JP2012051329A - Foaming base paper and insulating paper container using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insulating container can easily form a foaming inhibition part with an easy to see pattern of printing layer on a base paper, in a paper cup with an insulating layer formed by heating the base paper comprising a thermoplastic resin layer/paper base/thermoplastic resin layer and foaming the thermoplastic resin layer on a surface with a steam pressure of water contained in the paper.SOLUTION: A foaming base paper 1 and an insulating paper container using the same are provided, wherein the foaming base paper 1 is equipped at least with an outside thermoplastic resin layer 5 that foams by heating from outside, a base layer 2 composed mainly of paper, and an inside thermoplastic resin layer 6 and further a cut 7 is prepared on a part of surface of the outside thermoplastic resin layer 5 to form a foaming inhibition part 8 on the part where the cut 7 is prepared when the foaming base paper 1 is heated.

Description

  The present invention relates to a foam base paper and a heat insulating paper container using the same, and more particularly to a heat insulating cup in which a non-foamed portion is partially provided in a foam processed paper having a foamed layer of a thermoplastic synthetic resin. is there.

As the heat insulating container, many synthetic resins having foamability, in particular, those made of expanded polystyrene resin are used. Recently, a paper cup using a material in which both sides of paper are laminated with a polyethylene resin layer, and a foamed paper cup in which a polyethylene resin layer on the surface is foamed have begun to be used.
In the above-mentioned heat insulating container, the container made of expanded polystyrene resin is manufactured by molding a resin added with a foaming agent and is excellent in heat insulation, but it is difficult to treat as waste after use and is environmentally friendly. There was a problem in terms. In addition, there are disadvantages such as low surface smoothness and poor printability.

Other heat-insulating containers include non-foamed rigid plastic containers wrapped with a foamed resin sheet, or containers wrapped with corrugated material and heat-shrinkable plastic film. Are known.
For example, when a heat-shrinkable plastic film coated with a heat-foamable substance is coated on the surface of a ready-made container and then subjected to heat treatment, the heat-shrinkable plastic film is adhered to the outer surface of the container. At the same time, a method (Patent Document 1) is disclosed which comprises foaming a thermally foamable material applied to a heat-shrinkable plastic film.

  However, in this method, the process of coating the surface of a ready-made container with a heat-shrinkable plastic film coated with a heat-foamable substance is not easy, and the labor for this is complicated and intended for disposable use. The actual situation is that it cannot be adequately applied as a manufacturing method for obtaining an inexpensive container. Such a heat-insulating container is time-consuming in its production, which includes a step of winding a foamed resin sheet or a corrugated material and a step of packaging with a heat-shrinkable plastic film.

Polyethylene resin on the surface is characterized by heat insulation, printability, easy disposal as waste after use, simple manufacturing process and low cost. Paper cup with foamed layer.
This foamed paper cup uses thermoplastic foam / paper base material / thermoplastic resin in a foam base paper to evaporate and evaporate the moisture contained in the paper and soften it by heating. A foam heat insulation laminate is known in which a space generated by expansion and foaming of a resin layer is used as a heat insulation layer, and is widely used in cups of instant noodle containers and hot beverage containers such as coffee (Patent Document 2, Patent). Reference 3).

  The paper cup with the heat-treated layer formed by heating the polyethylene resin-treated paper and foaming the polyethylene resin layer on the surface by the vapor pressure of the water content of the paper, the printed layer on the paper base is the lower part of the foamed part (inside ), The pattern is difficult to see, and the foam layer surface lacks smoothness, so that there is a problem in that printing cannot be performed neatly.

A method of forming a foamed thermoplastic resin layer only in a portion excluding the printing region has also been proposed, but this method has a drawback that a difficult process has to be added for mass production. It was.
Furthermore, a film resin layer made of a coating agent capable of suppressing the fluidity of the thermoplastic resin layer (outer surface) softened by heating is provided on the thermoplastic resin layer serving as the foam layer, and the softening flow of the thermoplastic resin layer is reduced. Although the method of suppressing foaming by suppressing is also proposed, adjustment of the degree of foam suppression is difficult with this method (Patent Document 4).

