Method for producing resin foam sheet

Abstract

To provide an innovative technique for controlling the bubble condition of a resin foam sheet to bring it in a desired condition.SOLUTION: In this technique, a method for producing a resin foam sheet having a first surface and a second surface which is opposite to the first surface is provided, the method including a bubble control step for controlling a bubble condition by pressure-feeding the resin foam sheet between three or more pairs of rolls including a first roll pair, a second roll pair, and a third roll pair from an upstream side in an insertion direction of the resin foam sheet, and satisfying predetermined conditions (1) to (4).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present technology relates to a method for manufacturing a resin foam sheet. More specifically, it relates to a method for manufacturing a resin foam sheet having a step of adjusting the bubble state by pumping the resin foam sheet.

Background Art

[0002] Conventionally, resin foam sheets have been used in various applications because of their excellent cushioning, heat insulation, water repellency, moisture resistance, sound insulation, etc., and various technical improvements have been made to suit each application. In order to adjust the bubble state of the resin foam sheet to a desired state, a technique has been developed in which the resin foam sheet formed into a sheet shape is passed between a pair of rolls and compressed to rupture the bubble film and make it continuous.

[0003] For example, in Patent Document 1, a foam sheet made of a polyolefin resin and having closed cells is supplied to the gap between a pair of rolls that rotate at different peripheral speeds and have the same rotation direction on the opposing surfaces, and a compression force and a shear stress are simultaneously applied to the foam sheet having the closed cells to rupture a part of the closed cells of the foam sheet having the closed cells and communicate the closed cells with each other to form continuous cells, thereby producing a polyolefin resin cross-linked foam sheet having a small cell diameter, being applicable to various uses, and having excellent vacuum formability.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] As described above, a technique is being developed to adjust the cell state of a resin foam sheet to a desired state by passing the resin foam sheet formed in a sheet shape between a pair of rolls. However, there has been a problem in the conventional techniques that the sheet is twisted and wrinkled. Further, in the technique of Patent Document 1, it is premised on using two pairs of rolls. Further, when it is desired to increase the number of roll pairs, an even number of sets of roll pairs is required, and there has also been a problem of an increase in the size of the equipment. If the technique of Patent Document 1 is carried out with three pairs of rolls, it is predicted that a difference will occur in the cell-breaking force between one surface and the other surface of the sheet. Therefore, in order to equalize the cell-breaking force on both surfaces of the sheet, it is necessary to turn the sheet over and pass it through the roll pair a plurality of times, which also leads to problems such as an increase in manufacturing time and manufacturing cost.

[0006] Therefore, the main object of the present technology is to provide a novel technique for adjusting the cell state of a resin foam sheet to a desired state.

Means for Solving the Problems

[0007] The inventor of the present invention conducted intensive research to solve the above problems. As a result, the inventor succeeded in manufacturing a resin foam sheet having a good appearance by using three or more pairs of rolls and devising the speed of each pair of rolls, and thus completed the present technology.

[0008] That is, the present technology provides a method for manufacturing a resin foam sheet having a first surface and a second surface which is the opposite surface of the first surface, including a cell adjustment step of adjusting the cell state by feeding the resin foam sheet between three or more pairs of rolls including a first roll pair, a second roll pair, and a third roll pair from the upstream side in the insertion direction of the resin foam sheet, and satisfying the following conditions (1) to (4). (1) The speed V2-1 of the roll in contact with the first surface of the second roll pair and the speed V2-2 of the roll in contact with the second surface of the second roll pair satisfy V2-1 / V2-2 = 0.9 to 1.1. (2) The speed V1-1 of the roll in contact with the first surface of the first roll pair and the speed V1-2 of the roll in contact with the second surface of the first roll pair satisfy V1-1 > V1-2. (3) The speed V3-1 of the roll in contact with the first surface of the third roll pair and the speed V3-2 of the roll in contact with the second surface of the third roll pair satisfy V3-1 < V3-2. (4) V1-1 / V1-2 = 1.05 to 1.43, and / or V3-1 / V3-2 = 0.72 to 0.95. In the method for manufacturing a resin foam sheet according to the present technology, further, the following condition (5) may be satisfied. (5) The speed ratio between the speed V1-1 of the roll in contact with the first surface of the first roll pair and the average speed V2m of the speed V2-1 of the roll in contact with the first surface of the second roll pair and the speed V2-2 of the roll in contact with the second surface of the second roll pair is V1-1 / V2m = 0.90 to 1.14. Also, in the method for manufacturing a resin foam sheet according to the present technology, further, the following condition (6) may be satisfied. (6) The speed ratio between the speed V3-1 of the roll in contact with the first surface of the third roll pair and the average speed V2m of the speed V2-1 of the roll in contact with the first surface of the second roll pair and the speed V2-2 of the roll in contact with the second surface of the second roll pair is V3-1 / V2m = 0.86 to 1.10.

