JP5662743B2 - Urethane foam molding and method for producing the same - Google Patents

Description

  The present invention relates to a urethane foam molded article used as, for example, a sound absorbing material or a vibration absorbing material, and a method for producing the same.

  Urethane foam moldings are used in various fields such as automobiles as sound absorbing materials, vibration absorbing materials and the like. The urethane foam molded article has a large number of cells (bubbles) inside. For this reason, the thermal conductivity of the urethane foam molding is small. Therefore, when it arrange | positions around the components with heat_generation | fever, heat | fever accumulates in a urethane foam molding, and there exists a possibility of causing the temperature rise of the said component. In order to solve such a problem, it is necessary to improve the heat dissipation of the urethane foam molded article. For example, Patent Documents 1 and 2 disclose urethane foam molded articles having oriented magnetic particles.

JP 2007-230544 A JP 2009-51148 A JP 2006-219562 A JP 2007-44919 A

  As in the urethane foam molded articles disclosed in Patent Documents 1 and 2, when the magnetic particles are oriented in a polyurethane foam in a state of being connected to each other, a heat transfer path is formed in the orientation direction of the magnetic particles. Thereby, the heat dissipation of a urethane foam molding can be improved. However, the thermal conductivity of iron or stainless steel used as magnetic particles is relatively small. For this reason, it is difficult to improve the heat dissipation of the urethane foam molding to a satisfactory level only by orienting the magnetic particles.

  On the other hand, when magnetic particles are blended, there is a problem that the flame retardancy of the urethane foam molded article is lowered. That is, the urethane foam molded article to which flame retardancy is imparted has a dropping effect that suppresses the spread of fire by dropping a fire type even when exposed to flame. However, when magnetic particles are contained, the dropping action is impaired, and the self-digestibility of the urethane foam molded article is considered to be reduced.

  This invention is made | formed in view of such a situation, and makes it a subject to provide the urethane foam molded object which was high in heat conductivity, and was excellent in the flame retardance, and its manufacturing method.

  (1) In order to solve the above problems, the urethane foam molded article of the present invention has a base material made of polyurethane foam and a heat conductive filler blended in the base material, and the heat conductive filler. Includes magnetic particles and thermally conductive particles made of a non-magnetic material, at least a part of the thermally conductive filler is oriented, and the thermally conductive particles in the oriented thermally conductive filler are: And containing expanded graphite particles.

  The urethane foam molded article of the present invention contains magnetic particles and thermally conductive particles as a thermally conductive filler. The thermally conductive particles are made of a non-magnetic material and have a higher thermal conductivity than the magnetic particles. Since the thermally conductive particles are contained in addition to the magnetic particles, the urethane foam molded article of the present invention has high thermal conductivity.

  The thermally conductive particles are made of a nonmagnetic material. For this reason, the heat conductive particles cannot be oriented by magnetic force. However, in the urethane foam molded article of the present invention, the magnetic particles tend to be oriented along the lines of magnetic force by applying a magnetic field during foam molding. Under the present circumstances, when a foaming urethane resin raw material flows, heat conductive particles are also easy to be arranged so that a line of magnetic force may be met. Also, as will be described later, when the magnetic particles adhere to the surface of the thermally conductive particles to form a composite particle, as the magnetic particles attached to the surface try to align along the lines of magnetic force, The composite particles are oriented along the magnetic field lines. As described above, when all or a part of the thermally conductive filler is oriented, the heat applied to one end of the urethane foam molded article of the present invention is quickly transmitted through the magnetic particles and the thermally conductive particles, and the like. Easily released from the edge. Therefore, the thermal conductivity is further improved.

  Further, the thermally conductive particles in the oriented thermally conductive filler include expanded graphite particles. Expanded graphite is used as a flame retardant as disclosed in Patent Documents 3 and 4, for example. Expanded graphite is obtained by inserting a substance that generates gas by heating between scaly graphite layers. When heat is applied to expanded graphite, the generated gas expands the layers and forms a stable layer against heat and chemicals. The formed layer becomes an insulating layer and prevents heat transfer, thereby providing a flame retardant effect.

  According to the urethane foam molded article of the present invention, expanded graphite particles are blended as the heat conductive particles together with the magnetic particles. The expanded graphite particles are oriented. For this reason, compared with the case where the expanded graphite particles are simply blended and the expanded graphite particles are irregularly dispersed, the heat applied to the urethane foam molding is easily transferred to the expanded graphite particles. As a result, the expanded graphite particles reach the expansion start temperature early. Therefore, the flame retardant effect by the expanded graphite particles is more easily exhibited. Therefore, even if the urethane foam molded article of the present invention contains magnetic particles, the self-digestibility is not lowered and the flame retardancy is excellent.

