JP2004019055A - Carbon fiber and thermoplastic resin composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin composition having high electroconductivity, moldability of a thin film (fluidity or the like at molding), quality of appearance and mechanical characteristics; and to provide a molded product of the resin composition. <P>SOLUTION: The carbon fiber has a bulk resistance within a range of 1.0-8.0 Ω when measured after 2 min from the start of the measurement of an electric resistance of a carbon fiber assembly obtained by packing 50 g assembly of the carbon fiber cut into 6 mm length in a cylindrical container and compressed by loading 50 N load thereon. The cylindrical container is a nonconductive container having the bottom part made of a copper plate and 55 mm inner diameter. In the method for inserting the carbon fiber into the cylindrical container, 50 g of the carbon fiber cut into 6 mm length is equally divided to 20 portions, and the divided fiber portions are inserted into the cylindrical container one by one. In the method of compression, the carbon fiber assembly in the container is compressed from the upper part by a copper disk with 47 mm outer diameter as a pressure plate. <P>COPYRIGHT: (C)2004,JPO

Description

・解析方法：透過法により得られた面指数（００２）のピークの半価幅か　らＳｃｈｅｒｒｅｒの次式を用いて結晶サイズを求めた。
【００６３】
Ｌ（ｈｋｌ）＝Ｋλ／β_０ＣＯＳθ_Ｂ
Ｌ（ｈｋｌ）：微結晶（ｈｋｌ）面に垂直な方向の平均の大きさ
Ｋ　：１．０
λ　：Ｘ線の波長
β_０：（β_Ｅ ^２ーβ_１ ^２）^１／２
β_Ｅ：見かけの半値幅（測定値）
β_１：１．０５×１０^−２ｒａｄ（装置定数）
θ_Ｂ：ブラッグ角
（４）炭素繊維の平均単繊維直径Ｄｆ
下記式によって算出した。
【００６４】
Ｄｆ＝［（Ｗ×４）／（Ｎ×ρｆ×１００×３．１４）］^１／２×１００００
Ｄｆ：平均単繊維直径（μｍ）
Ｗ　：１ｍあたりの繊維束重量（ｇ）
Ｎ　：繊維束中のフィラメント数（本）
ρｆ　　：繊維の比重
また、上記炭素繊維の平均単繊維直径Ｄｆは、下記の方法でも測定した。この方法は成形品中の炭素繊維の断面を観察して求める方法である。
【００６５】
・無作為に抽出した１００本の繊維断面から短径の判別可能な形状（円形、楕円形、前記形状の一部が切り欠かれた形状）を選択して以下により直径（μｍ）を算出した。
【００６６】
Ｄｆ＝Ｄｓの平均値
Ｄｆ：平均単繊維直径（μｍ）
Ｄｓ：短径（μｍ）
（５）炭素繊維表面のＥＳＣＡ（Ｏ／Ｃ）測定
Ｘ線光電子分光法（島津製作所（株）製ＥＳＣＡ−７５０）を用いて測定を行った。
【００６７】
（Ａ）まず、サイジング剤などを溶媒で除去した炭素繊維を銅製の試料支持台上に拡げて並べた後、光電子脱出角度を９０°とし、Ｘ線源としてＭｇＫα１、２を用い、試料チャンバー中を１．３×１０^−６Ｐａ（１×１０^−８Ｔｏｒｒ）に保つ。
【００６８】
（Ｂ）測定時の帯電に伴うピークの補正としてＣ_１Ｓの主ピークの運動エネルギー値Ｂ．Ｅ．を２８４．６ｅＶに合わせる。Ｃ_１Ｓピーク面積は、２８２〜２９６ｅＶの範囲で直線のベースラインを引くことにより求める。Ｏ_１Ｓピーク面積は、５２８〜５４０ｅＶの範囲で直線のベースラインを引くことにより求める。
【００６９】
（Ｃ）ここで表面酸素濃度（Ｏ／Ｃ）とは、前記Ｏ_１Ｓピーク面積とＣ_１Ｓピーク面積の比から、装置固有の感度補正値を用いて原子数比として算出する。
（６）体積固有電気抵抗ＶＲ
ファンゲートにて射出成形した幅１２．７ｍｍ×長さ６５ｍｍ×厚さ２ｍｍの試験片を、絶乾状態（水分率０．１％以下）で測定に供した。まず、２面有る幅×厚さ面に導電性ペースト（藤倉化成株式会社製ドータイト）を塗布し、十分に導電性ペーストを乾燥させてから、その両面を電極に圧着し、電極間の電気抵抗値をデジタルマルチメーター（ＦＬＵＫＥ社製）にて測定する。前記電気抵抗値から測定機器、治具等の接触抵抗を減じた値に、導電性ペースト塗布面の面積を乗じ、次いで、その値を試験片長さで除したものを体積固有電気抵抗値とした（単位はΩ・ｃｍ）。なお射出成形は、シリンダ温度２８０℃、金型温度７０℃にて行った。
（７）曲げ剛性Ｅ
ＡＳＴＭ　Ｄ　７９０規格（スパン間距離Ｌ／板厚Ｄ＝１６）に準拠した曲げ剛性にて評価した（単位はＧＰａ）。用いた試験片の板厚は６ｍｍ厚で、水分率０．１％以下で試験に供した。なお射出成形は、シリンダ温度２８０℃、金型温度７０℃にて行った。
（８）ノッチ無しアイゾット衝撃
