JP2009256682A - Foam sheet of polystyrene-based resin for folding box, and folding box - Google Patents

Abstract

Openable / closable polystyrene-based resin foam sheet for folding box, which can withstand repeated bending operation of the corner portion only when the V-groove processing is performed while leaving only the surface layer portion of the sheet, and its manufacturing method, and Providing folding boxes.
The tensile strength of the sheet surface layer portion remaining when the V-groove is processed is in the range of 6.5 to 9.0 MPa, and the elongation at break of the sheet surface layer portion is 4.25 to 5.10%. And the density of the sheet surface layer portion is in the range of 0.13 to 0.17 g / cm ³ , and the surface hardness of the sheet surface layer on the side opposite to the surface on which the V-groove processing is performed is 65 to 76. A polystyrene-based resin foam sheet for folding boxes, which is within the range. A V-groove B is provided along a line corresponding to a corner portion when the sheet is folded, leaving a sheet surface layer portion of 0.05 to 0.2 mm, and is assembled into a box shape by bending the V-groove. A folding box characterized by
[Selection] Figure 1

Description

  The present invention relates to a folded box used for packaging of food and the like and a polystyrene-based resin foam sheet for folded boxes, and in particular, a folded box capable of providing a folding box that can be opened and closed by improving repeated bending operation durability of a sheet surface layer portion remaining after V-groove processing. The present invention relates to a polystyrene resin foam sheet and an openable / closable folding box.

  Conventionally, as a folding box, side plates are connected to two opposite sides of a substantially rectangular bottom plate, respectively, while two end plates are provided on opposite sides of the bottom plate, and either one of the side plates is provided. A top plate is continuously provided on the side opposite to the side where the bottom plate is continuously provided, and the bottom plate, each side plate, each end plate and the top plate are formed of a foamed resin plate-like body, and the bottom plate and each side plate are connected to each other. Hinges are formed at the connecting portions between the side plates and the top plate, and pivot portions are formed at the connecting portions between the bottom plate and the end plates, and the side plates are substantially perpendicular to the bottom plate. At this time, both end portions of each side plate are assembly boxes that abut each of the end plates substantially perpendicular to the bottom plate, and a convex portion is provided on the contact surface with the end portion of the side plate of each end plate, When concave portions that are detachably fitted to the convex portions are formed at both end portions of each side plate, An assembly box in which the rotating portion is formed so as to be rotatable between a state in which the end plate is substantially perpendicular to the bottom plate and a state in which the end plate falls inward and substantially contacts the bottom plate. Has been proposed (see, for example, Patent Document 1).

The styrene resin extruded foam sheet for folding boxes is a styrene resin extruded foam sheet having a density of 0.05 to 0.2 g / cm ³ and a thickness of 2 to 10 mm, and has at least one surface layer measured by static thermomechanical measurement. The sheet has a maximum shrinkage of 3% or more in the extruding direction, and the sheet has a tensile breaking strength of 14 kgf / 5 cm when a V-cut at an angle of 90 ° is made from the other side of the sheet leaving a thickness of 0.5 mm. A styrene resin extruded foam sheet characterized in that the surface hardness of the V-cut surface is 70 or less has been proposed (for example, see Patent Document 2).

  As a peripheral frame material for forming a container made of a styrene-based foamed resin sheet, it is a peripheral frame material that can be bent along the shape of the bottom plate of the container, and is formed of a polystyrene-based foam sheet, The sheet is divided into approximately four equal parts in the thickness direction, and the bubble shape having a thickness approximately ½ of the central portion of the thickness is 1.05 ≦ MD / VD ≦ 1.8, 1.0 ≦ TD / VD ≦ 1. 8, 0.85 ≦ MD / TD ≦ 1.2, and a bubble shape having a thickness of approximately ¼ of the thickness from both surfaces is 1.4 ≦ MD / VD ≦ 2.5, 1. 3 ≦ TD / VD ≦ 2.2, 0.9 ≦ MD / TD ≦ 1.8 (where MD is the bubble shape in the extrusion flow direction, TD is the bubble shape perpendicular to the MD, and VD is the bubble shape in the thickness direction) And the size of the ½-thick bubble is larger than that of the ¼ surface-side bubble, Circumferential side frame member for a container formed, wherein the hearing is proposed (e.g., see Patent Document 3.).

  Further, the groove of the corner forming portion provided in the band-shaped synthetic resin foam sheet is a plurality of parallel V-shaped foam sheets, and the foam sheet for folded boxes and the bottom plate, There has been proposed a folding box characterized by comprising (for example, see Patent Document 4).

