JP5187115B2 - Synthetic resin foam sheet and method for producing the same - Google Patents

Description

  The present invention relates to a synthetic resin air bubble sheet in which a flat sheet is joined to a concavo-convex sheet on which a large number of protrusions are formed, and more particularly to a structural material used in a low pressure environment.

Conventionally, a metal material has been used as a structural material used in outer space (see, for example, Patent Document 1). This Patent Document 1 describes a configuration in which a structural material is transferred to outer space in a folded state and deployed in outer space.
Japanese Patent Laid-Open No. 7-226620

  However, since the metal material is hard, a certain amount of storage space is required even if it is folded. Furthermore, the metal material has a large weight per area. For this reason, in order to transfer the structural material which consists of metal materials to outer space, much energy is required.

  In view of the above, an object of the present invention is to provide a material suitable for a structural material used in a low pressure environment.

In order to achieve the above-mentioned object, the invention according to claim 1 of the present invention includes a synthetic resin concavo-convex sheet (101) formed with a large number of protrusions (101a), and at least the concavo-convex sheet (101). A plurality of bubbles including a flat sheet (102) made of synthetic resin joined to the opening side of the protrusion (101a), and gas is sealed between the protrusion (101a) and the flat sheet (102). Part (104) is formed, and each of the plurality of bubble parts (104) is independent from other bubble parts, and the bubble part (104) has an upper limit value of the amount of gas that can be sealed at standard atmospheric pressure. It is characterized in that a gas of more than 0% and 65% or less is enclosed.

  In this way, by filling the bubble portion (104) with a gas not exceeding 65% of the upper limit of the amount of gas that can be enclosed in the bubble portion (104) at the standard atmospheric pressure, the bubble portion (104) at the standard atmospheric pressure. However, the bubble part (104) expand | swells in a low-pressure environment where use of a synthetic resin bubble sheet is assumed, and it will be in a usable state. In addition, since the bubble sheet has flexibility and the bubble portion (104) is in a contracted state at the standard atmospheric pressure, the bubble sheet can be folded in a compact manner, and the storage space at the time of transfer can be increased. Can be small. Furthermore, the air bubble sheet made of synthetic resin is significantly lighter than a metal material or the like, and does not require a large amount of energy during transfer. For this reason, the bubble sheet made of synthetic resin can be suitably used as a structural material used in a low-pressure environment such as outer space.

  The invention according to claim 2 is characterized in that the concavo-convex sheet (101) and the flat sheet (102) are composed of a gas barrier film. Thereby, the gas leak from a bubble part (104) can be suppressed and a synthetic resin foam sheet can be used over a long period of time.

  The invention described in claim 3 is characterized in that the concavo-convex sheet (101) and the flat sheet (102) are formed of a multilayer film. Thereby, the gas leak from a bubble part (104) can be suppressed more effectively, and a synthetic resin bubble sheet can be used over a long period of time.

  The invention according to claim 4 is characterized in that the adjacent bubble portions (104) are parallel to each other. Thereby, when adjacent bubble parts (104) contact, a contact area becomes large, the bending rigidity of a synthetic resin bubble sheet can be improved more, and it can use suitably as a structural material.

  Moreover, the durability of a bubble sheet is provided by providing a metal layer in the outer surface of a bubble sheet like the synthetic resin bubble sheet of Claim 5, and the manufacturing method of the synthetic resin bubble sheet of Claim 8. Can be improved.

  Moreover, according to the manufacturing method of Claim 6, the synthetic resin foam sheet of Claim 1 can be manufactured.

Further, as in the manufacturing method according to claim 7, in the protrusion forming step, the protrusion (101 a) is formed by sucking the first sheet (101) with the recess (204 a) of the forming roll (204). together, the Rukoto is disengaged from the wall surface of at least some of the recesses of the projections by feeding air into the recess (204a) after sucking the first sheet (101) (101a) (204a ), the protrusion (101a) volume at 0% and 65% or less and to Rukoto volume of the recess (204a) of the bubble portion in the standard atmospheric pressure (104) 65% or less of the gas bubbles of the upper limit value of the sealable gas amount in the The first sheet (101) and the second sheet (102) can be joined in a state of being enclosed in (104).

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. In the present embodiment, a synthetic resin air bubble sheet 100 is used as a structural material used in a low-pressure environment. The structural material of this embodiment is used as a panel of a solar cell, for example.

