JP2001122319A - Lid material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lid material including a sheet of paper for sealing a packaging container whose flange is made of a polyethylene with a heat seal wherein the lid material is free from curls and has preservability for contents, a metal sensor for sensing a metal piece which accidentally mixes into the container during a filling process can be used, a package using the lid material not only can be heated and cooked in a microwave oven but also the lid material can be easily peeled by cohesive failure of a hot melt layer when unsealing the container, and the lid material is plastic-deformable to keep it in a folded shape. SOLUTION: The lid material 10 comprises a laminate wherein a polyethylene layer 2 formed of a low density polyethylene by means of melt extrusion coating on one of surfaces of a base material 1 containing at least paper, an adhesive adjust layer 3 comprising an olefin-based copolymer with a thickness of 1 to 15 μm containing ethylene and a carboxyl radical and a hot melt layer 5 are laminated in this sequence.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a paper container in which polyethylene is laminated on a base material containing paper, and a laminate containing paper as a base material and containing no aluminum foil as a component is a heat sealant layer. The present invention relates to a lid material having easy-openability due to cohesive failure between certain hot melt layers. Then, the lid material to be supplied to the filling machine is curled, or the container is heat-sealed (hereinafter, referred to as HS) by excessive temperature or pressure, and can maintain the state when the lid material is opened from the container. It belongs to the container lid material with deformation.

[0002]

2. Description of the Related Art Conventionally, for example, cup-shaped containers molded into a predetermined shape are used for various solid or liquid foods, dessert foods such as yogurt, pudding, jelly, and liquid substances such as fruit juice, coffee, cocoa, milk drinks, and the like. Beverage containers, or packaging containers that also serve as dishes for solid foods such as instant noodles and snack foods.

[0003] For products sold in cup-shaped containers, after filling the contents into the container (cup), the hot melt layer side of the lid material and the polyethylene layer side of the container are sealed with HS to distribute, store and sell. Thereafter, the end consumer opens the HS portion from the container with the lid material sealed, and is used for eating and drinking. And the combination and configuration of the cup container and the lid material are suitable for the filling machine and the physical content required for storage and distribution,
In addition to chemical properties, convenience is taken into consideration so that customers consuming products at the end can easily handle them. In addition, molded containers such as cup containers that are excellent in maintaining the shape of the contents are proof of moisture, oxygen, light, and moisture, to prevent oxidation of the oil in the contents and chemical changes such as reduction in flavor and extend the storage period. It is made of a material considering various barrier properties such as flavor.

Conventionally, in order to obtain the above-mentioned various barrier properties, most of the physical properties have been satisfied by forming a metal aluminum foil on a container or a cover thereof. The aluminum foil must have a thickness of 15 μm or more in order to minimize the curling of the lid material and maintain the plastic deformation state of the lid material formed when the aluminum foil is opened. Thick ones were used. For example, the basic configuration of the lid material was a laminate composed of paper, aluminum foil, and a hot melt layer. However, a package sealed with a lid containing metal aluminum foil cannot be heated and cooked using a microwave oven, and detects a metal piece erroneously mixed into a container during a filling process. There is a problem that a metal detector cannot be used.
In addition, when a relatively thick aluminum foil is formed, even if the lid material is incinerated and incinerated, there is still a lot of ash, so not only is it difficult to dispose of it, but also resources including the power required for refining aluminum. There was a problem of waste.

[0005] The innermost layer of a cup container mainly made of paper is provided with a polyethylene layer having moisture resistance and HS property. The lid member is composed of a base sheet and a laminate having at least one HS layer on one surface thereof. The HS layer of the lid material is generally made of an easily-openable material that can be easily opened, for example, a hot-melt layer coated and formed with a hot-melt agent that can be peeled off by cohesive failure. The hot-melt layer is a thermoplastic polyethylene resin layer with a soft cushioning effect between the paper and the hot-melt layer for the purpose of stabilizing the close contact with the container and preventing the paper from being damaged during peeling. And complete ethylene by providing an ethylene / vinyl acetate copolymer. However, since the sealing of the lid material in the filling process is performed completely, the heat and pressure tend to be increased. The hot melt melted by the heat and pressure is extruded to the end of the flange of the container, and the polyethylene or ethylene-vinyl acetate copolymer of the lid material and the H
In some cases, the polyethylene of the flange forming the S portion is directly HS-bonded to form a strong HS portion. In such a case, when the lid is opened, it is not the cohesive failure of the hot melt layer, but the paper is torn due to the delamination of the paper and remains in the flange part and cannot be opened, or the lid cannot be peeled and the lid is torn. There was a problem of doing.

