JPH03146342A - Multilayer structure and easily openable container - Google Patents

Abstract

PURPOSE:To impart easy releasability, heat resistance and hot oil resistance to an opening peel ply by forming a surface layer composed of polypropylene onto a specific base material layer mainly comp rising polypropylene through an intermediate layer mainly comprising polyethylene and specifying peeling strength among each layer. CONSTITUTION:A surface layer A consisting of polypropylene is shaped onto a base material layer C made up of 50-95wt.% polypropylene, an ethylene propylene rubber and/or a 5-30wt.% ethyelene butene-1-copolymer and 0-20wt.% polyethylene through an intermediate layer B using polyethylene as a main component. Inter-layer peeling strength between A and B is brought to 0. 3-2.0kg/15mm (the rate of pulling of 300mm/min), and inter-layer peeling strength between B and C is brought to the 1.2 times or more of the inter layer peeling strength between A and B. Inter-layer peeling strength between A and B and between B and C is set in this manner, thus bringing the surface layer A and the intermediate layer B to an easily releasable state, then bringing the intermediate layer B and the base material layer C to a difficult releasable state. Accordingly, when the multilayer structure is used as a container, easily openable properties are obtained, and stable opening properties are acquired.

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a multilayer structure suitably used in the field of packaging, particularly in the manufacture of containers, and sealing properties for storing and packaging foods, medicines, cosmetics, etc. manufactured using the multilayer structure. and an easy-to-open container with excellent opening properties. [Prior Art] There is a rapid increase in the number of products in which food is sealed in a plastic container, subjected to retort sterilization, boiling sterilization, etc., and then reheated directly in a microwave oven by the final consumer. In this case, there is a growing consumer need for containers to not only be airtight but also easy to open. As a container with excellent sealability and ease of opening, instead of opening the seal during use by peeling off the seal, which is generally done, we use a multi-layer container as the container, and use a peel-off surface between the layers of the multi-layer container to seal the container. It is known that a line of weakness is provided in the innermost layer inside the container, so that the innermost layer of the multilayer container inside the line of weakness is peeled off together with the lid while leaving the innermost layer unpeeled. ing. This is a container that uses an easy-to-peel layer as the innermost layer to achieve both sealing and easy-opening properties. However, since the peeling layer of this container is made of PE (polyethylene), the retort processing temperature is 12
The range of its use is limited because the upper limit is 0''C, and the peeling layer swells when filled with microwave-cooked foods that contain a lot of oil. It is desired to improve the oiliness in order to expand the range of applications. [Problems to be Solved by the Invention] An object of the present invention is to provide an easy-to-open container in which a heat-sealing layer and a peeling layer are separate. It is an object of the present invention to provide a multilayer structure that is suitably used and has heat resistance and heat oil resistance while ensuring easy peelability of the unsealing release layer. An object of the present invention is to provide an easy-to-open container that uses a structure to have excellent sealing and unsealing properties, and has heat resistance and heat oil resistance. As a result of extensive research, the inventors discovered that the above-mentioned problem could be solved by making the multilayer structure used for manufacturing easy-to-open containers have a specific layer configuration, and based on this knowledge, the present invention was completed. That is, the present invention comprises 50 to 95% by weight of polypropylene,
Ethylene propylene rubber and/or ethylene butene
1 copolymer 5-30% by weight and polyethylene O-20
A surface layer N made of polypropylene is interposed between a base material layer (C) made of % by weight and an intermediate layer (B) made mainly of polyethylene.
(A), and the interlayer peel strength between (A) and (B) is 0°3 to 2.0 kg/15 kg (tensile speed 300 strokes/
), and the delamination strength between (B) and (C) is (A
) (B) The present invention provides a multilayer structure having an interlayer peel strength of 162 times or more than the interlayer peel strength between (B) and (B). The surface layer (A) of the present invention is made of polypropylene (PP), and by using polypropylene, a multilayer structure having heat resistance and oil resistance can be obtained. The types of polypropylene used are homo-polypropylene, block-polypropylene, and random-polypropylene when considering heat resistance.
