Urethane foam molded body and its manufacturing method

Abstract

This molded urethane foam comprises a base made of polyurethane foam and composite particles oriented and contained in the base. The composite particles comprise thermally conductive particles made of a nonmagnetic material and having a thermal conductivity of 200 W / m·K or greater and magnetic particles bonded to the surface of the thermally conductive particles with a binder, and have been surface-treated with one or more surfactants selected from among carboxylic acid type surfactants and succinic acid type surfactants. This method for producing the molded urethane foam comprises a step in which raw materials for granulation comprising a powder of the thermally conductive particles, a powder of the magnetic particles, the binder, one or more carboxylic acid type / succinic acid type surfactants, and water are stirred to produce composite particles, a step in which a powder of the composite particles is mixed with a raw material for urethane resin foam to produce a raw-material mixture, and a step in which the raw-material mixture is foamed and molded in a magnetic field.

Description

[Technical field]

[0001] The present disclosure relates to a urethane foam molded article having high thermal conductivity and a method for producing the same. [Background technology]

[0002] Urethane foam molded bodies are used as sound absorbing and vibration absorbing materials in various fields such as automobiles and electronic devices. Urethane foam molded bodies have a large number of cells (air bubbles) inside, so they have low thermal conductivity and poor heat dissipation. Therefore, when placed around engines, motors, etc. that generate heat, heat may accumulate in the urethane foam molded body, which may lead to an increase in temperature. To solve this problem, as described in Patent Document 1, for example, a urethane foam molded body has been developed in which particles with high thermal conductivity such as graphite are oriented in polyurethane foam to form a heat transfer path in the orientation direction, thereby improving heat dissipation. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-225833 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the urethane foam molding described in Patent Document 1, composite particles are used that are granulated by adhering magnetic particles to the surface of particles with high thermal conductivity (thermally conductive particles) in order to orient the particles. The composite particles are then mixed with a urethane foam resin raw material and foamed in a magnetic field to produce a urethane foam molding having oriented composite particles. When particles are mixed with the urethane foam resin raw material, if the particles are not uniform in composition or size, it becomes difficult to control the crosslinking reaction and foaming reaction during foam molding. In addition, if the mass difference of the particles to be mixed is large, the fluidity of the particles changes during foam molding, and the particles are not uniformly dispersed in the urethane foam resin raw material, resulting in a distribution in performance such as heat dissipation. In particular, when composite particles are mixed, the orientation is related to the formation of a heat transfer path, so the adhesion state of the magnetic particles to the thermally conductive particles, that is, the granulation property of the composite particles, becomes important. However, in the past, the granulation property of the composite particles was not sufficiently examined, so there was a risk of variation in the heat dissipation property and moldability of the urethane foam molding.

[0005] The present disclosure has been made in view of the above circumstances, and aims to provide a urethane foam molded product that exhibits good granulation properties of the blended composite particles and excellent thermal conductivity and moldability, as well as a method for producing the same. [Means for solving the problem]

[0006] (1) In order to solve the above problems, the present disclosure provides a urethane foam molded product comprising a substrate made of polyurethane foam and composite particles contained and oriented in the substrate, the composite particles comprising thermally conductive particles made of a non-magnetic material and having a thermal conductivity of 200 W / m K or more, and magnetic particles bonded to the surfaces of the thermally conductive particles with a binder, and the composite particles are surface-treated with one or more surfactants selected from a carboxylic acid type surfactant and a succinic acid type surfactant.

[0007] The composite particles contained in the urethane foam molded body of the present disclosure are surface-treated with a predetermined surfactant. This makes it easier for the magnetic particles to adhere to the thermally conductive particles. Many magnetic particles are poorly hydrophilic. For this reason, when a binder is added together with water during the production of the composite particles, the magnetic particles are less likely to adhere to the thermally conductive particles, and as a result, the desired composite particles cannot be produced, and there is a risk that magnetic particles that do not adhere to the thermally conductive particles will remain after granulation. As a result of repeated studies, the present inventor has found that the adhesiveness of the magnetic particles to the thermally conductive particles can be increased by using a binder and a surfactant in combination during granulation. The composite particles after granulation are blended with a urethane foam resin raw material and foam-molded in a magnetic field to produce a urethane foam molded body. Therefore, it is necessary to select a surfactant used during granulation that does not easily affect the crosslinking reaction and foaming reaction during foam molding. In this regard, in the urethane foam molded body of the present disclosure, one or more surfactants selected from a carboxylic acid type surfactant and a succinic acid type surfactant are used. Carboxylic acid type surfactants and succinic acid type surfactants are weakly acidic surfactants, and have little effect on the crosslinking reaction and foaming reaction of the urethane foam resin raw material. Therefore, by using these surfactants, it is possible to produce composite particles in which a desired amount of magnetic particles are attached to the surface of thermally conductive particles, and it is possible to produce a urethane foam molding without inhibiting foam molding. In addition, by surface treating the composite particles, the occurrence of rust in the composite particles is also suppressed.

[0008] According to the urethane foam molded article of the present disclosure, the orientation of the composite particles is good, and the composite particles connected to each other form a heat transfer path, so that high thermal conductivity can be realized. In addition, since the composition and size of the composite particles are small, it is easy to control the crosslinking reaction and the foaming reaction during foam molding, and the moldability is excellent. In addition, since the dispersibility of the composite particles is good, it is difficult for performance such as heat dissipation to be distributed depending on the part.

[0009] (2) In the above configuration, the surfactant may be a succinic acid type surfactant. The succinic acid type surfactant has little effect on foam molding and also exhibits excellent rust prevention. Therefore, even if a material that rusts easily, such as iron, is used as the magnetic particles, rust generation can be suppressed during granulation using water. According to this configuration, a relatively inexpensive material, such as iron, can be used as the magnetic particles, thereby reducing manufacturing costs.

[0010] (3) In any of the above configurations, the surfactant may be water-soluble. According to this configuration, the surfactant can be dissolved in water and added during granulation of the composite particles, so that the surface treatment can be easily performed.

