Polypropylene resin foamed particles and polypropylene resin foamed particle molded article

Abstract

Provided are: expanded polypropylene resin particles which contain a biomass-derived polypropylene resin and which are capable of providing an excellent expanded polypropylene resin particle molded body; and an expanded polypropylene resin particle molded body which is produced using the expanded particles. In the polypropylene resin foamed particles, the base resin of the foamed particles contains a biomass-derived polypropylene resin A containing a biomass-derived monomer component in the molecular chain, and a fossil fuel-derived polypropylene resin B, the base resin contains 3-60 wt% of a biomass-derived polypropylene resin A and 40-97 wt% of a fossil fuel-derived polypropylene resin B (the total amount of both is 100 wt%), and the foamed particle molded body is formed by in-mold molding of the polypropylene resin foamed particles.

Description

Technical Field

[0001] The present invention relates to polypropylene resin foamed particles containing a biomass-derived polypropylene resin and a polypropylene resin foamed particle molded article produced using the foamed particles. Background Art

[0002] It is known that by in-mold molding polypropylene resin foamed particles containing polypropylene resin, polypropylene resin foamed particle molded articles having excellent strength and cushioning properties can be obtained. Polypropylene resin foamed particle molded articles can be used in various applications such as packaging materials, automotive components, and building components.

[0003] However, in recent years, awareness of the environmental burdens of increasing atmospheric carbon dioxide concentrations and the depletion of fossil fuel resources has grown. In response, a technology for a polyethylene resin foam sheet comprising a plant-derived polyethylene resin with a high plant content has been proposed (e.g., Patent Document 1).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2013-60528 Summary of the Invention

[0007] (1) Technical issues to be resolved

[0008] On the other hand, regarding polypropylene resin foams, there has been no technology related to resin foamed particles using a biomass-derived polypropylene resin raw material including plant-derived polypropylene resin. Therefore, there is a desire to provide a technology related to polypropylene resin foamed particles and polypropylene resin foamed particle molded articles that utilize biomass-derived raw materials and can address the aforementioned reduction in environmental burden.

[0009] The present invention has been made in view of the above-mentioned needs. The polypropylene foamed beads of the present invention contain a polypropylene resin derived from biomass, and the polypropylene foamed beads can provide a polypropylene resin foamed bead molded article in a well-molded state.

[0010] (2) Technical solution

[0011] The polypropylene resin foamed particles of the present invention are characterized in that the base resin of the foamed particles comprises: a biomass-derived polypropylene resin A containing a monomer component derived from biomass in its molecular chain, and a fossil fuel-derived polypropylene resin B, wherein the base resin contains 3% by weight or more and 60% by weight or less of the biomass-derived polypropylene resin A, and 40% by weight or more and 97% by weight or less of the fossil fuel-derived polypropylene resin B (the total amount of the two being 100% by weight).

[0012] The polypropylene resin foamed bead molded article of the present invention is characterized in that it is formed by in-mold molding the polypropylene resin foamed beads of the present invention.

[0013] (3) Beneficial effects

[0014] The polypropylene resin foamed particles of the present invention are composed of a biomass-derived polypropylene resin, contributing to reduced environmental impact. Furthermore, the polypropylene resin foamed particles of the present invention exhibit excellent moldability, and the foamed particle molded articles of the present invention exhibit excellent molded properties, including weldability, secondary foaming properties, and recovery.

[0015] Therefore, the polypropylene resin foamed particle molded article of the present invention can achieve a reduction in environmental burden and can be used in various fields as in the past. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a DSC curve obtained by the thermal transition measurement method for plastics described in JIS K7122:2012, and is used to obtain the total heat of fusion and high-temperature peak heat of the polyolefin-based resin foamed particles as one embodiment of the present invention. DETAILED DESCRIPTION

[0017] The base resin of the polypropylene resin foamed particles of the present invention (hereinafter sometimes referred to as the foamed particles of the present invention) contains a polypropylene resin as a main component and includes: a biomass-derived polypropylene resin A containing a biomass-derived monomer component in its molecular chain; and a fossil fuel-derived polypropylene resin B.

[0018] The base resin in the foamed beads of the present invention contains 3% by weight or more and 60% by weight or less of the biomass-derived polypropylene resin A and 40% by weight or more and 97% by weight or less of the fossil fuel-derived polypropylene resin B (the total amount of the two being 100% by weight). That is, out of the total amount of 100% by weight of the biomass-derived polypropylene resin A and the fossil fuel-derived polypropylene resin B contained in the base resin, the content of the biomass-derived polypropylene resin A is 3% by weight or more and 60% by weight or less, and the content of the fossil fuel-derived polypropylene resin B is 40% by weight or more and 97% by weight or less.

[0019] The foamed beads of the present invention contain a polypropylene resin derived from biomass, contributing to reduced environmental impact. Furthermore, through in-mold molding of the foamed beads, a foamed bead molded article exhibiting excellent weldability, secondary foaming properties, and post-aging recovery can be provided.

[0020] In the present invention, biomass refers to renewable organic resources derived from living organisms (excluding organic resources derived from fossil fuels such as petroleum and coal). Biomass-derived polypropylene resin A refers to a polypropylene resin formed by polymerizing biomass-derived monomers and containing biomass-derived monomer components in its molecular chain. Polypropylene resin A may be composed solely of biomass-derived monomer components or may be composed of biomass-derived monomer components and fossil fuel-derived monomer components.

[0021] The fossil fuel-derived polypropylene resin B is a polypropylene resin obtained by substantially polymerizing only monomers derived from fossil fuels. The fossil fuel-derived polypropylene resin B preferably contains only monomer components derived from fossil fuels in its molecular chain.

[0022] In the present invention, a biomass-derived monomer refers to propylene, ethylene, or an α-olefin having 4 to 8 carbon atoms produced from a biomass raw material. In addition, in the present invention, a biomass-derived monomer component refers to a structural unit in a polymer produced by addition polymerization of propylene, ethylene, or an α-olefin having 4 to 8 carbon atoms as a monomer. The method for producing a biomass-derived monomer is not particularly limited, and a biomass-derived monomer can be obtained by conventional methods such as dehydrating an alcohol derived from a biomass raw material or decomposing naphtha derived from a biomass raw material. Examples of biomass raw materials used in the production of biomass-derived monomers include monosaccharides, polysaccharides, vegetable oils and fats, and animal oils and fats obtained from agricultural and livestock products, forestry products, algae, and the like. In the present invention, from the perspective of non-competitiveness with food and contribution to a recycling-oriented society by utilizing by-product and waste biomass, the biomass raw material used in the production of biomass-derived monomers is preferably bio-naphtha produced from waste cooking oil, black liquor, waste liquid from tall oil and palm oil production (palm oil mill effluent), oils and fats contained in microalgae, and the like. In the present invention, propylene obtained by decomposing this bio-naphtha is preferably used.

[0023] In the present invention, fossil fuel-derived monomers refer to propylene, ethylene, or α-olefins having 4 to 8 carbon atoms produced from fossil fuels. The method for producing fossil fuel-derived monomers is not limited, and fossil fuel-derived monomers can be produced using methods known in the petrochemical industry. For example, the fossil fuel-derived monomers can be obtained by pyrolysis and fractionation of naphtha obtained during petroleum purification.

[0024] Hereinafter, the present invention will be described in further detail. In addition, in the following description, the preferred numerical range of the present invention may be appropriately shown. In this case, the preferred range, more preferred range, and particularly preferred range involving the upper and lower limits of the numerical range can be determined by all combinations of the upper and lower limits. In addition, in the following description, the polypropylene resin A derived from biomass may be referred to as polypropylene resin A, and the polypropylene resin B derived from fossil fuels may be referred to as polypropylene resin B.

[0025] [Base resin]

[0026] As described above, the base resin in the present invention contains a biomass-derived polypropylene resin A in an amount ranging from 3 wt % to 60 wt % and a fossil fuel-derived polypropylene resin B in an amount ranging from 40 wt % to 97 wt % (the total amount of the two is 100 wt %).

[0027] Research by the inventors of the present application has confirmed that foamed beads using a biomass-derived polypropylene resin A as a base resin tend to suffer from poor moldability. In response to this, the inventors discovered that by blending the biomass-derived polypropylene resin A with a fossil fuel-derived polypropylene resin B and maintaining the blending ratio within the aforementioned range, a foamed bead molded article with a well-formed state can be provided.

