JP2007030925A - Laminated pulp container, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated pulp container which prevents a poor appearance from occurring by making the adhesiveness between a pulp layer and a plastic layer favorable, and at the same time increases the strength at the flange section. <P>SOLUTION: This laminated pulp container 1 comprises a laminated body for which the pulp layer 2 having air permeability and the plastic layer 3 are thermally fused through a hot melt adhesive layer 4. For the laminated pulp container 1, a recessed section for housing an article to be housed is formed of the bottom wall 1a and the peripheral side wall 1b, and the flange section 5 is connected with the upper end of the peripheral side wall 1b which is the opening end of the recessed section. The flange section 5 is annularly formed with a protruding section 5a which curves and protrudes into a semi-arc shape toward the opposite side from the bottom surface of the recessed section. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a laminated pulp container comprising a laminate of a pulp layer and a plastic layer suitable for packaging containers for foods and the like that are required to have water resistance, oil resistance, appropriate rigidity, and the like, and a method for producing the same.

  Patent Document 1 (Japanese Patent Laid-Open No. 2002-96813) discloses a pulp container suitable for packaging containers for foods and the like that are required to have water resistance, oil resistance, appropriate rigidity, and the like.

  FIG. 6 shows a pulp container disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2002-96813), (a) is a perspective view, and (b) is a partial cross-sectional view taken along line AA of (a). is there. The pulp container 101 is made of a laminate in which a plastic film layer 103 is bonded to a pulp layer 102 by heat fusion or an adhesive, and a flange portion 104 is continuously provided on the outer periphery of the opening of a concave portion that is a storage portion. .

  The pulp layer 102 and the plastic film layer 103 do not peel off during use as a container, but after use, if the knob piece 106 provided at the corner of the flange part 104 is pulled, the pulp layer 102 and the plastic film layer 103 are easily peeled off from the cut line 105 part. Then, the pulp layer 102 and the plastic film layer 103 can be separated and recovered.

Patent Document 2 (Japanese Patent Application Laid-Open No. 2003-34334) discloses a method for manufacturing a paper packaging container in which a plastic film is peelably laminated on the surface of a concave portion of a paper tray. After setting in the lower mold of the laminating mold, the plastic film is placed above the paper tray and heated by the heating plate, and then between the plastic film and the paper tray and between the paper tray and the lower mold. A manufacturing method is disclosed in which after evacuation with a mold is performed, compressed air pressure is applied to a plastic film and pressed against the surface on the concave side of the paper tray to be thermally fused.
JP 2002-96813 A JP 2003-34334 A

  In the pulp container disclosed in Patent Document 1, the pulp layer is thickened and a paste such as resin or starch is added to improve the rigidity and waterproofness of the pulp layer. There is no sex. Therefore, when a plastic film layer is laminated on the pulp layer, there is a possibility that an insufficiently bonded portion is formed between the pulp layer and the plastic layer, resulting in poor appearance.

  The manufacturing method of the pulp container disclosed in Patent Document 2 is a suction means for vacuum suction between the pulp layer and the plastic film layer when the pulp layer and the plastic film layer are bonded by thermal fusion or adhesive. And a suction means for vacuum suction between the pulp layer and the lower mold. For this reason, the process and the apparatus are complicated, and the efficiency of vacuum suction is not good.

  The present invention has been made in view of the above-mentioned unsolved problems of the prior art, and it is an object of the present invention to ensure that the adhesiveness between the pulp layer and the plastic layer is good and that appearance defects do not occur.

  In order to achieve the above object, a laminated pulp container according to a first aspect of the present invention is a laminated pulp container comprising a laminate in which a breathable pulp layer and a plastic layer are laminated via a hot melt adhesive layer. A flange portion is continuously provided at the opening end of the concave portion for accommodating the contents, and the flange portion has an annular protrusion projecting in a semicircular arc shape toward the opposite bottom side of the concave portion. It is formed.

