JP2000309334A - Package laminating material for paper container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paper packaging material of small water permeability, good waterproofness or water resistance and suitable for filling and packaging a liquid food, which is used for a paper packaging container for a milk or a liquid milk product and provided with the prolonged shelf-life, not generating the inconvenience of bulging out of a container main body of the container filled with a liquid food in the distribution process and retaining the mechanical strength of the entirety of the container. SOLUTION: A paper packaging material is used for manufacturing a paper container to be filled with a milk or a liquid milk product and formed of a blank sheet of a laminated constitution of a low density polyethylene layer 1, an anchor coat layer, an oriented polypropylene film (OPP) 2, an anchor coat layer, a low density polyethylene laminated layer 3, a paper base layer 4 and an outer low density polyethylene layer 5, all of which are laminated successively in the above order starting the innermost side toward the outermost side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packaging laminate material for paper containers suitable for filling and packaging liquid food. In more detail, a paper packaging material is cut into a predetermined shape, blanks sealed in the vertical direction of the container are obtained, the bottom of the blanks is sealed, then the liquid product is filled from the upper opening, and the upper portion is sealed. The present invention relates to a packaging laminate material for paper containers suitable for filling and packaging milk or liquid dairy products in a gable-top (roof type) paper packaging container obtained as described above.

[0002]

2. Description of the Related Art A packaging container for milk, juice or other beverages is, for example, a paper packaging container having a gable-top shape (roof type). After sealing the blanks in the filling machine, sealing the bottom of the blanks in a filling machine, filling the upper portion of the blanks with milk, juice or other beverage material, and sealing the upper portion. In these paper packaging containers, the innermost layer of the packaging material corresponding to the horizontal line seal portion and / or the vertical line seal portion is heat-sealed with the other innermost layer or outermost layer.

Conventionally, packaging laminates used in paper packaging products requiring refrigeration for milk or liquid dairy products, etc. include a printing ink layer / low-density polyethylene (LDPE) by high-pressure method / paper (fiber Quality) substrate layer / LDPE /
LDPE, LDPE / printing ink layer / paper base layer / LDP
E / LDPE, printing ink layer / LDPE / paper base layer / L
DPE and the like are known, and are currently widely used.

[0004] Gable-top (roof type) for milk or liquid dairy products due to extension of shelf life and extension of transport distance
There is a demand for stronger and more robust paper packaging containers. However, since LDPE has poor waterproofness (high water permeability), water penetrates from the moisture of milk or liquid dairy products inside and maintains the mechanical strength of the entire container unless the layer thickness is considerably increased. The paper base layer is weakened by water, and the container filled with the liquid food has a disadvantage that the container body expands during the distribution process.

[0005]

SUMMARY OF THE INVENTION The present invention has been made on the basis of the above background, and it is an object of the present invention to extend the shelf life of paper containers for milk or liquid dairy products, Even if the container is extended, the container filled with liquid food can maintain the mechanical strength of the entire container without inconvenience that the container body swells in the distribution process, and has low water permeability and waterproofness or water resistance An object of the present invention is to provide a packaging laminate material for paper containers suitable for filling and packaging liquid foods having good properties.

[0006]

