JP2020172031A - Fiber-reinforced composite material, and manufacturing method therefor - Google Patents
Fiber-reinforced composite material, and manufacturing method therefor Download PDFInfo
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- 239000000463 material Substances 0.000 title claims abstract description 127
- 239000003733 fiber-reinforced composite Substances 0.000 title claims abstract description 118
- 238000004519 manufacturing process Methods 0.000 title description 11
- 229920000049 Carbon (fiber) Polymers 0.000 claims abstract description 174
- 239000004917 carbon fiber Substances 0.000 claims abstract description 174
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 105
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- 239000000835 fiber Substances 0.000 claims description 61
- 239000004745 nonwoven fabric Substances 0.000 claims description 61
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- 238000002844 melting Methods 0.000 claims description 13
- 230000008018 melting Effects 0.000 claims description 13
- 238000000465 moulding Methods 0.000 claims description 6
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- 238000007906 compression Methods 0.000 description 6
- 238000005452 bending Methods 0.000 description 5
- 239000012299 nitrogen atmosphere Substances 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 4
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- 238000010304 firing Methods 0.000 description 4
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- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- 229910000013 Ammonium bicarbonate Inorganic materials 0.000 description 2
- 229920000742 Cotton Polymers 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
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- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
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- 239000011159 matrix material Substances 0.000 description 2
- 238000013001 point bending Methods 0.000 description 2
- 229920002647 polyamide Polymers 0.000 description 2
- 229920000098 polyolefin Polymers 0.000 description 2
- SCVFZCLFOSHCOH-UHFFFAOYSA-M potassium acetate Chemical compound [K+].CC([O-])=O SCVFZCLFOSHCOH-UHFFFAOYSA-M 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 238000004381 surface treatment Methods 0.000 description 2
- LWIHDJKSTIGBAC-UHFFFAOYSA-K tripotassium phosphate Chemical compound [K+].[K+].[K+].[O-]P([O-])([O-])=O LWIHDJKSTIGBAC-UHFFFAOYSA-K 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- PAWQVTBBRAZDMG-UHFFFAOYSA-N 2-(3-bromo-2-fluorophenyl)acetic acid Chemical compound OC(=O)CC1=CC=CC(Br)=C1F PAWQVTBBRAZDMG-UHFFFAOYSA-N 0.000 description 1
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 239000004734 Polyphenylene sulfide Substances 0.000 description 1
- 229920000297 Rayon Polymers 0.000 description 1
- 239000006087 Silane Coupling Agent Substances 0.000 description 1
- VMHLLURERBWHNL-UHFFFAOYSA-M Sodium acetate Chemical compound [Na+].CC([O-])=O VMHLLURERBWHNL-UHFFFAOYSA-M 0.000 description 1
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- LFVGISIMTYGQHF-UHFFFAOYSA-N ammonium dihydrogen phosphate Chemical compound [NH4+].OP(O)([O-])=O LFVGISIMTYGQHF-UHFFFAOYSA-N 0.000 description 1
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- 238000013459 approach Methods 0.000 description 1
- PRORZGWHZXZQMV-UHFFFAOYSA-N azane;nitric acid Chemical compound N.O[N+]([O-])=O PRORZGWHZXZQMV-UHFFFAOYSA-N 0.000 description 1
- 229910052788 barium Inorganic materials 0.000 description 1
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
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- 229920001577 copolymer Polymers 0.000 description 1
- 239000010779 crude oil Substances 0.000 description 1
- MNNHAPBLZZVQHP-UHFFFAOYSA-N diammonium hydrogen phosphate Chemical compound [NH4+].[NH4+].OP([O-])([O-])=O MNNHAPBLZZVQHP-UHFFFAOYSA-N 0.000 description 1
- 229910000388 diammonium phosphate Inorganic materials 0.000 description 1
- 235000019838 diammonium phosphate Nutrition 0.000 description 1
- MSJMDZAOKORVFC-UAIGNFCESA-L disodium maleate Chemical compound [Na+].[Na+].[O-]C(=O)\C=C/C([O-])=O MSJMDZAOKORVFC-UAIGNFCESA-L 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
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- 230000002093 peripheral effect Effects 0.000 description 1
- 239000005011 phenolic resin Substances 0.000 description 1
- 229920003207 poly(ethylene-2,6-naphthalate) Polymers 0.000 description 1
- 229920000412 polyarylene Polymers 0.000 description 1
- 229920001707 polybutylene terephthalate Polymers 0.000 description 1
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- 235000011056 potassium acetate Nutrition 0.000 description 1
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- 238000003825 pressing Methods 0.000 description 1
- 239000002964 rayon Substances 0.000 description 1
- 239000011208 reinforced composite material Substances 0.000 description 1
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- 239000001632 sodium acetate Substances 0.000 description 1
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- WXMKPNITSTVMEF-UHFFFAOYSA-M sodium benzoate Chemical compound [Na+].[O-]C(=O)C1=CC=CC=C1 WXMKPNITSTVMEF-UHFFFAOYSA-M 0.000 description 1
- 239000004299 sodium benzoate Substances 0.000 description 1
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- 239000001488 sodium phosphate Substances 0.000 description 1
- 229910000162 sodium phosphate Inorganic materials 0.000 description 1
- 235000011008 sodium phosphates Nutrition 0.000 description 1
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- 150000003568 thioethers Chemical class 0.000 description 1
- RYFMWSXOAZQYPI-UHFFFAOYSA-K trisodium phosphate Chemical compound [Na+].[Na+].[Na+].[O-]P([O-])([O-])=O RYFMWSXOAZQYPI-UHFFFAOYSA-K 0.000 description 1
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- Moulding By Coating Moulds (AREA)
Abstract
Description
本発明は、炭素繊維と熱可塑性樹脂を含有する繊維強化複合材料とその製造方法に関する。 The present invention relates to a fiber-reinforced composite material containing carbon fiber and a thermoplastic resin, and a method for producing the same.
炭素などの強化繊維とマトリックス樹脂からなる繊維強化複合材料は、比強度、比弾性率が高く、力学特性に優れること、耐候性、耐薬品性などの高機能特性を有することなどから、航空機、自動車等の他、一般産業用途においても利用されている。 A fiber-reinforced composite material composed of reinforcing fibers such as carbon and a matrix resin has high specific strength and specific elastic modulus, excellent mechanical properties, and high functional properties such as weather resistance and chemical resistance. In addition to automobiles, it is also used in general industrial applications.
優れた力学特性を有する高い繊維体積含有率の炭素繊維強化複合材料として、例えば、炭素繊維と樹脂とからなる繊維強化複合材料であって、炭素繊維は単繊維状態でランダムに配向し、該炭素繊維が見かけ密度が０．２５〜１．５ｇ／ｃｍ３のシート形状を構成し、該シート表面の炭素繊維表面におけるＥＳＣＡで測定したＣ１ｓピーク中に占めるＣＯＯ基、Ｃ−Ｏ基の比率の和が５％以上であり、かつ、炭素繊維の繊維体積含有率が２０〜８０％である繊維強化複合材料（例えば、特許文献１参照）が提案されている。近年、貨物輸送分野において、地球環境問題への取り組みとして二酸化炭素の排出量の削減や、原油価格高騰により消費エネルギーコストの削減が強く求められており、軽量化による燃費向上のため、繊維強化複合材料に対して軽量化の要求が高まっており、特許文献１に記載される繊維強化複合材料に対しても、さらなる軽量化が求められている。 As a carbon fiber reinforced composite material having a high fiber volume content having excellent mechanical properties, for example, a fiber reinforced composite material composed of carbon fiber and resin, the carbon fibers are randomly oriented in a single fiber state, and the carbon The fibers form a sheet shape with an apparent density of 0.25 to 1.5 g / cm 3 , and the sum of the ratios of COO groups and CO groups in the C1s peak measured by ESCA on the carbon fiber surface of the sheet surface. A fiber-reinforced composite material (see, for example, Patent Document 1) in which the amount of carbon fiber is 5% or more and the fiber volume content of carbon fibers is 20 to 80% has been proposed. In recent years, in the field of freight transportation, there has been a strong demand for reduction of carbon dioxide emissions and energy consumption cost due to soaring crude oil prices as an approach to global environmental problems. In order to improve fuel efficiency by reducing weight, fiber-reinforced composites There is an increasing demand for weight reduction of materials, and further weight reduction is also required for the fiber-reinforced composite material described in Patent Document 1.
そこで、樹脂と強化繊維を含む構造体の軽量化技術として、例えば、特定量の樹脂と強化繊維と空隙からなる構造体であって、強化繊維の長さ、強化繊維の配向角度、構造体の厚みが特定の関係を満たし、５０％圧縮時の面内方向の圧縮強度が３ＭＰａ以上である構造体（例えば、特許文献２参照）が提案されている。 Therefore, as a technique for reducing the weight of a structure containing resin and reinforcing fibers, for example, a structure composed of a specific amount of resin, reinforcing fibers and voids, such as the length of the reinforcing fibers, the orientation angle of the reinforcing fibers, and the structure of the structure. A structure (see, for example, Patent Document 2) in which the thickness satisfies a specific relationship and the compression strength in the in-plane direction at the time of 50% compression is 3 MPa or more has been proposed.
特許文献２の技術により軽量で圧縮特性に優れる構造体が得られるものの、曲げに対する耐性が低く、比曲げ弾性率が不十分である課題があった。そこで、本発明は、軽量で比曲げ弾性率に優れる繊維強化複合材料を提供することを課題とする。 Although a structure that is lightweight and has excellent compression characteristics can be obtained by the technique of Patent Document 2, there is a problem that the resistance to bending is low and the specific flexural modulus is insufficient. Therefore, an object of the present invention is to provide a fiber-reinforced composite material that is lightweight and has an excellent specific flexural modulus.
