Cross-linked polyolefin resin foam sheet and cylindrical body

Abstract

To provide a technology that improves the heat-sealability and heat resistance of sheet-shaped resin foams. [Solution] This technology provides a crosslinked polyolefin resin foam sheet having heat-sealable edges, wherein the resin component in the raw material has a density of 0.940 g / cm³. 3 Low-density polyethylene with a density of less than 0.940 g / cm³ 3 More than 0.955g / cm 3 The present invention provides a crosslinked polyolefin resin foam sheet containing the following high-density polyethylene, wherein the content of the high-density polyethylene is 16 to 45 parts by mass per 100 parts by mass of the resin component.

Description

[Technical Field]

[0001] This technology relates to a crosslinked polyolefin resin foam sheet. More specifically, it relates to a crosslinked polyolefin resin foam sheet having heat-sealable end faces, and a tubular body molded using the crosslinked polyolefin resin foam sheet. [Background technology]

[0002] Insulation materials are used in piping for buildings and home appliances, as well as in water supply pipes and fire-resistant water-resistant pipes, to prevent freezing and burns. For this piping insulation, resin foam is generally used due to its thermal insulation, cushioning properties, and ease of molding. Polyolefin resins, such as polyethylene, have excellent weather resistance and water resistance, and their durability is improved by cross-linking treatment, so they are also used in outdoor piping and components requiring high heat resistance, such as steam pipes that exceed 100°C.

[0003] For use as pipe insulation, a method is employed to form a tubular shape from resin foam by first creating slits of a predetermined width, then heating one side of the sheet-like resin foam, curving the heated surface, and heat-fusing the ends of the sheet together.

[0004] For example, Patent Document 1 discloses a technique for producing a crosslinked polyolefin resin foam sheet by crosslinking and foaming a resin composition using 100 parts by weight of a polyolefin resin consisting of 60 to 95% by weight of low-density polyethylene resin with a specific melt flow rate and 5 to 40% by weight of high-density polyethylene resin with a specific density, specific melting point, and specific melt flow rate, with 0.1 to 5 parts by weight of a peroxide decomposition type antioxidant and 0.1 to 5 parts by weight of a copper damage inhibitor, so that the gel fraction on at least one side is 65% or more. The foam sheet is then molded into a cylindrical shape so that the side with a gel fraction of 65% or more is the inner surface, thereby producing a heat-insulating pipe cover for copper pipes that maintains dimensional stability even when exposed to temperatures of 120°C or higher and does not discolor, without reducing processability or flexibility.

[0005] Patent Document 2 discloses a technique in which, when producing a polyolefin resin crosslinked foam using an organic decomposition type blowing agent, problems such as discoloration of the foam become particularly pronounced when a copper damage inhibitor mainly composed of a compound having a salicyloyl group is used. However, when a copper damage inhibitor mainly composed of a certain compound is used, discoloration and gel formation of the resulting foam are suppressed.

[0006] Patent Document 3 discloses a technology in which, when manufacturing a polyolefin resin crosslinked foam using an organic decomposition type foaming agent, problems such as increased tackiness of the foaming base sheet become significant when a copper damage inhibitor mainly composed of compounds having phenol groups is used. However, when a copper damage inhibitor mainly composed of a specific compound that does not contain phenol groups is used, excessive tackiness of the foaming base sheet to the conveyor does not occur, the color development of the pigment in the resulting foam is not inhibited, and gel formation is suppressed.

[0007] Patent Document 4 proposes a technique for manufacturing a thermoplastic resin foam sheet that can be easily bent into a tubular shape by designing the long foam sheet made of thermoplastic resin such that the dimensional change when heated at 120°C is greater in the width direction perpendicular to the longitudinal direction than in the longitudinal direction.

[0008] Patent Document 5 discloses a polyethylene resin foam sheet containing a polyethylene resin composition having specific physical properties, which has excellent rigidity, heat resistance, and high foaming processability, and is used as insulation material for air conditioner piping, refrigeration and freezing equipment, water supply and hot water pipes, etc. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 8-208872 [Patent Document 2] Japanese Patent Application Publication No. 9-278919 [Patent Document 3] Japanese Unexamined Patent Publication No. 11-060773 [Patent Document 4] Japanese Unexamined Patent Publication No. 2002-292729 [Patent Document 5] Japanese Unexamined Patent Publication No. 2012-211313 [Summary of the Invention] [Problems to be Solved by the Invention]

[0010] In the case of a molding method in which the end portions of a sheet-shaped resin foam are thermally fused to each other, if the thermal fusion is insufficient, the thermally fused portion will open. For example, when the product is used as a pipe heat insulating material as described above, there is a concern that required functions may be degraded, such as poor heat insulation. Further, even if the thermal fusion is sufficient, when the thickness shrinkage ratio is high or a non-crosslinked resin foam is used, there is also a concern that the heat resistance is insufficient.

[0011] Accordingly, the main object of the present technology is to improve the thermal fusibility of a sheet-shaped resin foam and provide a sheet-shaped resin foam with high heat resistance. [Means for Solving the Problems]

[0012] The inventors of the present invention conducted intensive studies to solve the above problems, and found that by using a specific amount of high-density polyethylene having a specific density, the thermal fusibility is improved and the thickness shrinkage ratio is reduced, which led to the completion of the present technology.