Polypropylene is preferred in this order. In addition, when considering sealability with other layers, lid materials, etc., random polypropylene, block polypropylene, and homobolypropylene are preferred in this order. Therefore, it is preferable to select the type of polypropylene depending on the purpose of use. The intermediate layer (B) of the present invention is provided to adjust the peel strength of the multilayer structure, and is mainly made of polyethylene. As the polyethylene, it is preferable to use a resin composition mainly composed of high-density polyethylene, in order to satisfy the coextrusion characteristics with other constituent resins and to consider the releasability from the polypropylene (A). Polyethylene has a melt flow index (MFI) of 0.
Those having a viscosity in the range of 0.05 to 15 g/710 min are preferably used. A resin composition mainly composed of high-density polyethylene is obtained by blending talc and/or polypropylene with such high-density polyethylene so that the content of high-density polyethylene in the resin composition is higher than each of the other components. Suitably used. The base material layer (C) of the present invention is polypropylene 50-95
Weight %, ethylene propylene rubber (EPR) and/or ethylene butene-1 copolymer (EB-1) 5-30
% by weight and 0 to 20% by weight of polyethylene (PE). The preferred range is 65 to 90% by weight of polypropylene.
, 5-20% by weight of ethylene propylene rubber and/or ethylene-butene-1 copolymer and 0% polyethylene.
~15% by weight. By using polypropylene as the main component resin (C), the heat resistance of the multilayer structure is improved. Ethylene propylene rubber and/or ethylene butene-1 copolymer are blended to maintain good adhesion with (B). Modified polyolefins other than ethylene propylene rubber and/or ethylene butene-1 copolymer may be used. Furthermore, it is preferable to blend polyethylene to improve adhesion with (B). By blending propylene rubber and ethylene-butene-1 copolymer polyethylene, the adhesive strength between (B) and (C) can be increased (A
) (B). Here, the ethylene propylene rubber to be blended preferably has a Mooney viscosity ML (at 100°C) in the range of 15 to 80. Further, the polyethylene may be high density polyethylene, medium density polyethylene, low density polyethylene, or a mixture thereof. The multilayer structure of the present invention has the above three layers (A), (B), and (C), and the interlayer peel strength between (A) and (B) is 0.3 to
2.0kg/15mm (pulling speed 300mm/min, same below), preferably 0.3~1.5kg/15I
nI11, and the interlayer peel strength between (B) and (C) must be at least 1.2 times the interlayer peel strength between (A) and CB). In the present invention, by setting the interlayer peel strength between (A) and (B) and between (B) and (C) in this way, the surface layer (A) and the intermediate layer 1 (B) are made easy to peel, Intermediate N (
B) and the base material layer (C) are made difficult to peel. As a result, when this multilayer structure is used as a container, it becomes easy to open,
In addition, stable unsealability can be obtained. Control of each interlayer peel strength can be easily performed by appropriately selecting the resin composition of the resin material as described above. The thickness of each layer is not particularly limited, but the layer (A) must be thick enough to allow delamination, and the thickness must be such that the material fracture strength is greater than the peel strength, and is usually 5 to 400 μm2. Preferably it is 5 to 200 μm. In addition, the layer (B) is 33% of the total thickness of the multilayer structure in consideration of film formability.
It is preferably 0% or less, preferably 20% or less, and usually 5 to 300 μm. Moreover, the thickness of the layer (C) is not particularly limited and is usually 10 to 3000 μm. The thickness ratio of each layer is not particularly limited either, but in consideration of heat resistance, it is preferable that the thickness of the layer (B) is smaller than the thickness of the layer CC"). Intermediate layer of the base material layer of the present invention On the opposite side, a layer made of another material may be provided for the purpose of improving oxygen gas barrier properties and reducing deformation when used as a container. Examples of the layer made of other material include ethylene. - Vinyl alcohol copolymer (EVOH), polyvinylidene chloride (PV)
DC), nylon, polyethylene terephthalate resin layer, aluminum vapor deposited layer, aluminum foil, aluminum, iron,
Examples include materials with excellent gas barrier properties such as copper. Here, EVOH has an ethylene unit content of 25 to
60 mol% is preferably used. Also, PVDC
As such, vinylidene chloride-vinyl chloride copolymer and vinylidene chloride-methacrylic acid copolymer are preferably used. The number of layers made of these other materials may be only one layer, or may be a multilayer body consisting of two or more layers, and
It may be a resin layer containing 10 to 80% by weight of an inorganic filler, or may be a composite material with metal, paper, etc., and an adhesive resin layer may be provided between these layers as necessary. . Although the shape of the multilayer structure of the present invention is arbitrary, the multilayer sheet I is preferably used in manufacturing an easy-to-open container. Multilayer sheets having a multilayer structure consisting of (A), CB) and (C) of the present invention can be obtained by coextrusion or lamination using the above-mentioned resins. As the lamination process, methods such as extrusion lamination, hot melt lamination, dry lamination, and wet lamination can be used. Usually, a two-layer structure consisting of layers (A) and (B) is preferably obtained by coextrusion molding. FIG. 1 is a partial sectional view showing an example of the multilayer structure of the present invention. (A) is a surface layer, (B) is an intermediate layer, (C) is a base material layer, and (E) is an oxygen gas barrier resin layer provided as necessary. Here, further adhesive resin layer (D),
A polyolefin resin layer (F) is provided. Here, the adhesive resin jw (D) has a barrier resin layer (E) of EVO.
