Carbamate foam molded article

Abstract

This urethane foam molded body is provided with: a base material comprising a polyurethane foam; and composite particles which are contained in the base material in an oriented manner. The composite particles have: first composite particles having expanded graphite particles, magnetic particles bonded to the surfaces of the expanded graphite particles by a binder; and second composite particles having expanded graphite particles, and magnetic particles bonded to the surfaces of the expanded graphite particles by a binder. When the total mass of the expanded graphite particles and the expanded graphite particles in the base material in the urethane foam molded body is 100 mass%, the content of the expanded graphite particles is from 20 mass% to 80 mass% (inclusive).

Description

Technical Field

[0001] The present disclosure relates to a urethane foam molded body having high thermal conductivity. Background Art

[0002] In vehicles such as motor vehicles, in order to reduce the noise leaking to the outside of the vehicle and into the passenger compartment, countermeasures for reducing the noise generated from engines, transmissions, etc. are sought. In electric vehicles (EVs) and hybrid electric vehicles (HEVs), the driving noise of the electric powertrain composed of an inverter, a motor, a gearbox, etc. is also an object to be reduced. As a noise countermeasure, for example, a sound insulation material made of a foam such as polyurethane foam is used. Since the foam has many small chambers (bubbles) inside, its thermal conductivity is small. Therefore, when it is arranged around a noise source accompanied by heat generation, there is a risk of heat accumulation and malfunction.

[0003] From the viewpoint of improving the heat dissipation of the sound insulation material using the foam, for example, in Patent Document 1, a urethane foam molded body is described: in a polyurethane foam, composite particles obtained by compounding thermally conductive particles, magnetic particles, and insulating inorganic particles are oriented and arranged, and a heat transfer path is formed in the orientation direction, thereby improving the heat dissipation. As the thermally conductive particles, expanded graphite, etc. are described. In Patent Document 2, a polyurethane foam containing a thermally conductive filler is described. As the thermally conductive filler, expanded graphite, expanded graphite, etc. are described.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: International Publication No. 2013 / 042611

[0007] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2022-72896 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] For sound insulation materials, depending on the use, in addition to the requirement for thermal conductivity, flame retardancy is also required. For example, a polyurethane foam imparted with flame retardancy has a dripping effect in which even when exposed to a flame, the ignition source drops and the spread of combustion is suppressed. In the urethane foam molded body described in Patent Document 1, in order to orient particles with relatively high thermal conductivity (thermal conductivity particles), composite particles obtained by granulating magnetic particles bonded to the surface of the particles are used. If magnetic particles are incorporated into the polyurethane foam, there is a risk that the dripping effect will be impaired and the self-extinguishing property will be reduced. Therefore, considering flame retardancy, as the thermal conductivity particles, expanded graphite having a flame retardant effect by inserting a substance that generates gas upon heating between the layers of flaky graphite is preferable. Thus, by using expanded graphite as the thermal conductivity particles of the composite particles, the flame retardancy of the urethane foam molded body is improved. However, in recent years, higher thermal conductivity has been required for sound insulation materials. In this case, the thermal conductivity of expanded graphite cannot be said to be sufficiently high, and the improvement in thermal conductivity is limited only by using expanded graphite.

[0010] In this regard, according to Patent Document 2, examples of the thermal conductivity filler include expanded graphite and exfoliated graphite. Exfoliated graphite is a material manufactured by heating and expanding expanded graphite and then making it finer. Since the interlayer substance disappears, its purity is high. Therefore, the thermal conductivity of exfoliated graphite is higher than that of expanded graphite. However, in Patent Document 2, as described in paragraph

[0006] , it is for the purpose of foam molding without applying a magnetic field. Therefore, even if the thermal conductivity filler in the polyurethane foam is not oriented, when expanded graphite and exfoliated graphite are used as the thermal conductivity filler, they are merely dispersed as monomers. According to the research of the present inventor, the effect of improving the thermal conductivity is small only by dispersing exfoliated graphite in the polyurethane foam.

[0011] The present disclosure has been completed in view of the above circumstances, and an object thereof is to provide a urethane foam molded body having excellent thermal conductivity and flame retardancy.

[0012] Means for Solving the Problem

[0013] (1) In order to solve the above problems, the urethane foam molded body of the present disclosure has: a base material composed of a polyurethane foam; and composite particles contained in the base material in an oriented manner. The composite particles have: first composite particles having exfoliated graphite particles and magnetic particles bonded to the surface of the exfoliated graphite particles by a binder; and second composite particles having expanded graphite particles and magnetic particles bonded to the surface of the expanded graphite particles by a binder. When the total mass of the exfoliated graphite particles and the expanded graphite particles in the base material is 100% by mass, the content of the exfoliated graphite particles is 20% by mass or more and 80% by mass or less.

[0014] The urethane foam-formed body of the present disclosure includes at least two types of composite particles, namely, first composite particles and second composite particles. In any of the composite particles, magnetic particles are bonded to the surface of the particles serving as the core by a binder. The core particles of the first composite particles are expanded graphite particles with a thermal conductivity greater than that of expanded graphite particles, which mainly contribute to the improvement of the thermal conductivity of the urethane foam-formed body. The core particles of the second composite particles are expanded graphite particles that exhibit a flame retardant effect, which mainly contribute to the improvement of the flame retardancy of the urethane foam-formed body. These composite particles are oriented and arranged in a base material composed of a polyurethane foam. The composite particles are connected and oriented, thereby forming a heat transfer path in the base material. As a result, heat is easily transferred to the composite particles, and the respective effects are more easily exerted compared to the case where the expanded graphite particles and the expanded graphite particles are each contained as monomers. In addition, both the expanded graphite particles and the expanded graphite particles are graphite-based materials, having thermal conductivity anisotropy and a high affinity for polyurethane.