Japanese Utility Model Publication No. 6-37130 Japanese Patent No. 3243332 Japanese Patent No. 3234146 Japanese Utility Model Publication No. 5-3123

Polystyrene resin foam sheets used for folding box applications need to bend each corner flexibly in order to assemble a folded box. However, due to the weakness of the polystyrene resin foam sheet and its poor flexibility, the corner parts If sharp V-groove processing is applied to the surface, cracks may occur at the bent portion. Conventionally, in order to prevent this cracking, a plurality of grooves are provided (see Patent Document 4). The strength of the surface layer is improved by devising the shape of the folded box corner or by adhering a polystyrene film to a polystyrene resin foam sheet. Thus, it has been possible to produce a folded box by V-groove processing.
Recently, after forming a folded box by bending a polystyrene-based resin foam sheet for folded boxes once, not only maintaining its shape, but also a box that can be opened and closed leaving a V-groove processed portion with a thickness of 0.2 mm or less It is being considered for use. However, the conventional polystyrene-based resin foam sheets and folding boxes for folding boxes described in Patent Documents 1 to 4 described above are insufficient to obtain a box that can be opened and closed.

The box of Patent Document 1 is open / closed because the sheet surface layer portion left after the V-groove processing of the foam sheet is easily broken due to repeated bending operations, or the sheet surface layer portion is too hard to close when opening and closing. It is difficult to stably produce possible boxes.
The sheet of Patent Document 2 defines a sheet to be used with a sheet groove breaking strength of the V-groove portion leaving 0.5 mm and the surface hardness of the V-cut surface, but a folding box that completes the shape by bending several times Then, since the surface layer part is left slightly by the V-groove processing, the slight surface layer part is easily cracked by repeated bending operations several tens of times, and it is difficult to provide an open / close type folding box.
The peripheral frame material of Patent Document 3 is intended to improve the flexibility by the bubble size configuration in the thickness direction of the polystyrene-based resin foam sheet, but has not reached the improvement of the flexibility by reinforcing the surface layer portion in the V-groove processing. However, when used in a folded box having a V-groove, there is a possibility that corners lack flexibility and cracks may occur.
Since the foam sheet for folding boxes of Patent Document 4 has a sheet thickness at the corner portion, the perpendicularity of the corner portion is impaired. Therefore, a folding box of an assembly system in which a V-groove is provided in the sheet and bent almost at right angles is formed. It is difficult.

  The present invention has been made in view of the above circumstances, and when the V-groove processing is performed while leaving only the surface layer portion of the sheet, it is possible to withstand repeated bending operation of the corner portion only by the surface layer portion. It aims at provision of a foam sheet, its manufacturing method, and a folding box.

In order to achieve the above object, according to the present invention, the tensile strength of the sheet surface layer portion remaining when V-groove processing is in the range of 6.5 to 9.0 MPa, and the elongation at break of the sheet surface layer portion is 4 The sheet surface layer surface density is within the range of 0.13 to 0.17 g / cm ^{3 and} the surface of the sheet surface layer on the side opposite to the surface on which the V-groove processing is performed. Provided is a polystyrene-based resin foam sheet for folding boxes, which has a surface hardness in the range of 65 to 76.
In the polystyrene-based resin foam sheet for folding boxes of the present invention, it is preferable that the surface hardness (H) of the sheet surface layer side opposite to the surface to be subjected to V-groove processing is in the range of 70 <H <76.
In the polystyrene-based resin foam sheet for folding boxes of the present invention, the density of the entire sheet is preferably in the range of 0.05 to 0.12 g / cm ³ .
The present invention also includes a polystyrene-based resin foam sheet for folding boxes according to the present invention described above, and leaves a sheet surface layer portion of 0.05 to 0.2 mm along a line corresponding to a corner portion when the sheet is folded. A folded box is provided which is provided with a V-groove and is assembled in a box shape by bending the V-groove.
The folding box of the present invention preferably includes a box-shaped main body portion and a lid that closes the opening of the main body portion so as to be openable and closable.

In the polystyrene-based resin foam sheet for folding boxes of the present invention, the tensile strength of the sheet surface layer portion remaining when the V-groove is processed is in the range of 6.5 to 9.0 MPa, and the elongation at break of the sheet surface layer portion is The sheet surface layer surface is in the range of 4.25 to 5.10% and the density of the sheet surface layer portion is in the range of 0.13 to 0.17 g / cm ³ and is opposite to the surface on which the V-groove processing is performed. Since the surface hardness of the sheet is in the range of 65 to 76, when this sheet is subjected to V-groove processing, even if the corner portion is formed only by the sheet surface layer portion remaining by the V-groove processing, the bending operation is repeated particularly. Cracks due to the bending operation are less likely to occur, and a folding box that can be opened and closed can be provided by assembling the folding box by subjecting the polystyrene-based resin foam sheet for folding boxes to V-groove processing.
In addition, a folded box having a corner portion that is sharply formed only by the sheet surface layer portion can be produced.

