JP2021054477A - Paper cup for microwave oven - Google Patents

Abstract

To provide a paper cup which is hardly burned even when being used in microwave and is stably self-supportable.SOLUTION: A paper cup 10 for microwave oven includes a cylindrical barrel member 11 whose inner surface and/or outer surface is coated with a thermoplastic resin, and a bottom member 12 whose inner surface and/or outer surface is coated with a thermoplastic resin, and that closes the lower end of the barrel member 11. The lower end of the barrel member 11 is bent to the inside thereof, and is superposed and joined onto the outer surface of the bottom member 12. Parts 15A and 15B of a joined part to the bottom member 12 and the lower end of the barrel member 11 are locally pressed over the whole circumference.SELECTED DRAWING: Figure 2

Description

The present invention relates to a microwave oven paper cup (paper container). "For microwave ovens" does not mean that it is limited to microwave ovens only, but that it can be used in microwave ovens.

Paper cups are widely used not only as containers for instant foods and snacks, but also as containers for prepared foods and beverages. In some cases, these paper cups are heated and cooked in a microwave oven with the contents such as food and drinking water in them.

When a paper cup containing contents is heated and cooked in a microwave oven, there is a problem that the so-called twisted portion formed by extending the lower end of the body of the paper cup may be burnt. It is considered that the amount of heat generated is particularly large (the amount of heat dissipated is not large) at the joint where the papers overlap, heat is easily stored, and charring is likely to occur. On the other hand, in the part in contact with the contents, the heat generated is taken away by the contents, so that charring is unlikely to occur.

Patent Document 1 describes a microwave oven paper cup that is composed of a body and a bottom, and the lower end (threading) of the body is bent inward and joined so as to cover the outer surface of the bottom. There is. Patent Document 2 describes a microwave oven-compatible paper cup in which a joint portion between a body portion and a bottom portion is curled inward to form an annular leg portion.

Japanese Unexamined Patent Publication No. 2003-81358 Japanese Unexamined Patent Publication No. 2003-192043

By bending or curling the lower end of the body (threading) inward and joining it to the bottom to eliminate the threading, it is possible to prevent the occurrence of charring even when heated in a microwave oven. .. However, there may be another problem that the papers are not sufficiently adhered to each other because the papers are piled up in multiple layers at the jointed portion where the twisted portion is joined to the bottom. Inadequate adhesion between papers at the joints impairs the self-sustaining stability of the paper cup.

An object of the present invention is to provide a paper cup which is hard to be burnt even when used in a microwave oven and can be stably and self-supporting.

Another object of the present invention is to reduce the problem of poor adhesion of joints.

The microwave oven paper cup according to the present invention has a tubular body portion whose inner surface and / or outer surface is coated with a thermoplastic resin, and a bottom portion whose inner surface and / or outer surface is coated with a thermoplastic resin and closes the lower end of the body portion. The lower end of the body is bent inward and overlapped with the outer surface of the bottom to be joined, and a part of the joint between the bottom and the lower end of the body is locally pressed over the entire circumference. It is characterized by being done.

Since the lower end of the body is bent inward and overlapped and joined to the outer surface of the bottom, the microwave oven paper cup according to the present invention does not have so-called twisting. A paper cup that does not easily burn when heated by a microwave oven is provided.

A part of the overlapping range (joint part, joint surface) between the bottom part and the lower end part of the body part is locally pressed. That is, in the paper cup according to the present invention, the entire joint between the bottom and the lower end of the body is not pressed, but a part thereof is locally pressed. The joint has a locally pressed portion (range) and a non-pressed portion (range). Since it is a paper cup, the paper is crushed in the locally pressed part (the part where the pressure is strong) compared to the part where it is not pressed (the part where the pressure is weak), and it is pressed as the locally pressed part. A stepped (raised, convex) shape appears at the boundary of the non-existing part.

Focusing on the stepped shape, the microwave oven paper cup of the present invention can be defined as follows.

That is, the microwave oven paper cup according to the present invention has a tubular body portion whose inner surface and / or outer surface is coated with a thermoplastic resin, and a tubular body portion whose inner surface and / or outer surface is coated with a thermoplastic resin to close the lower end of the body portion. A bottom portion is provided, and the lower end portion of the body portion is bent inward and overlapped with the outer surface of the bottom portion to be joined. On the inner surface of the bottom portion, a part of the joint portion between the bottom portion and the lower end portion of the body portion. It is characterized in that a stepped portion is locally formed over the entire circumference.