  In the laminated pulp container according to the second aspect of the invention, the pulp layer is made of a plant fiber that does not contain a resin and a paste additive that substantially impair the air permeability of the pulp layer, and then has an average wall thickness of 300. The concave portion and the flange portion, which are formed by compressing to ˜500 μm, are provided with a concave portion for accommodating an object to be accommodated and a flange portion connected to an opening end of the concave portion, and are on the accommodation side of the object to be accommodated. The film comprising a plastic layer as a base material and a hot melt adhesive layer for bonding sucks air on the pulp layer housing side from the outside of the pulp layer through the pulp layer. It is characterized by being bonded to the pulp layer.

  The method for producing a laminated pulp container according to the present invention is the method for producing a laminated pulp container according to claim 1 or 3, wherein the pulp for water is applied to a papermaking mold having a papermaking recess for making a pulp layer intermediate formed body. After the paper making step of making the pulp layer intermediate formed body by supplying the raw material liquid mixed and dispersed by adding fibers, the heat drying step of heating and drying the pulp layer intermediate formed body, and after the heat drying step The pulp layer intermediate formed body is compressed by a female mold having a cavity surface that regulates the concave outer surface side of the pulp layer and a male mold having a cavity surface that regulates the concave inner surface side of the pulp layer. A compression step for compression molding, placing the pulp layer on a lamination table, heating and placing a plastic layer in which a hot melt adhesive layer is laminated on the pulp layer, A lamination step in which vacuum suction is performed from the outer surface side of the concave portion of the pulp layer, and the plastic layer is adhered to the entire surface of the inner surface of the concave portion of the pulp layer through the hot melt adhesive layer. And

  Since this invention is comprised as mentioned above, there exists an effect as described below.

  Since the pulp layer is paper-made and has air permeability, it can be decompressed by vacuum suction between the pulp layer and the plastic layer through the pulp layer. As a result, the plastic layer and the pulp layer adhere to each other through the hot melt adhesive layer. In addition, the strength of the flange portion increases, and in addition, an easy peel is possible when the film is heat-sealed in the opening.

  An embodiment of a laminated pulp container according to the present invention will be described with reference to the drawings.

  FIG. 1: shows the laminated pulp container by one Embodiment, (a) is a schematic top view, (b) is a typical fragmentary sectional view which follows the AA line of (a).

The laminated pulp container 1 is composed of a laminate in which a breathable pulp layer 2 and a plastic layer 3 are heat-sealed through a hot-melt adhesive layer 4. The laminated pulp container 1 has a concave portion for accommodating an object to be accommodated, which is formed by a bottom wall 1a and a peripheral side wall 1b, and a flange portion 5 is continuously provided at the opening end of the concave portion which is the upper end of the peripheral side wall 1b. Yes. Separate concave and convex patterns P ₁ and P ₂ are formed on the inner and outer surfaces of the recess, respectively.

  The laminated pulp container 1 includes a bottom wall 1a, a peripheral side wall 1b that bends upward from the outer peripheral edge of the bottom wall 1a and increases in diameter as it goes upward, and a radially outer side from the upper end peripheral part of the peripheral side wall 1b. And a protruding portion 5a that curves and protrudes in a semicircular arc toward the upper side in the drawing (on the opposite bottom side of the concave portion). It is formed in an annular shape.

  By forming the protruding portion 5a in the flange portion 5 in an annular shape, the strength of the flange portion 5 is increased, and when the film is heat-sealed over the entire opening portion, the area of the seal portion is reduced, enabling easy peeling. Become.

  The pulp layer 2 has air permeability produced by papermaking and molding described later from a raw material liquid containing pulp fibers. Therefore, when the plastic layer 3 is heat-sealed to the pulp layer 2 via the hot melt adhesive layer 4, the plastic layer 3 is removed by vacuum suction from the side of the pulp layer 2 opposite to the plastic layer (the outer surface side of the recess). The pulp layer 2 can be deformed into a shape following the inner side surface of the concave portion. As a result, the inner surface of the concave portion of the pulp layer 2 and the plastic layer 3 are completely adhered to each other via the hot melt adhesive layer 4, and there is no possibility that a poorly bonded void portion is generated between the two, resulting in poor appearance. .

  Moreover, in a laminated pulp container, by using polyethylene terephthalate as a film base layer, it can be used as a container for cooked foods such as gratin heated in a microwave oven.

