Manufacturing method of flexible polyurethane foam

Abstract

To provide a method for producing a flexible polyurethane foam, capable of making it easy to disperse a thermally conductive filler.SOLUTION: The method for producing a flexible polyurethane foam from a raw material containing a polyol component, an isocyanate component, a foaming agent, and a thermally conductive filler includes a step of mixing a prepolymer obtained by reacting the polyol component with the isocyanate component, the foaming agent, and the thermally conductive filler. The amount of the thermally conductive filler is 100-650 pts.mass based on 100 pts.mass of the polyol component. Examples of the thermally conductive filler include graphite, aluminum oxide, magnesium oxide, silicon, and boron nitride.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing a flexible polyurethane foam.

Background Art

[0002] A technology is known in which a raw material containing a polyol component, an isocyanate component, a blowing agent, and a thermally conductive filler is mixed and reacted, and thermal conductivity is imparted to the flexible polyurethane foam by the thermally conductive filler. The polyurethane formation reaction for producing a flexible polyurethane foam basically consists of a resinification reaction that forms urethane bonds through the reaction between a polyol component and an isocyanate component, and a foaming reaction that forms urea bonds and carbon dioxide gas through the reaction between an isocyanate component and a blowing agent. When the blending amount of the thermally conductive filler is 50 to 400 parts by mass relative to 100 parts by mass of the polyol component, the reaction product becomes difficult to foam. Increasing the amount of the blowing agent can secure foaming of the reaction product, but burrs and cracks easily occur in the flexible polyurethane foam. In view of this, Patent Document 1 discloses a prior art in which the amount of the blowing agent is set to 0.3 to 0.4 wt% of the entire raw material, a foam-breaking agent is further mixed into the raw material, and bubbles in the reaction product are destroyed to reduce burrs and cracks in the flexible polyurethane foam.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] In the prior art, the viscosity increases considerably when the raw materials are mixed. In addition, the resinification reaction and the foaming reaction proceed simultaneously, so the viscosity of the reaction product increases sharply. Since the thermally conductive filler is difficult to mix into the reaction product whose viscosity has increased sharply, there is a problem that the thermally conductive filler is difficult to disperse in the flexible polyurethane foam.

[0005] This invention was made to solve this problem and aims to provide a method for manufacturing flexible polyurethane foam that facilitates the dispersion of thermally conductive fillers. [Means for solving the problem]

[0006] To achieve this objective, the present invention provides a method for producing a flexible polyurethane foam from raw materials comprising a polyol component, an isocyanate component, a blowing agent, and a thermal conductive filler, comprising the step of mixing a prepolymer obtained by reacting a polyol component and an isocyanate component, a blowing agent, and a thermal conductive filler, wherein the thermal conductive filler is in an amount of 100-650 parts by mass per 100 parts by mass of the polyol component. [Effects of the Invention]

[0007] According to the first embodiment, when a prepolymer obtained by reacting a polyol component with an isocyanate component, a foaming agent, and a thermal conductive filler are mixed, the foaming reaction of the polyurethane formation reaction proceeds mainly, so the increase in viscosity of the reactants can be made more gradual compared to the prior art. The thermal conductive filler is more easily mixed with the reactants, so it can be easily dispersed in the flexible polyurethane foam.

[0008] According to the second embodiment, in the first embodiment, a liquid in which a thermal conductive filler is dispersed in a foaming agent is mixed with a prepolymer. Since the liquid in which the thermal conductive filler is dispersed in a foaming agent, which has a lower viscosity than the prepolymer, is mixed with the prepolymer, the thermal conductive filler can be dispersed even more easily.

[0009] According to the third aspect, in the second aspect, the foaming agent is 200-300 parts by mass per 100 parts by mass of the polyol component. Since the viscosity of the liquid in which the thermal conductive filler is dispersed in the foaming agent can be reduced, the viscosity when the liquid and the prepolymer are mixed can be reduced. Therefore, the thermal conductive filler can be dispersed even more easily.

[0010] According to the fourth aspect, in the first to third aspects, the polyol component mainly consists of a hydrophilic polyol, and the blowing agent mainly consists of water. Since the prepolymer in which the polyol component mainly consists of a hydrophilic polyol is highly hydrophilic, it mixes easily with the blowing agent (water). Since there is more contact between the isocyanate groups of the prepolymer and water, the reactivity can be improved. [Modes for carrying out the invention]

[0011] Preferred embodiments of the present invention will be described below. The flexible polyurethane foam is made from raw materials comprising a polyol component, an isocyanate component, a foaming agent, and a thermal conductive filler.

