Laminate and paper container for liquid

Abstract

To provide a laminate in which laminates have sufficient sealability, and which can prevent generation of a pinhole, and a paper container for liquid using the laminate.SOLUTION: Provided is a laminate 1 that has a first polyethylene layer 12 on one surface of a paper substrate layer 10, has a second polyethylene layer 14 on the other surface, and has a third polyethylene layer 16 on the second polyethylene layer 14, where the second polyethylene layer 14 is constituted of mixed resin of high-density polyethylene resin and low-density polyethylene resin, the low-density polyethylene resin is contained by a larger amount than the high-density polyethylene resin, and the third polyethylene layer 16 is constituted of low-density polyethylene resin, and also provided is a paper container for liquid using the laminate 1.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a laminate and a paper container for liquids using the laminate. [Background technology]

[0002] 2. Description of the Related Art Paper containers used for juice, alcoholic beverages, and the like include paper containers in which a polyethylene layer, an aluminum layer, and the like are laminated to a paper base material (see Patent Document 1).

[0003] Such paper containers are manufactured by heating and bonding (sealing) a vertical seal panel connected to a body panel made of a paper base material having thermoplastic resin laminated on both sides to the edge of the body panel, to form the cylindrical body of the paper container, and by bonding the upper and lower ends of the body panel together, the top and bottom are sealed to form the paper container (see Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-2196 A [Patent Document 2] JP 2018-172128 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the paper container described in Patent Document 2, the upper ends of the body panels are bonded by hot air sealing an outer top seal panel provided at the upper ends of a pair of gable roof forming panels and an inner top seal panel provided at the upper ends of a pair of gable wall forming panels. However, when the thermoplastic resin flows due to heating, there are thin parts in the thermoplastic resin layer in the sealed part, or the thermoplastic resin layer becomes partially discontinuous, and so-called pinholes may occur, where the contents penetrate into these parts. It is preferable that pinholes do not occur, as they can lead to leakage of the contents.

[0006] The present invention has been made in consideration of the above circumstances, and aims to provide a laminate that has sufficient sealing properties between the laminates and can prevent the occurrence of pinholes, and a paper container for liquid using the same. [Means for solving the problem]

[0007] The present invention has been made to solve the above problems, and it has been found that the problems of the present invention can be solved by using a specific resin as the resin constituting the second polyethylene layer and the third polyethylene layer provided on the other side of the paper base layer, and the present invention has been completed based on this finding. The gist of the present invention is as follows.

[0008] [1] A laminate having a first polyethylene layer on one side of a paper base layer, a second polyethylene layer on the other side, and a third polyethylene layer on the second polyethylene layer, wherein the second polyethylene layer is composed of a mixed resin of high density polyethylene resin and low density polyethylene resin, the low density polyethylene resin being contained in greater amounts than the high density polyethylene resin, and the third polyethylene layer is composed of a low density polyethylene resin. [2] The laminate described in [1], wherein the second polyethylene layer and the third polyethylene layer have heat sealability. [3] The laminate described in [1] or [2], wherein at least one of the first polyethylene layer, the second polyethylene layer, and the third polyethylene layer contains biomass low-density polyethylene and has a biomass degree of 70% or more. [4] The basis weight of the paper constituting the paper base layer is 200 to 400 g / m 2 The laminate according to any one of [1] to [3], [5] A paper container for liquids, comprising the laminate according to any one of [1] to [4]. Effect of the Invention

[0009] According to the present invention, it is possible to provide a laminate in which the laminates have sufficient sealing properties and the occurrence of pinholes is suppressed, and a paper container for liquids using the same. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a conceptual diagram showing a laminate of the present invention. [Diagram 2] FIG. 2 is a conceptual diagram showing another example of the laminate of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The laminate and liquid-storing paper container according to the present invention will be described below with reference to the accompanying drawings. Fig. 1 is a conceptual diagram showing the laminate of the present invention.

[0012] [Laminate] The laminate 1 of the present invention has a first polyethylene layer 12 on one side of a paper base layer 10, a second polyethylene layer 14 on the other side, and a third polyethylene layer 16 on the second polyethylene layer 14. The third polyethylene layer 16 side of the laminate 1 of the present invention becomes the inner surface side of a paper container for liquids or a packaged product, and the first polyethylene layer 12 side becomes the surface side.

