Buffer molding method and finished product

Abstract

A method for forming a buffer body involves stretching and shaping a honeycomb core, the honeycomb core comprising a plurality of sheets extending along a width direction, the sheets being arranged along a stretching direction perpendicular to the width direction, each sheet having a plurality of joint portions and a plurality of unjoined portions, the joints of adjacent sheets forming a thick surrounding wall, each thick surrounding wall and each unjoined portion having a top deformable section, a bottom deformable section, and an intermediate section. The total height of the top deformable section and the bottom deformable section is less than the intermediate section, and the top deformable section and the bottom deformable section are bent relative to the intermediate section to form a folded portion to maintain the honeycomb core in a stretched state.

Description

[Technical Field]

[0001] This invention relates to a cushioning packaging material, and more particularly to a cushioning body molding method and the finished product thereof. [Previous Technology]

[0002] Cushioning packaging materials are used to fill the space between boxes and the items inside to protect the items from damage due to impact during transportation. In recent years, the logistics industry has flourished, and related industries, such as the production of cushioning packaging materials, have also prospered.

[0003] Existing cushioning packaging materials are mainly inflatable plastic film and honeycomb type. However, due to environmental protection issues, plastic-reducing cushioning packaging materials will inevitably be the focus of future development.

[0004] In recent years, paper-based cushioning packaging materials have been increasingly widely used because they are more adaptable to environmental requirements in terms of decomposition and dissociation.

[0005] US06871480B1 patent discloses a pleated layer disposed between two continuously rollable flat sheets. The top and bottom of the pleated layer each have a plurality of end edges adhered to the flat sheets.

[0006] US09649823B2 discloses a packaging material comprising a core and at least one liner. The core has a plurality of walls in a three-dimensional geometric pattern. The three-dimensional geometric pattern defines air spaces and enhances the structural strength of the packaging material.

[0007] As can be seen from the above-mentioned conventional technology, although unfoldable packaging materials are gradually being widely used in packaging, the form of packaging materials is still inseparable from corrugated paper, and they are all formed by joining flat sheets with folded parts.

[0008] Logically, the solid portion of existing packaging materials only occupies 5-20% of the total volume after molding, with the remaining volume being expansion space. Therefore, existing packaging materials cause significant transportation difficulties and high costs. Compared to plastics, paper packaging materials have already increased costs; if high transportation costs are added, it will be detrimental to the development of paper packaging materials.

[0009] The basic requirements for manufacturing a finished cushioning body are: (1) a folded extension forming a folded area. (2) at least one flat sheet joined to the folded area to position it. Because the packaging materials of US06871480B1 and US09649823B2 can only be transported after the folded area is positioned, it leads to transportation cost issues.

[0010] CN115593796A discloses a honeycomb grid shock-absorbing paper pad structure and its manufacturing method. The manufacturing method is as follows: First, the shrunken grid shock-absorbing paper pad is unfolded into hexagonal strips. These hexagonal strips are then evenly spaced and bonded together to form a honeycomb grid shock-absorbing paper pad. Then, while maintaining constant tensile stress, the honeycomb grid shock-absorbing paper pad is fed into a beveling scraper. The upper and lower ends of the stretched hexagonal strips are bent to one side. The deformed grid shock-absorbing paper pad is fed into a pair of rollers with a designed gap for shaping and rolling, forming a honeycomb grid shock-absorbing paper pad with a designed thickness. At this point, the upper and lower ends of the hexagonal strips form folded edges at the unbonded areas, while the bonded areas have a central bend.

[0011] The above-mentioned manufacturing method still has some problems. Since the stretched hexagonal paper strip actually has different folding resistance at the unbonded and bonded parts, when the edge is bent at the top and bottom of the unbonded part by the edge scraper, the bonded part is made of two paper pieces bonded together, which has high stiffness and is not easy to be deformed directly by the edge scraper. Therefore, it is necessary to use a pair of rollers with a preset gap for shaping and rolling.

[0012] During the shaping and rolling process, in order to overcome the high stiffness at the bonding point, the gap between these rollers is set to 30-50% of the paper height for feeding and pressing. However, this will severely damage the shock-absorbing effect of the honeycomb grid. Moreover, in order to stabilize the shaping, the paper height will be further compressed to 50-65% of the original height. In addition, bending the middle of the paper strip is actually equivalent to direct compression molding, which will excessively damage the cushioning effect and cause serious impact on production speed and output stability.