[0012] The polyol component is not particularly limited as long as it is a compound having two or more hydroxyl groups, and polyols used in the molding of known flexible polyurethane foams are selected. Examples of polyol components include one or more hydroxyl-terminated compounds selected from the group including polyethers, polyesters, polycarbonates, polydienes, and polycaprolactones. Examples of hydroxyl-terminated compounds containing polyethers include polyether polyols obtained by adding alkylene oxides such as ethylene oxide (EO) and propylene oxide (PO) to polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, neopentyl glycol, glycerin, pentaerythritol, trimethylolpropane, sorbitol, and sucrose.

[0013] Examples of hydroxyl-terminated compounds containing polyester include polyester polyols obtained by polycondensation of aliphatic carboxylic acids such as malonic acid, succinic acid, and adipic acid, or aromatic carboxylic acids such as phthalic acid, with aliphatic glycols such as ethylene glycol, diethylene glycol, and propylene glycol.

[0014] Examples of hydroxyl-terminated compounds containing polyethers and polyesters include polyether ester polyols obtained by reacting a polyether polyol with a polybasic acid, or polyether ester polyols having both polyether and polyester segments within a single molecule.

[0015] The polyol component may be selected from the group including hydroxyl-terminated polyhydrocarbons, hydroxyl-terminated polyformals, fatty acid triglycerides, hydroxyl-terminated polyesters, hydroxymethyl-terminated polyesters, hydroxymethyl-terminated perfluoromethylenes, polyalkylene ether glycols, polyalkylene arylene ether glycols, and polyalkylene ether triols. The polyol component may also be selected from the group including adipic acid-ethylene glycol polyesters, poly(butylene glycol), poly(propylene glycol), and hydroxyl-terminated polybutadienes.

[0016] The polyol component may include polymer polyols. Examples of polymer polyols include those obtained by graft copolymerizing a polymer component such as polyacrylonitrile or acrylonitrile-styrene copolymer onto a polyether polyol composed of polyalkylene oxide.

[0017] The polyol component preferably consists of one or more polyols having a hydroxyl value of 10-280 mgKOH / g, 2-4 functional groups, and a weight-average molecular weight of 800-10000 (more preferably 2000-7000).

[0018] The polyol component can be primarily a hydrophilic polyol. A hydrophilic polyol being the primary component means that the proportion of hydrophilic polyols in the polyol component exceeds 50% by mass. The alkylene oxide of the hydrophilic polyol may contain only ethylene oxide (EO), or it may contain a mixture of ethylene oxide and propylene oxide (PO). A hydrophilic polyol is defined as a polyol with a PO / EO ratio (PO / EO) of 0 / 100 or more and less than 50 / 50, where 100 parts by mass represent the total of propylene oxide and ethylene oxide. The PO / EO ratio can be determined by nuclear magnetic resonance spectrometry and mass spectrometry (ionization method: ESI).

[0019] The alkylene oxides of the hydrophilic polyol may be arranged in various forms, such as random (heterogeneous), block, capped, or combinations thereof. The hydrophilic polyol may contain a heterogeneous mixture of ethylene oxide and propylene oxide. The hydrophilic polyol may be capped at the ends with ethylene oxide, propylene oxide, or butylene oxide.

[0020] The isocyanate component includes aliphatic, alicyclic, or aromatic polyisocyanates having two or more isocyanate groups, mixtures thereof, and modified polyisocyanates obtained by modifying them. Examples of aliphatic polyisocyanates include hexamethylene diisocyanate, isophorone diisocyanate, and dicyclohexamethane diisocyanate. Examples of aromatic polyisocyanates include toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), naphthalene diisocyanate, xylylene diisocyanate, and polymeric MDI (crude MDI).

[0021] The prepolymer is a polymer obtained by reacting a polyol component with an excess isocyanate component, and has active isocyanate groups at molecular terminals. From the viewpoint of the viscosity and compatibility of the prepolymer, the prepolymer preferably has an isocyanate group content (JIS K7301:1995) of 7 to 22%. When the isocyanate group content is less than 7%, the foaming reaction tends to decrease, or the viscosity of the prepolymer tends to increase, which makes it difficult to uniformly disperse the thermally conductive filler. When the isocyanate group content exceeds 22%, the polyol component contained in the prepolymer decreases, and the properties as a flexible polyurethane foam tend to deteriorate.