[0013] That is, the present technology firstly provides a crosslinked polyolefin-based resin foam sheet having end surfaces to be thermally fused, wherein the resin component in the raw material includes: low-density polyethylene having a density of less than 0.940 g / cm 3 , and high-density polyethylene having a density of 0.940 g / cm 3 or more and 0.955 g / cm 3 or less, wherein The present invention provides a crosslinked polyolefin resin foam sheet in which the content of high-density polyethylene is 16 to 45 parts by mass per 100 parts by mass of resin component. The high-density polyethylene used in this technology may have a crystallization temperature of 115°C or higher. The high-density polyethylene used in this technology may have a melt viscosity of 500 Pa·s or less. The resin component used in this technology may have a melt viscosity of 700 to 1000 Pa·s.

[0014] This technology also provides a cylindrical body formed by heat-sealing the end faces of crosslinked polyolefin resin foam sheets related to this technology. [Modes for carrying out the invention]

[0015] The following describes preferred embodiments for implementing this technology. The embodiments described below are examples of typical embodiments of this technology, and any combination of these embodiments is possible. Furthermore, this does not mean that the scope of this technology will be narrowed.

[0016] 1. Cross-linked polyolefin resin foam sheet (1) Surface to be heat-fused The crosslinked polyolefin resin foam sheet according to this technology is a sheet having heat-sealed edges. In this technology, the heat-sealed edges include both the edges in the thickness direction of the sheet and the edges in the surface direction of the sheet (i.e., the top and bottom surfaces of the sheet), but it is preferable that the edges in the thickness direction of the sheet are the surfaces intended for heat sealing.

[0017] (2) Resin composition for producing crosslinked polyolefin resin foam sheet The crosslinked polyolefin resin foam sheet according to this technology can be molded from a foam of a resin composition containing a polyolefin resin. The resin composition for producing the polyolefin resin foam according to this technology (hereinafter also referred to as "the resin composition") may contain, as necessary, a foaming agent, a crosslinking agent, a crosslinking accelerator, and various other components that can be used in the production of the crosslinked polyolefin resin foam depending on the purpose. Each component will be described in detail below.

[0018] (2-1) Polyolefin resins The polyolefin resin that can be used in this technology is a resin whose main component is olefin component units. A resin whose main component is olefin component units is a resin that contains 50% by mass or more of olefin component units. In this technology, the content of olefin component units 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 consists only of polyolefin resin.

[0019] Examples of polyolefin resins that can be used in this technology include polyethylene resins, polypropylene resins, polybutene, polypentene, and copolymers of olefin monomers and monomers that can copolymerize with the olefin monomers. These can be used individually or in combination of two or more.

[0020] Examples of polyethylene-based 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.

[0021] Examples of the polypropylene-based resin 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.

[0022] Among these, the present technology is characterized by using a polyethylene-based resin. Further, in the present technology, among polyethylene-based resins, the density is 0.940 g / cm 3 3 or less low-density polyethylene (LDPE) and the density is 0.940 g / cm 3 3 or more and 0.955 g / cm 3 3 or less high-density polyethylene (HDPE) are used in combination.

[0023] [High-density polyethylene (HDPE) having a density of 0.940 g / cm 3 3 or more and 0.955 g / cm 3 3 or less] In the present technology, the density is 0.940 g / cm 3 3 or more and 0.955 g / cm 3 3 or less high-density polyethylene (HDPE) (hereinafter also referred to as "the above-mentioned high-density polyethylene") is contained in an amount of 16 to 45 parts by mass based on 100 parts by mass of the resin component in the raw material.

[0024] The lower limit of the content of high-density polyethylene per 100 parts by mass of resin component can be 16 parts by mass or more to achieve the effects of this technology, but preferably 17 parts by mass or more, more preferably 18 parts by mass or more, even more preferably 19 parts by mass or more, even more preferably 20 parts by mass or more, and particularly preferably 21 parts by mass or more. By setting the lower limit of the content of high-density polyethylene per 100 parts by mass of resin component within this range, the thickness shrinkage rate of the manufactured cross-linked polyolefin resin foam sheet can be reduced, and the peel strength of the heat-sealed portion of the tubular body manufactured using the manufactured cross-linked polyolefin resin foam sheet can be improved.

[0025] The upper limit of the content of high-density polyethylene per 100 parts by mass of resin component can be 45 parts by mass or less to achieve the effects of this technology, but preferably 40 parts by mass or less, more preferably 35 parts by mass or less, and even more preferably 30 parts by mass or less. By setting the upper limit of the content of high-density polyethylene per 100 parts by mass of resin component within this range, the foaming properties during the production of crosslinked polyolefin resin foam sheets can be improved.

[0026] The crystallization temperature of the high-density polyethylene used in this technology is not particularly limited as long as it does not impair the function or effect of this technology. The lower limit of the crystallization temperature of the high-density polyethylene used in this technology is, for example, 113°C or higher, preferably 114°C or higher, more preferably 115°C or higher, even more preferably 116°C or higher, and even more preferably 117°C or higher. By using high-density polyethylene with a crystallization temperature in this range, the heat-sealability of the cross-linked polyolefin resin foam sheet produced can be improved.

