Carbamate foam molded article

Abstract

The urethane foam molded body has a base material formed from a polyurethane foam, composite particles oriented and contained in the base material, and first insulating inorganic particles dispersed in the base material. The composite particles have thermally conductive particles, and magnetic particles bonded to the surfaces of the thermally conductive particles by means of a binder. The thermally conductive particles have expanded graphite particles, and the amount of alkali metal ions contained in the expanded graphite particles is from 500 ppm to 2000 ppm (inclusive).

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a urethane foamed molded body having high thermal conductivity. BACKGROUND

[0002] In a vehicle such as an automobile, in order to reduce noise leaked to the outside or the cabin, measures to reduce noise generated from an engine, a transmission, or the like are taken. In an electric vehicle (EV) or a hybrid electric vehicle (HEV), the driving sound of an electric powertrain composed of an inverter, a motor, a gear box, or the like is also an object to be reduced. As a noise countermeasure, for example, a soundproofing material composed of a foamed body such as a polyurethane foam is used. The foamed body has a plurality of cells (bubbles) inside, and thus has a small thermal conductivity. Therefore, in a case where it is disposed around a noise source that generates heat, there is a risk that heat is accumulated to cause an adverse situation.

[0003] From the viewpoint of improving the heat dissipation of a soundproofing material using a foamed body, for example, Patent Literature 1 describes a urethane foamed molded body in which a composite particle composed of a thermally conductive particle such as expanded graphite, a magnetic particle, and an insulating inorganic particle is oriented and disposed, and a heat transfer path is formed in the orientation direction thereof, thereby improving the heat dissipation. In addition, it is described in this document that by dispersing the insulating inorganic particle separately from the composite particle in the polyurethane foam, electrical insulation can be imparted, and the heat dissipation and flame retardancy can be improved depending on the characteristics of the insulating inorganic particle.

[0004] PRIOR ART DOCUMENTS PATENT LITERATURE Patent Literature 1: International Publication No. 2013 / 042611 SUMMARY PROBLEMS TO BE SOLVED BY THE INVENTION However, the conventional urethane foamed molded body has a problem of low heat resistance, and specifically, has a problem that the elongation and the like are reduced when left at a high temperature of about 150°C. If the heat resistance is low, it is difficult to apply to various ECUs (Electronic Control Units) mounted on a vehicle, a junction box, or the like, which become high-temperature components. In the above-described Patent Literature 1, only the thermal conductivity and the electrical insulation of the urethane foamed molded body were evaluated, and the heat resistance was not studied.

[0005] The present disclosure was completed in view of such a situation, and has a problem of providing a urethane foamed molded body having excellent thermal conductivity and heat resistance.

[0006] MEANS FOR SOLVING THE PROBLEM (1) To solve the above problems, the urethane foamed molded body of the present disclosure is characterized by having a base material formed of a polyurethane foam, composite particles contained in the base material and oriented, and first insulating inorganic particles dispersed in the base material, the composite particles having a thermally conductive particle, and a magnetic particle bonded to a surface of the thermally conductive particle by an adhesive, the thermally conductive particle having an expanded graphite particle, the amount of alkali metal ions contained in the expanded graphite particle being 500 ppm or more and 2000 ppm or less.

[0007] The urethane foamed molded body of the present disclosure has composite particles oriented and arranged in a base material, and first insulating inorganic particles dispersed in the base material. By connecting the composite particles in a string of beads with the thermally conductive particles as cores, a heat transfer path is formed in the base material. Thus, the desired thermal conductivity can be achieved. The thermally conductive particles have expanded graphite particles. The expanded graphite particles are manufactured by intercalating a substance that generates gas by heating between the layers of flaky graphite. If heat is applied to the expanded graphite particles, the layers expand by the generated gas, and a layer that is stable to heat and chemicals is formed. This stable layer forms a thermal barrier that hinders the movement of heat. Thus, the urethane foamed molded body is given flame retardancy. The first insulating inorganic particles are particles of an inorganic material that has insulating properties. By the presence of the first insulating inorganic particles, the composite particles are difficult to conduct to each other, and the urethane foamed molded body is given electrical insulation. In addition, in the case where the thermal conductivity of the first insulating inorganic particles is relatively large, a heat transfer path based on the first insulating inorganic particles is also formed in addition to the heat transfer path based on the composite particles. Thus, the thermal conductivity of the urethane foamed molded body is further improved. In addition, in the case where the first insulating inorganic particles have flame retardancy, the flame retardancy of the urethane foamed molded body is improved.

[0008] The inventors of the present invention repeatedly researched expanded graphite particles that constitute the composite particles in order to solve the problem of the heat resistance of the urethane foamed molded body, and as a result, found that the amount of alkali metal ions contained in the expanded graphite particles is one cause of the reduction in the heat resistance of the urethane foamed molded body. Generally, expanded graphite is manufactured by oxidizing graphite with sulfuric acid and an oxidizing agent, and then neutralizing the acidic substances adhering to the surface with a neutralizing agent. The neutralizing agent uses alkali metal compounds, ammonia, and the like, so if the neutralizing agent remains on the surface of the expanded graphite, it reacts with the water contained in the polyurethane foam of the base material to create an alkaline atmosphere. It is presumed that if exposed to high temperatures in this state, the hydrolysis of the polyurethane is promoted, and the deterioration is intensified. In addition, in an alkaline atmosphere, there is a risk that the first insulating inorganic particles will dissolve.

