Polyolefin resin foam

Abstract

[Problem] To provide a high-quality polyolefin resin foam despite the use of a biomass material therein. [Solution] Provided is a polyolefin resin foam containing a biomass material that has calcium carbonate as the main component. The biomass material can be contained in the polyolefin resin foam according to the present technology in an amount of 50 weight% or less. A biomass material derived from eggshells and / or seashells can be used as the biomass material used in the polyolefin resin foam according to the present technology.

Description

[Technical Field]

[0001] This technology relates to polyolefin resin foams. More specifically, it relates to polyolefin resin foams having a certain level of biomass content. [Background technology]

[0002] In recent years, there has been growing interest in how to utilize unused biomass, such as food waste, livestock manure, and sewage sludge, as a so-called carbon-neutral renewable resource, in order to contribute to the formation of a sustainable society. Technologies using biomass materials are also being developed for synthetic resins, which are used in a wide range of fields, including civil engineering and construction, packaging, vehicles, and various other general merchandise.

[0003] For example, Patent Document 1 proposes a resin composition containing 5 to 50 parts by weight of eggshell powder per 100 parts by weight of a high-molecular polymer. The resin composition described in Patent Document 1 is environmentally friendly and can reduce material costs because it uses recycled eggshells, which are food waste, as a plastic material. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Special Publication No. 2019-503411 [Overview of the project] [Problems that the invention aims to solve]

[0005] As mentioned above, technologies are being developed to incorporate waste materials such as food scraps into synthetic resins. However, when waste materials such as food scraps are incorporated into foams formed by foaming resin compositions, problems such as reduced foamability and decreased mechanical properties arise, making practical application difficult.

[0006] Therefore, the primary objective of this technology is to provide high-quality polyolefin-based resin foams despite using biomass materials. [Means for solving the problem]

[0007] This technology first provides a polyolefin resin foam containing a biomass material with calcium carbonate as its main component. The polyolefin resin foam according to this technology may contain the biomass material in an amount of 50% by weight or less. As the biomass material used in the polyolefin resin foam according to this technology, a biomass material derived from eggshells and / or seashells can be used. As biomass material derived from eggshells and / or seashells, eggshell powder and / or seashell powder can be used. In this case, eggshell powder and / or seashell powder with an average particle size of 8 to 200 μm can be used. [Modes for carrying out the invention]

[0008] 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.

[0009] 1. Polyolefin resin foam The polyolefin resin foam according to this technology contains a biomass material mainly composed of calcium carbonate. That is, the polyolefin resin foam according to this technology is a foam of a resin composition containing a biomass material mainly composed of calcium carbonate. Furthermore, the resin composition for producing the polyolefin resin foam according to this technology (hereinafter also referred to as "the resin composition according to this technology" or "the resin composition") may contain a foaming agent, a foaming aid, a crosslinking agent, a crosslinking accelerator, and various other components that can be used in the production of the polyolefin resin foam depending on the purpose. Each component will be described in detail below.

[0010] (1) Polyolefin resins The polyolefin resin that can be used in the polyolefin resin foam according to 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.

[0011] 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.

[0012] 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.

[0013] Examples of polypropylene resins include propylene homopolymers such as isotactic polypropylene, syndiotactic polypropylene, and atactic polypropylene; propylene-ethylene random copolymer, propylene-ethylene block copolymer, propylene-butene random copolymer, propylene-butene block copolymer, propylene-ethylene-butene ternary copolymer, propylene-acrylic acid copolymer, and propylene-maleic anhydride copolymer.

[0014] Among these, the use of polyethylene-based resins is preferred in this technology, and among polyethylene-based resins, low-density polyethylene (LDPE) and ethylene-vinyl acetate copolymer are preferred.

[0015] The melt flow rate (MFR) of polyolefin resins is not particularly limited as long as it does not impair the function or effect of this technology. For example, the melt flow rate (MFR) of low-density polyethylene (LDPE) is preferably 10.0 g / 10 min or less, more preferably 5.0 g / 10 min or less.