[0027] The upper limit of the crystallization temperature of the high-density polyethylene used in this technology is not particularly limited and can be, for example, 125°C or lower.

[0028] The melt viscosity of the high-density polyethylene used in this technology is not particularly limited as long as it does not impair the function or effect of this technology. The upper limit of the melt viscosity of the high-density polyethylene used in this technology is, for example, 750 Pa·s or less, preferably 600 Pa·s or less, and more preferably 500 Pa·s or less. By using high-density polyethylene with a melt viscosity in this range, the heat-sealability of the cross-linked polyolefin resin foam sheet produced can be improved.

[0029] The lower limit of the melt viscosity of the high-density polyethylene used in this technology is not particularly limited and can be, for example, 400 Pa·s or more.

[0030] The melt flow rate (MFR) of the high-density polyethylene used in this technology is not particularly limited as long as it does not impair the function or effect of this technology. The lower limit of the MFR of the high-density polyethylene used in this technology is, for example, 5 g / 10 min or more, preferably 6 g / 10 min or more, more preferably 7 g / 10 min or more, even more preferably 8 g / 10 min or more, even more preferably 9 g / 10 min or more, and particularly preferably 10 g / 10 min or more. By using high-density polyethylene with an MFR in this range, the thickness shrinkage rate of the manufactured cross-linked polyolefin resin foam sheet can be reduced and the heat resistance can be improved.

[0031] The upper limit of the MFR of the high-density polyethylene used in this technology is, for example, 30 g / 10 min or less, preferably 25 g / 10 min or less, and more preferably 22 g / 10 min or less.

[0032] [Density is 0.940 g / cm³ 3 [Low-density polyethylene] In this technology, the raw material has a density of 0.940 g / cm³. 3 This technology is characterized by the use of low-density polyethylene (hereinafter also referred to as "the low-density polyethylene") with a density of less than 1.5 mm. The content of the low-density polyethylene is not particularly limited, as long as it does not impair the function or effect of this technology.

[0033] The lower limit of the content of low-density polyethylene per 100 parts by mass of resin component is, for example, 55 parts by mass or more, preferably 60 parts by mass or more, more preferably 65 parts by mass or more, and even more preferably 70 parts by mass or more. By setting the lower limit of the content of low-density polyethylene per 100 parts by mass of resin component within this range, the foaming properties during the production of cross-linked polyolefin resin foam sheets can be improved.

[0034] The upper limit of the content of low-density polyethylene per 100 parts by mass of resin component is, for example, 84 parts by mass or less, preferably 83 parts by mass or less, more preferably 82 parts by mass or less, even more preferably 81 parts by mass or less, even more preferably 80 parts by mass or less, and particularly preferably 79 parts by mass or less. By setting the upper limit of the content of low-density polyethylene per 100 parts by mass of resin component within this range, the thickness shrinkage rate of the manufactured cross-linked polyolefin resin foam sheet can be reduced, and the peel strength of the heat-sealed portion of the tubular body manufactured using the manufactured cross-linked polyolefin resin foam sheet can be improved.

[0035] The crystallization temperature of the low-density polyethylene used in this technology is not particularly limited as long as it does not impair the function or effect of this technology. The upper limit of the crystallization temperature of the low-density polyethylene used in this technology is, for example, 116°C or less, preferably 115°C or less, more preferably 113°C or less, even more preferably 112°C or less, and even more preferably 110°C or less.

[0036] The lower limit of the crystallization temperature of the low-density polyethylene used in this technology is not particularly limited and can be, for example, 90°C or higher.

[0037] In this technology, the crystallization temperature of polyethylene is the value measured by the method described in the examples below.

[0038] The melt viscosity of the low-density polyethylene used in this technology is not particularly limited as long as it does not impair the operation or effect of this technology. The lower limit of the melt viscosity of the low-density polyethylene used in this technology is, for example, 750 Pa·s or more, preferably 760 Pa·s or more, and more preferably 770 Pa·s or more. By using low-density polyethylene with a melt viscosity in this range, the heat-sealability of the cross-linked polyolefin resin foam sheet produced can be improved.

[0039] The upper limit of the melt viscosity of the low-density polyethylene used in this technology is not particularly limited and can be, for example, 1300 Pa·s or less.

[0040] In this technology, the melt viscosity of polyethylene is the value measured by the method described in the examples below.

[0041] The melt flow rate (MFR) of the low-density polyethylene used in this technology is not particularly limited as long as it does not impair the function or effect of this technology. The lower limit of the MFR of the low-density polyethylene used in this technology is, for example, 0.1 g / 10 min or more, preferably 0.3 g / 10 min or more, and more preferably 0.5 g / 10 min or more.

[0042] The upper limit of the MFR of the low-density polyethylene used in this technology is, for example, 6 g / 10 min or less, preferably 5 g / 10 min or less, and more preferably 4 g / 10 min or less. By using low-density polyethylene with an MFR in this range, the thickness shrinkage rate of the manufactured cross-linked polyolefin resin foam sheet can be reduced, thereby improving its heat resistance.

