JP6266744B2 - Multilayer sheet and multilayer container using the same - Google Patents

Description

  The present invention is a multilayer sheet having a divided groove in which a polystyrene resin layer and a functional resin layer are bonded via an adhesive resin layer, and the functional resin layer and the adhesive resin layer are cut leaving the polystyrene resin layer. And a multilayer container obtained by molding the multilayer sheet with a polystyrene resin layer on the outside. This multilayer container is particularly suitable as a food container or a pharmaceutical container.

  From the viewpoint of safety, polyethylene and polypropylene are frequently used for food and pharmaceutical containers, and recently, polyethylene terephthalate is also frequently used. Containers with dividing grooves include multiple containers for storing yogurt, tofu, etc. in food, instant noodle containers that tear off the edges and peel off the seal pieces, and coffee milk containers. There are double bags that store liquids and mix them when used.

  For example, Patent Document 1 discloses a tofu container in which a connecting groove between two containers is provided with a groove for cutting. Usually, polypropylene, polystyrene, polyethylene terephthalate or the like is used for this container.

JP-A-10-218151

  The inventors of the present invention have examined a container having a dividing groove such as a multi-container container. Polystyrene is easy to break off at the dividing groove part, but the strength is weak in impact strength such as drop strength, and food. When used in pharmaceutical containers, it is known that trace amounts of residual styrene monomer, dimer, trimer, etc. may elute and cause health problems.

  The object of the present invention is to solve the problems of these polystyrenes, and to provide a multilayer sheet that is easy to break at the dividing groove portion but hardly breaks and has no health problems, and a multilayer container using the same. There is.

  The present inventors considered to laminate a functional resin layer on a polystyrene resin layer via an adhesive resin layer in order to solve the above-described problems and enhance the functions required according to the application. And, by dividing the adhesive resin layer from the functional resin layer to reach the polystyrene resin layer by dividing the groove, problems such as easy division, impact resistance of the container, elution of styrene monomer, oligomer, etc. The inventors have found that all can be solved, and have completed the present invention.

  That is, in the present invention, a polystyrene resin layer mainly composed of polystyrene is used as one surface, a functional resin layer mainly composed of a functional resin is used as the other surface, and the polystyrene resin layer and the functional resin layer are adhesive resins. A multilayer sheet container, which is a multilayer sheet bonded through layers, wherein the functional resin layer and the adhesive resin layer are cut and a dividing groove reaching the polystyrene resin layer is provided. As an example of the sheet manufacturing method, an adhesive resin is extruded from a T die, a polystyrene resin sheet is fed out from one side directly below the T die, and a functional resin film is fed out from the opposite side, and the polystyrene resin is passed through the adhesive resin layer. There is a method of laminating a sheet and a functional resin film. Other methods include a method for producing a multilayer sheet in which a coextruded multilayer film composed of an adhesive resin layer and a functional resin layer is prepared, and a polystyrene resin is extruded and laminated on the adhesive resin layer side.

  The present invention provides a multi-layer container for food or medicine molded using the above multi-layer sheet.

  According to the present invention, the split groove portion is easy to break off but strong in impact strength, and the polystyrene resin layer is a layer that does not come into contact with the contents. A sheet and a multilayer container using the sheet can be provided. The multilayer sheet of the present invention supplements the impact strength of the polystyrene resin with an adhesive resin and a functional resin, so the polystyrene sheet can be made significantly thinner, reducing costs and saving resources compared to the case of a single polystyrene resin. Can be achieved.

  Furthermore, when the polystyrene resin layer is a foamed layer, the heat insulation can be improved.

It is a fragmentary sectional view of an example in which the division groove part of the multilayer sheet of the present invention entered. It is the figure which showed typically the quadruple container of yogurt which is an example of the multilayer container of this invention, (a) is a top view, (b) is the sectional view on the AA line. It is a figure which shows the milk container for coffee which is another example of the multilayer container of this invention, (a) is a top view, (b) is a side view. It is the figure which showed the simple method of a press-cutting in the 4 series yoghurt cup which is another example of the multilayer container of this invention.

  The multilayer sheet of the present invention is composed of an adhesive resin layer that adheres a polystyrene resin layer and a functional resin layer to the surfaces in contact with each other.