When the barrier resin layer (E) is made of H, it is preferably made of acid-modified polypropylene or polyethylene, and when the barrier resin layer (E) is made of PVDC, it is preferably made of ethylene vinyl acetate copolymer (EVA) or EVA and PP.
Moreover, the polyolefin resin layer (F) is PP, PE or P
It is preferably made of P and PE, and may contain ethylene propylene rubber if necessary. The easy-to-open container of the present invention is a container having an opening periphery for annularly sealing the lid, and the periphery has a thermoplastic resin surface layer as a sealing surface, such as (A) or (B) as described above.
) and (C), and an annular weakened line is provided inside the annular seal portion of the surface layer. FIG. 2 is a partial sectional view of one embodiment of the easy-open container of the present invention obtained by molding a multilayer structure. 1 is a surface layer, 2 is an intermediate layer, and 3 is a base material layer. 1.2.
3 has a multilayer structure consisting of the above-mentioned (A), (B) and (C), and forms the container opening peripheral portion 4. 5 is a lid material that is annularly heat-sealed to the upper surface of the periphery of the opening of the container for packaging. It is preferable that the material of the lid material is the same as that of the surface layer from the viewpoint of sealing performance.A line of weakness 7 is provided inside the annular seal portion 6 of the surface layer. This is for cutting the surface layer inside the periphery of the container opening when the surface layer is peeled off.It is usually provided as an annular notch, but it can also be used to easily cut the surface layer when peeling off the lid material. It can be anything. Note that the distance between the inner peripheral edge of the heat seal and the weakening line is 0.
5 to 10 mm, preferably 1 ma or more, and 8 is a knob provided to facilitate peeling off of the lid. Although the shape of the periphery of the container is not particularly limited,
It is usually circular, square, etc., and is heat-sealed into an annular shape around the periphery of this shape. Further, the container shape may be cup-shaped or tray-shaped. To open the easy-open container of the present invention, lift the knob 8 upward as shown in FIG. Then, the surface layer l of the multilayer container
and the intermediate layer 2, and the surface layer is peeled off to the line of weakness 7, and is peeled off together with the lid material. The surface layer is then cut at the line of weakness and the container is opened. Therefore, even if the lid material and the surface layer of the multilayer container are heat-sealed to prevent peeling, the container can be easily opened. Moreover, since peeling is possible even if the peel strength of the heat seal is increased, the multilayer container can withstand boiling and retort processing. Furthermore, since the surface layer and the base layer are mainly made of polyethylene, it has excellent heat resistance, microwave oven properties, and heat oil resistance. Retort treatment can be performed at 130'C for 30 minutes, and the heat-resistant container deformation temperature is 140°C. Moreover, no swelling is observed in oil up to 140°C. In order to open the container, instead of using the line of weakness as described above, a thin section is provided in the surface layer at an inflection point on the inner surface of the container from the side wall to the periphery of the container body, and the breakage of the surface layer is detected at that point. You can go there. That is, the thickness of the surface layer at the sealing part with the lid material at the periphery is StIm, the thickness of the surface layer at the inflection point on the inner surface of the container from the side wall of the container body to the periphery is 1 μm, and the breaking strength of the surface layer material is StIm. When is U kg/cd, S≧1