[0013] Moreover, the paper strips are bent through high compression at the joint, and the height of the bends is not easy to be consistent, which makes the shockproof paper pad easy to produce an overall uneven state after pressing and shaping.

[0014] In summary, among the methods of using honeycomb cores as packaging materials, the continuous unfolding and shaping method is an important one, which can save high transportation costs and is conducive to environmental protection and reuse. However, how to maintain the paper strips as straight as possible to ensure the best cushioning effect while shaping and stretching the honeycomb core, and also to achieve smooth and fast continuous production, is a problem that urgently needs to be solved. [Summary of the Invention]

[0015] Therefore, one object of the present invention is to provide a method for forming a buffer body that can solve at least one existing problem.

[0016] Thus, the buffer forming method of the present invention includes the following steps: providing a honeycomb core, the honeycomb core comprising a plurality of sheets, each sheet having a plurality of joined portions and a plurality of unjoined portions, the unjoined portions and the joined portions being arranged alternately, for each pair of adjacent sheets, the joined portions of one sheet being respectively joined to the joined portions of another sheet, before the sheets are joined to each other, extending the top and bottom of each sheet to form two continuous chain cuts along a width direction, and dividing each sheet to form a top deformed section, a bottom deformed section and an intermediate section, wherein the height of the sheets along a height direction is substantially equal, the sum of the height of the top deformed section and the bottom deformed section along the height direction of each sheet is less than the height of the intermediate section, the height of the sheets along the height direction is between 1 and 6 cm, and the thickness is between 0.08 mm and 0.2 mm. An unfolding unit is provided to extend the honeycomb core along a stretching direction. In the extended state, the sheets are pressed to form a folded shape by the chain break cuts, so that the honeycomb core becomes a buffer.

[0017] The buffer forming method of the present invention includes the following steps: providing a honeycomb core, the honeycomb core comprising a plurality of sheets, each sheet having a plurality of joined portions and a plurality of unjoined portions, the unjoined portions and the joined portions being arranged alternately, for each pair of adjacent sheets, the joined portions of one sheet are respectively joined to the joined portions of another sheet, before the sheets are joined together, the top and bottom of each sheet are rolled and crushed along a width direction, and the sheets are separated to form a buffer core. The honeycomb core comprises a top deformation section, a bottom deformation section, and an intermediate section. Each of the top deformation section, bottom deformation section, and intermediate section has a rolling-damping portion extending along the width direction at their adjacent locations. The heights of the sheets along a height direction are substantially equal. The sum of the heights of the top and bottom deformation sections along the height direction is less than that of the intermediate section. The heights of the sheets along the height direction are substantially equal, and the heights of the sheets along the height direction are between 1 and 6 cm, with a thickness between 0.08 mm and 0.2 mm. An unfolding unit is provided to extend the honeycomb core along a stretching direction. In the extended state, the sheets are pressed to form a folded shape using the rolling-damping portions, thereby making the honeycomb core a buffer.

[0018] A honeycomb core is provided, the honeycomb core comprising a plurality of sheets, each sheet having a plurality of joined portions and a plurality of unjoined portions, the unjoined portions and the joined portions being arranged alternately, wherein for each pair of adjacent sheets, the joined portions of one sheet are respectively joined to the joined portions of another sheet, before the sheets are joined together, the top and bottom of each sheet are rolled and crushed along a width direction, and each sheet is divided into a top deformed section, a bottom deformed section and an intermediate section, wherein the height of the sheets along a height direction is substantially equal, the sum of the height of the top deformed section and the bottom deformed section along the height direction is less than the intermediate section, the height of the sheets along the height direction is substantially equal, the height of the sheets along the height direction is between 1 and 6 cm, and the thickness is between 0.08 mm and 0.2 mm. An unfolding unit is provided to extend the honeycomb core along a stretching direction. In the extended state, the sheets are pressed to form a folded shape by the chain break cuts, so that the honeycomb core becomes a buffer.

[0019] Another object of the present invention is to provide a buffer that can solve at least one existing problem.