[0009] Therefore, the amount of alkali metal ions contained in the expanded graphite particles is limited to 500 ppm or more and 2000 ppm or less. By limiting the amount of alkali metal ions to 2000 ppm or less, the polyurethane foam is inhibited from becoming excessively basic. Thus, the hydrolysis of the polyurethane is inhibited, and the first insulating inorganic particles become difficult to dissolve. As a result, even in the case where the urethane foamed molded body is placed in a high temperature, the deterioration of the polyurethane is inhibited, and the decrease in the physical properties such as elongation is inhibited. On the other hand, due to the influence of the interlayer compound of the expanded graphite particles, the raw materials used to manufacture the urethane foamed molded body sometimes tend to be acidic, and there is a risk of affecting the foaming and curing reaction. Therefore, by limiting the amount of alkali metal ions to 500 ppm or more, the pH balance of the raw materials is achieved, and the influence on the moldability is reduced. According to the above, the thermal conductivity and the heat resistance of the urethane foamed molded body of the present disclosure are excellent.

[0010] (2) It can also be configured such that, based on the above configuration, the alkali metal ions have sodium ions. Sodium ions are contained in hydroxides, oxides, and the like used as neutralizing agents, and have a large influence on the pH. Therefore, by limiting the amount of this sodium ions, the pH of the polyurethane foam is easily optimized.

[0011] (3) It can also be configured such that, based on any of the above configurations, the content of the composite particles is 5 vol% or more and 50 vol% or less, in the case where the volume of the urethane foamed molded body is set to 100 vol%. According to this configuration, the influence on the foaming and curing reaction, the moldability, and the like is reduced, and the effects of the improvement in the thermal conductivity and the like due to the composite particles are obtained.

[0012] (4) It can also be configured such that, based on any of the above configurations, the content of the first insulating inorganic particles is 5 vol% or more and 20 vol% or less, in the case where the volume of the urethane foamed molded body is set to 100 vol%. According to this configuration, the influence on the foaming and curing reaction, the moldability, and the like is reduced, and the effects of the imparting of the electrical insulation, the improvement in the thermal conductivity, and the like due to the first insulating inorganic particles are obtained.

[0013] (5) It can also be configured such that, based on any of the above configurations, the thermal conductivity of the first insulating inorganic particles is 5 W / m·K or more. According to this configuration, the effect of the improvement in the thermal conductivity due to the first insulating inorganic particles is obtained.

[0014] (6) It can also be configured as follows: on the basis of any of the above configurations, the first insulating inorganic particles have one or more selected from the group consisting of aluminum hydroxide, aluminum oxide, aluminum nitride, magnesium hydroxide, magnesium oxide, talc, calcium carbonate, clay, mica, and silicon dioxide. The first insulating inorganic particles of this configuration are relatively inexpensive and easy to obtain. Among them, aluminum hydroxide, aluminum oxide, aluminum nitride, magnesium hydroxide, magnesium oxide, and talc have a relatively large thermal conductivity, and thus are suitable for improving the thermal conductivity of the urethane foamed molded body.

[0015] (7) It can also be configured as follows: on the basis of any of the above configurations, the composite particles have second insulating inorganic particles adhered to the surface of the thermally conductive particles by an adhesive. In this configuration, the second insulating inorganic particles can be adhered directly to the surface of the thermally conductive particles as the core, or indirectly via magnetic particles. As the magnetic particles, a ferromagnetic substance such as stainless steel or iron is used. Thus, the composite particles in which the thermally conductive particles and the magnetic particles are combined have high electrical conductivity. If the second insulating inorganic particles are adhered to the composite particles in this state, even if the composite particles are oriented in contact with each other, the thermally conductive particles and the magnetic particles (electrically conductive particles) are less likely to come into contact with each other between adjacent composite particles. Thus, the resistance between the composite particles increases. In addition, by causing the composite particles to come into contact with each other with the second insulating inorganic particles therebetween, conduction between the composite particles can be cut off. As a result, in the urethane foamed molded body of the present disclosure, the desired electrical insulation can be achieved. In this way, according to this configuration, electrical insulation can be imparted on the basis of high thermal conductivity and heat resistance. Thus, the urethane foamed molded body of this configuration is also suitable for applications such as heat dissipation members in electronic devices that require both thermal dissipation and electrical insulation.

[0016] (8) It can also be configured as follows: on the basis of the configuration of (7) above, the second insulating inorganic particles have one or more selected from the group consisting of aluminum hydroxide, aluminum oxide, aluminum nitride, magnesium hydroxide, magnesium oxide, talc, calcium carbonate, clay, mica, and silicon dioxide. As explained in the configuration of (6) above, the second insulating inorganic particles of this configuration are relatively inexpensive and easy to obtain. Among them, talc and mica are in a flaky shape and have excellent coating properties. In addition, aluminum hydroxide, aluminum oxide, aluminum nitride, magnesium hydroxide, magnesium oxide, and talc have a relatively large thermal conductivity, and thus are less likely to hinder the thermal conductivity between the composite particles.

[0017] Effects of the Invention In the substrate of the urethane foamed molded body of the present disclosure, composite particles having thermally conductive particles as cores are oriented, and first insulating inorganic particles are dispersed. The thermally conductive particles have expanded graphite particles containing an alkali metal ion in an amount of 500 ppm or more and 2000 ppm or less. Thus, the pH of the polyurethane foam is adjusted to a desired range, and even when the urethane foamed molded body is placed at a high temperature, the deterioration of the polyurethane and the decrease in the elongation and the like can be suppressed. Thus, the thermal conductivity and the heat resistance of the urethane foamed molded body of the present disclosure are excellent. DETAILED DESCRIPTION

[0018] Hereinafter, an embodiment of the urethane foamed molded body of the present disclosure will be described. Furthermore, the embodiment is not limited to the following mode, and can be implemented in various modes of modification and improvement that can be made by those skilled in the art.

[0019] <URETHANE FOAMED MOLDED BODY> The urethane foamed molded body of the present disclosure has a substrate formed of a polyurethane foam, composite particles contained therein oriented, and first insulating inorganic particles dispersed in the substrate.