[0016] The origin of the polyolefin resin that can be used in this technology is not particularly limited; it is not limited to petroleum-derived polyolefin resins, but also biomass-derived polyolefin resins can be used. In addition to the biomass material mainly composed of calcium carbonate described later, the biomass content can be further improved by using biomass-derived polyolefin resin as the polyolefin resin.

[0017] In the present technology, the "biomass-derived polyolefin resin" means a resin containing a naturally-derived resin component. As a specific example, a resin containing a component derived from naturally-derived ethylene can be mentioned. Naturally-derived ethylene can be obtained, for example, by fermenting a saccharide such as sugarcane, which is a natural raw material, using a fermenting agent such as yeast (e.g., Saccharomyces cerevisiae), generating ethanol, and subjecting the generated ethanol to a catalytic reaction under high-temperature conditions (e.g., 300 °C or higher) using a catalyst such as γ-alumina to convert it into ethylene. transformation By doing so, naturally-derived ethylene, which is the raw material for naturally-derived polyethylene, can be obtained.

[0018] In addition, the polyolefin resin foam according to the present technology may contain, in addition to the polyolefin resin, resins other than the polyolefin resin such as other resins and elastomers as long as the object and effects of the present technology are not impaired. Examples of resins other than the polyolefin resin include thermoplastic resins such as polystyrene-based resins, polyamide-based resins, and polyester-based resins. Examples of elastomers other than the polyolefin resin include olefin-based thermoplastic elastomers and styrene-based thermoplastic elastomers.

[0019] (2) Biomass material mainly composed of calcium carbonate The biomass material mainly composed of calcium carbonate used in the polyolefin resin foam according to the present technology is a biomass material containing 50% by mass or more of calcium carbonate. In the present technology, the content of calcium carbonate in the biomass material is preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more.

[0020] The amount of biomass material used in the polyolefin resin foam according to this technology can be freely set as long as it does not impair the purpose and effects of this technology. In this technology, the upper limit of the biomass material content in the resin composition is, for example, 50% by weight or less, preferably 40% by weight or less, and more preferably 30% by weight or less. By setting the biomass material content in the resin composition to 50% by weight or less, it is possible to suppress a decrease in foamability during foam production and a decrease in the physical properties of the foam produced.

[0021] In this technology, the lower limit of the biomass material content in the resin composition is, for example, 1% by weight or more, preferably 10% by weight or more, more preferably 15% by weight or more, and even more preferably 20% by weight or more. By setting the biomass material content in the resin composition to 10% by weight or more, the biomass content can be improved, contributing to the formation of a sustainable society.

[0022] Examples of biomass materials primarily composed of calcium carbonate used in this technology include biomass materials derived from eggshells and / or seashells. Examples of eggshells include those of birds and reptiles. Examples of seashells include those of scallops, oysters, and surf clams. In particular, in this technology, eggshells are preferred because they contain a low amount of marine-derived alkaline components, and it is even more preferable to use eggshells from birds such as chickens, considering the resource recovery of waste such as food scraps, cost considerations, and the relatively low amount of impurities they contain.

[0023] As the biomass material derived from eggshells and / or seashells, it is preferable to use eggshell powder and / or seashell powder. By powdering, it is possible to improve the workability when kneading with resin components and other components described later, as well as the physical properties of the manufactured foam.

[0024] The average particle size of eggshell powder and / or seashell powder is not particularly limited and can be freely designed according to the application and desired physical properties of the foam. The lower limit of the average particle size of eggshell powder and / or seashell powder that can be used in this technology is, for example, 6 μm or more, preferably 8 μm or more, more preferably 10 μm or more, and even more preferably 13 μm or more. By using eggshell powder and / or seashell powder with an average particle size of 6 μm or more, the dispersibility in the resin composition during foam production is improved, and the grinding cost can be reduced.

[0025] Furthermore, the upper limit of the average particle size of the eggshell powder and / or seashell powder that can be used in this technology is, for example, 200 μm or less, preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 40 μm or less. By using eggshell powder and / or seashell powder with an average particle size of 200 μm or less, it is possible to improve the workability when mixing with resin components and other components described later, as well as the physical properties of the manufactured foam.

