JP2007030933A - Paper-made lid material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paper-made lid material which has consistent sealability through the heat seal with a flange part of a paper-made container, and can be unsealed without giving any damage to the flange part of the paper-made container when it is unsealed. <P>SOLUTION: In the paper-made lid material, a paper base material layer which is heat-sealed to a mouth edge part of a paper-made container to cover an opening part of the paper-made container, a thermoplastic resin intermediate layer and a sealant layer are laminated in this order. The sealant layer consists of a cohesive releasing layer consisting of a blend of a polybutene resin and a low-density polyethylene resin and laminated on the surface of the thermoplastic resin intermediate layer, and a heat-seal layer to be heat-sealed to the mouth edge part of the paper-made container. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a paper lid for a paper container, and more specifically, a lid for a paper container filled with dairy products such as yogurt, jelly, natto and other foods, while maintaining sealing properties. The present invention relates to a paper lid material having an easy-open property when the lid material is opened.

  In the food packaging field, a packaging form in which cups and trays are filled with yogurt, jelly, natto and the like has become the mainstream. These cups and trays are made of plastic containers such as polystyrene and polypropylene. However, recent environmental problems require resource saving, waste volume reduction, and recycling. Laminated paper cups and paper containers such as paper trays have been developed and used frequently.

  On the other hand, the base material layer constituting the cover material of the paper container includes paper, aluminum foil, plastic film, and the like. In particular, in the case of using paper as the base material layer, the paper container is used to maintain the shape of the container. It has been used as a material having a reinforcing action on the mouth edge (flange). For example, paper / aluminum foil (intermediate layer) / low density polyethylene (sealant layer), paper / polyester film (intermediate layer) / low density polyethylene (sealant layer), paper / nylon film (intermediate layer) / low Examples include laminated materials such as density polyethylene (sealant layer), paper / aluminum foil (intermediate layer) / low density polyethylene / hot melt (sealant layer). The intermediate layer prevents tearing of the paper lid material when the flange portion of the paper container and the heat-sealed paper lid material are opened.

  However, when these paper lid materials are used in a paper container whose inner surface is coated with a polyethylene layer, the intermediate layer is provided so that the paper lid material is not torn at the time of opening, but the opening strength is high. Strong, heat-sealed polyethylene on the paper container flange is peeled off with the paper lid when opened, and the paper container is exposed with fluffing on the flange (paper peeling phenomenon). There are things to do. When this phenomenon occurs, not only the appearance is damaged, but in the case of contents with a high moisture content, moisture is absorbed from the exposed flange part of the paper surface, and the rigidity of the paper container is reduced. However, there is a problem that the paper container is crushed and the contents are spilled, and a lid material that does not cause the paper peeling phenomenon has been desired.

  In order to meet the above demand, lid materials having various easy opening mechanisms have been studied. The easy-opening mechanism is roughly classified into three mechanisms of an interfacial peeling type, an interlayer peeling type, and an agglomerated peeling type, and each has been successful, but it is still insufficient. For example, as a cohesive peeling type, it consists of an aluminum foil / intervening resin layer / hot melt layer, and an interstitial resin layer made of polyolefin containing an unsaturated carboxylic acid or a derivative thereof. A lid material in which the resin layer on the surface is not peeled off is disclosed (for example, see Patent Document 1).

However, the lid material disclosed above has a poor heat resistance because the hot melt layer is used as a heat seal layer, and the problem of peeling between the lid material and the container body during transportation in the summer or during storage There is. Further, because of the cohesive peeling type, when the lid is opened, a part of the hot melt remains in the flange portion of the container, which is not fully satisfied by the user. In particular, when used in a container for dairy products, the hot melt layer is in direct contact with the contents, so there are restrictions on the use of the material of the container such as milk, which may be cumbersome such as an exception application.
JP-A-8-217147

  Therefore, the present invention has been made in view of the above problems, and has a stable sealing property by heat sealing with the flange portion of the paper container, and when the paper is opened, the flange portion of the paper container has a paper peeling phenomenon. The purpose of the present invention is to provide a paper lid material that can be opened without generation and that satisfies the Ministerial Ordinance Standards (such as Ministry of Health and Welfare Notification No. 52).