[0020] [SUBSTRATE] The polyurethane foam of the substrate is manufactured from a foaming urethane resin raw material of a polyisocyanate component and a polyol component, and the like. The foaming urethane resin raw material can be prepared from already known raw materials such as a polyol, a polyisocyanate, and the like. As the polyol, it is appropriate to select from among a polyhydric alcohol compound, a polyether polyol, a polyester polyol, a polymer polyol, a polyether polyamine, a polyester polyamine, an alkylene polyol, a urea dispersion polyol, a melamine-modified polyol, a polycarbonate polyol, an acrylic polyol, a polybutadiene polyol, a phenol-modified polyol, and the like. In addition, as the polyisocyanate, it is appropriate to select from among, for example, toluene diisocyanate, phenylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, triphenylmethane triisocyanate, polymethylene polyphenyl isocyanate, naphthalene diisocyanate, and derivatives thereof (for example, prepolymers obtained by reaction with a polyol, modified polyisocyanates), and the like.

[0021] A catalyst, a blowing agent, a foam stabilizer, a plasticizer, a crosslinking agent, a chain extender, a flame retardant, an antistatic agent, a viscosity reducer, a stabilizer, a filler, a coloring agent, and the like can be further appropriately incorporated in the foamed urethane resin raw material. For example, as the catalyst, amine-based catalysts such as tetraethylenediamine, triethylenediamine, dimethylethanolamine, and the like, and organometal-based catalysts such as tin laurate, tin octoate, and the like can be exemplified. In addition, as the blowing agent, water is preferable. In addition to water, dichloromethane, freon, CO2 gas, and the like can be exemplified. In addition, as the foam stabilizer, silicone-based foam stabilizers are preferable, and as the crosslinking agent, triethanolamine, diethanolamine, and the like are preferable.

[0022] The shape, size, and the like of the base material are not particularly limited, and can be appropriately determined according to the use. The composite particles contained in the base material can be arranged in any regularity. For example, the composite particles can be arranged in a straight line between one end and the other end of the urethane foamed molded body (the other end can not be the end opposite to the one end by 180°). In addition, the composite particles can be arranged radially from the center to the outer periphery.

[0023] [Composite particles] The composite particles contained in the base material are particles in which magnetic particles or the like are adhered to the surface of the thermally conductive particles as the core by an adhesive. The thermally conductive particles are non-magnetic bodies, and are particles having a large thermal conductivity. In the present specification, diamagnetic bodies and paramagnetic bodies other than ferromagnetic bodies and antiferromagnetic bodies are referred to as non-magnetic bodies. The thermally conductive particles have expanded graphite particles. The thermally conductive particles can be single particles, or can be aggregate particles in which a plurality of particles are integrated. As the composite particles, particles in which magnetic particles or the like are adhered to the surface of the expanded graphite particles, and particles in which magnetic particles or the like are adhered to the surface of the aggregate particles in which the expanded graphite particles and other particles are integrated can be exemplified. In addition, the composite particles can include particles in which magnetic particles or the like are adhered to the surface of particles other than the expanded graphite particles.

[0024] Generally, urethane foamed molded bodies imparted with flame retardancy have a melt dripping effect of suppressing the spread of fire even when exposed to a flame. However, if magnetic particles are incorporated, there is a risk of impairing the melt dripping effect and reducing the self-extinguishing property of the urethane foamed molded body. In the urethane foamed molded body of the present disclosure, the composite particles are oriented. Therefore, heat applied to the urethane foamed molded body is easily transferred to the thermally conductive particles, and the expanded graphite particles quickly reach the expansion start temperature. Thus, the flame retardant effect based on the expanded graphite particles is quickly exerted. Accordingly, according to the present configuration, it is possible to suppress the reduction in the self-extinguishing property of the urethane foamed molded body, and maintain the flame retardancy.

[0025] As the expanded graphite particles, it is possible to select appropriately the expansion start temperature, the expansion rate, and the like. The expansion start temperature must be higher than the heat generation temperature at the time of molding of the urethane molded body, and therefore it is preferable to use expanded graphite particles having an expansion start temperature of 150°C or higher. The amount of alkali metal ions contained in the expanded graphite particles is 500 ppm or more and 2000 ppm or less. By making the amount of alkali metal ions 2000 ppm or less, it is possible to suppress the polyurethane foam from becoming excessively basic. On the other hand, by making the amount of alkali metal ions 500 ppm or more, it is possible to achieve a pH balance between the raw materials used for the production of the urethane molded body and the interlayer compound, and to reduce the influence on the moldability.

[0026] As the alkali metal ions, it is possible to cite lithium ions, sodium ions, potassium ions, and the like. In the production process of expanded graphite, a neutralizing agent is used, and most of the neutralizing agents are sodium hydroxide, sodium oxide, and the like. Therefore, if the amount of sodium ions is limited, it is easy to optimize the pH of the polyurethane foam. The amount of alkali metal ions contained in the expanded graphite particles can be found by analyzing a liquid sample obtained by immersing 2 g of a powder of the expanded graphite particles in 50 mL of ion-exchanged water at 50°C for 2 hours, using ICP (inductively coupled plasma) emission spectrometry. In addition, the pH of a dispersion liquid obtained by dispersing 2 g of a powder of the expanded graphite particles in 50 mL of ion-exchanged water at room temperature (20°C ± 5°C, the same applies hereinafter) is preferably 6 or more and 8 or less.

[0027] As the thermally conductive particles other than the expanded graphite particles, it is possible to use particles having a thermal conductivity of 200 W / m-K or more. For example, it is possible to cite carbon materials such as natural graphite, artificial graphite, carbon fibers, and the like, aluminum, gold, silver, copper, and alloys using these as a base material, and the like.

[0028] The shape of the thermally conductive particles is not particularly limited as long as it can be compounded with other particles such as magnetic particles. For example, it is possible to adopt various shapes such as a flake shape, a fiber shape, a columnar shape, a spherical shape, an ellipsoidal shape, a prolate spheroidal shape (a shape in which a pair of opposing hemispheres are connected by a cylinder), and the like. In the case where the thermally conductive particles form a shape other than a sphere, the contact area between the composite particles becomes large. Thereby, it is easy to secure a heat transfer path, and the amount of heat transferred also becomes large.

