Polypropylene foam particles, polypropylene foam molded articles, and methods for manufacturing the same.

Abstract

The purpose of the present invention is to provide polypropylene-based foamed particles which enable providing a foamed molded article with excellent flame resistance. This purpose is met by polypropylene-based foamed particles that contain (A) a polypropylene resin, (B) an organic phosphorous compound, and (C) a hindered amine, and that, relative to the total 100 wt% of polypropylene-based foamed particles, contain more than 10.0 wt% and less than or equal to 20.0 wt% of (B) the organic phosphorous compound and 1.0-10.0 wt% of (C) the hindered amines.

Description

Technical Field

[0001] The present invention relates to polypropylene-based foamed particles, polypropylene-based foamed molded articles, and methods for producing them.

Background Art

[0002] Foamed molded articles obtained by in-mold foaming of thermoplastic resins (for example, polypropylene-based resins) are widely used in various applications, such as interior materials and cushioning materials for automobiles. Conventionally, materials having flame retardancy that satisfies the FMVSS302 standard have been adopted for interior materials of automobiles. However, recently, as automobiles shift to electric vehicles, higher flame-retardant members are required for peripheral members of electrical devices such as around lithium-ion battery packs. For example, Patent Document 1 discloses a technique for obtaining polyolefin-based pre-expanded particles that can provide a foamed molded article having excellent flame retardancy by adding a specific amount of an organic phosphorus compound and a hindered amine to polyolefin-based foamed particles.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the conventional technologies as described above are not sufficient from the viewpoint of flame retardancy, and there is room for further improvement.

[0005] In view of the above situation, an object of one embodiment of the present invention is to provide polypropylene-based foamed particles that can provide a polypropylene-based foamed molded article having more excellent flame retardancy than the conventional technologies.

Means for Solving the Problems

[0006] As a result of intensive studies to solve the above problems, the present inventors have completed the present invention.

[0007] That is, one embodiment of the present invention includes the following configuration.

[0008] Polypropylene-based foam particles containing a polypropylene-based resin (A), an organophosphorus compound (B), and a hindered amine (C), wherein the amount of the organophosphorus compound (B) is more than 10.0% by weight and 20.0% by weight or less, and the hindered amine (C) is 1.0% to 10.0% by weight, based on 100% by weight of the total amount of the polypropylene-based foam particles.

[0009] A dispersion step of dispersing polypropylene-based resin particles, an aqueous dispersion medium, and a foaming agent in a container, and a discharging step of discharging the dispersion obtained in the dispersion step into a region having a pressure lower than the pressure in the container, wherein the polypropylene-based resin particles contain an organophosphorus compound (B) in an amount of more than 10.0% by weight and 20.0% by weight or less, and a hindered amine (C) in an amount of 1.0% to 10.0% by weight, based on 100% by weight of the total amount of the polypropylene-based resin particles. A method for producing polypropylene-based foam particles.

Effect of the Invention

[0010] According to one embodiment of the present invention, it is possible to provide polypropylene-based foam particles capable of providing a polypropylene-based foam molded body having more excellent flame retardancy than the prior art.

Mode for Carrying Out the Invention

[0011] One embodiment of the present invention will be described below, but the present invention is not limited thereto. The present invention is not limited to each configuration described below, and various modifications are possible within the scope indicated in the claims. Also, embodiments or examples obtained by combining the technical means disclosed in different embodiments or examples are also included in the technical scope of the present invention. Furthermore, by combining the technical means disclosed in each embodiment, new technical features can be formed. All academic and patent documents described in this specification are incorporated herein by reference. Also, unless otherwise specified in this specification, "A~B" representing a numerical range is intended to mean "A or more (including A and greater than A) and B or less (including B and less than B)".

[0012] Also, unless otherwise specified in this specification, as a structural unit, X 1 a structural unit derived from a monomer, and X 2 a structural unit derived from a monomer, and ··· and X n a copolymer containing monomers (n is an integer of 2 or more) is also referred to as "X 1 / X 2 / ··· / X n copolymer". X 1 / X 2 / ··· / X n Unless otherwise indicated, the copolymerization mode of the X / X / ··· / X copolymer is not particularly limited, and it may be a random copolymer, an alternating copolymer, a block copolymer, or a graft copolymer.

[0013] Also, in this specification, the structural unit derived from the X monomer contained in the polymer or copolymer may be referred to as "X unit".

[0014] [1. Technical idea of the present invention] The technology described in Patent Document 1 was excellent considering the level of technology at the time Patent Document 1 was filed. However, in recent years, flame retardancy standards in various industrial fields (for example, electrical and electronic equipment, especially equipment used in electric vehicles, etc.) have tended to become stricter than when Patent Document 1 was filed, and there is a demand for polypropylene foam molded articles with superior flame retardancy.

[0015] In the future, polypropylene foam molded articles are expected to be required to meet stricter flame retardancy standards, such as oxygen index (OI) and vertical combustion test (UL94). In fact, under the Fire Service Act, substances with an oxygen index of 26% or less are designated as combustible materials. Here, OI is an index defined by JIS K7201, etc., and represents the minimum oxygen concentration (volume %) required for the material to sustain combustion. Foam molded articles that meet the OI standard (for example, OI of 26% or more) can be said to be foam molded articles with excellent non-ignition properties. UL94 is a standard for the duration of combustion of a material, and for ensuring that even if burning particles fall (dripping) during combustion, surrounding combustible materials do not ignite (this can also be described as the falling particles extinguishing before contact with surrounding combustible materials, or whether ignition occurs due to dripping). Foam molded articles that meet the UL94 standard (especially standard V-0) can be said to be foam molded articles with excellent self-extinguishing properties.

[0016] A technique for imparting flame retardancy to polypropylene foam molded articles by adding halogen-containing compounds is known. However, in recent years, halogen-containing compounds, particularly bromine-containing organic compounds (e.g., polybrominated diphenyl ethers), have been found to be harmful to the environment and human health, and have become a cause for concern. For example, under European Union regulations since July 2006, the manufacture and use of pentabromodiphenyl ether and octabromodiphenyl oxide are prohibited, and the use of decabromodiphenyl oxide is restricted.

[0017] In this situation, there is a need for a polypropylene-based foamed molded article that does not contain halogen-containing compounds and has superior flame retardancy compared to conventional foamed molded articles (for example, those described in Patent Document 1).

[0018] Given the circumstances described above, the inventors diligently conducted research to provide polypropylene foam particles that can provide a polypropylene foam molded article with superior flame retardancy. As a result, they discovered the following findings and completed the present invention: Polypropylene foam particles comprising a polypropylene resin (A), an organophosphorus compound (B), and a hindered amine (C), wherein the polypropylene foam particles contain more than 10.0% by weight and 20.0% by weight or less of cyclic phosphonate (B) and 1.0% to 10.0% by weight of hindered amine (C) per 100% by weight of the total amount of the polypropylene foam particles, thereby providing a polypropylene foam molded article with superior flame retardancy.

[0019] [2. Polypropylene foam particles] Polypropylene foam particles according to one embodiment of the present invention are polypropylene foam particles comprising a polypropylene resin (A), an organophosphorus compound (B), and a hindered amine (C), wherein the polypropylene foam particles contain, with respect to 100% by weight of the total amount of the polypropylene foam particles, more than 10.0% by weight and 20.0% by weight or less of the organophosphorus compound (B), and 1.0% by weight to 10.0% by weight of the hindered amine (C).

[0020] A polypropylene foamed molded article can be provided by molding polypropylene foamed particles according to one embodiment of the present invention using a known method.

[0021] In this specification, "polypropylene foam particles" may be referred to as "foam particles," "polypropylene foam particles relating to one embodiment of the present invention" may be referred to as "the foam particles," and "polypropylene resin foam molded article" may be referred to as "foam molded article."

[0022] Because these foamed particles have the above-described structure, they have the advantage of being able to provide a foamed molded article with excellent flame retardancy. It can also be said that these foamed particles can provide a polypropylene-based foamed molded article with excellent self-extinguishing and / or non-ignition properties.

[0023] <Polypropylene resin (A)> In this specification, polypropylene resin (A) refers to a resin in which at least 50 mol% of the total constituent units contained in the resin are derived from propylene monomers. In this specification, "constituent units derived from propylene monomers" may also be referred to as "propylene units."

[0024] The polypropylene resin (A) may be (a) a homopolymer of propylene, (b) a block copolymer, alternating copolymer, random copolymer, or graft copolymer of propylene and monomers other than propylene, or (c) a mixture of two or more of these. Among these, the polypropylene resin (A) is preferably a random copolymer of propylene and monomers other than propylene because it has the advantage of allowing the resin particles and foamed particles to be processed at a low heating temperature in the foaming process and in-mold foaming process described later. A "random copolymer of propylene and monomers other than propylene" can also be said to be a random copolymer containing constituent units derived from propylene and constituent units derived from monomers other than propylene.

[0025] Polypropylene resin (A) may contain one or more constituent units derived from monomers other than propylene monomers, in addition to propylene units, or may contain one or more of these units. The "monomers other than propylene monomers" used in the manufacture of polypropylene resin (A) are sometimes referred to as "comonomers." The "constituent units derived from monomers other than propylene monomers" contained in polypropylene resin are sometimes referred to as "comonomer units."

[0026] Examples of comonomers include α-olefins having 2 or 4 to 12 carbon atoms, such as ethylene, 1-butene, isobutene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3,4-dimethyl-1-butene, 1-heptene, 3-methyl-1-hexene, 1-octene, and 1-decene.

[0027] Specific examples of polypropylene resin (A) include polypropylene homopolymer, ethylene / propylene random copolymer, 1-butene / propylene random copolymer, 1-butene / ethylene / propylene random copolymer, ethylene / propylene block copolymer, 1-butene / propylene block copolymer, propylene / chlorinated vinyl copolymer, propylene / maleic anhydride copolymer, and styrene-modified polypropylene resin. One of these polypropylene resins (A) may be used alone, or two or more may be used in combination. Among these, ethylene / propylene random copolymer and 1-butene / ethylene / propylene random copolymer are preferred because the resulting foamed particles have good foaming properties and the molded article has good moldability. Note that 1-butene is synonymous with butene-1.

[0028] Let's consider the case where an ethylene / propylene random copolymer is used as the polypropylene resin (A) (let's call this Case A). In Case A, the ethylene content in the ethylene / propylene random copolymer is preferably 0.2% to 15.0% by weight, more preferably 0.5% to 10.0% by weight, and even more preferably 0.5% to 4.0% by weight, per 100% by weight of each copolymer. The ethylene content can also be said to be the content of constituent units derived from ethylene (ethylene units). When the ethylene unit content in the ethylene / propylene random copolymer is (i) 0.2% by weight or more, the foaming properties of the foamed particles produced in the manufacturing of these foamed particles and / or the moldability of the resulting foamed particles tend to be good, and when it is 15.0% by weight or less, there is no risk of the mechanical properties of the foamed molded article obtained from these foamed particles deteriorating.

[0029] Let's consider the case where a 1-butene / ethylene / propylene random copolymer is used as the polypropylene resin (A) (let's call this case B). The ethylene content in the 1-butene / ethylene / propylene random copolymer is preferably 0.1% to 10.0% by weight, more preferably 0.2% to 5.0% by weight, and even more preferably 0.5% to 1.0% by weight, per 100% by weight of each copolymer. When the ethylene unit content in the 1-butene / ethylene / propylene random copolymer is (i) 0.1% by weight or more, the foaming properties of the foamed particles produced in the manufacturing of these foamed particles and / or the moldability of the resulting foamed particles tend to be good, and when it is 10.0% by weight or less, there is no risk of the mechanical properties of the foamed molded article obtained from these foamed particles deteriorating.

[0030] Furthermore, in case B, the 1-butene content in the 1-butene / ethylene / propylene random copolymer is preferably 0.2% to 15.0% by weight, more preferably 1.0% to 10.0% by weight, and even more preferably 2.0% to 7.0% by weight, based on 100% by weight of the copolymer. The 1-butene content can also be said to be the content of constituent units (1-butene units) derived from 1-butene. When the 1-butene unit content in the 1-butene / ethylene / propylene random copolymer is (i) 0.2% by weight or more, the foaming properties of the foamed particles produced in the manufacture of these foamed particles and / or the moldability of the resulting foamed particles tend to be good, and when it is 15.0% by weight or less, there is no risk of the mechanical properties of the foamed molded article obtained from these foamed particles deteriorating.

[0031] Furthermore, in case B, the total content of ethylene units and 1-butene units in the 1-butene / ethylene / propylene random copolymer is preferably 0.5% to 15.0% by weight, more preferably 0.5% to 10.0% by weight, and even more preferably 2.0% to 6.0% by weight, per 100% by weight of the 1-butene / ethylene / propylene random copolymer. When the total content of ethylene units and 1-butene units in the 1-butene / ethylene / propylene random copolymer is (i) 0.5% by weight or more, the foaming properties of the foamed particles produced in the manufacturing of the foamed particles and / or the moldability of the resulting foamed particles tend to be good, and when it is 10.0% by weight or less, there is no risk of the mechanical properties of the foamed molded article obtained from the foamed particles deteriorating.

[0032] In polypropylene resin (A), the propylene unit content is 50 mol% or more, preferably 75 mol% or more, more preferably 90 mol% or more, and even more preferably 95 mol% or more, out of 100 mol% of the total constituent units contained in polypropylene resin (A). Having the propylene unit content in polypropylene resin (A) within the above range has the advantage of resulting in good heat resistance, mechanical strength, and impact resistance of the resulting foamed molded article. Furthermore, there is no particular upper limit to the propylene unit content in polypropylene resin (A); for example, it may be 97 mol% or less, or 100 mol%.

[0033] The melting point of the polypropylene resin (A) is preferably 125.0°C to 160.0°C, more preferably 130.0°C to 158.0°C, more preferably 135.0°C to 152.0°C, more preferably 138.0°C to 149.0°C, even more preferably 139.0°C to 146.0°C, and particularly preferably 141.0°C to 145.0°C. When the melting point of the polypropylene resin (A) is (i) 125.0°C or higher, a foamed molded article with excellent dimensional stability at high temperatures can be obtained, and when it is 160.0°C or lower, the foamed molded article can be foamed in a mold at a low water vapor pressure.

