Liquid paper container material and liquid paper container

Abstract

In order to obtain a material of a paper container for a liquid, and a paper container for a liquid, that are suitable for sealing a joining part through ultrasonic vibration sealing, there is provided a liquid paper container material in which: a thermoplastic resin layer (B layer) that has a polyethylene resin as a main component and serves as an outermost layer is laminated on the obverse surface of a paper substrate layer (A); and at least a thermoplastic resin layer (C layer) that has a polyethylene resin as a main component, a barrier layer (D layer), an adhesive resin layer (E layer), and a thermoplastic resin layer (F layer) that has a polyethylene resin as a main component and serves as an innermost layer are laminated on the reverse surface of the paper substrate layer (A layer) in the stated order from the reverse-surface side. The melt mass flow rate of the thermoplastic resin forming the thermoplastic resin layer (F layer) is higher than the melt mass flow rate of the adhesive resin forming the adhesive resin layer (E layer).

Description

Technical Field

[0001] The present invention relates to a liquid paper container material and a liquid paper container for packaging a liquid beverage with a sterile filling and packaging system.

Background Art

[0002] As a liquid paper container material used for gable-top liquid paper containers, brick-shaped liquid paper containers, etc. for packaging various liquid beverages such as milk, fruit juice beverages, green tea, alcoholic beverages, etc. with a sterile filling and packaging system, a thermoplastic resin layer mainly composed of a polyethylene resin as the outermost layer is laminated on the surface of a paper base material layer, and on the back surface of the paper base material layer, at least from the back surface side, a thermoplastic resin layer mainly composed of a polyethylene resin, a barrier layer, an adhesive resin layer, and a thermoplastic resin layer mainly composed of a polyethylene resin as the innermost layer are laminated in this order (see, for example, Patent Documents 1 and 2).

[0003] In the sealing of the joint part performed in the molding of the liquid paper container using the above liquid paper container material, the thermoplastic resin layer mainly composed of a polyethylene resin as the innermost layer becomes a sealant layer and is sealed. As a method of melting and sealing the innermost thermoplastic resin layer as the sealant layer, a high-frequency induction sealing method, a hot air sealing method, and an ultrasonic vibration sealing method are known. However, in the high-frequency induction sealing method, since a metal is used as a medium, it cannot be used when the barrier layer is other than aluminum because it cannot be heated. Also, in the hot air sealing method, it cannot be used in the usage environment. Therefore, the ultrasonic vibration sealing method, which can be used even when the barrier layer is other than aluminum and has no restrictions on the usage environment, is widely adopted.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the case of sealing by the ultrasonic vibration sealing method, since vibration is applied from the outside to melt the innermost layer by frictional heat, if the melting is insufficient due to restrictions on the melting time, etc., when there is a step at the joint, the step cannot be filled, and pinholes due to voids are likely to occur, and the sealing performance may be impaired. If the energy or pressure of ultrasonic vibration is increased to prevent such a situation, the adhesive resin layer adhered to the barrier layer may melt and flow out due to excessive heat generation, damaging the adhesion.

[0006] For this reason, in the sealing by the ultrasonic vibration sealing method, there has been a problem that it is difficult to ensure stable sealing conditions without pinholes. As a result of repeated test studies to solve such problems, the inventors of the present invention focused on the meltability of the thermoplastic resin layer mainly composed of polyethylene resin as the innermost layer, and completed the present invention.

[0007] An object of the present invention is to provide a liquid paper container material and a liquid paper container particularly suitable for sealing joints by the ultrasonic vibration sealing method.

Means for Solving the Problems

[0008] In order to achieve the above object, the invention according to claim 1 laminates a thermoplastic resin layer (B layer) mainly composed of polyethylene resin as the outermost layer on the surface of a paper base material layer (A), and on the back surface of the paper base material layer (A layer), at least from the back side, a thermoplastic resin layer (C layer) mainly composed of polyethylene resin, a barrier layer (D layer), an adhesive resin layer (E layer) mainly composed of polyethylene resin, and a thermoplastic resin layer (F layer) mainly composed of polyethylene resin as the innermost layer are laminated in this order. The thermoplastic resin forming the thermoplastic resin layer (F layer) has a melt mass flow rate higher than that of the adhesive resin forming the adhesive resin layer (E layer). <,> The melt mass flow rate of the adhesive resin forming the adhesive resin layer (E layer) is 6 g / 10 min to 9 g / 10 min, and the melt mass flow rate of the thermoplastic resin forming the thermoplastic resin layer (F layer) is 12 g / 10 min or more. It is characterized by this.