[0029] From the viewpoint of increasing the thermal conductivity, the median particle diameter of the thermally conductive particles is preferably 100 μm or more. It is more preferable to be 700 μm or more. On the other hand, if the thermally conductive particles are too large, there is a risk that cracks and the like will occur from this as a starting point, and the molded body will become brittle. Therefore, the median particle diameter of the thermally conductive particles is preferably 3000 μm or less. It is more preferable to be 2000 μm or less. Unless otherwise specified, the median particle diameter in this specification is a value (D50) found from a particle size distribution on a volume basis measured by a laser diffraction scattering method. 50). In addition, for a commercial product, a catalog value can also be used.

[0030] The magnetic particles only need to be able to orient the composite particles, and for example, particles of ferromagnetic substances such as iron, nickel, cobalt, gadolinium, stainless steel, magnetite, maghemite, manganese zinc ferrite, barium ferrite, strontium ferrite, antiferromagnetic substances such as MnO, Cr2O3, FeCl2, MnAs, and alloys using these are preferred. Of these, from the viewpoint of being easily obtained in the form of fine particles and having a high saturation magnetization, iron, nickel, cobalt, and iron-based alloys thereof (including stainless steel) are preferred. In particular, iron is inexpensive and easy to obtain, and thus can reduce manufacturing costs and is suitable for mass production.

[0031] The magnetic particles can be directly bonded to the surface of the thermally conductive particles, or can be indirectly bonded via the second insulating inorganic particles and the like described later. In addition, the magnetic particles can be bonded only to a part of the surface of the thermally conductive particles, or can be bonded in a manner of covering the entire surface. The size of the magnetic particles can be appropriately determined in consideration of the size of the thermally conductive particles, the orientation of the composite particles, and the thermal conductivity between the composite particles, and the like. For example, the particle diameter of the magnetic particles is preferably 1 / 10 or less of the particle diameter of the thermally conductive particles. The "particle diameter" in this case is the equivalent spherical diameter. If the size of the magnetic particles is reduced, there is a tendency for the saturation magnetization of the magnetic particles to decrease. Thus, in order to orient the composite particles with a smaller amount of magnetic particles, it is preferred that the median particle diameter of the magnetic particles be 100 nm or more. More preferably, it is 1 μm or more, and further preferably, it is 5 μm or more.

[0032] The shape of the magnetic particles is not particularly limited. For example, in the case where the shape of the magnetic particles is flat, the distance between adjacent thermally conductive particles is shorter compared to the case of a spherical shape. Thereby, the thermal conductivity between adjacent composite particles is improved. As a result, the thermal conductivity of the urethane foamed molded body is improved. In addition, in the case where the shape of the magnetic particles is flat, the magnetic particles and the thermally conductive particles are in surface contact. That is, the contact area of both is large. Thereby, the adhesion of the magnetic particles and the thermally conductive particles is improved. Therefore, the magnetic particles are difficult to peel off. On this basis, the thermal conductivity between the magnetic particles and the thermally conductive particles is also improved. For this reason, as the magnetic particles, it is preferred to use particles in the form of a thin sheet.

[0033] From the viewpoint of being able to orient the composite particles even in a lower magnetic field, the content of the magnetic particles is preferably 20% by mass or more, based on 100% by mass of the thermally conductive particles in the base material. In addition, from the viewpoint of achieving 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 further preferably, it is 80% by mass or less.

[0034] The binder for bonding the thermally conductive particles and the magnetic particles can be appropriately selected in consideration of the bonding property, influence on the foaming and curing reaction, and the like. From the viewpoint of having little influence on the foaming and curing reaction and being environmentally friendly, a water-soluble polymer is preferable. For example, methylcellulose, carboxymethylcellulose, hydroxypropylmethylcellulose, polyvinyl alcohol, starch, and the like can be exemplified. Among them, starch is relatively inexpensive, has high bonding property, and has excellent granulation property, and thus is preferable.

[0035] The thermally conductive particles and the magnetic particles have electrical conductivity. Therefore, by orienting the composite particles in connection, a conduction path is formed in the base material. For example, a second insulating inorganic particle can be bonded to the surface of the thermally conductive particle using a binder in addition to the magnetic particle, thereby constituting a composite particle. Thereby, even if the composite particles are oriented, it is possible to increase the resistance between adjacent composite particles or to cut the conduction. As a result, it is possible to impart electrical insulation to the urethane foamed molded body.

[0036] The second insulating inorganic particle can be a particle of an inorganic material having insulating property, like the first insulating inorganic particle dispersed in the base material. As the second insulating inorganic material, aluminum hydroxide, aluminum oxide, aluminum nitride, magnesium hydroxide, magnesium oxide, talc, calcium carbonate, clay, mica, silicon dioxide, and the like can be exemplified. One of them can be used alone, or two or more of them can be used in combination. Among them, talc and mica are in a flaky shape, and have excellent coating property, and thus are preferable. From the viewpoint of not hindering the thermal conductivity between the composite particles, a material having a large thermal conductivity coefficient can also be used.

[0037] The second insulating inorganic particle can be directly bonded to the surface of the thermally conductive particle, or can be indirectly bonded via the magnetic particle or the like. In addition, the second insulating inorganic particle can be bonded to only a part of the surface of the thermally conductive particle, or can be bonded in a manner of coating the entire surface. If the entire surface of the thermally conductive particle is coated with the second insulating inorganic particle, the influence of the interlayer substance of the expanded graphite particle, the remaining alkali metal ions, and the like is small, and thus is preferable. From the viewpoint of increasing the resistance between the composite particles and improving the electrical insulation of the urethane foamed molded body, the second insulating inorganic particle is preferably disposed at the outermost layer of the composite particle. The binder for bonding the thermally conductive particle and the magnetic particle can be the same as or different from the binder for bonding the insulating inorganic particle.