[0022] The prepolymer may be a mixture of a plurality of prepolymers, or may be a single prepolymer. When a plurality of prepolymers are mixed, the isocyanate group content of the prepolymer is a weighted average obtained by weighting the isocyanate group content of each prepolymer by the proportion (mass%) of each prepolymer.

[0023] Examples of the blowing agent include water and low-boiling organic compounds. Examples of the low-boiling organic compounds include hydrocarbons such as methane, ethane, propane, butane, pentane and hexane, and halogenated hydrocarbons including halogenated methanes, halogenated ethanes and fluorinated hydrocarbons. Examples of said halogenated hydrocarbons include methylene chloride, HCFC-141b, HFC-245fa and HFC-356mfc.

[0024] As the blowing agent, water and the low-boiling organic compound may each be used alone, or may be used in combination. The blowing agent is preferably mainly composed of water, because this makes handling easy. The phrase "mainly composed of water" means that the proportion of water in the blowing agent exceeds 50 mass%. When the main component of the polyol component is a hydrophilic polyol and the main component of the blowing agent is water, the reactivity between the prepolymer obtained by reacting the polyol component and the isocyanate component and the blowing agent can be improved.

[0025] The blending amount of the blowing agent is preferably 200 to 300 parts by mass with respect to 100 parts by mass of the polyol component. This is to ensure the moldability of the flexible polyurethane foam and the dispersibility of the thermally conductive filler. However, if the dispersibility of the thermally conductive filler and the moldability of the flexible polyurethane foam can be ensured by adjusting the specific gravity or the like, the blending amount of the blowing agent may depart from this range.

[0026] When the amount of the blowing agent relative to 100 parts by mass of the polyol component is less than 200 parts by mass, the viscosity of the liquid in which the thermally conductive filler as a raw material is dispersed in the blowing agent increases, which makes it difficult to mix the raw materials and tends to reduce the dispersibility of the thermally conductive filler. When the amount of the blowing agent relative to 100 parts by mass of the polyol component exceeds 300 parts by mass, cells are likely to collapse during molding, which tends to make it difficult to mold the flexible polyurethane foam.

[0027] Examples of materials for the thermally conductive filler include graphite, aluminum oxide, magnesium oxide, silicon (metallic silicon), boron nitride, and aluminum nitride. The thermally conductive filler is a powder of these materials. Examples of graphite include scaly graphite, expanded graphite, exfoliated graphite, and graphene. Graphene includes those having from 1 to about 10 layers of graphite. As the thermally conductive filler, graphite, which has a lower specific gravity than other fillers, is preferred, and scaly graphite with high crystallinity is particularly suitable.

[0028] For the thermally conductive filler, for example, the median diameter of the particle size is 0.3 to 400 μm. The median diameter is the particle diameter at which the cumulative frequency of the volume-based particle size distribution measured by laser diffraction method reaches 50%. A flexible polyurethane foam containing a thermally conductive filler having a median diameter of 0.3 to 400 μm can ensure thermal conductivity through heat transfer between the thermally conductive fillers.

[0029] The thermal conductive filler is preferably included in an amount of 100-650 parts by mass per 100 parts by mass of polyol component. This is because the thermal conductive filler improves the thermal conductivity of the flexible polyurethane foam while ensuring its moldability. When the amount of thermal conductive filler per 100 parts by mass of polyol component is less than 100 parts by mass, the thermal conductivity of the flexible polyurethane foam does not increase easily. When the amount of thermal conductive filler per 100 parts by mass of polyol component exceeds 650 parts by mass, the foam tends to become difficult to foam.

[0030] The raw materials may also contain additives such as foam stabilizers, catalysts, defoaming agents, flame retardants, anti-aging agents, antioxidants, and colorants. Foam stabilizers are components that promote and stabilize the formation of bubbles in flexible polyurethane foam. Examples of foam stabilizers include anionic surfactants such as organosilicon surfactants, fatty acid salts, sulfate esters, phosphate esters, and sulfonates. Depending on the application of the flexible polyurethane foam, foam stabilizers other than organosilicon surfactants (non-organosilicon surfactants) are preferable.

