Polyolefin resin foam sheet, cylindrical body, and method for producing polyolefin resin foam sheet

Abstract

To provide a technique for improving the heat fusible property of sheet-shaped resin foam.SOLUTION: The present technology provides a polyolefin resin foam sheet having an end face for heat fusion, wherein the number of cells at the end face for heat fusion is 30 cells per 25 mm or more. The present technology also provides a cylindrical body formed by heat fusion of end faces of a polyolefin resin foam sheet, wherein the tensile strength of the heat-fused portion is 0.15 MPa or more in accordance with JIS K6767:1999.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present technology relates to a polyolefin resin foam sheet. More specifically, the present technology relates to a polyolefin resin foam sheet having an end surface to be heat-sealed, a cylindrical body molded using the polyolefin resin foam sheet, and a method for manufacturing the polyolefin resin foam sheet. [Background technology]

[0002] Insulating materials are used in water supply pipes, fire-resistant pipes, etc. to prevent freezing and burns, and resin foams are generally used as pipe insulating materials because of their insulating properties, shock-absorbing properties, and ease of molding. In general, a method of molding a resin foam into a cylindrical shape for use as a pipe insulating material involves heating one side of a sheet-like resin foam and curving the heated surface to thermally fuse the ends of the sheet together to form a cylindrical shape.

[0003] For example, Patent Document 1 proposes a technology for producing a thermoplastic resin foam sheet that can be easily bent into a tubular shape by designing a long foam sheet made of thermoplastic resin so that the dimensional change upon heating at 120°C is greater in the width direction perpendicular to the longitudinal direction than in the longitudinal direction.

[0004] Furthermore, Patent Document 2 proposes a technology for producing a polyethylene-based resin insulation base material and a thermal insulation pipe cover made of the same, which are excellent in rigidity, heat resistance, and high foaming processability and are suitable for use as insulation materials for air conditioner piping, insulation materials for freezers and refrigerators, insulation materials for water supply and hot water pipes, etc., by using a polyethylene-based resin foamed sheet containing a polyethylene-based resin composition containing linear polyethylene (α) and high-pressure low-density polyethylene (β) and having specific physical properties. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2002-292729 A [Patent Document 2] JP 2000-143860 A Summary of the Invention [Problem to be solved by the invention]

[0006] In the case of a method in which the ends of a sheet-shaped resin foam are heat-fused together to form the foam, if the heat fusion is insufficient, the heat-fused parts will open up, and when the foam is used as a pipe insulation material as described above, for example, there is a concern that the required functionality will be reduced, such as poor insulation properties.

[0007] Therefore, a main object of the present technology is to provide a technology for improving the thermal fusion properties of a sheet-shaped resin foam. [Means for solving the problem]

[0008] The present inventors conducted intensive research to solve the above-mentioned problems and succeeded in improving the heat-sealing properties by controlling the number of cells on the heat-sealing surface of a resin foam, thereby completing the present technology.

[0009] That is, in the present technology, first, a polyolefin resin foam sheet having an end surface to be heat-sealed is provided, Provided is a polyolefin resin foam sheet having a cell count of 30 cells / 25 mm or more on an end surface to be heat-sealed. The polyolefin resin foam sheet according to the present technology can use, as a raw material, a polyolefin resin component having a melt flow rate (MFR) of 1.8 g / 10 min or less. The polyolefin resin foam sheet according to the present technology can be molded into a cylindrical body by heat fusing the end faces together.

[0010] Next, the present technology provides a method for producing a polyolefin resin foam sheet having an end surface to be heat-sealed, comprising the steps of: The present invention provides a method for producing a polyolefin resin foam sheet, which includes a melt flow rate (MFR) confirmation step for confirming that the MFR of a polyolefin resin component is 1.8 g / 10 min or less.

[0011] The present technology further provides a cylindrical body formed by thermally fusing end surfaces of a polyolefin-based resin foam sheet, A cylindrical body is provided, the heat-sealed portion of which has a tensile strength of 0.15 MPa or more as measured according to JIS K6767:1999. In the cylindrical body according to the present technology, the heat-sealed portion can have an elongation in accordance with JIS K6767:1999 of 50% or more. [Brief description of the drawings]

[0012] [Figure 1] 1 is a diagram for explaining a method for evaluating thermal adhesiveness in Examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] A preferred embodiment for carrying out the present technology will be described below. The embodiments described below are examples of typical embodiments of the present technology, and any of the embodiments can be combined. In addition, the scope of the present technology is not narrowly interpreted by these.