  (2) The method for producing a urethane foam molded article according to the present invention is a method for producing a urethane foam molded article having the configuration of (1) above, in which a foamed urethane resin raw material and the thermally conductive filler are mixed. A raw material mixing step to be a mixed raw material, and a foam molding step of injecting the mixed raw material into a foam mold cavity and performing foam molding while applying a magnetic field so that the magnetic flux density in the cavity is substantially uniform. It is characterized by.

  According to the production method of the present invention, the urethane foam molded article of the present invention can be easily produced. In the foam molding process, foam molding is performed in a magnetic field in which the magnetic flux density in the cavity is substantially uniform. Therefore, uneven distribution of the thermally conductive filler due to the difference in magnetic flux density can be suppressed. Thereby, even if the compounding quantity of a heat conductive filler is comparatively small quantity, the urethane foam molded object of the said this invention with high heat conductivity can be manufactured.

  According to the present invention, it is possible to provide a urethane foam molded article having high thermal conductivity and excellent flame retardancy, and a simple production method thereof.

In an Example, it is a perspective view of the magnetic induction foam molding apparatus used for manufacture of a urethane foam molding. It is sectional drawing of the same magnetic induction foam molding apparatus.

  Hereinafter, embodiments of the urethane foam molded article and the method for producing the same according to the present invention will be described. The urethane foam molded article and the method for producing the same according to the present invention are not limited to the following embodiments, and various modifications and improvements that can be made by those skilled in the art without departing from the gist of the present invention. It can implement with the form of.

<Urethane foam molding>
The urethane foam molded article of the present invention has a base material made of polyurethane foam and a heat conductive filler blended in the base material.

  The base polyurethane foam is produced from a foamed urethane resin material containing a polyisocyanate component and a polyol component. Details will be described in the method for producing a urethane foam molded article of the present invention described later.

  The thermally conductive filler includes magnetic particles and thermally conductive particles. Further, at least a part of the heat conductive filler is oriented in the polyurethane foam as the base material. Of course, all of the heat conductive filler may be oriented. For example, when magnetic particles and thermally conductive particles are blended as the thermally conductive filler, the magnetic particles are mainly oriented by foam molding in a magnetic field. Moreover, when the composite particle | grains which the magnetic particle adhered to the surface of a heat conductive particle are mix | blended as a heat conductive filler, a composite particle will orient. Moreover, when the composite particles and the heat conductive particles are blended as the heat conductive filler, the composite particles are mainly oriented.

  The content of the thermally conductive filler in the urethane foam molded article may be determined in consideration of the influence on foam molding, thermal conductivity, flame retardancy, and the like. For example, in order to obtain a urethane foam molded article having desired sound absorption characteristics and the like without hindering foam molding, the content of the heat conductive filler, when the volume of the urethane foam molded article is 100% by volume, It is desirable to be 20% by volume or less. On the other hand, in order to ensure the desired thermal conductivity and flame retardancy, the content of the thermal conductive filler is preferably 1% by volume or more.

The magnetic particles only need to have excellent magnetization characteristics, for example, iron, nickel, cobalt, gadolinium, stainless steel, magnetite, maghemite, manganese zinc ferrite, barium ferrite, strontium ferrite and other ferromagnetic materials, MnO, Cr Antiferromagnetic materials such as ₂ O ₃ , FeCl ₂ , and MnAs, and alloys particles using these are preferable. Among these, iron, nickel, cobalt, and powders of these iron-based alloys (including stainless steel) are preferable from the viewpoint of easy availability as fine particles and high saturation magnetization.

  The thermally conductive particles include expanded graphite particles. As the expanded graphite particles, a known expanded graphite powder may be used in consideration of the expansion start temperature, the particle diameter, the expansion rate, and the like. For example, it is necessary to select one having an expansion start temperature higher than the heat generation temperature at the time of molding the urethane foam molded article. Specifically, expanded graphite particles having an expansion start temperature of 150 ° C. or higher are suitable.

  As the thermally conductive particles, only expanded graphite particles may be used, or expanded graphite particles and other particles made of a non-magnetic material may be used in combination. When only expanded graphite particles are used as the heat conductive particles, the viscosity of the mixed raw material in which the foamed urethane resin raw material and the heat conductive filler (magnetic particles + heat conductive particles) are mixed during the production of the urethane foam molded product It has the advantage that can be suppressed. Moreover, the flame retardance improvement effect of a urethane foam molding can be heightened. However, the content of expanded graphite particles is increased by the amount not containing other particles. For this reason, there exists a possibility that the hardening reaction of urethane may be inhibited by the acid component between the layers of expanded graphite particles. Therefore, from the viewpoint of moldability of the urethane foam molded article, it is desirable to use the expanded graphite particles and other particles made of a nonmagnetic material in combination as the heat conductive particles. In addition, it is possible to suppress the fall of the moldability accompanying the increase in content of an expanded graphite particle by increasing the compounding quantity of the catalyst to mix | blend.