  In order to achieve the above object, the present invention according to claim 1 is a paper substrate layer, a thermoplastic resin, which covers an opening of a paper container and is heat-sealed to an edge of the paper container. A paper lid laminated in the order of an intermediate layer and a sealant layer, wherein the sealant layer is a cohesive release layer made of a blend of a polybutene resin and a low-density polyethylene resin laminated on the surface of the thermoplastic resin intermediate layer; and It consists of a heat-seal layer heat-sealed at the mouth edge of a paper container.

  Further, the present invention according to claim 2 is characterized in that, in the paper lid material according to claim 1, the weight of the paper base material layer is 51% or more with respect to the total weight of the paper lid material. To do.

  Further, in the present invention according to claim 3, in the paper lid material according to claim 1 or 2, the sealant layer comprising the agglomerated release layer and the heat seal layer is formed by a coextrusion lamination method. It is characterized by.

  Moreover, the present invention according to claim 4 is the paper lid material according to any one of claims 1 to 3, wherein the thickness of the cohesive release layer is 3 to 30 μm, and the thickness of the heat seal layer is 3 to 3. It is characterized by being 20 μm.

  Further, the present invention according to claim 5 is the paper lid material according to any one of claims 1 to 4, wherein a blend ratio of the polybutene resin and the low density polyethylene resin of the cohesive release layer is expressed by weight ratio. It is characterized by being 2/8 to 8/2.

  The invention according to claim 6 is characterized in that, in the paper lid material according to any one of claims 1 to 5, the heat seal layer is low-density polyethylene.

  The paper lid of the present invention is formed by laminating a paper base layer, a thermoplastic resin intermediate layer, and a sealant layer in this order, and the sealant layer is formed of a polybutene resin and a low-density polyethylene resin laminated on the surface of the thermoplastic resin intermediate layer. It consists of two layers: an agglomerated release layer made of a blend and a heat seal layer that is heat sealed to the edge of the paper container. The heat seal layer is welded to the flange of the paper container by heat sealing and has a sealing property. Retained. Further, at the time of opening, the cohesive failure of the cohesive release layer and the cutting of the heat seal layer occur, the heat seal layer remains in the flange portion of the paper container, and there is no occurrence of the paper peeling phenomenon of the flange portion, and an easy opening effect is achieved. Is.

  Furthermore, since the ratio of the paper base material layer in the paper lid material is 51% or more by weight, it is classified as paper by the Containers and Packaging Recycling Law and is easy to be discarded.

  Further, the sealant layer composed of the cohesive release layer and the heat seal layer is formed by a coextrusion lamination method, and the thickness ratio of the cohesive release layer and the heat seal layer can be arbitrarily selected, and the thickness of each layer is The film thickness can be reduced to 3 μm, and the thermoplastic resin intermediate layer is also subjected to hot melt extrusion lamination, whereby a paper lid material laminate can be produced in-line, and the paper lid material can be provided at low cost.

  In addition, when the thickness of the cohesive release layer is 3 to 30 μm, cohesive failure is likely to occur stably, and when the thickness of the heat seal layer is 3 to 20 μm, proper sealing strength with the paper container is obtained. And excellent sealing properties can be obtained.

  Further, by setting the blend ratio of the polybutene resin and the low-density polyethylene resin in the cohesive release layer to 2/8 to 8/2 by weight, uniform cohesive failure occurs, and stable opening strength can be obtained. is there.

  In addition, when the heat seal layer, which is the innermost layer of the paper cover material, is made of low-density polyethylene, when used as a cover material for paper containers whose inner surface is coated with polyethylene, ministerial ordinances such as material and sealing strength It has the effect of satisfying the standard and can be used for dairy products.

  The above-described present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing a laminated structure of a paper lid material according to the present invention. FIG. 2 is a schematic cross-sectional view showing a state when the paper lid material according to the present invention is opened.

