JP2020033475A - Heat-radiating material - Google Patents

Abstract

To provide a heat-radiating material exerting excellent cooling performance by having a high heat conductivity, and keeping contact of a superconductive wire with a coil-composing material or a member material around the superconductive wire except for the heat-radiating material good even when cooling.SOLUTION: The heat-radiating material comprises a fiber-reinforced resin containing 30-95 mass% of a fiber based on a total mass of a fiber-reinforced resin where the fiber has a tensile strength of 8 cN/dtex or more, the heat conductivity in a fiber direction at 77 K is 0.20-10 W/mK, and the heat strain in a fiber direction when the heat-radiating material is cooled to 77 K from 273 K is 2,500×10to 6,500×10.SELECTED DRAWING: None

Description

  The present invention relates to a heat dissipating material.

  The superconducting coil cooling method is roughly classified into conduction cooling and immersion cooling. The conduction cooling has an advantage over the immersion cooling that a cooling medium is not required and the cooling can be performed at an arbitrary temperature. On the other hand, problems such as a slow cooling rate or insufficient cooling performance when a normal conduction region occurs are pointed out. Therefore, in order to improve the cooling performance of a conduction cooling type HTS (oxide high temperature superconducting) coil, materials for forming a coil such as a bobbin or a bobbin for a coil, or an insulating material or a heat radiating material around a superconductive wire have been developed. For example, Patent Document 1 insulates a fiber cloth having a dynamic friction coefficient with stainless steel of 0.04 or more and 0.14 or less and a thickness of 0.01 mm or more and 10 mm or less in a temperature range of 280 K or more and 300 K or less. A resin-impregnated superconducting coil used as an interlayer sheet is disclosed.

A glass fiber reinforced composite material (hereinafter, abbreviated as “GFRP”) using epoxy resin as a matrix resin is generally used as a coil constituent material or a member material around a superconductive wire. For example, in Patent Document 2, in a cryogenic spacer obtained by cutting a fiber-reinforced plastic obtained by integrally molding an inorganic fiber and a resin, the stress retention after 48 hours at 20 ° C. at an initial compression load of 50 MPa is shown. A cryogenic spacer characterized by being 96% or more and having a coefficient of thermal expansion of 15 × 10 ⁻⁶ (1 / ° C.) or less under no load in the fiber axis direction is disclosed. An example is described in which glass fiber is used as the inorganic fiber and epoxy resin is used as the resin.

JP 2012-151319 A JP-A-10-310649

  Although GFRP has easy workability, it has low thermal conductivity because it is an electrical insulator, and shrinks when cooled, so that the superconducting wire and the coil material (made of GFRP) or the material around the superconducting wire can be used. There is a problem that the contact is loosened, and as a result, the heat transferability is reduced, and the whole or a part of the superconducting coil is easily moved during energization to generate frictional heat. Therefore, the problem to be solved by the present invention is to have a high thermal conductivity and to maintain good contact between the superconducting wire and the material around the superconducting wire other than the coil constituting material or the heat radiating material even during cooling. The purpose of the present invention is to provide a heat dissipating material that exhibits excellent cooling performance.

The present inventors have studied in detail in order to solve the above problems, and have completed the present invention. That is, the present invention includes the following preferred embodiments.
[1] A heat radiator made of a fiber reinforced resin containing 30 to 95% by mass of a fiber based on the total mass of the fiber reinforced resin, wherein the fiber has a tensile strength of 8 cN / dtex or more, and a fiber at 77K. The thermal conductivity in the direction is 0.20 to 10 W / mK, and the thermal strain in the fiber direction when the heat dissipating material is cooled from 273 K to 77 K is 2500 × 10 ^{−6 to} 6500 × 10 ^−6. Wood.
[2] The heat-dissipating material according to [1], wherein the fiber has a creep elongation of 10% or less after 100 hours under a load of 40% of a breaking load at 40 ° C.
[3] The heat dissipating material according to [1] or [2], wherein the fiber is a liquid crystalline polyester fiber.
[4] The heat radiating material according to any one of [1] to [3], wherein the fiber reinforced resin contains 5 to 70% by mass of an epoxy resin based on the total mass of the fiber reinforced resin.
[5] The heat dissipating material according to any one of [1] to [4], wherein the fibers in the fiber reinforced resin are aligned in one direction.
[6] The heat dissipating material according to any of [1] to [5], wherein the fibers extend between a heat absorbing surface and a heat dissipating surface of the heat dissipating material.
[7] A bobbin for a superconducting coil including the heat radiating material according to any one of [1] to [6].
[8] A superconducting coil including the heat radiating material according to any one of [1] to [6].

