Foamed molded article of non-crosslinked olefinic elastomer and method for producing same

Abstract

To provide a foamed molding of a non-crosslinked olefinic elastomer high in a fusion bonding rate, scarce in voids, and having good appearance, and a production method of the same, and to provide a foamed molding of a non-crosslinked olefinic elastomer high in a fusion bonding rate, scarce in voids, having good appearance, and having a high impact resilience inherent to an elastomer and good bending resistance.SOLUTION: A foamed molding of a non-cross linked olefinic elastomer comprising a fused body of a foamed particle includes: a non-crosslinked propylene-α olefin copolymer as a principal constituent; and further a polyethylene-based resin, where the total content of the non-crosslinked propylene-α olefin copolymer and the polyethylene-based resin is 80 mass% or more to a mass of the foamed molding, the foamed molding has two or more melting peak temperatures (Tm) measured by a differential scanning calorimeter (DSC), one (Tm1) of the melting peak temperatures exists within a range of 90-130°C, the other one (Tm2) of the melting peak temperatures exists within a range of 130-180°C, and the temperature deference between the melting peak temperature (Tm2) and the melting peak temperature (Tm1) is 20°C or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a foam-molded article of a non-crosslinked olefin-based elastomer and a method for producing the same. The foam-molded article of the present invention has excellent flexibility and recovery properties and can be used as seat core materials for railway vehicles, airplanes, and automobiles, as well as beds, cushions, etc. [Background technology]

[0002] Elastomers have excellent resilience and high mechanical strength, and are therefore considered as engineering elastomers, and their use in a variety of applications, such as household goods, electrical appliance parts, sporting goods, automobile parts, building and civil engineering materials, etc. Molded articles obtained by foaming these elastomers are expected to be lightweight and have the high resilience inherent to elastomers, and so, for example, foamed beads prepared from elastomer resins are heated in a mold to fuse and foam them.

[0003] Olefin-based elastomers include crosslinked products that have been crosslinked with a crosslinking agent. However, foam molded products made from crosslinked olefin-based elastomers are difficult to recycle, and their high density reduces the lightweight properties of the foam molded products. Therefore, in response to the increasing need for recycling in recent years, there has been a demand for alternatives to crosslinked olefin-based elastomer foam molded products, and foam molded products made from non-crosslinked olefin-based elastomers are being studied (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2016 / 052112 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a foam-molded article of a non-crosslinked olefinic elastomer which has a high fusion rate, few voids and a good appearance, and a method for producing the same. An object of the present invention is to provide a foam-molded article of a non-crosslinked olefinic elastomer which has a high fusion rate, a good appearance with few voids, and a high rebound resilience and high durability against bending, which are characteristic of elastomers. [Means for solving the problem]

[0006] The present inventors have found that when producing foamed molded articles from non-crosslinked olefinic elastomers, using a non-crosslinked olefinic elastomer with a relatively low melting point as a base resin from the viewpoint of reducing the energy required for foam molding (typically, reducing the temperature of the steam used in foam molding) has disadvantages such as the difficulty in obtaining a low-density foam and the tendency for the foam particles to adhere to each other, resulting in reduced foam moldability. Furthermore, the present inventors have found that the foam molded article of Patent Document 1 has room for improvement in terms of durability against bending. The present inventors have also found that when a non-crosslinked olefin-based elastomer with a relatively high melting point is used as the base resin, high-temperature steam is required for foam molding, and the foam molded article obtained under high-temperature conditions is prone to shrinkage, which makes wrinkles or voids (gaps) more likely to occur on the surface of the foam, and tends to have an adverse effect on the appearance.

[0007] Based on these findings, the present inventors have investigated solutions and discovered a foamed molded article that contains a non-crosslinked propylene-α-olefin copolymer as a non-crosslinked olefin-based elastomer as a main component and further contains a polyethylene-based resin, and that has two or more specific melting peak temperatures. Specifically, when a non-crosslinked propylene-α-olefin copolymer with a low melting peak temperature (e.g., below 140°C) is used as the base resin, foaming properties are poor, making it difficult to obtain foamed beads with low bulk density. On the other hand, when a non-crosslinked propylene-α-olefin copolymer with a high melting peak temperature (e.g., above 140°C) is used as the base resin, foamed beads are likely to coalesce, resulting in uneven foaming and poor moldability. Furthermore, the high temperatures required for foaming make it prone to thermal shrinkage, resulting in wrinkles or voids (gaps) on the foam surface. Here, the present inventors have discovered that by combining a non-crosslinked propylene-α-olefin copolymer with a polyethylene-based resin and setting the melting peak temperature of the resin within a specific range, these shortcomings can be improved and foamed molded articles with high rebound resilience and good flexibility can be obtained. Furthermore, the present inventors have found that the foamed molded article of the present invention can be produced by using a base resin (non-crosslinked propylene-α-olefin copolymer and polyethylene-based resin) mixed with a chemical foaming agent.