[0031] Examples of catalysts include amine catalysts such as triethylamine, triethylenediamine, diethanolamine, dimethylaminomorpholine, N-ethylmorpholine, and tetramethylguanidine; tin catalysts such as stanus octoate and dibutyltin dilaurate; and organometallic catalysts such as phenylmercury propionate and lead octenoate.

[0032] Examples of antifoaming agents include hydrocarbon-based agents such as polybutene, ester-based agents such as dimer acid diesters, and silicone-based agents such as cyclopentasiloxane. Examples of flame retardants include phosphate esters and halogenated phosphate esters. Examples of anti-aging agents include trizole-based and benzophenone-based agents. Examples of antioxidants include hindered phenol-based and hindered amine-based agents. Colorants include dyes and pigments.

[0033] Flexible polyurethane foam can be manufactured as follows, for example. As an example, a case using polyol components, isocyanate components, foam stabilizers, flame retardants, blowing agents, and thermal conductive fillers as raw materials will be described. First, a mixture is prepared by mixing a foam stabilizer with a prepolymer obtained by the reaction of polyol components and isocyanate components. After mixing a flame retardant with a liquid in which the thermal conductive filler is dispersed in the blowing agent, the mixture is immediately mixed and poured into a closed or open mold. The foaming reaction is carried out in the mold, and after curing for a predetermined time (e.g., 3-20 minutes), the mold can be demolded to obtain flexible polyurethane foam.

[0034] When polyol components, isocyanate components, blowing agents, and thermal conductive fillers are mixed simultaneously to manufacture flexible polyurethane foam, the reaction between the polyol components and isocyanate components (resinization reaction) and the reaction between the isocyanate components and blowing agents (foaming reaction) proceed simultaneously, causing a rapid increase in the viscosity of the reactants. Since thermal conductive fillers do not mix well with reactants whose viscosity has increased rapidly, clumps of thermal conductive fillers form in the reactants, making it difficult for the thermal conductive fillers to disperse in the flexible polyurethane foam.

[0035] Furthermore, when isocyanate components are added to a mixture of polyol components, foaming agents, and thermal conductive fillers to manufacture flexible polyurethane foam, the viscosity of the mixture increases, the dispersibility of the thermal conductive fillers deteriorates, and the fluidity of the mixture decreases. The reaction product when isocyanate components are added to the mixture also has high viscosity, and as the resinification reaction and foaming reaction proceed simultaneously, the viscosity of the reaction product increases rapidly, reducing the dispersibility of the thermal conductive fillers and decreasing the uniformity of the flexible polyurethane foam.

[0036] In contrast, a method of mixing a prepolymer obtained by reacting a polyol component with an isocyanate component, a foaming agent, and a thermal conductive filler allows the foaming reaction to proceed when the prepolymer and foaming agent come into contact, thus slowing the increase in the viscosity of the reactants. Since the thermal conductive filler is more easily mixed with the reactants, it becomes easier to disperse the thermal conductive filler in the flexible polyurethane foam.

[0037] By creating a liquid in which a thermal conductive filler is dispersed in an excess amount of foaming agent relative to the equivalent amount of isocyanate groups in the prepolymer, and then mixing this liquid with the prepolymer, the reactants can be injected into the mold before the viscosity of the reactants becomes too high. Furthermore, clumps of thermal conductive filler are less likely to form in the reactants, and the thermal conductive fillers dispersed in the foaming agent are mixed into the reactants. Thus, the thermal conductive fillers can be dispersed even more easily.

[0038] According to these methods, a flexible polyurethane foam with high thermal conductivity and low variation in thermal conductivity can be obtained by dispersing thermal conductive fillers in the flexible polyurethane foam. The resulting flexible polyurethane foam is suitable for sound-absorbing materials, cushions, backrests, mattresses (bedding mats), pillows, etc., which convert the vibrations of sound waves transmitted through the air into thermal energy to attenuate sound. This is because heat transfer by the thermal conductive fillers reduces the deterioration of sound-absorbing function due to temperature effects and also improves the comfort of cushions, etc. [Examples]

[0039] The present invention will be described in more detail by reference to examples, but the present invention is not limited to these examples.