本発明者らは上記の課題を達成するため鋭意検討した結果、繊維強化複合材料の面方向の半裁断面において、湾曲した炭素繊維が複数存在し、かつ、面方向に対する垂直断面において、３本以上の炭素繊維が束状にまとまった束状部位が複数存在する繊維強化複合材料とすることにより、軽量で比曲げ弾性率に優れる繊維強化複合材料が得られることを見出し、さらに鋭意検討を重ねることにより本発明を完成するに至った。すなわち、本発明の繊維強化複合材料は、炭素繊維と熱可塑性樹脂を含有する繊維強化複合材料であって、炭素繊維を１５〜７５重量％含有し、繊維強化複合材料の面方向の半裁断面において、湾曲した炭素繊維が複数存在し、かつ、面方向に対する垂直断面において３本以上の炭素繊維が束状にまとまった束状部位が複数存在する、見かけ密度が０．０４〜０．１５ｇ／ｃｍ３である繊維強化複合材料である。 As a result of diligent studies to achieve the above problems, the present inventors have found that a plurality of curved carbon fibers are present in the half-cut cross section of the fiber-reinforced composite material in the plane direction, and three or more in the cross section perpendicular to the plane direction. It was found that a fiber-reinforced composite material that is lightweight and has an excellent specific flexural modulus can be obtained by using a fiber-reinforced composite material in which a plurality of bundled parts in which the carbon fibers of the above are bundled are present, and further diligent studies will be conducted. This has led to the completion of the present invention. That is, the fiber-reinforced composite material of the present invention is a fiber-reinforced composite material containing carbon fibers and a thermoplastic resin, and contains 15 to 75% by weight of carbon fibers in a half-cut cross section in the plane direction of the fiber-reinforced composite material. , There are a plurality of curved carbon fibers, and there are a plurality of bundled portions in which three or more carbon fibers are bundled in a cross section perpendicular to the plane direction, and the apparent density is 0.04 to 0.15 g / cm. It is a fiber-reinforced composite material of 3 .
本発明により、軽量で比曲げ弾性率に優れる繊維強化複合材料を提供することができる。 INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a fiber-reinforced composite material that is lightweight and has an excellent specific flexural modulus.
本発明の繊維強化複合材料は、炭素繊維と熱可塑性樹脂を含有する。従来強化繊維として用いられているガラス繊維（密度：２．５ｇ／ｃｍ３）、鉄（密度：７．８ｇ／ｃｍ３）、アルミニウム（２．７ｇ／ｃｍ３）などに比べて、炭素繊維は密度が１．８ｇ／ｃｍ３と軽く、強度と弾性率に優れているため、強化繊維として炭素繊維を用いることにより、繊維強化複合材料を軽量化し、比曲げ弾性率を向上させることができる。また、熱可塑性樹脂は、低密度でマトリクス樹脂としての作用を有し、後述する本発明の繊維強化複合材料の製造方法において、スプリングバックさせることにより、繊維強化複合材料を軽量化することができる。 The fiber-reinforced composite material of the present invention contains carbon fibers and a thermoplastic resin. Glass fibers are conventionally used as reinforcing fibers (density: 2.5g / cm 3), iron (density: 7.8g / cm 3), aluminum (2.7 g / cm 3) as compared to the like, carbon fiber Since the density is as light as 1.8 g / cm 3 and the strength and elastic modulus are excellent, the weight of the fiber reinforced composite material can be reduced and the specific flexural modulus can be improved by using carbon fiber as the reinforcing fiber. Further, the thermoplastic resin has a low density and acts as a matrix resin, and in the method for producing a fiber-reinforced composite material of the present invention described later, the weight of the fiber-reinforced composite material can be reduced by springing back. ..
炭素繊維としては、例えば、ポリアクリロニトリル（以下、ＰＡＮと略す）系炭素繊維、ピッチ系炭素繊維、レーヨン系炭素繊維、フェノール樹脂系炭素繊維などが挙げられる。これらを２種以上含有してもよい。これらの中でも、強度や炭素繊維化時の残炭率に優れることからＰＡＮ系炭素繊維が好ましい。 Examples of the carbon fibers include polyacrylonitrile (hereinafter abbreviated as PAN) -based carbon fibers, pitch-based carbon fibers, rayon-based carbon fibers, and phenol resin-based carbon fibers. Two or more of these may be contained. Among these, PAN-based carbon fibers are preferable because they are excellent in strength and residual carbon content at the time of carbon fiber formation.
本発明の繊維強化複合材料中における炭素繊維の含有量は、１５〜７５重量％である。炭素繊維の含有量が１５重量％未満であると、炭素繊維による補強効果が低く、比曲げ弾性率が低下する。炭素繊維の含有量は、３０重量％以上が好ましく、４０重量％以上がより好ましい。一方、炭素繊維の含有量が７５重量％を超えると、相対的に熱可塑性樹脂の含有量が低くなり、炭素繊維同士の連結が弱くなることから、比曲げ弾性率が低下する。比曲げ弾性率をより向上させ、より軽量化する観点から、炭素繊維の含有量は、６５重量％以下が好ましく、５５重量％以下がより好ましい。 The content of carbon fibers in the fiber-reinforced composite material of the present invention is 15 to 75% by weight. When the content of the carbon fiber is less than 15% by weight, the reinforcing effect of the carbon fiber is low and the specific flexural modulus is lowered. The carbon fiber content is preferably 30% by weight or more, more preferably 40% by weight or more. On the other hand, when the content of the carbon fibers exceeds 75% by weight, the content of the thermoplastic resin becomes relatively low, and the connection between the carbon fibers becomes weak, so that the specific bending elastic modulus decreases. From the viewpoint of further improving the specific flexural modulus and further reducing the weight, the carbon fiber content is preferably 65% by weight or less, more preferably 55% by weight or less.
繊維強化複合材料中における炭素繊維の含有量（Ｗｃ（％））は、繊維強化複合材料から熱可塑性樹脂などの炭素繊維以外の成分を除去することにより測定することができる。具体的には、炭素繊維の含有量Ｗｃ（重量％）は、繊維強化材料の質量Ｗｓ（ｇ）と、熱可塑性樹脂などの炭素繊維以外の成分を除去した後に残った炭素繊維の質量Ｗｆ（ｇ）を測定し、次式により算出することができる。
Ｗｃ［％］＝（Ｗｆ［ｇ］／Ｗｓ［ｇ］）×１００
熱可塑性樹脂などの炭素繊維以外の成分を除去する手段としては特に限定されず、繊維強化複合材料を、空気中、５００℃で３０分間加熱して焼き飛ばす方法、熱可塑性樹脂を溶解・分解することができる溶液に溶解する方法、ＪＩＳ Ｋ ７０７５（１９９１）に記載される方法等を適用することができる。
The carbon fiber content (Wc (%)) in the fiber-reinforced composite material can be measured by removing components other than carbon fibers such as a thermoplastic resin from the fiber-reinforced composite material. Specifically, the carbon fiber content Wc (% by weight) is the mass Ws (g) of the fiber reinforced material and the mass Wf (mass Wf) of the carbon fiber remaining after removing components other than the carbon fiber such as the thermoplastic resin. g) can be measured and calculated by the following formula.
Wc [%] = (Wf [g] / Ws [g]) x 100
The means for removing components other than carbon fibers such as thermoplastic resin is not particularly limited, and a method of heating a fiber-reinforced composite material in air at 500 ° C. for 30 minutes to burn it off, and melting and decomposing the thermoplastic resin. A method of dissolving in a solution that can be used, a method described in JIS K 7075 (1991), and the like can be applied.
熱可塑性樹脂としては、炭素繊維に含浸する際の消費エネルギーを抑制し、特殊な設備が不要である観点から、融点が３００℃以下の樹脂が好ましい。融点が３００℃以下である熱可塑性樹脂としては、例えば、ポリエチレンテレフタレート、ポリブチレンテレフタレート、ポリトリメチレンテレフタレート、ポリエチレンナフタレートなどのポリエステル；ポリエチレン、ポリプロピレンなどのポリオレフィン；ポリアミド；ポリフェニレンスルフィド等のポリアリーレンスルフィドや、これらの共重合体、変性体等が挙げられる。これらを２種以上含有してもよい。これらの中でも、繊維強化複合材料をより軽量化する観点から、ポリオレフィンやポリアミドが好ましい。 As the thermoplastic resin, a resin having a melting point of 300 ° C. or lower is preferable from the viewpoint of suppressing energy consumption when impregnating carbon fibers and not requiring special equipment. Examples of the thermoplastic resin having a melting point of 300 ° C. or lower include polyesters such as polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, and polyethylene naphthalate; polyolefins such as polyethylene and polypropylene; polyamides; and polyarylene sulfides such as polyphenylene sulfide. , These copolymers, modified products and the like. Two or more of these may be contained. Among these, polyolefins and polyamides are preferable from the viewpoint of further reducing the weight of the fiber-reinforced composite material.
本発明の繊維強化複合材料は、繊維強化複合材料の面方向の半裁断面において、湾曲した炭素繊維が複数存在する。面方向の半裁断面とは、繊維強化複合材料の面方向に半裁して出した断面のことをいう。ここで、「湾曲した炭素繊維」とは、炭素繊維の単糸が多方向を向き、後述の方法により観察した繊維長１ｍｍ以上の炭素繊維において、連続した直線部分が１ｍｍ未満であることを言う。本発明においては、繊維強化複合材料を面方向に半裁して断面を出し、この半裁断面から無作為に選択した１０箇所において１ｃｍ２以上の試料を採取し、断面を、それぞれ光学顕微鏡を用いて倍率５０倍にて拡大観察し（観察視野１．７ｍｍ×２．３ｍｍ）、炭素繊維の単糸が多方向を向き、繊維長１ｍｍ以上の炭素繊維において、連続した直線部分が１ｍｍ未満である炭素繊維の数を計数する。このような形状を有する炭素繊維の数を１０箇所について計数してその平均値を算出し、小数点第１位を四捨五入した値を湾曲した炭素繊維数とし、湾曲する炭素繊維数が１０以上である場合に、「湾曲した炭素繊維が複数存在している」とする。炭素繊維が湾曲することにより、応力を分散し、比曲げ弾性率を向上させることができる。また、炭素繊維が多方向を向くことにより炭素繊維同士の重なりが増えるため、繊維強化複合材料中の空隙を増やして見かけ密度を低減することができる。湾曲した炭素繊維数は１５以上が好ましい。なお、繊維強化複合材料の面方向においては、炭素繊維は単繊維の状態でランダムに配向していることが好ましい。 In the fiber-reinforced composite material of the present invention, a plurality of curved carbon fibers are present in the half-cut cross section of the fiber-reinforced composite material in the plane direction. The half-cut cross section in the plane direction means a cross section obtained by half-cutting the fiber-reinforced composite material in the plane direction. Here, the "curved carbon fiber" means that the single yarn of the carbon fiber is oriented in multiple directions, and the continuous straight portion is less than 1 mm in the carbon fiber having a fiber length of 1 mm or more observed by the method described later. .. In the present invention, the fiber-reinforced composite material is cut in half in the plane direction to obtain a cross section, and samples of 1 cm 2 or more are collected at 10 randomly selected points from the half-cut cross section, and the cross sections are each cut using an optical microscope. When magnified and observed at a magnification of 50 times (observation field of view 1.7 mm x 2.3 mm), the single yarn of the carbon fiber faces in multiple directions, and in the carbon fiber having a fiber length of 1 mm or more, the continuous straight portion is less than 1 mm. Count the number of fibers. The number of carbon fibers having such a shape is counted at 10 locations, the average value is calculated, and the value rounded to the first decimal place is defined as the number of curved carbon fibers, and the number of curved carbon fibers is 10 or more. In the case, it is assumed that "there are a plurality of curved carbon fibers". By bending the carbon fiber, stress can be dispersed and the specific flexural modulus can be improved. Further, since the carbon fibers are oriented in multiple directions, the overlap between the carbon fibers is increased, so that the voids in the fiber-reinforced composite material can be increased and the apparent density can be reduced. The number of curved carbon fibers is preferably 15 or more. In the plane direction of the fiber-reinforced composite material, it is preferable that the carbon fibers are randomly oriented in the state of single fibers.