[0020] Thus, the buffer body of the present invention is formed by stretching and shaping a honeycomb core, the honeycomb core comprising a plurality of sheets extending along a width direction, the sheets being arranged along a stretching direction perpendicular to the width direction, each sheet having a plurality of joint portions and a plurality of unjoined portions, the unjoined portions and the joint portions being staggered along the width direction, for each pair of adjacent sheets, the joint portions of one sheet are respectively joined with the joint portions of another sheet, the joint of each joint portion forming a thick surrounding wall, each pair of adjacent sheets forming a plurality of hexagonal honeycomb cells with the unjoined portions, in each hexagonal honeycomb cell, four unjoined portions forming four sides of substantially equal width, and two thick surrounding walls forming a hexagonal honeycomb cell. The wall forms two other sides of substantially equal width. Each thick surrounding wall and each unjoined portion has a top deformable segment extending along the width direction, a bottom deformable segment spaced apart from the top deformable segment along a height direction and extending along the width direction, and an intermediate segment extending along the width direction and between the deformable segments. The total height of the top deformable segment and the bottom deformable segment is less than the height of the intermediate segment. Each thick surrounding wall, corresponding to the top and bottom in the height direction, is bent with the top deformable segment and the bottom deformable segment to form two folded portions extending from opposite ends of the intermediate segment. In each unjoined portion, the unjoined portion, corresponding to the top and bottom in the height direction, is bent with the top deformable segment and the bottom deformable segment to form two folded portions. These folded portions maintain the honeycomb core in an extended state.

[0021] The advantages of this invention are: by providing the folding portions, the honeycomb core can be continuously unfolded and shaped into the cushioning material, which can save high transportation costs and is conducive to environmentally friendly reuse. Furthermore, since the total height of the top deformation section and the bottom deformation section of each sheet is less than the middle section, the middle section of the sheets can be kept from bending during folding, thereby maintaining a better cushioning effect.

Implementation Method

[0023] Before the present invention is described in detail, it should be noted that similar elements are represented by the same numbers in the following description.

[0024] The relevant technical content, features, and effects of the present invention will be clearly presented in the following detailed description of the embodiments with reference to the accompanying drawings. Furthermore, it should be noted that the drawings of the present invention are only for illustrating the structural and / or positional relationships between elements and are not related to the actual dimensions of each element.

[0025] Referring to Figures 1 to 4, the method for forming the buffer body of the present invention is to stretch and form a honeycomb core 1 through a forming machine 100. The honeycomb core 1 includes a plurality of sheets 10 that extend along a width direction Y perpendicular to the stretching direction X.

[0026] The molding machine 100 has an unfolding unit 2 and a pushing unit 3. The pushing unit 3 conveys the honeycomb core 1 along a stretching direction X toward the unfolding unit 2. The unfolding unit 2 extends the honeycomb core 1 along the stretching direction X. When the unfolding unit 2 extends and shapes the honeycomb core 1, it can press the sheets 10 to form a folded shape, so that the honeycomb core 1 becomes a buffer.

[0027] The feeding unit 3 has a drivable rotating wheel 31 and a plurality of levers 32 spaced apart around the rotating wheel 31. After the leading edge of the honeycomb core 1 is pulled open along the stretching direction X with two adjacent sheets 10 (the first sheet 10 of the honeycomb core 1 and its adjacent sheet 10) and hung on the levers 32, the feeding unit 3 is activated to drive the rotating wheel 31 and the levers 32 to rotate. When the levers 32 rotate, they extend between the remaining two adjacent sheets 10 and push the honeycomb core 1 into the unfolding unit 2 for pressing along the stretching direction X.

