Classifications

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  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
  • C08J9/16—Making expandable particles
  • C08J9/18—Making expandable particles by impregnating polymer particles with the blowing agent
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
  • C08J9/0014—Use of organic additives
  • C08J9/0023—Use of organic additives containing oxygen
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  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
  • C08J9/0014—Use of organic additives
  • C08J9/0028—Use of organic additives containing nitrogen
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  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
  • C08J9/0014—Use of organic additives
  • C08J9/0038—Use of organic additives containing phosphorus
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  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
  • C08J9/22—After-treatment of expandable particles; Forming foamed products
  • C08J9/228—Forming foamed products
  • C08J9/232—Forming foamed products by sintering expandable particles
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  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2203/00—Foams characterized by the expanding agent
  • C08J2203/06—CO2, N2 or noble gases
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
  • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
  • C08J2323/10—Homopolymers or copolymers of propene
  • C08J2323/12—Polypropene
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  • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
  • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
  • C08J2323/10—Homopolymers or copolymers of propene
  • C08J2323/14—Copolymers of propene
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  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
  • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
  • C08J2323/16—Ethene-propene or ethene-propene-diene copolymers
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  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2423/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
  • C08J2423/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
  • C08J2423/04—Homopolymers or copolymers of ethene
  • C08J2423/06—Polyethene
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  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2423/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
  • C08J2423/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
  • C08J2423/10—Homopolymers or copolymers of propene
  • C08J2423/12—Polypropene
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  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
  • C08J9/0061—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof characterized by the use of several polymeric components
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
  • C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
  • C08J9/12—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
  • C08J9/122—Hydrogen, oxygen, CO2, nitrogen or noble gases

Definitions

• the present invention relates to polypropylene resin foamed beads and foamed bead moldings.
• Expanded polypropylene resin beads molded in a mold are lightweight and have excellent impact resistance, energy absorption properties, etc., and therefore have been used for vehicle components such as automobile bumpers.
• vehicle components such as automobile bumpers.
• high flame retardancy such as protective materials for batteries and electronic components mounted on vehicles.
• Patent Document 1 discloses polypropylene-based expanded particles containing specific amounts of a polypropylene resin, an organophosphorus compound, and a hindered amine, and a foamed molded article obtained by molding the particles, with the aim of obtaining a foamed molded article having excellent flame retardancy.
• An object of the present invention is to provide expanded polypropylene resin beads from which an expanded bead molding having excellent flame retardancy and fusion-bonding properties can be produced, and an expanded polypropylene resin bead molding having excellent flame retardancy and fusion-bonding properties.
• the present inventors have conducted intensive research and found that the above-mentioned problems can be solved by blending a specific phosphonate compound, a specific hindered amine compound, and a specific antioxidant in specific amounts and in specific ratios with the expanded polypropylene resin particles and molded articles.
• One aspect of the present invention is the following [1] to [10].
• a polypropylene-based resin expanded particle comprising a foamed layer constituting the expanded particle, the foamed layer having a polypropylene-based resin as a base resin, and comprising a cyclic phosphonate compound and a NOR-type hindered amine compound, the amount of the cyclic phosphonate compound in the foamed layer being 5 parts by mass or more and less than 25 parts by mass relative to 100 parts by mass of a resin component constituting the foamed layer, the amount of the NOR-type hindered amine compound in the foamed layer being 0.1 parts by mass or more and less than 5 parts by mass relative to 100 parts by mass of a resin component constituting the foamed layer, the foamed layer comprising a phenol-based antioxidant, the amount of the phenol-based antioxidant in the foamed layer being 0.01 parts by mass or more and less than 0.5 parts by mass relative to 100 parts by mass of a resin component constituting the foamed layer, and the ratio of the amount of the cyclic
• the present invention provides expanded polypropylene resin beads that can be used to produce expanded bead moldings with excellent flame retardancy and fusion properties, and expanded polypropylene resin bead moldings with excellent flame retardancy and fusion properties.
• the expanded polypropylene resin beads of the present invention are polypropylene resin beads, in which a foamed layer constituting the expanded beads has a polypropylene resin as a base resin and contains a cyclic phosphonate compound and a NOR hindered amine compound, the amount of the cyclic phosphonate compound in the foamed layer is 5 parts by mass or more and less than 25 parts by mass relative to 100 parts by mass of resin components constituting the foamed layer, the amount of the NOR hindered amine compound in the foamed layer is 0.1 parts by mass or more and less than 5 parts by mass relative to 100 parts by mass of resin components constituting the foamed layer, the foamed layer contains a phenolic antioxidant, the amount of the phenolic antioxidant in the foamed layer is 0.01 parts by mass or more and less than 0.5 parts by mass relative to 100 parts by mass of the foamed layer, and the ratio of the amount of the phenolic antioxidant to the amount of the NOR hinder
• the polypropylene resin expanded beads (hereinafter simply referred to as expanded beads) have a foamed layer (hereinafter simply referred to as expanded layer) in which a polypropylene resin is used as a base resin.
• expanded layer a foamed layer in which a polypropylene resin is used as a base resin.
• the foamed layer has a polypropylene resin as a base resin
• the content of the polypropylene resin in the resin components constituting the foamed layer is 70% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 99% by mass or more.
• the upper limit There is no particular limit to the upper limit, and it is 100% by mass or less.
• examples of the polypropylene resin include a propylene homopolymer, a propylene random copolymer, a propylene block copolymer, or an impact-resistant polypropylene (block polypropylene) composed of two or more phases including a continuous phase of a propylene polymer and a rubber phase such as an ethylene- ⁇ -olefin copolymer present as a dispersed phase in the continuous phase.
• block polypropylene composed of two or more phases including a continuous phase of a propylene polymer and a rubber phase such as an ethylene- ⁇ -olefin copolymer present as a dispersed phase in the continuous phase.
• the foam layer may contain other resins besides polypropylene-based resins as long as the purpose and effect of the present disclosure are not impaired.
• other resins include thermoplastic resins other than polypropylene-based resins, such as polyethylene-based resins and polystyrene-based resins, and elastomers.
• the content of other resin components in the resin components constituting the foam layer is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and even more preferably 0% by mass. In other words, it is particularly preferable that the foam layer contains substantially only polypropylene-based resins as resin components.
• the content of structural units derived from propylene in the polypropylene-based resin is preferably 80% by mass or more, more preferably 90% by mass or more.
• the content of structural units derived from propylene in the polypropylene-based resin is preferably 99% by mass or less, more preferably 98% by mass or less.
• propylene random copolymer examples include copolymers of propylene and ethylene and/or an ⁇ -olefin having 4 to 20 carbon atoms.
• examples of the ⁇ -olefin include 1-butene, 1-pentene, 1-hexene, 1-octene, and 4-methyl-1-butene.
• the polypropylene-based resin preferably contains, as a main component, an ethylene-propylene random copolymer, a propylene-butene random copolymer, an ethylene-propylene-butene random copolymer, or a mixture of two or more of these.
• the proportion of these propylene-based random copolymers in the polypropylene-based resin is preferably 60% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more.
• the propylene-based random copolymer contains a component derived from ethylene (ethylene component) and/or a component derived from butene (butene component) as a copolymerization component, from the viewpoint of further improving the moldability of the expanded beads in the mold under low molding pressure conditions
• the total content of the ethylene component and the butene component in the propylene-based random copolymer is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more.