[0015] The urethane foam-formed body of the present disclosure contains expanded graphite particles and expanded graphite particles with different functions as independent composite particles. Thus, the respective effects can be fully exerted without hindering each other's functions. As a result, the desired thermal conductivity and flame retardancy can be achieved. Among them, in the urethane foam-formed body of the present disclosure, a mode including composite particles in which magnetic particles are bonded to the surface of particles formed by integrating expanded graphite particles and expanded graphite particles is not excluded.

[0016] (2) In the above configuration, it may also be a configuration in which the average particle diameter of the expanded graphite particles is 100 μm or more and 3000 μm or less. According to this configuration, the effect of improving the thermal conductivity based on the expanded graphite particles can be exerted while reducing the influence on the formability and brittleness of the urethane foam-formed body.

[0017] (3) In any of the above configurations, it may also be a configuration in which the purity of the expanded graphite particles is 99% or more. According to this configuration, the effect of improving the thermal conductivity can be enhanced.

[0018] (4) In any of the above configurations, it may also be a configuration in which the average particle diameter of the expanded graphite particles is 100 μm or more and 3000 μm or less. According to this configuration, the flame retardant effect based on the expanded graphite particles can be exerted while reducing the influence on the formability and brittleness of the urethane foam-formed body.

[0019] (5) In any of the above configurations, it may also be a configuration in which the content of the composite particles is 5% by volume or more and 50% by volume or less when the volume of the urethane foam-formed body is 100% by volume. According to this configuration, it is suitable for balancing the formability of the urethane foam-formed body and the improvement of the thermal conductivity and flame retardancy.

[0020] (6) In any of the above configurations, it may also be a configuration in which the binder constituting the first composite particle and the second composite particle is a water-soluble polymer. According to this configuration, when manufacturing a urethane foam molded body, the influence on foam molding is small, and the environmental load is also small.

[0021] (7) In the configuration of the above (6), it may also be a configuration in which the water-soluble polymer is one or more selected from methyl cellulose, carboxymethyl cellulose, hydroxypropyl methyl cellulose, polyvinyl alcohol, and starch. The water-soluble polymer of this configuration has good adhesiveness and is easily obtained at a relatively low price.

[0022] (8) In any of the above configurations, it may also be a configuration in which the content of the magnetic particles constituting the first composite particle and the second composite particle is 20% by mass or more and 80% by mass or less when the total mass of the expanded graphite particles and the expanded graphite particles in the base material is 100% by mass. According to this configuration, since the amount of magnetic particles is relatively small, cost reduction and weight reduction can be achieved.

[0023] (9) In any of the above configurations, it may also be a configuration in which the magnetic particles constituting the first composite particle and the second composite particle are one or more selected from iron particles and iron-based alloy particles. Iron particles and iron-based alloy particles have high saturation magnetization and are easily obtained as fine particles.

[0024] (10) In any of the above configurations, it may also be a configuration in which at least one of the first composite particle and the second composite particle has insulating inorganic particles bonded to the surface of the expanded graphite particle or the expanded graphite particle by a binder.

[0025] In this configuration, the insulating inorganic particles can be directly bonded to the surface of the expanded graphite particles or the expanded graphite particles that form the core, or can be indirectly bonded, in other words, bonded to the surface of the magnetic particles adhered to each particle via the magnetic particles. As the magnetic particles, ferromagnetic materials such as stainless steel and iron are used. Therefore, the composite particles formed by the composite of the expanded graphite particles or the expanded graphite particles and the magnetic particles have high conductivity. If the insulating inorganic particles are bonded to the composite particles in this state, even if the composite particles are oriented in a contacting state with each other, it becomes difficult for the core particles and the magnetic particles (conductive particles) to contact each other between adjacent composite particles. Therefore, the resistance between the composite particles becomes large. In addition, the composite particles are in contact with each other via the insulating inorganic particles, so that the conduction between the composite particles can be disconnected. As a result, in the urethane foam molded body of the present disclosure, electrical insulation can be achieved. Thus, according to this configuration, while imparting high thermal conductivity and flame retardancy, electrical insulation can also be imparted. Therefore, the urethane foam molded body of this configuration is also suitable for applications that require both heat dissipation and electrical insulation, such as heat dissipation components in electronic devices.

[0026] (11) In the configuration of the above (10), it is also possible that the insulating inorganic particles have a configuration including one or more selected from aluminum hydroxide, alumina, magnesium hydroxide, magnesia, talc, calcium carbonate, clay, mica, and silica. Since the insulating inorganic particles of this configuration have a relatively large thermal conductivity, it is difficult to impede the thermal conductivity between the composite particles. In addition, they can be obtained relatively inexpensively.

