Foamable styrenic resin particle, styrenic resin foam particle, and styrenic resin foam molding

Abstract

To provide foamable styrenic resin foam particles which enable provision of a styrenic resin foam molding excellent in heat insulation performance and heat resistance performance, are excellent in moldability of the foam molding, can suppress mutual adhesion of foam particles during foaming, and can achieve a molding quality excellent in fusion.SOLUTION: Foamable styrenic resin foam particles contain a resin particle matrix containing a styrenic base material resin, a radiation heat transfer inhibitor, and a foaming agent, and zinc stearate externally added to the resin particle matrix. The base material resin contains at least a copolymer having a structural unit derived from a (meth)acrylic acid and a structural unit derived from styrene, 0.12 pts.wt. or more and 0.30 pts.wt. or less of the zinc stearate is contained with respect to 100 pts.wt. of the resin particle matrix, and a content of the externally added fatty acid glyceride or vegetable oil is 0 pts.wt. or more and less than 0.05 pts.wt. with respect to 100 pts.wt. of the resin particle matrix.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to expandable styrene-based resin particles, expanded styrene-based resin particles, and expanded molded styrene-based resin articles. [Background technology]

[0002] Foam molded articles using polystyrene as a base resin are lightweight and have excellent heat insulating properties, and are therefore widely used as heat insulating materials for housing, etc. One method for imparting heat insulating properties to such foam molded articles is to incorporate a radiation heat transfer inhibitor such as graphite into the foam molded articles (e.g., Patent Documents 1 to 3).

[0003] On the other hand, from the viewpoint of heat resistance, polystyrene foam molded products have a large dimensional change rate when heated, which may make them difficult to use in contact with high-temperature parts (for example, the surface of a hot water tank, etc.) One approach to address this problem is to use a copolymer of styrene and other monomers as the base resin, thereby reducing the dimensional change rate of the foam molded product and imparting heat resistance.

[0004] Furthermore, it is known that expandable styrene-based resin particles have a wide range of applications because they can be molded into foams of various shapes depending on the mold used. To take advantage of this advantage, it is preferable that the expandable styrene-based resin particles have excellent moldability. For example, it is desirable that the expandable styrene-based resin particles are capable of consistently producing high-quality foamed molded products without being significantly affected by the conditions during pre-expansion or molding. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2019 / 198790 [Patent Document 2] Japanese Patent Publication No. 2020-033481 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-148558 Summary of the Invention [Problem to be solved by the invention]

[0006] Patent Document 3 describes expandable styrene-based resin particles containing a styrene-(meth)acrylic acid copolymer, polystyrene, graphite, and a blowing agent. These expandable styrene-based resin particles are obtained by impregnating styrene-based polymer seed particles containing a styrene-(meth)acrylic acid copolymer and graphite with styrene, polymerizing the particles, and then impregnating the particles with a blowing agent. This is believed to result in a styrene-based resin expanded bead molding with few interparticle gaps and a good shape. On the other hand, when expandable styrene-based resin particles are produced by melt-kneading only a styrene-(meth)acrylic acid copolymer and a polystyrene resin without impregnating the seed particles with styrene and polymerizing the particles, either no expanded molded article can be formed or only an expanded molded article with large interparticle gaps is obtained, resulting in significantly poor moldability (Comparative Examples 1-3).

[0007] The present disclosure aims to provide expandable styrene-based resin particles and the like that can provide a styrene-based resin foam molded article having excellent heat insulating properties and heat resistance, and that have excellent foam moldability, can suppress adhesion of foam particles to each other during foaming, and can achieve a molded article quality with excellent fusion. [Means for solving the problem]

[0008] The present inventors have found that the fusion properties of foamed molded articles can be improved by externally adding a predetermined amount of zinc stearate to expandable styrene-based resin particles containing a (meth)acrylic acid-modified styrene-based resin, even though the external addition of a large amount of zinc stearate is generally thought to cause a decrease in the fusion properties of foamed molded articles.As a result, they have succeeded in providing expandable styrene-based resin particles that can achieve high-quality molded articles with excellent fusion properties, even though they are substantially free of fusion promoters such as vegetable oils as external additives.

[0009] One aspect of the present disclosure is expandable styrene-based resin particles comprising a resin particle matrix containing a styrene-based base resin, a radiation heat transfer inhibitor, and a blowing agent, and zinc stearate externally added to the resin particle matrix, wherein the base resin contains a copolymer having at least a structural unit derived from (meth)acrylic acid and a structural unit derived from styrene, and the expandable styrene-based resin particles contain 0.12 to 0.30 parts by weight of the zinc stearate per 100 parts by weight of the resin particle matrix, and the content of the externally added fatty acid glyceride or vegetable oil is 0 to 0.05 parts by weight per 100 parts by weight of the resin particle matrix.

[0010] Preferably, the content of the structural units derived from (meth)acrylic acid in the entire copolymer is 2% by weight or more and 20% by weight or less.

[0011] Preferably, the radiation heat transfer inhibitor includes a carbon-based radiation heat transfer inhibitor.

[0012] Preferably, the resin particle matrix further contains a brominated flame retardant.

[0013] Preferably, the laser scattering intensity per unit solution concentration of the radiation heat transfer inhibitor contained in the expandable styrene resin particles is 5.0 {% / (mg / ml)} / wt % or more.

[0014] Preferably, the copolymer is contained uniformly throughout the expandable styrene resin particles.

[0015] Preferably, the expandable styrene resin particles are pre-expanded 50 times and then molded to obtain a foamed molded article, which has a thermal conductivity of 0.030 W / mK or less.

[0016] Preferably, the resin particle matrix is ​​obtained by impregnating pellets of a resin composition containing the base resin and the radiant heat transfer inhibitor with the foaming agent.

[0017] Preferably, the resin particle matrix is ​​a pellet of a resin composition containing the base resin, the radiant heat transfer inhibitor, and the foaming agent.