• the total content of the ethylene component and the butene component in the propylene-based random copolymer is preferably 15% by mass or less. That is, the total content of the ethylene component and the butene component in the propylene-based random copolymer is preferably 1 to 15% by mass, more preferably 2 to 15% by mass, and even more preferably 3 to 15% by mass.
• the content of the components derived from ethylene and ⁇ -olefin in the propylene-based random copolymer is determined by IR spectrum measurement.
• the melting point of the polypropylene resin is preferably 130° C. or higher, more preferably 135° C. or higher, and even more preferably 140° C. or higher, from the viewpoint of improving the mechanical properties of the resulting expanded bead molding.
• the melting point of the polypropylene resin is preferably 155° C. or lower, more preferably 150° C. or lower, and even more preferably 146° C. or lower, from the viewpoint of improving the in-mold moldability of the expanded beads under conditions of low molding pressure. That is, the melting point of the polypropylene resin is preferably 130° C. to 155° C., more preferably 135° C. to 150° C., and even more preferably 140° C. to 146° C.
• the melting point of the polypropylene resin is measured based on JIS K 7121:2012 using the propylene resin or the expanded particles as a test piece. Specifically, the condition of the test piece is adjusted as "(2) Measurement of melting temperature after performing a certain heat treatment", and the test piece is heated from 23°C to 200°C at a heating rate of 10°C/min under the condition of a nitrogen inflow rate of 30 mL/min, then kept at that temperature for 10 minutes, cooled to 23°C at a cooling rate of 10°C/min, and heated again to 200°C at a heating rate of 10°C/min to obtain a DSC curve (DSC curve at the time of the second heating).
• DSC curve DSC curve at the time of the second heating
• the apex temperature of the melting peak in the DSC curve is obtained, and this value is taken as the melting point of the polypropylene resin. Note that, when multiple melting peaks appear in the DSC curve, the apex temperature of the melting peak with the highest melting peak height based on the baseline is adopted as the melting point.
• the melt flow rate (MFR) of the polypropylene resin is preferably 2 g/10 min or more, more preferably 5 g/10 min or more, from the viewpoint of increasing the expandability during expansion of the resin particles and increasing the secondary expandability during molding of the expanded particles in a mold, and is preferably 15 g/10 min or less, more preferably 10 g/10 min or less, from the viewpoint of increasing the uniformity of the bubbles in the expanded particles and increasing the physical properties of the expanded particle molded article. That is, the MFR of the polypropylene resin is preferably 2 to 15 g/10 min, more preferably 5 to 10 g/10 min.
• the MFR of the polypropylene resin is measured under conditions of a temperature of 230° C. and a load of 2.16 kg in accordance with JIS K 7210-1:2014.
• the polydispersity (Mw/Mn) of the polypropylene resin is preferably 4.0 or more and 25 or less, and more preferably 4.1 or more and 15 or less.
• the polydispersity (Mw/Mn) of polypropylene resin is the weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) using polystyrene as the standard substance, divided by the number average molecular weight (Mn).
• the polydispersity (Mw/Mn) of polypropylene resin is measured by gel permeation chromatography (GPC).
• GPC gel permeation chromatography
• the number average molecular weight Mn and weight average molecular weight Mw of the polypropylene resin are calculated, and then the polydispersity (Mw/Mn) is obtained.
• a high-temperature GPC device HLC-8321GPC/HT manufactured by Tosoh Corporation can be used as the measuring device.
• the MFR of the polypropylene resin contained in the base resin is 5 g/10 min or more and 10 g/10 min or less, and that the polydispersity (Mw/Mn) is 4.0 or more and 25 or less.
• the polypropylene resin foamed beads of the present invention contain specific amounts of a cyclic phosphonate compound, a NOR hindered amine compound, and a phenolic antioxidant in the foam layer, and further, the ratio of the amount of the NOR hindered amine compound to the amount of the phenolic antioxidant is within a specific range. Therefore, by molding the polypropylene resin foamed beads of the present invention in a mold, a foamed bead molding with excellent flame retardancy and fusion properties can be obtained.
• the cyclic phosphonate compound is a compound containing one or more cyclic phosphonate moieties in the molecule, and is preferably at least one selected from the group consisting of compounds represented by the following general formula (1), compounds represented by the following general formula (2), compounds represented by the following general formula (3), and compounds represented by the following general formula (4), and is more preferably pentaerythritol diphosphonate represented by the following general formula (1).
• the pentaerythritol diphosphonate of formula (1) is a spirocyclic compound containing two cyclic phosphonate moieties in the molecule.
• the cyclic phosphonate compound may be used alone or in combination of two or more.
• R 1 and R 2 are each an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, a benzyl group, a phenylethyl group, a phenyl group, or a naphthyl group;
• R 3 is an alkyl group having 1 to 22 carbon atoms or an aryl group having 6 to 15 carbon atoms;
• R 4 , R 8 , R 9 , and R 12 are each an alkyl group having 1 to 4 carbon atoms;
• R 5 , R 7 , and R 11 are each a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; and
• R 6 and R 10 are each an alkyl group having 1 to 22 carbon atoms, a cycloalkyl group having 9 to 22 carbon atoms, an aryl group having 9 to 22 carbon atoms, or an aralkyl group having 9 to 22 carbon atoms.
• R 1 and R 2 may be the same or different, and are preferably the same.
• R1 is an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, a benzyl group, a phenylethyl group, a phenyl group or a naphthyl group, preferably an alkyl group having 1 or 2 carbon atoms, and more preferably a methyl group.
• R2 is an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, a benzyl group, a phenylethyl group, a phenyl group or a naphthyl group, preferably an alkyl group having 1 or 2 carbon atoms, and more preferably a methyl group.
• R 1 and R 2 are both methyl groups are more preferable.
• R 3 is an alkyl group having 1 to 22 carbon atoms or an aryl group having 6 to 15 carbon atoms, and is preferably a phenyl group.
• R 4 and R 8 may be the same or different, and are preferably the same.
• R4 is an alkyl group having 1 to 4 carbon atoms, preferably a methyl group.
• R8 is an alkyl group having 1 to 4 carbon atoms, preferably a methyl group.
• R 5 and R 7 may be the same or different, and are preferably the same.
• R5 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and is preferably an ethyl group.
• R7 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and is preferably an ethyl group.
• R6 is an alkyl group having 1 to 22 carbon atoms, a cycloalkyl group having 9 to 22 carbon atoms, an aryl group having 9 to 22 carbon atoms, or an aralkyl group having 9 to 22 carbon atoms, and is preferably a linear alkyl group having 1 to 12 carbon atoms.
• R 9 and R 12 may be the same or different, and are preferably the same.
• R 9 is an alkyl group having 1 to 4 carbon atoms, preferably a methyl group.
• R 12 is an alkyl group having 1 to 4 carbon atoms, and is preferably a methyl group.
• R 10 is an alkyl group having 1 to 22 carbon atoms, a cycloalkyl group having 9 to 22 carbon atoms, an aryl group having 9 to 22 carbon atoms, or an aralkyl group having 9 to 22 carbon atoms, and is preferably a linear alkyl group having 1 to 12 carbon atoms.
• R 11 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and is preferably an ethyl group.
