Expandable resin particles, expanded particles, and foamed molded article

Abstract

To provide a novel foamable resin particle that can provide a foamed molding having excellent heat resistance and strength in a short molding cycle.SOLUTION: A foamable resin particle contains a base material resin and a foamer. The base material resin contains a constitutional unit derived from acrylonitrile, a constitutional unit derived from styrene and / or a constitutional unit derived from α-methylstyrene. The surface of the foamable resin particle contains a specific amount of specific fatty acid glyceride.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to expandable resin beads, expanded beads, and foamed molded articles. [Background technology]

[0002] Expandable resin particles can be easily expanded and molded to give expanded molded articles, and the production costs of the expandable resin particles and expanded molded articles are low, so the expanded molded articles are widely used.

[0003] To solve various problems, various types of expandable resin particles have been developed.

[0004] For example, Patent Document 1 discloses particles of an expandable thermoplastic copolymer containing alphamethylstyrene and acrylonitrile, the surface of which is coated with room temperature edible oil, with the aim of reducing tertiary expansion and dimensional change. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 1985-206844 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the above-mentioned conventional techniques are not sufficient in terms of heat resistance, production efficiency, and strength of foamed molded articles, and there is room for further improvement.

[0007] One embodiment of the present invention has been made in consideration of the above-mentioned problems, and its object is to provide novel expandable resin particles that can provide foamed molded articles having excellent heat resistance and strength in a short molding cycle. [Means for solving the problem]

[0008] As a result of intensive research to solve the above-mentioned problems, the inventors discovered that the above-mentioned problems can be achieved by using expandable resin particles having a specific amount of a specific fatty acid glyceride applied to the surface of the expandable resin particles, and thus completed the present invention.

[0009] That is, one embodiment of the present invention includes the following configuration. [1] Expandable resin particles comprising a base resin and a blowing agent, wherein the base resin comprises a structural unit derived from acrylonitrile, a structural unit derived from styrene, and / or a structural unit derived from α-methylstyrene, and the expandable resin particles contain 0.02 to 0.04 parts by weight of a fatty acid glyceride having a freezing point of 25°C or less on the surface of 100 parts by weight of the expandable resin particles. [2] The expandable resin particles according to [1], wherein the fatty acid glyceride is a fatty acid triglyceride having one or more fatty acids selected from the group consisting of ricinoleic acid, oleic acid, and lauric acid as a main component. [3] The expandable resin particles according to [1] or [2], wherein the fatty acid glyceride is a fatty acid triglyceride containing ricinoleic acid as a main component. [4] The expandable resin particles according to any one of [1] to [3], wherein the fatty acid glyceride is castor oil. [5] The expandable resin particles according to any one of [1] to [4], wherein the base resin contains 15 to 30 parts by weight of the structural unit derived from acrylonitrile per 100 parts by weight of the base resin. [6] Expandable resin particles according to any one of [1] to [5], containing 0.2 to 0.4 parts by weight of a metal salt of a higher fatty acid on the surface of 100 parts by weight of the expandable resin particles. [7] Expanded particles obtained by expanding the expandable resin particles according to any one of [1] to [6]. [8] A foamed molded article obtained by molding the foamed beads according to [7]. [Effects of the Invention]

[0010] According to one embodiment of the present invention, it is possible to provide novel expandable resin particles that can provide a foamed molded article having excellent heat resistance and strength in a short molding cycle. DETAILED DESCRIPTION OF THE INVENTION

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

[0012] In this specification, a constitutional unit derived from an X monomer is also referred to as an "X unit." Unless otherwise specified in this specification, X 1 Units and X 2 Units, and X n A copolymer containing X units (n is an integer of 2 or more) is referred to as "X 1 / X 2 / ··· / X n Also called "copolymer". X 1 / X 2 / ··· / X n Unless otherwise specified, the copolymer is not particularly limited in terms of the polymerization mode, and may be a random copolymer, a block copolymer, or a graft copolymer.

[0013] 1. Technical Concept of One Embodiment of the Present Invention Heat resistance may be required as a physical property of a foamed molded article. Among expandable resin particles, expandable resin particles having acrylonitrile units have the advantage of being able to provide a foamed molded article having excellent heat resistance. Therefore, the present inventors first investigated the provision of expandable resin particles having acrylonitrile units in order to provide a foamed molded article having excellent heat resistance.

[0014] On the other hand, the acrylonitrile units impart gas barrier properties to the expandable resin particles, and therefore, expanded particles obtained by expanding expandable resin particles containing acrylonitrile units have high gas barrier properties.

[0015] The present inventors have discovered a novel finding: when foamed beads obtained by expanding expandable resin beads containing acrylonitrile units are molded using a mold, the resulting foamed molded article tends to swell when removed from the mold compared to a typical polystyrene foamed molded article not containing acrylonitrile units. The expansion of the foamed molded article can cause problems such as (a) changes in the dimensions and shape of the resulting foamed molded article, making it unusable as a product, and (b) the expansion can make it impossible to release from the mold. After investigating the expansion of such foamed molded articles, the present inventors have come to the following conjecture: the direct cause of the expansion of the foamed molded article is that the gas (blowing agent) used in molding remains within the foamed beads of the foamed molded article after removal from the mold, causing the foamed molded article to expand due to this gas. Furthermore, as described above, foamed beads obtained by expanding expandable resin beads containing acrylonitrile units have high gas barrier properties, and therefore, when these foamed beads are molded using a mold, gas tends to be less likely to escape from the foamed molded article, and therefore, the foaming pressure within the foamed molded article tends to be less likely to decrease. Furthermore, it was speculated that the gas remaining in the foamed beads of the foamed molded article after molding is released from the foamed molded article during the cooling process in which the foamed molded article in the mold is cooled by cooling the mold after molding. In other words, if it is desired to obtain a foamed molded article with little expansion from foamed beads obtained by expanding expandable resin beads containing acrylonitrile units, it is necessary to set the cooling process time long, which tends to lengthen the molding cycle (which can also be said to be the time required for one molding).

[0016] Therefore, the present inventors have conducted extensive research to enable foamed molded articles to be produced in a short molding cycle even when expandable resin particles containing acrylonitrile units are used. As a result, the present inventors have surprisingly independently discovered that foamed molded articles can be produced in a short molding cycle by incorporating a fatty acid glyceride having a freezing point of 25°C or less into the surface of the expandable resin particles.

[0017] During the course of extensive research, the present inventors independently discovered that when the content of fatty acid glycerides on the surface of expandable resin particles is high, the strength of the resulting expanded molded article is reduced. The cause of this reduced strength of the expanded molded article is unclear, but it is speculated as follows: when a large amount of fatty acid glycerides is present on the surface of the expandable resin particles, many cracks may occur on the surface of the expanded beads obtained by expanding the expandable resin particles. It is speculated that these cracks also reduce the strength of the expanded molded article obtained by molding the expanded beads. However, one embodiment of the present invention is not limited to this speculation.

