JP4648376B2 - Production method of foamed paper - Google Patents

Description

  The present invention relates to a method for producing foamed paper, and more specifically, foamed paper having a non-foamed portion or a low-foamed portion in a foamed paper having a foamed layer of thermoplastic synthetic resin. It is about the law.

  Conventionally, as a processed paper with unevenness, the surface is physically given an uneven feeling by embossing or the like, or an uneven feeling is given by using foamed ink.

In addition, foamed paper (foamed paper) with a foamed polyethylene resin layer on the surface that has heat insulation, printability, easy disposal as waste after use, and simple manufacturing process and low cost. Sheet) is also disclosed (see, for example, Patent Document 1).
This publication is a method of manufacturing a concavo-convex pattern by heating a polyethylene resin processed paper and foaming a polyethylene resin layer on the surface by the vapor pressure of moisture contained in the paper.
In addition, an application to a paper cup is disclosed as a paper container composed of a barrel member and a bottom plate member in which a foamed layer of a thermoplastic synthetic resin layer is coated or laminated on one side wall surface of the barrel member (for example, Patent Document 2). reference.).
Furthermore, as a heat-insulating paper container having a printing layer made of colored ink between a polyolefin-based resin layer and a base material layer mainly composed of paper, a manufacturing method is disclosed in which a relatively thick foam layer is provided at the printed portion. (For example, refer to Patent Document 3).
Further, as a method of forming a non-foamed portion that does not foam in the foamed paper, a method is provided in which a slit is provided in a part of the thermoplastic resin layer to form a non-foamed portion in foaming by heating, or between the paper and the thermoplastic resin layer. There is disclosed a method in which a volatilization preventing coating layer (particularly, a coating material having a water vapor transmission barrier property) is partially provided between the portions, and the portion is a non-foamed portion (see, for example, Patent Document 4).
Japanese Patent Publication No. 48-32283 JP-A-57-110439 Japanese Patent Laid-Open No. 5-50536 Japanese Patent Laid-Open No. 7-232774

However, the methods according to Patent Documents 1 to 4 as described above for providing a non-foamed portion in a part of foamed paper so far have the following problems.
In the method of providing a slit, it is difficult to make a slit only in the thermoplastic resin layer on the surface, and there are disadvantages such as undesirable appearance, and in the method of applying a coating material, a smooth non-foamed surface is obtained. There were drawbacks such as difficulty.
Therefore, as shown in FIG. 1, in order to provide the outermost thermoplastic resin layer on the printing layer and the volatilization-preventing coating layer for suppressing foaming, the printed layer has poor visibility for confirming the pattern, display, etc. from the outside. There was a drawback.

  On the other hand, the present invention prints on the surface of the outermost thermoplastic resin the foam low-suppressing ink that prints a pattern, a display, and the like and the foam-suppressing ink that suppresses foaming in the same process. It is easy to synchronize the non-foamed part and foamed part, which are printed parts such as patterns and displays, or the low foamed part and foamed part, which are printed parts such as pictures and displays, and the outermost thermoplastic resin. Since the pattern and display are printed with the foam low suppression ink and the foam suppression ink is printed on the surface of the surface, the visibility of the printed pattern and display after foaming is good. Provided is a foamed paper having a unique appearance with unevenness in which a foamed portion and a pattern are synchronized.

As a result of studying to solve the above-mentioned problems, the present invention has at least a thermoplastic resin layer (outer surface) that is foamed by heating from the outer surface side, a base material layer mainly composed of paper, and a thermoplastic resin layer (inner surface). When the processed paper is heated, the foamed portion and the foamed low-suppressing ink are applied to at least a part of the surface of the thermoplastic resin layer (outer surface) in advance. The foamed paper is characterized in that a low-foamed portion is formed in the applied portion.
In addition, when a foam-suppressing ink and a foaming low-suppressing ink are applied in advance to at least a part of the surface of the thermoplastic resin layer (outer surface), and the processed paper is heated, a foamed portion and a portion subjected to the foam-suppressing ink A non-foamed portion and a low-foamed portion are formed.
Further, the resin component of the low foaming suppression ink is characterized by comprising at least an ethylene-vinyl acetate copolymer, a urethane resin, and a polyamide resin.