[0027] Advantages of the Invention

[0028] In the urethane foam molded body of the present disclosure, the expanded graphite particles and the expanded graphite particles are oriented and arranged in the base material as individual composite particles. Therefore, the urethane foam molded body of the present disclosure has excellent thermal conductivity and flame retardancy. Detailed Embodiments

[0029] Hereinafter, embodiments of the urethane foam molded body of the present disclosure will be described. In addition, the embodiments are not limited to the following methods, and can be implemented in various modified and improved methods that can be carried out by those skilled in the art.

[0030] <Urethane Foam Molded Body>

[0031] The urethane foam molded body of the present disclosure has: a base material composed of a polyurethane foam; and composite particles contained in the base material in an oriented manner.

[0032] [Base Material]

[0033] The polyurethane foam of the base material is manufactured from foaming urethane resin raw materials such as polyisocyanate components and polyol components. The foaming urethane resin raw materials can be prepared from known raw materials such as polyols and polyisocyanates. As the polyol, it can be appropriately selected from polyhydroxy compounds, polyether polyols, polyester polyols, polymer polyols, polyether polyamines, polyester polyamines, alkylene polyols, urea-dispersed polyols, melamine-modified polyols, polycarbonate polyols, acrylic polyols, polybutadiene polyols, phenol-modified polyols, etc. In addition, as the polyisocyanate, for example, it can be appropriately selected from toluene diisocyanate, phenylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, triphenylmethane triisocyanate, polymethylene polyphenyl isocyanate, naphthalene diisocyanate, and their derivatives (for example, prepolymers and modified polyisocyanates obtained by reaction with polyols).

[0034] In the foaming urethane resin raw materials, catalysts, foaming agents, foam stabilizers, plasticizers, crosslinking agents, chain extenders, flame retardants, antistatic agents, viscosity reducers, stabilizers, fillers, colorants, etc. can also be appropriately compounded. For example, as the catalyst, amine-based catalysts such as tetraethylenediamine, triethylenediamine, and dimethylethanolamine, and organometallic-based catalysts such as tin laurate and tin octoate can be cited. In addition, as the foaming agent, water is preferably used. In addition to water, dichloromethane, Freons, CO2 gas, etc. can be cited. In addition, as the foam stabilizer, a silicone-based foam stabilizer is preferably used, and as the crosslinking agent, triethanolamine, diethanolamine, etc. are preferably used.

[0035] There are no particular limitations on the shape, size, etc. of the base material, and it can be appropriately determined according to the use. The composite particles contained in the base material can be arranged with a certain regularity. For example, they can be arranged linearly between one end and the other end of the urethane foam-formed body (the other end may not be the end opposite to one end at 180°), or they can be arranged curvilinearly between one end and the other end of the urethane foam-formed body (the other end may not be the end opposite to one end at 180°). In addition, they can also be arranged radially from the center to the periphery.

[0036] [Composite particles]

[0037] The composite particles contained in the substrate in an oriented manner are particles in which magnetic particles or the like are bonded to the surface of non-magnetic particles serving as nuclei through a binder, and include first composite particles and second composite particles. The first composite particles have expanded graphite particles and magnetic particles bonded to the surface of the expanded graphite particles through a binder. The second composite particles have expanded graphite particles and magnetic particles bonded to the surface of the expanded graphite particles through a binder. The non-magnetic particles serving as nuclei may be single particles or multiple particles. For example, the expanded graphite particles constituting the first composite particles may be a single expanded graphite particle or an aggregate particle formed by integrating multiple expanded graphite particles. The expanded graphite particles constituting the second composite particles may be a single expanded graphite particle or an aggregate particle formed by integrating multiple expanded graphite particles. In addition, the composite particles may also be particles in a manner in which magnetic particles are bonded to the surface of particles formed by integrating expanded graphite particles and expanded graphite particles, or in a manner in which magnetic particles are bonded to the surface of other graphite particles, metal particles, etc., and include forms other than the first composite particles and the second composite particles.

[0038] The content of the composite particles may be determined in consideration of thermal conductivity, flame retardancy, the influence on the foaming reaction of the polyurethane foam, formability, etc. In order to achieve the desired thermal conductivity and flame retardancy, it is preferable that the content of the composite particles is 5% by volume or more when the volume of the urethane foam-formed body is 100% by volume. More preferably, it is 10% by volume or more. On the other hand, from the viewpoint of not hindering the foaming reaction, it is preferable that the content of the composite particles is 50% by volume or less. More preferably, it is 20% by volume or less.

[0039] In addition, when the total mass of the expanded graphite particles and the expanded graphite particles in the substrate is 100% by mass, the content of the expanded graphite particles is 20% by mass or more and 80% by mass or less. When the content of the expanded graphite particles is less than 20% by mass, the effect of improving the thermal conductivity is small. More preferably, it is 30% by mass or more. On the contrary, if the content of the expanded graphite particles is more than 80% by mass, the flame retardancy decreases. More preferably, it is 60% by mass or less.

[0040] The expanded graphite particles constituting the first composite particles can be manufactured by heating expanded graphite to expand it and then crushing the material formed into flakes, etc. The expanded graphite particles have a multilayer structure formed by stacking multiple graphene layers. From the viewpoint of improving the effect of improving the thermal conductivity, the purity (content ratio of the carbon component) of the expanded graphite particles is preferably 99% or more. The thermal conductivity of the expanded graphite particles is preferably 200 W / m·K or more.