[0018] Therefore, the present inventors have further conducted extensive research to provide a foamed molded article having excellent strength in a short molding cycle even when using expandable resin particles containing acrylonitrile units. As a result, the present inventors have surprisingly found that by adding 0.02 to 0.04 parts by weight of a fatty acid glyceride having a freezing point of 25°C or less to the surface of expandable resin particles containing acrylonitrile units, it is possible to obtain expandable resin particles that can provide a foamed molded article having excellent heat resistance and strength in a short molding cycle, and have completed the present invention.

[0019] [2. Expandable Resin Particles] The expandable resin particles according to one embodiment of the present invention are expandable resin particles comprising a base resin and a blowing agent, wherein the base resin comprises structural units derived from acrylonitrile, structural units derived from styrene, and / or structural units derived from α-methylstyrene, and 0.02 to 0.04 parts by weight of a fatty acid glyceride having a freezing point of 25°C or less is contained on the surface of 100 parts by weight of the expandable resin particles.

[0020] The expandable resin particles according to one embodiment of the present invention have the above-described structure, and therefore have the advantage that they can provide a foamed molded article having excellent heat resistance and strength in a short molding cycle.

[0021] In the following description of this specification, expandable resin particles that do not contain fatty acid glycerides on their surfaces (which may also be referred to as expandable resin particles themselves or expandable resin particles themselves) may be referred to as "expandable resin particle bodies," and expandable resin particles that contain fatty acid glycerides on their surfaces may be referred to as "expandable resin particles." Furthermore, in this specification, particles obtained by expanding expandable resin particles may be referred to as "expanded particles," and molded bodies obtained by molding such expanded beads may be referred to as "expanded molded bodies." Furthermore, in this specification, "expandable resin particle bodies according to one embodiment of the present invention" may be referred to as "the present expandable resin particle bodies," "expandable resin particles according to one embodiment of the present invention" may be referred to as "the present expandable resin particles," "expanded beads according to one embodiment of the present invention" may be referred to as "the present expanded beads," and "expanded molded bodies according to one embodiment of the present invention" may be referred to as "the present expanded molded bodies."

[0022] [Expandable resin particle body] The expandable resin particle body contains a base resin and a blowing agent.

[0023] [Base resin] In one embodiment of the present invention, the base resin comprises acrylonitrile units and styrene and / or α-methylstyrene units.

[0024] The base resin preferably contains 15 to 30 parts by weight, more preferably 18 to 27 parts by weight, even more preferably 20 to 25 parts by weight, and particularly preferably 24 to 25 parts by weight, of acrylonitrile units per 100 parts by weight of the base resin. This configuration provides the advantageous effect of providing a foamed molded article with (a) excellent expandability and (b) excellent heat resistance and fusion properties during molding. When the base resin contains (a) 15 or more parts by weight of acrylonitrile units per 100 parts by weight of the base resin, the heat resistance of the resulting foamed molded article tends to be sufficient. When the base resin contains (b) 30 or less parts by weight of acrylonitrile units, the expansion ratio of the foamed beads and the foamed molded article tends to be increased, and the fusion properties of the resulting foamed molded article tend to be good.

[0025] The base resin preferably contains 40 to 90 parts by weight, more preferably 50 to 85 parts by weight, even more preferably 65 to 80 parts by weight, and particularly preferably 70 to 76 parts by weight of styrene units per 100 parts by weight of the base resin. This configuration provides the advantageous effect of providing a foamed molded article with (a) excellent expandability and (b) an excellent balance between heat resistance and moldability. When the base resin contains (a) 40 or more parts by weight of styrene units per 100 parts by weight of the base resin, the expandability of the resulting expandable resin particles and the moldability of the resulting foamed molded article are both excellent, and high heating temperatures tend not to be required. When the base resin contains (b) 90 or less parts by weight of styrene units, a foamed molded article with good heat resistance tends to be easily obtained.

[0026] The base resin preferably contains 3 to 75 parts by weight, more preferably 3 to 40 parts by weight, even more preferably 3 to 20 parts by weight, and particularly preferably 4 to 10 parts by weight, of α-methylstyrene units per 100 parts by weight of the base resin. This configuration provides the advantageous effect of providing a foamed molded article with good heat resistance and low residual monomer components. When the base resin contains (a) 3 parts by weight or more of α-methylstyrene units per 100 parts by weight of the base resin, a foamed molded article with good heat resistance is likely to be obtained. When the base resin contains (b) 75 parts by weight or less, there is no risk of the polymerization reaction being difficult to complete, and a foamed molded article with low residual monomer components is likely to be obtained.

[0027] The ratio of styrene units, acrylonitrile units, and α-methylstyrene units in the base resin is not particularly limited and may be appropriately set depending on the desired properties of the foamed molded product. For example, the ratio of styrene units, acrylonitrile units, and α-methylstyrene units in the base resin (parts by weight of styrene units / parts by weight of acrylonitrile units / parts by weight of α-methylstyrene units) is preferably 65-82 / 15-30 / 3-20, more preferably 65-79 / 18-26 / 3-10, even more preferably 70-76 / 20-26 / 4-6, and particularly preferably 70-73 / 23-25 / 4-6, because this facilitates expansion of the expandable resin particles and molding of the expanded particles, and results in foamed molded products with good heat resistance and low residual monomer components. Foamed molded products with low residual monomer components can be suitably used as architectural interior materials, and foamed molded products with excellent heat resistance can be suitably used as outdoor insulation materials. Furthermore, since a foamed molded article having excellent heat resistance can be obtained, the content ratio of styrene units, acrylonitrile units, and α-methylstyrene units in the base resin (parts by weight of styrene units / parts by weight of acrylonitrile units / parts by weight of α-methylstyrene units) is preferably 20-80 / 10-30 / 10-50, more preferably 30-75 / 14-25 / 11-45, even more preferably 40-70 / 14-20 / 15-40, and particularly preferably 44-66 / 14-21 / 19-36. Furthermore, since a foamed molded article having excellent heat resistance can be obtained, although the expandability of the expandable resin particles is somewhat inferior, the content ratio of styrene units, acrylonitrile units, and α-methylstyrene units in the base resin (parts by weight of styrene units / parts by weight of acrylonitrile units / parts by weight of α-methylstyrene units) is preferably 0 / 15 to 50 / 50 to 85, more preferably 0 / 20 to 40 / 60 to 80, even more preferably 0 / 25 to 35 / 65 to 75, and particularly preferably 0 / 28 to 32 / 68 to 72.

[0028] The base resin may contain structural units derived from monomers other than styrene, acrylonitrile, and α-methylstyrene. Examples of monomers other than styrene, acrylonitrile, and α-methylstyrene include (a) styrene derivatives (other than styrene and α-methylstyrene), such as paramethylstyrene, t-butylstyrene, and chlorostyrene, and (b) acrylic acid ester monomers.

[0029] Examples of the acrylic acid ester monomer include alkyl acrylates such as methyl acrylate and butyl acrylate.