[0028] From the perspective of providing a more excellent foamed bead molded body in a molding state, and making full use of the polypropylene resin from biomass, it is very helpful to set out from the perspective of reducing the environmental burden, in the total amount 100 wt % of polypropylene resin A and polypropylene resin B, the ratio of the polypropylene resin A from biomass is preferably more than 5 wt % and less than 50 wt %, more preferably more than 7 wt % and less than 45 wt %, further preferably more than 10 wt % and less than 30 wt %. In addition, in the total amount 100 wt % of the polypropylene resin A from biomass and the polypropylene resin B from fossil fuels, the preferred numerical range of the polypropylene resin A from biomass, for example, can be listed: using any one of 5%, 7% or 10% as the lower limit and using any one of 50%, 45% or 40% as the upper limit. In 100 wt % of the base resin, the blending ratio of the total amount of the polypropylene resin A and polypropylene resin B in the base resin is preferably more than 80 wt %, more preferably 90 wt %, further preferably more than 95 wt %.

[0029] In this specification, a polypropylene resin refers to a polypropylene copolymer containing more than 50% by weight of a propylene homopolymer or a propylene structural unit. Examples of the propylene homopolymer include isotactic polypropylene, syndiotactic polypropylene, and atactic polypropylene.

[0030] Examples of the polypropylene-based copolymers include copolymers of propylene and ethylene or an α-olefin having 4 to 8 carbon atoms, such as propylene-ethylene copolymers, propylene-butene copolymers, and propylene-ethylene-butene copolymers, propylene-acrylic acid copolymers, and propylene-maleic anhydride copolymers. These copolymers may be block copolymers, random copolymers, or graft copolymers.

[0031] Furthermore, the above-mentioned polymer may be cross-linked, but is preferably a non-cross-linked polymer from the viewpoint of further contributing to reducing environmental burdens.

[0032] In addition to the above-mentioned polypropylene resin, the base resin in the present invention may further contain other polymers or additives.

[0033] Examples of other polymers include thermoplastic resins other than polypropylene resins such as polyethylene resins, polystyrene resins, polyamide resins, and polyester resins, and elastomers such as olefin thermoplastic elastomers and styrene thermoplastic elastomers. Two or more of these other polymers may be included.

[0034] In 100% by weight of the base resin, the blending ratio of other polymers in the base resin is preferably 5% by weight or less, more preferably 3% by weight or less, further preferably 1% by weight or less, and most preferably 0% by weight, that is, the foamed particles contain only polypropylene resin as a polymer.

[0035] In addition to the polymer, additives such as colorants, antioxidants, antistatic agents, surfactants, heat stabilizers, light stabilizers, ultraviolet absorbers, and flame retardants may be added. The proportion of the additives in the base resin is preferably 20% by weight or less, more preferably 10% by weight or less, and even more preferably 5% by weight or less, based on 100% by weight of the base resin.

[0036] In this specification, the biomass-derived polypropylene resin A is composed of the above-mentioned polypropylene resin. The polypropylene resin A may include two or more biomass-derived polypropylene resins. From the perspective of providing foamed beads that can achieve both an expansion of the steam pressure range within which the foamed bead molded article can be formed and a shortened molding cycle, the polypropylene resin A is preferably a propylene homopolymer or a propylene-ethylene block copolymer, and more preferably a propylene homopolymer.

[0037] In this specification, the fossil fuel-derived polypropylene resin B is composed of the above-mentioned polypropylene resin. The polypropylene resin B can be derived from a fossil fuel such as petroleum fuel, and can be a single type or a mixture of two or more fossil fuel-derived polypropylene resins. From the perspective of providing a foamed bead molded article exhibiting a well-formed state and good surface properties, the polypropylene resin B is preferably a propylene-ethylene random copolymer or a propylene-ethylene-butene random copolymer, and more preferably a propylene-ethylene random copolymer.

[0038] The polypropylene resin included in the polypropylene resin A and the polypropylene resin included in the polypropylene resin B constituting the base resin may be the same type of polypropylene resin or different types of polypropylene resins.

[0039] For example, the biomass-derived polypropylene resin A and the fossil fuel-derived polypropylene resin B may each be a propylene homopolymer or a polypropylene copolymer, or one may be a propylene homopolymer and the other a polypropylene copolymer.

[0040] In a preferred embodiment of the present invention, the fossil fuel-derived polypropylene resin B preferably comprises a polypropylene copolymer, more preferably a propylene-ethylene random copolymer. By blending the biomass-derived polypropylene resin A with a fossil fuel-derived polypropylene resin B comprising a polypropylene copolymer such as a propylene-ethylene random copolymer, a foamed particle molded article with a better molding state can be provided. From this perspective, the fossil fuel-derived polypropylene resin B is preferably a propylene-ethylene random copolymer, and the ethylene content of the propylene-ethylene random copolymer is more preferably 1% by weight or more and 5% by weight or less, and further preferably 1.5% by weight or more and 4% by weight or less.

[0041] For example, in the foamed beads of the present invention, it is preferred that the biomass-derived polypropylene resin A is a propylene homopolymer or a propylene-ethylene block copolymer, and the fossil fuel-derived polypropylene resin B is in the form of a polypropylene copolymer such as a propylene-ethylene random copolymer. In the foamed beads of the present invention, it is further preferred that the biomass-derived polypropylene resin A is a propylene homopolymer, and the fossil fuel-derived polypropylene resin B is in the form of a polypropylene copolymer such as a propylene-ethylene random copolymer.

[0042] (Bio-based carbon content of polypropylene resin A)

[0043] In the present invention, the biobased carbon content (biobased carbon content) measured by ASTM D6866-21 of the polypropylene resin A from biomass is preferably 1% or more and 100% or less. From the perspective of maintaining the molding state of the provided foamed particle molded body well and contributing to reducing the environmental burden, the biobased carbon content of the polypropylene resin A is more preferably 10% or more and 50% or less, further preferably 20% or more and 48% or less, particularly preferably 25% or more and 45% or less. In addition, the preferred numerical range of the biobased carbon content can, for example, be cited as a range with any one of 10%, 20% or 25% as the lower limit and any one of 50%, 48% or 45% as the upper limit.

[0044] (Bio-based carbon content of polypropylene resin B)

[0045] In the present invention, the polypropylene-based resin B derived from fossil fuels has a biobased carbon content of 0% as measured by ASTM D6866-21.

[0046] (Melting point of base resin)

[0047] Melting point Tm of base resin SThe melting point Tm is not particularly limited, but is preferably 135°C to 160°C, more preferably 140°C to 157°C. S The preferred numerical range of α can be exemplified by a range having either 135°C or 140°C as the lower limit and either 160°C or 157°C as the upper limit. Even when the polypropylene resin A and the polypropylene resin B contained in the foamed beads have different melting points, the base resin can be prepared by having a melting point Tm within the above range. S The method is adjusted, and the foamed particle molded body provided finally has a good molding state.

[0048] Melting point Tm of base resin S It can be determined according to JIS K7121: 2012. In this case, as the condition adjustment of the test piece, "(2) the case where the melting temperature is measured after a certain heat treatment" can be adopted.

[0049] More specifically, a pelletized base resin is formed into a test piece and, according to the heat-flow differential scanning calorimetry method described in JIS K7121:2012, the temperature is raised from 23°C to 200°C at a heating rate of 10°C / min, then cooled to 23°C at a cooling rate of 10°C / min, and then again raised from 23°C to 200°C at a heating rate of 10°C / min. The peak temperature of the melting peak determined by the resulting DSC curve is taken as the melting point of the polypropylene resin. If two or more melting peaks appear in the DSC curve, the peak temperature of the melting peak with the largest area is taken as the melting point. In this case, the melting peaks are separated by using the valley temperature of the DSC curve between the peak temperatures of the respective melting peaks as the boundary, and the areas (heats of fusion) of the respective melting peaks are compared to determine the melting peak with the largest area. The valley temperature of the DSC curve can be determined by referring to the DSC differential curve (DDSC) and judging the temperature at which the vertical axis of the differential curve reaches 0. Examples of measuring instruments include a heat flow differential scanning calorimeter (manufactured by SII NanoTechnology Inc., model: DSC7020).

