JP5829134B2 - Method for producing carbon fiber felt - Google Patents
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Description
本発明は、炭素繊維フェルトの製造方法に関する。 The present invention relates to a method for producing a carbon fiber felt.
炭素繊維系の断熱材は、熱的安定性や断熱性能に優れ且つ軽量であることから、種々の用途で使用されている。このような断熱材には、炭素繊維を交絡してなる炭素繊維フェルトや、炭素繊維フェルトに樹脂材料を含浸させ炭素化させた炭素繊維成形断熱材がある。炭素繊維フェルトは可とう性に優れるという長所を有し、炭素繊維成形断熱材は、形状安定性に優れ、微細な加工が可能であるという長所を有する。 Carbon fiber-based heat insulating materials are used in various applications because they are excellent in thermal stability and heat insulating performance and are lightweight. Examples of such a heat insulating material include a carbon fiber felt formed by entanglement of carbon fibers, and a carbon fiber formed heat insulating material obtained by impregnating a carbon fiber felt with a resin material and carbonizing it. Carbon fiber felt has the advantage of being excellent in flexibility, and the carbon fiber molded heat insulating material has the advantage of being excellent in shape stability and capable of being finely processed.
何れの断熱材を使用するかは、使用目的や用途に応じて適宜選択される。前者の炭素繊維フェルトは、可とう性に優れることから、単結晶シリコン引き上げ装置、多結晶シリコンキャスト炉、金属やセラミックスの焼結炉、真空蒸着炉等の高温炉の断熱材として使用されている。 Which heat insulating material is used is appropriately selected according to the purpose of use and application. The former carbon fiber felt has excellent flexibility and is used as a heat insulating material for high temperature furnaces such as single crystal silicon pulling equipment, polycrystalline silicon casting furnaces, sintering furnaces for metals and ceramics, and vacuum evaporation furnaces. .
炭素繊維フェルトに関する技術としては、例えば特許文献１がある。また、炭素繊維を製造する方法に関する技術としては、特許文献２がある。 As a technique related to the carbon fiber felt, there is, for example, Patent Document 1. Moreover, there exists patent document 2 as a technique regarding the method of manufacturing a carbon fiber.
特許文献１は、レーヨン繊維と、レーヨン繊維が炭化する温度以下の温度で軟化、溶融する有機質繊維とを、レーヨン繊維９０〜５０重量部、有機質繊維１０〜５０重量部の割合で混紡し、ニードルパンチした不織布を複数枚積層し、積層体の両面を耐熱性板で挟持して、１５０〜５００Ｐａの加圧力を付加しながら、非酸化性雰囲気中７００〜１０００℃の温度で一次熱処理して炭化し、更に２０００℃以上の温度で二次熱処理することを特徴とする炭素繊維質断熱材の製造方法を開示している。この技術によると、熱硬化性樹脂などの樹脂バインダーを使用せずに安価で能率よく、ハンドリング性に優れた強度と低熱伝導率を備えた炭素繊維質断熱材を提供できるとされる。 Patent Document 1 blends rayon fibers and organic fibers that are softened and melted at a temperature lower than the temperature at which the rayon fibers are carbonized at a ratio of 90 to 50 parts by weight of rayon fibers and 10 to 50 parts by weight of organic fibers. A plurality of punched nonwoven fabrics are laminated, both sides of the laminate are sandwiched between heat-resistant plates, and subjected to primary heat treatment at a temperature of 700 to 1000 ° C. in a non-oxidizing atmosphere while applying a pressure of 150 to 500 Pa, and carbonized. In addition, a method for producing a carbon fiber heat insulating material is disclosed in which a secondary heat treatment is performed at a temperature of 2000 ° C. or higher. According to this technique, it is said that a carbon fiber heat insulating material can be provided that is inexpensive and efficient without using a resin binder such as a thermosetting resin and has excellent strength and low thermal conductivity.
特許文献２は、渦流法により、粘稠物質から曲状の繊維を製造する方法を開示している。 Patent document 2 is disclosing the method of manufacturing a curved fiber from a viscous substance by the eddy current method.
しかしながら、特許文献１の技術にかかる炭素繊維フェルトや、特許文献２の技術で得られる繊維を炭素化した炭素繊維のみを用いた炭素繊維フェルトの断熱性能は、十分なものではなかった。 However, the heat insulation performance of the carbon fiber felt according to the technique of Patent Document 1 and the carbon fiber felt using only the carbon fiber obtained by carbonizing the fiber obtained by the technique of Patent Document 2 has not been sufficient.
本発明は上記の課題を解決するためになされたものであり、断熱性の高い炭素繊維フェルトの製造方法を提供することを目的とする。 The present invention has been made to solve the above-described problems, and an object thereof is to provide a method for producing a carbon fiber felt having high heat insulation.