  When other particles made of a non-magnetic material are used in combination, it is desirable to employ particles having a high thermal conductivity. For example, particles having a thermal conductivity of 200 W / m · K or more are suitable. In this specification, diamagnetic materials and paramagnetic materials other than ferromagnetic materials and antiferromagnetic materials are referred to as nonmagnetic materials. Examples of such particles include graphite particles other than expanded graphite, carbon fibers, diamond particles, and particles such as aluminum, gold, copper, and alloys based on these. Among them, it is desirable to employ graphite particles other than expanded graphite because it is inexpensive and has high thermal conductivity. Examples of graphite particles other than expanded graphite include natural graphite such as flaky graphite, scaly graphite, and earthy graphite, and artificial graphite. Artificial graphite is not easily scaled. For this reason, natural graphite particles are preferred because they are scaly and have a high effect of improving thermal conductivity.

  Moreover, the magnetic particles and the heat conductive particles may form composite particles. For example, composite particles can be produced by attaching magnetic particles to the surface of thermally conductive particles. In this case, the magnetic particles may be attached to only a part of the surface of the thermally conductive particles, or may be attached so as to cover the entire surface. Moreover, when the oriented heat conductive filler contains composite particles, the heat conductive particles constituting the composite particles include expanded graphite particles. Furthermore, the thermally conductive particles constituting the composite particles may contain graphite particles other than expanded graphite.

  The composite particles are oriented along the lines of magnetic force by applying a magnetic field during foam molding. Therefore, the expanded graphite particles can be oriented in the polyurethane foam as the base material by using the expanded graphite particles as composite particles. When the expanded graphite particles are oriented, the heat applied to the urethane foam molding is easily transferred to the expanded graphite particles. For this reason, the expanded graphite particles reach the expansion start temperature early. Thereby, the flame-retardant effect by an expanded graphite particle can be exhibited rapidly. Further, in the case of composite particles, the flame retardant effect of expanded graphite particles can be sufficiently exerted, so the content of expanded graphite particles can be reduced. That is, when the content of the expanded graphite particles is increased, the moldability may be affected, and physical properties such as sound absorption characteristics may be deteriorated. In addition, the mass of the urethane foam molding increases, and the cost increases. These problems are improved by using expanded graphite particles as composite particles.

  For example, when the expanded graphite particles are all contained as composite particles, the content of the expanded graphite particles is preferably 5% by mass or more when the mass of the entire urethane foam molded article is 100% by mass. .

  In addition, when only the composite particles are included as the thermally conductive filler, from the viewpoint of moldability, composite particles obtained by attaching magnetic particles to the surface of expanded graphite particles, and magnetic particles on the surface of graphite particles other than expanded graphite are used. It is desirable to include both of the composite particles to which are attached. The blending ratio of each composite particle may be appropriately determined in consideration of flame retardancy, moldability, and the like.

  The composite particles can be produced by a wet electrostatic adsorption method, a dry pulverization and mixing method, a stirring granulation method, a mechanochemical method, or the like. For example, in the stirring granulation method, a raw material containing a powder of heat conductive particles, a powder of magnetic particles, and a binder for bonding them together is granulated by stirring at high speed. According to the stirring granulation method, the heat conductive particles and the magnetic particles can be softly bonded with the binder. For this reason, even when the thermally conductive particles have a shape with a high thermal conductivity (a shape with a large aspect ratio), they can be combined with the magnetic particles without breaking the shape. The type of binder may be appropriately selected in consideration of the type of magnetic particles, the influence on foam molding, and the like. During the production of composite particles, frictional heat is generated by high-speed stirring. For this reason, as a binder, a non-volatile thing is desirable. In view of the environment, a water-based binder is preferable. Examples of the aqueous binder include methyl cellulose, carboxymethyl cellulose, hydroxypropyl methyl cellulose, and polyvinyl alcohol.

  When forming composite particles, it is desirable to determine the size of the thermally conductive particles in consideration of dispersibility, an apparatus used for foam molding, and the like. For example, it is desirable that the heat conductive particles have a particle size of 500 μm or less. 300 μm or less is more preferable. In the present specification, the maximum length of the thermally conductive particles is adopted as the particle diameter of the thermally conductive particles.

  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, the thermal conductivity between the composite particles, and the like. For example, when the size of the magnetic particles is reduced, 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 size of the magnetic particles needs to be 100 nm or more. It is more preferable that the thickness is 1 μm or more, further 5 μm or more. In the present specification, the maximum length of the magnetic particles is adopted as the particle diameter of the magnetic particles.