[0009] The invention according to claim 2 is a liquid paper container material in which a thermoplastic resin layer (layer B) mainly composed of a polyethylene resin as the outermost layer is laminated on the surface of a paper base material layer (A), and at least from the back side on the back surface of the paper base material layer (layer A), a thermoplastic resin layer (layer C) mainly composed of a polyethylene resin, a barrier layer (layer D), an adhesive resin layer (layer E) mainly composed of an ethylene-methacrylic acid copolymer resin, and a thermoplastic resin layer (layer F) mainly composed of a polyethylene resin as the innermost layer are laminated in this order, and the thermoplastic resin forming the thermoplastic resin layer (layer F) has a melt mass flow rate higher than that of the adhesive resin forming the adhesive resin layer (layer E). <,> The melt mass flow rate of the adhesive resin forming the adhesive resin layer (E layer) is 6 g / 10 min to 9 g / 10 min, and the melt mass flow rate of the thermoplastic resin forming the thermoplastic resin layer (F layer) is 12 g / 10 min or more. It is characterized by this.

[0012] Claim 3 The invention according to is a liquid paper container, characterized in that it is made using the liquid paper container material according to claim 1. Or 2 It is characterized by this.

Effect of the Invention

[0013] According to the invention of claim 1, a thermoplastic resin layer (layer B) mainly composed of a polyethylene resin as the outermost layer is laminated on the surface of a paper base material layer (A), and at least from the back side on the back surface of the paper base material layer (layer A), a thermoplastic resin layer (layer C) mainly composed of a polyethylene resin, a barrier layer (layer D), an adhesive resin layer (layer E) mainly composed of a polyethylene resin, and a thermoplastic resin layer (layer F) mainly composed of a polyethylene resin as the innermost layer are laminated in this order. Since the thermoplastic resin forming the thermoplastic resin layer (layer F) has a melt mass flow rate higher than that of the adhesive resin forming the adhesive resin layer (layer E), the thermoplastic resin layer (layer F) melts more easily than the adhesive resin layer or the thermoplastic resin layer (layer E). Thereby, even if the seal of the joint portion of the liquid paper container performed in the process of forming the liquid paper container is by an ultrasonic vibration sealing method, the thermoplastic resin layer (layer F) can be melted until it becomes sufficiently flowable before the adhesive resin layer (layer E) melts. is. And, since the melt mass flow rate of the adhesive resin forming the adhesive resin layer (E layer) is 6 g / 10 min to 9 g / 10 min, and the melt mass flow rate of the thermoplastic resin forming the thermoplastic resin layer (F layer) is 12 g / 10 min or more, in the sealing of the joint portion, before the adhesive resin layer (E layer) melts and flows out, the thermoplastic resin layer (F layer) will melt and flow out sufficiently, and without damaging the adhesion between the adhesive resin layer (E layer) and the barrier layer (D layer), a stable seal without pinholes can be ensured at the joint portion. Further, since the adhesive resin of the adhesive resin layer (E layer) is mainly composed of a polyethylene resin, it is suitable when the barrier layer (D layer) is a ceramic vapor deposition film other than a metal foil, an ethylene-vinyl alcohol copolymer (EVOH), a resin such as polyvinylidene chloride (PVDC), or nylon.

[0014] According to the invention described in claim 2, a thermoplastic resin layer (B layer) mainly composed of a polyethylene resin, which is the outermost layer, is laminated on the surface of the paper base material layer (A), and on the back surface of the paper base material layer (A layer), at least from the back surface side, a thermoplastic resin layer (C layer) mainly composed of a polyethylene resin, a barrier layer (D layer), an adhesive resin layer (E layer) mainly composed of an ethylene-methacrylic acid copolymer resin, and a thermoplastic resin layer (F layer) mainly composed of a polyethylene resin, which is the innermost layer, are laminated in this order. The thermoplastic resin forming the thermoplastic resin layer (F layer) has a melt mass flow rate higher than that of the adhesive resin forming the adhesive resin layer (E layer). Therefore, the thermoplastic resin layer (F layer) melts more easily than the adhesive resin layer or the thermoplastic resin layer (E layer). Thereby, even if the seal of the joint portion of the liquid paper container performed in the process of forming the liquid paper container is by an ultrasonic vibration sealing method, the thermoplastic resin layer (F layer) can be melted until it becomes sufficiently flowable before the adhesive resin layer (E layer) melts. is. And, since the melt mass flow rate of the adhesive resin forming the adhesive resin layer (E layer) is 6 g / 10 min to 9 g / 10 min, and the melt mass flow rate of the thermoplastic resin forming the thermoplastic resin layer (F layer) is 12 g / 10 min or more, in the sealing of the joint portion, before the adhesive resin layer (E layer) melts and flows out, the thermoplastic resin layer (F layer) will melt and flow out sufficiently, and without damaging the adhesion between the adhesive resin layer (E layer) and the barrier layer (D layer), a stable seal without pinholes can be ensured at the joint portion. Further, since the adhesive resin of the adhesive resin layer (E layer) is mainly composed of an ethylene-methacrylic acid copolymer resin, the ethylene-methacrylic acid copolymer resin has excellent adhesiveness to metals and is suitable when the barrier layer (D layer) is a metal foil such as an aluminum foil.