  FIG. 1A is a perspective view of the synthetic resin air bubble sheet 100, and FIG. 1B is a perspective view showing a state in which the synthetic resin air bubble sheet 100 is disassembled.

As shown to Fig.1 (a), (b), the bubble sheet 100 is comprised as a synthetic resin hollow member. In the present embodiment, a polyolefin resin such as polyethylene or polypropylene is used as the synthetic resin constituting the bubble sheet 100. In the case where flexibility is required as in the present embodiment, the bubble sheet 100 desirably has a weight per unit area (weight per unit area) of 30 to 300 g / m ² .

  The bubble sheet 100 has a three-layer structure including an uneven sheet 101 and two flat sheets 102 and 103 bonded to both surfaces of the uneven sheet 101. The sheets 101 to 103 constituting these bubble sheets 100 have flexibility. A plurality of hollow (for example, columnar) protrusions 101 a are embossed on the uneven sheet 101. Further, the first flat sheet 102 is bonded to the protrusion opening side (lower side in FIG. 1) of the uneven sheet 101, and the second flat sheet 103 is bonded to the protrusion front end side (upper side in FIG. 1) of the uneven sheet 101. Has been. Between the protrusion 101a of the concavo-convex sheet 101 and the first flat sheet 102, a bubble 104 in which a gas such as air is enclosed is formed. Adjacent bubble portions 104 are arranged at a predetermined interval. The bubble sheet 100 has an excellent buffering effect due to the presence of the bubble portion 104 and is generally used as a packaging material.

  The bubble sheet 100 of the present embodiment is assumed to be used in a low pressure environment such as outer space. Here, “low pressure environment” in the present specification means a pressure environment at an altitude of 20,000 meters or more. Under such a low-pressure environment, the volume of gas increases compared to a standard atmospheric pressure (atmospheric pressure at sea level) environment. For this reason, in the bubble sheet 100 of the present embodiment, the amount of gas sealed in the bubble portion 104 at the standard atmospheric pressure at which the bubble sheet 100 is manufactured is smaller than that for the purpose of buffering by the bubble portion 104.

  The amount of gas sealed in the bubble portion 104 at the standard atmospheric pressure is such that the bubble portion 104 expands in a low-pressure environment in which the bubble sheet 100 is used, and can maintain its own shape (cylindrical shape in this embodiment). It only has to be. Specifically, the gas amount enclosed in the bubble portion 104 at the standard atmospheric pressure is set to 65% or less of the upper limit value of the gas amount that can be enclosed in the bubble portion 104. The “upper limit value of the amount of gas that can be enclosed in the bubble portion 104” means the amount of gas that can be stored in the bubble portion 104 without the uneven sheet 101 itself constituting the bubble portion 104 being stretched.

  In this embodiment, the concavo-convex sheet 101 and the flat sheets 102 and 103 are formed of a gas barrier film having low gas permeability. As the gas barrier film, for example, nylon or EVOH (ethylene vinyl alcohol copolymer) can be used. Furthermore, if the uneven | corrugated sheet | seat 101 and the flat sheets 102 and 103 are comprised as a multilayer film using a gas barrier film, gas barrier property can be improved more.

  FIG. 2 shows an example of main components of a bubble sheet manufacturing apparatus 200 that manufactures the bubble board 100 of the present embodiment. As shown in FIG. 2, the bubble sheet manufacturing apparatus 200 is provided with three sheet supply units 201 to 203 that supply synthetic resin sheets. The first sheet supply unit 201 supplies the flat first sheet 101 before the protrusions 101a are formed, the second sheet supply unit 202 supplies the flat second sheet 102, and the third sheet. A flat third sheet 103 is supplied from the supply unit 203. Each of these sheet supply units 201 to 203 is composed of a flat die connected to an extruder (not shown).

  The bubble sheet manufacturing apparatus 200 is provided with a forming roll 204, a first pressure roll 205, a peeling roll 206, a second pressure roll 207, and a third pressure roll 208. These rolls 204 to 208 have a cylindrical shape and are arranged in parallel in the axial direction. These rolls 204 to 208 are configured to be driven to rotate by a driving device (not shown).

  The first sheet 101 supplied from the first sheet supply unit 201 is supplied to the forming roll 204 side between the forming roll 204 and the first pressure roll 205. The second sheet 102 supplied from the second sheet supply unit 202 is supplied to the first pressure roll 205 side between the forming roll 204 and the first pressure roll 205.