[0006]

SUMMARY OF THE INVENTION In a lid material containing at least paper for sheet supply, which seals a packaging container in which a flange of an HS portion is made of polyethylene with HS, there is no curling, the content is preserved, and a microwave oven is used. Can be used for heating and cooking, and not only can a metal detector be used to detect and remove metal pieces accidentally mixed into the container during the filling process, but also the aggregation of the hot melt layer when opening the container An object of the present invention is to provide a lid material that can be easily peeled off by breaking and has plastic deformation that can maintain the shape of the peeled lid material in a bent state.

[0007]

In order to solve the above-mentioned problems, according to the present invention, a polyethylene layer, an adhesion adjusting layer, and a hot-melt layer are formed on at least one side of a substrate containing paper in the order of layers. In the laminate, the adhesion adjusting layer is a lid material having a thickness of 1 to 15 μm and made of an olefin copolymer containing ethylene and a carboxyl group. Further, the above-mentioned polyethylene layer is a lid member having a thickness of 10 to 20 μm formed by melt extrusion coating of low density polyethylene.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a lid material according to the present invention comprises a polyethylene layer 2, an adhesion adjusting layer 3, and a hot melt layer 5 on at least one side of a base material 1 containing paper. The adhesion adjusting layer 3 is a lid member 10 made of an olefin-based copolymer containing ethylene and a carboxyl group and having a thickness of 1 to 15 μm. Further, the above-mentioned polyethylene layer 2 is a lid member 10 formed to have a thickness of 10 to 20 μm by melt extrusion coating of low density polyethylene.

As shown in FIG. 2, the lid material of the present invention
To a paper 11 containing a coated paper and / or a plastic film 4 by vapor deposition 7 of an inorganic compound, a barrier film 47 provided with a barrier agent by coating, or a stretched or non-stretched monolayer having a water vapor or gas barrier property. A layer or a multilayer film can be used as a component.

The paper used in the present invention provides rigidity to the cover material and serves as a printing substrate. Cellulose-based paper has little dimensional change due to moisture absorption and dehumidification, has whiteness that conceals the contents, and is suitable for printing on the surface or laminating on the reverse side (excellent transfer of printing ink, polyethylene layer, etc.). , And uniform adhesiveness of the adhesive during dry lamination with other film paper). And, if it has mechanical suitability such as tear strength and tensile strength and uniform thickness, and does not contain harmful heavy metals, fluorescent dyes, chlorine compounds that are environmental pollution sources, etc. required for food container materials, it is particularly suitable Is not limited. For example,
There are single gloss kraft paper, bleached kraft paper, imitation paper, and single-sided or double-sided coated paper. Then, in order to provide white hiding properties, white or extender pigments such as titanium oxide, calcium carbonate, zinc oxide, etc. may be formed into paper, or coated paper using a coating material containing these pigments may be used. The basis weight of the ^{paper, 30g / m 2 ~150g / m} 2, depending on specific applications can be used in thicker as about 350 g / m ^2.

The above-mentioned paper can be laminated with one or two layers of stretched or non-stretched plastic film to impart strength to the paper or various barrier properties. These plastics include polyethylene terephthalate, polybutylene terephthalate, 6 nylon, 6,6
Nylon, polystyrene, polystyrene, polypropylene and the like. In particular, a stretched polystyrene film is preferable as a material that can maintain plasticity when laminated with the above-described paper. A film in which silicon oxide, aluminum oxide, or the like is provided on a stretched polystyrene film by vapor deposition is a preferable material as a barrier film for water vapor or oxygen gas.

The deposited film of the inorganic oxide is provided for imparting moisture resistance to the cover material, and may be appropriately selected from silicon oxide, aluminum oxide, indium oxide, tin oxide, zirconium oxide and the like. it can. The inorganic oxide deposited film is formed by a vacuum deposition method such as an ion beam method or an electron beam method, a sputtering method, or a plasma chemical vapor deposition method (CVD) of a material containing an organic material as a raw material.
Method) or any other method.

The thickness of the deposited film of the inorganic oxide required for the present invention is preferably from 100 to 2000 °, so that a moisture permeability of 3 g / m ² · 24 hrs or less can be achieved. If the thickness of the inorganic oxide exceeds 2000 °, especially 3000 °, depending on the rigidity and thickness of the film to be deposited, there is a risk that cracks may occur in the deposited film of the inorganic oxide to deteriorate the moisture permeability, and the deposition time is long. This is unfavorable from the viewpoint that the processing cost and the material cost are increased and resource saving is required. The thickness of the inorganic oxide is 200 ° or less, further 100 μm
When it is less than m, it is difficult to stably exhibit a desired moisture-proof effect, which is not preferable. Further, by making the adhesion between the inorganic oxide deposited film and the biaxially stretched plastic film as strong as possible, a stable moisture-proof effect can be obtained. For this purpose, it is preferable to perform a corona discharge treatment, a primer treatment, or both treatments on the film to be deposited.