After bending the lower end of the body (threading part) inward, for example, put the mandrel in the paper cup (the part where the contents enter), or cover the mandrel with the paper cup, and then the lower end of the body (threading part). ) Is bent inward and ultrasonic waves are applied from the outside toward the overlapping range (joint) between the bottom of the paper cup and the lower end of the body, so that the joint is directed toward the mandrel while generating heat in the joint. Can be pressed (pressed, pressurized). When ultrasonic waves are applied, frictional heat is generated at the joint surface between the bottom of the paper cup and the lower end of the body. Since the inner and / or outer surfaces of the body and bottom are coated with a thermoplastic resin, the joints (joint surfaces) are bonded to each other by melting the thermoplastic resin.

By forming a convex part and a concave part in the part of the mandrel that contacts the joint part of the paper cup from the inside, not the whole joint part of the bottom part and the lower end part of the body part but a part of the joint part is locally strongly pressed. Can be done. Strongly pressed areas adhere more strongly than non-strongly pressed areas. The convex portion of the mandrel can be pressed over the entire circumference of the joint.

When the entire joint (joint surface) between the bottom and the lower end of the body is pressed evenly, the pressure at the time of pressing is naturally applied evenly to the entire joint between the bottom and the lower end of the body. This means that the pressure at the time of pressing is dispersed over the entire joint between the bottom and the lower end of the body, and strong pressing may not be possible, resulting in insufficient adhesion between the papers.

According to the present invention, since a part of the joint between the bottom and the lower end of the body is locally pressed over the entire circumference, a part of the joint between the bottom and the lower end of the body can be strongly pressed. As a result, the adhesiveness between the papers (paper that constitutes the body and paper that constitutes the bottom) at the joint can be improved, and the adhesive peeling of the joint (joint surface) between the bottom and the lower end of the body is effective. Can be prevented. Since the joint between the bottom and the lower end of the body is located on the bottom of the paper cup, this improves the self-sustaining stability of the final product, the microwave oven paper cup.

In one embodiment, each of the inside (inside, inner circumference side in the paper cup) and outside (outside, outer circumference side in the paper cup) of the joint between the bottom and the lower end of the body is locally pressed (inner joint by inner pressing, (Outer joint by outer pressing), an annular convex portion is formed on the inner surface of the bottom at a position facing each other between the inner side and the outer side of the locally pressed joint portion. The joint between the bottom and the lower end of the body can be bonded in a well-balanced and strong manner.

The pressing over the entire circumference can be a continuous pressing over the entire circumference. However, if the inner joint and the outer joint are to be formed, either of them may be formed intermittently (formation of the intermittent inner joint, formation of the intermittent outer joint). If both the inner and outer joints are intermittent, an outer joint is formed between adjacent inner joints and, on the contrary, adjacent outer joints. An inner joint may be formed at a corresponding location between the two (staggered arrangement). This form is also included in "pressing over the entire circumference". Further, the joint may be pressed in a mesh shape.

In one embodiment, a heat insulating layer is provided on the outermost layer at the bottom of the paper cup. Even if you put hot contents in a paper cup or the contents are heated by a microwave oven, even if you touch them with your fingers, you will not feel the heat.

A heat insulating layer may be provided on at least one of the outer surface and the inner surface of the body of the paper cup. Insulation effect (heat retention effect) can be expected. Also, you don't have to feel the heat when you touch the body with your hands.

In another embodiment, the outer cylinder member is covered and fixed to the outside of the body portion. In this embodiment as well, a heat insulating effect (heat retention effect) can be expected, and the heat is not felt when the body is touched.

Preferably, an inward barb is formed at the lower end of the outer cylinder member. For example, the above return can be realized by folding the lower end of the outer cylinder member inward or curling the lower end of the outer cylinder member inward. Since a heat insulating space is secured between the body of the paper cup and the outer cylinder member, the heat insulating effect of the microwave oven paper cup can be further enhanced.