[0014] 1.Polyolefin resin foam sheet (1) Surface to be heat-sealed The polyolefin resin foam sheet according to the present technology has an end surface to be heat-sealed. In the present technology, the end surface to be heat-sealed includes both the end surface in the thickness direction of the sheet and the end surface in the surface direction of the sheet (i.e., the upper surface or the lower surface of the sheet), but it is preferable that the end surface in the thickness direction of the sheet is the surface to be heat-sealed.

[0015] (2) Number of cells on the surface to be heat-sealed The polyolefin resin foam sheet according to the present technology is characterized in that the number of cells at the end surface to be heat-sealed is 30 cells / 25 mm or more. As shown in the examples described later, the present technology has succeeded in improving the heat fusion property of the end surface to be heat-sealed of the produced polyolefin resin foam sheet by producing a polyolefin resin foam sheet so that the number of cells at the end surface to be heat-sealed is 30 cells / 25 mm or more.

[0016] The action and effect of this technology can be achieved if the number of cells on the end surface to be heat-sealed is 30 cells / 25 mm or more, but 31 cells / 25 mm or more is preferable, and 32 cells / 25 mm or more is more preferable. By adjusting the number of cells on the end surface to be heat-sealed within this range, the heat-sealing property can be further improved.

[0017] Increasing the number of cells on the end surface to be heat-fused improves the heat fusion properties as well as the heat insulation properties, and as a result, the insulation performance can be improved. Therefore, the upper limit of the number of cells is not particularly limited in the present technology, but can be adjusted to, for example, 50 cells / 25 mm or less, 45 cells / 25 mm or less, 40 cells / 25 mm or less, etc.

[0018] In this technology, the number of cells at the end face to be heat-fused is a value measured in accordance with a method based on JIS K6400-1.

[0019] (3) Resin composition for producing a polyolefin resin foam sheet The polyolefin resin foam sheet according to the present technology can be formed from a foam of a resin composition containing a polyolefin resin. In addition, the resin composition for producing the polyolefin resin foam according to the present technology (hereinafter also referred to as "the resin composition") can contain various components such as a foaming agent, a crosslinking agent, a crosslinking accelerator, etc., and other components that can be used for producing a polyolefin resin foam depending on the purpose, as necessary. Each component will be described in detail below.

[0020] (3-1) Polyolefin resin The polyolefin resin that can be used in the present technology is a resin that is mainly composed of an olefin component unit. A resin that is mainly composed of an olefin component unit is a resin that contains 50% by mass or more of an olefin component unit. In the present technology, the content of the olefin component unit in the resin is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, and it is particularly preferable that the resin component is composed only of a polyolefin resin.

[0021] Examples of polyolefin-based resins 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 that can be copolymerized with the olefin-based monomers. These can be used alone or in combination of two or more kinds.

[0022] Examples of polyethylene resins include ethylene homopolymers 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, and ethylene-methyl methacrylate copolymers.

[0023] Examples of polypropylene-based resins include propylene homopolymers 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.

[0024] Among these, in the present technology, it is preferable to use a polyethylene-based resin, and among the polyethylene-based resins, it is preferable to use low-density polyethylene (LDPE).

[0025] In the present technology, the melt flow rate (MFR (Melt Flow Rate)) of the polyolefin resin component can be freely adjusted as long as it does not impair the action and effect of the present technology. The upper limit of the MFR of the polyolefin resin component is, for example, 2.0 g / 10 min or less, preferably 1.8 g / 10 min or less, more preferably 1.7 g / 10 min or less, even more preferably 1.6 g / 10 min or less, and particularly preferably 1.5 g / 10 min or less. By adjusting the upper limit of the MFR of the polyolefin resin component to this range, the heat fusion property of the produced polyolefin resin foam sheet can be further improved.

[0026] The lower limit of the MFR of the polyolefin resin component is, for example, 0.55 g / 10 min or more, preferably 0.60 g / 10 min or more, more preferably 0.65 g / 10 min or more, and even more preferably 0.70 g / 10 min or more. By adjusting the lower limit of the MFR of the polyolefin resin component within this range, the viscosity of the resin composition can be prevented from becoming too high, thereby preventing foaming in the extruder (improving extrusion moldability) and improving the physical properties of the produced polyolefin resin foam sheet.

[0027] Although one polyolefin resin having the above-described suitable MFR can be used, two or more polyolefin resins having different MFRs can be mixed to adjust the MFR of the polyolefin resin component. More specifically, for example, a method of blending a polyolefin resin having an MFR of 2.0g / 10min or more with a polyolefin resin having an MFR of less than 2.0g / 10min, a method of blending a polyolefin resin having an MFR of 2.0g / 10min or more with a polyolefin resin having an MFR of 1.0g / 10min or less, a method of blending a polyolefin resin having an MFR of 2.5g / 10min or more with a polyolefin resin having an MFR of 1.0g / 10min or less, etc. can be mentioned.