  A large number of recesses 204 a having a shape corresponding to the bubble portion 104 of the bubble sheet 100 are formed on the outer peripheral surface of the forming roll 204. The bottom of the recess 204a of the forming roll 204 is connected to a vacuum pump (not shown), and vacuum suction is possible by the recess 204a. Further, the forming roll 204 of the present embodiment can feed air into the concave portion 204a after performing vacuum suction in the concave portion 204a. The forming roll 204 is configured to rotate counterclockwise in FIG.

  The first pressure roll 205 is arranged so that the forming roll 204 and the outer peripheral surface are in contact with each other, and the outer peripheral surface of the first pressure roll 205 is pressed against the outer peripheral surface of the forming roll 204. As described above, the first pressure roll 205 applies an external force to the second sheet 102 in a direction in which the first pressure roll 205 is pressed against the first sheet 101. The pressure roll 205 rotates in the opposite direction to the forming roll 204 and is configured to rotate in the clockwise direction in FIG.

  The peeling roll 206 is for peeling the bubble sheet 100 from the outer peripheral surface of the forming roll 204, and is provided on the opposite side of the pressure roll 204 with the forming roll 204 as the center. The peeling roll 206 is configured to rotate clockwise in FIG.

  The second and third pressure rolls 207 and 208 are arranged on the sheet flow downstream side of the peeling roll 206. The 2nd pressurization roll 207 and the 3rd pressurization roll 208 are arrange | positioned facing each other so that a mutual outer peripheral surface may contact. The first sheet 101 and the second sheet 102 joined to each other are supplied between the second pressure roll 207 and the third pressure roll 208. In the present embodiment, the second pressure roll 207 is disposed on the opposite side (the upper side in FIG. 2) of the first sheet 101 to which the second sheet 102 is bonded, and the third pressure roll 208 is the first pressure roll 208. It arrange | positions in the surface side (lower side in FIG. 2) to which the 2nd sheet | seat 102 in the sheet | seat 101 was joined.

  The third sheet 103 supplied from the third sheet supply unit 203 is supplied between the second pressure roll 207 and the third pressure roll 208. The second pressure roll 207 is disposed so that the third pressure roll 208 and the outer peripheral surfaces are in contact with each other, and the outer peripheral surfaces of these pressure rolls 207 and 208 are pressed against each other. As described above, the second pressure roll 207 applies an external force in the direction of pressing the third sheet 103 against the first sheet 101.

  Next, the manufacturing method of the bubble sheet 100 of this embodiment is demonstrated. The production of the bubble sheet 100 is performed at standard atmospheric pressure.

  First, the first sheet 101 before the formation of the protrusion having a melting point or higher is supplied from the first sheet supply unit 201 to the outer peripheral surface of the forming roll 204 (first sheet supply step). The first sheet 101 moves as the forming roll 204 rotates. The first sheet 101 having a melting point or higher is vacuum-sucked by the concave portion 204a of the forming roll 204, thereby forming a large number of protruding portions 101a constituting the bubble portion 104, thereby forming an uneven sheet (projecting portion forming step). After the projection 101a is formed, air is sent into the recess 204a of the forming roll 204, and at least a part of the projection 101a is detached from the wall surface of the recess 204a. That is, the top of the protrusion 101 a is recessed, and the volume of the protrusion 101 a is smaller than the recess 204 a of the forming roll 204. At this time, the volume of the protrusion 101a is set to 65% or less of the volume of the recess 204a of the forming roll 204. The first sheet (concave / convex sheet) 101 on which the protrusions 101 a are formed is supplied between the forming roll 204 and the first pressure roll 205.

  Next, the second sheet (flat sheet) 102 having a melting point or higher is supplied from the second sheet supply unit 202 between the forming roll 204 and the first pressure roll 205 (second sheet supply step). Then, the melt surface of the second sheet 102 is pressed against the first sheet 101 by the first pressure roll 205, and the second sheet 102 and the first sheet 101 are fused and joined (joining step). The second sheet 102 is joined to the opening side of the protrusion 101 a of the first sheet 101.