[0008] The present invention typically includes the following aspects. Section 1. A foamed molded article of a non-crosslinked olefin-based elastomer composed of a fused body of foamed beads, Contains non-crosslinked propylene-α-olefin copolymer as the main component, Further containing a polyethylene resin, the total content of the non-crosslinked propylene-α-olefin copolymer and the polyethylene resin is 80% by mass or more relative to the mass of the foamed molded article, The foamed molded product has two or more melting peak temperatures (Tm) measured by a differential scanning calorimeter (DSC), One of the melting peak temperatures (Tm1) is in the range of 90 to 130°C, Another melting peak temperature (Tm2) is in the range of 130 to 180°C, The temperature difference between the melting peak temperature (Tm2) and the melting peak temperature (Tm1) is 20°C or more. Foam molding. Section 2. the mass ratio of the content of the non-crosslinked propylene-α-olefin copolymer to the content of the polyethylene resin is 55:45 to 90:10; Item 1. A foam-molded product of the non-crosslinked olefin-based elastomer according to item 1. Section 3. Item 3. The foam-molded product of a non-crosslinked olefin-based elastomer according to Item 1 or 2, wherein the temperature difference between the melting peak temperature (Tm2) and the melting peak temperature (Tm1) is 20 to 80°C. Section 4. Item 4. The non-crosslinked olefin elastomer foam molded article according to any one of Items 1 to 3, wherein the polyethylene resin is one or more resins selected from the group consisting of high-density polyethylene and low-density polyethylene. Section 5. Item 5. The foam-molded product of a non-crosslinked olefin-based elastomer according to any one of items 1 to 4, which has a xylene-insoluble content of 3% or less as determined by hot xylene extraction. Section 6. 0.05~0.3g / cm 3 Item 6. The foam-molded article of a non-crosslinked olefin-based elastomer according to any one of Items 1 to 5, having at least one property selected from the group consisting of a density of 0.1 to 1.0 MPa, a rebound resilience of 35% or more, and an Asker C hardness of 60 or less. Section 7. Item 7. A foam-molded article of a non-crosslinked olefin-based elastomer according to any one of Items 1 to 6, which has flexural durability such that no cracks of a depth of 50% or more and a length of 10 mm or more occur between the foam particles in a 90° flex test (test piece size: 150 mm x 24 mm x 11 mm thick) of 10,000 times in accordance with ASTM D1052. Section 8. Item 8. A method for producing a foamed molded article of a non-crosslinked olefin-based elastomer according to any one of Items 1 to 7, comprising: a step of mixing a non-crosslinked propylene-α-olefin copolymer, a polyethylene-based resin, and a chemical foaming agent to obtain resin particles containing the non-crosslinked propylene-α-olefin copolymer as a main component; a step of impregnating the resin particles with a physical foaming agent and then pre-foaming the particles to obtain foamed particles; and a step of foaming the foamed particles in a mold to obtain a foamed molded article. Section 9. Item 9. The method for producing a foamed molded article of a non-crosslinked olefin elastomer according to Item 8, wherein the chemical foaming agent is a sodium bicarbonate-citric acid-based chemical foaming agent, and the amount of the chemical foaming agent mixed in the step of obtaining resin particles is 0.1 to 2 parts by mass per 100 parts by mass of the total amount of the non-crosslinked propylene-α-olefin copolymer and the polyethylene resin. Section 10. Item 10. The method for producing a foamed molded article of a non-crosslinked olefin-based elastomer according to Item 8 or 9, wherein the mass ratio of the non-crosslinked propylene-α-olefin copolymer to the polyethylene-based resin in the step of obtaining resin particles is 55:45 to 90:10. [Effects of the Invention]

[0009] According to one embodiment of the present invention, it is possible to provide a foamed molded article of a non-crosslinked olefinic elastomer having few voids and a good appearance, and a method for producing the same. According to one embodiment of the present invention, it is possible to provide a foamed molded article of a non-crosslinked olefin-based elastomer in which the foamed particles have strong fusion with each other during foam molding, and a method for producing the same. According to one embodiment of the present invention, it is possible to provide a foam-molded article of a non-crosslinked olefin-based elastomer that can be foam-molded at a low temperature, and a method for producing the same. According to one embodiment of the present invention, it is possible to provide a foam molded article of a non-crosslinked olefin-based elastomer having a high impact resilience and a method for producing the same. According to one embodiment of the present invention, it is possible to provide a foam molded article of a non-crosslinked olefin-based elastomer having good flexibility, and a method for producing the same. DETAILED DESCRIPTION OF THE INVENTION

[0010] As used herein, the phrase "comprising" is intended to encompass the phrases "consisting essentially of" and "consisting of." In this specification, the term "major component" is used to mean a component contained in a target substance in an amount of more than 50% and, unless otherwise specified, means more than 50% by mass of the target substance. In this specification, when the specifying method is described in the examples, the numerical values ​​of the physical properties, contents, etc. of materials, intermediate products, final products, etc. are the numerical values ​​determined by the specifying method described in the examples.

[0011] In-mold foam molded articles are usually produced through the following steps. These steps can be applied to the present invention as is or with appropriate modifications. A base resin is cut to an appropriate size to form base resin particles, which are impregnated with a blowing agent to form expandable particles. The expandable particles are pre-expanded to prepare expanded particles. These expanded particles are then subjected to an in-mold foam molding process and heated, whereby the expanded particles are expanded and fused to form a fused body, thereby producing a foam molded article. In the present invention, a base resin containing at least a non-crosslinked propylene-α-olefin copolymer and a polyethylene-based resin is used.

[0012] In this specification, "non-crosslinked" means that when a sample is dissolved in an organic solvent such as xylene that can dissolve the elastomer, the gel fraction of the insoluble portion is 3.0 mass % or less. The gel fraction is a value measured as follows.

[0013] The mass W1 of a sample (e.g., base resin, resin particles, expandable particles, expanded particles, foamed molded article, etc.) is measured. Next, the sample is refluxed in 80 milliliters of boiling xylene for 3 hours. The residue in the xylene is then filtered using an 80-mesh wire netting, and the residue remaining on the wire netting is dried at 130°C for 1 hour. The mass W2 of the residue remaining on the wire netting is measured, and the gel fraction of the sample can be calculated using the following formula: Gel fraction (mass%) = 100 × W2 / W1

[0014] In the present invention, the base resin, resin particles, expandable particles, expanded particles, and foamed molded article contain a non-crosslinked propylene-α-olefin copolymer as a main component, and further contain a polyethylene resin.

[0015] (Non-crosslinked olefin elastomer) As the non-crosslinked olefin elastomer, at least a non-crosslinked propylene-α-olefin copolymer is used. The non-crosslinked propylene-α-olefin copolymer may be used alone or in combination of two or more. It is preferable to combine two, three, or four (preferably two or three, more preferably two) non-crosslinked propylene-α-olefin copolymers having different melting peak temperatures. The non-crosslinked propylene-α-olefin copolymer may or may not be used in combination with another non-crosslinked olefin-based elastomer. When the non-crosslinked olefin-based elastomer is used in combination, the amount of the elastomer used may be 0.01 to 20 parts by mass, 0.01 to 10 parts by mass, or 0.01 to 5 parts by mass per 100 parts by mass of the non-crosslinked propylene-α-olefin copolymer. Non-crosslinked olefinic elastomers include, for example, those having a structure combining hard and soft segments, which exhibits rubber elasticity at room temperature and plasticizes and becomes moldable at elevated temperatures. The former polypropylene-based resin may be a resin containing polypropylene as a main component, and may have a stereoregularity selected from isotactic, syndiotactic, atactic, etc. The latter polyethylene resin may be a resin containing polyethylene as the main component, and examples of components other than polyethylene include polyolefins such as polypropylene and polybutylene, and vinyl acetate.