[0018] One aspect of the present disclosure is expanded styrene-based resin beads obtained by expanding the expandable styrene-based resin beads described above.

[0019] One aspect of the present disclosure is a styrene-based resin foam molded article obtained by molding the above-described styrene-based resin foam beads. [Effects of the Invention]

[0020] According to the present disclosure, it is possible to provide a styrene-based resin foam molded article having excellent heat insulating properties and heat resistance, and to provide expandable styrene-based resin particles and the like that have excellent foam moldability, can suppress adhesion of foam particles to each other during foaming, and can achieve molded article quality with excellent fusion. DETAILED DESCRIPTION OF THE INVENTION

[0021] <Expandable styrene resin particles> The expandable styrene-based resin particles according to one embodiment of the present disclosure comprise a resin particle matrix containing a styrene-based base resin, a radiant heat transfer inhibitor, and a blowing agent, and zinc stearate externally added to the resin particle matrix, and have various properties.

[0022] <Resin particle matrix> The resin particle matrix in the present disclosure refers to resin particles to which zinc stearate as an external additive is applied, and includes a styrene-based base resin, a radiation heat transfer inhibitor, and a foaming agent.

[0023] <Styrene-based base resin> The styrene-based base resin contained in the resin particle matrix contains a copolymer having at least structural units derived from (meth)acrylic acid and structural units derived from styrene (hereinafter, sometimes referred to as a first styrene-based resin). That is, the copolymer is a styrene-(meth)acrylic acid copolymer. The content of structural units derived from (meth)acrylic acid in the first styrene-based resin is not particularly limited, but is usually 2 to 20% by weight, preferably 3 to 15% by weight, and more preferably 4 to 12% by weight. The first styrene-based resin may be a single resin or a combination of two or more resins having different ratios of structural units derived from (meth)acrylic acid. The first styrene-based resin preferably has a total of 50% by weight or more of structural units derived from (meth)acrylic acid and structural units derived from styrene. The first styrene-based resin may have structural units derived from other monomers other than the structural units derived from (meth)acrylic acid and the structural units derived from styrene. In this specification, "(meth)acrylic acid" means methacrylic acid and / or acrylic acid.

[0024] The content of the first styrene-based resin in the entire base resin is not particularly limited, but is preferably 70% by weight or more. The content may be 80% by weight or more, 90% by weight or more, or 100% by weight (total amount). By making the content of the first styrene-based resin 70% by weight or more, a foamed molded article with excellent heat resistance can be obtained.

[0025] The Vicat softening temperature of the first styrene-based resin is not particularly limited, but is preferably 110° C. or higher and 130° C. or lower, and more preferably 110° C. or higher and 125° C. or lower. When the Vicat softening temperature of the first styrene-based resin is 110° C. or higher, a foam molded article with excellent heat resistance can be obtained, and when it is 130° C. or lower, a good foam molded article can be obtained using a general EPS molding machine.

[0026] The base resin contains a first styrene-based resin as an essential component, but may further contain a resin other than the first styrene-based resin. The resin other than the first styrene-based resin may be one type only, or two or more types. The resin is preferably a styrene-based resin of a type different from the first styrene-based resin. In particular, among styrene-based resins, at least one selected from the group consisting of a styrene homopolymer, a styrene-acrylonitrile copolymer, a styrene-methyl(meth)acrylate copolymer, and a styrene-butyl(meth)acrylate copolymer is preferred because it is relatively inexpensive, can be foam-molded using low-pressure steam or the like without using a special method, and has an excellent balance of heat insulation, flame retardancy, and cushioning properties.

[0027] In one preferred embodiment, the base resin further contains a second styrene-based resin different from the first styrene-based resin and having a glass transition temperature of 95°C or higher and 110°C or lower. Examples of the second styrene-based resin include the above-mentioned styrene homopolymer, styrene-acrylonitrile copolymer, styrene-methyl (meth)acrylate copolymer, and styrene-butyl (meth)acrylate copolymer. The glass transition temperature of the second styrene-based resin is preferably 95°C or higher and 110°C or lower, and more preferably 100°C or higher and 110°C or lower. If the glass transition temperature of the second styrene-based resin is 95°C or higher, heat resistance is not impaired, and if it is 110°C or lower, moldability is not impaired.

[0028] In one preferred embodiment, the second styrene-based resin contains a styrene homopolymer. Also, in one preferred embodiment, the base resin is composed of the first styrene-based resin and the second styrene-based resin.

[0029] <Radiation heat transfer inhibitor> The expandable styrene-based resin particles according to one embodiment of the present disclosure contain a radiation heat transfer inhibitor. Specifically, the radiation heat transfer inhibitor is contained in a resin particle matrix. Therefore, by using the expandable styrene-based resin particles according to the present disclosure, a foamed molded article having high thermal insulation properties can be obtained. Here, the term "radiation heat transfer inhibitor" refers to a substance that has the property of reflecting, scattering, or absorbing light in the infrared region (e.g., a wavelength region of approximately 0.8 μm to 100 μm).

[0030] The radiation heat transfer inhibitor is not particularly limited, but carbon-based radiation heat transfer inhibitors are preferred in terms of dispersibility in polystyrene-based resins and cost. Examples of carbon-based radiation heat transfer inhibitors include graphite, carbon black, activated carbon, graphene, and carbon nanotubes, with graphite being more preferred. That is, it is particularly preferred that the radiation heat transfer inhibitor contains graphite as a main component. Here, "contains as a main component" refers to a content ratio of more than 50 wt%. In a preferred embodiment, the content ratio of graphite relative to the entire radiation heat transfer inhibitor is more than 50 wt%, more preferably 80 wt% or more, even more preferably 90 wt% or more, and particularly preferably 100 wt% (total amount).