[0034] In this specification, the melting point of polypropylene resin is a value obtained by measurement using differential scanning calorimetry (hereinafter referred to as the "DSC method"). The specific operating procedure is as follows: (1) Melt the polypropylene resin by raising the temperature of 5 mg to 6 mg of polypropylene resin from 40.0 °C to 220.0 °C at a heating rate of 10.0 °C / min; (2) Then, crystallize the polypropylene resin by lowering the temperature of the molten polypropylene resin from 220.0 °C to 40.0 °C at a cooling rate of 10.0 °C / min; (3) Then, further raise the temperature of the crystallized polypropylene resin from 40.0 °C to 220.0 °C at a heating rate of 10 °C / min. The temperature of the peak (melting peak) of the DSC curve of the polypropylene resin obtained during the second heating (i.e., at (3)) can be determined as the melting point of the polypropylene resin. Furthermore, if multiple peaks (melting peaks) exist in the DSC curve of the polypropylene resin obtained during the second heating cycle using the method described above, the temperature of the peak with the largest heat of fusion (melting peak) is defined as the melting point of the polypropylene resin. As a differential scanning calorimeter, for example, the DSC6200 model manufactured by Seiko Instruments Inc. can be used.

[0035] The melt index (MI) of the polypropylene resin (A) is not particularly limited, but is preferably 3.00 g / 10 min to 30.00 g / 10 min, more preferably 4.00 g / 10 min to 20.00 g / 10 min, even more preferably 5.00 g / 10 min to 15.00 g / 10 min, and particularly preferably 6.00 g / 10 min to 13.00 g / 10 min. Note that MI may also be referred to as "melt flow rate (MFR)".

[0036] When the MI of the polypropylene resin is 3.00 g / 10 min or higher, the polypropylene resin exhibits good fluidity during foaming and foaming is easy. Furthermore, when the MI of the polypropylene resin is 30.00 g / 10 min or lower, the polypropylene resin has appropriate fluidity, allowing for the production of foamed particles with a high foaming ratio. In particular, when the MI of the polypropylene resin (A) is between 3.00 g / 10 min and 8.00 g / 10 min, foamed particles that can suitably provide foamed molded articles with relatively high density (e.g., density exceeding 92.0 g / L) can be efficiently produced.

[0037] In this specification, the MI value of polypropylene resins is the value obtained by measuring using the MI measuring instrument described in JIS K7210:1999 under the following conditions: orifice diameter of 2.0959 ± 0.005 mmφ, orifice length of 8.000 ± 0.025 mm, load of 2.16 kgf, and temperature of 230 °C (230 ± 0.2 °C). Note that if the polypropylene resin (A) is a mixture of multiple copolymers, the MI of the polypropylene resin (A) refers to the melting point of the mixture.

[0038] The foamed particles preferably contain 70.0% by weight or more and less than 89.0% by weight of polypropylene resin (A) relative to 100% by weight of the total amount of polypropylene foamed particles, more preferably 75% to 85% by weight, and even more preferably 77% to 87% by weight. When the foamed particles contain (i) 70.0% by weight or more of polypropylene resin (A), a foamed molded article with no shrinkage and excellent strength (e.g., compressive strength) can be obtained, and when it contains less than 89.0% by weight, a foamed molded article with excellent flame retardancy can be stably obtained.

[0039] Polypropylene resin (A) can be obtained by known methods. There are no particular restrictions on the polymerization catalyst used when synthesizing polypropylene resin (A), and Ziegler catalysts and metallocene catalysts can be used.

[0040] <Organophosphorus compounds (B)> These foamed particles contain more than 10.0% by weight and no more than 20.0% by weight of an organophosphorus compound (B) relative to 100% by weight of the total polypropylene foamed particles. These foamed particles, having the above composition, have the advantage of providing foamed molded articles with excellent flame retardancy.

[0041] The foamed particles contain more than 10.0% by weight and 20.0% by weight or less of organophosphorus compound (B) per 100% by weight of the total amount of polypropylene foamed particles, preferably 12.0% to 19.0% by weight, and more preferably 13.0% to 18.0% by weight. When the foamed particles contain (i) more than 10.0% by weight of organophosphorus compound (B), a foamed molded article with excellent flame retardancy can be stably obtained, and when they contain 20.0% by weight or less, a foamed molded article with no shrinkage and excellent strength (e.g., compressive strength) can be obtained.

[0042] The organophosphorus compound (B) is not particularly limited as long as it is an organophosphorus compound other than phosphate esters, phosphates, and triarylphosphine oxides, and many other organophosphorus compounds (subclasses of organophosphorus compounds) that are well known to those skilled in the art can be suitably used. These organophosphorus compounds (B) may be used individually or in combination of two or more types.

[0043] More specifically, the organophosphorus compound (B) according to one embodiment of the present invention includes phosphonates; organic phosphites; organic phosphinites; and metal salts of phosphinic acid or diphosphinic acid; phosphinates; polyol phosphate alcohols; and other nitrogen-containing organophosphorus compounds. Among these, phosphonates are preferred as organophosphorus compound (B) because they can provide a foamed molded article with superior non-ignition and / or self-extinguishing properties. Of the above organophosphorus compounds, it is preferable that compounds other than other nitrogen-containing organophosphorus compounds do not contain nitrogen. That is, it is preferable that organophosphorus compounds (B) other than nitrogen-containing organophosphorus compounds do not contain nitrogen.

[0044] (phosphonate) A phosphonate is a compound containing two R-PO(OH) groups and / or R-PO(OR 1 )2 groups (where R is a hydrocarbyl group such as a methyl group, benzyl group, aryl group, alkynyl group, allenyl group, vinyl group or substituted vinyl group, R 1 This refers to esters and partial esters containing a hydrocarbyl group (such as an alkyl or aryl group), as well as salts thereof.

[0045] More specifically, phosphonates include subgroups such as alkylphosphonic acids, arylphosphonic acids, and their esters; monophosphonates; acyclic bisphosphonates; and cyclic phosphonates. Among these, cyclic phosphonates are preferred, and among cyclic phosphonates, cyclic bisphosphonates are particularly preferred. Therefore, the organophosphorus compound (B) according to one embodiment of the present invention is preferably at least one nitrogen-free organophosphorus compound selected from the group consisting of (i) alkylphosphonic acids, arylphosphonic acids, and their esters, and (ii) cyclic phosphonates, more preferably a cyclic phosphonate, and among cyclic phosphonates, particularly preferably a cyclic bisphosphonate.

[0046] Examples of cyclic phosphonates include organophosphorus compounds represented by the following structural formula (i):

[0047] [ka] In the above structural formula (i), R 1 and R 2 Independently, C 1-4 It is an alkyl group, R 3 is H or C 1-4 It is an alkyl group, R 4 C 9-22 Alkyl alkyl group, C 9-22 Cycloalkyl groups, C 9-22Aryl group or C 9-22 It is an aralkyl group and n=0 or 1.

[0048] The cyclic phosphonate represented by the above structural formula (i) is described in more detail in French Patent Application Publication No. 1503429.

[0049] As a cyclic phosphonate, cyclic bisphosphonates, such as pentaerythrityl diphosphonate, which are organophosphorus compounds represented by the following structural formula (ii), can also be suitably used:

[0050] [ka] In the above structural formula (ii), A 1 and A 2 Independently, C 1-10 Alkyl alkyl group, C 2-10 These are alkenyl groups, benzyl groups, phenylethyl groups, phenyl groups, or naphthyl groups.

[0051] In other words, the cyclic bisphosphonate is particularly preferably pentaerythrityl diphosphonate.

[0052] More details about cyclic bisphosphonates are disclosed in U.S. Patent No. 4,174,343 and UK Patent Application Publication No. 1515,223.

[0053] Among cyclic bisphosphonates, pentaerythrityl diphosphonate (AFLAMMIT® PCO 900 (phosphorus content 24%)), represented by the following structural formula (iii), is particularly preferred because it can produce foamed molded articles with excellent heat resistance and dimensional stability.

[0054] [ka] Alternatively, other cyclic phosphate esters may be used, such as the compounds disclosed in French Patent Application Publication No. 1503429.

[0055] (Organic phosphite ester) Examples of organic phosphites include alkyl phosphites and arylalkyl phosphites (where the alkyl group preferably has 1 to 4 carbon atoms), such as dimethyl phosphite, diethyl phosphite, trimethyl phosphite, dibutyl phosphite, triisopropyl phosphite, dibenzyl phosphite, bis(2,2,2-trifluoroethyl) phosphite, tris(2,2,2-trifluoroethyl) phosphite, tris(1,1,1,3,3,3-hexafluoro-2-propyl) phosphite, and diphenyl phosphite; and trimethylolethane cyclic phosphite (also known as 4-methyl-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane). Examples include cyclic phosphies such as ), and cyclic hydrogen phosphies outlined in U.S. Patent No. 3,152,164, such as 2-hydroxy-4,5-dimethyl-1,3,2-dioxaphosphorane (2,3-butylene hydrogen phosphite), 2-hydroxy-4-methyl-1,3,2-dioxaphospholinane, 2-hydroxy-4-methyl-1,3,2-dioxaphospholinane (propylene hydrogen phosphite), 2-hydroxy-1,3,2-dioxaphospholinane (trimethylene hydrogen phosphite), 2-hydroxy-5,5-dimethyl-1,3,2-dioxaphospholinane, and 2-hydroxy-4-propyl-5-ethyl-1,3,2-dioxaphospholinane.

[0056] (Organophosphinites, and metal salts of phosphinic acid or diphosphinic acid) Metal salts of phosphinic acid or diphosphinic acid are those with the chemical formulas RR'P(=O)-OMe and MeO-PR(=O)-R 1This refers to the metal salt of a compound (phosphinic acid or diphosphinic acid) represented by -PR'(=O)-OMe, where R and R' are independently C 1-6 Alkyl alkyl group, C 3-8 Cycloalkyl groups, C 6-16 Selected from the group consisting of aryl groups or alkyl groups, Me is a metal derived from Group I (alkali), Group II (alkaline earth elements, or zinc), or Group III (e.g., aluminum) of the periodic table, and R 1 C 1-6 These are alkylene groups, arylene groups, arylalkylene groups, or arene-bisalkylene linkage groups.

[0057] Examples of metal salts of organic phosphinites, phosphinic acids, or diphosphinic acids include, more specifically, alkali salts, magnesium salts, zinc salts, and aluminum salts of dimethylphosphinic acid, methylethylphosphinic acid, methylpropylphosphinic acid, methylhexylphosphinic acid, ethylphenylphosphinic acid, diethylphosphinic acid, ethane-1,2-dimethylphosphinic acid, ethane-1,2-diethylphosphinic acid, ethane-1,2-diphenylphosphinic acid, and butane-1,4-dimethylphosphinic acid, but are not particularly limited.

[0058] (phosphinato) Examples of phosphinates include aluminum diethyl phosphinate.

[0059] (Polyol phosphate alcohol) Examples of polyol phosphate alcohols include commercially available compounds such as bis(pentaerythritol phosphate alcohol)alkyl phosphonates (where the alkyl group has 1 to 4 carbon atoms) or (pentaerythritol phosphate alcohol) phosphites.

[0060] (Other nitrogen-containing organophosphorus compounds) As the organophosphorus compound (B), a nitrogen-containing organophosphorus compound may be used. A nitrogen-containing organophosphorus compound is defined as an organophosphorus compound that contains at least one N atom in its structural formula. Examples of nitrogen-containing organophosphorus compounds include phosphoramides, organophosphazenes (and their salts), phosphoramidites, phosphonamides, and phosphineamides.

[0061] As a phosphoramidate, compounds represented by the following structural formula (iv) are preferred:

[0062] [ka] In the above structural formula (iv), R is CH3 or CH2CH3, and n1 is 2 to 10. The compound represented by the above structural formula (iv) is described in detail in International Publication No. 2009 / 153034.

[0063] Organic phosphazenes (also known as iminophosphoranes or phosphinimides) and their salts (specifically, chlorides and fluorides) refer to compounds containing a phosphorus atom, which is covalently bonded to the nitrogen atom by a double bond and to three other atoms or radicals by single bonds. Specifically, these include bis(triphenylphosphine)iminium chloride, BEMP (2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine), BTPP ((tert-butylimino)tris-(pyrrolidino)phosphoran), and t-Bu-P4 (3-t-butylimino-1,1,1,5,5,5-hexakis(dimethylamino)-3{[tris(dimethylamino)phosphoranylidene]amino}-1λ 5 ,3λ 5 ,5λ 5 Examples include -1,4-triphosphazadiene. Among these, cyclic organic phosphazenes represented by the following structural formula (v) are preferred:

[0064] [ka] Here, in the above structural formula (v), m is between 3 and 20, and each Q group is one or more selected from the group consisting of a phosphate group, a phosphorus atom, an aryloxy group that does not contain a halogen atom, or an alkoxy group.

[0065] The compound represented by the above structural formula (v) is described in detail in International Publication No. 2009 / 055993.

[0066] A specific example of a cyclic organic phosphazene is the compound DPPPZ, represented by the following structural formula (vi) (wherein Ph represents a phenyl group):

[0067] [ka] (Hindered amine (C)) These foamed particles contain 1.0% to 10.0% by weight of hindered amine (C) based on 100% by weight of the total amount of polypropylene-based foamed particles. Having the above composition, these foamed particles have the advantage of providing foamed molded articles with excellent flame retardancy.

[0068] The foamed particles contain 1.0% to 10.0% by weight of hindered amine (C) per 100% by weight of the total amount of polypropylene foamed particles, preferably 2.0% to 8.0% by weight, more preferably 2.5% to 7.0% by weight, and even more preferably 3.0% to 6.0% by weight. When the foamed particles contain (i) more than 0.1% by weight of hindered amine (C), a foamed molded article with excellent non-ignition and self-extinguishing properties can be obtained, and when they contain 10.0% by weight or less, adhesion (blocking) between resin particles can be suppressed in the foaming process described later.