[0016] The non-crosslinked propylene-α-olefin copolymer may have a melting peak temperature of, for example, 130 to 180° C., 130 to 170° C., 130 to 165° C., greater than 130° C. and 180° C. or less, greater than 130° C. and 170° C. or less, greater than 130° C. and 165° C. or less, 131 to 180° C., 131 to 170° C., 131 to 165° C., or 140 to 180° C., preferably 140 to 170° C., more preferably 140 to 165° C. When the melting peak temperature of the non-crosslinked propylene-α-olefin copolymer is within this range, low-density expanded beads are easily obtained.

[0017] The non-crosslinked propylene-α-olefin copolymer preferably has a structure in which a polypropylene resin is used as a hard segment and an ethylene-vinyl acetate copolymer is used as a soft segment. As the non-crosslinked propylene-α-olefin copolymer, commercially available products can be used, such as the TAFMER series manufactured by Mitsui Chemicals, Inc., the ESPOLEX series manufactured by Sumitomo Chemical Co., Ltd., and the TPO series manufactured by Prime Polymer Co., Ltd., which have a melting peak temperature of 130 to 180°C.

[0018] Non-crosslinked olefin elastomers also have the effect of improving the recyclability of the foamed molded articles produced. Furthermore, they can be easily produced using a foaming machine similar to that used to foam mold ordinary polyolefin resins. Therefore, even when the foamed molded articles are recycled and fed back to the foaming machine for foam molding, poor foaming due to the generation of rubber components can be suppressed.

[0019] The content of the non-crosslinked olefin-based elastomer in the resin particles, expandable particles, expanded particles and foamed molded articles can be, for example, from over 50 to 90 mass%, 60 to 90 mass%, 70 to 90 mass%, or 60 to 80 mass%.

[0020] (Polyethylene resin) The polyethylene resin may have a peak melting temperature of, for example, 90 to 130°C, 95 to 130°C, 100 to 130°C, 90°C or more but less than 130°C, 95°C or more but less than 130°C, 100°C or more but less than 130°C, 90 to 129°C, 95 to 129°C, or 100 to 129°C, and preferably has a peak melting temperature of 100 to 120°C, and more preferably has a peak melting temperature of 105 to 115°C. When the peak melting temperature of the polyethylene resin is within this range and the temperature difference between Tm2 and Tm1 is within the range described below, coalescence of the expanded particles is unlikely to occur, thereby improving moldability and fusion properties, and thermal shrinkage is unlikely to occur even when high temperatures are required for expansion molding, and the occurrence of wrinkles and voids (gaps) on the surface of the foam is suppressed.

[0021] Examples of polyethylene resins include low-density polyethylene (branched low-density polyethylene, linear low-density polyethylene), high-density polyethylene, etc., with low-density polyethylene and high-density polyethylene being preferred. The polyethylene resins may be used alone or in combination. As the polyethylene-based resin, commercially available products may be used, such as the Green Polyethylene series from Braskem, the Novatec series from Japan Polyethylene, the Suntech series from Asahi Kasei, and the UBE Polyethylene series from Ube Maruzen Polyethylene. Of these, those having a melting peak temperature of 90 to 130°C are preferred.

[0022] The content of polyethylene resin in the resin particles, expandable particles, expanded particles and foamed molded articles can be, for example, 10 to less than 50% by mass, 10 to 40% by mass, 10 to 30% by mass, 20 to 40% by mass, and the like.

[0023] The resin particles, expandable particles, expanded particles and foamed molded article each contain a non-crosslinked propylene-α-olefin copolymer as a main component and further contain a polyethylene resin. In each of the resin particles, expandable particles, expanded particles, and expanded molded article, the total content of the non-crosslinked propylene-α-olefin copolymer and the polyethylene resin may be 80 mass% or more relative to the mass of the resin particles, expandable particles, expanded particles, and expanded molded article. Here, the total content of the non-crosslinked propylene-α-olefin copolymer and the polyethylene resin may be, for example, 80 to 100 mass%, 80 to 99 mass%, 80 to 95 mass%, 85 to 100 mass%, 85 to 99 mass%, 85 to 95 mass%, 90 to 100 mass%, 90 to 99 mass%, 90 to 95 mass%, etc.

[0024] The mass ratio of the content of the non-crosslinked propylene-α-olefin copolymer to the content of the polyethylene resin in the resin particles, expandable particles, expanded particles and foamed molded article is preferably 55:45 to 90:10, more preferably 60:40 to 90:10.

[0025] The resin particles, expandable particles, expanded particles, and foamed molded articles may each have two or more melting peak temperatures (Tm) measured by a differential scanning calorimeter (DSC), preferably two or three, and more preferably two. One of the melting peak temperatures (Tm1) may be in the range of 90 to 130°C, and the other of the melting peak temperatures (Tm2) may be in the range of 130 to 180°C.

[0026] Tm1 may be within a range of, for example, 90 to 130°C, 95 to 130°C, 100 to 130°C, 90°C or more but less than 130°C, 95°C or more but less than 130°C, 100°C or more but less than 130°C, 90 to 129°C, 95 to 129°C, or 100 to 129°C, and preferably has a melting peak temperature of 100 to 120°C, more preferably has a melting peak temperature of 105 to 115°C.

[0027] Tm2 may be within a range of, for example, 130 to 180°C, 130 to 170°C, 130 to 165°C, greater than 130°C and 180°C or less, greater than 130°C and 170°C or less, greater than 130°C and 165°C or less, 131 to 180°C, 131 to 170°C, 131 to 165°C, or 140 to 180°C, and preferably has a peak melting temperature of 135 to 170°C, more preferably 135 to 165°C.

[0028] The temperature difference between the melting peak temperature (Tm2) and the melting peak temperature (Tm1) is preferably 20° C. or more, more preferably 20 to 80° C., even more preferably 20 to 60° C., and particularly preferably 20 to 55° C. When the temperature difference is within this range, the expanded particles are less likely to coalesce with each other, thereby improving moldability and fusion properties, and heat shrinkage is less likely to occur even when high temperatures are required for expansion molding, thereby suppressing the occurrence of wrinkles and voids (gaps) on the surface of the foam, and further providing an expanded molded article with the high rebound resilience and good flexibility inherent to elastomers.