ＡＳＴＭ　Ｄ　２５６規格に準拠したモールドノッチ無しＩＺＯＤ衝撃強度にて評価した（単位はｋＪ／ｍ^２）。用いた試験片の板厚は３ｍｍ厚で、水分率０．１％以下で試験に供した。なお射出成形は、シリンダ温度２８０℃、金型温度７０℃にて行った。
（９）平均繊維長ｌｗ
算出は、成形品から炭素繊維のフィラメントのみを、任意に少なくとも４００本以上抽出し、その長さを１μｍ単位まで光学顕微鏡もしくは走査型電子顕微鏡にて測定して、下記の（１）式、もしくは（２）式を用いて算出した。但し、ｌｗは平均繊維長、Ｗｉは長さｌｉの炭素繊維の重量、Ｎｉは長さｌｉの炭素繊維の本数とする。
【００７０】
ｌｗ＝Σ（Ｗｉ×ｌｉ）／ΣＷｉ　…………（１）
（１）式は一定直径の炭素繊維に対しては、（２）式の様に表すことができる。
【００７１】
ｌｗ＝Σ（Ｎｉ×ｌｉ^２）／Σ（Ｎｉ×ｌｉ）……（２）
本発明では、ｌｗを測定する際の炭素繊維以外の成分を除去する方法として、炭素繊維以外の成分のみを溶解させ、含有される炭素繊維は溶解させない溶媒などに成形品を一定時間浸漬し、炭素繊維以外の成分を十分溶解させた後、濾過などにより炭素繊維と分離する手法を採用した。
【００７２】
実施例１ａ〜１ｄ
アクリロニトリル９９．４モル％とメタクリル酸０．６モル％からなる共重合体を用いて、乾湿式紡糸方法により単繊維デニール１ｄ、フィラメント数２４０００本のアクリル系繊維を得た。得られた繊維束を２４０〜２８０℃の空気中で、延伸比１．０５で加熱し、耐炎化繊維に転換し、ついで窒素雰囲気中で３００〜１８００℃で延伸比１．００で加熱しながら焼成し炭素繊維を得た。さらにこの炭素繊維を濃度０．１モル／ｌの硫酸水溶液で２〜１０クーロン／ｇの電流を流して電解処理し、さらにアルコール可溶ナイロン（アミランＣＭ４０００、東レ株式会社製）をサイジング剤として付与させた。サイジング剤付与はＣＭ４０００の１％メタノール溶液中に炭素繊維束を通した後、乾燥してメタノールを除去することにより行った。付着量は０．５％であった。このようにして得られた炭素繊維は、ストランド強度４５００ＭＰａ、弾性率２７０ＧＰａ、繊維断面直径は７μｍ、結晶サイズは２．３ｎｍであった。
【００７３】
上記の炭素繊維のＩＬＳＳとカッターで６ｍｍにカットして測定した嵩抵抗の結果を表１に示す。
【００７４】
上記炭素繊維を３０ｍ／分の速度で走行させながら連続的に処理した。
【００７５】
１３０℃加熱されたロール上で、テルペンフェノール重合体（単環式モノテルペンフェノールとフェノールの付加物、ヤスハラケミカル株式会社製ＹＰ９０２、重量平均分子量４６０）を炭素繊維に連続的に付与し、さらに１８０℃に加熱した雰囲気でしごきを加えて重合体を炭素繊維束中に含浸させた。
【００７６】
ナイロン樹脂ペレット（東レ株式会社製アミランＣＭ１００１　ηｒ＝約２．３５）を１軸押出機にて、その先端に取り付けたクロスヘッドダイ中に十分混練された状態で押し出すと同時に、前記重合体を含浸させた炭素繊維の連続糸も前記クロスヘッドダイ中に連続的に供給することによって、重合体を含浸した炭素繊維をナイロン樹脂が被覆したストランドを得た。さらに、その得られた樹脂ストランドを、カッターで７ｍｍの長さに切断して長繊維ペレットを得た。
【００７７】
得られた長繊維ペレットとナイロン樹脂ペレットとを乾燥後の成形品中の炭素繊維含有量は２７重量％となるようにドライブレンドし、８０℃にて５時間以上真空中で乾燥させた後、（１）〜（９）項記載の各試験の射出成形に供した。結果を表１に示す。
【００７８】
実施例２
実施例１のアクリル繊維束を窒素雰囲気中で３００〜１３００℃で焼成した以外は実施例１と同様にして電解電気量を２クーロン／ｇで炭素繊維を得た。このようにして得られた炭素繊維は、ストランド強度４９００ＭＰａ、弾性率２３０ＭＰａ繊維断面直径は７μｍ、結晶サイズは１．７ｎｍであった。
【００７９】
上記の炭素繊維を実施例１と同様な方法にて嵩抵抗とＩＬＳＳを測定した。さらに実施例１と同様な方法で長繊維ペレットを得、さらに実施例１と同様に射出成形して評価した。結果を表１に示す。
【００８０】
実施例３
アクリロニトリル９９．４モル％とメタクリル酸０．６モル％からなる共重合体を用いて、乾湿式紡糸方法により単繊維デニール０．８ｄ、フィラメント数２４０００本のアクリル系繊維を得た。得られた繊維束を２４０〜２８０℃の空気中で、延伸比１．０５で加熱し、耐炎化繊維に転換し、ついで窒素雰囲気中で３００〜２１００℃で延伸比１．０３で加熱しながら焼成し炭素繊維を得た。さらにこの炭素繊維を濃度０．１モル／ｌの硫酸水溶液で１０クーロン／ｇの電流を流して電解処理し、さらにサイジング剤を実施例１ａと同様な方法で付与した。このようにして得られた炭素繊維は、ストランド強度４５００ＭＰａ、弾性率３６０ＧＰａ、繊維断面直径は約５．３μｍ、結晶サイズは２．８ｎｍであった。
【００８１】
実施例１と同様な方法にて嵩抵抗とＩＬＳＳを測定した。さらに実施例１と同様な方法で長繊維ペレットを得、さらに実施例１と同様に射出成形して評価した。結果を表１に示す。
【００８２】
比較例１
実施例１にて電解処理の電流を流さずに処理した以外は実施例１と同様に実施した。結果を表１に示す。
【００８３】
比較例２
実施例１にて電解処理の電流を１２クーロンで処理した以外は実施例１と同様に実施した。以上の実施例と比較例の結果を表１に示す。
【００８４】
【表１】

【００８５】
表１の結果から、嵩抵抗が１〜８Ωの範囲外である比較例１〜２に比べて、範囲内である実施例１ａ〜３は、導電性が安定して高い成形品特性を得ることができ、しかも衝撃性や剛性も安定して高い。よって、その優位性は明らかである。
【００８６】
【発明の効果】
本発明によれば、高い導電性と力学特性を発現する繊維強化熱可塑性樹脂組成物およびその成形品を提供することができる。このような樹脂組成物およびその成形品は、特に電子機器類のハウジングなどを始め、前記特性を必要とする幅広い産業分野に好適に用いることができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a carbon fiber as a reinforcing fiber for exhibiting excellent electrical characteristics in a fiber-reinforced resin molded article, and a fiber-reinforced thermoplastic resin composition using the carbon fiber.