Japanese Patent Publication No. 58-52904 Japanese Patent Laid-Open No. 5-50536 JP 11-314629 A JP 10-226033 A

  An object of the present invention is to provide a paper cup in which a base paper composed of a thermoplastic resin layer / paper base material / thermoplastic resin layer is heated and the surface thermoplastic resin layer is foamed by the vapor pressure of moisture contained in the paper to form a heat insulating layer. An object of the present invention is to provide a heat-insulating container that can easily form a foam suppression part in which a pattern of a printed layer on a paper substrate is easily visible.

  The invention according to claim 1 of the present invention is a foam base paper provided with an outer thermoplastic resin layer foamed by heating from at least the outer surface side, a base material layer mainly composed of paper, and an inner thermoplastic resin layer, The foamed base paper is characterized in that a cut is provided in a part of the surface of the plastic resin layer, and the foam suppression part is formed in a portion where the cut is provided when the foamed base paper is heated.

  The invention according to claim 2 is characterized in that a printing layer is provided on the surface of the base material layer, and a plurality of cuts are provided in a part of the surface of the outer thermoplastic resin layer on the printing region. The foam base paper described.

  The invention according to claim 3 is characterized in that the interval between the plurality of cuts provided in a part of the surface of the outer thermoplastic resin layer on the printing region is in the range of 6 mm to 8 mm. Foam base paper.

  Moreover, invention of Claim 4 is the heat insulating paper container produced using the foaming base paper in any one of Claims 1-3.

  According to the invention of claim 1 of the present invention, there is provided a foam base paper comprising an outer thermoplastic resin layer foamed by heating from at least an outer surface side, a base material layer mainly composed of paper, and an inner thermoplastic resin layer, A foamed base paper, wherein the foamed base paper is characterized in that a notch is provided in a part of the surface of the outer thermoplastic resin layer, and the foamed base paper is formed in a portion where the notch is provided when the foamed base paper is heated. When the container is heated after being assembled into a container, only the vicinity of the portion provided with the notch is suppressed from foaming and becomes a low foaming region.

  As a result, a foam layer having heat insulation properties is formed on the outer surface of the container in the region where the notch is not provided, and at the same time, water vapor generated from the paper base material through the notch or heated air is formed on the outer surface of the container in the other region. By escaping, foaming is suppressed and a low-foamed foam layer or a non-foamed layer is formed.

In this way, the step formed by forming the low foaming area adjacent to the high foaming area on the outer surface of the container is an insulating container that has the effect of being hard to slip while holding a certain degree of heat insulation when held by hand. Easy to make.

According to invention of Claim 2 of this invention, by using the foam base paper which provided the printing layer in the surface of the base material layer, and provided the some notch in a part of surface of the outer side thermoplastic resin layer on a printing area | region. In addition, a low-foamed foam layer region in which the pattern of the printed layer on the outer surface of the container can be seen through can be formed on the print region.
As a result, the printed pattern of the container can be seen from the outside, and a heat-insulating container that is not slippery while maintaining a certain degree of heat insulation can be obtained.

  Further, according to the invention of claim 3, by using the foam base paper in which the intervals of the plurality of cuts provided in a part of the surface of the outer thermoplastic resin layer on the printing region are in the range of 6 mm to 8 mm, In addition, it is possible to form a low-foamed foam layer region on the print region in such a range that the base pattern can be seen through while maintaining anti-slip properties.

When the interval between the plurality of cuts is 5 mm or less, the escape of water vapor from the cuts is large, so that the thermoplastic resin layer in the region where the cuts are provided does not foam but remains in a non-foamed state. As a result, the background pattern can be clearly seen, but the heat insulation and slip resistance are deteriorated.
In addition, if the interval between the plurality of cuts exceeds 8 mm, the escape of water vapor from the cuts is small, and therefore the thermoplastic resin layer in the vicinity of the cuts has both foamed and non-foamed regions. As a result, the perspective of the base pattern becomes unclear, and the heat insulation becomes unstable.

  According to the invention of claim 4, the heat insulating container made using the foamed base paper according to any of claims 1 to 3 is a base paper comprising a thermoplastic resin layer / paper base material / thermoplastic resin layer. Heat insulation that can easily form a foam-suppressed part that makes it easy to see the pattern of the printed layer on the paper substrate in a paper cup that has a heat insulating layer formed by foaming the surface thermoplastic resin layer with the vapor pressure of the moisture contained in the paper. Sex containers can be provided.