  Advantageous Effects of Invention According to the present invention, it has a high thermal conductivity, and maintains excellent contact between superconducting wires and member materials around the superconducting wires other than the coil constituent material or heat radiating material even during cooling, and exhibits excellent cooling performance. A heat dissipating material can be provided.

It is the schematic of the measuring apparatus of a thermal conductivity.

The heat dissipating material of the present invention is made of a fiber reinforced resin containing 30 to 95% by mass of fibers based on the total mass of the fiber reinforced resin. The fiber has a tensile strength of 8 cN / dtex or more, a thermal conductivity in the fiber direction at 77 K of 0.20 to 10 W / mK, and a heat in the fiber direction when the radiator is cooled from 273 K to 77 K. The distortion is 2500 × 10 ^{−6 to} 6500 × 10 ⁻⁶ .

[fiber]
If the tensile strength of the fiber is less than 8 cN / dtex, the above specific thermal strain cannot be obtained. The tensile strength of the fiber is preferably 10 cN / dtex or more, more preferably 15 cN / dtex or more, and particularly preferably 18 cN / dtex or more. The upper limit of the tensile strength of the fiber is not particularly limited. The tensile strength of the fiber is usually 35 cN / dtex or less. The tensile strength is a tensile strength measured according to JIS L1013.

  When the content of the fiber is less than 30% by mass based on the total mass of the fiber-reinforced resin, the above-described specific thermal conductivity and thermal strain cannot be obtained. When the content of the fiber is more than 95% by mass based on the total mass of the fiber reinforced resin, the heat radiating material in which the fiber and the resin contained in the fiber reinforced resin (hereinafter, also referred to as “matrix resin”) are well integrated. It is difficult to get. The fiber content is preferably 35 to 95% by mass, more preferably 45 to 85% by mass. When the content of the fiber is within the above range, desired heat conductivity and thermal strain are easily obtained, and a heat radiating material in which the fiber and the matrix resin are well integrated is easily obtained. The content of the fiber can be determined by the method described in Examples described later.

  The fiber has a creep elongation after 100 hours under a load of 40% of the breaking load at 40 ° C. of preferably 10% or less, more preferably 8% or less, particularly preferably 5% or less. When the creep elongation is equal to or less than the upper limit, a heat radiating material having durability can be easily obtained. The creep elongation can be adjusted to the upper limit or less by selecting a liquid crystalline polyester fiber as the fiber. Creep elongation is usually 1% or more. Creep elongation can be measured according to the method described in Examples described later.

  Examples of the fiber having a tensile strength of 8 cN / dtex or more include high-strength polyethylene fiber, aramid fiber, liquid crystalline polyester fiber, polyparaphenylene benzobisoxazole fiber, polyparaphenylene benzobisimidazole fiber, and polyparaphenylene benzobisthiazole. Fiber. Among these, liquid crystalline polyester fibers are preferred from the viewpoint of easily obtaining the specific thermal conductivity and thermal strain described above, or from the viewpoint of easily obtaining desired creep elongation.

<Liquid crystal polyester fiber>
The “liquid crystalline polyester fiber” in the present invention can be produced by melt-spinning a liquid crystalline polyester. Liquid crystalline polyester is a polyester that exhibits optical anisotropy (liquid crystalline properties) in the molten phase. For example, a sample is placed on a hot stage, heated under a nitrogen atmosphere, and the transmitted light of the sample is observed with a polarizing microscope. it can. In addition, the liquid crystalline polyester is composed of, for example, a repeating structural unit derived from an aromatic diol, an aromatic dicarboxylic acid, an aromatic hydroxycarboxylic acid, or the like, and as long as the effects of the present invention are not impaired, the structural unit has a chemical structure. Is not particularly limited. Further, the liquid crystalline polyester may contain a structural unit derived from an aromatic diamine, an aromatic hydroxyamine or an aromatic aminocarboxylic acid, as long as the effects of the present invention are not impaired.