[0029] (resin particles) The resin particles contain a non-crosslinked propylene-α-olefin copolymer as a main component, and further contain a polyethylene resin.

[0030] The shape of the particulate resin is not particularly limited, and examples thereof include a spherical shape, an oval spherical shape (egg-shaped), a cylindrical shape, a prismatic shape, a pellet shape, and a granular shape. The size of the resin particles is not particularly limited as long as the desired expandability and moldability are obtained, and for example, an average particle diameter of 0.5 mm to 8.0 mm is preferred from the viewpoint of expandability and moldability. The average particle diameter is preferably 0.5 mm to 6.0 mm, and more preferably 0.5 mm to 3.0 mm.

[0031] The resin particles, expandable particles, expanded particles, and expanded molded articles may each contain other components such as flame retardants, colorants, antibonding agents, antistatic agents, spreaders, plasticizers, flame retardant aids, fillers, lubricants, and cell control agents. The content of the other components may be 10% by mass or less, preferably 5% by mass or less, and particularly preferably 2% by mass or less, based on the mass of the resin particles, expandable particles, expanded particles, and expanded molded articles. When the resin particles, expandable particles, expanded particles, and expanded molded articles contain other components, the lower limit of the content can be, for example, 0.01% by mass, 0.05% by mass, 0.1% by mass, 0.5% by mass, 1% by mass, 2% by mass, etc. These lower limits can be appropriately combined with the upper limits, i.e., 10%, 5%, and 2% by mass, to form the range of the content of the other components.

[0032] Examples of the flame retardant include hexabromocyclododecane and triallyl isocyanurate hexabrominated. Examples of colorants include carbon black, iron oxide, graphite, and the like. Examples of anti-binding agents (anti-coalescence agents) include talc, calcium carbonate, and aluminum hydroxide. Examples of the antistatic agent include polyoxyethylene alkylphenol ether and stearic acid monoglyceride. Examples of the spreading agent include polybutene, polyethylene glycol, and silicone oil. Examples of the foam control agent include higher fatty acid amides, higher fatty acid bisamides, higher fatty acid salts, and inorganic foam nucleating agents.

[0033] The resin particles can be obtained using known production methods and production equipment. For example, they can be produced by feeding a non-crosslinked propylene-α-olefin copolymer, a polyethylene resin, and a chemical foaming agent into an extruder, melt-kneading the mixture, and extruding the mixture from the extruder and cutting it into a desired size and shape. The temperature, time, pressure, etc. during melt-kneading can be appropriately set according to the raw materials used and the production equipment. The melt-kneading temperature in the extruder during melt-kneading is the temperature at which the resin is sufficiently softened. Therefore, it can be set appropriately depending on the resin used. It is preferably 160 to 260°C, more preferably 200 to 250°C. The melt-kneading temperature means the temperature of the molten mixture inside the extruder, measured by a thermocouple thermometer at the center of the flow path of the molten mixture near the extruder head.

[0034] (chemical foaming agent) Chemical foaming agents include sodium bicarbonate-citric acid-based chemical foaming agents, bicarbonate-based foaming agents, carbonate-based foaming agents, etc., and can be used alone or in combination of two or more. Sodium bicarbonate-citric acid-based chemical foaming agents decompose at the melt-kneading temperature to generate water (and CO2), so their use is generally avoided. However, in the present invention, sodium bicarbonate-citric acid-based chemical foaming agents are more preferred.

[0035] A baking soda-citric acid-based chemical blowing agent is an inorganic chemical blowing agent that uses baking soda and citric acid or a citrate salt. This chemical blowing agent generates carbon dioxide gas through a chemical reaction between an acid (citric acid) and a base (baking soda), and is used to foam thermoplastic resins with this gas. While baking soda and citric acid can each be used in powder form, from the standpoint of ease of handling, it is common to combine baking soda and citric acid into a single masterbatch, which is then kneaded with a base resin. As the sodium bicarbonate-citric acid based chemical foaming agent, commercially available products can be used, such as the Fine Cell Master series (eg, PO412K) manufactured by Dainichi Seika Chemicals Co., Ltd.

[0036] Bicarbonate-based and carbonate-based blowing agents are thermally decomposed to generate carbon dioxide gas, which is used to foam thermoplastic resins. Examples of bicarbonate-based blowing agents that can be used include sodium bicarbonate. Examples of carbonate-based blowing agents that can be used include sodium carbonate, calcium carbonate, and magnesium carbonate.

[0037] The amount of the chemical foaming agent mixed in the step of obtaining resin particles is preferably 0.1 to 2 parts by mass, more preferably 0.3 to 1.8 parts by mass, per 100 parts by mass of the total content of the non-crosslinked propylene-α-olefin copolymer and the polyethylene resin.

[0038] (foam particles) The expanded beads contain a non-crosslinked propylene-α-olefin copolymer as a main component, and further contain a polyethylene resin. The expanded particles are particles obtained by pre-expanding resin particles impregnated with a physical blowing agent, and can be obtained using known manufacturing methods and manufacturing equipment. For example, the expanded particles can be obtained by impregnating resin particles with a physical blowing agent to form expandable particles, and then pre-expanding the expandable particles. The resin particles can be impregnated with the physical foaming agent by a known method, for example, by injecting the physical foaming agent under pressure into a sealed container containing the resin particles. The pre-expansion conditions, such as the type and amount of the physical foaming agent and the pre-expansion temperature, may be adjusted so that the bulk density of the resulting expanded beads is at a desired value.

[0039] Examples of physical blowing agents that can be used include organic gases such as propane, n-butane, isobutane, n-pentane, isopentane, cyclopentane, n-hexane, and isohexane, and inorganic gases such as carbon dioxide, nitrogen, helium, argon, and air. These physical blowing agents can be used alone or in combination. Suitable organic gases are n-butane, isobutane, n-pentane, and isopentane, or a combination thereof.