The lamination of the paper and the vapor-deposited film is performed, as a general rule, such that the vapor-deposited film applied to the biaxially stretched film is opposed to the paper. By doing so, the relatively brittle vapor deposited film does not come into direct contact with the outside in the post-process of providing the adhesion adjustment layer, so that the vapor deposited film is not damaged and the initial barrier property can be maintained. it can. Lamination of paper and barrier film can be performed by conventional wet lamination, dry lamination using a curable adhesive (lacquer lamination, in which the components of the adhesive are dissolved in a solvent, and an adhesive containing no volatile components). Non-solami laminating), wax lamination using a hot-melt adhesive layer as an adhesive layer, a kind of dry lamination using an adhesive as an adhesive layer, and adhesion of thermoplastic resin such as melt-extruded polyethylene. There is sandwich lamination as a resin layer.

When the base material of the lid material of the present invention is a laminate of paper and plastic, a water retention layer is provided on the side of the paper opposite to the plastic film in order to prevent curling of the laminate. Is preferred. That is, the water retention layer for preventing curling is provided by applying water or a resin dissolved in water and alcohol on the opposite side of the base material from the plastic film. The water-soluble resin used for the water retention layer includes starch, polyvinyl alcohol, ammonium salt of polyacrylic acid or polymethacrylic acid, polyethyleneimine, melamine, methylcellulose, ethylcellulose or glycerin fatty acid ester, sorbitan fatty acid ester, sucrose fatty acid ester, Examples include pentaerythritol fatty acid esters, trimethylolpropane fatty acid esters, and polyoxyethylene glycerin fatty acid esters.

The water-retaining layer is formed by diluting one or three or more kinds of the above-mentioned resins into water, or a coating solution obtained by diluting water and alcohol (methanol, ethanol, isopropyl alcohol) in the opposite direction to the hot melt layer of paper. It is applied to the surface. And the thickness of the coating is 1/10 to 8 /
It is preferable to form a portion that does not contain a coating liquid so as to be 10. When the paper coated in this way is dried, the coated surface of the paper shrinks, causing curling of the coated surface. On the other hand, when a polyethylene layer, an adhesion control layer of an olefin copolymer composed of ethylene and a carboxyl group, and a hot melt layer are applied and formed on the side opposite to the water retention layer of the paper, the adhesion control layer and the hot melt layer are formed. The shrinkage that occurs when the melt layer cools and solidifies generates a curling force that makes the hot melt layer side concave. As described above, the curling force of the water retaining layer side of the paper and the curling force of the concave side of the hot melt layer of the paper are offset, and as a result, the lid material that is a laminate is flat without curling. It constitutes a lid material.

[0017] The polyethylene layer of the present invention has a function of a cushioning material for completely forming a close contact between the lid member and the container to prevent a gap such as liquid leakage, and a paper surface for preventing the paper from peeling when the lid member is peeled off. It has a function as a reinforcing layer. As a simple cushion layer, a polyethylene layer can be formed by dry lamination of an existing polyethylene film or sandwich lamination provided with an adhesive resin layer such as molten polyethylene. The polyethylene layer
It is preferable that the non-stretched low-density polyethylene having a thickness of 10 to 25 μm is directly melt-extruded on paper and quenched and formed by coating. As a result, polyethylene
Compared to a single film formed of a 25 μm thin film, a laminate having less shrinkage after film formation and less curling can be formed.
The polyethylene layer may be applied to the substrate provided with the pattern on the side opposite to the pattern, or the pattern and the water retention layer may be printed on the side opposite to the polyethylene layer of the substrate provided with the polyethylene layer. Either method, such as providing, can be adopted.

The adhesion adjusting layer has an effect of uniformizing the adhesion between the two by the cushion effect when the lid material is pressed against the container, similarly to the above-mentioned polyethylene layer. Also, the action of preventing the hot melt layer of the lid material from being eluted by overheating and making the HS portion formed by direct contact between the polyethylene, which is the HS portion of the container flange, and the polyethylene layer become strong. It has something. Further, it is preferable that the adhesive strength between the adhesion adjusting layer and the hot melt layer is higher than the cohesive failure strength of the hot melt layer and higher than the HS strength between the polyethylene of the container and the adhesion adjusting layer. As a material for adjusting the HS strength of polyethylene having such an effect, 70 to 95 mol% ethylene, 30 to 5 mol% ethylene,
Olefin-based copolymers containing mol% of carboxyl groups can be preferably used. For example, there are ethylene / vinyl acetate copolymer, ethylene / acrylic acid copolymer, ethylene / methacrylic acid copolymer, ethylene / acrylic ester copolymer, ethylene / methacrylic ester copolymer, ionomer, etc. .

