JP2023016623A - Polyurethane foam, polyol composition and method for producing polyurethane foam - Google Patents

Abstract

To provide a thermally conductive polyurethane foam that prevents raw material from being inactivated due to stirring of the raw material, and shows a good foaming state.SOLUTION: A polyurethane foam is obtained from polyurethane foam raw material that contains a polyol composition containing a polyol and a thermally conductive filler and a polyisocyanate. As the thermally conductive filler, a carbon-based filler and a metal filler are used in combination. Preferably, the content of the carbon-based filler is 20-100 pts.wt. relative to the polyol 80 pts.wt., and the content of the metal filler is 10-50 pts.wt. relative to the polyol 80 pts.wt.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a polyurethane foam having good thermal conductivity, a polyol composition, and a method for producing a polyurethane foam.

Conventionally, polyurethane foams have been used as vibration-damping materials and sound-insulating materials in OA equipment, electric appliances, and the like. For example, hard disk drives of PCs and electric motors of electric vehicles are provided with polyurethane foam on the inside and outside of their housings to improve damping and soundproofing properties. In addition, since hard disk drives and electric motors can reach high temperatures due to heat generated during operation, polyurethane foam is required to have good thermal conductivity from the viewpoint of heat dissipation to the outside.

As a method for imparting thermal conductivity to polyurethane foam, a thermally conductive filler such as graphite is added to a polyurethane foam raw material.
In addition, a foamed urethane resin raw material containing magnetic particles bonded to the surface of the thermally conductive particles with a binder is put (injected) into the cavity of the foaming mold, and a magnetic field is applied so that the magnetic flux density in the cavity becomes substantially uniform. There is a method of producing a polyurethane foam by foaming and molding (Patent Document 1).

Japanese Patent No. 5829279

However, depending on the type of thermally conductive filler, when the polyurethane foam raw material containing the thermally conductive filler is stirred and mixed, acidic substances may leak from the thermally conductive filler and the polyurethane foam raw material may become acidic. be. As a result, the reaction activity of the raw material for the polyurethane foam is lowered (deactivated), and it may not be possible to obtain a polyurethane foam having a good foaming state.
The present invention has been made in view of the above points, and an object of the present invention is to provide a thermally conductive polyurethane foam having a good foaming state.

A first aspect is a polyurethane foam obtained from a polyurethane foam raw material containing a polyol composition containing a polyol and a thermally conductive filler, and a polyisocyanate, wherein the thermally conductive filler includes a carbon-based filler and a metal-based It is characterized by using together with a filler.

In a second aspect, in the first aspect, the content of the carbon-based filler is 20 to 100 parts by weight with respect to 80 parts by weight of the polyol, and the content of the metal-based filler is 80 parts by weight of the polyol. It is characterized by being 10 to 50 parts by weight per part.

A third aspect is characterized in that the polyol composition of the first or second aspect includes a monool.

A fourth aspect is a polyol composition containing a polyol and a thermally conductive filler, and as the thermally conductive filler, a carbon-based filler selected from flake graphite and expanded graphite, and a metal-based filler are used in combination. characterized by

A fifth aspect is a method for producing a polyurethane foam in which the polyol composition in the fourth aspect is stirred, mixed with a polyisocyanate, and foamed.

In the present invention, since the carbon-based filler contained in the polyol composition is selected from flaky graphite and expanded graphite, the reaction activity is less likely to decrease (deactivation), and the foamed state has good thermal conductivity. A polyurethane foam is obtained.

1 is a table showing the composition of raw materials for polyurethane foam, properties of raw materials, and measurement results of physical properties of moldings molded by molds in Examples 1, 2, 3, and 4 and Comparative Examples 1 and 2. FIG. 1 is a table showing the results of measurement of raw material properties and polyurethane foam physical properties for Example 1 and Comparative Example 1 while varying the circulation time with a low-pressure injector.

Embodiments of the present invention will be described below. The polyurethane foam of the present invention is obtained from a polyurethane foam raw material containing a polyol composition containing a polyol and a thermally conductive filler, and a polyisocyanate.

Polyols are polyhydric alcohols or polyols to which alkylene oxides such as ethylene oxide (EO) and propylene oxide (PO) are added, and polyols for polyurethane foams can be used. For example, polyether polyol, polyester polyol, polyether ester polyol, etc. may be used, and one or more of them may be used.