[0002]
[Prior art]
Composite materials reinforced with a thermoplastic resin with carbon fibers, glass fibers, etc. (hereinafter referred to as FRTP) are more impact-resistant and have higher impact resistance than composite materials reinforced with a thermosetting resin with these fibers (hereinafter referred to as FRTS). It has excellent moldability and is widely used in various industrial fields such as the space and aviation fields, the automobile industry field, the energy field, the sports equipment field, and the leisure equipment field, and further demand is expected. In particular, fiber-reinforced thermoplastic resin composite materials using carbon fibers (hereinafter referred to as CFRTP) are widely used in IC trays and personal computers, etc., which require electromagnetic shielding and antistatic properties because the carbon fiber substrate is conductive. It is used.
[0003]
Heretofore, carbon fibers have been mostly used in the field of composite materials, mainly in fields where mechanical properties are emphasized by taking advantage of their excellent properties. However, in recent years, it has been widely used in the field of electromagnetic wave shielding and the like as described above.
[0004]
In other words, Japanese Patent Application Laid-Open No. 61-23629 discloses an attempt to use carbon fibers as a material used for reinforcing the mechanical strength of a fiber-reinforced composite material, and to use the electrical characteristics of the carbon fibers together with other performance improvements. Is disclosed. However, a significant improvement in electrical properties cannot be obtained simply by mixing carbon fibers as a conductive substance in connection with other performance enhancements, and a large amount of carbon fibers must be mixed. Therefore, when a large amount of carbon fiber is kneaded and used, there are problems such as an increase in the viscosity of the mixture of the matrix resin and the carbon fiber at the time of melting and an increase in cost, and the use thereof is limited.
[0005]
As a method for producing such CFRTP, for example, Japanese Patent Publication No. 5-83044 discloses a method for producing compound pellets in which chopped carbon fiber and PBT resin are extruded with a short-screw extruder and then cut to a fixed length. ing. However, such compound pellets have a problem that the carbon fiber is cut short in the extrusion process and the carbon fiber is further cut in the injection molding process, so that the fiber length of the carbon fiber is shortened. There are limits to how to improve the mechanical properties.