[0040] The content of the physical blowing agent in the expandable particles is preferably 5 to 25 parts by mass relative to 100 parts by mass of the expandable particles. The content (impregnation amount) of the physical blowing agent relative to 100 parts by mass of the resin particles is measured as follows. The mass of resin particles is measured in Xg before they are placed in a pressure vessel. After the resin particles are impregnated with a physical blowing agent in the pressure vessel, the mass of the impregnated material is measured in Yg after it is removed from the pressure vessel. The content of the physical blowing agent impregnated per 100 parts by mass of resin particles (impregnation amount) can be calculated using the following formula: Physical foaming agent content (parts by mass) = ((YX) / X) x 100

[0041] The bulk density of the expanded particles is 0.02 g / cm 3 ~0.45g / cm 3 is preferable, and 0.03 g / cm 3 ~0.4g / cm 3 is more preferable, and 0.05 g / cm 3 ~0.3g / cm 3 It is more preferable that the bulk density is within this range. It is advantageous in that wrinkles and voids in the foamed molded article are suppressed and the foamed molded article is lightweight. The bulk density can be determined by the method described in the examples.

[0042] The expanded beads preferably have a spherical or nearly spherical shape. The average particle diameter is preferably 1.0 mm to 9.0 mm, and more preferably 2.0 mm to 6.0 mm. An average particle diameter within the above range is advantageous in that it allows for good mold filling properties.

[0043] The expanded particles can be obtained by pre-expanding the expandable particles to a desired bulk density by a known method. The pre-expanding can be performed by expanding the expandable particles using heated steam at a pressure of preferably 0.005 MPa to 0.05 MPa (gauge pressure), more preferably 0.006 MPa to 0.04 MPa.

[0044] (foam molded body) The foamed molded article contains a non-crosslinked propylene-α-olefin copolymer as a main component and further contains a polyethylene-based resin. The foamed beads are less likely to coalesce with each other, resulting in excellent foam moldability. Furthermore, even when the foamed beads are foamed at high temperatures, wrinkles and voids are less likely to occur on the surface of the foamed molded article, contributing to a good appearance of the foamed molded article. Furthermore, the foamed molded article from the foamed beads has a high rebound resilience and good flexibility.

[0045] The foamed molded article can be obtained by in-mold foaming of the foamed beads using a known method. For example, the foamed beads are filled into the mold of an expansion molding machine, and heated to expand the foamed beads while thermally fusing the foamed beads together. Steam is preferably used as the heating medium. Heating is carried out at a gauge pressure of, for example, 0.05 MPa to 0.35 MPa, preferably 0.06 MPa to 0.30 MPa.

[0046] The density of the foamed molded article is preferably 0.05 g / cm 3 ~0.3g / cm 3 , more preferably 0.05 g / cm 3 ~0.2g / cm 3 , and more preferably 0.10 g / cm 3 ~0.20g / cm 3 If the density is within this range, it is advantageous in that it is easy to achieve both a high rebound resilience, good flexibility, and excellent lightness. The density can be determined by the method described in the examples.

[0047] The fusion rate of the foamed molded article may be 80 to 100%, preferably 90 to 100%, and more preferably 95 to 100%. A fusion rate within this range is advantageous in that it can impart sufficient strength and good flexibility to the foamed molded article. The fusion rate can be determined by counting the number of broken foam beads in an arbitrary area (an area containing 100 foam beads) on a fracture surface obtained by dividing a foamed molded article measuring 400 mm x 300 mm x 20 mm thick in half, and specifically, can be determined by the method described in the Examples.

[0048] The rebound resilience of the foamed molded article may be 35% or more, 35 to 60%, 40% or more, 40 to 60%, 40 to 55%, 40 to 50%, etc., preferably 35 to 55%, more preferably 35 to 50%. The rebound resilience can be determined by Method A described in JIS K6400-3:2011, and specifically, can be determined by the method described in the examples.

[0049] The surface hardness (Asker C hardness) of the foamed molded article is preferably 60 or less, more preferably 50 or less, and even more preferably 45 or less. The surface hardness may be 30 to 60, 30 to 50, 30 to 45, or 35 to 45, for example. A surface hardness within this range is advantageous in that bottoming out does not occur when used as a shock-absorbing member in sports goods such as shoes. The surface hardness can be determined by the method described in JIS K7312:1996, and specifically, can be determined by the method described in the Examples.

[0050] The foamed molded article preferably has sufficient flexibility that no cracks occur between the foamed particles that make up the foamed molded article in a 90° flex test (test piece size: 150 mm x 24 mm x 11 mm thick) conducted 10,000 times in accordance with ASTM D1052. The cracks may be at least 50% deep and at least 10 mm long. Details of this flex test are described in the Examples. The measuring device used for the flex test is preferably a Rothflexing Tester manufactured by Yasuda Seiki Seisakusho.

[0051] The foamed molded articles can be used, for example, for midsoles, insoles, outsoles, etc. that make up the soles of shoes, core materials for hitting implements such as rackets and bats, protective gear for sports such as pads and protectors, medical, nursing care, welfare and healthcare products such as pads and protectors, tire core materials for bicycles and wheelchairs, interior materials for transportation equipment such as automobiles, seat core materials, shock absorbing members and vibration absorbing members, shock absorbing materials such as fenders and floats, toys such as balls, blocks and building blocks, floor underlayment materials, wall materials, seat core materials for railway cars and airplanes, bed mattresses, cushions, etc.

[0052] In the production of conventional foamed molded articles, a non-crosslinked olefin-based elastomer with a relatively high melting point is used as the base resin, which requires a foaming process using high-temperature steam. However, the foamed molded article production method of the present invention makes it difficult for voids to occur on the surface of the foamed molded article, resulting in foamed molded articles with good appearance. This is thought to be because the fusion between the foamed particles is promoted and thermal shrinkage during the foaming process is suppressed, thereby improving the expansion of the surface of the foamed molded article. The foamed molded article has sufficient impact resilience and good flexibility, which is thought to be due to the high fusion rate and good surface expansion. The foamed molded article is easy to recycle because it is mainly composed of a non-crosslinked olefin-based elastomer.

[0053] Hereinafter, one embodiment of the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. Methods for specifying various physical properties, raw materials, etc. in the examples are described below.