[0050] (Melting point of resin constituting base resin)

[0051] In the present invention, the melting point Tm of the biomass-derived polypropylene resin A is A There is no particular limitation. As an example, the melting point Tm can be listed. A The polypropylene resin A has a temperature of 155°C to 170°C. A It is preferably 158°C or higher and 170°C or lower, and the melting point Tm is more preferably AThe polypropylene resin A having a melting point of 160°C or higher and 170°C or lower is used as the resin constituting the base resin. B The melting point Tm of the base resin can be easily adjusted by blending the polypropylene resin A and the polypropylene resin B within this melting point range. S Adjust to the desired range, and the final foamed particle molded body provided is in good molding state. From the above perspective, the base resin preferably contains a melting point Tm A The biomass-derived polypropylene A has a melting point of 158°C or higher and 170°C or lower, and a melting point Tm B The polypropylene resin B derived from fossil fuels has a melting point of 130°C or higher and 150°C or lower, and preferably has a melting point Tm A The biomass-derived polypropylene A has a melting point of 160°C or higher and 170°C or lower, and a melting point Tm B The polypropylene resin B is derived from fossil fuels and has a temperature of 135°C to 145°C.

[0052] The melting point Tm of the above-mentioned base resin was measured by using the pelletized polypropylene resin A or the pelletized polypropylene resin B instead of the base resin. S The same determination method was used to measure the melting point Tm of polypropylene resin A. A and the melting point Tm of polypropylene resin B B .

[0053] (Crystallization temperature of resin constituting base resin)

[0054] In the present invention, from the perspective of shortening the molding cycle when molding the foamed beads, the crystallization temperature Tc of the biomass-derived polypropylene resin A is A It is preferably 110°C to 130°C, more preferably 113°C to 128°C, and even more preferably 115°C to 123°C. A The preferred numerical range of can be set to, for example, a range with any one of 110°C, 113°C, or 115°C as the lower limit and any one of 130°C, 128°C, or 123°C as the upper limit. From the perspective of obtaining foamed particles with an excellent molding range, the crystallization temperature Tc of the polypropylene resin B derived from fossil fuels is preferably 0.05. B It is preferably 90°C or higher and 110°C or lower, more preferably 92°C or higher and 109°C or lower, and even more preferably 94°C or higher and 108°C or lower. BFor example, a preferred numerical range includes a range having any one of 90°C, 92°C, and 94°C as the lower limit and any one of 110°C, 109°C, and 108°C as the upper limit.

[0055] Crystallization temperature Tc of polypropylene resin A A and the crystallization temperature Tc of polypropylene resin B B This refers to the temperature at the top of the crystallization peak determined by heat-flow differential scanning calorimetry according to JIS K7121:2012. The test piece condition was adjusted using "(2) Melting temperature measurement after a certain heat treatment," and a cooling rate of 10°C per minute was used. If two or more crystallization peaks appeared, the temperature at the top of the crystallization peak with the largest area was used as the crystallization temperature.

[0056] (Melt flow rate (MFR) of polypropylene resin A A ))

[0057] The biomass-derived polypropylene resin A preferably has a melt flow rate (MFR) of A ) is 1 g / 10 min or more and 100 g / 10 min or less. Furthermore, it is more preferable to use a polypropylene resin A that satisfies (I) or (II) shown below.

[0058] (I) Biomass-derived polypropylene resin A is a homopolymer of propylene, and its melt flow rate (MFR) measured at 230°C and under a load of 2.16 kg is A ) is 1 g / 10 min or more and 5 g / 10 min or less.

[0059] (II) Biomass-derived polypropylene resin A is a propylene-ethylene block copolymer, and its melt flow rate (MFR) measured at 230°C and a load of 2.16 kg is A ) is 50 g / 10 min or more and 80 g / 10 min or less.

[0060] As a particularly preferred range, the range of (I) mentioned above can be mentioned.

[0061] By making the melt flow rate (MFR A ) within the above range, the steam pressure range that can be formed when the foamed particles are in-mold molded becomes wider, and foamed particles with an excellent molding range can be obtained.

[0062] (Melt flow rate (MFR) of polypropylene resin B B ))

[0063] The melt flow rate (MFR) of the polypropylene resin B derived from fossil fuels measured at 230°C and a load of 2.16 kg is preferably B ) is 5 g / 10 min or more and 20 g / 10 min or less. It is particularly preferred that the polypropylene resin B derived from fossil fuels is a polypropylene copolymer such as a propylene-ethylene random copolymer, and the melt flow rate (MFR) measured at 230°C and a load of 2.16 kg is B ) is 5 g / 10 min or more and 15 g / 10 min or less.

[0064] By making the melt flow rate (MFR B ) within the above range, the steam pressure range that can be formed when the foamed particles are in-mold molded becomes wider, and foamed particles with an excellent molding range can be obtained.

[0065] (MFR A / MFR B )

[0066] The melt flow rate (MFR) of the biomass-derived polypropylene resin A measured at 230°C and a load of 2.16 kg was A ) Melt flow rate (MFR) of the polypropylene resin B derived from fossil fuels measured at 230°C and a load of 2.16 kg B ) ratio (MFR A / MFR B ) is preferably 0.2 or more and 0.8 or less, more preferably 0.3 or more and 0.7 or less.

[0067] The melt flow rate (MFR) of the polypropylene resin A, which is a homopolymer of propylene, is particularly preferred. A ) is 1 g / 10 min or more and 5 g / 10 min or less, and the ratio (MFR A / MFR B ) is greater than or equal to 0.2 and less than or equal to 0.8.

[0068] By making the ratio (MFR A / MFR B ) is within the above range, even if the melt flow rate (MFR A ) is a relatively low value when conventionally producing a polypropylene resin foamed bead molded body, it is also easy to increase the melt flow rate (MFR) of the base resin. S ) is adjusted within the desired range. As a result, it is easy to provide a good foamed particle molded body.

[0069] (Melt flow rate (MFR) of the base resin S ))

[0070] The melt flow rate (MFR) of the base resin was measured at 230°C and a load of 2.16 kg. S ) is preferably 5 g / 10 min or more and 15 g / 10 min or less. From the perspective of providing a foamed particle molded body with good surface properties, the melt flow rate (MFR) of the substrate resin is preferably 5 g / 10 min or more and 15 g / 10 min or less. S ) is preferably 5 g / 10 min or more and 15 g / 10 min or less, more preferably 6 g / 10 min or more and 12 g / 10 min or less, and further preferably 7 g / 10 min or more and 10 g / 10 min or less. In addition, the melt flow rate (MFR s ) can be exemplified by a range having any one of 5 g / 10 min, 6 g / 10 min or 7 g / 10 min as a lower limit and any one of 15 g / 10 min, 12 g / 10 min or 10 g / 10 min as an upper limit.

[0071] For example, from the viewpoint of widening the steam pressure range that can be molded when the foamed beads are molded in the mold, and obtaining foamed beads with an excellent molding range, it is preferable to adjust the ratio (MFR A / MFR B ) is within the range of 0.2 or more and 0.8 or less, and the melt flow rate (MFR S ) is 5 g / 10 min or more and 15 g / 10 min or less.

[0072] The melt flow rates of each of the polypropylene resin A, the polypropylene resin B, and the base resin were measured at 230° C. and under a load of 2.16 kg in accordance with JIS K7210-1:2014.

[0073] [Foaming particles]

[0074] (Bio-based carbon content of foamed particles)

[0075] The expanded beads of the present invention, which are composed of the above-mentioned base resin, contain the biomass-derived polypropylene resin A, contribute to reducing environmental burdens, and can provide a favorable expanded bead molded article of the present invention described later.

[0076] The polypropylene-based foamed particles of the present invention preferably have a bio-based carbon content measured by ASTM D6866-21 of 1% or more and 30% or less. From the perspective of making a more sufficient contribution to reducing the environmental burden, and maintaining the molding state of the provided foamed particle molded body well and helping to reduce the environmental burden, the bio-based carbon content of the foamed particles is preferably 1% or more and 30% or less, more preferably 2% or more and 25% or less, further preferably 5% or more and 21% or less, and particularly preferably 10% or more and 18% or less. In addition, the preferred numerical range of the bio-based carbon content can be, for example, a range with any one of 1%, 2%, 5% or 10% as the lower limit and any one of 30%, 25%, 21% or 18% as the upper limit.

