Polyolefin resin foam particles and polyolefin resin foam particle molded articles

Abstract

To provide polyolefin-based resin foam particles which enable provision of a foam particle molding that exhibits good in-mold moldability and excellent flame retardancy, and a polyolefin-based resin foam particle molding which is excellent in flame retardancy.SOLUTION: Polyolefin-based resin foam particles contain an NOR type hindered amine-based compound which has bulk density of 10 kg / m3 or more and 100 kg / m3 or less and is represented by a specific structural formula, wherein a content of the NOR type hindered amine-based compound in the polyolefin-based resin foam particles is 0.01 mass% or more and 3 mass% or less. A polyolefin-based resin foam particle molding has a density of 10 kg / m3 or more and 100 kg / m3 or less, and a content of the NOR type hindered amine-based compound represented by a specific structural formula in the polyolefin-based resin foam particle molding is 0.01 mass% or more and 3 mass% or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to polyolefin resin foamed particles containing a flame retardant and a polyolefin resin foamed particle molded body excellent in flame retardancy obtained by molding the polyolefin resin foamed particles in a mold.

Background Art

[0002] A polyolefin resin foamed particle molded body obtained by molding polyolefin resin foamed particles is used in various applications such as packaging materials, vehicle members, and building materials. This type of foamed particle molded body may be colored with carbon black or the like. Further, in order to make the foamed particle molded body difficult to burn, a NOR type hindered amine compound may be added as a flame retardant to polypropylene resin foamed particles (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Foam particle molded articles with reduced density and lighter weight, or those containing a large amount of carbon material such as carbon black, tend to be highly flammable. Therefore, in order to achieve the desired flame retardancy, it may be necessary to increase the amount of NOR-type hindered amine compounds added to the foam particles. However, for example, increasing the amount of NOR-type hindered amine compounds described in Patent Document 1 may reduce the in-moldability of the foam particles. In other words, to maintain good in-moldability of the foam particles, it is preferable to add a small amount of NOR-type hindered amine compounds. However, when the amount of NOR-type hindered amine compounds added to the foam particles is kept to a small amount, taking into consideration the impact on in-moldability, etc., foam particle molded articles manufactured using these foam particles have difficulty stably exhibiting the desired flame retardancy.

[0005] This invention was made in view of the above background. Specifically, this invention provides polyolefin resin foam particles that can be obtained to produce a foam particle molded article that exhibits excellent in-moldability and stable excellent flame retardancy, and a polyolefin resin foam particle molded article obtained by in-molding the polyolefin resin foam particles. [Means for solving the problem]

[0006] The polyolefin resin foam particles of the present invention have a bulk density of 10 kg / m³. 3 More than 100kg / m 3 The following is a polyolefin resin foam particle containing a NOR-type hindered amine compound, wherein the NOR-type hindered amine compound is represented by the following general formula (I), and the content of the NOR-type hindered amine compound in the polyolefin resin foam particle is 0.01% by mass or more and 3% by mass or less. [ka] (In general formula (I), R 1 , R 2 , R 3 and R 4Each independently represents a hydrocarbon group, and X represents an alkanolamine group.)

[0007] In addition, the polyolefin resin foam particle molded body of the present invention has a density of 10 kg / m 3 or more and 100 kg / m 3 or less, and is a polyolefin resin foam particle molded body containing a NOR type hindered amine compound. The NOR type hindered amine compound is represented by the following general formula (I), and the content of the NOR type hindered amine compound in the polyolefin resin foam particle molded body is 0.01% by mass or more and 3% by mass or less. [Chemical formula] (In general formula (I), R 1 , R 2 , R 3 and R 4 each independently represents a hydrocarbon group, and X represents an alkanolamine group.) [Advantages of the Invention]

[0008] According to the present invention, it is possible to provide polyolefin resin foam particles capable of obtaining a foam particle molded body that is excellent in in-mold formability and stably exhibits excellent flame retardancy, and a polyolefin resin foam particle molded body obtained by in-mold molding of the polyolefin resin foam particles. [Brief Description of the Drawings]

[0009] [Figure 1] It is a DSC curve obtained according to the method for measuring the transition heat of plastics described in JIS K7122:1987 in order to obtain the total heat of fusion and the heat of fusion at the high-temperature peak of the polyolefin resin foam particles which is one embodiment of the present invention. [Embodiments for Carrying Out the Invention]

[0010] The following describes the polyolefin resin foam particles of the present invention (hereinafter sometimes simply referred to as "the foam particles of the present invention") and the molded articles of the polyolefin resin foam particles of the present invention (hereinafter sometimes simply referred to as "the molded articles of the foam particles of the present invention").

[0011] The foamed particles of the present invention have a bulk density of 10 kg / m³. 3 More than 100kg / m 3 The following is true, and it contains a NOR-type hindered amine compound represented by the following general formula (I). In the following description, the NOR-type hindered amine compound represented by the following general formula (I) may be referred to as a specific hindered amine compound. The content of the specific hindered amine compound in the foamed particles of the present invention is adjusted to be between 0.01% by mass and 3% by mass. [ka] (In general formula (I), R 1 , R 2 , R 3 and R 4 Each of these independently represents a hydrocarbon group, and X represents an alkanolamine group.

[0012] The foamed particles of the present invention, having the above-described configuration, are excellent in terms of lightness and in-moldability, as well as excellent in flame retardancy. Therefore, the foamed particles of the present invention can provide a foamed particle molded article that has low density, excellent fusion between foamed particles, and stably exhibits excellent flame retardancy. In other words, by using a specific hindered amine compound as a flame retardant, the present invention does not easily reduce the in-moldability of the foamed particles even when a relatively large amount of flame retardant is included. Therefore, the present invention can successfully provide polyolefin resin foamed particles that can obtain a foamed particle molded article that exhibits the desired flame retardancy. Furthermore, the present invention can obtain a foamed particle molded article that exhibits the desired flame retardancy even when a relatively small amount of flame retardant is included. Therefore, the present invention can provide polyolefin resin foamed particles in which the reduction in in-moldability of the foamed particles caused by the flame retardant is further suppressed. The foamed particles of the present invention will be described in more detail below.

[0013] [Polyolefin resins] The foamed particles of the present invention contain a polyolefin resin as the base resin. In relation to the present invention, a polyolefin resin refers to a homopolymer of olefin monomers such as ethylene, propylene, butene, and pentene, and a copolymer containing 50 mol% or more of components derived from olefin monomers. The base resin may be a single type of polyolefin resin, or a mixed resin of two or more types of polyolefin resins.

[0014] The polyolefin resin is preferably a polyethylene resin and / or a polypropylene resin. Examples of polyethylene-based resins include resins containing 50 mol% or more of ethylene components. Specifically, examples include high-density polyethylene, low-density polyethylene, linear low-density polyethylene, ultra-low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, and ethylene-ethyl acrylate copolymer. Among these, from the viewpoint of stably producing foamed particles with excellent in-moldability, it is preferable that the polyethylene-based resin mainly consists of linear low-density polyethylene. More specifically, it is preferable that the proportion of linear low-density polyethylene in the polyethylene-based resin be 50% by mass or more, more preferably 60% by mass or more, and even more preferably 80% by mass or more.

[0015] Furthermore, examples of polypropylene resins include resins containing 50 mol% or more of propylene component units. Specifically, examples include propylene homopolymers, impact-resistant polypropylenes commercially available as block polypropylene in which rubber components such as ethylene-propylene rubber are dispersed in polypropylene, propylene-ethylene random copolymers, propylene-ethylene block copolymers, propylene-butene random copolymers, propylene-butene block copolymers, and propylene-ethylene-butene random copolymers. Among these, from the viewpoint of stably producing foamed particles with excellent in-moldability, it is preferable that the polypropylene resin mainly consists of propylene-ethylene random copolymer and / or propylene-ethylene-butene random copolymer. More specifically, it is preferable that the proportion of propylene-ethylene random copolymer and / or propylene-ethylene-butene random copolymer in the polypropylene resin is 50% by mass or more, more preferably 60% by mass or more, and even more preferably 80% by mass or more.