  As shown in FIG. 1, the paper lid 1 according to the present invention comprises a laminate in which a paper base layer 2, a thermoplastic resin intermediate layer 3 and a sealant layer 4 are laminated in order, and the sealant layer 4 further comprises: The cohesive peeling layer 5 and the heat seal layer 6 are comprised, and the cohesive peeling layer 5 is laminated | stacked on the thermoplastic resin intermediate | middle layer 3. FIG. The heat seal layer 6 covers the opening of the paper container and is heat sealed to the flange of the paper container to seal the contents.

Hereinafter, each layer will be described in detail.
(Paper base layer)
The paper base material layer 2 is not particularly limited as long as it can provide strength as a lid, heat resistance, heat resistance at the time of heat sealing, and the like, such as cup base paper, coated ball, milk carton paper, cardboard, micro flute and the like. Cardboard with an amount of 100-500 g / m ² can be used. In addition, by selecting the basis weight so that the ratio of the paper base material layer 2 to the paper cover material 1 is 51% or more by weight, it is classified into paper by the Containers and Packaging Recycling Law and is easy to dispose. Become. In addition, the surface is provided with decoration, display of contents, display of the best-before period, and printing by the manufacturer and seller, etc., so that it has printability and is laminated with other substrates. It is desirable to have.

[Thermoplastic resin intermediate layer]
The thermoplastic resin intermediate layer 3 is laminated on the paper base material layer 2 to provide cushioning properties as the paper cover material 1 to prevent uneven sealing and to heat seal the paper cover material with the flange portion of the paper container. When opening 1, the paper base material layer 2 is prevented from being broken. For the thermoplastic resin intermediate layer 3, polyolefin resin such as low density polyethylene, medium density polyethylene, high density polyethylene and polypropylene, polyester resin, polyamide resin and the like can be used, and the thickness is preferably 15 to 30 μm. . Further, in the heat seal between the paper container and the paper cover material, in consideration of abnormal sealing conditions at high temperature and high pressure, a resin that does not have heat sealability with the paper container is preferable. Further, the thermoplastic resin intermediate layer 3 may be provided by hot-melt extrusion lamination on the paper base material layer 2. The thermoplastic resin intermediate layer 3 is made of a polyolefin film, a polyester film, or a polyamide (nylon) film previously formed on a film, sandwich lamination using polyethylene, dry lamination using a reactive adhesive, and an emulsion adhesive. You may provide using well-known lamination | stacking methods, such as wet lamination by. The film can be either stretched or unstretched. In addition, adhesion auxiliary means such as corona treatment and anchor coating can be applied to the surface of the paper base material layer 2 to be laminated with the thermoplastic resin layer 3 as necessary.

[Sealant layer]
The sealant layer 4 is composed of a cohesive release layer 5 and a heat seal layer 6. The agglomerated release layer 5 is made of a blend containing a polybutene resin and a low density polyethylene resin, and the blend ratio of the polybutene resin and the low density polyethylene resin is 2/8 to 8/2, more preferably 3/7 to 7/3. When the ratio of the polybutene resin is 20% or less, the cohesive peelability is lowered, the opening strength is increased when the paper lid 1 is opened, and a paper peeling phenomenon occurs in the flange portion of the paper container. Further, when the polybutene resin ratio is 80% or more, the adhesive strength between the cohesive release layer 5 and the heat seal layer 6 becomes weak, and the delamination between the cohesive peel layer 5 and the heat seal layer 6 occurs when the paper lid 1 is opened. Occurs, and the heat seal layer 6 remains in the flange portion and the opening portion of the paper container, and a phenomenon that the contents cannot be taken out occurs. Further, the film forming property is also unstable. The thickness is desirably 3 μm to 30 μm. On the other hand, the heat seal layer 6 is preferably a resin that can be heat-sealed with a resin that covers the inner surface of the paper container, and is usually made of a polyolefin resin such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and polypropylene, or a polyester resin. You can choose. The thickness is desirably 3 μm to 20 μm. If it is 3 μm or less, the heat sealability becomes unstable, and if it is 20 μm or more, the heat seal layer 6 is not cut at the time of opening (described later), the heat seal layer 6 remains in the flange portion and the opening of the paper container, and the contents can be taken out. No phenomenon occurs. The thicknesses of the cohesive release layer 5 and the heat seal layer 6 may be appropriately selected depending on the required opening strength of the paper lid 1 and the paper container. Moreover, the thickness of the cohesive peeling layer 5 and the heat seal layer 6 is a thin film, and the sealant layer 4 is preferably formed by a coextrusion lamination method from the viewpoint of film forming suitability by hot melt extrusion.