[0006]
On the other hand, JP-B-63-37694 discloses a fiber reinforced structure in which aligned reinforcing filaments are impregnated with a thermoplastic resin. Further, Japanese Patent Publication No. 262012 discloses a pellet containing 30% by weight or more of reinforcing fibers arranged in parallel and having a length in the fiber arrangement direction of 3 to 60 mm (hereinafter referred to as a long fiber pellet). ). When this long fiber pellet is injection molded, the length of the reinforcing fiber contained in the molded product after molding is much longer than that of the compound pellet, and the impact resistance, bending elastic modulus, etc. of the molded product are improved. Is described.
[0007]
Such long fiber pellets have recently been used for applications requiring electromagnetic shielding properties and high rigidity (for example, personal computer housings) using carbon fibers, taking advantage of their features.
[0008]
In the above-mentioned prior example, there is no description about the performance and conductivity of the carbon fiber used, and it is clear whether it is preferable to use the carbon fiber having what kind of property, or what range the property is preferable. I have not done so. In particular, CFRTP, which is expanding to applications requiring conductivity, tends to have more important electrical characteristics than CFRTS using a thermosetting resin as a matrix, and there has been a demand for an immediate response.
[0009]
[Problems to be solved by the invention]
In view of the problems of the prior art, the present invention obtains a molded article made of a fiber-reinforced thermoplastic resin having high conductivity and mechanical properties, in particular, rigidity and the like, and quantifies the performance of the carbon fiber to be used. An object of the present invention is to stably obtain a fiber-reinforced thermoplastic resin molded article having excellent properties and rigidity.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, the present invention has the following configurations. That is, the carbon fiber of the present invention is a carbon fiber aggregate obtained by packing 50 g of an aggregate of carbon fibers cut to a length of 6 mm into a cylindrical container under the following conditions and compressing the same under a load of 50 N from above. The measurement of the electric resistance value is started, and the bulk electric resistance value two minutes after the measurement is within a range of 1.0 to 8.0Ω.
[0011]
Cylindrical container: Insulated cylindrical container with an inner diameter of 55 mm whose bottom is a copper plate
Method for charging carbon fiber into cylindrical container: 50 g of carbon fiber cut into 6 mm is divided into 20 equal parts, which are sequentially charged into the cylindrical container.
[0012]
Compression method: The carbon fiber aggregate in the container is compressed from above with a copper disk having an outer diameter of 47 mm as a pressure plate.
[0013]
Further, the carbon fiber for a thermoplastic resin composition of the present invention has a fiber length of 1 to 15 mm in the carbon fiber, and the thermoplastic resin composition of the present invention has at least , A thermoplastic resin and the carbon fiber.
[0014]
Further, the long fiber pellets of the present invention are constituted by the thermoplastic resin composition, and the injection molded article of the present invention is obtained by injection molding a pellet containing the long fiber pellets.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described.
[0016]
The carbon fiber used in the present invention has a bulk electric resistance in the range of 1.0 to 8.0 Ω when the aggregate is measured by the method described in the section of Examples described later. When the bulk electric resistance is 1.0Ω or less, it is preferable that the bulk electric resistance has a low value, but it is not preferable because the performance of the carbon fiber is impaired. For example, a carbon fiber having such a low bulk electric resistance generally has a large crystal size of the carbon fiber, and in this case, the amount of strain until fracture is caused by stress such as tensile or bending is reduced. Therefore, for example, when kneading with a screw or the like at the time of injection molding or the like, the carbon fibers are easily cut, so that the fiber length in the molded product is shortened, and the electromagnetic wave shielding property and the antistatic property are reduced. On the other hand, when the bulk electric resistance is larger than 8.0Ω, the electric resistance of the molded article when the carbon fibers are in contact with each other is large, so that the conductivity of the molded article is deteriorated, and the electromagnetic wave shielding property and the antistatic property are reduced. A more preferable bulk electric resistance is 2 to 7Ω, and further preferably 3 to 6Ω.
[0017]
The use of the carbon fiber in the present invention is exclusively for a thermoplastic resin composition.
[0018]
An object of the present invention is to provide a conductive resin composition having specific high conductivity, thin-wall moldability (particularly fluidity at the time of molding), and appearance quality when a carbon fiber having the above requirements is used. Is what we can do. That is, they have found that the use of carbon fibers having a bulk resistance in the above range achieves an excellent effect of simultaneously satisfying the above-described high conductivity, thin-wall moldability, and appearance quality. By measuring the bulk resistance in this way, without measuring various practical properties of the carbon fiber, it is possible to easily and accurately determine the properties. It is a meaningful index.
