JP2009040460A - Packaging laminated material and method for manufacturing packaging laminated material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a packaging laminated material in which the extrusion lamination processablity of polypropylene polymerized using a metallocene catalyst is improved, and to provide a method for manufacturing the packaging laminated material. <P>SOLUTION: The packaging laminated material is formed from at least a paper layer and an innermost layer made of a heat-sealable thermoplastic resin. The innermost layer is formed by extrusion lamination. The innermost layer includes 100 pts.wt. of polypropylene having a melt index of 5 to 20 g/min and obtained using a metallocene catalyst, and 5 to 30 pts.wt. of polyethylene having a melt index of 7 to 20 g/min and obtained using a metallocene catalyst. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a laminated material for packaging comprising a paper layer, a heat-sealable thermoplastic resin innermost layer laminated by extrusion lamination, and a method for producing the packaging material.

For packaging containers for milk, juice, sake, shochu, mineral water and other beverages, for example, a web-like packaging material with a crease line attached to a laminate consisting of a paper layer / plastic layer is sealed by a longitudinal vertical line seal. Molded into a tube shape, filled with the contents in the tube-shaped packaging material, applied with a horizontal line seal in the transverse direction of the tube-shaped packaging material, first molded into a pillow-shaped primary shape, and the packaging material was strip-shaped In this case, it is cut into individual pieces at regular intervals, folded along a crease line, and formed into a final shape. The final shapes include brick shapes (parallelepipeds), hexagonal column shapes, octagonal column shapes, tetrahedral shapes, and the like.

In a gable top (roof type) paper packaging container, paper packaging material is cut into a predetermined shape, blanks sealed in the vertical direction of the container are obtained, and after the bottom of the blanks is sealed in the filling machine, milk is introduced from the top opening. Filled with juice or other beverage filling and sealed at the top. These packaging materials have the appearance design of the packaging container product printed on the surface thereof.

Packaging materials used for packaging container products are low density polyethylene (LDPE) / printing ink layer / paper layer / LDPE / aluminum foil (as gas barrier layer) / LDPE / LDPE, LDPE / printing ink layer / paper Layer / LDPE / LDPE, printing ink layer / LDPE / paper layer / LDPE / LDPE, LDPE / printing ink layer / paper layer / LDPE / aluminum foil / polyester (PET), etc. are known and are actually It is widely used.

In general, the above-mentioned packaging laminate is obtained by carrying a base paper roll of a paper layer into a printing machine, printing on the base paper surface, winding the printed paper again into a roll, feeding it to an extrusion laminator, and melting from an extrusion die. When a polyolefin (for example, LDPE or the like) is extruded onto the base paper surface and there is a gas barrier layer (aluminum foil or the like) in addition to the base paper, it is manufactured by extruding the molten polyolefin between the gas barrier layer and applying a laminate coating. When laminating the gas barrier layers as described above or adding other functional layers, instead of laminating all the layers at once, prepare a partial laminate (semi-material) separately. Then, it is formed into a roll shape, and these partial laminates are further laminated to obtain a final laminate.

Each layer of the packaging laminate has a function and a function. The paper layer assembled in the packaging container is provided with a plastic coating for liquid tightness on both sides of the paper layer to effectively protect the liquid absorbent fibrous paper layer from penetration by moisture. These laminated outer layers usually impart excellent heat sealability to the packaging material and, as mentioned above, consist of a thermoplastic material such as low density polyethylene.

A packaging laminated material consisting only of paper and a thermoplastic outer layer lacks mechanical strength and is inferior in barrier properties against gas from the outside of the container, particularly oxygen gas. For example, when the liquid food is citrus fruit juice or the like and stored at room temperature for a long period of time, oxygen barrier properties are required in addition to aroma retaining properties such as fragrances and flavors. This liquid food penetrates oxygen through the carton walls and therefore loses their nutritional value. It is common to add a gas barrier layer to the laminate material to reduce oxygen penetration into the carton and minimize degradation of nutrients such as vitamin C.

  As described above, in order to maintain the quality of the content food, it is possible to prevent the fragrance, flavor, etc. of the content product from being transmitted to the outside through the packaging material, or the fragrance, flavor, etc. Gas that interferes with the quality of the contained product, preventing it from being absorbed by the packaging material that comes into contact with it, or preventing odors from oozing out of the packaged material into the contained product and inhibiting its fragrance, flavor, etc. The packaging material is required to have a gas barrier property that (such as oxygen gas) permeates the laminated material container wall of the packaging container and protects the contents product, and a packaging material having sufficient aroma retention and gas barrier properties is preferable.