  As described above, before the first sheet 101 and the second sheet 102 are joined, air is fed into the recess 204a of the forming roll 204, and the volume of the protrusion 101a is 65% or less of the volume of the recess 204a of the forming roll 204. It has become. Since the “volume of the concave portion 204a of the forming roll 204” is equal to the upper limit value of the volume of the protruding portion 101a, a gas that is 65% or less of the upper limit value of the amount of gas that can be sealed in the protruding portion 101a. The first sheet 101 and the second sheet 102 are joined in a state of being enclosed in the.

  Next, the first sheet 101 and the second sheet 102 that are joined together move with the rotation of the forming roll 204, the direction of travel is changed by the peeling roll 206, is peeled off from the outer peripheral surface of the forming roll 204, and the second added Supplied between the pressure roll 207 and the third pressure roll 208.

  Next, after the third sheet (flat sheet) 103 having a melting point or higher from the third sheet supply unit 203 is brought into contact with the outer peripheral surface of the second pressure roll 207 for a predetermined period, the second pressure roll 207 is moved. And the third pressure roll 208. Then, by the rotation of the second pressure roll 207, the third sheet 103 is supplied between the second pressure roll 207 and the third pressure roll 208, and the molten surface of the third sheet 103 is pressed against the first sheet 101. The third sheet 103 and the first sheet 101 are fused and joined. The third sheet 103 is joined to the leading end side of the protrusion of the first sheet 101.

  Through the above steps, the second sheet 102 and the third sheet 102 are fused and joined to both sides of the first sheet 101, and the bubble sheet 100 in which the gas is sealed in the bubble portion 104 is formed.

  Next, the change of the bubble part 104 when using the bubble sheet 100 mentioned above in a low-pressure environment is demonstrated.

FIG. 3 is a cross-sectional view showing a change in the bubble portion 104 when the bubble sheet 100 is used in a low-pressure environment. As described above, the protrusion 101a of the bubble sheet 100 is filled with gas that is 65% or less of the upper limit of the amount of gas that can be sealed in the protrusion 101a. For this reason, as shown in FIG. 3A, the bubble portion 104 of the bubble sheet 100 is contracted at the standard atmospheric pressure. When this bubble sheet 100 is used under a low pressure environment (a pressure environment corresponding to an altitude of 20,000 m or more), the gas volume in the bubble portion 104 increases as shown in FIG. Reach the upper limit of the amount of gas that can be sealed in. In the bubble sheet 100 of the present embodiment, the gas volume in the bubble portion 104 increases beyond the upper limit value of the amount of gas that can be sealed in the protruding portion 101a, as shown in FIG. The concavo-convex sheet 101 corresponding to the side wall of the protruding portion 101a expands, and the adjacent bubble portions 104 come into contact with each other.

  FIG. 4 is a plan view showing only the bubble portion 104 of the bubble sheet 100. 4A corresponds to the state of FIG. 3B, and FIG. 4B corresponds to the state of FIG. When the gas volume in the bubble portion 104 increases beyond the upper limit of the amount of gas that can be sealed in the protrusion 101a, the side wall of the protrusion 101a extends from the state shown in FIG. It will be in the state which the adjacent bubble parts 104 shown in b) contact. Thus, the bending rigidity of the bubble sheet 100 can be improved because the adjacent bubble parts 104 contact.

  According to the configuration of the present embodiment described above, the bubble portion 104 of the bubble sheet 100 is filled with a gas that is 65% or less of the upper limit of the amount of gas that can be enclosed in the bubble portion 104 at the standard atmospheric pressure. Therefore, although the bubble part 104 is in a contracted state at the standard atmospheric pressure, the bubble part 104 expands in a low pressure environment where the use of the bubble sheet 100 is assumed, and becomes usable as a structural material. In addition, since the bubble sheet 100 is flexible and the bubble portion 104 is in a contracted state at the standard atmospheric pressure, the bubble sheet 100 can be folded in a compact manner, and the storage space during transfer can be increased. Can be small. Further, the synthetic resin air bubble sheet 100 is significantly lighter than a metal material or the like, and does not require much energy during transfer. For this reason, the synthetic resin foam sheet 100 can be suitably used as a structural material used in a low-pressure environment such as outer space.

  Further, as described with reference to FIGS. 3C and 4B, the bubble sheet 100 of the present embodiment is such that the bubble portions 104 are in contact with each other in a low-pressure environment. The bending rigidity of the bubble sheet 100 can be improved as compared with the configuration in which the bubble sheet 100 does not contact. For this reason, the bubble sheet 100 can be used suitably as a structural material. In addition, since the air bubble sheet 100 is provided with a large number of air bubbles 104, even if it comes into contact with an obstacle such as space debris in space, for example, only some of the air bubbles 104 need to be damaged, and the rest The function as a structural material can be maintained by the bubble portion 104.