[0030] The structural units derived from monomers other than styrene, acrylonitrile, and α-methylstyrene that can be contained in the base resin may be one type or a combination of two or more types.

[0031] [Blowing Agent] The blowing agent contained in the expandable resin particles is not particularly limited. Specific examples of the blowing agent include volatile blowing agents such as (a) aliphatic hydrocarbons having 3 to 5 carbon atoms, such as propane, n-butane, isobutane, n-pentane, isopentane, and neopentane; and (b) fluorocarbons with an ozone depletion potential of zero, such as difluoroethane and tetrafluoroethane. These blowing agents may be used alone or in combination of two or more. The content of the blowing agent is preferably 3 to 10 parts by weight, and more preferably 4 to 8 parts by weight, per 100 parts by weight of the base resin. When the content of the blowing agent is (a) 3 parts by weight or more, per 100 parts by weight of the base resin, it tends to be easier to obtain a desired expansion ratio, while when the content of the blowing agent is (b) 10 parts by weight or less, it tends to be less likely that the expandable resin particle bodies will aggregate during the process of impregnating the blowing agent. Furthermore, from the viewpoint of stably carrying out the impregnation step and obtaining expandable resin particles with sufficient expandability, it is particularly preferable that the content of (a) the blowing agent is 4 parts by weight or more and 6 parts by weight or less per 100 parts by weight of the base resin, and it is preferable to use a combination of n-butane and isobutane as the (b) blowing agent.

[0032] The expandable resin particle body can be produced by preparing (polymerizing) a base resin and then impregnating the resulting base resin with a blowing agent. The base resin preparation method (polymerization method) and the blowing agent impregnation method can be any known production method, and are not particularly limited. However, when a seed suspension polymerization method is used to prepare the base resin, the constituent units in the resin particle body that serve as seeds (i.e., the constituent units contained in the seeds) are also included as constituent units of the expandable resin particle body.

[0033] [Fatty acid glycerides] The fatty acid glyceride according to one embodiment of the present invention has a freezing point of 25° C. or lower. By applying the fatty acid glyceride to the surface of the expandable resin particle body, expandable resin particles containing the fatty acid glyceride on the surface of the expandable resin particle can be obtained. The fatty acid glyceride can also be considered an external additive.

[0034] The fatty acid glyceride applied to the expandable resin particle body adheres to the expandable resin particle body in substantially its entirety and is contained in the expandable resin particle (i.e., acts as an external additive). The amount of fatty acid glyceride applied to the expandable resin particle body can be said to be the fatty acid glyceride content in the expandable resin particle.

[0035] The present expandable resin beads contain fatty acid glycerides having a freezing point of 25°C or lower on their surfaces, enabling foamed molded articles to be produced in a short molding cycle. The reason why the use of fatty acid glycerides having a freezing point of 25°C or lower shortens the molding cycle for foamed molded articles is unclear, but it is speculated as follows: when foamed (heated) expandable resin beads containing fatty acid glycerides having a freezing point of 25°C or lower on their surfaces, the fatty acid glycerides on the surfaces of the expandable resin beads plasticize the surfaces. This can lead to cracks on the surfaces of the resulting expanded beads. When foamed beads containing fatty acid glycerides having a freezing point of 25°C or lower on their surfaces are molded using a mold, the plasticization and cracks on the surfaces of the expanded beads promote gas escape from the foamed molded article. Therefore, the cooling time for the foamed molded article can be shortened when molding the expanded beads, and as a result, the foamed molded article can be produced using the expanded beads in a short molding cycle. However, the present invention is not limited to this speculation.

[0036] As used herein, the term "fatty acid glyceride" refers to an ester of a fatty acid and glycerin, and includes fatty acid monoglycerides, fatty acid diglycerides, and fatty acid triglycerides. Furthermore, the fatty acid glyceride may consist of one type of fatty acid glyceride, or may be a mixture of two or more types of fatty acid glycerides. When the fatty acid glyceride is a mixture of two or more types of fatty acid glycerides, the term "fatty acid glyceride having a freezing point of 25°C or lower" refers to a mixture of two or more types of fatty acid glycerides having a freezing point of 25°C or lower. As used herein, the term "fatty acid glyceride" encompasses both fatty acid glycerides and mixtures of fatty acid glycerides.

[0037] The fatty acid glyceride is preferably one prepared using as a raw material a fatty acid mixture containing fatty acids having 12 to 18 carbon atoms. The fatty acid glyceride is preferably one prepared using as a raw material a fatty acid mixture containing 40% by weight or more of fatty acids having 12 to 18 carbon atoms, based on 100% by weight of the fatty acids of the raw material. Of the fatty acids used as the raw material for the fatty acid glyceride, the fatty acid that is contained in the largest amount, based on 100% by weight of the fatty acids, may be referred to as the "main component" of the fatty acid glyceride. In other words, the fatty acid glyceride is preferably one whose main component is a fatty acid having 12 to 18 carbon atoms. This configuration provides the advantageous effect of enabling the production of expanded molded articles in a shorter molding cycle.

[0038] When fatty acid glycerides are hydrolyzed, they separate into fatty acids (a mixture of fatty acids) and glycerin. Therefore, "fatty acid glycerides are fatty acid glycerides whose main component is a fatty acid having 12 to 18 carbon atoms" can also be said to mean "the main component of the fatty acid (fatty acid mixture) obtained by hydrolysis of the fatty acid glycerides is a fatty acid having 12 to 18 carbon atoms."

[0039] The fatty acid glyceride is preferably a fatty acid glyceride mainly composed of a fatty acid having 12 to 18 carbon atoms, more preferably a fatty acid glyceride mainly composed of a fatty acid having 16 to 18 carbon atoms, even more preferably a fatty acid glyceride mainly composed of an unsaturated fatty acid having 16 to 18 carbon atoms, and particularly preferably a fatty acid glyceride mainly composed of an unsaturated fatty acid having 18 carbon atoms. According to this configuration, the resulting expandable resin particles have the advantage that foamed molded articles can be provided in a shorter molding cycle.

[0040] The fatty acid glyceride is preferably a fatty acid triglyceride mainly composed of a fatty acid having 12 to 18 carbon atoms, more preferably a fatty acid triglyceride mainly composed of a fatty acid having 16 to 18 carbon atoms, even more preferably a fatty acid triglyceride mainly composed of an unsaturated fatty acid having 16 to 18 carbon atoms, and particularly preferably a fatty acid triglyceride mainly composed of an unsaturated fatty acid having 18 carbon atoms. According to this configuration, the resulting expandable resin particles have the advantage that foamed molded articles can be provided in a shorter molding cycle.

[0041] The fatty acids constituting the fatty acid glyceride may be saturated fatty acids or unsaturated fatty acids. When the fatty acids constituting the fatty acid glyceride are unsaturated fatty acids, the number of carbon-carbon double bonds or triple bonds present in the hydrocarbon chain of the fatty acid is not particularly limited, and may be one or two or more.