[0069] In this specification, hindered amine (C) refers to a hindered amine having an OR group directly substituted on the N atom (where R is a saturated or unsaturated hydrocarbyl group) (hereinafter sometimes referred to as an N-substituted hindered amine). In other words, in this specification, a hindered amine that does not have an OR group directly substituted on the N atom is not considered a hindered amine (C). Hindered amine (C) is not particularly limited as long as it is a hindered amine having an OR group directly substituted on the N atom (where R is a saturated or unsaturated hydrocarbyl group), and many known subclasses of hindered amines can be used. Hindered amine (C) may be a single hindered amine used alone, or two or more hindered amines may be used in combination.

[0070] In one embodiment of the present invention, the hindered amine (C) is preferably an N-substituted hindered amine containing a triazine component. The N-substituted hindered amine containing a triazine component (hereinafter sometimes referred to as a triazine skeleton-containing hindered amine) is not particularly limited, but (i) the compound of CAS number 191680-81-6 ((i-1) a product obtained by reacting the reaction product of peroxidized N-butyl-2,2,6,6-tetramethyl-4-piperidineamine with 2,4,6-trichloro-1,3,5-triazine with cyclohexane and the reaction product with N,N'-bis(3-aminopropyl)ethylenediamine, (i-2) 2,4-bis((1-cyclohexyloxy-2,2,6,6 It can also be said to be a reaction product of -tetramethylpiperidine-4-yl)butylamino)-6-chloro-S-triazine and N,N'-bis(3-aminopropyl)ethylenediamine, and is preferably (i-3)N,N',N'''-tris{2,4-bis[(1-hydrocarbyloxy-2,2,6,6-tetramethylpiperidine-4-yl)alkylamino]-s-triazine-6-yl}-3,3'-ethylenediiminodipropylamine), or (ii) bis(1-undecaneoxy-2,2,6,6-tetramethylpiperidine-4-yl)carbonate. In addition, isomers of these or crosslinked derivatives can also be used. Triazine skeleton-containing hindered amines are described in detail on page 2, line 32 to page 4, line 6 of European Patent No. 0889085.

[0071] Commercially available hindered amines containing a triazine skeleton can also be suitably used. Examples of commercially available hindered amines containing a triazine skeleton include BASF's FLAMSTAB® NOR116 (compound with CAS number 191680-81-6), CLARIANT's HOSTAVIN® NOW XP, and ADEKA's ADEKA STAB LA-81 (bis(1-undecaneoxy-2,2,6,6-tetramethylpiperidine-4-yl)carbonate).

[0072] In one embodiment of the present invention, the hindered amine (C) may be a compound represented by the following structural formula (vii):

[0073] [ka] In the above structural formula (vii), G 1 and G 2 Independently, C 1-8 Alkyl alkyl group, or pentamethylene; Z 1 and Z 2 These are either methyl groups or Z 1 and Z 2 They together form a bonding component, which may be additionally substituted with an ester group, ether group, amide group, amino group, carboxyl group or urethane group; and E is C 1-8 Alkoxy group, C 5-12 Cycloalkoxy group, C 7-15 Aralcooxy group, -OC(O)-C 1-18 Alkyl group, or -OT-(OH) b It is a base; here T is C 1-18 Alkylene chain, C 5-18 Cycloalkylene chain or C 5-18 Cycloalkenylene chain, phenyl group, or C 1-4 C substituted with alkyl-substituted phenyl groups 1-4 It is an alkylene chain; b is 1 to 3 and less than or equal to the number of carbon atoms in T; and when b is 2 or 3, each hydroxyl group is linked to a different carbon atom of T.

[0074] The compound represented by the above structural formula (vii) is described in detail in European Patent No. 2225318, and more specifically, is illustrated on pages 5, line 35 to page 25, line 48 of European Patent No. 2225318.

[0075] In one embodiment of the present invention, the hindered amine (C) may be a compound represented by the following structural formula (viii):

[0076] [ka] In the above structural formula (viii), R is either a hydrogen atom or a methyl group, and R 1 C 1-18 Alkyl alkyl group, C 2-18 Alkenyl group, C 2-18 Alkynyl group, C 5-12 Cycloalkyl groups, C 5-8 Cycloalkenyl group, C 6-10 Aryl group and C 7-9 It is a group selected from the group consisting of aralkyl groups.

[0077] More specifically, the compound represented by the above structural formula (viii) is illustrated in pages 33 to 8, line 58 of European Patent No. 0309402.

[0078] In one embodiment of the present invention, the hindered amine (C) may be a compound represented by the following structural formula (ix):

[0079] [ka] In the above structural formula (ix), E, ​​k, Y, W, R1-R7 and G1-G4 are as defined in U.S. Patent No. 8,598,369.

[0080] More specifically, the compound represented by the above structural formula (ix) is illustrated in Examples 1 to 12 and Tables 1 to 5 of U.S. Patent No. 8,598,369.

[0081] <Ratio of each component in foamed particles> (Ratio of hindered amine (C) to organophosphorus compound (B)) In this specification, the ratio of hindered amine (C) to organophosphorus compound (B) (hereinafter referred to as the ratio (B) / (C)) means the ratio of the weight of hindered amine (C) contained in the foamed particle to the weight of organophosphorus compound (B) contained in the foamed particle. In these foamed particles, the ratio (B) / (C) is not particularly limited.

[0082] In one embodiment of the present invention, the ratio (B) / (C) cannot be defined in general terms as it varies depending on the type of organophosphorus compound (B) and hindered amine (C) contained in the foam particles, but it is preferably 1.0 to 20.0, more preferably 2.0 to 10.0, and even more preferably 3.0 to 5.0. When the ratio (B) / (C) is 1.0 to 20.0, the resulting foam molded article has excellent flame retardancy and can suppress ignition of surrounding combustible materials due to the generation of burning particles during combustion (i.e., it has excellent self-extinguishing properties), and there is no risk of impairing the various physical properties (mechanical properties, buffering properties, etc.) of the foam molded article.

[0083] (Ratio of the total amount of organophosphorus compounds (B) and hindered amines (C) to polypropylene resin (A)) In this specification, the ratio of the total amount of organophosphorus compound (B) and hindered amine (C) to the polypropylene resin (A) (hereinafter referred to as the ratio (A) / {(B)+(C)}) means the ratio of the weight of the polypropylene resin (A) contained in the foamed particles to the total weight of the organophosphorus compound (B) and hindered amine (C) contained in the foamed particles. In the foamed particles, the ratio (A) / {(B)+(C)} is not particularly limited.

[0084] In one embodiment of the present invention, the ratio (A) / {(B)+(C)} is preferably 1 to 10, more preferably 1 to 7, and even more preferably 1 to 5. When the ratio (A) / {(B)+(C)} in the foamed particles is (i) 10 or less, the resulting foamed molded article has better flame retardancy. Also, when it is 1 or more, the resulting foamed molded article has better surface aesthetics.

[0085] (Other additives) In addition to organophosphorus compounds and hindered amines, these foamed particles may optionally contain other additives as long as they do not impair the effects of the present invention. Examples of other additives include antioxidants, UV light absorbers, peroxide scavengers, inorganic nucleating agents, organic nucleating agents, water-absorbing substances, antistatic agents, antioxidants, light stabilizers, crystal nucleating agents, conductive agents, lubricants, fillers, carbon black, and powdered activated carbon. Such other additives may be added directly to the blend or polypropylene resin composition described later when manufacturing the resin particles in the production of these foamed particles, or they may be pre-mixed into a masterbatch containing the additives at a high concentration in another resin, and the resulting masterbatch resin may be added to the blend or polypropylene resin composition. A polypropylene resin is preferred as the resin used to produce the masterbatch resin.

[0086] Examples of antioxidants include alkylated monophenols, alkylthiomethylphenols, hydroquinones and alkylated hydroquinones, tocopherols, hydroxylated thiodiphenyl ethers, alkylidenebisphenols, oxygen-containing benzyl compounds, nitrogen-containing benzyl compounds, sulfur-containing benzyl compounds, hydroxybenzylated malonates, aromatic hydroxybenzyl compounds, acylaminophenols, and amides and esters of hydroxyphenylpropionic acid. These antioxidants may be used individually or in combination of two or more types.

[0087] The antioxidant content in these foamed particles is preferably 0.03% to 1.00% by weight, more preferably 0.05% to 0.70% by weight, and even more preferably 0.10% to 0.50% by weight, based on 100% by weight of the total amount of polypropylene foamed particles, in order to suppress the degradation of the resulting foamed molded product at high temperatures (e.g., around 110°C), and as a result, to maintain flame retardancy for a longer period.

[0088] Examples of UV light absorbers include benzotriazole, benzophenone, benzoic acid esters, nickel complexes, hindered amines that do not have an OR group directly linked to the N atom (not included in the hindered amine (C) of the present invention), and oxamide. These UV light absorbers may be used individually or in combination of two or more types.

[0089] The amount of UV light absorber in these foamed particles is preferably 0.01% to 1.00% by weight, more preferably 0.05% to 0.50% by weight, and even more preferably 0.10% to 0.30% by weight, based on 100% by weight of the total amount of polypropylene foamed particles.

[0090] Examples of inorganic nucleating agents include talc, titanium dioxide, silica (silicon dioxide), silicates, alumina, diatomaceous earth, calcium carbonate, magnesium oxide, magnesium carbonate, magnesium sulfate, calcium phosphate, feldspar apatite, and barium sulfate. Examples of silicates include talc, magnesium silicate, kaolin, halloysite, deckite, aluminum silicate, and zeolite. These inorganic nucleating agents may be used individually or in combination of two or more types.

[0091] From the viewpoint of uniformity of average cell diameter, the content of the inorganic nucleating agent in these foamed particles is preferably 0.005% to 3.000% by weight, more preferably 0.010% to 2.000% by weight, even more preferably 0.030% to 1.000% by weight, and particularly preferably 0.030% to 0.500% by weight, based on 100% by weight of the total amount of polypropylene foamed particles. In particular, by setting the inorganic nucleating agent content in these foamed particles to 0.030% to 0.500% by weight, it is possible to provide a foamed molded article with a uniform average cell diameter and superior flame retardancy.

[0092] Examples of organic nucleating agents include monocarboxylic acids or polycarboxylic acids (e.g., adipic acid or diphenylacetic acid) and their salts, ionic copolymers, etc. These organic nucleating agents may be used individually or in combination of two or more types.

[0093] From the viewpoint of uniformity of average bubble diameter, the content of the organic nucleating agent in these foamed particles is preferably 0.005% to 2.000% by weight, more preferably 0.010% to 1.000% by weight, and most preferably 0.030% to 0.500% by weight, based on 100% by weight of the total amount of polypropylene foamed particles.

[0094] Examples of absorbent substances include glycerin, diglycerin, polyethylene glycol, C12-C18 fatty alcohols (e.g., pentaerythritol, cetyl alcohol, stearyl alcohol), melamine, isocyanuric acid, melamine-isocyanuric acid condensate, and zinc borate. These absorbent substances may be used individually or in combination of two or more.

[0095] Among these, glycerin and polyethylene glycol are preferred because they do not promote the refinement of the average bubble diameter of the foamed particles and have good affinity with polypropylene resin (A).

[0096] In these foamed particles, the content of the water-absorbing substance is preferably 0.01% to 1.00% by weight, more preferably 0.05% to 0.70% by weight, and even more preferably 0.10% to 0.60% by weight, based on 100% by weight of the total amount of polypropylene foamed particles, in order to efficiently obtain foamed particles with low density (e.g., 40.0 g / L or less). When the content of the water-absorbing substance is (i) 0.01% by weight or more, the foaming effect of the water-absorbing substance can be sufficiently obtained, and (ii) when it is 1.00% by weight or less, there is no risk of the foamed particles shrinking excessively. When creating foamed particles with relatively high density (e.g., density greater than 40.0 g / L and 400.0 g / L or less), foamed particles can be efficiently obtained without adding water-absorbing substances.

[0097] Examples of lubricants include fatty acid esters, polyethylene wax (which may optionally be partially saponified), zinc stearate, glycerol esters, and alkaline earth metal soaps. These lubricants may be used individually or in combination of two or more types.

[0098] The lubricant content in these foamed particles is preferably 0.01% to 1.00% by weight, more preferably 0.05% to 0.50% by weight, and even more preferably 0.10% to 0.30% by weight, based on 100% by weight of the total amount of polypropylene foamed particles, as this can improve the dispersibility of other additives.

[0099] Examples of fillers include silicate, glass fiber, kaolin, wood powder, graphite, graphene, and cellulose nanofiber. These fillers may be used individually or in combination of two or more types.

[0100] The filler content in these foamed particles is preferably 0.01% to 10.00% by weight, more preferably 0.05% to 7.00% by weight, and even more preferably 0.10% to 5.00% by weight, based on 100% by weight of the total amount of these foamed particles.

[0101] The foamed particles may further contain pigments such as carbon black and graphite to color the resulting foamed molded body gray or black. From the viewpoint of not impairing flame retardancy and ensuring uniform coloring, the carbon black content in the foamed particles is preferably 0.01% to 6.00% by weight, more preferably 0.30% to 4.00% by weight, and even more preferably 0.50% to 3.00% by weight, based on 100% by weight of the total amount of the foamed particles.

[0102] The foamed particles may further contain powdered activated carbon to further improve the flame retardancy of the resulting foamed molded article. The powdered activated carbon content in the foamed particles is preferably 0.8% to 2.8% by weight, and more preferably 1.0% to 2.5% by weight, based on 100% by weight of the total amount of the foamed particles.

[0103] <Physical properties of polypropylene foam particles> (Average bubble diameter) The average bubble diameter of the foamed particles is not particularly limited, but is preferably 150 μm to 600 μm, more preferably 180 μm to 450 μm, and even more preferably 200 μm to 400 μm. When the average bubble diameter of the foamed particles is (i) 150 μm or more, a foamed molded article with excellent surface beauty can be obtained. When it is (ii) 600 μm or less, the secondary foaming properties during in-mold foaming of the foamed particles are good, and a foamed molded article with excellent surface beauty can be obtained. The average bubble diameter of the foamed particles can also be said to be the cell diameter of the foamed particles.