[0031] Examples of the graphite include flake graphite, amorphous graphite, spherical graphite, and artificial graphite. In the present disclosure, the term "flake" also includes scaly, thin, or plate-like graphite. These graphites can be used alone or in combination of two or more. Among these, a graphite mixture containing flake graphite as a main component is preferred, and flake graphite is more preferred, because of its high radiation heat transfer suppression effect.

[0032] Examples of radiation heat transfer inhibitors other than carbon-based radiation heat transfer inhibitors include aluminum-based compounds, zinc-based compounds, magnesium-based compounds, titanium-based compounds, heat ray reflectors, metal sulfates, antimony-based compounds, metal oxides, heat ray absorbers, metal particles, etc. Specific examples include titanium oxide, aluminum, copper, etc.

[0033] The above-mentioned radiation heat transfer inhibitors may be used alone or in combination of two or more.

[0034] The average particle size of the radiation heat transfer inhibitor in the present disclosure is not particularly limited, but is preferably 12 μm to 2 μm, more preferably 10 μm to 2 μm, and even more preferably 7 μm to 2 μm. By setting the average particle size to 12 μm or less, the moldability during foam molding of the resin particles is improved, and by setting the average particle size to 2 μm or more, the resin particles can be handled without impairing their handleability. The average particle size of the radiation heat transfer inhibitor referred to here refers to the particle size D50 (i.e., 50% volume cumulative particle size) at which the cumulative volume of the total particles is 50% as measured and analyzed by a laser diffraction scattering method based on the Mie theory in accordance with ISO 13320:2009 and JIS Z8825-1.

[0035] The content of the radiation heat transfer inhibitor is not particularly limited, but may be, for example, 2 to 20 parts by weight per 100 parts by weight of the base resin. The radiation heat transfer inhibitor may be 3 to 15 parts by weight, 3 to 10 parts by weight, or 4 to 10 parts by weight per 100 parts by weight of the base resin. The content of the radiation heat transfer inhibitor relative to the total expandable styrene-based resin particles may be 2.0 to 10.0 parts by weight, 3.0 to 8.0 parts by weight, or the like. When the content of the radiation heat transfer inhibitor is 20 parts by weight or less, it becomes easier to control the expansion ratio during production of a foamed molded article, making it easier to achieve a high expansion ratio. When the content of the radiation heat transfer inhibitor is 2 parts by weight or more, desired thermal insulation properties can be achieved.

[0036] <Laser scattering intensity> In the expandable styrene-based resin particles according to one embodiment of the present disclosure, the laser scattering intensity per unit solution concentration of the radiation heat transfer inhibitor contained in the expandable styrene-based resin particles is 5.0 {% / (mg / ml)} / wt% or more. In this embodiment, the laser scattering intensity being equal to or greater than a predetermined value ensures good dispersibility of the radiation heat transfer inhibitor in the resin particles. As a result, the thermal conductivity of the foamed molded article is reduced and the thermal insulation properties are improved. Specific methods for measuring the laser scattering intensity are described in the Examples below.

[0037] <Foaming agent> The blowing agent used in the present disclosure is not particularly limited. However, from the viewpoints of achieving a good balance between foaming ability and product life and facilitating high foaming ratios in actual use, volatile blowing agents are preferred, saturated hydrocarbons are more preferred, and aliphatic hydrocarbons having 4 or 5 carbon atoms are even more preferred. Examples of such hydrocarbons include normal butane, isobutane, normal pentane, isopentane, neopentane, and cyclopentane. These blowing agents may be used alone or in combination of two or more. In one preferred embodiment, the blowing agent contains an aliphatic hydrocarbon having 4 carbon atoms and / or an aliphatic hydrocarbon having 5 carbon atoms. In another preferred embodiment, the blowing agent contains at least an aliphatic hydrocarbon having 5 carbon atoms, and the content of the aliphatic hydrocarbon having 5 carbon atoms relative to the total blowing agent is 50% by weight or more, and more preferably 70% by weight or more.

[0038] The content of the foaming agent is not particularly limited, but for example, assuming a mixture consisting of all components constituting the resin particle matrix except for the foaming agent, the content of the foaming agent is 4.0 parts by weight to 10.0 parts by weight per 100 parts by weight of the mixture, preferably 4.5 parts by weight to 9.5 parts by weight, more preferably 5.0 parts by weight to 9.0 parts by weight per 100 parts by weight of the mixture.

[0039] <Zinc stearate> In general, in the case of expandable styrene-based resin particles, an anti-blocking agent is often added externally to the resin particles to prevent blocking, which occurs when the resin softens due to steam heating during pre-expansion and the expanded particles stick to each other. Furthermore, additives (fusion promoters) such as fatty acid triglycerides, fatty acid diglycerides, fatty acid monoglycerides, and vegetable oils are added externally to promote fusion between the expanded particles during molding. Because the anti-blocking agent and the fusion promoter have opposing mechanisms of action, they are generally used in combination. In simple styrene-based resins, the external addition of a large amount of zinc stearate inhibits fusion during in-mold molding. However, we have found that the external addition of a large amount of zinc stearate in (meth)acrylic acid-modified styrene-based resin systems improves fusion during in-mold molding and minimizes the amount of fusion promoter used.

[0040] The expandable styrene-based resin particles according to one embodiment of the present disclosure contain zinc stearate externally added to the resin particle matrix. The amount of the externally added zinc stearate is typically 0.12 to 0.30 parts by weight (0.12 to 0.30 parts by weight) per 100 parts by weight of the resin particle matrix. Alternatively, the amount of the externally added zinc stearate may be 0.13 to 0.28 parts by weight, 0.14 to 0.26 parts by weight, or 0.15 to 0.25 parts by weight, per 100 parts by weight of the resin particle matrix.