[0043] In this technology, the MFR of polyethylene is the value measured by the method described in the examples below.

[0044] Furthermore, in this technology, within a range that does not impair the function or effect of this technology, the density is 0.955 g / cm³. 3 It is also possible to use high-density polyethylene (HDPE) with a density exceeding 0.955 g / cm³.3 When using high-density polyethylene (HDPE) exceeding 0.955 g / cm³, the content is not limited, but is, for example, 15 parts by mass or less, preferably 10 parts by mass or less, and more preferably 5 parts by mass or less, per 100 parts by mass of the resin component. 3 By setting the amount of high-density polyethylene (HDPE) exceeding this value within this range, the heat-sealability of the manufactured cross-linked polyolefin resin foam sheet can be improved.

[0045] Furthermore, the cross-linked polyolefin resin foam sheet relating to this technology may contain other resins, thermoplastic elastomers, thermosetting elastomers, etc., in addition to the polyolefin resin, to the extent that it does not impair the function or effect of this technology. 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.

[0046] The melt viscosity of the resin component is not particularly limited as long as it does not impair the function or effect of this technology. The lower limit of the melt viscosity of the resin component used in this technology is, for example, 650 Pa·s or more, preferably 700 Pa·s or more, and more preferably 750 Pa·s or more. The upper limit of the melt viscosity of the resin component used in this technology is, for example, 1100 Pa·s or less, preferably 1000 Pa·s or less, and more preferably 900 Pa·s or less. By setting the melt viscosity of the resin component within this range, the heat-sealability of the manufactured cross-linked polyolefin resin foam sheet can be improved.

[0047] (2-2) Foaming agent The resin composition used in this technology may contain a foaming agent. As for the foaming agent that can be used in this technology, one or more foaming agents that can be used in polyolefin resin foams can be freely selected and used, as long as they do not impair the action or effect of this technology.

[0048] Examples of blowing agents that can be used in this technology include organic or inorganic pyrolysis-type chemical blowing agents. Examples of organic blowing agents include azo compounds such as azodicarbonamide (ADCA), azodicarboxylic acid metal salts (such as barium azodicarboxylic acid), and azobisisobutyronitrile (AIBN); nitroso compounds such as N,N'-dinitrosopentamethylenetetramine (DPT); hydrazine derivatives such as hydrazodicarbonamide, 4,4'-oxybis(benzenesulfonyl hydrazide), and toluenesulfonyl hydrazide (TSH); and semicarbazide compounds such as toluenesulfonyl semicarbazide. Examples of inorganic blowing agents include ammonium carbonate, sodium carbonate, ammonium bicarbonate, sodium bicarbonate, ammonium nitrite, sodium borohydride, and anhydrous monosodium citrate.

[0049] Among these, in this technology, it is preferable to use an organic blowing agent, and among organic blowing agents, it is preferable to use azodicarbonamide (ADCA).

[0050] The amount of foaming agent used in this technology can be freely set as long as it does not impair the function or effect of this technology. In this technology, the content of the foaming agent per 100 parts by mass of the resin component in the resin composition is, for example, 5.0 parts by mass or more, preferably 10.0 parts by mass or more, and more preferably 15.0 parts by mass or more. By setting the content of the foaming agent in the resin composition within this range, the foaming properties during foam production can be improved, and the physical properties of the foam produced can be improved.

[0051] In this technology, the content of the foaming agent in the resin composition is, for example, 35.0 parts by mass or less, preferably 30.0 parts by mass or less, and more preferably 25.0 parts by mass or less, per 100 parts by mass of the resin component. By setting the content of the foaming agent in the resin composition within this range, it is possible to suppress molding defects due to excessive foaming and also contribute to cost reduction.

[0052] (2-3) Crosslinking agents By performing crosslinking during the manufacturing of the crosslinked polyolefin resin foam sheet according to this technology, the viscosity of the composition (kneaded material) before foaming can be improved, thereby improving foamability. Furthermore, the heat resistance of the manufactured foam sheet can be improved.

[0053] This technology allows for crosslinking by ionizing radiation irradiation, but it can also be chemically crosslinked using a crosslinking agent. As long as the action and effects of this technology are not impaired, one or more crosslinking agents suitable for polyolefin resin foams can be freely selected and used.

[0054] Examples of crosslinking agents that can be used in this technology include those having chemical structures such as silane groups, peroxides, hydroxyl groups, amide groups, and ester groups. Among these, it is preferable to use organic peroxides as the crosslinking agent in this technology.

[0055] Examples of organic peroxides 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)hexine-3, di-t-butylperoxide, di-t-butylperoxy-3,3,5-trimethylcyclohexane, and t-butylhydroperoxide. Among these, dicumyl peroxide (DCP) is preferred as the crosslinking agent in this technology.

[0056] The amount of crosslinking agent used in the production of the crosslinked polyolefin resin foam sheet according to this technology can be freely set as long as it does not impair the function and effects of this technology. In this technology, the content of the crosslinking agent per 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, viscosity can be improved and foamability can be enhanced. Furthermore, mechanical properties such as heat resistance of the manufactured foam can be improved.