[0026] In this technology, "average particle diameter" refers to the particle diameter (D-50) at which the cumulative frequency reaches 50% in the particle size distribution measured by laser diffraction.

[0027] It is preferable to use heat-treated biomass material derived from eggshells and / or seashells. Heat treatment removes protein components and other impurities from the biomass material, and by using heat-treated biomass material derived from eggshells and / or seashells, the foaming properties during foam production are improved, and the physical properties of the foam produced can be improved.

[0028] (3) Foaming agent The resin composition for producing the polyolefin resin foam according to this technology may contain a blowing agent. As for the blowing agent that can be used in this technology, one or more blowing agents that can be used in polyolefin resin foams can be freely selected and used, as long as they do not impair the purpose or effects of this technology.

[0029] 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.

[0030] 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).

[0031] The amount of foaming agent used in the production of polyolefin resin foam according to this technology can 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 foaming agent content in the resin composition is, for example, 0.5% by weight or more, preferably 1.5% by weight or more, and more preferably 2.5% by weight or more. The amount of foaming agent blended per 100 parts by weight of resin component in the resin composition is, for example, 0.7 parts by weight or more, preferably 2.0 parts by weight or more, and more preferably 4.0 parts by weight or more. By setting the foaming agent content in the resin composition to 0.5% by weight or more, or 0.7 parts by weight or more per 100 parts by weight of resin component, the foaming properties during foam production can be improved, and the physical properties of the foam produced can be improved.

[0032] In this technology, the upper limit of the foaming agent content in the resin composition is, for example, 15% by weight or less, preferably 13% by weight or less, and more preferably 10% by weight or less. The amount of foaming agent blended in the resin composition per 100 parts by weight of the resin component is, for example, 25 parts by weight or less, preferably 20 parts by weight or less, and more preferably 15 parts by weight or less. By setting the foaming agent content in the resin composition to 15% by weight or less, or 25 parts by weight or less per 100 parts by weight of the resin component, it is possible to suppress molding defects due to excessive foaming and also contribute to cost reduction.

[0033] (4) Foaming agent The resin composition for producing the polyolefin resin foam according to this technology may contain a foaming aid. As for the foaming aid that can be used in this technology, one or more foaming aids that can be used in polyolefin resin foams can be freely selected and used, as long as they do not impair the purpose or effects of this technology.

[0034] Examples of foaming agents that can be used in this technology include urea-based additives such as urea, metal oxides, and fatty acid metal salts. Examples of metal oxides include zinc oxide, zinc chloride, zinc acetate, zinc nitrate, lead oxide, dibasic lead phosphite, and tribasic lead sulfate. Examples of fatty acid metal salts include zinc stearate, lead stearate, magnesium stearate, and calcium stearate. Among these, zinc oxide is preferably used as the foaming agent in this technology.

[0035] The amount of foaming aid used in the production of polyolefin resin foam according to this technology can 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 foaming aid content in the resin composition is, for example, 0.05% by weight or more, preferably 0.1% by weight or more, and more preferably 0.2% by weight or more. The amount of foaming aid blended per 100 parts by weight of resin component in the resin composition is, for example, 0.1 parts by weight or more, preferably 0.2 parts by weight or more, and more preferably 0.3 parts by weight or more. By setting the foaming aid content in the resin composition to 0.05% by weight or more, or 0.1 parts by weight or more per 100 parts by weight of resin component, the foaming properties during foam production can be improved, and the physical properties of the foam produced can be improved.

[0036] In this technology, the upper limit of the foaming agent content in the resin composition is, for example, 4.0% by weight or less, preferably 3.0% by weight or less, and more preferably 2.5% by weight or less. The amount of foaming agent blended per 100 parts by weight of resin component in the resin composition is, for example, 6.0 parts by weight or less, preferably 4.0 parts by weight or less, and more preferably 3.5 parts by weight or less. By setting the foaming agent content in the polyolefin resin foam to 4.0% by weight or less, or 6.0 parts by weight or less per 100 parts by weight of resin component, it is possible to suppress formation defects due to excessive foaming and also contribute to cost reduction.