[0028] In this way, when blending a polyolefin resin with a higher MFR and a polyolefin resin with a lower MFR than the polyolefin resin, the mixing ratio can be freely set as long as it does not impair the action and effect of the present technology. For example, the polyolefin resin with a higher MFR and the polyolefin resin with a lower MFR than the polyolefin resin can be blended at 10:90 to 90:10, preferably 20:80 to 80:20, more preferably 30:70 to 70:30, and even more preferably 40:60 to 60:40.

[0029] In addition, the polyolefin resin foam sheet according to the present technology may contain other resins, thermoplastic elastomers, thermosetting elastomers, etc., in addition to the polyolefin resin, as long as the purpose and effect of the present technology are not impaired. Examples of resins other than polyolefin resins include thermoplastic resins such as polystyrene resins, polyamide resins, and polyester resins. Examples of thermoplastic elastomers include olefin-based thermoplastic elastomers and styrene-based thermoplastic elastomers. Examples of thermosetting elastomers include synthetic rubbers such as ethylene propylene rubber (EPDM) and natural rubber.

[0030] (3-2) Foaming agent The resin composition used in the present technology may contain a foaming agent. As the foaming agent that can be used in the present technology, one or more foaming agents that can be used for polyolefin resin foams may be freely selected and used as long as the purpose and effect of the present technology are not impaired.

[0031] Examples of the blowing agent that can be used in the present technology include organic or inorganic thermal decomposition type chemical blowing agents. Examples of organic blowing agents include azo compounds such as azodicarbonamide (ADCA), azodicarboxylate metal salts (e.g., 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.; and semicarbazide compounds such as toluenesulfonylsemicarbazide, etc. Examples of inorganic blowing agents include ammonium carbonate, sodium carbonate, ammonium hydrogen carbonate, sodium hydrogen carbonate, ammonium nitrite, sodium borohydride, anhydrous monosodium citrate, etc.

[0032] Among these, in the present technology, it is preferable to use an organic blowing agent as the blowing agent, and among the organic blowing agents, it is preferable to use azodicarbonamide (ADCA).

[0033] The amount of the foaming agent used in the present technology can be freely set as long as it does not impair the purpose and effect of the present technology. In the present technology, the content of the foaming agent relative to 100 parts by mass of the resin component in the resin composition is, for example, 10.0 parts by mass or more, preferably 15.0 parts by mass or more, and more preferably 20.0 parts by mass or more. By setting the content of the foaming agent in the resin composition within this range, the foamability during foam production can be improved, and the physical properties of the produced foam can be improved.

[0034] In the present technology, the content of the foaming agent relative to 100 parts by mass of the resin component in the resin composition is, for example, 40.0 parts by mass or less, preferably 35.0 parts by mass or less, and more preferably 30.0 parts by mass or less. By setting the content of the foaming agent in the resin composition within this range, formation defects due to excessive foaming can be suppressed, and also contribute to cost reduction.

[0035] (3-3) Crosslinking agent The polyolefin resin foam sheet according to the present technology may be a sheet made of a crosslinked foam. By performing crosslinking during the production of the polyolefin resin foam sheet according to the present technology, the viscosity of the composition (kneaded material) before foaming can be increased, thereby improving the foamability. In addition, the physical properties of the produced foam sheet can be improved.

[0036] When the polyolefin resin foam sheet according to the present technology is a sheet made of a crosslinked foam, crosslinking can be performed by irradiation with ionizing radiation, but crosslinking can also be performed chemically using a crosslinking agent. As the crosslinking agent that can be used in the present technology, one or more crosslinking agents that can be used for polyolefin resin foams can be freely selected and used as long as they do not impair the purpose and effect of the present technology.

[0037] Examples of crosslinking agents that can be used in the present technology include crosslinking agents having chemical structures such as silane groups, peroxides, hydroxyl groups, amide groups, ester groups, etc. Among these, in the present technology, it is preferable to use an organic peroxide as the crosslinking agent.

[0038] Examples of organic peroxides include dicumyl peroxide, 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-butylperoxide, di-t-butylperoxy-3,3,5-trimethylcyclohexane, and t-butylhydroperoxide. Among these, in the present technology, it is preferable to use dicumyl peroxide as a crosslinking agent.

[0039] The amount of the crosslinking agent used in the production of the polyolefin resin foam sheet according to the present technology can be freely set as long as it does not impair the purpose and effect of the present technology. In the present technology, the content of the crosslinking agent relative to 100 parts by mass of the resin component in the resin composition is, for example, 0.1 parts by mass or more, preferably 0.2 parts by mass or more, and more preferably 0.3 parts by mass or more. By setting the content of the crosslinking agent in the resin composition within this range, the viscosity can be improved to improve the foamability. In addition, the mechanical properties such as the durability of the produced foam can be improved.