According to the present invention, a pattern, display, and the like are printed on the surface of the outermost thermoplastic resin with the foaming low-suppression ink, and after foaming, a low foaming portion is formed, so that the printed pattern, display, etc. Visibility is good.
In addition, on the surface of the outermost thermoplastic resin, by printing and processing the foam low suppression ink that prints the pattern and display and the foam suppression ink that suppresses foaming in the same process, the pattern, display, etc. It is easy to synchronize the non-foamed part and foamed part that are printed parts, or the low-foamed part and foamed parts that are printed parts such as patterns and displays, and suppresses foaming on the surface of the outermost thermoplastic resin. Since the pattern, display, etc. are printed with the ink, and the foam suppression ink is printed thereon, the foamed paper having a unique uneven appearance with good visibility such as the printed pattern, display after foaming is obtained. Can do.

Below, the manufacturing method of the foaming paper 1 of this invention is demonstrated in detail, referring drawings.
First, FIG. 2 is a diagram illustrating a material configuration according to a method for manufacturing foamed paper 11 having no non-foamed portion.
The foamed paper 11 has paper as a base material layer 2 and an intermediate printing layer 3 and a transparent varnish layer 4 provided on the outer surface side.
However, the intermediate printing layer 3 and the transparent varnish layer 4 are not necessarily required.
Moreover, the order which provides the intermediate | middle printing layer 3 and the transparent varnish layer 4 is possible in any case.
Further, these layers are covered with a thermoplastic resin layer (outer surface) 5.
There is a thermoplastic resin layer (inner surface) 6 on the inner surface side of the base material layer 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 can be provided between the base material layer 2 and the thermoplastic resin layer (inner surface) 6 in order to improve barrier properties. .

The basis weight of the paper used as the base material layer 2 is preferably in the range of 100 to 500 g / m ² in the production of a paper container.
The moisture content of the paper is desirably 3 to 10%, more preferably 5 to 8%.
When the moisture in the paper is evaporated and the surface thermoplastic resin layer is foamed by the force of the vapor pressure, if the water content is less than 3%, foaming is insufficient and the thickness of the foamed layer cannot be obtained. If the water content exceeds 10%, the foamed surface may be ruptured, which is not preferable.

The intermediate printing layer 3 is applied on the paper surface of the base material layer 2 or the transparent varnish layer 4 as described above.
This intermediate printing layer 3 may be printed partially with colored ink or may be printed with colored ink over the entire surface.
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 transparent varnish layer 4 is provided on the paper surface of the base material layer 2 or on the intermediate printing layer 3.
As a method for applying the transparent varnish, there are methods by printing and coating.
Among these, a method by gravure printing is preferable.
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.
As extender pigments, titanium oxide, calcium carbonate, magnesium carbonate, a mixture of two or more of these, and the like can be used.
The coating amount of the transparent varnish is preferably ² to 3 g / m ^{2 in} a dry state after coating.

The thermoplastic resins forming the thermoplastic resin layer (outer surface) 5 and the thermoplastic resin layer (inner surface) 6 are low density polyethylene resin, linear low density polyethylene resin, medium density polyethylene resin, high density polyethylene resin, polypropylene resin, Ionomer, ethylene / vinyl acetate copolymer, ethylene / acrylic acid copolymer, ethylene / acrylic acid ester copolymer, ethylene / vinyl alcohol copolymer, polypropylene resin, polyester resin, polyvinyl chloride resin, polystyrene resin, etc. Can be used.
The thermoplastic resin layer (outer surface) 5 and the thermoplastic resin layer (inner surface) 6 are laminated on the outer surface and the inner surface of the base material layer 2 on which printing and transparent varnish have been applied.
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 surface thermoplastic resin layer (outer surface) 5 to be the foam layer is preferably in the range of 10 to 100 μm.
If it is less than 10 μm or exceeds 100 μm, foaming is difficult.
On the other hand, the thickness of the inner surface thermoplastic resin layer (inner surface) 6 is not particularly limited.
Further, in order to foam only the outer surface thermoplastic resin layer (outer surface) 5 without foaming the inner surface thermoplastic resin layer (inner surface) 6, as a method for preventing evaporation of water vapor from the inner surface, inner surface thermoplasticity As the resin, a thermoplastic resin having a softening point higher than that of the outer surface thermoplastic resin is used.
For example, taking a polyethylene resin as an example, a low-density polyethylene resin having a low softening point can be used as the outer surface thermoplastic resin, and a high-density polyethylene resin having a high softening point can be used as the inner surface thermoplastic resin.