[0037] (5) Crosslinking agents The polyolefin resin foam according to this technology may be a non-crosslinked foam or a crosslinked foam. By performing crosslinking during the manufacturing of the polyolefin resin foam according to this technology, the viscosity of the composition (kneaded material) before foaming can be improved, thereby improving foamability. Furthermore, the physical properties of the manufactured foam can be improved.

[0038] When the polyolefin resin foam related to this technology is a crosslinked foam, crosslinking can be performed by ionizing radiation irradiation, but it can also be chemically crosslinked using a crosslinking agent. As long as the purpose and effects of this technology are not impaired, one or more crosslinking agents that can be used with polyolefin resin foams can be freely selected and used.

[0039] 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 crosslinking agents in this technology.

[0040] 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)hexine-3, di-t-butyl peroxide, di-t-butylperoxy-3,3,5-trimethylcyclohexane, and t-dibutylhydroperoxide. Among these, dicumyl peroxide is preferred as the crosslinking agent in this technology.

[0041] The amount of crosslinking agent used in the production of polyolefin resin foam according to this technology can 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 crosslinking agent content in the resin composition is, for example, 0.1% by weight or more, preferably 0.3% by weight or more, and more preferably 0.4% by weight or more. The amount of crosslinking agent blended per 100 parts by weight of resin component in the resin composition is, for example, 0.2 parts by weight or more, preferably 0.4 parts by weight or more, and more preferably 0.6 parts by weight or more. By setting the crosslinking agent content in the resin composition to 0.1% by weight or more, or 0.2 parts by weight or more per 100 parts by weight of resin component, viscosity can be improved and foamability can be enhanced. Furthermore, mechanical properties such as heat resistance and durability of the manufactured foam can be improved.

[0042] In this technology, the upper limit of the crosslinking agent content in the resin composition is, for example, 3.0% by weight or less, preferably 2.0% by weight or less, and more preferably 1.5% by weight or less. The amount of crosslinking agent blended per 100 parts by weight of resin component in the resin composition is, for example, 4.0 parts by weight or less, preferably 3.0 parts by weight or less, and more preferably 2.0 parts by weight or less. By setting the crosslinking agent content in the resin composition to 3.0% by weight or less, or 4.0 parts by weight or less per 100 parts by weight of resin component, it is possible to prevent cracking and other damage during foaming and improve moldability.

[0043] (6) Crosslinking promoter When a crosslinking agent is used in the production of polyolefin resin foam related to this technology, a crosslinking accelerator may also be used for the purpose of promoting crosslinking by the crosslinking agent. As for the crosslinking accelerators that can be used in this technology, one or more crosslinking accelerators that can be used in polyolefin resin foam can be freely selected and used, as long as they do not impair the purpose or effects of this technology.

[0044] Examples of crosslinking accelerators that can be used in this technology include triallyl trimelite, Ji Allyl phthalate, divinylbenzene, trimethylolpropane trimethacrylate, 1,9-nonanediol dimethacrylate, 1,10-decanediol dimethacrylate, to Realyl isocyanurate, ethyl vinylbenzene, neopentyl glycol dimethacrylate, Reach Examples include 1,6-hexanediol dimethacrylate.

[0045] (7) Others In the production of polyolefin resin foams related to this technology, one or more other components that can be used in the production of polyolefin resin foams may be freely selected and used as other components, as long as they do not impair the purpose or effect of this technology.

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

[0047] (8) Physical properties of the polyolefin-based resin foam according to the present technology [Biomass content] The biomass content of the polyolefin-based resin foam according to the present technology can be freely set as long as the functions and effects of the present technology are not impaired. The lower limit of the biomass content of the polyolefin-based resin foam according to the present technology is, for example, 5% or more, preferably 10% or more, more preferably 15% or more, still more preferably 20% or more. The higher the biomass content of the polyolefin-based resin foam according to the present technology, the more it can contribute to the environment, so there is no limit to the upper limit of the biomass content.