[0040] In the present technology, the content of the crosslinking agent relative to 100 parts by mass of the resin component in the resin composition is, for example, 4.0 parts by mass or less, preferably 3.0 parts by mass or less, and 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 cracks and the like from occurring during foaming and improve moldability.

[0041] (3-4) Crosslinking accelerator When a crosslinking agent is used in the production of the polyolefin resin foam sheet according to the present technology, a crosslinking accelerator can also be used to promote crosslinking by the crosslinking agent. As the crosslinking accelerator that can be used in the present technology, one or more crosslinking accelerators that can be used for polyolefin resin foam can be freely selected and used as long as they do not impair the purpose and effect of the present technology.

[0042] Examples of crosslinking accelerators that can be used in the present technology include trimethylolpropane trimethacrylate, triallyl trimellitate, diallyl trimellitate, diallyl phthalate, divinylbenzene, 1,9-nonanediol dimethacrylate, 1,10-decanediol dimethacrylate, trimellitic acid triallyl ester, triallyl isocyanurate, neopentyl glycol dimethacrylate, and 1,6-hexanediol dimethacrylate. Among these, it is preferable to use trimethylolpropane trimethacrylate in the present technology.

[0043] The amount of the crosslinking accelerator used in the production of the polyolefin resin foam according to the present technology can be freely set as long as it does not impair the purpose and effect of the present technology. In the present technology, the content of the crosslinking accelerator relative to 100 parts by mass of the resin component in the resin composition is, for example, 0.01 parts by mass or more, preferably 0.02 parts by mass or more, and more preferably 0.03 parts by mass or more. By setting the content of the crosslinking accelerator in the resin composition within this range, the foamability during the production of the foam can be improved.

[0044] In the present technology, the content of the crosslinking accelerator in the resin composition relative to 100 parts by mass of the resin component is, for example, 3.0 parts by mass or less, preferably 2.0 parts by mass or less, and more preferably 1.0 part by mass or less. By setting the content of the crosslinking accelerator in the resin composition within this range, formation defects due to excessive foaming can be suppressed, and also contribute to cost reduction.

[0045] (3-5)Other In the production of the polyolefin resin foam according to the present technology, one or more of various components that can be used in the production of polyolefin resin foam can be freely selected and used as other components depending on the purpose, as long as the purpose and effects of the present technology are not impaired.

[0046] Examples of components that can be used in the production of the polyolefin resin foam according to the present technology include foaming assistants, inorganic fillers, foam stabilizers, flame retardants, stabilizers, plasticizers, colorants, antioxidants, dispersants, UV absorbers, and lubricants.

[0047] (4) Density The density of the polyolefin resin foam sheet according to the present technology can be freely set as long as it does not impair the purpose and effect of the present technology. In the present technology, the lower limit of the density of the polyolefin resin foam sheet is set to, for example, 10 kg / m 3 More than 12kg / m 3 More preferably, 15 kg / m 3 More preferably, 20 kg / m 3 By setting the lower limit of the density of the polyolefin resin foam sheet within this range, it is possible to prevent the sheet from becoming too soft and to impart appropriate elasticity to the sheet.

[0048] The upper limit of the density of the polyolefin resin foam sheet according to the present technology can be freely set as long as it does not impair the purpose and effect of the present technology. For example, it is set to 50 kg / m 3 Less than 40 kg / m 3 Less than or equal to 30 kg / m 3 By setting the density of the polyolefin resin foam sheet within this range, the polyolefin resin foam sheet can be prevented from becoming too hard, which would result in a loss of flexibility, and appropriate cushioning properties can be imparted to the polyolefin resin foam sheet.

[0049] In the present technology, the density of the polyolefin resin foam is a value measured in accordance with a method based on JIS K6767:1999.

[0050] (5) Tensile strength The tensile strength of the polyolefin resin foam sheet according to the present technology can be freely set as long as it does not impair the purpose and effect of the present technology. In the present technology, the lower limit of the tensile strength of the polyolefin resin foam sheet is, for example, 0.10 MPa or more, preferably 0.13 MPa or more, and more preferably 0.15 MPa or more.

[0051] The upper limit of the tensile strength of the polyolefin resin foam sheet according to the present technology can be freely set as long as it does not impair the purpose and effect of the present technology, and can be set to, for example, 0.40 MPa or less.

[0052] In the present technology, the tensile strength of the polyolefin resin foam is a value measured in accordance with a method based on JIS K6767:1999.

[0053] (6) Elongation The elongation of the polyolefin resin foam sheet according to the present technology can be freely set as long as it does not impair the purpose and effect of the present technology. In the present technology, the lower limit of the elongation of the polyolefin resin foam sheet is, for example, 80% or more, preferably 90% or more, and more preferably 100% or more. By setting the lower limit of the elongation of the polyolefin resin foam sheet within this range, it is possible to prevent the sheet from becoming too hard and losing flexibility.