Brief Description of the Drawings

[0009]

Figure 1

Embodiments for Carrying Out the Invention

[0010] Hereinafter, preferred embodiments for implementing the present technology will be described. The embodiments described below show examples of typical embodiments of the present technology, and any of the embodiments can be combined. Also, the scope of the present technology is not construed narrowly by these.

[0011] 1. Manufacturing method of the resin foam sheet 1 The manufacturing method of the resin foam sheet 1 according to the present technology is a method of performing a bubble adjustment step. In addition, in the manufacturing method according to the present technology, kneading steps, foaming steps, molding steps, etc. performed in the manufacturing process of general resin foam sheets can be performed as necessary.

[0012] Note that the manufacturing method according to the present technology is a method of performing at least a bubble adjustment step, and the production of the resin foam sheet before bubble adjustment to be subjected to the bubble adjustment step can also be performed by another institution. That is, using a resin foam sheet before bubble adjustment manufactured by a certain institution performing a kneading step, a foaming step, and a molding step as necessary, another institution performs the bubble adjustment step of the present technology to manufacture the bubble-adjusted resin foam sheet 1 according to the present technology. It is also possible, or after the same institution performs a kneading step, a foaming step, and a molding step as necessary to manufacture a resin foam sheet before bubble adjustment, a bubble adjustment step is performed to manufacture the bubble-adjusted resin foam sheet 1 according to the present technology. Hereinafter, each step will be described in detail.

[0013] (A) Bubble adjustment step FIG. 1 is a schematic conceptual diagram schematically showing three sets of roll pairs R1-1, R1-2, R2-1, R2-2, R3-1, R3-2 that can be used in the manufacturing method of the resin foam sheet 1 according to the present technology, and the state in which the resin foam sheet 1 is pressure-fed between each roll pair. Each arrow in FIG. 1 indicates the rotation direction of each roll or the insertion direction of the resin foam sheet 1. The resin foam sheet 1 manufactured by the manufacturing method according to the present technology has a first surface 11 and a second surface 12 that is the surface on the opposite side of the first surface 11. Details of the resin foam sheet 1 will be described later.

[0014] The manufacturing method of the resin foam sheet 1 according to the present technology includes a bubble adjustment step. In the bubble adjustment step, the resin foam sheet 1 is pumped between three or more pairs of rolls including the first roll pair R1-1, R1-2, the second roll pair R2-1, R2-2, and the third roll pair R3-1, R3-2 from the upstream side in the insertion direction of the resin foam sheet 1 to adjust the bubble state.

[0015] In addition, in FIG. 1, for the sake of convenience, an example of performing the bubble adjustment step while transporting the resin foam sheet 1 in the horizontal direction is described, but it is not limited thereto. For example, although not shown, it is also possible to perform the bubble adjustment step while transporting in the vertical direction or the diagonal direction. Further, in FIG. 1, for the sake of convenience, the upper surface of the resin foam sheet 1 is defined as the first surface 11 and the lower surface is defined as the second surface 12 facing the drawing, but it is not limited thereto. Although not shown, when the lower surface of the resin foam sheet 1 is defined as the first surface 11 facing the drawing, the upper surface becomes the second surface 12.

[0016] The bubble adjustment step is characterized by satisfying the following conditions (1) to (4) described later. It is also preferable to further satisfy the following conditions (5) to (7). Hereinafter, each condition will be described in detail.

[0017] [Condition (1)] Condition (1) is that in the second roll pair R2-1, R2-2, the speed V2-1 of the roll R2-1 in contact with the first surface 11 of the resin foam sheet 1 and the speed V2-2 of the roll R2-2 in contact with the second surface 12 satisfy V2-1 / V2-2 = 0.9 to 1.1. That is, the difference in the speeds of the second roll pair R2-1, R2-2 is within ±10%, preferably within ±5%, more preferably within ±3%, still more preferably within ±2%, and even more preferably within ±1%. It is particularly preferable that the speeds of the second roll pair R2-1, R2-2 are substantially the same.

[0018] In the prior art, for example, as in the prior art described in Patent Document 1, it was common general knowledge to use a pair of rolls having different peripheral speeds. However, in the present technology, by providing a pair of rolls (the first roll pair R1-1, R1-2 and the third roll pair R3-1, R3-2 in the present technology) with a speed difference and a roll pair (the second roll pair R2-1, R2-2 in the present technology) with a small speed difference therebetween, success has been achieved in manufacturing a resin foam sheet 1 having a good appearance.

[0019] [Conditions (2) to (4)] Condition (2) is that in the first roll pair R1-1, R1-2, the speed V1-1 of the roll R1-1 in contact with the first surface 11 of the resin foam sheet 1 and the speed V1-2 of the roll R1-2 in contact with the second surface 12 are such that V1-1 > V1-2.

[0020] Condition (3) is that in the third roll pair R3-1, R3-2, the speed V3-1 of the roll R3-1 in contact with the first surface 11 of the resin foam sheet 1 and the speed V3-2 of the roll R3-2 in contact with the second surface 12 are such that V3-1 < V3-2.