The above-mentioned olefin copolymer can be formed by melt-extrusion coating or coating a copolymer dispersion on the polyethylene layer of the lid material as shown in FIG. 1 or FIG. And in order to stabilize the adhesion between the adhesion adjustment layer and the polyethylene more firmly,
It is preferable that the polyethylene layer is a surface subjected to corona discharge treatment. The corona discharge treatment may be performed immediately after the polyethylene layer is melt-extruded and coated, or immediately before the adhesion adjusting layer is applied. And the thickness of the adhesion adjusting layer is 1
When the thickness is 1 μm or less, a film as an adhesion adjustment layer cannot be formed stably. When the thickness is 15 μm or more, it causes curling, impairs plasticity, which is a feature of the present invention, or is expensive. Wasted.

The hot melt layer of the present invention is constituted by a hot melt which is easily peelable by cohesive failure. The hot melt contains 30 to 50% by weight of an ethylene / vinyl acetate copolymer containing 10 to 40% by weight of normal vinyl acetate, and 30 to 40% by weight of wax or microcrystalline wax.
And 15 to 30% by weight of a tackifier as a main component, and if necessary, a lubricant, an antiblocking agent, a plasticizer,
It is constituted by appropriately adding a filler, an antioxidant and the like. Examples of the tackifier include hydrogenated rosin or its ester with glycerin, pentaerythritol, and trimethylolpropane (ester gum), and cumarone indene.
Select from among styrene resins. Preference is given to thermally stabilized hydrogenated rosin or its esters with glycerin and pentaerythritol. The hot melt layer extrudes and heat-melts the material,
Coating is formed by roll coating or gravure coating. The extrusion coating method is suitable for high-viscosity materials, but the gravure coating method can form a hot melt layer with a stable coating amount.
In addition, when the melt viscosity of the above hot melt is high, and application is difficult at 80 ° to 150 ° C., which is the applicable range of a normal hot melt coater, a hot solvent is applied by adding a volatile solvent and heating and melting. Lacquer can also be used. The coating amount is 10 to 40 g / m ² , preferably 25 to 30 g / m ² .
m ² .

As shown in FIG. 2, the lamination of the paper and the vapor-deposited barrier film is performed by providing an adhesive 6 on the vapor-deposited 7 of the barrier film 47 which is a non-absorbing film and dry laminating the paper 11 with the paper. The base material 1 is prepared by providing a primer layer on a non-absorbing film and sandwiching and laminating a thermoplastic resin as an adhesive resin layer.

The dry lamination adhesive layer may be a lacquer type adhesive obtained by dissolving ordinary polyester / polyisocyanate, polyether / polyisocyanate, polyester, or epoxy adhesive in a solvent, or a so-called non-sol type adhesive containing no solvent. The agent is coated with ² to 10 g / m ² (a coating amount when dried, hereinafter similarly described) on a vapor-deposited film and laminated. The dry lamination method is a preferred method in which the temperature at which the deposited film is applied is lower than that of the sandwich lamination, and curling promoted by shrinkage of the adhesive resin layer formed by melt extrusion coating is small.

The primer layer of the film used for sandwich lamination is subjected to a primer treatment by providing a solution of polyethyleneimine, polybutadiene, an organotitanium compound, isocyanate, polyurethane or the like at a coating amount of 0.1 to ² g / m ² . Further, the film used for lamination may be subjected to corona discharge treatment, or the adhesive resin to be extrusion-coated may be subjected to ozone treatment to strengthen the bond between the paper, the adhesive resin, and the barrier film.

Hereinafter, the present invention will be described in more detail with reference to examples. (Example 1) As shown in FIG. 1, one side of a double-side coated paper (basis weight 100 g / m ² : base material 1) had a thickness of 20 μm
Was melt-extruded and coated to form a polyethylene layer 2. Next, a predetermined pattern 8 was provided by gravure rotary printing on the surface of the substrate 1 on which the polyethylene layer 2 was not formed. Then, 3 g / m ² of the dispersion of the ethylene / vinyl acetate copolymer was applied to the polyethylene layer.
After coating and drying, an adhesion adjusting layer 3 was provided. Next, the above-mentioned adhesion adjusting layer 3 is made of ethylene containing 20% by weight of vinyl acetate.
A vinyl acetate copolymer and a hot melt agent containing rosin pentaerythritol and microcrystalline wax as main components are melt-gravure coated at 30 g / m ^2.
Example 1 of the present invention by coating and forming a hot melt layer 5
Was prepared.