  In the heat-insulating container of the present invention, the foam thickness can be changed depending on the surface area, so that it is possible to express the pattern by the unevenness of the foam surface by using this, and to provide an expression effect other than the perspective of the printed pattern. You can also. In this case, it is not always necessary to synchronize the printed pattern and the foam suppression region.

The cross-sectional schematic diagram of an example of the heat insulation paper container (paper cup) using the foam base paper of this invention. (A) after cup molding and before heating, (b) after heating and foaming. The cross-sectional schematic diagram of an example of the heat insulation paper container (paper cup) using the conventional foam base paper. (A) after cup molding and before heating, (b) after heating and foaming. The expanded cross-section schematic diagram of an example of the heat insulation paper container (paper cup) using the foam base paper of this invention. (A) after cup molding and before heating, (b) after heating and foaming. The schematic diagram of the shape (arrangement | positioning) example of the cut | incision of the foam base paper of this invention.

  Hereinafter, an example of an embodiment of a foam base paper of the present invention and a heat insulating paper container using the same will be described with reference to the drawings if necessary.

The foam base paper of the present invention is a paper cup or the like that suppresses foaming of the thermoplastic resin by cutting into the thermoplastic resin layer that is foamed by the moisture evaporated from the paper substrate and allowing the generated water vapor to escape to the outside. This is a foam base paper for an insulated container.
By making a plurality of cuts in the region where foaming of the base paper is desired to be suppressed, foaming of the thermoplastic resin layer can be suppressed as compared with a region where no cut is made.

This foam base paper is composed of a laminate in which both sides of a paper base such as paperboard are laminated with a thermoplastic resin such as polyethylene resin.
Since the heat insulation layer is usually formed on the outside of the container, this thermoplastic resin is often made of a low-melting low-density polyethylene resin (LDPE) on the outside and a high-melting high-density polyethylene resin (HDPE) on the inside. .

  In this way, by providing a difference in melting point between the thermoplastic resin layers on both sides of the paper substrate, water vapor generated in the paper substrate due to heating is blocked by the inner thermoplastic resin layer, so that it is in a molten state first. A large number of bubbles are formed in the outer thermoplastic resin layer to form a heat-insulating foam layer.

  For example, when the outer thermoplastic resin layer is a polyethylene resin having a melting point of 105 ° C. and the inner thermoplastic resin layer is a polyethylene resin layer having a melting point of 130 ° C., the foamed base paper is heated to a temperature intermediate between the melting points of both thermoplastic resins. By doing so, the outer polyethylene resin layer foams to form a heat insulating layer.

In the foam base paper of the present invention, a part of the outer thermoplastic resin layer described above is provided with a portion where the water vapor escapes in the paper base material when the container is heated by cutting a depth reaching the paper base material, and the foam layer A portion with a small thickness can be made partially.
First, the foam base paper of the present invention will be described with reference to FIGS. 1 and 3 by taking the case of a paper cup as an example. FIG. 2 is used as necessary for comparison with the prior art.

In FIG. 1, the cross-sectional schematic diagram of an example of the heat insulation paper container (paper cup) using the foam base paper of this invention was shown. The top part and the bottom part of the cup are simplified, and the cross section of the body part into which the notch of the present invention is cut is shown in a direction in which the top part is the top part.
FIG. 1 (a) shows a state after molding in a cup shape using blanks of foam base paper for the body, and (b) shows a state after heating and foaming.

FIG. 3 is an enlarged schematic cross-sectional view showing an example of a heat insulating paper container (paper cup) using the foam base paper of the present invention in the vicinity of the body part cut. FIG. 3A shows the state after cup molding and before heating, and FIG. 3B shows the state after heating and foaming.
In FIG. 2, the cross-sectional schematic diagram of an example of the heat insulation paper container (paper cup) using the conventional foam base paper was shown. FIG. 2A shows the state after the cup molding and before the heating, and FIG.

