JPH08169992A - Easily openable resin composition and package made using the same - Google Patents

Abstract

PURPOSE: To provide an easily openable resin compsn. excellent in processability, easily openable with a stable heat-seal strength and free of legginess at the time of opening, and a package made using the same. CONSTITUTION: The compsn. comprises a mixture of 60-99wt.% polypropylene with 1-40wt.% polyethylene-modified adhesive resin. Examples of the compsn. include one wherein the polyethylene-modified adhesive resin is a modified polyethylene grafted with maleic anhydride, one wherein the polyproplyene is crystalline polypropylene having a density of at least 0.9, and any of the above compsns. having a melt flow rate of 0.5 to 40g/10min and capable of extrusion molding. An easily openable package has a sealing layer made of any one of the above compsns.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sealable resin for a package, particularly an easily-openable resin composition which can be easily opened, and a package using the same.

[0002]

2. Description of the Related Art In order to prevent the deterioration of the contents of packaging such as food, it is necessary to shield the contents from the outside air to prevent oxidation of the contents,
Prevent its promotion by shading. In addition, in order to sterilize the contents, after packaging, a treatment such as boil or retort is performed. Further, the quality of the contents is prevented from being deteriorated due to moisture absorption during storage or conversely drying. On the other hand, in the package, there are one that is composed of a container and a lid and one that takes the form of a pouch-shaped soft packaging material, but they are heat-sealed by a heat-sealing layer provided on the inner surface of the package. Therefore, a method of sealing is generally used. Therefore, in order to achieve the purpose of the above-mentioned package, it is necessary that the heat-sealing layer has a sufficient sealing property, and that the heat-sealing strength is sufficient so that the sealing portion does not come off during the process of transportation and the like. Is needed to have.

However, the excessive heat seal strength for protecting the contents cannot be easily opened by hand when used by the consumer, and it is less necessary to use tools such as scissors. There wasn't. From such a problem, a resin composition has been proposed which has sufficient sealing property for protecting the content and easy opening property that can be easily opened by hand when opening.

Examples of such a resin composition include a resin composition prepared by mixing polyethylene and polypropylene, and a resin composition prepared by mixing a copolymer of ethylene and vinyl acetate and a low crystalline polyolefin resin. They are,
Since the resin is easily broken at the time of opening based on the low adhesive strength between the mixed two or more kinds of resins, an easily openable sealant is achieved. However, in the former case, each resin destroyed at the time of opening causes a so-called stringing in which the resin becomes a thread and extends, which is not good in appearance and there is a possibility that the thread-shaped resin is mixed into the contents. On the other hand, in a system containing a copolymer of ethylene and vinyl acetate, inferior in processability such that the vinyl acetate component is decomposed during processing, low crystalline polyolefin has no rigidity when formed into a film,
Further, the stringing state was not always satisfactory.

Another example is a resin composition prepared by mixing polyethylene and polybutylene. However, this resin composition also has a drawback that stringing is likely to occur and that the heat-sealing strength after heat-sealing is reduced and it takes several days to stabilize.

[0006] Further, since the easily openable resin composition and the package thereof which have been proposed so far are the resin compositions based on polyethylene, the pressure resistance when an external force is applied to the package is insufficient. There was a problem with the resistance to oily contents.

[0007]

In view of the above problems, the present invention has excellent workability, has stable heat seal strength, is easy to open, and is easy to open without causing stringing at the time of opening. The present invention also provides a resin composition, and a package using the resin composition.

[0008]

In order to solve the above problems, the present invention is an easily openable resin composition comprising a mixture of 60 to 99% by weight of polypropylene and 1 to 40% by weight of a polyethylene-modified adhesive resin. . In an embodiment, the polyethylene-modified adhesive resin is an easily openable resin composition that is maleic anhydride graft-modified polyethylene, and the polypropylene is an easily openable resin composition that is crystalline polypropylene having a density of 0.9 or more, and a melt. The flow rate is 0.
The easily-openable resin composition which can be extruded and is 5 to 40 g / 10 minutes can be mentioned. Further, it is an easily openable package having a seal layer made of any of the above easily openable resin compositions.