  Moreover, in the bubble sheet 100 of this embodiment, since the gas barrier film is used, the gas leakage from the bubble part 104 can be suppressed and the bubble sheet 100 can be used over a long period of time. Furthermore, since the bubble sheet 100 of the present embodiment uses a multilayer film, gas leakage from the bubble portion 104 can be more effectively suppressed, and the bubble sheet 100 can be used for a long period of time.

(Other embodiments)
In the above-described embodiment, the bubble sheet 100 is configured as a three-layer product in which the flat sheets 102 and 103 are provided on both sides of the concavo-convex sheet 101. However, the present invention is not limited to this, and is provided only on the opening side of the protrusion 101a. The present invention can also be applied to a two-layer product in which the flat sheet 102 is bonded.

  Moreover, in the said embodiment, although the shape of the bubble part 104 of the bubble sheet 100 was comprised as a cylinder shape, it is good not only as this but another shape. 5 and 6 are plan views showing only the bubble part 104 of the bubble sheet 100, FIG. 5 shows an example in which the bubble part 104 is formed in a quadrangular prism shape, and FIG. 6 shows the bubble part 104 in a hexagonal column shape. An example is shown. 5 (a) and 6 (a) correspond to the state of FIG. 3 (b), and FIGS. 5 (b) and 6 (b) correspond to the state of FIG. 3 (c). As shown in FIG. 5B and FIG. 6B, when the bubble portion 104 has a quadrangular prism shape or a hexagonal column shape, the sides of the adjacent bubble portions 104 facing each other are parallel to each other. For this reason, when adjacent bubble part 104 contacts, a contact area becomes large and the bending rigidity of the bubble sheet 100 can be improved more.

  Moreover, in the bubble sheet 100 of the said embodiment, although each bubble part 104 was comprised so that gas might be enclosed independently from the other bubble part 104, not only this but the adjacent bubble parts 104 mutually. You may comprise so that it may communicate. For example, as shown in FIG. 7, the concave-convex sheet 101 and the first flat sheet 102 can be joined only at the peripheral edge of the bubble sheet 100 (part indicated by A in FIG. 7). Thereby, in the site | part away from the peripheral part in the bubble sheet 100, the uneven | corrugated sheet | seat 101 and the 1st flat sheet 102 will be in the state which is not joined.

  In the air bubble sheet 100 having such a configuration, the air bubble portion 101a of the air bubble sheet 100 is contracted at the standard atmospheric pressure as shown in FIG. When the bubble sheet 100 is used in a low-pressure environment, as shown in FIG. 7B, the gas volume in the bubble portion 104 increases and reaches the upper limit of the amount of gas that can be enclosed in the protruding portion 101a. Then, the gas volume in the bubble portion 104 increases beyond the upper limit of the amount of gas that can be sealed in the protrusion 101a, and the side wall of the protrusion 101a expands as shown in FIG. The matching bubble portions 104 come into contact with each other. In the bubble sheet 100 having the configuration shown in FIG. 7, since the adjacent bubble portions 104 communicate with each other, the gas volume in the bubble portion 104 increases beyond the upper limit value of the amount of gas that can be enclosed in the protrusion 101a. In addition, it is possible to cope with an increase in the gas volume in the entire bubble portion 104 that is in communication, and it is possible to suppress the side wall of the protruding portion 101a from being damaged due to an increase in the gas volume in the bubble portion 104.

  In addition to the configuration of the above embodiment, the durability of the bubble sheet 100 can be improved by providing a metal layer such as an aluminum foil on the outer surfaces of the flat sheets 102 and 103. Specifically, after forming the bubble sheet 100, a metal layer forming step of forming a metal layer on the outer surfaces on both sides of the bubble sheet 100 by vacuum deposition may be performed.

  Moreover, in the said embodiment, although the bubble sheet 100 was comprised with the olefin resin, you may use not only this but another synthetic resin. For example, heat resistance can be improved by comprising the bubble sheet 100 with a polyimide or a fluororesin. As the fluororesin, PTFE (polytetrafluoroethylene), ETFE (ethylene-tetrafluoroethylene copolymer), PFA (perfluoroalkoxyalkane), PVDF (polyvinylidene fluoride), or the like can be used. Thus, even when the bubble sheet 100 is made of polyimide or fluororesin, the durability of the bubble sheet 100 can be improved by providing the metal layer on the outer surface of the bubble sheet 100.