  The polystyrene resin layer is a layer mainly composed of polystyrene. Polystyrene is called polystyrene for general use called GPPS (General Purpose Polystyrene) and HIPS (High Impact Polystyrene) in which rubber latex such as polybutadiene is added at the time of polymerization of styrene monomer to increase impact resistance. There are high-impact polystyrenes and some of their intermediate properties called MIPS blended together, both of which can be used. In terms of physical properties, the MFR is desirably about 1 to 12 g / 10 minutes, preferably about 2 to 10 g / 10 minutes.

  By making polystyrene foam, heat insulation and heat retention can be enhanced. In addition, the resin used can be saved, and advantages such as weight reduction, manufacturing cost reduction, and combustion load reduction at the time of disposal can be obtained. The foaming method is a physical method of foaming by adding a gas such as carbon dioxide or butane or a volatile liquid such as ether or hexane, or by thermally decomposing a carbonate such as ammonium carbonate or sodium hydrogen carbonate or an azo compound. There are chemical methods for generating gas or generating carbon dioxide by adding citric acid or the like to the carbonate, and any of them can be used. Among these, a physical method using an inert gas such as carbon dioxide gas or nitrogen gas is particularly preferable for food and pharmaceutical containers because there is no problem such as toxicity. The expansion ratio is suitably about 1.1 to 3 times, particularly about 1.4 to 2.5 times.

The thickness of the polystyrene resin layer is about 200 to 1000 μm, particularly about 500 to 700 μm in the case of a non- foamed layer, and about 300 to 1500 μm, particularly about 400 to 800 μm in the case of a firing layer. If the thickness is less than 200 μm for the non-foamed layer and less than 300 μm for the foamed layer, the rigidity becomes insufficient. On the other hand, if the thickness exceeds 1000 μm for the non-foamed layer and 1500 μm for the foamed layer, the container already satisfies the required performance. Since it becomes too heavy, it is not preferable.

  The adhesive resin is a layer that bonds the polystyrene resin layer and the functional resin layer, and a resin that can bond both layers is used. As a resin having such a function, there is a modified polyolefin in which an unsaturated dicarboxylic acid anhydride is glazed to a polyolefin. Examples of the unsaturated dicarboxylic acid anhydride include maleic anhydride, phthalic anhydride, itaconic anhydride, citraconic anhydride, mesaconic anhydride, and fumaric anhydride. Of these, maleic anhydride and phthalic anhydride, which are commonly used from the viewpoint of easy handling and heat resistance, are preferred. Polypropylene and polyethylene are commonly used as examples of polyolefin. These modified polyolefins are commercially available and can be used.

  The thickness of the adhesive resin layer is about 10 to 100 μm, particularly about 30 to 60 μm.

The functional resin layer supplements the weakness of the breaking strength of the polystyrene resin layer together with the adhesive resin layer, and depending on the use of the container and the required physical properties, polyethylene, polypropylene, ethylene-vinyl acetate copolymer, It is selected from polyethylene terephthalate, polyamide, ethylene - vinyl alcohol copolymer and the like.

  Polyethylene has features such as non-toxicity, high safety, easy heat sealing, excellent cold resistance, excellent thermal stability and easy molding, and is widely used as a packaging resin. The polyethylene includes low density polyethylene, high density polyethylene, linear low density polyethylene, and the like, and is selected from these depending on required physical properties. As the physical property values, those having an MFR of about 0.1 to 8 g / 10 minutes, preferably about 0.5 to 3 g / 10 minutes are desirable.

  The above polyethylene resin is used for the standards specified in “Ministerial Ordinance on Component Standards of Milk and Dairy Products (December 27, 1951, Ministry of Health and Welfare Ordinance No. 52)” and “Packaging or containers of food during cooking” It is preferable in terms of food safety to meet the polyethylene standard for products (FDA CFR21 § 177.1520 (c) 2.2). Examples of the polyethylene resin that meets such criteria include an additive-free polyethylene resin, that is, a polyethylene that does not contain a resin additive. When the polyethylene resin in the polyethylene resin layer meets the above criteria, the multilayer container according to the present invention, which is a molded product of the multilayer sheet according to the present invention, can contain dairy products that meet the above criteria. is there.

  When polyethylene is used for the functional resin layer, the layer thickness is about 20 to 250 μm, particularly about 50 to 150 μm.