It is a partially broken front view of a microwave oven paper cup. It is an enlarged sectional view of an annular joint part. It is a top view of the microwave oven paper cup along the line III-III of FIG. It is a bottom view of the microwave oven paper cup along the IV-IV line of FIG. The bottom molding process is shown. The bottom molding process is shown. The bottom molding process is shown. It shows the bottom molding process and shows the vertical cross-sectional view of the mandrel covered with the paper cup. It is a plane end view of the mandrel along the IX-IX line of FIG. It is a plane end view of the mandrel of a modification. It is a plane end view of the mandrel of another modification. It is a plane end view of the mandrel of still another modification. It is a plane end view of the mandrel of still another modification. It is a plane end view of the mandrel of still another modification. It is a plane end view of the mandrel of still another modification. It is a partially broken front view of the microwave oven paper cup of a modification. It is a partially broken front view of the microwave oven paper cup of another modification. It is a partially broken front view of the microwave oven paper cup covered with the outer cylinder member. It is a partially broken front view of another microwave oven paper cup covered with an outer cylinder member. It is a partially broken front view of the microwave oven paper cup of another modification. It is a partially broken front view of the microwave oven paper cup of still another modification.

Hereinafter, the microwave oven paper cup according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a front view showing a part of a microwave oven paper cup according to an embodiment of the present invention in a broken state. FIG. 2 is an enlarged cross-sectional view of the lower corner of the microwave oven paper cup. FIG. 3 shows a plan view of the microwave oven paper cup along the line III-III of FIG. 1, and FIG. 4 shows a bottom view of the microwave oven cup along the line IV-IV of FIG. In FIGS. 1 and 2, the thickness of the members constituting the paper cup is shown with considerable emphasis for the sake of clarity.

The microwave oven paper cup 10 is composed of a body member 11 and a bottom member 12 whose main strength material is paper. The body member 11 has an inverted truncated cone shape in which the diameter at the top is large and the diameter becomes smaller toward the bottom. The upper end portion of the body member 11 is wound outward (direction away from the portion of the paper cup 10 in which the contents enter, outward), and a so-called curl portion (top curl portion) 11A is formed. The curl portion 11A is covered with a lid (not shown) or joined (bonded or welded).

The lower end of the body member 11 is bent at a right angle to the inside (the direction toward the part where the contents of the paper cup 10 are inserted, the inside) (the part that is bent and along the bottom surface is called the bent part 11B), and further the bent part 11B. The tip of the is folded inward (the folded portion is indicated by reference numeral 11C). The bottom member 12 is circular, and its peripheral edge portion 12A fits snugly into the lower end portion of the body member 11. The peripheral edge portion 12A of the bottom member 12 is folded outward (the folded portion is indicated by reference numeral 12B), and the folded portion 12B of the bottom member 12 is sandwiched between the bent portion 11B and the folded portion 11C of the body member 11. It has been. These sandwiching portions 11C, 12B, and 11B are adhered (bonded, welded) (fixed) to each other at least partially, preferably entirely, but as described later, they are evenly adhered to each other. There is no such thing, and a part of it is strongly adhered.

The inner and / or outer surfaces of the body member 11 and the bottom member 12 are coated with a thermoplastic resin (protective film, resin film) (the illustration of the thermoplastic resin is omitted). Specific examples of the thermoplastic resin include polyethylene (PE), polypropylene (PP), polyester, ethylene-vinyl acetate copolymer and the like. These have the advantage that they can be used not only for preventing the infiltration of contents, but also for ultrasonic welding (crimping).

At the peripheral edge of the outer surface of the bottom member 12 of the paper cup 10, the bent portion 11B and the folded portion 11C of the body member 11 and the folded portion 12B of the bottom member 12 overlap in the vertical direction and are joined to the outer surface of the bottom member 12 in an annular shape. ing. Hereinafter, the entire annular portion joined to the peripheral edge of the outer surface of the bottom member 12 of the paper cup 10 will be referred to as “annular joint 20”. The annular joint 20 has a joint surface between the bottom member 12 and the folded portion 11C of the body member 11, a joint surface between the folded portion 11C of the body member 11 and the folded portion 12B of the bottom member 12, and the folded portion 12B and the body of the bottom member 12. The joint surface of the bent portion 11B of the member 11 is included.