[0016] From the viewpoint of obtaining a foamed particle molded article that has an excellent balance of mechanical properties such as compressive strength and lightweight properties, and can be used particularly suitably for applications such as packaging materials, vehicle components, and building materials, it is preferable that the foamed particles in the present invention use a polypropylene-based resin as the base resin. In this case, the melting point of the polypropylene resin constituting the foamed particles is preferably 125°C to 160°C, more preferably 130°C to 155°C, and even more preferably 135°C to 150°C. By using a polypropylene resin exhibiting a melting point within the above range as the base resin, it is possible to achieve a good balance between the good in-moldability of the foamed particles and the good compressibility of the foamed particle molded article obtained by in-molding the foamed particles.

[0017] The melting point of the polypropylene resin constituting the foamed particles is measured in accordance with JIS K 7121:2012. Specifically, the foamed particles are used as test specimens, and conditioning is performed according to "(2) When measuring the melting temperature after performing a certain heat treatment" in "3. Conditioning of test specimens" of JIS K 7121:2012. In conditioning, the test specimen is heated from 23°C to 200°C at a heating rate of 10°C / min, maintained at 200°C for 10 minutes, and then cooled to 23°C at a cooling rate of 10°C / min. After conditioning the test specimen in this manner, the test specimen is heated again to 200°C at a heating rate of 10°C / min, and a DSC curve is obtained. The flow rate of nitrogen gas in the measurement environment is set to 30 mL / min. The peak temperature of the melting peak that appears in the DSC curve obtained is taken as the melting point of the polypropylene resin constituting the foamed particles. If multiple melting peaks appear in the DSC curve, the peak temperature of the melting peak with the highest height relative to the baseline is considered the melting point of the polypropylene resin constituting the foamed particles.

[0018] In addition to the base resin, the foamed particles of the present invention may also contain other resins or elastomers other than polyolefin resins, to the extent that they do not impair the objectives and effects of the present invention. Examples of resins other than polyolefin resins include thermoplastic resins such as polystyrene resins, vinyl acetate resins, thermoplastic polyester resins, acrylic ester resins, methacrylic ester resins, and polyarylene sulfide resins. Examples of the elastomer include olefin-based thermoplastic elastomers, styrene-based thermoplastic elastomers, and amide-based thermoplastic elastomers. Resins and elastomers other than olefin-based resins are preferably included in an amount of 20 parts by mass or less, and more preferably in an amount of 10 parts by mass or less, per 100 parts by mass of the polyolefin-based resin (base resin). It is particularly preferable that the foamed particles of the present invention substantially contain no other resins or elastomers other than polyolefin-based resins.

[0019] [NOR-type hindered amine compounds] The foamed particles of the present invention contain a NOR-type hindered amine compound represented by the following general formula (I) in an amount of 0.01% by mass or more and 3% by mass or less. From the viewpoint of being able to exhibit flame retardancy that meets high standards, the foamed particles of the present invention preferably contain a specific hindered amine compound in an amount of 0.02% by mass or more, and more preferably in an amount of 0.03% by mass or more. Furthermore, from the viewpoint of being able to exhibit high flame retardancy and sufficiently excellent in-moldability, the foamed particles of the present invention preferably contain a specific hindered amine compound in an amount of 2% by mass or less, and more preferably in an amount of 1.5% by mass or less. When the foamed particles contain two or more specific NOR-type hindered amine compounds, the sum of their contents shall be considered as the content of the specific NOR-type hindered amine compound in the foamed particles. Hindered amine compounds in which the nitrogen atom in the 2,2,6,6-tetramethyl-4-piperidine structure is bonded to a carbon-hydrogen group via an oxygen atom, as shown in the general formula (I) below, are called NOR-type hindered amines. [ka] (In general formula (I), R 1 , R 2 , R 3 and R 4 Each of these independently represents a hydrocarbon group, and X represents an alkanolamine group.

[0020] The content of NOR-type hindered amine compounds in the foamed particles is determined, for example, by proton nuclear magnetic resonance ( 1 This can be determined by subjecting the sample to H-NMR, etc. (Proton nuclear magnetic resonance) 1 When determining the content of NOR-type hindered amine compounds by 1H-NMR, for example, the following method can be employed. First, Soxhlet extraction is performed on the cryopreserved foam particles using chloroform as the solvent to remove polymer components and other parts that are insoluble in chloroform. Next, the chloroform-soluble part obtained from Soxhlet extraction is mixed with acetone to remove the acetone-insoluble part. The solid obtained by removing the solvent from the acetone-soluble part is used as the measurement sample, and proton nuclear magnetic resonance (M / A) is performed. 1 Measurement is performed using 1H-NMR. The content of NOR-type hindered amine compounds in the foam particles can be determined from the relationship between this measurement result and the measurement result of a standard sample with a known concentration (internal standard sample). (Proton nuclear magnetic resonance) 1 For measurements using 1H-NMR, for example, the AL-400 model manufactured by JEOL Ltd. can be used. In addition, the following measurement conditions can be adopted for the above measurement: solvent: CDCl3, internal standard sample: tetrachloroethane (TCE).

[0021] The specific hindered amine compound used in the present invention differs from other NOR-type hindered amine compounds conventionally used as flame retardants in that X in general formula (I) is an alkanolamine group. The reason why using this specific hindered amine compound as a flame retardant improves the flame retardancy of foamed particles and maintains good moldability in the mold is not clear. However, the reason why such excellent effects are exhibited in the present invention is presumed to be as follows: In other words, X in general formula (I) is an alkanolamine group, and it is presumed that the -OH group in this X acts as a catalyst to form an intermediate for the synthesis of non-combustible gases during the combustion of foamed particles (molded foamed particle body). Therefore, it is presumed that high flame retardancy is exhibited and good moldability in the mold is maintained even when the amount of the specific hindered amine compound is suppressed. In X, by bringing the -OH group close to the -NH group, the catalytic action described above is facilitated, and from the viewpoint of obtaining foamed particles that exhibit excellent flame retardancy stably, the number of carbon atoms in X in the general formula (I) is preferably 1 to 8, more preferably 1 to 6, and even more preferably 1 to 4.

[0022] From the viewpoint of obtaining foamed particles that have good in-moldability and exhibit high flame retardancy standards more stably, R in the general formula (I) 1 and R 2 The number of carbon atoms in the hydrocarbon group is preferably 1 to 20, preferably 2 to 16, and more preferably 3 to 10. Also, R 1 and R 2 The hydrocarbon group is preferably an alkyl group or a cycloalkyl group. Furthermore, from a similar perspective, R in the general formula (I) 3 and R 4 The number of carbon atoms in the hydrocarbon group is preferably 1 to 20, preferably 2 to 10, and more preferably 3 to 8. 3 and R 4 The hydrocarbon group is preferably an alkyl group or a cycloalkyl group. Furthermore, it is even more preferable that either embodiment 1 or embodiment 2 below be satisfied, and it is particularly preferable that both be satisfied. Appearance 1: R in General Formula (I) 1 and R 2 This is a cyclohexyl group. Appearance 2: R in General Formula (I) 3 and R 4 This is a butyl group.