[0021] That is, the first roll pair R1-1, R1-2 and the third roll pair R3-1, R3-2 each have a speed difference between the paired rolls, and the roll having a higher speed in the first roll pair R1-1, R1-2 (the roll R1-1 in the present embodiment) and the roll having a higher speed in the third roll pair R3-1, R3-2 (the roll R3-2 in the present embodiment) each contact the opposite surface of the resin foam sheet 1. By arranging the first roll pair R1-1, R1-2 and the third roll pair R3-1, R3-2 each having a speed difference between the paired rolls in this way, the foam-breaking force on both sides of the sheet becomes uniform, and in addition to improving the appearance of the manufactured resin foam sheet 1, since it is not necessary to turn the sheet over and pass it through the roll pair a plurality of times, it can also contribute to reducing the manufacturing time and manufacturing cost.

[0022] Condition (4) is that the speed ratio in the first roll pair R1-1, R1-2 is V1-1 / V1-2 = 1.05 to 1.43, and / or the speed ratio in the third roll pair R3-1, R3-2 is V3-1 / V3-2 = 0.72 to 0.95.

[0023] That is, in the first roll pair R1-1, R1-2, the speed of the roll with a higher speed (roll R1-1 in this embodiment) relative to the roll with a lower speed (roll R1-2 in this embodiment) is 1.05 times or more and 1.43 times or less, and / or in the third roll pair R3-1, R3-2, the speed of the roll with a lower speed (roll R3-1 in this embodiment) relative to the roll with a higher speed (roll R3-2 in this embodiment) is 0.72 times or more and 0.95 times or less. As in Comparative Examples 1 and 2 of the examples described later, even when Conditions (1) to (3) are satisfied, there was a problem that wrinkles and twists occurred in the resin foam sheet. However, in the present technology, by satisfying Condition (4), the occurrence of wrinkles and twists can be prevented, and the resin foam sheet 1 with excellent appearance has been successfully manufactured.

[0024] In the first roll pair R1-1, R1-2, the speed of the roll with a higher speed (roll R1-1 in this embodiment) relative to the roll with a lower speed (roll R1-2 in this embodiment) can exhibit the functions and effects of the present technology if it is 1.05 times or more, preferably 1.10 times or more, more preferably 1.15 times or more, still more preferably 1.20 times or more, and even more preferably 1.25 times or more.

[0025] In the first roll pair R1-1, R1-2, the speed of the roll with a higher speed (roll R1-1 in this embodiment) relative to the roll with a lower speed (roll R1-2 in this embodiment) can exhibit the functions and effects of the present technology if it is 1.43 times or less, preferably 1.42 times or less, more preferably 1.41 times or less, still more preferably 1.40 times or less, even more preferably 1.39 times or less, and particularly preferably 1.38 times or less.

[0026] In the third roll pair R3-1 and R3-2, if the speed of the roll with a slower speed (roll R3-1 in this embodiment) relative to the roll with a faster speed (roll R3-2 in this embodiment) is 0.72 times or more, the functions and effects of the present technology can be exerted. Preferably, it is 0.73 times or more, more preferably 0.74 times or more, still more preferably 0.75 times or more.

[0027] In the third roll pair R3-1 and R3-2, if the speed of the roll with a slower speed (roll R3-1 in this embodiment) relative to the roll with a faster speed (roll R) is 0.95 times or less, the functions and effects of the present technology can be exerted. Preferably, it is 0.93 times or less, more preferably 0.90 times or less, still more preferably 0.87 times or less, even more preferably 0.85 times or less, and particularly preferably 0.83 times or less.

[0028] [Condition (5)] Condition (5) is that the speed ratio of the speed V1-1 of the roll R1-1 in contact with the first surface 11 of the resin foam sheet 1 in the first roll pair and the average speed V2m of the second roll pair R2-1 and R2-2 is V1-1 / V2m = 0.90 to 1.14. That is, with respect to the average speed V2m of the second roll pair R2-1 and R2-2, the speed of the roll with a faster speed (roll R1-1 in this embodiment) in the first roll pair R1-1 and R1-2 is 0.90 times or more and 1.14 times or less. In the present technology, by satisfying the above-mentioned conditions (1) to (4), the functions and effects of the present technology can be exerted, and by satisfying condition (5), a resin foam sheet 1 with a more excellent appearance can be manufactured.

[0029] With respect to the average speed V2m of the second roll pair R2-1 and R2-2, the lower limit value of the speed of the roll with a faster speed (roll R1-1 in this embodiment) in the first roll pair R1-1 and R1-2 is preferably 0.90 times or more, more preferably 0.95 times or more, still more preferably 1.00 times or more. The upper limit value is preferably 1.14 times or less, more preferably 1.13 times or less, still more preferably 1.12 times or less, even more preferably 1.11 times or less, and particularly preferably 1.10 times or less.

