) / (A), has a concave portion having an opening, and an opening peripheral portion for annularly sealing the lid member, and the sealing surface at the peripheral portion is a styrene-based resin layer. FIG. 2 is a cross-sectional view of one embodiment of the present invention. The container 1 shown in the figure has a concave portion 2 having an opening and an opening peripheral portion 3 for sealing the lid material in a ring shape, and the sealing surface at the peripheral portion is a polystyrene resin layer (A).

This container can be produced by heating and melting the multilayer sheet of the present invention and shaping it into a desired shape, and is suitably obtained by ordinary vacuum forming, pressure forming or the like.
Further, it can also be obtained by molding by injection molding, injection blow molding, blow molding or the like using the resin material of each layer.

The shape of the concave portion of the container is not particularly limited as long as the shape can accommodate the contents, and may be, for example, a cup shape or a tray shape. The shape of the peripheral edge of the opening is not particularly limited, but is usually a circle, a square, or the like, and the lid is heat-sealed annularly on the peripheral edge.

As the cover material, a hot melt type adhesive (E
A material having a sealant layer such as a (VA-based adhesive) is suitably used. To firmly adhere the lid material by heat sealing, it is preferable to further provide a layer of polyethylene or the like as described above on the styrene resin layer (A) on the sealing surface side. As the lid material, a material having a metal foil such as an aluminum foil, a heat-resistant film, or the like outside the sealant layer is usually used.

The multilayer sheet of the present invention can be used not only for producing containers, but also for producing bag-like packages. Further, the container of the present invention having a multilayer structure of the multilayer sheet is a container in which a lid material capable of delamination is heat-sealed, and is a container of an easy-opening container which is opened using delamination of the lid material. Can also be used.

[0032]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples.

Examples 1 to 3 Using three extruders, extruder A, extruder B and extruder C, styrene resin layers (A1) and (A)
2) The extruder B simultaneously extrudes the material resin of the adhesive layers (B1) and (B2) from the extruder B, and the extruder C simultaneously extrudes the material resin of the EVOH layer (C).
Using a flat die, a 5-layer sheet (layer configuration = A1 / B1 / C / B2 / A2) shown in Table 1 was obtained. The temperature of the material resin in each extruder was as follows: the temperature of the material resin in the extruder A: 200 ° C., the temperature of the material resin in the extruder B: 190 ° C.
Material resin temperature in extruder (C): 230 ° C.

Using the multilayer sheet obtained above, an opening of 120 m was formed by vacuum forming (sheet heating temperature: 120 ° C.).
A rectangular container having an m-square, a drawing ratio of 1, a depth of 90 mm, and an opening peripheral portion width of 5 mm was formed.

Comparative Examples 1 and 2 The procedure of Example 1 was repeated except that the material resins of the styrene resin layers (A1) and (A2) were changed to those shown in Table 1.
Layer sheets and containers were produced.

Evaluation of Physical Properties of Sheet The tensile properties, rigidity, impact resistance and haze value indicating haze of the multilayer sheets obtained in Examples and Comparative Examples were measured by the following methods. Table 1 shows the results. Tensile properties Elastic modulus: In accordance with JIS K 6301 Yield strength: In accordance with JIS K 6301 Breaking strength: In conformity with JIS K 6301 Elongation: In accordance with JIS K 6301 Rigidity Olsen's rigidity: In accordance with ASTM D 747 Impact resistance Tensile impact strength: According to ASTM D 1822 Dupont impact strength: Complies with JIS K 7211 Haze: Complies with JIS K 7105 Further, the characteristics of the containers obtained in Examples and Comparative Examples were measured by the following methods. Table 2 shows the results.

Drop impact resistance: For each example and comparative example,
Prepare 5 containers each containing 1 kg of miso, cover the top with gum tape to prevent the miso from scattering, and drop it in increments of 10 cm from a height of 50 cm in a 5 ° C. constant temperature room from a height of 50 cm. The majority showed the drop impact resistance with the cracked height.