When the bottom member 12 of the paper cup 10 is viewed from the inner surface with reference to FIG. 3, it is confirmed that an annular convex portion (step portion) 12C is formed on the peripheral edge portion of the inner surface of the bottom member 12. This is because in the joining process of the annular joint portion 20, the annular portions on both the inner and outer sides of the annular convex portion 12C (outer pressing range (outer joining portion) 15A, inner pressing range (inner joining portion) 15B) (see FIGS. 1 and 2). ) Is strongly pressed. Details of the joining process of the annular joining portion 20 will be described later.

When the bottom member 12 of the paper cup 10 is viewed from the outer surface with reference to FIG. 4, it is confirmed that the annular joint portion 20 is provided in an annular shape on the peripheral edge of the outer surface of the bottom member 12. On the surface of the annular joint portion 20, substantially rectangular concave surface portions 21 and convex surface portions 22 are alternately formed and arranged in an annular shape. The widths of the concave surface portion 21 and the convex surface portion 22 (the length in the annular direction) are almost the same, or the width of the concave surface portion 21 is slightly longer. In the paper cup 10 of this embodiment, 16 concave portions 21 and 16 convex portions 22 are alternately arranged. The number of concave portions 21 and convex portions 22 can be adjusted as appropriate.

The surfaces of the plurality of concave surface portions 21 are at substantially the same height position, and the surfaces of the plurality of convex surface portions 22 are also at substantially the same height position. The convex portion 22 protrudes slightly outward (that is, toward the bottom of the paper cup 10) from the concave portion 21. Further, the boundary 25 between the concave surface portion 21 and the convex surface portion 22 is slightly inclined so as to bite toward the base of the convex surface portion 22. Since the base of the convex portion 22 bites into the boundary 25 between the concave portion 21 and the convex portion 22, the concave portion 21 and the convex portion 22 slightly overlap each other, and the step between the concave portion 21 and the convex portion 22 becomes large. It's getting pretty small. When viewed from the bottom surface, the boundary 25 between the concave surface portion 21 and the convex surface portion 22 looks like a short streak (ruled line) extending in the direction toward the center of the bottom member 12. When the 16 concave surface portions 21 and the 16 convex surface portions 22 are arranged alternately, 32 streaks (ruled lines) appear at intervals (equally angular intervals) in the annular joint portion 20.

If the annular joint 20 is simply bent inward without any treatment, the annular joint 20 will be randomly wrinkled due to the excess portion. If wrinkles are randomly formed, the bottom of the cup (the surface of the annular joint 20) is difficult to flatten, and the cup lacks a sense of stability when it is made to stand on its own. On the other hand, in the above-mentioned paper cup 10, 16 concave surface portions 21 and 16 convex surface portions 22 are regularly and alternately formed and arranged in an annular shape, and the concave surface portion in which the base of the convex surface portion 22 bites. The boundaries (streaks, ruled lines) 25 between 21 and the convex portion 22 are also regularly arranged at equal angular intervals. The surface of the convex portion 22 is at approximately the same height position, and this is regularly present over the entire circumference of the annular joint portion 20. Further, since the surplus portion when the annular joint portion 20 is bent inward is absorbed by the step (bite) between the concave surface portion 21 and the convex surface portion 22, random wrinkles do not occur in the annular joint portion 20. The paper cup 10 can be stably self-supporting.

Since the paper cup 10 has a flat bottom that does not have so-called twisting, it does not easily burn even when heated in a microwave oven.

5 to 7 show a state of manufacturing the above-mentioned paper cup 10. 5 to 7 show the paper cup 10 in an upside down state.

With reference to FIG. 5, first, a paper cup having a so-called thread twist, in which the portion to be the annular joint 20 is not bent, is created.

With reference to FIG. 6, a stamp having a width obtained by dividing the peripheral length of the annular joint 20 into, for example, 32 is pressed from the outside of the annular joint 20 at predetermined intervals to press. The pressed portion becomes the concave portion 21, and the unpressed portion becomes the convex portion 22. The annular joint portion 20 is formed with 16 concave surface portions 21 and 16 convex surface portions 22 alternately arranged in an annular shape. By being pressed from the outside, the entire annular joint 20 is tilted inward.

