Polyolefin resin foamed particles, a foamed particle molded body obtained by in-mold molding the foamed particles, a method for producing the foamed particles, and a method for determining the flame retardancy of the foamed particles

Abstract

The present invention relates to a polyolefin resin foamed particle, a foamed particle molded body obtained by in-mold molding the foamed particle, a manufacturing method of the foamed particle, and a method for determining the flame retardancy of the foamed particle. The polyolefin resin foamed particle contains a polyolefin resin and a phosphonate compound, the phosphorus content P of the foamed particle is 0.1 to 6 mass%, and the foamed particle satisfies the following formula (1): {(m 215 -m 235 ) / m 215} × 100 / P tot ≤ 35 (1) In formula (1), m 215 is the mass of the foamed particle measured by thermal gravimetric analysis at 215°C, m 235 is the mass of the foamed particle measured by thermal gravimetric analysis at 235°C, and P tot is a value showing the mass fraction of phosphorus in the foamed particle, and is in the range of 0.001 to 0.06.

Description

Technical Field

[0001] This invention relates to polyolefin resin foamed granules, a foamed granule molded body formed by in-mold molding of the foamed granules, and a method for manufacturing the foamed granules. Background Technology

[0002] Polyolefin resin foam particles containing phosphonate compounds are generally known. Phosphonate compounds typically impart specific functions to foam particles. Representatively, phosphonate compounds can impart flame-retardant properties to foam particles. Therefore, phosphonate compounds can be flame-retardant materials that impart flame retardancy to polyolefin resin foam particles, or can form part of flame-retardant materials.

[0003] Different flame retardancy may be required for various components and technical parts molded from different polyolefin resin foam particles. As a non-limiting example, in vehicle applications, especially automotive applications, in-mold molded foam particles made from different polyolefin resin foam particles are generally required to have good flame retardancy. As a more specific example, non-limiting examples of different vehicle parts in-mold molded from different polyolefin resin foam particles that are required to have good flame retardancy include housing elements and protective elements for battery devices, electrical devices, electronic devices, etc. Summary of the Invention

[0004] The problem the invention aims to solve Therefore, in the manufacture of polyolefin resin foam granules, it is crucial that the phosphonate compounds remain essentially unchanged or undecomposed to ensure that the resulting polyolefin resin foam granules retain the desired properties due to sufficient amounts of undegraded or undecomposed phosphonate compounds. As with the conventional autoclave process for manufacturing foam granules, the pressure and temperature conditions used in the production of polyolefin resin foam granules, combined with the presence of heated water and prolonged exposure, can cause undesirable deterioration or decomposition of the phosphonate compounds, resulting in the polyolefin resin foam granules failing to exhibit the desired flame retardant properties.

[0005] Experiments show that in the autoclave-based process for manufacturing various polyolefin resin foam particles in the presence of water, the hydrolysis of phosphate ester compounds may negatively impact the properties of the polyolefin resin foam particles. Furthermore, once phosphonate ester compounds undergo hydrolysis or other decomposition during the manufacturing process of various polyolefin resin foam particles, it becomes difficult to obtain the desired flame retardancy.

[0006] Therefore, the object of the present invention is to provide polyolefin resin foamed granules with improved properties. The improved properties are based on suppressing the deterioration and decomposition of phosphonate compounds after the manufacturing process of polyolefin resin foamed granules, so that undeteriorated and undecomposed phosphonate compounds are sufficiently present in the foamed granules.

[0007] Another object of the present invention is to provide a foamed particle molded body formed by in-mold molding of polyolefin resin foamed particles with improved properties, and a method for manufacturing polyolefin resin foamed particles with improved properties.

[0008] Solution to the problem The first embodiment of the present invention is a polyolefin resin foamed granule, characterized in that, The foamed particles contain polyolefin resins and phosphonate compounds. The phosphorus content (P) of the foamed granules is 0.1-6% by mass. The foamed particles satisfy the following formula (1): {(m 215 -m 235 ) / m 215}×100 / P tot ≤35 (1) In equation (1), m 215 The mass of the foamed particles was determined by thermogravimetry at 215℃. m 235 The mass of the foamed particles was determined by thermogravimetric analysis at 235℃. P tot The value of the mass fraction of phosphorus in the foamed granules is displayed in the range of 0.001 to 0.06. Attached Figure Description

[0009] Figure 1A For the implementation of resin particles 31 The schematic diagram of the P-NMR analysis shows the presence of degraded / decomposed phosphonate compounds.

[0010] Figure 1B For the implementation of resin particles 31 The schematic diagram of the P-NMR analysis shows the presence of degraded / decomposed phosphonate compounds.

[0011] Figure 2 This is a schematic diagram of the TGA curves of phosphonate compounds before and after deterioration and decomposition. Detailed Implementation

[0012] The first embodiment of the present invention relates to polyolefin resin foamed particles, hereinafter referred to as "foamed particles". Typically, the foamed particles have a foamed bubble structure, and more particularly, have an expandable foamed bubble structure. Typically, the bubble structure of each foamed particle is composed of bubble walls defining one or more bubble spaces. When no additional coating layer is provided to the foamed particles, the particles generally constitute a foam layer, or represent a foam layer. When a coating layer is provided to the foamed particles, the foam layer constitutes the core layer of each foamed particle, or the foam layer represents the core layer. It should be noted that the foamed particles can be considered as "cellular beads" or "expanded beads".

[0013] The foam layer is typically based on polyolefin resins. Here, "polyolefin resins" refers to polypropylene resins, polyethylene resins, and mixtures of two or more of them.

[0014] When it is desired to fully exhibit the mechanical properties and other characteristics of the polypropylene resin in the foamed particles, the proportion of polypropylene resin in the polyolefin resin is preferably 60% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0015] Furthermore, when it is desired to fully exhibit the mechanical properties and other characteristics of the polyethylene-based resin in the foamed particles, the proportion of polyethylene-based resin in the polyolefin-based resin is preferably 60% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0016] Polypropylene resins refer to polypropylene homopolymers or propylene copolymers containing more than 50% by mass of propylene monomers.

[0017] Examples of propylene homopolymers, without limitation, include propylene-based resins such as isotactic polypropylene, syndiotactic polypropylene, and atactic polypropylene. These resins, as exemplified as propylene homopolymers, can be used alone or in combination of two or more.

[0018] In the aforementioned propylene copolymers, the content of the propylene monomer component in the polypropylene resin is preferably 80% by mass or more, more preferably 90% by mass or more. The content of the propylene monomer component in the aforementioned propylene copolymers is preferably 99% by mass or less, more preferably 98% by mass or less.

[0019] Examples of propylene-based copolymers are copolymers of propylene with ethylene and / or at least one of α-olefins having 4 to 20 carbon atoms. Examples of the aforementioned α-olefins include 1-butene, 1-pentene, 1-hexene, 1-octene, and 4-methyl-1-butene.

[0020] These propylene copolymers can be, for example, random copolymers or block copolymers, with random copolymers being preferred. More preferably, they are ethylene-propylene random copolymers, propylene-butene random copolymers, and ethylene-propylene-butene random copolymers.

[0021] Furthermore, as an example of the aforementioned propylene copolymer, impact-resistant polypropylene (block polypropylene) is also included, which is composed of two or more phases, including a continuous phase comprising a propylene polymer and a rubber phase such as an ethylene-α-olefin copolymer existing as a dispersed phase in the continuous phase.

[0022] A mixture of two or more of these propylene copolymers can also be used as the main polymer component of the foam layer. In this case, the total content of propylene copolymers in the polypropylene resin is preferably 60% by mass or more, 70% by mass or more, and further 80% by mass or more.

[0023] When propylene-based random copolymers contain components derived from ethylene (ethylene component) and / or components derived from butene (butene component) as comonomers, the in-mold moldability of foamed particles under low molding pressure conditions can be further improved.

[0024] When the polypropylene resin is a propylene-ethylene-butene random copolymer, the combined ethylene and butene content is preferably 1-15% by mass, more preferably 2-15% by mass, and even more preferably 3-15% by mass. In such an embodiment, by molding the foamed particles in a mold, a composition with good formability and good mechanical properties (e.g., compressive strength) can be obtained for the foamed particles under low molding pressure conditions. The ethylene and butene content in each propylene-based random copolymer can be determined by IR spectroscopy.

[0025] Polypropylene resins can be linear polypropylene resins, branched polypropylene resins, or a combination of both.

[0026] Polyethylene-based resins refer to polyethylene homopolymers and ethylene-based copolymers containing 50% by mass or more of a component derived from ethylene monomers. Specifically, examples of polyethylene-based resins include high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), ethylene-vinyl acetate (EVA) copolymers, ethylene-methyl acrylate (EMA) copolymers, and other linear ethylene-based copolymers. Among these, linear low-density polyethylene is preferred. Linear low-density polyethylene is a copolymer of ethylene and α-olefins exhibiting a linear structure. Examples of preferred linear low-density polyethylene include ethylene-1-butene copolymers, ethylene-1-pentene copolymers, ethylene-1-hexene copolymers, ethylene-4-methyl-1-pentene copolymers, and ethylene-1-octene copolymers. Linear low-density polyethylene is preferably a random copolymer. The content of the ethylene monomer-derived component in such ethylene-based copolymers is preferably 80% by mass or more, 90% by mass or more, more preferably 95% by mass or more, and even more preferably 98% by mass or more.

[0027] There are no restrictions on the preparation methods of polyolefin resins. For example, polyolefin resins can be manufactured by polymerizing olefin monomers in the presence of a polymerization catalyst. Examples of polymerization catalysts include Ziegler-Natta type polymerization catalysts and metallocene type polymerization catalysts.

[0028] To the extent that it does not impair the purpose and effects of the present invention, the foaming layer of the present invention may comprise other polymeric materials besides the polyolefin resins described above. These other polymers are, for example, thermoplastic polymers, and more specifically, thermoplastic resins other than polyolefin resins such as polystyrene resins, polyamide resins, polyester resins, polycarbonate resins, and polyphenylene ether resins. Other examples of other polymers include olefin-based thermoplastic elastomers (TPO) and polyurethane-based thermoplastic elastomers (TPU). Furthermore, mixtures of at least two of these other polymeric materials are also feasible.

[0029] The content of other thermoplastic polymers in the foamed layer besides the aforementioned polyolefin resin is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and particularly preferably 0% by mass. That is, it is particularly preferred that the foamed layer contains only polyolefin resin as a thermoplastic polymer.

[0030] Polyolefin resins typically exhibit a flexural modulus of 100 MPa or higher. From the viewpoint of improving the moldability of foamed granules, the flexural modulus of polyolefin resins is preferably 3000 MPa or less, more preferably 2000 MPa or less, further preferably 1500 MPa or less, and particularly preferably 1200 MPa or less. It should be noted that thermoplastic elastomers exhibit rubber elasticity at room temperature and typically show a flexural modulus of less than 100 MPa. The flexural modulus of thermoplastic resins is determined based on JIS K7171:2008.

[0031] Furthermore, without impairing the purpose and effects of the present invention, the foaming layer in the present invention may also contain a non-thermoplastic polymer. Examples of non-thermoplastic polymers include thermosetting resins and rubber.

[0032] When the foam layer contains a non-thermoplastic polymer, the content of the non-thermoplastic polymer in the foam layer is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and particularly preferably 0% by mass.

[0033] When the polyolefin resin is a polypropylene resin, the melting point of the polypropylene resin is preferably 130°C or higher, more preferably 135°C or higher, and even more preferably 140°C. Using a polypropylene resin with a melting point within the above range to prepare foamed granules, typically, by molding the foamed granules in a mold, a molded body with good mechanical properties (e.g., compressive strength) can be obtained. On the other hand, the melting point of the polypropylene resin is preferably 155°C or lower, more preferably 150°C or lower, and even more preferably 148°C or lower. Using a polypropylene resin with a melting point within the above range to prepare foamed granules makes it possible to process the foamed granules under low molding pressure conditions. That is, the melting point of the polypropylene resin is preferably 130°C or higher and 155°C or lower, more preferably 135°C or higher and 150°C or lower, and even more preferably 140°C or higher and 148°C or lower.

[0034] When the polyolefin resin is a polyethylene resin, the melting point of the polyethylene resin is preferably 110°C or higher. When foamed granules are prepared using a polyethylene resin with a melting point within the above range, the resulting molded body, formed in a mold, is less prone to shrinkage and exhibits good shape recovery after molding. From the viewpoint of further improving moldability, the melting point of the polyethylene resin is preferably 112°C or higher, more preferably 115°C or higher. On the other hand, the melting point of the polyethylene resin is preferably 130°C or lower. When foamed granules are prepared using a polyethylene resin with a melting point within the above range, even when molded at low molding temperatures, molded bodies with good weldability can be obtained, and foamed granules with good moldability are easily obtained. From the viewpoint of further improving moldability, the melting point of the polyethylene resin is preferably 128°C or lower, more preferably 125°C or lower. That is, the melting point of the polyethylene resin is preferably 110°C or higher and 130°C or lower, more preferably 112°C or higher and 128°C or lower, and even more preferably 115°C or higher and 125°C or lower.