As shown in FIG. 1, in the foam base paper (1) of the present invention, the printing layer (3) is partially provided on the outer surface side of the paper substrate (2), and these layers are formed of the outer thermoplastic resin. It is covered with a layer (5), and is made of blanks having a laminated structure in which an inner thermoplastic resin layer (6) is provided on the inner surface side of the paper substrate (2).
In addition, a barrier layer such as a metal vapor deposition layer such as aluminum or an inorganic vapor deposition layer such as silica is provided between the paper substrate (2) and the inner thermoplastic resin layer (6) in order to improve barrier properties. You can also.

In the foamed base paper (1) of the present invention, a plurality of cuts (7) are usually provided on a part of the surface of the outer thermoplastic resin layer (5), and the foamed base paper (1) is cut when heated after cup molding. Only the vicinity of the region provided with (7) is a foamed base paper in which foaming is suppressed to form a low foaming region.
When a conventional foam base paper not provided with the notch (7) is used (FIG. 2 (a)), when the foam base paper (1) is heated and foamed after the cup is formed, the cup body as shown in FIG. 2 (b). The outer thermoplastic resin layer (5) of (13) foams to form a foam layer (4) having a substantially uniform thickness with heat insulation.

In the foamed base paper (1) of the present invention, a plurality of cuts (7) provided in the outer thermoplastic resin layer (5) are provided, and the cuts (7) are provided when the foamed base paper (1) is heated after cup formation. Only a portion near the region is suppressed in foaming to form a low foaming region (8) (FIG. 1 (b)).
As a result, a stepped foam layer (4) having a low low foam region (8) is formed on the outer surface of the cup, and not only a cup that is not slippery while maintaining heat insulation is obtained, but also a paper base (2) The pattern of the printed layer (3) printed on the surface of the film can be seen through, and the effects of obtaining necessary information and improving the design can be obtained.

As shown in FIG. 3, the foam layer (4) in the vicinity of the notch (7) reaching the paper substrate (2) provided on the outer thermoplastic resin layer (5) of the foam base paper (1) of the present invention. The cross section has a shape that is the thinnest at the position of the notch where the water vapor inside the paper substrate (2) escapes to the outside, and becomes thicker as the distance from the notch increases.
Therefore, when the foam base paper is arranged so as to be dotted with isolated cuts (7), a foam layer having a thin film thickness is obtained only in the very vicinity of the cut position in a linear or dot shape, and only that portion is a paper base ( 2) or a cup in which the color of the printing layer (3) can be seen through. An example of an arrangement in which isolated cuts (7) are dotted in (a) of FIG. 4 is shown in a schematic diagram of a trunk member blank.

In the case where a plurality of cuts (7) close to each other are provided, the foam layer obtained in the region formed by the plurality of cuts becomes the foam suppression region (8) as a whole and has a low foaming among the foam layers (4). A thin film layer is formed.
As a result, the foam suppression region (8) becomes a cup having a width that allows the color of the paper substrate (2) or the printing layer (3) to be seen through.
In FIG. 4B, an example of the arrangement in the case where a plurality of notches (7) close to each other is provided is shown in a schematic diagram of the body member blanks.

In order to be able to see through the printed layer (3) on the surface of the paper substrate (2) while maintaining a certain degree of heat insulation and slip resistance, it is provided on a part of the surface of the thermoplastic resin layer (5) on the printing area. It is desirable that the interval between the plurality of cuts (7) is in the range of 6 mm to 8 mm.
When the interval between the plurality of cuts (7) is small, there is much escape of water vapor from the cuts, and therefore the outer thermoplastic resin layer (5) in the region where the cuts are provided does not foam, so the picture is clearly visible. However, the necessary functions of heat insulation and slip resistance are deteriorated.
When the interval between the plurality of cuts (7) exceeds 8 mm, the foam layer (4) in the vicinity of the cuts is not only transparent in the background pattern but also unstable in heat insulation. turn into.
It is appropriate that the depth (h) of the cut (7) reaches the paper substrate (2).

The basis weight of the paper substrate (2) is preferably in the range of 200 to 450 g / m ² in terms of manufacturing a paper container. Further, the water content of the paper is desirably 3 to 10%, preferably 5 to 8%.

The print layer (3) is applied to the surface of the paper substrate (2) as described above. This print layer (3) is usually partially printed with colored ink.
For the printing position, the size of the printing area, the printing method, the ink used, etc., a conventionally known technique can be appropriately selected and used.