[0042] The fatty acid glyceride is preferably a fatty acid glyceride having as its main component one or more selected from the group consisting of ricinoleic acid, oleic acid, lauric acid, palmitic acid, linoleic acid, stearic acid, and myristic acid, more preferably a fatty acid glyceride having as its main component one or more selected from the group consisting of ricinoleic acid, oleic acid, and lauric acid, and even more preferably a fatty acid glyceride having as its main component ricinoleic acid. According to this configuration, the resulting expandable resin particles have the advantage that foamed molded articles can be provided in an even shorter molding cycle.

[0043] The fatty acid glyceride is preferably a fatty acid triglyceride having as a main component one or more selected from the group consisting of ricinoleic acid, oleic acid, lauric acid, palmitic acid, linoleic acid, stearic acid, and myristic acid, more preferably a fatty acid triglyceride having as a main component one or more selected from the group consisting of ricinoleic acid, oleic acid, and lauric acid, and even more preferably a fatty acid triglyceride having as a main component ricinoleic acid. According to this configuration, the resulting expandable resin particles have the advantage that foamed molded articles can be provided in an even shorter molding cycle.

[0044] As the fatty acid glyceride, vegetable oils can also be used as a mixture of two or more fatty acid glycerides.

[0045] For example, castor oil is a fatty acid triglyceride composed of glycerin and a fatty acid mixture containing ricinoleic acid and other fatty acids (e.g., oleic acid), and the fatty acid mixture may contain 80% to 90% by weight of ricinoleic acid in 100% by weight of the fatty acid mixture. In other words, castor oil is a fatty acid triglyceride whose main component is ricinoleic acid.

[0046] Coconut oil is a fatty acid triglyceride consisting of glycerin and a fatty acid mixture containing lauric acid and other fatty acids (such as myristic acid and palmitic acid), and the fatty acid mixture may contain 50 to 60% by weight of lauric acid per 100% by weight of the fatty acid mixture. In other words, coconut oil is a fatty acid triglyceride whose main component is lauric acid. Olive oil is a fatty acid triglyceride consisting of a fatty acid mixture containing oleic acid and other fatty acids (e.g., palmitic acid) and glycerin, and the fatty acid mixture may contain 60% to 80% by weight of oleic acid in 100% by weight of the fatty acid mixture. In other words, oleic oil is a fatty acid triglyceride whose main component is oleic acid.

[0047] The fatty acid glyceride is preferably one or more selected from the group consisting of castor oil, coconut oil, and olive oil, and particularly preferably castor oil. According to this configuration, the resulting expandable resin particles have the advantage that foamed molded articles can be produced in a shorter molding cycle.

[0048] The content of fatty acid glyceride in the present expanded resin beads (in other words, the amount of fatty acid glyceride applied per 100 parts by weight of the expandable resin bead body) is 0.02 to 0.04 parts by weight, and 0.03 parts by weight is particularly preferred, per 100 parts by weight of the expandable resin bead. When the content of fatty acid glyceride is 0.02 parts by weight or more per 100 parts by weight of the expandable resin bead, there is an advantage that the effect of the fatty acid glyceride in shortening the molding cycle is fully exerted. When the content of fatty acid glyceride is 0.04 parts by weight or less per 100 parts by weight of the expandable resin bead, the plasticization of the surface of the expanded beads obtained by expanding the expandable resin beads is within an appropriate range, and cracks present on the surface of the expanded beads are also within an appropriate range. As a result, there is an advantage that the expanded molded article finally obtained from the resulting expandable resin beads has sufficient strength (e.g., bending strength).

[0049] The method for applying the fatty acid glyceride to the surface of the expandable resin particle body is not particularly limited, and for example, the fatty acid glyceride can be applied to the surface of the expandable resin particle body by adding the fatty acid glyceride to the expandable resin particle body and mixing the resulting mixture. More specifically, a method can be used in which the expandable resin particle body and the fatty acid glyceride are thoroughly mixed using a mixing device such as a blender.

[0050] [Metal salts of higher fatty acids] The expandable resin particles preferably contain a metal salt of a higher fatty acid on the surface of the expandable resin particles. According to this configuration, the resulting expandable resin particles have the advantages of excellent blocking resistance and ease of uniform application to the particles. The term "blocking resistance" refers to the ability to suppress blocking of the expanded resin particles (expanded particles bonding together and agglomerating together) when the expandable resin particles are expanded to form expanded beads. In other words, the less blocking of the expanded resin particles when the expandable resin particles are expanded to form expanded beads, the more excellent the blocking resistance of the expandable resin particles.

[0051] By applying a metal salt of a higher fatty acid to the surface of the expandable resin particle body, it is possible to obtain expandable resin particles containing a metal salt of a higher fatty acid on the surface of the expandable resin particle. The metal salt of a higher fatty acid can also be considered an external additive.

[0052] The metal salt of a higher fatty acid applied to the expandable resin particle body is substantially entirely attached to the expandable resin particle body and is contained in the expandable resin particle (i.e., acts as an external additive). The amount of the metal salt of a higher fatty acid applied to the expandable resin particle body can be said to be the content of the metal salt of a higher fatty acid in the expandable resin particle.

[0053] The number of carbon atoms in the alkyl group of the metal salt of a higher fatty acid is preferably 12 to 20, and more preferably 16 to 18. According to this configuration, the expandable resin particles obtained have the advantages of being more excellent in blocking resistance and being easy to handle.

[0054] Specific examples of metal salts of higher fatty acids include (a) metal stearates such as zinc stearate, calcium stearate, magnesium stearate, and aluminum stearate; (b) metal oleates such as zinc oleate and magnesium oleate; and (c) metal laurates such as zinc laurate and calcium laurate. These metal salts of higher fatty acids may be used alone or in combination of two or more. Among these, metal stearates are more preferred because they have a particle size distribution suitable for handling and a melting point suitable for application.

[0055] Furthermore, the metal salt of a higher fatty acid is more preferably zinc stearate, since this is less likely to inhibit fusion between the expanded particles during molding.

[0056] The content of the metal salt of a higher fatty acid in the present expanded resin beads (in other words, the amount of the metal salt of a higher fatty acid applied to 100 parts by weight of the expandable resin bead body) is preferably 0.2 to 0.4 parts by weight, and particularly preferably 0.3 parts by weight, per 100 parts by weight of the expandable resin bead. When the content of the metal salt of a higher fatty acid is 0.2 parts by weight or more per 100 parts by weight of the expandable resin bead, there is an advantage that the blocking-reducing effect of the metal salt of a higher fatty acid is fully exerted. When the content of the metal salt of a higher fatty acid is 0.4 parts by weight or less per 100 parts by weight of the expandable resin bead, there is an advantage that the fusion properties when molding the expanded beads are less likely to be impaired.

[0057] The method for applying the metal salt of a higher fatty acid to the surface of the expandable resin particle body is not particularly limited, and for example, the metal salt of a higher fatty acid can be applied to the surface of the expandable resin particle body by adding the metal salt of a higher fatty acid to the expandable resin particle body and mixing the resulting mixture. More specifically, a method can be mentioned in which the expandable resin particle body and the metal salt of a higher fatty acid are thoroughly mixed using a mixing device such as a blender.