Examples of polyether polyols include polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, neopentyl glycol, glycerin, pentaerythritol, trimethylolpropane, sorbitol, sucrose, and ethylene oxide (EO ) and polyether polyols to which alkylene oxides such as propylene oxide (PO) are added.

Examples of polyester polyols include polycondensation from aliphatic carboxylic acids such as malonic acid, succinic acid and adipic acid, aromatic carboxylic acids such as phthalic acid, and aliphatic glycols such as ethylene glycol, diethylene glycol and propylene glycol. Polyester polyols obtained by
Examples of polyether ester polyols include those obtained by reacting the above polyether polyols with polybasic acids to form polyesters, and those having both polyether and polyester segments in one molecule.

As for the polyol, it is preferable to use a polyol having a hydroxyl value (OHV) of 10 to 280 mgKOH/g, a functional group number of 2 to 4, and a weight average molecular weight of 800 to 10,000 (more preferably 2,000 to 7,000) alone or in combination. .

A carbon-based filler and a metal-based filler are used together as the thermally conductive filler.
Carbon-based fillers include conductive carbon compounds such as graphite and graphene, and include plate-like graphite, scale-like graphite, granular graphite, amorphous graphite, crushed-like graphite, scale-like graphite, and expanded graphite. More preferably, one or more selected from flake graphite, flake graphite and expanded graphite is used.
Flaky graphite has a composition in which a large number of plate-shaped (graphene) structures having hexagonal crystals are superimposed.
On the other hand, expanded graphite can be obtained, for example, by chemically treating graphite such as flake graphite with sulfuric acid to expand the expandable graphite by heat treatment, and then pulverizing the expanded graphite.

The carbon-based filler preferably has an average particle diameter (D50) shown in (1) below, or a particle size distribution in (2).
(1) Preferred Range of Average Particle Size (D50) The average particle size (D50) is preferably 30 µm or more, more preferably 40 µm or more, still more preferably 90 µm or more, and even more preferably 150 µm or more. On the other hand, the upper limit is preferably 400 μm or less, more preferably less than 300 μm.

(2) Preferable range by sieving Particle classification was measured in accordance with "JIS K0069 Chemical product sieving test method".
For the sieve residue, place the sieve with the larger opening on the top, stack multiple sieves on top of the tray, insert the sample into the top sieve, and perform the sieving test. Weigh the mass and find the sieve residue.
The sieve residue corresponding to the particle size range is determined, and the sieve residue is determined in descending order of particle size.
Specifically, they are stacked on the tray so that the ones with smaller openings are on the lower stage and the ones with larger openings are on the upper stage. Next, load the top sieve with the sample and cover it. After that, vibration is given by a vibrator and sieving is performed. After the sieving is completed, the sieve residue (particle size distribution) is determined by measuring the mass above and below the sieve at each stage.

After obtaining the sieve residue in descending order of the particle size range, the sieve residue is integrated to determine the integrated percentage corresponding to each sieve opening.
As an average particle size, for example, as an average particle size (D50), the opening of a sieve corresponding to a cumulative distribution of 50% by weight (particle size of a cumulative distribution of 50 wt%) is treated as the average particle size.
That is, prepare sieves with a plurality of openings, and open a sieve opening corresponding to an accumulated distribution of 50% by weight or more (particle diameter with an accumulated distribution of 50% by weight or more), and a sieve opening that is coarser than the sieve (accumulated distribution A particle diameter of less than 50 wt%) was focused on. That is, the 50 wt% cumulative distribution particle size corresponding to the average particle size corresponds to the size between the particle size of the cumulative distribution of 50 wt% or more and the particle size of the cumulative distribution of less than 50 wt%. Therefore, the cumulative distribution of 50 wt% particle size corresponding to the average particle size exists in the particle size range from the cumulative distribution of 50 wt% or more to less than the cumulative distribution of 50 wt%.
The 50 wt% cumulative distribution particle size, which corresponds to the average particle size of the carbon-based filler, preferably has the following range.
Among the sieves with a plurality of openings, the sieve opening on the small side has a particle diameter (opening) corresponding to an integrated distribution of 50 wt% or more, preferably 45 μm or more, more preferably 90 μm or more, and further preferably 180 μm or more.
On the other hand, among the sieves with a plurality of openings, the sieve opening on the large side has a particle diameter (opening) corresponding to an integrated distribution of less than 50 wt%, preferably 500 μm or less, more preferably 355 μm or less, and even more preferably 300 μm. .