[0038] The size of the second insulating inorganic particles is appropriately determined in consideration of the adhesion to the thermally conductive particles and the magnetic particles, the electrical insulation between the composite particles, and the thermal conductivity. If the second insulating inorganic particles are too large, the adhesion and the thermal conductivity between the composite particles decrease. For example, the particle diameter of the second insulating inorganic particles is preferably 1 / 10 or less of the particle diameter of the thermally conductive particles. The "particle diameter" in this case is the equivalent spherical diameter. In addition, the second insulating inorganic particles are adhered to the thermally conductive particles, and are only a part of the composite particles. Therefore, unlike the first insulating inorganic particles described later, the contact area of the substrate with the polyurethane foam is small, and the influence on the polyurethane foam is small. Therefore, the median particle diameter of the second insulating inorganic particles can be 1 μm or more and 20 μm or less.

[0039] The shape of the second insulating inorganic particles is not particularly limited. For example, in the case where the second insulating inorganic particles have a flat shape, the distance between adjacent thermally conductive particles can be shortened compared to the case of a spherical shape. Therefore, the thermal conductivity between adjacent composite particles is less likely to be hindered. In addition, by increasing the contact area with the thermally conductive particles, the second insulating inorganic particles are less likely to peel off.

[0040] The content of the composite particles is determined in consideration of the thermal conductivity, the influence on the foaming and curing reaction of the polyurethane foam, moldability, and the like. In order to achieve the desired thermal conductivity, in the case where the volume of the urethane foamed molded body is taken as 100 vol%, the content of the composite particles is preferably taken to be 5 vol% or more. More preferably, it is taken to be 10 vol% or more. On the other hand, from the viewpoint of not hindering the foaming and curing reaction and allowing good moldability, the content of the composite particles is preferably taken to be 50 vol% or less. More preferably, it is taken to be 20 vol% or less.

[0041] [First Insulating Inorganic Particles] The kind of the first insulating inorganic particles dispersed in the substrate can be the same as the second insulating inorganic particles added as the constituent particles of the composite particles, or can be different. The shape of the first insulating inorganic particles is not particularly limited, and can be spherical or flaky. The first insulating inorganic particles can be one kind, or two or more kinds. For the first insulating inorganic particles, it is also preferable that the above-mentioned aluminum hydroxide, aluminum oxide, aluminum nitride, magnesium hydroxide, magnesium oxide, talc, calcium carbonate, clay, mica, silica, and the like are used. In addition, from the viewpoint of improving the thermal conductivity of the urethane foamed molded body, a material having a large thermal conductivity is preferable. For example, the thermal conductivity of the first insulating inorganic particles is preferably 5 W / m·K or more. Among them, aluminum hydroxide also has flame retardancy, and is therefore preferable.

[0042] The size of the first insulating inorganic particles is appropriately determined in consideration of the electrical insulation, thermal conductivity, moldability, and the like of the urethane foamed molded body. In the case where the contact area of the first insulating inorganic particles with the polyurethane foam is large, there is a risk that the heat resistance of the urethane foamed molded body is reduced due to the influence of the first insulating inorganic particles. For example, in the case where the first insulating inorganic particles are particles that exhibit alkalinity in reaction with water, they react with water contained in the polyurethane foam to generate an alkaline atmosphere. It is presumed that in this state, when exposed to high temperature, the hydrolysis of the polyurethane is promoted, and the deterioration is intensified. Therefore, from the viewpoint of reducing the influence on the polyurethane foam, the first insulating inorganic particles preferably have large-diameter particles with a median particle diameter of 55 μm or more and 200 μm or less. In the case where the median particle diameter is 55 μm or more, the contact area with the polyurethane foam becomes small, and the influence on the polyurethane foam becomes small. For example, in the case where the large-diameter particles are particles that exhibit alkalinity in reaction with water (alkaline inorganic particles), the deterioration due to the hydrolysis of the polyurethane is suppressed, and even in the case where the urethane foamed molded body is placed under high temperature, the physical properties such as elongation are not easily reduced. In the present specification, the "particles that exhibit alkalinity in reaction with water" refer to particles in which, in the case where the pH of a dispersion liquid in which 2 g of the powder of the subject particles is dispersed in ion exchange water of 50 mL at room temperature is measured, the pH is greater than 7. On the other hand, in the case where the median particle diameter is 200 μm or less, the influence on the moldability is small, and the generation of cracks and the like can be suppressed. From the viewpoint of further improving the moldability and the physical properties in the normal state, the median particle diameter of the large-diameter particles can be 150 μm or less. The first insulating inorganic particles can be composed only of the large-diameter particles, or can be composed of particles other than the large-diameter particles, as long as the desired heat resistance and moldability can be achieved.

[0043] In consideration of the influence on the foaming and curing reaction of the polyurethane foam, moldability, and the like, the content of the first insulating inorganic particles is preferably 20% by volume or less, in the case where the volume of the urethane foamed molded body is taken as 100% by volume. More preferably, it is 15% by volume or less. In addition, in order to obtain the desired effects of imparting electrical insulation, improving thermal conductivity, and the like, it is preferably 5% by volume or more. More preferably, it is 8% by volume or more.

[0044] <Method for producing urethane foamed molded body> The method for producing the urethane foamed molded body of the present disclosure is not particularly limited. As one mode of the preferred production method, the method for producing the urethane foamed molded body of the present disclosure has a composite particle production step, a raw material mixing step, and a foaming and molding step. Hereinafter, each step will be described.

[0045] [Composite particle production step] This process is a process of manufacturing composite particles by stirring a granulation raw material of a powder of thermally conductive particles, a powder of magnetic particles, a powder of a second insulating inorganic particle as needed, a binder, and water. The amount of the binder to be added is appropriately adjusted in consideration of the magnetic field orientation of the composite particles, the electrical insulation of the urethane foamed molded body, the thermal conductivity, and the like.