  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 heat conductive particles is shortened. Thereby, the thermal conductivity between adjacent composite particles is improved. As a result, the thermal conductivity of the urethane foam molding is improved. When the shape of the magnetic particles is flat, the magnetic particles and the heat conductive particles are in contact with each other on the surface. That is, the contact area between the two becomes large. Thereby, the adhesive force of a magnetic particle and a heat conductive particle improves. Therefore, the magnetic particles are difficult 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 employ flaky particles as the magnetic particles.

<Method for producing urethane foam molding>
The manufacturing method of the urethane foam molding of this invention has a raw material mixing process and a foam molding process. Hereinafter, each step will be described.

(1) Raw material mixing step This step is a step of mixing a foamed urethane resin raw material and a thermally conductive filler to obtain a mixed raw material.

  The foamed urethane resin raw material may be prepared from already known raw materials such as polyol and polyisocyanate. Polyols include polyhydric hydroxy compounds, polyether polyols, polyester polyols, polymer polyols, polyether polyamines, polyester polyamines, alkylene polyols, urea-dispersed polyols, melamine-modified polyols, polycarbonate polyols, acrylics What is necessary is just to select suitably from polyols, polybutadiene polyols, phenol modified polyols, etc. Examples of the polyisocyanate include tolylene diisocyanate, phenylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, triphenylmethane triisocyanate, polymethylene polyphenyl isocyanate, naphthalene diisocyanate, and derivatives thereof (for example, by reaction with polyols). What is necessary is just to select suitably from prepolymers obtained, modified polyisocyanate, etc.).

In addition to the foamed urethane resin raw material, a catalyst, a foaming agent, a foam stabilizer, a plasticizer, a crosslinking agent, a flame retardant, an antistatic agent, a viscosity reducing agent, a stabilizer, a filler, a colorant, and the like may be appropriately blended. Good. For example, examples of the catalyst include amine-based catalysts such as tetraethylenediamine, triethylenediamine, and dimethylethanolamine, and organometallic catalysts such as tin laurate and tin octoate. Moreover, water is suitable as the foaming agent. In addition to water, methylene chloride, chlorofluorocarbons, CO ₂ gas and the like can be mentioned. Moreover, a silicone type foam stabilizer is suitable as the foam stabilizer, and triethanolamine, diethanolamine and the like are suitable as the crosslinking agent.

  As described above, the thermally conductive filler may be blended with magnetic particles and thermally conductive particles, or may be blended with composite particles in which the magnetic particles adhere to the surface of the thermally conductive particles. You may mix | blend particle | grains and heat conductive particle | grains. The types of magnetic particles and heat conductive particles are as described in the description of the urethane foam molded article of the present invention. Therefore, the description is omitted here.

  The mixed raw material can be produced, for example, by mechanically stirring the urethane foam resin raw material and the heat conductive filler using a propeller or the like. In addition, at least one of the two components of the foamed urethane resin material (polyol material, polyisocyanate material) is added with a heat conductive filler to prepare two types of materials, and then the two materials are mixed and manufactured. Also good. In the latter case, for example, this step is performed by preparing a polyol raw material containing a polyol, a catalyst, and a foaming agent and a polyisocyanate raw material containing a polyisocyanate as a foamed urethane resin raw material, and the polyol raw material and the polyisocyanate raw material. A raw material preparation step in which a heat conductive filler is blended in at least one of the above, a polyol raw material and a polyisocyanate raw material, respectively, and fed to the mixing head, and both raw materials are mixed in the mixing head and mixed raw material And a mixing step.

  According to this configuration, it is possible to employ a collision stirring method in which a polyol raw material and a polyisocyanate raw material are each injected and collided at a high pressure in the mixing head. According to the collision stirring method, continuous production becomes possible. Therefore, the collision stirring method is suitable for mass production. Further, according to the collision stirring method, the container cleaning step which is necessary every time of mixing is not required and the yield is improved as compared with the mechanical stirring method. Therefore, the manufacturing cost can be reduced.

  In the collision stirring method, a polyol raw material and a polyisocyanate raw material preliminarily blended with a heat conductive filler are each caused to collide by being injected at a high pressure from an injection hole provided in a mixing head of a high pressure foaming apparatus. If the size of the thermally conductive filler is larger than the hole diameter of the injection hole, the injection hole is likely to be damaged due to contact with the heat conductive filler. Thereby, there exists a possibility that durability of a mixing head may fall. Moreover, the larger the size of the heat conductive filler, the more easily the heat conductive filler settles in the polyol raw material. For this reason, uniform mixing is difficult. Therefore, when the collision stirring method is adopted, it is desirable that the maximum length of the heat conductive filler is smaller than the diameter of the injection hole into which the polyol raw material and the polyisocyanate raw material are injected. By doing so, it is possible to reduce the load on the mixing head and extend the life of the high-pressure foaming apparatus. Moreover, sedimentation of the heat conductive filler is suppressed, and an increase in viscosity in the polyol raw material can be reduced. For example, the maximum length of the heat conductive filler is desirably 500 μm or less.