[0019]
Here, explaining the present invention from another viewpoint, it is preferable that the electric resistance of the carbon fiber surface be as low as possible, since the current tends to selectively flow on the carbon fiber surface. Further, when the carbon fibers come into contact with each other, a low contact resistance exerts a favorable effect on improving the conductivity of the molded article. The contact resistance varies greatly depending on the conductivity of the carbon fiber surface, surface irregularities, cross-sectional shape, surface condition of the sizing agent and the like, and this often affects the degree of conductivity of the molded product.
[0020]
However, in the carbon fiber manufacturing process, an electrolytic surface treatment is usually performed in an aqueous acid or alkaline electrolyte solution after the firing process. This is a treatment performed to improve the mechanical properties of the composite.However, in many cases, the surface state after the treatment has undergone some change, and the present inventors found that the crystallinity of the surface decreased. I suspected that. Such a decrease in crystallinity results in a decrease in conductivity and is not preferred.
[0021]
The carbon fiber of the present invention has an interlayer shear strength (ILSS) of 60 to 85 MPa as measured by the method described in the text as a surface property for satisfying both the mechanical properties and conductivity of the composite. That is, when the ILSS is 60 MPa or less, the conductivity of the molded product is good, but the adhesion between the carbon fiber and the resin is poor, and the mechanical characteristics are undesirably reduced. On the other hand, when the pressure is 85 MPa or more, the adhesiveness to the resin is good, but the crystallinity of the surface of the carbon fiber is reduced, so that the conductivity of the molded product is undesirably reduced. More preferably, it is 65 to 80 MPa.
[0022]
Further, the carbon fiber of the present invention has a crystal size measured by a wide-angle X-ray diffraction method in the range of 1.6 to 4.5 nm. When the crystal size is smaller than 1.6 nm, the crystal structure of the carbon fiber is not sufficiently developed, and mechanical properties originally expected of the carbon fiber such as tensile strength and bending strength are reduced. On the other hand, if the thickness exceeds 4.5 nm, the elastic modulus of the carbon fiber becomes high, and the amount of strain up to breakage due to stress such as tension and bending becomes small. Therefore, when kneading with a screw or the like at the time of injection molding, for example, In addition, as a result of the carbon fibers being easily cut, the fiber length in the molded product is shortened, and the conductivity and the antistatic property are reduced. More preferably, the crystal size of the carbon fiber is 1.8 to 3.0 nm, more preferably, 2.1 to 2.5 nm.
[0023]
The carbon fiber used in the present invention has a carbon / oxygen atomic ratio (O / C) of 0.02 to 0.2 on the carbon fiber surface measured by ESCA. When the (O / C) is less than 0.02, the amount of functional groups on the surface of the carbon fiber is small, and the adhesiveness between the carbon fiber and the thermoplastic resin is reduced. On the other hand, if it exceeds 0.2, the conductivity of the molded article made of the thermoplastic resin composition decreases, which is not preferable. It is more preferably in the range of 0.025 to 0.15, still more preferably 0.03 to 0.1, particularly preferably in the range of 0.03 to less than 0.05.
[0024]
The carbon fibers used in the present invention have an average diameter of the cross section of the single fiber (average single fiber diameter) in the range of 3 to 15 μm. If the average single fiber diameter is less than 3 μm, it becomes difficult to impregnate the thermoplastic resin into the carbon fiber bundle, which causes problems such as poor dispersibility of the carbon fiber in the molded product. On the other hand, when the average single fiber diameter exceeds 20 μm, it becomes difficult to obtain carbon fibers having excellent mechanical properties, and it is difficult to obtain a desired reinforcing effect. It is more preferably in the range of 4 to 11 μm, and still more preferably in the range of 5 to 8 μm. Note that the average single fiber diameter is obtained by mainly determining the diameter of the carbon fiber when the cross section is a perfect circle from the weight of the carbon fiber bundle, the number of the fiber bundles, and the specific gravity of the carbon fiber, but is not limited to this method. Details are as described in Examples.
[0025]
The carbon fiber of the present invention can be made of acrylic fiber, pitch, rayon, or the like as a raw material. In particular, acrylic carbon fiber produced from acrylic fiber containing acrylonitrile as a main component is excellent in industrial productivity. It is also preferable because of its excellent mechanical properties.
[0026]
The acrylic fiber is not particularly limited as long as it contains a monomer component that promotes a flame-resistant reaction, and itaconic acid, acrylic acid, methacrylic acid and their methyl esters, ethyl esters, propyl esters, alkali metal salts , Ammonium salts, allylsulfonic acid, methallylsulfonic acid, styrenesulfonic acid, and alkali metal salts thereof, but are not limited thereto. The spinning method is preferably a wet spinning method or a dry-wet spinning method, but is not particularly limited.