[0035] The melting point of polyolefin resins can be determined using polyolefin resins, resin particles, or foamed particles as test samples according to JIS K 7121:2012. Under a nitrogen inflow rate of 30 mL / min, the test sample is heated from 23°C to 200°C at a rate of 10°C / min, held at this temperature for 10 minutes, then cooled to 23°C at a rate of 10°C / min, and then heated again to 200°C at a rate of 10°C / min, yielding a differential scanning calorimetry (DSC) curve (the DSC curve after the second heating). The peak temperature of the melting peak in the DSC curve is then obtained and taken as the melting point of the polyolefin resin. When multiple melting peaks appear in the DSC curve, the baseline is used as a reference, and the peak temperature of the melting peak with the highest melting peak height is taken as the melting point.

[0036] The melt flow rate (MFR) of the polypropylene resin, measured at 230°C and a load of 2.16 kg, is preferably 3 g / 10 min or more, more preferably 4 g / 10 min or more. With an MFR within the above range, the foaming performance of the foamed particles during foaming and the secondary foaming performance of the foamed particles during in-mold molding become excellent. On the other hand, the MFR of the polypropylene resin is preferably 15 g / 10 min or less, more preferably 10 g / 10 min or less. With an MFR within the above range, it is easier for the bubbles in the foamed particles to form uniformly, and it is easier to improve the physical properties of the molded article obtained thereby. That is, the MFR of the polypropylene resin is preferably 3 to 15 g / 10 min, more preferably 4 to 10 g / 10 min.

[0037] The melt flow rate (MFR) of the polyethylene-based resin, measured at 190°C and a load of 2.16 kg, is preferably 0.5 g / 10 min or more, more preferably 0.8 g / 10 min or more. With an MFR within the above range, the foaming performance of the foamed particles during foaming and the secondary foaming performance of the foamed particles during in-mold molding become excellent. On the other hand, the MFR of the polyethylene-based resin is preferably 4 g / 10 min or less, more preferably 3 g / 10 min or less. These values ​​make it easier for bubbles in the foamed particles to form uniformly and improve the physical properties of the molded article obtained thereby. That is, the MFR of the polyethylene-based resin is preferably 0.5 to 4 g / 10 min, more preferably 0.8 to 3 g / 10 min.

[0038] The molecular weight filtration rate (MFR) of polyolefin resins such as polypropylene and polyethylene resins can be determined according to JIS K 7210-1:2014. Alternatively, resin particles (foamed particles) can be used as samples (test pieces) for determination. MFR can be measured using, for example, an MFR measuring device called "LMI400" available from Dynisco Corporation (address: 38 Forge Parkway, Franklin MA 02038, USA).

[0039] The polydispersity index (Mw / Mn) of polypropylene resins can be between 4.0 and 25, or between 4.1 and 15. The polydispersity index (Mw / Mn) of polypropylene resins is obtained by dividing the weight-average molecular weight (Mw) determined by gel permeation chromatography (GPC) using polystyrene as a standard by the number-average molecular weight (Mn).

[0040] The polydispersity index (Mw / Mn) of polypropylene resins can be determined by gel permeation chromatography (GPC). According to an exemplary method, firstly, the polypropylene resin is dissolved in o-dichlorobenzene to prepare a sample solution with a concentration of 2.2 mg / ml. Using this sample solution, GPC analysis is performed on two TSKgel (registered trademark) GM H6-HT columns and two TSKgel GMH6-HTL columns; the eluent is o-chlorobenzene; the flow rate is 1.0 ml / min; and the temperature is 140°C. Then, the number-average molecular weight Mn and weight-average molecular weight Mw of the polypropylene resin are calculated based on a calibration curve prepared using polystyrene as a standard, and subsequently, the polydispersity index (Mw / Mn) is calculated. The high-temperature GPC system HLC-8321GPC / HT, obtained from Tosoh Bioscience, can be used as the measuring apparatus.

[0041] The foamed particles are preferably (basically) spherical. The average particle size of the foamed particles is preferably 0.3 to 8 mm, more preferably 0.5 to 5 mm, and even more preferably 0.8 to 4.5 mm. The arithmetic mean particle size of the foamed particles can be obtained by the following method. First, the volumetric particle size distribution of the foamed particles is measured. The volumetric particle size distribution of the foamed particles can be measured using a particle size distribution measuring device (for example, a Millitrac JPA manufactured by Nikkiso Corporation). The number of foamed particles used for measurement is, for example, 2000 or more.

[0042] Next, based on the volume-based particle size distribution of the foamed particles, the particle size distribution is converted from an assumed spherical shape to a number-based particle size distribution to obtain the number-based particle size distribution of the foamed particles. At this point, the diameter of the imaginary sphere with the same volume as the particle is taken as the particle size. Then, by calculating the arithmetic mean of the particle sizes based on this particle size distribution, the arithmetic mean particle size based on the number of foamed particles can be obtained.

[0043] The average diameter of bubbles within polyolefin-based foamed granules is preferably 50 μm to 250 μm, more preferably 60 μm to 200 μm, and even more preferably 65 μm to 150 μm. When the average diameter of bubbles within the polyolefin-based foamed granules is within the above range, the in-mold foaming performance of the foamed granules is improved when the molded body is formed from the foamed granules. The average bubble diameter is determined, for example, by drawing a line segment from the outer edge of the bubble on the outermost surface of the foamed granule to the outer edge of the bubble on the opposite outermost surface, passing through the center of the foamed granule, in an image of a roughly bisected cross-section of the foamed granule observed under a microscope, and measuring the number of bubbles intersecting the line segment. Thus, the average bubble diameter can be calculated by dividing the length of the line segment by the measured number of bubbles. The average bubble diameter can be obtained within a desired range by adjusting the type and amount of bubble regulator added to the resin granules used to form the foamed granules, and the pressure applied when the resin granules foam.

[0044] Therefore, foamed granules generally refer to polyolefin resin granular materials composed of polyolefin resin foamed granules having a foamed bubble structure (especially a foamed bubble structure capable of further expansion). In this specification, "polyolefin resin foamed granules" and "polyolefin resin granular materials" are used interchangeably.

[0045] The foamed granules comprise polyolefin resins and phosphonate compounds, particularly cyclic phosphonate compounds. The polyolefin resin can be, for example, a polyethylene resin, a polypropylene resin, or a combination of polyethylene and polypropylene resins as a base component. The polyolefin resin serves as the substrate for the foamed granules containing phosphonate compounds. In particular, the polyolefin resin can contain phosphonate compounds. This applies to the individual granules constituting the foamed granules. That is, each granule is composed of a polyolefin resin and contains phosphonate compounds, especially the polyolefin resin serving as the substrate for the foamed granules containing phosphonate compounds. Examples of various phosphonate compounds are further provided below.

[0046] Phosphonate compounds can possess specific functions, thus imparting specific properties to foamed particles. In particular, phosphonate compounds can possess flame-retardant properties, thereby imparting flame retardancy to foamed particles.

[0047] Therefore, phosphonate compounds can form flame retardants or part of flame retardants. Cyclic phosphonate compounds are particularly preferred.

[0048] Because the foamed particles contain only a small amount of degraded or decomposed phosphonate compounds, their properties are improved compared to conventional foamed particles containing phosphonate compounds. The degraded or decomposed nature of various phosphonate compounds specifically refers to changes in their chemical structure. As an example, the chemical structure of phosphonate compounds can be transformed into phosphonic acid through hydrolysis. Experimental results show that when the foamed particles conform to the following formula (1), they exhibit the desired properties, especially good flame retardancy.

[0049] This formula is a reliable indicator of whether the amount of degraded or decomposed phosphonate compounds in the foamed particles is below a threshold. If the amount is below the threshold, it indicates that the foamed particles possess desirable properties, especially regarding flame retardancy. On the other hand, if the amount of degraded or decomposed phosphonate compounds in the foamed particles exceeds the threshold, it indicates that the foamed particles do not possess the desired properties, especially flame retardancy.

[0050] Therefore, as a characteristic of foamed particles with improved properties, it satisfies the following equation (1): {(m 215 -m 235 ) / m 215}×100 / P tot ≤35 ···(1) In equation (1), m 215 The mass of the foamed particles was determined by thermogravimetric analysis at 215℃. m 235 The mass of the foamed particles was determined by thermogravimetric analysis at 235℃. P tot It displays the mass fraction of phosphorus in the foamed granules, ranging from 0.001 to 0.06.

[0051] The inventors of this application have discovered that by mathematically correlating the results of thermogravimetric analysis of foamed particles with a specific phosphorus content P in foamed particles that are in the range of 0.1 to 6% by mass relative to the mass of the foamed particles (the value expressed as the mass fraction of phosphorus to the mass of the foamed particles is 0.001 to 0.06), and by determining whether this relationship is below 35, foamed particles exhibiting desired properties can be obtained, especially foamed particles exhibiting good flame retardancy.

[0052] As shown in equation (1) above, the mass (m) of the foamed particles at 215℃ determined by thermogravimetric analysis is... 215 Subtract the mass of the foamed particles at 235℃ determined by thermogravimetric analysis (m) 235 ), the difference (m) 215 -m 235 Divide by the mass of the foamed particles at 215℃ as determined by thermogravimetric analysis (m). 215 ), and its quotient {(m 215 -m 235 ) / m 215 Multiply by 100 / P tot Then, confirm whether the product is below 35. Wherein, in equation (1), P... tot The numerical value representing the mass fraction of phosphorus in foamed granules ranges from 0.001 to 0.06. The phosphorus content P and numerical value of the foamed granules are also shown. tot The phosphorus content is determined by taking into account the phosphorus content of undeteriorated phosphonate compounds, the phosphorus content of deteriorated / decomposed phosphonate compounds, and all phosphorus substances produced therefrom in the calculation.

[0053] It should be noted that the temperature range of 215°C to 235°C is the temperature region where the mass of degraded / decomposed phosphonate compounds decreases significantly. On the other hand, it is the temperature region where the mass of polyolefin resins and undegraded / decomposed phosphonate compounds is difficult to decrease. Therefore, the mass change in the above temperature range is divided by the amount of phosphorus from the phosphonate compounds, and the resulting value is used as an indicator of the proportion of degraded / decomposed phosphonate compounds present. Therefore, the smaller the value on the left side of the above equation (1), the lower the proportion of degraded / decomposed phosphonate compounds contained in the foamed particles.

[0054] In thermogravimetric analysis (TGA), mass values ​​at 215℃ and 235℃ are used because if a lower temperature is used as the lower determination temperature, the influence of residual moisture in the foamed particles will increase. On the other hand, if a higher temperature is used as the higher determination temperature, the influence of phosphonate decomposition will increase. In either case, the parallel occurrence of different decomposition mechanisms and / or thermodynamic mechanisms could potentially reduce the accuracy of TGA.

[0055] The experimental results unexpectedly and reliably showed that when the foamed particles satisfied Equation (1), resulting in a value of 35 or less, the foamed particles exhibited good flame retardancy, especially showing improved flame retardancy compared to conventional foamed particles. The value on the left side of Equation (1) above is preferably 34 or less, more preferably 33 or less, more preferably 32 or less, more preferably 31 or less, more preferably 30 or less, more preferably 29 or less, more preferably 28 or less, more preferably 27 or less, more preferably 26 or less, more preferably 25 or less, more preferably 24 or less, more preferably 23 or less, more preferably 22 or less, more preferably 21 or less, more preferably 20 or less, more preferably 19 or less, more preferably 18 or less, more preferably 17 or less, more preferably 16 or less, more preferably 15 or less, more preferably 14 or less, more preferably 13, more preferably 12 or less, more preferably 11 or less, more preferably 10 or less, more preferably 9 or less, more preferably 8 or less, more preferably 7 or less, more preferably 6 or less, more preferably 5 or less. Therefore, as an example, the value on the left can range from 0 to 35, or from 1 to 34. Alternatively, the above range can also be expressed as an interval threshold. For example, the value can be between 5 and 35, 7 and 29, or 16 and 24, etc. Typically, experimental results unexpectedly show that the foamed granules exhibit good flame retardancy when the value is in the range of 1 to 35.

[0056] Foamed particles that satisfy formula (1) above can meet at least one of the following UL standard classifications: HBF, HF-2, HF-1, V-2, V-1, V-0. Foamed particles that satisfy formula (1) can also show good flame retardancy according to other combustion performance standards.