  Polypropylene is often used when heat resistance is required. Polypropylene includes, in addition to homopolypropylene, copolymers of propylene and ethylene, which are called random polypropylene, block polypropylene, and the like, and are selected from these according to required physical properties. As the physical property values, those having an MFR of about 0.4 to 12 g / 10 min, preferably about 3 to 8 g / 10 min are desirable.

  When polypropylene is used for the functional resin layer, the layer thickness is about 20 to 200 μm, particularly about 50 to 150 μm.

Ethylene - vinyl acetate copolymer, flexible, other low-temperature characteristics, has been used as widely general packaging resin because it is excellent in moldability. As the physical property values, those having an MFR of about 0.5 to 8 g / 10 minutes, preferably about 1 to 4 g / 10 minutes are desirable.

  Polyethylene terephthalate is excellent in gas barrier properties and non-adsorptive properties, and recently, a film imparted with heat sealability has been developed, and its application is widened. This physical property value is generally expressed as an IV value (inherent viscosity), and is about 0.5 to 0.9 dl / g, preferably about 0.6 to 0.8 dl / g.

  Polyamide is not only excellent in strength properties such as puncture resistance but also excellent in chemical resistance and oil resistance, and is widely used as a film for functional packaging materials. The polyamide is typically nylon, such as 6-nylon and 66-nylon, and is selected from these depending on the required physical properties.

  The ethylene-vinyl alcohol copolymer is excellent in gas barrier properties and chemical resistance, and is used as a functional packaging film.

  The functional resin layer of the present invention is a layer mainly composed of the above functional resin, and can contain other resins and the like as long as the required function is satisfied.

  The total thickness of the multilayer sheet of the present invention is about 230 to 1300 μm, usually about 600 to 800 μm when polystyrene is a non-foamed layer, and about 330 to 1800 μm, usually about 600 to 1000 μm is appropriate for a foamed layer. .

  The method of forming the multilayer sheet is not particularly limited, but the adhesive resin is extruded with a T-die, the polystyrene resin sheet is drawn out from one side immediately below the T-die, and the functional resin film is drawn out from the other side and passed through a pressure-bonding roll and laminated. Sandwich extrusion lamination method, co-extrusion of adhesive resin and functional resin, method of crimping polystyrene resin sheet to this, method of co-extruding adhesive resin and polystyrene resin, and crimping functional resin film to this, polystyrene resin, There is a method of co-extruding an adhesive resin and a functional resin in three layers. Among these, co-extrusion of adhesive resin and functional resin to produce a co-extruded film, and the method of extruding and laminating polystyrene resin on the adhesive resin layer side uses widely used existing equipment It is advantageous and most preferable because it can be performed. In any of the above-described crimping methods, the crimping temperature is preferably 180 to 250 ° C. to ensure adhesion.

  The multi-layer sheet of the present invention is provided with a dividing groove, which is divided into individual containers when formed into multiple containers, for example, and when formed into a coffee milk container or the like, the tab piece is broken off. This is for peeling the cover sheet. Therefore, the position of the dividing groove is provided at the connecting portion between the individual containers in the case of multiple containers, and in the tab portion in the case of a milk container for coffee or instant noodle containers. As a rule, the dividing groove is provided over the entire length of the dividing part, and the depth of the groove is provided so that the functional resin layer and the adhesive resin layer are completely cut to reach the polystyrene resin layer. . On the other hand, the dividing groove needs to have a strength capable of maintaining the state in which both sides of the groove are connected before being divided. For this reason, the groove depth is about 1 to 150 μm regardless of whether the polystyrene resin layer is a non-foaming layer or a firing layer. It is preferable to make it small. The cross-sectional shape is usually V-shaped so that it can be easily broken. That is, as shown in FIG. 1, the multilayer sheet 1 of the present invention has a polystyrene resin layer 2 (this layer is a firing layer), an adhesive resin layer 3 and a functional resin layer 4 laminated in this order. The dividing groove 5 is provided so as to cut the adhesive resin layer 3 from the functional resin layer 4 side to reach the polystyrene resin layer 2. This dividing groove is usually a straight line, but may be a dotted line or a broken line with a part thereof cut completely, or may be a curved line or a jagged broken line.