[0041] <Fusion accelerator> In the expandable styrene-based resin particles according to one embodiment of the present disclosure, the content of externally added fatty acid glyceride or vegetable oil (hereinafter sometimes abbreviated as fusion accelerator) is zero or very small, typically less than 0.05 parts by weight per 100 parts by weight of the resin particle matrix. The content of externally added fatty acid glyceride or vegetable oil is preferably less than 0.04 parts by weight, more preferably less than 0.02 parts by weight, and even more preferably 0 part by weight (not present), per 100 parts by weight of the resin particle matrix. Fatty acid glycerides include fatty acid triglycerides, fatty acid diglycerides, and fatty acid monoglycerides. Examples of fatty acids constituting fatty acid glycerides include fatty acids having 10 to 30 carbon atoms, such as lauric acid, stearic acid, and linoleic acid. Examples of vegetable oils include castor wax, castor oil, and olive oil.

[0042] <Other ingredients> The expandable styrene-based resin particles according to one embodiment of the present disclosure may contain other components within a range that does not impair the performance of the particles. For example, the resin particle matrix may contain a bromine-based flame retardant or a heat stabilizer.

[0043] The brominated flame retardant is not particularly limited, and various brominated flame retardants can be used. In one preferred embodiment, a brominated flame retardant is used that has a 1% weight loss temperature in thermogravimetric analysis of 210°C or higher and 280°C or lower and a bromine content of 60% by weight or higher but lower than 70% by weight.

[0044] Examples of brominated flame retardants include brominated bisphenol compounds, brominated styrene-butadiene copolymers, and brominated isocyanurate compounds. Specific examples of brominated bisphenol compounds include 2,2-bis[4-(2,3-dibromo-2-methylpropoxy)-3,5-dibromophenyl]propane (also known as tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether)), 2,2-bis[4-(2,3-dibromopropoxy)-3,5-dibromophenyl]propane (also known as tetrabromobisphenol A-bis(2,3-dibromopropyl ether)), and the like. Brominated styrene-butadiene copolymers include brominated styrene-butadiene block copolymers, brominated random styrene-butadiene copolymers, and brominated styrene-butadiene graft copolymers. Examples of brominated isocyanurate compounds include tris(2,3-dibromopropyl)isocyanurate, etc. Other examples include tetrabromocyclooctane, etc. These brominated flame retardants may be used alone or in combination of two or more.

[0045] The amount of brominated flame retardant used is not particularly limited, but for example, the content of the brominated flame retardant in the expandable styrene-based resin particles produced can be 0.8% by weight or more and 5.0% by weight or less relative to the total resin particles. When the content of the brominated flame retardant is 0.8% by weight or more, the desired flame retardant performance can be achieved. When the content of the brominated flame retardant is 5.0% by weight or less, adverse effects on foam moldability can be suppressed.

[0046] The inclusion of a heat stabilizer can suppress deterioration of flame retardancy due to decomposition of the brominated flame retardant during the manufacturing process and deterioration of the expandable styrene-based resin particles. The heat stabilizer is not particularly limited, and is appropriately selected depending on the type of base resin, the type and content of the blowing agent, the type and content of inorganic substances such as radiant heat transfer inhibitors, the type and content of the brominated flame retardant, etc. Examples of heat stabilizers include hindered amine compounds, phosphorus-based compounds, and epoxy compounds, with hindered amine compounds and phosphorus-based compounds being particularly preferred. These heat stabilizers may be used alone or in combination of two or more.

[0047] Examples of further components other than the bromine-based flame retardant and heat stabilizer include a radical generator, a processing aid, a light resistance stabilizer, a nucleating agent, a foaming aid, an antistatic agent, and a colorant such as a pigment.

[0048] <Uniformity of copolymers containing structural units derived from (meth)acrylic acid and structural units derived from styrene> In one preferred embodiment, the expandable styrene-based resin particles uniformly contain a copolymer having structural units derived from (meth)acrylic acid and structural units derived from styrene throughout the entire particle. The resin particles uniformly containing the copolymer can be obtained, for example, by producing the expandable styrene-based resin particles by the "melt-kneading method" described below. On the other hand, resin particles produced by a method of impregnating styrene into styrene-based polymer seed particles and polymerizing them do not contain the copolymer uniformly because the content of the copolymer discontinuously changes between the seed particles and the polymer (styrene resin).

[0049] <Method of manufacturing resin particle base> The method for producing the resin particle matrix constituting the expandable styrene-based resin particles according to one embodiment of the present disclosure is not particularly limited, but is preferably a melt-kneading method in which a base resin and various components are melt-kneaded using an extruder and then cut into particles. By using the melt-kneading method, the uniformity of the (meth)acrylic acid component units in the resin particles is improved. Furthermore, the radiation heat transfer inhibitor is more uniformly dispersed throughout the resin particles. Examples of the melt-kneading method include the following first and second melt-kneading methods.

[0050] In the first melt-kneading method, the base resin, the radiation heat transfer inhibitor, and optionally other components are first melt-kneaded in an extruder. Next, a blowing agent is dissolved and dispersed in the molten mixture using the extruder or a mixing device installed downstream of the extruder. The molten mixture containing the blowing agent is then extruded through a die with multiple small holes installed downstream of the extruder or the mixing device into a cutter chamber filled with pressurized circulating water. Immediately after extrusion, the molten mixture is cut with a rotating cutter and cooled and solidified using the pressurized circulating water. This results in the desired resin particle matrix (pellets). The melt-kneading using the extruder can be performed using a single extruder, multiple extruders connected together, or a second kneading device such as an extruder, a static mixer, or a mixer without a screw. This can be selected as appropriate.

[0051] In the second melt-kneading method, a base resin, a radiation heat transfer inhibitor, and other components, if necessary, are melt-kneaded in an extruder. The melt-kneaded mixture is then extruded through a die with many small holes and cut with a cutter to obtain resin particles (pellets) (cold cut method or hot cut method). The resin particles are then suspended in water and a blowing agent is added to the resin particles. This results in the desired resin particle matrix. The average particle diameter of the resin particle matrix is ​​preferably 2 mm or less, more preferably 1.5 mm or less. An average particle diameter of 2 mm or less ensures sufficient mold filling of the expanded particles after pre-expansion.