[0057] Thermogravimetric analysis (TGA) for determining the mass of foamed particles at 215°C and 235°C can be performed under an inert atmosphere (e.g., 100% nitrogen) at a heating rate of 10°C / min using a single procedure controlled by a temperature gradient from 40°C to 800°C, using approximately 15 mg of pulverized sample. TGA for determining the mass of foamed particles at 215°C and 235°C can be performed using a TGA apparatus called "TGA 2" from Mettler-Toledo (Mettler-Toledo GmbH, 35396 Giessen, Germany) and a "MicroBalance XP5" from Mettler-Toledo. Similar TGA apparatuses are also generally available. The pulverization of the sample before analysis can be performed using an ultra-low temperature centrifugal pulverizer called "Ultra Centrifugal Mill ZM200", which is available from Retsch GmbH (address: Retsch-Allee 1-5, 42781 Haan, Germany).

[0058] The determination of phosphorus content (P) in foamed particles can be performed using inductively coupled plasma atomic emission spectrometry (ICP-OES) spectrophotometer. The determination can be performed using a test sample with a mass of 0.1 g ± 0.1 mg. First, the test sample is dissolved in 6 mL of concentrated nitric acid to obtain a solution, which is then supplied to a sealed fluoropolymer (tetrafluoromethoxy polymer: TFM (registered trademark)) reactor placed in a microwave oven for sample inorganization. Furthermore, as part of the microwave inorganization process, the test sample solution is heated from room temperature to 220°C over 30 minutes and maintained at that temperature for 20 minutes for the inorganization determination. After inorganization, the reactor is rinsed with Milli-Q (registered trademark) water, and the volume is increased for homogenization. The homogenized solution is then transferred to a 50 mL volumetric flask. Based on the phosphorus content of the sample, the resulting solution was diluted to different volumes, then transferred to an ICP-OES spectrometer, and the phosphorus content in the solution was measured. The phosphorus content P of the foaming particles was calculated based on the relationship between the measured phosphorus content and the mass of the foaming particles used as the sample for testing.

[0059] The ICP-OES spectrometer can use the "Activa M" spectrometer sold by HORIBA Europe GmbH (address: 61440 Oberwürzäur, Germany). Similar ICP-OES spectrometers are also generally compatible.

[0060] Optionally, if the phosphorus content P in the foamed particles is very low, for example, less than 1% by mass, the above formula (1) may take into account an offset coefficient OC. This offset coefficient takes into account the thermal decomposition of some of the polyolefin resin in the measurement when heated from 215°C to 235°C. As an example, studies have shown that when polyolefin resin is heated from 215°C to 235°C, its mass loss in the measurement is about 0.03% by mass. Therefore, the exemplary offset coefficient can be numerically 0.0001 to 0.0005, preferably 0.0002 to 0.0004, and more preferably 0.0003. When the phosphorus content P of the foamed particles is less than 1% by mass, the offset coefficient OC is preferably applied. In this case, it is preferable that in the above formula (1), {(m 215 -m 235 ) / m 215 Subtract OC from the value of} and multiply that value by 100 / P. tot Let be the left side of equation (1).

[0061] Generally, when the phosphorus content P in foamed granules is above 1% by mass, the offset factor OC is not required. This is because the mass loss caused by the thermal decomposition of polyolefin resins is relatively small compared to the mass loss caused by the deterioration or decomposition of phosphonate compounds, and such an offset factor OC can be ignored.

[0062] The phosphorus content P of the foamed granules is preferably in the range of 1 to 4.8% by mass, more preferably 1.5 to 4.8% by mass, and even more preferably 1.8 to 4.8% by mass. In addition, the phosphorus content P of the foamed granules is preferably in the range of 1.8 to 4.4% by mass, and even more preferably in the range of 1.8 to 3.6% by mass.

[0063] When the phosphorus content P of the foamed granules is within the above-mentioned range, the foamed granules exhibit good properties, especially the desired flame retardancy. In particular, by setting the phosphorus content P to a specified value or higher, the flame retardancy of the molded article can be steadily improved. Furthermore, by setting the phosphorus content P to a specified value or lower, the in-mold moldability of the foamed granules is easily improved.

[0064] Furthermore, from the viewpoint of easily obtaining foamed particles with good weldability between them and being able to manufacture foamed particle molded bodies with good flame retardancy, the phosphorus content P of the foamed particles is preferably 1% by mass or more and 3.2% by mass or less, more preferably 1.5% by mass or more and less than 3.0% by mass.

[0065] In one exemplary embodiment, the foamed particles may further contain a NOR-type hindered amine compound. The NOR-type hindered amine compound can form a flame retardant or a portion of a flame retardant, and therefore can affect the flame retardancy of the foamed particles. The amount of the NOR-type hindered amine compound in the foamed particles is preferably 0.1 to 5% by mass, more preferably 0.3 to 4% by mass, and even more preferably 0.5 to 3% by mass. When the foamed particles contain a NOR-type hindered amine compound and the amount of the NOR-type hindered amine compound in the foamed particles is 3% by mass or less, foamed particles with improved flame retardancy and good weldability of the resulting molded article can be obtained.

[0066] In particular, the phosphorus content (P) of the foamed granules can range from 1 to 4.8% by mass, and the amount of NOR-type hindered amine compound can range from 0.1 to 5% by mass.

[0067] In one exemplary embodiment, the total amount of polyolefin resin in the foamed granules is at least 80% by mass. Particularly preferably, the total amount of polyolefin resin in the foamed granules is greater than 82% by mass, and more preferably greater than 85% by mass. When the total amount of polyolefin resin is above the aforementioned threshold, foamed granules with excellent flame retardancy and good weldability can be manufactured with a smaller amount of flame retardant.

[0068] In another exemplary embodiment, the foamed particles further comprise a phenolic antioxidant. The amount of the phenolic antioxidant in the foamed particle compound can be 0.01 to 0.5% by mass, particularly 0.02 to 0.3% by mass, and more preferably 0.03 to 0.2% by mass. In particular, the phosphorus content (P) of the foamed particles can be in the range of 1 to 4.8% by mass, and the amount of the phenolic antioxidant can be in the range of 0.01 to 0.5% by mass.

[0069] The amount of phosphonate compound in the foamed granules is preferably 1% by mass or more and 15% by mass or less, more preferably 2% by mass or more and 13% by mass or less, and even more preferably 3% by mass or more and 12% by mass or less. At this point, even when the density of the foamed granules is 120 kg / m³, [the desired effect is achieved]. 3 Even with low bulk density foamed particles like the one described below, it is possible to obtain foamed particles with good weldability between the foamed particles and to manufacture foamed particle molded bodies with good flame retardancy.

[0070] Furthermore, from the viewpoint of further improving the weldability between foamed particles during in-mold molding, the sum of the amount of phosphonate compound and NOR-type hindered amine compound in the foamed particles is preferably 15% by mass or less, more preferably 14% by mass or less. The lower limit of the sum of the amount of phosphonate compound and NOR-type hindered amine compound in the foamed particles is preferably 1% by mass, more preferably 3% by mass, and even more preferably 5% by mass.

[0071] Furthermore, the melting point of the phosphonate compound is preferably in the range of 200 to 300°C. The melting point of the phosphonate compound can be determined according to JIS K 0064:1992.

[0072] In one exemplary embodiment, the phosphonate compound preferably comprises a cyclic phosphonate compound represented by the following general formula (1): In general formula (1), R 1 and R 2 Representing hydrocarbon groups respectively, preferably, R 1 and R 2 Each represents a methyl group.

[0073] As a specific and non-limiting example of a cyclic phosphonate compound, one could cite as the flame retardant named "Aflammit (registered trademark) PCO 900" obtained from Thor GmbH (address: 67329 Speyer, Germany).

[0074] In general formula (1), R 1 and R 2 They can be the same or different, but the same is preferred. R 1 Preferably, it is an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, a benzyl group, a phenethyl group, or a naphthyl group, more preferably an alkyl group having 1 or 2 carbon atoms, and more preferably a methyl group. 2 Preferably, it is an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, a benzyl group, a phenethyl group, a phenyl group, or a naphthyl group, more preferably an alkyl group having 1 or 2 carbon atoms, and even more preferably a methyl group.

[0075] Generally, cyclic phosphonate compounds are any compounds containing one or more cyclic phosphonic acid moieties in their molecules. Preferably, they are selected from compounds represented by the above general formula (1), compounds represented by the following general formula (2), compounds represented by the following general formula (3), and compounds represented by the following general formula (4). The amount of cyclic phosphonate compound in the foamed particles is preferably 1% or more and 15% or less by mass, more preferably 2% or more and 13% or less by mass, and even more preferably 3% or more and 12% or less by mass.

[0076] Pentaerythritol diphosphonate, as shown in general formula (1) above, is a spirocyclic compound containing two cyclic phosphonate moieties in its molecule. Cyclic phosphonate compounds can be used alone or in combination of two or more.

[0077] In general formula (3) or (4), R4 R 8 R 9 and R 12 R represents alkyl groups with 1 to 4 carbon atoms. 5 and R 7 R represents either a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. 6 and R 10 These respectively represent alkyl groups with 1 to 22 carbon atoms, cycloalkyl groups with 9 to 22 carbon atoms, aryl groups with 9 to 22 carbon atoms, or aralkyl groups with 9 to 22 carbon atoms.

[0078] In general formula (2), R 3 Preferably, it is an alkyl group having 1 to 22 carbon atoms or an aryl group having 6 to 15 carbon atoms, and more preferably a phenyl group.

[0079] In general formula (3), R 4 and R 8 They can be the same or different, but the same is preferred. R 4 Preferably, it is an alkyl group having 1 to 4 carbon atoms, more preferably a methyl group. R 8 Preferably, it is an alkyl group having 1 to 4 carbon atoms, and more preferably a methyl group.

[0080] R 5 and R 7 They can be the same or different, but the same is preferred. R 5 Preferably, it is an alkyl group having 1 to 4 hydrogen atoms, more preferably an ethyl group. 7 Preferably, it is an alkyl group having 1 to 4 hydrogen atoms, more preferably an ethyl group. 6 Preferably, it is an alkyl group having 1 to 22 carbon atoms, a cycloalkyl group having 9 to 22 carbon atoms, an aryl group having 9 to 22 carbon atoms, or an aralkyl group having 9 to 22 carbon atoms, and more preferably a straight-chain alkyl group having 1 to 12 carbon atoms.

[0081] In general formula (4), R 9 and R 12 They can be the same or different, but the same is preferred. R 9 Preferably, it is an alkyl group having 1 to 4 carbon atoms, more preferably a methyl group. 12 Preferably, it is an alkyl group having 1 to 4 carbon atoms, more preferably a methyl group. 10 Preferably, it is an alkyl group having 1 to 22 carbon atoms, a cycloalkyl group having 9 to 22 carbon atoms, an aryl group having 9 to 22 carbon atoms, or an aralkyl group having 9 to 22 carbon atoms; more preferably, it is a straight-chain alkyl group having 1 to 12 carbon atoms. 11 Preferably, it is an alkyl group having 1 to 4 hydrogen atoms or carbon atoms, and more preferably an ethyl group.

[0082] Furthermore, preferably, the above-mentioned NOR-type hindered amine compound has a 2,2,6,6-tetramethyl-4-piperidinamine moiety as shown in the following general formula (5), which has a hydrocarbon group bonded to a nitrogen atom via an oxygen atom. In this case, the flame retardancy of the foamed particles can be further improved: In general formula (5), R 13 It indicates a hydrocarbon group.

[0083] When a molecule of a NOR-type hindered amine contains two or more hindered amine moieties represented by general formula (5), multiple R 13 They can be the same or different, and multiple R values ​​are preferred. 13 same.

[0084] R 13 Preferably, it is selected from at least one of alkyl and cycloalkyl groups, more preferably cycloalkyl. R 13 When R is an alkyl group, 13 More preferably, it is an alkyl group having 1 to 20 carbon atoms, and even more preferably, it is an undecylalkyl group.

[0085] R 13 When it is a cycloalkyl group, R 13 More preferably, it is a cycloalkyl group having 4 to 10 carbon atoms, and even more preferably, it is a cyclohexyl group.

[0086] NOR-type hindered amine compounds can be used alone or in combination of two or more.

[0087] The molecular weight of the aforementioned NOR-type hindered amine compound is preferably 600 or more, more preferably 1500 or more. This facilitates the suppression of so-called bleed-out in the molded article prepared from foamed granules. To ensure good dispersibility of the NOR-type hindered amine compound in polyolefin resins, the molecular weight of the aforementioned NOR-type hindered amine compound is preferably 3000 or less, more preferably 2500 or less.