図１に、本発明の繊維強化複合材料の面方向の半裁断面の光学顕微鏡写真の一例を示す。繊維強化複合材料１に、湾曲した炭素繊維２が複数存在し、炭素繊維間を結合する熱可塑性樹脂３が存在する。 FIG. 1 shows an example of an optical micrograph of a half-cut cross section in the plane direction of the fiber-reinforced composite material of the present invention. A plurality of curved carbon fibers 2 are present in the fiber-reinforced composite material 1, and a thermoplastic resin 3 that bonds the carbon fibers is present.
湾曲した炭素繊維を複数存在させる方法としては、例えば、後述する繊維強化複合材料の製造方法において、炭素繊維の前駆体繊維に捲縮を付与することが好ましい。 As a method for allowing a plurality of curved carbon fibers to exist, for example, in the method for producing a fiber-reinforced composite material described later, it is preferable to impart crimp to the precursor fibers of the carbon fibers.
また、本発明の繊維強化複合材料は、面方向に対する垂直断面において、３本以上の炭素繊維が束状にまとまった束状部位が複数存在する。ここで、「束状部位」とは、後述の方法により観察した炭素繊維強化材料断面において、配向した炭素繊維が束状に３本以上まとまった形態が、観察視野中の繊維強化複合材料の厚さの１ｍｍ以上の長さにわたって連続していることを言う。本発明においては、繊維強化複合材料から無作為に選択した１０箇所において面方向に対する垂直断面を切り出し、光学顕微鏡を用いて倍率１６倍にて拡大観察し（観察視野５．５ｍｍ×７．３ｍｍ）、厚さ方向に配向した炭素繊維が束状に３本以上まとまった形態が、観察視野における繊維強化複合材料の厚さ方向に１ｍｍ以上の長さで連続している束状部位の数を計数する。このような形状を有する束状部位の数を１０箇所について計数してその平均値を算出し、小数点第２位を四捨五入した値を束状部位数とし、束状部位数が２以上である場合に、「３本以上の炭素繊維が束状にまとまった束状部位が複数存在する」とする。束状部位が複数存在することにより、繊維強化複合材料の製造におけるスプリングバックを大きくすることができ、見かけ密度を低減し、比曲げ弾性率を向上させることができる。一方、束状部位が複数存在しない場合や、炭素繊維の束が２本以下の場合には、これらの効果を十分に得ることができない。束状部位数は、繊維強化複合材料の面方向の垂直断面において幅方向に５か所／ｃｍ以上が好ましく、８か所／ｃｍ以上がより好ましい。 Further, the fiber-reinforced composite material of the present invention has a plurality of bundle-shaped portions in which three or more carbon fibers are bundled together in a cross section perpendicular to the plane direction. Here, the "bundle-shaped portion" refers to the thickness of the fiber-reinforced composite material in the observation field in which three or more oriented carbon fibers are bundled together in the cross section of the carbon fiber-reinforced material observed by the method described later. It means that it is continuous over a length of 1 mm or more. In the present invention, a cross section perpendicular to the plane direction is cut out at 10 randomly selected points from the fiber-reinforced composite material, and magnified and observed at a magnification of 16 times using an optical microscope (observation field of view 5.5 mm × 7.3 mm). , Count the number of bundled parts in which three or more carbon fibers oriented in the thickness direction are bundled together in a length of 1 mm or more in the thickness direction of the fiber-reinforced composite material in the observation field of view. To do. When the number of bundled parts having such a shape is counted for 10 parts and the average value is calculated, the value rounded to the first decimal place is used as the number of bundled parts, and the number of bundled parts is 2 or more. In addition, it is assumed that "there are a plurality of bundled portions in which three or more carbon fibers are bundled together". The presence of a plurality of bundled portions makes it possible to increase the springback in the production of the fiber-reinforced composite material, reduce the apparent density, and improve the specific flexural modulus. On the other hand, when there are no plurality of bundled portions or when the number of carbon fiber bundles is two or less, these effects cannot be sufficiently obtained. The number of bundled portions is preferably 5 locations / cm or more in the width direction, and more preferably 8 locations / cm or more in the vertical cross section of the fiber-reinforced composite material in the plane direction.
図２に、本発明の繊維強化複合材料の面方向に対する垂直断面の光学顕微鏡写真の一例を示す。繊維強化複合材料１は、束状部位４が複数存在する。 FIG. 2 shows an example of an optical micrograph of a cross section perpendicular to the plane direction of the fiber-reinforced composite material of the present invention. The fiber-reinforced composite material 1 has a plurality of bundle-shaped portions 4.
束状部位を複数存在させる方法としては、例えば、後述する繊維強化複合材料の製造方法において、炭素繊維の前駆体繊維に捲縮を付与したウェブや抄紙を、後述する好ましい本数のニードルパンチにより不織布化した後、焼成して炭素繊維不織布とすることが好ましい。 As a method for allowing a plurality of bundled portions to exist, for example, in the method for producing a fiber-reinforced composite material described later, a non-woven fabric is obtained by using a preferred number of needle punches described later on a web or paper machine in which the precursor fibers of carbon fibers are crimped. It is preferable that the material is converted into a carbon fiber non-woven fabric and then fired to obtain a carbon fiber non-woven fabric.
本発明の繊維強化複合材料は、見かけ密度が０．０４〜０．１５ｇ／ｃｍ３である。見かけ密度が０．０４ｇ／ｃｍ３未満であると、繊維強化複合材料中の空隙増加により炭素繊維同士の連結が弱くなり、比曲げ弾性率が低下する。一方、見かけ密度が０．１５ｇ／ｃｍ３を超えると、軽量化が不十分となる。見かけ密度は０．１ｇ／ｃｍ３以下が好ましい。 The fiber-reinforced composite material of the present invention has an apparent density of 0.04 to 0.15 g / cm 3 . When the apparent density is less than 0.04 g / cm 3 , the connection between the carbon fibers becomes weak due to the increase in voids in the fiber-reinforced composite material, and the specific flexural modulus decreases. On the other hand, if the apparent density exceeds 0.15 g / cm 3 , the weight reduction becomes insufficient. The apparent density is preferably 0.1 g / cm 3 or less.
本発明の繊維強化複合材料の見かけ密度は、以下の方法により求めることができる。まず、繊維強化複合材料をタテ１００ｍｍ、ヨコ１００ｍｍの寸法でカットした試験片を用意し、マイクロメーターを用いて試験片の９箇所の厚さを０．０１ｍｍ単位で測定し、その平均値を厚さとする。また、試験片の質量を測定する。この厚さ（ｍｍ）と試験片の面積（１００ｍｍ×１００ｍｍ）、繊維強化複合材料の質量Ｗｓ（ｇ）から、次式により見かけ密度を算出し、小数第３位を四捨五入した値を繊維強化複合材料の見かけ密度ρとする。
ρ［ｇ／ｃｍ３］＝Ｗｓ［ｇ］／（タテ寸法１００［ｍｍ］×ヨコ寸法１００［ｍｍ］×厚さ［ｍｍ］／１，０００）。
The apparent density of the fiber-reinforced composite material of the present invention can be determined by the following method. First, a test piece obtained by cutting a fiber-reinforced composite material into dimensions of 100 mm in length and 100 mm in width is prepared, and the thickness of 9 points of the test piece is measured in units of 0.01 mm using a micrometer, and the average value is measured as the thickness. Sato. Also, the mass of the test piece is measured. From this thickness (mm), the area of the test piece (100 mm × 100 mm), and the mass Ws (g) of the fiber-reinforced composite material, the apparent density is calculated by the following formula, and the value rounded to the third decimal place is the value obtained by rounding off the third decimal place. Let the apparent density of the material be ρ.
ρ [g / cm 3 ] = Ws [g] / (vertical dimension 100 [mm] x horizontal dimension 100 [mm] x thickness [mm] / 1,000).
繊維強化複合材料の見かけ密度を上記範囲にする方法としては、例えば、後述する繊維強化複合材料の製造方法において、炭素繊維の前駆体繊維に捲縮を付与したウェブをニードルパンチにより不織布とした後、焼成して得られた見かけ密度が後述する好ましい範囲にある炭素繊維不織布を、熱可塑性樹脂とともに、熱可塑性樹脂の融点以上の温度で加圧成形して熱可塑性樹脂を炭素繊維に含浸させた後、加熱しながら圧力を解放してスプリングバックを発生させることが好ましい。 As a method for adjusting the apparent density of the fiber-reinforced composite material to the above range, for example, in the method for producing a fiber-reinforced composite material described later, after the web obtained by imparting crimp to the carbon fiber precursor fiber is made into a non-woven fabric by needle punching. The carbon fiber non-woven fabric obtained by firing and having an apparent density in a preferable range described later was pressure-molded together with the thermoplastic resin at a temperature equal to or higher than the melting point of the thermoplastic resin to impregnate the carbon fibers with the thermoplastic resin. After that, it is preferable to release the pressure while heating to generate springback.