[0028] The sheets 10 of the honeycomb core 1 are arranged along the stretching direction X. Each sheet 10 has a plurality of joints 11 and a plurality of unjoined portions 12. The unjoined portions 12 and the joints 11 are staggered along the width direction Y. The joints 11 of two adjacent sheets 10 are correspondingly joined together, and a thick surrounding wall 13 is formed at the joint of each corresponding joint 11. The height of each sheet 10 is substantially equal along a height direction Z perpendicular to the width direction Y and the stretching direction X. Each pair of adjacent sheets 10 has a thick surrounding wall 13 and an unjoined portion 12 forming a plurality of hexagonal honeycomb cells. In each hexagonal honeycomb cell, four unjoined portions 12 form four sides of substantially equal length perpendicular to the height direction Z, and two thick surrounding walls 13 form two sides of substantially equal length perpendicular to the height direction Z. In this embodiment, the joint portions 11 of two adjacent sheets 10 are glued together after being rolled with adhesive along the stretching direction X. Alternatively, the joint portions 11 can be joined together by binding instead of adhesive. Furthermore, before the sheets 10 are joined together, each sheet 10 has a continuous chain-break slit 101 (or a rolling crushing process) formed at its top and bottom along the width direction Y, thus forming a top deformed section 102, a bottom deformed section 103, and an intermediate section 104 along the height direction Z. The top deformed section 102 and the bottom deformed section 103 are substantially equal in height along the sheet 10, and their combined height along the sheet 10 is 10% to 50% of the height of the intermediate section 104, more preferably 15% to 30%. Referring to Figure 5, each of the thick surrounding walls 13 utilizes the chain break slits 101 at its top and bottom in the height direction Z, and the top deformed section 102 and the bottom deformed section 103 are bent to form two folded portions 14 extending from opposite ends of the middle section 104. As shown in Figure 6, in each unjoined portion 12, the top and bottom of the unjoined portion 12 also utilize the chain break slits 101 at its top and bottom in the height direction Z, and the top deformed section 102 and the bottom deformed section 103 are bent to form two folded portions 14 extending from opposite ends of the middle section 104. These folded portions 14 keep the honeycomb core 1 in an extended state.

[0029] Each of the sheets 10 of the honeycomb core 1 can be made of environmentally friendly materials such as recyclable fiber materials or biodegradable materials. Preferably, each of the sheets 10 is recycled paper with a basis weight of 80g / m2 to 200g / m2, a thickness of 0.08mm to 0.2mm, a length of 10cm to 80cm along the width direction Y, a length of 1cm to 6cm along the height direction Z, and a length of 0.5cm to 5cm along the width direction Y for each of the unbonded portions 12. In this embodiment, each of the sheets 10 is made of recycled paper with a basis weight of 120g / m2, a thickness of 0.12mm, a length of 30cm along the width direction Y, a length of 2cm along the height direction Z, a length of 2cm along the width direction Y for each of the unbonded portions 12, and a length of 0.9cm along the width direction Y for each of the bonded portions 11.

[0030] Regarding the chain break cutting on the sheet 10, it can be formed by winding and feeding the paper and using a rolling chain break cutter before the paper is cut to form the sheet 10. The chain break pattern can be of various geometric shapes, as long as the two chain break patterns have an appropriate spacing. In this embodiment, a long strip of chain break is used, with the longest distance between each chain break being 0.2 mm and the relative spacing being 0.2 mm.

[0031] Referring to Figure 7, the rolling and crushing process on the sheets 10 can be performed by winding and feeding the paper and rolling and crushing the fibers to form the top deformed portion 101 and the bottom deformed portion 102 on each sheet 10 before the paper is cut into sheets. The two portions and the middle section 104 will form a small deformation resistance characteristic. At this time, the stretching and shaping buffer can be easily and continuously pressed out by pressing.

[0032] Regarding the unfolding unit 2, in this embodiment, a set of rollers 21 with spacing and capable of clamping and feeding is used. When the unfurled honeycomb core 1 is fed into the rollers 21, it can be pulled by the rollers 21 and resisted by the gravity or friction of the unfurled honeycomb core 1, thereby stably unfolding it. Then, by pressing the relative spacing difference of the rollers 21, each of the top deformation segments 102 and each of the bottom deformation segments 103 are bent to form two folded portions 14. These folded portions 14 can keep the honeycomb core 1 in an extended state.

[0033] Regarding the aforementioned pressing method, in addition to pressing and forming simultaneously during feeding via the roller assembly 21, it can also be pressed out via a clamping mold.