(2) Foam molding step In this step, the mixed raw material obtained in the previous raw material mixing step is injected into a foam mold cavity and foamed while applying a magnetic field so that the magnetic flux density in the cavity is substantially uniform. This is a molding step.

  What is necessary is just to form a magnetic field in the direction which orientates a heat conductive filler. For example, when the thermally conductive filler is oriented linearly, it is desirable that the magnetic lines of force in the foam-type cavity are substantially parallel from one end of the cavity to the other end. Moreover, it is desirable that the magnetic field lines constituting the magnetic field form a closed loop. By doing so, leakage of magnetic field lines is suppressed, and a stable magnetic field can be formed in the cavity.

  In this step, the magnetic field is formed so that the magnetic flux density in the cavity is substantially uniform. For example, the difference in magnetic flux density in the cavity is preferably within ± 10%. It is more preferable that it is within ± 5%, more preferably within ± 3%. By forming a uniform magnetic field in the cavity, uneven distribution of the thermally conductive filler can be suppressed, and a desired orientation state can be obtained. The foam molding may be performed with a magnetic flux density of 200 mT or more. By carrying out like this, the heat conductive filler in a mixed raw material becomes easy to orient.

  It is desirable that the magnetic field be applied while the viscosity of the foamed urethane resin material is relatively low. If the foamed urethane resin material is thickened and a magnetic field is applied when foam molding is completed to some extent, it is difficult to obtain the desired thermal conductivity because the thermally conductive filler is difficult to orient. In addition, it is not necessary to apply a magnetic field in all the time for performing foam molding. After foam molding is completed in this step, the mold is removed to obtain the urethane foam molded article of the present invention.

  Next, the present invention will be described more specifically with reference to examples.

<Production of composite particles>
Four types of composite particles A to D were produced as follows.

[Composite particle A]
As thermal conductive particles, expanded graphite powder (“SYZR502FP” purchased from Sanyo Trading Co., Ltd.) and natural graphite powder (“F # 2” manufactured by Nippon Graphite Industries Co., Ltd.) are used, and stainless steel is used as magnetic particles. Composite particles were produced using powder (“DAP410L”, SUS410, spherical shape, average particle diameter 10 μm, manufactured by Daido Steel Co., Ltd.). First, expanded graphite powder, natural graphite powder, stainless steel powder, and hydroxypropyl methylcellulose (“TC-5” manufactured by Shin-Etsu Chemical Co., Ltd.) as a binder are mixed at high speed with a mixing granulator ((Co., Ltd.). ) “NMG-1L” manufactured by Nara Machinery Co., Ltd.) and mixed for about 3 minutes. Next, water was added and mixed for another 20 minutes. The obtained powder was dried to obtain composite particles A. In addition, about the compounding ratio of the used material, it shows in following Table 1 (it is the same also about the following composite particles BD).

[Composite particle B]
Composite particles B were produced in the same manner as the composite particles A except that the blending ratios of the magnetic particles and the binder were changed.

[Composite particle C]
Composite particles C were produced without using expanded graphite powder. That is, composite particles C were produced in the same manner as the composite particles A using natural graphite powder, stainless steel powder, and a binder.

[Composite particle D]
Composite particles D were produced without using natural graphite powder. That is, composite particles D were produced in the same manner as the composite particles A using expanded graphite powder, stainless steel powder, and a binder.

<Manufacture of urethane foam molding>
[Example 1]
A urethane foam molded article was produced using the produced composite particles A as a thermally conductive filler. Of the composite particles A, the particles having expanded graphite particles as thermally conductive particles are 50% by mass, and the particles having natural graphite particles as thermally conductive particles are 50% by mass. First, polyether polyol (“S-0248” manufactured by Sumika Bayer Urethane Co., Ltd., average molecular weight 6000, functional group number 3, OH value 28 mg KOH / g) 100 parts by mass, and diethylene glycol as a crosslinking agent (Mitsubishi Chemical Co., Ltd.) ) 2 parts by mass, 2 parts by mass of foaming agent water, 1.5 parts by mass of a tetraethylenediamine catalyst (“Kaorizer (registered trademark) No. 31” manufactured by Kao Corporation), and a silicone foam stabilizer ( A polyol raw material was prepared by mixing 0.5 part by mass of “SZ-1333” manufactured by Toray Dow Corning Co., Ltd. Moreover, diphenylmethane diisocyanate (MDI) ("NE1320B" manufactured by BASFINOAC Polyurethane Co., Ltd., NCO = 44.8 wt%) was prepared as a polyisocyanate raw material.