[0027]
The acrylic carbon fiber is obtained by heating an acrylic fiber obtained by polymerizing acrylonitrile as a main component in an air atmosphere at 200 to 400 ° C. to convert it into an oxidized fiber, and a non-flammable process such as nitrogen, helium, and argon. It is obtained by passing through a carbonization step in which carbonization is performed by heating at an even higher temperature in an active atmosphere (the flameproofing step and the carbonization step are collectively referred to as a firing step). The carbon fiber used in the present invention renders the acrylic fiber flame resistant and then carbonizes. It is preferable to employ 1200 to 2200 ° C. as the carbonization temperature. Preferably it is 1500-2100 degreeC.
[0028]
The acrylic carbon fiber preferably has an interlaminar shear strength (ILSS) in the range of 60 to 85 MPa and a strand tensile modulus in the range of 230 to 400 GPa. That is, when the ILSS is 60 MPa or less, the conductivity of the molded product is good, but the adhesion between the carbon fiber and the resin is poor, and the mechanical characteristics are undesirably reduced. On the other hand, when the pressure is 85 MPa or more, the adhesiveness to the resin is good, but the crystallinity of the surface of the carbon fiber is reduced, so that the conductivity of the molded product is undesirably reduced. More preferably, it is 65 to 80 MPa. On the other hand, if the strand tensile modulus is less than 230 GPa, the crystal structure of the carbon fiber may not be sufficient and the mechanical performance of the molded product is poor and the conductivity is also poor, which is not preferable. At 400 GPa or more, as described above, since the crystal size of the carbon fiber becomes large and the amount of strain until breaking due to stress such as tensile and bending becomes small, for example, when kneading with a screw or the like at the time of injection molding In addition, as a result of the carbon fibers being easily cut, the fiber length in the molded article is shortened, and as a result, the conductivity is lowered, which is not preferable. More preferably, it is 250 to 300 GPa.
[0029]
When the carbon fiber of the present invention is used as a carbon fiber for a thermoplastic resin composition, the length of the carbon fiber is preferably in the range of 1 to 15 mm. When the length is shorter than 1 mm, the length of the carbon fiber in the molded product is short when kneaded with a resin, formed into a pellet, and injected, extruded, or the like, and the conductivity and mechanical properties may be reduced. If the length is longer, the fluidity when the pellets are melted and injection-molded is poor, resulting in poor appearance of the molded product, and reduced conductivity and mechanical properties due to reduced dispersibility of carbon fibers.
[0030]
The use of the carbon fiber of the present invention is to form a thermoplastic resin composition solely with a thermoplastic resin. The carbon fiber of the present invention is preferably contained in the thermoplastic resin composition in a range of 10 to 60% by weight. If the amount is less than 10% by weight, the strength, rigidity and conductivity, especially the electromagnetic wave shielding properties of the resin composition and the molded product thereof may be reduced. If the amount exceeds 60% by weight, the fluidity at the time of molding decreases. This is because the mold cavity may not be completely filled with the resin composition. It is more preferably in the range of 15 to 40% by weight, and still more preferably 18 to 30% by weight.
[0031]
In order to impart high mechanical properties, the tensile elongation at break is 1.5% or more, more preferably 1.7% or more, even more preferably 1.9% or more. It is preferable to use carbon fiber. The tensile elongation at break of the carbon fiber used in the present invention has no upper limit, but is generally preferably less than 5%.
[0032]
As the surface treatment, an electrolytic treatment is preferable. Examples of the electrolytic solution used for the electrolytic treatment include inorganic acids such as sulfuric acid, nitric acid, and hydrochloric acid, inorganic hydroxides such as sodium hydroxide, potassium hydroxide, and barium hydroxide, ammonia, and sodium carbonate, sodium hydrogen carbonate, and the like. And aqueous solutions of organic salts such as sodium acetate and sodium benzoate, and potassium salts, barium salts or other metal salts thereof, and ammonium salts, and organic compounds such as hydrazine. Of these, inorganic acids are preferred as the electrolytic solution, and sulfuric acid and nitric acid are preferably used. The degree of the electrolytic treatment can control the (O / C) of the carbon fiber surface by setting the amount of electricity flowing in the electrolytic treatment.
[0033]
The carbon fibers of the present invention include coupling agents such as silane coupling agents, aluminate coupling agents, titanate coupling agents, urethane resins, epoxy resins, ester resins, styrene resins, olefin resins, and amide resins. It may be treated with a sizing agent such as a resin, a phenolic copolymer such as terpene / phenol, or a liquid crystalline resin.
[0034]
Examples of the thermoplastic resin preferably used in the present invention include polyamides (eg, nylon 6, nylon 66, nylon 11, nylon 12, nylon 610, nylon 612, nylon 6I, nylon 6T, nylon 9T) and copolymerized polyamides thereof. (Including liquid crystalline polyamide), polyester (polyethylene terephthalate, polybutylene terephthalate, etc.) and their copolyesters (including liquid crystalline polyester), polycarbonate, acrylonitrile / butadiene / styrene copolymer (abbreviation: ABS), acrylonitrile / styrene Copolymer (abbreviation: AS), polyolefin (polyethylene, polypropylene, etc.), polystyrene, polyetherimide, polysulfone, polyethersulfone, polyphenylene sulfide, poly E two alkylene oxide, polyether ether ketone, and a polymer alloy including a combination thereof, can be used almost all thermoplastic resins. Among them, polyamide, polycarbonate, ABS and polyphenylene oxide are preferred.