[0046] The amount of the powder of magnetic particles is preferably 20 parts by mass or more relative to 100 parts by mass of the powder of thermally conductive particles in consideration of the magnetic field orientation of the composite particles. On the other hand, it is preferably 130 parts by mass or less in consideration of the cost and weight reduction. It is more preferably 100 parts by mass or less, and further preferably 80 parts by mass or less. The amount of the binder is preferably 2% by mass or more in consideration of an amount sufficient for the adhesion of the particles, with the total amount of the powders to be adhered being set to 100% by mass. On the other hand, if the binder is excessive, there is a risk that the composite particles will agglomerate. Therefore, the amount of the binder is preferably 10% by mass or less. It is more preferably 5% by mass or less. The binder can be either solid or liquid. In the case where a water-soluble powder is used as the binder, the binder and the other powder raw materials can be stirred in advance and then water can be added. Thereby, the agglomeration of the particles can be suppressed.

[0047] In the case where the powder of the second insulating inorganic particle is included in the granulation raw material and the second insulating inorganic particle is disposed in the outermost layer of the composite particles, this process can be configured to have a first stirring process of stirring a first raw material of the powder of thermally conductive particles, the powder of magnetic particles, and the binder, and a second stirring process of adding the powder of the second insulating inorganic particle to the stirred product of the first raw material and further stirring.

[0048] [Manufacturing process of mixed raw material] This process is a process of mixing the powder of the composite particles manufactured in the previous process, the powder of the first insulating inorganic particle, and the foamed urethane resin raw material to manufacture a mixed raw material.

[0049] The foamed urethane resin raw material can be prepared from the raw materials such as polyol, polyisocyanate, catalyst, blowing agent, and foam stabilizer, as described above. The mixed raw material can be manufactured, for example, by mechanically stirring the powder of the composite particles, the powder of the first insulating inorganic particle, and the foamed urethane resin raw material using a stirring blade or the like. Alternatively, the powder of the composite particles and the powder of the first insulating inorganic particle can be added to at least one of the two components (polyol raw material, polyisocyanate raw material) of the foamed urethane resin raw material, the two raw materials can be prepared, and the two raw materials can be mixed to manufacture the mixed raw material.

[0050] [Manufacturing process of mixed raw material] This process is a process of injecting the mixed raw material manufactured in the previous process into a cavity of a foaming mold, and performing foaming molding while applying a magnetic field in such a manner that the magnetic flux density in the cavity is substantially uniform.

[0051] The magnetic field only needs to be formed in a direction in which the composite particles are oriented. For example, in the case where the composite particles are oriented in a straight line, it is preferable that the magnetic lines of force in the cavity of the foaming mold be formed to be substantially parallel from one end of the cavity toward the other end. In order to form such a magnetic field, for example, magnets can be disposed near both the one end and the other end of the foaming mold in such a manner as to sandwich the foaming mold. The magnets can use permanent magnets or electromagnets. If electromagnets are used, the on and off of the magnetic field formation can be switched instantaneously, and the strength of the magnetic field can be easily controlled. Thus, the foaming molding can be easily controlled. In addition, it is preferable that the magnetic lines of force constituting the magnetic field form closed loops. Thereby, leakage of the magnetic lines of force can be suppressed, and a stable magnetic field can be formed in the cavity.

[0052] In this process, the magnetic field is formed in such a manner that the magnetic flux density in the cavity is substantially uniform. For example, the difference in the magnetic flux density in the cavity can be within ±10%. More preferably, it is within ±5%, and further preferably, it is within ±3%. By forming a uniform magnetic field in the cavity of the foaming mold, the biased presence of the composite particles can be suppressed, and the desired orientation state can be obtained. In addition, the foaming molding can be performed at a magnetic flux density of 150 mT or more and 350 mT or less. Thereby, the composite particles in the mixed raw material can be reliably oriented. The magnetic field is preferably applied during a period in which the viscosity of the foaming urethane resin raw material is low. If the magnetic field is applied when the foaming urethane resin raw material is thickened and the foaming molding is substantially completed, the composite particles are difficult to orient, and thus it is difficult to obtain the desired thermal conductivity. Furthermore, it is not necessary to apply the magnetic field for the entire time during which the foaming molding is performed.

[0053] After the foaming molding is completed in this process, demolding is performed, and the urethane foaming molded body of the present disclosure is obtained. At this time, depending on the method of foaming molding, a skin layer is formed in at least one of the one end and the other end of the urethane foaming molded body. The skin layer can be cut off depending on the use (of course, it can not be cut off).

[0054] Example Next, examples are presented, and the present disclosure is more specifically described. In this example, urethane foaming molded bodies were manufactured using powders of expanded graphite particles having different amounts of sodium ions, and the characteristics thereof were evaluated.

[0055] <Manufacture of Composite Particles> The granulation raw materials of the expanded graphite powder as the thermally conductive particles, the stainless steel powder as the magnetic particles, the starch powder as the binder, the talc powder as the second insulating inorganic particles, and water were stirred to produce the composite particles. As the powder of the expanded graphite particles, four kinds of A to D were used, which differ in the amount of sodium (Na) ions, to produce four kinds of composite particles. First, the expanded graphite powder 1000 parts by mass, the stainless steel powder 600 parts by mass, and the starch powder 100 parts by mass were put into the container of the high-speed stirring type mixing granulator, mixed by the blade stirring, further added with water 400 parts by mass, and mixed for 1 minute. Next, the talc powder 400 parts by mass was put in and mixed for 4 minutes. The stirring speed was 400 rpm. The obtained powder was dried to produce the powder of the composite particles. The details of the materials used are shown in (a) to (d) below, and the respective amounts of the components are shown in Table 1 below.