If the carbon-based filler has the average particle diameter (D50) shown in (1) above, or has the particle size distribution of (2), the carbon-based filler is densely dispersed in the polyurethane foam, and heat conduction is achieved. can be made more sexual.
The content of the carbon-based filler is 20 to 100 parts by weight, preferably 30 to 100 parts by weight, more preferably 50 to 100 parts by weight, based on 80 parts by weight of the polyol. If the amount of the carbon-based filler is too small, the thermal conductivity of the polyurethane foam will be low, and if it is too large, the foaming of the polyurethane foam will be poor.

Metal-based fillers include conductive metal powders made of fine particles of various metals, various ferrites such as soft magnetic ferrites, metal oxides such as zinc oxide, titanium oxide, aluminum oxide, magnesium oxide, and silicon oxide, boron nitride, nitride metal nitrides such as aluminum and silicon nitride; metal carbides such as silicon carbide; and metal carbonates such as magnesium carbonate.
Alumina, magnesium oxide, metal silicon (silicon), boron nitride and the like are more preferable. These can be used singly or in combination.
The particle size of the metallic filler is preferably 5 to 25 μm.
The content of the metallic filler is 10 to 50 parts by weight, more preferably 15 to 30 parts by weight, based on 80 parts by weight of the polyol. If it is too low, foaming of the polyurethane foam will be deteriorated.

The polyol composition contains a catalyst and a blowing agent.
As the catalyst, those known for polyurethane foam can be used. For example, amine catalysts such as triethylamine, triethylenediamine, diethanolamine, dimethylaminomorpholine, N-ethylmorpholine and tetramethylguanidine; tin catalysts such as stannus octoate and dibutyltin dilaurate; phenylmercuric propionate and lead octoate. metal catalysts (also referred to as organometallic catalysts) such as The amount of catalyst is preferably about 0.5 to 2.0 parts by weight with respect to 80 parts by weight of polyol.

The foaming agent preferably contains water from the viewpoint of mixing the raw materials. The amount of foaming agent (water) is preferably 0.5 to 2.0 parts by weight with respect to 80 parts by weight of polyol. If the amount of the foaming agent (water) is less than 0.5 parts by weight, the mixing and reactivity of the raw materials will be poor, resulting in poor molding. On the other hand, if it exceeds 2.0 parts by weight, the amount of foaming gas increases, cracks occur inside the polyurethane foam, and the thermal conductivity decreases.

Preferred ingredients included in the polyol composition include monools and dispersants.
Monol is a monohydric alcohol, has a hydroxyl value (OHV) of 10 to 50 mgKOH/g, a weight average molecular weight of 300 to 3500, more preferably 400 to 1000, and can be used singly or in combination.
The amount of monool compounded is preferably 5 to 20 parts by weight with respect to 80 parts by weight of polyol.
By adding the monool to the polyol composition, it is possible to suppress the increase in the viscosity of the polyurethane foam material due to the addition of the thermally conductive filler, and to make it difficult for the polyurethane foam material to be agitated and mixed poorly.

Examples of dispersants include urethane-based dispersants, polyethyleneimine-based dispersants, polyoxyethylene alkyl ether-based dispersants, polyoxyethylene glycol diester-based dispersants, and sorbitan aliphatic ester-based dispersants. You may use a dispersing agent individually or in mixture of 2 or more types. When blending a dispersant, it is preferably about 1.0 to 3.0 parts by weight with respect to 80 parts by weight of polyol.
By blending the dispersant into the polyol composition, it is possible to suppress an increase in the viscosity of the polyurethane foam raw material due to the blending of the thermally conductive filler, thereby making it difficult for the polyurethane foam raw material to be agitated and poorly mixed.