[0088] In the above-mentioned NOR-type hindered amine compounds, the number of 2,2,6,6-tetramethyl-4-piperidineamine moieties represented by the above general formula (5) is preferably 2 to 8, more preferably 2 to 6, and even more preferably 2 or 6.

[0089] As a specific example of a NOR-type hindered amine compound, a NOR-type hindered amine compound named "Flamestab NOR 116" can be obtained from BASF Japan Co., Ltd. (Tokyo, Japan).

[0090] Phenolic antioxidants include those having one or more phenolic structures in their molecules, wherein the phenolic structure has one or more hydroxyl groups bonded to the aromatic ring. Preferably, phenolic antioxidants have two or more phenolic structures in their molecules, and more preferably, they have three or more phenolic structures in their molecules.

[0091] At high temperatures (e.g., above 180°C) during processes such as melt-blending of polyolefin resins, the polyolefin resins can decompose in a short time. The aforementioned phenolic antioxidant is a compound that can inhibit the decomposition of polyolefin resins in a short time at such high temperatures.

[0092] Specific examples of phenolic antioxidants include 1,3,5-trimethyl-2,4,6-tris(3',5'-di-tert-butyl-4'-hydroxybenzyl)benzene, 2,6-dibutyl-p-cresol, triethylene glycol bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate], 2,2-methylene bis(4-methyl-6-tert-butylphenol), 1,6-hexanediol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and pentaerythritol tetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. They can be used alone or in combination of two or more.

[0093] To obtain a molded body with higher flame retardancy through the molding of foamed particles, the melting point of the phenolic antioxidant is preferably 50°C to 350°C. More preferably, the melting point of the phenolic antioxidant is 80°C or higher and 330°C or lower, even more preferably 100°C or higher and 320°C or lower, even more preferably 150°C or higher and 310°C or lower, and even more preferably 200°C or higher and 300°C or lower. The melting point of the phenolic antioxidant can be determined according to JIS K 0064:1992.

[0094] The difference between the melting point of the phenolic antioxidant and the melting point of the phosphonate compound can be -150°C or higher and 150°C or lower, preferably -100°C or higher and +100°C or lower, and more preferably -50°C or higher and +50°C or lower. When the difference between the melting point of the phenolic antioxidant and the melting point of the phosphonate compound is within the above range, foamed granules with improved flame retardancy can be obtained.

[0095] In embodiments where the foamed granules further contain NOR-type hindered amines and phenolic antioxidants, the ratio of the amount of phenolic antioxidant to the amount of NOR-type hindered amine in the foamed granules is preferably 0.03 to 0.9, more preferably 0.04 to 0.9, more preferably 0.06 to 0.9, more preferably 0.07 to 0.9, and even more preferably in the range of 0.14 to 0.9. Furthermore, the ratio of the amount of phenolic antioxidant to the amount of NOR-type hindered amine in the foamed granules is more preferably 0.04 to 0.5, and even more preferably 0.06 to 0.3.

[0096] Specifically, the aforementioned ratio is considered beneficial for the following reasons. NOR-type hindered amine compounds, when used in combination with phosphonate compounds, can exhibit high flame retardancy. However, when the foamed particles contain a large amount of NOR-type hindered amine compounds, the weldability of the molded body obtained by in-mold molding of the foamed particles tends to decrease. On the other hand, when the amount of NOR-type hindered amine compounds is too small, it is difficult to impart high flame retardancy to the molded body obtained by in-mold molding of foamed particles. Therefore, by combining phenolic antioxidants and NOR-type hindered amine compounds in specific amounts and ratios, high flame retardancy can be imparted to the molded body even when the amount of NOR-type hindered amine compounds is relatively small. As described above, by combining phenolic antioxidants and NOR-type hindered amine compounds in specific amounts and ratios, the phenolic antioxidants can not inhibit the flame-retardant effect of the NOR-type hindered amine compounds and can even contribute to improving flame retardancy. Therefore, even when the amount of NOR-type hindered amine compounds is reduced, high flame retardancy can be imparted to the molded body. Furthermore, since phenolic antioxidants do not readily inhibit the fusion between foamed particles during molding, the flame retardancy of the molded article can be improved by incorporating phenolic antioxidants while reducing the amount of NOR-type hindered amine compounds. Therefore, the foamed particles can be fully fused during molding. The results show that molded articles with high flame retardancy, excellent fusion properties, and superior structural characteristics can be obtained by molding the foamed particles.

[0097] In another exemplary embodiment, the foamed particles may further comprise at least one sulfur-based antioxidant. Sulfur-based antioxidants have a positive effect on the thermal stability of the foamed particles. The amount of sulfur-based antioxidant is preferably 0.01 to 0.5% by mass, more preferably 0.02 to 0.3% by mass, and even more preferably in the range of 0.03 to 0.2% by mass. In particular, the phosphorus content (P) of the foamed particles can be in the range of 0.8 to 4.8% by mass, and the amount of sulfur-based antioxidant can be in the range of 0.01 to 0.5% by mass.

[0098] In an exemplary embodiment where the foamed granules also contain a sulfur-based antioxidant and a NOR-type hindered amine compound, the ratio of the amount of the sulfur-based antioxidant to the amount of the NOR-type hindered amine compound can be 0.03 to 0.9. When this ratio is 0.03 or higher, it is easy to obtain a molded article with excellent mechanical properties such as compression characteristics even when exposed to high temperatures for a long time. Preferably, the ratio of the amount of the sulfur-based antioxidant to the amount of the NOR-type hindered amine compound is 0.07 or higher, particularly preferably 0.11 or higher, and even more preferably 0.14 or higher. On the other hand, when the ratio is 0.9 or lower, it is easy to obtain a molded article with high flame retardancy while improving the weldability between the foamed granules. From this viewpoint, the above-mentioned ratio is preferably 0.07 to 0.8, more preferably 0.11 to 0.7, and even more preferably 0.14 to 0.6.

[0099] As sulfur-based antioxidants, esters containing intramolecular sulfur bonds can be listed. Specific examples of esters with intramolecular sulfur bonds include di(dodecyl)-3,3'-thiodipropionate, di(tridecyl)-3,3'-thiodipropionate, di(tetradecyl)-3,3'-thiodipropionate, di(octadecyl)-3,3'-thiodipropionate, pentaerythritol tetra(3-dodecylthiopropionate), pentaerythritol tetra(3-tridecylthiopropionate), pentaerythritol tetra(3-tetradecylthiopropionate), and pentaerythritol tetra(3-octadecylthiopropionate). They can be used alone or in combination of two or more.

[0100] Foamed granules can have a density of 10~500 kg / m³ 3 The bulk density. In one exemplary embodiment, specifically, the foamed particles can have a bulk density of 10~200 kg / m³. 3 The bulk density. In particular, the bulk density of foamed granules can be 20 kg / m³. 3 Above, 30 kg / m 3 Above, 40 kg / m 3 Above, 50 kg / m 3 Above, 60 kg / m 3 Above, 70 kg / m 3 Above, 80kg / m 3 Above, 90 kg / m 3 Above, 100 kg / m 3 Above, or 110 kg / m 3 That's all. Additionally, the bulk density of the foamed granules can be less than 180 kg / m³. 3 Less than 150 kg / m 3 Less than 130 kg / m 3 or less than 120 kg / m 3 The above-mentioned example values ​​enable the molding of lightweight molded bodies with good flame retardancy and weldability, and are therefore preferred examples of bulk density values. Furthermore, the above range can also be expressed as a threshold range. As an example, the bulk density range can be 20~200 kg / m³. 3 30~150 kg / m 3 Or 80~130 kg / m 3 The range.

[0101] The bulk density of foamed granules can be determined using the following method. First, the foamed granules to be tested are allowed to stand for at least 24 hours at 23°C, 50% relative humidity, and 1 atmosphere to adjust their state. After adjustment, a sample of foamed granules with a mass W (g) is filled into a cylinder using a natural stacking method. The bottom of the cylinder is gently tapped several times on a horizontal surface to stabilize the filling height of the foamed granules. The bulk volume V (L) of the foamed granules is read from the cylinder's scale. The bulk density (kg / m³) of the foamed granules is calculated by dividing the mass W of the foamed granules by the bulk volume V and converting the units. 3 ).

[0102] In an exemplary embodiment, preferably, the foamed particles specified in this specification, in the DSC curve obtained by differential scanning calorimetry (DSC) measured according to JISK7122-2012, have the resin-inherent melting peak (resin-inherent peak) of the aforementioned polyolefin resin and one or more melting peaks (high-temperature peaks) located on the high-temperature side of the resin-inherent peak. These melting peaks can be obtained by the following methods.

[0103] Specifically, using a differential scanning calorimeter (DSC), 1–3 mg of foamed particles were heated from 23°C to 200°C at a heating rate of 10°C / min to obtain DSC curves. The peak with the highest heat of fusion is the inherent melting peak of the polyolefin resin, i.e., the resin-inherent peak. Any melting peaks occurring at higher temperatures are considered high-temperature peaks. It should be noted that the DSC curve refers to the curve obtained by heating the foamed particles using the above measurement method (i.e., the DSC curve from the first heating). Furthermore, the resin-inherent peak refers to the endothermic peak generated by the inherent melting of the crystals of the polyolefin resin constituting the foamed particles. In other words, the resin-inherent peak is an endothermic peak that occurs due to the melting of the crystals typically present in the polyolefin resin constituting the foamed particles.

[0104] To determine the peaks corresponding to the resin's inherent peaks or high-temperature peaks, the following method can be used. The foamed particles are heated from 23°C to 200°C at a heating rate of 10°C / min (first heating), then cooled from 200°C to 23°C at a cooling rate of 10°C / min, and then heated again from 23°C to 200°C at a heating rate of 10°C / min (second heating). In the DSC curve obtained after the second heating, only the endothermic peak caused by the melting of the inherent crystals of the polyolefin resin constituting the foamed particles appears; the high-temperature peak does not appear in the DSC curve obtained after the second heating.

[0105] The resin-specific peaks appear in both the DSC curves from the first heating and the second heating. Although the peak temperatures differ slightly between the first and second heating, each peak can be definitively identified as resin-specific. On the other hand, high-temperature peaks refer to one or more endothermic peaks appearing on the high-temperature side of the resin-specific peaks in the DSC curve from the first heating. The presence of such high-temperature peaks presupposes the presence of secondary crystals in the polyolefin resin.

[0106] The heat of fusion of the high-temperature peak of the foamed particles is preferably in the range of 5~40 J / g, more preferably 6~30 J / g, and even more preferably 7~25 J / g. When the heat of fusion of the high-temperature peak of the foamed particles is within the above range, it is easy to obtain foamed particles with a wide processing window, and better molded bodies can be obtained through molding. The heat of fusion of the high-temperature peak can be determined by the following method. On the DSC curve after initial heating, draw a straight line (α-β) connecting point α on the DSC curve corresponding to 80°C and point β on the DSC curve corresponding to the melting endpoint temperature T of the foamed particles. The melting endpoint temperature T is the endpoint of the high-temperature side of the high-temperature peak, or, in the case of multiple high-temperature peaks, the endpoint of the highest temperature high-temperature peak, which is a point on the baseline. Then, draw a straight line parallel to the vertical axis of the graph from point γ on the DSC curve. Point γ corresponds to the lowest heat point in the valley between the inherent resin peak and the high-temperature peak, or, in the case of multiple high-temperature peaks, the lowest heat point in the valley between the inherent resin peak and the lowest temperature high-temperature peak. The intersection of the straight line parallel to the vertical axis of the graph from point γ and the straight line (α-β) is taken as δ. The melting heat of the high-temperature peak expressed in J / g corresponds to the melting heat obtained by dividing the area of ​​the high-temperature peak enclosed by the curve, line segment (δ-β), and line segment (γ-δ) based on the high-temperature peak portion of the DSC curve by the mass of the foamed particles used in the test.

[0107] The foamed granules can have an average individual mass of 0.1 to 20 mg, more preferably 0.2 to 10 mg, even more preferably 0.3 to 5 mg, and even more preferably 0.4 to 2 mg (arithmetic mean mass of individual granules determined by randomly selected 200 granules).

[0108] In any embodiment, the foamed particles may also contain one or more other additives. Examples of such other additives include, for instance, other antioxidants, ultraviolet absorbers that absorb ultraviolet light, light stabilizers that absorb light with wavelengths of 300-400µm, antistatic agents, colorants such as pigments and dyes, fillers, conductive fillers, bubble regulators, and other commonly known additives. These additives can be incorporated into the foamed particles, for example, by adding them during the manufacturing process.