[0011] (4) In any of the above configurations, the content ratio of small particles having a particle diameter of 100 μm or less in the particle size distribution of the composite particles may be 10 mass% or less when the total mass of the composite particles is 100 mass%. As described later, since many thermally conductive particles have a particle diameter exceeding 100 μm, small particles having a particle diameter of 100 μm or less become magnetic particles that do not constitute composite particles. In this configuration, the proportion of magnetic particles that are not adhered to the thermally conductive particles is small, in other words, the proportion of composite particles having good granulation properties and magnetic particles adhered to the surfaces of the thermally conductive particles is large, which is effective in realizing high thermal conductivity and moldability.

[0012] (5) In any of the above configurations, the average particle size of the thermally conductive particles may be 200 μm or more and 2000 μm or less. This configuration is advantageous for forming a heat transfer path and can also ensure the dispersibility of the composite particles.

[0013] (6) In any of the above configurations, the magnetic particles may include iron particles. Since iron is relatively inexpensive, this configuration can reduce manufacturing costs. In addition, the composite particles are surface-treated with a surfactant. The surfactant exerts a rust-preventing effect, thereby suppressing rusting of the iron particles.

[0014] (7) In any of the above configurations, the composite particles may have insulating inorganic particles bonded to the surface of the thermally conductive particles by a binder. The insulating inorganic particles may be directly bonded to the surface of the thermally conductive particles, or may be indirectly bonded via magnetic particles, that is, to the surface of the magnetic particles bonded to the thermally conductive particles. As the magnetic particles, ferromagnetic materials such as stainless steel and iron are used. For this reason, composite particles having magnetic particles bonded to the surface of the thermally conductive particles have high electrical conductivity. Here, when insulating inorganic particles are further bonded to the surface of the thermally conductive particles, even if the composite particles are oriented in a state of contact with each other, the thermally conductive particles and the magnetic particles (conductive particles) are less likely to come into contact with each other between adjacent composite particles. Therefore, the electrical resistance between the composite particles increases. In addition, the composite particles come into contact with each other via the insulating inorganic particles, so that the conduction between the composite particles can be cut off. As a result, electrical insulation can be achieved in the urethane foam molded body of the present disclosure. In this way, according to this configuration, both high thermal conductivity and electrical insulation can be achieved. Therefore, the urethane foam molded product of the present disclosure can be used in applications requiring both heat dissipation and electrical insulation, such as heat dissipation members in electronic devices. In addition, it is more effective to combine this configuration with all of the above configurations (2) to (6).

[0015] (8) A method for producing a urethane foam molded product of the present disclosure, which is one embodiment of the method for producing a urethane foam molded product of the present disclosure, is characterized by comprising: a composite particle production step of producing composite particles by stirring a granulation raw material containing a powder of thermally conductive particles made of a non-magnetic material and having a thermal conductivity of 200 W / m K or more, a powder of magnetic particles, a binder, one or more surfactants selected from a carboxylic acid surfactant and a succinic acid surfactant, and water; a mixed raw material production step of producing a mixed raw material by mixing the composite particle powder with a foamed urethane resin raw material; and a foam molding step of injecting the mixed raw material into a cavity of a foaming mold and foam-molding the mixed raw material while applying a magnetic field so that the magnetic flux density in the cavity is approximately uniform.

[0016] In the composite particle manufacturing process, a specific surfactant is used when the magnetic particles are bonded to the surface of the thermally conductive particles with a binder. This makes it easier for the magnetic particles to adhere to the thermally conductive particles, and it is possible to manufacture the desired composite particles with a relatively large amount of magnetic particles attached. By relatively increasing the amount of magnetic particles constituting the composite particles, it is possible to realize an orientation state of the composite particles even in a relatively low magnetic field in the subsequent foam molding process. In addition, the surfactant used is unlikely to affect the foam molding of the foamed urethane resin raw material. In this way, according to the manufacturing method of the present disclosure, it is possible to manufacture the desired composite particles in which the magnetic particles are bonded to the surface of the thermally conductive particles, and it is also possible to easily manufacture the urethane foam molded body of the present disclosure, which has high thermal conductivity, without impeding the foam molding.

[0017] (9) A method for producing a urethane foam molded body according to the present disclosure, which is one embodiment of the method for producing a urethane foam molded body having the configuration described above in (7), includes a composite particle production step for producing composite particles, a mixed raw material production step for mixing a powder of the composite particles with a urethane foam resin raw material to produce a mixed raw material, and a foam molding step for injecting the mixed raw material into a cavity of a foaming mold and foam molding the mixture while applying a magnetic field so that the magnetic flux density in the cavity is approximately uniform, and the composite particle production step includes a first stirring step for stirring a first raw material containing a powder of thermally conductive particles made of a non-magnetic material and having a thermal conductivity of 200 W / m·K or more, a powder of magnetic particles, a binder, one or more surfactants selected from a carboxylic acid type surfactant and a succinic acid type surfactant, and water, and a second stirring step for adding a powder of insulating inorganic particles to the stirred first raw material and further stirring the mixture. Hereinafter, the previous production method may be referred to as the "first production method" and this production method may be referred to as the "second production method".

[0018] According to the second manufacturing method of the present disclosure, composite particles having insulating inorganic particles arranged on the outermost layer can be easily manufactured. When the composite particles are used, the thermally conductive particles and the magnetic particles are less likely to come into contact with each other, so that the electrical resistance between the composite particles increases. Therefore, according to the second manufacturing method of the present disclosure, a urethane foam molded article having high electrical insulation in addition to high thermal conductivity can be manufactured.