[0048] [Density] The density of the polyolefin-based resin foam according to the present technology can be freely set as long as the functions and effects of the present technology are not impaired. The lower limit of the density of the polyolefin-based resin foam according to the present technology is, for example, 30 kg / m 3 or more, preferably 40 kg / m 3 or more, more preferably 45 kg / m 3 or more, still more preferably 50 kg / m 3 or more, particularly preferably 55 kg / m 3 or more. The upper limit of the density of the polyolefin-based resin foam according to the present technology is, for example, 120 kg / m 3 or less, preferably 115 kg / m 3 or less, more preferably 110 kg / m 3 or less, still more preferably 105 kg / m 3 or less.

[0049] [25% compression stress] The compressive stress of the polyolefin resin foam according to this technology can be freely set as long as it does not impair the function and effect of this technology. The lower limit of the compressive stress of the polyolefin resin foam according to this technology is, for example, 60 kPa or more, preferably 65 kPa or more, more preferably 70 kPa or more, and even more preferably 75 kPa or more. The upper limit of the compressive stress of the polyolefin resin foam according to this technology is, for example, 300 kPa or less, preferably 290 kPa or less, more preferably 280 kPa or less, and even more preferably 270 kPa or less.

[0050] [Compression permanent strain] The compression set of the polyolefin resin foam according to this technology can be freely set as long as it does not impair the function and effect of this technology. There is no specific lower limit for the compression set of the polyolefin resin foam according to this technology, but it is usually 0.5% or more. The upper limit for the compression set of the polyolefin resin foam according to this technology is, for example, 6.5% or less, preferably 6.0% or less, more preferably 5.5% or less, and even more preferably 5.0% or less.

[0051] [Tensile strength] The tensile strength of the polyolefin resin foam according to this technology can be freely set as long as it does not impair the function and effect of this technology. The lower limit of the tensile strength of the polyolefin resin foam according to this technology is, for example, 0.15 MPa or more, preferably 0.20 MPa or more, more preferably 0.25 MPa or more, and even more preferably 0.30 MPa or more. There is no particular upper limit for the tensile strength of the polyolefin resin foam according to this technology, but it is usually 3.00 MPa or less.

[0052] [Tensile elongation] The tensile elongation of the polyolefin resin foam according to this technology can be freely set as long as it does not impair the function and effect of this technology. The lower limit of the tensile elongation of the polyolefin resin foam according to this technology is, for example, 30% or more, preferably 50% or more, more preferably 70% or more, even more preferably 90% or more, and particularly preferably 105% or more. There is no particular upper limit for the tensile elongation of the polyolefin resin foam according to this technology, but it is usually 500% or less.

[0053] [Thermal shrinkage rate] The thermal shrinkage rate of the polyolefin resin foam according to this technology can be freely set as long as it does not impair the function and effect of this technology. There is no lower limit to the thermal shrinkage rate of the polyolefin resin foam according to this technology, but it is usually 0.25% or more. The upper limit to the thermal shrinkage rate of the polyolefin resin foam according to this technology is, for example, 3.0% or less, preferably 2.0% or less, more preferably 1.5% or less, and even more preferably 1.1% or less. In this technology, unless otherwise specified, "thermal shrinkage rate" refers to the thermal shrinkage rate without limiting the direction such as vertical, horizontal, up, or down.

[0054] [Number of cells] The number of cells in the polyolefin resin foam according to this technology can be freely set as long as it does not impair the function and effect of this technology. The lower limit of the number of cells in the polyolefin resin foam according to this technology is, for example, 55 cells / 25 mm or more, preferably 60 cells / 25 mm or more, more preferably 65 cells / 25 mm or more, and even more preferably 70 cells / 25 mm or more. There is no particular upper limit for the number of cells in the polyolefin resin foam according to this technology, but it is usually 250 cells / 25 mm or less.

[0055] 2. Method for producing polyolefin resin foam The polyolefin resin foam according to this technology is characterized by its composition, and its manufacturing method is not particularly limited. For example, a method can be employed in which a foaming agent is added to a polyolefin resin, and if necessary, a crosslinking agent or other additives are optionally added and mixed, and then foamed and molded. Preferably, the manufacturing method of the polyolefin resin foam may be any of the following: a one-stage block foaming method, a two-stage block foaming method, a long foaming method using chemical crosslinking, or a long foaming method using electron beam crosslinking.