[0023] In general formula (I), X is an alkanolamine group, which is a substituent having a hydroxyl group and an amino group on an alkane skeleton. The specific hindered amine compound used in the present invention is preferably an ethanolamine group in which the alkane skeleton of X has two carbon atoms, and more preferably an ethanolamine group in which the alkane skeleton of X has two carbon atoms and satisfies the above embodiments 1 and 2.

[0024] The melting point of the specific hindered amine compound is preferably 60°C to 100°C, more preferably 70°C to 95°C, and even more preferably 75°C to 90°C. Having the melting point of the specific hindered amine compound within this range makes it easier to disperse the hindered amine compound well in the base resin, allowing for the stable production of foamed particles with excellent in-moldability. Furthermore, in foamed particle molded articles formed using these particles, the hindered amine compound tends to migrate less easily to the surface of the molded article. As a result, foamed particle molded articles exhibiting excellent flame retardancy over long periods can be stably obtained. The melting point of NOR-type hindered amine compounds can be measured by "(1) Visual method" in "3. Method for measuring melting point" of JIS K 0064:1992. Furthermore, the foam particles are subjected to proton nuclear magnetic resonance ( 1 The structure of the NOR-type hindered amine compound contained in the foam particles can be identified by subjecting it to 1H-NMR or the like, and the melting point of the NOR-type hindered amine compound containing the foam particles can be determined by measuring the melting point of the NOR-type hindered amine compound having such a structure.

[0025] The molecular weight of the specific hindered amine compound is preferably 1000 or less, and more preferably 900 or less. Having the molecular weight of the specific hindered amine compound within this range allows the hindered amine compound to be well dispersed in the base resin, enabling the stable production of foamed particles with excellent in-moldability. The lower limit of the molecular weight is generally 550, and preferably 600. Here, the molecular weight of a NOR-type hindered amine compound can be determined as the sum of the atomic weights of the atoms constituting the NOR-type hindered amine compound. Note that foam particles are subjected to proton nuclear magnetic resonance ( 1 The structure of the NOR-type hindered amine compound contained in the foamed particles can be identified by subjecting it to 1H-NMR or the like, and the molecular weight of the NOR-type hindered amine compound can be determined from this structure.

[0026] The foamed particles of the present invention contain one or more compounds selected from the specific hindered amine compounds represented by the general formula (I) as a flame retardant. Furthermore, to the extent that it does not impede the purpose and effects of the present invention, the foamed particles of the present invention may also contain other flame retardants other than the specific hindered amine compounds represented by the general formula (I). Examples of other flame retardants include NOR-type hindered amine flame retardants other than the specific hindered amine compounds, halogen-based flame retardants, phosphorus-based flame retardants, metal hydroxides, and the like. The amount of flame retardant other than the specific hindered amine compound represented by general formula (I) is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferably 10 parts by mass or less, per 100 parts by mass of the specific hindered amine compound in the foamed particles. It is particularly preferable that the foamed particles of the present invention substantially contain no flame retardant other than the specific hindered amine compound.

[0027] [Carbon materials] The foamed particles of the present invention may further contain a carbon material. Generally, foamed particle molded bodies obtained by in-mold molding of foamed particles containing a carbon material tend to be highly flammable. However, the foamed particles of the present invention, which contain a specific hindered amine compound, can exhibit excellent flame retardancy even when they contain a carbon material. The amount of carbon material blended in the foamed particles of the present invention is not particularly limited, but from the viewpoint of easily exhibiting excellent flame retardancy, the carbon material content in the foamed particles is preferably 0.1% by mass or more and 10% by mass or less, more preferably 0.5% by mass or more and 7% by mass or less, and even more preferably 1% by mass or more and 5% by mass or less.

[0028] Examples of the carbon material include at least one carbon powder selected from carbon black, carbon nanotubes, graphite, graphene, carbon nanofibers, carbon microfibers, carbon microcoils, and carbon nanocoils. Among these, the foamed particles of the present invention containing carbon black in an amount of 1% to 10% by mass, more preferably 1% to 5% by mass, are preferred because they provide a black foamed particle molded article that is excellent in flame retardancy, as well as in fusion properties, surface appearance, and recovery properties. The carbon material contained in the foamed particles of the present invention may be one type or two or more types.

[0029] The carbon black mentioned above includes gas furnace black, oil furnace black, acetylene black, channel black, roller black, thermal black, Ketjen black, and the like.

[0030] The carbon content in the foamed particles can be determined, for example, by a thermogravimetric differential thermal analyzer (i.e., TG-DTA). In this case, measurements are first performed on the foamed particles according to JIS K7120-1987. Then, the carbon content in the foamed particles can be determined based on the mass loss rate of the TG curve obtained from the measurement within a predetermined temperature range (for example, from 400°C to 1000°C).

[0031] [Other additives] The foamed particles of the present invention may contain any additives as long as they do not impair the purpose and effects. Examples of optional additives include one or more additives selected from flame retardant aids, foam regulators, catalyst neutralizers, lubricants, crystal nucleating agents, antistatic agents, conductivity imparters, antioxidants, ultraviolet absorbers, and the like.

[0032] [Fusing layer] The foam particles of the present invention may have a fusion layer on their surface to facilitate fusion of the foam particles with each other even at lower molding pressures during in-mold molding. The fusion layer may be present on the entire surface of the foam particles or on only a part of the surface. Examples of resins constituting the fusion layer include crystalline polyolefin resins having a melting point lower than the melting point of the base resin constituting the foam particle body (core layer), and amorphous polyolefin resins having a softening point lower than the melting point of the base resin constituting the foam particle body (core layer). In the case of foam particles having a fusion layer, the foam particle body on which the fusion layer is provided on the surface may be referred to as the core layer. When foam particles have a fusion layer, the proportion of the fusion layer in the foam particles is generally 0.5% by weight or more and 20% by weight or less, and preferably 1% by weight or more and 10% by weight or less. Furthermore, when the foamed particles include a fusion layer with a crystalline polyolefin resin as the base resin, the difference between the melting point of the base resin constituting the foamed particle body and the melting point of the base resin constituting the fusion layer is generally 1°C to 30°C, preferably 2°C to 25°C, and more preferably 5°C to 20°C. The method for forming a fusion layer on the surface of the foamed particle body is not particularly limited. Examples include a method of foaming resin particles having a fusion layer on their surface, or a method of obtaining foamed particles and then attaching a fusion layer to the surface of the foamed particles. When obtaining foamed particles by foaming resin particles having a fusion layer on their surface, it is preferable to employ a method in which, when manufacturing the resin particles, a fusion layer is laminated onto the surface of the resin particles by co-extruding a molten mixture for forming the core layer and a molten resin for forming the fusion layer using an extruder capable of co-extrusion.

[0033] [Bulk density of foamed particles] The bulk density of the foamed particles of the present invention is 10 kg / m³. 3 More than 100kg / m 3The following is true. Generally, when the bulk density of foamed particles decreases, the amount of base resin constituting the foamed particles decreases, and therefore the combustion rate of foamed particle molded articles made using foamed particles with low bulk density tends to increase. However, the foamed particles of the present invention contain a specific hindered amine compound as a flame retardant. As a result, the bulk density of the foamed particles of the present invention is adjusted to the low range described above, but the increase in the combustion rate of foamed particle molded articles made using these foamed particles can be suppressed. In other words, the foamed particles of the present invention can provide foamed particle molded articles that are lightweight and exhibit excellent flame retardancy.