[0104] In this specification, the method for measuring the average bubble diameter of foamed particles is as follows (1) to (5): (1) Using a razor (for example, a high-stainless double-edged razor manufactured by Feather Corporation), the foamed particle is cut so as to pass through the center of the foamed particle; (2) The cut surface of the obtained foamed particle is observed at a magnification of 50x using an optical microscope (VHX-5000 manufactured by Keyence Corporation); (3) A straight line is drawn in the image obtained from the observation, passing through the center or approximate center of the cut surface of the foamed particle; (4) (4-1) The number of bubbles n present on the straight line is measured, and (4-2) The length of the line segment cut off from the straight line at the intersection of the straight line and the surface of the foamed particle is measured and defined as the foamed particle diameter L; (5) The average bubble diameter of the foamed particle is calculated using the following formula: Average bubble diameter (μm) = L / n.

[0105] (High-temperature heat of fusion for foamed particles) The high-temperature heat of fusion of the foam particles is preferably 5.0 J / g to 25.0 J / g, more preferably 8.0 J / g to 22.0 J / g, and even more preferably 10.0 J / g to 20.0 J / g. When the high-temperature heat of fusion of the foam particles is (i) 5.0 J / g or more, the occurrence of sink marks on the surface of the foam molded article and dimensional shrinkage during in-mold foam molding can be suppressed, and when it is 25.0 J / g or less, a foam molded article with excellent internal fusion properties and a smooth surface can be obtained. The high-temperature heat of fusion can also be called the high-temperature peak heat of fusion.

[0106] In this specification, the high-temperature heat of fusion of foamed particles is a value measured by the following procedure (1) to (5): (1) Weigh out approximately 5 mg of foamed particles; (2) Heat the weighed foamed particles from 10°C to 190°C at a heating rate of 10°C / min to melt the foamed particles; (3) In the DSC curve of the foamed particles obtained in the process of (2), draw a straight line connecting the point representing the temperature before the start of melting and the point representing the temperature after the end of melting to create a baseline; (4) Draw a straight line perpendicular to the X-axis passing through the high-temperature melting peak or the maximum point between the hottest melting peak and the adjacent melting peak; (5) The amount of heat (J / g) calculated from the high-temperature region enclosed by the baseline, the straight line passing through the maximum point, and the DSC curve is defined as the high-temperature heat of fusion of the foamed particles.

[0107] (Particle weight of foamed particles) The particle weight of the foam particles (the weight per foam particle) is not particularly limited, but from the viewpoint of filling into the molding die and the surface beauty of the resulting foam molded product, it is preferably 0.5 mg to 10.0 mg per foam particle, more preferably 0.5 mg to 5.0 mg, and even more preferably 0.5 mg to 2.0 mg.

[0108] In this specification, the particle weight of foam particles (the weight per foam particle) can be measured, for example, by the following procedure (1) to (5): (1) Using an electronic balance, measure the weight of 100 randomly sampled foam particles; (2) Calculate the particle weight per foam particle based on the following formula: The weight of one foamed particle (mg) = (weight of 100 foamed particles (mg)) / 100.

[0109] A foamed particle according to another embodiment of the present invention may also be configured as follows: a polypropylene foamed particle comprising 100 parts by weight of a polypropylene resin (A), more than 10.0 parts by weight and 20.0 parts by weight or less of an organophosphorus compound (B), and 1.0 to 10.0 parts by weight of a hindered amine (C).

[0110] [3. Method for producing polypropylene foam particles] A method for producing polypropylene foam particles according to one embodiment of the present invention includes a dispersion step of dispersing polypropylene resin particles, an aqueous dispersion medium, and a foaming agent in a container, and a release step of releasing the dispersion obtained in the dispersion step into a region with a pressure lower than the pressure inside the container, wherein the polypropylene resin particles contain, based on 100% by weight of the total amount of polypropylene resin particles, more than 10.0% by weight and 20.0% by weight or less of an organophosphorus compound (B) and 1.0% to 10.0% by weight of a hindered amine (C).

[0111] In this specification, "a method for producing polypropylene-based foamed particles according to one embodiment of the present invention" may be referred to as "this manufacturing method."

[0112] (granulation process) This manufacturing method may include a granulation step for preparing polypropylene resin particles before the foaming step. In this specification, "polypropylene resin particles" may be referred to as "resin particles."

[0113] The granulation process in this manufacturing method is not particularly limited as long as it can produce resin particles containing more than 10.0% by weight and 20.0% by weight or less of an organophosphorus compound (B) and 1.0% to 10.0% by weight of a hindered amine (C) based on 100% by weight of the total amount of polypropylene resin particles. For example, a method using an extruder can be used. Specifically, resin particles can be produced by the following methods (1) to (5): (1) Blend a predetermined amount of polypropylene resin (A), an organophosphorus compound (B), a hindered amine (C), and other additives as needed to produce a blend; (2) Put the blend into an extruder and melt-knead it to prepare a polypropylene resin composition; (3) Extrude the polypropylene resin composition through a die provided in the extruder; (4) Solidify the extruded polypropylene resin composition by cooling it by passing it through water or the like; (5) Then, cut the solidified polypropylene resin composition with a cutter into desired shapes such as cylindrical, elliptical, spherical, cubic, or rectangular parallelepiped to obtain polypropylene resin particles. Alternatively, in (3), the melt-kneaded polypropylene resin composition may be directly extruded into water through a die provided in the extruder, and immediately after extrusion, the polypropylene resin composition may be cut into particle shapes, cooled, and solidified to obtain resin particles. In this way, by melting and kneading the blended materials, more uniform resin particles can be obtained.

[0114] Furthermore, the ratio of the amounts of polypropylene resin (A), organophosphorus compound (B), and hindered amine (C) contained in the resin particles is the same as the ratio of the amounts of polypropylene resin (A), organophosphorus compound (B), and hindered amine (C) in the blend prepared in step (1), and can also be said to be the same as the ratio of the amounts of polypropylene resin (A), organophosphorus compound (B), and hindered amine (C) contained in the foamed particles. Therefore, the descriptions in the above sections <Polypropylene resin (A)>, <Organophosphorus compound (B)>, and <Hindered amine (C)> can be appropriately applied to the characteristics of each component of polypropylene resin (A), organophosphorus compound (B), and hindered amine (C) in the resin particles.

[0115] Furthermore, in order to more uniformly disperse the organophosphorus compound (B) and hindered amine (C) in the resin particles, a mixture may be prepared by pre-melting and kneading the organophosphorus compound (B) and hindered amine (C) in an extruder. Resin particles can also be prepared by melting and kneading this mixture with polypropylene resin (A) and, if necessary, other additives.

[0116] (Physical properties of polypropylene resin particles) (Melting point of resin particles) The melting point of the resin particles is not particularly limited, but is preferably 122.0°C to 159.0°C, more preferably 127.0°C to 157.0°C, more preferably 132.0°C to 151.0°C, more preferably 135.0°C to 148.0°C, even more preferably 136.0°C to 145.0°C, and particularly preferably 138.0°C to 144.0°C. When the melting point of the resin particles is (i) 122.0°C or higher, a foamed molded article with excellent dimensional stability at high temperatures can be obtained, and when it is 159.0°C or lower, the foamed molded article can be foamed in a mold at a low water vapor pressure.

[0117] In this specification, the melting point of the resin particles is a value obtained by measurement using differential scanning calorimetry (hereinafter referred to as the "DSC method"). The specific operating procedure is as follows: (1) The resin particles are melted by raising the temperature of 5 mg to 6 mg of resin particles from 40.0 °C to 220.0 °C at a heating rate of 10.0 °C / min; (2) The molten resin particles are then crystallized by lowering the temperature from 220.0 °C to 40.0 °C at a cooling rate of 10 °C / min; (3) The crystallized resin particles are then further heated from 40.0 °C to 220.0 °C at a heating rate of 10 °C / min. The temperature of the peak (melting peak) of the DSC curve of the resin particles obtained during the second heating (i.e., at (3)) can be determined as the melting point of the resin particles. Furthermore, if multiple peaks (melting peaks) exist in the DSC curve of the resin particles obtained during the second heating cycle using the method described above, the temperature of the peak with the largest heat of fusion (melting peak) is defined as the melting point of the resin particles. As a differential scanning calorimeter, for example, the DSC6200 model manufactured by Seiko Instruments Inc. can be used.

[0118] (Dispersion process) The dispersion process can also be described as the process of preparing a dispersion in which resin particles, a foaming agent, and, if necessary, a dispersant and / or a dispersion aid are dispersed in an aqueous dispersion medium.

[0119] The container is not particularly limited, but it is preferable that it be able to withstand the foaming temperature and pressure described later. For example, a pressure-resistant container is preferred, and an autoclave-type pressure-resistant container is more preferable.

[0120] The aqueous dispersion medium is not particularly limited, as long as it can uniformly disperse resin particles, foaming agents, etc. Examples of aqueous dispersion mediums include (a) dispersion mediums obtained by adding methanol, ethanol, ethylene glycol, glycerin, etc. to water, and (b) tap water and industrial water. In order to enable stable production of foaming particles, it is preferable to use pure water and ultrapure water such as RO water (water purified by reverse osmosis membrane method), distilled water, and deionized water (water purified by ion exchange resin) as the aqueous dispersion medium.

[0121] The amount of aqueous dispersion medium used is not particularly limited, but 100 to 500 parts by weight is preferred per 100 parts by weight of resin particles. (a) When the amount of aqueous dispersion medium used is 100 parts by weight or more, there is no risk of the stability of the dispersion being reduced (in other words, the dispersion of resin particles will be good), and (b) when the amount used is 500 parts by weight or less, there is no risk of productivity being reduced.

[0122] Examples of blowing agents include (a) (a-1) inorganic gases such as nitrogen, carbon dioxide, and air (a mixture of oxygen, nitrogen, and carbon dioxide), and (a-2) water; and (b) (b-1) saturated hydrocarbons having 3 to 5 carbon atoms such as propane, n-butane, isobutane, n-pentane, isopentane, and neopentane; (b-2) ethers such as dimethyl ether, diethyl ether, and methyl ethyl ether; and (b-3) halogenated hydrocarbons such as monochloromethane, dichloromethane, and dichlorodifluoroethane. At least one type of blowing agent selected from the group consisting of the inorganic and organic blowing agents described above can be used. When using a mixture of two or more blowing agents, the mixing ratio may be adjusted as appropriate depending on the purpose. From the viewpoint of environmental impact and blowing power, inorganic blowing agents are preferred among the blowing agents described above. Furthermore, because the blowing agent has a moderately high plasticizing effect and easily improves the foaming properties of the foamed particles in the production of these foamed particles, it is more preferable that the blowing agent be an inorganic blowing agent containing carbon dioxide, and even more preferable that it be carbon dioxide.

[0123] The amount of foaming agent used is not particularly limited and should be used appropriately depending on (a) the type of foaming agent and / or (b) the desired foaming ratio of the foamed particles. The amount of foaming agent used is preferably 1 to 10,000 parts by weight, more preferably 1 to 5,000 parts by weight, and even more preferably 1 to 1,000 parts by weight per 100 parts by weight of resin particles. When the amount of foaming agent used is 1 part by weight or more per 100 parts by weight of resin particles, foamed particles with a suitable density can be obtained. On the other hand, when the amount of foaming agent used is 10,000 parts by weight or less per 100 parts by weight of resin particles, the effect corresponding to the amount of foaming agent used is obtained, so there is no economic waste. The amount of foaming agent used may be, for example, 1 to 100 parts by weight or 1 to 10 parts by weight per 100 parts by weight of resin particles.

[0124] When water is used as a foaming agent, the water in the dispersion in the container can be used as the foaming agent. Specifically, when using water in the dispersion as a foaming agent, it is preferable to include a water-absorbing substance in the resin particles beforehand. This makes it easier for the resin particles to absorb the water in the dispersion in the container, and as a result, it becomes easier to use water as a foaming agent.

[0125] In this method for producing foamed particles, it is preferable to use a dispersant. Using a dispersant has the advantage of reducing adhesion between resin particles (sometimes referred to as blocking) and enabling the stable production of foamed particles. Examples of dispersants include inorganic substances such as tricalcium phosphate, trimagnesium phosphate, basic magnesium carbonate, calcium carbonate, barium sulfate, kaolin, talc, clay, aluminum oxide, titanium oxide, and aluminum hydroxide. One of these dispersants may be used alone, or two or more may be used in mixture. Furthermore, when using a mixture of two or more dispersants, the mixing ratio may be appropriately adjusted depending on the purpose.

[0126] The amount of dispersant used in the dispersion in one embodiment of the present invention is preferably 0.01 to 3.00 parts by weight, more preferably 0.05 to 2.00 parts by weight, and even more preferably 0.10 to 1.50 parts by weight, per 100 parts by weight of resin particles. When the amount of dispersant used is (a) 0.01 parts by weight or more, there is no risk of causing poor dispersion of resin particles, and (b) when the amount is 3.00 parts by weight or less, there is no risk of causing poor fusion between foam particles during in-molding foam molding using the resulting foam particles.

[0127] In this method for producing foamed particles, it is preferable to use a dispersion aid to (a) improve the effect of reducing adhesion between resin particles, and / or (b) improve the stability of the dispersion in the container. Examples of dispersion aids include anionic surfactants. Examples of anionic surfactants include sodium alkylbenzenesulfonates such as sodium dodecylbenzenesulfonate (DBS), sodium alkanesulfonates, sodium alkylsulfonates, sodium alkyldiphenyl ether disulfonates, and sodium α-olefin sulfonates. One of these dispersion aids may be used alone, or two or more may be used in combination. When two or more dispersion aids are used in combination, the mixing ratio may be appropriately adjusted depending on the purpose.

[0128] The amount of dispersion aid used in the dispersion liquid in one embodiment of the present invention is preferably 0.001 to 0.500 parts by weight, more preferably 0.001 to 0.200 parts by weight, and even more preferably 0.010 to 0.200 parts by weight, per 100 parts by weight of resin particles. When the amount of dispersion aid used is within the above range, there is no risk of causing poor dispersion of the resin particles.

[0129] When the stability of the dispersion decreases, multiple resin particles may adhere to each other or form clumps in the container. As a result, (i) adhered foam particles may be obtained, (ii) clumps of resin particles may remain in the container, preventing the production of foam particles, or (iii) the productivity of foam particles may decrease.