Other auxiliaries may be added to the polyol composition. Auxiliaries include foam stabilizers, foam breakers, colorants, flame retardants, and the like.
As the foam stabilizer, those known for polyurethane foam can be used. Examples thereof include silicone foam stabilizers, fluorine foam stabilizers and known surfactants.

Hydrocarbon-based, ester-based, and silicone-based foam breakers may be used, and two or more of them may be used.
Hydrocarbon-based foam breakers include oils such as polybutene. Examples of ester-based foam breakers include dimer acid diesters. Cyclopentasiloxane etc. can be mentioned as a silicone type foam breaker.

As the colorant, a carbon pigment or the like can be used according to the use of the polyurethane foam.
Flame retardants include powder flame retardants such as phosphorous and ammonium polyphosphate, and liquid flame retardants such as phosphate ester flame retardants, and either one or both of them may be used in combination.

As the polyisocyanate, aliphatic or aromatic polyisocyanates having two or more isocyanate groups, mixtures thereof, and modified polyisocyanates obtained by modifying them can be used. 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, xyloxy Examples include diisocyanate, polymeric MDI (crude MDI), and the like. In addition, other prepolymers can also be used.

The isocyanate index (INDEX) is preferably 75-120. The isocyanate index is calculated by [(isocyanate equivalent in polyurethane foam raw material/active hydrogen equivalent in polyurethane foam raw material)×100].

Polyurethane foam is produced by stirring the polyol composition and mixing with polyisocyanate to foam. An injection machine is one of the devices used in the production of polyurethane foam. The injector circulates and stirs the A liquid containing the polyol composition in a state separated from the B liquid containing the polyisocyanate, supplies the A liquid and the B liquid to the mixing head and mixes them when foaming, It is a device that discharges from the nozzle of the mixing head and foams. The injector includes a high-pressure injector that mixes the A and B liquids supplied to the mixing head by colliding them at high pressure, and a low-pressure injector that mechanically mixes the A and B liquids supplied to the mixing head with a stirring blade. there is a machine

In the case of producing a polyurethane foam molded article molded into a predetermined shape, the polyol composition is stirred, and the polyurethane foam raw material mixed with polyisocyanate is charged (injected) into a mold, foamed, and then A mold foam molding method is preferred in which the opening is opened and the molded article is taken out. The cavity of the mold has a product shape according to the use of the polyurethane foam.

The density (JIS K 7222) of the polyurethane foam of the present invention is preferably about 0.20 to 1.20 g/cm ³ for molded articles.

The thermal conductivity of the polyurethane foam of the present invention (measured using a measuring instrument QTM500 manufactured by Kyoto Electronics Industry Co., Ltd., which measures thermal conductivity using the hot wire method) is 0.10 W/m· K or more is preferable.

Polyurethane foams of Examples 1, 2, 3 and 4 and Comparative Examples 1 and 2 were produced by open foaming using the following raw materials, and raw material properties and molded product properties were measured and confirmed.

Polyol: polyether polyol, Mw 5000, hydroxyl value 34 mgKOH / g, functional group number 3, product number: Sannix FA-703, Sanyo Chemical Industries Co., Ltd. ・Catalyst: product number; DABCO 33LSI, EVONIK Co., Ltd. Foam stabilizer: silicone foam stabilizer Agent, product number: B8738LF2, EVONIK ・Foam breaking agent: Dimer acid diester, product number: ADDITIVE T, Hitachi Kasei Polymer Co., Ltd. ・Blowing agent: water

Expanded graphite: average particle size (D50) 300 μm, product number: SYZR502FP, Sanyo Trading Co., Ltd. Flaky graphite: particle size (opening) corresponding to an integrated distribution of 50 wt% or more is 180 μm, particle size corresponding to an integrated distribution of less than 50 wt% The (opening) is 300 μm, and the particle diameter range corresponding to the cumulative distribution of 50 wt % is 180 μm to 300 μm. Product number: CRC-80N, East Japan Carbon Co., Ltd. expanded graphite 1, average particle size (D50) 200 μm, product number: AED-200, Fuji Graphite Industry Co., Ltd. expanded graphite 2, average particle size (D50) 100 μm, product number: AED -100, Fuji Graphite Industries Co., Ltd. Metallic silicon, average particle size 20 μm, product number; #200, Kinseimatec Co., Ltd. Monool: polyoxyethylene polyoxypropylene butyl ether, Mw 600 to 1000, hydroxyl value 42 mgKOH / g, functional group number 1, Product number: Newpol 50HB-400, Sanyo Chemical Industries, Ltd. Dispersant: Salt of unsaturated polyaminoamide and low molecular weight polyester acid, Product number: ANTI-TERRA-U100, BYK Co., Ltd. Polyisocyanate 1: Crude MDI, NCO% = 31 .5%, product number: Lupranate M5S, BASFINOAC Polyurethane Co., Ltd. Polyisocyanate 2: prepolymer-based MDI, NCO% = 27%, product number: M249, Sumika Covestro Urethane Co., Ltd.