[0054] (Peak melting temperature (melting point) of foamed molded product) The melting peak temperature was measured by the method described in JIS K7121:2012, except that the sampling method and temperature conditions were as follows. 5.5±0.5 mg of sample was packed into the bottom of an aluminum measurement container without leaving any gaps, and then an aluminum lid was placed on it. Differential scanning calorimetry was then performed using a Hitachi High-Tech Science DSC7000X, AS-3 differential scanning calorimeter. The sample was heated and cooled in the following steps under a nitrogen gas flow rate of 20 mL / min, to obtain a DSC curve. (Step 1) Lower the temperature from 30°C to -40°C and hold for 10 minutes. (Step 2) Heat from -40°C to 220°C (first heating) and hold for 10 minutes. (Step 3) Cool from 220°C to -40°C and hold for 10 minutes. (Step 4) Heat from -40°C to 220°C (second heating). All heating and cooling was performed at a rate of 10°C / min. Alumina was used as the reference material. Using the analysis software provided with the instrument, the temperature indicated by the top of the melting peak observed during the second heating process was read and determined as the melting peak temperature (melting point). The highest peak temperature within the range of 90 to 130°C was designated as melting peak temperature Tm1, and the highest peak temperature within the range of 130 to 180°C was designated as melting peak temperature Tm2. When there were two peak tops near 130°C and they were very close to each other, the higher melting peak temperature was designated as Tm2 and the lower melting peak temperature was designated as Tm1. The melting peak temperatures of the resin and the expanded particles can be measured in the same manner.

[0055] (Bulk density of expanded particles) Wg of foam particles are collected as a measurement sample, and the measurement sample is allowed to fall naturally into a measuring cylinder. The bottom of the measuring cylinder is then struck to determine the apparent volume (V) cm of the sample. 3 The mass of the measuring sample (W) g was calculated by subtracting the mass of the empty measuring cylinder. The bulk density of the expanded beads was measured based on the following formula. Bulk density (g / cm 3 ) = mass of measurement sample (W) / apparent volume of measurement sample (V)

[0056] (Average particle size of resin particles and expanded particles) Using a low-tap sieve shaker (manufactured by Iida Seisakusho), approximately 25 g of sample was sieved for 10 minutes using JIS standard sieves (JIS Z8801-1:2006) with mesh openings of 4.00 mm, 3.35 mm, 2.80 mm, 2.36 mm, 2.00 mm, 1.70 mm, 1.40 mm, 1.18 mm, 1.00 mm, 0.85 mm, 0.71 mm, 0.60 mm, 0.50 mm, 0.425 mm, 0.355 mm, 0.300 mm, 0.250 mm, 0.212 mm, and 0.180 mm. The weight of the sample on the sieve was measured. A cumulative weight distribution curve was created from the results, and the particle size (median diameter) at which the cumulative weight reached 50% was defined as the average particle size.

[0057] (Density of foamed molded product) The density was measured by the method described in JIS K7222:2005. First, the sample was cut so as not to change the original cell structure, and a volume of 100 cm was obtained. 3 The above test specimens were prepared and conditioned as follows: Next, the mass of the conditioned test specimens was measured, and the density was calculated using the following formula. Density (g / cm 3 ) = mass of test piece (g) / volume of test piece (cm 3 ) Specimen Conditioning The test pieces for measurement were cut from samples that had been in operation for at least 72 hours after molding. The test pieces were conditioned for at least 16 hours in a standard atmosphere of JIS K7100:1999, symbol "23 / 50", grade 2, before measuring their mass and volume.

[0058] (Appearance evaluation of foam molded product) The state of gaps (voids) between foam particles on the surface of a 400 mm x 300 mm foam molded article (400 mm x 300 mm x 20 mm thick) was visually observed and evaluated according to the following criteria. ◯: No voids between foam particles. △: 10 or less voids between foam particles. ×: There are 11 or more voids between the foam particles. Here, a void refers to one that is 2 mm square or larger.

[0059] (Fusion rate) A 400mm x 300mm x 20mm thick foam molded article was cut with a cutter knife along the center line of one long side of the 400mm x 300mm surface, and then the foam molded article was divided into two along this cut line. An arbitrary area containing 100 foam beads that appeared on the fracture surface of the divided foam molded article was set, and the number of foam beads that had broken within the foam beads (a) and the number of foam beads that had broken at the interface between the foam beads (b) were counted within this area, and the fusion rate F (%) was calculated using the following formula. F(%)=a / (a+b)×100

[0060] (Surface hardness of foam molded product (Asker C hardness)) Surface hardness was measured according to the method described in JIS K7312:1996. The samples were conditioned for 88 hours under a standard atmosphere of JIS K7100:1999, "23 / 50," grade 2, before being used for measurement. The sample size was 50 x 50 x 10 mm thick. Five samples were used. Surface hardness was measured using an "Asker Rubber and Plastic Hardness Tester, Type C" manufactured by Kobunshi Keiki Co., Ltd. A 1 kg load was applied to the sample with this hardness tester, and the value immediately read was used as the surface hardness. The surface hardness was calculated by averaging the five measurements.

[0061] (Rebound resilience of foam molded product) The rebound resilience was measured according to Method A of JIS K6400-3:2011. A Rebound Resilience Tester Model FR-1 manufactured by Kobunshi Keiki Co., Ltd. was used for the measurement. The test piece was 100 mm square and 20 mm thick. A steel ball (diameter 16±0.5 mm, mass 16.8±1.5 g) with a nominal size of 16 mm and a grade of G40, as specified in JIS B1501, was used for the measurement. The rebound resilience was calculated using the following formula. The ball was dropped over a distance of 500 mm. Rebound elasticity (%) = Maximum rebound distance (mm) / Fall distance (500mm) x 100 The test specimens were conditioned for 16 hours in a standard atmosphere of JIS K 7100:1999, symbol "23 / 50", grade 2, before being used for measurement. Measurements were carried out in the same standard atmosphere.

[0062] (Bending test of foam molded body) The bending test was performed according to the method described in ASTM D1052. The test piece size was 150 mm x 24 mm x 11 mm thick. A Ross Flexing Tester (manufactured by Yasuda Seiki Seisakusho Co., Ltd.) was used as the measuring device. Both ends of the test piece were fixed to the measuring device, and the piece was bent 90° at a frequency of 100 times / minute. After 10,000 times, the occurrence of cracks was visually confirmed and evaluated according to the following criteria. ◯: No cracks on the surface of the test piece. ×: There is one or more cracks on the surface of the test piece that are 50% or more deep and 10 mm or longer.