[0035]
Further, according to the necessity of improving impact resistance, one or more kinds of mixtures selected from elastomers such as olefin copolymers, polyester polyether elastomers and polyester polyester elastomers are added to obtain desired properties. Can be used. Further, depending on required properties such as moldability, heat resistance and low water absorption, these copolymers and resins obtained by mixing two or more kinds thereof can be used in the present invention. Further, in order to further improve impact resistance, etc., a resin obtained by adding an elastomer or a rubber component to the above resin, or a resin whose terminal group is modified or sealed for controlling compatibility when mixing the resin, or the like. Are also included in the present invention.
[0036]
Such a resin composition may contain, depending on its purpose, a filler, a flame retardant other than the present invention, a flame retardant auxiliary, a pigment, a dye, a lubricant, a mold release agent, a compatibilizer, a dispersant, a crystal nucleating agent, and a plastic nucleating agent. Agents, heat stabilizers, antioxidants, anticolorants, ultraviolet absorbers, flow modifiers, foaming agents, antibacterial agents, vibration dampers, deodorants, slidability modifiers, conductivity improvers, electrification Optional additives such as inhibitors and stiffeners can be used.
[0037]
The form of the resin composition of the present invention is preferably a material that can be molded by a press molding machine or an injection molding machine as a molding material. In particular, it is preferable to use pellets for injection molding.
[0038]
As the injection molding pellets, preferably, a compound obtained by melt-kneading and extruding carbon fiber and a thermoplastic resin (and additives as necessary) with a single-screw or twin-screw extruder, and further cutting as necessary. There is a pellet or a long fiber pellet obtained by coating or impregnating a carbon fiber bundle with a thermoplastic resin and cutting the molding material to an appropriate length with a substantially same cross-sectional shape as appropriate according to a molding method.
[0039]
In order for the molded article formed by molding the resin composition of the present invention, particularly the injection molded pellet, to have both conductivity and mechanical properties (strength, rigidity, impact strength, etc.), the length of the carbon fiber in the molded article is required. Although it is effective to increase the length, it is desirable to take the form of long fiber pellets among the aforementioned pellets in order to obtain conductivity and mechanical properties that cannot be obtained with compound pellets.
[0040]
The long fiber pellets referred to in the present invention are, for example, as shown in JP-B-63-37694, in which the fibers are arranged substantially parallel to the longitudinal direction of the pellets, and the length of the fibers in the pellet is substantially the same as the pellet length. , Or higher. The length is preferably between 1 and 15 mm.
[0041]
As a method of impregnating the resin into the reinforcing fiber bundle when producing long fiber pellets, for example,
(1) a method of impregnating each component of the present invention such as a resin through a reinforcing fiber bundle in an impregnation tank containing a resin emulsion, suspension, solution or melt;
(2) a method of impregnating each component of the present invention such as resin by heating the resin powder and the like through a reinforcing fiber bundle to penetrate the reinforcing fiber bundle into a state where the resin powder and the like are dispersed by vibration or gas;
(3) a method of impregnating each component of the present invention such as a resin while pulling out a reinforcing fiber bundle using a crosshead die extruding a molten resin;
Although a known impregnation method such as that described above can be used, it is preferable to use the impregnation method described in (3) above in order to uniformly and desirably mix the components of the present invention.
[0042]
More preferably, at least the reinforcing resin bundled carbon fiber as described in Japanese Patent Application Laid-Open No. 10-138379 has a higher mixing ratio than the thermoplastic resin (hereinafter referred to as a main thermoplastic resin) having the largest amount of the thermoplastic resin. It is a core-sheath type long-fiber pellet comprising a core made of a composite impregnated with a low-viscosity resin (hereinafter, referred to as a low-viscosity resin) and a sheath made of a main thermoplastic resin. In the case of the core-sheath type long fiber pellet, the reinforcing fiber bundle is made of a low-viscosity resin (the viscosity difference is preferably 50 to 500 Pa · s, and the viscosity is 10³s^-1The melt viscosity at 240 ° C. is measured by a capillary rheometer in advance), and the mixture is preliminarily impregnated (the content in the resin is preferably 0.1 to 20% by weight), and a composite of carbon fiber and the low-viscosity resin is prepared. It is preferable that the coating is at least coated with a main thermoplastic resin. Preferably, the composite has a carbon fiber surface coated with the low-viscosity resin.