本発明の繊維強化複合材料は、比曲げ弾性率が６〜１５（ＧＰａ）１／３／（ｇ／ｃｍ３）であることが好ましい。ここで、比曲げ弾性率とは、曲げ剛性に対する質量効率のことであり、この値が大きい程、同重量で曲げに対する剛性が高いことを意味する。弾性率Ｅｃ（ＧＰａ）と見かけ密度ρ（ｇ／ｃｍ３）から、Ｅｃ１／３／ρにより算出することができる。鋼材やアルミニウムの比曲げ弾性率は１〜１．５（ＧＰａ）１／３／（ｇ／ｃｍ３）程度であり、従来の繊維強化複合材料は２〜２．３（ＧＰａ）１／３／（ｇ／ｃｍ３）程度であり、比曲げ弾性率が６（ＧＰａ）１／３／（ｇ／ｃｍ３）以上である本発明の繊維強化複合材料は、これらの材料に比べて優れた比曲げ弾性率を有することを意味する。比曲げ弾性率は、７（ＧＰａ）１／３／（ｇ／ｃｍ３）以上が好ましく、９（ＧＰａ）１／３／（ｇ／ｃｍ３）以上がより好ましい。一方、比曲げ弾性率は１５（ＧＰａ）１／３／（ｇ／ｃｍ３）以下が好ましい。 The fiber-reinforced composite material of the present invention preferably has a specific flexural modulus of 6 to 15 (GPa) 1/3 / (g / cm 3 ). Here, the specific flexural modulus is the mass efficiency with respect to the bending rigidity, and the larger this value is, the higher the rigidity with respect to bending is at the same weight. It can be calculated by Ec 1/3 / ρ from the elastic modulus Ec (GPa) and the apparent density ρ (g / cm 3 ). The specific flexural modulus of steel and aluminum is about 1 to 1.5 (GPa) 1/3 / (g / cm 3 ), and the conventional fiber-reinforced composite material is 2 to 2.3 (GPa) 1/3 /. The fiber-reinforced composite material of the present invention having a specific flexural modulus of about (g / cm 3 ) and a specific flexural modulus of 6 (GPa) 1/3 / (g / cm 3 ) or more has an excellent ratio as compared with these materials. It means having a flexural modulus. The specific flexural modulus is preferably 7 (GPa) 1/3 / (g / cm 3 ) or more, and more preferably 9 (GPa) 1/3 / (g / cm 3 ) or more. On the other hand, the specific flexural modulus is preferably 15 (GPa) 1/3 / (g / cm 3 ) or less.
繊維強化複合材料の比曲げ弾性率は、以下の方法により算出することができる。まず、ＪＩＳ Ｋ７０１７（１９９９）クラスＩに従い繊維強化複合材料から試験片を切り出し、小型卓上試験機ＥＺ−ＬＸ（（株）島津製作所製）を用いて、３点曲げにて曲げ弾性率を測定する。試験片は、任意の方向を０°方向とした場合に＋４５°、−４５°、９０°方向の４方向について切り出した試験片を作製し、それぞれの方向について測定数ｎ＝５とし、算術平均値を曲げ弾性率Ｅｃ（ＧＰａ）とする。前述の方法により測定した見かけ密度をρ（ｇ／ｃｍ３）として、次式により比曲げ弾性率を算出することができる。
比曲げ弾性率［ＧＰａ］１／３／［ｇ／ｃｍ３］＝Ｅｃ［ＧＰａ］１／３／ρ［ｇ／ｃｍ３］。
The specific flexural modulus of the fiber-reinforced composite material can be calculated by the following method. First, a test piece is cut out from a fiber-reinforced composite material according to JIS K7017 (1999) Class I, and the flexural modulus is measured by three-point bending using a small tabletop tester EZ-LX (manufactured by Shimadzu Corporation). .. As the test piece, when the arbitrary direction is 0 °, a test piece cut out in four directions of + 45 °, -45 °, and 90 ° is prepared, and the number of measurements n = 5 in each direction, and the arithmetic mean. The value is defined as the flexural modulus Ec (GPa). The specific flexural modulus can be calculated by the following equation, where the apparent density measured by the above method is ρ (g / cm 3 ).
Specific flexural modulus [GPa] 1/3 / [g / cm 3 ] = Ec [GPa] 1/3 / ρ [g / cm 3 ].
次に、本発明の繊維強化複合材料の製造方法について説明する。繊維強化複合材料の製造方法としては、例えば、炭素繊維の前駆体繊維に捲縮を付与したウェブや抄紙をニードルパンチにより不織布化した後、焼成して炭素繊維不織布とし、熱可塑性樹脂のフィルムまたはシートとともに加圧加熱成形して熱可塑性樹脂を炭素繊維に含浸させた後、加熱しながら圧力を解放してスプリングバックを発生させる方法が好ましい。剛直な炭素繊維ではなく、柔軟な前駆体繊維に予め捲縮を付与し、前駆体繊維の状態でニードルパンチにより不織布化することにより、炭素繊維を湾曲させ、前述の束状部位を形成することができる。炭素繊維に捲縮加工を施しても、炭素繊維が剛直で可撓性が低いため、本発明における湾曲した炭素繊維を複数存在させることは困難である。また、炭素繊維にニードルパンチ加工を施しても、炭素繊維が剛直で可撓性が低いため、炭素繊維が破損しやすく、垂直断面に前述の束状部位を形成することは困難である。また、このようにして得られた炭素繊維不織布を用いてスプリングバックを発生させることにより、見かけ密度を前述の範囲に容易に調整することができる。 Next, the method for producing the fiber-reinforced composite material of the present invention will be described. As a method for producing a fiber-reinforced composite material, for example, a web or paper made by imparting crimp to a carbon fiber precursor fiber is made into a non-woven fabric by needle punching, and then fired to obtain a carbon fiber non-woven fabric, and a thermoplastic resin film or A method is preferable in which the carbon fibers are impregnated with the thermoplastic resin by pressure heating molding together with the sheet, and then the pressure is released while heating to generate springback. By preliminarily applying crimp to a flexible precursor fiber instead of a rigid carbon fiber and forming a non-woven fabric with a needle punch in the state of the precursor fiber, the carbon fiber is curved to form the above-mentioned bundled portion. Can be done. Even if the carbon fibers are crimped, it is difficult to have a plurality of curved carbon fibers in the present invention because the carbon fibers are rigid and have low flexibility. Further, even if the carbon fibers are subjected to needle punching, the carbon fibers are rigid and have low flexibility, so that the carbon fibers are easily damaged and it is difficult to form the above-mentioned bundled portion in the vertical cross section. Further, by generating the springback using the carbon fiber non-woven fabric thus obtained, the apparent density can be easily adjusted within the above-mentioned range.
具体的には、少なくとも、
（１）捲縮を付与した炭素繊維前駆体繊維のウェブをニードルパンチにより絡合し、炭素繊維前駆体繊維不織布を得る工程、
（２）炭素繊維前駆体繊維不織布を不活性雰囲気下で焼成し、見かけ密度が０．１５ｇ／ｃｍ３未満の炭素繊維不織布を得る工程、
（３）炭素繊維不織布と熱可塑性樹脂のフィルムまたはシートとを重ね、熱可塑性樹脂の融点以上の温度において加圧成形により熱可塑性樹脂を溶融含浸する工程、
（４）熱可塑性樹脂の融点以上の温度において圧力を解放してスプリングバックさせた後に冷却する工程
をこの順に有することが好ましい。以下に、材料と各工程について詳述する。
Specifically, at least
(1) A step of entwining a web of carbon fiber precursor fibers with crimps by a needle punch to obtain a carbon fiber precursor fiber non-woven fabric.
(2) A step of calcining a carbon fiber precursor fiber non-woven fabric in an inert atmosphere to obtain a carbon fiber non-woven fabric having an apparent density of less than 0.15 g / cm 3 .
(3) A step of laminating a carbon fiber non-woven fabric and a film or sheet of a thermoplastic resin, and melt-impregnating the thermoplastic resin by pressure molding at a temperature equal to or higher than the melting point of the thermoplastic resin.
(4) It is preferable to have a step of releasing pressure at a temperature equal to or higher than the melting point of the thermoplastic resin to spring back and then cooling in this order. The materials and each process will be described in detail below.
まず、（１）捲縮を付与した炭素繊維前駆体繊維のウェブをニードルパンチにより絡合し、炭素繊維前駆体繊維不織布を得る工程について説明する。 First, (1) a step of entwining a web of carbon fiber precursor fibers with crimps by a needle punch to obtain a carbon fiber precursor fiber non-woven fabric will be described.
炭素繊維前駆体繊維としては、例えば、ＰＡＮ系耐炎糸が挙げられる。を用いることができ、耐炎化は、通常、空気中で、処理時間を１０〜１００分間、温度を１５０〜３５０℃の条件で行うことが一般的である。ＰＡＮ系耐炎糸の比重が１．３〜１．３８（ｇ／ｃｍ３）の範囲となるように設定することが好ましい。 Examples of the carbon fiber precursor fiber include PAN-based flame-resistant yarn. Can be used, and flame resistance is generally carried out in air under the conditions of a treatment time of 10 to 100 minutes and a temperature of 150 to 350 ° C. It is preferable to set the specific gravity of the PAN-based flame-resistant yarn to be in the range of 1.3 to 1.38 (g / cm 3 ).
次いで、炭素繊維の前駆体繊維に捲縮を付与する。捲縮付与方法としては、例えば、機械捲縮による捲縮付与や、熱処理による捲縮付与などが挙げられる。本発明においては、捲縮構造を制御しやすく、捲縮状態のバラツキを抑制しやすいことから、機械捲縮により捲縮を付与することが好ましい。 The carbon fiber precursor fibers are then crimped. Examples of the method for imparting crimping include crimping by mechanical crimping and crimping by heat treatment. In the present invention, it is preferable to apply crimping by mechanical crimping because it is easy to control the crimping structure and suppress the variation in the crimped state.