[0058] The metal salt of a higher fatty acid is preferably applied to the expandable resin particle body after the application of the fatty acid glyceride has been completed. The present inventors have independently found that, surprisingly, the blocking-reducing effect of the metal salt of a higher fatty acid is more pronounced when the metal salt of a higher fatty acid is applied to the expandable resin particle body after the application of the fatty acid glyceride has been completed, compared to when the metal salt of a higher fatty acid is applied to the expandable resin particle body before the application of the fatty acid glyceride.

[0059] [Additives, etc.] The expandable resin particles may further contain additives such as solvents, plasticizers, blowing agents, cell regulators, nucleating agents, flame retardants, and flame retardant assistants, or monomer components, to the extent that the effects of one embodiment of the present invention are not impaired.

[0060] The additives may be added to the expandable resin bead bodies during the production of the expandable resin bead bodies, for example. The timing and / or method of adding these additives to the expandable resin bead bodies is not particularly limited.

[0061] The solvent preferably has a boiling point of 50° C. or higher. Specific examples of the solvent include (a) aliphatic hydrocarbons having 6 or more carbon atoms, such as toluene, hexane, and heptane; and (b) alicyclic hydrocarbons having 6 or more carbon atoms, such as cyclohexane and cyclooctane. These solvents may be used alone or in combination of two or more.

[0062] The plasticizer can be added (used) during the production (polymerization) of the expandable resin particle body. The plasticizer is preferably a compound having a boiling point of 200°C or higher and generally used as a plasticizer. For example, one of the above-mentioned compounds may be used as the plasticizer, or two or more of them may be used in combination.

[0063] Specific examples of the cell regulator include (a) aliphatic bisamides such as methylene bisstearic acid amide and ethylene bisstearic acid amide; and (b) polyethylene wax. These cell regulators may be used alone or in combination of two or more.

[0064] Specific examples of the nucleating agent include methyl methacrylate copolymers, polyethylene wax, talc, fatty acid bisamides, ethylene-vinyl acetate copolymers, etc. Specific examples of fatty acid bisamides include methylene bisstearylamide, ethylene bisstearylamide, hexamethylene bispalmitic acid amide, ethylene bisoleic acid amide, etc. These nucleating agents may be used alone or in combination of two or more.

[0065] Specific examples of the flame retardant include: (a) halogenated aliphatic hydrocarbon compounds such as hexabromocyclododecane, tetrabromobutane, and hexabromocyclohexane; (b) brominated phenols such as tetrabromobisphenol A, tetrabromobisphenol F, and 2,4,6-tribromophenol; and (c) tetrabromobisphenol A-bis(2,3-dibromopropyl ether), tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether), and tetrabromobisphenol A-diglycerides. and (d) brominated phenol derivatives such as brominated styrene-butadiene block copolymers, brominated random styrene-butadiene copolymers, and brominated styrene-butadiene graft copolymers (e.g., EMERALD3000 manufactured by Chemtura or the copolymers described in JP-A-2009-516019). Other known flame retardants than those mentioned above can also be used as the flame retardant. These flame retardants may be used alone or in combination of two or more.

[0066] Specific examples of the flame retardant aid include cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, and 2,3-dimethyl-2,3-diphenylbutane. Known flame retardant aids other than those mentioned above can also be used as the flame retardant aid. These flame retardant aids may be used alone or in combination of two or more.

[0067] [Other external additives] The expandable resin particles may further contain known external additives, such as antiblocking agents, antistatic agents, water repellents, and fusion accelerators, on the surface of the expandable resin particles, to the extent that the effects of one embodiment of the present invention are not impaired. Examples of fusion accelerators include castor wax (hydroxystearic acid triglyceride), sorbitan stearate esters, and other higher fatty acid triesters, diesters, and monoesters, as well as sucrose esters, which are solid at room temperature. The timing of adding (using) these other external additives is not particularly limited. When the other external additive is solid at room temperature, it is preferable to add the external additive to the expandable resin particle body after the fatty acid glyceride has been applied, as this provides good fluidity. In this specification, the term "external additive" refers to an additive, particularly one contained on the surface of the expandable resin particles, or in other words, one applied to the surface of the expandable resin particle body.

[0068] [Mixing equipment] In one embodiment of the present invention, an external additive such as a fatty acid glyceride is added to the expandable resin particle body, and the resulting mixture is mixed to coat the surface of the expandable resin particle body. In this case, to coat the surface of the expandable resin particle body with the external additive such as a fatty acid glyceride as uniformly as possible, it is preferable to use a mixer capable of uniformly mixing the mixture of the expandable resin particle body and the external additive such as a fatty acid glyceride. Examples of such mixers include (a) mixers such as Super Mixers, Nauta Mixers, Universal Mixers, Proshare Mixers, Apex Mixers, Henschel Mixers, and Loedige Mixers; and (b) blenders such as ribbon blenders and tumbler blenders. Mixing conditions, such as the mixing time, can be adjusted taking into account (a) mixing capacity and (b) the type and application amount of the external additive such as a fatty acid glyceride.

[0069] [Method for producing expandable resin particles] The method for producing expandable resin particles according to one embodiment of the present invention is not particularly limited, and examples thereof include the following: a method in which expandable resin particles and a fatty acid glyceride (and, if necessary, additives and external additives) are introduced into a mixer and mixed to coat the surfaces of the resin particles with the fatty acid glyceride, thereby obtaining expandable resin particles. This method has the advantage of easily providing expandable resin particles that can provide foamed molded articles with excellent heat resistance and strength in a short molding cycle.

[0070] A method for producing expandable resin particles according to one embodiment of the present invention may be configured as follows: (i) A method for producing expandable resin particles, comprising a step of charging expandable resin particle bodies and a fatty acid glyceride (and, if necessary, additives and external additives) into a mixing device, mixing the expandable resin particle bodies and the fatty acid glyceride (and, if necessary, additives and external additives), and thereby coating the surfaces of the resin particles with a fatty acid glyceride (a fatty acid glyceride coating step).The above-described production method has the advantage of more easily providing expandable resin particles that can provide expanded molded articles with excellent heat resistance and strength in a short molding cycle.

[0071] The method for producing expandable resin particles according to one embodiment of the present invention may further include, after the fatty acid glyceride coating step, a step of adding a metal salt of a higher fatty acid (and, if necessary, additives and external additives) to the mixer and mixing the expandable resin particle bodies coated with at least the fatty acid glyceride with the metal salt of a higher fatty acid (and, if necessary, additives and external additives), thereby coating the surfaces of the expandable resin particle bodies coated with at least the fatty acid glyceride with a metal salt of a higher fatty acid (metal salt coating step). The above-described production method has the advantage of being able to provide, in a short molding cycle, expanded molded articles having excellent heat resistance and strength, and more easily provide expandable resin particles that can provide expandable resin particles having excellent blocking resistance.