[0013] <Paper base layer> The paper base material constituting the paper base material layer 10 is not particularly limited as long as it does not impair the effects of the present invention, and any known paper base material used for liquid paper containers and packaging products can be used. Specifically, the paper may be made from pulp or recycled pulp and may be any of the following: acidic paper made at a papermaking pH in the acidic range; pseudo-neutral paper made at a papermaking pH in the pseudo-neutral range; neutral paper made at a papermaking pH in the neutral range; and alkaline paper made at a papermaking pH in the alkaline range.

[0014] The basis weight of the paper base material is 200 to 400 g / m 2 The basis weight is preferably in the range of 200 g / m 2If the stiffness is more than 400 g / m, the stiffness is sufficient and there is no risk of molding defects. 2 If the paper base material is less than 250 g / m2, the stiffness is not too high and molding is easy. 2 More preferably, the range is 280 to 320 g / m 2 It is more preferable that the range is .

[0015] <First polyethylene layer> The laminate 1 of the present invention has a first polyethylene layer 12 on one surface (front side) of a paper base layer 10. The first polyethylene layer 12 may be polyethylene derived from fossil fuels, polyethylene derived from biomass, or a mixture of these.

[0016] In the production of biomass-derived ethylene, it is preferable to use biomass-derived fermented ethanol obtained from a plant raw material as a raw material. Examples of plant raw materials include, but are not limited to, corn, sugarcane, and beet. In addition, the method for polymerizing a monomer containing biomass-derived ethylene is not particularly limited, and can be carried out by a known method.

[0017] The polyethylene constituting the first polyethylene layer 12 preferably contains low density polyethylene (LDPE) with a biomass ratio of 70% or more. With a biomass ratio of 70% or more, the amount of fossil fuel used can be significantly reduced, and the environmental load can be reduced to fully meet the needs of global warming countermeasures and the creation of a recycling-oriented society. From the above viewpoints, the biomass ratio is more preferably 80% or more, even more preferably 90% or more, and may be 100%.

[0018] In addition, when there is an odor originating from the biomass, it is also preferable to incorporate a deodorant into the biomass polyethylene layer. Examples of the deodorant include porous substances, metal oxides, and chemically adsorbent substances having acidic or basic groups. The biomass content is only included in materials of biological origin. 14 It can be identified by measuring C.

[0019] The thickness of the first polyethylene layer 12 is preferably in the range of 10 to 30 μm. When the thickness of the first polyethylene layer 12 is 10 μm or more, the heat sealability is sufficient, and when it is 30 μm or less, the repulsion is not strong and molding is easy. From the above viewpoints, the thickness of the polyethylene layer is more preferably in the range of 15 to 25 μm, and further preferably in the range of 18 to 23 μm. The melt flow rate (hereinafter sometimes referred to as "MFR") of the first polyethylene layer 12 is preferably 0.8 to 10 g / 10 min. When the MFR is in this range, sufficient strength and good film formability can be obtained.

[0020] The method for forming the first polyethylene layer 12 is not particularly limited, but for example, a resin composition for forming the first polyethylene layer 12 can be prepared, and this resin composition can be extruded onto the paper base layer 10 to form the first polyethylene layer 12 by an extrusion lamination method.

[0021] <Second polyethylene layer> The laminate 1 of the present invention has a second polyethylene layer 14 on the opposite side of the paper base layer 10 to the first polyethylene layer 12. The resin forming the second polyethylene layer 14 is composed of a mixed resin of high density polyethylene resin (HDPE: High Density Polyethylene) and low density polyethylene resin. The content of the high density polyethylene resin and the low density polyethylene resin is higher than that of the high density polyethylene resin. If the second polyethylene layer 14 does not contain high density polyethylene, i.e., if it is made only of low density polyethylene, the low density polyethylene has a low melting point and flows when heated during heat sealing, so that the layer is not formed uniformly and pinholes are likely to occur. In addition, if the content of the high density polyethylene resin is high and the content of the low density polyethylene resin is lower than the content of the high density polyethylene resin, the adhesion to the paper base layer 10 will be poor. The ratio of high density polyethylene resin to low density polyethylene resin, LDPE / HDPE, is preferably 6 / 4 or more and 9.5 / 0.5 or less, and more preferably 7 / 3 or more and 9 / 1 or less.

[0022] The MFR of the second polyethylene layer 14 is preferably 0.5 to 9.0 g / 10 min. By setting the MFR within this range, the materials constituting the second polyethylene layer 14 can be well mixed, and the second polyethylene layer 14 can have sufficient strength.

