JPH0976375A - Paper cup container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve sealability of an uneven seal part and to produce paper cup containers by using ethylene-α.olefin copolymer prepared by the polymeriza tion using a single site type catalyst at least for the innermost layer. SOLUTION: A paper cup in which ethylene-α.olefin copolymer prepared by the polymerization with the use of a single site type catalyst is used at least for the innermost layer. In forming the paper cup, bottom paper F is formed in a U-shape to make a skirt part, the bottom part of barrel paper W is folded inside to hold the skirt part of the bottom paper to be heat-bonded in a knurling seal part N. In this process, it is necessary for a barrel seal part M to be sealed completely in the part in contact with the skirt part of the bottom paper. Sealing is performed by filling a void K formed in the intersection part X between the barrel seal part M and the knurling seal part N of the bottom part with an inner surface resin which is melted by heat when the cup is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION In the production of paper cup containers, blanks for punching paper and bottom paper are adhered by heat sealing, high frequency sealing, etc. by a molding machine, but the steps of the sealing portion due to the thickness of the cup base paper are completely filled. You have to make a leak-free cup. Further, the molten resin of the sealant at the time of sealing must have good characteristics corresponding to the molding speed of the cup. The present invention relates to a material that can be used stably and efficiently in manufacturing such a cup.

[0002]

2. Description of the Related Art FIG. 1 shows a perspective view of the outer appearance of the shape of a paper cup container and a peripheral wall forming material and a bottom forming material before molding.
For example, in the case of a round cup, the material forming the cup forms a blank W (hereinafter referred to as a cardboard) punched into a shape similar to the paper stuck to a fan and forms the bottom, which forms the peripheral wall of the cup. , A circular blank F (hereinafter referred to as bottom paper). Depending on the shape to be molded, the shape of the paperboard and the bottom paper is designed and punched out, but the body of what is commonly called a paper cup container consists of the two parts. The case paper and the bottom paper may be supplied to the cup forming machine in a state of being punched into each of the above shapes, or may be supplied in a winding state and may be punched in-line and formed into a cup in the cup forming machine. is there. As a material for forming a paper cup container, specifications such as cup base paper / PE and PE / cup base paper / PE are generally used, but other materials such as aluminum foil and various vapor depositions are used for decoration and imparting a barrier property. A plastic film including a processed film may be laminated on the front and back of the cup base paper.

Due to the structure of the paper cup container, the paper cup container is composed of two seals, a seal M (hereinafter referred to as a body seal) and a bottom seal N (hereinafter referred to as a knurl seal). Of course, these seals must be completely hermetically sealed. The most important thing to note when sealing is that the body seals are skirts formed by press molding bottom paper. It is to completely fill the gap between the steps of the knurled seal and ensure the hermeticity. As a material for forming the paper cup container, a synthetic resin capable of being heat-bonded is provided on the inner surface after the cup is molded or on both surfaces of the cup base paper. Conventionally, low-density polyethylene was used as the heat-bondable synthetic resin, but in order to ensure the above-mentioned hermeticity, the grade of the low-density polyethylene resin has been sufficiently selected, and even a little suitable. In addition, the production was done with great care in order to keep the molding conditions appropriate.
Due to variations in conditions and the like, poor sealing occurred. In a paper cup container used for a one-point application such as a vending machine, even a minute pinhole with almost no hindrance is not allowed when used for distribution or as a container for contents with high permeability. Therefore, within the proper range of the heating temperature and the pressurizing condition of the cup molding machine, it is necessary to completely fill the stepped portion with the resin melted under strict control so that the sealing property does not have a problem.

[0004]

In molding a paper cup container, the sealing property of the step seal portion is improved, and a paper cup container of stable quality is produced with high efficiency.

[0005]

An object of the present invention is to provide a paper cup container which is leakproof and has a good hermeticity. In order to achieve this object, a paper cup using an ethylene-α-olefin copolymer polymerized by using a single-site catalyst in at least the innermost layer is used.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Recently, paper cup containers have become widely used. That is, in the past, it was often used for disposable beverage cups or tableware substitutes that are often used in vending machines, but recently it has come to be used for long-term distribution or storage containers. . A cup for a vending machine, a cup as a substitute for tableware, should have been able to withstand use for a short period of time, but the required quality as a container for long-term distribution and storage mentioned above requires a small pinhole or seal. The existence of unstable parts of
Vibration and shock during transportation may cause leakage of contents and destruction of the container. Therefore, it is necessary to completely seal and seal the step.

Conventionally, the inner surface of the cup base paper was extrusion-coated with low density polyethylene, but particularly in the case of high speed molding, a minute gap formed between the seal portion of the body and the inner surface of the bottom paper. Fill the part with melted sealing resin,
In order to obtain a seal in which the liquid content does not leak, it may not be possible to stably fill the voids following the speed, which has been a problem.