  Next, the peeling mechanism of the flange 11 of the paper container 10 and the heat-sealed paper lid 1 will be described with reference to FIG. FIG. 2 is a schematic cross-sectional view showing a state of opening the paper lid 1 according to the present invention, and an enlarged view of the opening start portion is shown in a circle. As shown in FIG. 2, when the knob 7 provided on the paper lid 1 is picked by hand and pulled upward, the heat seal layer 6 of the sealant layer 4 is formed at the peripheral edge of the flange 11 of the paper container 10. Cut and agglomerated and broken and part 5 ′ of the cohesive release layer 5 remains attached to the flange 11 of the paper container 10, and further, the heat seal layer 6 is cut at the peripheral edge of the opening of the paper container 10, The flange portion 11 of the paper container 10 can be opened without a paper peeling phenomenon. As the resin for the heat seal layer 6 of the paper lid 1, a resin that can be heat sealed with the heat seal layer 12 coated on the inner surface of the paper container 10 is selected.

  Next, the present invention will be described in more detail with reference to the following examples.

Describing with reference to FIG. 1, a base paper of 300 g / m ² (Fuji Paper Co., Ltd.) is used for the paper base layer 2, and low-density polyethylene (Mitsui Sumitomo Polyolefin Co., Ltd., trade name: Mirason 16P) is used on one side. ) Is melt-extruded and laminated at a thickness of 20 μm to form a thermoplastic resin intermediate layer 3, and a polybutene resin (trade name Toughmer BL manufactured by Mitsui Chemicals, Inc.) and a low-density polyethylene resin (Sumitomo Mitsui) are formed on the cohesive release layer 5. Polyolefin Co., Ltd., trade name Mirason 11P) blended at a ratio of 4/6, and heat seal layer 6 using low density polyethylene (Mitsui Sumitomo Polyolefin Co., Ltd., trade name Mirason 16P), Paper cover material made by coextrusion lamination with the thickness of the cohesive release layer 5 being 20 μm and the thickness of the heat seal layer 6 being 5 μm It was created. A flange portion 11 provided on the periphery of the opening of the paper container 10 having a PE 40 μm surface as an inner surface of a laminated structure of 5 μm low density polyethylene (hereinafter referred to as PE) / 300 g / m ² paper 40 μm. The sealing strength measurement and the unsealed state were evaluated using a sample sealed with heat sealing using a heat sealer under heat sealing conditions of a heat sealing temperature of 220 ° C., a pressure of 2 kg / cm ² and a time of 1 second. In addition, about heat seal temperature, it implemented at two levels, 140 degreeC and 160 degreeC. The evaluation method is shown below.
(1) Sealing strength A
A hole with a diameter of 0.5 cm is formed in the center of the side surface or bottom surface of the sealed paper container 10 for the sample to be tested, a nozzle for air supply is installed, the compressor is operated, the pressure is applied, and the paper lid 1 Was measured by a method according to Ordinance No. 52 of the Ministry of Health and Welfare when peeling from the flange portion 11 of the paper container 10.
(2) Sealing strength B
A hole with a diameter of 0.5 cm is formed in the center of the side surface or bottom surface of the sealed paper container 10 for the test sample, a nozzle for supplying air is mounted, the compressor is operated, and the pressure is increased to 13.3 kPa. It was measured by a method based on Ordinance No. 52 of the Ministry of Health and Welfare whether there was no breakage of the paper container packaging in the second or air leakage. The evaluation criteria are as follows.
○: No damage to paper containers and packaging and no air leakage.
X: Damage to the paper container or packaging occurs or air leakage occurs.
(3) Opened state Grasp the paper container 10 of the sample to be tested with one hand, pick the knob 7 of the paper lid 1 with the other hand, open the paper lid 1 while pulling it, and observe and evaluate the state did. The evaluation criteria are as follows.
◯: Peeled with the cohesive peeling layer 5, and the flange part 11 can be opened well without paper peeling.
X: Paper peeling occurs in the flange portion 11 and the flange portion 11 is damaged.

