JP2007276485A - Method for forming paper container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a paper container suitable for materials provided with a polypropylene resin coating layer. <P>SOLUTION: The method for forming the paper cup 10 joins a paper bottom plate 6, which has a resin coating layer on its inside surface and a cylindrical folded back portion 6a on its outside periphery, to the inside of a bottom end portion 3a of a paper cup body 3 having the resin coating layer formed on its inside surface, in which a joint portion, in the inside peripheral surface of the bottom end portion 3a, for the outside peripheral surface of the folded back portion 6a is heated with bottom plate 6 arranged inside the bottom end portion 3a of the cup body 3, and then, a joint portion, in the inside peripheral surface of the bottom end portion 3a, for the inside peripheral surface of the folded back portion 6a is heated by flames. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for forming a paper container in which a material obtained by coating paper with a resin is joined.

  In the case where various materials are formed by bonding materials coated with paper with resin, a method in which the bonding surfaces are pressure-bonded in a state where the resin-coated layer is heated and melted is often used. As a heating method of the resin coat layer, there are hot air heating in which hot air is blown to the bonding surface, or frame heating in which the bonding surface is blown with a flame (frame).

  In recent years, it has been studied to use a paper cup as a container for a microwave oven. Paper cups intended for such applications require higher heat resistance and water resistance than conventional paper cups, and as a result, resin materials coated on the paper used as the material have a higher melting point than conventional products. Is done. For example, polypropylene resin has been studied as a coating material for the inner surface of a paper cup.

  However, when a material coated with polypropylene resin is molded by a conventional molding machine, the surfaces covered with the resin coating layer, or the surface covered with the resin coating layer and the surface where the paper material is exposed. In some cases, poor bonding or poor sealing may occur.

  Then, an object of this invention is to provide the shaping | molding method of the paper container suitable for the raw material in which the coating layer made from a polypropylene resin was provided.

  The present invention solves the above-described problems by a molding method as described below. Here, in order to facilitate understanding of the present invention, reference numerals in the accompanying drawings are added in parentheses, but the present invention is not limited to the illustrated form.

  In the method for forming a paper container of the present invention, a first member (6) and a second member (3) are formed from a material provided with a coating layer (12, 14) made of polypropylene resin on one side of paper. The second member is bent so that the end (6a) of the first member is wrapped by the second member while being in contact with the coat layer of the second member. In the method for forming a paper container in which the first member is joined to the second member by a first joint portion where polypropylene resins are in contact with each other and a second joint portion where the polypropylene resin and paper are in contact with each other, Is heated by hot air, and the second joining portion is heated by a frame.

  According to this molding method, hot air heating and frame heating can be used properly according to the state of the joint surface between the first member and the second member, so that, for example, the joint portion between the body portion and the bottom plate of the paper cup , Other joining parts of the cup material can be reliably joined. Thereby, a highly reliable paper container seal structure can be obtained.

  In this molding method, the first joint portion includes a joint surface of the first member on the side where the coat layer is provided and a joint surface of the second member on the side where the coat layer is provided. In addition, at least one of these bonding surfaces may be heated with hot air, and then the bonding surfaces may be pressed against each other. The second bonding portion includes a bonding surface on the side where the paper of the first member is exposed and a bonding surface on the side where the coat layer of the second member is provided, and these bonding surfaces. At least one of the joining surfaces may be heated with a frame, and then the joining surfaces may be pressed against each other.

  According to these methods, reliable bonding is performed by appropriately using hot air heating or frame heating on the bonding portion between polypropylene resins or the bonding portion between polypropylene resin and paper, thereby achieving high reliability. A seal structure can be obtained.

  According to the molding method of the present invention, each bonding surface is subjected to a heat treatment suitable for the combination of the bonding portions on the paper container in which the bonding portions of the polypropylene resins and the bonding portions of the polypropylene resin and the paper are mixed. Can be reliably bonded, and thereby a highly reliable container sealing structure can be obtained.

  FIG. 1 shows an outline of a method for forming a paper cup which is an embodiment of the present invention. In FIG. 1, a blank 1 is formed by punching a cup base paper provided with a resin coat layer made of polypropylene on at least one side into a developed shape of the body of the cup. The blank 1 is wound in a cylindrical shape on a mandrel (not shown) so that the resin coat layer becomes the inner surface, and both side edges thereof are overlapped with a predetermined width. The overlapping portion 1A is struck by a frame 2a generated by igniting the combustion gas blown from the gas nozzle 2, whereby the resin coat layer is heated to the melting point or higher. In this heated state, a not-illustrated iron is pressed against the overlapping portion 1A, whereby the barrel portion 3 is formed. On the other hand, the disc 5 is punched out from the continuous strip 4 made of the same material as the blank 1, and the outer periphery of the disc 5 is bent into a cylindrical shape to form the bottom plate 6 having the folded portion 6a. The folded portion 6a is bent toward the side where the resin coat layer made of polypropylene is not formed.