The above object is achieved by the present invention. That is, the packaging laminate material for a paper container according to the present invention comprises an inner low-density polyethylene layer / anchor coat layer / oriented polypropylene film (OPP) / anchor coat layer / low-density polyethylene laminate layer / paper base in order from the inner layer to the outer layer. It is made from a blank sheet having a laminated structure of a layer and an outer low-density polyethylene layer, and is characterized by being filled with milk or a liquid dairy product.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS How to implement the present invention will be described below in detail and concretely. The packaging laminate material for a paper container according to a preferred embodiment of the present invention comprises an inner low-density polyethylene layer / anchor coat layer / stretched polypropylene film (O
PP) / anchor coat layer / low density polyethylene laminate layer / paper substrate layer / outer low density polyethylene layer. In particular, the packaging laminate material for paper containers of the present invention is mainly used for milk or liquid dairy products, and condensation may occur on the surface of the container due to refrigeration, ice cooling, etc. Use the one coated with lamination.
Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of an embodiment of the packaging laminate material of the present invention, and a perspective view of a paper container molded from the packaging material with a part cut away. In the present invention, from the inside of the container to the outside of the raw material,
Inner low density polyethylene layer 1 / anchor coat layer / stretched polypropylene film (OPP) 2 / anchor coat layer / low density polyethylene laminate layer 3 / paper base layer 4 /
This is a milk or liquid dairy product paper container mainly made of a blank sheet on which an outer low-density polyethylene layer 5 is laminated. The container is not particularly limited, but is a brick-shaped or gable-top liquid container, preferably a gable-top liquid container.

[0008] The paper substrate that can be used in the present invention is usually made of 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 laminated paper (DUPLEX), clay-coated paper and multilayer laminated paper (MB). Either may be used.

In the present invention, the inner low-density polyethylene layer, the low-density polyethylene laminate layer, and the outer low-density polyethylene layer are made of low-density polyethylene (LDPE) obtained by a high-pressure method, resistance to contents (oil resistance, acid resistance,
Linear low density polyethylene (LL with excellent penetration resistance etc.)
DPE), coextruded films containing polyethylene, linear low density polyethylene with a narrow molecular weight distribution, and the like. Preferred linear low density polyethylenes having a narrow molecular weight distribution are 0.910 to 0.930, preferably
Average density of 0.922 to 0.927, peak melting point of 115 ° C. or higher by differential scanning calorimetry, melt flow index of 5 to 15, preferably 9 to 11, 1.3 to
It has a characteristic parameter of swelling ratio of 1.8, preferably 1.45 to 1.55, more preferably 1.5 and its vicinity.

Examples of such a linear low-density polyethylene having a narrow molecular weight distribution include linear low-density polyethylene having a narrow molecular weight distribution polymerized using a metallocene catalyst (mLLDPE) and linear low-density polyethylene using a multi-site catalyst. (LLDPE) and blended polymers thereof, as well as blended polymers of the above polymers with other polymers. As the mLLDPE, for example, a catalyst obtained by combining a metallocene complex such as a catalyst obtained by combining zirconocene dichloride with methylalumoxane and alumoxane, that is, an ethylene-α-olefin copolymer obtained by polymerization using a metallocene catalyst Can be used. Metallocene catalysts
Current catalysts have non-uniform active sites and are called multi-site catalysts, whereas active sites are uniform and are also called single-site catalysts.

As the resin of mLLDPE, specifically,
Mitsubishi Chemical Co., Ltd. product name "Cannel", Mitsui Petrochemical Industry Co., Ltd. product name "Evolu", United States, Exxon Chemical (EXXON CHEMICAL) Co., Ltd. product name "EXACT (EXACT)", United States, Dow
An ethylene-α-olefin copolymer polymerized using a metallocene catalyst such as “Affinity” (trade name) or “ENGAGE” (trade name) manufactured by DOW CHEMICAL can be used. . Basically, use no additive,
Antioxidants, ultraviolet absorbers, antistatic agents,
Various additives such as a lubricant, an antiblocking agent, a flame retardant, an inorganic or organic filler, a paint, and a pigment can be appropriately added.

The stretched polypropylene film (OPP) of the constituent layer of the packaging material which can be used in the paper container of the present invention is a vertically or horizontally uniaxially stretched polypropylene film or a vertically and horizontally biaxially stretched polypropylene film, and is large in the stretching direction. The toughness of the tensile strength and the water vapor transmission rate are very small, and it has a moisture-proof property suitable for packaging for those that easily absorb moisture and those that retain moisture. In the present invention, the preferred water vapor transmission rate of the stretched polypropylene film is
1 to 15 g / cm ² / 24H, more preferably 1 to 7
g / cm ² / 24H.