[0019] (10) In the above configuration (8) or (9), the amount of the surfactant in the composite particle manufacturing process may be 0.1 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the powder of the thermally conductive particles. This configuration is suitable for achieving both improved adhesion of the magnetic particles and reduced influence on the foam molding of the urethane foam resin raw material. Effect of the Invention

[0020] According to the urethane foam molded body of the present disclosure, the orientation of the composite particles is good, and the composite particles connected to each other form a heat transfer path, so that high thermal conductivity can be realized. In addition, since the variation in the configuration and size of the composite particles is small, it is easy to control the crosslinking reaction and the foaming reaction during foam molding, and the moldability is excellent. In addition, since the dispersibility of the composite particles is good, it is difficult for performance such as heat dissipation to be distributed depending on the part. The manufacturing method of the urethane foam molded body of the present disclosure is excellent in the granulation of the composite particles. In addition, according to the manufacturing method of the present disclosure, the urethane foam molded body of the present disclosure, which has high thermal conductivity, can be easily manufactured without inhibiting the foam molding. [Brief description of the drawings]

[0021] [Figure 1] 3 shows particle size distributions of powders of composite particles A to C produced in the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, embodiments of the urethane foam molded article and the manufacturing method thereof according to the present disclosure will be described. Note that the embodiments are not limited to the following embodiments, and various modifications and improvements that can be made by those skilled in the art can be made.

[0023] <Urethane foam molding> The urethane foam molded article of the present disclosure has a substrate made of polyurethane foam and composite particles contained and oriented in the substrate.

[0024] [Base material] The polyurethane foam of the substrate is produced from urethane foam resin raw materials such as a polyisocyanate component and a polyol component. Details will be described later in the manufacturing method of the urethane foam molded body of the present disclosure. The shape, size, etc. of the substrate are not particularly limited and may be appropriately determined depending on the application. The composite particles contained in the substrate may be arranged with a certain regularity. For example, they may be arranged in a straight line or a curved line between one end and the other end of the urethane foam molded body (which may not be the end opposite to the one end by 180°). They may also be arranged radially from the center to the outer periphery.

[0025] [Composite particles] The composite particles have thermally conductive particles made of a non-magnetic material and having a thermal conductivity of 200 W / m·K or more, and magnetic particles bonded to the surfaces of the thermally conductive particles with a binder.

[0026] The thermally conductive particles are made of a non-magnetic material. In this specification, diamagnetic and paramagnetic materials other than ferromagnetic and antiferromagnetic materials are referred to as non-magnetic materials. The thermal conductivity of the thermally conductive particles is 200 W / m·K or more. Examples of thermally conductive particles include carbon materials such as graphite and carbon fiber, aluminum, gold, silver, copper, and alloys using these as base materials. As the thermally conductive particles, one type of particle may be used, or two or more types of particles may be used in combination.

[0027] The shape of the thermally conductive particles is not particularly limited as long as they can be composited with the magnetic particles. For example, various shapes such as flakes, fibers, columns, spheres, ellipsoids, and oval spheres (a pair of opposing hemispheres connected by a cylinder) can be adopted. When the thermally conductive particles have a shape other than a sphere, the contact area between the composite particles becomes large. This makes it easier to ensure a heat transfer path and increases the amount of heat transferred. For example, graphite particles are suitable because they are available at a relatively low cost in a shape with a large aspect ratio.

[0028] Examples of graphite include natural graphite such as flake graphite, scaly graphite, and earthy graphite, and artificial graphite. Artificial graphite is not easily scaly. For this reason, natural graphite is preferred because it is scaly and has a high effect of improving thermal conductivity. In addition, as graphite, expanded graphite in which a substance that generates gas when heated is inserted between the layers of scaly graphite may be used. When heat is applied to the expanded graphite, the generated gas expands the gap between the layers and forms a layer that is stable against heat and chemicals. This stable layer becomes an insulating layer and prevents the transfer of heat, thereby providing a flame retardant effect. As the expanded graphite, a suitable one may be selected in consideration of the expansion start temperature and expansion rate. For example, the expansion start temperature of the expanded graphite must be higher than the heat generation temperature during molding of the urethane foam molded body. Specifically, expanded graphite with an expansion start temperature of 150°C or more is preferred.

[0029] Normally, even when exposed to a flame, a urethane foam molded body has a dropping action that drops the fire and suppresses the spread of the fire. However, if magnetic particles are blended, the dropping action is impaired, and the self-extinguishing property of the urethane foam molded body may decrease. In this respect, in the urethane foam molded body of the present disclosure, the composite particles are oriented. Therefore, the heat applied to the urethane foam molded body is easily transferred to the thermally conductive particles. Therefore, when the thermally conductive particles are made of expanded graphite, the expanded graphite quickly reaches the expansion start temperature. This allows the flame retardant effect of the expanded graphite to be exerted quickly. Therefore, by using expanded graphite as the thermally conductive particles, the decrease in the self-extinguishing property of the urethane foam molded body can be suppressed and the flame retardant property can be maintained.

[0030] The size of the thermally conductive particles may be determined taking into consideration dispersibility, the size of the base material, etc. From the viewpoint of increasing the thermal conductivity of the urethane foam molding, the average particle size of the thermally conductive particles is desirably 200 μm or more. On the other hand, in consideration of the dispersibility of the composite particles, it is desirably 2000 μm or less. Unless otherwise specified, the average particle size in this specification refers to the median diameter (D 50For commercially available products, the catalog value may be used.

[0031] The magnetic particles are attached to the surface of the thermally conductive particles by a binder and serve to orient the thermally conductive particles. The magnetic particles may be any particles having excellent magnetization properties, and may be, for example, ferromagnetic materials such as iron, nickel, cobalt, gadolinium, stainless steel, magnetite, maghemite, manganese zinc ferrite, barium ferrite, and strontium ferrite, MnO, Cr 2 O 3 , FeCl 2 Particles of antiferromagnetic materials such as MnAs and alloys using these are preferred. Among these, iron, nickel, cobalt, and their iron-based alloys (including stainless steel) are preferred from the viewpoints of being easily available as fine particles and having high saturation magnetization. Iron, in particular, is relatively inexpensive and easily available, so that it is possible to reduce manufacturing costs and is suitable for mass production.