[0057] In this technology, the amount of crosslinking agent per 100 parts by mass of 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 amount of crosslinking agent in the resin composition within this range, cracking and other defects during foaming can be prevented, and moldability can be improved.

[0058] (2-4) Crosslinking accelerators When manufacturing the crosslinked polyolefin resin foam sheet according to this technology, a crosslinking accelerator may be used to promote crosslinking by the crosslinking agent. As long as the action and effects of this technology are not impaired, one or more crosslinking accelerators that can be used with polyolefin resin foams may be freely selected and used.

[0059] Examples of crosslinking accelerators that can be used in this technology include trimethylolpropane trimethacrylate (TMPT), triallyl trimellitate, diallyl trimellitate, diallyl phthalate, divinylbenzene, 1,9-nonanediol dimethacrylate, 1,10-decanediol dimethacrylate, trimellitate trialyl ester, triallyl isocyanurate, neopentyl glycol dimethacrylate, and 1,6-hexanediol dimethacrylate. Among these, crosslinking agents having multiple double bonds are preferred in this technology, and the use of trimethylolpropane trimethacrylate (TMPT) is more preferred.

[0060] The amount of crosslinking accelerator used in the production of polyolefin resin foam according to this technology can be freely set as long as it does not impair the action or effect of this technology. In this technology, the content of the crosslinking accelerator per 100 parts by mass of 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 foaming properties during foam production can be improved.

[0061] In this technology, the amount of crosslinking accelerator in the resin composition per 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 amount of crosslinking accelerator in the resin composition within this range, it is possible to suppress defects in the formation of polyolefin-based resin foams and also contribute to cost reduction.

[0062] (2-5) Others In the production of polyolefin resin foams related to this technology, one or more components that can be used in the production of polyolefin resin foams may be freely selected and used as other components, depending on the purpose, as long as they do not impair the function or effect of this technology.

[0063] Examples of components that can be used in the production of polyolefin-based resin foams related to this technology include foaming aids, inorganic fillers, foam stabilizers, flame retardants, stabilizers, plasticizers, colorants, antioxidants, dispersants, UV absorbers, and lubricants.

[0064] (3) Tensile stress (10% strain) The tensile stress (10% strain) of the crosslinked polyolefin resin foam sheet according to this technology can be freely set as long as it does not impair the function and effects of this technology. In this technology, the lower limit of the tensile stress (10% strain) of the crosslinked polyolefin resin foam sheet is, for example, 100 kPa or more, preferably 110 kPa or more, and more preferably 130 kPa or more, in both the MD and TD directions. By setting the tensile stress (10% strain) of the crosslinked polyolefin resin foam sheet within this range, the heat resistance of the manufactured crosslinked polyolefin resin foam sheet can be improved.

[0065] The upper limit of the tensile stress (10% strain) of the cross-linked polyolefin resin foam sheet related to this technology can be freely set as long as it does not impair the function or effect of this technology, but it can be set to, for example, 400 kPa or less.

[0066] The ratio of the tensile stress (10% strain) in the TD direction to the tensile stress (10% strain) in the MD direction to the tensile stress (10% strain) in the crosslinked polyolefin resin foam sheet according to this technology (TD / MD) is, for example, 0.65 or more, preferably 0.70 or more, and more preferably 0.75 or more. By setting the ratio of the tensile stress (10% strain) in the TD direction to the tensile stress (10% strain) in the MD direction to the tensile stress (10% strain) (TD / MD) within this range, the heat resistance of the manufactured crosslinked polyolefin resin foam sheet can be improved.

[0067] The upper limit of the ratio of the tensile stress (10% strain) in the TD direction to the tensile stress (10% strain) in the MD direction (TD / MD) can be, for example, 1.00 or less.

[0068] In this technology, the tensile stress (10% strain) of the cross-linked polyolefin resin foam was measured according to the method based on JIS K6767.

[0069] (4) Thickness The thickness of the cross-linked polyolefin resin foam sheet related to this technology can also be freely set as long as it does not impair the purpose and effects of this technology. In this technology, the lower limit of the thickness of the cross-linked polyolefin resin foam sheet is, for example, 4.0 mm or more, preferably 5.0 mm or more, and more preferably 6.0 mm or more. By setting the lower limit of the thickness of the cross-linked polyolefin resin foam sheet within this range, the heat insulation and heat retention properties can be improved.

[0070] The upper limit of the thickness of the cross-linked polyolefin resin foam sheet is, for example, 15.0 mm or less, preferably 14.5 mm or less, and more preferably 13.0 mm or less. By setting the thickness of the cross-linked polyolefin resin foam sheet within this range, moldability can be improved.

[0071] 2. Method for manufacturing cross-linked polyolefin resin foam sheets The crosslinked polyolefin resin foam sheet relating to this technology has distinctive physical properties, and its manufacturing method is not particularly limited. For example, a method can be employed in which a polyolefin resin is mixed with a foaming agent, crosslinking agent, and other additives as needed, and then crosslinked and foamed.

[0072] The method for producing the crosslinked polyolefin resin foam sheet may be either a long-length foaming method using chemical crosslinking or a long-length foaming method using electron beam crosslinking, with the long-length foaming method using chemical crosslinking being more preferable.