[0034] Therefore, the present invention provides a buffer body. The buffer body is formed by stretching and shaping the honeycomb core 1, which includes a plurality of sheets 10 extending along the width direction Y. The sheets 10 are arranged along a stretching direction X perpendicular to the width direction Y. Each sheet 10 has a plurality of joining portions 11 and a plurality of unjoined portions 12. The unjoined portions 11 and the joining portions 12 are staggered along the width direction Y. For each pair of adjacent sheets 10, the joining portions 11 of one sheet 10 are respectively joined to the joining portions 11 of another sheet 10. The joining points of each joining portion 11 form a thick surrounding wall 13. Each pair of adjacent sheets 10... The equal-thickness surrounding wall 13 and the unjoined portions 12 form a plurality of hexagonal honeycomb structures. In each hexagonal honeycomb structure, four unjoined portions 12 form four sides of substantially equal width, and two thick surrounding walls 13 form two other sides of substantially equal width. Each thick surrounding wall 13 and each unjoined portion 12 has a top and a bottom in a height direction and a top deformable segment 102 and a bottom deformable segment 103 extending along the width direction, and an intermediate segment 104 extending along the height direction Z and between the top deformable segment 102 and the bottom deformable segment 103. The total height of the top deformable segment 102 and the bottom deformable segment 103 is less than the height of the intermediate segment 104. Preferably, the top deformable segment 102 and the bottom deformable segment 103 are substantially equal in height along each of the sheets 10, and the sum of the heights along the height direction Z of each sheet 10 is between 10% and 50% of the height of the intermediate segment 104. Each thick surrounding wall 13 is bent at the top and bottom of the height direction Z by the top deformable segment 102 and the bottom deformable segment 103 to form two folded portions 14 extending from opposite ends of the intermediate segment 104. In each unjoined portion 12, the unjoined portion 12 is bent at the top and bottom of the height direction Z by the top deformable segment 102 and the bottom deformable segment 103 to form two folded portions 14, which keep the honeycomb core in an extended state.

[0035] When the honeycomb core 1 is stretched, the folding portions 14 allow the honeycomb core 1 to be continuously unfolded and shaped into a cushioning material, which can save high transportation costs and is conducive to environmentally friendly reuse. In addition, the total height of the top deformation section 102 and the bottom deformation section 103 is less than that of the middle section 104, so that the middle of the sheet 10 can be kept from bending when the edges are folded, thus maintaining a better cushioning effect.

[0036] However, the above description is only an embodiment of the present invention and should not be construed as limiting the scope of the present invention. Any simple equivalent changes and modifications made in accordance with the scope of the patent application and the contents of the patent specification of the present invention shall still fall within the scope of the patent of the present invention. [Simplified Explanation of the Diagram]

[0022] Other features and effects of the present invention will be clearly presented in the embodiments with reference to the drawings, wherein: FIG1 is a plan view of a molding machine, illustrating a buffer molding method of an embodiment of the present invention through the molding machine; FIG2 is a perspective view illustrating the state of a honeycomb core before stretching molding in this embodiment; FIG3 is a plan view illustrating the state of the honeycomb core after stretching molding; FIG4 is a partially enlarged view of FIG3; FIG5 is a cross-sectional view along line V-V in FIG4; FIG6 is a cross-sectional view along line VI-VI in FIG4; and FIG7 is another perspective view illustrating the state of a honeycomb core before stretching molding in another embodiment of the present invention.

Claims

1. A method for forming a buffer body, comprising the following steps: providing a honeycomb core, the honeycomb core comprising a plurality of sheets, each sheet having a plurality of joined portions and a plurality of unjoined portions, the unjoined portions and the joined portions being arranged alternately, wherein for each pair of adjacent sheets, the joined portions of one sheet are respectively joined to the joined portions of another sheet, before the sheets are joined together, extending the top and bottom of each sheet to form two continuous chain slits along a width direction, and dividing each sheet into a top deformed section, a bottom deformed section and an intermediate section, wherein, The sheets are substantially equal in height along a height direction, the top deformed section and the bottom deformed section are substantially equal in height along the sheet, the sum of the height of the top deformed section and the bottom deformed section along the height direction is between 10% and 50% of the middle section, the height of the sheets along the height direction is between 1 and 6 cm, and the thickness is between 0.08 mm and 0.2 mm; and a unfolding unit is provided to extend the honeycomb core along a stretching direction, and in the extended state, the sheets are pressed to form a folding shape by the chain break cuts so that the honeycomb core becomes a buffer body and keeps the middle sections of the sheets from bending.

2. The buffer forming method as described in claim 1, wherein: The sheets are made of fibrous material with a basis weight of 80 g / m2 to 200 g / m2 and a thickness of 0.08 mm to 0.2 mm, and a length of 10 cm to 80 cm along the width direction; a thick surrounding wall is formed at the joint of each of the joints of each pair of adjacent sheets; each of the thick surrounding walls of each pair of adjacent sheets and the unjoined parts form a plurality of hexagonal honeycomb structures; and in each hexagonal honeycomb structure, four unjoined parts form four sides of substantially equal length perpendicular to the height direction, and two thick surrounding walls form two other sides of substantially equal length perpendicular to the height direction.