[0063] (A: Non-crosslinked propylene-α-olefin copolymer) Elastomer A1: Toughmer PN-2060 (Mitsui Chemicals, Inc.); melting peak temperature 160°C Elastomer A2: ESPOLEX 901 (Sumitomo Chemical Co., Ltd.); melting peak temperature 144°C Elastomer A3: Toughmer PN-2070 (Mitsui Chemicals, Inc.); melting peak temperature 140°C Elastomer A4: Toughmer PN-3560 (Mitsui Chemicals, Inc.); melting peak temperature 160°C Elastomer A5: Prime TPO R110E (Prime Polymer Co., Ltd.); melting peak temperature 156°C Elastomer A6: Vistamaxx 3980FL (ExxonMobil); melting peak temperature 74.5°C

[0064] (B: Polyethylene resin) Resin B1: Braskem Green PE SEB853; peak melting temperature 111°C Resin B2: Braskem Green SHC7260; peak melting temperature 134°C Resin B3: Braskem Green SLH218; peak melting temperature 125°C

[0065] (acrylic polymer) Metablen P-1050 (Mitsubishi Chemical Corporation)

[0066] (baking soda-citric acid based chemical foaming agent) Fine Cell Master PO410K (Dainichiseika Color & Chemicals Mfg. Co., Ltd.)

[0067] Example 1 (1) Resin particles 53 parts by weight of Elastomer A1, 24 parts by weight of Elastomer A2, 23 parts by weight of polyethylene-based resin B1, 5 parts by weight of an acrylic polymer as a processing aid, and 1 part by weight of a sodium bicarbonate-citric acid-based chemical blowing agent were fed into a single-screw extruder at a rate of 10 kg / h and melt-kneaded. The materials were initially melt-kneaded at 160°C, then heated to 200°C. The molten resin was then cooled and extruded through each nozzle of a multi-nozzle die (with nine 1.0 mm diameter nozzles) attached to the front end of the single-screw extruder. The extruded resin was then cut in water at 20-50°C to obtain resin particles. The average particle diameter D50 of the resin particles was 1.52-1.55 mm.

[0068] (2) Expandable particles 2.0 kg (100 parts by mass) of the resulting resin particles, 1.5 L of distilled water, and 3 g of a surfactant (sodium linear alkylbenzene sulfonate, trade name: "Newlex R", manufactured by Yuka Sangyo Co., Ltd.) were placed in a 5 L autoclave equipped with a stirrer and sealed. After stirring, 10 parts by mass of the blowing agent butane (normal butane:isobutane = 7:3 (volume ratio)) was added under pressure. The autoclave was then heated at 30°C for 2 hours and cooled to 25°C. After cooling was complete, the autoclave was depressurized, and the surfactant was immediately washed with distilled water and dehydrated to obtain expandable particles. The amount of gas impregnated in the expandable particles was 7.7% by mass.

[0069] (3) Foam particles 2.0 kg of the obtained expandable particles were placed in a 50 L cylindrical pre-expander equipped with a stirrer, and pre-expanded by heating with steam at a gauge pressure of 0.01 MPa while stirring to obtain expanded particles. The bulk density and average particle size of the obtained expanded particles were measured.

[0070] (4) Foam molded body The resulting expanded beads were placed in an autoclave, and air was injected at a gauge pressure of 0.25 MPa. The expanded beads were then allowed to stand at room temperature for 18 hours to impregnate the expanded beads with air (apply internal pressure). The amount of impregnated air was 0.75% by mass. The pressurized expanded beads were removed from the autoclave and immediately filled into a molding cavity (400 mm × 300 mm × 20 mm thick) equipped with a steam vent, followed by heat molding with steam at 0.20 MPa to obtain a foamed molded article. The physical properties of the obtained expanded beads and foamed molded article are shown in Table 1.

[0071] Example 2 Except for using 64 parts by mass of elastomer A1 and 12 parts by mass of polyethylene resin B1, a foamed molded article was produced in the same manner as in Example 1. The physical properties of the obtained foamed beads and foamed molded article are shown in Table 1.

[0072] Example 3 Except for using 32 parts by mass of Elastomer A1 and 45 parts by mass of Elastomer A2, a foamed molded article was produced in the same manner as in Example 1. The physical properties of the obtained foamed beads and foamed molded article are shown in Table 1.

[0073] Example 4 Except for using 13 parts by mass of elastomer A2 and 34 parts by mass of polyethylene resin B1, a foamed molded article was produced in the same manner as in Example 1. The physical properties of the obtained foamed beads and foamed molded article are shown in Table 1.

[0074] Example 5 Except for using Elastomer A3 instead of Elastomer A1, a foamed molded article was produced in the same manner as in Example 1. The physical properties of the obtained foamed beads and foamed molded article are shown in Table 1.

[0075] Example 6 Except for using Elastomer A4 instead of Elastomer A1, a foamed molded article was produced in the same manner as in Example 1. The physical properties of the obtained foamed beads and foamed molded article are shown in Table 1.

[0076] (Comparative Example 1) Expanded beads were produced in the same manner as in Example 1, except that 100 parts by mass of elastomer A1 was used and neither elastomer A2 nor polyethylene-based resin B1 was used. However, since the expanded beads remained in a bead-like form even when heated in the expansion molding process, a fused body of the expanded beads was not formed, and an expanded molded product was not obtained.

[0077] (Comparative Example 2) Except for using 100 parts by mass of Elastomer A5 instead of Elastomer A1 and not using Elastomer A2 or polyethylene resin B1, a foamed molded article was produced in the same manner as in Example 1. The physical properties of the obtained foamed beads and foamed molded article are shown in Table 2.

[0078] (Comparative Example 3) A foamed molded article was produced in the same manner as in Example 1, except that Elastomer A1 was not used and 77 parts by mass of Elastomer A2 was used. The physical properties of the obtained foamed beads and foamed molded article are shown in Table 2.

[0079] Comparative Example 4 Except for using 77 parts by mass of Elastomer A6 instead of Elastomers A1 and A2, a foamed molded article was produced in the same manner as in Example 1. The physical properties of the obtained foamed beads and foamed molded article are shown in Table 2.