[0056] <Single-block foaming method> The single-stage block foaming method comprises, for example, the following steps (1)-(2). (1) Mixing process A foamable resin composition is obtained by melt-kneading a polyolefin resin, eggshell powder, a foaming agent, and, as needed, a crosslinking agent, foaming aid, crosslinking accelerator, and other optional components at a temperature below the decomposition temperature of the foaming agent using a kneading device such as an extruder, Banbury mixer, kneader, or roll. (2) Foaming process The foamed resin composition obtained in the kneading process is filled into a mold, sealed, and heated under pressure at a temperature above the decomposition temperature of the foaming agent and crosslinking agent (if a crosslinking agent is used) for a predetermined time to allow the decomposition of the foaming agent and crosslinking agent (if a crosslinking agent is used) to proceed. After that, the mold is opened and the pressure is released to obtain a polyolefin resin foam.

[0057] <Two-stage block foaming method> The two-stage block foaming method comprises, for example, the following steps (1)-(3). (1) Mixing process A foamable resin composition is obtained by melt-kneading a polyolefin resin, eggshell powder, a foaming agent, and, as needed, a crosslinking agent, foaming aid, crosslinking accelerator, and other optional components at a temperature below the decomposition temperature of the foaming agent using a kneading device such as an extruder, Banbury mixer, kneader, or roll. (2) Primary foaming process The foamed resin composition obtained in the kneading process is filled into the molding space of the primary mold and heated under pressure. This decomposes some of the foaming agent and some or all of the crosslinking agent (if a crosslinking agent is used). The pressure is then released and the foamed resin composition intermediate is removed. The heating temperature is usually determined to be in the range of 130-150°C, and the heating time is usually determined to be in the range of 25-50 minutes. (3) Secondary foaming process The foamable resin composition intermediate obtained in the primary foaming process is placed in the molding space of an unsealed secondary mold, heated under atmospheric pressure to induce secondary foaming, and then the resin foam is removed from the secondary mold.

[0058] <Long-length foaming method using chemical crosslinking> The long foaming method comprises, for example, the following steps (1)-(2). (1) Mixing process Polyolefin resin, eggshell powder, foaming agent, crosslinking agent, and as needed foaming aids, crosslinking accelerators, and other optional components are kneaded together using a single-screw extruder, twin-screw extruder, etc., and then extruded into a sheet to extrude a foamed resin composition (hereinafter referred to as a base sheet) in a predetermined shape such as a sheet. Mixing and extrusion can be performed simultaneously using an extruder. (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.

[0059] <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, eggshell powder, foaming agent, and as needed crosslinking agents, foaming aids, crosslinking accelerators, and other optional components are kneaded using a single-screw extruder, twin-screw extruder, etc., 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. (2) Crosslinking process The base plate obtained in the kneading process is crosslinked. As a crosslinking method, a method of irradiation 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, crosslinking agents such as the aforementioned organic peroxides may be used in combination. (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.

[0060] In the method for producing polyolefin resin foam 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.

[0061] 3. Applications of polyolefin resin foams The polyolefin resin foam related to this technology can be used in a wide range of applications in a wide range of fields, taking advantage of its high quality. For example, it can be suitably used in concrete expansion joint materials, concrete formwork, building joint materials, building cushioning materials, building sealants, home appliance sealants, packaging materials, vehicle insulation materials, condensation prevention materials, interior materials, home appliance insulation materials, pipe insulation materials, various covers, cushioning materials, toys, general merchandise, cleaners, various sponges, toys, kickboards, floats, sports goods, etc.

[0062] Furthermore, this technology can also be configured as follows: [1] A polyolefin-based resin foam containing biomass material with calcium carbonate as its main component. [2] A polyolefin resin foam according to [1], containing 50% by weight or less of the biomass material. [3] The biomass material is derived from eggshells and / or seashells, and is a polyolefin resin foam according to [1] or [2]. [4] The polyolefin resin foam according to [3], wherein the biomass material is eggshell powder and / or seashell powder. [5] The polyolefin resin foam according to [4], wherein the average particle size of the eggshell powder and / or seashell powder is 8 to 200 μm. [Examples]

[0063] 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.