With reference to FIG. 7, ultrasonic bonding is performed from the outside of the annular bonding portion 20 inclined inward (details will be described below). The annular joint 20 is completely bent and joined to the bottom member 12. Further, the above-mentioned step (bite) is formed at the boundary 25 between the concave surface portion 21 and the convex surface portion 22. A microwave oven paper cup 10 with a flat bottom is completed.

FIG. 8 schematically shows the state of ultrasonic bonding, and shows the vertical cross section of the mandrel used for ultrasonic bonding and the ultrasonic horn. FIG. 9 shows the pressed surface (upper surface) of the mandrel along the IX-IX line of FIG.

The mandrel 30 is made of metal and has an inverted truncated cone shape with a small upper diameter and a larger diameter toward the bottom. A cylindrical cavity 34 is formed in the center to reduce the weight. The outer shape of the mandrel 30 is almost equal to the outer shape of the paper cup 10 (slightly smaller), and the paper cup 10 can be completely covered.

The upper surface of the small diameter is the pressed surface of the mandrel 30. An outer annular convex portion 31 slightly protruding outward (upward) is formed on the outer peripheral edge portion of the surface to be pressed, and an inner annular convex portion 32 is also formed at intervals from the outer annular convex portion 31. An annular groove 33 is formed between these outer and inner annular protrusions 31 and 32. The annular joint 20 of the paper cup 10 is pressed from the inside against the outer annular protrusion 31, the annular groove 33, and the inner annular protrusion 32.

An ultrasonic horn 40 is placed above the mandrel 30. The ultrasonic horn 40 is provided with an annular ultrasonic vibrating surface 41 at its tip, and the ultrasonic vibrating surface 41 faces the pressed surface of the mandrel 30. When the ultrasonic vibration surface 41 vibrates, the ultrasonic vibration is transmitted to the annular joint 20 of the paper cup 10. Since the inner and / or outer surfaces of the body member 11 and the bottom member 12 of the paper cup 10 are coated with the thermoplastic resin as described above, the thermoplastic resin is fine ultrasonic waves at the annular joint 20 of the paper cup 10. It is instantly melted by vibration and pressure and joined to each other.

As described above, since the outer and inner annular protrusions 31 and 32 are formed on the pressed surface of the mandrel 30, the annular joint 20 of the paper cup 10 in contact with the outer and inner annular protrusions 31 and 32 is formed. That is, the outer peripheral portion and the inner peripheral portion, which are a part of the annular joint portion 20, are locally strongly pressed (pressurized) over the entire circumference (formation of the outer joint portion, formation of the inner joint portion). By partially concentrating the pressurization by the ultrasonic horn 40 not on the entire annular joint 20 but on the outer peripheral portion and the inner peripheral portion thereof, the outer peripheral portion and the inner peripheral portion of the annular joint 20 are strongly adhered. This can be done, and the adhesive peeling at the annular joint 20 can be effectively prevented. Since the annular joint 20 is located on the bottom surface of the paper cup 10, this improves the self-sustaining stability of the final product, the microwave oven paper cup 10.

In the annular groove portion 33 formed between the outer and inner annular convex portions 31 and 32 on the pressed surface of the mandrel 30, the annular joint portion 20 of the paper cup 10 is not pressed more strongly than the inner and outer peripheral portions. However, since the thermoplastic resin is melted, the portion of the annular joint 20 corresponding to the annular groove 33 is also welded. Further, since a part of the annular joint portion 20 is pushed into the annular groove portion 33, an annular convex portion (step portion) 12C is formed on the inner surface of the bottom member 12 of the paper cup 10 that has undergone the joining process. (See Fig. 2).

FIG. 10 shows the pressed surface of the mandrel 30A of the modified example, and is different from the mandrel 30 shown in FIG. 9 in that the inner annular convex portion 32A has a wide width. By using the mandrel 30 of this modified example in the joining step, the widths of the outer pressing range 15A and the inner pressing range 15B (see FIG. 2) can be made different in the paper cup 10. A mandrel in which the outer annular protrusion 31 is wider than the inner annular protrusion 32 may be used.