[0041] The shape of the expanded graphite particles is flaky, fibrous, spherical, etc., and there is no particular limitation. From the viewpoint of increasing the thermal conductivity, the average particle diameter of the expanded graphite particles is preferably 100 μm or more. More preferably, it is 700 μm or more. On the other hand, if the expanded graphite particles are too large, there is a risk that cracks etc. will occur starting from them and the formed body will become brittle. Therefore, the average particle diameter of the expanded graphite particles is preferably 3000 μm or less. More preferably, it is 2000 μm or less. As the average particle diameter in this specification, unless otherwise specifically stated, the median diameter (D50) obtained from the volume-based particle size distribution measured by the laser-diffraction / scattering method is adopted. In addition, for commercially available products, the catalog value can also be adopted.

[0042] The expanded graphite particles constituting the second composite particles are materials in which a gas-generating substance by heating is inserted between the layers of flaky graphite through acid treatment etc. If heat is applied to the expanded graphite particles, the layers expand due to the generated gas, and a layer that is stable against heat and chemicals is formed. This stable layer becomes a heat-insulating layer and hinders the movement of heat, thereby bringing a flame-retardant effect. As the expanded graphite particles, they can be appropriately selected in consideration of the expansion start temperature, expansion rate, etc. Since the expansion start temperature must be higher than the heat generation temperature during the forming of the urethane foam molding, for example, expanded graphite particles with an expansion start temperature of 150 °C or more are preferably used.

[0043] The shape of the expanded graphite particles is flaky, fibrous, spherical, etc., and there is no particular limitation. If the dispersibility in the polyurethane foam is considered, the average particle diameter of the expanded graphite particles is preferably 100 μm or more. More preferably, it is 700 μm or more. On the other hand, similar to the case of the expanded graphite particles, if the expanded graphite particles are too large, there is a risk that cracks etc. will occur starting from them and the formed body will become brittle. Therefore, the average particle diameter of the expanded graphite particles is preferably 3000 μm or less. More preferably, it is 2000 μm or less. When the size of the expanded graphite particles is of the same level as that of the expanded graphite particles, there is an advantage that granulation etc. of the composite particles can be concentrated.

[0044] In the first composite particle and the second composite particle, the magnetic particles adhered to the surface of the expanded graphite particles or expanded graphite particles that serve as the core (collectively referred to as "core particles" when referring to one or both of them) can be the same or different. It is sufficient that the magnetic particles can orient the composite particles. For example, ferromagnetic substances such as iron, nickel, cobalt, gadolinium, stainless steel, magnetite, maghemite, manganese-zinc ferrite, barium ferrite, strontium ferrite, etc., antiferromagnetic substances such as MnO, Cr2O3, FeCl2, MnAs, etc., and particles of alloys using them are preferred. Among them, from the viewpoints of being easily obtained as fine particles and having a high saturation magnetization, iron, nickel, cobalt, and their iron-based alloys (including stainless steel) are preferred. In particular, iron is suitable for mass production because it can be obtained at a relatively low cost, thus reducing the manufacturing cost.

[0045] The magnetic particles can be directly adhered to the surface of the core particles, or can be indirectly adhered to the surface of the core particles via other particles such as the insulating inorganic particles described later. In addition, the magnetic particles can be adhered only to a part of the surface of the core particles, or can be adhered in a manner covering the entire surface. The size of the magnetic particles can be appropriately determined in consideration of the size of the core particles, the orientation of the composite particles, and the heat conductivity between the composite particles, etc. For example, the particle diameter of the magnetic particles is preferably 1 / 10 or less of the particle diameter of the core particles. If the size of the magnetic particles becomes smaller, there is a tendency for the saturation magnetization of the magnetic particles to decrease. Therefore, in order to orient the composite particles with a smaller amount of magnetic particles, it is preferred that the average particle diameter of the magnetic particles is 100 nm or more. More preferably, it is 1 μm or more, and further preferably, it is 5 μm or more.

[0046] There is no particular limitation on the shape of the magnetic particles. For example, when the shape of the magnetic particles is flat, the distance between adjacent core particles becomes shorter compared to the spherical case. As a result, the heat conductivity between adjacent composite particles is improved. As a result, the heat conductivity of the urethane foam molded body is improved. In addition, when the shape of the magnetic particles is flat, the magnetic particles and the core particles are in surface contact. In other words, the contact area between the two becomes larger. As a result, the adhesion force between the magnetic particles and the core particles is improved. Therefore, it becomes difficult for the magnetic particles to peel off. On top of that, the heat conductivity between the magnetic particles and the core particles is also improved. For the reasons described above, it is preferred to use flaky particles as the magnetic particles.

[0047] From the viewpoint of enabling the orientation of the composite particles even in a relatively low magnetic field, the content of the magnetic particles is preferably 20% by mass or more based on the total mass of 100% by mass of the expanded graphite particles and the expanded graphite particles in the base material. Further, from the viewpoints of cost reduction and weight reduction, the content of the magnetic particles is preferably 130% by mass or less. More preferably, it is 100% by mass or less, and still more preferably, it is 80% by mass or less. In the urethane foam molded body of the present disclosure, since the expanded graphite particles having a high thermal conductivity are contained as the first composite particles, even if the content of the magnetic particles is reduced, the thermal conductivity is hardly reduced.