[0064] <Experimental Example 1> In Experimental Example 1, we investigated the differences in physical properties of polyolefin resin foam produced using a single-stage foaming method, depending on the presence or absence of a biomass material mainly composed of calcium carbonate.

[0065] (1) Raw materials Resin component 1: Low-density polyethylene (LDPE) (Density: 0.924 g / cm³) 3 MFR: 3.0g / 10min (Petroleum-derived) Resin component 2: Polyolefin resin (included in the foaming agent masterbatch) Resin component 3: Low-density polyethylene (LDPE) (Density: 0.921 g / cm³) 3 MFR: 1.9g / 10min (Petroleum-derived) Resin component 4: Low-density polyethylene (LDPE) (Density: 0.923 g / cm³) 3 MFR: 2.7g / 10min, derived from biomass (sugarcane) (biomass content 95% or higher) Biomass material 1: Eggshell powder (average particle size 15 μm, 70%~90% membrane treatment) ("D-50" 15 μm, manufactured by Green Techno 21 Co., Ltd.) Biomass material 2: Eggshell powder (average particle size 30 μm, 70%~90% membrane treatment) ("D-50" 30 μm, manufactured by Green Techno 21 Co., Ltd.) Foaming agent: Azodicarbonamide (ADCA) Crosslinking agent: Dicumyl peroxide Foaming agent: Zinc oxide

[0066] (2) Manufacturing of foam Each foam was produced by kneading the foam raw materials shown in Table 1 in a kneader, filling the mixture into a mold, heating and pressurizing it at the temperatures shown in Table 1, and then releasing the pressure to allow it to foam.

[0067] (3) Evaluation The physical properties of the manufactured foam were evaluated using the following method.

[0068] [Biomass content] The biomass content was calculated using the following formula. Biomass percentage (%) = (Total weight of biomass-derived materials / Total weight of raw materials) × 100 When using biomass-derived resin, the "total weight of biomass-derived materials" in the above formula is the total weight of the biomass material mainly composed of calcium carbonate plus the biomass-derived resin. The calculation assumes a biomass content of 95% for resin component 4.

[0069] [density] Density was measured according to JIS K7222:2005.

[0070] [Compressive stress][Compression set][Tensile strength][Tensile elongation][Thermal shrinkage] Compressive stress, compression set, tensile strength, tensile elongation, and thermal shrinkage were measured in accordance with JIS K6767:1999.

[0071] [Number of cells] The number of cells was calculated according to JIS K6767:1999, using a scanning electron microscope (SEM) at 35x magnification, counting the number of cells per 2000 μm length and converting it to the number of cells per 25 mm.

[0072] [Cell status] The cell status was evaluated based on the following evaluation criteria. ○: No pinholes, cracks, blisters, etc., and the cells are uniform in condition. ×: Contains pinholes, cracks, blisters, etc., resulting in an uneven cell structure.

[0073] (4) Results The results are shown in Table 1 below. [Table 1]

[0074] (5) Discussion As shown in Table 1, Examples 1-3, 6, and 7, which used biomass materials mainly composed of calcium carbonate, had equivalent or better physical properties than Comparative Example 1, which did not use biomass materials. Specifically, the evaluation of compression set, tensile strength, tensile elongation, and thermal shrinkage of Examples 1 and 3, which used biomass materials mainly composed of calcium carbonate, was equivalent to that of Comparative Example 1, which did not use biomass materials, and the evaluation of compressive stress and cell number of Examples 1, 3, 6, and 7 was better than that of Comparative Example 1. From these results, it was confirmed that by using biomass materials mainly composed of calcium carbonate in polyolefin resin foams, high-quality foams can be obtained despite a high biomass content. Furthermore, although Example 2 had the same density as Comparative Example 1, the evaluation of the cell number of Example 2 was better than that of Comparative Example 1.