• the melting point Tm A of the cyclic phosphonate compound is preferably 80°C or higher and 350°C or lower, more preferably 150°C or higher and 330°C or lower, and even more preferably 200°C or higher and 300°C or lower.
• the melting point Tm A of the cyclic phosphonate compound is measured in accordance with JIS K 0064:1992.
• the amount of the cyclic phosphonate compound in the foam layer of the polypropylene resin foamed beads of the present invention is 5 parts by mass or more and less than 25 parts by mass per 100 parts by mass of the resin components constituting the foam layer. If the amount of the cyclic phosphonate compound is too small, a foamed bead molding having a high level of flame retardancy cannot be obtained. From the viewpoint of obtaining a foamed bead molding having a higher level of flame retardancy, the amount of the cyclic phosphonate compound in the foam layer is preferably 6 parts by mass or more, more preferably 7 parts by mass or more, and even more preferably 8 parts by mass or more, per 100 parts by mass of the resin components constituting the foam layer.
• the amount of the cyclic phosphonate compound in the foam layer is preferably 22 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 17 parts by mass or less, per 100 parts by mass of the resin components constituting the foam layer.
• the amount of the cyclic phosphonate compound in the foam layer is preferably 6 parts by mass or more and 22 parts by mass or less, more preferably 7 parts by mass or more and 20 parts by mass or less, and even more preferably 8 parts by mass or more and 17 parts by mass or less, relative to 100 parts by mass of the resin component that constitutes the foam layer.
• the NOR type hindered amine compound has, in its structure, a 2,2,6,6-tetramethyl-4-piperidinamine moiety having a hydrocarbon group bonded to a nitrogen atom via an oxygen atom, as shown in the following formula (5), and thereby can improve the flame retardancy of a molded article.
• R 13 represents a hydrocarbon group.
• R 13 represents a hydrocarbon group.
• the multiple R 13s may be the same or different, but it is preferable that the multiple R 13s are the same.
• R 13 is preferably at least one selected from the group consisting of an alkyl group and a cycloalkyl group, and more preferably a cycloalkyl group.
• R 13 is more preferably an alkyl group having 1 to 20 carbon atoms, and further preferably an undecyl group.
• R 13 is a cycloalkyl group
• R 13 is more preferably a cycloalkyl group having 4 to 10 carbon atoms, and even more preferably a cyclohexyl group.
• the NOR type hindered amine compounds may be used alone or in combination of two or more.
• the molecular weight of the NOR type hindered amine compound is preferably 600 or more, more preferably 1500 or more. Moreover, from the viewpoint of improving the dispersion of the NOR type hindered amine compound in a resin, the molecular weight of the NOR type hindered amine compound is preferably 3000 or less, more preferably 2500 or less.
• the number of 2,2,6,6-tetramethyl-4-piperidineamine moieties having a hydrocarbon group bonded to nitrogen through an oxygen bond represented by the general formula (5), is preferably 2 or more and 8 or less, more preferably 2 or more and 6 or less, and even more preferably 2 or 6.
• the amount of the hindered amine compound in the foam layer of the polypropylene resin foam beads of the present invention is 0.1 parts by mass or more and less than 5 parts by mass per 100 parts by mass of the resin components constituting the foam layer. If the amount of the hindered amine compound is too small, a foamed bead molding having high flame retardancy cannot be obtained. From the viewpoint of obtaining a foamed bead molding having higher flame retardancy, the amount of the hindered amine compound in the foam layer is preferably 0.2 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.4 parts by mass or more, per 100 parts by mass of the resin components constituting the foam layer.
• the amount of the hindered amine compound in the foam layer is preferably 3.5 parts by mass or less, more preferably 3 parts by mass or less, even more preferably 2 parts by mass or less, and even more preferably 1 part by mass or less, per 100 parts by mass of the resin components constituting the foam layer.
• the amount of the hindered amine compound in the foam layer is preferably 0.2 parts by mass or more and 3.5 parts by mass or less, more preferably 0.3 parts by mass or more and 3 parts by mass or less, even more preferably 0.4 parts by mass or more and 2 parts by mass or less, and even more preferably 0.4 parts by mass or more and 1 part by mass or less.
• the phenol-based antioxidant is an antioxidant having one or more phenol structures in the molecule, each of which has one or more hydroxyl groups bonded to an aromatic ring, preferably having two or more phenol structures in the molecule, more preferably having three or more phenol structures in the molecule.
• high temperatures e.g., 180°C or higher
• the phenol-based antioxidant is a compound that suppresses the decomposition of the resin in a short time at such high temperatures.
• phenol-based antioxidant examples include 1,3,5-trimethyl-2,4,6-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)benzene, 2,6-di-t-butyl-p-cresol, triethylene glycol bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate], 2,2-methylene bis(4-methyl-6-t-butylphenol), 1,6-hexanediol-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], and pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].
• pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 1,3,5-trimethyl-2,4,6-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)benzene are preferred, and 1,3,5-trimethyl-2,4,6-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)benzene is particularly preferred.
• the melting point Tm B of the phenol-based antioxidant is preferably 50° C. or more and 350° C. or less, more preferably 80° C. or more and 330° C. or less, even more preferably 100° C. or more and 320° C. or less, even more preferably 150° C. or more and 310° C. or less, and even more preferably 200° C. or more and 300° C. or less.
• the melting point Tm B of the phenol-based antioxidant is measured in accordance with JIS K 0064:1992.
• the melting point difference (Tm A - Tm B ) between the melting point Tm A of the cyclic phosphonate compound and the melting point Tm B of the phenolic antioxidant is preferably -150°C or more and 150°C or less, preferably -100°C or more and 100°C or less, and more preferably -50°C or more and 50°C or less.
• the melting point difference (Tm A -Tm B ) can be calculated from the melting point Tm A of the cyclic phosphonate compound and the melting point Tm B of the phenolic antioxidant, both measured by the above-mentioned method.
• the amount of the phenolic antioxidant in the foam layer of the polypropylene resin foam beads of the present invention is 0.01 parts by mass or more and less than 0.5 parts by mass per 100 parts by mass of the resin components constituting the foam layer. If the amount of the phenolic antioxidant is too small, a foamed bead molding having high flame retardancy and good fusion properties cannot be obtained. From the viewpoint of obtaining a foamed bead molding having higher flame retardancy, the amount of the phenolic antioxidant in the foam layer is preferably 0.02 parts by mass or more, more preferably 0.04 parts by mass or more, even more preferably 0.06 parts by mass or more, and even more preferably 0.08 parts by mass or more per 100 parts by mass of the resin components constituting the foam layer.
• the amount of the phenolic compound in the foam layer is preferably 0.4 parts by mass or less, more preferably 0.3 parts by mass or less, even more preferably 0.2 parts by mass or less, and even more preferably 0.15 parts by mass or less, relative to 100 parts by mass of the resin components constituting the foam layer.
• the amount of the phenolic antioxidant in the foam layer is preferably 0.02 parts by mass or more and 0.4 parts by mass or less, more preferably 0.04 parts by mass or more and 0.3 parts by mass or less, even more preferably 0.06 parts by mass or more and 0.2 parts by mass or less, and even more preferably 0.08 parts by mass or more and 0.15 parts by mass or less.