[0017] Claim 3 According to the invention described in, since the liquid paper container is formed using the liquid paper container material described in claim 1 Or 2 above, even if the seal of the joint portion is by an ultrasonic vibration sealing method, a liquid paper container without pinholes at the joint portion and securely sealed can be obtained.

Brief Description of the Drawings

[0018]

Figure 1

Modes for Carrying Out the Invention

[0019] Hereinafter, an example of an embodiment of a liquid paper container material according to the present invention and a liquid paper container using this liquid paper container material will be described in detail with reference to the drawings.

[0020] First, an example of an embodiment of the liquid paper container material according to the present invention will be described. FIG. 1 is an explanatory drawing showing an example of the laminated structure of the liquid paper container material according to the present invention. The liquid paper container material of this example has a thermoplastic resin layer (layer B) mainly composed of a polyethylene resin laminated on the surface of the paper base material layer (A), and on the back surface of the paper base material layer (layer A), at least from the back surface side, a thermoplastic resin layer (layer C) mainly composed of a polyethylene resin, a barrier layer (layer D), an adhesive resin layer (layer E), and a thermoplastic resin layer (layer F) mainly composed of a polyethylene resin as the innermost layer are laminated in this order.

[0021] The polyethylene resin used for the thermoplastic resin layer (layer B) mainly composed of a polyethylene resin laminated on the surface of the paper base material layer (layer A) and the thermoplastic resin layer (layer C) mainly composed of a polyethylene resin laminated on the back surface of the paper base material layer (layer A) is not particularly limited. For example, one or more polyethylenes selected from low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, and high-density polyethylene are used. Also, the thermoplastic resin layer (layer B) mainly composed of a polyethylene resin and the thermoplastic resin layer (layer C) mainly composed of a polyethylene resin can be composed only of a polyethylene resin, or other heat-sealable thermoplastic resins can be mixed. Examples of the thermoplastic resin to be mixed include, for example, polypropylene, modified poly Examples thereof include a re-ester and the like.

[0022] As the thermoplastic resin forming the thermoplastic resin layer (F layer), a thermoplastic resin having a melt mass flow rate higher than that of the adhesive resin forming the adhesive resin layer (E layer) is used.

[0023] The melt mass flow rate of the adhesive resin forming the adhesive resin layer (E layer) is preferably 6 g / 10 min to 9 g / 10 min, and the melt mass flow rate of the thermoplastic resin forming the thermoplastic resin layer (F layer) is preferably 12 g / 10 min or more. In this example, an adhesive resin having a melt mass flow rate of 8 g / 10 min is used as the adhesive resin forming the adhesive resin layer (E layer), and a thermoplastic resin having a melt mass flow rate of 15 g / 10 min is used as the thermoplastic resin forming the thermoplastic resin layer (F layer). The measurement of the melt mass flow rate is carried out in accordance with JIS-K7210, and the measurement temperature is 190°C.

[0024] The adhesive resin for forming the adhesive resin layer (E layer) is used to bond the barrier layer (D layer) and the thermoplastic resin layer (F layer), and a thermoplastic resin that melts by heat to generate adhesiveness is used. Examples of the adhesive resin include EAA (ethylene-acrylic acid copolymer resin), EMAA (ethylene-methacrylic acid copolymer resin), ionomer, EMA (ethylene-methyl acrylate copolymer resin), EMMA (ethylene-methyl methacrylate copolymer resin), and a type obtained by graft-polymerizing maleic anhydride onto polyethylene (specifically, Admer manufactured by Mitsui Chemicals, Inc.). Among these adhesive resins, a thermoplastic resin mainly composed of ethylene-methacrylic acid copolymer resin or ethylene-methacrylic acid copolymer resin has excellent adhesiveness to metal, and is particularly suitable as the adhesive resin used for the adhesive resin layer (E layer) when the barrier layer (D layer) is a metal foil such as aluminum foil. Also, a thermoplastic resin mainly composed of polyethylene resin is suitable as the adhesive resin used for the adhesive resin layer (E layer) when the barrier layer (D layer) is a ceramic vapor-deposited film, ethylene-vinyl alcohol copolymer (EVOH), polyvinylidene chloride (PVDC), nylon, or other resins other than metal foil.