[0023] The thickness of the second polyethylene layer 14 is preferably in the range of 10 μm to 30 μm. By setting the thickness of the second polyethylene layer 14 in the above range, curling of the laminate 1 can be suppressed, making it easier to manufacture the paper container for liquids. Furthermore, by setting the thickness to 10 μm or more, heat sealing properties can be improved. The thickness of the second polyethylene layer 14 is more preferably 15 μm to 25 μm.

[0024] The polyethylene constituting the second polyethylene layer 14 may be fossil-derived polyethylene, biomass-derived polyethylene, or a mixture thereof, similar to the first polyethylene layer 12. From the viewpoint of reducing the environmental load sufficient to meet the needs of global warming countermeasures and the establishment of a recycling-oriented society, the biomass ratio is preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more, and may be 100%.

[0025] <Third polyethylene layer> The laminate 1 of the present invention has a third polyethylene layer 16 on the second polyethylene layer 14. The third polyethylene layer 16 is composed of a low-density polyethylene resin.

[0026] The third polyethylene layer 16 preferably has an MFR of 0.8 to 10 g / 10 min. When the MFR is in this range, sufficient strength is obtained and good film formability is obtained.

[0027] The thickness of the third polyethylene layer 16 is preferably in the range of 5 μm to 25 μm. By setting the thickness of the third polyethylene layer 16 in the above range, sufficient heat sealability can be achieved and the repulsion is not strong, so that the liquid paper container can be easily formed. The thickness of the third polyethylene layer 16 is more preferably 10 μm to 20 μm.

[0028] The polyethylene constituting the third polyethylene layer 16 may be fossil-derived polyethylene, biomass-derived polyethylene, or a mixture thereof, similar to the first polyethylene layer 12 and the second polyethylene layer 14. From the viewpoint of reducing the environmental load sufficient to meet the needs of global warming countermeasures and the establishment of a recycling-oriented society, the biomass ratio is preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more, and may be 100%.

[0029] In addition, since a paper container for liquid is produced using the laminate 1 of the present invention, it is preferable that the second polyethylene layer 14 and the third polyethylene layer 16 have heat sealability. There are no particular limitations on the heat sealability, and for example, there are methods of heating and melting the polyethylene to seal it using the action of hot air, ultrasonic vibration, high-frequency induction, high-frequency dielectric, and laser light. Of these, hot air sealing is preferable because it is possible to stably melt and seal the polyethylene of the paper container for liquid in terms of the mechanism of the filling machine.

[0030] In addition, the method of forming the second polyethylene layer 14 and the third polyethylene layer 16 on the paper base layer 10 is not particularly limited, but for example, a resin composition forming the second polyethylene layer 14 and a resin composition forming the third polyethylene layer 16 are prepared, respectively, and the resin composition forming the second polyethylene layer 14 is extruded onto the paper base layer 10 to form the second polyethylene layer 14 by extrusion lamination. Thereafter, the resin composition forming the third polyethylene layer 16 is further extruded onto the second polyethylene layer 14, and the third polyethylene layer 16 is formed by extrusion lamination, thereby forming the second polyethylene layer 14 and the third polyethylene layer 16.

[0031] By forming the third polyethylene layer 16 by extrusion lamination, even if the third polyethylene layer 16 is made of a low-density polyethylene resin, as in this embodiment, the third polyethylene layer 16 can be easily formed.

[0032] As described above, the second polyethylene layer 14 and the third polyethylene layer 16 may be formed after the second polyethylene layer 14 is formed, or the second polyethylene layer 14 and the third polyethylene layer 16 may be formed simultaneously by laminating them by co-extrusion.

[0033] <Another embodiment> Fig. 2 is a conceptual diagram showing a laminate according to another embodiment of the present invention. The laminate 31 shown in Fig. 2 differs from the laminate 1 shown in Fig. 1 in that an adhesive layer 38 is provided between the paper base layer 10 and the second polyethylene layer 14. The configurations of the paper base layer 10, the first polyethylene layer 12, the second polyethylene layer 14, and the third polyethylene layer 16 are the same as those of the laminate 1 shown in Fig. 1, so they are denoted by the same reference numerals and their description will be omitted.

[0034] (adhesive layer) In the laminate 31 of the embodiment shown in Fig. 2, the second polyethylene layer 14 is formed on the paper base layer 10 via the adhesive layer 38. By providing the adhesive layer 38, the adhesion (adhesion) between the paper base layer 10 and the second polyethylene layer 14 can be improved. From the viewpoint of improving adhesion between the paper base layer 10 and the second polyethylene layer 14, it is preferable to use low-density polyethylene resin or linear low-density polyethylene resin (LLDPE: Linear Low Density Polyethylene) as the adhesive layer 38, and linear low-density polyethylene resin is particularly preferable.