• the ratio of the amount of the phenolic antioxidant to the amount of the NOR-type hindered amine compound (phenolic antioxidant/NOR-type hindered amine compound) is 0.03 or more and 0.9 or less. If the mixing ratio is too low, it is not possible to obtain an expanded bead molding that has both high flame retardancy and good fusion properties. From the viewpoint of obtaining expanded beads having higher flame retardancy and excellent fusion properties, the mixing ratio is preferably 0.07 or more, more preferably 0.11 or more, and even more preferably 0.14 or more. On the other hand, if the mixing ratio is too high, it is not possible to obtain an expanded bead molding having high flame retardancy.
• the mixing ratio is preferably 0.8 or less, more preferably 0.7 or less, and even more preferably 0.6 or less. That is, the ratio of the amount of the phenolic antioxidant to the amount of the NOR type hindered amine compound is preferably 0.07 or more and 0.8 or less, more preferably 0.11 or more and 0.7 or less, and even more preferably 0.14 or more and 0.6 or less.
• the ratio of the blending amounts is within the above range, the expanded beads can produce an expanded bead molding having excellent flame retardancy and fusion-bonding properties.
• the NOR hindered amine compound has a 2,2,6,6-tetramethyl-4-piperidineamine moiety having a hydrocarbon group bonded to a nitrogen atom via an oxygen atom, and is therefore considered to be able to impart high flame retardancy to an expanded bead molding when used in combination with a cyclic phosphonate compound.
• the NOR hindered amine compound if a large amount of the NOR hindered amine compound is contained in the expanded beads, the fusion properties of the molding deteriorate. On the other hand, if the amount of the NOR hindered amine compound is too small, it is not possible to impart high flame retardancy to the expanded bead molding.
• a phenolic antioxidant in a specific amount and in a specific ratio in combination with a NOR hindered amine compound, high flame retardancy can be imparted to the expanded bead molding even when the blending amount of the NOR hindered amine compound is in a small range.
• the phenolic antioxidant can contribute to improving flame retardancy without inhibiting the flame retardancy improving effect of the NOR hindered amine compound. Therefore, it is considered that it is possible to impart high flame retardancy to the expanded bead molding even if the amount of the NOR hindered amine compound is reduced.
• the phenolic antioxidant is unlikely to inhibit the fusion of the expanded beads during in-mold molding, and it is possible to reduce the amount of the NOR hindered amine compound. Therefore, it is considered that it is possible to sufficiently fuse the expanded beads during in-mold molding. As a result, it is considered that it is possible to obtain an expanded bead molding having high flame retardancy and excellent fusion property by in-mold molding the expanded beads of the present invention.
• the foamed layer of the expanded polypropylene resin beads of the present invention preferably contains a sulfur-based antioxidant.
• the sulfur-based antioxidant includes an ester having a sulfide bond in the molecule. Specific examples of the ester having a sulfide bond in the molecule include didodecyl-3,3'-thiodipropionate, ditridecyl-3,3'-thiodipropionate, ditetradecyl-3,3'-thiodipropionate, dioctadecyl-3,3'-thiodipropionate, pentaerythritol tetrakis (3-dodecylthiopropionate), pentaerythritol tetrakis (3-tridecylthiopropionate), pentaerythritol tetrakis (3-tetradecylthiopropionate), and pentaerythritol
• the amount of the sulfur-based antioxidant in the foam layer of the polypropylene resin foam beads of the present invention is preferably 0.02 parts by mass or more, more preferably 0.04 parts by mass or more, even more preferably 0.06 parts by mass or more, and even more preferably 0.08 parts by mass or more, relative to 100 parts by mass of the resin components constituting the foam layer, in order to obtain a foam bead molding having excellent mechanical properties such as compression properties even when the foam bead molding is placed in a high-temperature environment for a long period of time.
• the amount of the sulfur-based compound in the foam layer is preferably 0.4 parts by mass or less, more preferably 0.3 parts by mass or less, even more preferably 0.2 parts by mass or less, and even more preferably 0.15 parts by mass or less, relative to 100 parts by mass of the resin components constituting the foam layer, in order to obtain a foam bead molding having high flame retardancy.
• the ratio of the amount of the sulfur-based antioxidant to the amount of the NOR-type hindered amine compound (sulfur-based antioxidant/NOR-type hindered amine compound) is preferably 0.03 or more, more preferably 0.07 or more, and even more preferably 0.14 or more, from the viewpoint of obtaining an expanded bead molding having excellent mechanical properties such as compression properties even when the expanded bead molding is placed in a high-temperature environment for a long period of time.
• the mixing ratio is preferably 0.9 or less, more preferably 0.8 or less, and even more preferably 0.7 or less.
• the ratio of the amount of the sulfur-based antioxidant to the amount of the NOR-type hindered amine compound is preferably 0.03 or more and 0.9 or less, more preferably 0.07 or more and 0.8 or less, and even more preferably 0.14 or more and 0.7 or less.
• the expanded polypropylene resin particles of the present invention contain specific amounts of a cyclic phosphonate compound, a NOR-type hindered amine compound, and a phenolic antioxidant, and preferably have the following properties.
• the average bubble diameter of the foamed layer of the polypropylene resin expanded beads of the present invention is preferably 50 ⁇ m or more and 250 ⁇ m or less.
• the average bubble diameter of the foamed layer of the polypropylene resin expanded beads of the present invention is more preferably 60 ⁇ m or more, and even more preferably 65 ⁇ m or more.
• the average bubble diameter of the foamed layer of the polypropylene resin expanded beads of the present invention is more preferably 200 ⁇ m or less, more preferably 150 ⁇ m or less, and even more preferably 120 ⁇ m or less.
• the average bubble diameter of the foamed layer is more preferably 60 ⁇ m or more and 200 ⁇ m or less, more preferably 65 ⁇ m or more and 150 ⁇ m or less, and even more preferably 65 ⁇ m or more and 120 ⁇ m or less.
• the foamed beads have excellent moldability in a mold, and by molding the foamed beads in a mold, a foamed bead molded product with excellent mechanical properties can be obtained.
• the average cell diameter is measured by drawing a line from the outer edge of a cell located on the outermost surface side of an expanded bead through the center to the outer edge of a cell located on the outermost surface side of the opposite side in an enlarged photograph of a cross section of the expanded bead divided into two, and dividing the number of cells intersecting the line by the length of the line.
• the average cell diameter can be measured by the method described in the Examples.
• the average cell diameter of the foamed layer can be adjusted to a desired range by adjusting the type and amount of the cell-regulating agent added to the resin particles, the amount of the cyclic phosphonate compound and the hindered amine compound added, or the foaming pressure during foaming of the resin particles.
• the bulk density of the polypropylene-based resin expanded beads of the present invention is preferably 10 g/L or more and 500 g/L or less.
• the bulk density of the polypropylene-based resin expanded beads of the present invention is more preferably 20 g/L or more, and even more preferably 30 g/L or more.
• the bulk density of the polypropylene-based resin expanded beads of the present invention is more preferably 100 g/L or less, even more preferably 70 g/L or less, and even more preferably 60 g/L or less.
• the bulk density of the polypropylene-based resin expanded beads is more preferably 20 g/L or more and 100 g/L or less, even more preferably 30 g/L or more and 70 g/L or less, and even more preferably 30 g/L or more and 60 g/L or less.