機械捲縮による捲縮付与方法としては、例えば、直線状の前駆体繊維に対して押し込み式クリンパー等の捲縮付与装置によって捲縮を付与する方法や、２枚以上のギヤの間に前駆体繊維を導入して捲縮を付与する方法などが挙げられる。これらの機械捲縮においては、ライン速度の周速差・熱・加圧などによって、捲縮数や捲縮率を調整することができる。 Examples of the method of applying the crimp by mechanical crimp include a method of applying the crimp to the linear precursor fiber by a crimp applying device such as a push-in crimper, or a method of applying the crimp between two or more gears. Examples thereof include a method of introducing fibers to impart crimping. In these mechanical crimps, the number of crimps and the crimp ratio can be adjusted by the peripheral speed difference of the line speed, heat, pressurization, and the like.
次に、捲縮を付与した炭素繊維前駆体繊維を切断して短繊維化し、ウェブ化または抄紙化することが好ましい。ウェブ化する際のカーディングの通過性の観点から、短繊維化繊維の平均繊維長は、３０〜１００ｍｍが好ましい。短繊維をウェブ化する方法としては、例えば、短繊維をカーディングしてクロスレイやエアレイにより乾式ウェブ化する方法が挙げられる。短繊維を抄紙化する方法としては、例えば、抄造機を用いて湿式抄紙化する方法が挙げられる。本発明においては、基材１枚の高目付化が容易で、後述する加圧加熱工程にける基材の積層枚数を削減することができることから、乾式ウェブ化法が好ましい。得られたウェブを、例えばクロスラッパーを用いて重ね合わせることが好ましい。 Next, it is preferable to cut the crimped carbon fiber precursor fiber to shorten the fiber and make it into a web or paper. From the viewpoint of the passability of carding when forming a web, the average fiber length of the short fiber is preferably 30 to 100 mm. Examples of the method of converting the short fibers into a web include a method of carding the short fibers and converting them into a dry web by using a cloth ray or an air array. Examples of the method of making short fibers into paper include a method of making wet paper using a paper machine. In the present invention, the dry web method is preferable because it is easy to increase the basis weight of one base material and the number of laminated base materials in the pressurizing and heating step described later can be reduced. It is preferable to superimpose the obtained webs using, for example, a cross wrapper.
次に、ウェブや抄紙をニードルパンチにより絡合し、不織布化する。ニードルパンチを行う際、ニードルに形成されたバーブと呼ばれる前駆体繊維を引っかける部位の深さを、前駆体繊維の太さに対して３倍以上となるものを用いることにより、束状部位を構成する炭素繊維を３本以上とすることができる。束状部位の数を増やすことにより後述する繊維強化複合材料のスプリングバックを大きくし、繊維強化複合材料を軽量化できることから、ニードルパンチの本数は、２００本／ｃｍ２以上が好ましく、５００本／ｃｍ２以上がより好ましく、１，０００本／ｃｍ２以上がさらに好ましい。一方、比曲げ弾性率をより向上させる観点から、ニードルパンチの本数は、２，０００本／ｃｍ２以下が好ましい。 Next, the web and paper are entwined with a needle punch to make a non-woven fabric. When performing needle punching, a bundle-shaped portion is formed by using a barb formed on the needle so that the depth of the portion where the precursor fiber is hooked is three times or more the thickness of the precursor fiber. The number of carbon fibers to be used can be three or more. By increasing the number of bundled portions, the springback of the fiber-reinforced composite material described later can be increased and the weight of the fiber-reinforced composite material can be reduced. Therefore, the number of needle punches is preferably 200 / cm 2 or more, and 500 / cm. cm 2 or more is more preferable, and 1,000 pieces / cm 2 or more is further preferable. On the other hand, from the viewpoint of further improving the specific flexural modulus, the number of needle punches is preferably 2,000 / cm 2 or less.
工程（２）における炭素繊維不織布の密度を後述する好ましい範囲にするために、炭素繊維前駆体不織布の見かけ密度は０．２３ｇ／ｃｍ３未満が好ましい。また、プレスなどの圧縮工程を行うことなく工程（２）に進めることが好ましい。なお、炭素繊維前駆体繊維不織布の見かけ密度は、以下の方法により求めることができる。まず、炭素繊維前駆体繊維不織布の無作為に選択した５箇所から、タテ４０ｍｍ、ヨコ４０ｍｍの寸法で試験片をカットし、質量Ｗ（ｇ）を測定する。小型卓上試験機ＥＺ−ＬＸ（（株）島津製作所製）を用いて、試験種類を圧縮試験とし、試験片を挟まない状態で上部の圧縮治具を下降させて下部の治具に接触した地点を厚さのゼロ点とする。次に、試験片を治具の中央に置いて、速度２ｍｍ／分の速度で圧縮を行い、８．８ＫＰａ荷重下での厚みとなるように１，４４０ｇの荷重がかかった際の厚さ（μｍ）を測定し、小数点第１位を四捨五入する。試験片５枚についてそれぞれ厚さ（μｍ）を測定し、数平均値を算出して小数点第１位を四捨五入した値を炭素繊維前駆体繊維不織布の厚さとする。この厚さと試験片の面積（４０ｍｍ×４０ｍｍ）、質量Ｗ（ｇ）から、次式により見かけ密度を算出し、小数第３位を四捨五入した値を炭素繊維前駆体繊維不織布の見かけ密度ρ０とする。
ρ０［ｇ／ｃｍ３］＝Ｗ［ｇ］／（タテ寸法４０［ｍｍ］×ヨコ寸法４０［ｍｍ］×厚さ［μｍ］／１００，０００）。
In order to keep the density of the carbon fiber non-woven fabric in the step (2) within a preferable range described later, the apparent density of the carbon fiber precursor non-woven fabric is preferably less than 0.23 g / cm 3 . Further, it is preferable to proceed to step (2) without performing a compression step such as pressing. The apparent density of the carbon fiber precursor fiber non-woven fabric can be determined by the following method. First, a test piece is cut from five randomly selected carbon fiber precursor fiber non-woven fabrics to a length of 40 mm and a width of 40 mm, and the mass W (g) is measured. Using a small desktop tester EZ-LX (manufactured by Shimadzu Corporation), the test type is a compression test, and the upper compression jig is lowered without sandwiching the test piece to contact the lower jig. Let be the zero point of thickness. Next, the test piece was placed in the center of the jig, compressed at a speed of 2 mm / min, and the thickness when a load of 1,440 g was applied so as to have a thickness under a load of 8.8 KPa ( μm) is measured and the first decimal place is rounded off. The thickness (μm) of each of the five test pieces is measured, the number average value is calculated, and the value rounded to the first decimal place is taken as the thickness of the carbon fiber precursor fiber non-woven fabric. From this thickness, the area of the test piece (40 mm × 40 mm), and the mass W (g), the apparent density is calculated by the following formula, and the value rounded to the third decimal place is defined as the apparent density ρ0 of the carbon fiber precursor fiber non-woven fabric. ..
ρ0 [g / cm 3 ] = W [g] / (vertical dimension 40 [mm] x horizontal dimension 40 [mm] x thickness [μm] / 100,000).
次に、（２）炭素繊維前駆体繊維不織布を不活性雰囲気下で焼成し、見かけ密度が０．１５ｇ／ｃｍ３未満の炭素繊維不織布を得る工程について説明する。 Next, (2) a step of firing the carbon fiber precursor fiber nonwoven fabric in an inert atmosphere to obtain a carbon fiber nonwoven fabric having an apparent density of less than 0.15 g / cm 3 will be described.
前述の工程（１）において得られた不織布を不活性雰囲気下において焼成することにより、炭素繊維不織布化することが好ましい。具体的には、ニードルパンチにより得られた前駆体繊維不織布を、窒素雰囲気中、温度６００〜１，０００℃の条件で焼成して前炭化不織布とした後、窒素雰囲気中、温度１，２００〜２，０００℃の条件で焼成することにより、炭素繊維不織布を得ることが好ましい。 It is preferable to convert the non-woven fabric obtained in the above step (1) into a carbon fiber non-woven fabric by firing it in an inert atmosphere. Specifically, the precursor fiber non-woven fabric obtained by needle punching is fired in a nitrogen atmosphere at a temperature of 600 to 1,000 ° C. to obtain a pre-carbonized non-woven fabric, and then in a nitrogen atmosphere, the temperature is 1,200 to 1. It is preferable to obtain a carbon fiber non-woven fabric by firing under the condition of 2,000 ° C.
繊維強化複合材料をより軽量化する観点から、炭素繊維不織布の密度は０．１５ｇ／ｃｍ３未満が好ましい。炭素繊維不織布の見かけ密度は、炭素繊維前駆体繊維不織布の見かけ密度と同様に測定することができる。 From the viewpoint of further reducing the weight of the fiber-reinforced composite material, the density of the carbon fiber non-woven fabric is preferably less than 0.15 g / cm 3 . The apparent density of the carbon fiber non-woven fabric can be measured in the same manner as the apparent density of the carbon fiber precursor fiber non-woven fabric.
得られた炭素繊維不織布に表面処理を施すことが好ましく、炭素繊維と熱可塑性樹脂との接着性を向上させることができる。表面処理方法としては、例えば、電解処理等による繊維表面酸化処理やシランカップリング剤処理などが挙げられる。これらの中でも、電解酸化処理が好ましい。 It is preferable to apply a surface treatment to the obtained carbon fiber non-woven fabric, and the adhesiveness between the carbon fiber and the thermoplastic resin can be improved. Examples of the surface treatment method include fiber surface oxidation treatment by electrolytic treatment and the like, silane coupling agent treatment, and the like. Among these, electrolytic oxidation treatment is preferable.
電解酸化処理に用いる電解質としては、例えば、硫酸、硝酸、塩酸、炭酸、硝酸アンモニウム、硝酸水素アンモニウム、リン酸２水素アンモニウム、リン酸水素２アンモニウムなどの酸；水酸化ナトリウム、水酸化カリウム、水酸化バリウムなどの水酸化物；炭酸ナトリウム、炭酸水素ナトリウム、リン酸ナトリウム、リン酸カリウム等の無機塩；マレイン酸ナトリウム、酢酸ナトリウム、酢酸カリウム、安息香酸ナトリウム等の有機塩；アンモニア、炭酸アンモニウム、炭酸水素アンモニウムなどアルカリなどが挙げられる。これらを２種以上用いてもよい。 Examples of the electrolyte used in the electrolytic oxidation treatment include acids such as sulfuric acid, nitric acid, hydrochloric acid, carbonic acid, ammonium nitrate, ammonium hydrogen nitrate, ammonium dihydrogen phosphate and diammonium hydrogen phosphate; sodium hydroxide, potassium hydroxide and hydroxide. Hydroxide such as barium; inorganic salts such as sodium carbonate, sodium hydrogencarbonate, sodium phosphate, potassium phosphate; organic salts such as sodium maleate, sodium acetate, potassium acetate, sodium benzoate; ammonia, ammonium carbonate, carbonic acid Examples include alkalis such as ammonium hydrogen hydrogen. Two or more of these may be used.