[0109] Specifically, examples of bubble control agents include talc, metal borates, glycerin, polyethylene glycol, polyols such as pentaerythritol, and aliphatic alcohols such as hexadecyl alcohol and octadecyl alcohol. Metal borates such as zinc borate and magnesium borate are preferred as bubble control agents, and zinc borate is more preferred. The amount of metal borate in the resin particles used to form foamed particles is preferably 0.005 to 0.5% by mass, more preferably 0.01 to 0.2% by mass, and even more preferably 0.015 to 0.15% by mass.

[0110] When zinc borate is used or present, ideally, its quantity-based arithmetic mean particle size is 0.5–15 μm, preferably 1–10 μm. The average particle size of zinc borate can be obtained by converting a volume-based particle size distribution determined by laser diffraction scattering into a quantity-based particle size distribution assuming the particle shape to be spherical, and then calculating the particle size by arithmetic averaging the particle sizes according to this quantity-based particle size distribution. The particle size is obtained by arithmetic averaging the particle sizes according to this quantity-based particle size distribution. The aforementioned particle size refers to the diameter of an imaginary sphere having the same volume as the particle.

[0111] When foamed granules contain colorants, red, blue, green, yellow, and purple pigments or dyes can be used, especially. These pigments or dyes can be inorganic or organic. Examples of inorganic pigments or dyes include chromates such as chrome yellow, zinc yellow, and barium yellow; ferrocyanides such as Prussian blue; sulfides such as cadmium yellow and cadmium red; oxides such as ochre (flagellate); and silicates such as ultramarine. Examples of organic pigments include monoazo pigments, diazo pigments, azo lakes, condensed azo pigments, chelated azo pigments, and polycyclic pigments such as phthalocyanine, anthraquinone, perylene, perinone, indigo sulfide, quinacridone, dioxazine, isoindolinone, and quinophthalone.

[0112] When it is desired that the foamed particles have a uniform black or gray appearance, iron oxide, titanium black, or carbon particles are preferably used as the pigment. Carbon particles refer to particles composed of carbon, and examples include materials selected from one or more of the following: carbon black, conductive carbon, carbon nanotubes, graphene, graphite, and activated carbon. Among these, carbon black is preferred from the viewpoint of achieving excellent dispersibility and cost balance with polyolefin resins. Specific examples of carbon black include channel black, drum black, furnace black, thermal cracking black, acetylene black, and Ketjen black.

[0113] When adding colorants, in order to maintain uniform coloring and not impair flame retardancy, the amount of colorant added to the foamed granules is preferably 0.01 to 6% by mass, more preferably 0.1 to 5% by mass, and even more preferably 0.5 to 4% by mass.

[0114] When coloring a molded body formed from foamed granules using the above-mentioned colorant, carbon black, titanium dioxide, talc, calcium carbonate, magnesium hydroxide, magnesium carbonate, or combinations thereof can be added in order to adjust the brightness and make the appearance of the molded product uniform.

[0115] When ultraviolet absorbers are used or present, examples of ultraviolet absorbers include benzophenone compounds, benzotriazole compounds, triazine compounds, and benzoic acid compounds. Examples of benzophenone compounds include 2-hydroxy-4-octoxybenzophenone. Examples of benzotriazole compounds include 2-(5-methyl-2-hydroxyphenyl)benzotriazole, 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzylphenyl)]-2H-benzotriazole, 2-(3,5-di-tert-butyl-2-hydroxyphenyl)benzotriazole, 2-(3-tert-butyl-5-methyl-2-hydroxyphenyl)-5-chlorobenzotriazole, or 2-(3,5-di-tert-butyl-2-hydroxyphenyl)-5-chlorobenzotriazole. Examples of triazine compounds include 2-(3,5-di-tert-pentyl-2-hydroxyphenyl)benzotriazole, 2-(3,5-di-pentyl-2-hydroxyphenyl)benzotriazole, and 2-(2'-hydroxy-5'-octylphenyl)benzotriazole. Examples of triazine compounds include 2-[4,6-diphenyl-1,3,5-triazin-2-yl]-5-(hexyloxy)phenol and 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl]-. Examples of benzoic acid ester compounds include 2,4-di-tert-butylphenyl-3,5-di-tert-butyl-4-hydroxybenzoate and hexadecyl-3,5-di-tert-butyl-4-hydroxybenzoate. The amount of ultraviolet absorber in the foamed particles can be 0.01 to 2% by mass, preferably 0.05 to 1.5% by mass, and more preferably 0.1 to 1% by mass.

[0116] Hindered amine compounds (HALS) can be listed as light stabilizers. Among hindered amine compounds, compounds having a 2,2,6,6-tetramethyl-4-piperidinamine moiety having only hydrogen or carbon atom directly bonded to the nitrogen atom can be listed. The amount of light stabilizer in the foamed particles is preferably 0.01 to 2% by mass, more preferably 0.05 to 1.5% by mass, and most preferably in the range of 0.1 to 1% by mass.

[0117] As further illustrated above, the foamed particles consist of a foamed layer. Alternatively, the foamed particles may consist of a foamed layer and at least one covering layer disposed on the foamed layer. Such foamed particles can be considered as multilayer foamed particles consisting of a foamed layer as a core layer and at least one covering layer covering the core layer. The covering layer may be a resin layer, particularly a polyolefin resin layer such as a polyethylene-based resin layer or a polypropylene-based resin layer. In each multilayer foamed particle, at least one covering layer may cover a portion of the foamed layer or cover the entire foamed layer.

[0118] When the coating layer is a resin layer such as a polyolefin resin layer, it is preferable that the melting point of the resin component constituting the coating layer is lower than the melting point of the resin component constituting the foamed layer. Furthermore, it is preferable that the coating layer is a substantially non-foaming resin layer. In this case, a molded article with good mechanical strength can be stably provided.

[0119] In at least one coating layer, phosphonate compounds, NOR-type hindered amine compounds, phenolic antioxidants, and sulfuric acid antioxidants may be combined in the same proportion as the foaming layer, in a different proportion than the foaming layer, or none of them may be used. At least one of cyclic phosphonate compounds, NOR-type hindered amine compounds, phenolic antioxidants, and sulfuric acid antioxidants may be incorporated into at least one coating layer.

[0120] Preferably, the sum of the amounts of phosphonate compounds and NOR-type hindered amine compounds in the coating layer is less than the sum of the amounts of phosphonate compounds and NOR-type hindered amine compounds in the foam layer. Furthermore, preferably, the amount of phosphonate compounds in the coating layer is less than the amount of phosphonate compounds in the foam layer; more preferably, the amount of NOR-type hindered amine compounds in the coating layer is less than the amount of NOR-type hindered amine compounds in the foam layer. When the amounts of both phosphonate compounds and NOR-type hindered amine compounds in the coating layer are low, the weldability of the foamed particles during molding can be improved, and the moldability can be further improved. Preferably, at least one coating layer does not contain phosphonate compounds or NOR-type hindered amine compounds.

[0121] The mass ratio of the component constituting the foam layer to the component constituting the coating layer is preferably 99:1 to 70:30, more preferably 98:2 to 80:20, and even more preferably 97:3 to 85:15.

[0122] The second embodiment of the present invention relates to a molded body formed from the foamed particles of the first embodiment of the present invention. Therefore, this molded body can be referred to as a foamed body. The molded body can be a vehicle component, i.e., a component disposed in a vehicle, for example, particularly for automobiles, airplanes, jet skis, etc. As specific but non-limiting examples, molded bodies obtained by in-mold molding of foamed particles can be cited as examples, which can serve as housing elements, enclosure elements, and protective elements for battery devices, electrical devices, electronic devices, etc.

[0123] The molded body described above is a molded body of the aforementioned foamed particles obtained by in-mold molding. This molded body is composed of a foamed structure using a polyolefin resin as the matrix resin. As explained in the description of the foamed particles, examples of polyolefin resins include polypropylene resins, polyethylene resins, and mixtures of polypropylene and polyethylene resins.

[0124] By using foamed particles with the aforementioned bulk density for in-mold molding, it is possible to obtain a density of, for example, 10~500 kg / m³. 3 The molded body.

[0125] The density of the molded body can be 20 kg / m³ 3 The above can also be 30 kg / m 3 That's all. Furthermore, the density of the molded body can be 200 kg / m³. 3 The following can be 150 kg / m 3 The following can be 130 kg / m 3 The following may be 120 kg / m 3 the following.

[0126] The molding process for manufacturing molded articles can be performed by filling foamed particles into a molding die and heating them. Specifically, after filling the molding die with foamed particles, the foamed particles are heated to cause secondary foaming, while simultaneously fusing the foamed particles together, thereby obtaining a molded article having the shape of the molding die cavity. Examples of methods for heating the foamed particles include introducing a heating medium such as water vapor into the molding die and heating the foamed particles through the heating medium, irradiating electromagnetic waves such as high-frequency electromagnetic waves, introducing a specific adhesive (e.g., ATECARMA (trademark)) to bond the particles, electrically heating the molding die without introducing water vapor into the cavity to fuse the particles within the molding die, and combining them, etc.

[0127] As a method for filling foamed particles into a molding die, known methods can be employed. For example, there is a method of directly compressing the foamed particles with pressurized gas inside a pressurized die and then releasing the pressure inside the die (pressurized filling method), or, as a method of mechanically compressing the foamed particles, there is a method of pre-opening the die to expand the molding space, then filling the die with the foamed particles, and finally closing the die after filling (cracking filling method). Alternatively, it is also possible to optionally pressurize the foamed particles with pressurized gas before filling to apply a specified internal pressure to the air bubbles in the foamed particles and impart a certain degree of further expansion to the foamed particles.

[0128] A third embodiment of the present invention relates to a method for manufacturing polyolefin resin foamed granules. The method generally includes the following steps: a step of preparing a component (A) containing a polyolefin resin; and a step of preparing a component (B) containing a phosphonate compound; and the manufacturing method includes a step of treating a mixture of the above-mentioned components (A) and the above-mentioned components (B) for a specific time at a specific temperature and / or a specific pressure in the presence of a foaming agent, thereby manufacturing polyolefin resin foamed granules that satisfy the following formula (1): {(m 215 -m 235 ) / m 215}×100 / P tot ≤35 (1) In equation (1), m 215 The mass of the foamed particles was determined by thermogravimetric analysis at 215℃. m 235 The mass of the foamed particles was determined by thermogravimetric analysis at 235℃. P tot This displays the mass fraction of phosphorus in the foamed granules, ranging from 0.001 to 0.06.

[0129] Component (A) is preferably a polyolefin resin. Furthermore, component (B) is preferably a phosphonate compound. It should be noted that, regarding the polyolefin resin and phosphonate compound, the description of the polyolefin resin and phosphonate compound in the first embodiment can be appropriately referred to.

[0130] There are no particular limitations on the method of mixing components (A) and (B) to obtain a mixture of components (A) and (B). Typically, known extrusion molding methods can be referenced. The mixture of components (A) and (B) can be manufactured separately, for example, in the initial step of manufacturing polyolefin resin granules. Then, in subsequent steps such as autoclaving, the manufactured mixture (polyolefin resin granules) is treated with a foaming agent using a specific temperature and / or pressure, thereby enabling the production of polyolefin resin foamed granules.

[0131] In addition, for example, the extrusion foaming method described below can form a mixture of components (A) and (B) in the same process, while adding a foaming agent to the mixture and treating it with a specific temperature and / or pressure, thereby producing polyolefin resin foamed granules.

[0132] In particular, the amount of component (B) in the mixture is preferably 3 to 20% by mass, more preferably 5 to 18% by mass, and even more preferably 7.5 to 15% by mass. When the content of component (B) is within the above range, the foamed granules produced by the method of the present invention have good properties, especially regarding the desired flame retardancy. In addition, the amount of component (A) in the mixture is preferably 80% by mass or more, preferably 82% by mass or more, and even more preferably 85% by mass or more.

[0133] Typically, the mixture of components (A) and (B) may also contain one or more other additives. Examples of the additives are further disclosed in the exemplary embodiments described above.