It is a side view which shows an example of the sheet | seat of this invention. It is a block diagram which illustrates the extruder used for manufacture of the sheet | seat of this invention. It is a perspective view which shows one Embodiment of the folding box which concerns on this invention. It is a perspective view which shows the folding box before an assembly. It is a top view which shows the folding box before an assembly. It is a perspective view which shows the state which stood up the wife board in the assembly process to a folding box. It is a perspective view which shows the folding box which opened the lid | cover.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a view showing an example of a polystyrene-based resin foam sheet (hereinafter abbreviated as a sheet) for folding boxes according to the present invention, FIG. 1 (a) is a side view showing a V-grooved sheet, and FIG. FIG. 3 is a side view showing a state in which the sheet is bent. In FIG. 1, symbol A is a sheet, B is a V groove, and C is a sheet surface layer portion. This sheet A is made of a polystyrene-based resin foam, the tensile strength of the sheet surface layer portion C remaining when the V-groove is processed is in the range of 6.5 to 9.0 MPa, and the density of the sheet surface layer portion is 0. It is characterized by being in the range of .13 to 0.17 g / cm ³ .

  As the polystyrene-based resin constituting the sheet A of the present invention, any resin can be used as long as it can usually be a foam and can be a rigid foam. Examples include styrene, methyl styrene, ethyl styrene, isopropyl styrene, dimethyl styrene, paramethyl styrene, chloro styrene, bromo styrene, vinyl toluene, vinyl xylene homopolymer, or maleic anhydride, acrylic acid, butadiene, etc. Polymers can be used. Of these, polystyrene, styrene-maleic anhydride copolymer, styrene-acrylic acid copolymer, impact-resistant polystyrene, styrene-acrylonitrile copolymer, and acrylonitrile-butadiene-styrene copolymer are preferably used.

  A foaming agent is used to foam the polystyrene resin. As such a blowing agent, nitrogen dioxide, carbon dioxide, propane, n-butane, i-butane, n-pentane, i-pentane, and a mixture of two or more thereof are used. When producing the sheet A of the present invention, an extruder is used to add the foaming agent to the polystyrene-based resin to cause foaming. The screw of the extruder may be uniaxial or biaxial. Further, for example, it can be used in a configuration in which two having an inner diameter of 90 mm and one having an inner diameter of 150 mm are connected. An extruder having a structure in which two are connected is preferably used because it has good kneadability between a polystyrene resin and a foaming agent and is excellent in foamability.

  FIG. 2 is a view showing an example of an extruder for producing the sheet A of the present invention. The extruder D is connected to a hopper E for supplying the raw resin into the extruder D on the upstream side in the resin flow direction, and a die F (having a circular opening at the resin discharge end of the extruder D). Circular die) is attached. The extruded foam sheet H extruded from the die F into a tube shape is cooled by blowing cooling air from the cooling air blowing device G. In FIG. 2, symbol T1 indicates the resin temperature during extrusion, and T2 indicates the die tip temperature.

  In this sheet A, the tensile strength of the sheet surface layer portion C remaining after the V-groove processing is in the range of 6.5 to 9.0 MPa, preferably in the range of 7.4 to 8.7 MPa. If the tensile strength of the sheet surface layer portion C is within the above range, the sheet surface layer portion C is less likely to be cracked even if the corner portion composed of the sheet surface layer portion C is repeatedly bent after the V-groove processing. Can provide. If the tensile strength of the sheet surface layer portion C is less than 6.5 MPa, the strength of the sheet surface layer portion C is weak, and cracking is likely to occur if the corner portion formed of the sheet surface layer portion C is repeatedly bent after V-groove processing. On the other hand, if the tensile strength of the sheet surface layer portion C exceeds 9.0 MPa, the strength of the sheet surface layer portion C is strong, and the corner portion composed of the sheet surface layer portion C rebounds against bending after V-groove processing, and cannot be completely bent. As a result, it is difficult to assemble the folded box, and in the case of a folded box that opens and closes the lid, the lid is difficult to close.