  The method of cutting the dividing groove in the present invention is not particularly limited, but a press cutting blade corresponding to the dividing position is generally used, and the blade used therefor is also used in a punching die of a thermoformed product. As a material used for the Thomson blade, Swedish steel which is a high-tensile steel plate is preferable. The time for providing the dividing groove may be before or after the container is formed, but usually the container is formed first.

  An example of a method for forming the dividing grooves is shown in FIG. This is an example in which four yogurt cups are provided, and a dividing groove is provided at a set depth by lowering a V-shaped Thomson blade attached in a cross shape on the lower surface of the blade fixing plate by a predetermined distance.

  The shape of the container can vary depending on the application, but the multilayer container of the present invention usually has a flange portion in addition to the chamber for containing the packaged object, and the dividing groove is usually provided in this flange portion. It is done. The multilayer container is generally cup-shaped or tray-shaped, and typical examples of the multilayer container of the present invention include a multi-layer container and a portion pack.

  Multiple containers are obtained by connecting individual containers via flanges or the like, and there are some containers in which a considerable number, for example, 20 or 100 are connected from two containers. An example of multiple containers is shown in FIG. This container is a quadruple container of yogurt, (a) is a plan view with the cover sheet removed, and (b) is a sectional view taken along the line AA. As shown in the figure, each container 6 is composed of a container chamber 7 having the same shape and a substantially bottomed cylindrical shape and a square flange portion 8 extending horizontally from the outer edge of the upper end thereof, and four containers 6 are interposed via the flange portions 8. It is connected to the rice field. And the division | segmentation groove | channel 5 is provided in the connection part, and each container 6 can be broken now. Each container 6 is thin because the storage chamber 7 is formed by deep drawing, and only the flange portion 8 has the thickness of the original multilayer sheet remaining. In the food field, this multiple container includes, in addition to containers for storing yogurt, tofu, etc., a container made of two containers in which matcha pudding and black honey are separated and folded between them.

  In the portion pack, a part of the flange portion provided at the upper edge of the individual container protrudes into a tab portion, and a dividing groove is provided there. The tab portion is opened and the cover sheet bonded thereto is pulled up to open. An example of this portion pack is shown in FIG. This container is a milk container for coffee, (a) is a plan view, and (b) is a side view. As shown in the figure, this container is composed of a tapered frustoconical storage chamber 7 and an annular flange portion 8 extending in the horizontal direction from the outer edge of the upper end thereof, and a tab portion 10 protruding in a substantially triangular shape from one end of the flange portion. Is provided. The tab portion 10 is provided with a dividing groove 5. The upper surface of the container 6 is sealed with a cover sheet 9 bonded thereto. This portion pack is used in the food field for instant noodles, milk for coffee, and the like.

  Also in the pharmaceutical field, it is used in double bags that contain two liquids and mix them at the time of use.

  The production method of the multilayer container of the present invention is not particularly limited, but usually vacuum forming or vacuum / pressure forming is used.

Resin Polystyrene MFR 9g / 10min, density 1.04g / cc general-purpose polystyrene (GPPS) 70% by mass and MFR 2.7g / 10min, density 1.04g / cc density polystyrene 30% by mass mixed resin used. As the expanded polystyrene, N ₂ gas was injected into this mixed resin at a rate of 0.25 kg / h and the expansion ratio was 1.6 times.

Adhesive Resin A modified polyolefin having an MFR of 1 g / 10 min and a density of 0.91 g / cc in which an unsaturated dicarboxylic acid anhydride was grafted to polypropylene was used.

Functional resin The following resin was used.
(1) Low density polyethylene (LDPE)
MFR 2g / 10min Density 0.919g / cc
Applicable to Ministry of Ordinances 1 group without adding resin additives

(2) Ethylene-vinyl acetate copolymer (EVA)
MFR 2g / 10min 4% by mass containing vinyl acetate

(3) Polyethylene terephthalate (PET)
Intrinsic viscosity 0.62 dl / g Density 1.34 g / cc

(4) Polyamide (NY)
Unitika emblem ON 25μm

Molding method (1) Sand extrusion laminating method of adhesive resin Adhesive resin is extruded to a thickness of 50 μm with a T die, a foamed PS sheet of 600 μm from one side immediately below the T die, and a low density polyethylene of 100 μm from the other side. The film is drawn out to form a multilayer sheet.
The molding equipment used in this case can be any general extrusion laminating machine that has the function of feeding the substrate from both sides directly under the T die. In this case, it has a φ90 mm extruder. Molded using molding equipment.