上記課題を解決するための本発明は、次のように構成されている。
曲状の炭素繊維と、不融繊維と、を交絡させ、ニードリングを行って、前記曲状の炭素繊維と、前記不融繊維とからなる混紡フェルトとなす混紡工程と、前記混紡フェルトを非酸化性雰囲気で焼成して、前記不融繊維を炭素化させる炭素化工程と、を備え、前記曲状の炭素繊維が、繊維を直線状に引っ張ったときの長さをＬ１、湾曲した繊維の自然状態での最大長さをＬ２とするとき、Ｌ１／Ｌ２が１．３以上で規定される湾曲形状を有し、前記曲状の炭素繊維と、前記不融繊維と、の質量比が２０：８０〜５０：５０であり、前記不融繊維は、不活性雰囲気下２０００℃で５時間熱処理した場合の質量残存率が７〜３０％である炭素繊維フェルトの製造方法。
The present invention for solving the above problems is configured as follows.
A blending step of entangled a curved carbon fiber and an infusible fiber and performing needling to form a blended felt made of the curved carbon fiber and the infusible fiber; and A carbonization step in which the infusible fiber is carbonized by firing in an oxidizing atmosphere, and the curved carbon fiber has a length L1 when the fiber is pulled linearly, When the maximum length in the natural state is L2, L1 / L2 has a curved shape defined by 1.3 or more, and the mass ratio of the curved carbon fiber to the infusible fiber is 20 : 50 to 50:50, and the infusible fiber is a method for producing a carbon fiber felt having a mass residual ratio of 7 to 30% when heat-treated at 2000 ° C. for 5 hours in an inert atmosphere.
ここで、本明細書における炭素化工程とは、主要な構成元素がほぼ炭素のみとなる１０００℃程度の温度や、それ以上の温度、例えば２０００〜２８００℃という温度領域をも含む温度で、熱処理する工程をいう。従って、本明細書でいう炭素化は、黒鉛化をも含む広義の意味で使用される。 Here, the carbonization step in the present specification means a heat treatment at a temperature of about 1000 ° C. at which the main constituent element is almost only carbon, or a temperature higher than that, for example, a temperature range of 2000 to 2800 ° C. The process to do. Therefore, carbonization as used herein is used in a broad sense including graphitization.
この構成の技術的意義を説明する。炭素繊維を細くし、炭素繊維を通じる固体伝導を小さくするとともに、また、繊維間の空隙を大きくして熱輻射のロスが大きくなるようにすると、断熱性を高めることができる。ここで、炭素繊維フェルトの断熱性とは、フェルトの厚み方向の断熱性を意味し、フェルトの面方向に繊維がより配向する構造とすることにより炭素繊維による固体伝導がフェルトの厚み方向に向かうのをより少なくすることができる。 The technical significance of this configuration will be described. When the carbon fiber is thinned, the solid conduction through the carbon fiber is reduced, and the gap between the fibers is increased to increase the loss of heat radiation, the heat insulation can be improved. Here, the heat insulating property of the carbon fiber felt means the heat insulating property in the thickness direction of the felt, and the solid conduction by the carbon fiber goes in the thickness direction of the felt by adopting a structure in which the fibers are more oriented in the surface direction of the felt. Can be reduced.
上記本発明のように、不融繊維と曲状の炭素繊維とからなる混紡フェルトを作製した後に炭素化して炭素繊維フェルトを製造する方法によると、ニードリングの際にしなやかな不融繊維が面方向により配向し易い。そして、この混紡フェルトの炭素化を行うと、不融繊維から水素や酸素等の炭素以外の構成元素が除かれて、残存質量が元の質量の７〜３０％となるとともに、比重が１．５程度と、一般的な不融繊維と同程度（おおむね比重１．３〜１．６程度）となるので、その体積が顕著に小さくなる。このとき、不融繊維の長さ方向にはほとんど体積収縮が起きず、繊維径が顕著に縮小する結果、繊維径はおよそ３０〜４５％程度に顕著に小さくなる（細径化する）。 According to the method of producing a carbon fiber felt by carbonizing after producing a blended felt made of infusible fiber and a curved carbon fiber as in the present invention, the surface of the infusible fiber that is supple is needed for needling. It is easy to orient depending on the direction. When carbonization of the blended felt is performed, constituent elements other than carbon such as hydrogen and oxygen are removed from the infusible fiber, the residual mass becomes 7 to 30% of the original mass, and the specific gravity is 1. Since it is about 5 and about the same as a general infusible fiber (generally, specific gravity is about 1.3 to 1.6), the volume is remarkably reduced. At this time, there is almost no volume shrinkage in the length direction of the infusible fiber, and the fiber diameter is remarkably reduced. As a result, the fiber diameter is remarkably reduced to about 30 to 45% (reduced in diameter).
一方、曲状の炭素繊維はすでに炭素化されており、炭素化工程での体積収縮が起こらない。よって、炭素化工程では、フェルト骨格が曲状の炭素繊維により維持されつつ、不融繊維が質量減少を伴って細径化する。 On the other hand, the curved carbon fiber has already been carbonized, and volume shrinkage does not occur in the carbonization process. Therefore, in the carbonization step, the infusible fiber is reduced in diameter with a decrease in mass while the felt skeleton is maintained by the curved carbon fiber.