The printed layer (3) is not necessarily colored ink. For example, when it is desired to express a pattern with unevenness due to the difference in foam thickness, it is provided on the surface of the paper substrate (2) with a transparent varnish. As a method for applying the transparent varnish, there are known printing and coating methods.
The composition of the transparent varnish is mainly composed of a synthetic resin containing extender pigments. As the synthetic resin, nitrified cotton, polyurethane resin, polyamide resin, polyvinyl chloride resin, acrylic resin, a resin in which two or more of these are mixed, and the like can be used.

  The thermoplastic resins forming the outer thermoplastic resin layer (5) and the inner thermoplastic resin layer (6) are low density polyethylene resin (LDPE), linear low density polyethylene resin (LLDPE), and medium density polyethylene resin (MDPE). , High density polyethylene resin (HDPE), polypropylene resin (PP), ionomer, ethylene / vinyl acetate copolymer, ethylene / acrylic acid copolymer, ethylene / acrylic acid ester copolymer, ethylene / vinyl alcohol copolymer, Polyester resin, polyvinyl chloride resin, polystyrene resin and the like can be used.

The outer thermoplastic resin layer (5) and the inner thermoplastic resin layer (6) are laminated on the outer surface and inner surface of the printed paper base layer (2).
The lamination method includes an extrusion coating method in which a resin is melted and applied, or a lamination method in which a film is bonded. The thickness of the outer thermoplastic resin layer (5) serving as the foam layer is preferably in the range of 40 to 100 μm.
If it is less than 40 μm or exceeds 100 μm, foaming is difficult. On the other hand, the thickness of the inner thermoplastic resin layer (6) is preferably in the range of 10 to 50 μm.

  Further, in order to foam only the outer thermoplastic resin layer (5) without foaming the inner thermoplastic resin layer (6), as a method for preventing evaporation of water vapor from the inner surface, the paper substrate (2) and the inner There are a method of providing a barrier layer such as an aluminum foil between the thermoplastic resin layers (6), or a method of using a thermoplastic resin having a softening point higher than that of the outer thermoplastic resin inside. In the latter case, for example, when a polyethylene resin is taken as an example, a high-density polyethylene resin having a high softening point can be used as the inner thermoplastic resin.

  The heat insulating container using the foamed base paper of the present invention can be manufactured by, for example, laminating a thermoplastic resin layer on both the front and back surfaces of a paper substrate having a printing layer made of colored ink on the surface. A step of obtaining a blank board (foaming base paper) for forming a paper container having a sandwich structure comprising a paper substrate having a layer / colored printing layer / thermoplastic resin layer, and molding of the paper container with the blank board for forming the paper container Forming the blank plate for forming the paper container by heating the obtained paper container, evaporating the moisture contained in the paper base material and expanding the air in the paper base material. And forming a heat-insulating layer by forming a foamed structure containing a large number of bubbles between the thermoplastic resin layer and the paper substrate.

  At this time, in the region of the thermoplastic resin layer applied to the surface of the printing layer with the colored ink, the depth of reaching the paper substrate is provided in the first step or the second step, so that the third step In the heating and foaming process, the foaming is suppressed in the colored printing layer portion as compared with other regions, and the thickness of the heat insulating layer is reduced.

This incision can be made at the same time as blanks are punched out with a Thomson blade, or between the layers of the paper base material layer, or a rotary die cutter (with a blade installed on a cylinder) can be used, and can be put in a known manner.
Examples of embodiments of the present invention will be described below by way of examples.

<Example 1>
A base paper of 300 g / m ² basis weight is used as the paper base, and the surface is printed with the printing ink Carton X (Toyo Ink Co., Ltd.) using the offset printing method. A laminated body was prepared by laminating a high density polyethylene resin layer having a thickness of 30 μm on the opposite surface of the density polyethylene resin layer.
The laminate was cut with a rotary die cutter so as to cut from the surface of the low density polyethylene resin layer in the pattern printing area to the paper base material layer, and simultaneously punched into a predetermined shape to create blanks.