[0030] [Condition (6)] Condition (6) is that the speed ratio of the speed V3-1 of the roll R3-1 in contact with the first surface 11 of the resin foam sheet 1 in the third roll pair and the average speed V2m of the second roll pair R2-1, R2-2 is V3-1 / V2m = 0.86 to 1.10. That is, with respect to the average speed V2m of the second roll pair R2-1, R2-2, the speed of the roll having a slower speed in the third roll pair R3-1, R3-2 (roll R3-1 in this embodiment) is 0.86 times or more and 1.10 times or less. In this technology, by satisfying the above-mentioned conditions (1) to (4), the functions and effects of this technology can be exerted. By satisfying condition (6), a resin foam sheet 1 with an even better appearance can be manufactured.

[0031] With respect to the average speed V2m of the second roll pair R2-1, R2-2, the lower limit value of the speed of the roll having a slower speed in the third roll pair R3-1, R3-2 (roll R3-1 in this embodiment) is preferably 0.86 times or more, more preferably 0.87 times or more, still more preferably 0.88 times or more, even more preferably 0.89 times or more, and particularly preferably 0.90 times or more. The upper limit value is preferably 1.10 times or less, more preferably 1.07 times or less, still more preferably 1.04 times or less, even more preferably 1.02 times or less, and particularly preferably 1.00 times or less.

[0032] [Condition (7)] Condition (7) is that the average speed V1m of the first roll pair R1-1, R1-2, the average speed V2m of the second roll pair R2-1, R2-2, and the average speed V3m of the third roll pair R3-1, R3-2 satisfy V1m < V2m < V3m. By satisfying the above-mentioned conditions (1) to (4), the functions and effects of this technology can be exerted. By satisfying condition (7), a resin foam sheet 1 with an even better appearance can be manufactured.

[0033] (B) Material of the resin foam sheet 1 [Resin component] As the resin component that can be used as the material of the resin foam sheet 1 manufactured by the manufacturing method according to the present technology, one or more resin components that can be used for general resin foam sheets can be freely selected and used as long as the object, action, and effect of the present technology are not impaired.

[0034] Examples of the resin component that can be used in the present technology include thermoplastic resins such as polyolefin-based resins, polystyrene-based resins, polyamide-based resins, and polyester-based resins; thermoplastic elastomers such as olefin-based thermoplastic elastomers and styrene-based thermoplastic elastomers; synthetic rubbers such as ethylene-propylene rubber (EPDM), and thermosetting elastomers such as natural rubber.

[0035] Among these, in the present technology, it is preferable to use polyolefin-based resins. The polyolefin-based resin that can be used in the present technology is a resin mainly composed of olefin component units. The resin mainly composed of olefin component units is a resin containing 50% by mass or more of olefin component units. In the present technology, the content of olefin component units in the resin is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and it is particularly preferable that the resin component is composed only of polyolefin-based resins.

[0036] Examples of the polyolefin-based resin that can be used in the present technology include polyethylene-based resins, polypropylene-based resins, polybutene, polypentene, and copolymers of olefin-based monomers and monomers copolymerizable with the olefin-based monomers. These can also be used alone or in combination of two or more.

[0037] Examples of the polyethylene resin include homopolymers of ethylene such as high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and very-low-density polyethylene (VLDPE); ethylene-propylene random copolymers, ethylene-propylene block copolymers, ethylene-butene block copolymers, ethylene-butene random copolymers, ethylene-vinyl acetate copolymers (EVA), and ethylene-methyl methacrylate copolymers.

[0038] Examples of the polypropylene resin include homopolymers of propylene such as isotactic polypropylene, syndiotactic polypropylene, and atactic polypropylene; propylene-ethylene random copolymers, propylene-ethylene block copolymers, propylene-butene random copolymers, propylene-butene block copolymers, propylene-ethylene-butene terpolymers, propylene-acrylic acid copolymers, and propylene-maleic anhydride copolymers.

[0039] Among these, in this technology, it is preferable to use a polyethylene resin, and among the polyethylene resins, it is preferable to use low-density polyethylene (LDPE) or ethylene-vinyl acetate copolymer (EVA).

[0040] [Blowing agent] As the blowing agent that can be used as the material of the resin foam sheet 1 manufactured by the manufacturing method according to this technology, one or more blowing agents that can be used for general resin foam sheets can be freely selected and used as long as the object, function, and effect of this technology are not impaired.

[0041] As the foaming agent that can be used in this technology, for example, organic or inorganic thermal decomposition-type chemical foaming agents can be used. Examples of organic foaming agents include azo compounds such as azodicarbonamide (ADCA), metal salts of azodicarboxylic acid (such as barium azodicarboxylate), azobisisobutyronitrile (AIBN), etc.; nitroso compounds such as N,N'-dinitrosopentamethylenetetramine (DPT), etc.; hydrazine derivatives such as hydrazodicarbonamide, 4,4’-oxybis(benzenesulfonylhydrazide), toluenesulfonylhydrazide (TSH), etc.; semicarbazide compounds such as toluenesulfonyl semicarbazide, etc. Examples of inorganic foaming agents include ammonium carbonate, sodium carbonate, ammonium bicarbonate, sodium bicarbonate, ammonium nitrite, sodium borohydride, monosodium anhydrous citrate, etc.