FIG. 11 shows the pressed surface of the mandrel 30B, which is a further modified example. It differs from the mandrel 30 shown in FIG. 9 in that the inner annular convex portions 32B are not continuous and are intermittently arranged in an annular shape at intervals. By intermittently forming the inner annular convex portion 32B, the range pressed against the inner annular convex portion 32B can be pressed more strongly and the adhesiveness can be improved.

Needless to say, the outer annular convex portion 31 may be formed intermittently instead of the inner annular convex portion 32. Further, as shown in a further modification of FIG. 12, both the outer annular convex portion 31A and the inner annular convex portion 32B may be formed intermittently. In the mandrel 30C of the further modification, the inner annular convex portion 32B is arranged at a position corresponding to the adjacent outer annular convex portion 31A, and on the contrary, the inner annular convex portion 32B corresponds to the adjacent inner annular convex portion 32B. The outer annular convex portion 31A is arranged at the location (staggered arrangement).

Only the annular convex portion 35 is formed on the pressed surface of the mandrel 30D of the further modified example shown in FIG. Of the annular joint 20 of the paper cup 10, the portion pressed against the annular convex portion 35 is strongly adhered.

In the mandrel 30E of the further modified example of FIG. 14, an intermediate annular convex portion 35 is further formed between the outer annular convex portion 31 and the inner annular convex portion 32. Of the annular joints 20 of the paper cup 10, the portions pressed against these three annular protrusions 31, 32, and 35 are strongly adhered.

As shown in FIG. 15, a mandrel 30F having a mesh-like unevenness formed on the entire surface to be pressed can also be used. Of the annular joint 20 of the paper cup 10, the portion pressed against the convex portion of the mesh-like unevenness is strongly adhered.

FIG. 16 shows a modified example of the annular joint. In this modification, the peripheral edge portion 12A of the bottom member 12 is folded outward, and the bent portion 11B at the lower end of the body member 11 is welded to the outer surface of the folded portion 12B. In the modified example shown in FIG. 16, the bent portion 11B of the body member 11 and the folded portion of the bottom member 12 are flush with each other so that the end surface of the bent portion 11B of the body member 11 and the end surface of the folded portion 12B of the bottom member 12 are flush with each other. The length of 12B is adjusted. The length of the bent portion 11B of the body member 11 may be increased so that the entire folded portion 12B of the bottom member 12 at the annular joint portion 20 is covered by the bent portion 11B of the body member 11. On the contrary, the length of the folded portion 12B of the bottom member 12 may be longer than that of the bent portion 11B of the body member 11.

FIG. 17 shows yet another modification. In this modification, the heat insulating layer 51 is provided on the outer surface of the bottom member 12. The heat insulating layer 51 is made of foamed plastic such as low-density polyethylene mixed with a foaming agent (sodium hydrogen carbonate, etc.), for example. Foaming occurs by heating the foamed plastic mixed with the foaming agent. The foaming is performed after the paper cup 10 is molded, and the foaming of the joint portion such as the folded portion 12B is suppressed. By providing the heat insulating layer 51 on the bottom member 12, when the paper cup 10 containing the hot contents or the paper cup 10 heated in the microwave oven is held by hand, the heat is not felt even if the finger touches the bottom.

FIG. 18 shows still another modification, in which the body member 11 is covered with the outer cylinder member 13. The outer cylinder member 13 is a tubular body having a diameter slightly larger than that of the lower portion, and the lower end portion is folded inward (folded portion 13A). The body member 11 having the bottom member 12 is completely inserted (fitted) into the outer cylinder member 13 from above. The upper end of the outer cylinder member 13 enters the gap inside the curl portion 11A of the body member 11. A heat insulating space (gap) is formed between the outer surface of the body member 11 and the inner surface of the outer cylinder member 13. The outer cylinder member 13 is fixed to the body member 11 with an adhesive at one or both of the curl portion 11A and the folded portion 13A.

By providing the outer cylinder member 13 on the outside of the body member 11, the heat is not felt even when the body portion of the paper cup 10 is held by hand. In addition, the heat insulation (heat retention) of the entire paper cup 10 is also improved.

As shown in FIG. 19, a curl portion 13B wound inside may be formed at the lower end portion of the outer cylinder member 13. The heat insulating space (gap) between the outer surface of the body member 11 and the inner surface of the outer cylinder member 13 can be increased.

