Paper container and paper container manufacturing method

Abstract

This paper container comprises: a cylindrical body portion formed from a paper body member; a flange portion which is formed by rolling one end of the body member outward and which is coated with a thermoplastic resin, a sealing material being bonded to the flange portion by heat sealing; and a bottom portion formed by the other end of the body member and a bottom member. The flange portion has a level difference portion having a prescribed height and a prescribed width at the outer peripheral end of the upper surface thereof. The level difference portion has, in at least a portion thereof in the circumferential direction, a protruding portion that protrudes outward in the radial direction of the body portion from a side surface of the level difference portion. At least a portion of the upper surface of the protruding portion is bonded to the sealing material.

Description

Paper container and paper container manufacturing method

[0001] The present invention relates to a paper container for food and beverages and a method for manufacturing the same.

[0002] BACKGROUND ART Conventionally, widely used paper containers (paper cups) for food and beverages are those which have a body made of a sheet-like material with a side seam (bonded portion) and a bottom attached to the inside of the body, the open end of which is sealed with a film-like lid (top seal material).

[0003] The open end of the container has a flange portion that faces outward from the container, and after the container is filled with contents such as a beverage, a lid material is attached to the flange portion by, for example, heat sealing.

[0004] The following Patent Document 1 describes forming the flange portion (mouth roll) so that its cross section is circular (curled).

[0005] The following Patent Document 2 describes that the flange portion (cup rim portion) is pressed from above and below to be formed flat.

[0006] JP-T-2008-507458A JP-A-2004-042987A

[0007] However, because the paper cups described above have a seam (glued part) in the body, a sealing load is applied to the seam, which is the thickest part when the top is sealed, and if the seal tab is located at this seam, the opening strength becomes high. This situation can occur even under appropriate sealing conditions.

[0008] In view of the above circumstances, an object of the present invention is to provide a paper container that can improve the openability of a top seal material and a method for manufacturing such a paper container.

[0009] To achieve the above object, one embodiment of the present invention provides a paper container comprising: a cylindrical body portion formed from a paper body member; a flange portion formed by folding one end of the body member outward, coated with a thermoplastic resin, and heat-sealed with a sealing material; and a bottom portion formed by the other end of the body member and a bottom member. The flange portion has a step portion at the outer peripheral edge of its upper surface. The step portion has a protrusion, at least in part of its circumferential direction, that protrudes from the side surface of the step portion radially outward of the body portion. At least a portion of the upper surface of the protrusion is adhered to the sealing material.

[0010] With this configuration, when the sealant is heat-sealed, the molten thermoplastic resin of the sealant and flange flows onto both circumferential sides of the convex portion, preventing resin pooling at the stepped portion of the convex portion where stress concentrates when opening, improving ease of opening. Furthermore, while the sealant is adhered to the convex portion, the seal strength between adjacent convex portions is weakened, and stress concentrates on the convex portion when opening, improving the ease of opening the top sealant.

[0011] The flange portion of the body portion has an overlapping portion where the body members overlap and an overlapping step portion formed on the side of the overlapping portion in the circumferential direction of the body portion, and the convex portion may be provided on at least the overlapping portion.

[0012] This makes it possible to improve the ease of opening, even when a seal tab is provided at the overlapping portion (the portion corresponding to the side seam portion) where a seal load is applied and the opening strength is particularly high.

[0013] The protrusions may be provided at a predetermined pitch in the circumferential direction so that at least one protrusion is provided across the width of the overlapping portion of the flange portion.

[0014] This improves the ease of opening the container regardless of whether the seal tab is provided at the overlapping portion (side seam portion) or anywhere around the flange in the circumferential direction, eliminating the need to adjust the position of the seal tab and the overlapping portion (side seam portion).

[0015] The step portion may have a plurality of the protruding portions in the circumferential direction and a recessed portion formed by adjacent protruding portions. In this case, the recessed portion may be formed so as to cross the overlapping step portion.

[0016] As a result, when the sealing material is heat-sealed, the molten resin in the convex portions at the overlapping portions (side seams) flows into the concave portions between adjacent convex portions, and the molten resin that has flowed in fills the gap between the sealing material and the step, thereby preventing leakage of the filled contents.