[0042] Among these, in this technology, it is preferable to use an organic foaming agent as the foaming agent, and among the organic foaming agents, it is preferable to use azodicarbonamide (ADCA).

[0043] The amount of the foaming agent used in this technology can be freely set as long as the object and effects of this technology are not impaired. In this technology, as the content of the foaming agent relative to 100 parts by mass of the resin component, for example, it is 5.0 parts by mass or more, preferably 10.0 parts by mass or more, more preferably 15.0 parts by mass or more. By setting the content of the foaming agent within this range, the foamability during the production of the foam can be improved.

[0044] In this technology, as the content of the foaming agent relative to 100 parts by mass of the resin component, for example, it is 30.0 parts by mass or less, preferably 25.0 parts by mass or less, more preferably 20.0 parts by mass or less. By setting the content of the foaming agent within this range, the formation defects due to excessive foaming can be suppressed, and it can also contribute to cost reduction.

[0045] [Crosslinking agent] The resin foam sheet 1 manufactured by the manufacturing method according to the present technology may be a sheet made of a crosslinked foam. By performing crosslinking during the production of the resin foam sheet 1 according to the present technology, the viscosity of the composition (kneaded product) before foaming can be improved, and the foamability can be improved.

[0046] When the resin foam sheet 1 manufactured by the manufacturing method according to the present technology is a sheet made of a crosslinked foam, crosslinking by irradiation with ionizing radiation can be performed, but chemical crosslinking using a crosslinking agent can also be performed. As the crosslinking agent that can be used as the material of the resin foam sheet 1 manufactured by the manufacturing method according to the present technology, one or more crosslinking agents that can be used for general resin foam sheets can be freely selected and used as long as the object and effects of the present technology are not impaired.

[0047] Examples of the crosslinking agent that can be used in the present technology include crosslinking agents having chemical structures such as silane groups, peroxides, hydroxyl groups, amide groups, and ester groups. Among these, in the present technology, it is preferable to use an organic peroxide as the crosslinking agent.

[0048] Examples of the organic peroxide include dicumyl peroxide (DCP), 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, di-t-butyl peroxide, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, and t-butyl hydroperoxide. Among these, in the present technology, it is preferable to use dicumyl peroxide (DCP) as the crosslinking agent.

[0049] The amount of the crosslinking agent used in the present technology can be freely set as long as the object and effect of the present technology are not impaired. In the present technology, the content of the crosslinking agent with respect to 100 parts by mass of the resin component is, for example, 0.1 part by mass or more, preferably 0.2 part by mass or more, more preferably 0.3 part by mass or more. By setting the content of the crosslinking agent in the resin composition within this range, the viscosity can be improved and the foamability can be improved.

[0050] In the present technology, the content of the crosslinking agent with respect to 100 parts by mass of the resin component is, for example, 4.0 parts by mass or less, preferably 3.0 parts by mass or less, more preferably 2.0 parts by mass or less. By setting the content of the crosslinking agent in the resin composition within this range, it is possible to prevent tearing or the like from occurring during foaming and improve the moldability.

[0051] [Other components] In the resin foam sheet 1 produced by the production method according to the present technology, as long as the object and effect of the present technology are not impaired, as other components, various components that can be used in the production of general resin foam sheets can be freely selected and used one kind or two or more kinds according to the purpose.

[0052] Examples of other components that can be used in the present technology include a foaming aid, a crosslinking accelerator, an inorganic filler, a foam stabilizer, a flame retardant, a stabilizer, a plasticizer, a colorant, an antioxidant, a dispersant, an ultraviolet absorber, a lubricant, and the like.

[0053] (C) Manufacturing method of the resin foam sheet before bubble adjustment The manufacturing method of the resin foam sheet before bubble adjustment to be subjected to the above-described bubble adjustment step is not particularly limited, and a general manufacturing method of a resin foam sheet can be freely selected and used. For example, a long foaming method using chemical crosslinking, a long foaming method using electron beam crosslinking, a one-stage block foaming method, a two-stage block foaming method, etc. can be mentioned. In the present technology, in particular, it is preferable to select a long foaming method, and among the long foaming methods, it is more preferable to use a long foaming method using chemical crosslinking. Hereinafter, each method will be described.