  The bottom plate 6 is disposed inside the bottom end 3a of the body 3, and a resin coat layer is formed by spraying hot air 7 on a portion of the inner peripheral surface of the bottom end 3a that is joined to the outer peripheral surface of the folded portion 6a. Heat. Subsequently, of the inner peripheral surface of the bottom end portion 3a, the portion to be joined to the inner peripheral surface of the folded portion 6a is heated by the flame 8a generated by igniting the combustion gas blown from the gas nozzle 8, and the resin coat layer is heated. To do. Next, the bottom end portion 3a of the body portion 3 is bent inward with a predetermined mold so that the folded portion 6a of the bottom plate 6 is wrapped. Thereafter, the outer side of the bent bottom end 3a is held by a female mold (not shown), and the roller 9 as a male mold is pressed against the inner side of the bottom end 3a to tighten the bottom end 3a in the radial direction. The roller 9 is turned in the circumferential direction to join the bottom end 3 a and the folded portion 6 a of the bottom plate 6. Further, the upper end 3b of the body 3 is curled outward. The paper cup 10 as a paper container is shape | molded by the above process.

  2A and 2B show the joint portion of the paper cup 10 molded as described above, wherein FIG. 2A is an enlarged view of the overlapping portion 1A of the body portion 3, and FIG. 2B is an enlarged view of the yarn bottom portion. As shown in FIG. 2A, in the overlapping portion 1A, the resin coat layer 12 of the cup base paper 11 arranged on the outer peripheral side and the cup base paper 11 arranged on the inner peripheral side are joined. On the other hand, as shown in FIG. 2B, since the resin coat layer 14 is provided on the inner surface side of the cup base paper 13 of the bottom plate 6 at the yarn bottom portion, the resin coat layer 14 is provided on the outer periphery of the folded portion 6a. And the cup base paper 13 is exposed on the inner periphery of the folded portion 6a. On the other hand, the resin coat layer 12 is exposed at the inner and outer sides of the folded portion 6a at the joint portion between the bottom end portion 3a of the trunk portion 3 and the folded portion 6a. Therefore, the resin coat layers 12 and 14 are joined on the outer peripheral side of the folded portion 6a, and the resin coat layer 12 and the cup base paper 13 are joined on the inner peripheral side of the folded portion 6b. In this embodiment, the bottom plate 6 corresponds to the first member, the trunk portion 3 corresponds to the second member, and the folded portion 6a corresponds to the end portion of the first member. Further, a portion where the resin coat layers 12 and 14 are bonded corresponds to a first bonding portion, and a portion where the resin coat layer 12 and the cup base paper 13 are bonded corresponds to a second bonding portion.

  According to the study by the inventors, when polypropylene is used for the resin coat layers 12 and 14, the joint portion between the resin coat layer 12 and the cup base paper 11 and 13 and the joint portion between the resin coat layers 12 and 14 are appropriate. Different heating methods were found to be different. That is, it is desirable to heat the bonding portion between the resin coating layer 12 and the cup base papers 11 and 13 using a frame, and the bonding portion between the resin coating layers 12 and 14 is heated using hot air. It is desirable to do. Therefore, in the procedure of FIG. 1, the joining portion is heated using the frame 2a when the overlapping portion 1A of the trunk portion 3 is bonded. As for the joint portion between the body portion 3 and the bottom plate 6, the joint portion between the inner peripheral surface of the bottom end portion 3 a of the body portion 3 and the outer periphery of the folded portion 6 a is heated by hot air 7. The joined portion with the inner periphery of the folded portion 6a is heated by the frame 8a.

  FIG. 3 shows an example of a molding machine 20 used for the paper cup molding method described above. The molding machine 20 in FIG. 3 is provided for joining the body 3 and the bottom plate 6. The molding machine 20 has a turret 21 installed horizontally. A plurality (eight in the figure) of mandrels 22 are provided on the turret 21 at an equal pitch in the circumferential direction. As shown in FIGS. 4 and 5, the mandrel 22 is disposed so as to be movable in the vertical direction at the center of the inverted cone type body 22a that can be held in a state where the body portion 3 is inverted up and down. And a slider 22b.

  The turret 21 is rotationally driven intermittently by a pitch (45 ° in the illustrated example) of the mandrels 22 by a driving device (not shown). In addition, in FIG. 3, the stop position of each mandrel 22 is shown by P1-P8. At the stop position P1, there is provided a bottom plate supply device 31 that supplies the bottom plate 6 formed by a bottom plate forming device (not shown) to the upper end of the mandrel 22 with the folded portion 6a facing upward. In addition, at the stop position P3, there is provided a body part supply device 33 that covers the body part 3 formed by a body part forming device (not shown) in a state where it is turned upside down with respect to the mandrel 22 to which the bottom plate 6 is supplied. It has been. By covering the mandrel 22 with the body portion 3 by the body portion supply device 33, the bottom plate 6 is disposed inside the bottom end portion 3 a of the body portion 3.