Examples of gas barrier materials that impart gas barrier properties to packaging materials include materials having excellent oxygen gas barrier properties such as aluminum foil, EVOH (ethylene vinyl alcohol), PVOH (polyvinyl alcohol), and vapor-deposited layers of inorganic oxides. Known.
In order to impart barrier properties including aroma retention to the packaging material or film, polyamide, so-called nylon is laminated on the packaging material or film.

The polyethylene of the laminated material used in the liquid food paper packaging container field is usually low density polyethylene (LDPE), and particularly high pressure method low density polyethylene. The low molecular weight component contained in the innermost high-pressure low-density polyethylene migrates to the contents in the paper packaging container, and the taste of the contents may change when stored for a long time. In addition, the ethylene-α-olefin copolymer obtained using a Ziegler catalyst has a high sealing temperature and is inferior in processability. When a lubricant is added to improve it, the lubricant shifts to the contents and lowers its taste. .

On the other hand, there is a paper packaging material that uses an ethylene-α-olefin copolymer (so-called metallocene PE or mLLDPE) polymerized using a metallocene catalyst in the innermost layer. It is known that this metallocene PE is excellent in hygiene due to low temperature sealing properties, film processability and narrow molecular weight distribution, and can be applied to containers.

Polypropylene is one of the most widely used thermoplastic resins as a typical general-purpose plastic. Propylene (CH3CH = CH2) purified from naphtha decomposition and the like is subjected to addition polymerization in the presence of a catalyst. can get. Its properties are light weight, relatively high strength, high heat resistance, high resistance to various chemicals, solvents, etc., and easy to process, so it can be used for daily packaging, various packaging materials (films, containers), industrial parts. Widely used as a material.

There are paper packaging materials using polypropylene polymerized using a metallocene catalyst (so-called metallocene PP, called mPP) and paper containers using the same. (For example, refer to Patent Documents 1 and 2.)
JP 2001-278330 A JP2007-144687

Polypropylene having excellent properties, however, polypropylene (metallocene PP) polymerized using a metallocene catalyst is not suitable for processing properties, particularly extrusion lamination. In this extrusion lamination, a characteristic called neck-in is increased, which is not suitable for processing for producing a laminate for packaging.
Neck in means that when the width of the extrudate from the T die comes out of the die, it becomes narrower than the width of the die due to shrinkage in the width direction of the die.

In the present invention, the above-mentioned disadvantages are eliminated, and the processing characteristics, particularly for polypropylene (metallocene PP) polymerized using a metallocene catalyst that is lightweight, relatively high strength, high heat resistance, resistant chemicals, and high solvent resistance. Provided are a packaging laminate material with improved extrusion lamination processability and a method for producing the packaging laminate material.

The packaging laminate material of this invention is a packaging laminate material comprising at least a paper layer and a heat-sealable thermoplastic resin innermost layer,
The innermost layer is laminated by extrusion lamination,
Polyethylene 5 having an innermost layer having a melt index of 5 to 20 g / min and 100 parts by weight of polypropylene obtained using a metallocene catalyst, and having a melt index of 7 to 20 g / min and using a metallocene catalyst And 30 parts by weight.

In a preferred embodiment of the present invention, the innermost layer has a melt index of 6 to 8 g / min, 100 parts by weight of polypropylene obtained using a metallocene catalyst, a melt index of 11 to 15 g / min, and a metallocene catalyst. 7 to 13 parts by weight of polyethylene obtained by use.

In a preferred embodiment of this invention, the packaging laminate material comprises at least a paper layer, a thermoplastic resin outermost layer and a heat sealable thermoplastic resin innermost layer,
The outermost layer and innermost layer are laminated by extrusion lamination,
The outermost layer and the innermost layer have a melt index of 5 to 20 g / min, 100 parts by weight of polypropylene obtained using a metallocene catalyst, and have a melt index of 7 to 20 g / min and are obtained using a metallocene catalyst. 5 to 30 parts by weight of polyethylene.

In a preferred embodiment of the present invention, the packaging laminate material has a barrier intermediate layer laminated inside the paper layer.

In a preferred embodiment of the present invention, the barrier intermediate layer comprises an aluminum foil, EVOH (ethylene vinyl alcohol), PVOH (polyvinyl alcohol), an inorganic oxide vapor deposition layer, a condensation polymer of metaxylenediamine and adipic acid (nylon-MXD6 Or a blend polymer thereof.