[0017] A paper container manufacturing method according to another embodiment of the present invention includes joining the sides of a paper body member to form a cylindrical body portion, joining one end of the body member to a bottom member to form a bottom portion, rolling the other end of the body member outward to form a curled flange portion, and press-molding the outer peripheral edge of the flange portion to form a step portion, and forming a convex portion that protrudes radially outward from the side of the step portion on at least a portion of the circumferential direction of the step portion.

[0018] As described above, according to the present invention, it is possible to provide a paper container and a method for manufacturing a paper container that can improve the openability of the top seal material. However, this effect does not limit the present invention.

[0019] 1. A perspective view showing the appearance of a paper cup according to one embodiment of the present invention. A view showing the front appearance of the paper cup. A plan view of the paper cup. An enlarged view of part F in FIG. 3. An enlarged view of part E in FIG. 1, which is a cross-sectional view A-A and a cross-sectional view B-B of FIG. 4. A view showing experimental results of the openability of the flange part of the paper cup in comparison with a comparative example. A cross-sectional view showing the flange part of the paper cup in comparison with a comparative example. A flowchart showing the manufacturing process of the paper cup. A perspective view showing the appearance of a paper cup according to a modified example of the present invention. A plan view of the paper cup of FIG. 9. A perspective view showing the appearance of a paper cup according to another modified example of the present invention. A plan view of the paper cup of FIG. 11.

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0021] [Appearance of Paper Cup] Fig. 1 is a perspective view showing the appearance of a paper cup as a container according to one embodiment of the present invention. Fig. 2 is a view showing the front appearance of the paper cup, part of which is shown in cross section. Fig. 3 is a plan view of the paper cup.

[0022] As shown in these figures, the paper cup 100 according to this embodiment has a body 1 and a bottom 2 .

[0023] The body 1 is made by punching out a fan-shaped blank (body member) from a paper material (base paper) that is coated (laminated) with a thermoplastic resin such as polyethylene, polypropylene, or polyester, and then wrapping the blank around a cylindrical mold and gluing the side edges together. The gluing of the side edges together forms a side seam 4 on the top and bottom of the side of the body 1.

[0024] The bottom 2 is made by drawing a circular bottom paper (bottom member) punched out from the same paper material as the body 1, and then adhering it to the inside of the lower end of the body 1 at the same time as adhering the body 1. The bottom 2 may also be made of a material other than paper, such as resin.

[0025] The bottom end of the body 1, to which the bottom 2 is attached, has a paper material folded inward and pressed against it. The top end of the body 1 has a flange 3 formed by folding one end of the body material outward, and the body 1 is open at this flange 3.

[0026] After the paper cup 100 is filled with contents such as beverages or ice, a sealing material such as polyethylene film is heat-sealed to the flange portion 3, thereby sealing the paper cup 100.

[0027] The paper material used as the raw material for the body 1 and bottom 2 may be made up of multiple layers, for example. In addition to the thermoplastic resin laminate layer, the paper material may also be laminated with a synthetic resin layer, a foam layer, a metal layer, an inorganic vapor deposition film, or the like.

[0028] To make the paper cup 100 less likely to break when the contents are hard objects such as ice, the body 1 and bottom 2 may be further laminated with a resin film such as polyethylene terephthalate.

[0029] The flange portion 3 is provided with a step portion 33, and the step portion 33 is formed with a convex portion 41 and a concave portion 42. These will be described in detail below.

[0030] As shown in FIG. 2 , the flange portion 3 has an overlapping portion 34 where two overlapping body members are wrapped around the portion corresponding to the side seam portion 4, and an overlapping step portion 35 (the boundary between the overlapping portion 34 and a portion where the body members do not overlap) formed on the side of the overlapping portion 34 in the circumferential direction of the body portion 1.