それゆえ、上記製造方法によると、炭素繊維フェルトのかさ密度を小さくすることができる。そして、不融繊維の炭素化繊維は炭素繊維フェルトの面方向に配向しやすくなるとともに、径の細い不融繊維の炭素化繊維の存在により繊維間の空隙が大きい構造の炭素繊維フェルトを製造することができる。このため、上記製造方法によると、フェルトの面方向に繊維がより配向することにより炭素繊維による固体伝導がフェルトの厚み方向に向かうのをより少なくすることができると同時に、熱輻射を発現させる繊維間の空隙をより効果的に作ることができる。すなわち、上記製造方法により得られる炭素繊維フェルトは、炭素繊維を通じる固体伝導が小さくなり、また、繊維間の空隙による熱輻射のロスが大きくなるので、熱伝導率が顕著に小さい。なお、フェルトの面方向とはフェルトの長手方向と幅方向で仕切られる面およびそれに平行な方向であり、厚み方向とはフェルトの厚みの方向であって面方向に垂直な方向である。 Therefore, according to the manufacturing method, the bulk density of the carbon fiber felt can be reduced. The infusible carbonized fiber is easily oriented in the plane direction of the carbon fiber felt, and the presence of the infusible fiber carbonized fiber having a small diameter produces a carbon fiber felt having a large gap between the fibers. be able to. For this reason, according to the above manufacturing method, the fibers are more oriented in the felt surface direction, so that the solid conduction by the carbon fibers can be reduced in the thickness direction of the felt, and at the same time, the fibers that develop thermal radiation. The space between them can be created more effectively. That is, the carbon fiber felt obtained by the above production method has a low solid conductivity because the solid conduction through the carbon fiber is small and the loss of heat radiation due to the voids between the fibers is large. The surface direction of the felt is a surface partitioned by the longitudinal direction and the width direction of the felt and a direction parallel thereto, and the thickness direction is the direction of the thickness of the felt and perpendicular to the surface direction.
なお、不融繊維を炭素化させた炭素化繊維と、曲状の炭素繊維とを用いて炭素繊維フェルトを作製する場合には、本発明のような効果が得られない。例えば熱伝導し難い細径の炭素化繊維を用いると、混紡工程でのニードリングによって炭素化繊維が折れ易くなり、良質な炭素繊維フェルトの作製が困難となる。他方、折れを防止するために太径の炭素化繊維を用いると、炭素繊維を介した熱伝導が起こり易くなるという問題を生じる。 In addition, when producing a carbon fiber felt using a carbonized fiber obtained by carbonizing an infusible fiber and a curved carbon fiber, the effect as in the present invention cannot be obtained. For example, when a small-diameter carbonized fiber that is difficult to conduct heat is used, the carbonized fiber is easily broken by needling in the blending process, and it becomes difficult to produce a high-quality carbon fiber felt. On the other hand, when a large-diameter carbonized fiber is used to prevent breakage, there arises a problem that heat conduction via the carbon fiber easily occurs.
また、不融繊維のみからなるフェルトを炭素化させた炭素繊維フェルトでは、フェルトの骨格が維持されることなく全体的に均質に細径化するので、かさ密度を小さくし難く、且つ、熱伝導率を小さくし難い。他方、曲状の炭素繊維のみからなる炭素繊維フェルトでは、かさ密度を小さくし難いとともに、炭素繊維を介した熱伝導が起こり易くなる。 In addition, carbon fiber felts made from carbonized felt consisting only of infusible fibers are reduced in size uniformly without maintaining the felt skeleton, making it difficult to reduce bulk density and heat conduction. It is difficult to reduce the rate. On the other hand, in a carbon fiber felt made only of curved carbon fibers, it is difficult to reduce the bulk density, and heat conduction through the carbon fibers easily occurs.
また、不活性雰囲気下２０００℃で５時間熱処理した場合の質量残存率が３０％より大きい不融繊維を用いる場合、不融繊維の細径化が十分ではなく、熱伝導率を十分に低下させることができない。他方、不活性雰囲気下２０００℃で５時間熱処理した場合の質量残存率が７％より小さい不融繊維を用いる場合、炭素化によって繊維が破断するおそれが高まり、炭素繊維フェルトの強度の低下を招く。よって、本発明では、不活性雰囲気下２０００℃で５時間熱処理した後の不融繊維の質量残存率を、７〜３０％とする。 In addition, when using an infusible fiber having a mass residual ratio of greater than 30% when heat-treated at 2000 ° C. for 5 hours under an inert atmosphere, the infusible fiber is not sufficiently thinned and the thermal conductivity is sufficiently reduced. I can't. On the other hand, when an infusible fiber having a mass residual ratio of less than 7% when heat-treated at 2000 ° C. for 5 hours under an inert atmosphere is used, the possibility of the fiber breaking due to carbonization increases, leading to a decrease in strength of the carbon fiber felt. . Therefore, in this invention, the mass residual rate of the infusible fiber after heat-processing at 2000 degreeC for 5 hours by inert atmosphere shall be 7-30%.
なお、曲状の炭素繊維と、不融繊維と、の混合比を、２０：８０〜５０：５０とするのは、不融繊維と曲状の炭素繊維の両方の作用を十分に得るためである。 The reason why the mixing ratio between the curved carbon fiber and the infusible fiber is set to 20:80 to 50:50 is to sufficiently obtain the effects of both the infusible fiber and the curved carbon fiber. is there.