[0048] In the first composite particles and the second composite particles, the binder that binds the core particles and the magnetic particles can be appropriately selected in consideration of the effects on adhesiveness, foam molding, etc. From the reasons of less influence on foam molding and being environmentally friendly, a water-soluble polymer is preferred. For example, methyl cellulose, carboxymethyl cellulose, hydroxypropyl methyl cellulose, polyvinyl alcohol, starch, etc. can be mentioned. Among them, starch is preferred because it is relatively inexpensive, has high adhesiveness, and excellent granulation properties. The binder of the first composite particles and the binder of the second composite particles may be the same or different.

[0049] The expanded graphite particles, the expanded graphite particles, and the magnetic particles have conductivity. Therefore, the first composite particles and the second composite particles are connected and oriented to form a conduction path in the base material. For example, on the surface of the core particles, insulating inorganic particles can be bonded on the basis of the magnetic particles to form composite particles. Thus, even if the composite particles are oriented, the resistance between adjacent composite particles can be increased or the conduction can be interrupted. As a result, electrical insulation can be imparted to the urethane foam molded body. The urethane foam molded body of the present disclosure in which at least one of the first composite particles and the second composite particles has insulating inorganic particles is suitable for applications requiring electrical insulation such as heat dissipation members in electronic devices.

[0050] The insulating inorganic particles may be particles of an inorganic material having insulating properties. Among them, from the viewpoint of not hindering the thermal conductivity between the composite particles, particles having a relatively high thermal conductivity are desired. For example, the thermal conductivity of the insulating inorganic particles is preferably 5 W / m·K or more. As the insulating inorganic material having a thermal conductivity of 5 W / m·K or more, aluminum hydroxide, alumina, magnesium hydroxide, magnesium oxide, talc, calcium carbonate, clay, mica, silica, etc. can be mentioned. One of them can be used alone, or two or more of them can be used in combination. Among them, talc and mica are preferred because they are in the form of thin flakes and have excellent covering properties.

[0051] The insulating inorganic particles can be directly bonded to the surface of the core particles, or indirectly bonded to the surface of the core particles via magnetic particles. In addition, the insulating inorganic particles can be bonded only to a part of the surface of the core particles, or can be bonded in a manner covering the entire surface. From the viewpoint of increasing the resistance between composite particles and improving the electrical insulation of the urethane foam molded body, the insulating inorganic particles are preferably disposed on the outermost layer of the composite particles. The binder for bonding the magnetic particles to the core particles and the binder for bonding the insulating inorganic particles can be the same or different.

[0052] The size of the insulating inorganic particles can be appropriately determined in consideration of the adhesiveness to the core particles and the magnetic particles, the electrical insulation and the heat conductivity between the composite particles. If the insulating inorganic particles are too large, the adhesiveness and the heat conductivity between the composite particles decrease. For example, the particle diameter of the insulating inorganic particles is preferably 1 / 100 or more and 1 / 10 or less of the particle diameter of the core particles. There is no particular limitation on the shape of the insulating inorganic particles. For example, when the shape of the insulating inorganic particles is flat, the distance between adjacent core particles can be shortened compared with the spherical case. Therefore, it is difficult to hinder the heat conductivity between adjacent composite particles. In addition, the contact area becomes larger, so that the insulating inorganic particles are difficult to peel off.

[0053] The insulating inorganic particles can be dispersed only in the base material without being a part of the composite particles, or can form composite particles and be further dispersed in the base material. The insulating inorganic particles dispersed in the base material can be the same as or different from the insulating inorganic particles added as constituent particles of the composite particles. In addition, the insulating inorganic particles dispersed in the base material can be one kind or two or more kinds. For the insulating inorganic particles dispersed in the base material, particles with a relatively large thermal conductivity are also desired, and preferably the aforementioned aluminum hydroxide, alumina, magnesium hydroxide, magnesium oxide, talc, calcium carbonate, clay, mica, silica, etc. If the insulating inorganic particles are dispersed in the base material, the insulating inorganic particles enter between the composite particles, and it becomes difficult for the composite particles to conduct to each other. Therefore, the electrical insulation of the urethane foam molded body is improved. In addition, when the thermal conductivity of the insulating inorganic particles is relatively large, a heat transfer path based on the insulating inorganic particles is also formed on the basis of the heat transfer path of the composite particles. As a result, the heat conductivity of the urethane foam molded body is further improved. In addition, when the insulating inorganic particles have flame retardancy, the flame retardancy of the urethane foam molded body is improved.

[0054] <Manufacturing method of urethane foam molded body>

[0055] There are no particular limitations on the method for manufacturing the urethane foam molded body of the present disclosure. As one mode of the preferred manufacturing method, the method for manufacturing the urethane foam molded body of the present disclosure has a composite particle manufacturing step, a mixed raw material manufacturing step, and a foam molding step. Hereinafter, each step will be described.

[0056] [Composite Particle Manufacturing Step]

[0057] This step is a step of manufacturing composite particles by stirring granulation raw materials including powder having particles to be nuclei, powder of magnetic particles, a binder, and water. For the composite particles, the first composite particles having expanded graphite particles and the second composite particles having expanded graphite particles can be manufactured collectively, or the first composite particles having expanded graphite particles and the second composite particles having expanded graphite particles can be manufactured separately. Since the specific gravities of the expanded graphite powder and the expanded graphite powder are close and there is no significant difference in granulation properties, the first composite particles and the second composite particles can be manufactured collectively, thereby improving productivity.