[0032] The magnetic particles may be directly attached to the surface of the thermally conductive particles, or may be indirectly attached via other particles such as insulating inorganic particles described later. The magnetic particles may be attached only to a part of the surface of the thermally conductive particles, or may be attached so as to cover the entire surface. The size of the magnetic particles may 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. For example, the particle diameter of the magnetic particles is preferably 1 / 10 or less of the particle diameter of the thermally conductive particles. When the size of the magnetic particles becomes smaller, the saturation magnetization of the magnetic particles tends to decrease. Therefore, in order to orient the composite particles with a smaller amount of magnetic particles, the average particle diameter of the magnetic particles needs to be 100 nm or more. It is more preferable to set it to 1 μm or more, and even more preferably to set it to 5 μm or more.

[0033] The shape of the magnetic particles is not particularly limited. For example, when the shape of the magnetic particles is flat, the distance between adjacent thermally conductive particles is shorter than when the magnetic particles are spherical. This improves the thermal conductivity between adjacent composite particles. As a result, the thermal conductivity of the urethane foam molding is improved. In addition, when the shape of the magnetic particles is flat, the magnetic particles and the thermally conductive particles are in contact with each other on the surface. In other words, the contact area between the two particles is large. This improves the adhesive force between the magnetic particles and the thermally conductive particles. Therefore, the magnetic particles are less likely to peel off. In addition, the thermal conductivity between the magnetic particles and the thermally conductive particles is also improved. For these reasons, it is desirable to use flaky particles as the magnetic particles.

[0034] When a material with high electrical conductivity is used for the thermally conductive particles or the magnetic particles, the composite particles are connected and oriented to form a conductive path in the substrate. Therefore, in order to apply the urethane foam molded body of the present disclosure to a member that requires electrical insulation, such as a heat dissipation member in an electronic device, it is desirable to impart electrical insulation to the urethane foam molded body. For example, a composite particle may be formed by adhering insulating inorganic particles in addition to magnetic particles to the surface of the thermally conductive particles. By doing so, even if the composite particles are oriented, the thermally conductive particles and magnetic particles (conductive particles) are unlikely to come into contact with each other between adjacent composite particles. Therefore, the electrical resistance between the composite particles increases. In addition, the composite particles come into contact with each other via the insulating inorganic particles, thereby cutting off the electrical continuity between the composite particles.

[0035] The insulating inorganic particles may be particles of an inorganic material having insulating properties. In particular, those with a relatively high thermal conductivity are desirable from the viewpoint of not impeding the thermal conductivity between composite particles. For example, it is preferable that the insulating inorganic particles have a thermal conductivity of 5 W / m·K or more. Examples of insulating inorganic materials with a thermal conductivity of 5 W / m·K or more include aluminum hydroxide, aluminum oxide (alumina), magnesium hydroxide, magnesium oxide, talc, calcium carbonate, clay, mica, and silica.

[0036] The insulating inorganic particles may be directly attached to the surface of the thermally conductive particles, or may be indirectly attached via magnetic particles. The insulating inorganic particles may be attached only to a part of the surface of the thermally conductive particles, or may be attached so as to cover the entire surface. From the viewpoint of increasing the electrical resistance between the composite particles and improving the electrical insulation of the urethane foam molding, it is desirable that the insulating inorganic particles are arranged in the outermost layer of the composite particles.

[0037] The size of the insulating inorganic particles may be appropriately determined in consideration of the adhesiveness to the thermally conductive particles and the magnetic particles, and the electrical insulation and thermal conductivity between the composite particles. If the insulating inorganic particles are too large, the adhesiveness and the thermal conductivity between the composite particles are reduced. For example, the particle diameter of the insulating inorganic particles is desirably 1 / 100 or more and 1 / 10 or less of the particle diameter of the thermally conductive particles. The shape of the insulating inorganic particles is not particularly limited. For example, when the insulating inorganic particles are flat, the distance between adjacent thermally conductive particles can be shortened compared to when the insulating inorganic particles are spherical. Therefore, the thermal conductivity between adjacent composite particles is less likely to be hindered. In addition, the contact area is increased, making it difficult for the insulating inorganic particles to peel off.

[0038] The binder for bonding the thermally conductive particles and the magnetic particles may be appropriately selected in consideration of the type of each particle, the effect on foam molding, etc. A water-soluble binder is preferable because it has little effect on foam molding and is environmentally friendly. Examples include methyl cellulose, carboxymethyl cellulose, hydroxypropyl methyl cellulose, polyvinyl alcohol, and starch. The binder for bonding the magnetic particles and the binder for bonding the insulating inorganic particles may be the same or different.

[0039] The composite particles are surface-treated with one or more surfactants selected from carboxylic acid surfactants and succinic acid surfactants (hereinafter referred to as "carboxylic acid / succinic acid surfactants" as appropriate). The surface treatment may be performed on a part of the composite particles (for example, only the surface of the magnetic particles) or on the entire composite particles.

[0040] Carboxylic acid type / succinic acid type surfactants have a carboxyl group (-COOH) as a polar group. The polar group reacts with hydroxyl groups (-OH) present on the surface of thermally conductive particles or magnetic particles, promoting adhesion between the two. In addition, the polar group adsorbs to the surface of thermally conductive particles or magnetic particles, and the hydrophobic group on the opposite side blocks water and oxygen, providing rust prevention. Therefore, even if water is used during granulation, the materials that make up the composite particles are less likely to rust. In this way, the use of carboxylic acid type / succinic acid type surfactants not only improves the adhesion between particles, but is also effective in preventing rusting of composite particles. This makes it possible to use relatively inexpensive materials such as iron for the magnetic particles, thereby reducing manufacturing costs.

[0041] Examples of carboxylic acid type surfactants include alkyl ether carboxylates. Examples of succinic acid type surfactants include metal alkenyl succinates. Among them, succinic acid type surfactants are suitable because they have little effect on foam molding and also exhibit excellent rust prevention properties. In addition, carboxylic acid type / succinic acid type surfactants are water-soluble and can be dissolved in water and added during granulation of composite particles, making it easy to perform surface treatment.