[0052] In the melt-kneading method described above, the resin temperature of the molten resin during melt-kneading is preferably 130 to 250°C, more preferably 140 to 240°C, and even more preferably 150 to 220°C. If the resin temperature is 130°C or higher, the resin viscosity decreases, allowing for sufficient melt-kneading in the extruder. If the resin temperature exceeds 250°C, there is a risk of decomposition of the styrene-based resin and, if necessary, additives used in combination, which may result in deterioration of the expandable styrene-based resin particles and lead to a decrease in expandability.

[0053] The die used in the melt-kneading method is not particularly limited, but examples thereof include those preferably having small holes with a diameter of 0.3 mm to 2.0 mm, more preferably 0.35 mm to 1.0 mm.

[0054] The cutting device for cutting the molten resin extruded into the circulating pressurized cooling water is not particularly limited, but examples include a device in which the resin particles are cut by a rotary cutter that comes into contact with a die to form small pellets, and then the pellets are transported to a centrifugal dehydrator to be dehydrated and collected without foaming in the circulating pressurized cooling water.

[0055] The conditions for the pressurized circulating cooling water should be adjusted depending on the type and content of the resin, additives, blowing agent, etc. used, but conditions that suppress foaming of the molten resin extruded from the die and allow stable cutting with a cutter are preferred. Specifically, the temperature condition for the pressurized circulating cooling water is preferably 50°C to 99°C, more preferably 55°C to 95°C, and even more preferably 60°C to 90°C. The pressure condition depends on the type of blowing agent used, but is preferably 0.5MPa to 2.0MPa, more preferably 0.6MPa to 1.8MPa, and even more preferably 0.7MPa to 1.6MPa.

[0056] <Method for producing expandable styrene resin particles> The expandable styrene-based resin particles according to one embodiment of the present disclosure can be produced by externally adding a predetermined amount of zinc stearate to the resin particle matrix. The method for externally adding zinc stearate is not particularly limited, and examples thereof include a method in which zinc stearate is added to the resin particle matrix, followed by stirring and mixing, to coat the surface of the resin particle matrix with zinc stearate. If necessary, an external additive other than zinc stearate may be used in combination.

[0057] <Method of manufacturing styrene resin foam molded article> A known method can be used to produce a foamed molded article using the expandable styrene-based resin particles according to one embodiment of the present disclosure. For example, the expandable styrene-based resin particles are pre-expanded to produce expanded styrene-based resin particles. The expanded particles are then molded using a molding machine to produce a foamed styrene-based resin article.

[0058] <Styrene-based resin foam particles> Expanded styrene resin beads can be produced, for example, by expanding expandable styrene resin beads 10 to 110 times with heated steam. The expanded beads are optionally cured for a certain period of time before being used for molding. The resulting expanded beads are molded (e.g., molded in a mold) with steam using a known molding machine to produce a foamed molded article. Depending on the shape of the mold used, molded articles with complex shapes and block-like molded articles can be obtained.

[0059] <Characteristics of styrene resin foam molded products> In one embodiment of the present disclosure, the thermal conductivity of a foamed molded article obtained by pre-expanding the expandable styrene-based resin particles 50 times and molding the pre-expanded resin has a value of 0.030 W / mK or less. The thermal conductivity can be measured at an average temperature of 23°C and a temperature difference of 20°C using a heat flow meter method in accordance with JIS A1412-2:1999.

[0060] The styrene resin foam molded article having the above-mentioned properties is suitably used as a heat insulating material for houses, warehouses, hot water tanks, etc., but is not limited to this use.

[0061] As described above, the expandable styrene-based resin particles according to one embodiment of the present disclosure have a specific range of externally added zinc stearate content, which provides the excellent effect of realizing a molded article of excellent fusion quality while substantially not containing a fusion promoter such as vegetable oil. The reason for the improved fusion properties of the foamed molded article is unclear, but it is speculated that this is due to the inclusion of a copolymer component having structural units derived from (meth)acrylic acid and structural units derived from styrene, which increases the glass transition temperature of the resin and increases the amount of heat required for foam molding.

[0062] The present disclosure includes the following items (1) to (11).

[0063] (1) Expandable styrene-based resin particles comprising a resin particle matrix containing a styrene-based base resin, a radiation heat transfer inhibitor, and a blowing agent, and zinc stearate externally added to the resin particle matrix, the base resin contains a copolymer having at least a structural unit derived from (meth)acrylic acid and a structural unit derived from styrene, The zinc stearate is contained in an amount of 0.12 parts by weight or more and 0.30 parts by weight or less relative to 100 parts by weight of the resin particle base material, Expandable styrene-based resin particles, wherein the content of externally added fatty acid glyceride or vegetable oil is 0 part by weight or more and less than 0.05 part by weight per 100 parts by weight of the resin particle matrix.

[0064] (2) The expandable styrene-based resin particles according to (1), wherein the content of the structural units derived from (meth)acrylic acid relative to the entire copolymer is 2% by weight or more and 20% by weight or less.

[0065] (3) The expandable styrene-based resin particles according to (1) or (2), wherein the radiation heat transfer inhibitor includes a carbon-based radiation heat transfer inhibitor.

[0066] (4) The expandable styrene-based resin particles according to any one of (1) to (3), wherein the resin particle matrix further contains a brominated flame retardant.

[0067] (5) Expandable styrene-based resin particles according to any one of (1) to (4), in which the laser scattering intensity per unit solution concentration of the radiation heat transfer inhibitor contained in the expandable styrene-based resin particles is 5.0 {% / (mg / ml)} / wt% or more.

[0068] (6) The expandable styrene-based resin particles according to any one of (1) to (5), wherein the copolymer is uniformly contained throughout the expandable styrene-based resin particles.