[0054] [Long-strip Foaming Method Using Chemical Crosslinking] The long-strip foaming method is a method that performs the following steps (1)-(3), for example. (1) Kneading step The resin component, crosslinking agent, foaming agent, and any other optional components as described above are kneaded with a single-screw extruder, twin-screw extruder, etc., and extruded into a sheet shape to extrude a foaming resin composition (hereinafter referred to as a mother board) having a predetermined shape such as a sheet. Kneading and extrusion can be performed collectively by an extruder. In order to perform uniform kneading, it is preferable to perform extrusion after mixing each component in advance. (2) Foaming step While transporting the mother board obtained in the kneading step in a heating device such as an oven, it is heated at a temperature equal to or higher than the decomposition temperature of the foaming agent and crosslinking agent (for example, 120-250 °C) for a predetermined time (for example, 5-20 minutes) to cause foaming, thereby obtaining a resin foamed sheet. It is preferable to use a device in which a heating device such as an oven and a transport device are integrated, because the mother board can be continuously processed. (3) Forming step The resin foamed sheet obtained in the foaming step can be directly subjected to the above-described bubble adjustment step, but it is also possible to perform a forming step of forming it into a desired form by slicing or the like as necessary, and then subject it to the above-described bubble adjustment step.

[0055] [Long-strip Foaming Method Using Electron Beam Crosslinking] (1) Kneading step The resin component, crosslinking agent, foaming agent, and any other optional components as described above are kneaded with a single-screw extruder, twin-screw extruder, etc., and a resin composition (mother board) having a predetermined shape such as a sheet shape is extruded. Kneading and extrusion can be performed collectively by an extruder. In order to perform uniform kneading, it is preferable to perform extrusion after mixing each component in advance. (2) Crosslinking step The masterbatch obtained in the kneading process is crosslinked. As the crosslinking method, a method of crosslinking with ionizing radiation such as electron beams or γ-rays can be used. As the crosslinking method, crosslinking by electron beam irradiation (electron beam crosslinking) is preferred. This is because electron beam crosslinking can achieve refinement of the cells formed in the foam and control the cell diameter within a predetermined range. Electron beam crosslinking can be performed using an electron beam irradiator. Optionally, a crosslinking agent such as the aforementioned organic peroxide may be blended and chemical crosslinking may be used in combination. The irradiation dose of the electron beam is preferably 1.0 Mrad - 10.0 Mrad (10 kGy - 100 kGy). If the irradiation dose is less than 1.0 Mrad, good foaming may not occur in the subsequent foaming process. If the irradiation dose exceeds 10.0 Mrad, the crosslinking is strong and the resin becomes hard, so there is a concern that cracks may occur during foaming. The acceleration voltage of the electron beam may be appropriately adjusted according to the thickness of the masterbatch, etc., and is not particularly limited. (3) Foaming process While transporting the crosslinked masterbatch obtained in the crosslinking process in a heating device such as an oven, it is heated at a temperature above the decomposition temperature of the foaming agent and the crosslinking agent (for example, 120 - 250 °C) for a predetermined time (for example, 5 - 20 minutes) to cause foaming, thereby obtaining a resin foam sheet. It is preferable to use a device in which a heating device such as an oven and a transport device are integrated, because the masterbatch can be continuously processed. (4) Molding process The resin foam sheet obtained in the foaming process can be directly subjected to the aforementioned bubble adjustment process, but it is also possible to perform a molding process to form it into a desired shape using slicing or the like as necessary, and then subject it to the aforementioned bubble adjustment process.

[0056] [One-step block foaming method] (1) Kneading process The aforementioned resin component, crosslinking agent, foaming agent, and any other components that are appropriately required are melt-kneaded at a temperature below the decomposition temperature of the foaming agent using a kneading device such as an extruder, Banbury mixer, kneader, or roll to obtain a foamable resin composition. (2) Foaming process The foamable resin composition obtained in the kneading step is filled into a mold, sealed, and heated under pressure for a predetermined time (heated at a temperature equal to or higher than the decomposition temperatures of the foaming agent and the crosslinking agent), thereby promoting the crosslinking of the crosslinking agent and the decomposition of the foaming agent. Thereafter, the mold is opened and depressurized to obtain a resin foam. (3) Forming step The resin foam obtained in the foaming step is, if necessary, subjected to ear cutting, slicing, etc. to form a resin foam sheet in a desired form. The obtained resin foam sheet is subjected to the above-described cell structure adjustment step.

[0057] [Two-stage block foaming method] (1) Kneading step The above-described resin component, crosslinking agent, foaming agent, and any other components that may be required as appropriate are melt-kneaded at a temperature equal to or lower than the decomposition temperature of the foaming agent using a kneading apparatus such as an extruder, Banbury mixer, kneader, or roll to obtain a foamable resin composition. (2) Primary foaming step The foamable resin composition obtained in the kneading step is filled into the molding space of a primary mold and heated under pressure. Thereby, a part of the crosslinking agent, or a part of the crosslinking agent and the foaming agent is decomposed. Thereafter, the pressure is released and an intermediate of the foamable resin composition is taken out. The heating temperature is usually determined in the range of 120 - 160°C, and the heating time is usually in the range of 10 - 60 minutes. (3) Secondary foaming step The intermediate of the foamable resin composition obtained in the primary foaming step is placed in the molding space of a secondary mold, heated under normal pressure for secondary foaming, and then the resin foam is taken out from the secondary mold. (4) Forming step The resin foam obtained in the foaming step is, if necessary, subjected to ear cutting, slicing, etc. to form a resin foam sheet in a desired form. The obtained resin foam sheet is subjected to the above-described cell structure adjustment step.