[0077] (Method for producing foamed particles)

[0078] The foamed beads of the present invention can be produced using a base resin containing 3% by weight or more and 60% by weight or less of a polypropylene resin A derived from biomass and 40% by weight or more and 97% by weight or less of a polypropylene resin B derived from fossil fuels (the total amount of the two being 100% by weight), according to a known foamed bead production method. In addition, as described above, in addition to the polypropylene resin A and the polypropylene resin B, the base resin may appropriately contain other polymers or additives.

[0079] For example, the foamed particles of the present invention can be produced by using raw materials such as the above-mentioned polypropylene resin A and polypropylene resin B, producing resin particles by an extrusion method, and then foaming the resin particles. More specifically, first, the specified raw materials are supplied to an extruder and kneaded to produce small granular resin particles with adjusted weight and shape. Next, the resin particles are supplied to a pressure vessel containing an aqueous dispersion medium such as water, an inorganic dispersant, and a dispersing aid such as a surfactant, and the foamed particle production process is carried out, including a dispersion step, a foaming agent impregnation step, and a foaming step.

[0080] The dispersion step involves dispersing the resin particles in an aqueous dispersion containing an inorganic dispersant within a pressure vessel. The blowing agent impregnation step involves impregnating the resin particles with a blowing agent such as carbon dioxide within the pressure vessel. The foaming step involves simultaneously releasing the resin particles containing the blowing agent and the aqueous dispersion medium from the pressure vessel to cause foaming. In addition to the aforementioned steps, the method for producing the foamed particles of the present invention may include any additional steps as appropriate.

[0081] (High temperature peak of expanded particles, heat of fusion of high temperature peak, total heat of fusion)

[0082] From the perspective of adjusting the expanded beads of the present invention to a good crystal state, the DSC curve obtained by heat flow differential scanning calorimetry (refer to Figure 1 ), it is preferred that a melting peak (high temperature peak) having a peak temperature appear on a side higher than the peak temperature of the main melting peak (intrinsic peak) of the foamed particles.

[0083] The DSC curve in this case refers to the DSC curve obtained by heating the foamed beads using the above-described measurement method (DSC curve during the first heating). Furthermore, the main melting peak (intrinsic peak) of the foamed beads refers to a peak resulting from the melting of intrinsic crystals of the base resin constituting the foamed beads. Furthermore, the intrinsic peak is considered to be a peak resulting from the melting of crystals typically present in the base resin constituting the foamed beads.

[0084] On the other hand, a melting peak (high temperature peak) having a peak temperature on a side higher than the peak temperature of the intrinsic peak refers to a peak that can be confirmed by the first DSC curve and exists on a side higher than the intrinsic peak. It is speculated that when this high temperature peak appears, secondary crystals different from the crystals usually present are present in the base resin constituting the foamed particles. In addition, in the DSC curve of the second heating, only the intrinsic peaks generated by the melting of the crystals usually present in the base resin constituting the foamed particles appear. The DSC curve of the second heating refers to the DSC curve obtained when 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). This intrinsic peak appears in both the DSC curve of the first heating and the DSC curve of the second heating. In summary, by comparing the shapes and peak positions of the first and second DSC curves, it is possible to distinguish between the intrinsic peak and the high-temperature peak.

[0085] From the perspective of obtaining a foamed bead molded article with an excellent balance between cushioning and rigidity, the heat of fusion of the high temperature peak is preferably 10 J / g or more and 50 J / g or less, more preferably 10 J / g or more and 30 J / g or less, and even more preferably 15 J / g or more and 25 J / g or less. Furthermore, the heat of fusion of the high temperature peak can be, for example, a range with either 10 J / g or 15 J / g as the lower limit and either 50 J / g, 30 J / g, or 25 J / g as the upper limit.

[0086] Furthermore, from the perspective of widening the steam pressure range that can be molded during in-mold molding of the foamed particles and obtaining foamed particles with an excellent molding range, the total heat of fusion of the foamed particles of the present invention is preferably from 60 J / g to 100 J / g, and more preferably from 70 J / g to 90 J / g.

[0087] The high-temperature peak can be adjusted, for example, by controlling the rate of temperature increase within the pressure vessel during the dispersion step and / or the blowing agent impregnation step, or by maintaining the temperature within the pressure vessel at a predetermined temperature for a predetermined time. More specifically, for example, during the dispersion step and / or the blowing agent impregnation step, a first-stage holding step is performed, in which the temperature within the pressure vessel is maintained at a temperature above (the melting point of the base resin - 20°C) and below (the melting end temperature of the base resin) for approximately 10 to 60 minutes. The temperature within the pressure vessel is then adjusted from (the melting point of the base resin - 15°C) to a temperature below (the melting end temperature of the base resin). A second-stage holding step is then performed, optionally maintaining the temperature at this temperature for an additional 10 to 60 minutes. Subsequently, a foaming step is performed to produce expanded particles having a high-temperature peak.

[0088] The high temperature peak heat and total melting heat of the foamed particles are determined by the DSC curve of the first heating (refer to Figure 1 ) was obtained, and the DSC curve of the first heating was obtained as follows: according to the thermal transition determination method for plastics described in JIS K7122:2012, 1~3 mg of foamed particles were made into a test piece, and it was heated from 23°C at a heating rate of 10°C / min to a temperature 30°C higher than the end of the melting peak of the test piece.

[0089] More specifically, in Figure 1 In the DSC curve shown, a straight line is drawn connecting point I, corresponding to 80°C, and point II, corresponding to the melting end temperature of the expanded beads. The melting end temperature is the high-temperature endpoint of high-temperature peak b, and is the intersection of high-temperature peak b and the baseline on the higher-temperature side of the DSC curve.

[0090] like Figure 1 As shown, after drawing a straight line connecting point I and point II, the intersection of a straight line passing through the maximum point III between the inherent peak a and the high-temperature peak b and parallel to the vertical axis of the graph and the straight line connecting point I and point II is set to IV.

[0091] Next, the area enclosed by the straight line connecting points I and IV, the straight line connecting points III and IV, and the DSC curve connecting points I and III was taken as the area of intrinsic peak a. Furthermore, the area enclosed by the straight line connecting points IV and II, the straight line connecting points III and IV, and the DSC curve connecting points III and II (the shaded area) was taken as the area of high-temperature peak b. The total heat of fusion of the foamed particles was calculated based on the sum of the areas of intrinsic peak a and high-temperature peak b, and the high-temperature peak calorific value of the foamed particles was calculated based on the area of high-temperature peak b.

[0092] (Apparent density of foamed particles)

[0093] From the perspective of achieving energy saving by reducing the amount of steam used during molding, the apparent density of the foamed beads of the present invention is preferably 20 kg / m 3 Above and 120kg / m 3 Below, more preferably 30kg / m 3 Above and 90kg / m 3 the following.

[0094] The apparent density of the foamed particles can be measured by the following method. First, place the foamed particles to be measured in an environment with a temperature of 23°C, a relative humidity of 50%, and 1 atm for more than 24 hours. Fill the foamed particle group with a weight of W (g) obtained in this way into a measuring cylinder, and gently tap the horizontal surface with the bottom of the measuring cylinder several times to stabilize the filling height of the foamed particle group in the measuring cylinder. Read the bulk volume V (L) of the foamed particle group shown on the scale of the measuring cylinder, and divide the weight W of the foamed particle group by the bulk volume V (W / V) of the foamed particle group. Convert the value obtained in this way into kg / m 3 , from which the apparent density of the foamed particles (kg / m 3 ).

[0095] (Average bubble diameter of foamed particles)

[0096] From the viewpoint of further improving the surface smoothness of the expanded bead molded article, the average cell diameter of the expanded beads of the present invention is preferably 40 μm or more and 200 μm or less, and more preferably 60 μm or more and 180 μm or less.