For example, examples shown in Table 1 are preferable examples of the structural unit.

  Here, Y exists in the range of 1 to the maximum number that can be substituted in the aromatic ring, and each independently represents a hydrogen atom, a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, and the like). An alkyl group (for example, an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, an isopropyl group, and a t-butyl group); an alkoxy group (for example, a methoxy group, an ethoxy group, an isopropoxy group, and an n-butoxy group). Group), an aryl group (eg, phenyl group, naphthyl group, etc.), an aralkyl group [benzyl group (phenylmethyl group), a phenethyl group (phenylethyl group), etc.], an aryloxy group (eg, phenoxy group, etc.) and aralkyl It is selected from the group consisting of oxy groups (for example, benzyloxy groups and the like).

  More preferred structural units include the structural units described in Examples (1) to (18) shown in Tables 2, 3 and 4 below. When the structural unit in the formula is a structural unit capable of showing a plurality of structures, two or more such structural units may be combined and used as a structural unit constituting a polymer.

In the structural units in Tables 2, 3 and 4, n is an integer of 1 or 2, and each structural unit n = 1, n = 2 may be present alone or in combination; Y ₁ and Y ₂ Are each independently a hydrogen atom, a halogen atom (eg, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc.), an alkyl group (eg, a methyl group, an ethyl group, an isopropyl group, a t-butyl group, etc.) Alkyl groups of formulas 1 to 4, etc.), alkoxy groups (eg, methoxy group, ethoxy group, isopropoxy group, n-butoxy group, etc.), aryl groups (eg, phenyl group, naphthyl group, etc.), aralkyl groups [benzyl group (Phenylmethyl group), phenethyl group (phenylethyl group), etc.], aryloxy group (eg, phenoxy group, etc.), aralkyloxy group (eg, benzyloxy group, etc.) It may be at. Among these, preferable Y includes a hydrogen atom, a chlorine atom, a bromine atom and a methyl group.

In addition, Z includes a substituent represented by the following formula.

  Preferred liquid crystalline polyesters preferably have two or more naphthalene skeletons as constituent units. Particularly preferably, the liquid crystalline polyester contains both the structural unit (A) derived from hydroxybenzoic acid and the structural unit (B) derived from hydroxynaphthoic acid. For example, the structural unit (A) includes the following formula (A), and the structural unit (B) includes the following formula (B). From the viewpoint of easily improving melt moldability, the structural unit (A) The ratio of the structural unit (B) may be in the range of preferably 9/1 to 1/1, more preferably 7/1 to 1/1, and still more preferably 5/1 to 1/1.

  Further, the total of the constitutional units of (A) and (B) may be, for example, 65 mol% or more, more preferably 70 mol% or more, and still more preferably 80 mol%, based on all the constitutional units. That is all. Among the polymers, a liquid crystalline polyester in which the structural unit (B) is 4 to 45 mol% is particularly preferable.

  The melting point of the liquid crystalline polyester suitably used in the present invention is preferably from 250 to 360 ° C, more preferably from 260 to 320 ° C. Here, the melting point is a main absorption peak temperature that is measured and observed with a differential scanning calorimeter (DSC; “TA3000” manufactured by METTLER CORPORATION) according to JIS K7121 test method. Specifically, after taking 10 to 20 mg of the sample in the DSC device and sealing the sample in an aluminum pan, nitrogen as a carrier gas was passed at 100 cc / min, and the endothermic peak when the temperature was increased at 20 ° C./min. Measure. If a clear peak does not appear at 1st run in the DSC measurement depending on the type of polymer, the temperature is raised to a temperature 50 ° C. higher than the expected flow temperature at a heating rate of 50 ° C./min and held at that temperature for 3 minutes. Then, after completely melting, it is preferable to cool to 50 ° C. at a temperature lowering rate of −80 ° C./min, and then measure the endothermic peak at a temperature increasing rate of 20 ° C./min.

  To the liquid crystalline polyester, thermoplastic polymers such as polyethylene terephthalate, modified polyethylene terephthalate, polyolefin, polycarbonate, polyamide, polyphenylene sulfide, polyether ether ketone, and fluororesin are added as long as the effects of the present invention are not impaired. May be. Further, various additives such as inorganic substances such as titanium oxide, kaolin, silica and barium oxide, coloring agents such as carbon black, dyes and pigments, antioxidants, ultraviolet absorbers and light stabilizers may be added.