• the expanded polypropylene resin beads of the present invention preferably have one or more melting peaks (high-temperature peaks) on the high-temperature side of the resin-specific melting peak (resin-specific peak) of the polypropylene resin in a differential scanning calorimetry (DSC) curve measured based on JIS K7122-2012.
• melting peaks can be obtained by the following method. Specifically, a DSC curve is obtained by heating 1 to 3 mg of the expanded beads from 23° C. to 200° C. at a heating rate of 10° C./min using a differential scanning calorimeter, and the melting peak (high-temperature peak) can be confirmed from the DSC curve.
• the peak having the maximum heat of fusion is the melting peak inherent to the polypropylene resin (resin inherent peak), and the melting peak appearing at a higher temperature than that is the high-temperature peak.
• the DSC curve means a DSC curve obtained by heating the expanded beads by the above-mentioned measurement method (DSC curve in the first heating).
• the resin-specific endothermic peak means an endothermic peak due to melting of crystals specific to the polypropylene-based resin constituting the expanded beads.
• the resin-specific peak is considered to be an endothermic peak that appears due to endothermic heat caused by melting of crystals that the polypropylene-based resin constituting the expanded beads usually has.
• the endothermic peak (high-temperature peak) on the high-temperature side of the resin-specific peak is an endothermic peak that appears on the high-temperature side of the resin-specific peak in the first DSC curve.
• this high-temperature peak appears, it is presumed that secondary crystals exist in the resin.
• the expanded beads are preferably those which exhibit only a melting peak (intrinsic peak) specific to the polypropylene resin in a DSC curve obtained in a second heating step by heating the expanded beads from 23° C. to 200° C. at a heating rate of 10° C./min, cooling from 200° C. to 23° C. at a cooling rate of 10° C./min, and then heating from 23° C. to 200° C. at a heating rate of 10° C./min.
• the heat of fusion of the high-temperature peak of the expanded polypropylene resin beads of the present invention is preferably 5 to 40 J/g, more preferably 10 to 30 J/g, and even more preferably 15 to 25 J/g, since the range of molding conditions for obtaining a good expanded bead molded article becomes wider when the expanded beads are molded in a mold.
• the heat of fusion of the high-temperature peak is measured by the method described above, but more specifically, it can be measured by the method described in the Examples.
• the average mass of each expanded polypropylene resin particle of the present invention is preferably 0.1 to 20 mg, more preferably 0.2 to 10 mg, even more preferably 0.3 to 5 mg, and even more preferably 0.4 to 2 mg.
• additives may be appropriately added to the foamed layer of the polypropylene resin foamed particles of the present invention, so long as the effects of the present invention are not impaired.
• additives include various conventionally known additives such as other antioxidants, ultraviolet absorbers, other light stabilizers, antistatic agents, pigments, dyes, fillers, conductive fillers, and bubble regulators. These additives can be incorporated into the foamed particles, for example, by adding them during the process of producing the resin particles.
• the cell regulator examples include metal borate, polyhydric alcohols such as glycerin, polyethylene glycol, and pentaerythritol, and aliphatic alcohols such as cetyl alcohol and stearyl alcohol.
• Metal borate such as zinc borate and magnesium borate is preferably used, and zinc borate is more preferably used.
• the amount of metal borate contained in the resin portion for forming the foamed layer is preferably 0.005 parts by mass or more and 0.5 parts by mass or less, more preferably 0.01 parts by mass or more and 0.2 parts by mass or less, and even more preferably 0.015 parts by mass or more and 0.15 parts by mass or less, relative to 100 parts by mass of the resin component for forming the foamed layer.
• the amount of metal borate in the foamed layer of the obtained polypropylene-based resin expanded particles is preferably 0.005 parts by mass or more and 0.5 parts by mass or less, more preferably 0.01 parts by mass or more and 0.2 parts by mass or less, and even more preferably 0.015 parts by mass or more and 0.15 parts by mass or less, relative to 100 parts by mass of the resin component constituting the foamed layer.
• the arithmetic mean particle size based on number is preferably 0.5 ⁇ m or more and 15 ⁇ m or less, and more preferably 1 ⁇ m or more and 10 ⁇ m or less.
• the number-based arithmetic mean particle size of zinc borate is obtained by converting the volume-based particle size distribution measured by the laser diffraction scattering method into a number-based particle size distribution by assuming that the particle shape is spherical, and then calculating the arithmetic mean of the particle sizes based on the number-based particle size distribution.
• the particle size refers to the diameter of a hypothetical sphere having the same volume as the particle.
• the expanded polypropylene resin particles of the present invention may contain a pigment or dye as a coloring agent for the purpose of imparting a color such as a chromatic color, black, or gray.
• a pigment or dye as a coloring agent for the purpose of imparting a color such as a chromatic color, black, or gray.
• the chromatic pigments red pigments, blue pigments, green pigments, yellow pigments, and purple pigments are used.
• the chromatic pigments may be inorganic pigments or organic pigments. Examples of inorganic pigments include chromates such as yellow lead, zinc yellow, and barium yellow, ferrocyanides such as Prussian blue, sulfides such as cadmium yellow and cadmium red, oxides such as red iron oxide, and silicates such as ultramarine.
• organic pigments examples include azo pigments such as monoazo pigments, disazo pigments, azo lakes, condensed azo pigments, and chelate azo pigments, or polycyclic pigments such as phthalocyanines, anthraquinones, perylenes, perinones, thioindigo, quinacridones, dioxazines, isoindolinones, and quinophthalones.
• azo pigments such as monoazo pigments, disazo pigments, azo lakes, condensed azo pigments, and chelate azo pigments
• polycyclic pigments such as phthalocyanines, anthraquinones, perylenes, perinones, thioindigo, quinacridones, dioxazines, isoindolinones, and quinophthalones.
• iron oxide, titanium black, or carbon black as the pigment.
• carbon black examples include channel black, roller black, furnace black, thermal black, and acetylene black.
• the blended amount of pigment in the foam layer is preferably 0.01 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the resin components constituting the foam layer. From the viewpoint of obtaining a more uniformly colored expanded bead molding, the blended amount is more preferably 0.05 parts by mass or more, even more preferably 0.1 parts by mass or more, and even more preferably 0.5 parts by mass or more. Furthermore, from the viewpoint of obtaining an expanded bead molding with higher flame retardancy, the blended amount is more preferably 4 parts by mass or less, and even more preferably 3 parts by mass or less.
• carbon black, titanium oxide, talc, calcium carbonate, magnesium hydroxide, and magnesium carbonate may be combined with the above pigments in order to adjust the brightness of the color imparted to the molding or to make the appearance of the molding uniform.
• the expanded polypropylene resin particles of the present invention may contain an ultraviolet absorbing agent.
• the ultraviolet absorbing agent include benzophenone compounds, benzotriazole compounds, triazine compounds, and benzoate compounds.
• the benzophenone compounds include 2-hydroxy-4-octyloxybenzophenone, and examples of the benzotriazole compounds include 2-(5-methyl-2-hydroxyphenyl)benzotriazole, 2-[2-hydroxy-3,5-bis( ⁇ , ⁇ -dimethylbenzylphenyl)]-2H-benzotriazole, 2-(3,5-di-t-butyl-2-hydroxyphenyl)benzotriazole, 2-(3-t-butyl-5-methyl-2-hydroxyphenyl)-5-chlorobenzotriazole, 2-(3,5-di-t-butyl-2-hydroxyphenyl)-5-chlorobenzotriazole, 2-(3,5-di-t-amyl-2-
• the triazine-based compounds include 2-
• the benzoate-based compounds include 2,4-di-t-butylphenyl-3,5-di-t-butyl-4-hydroxybenzoate and hexadecyl-3,5-di-t-butyl-4-hydroxybenzoate.