[0034] From the viewpoint of further improving the lightweight properties of the foam particle molded article produced by in-mold molding of the foam particles of the present invention, the bulk density of the foam particles is 80 kg / m³. 3 Preferably, it is 60 kg / m 3 More preferably, it is 50 kg / m 3 The following is even more preferable: Furthermore, from the viewpoint of improving the mechanical properties such as compressive strength of the foam particle molded body produced by in-mold molding of the foam particles of the present invention, the bulk density of the foam particles should be 12 kg / m³. 3 Preferably, it should be 15 kg / m 3 It is more preferable that the amount be greater than or equal to 18 kg / m 3 It is even more preferable that the above conditions are met.

[0035] The bulk density of the foamed particles described above is calculated by the following method. First, the foamed particles to be used for measurement are left for 24 hours or more in an environment with a temperature of 23°C, relative humidity of 50%, and 1 atm. The resulting foamed particle group is then filled into a graduated cylinder with a volume of 1 L or more by a bulk volume of 1 L or more. After stabilizing the height of the filled foamed particles, the bulk volume (unit: L) of the foamed particle group is read from the scale of the graduated cylinder. Then, the bulk density (unit: kg / m³) of the foamed particle group is calculated by dividing the mass (unit: g) of the foamed particle group in the graduated cylinder by the aforementioned bulk volume and converting the value to units. 3 ) can be obtained.

[0036] [Average bubble diameter of foamed particles] The average bubble diameter of the foamed particles is preferably 50 μm to 250 μm, more preferably 55 μm to 200 μm, even more preferably 60 μm to 150 μm, and even more preferably 60 μm to 120 μm. By having the average bubble diameter of the foamed particles within the above range, it is possible to stably obtain foamed particles that have good in-moldability and can be used to produce foamed particle molded articles exhibiting excellent flame retardancy. The average bubble diameter of a foamed particle can be measured by drawing multiple line segments from the outermost surface of the foamed particle through the center to the outermost surface of the opposite side in a magnified photograph of the cross-section of the foamed particle, which has been divided into two halves, and dividing the number of bubbles intersecting each line segment by the total length of the line segments. Specifically, it can be measured by the method described in the examples.

[0037] [High temperature peak of foamed particles] Preferably, the foamed particles have a crystalline structure in which one or more melting peaks (hereinafter referred to as "high-temperature peaks") appear on the high-temperature side of the peak of the polyolefin resin-specific melting peak (hereinafter referred to as "specific peak") in the DSC curve obtained by differential scanning calorimetry. By using foamed particles exhibiting high-temperature peaks in in-mold molding, the molding conditions when molding the foamed particle molded body can be selected from a wide range, and the mechanical properties such as the compressive strength of the resulting foamed particle molded body can be further improved. From this viewpoint, the melting heat of the high-temperature peak (hereinafter also referred to as "high-temperature peak heat") is preferably 5 J / g or more, and more preferably 8 J / g or more. Furthermore, the high-temperature peak heat is preferably 50 J / g or less, and more preferably 40 J / g or less.

[0038] The high-temperature peak heat of foamed particles can be calculated by the following method. First, approximately 3 mg of foamed particles are used as a test specimen, and a DSC curve is obtained when the test specimen is heated and melted according to the method for measuring the transition heat of plastics specified in JIS K7122-1987. The temperature range of the DSC curve is from 23°C to a temperature 30°C higher than the temperature at which the melting peak ends, and the heating rate during heating is 10°C / min. The flow rate of nitrogen gas in the measurement environment is 30 mL / min. If the foamed particles have a high-temperature peak, the DSC curve will show an intrinsic peak a and a high-temperature peak b whose peak is on the higher side of the peak of intrinsic peak a, as shown in Figure 1. Figure 1 is an example of a DSC curve measured based on differential scanning calorimetry for polyolefin resin foamed particles. Although one high-temperature peak b is shown in Figure 1, there may be two or more high-temperature peaks b.

[0039] Next, draw a straight line connecting point I, which corresponds to 80°C on the DSC curve, and point II, which corresponds to the melting termination temperature of the foamed particles. Note that the melting termination temperature is the high-temperature endpoint of the high-temperature peak b, that is, the point on the DSC curve where the high-temperature peak b returns to the high-temperature baseline.

[0040] Next, as shown in Figure 1, let IV be the intersection point of the line passing through the maximum point III, which lies between intrinsic peak a and high-temperature peak b, and the line connecting point I and point II. The area enclosed by the line connecting point I and point IV, the line connecting point III and point IV, and the DSC curve connecting point I and point III is defined as the area of ​​intrinsic peak a. The area enclosed by the line connecting point IV and point II, the line connecting point III and point IV, and the DSC curve connecting point III and point II (shaded area) is defined as the area of ​​high-temperature peak b. The total heat of fusion value of the foamed particles is calculated from the sum of the areas of intrinsic peak a and high-temperature peak b obtained as described above, and the heat of fusion value of high-temperature peak b is calculated from the area of ​​high-temperature peak b.

[0041] Furthermore, if, after obtaining a DSC curve using the method described above, the foamed particles are cooled to 23°C at a cooling rate of 10°C / min, and then heated again at a heating rate of 10°C / min to obtain a DSC curve, only the intrinsic peak a will appear in the DSC curve, and the high-temperature peak b will disappear from the DSC curve.

[0042] [Polyolefin-based resin foam particle molded product] Next, the foamed particle molded article of the present invention will be described. The foamed particle molded body of the present invention has a density of 10 kg / m³ 3 More than 100kg / m 3 The following applies, and it contains a NOR-type hindered amine compound (a specific hindered amine compound) represented by the following general formula (I). The content of the specific hindered amine compound in the foamed particle molded body is 0.01% by mass or more and 3% by mass or less. [ka] (In general formula (I), R 1 , R 2 , R 3 and R 4 Each of these independently represents a hydrocarbon group, and X represents an alkanolamine group.

[0043] The foamed particle molded articles of the present invention, which contain a specific hindered amine compound in a predetermined range of amounts, exhibit an excellent balance between lightness and mechanical properties such as compressive strength, as well as excellent flame retardancy. Furthermore, the foamed particle molded articles of the present invention, manufactured by in-mold molding of the foamed particles, also exhibit excellent fusion properties, surface appearance, and recovery properties. Therefore, the foamed particle molded articles of the present invention can be suitably used in various applications such as vehicle components and building materials. Furthermore, the content of NOR-type hindered amine compounds in the foamed particle molded body can be determined in the same way as the method for determining the content of NOR-type hindered amine compounds in foamed particles, for example, by proton nuclear magnetic resonance ( 1 This can be determined by subjecting the sample to 1H-NMR, etc.

[0044] As described above, the density of the foamed particle molded article of the present invention is 10 kg / m³3 More than 100kg / m 3 The following is the reason: From the viewpoint of balancing lightness and mechanical properties such as rigidity, and ensuring flame retardancy, the density is 12 kg / m³. 3 More than 80kg / m 3 Preferably, it is 15 kg / m 3 More than 60kg / m 3 The following is more preferable:

[0045] The density of a foamed particle molded body is calculated by dividing the mass of the foamed particle molded body by the volume calculated based on its external dimensions.

[0046] <Flame-retardant> The flame retardancy of a foamed particle molded product can be evaluated based on the combustion termination position, combustion duration, and combustion distance when a flammability test is performed according to FMVSS (Federal Motor Vehicle Safety Standard) No. 302. Specifically, the flammability test method specified in FMVSS No. 302 is as follows:

[0047] First, the foamed particles are molded in a mold, and then the resulting foamed particle molded body is cut to produce a plate-shaped test specimen. Next, the test specimen is left for 24 hours in an environment with a temperature of 21°C and a relative humidity of 50% to adjust its condition. After adjusting the condition, a start line is drawn on the test specimen at a position 38 mm away from the base end in the longitudinal direction, and an end line is drawn at a position 292 mm away from the base end. Then, the test specimen is mounted on the U-shaped frame of the FMVSS No.302 dedicated chamber.