  The liquid crystalline polyester fiber contained in the heat radiating material of the present invention can be produced by melt-spinning the liquid crystalline polyester by a conventional method. Usually, spinning is performed at a temperature 10 to 50 ° C. higher than the melting point of the liquid crystalline polyester. The fiber after spinning may be subjected to a heat treatment. The heat treatment causes solid-phase polymerization (sometimes accompanied by a cross-linking reaction), improving strength and elastic modulus, and further increasing the melting point.

  The heat treatment can be performed in an inert atmosphere such as nitrogen or an oxygen-containing active atmosphere such as air or under reduced pressure. The heat treatment is preferably performed in a gas atmosphere having a dew point of −40 ° C. or less. Preferred temperature conditions include a temperature condition in which the temperature is sequentially increased from the melting point of the liquid crystalline polyester fiber or lower. The heat treatment can be performed for several seconds to several tens of hours, depending on the desired performance. Usually, the heat treatment is performed in the state of fibers, but may be performed in the state of UD (Unidirectional), non-woven fabric, woven fabric or knitted fabric, if necessary.

  The liquid crystalline polyester fiber in the present invention may be any of monofilament, multifilament, short fiber and tow. Since the impregnation or adhesion of the matrix resin described later is often performed in a state where the fibers are aligned and bundled in one direction, the liquid crystalline polyester fiber is preferably a multifilament from the viewpoint of productivity.

  The single fiber fineness of the liquid crystalline polyester fiber is preferably 0.1 to 50 dtex, more preferably 1 to 20 dtex, and particularly preferably 1 to 10 dtex. When the single-fiber fineness is within the above range, it is easy to obtain sufficient adhesiveness with the matrix resin.

  The multifilament or tow may be twisted, but is preferably substantially untwisted. Further, the multifilament may be subjected to an opening process and / or a smoothing process. By producing a UD, a woven fabric, or a knitted fabric using the multifilament or the tow that has been subjected to such opening processing and / or smoothing treatment, it becomes easy to obtain a fiber-reinforced resin with aligned fibers.

  As the "liquid crystalline polyester fiber", a commercially available product can also be used. As such commercially available products, for example, Kuraray Co., Ltd. Vectran UM (trade name), Kuraray Co., Ltd. Vectran HT (trade name), Kuraray Co., Ltd. Vectran NT (trade name), Kuraray Co., Ltd. Vectran EX (product name) Name), Siveras (trade name) manufactured by Toray Industries, Inc., and XXION (trade name) manufactured by KB Seiren Co., Ltd.

  Liquid crystalline polyester fibers can be used alone or in combination.

  In the fiber reinforced resin of the present invention, the fibers may be included in a unidirectionally aligned form (UD) or as a nonwoven fabric, a woven fabric (for example, cut pile) or a knitted fabric. Above all, the aspect in which the fibers are aligned in one direction is preferable because the manufacturing process of impregnating or adhering the matrix resin to the fibers aligned in one direction can be easily performed even when the fiber content is increased. . Further, the present inventors have found that the thermal conductivity in the fiber direction of the fiber reinforced resin is higher than the thermal conductivity in directions other than the fiber direction. Therefore, this embodiment is also preferable from the viewpoint of easily obtaining a higher thermal conductivity in the fiber direction.

  In a preferred embodiment, the fibers extend between the heat absorbing surface and the heat dissipating surface of the heat dissipating material. Here, the heat-absorbing surface means a surface to be brought into contact with a member to be absorbed, and the heat-radiating surface means a surface opposite to the heat-absorbing surface. More specifically, for example, when the heat dissipating material is in a sheet shape, the heat absorbing surface means one surface (surface) of the sheet to be brought into contact with the member to be absorbed, and the heat dissipating surface is the other surface ( Back). The present inventors have found that fiber reinforced resins tend to conduct heat easily through or along the fibers. Therefore, in this embodiment, the heat absorbed from the heat absorbing surface is conducted in or along the fiber and is radiated from the heat radiating surface, so that a higher thermal conductivity can be obtained.