[0069] (7) The expandable styrene-based resin particles according to any one of (1) to (6), wherein the expandable styrene-based resin particles are pre-expanded 50 times and then molded to obtain a foamed molded article having a thermal conductivity of 0.030 W / mK or less.

[0070] (8) The expandable styrene-based resin particles according to any one of (1) to (7), wherein the resin particle base is obtained by impregnating pellets of a resin composition containing the base resin and the radiant heat transfer inhibitor with the blowing agent.

[0071] (9) The expandable styrene-based resin particles according to any one of (1) to (7), wherein the resin particle matrix is ​​a pellet of a resin composition containing the base resin, the radiant heat transfer inhibitor, and the blowing agent.

[0072] (10) Expanded styrene resin particles obtained by expanding the expandable styrene resin particles according to any one of (1) to (9).

[0073] (11) A foamed styrene resin molded article obtained by molding the foamed styrene resin beads according to (10). [Example]

[0074] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0075] First, the raw materials used in each experimental example are listed below. <Styrene-based resin> (A1) Methacrylic acid-modified styrene resin [PS Japan Co., Ltd., MR100] (A2) Styrene homopolymer [PS Japan Co., Ltd., 680] (A1) corresponds to the first styrene-based resin, and (A2) corresponds to the second styrene-based resin.

[0076] <Radiation heat transfer inhibitor> (B) Graphite [Marutoyo Foundry Manufacturing Co., Ltd., flake graphite SGP-40B]

[0077] <Brominated flame retardants> (C) 2,2-bis[4-(2,3-dibromo-2-methylpropoxy)-3,5-dibromophenyl]propane [manufactured by Daiichi Kogyo Seiyaku Co., Ltd., SR-130, bromine content = 66 wt%]

[0078] <Heat stabilizer> (D1) Tetrakis(2,2,6,6-tetramethylpiperidyloxycarbonyl)butane [ADEKA Corporation, LA-57] (D2) Bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite [ADEKA Corporation, PEP-36]

[0079] <Foaming agent> (E1) Normal pentane [SK Sangyo Co., Ltd.] (E2) Isopentane [SK Industries Co., Ltd.]

[0080] <External additives> (F1) Zinc stearate [NOF Corporation, Zinc Stearate GF200] (F2) Magnesium stearate [Fujifilm Wako Pure Chemical Industries, Ltd., reagent product]

[0081] <Mixture of brominated flame retardants and heat stabilizers> Brominated flame retardant (C), heat stabilizers (D1) and (D2) were mixed in a mixer to obtain a mixture of brominated flame retardant and heat stabilizer (G) (hereinafter sometimes abbreviated as mixture (G)). The weight ratio of each material (wt%) was (C):(D1):(D2) = 94.7:2.1:3.2 ((C) + (D1) + (D2) = 100 wt%).

[0082] (Experimental Example 1) 1. Preparation of resin particle matrix for expandable styrene resin particles The styrene-based resin (A1), styrene-based resin (A2), radiation heat transfer inhibitor (B), and mixture (G) were fed into a tandem two-stage extruder consisting of a 40 mm diameter co-rotating twin-screw extruder (extruder 1) and a 90 mm diameter single-screw extruder (extruder 2) connected in series. The melt-kneading was performed at a set temperature of 200°C and a rotation speed of 167 rpm. The weight ratio of each material was (A1):(A2):(B):(G) = 74.4:18.6:4.5:2.5, and the total feed rate was 55.7 kg / h.

[0083] A mixed pentane mixture was prepared by mixing 80 parts by weight of normal pentane (E1) and 20 parts by weight of isopentane (E2). The mixed pentane was injected into the first extruder at a ratio of 8 parts by weight per 100 parts by weight of the melted resin mixture, and a blowing agent was added. The mixture was then fed to the second extruder through a continuation pipe set at 210°C.

[0084] The molten resin was cooled to 160°C in the second extruder, and then extruded through a die equipped with 60 small holes, each 0.65 mm in diameter and 5.0 mm in length, attached to the tip of the second extruder, set at 255°C, into pressurized circulating water at 73°C and 0.95 MPa. The extruded molten resin was cut and pelletized using a rotary cutter with eight blades that contacted the die, and then transferred to a centrifugal dehydrator to obtain a resin particle matrix for expandable styrene-based resin particles. The residence time in the first extruder was 2 minutes, and the residence time in the second extruder was 5 minutes.

[0085] 2. Preparation of expandable styrene resin particles and expanded styrene resin particles The obtained resin particle base was stored at 15°C for more than one week. 0.15 parts by weight of zinc stearate (F1), an external additive, was dry-blended with 100 parts by weight of the resin particle base to obtain expandable styrene-based resin particles. 400 g of the obtained expandable styrene-based resin particles were placed in a pre-expander (batch-type pre-expander manufactured by Daikai Kogyo Co., Ltd.), the internal pressure was set to 0.010 MPa to 0.020 MPa, and steam at 0.10 MPa was introduced into the pre-expander to expand the resin to a bulk expansion ratio of 50 times, yielding expanded styrene-based resin particles.

[0086] 3. Preparation of styrene-based resin foam molded body The resulting styrene-based resin foam particles were cured at 30°C for 24 hours and then loaded into an in-mold molding die (400mm long x 400mm wide x 25mm thick) attached to a polystyrene foam molding machine [Daisen Kogyo Co., Ltd., KR-57]. Steam at 0.06 MPa was introduced to cause in-mold foaming, followed by spraying water onto the die to cool. The foam was held in the die until the pressure pushing the die down to 0.03 MPa (gauge pressure), after which the foam was removed to obtain a styrene-based resin foam. The resulting styrene-based resin foam had an expansion ratio of 50x.

[0087] (Experimental Example 2) A styrene resin foam molded article was obtained in the same manner as in Experimental Example 1, except that the amount of zinc stearate (F1) used was changed to 0.20 parts by weight per 100 parts by weight of the resin particle base material.