[Comparative Example 1]
Using a base paper of 300 g / m ² (Fuji Paper Co., Ltd.) for the paper base material layer 2, PE (trade name: Mirason 16P, manufactured by Sumitomo Mitsui Polyolefin Co., Ltd.) on one side was hot melt extruded and laminated at a thickness of 45 μm. Thus, a paper lid 1 was prepared. Thereafter, the same evaluation as in Example 1 was performed.

[Comparative Example 2]
Using a base paper of 300 g / m ² (Fuji Paper Co., Ltd.) for the paper base material layer 2, PE (trade name: Mirason 16P, manufactured by Sumitomo Mitsui Polyolefin Co., Ltd.) is hot melt extruded and laminated on one side with a thickness of 20 μm. Then, a thermoplastic resin intermediate layer 3 is formed, and a polybutene resin (Mitsui Chemical Co., Ltd., trade name Toughmer BL) and PE (Mitsui Sumitomo Polyolefin Co., Ltd., trade name Mirason 11P) are mixed in the cohesive release layer 5 at a ratio of 4 / Using the blend blended in No. 6, a paper lid 1 was prepared by hot melt extrusion lamination at a thickness of 25 μm. Thereafter, the same evaluation as in Example 1 was performed.

  As shown in Table 1, the evaluation results show that Example 1 is good in both sealing strength A and sealing strength B, and the unsealed state is peeled off by the cohesive peeling layer, and the flange portion 11 is not damaged. It was. In Comparative Example 1, the sealing strength was strong, but paper peeling occurred during opening. In Comparative Example 2, the paper was not peeled off, but the strength was weak and it did not satisfy the standards of the ministerial ordinance such as milk. By using PE for the heat seal layer 6, the paper lid material 1 of the present invention satisfies the standards of ministerial ordinances such as milk in terms of strength and container packaging material, and paper for yogurt, dairy products, jelly, etc. It can be used as a lid material.

It is a cross-sectional schematic diagram which shows the laminated structure of the paper lid | cover material concerning this invention. It is the cross-sectional schematic which shows the state at the time of opening of the paper lid | cover material concerning this invention. Aggregated release layer 5 Aggregated release layer Heat seal layer 6 Pick section 7 Paper container 10 Flange section 11 Heat seal layer 12

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Paper lid | cover material 2 Paper base material layer 3 Thermoplastic resin intermediate | middle layer 4 Sealant layer 5, 5 'Aggregation peeling layer 6, 12 Heat seal layer 7 Knob part 10 Paper container 11 Flange part

Claims (6)

A paper lid that covers an opening of a paper container and is laminated in the order of a paper base material layer, a thermoplastic resin intermediate layer, and a sealant layer that are heat-sealed to the rim of the paper container, the sealant layer Characterized in that it comprises a cohesive release layer made of a blend of a polybutene resin and a low density polyethylene resin laminated on the surface of the thermoplastic resin intermediate layer, and a heat seal layer heat sealed to the lip of a paper container. Paper cover material. The paper lid material according to claim 1, wherein the weight of the paper base material layer is 51% or more with respect to the total weight of the paper lid material. The paper lid material according to claim 1 or 2, wherein the sealant layer comprising the agglomerated release layer and the heat seal layer is formed by a coextrusion lamination method. The paper lid material according to any one of claims 1 to 3, wherein the thickness of the cohesive release layer is 3 to 30 µm, and the thickness of the heat seal layer is 3 to 20 µm. The paper lid according to any one of claims 1 to 4, wherein a blend ratio of the polybutene resin and the low-density polyethylene resin in the agglomerated release layer is 2/8 to 8/2 by weight. Wood. The paper lid material according to any one of claims 1 to 5, wherein the heat seal layer is low-density polyethylene.

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