[0134] Typically, when processing polyolefin resins and phosphonate compounds to manufacture foamed granules, the raw materials are melt-blended using an extruder, extruded into strips, and cut into specified lengths to produce resin granules. These resin granules can be placed in a pressure vessel with an aqueous dispersion medium such as water, appropriately heated, and then released to a lower pressure environment for foaming. In this series of steps, the polyolefin resin is melt-blended with the phosphonate compound, which is a hygroscopic compound, thereby significantly increasing the hygroscopicity of the resin granules themselves. This increased hygroscopicity of the polyolefin resin reduces the proportion of independent air bubbles in the resulting foamed granules, thereby reducing the weldability of the foamed granules during in-mold molding and making it easier for the surface shape of the resulting foamed granule molded body to be imperfect (insufficient). The inventors of this application unexpectedly discovered that when a method is implemented by treating a mixture of components (A) and (B) of the present invention with a foaming agent at a specific temperature and / or pressure for a specific time using a process involving the use of an aqueous liquid dispersion medium, as shown in the embodiments of the present invention, it is observed that the hygroscopicity of the foamed granules is difficult to affect. Compared to prior art processes, the reduced hygroscopic effect of the foamed particles is believed to be related to the milder conditions of temperature and / or pressure and / or residence time when the resin particles are treated for a specific time using a specific temperature and / or a specific time. Similarly, the inventors of this application have unexpectedly discovered that, when the method of the present invention for treating a mixture of components (A) and (B) containing a foaming agent for a specific time using a specific temperature and / or pressure is implemented by a process accompanied by the use of an aqueous liquid dispersion medium, as shown in the embodiments of the present invention, a larger amount of phosphorus compounds initially introduced when mixing components (A) and (B) remain in the resulting foamed particles in a less degraded or decomposed state. Compared to prior art processes, the milder conditions of temperature and / or pressure and / or residence time during the treatment of resin particles using a specific temperature and / or pressure and / or a specific time are also believed to be related to a further reduction in the dissolution of hygroscopic phosphorus compounds from the resin particles into the aqueous liquid dispersion medium.

[0135] In particular, the method of treating a mixture of components (A) and (B) at a specific temperature for a specific time in the presence of a foaming agent involves heating the mixture of components (A) and (B) to a specific temperature of at least 80°C, more preferably 100°C, while maintaining the mixture at that specific temperature for preferably less than 60 minutes, more preferably less than 50 minutes, more preferably less than 45 minutes, more preferably less than 40 minutes, and more preferably less than 35 minutes. In other words, using a specific temperature of at least 80°C (preferably 100°C) for preferably less than 60 minutes, more preferably less than 50 minutes, more preferably less than 45 minutes, more preferably less than 40 minutes, and more preferably less than 35 minutes. The specific temperature is preferably used in the range of 80 to 180°C, especially 80 to 160°C.

[0136] The temperature of at least 80°C in the above manufacturing method is a temperature selected taking into account the decomposition temperature of the phosphonate compound and / or the melting of the polyolefin resin (a crystalline polyolefin resin) crystals. Test results show that the phosphonate compound is significantly more prone to decomposition at temperatures above 80°C. Furthermore, depending on the type of polyolefin resin, the low-melting-point crystalline components of the polyolefin resin also tend to begin melting at this temperature. Therefore, by selecting 80°C as the specific temperature for heating the mixture of components (A) and (B) in the presence of a foaming agent and processing it within the time range described later, the desired results can be obtained.

[0137] The temperature in the above manufacturing method can preferably be in the range of 10 to 60 minutes, more preferably in the range of 20 to 50 minutes, further preferably in the range of 25 to 45 minutes, and even more preferably in the range of 25 to 35 minutes. When the time is within the above range, the phosphonate compound contained in component (B) is exposed to severe deterioration conditions for a short time, thus reducing the deterioration of the phosphonate compound contained in component (B) and allowing the mixture to foam well. The temperature and time in the above manufacturing method are applicable when the mixture of components (A) and (B) and the foaming agent are present in an autoclave, especially when aqueous or non-aqueous liquid dispersion media such as water or (silicone) oil are present, for example. In addition, for example, when heating the mixture of components (A) and (B) containing the foaming agent in the absence of a liquid dispersion medium, the temperature and time in the above manufacturing method are also applicable to mixtures containing the foaming agent.

[0138] In particular, the method includes the step of treating a mixture of components (A) and (B) at a specific temperature for a specific time in the presence of a foaming agent, and the step of heating the mixture of components (A) and (B) to a specific foaming temperature of at least 100°C while maintaining it at that specific foaming temperature for a specific time in the presence of a foaming agent. Furthermore, while heating the mixture and maintaining the specific foaming temperature, the mixture is exposed to a temperature of at least 80°C for a period of 60 minutes or less. Thus, when treating the mixture by heating it to a specific foaming temperature and maintaining that specific foaming temperature in the presence of a foaming agent, the mixture is exposed to a temperature of at least 80°C for a period of 60 minutes or less.

[0139] The specific pressure (gauge pressure) used in the above manufacturing method can preferably be in the range of 0.1 to 10 MPa(G), more preferably in the range of 0.2 to 7.5 MPa(G), even more preferably in the range of 0.3 to 5 MPa(G), even more preferably in the range of 0.4 to 5 MPa(G), and even more preferably in the range of 0.5 to 4.5 MPa(G). The above pressure can be used for a period of preferably 10 to 60 minutes, more preferably in the range of 20 to 50 minutes, even more preferably in the range of 25 to 45 minutes, and even more preferably in the range of 25 to 35 minutes. When the pressure is used for a period within the above range, the phosphonate compounds contained in component (B) are exposed to severe deterioration conditions for a short time, thus reducing the deterioration of the phosphonate compounds contained in component (B) and allowing the mixture to foam well. The pressure and time in the above manufacturing method can be applied to the mixture of components (A) and (B) in an autoclave when the mixture of components (A) and (B) and the foaming agent are present, especially in the presence of an aqueous or non-aqueous liquid dispersion medium such as water or (silicone) oil. Furthermore, for example, when the mixture of components (A) and (B) and the foaming agent are present in a pressure vessel in the absence of a liquid dispersion medium, the pressure and time in the above manufacturing method can also be applied to the mixture within the pressure vessel.

[0140] The mixture of components (A) and (B) can be processed in a liquid dispersion medium consisting of a non-aqueous liquid. The mixture can be processed, for example, in an autoclave. Alternatively, the mixture can also be processed, for example, in a pressure vessel without a liquid dispersion medium. When the mixture is processed in a non-aqueous liquid or without a liquid dispersion medium, the degradation of the phosphonate compounds contained in component (B) is reduced because there is no substantial water causing degradation of the phosphonate compounds.

[0141] An exemplary method for preparing foamed granules includes a dispersion step of dispersing a mixture comprising at least components (A) and (B), and, as appropriate, a NOR-type hindered amine compound and / or a phenolic antioxidant and / or a sulfur-based antioxidant and / or other respective additives, into an aqueous dispersion medium containing an inorganic solid dispersant in a container. The method can include a foaming step of wetting the mixture with a foaming agent under the influence of pressure and temperature; and a foaming step of releasing the mixture containing the foaming agent (resin granules) together with the aqueous medium from the container into a pressure atmosphere lower than the pressure inside the container for foaming.

[0142] As another exemplary method for manufacturing foamed granules, a method of manufacturing foamed granules by extrusion foaming using an extruder can be listed. Specifically, a method can be listed where components (A), (B), and a foaming agent are supplied to an extruder for mixing, and then a resin melt containing the foaming agent is extruded from the downstream side of the extruder for foaming, while the extruded foam is cut into granules to obtain foamed granules.

[0143] This process is a non-limiting example of a one-step process in the manufacture of foamed granules.

[0144] A two-step process for manufacturing polyolefin resin granules can be described as follows. First, a mixture comprising a polyolefin resin (component (A)), a phosphonate compound (component B), an optional NOR-type hindered amine compound, an optional phenolic antioxidant and / or a sulfur-based antioxidant, and optional additives as needed, is supplied to an extruder and heated and kneaded to obtain a resin melt. Next, the resin melt is extruded from the extruder and granulated by methods such as strand cutting, hot cutting, or underwater cutting to produce polyolefin resin granules. When manufacturing multilayer polyolefin resin granules, a manufacturing apparatus comprising a core-forming extruder, a multilayer strand-forming die disposed downstream of the core-forming extruder, and a coating layer-forming extruder can be used. It should be noted that the coating layer-forming extruder is connected to the multilayer strand-forming die via its downstream side, forming a structure that allows the resin melts formed by each extruder to be stacked within the die.

[0145] The average mass of the resin particles (the average mass of the additive per particle determined from the mass of 200 randomly selected particles) is preferably 0.1 to 20 mg, more preferably 0.2 to 10 mg, even more preferably 0.3 to 5 mg, and even more preferably 0.4 to 2 mg.

[0146] In particular, in the case of the strand cutting method, cylindrical resin particles are formed. When the resin particles are cylindrical, the particle length in the extrusion direction of the polyolefin resin particles is preferably 0.1 to 4.0 mm, more preferably 0.3 to 3 mm, and even more preferably 0.5 to 2.5 mm. The length-to-diameter ratio (length / diameter ratio) is preferably 0.5 to 5.0, more preferably 1.0 to 3.0. In the strand cutting method, the particle size, length / diameter ratio, and average mass of the resin particles can be adjusted by appropriately changing the extrusion speed, traction speed, and cutter speed by cutting the strand during melt extrusion.

[0147] In a preferred method for manufacturing polyolefin foamed granules, polyolefin resin granules comprising a mixture containing a phosphonate compound (especially a cyclic phosphonate compound), a NOR-type hindered amine compound, a phenolic antioxidant, and a sulfur-based antioxidant are dispersed in an aqueous dispersion medium containing a solid dispersant in a container. A foaming agent is then impregnated into the polyolefin resin granules in the container. The polyolefin resin granules containing the foaming agent, together with the aqueous dispersion medium, are released into a pressure atmosphere lower than the pressure inside the container, thereby manufacturing polyolefin resin foamed granules.

[0148] As the dispersion medium for dispersing the aforementioned resin particles into the container, an aqueous dispersion medium is preferably used. The proportion of water used as the aqueous dispersion medium is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. The proportion of water in the aqueous dispersion medium can also be 100% by mass. Examples of dispersion media other than water include ethylene glycol, glycerol, methanol, ethanol, and silicone oil. Examples of silicone oils include, for example, polydimethylsiloxane (PDMS).

[0149] In the dispersion process, to prevent the heated polyolefin resin particles in the container from fusing together, it is preferable to add a solid dispersant to the dispersion medium. For the solid dispersant, both organic and inorganic solid dispersants can be used as long as they can prevent the polyolefin resin particles in the container from fusing together; however, inorganic solid dispersants are preferred, and particulate inorganic solid dispersants are more preferred due to their ease of operation. Examples of inorganic solid dispersants include natural or synthetic clay minerals such as kaolin, mica, and clay; alumina; titanium dioxide; basic magnesium carbonate; basic zinc carbonate; calcium carbonate; and iron oxide. One or more of these can be used. Among these, natural or synthetic clay minerals are preferred as solid dispersants. The amount of solid dispersant in the container is preferably in the range of 0.001% to 5% by mass, relative to the mass of the polyolefin resin particles introduced into the container (taking 100% by mass as the unit).

[0150] When using solid dispersants, it is preferable to use them in combination with anionic surfactants such as sodium dodecylbenzenesulfonate, sodium alkyl sulfonate, and sodium oleate as dispersing aids. The above-mentioned dispersing aids are preferably added at approximately 0.001 to 1 part by weight relative to 100 parts by weight of polyolefin resin particles in the aqueous dispersion medium.

[0151] As a blowing agent for foaming polyolefin resin particles, a physical blowing agent is preferred. The physical blowing agent can be either inorganic or organic. Examples of inorganic physical blowing agents include carbon dioxide, air, nitrogen, helium, and argon. Examples of organic physical blowing agents include aliphatic hydrocarbons such as propane, n-butane, isobutane, n-pentane, isopentane, hexane, cyclopentane, and cyclohexane, and halogenated hydrocarbons such as chlorofluoromethane, trifluoromethane, 1,1-difluoroethane, 1-chloro-1,1-difluoroethane, 1,1,1,2-tetrafluoroethane, chloromethane, chloroethane, and dichloromethane. These physical blowing agents can be used alone. Alternatively, two or more blowing agents can be mixed. Furthermore, inorganic and organic physical blowing agents can be used in combination. The preferred foaming agent is an inorganic physical foaming agent that can improve the environmental impact and flame retardancy of the molded body formed from the foamed particles. Carbon dioxide can be used as an example of an inorganic physical foaming agent.

[0152] The amount of foaming agent added is preferably 0.1 to 30% by mass relative to 100% by mass of polyolefin resin particles, more preferably in the range of 0.5 to 15% by mass.

[0153] The preferred method for impregnating the foaming agent into the resin particles is to disperse the resin particles in an aqueous dispersion medium in a closed container (e.g., an autoclave), add the foaming agent into the closed container, pressurize the container, and maintain the closed container at a specified temperature and pressure.

[0154] During the foaming process, the internal pressure inside the container, i.e., the pressure inside the container just before the resin particles and the aqueous dispersion medium are released, is preferably 0.1 MPa (G) or higher, more preferably 0.2 MPa (G) or higher, and even more preferably 0.5 MPa (G) or higher. The upper limit is preferably 5 MPa (G) or lower, more preferably 4 MPa (G) or lower. Within the above range, the sealed container will not break or explode, and the desired foamed particles can be safely manufactured.