[0088] (Experimental Example 3) A styrene resin foam molded article was obtained in the same manner as in Experimental Example 1, except that the amount of zinc stearate (F1) used was changed to 0.25 parts by weight per 100 parts by weight of the resin particle base material.

[0089] (Experimental Example 4) A styrene resin foam molded article was obtained in the same manner as in Experimental Example 1, except that the amount of zinc stearate (F1) used was changed to 0 part by weight (not used) per 100 parts by weight of the resin particle base material.

[0090] (Experimental Example 5) A styrene resin foam molded article was obtained in the same manner as in Experimental Example 1, except that 0.25 parts by weight of magnesium stearate (F2) was used per 100 parts by weight of the resin particle base instead of zinc stearate (F1).

[0091] The expandable styrene resin particles and the styrene resin foam molded articles produced in each experimental example were measured for various properties by the following methods.

[0092] <Measurement of average particle size D50 and laser scattering intensity of graphite> (1) Preparation of sample solution 500 mg of expandable styrene resin particles were dissolved and dispersed in 20 mL of a 0.1 wt % Span 80 toluene solution to prepare a sample solution. The above-mentioned dissolution and dispersion refers to a state in which the resin is dissolved and the graphite is dispersed. The 0.1 wt % Span 80 toluene solution refers to toluene to which 0.1 wt % of the surfactant Span 80 has been added.

[0093] Next, the sample solution was irradiated with ultrasonic waves in an ultrasonic cleaner to relax the aggregation of graphite.

[0094] (2) Ultrasonic irradiation conditions Equipment used: AS ONE Corporation ultrasonic cleaner, model USM Oscillation frequency: 42kHz Irradiation time: 10 minutes Temperature: room temperature

[0095] (3) Particle size measurement conditions Measurement equipment: Malvern Laser Diffraction Particle Size Distribution Analyzer Mastersizer 3000 Light source: 632.8nm red He-Ne laser and 470nm blue LED Dispersion unit: Wet dispersion unit Hydro MV

[0096] The analysis was carried out under the following settings, and the volume distribution was determined and the D50 particle size of the carbon in the sample was calculated by measurement and analysis using a laser diffraction and scattering method based on the Mie theory in accordance with ISO13320:2009 and JIS Z8825-1. Particle type: non-spherical Graphite refractive index: 2.42 Graphite absorption rate: 1.0 Dispersion medium: 0.1% by weight Span 80 toluene solution Refractive index of dispersion medium: 1.49 Agitation speed in dispersion unit: 2500 rpm Analysis model: General, single mode preserving Measurement temperature: room temperature

[0097] (4) Measurement procedure 120 mL of 0.1 wt% Span 80 toluene solution was poured into the dispersion unit and stirred at 2500 rpm to stabilize. The light intensity measured by the central detector when irradiating the dispersion medium with a 632.8 nm red He-Ne laser beam without the sample solution sample in the measurement cell was taken as the transmitted light intensity Lb. Next, 2 mL of the ultrasonically treated sample solution was taken and added to the dispersion unit. One minute after adding the sample solution, the light intensity measured by the central detector when irradiating the dispersion medium with a 632.8 nm red He-Ne laser beam was taken as the transmitted light intensity Ls. The particle size (D50) was also measured at the same time. The laser scattering intensity Ob of the sample solution was calculated from the obtained Ls and Lb using the following formula: Ob = (1 - Ls / Lb) x 100 (%)

[0098] The central detector is a detector located in front of the laser light output, and the light detected here is a measure of the transmitted light that was not used for scattering. The laser scattering intensity is a measure of the amount of laser light lost when the sample scatters the laser of the analytical device.

[0099] (5) Calculation of laser scattering intensity per unit solution concentration of expandable styrene resin particles The laser scattering intensity X (% / (mg / ml)) per unit solution concentration of the expandable styrene resin particles was calculated using the following formula. X (% / (mg / ml)) = laser scattering intensity (Ob) / {sample weight (500 mg) / toluene amount (20 mL) × sample injection amount (2 mL) / total toluene amount in dispersion unit (120 mL + 2 mL)}

[0100] Here, the laser scattering intensity per unit solution concentration is the value obtained by dividing the measured laser scattering intensity by the sample concentration in toluene. Because the measurement device used here is an instrument that requires measurement in solution, the sample concentration in the toluene solution was kept constant, and measurements were obtained for a constant sample amount.

[0101] (6) Calculation of laser scattering intensity per unit solution concentration of the radiation heat transfer inhibitor contained in the expandable styrene resin particles The laser scattering intensity Y {% / (mg / ml)} / wt% per unit solution concentration of the radiation heat transfer inhibitor contained in the expandable styrene-based resin particles (hereinafter referred to as "measurement object") was calculated using the following formula. Y{% / (mg / ml)} / weight% = laser scattering intensity per unit solution concentration of the target object (% / (mg / ml)) / graphite content of the target object (weight%)

[0102] <Evaluation of adhesion between foam particles> All the expanded particles discharged from the pre-expanding machine were visually evaluated based on the following criteria. Inter-adhesion: There are clumps of foam particles 20 mm or larger that are inter-adhered to each other No adhesion: No clumps of foam particles larger than 20 mm that are adhered to each other

[0103] <Expansion ratio of styrene-based resin foam molded products> The styrene-based resin foam molded article was removed from the mold and dried at 30°C for 24 hours. The weight (g) of the foam molded article was then measured, and the length, width, and thickness of the foam molded article were measured using a vernier caliper. The volume (cm 3) was calculated, and the expansion ratio was calculated according to the following formula. Foaming ratio (cm 3 / g) = test piece volume (cm 3 ) / test piece weight (g) The expansion ratio of styrene resin foam moldings is conventionally expressed as "cm 3 It is also expressed as " / g".