[0130] (i) the adhesion between resin particles can be further reduced, allowing for more stable production of foamed particles, and (ii) the stability of the dispersion in the container can be further enhanced. Therefore, in this method for producing foamed particles, it is preferable to use a combination of tricalcium phosphate and kaolin as a dispersant, and sodium dodecylbenzenesulfonate as a dispersion aid. In other words, it is preferable that the dispersion prepared in the dispersion step of this method for producing foamed particles contains tricalcium phosphate, kaolin, and sodium dodecylbenzenesulfonate.

[0131] (Heating-pressure boosting process and holding process) The present manufacturing method preferably further includes, after the dispersion step and before the release step, (i) a heating-pressure step in which the temperature inside the container is raised to a constant temperature and the pressure inside the container is raised to a constant pressure, and (ii) a holding step in which the temperature and pressure inside the container are maintained at a constant temperature and a constant pressure. The holding step is preferably performed after the heating-pressure step. In this specification, (a) the constant temperature in the heating-pressure step and the holding step may be referred to as the foaming temperature, and (b) the constant pressure may be referred to as the foaming pressure.

[0132] The foaming temperature varies depending on the type of polypropylene resin (A), organophosphorus compound (B), hindered amine (C) contained in the resin particles, the type of foaming agent, etc., so it cannot be specified in general terms. The foaming temperature is preferably (i) a mixture of (a) a polypropylene resin (A), an organophosphorus compound (B), and a hindered amine (C), (b) a polypropylene resin composition, or (c) resin particles between -20.0°C and +20.0°C, more preferably (ii) a mixture of (a) a polypropylene resin (A), an organophosphorus compound (B), and a hindered amine (C), (b) a polypropylene resin composition, or (c) resin particles between -10.0°C and +15.0°C, and even more preferably (iii) a mixture of (a) a polypropylene resin (A), an organophosphorus compound (B), and a hindered amine (C), (b) a polypropylene resin composition, or (c) resin particles between -5.0°C and +13.0°C.

[0133] The foaming pressure is preferably 0.5 MPa (gauge pressure) to 10.0 MPa (gauge pressure), more preferably 0.6 MPa (gauge pressure) to 5.0 MPa (gauge pressure), and even more preferably 0.6 MPa (gauge pressure) to 2.5 MPa (gauge pressure). If the foaming pressure is 0.5 MPa (gauge pressure) or higher, foamed particles with a suitable density can be obtained.

[0134] In the holding process, the time for holding the dispersion in the container at or near the foaming temperature and pressure (holding time) is not particularly limited. The holding time is preferably 10 to 60 minutes, more preferably 12 to 50 minutes, and even more preferably 15 to 40 minutes. When the holding time is 10 minutes or more, a sufficient amount of unmelted crystals (crystals of polypropylene resin) are present, which has the advantage of reducing the shrinkage of the resulting foamed particles and / or the increase in the open-cell ratio. On the other hand, when the holding time is 60 minutes or less, there is no excessive amount of unmelted crystals, which has the advantage of allowing the foamed particles to be molded at a lower molding temperature.

[0135] (Release process) The release step is preferably performed (a) after the heating-pressure step if the heating-pressure step is performed but the holding step is not, or (b) after the holding step if both the heating-pressure step and the holding step are performed. The release step allows the resin particles to foam, resulting in foamed particles. The release step can also be described as a step of opening one end of the container and releasing the dispersion liquid inside the container into a region (space) with a pressure lower than the foaming pressure (i.e., the pressure inside the container).

[0136] In the release process, the "region with a pressure lower than the foaming pressure" refers to the "region under a pressure lower than the foaming pressure" or the "space under a pressure lower than the foaming pressure," and can also be described as "an atmosphere with a pressure lower than the foaming pressure." The region with a pressure lower than the foaming pressure is not particularly limited as long as the pressure is lower than the foaming pressure; for example, it may be a region under atmospheric pressure.

[0137] In the discharge process, when discharging the dispersion into a region with a pressure lower than the foaming pressure, the dispersion can be discharged through an open orifice with a diameter of 1 mm to 5 mm for purposes such as adjusting the flow rate of the dispersion and reducing variations in the foaming ratio of the resulting foamed particles. Furthermore, to improve foaming properties, the low-pressure region (space) may be filled with saturated water vapor.

[0138] (Foaming process) The process from dispersion to release is sometimes referred to as the foaming process. Furthermore, the process of producing foamed particles from resin particles in this manner is called the "single-stage foaming process," and the resulting foamed particles are called "single-stage foamed particles."

[0139] (Two-stage foaming process) Incidentally, in order to obtain foamed particles with a high foaming ratio, one method is to use a large amount of inorganic foaming agent in the first foaming process (hereinafter referred to as Method 1). Furthermore, as an alternative to Method 1, it is also possible to obtain foamed particles with a relatively low foaming ratio (foaming ratio of approximately 2.0 to 35.0 times) in the first foaming process (first-stage foamed particles), and then foam the obtained first-stage foamed particles again to increase the foaming ratio (hereinafter referred to as Method 2).

[0140] As an example of Method 2, a method comprising the following steps in order is provided: (a1) producing one-stage foamed particles with a foaming ratio of 2.0 to 35.0 times in a one-stage foaming process; (a2) placing the one-stage foamed particles in a pressure vessel and pressurizing them with nitrogen, air, carbon dioxide, etc., at 0.2 MPa (gauge pressure) to 0.6 MPa (gauge pressure) to raise the pressure inside the one-stage foamed particles (hereinafter sometimes referred to as "internal pressure") above atmospheric pressure; (a3) ​​then heating the one-stage foamed particles with increased internal pressure using steam, etc., to further foam them. The process of increasing the foaming ratio of the one-stage foamed particles, as in Method 2, is called the "two-stage foaming process," and the polypropylene resin foamed particles obtained by the method of Method 2 are called "two-stage foamed particles."

[0141] In step (a3) ​​of the two-stage foaming process, it is preferable to adjust the pressure of the steam used to heat the first-stage foamed particles to 0.03 MPa (gauge pressure) to 0.20 MPa (gauge pressure), taking into consideration the foaming ratio of the second-stage foamed particles. When the steam pressure in the two-stage foaming process is 0.03 MPa (gauge pressure) or higher, the foaming ratio tends to improve, and when it is 0.20 MPa (gauge pressure) or lower, the possibility of the resulting second-stage foamed particles adhering to each other decreases. If the second-stage foamed particles adhere to each other, the resulting second-stage foamed particles may not be usable for subsequent in-mold foaming.

[0142] The internal pressure of the first-stage foamed particles, obtained by impregnating the first-stage foamed particles with nitrogen, air, carbon dioxide, etc., should be appropriately varied considering the foaming ratio of the second-stage foamed particles and the water vapor pressure of the second-stage foaming process. The internal pressure of the first-stage foamed particles is preferably 0.15 MPa (absolute pressure) to 0.60 MPa (absolute pressure), more preferably 0.20 MPa (absolute pressure) to 0.60 MPa (absolute pressure), and even more preferably 0.30 MPa (absolute pressure) to 0.60 MPa (absolute pressure). When the internal pressure of the first-stage foamed particles is 0.15 MPa (absolute pressure) or higher, high-pressure water vapor is not required to improve the foaming ratio, thus reducing the possibility of the second-stage foamed particles adhering together. When the internal pressure of the first-stage foamed particles is 0.6 MPa (absolute pressure) or lower, the possibility of the second-stage foamed particles becoming interconnected decreases. As a result, the possibility of a decrease in rigidity, such as compressive strength, of the final in-molded foamed article decreases. Note that "connecting bubbles" can also be called "connecting air bubbles".

[0143] [4. Polypropylene-based foamed molded articles] A polypropylene-based foamed molded article according to one embodiment of the present invention is a foamed molded article obtained by molding the foamed particles (for example, by in-mold foaming). In this specification, "a polypropylene-based foamed molded article according to one embodiment of the present invention" may be referred to as "the foamed molded article".

[0144] Because this foamed molded article has the above-described structure, it has the advantage of being highly flame-retardant.

[0145] (Flame retardancy of foamed molded material) In this specification, the flame retardancy of foamed molded articles is evaluated by the oxygen index and the UL94 “Vertical Combustion Foamed Material Test”.

[0146] (Oxygen index) The oxygen index is an indicator that represents the minimum oxygen concentration (volume %) required for a material (foamed molded product) to sustain combustion. Here, "sustaining combustion" means that the burning time of the ignited material is 180 seconds or less and the burning distance is 50 mm or less.

[0147] The foamed molded article preferably has an oxygen index of 26.0% or higher, more preferably 26.5% or higher, and even more preferably 27.0% or higher. A foamed molded article with an oxygen index of 26.0% or higher can be said to be a foamed molded article with excellent flame retardancy and also a foamed molded article with excellent non-ignition properties. Furthermore, since a foamed molded article with even better flame retardancy can be provided, a higher oxygen index is preferable, and although there is no particular upper limit to the oxygen index, it may be, for example, 45.0% or less, or 35.0% or less.

[0148] In this specification, the oxygen index is a value measured in accordance with JIS K7201 (Test method for flammability by oxygen index).

[0149] (UL94) The UL94 "Vertical Combustion Foam Material Test" test method is as follows (1) to (5): (1) The top of the test specimen (foam molded body) of the desired thickness (thickness (t) of the specimen (13 mm, 8 mm, or 5 mm) is fixed with a fixing clamp to hold the specimen vertically, and cotton wool is placed directly below it; (2) The flame of a gas burner is applied to the lower end of the held specimen for 10 seconds to cause combustion (first combustion); (3) The burning time and red-hot time of the specimen are measured (note that the flame application time (10 seconds) is not included in the burning time), and if combustion stops within 30 seconds, the flame of the gas burner is applied to the lower end of the specimen again for 10 seconds to cause combustion (second combustion); (4) The burning time and red-hot time of the specimen are measured again; (5) The procedure from (1) to (4) is repeated a total of 5 times with a different specimen, and the flame retardancy is evaluated according to the following evaluation criteria.

[0150] Evaluation Criteria [Fail (NG)]: During the first or second combustion, some samples continue to burn for more than 30 seconds, or burn up to the position of the fixing clamp; [V-2]: After the first flame contact, no samples continued to burn for more than 30 seconds. The total burning time after 10 flame applications for 5 samples is 250 seconds or less. There was no sample burning down to the position of the fixing clamp. After the second flame application, there were no samples where the sum of the burning time and the red-hot time was 250 seconds or more, In some test samples, particles from the sample that fall during combustion can ignite cotton wool placed below the sample; [V-1]: After both the first and second flame applications, none of the samples continued to burn for more than 30 seconds. The total burning time after 10 flame applications for 5 samples is 250 seconds or less. There was no sample burning down to the position of the fixing clamp. After the second flame application, there were no samples where the sum of the burning time and the red-hot time exceeded 250 seconds, and In all combustion cases, there were no instances where the cotton wool placed below the test sample ignited due to particles from the fallen test sample; [V-0]: After both the first and second flame applications, none of the samples continued to burn for more than 10 seconds. The total burning time after 10 flame applications for 5 samples was 50 seconds or less. There was no sample burning down to the position of the fixing clamp. After the second flame application, there were no samples where the sum of the burning time and the red-hot time was 30 seconds or more, and In all combustion tests, there were no instances where the cotton wool placed below the test sample ignited due to particles from the fallen test sample.

[0151] As described above, among the foamed molded articles that meet standard V-0, none of the samples burned for more than 10 seconds, and none of the samples had a sum of burning time and red-hot time of 30 seconds or more after flame contact. In other words, these molded articles have superior flame retardancy compared to foamed molded articles that satisfy only V-2 and / or V-1.

[0152] Furthermore, in molded bodies that satisfy V-0, the cotton wool placed below the test sample does not ignite due to particles from the fallen test sample during any combustion. In other words, even if flammable particles are generated during combustion, they are extinguished before reaching the cotton wool (flammable material), indicating that the molded body has excellent self-extinguishing properties.

[0153] In other words, a foamed molded article that satisfies V-0 has superior flame retardancy and self-extinguishing properties compared to a foamed molded article that satisfies only V-2 and / or V-1.

[0154] In this specification, a foamed molded article that satisfies the V-0 standard when its flame retardancy is measured and evaluated according to UL94 under all conditions of a test sample thickness of 13 mm, 8 mm, or 5 mm can be evaluated as a foamed molded article with excellent flame retardancy.

[0155] As described above, a foamed molded body can be determined to be a foamed molded body with excellent flame retardancy if it satisfies either (a) an oxygen index of 26.0% or higher, and / or (b) the standard V-0 under all conditions of a test sample thickness of 13 mm, 8 mm, or 5 mm. In other words, this foamed molded body satisfies (a) and / or (b) above. It is preferable that this foamed molded body satisfies both (a) and (b) above, as this results in a foamed molded body with even better flame retardancy.

[0156] (Density of foamed molded material) The density of the foamed molded article is preferably 15.0 g / L to 400.0 g / L. If the density of the molded article is 15.0 g / L or higher, there is an advantage in obtaining a foamed molded article that is free of shrinkage on the surface, smooth, and has excellent surface beauty. If the density is 400.0 g / L or lower, a sufficiently lightweight foamed molded article can be obtained. Furthermore, the density of the foamed molded article may be (I) 15.0 g / L to 92.0 g / L, or (II) greater than 92.0 g / L and 400.0 g / L or less. If the density of the foamed molded article is within the range of (I), a foamed molded article with superior lightness and cushioning properties can be obtained. Furthermore, if the density is within the range of (II), a foamed molded article with superior molded article strength, dimensional stability, and self-extinguishing properties can be obtained.

[0157] In this specification, the density of a foamed molded article is a value measured by following the following procedure (1) to (3): (1) Measure the length (mm) in the length direction (mm), width direction (mm), and thickness direction (mm) of the foamed molded article and calculate the volume V (L); (2) Measure the weight W (g) of the foamed molded article; (3) Calculate the density of the foamed molded article based on the following formula: Density of foamed molded article (g / L) = W / V.