[0155] The foaming temperature can be selected based on the polyolefin resin contained in the polyolefin resin particles. The temperature inside the container is raised to the set foaming temperature and maintained at this temperature for 1 to 30 minutes. Then, the resin particles containing the foaming agent are released from the sealed container into a pressure atmosphere (e.g., atmospheric pressure) that is lower than the pressure inside the container to produce foamed particles.

[0156] When the polyolefin resin particles are based on polypropylene resin, the foaming temperature is preferably below 160°C, more preferably below 155°C, and even more preferably below 150°C.

[0157] When the polyolefin resin particles are based on polyethylene resin, the foaming temperature is preferably below 140°C, more preferably below 135°C, and even more preferably below 130°C.

[0158] By selecting a lower foaming temperature during the manufacturing of foamed granules, the resin granules are less likely to be exposed to an environment where the phosphonate compounds contained in component (B) are prone to deterioration. Therefore, the deterioration of the phosphonate compounds contained in component (B) can be suppressed. That is, by selecting a polyolefin resin with a (relatively) lower foaming temperature, it is easy to obtain foamed granules that satisfy the following formula (1). In addition, when using an aqueous liquid dispersion medium, selecting a higher foaming pressure and simultaneously selecting a lower foaming temperature, and shortening the exposure time to water above 80°C during the foaming process, is preferable in suppressing the deterioration of the phosphonate compounds contained in component (B) and obtaining foamed granules that satisfy the following formula (1). Furthermore, it is also preferable to use a non-aqueous liquid dispersion medium for the foaming process, or to perform the foaming process in the absence of an aqueous dispersion medium, such as infrared heating, in order to obtain foamed granules that satisfy the following formula (1).

[0159] {(m 215 -m 235 ) / m 215}×100 / P tot ≤35 (1) In equation (1), m 215 The mass of the foamed particles was determined by thermogravimetric analysis at 215℃. m 235 The mass of the foamed particles was determined by thermogravimetric analysis at 235℃. P tot This displays the mass fraction of phosphorus in the foamed granules, ranging from 0.001 to 0.06.

[0160] The polyolefin resin foamed particles obtained as described above can also become high-expansion-ratio (low bulk density) foamed particles in a secondary process. In the secondary process, the polyolefin resin foamed particles obtained as described above are pressurized by using a pressurized fluid (such as air or carbon dioxide) to increase the pressure (internal pressure) inside the foamed layer bubbles. Then, the pressurized foamed particles are heated by water vapor, high frequency, infrared heating, etc., to further foam (two-step foaming).

[0161] A fourth embodiment of the present invention relates to a method for at least qualitatively determining the flame-retardant behavior of the foamed particles of the first embodiment of the present invention. The method further includes the steps of preparing and determining each foamed particle, particularly determining the mass of each foamed particle and the phosphorus content P of the foamed particles in thermogravimetric analysis at 215°C and 235°C based on the aforementioned TGA-measurement and spectroscopic-measurement (inductively coupled plasma atomic emission spectrometry), and determining whether the phosphorus content P of the foamed particles is within the range of 0.1 to 6% by mass. If the phosphorus content P of the foamed particles is within the range of 0.1 to 6% by mass, the method further determines whether the foamed particles satisfy the following formula (1): {(m 215 -m 235 ) / m 215}×100 / P tot ≤35 (1) In equation (1), m 215 The mass of the foamed particles was determined by thermogravimetric analysis at 215℃. m 235 The mass of the foamed particles was determined by thermogravimetric analysis at 235℃. P tot This displays the mass fraction of phosphorus in the foamed granules, ranging from 0.001 to 0.06.

[0162] When the foamed particles satisfy the above formula (1), the foamed particles are determined to have sufficiently high flame retardant behavior; otherwise, the foamed particles are determined not to have sufficiently high flame retardant behavior. Sufficiently high flame retardant behavior can satisfy at least one of the following UL94 standard classifications: HB-F, HF-2, HF-1, V-2, V-1, V-0. Thus, when the foamed particles satisfy formula (1), the foamed particles can satisfy at least one of the following UL94 standard classifications: HB-F, HF-2, HF-1, V-2, V-1, V-0.

[0163] This method can be at least partially implemented under the control of a controller embedded in hardware and / or software, which uses the aforementioned parameter m. 215 m 235 and P tot The input parameters are used to determine whether they satisfy the above equation (1). The determination result can be output to the user and / or other functional devices equipped with hardware and / or software.

[0164] All notes regarding the foaming granules of the first embodiment of the present invention also apply to the components of the second embodiment of the present invention and / or the methods of the third embodiment of the present invention and / or the methods of the fourth embodiment of the present invention, and vice versa.

[0165] The present invention will be further described in detail below by way of examples, but the present invention is not limited to these examples in any way.

[0166] Tables 1A, 1B, 2A, and 2B below show 11 embodiments of foamed granules according to various embodiments of the present invention, wherein the parameters of the original (dense) polyolefin resin particles processed for manufacturing the foamed granules and the parameters of the process for manufacturing the foamed granules from the resin particles are different. As an example, different liquid dispersion media such as water and polydimethylsiloxane (PDMS, silicone oil) and different temperatures, pressures, and heating times were used in the embodiments.

[0167] PP1 polypropylene resin is composed of an ethylene-propylene copolymer with a melting point of 143℃, an ethylene content of 2.1% by mass, and an MFR of 6 g / 10 min (load 2.16 kg, 230℃, determined based on JIS K7210-1:2014).

[0168] PP2 polypropylene resin is composed of an ethylene-propylene copolymer with a melting point of 133℃, an ethylene content of 3.5% by mass, and an MFR of 6 g / 10 min (load 2.16 kg, 230℃, determined based on JIS K7210-1:2014).

[0169] The polyethylene resin composed of PE is made of linear low-density polyethylene (LLDPE) with a melting point of 120°C and an MFR of 1.5 g / 10 min (load 2.16 kg, determined at 190°C based on JIS K7210-1:2014).

[0170] The term "single-layer" indicates that the resin particles consist only of a foamed layer and have no coating layer. The term "multi-layer" indicates that the resin particles have a foamed layer as the core layer and a substantially unfoamed resin layer as a coating layer covering the core layer.

[0171] The phosphonate compound used in the examples is “Aflammit (registered trademark) PCO 900”, which is available from Thor Ltd. (address: 67329 Speyer, Germany). It has a melting point of 240°C and is a cyclic phosphonate compound represented by the following general formula (1), where R1 and R2 are methyl groups.

[0172] The NOR-type hindered amine compound used in the examples is "Flamestab (registered trademark) NOR 116", which is available from BASF Japan Co., Ltd. (Tokyo) and has a molecular weight of 2261, represented by the following chemical formula.

[0173] The phenolic antioxidant is traded under the name "Irganox (registered trademark) 1330," manufactured by BASF, with a melting point of 245°C. The following chemical formula represents the compound: The sulfur-based antioxidant is di(octadecyl)-3,3'-thiodipropionate, manufactured by BASF under the trade name "Irganox PS 802". The following chemical formula represents the compound: Example 1 An extruder with an inner diameter of 50 mm and a die for forming strands on the downstream side of the extruder is to be prepared.

[0174] PP1, zinc borate (arithmetic mean particle size on a number basis: 9 μm), Aflammit PCO 900, Flamesterab NOR 116, Irganox 1330 and Irganox PS 802 were supplied to an extruder in the proportions specified in Table 1A and melt-blended to form a resin melt.

[0175] The obtained resin melt is extruded from a strand forming die to form a strand. After the extruded strand is cooled with water, it is cut into polypropylene resin particles by a granulator (average mass of each resin particle: 1.0 mg).

[0176] In a 100L sealed container, 2 kg of the above-mentioned polypropylene resin particles, 75L of water as a liquid dispersion medium, 65 g of kaolin, and 43 g of sodium dodecylbenzenesulfonate were placed.

[0177] Then, carbon dioxide was added to the sealed container as a foaming agent until the gauge pressure reached 0.5 MPa (G), pressurizing the container. The contents of the sealed container were then heated to the foaming temperature shown in Table 1A. Carbon dioxide was then added to the sealed container until the gauge pressure (foaming pressure) shown in Table 1B was reached, and this temperature and pressure were maintained for 9 minutes. The total time the polypropylene resin particles were exposed to temperatures above 80°C is detailed in Table 1B.

[0178] Subsequently, the contents of the sealed container were released to atmospheric pressure to cause the polypropylene resin particles to foam, thereby obtaining polypropylene resin foamed particles. The results of the physical property determination of the polypropylene resin foamed particles are shown in Table 1B.

[0179] Examples 2-6 and Comparative Examples 1-7 Except for changes in the proportions of each component and the process conditions, polypropylene resin foamed granules were obtained in the same manner as in Example 1. The proportions of each component and the relevant process conditions are shown in Tables 1A, 1B, 3A, and 3B. The results of the physical property determination of the obtained polypropylene resin foamed granules are shown in Tables 1B and 3B.

[0180] It should be noted that in Examples 2-7 and 11, and Comparative Examples 2-6 and 8, resin particles were manufactured using an extrusion apparatus capable of producing multilayer polyolefin resin particles, and foamed to obtain multilayer foamed particles having a foamed core layer and a resin layer covering the core layer. In manufacturing the resin particles, a manufacturing apparatus was used, comprising a core-forming extruder, a multilayer strand-forming die disposed downstream of the core-forming extruder, and a coating layer-forming extruder. The multilayer resin particles were manufactured according to the proportions of each component and the relevant process conditions listed in Tables 1A, 1B, 3A, and 3B. It should be noted that the coating layer-forming extruder is connected to the multilayer strand-forming die via its downstream side, creating a structure that allows the resin melts formed by each extruder to be stacked within the die.

[0181] Example 7 Except for changes to the proportions of each component and the process conditions, and the use of polyethylene-based resin as the polyolefin-based resin, polyolefin-based resin foamed granules (polyethylene-based resin foamed granules) were obtained in the same manner as in Examples 1-6. The proportions of each component and the related process conditions are shown in Tables 2A and 2B.

[0182] Examples 8-10 Except for changes in the proportions of each component and the process conditions, and the use of polydimethylsiloxane (PDMS) as the liquid dispersion medium, polyolefin resin foamed particles (polypropylene resin foamed particles) were obtained in the same manner as in Examples 1-6. The proportions of each component and the related process conditions are shown in Tables 2A and 2B.

[0183] For the foamed particles obtained in Examples 8-10, before measuring the density, residual PDMS oil was carefully cleaned by solvent washing, and the solvent was removed by drying. Then, the foamed particles were used for the following molding process, and the weld ratio of the resulting molded body was evaluated. A flat mold with a molding space of 400 mm long × 300 mm wide × 30 mm thick was prepared as the mold. The foamed particles were filled into the molding space, and the mold was closed. Then, steam was supplied into the mold to heat the foamed particles, thereby forming a plate-shaped foamed particle molded body.

[0184] First, steam is supplied to the molds with the drain valves of both molds open (venting step). Then, with the drain valve of the other mold open, steam is supplied to one mold for heating (one-sided heating step). Next, with the drain valve of one mold open, steam is supplied from the other mold (opposite-sided heating step). Then, with the drain valves of both molds closed, steam is supplied from both molds until the molding steam pressure inside the mold reaches 0.32 MPa(G) (double-sided heating step). After the double-sided heating step is completed, the pressure inside the mold is released, and the mold is water-cooled until the pressure (surface pressure) generated on the molding surface by the secondary foaming force of the foamed particles reaches 0.05 MPa(G).

[0185] Next, open the mold and remove the expanded granules from it. The molded product removed from the mold is cured in an 80°C oven for 12 hours, and then slowly cooled to room temperature.

[0186] The foamed particle molded body obtained by bending failure is then tested, and the number of foamed particles present on the failure surface (C1) and the number of foamed particles that break the material (C2) are measured.

[0187] The ratio of the number of foamed particles that break down to the total number of foamed particles (C2 / C1×100) is calculated as the material failure rate.

[0188] The above tests were performed on the three molded bodies, and the arithmetic mean of the failure rates of each material was taken as the weld ratio. The obtained weld ratio was evaluated according to the following criteria. It should be noted that the higher the weld ratio value, the better the weldability between the foamed particles.

[0189] The results of the welding rate determination were as follows: the welding rate of Example 8 was evaluated as above 60%, and the welding rate of Examples 9 and 10 was evaluated as above 30% and less than 60%.

[0190] Example 11 An extruder with an inner diameter of 50 mm and a die for forming strands on the downstream side of the extruder is to be prepared.