[0042] The content of the composite particles in the urethane foam molded product of the present disclosure may be determined taking into consideration the effect of improving thermal conductivity, the influence on the foaming reaction, moldability, etc. For example, in order to obtain a urethane foam molded product having desired physical properties without inhibiting the foaming reaction, the content of the composite particles is desirably 20% by volume or less, where the volume of the urethane foam molded product is taken as 100% by volume. It is more preferable to set the content of the composite particles to 15% by volume or less. On the other hand, in order to increase thermal conductivity, it is desirably 3% by volume or more, and it is more preferable to set the content of the composite particles to 10% by volume or more.

[0043] In addition, from the viewpoint of improving granulation and reducing the amount of magnetic particles that do not constitute the composite particles, it is desirable that the content of small particles having a particle diameter of 100 μm or less in the particle size distribution of the composite particles is 10 mass% or less when the total mass of the composite particles is 100 mass%. In this specification, the particle size distribution of the composite particles is adopted as a mass-based frequency distribution obtained by a sieving method, and the content of small particles is calculated based on the frequency distribution.

[0044] The urethane foam molded body of the present disclosure may further have insulating inorganic particles dispersed in the substrate. That is, in addition to the oriented composite particles, insulating inorganic particles may be dispersed in the substrate. The insulating inorganic particles dispersed in the substrate may be the same as or different from the insulating inorganic particles added as constituent particles of the composite particles to impart electrical insulation. In addition, the insulating inorganic particles dispersed in the substrate may be one type or two or more types. The insulating inorganic particles dispersed in the substrate are also preferably those having a relatively high thermal conductivity, and aluminum hydroxide, aluminum oxide (alumina), magnesium hydroxide, magnesium oxide, talc, calcium carbonate, clay, mica, silica, and the like are suitable. When the insulating inorganic particles are dispersed in the substrate, the insulating inorganic particles enter between the composite particles, making it difficult for the composite particles to be electrically connected 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 high, in addition to the heat transfer path by the composite particles, a heat transfer path by the insulating inorganic particles is also formed. This further improves the thermal conductivity of the urethane foam molded body. Furthermore, when the insulating inorganic particles have flame retardancy, the flame retardancy of the urethane foam molded article is improved.

[0045] <Method of manufacturing urethane foam molded body> The method for producing the urethane foam molded article of the present disclosure is not particularly limited. As a preferred embodiment of the production method, the method for producing the urethane foam molded article of the present disclosure includes a composite particle production step, a mixed raw material production step, and a foam molding step. Each step will be described below.

[0046] [Composite particle manufacturing process] This process is a process for producing composite particles by stirring a granulation raw material containing a powder of thermally conductive particles made of a non-magnetic material and having a thermal conductivity of 200 W / m·K or more, a powder of magnetic particles, a binder, one or more surfactants selected from a carboxylic acid type surfactant and a succinic acid type surfactant, and water.

[0047] The thermally conductive particles, magnetic particles, binder, and surfactant are as described above. Therefore, the description will be omitted here. The blending amounts of the thermally conductive particles, magnetic particles, and binder may be appropriately adjusted in consideration of the magnetic field orientation of the composite particles to be produced and the thermal conductivity when the composite particles are blended in a urethane foam molding.

[0048] For example, when graphite is used as the thermally conductive particles, the amount of magnetic particle powder is desirably 100 to 200 parts by mass per 100 parts by mass of graphite powder. If the amount of magnetic particle powder is less than 100 parts by mass, the amount of magnetic particles adhered is small, and the magnetism required for the orientation of the composite particles may be insufficient. On the other hand, if the amount exceeds 200 parts by mass, the amount of magnetic particles adhered becomes excessive. This leads to an increase in the mass of the urethane foam molding and an increase in costs.

[0049] The amount of binder is preferably 2% by mass or more and 4% by mass or less, based on the total mass of the powders to be bonded being 100% by mass, as a necessary and sufficient amount for particle adhesion. If the amount of binder is less than 2% by mass, the binder will not spread over the particle surface, and the adhesiveness will decrease. On the other hand, if the amount is more than 4% by mass, the composite particles may aggregate due to the excess binder. The binder may be solid or liquid. When a water-soluble powder is used as the binder, it is recommended to add water after stirring the binder and other raw material powders in advance. This can suppress particle aggregation.

[0050] The amount of the carboxylic acid type / succinic acid type surfactant to be blended may be appropriately determined depending on the amounts of the thermally conductive particles, magnetic particles, etc. From the viewpoint of increasing the adhesiveness of the magnetic particles, the amount of the carboxylic acid type / succinic acid type surfactant to be blended is desirably 0.1 parts by mass or more per 100 parts by mass of the thermally conductive particle powder. 0.3 parts by mass or more is more preferable. On the other hand, in consideration of the influence on the foam molding of the urethane foam resin raw material, it is desirably 30 parts by mass or less. 20 parts by mass or less is more preferable.

[0051] This process may include a preliminary stirring process for stirring a raw material containing water, a powder of thermally conductive particles, a powder of magnetic particles, and a binder, and a main stirring process for adding a surface treatment agent in which a carboxylic acid type / succinic acid type surfactant is dissolved in water to the stirred raw material and further stirring. First, in the preliminary stirring process, water is added to the powder raw material and the binder and stirred, thereby suppressing the aggregation of the particles of the powder raw material. Next, in the main stirring process, by adding a surface treatment agent in which a surfactant is dissolved in water in advance, the surface treatment agent is distributed throughout the magnetic particles and is more likely to react than if the surfactant is added directly. In addition, it is easy to apply even when a surfactant with low solubility in water is used.

[0052] In addition, when insulating inorganic particles are added as constituent particles of the composite particles, the powder of insulating inorganic particles may be included in the granulation raw material. In the case where the insulating inorganic particles are arranged in the outermost layer of the composite particles, this step may be configured to include a first stirring step of stirring a first raw material containing a powder of thermally conductive particles made of a non-magnetic material and having a thermal conductivity of 200 W / m·K or more, a powder of magnetic particles, a binder, one or more surfactants selected from a carboxylic acid type surfactant and a succinic acid type surfactant, and water, and a second stirring step of adding a powder of insulating inorganic particles to the stirred first raw material and further stirring (second manufacturing method). In addition, as described above, when this step is configured from a preliminary stirring step and a main stirring step, insulating inorganic particles may be added and stirred after the main stirring step.