ここで、不融繊維とは、熱硬化性樹脂繊維、天然繊維、植物系再生繊維等の熱溶融を起こさない材料からなる繊維や、所定の熱処理等を行うことにより不融化された材料からなる繊維を意味する。 Here, the infusible fiber is made of a fiber made of a material that does not cause heat melting, such as a thermosetting resin fiber, a natural fiber, or a plant regenerated fiber, or a material made infusible by performing a predetermined heat treatment or the like. Means fiber.
また、自然状態の長さＬ２は、一度長さＬ１となるように繊維を引っ張った後、繊維を所定の高さ（３０ｃｍ）から自由落下させた後、当該繊維に重力及びその応力以外の力を作用させない状態で測定した最大長さとする。 The length L2 in the natural state is that after pulling the fiber so as to be once the length L1, the fiber is allowed to fall freely from a predetermined height (30 cm), and then a force other than gravity and its stress is applied to the fiber. It is the maximum length measured in the state that does not act.
上記構成において、前記炭素工程後の炭素繊維フェルトのかさ密度は、０．０５〜０．０９ｇ／ｃｍ３とすることが好ましい。 The said structure WHEREIN: It is preferable that the bulk density of the carbon fiber felt after the said carbon process shall be 0.05-0.09 g / cm < 3 >.
また、曲状の炭素繊維としては、安価でＬ１／Ｌ２を１．３以上に規制し易い等方性ピッチ系炭素繊維を用いることが好ましい。 Further, as the curved carbon fiber, it is preferable to use an isotropic pitch-based carbon fiber that is inexpensive and easily regulates L1 / L2 to 1.3 or more.
不融繊維としては、炭素繊維よりも伸延性が良いために混紡フェルトの製造が容易であり、不活性雰囲気下２０００℃で５時間熱処理した場合の質量残存率が７〜３０％程度である熱硬化性樹脂繊維を用いることが好ましく、なかでも、安価なレーヨン繊維を用いることが好ましい。 As an infusible fiber, it is easy to produce a blended felt because it has better extensibility than carbon fiber, and the mass residual rate when heat treated at 2000 ° C. for 5 hours in an inert atmosphere is about 7 to 30%. It is preferable to use a curable resin fiber, and it is particularly preferable to use an inexpensive rayon fiber.
また、Ｌ１／Ｌ２の値は、３以下であることが好ましく、１．４〜２．５であることがより好ましい。 Further, the value of L1 / L2 is preferably 3 or less, and more preferably 1.4 to 2.5.
また、レーヨン繊維等の不融繊維の繊維径は、１．７〜３．３デシテックスであることが好ましい。 The fiber diameter of infusible fibers such as rayon fibers is preferably 1.7 to 3.3 dtex.
以上に説明したように、本発明によると、断熱性能に優れた炭素繊維フェルトを簡便な手法で製造することができる。 As described above, according to the present invention, a carbon fiber felt excellent in heat insulation performance can be manufactured by a simple technique.
（実施の形態）
本発明を実施するための形態を、実施例を参照して以下に説明する。
(Embodiment)
EMBODIMENT OF THE INVENTION The form for implementing this invention is demonstrated below with reference to an Example.
〈実施例１〉
等方性ピッチを渦流法により溶融紡糸して、曲状の繊維を得た。この繊維を空気雰囲気下常温から約３００℃まで２時間熱処理して、不融化した。この後、この繊維を不活性ガス雰囲気中で、１０００℃で３０分処理して炭素化した。このピッチ系炭素繊維の平均直径は、１３μｍであった。
<Example 1>
An isotropic pitch was melt-spun by a vortex method to obtain a curved fiber. The fiber was heat-treated from room temperature to about 300 ° C. for 2 hours in an air atmosphere to be infusible. Thereafter, the fiber was carbonized by treatment at 1000 ° C. for 30 minutes in an inert gas atmosphere. The average diameter of the pitch-based carbon fiber was 13 μm.
上記ピッチ系炭素繊維をランダムに２５抽出し、繊維を直線状に引っ張ったときの長さＬ１と、湾曲した繊維の自然状態での最大長さＬ２とを測定し、Ｌ１／Ｌ２を算出した。この時、Ｌ１／Ｌ２の値が高いほうから２つと、低いほうから２つと、を除いた２１個の値の平均値を算出したところ、１．９３であった。なお、２５のＬ１／Ｌ２は、下記表１に示す。なお、下記表１におけるｘは、平均値算出の際に除いたサンプルであることを示すものである。また、Ｌ２は、湾曲した繊維の自然状態での最大長さ（湾曲した繊維上の任意の２点間の距離を測定したとき、この距離が最も大きくなる長さ）を意味し、繊維の両端点間距離を必ずしも意味するものではない。 25 pitch-carbon carbon fibers were extracted at random, and the length L1 when the fibers were pulled linearly and the maximum length L2 in the natural state of the curved fiber were measured, and L1 / L2 was calculated. At this time, an average value of 21 values excluding two from the higher value of L1 / L2 and two from the lower value was calculated to be 1.93. The L1 / L2 of 25 is shown in Table 1 below. In addition, x in the following Table 1 indicates that the sample is excluded when calculating the average value. L2 means the maximum length of the curved fiber in the natural state (the length at which this distance becomes the largest when the distance between any two points on the curved fiber is measured). It does not necessarily mean the distance between points.