3. A method for forming a buffer body includes the following steps: providing a honeycomb core, the honeycomb core comprising a plurality of sheets, each sheet having a plurality of joined portions and a plurality of unjoined portions, the unjoined portions and the joined portions being arranged alternately, wherein for each pair of adjacent sheets, the joined portions of one sheet are respectively joined to the joined portions of another sheet; before the sheets are joined together, the top and bottom of each sheet are rolled and crushed along a width direction, and each sheet is divided into a top deformed section, a bottom deformed section and an intermediate section, wherein each of the top deformed section, the bottom deformed section and the intermediate section of each sheet has a rolled and crushed portion extending along the width direction at the adjacent locations, wherein... The sheets are substantially equal in height along a height direction, the top deformed section and the bottom deformed section are substantially equal in height along the sheet, the sum of the height of each top deformed section and each bottom deformed section along the height direction of each sheet is between 10% and 50% of the middle section, the sheets are substantially equal in height along the height direction, the height of each sheet along the height direction is between 1 and 6 cm, and the thickness is between 0.08 mm and 0.2 mm; and a unfolding unit is provided to extend the honeycomb core along a stretching direction, and in the extended state, the sheets are pressed to form a folded shape with the rolling and breaking parts so that the honeycomb core becomes a buffer body and keeps the middle sections of the sheets from bending.

4. The buffer forming method as described in claim 3, wherein: The sheets are made of fibrous material with a basis weight of 80 g / m2 to 200 g / m2 and a thickness of 0.08 mm to 0.2 mm, and a length of 10 cm to 80 cm along the width direction; a thick surrounding wall is formed at the joint of each of the joints of each pair of adjacent sheets; each of the thick surrounding walls of each pair of adjacent sheets and the unjoined parts form a plurality of hexagonal honeycomb structures; and in each hexagonal honeycomb structure, four unjoined parts form four sides of substantially equal length perpendicular to the height direction, and two thick surrounding walls form two other sides of substantially equal length perpendicular to the height direction.

5. A buffer body formed by stretching and shaping a honeycomb core, the honeycomb core comprising a plurality of sheets extending along a width direction, the sheets being arranged along a stretching direction perpendicular to the width direction, each sheet having a plurality of joined portions and a plurality of unjoined portions, the unjoined portions and the joined portions being staggered along the width direction, wherein, for each pair of adjacent sheets, the joined portions of one sheet are respectively joined to the joined portions of another sheet, the joined portions being... A thick surrounding wall is formed at the joint. Each pair of adjacent sheets forms a plurality of hexagonal honeycomb structures with the surrounding walls of equal thickness and the unjoined portions. In each hexagonal honeycomb structure, four unjoined portions form four sides of substantially equal width, and two thick surrounding walls form two other sides of substantially equal width. Each thick surrounding wall and each unjoined portion has a top deformed section extending along the width direction and a bottom deformed section spaced apart from the top deformed section along a height direction and extending along the width direction. The sheet includes a section and an intermediate section extending along the height direction and between the top deformed section and the bottom deformed section. The top deformed section and the bottom deformed section are substantially equal in height along each sheet. The sum of the height of the top deformed section and the bottom deformed section along the height direction of the sheet is between 10% and 50% of the height of the intermediate section. Each thick surrounding wall, corresponding to the top and bottom of the height direction, is bent by the top deformed section and the bottom deformed section to form two folded portions extending from opposite ends of the intermediate section. In the unjoined portion, the unjoined portion corresponds to the top and bottom in the height direction, respectively, by bending the top deformation section and the bottom deformation section to form two folded portions. The folded portions maintain the honeycomb core in an extended state. Each of the sheets has a broken chain slit or rolling damage portion extending along the width direction at the adjacent position of the top deformation section, the bottom deformation section and the middle section. The folded portions are bent relative to the middle section by the broken chain slit or the rolling damage portion. The middle section of the sheets is not bent.

6. The buffer as described in claim 5, wherein, The sheets are made of fibrous material with a basis weight of 80g / m2 to 200g / m2 and a thickness of 0.08mm to 0.2mm. The length along the width direction is 10cm to 80cm, the length along the height direction is 1cm to 6cm, and the length of each of the unjoined portions along the width direction is 0.5cm to 5cm.

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