  Further, in the laminated pulp container, the plastic layer is made of a polyethylene terephthalate film, and the hot melt adhesive layer is an ester compound of an unsaturated carboxylic acid selected from ethylene / methyl methacrylate, ethylene / ethyl acrylate, and ethylene / methyl acrylate. The film may have a melting point of 70 to 120 ° C.

  If the thickness of the polyethylene terephthalate is less than 8 μm, pinholes are likely to occur during vacuum suction, and if it exceeds 40 μm, the three-dimensional shape reproducibility during vacuum suction is poor.

  A hot melt adhesive comprising an ester compound of an unsaturated carboxylic acid selected from ethylene / methyl methacrylate, ethylene / ethyl acrylate and ethylene / methyl acrylate, and having a melting point of 70 to 120 ° C. It is suitable for a container having a ridge on the circumference of the flange. In other words, since the film has a low melting point and excellent adhesion, the film first adheres to the flange during vacuum suction, and during suction, gas can be satisfactorily bonded without leaking from the outer peripheral end surface where the film and the pulp layer overlap. It becomes.

  The laminated pulp container of Claim 3 WHEREIN: A pulp layer does not contain the component which inhibits air permeability like patent document 1 substantially. Therefore, it is excellent in reproducibility even if it is a fine three-dimensional shape, without using the large and complicated vacuum suction apparatus like patent document 2. FIG.

  Further, when pulp fibers are made and then compressed, a thin and rigid pulp layer is obtained.

  As a result of trial production and experiment of a laminated pulp container, the present inventor found that the average thickness of the pulp layer was less than 300 μm, and when the filling / packaging process was performed in a state in which an object such as gratin was accommodated, The shape maintainability enough to hold the part is lost.

  On the other hand, if the average thickness of the pulp layer exceeds 500 μm, even if the film is placed on the storage side and the air on the storage side of the pulp layer is sucked directly through the pulp layer, the corner portion and the fine three-dimensional shape It was found that good adhesion could not be obtained.

  Furthermore, in the laminated pulp container 1, a three-dimensional display portion made of a pulp layer having a letter or a pattern is formed in the concave portion, and the three-dimensional display portion is laminated with a film made of a plastic layer and a hot melt adhesive layer. Shall.

  Then, one Embodiment of the manufacturing method of the laminated pulp container which concerns on this invention is described.

  The method for producing a laminated pulp container according to the present invention includes a paper making step for making a pulp layer intermediate formed body 2a and a paper making pulp layer intermediate formed body 2a in the method for producing a laminated pulp container according to the embodiment described above. And compressing and molding the pulp layer 2, and simultaneously forming a separate uneven pattern on the inner and outer surfaces of the recess, and a hot melt adhesive layer on the inner surface of the recess of the pulp layer 2 on which the uneven pattern is formed And a laminating process for joining the plastic layer 3 through 4.

  In the papermaking apparatus used in the papermaking process, as shown in FIG. 2, a papermaking mold 11 having a large number of liquid passage holes (not shown) is disposed at a substantially intermediate position in the depth direction of the papermaking tank 12. The papermaking mold 11 includes a papermaking recess 11a having a shape that regulates the outer surface side of the recess for papermaking the pulp layer intermediate formed body 2a, which is a preformed product of the pulp layer 2. When the raw material liquid 14 in which pulp fibers are added to water and mixed and dispersed is introduced above the papermaking mold 11, the pulp fibers remain on the papermaking recesses 11a and the pulp layer intermediate formed body 2a (see FIG. 2) is made. In addition, only water is configured to fall into the liquid discharge chamber 12a through the plurality of liquid passage holes and be discharged from the discharge port 13 to the outside.

  As shown in FIG. 3, the compression device used in the compression step corresponds to a female die 21 having a cavity surface 21 a shaped to regulate the outer surface side of the concave portion of the pulp layer 2, and a cavity surface 21 a of the female die 21. It has a male mold 22 having a cavity surface 22a shaped to regulate the inner surface of the concave portion of the pulp layer 2, and is configured to be able to approach and separate from each other by an actuator such as a fluid pressure cylinder (not shown).