The anchor coating agent, adhesive or adhesive resin used for laminating some of the constituent layers of the packaging material usable in the paper container of the present invention is a urethane-based, imine-based or titanate-based adhesive. (Anchor coating agent), a material selected from linear low-density polyethylene having a narrow molecular weight distribution, ethylene-vinyl acetate copolymer (EVA) and an ionomer. When the dry laminating method is used, the adhesive constituting the adhesive layer at that time is, specifically, a two-part curable urethane-based adhesive or polyester urethane-based adhesive used in dry laminating or the like. Agent, polyether urethane adhesive, acrylic adhesive, polyester adhesive, polyamide adhesive,
A polyvinyl acetate-based adhesive, an ethoxy-based adhesive, a rubber-based adhesive, and the like can be used. Further, when the stretched polypropylene film (OPP) is laminated on the adjacent constituent layer, as the anchor coating agent, urethane-based dry lamination and urethane-based, imine-based, and titanate-based extrusion lamination can be used. In addition, a synthetic resin of an ethylene-vinyl acetate copolymer (EVA) having an adhesive property to a metal foil by an extrusion laminating method or an ionomer (IO) in which an ethylene-vinyl methacrylate copolymer is crosslinked with metal ions. Then, these film forming layers can be laminated as an adhesive layer. It is preferable to use an adhesive layer having a thickness of about 10 to 50 μm, and preferably, the adhesive layer has a layer thickness of 10 μm to 18 μm.
μVA or IO.

A packaging material for a paper packaging container according to the present invention comprises a printed ink layer provided on an outer surface of a semi-material on which an outermost resin layer is not yet laminated, or
At least an ink layer formed on the outer surface of the outer resin layer having a sealing property can be included. Inks include aqueous or oil-based inks for flexographic printing, oil-based inks for gravure printing, curable inks for offset printing, and the like. In a preferred embodiment of the packaging material for paper packaging containers of the present invention, the ink layer has A component (for example, an imine-based component) that is partially common to the component included in the anchor agent layer that adheres to the layer is included.

[0015] In the embodiment of the packaging material for a paper packaging container of the present invention, a barrier layer may be provided on the inner laminate of the packaging material. As the barrier layer, aluminum foil, metal / inorganic oxide thin film, ethylene vinyl alcohol copolymer layer (E
VOH layer), a nylon layer, a polyvinylidene chloride film, and a polyvinylidene chloride coated film. Here, as the vapor-deposited film of the inorganic oxide as the barrier layer, for example, a thermoplastic resin film having a thickness of about 10 to 30 μm of polyolefin, nylon, polyester, polyvinyl alcohol, or the like is used for silicon oxide, tin oxide, or oxide. Thickness of inorganic oxide such as zinc, indium oxide, titanium oxide, aluminum oxide, etc. 100 to 5000５, preferably 200 to 1000
A thin film layer of about Å is formed by vacuum deposition, sputtering, chemical vapor deposition, plasma chemical vapor deposition (PCVD) or the like.

In the liquid food filling field for carrying out the present invention, preferably, a paper packaging material is cut into a predetermined shape to obtain blanks sealed in the vertical direction of the container. Alternatively, it is a gable-top (roof type) paper packaging container obtained by filling a liquid milk product with a filling material and sealing the upper portion.

The paper packaging container formed from the packaging laminate in the present invention is further converted into a processed paper container (one-piece type, two-piece type, three-piece type, etc.), a composite can, an insert molded container, a double container, and the like. Can be assembled. In this case, the packaging material is punched as shown in the developed view of the composite paper packaging container, processed into a ruled line, and then folded along the ruled line and sealed to form various types of paper packaging containers. At this time, as a sealing method, there are a heat seal, a frame seal, a hot air seal, an ultrasonic seal, a high frequency seal and the like. Further, in a filling machine, these laminates are supplied in a roll shape, a sleeve shape or a cup shape, and after filling the contents, they are sealed using the above various sealing methods to form a paper packaging container.