[0053] For example, when graphite is used as the thermally conductive particles, the amount of the insulating inorganic particles is desirably 30 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the graphite powder. If it is less than 30 parts by mass, the amount of the insulating inorganic particles adhered is small, so the effect of imparting electrical insulation is small. On the other hand, if it exceeds 100 parts by mass, the amount of the insulating inorganic particles adhered is large, and the thermal conductivity between the composite particles is reduced. This reduces the thermal conductivity of the urethane foam molding.

[0054] After stirring the granulation raw materials (in the above-mentioned second manufacturing method, the stirred product obtained in the second stirring step) can be dried appropriately to obtain composite particles. In the obtained composite particles, it is desirable that the content of small particles having a particle diameter of 100 μm or less is 10 mass % or less when the total mass of the composite particles is taken as 100 mass %. If the content of small particles is low, it can be assumed that the desired composite particles having a relatively large amount of adhesion of magnetic particles and the like are produced, and the composite particles can be oriented even in a relatively weak magnetic field in the subsequent expansion molding step. In addition, a step of removing small particles is not required in consideration of moldability.

[0055] [Mixed raw material manufacturing process] This step is a step of producing a mixed raw material by mixing the powder of the composite particles produced in the previous step with a urethane foam resin raw material. The powder of the composite particles may be used as it is, or may be used after removing large particles as appropriate depending on the application.

[0056] The urethane foam resin raw material may be prepared from known raw materials such as polyols and polyisocyanates. The polyol may be appropriately selected from polyhydric hydroxy 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, and phenol-modified polyols. The polyisocyanate may be appropriately selected from tolylene diisocyanate, phenylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, triphenylmethane triisocyanate, polymethylene polyphenyl isocyanate, naphthalene diisocyanate, and derivatives thereof (e.g., prepolymers obtained by reaction with polyols, modified polyisocyanates), and the like.

[0057] The urethane foam resin raw material may further contain 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 colorant, etc. Examples of the catalyst include amine catalysts such as tetraethylenediamine, triethylenediamine, and dimethylethanolamine, and organometallic catalysts such as tin laurate and tin octanoate. Water is a suitable blowing agent. Other than water, methylene chloride, fluorocarbons, CO 2 Gases and the like are included. In addition, a silicone-based foam stabilizer is suitable as the foam stabilizer, and triethanolamine, diethanolamine, and the like are suitable as the crosslinking agent. As described above, in the urethane foam molded product of the present disclosure, insulating inorganic particles may be dispersed in the base material in addition to the composite particles. When manufacturing a urethane foam molded product of this type, a powder of the composite particles and a powder of the insulating inorganic particles may be mixed into the urethane foam resin raw material.

[0058] The mixed raw material can be produced, for example, by mechanically stirring the composite particle powder and the urethane foam resin raw material using a stirring blade or the like. Alternatively, the composite particle powder may be added to at least one of the two components of the urethane foam resin raw material (polyol raw material, polyisocyanate raw material) to prepare two types of raw materials, and then the two raw materials may be mixed to produce the mixed raw material. As described above, in order to obtain a urethane foam molded body having desired physical properties without inhibiting the foaming reaction, it is desirable to set the blending amount of the composite particle powder to 20 volume % or less when the volume of the urethane foam molded body is taken as 100 volume %. It is more desirable to set it to 15 volume % or less. On the other hand, in order to obtain the effect of improving thermal conductivity, it is desirable to set the blending amount of the composite particle powder to 3 volume % or more. It is more desirable to set it to 10 volume % or more.

[0059] [Foam molding process] In this process, the mixed raw material produced in the previous process is injected into the cavity of a foaming mold, and foam-molded while applying a magnetic field so that the magnetic flux density in the cavity becomes approximately uniform.

[0060] The magnetic field may be formed in the direction in which the composite particles are oriented. For example, when the composite particles are oriented in a linear manner, it is desirable to form the magnetic field lines in the cavity of the foaming mold so that they are approximately parallel from one end to the other end of the cavity. In order to form such a magnetic field, for example, magnets may be placed near both sides of one end and the other end of the foaming mold so as to sandwich the foaming mold. The magnets may be permanent magnets or electromagnets. When an electromagnet is used, the magnetic field formation can be instantly switched on and off, and the strength of the magnetic field can be easily controlled. Therefore, it is easy to control the foaming molding. In addition, it is desirable that the magnetic field lines that constitute the magnetic field form a closed loop. In this way, leakage of the magnetic field lines is suppressed, and a stable magnetic field can be formed in the cavity.

[0061] In this process, the magnetic field is formed so that the magnetic flux density in the cavity is approximately uniform. For example, the difference in magnetic flux density in the cavity is preferably within ±10%, more preferably within ±5%, and even more preferably within ±3%. By forming a uniform magnetic field in the cavity of the foaming mold, uneven distribution of the composite particles can be suppressed, and a desired orientation state can be obtained. In addition, the foaming molding is preferably performed 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.

[0062] It is desirable to apply the magnetic field while the viscosity of the urethane foam resin raw material is relatively low. If the magnetic field is applied when the urethane foam resin raw material has thickened and the foam molding has been completed to a certain extent, the composite particles will not be oriented easily, making it difficult to obtain the desired thermal conductivity. It is not necessary to apply the magnetic field for the entire time of foam molding.

[0063] After the foam molding is completed in this step, the mold is removed to obtain the urethane foam molded article of the present disclosure. At this time, a skin layer is formed on at least one of one end and the other end of the urethane foam molded article depending on the foam molding method. The skin layer may be cut off depending on the application (or may not be cut off). EXAMPLES

[0064] Next, the present disclosure will be described more specifically with reference to examples.