[0056] (a) Thermally conductive particles Expanded graphite powder A: "EXA-50" manufactured by Fuji Graphite Industry, Co., Ltd., Na ion amount 500 ppm, pH 6, median particle diameter 300 μm (the same as expanded graphite powders B to D).

[0057] Expanded graphite powders B to D were produced by adding a 10 mass% sodium hydroxide aqueous solution dropwise to the expanded graphite powder A and drying. In addition, the pH of the expanded graphite powder was measured by dispersing 2 g of the expanded graphite powder in 50 mL of ion exchange water at room temperature and using a glass electrode type pH meter to measure the pH of the dispersion after 5 minutes.

[0058] Expanded graphite powder B: Na ion amount 1000 ppm, pH 7.

[0059] Expanded graphite powder C: Na ion amount 2000 ppm, pH 8.

[0060] Expanded graphite powder D: Na ion amount 3500 ppm, pH 10.

[0061] (b) Magnetic particles Stainless steel powder: "AKT" manufactured by Mitsubishi Steel, Co., Ltd., median particle diameter 8.5 to 13.0 μm.

[0062] (c) Binder Starch powder: "INSTANT TENDER-JEL C" manufactured by Nihon Cornstarch, Co., Ltd.

[0063] (d) Second insulating inorganic particles Talc powder: "MICRO ACE (registered trademark) K-1" manufactured by Nihon Talc, Co., Ltd., median particle diameter 8 μm.

[0064] <Manufacture of urethane foamed molded body> A urethane foamed molded body was manufactured using the manufactured composite particle powder and an aluminum hydroxide powder as first insulating inorganic particles. First, a polyol raw material was prepared by mixing 100 parts by mass of a polyether polyol ("SBU (registered trademark) Polyol 0248" manufactured by Sumika Covestro Urethane (Co., Ltd.), 2 parts by mass of a chain extender, diethylene glycol (manufactured by Mitsubishi Chemical (Co., Ltd.), 2 parts by mass of a foaming agent, water, 1.5 parts by mass of a tetraethylenediamine-based catalyst ("KAOLIZER (registered trademark) No. 31" manufactured by Kawako (Co., Ltd.), and 0.5 parts by mass of a silicone-based foam stabilizer ("SZ-1333" manufactured by DOW CORNING TORAY SILICONE CO., LTD.). As a polyisocyanate raw material, a modification of diphenylmethane diisocyanate (MDI) was prepared. The MDI modification was manufactured by mixing a polyether polyol (the same as above) and 4,4'-diphenylmethane diisocyanate ("MILLIONATE MT" manufactured by DOW CORNING TORAY SILICONE CO., LTD.) in such a manner that the isocyanate (NCO) content became 70% by mass, and reacting at 100°C for 180 minutes under nitrogen purge. Next, a premixed polyol was prepared by adding and mixing 80 parts by mass of the composite particle powder and 60 parts by mass of an aluminum hydroxide powder ("SB53" manufactured by Japan Light Metal (Co., Ltd.), with a median particle diameter of 55 μm and a thermal conductivity of 8 W / m-K) in 100 parts by mass of the polyol raw material. Next, a mixed raw material was prepared by mixing 100 parts by mass of the premixed polyol and 10 parts by mass of the polyisocyanate raw material (MDI modification). In addition, 2 g of the aluminum hydroxide powder was dispersed in 50 mL of ion exchange water at room temperature, and the pH of the dispersion after 5 minutes was measured using a glass electrode pH meter, and the result was that the pH was 8.

[0065] Then, the mixed raw material was injected into an aluminum foaming mold (cavity: 130 mm long x 130 mm wide x 5 mm thick rectangular parallelepiped), and the foaming mold was closed. Then, the foaming mold was set in a magnetic induction foaming molding device, and foaming molding was performed. In the cavity of the foaming mold, a uniform magnetic field was formed using magnetic lines of force that were approximately parallel from the top to the bottom. The magnetic flux density in the cavity was 200 mT, and the difference in the magnetic flux density in the cavity was within ±3%. Foaming molding was performed while applying a magnetic field for the first 2 minutes, and then for about 5 minutes without applying a magnetic field. After the foaming molding was completed, demolding was performed, and a urethane foamed molded body was obtained. The urethane foamed molded body obtained was referred to as urethane foamed molded bodies A to D corresponding to the type of the powder of the expanded graphite particles used. The content of the composite particles in the urethane foamed molded bodies A to D was 7.5% by volume, and the content of the first insulating inorganic particles was 12.5% by volume (the volume of the urethane foamed molded body was assumed to be 100% by volume). The urethane foamed molded bodies A, B, and C are included in the concept of the urethane foamed molded body of the present disclosure.

[0066] [Evaluation of the urethane foamed molded body] The thermal conductivity, elongation, heat resistance, moldability, and flame retardancy of the manufactured urethane foamed molded body were evaluated. The evaluation results are summarized in Table 1 described below. The evaluation methods were as follows.

[0067] [Thermal conductivity] The thermal conductivity of the urethane foamed molded body was measured using "HC-110" manufactured by Eiho Seiki (Co., Ltd.) according to the heat flow meter method of JIS A1412-2:1999.

[0068] [Elongation] Five test pieces of dumbbell No. 1 shape prescribed in JIS K 6251:2017 were prepared from the urethane foamed molded body, and for each test piece, a tensile test prescribed in the JIS was performed at a tensile speed of 200 mm / min, and the elongation at break (Eb) was calculated. Then, the case where the elongation at break of all the test pieces was 50% or more was evaluated as extremely good in normal-time physical properties (indicated by a mark of in Table 1 described below), and although not all the test pieces, as long as one test piece had an elongation at break of 50% or more, it was evaluated as good in normal-time physical properties, and the case where the elongation at break of all the test pieces was less than 50% was evaluated as poor in normal-time physical properties.