Below, the manufacturing method of the foaming paper 1 which has a foaming part of this invention, a low foaming part, and a non-foaming part is demonstrated.
As shown in FIG. 3A, on the surface portion of the thermoplastic resin layer (outer surface) 5 to be made into a non-foamed portion in advance in the process before heat foaming, the foam-suppressed ink printing portion 7 and the foaming low-suppressed ink print A portion 8 is provided.
By providing the foam suppression ink printing portion 7 on the surface of the thermoplastic resin layer (outer surface) 5, as shown in FIG. 3B, foaming of the thermoplastic resin layer (outer surface) 5 due to heating is prevented, and a non-foamed portion C is formed.
In other words, the thermoplastic resin layer (outer surface) 5 below the foam-suppressed ink printed portion 7 to which the foam-suppressing ink has been applied is suppressed in fluidity even when heated, or water vapor is difficult to permeate. Foaming will be suppressed.
In addition, by providing the foaming low-suppression ink printing portion 8, the portion of the thermoplastic resin layer (outer surface) 5 to which the foaming low-suppression ink has been applied foams to a thickness of about 2 to 10 times even when heated. Although the low foaming part B is formed, the degree is less than that when the foaming part A is formed with a thickness of about 5 to 20 times that of the part not subjected to the foaming suppression ink and the foaming low suppression ink.
Therefore, by providing the foam suppression ink printing portion 7 and the foaming low suppression ink printing portion 8, it is possible to obtain surface portions having different levels of foaming in three stages of the non-foaming portion C, the low foaming portion B, and the foaming portion A.

  Further, as shown in FIG. 4A, the foam low suppression ink printing portion 8 is printed with a pattern, a display, for example, an optical reading code of a barcode, and a part of the foam low suppression ink printing portion 8. Or by providing the foam suppression ink printing part 7 using transparent ink on the whole, the foam provided under the foam suppression ink printing part 7 after foaming as shown in FIG. The visibility of the pattern, display, for example, an optical reading code of a barcode, which is the low suppression ink printing portion 8, is particularly improved.

  Furthermore, as shown in FIGS. 5-a and 5-b, even when only the foaming low-suppression ink printing portion 8 such as a pattern or display is provided on the surface of the thermoplastic resin layer (outer surface) 5, the thermoplastic resin layer Compared with the case where a pattern, a display, or the like is provided on the intermediate printing layer under (outer surface) 5, visibility is better because it is not viewed through the thermoplastic resin layer (outer surface) 5.

As a material of the foaming low suppression ink, at least one kind of ethylene-vinyl acetate copolymer, urethane resin, and polyamide resin is used as the binder resin.
The printing process can be performed mainly by gravure printing.
This foaming low suppression ink may be colored or colorless.
When the amount of ink applied in printing is small, the expansion ratio is high, and when it is large, the expansion ratio is low.
A thickness of 1-2 μm is preferred after drying.

As a material of the foam suppression ink, a resin generally used in packaging materials can be used.
For example, at least one kind of resin such as nitrified cotton, polyamide resin, polyvinyl chloride resin, acrylic resin, and ketone resin is used.
The printing process can be performed mainly by gravure printing.
The foam suppression ink may be colored or colorless.
The amount of ink applied in printing is usually normal or more than normal, and a thickness of 3 to 5 μm is preferable after drying.