[Matrix resin]
The fiber reinforced resin in the present invention contains a matrix resin in addition to the fibers. By including the resin, the superconducting wire can be fixed more favorably than the coil constituting material made of fiber cloth without containing the resin or the member material around the superconducting wire. In addition, the fixing can be favorably maintained during cooling due to the specific thermal strain of the fiber reinforced resin in the present invention. And since the fiber reinforced resin in the present invention has high thermal conductivity, heat storage hardly occurs inside the superconducting wire or the fiber reinforced resin. Therefore, with the configuration according to the present invention including the specific fiber and the matrix resin, it is possible to eliminate the problem that the whole or a part of the superconducting coil easily moves during energization.

  As the matrix resin, an epoxy resin, a urethane resin, an unsaturated polyester resin, a vinyl ester resin or a urethane acetate resin can be used. Among them, a preferable matrix resin is an epoxy resin from the viewpoint of strength.

  The fiber reinforced resin in the present invention is preferably 5 to 70% by mass, more preferably 5 to 65% by mass, still more preferably 10 to 65% by mass, and particularly preferably 15 to 55% by mass, based on the total mass of the fiber reinforced resin. Contains epoxy resin by weight. When the content of the epoxy resin is within the above range, desired thermal conductivity and thermal strain are easily obtained, and a heat radiating material in which the fiber and the matrix resin are well integrated is easily obtained. The content of the epoxy resin can be determined by the method described in Examples described later.

[Heat dissipation material]
The thermal conductivity of the heat radiating material of the present invention in the fiber direction at 77K is 0.20 to 10 W / mK. When the thermal conductivity is less than 0.20 W / mK, the performance as a heat radiating material is not sufficiently exhibited. The thermal conductivity is preferably 0.25 to 5.0 W / mK, more preferably 0.30 to 3.0 W / mK, and particularly preferably 0.35 to 2.0 W / mK. When the thermal conductivity is within the above range, the performance as a heat radiating material is likely to be sufficiently exhibited. By adjusting the fiber content, selecting the fiber type, or adjusting the fiber orientation, the thermal conductivity can be adjusted within the above range. The thermal conductivity can be measured according to the method described in Examples described later.

The thermal strain in the fiber direction when the radiator is cooled from 273K to 77K is 2500 × 10 ^{−6 to} 6500 × 10 ⁻⁶ . As used herein, the term “thermal strain” means a phenomenon in which a heat radiating material expands or contracts as the temperature decreases. When the thermal strain has a positive value as described above, the heat-dissipating material exhibits a negative expansion characteristic in which the heat-dissipating material expands in the fiber direction as the temperature decreases. Excellent cooling performance can be exhibited by maintaining good contact with the member material. When the thermal strain is less than 2500 × 10 ⁻⁶ , the thermal expansion in the fiber direction at the time of cooling is insufficient, so that the performance as a heat radiating material is not sufficiently exhibited. The thermal strain is preferably from 3000 × 10 ^{−6 to} 6000 × 10 ⁻⁶ , more preferably from 3500 × 10 ^{−6 to} 5500 × 10 ⁻⁶ . When the thermal strain is within the above range, it is easy to achieve both thermal strain and good thermal conductivity, so that the performance as a heat radiating material is easily exhibited. By adjusting the fiber content, selecting the fiber type, or adjusting the fiber orientation, the thermal strain can be adjusted within the above range. The thermal strain can be measured according to the method described in Examples described later.

[Production method of heat dissipation material]
The heat dissipating material of the present invention prepares fibers, UD, nonwoven fabric, woven fabric or knitted fabric (hereinafter collectively referred to as “fiber products”), and impregnates the fiber products with a resin composition for forming a fiber reinforced resin. Alternatively, it can be produced by attaching.

  In the preparation step of preparing the fiber product, a physical and / or chemical treatment may be performed on the fiber product as needed in order to improve the adhesiveness with the resin composition to be impregnated or adhered.

  Examples of the physical treatment include corona discharge treatment, glow discharge treatment, plasma treatment, electron beam treatment, ultraviolet treatment, heat treatment in an oxygen-containing atmosphere, and heat treatment in a moisture-containing atmosphere. Examples of the chemical treatment include an acid treatment, an alkali treatment, and a treatment using an oxidizing agent. The chemical treatment may be performed at room temperature or under heating, but is preferably performed under heating. These processes may be performed alone or in combination of two or more.