After forming the blanks with a cup molding machine, the blanks were heated and foamed at 120 ° C. for 5 minutes to obtain a heat insulating paper cup. This heat insulating paper cup could see through the pattern in the pattern printing area and easily read information such as product name and expiration date.
Furthermore, hot water was poured into the heat insulating paper cup and held with bare hands to evaluate the heat insulating property and anti-slip property. The heat insulating property was excellent at 4 in a 5 grade evaluation, and the anti-slip property was 5 as well, and it was possible to have it without any anxiety.

<Example 2>
A base paper of 300 g / m ² basis weight is used as the paper base, and the entire surface is printed by the offset printing method using the printing ink Carton X (Toyo Ink Manufacturing Co., Ltd.), and the printed surface has a low thickness of 75 μm. A laminated body was prepared by laminating a high density polyethylene resin layer having a thickness of 30 μm on the opposite surface of the density polyethylene resin layer.
Triangles made of isolated notches reaching the paper base material layer from the surface of the low-density polyethylene resin layer were engraved on this laminate with a rotary die cutter, and simultaneously blanks were created in a predetermined shape.

After forming the blanks with a cup molding machine, the blanks were heated and foamed at 120 ° C. for 5 minutes to obtain a heat insulating paper cup. This heat-insulating paper cup has a soft design effect in which the color of the printed layer can be seen through only the triangular portion of the notch, and it appears to be synchronized with foaming.
Furthermore, hot water was poured into the heat insulating paper cup and held with bare hands to evaluate the heat insulating property and anti-slip property. The heat insulating property was excellent at 4 in a 5 grade evaluation, and the anti-slip property was 5 as well, and it was possible to have it without worry.

<Comparative Example 1>
A base paper of 300 g / m ² basis weight is used as the paper base, and the surface is printed with the printing ink Carton X (Toyo Ink Co., Ltd.) using the offset printing method. A laminated body was prepared by laminating a high density polyethylene resin layer having a thickness of 30 μm on the opposite surface of the density polyethylene resin layer.
This laminate was punched into a predetermined shape with a rotary die cutter to create blanks.

After forming the blanks with a cup molding machine, the blanks were heated and foamed at 120 ° C. for 5 minutes to obtain a heat insulating paper cup. In this heat insulating paper cup, the pattern in the pattern printing area cannot be seen through by the foam layer, and it is difficult to read the printing information.
Furthermore, hot water was poured into the heat insulating paper cup and held with bare hands to evaluate the heat insulating property and anti-slip property. The heat insulating property was inferior to 1 in a 5-grade evaluation, and the anti-slip property was hardly felt.

From the results of Examples 1 and 2 and Comparative Example 1, in the heat insulating paper container (paper cup) using the foam base paper of the present invention, it is possible to easily form a foam suppression portion where the pattern of the paper base printing layer is easily visible from the outside of the cup. .
Further, since the foam thickness can be changed depending on the surface area, it is possible to express the pattern by the unevenness of the foam surface by using this, and it is possible to obtain an expression effect other than the perspective of the printed pattern.

DESCRIPTION OF SYMBOLS 1 ... Foam base paper 2 ... Paper base material 3 ... Print layer 4 ... Foam layer (heat insulation layer)
DESCRIPTION OF SYMBOLS 5 ... Outer side thermoplastic resin layer 6 ... Inner thermoplastic resin layer 7 ... Notch 8 ... Foam suppression area | region 10 ... Paper cup 11 ... Cup top surface 12 ... Cup bottom face 13 ... Cup trunk | drum 15 ... Cup inner side h ... Depth of notch | incision

Claims (4)

  A foam base paper having an outer thermoplastic resin layer that is foamed by heating from at least the outer surface side, a base material layer mainly composed of paper, and an inner thermoplastic resin layer, and is cut into a part of the surface of the outer thermoplastic resin layer The foam base paper is characterized in that when the foam base paper is heated, a foam suppression portion is formed in a portion where the cut is provided.   2. The foam base paper according to claim 1, wherein a printing layer is provided on the surface of the base material layer, and a plurality of cuts are provided in a part of the surface of the outer thermoplastic resin layer on the printing region.   3. The foam base paper according to claim 2, wherein the interval between the plurality of cuts provided in a part of the surface of the outer thermoplastic resin layer on the printing region is in the range of 6 mm to 8 mm.   A heat insulating paper container made using the foam base paper according to any one of claims 1 to 3.

Images