Examples 1, 2, 3 and 4 and Comparative Examples 1 and 2 will be described.
A raw material for polyurethane foam was prepared according to the formulation shown in FIG.
Raw material deactivation was measured by measuring the pH of liquid A before stirring with a lab mixer and after stirring for 15 minutes based on JIS 1557-5:2007. Judgment was made by visually observing the state of foaming. The rotating blades of the lab mixer used have a diameter of 80 mm and a rotation speed of 2000 rpm.

The viscosity of liquid A was measured at 20°C, 30°C and 40°C using a Brookfield viscometer (TVB-15, manufactured by Toki Sangyo Co., Ltd.).

Further, after stirring the liquid A and the polyisocyanate of the formulation shown in FIG. 1 with a lab mixer, the mixture was put into a 150×400×t10 mm or 150×100×t10 mm mold and foamed to form a polyurethane foam. The stirring time of liquid A and polyisocyanate here is set to 10 seconds, which is shorter than the stirring time when measuring the deactivation of the raw material, to reduce the pH change of liquid A and enable foam molding in Comparative Examples 1 and 2. bottom.

Regarding the polyurethane foam, density, thermal conductivity, and thermal conductivity were investigated as the physical properties of the molded product.
Density (g/cm ³ ) was measured based on JIS K 7222.
Thermal conductivity (W/m·K) was measured using a measuring instrument (QTM500, manufactured by Kyoto Electronics Industry Co., Ltd.) that measures thermal conductivity using a hot wire method.
Thermal conductivity was calculated as thermal conductivity/density [(W/m·K)/(g/cm ³ )].

・Example 1
Example 1 is an example of using flaky graphite as a carbon-based filler, comprising 80 parts by weight of polyol, 0.50 parts by weight of catalyst, 0.20 parts by weight of foam stabilizer, 0.75 parts by weight of foaming agent, and flaky 60 parts by weight of graphite, 15 parts by weight of metal silicon, 20 parts by weight of monol, and 1.5 parts by weight of a dispersant were blended.

As for the raw material properties of Example 1, the pH of liquid A was 8.98 before stirring and 8.93 after stirring, and there was almost no pH change (acidification) of liquid A before and after stirring. In addition, foam molding was possible without curing failure of the polyurethane foam.
The viscosity (mPa·s) of liquid A was 12,000 at 20°C, 8,900 at 30°C, and 4,200 at 40°C.
The polyurethane foam has a density (g/cm ³ ) of 0.48, a thermal conductivity (W/m·K) of 0.34, and a thermal conductivity [(W/m·K)/(g/cm ³ )]. was 0.71.
As described above, in Example 1, there was almost no change in pH (almost no acidification) before and after the liquid A was stirred, and good foam molding was possible, and good thermal conductivity was obtained.

・Example 2
In Example 2, the flake graphite in Example 1 was changed from 60 parts by weight to 70 parts by weight, the metal silicon (silicon) was changed from 15 parts by weight to 18 parts by weight, and the foaming agent was changed from 0.75 parts by weight to 1.40 parts by weight. This is an example in which each part is increased.

As for the raw material properties of Example 2, the pH of liquid A was 8.94 before stirring and 8.92 after stirring, and there was almost no change in pH (acidification) of liquid A before and after stirring. was value. In addition, foam molding was possible without curing failure of the polyurethane foam.
The viscosity (mPa·s) of liquid A was 16,000 at 20°C, 9,300 at 30°C, and 4,600 at 40°C.
The polyurethane foam has a density (g/cm ³ ) of 0.24, a thermal conductivity (W/m·K) of 0.13, and a thermal conductivity [(W/m·K)/(g/cm ³ )]. was 0.54.
As described above, in Example 2, there was almost no change in pH (almost no acidification) before and after the liquid A was stirred, and good foam molding was possible, and good thermal conductivity was obtained.