  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. Subsequently, 100.6 g of the premix polyol and 13.7 g of the polyisocyanate raw material were mixed to obtain a mixed raw material.

  Then, the mixed raw material was poured into an aluminum foaming mold (see FIGS. 1 and 2 described later. The cavity was a rectangular parallelepiped having a length of 130 mm × width of 130 mm × thickness of 20 mm), and the foaming mold was sealed. Then, the foaming mold was installed in a magnetic induction foam molding apparatus to perform foam molding. FIG. 1 is a perspective view of a magnetic induction foam molding apparatus. FIG. 2 shows a sectional view of the apparatus. In FIG. 2, hatching of the yoke part and the core part is omitted for convenience of explanation. As shown in FIGS. 1 and 2, the magnetic induction foam molding apparatus 1 includes a gantry 2, an electromagnet unit 3, and a foaming mold 4.

  The electromagnet unit 3 is placed on the upper surface of the gantry 2. The electromagnet unit 3 and the gantry 2 are fixed by screwing a bracket 21 to each. The electromagnet portion 3 includes yoke portions 30U and 30D, coil portions 31L and 31R, and pole pieces 32U and 32D.

  The yoke portion 30U is made of iron and has a flat plate shape. Similarly, the yoke part 30D is made of iron and has a flat plate shape. The yoke portions 30U and 30D are arranged to face each other in the vertical direction.

  The coil portion 31L is interposed between the yoke portions 30U and 30D. The coil part 31 </ b> L is disposed on the left side of the foaming mold 4. Two coil portions 31L are arranged in the vertical direction. Each of the coil portions 31L includes a core portion 310L and a conductive wire 311L. The core portion 310L is made of iron and has a columnar shape extending in the vertical direction. The conducting wire 311L is wound around the outer peripheral surface of the core portion 310L. The conducting wire 311L is connected to a power source (not shown).

  The coil portion 31R is interposed between the yoke portions 30U and 30D. The coil portion 31 </ b> R is disposed on the right side of the foaming mold 4. Two coil portions 31 </ b> R are arranged in the vertical direction. The coil portions 31R each have the same configuration as the coil portion 31L. That is, the coil portion 31R includes a core portion 310R and a conducting wire 311R. The conducting wire 311R is wound around the outer peripheral surface of the core portion 310R. The conducting wire 311R is connected to a power source (not shown).

  The pole piece 32U is made of iron and has a flat plate shape. The pole piece 32U is disposed at the center of the lower surface of the yoke portion 30U. The pole piece 32U is interposed between the yoke portion 30U and the foaming mold 4. The pole piece 32D is made of iron and has a flat plate shape. The pole piece 32D is disposed at the center of the upper surface of the yoke portion 30D. The pole piece 32D is interposed between the yoke portion 30D and the foaming mold 4.

  The foaming mold 4 is disposed between the coil portion 31L and the coil portion 31R. The foaming mold 4 includes an upper mold 40U and a lower mold 40D. The upper mold 40U has a prismatic shape. A recess is formed in the lower surface of the upper mold 40U. Similarly, the lower mold 40D has a prismatic shape. A recess is formed on the upper surface of the lower mold 40D. The upper mold 40U and the lower mold 40D are arranged so that the openings of the recesses face each other. A rectangular parallelepiped cavity 41 is defined between the upper mold 40U and the lower mold 40D by combining the concave portions. As described above, the cavity 41 is filled with the mixed raw material.

  When both the power source connected to the conducting wire 311L and the power source connected to the conducting wire 311R are turned on, the upper end of the core portion 310L of the coil portion 31L is magnetized to the N pole and the lower end is magnetized to the S pole. For this reason, a magnetic force line L (indicated by a dotted line in FIG. 2) is generated in the core portion 310L from the bottom to the top. Similarly, the upper end of the core portion 310R of the coil portion 31R is magnetized to the N pole and the lower end is magnetized to the S pole. For this reason, lines of magnetic force L are generated in the core portion 310R from the bottom to the top.

  The lines of magnetic force L radiated from the upper end of the core portion 310L of the coil portion 31L flow into the cavity 41 of the foaming mold 4 through the yoke portion 30U and the pole piece 32U. Then, it flows into the lower end of the core part 310L through the pole piece 32D and the yoke part 30D. Similarly, the lines of magnetic force L radiated from the upper end of the core portion 310R of the coil portion 31R flow into the cavity 41 of the foaming mold 4 through the yoke portion 30U and the pole piece 32U. Then, it flows into the lower end of the core portion 310R through the pole piece 32D and the yoke portion 30D. Thus, since the magnetic lines L constitute a closed loop, the leakage of the magnetic lines L is suppressed. In the cavity 41 of the foaming mold 4, a uniform magnetic field is formed by magnetic lines of force L that are substantially parallel from the top to the bottom. Specifically, the magnetic flux density in the cavity 41 was about 200 mT. Further, the difference in magnetic flux density in the cavity 41 was within ± 3%.