次に、（３）炭素繊維不織布と熱可塑性樹脂のフィルムまたはシートとを重ね、熱可塑性樹脂の融点以上の温度において加圧成形により熱可塑性樹脂を溶融含浸する工程について説明する。 Next, (3) a step of stacking the carbon fiber non-woven fabric and the film or sheet of the thermoplastic resin and melt-impregnating the thermoplastic resin by pressure molding at a temperature equal to or higher than the melting point of the thermoplastic resin will be described.
得られた炭素繊維不織布と、熱可塑性樹脂のフィルムやシートとを重ね、熱可塑性樹脂の融点以上の温度において加圧成形により熱可塑性樹脂を炭素繊維に含浸することが好ましい。加熱加圧成形機としては、例えば、バッチ式の圧縮成形機やダブルベルトプレス機などが挙げられる。炭素繊維不織布の上下に熱可塑性樹脂のフィルムやシートを配置し、熱可塑性樹脂の融点以上に加熱して溶融させた後、次第に圧力を増加させて炭素繊維不織布に熱可塑性樹脂を含浸させることが好ましい。 It is preferable to superimpose the obtained carbon fiber non-woven fabric and a film or sheet of a thermoplastic resin, and impregnate the carbon fibers with the thermoplastic resin by pressure molding at a temperature equal to or higher than the melting point of the thermoplastic resin. Examples of the heat and pressure molding machine include a batch type compression molding machine and a double belt press machine. A thermoplastic resin film or sheet is placed above and below the carbon fiber non-woven fabric, heated above the melting point of the thermoplastic resin to melt it, and then the pressure is gradually increased to impregnate the carbon fiber non-woven fabric with the thermoplastic resin. preferable.
次に、（４）熱可塑性樹脂の融点以上の温度において圧力を解放してスプリングバックさせた後に冷却する工程について説明する。 Next, (4) a step of releasing pressure at a temperature equal to or higher than the melting point of the thermoplastic resin to cause springback and then cooling will be described.
スプリングバックさせる際の加熱温度は、スプリングバック中の熱可塑性樹脂の流動性を向上させる観点から、熱可塑性樹脂の融点＋２０℃以上が好ましい。一方加熱温度は、熱可塑性樹脂の熱分解温度−１０℃以下が好ましい。また、冷却に際して、必要に応じて再度加圧して、繊維強化複合材料の見かけ密度を前述の範囲に調整してもよい。 The heating temperature at the time of springback is preferably + 20 ° C. or higher, which is the melting point of the thermoplastic resin, from the viewpoint of improving the fluidity of the thermoplastic resin during springback. On the other hand, the heating temperature is preferably a thermal decomposition temperature of the thermoplastic resin of −10 ° C. or lower. Further, upon cooling, the apparent density of the fiber-reinforced composite material may be adjusted to the above-mentioned range by pressurizing again if necessary.
以下、実施例により本発明をさらに詳細に説明する。まず、各実施例および比較例における評価方法について説明する。 Hereinafter, the present invention will be described in more detail with reference to Examples. First, the evaluation method in each Example and Comparative Example will be described.
（１）炭素繊維含有量 Ｗｃ
各実施例および比較例により得られた繊維強化複合材料の質量Ｗｓ（ｇ）を測定した後、繊維強化複合材料を空気中５００℃で３０分間加熱して熱可塑性樹脂を焼き飛ばし、残った強化繊維の質量Ｗｆ（ｇ）を測定し、次式により炭素繊維含有量Ｗｃ（重量％）を算出した。
Ｗｃ［％］＝（Ｗｆ［ｇ］／Ｗｓ「ｇ」）×１００。
(1) Carbon fiber content Wc
After measuring the mass Ws (g) of the fiber-reinforced composite material obtained in each Example and Comparative Example, the fiber-reinforced composite material was heated in air at 500 ° C. for 30 minutes to burn off the thermoplastic resin, and the remaining reinforcement was obtained. The mass Wf (g) of the fiber was measured, and the carbon fiber content Wc (% by weight) was calculated by the following formula.
Wc [%] = (Wf [g] / Ws "g") x 100.
（２）湾曲した炭素繊維
各実施例および比較例により得られた繊維強化複合材料を刃物で面方向に半裁して断面を出し、この半裁断面から無作為に選択した１０箇所において１ｃｍ２以上の試料を採取し、断面を、それぞれ光学顕微鏡（Ｌｅｉｃａ製Ｍ２０５Ｃ）を用いて倍率５０倍にて拡大観察し（観察視野１．７ｍｍ×２．３ｍｍ）、炭素繊維の単糸が多方向を向き、繊維長１ｍｍ以上の炭素繊維において、連続した直線部分が１ｍｍ未満である炭素繊維の数を計数した。このような形状を有する炭素繊維の数を１０箇所について計数してその平均値を算出し、小数点第１位を四捨五入した値を湾曲した炭素繊維数とした。湾曲する炭素繊維数が１０以上である場合に、湾曲した炭素繊維が複数存在しているとした。
(2) Curved carbon fiber The fiber-reinforced composite material obtained in each Example and Comparative Example was cut in half in the plane direction with a knife to obtain a cross section, and 1 cm 2 or more was obtained at 10 randomly selected positions from this half-cut cross section. A sample was taken, and the cross section was magnified and observed at a magnification of 50 times using an optical microscope (M205C manufactured by Leica) (observation field of view 1.7 mm x 2.3 mm), and the carbon fiber single yarns were oriented in multiple directions. Among the carbon fibers having a fiber length of 1 mm or more, the number of carbon fibers having a continuous straight portion of less than 1 mm was counted. The number of carbon fibers having such a shape was counted at 10 locations, the average value was calculated, and the value rounded off to the first decimal place was taken as the number of curved carbon fibers. When the number of curved carbon fibers is 10 or more, it is assumed that a plurality of curved carbon fibers are present.
（３）束状部位
各実施例および比較例により得られた繊維強化複合材料から無作為に選択した１０箇所において面方向に対する垂直断面を切り出し、光学顕微鏡（Ｌｅｉｃａ製Ｍ２０５Ｃ）を用いて倍率１６倍にて拡大観察し（観察視野５．５ｍｍ×７．３ｍｍ）、厚さ方向に配向した炭素繊維が束状にまとまった形態が、観察視野における繊維強化複合材料の厚さ方向に１ｍｍ以上の長さで連続している束状部位の数を計数した。このような形状を有する束状部位の数を１０箇所について計数してその平均値を算出し、小数点第２位を四捨五入した値を束状部位数とし、束状部位数が２以上である場合に炭素繊維が束状にまとまった束状部位が複数存在するとした。
(3) Bundled parts A cross section perpendicular to the plane direction was cut out at 10 randomly selected parts from the fiber-reinforced composite materials obtained in each Example and Comparative Example, and the magnification was 16 times using an optical microscope (M205C manufactured by Leica). (Observation field of view 5.5 mm x 7.3 mm), the form in which carbon fibers oriented in the thickness direction are bundled together is 1 mm or more in the thickness direction of the fiber-reinforced composite material in the observation field of view. The number of continuous bundled parts was counted. When the number of bundled parts having such a shape is counted for 10 parts and the average value is calculated, the value rounded off to the second decimal place is defined as the number of bundled parts, and the number of bundled parts is 2 or more. It is assumed that there are a plurality of bundled parts in which carbon fibers are bundled together.
（４）繊維強化複合材料の見かけ密度 ρ
各実施例および比較例により得られた繊維強化複合材料をタテ１００ｍｍ、ヨコ１００ｍｍの寸法でカットした試験片を用意し、マイクロメーターを用いて試験片の９箇所の厚さを０．０１ｍｍ単位で測定し、その平均値を厚さとした。また、試験片の質量を測定した。この厚さ（ｍｍ）と試験片の面積（１００ｍｍ×１００ｍｍ）、繊維強化複合材料の質量Ｗｓ（ｇ）から、次式により見かけ密度を算出し、小数第３位を四捨五入した値を繊維強化複合材料の見かけ密度ρとした。
ρ［ｇ／ｃｍ３］＝Ｗｓ［ｇ］／（タテ寸法１００［ｍｍ］×ヨコ寸法１００［ｍｍ］×厚さ［ｍｍ］／１，０００）。
(4) Apparent density of fiber-reinforced composite material ρ
Prepare a test piece obtained by cutting the fiber-reinforced composite material obtained in each Example and Comparative Example to the dimensions of 100 mm in length and 100 mm in width, and use a micrometer to measure the thickness of the test piece at 9 points in units of 0.01 mm. The measurement was performed, and the average value was taken as the thickness. Moreover, the mass of the test piece was measured. From this thickness (mm), the area of the test piece (100 mm × 100 mm), and the mass Ws (g) of the fiber-reinforced composite material, the apparent density is calculated by the following formula, and the value rounded to the third decimal place is the value obtained by rounding off the third decimal place. The apparent density of the material was ρ.
ρ [g / cm 3 ] = Ws [g] / (vertical dimension 100 [mm] x horizontal dimension 100 [mm] x thickness [mm] / 1,000).