[0097] The average cell diameter of the foamed beads can be calculated as follows. First, take a photograph of a cross-section of the foamed beads, dividing them into two equal parts. Draw a straight line across the photograph to roughly bisect the cross-section of the foamed beads. Divide the length (L) of the line segment from the periphery of the foamed bead to the periphery of the opposite side by the number (N) of all bubbles connected to the line segment to obtain the average cell diameter of the foamed bead (L / N). Repeat this process for 10 or more foamed beads, and take the arithmetic mean of the results as the average cell diameter of the foamed beads.

[0098] (Closed-cell ratio of foamed particles)

[0099] From the perspective of broadening the steam pressure range that can be molded during in-mold molding of the foamed beads and obtaining foamed beads with an excellent molding range, the closed cell ratio of the foamed beads of the present invention is preferably from 70% to 99%, and more preferably from 80% to 99%.

[0100] The closed cell ratio of the foamed particles is determined as follows. First, the closed cell ratio is determined by measuring the volume of the foamed particles to a value of approximately 20 cm 3 The foamed particle group is immersed in water, and the apparent volume Va of the foamed particle group is measured. Then, after the foamed particle group after the apparent volume Va is measured is fully dried, the volume of the foamed particle group (the sum of the volume of the resin constituting the foamed particles and the total volume of the bubbles in the independent bubble part of the foamed particles) is measured according to step C described in ASTM-D2856-94 (true volume Vx). An air comparison pycnometer can be used in the measurement of the true volume Vx. As the air comparison pycnometer, for example, the air comparison pycnometer 1000 manufactured by Tokyo-Science. Co, Ltd. can be cited. Then, the closed cell ratio is calculated by the following mathematical formula (1). Using different measurement samples, the closed cell ratio is measured 5 times with the same steps as above, and the arithmetic mean of the values obtained in each measurement is calculated, and the value is used as the closed cell ratio of the foamed particles.

[0101] [Mathematical formula 1]

[0102] Closed cell ratio (%) = (Vx-W / ρ) × 100 / (Va-W / ρ) (1)

[0103] Vx: True volume of the expanded particle group measured by the above method (cm 3 )

[0104] Va: Apparent volume of the expanded particles measured by the rise in water level when the expanded particles are immersed in water in a graduated cylinder (cm 3 )

[0105] W: Weight of the foamed particle group (g)

[0106] ρ: Density of the resin constituting the foamed particles (g / cm 3 )

[0107] [Foamed particle molded article]

[0108] Next, the polypropylene resin foamed bead molded article of the present invention (hereinafter sometimes simply referred to as the foamed bead molded article of the present invention) is described. The foamed bead molded article of the present invention is obtained by in-mold molding the polypropylene resin foamed beads of the present invention described above.

[0109] The foamed particle molded body of the present invention comprises a polypropylene raw material from biomass. When contributing to reducing the environmental burden, the weldability, secondary foaming and the recoverability after aging of the foamed particle molded body are excellent, and good moldability can be shown. In addition, the surface smoothness of the foamed particle molded body of the present invention is excellent, and the apparent density can be adjusted within a preferred range. Therefore, the foamed particle molded body is identical to the foamed particle molded body (hereinafter, sometimes referred to as the foamed particle molded body in the past) manufactured by using the foamed particles manufactured only by the polypropylene resin from fossil fuels. The foamed particle molded body of the present invention can be suitable for various purposes such as packaging materials or automotive components, building materials.

[0110] (Apparent density of foamed particle molded article)

[0111] From the perspective of excellent balance between physical properties such as lightness and rigidity, the apparent density of the expanded bead molded article of the present invention is preferably 20 kg / m 3 Above and 120kg / m 3 Below, more preferably 30kg / m 3 Above and 90kg / m 3 the following.

[0112] The apparent density of the expanded bead molded article can be calculated by dividing the weight of the expanded bead molded article by the volume calculated from the external dimensions. In addition, when it is difficult to calculate the volume from the external dimensions, the volume of the expanded bead molded article can be obtained by the immersion method.

[0113] (Shrinkage of Foamed Bead Molded Article)

[0114] The foamed bead molded article formed by in-mold molding the foamed beads of the present invention can exhibit a minimal shrinkage. For example, the foamed bead molded article of the present invention can exhibit a shrinkage of 2.5% or less, and further can exhibit a shrinkage of 2.0% or less. Thus, the present invention can provide a foamed bead molded article having a desired shape.

[0115] The shrinkage rate here refers to the rate of change of the size of the foamed particle molded body relative to the size of the molding die used in the in-mold molding, which is measured in the following manner. First, after the in-mold molding is carried out, the foamed particle molded body taken out from the molding die is left to stand for 24 hours at a temperature of 23°C and a relative humidity of 50% for aging. Then, the size (LB) of the long side of the foamed particle molded body is measured. The ratio of the difference between the size (LA) of the long side of the molding die and the size (LB) of the long side of the foamed particle molded body to the size (LA) of the long side of the molding die is calculated (([LA-LB] / LA)×100) to obtain the shrinkage rate of the foamed particle molded body relative to the size of the molding die.

[0116] (Method for producing foamed particle molded article)

[0117] The foamed particle molded body of the present invention uses the foamed particles of the present invention described above and is manufactured by in-mold molding. The in-mold molding widely includes the well-known in-mold molding method using foamed particles. For example, the foamed particle molded body of the present invention can be manufactured in the following manner. First, the foamed particles of the present invention are filled in a molding die having an inner cavity corresponding to the shape of the desired foamed particle molded body, and a predetermined molding pressure is applied to the foamed particles filled in the molding die by a heating medium such as steam and heated. The molding pressure can be adjusted, for example, within a range of 0.2 MPa (G) to 0.5 MPa (G). In addition, in this specification, (G) represents a gauge pressure, that is, a pressure value based on atmospheric pressure as a standard. The foamed particles in the inner cavity are heated in the above manner to further foam them, and at the same time, the foamed particles are welded to each other. Then, after the heating by steam or the like is completed, the pressure in the inner cavity is released and the cooling of the molding die and the molded body in the molding die is quickly started. After confirming that the pressure (surface pressure) generated on the inner surface of the molding die is 0.04 MPa(G), cooling is completed and the foamed bead molded article is removed from the molding die. The cooling method is not particularly limited, and examples thereof include water cooling. Through the above series of molding steps, a foamed bead molded article corresponding to the shape of the inner cavity can be obtained.

[0118] The cooling time after in-mold molding is measured from the time steam heating ends and cooling begins until the pressure (surface pressure) generated on the inner surface of the molding die reaches 0.04 MPa(G). This cooling time can be used as an indicator of the molding cycle of the expanded bead molded article.

[0119] (Surface smoothness of foamed particle molded article)

[0120] The foamed particle molded article of the present invention exhibits excellent surface smoothness despite being made from biomass raw materials. To provide a foamed particle molded article exhibiting particularly excellent surface smoothness, the biobased carbon content of the foamed particle molded article is preferably less than 20%, more preferably 18% or less. For a specific method for evaluating the surface smoothness of the foamed particles, refer to the examples described below.

[0121] Example

[0122] The present invention will be described in detail below by way of examples, but the present invention is not limited to these examples. The foaming temperature and foaming pressure when making foamed beads using various base resins are shown in Tables 1 and 2. In addition, the molding pressure when making foamed bead molded bodies adopts the lower limit molding pressure confirmed during the production of preparatory foamed bead molded bodies. The polypropylene resins used in the examples and comparative examples are as follows.

[0123] Biomass-derived polypropylene resin A

[0124] PPA1 (propylene homopolymer, product number HP456J, manufactured by LyondellBasell Industries NV, flexural modulus of 1500 MPa)

[0125] PPA2 (propylene homopolymer, product number HP640J, manufactured by LyondellBasell Industries NV, flexural modulus of 1600 MPa)

[0126] PPA3 (propylene-ethylene block copolymer, product number EP348U, manufactured by LyondellBasell Industries N.V., flexural modulus of 950 MPa)

[0127] <Polypropylene resin B derived from fossil fuels>

[0128] PPB1 (propylene-ethylene random copolymer, 3.1% ethylene content, 0% bio-based carbon content, flexural modulus of 950 MPa)

[0129] <Example 1>

[0130] (Production of resin pellets)

[0131] A production apparatus including an extruder having an inner diameter of 50 mm and a strand forming die attached to the downstream side of the extruder was prepared.