  The method of impregnating or adhering the resin composition to the fiber product is not particularly limited, and a conventionally known method, for example, impregnating or adhering the resin composition to the fiber product, forming the resin product into a desired shape, drying and / or Or a method of curing, a method of forming a layer of the resin composition on a film or sheet having releasability, transferring the layer to a fiber product, forming it into a desired shape, and then drying and / or curing. it can. In these methods, the fibers are preferably aligned in one direction before impregnation, adhesion or transfer of the resin composition. As a method of drawing the fibers in a sheet shape in one direction within the sheet surface, a method according to a normal UD manufacturing method can be adopted. Further, as a method of aligning the fibers in the direction perpendicular to the sheet surface, for example, a method using needle punching treatment of a nonwoven fabric, hydroentanglement treatment, flocking of short fibers, or the like can be adopted.

  The resin composition may optionally contain additives other than the resin. Such additives are not particularly limited as long as the effects of the present invention are not impaired, and for example, a curing agent, a curing accelerator, a solvent, an inorganic filler, a flame retardant, a weathering agent, or the like can be used. When the resin composition contains these additives, the amount thereof may be appropriately changed according to the purpose of the addition.

  The heat dissipating material of the present invention has a high thermal conductivity at 77K and does not shrink as the temperature decreases, and has a specific thermal strain, so that it can be used favorably as a member around a superconducting wire. Therefore, the present invention also relates to a superconducting coil bobbin including the heat dissipating material or a superconducting coil including the heat dissipating material.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the examples.

[Measurement method or evaluation method]
<Fiber content and resin content in fiber reinforced resin>
As described in Example 1 below, the fibers were bundled in one direction and weighed. After the matrix resin was applied to the fiber bundle, it was inserted into a heat-shrinkable tube, and after the matrix resin was thermally cured, the heat-shrinkable tube was removed and weighed. From these weighed values, the fiber content in the fiber reinforced resin was determined. The difference between these weighed values was defined as the resin content in the fiber reinforced resin.

<Tensile strength of fiber>
It was measured in accordance with JIS L1013.

<Fiber creep elongation>
The fiber was set on a creep tester (No. 525-R manufactured by Mize Co., Ltd.), and a load of 40% of the fiber breaking load at 40 ° C. was loaded at an ambient temperature of 40 ° C. The elongation was measured. The ratio of the measured elongation to the fiber length before the test was defined as creep elongation (%).

<Thermal conductivity of fiber reinforced resin>
The steady-state heat flow method was employed, and the thermal conductivity was measured using the measuring apparatus shown in FIG. 1 according to the following procedure.
(1) A part of the sample was inserted into a copper sample table and fixed to a cold head of a refrigerator.
(2) The sample was cooled to 77K by a refrigerator under the condition of vacuum insulation.
(3) The sample was continuously heated with a constant power (0.03 W) using a heater attached to the upper end of the sample to form a steady-state temperature gradient in the sample.
(4) The temperature gradient of the sample was measured using two thermocouples.
(5) From the measured temperature, the thermal conductivity λ was calculated by the following equation.
In the formula, L is the distance between thermocouples (unit: m), Q is the heating amount of the heater (unit: W), S is the sample cross-sectional area (unit: m ² ), and T ₁ and T ₂ are measured by each thermocouple. Temperature (unit: K).

<Thermal distortion of fiber reinforced resin>
A strain gauge was attached to measure the thermal strain in the fiber direction of the sample. Next, the sample was immersed in ice water to clarify the reference temperature of 273K. Thereafter, the sample was immersed in liquid nitrogen and the expansion or contraction when cooled from 273K to 77K was measured. The measurement was performed three times, and the average value was defined as the thermal strain of the fiber reinforced resin.