Further, in this sheet A, the density of the sheet surface layer portion C is in the range of 0.13 to 0.17 g / cm ³ , preferably in the range of 0.14 to 0.17 g / cm ³ . If the density of the sheet surface layer portion C is less than 0.13 g / cm ³ , the strength of the sheet surface layer portion C is weak, and cracks are likely to occur if the corner portion formed of the sheet surface layer portion C is repeatedly bent after V-groove processing. On the other hand, when the density of the sheet surface layer portion C exceeds 0.17 g / cm ³ , the strength of the sheet surface layer portion C is strong, and the corner portion composed of the sheet surface layer portion C rebounds against bending after the V-groove processing, and completely There is a possibility that it cannot be bent, making it difficult to assemble the folded box, and in the case of a folded box that opens and closes the lid, the lid is difficult to close.

  In addition, the sheet A preferably has a surface hardness of the surface of the sheet on the side opposite to the surface subjected to V-grooving within a range of 65 to 76, and the surface hardness (H) is 70 <H <76. More preferably within the range. In the present invention, the surface hardness is a value measured using a spring tester in accordance with the Japan Rubber Association standard SRISO 101 “Physical property test of expanded rubber”. If the surface hardness is less than 65, the strength of the sheet surface layer portion C is weak, and cracking is likely to occur if the corner portion made of the sheet surface layer portion C is repeatedly bent after the V-groove processing. On the other hand, if the surface hardness exceeds 76, the sheet surface layer portion C strength is strong, and the corner portion composed of the sheet surface layer portion C rebounds after bending and may not be bent completely. Assembling becomes difficult, and in the case of a folded box that opens and closes the lid, the lid is difficult to close.

In addition, the sheet A preferably has a density of the entire sheet in the range of 0.05 to 0.12 g / cm ³ . When the density of the entire sheet is within the above range, V-groove processing is easy and advantageous in terms of cost. When the density of the entire sheet is less than 0.05 g / cm ³ , the strength of the sheet surface layer portion C is weak, and cracking is likely to occur when the corner portion formed of the sheet surface layer portion C is repeatedly bent after V-groove processing. On the other hand, if the density of the entire sheet exceeds 0.12 g / cm ³ , the strength of the sheet surface layer portion C is strong, and the corner portion formed by the sheet surface layer portion C rebounds against bending after V-groove processing, and may not be bent completely. As a result, it is difficult to assemble the folded box, and in the case of a folded box that opens and closes the lid, the lid is difficult to close.

  In the example shown in FIG. 1A, the corner portion where the V-groove B is formed is bent at a right angle as shown in FIG. 1B, so the formation angle θ of the V-groove B is approximately 90 °. However, the formation angle θ of the V-groove B is not limited to this example, and can be appropriately changed according to the bending angle of the corner portion of the folding box.

  The V-groove B remains in the sheet surface layer portion C within the range of 0.05 to 0.2 mm, preferably within the range of 0.07 to 0.15 mm, and more preferably within the range of 0.1 mm ± 0.05 mm. Thus, the sheet A is formed by grinding. If the thickness of the sheet surface layer portion C remaining by the V-groove processing is less than 0.05 mm, the sheet surface layer portion C is too thin and the strength of the sheet surface layer portion C is weak. If the corner portion is bent repeatedly, cracking is likely to occur. On the other hand, when the thickness of the sheet surface layer portion C exceeds 0.2 mm, the sheet surface layer portion C is too thick, the strength of the sheet surface layer portion C is strong, and the corner portion composed of the sheet surface layer portion C is bent after the V-groove processing. In the case of a folding box that opens and closes the lid, it is difficult to close the lid.

As described above, the sheet A of the present invention adheres a thermoplastic film such as a polystyrene film to the sheet A by setting the tensile strength and density of the sheet surface layer portion C to be left after the V-groove processing to an optimum range. Furthermore, the strength of the sheet surface layer portion C remaining after the V-groove processing is improved and the flexibility is maintained while the flexibility is maintained while the corner portion formed of the sheet surface layer portion C can withstand repeated bending operations.
If the sheet surface layer portion C is weak, the sheet surface layer portion C that is slightly left by the V-groove processing is easily broken during bending, so that it is not possible to provide an openable and foldable folding box that requires repeated bending operation of the corner portion. On the other hand, if the sheet surface layer portion C is too strong, when it is bent after the V-groove processing, the repulsive force is strong and it is not completely bent. Therefore, in order to provide a folding box that can be opened and closed, it is necessary to form an optimum sheet surface layer portion C in consideration of these.

  In order to form the optimum sheet surface layer portion C, it is determined by controlling the tensile strength of the sheet surface layer portion C based on the balance between the die tip portion temperature T2 and the cooling air spray amount during sheet manufacture. In other words, the tensile strength of the sheet surface layer portion C decreases the foaming property of the sheet surface layer portion C when the die tip temperature T2 is lowered, and the tensile strength of the sheet surface layer portion C increases, and the cooling air spray amount is similarly increased. However, the tensile strength of the sheet surface layer portion C is also increased by forming a stronger sheet surface layer portion C. The optimum sheet surface layer portion C can be formed by adjusting both of them.