In the method for producing a laminated material for packaging according to the present invention, a method for producing a laminated material for packaging comprising at least a paper layer and a heat sealable thermoplastic resin innermost layer,
100 parts by weight of polypropylene having a melt index of 5 to 20 g / min and obtained using a metallocene catalyst, and 5 to 30 parts by weight of polyethylene having a melt index of 7 to 20 g / min and obtained using a metallocene catalyst And prepare
Dry blending polypropylene and polyethylene,
The blended polypropylene and polyethylene are extruded by an extrusion lamination method to laminate the innermost layer.

In the production method of a preferred embodiment of the present invention, a pellet-shaped polypropylene and a pellet-shaped polyethylene are prepared,
Polypropylene and polyethylene are pellet blended.

The present invention having the above-described configuration functions and functions as follows.
With the laminated material for packaging of the present invention, the innermost layer of the heat-sealable thermoplastic resin can be practically extrusion coated and laminated, and therefore the packaging laminated material is effectively (efficiently) produced (converted). be able to.

In a preferred embodiment of the present invention having a barrier intermediate layer, a packaging laminate material excellent in aroma retention and gas barrier properties can be provided.
Polyolefin propylene obtained using a metallocene catalyst is used, so it can seal well in a wide range of sealing temperatures from high to low, and therefore it is easy to fill and pack into paper packaging containers and heat quickly. It is possible to provide a paper packaging laminate material that can be sealed and that is able to obtain a good seal without being affected by the temperature of the filled contents and has quality retention.

  Furthermore, it can be extrusion coated (laminated), has high cost performance, excellent mechanical strength of the container, can reduce the paper load, reduce the environmental impact, and can be heat sealed in a wide range of temperature environments Provide a laminated material.

In the production method of a preferred embodiment of the present invention in which pellet blending is performed, blending can be easily performed, and it can contribute to improvement of processing characteristics (extrusion lamination processability) of metallocene PP.

Hereinafter, embodiments of the present invention will be described in detail.
The paper layer that can be used in the present invention is usually made from kraft pulp and is required to have excellent strength and low water absorption. The types include bleached paper (FBL), unbleached paper (UBL), bleached and unbleached combined paper (DUPLEX), clay-coated paper, and multilayered laminated paper (MB).

The innermost layer according to the present invention is laminated by extrusion lamination, and the innermost layer is composed of polypropylene obtained using a metallocene catalyst and polyethylene obtained using a metallocene catalyst.
Extrusion lamination here involves the application and extrusion of an extrudable layer of molten plastic onto a substrate and the extrusion of an adhesive layer of molten plastic between the web of the substrate layer and the prefabricated film layer. Means to form a laminate of base layer / adhesive layer / film layer.

As this polypropylene, there is a polypropylene having a narrow molecular weight distribution polymerized by using a metallocene catalyst, or a blend polymer containing at least the polypropylene, which is a polymer having a good heat sealability. The melt index of polypropylene polymerized using a metallocene catalyst is 5 to 20 g / min, preferably 6 to 8 g / min.
As this metallocene catalyst, for example, a catalyst based on a combination of a metallocene complex and an alumoxane such as a catalyst based on a combination of zirconocene dichloride and methylalumoxane.

The polyethylene obtained using the metallocene catalyst has a melt index of 7 to 20 g / min, preferably a melt index of 11 to 15 g / min. Preferably, it has the characteristics of so-called polyethylene for extrusion lamination.

  Examples of comonomers copolymerized with propylene or ethylene include butene-1, hexene-1, 4-methylpentene-1, and octene-1. These α-olefins may be used alone or in combination of two or more.

The innermost layer has 100 parts by weight of polypropylene obtained using the metallocene catalyst and 5 to 30 parts by weight of polyethylene obtained using the metallocene catalyst, preferably 7 to 13 parts by weight.

In a preferred embodiment of this invention, the thermoplastic resin outermost layer is also laminated by extrusion lamination, has a melt index of 5 to 20 g / min, and 100 parts by weight of polypropylene obtained using a metallocene catalyst, and a melt index of 7 to It has 20 g / min and consists of 5 to 30 parts by weight of polyethylene obtained using a metallocene catalyst.

In the laminated material for packaging according to a preferred embodiment of the present invention, a barrier intermediate layer is laminated inside the paper layer.
Examples of the barrier intermediate layer include aluminum foil, EVOH (ethylene vinyl alcohol), PVOH (polyvinyl alcohol), an inorganic oxide vapor deposition layer, a condensation polymer of metaxylenediamine and adipic acid (nylon-MXD6), or a blend polymer thereof. There is.