[0158] <Method for manufacturing foamed molded products> The method for manufacturing this foamed molded article is not particularly limited, and known methods can be applied. Specific embodiments of the method for manufacturing this foamed molded article include, for example, a manufacturing method (in-mold foaming method) that includes (b1) to (b6) in order below, but is not limited to such a method: (b1) A mold consisting of a fixed mold that cannot be driven and a movable mold that can be driven is mounted on an in-mold foaming machine. Here, the fixed mold and the movable mold can be formed inside the fixed mold and the movable mold by driving the movable mold toward the fixed mold (this operation may be referred to as "mold closing"); (b2) Drive the movable mold toward the fixed mold so that a small gap (also called cracking) is formed between the fixed mold and the movable mold, so that the mold is not completely closed; (b3) Fill the molding space formed inside the fixed and mobile molds with foam particles, for example, through a filling machine; (b4) Drive the movable part so that the fixed part and the movable part are completely closed (i.e., completely closed); (b5) After preheating the mold with steam, the mold is heated in one direction and then in the other direction with steam, and then both sides of the mold are heated with steam to perform in-mold foam molding; (b6) The in-mold foamed product is removed from the mold and dried (for example, at 75°C) to obtain a foamed molded body.

[0159] In (b3) above, the following methods (b3-1) to (b3-4) can be listed as methods for filling the molding space with foamed particles: (b3-1) A method of filling a molded space with foamed particles (including the two-stage foamed particles described above, the same applies hereinafter) after pressurizing them with an inorganic gas in a container to impregnate the foamed particles with the inorganic gas and applying a predetermined internal pressure to the foamed particles; (b3-2) A method of filling a molding space with foamed particles and then compressing the mold so that the volume inside the mold is reduced by 10% to 75%; (b3-3) A method of compressing foamed particles with gas pressure and filling them into the molding space; (b3-4) A method for filling a molding space with foamed particles without any special pretreatment.

[0160] In the method for producing this foamed molded article, at least one inorganic gas selected from the group consisting of air, nitrogen, oxygen, carbon dioxide, helium, neon, argon, etc., can be used as the inorganic gas in method (b3-1) described above. Among these inorganic gases, air and / or carbon dioxide are preferred.

[0161] In the method for producing this foamed molded article, the internal pressure of the foamed particles in method (b3-1) is preferably 0.11 MPa (absolute pressure) to 0.40 MPa (absolute pressure), and preferably 0.13 MPa (absolute pressure) to 0.30 MPa (absolute pressure).

[0162] In the manufacturing method of this foamed molded product, the temperature inside the container when impregnating the foamed particles with inorganic gas in method (b3-1) is preferably 10°C to 90°C, and more preferably 40°C to 90°C.

[0163] In the methods described in (b3-2) and (b3-3) above, the recovery force of the foamed particles compressed by gas pressure is utilized in the subsequent step (b5) to fuse the foamed particles together.

[0164] One embodiment of the present invention may have the following configuration:

[0165] [1] Polypropylene foam particles comprising a polypropylene resin (A), an organophosphorus compound (B), and a hindered amine (C), wherein the polypropylene foam particles contain, with respect to 100% by weight of the total amount of the polypropylene foam particles, more than 10.0% by weight and 20.0% by weight or less of the organophosphorus compound (B), and 1.0% by weight to 10.0% by weight of the hindered amine (C).

[0166] [2] The polypropylene foam particle according to [1], wherein the organophosphorus compound (B) is a cyclic phosphonate.

[0167] [3] The polypropylene foam particle according to [2], wherein the cyclic phosphonate is a cyclic bisphosphonate.

[0168] [4] The polypropylene foam particle according to [3], wherein the cyclic bisphosphonate is pentaerythrityl diphosphonate.

[0169] [5] The polypropylene foam particle according to any one of [1] to [4], wherein the weight ratio of the hindered amine (C) to the organophosphorus compound (B) (ratio (B) / (C)) is 1.0 to 20.0.

[0170] [6] The polypropylene foam particle according to any one of [1] to [5], wherein the ratio of the total weight of the organophosphorus compound (B) and the hindered amine (C) to the polypropylene resin (A) (ratio (A) / {(B)+(C)}) is 1 to 10.

[0171] [7] Polypropylene foam particles according to any one of [1] to [6], having two melting peaks measured by differential scanning calorimeter and a high-temperature melting heat of 5.0 J / g to 25.0 J / g.

[0172] [8] Polypropylene foam particles according to any one of [1] to [7], wherein the MI of the polypropylene resin (A) is 3.00 g / 10 min to 30.00 g / 10 min.

[0173] [9] The polypropylene foamed particle according to any one of [1] to [8], wherein the polypropylene resin (A) is a random copolymer of propylene and a monomer other than propylene.

[0174]

[10] Polypropylene foamed particles as described in any one of [1] to [9], having an average bubble diameter of 180 μm to 450 μm.

[0175]

[11] Polypropylene foam particles as described in any one of [1] to

[10] , with a particle weight of 0.5 mg to 10.0 mg.

[0176] A polypropylene foamed molded article obtained by molding polypropylene foamed particles described in any one of [1] to

[11] .

[0177]

[13] The polypropylene foamed molded article according to

[12] , wherein the oxygen index of the foamed molded article measured in accordance with JIS K7201 is 26.0% or higher.

[0178]

[14] A polypropylene foam molded article according to

[12] or

[13] , having a density of 15.0 g / L to 92.0 g / L.

[0179]

[15] A polypropylene foam molded article according to

[12] or

[13] , having a density greater than 92.0 g / L and 400.0 g / L or less.

[0180]

[16] A method for producing polypropylene foamed particles, comprising: a dispersion step of dispersing polypropylene resin particles, an aqueous dispersion medium, and a foaming agent in a container; and a release step of releasing the dispersion obtained in the dispersion step into a region with a pressure lower than the pressure inside the container, wherein the polypropylene resin particles contain, based on 100% by weight of the total amount of the polypropylene resin particles, more than 10.0% by weight and 20.0% by weight or less of an organophosphorus compound (B) and 1.0% to 10.0% by weight of a hindered amine (C).

[0181]

[17] The method for producing polypropylene foamed particles according to

[16] , wherein the dispersion contains tricalcium phosphate, kaolin, and sodium dodecylbenzenesulfonate.

[0182]

[18] Polypropylene foam particles according to any one of [1] to

[11] , wherein the melting point of the polypropylene resin (A) is 125.0°C to 160.0°C.

[0183]

[19] The polypropylene foam particle according to any one of [1] to

[11] and

[18] , wherein the hindered amine (C) has an OR group directly substituted on the N atom.

[0184]

[20] The polypropylene foam particles according to any one of [1] to

[11] ,

[18] and

[19] , wherein the hindered amine (C) contains a triazine component.

[0185]

[21] Polypropylene foam particles according to any one of [1] to

[11] and

[18] to

[20] , wherein the inorganic nucleating agent is contained in an amount of 0.030% to 0.500% by weight per 100% by weight of the total amount of polypropylene foam particles.

[0186]

[22] Polypropylene foam particles according to any one of [1] to

[11] and

[18] to

[21] , wherein the hindered amine (C) is a compound of CAS number 191680-81-6 and / or bis(1-undecaneoxy-2,2,6,6-tetramethylpiperidine-4-yl)carbonate.

[0187] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Examples]

[0188] The present invention will be specifically described below with reference to examples, but the technical scope of the present invention is not limited by these examples.

[0189] 〔material〕 The substances used in the examples and comparative examples are shown below.

[0190] <Polypropylene resin (A)> Polypropylene (A1): Ethylene random polypropylene (ethylene / propylene random copolymer), MI = 7.00 g / 10 min, melting point 144°C, ethylene content 3.2% Polypropylene (A2): Ethylene random polypropylene (ethylene / propylene random copolymer), MI = 5.00 g / 10 min, melting point 143°C, ethylene content 3.5% Polypropylene (A3): Ethylene random polypropylene (ethylene / propylene random copolymer), MI = 4.00 g / 10 min, melting point 143°C, ethylene content 3.4% Polypropylene (A4): Ethylene random polypropylene (ethylene / propylene random copolymer), MI = 6.00 g / 10 min, melting point 143°C, ethylene content 3.4% <Organophosphorus compounds (B)> Pentaerythrityl diphosphonate: AFLAMMIT(registered trademark) PCO900, manufactured by Thor GmbH. <Hindered amine (C)> Compound with CAS number 191680-81-6: FLAMESTAB® NOR116, manufactured by BASF. <Other additives> (Inorganic nucleating agent) Talc: Hayashi Chemical Co., Ltd. Talc Powder PK-S (Antioxidant) BASF Irgafos 168 BASF Irganox 1010 (UV protection agent) BASF Tinuvin 622 <Foaming agent> Carbon dioxide: Manufactured by Air Water Inc.

[0191] <Dispersant> Kaolin: BASF ASP-170 Kaolin Tricalcium phosphate: Manufactured by Taihei Chemical Co., Ltd. <Dispersing agent> Sodium dodecylbenzenesulfonate: Kao Corporation DBS G-15 Furthermore, since the dispersants and dispersion aids are added to the dispersion liquid or pressure-resistant sealed container during the dispersion process described later, they either do not remain in the resin particles and foamed particles, or only remain in very small amounts. In addition, the carbon dioxide used as a blowing agent is released from the resulting foamed particles due to the high gas permeability of the foamed particles. Also, water, which can function as a foaming component, is released as vapor from the resulting foamed particles or evaporates when the foamed particles are dried. For these reasons, water, blowing agents, dispersants, and dispersion aids are not included in the calculation of the composition of the foamed particles.

[0192] [Measurement method] The evaluation methods used in the examples and comparative examples are described below.

[0193] (MI of polypropylene resin (A)) The molecular weight (MI) of polypropylene resin (A) was measured using an MI measuring instrument described in JIS K7210:1999, under the conditions of an orifice diameter of 2.0959 ± 0.005 mmφ, an orifice length of 8.000 ± 0.025 mm, a load of 2160 g, and a temperature of 230 ± 0.2 °C.

[0194] (Melting point of resin particles) The melting point of the resin particles was measured using a differential scanning calorimeter (Seiko Instruments Inc., DSC6200 model). The specific measurement method was as follows (1) to (3): (1) The resin particles were melted by raising the temperature of 5 mg to 6 mg of resin particles from 40.0 °C to 220.0 °C at a heating rate of 10.0 °C / min; (2) The molten resin particles were then crystallized by lowering the temperature from 220.0 °C to 40.0 °C at a cooling rate of 10.0 °C / min; (3) The crystallized resin particles were then further heated from 40.0 °C to 220.0 °C at a heating rate of 10 °C / min. The temperature of the peak (melting peak) of the DSC curve of the resin particles obtained during the second heating (i.e., at (3)) was defined as the melting point of the resin particles. Furthermore, if multiple peaks (melting peaks) exist in the DSC curve of the resin particles obtained during the second heating step using the method described above, the temperature of the peak with the largest heat of fusion (melting peak) was defined as the melting point of the resin particles.

[0195] (Measurement of the average bubble diameter of foamed particles) The method for measuring the average bubble diameter of foam particles was as follows (1) to (5): (1) Using a razor (Feather High Stainless Double-Edged), the foam particle was cut so as to pass through its center; (2) The resulting cut surface of the foam particle was observed at 50x magnification using an optical microscope (Keyence VHX-5000); (3) A straight line was drawn through the center or approximate center of the cut surface of the foam particle in the image obtained from the observation; (4) (4-1) The number of bubbles n present on the straight line was measured; (4-2) The length of the line segment cut off from the straight line at the intersection of the straight line and the surface of the foam particle was measured and defined as the foam particle diameter L; (5) The average bubble diameter of the foam particle was calculated using the following formula: Average bubble diameter (μm) = L / n.

[0196] (High-temperature heat of fusion for foamed particles) The high-temperature heat of fusion of the foamed particles was measured by the following procedure (1) to (5): (1) Approximately 5 mg of foamed particles were weighed out; (2) The temperature of the weighed foamed particles was increased from 10°C to 190°C at a heating rate of 10°C / min to melt the foamed particles; (3) In the DSC curve of the foamed particles obtained in the process of (2), a baseline was created by drawing a straight line connecting the point representing the temperature before the start of melting and the point representing the temperature after the end of melting; (4) A straight line passing through the maximum point between the high-temperature melting peak or the hottest melting peak and the adjacent melting peak was drawn perpendicular to the X-axis; (5) The amount of heat (J / g) calculated from the high-temperature region enclosed by the baseline, the straight line passing through the maximum point, and the DSC curve was taken as the high-temperature heat of fusion of the foamed particles.

[0197] (Density of foamed molded material) The method for measuring the density of the foamed molded body (foamed molded body density) was as follows: (1) The length (mm) in the length direction (mm), width direction (mm), and thickness direction (mm) of the foamed molded body was measured, and the volume V (L) of the foamed molded body was calculated; (2) The weight W (g) of the foamed molded body was measured; (3) The density of the foamed molded body was calculated based on the following formula: The density of a foamed molded product (g / L) = W / V.

[0198] (Flame retardancy of foamed molded material) The flame retardancy of the foamed molded material was measured and evaluated using the oxygen index (OI) and the UL94 “Vertical Combustion Foamed Material Test”.

[0199] (Oxygen index) The oxygen index of the foamed molded material was measured as follows: (1) A sample measuring 150 mm in length, 10 mm in width, and 10 mm in thickness was cut from the foamed molded material; (2) The oxygen index of the cut sample was measured in accordance with JIS K7201 (Test method for flammability by oxygen index).

[0200] (UL94 “Vertical Combustion Foamed Material Test”) The test method for UL94 “Vertical Combustion Foamed Material Test” was as follows (1) to (5): (1) A test specimen (sample) having specific dimensions (length 125 ± 5 mm × width 13 ± 0.5 mm) and a specific thickness (thickness (t) of the test specimen = 13 mm, 8 mm, or 5 mm) was cut from the foamed molded body; (2) The top of the cut test specimen was fixed with a fixing clamp to hold the test specimen vertically, and cotton wool was placed directly below it; (2) The held test (1) The lower end of the sample was exposed to the flame of a gas burner for 10 seconds to ignite it (first combustion); (2) The burning time and red-hot time of the test sample were measured, and if the combustion stopped within 30 seconds, the lower end of the test sample was exposed to the flame of the gas burner again for 10 seconds to ignite it (second combustion); (3) The burning time and red-hot time of the test sample were measured again; (4) The procedure from (1) to (4) was repeated a total of 5 times with a different test sample, and the flame retardancy was evaluated according to the following evaluation criteria.