（５）炭素繊維前駆体繊維不織布および炭素繊維不織布の見かけ密度
各実施例および比較例により得られた炭素繊維前駆体繊維不織布および炭素繊維不織布のそれぞれ無作為に選択した５箇所から、タテ４０ｍｍ、ヨコ４０ｍｍの寸法で試験片をカットし、質量Ｗ（ｇ）を測定した。小型卓上試験機ＥＺ−ＬＸ（（株）島津製作所製）を用いて、試験種類を圧縮試験とし、試験片を挟まない状態で上部の圧縮治具を下降させて下部の治具に接触した地点を厚さのゼロ点とした。次に、試験片を治具の中央に置いて、速度２ｍｍ／分の速度で圧縮を行い、８．８ＫＰａ荷重下での厚みとなるように１，４４０ｇの荷重がかかった際の厚さ（μｍ）を測定し、小数点第１位を四捨五入した。試験片５枚についてそれぞれ厚さ（μｍ）を測定し、数平均値を算出して小数点第１位を四捨五入した値を炭素繊維前駆体繊維不織布または炭素繊維不織布の厚さとした。この厚さと試験片の面積（４０ｍｍ×４０ｍｍ）、質量Ｗ（ｇ）から、次式により見かけ密度を算出し、小数第３位を四捨五入した値を炭素繊維前駆体繊維不織布および炭素繊維不織布の見かけ密度ρ０とした。
ρ０［ｇ／ｃｍ３］＝Ｗ［ｇ］／（タテ寸法４０［ｍｍ］×ヨコ寸法４０［ｍｍ］×厚さ［μｍ］／１００，０００）。
(5) Apparent density of carbon fiber precursor fiber non-woven fabric and carbon fiber non-woven fabric Vertical 40 mm, from 5 randomly selected locations of carbon fiber precursor fiber non-woven fabric and carbon fiber non-woven fabric obtained in each Example and Comparative Example. The test piece was cut to a width of 40 mm, and the mass W (g) was measured. Using a small desktop tester EZ-LX (manufactured by Shimadzu Corporation), the test type is a compression test, and the upper compression jig is lowered without sandwiching the test piece to contact the lower jig. Was set as the zero point of thickness. Next, the test piece was placed in the center of the jig, compressed at a speed of 2 mm / min, and the thickness when a load of 1,440 g was applied so as to have a thickness under a load of 8.8 KPa ( μm) was measured and the first decimal place was rounded off. The thickness (μm) of each of the five test pieces was measured, the number average value was calculated, and the value rounded off to the first decimal place was taken as the thickness of the carbon fiber precursor fiber non-woven fabric or the carbon fiber non-woven fabric. From this thickness, the area of the test piece (40 mm × 40 mm), and the mass W (g), the apparent density is calculated by the following formula, and the value rounded to the third fraction is the apparent value of the carbon fiber precursor fiber non-woven fabric and the carbon fiber non-woven fabric. The density was ρ0.
ρ0 [g / cm 3 ] = W [g] / (vertical dimension 40 [mm] x horizontal dimension 40 [mm] x thickness [μm] / 100,000).
（６）比曲げ弾性率
各実施例および比較例により得られた繊維強化複合材料から試験片を切り出し、ＪＩＳ Ｋ７０１７（１９９９）クラスＩに従い、小型卓上試験機ＥＺ−ＬＸ（（株）島津製作所製）を用いて、３点曲げにて曲げ弾性率を測定した。試験片は、任意の方向を０°方向とした場合に＋４５°、−４５°、９０°方向の４方向について切り出した試験片を作製し、それぞれの方向について測定数ｎ＝５とし、算術平均値を曲げ弾性率Ｅｃ（ＧＰａ）とした。測定装置としては小型卓上試験機ＥＺ−ＬＸ（（株）島津製作所製）を使用した。前述の方法により測定した見かけ密度をρ（ｇ／ｃｍ３）として、次式により比曲げ弾性率を算出した。
比曲げ弾性率［ＧＰａ］１／３／［ｇ／ｃｍ３］＝Ｅｃ［ＧＰａ］１／３／ρ［ｇ／ｃｍ３］。
(6) Specific flexural modulus A test piece was cut out from the fiber-reinforced composite material obtained in each Example and Comparative Example, and according to JIS K7017 (1999) Class I, a small tabletop tester EZ-LX (manufactured by Shimadzu Corporation). ) Was used to measure the flexural modulus by 3-point bending. As the test piece, when the arbitrary direction is 0 °, a test piece cut out in four directions of + 45 °, -45 °, and 90 ° is prepared, and the number of measurements n = 5 in each direction, and the arithmetic mean. The value was defined as the flexural modulus Ec (GPa). As a measuring device, a small desktop testing machine EZ-LX (manufactured by Shimadzu Corporation) was used. The specific flexural modulus was calculated by the following equation, where the apparent density measured by the above method was ρ (g / cm 3 ).
Specific flexural modulus [GPa] 1/3 / [g / cm 3 ] = Ec [GPa] 1/3 / ρ [g / cm 3 ].
（実施例１）
単繊維デニール１ｄのＰＡＮ系耐炎糸を押し込み式クリンパーにより捲縮糸とした。この耐炎糸を数平均繊維長７６ｍｍに切断した後、カード、クロスラッパーを用いてウェブシートとし、ついでシングルバーブのニードルを用いて針密度２００本／ｃｍ２でニードルパンチを行い、ＰＡＮ系耐炎糸不織布とした。この不織布の見かけ密度は０．１４ｇ／ｃｍ３であった。次いで窒素雰囲気中１，５００℃の温度まで昇温して焼成し、目付７７０ｇ／ｍ２、密度０．０５ｇ／ｃｍ３の炭素繊維不織布とした後（炭素繊維の密度：１．８０ｇ／ｃｍ３）、この炭素繊維不織布を炭酸水素アンモニウム水溶液（０．１モル／リットル）中に浸漬し、７６クーロン／ｇの電気量となるように電解酸化処理を行い、水洗および乾燥を行った
この炭素繊維不織布の上下面に未変性ポリプロピレン樹脂（プライムポリマー（株）製“プライムポリプロ”（登録商標）Ｊ１０５Ｇ）８０質量％と、酸変性ポリプロピレン樹脂（三井化学（株）製“アドマー”ＱＢ５１０）２０質量％とからなる樹脂シートを炭素繊維の重量含有率が３３．３％となるように重ね、ポリプロピレンの融点以上である２３０℃に予熱したプレス機に配置して平板の金型を閉じ、次いで、３分間保持した後、２ＭＰａの圧力を付与してさらに３分間保持した。次いで、金型を全開放して炭素繊維不織布をスプリングバックさせた後、５０℃まで冷却して繊維強化複合材料を得た。得られた繊維強化複合材料について、空気中５００℃で３０分間加熱して熱可塑性樹脂を焼き飛ばし、炭素繊維含有量を求めた。得られた繊維強化複合材料の特性を表１に示す。
(Example 1)
A PAN-based flame-resistant yarn of single fiber denier 1d was made into a crimped yarn by a push-in crimper. After cutting this flame-resistant yarn to a number average fiber length of 76 mm, a web sheet is made using a card and a cross wrapper, and then needle punching is performed using a single barb needle at a needle density of 200 lines / cm 2 , and a PAN-based flame-resistant yarn is used. It was made of non-woven fabric. The apparent density of this non-woven fabric was 0.14 g / cm 3 . Then calcined by heating to a temperature of 1,500 ° C. in a nitrogen atmosphere, basis weight 770 g / m 2, after the carbon fiber nonwoven fabric of density 0.05 g / cm 3 (density of the carbon fibers: 1.80 g / cm 3 ), This carbon fiber non-woven fabric was immersed in an aqueous solution of ammonium hydrogencarbonate (0.1 mol / liter), electrolytically oxidized so as to have an electric amount of 76 coulomb / g, washed with water and dried. 80% by mass of unmodified polypropylene resin (“Prime Polypro” (registered trademark) J105G manufactured by Prime Polymer Co., Ltd.) and 20% by mass of acid-modified polypropylene resin (“Admer” QB510 manufactured by Mitsui Chemicals Co., Ltd.) on the upper and lower surfaces of the non-woven fabric. The resin sheets made of After holding for 1 minute, a pressure of 2 MPa was applied to hold for another 3 minutes. Next, the mold was fully opened to spring back the carbon fiber non-woven fabric, and then cooled to 50 ° C. to obtain a fiber-reinforced composite material. The obtained fiber-reinforced composite material was heated in air at 500 ° C. for 30 minutes to burn off the thermoplastic resin, and the carbon fiber content was determined. The characteristics of the obtained fiber-reinforced composite material are shown in Table 1.
（実施例２）
ニードルパンチ時の針密度を５００本／ｃｍ２とした以外は、実施例１と同様にして繊維強化複合材料を得た。得られた繊維強化複合材料の特性を表１に示す。
(Example 2)
A fiber-reinforced composite material was obtained in the same manner as in Example 1 except that the needle density at the time of needle punching was 500 needles / cm 2 . The characteristics of the obtained fiber-reinforced composite material are shown in Table 1.
（実施例３）
ニードルパンチ時の針密度を１，０００本／ｃｍ２とした以外は、実施例１と同様にして繊維強化複合材料を得た。得られた繊維強化複合材料の特性を表１に示す。
(Example 3)
A fiber-reinforced composite material was obtained in the same manner as in Example 1 except that the needle density at the time of needle punching was 1,000 needles / cm 2 . The characteristics of the obtained fiber-reinforced composite material are shown in Table 1.
（実施例４）
ニードルパンチ時の針密度を１，５００本／ｃｍ２とした以外は、実施例１と同様にして繊維強化複合材料を得た。得られた繊維強化複合材料の特性を表１に示す。
(Example 4)
A fiber-reinforced composite material was obtained in the same manner as in Example 1 except that the needle density at the time of needle punching was 1,500 / cm 2 . The characteristics of the obtained fiber-reinforced composite material are shown in Table 1.
（実施例５）
炭素繊維含有量が４６．２重量％となるようにした以外は、実施例２と同様にして繊維強化複合材料を得た。得られた繊維強化複合材料の特性を表１に示す。
(Example 5)
A fiber-reinforced composite material was obtained in the same manner as in Example 2 except that the carbon fiber content was adjusted to 46.2% by weight. The characteristics of the obtained fiber-reinforced composite material are shown in Table 1.
（実施例６）
炭素繊維含有量が４６．２重量％となるようにした以外は、実施例３と同様にして繊維強化複合材料を得た。得られた繊維強化複合材料の特性を表１に示す。
(Example 6)
A fiber-reinforced composite material was obtained in the same manner as in Example 3 except that the carbon fiber content was adjusted to 46.2% by weight. The characteristics of the obtained fiber-reinforced composite material are shown in Table 1.