(A) is a perspective view of the bubble sheet 100, (b) is a perspective view showing a state in which the bubble sheet 100 is disassembled. It is a figure which shows an example of the main components of the bubble sheet manufacturing apparatus 200 which manufactures the bubble board. It is sectional drawing which shows the change of the bubble part 104 when using the bubble sheet 100 in a low-pressure environment. 4 is a plan view showing only the bubble part 104 of the bubble sheet 100. FIG. It is a top view which shows only the bubble part 104 of the bubble sheet 100 which concerns on the modification of the said embodiment. It is a top view which shows only the bubble part 104 of the bubble sheet 100 which concerns on the modification of the said embodiment. It is sectional drawing of the bubble sheet 100 which concerns on the modification of the said embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 ... Bubble sheet made of synthetic resin, 101 ... Uneven sheet, 101a ... Projection part, 102, 103 ... Flat sheet, 104 ... Bubble part.

Claims (8)

Synthetic resin concavo-convex sheet (101) on which a large number of protrusions (101a) are formed, and a synthetic resin flat sheet bonded to at least the opening side of the protrusion (101a) in the concavo-convex sheet (101) ( 102)
A large number of bubble portions (104) in which gas is sealed are formed between the protrusion (101a) and the flat sheet (102),
Each of the plurality of bubble portions (104) is independent of other bubble portions,
A gas bubble sheet made of synthetic resin, characterized in that the bubble portion (104) is filled with a gas that is greater than 0% and 65% or less of the upper limit of the amount of gas that can be filled at standard atmospheric pressure.   The synthetic resin foam sheet according to claim 1, wherein the uneven sheet (101) and the flat sheet (102) are made of a gas barrier film.   The synthetic resin foam sheet according to claim 1 or 2, wherein the uneven sheet (101) and the flat sheet (102) are formed of a multilayer film.   4. The synthetic resin bubble sheet according to claim 1, wherein the adjacent bubble portions (104) are parallel to each other.   The synthetic resin foam sheet according to any one of claims 1 to 4, wherein a metal layer is provided on an outer surface. A synthetic resin second sheet (102) at least on the opening side of the protrusion (101a) in the first sheet (101) in the first sheet (101) made of synthetic resin on which a large number of protrusions (101a) are formed. ) Are joined, and a plurality of bubble portions (104) in which gas is sealed are formed between the protrusion (101a) and the second sheet (102), and each of the plurality of bubble portions (104) A method for producing a synthetic resin bubble sheet independent of the bubble part of
A first sheet supply step of supplying the first sheet (101) having a melting point or higher to a forming roll (204) having a recess (204a) corresponding to the protrusion (101a) formed on the outer peripheral surface;
A protrusion forming step of forming the protrusion (101a) on the first sheet (101) on the outer peripheral surface of the forming roll (204);
A second sheet supply step of supplying the second sheet (102) heated to the melting point or higher to the opening side surface of the protrusion (101a) in the first sheet (101);
An external force is applied by the first pressurizing means (205) so as to press the second sheet (102) against the first sheet (101), thereby joining the first sheet (101) and the second sheet (102). And a joining process to
In the joining step, the first gas in a state in which a gas of more than 0% and 65% or less of the upper limit of the amount of gas that can be enclosed in the bubble portion (104) at standard atmospheric pressure is enclosed in the bubble portion (104). A method for producing a bubble sheet made of a synthetic resin, comprising joining a sheet (101) and the second sheet (102). In the protruding portion forming step, the protruding portion (101a) is formed by sucking the first sheet (101) with the concave portion (204a) of the forming roll (204), and the first sheet (101) is at least Rukoto part is disengaged from the wall surface of the recess (204a) of the protrusion by feeding air into the recess (204a) after aspiration (101a), the recess volume of the protrusions (101a) (204a) method for producing a synthetic resin foam sheet according to claim 6, 0% and 65% or less and be characterized Rukoto volume of.   The method for producing a synthetic resin foam sheet according to claim 6 or 7, further comprising a metal layer forming step of providing a metal layer on an outer surface of the foam sheet.

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