[0201] Evaluation Criteria [Fail (NG)]: During the first or second combustion, some samples continue to burn for more than 30 seconds, or burn up to the position of the fixing clamp; [V-2]: After the first flame contact, no sample continued to burn for more than 30 seconds. The total burning time after 10 flame applications for 5 samples was 250 seconds or less. There was no sample burning down to the position of the fixing clamp. After the second flame application, there were no samples where the sum of the burning time and the red-hot time was 250 seconds or more, In some test samples, particles from the sample that fall during combustion can ignite cotton wool placed below the sample; [V-1]: After either the first or second flame application, no samples continued to burn for more than 30 seconds. The total burning time after 10 flame applications for 5 samples was 250 seconds or less. There was no sample burning down to the position of the fixing clamp. After the second flame application, there were no samples where the sum of the burning time and the red-hot time exceeded 250 seconds, and In all combustion tests, there were no instances where the cotton wool placed below the test sample ignited due to particles from the fallen test sample.

[0202] [V-0]: No samples continued to burn for more than 10 seconds after either the first or second flame application. The total burning time after 10 flame applications for the 5 samples was 50 seconds or less. There was no sample burning down to the position of the fixing clamp. After the second flame application, there were no samples where the sum of the burning time and the red-hot time was 30 seconds or more, and In all combustion tests, there were no instances where the cotton wool placed below the test sample ignited due to particles from the fallen test sample.

[0203] [Example 1] (Preparation of polypropylene resin particles) The blend was dry-blended so that, out of 100% by weight of the mixture, polypropylene resin (A2) constituted 83.6% by weight, organophosphorus compounds (B) 11.0% by weight, hindered amines (C) 5.0% by weight, and other additives totaling 0.4% by weight included the inorganic nucleating agent talcan powder PK-S, the antioxidants Irgafos 168 and Irganox 1010, and the UV inhibitor Tinuvin 622.

[0204] The resulting blend was fed into a twin-screw extruder [Shibaura Machinery, TEM26SX] and melt-kneaded at a resin temperature of 250°C. The melt-kneaded polypropylene resin composition was extruded in strand form through a die with a circular hole attached to the tip of the extruder. The extruded polypropylene resin composition was water-cooled and then cut with a cutter to obtain resin particles (granulation process). The melting point of the obtained resin particles was measured. The results are shown in Table 1.

[0205] (Preparation of polypropylene foamed particles (single-stage foamed particles)) 100 parts by weight of the obtained resin particles, 442 parts by weight of pure water, 1.1 parts by weight of tricalcium phosphate and 0.22 parts by weight of kaolin ASP-170 as dispersants, and 0.027 parts by weight of DBS as a dispersion aid were placed in a pressure-resistant sealed container. Then, while stirring the raw materials in the pressure-resistant sealed container, 2.1 parts by weight of carbon dioxide was introduced into the pressure-resistant sealed container as a foaming agent to prepare a dispersion (dispersion step). Next, the temperature inside the pressure-resistant sealed container was heated to a foaming temperature of 150.0°C. Then, carbon dioxide was further injected into the pressure-resistant sealed container, and the pressure inside the container was increased to a foaming pressure of 1.1 MPa (gauge pressure) (heating-pressure step). Next, the contents of the pressure-resistant sealed container were held at the aforementioned foaming temperature and pressure for 20 minutes (holding step). Then, the valve at the bottom of the sealed container was opened, and the dispersion was released through a 3.6 mm diameter orifice into a foaming cylinder under atmospheric pressure to obtain foamed particles (single-stage foamed particles) (release step). During this process, carbon dioxide was added to the pressure-resistant sealed container to maintain the pressure at 1.1 MPa (gauge pressure) while the dispersion was being released, so that the pressure inside the container would not drop below the foaming pressure. The average bubble diameter and the heat of fusion at high temperature were measured for the obtained foamed particles, and the results are shown in Table 1. The obtained foamed particles contained 11.0% by weight of an organophosphorus compound (B) and 5.0% by weight of a hindered amine (C) based on 100% by weight of the total amount of foamed particles.

[0206] (Preparation of polypropylene foam molded articles) The obtained foamed particles (single-stage foamed particles) were placed in a pressure-resistant sealed container. Air was introduced into the pressure-resistant sealed container, impregnating the foamed particles with pressurized air and applying an internal pressure (absolute pressure) of 0.25 MPa (absolute pressure) to the foamed particles. The air-impregnated foamed particles were heated and molded using a molding machine (polypropylene mold foam molding machine manufactured by Daisen Co., Ltd.) with steam at 0.32 MPa (gauge pressure) to obtain a foamed molded body. The obtained foamed molded body was left at room temperature for 1 hour, then cured and dried in a constant temperature room at 75°C for 12 hours, and then left at room temperature again for 4 hours. Subsequently, the density and flame retardancy of the obtained foamed molded body were measured and evaluated using the method described above. The results are shown in Table 1.

[0207] [Example 2] Each component was dry-blended so that, in 100% by weight of the blend, polypropylene resin (A1) accounted for 81.6% by weight, organophosphorus compound (B) for 13.0% by weight, and hindered amine (C) for 5.0% by weight. Resin particles, foamed particles, and foamed molded articles were obtained using the same method as in Example 1, except that the foaming temperature was 150.9°C and the foaming pressure was 1.0 MPa (gauge pressure). The physical properties of each were measured and evaluated. The results are shown in Table 1. The obtained foamed particles contained 13.0% by weight of organophosphorus compound (B) and 5.0% by weight of hindered amine (C) based on 100% by weight of the total amount of foamed particles.

[0208] [Example 3] Each component was dry-blended so that, in 100% by weight of the blend, polypropylene resin (A3) accounted for 76.6% by weight, organophosphorus compound (B) for 15.0% by weight, and hindered amine (C) for 8.0% by weight. Resin particles, foamed particles, and foamed molded articles were obtained using the same method as in Example 1, except that the foaming temperature was 150.3°C and the foaming pressure was 1.0 MPa (gauge pressure). The physical properties of each were measured and evaluated. The results are shown in Table 1. The obtained foamed particles contained 15.0% by weight of organophosphorus compound (B) and 8.0% by weight of hindered amine (C) based on 100% by weight of the total amount of foamed particles.

[0209] [Example 4] Each component was dry-blended so that, in 100% by weight of the blend, polypropylene resin (A3) accounted for 74.6% by weight, organophosphorus compound (B) for 20.0% by weight, and hindered amine (C) for 5.0% by weight. Resin particles, foamed particles, and foamed molded articles were obtained using the same method as in Example 1, except that the foaming temperature was 150.5°C and the foaming pressure was 1.2 MPa (gauge pressure). The physical properties of each were measured and evaluated. The results are shown in Table 1. The obtained foamed particles contained 20.0% by weight of organophosphorus compound (B) and 5.0% by weight of hindered amine (C) based on 100% by weight of the total amount of foamed particles.

[0210] [Example 5] Each component was dry-blended so that, in 100% by weight of the blend, polypropylene resin (A2) accounted for 81.6% by weight, organophosphorus compound (B) for 13.0% by weight, and hindered amine (C) for 5.0% by weight. Resin particles, foamed particles, and foamed molded articles were obtained using the same method as in Example 1, except that the foaming temperature was 150.2°C and the foaming pressure was 1.5 MPa (gauge pressure). The physical properties of each were measured and evaluated. The results are shown in Table 1. The obtained foamed particles contained 13.0% by weight of organophosphorus compound (B) and 5.0% by weight of hindered amine (C) based on 100% by weight of the total amount of foamed particles.

[0211] [Example 6] Each component was dry-blended so that, in 100% by weight of the blend, polypropylene resin (A1) accounted for 79.6% by weight, organophosphorus compound (B) for 15.0% by weight, and hindered amine (C) for 5.0% by weight. Resin particles, foamed particles, and foamed molded articles were obtained using the same method as in Example 1, except that the foaming temperature was 151.8°C and the foaming pressure was 0.8 MPa (gauge pressure). The physical properties of each were measured and evaluated. The results are shown in Table 1. The obtained foamed particles contained 15.0% by weight of organophosphorus compound (B) and 5.0% by weight of hindered amine (C) based on 100% by weight of the total amount of foamed particles.

[0212] [Example 7] Each component was dry-blended so that, in 100% by weight of the blend, polypropylene resin (A1) accounted for 79.6% by weight, organophosphorus compound (B) for 15.0% by weight, and hindered amine (C) for 5.0% by weight. Resin particles, foamed particles, and foamed molded articles were obtained using the same method as in Example 1, except that the foaming temperature was 151.9°C and the foaming pressure was 0.7 MPa (gauge pressure). The physical properties of each were measured and evaluated. The results are shown in Table 1. The obtained foamed particles contained 15.0% by weight of organophosphorus compound (B) and 5.0% by weight of hindered amine (C) based on 100% by weight of the total amount of foamed particles.

[0213] [Example 8] Each component was dry-blended so that, in 100% by weight of the blend, polypropylene resin (A1) accounted for 79.6% by weight, organophosphorus compound (B) for 15.0% by weight, and hindered amine (C) for 5.0% by weight. Resin particles, foamed particles, and foamed molded articles were obtained using the same method as in Example 1, except that the foaming temperature was 151.6°C and the foaming pressure was 1.0 MPa (gauge pressure). The physical properties of each were measured and evaluated. The results are shown in Table 1. The obtained foamed particles contained 15.0% by weight of organophosphorus compound (B) and 5.0% by weight of hindered amine (C) based on 100% by weight of the total amount of foamed particles.

[0214] [Example 9] Each component was dry-blended so that, in 100% by weight of the blend, polypropylene resin (A1) accounted for 79.6% by weight, organophosphorus compound (B) for 15.0% by weight, and hindered amine (C) for 5.0% by weight. Resin particles, foamed particles, and foamed molded articles were obtained using the same method as in Example 1, except that the foaming temperature was 151.9°C and the foaming pressure was 1.1 MPa (gauge pressure). The physical properties of each were measured and evaluated. The results are shown in Table 1. The obtained foamed particles contained 15.0% by weight of organophosphorus compound (B) and 5.0% by weight of hindered amine (C) based on 100% by weight of the total amount of foamed particles.

[0215] [Table 1] [Example 10] (Preparation of polypropylene resin particles and polypropylene foam particles) In 100% by weight of the blend, the components were dry-blended such that the polypropylene-based resin (A1) was 79.6% by weight, the organophosphorus compound (B) was 15.0% by weight, and the hindered amine (C) was 5.0% by weight. Resin particles and foamed particles (single-stage foamed particles) were obtained in the same manner as in Example 1, except that the foaming temperature was 150.3°C and the foaming pressure was 1.2 MPa (gauge pressure), and the physical properties of each were measured and evaluated. The results are shown in Table 1. The obtained foamed particles contained 15.0% by weight of the organophosphorus compound (B) and 5.0% by weight of the hindered amine (C) with respect to 100% by weight of the total amount of the foamed particles.

[0216] (Production of polypropylene-based foamed particles (two-stage foamed particles)) The obtained single-stage foamed particles were dried at 60°C for 6 hours and then put into a pressure-resistant sealed container. Air was introduced into the pressure-resistant sealed container, and the single-stage foamed particles in the pressure-resistant sealed container were impregnated with pressurized air to impart an internal pressure (absolute pressure) of 0.30 MPa (absolute pressure) to the single-stage foamed particles. Approximately 20 L of the single-stage foamed particles impregnated with air (to which the internal pressure of the foamed particles was imparted) were put into a foaming machine. Then, the single-stage foamed particles in the foaming machine were heated with steam at 0.10 MPa (gauge pressure) for 30 seconds to further foam (two-stage foam) the single-stage foamed particles, and foamed particles (two-stage foamed particles) were obtained.

[0217] (Production of polypropylene-based foamed molded body) A foamed molded body was obtained in the same manner as in Example 1, except that the obtained foamed particles (two-stage foamed particles) were put into a pressure-resistant sealed container, and the physical properties of each were measured and evaluated. The results are shown in Table 1.

[0218] [Example 11] In 100% by weight of the blend, the components were dry-blended so that the polypropylene-based resin (A3) was 74.6% by weight, the organic phosphorus-based compound (B) was 20.0% by weight, and the hindered amine (C) was 5.0% by weight. Resin particles, foamed particles, and a foamed molded article were obtained in the same manner as in Example 10, except that the foaming temperature was 150.5°C and the foaming pressure was 1.2 MPa (gauge pressure), and each physical property was measured and evaluated. The results are shown in Table 2. The obtained foamed particles contained 20.0% by weight of the organic phosphorus-based compound (B) and 5.0% by weight of the hindered amine (C) with respect to 100% by weight of the total amount of the foamed particles.

[0219] [Example 12] In 100% by weight of the blend, the components were dry-blended so that the polypropylene-based resin (A3) was 74.6% by weight, the organic phosphorus-based compound (B) was 20.0% by weight, and the hindered amine (C) was 5.0% by weight. Resin particles, foamed particles, and a foamed molded article were obtained in the same manner as in Example 1, except that the foaming temperature was 150.5°C and the foaming pressure was 1.2 MPa (gauge pressure), and each physical property was measured and evaluated. The results are shown in Table 2. The obtained foamed particles contained 20.0% by weight of the organic phosphorus-based compound (B) and 5.0% by weight of the hindered amine (C) with respect to 100% by weight of the total amount of the foamed particles.

[0220] [Example 13] In 100% by weight of the blend, the components were dry-blended so that the polypropylene-based resin (A2) was 81.6% by weight, the organic phosphorus-based compound (B) was 13.0% by weight, and the hindered amine (C) was 5.0% by weight. Resin particles, foamed particles, and a foamed molded article were obtained in the same manner as in Example 1, except that the foaming temperature was 148.5°C and the foaming pressure was 2.3 MPa (gauge pressure), and each physical property was measured and evaluated. The results are shown in Table 2. The obtained foamed particles contained 13.0% by weight of the organic phosphorus-based compound (B) and 5.0% by weight of the hindered amine (C) with respect to 100% by weight of the total amount of the foamed particles.