Also, the pattern is not limited, but by providing the same shape of the foam suppression ink printing portion 7 in the same printing process in accordance with the foaming low suppression ink printing portion 8, as shown in FIG. However, it is possible to manufacture the foamed paper 1 having irregularities synchronized with the register accuracy in the non-foamed portion.
Further, the foam suppression ink printing portion 7 and the foaming low suppression ink printing portion 8 can be provided in combination with the pattern of the intermediate printing layer.

  2-a, FIG. 3-a, FIG. 4-a, and FIG. 5-a are foamed unfoamed foamed paper, and FIG. 2-b, FIG. 3-b, FIG. 4-b, FIG. As a heating method for obtaining the foamed paper 1 as shown in -b, there is a method using hot air, infrared rays, far infrared rays, microwaves, high frequency, etc., a method of heating by standing using an oven, There are a method of heating while feeding by a conveyor, a method of feeding from a winding state, and heating through a foaming furnace. As heating conditions, the temperature is preferably in the range of 100 to 200 ° C., and the time is preferably in the range of 10 seconds to 5 minutes.

Next, the present invention will be described more specifically with reference to examples.
A low-density polyethylene resin layer having a thickness of 40 μm was provided on the surface of a cup base paper having a basis weight of 220 g / m ² and a water content of 8.0%, and a 20 μm medium-low density polyethylene resin layer was provided on the back side by an extrusion coating method. .
On the surface, use a gravure ink (trade name-LOKTR ink manufactured by The Inktec Co., Ltd.), which is an ethylene-vinyl acetate copolymer binder resin that is a low foaming suppression ink, with a pattern, content display and POS barcode. As shown in Fig. 7, gravure printing of the same process is performed on the part containing the content display and POS barcode as shown in Fig. 7 using the resin of the binder, which is the foam suppression ink, and the gravure ink of nitrified cotton. Printed.
This laminated body was punched into a blank for the body, and a paper cup was created by a paper cup molding machine.
Further, this paper cup was heated in a dryer at 120 ° C. for 3 minutes, and as shown in FIG. 6, a foamed paper cup 9 using foamed paper having a foamed portion, a low foamed portion, and a non-foamed portion on the surface was used. Obtained.
Since the portion including the content display and the POS barcode is a non-foamed portion, the visibility is very good, and the pattern portion is also a low-foamed portion and has sufficient visibility.
Furthermore, since the printing layer on the surface is lower than the surface of the foamed portion, there is no danger that the printing ink will move to another surface and become dirty when they are stacked in a blank or product state.

According to the present invention, a pattern, display, and the like are printed on the surface of the outermost thermoplastic resin with the foaming low-suppression ink, and after foaming, a low foaming portion is formed, so that the printed pattern, display, etc. Visibility is good.
In addition, on the surface of the outermost thermoplastic resin, by printing and processing the foam low suppression ink that prints the pattern and display and the foam suppression ink that suppresses foaming in the same process, the pattern, display, etc. It is easy to synchronize the non-foamed part and foamed part that are printed parts, or the low-foamed part and foamed parts that are printed parts such as patterns and displays, and suppresses foaming on the surface of the outermost thermoplastic resin. Since the pattern, display, etc. are printed with ink, and the foam suppression ink is printed on it, the visibility of the printed pattern, display, etc. after foaming is good, and the printed layer on the surface is better than the surface of the foamed part. Due to the reduced height, a foamed paper with a unique uneven appearance is obtained without the danger of printing ink moving to another side and becoming dirty when superimposed in a blank or product state. Door can be.
The foamed paper of the present invention can be used as a heat-insulating container or a container having design properties due to surface irregularities.