(2) Sand Extrusion Lamination Method for Adhesive Resin Adhesive resin is extruded 50 μm with a T-die, and a 600 μm foam PS sheet is drawn from one side directly below the T-die, and a 25 μm polyamide film is drawn from the other to produce a multilayer sheet. Mold.
The molding equipment used in this case can be any general extrusion laminating machine that has the function of feeding the substrate from both sides directly under the T die. In this case, it has a φ90 mm extruder. Molded using molding equipment.

(3) Co-extrusion lamination method of adhesive resin and EVA resin Adhesive resin 50 μm and EVA resin 100 μm are co-extruded with a T-die (150 μm), and a 600 μm foamed PS sheet is formed on the adhesive resin surface side directly under the T-die. The multilayer sheet was formed by feeding and welding.
The molding equipment used in this case can be used as long as it is a general extrusion laminating machine having the function of feeding the substrate from one side directly under the T die, and in this case, two φ90 mm extruders are used. Molded using a coextrusion molding facility.

(4) Co-extrusion laminating method of adhesive resin and polyethylene terephthalate Adhesive resin 50 μm and polyethylene terephthalate resin 60 μm are co-extruded with a T-die (110 μm), and a 600 μm foamed PS sheet directly on the adhesive resin surface side immediately below the T-die Were fed out and welded to form a multilayer sheet.
The molding equipment used in this case can be used as long as it is a general extrusion laminating machine having the function of feeding the substrate from one side directly under the T die, and in this case, two φ90 mm extruders are used. Molded using a coextrusion molding facility.

(5) Multilayer molding method in which a multilayer film of adhesive resin and polyethylene resin is welded to PS extrusion resin PS foam resin is extruded to a thickness of 600 μm with a T die, and an adhesive resin layer of 50 μm from one side directly below the T die And a co-extruded film composed of a low-density polyethylene resin layer of 100 μm is drawn out so that the adhesive resin comes to the PS surface, and a multilayer sheet is formed.
The molding equipment used in this case can be used as long as it is a general extrusion laminating machine having a function of feeding the substrate from one side directly under the T die. In this case, a φ90 mm extruder is used. Molded.

  The obtained results are shown in Table 1.

  The multilayer sheet of the present invention has a polystyrene resin layer as an outer layer when used in a container, so that the leakage of a trace amount of styrene monomer or oligomer contained therein does not affect the package, and breakage is caused. On the other hand, since it has high strength and excellent splitting ability from the split groove, it can be widely used for multiple containers, potion packs, etc., and is particularly suitable for food and pharmaceutical packaging containers.

DESCRIPTION OF SYMBOLS 1 Multilayer sheet 2 Polystyrene resin layer 3 Adhesive resin layer 4 Functional resin layer 5 Dividing groove (connection part)
6 Multilayer container 7 Storage chamber 8 Flange 9 Cover sheet 10 Tab

Claims (4)

Polystyrene as a main component, in the case of thick non-foamed layer is 500-700, with one surface of 400~800μm der Ru polystyrene resin layer in the case of the foam layer,
Polyethylene, polypropylene or the functional resin layer mainly composed of functional resin is polyethylene terephthalate and the other surface, said poly scan styrene resin layer and the functional resin layer is grafted to the adhesive resin is an unsaturated dicarboxylic acid polyolefin the total thickness of the thickness is a modified polyolefin bonded to that is bonded via an adhesive resin layer of 30~60μm is the case of the polystyrene resin layer is non-foamed layer 600～800Myuemu, in the case of the foamed layer 600 A multilayer sheet having a thickness of 1000 μm is formed with a polystyrene resin layer as an outer layer, and a dividing groove in which the functional resin layer and the adhesive resin layer are cut is provided to reach the inside of the polystyrene resin layer at a depth of 1 to 40 μm. Multi-layer container for food or medicine . Multilayer sheet of the polystyrene resin is a foamed resin, the multilayer container according to claim 1 Symbol placement functional resin is polyethylene. A flange portion, the dividing groove multilayer container according to claim 1 or 2, wherein provided in the flange portion. The multilayer container according to any one of claims 1 to 3, which is a container for storing a dairy product.

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