[0073] <Long-length foaming method using chemical crosslinking> The long foaming method comprises, for example, the following steps (1)-(2). (1) Mixing process Polyolefin resin, along with foaming agents, crosslinking agents, and other optional additives as needed, are kneaded and extruded into a sheet using a single-screw or twin-screw extruder to produce a foamed resin composition (hereinafter referred to as a base sheet) in a predetermined shape, such as a sheet. The kneading and extrusion can be performed simultaneously using the extruder.

[0074] (2) Foaming process The base material obtained in the kneading process is transported into a heating device such as an oven and heated at 120-250°C (above the decomposition temperature of the foaming agent and crosslinking agent) for 5-20 minutes to produce a foamed resin material. It is preferable to use a device in which the heating device such as an oven and the transport device are integrated, as this allows for continuous processing of the base material.

[0075] <Long foaming method using electron beam crosslinking> The long foaming method using electron beam crosslinking comprises, for example, the following steps (1)-(3). (1) Mixing process Polyolefin resin, along with foaming agents, crosslinking agents, and other optional additives as needed, are kneaded using a single-screw or twin-screw extruder, and a resin composition in a predetermined shape, such as a sheet (hereinafter referred to as a base plate), is extruded. Kneading and extrusion can be performed simultaneously using an extruder.

[0076] (2) Crosslinking process The base plate obtained in the kneading process is crosslinked. The crosslinking method can involve irradiation with ionizing radiation such as electron beams or gamma rays, with electron beam irradiation (electron beam crosslinking) being preferred. Electron beam crosslinking can be performed using an electron beam irradiator. If necessary, crosslinking agents such as the aforementioned organic peroxides may be used in combination.

[0077] (3) Foaming process The crosslinked base plate obtained in the crosslinking process is transported into a heating device such as an oven and heated at 120-250°C (above the decomposition temperature of the foaming agent) for 5-20 minutes to produce a foamed resin. It is preferable to use a device in which the heating device such as an oven and the transport device are integrated, as this allows for continuous processing of the base plate.

[0078] In the method for manufacturing crosslinked polyolefin resin foam sheets related to this technology described above, other processes can be performed depending on the purpose. For example, cooling processes, maturation processes, etc., can be performed after the crosslinking and foaming processes. It is also possible to perform molding processes such as trimming the edges or slicing the manufactured foam.

[0079] 3. Cylindrical body The cross-linked polyolefin resin foam sheet according to this technology can be used in molded articles formed by heat sealing, taking advantage of its high heat-sealability and heat resistance. In particular, it can be suitably used in molded articles where the heat-sealed surface is prone to opening, such as cylindrical articles. The cylindrical article according to this technology can be formed by heat sealing the end faces of the cross-linked polyolefin resin foam sheets.

[0080] The method of heat fusion is not particularly limited as long as it does not impair the function or effect of this technology, and general heat fusion methods can be used. For example, one method is to heat the heat fusion surface of a cross-linked polyolefin resin foam sheet using a welding machine or hot plate, then form it into a cylindrical shape using a general molding method such as a molded pipe, and then cool the fused portion using air or water.

[0081] (1) Density The density of the cylindrical body related to this technology can be freely set as long as it does not impair the function or effect of this technology. In this technology, the lower limit of the density of the cylindrical body is, for example, 10 kg / m³. 3 Preferably 15 kg / m 3 More than 20 kg / m 3 More preferably 23 kg / m 3 That concludes the explanation. By setting the lower limit of the density of the cylindrical body within this range, it is possible to prevent it from becoming too soft and to impart appropriate elasticity.

[0082] The upper limit of the density of the cylindrical body related to this technology can be freely set as long as it does not impair the function or effect of this technology, but for example, 70 kg / m³ 3 Preferably 50 kg / m 3 More preferably 40 kg / m 3 More preferably, 35 kg / m 3 The following is true: By keeping the density of the cylindrical body within this range, it is possible to prevent the cylindrical body from becoming too rigid and losing its flexibility, while providing appropriate cushioning.

[0083] In this technology, the density of the cylindrical body is a value measured in accordance with the method based on JIS A9511.

[0084] (2) Number of cells The number of cells in the cylindrical body related to this technology can be freely set as long as it does not impair the function or effect of this technology. In this technology, the lower limit of the number of cells in the cylindrical body is, for example, 15 cells / 25 mm or more, preferably 18 cells / 25 mm or more, and more preferably 20 cells / 25 mm or more. By adjusting the number of cells within this range, the heat-sealing properties can be further improved.

[0085] The upper limit for the number of cells in the cylindrical body can be adjusted to, for example, 50 cells / 25 mm or less, 40 cells / 25 mm or less, 35 cells / 25 mm or less, etc.

[0086] In this technology, the number of cells in the cylindrical body is a value measured in accordance with the method based on JIS K6400-1.

[0087] (3) Gel fraction The gel fraction of the tubular body in this technology can be freely set as long as it does not impair the function or effect of this technology. In this technology, the lower limit of the gel fraction of the tubular body is, for example, 20% or more, preferably 25% or more, and more preferably 30% or more.