Example 1
200 liquid crystalline polyester fibers 1 ("Vectran" manufactured by Kuraray Co., Ltd., total fineness: 1670 dtex, tensile strength: 22.9 cN / dtex, creep elongation: 2.1%) were bundled and weighed in one direction. An epoxy resin (main agent: grade 827 manufactured by Mitsubishi Chemical Corporation, curing agent: HN-5500 manufactured by Hitachi Chemical Co., Ltd.) was applied to the fiber bundle, and inserted into a heat-shrinkable tube having a diameter of about 10 mm. After the epoxy resin was cured by heating in a dry oven set at 120 ° C. for 2 hours, the heat-shrinkable tube was removed and weighed. Both ends of the fiber-reinforced resin were cut so as to have a length of about 60 mm, and the end faces were trimmed to obtain a fiber-reinforced resin test piece. In the fiber-reinforced resin test piece, the fibers were aligned in one direction and extended between one cut end face and the other cut end face.
The measurements and evaluations described above were performed on the obtained fiber-reinforced resin test pieces. Table 5 shows the results.

Example 2
A liquid crystal polyester fiber 2 (“Vectran” manufactured by Kuraray Co., Ltd., total fineness: 1680 dtex, tensile strength: 8.8 cN / dtex, creep elongation: 1.8%) was used in the same manner as in Example 1, except that Fibers were aligned in one direction, and a fiber-reinforced resin test piece extending between one cut end face and the other cut end face was obtained, and the above-described measurement and evaluation were performed. Table 5 shows the results.

Example 3
A liquid crystal polyester fiber 3 ("Vectran" manufactured by Kuraray Co., Ltd., total fineness: 1670 dtex, tensile strength: 20.3 cN / dtex, creep elongation: 1.5%) was used in the same manner as in Example 1 except that Fibers were aligned in one direction, and a fiber-reinforced resin test piece extending between one cut end face and the other cut end face was obtained, and the above-described measurement and evaluation were performed. Table 5 shows the results.

Example 4
Except that the fiber content was changed to 72.4% by mass, the fibers were aligned in one direction in the same manner as in Example 1, and between the cut one end surface and the other end surface. Was obtained, and the above-described measurement and evaluation were performed. Table 5 shows the results.

Comparative Example 1
The GFRP test piece having the fiber content described in Table 5, the fibers being aligned in one direction, and extending between one cut end surface and the other end surface, Thermal conductivity and thermal strain were measured. Table 5 shows the results.

  As can be seen from Table 5, all of the fiber-reinforced resin test pieces according to the present invention have high thermal conductivity and can expand in the fiber direction during cooling, so that excellent cooling performance can be exhibited even during cooling. It was suitable for a heat dissipating material. On the other hand, the GFRP test piece as the comparative example had a low thermal conductivity, and shrunk greatly in the fiber direction during cooling, so that the cooling performance was low. Therefore, by using a radiator made of the fiber-reinforced resin according to the present invention instead of GFRP generally used as a coil constituent material, the cooling characteristics or thermal stability of the superconducting coil can be improved.

  The fiber reinforced resin according to the present invention has a high thermal conductivity and exhibits excellent cooling performance even during cooling, and thus can be suitably used as a heat radiating material.

1 heater 2 thermocouple 1
3 Thermocouple 2
4 samples (fibre-reinforced resin test pieces)
5 Sample table 6 Cold head

Claims (8)

A heat radiating material comprising a fiber reinforced resin containing 30 to 95% by mass of a fiber based on the total mass of the fiber reinforced resin, wherein the fiber has a tensile strength of 8 cN / dtex or more, and has a tensile strength in a fiber direction at 77K. A heat dissipating material having a thermal conductivity of 0.20 to 10 W / mK and a thermal strain in the fiber direction of 2500 × 10 ^{−6 to} 6500 × 10 ⁻⁶ when the heat dissipating material is cooled from 273K to 77K.   The heat radiating material according to claim 1, wherein the fiber has a creep elongation of 10% or less after 100 hours under a load of 40% of a breaking load at 40 ° C.   The heat dissipation material according to claim 1, wherein the fiber is a liquid crystalline polyester fiber.   The heat dissipation material according to any one of claims 1 to 3, wherein the fiber reinforced resin contains 5 to 70% by mass of an epoxy resin based on the total mass of the fiber reinforced resin.   The heat dissipation material according to any one of claims 1 to 4, wherein the fibers in the fiber reinforced resin are aligned in one direction.   The heat radiating material according to any one of claims 1 to 5, wherein the fibers extend between a heat absorbing surface and a heat radiating surface of the heat radiating material.   A bobbin for a superconducting coil, comprising the heat dissipating material according to claim 1.   A superconducting coil comprising the heat radiating material according to claim 1.