  Foam molding was performed while applying a magnetic field for the first about 2 minutes, and for about 5 minutes without applying a magnetic field. After the foam molding was completed, the mold was removed to obtain a urethane foam molded article. The obtained urethane foam molded article was used as the urethane foam molded article of Example 1. In the urethane foam molded article of Example 1, the content of the thermally conductive filler (composite particles A) was 4% by volume when the volume of the urethane foam molded article was 100% by volume.

[Example 2]
Using the produced composite particle B as a thermally conductive filler, a urethane foam molded article was produced. Of the composite particles B, 50% by mass is particles with expanded graphite particles as thermally conductive particles, and 50% by mass with natural graphite particles as thermally conductive particles. First, to 100 parts by mass of the polyol raw material used in Example 1 above, 261.5 parts by mass of composite particles B and 20 parts by mass of a plasticizer were added and mixed to prepare a premix polyol. Next, 381 g of the premix polyol and 15.1 g of the polyisocyanate raw material used in Example 1 were mixed to obtain a mixed raw material. Then, the mixed raw material was poured into a foaming mold (same as above), the foaming mold was sealed, and foam molding was performed in a magnetic field in the same manner as in Example 1 above. The obtained urethane foam molded article was used as the urethane foam molded article of Example 2. In the urethane foam molded article of Example 2, the content of the heat conductive filler (composite particle B) was 19.3 volume% when the volume of the urethane foam molded article was 100 volume%.

[Example 3]
A urethane foam molded article was produced using the produced composite particles D as a thermally conductive filler. The thermally conductive particles constituting the composite particle D are all expanded graphite particles. First, 129.7 parts by mass of composite particles D were added to and mixed with 100 parts by mass of the polyol raw material used in Example 1 to prepare a premix polyol. Next, 100.6 g of the premix polyol and 13.7 g of the polyisocyanate raw material used in Example 1 were mixed to obtain a mixed raw material. Then, the mixed raw material was poured into a foaming mold (same as above), the foaming mold was sealed, and foam molding was performed in a magnetic field in the same manner as in Example 1 above. The obtained urethane foam molded article was used as the urethane foam molded article of Example 3. In the urethane foam molded article of Example 3, the content of the thermally conductive filler (composite particles D) was 4% by volume when the volume of the urethane foam molded article was 100% by volume.

[Comparative Example 1]
Using the produced composite particle C as a thermally conductive filler, a urethane foam molded article was produced. The heat conductive particles constituting the composite particle C are all natural graphite particles. That is, in Comparative Example 1, no expanded graphite particles are blended. First, 129.7 parts by mass of composite particles C were added to and mixed with 100 parts by mass of the polyol raw material used in Example 1 to prepare a premix polyol. Next, 100.6 g of the premix polyol and 13.7 g of the polyisocyanate raw material used in Example 1 were mixed to obtain a mixed raw material. Then, the mixed raw material was poured into a foaming mold (same as above), the foaming mold was sealed, and foam molding was performed in a magnetic field in the same manner as in Example 1 above. The obtained urethane foam molded article was used as the urethane foam molded article of Comparative Example 1. In the urethane foam molded article of Comparative Example 1, the content of the heat conductive filler (composite particles C) was 4% by volume when the volume of the urethane foam molded article was 100% by volume.

[Comparative Example 2]
A urethane foam molded article was produced using only expanded graphite particles as the heat conductive filler. That is, in Comparative Example 2, no magnetic particles are blended. First, 21.2 parts by mass of expanded graphite powder (same as above) was added to and mixed with 100 parts by mass of the polyol raw material used in Example 1 to prepare a premix polyol. Next, 51.5 g of the premix polyol and 13.7 g of the polyisocyanate raw material used in Example 1 were mixed to obtain a mixed raw material. The mixed raw material was poured into a foaming mold (same as above), the foaming mold was sealed, and foam molding was performed without applying a magnetic field. The obtained urethane foam molded article was used as the urethane foam molded article of Comparative Example 2. In the urethane foam molded article of Comparative Example 2, the content of the heat conductive filler (expanded graphite particles) was 0.7% by volume when the volume of the urethane foam molded article was 100% by volume.