[0054] The upper limit of the elongation of the polyolefin resin foam sheet according to the present technology can be freely set as long as it does not impair the purpose and effect of the present technology, and is, for example, 150% or less, preferably 140% or less, and more preferably 130% or less. By setting the elongation of the polyolefin resin foam sheet within this range, the polyolefin resin foam sheet can be prevented from becoming too soft and can be provided with appropriate elasticity.

[0055] In the present technology, the elongation of the polyolefin resin foam is a value measured in accordance with a method based on JIS K6767:1999.

[0056] (8) Tear strength The tear strength of the polyolefin resin foam sheet according to the present technology can be freely set as long as it does not impair the purpose and effect of the present technology. In the present technology, the lower limit of the tear strength of the polyolefin resin foam sheet is, for example, 10.0 N / cm or more, preferably 11.0 N / cm or more, and more preferably 12.0 N / cm or more.

[0057] The upper limit of the tear strength of the polyolefin resin foam sheet according to the present technology can be freely set as long as it does not impair the purpose and effect of the present technology, and can be set to, for example, 18.0 N / cm or less.

[0058] In the present technology, the tear strength of the polyolefin resin foam is a value measured in accordance with a method based on JIS K6767:1999.

[0059] (9) Water absorption rate The water absorption rate of the polyolefin resin foam sheet according to the present technology can be freely set as long as it does not impair the purpose and effect of the present technology. The upper limit of the water absorption rate of the polyolefin resin foam sheet according to the present technology can be freely set as long as it does not impair the purpose and effect of the present technology, but it is not particularly limited, for example, to 0.01 g / cm. 2 It can be set as follows:

[0060] In this technology, the lower limit of the water absorption rate of the polyolefin resin foam sheet is 0 g / cm 2 may be also possible.

[0061] In the present technology, the water absorption rate of the polyolefin resin foam is a value measured in accordance with a method based on JIS K6767:1999.

[0062] (10) Compression set [half an hour] The compression set of the polyolefin resin foam sheet according to the present technology after 30 minutes of compression and release can be freely set as long as it does not impair the purpose and effect of the present technology. In the present technology, the upper limit of the compression set of the polyolefin resin foam sheet after 30 minutes of compression and release is, for example, 30% or less, preferably 25% or less, and more preferably 20% or less.

[0063] The lower limit of the compression set of the polyolefin resin foam sheet according to the present technology 30 minutes after release from compression can be freely set as long as it does not impair the purpose and effect of the present technology, and can be set to, for example, 5% or more.

[0064] [24 hours] The compression set of the polyolefin resin foam sheet according to the present technology for 24 hours after release from compression can be freely set as long as it does not impair the purpose and effect of the present technology. In the present technology, the upper limit of the compression set of the polyolefin resin foam sheet for 24 hours after release from compression is, for example, 20% or less, preferably 15% or less, and more preferably 12% or less.

[0065] The lower limit of the compression set of the polyolefin resin foam sheet according to the present technology for 24 hours after release from compression can be freely set as long as it does not impair the purpose and effect of the present technology, and can be set to, for example, 3% or more.

[0066] In the present technology, the compression set of the polyolefin resin foam is a value measured in accordance with a method based on JIS K6767:1999.

[0067] (11) Compressive stress-strain [10% compressive stress-strain] The 10% compressive stress-strain of the polyolefin resin foam sheet according to the present technology can be freely set as long as it does not impair the purpose and effect of the present technology. In the present technology, the upper limit of the 10% compressive stress-strain of the polyolefin resin foam sheet is, for example, 30 kPa or less, preferably 25 kPa or less, and more preferably 20 kPa or less.

[0068] The lower limit of the 10% compressive stress-strain of the polyolefin resin foam sheet according to the present technology can be freely set as long as it does not impair the purpose and effect of the present technology, and can be set to, for example, 5 kPa or more.

[0069] [25% compressive stress-strain] The 25% compressive stress-strain of the polyolefin resin foam sheet according to the present technology can be freely set as long as it does not impair the purpose and effect of the present technology. In the present technology, the upper limit of the 25% compressive stress-strain of the polyolefin resin foam sheet is, for example, 50 kPa or less, preferably 45 kPa or less, and more preferably 40 kPa or less.

[0070] The lower limit of the 25% compressive stress-strain of the polyolefin resin foam sheet according to the present technology can be freely set as long as it does not impair the purpose and effect of the present technology, and can be set to, for example, 10 kPa or more.