  A first heating device 35 is provided at the stop position P4. As shown in FIG. 4, the first heating device 35 has an air nozzle 36 inserted inside the bottom end 3 a of the body 3, and hot air 7 extends from the air nozzle 36 to the entire circumference of the inner peripheral surface of the bottom end 3 a. Is to blow. The position where the hot air 7 is blown from the air nozzle 36 is set to a joint portion A with respect to the outer peripheral surface of the folded portion 6a among the inner peripheral surface of the bottom end portion 3a. In order to enable the hot air to be blown onto the joint A, the slider 22b of the mandrel 22 is stored in the main body 22a in the first heating device 35, so that the bottom plate 6 is the original line 6 'shown in FIG. It is held at a position retracted to the upper end side (lower side in FIG. 4) of the body part 3 from the attachment position. The temperature of hot air blown by the first heating device 35 (however, the value measured immediately after the heater inside the air nozzle 36) is preferably in the range of 500 ° C to 650 ° C.

  As shown in FIG. 3, a second heating device 37 is provided at the stop position P5. As shown in FIG. 5, the second heating device 37 is configured such that the gas nozzle 8 is inserted inside the bottom end 3 a of the body 3, and the inner peripheral surface of the bottom end 3 a is blown out by a frame 8 a that blows out from the gas nozzle 8. It goes around the entire circumference. The heating position by the frame 8a is set to a joint portion B with respect to the inner peripheral surface of the folded portion 6a among the inner peripheral surface of the bottom end portion 3a. The joint portion B corresponds to a portion of the bottom end portion 3a of the body portion 3 that is bent back so as to wrap the folded portion 6a.

  At the time of carrying into the second heating device 37, the slider 22b of the mandrel 22 protrudes upward by a predetermined amount from the main body 22a. Thereby, the bottom plate 6 is pushed up to the original mounting position indicated by an imaginary line 6 ′ in FIG. 4, and the outer peripheral surface of the folded portion 6 a is the inner peripheral surface of the bottom end portion 3 a heated by the first heating device 35. It faces the joining portion A (see FIG. 4). Such an operation of the slider 22b can be realized, for example, by arranging a cam that the slider 22b rides at the stop position P5. As shown in FIG. 7A, a flange-like pushing portion 36a is provided in the air nozzle 36 for supplying hot air, and after the joining portion A is heated, the air nozzle 36 is pushed into the bottom plate 6 side as shown in FIG. 7B. The bottom end portion 3a of the body portion 3 may be pushed in by the pushing portion 36a by an amount corresponding to the width of the joining portion B. Instead of the air nozzle 36, the gas nozzle 8 is provided with a similar pushing portion, and when the gas nozzle 8 is inserted inside the bottom end portion 3a, the pushing portion is brought into contact with the bottom end portion 3a and the body portion 3 is pushed in. Good.

  Note that the amount of heat generated by the second heating device 37 is set to, for example, 6000 kcal / hour. This calorific value corresponds to 7 KW for an electric heater. For example, propane gas can be used as the combustion gas supplied to the gas nozzle 8. The pressure of the propane gas can be set to 0.3 kPa. Combustion air is supplied to the gas nozzle 8 together, and the air pressure is set to 2 kPa, for example.

  Returning to FIG. 3, a bending device 41 and a tightening device 43 are provided at stop positions P6 and P7 following the second heating device 37, respectively. The bending device 41 is a device that bends the bottom end portion 3a of the body portion 3 inward with a mold (not shown) (see FIG. 1). By the processing of the bending apparatus 41, the bottom end portion 3a of the body portion 3 is bent so that the folded portion 6a of the bottom plate 6 is wrapped. Further, the fastening device 43 is a device for fastening the bottom end portion 3a in the radial direction over the entire circumference using the roller 9 of FIG. Instead of the tightening device using the roller 9, a type of tightening device that simultaneously tightens the entire circumference of the bottom end portion 3a using a chuck may be provided. A clamping device using a roller and a clamping device using a chuck may be provided side by side.

  The body 3 and the bottom plate 6 that have been tightened by the tightening device 43 are transferred to the stop position P8 in FIG. At the stop position P8, a take-out device 45 for removing the body portion 3 and the bottom plate 6 from the mandrel 22 is provided. The cup in the middle of molding that has been taken out from the mandrel 22 by the take-out device 45 is sent to a curling device (not shown), where the upper end 3b of the barrel 3 is subjected to curling.