[0031] [Details of the flange portion] Fig. 4 is an enlarged view of part F in Fig. 3. Fig. 5 is an enlarged view of part E in Fig. 2, which is a cross-sectional view taken along line A-A in Fig. 4 (Fig. 4A) and a cross-sectional view taken along line B-B in Fig. 4 (Fig. 4B).

[0032] As shown in FIG. 5, the flange portion 3 has a sealing surface 31 to which the sealing material is adhered, a curled portion 32 around which the body portion 1 is rolled, and a step portion 33.

[0033] The width A (length in the X direction) of the flange portion 3 is greater than the height B (thickness: length in the Y direction) of the flange portion 3. In other words, unlike the conventional round curl shape, the flange portion 3 of this embodiment has a shape that is flattened in the height direction (Y direction).

[0034] The width A of the flange portion 3 is, for example, 2 to 5 mm, and the thickness B of the flange portion 3 is about 1 to 1.5 mm, which is four times or more the thickness T of the paper material (for example, 0.3 mm).

[0035] A space S is formed inside the curled portion 32. The space S is secured to be equal to or larger than the thickness T of the paper material in the Y direction (approximately 1.5 times the thickness T in the example shown in the figure), for example.

[0036] The step portion 33 is formed at the outer peripheral edge of the upper surface of the flange portion 3. As will be described later, the step portion 33 is formed by press-molding the outer peripheral edge of the rounded flange portion.

[0037] By providing the step portion 33, when the seal material is sealed, the seal head does not come into contact with the step portion 33 but only comes into contact with the inside of the flange portion 3 (seal surface 31) (or if it does come into contact, it is only weak contact), thereby preventing deformation of the outer diameter of the opening of the flange portion 3. Furthermore, when the seal material is opened, the point of action of the fulcrum of the opening force (the boundary between the body portion 1 and the flange portion 3) is located inside the outer peripheral edge of the flange portion 3 (the starting point of the step portion 33), so the moment of force is smaller, which is effective in making it easy to open (easy peel). Furthermore, when providing the step portion 33, pressing the curl (crushing it once before sealing) can suppress deformation of the seal head and the flange portion 3 when the seal material is opened.

[0038] Here, the height C of the step portion 33 (the distance between the sealing surface 31 and the bottom surface of the step portion 33) is set to be larger than the thickness T of the paper material, for example, about 0.7 mm.

[0039] 4 and 5, a plurality of protrusions 41 are formed in the circumferential direction of the step portion 33, protruding from the side surface of the step portion 33 outward in the radial direction of the body portion 1, and a recess 42 is formed between adjacent protrusions 41. As will be described later, the protrusions 41 and the recess 42 are formed by press molding simultaneously with the step portion 33.

[0040] The protrusions 41 are provided at a predetermined pitch (approximately 7 mm in the example shown in the figure) in the circumferential direction. The pitch is designed (less than approximately 9.5 mm) (less than 12°) so that one or more protrusions 41 are included in the joining width (approximately 9.5 mm) of the overlapping portion 34 (side seam portion 4).

[0041] As shown in FIG. 5, the upper surface of the protrusion 41 is shared with the sealing surface 31, and is sealed together with the sealing surface 31 when the sealing material is sealed.

[0042] The protruding width H of the convex portion 41 shown in FIG. 4 (the distance between the outer end of the convex portion 41 and the outer end of the concave portion 42) is, for example, equal to or greater than the thickness T of the paper material (for example, 1.2 to 1.7 mm). The larger the protruding width H, the easier it is for the molten resin to flow into the concave portion, making it even more difficult for resin to accumulate at the step of the convex portion, improving ease of opening. A minimum protruding width for improving openability can be ensured. Furthermore, the convex portion 41 can be formed more clearly (at an acute angle), improving the openability of the seal material.

[0043] 6 is a diagram showing the results of an experiment on the openability of the flange 3 of the paper cup 100, in comparison with a comparative example. As the comparative example, a flange 3 similar to that of the present embodiment was used, except that it did not have the protrusion 41.