[0191] PP1, zinc borate (arithmetic mean particle size on a number basis: 9 μm), Aflammit PCO900, Flamesterab NOR 116, Irganox 1330 and Irganox PS 802 were supplied to an extruder in the proportions specified in Table 1 and melt-blended to form a resin melt.

[0192] The obtained resin melt is extruded from a ply forming die to form a ply. The extruded ply is then cooled with water and cut into polypropylene resin particles using a granulator (average mass of each resin particle: 1.0 mg).

[0193] Under a pressure of approximately 5.0 MPa (G), carbon dioxide, which serves as a foaming agent, is carried onto the aforementioned polypropylene resin particles for 1000 hours without heating or temperature control to obtain pressurized polypropylene resin particles.

[0194] Then, foamed granules are obtained by transporting pressurized polypropylene resin granules into a continuous infrared oven consisting of multiple infrared emitters to foam them.

[0195] The physical property test results of the obtained polypropylene resin foamed particles are shown in Table 2B.

[0196] Tables 1A, 1B, 2A, and 2B show that all 11 embodiments satisfy the above formula (1) (see the values ​​recorded in the last row of Tables 1B and 2B). Therefore, all 11 embodiments show good flame retardancy. Tables 3A and 3B show 8 comparative examples ("C1~C8"), where Comparative Example 1 corresponds to Example 1, Comparative Example 2 corresponds to Example 2, Comparative Example 3 corresponds to Example 3, Comparative Example 4 corresponds to Example 4, Comparative Example 5 corresponds to Example 5, Comparative Example 6 corresponds to Example 6, Comparative Example 7 corresponds to Example 10, and Comparative Example 8 corresponds to Example 11.

[0197] In contrast to the examples, the comparative examples do not satisfy the above formula (1) (see the values ​​shown in the last row of Table 3B). This is believed to be due to the presence of more degraded / decomposed phosphonate compounds in the foamed particles of the comparative examples.

[0198] The examples shown in Tables 1A, 1B, 2A, and 2B should not be considered as the entirety of measures for mitigating the decomposition of phosphonate compounds. Other measures that influence the chemical reactions involved in the decomposition, such as altering pH, pressure, etc., should also be considered.

[0199] The presence of such degraded / decomposed phosphonate compounds can be detected by, for example, solid phosphorus NMR analysis. Typically, foamed particles... 31 The results of the P-NMR analysis showed additional peaks relative to the original resin particles used to manufacture the foamed granules, which indicated the deterioration / decomposition of phosphonate compounds.

[0200] Table 1A Table 1B Table 2A Table 2B Table 3A Table 3B The molded articles formed by in-mold molding of foamed granules from Examples 4 and 11, as well as Comparative Examples 4 and 8, were evaluated using UL94 testing. Examples 4 and 4, and Examples 11 and 8, used the same polyolefin resin granules and were manufactured under different process conditions shown in the table.

[0201] In Example 4, three out of five test pieces were evaluated as "V-0" according to the UL94 standard, whereas none of the five test pieces in Comparative Example 4 were evaluated as "V-0". In Example 11, all five test pieces were evaluated as "V-0" according to the UL94 standard, whereas none of the five test pieces in Comparative Example 8 were evaluated as "V-0".

[0202] In addition, as in Example 12, as described below, single-layer foamed particles are manufactured by extrusion foaming.

[0203] First, prepare an extrusion foaming device with an extruder (manufactured by IKG Corporation) with an inner diameter of 50 mm and an underwater cutting machine (manufactured by ECON Corporation).

[0204] 48 parts by mass of branched homopolymer polypropylene (WB140 manufactured by Borealis, melting point 161°C), 38 parts by mass of ethylene-propylene random copolymer (ethylene content 3.1% by mass, MFR 7 g / 10 min, melting point 143°C), 11 parts by mass of Aflammit PCO 900, 3 parts by mass of Flamesterab NOR 116, and 1 part by mass of sodium bicarbonate-citric acid chemical foaming agent (FineCell Master PO217K manufactured by Daihisei Chemical Co., Ltd.) were fed into the extruder inlet of the extrusion foaming unit. Next, after melt-blending the raw materials in the extruder, isobutane was added as a foaming agent in the middle section of the extruder and further blended to adjust the foaming resin melt. At this point, the amount of isobutane added to the foaming resin melt was 6% by mass. Subsequently, the foaming resin melt is extruded from a die plate located downstream of the extruder for foaming. Simultaneously, a four-blade cutter cuts the extruded foam to create foamed granules. The die plate has five 2.3 mm diameter holes as extrusion orifices. During extrusion, the resin temperature (foaming temperature) at the diverter is 162°C, the foaming pressure is 3.4 MPa(G), and the mixture is exposed to temperatures above 80°C for a total of 7 minutes during the foaming process. Furthermore, the molten resin discharge rate is 13 kg / h, and the cutter rotation speed is 1000 rpm.

[0205] The foamed particles obtained in Example 12 had an average mass of 11 mg / particle and a density of 122 kg / m³. 3 The phosphorus content (P) is 2.7% by mass, {(m 215 -m 235 ) / m 215}×100 is 2.9, {(m 215 -m 235 ) / m 215}×100 / P tot It is 1.1.

[0206] In addition, the foamed granules obtained in Example 12 were in-mold molded to produce granules with dimensions of 400 mm long × 300 mm wide × 20 mm thick and a density of 200 kg / m³. 3 The molded body was then subjected to a UL94 vertical test for evaluation. According to the UL94 standard, the molded body was rated as "V-0".

[0207] Further exemplary embodiments of the present invention will become clear from the accompanying drawings: Figure 1A For the resin particles (curve 1) 31 Schematic diagram of p-NMR analysis Figure 1B To implement on foamed particles (curve 2) obtained through conventional foaming processes 31 The schematic diagram of the p-NMR analysis. Curve 2, showing the foamed particles, shows a second peak from phosphorus, thus indicating the presence of altered / decomposed phosphonate compounds in the foamed particles. This second peak is not present in curve 1, which represents resin particles before the foaming process under applicable specified temperature and / or pressure. This example demonstrates the degradation / decomposition products induced by a state-of-the-art autoclave-based foaming process. As demonstrated in the comparative example above, if such degradation / decomposition products are present in large quantities, the foamed particles will not satisfy equation (1).

[0208] Figure 2 This is a schematic diagram of the TGA curves of the phosphonate compounds used in the examples before and after deterioration and decomposition within a temperature range of 215°C to 235°C. The upper curve represents the phosphonate compound that has not deteriorated / decomposed, and the lower curve represents the phosphonate compound that has deteriorated / decomposed, showing different thermal behaviors. In particular, compared to the phosphonate compound that has not deteriorated or decomposed, the deteriorated and decomposed phosphonate compound has a greater thermally induced mass loss and will adversely affect the original flame retardant properties of the phosphonate compound.

[0209] This application claims priority based on European Patent Application No. 23315445.9, filed on November 30, 2023.

Claims

1. A polyolefin resin foaming granule, characterized in that, The foamed particles contain polyolefin resins and phosphonate compounds. The phosphorus content (P) of the foamed granules is 0.1-6% by mass. The foamed particles satisfy the following formula (1): {(m 215 -m 235 ) / m 215 }×100 / P tot ≤35 (1) In equation (1), m 215 The mass of the foamed particles was determined by thermogravimetric analysis at 215℃. m 235 The mass of the foamed particles was determined by thermogravimetric analysis at 235℃. P tot The value of the mass fraction of phosphorus in the foamed granules is displayed in the range of 0.001 to 0.

06.

2. The polyolefin resin foamed granules as described in claim 1, wherein, The foamed particles contain NOR-type hindered amine compounds. The amount of the NOR-type hindered amine compound in the foamed particles is more than 0.1% by mass and less than 5% by mass.

3. The polyolefin resin foamed granules as described in claim 1 or 2, wherein, In the foamed particles, the sum of the amount of phosphonate compound and the amount of NOR-type hindered amine compound is less than 15% by mass.

4. The polyolefin resin foamed granules according to any one of claims 1 to 3, wherein, The phosphorus content (P) of the foamed granules is 1 to 4.8% by mass.

5. The polyolefin resin foamed granules according to any one of claims 1 to 4, wherein, The foamed granules contain phenolic antioxidants. In the foamed granules, the amount of the phenolic antioxidant is 0.01~0.5% by mass.

6. The polyolefin resin foamed granules according to any one of claims 1 to 5, wherein, The foamed particles contain NOR-type hindered amines and phenolic antioxidants. In the foamed particles, the ratio of the amount of phenolic antioxidant to the amount of NOR-type hindered amine compound is 0.03~0.

9.

7. The polyolefin resin foamed granules according to any one of claims 1 to 6, wherein, The phosphonate compound comprises a cyclic phosphonate compound represented by any of the following general formulas (1) to (4). In general formula (1), R 1 and R 2 They represent hydrocarbon groups, In general formula (2), R 3 This indicates an alkyl group with 1 to 22 carbon atoms or an aryl group with 6 to 15 carbon atoms. In general formula (3), R 4 and R 8 These represent alkyl groups with 1 to 4 carbon atoms, R 5 and R 7 These represent either hydrogen atoms or alkyl groups having 1 to 4 carbon atoms, respectively. R 6 This refers to alkyl groups with 1 to 22 carbon atoms, cycloalkyl groups with 9 to 22 carbon atoms, aryl groups with 9 to 22 carbon atoms, or aralkyl groups with 9 to 22 carbon atoms. In general formula (4), R 9 and R 12 These represent alkyl groups with 1 to 4 carbon atoms, R 10 This refers to alkyl groups with 1 to 22 carbon atoms, cycloalkyl groups with 9 to 22 carbon atoms, aryl groups with 9 to 22 carbon atoms, or aralkyl groups with 9 to 22 carbon atoms. R 11 It refers to an alkyl group having 1 to 4 hydrogen atoms or carbon atoms.

8. The foamed granules as described in any one of claims 1 to 7, wherein, The foamed granules contain sulfur-based antioxidants. The amount of sulfur-based antioxidant in the foamed particles is 0.01~0.5% by mass.

9. The foamed granules as described in any one of claims 1 to 8, wherein, The foamed particles contain NOR-type hindered amine compounds and sulfur-based antioxidants. In the foamed particles, the ratio of the amount of the NOR-type hindered amine compound to the amount of the sulfur-based antioxidant is 0.03 to 0.

9.

10. The foamed granules as described in any one of claims 1 to 9, wherein, The polyolefin resin includes polypropylene resin.

11. A foamed granular molded body, wherein, It is obtained by in-mold molding of the foamed particles according to any one of claims 1 to 10.

12. A method for manufacturing polyolefin resin foamed granules, the method comprising: The process of preparing component (A) containing polyolefin resin; and, The process of preparing component (B) containing phosphonate compounds; and, The manufacturing method includes the step of treating a mixture of component (A) and component (B) at a specific temperature and / or a specific pressure for a specific time in the presence of a foaming agent; The polyolefin resin foam particles satisfy the following formula (1): {(m 215 -m 235 ) / m 215 }×100 / P tot ≤35 (1) In equation (1), m 215 The mass of the foamed particles was determined by thermogravimetric analysis at 215℃. m 235 The mass of the foamed particles was determined by thermogravimetric analysis at 235℃. P tot This displays the mass fraction of phosphorus in the foamed granules, ranging from 0.001 to 0.

06.

13. The method for manufacturing polyolefin resin foamed granules as described in claim 12, wherein, The step of treating the mixture and the foaming agent at the specific temperature for a specific time consists of heating the mixture to a specific foaming temperature of at least 100°C while holding the mixture at the specific foaming temperature for a specific time. When the mixture is heated and held at the specific foaming temperature, the mixture is exposed to a temperature of at least 80°C for less than 60 minutes.

14. The method for manufacturing polyolefin resin foamed granules as described in claim 12 or 13, wherein, The mixture is processed in a non-aqueous liquid, or the mixture is processed in the absence of a liquid dispersion medium.

15. The method for manufacturing polyolefin resin foamed granules according to any one of claims 12 to 14, wherein, The amount of component (B) in the mixture is 3 to 20% by mass.

16. A method for at least qualitatively determining the flame-retardant behavior of the foamed particles of claim 1. The method includes determining the mass of each foamed particle and the phosphorus content P of the foamed particles in thermogravimetric analysis at 215℃ and 235℃, and determining whether the foamed particles satisfy the following formula (1) when the phosphorus content P of the foamed particles is 0.1~6% by mass: {(m 215 -m 235 ) / m 215 }×100 / P tot ≤35 (1) In equation (1), m 215 The mass of the foamed particles was determined by thermogravimetric analysis at 215℃. m 235 The mass of the foamed particles was determined by thermogravimetric analysis at 235℃. P tot This displays the mass fraction of phosphorus in the foamed granules, ranging from 0.001 to 0.06.

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