In the sheet A of the present invention, the tensile strength of the sheet surface layer portion C remaining when the V-groove is processed is in the range of 6.5 to 9.0 MPa, and the density of the sheet surface layer portion C is 0.13 to 0.3 mm. Since it is within the range of 17 g / cm ³ , when this sheet A is subjected to V-groove processing, even if a corner portion is formed only by the sheet surface layer portion C remaining after V-groove processing, bending operation, particularly repeated bending Cracks due to operation are less likely to occur, and a folded box that can be opened and closed can be provided by assembling a folded box by subjecting this sheet A to V-groove processing.
In addition, a folded box having a corner portion that is sharply formed only by the sheet surface layer portion C can be produced.

Next, an embodiment of a folding box according to the present invention will be described with reference to the drawings.
FIGS. 3-7 is a figure which shows one Embodiment of the folding box based on this invention, FIG. 3 is a perspective view which shows the folding box I after an assembly, FIG. 4 is the state before the folding box I was assembled (or the folding box I was returned) FIG. 5 is a plan view showing a state before the folding box I is assembled (or a state in which the folding box I is returned), and FIG. 6 is a state in which the end plates 2 and 2 are raised in the process of assembling the folding box I. FIG. 7 is a perspective view showing the folded box I with the lid 4 opened.

  The folding box I of the present embodiment is composed of the sheet A according to the present invention described above, and is a sheet having a thickness of 0.05 to 0.2 mm along a line corresponding to a corner portion when the folding box of the sheet A is assembled. A V-groove B is provided leaving the surface layer C, and the V-groove B is bent to assemble the base plate 1, the end plates 2 and 2, the side plates 3 and 3 and the lid 4 (top plate) having substantially the same thickness. Is formed. As shown in FIGS. 4 and 5 showing the state before assembly, the folding box I has side plates 3 and 3 connected to both ends 1a and 1a in the short direction of the bottom plate 1, respectively, and the longitudinal direction of the bottom plate 2 The end plates 2 and 2 are provided in the vicinity of both end portions 1b and 1b, respectively. A lid 4 is connected to the side plate upper end 3b of one side plate 2.

  The outer wall of the side plate lower end portion 3a of the side plate 3 is connected to the outer wall of the bottom plate 1 in the short direction 1a by the sheet surface layer portion C, and this connecting portion is a hinge portion 5a (corner portion). As shown in FIG. 1 (a), the hinge portion 5a is provided with a V-groove B of about 90 ° extending from the outer wall toward the inner wall, and as shown in FIG. The bottom plate 1 can be bent at a substantially right angle. Further, the hinge portion 5a can bend the side plate 3 in the direction opposite to the direction in which the folding box I is assembled. Accordingly, the side plates 3 and 3 can be bent between about 270 degrees from a state of being substantially perpendicular to the bottom plate 1 to a state of falling outward and being substantially in contact with the outer wall of the bottom plate 1.

  Similarly, the outer wall of the short-side end 4a of the lid 4 is connected to the outer wall of the side plate upper end 3b of the side plate 3 by the sheet surface layer portion C, and this connecting portion serves as a hinge portion 5b (corner portion). Yes. The hinge portion 5b is provided with a substantially 90 ° V-groove B extending from the outer wall toward the inner wall, so that the lid 4 can be bent at a substantially right angle with respect to the bottom plate 1.

  On the other hand, the inner wall of the lower end 2 a of the end plate 2 of the end plate 2 is connected to the end plate attaching portion 7 by the sheet surface layer portion C, and this connecting portion forms a rotating portion 8. Moreover, the inner wall of the bottom plate 1 in the vicinity of the longitudinal end 1b is formed with a groove having a depth capable of embedding the end plate attaching portion 7, and the end plate attaching portion 7 is embedded in the groove and is necessary. It is bonded and fixed with adhesive. When the end plates 2 and 2 are substantially perpendicular to the bottom plate 1, the bottom end portions 2 a of the end plates come into contact with the inner wall of the bottom plate 1. Therefore, each of the end plates 2 and 2 cannot fall outward from a substantially vertical state with respect to the bottom plate 1 and is substantially perpendicular to the bottom plate 1 as shown in FIG. It is rotatable between about 90 ° from the state to the state where it falls inward and substantially contacts the inner wall of the bottom plate 1. In addition, what is necessary is just to form a groove | channel in the position where the outer wall of the end plate 2 and the longitudinal direction edge part 1b of the base plate 1 become the same surface, for example, when the end plate 2 stands substantially perpendicularly with respect to the base plate 1.