[0035] The thickness of the adhesive layer 38 is preferably in the range of 1 to 30 μm. If the thickness of the adhesive layer 38 is 1 μm or more, the adhesion between the paper base layer 10 and the second polyethylene layer 14 is sufficient. On the other hand, if the thickness is 30 μm or less, the repulsion is not strong and molding is easy. From the above viewpoints, the thickness of the adhesive layer 16 is more preferably in the range of 3 to 20 μm, and even more preferably in the range of 5 to 15 μm.

[0036] The method for forming the second polyethylene layer 14 and the third polyethylene layer 16 of the laminate 31 of the embodiment shown in Fig. 2 is not particularly limited, but for example, a resin composition for forming the second polyethylene layer 14 and a resin composition for forming the third polyethylene layer 16 are prepared, and the resin compositions are extruded by co-extrusion to form a laminate film consisting of the second polyethylene layer 14 and the third polyethylene layer 16. By bonding this laminate film onto the paper base layer 10 provided with the adhesive layer 38, a laminate 31 in which the second polyethylene layer 14 and the third polyethylene layer 16 are formed on the paper base layer 10 can be formed. Alternatively, a film consisting of the second polyethylene layer 14 and a film consisting of the third polyethylene layer 16 can be manufactured, and the films can be heat sealed or joined together with an adhesive layer to form a laminated film, and then the laminated film can be joined to a paper base layer 10 having an adhesive layer 38 formed thereon to form the laminate 31.

[0037] In the laminates 1 and 31 of the present invention, the second polyethylene layer 14 on the inner side of the paper base layer 10 where the liquid contents are contained is made of a mixed resin of high-density polyethylene resin and low-density polyethylene resin, so that pinholes can be suppressed.Furthermore, the third polyethylene layer 16 is made of low-density polyethylene resin, so that the sealing properties can be maintained when the liquid paper container is manufactured.

[0038] [Liquid paper containers] The paper container for liquids of the present invention is formed by using the laminate of the present invention in accordance with a known forming process. For example, the manufacturing process of a paper container for liquids to hold liquid beverages such as milk or juice usually includes the steps of creating a base material, printing, creasing, punching (creating a blank), pasting, filling with contents, and sealing. The shape of the liquid paper container to be formed is not particularly limited, and the liquid paper container may be formed into any shape, such as a substantially conical shape, a cube, or a tetrahedron. Furthermore, by using biomass-derived polyethylene for the first polyethylene layer 12, the second polyethylene layer 14 and the third polyethylene layer 16, a paper container for liquid of the present invention can be obtained that reduces the environmental burden and is fully responsive to measures against global warming and the creation of a circular society. EXAMPLES

[0039] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0040] (Experimental Example 1) The resins used in Experimental Example 1 are shown in Table 1 below. The paper base layer used in Experimental Example 1 was NDP (Nippon Dynawave Packaging) base paper (basis weight: 313 g / m 2A paper base layer (1,181 mm wide x 4,000 m) was used. A first polyethylene layer was formed on one side of this paper base layer by extrusion lamination. A second polyethylene layer was formed on the side of the paper base layer opposite the first polyethylene layer by extrusion lamination, and a laminate was produced by forming a third polyethylene layer on the second polyethylene layer by extrusion lamination. A liquid paper container was manufactured using the produced laminate. As the resins constituting the first polyethylene layer, the second polyethylene layer, and the third polyethylene layer, resin compositions were produced using the resins and compounding ratios shown in Table 2. Furthermore, each polyethylene layer was formed to have a film thickness (design value) shown in Table 2.

[0041] [Table 1]

[0042] [Table 2]