[0132] The base resins, consisting of biomass-derived polypropylene resin A (biomass-derived PP) and petroleum-derived polypropylene resin B (petroleum-derived PP) shown in Table 1, and zinc borate (0.1 parts by weight per 100 parts by weight of base resin) as a cell control agent, were fed into an extruder and melt-kneaded to produce a resin melt. This resin melt was introduced into a strand-forming die, where strands were extruded. The extruded strands were water-cooled and cut using a pelletizer to produce resin pellets each weighing an average of 1.0 mg.

[0133] (Production of Foamed Particles)

[0134] 1 kg of the resulting resin pellets was placed into a 5 L pressurized pressure vessel along with 3 L of water as an aqueous dispersion medium. Furthermore, 0.3 parts by weight of kaolin as an inorganic dispersant and 0.004 parts by weight (as active ingredient) of a surfactant (product name: NEOGEN, manufactured by DKS Co. Ltd., sodium dodecylbenzenesulfonate) were added to the pressure vessel, relative to 100 parts by weight of the resin pellets.

[0135] The pressure vessel was then heated at a rate of 2°C / minute while stirring until the foaming temperature (164.5°C) was reached. Carbon dioxide was then introduced into the pressure vessel as a blowing agent, and the pressure was increased to 1.8 MPa(G). The pressure was then maintained at the same temperature and pressure for 15 minutes. This was done so that a high-temperature peak appeared on the DSC curve of the resulting foamed beads.

[0136] Then, the contents of the pressure vessel (resin pellets and water) were released to atmospheric pressure to obtain a bulk density of 45 kg / m 3 of foaming particles.

[0137] (Manufacturing of Foamed Bead Molded Article)

[0138] The obtained expanded beads were filled in a molding die having a molding cavity capable of molding an expanded bead molded body into a cube of 250 mm long x 200 mm wide x 20 mm high, and heated by the following heating method. A metal mold was used as the molding die.

[0139] As a heating method, steam is supplied to the forming mold while the drain valves provided on both sides of the forming mold are opened for preheating (exhaust process). Then, steam is supplied from one side of the forming mold for heating, and further steam is supplied from the other side of the forming mold for heating. Next, steam is supplied from both sides of the forming mold at the lower limit forming pressure shown in the table, that is, at a forming pressure of 0.3 MPa (G), for heating. After the heating is completed, water cooling is quickly started while the pressure is released, and the water cooling is carried out until the surface pressure generated by the foaming force of the foamed particle molded body becomes 0.04 MPa (G). After the water cooling is completed, the foamed particle molded body is taken out from the forming mold and is used as Example 1. In addition, the time required from the start of water cooling until the pressure (surface pressure) generated on the inner surface of the forming mold becomes 0.04 MPa (G) is measured and is used as the molding cycle (cooling time (seconds)) and is shown in Table 1.

[0140] The base resin and expanded beads used in Example 1 were subjected to the measurements and evaluations described below. Furthermore, the expanded bead molded article of Example 1 was subjected to the measurements and evaluations described below. The results are shown in Table 1.

[0141] <Examples 2 to 9, Comparative Examples 1 to 3>

[0142] Except for the changes described in Tables 1 and 2, expanded bead molded articles were produced in the same manner as in Example 1. These expanded bead molded articles were designated as Examples 2 to 9 and Comparative Examples 1 to 3. Measurements and evaluations were then performed on the other Examples and Comparative Examples in the same manner as in Example 1. The results are shown in Tables 1 and 2.

[0143] <Base resin>

[0144] (Bio-based carbon content of polypropylene resin A)

[0145] The bio-based carbon content of the polypropylene resin A blended in the base resin was measured in the following manner in accordance with ASTM D6866-21.

[0146] The polypropylene resin A blended in the base resin was used as the resin for measurement. Carbon dioxide (CO2) was generated by burning the resin, and the carbon dioxide was purified using a vacuum tube. Iron was used as a catalyst, and the purified carbon dioxide was reduced with hydrogen to produce graphite (C). Then, using a manual press, the graphite was packed into a cathode with an inner diameter of 1 mm. The cathode was embedded in a wheel and mounted on a tandem accelerator manufactured by NEC Corporation as a base. 14The measurement performed by the C-AMS dedicated device is 14 The number of C, 13 C concentration ( 13 C / 12 C) 14 C concentration ( 14 C / 12 C) Measurement was performed. Oxalic acid (HOxII) provided by the National Institute of Standards and Technology (NIST) was used as a standard sample. This standard sample and the background sample were measured simultaneously.

[0147] The carbon content of the sample relative to the modern carbon content of the standard sample is calculated from the obtained measurement results. 14 C ratio, then, the 13 The error of C concentration was corrected to obtain the corrected pMC (percent Modern Carbon) value.

[0148] The biobased carbon content was calculated using the corrected pMC. The atmospheric correction factor used was the value (100.0 pMC) specified in ASTM D6866-21 for the years 2019-2021. In determining the biobased carbon content of the polypropylene resins involved in the present invention, the atmospheric correction factor specified in ASTM D6866 for the year in which the polypropylene resins were manufactured was used to determine the biobased carbon content.

[0149] (Melting Point)

[0150] The melting point Tm of the polypropylene resin A blended in the base resin is determined based on JIS K7121:2012. A At this time, as the state adjustment of the test piece, "(2) the case of measuring the melting temperature after a certain heat treatment" is adopted. Specifically, first, a pelletized polypropylene resin A (5 mg) is made into a test piece, and according to the heat flow differential scanning calorimetry method described in JIS K7121: 2012, the top temperature of the melting peak determined by the obtained DSC curve is taken as the melting point Tm of the polypropylene resin A. A The DSC curve was obtained by heating from 23°C to 200°C at a heating rate of 10°C / min, cooling to 23°C at a cooling rate of 10°C / min, and then heating from 23°C to 200°C again at a heating rate of 10°C / min. A heat flow differential scanning calorimeter (manufactured by SII NanoTechnology Inc., model: DSC7020) was used as the measuring apparatus.

[0151] The melting point Tm of the polypropylene resin B was measured in the same manner as above except that granular polypropylene resin B (5 mg) was used. B The melting point Tm of the base resin was determined by measuring the melting point in the same manner as above except that the base resin (5 mg) was pelletized. S .

[0152] (Crystallization temperature Tc)

[0153] Polypropylene resin A and polypropylene resin B were used as test samples, and the temperature of the top of the crystallization peak was determined by heat flow differential scanning calorimetry according to JIS K 7121: 2012. The obtained temperatures were defined as the crystallization temperature Tc of polypropylene resin A. A and the crystallization temperature Tc of polypropylene resin B B In addition, as the state adjustment of the test piece, "(2) After a certain heat treatment, the melting temperature is measured" was adopted, and as the cooling rate, 10°C per minute was adopted. In addition, when two or more crystallization peaks appeared, the temperature at the top of the crystallization peak with the largest area was taken as the crystallization temperature.

[0154] (Melt Flow Rate (MFR))

[0155] The melt flow rate (MFR) of the polypropylene resin A was determined at 230°C and a load of 2.16 kg according to JIS K7210-1:2014. A ), the melt flow rate (MFR) of the polypropylene resin B B ), the melt flow rate (MFR) of the base resin S ).

[0156] Furthermore, the MFR of the polypropylene resin A obtained in the above manner was calculated. A MFR relative to polypropylene resin B B Ratio (MFR A / MFR B ).

[0157] <Foaming particles>

[0158] (High temperature peak heat, total heat of fusion)

[0159] The high-temperature peak heat and total heat of fusion of the expanded beads are obtained from a DSC curve obtained by the following method: 1 to 3 mg of the expanded beads are prepared as a test piece according to the thermal transition determination method for plastics described in JIS K7122:2012, and the test piece is heated at a heating rate of 10°C / min from 23°C to a temperature 30°C higher than the end of the melting peak of the test piece. Specifically, if Figure 1As described above, in the DSC curve obtained using each expanded bead, a straight line is drawn connecting point I corresponding to 80°C on the DSC curve and point II corresponding to the melting end temperature of the expanded bead. The melting end temperature is the high-temperature endpoint of high-temperature peak b, and is the intersection of high-temperature peak b and the baseline on the higher-temperature side of high-temperature peak b in the DSC curve.