[0040] Table 1 shows the raw material formulations for the flexible polyurethane foam in Examples 1-9 and Comparative Examples 1-3. Except for Comparative Example 3, the values ​​in Table 1 represent the unit mass (parts by mass) when the prepolymer is 100 parts by mass. However, the values ​​in parentheses in the rows marked *1 in Table 1 represent the unit mass of the thermal conductive filler per 100 parts by mass of polyol, and the values ​​in parentheses in the rows marked *2 represent the percentage (mass%) of the thermal conductive filler in the product. The values ​​for Comparative Example 3 represent the unit mass (parts by mass) when the polyol is 100 parts by mass.

[0041] [Table 1] The components shown in Table 1 are as follows:

[0042] Polyol 1: Weight-average molecular weight 3200, hydroxyl value 52 mgKOH / g, number of functional groups 3, PO / EO = 25 / 75 Polyol 2: Weight-average molecular weight 7000, hydroxyl value 24 mgKOH / g, number of functional groups 3, PO / EO = 85 / 15 Polyol 3: Weight-average molecular weight 5100, hydroxyl value 33 mgKOH / g, number of functional groups 3, PO / EO = 80 / 20 Polyol 4: Weight-average molecular weight 3000, hydroxyl value 57 mgKOH / g, number of functional groups 3, PO / EO = 100 / 0 Isocyanate 1: Toluene diisocyanate (TDI) Isocyanate 2: Diphenylmethane diisocyanate (MDI) Isocyanate 3: Modified diphenylmethane diisocyanate (MDI) Thermal conductive filler 1: Scaly graphite, particle size 250-350 μm Thermal conductive filler 2: Aluminum oxide, particle size 0.3-40 μm Foam stabilizer: Nonionic surfactant (polyoxyethylene-polyoxypropylene condensate) Flame retardants: Phosphorus and nitrogen compounds Antifoaming agent: Dimer acid diester Catalyst: Aliphatic amine composition Foaming agent: Water The weight-average molecular weights of polyols 1-4 were measured using the GPC (gel permeation chromatography) method.

[0043] Prepolymer 1 is the reaction product of 57.0 parts by mass of polyol 1 and 23.0 parts by mass of isocyanate. Prepolymer 2 is the reaction product of 71.3 parts by mass of polyol 1 and 28.7 parts by mass of isocyanate. Prepolymer 3 is the reaction product of 63.3 parts by mass of polyol 1 and 16.7 parts by mass of isocyanate. Prepolymer 4 is the reaction product of 40.3 parts by mass of polyol 1 and 39.7 parts by mass of isocyanate. Prepolymer 5 is the reaction product of 16.2 parts by mass of polyol 2 and 3.8 parts by mass of isocyanate. Prepolymer 6 is the reaction product of 15.9 parts by mass of polyol 3 and 4.1 parts by mass of isocyanate. Prepolymer 7 is the reaction product of 15.4 parts by mass of polyol 4 and 4.6 parts by mass of isocyanate. Prepolymer 8 is a reaction product of 62.9 parts by mass of polyol 1 and 37.1 parts by mass of isocyanate 2.

[0044] The flexible polyurethane foams in Examples 1-9 and Comparative Examples 1 and 2 were molded as follows: After preparing prepolymers 1-8 in advance, the prepolymers and foam stabilizers were weighed and stirred for 20 seconds to obtain a mixture. The heat conductive filler, flame retardant, catalyst, and blowing agent were weighed and mixed by stirring for 1 minute and 30 seconds. Immediately after, this mixture was combined with the previously prepared mixture and stirred for 5 seconds. The mixture was then poured into a mold heated to 30-35°C and molded as a flexible polyurethane foam with a curing time of 9 minutes.

[0045] Examples 1-9 were able to inject a reaction mixture containing a sufficient amount of heat-conductive filler into a mold while maintaining low viscosity. As a result, Examples 1-9 were able to obtain a flexible polyurethane foam containing a sufficient amount of heat-conductive filler.

[0046] The flexible polyurethane foam in Comparative Example 3 was attempted to be molded as follows: Polyol 3, thermal conductive filler 1, thermal conductive filler 2, foam stabilizer, foam breaker, catalyst, and foaming agent were weighed and stirred for 1 minute and 30 seconds to obtain a mixture. Isocyanate 3 was weighed and added to the mixture, stirred for 10 seconds, and poured into a cubic container with an inner side length of 150 mm, and molded by free foaming.