[0043] The laminate produced in Experimental Example 1 was evaluated by the following evaluation method. (Evaluation method) (1) Suitability for lamination Using the resins in Table 1, laminate samples were prepared as shown in Table 2. Table 3 shows the processing conditions when the second polyethylene layer and the third polyethylene layer were formed by extrusion lamination. Each polyethylene layer was formed by extruding from a 1195 mm wide T-die provided at the tip of the extruder using a single screw extruder at the forming speed and extrusion rotation speed shown in Table 3. The film thickness in Table 3 is the total film thickness of the second polyethylene layer and the third polyethylene layer, and in Comparative Example 1, it is the film thickness of the second polyethylene layer. The same applies to the lamination width. The lamination suitability of the second polyethylene layer and the third polyethylene layer was evaluated according to the following criteria. The processing conditions and results are shown in Table 3. ○: When the heat-sealed surface of the sample was peeled off, there was no problem with the adhesion between the base paper and the polyethylene layer (when the heat-sealed surface was peeled off from the paper other than the polyethylene interface, the so-called "paper peeling" state), and no other processing problems occurred. ×: The amount of resin discharged is reduced, and changes to conditions such as the rotation speed must be made to obtain the same film thickness; problems with processing such as the generation of oily smoke occur; or the adhesive strength of the sample is weak, and delamination occurs between the base paper and polyethylene layer when the heat seal surface is peeled off.

[0044] [Table 3]

[0045] (2) Sealing check The top and bottom heater temperatures during the manufacture of liquid paper containers were set at the temperatures shown in Table 4, and water-filled samples were prepared. Each paper container sealed at each temperature in Table 4 was cut at the center of the top and bottom, and the filled water was removed. 10 ml of colored penetrant liquid was poured into the cut top and bottom parts, left to stand for 1 minute, and the state of penetration into the paper layer was visually confirmed. The penetrant liquid used was 1% red dye (food coloring) and 1% dishwashing surfactant dissolved in 1 L of water. The evaluation criteria for pinholes, bleeding, and paper peeling are as follows. Pinhole The state in which the penetrant liquid penetrated into the paper base material and the penetrated portion was strongly colored was evaluated as the occurrence of pinholes. Bleeding The occurrence of bleeding was evaluated as occurring when the penetrating liquid spread from the pinhole to the surrounding area, and although the coloring was weaker than that of the pinhole, some coloring was visible around the pinhole, or when a pinhole could not be clearly seen but some coloring was visible. Paper peeling When the heat-sealed surface was peeled off, if it peeled off from the paper part other than the polyethylene interface, it was rated as "paper peeled off," and if it peeled off at the polyethylene interface of the sealed part, it was rated as not paper peeled off.

[0046] The results were evaluated according to the following criteria and are shown in Table 4. ○: No pinholes or bleeding, and the entire sticker surface has been peeled off △: No pinholes were clearly observed, but bleeding occurred. The paper was not peeled off partially from the seal surface. × Pinholes have occurred and the penetrating liquid has stained the paper layer, or the paper has not been peeled off completely from the sealing surface. The results are shown in Table 4.

[0047] [Table 4]

[0048] By making the second polyethylene layer from a mixed resin of high density polyethylene resin and low density polyethylene resin and increasing the ratio of high density polyethylene resin to low density polyethylene resin, it was possible to suppress the occurrence of pinholes. However, in Comparative Example 2, in which the ratio of high density polyethylene resin to low density polyethylene resin was the same, the adhesion between the paper base layer and the second polyethylene layer was not good. Furthermore, when the paper container for liquids is made, the third polyethylene layer on the inner surface side can be a low-density polyethylene layer, thereby improving the sealing properties when the paper container for liquids is manufactured. [Industrial Applicability]

[0049] INDUSTRIAL APPLICABILITY The present invention provides excellent adhesion between the layers of the laminate and can suppress the occurrence of pinholes, making it suitable for use in paper containers for liquids such as juices and alcoholic beverages. [Explanation of symbols]

[0050] 1, 31 Laminate 10 Paper base layer 12 First polyethylene layer 14 Second polyethylene layer 16 Third polyethylene layer 38 First adhesive layer

Claims

1. A laminate having a first polyethylene layer on one side of a paper base layer, a second polyethylene layer on the other side of the paper base layer, and a third polyethylene layer on the second polyethylene layer, the second polyethylene layer is composed of a mixed resin of a high-density polyethylene resin and a low-density polyethylene resin, and the low-density polyethylene resin is contained in a larger amount than the high-density polyethylene resin; The third polyethylene layer is composed of a low density polyethylene resin.

2. 2. The laminate of claim 1, wherein the second polyethylene layer and the third polyethylene layer are heat sealable.

3. 3. The laminate according to claim 1 or 2, wherein at least one of the first polyethylene layer, the second polyethylene layer, and the third polyethylene layer contains biomass low density polyethylene and has a biomass content of 70% or more.

4. The basis weight of the paper constituting the paper base layer is 200 to 400 g / m ２ The laminate according to claim 1 or 2,

5. A paper container for liquids, comprising the laminate according to claim 1 or 2.

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