[0072] However, the method for producing expandable resin particles according to one embodiment of the present invention is not particularly limited as long as it is a method capable of applying fatty acid glyceride to the surface of the expandable resin particle body in the amount (content) described above.

[0073] [3. Foam particles] The expanded beads according to one embodiment of the present invention are obtained by expanding the expandable resin beads described in the above section [2. Expandable Resin Beads].

[0074] The present expanded beads have the above-mentioned structure, and therefore have the advantage that expanded molded articles excellent in heat resistance and strength can be provided in a short molding cycle.

[0075] Here, when obtaining a foamed molded article from expandable resin beads, there is a case where the expandable resin beads are first expanded to obtain expanded beads, and then the expanded beads are molded to obtain a foamed molded article. Therefore, in the process of obtaining a foamed molded article from expandable resin beads, the expansion of the expandable resin beads is sometimes referred to as "pre-expanding" or "primary expanding," and the obtained expanded beads are sometimes referred to as "pre-expanded beads" or "primary expanded beads."

[0076] The expandable resin particles can be expanded by a conventional method, such as by using a cylindrical pre-expansion device and heating the expandable resin particles with a heating medium such as steam to expand them. The device used for expanding the expandable resin particles and the expansion conditions are not particularly limited and may be appropriately set depending on the composition of the expandable resin particle body and / or the desired expansion ratio, etc.

[0077] [4. Foam Molded Product] The expanded beads according to one embodiment of the present invention are obtained by molding the expanded beads described in the above section [3. Expanded Beads]. It can also be said that the expanded beads according to one embodiment of the present invention are obtained by heating and expanding the expanded beads described in the above section [3. Expanded Beads]. Here, the heating and expansion of the expanded beads in the process of obtaining a foamed molded article from the expanded beads is sometimes referred to as "secondary expansion."

[0078] The foamed molded article has the above-described structure and therefore has the advantages of excellent heat resistance and strength.

[0079] As a method for molding (heat-foaming) the expanded beads, a conventional method such as in-mold foam molding can be used. In-mold foam molding is a method in which expanded beads are filled into a mold, and a heating medium such as steam is blown into the mold to heat the expanded beads, thereby expanding the expanded beads and fusing the expanded beads together to obtain a foamed molded article. Molding of expanded beads by in-mold foam molding is sometimes referred to as in-mold molding. Expanded beads according to one embodiment of the present invention may be obtained by in-mold molding of the expanded beads described in the above section [3. Expanded Beads].

[0080] The apparatus used for molding (heat-foaming) the expanded beads and the molding (heat-foaming) conditions may be appropriately set depending on the composition of the expandable resin bead body, the composition of the expanded beads, and / or the desired expansion ratio, and are not particularly limited.

[0081] [5.Applications] A foamed molded article (the foamed molded article) obtained by molding expanded beads (the foamed beads) obtained by expanding the expandable resin beads (the foamed beads) has the advantages of excellent heat resistance and strength. The expandable resin beads, the foamed beads, and the foamed molded article also have the advantages of being lightweight and having excellent shock-absorbing and heat-insulating properties. Therefore, the expandable resin beads, the foamed beads, and the foamed molded article are suitable for use as packaging materials (trays) for food containers and the like, various packaging materials, building and civil engineering components, automotive components, insulation for relatively high-temperature piping, roof insulation, solar system insulation, water heater insulation, and the like. The expandable resin beads, the foamed beads, and the foamed molded article are particularly suitable for use as automotive components, insulation for relatively high-temperature piping, roof insulation, solar system insulation, water heater insulation, and the like. [Example]

[0082] EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0083] The manufacturing methods, measurement methods, and evaluation methods for the expanded beads and foamed molded articles in the examples and comparative examples are as follows. Furthermore, "parts" and "%" are by weight (parts by weight and % by weight) unless otherwise specified.

[0084] <Production of expanded beads> The expandable resin particles were placed in a pressurized pre-expansion machine (manufactured by Daikai Kogyo Co., Ltd., BHP). The expandable resin particles were heated using steam as a heating medium at a blown-in steam pressure of 0.08 MPa (gauge pressure) to 0.12 MPa (gauge pressure) to expand the expandable resin particles (pre-expansion / primary expansion). The resulting expanded particles were then left at room temperature for 24 hours to obtain expanded particles with an expansion ratio of 50 times.

[0085] <Measurement of expansion ratio of expanded beads and evaluation of expandability> The expandable resin particles were placed in a pressure type foaming machine BHP-300 (manufactured by Daikai Kogyo Co., Ltd.). Next, water vapor was introduced into the foaming machine at a blowing steam pressure of 0.1 MPa (gauge pressure). Next, the foaming machine was heated in a non-pressurized state for 30 seconds, and then the pressure inside the foaming machine was controlled to be between 0.015 MPa (gauge pressure) and 0.025 MPa (gauge pressure) to pressurize and foam the expandable resin particles, and the expandable resin particles were expanded until the expansion ratio reached 50 times as measured by a level meter. The expansion ratio of the obtained expandable resin particles was measured by the following procedures (1) to (3): (1) 10 g of the expanded particles was weighed out, and 1000 cm 3 (2) The volume of 10 g of expanded beads was measured from the scale of the measuring cylinder; (3) The expansion ratio of the expanded beads was calculated using the following formula: Foaming ratio (cm 3 / g): Volume of foam particles (cm 3 ) / 10g.

[0086] In the above-mentioned expansion process, the heating time from the start of pressure expansion until 50 times expanded particles were obtained was measured, and the expandability was evaluated according to the following criteria (3-level evaluation). A higher number indicates better expandability, and a number of 2 or higher was considered acceptable. If the expansion ratio stopped increasing (plateaued) without reaching 50 times after the start of pressure expansion, it was judged as "did not reach 50 times." 3:150 seconds or less Over 2:150 seconds It did not reach 1:50.

[0087] <Production of foam molded products and molding cycle> The foamed molded article was produced using a mold measuring 450 mm long x 300 mm wide x 25 mm deep and a molding machine (KR-57, manufactured by Daisen Co., Ltd.). Specifically, the process was as follows: (1) the foamed particles produced by the above-mentioned method were filled into a mold; (2) using steam as a heating medium, the pressure on the fixed mold side (referred to as the "fixed side") was 0.04 MPa (gauge pressure), the pressure on the movable mold side (referred to as the "moving side") was 0.07 MPa (gauge pressure), and in-mold foam molding was performed under the molding conditions of 2 seconds of mold preheating, 6 seconds of one-sided heating (fixed side), 4 seconds of reverse one-sided heating (moving side), 10 seconds of double-sided heating, and 3 seconds of supplemental heating, resulting in heating and foaming (secondary foaming) to an expansion ratio (bulk ratio) of 50 times; (3) water cooling was performed for 3 seconds, followed by cooling by air injection for 5 seconds, and then vacuum cooling. Vacuum cooling was terminated when the surface pressure reached 0.3 MPa (gauge pressure) or less; (4) the foamed molded product was removed from the mold to obtain a foamed molded product.