The manufacturing method of the packaging laminated material of this invention produces the packaging laminated material which consists of a paper layer and a heat sealable thermoplastic resin innermost layer by the following step.
(A) 100 parts by weight of polypropylene having a melt index of 5 to 20 g / min and obtained using a metallocene catalyst, and 5 to 5 of polyethylene having a melt index of 7 to 20 g / min and obtained using a metallocene catalyst Providing 30 parts by weight, preferably 7 to 13 parts by weight;
(B) a step of dry blending polypropylene and polyethylene;
(C) A step of extruding the blended polypropylene and polyethylene by an extrusion lamination method to laminate the innermost layer.

In the production method of a preferred embodiment of the present invention, pellet-shaped polypropylene and pellet-shaped polyethylene are prepared, and polypropylene and polyethylene are pellet-blended.

Examples will be described below.
Preparation of 100 parts by weight of pellet-shaped polypropylene (melt index 7 g / min) obtained using a metallocene catalyst and 10 parts by weight of pelletized polyethylene for extrusion lamination (melt index 13 g / min) obtained using a metallocene catalyst did.
Pellet polypropylene and pellet polyethylene were dry blended, that is, pellet blended.
Next, the blended material was inserted into an apparatus for extrusion lamination, extruded from a T-die on a continuously conveyed web-like paper layer, and laminated to make a prototype of a laminated material for packaging.

During the trial production of the packaging laminate material described above, neck-in (a phenomenon in which the width of the extrudate from the T-die emerges from the die and becomes narrower than the width of the die due to shrinkage in the width direction of the die) was measured.
The shrinkage width in the die width direction of the extrudates in the above examples was 30 mm on one side.

As a comparative example, a laminate material for packaging was made as a prototype using only polypropylene as in the example.
Neck-in was measured during trial production of the packaging laminate material.
The shrinkage width in the die width direction of the extrudate of the comparative example was 60 mm on one side.
From the comparison of the shrinkage width between the example and the comparative example, in the example, the neck-in showed the same numerical value as the low density polyethylene for extrusion lamination, and the workability was remarkably improved.

In addition, this invention is not limited to this embodiment, It can change variously based on the meaning of this invention, and does not exclude them from the scope of the present invention.

The present invention can be applied to the production of laminated materials for packaging foods and the like.

Claims (7)

A laminated material for packaging comprising at least a paper layer and a heat-sealable thermoplastic resin innermost layer,
The innermost layer is laminated by extrusion lamination,
The innermost layer has a melt index of 5 to 20 g / min, 100 parts by weight of polypropylene obtained by using a metallocene catalyst, and a polyethylene having a melt index of 7 to 20 g / min and obtained by using a metallocene catalyst A laminated material for packaging, comprising 5 to 30 parts by weight. The innermost layer has a melt index of 6 to 8 g / min, 100 parts by weight of polypropylene obtained using a metallocene catalyst, and a polyethylene having a melt index of 11 to 15 g / min and obtained using a metallocene catalyst The laminated material for packaging according to claim 1, which has 7 to 13 parts by weight. The packaging laminate material comprises at least a paper layer, an outermost thermoplastic resin layer and an innermost heat-sealable thermoplastic resin layer,
The outermost layer and the innermost layer are laminated by extrusion lamination,
The outermost layer and the innermost layer have a melt index of 5 to 20 g / min, have 100 parts by weight of polypropylene obtained using a metallocene catalyst, have a melt index of 7 to 20 g / min, and use a metallocene catalyst. The laminated material for packaging according to claim 1, comprising 5 to 30 parts by weight of the obtained polyethylene. The packaging laminate material according to claim 1, wherein the packaging laminate material has a barrier intermediate layer laminated inside the paper layer. The packaging laminate material according to claim 5, wherein the barrier intermediate layer is an aluminum foil, EVOH, PVOH, a vapor deposition layer of an inorganic oxide, a condensation polymer of metaxylenediamine and adipic acid, or a blend polymer thereof. A method for producing a laminated material for packaging comprising at least a paper layer and a heat sealable thermoplastic resin innermost layer,
100 parts by weight of polypropylene having a melt index of 5 to 20 g / min and obtained using a metallocene catalyst, and 5 to 30 parts by weight of polyethylene having a melt index of 7 to 20 g / min and obtained using a metallocene catalyst And prepare
Dry blending the polypropylene and the polyethylene,
The blended polypropylene and polyethylene are extruded by an extrusion lamination method to laminate the innermost layer.
A method for producing a laminated material for packaging. Preparing the pellet-shaped polypropylene and the pellet-shaped polyethylene;
Pellet blending the polypropylene and the polyethylene;
The manufacturing method of the laminated material for packaging of Claim 6.