[0044] For both the flange portion 3 of this embodiment and the flange portion of the comparative example, the overlapping portion 34 (side seam portion 4) was positioned at the 0 o'clock position in the circumferential direction, and seal tabs were provided at four locations shifted by 45 degrees from there: the 3 o'clock position, the 6 o'clock position, and the 9 o'clock position.The sealant was sealed under appropriate sealing conditions, and the opening strength when opened was measured.

[0045] As shown in the figure, in the flange portion of the comparative example, the opening strength at the overlapping portion (side seam portion) (0 o'clock) where the sealing load is applied is always stronger than the opening strength at the other three locations (3 o'clock, 6 o'clock, and 9 o'clock).

[0046] In contrast, in the flange portion 3 according to this embodiment, the opening strength at the overlap portion 34 (side seam portion 4) was not stronger than that at the other three locations, and the overall average opening strength was low.

[0047] This is thought to be because, when sealing, the molten resin from the sealing material and the inner surface of the paper cup 100 escapes into the recess 42, preventing resin from pooling at the protrusion 41, which is the starting point for opening, and improving ease of opening. Also, when sealing the sealant, the protrusion 41 acts as a support, preventing the seal head from strongly hitting the recess 42, and forming an unattached or weakly adhered portion of the sealant, weakening the seal strength of the recess 42, and when opening the sealant, even if the seal tab is located at the overlapping portion 34 (side seam portion 4), stress is concentrated on the protrusion 41, improving ease of opening.

[0048] Here, the sealing strength of the flange portion 3 in this embodiment compared with other flange portions will be described. Figure 7 is a cross-sectional view showing the flange portion 3 in comparison with two comparative examples A and B.

[0049] Comparative example A in the same figure is a flange portion that does not have the convex portion 41 and concave portion 42 like the flange portion 3 of this embodiment, and although a step portion and an internal space are formed, the height is smaller than the step portion 33 of this embodiment.

[0050] In addition, Comparative Example B in the same figure is a flange portion in which the curled portion of the flange portion is crushed (so-called flange press processing) so as to eliminate any gaps, and does not have any stepped portions, convex portions, or concave portions.

[0051] Although not shown in the figure, the inventors measured the sealing strength of the sealing material for each of these three flange portions, and found that the sealing strength was highest for flange portion 3 of this embodiment, followed by comparison example A, and lowest for comparison example B.

[0052] This is thought to be because, although the total area of ​​the sealing surface 31 in Comparative Example A is smaller than that in Comparative Example B, and the sealing head hits harder during sealing, which has the effect of improving sealing strength, the flange portion 3 of this embodiment has a larger height C (Figure 5) of the step portion 33 and an even smaller total area of ​​the sealing surface 31 than in Comparative Example A, and the sealing head hits harder during sealing, which results in a larger resin accumulation on the inner diameter side of the flange portion 3 and higher sealing strength.

[0053] In this embodiment, the height C of the step portion 33 was able to be made large because, for the press processing of the step portion 33, the convex portion 41, and the concave portion 42, the flange portion 3 of this embodiment uses a mold having a convex portion with a larger convex surface area than the convex portion of the mold used in comparison example A, which increases the area of ​​the bottom surface of the step portion 33 and increases the amount of paper that escapes from the step portion 33 toward the convex portion 41 and the concave portion 42.

[0054] In addition, in this embodiment, the seal head can be applied more firmly to the step portion 33 (and the convex portion 41) because the flange portion 3 has more bending (the convex portion 41 and the concave portion 42), which increases its strength and makes it less likely for springback (the flange step to return) to occur when pressed by the seal head.

[0055] Furthermore, the large height C of the step portion 33 not only improves the sealing strength, but also makes it possible to form a clearer boundary between the convex portion 41 and the concave portion 42, making it less likely for resin to accumulate in the convex portion 41, thereby improving the ease of opening compared to the above comparison example A.

[0056] [Manufacturing Method of Paper Cup] Next, a description will be given of a manufacturing method of the paper cup 100. Fig. 8 is a flowchart showing the flow of the manufacturing process of the paper cup 100.

[0057] As shown in the figure, first, a fan-shaped blank is punched out from the paper material laminated with the thermoplastic resin, and both ends of the blank are melted with a gas burner or the like and then wrapped around a cylindrical mold and glued together to form the body 1 (step 61).