[0088] In the production of foamed molded articles, the time required for the processes from filling the mold with foamed beads to removing the foamed molded article from the mold (the above-mentioned processes (1) to (4)) was measured, and the obtained value was taken as the "molding cycle." Based on the obtained molding cycle, the molding cycle shortening ability was evaluated using the following criteria (4-point evaluation). The shorter the molding cycle, i.e., the higher the evaluation result number, the better the production efficiency, and a score of 2 or higher was considered acceptable. 4: The molding cycle is 300 seconds or less 3: The molding cycle is more than 300 seconds and less than 350 seconds. 2: The molding cycle is more than 350 seconds and less than 400 seconds. 1: The molding cycle is longer than 400 seconds.

[0089] <Heat resistance measurement> Heat resistance was measured using the following method. Five test pieces measuring 150 mm long x 150 mm wide x 25 mm thick were cut from the foam molded article obtained using the method described above in the section <Production of Foam Molded Articles and Molding Cycle>. The average longitudinal and lateral dimensions of the obtained test pieces were then measured and recorded as the "dimensions before heating [mm]." The test pieces were then placed in a 95°C dryer and heated for 178 hours. After heating, the average longitudinal and lateral dimensions of the test pieces were measured and recorded as the "dimensions after heating [mm]." The dimensions of the test pieces were measured at the center (75 mm from the edge) in both the longitudinal and lateral directions both before and after heating. The heat dimensional shrinkage was calculated using the following formula and evaluated according to the following criteria. The smaller the heat dimensional shrinkage, the less deformation of the foam molded article due to heat and the better its heat resistance; a value of 2 or higher was considered acceptable. Heat shrinkage rate [%] = (dimension before heating [mm] - dimension after heating [mm]) / dimension before heating [mm] x 100 3: The heat shrinkage rate is less than 0.5% 2: The heat shrinkage rate is 0.5% or more and less than 1% 1: Heat shrinkage exceeds 1% <Measurement of bending strength of foam molded product> Five test pieces measuring 300 mm long x 75 mm wide x 25 mm thick were cut from the foamed molded article obtained by the above method. The maximum stress of each test piece was measured when it was deformed at a rate of 10 mm / min in accordance with JIS K 7221. The average of the maximum stresses of the five test pieces was taken as the "average maximum stress" of the foamed molded article. Based on the obtained average maximum stress, the bending strength was evaluated using the following criteria (2-level evaluation). The higher the maximum stress, i.e., the higher the evaluation result number, the better the bending strength, with a score of 2 or higher being considered a pass. 2: Maximum point stress exceeds 0.40 MPa 1: Maximum point stress is 0.40 MPa or less Example 1 The expandable resin particle body was prepared by classifying Kanepearl (registered trademark) FQ (manufactured by Kaneka Corporation) through a sieve to obtain particles with a particle diameter of 0.6 mm to 1.12 mm. Kanepearl (registered trademark) FQ contains (i) a base resin and a blowing agent, (ii) the base resin contains styrene units, acrylonitrile units, and α-methylstyrene units in a ratio of styrene / acrylonitrile / α-methylstyrene = 71 / 24 / 5, and (iii) butane (a mixture of 75% normal butane and 25% isobutane) as a blowing agent in an amount of 4.5 parts by weight per 100 parts by weight of the expandable resin particle body.

[0090] 100 parts by weight of the expandable resin particle bodies were added to a Nauta Mixer (manufactured by Hosokawa Micron Corporation), followed by 0.03 parts by weight of castor oil (Ito Oil Mills, Special Castor Oil A) over 120 seconds, and the ingredients in the Nauta Mixer were stirred for 15 minutes. Then, 0.3 parts by weight of zinc stearate (NOF Corp., Zinc Stearate GF200) was added to the Nauta Mixer, and the ingredients in the Nauta Mixer were stirred for another 15 minutes. This procedure yielded expandable resin particles containing fatty acid glycerides and metal salts of higher fatty acids with a freezing point of 25°C or below on the surface of the expandable resin particles.

[0091] Expanded beads and expanded molded articles were produced according to the above-mentioned <Production of Expanded Beads> and <Production of Expanded Molded Articles and Molding Cycle>. The obtained expanded beads and expanded molded articles were subjected to the above-mentioned various measurements and evaluations, and the results are shown in Table 1, together with the composition of the expandable resin beads and other evaluations.

[0092] [Examples 2 to 12, Comparative Examples 1 to 9] Expandable resin beads, expanded beads, and foamed molded articles were obtained in the same manner as in Example 1, except that the type of expandable resin bead body, the type and application amount of fatty acid glyceride, and the type and application amount of metal salt of higher fatty acid were changed to the types and application amounts shown in Table 1 or Table 2. The obtained expanded beads and foamed molded articles were subjected to the various measurements and evaluations described above, and the results are shown in Table 1 or 2, along with the composition of the expandable resin beads and other evaluations.

[0093] In Example 4 and Comparative Example 5, palm oil (edible palm oil manufactured by Kaneka Corporation) was used as the fatty acid glyceride; in Example 5 and Comparative Example 6, olive oil (refined olive oil manufactured by OLEOMONTERREAL) was used; in Comparative Example 8, hardened castor oil (Kastarwax A manufactured by NOF Corporation) was used; and in Comparative Example 9, hydrogenated soybean oil (VT-10Z manufactured by Dainichi Chemical Industry Co., Ltd.) was used.

[0094] In Example 8, particles obtained by the following production method were used as the expandable resin particle bodies.

[0095] A 6 L autoclave equipped with a stirrer was charged with 110 parts by weight of water, 0.105 parts by weight of tricalcium phosphate (dispersant), 0.0075 parts by weight of sodium α-olein sulfonate (surfactant), 0.15 parts by weight of benzoyl peroxide and 0.29 parts by weight of t-butylperoxy-2-ethylhexyl monocarbonate as polymerization initiators, 2.0 parts by weight of tetrabromobisphenol-A-(2,3-dibromocyclododecane-2-methylpropyl) ether as a flame retardant, 1.1 parts by weight of dicumyl peroxide as a flame retardant aid, and 0.4 parts by weight of α-methylstyrene dimer as a chain transfer agent. The autoclave was then degassed using a vacuum pump until the pressure (gauge pressure) inside the autoclave reached 0.06 MPa.

[0096] Then, stirring of the raw materials charged in the autoclave was started using a stirrer. While stirring the raw materials, 76 parts by weight of styrene and 24 parts by weight of acrylonitrile were further charged into the autoclave. Then, the raw materials charged in the autoclave were stirred using a stirrer for 30 minutes. Then, the temperature inside the autoclave was raised to 90°C and maintained at 90°C for 6 hours to carry out polymerization (polymerization step). After completion of the polymerization step, 5 parts by weight of butane (a mixture consisting of 75% by weight of normal butane and 25% by weight of isobutane) was charged into the autoclave. Then, the temperature inside the autoclave was raised to 114°C and maintained at 114°C for 5 hours to carry out a blowing agent impregnation step. Then, the temperature inside the autoclave was cooled to 40°C, and the reaction product inside the autoclave was dehydrated and dried to obtain particles (expandable resin particle bodies). The obtained particles were classified using a sieve to obtain particles with particle diameters of 0.6 mm to 1.12 mm.