（混紡工程）
曲状のピッチ系炭素繊維５０質量部と、レーヨン繊維（２．２デシテックス）５０質量部と、を混合器により混合した。この後、カード機を用いてカーディングしてウェブを作製した。この後、ウェブを重ね合わせながらニードルパンチ機を用いてニードリングして、混紡フェルト（厚み１２ｍｍ）を作製した。
(Mixing process)
Curved pitch-based carbon fiber 50 parts by mass and rayon fiber (2.2 dtex) 50 parts by mass were mixed with a mixer. Thereafter, carding was performed using a card machine to prepare a web. After that, the blended felt (thickness: 12 mm) was produced by needling using a needle punch machine while superposing the webs.
こののち、混紡フェルトを不活性雰囲気で２０００℃で５時間熱処理して、レーヨン繊維を炭素化させて、実施例１に係る炭素繊維フェルトを作製した。なお、実施例１に係る炭素繊維フェルトの厚みは１０ｍｍ、かさ密度は、０．０７ｇ／ｃｍ３であった。 After that, the blended felt was heat-treated at 2000 ° C. for 5 hours in an inert atmosphere to carbonize the rayon fiber, and the carbon fiber felt according to Example 1 was produced. The carbon fiber felt according to Example 1 had a thickness of 10 mm and a bulk density of 0.07 g / cm 3 .
〈実施例２〉
混紡工程において、ピッチ系炭素繊維と、レーヨン繊維と、を質量比２０：８０で混合したこと以外は、上記実施例１と同様にして、実施例２に係る炭素繊維フェルトを作製した。なお、実施例２に係る炭素繊維フェルトの厚みは１０ｍｍ、かさ密度は、０．０６ｇ／ｃｍ３であった。
<Example 2>
A carbon fiber felt according to Example 2 was produced in the same manner as in Example 1 except that pitch-based carbon fiber and rayon fiber were mixed at a mass ratio of 20:80 in the blending step. The carbon fiber felt according to Example 2 had a thickness of 10 mm and a bulk density of 0.06 g / cm 3 .
〈比較例１〉
曲状のピッチ系炭素繊維のみを用いたこと以外は、上記実施例１と同様にして、比較例１に係る炭素繊維フェルトを作製した。なお、比較例１に係る炭素繊維フェルトの厚みは３０ｍｍ、かさ密度は、０．０７ｇ／ｃｍ３であった。
<Comparative example 1>
A carbon fiber felt according to Comparative Example 1 was produced in the same manner as in Example 1 except that only a curved pitch-based carbon fiber was used. The carbon fiber felt according to Comparative Example 1 had a thickness of 30 mm and a bulk density of 0.07 g / cm 3 .
〈比較例２〉
レーヨン繊維のみを用いたしたこと以外は、上記実施例１と同様にして、比較例２に係る炭素繊維フェルトを作製した。なお、比較例２に係る炭素繊維フェルトの厚みは３０ｍｍ、かさ密度は、０．０９ｇ／ｃｍ３であった。
<Comparative example 2>
A carbon fiber felt according to Comparative Example 2 was produced in the same manner as in Example 1 except that only rayon fiber was used. The carbon fiber felt according to Comparative Example 2 had a thickness of 30 mm and a bulk density of 0.09 g / cm 3 .
〈比較例３〉
ポリアクリロニトリル（ＰＡＮ）の耐炎化繊維５０質量％と曲状のピッチ系炭素繊維５０重量％とを混合器を用いて均一に混合し、ウェブを重ね合わせながらニードルパンチ機を用いてニードリングして、厚み１２ｍｍの混紡フェルトを得たこと以外は、上記実施例１と同様にして、比較例３に係る炭素繊維フェルトを作製した。なお、比較例３に係る炭素繊維フェルトの厚みは１０ｍｍ、かさ密度は０．０９ｇ／ｃｍ３であった。
<Comparative Example 3>
Polyacrylonitrile (PAN) flameproof fiber 50% by mass and curved pitch-based carbon fiber 50% by weight are mixed uniformly using a mixer, and then needled using a needle punch machine while overlapping the web. A carbon fiber felt according to Comparative Example 3 was produced in the same manner as in Example 1 except that a 12 mm thick mixed felt was obtained. The carbon fiber felt according to Comparative Example 3 had a thickness of 10 mm and a bulk density of 0.09 g / cm 3 .