[0058] In the case of manufacturing the two types of composite particles collectively, it is only necessary to stir both the expanded graphite powder and the expanded graphite powder together with other raw materials such as water. In this case, considering the granulation properties, it is preferable to reduce the difference in the average particle diameter between the expanded graphite powder and the expanded graphite powder. In addition, it is preferable that the blending amount of the expanded graphite powder is 20% by mass or more and 80% by mass or less when the total mass of the expanded graphite powder and the expanded graphite powder is 100% by mass. On the other hand, in the case of manufacturing the two types of composite particles separately, it is only necessary to stir the expanded graphite powder together with other raw materials such as water to manufacture the first composite particles, and stir the expanded graphite powder together with other raw materials such as water to manufacture the second composite particles. The manufacturing of the composite particles can be carried out using a high-speed stirring type mixing granulator or the like. The blending amounts of the powder of magnetic particles, the binder, and water relative to the powder having particles to be nuclei can be appropriately adjusted in consideration of granulation properties, magnetic field orientation of the composite particles, and the like.

[0059] Regarding the blending amount of the powder of magnetic particles, in consideration of the magnetic field orientation of the composite particles, it is preferably 20 parts by mass or more with respect to 100 parts by mass of the powder of the particles serving as the core. On the other hand, in consideration of cost and weight reduction, it is preferably 130 parts by mass or less. More preferably, it is 100 parts by mass or less, and further preferably 80 parts by mass or less. As a sufficient amount required for bonding the particles, the blending amount of the binder is preferably 2% by mass or more when the total mass of the powder to be bonded is 100% by mass. On the other hand, if the binder is excessive, there is a risk of condensation between the composite particles. Therefore, the blending amount of the binder is preferably 10% by mass or less. More preferably, it is 5% by mass or less. The binder can be solid or liquid. When using a water-soluble powder as the binder, it is preferably to stir the binder and other powder raw materials in advance and then add water. Thus, condensation of the particles can be suppressed.

[0060] When adding insulating inorganic particles as constituent particles of the composite particles, it is sufficient to include the powder of insulating inorganic particles in the granulation raw material. When arranging the insulating inorganic particles on the outermost layer of the composite particles, this step can also be configured as follows: having a first stirring step in which a first raw material including the powder of the particles serving as the core, the powder of magnetic particles, a binder, and water is stirred; and a second stirring step in which the powder of insulating inorganic particles is added to the stirred product of the first raw material and further stirred.

[0061] [Mixed raw material manufacturing process]

[0062] This process is a process of manufacturing a mixed raw material by mixing the powder of the composite particles (including the first composite particles and the second composite particles) manufactured in the previous process with a foamed urethane resin raw material.

[0063] For the foamed urethane resin raw material, as described above, it can be prepared from raw materials such as polyols, polyisocyanates, catalysts, foaming agents, foam stabilizers, etc. In the urethane foam-formed body of the present disclosure, insulating inorganic particles can also be dispersed in the base material in addition to the composite particles. When manufacturing the urethane foam-formed body in this manner, it is sufficient to mix the powder of the composite particles and the powder of insulating inorganic particles with the foamed urethane resin raw material. The mixed raw material can be manufactured, for example, by mechanically stirring the powder of the composite particles and the foamed urethane resin raw material using a stirring blade or the like. In addition, the powder of the composite particles can also be added to at least one of the two components (polyol raw material, polyisocyanate raw material) of the foamed urethane resin raw material, and after preparing the two raw materials, the two raw materials can be mixed and manufactured.

[0064] [Foaming forming process]

[0065] This step is a step of injecting the mixed raw material manufactured in the previous step into the cavity of the foaming mold, and foaming and forming while applying a magnetic field in such a way that the magnetic flux density in the cavity is substantially uniform.

[0066] It is only necessary to form a magnetic field in the direction in which the composite particles are oriented. For example, in the case where the composite particles are linearly oriented, it is preferably formed such that the magnetic field lines in the cavity of the foaming mold are substantially parallel from one end of the cavity to the other end. In order to form the magnetic field as described above, for example, by sandwiching the foaming mold, magnets may be arranged near both sides of one end and the other end of the foaming mold. For the magnets, permanent magnets or electromagnets may be used. If an electromagnet is used, the on and off of the magnetic field formation can be instantaneously switched, and the control of the magnetic field strength is easy. Therefore, the foaming and forming is easily controlled. In addition, the magnetic field lines constituting the magnetic field preferably form a closed loop. In this way, the leakage of the magnetic field lines is suppressed, and a stable magnetic field can be formed in the cavity.

[0067] In this step, the magnetic field is formed such that the magnetic flux density in the cavity is substantially uniform. For example, the difference in the magnetic flux density in the cavity is preferably within ±10%. More preferably, it is within ±5%, and further preferably within ±3%. By forming a uniform magnetic field in the cavity of the foaming mold, the non-uniform distribution of the composite particles can be suppressed, and the desired orientation state can be obtained. In addition, the foaming and forming is preferably carried out at a magnetic flux density of 150 mT or more and 350 mT or less. In this way, the composite particles in the mixed raw material can be reliably oriented. The magnetic field is preferably applied during the period when the viscosity of the foaming urethane resin raw material is relatively low. If the magnetic field is applied when the foaming urethane resin raw material increases in viscosity and the foaming and forming is somewhat completed, it is difficult to obtain the desired thermal conductivity because the composite particles are difficult to orient. In addition, it is not necessary to apply the magnetic field throughout the entire period of the foaming and forming.