[0080] (Comparative Example 5) Except for using polyethylene resin B2 instead of polyethylene resin B1, a foamed molded article was produced in the same manner as in Example 1. The physical properties of the obtained foamed beads and foamed molded article are shown in Table 2.

[0081] (Comparative Example 6) Except for using Elastomer A3 instead of Elastomer A1 and Polyethylene Resin B3 instead of Polyethylene Resin B1, a foamed molded article was produced in the same manner as in Example 1. The physical properties of the obtained foamed beads and foamed molded article are shown in Table 2.

[0082] (Comparative Example 7) The same procedure as in Example 1 was conducted except that 53 parts by mass of elastomer A1, 13 parts by mass of elastomer A2, and 34 parts by mass of polyethylene-based resin B1 were used and no chemical foaming agent was used. However, the expandable particles were not pre-expanded, and expanded particles were not obtained.

[0083] [Table 1]

[0084] [Table 2]

[0085] In Examples 1 to 6, foam molding was possible using steam at 0.20 MPa. Furthermore, in Examples 1 to 6, Tm2-Tm1 was 30 to 52° C. In Examples 1 to 6, foam molded articles excellent in appearance, fusion rate, hardness, rebound resilience, and flexibility were obtained. In Comparative Example 2, a peak top was observed in the temperature range of Tm2 (130 to 180°C) in the measurement of the peak melting temperature of the foamed molded article. However, since no polyethylene resin was used in combination with the non-crosslinked polypropylene-α-olefin copolymer, no other peak tops were observed. In Comparative Example 3, a polyethylene resin was used in combination with a non-crosslinked polypropylene-α-olefin copolymer, and Tm2-Tm1 was 31°C. In Comparative Example 4, a polyethylene resin was used in combination with a non-crosslinked polypropylene-α-olefin copolymer, and two peak tops were observed in the measurement of the peak melting temperature of the foamed molded article. A peak top was observed at 106°C within the temperature range of Tm1 (90 to 130°C), but no peak top was observed within the temperature range of Tm2 (130 to 180°C), and a peak top was observed at 75°C. In Comparative Example 5, two types of non-crosslinked polypropylene-α-olefin copolymer and a polyethylene resin were used in combination, and two peak tops were observed in the measurement of the peak melting temperature of the foamed molded article. Peak tops were observed at 134°C and 159°C within the temperature range of Tm2 (130 to 180°C), but no peak top was observed within the temperature range of Tm1 (90 to 130°C). In Comparative Example 6, two types of non-crosslinked polypropylene-α-olefin copolymers and a polyethylene resin were used in combination, and two peak tops were observed in the measurement of the peak melting temperature of the foamed molded article. Tm2 - Tm1 was 13°C.

Claims

1. A foamed molded article of a non-crosslinked olefin-based elastomer composed of a fused body of foamed beads, Contains two or more non-crosslinked propylene-α-olefin copolymers as main components, One of the two or more non-crosslinked propylene-α-olefin copolymers has a melting peak temperature of 144°C as measured by differential scanning calorimetry (DSC); Further containing a polyethylene resin, the total content of the non-crosslinked propylene-α-olefin copolymer and the polyethylene resin is 80% by mass or more relative to the mass of the foamed molded article, The foamed molded product has two or more melting peak temperatures (Tm) measured by a differential scanning calorimeter (DSC), One of the melting peak temperatures (Tm1) of the foamed molded product is in the range of 90 to 130°C, Another melting peak temperature (Tm2) of the foamed molded product is in the range of 139 to 180°C, the temperature difference between the melting peak temperature (Tm2) and the melting peak temperature (Tm1) is 20°C or more; Foam molding.

2. the mass ratio of the content of the non-crosslinked propylene-α-olefin copolymer to the content of the polyethylene resin is 55:45 to 90:10; A foamed molded article of the non-crosslinked olefinic elastomer according to claim 1.

3. 3. The foam-molded article of a non-crosslinked olefin-based elastomer according to claim 1, wherein the temperature difference between the melting peak temperature (Tm2) and the melting peak temperature (Tm1) is 20 to 80°C.

4. The non-crosslinked olefin-based elastomer foam molded article according to any one of claims 1 to 3, wherein the polyethylene-based resin is one or more resins selected from the group consisting of high-density polyethylene and low-density polyethylene.

5. 5. The foam-molded article of a non-crosslinked olefin-based elastomer according to claim 1, wherein the proportion of xylene-insoluble matter measured by hot xylene extraction is 3% or less.

6. 0.05~0.3g / cm ３ 6. The foam-molded article of a non-crosslinked olefin-based elastomer according to claim 1, having at least one property selected from the group consisting of a density of 0.01 to 0.15 MPa, a rebound resilience of 35% or more, and an Asker C hardness of 60 or less.

7. 7. The foam-molded article of a non-crosslinked olefin-based elastomer according to claim 1, which has flexural durability such that no cracks with a depth of 50% or more and a length of 10 mm or more occur between the foamed particles in a 90° flex test of 10,000 times (test piece size: 150 mm x 24 mm x 11 mm thick) in accordance with ASTM D1052.

8. 8. A method for producing a foamed molded article of a non-crosslinked olefin-based elastomer according to claim 1, comprising the steps of: mixing a non-crosslinked propylene-α-olefin copolymer, a polyethylene-based resin, and a chemical foaming agent to obtain resin particles containing the non-crosslinked propylene-α-olefin copolymer as a main component; impregnating the resin particles with a physical foaming agent and then pre-foaming the resin particles to obtain foamed particles; and foaming the foamed particles in a mold to obtain a foamed molded article.

9. 9. The method for producing a foamed molded article of a non-crosslinked olefin-based elastomer according to claim 8, wherein the chemical foaming agent is a sodium bicarbonate-citric acid-based chemical foaming agent, and the amount of the chemical foaming agent mixed in the step of obtaining resin particles is 0.1 to 2 parts by mass per 100 parts by mass of the total amount of the non-crosslinked propylene-α-olefin copolymer and the polyethylene-based resin.

10. 10. The method for producing a foamed molded article of a non-crosslinked olefin-based elastomer according to claim 8 or 9, wherein the mass ratio of the mixed amount of the non-crosslinked propylene-α-olefin copolymer to the mixed amount of the polyethylene-based resin in the step of obtaining resin particles is 55:45 to 90:10.

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