[0075] Generally, incorporating fillers and other materials into resin foams tends to result in a decrease in physical properties. However, the biomass material primarily composed of calcium carbonate used in this technology, while fulfilling the function of a filler, was found to produce a polyolefin-based resin foam using this material that possesses physical properties equivalent to or better than conventional polyolefin-based resin foams.

[0076] Furthermore, the preferred range of density varies depending on the purpose. For example, a lower density may be preferable when considering transportation costs, but generally, incorporating fillers into resin foams has resulted in a problem of increased density. Conversely, performing any operation to lower the density tends to lead to a decrease in physical properties. However, comparing Example 2 with Comparative Example 1, it was confirmed that Example 2, despite containing a biomass material mainly composed of calcium carbonate that functions as a filler, had the same density as Comparative Example 1 and possessed physical properties equivalent to or better than Comparative Example 1.

[0077] <Experimental Example 2> In Experimental Example 2, we investigated the differences in physical properties of polyolefin resin foam produced using a two-stage foaming method, specifically comparing the presence or absence of a biomass material primarily composed of calcium carbonate, and the use of calcium carbonate as an inorganic powder.

[0078] (1) Raw materials Resin component 5: Low-density polyethylene (LDPE) (Density: 0.924 g / cm³) 3 MFR: 1.9g / 10min (Petroleum-derived) Resin component 6: Low-density polyethylene (LDPE) (Density: 0.927 g / cm³) 3 MFR: 3.0g / 10min (Petroleum-derived) Inorganic powder: Calcium carbonate (average particle size 20 μm) The other raw materials used were the same as those used in Experimental Example 1.

[0079] (2) Manufacturing of foam Each foaming material shown in Table 2 below was kneaded in a kneader, then filled into a mold, heated and pressurized at 130-150°C, and then depressurized to induce primary foaming, thereby preparing each primary foam. Next, each prepared primary foam was placed in an open mold and heated at 150-170°C to induce secondary foaming, thereby producing each foam.

[0080] (3) Evaluation The properties of the manufactured foam were evaluated using the same method as in Experimental Example 1.

[0081] (4) Results The results are shown in Table 2 below. [Table 2]

[0082] (5) Discussion As shown in Table 2, Examples 4, 5, and 8-10, which used biomass materials mainly composed of calcium carbonate, had physical properties equivalent to Comparative Example 2, which did not use biomass materials, and also had physical properties equivalent to or better than Comparative Example 3, which used inorganic calcium carbonate powder. Specifically, the evaluation of tensile strength, thermal shrinkage, and cell count of Examples 4 and 5, which used biomass materials mainly composed of calcium carbonate, was equivalent to that of Comparative Example 3, which used inorganic calcium carbonate powder, and the evaluation of compressive stress of Examples 4 and 5 was better than that of Comparative Example 3. Furthermore, it was found that the evaluation of tensile strength and cell count could be improved by changing the type of resin component, as in Examples 8 and 9. Moreover, when comparing Example 10, which used biomass-derived resin components, with Comparative Example 4, Example 10, which used biomass materials mainly composed of calcium carbonate, had physical properties equivalent to Comparative Example 4 despite having an even higher biomass content. From these results, it was confirmed that by using biomass materials mainly composed of calcium carbonate in polyolefin resin foams, high-quality foams can be obtained despite a high biomass content.

[0083] Furthermore, these results confirm that even when manufactured using a two-stage foaming method, the polyolefin resin foam related to this technology has physical properties equivalent to or better than those of general polyolefin resin foams that do not use biomass materials.

Claims

1. A polyolefin-based resin foam containing 40% by weight or less of eggshell powder with an average particle size of 6 μm or more.

2. The polyolefin resin foam according to claim 1, which contains eggshell powder with an average particle size of 10 μm or more.

3. It contains 20-40% by weight of biomass material derived from eggshells. Density of 30-120 kg / m³ ３ It is a polyolefin-based resin foam.

4. An article comprising a polyolefin resin foam according to any one of claims 1 to 3, Articles selected from concrete expansion joint materials, concrete formwork, home appliance sealants, vehicle insulation materials, condensation prevention materials, home appliance insulation materials, general merchandise, cleaners, sponges, toys, kickboards, and floats.

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