[0088] The upper limit of the gel fraction of the tubular body relating to this technology can be freely set as long as it does not impair the function or effect of this technology, but for example, it is 80% or less, preferably 75% or less, more preferably 70% or less, and even more preferably 65% ​​or less.

[0089] In this technology, the gel fraction of the tubular body was measured according to the method based on JIS K6769.

[0090] (4) Thickness shrinkage rate The thickness shrinkage rate of the cylindrical body in this technology can be freely set as long as it does not impair the function or effect of this technology. In this technology, the upper limit of the thickness shrinkage rate of the cylindrical body is, for example, 7.1% or less, preferably 7.0% or less. Lowering the thickness shrinkage rate of the cylindrical body improves heat resistance and also contributes to improved dimensional stability.

[0091] The lower limit of the thickness shrinkage rate of the cylindrical body related to this technology is not particularly limited and may be 0%.

[0092] In this technology, the thickness shrinkage rate of the cylindrical body is a value measured in accordance with the method based on JIS A9511.

[0093] (5) Peel strength The peel strength of the heat-sealed portion of the cylindrical body related to this technology can be freely set as long as it does not impair the function or effect of this technology. In this technology, the lower limit of the peel strength of the heat-sealed portion of the cylindrical body is, for example, 18 N / cm. 2 Preferably 19 N / cm² 2 More preferably 20 N / cm 2 This concludes the explanation. By adjusting the peel strength within this range, the heat-sealing properties can be further improved. If the peel strength of the heat-sealed portion is increased, it will be less likely to peel even when the molding speed of the cylindrical body is increased, thus contributing to improved productivity.

[0094] The upper limit of the peel strength of the heat-sealed portion of the cylindrical body is not particularly limited, for example, 30 N / cm 2 The following adjustments can be made:

[0095] (6) Inner diameter The inner diameter of the tubular resin foam used in the tubular body according to this technology can be freely set as long as it does not impair the purpose or effect of this technology. The lower limit of the inner diameter of the tubular body is, for example, 10 mm or more, preferably 13 mm or more, more preferably 14 mm or more, and even more preferably 15 mm or more. By setting the lower limit of the inner diameter of the tubular body within this range, moldability can be improved.

[0096] The upper limit of the inner diameter of the cylindrical body is, for example, 120 mm or less, preferably 110 mm or less, and more preferably 100 mm or less. By setting the inner diameter of the cylindrical body within this range, it is possible to give the cylindrical body an appropriate thickness, thereby improving its heat insulation and heat retention properties.

[0097] (7) Outer diameter Furthermore, the outer diameter of the cylindrical body can be freely set as long as it does not impair the purpose and effects of this technology. The lower limit of the outer diameter of the cylindrical body is, for example, 14 mm or more, preferably 17 mm or more, more preferably 18 mm or more, and even more preferably 19 mm or more. By setting the lower limit of the outer diameter of the cylindrical body within this range, it is possible to give the cylindrical body an appropriate thickness, thereby improving its heat insulation and heat retention properties.

[0098] The upper limit of the outer diameter of the cylindrical body is, for example, 135 mm or less, preferably 125 mm or less, and more preferably 115 mm or less. By setting the outer diameter of the cylindrical body within this range, moldability can be improved.

[0099] 4. Applications of cross-linked polyolefin resin foam sheets and tubular bodies The cross-linked polyolefin resin foam sheets and tubular bodies related to this technology can be used in a wide range of fields and applications due to their high quality. For example, they can be suitably used as pipe insulation, building cushioning material, building soundproofing material, packaging material, vehicle cushioning material, building interior material, and vehicle interior material. Among these, the cross-linked polyolefin resin foam sheets and tubular bodies related to this technology can be suitably used for thermal insulation applications, particularly as pipe insulation. [Examples]

[0100] The present technology will be described in more detail below based on the following examples. The examples described below are representative examples of the present technology and should not be interpreted as narrowing the scope of the present technology.

[0101] (1) Measurement of the physical properties of raw materials The physical properties of the resin components used were measured using the following method.

[0102] [Melt Flow Rate (MFR)] The melt flow rate (MFR) of the resin was measured in accordance with JIS K 7210.

[0103] [Crystallization temperature] The crystallization temperature of the resin was determined using a differential scanning calorimeter (Hitachi High-Tech Science Corporation "DSC7000X") by heating the sample from 25°C to 200°C in a nitrogen atmosphere (heating rate: 20°C / min), maintaining the temperature at 200°C for 5 minutes, and then cooling it down (cooling rate: 5°C / min). The temperature at which exothermic reaction began was defined as the crystallization temperature.

[0104] [Melting viscosity] The melt viscosity of the resin component was determined in accordance with JIS K 7199:1999, at 150°C and a shear rate of 243 sec. -1 It was measured using [this method].

[0105] (2) Manufacturing of cross-linked polyolefin resin foam sheets <Examples 1-3, 5, 6, Comparative Examples 1-7> The raw materials shown in Table 1 below were melt-kneaded at 120-130°C and extruded into a sheet. The sheet was heated in an oven from 180°C, gradually increasing the temperature to a final temperature of 230-250°C to obtain a 9.0 mm thick cross-linked polyolefin resin foam sheet.