[0065] <Production of composite particles> First, three types of composite particles A to C were produced as follows. [Composite particle A] The powder of thermally conductive particles, the powder of magnetic particles, the binder, the succinic acid type surfactant, the powder of insulating inorganic particles, and the granulation raw material containing water were stirred to produce composite particles A (composite particle production process). First, the powder of two types of thermally conductive particles, the powder of two types of magnetic particles, and the binder were put into the container of a high-speed stirring type mixer granulator and mixed by impeller stirring, and water was further added and mixed for 1 minute. Next, a surface treatment agent in which a succinic acid type surfactant was dissolved in water was added over a period of about 1.5 minutes while stirring. Then, the powder of insulating inorganic particles was added and mixed for another 4 minutes. The stirring speed was 400 rpm. The obtained powder was dried to produce the powder of composite particles A. Details of the materials used are as follows, and the blending amounts are shown in Table 1 (the same applies to the composite particles B and C below).

[0066] (a) Thermally conductive particles Expanded graphite powder-1: "SYZR 502FP" manufactured by Shijiazhuang Aidi Trading Co., Ltd., particle size 300~500μm, thermal conductivity 200W / m·K. Expanded graphite powder-2: "AED-03" manufactured by Fuji Graphite Industries Co., Ltd., particle size (opening)-3 mm: 80%, thermal conductivity 200 W / m K. (b) Magnetic particles Stainless steel powder: "AKT" manufactured by Mitsubishi Steel Corporation, average particle size 11.5 μm. Iron powder: "SDP-4" manufactured by DOWA Electronics Co., Ltd., average particle size 45 μm. (c) Insulating inorganic particles Talc powder: "Microace (registered trademark) K-1" manufactured by Nippon Talc Co., Ltd., average particle size 8 μm. (d) Binder Starch: "Instant Tender Gel C" manufactured by Nippon Corn Starch Co., Ltd. (e) Succinic acid type surfactants Succinic acid type anionic surfactant: Sanhibitor (registered trademark) OMA-10, manufactured by Sanyo Chemical Industries, Ltd. [Table 1]

[0067] [Composite particle B] Composite particles B were produced in the same manner as composite particles A, except that the succinic acid type surfactant was changed to an amine-based nonionic surfactant (Sanyo Chemical Industries, Ltd., "Sanhibitor No. 50").

[0068] [Composite particle C] Composite particles C were produced in the same manner as composite particles A, except that no surfactant was used. That is, two types of thermally conductive powders, two types of magnetic powders, and a binder were mixed, water was added and mixed for 1 minute, and then insulating inorganic powder was added and mixed for 4 minutes. The obtained powder was then dried to produce composite particles C.

[0069] [Particle size distribution] The powders of composite particles A to C were sieved to measure the particle size distribution. The sieving was performed using metal mesh sieves with mesh sizes of 45 μm, 100 μm, 300 μm, 500 μm, 710 μm, 1000 μm, 2000 μm, and 3350 μm. FIG. 1 shows the particle size distribution of the powders of each composite particle. As shown in FIG. 1, it was confirmed that the particle size distribution of the powders of composite particles A and B granulated using a surfactant has a smaller proportion of small particles with a particle diameter of 100 μm or less than the particle size distribution of the powder of composite particle C granulated without using a surfactant. In Table 2 described later, the case where the content ratio of small particles with a particle diameter of 100 μm or less was 10 mass% or less of the entire composite particle is indicated by a circle, and the case where it exceeded 10 mass% is indicated by a triangle.

[0070] [Rust prevention] The powders of composite particles A to C were visually observed to check for the presence or absence of rust. As a result, as shown in Table 2 below, no rust was observed in composite particles A and B granulated using a surfactant, whereas rust was observed in composite particle C granulated without using a surfactant.

[0071] <Production of urethane foam molded body> [Sample 1] A urethane foam molded body was produced using the produced composite particle A. First, 100 parts by mass of polyether polyol (Sumika Covestro Urethane Co., Ltd., "S-0248"), 2 parts by mass of diethylene glycol (Mitsubishi Chemical Co., Ltd.) as a chain extender, 2 parts by mass of water as a blowing agent, 1.5 parts by mass of tetraethylenediamine catalyst (Kao Corporation, "Kao Raiser (registered trademark) No. 31"), and 0.5 parts by mass of a silicone foam stabilizer (Dow Corning Toray Co., Ltd., "SZ-1333") were mixed to prepare a polyol raw material. In addition, a diphenylmethane diisocyanate (MDI) modified product was prepared as a polyisocyanate raw material. The MDI modified product was produced by mixing polyether polyol (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 them at 100°C for 180 minutes under nitrogen purging. Next, 129.7 parts by mass of composite particles A were added to 100 parts by mass of the polyol raw material and mixed to prepare a premix polyol. Next, 100.6 g of the premix polyol was mixed with 13.7 g of the polyisocyanate raw material to obtain a mixed raw material (mixed raw material production process).

[0072] Then, the mixed raw material was poured into an aluminum foaming mold (cavity is a rectangular parallelepiped of length 130 mm × width 130 mm × thickness 20 mm), and the foaming mold was sealed. Then, the foaming mold was placed in a magnetic induction foaming molding device to perform foaming molding. In the cavity of the foaming mold, a uniform magnetic field was formed by magnetic lines of force that were approximately parallel from above to below. The magnetic flux density in the cavity was 200 mT, and the difference in magnetic flux density in the cavity was within ±3%. The foaming molding was performed with a magnetic field applied for the first 2 minutes, and without a magnetic field applied for the following 5 minutes (foaming molding process). After the foaming molding was completed, the mold was removed to obtain a urethane foam molding. The obtained urethane foam molding is referred to as the urethane foam molding of sample 1. The content of composite particles A in the urethane foam molding of sample 1 was 4% by volume when the volume of the urethane foam molding was 100% by volume, and 42% by mass when the mass of the urethane foam molding was 100% by mass. The urethane foam molded article of Sample 1 falls within the concept of the urethane foam molded article of the present disclosure.

[0073] [Sample 2] A urethane foam molded article of Sample 2 was produced in the same manner as Sample 1, except that Composite Particles A were changed to Composite Particles B.