[0048] Next, the burner is ignited, and the gas and air volumes are adjusted so that the flame height is 38 mm. With the burner in this state, the center of the tip of the burner is moved so that it aligns with the center of the width of the base of the test specimen, and the burner flame is brought into contact with the test specimen for 15 seconds. After that, the burner flame is removed from the test specimen, and the burning duration is measured from the time the burning position of the test specimen reaches the start line until the burning ends.

[0049] In relation to the present invention, the flame retardancy of the foamed particle molded article is evaluated in terms of self-extinguishing properties and average combustion rate. Specifically, if the test specimen does not ignite, if the combustion of the test specimen ends before reaching the start line, or if the combustion end position of the test specimen is within 51 mm from the start line and the combustion duration is within 60 seconds, the foam particle molded body is determined to have self-extinguishing properties. If the self-extinguishing properties described above are not met, the combustion rate can be determined by dividing the combustion distance from the start line by the combustion duration. Ten or more test specimens are prepared, the combustion rate of each is determined, and the arithmetic mean of these is taken as the average combustion rate.

[0050] As a result of the flammability test specified in the FMVSS (Federal Motor Vehicle Safety Standard) No. 302, a burning rate of 102 mm / min or less is preferable, a burning rate of less than 80 mm / min is more preferable, and self-extinguishing properties are even more preferable. Foamed particle molded articles that are evaluated as having more or even more preferable flammability can be suitably used in applications that require particularly high flame retardancy. Among these, foamed particle molded articles with self-extinguishing properties are suitable for vehicle components such as automobile bumpers and seat core materials.

[0051] The foamed particle molded article of the present invention is suitably manufactured, for example, by in-mold molding of the foamed particles of the present invention. The foamed particle molded article of the present invention, manufactured by in-mold molding of the foamed particles of the present invention, enjoys the excellent effects of the foamed particles of the present invention described above. For example, the foamed particle molded article of the present invention may be manufactured by in-mold molding of the foamed particles of the present invention, which exhibit a black color. In this case, the foamed particle molded article will exhibit a black color and may also exhibit good flame retardancy. From this viewpoint, when the foamed particle molded article contains a carbon material, the carbon material content in the foamed particle molded article is preferably 0.1% by mass or more and 10% by mass or less, more preferably 0.5% by mass or more and 7% by mass or less, and even more preferably 1% by mass or more and 5% by mass or less. Furthermore, if the foamed particle molded body contains carbon black, the carbon black content in the foamed particle molded body is preferably 1% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 5% by mass or less.

[0052] [Method for producing polyolefin-based resin foamed particles] The method for producing foamed particles of the present invention is not particularly limited as long as it is a method that can produce foamed particles in which the content of a specific NOR-type hindered amine compound contained in the foamed particles is within a specific range. Examples include a method of foaming resin particles containing a specific NOR-type hindered amine compound, or a method of impregnating foamed particles with a specific NOR-type hindered amine compound. Next, a preferred embodiment of the method for producing foamed particles of the present invention will be described. The foamed particles of the present invention can be obtained by foaming polyolefin resin particles containing a foaming agent. For example, foamed particles can be produced by a manufacturing method that includes a foaming step in which polyolefin resin particles containing a foaming agent are released from a pressure vessel together with an aqueous medium under a pressure lower than that inside the pressure vessel, causing foaming. The polyolefin resin particles use a polyolefin resin as the base resin. Furthermore, it is preferable that the resin particles contain a specific NOR-type hindered amine compound.

[0053] In the above manufacturing method, the foamed particles obtained in the foaming step may be used as foamed particles as they are. Alternatively, as will be described later, foamed particles can be produced by using the foamed particles obtained in the foaming step as first-stage foamed particles and then performing a second-stage foaming step using the first-stage foamed particles. From the viewpoint of obtaining foamed particles with a lower bulk density, it is preferable to perform the second-stage foaming step after the foaming step.

[0054] <Granulation process> The method for producing foamed particles preferably includes a granulation step prior to the foaming step, in which polyolefin resin particles (hereinafter referred to as "resin particles") are produced using a polyolefin resin as the base resin and containing at least a specific NOR-type hindered amine compound. The method for producing the resin particles in the granulation step is not particularly limited. For example, a strand can be produced by extruding a polyolefin resin and a specific NOR-type hindered amine compound while kneading them together, and then the resin particles can be obtained by cutting the strand to a desired size using a pelletizer or the like.

[0055] <Foaming Process> In the foaming process, resin particles are first supplied into a pressure vessel and dispersed in an aqueous dispersion medium such as water. At this time, if necessary, dispersants, dispersion aids, surfactants, etc., may be added to the dispersion medium in the pressure vessel to disperse the resin particles.

[0056] As dispersants, inorganic fine particles such as aluminum oxide, tricalcium phosphate, magnesium pyrophosphate, zinc oxide, kaolin, and mica can be used. These inorganic fine particles may be used alone or in combination of two or more. As a dispersing aid, aluminum sulfate can be used, for example. As a surfactant, anionic surfactants such as sodium alkylbenzenesulfonate, sodium dodecylbenzenesulfonate, and sodium alkanesulfonate can be used. These surfactants may be used alone or in combination of two or more.

[0057] After sealing the pressure vessel, a foaming agent is added to the vessel. This allows the foaming agent to impregnate the resin particles. Heating the inside of the pressure vessel at this time can accelerate the impregnation of the foaming agent into the resin particles. Alternatively, resin particles that have already been impregnated with the foaming agent may be supplied to the pressure vessel.

[0058] After impregnating resin particles with a predetermined amount of foaming agent, the contents of a pressure vessel are released under a pressure lower than the internal pressure of the vessel, causing the resin particles to foam and obtain foamed particles (single-stage foamed particles).

[0059] Furthermore, optional additives such as carbon black can be incorporated into the resin particles, for example, by kneading them with the base resin during the granulation process.

[0060] As blowing agents used in the foaming process, for example, organic physicoblasting agents such as hydrocarbons and halogenated hydrocarbons, and inorganic physicoblasting agents such as carbon dioxide, nitrogen, air, and water can be used. Examples of hydrocarbons that can be used as organic physicoblasting agents include butane, pentane, and hexane. Examples of halogenated hydrocarbons that can be used as organic physicoblasting agents include trichlorofluoromethane, dichlorofluoromethane, and tetrachlorodifluoroethane. As organic physicoblasting agents, the above-mentioned substances may be used individually or in combination of two or more. Similarly, as inorganic physicoblasting agents, the above-mentioned substances may be used individually or in combination of two or more.

[0061] In the production of foamed particles of the present invention, the blowing agent is preferably an inorganic physical blowing agent, and more preferably carbon dioxide. By foaming resin particles using such a blowing agent, foamed particles can be easily obtained that ultimately produce a foamed particle molded article with a high foaming ratio and good flame retardancy. Furthermore, since carbon dioxide is non-flammable, using carbon dioxide as a blowing agent can avoid deterioration of the flame retardancy of the foamed particle molded article caused by the blowing agent.

[0062] The amount of foaming agent added can be appropriately set according to the type of base resin, the type of foaming agent, the bulk density of the desired foamed particles, etc. For example, when carbon dioxide is used as the foaming agent, the amount added is preferably 0.1 parts by mass or more and 30 parts by mass or less per 100 parts by mass of resin particles, more preferably 0.5 parts by mass or more and 15 parts by mass or less, and even more preferably 1 part by mass or more and 10 parts by mass or less.