With respect to this problem, the present inventors have studied and tested various materials, and as a result, have found that ethylene-α-olefin copolymers (hereinafter,
(S-PE) is molded on the inner surface of the laminate to fill the voids and produce a tightly sealed paper cup stably over a long period of time. Also confirmed that it is wide. The S-PE usable in the present invention has a density of 0.890 to 0.92.
It preferably has a melt index of 0 g / cm ³ and a melt index of 0.5 to 20. Even when the density is 0.920 g / cm ³ or more, the sealing property tends to be inferior, but this is presumed to be due to poor flow of the S-PE resin during melting and insufficient low-temperature sealing property. The suitable melt index of S-PE is 0.5 to 20, and within this range, stable film formation is possible by ordinary methods such as extrusion method, T die casting method and inflation method.

Further, in the present invention, the same effect can be obtained even if the paper cup container is used in which the S-PE and another resin are coextruded to form a multilayer film, and the S-PE layer is used as the innermost surface of the cup. Obtainable. For example, as a co-extruded film of S-PE and medium density polyethylene (hereinafter referred to as MDPE), the total thickness is 30 ~
A 2-layer film of 60 μm or the like is effective for obtaining excellent sealing property. In this case, the layer thickness ratio is S-PE: MDPE =
(40 to 80): (60 to 20), but it is not particularly limited. In the production of paper cups, the bottom paper is press-molded into a U-shape, but as a result of the press-molding with the S-PE as the inner surface, there is no decrease in the molding speed, and there is no problem. confirmed.

FIGS. 3 and 4 are views showing the relationship between the body seal and the knurled seal at the bottom of the paper cup container. The bottom paper F is formed in a U shape to form a skirt portion,
The bottom portion of the body paper W is folded inward, the skirt portion of the bottom paper is sandwiched, and the knurled seal portion N is heat-bonded.
At this time, the most noticeable position for sealing is the portion where the body sealing portion M contacts the bottom skirt portion, and it is necessary to completely seal the portion at this portion. In the body seal portion M and the knurled seal portion N of the bottom paper, a gap K is formed due to a step difference in the thickness of the body paper. The knurled seal melts and presses the thermoplastic synthetic resin laminated on the inner surface or both surfaces of the bodyboard and the bottom paper to fill the gap K and complete the sealing. In the present invention, S-PE is used as the thermoplastic synthetic resin, and when a cup is formed from a material laminated with a cup base paper, the void K is melted due to the low-temperature sealing property of S-PE and the flow characteristics at the time of melting. -It was found that it was filled with PE, and as a result, it had an extremely excellent effect on sealing performance.

As for the above-mentioned hermeticity, the inner surface resin (or the outer surface resin depending on the specifications) melted by the heat at the time of cup molding is formed in the space K formed at the intersection X of the body seal portion M and the bottom knurl seal portion N. The sealing level can be confirmed as the degree of bleeding by the seal check liquid. Specifically, it can be determined by pouring the seal check liquid into a molded paper cup container and seeing how much the seal check liquid having good permeability soaks into the void K. In addition, another void K '
Is located below the bottom sheet F, and therefore is not related to the hermeticity.

Furthermore, by laminating S-PE to form an adhesive layer, the S-PE has a very small amount of low molecular weight components as compared with LDPE. It was revealed that the selective absorption of the components of the product had little effect on the taste.

Further, the structure of the base material of the cup body for storage and distribution is to have a suitable barrier property. For example, by laminating an aluminum foil on the inner surface of the cup base paper and extrusion-coating the innermost layer with S-PE, the gas barrier property, the water vapor barrier property, etc. can be greatly improved. Even in the case of such a paper cup container having a barrier property, the above-mentioned sealing effect can be obtained by the structure in which S-PE is laminated on the inner surface.

The paper cup container has a flange curl (or lip curl), which not only retains the shape of the cup opening and improves the mouthfeel when the contents are directly drunk, but as described above. It can be used as a flange when sealing a lid when a paper cup is used as a distribution container or when fitting an overcap. When used as the distribution container, the flange curl portion may be pressed and flattened in order to improve the sealing property with the lid member. When the flange curl is applied to the flange of the paper cup container, a step of the thickness of the body paper is formed in the body seal M. Regarding the sealing property of the step due to the lid material, S-PE is used as a sealant layer. By using the lid material, the same effect as the sealing performance of the bottom portion can be obtained.

Although the round cup has been described above as an example of the paper cup, the present invention can be applied to a paper container formed by the cylinder paper and the bottom paper, for example, an elliptical cup, a rectangular cup, a round tube container, and various types of containers. This is a technique that can be applied to a paper cup container having a shape different from the round shape such as a cylindrical container, and is not limited to the round paper cup. Other materials such as body paper and bottom paper, for example, aluminum foil, can be used as a laminate (eg: S-PE / aluminum foil / paper / S-PE), or cup base paper as a member equivalent to the bottom paper. Instead of the above, a plastic sheet is used, laminated with a sealant as an adhesive layer (for example, polystyrene / S-PE), and can also be applied when it is formed into a U shape by vacuum forming. Therefore,
The present invention can be similarly applied to a container having a non-tapered rectangular tubular container shape in which the body portion is formed of a laminated body mainly composed of paper, and the top portion and the bottom portion formed of a laminated body mainly composed of aluminum foil.