[0069] [Heat resistance] The dumbbell-shaped test pieces No. 1 were produced in the same manner as in the evaluation of the elongation at break, and were left in an oven adjusted to 150°C for 400 hours. After the test pieces were returned to room temperature, a tensile test was performed under the same conditions as in the evaluation of the elongation at break, and the elongation at break (Eb) was calculated. Then, the case where the elongation at break of all the test pieces was 30% or more was evaluated as extremely good in heat resistance (indicated by a mark of O in Table 1 described later), the case where the elongation at break of not all but at least one of the test pieces was 30% or more was evaluated as good in heat resistance (indicated by a mark of Δ in the table), and the case where the elongation at break of all the test pieces was less than 30% was evaluated as poor in heat resistance (indicated by a mark of X in the table).

[0070] [Formability] At the time of demolding after the foaming molding, whether or not the urethane foamed molded body was deformed was observed visually. Then, the case where no deformation was observed in appearance was evaluated as extremely good in formability (indicated by a mark of O in Table 1 described later), the case where a small deformation was observed in part of the appearance was evaluated as good in formability (indicated by a mark of Δ in the table), and the case where a large deformation was observed in appearance was evaluated as poor in formability.

[0071] [Flame Retardancy] A vertical burning test according to the UL94 standard was performed. In the vertical burning test, the flame of a gas burner was brought into contact with the lower end of a test piece kept vertical for 10 seconds. In the case where the burning was stopped within 30 seconds, the flame was further brought into contact for 10 seconds. Then, in the case where all of the following five criteria were satisfied, the flame retardancy was determined to be V-0 level. (1) In both of the flame contacts, the test piece did not burn for longer than 10 seconds. (2) The total burning time for the respective two flame contacts of five test pieces was not more than 50 seconds. (3) There was no test piece that burned to the position of the fixing jig. (4) There was no test piece that caused the dropping of burning particles to cause the cotton placed below the test piece to catch fire. (5) After the second flame contact, the test piece did not continue to glow red for longer than 30 seconds. In addition, in the case where all of the following five criteria were satisfied, it was determined to be V-2 level. (1) In both of the flame contacts, the test piece did not burn for longer than 30 seconds. (2) The total burning time for the respective two flame contacts of five test pieces was not more than 250 seconds. (3) There was no test piece that burned to the position of the fixing jig. (4) There was a test piece that caused the dropping of burning particles to cause the cotton placed below the test piece to catch fire. (5) After the second flame contact, the test piece did not continue to glow red for longer than 60 seconds.

[0072] [Table 1]

[0073] As shown in Table 1, the urethane foam molded bodies A to C have composite particles prepared by granulating the expanded graphite powder having a sodium ion amount of 500 ppm or more and 2000 ppm or less. Therefore, the elongation at normal times is good, and the decrease in elongation after retention at high temperature is small. In addition, the thermal conductivity of the urethane foam molded bodies A to C is as large as 0.5 W / m-K or more. In the urethane foam molded body A, the amount of sodium ions is less than that in the urethane foam molded bodies B and C. It is thus considered that the raw materials tend to be acidic, which affects the curing reaction, and this results in a decrease in moldability and flame retardancy. In the urethane foam molded body C, the amount of sodium ions is more than that in the urethane foam molded bodies A and B. Therefore, the heat resistance is slightly decreased. From the above, it is confirmed that the urethane foam molded bodies A to C satisfy the thermal conductivity and the heat resistance. On the contrary, the urethane foam molded body D having composite particles prepared by granulating the expanded graphite powder having a sodium ion amount of as much as 3500 ppm satisfies the thermal conductivity, the physical properties at normal times, and the flame retardancy, but becomes poor in heat resistance.

[0074] Industrial applicability The urethane foam molded body of the present disclosure is suitable as a soundproofing material for a battery cover, an electric axle cover, a seat motor cover, a floor mat, a front wall silencer, an engine cover silencer, various ECUs, a junction box, and the like for a vehicle, and a soundproofing material for an electronic device such as a personal computer.

Claims

1. A urethane foamed molded article, characterized in that: The urethane foam molded article comprises a base material formed of polyurethane foam, composite particles oriented and contained in the base material, and first insulating inorganic particles dispersed in the base material. The composite particles include thermally conductive particles and magnetic particles bonded to the surfaces of the thermally conductive particles via a binder. The thermally conductive particles include expanded graphite particles, and the amount of alkali metal ions contained in the expanded graphite particles is 500 ppm or more and 2000 ppm or less.

2. The urethane foamed molded article according to claim 1, wherein The alkali metal ion includes a sodium ion.

3. The urethane foamed molded article according to claim 1 or 2, characterized in that: When the volume of the urethane foam molded product is 100 volume %, the content of the composite particles is 5 volume % or more and 50 volume % or less.

4. The urethane foamed molded article according to any one of claims 1 to 3, characterized in that When the volume of the urethane foam molded product is 100 volume %, the content of the first insulating inorganic particles is 5 volume % or more and 20 volume % or less.

5. The urethane foamed molded article according to any one of claims 1 to 4, characterized in that The thermal conductivity of the first insulating inorganic particles is 5 W / m·K or higher.

6. The urethane foamed molded article according to any one of claims 1 to 5, characterized in that The first insulating inorganic particles include one or more selected from the group consisting of aluminum hydroxide, aluminum oxide, aluminum nitride, magnesium hydroxide, magnesium oxide, talc, calcium carbonate, clay, mica, and silica.

7. The urethane foamed molded article according to any one of claims 1 to 6, characterized in that The composite particles include second insulating inorganic particles bonded to the surfaces of the thermally conductive particles via a binder.

8. The urethane foamed molded article according to claim 7, wherein The second insulating inorganic particles include one or more selected from the group consisting of aluminum hydroxide, aluminum oxide, aluminum nitride, magnesium hydroxide, magnesium oxide, talc, calcium carbonate, clay, mica, and silica.

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