（熱伝導率の測定）
上記のように作製された実施例１、２、比較例３に係る炭素繊維フェルトを、厚みが３０ｍｍとなるように重ね合わせた。厚みが３０ｍｍにそろえられた実施例１、２、比較例１〜３に係る炭素繊維フェルトを、直径３５０ｍｍのサイズに切断して、試験片を作製した。この試験片を用いて、窒素ガス雰囲気中で標準平板法により、試料平均温度が６００℃、１０００℃、１５００℃での熱伝導率を測定した。この試験結果を下記表２に示す。なお、試料平均温度とは、試料の高温側（加熱側）と低温側の両面の温度の算術平均値を意味する。
(Measurement of thermal conductivity)
The carbon fiber felts according to Examples 1 and 2 and Comparative Example 3 manufactured as described above were overlapped so that the thickness was 30 mm. The carbon fiber felts according to Examples 1 and 2 and Comparative Examples 1 to 3 having a thickness of 30 mm were cut into a size of 350 mm in diameter to produce a test piece. Using this test piece, the thermal conductivity at a sample average temperature of 600 ° C., 1000 ° C., and 1500 ° C. was measured by a standard plate method in a nitrogen gas atmosphere. The test results are shown in Table 2 below. The sample average temperature means an arithmetic average value of temperatures on both the high temperature side (heating side) and the low temperature side of the sample.
上記表１より、実施例１、２に係る炭素繊維フェルトは、熱伝導率が低温側から順に、０．１５〜０．１７、０．２６〜０．２８、０．４７〜０．４９であり、比較例１〜３に係る炭素繊維フェルトの熱伝導率、０．２４〜０．４１、０．３５〜０．４９、０．６０〜０．７０よりも低いことが分かる（単位はいずれもＷ／ｍ・Ｋ）。 From Table 1 above, the carbon fiber felts according to Examples 1 and 2 have a thermal conductivity of 0.15 to 0.17, 0.26 to 0.28, and 0.47 to 0.49 in order from the low temperature side. Yes, it is understood that the thermal conductivity of the carbon fiber felt according to Comparative Examples 1 to 3 is lower than 0.24 to 0.41, 0.35 to 0.49, and 0.60 to 0.70 (the unit is any W / m · K).
炭素繊維を細くし、炭素繊維を通じる固体伝導を小さくするとともに、また、繊維間の空隙を大きくして熱輻射のロスが大きくなるようにすると、断熱性を高めることができる。ここで、炭素繊維フェルトの断熱性とは、フェルトの厚み方向の断熱性を意味し、フェルトの面方向に繊維がより配向する構造とすることにより炭素繊維による固体伝導がフェルトの厚み方向に向かうのをより少なくすることができる。 When the carbon fiber is thinned, the solid conduction through the carbon fiber is reduced, and the gap between the fibers is increased to increase the loss of heat radiation, the heat insulation can be improved. Here, the heat insulating property of the carbon fiber felt means the heat insulating property in the thickness direction of the felt, and the solid conduction by the carbon fiber goes in the thickness direction of the felt by adopting a structure in which the fibers are more oriented in the surface direction of the felt. Can be reduced.
実施例１、２のように、レーヨン繊維と曲状の炭素繊維との混紡フェルトを作製した後に炭素化する製造方法では、ニードリングによってレーヨン繊維が面方向に配向し易い。そして、この混紡フェルトの炭素化を行うと、重縮合反応により、レーヨン繊維から水素や酸素等の炭素以外の構成元素が除かれて、残存質量が元の質量の７〜３０％程度となるとともに、その比重が１．５程度であり、炭素化前のレーヨン繊維と同程度であるので、繊維体積が顕著に小さくなる。このとき、レーヨン繊維は長さ方向への体積収縮が少ないので、繊維径を顕著に（およそ３０〜４０％程度に）減少できる。 As in Examples 1 and 2, in the production method in which carbonized carbon fiber is produced after producing a blended felt of rayon fiber and curved carbon fiber, the rayon fiber is easily oriented in the plane direction by needling. And when carbonization of this blended felt is carried out, constituent elements other than carbon such as hydrogen and oxygen are removed from the rayon fiber by the polycondensation reaction, and the residual mass becomes about 7 to 30% of the original mass. The specific gravity is about 1.5, which is about the same as that of the rayon fiber before carbonization, so that the fiber volume is remarkably reduced. At this time, since the volume shrinkage of the rayon fiber in the length direction is small, the fiber diameter can be remarkably reduced (about 30 to 40%).
一方、曲状の炭素繊維はすでに炭素化されており、この炭素化工程では体積収縮が起こらない。よって、炭素化工程では、フェルト骨格が曲状の炭素繊維により維持されつつ、不融繊維が質量減少を伴って体積収縮する。 On the other hand, the curved carbon fiber has already been carbonized, and volume shrinkage does not occur in this carbonization process. Therefore, in the carbonization step, the infusible fiber shrinks in volume with a decrease in mass while the felt skeleton is maintained by the curved carbon fiber.
それゆえ、実施例１，２の製造方法によると、かさ密度が小さく、炭素繊維は炭素繊維フェルトの面方向により配向された、径の細い不融繊維の炭素化繊維の存在により繊維間の空隙が大きい構造の炭素繊維フェルトを製造することができる。したがって、実施例に係る炭素繊維フェルトは、繊維が細くかさ密度が小さくなっており、不融繊維の炭素化繊維は炭素繊維フェルトの面方向により配向され、且つ、径の細い不融繊維の炭素化繊維の存在により繊維間の空隙が大きい構造となる。 Therefore, according to the production methods of Examples 1 and 2, the bulk density is small and the carbon fibers are oriented in the plane direction of the carbon fiber felt, and the voids between the fibers are present due to the presence of carbonized fibers of infusible fibers with a small diameter. Can produce a carbon fiber felt having a large structure. Therefore, the carbon fiber felt according to the example has a fine fiber and a small bulk density, and the carbonized fiber of the infusible fiber is oriented in the surface direction of the carbon fiber felt and the carbon of the infusible fiber having a small diameter. Due to the presence of the modified fibers, the gap between the fibers is large.