• the amount of the ultraviolet absorber in the foam layer is preferably 0.01 parts by mass or more and 2 parts by mass or less, more preferably 0.05 parts by mass or more and 1 part by mass or less, and even more preferably 0.1 parts by mass or more and 0.8 parts by mass or less, relative to 100 parts by mass of the resin component constituting the foam layer.
• the ultraviolet absorbent is a compound that has the property of absorbing ultraviolet rays, and is a compound that can mainly absorb light with a wavelength of 300 to 400 ⁇ m.
• the expanded polypropylene resin particles of the present invention may contain other light stabilizers.
• light stabilizers include non-NOR type hindered amine compounds.
• Non-NOR type hindered amine compounds are compounds having a 2,2,6,6-tetramethyl-4-piperidineamine moiety in which the only atom directly bonded to the nitrogen atom is hydrogen or carbon.
• the content of the other light stabilizer in the foam layer is preferably 0.01 parts by mass or more and 2 parts by mass or less, more preferably 0.05 parts by mass or more and 1 part by mass or less, and even more preferably 0.1 parts by mass or more and 0.8 parts by mass or less, relative to 100 parts by mass of the resin component constituting the foam layer.
• the polypropylene-based expanded beads of the present invention may be expanded beads having only a particulate foam layer, or may be expanded beads having a multi-layer structure having a particulate foam layer as a core layer and a resin layer covering the foam layer.
• the foam layer may have through holes.
• the resin layer may cover the entire surface of the foamed layer, or may cover only a part of the surface of the foamed layer.
• the resin component constituting the coating layer include polyethylene-based resins and polypropylene-based resins.
• the melting point of the resin component constituting the coating layer is preferably lower than the melting point of the resin component constituting the foamed layer.
• the coating layer is preferably in a non-foamed state.
• the ratio of the mass of the resin component constituting the foam layer to the mass of the resin component constituting the coating layer is preferably 99:1 to 80:20, more preferably 98:2 to 85:15, and particularly preferably 98:2 to 90:10.
• the coating layer may contain the cyclic phosphonate compound, NOR hindered amine compound, and phenolic antioxidant in the same mixing ratio as the foamed layer, or in a different mixing ratio from the foamed layer, or none of them may be mixed in. Also, one or two of the cyclic phosphonate compound, NOR hindered amine compound, and phenolic antioxidant may be selected and mixed in the coating layer.
• the polypropylene-based resin expanded beads of the present invention are polypropylene-based resin expanded beads, and the manufacturing method thereof is not particularly limited as long as the expanded layer constituting the expanded beads has a polypropylene-based resin as a base resin, and contains a cyclic phosphonate compound and a NOR-type hindered amine compound, the amount of the cyclic phosphonate compound in the foamed layer is 5 parts by mass or more and less than 25 parts by mass relative to 100 parts by mass of the resin components constituting the foamed layer, the amount of the NOR-type hindered amine compound in the foamed layer is 0.1 parts by mass or more and less than 5 parts by mass relative to 100 parts by mass of the resin components constituting the foamed layer, the foamed layer contains a phenolic antioxidant, the amount of the phenolic antioxidant in the foamed layer is 0.01 parts by mass or more and less than 0.5 parts by mass relative to 100
• Such expanded beads can be produced by a conventional method, for example, a method in which polypropylene resin particles containing a blowing agent, a cyclic phosphonate compound, a NOR-type hindered amine compound and a phenolic antioxidant dispersed in an aqueous medium in a container are released from the container together with the aqueous medium under a pressure atmosphere lower than the pressure in the container to expand the resin particles.
• a suitable production method is shown below.
• a preferred method for producing the polypropylene-based resin expanded particles of the present invention includes a dispersing step of dispersing polypropylene-based resin particles containing a cyclic phosphonate compound, a NOR-type hindered amine compound, and a phenol-based antioxidant in an aqueous medium containing an inorganic dispersant in a container, a foaming agent impregnation step of impregnating the polypropylene-based resin particles with a foaming agent in the container, and a foaming step of releasing the polypropylene-based resin particles containing the foaming agent together with the aqueous medium from the container to cause foaming.
• the resin particles can be obtained by supplying the polypropylene resin, a cyclic phosphonate compound, a NOR-type hindered amine compound, a phenolic antioxidant, and other additives such as a bubble regulator, a pigment, and an ultraviolet absorber which are blended as necessary, into an extruder, heating and kneading the mixture to form a resin melt, and then extruding the resin melt from the extruder and pelletizing it by a strand cut method, a hot cut method, an underwater cut method, or the like.
• the average mass per resin particle (the arithmetic mean value per particle obtained by measuring the masses of 200 randomly selected particles) is preferably adjusted to 0.1 to 20 mg, more preferably 0.2 to 10 mg, even more preferably 0.3 to 5 mg, and still more preferably 0.4 to 2 mg.
• the outer shape of the particles is not particularly limited as long as it is within a range in which the intended object of the present invention can be achieved, but in the strand cut method, it is cylindrical.
• the particle diameter (length in the extrusion direction) of the resin particles is preferably 0.1 to 3.0 mm, more preferably 0.3 to 1.5 mm.
• the ratio (length/diameter ratio) of the length of the resin particles in the extrusion direction to the length of the resin particles in the direction perpendicular to the extrusion direction (diameter of the resin particles) is preferably 0.5 to 5.0, more preferably 1.0 to 3.0.
• the particle size, length/diameter ratio, and average mass of the resin particles can be adjusted by appropriately changing the extrusion speed, take-up speed, cutter speed, etc. when extruding the molten resin to cut the strands.
• the preferred method for producing the polypropylene resin expanded particles of the present invention includes a dispersing step of dispersing polypropylene resin particles containing a cyclic phosphonate compound, a NOR-type hindered amine compound and a phenolic antioxidant in an aqueous medium containing an inorganic dispersant in a container, a foaming agent impregnating step of impregnating the polypropylene resin particles with a foaming agent in the container, and a foaming step of releasing the polypropylene resin particles containing a foaming agent together with the aqueous medium from the container under a pressure lower than that of the container to foam, and preferably includes these steps in this order.
• each step of the preferred method for producing the polypropylene resin of the present invention will be described.
• the aqueous dispersion medium is a dispersion medium mainly composed of water.
• the proportion of water in the aqueous dispersion medium is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, and may be 100% by mass.
• Examples of the dispersion medium other than water in the aqueous dispersion medium include ethylene glycol, glycerin, methanol, ethanol, etc.
• the dispersant any dispersant that prevents the polypropylene resin particles from fusing in the container may be used, and although both organic and inorganic dispersants can be used, it is preferable to use an inorganic dispersant, and fine inorganic dispersants are more preferable because of ease of handling.