[0063] The foaming process may include a step of generating the aforementioned high-temperature peak before foaming the resin particles. As a method for generating the high-temperature peak, for example, a method of heat treatment can be employed in which the resin particles are held within a specific temperature range in a dispersion medium in a pressure vessel. The timing of the heat treatment is not particularly limited, and the heat treatment may be performed at any point before, during, or after impregnation with the foaming agent, or it may be performed across two or more of the aforementioned points in time. This heat treatment makes it possible to obtain foamed particles having a crystalline structure that shows a melting peak (intrinsic peak) originating from the crystals intrinsic to the polyolefin resin and a melting peak (high-temperature peak) located at a higher temperature than the intrinsic peak. As for the heat treatment, for example, after introducing the resin particles into the pressure vessel, a temperature holding step may be performed in the middle of the heating step in which the temperature inside the pressure vessel is raised, in which a predetermined temperature is maintained for a predetermined time.

[0064] <Two-stage foaming process> The above manufacturing method may further include a two-stage foaming step. The two-stage foaming step is carried out, for example, by pressurizing a pressure vessel filled with the first-stage foamed particles obtained in the foaming step with air or the like to impregnate the first-stage foamed particles with air or the like to increase the pressure inside the bubbles, and then heating the pressurized first-stage foamed particles to cause foaming. The heating of the foamed particles in the two-stage foaming step may be carried out in a pressure vessel with controlled pressure, or it may be carried out at a pressure lower than the pressure inside the bubbles after removing them from the pressure vessel. It is preferable to use first-stage foamed particles that have been cured under atmospheric pressure after the foaming step is completed as the first-stage foamed particles used in the two-stage foaming step.

[0065] In the above manufacturing method, low-density foamed particles can be obtained more easily by foaming the resin particles in two stages: the foaming step and the two-stage foaming step. Although the two-stage foaming step has been described here, the foamed particles obtained in the two-stage foaming step may be used to perform a further foaming step of three or more stages.

[0066] In this specification, the container used in the foaming process is referred to as a "pressure vessel," and the container used in the two-stage foaming process is referred to as a "pressure-resistant vessel." However, any container that can be sealed and to which pressure can be applied is acceptable.

[0067] [Method for manufacturing polyolefin-based resin foam particle molded articles] The method for manufacturing a foamed particle molded article of the present invention is not particularly limited as long as a foamed particle molded article having the above-described configuration can be obtained. For example, one preferred embodiment of the method for manufacturing a foamed particle molded article of the present invention is in-mold molding using the foamed particles of the present invention as described above. The aforementioned in-mold molding broadly includes known in-mold molding methods using foamed particles. For example, the in-mold molding of the foamed particle molded body of the present invention can be carried out as follows.

[0068] First, the foam particles of the present invention are filled into a mold having a cavity corresponding to the desired shape of the foam particle molded body, and the foam particles filled in the mold are heated by applying a predetermined molding pressure using a heating medium such as steam. By heating the foam particles in the cavity in this way, they are further foamed and fused together. Next, after heating with steam or the like is completed, the pressure is released, and the cooling of the mold and the molded body inside the mold is started immediately. Once it is confirmed that the pressure (surface pressure) generated on the inner surface of the mold has fallen below a predetermined value, the cooling is stopped, the mold is opened, and the foam particle molded body is removed from the mold. The cooling method here is not particularly limited, but for example, water cooling can be used. Through this series of molding steps, a foam particle molded body corresponding to the shape of the cavity is obtained. [Examples]

[0069] The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. Tables 1 and 2 show the NOR-type hindered amine compounds used and their content (mass%) in 100% by mass of foamed particles.

[0070] (Example 1) <Granulation process> A strand containing polypropylene resin, carbon black, a NOR-type hindered amine compound, and a foam regulator was prepared by supplying these to an extruder and extruding them while kneading them in the extruder. Subsequently, the obtained strand was cut using a pelletizer to obtain resin particles with a length / diameter ratio of 2.0 and an average mass of 1.0 mg. As the polypropylene resin, a propylene-ethylene random copolymer with a melt flow rate of 7 g / 10 min at melting points of 143°C and 230°C and a load of 2.16 kg was used. Furnace black was used as the carbon black, and it was added so that the carbon black content in the foamed particles was 3% by mass. As the NOR-type hindered amine compound, a compound having the structure of general formula (I) described above and exhibiting the structure of chemical formula (II) below (product name: Tinuvin 152, manufactured by BASF, melting point 83°C, molecular weight 757) was used. The NOR-type hindered amine compound was added so that its content in the foamed particles was the value shown in Table 1. Zinc borate powder was used as the foam regulator, and it was added so that its content in the foamed particles was 0.05% by mass. [ka]

[0071] <Foaming Process> A 5L autoclave (pressure vessel) was filled with 0.3 parts by mass of dispersant, 0.01 parts by mass of dispersion aid, 0.004 parts by mass of surfactant, and 300 parts by mass of dispersion medium per 100 parts by mass of resin particles. The dispersant was kaolin, the dispersion aid was aluminum sulfate, the surfactant was sodium dodecylbenzenesulfonate, and the dispersion medium was water. Next, carbon dioxide was supplied as a foaming agent into the autoclave, and the autoclave was pressurized until the gauge pressure reached 1.0 MPa(G). Then, while stirring the contents of the autoclave, the temperature was raised at a rate of 2°C / min until it reached 144°C. After the temperature inside the autoclave reached 144°C, this temperature was maintained for 15 minutes while stirring continued. Next, the autoclave was heated at a rate of 2°C / min while stirring until it reached 149°C. After the temperature inside the autoclave reached 149°C, carbon dioxide was supplied to the autoclave to adjust the pressure to 2.7 MPa(G) and the temperature was maintained at 149°C for 15 minutes. After that, the autoclave was opened and the contents were released to atmospheric pressure. As a result, the resin particles were foamed, and the bulk density was 45 kg / m³. 3 A single-stage foamed particle was obtained. In this specification, the unit of pressure indicated by (G) means gauge pressure, that is, the pressure value relative to atmospheric pressure.

[0072] <Two-stage foaming process> The first-stage foamed particles obtained in the foaming process were left to cure for 24 hours in an environment of 23°C, 50% relative humidity, and 1 atm. After curing, the first-stage foamed particles were filled into a pressure vessel. Next, air was injected into the pressure vessel, and the pressure inside the vessel was increased from atmospheric pressure to 0.60 MPa(G) over 24 hours. This pressure was maintained for 24 hours to impregnate the bubbles with air. Next, the single-stage foamed particles removed from the pressure vessel were filled into a two-stage foaming machine, and the single-stage foamed particles were further foamed by supplying steam at a pressure of 0.15 MPa (G) to obtain two-stage foamed particles. Table 1 shows the bulk density, average bubble diameter, and heat of fusion at high temperature peak of the obtained two-stage foamed particles.

[0073] Furthermore, the bulk density of the two-stage foamed particles was measured according to the method for measuring the bulk density of foamed particles described above. Specifically, first, the foamed particles were left for more than 24 hours in an environment of 23°C, 50% relative humidity, and 1 atm. The resulting foamed particle group was then filled into a graduated cylinder marked with a 1L scale, and the bottom of the graduated cylinder was lightly tapped against the floor several times to stabilize the height of the foamed particle group in the graduated cylinder so that it was at the 1L mark. The mass (in units: g) of the foamed particle group with a bulk volume of 1L in the graduated cylinder was measured, and the bulk density (in units: kg / m³) of the foamed particles was determined by unit conversion. 3 ) was calculated. Furthermore, the heat of fusion of the high-temperature peak of the two-stage foamed particles was measured according to the method for measuring the heat of fusion of high-temperature peak b described above. Furthermore, the average bubble diameter of the two-stage foamed particles was measured as follows. First, 30 foamed particles were randomly selected. Each foamed particle was cut in half through its center, and magnified photographs of one of the cross-sections were taken. In each cross-sectional photograph, four line segments were drawn from the outermost surface of the foamed particle through the center to the outermost surface of the opposite side, such that the angles between adjacent line segments were equal. The number of bubbles intersecting each line segment was measured, and the average bubble diameter of each foamed particle was calculated by dividing the total length of the four line segments by the total number of bubbles intersecting the line segments. The average bubble diameter of each foamed particle was then calculated by taking the arithmetic mean of the values ​​of the average bubble diameters of each foamed particle.