FIG. 20 shows a modified example paper cup 10A in which the heat insulating layer 52 is provided on the outer surface of the body member 11. The heat insulating layer 52 is formed by, for example, foaming low-density polyethylene. Foaming is performed after forming the paper cup 10A, and foaming of the joint portion such as the folded portion 12B is suppressed. You do not feel the heat when you hold the body of the paper cup 10A containing the hot contents or the paper cup 10A heated in the microwave oven by hand. In addition, a heat retaining effect can be expected.

When the body member 11 (paper layer) is heated, the water contained in the body member 11 evaporates. The water that evaporates from the body member 11 can be used to foam the low density polyethylene. In order to prevent the evaporated water from escaping, a water vapor blocking layer, for example, medium density polyethylene is preferably provided on the inner surface of the body member 11 (not shown), thereby reducing the water content contained in the body member 11. It can be efficiently evaporated toward high density polyethylene. A rough surface may be formed on the outer surface (surface) of the low-density polyethylene (insulation layer) 52 that has been foamed by corona treatment or the like. It is possible to easily attach ink for printing to the outer surface of the heat insulating layer 52.

FIG. 21 shows a modified example paper cup 10B in which the heat insulating layer 53 is provided on the inner surface of the body member 11. For example, a polyethylene layer containing a foaming agent (for example, sodium hydrogen carbonate) is laminated on the inner surface of the body member 11, and a polyethylene layer containing no foaming agent is further laminated on the inner surface thereof. By heating, the polyethylene layer containing a foaming agent foams to form a heat insulating layer 53. Foaming of the joint portion such as the folded portion 12B is suppressed. In addition, foaming can be suppressed by not heating the area around the curl portion 11A. Insulation layers can also be provided on both the outer and inner surfaces of the body member 11.

10, 10A, 10B microwave oven paper cup
11 Body member
12 Bottom member
12C Convex part (step part)
13 Outer cylinder member
15A outer joint
15B inner joint
20 Circular joint
21 Concave part
22 Convex surface
30, 30A, 30B, 30C, 30D, 30E, 30F Mandrel
31, 31A Outer annular convex part
32, 32A, 32B Inner annular convex part
33 Ring groove
35 Ring convex part
40 ultrasonic horn
51, 52, 53 Insulation layer

Claims (10)

It has a tubular body whose inner and / or outer surface is coated with a thermoplastic resin, and a bottom portion whose inner and / or outer surface is coated with a thermoplastic resin and closes the lower end of the body.
The lower end of the body is bent inward and is overlapped and joined to the outer surface of the bottom.
A part of the joint between the bottom and the lower end of the body is locally pressed over the entire circumference.
Microwave paper cup. It has a tubular body whose inner and / or outer surface is coated with a thermoplastic resin, and a bottom portion whose inner and / or outer surface is coated with a thermoplastic resin and closes the lower end of the body.
The lower end of the body is bent inward and is overlapped and joined to the outer surface of the bottom.
On the inner surface of the bottom portion, a step portion is locally formed over the entire circumference at a part of the joint portion between the bottom portion and the lower end portion of the body portion.
Microwave paper cup. The inside and outside of the joint between the bottom and the bottom of the body are locally pressed, respectively.
An annular protrusion is formed on the inner surface of the bottom at opposite positions between the inside and the outside of the locally pressed joint.
The microwave oven paper cup according to claim 1 or 2. At least one of the inner and outer joints is intermittently formed,
The microwave oven paper cup according to claim 3. Both the inner and outer joints are intermittently formed.
The outer joint is located between the adjacent inner joints, and the inner joint is located between the adjacent outer joints.
The microwave oven paper cup according to claim 3. The joint is pressed in a mesh pattern,
The microwave oven paper cup according to claim 1 or 2. A heat insulating layer is provided on the outermost layer of the bottom.
The microwave oven paper cup according to claim 1 or 2. A heat insulating layer is provided on at least one of the outer surface and the inner surface of the body.
The microwave oven paper cup according to claim 1 or 2. The outer cylinder member is covered and fixed on the outside of the body.
The microwave oven paper cup according to claim 1 or 2. An inward barb is formed at the lower end of the outer cylinder member,
The microwave oven paper cup according to claim 9.

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