・Example 3
Example 3 is an example using expanded graphite as a carbon-based filler, and contains 100 parts by weight of a polyol, 0.70 parts by weight of a catalyst, 1.00 parts by weight of a foam stabilizer, 10 parts by weight of a foam breaker, and 0 parts by weight of a foaming agent. .70 parts by weight, 37 parts by weight of expanded graphite 1, and 45 parts by weight of metallic silicon were blended.

Regarding the raw material properties of Example 3, although the pH and viscosity of liquid A were not measured, there was no curing failure of the polyurethane foam, and foam molding was possible.
The polyurethane foam has a density (g/cm ³ ) of 0.89, a thermal conductivity (W/m·K) of 1.44, and a thermal conductivity [(W/m·K)/(g/cm ³ )]. was 1.62.
As described above, in Example 3, good foam molding can be performed and good thermal conductivity can be obtained.

・Example 4
Example 4 is an example using expanded graphite as a carbon-based filler, and contains 100 parts by weight of a polyol, 0.70 parts by weight of a catalyst, 1.00 parts by weight of a foam stabilizer, 10 parts by weight of a foam breaker, and 0 parts by weight of a foaming agent. .70 parts by weight, 25 parts by weight of expanded graphite 2, and 30 parts by weight of metal silicon were blended.

Regarding the raw material properties of Example 4, although the pH and viscosity of liquid A were not measured, there was no curing failure of the polyurethane foam, and foam molding was possible.
The polyurethane foam has a density (g/cm ³ ) of 0.73, a thermal conductivity (W/m·K) of 0.75, and a thermal conductivity [(W/m·K)/(g/cm ³ )]. was 1.03.
As described above, in Example 4, good foam molding can be performed and good thermal conductivity can be obtained.

・Comparative example 1
In Comparative Example 1, 100 parts by weight of expanded graphite was blended in place of the flake graphite of Example 1, 25 parts by weight of metal silicon and 3.0 parts by weight of a dispersant were used, and the rest was the same as in Example 1. For example.
As for the raw material properties of Comparative Example 1, the pH of liquid A was 9.40 before stirring and 5.43 after stirring, and after stirring for 15 minutes, the pH value of liquid A greatly decreased and was acidified. In addition, foam molding was not possible due to insufficient curing of the polyurethane foam.
The viscosity (mPa·s) of liquid A was 20,000 at 20°C, 9,300 at 30°C, and 4,900 at 40°C.
The polyurethane foam has a density (g/cm ³ ) of 0.51, a thermal conductivity (W/m·K) of 0.32, and a thermal conductivity [(W/m·K)/(g/cm ³ )]. was 0.63. In Comparative Example 1, although the blending amount of the thermally conductive filler was larger than that in Example 1, the thermal conductivity was lowered.
As described above, in Comparative Example 1, the stirring of liquid A caused a large decrease in the pH value (acidification), and deactivation of the raw material occurred.

・Comparative example 2
In Comparative Example 2, 100 parts by weight of expanded graphite was blended in place of the flake graphite of Example 2, 25 parts by weight of metal silicon and 1.70 parts by weight of foaming agent were added, and other aspects were the same as in Example 2. For example.
As for the raw material properties of Comparative Example 2, the pH of liquid A was 9.21 before stirring and 5.56 after stirring, and after stirring for 15 minutes, the pH value of liquid A was significantly lowered and acidified. In addition, foam molding was not possible due to insufficient curing of the polyurethane foam.
The viscosity (mPa·s) of liquid A was 21,000 at 20°C, 13,000 at 30°C, and 7,400 at 40°C.
The polyurethane foam has a density (g/cm ³ ) of 0.24, a thermal conductivity (W/m·K) of 0.10, and a thermal conductivity [(W/m·K)/(g/cm ³ )]. was 0.42. In Comparative Example 2, although the amount of the thermally conductive filler compounded was higher than in Example 2, the thermal conductivity was lowered.
As described above, in Comparative Example 2, the stirring of liquid A caused a large decrease in the pH value (acidification), and deactivation of the raw material occurred.