[0160] like Figure 1 As shown in the reference, after drawing a straight line connecting point I and point II, the intersection of a straight line passing through the maximum point III between the inherent peak a and the high-temperature peak b and parallel to the vertical axis of the graph and the straight line connecting point I and point II is set to IV.

[0161] Next, the area enclosed by the straight line connecting points I and IV, the straight line connecting points III and IV, and the DSC curve connecting points I and III was defined as the area of intrinsic peak a. Furthermore, the area enclosed by the straight line connecting points IV and II, the straight line connecting points III and IV, and the DSC curve connecting points III and II (the shaded area) was defined as the area of high-temperature peak b. The total heat of fusion (J / g) of the foamed particles was calculated from the sum of the areas of intrinsic peak a and high-temperature peak b, and the high-temperature peak calorific value (J / g) of the foamed particles was calculated from the area of high-temperature peak b.

[0162] (biobased carbon content)

[0163] The bio-based carbon content of the base resin was measured in the same manner as described above, except that expanded beads were used as the test specimen, in accordance with ASTM D6866-21.

[0164] (Apparent density)

[0165] Place the foamed particles to be measured in an environment with a temperature of 23°C, a relative humidity of 50%, and 1 atm for more than 24 hours. Fill the foamed particle group with a weight of W (g) obtained in the above manner into a measuring cylinder, and gently tap the horizontal surface with the bottom of the measuring cylinder several times to stabilize the filling height of the foamed particle group in the measuring cylinder. Read the bulk volume V (L) of the foamed particle group shown on the scale of the measuring cylinder, and divide the weight W of the foamed particle group by the bulk volume V (W / V) of the foamed particle group. Convert the value obtained in this way into kg / m 3 , thus obtaining the apparent density of the foamed particles (kg / m 3 ).

[0166] (Average bubble diameter)

[0167] Take a photograph of a cross-section of the foamed beads, bisecting them. Draw a straight line on the photograph to roughly bisect the cross-section of the foamed beads. Divide the length (L) of the line segment from the periphery of the foamed bead to the periphery of the opposite side by the number (N) of all cells connected to the line segment (L / N) as the average cell diameter per foamed bead. Repeat this process for 10 or more foamed beads, and take the arithmetic mean of the values as the average cell diameter of the foamed beads.

[0168] (Closed Porosity)

[0169] By setting the stack volume to approximately 20 cm 3 The foamed particles were immersed in water, and the apparent volume Va of the foamed particles was measured. After the apparent volume Va was measured, the foamed particles were thoroughly dried. The volume of the foamed particles (the sum of the volume of the resin constituting the foamed particles and the total volume of the closed cells within the foamed particles) (true volume Vx) was measured according to procedure C described in ASTM-D2856-94. This true volume Vx was measured using an air comparison pycnometer model 1000 manufactured by Tokyo-Science Co., Ltd.

[0170] Next, the closed cell ratio was calculated using the following formula (1): The closed cell ratio was measured five times using different measurement samples in the same procedure as above, and the arithmetic mean of the values obtained in each measurement was calculated and used as the closed cell ratio of the foamed beads.

[0171] [Mathematical formula 2]

[0172] Closed cell ratio (%) = (Vx-W / ρ) × 100 / (Va-W / ρ) (1)

[0173] Vx: True volume of the foamed particle group measured by the method (cm 3 )

[0174] Va: Apparent volume of the expanded particles measured by the rise in water level when the expanded particles are immersed in water in a graduated cylinder (cm 3 )

[0175] W: Weight of the foamed particle group (g)

[0176] ρ: Density of the resin constituting the foamed particles (g / cm 3 )

[0177] The lower limit molding pressure and the moldable range were evaluated according to the following criteria: The lower the lower limit molding pressure or the wider the moldable range, the better the moldability of the expanded beads.

[0178] (Lower molding pressure)

[0179] Except the molding pressure during in-mold molding, with the same method as the manufacture of each embodiment or each comparative example, preliminarily manufacture the expanded particle molded body.Then, carry out the evaluation of the fusion bonding rate, secondary foaming property and recoverability described later, and the lowest molding pressure among the molding pressures of the expanded particle molded body that can produce 3 items and is all qualified (excellent) is used as the lower molding pressure.For the expanded particles that can't obtain 3 items and are all qualified expanded particle molded body, the lowest molding pressure among the molding pressures of the expanded particle molded body that can produce 2 items of fusion bonding rate and recoverability is used as the lower molding pressure.

[0180] (Moldable Range, Evaluation of Moldable Range)

[0181] Except that the molding pressure is changed at intervals of 0.02MPa (G) from the lower limit molding pressure determined by the above method, the foamed particle molded body is molded in the same manner as in each embodiment or each comparative example. Then, the foamed particle molded body obtained is used to evaluate the welding rate, secondary foaming property and recoverability in the same manner as described below. Then, the molding pressure of the foamed particle molded body that can produce 3 items that are all qualified (excellent or above) is judged to be the molding pressure that can mold the foamed particle molded body, and is evaluated in the following manner. In addition, the specific number of points of the range that can be molded is shown together.

[0182] Very good: The molding pressure range for obtaining a foamed bead molded article that passes all three items is 2 points or more.

[0183] Excellent: The range of molding pressure that can obtain a foamed bead molded article that passes all three items is 1 point.

[0184] Poor: There is no range of molding pressure within which a foamed bead molded article having acceptable results in all three items can be obtained.

[0185] <Foamed particle molded products>

[0186] (Apparent density)

[0187] The apparent density of the expanded beads molded article was calculated by dividing the weight of the expanded beads molded article by the volume calculated based on the outer dimensions.

[0188] (Shrinkage)

[0189] The rate of change (shrinkage) of the size of the foamed particle molded body relative to the size of the molding die used in the in-mold molding is measured in the following manner. First, after the in-mold molding is carried out, the foamed particle molded body taken out from the molding die is left to stand for 24 hours at a temperature of 23°C and a relative humidity of 50% for aging. Then, the size (LB) of the long side of the foamed particle molded body is measured. The ratio of the difference between the size (LA) of the long side of the molding die and the size (LB) of the long side of the foamed particle molded body to the size (LA) of the long side of the molding die is calculated (([LA-LB] / LA)×100) to obtain the shrinkage rate of the foamed particle molded body relative to the size of the molding die.

[0190] (Molding cycle)

[0191] As described above, after in-mold molding, the pressure is released and water cooling begins simultaneously. Water cooling continues until the pressure (surface pressure) generated on the inner surface of the mold decreases to 0.04 MPa(G). The time from the start of water cooling until the pressure (surface pressure) generated on the inner surface of the mold decreases to 0.04 MPa(G) is measured and used as the cooling time (seconds), which serves as an indicator of the molding cycle. A shorter water cooling time indicates a better molding cycle.

[0192] (Welding rate)

[0193] A test piece (length 100 mm × width 100 mm × thickness: thickness of the foamed particle molded body) was cut from the center of the foamed particle molded body. After a cut of about 5 mm in the thickness direction of each test piece was made with a utility knife, the test piece was broken from the cut portion. Next, the number of foamed particles (n) present on the broken surface of the foamed particle molded body and the number of foamed particles that underwent material damage (b) were measured. Then, the number of foamed particles that underwent material damage (b) relative to the number of all foamed particles (n) was expressed as a percentage as the welding rate (%), and the following evaluation was performed. In addition, Tables 1 and 2 show the values of the welding rates (%) obtained in the above manner.

[0194] Excellent: The welding rate is above 80%.

[0195] Poor: The welding rate is less than 80%.

[0196] (Secondary foaming)

[0197] The surface of the expanded bead molded article was visually observed, and the secondary expansion properties were evaluated as follows.

[0198] Excellent: The gaps between the foamed particles on the surface of the foamed particle molded article are fully filled.

[0199] Poor: The gaps between the foamed particles on the surface of the foamed particle molded article are obviously not filled.

[0200] (Restoration)

[0201] After the in-mold molding, the expanded particle molded body was taken out of the molding mold and allowed to stand for 24 hours in an environment of a temperature of 23° C. and a relative humidity of 50% for aging.