  Further, when the end plate 2 is in contact with the side plates 3 and 3 and the lid 4, that is, the end plate upper end portion 2 b and the end plate side end portions 2 c and 2 c, when the end plate 2 stands substantially perpendicular to the bottom plate 1, Protrusions 10 extending substantially vertically from the end portions 2b, 2c, and 2c toward the side plates 3 and 3 and the lid 4 are formed. On the other hand, the projections 10 are inserted into and removed from the end portions of the side plates 3 and 3 and the lid 4 that contact the end plate 2, that is, the side plate side end portions 3c and 3c of the side plates 3 and 3 and the longitudinal end portion 4c of the lid 4. Concave portions 11 that can be freely fitted are formed. The height and width of the convex portion 10 are each approximately half of the plate thickness, for example. Thus, when the bottom plate 1, the end plates 2, 2, the side plates 3, 3 and the lid 4 are assembled to form the folded box I, the convex portions 10, 10 formed on the end plates 2, 2 become the side plates 3, 3 and the lid 4 is fitted into the recesses 11 formed in 4 to bend and turn the end plates 2 and 2, the side plates 3 and 3 and the lid 4. Since the sheet A forming the folding box I has appropriate elasticity, the convex portion 10 fitted in the concave portion 11... It is designed not to come off.

  Next, a method for assembling the folded box I will be described. In order to assemble the folded box I from the flat sheet A as shown in FIGS. 4 and 5, first, the end plates 2 and 2 are set up substantially perpendicular to the bottom plate 1 as shown in FIG. Next, as shown in FIG. 7, the side plates 3, 3 are erected substantially perpendicular to the bottom plate 1, and the convex portions 10, 10 formed on the end plates 2, 2 are recessed portions 11 formed on the side plates 3, 3. To fit. As a result, the folding and rotation of the end plates 2 and 2 and the side plates 3 and 3 are locked, and the articles can be stored inside the folding box I. Thereafter, the lid 4 is erected substantially perpendicular to the side plate 3, the convex portions 10, 10 formed on the end plates 2, 2 are fitted into the concave portions 11, 11 formed on the lid 4, and the lid 4 is rotated. Lock. In this way, a folded box I as shown in FIG. 3 can be obtained.

  In the folding box I shown in FIG. 3, the side plates 3 and 3 can be bent outwardly with respect to the bottom plate 1 by hinges 5a and 5a (corner portions). Therefore, when the folding box I is not used, the lid 4 Is bent until the side plate 3 that is connected to the outer wall of the bottom plate 1 is substantially in contact with the outer wall of the bottom plate 1, and the end plates 2 and 2 are rotated to the state of being substantially in contact with the inner wall of the bottom plate 1. It can be folded compactly.

The folding box I uses the sheet A according to the present invention described above, and leaves the sheet surface layer portion C with a thickness of 0.05 to 0.2 mm along a line corresponding to a corner portion when the folding box of the sheet A is assembled. Since the V-groove B is provided and is assembled in a box shape by bending the V-groove B, the corner portion is flexible but strong against bending, and even if repeated bending operations are performed, the corner portion is cracked. It is hard to produce. Therefore, the folding box 1 can be repeatedly opened and closed, and becomes a folding box I that can be opened and closed.
Further, the folded box I having a corner portion sharply formed only by the sheet surface layer portion C can be produced.

[Example 1]
A sheet was produced using an extruder configured as shown in FIG. For 100 parts by mass of polystyrene resin particles (trade name: G-13-50B, manufactured by Toyo Styrene Co., Ltd.) having an MFR value of 6.0, 0.5 parts by mass of powder talc and 0.1 parts by mass of calcium stearate as a cell nucleating agent Were added and mixed uniformly, and supplied from an 115 mm hopper to an extruder having an inner diameter of 115 mm to 150 mm.
The extruder cylinder temperature was set to a maximum value of 250 ° C., and 4.3 parts by mass of butane gas (isobutane / normal butane ratio = 55/45) as a blowing agent was melted and kneaded from the middle of the extruder, and the resin temperature T1 at the time of extrusion = At 154 ° C., a polystyrene foam sheet was extruded in a tubular shape from a circular die attached to the tip of the extruder. The die tip temperature T2 at this time was 110 ° C.
Next, the tubular foamed sheet was passed between rolls having a cooling function, and the inner surface of the tubular foamed sheet was fused to form a sheet. This sheet was flat and had a total density of 0.075 g / cm ³ and a thickness of 7 mm.
In this sheet, cooling air of 40 ° C. was blown immediately after being extruded from the circular die. The amount of the cooling air sprayed was 0.04 Nm ³ / m ² as the air volume when converted to 0 ° C. and 1 atmosphere, ie, normal m ³ (Nm ³ ).
For the sheet of Example 1, (1) tensile strength, (2) elongation at break, (3) sheet surface layer density (hereinafter abbreviated as surface layer density), (4) surface hardness, (5) foaming The overall density of the sheet was examined. Further, the sheet was subjected to V-groove processing, and (6) surface layer cracking of the V-groove and (7) bending after the V-groove processing were examined. Test methods and evaluation criteria for each item of (1) to (7) are as follows. The results are shown in Table 1.