．． 1XT. T≦(1,33/U) x 10', and the breaking strength of the surface layer at the inflection point is smaller than the peel strength between the surface layer and the intermediate layer. FIG. 3 is a partial sectional view showing an example of an easily openable container in which a thin wall portion is provided in the surface layer at an inflection point on the inner surface of the container from the side wall to the peripheral edge of the container body. This easy-open container is the second
In place of the line of weakness in the figure, there is a thin part of the surface layer at an inflection point 9 on the inner surface of the container from the side wall to the peripheral edge of the container body. The thickness of this thin portion is Tpm. The thickness of the surface layer of the sealed portion 6 with the lid material 5 on the peripheral edge is Sl1m. When opening the lid material sealed on the peripheral portion, the surface layer is broken at this inflection point 9 and the lid material is sealed. It peels off along with it. Here, if there is a peripheral stepped part between the peripheral edge and the side wall of the container body, a thin wall part (thickness T'
In addition, if the peripheral edge has a rim or rim roll, a thin part (thickness T If the surface layer can be broken even at this thin wall portion by providing a container, the container can be easily opened even if there is a rim portion or a rim roll portion. Surface layer thickness (μm) S, T and surface layer breaking strength (kg
/c4) It is necessary that the above relational expression holds true between U. The same applies to the relationship between S, T', and U, and the relationship between S, T'', and U. If the thickness of S is thin, the sealing strength of the sealant will be reduced, and the container cannot be called a sealed container. Also, T, , T' , T' is too thick, the surface layer cannot be broken and the container cannot be opened.The easy-open container of the present invention is formed by vacuum forming, pressure forming, press forming, etc. using the multilayer structure. or by molding the resin by injection molding, injection blow molding, blow molding, etc. The multilayer structure of the present invention can be used not only for containers but also for bag-like packaging and lid materials. It can also be used as a lid material for easy-to-open containers that are opened using delamination. [Examples] The present invention will be explained in detail based on Examples below, but the present invention is not limited to these. Examples 1 to 23 and Comparative Examples 1 to 3 Tables 1 to 3 and Table 5 show the multilayer structures of the present invention manufactured in Examples 1 to 23 and Comparative Examples 1 to 3; This table shows the peel strength between the constituent resin and the layers of the multilayer structure of the comparative example, the peelability, heat resistance, and heat oil resistance when packaging containers are manufactured using this multilayer structure.The symbols in the table indicates the following: pp, : manufactured by Idemitsu Petrochemical ■, Idemitsu PolyBlow-100CM (MF I-0,5) pp, : manufactured by Idemitsu Petrochemical ■, Idemitsu Polypro F
-20O3 (MFI=2) pp, : Idemitsu Petrochemical ■, Idemitsu Polypro J
-4508 (MFI-2,5) PP4: Manufactured by Idemitsu Petrochemical ■, Idemitsu Polypro F
-744N (MFI-7) HDPE: Manufactured by Idemitsu Petrochemical ■, Idemitsu Polyethylene 540B (MFI-0,12) HDPf! z ” Manufactured by Idemitsu Petrochemical ■, Idemitsu polyethylene 440M (MF I-0,9) LDPE: )-Manufactured by So ■, Vetrocene 1722
PR: Made by Japan Synthetic Rubber ■, EP-07P (Mooney viscosity MLI-4 (100°C) -70) EB-17 Made by Mitsui Petrochemical ■, Tafmer A-4085 Multi, MJ! The resin (A) and the resin (B) were extruded using two extruders with a screw diameter of 50 mm, and the resin (C) was extruded with a screw diameter of 65 mm.