[0068] After the foaming and forming is completed through this step, demolding is performed to obtain the urethane foam molded body of the present disclosure. At this time, by the method of foaming and forming, a skin layer is formed on at least one of one end and the other end of the urethane foam molded body. This skin layer may be cut off according to the use (of course, it may not be cut off).

[0069] Examples

[0070] Next, examples are listed to more specifically illustrate the present disclosure.

[0071] <Manufacture of composite particles>

[0072] First, eight types of composite particles A to H were manufactured as follows (composite particle manufacturing step). In composite particles B to G, both expanded graphite powder and exfoliated graphite powder were stirred together, and two types of composite particles, a first composite particle and a second composite particle, were manufactured collectively.

[0073] [Composite Particle A]

[0074] A granulation raw material containing expanded graphite powder, stainless steel powder, starch powder, talc powder, and water was stirred to produce Composite Particle A as the second composite particle. First, the expanded graphite powder, stainless steel powder, and starch powder were put into the container of a high-speed stirring type mixing granulator and stirred and mixed by blades. Further, water was added and mixed for 1 minute. Next, talc powder was added and further mixed for 4 minutes. The stirring speed was set at 400 rpm. The obtained powder was dried to become the powder of Composite Particle A. The details of the materials used are collectively shown in the following (a) to (d), and the blending amounts are shown in Table 1 below (the same applies to the following Composite Particles B to H).

[0075] [Composite Particles B to G]

[0076] Except for the point that expanded graphite powder was added as a granulation raw material, Composite Particles B to G were produced by the same method as the production method of Composite Particle A. Composite Particles B to G were produced by changing the blending ratio of expanded graphite powder and expanded graphite powder, and both the first composite particle and the second composite particle were included in Composite Particles B to G.

[0077] [Composite Particle H]

[0078] Except for the point that expanded graphite powder was used instead of expanded graphite powder, Composite Particle H as the first composite particle was produced by the same method as the production method of Composite Particle A.

[0079] (a) Core Particle

[0080] Expanded graphite powder: "SYZR 502FP" manufactured by Shijiazhuang Aidi Te Trading Co., Ltd., particle size 300 μm or more: 80% or more.

[0081] Expanded graphite powder: "AED-01" manufactured by Fuji Graphite Industry Co., Ltd., purity 99% or more, particle size 1000 μm or more: 80% or more.

[0082] (b) Magnetic Particle

[0083] Stainless steel powder: "AKT" manufactured by Mitsubishi Steel Co., Ltd., average particle diameter 8.5 to 13.0 μm.

[0084] (c) Binder

[0085] Starch powder: "Instant Tender-JelC" manufactured by Nippon Cornstarch Co., Ltd.

[0086] (d) Insulating Inorganic Particle

[0087] Talc powder: "MICRO ACE (registered trademark) K-1" manufactured by Nippon Talc Co., Ltd., with an average particle size of 8 μm.

[0088]

[0089] <Manufacture of urethane foam molded body>

[0090] Urethane foam molded bodies were manufactured using the prepared composite particles A to H. First, 100 parts by mass of polyether polyol ("SBU (registered trademark) polyol 0248" manufactured by Sumika Covestro Urethane Co., Ltd.), 2 parts by mass of diethylene glycol as a chain extender (manufactured by Mitsubishi Chemical Corporation), 2 parts by mass of water as a foaming agent, 1.5 parts by mass of tetraethylenediamine-based catalyst ("KAOLIZER (registered trademark) No. 31" manufactured by Kao Corporation), and 0.5 parts by mass of silicone-based foam stabilizer ("SZ-1333" manufactured by Dow Corning Toray Co., Ltd.) were mixed to prepare a polyol raw material. In addition, as a polyisocyanate raw material, a diphenylmethane diisocyanate (MDI) modified product was prepared. The MDI modified product was manufactured by mixing polyether polyol (the same as above) and 4,4'-diphenylmethane diisocyanate ("Millionate MT" manufactured by Tosoh Corporation) so that the isocyanate (NCO) content was 70% by mass, and reacting at 100 °C for 180 minutes under nitrogen purging. Next, 80 parts by mass of composite particles and 60 parts by mass of aluminum hydroxide powder as insulating inorganic particles ("SB93" manufactured by Nippon Light Metal Co., Ltd.) were added to 100 parts by mass of the polyol raw material and mixed to prepare a premixed polyol. Then, 100 parts by mass of the premixed polyol and 10 parts by mass of the polyisocyanate raw material (MDI modified product) were mixed to obtain a mixed raw material (mixed raw material manufacturing process).

[0091] Then, the mixed raw materials were injected into an aluminum foaming mold (the chamber is a cuboid with a length of 130 mm × a width of 130 mm × a thickness of 5 mm), and the foaming mold was sealed. Then, the foaming mold was placed in a magnetic induction foaming forming device for foaming forming. In the chamber of the foaming mold, a uniform magnetic field was formed by magnetic field lines that are approximately parallel from top to bottom. The magnetic flux density in the chamber was 200 mT, and the difference in magnetic flux density in the chamber was within ±3%. Foaming forming was carried out while applying a magnetic field for the first 2 minutes, and then (foaming forming process) was carried out without applying a magnetic field for the next approximately 5 minutes. After the foaming forming was completed, demolding was performed to obtain a urethane foamed formed body. The obtained urethane foamed formed bodies were called urethane foamed formed bodies A to H corresponding to the types of composite particles used. The content of the composite particles in the urethane foamed formed bodies A to H was 10% by volume when the volume of the urethane foamed formed body was 100% by volume. The urethane foamed formed bodies C to F are included in the concept of the urethane foamed formed bodies of the present disclosure.