[0221] [Example 14] Each component was dry-blended so that, in 100% by weight of the blend, polypropylene resin (A2) accounted for 81.6% by weight, organophosphorus compound (B) for 13.0% by weight, and hindered amine (C) for 5.0% by weight. Resin particles, foamed particles, and foamed molded articles were obtained using the same method as in Example 1, except that the foaming temperature was 148.5°C and the foaming pressure was 2.3 MPa (gauge pressure). The physical properties of each were measured and evaluated. The results are shown in Table 2. The obtained foamed particles contained 13.0% by weight of organophosphorus compound (B) and 5.0% by weight of hindered amine (C) based on 100% by weight of the total amount of foamed particles.

[0222] [Example 15] Each component was dry-blended so that, in 100% by weight of the blend, polypropylene resin (A1) accounted for 79.6% by weight, organophosphorus compound (B) for 15.0% by weight, and hindered amine (C) for 5.0% by weight. Resin particles, foamed particles, and foamed molded articles were obtained using the same method as in Example 1, except that the foaming temperature was 150.3°C and the foaming pressure was 2.3 MPa (gauge pressure). The physical properties of each were measured and evaluated. The results are shown in Table 2. The obtained foamed particles contained 15.0% by weight of organophosphorus compound (B) and 5.0% by weight of hindered amine (C) based on 100% by weight of the total amount of foamed particles.

[0223] [Example 16] Each component was dry-blended so that, in 100% by weight of the blend, polypropylene resin (A1) accounted for 79.6% by weight, organophosphorus compound (B) for 15.0% by weight, and hindered amine (C) for 5.0% by weight. Resin particles, foamed particles, and foamed molded articles were obtained using the same method as in Example 1, except that the foaming temperature was 150.3°C and the foaming pressure was 2.3 MPa (gauge pressure). The physical properties of each were measured and evaluated. The results are shown in Table 2. The obtained foamed particles contained 15.0% by weight of organophosphorus compound (B) and 5.0% by weight of hindered amine (C) based on 100% by weight of the total amount of foamed particles.

[0224] [Example 17] Each component was dry-blended so that, in 100% by weight of the blend, polypropylene resin (A1) accounted for 79.6% by weight, organophosphorus compound (B) for 15.0% by weight, and hindered amine (C) for 5.0% by weight. Resin particles, foamed particles, and foamed molded articles were obtained using the same method as in Example 1, except that the foaming temperature was 150.3°C and the foaming pressure was 2.3 MPa (gauge pressure). The physical properties of each were measured and evaluated. The results are shown in Table 2. The obtained foamed particles contained 15.0% by weight of organophosphorus compound (B) and 5.0% by weight of hindered amine (C) based on 100% by weight of the total amount of foamed particles.

[0225] [Example 18] In the blend, 83.6% by weight of polypropylene resin (A2), 13.0% by weight of organophosphorus compound (B), and 3.0% by weight of hindered amine (C) were used. The components were dry-blended, and resin particles, foamed particles, and foamed molded articles were obtained using the same method as in Example 1, except that the foaming temperature was 150.2°C and the foaming pressure was 1.3 MPa (gauge pressure). The physical properties of each were measured and evaluated. The results are shown in Table 2. The obtained foamed particles contained 13.0% by weight of organophosphorus compound (B) and 3.0% by weight of hindered amine (C) based on 100% by weight of the total amount of foamed particles.

[0226] [Example 19] Each component was dry-blended so that, in 100% by weight of the blend, polypropylene resin (A2) accounted for 81.6% by weight, organophosphorus compound (B) for 13.0% by weight, and hindered amine (C) for 5.0% by weight. Resin particles, foamed particles, and foamed molded articles were obtained using the same method as in Example 1, except that the foaming temperature was 150.2°C and the foaming pressure was 1.5 MPa (gauge pressure). The physical properties of each were measured and evaluated. The results are shown in Table 2. The obtained foamed particles contained 13.0% by weight of organophosphorus compound (B) and 5.0% by weight of hindered amine (C) based on 100% by weight of the total amount of foamed particles.

[0227] [Table 2] [Comparative Example 1] Each component was dry-blended so that, in 100% by weight of the blend, polypropylene resin (A1) accounted for 95.6% by weight, organophosphorus compound (B) for 2.7% by weight, and hindered amine (C) for 1.3% by weight. Resin particles, foamed particles, and foamed molded articles were obtained using the same method as in Example 1, except that the foaming temperature was 150.7°C and the foaming pressure was 1.7 MPa (gauge pressure). The physical properties of each were measured and evaluated. The results are shown in Table 3. Furthermore, the obtained foamed particles contained 2.7% by weight of organophosphorus compound (B) and 1.3% by weight of hindered amine (C) based on 100% by weight of the total amount of foamed particles.

[0228] [Comparative Example 2] Each component was dry-blended so that, in 100% by weight of the blend, polypropylene resin (A1) accounted for 96.6% by weight, organophosphorus compound (B) for 2.7% by weight, and hindered amine (C) for 0.3% by weight. Resin particles, foamed particles, and foamed molded articles were obtained using the same method as in Example 1, except that the foaming temperature was 150.7°C and the foaming pressure was 1.7 MPa (gauge pressure). The physical properties of each were measured and evaluated. The results are shown in Table 3. Furthermore, the obtained foamed particles contained 2.7% by weight of organophosphorus compound (B) and 0.3% by weight of hindered amine (C) based on 100% by weight of the total amount of foamed particles.

[0229] [Comparative Example 3] In the blend, the components were dry-blended so that polypropylene resin (A2) accounted for 79.6% by weight and organophosphorus compound (B) accounted for 20.0% by weight of 100% by weight of the blend. Hindered amine (C) was not used, and other additives totaled 0.50 parts by weight. The foaming temperature was 150.2°C and the foaming pressure was 1.3 MPa (gauge pressure). Resin particles, foamed particles, and foamed molded articles were obtained using the same method as in Example 1, and their physical properties were measured and evaluated. The results are shown in Table 3. The obtained foamed particles contained 20.0% by weight of organophosphorus compound (B) based on 100% by weight of the total amount of foamed particles.

[0230] [Comparative Example 4] In 100% by weight of the blend, the polypropylene-based resin (A1) was 95.9% by weight, the organophosphorus compound (B) was 2.7% by weight, and the hindered amine (C) was 1.0% by weight. Each component was dry-blended, and resin particles, foamed particles, and a foamed molded body were obtained in the same manner as in Example 1 except that the foaming temperature was 150.3 °C and the foaming pressure was 2.3 MPa (gauge pressure). Each physical property was measured and evaluated. The results are shown in Table 3. The obtained foamed particles contained 2.7% by weight of the organophosphorus compound (B) and 1.0% by weight of the hindered amine (C) with respect to 100% by weight of the total amount of the foamed particles.

[0231] [Comparative Example 5] In 100% by weight of the blend, the polypropylene-based resin (A1) was 95.6% by weight, the organophosphorus compound (B) was 2.7% by weight, and the hindered amine (C) was 1.3% by weight. Each component was dry-blended, and resin particles, foamed particles, and a foamed molded body were obtained in the same manner as in Example 1 except that the foaming temperature was 150.5 °C and the foaming pressure was 2.0 MPa (gauge pressure). Each physical property was measured and evaluated. The results are shown in Table 3. The obtained foamed particles contained 2.7% by weight of the organophosphorus compound (B) and 1.3% by weight of the hindered amine (C) with respect to 100% by weight of the total amount of the foamed particles.

[0232] [Comparative Example 6] In 100% by weight of the blend, the polypropylene-based resin (A1) was 93.6% by weight, the organophosphorus compound (B) was 4.5% by weight, and the hindered amine (C) was 1.5% by weight. Each component was dry-blended, and resin particles, foamed particles, and a foamed molded body were obtained in the same manner as in Example 1 except that the foaming temperature was 150.7 °C and the foaming pressure was 1.7 MPa (gauge pressure). Each physical property was measured and evaluated. The results are shown in Table 3. The obtained foamed particles contained 4.5% by weight of the organophosphorus compound (B) and 1.5% by weight of the hindered amine (C) with respect to 100% by weight of the total amount of the foamed particles.

[0233] [Comparative Example 7] Each component was dry-blended so that, in 100% by weight of the blend, polypropylene resin (A4) accounted for 85.6% by weight, organophosphorus compound (B) for 9.0% by weight, and hindered amine (C) for 5.0% by weight. Resin particles, foamed particles, and foamed molded articles were obtained using the same method as in Example 1, except that the foaming temperature was 150.5°C and the foaming pressure was 1.4 MPa (gauge pressure). The physical properties of each were measured and evaluated. The results are shown in Table 3. The obtained foamed particles contained 9.0% by weight of organophosphorus compound (B) and 5.0% by weight of hindered amine (C) based on 100% by weight of the total amount of foamed particles.

[0234] In all of Examples 1-19 and Comparative Examples 1-7, the DSC curves obtained by differential scanning calorimetering (DSC) showed two melting peaks. Furthermore, in all of Examples 1-19 and Comparative Examples 1-7, the particle weight of the obtained polypropylene foam particles was 1.2 mg.

[0235] [Table 3] 〔summary〕 From Tables 1 to 3, the following is clearly evident: The foamed molded articles obtained by molding the foamed particles of Examples 1 to 19 all have an oxygen index of 26.0% or higher. Furthermore, the foamed molded articles of Examples 1 to 4 and 6 to 7 satisfy the standard V-0 under all conditions of sample thickness of 5 mm, 8 mm, and 13 mm. On the other hand, the foamed molded articles obtained by molding the foamed particles of Comparative Examples 1 to 7 all have an oxygen index of less than 26.0%, and none of the foamed molded articles satisfy the standard V-0 under all conditions of sample thickness of 5 mm, 8 mm, and 13 mm. As described above, it has been shown that the present invention's configuration makes it possible to obtain a foamed molded article that satisfies an oxygen index of 26.0% or higher and / or satisfies the standard V-0 under all conditions of sample thickness of 5 mm, 8 mm, and 13 mm, that is, it is possible to provide a foamed molded article with excellent flame retardancy. [Industrial applicability]

[0236] By in-mold foam molding of polypropylene foam particles according to one embodiment of the present invention, a polypropylene foam molded article with excellent flame retardancy can be provided. This flame-retardant polypropylene foam molded article can be used in a variety of applications, such as cushioning packaging materials, logistics materials, heat insulation materials, civil engineering and construction materials, and automotive materials. In particular, it can be suitably used in various fields where strict flame retardancy standards are required, such as transportation, buildings, structures, furniture, electrical equipment, and electronic equipment.

Claims

1. Polypropylene foam particles comprising a polypropylene resin (A), an organophosphorus compound (B), and a hindered amine (C), With respect to 100% by weight of the total amount of the aforementioned polypropylene foam particles, Organophosphorus compounds (B) exceeding 10.0% by weight and 20.0% by weight or less, It contains 1.0% to 10.0% by weight of hindered amine (C), The organophosphorus compound (B) is a phosphonate, Polypropylene foam particles, wherein the hindered amine (C) is a hindered amine having an OR group directly substituted on the N atom (where R is a saturated or unsaturated hydrocarbyl group).

2. The polypropylene foamed particle according to claim 1, wherein the organophosphorus compound (B) is a cyclic phosphonate.

3. The polypropylene foamed particle according to claim 2, wherein the cyclic phosphonate is a cyclic bisphosphonate.

4. The polypropylene foamed particle according to claim 3, wherein the cyclic bisphosphonate is pentaerythrityl diphosphonate.

5. The polypropylene foamed particle according to any one of claims 1 to 4, wherein the weight ratio (ratio (B) / (C)) of the hindered amine (C) to the organophosphorus compound (B) is 1.0 to 20.

0.

6. The polypropylene foamed particle according to any one of claims 1 to 5, wherein the weight ratio (ratio (A) / {(B) + (C)}) of the total amount of the organophosphorus compound (B) and the hindered amine (C) to the polypropylene resin (A) is 1 to 10.

7. Polypropylene foam particles according to any one of claims 1 to 6, wherein the particle has two melting peaks as measured by differential scanning calorimeter, and the high-temperature side melting heat is 5.0 J / g to 25.0 J / g.

8. Polypropylene foamed particles according to any one of claims 1 to 7, wherein the MI of the polypropylene resin (A) is 3.00 g / 10 min to 30.00 g / 10 min.

9. The polypropylene foamed particle according to any one of claims 1 to 8, wherein the polypropylene resin (A) is a random copolymer of propylene and a monomer other than propylene.

10. Polypropylene foamed particles according to any one of claims 1 to 9, wherein the average bubble diameter is 180 μm to 450 μm and the particle weight is 0.5 mg to 10.0 mg.

11. A polypropylene foamed molded article obtained by molding polypropylene foamed particles according to any one of claims 1 to 10.

12. The polypropylene foamed molded article according to claim 11, wherein the oxygen index of the foamed molded article measured in accordance with JIS K7201 is 26.0% or higher.

13. A polypropylene-based foamed molded article according to claim 11 or 12, wherein the density is 15.0 g / L to 92.0 g / L.

14. A polypropylene-based foamed molded article according to claim 11 or 12, wherein the density is greater than 92.0 g / L and 400.0 g / L or less.

15. A dispersion step in which polypropylene resin particles, an aqueous dispersion medium, and a foaming agent are dispersed in a container, The process includes a discharge step of releasing the dispersion obtained in the above-mentioned dispersion step into a region with a pressure lower than the pressure inside the container, The polypropylene resin particles contain, based on 100% by weight of the total amount of the polypropylene resin particles, more than 10.0% by weight and 20.0% by weight or less of an organophosphorus compound (B), and 1.0% by weight to 10.0% by weight of a hindered amine (C). The organophosphorus compound (B) is a phosphonate, A method for producing polypropylene foam particles, wherein the hindered amine (C) is a hindered amine having an OR group directly substituted on the N atom (where R is a saturated or unsaturated hydrocarbyl group).

16. The method for producing polypropylene foamed particles according to claim 15, wherein the dispersion comprises tricalcium phosphate, kaolin, and sodium dodecylbenzenesulfonate.

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