[0074] <In-mold molding> The two-stage foamed particles obtained by the aforementioned method were filled into a mold capable of forming a flat plate measuring 350 mm in length, 250 mm in width, and 50 mm in thickness, and heated using the following heating method to produce a foamed particle molded body. First, preheating (exhaust process) was performed by supplying steam to the mold with the drain valves on both sides of the mold open. Then, heating was performed by supplying steam from one side of the mold, and then by supplying steam from the other side of the mold. Subsequently, heating was performed by supplying steam from both sides of the mold at a predetermined molding pressure (molding steam pressure) (main heating). After the main heating was completed, the pressure was released, and the mold was water-cooled until the pressure on the molding surface of the mold reached 0.04 MPa (G). Then, the mold was opened and the foamed particle molded body was removed. The obtained molded body was cured in an 80°C oven for 12 hours to obtain a foamed particle molded body. The molding pressure range for foamed particles was evaluated using the following method.

[0075] (Molding pressure range (the range of molding steam pressures that can produce good quality products)) In the in-mold molding described above, foam particle molded bodies were formed by varying the molding pressure during in-mold molding in increments of 0.01 MPa. The fusion properties, surface appearance, and recovery properties of the obtained foam particle molded bodies were evaluated as follows. The molding pressure (molding steam pressure) during in-mold molding that allowed for the formation of foam particle molded bodies that passed all three items shown below was identified, and the range from the lower limit to the upper limit of the molding steam pressure was defined as the molding pressure range. This confirmed the in-moldability of the foam particles used. Furthermore, the wider the range from the lower limit to the upper limit of the molding steam pressure at which a foam particle molded body that meets the acceptance criteria can be formed, the wider the range of molding steam pressures at which good products can be formed, and therefore more desirable. Also, the lower the lower limit of the molding steam pressure at which good products can be formed, the better the productivity, as good foam particle molded bodies can be obtained even at low molding steam pressures. The range (molding pressure range) from the lower limit to the upper limit of the molding steam pressure at which a foam particle molded article meeting the acceptance criteria can be formed is preferably 0.02 MPa or higher, more preferably 0.03 MPa or higher, and even more preferably 0.04 MPa or higher.

[0076] Fusibility: The resulting foam particle molded body was bent and fractured, and the number of foam particles present on the fracture surface (C1) and the number of fractured foam particles (C2) were determined. The ratio of the number of fractured foam particles to the number of foam particles (C2 / C1 × 100) was calculated as the material fracture rate. The above measurement was performed five times using different test pieces, and the material fracture rate for each was determined. A material fracture rate of 80% or higher obtained by arithmetic mean was considered a pass, and a rate below 80% was considered a fail.

[0077] Surface appearance: A 100mm x 100mm square was drawn in the center of the obtained foam particle molded body, and a line was drawn diagonally from one corner of the square. The number of voids (gaps) of 1mm x 1mm or larger along this line was counted. A product was deemed acceptable if the number of voids was less than 5 and the surface was smooth; otherwise, it was deemed unacceptable.

[0078] Resilience: The thickness of a flat foam particle molded body measuring 350 mm in length, 250 mm in width, and 50 mm in thickness, obtained by in-mold molding, was measured near the four corners and at the center. The area near the four corners refers to the region 10 mm inward from the corners toward the center of the plate surface. The center refers to the intersection of the line that bisects the foam particle molded body vertically and the line that bisects it horizontally. Next, the ratio (%) of the thickness at the center to the thickness at the thickest point near the four corners was calculated. A ratio of 95% or higher was considered a pass, and a ratio below 95% was considered a fail.

[0079] (density) A foamed particle molded body was obtained by in-mold molding at the lowest molding pressure within the aforementioned moldable range. After drying this foamed particle molded body at 80°C for 24 hours, the mass (in g) of the foamed particle molded body was measured. Then, the mass of the foamed particle molded body was divided by the volume (in L) calculated from the external dimensions of the foamed particle molded body, and the density (in kg / m³) of the molded body was calculated by converting the units. 3 ) was calculated.

[0080] (50% compressive strength) A foamed particle molded body was obtained by in-mold molding at the lowest molding pressure within the aforementioned moldable range. After drying this foamed particle molded body at 80°C for 24 hours, a rectangular parallelepiped test specimen measuring 50 mm in length, 50 mm in width, and 25 mm in thickness was taken from the center of the foamed particle molded body. A compression test was performed on the test specimen at a compression rate of 10 mm / min according to the method specified in JIS K7220:2006, and a stress-strain curve was obtained. The compression test was performed in a laboratory at 23°C. Based on this stress-strain curve, the 50% deformation compressive stress of the test specimen was calculated, and this value was taken as the 50% compressive strength of the molded body.

[0081] (FMVSS test) The flame retardancy was evaluated using a method in accordance with the flammability test method specified in FMVSS (Federal Motor Vehicle Safety Standard) No. 302. Specifically, a test specimen was prepared by cutting a foam particle molded body to create a plate-like shape with a length of 350 mm, a width of 102 mm, and a thickness of 12.7 mm, where one of the surfaces enclosed by the 350 mm length side and the 102 mm width side was the skin surface. On this test specimen, a start line was drawn 38 mm from the base end in the longitudinal direction, and an end line was drawn 292 mm from the base end. Using this test specimen, a flammability test was performed in the same manner as FMVSS No. 302, with the skin surface in contact with the burner flame.

[0082] Average combustion rate and self-extinguishing rate: Ten FMVSS tests were conducted, and the average combustion rate and self-extinguishing rate were calculated based on these test results. The average combustion rate was determined by arithmetic mean of the combustion rates measured for each test specimen. The combustion rate of each test specimen was calculated using the following formula (1). [Mathematics 1] B = 60 × D / T ·····(1)

[0083] However, in equation (1) above, symbol B represents the combustion rate (unit: mm / min), symbol D represents the distance the flame traveled (unit: mm), and symbol T represents the time required for the flame to travel D mm (unit: seconds). Furthermore, if the test specimen self-extinguished, the combustion rate was treated as 0 mm / min. Here, the test specimen was judged to have self-extinguished if "the test specimen did not ignite," "the combustion of the test specimen ended before reaching the starting position for combustion time measurement (i.e., the starting line mentioned above)," or "the combustion of the test specimen ended within 60 seconds of reaching the starting position for combustion time measurement, and the distance from the starting position to the end position of combustion was within 51 mm."

[0084] The self-extinguishing rate was calculated by dividing the number of tests in which the fire was evaluated as having "self-extinguished" by the total number of tests (10), and expressing the result as a percentage.

[0085] (Examples 2-4) Except for changing the content of the NOR-type hindered amine compound in the foamed particles to the values ​​shown in Table 1, single-stage foamed particles and double-stage foamed particles were manufactured in the same manner as in Example 1. Using these double-stage foamed particles, in-mold molding was performed in the same manner as in Example 1 to obtain foamed particle molded bodies. These were designated as Examples 2 to 4, respectively.