[0071] [50% compressive stress-strain] The 50% compressive stress-strain of the polyolefin resin foam sheet according to the present technology can be freely set as long as it does not impair the purpose and effect of the present technology. In the present technology, the upper limit of the 50% compressive stress-strain of the polyolefin resin foam sheet is, for example, 110 kPa or less, preferably 105 kPa or less, and more preferably 100 kPa or less.

[0072] The lower limit of the 50% compressive stress-strain of the polyolefin resin foam sheet according to the present technology can be freely set as long as it does not impair the purpose and effect of the present technology, and can be set to, for example, 50 kPa or more.

[0073] In this technique, the compressive stress-strain of the polyolefin resin foam is a value measured in accordance with a method based on JIS K6767:1999.

[0074] (12) Dimensional change rate The dimensional change rate of the polyolefin resin foam sheet according to the present technology can be freely set as long as it does not impair the purpose and effect of the present technology. The lower limit of the dimensional change rate of the polyolefin resin foam sheet according to the present technology can be freely set as long as it does not impair the purpose and effect of the present technology, and is, for example, -15% or more, preferably -10% or more, more preferably -5% or more.

[0075] In the present technology, the upper limit of the dimensional change rate of the polyolefin resin foam sheet may be 0%.

[0076] In the present technology, the dimensional change rate of the polyolefin resin foam is a value measured in accordance with a method based on JIS K6767:1999.

[0077] (13) Gel fraction The gel fraction of the polyolefin resin foam sheet according to the present technology can be freely set as long as it does not impair the purpose and effect of the present technology. In the present technology, the lower limit of the gel fraction of the polyolefin resin foam sheet is, for example, 45% or more, preferably 50% or more, and more preferably 55% or more.

[0078] The upper limit of the gel fraction of the polyolefin resin foam sheet according to the present technology can be freely set as long as it does not impair the purpose and effects of the present technology, and is, for example, 80% or less, preferably 75% or less, and more preferably 70% or less.

[0079] In the present technology, the gel fraction of the polyolefin resin foam is a value measured in accordance with a method based on JIS K6769.

[0080] (14) Thermal conductivity The thermal conductivity of the polyolefin resin foam sheet according to the present technology can be freely set as long as it does not impair the purpose and effect of the present technology. In the present technology, the lower limit of the thermal conductivity of the polyolefin resin foam sheet is, for example, 0.020 W / m K or more, preferably 0.025 W / m K or more, and more preferably 0.030 W / m K or more.

[0081] The upper limit of the thermal conductivity of the polyolefin resin foam sheet according to the present technology can be freely set as long as it does not impair the purpose and effects of the present technology; for example, it is not more than 0.055 W / m K, preferably not more than 0.050 W / m K, and more preferably not more than 0.045 W / m K.

[0082] In the present technology, the thermal conductivity of the polyolefin resin foam is a value measured in accordance with a method based on JIS A1412-2.

[0083] 2. Manufacturing method of polyolefin resin foam sheet The polyolefin resin foam sheet according to the present technology has characteristic physical properties, and the method for producing the sheet is not particularly limited. For example, a method can be adopted in which a polyolefin resin is mixed with a foaming agent, a crosslinking agent, and other additives as necessary, and then foamed and molded.

[0084] In the manufacturing method according to the present technology, it is preferable to carry out an MFR confirmation step for confirming the melt flow rate (MFR) of the polyolefin resin component. As described above, by adjusting the MFR of the polyolefin resin component, the thermal fusion property and physical properties of the produced polyolefin resin foam sheet can be improved. The preferred MFR of the polyolefin resin component is the same as that described above, and therefore will not be described here.

[0085] In the MFR confirmation step, a polyolefin resin having a preferred MFR can be selected, or, as described above, when adjusting the MFR of the polyolefin resin component by mixing two or more polyolefin resins having different MFRs, two or more polyolefin resins having MFRs suitable for adjusting the MFR can be selected.

[0086] After the MFR confirmation step, the polyolefin resin foam sheet can be produced by a general method. Specifically, the method for producing the polyolefin resin foam sheet may be, for example, a long-length foaming method using chemical crosslinking or a long-length foaming method using electron beam crosslinking, and it is more preferable to use the long-length foaming method using chemical crosslinking.

[0087] <Long-length foaming method using chemical crosslinking> The long length foaming method includes, for example, the following steps (1) and (2). (1) Mixing process A polyolefin resin, and if necessary, a foaming agent, a crosslinking agent, and other optional additives are kneaded and extruded into a sheet using a single-screw extruder, a twin-screw extruder, or the like to extrude a foamable resin composition of a predetermined shape such as a sheet (hereinafter referred to as a mother plate). Kneading and extrusion can be performed simultaneously using an extruder.