[0092] <Evaluation of Urethane Foamed Formed Body>

[0093] The thermal conductivity and flame retardancy of the manufactured urethane foamed formed bodies were evaluated. The evaluation results of the thermal conductivity and flame retardancy are collectively shown in Table 1 above. The evaluation methods are as follows.

[0094] [Thermal Conductivity]

[0095] The thermal conductivity of the urethane foamed formed body was measured using "HC-110" manufactured by EIHOKEI SEISAKUSHO CO., LTD. according to the heat flow meter method in accordance with JIS A1412-2:1999.

[0096] [Flame Retardancy]

[0097] A vertical burning test of UL94 standard was carried out. In the vertical burning test, the lower end of the vertically held specimen was brought into contact with the flame of a gas burner for 10 seconds. When all of the following five criteria were met, it was judged as V-0 grade. (1) In the two contacts with the flame, the combustion of the specimen was not longer than 10 seconds. (2) The total combustion time of the two contacts with the flame for each of the five specimens did not exceed 50 seconds. (3) There was no specimen that burned to the position of the fixing clip. (4) There was no specimen in which burning particles dripped and caused the cotton placed below the specimen to catch fire. (5) After the second contact with the flame, the specimen did not maintain red heat for a time longer than 30 seconds.

[0098] As shown in Table 1, in the urethane foam molded articles C to F, there are composite particles C to F containing both the first composite particles and the second composite particles, and the content of the expanded graphite particles is 20% by mass or more and 80% by mass or less based on the total mass of the expanded graphite particles and the expanded graphite particles being 100% by mass. Therefore, it has been confirmed that the thermal conductivity of the urethane foam molded articles C to F is 0.65 W / m·K or more and the flame retardancy is V-0, and the urethane foam molded articles C to F satisfy both thermal conductivity and flame retardancy. In contrast, for the urethane foam molded article A using the composite particle A containing only the second composite particles and the urethane foam molded article B with a small content of the expanded graphite particles, as a result, the flame retardancy is satisfied, but the thermal conductivity is poor. In addition, for the urethane foam molded article H using the composite particle H containing only the first composite particles and the urethane foam molded article G with a large content of the expanded graphite particles, as a result, the thermal conductivity is satisfied, but the flame retardancy is poor.

[0099] [Industrial Applicability]

[0100] The urethane foam molded article of the present disclosure is suitable as a sound insulation material for vehicle components such as an inverter, a motor, a gearbox, a cylinder head of an engine, and a cylinder head cover for an electric powertrain, and electronic devices such as personal computers.

Claims

1. A urethane foam-formed body, characterized in that: the urethane foam-formed body has: a substrate composed of a polyurethane foam; and composite particles contained in the substrate in an oriented manner; the composite particles have: first composite particles having expanded graphite particles and magnetic particles bonded to the surface of the expanded graphite particles by a binder; and second composite particles having expanded graphite particles and magnetic particles bonded to the surface of the expanded graphite particles by a binder, when the total mass of the expanded graphite particles and the expanded graphite particles in the substrate is 100% by mass, the content of the expanded graphite particles is 20% by mass or more and 80% by mass or less.

2. The urethane foam molded body according to claim 1, wherein, The average particle size of the expanded graphite particles is 100 μm or more and 3000 μm or less.

3. The urethane foam molded body according to claim 1 or 2, wherein, The purity of the expanded graphite particles is 99% or more.

4. The urethane foam molded body according to any one of claims 1 to 3, wherein, The average particle size of the expanded graphite particles is 100 μm or more and 3000 μm or less.

5. The urethane foam molded body according to any one of claims 1 to 4, wherein, When the volume of the urethane foam-formed body is 100% by volume, the content of the composite particles is 5% by volume or more and 50% by volume or less.

6. The urethane foam molded body according to any one of claims 1 to 5, wherein, The binder constituting the first composite particles and the second composite particles is a water-soluble polymer.

7. The urethane foam molded body according to claim 6, wherein, The water-soluble polymer is one or more selected from methyl cellulose, carboxymethyl cellulose, hydroxypropyl methyl cellulose, polyvinyl alcohol, and starch.

8. The urethane foam molded article according to any one of claims 1 to 7, wherein, When the total mass of the expanded graphite particles and the expanded graphite particles in the substrate is 100% by mass, the content of the magnetic particles constituting the first composite particles and the second composite particles is 20% by mass or more and 80% by mass or less.

9. The urethane foam molded body according to any one of claims 1 to 8, wherein, The magnetic particles constituting the first composite particles and the second composite particles have one or more selected from iron particles and iron-based alloy particles.

10. The urethane foam molded body according to any one of claims 1 to 9, wherein, At least one of the first composite particles and the second composite particles has insulating inorganic particles bonded to the surface of the expanded graphite particles or the expanded graphite particles by a binder.

11. The urethane foam molded article according to claim 10, wherein, The insulating inorganic particles have one or more selected from aluminum hydroxide, alumina, magnesium hydroxide, magnesia, talc, calcium carbonate, clay, mica, and silica.

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