  As described above, in the molding machine 20, the first heating device 35 that heats the inner peripheral joint portion A of the bottom end 3a with hot air and the inner peripheral joint portion B of the bottom end 3a as a frame. 2 of the yarn end portion shown in FIG. 2 (b), the inner circumference of the bottom end 3a where the polypropylene resin coat layers 12 and 14 are in contact with each other. The surface and the outer peripheral surface of the folded portion 6a are joined by hot air heating, and the bottom end portion 3a where the polypropylene resin coat layer 12 and the cup base paper 13 are in contact with the inner peripheral surface of the folded portion 6a is based on frame heating. Are joined. Thereby, it is possible to select an appropriate heating method according to the combination of the joining surfaces and reliably join the surfaces, thereby obtaining a highly reliable seal structure.

  In the above embodiment, the position of the bottom plate 6 is changed between the first heating device 35 and the second heating device 37 by operating the slider 22b of the mandrel 22, but the present invention is not limited to such an example. Absent. For example, as shown in FIG. 6, the folded portion 6a is folded slightly larger inside than the inner peripheral surface of the bottom end portion 3a, and in the first heating device 35, between the bottom end portion 3a and the folded portion 6a. The hot air 7 may be blown toward the gap formed in

  In the above embodiment, the heating devices 35 and 37 are arranged side by side at the adjacent stop positions P4 and P5, but the present invention is not limited to such a form. For example, the air nozzle and the gas nozzle may be arranged at the same stop position, and both the nozzles may be selectively inserted into the heating portion so that the hot air heating and the frame heating are completed at one place. That is, the first heating device and the second heating device may be arranged at the same position and share a part (for example, a portion that supports the cup).

  According to the present invention, hot air heating and frame heating were sequentially performed to join the body portion of the paper cup and the bottom plate. The body and bottom plate of the used paper cup both have a polypropylene resin coating layer formed on the inner surface, and the joint portion between the outer peripheral surface of the folded portion of the bottom plate and the inner surface of the body portion is the joint surface between the resin coat layers. The joint portion between the inner peripheral surface of the folded portion of the bottom plate and the folded portion of the bottom end portion of the body portion is a joint surface between the resin coat layer and the cup base paper. The bottom plate is joined by changing the pressure and temperature of the air supplied at the time of hot air heating, the pressure of the air supplied at the time of flame heating, the pressure of the combustion gas, and the mixed gas, and 100 paper cups are manufactured for each condition to join the bottom plate. The number of contents that could be confirmed from the parts was counted. The results are shown in the following table.

  From this result, it was confirmed that the bottom plate and the body can be reliably joined by appropriately setting the respective conditions of hot air heating and frame heating. In particular, it was confirmed that the temperature of hot air is preferably in the range of 500 ° C. or higher and 650 ° C. (see Samples A and F).

The figure which shows the schematic procedure of the shaping | molding method of the paper cup which concerns on one form of this invention. The joint part of the paper cup shape | molded by the method of FIG. 1 is shown, (a) is an enlarged view of the overlapping part of a trunk | drum, (b) is an enlarged view of a thread | yarn bottom part. FIG. 2 is a schematic plan view of a paper cup molding machine used to implement the method of FIG. 1. Sectional drawing which shows the outline | summary of the 1st heating apparatus contained in the molding machine of FIG. Sectional drawing which shows the outline | summary of the 2nd heating apparatus contained in the molding machine of FIG. The figure which shows the modification of a 1st heating apparatus. The figure which shows other embodiment regarding the structure which moves a trunk | drum and a baseplate relatively after the heating by hot air.

Explanation of symbols

3 Body 3a Bottom end 6 Bottom plate 6a Turned back 10 Paper cup

Claims (3)

A first member and a second member are formed from a material provided with a polypropylene resin coat layer on one side of the paper, and an end of the first member is in contact with the coat layer of the second member. While bending the second member so as to be wrapped by the second member, the first member and the second member are joined together with a first joint portion where polypropylene resins are in contact with each other, and polypropylene resin. In a method for forming a paper container to be joined with a second joining portion that comes into contact with paper,
The method for forming a paper container, wherein the first joint portion is heated with hot air, and the second joint portion is heated with a frame. The first bonding portion includes a bonding surface on the side where the coat layer of the first member is provided and a bonding surface on the side where the coat layer of the second member is provided,
The method for forming a paper container according to claim 1, wherein at least one of the bonding surfaces is heated with hot air, and then the bonding surfaces are pressed against each other. The second bonding portion includes a bonding surface on the side where the paper of the first member is exposed and a bonding surface on the side where the coat layer of the second member is provided,
The method for forming a paper container according to claim 1, wherein at least one of the joining surfaces is heated by a frame, and then the joining surfaces are pressed against each other.

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