[0088] (2) Foaming process The mother plate obtained in the kneading step is heated and foamed at 120-250°C (above the decomposition temperature of the foaming agent and crosslinking agent) for 5-20 minutes while being transported into a heating device such as an oven, to obtain a resin foam. Note that it is preferable to use a device in which a heating device such as an oven and a transport device are integrated, since this allows the mother plate to be treated continuously.

[0089] <Long-length foaming method using electron beam crosslinking> The long length foaming method using electron beam crosslinking includes, for example, the following steps (1) to (3). (1) Mixing process A polyolefin resin, and optionally a foaming agent, a crosslinking agent, and other optional additives are kneaded in a single-screw extruder, a twin-screw extruder, or the like, and a resin composition having a predetermined shape such as a sheet (hereinafter referred to as a mother plate) is extruded. Kneading and extrusion can be performed simultaneously using an extruder.

[0090] (2) Crosslinking process The base plate obtained in the kneading step is crosslinked. As a crosslinking method, a method of irradiating with ionizing radiation such as electron beams or gamma rays can be used, and crosslinking by electron beam irradiation (electron beam crosslinking) is preferred. Electron beam crosslinking can be performed using an electron beam irradiator. If necessary, a crosslinking agent such as the above-mentioned organic peroxide may be used in combination.

[0091] (3) Foaming process The crosslinked mother plate obtained in the crosslinking step is heated at 120-250°C (above the decomposition temperature of the foaming agent) for 5-20 minutes while being transported into a heating device such as an oven to foam the mother plate, thereby obtaining a resin foam. Note that it is preferable to use a device in which a heating device such as an oven and a transport device are integrated, since this allows the mother plate to be treated continuously.

[0092] In the method for producing a polyolefin resin foam sheet according to the present technology described above, other steps can be performed depending on the purpose. For example, after the crosslinking step or the foaming step, a cooling step, an aging step, etc. can be performed. In addition, a molding step such as cutting the edges or slicing the produced foam can also be performed.

[0093] 3. Cylindrical body The polyolefin resin foam sheet according to the present technology can be used for a molded article formed by heat fusion, taking advantage of its high heat fusion property. In particular, it can be suitably used for a molded article such as a cylindrical body, whose heat fusion surface is easily opened.

[0094] (1) Tensile strength of heat-sealed parts The cylindrical body according to the present technology is a cylindrical body formed by heat fusion of the end faces of a polyolefin resin foam sheet. The tensile strength of the heat fused portion can be freely set according to the use of the cylindrical body, and is, for example, 0.15 MPa or more, preferably 0.16 MPa or more, more preferably 0.17 MPa or more, and even more preferably 0.18 MPa or more. When the tensile strength of the heat fused portion is within this range, the opening of the heat fused portion can be more reliably prevented, and for example, when the cylindrical body according to the present technology is used as a heat insulating material, the heat insulating performance can be further improved.

[0095] The upper limit of the tensile strength of the heat-sealed portion is not particularly limited, but can be set to, for example, 0.40 MPa or less.

[0096] In this technology, the tensile strength of the heat-sealed portion is a value measured in accordance with a method based on JIS K6767:1999.

[0097] (2) Elongation of heat-sealed parts The elongation of the heat-sealed portion of the cylindrical body according to the present technology can be freely set depending on the application of the cylindrical body, and is, for example, 50% or more, preferably 55% or more, more preferably 60% or more, even more preferably 65% ​​or more, and particularly preferably 70% or more. When the elongation of the heat-sealed portion is within this range, the opening of the heat-sealed portion can be more reliably prevented, and for example, when the cylindrical body according to the present technology is used as a heat insulating material, the heat insulating performance can be further improved.

[0098] The upper limit of the tensile strength of the heat-sealed portion is not particularly limited, but can be set to, for example, 100% or less.

[0099] In this technique, the elongation of the heat-sealed portion is a value measured in accordance with a method based on JIS K6767:1999.

[0100] (3) Manufacturing method of the cylindrical body The cylindrical body according to the present technology can be formed by heat fusing the end faces of the polyolefin resin foam sheet, and the end faces to be heat-fusing preferably have a cell number of 30 / 25 mm or more. In other words, the cylindrical body according to the present technology is preferably formed by heat fusing the end faces having a cell number of 30 / 25 mm or more. The details of the cell number of the end faces are the same as those described above, so the explanation is omitted here.

[0101] 4. Applications of polyolefin resin foam sheets and cylindrical bodies The polyolefin-based resin foam sheet according to the present technology and the cylindrical body according to the present technology can be used for various applications in various fields by utilizing their high quality. For example, they can be suitably used as pipe insulation materials, building cushioning materials, building insulation materials, building soundproofing materials, packaging materials, vehicle cushioning materials, building interior materials, vehicle interior materials, etc. Among these, the polyolefin-based resin foam sheet according to the present technology and the cylindrical body according to the present technology can be suitably used for insulation applications, particularly as pipe insulation materials. EXAMPLES

[0102] The present technology will be described in more detail below based on examples. Note that the examples described below are representative examples of the present technology, and the scope of the present technology is not to be interpreted narrowly by these examples.