[0047] In Comparative Example 3, the viscosity of the mixture obtained by mixing polyol 3, thermal conductive filler, foam stabilizer, foam breaker, catalyst, and blowing agent increased, the dispersibility of the thermal conductive filler was poor, and the fluidity of the mixture decreased. When isocyanate 3 was added to the mixture, the viscosity of the reactant increased rapidly, reducing the uniformity of the reaction and making it impossible to mold a flexible polyurethane foam.

[0048] The density and thermal conductivity of the flexible polyurethane foam in Examples 1-6, 9 and Comparative Examples 1, 2 were measured. In Examples 7 and 8, moldability was confirmed, but the density and thermal conductivity of the obtained foam were not measured. The density was determined by apparent total density based on JIS K7222:2005. The thermal conductivity was determined for a test specimen measuring 200 mm in length, 200 mm in width, and 20 mm in thickness, based on JIS A1412-2:1999. A thermal conductivity of 0.1 W / mk or higher was evaluated as good (EX), and a thermal conductivity of less than 0.1 W / mk was evaluated as poor (poor). The density, thermal conductivity, and evaluation are shown in Table 1.

[0049] Comparative Example 1 did not contain thermal conductive filler, and Comparative Example 2 contained only a small amount of thermal conductive filler, resulting in low thermal conductivity of the resulting flexible polyurethane foam. In contrast, Examples 1-6 and 9 were able to obtain flexible polyurethane foam with high thermal conductivity due to the dispersion of a sufficient amount of thermal conductive filler. The density and thermal conductivity of the foams in Examples 7 and 8 are estimated to be equivalent to those of the foams in Examples 2 and 4-6.

[0050] In Examples 1-9, a hydrophilic polyol (polyol 1 with PO / EO = 25 / 75) was the main component of the polyol component constituting the prepolymer. It is presumed that the increased hydrophilicity of the prepolymer made it easier for the blowing agent (water) to mix into the mixture. Because there was more contact between the isocyanate groups of the prepolymer and water, it is presumed that in Example 1-8, the reaction rate could be ensured even without a catalyst in the raw materials. In Example 9, although the thermal conductive filler and isocyanate differed from those in Examples 1-8, a flexible polyurethane foam could be molded by adding a catalyst to the raw materials.

[0051] Although the present invention has been described above based on embodiments, it can be easily inferred that the present invention is not limited in any way to the above embodiments, and that various improvements and modifications are possible without departing from the spirit of the present invention.

Claims

1. A method for producing flexible polyurethane foam from raw materials containing a polyol component, an isocyanate component, a blowing agent mainly composed of water, and a heat-conducting filler, The process includes a step of mixing a prepolymer obtained by reacting the polyol component with the isocyanate component, the blowing agent, the flame retardant, and the heat conductive filler, In the above step, the prepolymer and the liquid in which the heat conductive filler is dispersed in the foaming agent are mixed. The thermal conductive filler is in an amount of 100-650 parts by mass per 100 parts by mass of the polyol component. The aforementioned prepolymer has an isocyanate content of 7-22%. The foaming agent is in an amount of 200-300 parts by mass per 100 parts by mass of the polyol component. The aforementioned flexible polyurethane foam has a thermal conductivity of 0.1 W / mK or higher according to JIS A1412:1999. A method for producing flexible polyurethane foam, wherein the proportion of the thermal conductive filler in the flexible polyurethane foam is 38.4% by mass or more and 47.6% by mass or less.

2. A method for producing flexible polyurethane foam from raw materials containing a polyol component, an isocyanate component, a blowing agent mainly composed of water, and a heat-conducting filler, The process includes a step of mixing a prepolymer obtained by reacting the polyol component with the isocyanate component, the blowing agent, the flame retardant, and the heat conductive filler, In the above step, the prepolymer and the liquid in which the heat conductive filler is dispersed in the foaming agent are mixed. The thermal conductive filler is in an amount of 100-650 parts by mass per 100 parts by mass of the polyol component. The aforementioned prepolymer has an isocyanate content of 7-22%. The foaming agent is in an amount of 200-300 parts by mass per 100 parts by mass of the polyol component. A method for manufacturing a flexible polyurethane foam, wherein the flexible polyurethane foam has a thermal conductivity of 0.1 W / mK or higher according to JIS A1412:1999 and a density of 241 kg / m³ or more and 259 kg / m³ or less.

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