On the cavity surface 21a of the female mold 21 and the cavity surface 22a of the male mold 22, grooves 21b and 22b are formed for forming separate uneven patterns P ₁ and P ₂ , respectively. Further, as shown in FIG. 5, the stacking table 31 is provided with a plurality of vacuum suction holes 31 b penetrating from the cavity surface 31 a to the vacuum suction chamber, and a vacuum such as a vacuum pump (not shown) connected to the exhaust port 33. It is comprised so that vacuum suction can be carried out with the generation source.

  (1) The raw material liquid 14 is put above the papermaking mold 11 in the papermaking tank 12, and the pulp fibers in the raw material liquid are left on the papermaking recess 11a of the papermaking mold 11, and only water is dropped into the drainage chamber 12a. Then, the pulp layer intermediate formed body 2a is made on the paper making recess 11a by discharging to the outside through the discharge port 13.

  (2) After the above (1), the pulp layer intermediate formed body 2a is released from the papermaking mold 11 and dried by heating in a drying furnace (not shown).

(3) After the above (2), as shown in FIG. 3, the dried pulp layer intermediate formed body 2a is placed on the cavity surface 21a of the female die 21 of the compression device, and an actuator (not shown) is activated. As shown in FIG. 4, the female mold 21 and the male mold 22 are brought close to each other and the pulse layer intermediate molded body 2 a is sandwiched to compress the pulp layer 2. At the same time, the female mold 21 and the male mold 22 are provided. Separate concavo-convex patterns composed of the grooves 21b and 22b are respectively transferred to the outer surface and the inner surface of the bottom wall 1a of the pulp layer 2, and the separate concavo-convex patterns P ₁ and P ₂ are formed on the inner and outer surfaces of the bottom wall 1a of the pulp layer 2. Form.

  (4) After (3) above, the pulp layer 2 is placed on the cavity surface 31a of the stacking table 31, as shown in FIG.

  (5) After the above (4), the plastic layer 3 on which the hot-melt adhesive layer 4 is laminated is held by a pair of upper and lower holding members 34 a and 34 b and heated and placed on the pulp layer 2. Next, a vacuum pump (not shown) connected to the exhaust port 33 is activated to depressurize the vacuum suction chamber, and vacuum suction is performed between the cavity surface 31a and the pulp layer 2 through the plurality of vacuum suction holes 31b. 2, the plastic layer 3 is vacuum-formed into a shape along the inner surface of the concave portion of the pulp layer 2.

In this step, the plastic layer 3 is heat-sealed to the inner surface of the concave portion of the pulp layer 2 via the hot melt adhesive layer 4. At the same time, the plastic layer 3 is brought into close contact with the concave / convex pattern P ₁ formed on the inner surface of the concave portion of the pulp layer 2 to transfer the concave / convex pattern P (see FIG. 1).

  (6) After (5), the laminated pulp container 1 is released from the female mold 21.

  The pulp layer in the present invention is composed of a non-wood-based or wood-based pulp raw material. Non-wood pulp raw materials include native plants (bamboo, bamboo, esparto, weeds, etc.), fiber crops (kenaf, cotton linter, aqaba, sisal, jute, flax, kozo, mitsumata etc.), agricultural crops Waste (sugar cane, straw, rice straw, palm palm, banana, etc.). In addition, wood-based pulp raw materials are birch (such as oak) and conifer (such as cedar and cypress).

  As the plastic layer, a polypropylene resin such as a propylene homopolymer, a propylene block polymer, or a polypropylene random polymer is used. Polyethylene resins such as low density polyethylene, high density polyethylene, and linear low density polyethylene are used. Furthermore, a polyester resin, a polyamide resin, a polyacrylic resin, or a polystyrene resin is used.

  Examples of hot melt adhesive layers include ethylene terpolymers (eg, ethylene / acrylic acid ester, maleic anhydride terpolymer), ethylene copolymers (eg, ethylene / vinyl acetate copolymer, ionomer). ), Acid-modified polypropylene (for example, maleic anhydride-modified polypropylene) and the like may be used.