[0103] (1) Raw materials Resin 1: Low-density polyethylene (LDPE) (MFR: 0.6 g / 10 min, melting point: 109°C) Resin 2: Low-density polyethylene (LDPE) (MFR: 3.0 g / 10 min, melting point: 109°C) Blowing agent: Azodicarbonamide (ADCA) Crosslinker: Dicumyl peroxide (DCP) Crosslinking accelerator: Trimethylolpropane trimethacrylate (TMPTMA)

[0104] (2) Manufacturing of polyolefin resin foam sheets The raw materials shown in Table 1 below were melt-kneaded in a kneader, then introduced into an extruder and extruded into a sheet from a die attached to the tip of the extruder. The extruded sheet-like resin composition was heated to crosslink and foam, producing a polyolefin resin foam sheet having a thickness of 2.6 mm.

[0105] (3) Physical property measurements The produced foams were evaluated for density and appearance by the following methods.

[0106] [Density][Tensile strength][Elongation][Tear strength][Water absorption][Compression set][Compression stress-strain][Dimensional change rate] The density, tensile strength, elongation, tear strength, water absorption, compression set, compression stress-strain, and dimensional change rate were measured in accordance with JIS K6767:1999.

[0107] [Gel fraction] The gel fraction was measured in accordance with JIS K6769.

[0108] Number of Cells The cell number was measured in accordance with JIS K6400-1.

[0109] [Thermal Conductivity] The thermal conductivity was measured in accordance with JIS A1412-2.

[0110] (4) Evaluation <Thermal adhesiveness> The heat-sealing property was evaluated by cutting the produced polyolefin resin foam sheet in the MD direction (see B in Fig. 1) and measuring the tensile strength and elongation in the TD direction when the cut end faces were heat-sealed together (see C in Fig. 1) as shown in Fig. 1. In addition, the heat-sealed part of the cylindrical body formed by heat-sealing the end faces of the produced polyolefin resin foam sheet was visually evaluated based on the following evaluation criteria.

[0111] [Tensile strength in TD direction] The heat-sealed portion was positioned at the center of the dumbbell, and the tensile strength in the TD direction was measured in accordance with JIS K6767:1999.

[0112] [Extension in TD direction] The elongation in the TD direction was measured in accordance with JIS K6767:1999.

[0113] [Visual evaluation] ○: No openings at all in the heat-sealed portion △: There is a slight gap in the heat-sealed area, but it is within the acceptable range. ×: Openings occurred in the heat-sealed portion

[0114] (5) Results The results are shown in Table 1 below. [Table 1]

[0115] (5) Discussion As shown in Table 1, Examples 1 to 3, in which the number of cells on the end surface to be heat-sealed is 30 cells / 25 mm or more, had improved heat fusion properties compared to Comparative Examples 1 and 2, in which the number of cells on the end surface to be heat-sealed is less than 30 cells / 25 mm.

[0116] Comparing the Examples, it was found that the tensile strength and elongation of the heat-sealed portion were improved in Examples 2 and 3, where the MFR of the resin component was 0.65 g / min or more, compared to Example 1, where the MFR of the resin component was less than 0.65 g / 10 min. From these results, it was found that the MFR of the resin component is preferably 0.60 g / min or more, and more preferably 0.65 g / min or more.

Claims

1. A polyolefin resin foam sheet having an end surface to be heat-sealed, A polyolefin resin foam sheet having a cell count of 30 cells / 25 mm or more at an end surface to be heat-sealed.

2. The polyolefin resin foam sheet according to claim 1, wherein the polyolefin resin component in the raw material has a melt flow rate (MFR) of 1.8 g / 10 min or less.

3. A cylindrical body formed by heat-sealing the end faces of the polyolefin resin foam sheet according to claim 1 or 2.

4. A method for producing a polyolefin resin foam sheet having an end surface to be heat-sealed, comprising the steps of: A method for producing a polyolefin resin foam sheet, comprising a melt flow rate (MFR) confirmation step for confirming that the melt flow rate (MFR) of a polyolefin resin component is 1.8 g / 10 min or less.

5. A cylindrical body formed by heat-sealing end faces of a polyolefin resin foam sheet, A cylindrical body having a tensile strength of 0.15 MPa or more in accordance with JIS K6767:1999 of the heat-sealed portion.

6. The cylindrical body according to claim 5 , wherein the heat-sealed portion has an elongation of 50% or more in accordance with JIS K6767:1999.

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