It is a figure which shows the material structure of the foaming paper which has the conventional non-foaming part. It is a figure which shows the material structure of the foaming paper which does not have a non-foaming part. It is a figure which shows the material structure of the foaming paper by this invention. It is a figure which shows another material structure of the foaming paper by this invention. It is a figure which shows another material structure of the foaming paper by this invention. It is a figure which shows another material structure of the foaming paper by this invention. It is a figure which shows one Example of the foaming paper by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Foam processed paper by this invention 2 Base material layer 3 Intermediate | middle printing layer 4 Transparent varnish layer 5 Thermoplastic resin layer (outer surface)
6 Thermoplastic resin layer (inner surface)
7 Foaming suppression ink printing part 8 Foaming low suppression ink printing part 9 Foamed paper cup 11 Foamed paper without non-foaming part A Foaming part B Low foaming part C Non-foaming part

Claims (3)

A thermoplastic resin layer (outer surface) that is foamed by heating is provided on the outer surface of the base material layer mainly composed of paper, while the thermoplastic material that is foamed by heating is formed on the inner surface of the base material layer mainly composed of paper. Producing a processed paper by providing a thermoplastic resin layer having a higher softening point than the thermoplastic resin constituting the resin layer (outer surface),
Next, the foaming suppression ink and the foaming low suppression ink are used on at least a part of the surface of the thermoplastic resin layer (outer surface) foamed by the above heating, and the foaming low suppression ink is at least ethylene-vinyl acetate in the binder resin. One type of copolymer or urethane resin is used, and the foam suppression ink uses at least one type of resin selected from nitrified cotton, polyamide resin, polyvinyl chloride resin, acrylic resin, and ketone resin. Forming a portion that has been subjected to the foam suppression ink, a portion that has been subjected to the foam low suppression ink, and a portion that is not subjected to any of the foam suppression ink and the foam low suppression ink,
After that, heat the above processed paper,
By the heat treatment, moisture in the paper constituting the base material layer is evaporated, and the thermoplastic resin layer constituting the outer surface is foamed by the force of the vapor pressure,
Non-foamed portion on the portion subjected to the above-described foam-suppressing ink, low-foamed portion on the portion on which the above-described foaming low-inhibiting ink has been applied, and foamed portion on the portion on which neither the above-mentioned foaming-suppressing ink nor the foaming-low-inhibiting ink is applied A method for producing foamed paper, characterized in that surface portions having different foaming levels in three stages are formed. A thermoplastic resin layer (outer surface) that is foamed by heating is provided on the outer surface of the base material layer mainly composed of paper, while the thermoplastic material that is foamed by heating is formed on the inner surface of the base material layer mainly composed of paper. Producing a processed paper by providing a thermoplastic resin layer having a higher softening point than the thermoplastic resin constituting the resin layer (outer surface),
Next, using at least a part of the surface of the thermoplastic resin layer (outer surface) that foams by the above heating, using a foaming low suppression ink, printing an optical reading code,
After that, at least on the printed part of the optical reading code with the above-described foaming low-suppression ink, a printed part of foam-suppressing ink using a transparent ink is formed,
The foaming low suppression ink uses at least one kind of ethylene-vinyl acetate copolymer or urethane resin as a binder resin, and the foaming suppression ink is nitrified cotton, polyamide resin, polyvinyl chloride resin, acrylic resin, or Use at least one kind of ketone resin,
Next, the processed paper is heat-treated,
By the heat treatment, moisture in the paper constituting the base material layer is evaporated, and the thermoplastic resin layer constituting the outer surface is foamed by the force of the vapor pressure,
A non-foamed portion, a portion subjected to the above-described foaming low-suppression ink, and a printed portion of the above-described foaming-suppressing ink, a portion subjected to the above-described foaming-suppressing ink and a portion overlapping the above-described foaming-suppressing ink printing portion, Low foaming part is formed on the part that has been subjected to foaming low suppression ink other than the part that overlaps the printed part of the above foaming suppression ink, and foaming part is formed on the part that is not subjected to any of the above foaming suppression ink or foaming low suppression ink A method for producing foamed paper, characterized by producing surface portions having different degrees of foaming in three stages. The base material layer mainly composed of paper is provided with one or two layers of an intermediate printing layer and a transparent varnish layer on one or both sides thereof. Process for producing foamed paper to be described.

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