すなわち、実施例に係る炭素繊維フェルトは、炭素繊維を通じる固体伝導が小さくなり、また、繊維間の空隙により熱輻射のロスが大きくなるとともに、熱輻射を発現させる繊維間の空隙が効果的に形成されている。このため、実施例１，２の炭素繊維フェルトの熱伝導率は顕著に小さくなる。 That is, in the carbon fiber felt according to the example, the solid conduction through the carbon fiber is reduced, and the loss of heat radiation is increased due to the gap between the fibers, and the gap between the fibers that develops the heat radiation is effective. Is formed. For this reason, the thermal conductivity of the carbon fiber felts of Examples 1 and 2 is significantly reduced.
なお、レーヨン繊維を炭素化させたレーヨン炭素化繊維と、曲状の炭素繊維とを用いて炭素繊維フェルトを作製する場合には、実施例のような効果が得られない。例えば、細径のレーヨン炭素化繊維を用いる場合、混紡工程でのニードリング等によって炭素繊維が折れ易くなり、良質な炭素繊維フェルトの作製が困難となる。他方、折れを防止するために太径のレーヨン炭素化繊維を用いる場合、この、炭素繊維を介した熱伝導が起こり易くなるという問題がある。 In addition, when producing a carbon fiber felt using rayon carbonized fiber obtained by carbonizing rayon fiber and a curved carbon fiber, the effect as in the embodiment cannot be obtained. For example, in the case of using a small-diameter rayon carbonized fiber, the carbon fiber is easily broken due to needling or the like in the blending process, making it difficult to produce a high-quality carbon fiber felt. On the other hand, when a large-diameter rayon carbonized fiber is used to prevent breakage, there is a problem that heat conduction via the carbon fiber is likely to occur.
また、曲状の炭素繊維のみからなる比較例１では、かさ密度を小さくし難いとともに、炭素繊維を介した熱伝導が起こり易くなる。他方、レーヨン繊維のみからなるフェルトを炭素化させた比較例２では、フェルトの骨格が維持されることなく全体的に均質に細径化するので、かさ密度を小さくし難く、且つ、熱伝導率を小さくし難い。このため、比較例１，２の熱伝導率は、実施例１，２よりも高くなる。 Moreover, in the comparative example 1 which consists only of a curved carbon fiber, while it is difficult to make a bulk density small, heat conduction via a carbon fiber becomes easy to occur. On the other hand, in Comparative Example 2 in which the felt made only of rayon fibers is carbonized, the overall diameter is uniformly reduced without maintaining the felt skeleton, so that it is difficult to reduce the bulk density and the thermal conductivity. It is difficult to make small. For this reason, the thermal conductivity of Comparative Examples 1 and 2 is higher than that of Examples 1 and 2.
また、レーヨン繊維に代えて、不活性雰囲気下２０００℃で５時間熱処理した場合の質量残存率が４０〜５０％程度のポリアクリロニトリル耐炎化繊維を用いた比較例３では、炭素化によるポリアクリロニトリル耐炎化繊維の細径化が十分に行えず、熱伝導率を十分に低下させることができない。このため、混紡フェルトに用いる不融繊維の不活性雰囲気下２０００℃で５時間熱処理した場合の質量残存率は、７〜３０％とする。 In addition, in Comparative Example 3 using a polyacrylonitrile flame-resistant fiber having a mass residual ratio of about 40 to 50% when heat-treated at 2000 ° C. for 5 hours in an inert atmosphere instead of the rayon fiber, the polyacrylonitrile flame-resistant by carbonization is used. The diameter of the modified fiber cannot be sufficiently reduced, and the thermal conductivity cannot be sufficiently reduced. For this reason, the mass residual ratio at the time of heat-processing at 2000 degreeC for 5 hours in the inert atmosphere of the infusible fiber used for a blended felt shall be 7-30%.
ここで、実施例１で用いたレーヨン繊維３の顕微鏡写真（図１）と、実施例１に係る炭素繊維フェルトの顕微鏡写真（図２）とを比較すると、レーヨン繊維は炭素化によって、径が１／３程度に小さくなっていることが分かる。そして、実施例１に係る炭素繊維フェルトでは、径の細いレーヨン系炭素繊維１と、径の太い曲状のピッチ系炭素繊維２とが交絡していることが分かる。 Here, comparing the micrograph (FIG. 1) of the rayon fiber 3 used in Example 1 and the micrograph (FIG. 2) of the carbon fiber felt according to Example 1, the diameter of the rayon fiber is reduced by carbonization. It turns out that it has become small about 1/3. And in the carbon fiber felt which concerns on Example 1, it turns out that the thin diameter rayon type | system | group carbon fiber 1 and the pitch-shaped carbon fiber 2 of a thick curved shape are entangled.