[0058] A circular bottom paper sheet punched from the same paper material as above is drawn and vacuum-adsorbed onto the cylindrical mold, and is simultaneously adhered to the ends of the body 1 and to the inside of the lower end of the body 1. The lower end of the body 1 is then folded toward the bottom 2 and crimped, thereby joining the bottom 2 to the body 1 (step 62).

[0059] Next, a curling process is performed in which the upper end of the body 1 is rotated by a tool and curled outward, thereby forming a flange portion (round curl) having a circular cross section in the radial direction (X direction) of the body 1 (step 63).

[0060] At this time, before the body 1 is rolled up, the vicinity of its upper end is melted in the circumferential direction by hot air, a gas burner, ultrasonic waves, or the like, and then rolled up, thereby bonding adjacent pieces of paper material together inside the curled portion 32. Furthermore, by forming this adhesive portion, a space S is also formed inside the curled portion 32.

[0061] Next, the circular cross-sectional flange is pressed using a mold having unevenness formed on its outer periphery along the shapes of the stepped portion 33 and the convex portions 41 and concave portions 42, thereby forming the stepped portion 33, the convex portions 41 and concave portions 42, and forming the flange 3 that is flattened in the height direction (horizontally elongated in cross section) (step 64). This produces the paper cup 100 with an open top.

[0062] Then, the paper cup 100 is filled with ice, beverages, or other contents, and the sealing material is heat-sealed to adhere to the sealing surface 31 of the flange portion 3 (and the upper surface of the convex portion 41), thereby sealing the paper cup 100 (step 65).

[0063] During this heat sealing, the convex portions 41 are sealed while the concave portions 42 are partially weakly sealed, thereby improving the ease of opening as described above.

[0064] As described above, an overlapping portion 34 where two body members overlap is formed in the portion of the flange 3 corresponding to the side seam portion 4, and an overlapping step portion 35 is formed at the boundary with the portion of the flange 3 on which only one body member is formed, so that a gap occurs in the overlapping step portion 35 when the sealing material is heat-sealed. However, in this embodiment, when the convex portion 41 and the concave portion 42 are formed in the flange 3, the concave portion 42 is press-molded so that it crosses the overlapping step portion 35 of the flange 3, thereby reducing the gap in the overlapping step portion 35. In particular, because the concave portion 42 crosses the overlapping step portion 35, when the sealing material is heat-sealed, the molten resin in the convex portion 41 flows into the concave portion 42, filling the gap and preventing leakage of the filled contents.

[0065] [Summary] As described above, according to this embodiment, the molten thermoplastic resin of the top seal material and flange portion 3 flows into the recess 42 of the flange portion 3, so that resin does not accumulate at the protrusion 41 (the step portion thereof), which is the starting point for stress concentration when opening, and the recess 42 has a weaker seal strength, thereby improving the openability of the top seal material even under appropriate sealing conditions.

[0066] [Modifications] The present technology is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present technology.

[0067] The pitch of the convex portions 41 shown in the above-described embodiment can be changed as appropriate. For example, as shown in Figures 9 and 10, the pitch of the convex portions 41 may be smaller than that of the above-described embodiment. In both figures, the pitch of the convex portions 41 is about 3.5 mm, half that of the above-described embodiment. As a result, the circumferential width of the concave portions 42 is also about half that of the above-described embodiment.

[0068] 11 and 12, the size and pitch of the protrusions 41 may be larger than those of the above-described embodiment. In both figures, the pitch of the protrusions 41 is about two-thirds that of the above-described embodiment, and the circumferential width of the protrusions 41 is about three times that of the above-described embodiment. This also makes the circumferential width of the recesses 42 relatively smaller.

[0069] In the above-described embodiment, the convex portion 41 and the concave portion 42 are formed over the entire circumferential surface of the step portion 33, but they may be formed over only a portion of the step portion 33. In this case, for the reasons described above, the convex portion 41 and the concave portion 42 may be provided at least in the overlap portion 34 (side seam portion 4).