The present invention will be described in more detail below.

As the polypropylene used in the present invention, a homopolymer of propylene, a random copolymer with ethylene, butene-1, pentene-1, hexene-1, etc., or a block copolymer may be used. it can. In the case of these copolymers, it becomes amorphous depending on the ratio of the copolymerization components, but it is preferable to use crystalline polypropylene having a density of 0.9 or more in terms of processability, suitability for contents, resistance and the like. .

The polyethylene-modified adhesive resin used in the present invention generally comprises polyethylene such as low-density polyethylene, high-density polyethylene, linear low-density polyethylene and nylon, saponified ethylene-vinyl acetate copolymer, polystyrene and the like. It is used as an adhesive resin for multi-layer coextrusion. These are obtained by grafting polyethylene such as low density polyethylene, high density polyethylene and linear low density polyethylene with unsaturated acid such as acrylic acid, methacrylic acid and maleic anhydride using radicals such as peroxide as an initiator. It is a polyethylene-modified resin obtained by introducing a polar group into polyethylene.

In particular, those modified with maleic anhydride are preferable from the viewpoint of stability of physical properties of the modified products and easiness of handling. Specific examples of these resins include Admer (manufactured by Mitsui Petrochemical Co., Ltd.), Adtex ER (manufactured by Showa Denko KK), Nisseki N Polymer (Nippon Petrochemical Co., Ltd.).
Manufactured by Mitsubishi Yuka Co., Ltd.). Although these resins include those having various grafting rates, they can be selected according to the desired heat sealing strength.

The polypropylene and the polyethylene-modified adhesive resin can be mixed and used at an appropriate ratio according to the desired heat-sealing strength. If the polypropylene content is less than 60% by weight, the elongation of the resin composition will increase. The polypropylene content is 60% by weight or more, and preferably 70% by weight or more, because the heat-sealing layer is likely to be broken and the heat seal layer is easily broken. Further, when the polypropylene content is 99% by weight or more, substantially no heat-sealing strength that makes opening easy is obtained, and it is preferably 90% by weight or less, more preferably 80% by weight or less. That is, polypropylene is most preferably 70 to 80% by weight.

The polypropylene and the polyethylene-modified adhesive resin can be mixed in advance with a biaxial kneading extruder or the like to form pellets, and then molded into a film or sheet with the extruder. In this case, pellets may be pelletized at an appropriate mixing ratio when biaxially kneading, and prepared at the mixing ratio of the present invention at the time of molding. Alternatively, pellets of each resin can be dry blended and kneaded and molded in an extruder.

The melt flow rate of the present resin composition is determined by the combination of the respective melt flow rates of the polypropylene and the polyethylene-modified adhesive resin to be mixed, and is 0.5 at 230 ° C. under a load of 2.16 kg.
It is preferable to be set to -40 g / 10min, and 1-20g /
More preferably, it is 10 minutes. If the melt flow rate is less than 0.5, it will be difficult to process with a general-purpose extruder in terms of load and resin pressure. On the other hand, if it exceeds 40, resin breakage will occur during film molding, resulting in poor moldability.

The resin composition according to the present invention can be molded as a single layer film by a molding method such as an inflation method or a T-die method. In addition, a multi-layer film can be obtained by using a coextrusion method in combination with polyethylene or the like and an adhesive resin. These films are made of polypropylene, polyester, nylon, etc. using urethane or polyester adhesives.
It can be used as a package by laminating it with an axially stretched base material. Further, the package may be laminated with the above-mentioned base material coated with vinylidene chloride for imparting an oxygen barrier property, the above-mentioned base material with aluminum or silicon oxide vapor-deposited thereon, or an aluminum foil. It is also possible to apply an adhesive to a substrate and then extrusion-coat the resin composition of the present invention to use as a multilayer film.

The easily-openable resin composition of the present invention produced by the above method has a film thickness of 10 μm to 100 μm, preferably 20 μm to 50 μm when the heat-sealing layer is formed alone. Is good. Further, when combined with other thermoplastic resin layers such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, ionomer, etc., 10 μm.
It is preferably set to -30 μm.