なお、曲状の炭素繊維と、レーヨン繊維と、の両者の作用を十分に得るためには、曲状の炭素繊維と、不融繊維と、の混合比を、２０：８０〜５０：５０とする。 In addition, in order to fully obtain the action of both the curved carbon fiber and the rayon fiber, the mixing ratio of the curved carbon fiber and the infusible fiber is 20:80 to 50:50. To do.
以上のことから、不活性雰囲気下２０００℃で５時間熱処理した場合の質量残存率が７〜３０％の不融繊維（レーヨン繊維等）を炭素化させる前に曲状の炭素繊維と混合・交絡させ、その後炭素化を行うことにより、断熱性に優れた炭素繊維フェルトが得られることが分かる。 From the above, mixed and entangled with curved carbon fibers before carbonizing infusible fibers (rayon fibers etc.) with a mass residual rate of 7-30% when heat treated at 2000 ° C. for 5 hours under inert atmosphere Then, it is understood that a carbon fiber felt excellent in heat insulation can be obtained by performing carbonization thereafter.
なお、上記実施例では平均直径１３μｍの炭素繊維を用いたが、この太さに限定されることはない。ただし、繊維の直径は、製造される炭素繊維フェルトの断熱性能やかさ密度等に影響を及ぼすので、目的とする断熱性能・かさ密度に応じて直径等を選択すればよい。 In the above embodiment, carbon fibers having an average diameter of 13 μm are used, but the thickness is not limited to this. However, since the fiber diameter affects the heat insulation performance, bulk density, etc. of the carbon fiber felt to be produced, the diameter may be selected according to the desired heat insulation performance / bulk density.
また、不融繊維としては、不活性雰囲気下２０００℃で５時間熱処理した場合の質量残存率が７〜３０％であればよく、レーヨン繊維以外に、天然繊維や熱硬化性樹脂繊維等を用いることができる。 Moreover, as an infusible fiber, the mass residual rate should just be 7 to 30% when heat-processed at 2000 degreeC for 5 hours by inert atmosphere, and natural fiber, a thermosetting resin fiber, etc. are used other than rayon fiber. be able to.
本発明に係る炭素繊維フェルトは、そのまま断熱材として使用できることはもちろん、樹脂を含浸させ、焼成することにより、成形断熱材とすることもできる。 The carbon fiber felt according to the present invention can be used as a heat insulating material as it is, and can also be used as a molded heat insulating material by impregnating and baking a resin.
上記で説明したように、本発明によると、断熱性能に優れた炭素繊維フェルトを簡便な手法で製造できるので、その産業上の利用可能性は大きい。 As described above, according to the present invention, a carbon fiber felt excellent in heat insulation performance can be manufactured by a simple method, and therefore, its industrial applicability is great.
１ レーヨン系炭素繊維（炭素化工程後のレーヨン繊維）
２ 曲状のピッチ系炭素繊維
３ レーヨン繊維
1 Rayon-based carbon fiber (rayon fiber after carbonization process)
2 Curved pitch-based carbon fiber 3 Rayon fiber
Claims (4)
前記混紡フェルトを非酸化性雰囲気で焼成して、前記不融繊維を炭素化させる炭素化工程と、
を備え、
前記曲状の炭素繊維が、繊維を直線状に引っ張ったときの長さをＬ１、湾曲した繊維の自然状態での最大長さをＬ２とするとき、Ｌ１／Ｌ２が１．３以上で規定される湾曲形状を有し、
前記曲状の炭素繊維と、前記不融繊維と、の質量比が２０：８０〜５０：５０であり、
前記不融繊維は、不活性雰囲気下２０００℃で５時間熱処理した場合の質量残存率が７〜３０％である、炭素繊維フェルトの製造方法。 A blending step of confounding a curved carbon fiber and an infusible fiber, performing needling, and forming a blended felt made of the curved carbon fiber and the infusible fiber ;
A carbonization step of firing the blended felt in a non-oxidizing atmosphere to carbonize the infusible fiber;
With
When the length of the curved carbon fiber is L1 when the fiber is pulled in a straight line and the maximum length of the curved fiber in a natural state is L2, L1 / L2 is defined as 1.3 or more. Have a curved shape
The mass ratio of the curved carbon fiber and the infusible fiber is 20:80 to 50:50,
The said infusible fiber is a manufacturing method of carbon fiber felt whose mass residual rate is 7 to 30% when heat-processed at 2000 degreeC for 5 hours by inert atmosphere.
ことを特徴とする請求項１に記載の炭素繊維フェルトの製造方法。 The bulk density of the carbon fiber felt after the carbonization step is 0.05 to 0.09 g / cm 3 .
The method for producing a carbon fiber felt according to claim 1.
ことを特徴とする請求項１又は２に記載の炭素繊維フェルトの製造方法。 The curved carbon fiber is an isotropic pitch-based carbon fiber,
The method for producing a carbon fiber felt according to claim 1 or 2.
ことを特徴とする請求項１、２又は３に記載の炭素繊維フェルトの製造方法。 The infusible fiber is rayon fiber,
The method for producing a carbon fiber felt according to claim 1, 2 or 3.
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