Next, a method for producing a packaging material for a paper packaging container according to the present invention will be described. A method of laminating a usual packaging material, for example, a wet lamination method, a dry lamination method, a solventless dry lamination method,
Extrusion lamination method, T die co-extrusion molding method,
Coextrusion lamination, inflation, etc. can be used. In the present invention, when performing the above-mentioned lamination, if necessary, a pretreatment such as a corona treatment or an ozone treatment can be applied to the film. As described above, for example, an isocyanate ( (Urethane-based), polyethyleneimine-based, polybutadiene-based, organic titanium-based anchor coating agents, or polyurethane-based, polyacryl-based, polyester-based, epoxy-based, polyvinyl acetate-based, cellulose-based, etc. Known anchor coating agents and adhesives such as an adhesive for laminating can be used. In the above method for producing a packaging material, a low-density polyethylene is used as the extruded resin when the low-density polyethylene laminate layer of the intermediate layer of the packaging laminate material according to the present invention is extruded and laminated.

These packaging materials are prepared, for example, by punching a blank plate for a paper packaging container which has been subjected to a ruled process for producing a paper packaging container having a predetermined shape, and then overlapping the edges of the blank plates.
The heat-sealing film on the inner surface side of the polymerization end and the heat-sealing film on the outer surface side are welded to form a welded portion to produce a sleeve. Next, the sleeve is mounted on a filling machine, and the bottom portion is folded along a predetermined ruled line and heat-sealed by hot-air treatment to form a bottom portion, and then the contents are filled from the opening at the top portion, Thereafter, the top portion is folded along a predetermined ruled line and heat-sealed by hot air treatment, for example, to form a top portion in the shape of a gabelle top, and to manufacture a packed and packed product. Can be. The above-mentioned examples are merely examples of the packaging container according to the present invention, and the present invention is not limited thereto.

In the case where the paper packaging container formed from the packaging laminated material according to the present invention has a strip for liquid-tightly covering the discontinuous section of the innermost layer between the end faces of the packaging material, specifically, When the material is formed into a tube with a vertical line seal in the longitudinal direction, the innermost step section is covered with a strip tape for liquid tightness to protect the packaging material end surface at the vertical line seal part of the packaging material, and packaging is performed. In order to provide a spout in the container, a through-hole may be formed in the container wall (usually the upper surface), and a strip patch may be attached to the innermost layer so as to cover the through-hole.

The paper container formed from the packaging laminate material according to the present invention is a liquid dairy product such as unconditioned milk, processed milk, coffee milk, whey beverage, lactic acid bacteria beverage and the like. Although the mechanism of action and mechanism are not always clear, specific components contained in milk or liquid dairy products are prolonged, but during the long shelf life and during the distribution process during transportation, the inside of the package laminate from the side of the container wall It is considered that the waterproof property of the plastic layer such as polyethylene and the mechanical properties of the container were degraded by some action, and as a result, the container body was swollen. Surprisingly, the composite laminate of the innermost low density polyethylene layer and the inner layer oriented polypropylene film (OPP) retains the mechanical strength of the entire container when the container is filled with liquid dairy products, It has been found that there is provided a packaging laminate material for paper containers suitable for filling and packaging liquid foods having low water permeability and good waterproofness or water resistance.