Buckling strength: Using an Instron universal tester and a flat jig, the container is placed on a flat jig with the bottom facing upward, and the container is compressed at a speed of 10 mm / min. The stress when bending occurred was measured.

Haze value, light transmittance: JIS K71
The haze value and light transmittance of the bottom of the container were measured according to the method described in No. 05.

The details of the resin materials shown in Table 1 used in Examples and Comparative Examples are as follows.

SD120 (trade name, Asahi Kasei Corporation)
Continuous phase = styrene / methyl acrylate / methyl methacrylate copolymer (52% by weight of styrene unit, 18% by weight of methyl acrylate unit, 30% by weight of methyl methacrylate unit); dispersion layer = styrene-butadiene rubber (butadiene unit:
50% by weight, styrene unit: 50% by weight); Terpene resin added Continuous phase: dispersed phase: terpene resin = 80: 20: 0.1
(Weight ratio); MI value: 3.5 g / 10 min; Clearpact TI300 (trade name, manufactured by Dainippon Ink and Chemicals, Inc.): continuous phase = styrene / methyl acrylate / methyl methacrylate copolymer (48 styrene units) % By weight, 22% by weight of methyl acrylate unit, 30% by weight of methyl methacrylate unit); Dispersion layer = styrene-butadiene rubber (butadiene unit:
Continuous phase: dispersed phase = 87: 13 (weight ratio); MI value: 3.0 g / 10 min; KR-05 (trade name, manufactured by Philips): styrene- Butadiene copolymer (butadiene content: 15% by weight,
GPPS: general-purpose polystyrene (trade name: Idemitsu HH30)
E, manufactured by Idemitsu Petrochemical Co., Ltd., MI value: 4 g / 10 min); TPA (trade name, manufactured by Asahi Kasei Kogyo Co., Ltd.): styrene-butadiene copolymer (styrene content 40% by weight, butadiene content 60% by weight, MI value 13 g / 10 min) Mersen 5420 (trade name, manufactured by Tosoh Corporation): EVA
System adhesive (40% by weight of EVA, 30% by weight of adhesive, 30% by weight of wax, plasticizer, filler, etc., MI value 4g / 1
EVOH: ethylene-vinyl alcohol copolymer (ethylene content 32 mol%, MI value 2 g / 10 min)

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

According to the present invention, a styrene-based barrier sheet and a container having excellent transparency, high rigidity and high impact resistance can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view illustrating a structure of a multilayer sheet of the present invention.

FIG. 2 is a cross-sectional view illustrating one embodiment of the container of the present invention.

[Explanation of symbols]

 (A) Styrene-based resin layer (B) Adhesive layer (C) EVOH layer 1 Container 2 Depression 3 Opening edge

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI B65D 65/40 B65D 65/40 D

Claims (4)

[Claims] 1. A copolymer comprising (a) a styrene-based unit, (b) a methacrylate unit other than an acrylate unit or methyl methacrylate unit, and (c) a methyl methacrylate unit as a continuous phase, A transparent adhesive is provided between two styrene resin layers (A) composed of a styrene resin having a rubbery elastic body composed of a hydrogen polymer block and a polymer block mainly composed of a conjugated diene as a dispersed phase. (A) / (B) / (C) / (B) / having an EVOH layer (C) made of a transparent ethylene-vinyl alcohol copolymer resin via an adhesive layer (B)
A multilayer sheet having the multilayer structure of (A). 2. The multilayer sheet according to claim 1, wherein the styrene resin forming the styrene resin layer (A) further contains a terpene resin. 3. A multilayered structure according to claim 1, comprising a concave portion having an opening, and an opening peripheral portion for annularly sealing the lid member, wherein the sealing surface at the peripheral portion is formed of a styrene resin layer (A). ). 4. A multilayer structure according to claim 2, comprising a concave portion having an opening, and an opening peripheral portion for sealing the lid material in an annular shape, wherein the sealing surface at the peripheral portion is formed of a styrene resin layer (A). ).