[Comparative Example 3]
A urethane foam molded article was produced using the produced composite particles C and expanded graphite particles as a thermally conductive filler. The heat conductive particles constituting the composite particle C are all natural graphite particles. That is, in Comparative Example 3, the expanded graphite particles were blended alone, not as composite particles. First, to 100 parts by mass of the polyol raw material used in Example 1, 129.7 parts by mass of composite particles C and 21.2 parts by mass of expanded graphite powder (same as above) are added and mixed to prepare a premix polyol. did. Next, 109.1 g of the premix polyol and 13.7 g of the polyisocyanate raw material used in Example 1 were mixed to obtain a mixed raw material. Then, the mixed raw material was poured into a foaming mold (same as above), the foaming mold was sealed, and foam molding was performed in a magnetic field in the same manner as in Example 1 above. The obtained urethane foam molded article was used as the urethane foam molded article of Comparative Example 3. In the urethane foam molded article of Comparative Example 3, the content of the heat conductive filler (composite particles C + expanded graphite particles) was 4.7% by volume when the volume of the urethane foam molded article was 100% by volume.

<Evaluation of flame retardancy>
Flame retardancy was evaluated for each of the urethane foam molded articles of Examples and Comparative Examples. Flame retardant evaluation was performed by Underwriters Laboratories, Inc., USA. Based on the combustion test standard (UL94) established by And the case where the criterion of “V-0” was satisfied was evaluated as pass (indicated by ◯ in Table 2), and the case where it was not satisfied was evaluated as unacceptable (indicated by x in Table 2). An evaluation result is shown in Table 2 with the compounding quantity of the raw material in each urethane foaming molding.

  As shown in Table 2, UL94 V-0 standards were cleared for each urethane foam molded product of the examples. Thereby, even if the urethane foam molding of this invention contained the magnetic particle, it was confirmed that it is excellent in a flame retardance. On the other hand, the urethane foam molded article of Comparative Example 1 containing no expanded graphite particles could not achieve flame retardancy based on V-0. Further, in the urethane foam molded article of Comparative Example 2 that contained expanded graphite particles but did not contain magnetic particles and was not subjected to foam molding in a magnetic field, the expanded graphite particles were not oriented, so the V-0 standard The flame retardancy of could not be achieved. Further, the expanded graphite particles blended in the urethane foam molded article of Comparative Example 3 were not oriented. For this reason, the flame retardancy of the V-0 standard could not be achieved.

  The urethane foam molded article of the present invention can be used in a wide range of fields such as automobiles, electronic equipment, and architecture. In particular, it is suitable for applications that require high flame resistance in addition to heat dissipation. Specific applications include anti-vibration materials used in reactors for power conditioners in photovoltaic power generation systems, engine covers and side covers placed in the engine room of vehicles to reduce engine noise, and OA (Office Automation). ) Sound absorbing materials for motors of devices and home appliances, sound absorbing materials for electronic devices such as personal computers, and sound absorbing materials for inner and outer walls of houses.

1: Magnetic induction foam molding apparatus 2: Stand 21: Bracket 3: Electromagnet part 30D, 30U: Yoke part 31L, 31R: Coil part 32D, 32U: Pole piece 310L, 310R: Core part 311L, 311R: Conductor 4: Foam type 40U: Upper mold 40D: Lower mold 41: Cavity L: Magnetic field line

Claims (6)

A base material made of polyurethane foam, and a thermally conductive filler blended in the base material,
The thermally conductive filler includes magnetic particles and thermally conductive particles made of a non-magnetic material, and at least a part of the thermally conductive filler is oriented,
At least a part of the oriented thermally conductive filler is composed of composite particles in which the magnetic particles are attached to the surface of the thermally conductive particles, and the thermally conductive particles constituting the composite particles are expanded graphite particles. urethane foam molded article which comprises a. The urethane foam molded article according to claim 1 , wherein the thermally conductive particles constituting the composite particles further include graphite particles other than expanded graphite. The composite particles are produced by a stirring granulation method,
The urethane foam molded article according to claim 1 or 2 , wherein the thermally conductive particles and the magnetic particles constituting the composite particles are bonded with a binder. All the expanded graphite particles contained constitute the composite particles,
The content of the expanded graphite particles, urethane foam molded article according to any one of claims 1 to 3 5 mass% or more in the case where the mass of the entire urethane foam molded body is 100 mass%. The urethane foam molded article according to any one of claims 1 to 4, wherein the thermally conductive particles include graphite particles other than expanded graphite. A method for producing a urethane foam molded article according to any one of claims 1 to 5 ,
A raw material mixing step of mixing a foamed urethane resin raw material and the thermally conductive filler into a mixed raw material,
A foam molding step of injecting the mixed raw material into the cavity of the foaming mold, and foam-molding while applying a magnetic field so that the magnetic flux density in the cavity is substantially uniform;
A method for producing a urethane foam molded article comprising:

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