• examples include natural or synthetic clay minerals such as kaolin, mica, and clay, aluminum oxide, titanium oxide, basic magnesium carbonate, basic zinc carbonate, calcium carbonate, and iron oxide, and one or more of these may be used in combination. Of these, it is preferable to use a natural or synthetic clay mineral as the dispersion material.
• the amount of the dispersant added is preferably 0.001 to 5 parts by mass per 100 parts by mass of the resin particles.
• an anionic surfactant such as sodium dodecylbenzenesulfonate, sodium alkylsulfonate, or sodium oleate in combination with the dispersant as a dispersing aid. It is preferable to add about 0.001 to 1 part by mass of the dispersing aid to the aqueous medium per 100 parts by mass of the resin particles.
• a physical foaming agent As a foaming agent for expanding the polypropylene-based resin particles, a physical foaming agent is preferably used.
• the physical foaming agent may be an inorganic physical foaming agent or an organic physical foaming agent. Examples of the inorganic physical foaming agent include carbon dioxide, air, nitrogen, helium, and argon.
• organic physical foaming agent examples include aliphatic hydrocarbons such as propane, n-butane, i-butane, n-pentane, i-pentane, hexane, cyclopentane, and cyclohexane, and halogenated hydrocarbons such as chlorofluoromethane, trifluoromethane, 1,1-difluoroethane, 1-chloro-1,1-difluoroethane, 1,1,1,2-tetrafluoroethane, methyl chloride, ethyl chloride, and methylene chloride.
• these physical foaming agents may be used alone or in combination of two or more.
• an inorganic physical foaming agent and an organic physical foaming agent may be used in combination.
• the foaming agent is preferably an inorganic physical foaming agent, and more preferably carbon dioxide.
• the amount of foaming agent added per 100 parts by mass of resin particles is preferably 0.1 to 30 parts by mass, and more preferably 0.5 to 15 parts by mass.
• the preferred method for impregnating the resin particles with the blowing agent is to disperse the resin particles in an aqueous dispersion medium in a sealed container, then pressurize the blowing agent into the sealed container and maintain the inside of the sealed container at a specified temperature and pressure, thereby impregnating the resin particles with the blowing agent.
• the pressure (internal pressure) in the sealed container during foaming is preferably 0.5 MPa (G) or more, more preferably 0.8 MPa (G) or more.
• the upper limit is preferably 4 MPa (G) or less, more preferably 3 MPa (G) or less. If it is within the above range, the desired expanded particles can be safely produced without risk of damage or explosion of the sealed container.
• the temperature is also preferable to raise the temperature to preferably 100 to 200°C, more preferably 130 to 160°C, and hold the temperature for about 5 to 30 minutes, and then release the resin particles containing the foaming agent from the sealed container into an atmosphere (e.g., atmospheric pressure) with a pressure lower than the pressure in the sealed container to foam the resin particles.
• atmosphere e.g., atmospheric pressure
• the polypropylene resin foamed particles obtained as described above can be pressurized with air or the like to increase the pressure (internal pressure) within the bubbles of the foamed layer, and then heated with steam or the like for further foaming (two-stage foaming) to produce foamed particles with a higher expansion ratio (lower bulk density).
• the expanded bead molding of the present invention is produced by molding the expanded polypropylene resin beads in a mold.
• the expanded bead molding of the present invention is an in-mold molding of the expanded polypropylene resin beads.
• the expanded bead molding of the present invention is an expanded bead molding having a foam layer constituting the expanded beads, the foam layer being formed by in-mold molding of expanded polypropylene resin beads containing a polypropylene resin as a base resin and a cyclic phosphonate compound and a NOR hindered amine compound, the amount of the cyclic phosphonate compound in the foam layer being 5 parts by mass or more and less than 25 parts by mass relative to 100 parts by mass of the resin components constituting the foam layer, the amount of the NOR hindered amine compound in the foam layer being 0.1 parts by mass or more and less than 5 parts by mass relative to 100 parts by mass of the resin components constituting the foam layer, the foam layer containing a phenolic antioxidant, the amount of the phenolic antioxidant in the foam layer being 0.01 parts by mass or more and less than 0.5 parts by mass relative to 100 parts by mass of the resin components constituting the foam layer, and the ratio of the amount of the phenolic antioxidant to the amount of the NOR
• the in-mold molding method is carried out by filling the foamed beads into a mold and then heating and molding the foamed beads. Specifically, after filling the mold with the foamed beads, the foamed beads are heated to cause secondary foaming and are fused together to obtain a foamed bead molded body in which the shape of the molding space is formed.
• Examples of the method of heating the foamed beads include a method of introducing a heating medium such as steam into the mold and heating the foamed beads with the heating medium, a method of irradiating the foamed beads with electromagnetic waves such as microwaves and heating the foamed beads, and a combination of both.
• a method of filling the mold with the foamed beads known methods can be adopted.
• Examples include a method of pressurizing the foamed beads with a pressurized gas to give the foamed beads a predetermined internal pressure and then filling the mold (pressurized filling method), a method of filling the mold with the foamed beads in a compressed state with a pressurized gas and then releasing the pressure in the mold (compression filling method), a method of opening the mold in advance before filling the mold with the foamed beads to expand the molding space, and then closing the mold after filling to mechanically compress the foamed beads (cracking filling method), and a combination of these filling methods.
• pressurized filling method a method of pressurizing the foamed beads with a pressurized gas to give the foamed beads a predetermined internal pressure and then filling the mold
• compression filling method a method of filling the mold with the foamed beads in a compressed state with a pressurized gas and then releasing the pressure in the mold
• compression filling method a method of opening the mold in advance before fill
• the density of the expanded bead molding of the present invention is preferably 10 g/L or more and 300 g/L or less, more preferably 20 g/L or more, more preferably 30 g/L or more, even more preferably 40 g/L or more, and even more preferably 50 g/L or more. Also, it is more preferably 120 g/L or less, more preferably 90 g/L or less, even more preferably 80 g/L or less, even more preferably 70 g/L or less, and even more preferably 63 g/L or less.
• the density of the expanded bead molding is calculated by dividing the mass of the expanded bead molding by the volume calculated based on its dimensions.
• the foamed bead molding of the present invention has excellent adhesion and flame retardancy, so it can be used favorably in applications that require a high level of flame retardancy, such as protective materials for batteries and electronic components mounted in vehicles.
• the high-temperature peak heat of fusion of the expanded beads was measured by heat flux differential scanning calorimetry based on JIS K7122-2012. Specifically, about 2 mg of the expanded beads was sampled and heated from 23°C to 200°C at a rate of 10°C/min using a differential scanning calorimeter (DSC7020, Hitachi High-Tech Science Corporation) to obtain a DSC curve with one or more melting peaks.
• DSC7020 differential scanning calorimeter
• the resin-specific peak is designated as A
• the high-temperature peak appearing on the higher temperature side is designated as B.
• a straight line ( ⁇ - ⁇ ) was drawn connecting point ⁇ corresponding to 80° C.
• the melting end temperature T is the high temperature end point of high temperature peak B, and refers to the intersection point of the high temperature peak and the high temperature side baseline.
• a straight line parallel to the vertical axis of the graph was drawn from point ⁇ on the DSC curve corresponding to the valley between the resin intrinsic peak A and high temperature peak B, and the point where this straight line intersected with the straight line ( ⁇ - ⁇ ) was designated as ⁇ .