The laminated pulp container by one Embodiment is shown, (a) is a schematic plan view, (b) is a typical fragmentary sectional view which follows the AA line of (a). It is a schematic cross section of the papermaking apparatus used for the papermaking process in the manufacturing method of the laminated pulp container by one Embodiment. In the manufacturing method of the laminated pulp container by one Embodiment, it is a schematic cross section which shows the state which has arrange | positioned the pulp layer in the compression molding process of a pulp layer to the female type | mold. It is a schematic cross section which shows the state which compression-molded the pulp layer following FIG. 1 shows one step in a method of manufacturing a laminated pulp container according to an embodiment, (a) is a schematic cross-sectional view showing a state in which a plastic layer is arranged on the pulp layer, and (b) is a vacuum suction of the plastic layer through the pulp layer. It is a schematic cross section which shows the state which heat-fused the plastic layer through the hot-melt-adhesive layer by this. The pulp container of a prior art example is shown, (a) is a model perspective view, (b) is a model fragmentary sectional view which follows the AA line of (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laminated pulp container 2 Pulp layer 2a Pulp layer intermediate molded body 3 Plastic layer 4 Hot-melt-adhesion layer 5 Flange part 5a Protrusion part 11 Papermaking type | mold 12 Papermaking tank 12a Drainage chamber 13 Outlet 14 Raw material liquid 21 Female type | mold 21a, 22a , 31a Cavity surface 22 Male 31 Stacking base 31b Vacuum suction hole 33 Exhaust port 34a, 34b Holding member

Claims (5)

A laminated pulp container comprising a laminate in which a breathable pulp layer and a plastic layer are laminated via a hot melt adhesive layer,
A flange portion is continuously provided at the opening end of the concave portion for accommodating the objects to be accommodated,
The laminated pulp container, wherein the flange portion is formed with an annular projecting portion that curves and projects in a semicircular arc shape toward the opposite bottom side of the recess.   The plastic layer is made of a polyethylene terephthalate film, and the hot melt adhesive layer has a melting point of 70 to 120 made of an ester compound of an unsaturated carboxylic acid selected from ethylene / methyl methacrylate, ethylene / ethyl acrylate, and ethylene / methyl acrylate. The laminated pulp container according to claim 1, wherein the laminated pulp container is a film at 0 ° C. The pulp layer is formed by making a plant fiber that does not contain the resin and paste additives that substantially impair the breathability of the pulp layer, and then compressing the average wall thickness to 300 to 500 μm, A flange portion is connected to the concave portion for accommodating the object to be accommodated and the opening end of the concave portion,
A film made of a plastic layer as a base material and a hot-melt adhesive layer for adhesion is formed in the concave portion and the flange portion on the accommodation side of the object to be contained, and the pulp layer draws air on the pulp layer accommodation side from the outside of the pulp layer. A laminated pulp container, characterized in that the hot melt adhesive layer is bonded to the pulp layer by being sucked through and bonded to the pulp layer.   4. A three-dimensional display portion made of a convex pulp layer with letters or designs formed in the recess, and the three-dimensional display portion is laminated with a film made of a plastic layer and a hot melt adhesive layer. 1. A laminated pulp container according to item 1. In the method of manufacturing the laminated pulp container according to claim 1 or 3,
A paper making process having a paper making recess having a paper making recess for making the pulp layer intermediate formed body, and supplying the raw material liquid mixed and dispersed by adding pulp fibers to water, and making the pulp layer intermediate formed body; ,
A heating and drying step of heating and drying the pulp layer intermediate formed body;
After the heating and drying step, the pulp layer intermediate formed body is compressed by a female mold having a cavity surface that regulates the concave outer surface side of the pulp layer and a male mold having a cavity surface that regulates the concave inner surface side of the pulp layer. And a compression step of compression-molding the pulp layer,
The pulp layer is placed on a stacking table, and a plastic layer in which a hot melt adhesive layer is laminated on the pulp layer is heated and arranged, and then vacuum suction is performed from the concave outer surface side of the pulp layer, And a laminating step in which the plastic layer is adhered to the entire surface of the inner surface of the concave portion of the pulp layer via the hot melt adhesive layer and bonded thereto.

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