Example 2 A polyethylene layer 2 was provided on a substrate 1 in the same manner as in Example 1, and then a predetermined pattern was formed on the surface of the substrate 1 on which the polyethylene layer 2 was not formed as shown in FIG. 8 and an overprint 9 consisting of a varnish dissolved in alcohol containing polyethyleneimine,
m was applied to the entire surface by gravure rotary printing. Then, a dispersion of an ethylene / methacrylic acid copolymer was applied to the polyethylene layer 2 at 3 g / m ² and dried to provide an adhesion adjusting layer 3. Next, the same hot melt agent as in Example 1 was applied to the adhesion adjusting layer 3 by a melt gravure coating at a rate of 30 g / m ² to form a hot melt layer 5.
Was formed, and the lid member 10 of Example 2 of the present invention was formed.

Comparative Example 1 A lid material of Comparative Example 1 was prepared in the same manner as in Example 1 except that the hot melt layer was formed directly on the surface on which the polyethylene layer was provided with a thickness of 25 μm. .

(Evaluation Results) Each of the lids of Examples 1 and 2 and Comparative Example 1 was punched out in the shape of a lid of a container having a circular shape with a diameter of 100 mm and a knob piece provided on a part of the outer periphery, and a single-sheet lid. Table 1 shows the results of preparing the materials and evaluating the properties. Curling: Twenty samples of each sample were sampled and placed one by one on a horizontal glass plate with the paper side of the lid facing upward, and the highest curling portion was measured.・ Easy opening: Each sample was pressed with a ring sealer on the flange of a paper cup (container) in which low-density polyethylene having a thickness of 20 μm was laminated on the inner surface, at a pressure of 2 kg / m ² and an HS time of 1
HS for 10 seconds each at 140 ° C and 160 ° C for seconds,
After a lapse of 24 hours, the lid material was peeled off, and the peeling strength and the state of the peeled portion were evaluated.

[0028]

[Table 1]

[0029]

According to the present invention, a polyethylene layer 2 formed by melt-extrusion coating of low-density polyethylene on a base material containing paper, and an adhesion adjusting layer 3 made of ethylene and an olefin-based copolymer containing a carboxyl group having a thickness of 1 to 15 μm. , And a lid member made of a laminate composed of the hot melt layer 5,
There is no curling and aluminum foil is not a constituent element. Therefore, heat the package in a microwave
In addition to being able to cook, metal mixed in as a foreign substance can be removed using a detector. Then, when the lid material is opened from the container, the hot melt layer can be stably peeled easily due to cohesive failure of the hot melt layer, and the peeled lid material has an effect of plastic deformation that can maintain the folded state as it is.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a cross section of a basic configuration of the present invention.

FIG. 2 is a schematic sectional view showing another configuration of the present invention.

FIG. 3 is a schematic cross-sectional view for explaining the configuration of the embodiment.

[Description of Signs] 1 Base material 2 Polyethylene layer 3 Adhesion adjustment layer 4 Film 5 Hot melt layer 6 Adhesive 7 Deposition 8 Picture 9 Overprint 10 Lid 11 Paper 47 Barrier film

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B29K 23:00 B29K 23:00 F term (Reference) 3E067 AA03 AA04 AB16 AB26 BA07A BB01A BB15A BB25A BB26A BC07A CA04 CA24 EA13 3E084 BA07 BA08 BA09 CC03 CC07 CC08 FD13 GB08 HB01 HC08 4F100 AK04B AK06B AK68C AK70C AK71C BA04 BA10A BA10D CB00 CB00C CB03D DA03 DG10A EH23B EJ99 GB18 JD02 JL04 J12A12A12 A12A07 KB13 KF01 KJ09 KK82

Claims (2)

[Claims] 1. A laminate in which a polyethylene layer, an adhesion adjusting layer, and a hot melt layer are arranged in a layer order on at least one side of a base material containing paper, wherein the adhesion adjusting layer is
A lid material characterized by being an olefin-based copolymer having a thickness of 1 to 15 μm and containing ethylene and a carboxyl group. 2. The lid material according to claim 1, wherein the polyethylene layer has a thickness of 10 to 20 μm formed by melt extrusion coating of low density polyethylene.