[0070] In the above-described embodiment, a space S was formed in the flange portion 3, but as long as the step portion 33, convex portion 41, and concave portion 42 can be formed, the space S may not be formed and the flange portion 3 may be formed in a flatter shape.

[0071] The shapes of the flange portion 3 and the step portion 33 are not limited to those shown in FIG. 2, and the shapes of the convex portion 41 and the concave portion 42 can also be changed accordingly.

[0072] For example, in the above-described embodiment, the convex portions 41 are provided so as to protrude radially outward from the side surface of the step portion 33, and the concave portions 42 are formed as portions of the side surface of the step portion 33 between adjacent convex portions 41. However, the convex portions 41 may be provided so as to protrude from the side surface of the step portion 33 as described above, while the concave portions 42 may be provided so as to recess from the side surface of the step portion 33 radially inward of the body portion 1. That is, in this case, the side surface of the step portion 33 includes areas where the convex portions 41 are formed, areas where the concave portions 42 are formed, and areas where neither the convex portions 41 nor the concave portions 42 are formed. However, the convex portions 41 and the concave portions 42 may be formed alternately, with no areas where neither the convex portions 41 nor the concave portions 42 are formed.

[0073] In the above-described embodiment, the body 1 and the bottom 2 are manufactured as separate parts, and the paper cup 100 is manufactured by adhering the bottom 2 to the body 1. However, a container such as a paper cup may also be manufactured by integrally forming the body and the bottom from a single sheet of paper material, and in this case, the flange portion can be formed in the same manner as in the above-described embodiment.

[0074] In the above-described embodiment, the paper cup 100 is formed by molding the body 1 having the side seam 4 and the bottom 2 from paper material that has been coated in advance with a thermoplastic resin and then connecting the two. However, the paper cup 100 may be formed as a composite paper container by molding the body and bottom from paper material that is not coated with a thermoplastic resin, joining the body (side seam) and the bottom with a resin (adhesive) to form a paper container, and then attaching a resin film to the inner surface of the paper container by vacuum and / or pressure molding.

[0075] In the above embodiment, a paper cup 100 is shown as a container, but the use of the container is not limited to a cup, and it may be something that holds food such as sweets, for example.

[0076] DESCRIPTION OF SYMBOLS 1: Body 2: Bottom 3: Flange 4: Side seam 31: Sealing surface 32: Curl 33: Step 34: Overlapping 35: Overlapping step 41: Convex 42: Concave 100: Paper cup S: Space

Claims

1. A paper container comprising: a cylindrical body portion formed from a paper body member; a flange portion formed by folding one end of the body member outward and coated with thermoplastic resin, and a sealing material adhered by heat sealing; and a bottom portion formed by the other end of the body member and a bottom member, wherein the flange portion has a step portion at the outer circumferential edge of its upper surface, and the step portion has a protrusion, at least in part in the circumferential direction, that protrudes radially outward from the side of the step portion of the body portion, and at least a portion of the upper surface of the protrusion is adhered to the sealing material.

2. A paper container as described in claim 1, wherein the body portion has a side seam portion on a side surface formed by bonding the body members, the flange portion has an overlapping portion where the body members overlap and an overlapping step portion formed on the side of the overlapping portion in the circumferential direction of the body portion, and the convex portion is provided on at least the overlapping portion of the flange portion.

3. A paper container according to claim 2, wherein the convex portions are provided at a predetermined pitch in the circumferential direction so that at least one convex portion is provided in the overlapping portion of the flange portion.

4. A paper container as described in claim 2, wherein the step portion has a plurality of the protruding portions in the circumferential direction and has a recess formed by adjacent protruding portions, and the recess is formed so as to cross the overlapping step portion.

5. A paper container manufacturing method comprising: joining sides of a paper body member to form a cylindrical body portion; joining one end of the body member to a bottom member to form a bottom portion; rolling the other end of the body member outward to form a curled flange portion; and press-molding the outer peripheral edge of the flange portion to form a step portion, and forming a convex portion that protrudes radially outward from the side of the step portion on at least a portion of the circumference of the step portion.

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