[0025] The barrier layer (D layer) only needs to have oxygen barrier properties to prevent oxygen permeation, and is not particularly limited. For example, aluminum foil, ceramic vapor-deposited film, or ethylene-vinyl alcohol copolymer (EVOH) is used. In this example, aluminum foil is used as the barrier layer (D layer).

[0026] According to the liquid paper container material configured as described above, as the thermoplastic resin for forming the thermoplastic resin layer (F layer), a thermoplastic resin having a melt mass flow rate higher than that of the adhesive resin for forming the adhesive resin layer (E layer) is used. Therefore, the thermoplastic resin layer (F layer) melts more easily than the adhesive resin layer (E layer).

[0027] Thus, even if the seal of the joint of the liquid paper container performed in the process of forming the liquid paper container is by an ultrasonic vibration sealing method, the thermoplastic resin layer (F layer) can be melted until it becomes sufficiently flowable before the adhesive resin layer (E layer) melts, and thus even if there is a step at the joint of the liquid paper container, the step can be surely filled, and a stable seal without pinholes at the joint can be ensured.

[0028] Also, the melt mass flow rate of the adhesive resin forming the adhesive resin layer (E layer) is preferably 6 g / 10 min to 9 g / 10 min, and the melt mass flow rate of the thermoplastic resin forming the thermoplastic resin layer (F layer) is preferably 12 g / 10 min or more. By doing so, in the seal of the joint of the liquid paper container, the thermoplastic resin layer (F layer) will be sufficiently melted and flow out before the adhesive resin layer (E layer) melts and flows out, and a stable seal without pinholes at the joint can be ensured without damaging the adhesion between the adhesive resin layer (E layer) and the barrier layer (D layer).

[0029] In this example, aluminum foil is used as the barrier layer (D layer), but when a resin such as a ceramic vapor deposition film, ethylene vinyl alcohol copolymer (EVOH), polyvinylidene chloride (PVDC), or nylon other than metal is used as the barrier layer (D layer), the seal of the joint of the liquid paper container performed in the process of forming the liquid paper container can be sealed not only by the ultrasonic vibration sealing method but also by a high-frequency induction sealing method or a hot air sealing method.

[0030] Next, an example of an embodiment of a liquid paper container using the above liquid paper container material will be described. The liquid paper container according to the present invention is formed using the above liquid paper container material and is formed according to the forming process of a conventional aseptic filling and packaging system. The shape of the liquid paper container to be formed is not particularly limited, and there are liquid paper containers such as a gable top type and a brick type.

[0031] According to the liquid paper container formed using the above-described liquid paper container material, even if the seal of the joint of the liquid paper container is by an ultrasonic vibration sealing method, a liquid paper container without pinholes at the joint and securely sealed can be obtained.

Claims

1. A liquid paper container material in which a thermoplastic resin layer (layer B) mainly composed of a polyethylene resin as the outermost layer is laminated on the surface of a paper base material layer (A), and on the back surface of the paper base material layer (layer A), at least from the back surface side, a thermoplastic resin layer (layer C) mainly composed of a polyethylene resin, a barrier layer (layer D), an adhesive resin layer (layer E) mainly composed of a polyethylene resin, and a thermoplastic resin layer (layer F) mainly composed of a polyethylene resin as the innermost layer are laminated in this order. The thermoplastic resin forming the thermoplastic resin layer (layer F) has a melt mass flow rate higher than that of the adhesive resin forming the adhesive resin layer (layer E). The melt mass flow rate of the adhesive resin forming the adhesive resin layer (layer E) is 6 g / 10 min to 9 g / 10 min, and the melt mass flow rate of the thermoplastic resin forming the thermoplastic resin layer (layer F) is 12 g / 10 min or more.

2. A liquid paper container material in which a thermoplastic resin layer (layer B) mainly composed of a polyethylene resin as the outermost layer is laminated on the surface of a paper base material layer (A), and on the back surface of the paper base material layer (layer A), at least from the back surface side, a thermoplastic resin layer (layer C) mainly composed of a polyethylene resin, a barrier layer (layer D), an adhesive resin layer (layer E) mainly composed of an ethylene-methacrylic acid copolymer resin, and a thermoplastic resin layer (layer F) mainly composed of a polyethylene resin as the innermost layer are laminated in this order. The thermoplastic resin forming the thermoplastic resin layer (layer F) has a melt mass flow rate higher than that of the adhesive resin forming the adhesive resin layer (layer E). The melt mass flow rate of the adhesive resin forming the adhesive resin layer (layer E) is 6 g / 10 min to 9 g / 10 min, and the melt mass flow rate of the thermoplastic resin forming the thermoplastic resin layer (layer F) is 12 g / 10 min or more.

3. A liquid paper container characterized by using the liquid paper container material according to Claim 1 or 2.

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