[0016]

【Example】

1) Preparation of sample As the constitution according to the present invention, laminated sheets of three kinds of constitutions were combined with Examples 1 and 2 and Comparative Example, and formed into a paper cup. The same specifications are used for the body and bottom paper. Example 1: S-1 ²⁰ / cup base paper ³⁰⁰ / S-2 ⁴⁰ (S-PE single layer) * 1 Example 2: S-1 ²⁰ / cup base paper ³⁰⁰ / PE ¹⁵ / S-2
²⁵ (2 layers of coextrusion) * 2 Comparative example: S-1 ²⁰ / cup base paper ³⁰⁰ / S-2 ⁴⁰ (LDPE)
* 3 (shoulder paper and bottom paper have the same specifications, shoulder numbers indicate the thickness of the material, S-1 and S-2 are μm, cup base paper is g / m ² ) The clades used are as follows ( (D is density, MI is melt index) * 1 S-PE is kernel 57L (trade name of Mitsubishi Chemical Corporation
MI = 11.0 D = 0.905) Film formation by EC method. * 2 S-PE / MDPE coextrusion 2 layers (layer thickness 15 μm / 10 μm) combined with sand PE 40 μm S-PE is kernel 57L (previously) MDPE is NeoZex 40150C (Mitsui Petrochemical Co., Ltd. product name D = 0.940 MI = 15) The laminate with the substrate was laminated by the extrusion coating (EC) method. * 3 LDPE is Mirason 18SP (Mitsui Petrochemical Industry Co., Ltd. product name MI = 7.0D = 0.921). Film formation by EC method. <Test Method> The above-mentioned respective examples and comparative examples were laminated in the above-mentioned constitution and molded by a cup molding machine, and 500 molded cups were prepared and the hermetic sealing property was confirmed.
In that method, a seal check liquid was put into a molded cup, and the degree of permeation of the seal check liquid was confirmed. Seal check liquid used: Ageless check liquid (trade name, manufactured by Mitsubishi Gas Chemical Co., Inc.) To the bottom of the cup. Ageless check solution penetrates to the bottom of the cup by 2/3 or 1 /
There were 3 stages of penetration up to 2. (Indicated by the number that reached each of the above penetration levels in 500 tests). “Results” Penetration to the bottom Penetration up to 2/3 Penetration up to 1/2 Example 1 0/500 0/500 10/500 Example 2 0/500 0/500 8/500 Comparative example 2/500 80/500 190/500 The paper cup container of the present invention, of course, has penetrated to the bottom,
While none of them penetrated to 2/3, the comparative example
There were 2 pieces that penetrated to the bottom, and 80 pieces that penetrated to 2/3. It was confirmed that the paper container of the present invention was extremely excellent in sealing property of the paper cup container since only a few penetrated to half.

[0017]

[Effects of the Invention] A single layer of an ethylene-α-olefin copolymer polymerized by using a single-site catalyst, or a multilayer film by co-extruding another resin and the ethylene-α-olefin copolymer, By stacking with the base material so that the inner surface of the paper cup container becomes a layer of the ethylene-α-olefin copolymer, and molding the paper cup container, the low temperature sealing property and the hot tack strength are good in the molding. In addition, the resin filling of the gap was also good, and it became possible to produce a paper cup container with stable leak tightness at high speed and with stable quality. It is not limited to the shape of the cup, and can be applied to a container of a type in which the body paper is sealed and the skirt portion of the press-molded bottom paper is knurled. Further, even when the member corresponding to the bottom paper uses another material, the same effect can be obtained as long as the surface sealing with the body paper is S-PE.

[Brief description of drawings]

FIG. 1 is a perspective view of a paper cup container of the present invention and a plan view of a pre-molding member.

FIG. 2 is a cross-sectional view of a laminated body that constitutes the paper container of the present invention.

FIG. 3 is an enlarged cross-sectional view of a bottom knurled seal (vertical).

FIG. 4 is an enlarged (horizontal) cross-sectional view of an intersection of a body seal portion and a knurled seal portion.

[Explanation of symbols]

1 Cup base paper 2 Inner surface resin layer 3 Outer surface resin layer P Paper container W Body paper F Bottom paper M Body seal part N Knurl seal part X Crossing part of body seal part M and knurl seal part N K, K 'Void part

Claims (1)

[Claims] 1. A paper cup container characterized by using an ethylene-α-olefin copolymer polymerized by using a single-site catalyst in at least the innermost layer.