[0058] 2. Physical properties of the resin foam sheet 1 This technology is characterized by the above-described manufacturing method, and the physical properties of the manufactured resin foam sheet 1 are not particularly limited, and can be freely adjusted according to the purpose of use of the sheet, etc.

[0059] (1) Density The density of the resin foam sheet 1 produced by the production method according to the present technology can be freely set as long as the object and effect of the present technology are not impaired. In the present technology, as the lower limit value of the density of the resin foam sheet 1, for example, 10 kg / m 3 or more, preferably 15 kg / m 3 or more, more preferably 20 kg / m 3 or more, still more preferably 25 kg / m 3 or more. By setting the lower limit value of the density of the resin foam sheet 1 within this range, it is possible to prevent the sheet from becoming too soft and impart appropriate elasticity.

[0060] The upper limit value of the density of the resin foam sheet 1 is, for example, 50 kg / m 3 or less, preferably 45 kg / m 3 or less, more preferably 40 kg / m 3 or less. By setting the density of the resin foam sheet 1 within this range, it is possible to prevent the resin foam sheet 1 from becoming too hard and losing its flexibility, and to impart appropriate cushioning properties.

[0061] In the present technology, the density of the resin foam sheet 1 is a value measured in accordance with the method based on JIS K6767:1999.

[0062] (2) Foaming ratio The foaming ratio of the resin foam sheet 1 produced by the production method according to the present technology can be freely set as long as the object and effect of the present technology are not impaired. In the present technology, as the lower limit value of the foaming ratio of the resin foam sheet 1, for example, 10 times or more, preferably 15 times or more, more preferably 20 times or more. By setting the lower limit value of the foaming ratio of the resin foam sheet 1 within this range, it is possible to prevent the resin foam sheet 1 from becoming too hard and losing its flexibility, and to impart appropriate cushioning properties.

[0063] The upper limit of the expansion ratio of the resin foam sheet 1 is, for example, 50 times or less, preferably 45 times or less, more preferably 40 times or less. By setting the expansion ratio of the resin foam sheet 1 within this range, it is possible to prevent it from becoming too soft and impart appropriate elasticity.

[0064] In the present technology, the expansion ratio is a value calculated by the following formula. Expansion ratio (times) = 1000 / density (kg / m 3 )

[0065] (3) Compression stress strain (50%) The 50% compression stress strain of the resin foam sheet 1 manufactured by the manufacturing method according to the present technology can be freely set as long as the object and effect of the present technology are not impaired. In the present technology, as the upper limit value of the 50% compression stress strain of the resin foam sheet 1, for example, it is 40 kPa or less, preferably 20 kPa or less, more preferably 10 kPa or less. The lower limit value of the 50% compression stress strain of the resin foam sheet 1 can be set to, for example, 3 kPa or more.

[0066] In the present technology, the 50% compression stress strain of the resin foam sheet 1 is a value measured in accordance with the method based on JIS K6767:1999.

[0067] (4) Asker F hardness The Asker F hardness of the resin foam sheet 1 manufactured by the manufacturing method according to the present technology can be freely set as long as the object and effect of the present technology are not impaired. In the present technology, as the upper limit value of the Asker F hardness of the resin foam sheet 1, for example, it is 80 or less, preferably 70 or less, more preferably 60 or less. The lower limit value of the Asker F hardness of the resin foam sheet 1 can be set to, for example, 10 or more.

[0068] In the present technology, the Asker F hardness of the resin foam sheet 1 is a value measured in accordance with JIS 6253-3 using a type F durometer (Polymer Instrument Co., Ltd.).

[0069] (5) Gel fraction The gel fraction of the resin foam sheet 1 produced by the manufacturing method according to the present technology can be freely set as long as the objectives and effects of the present technology are not impaired. In the present technology, as the lower limit value of the gel fraction of the resin foam sheet 1, for example, it is 30% or more, preferably 40% or more, more preferably 50% or more. The upper limit value of the gel fraction of the resin foam sheet 1 is, for example, 90% or less, preferably 80% or less, more preferably 70% or less.

[0070] In addition, in the present technology, the gel fraction of the resin foam sheet 1 is a value measured in accordance with the method based on JIS K6769.

[0071] 4. Use of the resin foam sheet 1 The resin foam sheet 1 produced by the manufacturing method according to the present technology can be used for various applications in all fields by taking advantage of its high quality. Specifically, for example, sealing materials, shock absorbers, cushioning materials, sound absorbers, heat insulating materials, heat retaining materials, etc. can be mentioned.