[0022]

EXAMPLES The present invention will be specifically described with reference to the following examples. <Example 1> Low-density polyethylene (density =
0.920 g / cm ³ , MI = 5.1) with a thickness of 20 μm
Extrusion temperature 330 on paper base (basis weight = 320 g / m ² )
Extrusion coating at ℃ and laminating the outer thermoplastic material layer, and subsequently, on the inner back surface of the paper base, a biaxially oriented polypropylene film coated with an anchor coat agent on both sides, low density polyethylene extruded and melted At the same time, the low-density polyethylene is laminated on the innermost layer to obtain the packaging laminated material of one embodiment according to the present invention. From this packaging laminated material, a blank plate for a paper packaging container subjected to a ruled line processing is punched, and then the edges of the blank plates are overlapped and welded to produce a sleeve. Next, the sleeve is mounted on a liquid food filling machine, and the bottom portion is folded along a predetermined ruled line and heat-sealed by hot air treatment to form a bottom portion. )
Thereafter, the top portion is folded along a predetermined ruled line and heat-sealed by hot-air treatment to produce a package product having a gable-top shape. The obtained packaged milk product is stored in a chilled atmosphere for 4 weeks, and the swelling of the container body due to a decrease in mechanical strength is evaluated.

<Example 2> As in Example 1, a low density polyethylene layer / anchor coating agent layer / biaxially oriented polypropylene film / anchor coating agent layer / low density polyethylene layer / paper basis of 260 g / m ² Blank sheet consisting of material layer / low density polyethylene layer, width 2mm, height 1m
using a concave / convex type blade having a blade having a shape of m and a pressure of 50 kg /
A pressure is applied in cm ² to prepare a liquid paper container having an internal volume of 1500 ml, and the container is filled with a coffee milk beverage. The obtained packaged milk product is stored in a chilled atmosphere for 4 weeks, and the swelling of the container body due to a decrease in mechanical strength is evaluated.

Comparative Example 1 The procedure of Example 1 was repeated except that orange juice was used instead of milk.
A packaging material and a paper packaging container are prepared in the same manner as in the above. Further, the obtained paper packaging container is evaluated in the same manner as in the examples.

<Comparative Example 2> A packaging material and a paper packaging container are prepared in the same manner as in Example 1 except that mineral water is used instead of milk. Further, the obtained paper packaging container is evaluated in the same manner as in the examples.

The packaging products obtained in Examples 1 and 2 and Comparative Examples 1 and 2 are stored in a chilled atmosphere for 4 weeks, and the swelling of the container body due to a decrease in mechanical strength is evaluated. As a result, the example is superior to the comparative example. That is, comparing the example with the comparative example, in the milk-filled packaging container according to the example, there is almost no decrease in mechanical strength of the container after storage in a chilled atmosphere for 4 weeks, and no swelling of the container body is observed. On the other hand, in the comparative example, it is observed that the mechanical strength of the container after storage for 4 weeks in a chilled atmosphere is reduced and the lower part of the container body is swollen.

[0027]

According to the present invention demonstrated in the above embodiment, the following effects can be obtained. Even if the expiration date is extended for paper packaging containers of milk or liquid dairy products, and the transport distance is extended, the containers filled with liquid food will not have the disadvantage that the container body will expand during the distribution process, and the entire container will not be inflated. Retains mechanical strength. In addition, since water permeability is low and water resistance or water resistance is good, it can be stored for a long time even in an atmosphere such as chilled, and a paper packaging container suitable for filling and packaging liquid milk products such as milk can be provided. it can.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a layer structure of a laminated material for paper packaging of the present invention, and a partially cutaway perspective view of a paper packaging container molded from the packaging material.

[Explanation of symbols]

 1 inner low density polyethylene layer 2 stretched polypropylene film 3 low density polyethylene laminate layer 4 paper base layer 5 outer low density polyethylene layer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3E060 AA05 AB04 BC01 BC04 DA11 DA21 EA03 4F100 AK06A AK06C AK06E AK07B BA05 BA07 BA10A BA10E DA01 DG10D EH23 EJ37B GB16 GB23 JC00 JD07 JK01 JL04

Claims (1)

[Claims] 1. A laminated structure of an inner low density polyethylene layer / anchor coat layer / stretched polypropylene film / anchor coat layer / low density polyethylene laminate layer / paper base layer / outside low density polyethylene layer in order from an inner layer to an outer layer. A packaging laminate material for paper containers, which is made from a blank sheet and filled with milk or liquid dairy products.