[0202] The thickness of the foamed particle molded body was measured at a position 10 mm from the center of the plane at four corners on which the matured foamed particle molded body was viewed from the thickness direction. The maximum value among these thicknesses was then used as the thickness of the corner of the foamed particle molded body. In addition, the thickness of the foamed particle molded body was measured at a central position in any direction of the length direction and the width direction on a plane on which the foamed particle molded body was viewed from the thickness direction, and this value was used as the thickness of the central portion of the foamed particle molded body. The ratio (%) of the thickness of the central portion relative to the thickness of the corner of the foamed particle molded body was then calculated and evaluated as follows.

[0203] Excellent: The ratio (%) is 90% or more.

[0204] Poor: The ratio (%) is less than 90%.

[0205] (biobased carbon content)

[0206] The biobased carbon content of the expanded beads was measured in the same manner as that for the base resin, in accordance with ASTM D6866-21, except that the expanded beads were used as the resin.

[0207] (Closed Porosity)

[0208] The closed cell ratio of the expanded beads molded article was measured in the same manner as the above-mentioned closed cell ratio of the expanded beads, except that a 15 mm square cube cut out from the inside of the expanded beads molded article was used as the measurement object.

[0209] (Surface smoothness)

[0210] The surface smoothness of the expanded bead molded article was observed with the naked eye and evaluated in the following manner.

[0211] Very good: The surface of the expanded particle molded article has no wrinkles, shrinkage, or unevenness due to collapse, and is in good condition.

[0212] Excellent: A small amount of irregularities due to wrinkles, shrinkage, or collapse was observed on the surface of the expanded particle molded article.

[0213] Poor: The surface of the expanded particle molded article has obvious irregularities due to wrinkles, shrinkage, or collapse.

[0214] [Table 1]

[0215]

[0216] [Table 2]

[0217]

[0218] The embodiment includes the following technical concepts.

[0219] (1) A polypropylene resin foamed bead, characterized in that the base resin of the foamed bead comprises: a biomass-derived polypropylene resin A containing a monomer component derived from biomass in its molecular chain, and a fossil fuel-derived polypropylene resin B, wherein the base resin contains 3 wt % or more and 60 wt % or less of the biomass-derived polypropylene resin A, and 40 wt % or more and 97 wt % or less of the fossil fuel-derived polypropylene resin B (the total amount of the two being 100 wt %).

[0220] (2) The polypropylene resin foamed particles according to (1) above, wherein the biomass-derived polypropylene resin A has a biobased carbon content of 10% or more and 50% or less as measured by ASTM D6866-21.

[0221] (3) The polypropylene resin foamed particles according to (1) or (2) above, wherein the foamed particles have a bio-based carbon content of 1% or more and 30% or less as measured by ASTM D6866-21.

[0222] (4) The polypropylene resin foamed particles according to any one of (1) to (3) above, wherein the melting point Tm of the base resin is S It is 135°C or higher and 160°C or lower.

[0223] (5) The polypropylene resin foamed particles according to any one of (1) to (4) above, wherein the melting point Tm of the biomass-derived polypropylene resin A is A The melting point Tm of the polypropylene resin B derived from fossil fuels is 160°C or higher and 170°C or lower. B It is 135°C or higher and 145°C or lower.

[0224] (6) The polypropylene foamed beads according to any one of (1) to (5) above, wherein the biomass-derived polypropylene resin A is a homopolymer of propylene, and the melt flow rate (MFR) of the biomass-derived polypropylene resin A measured at 230° C. and under a load of 2.16 kg is A ) is 1 g / 10 min or more and 5 g / 10 min or less.

[0225] (7) The polypropylene resin foamed particles according to any one of (1) to (6) above, wherein the fossil fuel-derived polypropylene resin B is a propylene-ethylene random copolymer having an ethylene content of 1 wt% or more and 5 wt%.

[0226] (8) The polypropylene resin foamed beads according to any one of (1) to (7) above, wherein the melt flow rate (MFR) of the base resin measured at 230°C and under a load of 2.16 kg is S ) is 5 g / 10 min or more and 15 g / 10 min or less.

[0227] (9) The polypropylene resin foamed beads according to any one of (1) to (8) above, wherein the melt flow rate (MFR) of the biomass-derived polypropylene resin A measured at 230°C and under a load of 2.16 kg is A ) relative to the melt flow rate (MFR) of the fossil fuel-derived polypropylene resin B measured at 230°C and a load of 2.16 kg. B ) ratio (MFR A / MFR B ) is greater than or equal to 0.2 and less than or equal to 0.8.

[0228] (10) The polypropylene resin foamed particles according to any one of (1) to (9) above, wherein, in a DSC curve obtained by heat flow differential scanning calorimetry (DSC) of the foamed particles from 23°C to 200°C at a heating rate of 10°C / min, the DSC curve has a main melting peak and a melting peak having a peak temperature at a higher temperature than the peak temperature of the main melting peak, the melting peak being a high temperature peak, and the heat of fusion of the high temperature peak being greater than 10 J / g and less than 30 J / g.

[0229] (11) A polypropylene resin foamed particle molded article obtained by in-mold molding the polypropylene resin foamed particles according to any one of (1) to (10) above.

Claims

1. A polypropylene resin foam particle, wherein: The base resin of the foamed beads comprises: a biomass-derived polypropylene resin A containing a monomer component derived from biomass in its molecular chain, and a fossil fuel-derived polypropylene resin B. The base resin contains 3 wt % to 60 wt % of the biomass-derived polypropylene resin A and 40 wt % to 97 wt % of the fossil fuel-derived polypropylene resin B, and the total amount of the two is 100 wt %.

2. The polypropylene resin foamed particles according to claim 1, wherein The biomass-derived polypropylene-based resin A has a biobased carbon content of 10% or more and 50% or less as measured by ASTM D6866-21.

3. The polypropylene resin foamed particles according to claim 1 or 2, wherein The bio-based carbon content of the expanded particles measured by ASTM D6866-21 is 1% or more and 30% or less.

4. The polypropylene resin foamed particles according to any one of claims 1 to 3, wherein The melting point Tm of the base resin S It is 135°C or higher and 160°C or lower.

5. The polypropylene resin foamed particles according to any one of claims 1 to 4, wherein The melting point Tm of the biomass-derived polypropylene resin A is A The melting point Tm of the polypropylene resin B derived from fossil fuels is 160°C or higher and 170°C or lower. B It is 135°C or higher and 145°C or lower.

6. The polypropylene resin foamed particles according to any one of claims 1 to 5, wherein The biomass-derived polypropylene resin A is a homopolymer of propylene, and the melt flow rate (MFR) of the biomass-derived polypropylene resin A measured at 230° C. and a load of 2.16 kg is A It is 1 g / 10 min or more and 5 g / 10 min or less.

7. The polypropylene resin foamed particles according to any one of claims 1 to 6, wherein The fossil fuel-derived polypropylene resin B is a propylene-ethylene random copolymer, and the ethylene content of the propylene-ethylene random copolymer is 1% by weight or more and 5% by weight.

8. The polypropylene resin foamed particles according to any one of claims 1 to 7, wherein The melt flow rate (MFR) of the base resin measured at 230°C and a load of 2.16 kg is S It is 5 g / 10 min or more and 15 g / 10 min or less.

9. The polypropylene resin foamed particles according to any one of claims 1 to 8, wherein The melt flow rate (MFR) of the biomass-derived polypropylene resin A measured at 230°C and a load of 2.16 kg is: A The melt flow rate MFR of the fossil fuel-derived polypropylene resin B measured at 230°C and a load of 2.16 kg is B MFR A / MFR B It is 0.2 or more and 0.8 or less.

10. The polypropylene resin foamed particles according to any one of claims 1 to 9, wherein In a DSC curve obtained by heat-flow differential scanning calorimetry (DSC) of foamed particles heated from 23°C to 200°C at a heating rate of 10°C / min, the DSC curve has a main melting peak and a melting peak having a peak temperature at a higher temperature than the peak temperature of the main melting peak, the melting peak being a high-temperature peak, and the heat of fusion of the high-temperature peak being greater than or equal to 10 J / g and less than or equal to 30 J / g.

11. A polypropylene resin foamed particle molded body, characterized in that: The foamed polypropylene resin particles according to any one of claims 1 to 10 are formed by in-mold molding.

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