Examples

[0072] Hereinafter, the present technology will be described in more detail based on examples. The examples described below show an example of a typical example of the present technology, and the scope of the present technology is not construed narrowly thereby.

[0073] (1) Raw materials Resin 1: Ethylene vinyl acetate copolymer (EVA) (vinyl acetate content 19% by mass, density 941 kg / m3, MFR 2.5 g / 10 min): 40.0 parts by mass Resin 2: Low density polyethylene (LDPE) (density 924 kg / m3, MFR 3.0 g / 10 min): 60.0 parts by mass Blowing agent: Azodicarbonamide (ADCA): 18.0 parts by mass Crosslinking agent: Dicumyl peroxide (DCP): 1.1 parts by mass Other additives: 7.9 parts by mass

[0074] (2) Manufacture of the resin foam sheet After melting and kneading the above raw materials in a kneader, they were introduced into an extruder and extruded into a sheet form through a die attached to the tip of the extruder. The extruded sheet-shaped resin composition was heated to cause crosslinking and foaming to produce a resin foam sheet before bubble adjustment. The produced resin foam sheet before bubble adjustment was passed through between three pairs of rolls six times under the conditions shown in Table 1 below to adjust the bubble state by pumping the resin foam sheet before bubble adjustment, thereby producing a resin foam sheet.

[0075] (3) Evaluation The appearance of the produced resin foam sheet was evaluated according to the following evaluation criteria. ○: No wrinkles or twists, and the appearance is good ×: There are wrinkles and / or twists

[0076] (4) Physical Property Measurement Regarding the resin foam sheet of Example 3, density, expansion ratio, 50% compression stress strain, Asker F hardness, and gel fraction were measured before the bubble adjustment process (0 times), after 6 times of the bubble adjustment process, and after 10 times of the bubble adjustment process. The measurement methods for each physical property are shown below.

[0077] [Density] Measured in accordance with the method based on JIS K6767:1999.

[0078] [Expansion Ratio] Calculated by the following formula. Expansion ratio (times) = 1000 / density (kg / m 3 )

[0079] [50% Compression Stress Strain] Measured in accordance with the method based on JIS K6767:1999.

[0080] [Asker F Hardness] Measured in accordance with JIS 6253-3 using a type F durometer (Polymer Instruments Co., Ltd.).

[0081] [Gel Fraction] Measured in accordance with the method based on JIS K6769.

[0082] (5) Results The evaluation results are shown in Table 1 below. Also, the physical property measurement results before, after 6 times, and after 10 times in the bubble adjustment step in Example 3 are shown in Table 2.

Table 1

[0083]

Table 2

[0084] (5) Considerations As shown in Table 1, Examples 1 to 3 produced by performing the bubble adjustment step that satisfies conditions (1) to (4) had no wrinkles or twists in the produced resin foam sheet and had a good appearance.

Claims

Claim 1 A method for manufacturing a foamed resin sheet having a first surface and a second surface opposite to the first surface, comprising: a bubble adjusting step of adjusting the bubble state by feeding the foamed resin sheet between three or more pairs of rolls including a first roll pair, a second roll pair, and a third roll pair from the upstream side in the insertion direction of the foamed resin sheet, and satisfying the following conditions (1) to (4). A method for manufacturing a foamed resin sheet. (1) The speed V2-1 of the roll in contact with the first surface of the second roll pair and the speed V2-2 of the roll in contact with the second surface of the second roll pair satisfy V2-1 / V2-2 = 0.9 to 1.

1. (2) The speed V1-1 of the roll in contact with the first surface of the first roll pair and the speed V1-2 of the roll in contact with the second surface of the first roll pair satisfy V1-1 > V1-2. (3) The speed V3-1 of the roll in contact with the first surface of the third roll pair and the speed V3-2 of the roll in contact with the second surface of the third roll pair satisfy V3-1 < V3-2. (4) V1-1 / V1-2 = 1.05 to 1.43, and / or V3-1 / V3-2 = 0.72 to 0.

95. Claim 2 The method for manufacturing a foamed resin sheet according to claim 1, further satisfying the following condition (5). (5) The speed ratio of the speed V1-1 of the roll in contact with the first surface of the first roll pair, the average speed V2m of the speed V2-1 of the roll in contact with the first surface of the second roll pair and the speed V2-2 of the roll in contact with the second surface of the second roll pair is V1-1 / V2m = 0.90 to 1.

14. Claim 3 The method for manufacturing a foamed resin sheet according to claim 1 or 2, further satisfying the following condition (6). (6) The speed ratio of the speed V3-1 of the roll in contact with the first surface of the third roll pair, the average speed V2m of the speed V2-1 of the roll in contact with the first surface of the second roll pair and the speed V2-2 of the roll in contact with the second surface of the second roll pair is V3-1 / V2m = 0.86 to 1.10.

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