[0097] In Example 9, particles obtained by the following production method were used as the expandable resin particle bodies.

[0098] A 6-liter autoclave equipped with a stirrer was charged with 110 parts by weight of water, 0.105 parts by weight of tricalcium phosphate (dispersant), 0.0075 parts by weight of sodium α-olein sulfonate (surfactant), 0.15 parts by weight of benzoyl peroxide and 0.29 parts by weight of t-butylperoxy-2-ethylhexyl monocarbonate as polymerization initiators, 2.0 parts by weight of tetrabromobisphenol-A-(2,3-dibromocyclododecane-2-methylpropyl) ether as a flame retardant, 1.1 parts by weight of dicumyl peroxide as a flame retardant aid, and 0.4 parts by weight of α-methylstyrene dimer as a chain transfer agent. The autoclave was then degassed using a vacuum pump until the pressure (gauge pressure) inside the autoclave reached 0.06 MPa.

[0099] Then, stirring of the raw materials charged in the autoclave was started using a stirrer. While stirring the raw materials, 82 parts by weight of styrene and 15 parts by weight of acrylonitrile were further charged into the autoclave. Then, the raw materials charged in the autoclave were stirred using a stirrer for 30 minutes. Then, the temperature inside the autoclave was raised to 90°C and maintained at 90°C for 6 hours to carry out polymerization (polymerization step). During the polymerization step, 5 hours after the start of the polymerization step (start of maintaining at 90°C), 3 parts by weight of acrylonitrile was added to the autoclave. After the polymerization step was completed, 5 parts by weight of butane (a mixture consisting of 75% by weight of normal butane and 25% by weight of isobutane) was charged into the autoclave. Then, the temperature inside the autoclave was raised to 114°C, and the temperature inside the autoclave was maintained at 114°C for 5 hours to carry out a blowing agent impregnation step. The temperature inside the autoclave was then cooled to 40°C, and the reaction product inside the autoclave was dehydrated and dried to obtain particles (expandable resin particle bodies). The obtained particles were classified using a sieve to obtain particles with particle diameters of 0.6 mm to 1.12 mm.

[0100] In Example 10, particles with particle diameters of 0.8 mm to 1.4 mm obtained by classifying a product named Kanepearl (registered trademark) HM-M (manufactured by Kaneka Corporation) using a sieve were used as the expandable resin particle body. Kanepearl (registered trademark) HM-M contains (i) a base resin and a blowing agent, (ii) the base resin has styrene units, acrylonitrile units, and α-methylstyrene units in a weight ratio of styrene / acrylonitrile / α-methylstyrene = 45 / 20 / 35, and (iii) butane (a mixture of 75 wt% normal butane and 25 wt% isobutane) as a blowing agent in an amount of 4.5 parts by weight per 100 parts by weight of the expandable resin particle body.

[0101] In Example 11, particles with particle diameters of 0.6 mm to 1.12 mm obtained by classifying Kanepearl (registered trademark) HM5-B (manufactured by Kaneka Corporation) using a sieve were used as the expandable resin particle bodies. Kanepearl (registered trademark) HM5-B contains (i) a base resin and a blowing agent, (ii) the base resin contains styrene units, acrylonitrile units, and α-methylstyrene units in a weight ratio of styrene / acrylonitrile / α-methylstyrene = 0 / 30 / 70, and (iii) butane (a mixture of 75 wt% normal butane and 25 wt% isobutane) as a blowing agent in an amount of 4.5 parts by weight per 100 parts by weight of the expandable resin particle bodies.

[0102] In Example 12, particles with particle diameters of 0.6 mm to 1.4 mm obtained by classifying Kanepearl (registered trademark) LFR (manufactured by Kaneka Corporation) using a sieve were used as the expandable resin particle body. Kanepearl (registered trademark) LFR contains (i) a base resin and a blowing agent, (ii) the base resin has styrene units, acrylonitrile units, and α-methylstyrene units in a weight ratio of styrene / acrylonitrile / α-methylstyrene = 65 / 15 / 20, and (iii) butane (a mixture of 75 wt% normal butane and 25 wt% isobutane) as a blowing agent in an amount of 4.5 parts by weight per 100 parts by weight of the expandable resin particle body.

[0103] In Comparative Example 7, particles with particle diameters of 0.6 mm to 1.12 mm obtained by classifying Kanepearl (registered trademark) NSG-B (manufactured by Kaneka Corporation) using a sieve were used as the expandable resin particle body. Kanepearl (registered trademark) NSG-B contains (i) a base resin and a blowing agent, (ii) the base resin has styrene units, acrylonitrile units, and α-methylstyrene units in a weight ratio of styrene / acrylonitrile / α-methylstyrene = 100 / 0 / 0 (i.e., a styrene homopolymer), and (iii) the blowing agent contains butane (a mixture of 75% by weight of normal butane and 25% by weight of isobutane) in an amount of 5.5 parts by weight per 100 parts by weight of the expandable resin particle body, and cyclohexane in an amount of 2.1 parts by weight per 100 parts by weight of the expandable resin particle body.

[0104] [Table 1]

[0105] [Table 2] [Industrial Applicability]

[0106] One embodiment of the present invention can provide novel expandable resin particles that can produce foamed molded articles having excellent heat resistance and strength in a short molding cycle. Therefore, one embodiment of the present invention can be suitably used in fields such as insulation for pipes that are exposed to relatively high temperatures, roof insulation, automotive components, insulation for solar systems, and insulation for water heaters.

Claims

1. Expandable resin particles comprising a base resin and a blowing agent, the base resin contains a structural unit derived from acrylonitrile, and a structural unit derived from styrene and / or a structural unit derived from α-methylstyrene; 0.02 to 0.04 parts by weight of a fatty acid glyceride having a freezing point of 25°C or less is contained on the surface of 100 parts by weight of the expandable resin particles, The fatty acid glyceride is a fatty acid triglyceride containing ricinoleic acid as a main component, The expandable resin particles contain 15 to 30 parts by weight of the structural unit derived from acrylonitrile per 100 parts by weight of the base resin.

2. 2. The expandable resin particles according to claim 1, wherein the fatty acid glyceride is castor oil.

3. 3. The expandable resin particles according to claim 1, wherein 0.2 to 0.4 parts by weight of a metal salt of a higher fatty acid is contained on the surface of 100 parts by weight of said expandable resin particles.

4. Expanded particles obtained by expanding the expandable resin particles according to any one of claims 1 to 3.

5. A foamed molded article obtained by molding the foamed beads according to claim 4.

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