Extruded simultaneously by an extruder, laminated using a 3-employment feed block, and then laminated using a conventional single manifold type T
- A flat sheet-like multilayer structure was produced using a die. The thickness of each layer was set so that the total sheet thickness was 800 μm. The interlayer peel strength of the obtained multilayer structure was evaluated. The interlayer peel strength was the value obtained by taking out a 15 mm wide test piece from the multilayer structure and conducting a 180'' peel test at a peel rate of 300 mm/min. A round container having a diameter of 72 mm and a drawing ratio of 0.3 as shown in FIG. 2 was obtained by vacuum forming the multi-layered structure which was heated to a molten state using the multi-layered structure. A notch was placed on the flange of the container as a line of weakness. After filling these containers with water, the container surface layer (sealed side)
After heat-sealing using the same type of resin film (80 μm) with a distance between the heat-sealed inner peripheral edge and the weakening line of t −1.5M, retort treatment was performed at 130° C. for 30 minutes. Thereafter, when the containers were peeled and opened, all containers obtained using the multilayer structure of the present invention showed excellent peelability. Further, when the heat resistance and heat oil resistance of this container were evaluated, all the containers obtained using the multilayer structure of the present invention showed excellent heat resistance and heat oil resistance. In addition, in Example 23, using the multilayer structure listed in Table 3, the multilayer structure heated to a molten state was air-formed using plug assist to obtain a diameter of 72 mmφ and a drawing ratio as shown in FIG. A round container of 0°5 was obtained. During the plug-assisted air pressure forming, the multilayer structure was held by a clamp and a mold, and the container forming conditions were as shown in Table 4. The resulting container had a thin walled portion at the inflection point 9, as shown in FIG. After filling the container with water, it was heat-sealed using a resin film. Further, retort treatment was performed at 130°C for 130 minutes. Thereafter, peelability, heat resistance, and hot oil resistance were evaluated, and all showed excellent results. Here, the heat oil resistance was evaluated by filling the above container with salad oil instead of water, heating it in a microwave oven, taking out the container when the temperature reached 130"C, and observing the state of the resin inside the container. Comparative Example 1 uses HDPE for (A), so 13
It was impractical because it swelled with 0°C salad oil. In Comparative Examples 2 and 3, the resin compositions constituting the layer (C) both lacked heat resistance and deformed during retorting. [Effects of the Invention] The multilayer structure of the present invention can stably control interlayer peel strength, and has heat resistance and heat oil resistance. In addition, the easy-to-open container obtained from this multilayer structure has excellent sealing and opening properties, stable peel strength when opened, and is heat resistant and resistant to hot oil, so its practical value is great. It is. more than

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view showing an example of the multilayer structure of the present invention. FIG. 2 is a partial sectional view of one embodiment of the easy-open container of the present invention obtained by molding a multilayer structure. FIG. 3 is a partial sectional view of another embodiment of the easy-open container of the present invention obtained by molding a multilayer structure. (C) (D) (E) CF) 1゜3゜4゜5゜6゜7゜8゜9゜Base material layer Adhesive resin layer Barrier resin layer Polyolefin resin layer Surface layer Intermediate layer Base material layer Opening periphery lid Material seal part weakening line knob part inflection point part

Claims (1)

[Claims] 1. 50 to 95% by weight of polypropylene, ethylene propylene rubber and/or ethylene butene-1 copolymer 5
A surface layer (A) made of polypropylene is formed on a base material layer (C) made of ~3% by weight and 0-20% by weight of polyethylene via an intermediate layer (B) mainly made of polyethylene. The interlayer peel strength between (B) is 0.3 to 2.0 kg/15 mm (tensile speed 300 mm/min), and the interlayer peel strength between (B) and (C) is between (A) and (B). A multilayer structure with a peel strength of 1.2 times or more. 2. The multilayer structure according to claim 1, wherein the intermediate layer (B) is made of a resin composition mainly consisting of high-density polyethylene. 3. The middle layer (B) is made of high density polyethylene, talc and/or
The multilayer structure according to claim 1 or 2, wherein the multilayer structure is made of polypropylene or polypropylene, and the content of high density polyethylene is greater than each of the other components. 4. Multilayer sheets having a multilayer structure consisting of (A), (B) and (C) according to claim 1 or 2. 5. A container having an opening periphery for annularly sealing the lid, wherein the sealing surface of the periphery is the surface layer (A) (A), (B) and ( An easy-to-open container having a multilayer structure consisting of C), in which an annular line of weakening is provided inside the annular seal portion of the surface layer. 6. A container having an opening periphery for annularly sealing the lid, wherein the sealing surface of the periphery is the surface layer (A) (A), (B), and ( It has a multilayer structure consisting of C), and the surface layer thickness of the sealing part with the lid material at the periphery is Sμm,
The thickness of the surface layer at the inflection point on the inner surface of the container from the side wall to the periphery of the container body is Tμm, and the breaking strength of the surface layer material is U.
When kg/cm^2, S≧1.1×T, T≦(1
．． 33/U)×10^4, and the breaking strength of the surface layer at the inflection point is smaller than the peel strength of the surface layer and the intermediate layer.