[0074] [Sample 3] A urethane foam molded article of Sample 3 was produced in the same manner as Sample 1, except that Composite Particles A were changed to Composite Particles C.

[0075] <Evaluation of urethane foam molded products> The moldability and thermal conductivity of the three samples produced were evaluated. Regarding moldability, the Asker C hardness of each sample was measured using an "Asker Rubber Hardness Tester Type C" manufactured by Kobunshi Keiki Co., Ltd., and the evaluation was based on the Asker C hardness value of sample 3 having composite particles C granulated without using a surfactant. In other words, if the Asker C hardness value was within ±5 of that of sample 3, it was evaluated as having no effect on foam molding (indicated by a circle in Table 2 below), and otherwise it was evaluated as having an effect on foam molding (indicated by a cross in the same table). Regarding thermal conductivity, the thermal conductivity of each sample was measured using an "HC-110" manufactured by Eiko Seiki Co., Ltd. that complies with the heat flow meter method of JIS A1412-2:1999, and the evaluation was based on the thermal conductivity value of sample 3 having composite particles C. That is, if the thermal conductivity value was equal to or greater than that of sample 3, it was evaluated as having good thermal conductivity (indicated by a circle in Table 2 below), and if it was less than that, it was evaluated as having poor thermal conductivity (indicated by a cross in the same table). Table 2 shows the evaluation results of moldability and thermal conductivity. [Table 2]

[0076] As shown in Table 2, in the urethane foam molding of Sample 1 having composite particles A surface-treated with a succinic acid-type surfactant, there was no decrease in thermal conductivity and no effect on foam molding was observed, whereas in the urethane foam molding of Sample 2 having composite particles B surface-treated with an amino-based surfactant, there was a decrease in thermal conductivity and hardness, and an effect on foam molding was confirmed. [Industrial Applicability]

[0077] The urethane foam molded article of the present disclosure can be used in a wide range of fields, such as automobiles, electronic devices, architecture, etc. For example, it is suitable as a soundproofing material for engines, motors, EGR valves, etc., arranged in the engine compartment of a vehicle, a soundproofing material for motors used in OA (Office Automation) devices and home appliances, and a soundproofing material used in electronic devices such as personal computers.

Claims

1. The present invention has a substrate made of polyurethane foam and composite particles contained in the substrate in an oriented manner, The composite particles include thermally conductive particles made of a non-magnetic material and having a thermal conductivity of 200 W / m·K or more, and magnetic particles bonded to the surfaces of the thermally conductive particles with a binder, The thermally conductive particles include at least one of graphite particles and expanded graphite particles, the magnetic particles include at least one of iron particles and stainless steel particles; A urethane foam molded article, characterized in that it is surface-treated with one or more surfactants selected from a carboxylic acid type surfactant and a succinic acid type surfactant.

2. The urethane foam molded article according to claim 1 , wherein the surfactant comprises a succinic acid type surfactant.

3. The urethane foam molded article according to claim 1 , wherein the surfactant is water-soluble.

4. 2. The urethane foam molded article according to claim 1, wherein in the particle size distribution of the composite particles, the content of small particles having a particle diameter of 100 μm or less is 10 mass % or less, when the total mass of the composite particles is 100 mass %.

5. The urethane foam molded article according to claim 1 , wherein the thermally conductive particles have an average particle size of 200 μm or more and 2000 μm or less.

6. The urethane foam molded article according to claim 1 , wherein the magnetic particles include iron particles.

7. The urethane foam molded article according to claim 1 , wherein the composite particles have insulating inorganic particles bonded to the surfaces of the thermally conductive particles with a binder.

8. The average particle size of the thermally conductive particles is 200 μm or more and 2000 μm or less, The magnetic particles include the iron particles, The composite particles have insulating inorganic particles bonded to the surfaces of the thermally conductive particles by a binder, In the particle size distribution of the composite particles, the content of small particles having a particle diameter of 100 μm or less is 10 mass % or less when the total mass of the composite particles is 100 mass %, The urethane foam molded article according to claim 1 , wherein the surfactant comprises a succinic acid type surfactant and is water-soluble.

9. A method for producing the urethane foam molded article according to claim 1, comprising the steps of: a composite particle production process for producing composite particles by stirring a granulation raw material containing a powder of thermally conductive particles made of a non-magnetic material and having a thermal conductivity of 200 W / m K or more, the powder including at least one of graphite particles and expanded graphite particles, a powder of magnetic particles including at least one of iron particles and stainless steel particles, a binder, one or more surfactants selected from a carboxylic acid type surfactant and a succinic acid type surfactant, and water; a mixed raw material production step of producing a mixed raw material by mixing the composite particle powder with a urethane foam resin raw material; a foaming molding step of injecting the mixed raw material into a cavity of a foaming mold and foaming the mixture while applying a magnetic field so that the magnetic flux density in the cavity is approximately uniform; 2. A method for producing a urethane foam molded article, comprising the steps of:

10. A method for producing the urethane foam molded article according to claim 7, comprising the steps of: A composite particle production process for producing composite particles; a mixed raw material production step of producing a mixed raw material by mixing the composite particle powder with a urethane foam resin raw material; a foaming molding step of injecting the mixed raw material into a cavity of a foaming mold and foaming the mixture while applying a magnetic field so that the magnetic flux density in the cavity is approximately uniform; having The composite particle production process includes: a first stirring step of stirring a first raw material including a powder of thermally conductive particles made of a non-magnetic material and having a thermal conductivity of 200 W / m K or more, the powder including at least one of graphite particles and expanded graphite particles, a powder of magnetic particles including at least one of iron particles and stainless steel particles, a binder, one or more surfactants selected from a carboxylic acid type surfactant and a succinic acid type surfactant, and water; a second stirring step of adding a powder of insulating inorganic particles to the stirred mixture of the first raw material and further stirring the mixture; 2. A method for producing a urethane foam molded article, comprising the steps of:

11. 11. The method for producing a urethane foam molded product according to claim 9, wherein the amount of the surfactant blended in the composite particle production step is 0.1 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the powder of the thermally conductive particles.

Images