At the manufacturing site, liquid A is stored and circulated in the injection machine, and at the timing of foaming, liquid A and B (polyisocyanate) are supplied to the mixing head and mixed, discharged from the nozzle, and then foamed again. Since the A liquid is circulated until the timing, the influence of the deactivation of the raw material of the A liquid and the increase in viscosity increases.

Therefore, the liquid A of Example 1 and Comparative Example 1 was circulated in the injector, and the raw material properties were measured depending on the difference in the circulation time in the injector. The physical properties of the polyurethane foam molded product discharged into a container and foamed (opened) were measured. The pH and viscosity of the A liquid were measured by taking out only the A liquid from the injector at the time of viscosity measurement. A low-pressure injector manufactured by Nippon Sosay Industry Co., Ltd. was used as the injector. The measurement results are shown in FIG.

・Example 1
In Example 1, the pH, viscosity (20° C.), presence or absence of poor curing, moldability, molded product density (g/cm ³ ), Thermal conductivity (W/m·K) and thermal conductivity [(W/m·K)/(g/cm ³ )] were measured.

In Example 1, the pH value of liquid A was 8.92 to 8.94, the viscosity (mPa s) was 13000 to 54000, there was no curing failure, and the polyurethane was moldable within a circulation time of 0 to 180 minutes. The density of the foam (g/cm ³ ) is 0.48, the thermal conductivity (W/m·K) is 0.33 to 0.41, and the thermal conductivity [(W/m·K)/(g/cm ³ )] was 0.69 to 0.85.

In Example 1, when the circulation time was between 0 and 180 minutes, the pH value of the liquid A was 8.92 to 8.94, with little change, no raw material deactivation occurred, and good foam molding was possible. , the thermal conductivity was also good.

・Comparative example 1
In Comparative Example 1, the pH, viscosity (20 ° C.), presence or absence of poor curing, moldability, molded product density ( g/cm ³ ), thermal conductivity (W/m·K), and thermal conductivity [(W/m·K)/(g/cm ³ )] were measured.

In Comparative Example 1, the pH value of liquid A greatly decreased from 8.52 at 0 minutes of circulation to 3.84 at 60 minutes of circulation (acidification), and the viscosity (mPa s) decreased at 0 minutes of circulation. from 27,000 at 60 min to 88,000 at 60 min circulation time.
Further, in Comparative Example ¹ , there was no curing failure when the circulation time was 0 minutes, and molding was possible. , The thermal conductivity [(W/m·K)/(g/cm ³ )] was 0.65. , thermal conductivity and thermal conductivity could not be measured.

As described above, in Comparative Example 1, a polyurethane foam could be molded when the circulation time was 0 minute, but when the circulation time was 5 minutes or more, deactivation of the raw material occurred and good foam molding could not be performed. In an actual manufacturing site, the raw material is circulated even during the timing of foaming (discharging).

Thus, according to the present invention, a thermally conductive polyurethane foam having a good foaming state can be obtained.
It should be noted that the present invention is not limited to the above embodiments, and can be modified without departing from the scope of the invention.

Claims (5)

A polyurethane foam obtained from a polyurethane foam raw material containing a polyol composition containing a polyol and a thermally conductive filler, and a polyisocyanate,
A polyurethane foam characterized by using both a carbon-based filler and a metal-based filler as the thermally conductive filler. The content of the carbon-based filler is 20 to 100 parts by weight with respect to 80 parts by weight of the polyol,
2. The polyurethane foam according to claim 1, wherein the content of the metallic filler is 10 to 50 parts by weight with respect to 80 parts by weight of the polyol. 3. The polyurethane foam according to claim 1 or 2, wherein the polyol composition contains a monol. A polyol composition containing a polyol and a thermally conductive filler,
A polyol composition characterized by using, as the thermally conductive filler, a carbon-based filler selected from flake graphite and expanded graphite, and a metal-based filler in combination. A method for producing a polyurethane foam by stirring the polyol composition according to claim 4, mixing the polyisocyanate, and foaming.

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