• the area of high-temperature peak B is the area surrounded by the curve of high-temperature peak B in the DSC curve, the line segment ( ⁇ - ⁇ ), and the line segment ( ⁇ - ⁇ ), and this was defined as the heat of fusion of the high-temperature peak.
• PP2 Ethylene-propylene random copolymer, melting point 134°C, ethylene content 3.5% by mass, MFR (load 2.16 kg, 230°C, JIS K7210-1:2014) 5g/10min, polydispersity (Mw/Mn) 5.0
• PP3 High melt tension polypropylene, melting point 159°C, MFR (load 2.16 kg, 230°C, JIS K7210-1:2014) 1.7g/10min Melt tension: 390mN (measurement temperature: 230°C, measurement device: Capillograph 1D manufactured by Toyo Seiki Seisakusho Co., Ltd., orifice nozzle diameter: 2.095mm, orifice length: 8.0mm, pulley diameter: 45mm, take-up speed: initial speed 0m/min, speed increased at a constant rate to reach 200m/min in 4 minutes, and the maximum value just before the strand being taken up broke was recorded.)
• PE1 Linear low-density polyethylene, melting point 120°C, density 0.923 cm/cm 3 , MFR (load 2.16 kg, 190°C, JIS K7210-1:2014) 1.5 g/10 min
• PCO900 Aflamit PCO900, manufactured by Thor, melting point 240° C., a compound represented by the following formula (6)
• NOR type hindered amine compound NOR116: BASF Corporation, product name "Flamestab NOR116", a compound represented by the following formula (7), molecular weight 2261
• Example 1 An extruder having an inner diameter of 50 mm and equipped with a strand-forming die on the outlet side was prepared. PP1, zinc borate (arithmetic mean particle size based on number: 9 ⁇ m), PCO900, NOR116, 1330, and the sulfur-based antioxidant were fed to an extruder in the amounts shown in Table 1, and melt-kneaded to form a resin melt. The obtained molten resin was extruded as a strand from a strand forming die, and the extruded strand was cooled with water and cut with a pelletizer to obtain polypropylene resin particles each having an average mass of 1.0 mg.
• a split die for plate molding having inner dimensions of a rectangular parallelepiped of length 400 mm x width 300 mm x thickness 30 mm when completely closed was used.
• the mold was filled with foamed beads in a state where the mold was opened 3 mm in the thickness direction from a completely closed state. After the filling was completed, the mold was completely closed (crack amount 3 mm, 10%).
• steam was supplied into the mold to heat the foamed beads, and a plate-shaped foamed bead molded body was obtained by cracking molding. Heating with steam was performed as follows. First, steam was supplied into the mold with the drain valves of both molds open (exhaust process).
• Examples 2 to 7 and Comparative Examples 1 to 5 Expanded polypropylene resin particles were obtained in the same manner as in Example 1, except that the amount of each component was changed so that the amount of each component per 100 parts by mass of the resin component constituting the foamed layer was as shown in Tables 1 and 3. Measurement results of the physical properties of the obtained expanded polypropylene resin particles are shown in Tables 1 and 3.
• the expanded polypropylene resin beads thus obtained were used to obtain expanded bead moldings in the same manner as in Example 1, except that the molding steam pressure was adjusted to the steam pressure shown in Tables 1 and 3.
• the results of the density, fusion property evaluation, and flame retardancy evaluation of the expanded bead moldings thus obtained are shown in Tables 1 and 3.
• Example 8 Expanded polypropylene resin beads were obtained in the same manner as in Example 6, except that the phenolic antioxidant 1330 was changed to 1010. Measurement results of the physical properties of the expanded polypropylene resin beads obtained are shown in Table 2. The expanded polypropylene resin beads thus obtained were used to obtain an expanded bead molding in the same manner as in Example 6. The results of the density, fusion property evaluation and flame retardancy evaluation of the obtained expanded bead molding are shown in Table 2.
• Example 9 A manufacturing apparatus was prepared, which was equipped with an extruder for forming a core layer with an inner diameter of 50 mm, an extruder for forming a coating layer with an inner diameter of 30 mm, and a co-extrusion die for forming a multilayer strand consisting of a cylindrical core layer and a coating layer covering the side of the core layer.
• PP1 zinc borate (arithmetic mean particle size based on number: 9 ⁇ m)
• PCO900, NOR116, 1330, and the sulfur-based antioxidant were supplied to an extruder for forming a core layer in the amounts shown in Table 2, and these were melt-kneaded to form a resin molten material for forming the core layer.
• the obtained resin melt for forming the core layer and the resin melt for forming the coating layer are introduced into a co-extrusion die for forming a multi-layer strand, and are merged in the die, and a multi-layer strand having a two-layer structure (coating layer/core layer structure) consisting of a cylindrical core layer and a coating layer that covers the side of the core layer is extruded from the co-extrusion die.
• the ratio of the coating layer to the core layer is adjusted to be 3/97 by mass.
• the extruded strand is water-cooled and cut by a pelletizer to obtain polypropylene-based resin particles having an average mass of 1.0 mg per particle, which have a two-layer structure consisting of a cylindrical core layer and a coating layer that covers the side of the core layer.
• the obtained polypropylene resin particles were treated in the same manner as in Example 1 to obtain polypropylene resin expanded particles having a multi-layer structure having a foamed layer and a coating layer.
• the core layer of the resin particles was expanded to become a particulate foamed layer, and the coating layer was a non-foamed resin layer.
• the measurement results of the physical properties of the obtained polypropylene resin expanded particles are shown in Table 2.
• the expanded polypropylene resin beads thus obtained were used to obtain an expanded bead molding in the same manner as in Example 1.
• the results of the density, fusion property evaluation and flame retardancy evaluation of the expanded bead molding thus obtained are shown in Table 2.
• Example 10 Except for feeding polypropylene-based resin PP1 and polypropylene-based resin PP3 in a mass ratio of 85/15 (PP1/PP3) instead of polypropylene-based resin PP1, polypropylene-based resin expanded beads were obtained in the same manner as in Example 1. Measurement results of the physical properties of the obtained polypropylene-based resin expanded beads are shown in Table 2.
• Example 11 Except for feeding polypropylene-based resin PP1 and polyethylene-based resin PE1 in a mass ratio of 85/15 (PP1/PE1) instead of polypropylene-based resin PP1, polypropylene-based resin expanded beads were obtained in the same manner as in Example 1. Measurement results of the physical properties of the obtained polypropylene-based resin expanded beads are shown in Table 2.
• Example 12 Expanded polypropylene resin particles were obtained in the same manner as in Example 1, except that conductive carbon black (Ketjen Black EC300J, manufactured by Lion Corporation) was fed as the conductive filler to the extruder in the amount shown in Table 2. Measurement results of the physical properties of the expanded polypropylene resin particles obtained are shown in Table 2.
• Example 13 Expanded polypropylene resin particles were obtained in the same manner as in Example 1, except that PTFE powder (polytetrafluoroethylene fibril, manufactured by Mitsubishi Chemical Corporation, product name Metablen A-3800) was fed as a filler to the extruder in the amount shown in Table 2. Measurement results of the physical properties of the expanded polypropylene resin particles obtained are shown in Table 2.
• PTFE powder polytetrafluoroethylene fibril, manufactured by Mitsubishi Chemical Corporation, product name Metablen A-3800

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