(1) Tensile strength and (2) Elongation at break Slicer (Fortuna (Germany) made splitting machine, model AB-320-D), sliced the test piece to a thickness of 0.4 mm from the surface layer, Tensylon Universal Testing Machine (Orientic Co., Model UCT-10T) was cut to a width of 50 mm and a length of 150 mm, and then a tensile test was performed at a test speed of 10 mm / min, and the tensile strength (unit: MPa). And the elongation at break (unit:%) is measured.

(3) Surface layer density Using a slicer similar to the above-described tensile test, after slicing the test piece to a thickness of 0.4 mm from the surface layer to a width of 50 mm and a length of 150 mm, the mass and volume were measured. The surface layer density is calculated from the following formula.
Surface layer density (g / cm ³ ) = Test piece mass (g) / Test piece volume (mm ³ ) × 10 ³
However, the test specimen for measurement is cut out from a sample that has passed 72 hours or more after molding, and is subjected to atmospheric conditions of 23 ° C. ± 2 ° C./50 RH% ± 5 RH% or 27 ° C. ± 2 ° C./65 RH% ± 5 RH% for 16 hours or more. It is what was left.

(4) Surface hardness The surface hardness was measured according to the Japan Rubber Association edited by the Japan Rubber Association standard SRISO101 “Physical property test of expanded rubber”, and a spring tester (CL-150, manufactured by Kobunshi Keiki Co., Ltd.). ).
The test machine is brought into close contact with the surface of the test piece, and the scale displayed by the push needle protruding from the center hole of the pressurizing surface with the spring pressure being pushed back by the test piece is read to determine the surface hardness.
In this example, the surface hardness was measured on the surface opposite to the surface on which V-grooving was performed.

(5) The whole density of the foam sheet 50 cm ³ or more (100 cm ³ or more in the case of semi-rigid and soft materials) is cut so as not to change the original cell structure of the material, its mass and volume are measured, The overall density is calculated by the following formula.
Total density (g / cm ³ ) = test piece mass (g) / test piece volume (mm ³ ) × 10 ³
However, the test specimen for measurement is cut out from a sample that has passed 72 hours or more after molding, and is subjected to atmospheric conditions of 23 ° C. ± 2 ° C./50 RH% ± 5 RH% or 27 ° C. ± 2 ° C./65 RH% ± 5 RH% for 16 hours or more. It is what was left.

(6) V-groove surface layer crack As shown in FIG. 1 (a), a V-groove is formed in the sheet by cutting, and the sheet surface layer C remaining after the V-groove machining (thickness 0.1 mm ± 0.05 mm) In Fig. 2, it was examined whether or not cracking occurred when the portion was bent. With respect to 30 repeated bending operations, the case where no cracks occurred in the surface layer portion of the sheet was evaluated as “No”, and the case where cracks occurred was evaluated as “Yes”.

(7) Bending after V-groove processing V-groove processing is performed on the sheet, and the repelling force is superior to the sheet's own weight immediately after assembling the folded box as shown in FIGS. Thus, the case where the angle indicated by the symbol α in FIG. 3 opens 10 ° or more is “No”, and the case where the angle is less than 10 ° is “Good”.

[Example 2]
A sheet was produced in the same manner as in Example 1 except that the overall density was lower than in Example 1, the die tip temperature T2 was lowered, and the cooling air spray amount was lowered. The results are shown in Table 1.

[Example 3]
A sheet was produced in the same manner as in Example 1 except that the overall density was smaller than that in Example 1 and the cooling air spray amount was lowered, and each test was performed in the same manner. The results are shown in Table 1.

[Example 4]
A sheet was produced in the same manner as in Example 1 except that the overall density was smaller than that in Example 1 and the cooling air spray amount was lowered, and each test was performed in the same manner. The results are shown in Table 1.

[Comparative Example 1]
A sheet was produced in the same manner as in Example 1 except that the cooling air spray amount was increased more than in Example 1, and each test was performed in the same manner. The results are shown in Table 1.