（実施例７）
炭素繊維含有量が１８．２重量％となるようにした以外は、実施例４と同様にして繊維強化複合材料を得た。得られた繊維強化複合材料の特性を表１に示す。
(Example 7)
A fiber-reinforced composite material was obtained in the same manner as in Example 4 except that the carbon fiber content was adjusted to 18.2% by weight. The characteristics of the obtained fiber-reinforced composite material are shown in Table 1.
（実施例８）
炭素繊維含有量が４６．２重量％となるようにした以外は、実施例４と同様にして繊維強化複合材料を得た。得られた繊維強化複合材料の特性を表１に示す。
(Example 8)
A fiber-reinforced composite material was obtained in the same manner as in Example 4 except that the carbon fiber content was adjusted to 46.2% by weight. The characteristics of the obtained fiber-reinforced composite material are shown in Table 1.
（実施例９）
炭素繊維含有量が５７．１重量％となるようにした以外は、実施例４と同様にして繊維強化複合材料を得た。得られた繊維強化複合材料の特性を表１に示す。
(Example 9)
A fiber-reinforced composite material was obtained in the same manner as in Example 4 except that the carbon fiber content was set to 57.1% by weight. The characteristics of the obtained fiber-reinforced composite material are shown in Table 1.
（実施例１０）
炭素繊維含有量が７０．０重量％となるようにした以外は、実施例４と同様にして繊維強化複合材料を得た。得られた繊維強化複合材料の特性を表１に示す。
(Example 10)
A fiber-reinforced composite material was obtained in the same manner as in Example 4 except that the carbon fiber content was adjusted to 70.0% by weight. The characteristics of the obtained fiber-reinforced composite material are shown in Table 1.
（比較例１）
実施例１により得られたＰＡＮ系耐炎糸不織布を２４０℃に加熱したプレス機を用いて圧縮し、見かけ密度０．５４ｇ／ｃｍ３とした。次いで窒素雰囲気中１，５００℃の温度まで昇温して焼成し、目付７７０ｇ／ｍ２、密度０．３５ｇ／ｃｍ３の炭素繊維不織布とした以外は実施例１と同様にして繊維強化複合材料を得た。得られた繊維強化複合材料の特性を表２に示す。
(Comparative Example 1)
The PAN-based flame-resistant non-woven fabric obtained in Example 1 was compressed using a press machine heated to 240 ° C. to obtain an apparent density of 0.54 g / cm 3 . Next, the fiber-reinforced composite material was heated to a temperature of 1,500 ° C. in a nitrogen atmosphere and fired to obtain a carbon fiber non-woven fabric having a grain size of 770 g / m 2 and a density of 0.35 g / cm 3. Got The characteristics of the obtained fiber-reinforced composite material are shown in Table 2.
（比較例２）
ニードルパンチ時の針密度を２０本／ｃｍ２とした以外は、実施例１と同様にして繊維強化複合材料を得た。得られた繊維強化複合材料の特性を表２に示す。
(Comparative Example 2)
A fiber-reinforced composite material was obtained in the same manner as in Example 1 except that the needle density at the time of needle punching was 20 needles / cm 2 . The characteristics of the obtained fiber-reinforced composite material are shown in Table 2.
（比較例３）
実施例１により得られた耐炎糸を窒素雰囲気中１，５００℃の温度まで昇温して焼成して炭素繊維（炭素繊維の密度：１．８０ｇ／ｃｍ３）を得た。次いで、炭酸水素アンモニウム水溶液（０．１モル／リットル）中に浸漬し、７６クーロン／ｇの電気量となるように電解酸化処理を行い、水洗および乾燥を行ったものを長さ５ｍｍにカットし、チョップド炭素繊維を得た。チョップド炭素繊維を開綿機に投入して綿状の炭素繊維集合体を得た。この炭素繊維集合体をカーディング装置に投入し、密度０．０６ｇ／ｃｍ３のシート状の炭素繊維ウェブを作製した。この炭素繊維ウェブを目付７７０ｇ／ｍ２になるように重ねて用いた以外は実施例１と同様にして繊維強化複合材料を得た。得られた繊維強化複合材料の特性を表に示す。
(Comparative Example 3)
The flame-resistant yarn obtained in Example 1 was heated to a temperature of 1,500 ° C. in a nitrogen atmosphere and fired to obtain carbon fibers (carbon fiber density: 1.80 g / cm 3 ). Next, it was immersed in an aqueous solution of ammonium hydrogen carbonate (0.1 mol / liter), subjected to electrolytic oxidation treatment so as to have an electric energy of 76 coulombs / g, washed with water and dried, and cut into a length of 5 mm. , Chopped carbon fiber was obtained. The chopped carbon fibers were put into a cotton opener to obtain a cotton-like carbon fiber aggregate. This carbon fiber aggregate was put into a carding apparatus to prepare a sheet-shaped carbon fiber web having a density of 0.06 g / cm 3 . A fiber-reinforced composite material was obtained in the same manner as in Example 1 except that the carbon fiber webs were used in layers so as to have a basis weight of 770 g / m 2 . The characteristics of the obtained fiber-reinforced composite material are shown in the table.
（比較例４）
比較例３により得られた炭素繊維を平均繊維長５１ｍｍにカットし、炭素繊維含有量が３３．３重量％となるようにカット長５１ｍｍのポリプロピレンステープルファイバー（（株）トーア紡製）を混ぜて開綿機に投入して混綿し、炭素繊維とポリプロピレンからなる綿状の混合繊維集合体を得た。この混合繊維集合体をカーディング装置に投入し、シート状の混合繊維ウェブを作製した。次いで、炭素繊維分の目付が７７０ｇ／ｍ２となるように混合繊維ウェブを重ね実施例１と同様に針密度２００本／ｃｍ２でニードルパンチを行い、密度０．０８ｇ／ｃｍ３の炭素繊維とポリプロピレンの混合繊維不織布を得た。この混合繊維不織布を２３０℃に予熱したプレス機に配置して平板の金型を閉じ、次いで、３分間保持した後、２ＭＰａの圧力を付与してさらに３分間保持した。次いで、金型を全開放して炭素繊維不織布をスプリングバックさせた後、５０℃まで冷却して繊維強化複合材料を得た。得られた繊維強化複合材料の特性を表２に示す。
(Comparative Example 4)
The carbon fibers obtained in Comparative Example 3 were cut to an average fiber length of 51 mm, and polypropylene staple fibers (manufactured by Toa Spinning Co., Ltd.) having a cut length of 51 mm were mixed so that the carbon fiber content was 33.3% by weight. It was put into a cotton opener and mixed to obtain a cotton-like mixed fiber aggregate composed of carbon fiber and polypropylene. This mixed fiber aggregate was put into a carding apparatus to prepare a sheet-shaped mixed fiber web. Next, the mixed fiber webs were stacked so that the carbon fiber content had a texture of 770 g / m 2, and needle punching was performed at a needle density of 200 lines / cm 2 in the same manner as in Example 1, and carbon fibers having a density of 0.08 g / cm 3 were performed. And polypropylene mixed fiber non-woven fabric was obtained. The mixed fiber non-woven fabric was placed in a press machine preheated to 230 ° C. to close the flat die, and then held for 3 minutes, and then a pressure of 2 MPa was applied to hold the mixed fiber non-woven fabric for another 3 minutes. Next, the mold was fully opened to spring back the carbon fiber non-woven fabric, and then cooled to 50 ° C. to obtain a fiber-reinforced composite material. The characteristics of the obtained fiber-reinforced composite material are shown in Table 2.
（比較例５）
炭素繊維含有量が９．５重量％となるようにした以外は、実施例４と同様にして繊維強化複合材料を得た。得られた繊維強化複合材料の特性を表２に示す。
(Comparative Example 5)
A fiber-reinforced composite material was obtained in the same manner as in Example 4 except that the carbon fiber content was set to 9.5% by weight. The characteristics of the obtained fiber-reinforced composite material are shown in Table 2.
（比較例６）
炭素繊維含有量が８０．０重量％となるようにした以外は、実施例４と同様にして繊維強化複合材料を得た。得られた繊維強化複合材料は炭素繊維不織布へのポリプロピレン樹脂の付着状態が不均一で未含浸部分も見られた。得られた繊維強化複合材料の特性を表２に示す。
(Comparative Example 6)
A fiber-reinforced composite material was obtained in the same manner as in Example 4 except that the carbon fiber content was set to 80.0% by weight. In the obtained fiber-reinforced composite material, the state of adhesion of polypropylene resin to the carbon fiber non-woven fabric was non-uniform, and unimpregnated portions were also observed. The characteristics of the obtained fiber-reinforced composite material are shown in Table 2.
１ 繊維強化複合材料
２ 湾曲した炭素繊維
３ 熱可塑性樹脂
４ 束状部位
1 Fiber reinforced composite material 2 Curved carbon fiber 3 Thermoplastic resin 4 Bundled part
Claims (3)
（１）捲縮を付与した炭素繊維前駆体繊維のウェブをニードルパンチにより絡合し、炭素繊維前駆体繊維不織布を得る工程、
（２）炭素繊維前駆体繊維不織布を不活性雰囲気下で焼成し、見かけ密度が０．１５ｇ／ｃｍ３未満の炭素繊維不織布を得る工程、
（３）炭素繊維不織布と熱可塑性樹脂のフィルムまたはシートとを重ね、熱可塑性樹脂の融点以上の温度において加圧成形により熱可塑性樹脂を溶融含浸する工程、
（４）熱可塑性樹脂の融点以上の温度において圧力を解放してスプリングバックさせた後に冷却する工程
をこの順に有する請求項１または２に記載の繊維強化複合材料。 at least,
(1) A step of entwining a web of carbon fiber precursor fibers with crimps by a needle punch to obtain a carbon fiber precursor fiber non-woven fabric.
(2) A step of calcining a carbon fiber precursor fiber non-woven fabric in an inert atmosphere to obtain a carbon fiber non-woven fabric having an apparent density of less than 0.15 g / cm 3 .
(3) A step of laminating a carbon fiber non-woven fabric and a film or sheet of a thermoplastic resin, and melt-impregnating the thermoplastic resin by pressure molding at a temperature equal to or higher than the melting point of the thermoplastic resin.
(4) The fiber-reinforced composite material according to claim 1 or 2, further comprising a step of releasing pressure at a temperature equal to or higher than the melting point of the thermoplastic resin to cause springback and then cooling.
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