[0086] (Example 5) Single-stage foamed particles and double-stage foamed particles were manufactured in the same manner as in Example 1, except that resin particles manufactured by the following method were used. Using these double-stage foamed particles, in-mold molding was performed in the same manner as in Example 1 to obtain a foamed particle molded body. Furthermore, the polypropylene resin, carbon black, NOR-type hindered amine compound, and bubble regulator used to form the core layer in Example 5 were the same materials as those used in Example 1.

[0087] First, a manufacturing apparatus was prepared comprising a core layer forming extruder, a multilayer strand forming die attached downstream of the core layer forming extruder, and a fusion layer forming extruder. The manufacturing apparatus was configured such that the downstream side of the fusion layer forming extruder was connected to the multilayer strand forming die, allowing for the lamination of molten resin for forming each layer within the die, as well as enabling co-extrusion.

[0088] As a core-forming material, polypropylene resin, carbon black, a specific NOR-type hindered amine compound, and a foam regulator were supplied to a core-forming extruder and melt-kneaded to form a polypropylene resin molten product. At this time, the proportions of each material were adjusted so that the core layer of the resulting foamed particles contained 3% by mass of carbon black, 0.1% by mass of the specific NOR-type hindered amine compound, and 0.05% by mass of the foam regulator. Furthermore, as materials for forming the fusion layer, polypropylene resin, carbon black, and a specific NOR-type hindered amine compound were supplied to an extruder for fusion layer formation and melt-kneaded to form a polypropylene resin molten product. At this time, the blending amounts of each material were adjusted so that the fusion layer of the resulting foamed particles contained 3% by mass of carbon black and 0.1% by mass of the specific NOR-type hindered amine compound. Furthermore, a propylene-ethylene-butene random copolymer with a melt flow rate of 6 g / 10 min at melting points of 133°C and 230°C and a load of 2.16 kg was used as the polypropylene resin for forming the fusion layer.

[0089] As described above, the molten resin for each layer was introduced into a die for forming multilayer strands and merged within the die. A multilayer strand with a two-layer structure (fused layer / core layer) was then extruded through the pores of a nozzle attached to the downstream side of the die. The extruded strand was water-cooled and cut with a pelletizer to obtain polypropylene resin particles (core layer / fused layer = 95 / 5) with a length / diameter ratio of 2.0 and an average mass of 1.0 mg.

[0090] (Example 6) Except for not using carbon black, single-stage foamed particles and double-stage foamed particles were manufactured in the same manner as in Example 1. Using these double-stage foamed particles, in-mold molding was performed in the same manner as in Example 1 to obtain a foamed particle molded body. This was designated as Example 6.

[0091] (Example 7) Using the single-stage foamed particles produced in the manufacturing process of Example 1, in-mold molding was performed in the same manner as in Example 1 to obtain a foamed particle molded body. This was designated as Example 7.

[0092] (Comparative Examples 1-4) Except for the change in the NOR-type hindered amine compound used, as shown in Table 2, single-stage foamed particles and double-stage foamed particles were produced in the same manner as in Example 1. Using these double-stage foamed particles, in-mold molding was performed in the same manner as in Example 1 to obtain foamed particle molded articles. These were designated as Comparative Examples 1 to 4. In Comparative Examples 1 to 4, NOR-type hindered amine compounds that do not have the structure of general formula (I) described above were used. Specifically, the NOR-type hindered amine compounds used in Comparative Examples 1 and 2 were "trade name; NOR116FF, manufactured by BASF, melting point 108°C, molecular weight 2261", the NOR-type hindered amine compound used in Comparative Example 3 was "trade name; EVERSORB95, manufactured by Everlight Chemical, liquid at room temperature, molecular weight 737", and the NOR-type hindered amine compound used in Comparative Example 4 was a polymer-type hindered amine compound, "trade name; NOR371FF, manufactured by BASF, melting point 91°C, molecular weight 2800-4000".

[0093] For Examples 2 to 7 and Comparative Examples 1 to 4, the high-temperature peak, bulk density, average bubble diameter, density of the foamed particles, and FMVSS test of the foamed particle molded article were performed in the same manner as in Example 1. Note that in Example 7, a two-stage foaming process was not performed, so single-stage foamed particles were used for each of the measurements described above.

[0094] [Table 1]

[0095] [Table 2]

[0096] The present invention described above encompasses the following technical concepts. (1) Bulk density of 10 kg / m³ 3 More than 100kg / m 3 The following are polyolefin resin foam particles containing a NOR-type hindered amine compound, The aforementioned NOR-type hindered amine compounds are represented by the following general formula (I): Polyolefin resin foam particles wherein the content of the NOR-type hindered amine compound in the polyolefin resin foam particles is 0.01% by mass or more and 3% by mass or less. [ka] (In general formula (I), R 1 , R 2 , R 3 and R 4 Each of these independently represents a hydrocarbon group, and X represents an alkanolamine group. (2) Polyolefin resin foam particles as described in (1), wherein the melting point of the NOR-type hindered amine compound is 60°C or higher and 100°C or lower. (3) Polyolefin resin foam particles according to (1) or (2), wherein the molecular weight of the NOR-type hindered amine compound is 1000 or less. (4) Polyolefin resin foam particles according to any one of (1) to (3) above, wherein X in the general formula (I) is an ethanolamine group. (5) The polyolefin resin foam particles according to any one of (1) to (4) above, wherein the polyolefin resin foam particles further contain a carbon material. (6) Density is 10 kg / m³ 3 More than 100kg / m 3 The following is a polyolefin resin foam particle molded article containing a NOR-type hindered amine compound: The aforementioned NOR-type hindered amine compounds are represented by the following general formula (I): A polyolefin resin foam particle molded article wherein the content of the NOR-type hindered amine compound in the polyolefin resin foam particle molded article is 0.01% by mass or more and 3% by mass or less. [ka] (In general formula (I), R 1 , R 2 , R 3 and R 4 Each of these independently represents a hydrocarbon group, and X represents an alkanolamine group.

Claims

1. Bulk density is 10 kg / m³ 3 More than 100kg / m 3 The following are polyolefin resin foam particles containing a NOR-type hindered amine compound, The aforementioned NOR-type hindered amine compound is represented by the following general formula (I): Polyolefin resin foam particles wherein the content of the NOR-type hindered amine compound in the polyolefin resin foam particles is 0.01% by mass or more and 3% by mass or less. 【Chemistry 1】 (In general formula (I), R １ , R ２ , R ３ and R ４ Each of the symbols independently represents a hydrocarbon group, and X represents an alkanolamine group.

2. The polyolefin resin foam particles according to claim 1, wherein the melting point of the NOR-type hindered amine compound is 60°C or higher and 100°C or lower.

3. The polyolefin resin foam particles according to claim 1 or 2, wherein the molecular weight of the NOR-type hindered amine compound is 1000 or less.

4. The polyolefin resin foam particle according to claim 1 or 2, wherein X in the general formula (I) is an ethanolamine group.

5. The polyolefin-based resin foam particles according to claim 1 or 2, wherein the polyolefin-based resin foam particles further contain a carbon material.

6. Density is 10 kg / m³ 3 More than 100kg / m 3 The following is a polyolefin resin foam particle molded article containing a NOR-type hindered amine compound: The aforementioned NOR-type hindered amine compound is represented by the following general formula (I): A polyolefin resin foam particle molded article wherein the content of the NOR-type hindered amine compound in the polyolefin resin foam particle molded article is 0.01% by mass or more and 3% by mass or less. 【Chemistry 2】 (In general formula (I), R １ , R ２ , R ３ and R ４ each independently represent a hydrocarbon group, and X represents an alkanolamine group.)

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