The packaging body of the present invention can be used as a soft packaging body as it is as a three-sided or four-sided-sealed pouch or pillow package. Alternatively, it can be used as an inner layer of a container such as polypropylene or a sealing layer of a lid material for those containers.

[0019]

The easily openable resin composition of the present invention is a resin composition mainly composed of polypropylene, to which a polyethylene-modified adhesive resin is added. It is considered that when the resin composition of the present invention is peeled off after heat-sealing, it is satisfactorily opened by being mainly broken at the interface between the polypropylene and the polyethylene-modified adhesive resin. The interfacial peel strength between the two resins is considered to be related to the chemical affinity between the two resins. By changing the resin added to polypropylene from polyethylene to a polyethylene-modified adhesive resin, heat-sealing with better openability can be achieved. It is believed that layers can be obtained.

[0020]

EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited to the following examples.

<Example> As a polypropylene, Hipol J600 manufactured by Mitsui Petrochemical Co., Ltd. (density 0.9)
1, melt flow rate 7.0 (230 ℃)) and Admer LB54 manufactured by the same company as polyethylene modified adhesive resin
0 (melt flow rate 1.5) and weight ratio 80: 2
The mixture was kneaded with a twin-screw extruder at 220 ° C. so as to be 0 to prepare pellets of the easily openable resin composition according to the present invention. The melt flow rate of this resin composition is 230 ° C., 2.16 k
It was 6.5 g / 10 minutes under a load of g. Then, the pellets are extruded from a T-die extruder at 220 ° C. to a thickness of 30 μm.
m film was prepared, and one side of this film was corona-treated, and then a biaxially stretched polyester film (thickness: 12 μ
m) and a urethane adhesive were used for dry lamination.

The surfaces of the easily openable resin composition of this multilayer film were put together, and heat-sealed at a pressing pressure of 2 kgf / cm ² and a heat-sealing time of 1 second. This seal part is cut into a strip with a width of 15 mm, and 300 mm with a tensile tester.
The heat seal strength was measured at a pulling speed of / min. The heat seal strength at each temperature is as shown in Table 1,
The heat seal strength was stable at about 0.6 kgf / 15 mm. Further, when peeled by hand, it was easily peeled off, the feel was good, and no stringing occurred.

Comparative Example In the examples, the polyethylene-modified adhesive resin was used as the low density polyethylene Mirason F31.
2 (Mitsui Petrochemical Industry Co., Ltd., melt flow rate 2) was used in the same manner as above to prepare a laminated product with a biaxially stretched polyester film, and the same test was conducted.
As shown in the results in Table 1, the heat-sealing strength was temperature-dependent, and when peeled by hand, stringing occurred.

[0024]

[Table 1]

[0025]

Industrial Applicability According to the present invention, it is possible to provide a resin composition which is excellent in processability, has a stable heat seal strength, is easy to open, and does not cause stringing at the time of opening. It is possible to provide an easily openable package using.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuo Furusawa 1-5-1 Taito, Taito-ku, Tokyo Toppan Printing Co., Ltd. (72) Inventor Katsuhiko Kimura 1-1-5 Taito, Taito-ku, Tokyo Toppan Imprint Co., Ltd.

Claims (5)

[Claims] 1. An easily-openable resin composition comprising a mixture of 60 to 99% by weight of polypropylene and 1 to 40% by weight of a polyethylene-modified adhesive resin. 2. The easily openable resin composition according to claim 1, wherein the polyethylene-modified adhesive resin is maleic anhydride graft-modified polyethylene. 3. The easily openable resin composition according to claim 1, wherein the polypropylene is crystalline polypropylene having a density of 0.9 or more. 4. A melt flow rate of 0.5 to 40 g / 1.
It is 0 minutes, The extrusion-moldable easy-opening resin composition in any one of Claim 1 thru | or 4 characterized by the above-mentioned. 5. An easily openable package having a seal layer made of the easily openable resin composition according to any one of claims 1 to 4.