[0106] <Example 4> The raw materials shown in Table 1 below were melt-kneaded at 120-130°C and extruded into a sheet. The sheet was irradiated with an electron beam at 6.5 Mrad, and then heated in an oven from 180°C to a final temperature of 230-250°C to obtain a 9.0 mm thick crosslinked polyolefin resin foam sheet.

[0107] (3) Measurement and evaluation of physical properties of cross-linked polyolefin resin foam sheets The physical properties of the manufactured cross-linked polyolefin resin foam sheets were measured using the following method. The foaming properties of the cross-linked polyolefin resin foam sheets were evaluated visually.

[0108] [Tensile stress (10% strain)] The tensile stress (10% strain) of the cross-linked polyolefin resin foam sheet was measured in accordance with JIS K 6767. Measurements were taken in both the MD and TD directions.

[0109] (4) Manufacturing of cylindrical bodies The foam sheet was cut with a slit width of 135 mm in the width direction so that the inner diameter was 20 mm. The ends in the width direction were heated using a welding machine manufactured by Leister, then rolled with a forming pipe, and the fused parts were cooled with water to form a cylindrical shape.

[0110] (5) Measurement and evaluation of the physical properties of cylindrical bodies The moldability of the manufactured cylindrical bodies was evaluated visually. Furthermore, the physical properties of the manufactured cylindrical body were measured using the following method.

[0111] [density] The density of the cylindrical body was measured in accordance with JIS A 9511.

[0112] [Number of cells] The number of cells in the cylindrical body was measured in accordance with JIS K 6400-1.

[0113] [Gel fraction] The gel fraction of the tubular body was measured in accordance with JIS K6769.

[0114] [Thickness reduction rate] The thickness shrinkage rate of the cylindrical body was measured in accordance with JIS A 9511.

[0115] [Peel strength] A test sample (20 mm wide, 150 mm long) was cut so that the heat-sealed portion of the manufactured cylindrical body was perpendicular to the center in the longitudinal direction. A tensile test was performed using a tensile testing machine (Shimadzu Corporation "AGS-J 500N") at a speed of 500 mm / min, and the load at fracture was measured.

[0116] (6) Results The results are shown in Table 1 below. [Table 1]

[0117] (7) Discussion As shown in Table 1, Comparative Examples 1 and 6, which did not use high-density polyethylene, deformed, making it impossible to measure the thickness shrinkage rate. Furthermore, the cross-linked polyolefin resin foam sheet of Comparative Example 2, which did not use high-density polyethylene, could not be heat-sealed and peeled off, making it impossible to manufacture a tubular body.

[0118] Even high-density polyethylene has a density of 0.955 g / cm³. 3 Comparative Example 5, which used high-density polyethylene exceeding [a certain value], also failed to heat-seal and peeled off, making it impossible to manufacture a tubular body.

[0119] Density is 0.940 g / cm³ 3 More than 0.955g / cm 3 Even when using the following high-density polyethylene, Comparative Example 3, in which the content of the resin component was less than 16 parts by mass per 100 parts by mass, showed a thickness shrinkage rate exceeding 7.0. Furthermore, the density was 0.940 g / cm³. 3 More than 0.955g / cm 3 Even when using the following high-density polyethylene, Comparative Example 4, in which the content of the resin component exceeded 45 parts by mass per 100 parts by mass, did not undergo foaming and could not produce a cross-linked polyolefin resin foam sheet.

[0120] In Comparative Example 7, where polyolefin elastomer was used instead of high-density polyethylene, foaming did not proceed, and it was not possible to produce a cross-linked polyolefin resin foam sheet.

[0121] On the other hand, the density is 0.940 g / cm³ 3 Low-density polyethylene with a density of less than 0.940 g / cm³ 3 More than 0.955g / cm 3 The cylindrical bodies of Examples 1 to 6, formed using a cross-linked polyolefin resin foam sheet containing the following high-density polyethylene, wherein the content of the high-density polyethylene per 100 parts by mass of the resin component is 16 to 45 parts by mass, exhibited good moldability, low thickness shrinkage, and high peel strength.

Claims

1. A crosslinked polyolefin resin foam sheet having heat-sealable end faces, The resin components in the raw materials include: Density is 0.940 g / cm³ ３ Low-density polyethylene of less than, Density is 0.940 g / cm³ ３ 0.955g / cm or more ３ The following high-density polyethylene and, A cross-linked polyolefin resin foam sheet, wherein the content of high-density polyethylene per 100 parts by mass of resin component is 16 to 45 parts by mass.

2. The crosslinked polyolefin resin foam sheet according to claim 1, wherein the crystallization temperature of the high-density polyethylene is 115°C or higher.

3. The crosslinked polyolefin resin foam sheet according to claim 1, wherein the melt viscosity of the high-density polyethylene is 500 Pa·s or less.

4. The crosslinked polyolefin resin foam sheet according to claim 1, wherein the melt viscosity of the resin component is 700 to 1000 Pa·s.

5. A cylindrical body formed by heat-sealing the end faces of a crosslinked polyolefin resin foam sheet according to any one of claims 1 to 4.

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