[Comparative Example 2]
A sheet was produced in the same manner as in Example 1 except that the overall density was smaller than that in Example 1, the die tip temperature T2 was lowered, and the cooling air spray amount was lowered. The results are shown in Table 1.

[Comparative Example 3]
A sheet was produced in the same manner as in Example 1 except that the overall density was smaller than that in Example 1, the die tip temperature T2 was increased, and the cooling air spray amount was decreased. The results are shown in Table 1.

[Comparative Example 4]
A sheet was produced in the same manner as in Example 1 except that the overall density was smaller than that in Example 1, the die tip temperature T2 was increased, and the cooling air spray amount was decreased. The results are shown in Table 1.

[Comparative Example 5]
A sheet was produced in the same manner as in Example 1 except that the overall density was smaller than that in Example 1 and the die tip temperature T2 was increased, and each test was performed in the same manner. The results are shown in Table 1.

[Comparative Example 6]
A sheet was produced in the same manner as in Example 1 except that the overall density was smaller than that in Example 1, the die tip temperature T2 was lowered, and the cooling air spray amount was increased. The results are shown in Table 1.

[Comparative Example 7]
A sheet was produced in the same manner as in Example 1 except that the overall density was smaller than that in Example 1, the die tip temperature T2 was increased, and the cooling air spray amount was increased. The results are shown in Table 1.

From the results of Table 1, the tensile strength of the sheet surface layer portion remaining after the V-groove processing is adjusted to 6.5 to 9.0 MPa by appropriately adjusting the die tip temperature T2 and the cooling air blowing amount at the time of manufacturing the sheet. In addition, the sheets of Examples 1 to 4 according to the present invention in which the density of the sheet surface layer portion is in the range of 0.13 to 0.17 g / cm ³ were obtained. The sheets of Examples 1 to 4 had excellent bendability in which cracks were not generated by repeated bending operations while the sheet surface layer portion remaining after the V-groove processing was kept flexible. Therefore, the sheet | seat of Examples 1-4 which concerns on this invention was equipped with the preferable characteristic in order to manufacture the folding box which can be opened and closed.

On the other hand, in Comparative Example 1, the tensile strength, the surface layer density, and the surface strength were larger than those in Example 1, the strength of the sheet surface layer portion was increased, and the bending after the V-groove processing was poor.
In Comparative Examples 2 to 5, the tensile strength, the surface layer density, and the surface strength were smaller than those in Example 1, the strength of the sheet surface layer portion was weak, and cracking occurred due to repeated bending operations of the sheet surface layer portion.
Further, in Comparative Example 6, the tensile strength was larger than that in Example 1, and the bending after the V-groove processing was poor.
In Comparative Example 7, the surface layer density was higher than that in Example 1, and bending after the V-groove processing was poor.

  A ... sheet (polystyrene resin foam sheet for folding box), B ... V groove, C ... sheet surface layer part, D ... extruder, E ... hopper, F ... die, G ... cooling air spray device, H ... extruded foam sheet , I ... folding box, 1 ... bottom plate, 2 ... end plate, 3 ... side plate, 4 ... lid, 5a, 5b ... hinge part (corner part), 7 ... end plate attaching part, 8 ... rotating part, 10 ... convex part, 11 ... concave.

Claims (5)

The tensile strength of the sheet surface layer portion remaining when the V-groove is processed is in the range of 6.5 to 9.0 MPa, and the elongation at break of the sheet surface layer portion is in the range of 4.25 to 5.10%. And the density of the sheet surface layer part is in the range of 0.13 to 0.17 g / cm ³ , and the surface hardness of the sheet surface layer side opposite to the surface on which the V-groove processing is performed is in the range of 65 to 76. A polystyrene-based resin foam sheet for folding boxes.   2. The polystyrene-based resin foam sheet for folding boxes according to claim 1, wherein the surface hardness (H) of the surface of the sheet opposite to the surface on which the V-groove processing is performed is in the range of 70 <H <76. The polystyrene-based resin foam sheet for folded boxes according to claim 1, wherein the density of the entire sheet is in the range of 0.05 to 0.12 g / cm ³ .   It comprises the polystyrene-based resin foam sheet for folding boxes according to any one of claims 1 to 3, and leaves a sheet surface layer part of 0.05 to 0.2 mm along a line corresponding to a corner part during folding box assembly of the sheet. And a V-groove, which is assembled into a box shape by bending the V-groove.   The folded box according to claim 4, further comprising: a box-shaped main body part and a lid that closes an opening of the main body part so as to be opened and closed.

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