[0104] <Evaluation of fusion of styrene-based resin foam molded products> The obtained styrene-based resin foam molded article was broken. The fracture surface was visually observed to determine the area of ​​the entire fracture surface where the particles themselves, not the particle interfaces, were broken. The percentage of the area where the particles themselves were broken relative to the entire fracture surface area was determined.

[0105] <Measurement of thermal conductivity of styrene-based resin foam molded body> It is generally known that the higher the average temperature at which thermal conductivity is measured, the higher the thermal conductivity value, and so it is necessary to determine the average measurement temperature in order to compare thermal insulation properties. In this specification, the standard temperature of 23°C, as specified in JIS A9511:2006R, the standard for foamed plastic insulation materials, was used. Thermal conductivity was measured after leaving a styrene-based resin foam molded body at 60°C for 48 hours, cutting out a sample for thermal conductivity measurement, and leaving it at 23°C for another 24 hours. More specifically, the styrene resin foam molded article was left to stand at 60°C for 48 hours, and then a sample measuring 300 mm in length, 300 mm in width, and 25 mm in length was cut out. The sample was then left to stand at 23°C for 24 hours, and then its thermal conductivity was measured at an average temperature of 23°C and a temperature difference of 20°C by the heat flow meter method using a thermal conductivity measuring device (HC-074, manufactured by Eiko Seiki Co., Ltd.) in accordance with JIS A1412-2:1999.

[0106] <Measurement of dimensional change rate of styrene resin foam molded body> Dimensional change was measured according to Method B for dimensional stability at high temperatures as specified in JIS K6767. A sample measuring 150 mm in length, 150 mm in width, and 25 mm in thickness was cut from a styrene-based resin foam molded article. After leaving the sample at 23°C for 24 hours, three parallel lines were drawn on the sample at 50 mm intervals in both the vertical and horizontal directions. The lengths of the three lines were measured in both the vertical and horizontal directions, and the average was taken as the initial dimension (L1). The sample was heated at 90°C for 168 hours, removed, and left at 23°C for 1 hour. The lengths of the three lines were measured in both the vertical and horizontal directions, and the average was taken as the post-heat dimension (L2). The dimensional change was calculated according to the following formula: Dimensional change rate (%) = (L2 (mm) - L1 (mm)) / (L1 (mm)) x 100

[0107] <Flame retardancy evaluation - oxygen index> The foamed molded article thus produced was allowed to stand at 70°C for 168 hours, and then at 23°C for 24 hours, after which the oxygen index was measured in accordance with JIS K7201.

[0108] Table 1 shows the blending of expandable styrene resin particles and the measurement results of each evaluation item in each experimental example.

[0109] [Table 1]

[0110] In the foamed molded articles of Experimental Examples 1 to 3, to which a predetermined amount of zinc stearate was externally added, the mutual adhesion of the foamed particles was "no" and the fusion property was 90%, even without the use of a fusion promoter, and they received high evaluations in both items. The foamed molded articles of Experimental Examples 1 to 3 also had excellent thermal conductivity, dimensional change rate, and oxygen index.

[0111] On the other hand, in the foamed molded article of Experimental Example 4, which did not use an external additive, the foamed beads adhered to each other. Furthermore, in the foamed molded article of Experimental Example 5, which used magnesium stearate as an external additive, the foamed beads were prevented from adhering to each other, but the fusion property of the foamed beads was 0%, which was extremely poor. It was considered essential to further use a fusion promoter to produce a foamed molded article with the formulation of Experimental Example 5.

Claims

1. Expandable styrene-based resin particles comprising a resin particle matrix containing a styrene-based base resin, a radiation heat transfer inhibitor, and a blowing agent, and zinc stearate externally added to the resin particle matrix, the base resin contains a copolymer having at least a structural unit derived from (meth)acrylic acid and a structural unit derived from styrene, The zinc stearate is contained in an amount of 0.12 parts by weight or more and 0.30 parts by weight or less relative to 100 parts by weight of the resin particle base material, The expandable styrene-based resin particles have an externally added fatty acid glyceride or vegetable oil content of 0 part by weight or more and less than 0.05 part by weight per 100 parts by weight of the resin particle matrix.

2. 2. The expandable styrene-based resin particles according to claim 1, wherein the content of the structural units derived from (meth)acrylic acid relative to the entire copolymer is 2% by weight or more and 20% by weight or less.

3. The expandable styrene-based resin particles according to claim 1 , wherein the radiation heat transfer inhibitor comprises a carbon-based radiation heat transfer inhibitor.

4. The expandable styrene-based resin particles according to claim 1 , wherein the resin particle matrix further contains a bromine-based flame retardant.

5. 2. The expandable styrene-based resin particles according to claim 1, wherein the laser scattering intensity per unit solution concentration of the radiation heat transfer inhibitor contained in the expandable styrene-based resin particles is 5.0 {% / (mg / ml)} / wt% or more.

6. 2. The expandable styrene-based resin particles according to claim 1, wherein the copolymer is uniformly contained throughout the expandable styrene-based resin particles.

7. 2. The expandable styrene-based resin particles according to claim 1, wherein the expandable styrene-based resin particles are pre-expanded 50 times and then molded to obtain a foamed molded article having a thermal conductivity of 0.030 W / mK or less.

8. 2. The expandable styrene-based resin particles according to claim 1, wherein the resin particle matrix is ​​obtained by impregnating pellets of a resin composition containing the base resin and the radiant heat transfer inhibitor with the blowing agent.

9. The expandable styrene-based resin particles according to claim 1 , wherein the resin particle matrix is ​​a pellet of a resin composition containing the base resin, the radiant heat transfer inhibitor, and the blowing agent.

10. Expanded styrene resin particles obtained by expanding the expandable styrene resin particles according to any one of claims 1 to 9.

11. A styrene-based resin foamed molded article obtained by molding the expanded styrene-based resin beads according to claim 10.

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