[0043]
Here, the low-viscosity resin is a resin that promotes the impregnation of the carbon fiber with the main thermoplastic resin, such as an epoxy resin, an alcohol-soluble or water-soluble polyamide resin or a polyester resin, and a thermoplastic resin. Also low-molecular-weight thermoplastic resins, phenolic resins (for example, phenolic resins such as novolak phenol and cresol phenol, for example, modified phenolic resins such as alkylbenzene-modified, cashew-modified and terpene-modified, phenolic copolymer resins, etc.), and liquid crystalline resins. Can be mentioned.
[0044]
The blending form of the pellets of the present invention is not particularly limited, but preferably, the low-viscosity resin is impregnated with a reinforcing fiber bundle (carbon fiber) to form a composite, and then the composite is coated with a main thermoplastic resin. It is preferable that the obtained long fiber pellets are used alone, or the long fiber pellets are dry-blended with a molding material containing the main thermoplastic resin, for example, a thermoplastic resin pellet.
[0045]
In the long fiber pellets of the present invention, the number of filaments of carbon fibers constituting the pellets is preferably in the range of 3,000 to 150,000. If the number is less than 3,000, the productivity may be low and the cost may increase. In addition, due to the thinness in the step of coating the carbon fiber bundle, a process trouble due to fluff or the like may occur in the coating step. If it exceeds 150,000, the strand becomes thick, so that it becomes difficult to impregnate with the thermoplastic resin and the resin having a low melt viscosity, and the surface properties, mechanical properties and conductivity of the molded product may be reduced. . More preferably, the number is from 10,000 to 100,000.
[0046]
The molded article of the present invention is a molded article obtained by using the above-mentioned pellets for injection molding. In this case, it is also preferable to dry blend a thermoplastic resin with the pellets for injection molding of the present invention in order to obtain a desired carbon fiber content.
[0047]
In addition, pellets to be dry-blended may contain talc, carbon fiber, and the like, in addition to the thermoplastic resin, as long as the effects of the present invention are not hindered. Also in the mixed pellets after dry blending, the average value of the characteristics (crystal size, atomic ratio of carbon and oxygen, etc.) of the carbon fibers contained therein is within the range of the characteristics of the carbon fibers of the present invention (crystal size). Is preferably 1.6 to 3 nm, and the atomic ratio of carbon and oxygen (O / C) is 0.02 to 0.2).
[0048]
As described above, it is effective to increase the length of carbon fibers in a molded product to simultaneously achieve conductivity and mechanical properties (especially stiffness and impact strength). However, in this case, the effects of the molding conditions, the injection molding machine, and the mold must be considered. As for the molding conditions, the lower the back pressure, the lower the injection speed, and the lower the screw rotation speed, the longer the length of the carbon fiber in the molded product tends to be. It is preferable to set the temperature as low as possible so as not to be stable. Desirable back pressure is 0.1-1 MPa. As for the injection molding machine, there is a tendency that the longer the diameter of the nozzle, the smaller the taper angle of the nozzle, the deeper the screw groove depth, and the lower the compression ratio, the longer the carbon fiber in the molded product. As for the mold, as the diameter of the sprue increases and the diameter of the gate increases, the length of the carbon fiber in the molded article tends to increase.
[0049]
As described above, in order for the molded article of the present invention to have both high electrical conductivity and mechanical properties, the carbon fiber as a reinforcing material contained in the molded article must have a weight average fiber length (lw) of 0.25. １1 mm, preferably 0.3-1 mm, more preferably 0.35-1 mm. Further, the fiber length of at least 3% by weight of the total amount of carbon fibers in the molded product is preferably in the range of 1 to 15 mm. More preferably, at least 5% by weight of the total amount of carbon fibers is in the range of 1 to 10 mm, and even more preferably, at least 5% by weight of the total amount of carbon fibers is in the range of 1 to 7 mm. Particularly preferably, at least 8% by weight of the total amount of carbon fibers is in the range from 1 to 7 mm.
[0050]
In the present invention, it is preferable that the CFRTP molded product molded by a press or an injection molding machine has a volume specific electric resistance VR of 100 Ω · cm or less, particularly of a molded product molded by injection molding. This is because the present invention can maintain the length of the carbon fiber in the molded article long by injection molding the long fiber pellets. To provide. In particular, when the compounding amount of the carbon fiber is as low as 20% by weight or less, the effect of expressing the conductivity is remarkable as compared with the ordinary pellets. The use of long fiber pellets is very effective in achieving high conductivity. Of course, the effect of improving the mechanical properties is also enormous. A more desirable volume specific electric resistance value is 50 Ω · cm or less. Particularly, when the compounding ratio of the carbon fiber is 20% by weight or more, the volume specific electric resistance is 10 Ω · cm or less. Preferably it is 5 Ω · cm or less.
[0051]
In the present invention, the electromagnetic wave shielding property at this time is preferably 20 dB or more, and more preferably 25 dB or more. In addition, the electromagnetic wave shielding property is measured according to the Advantest method, and is a numerical value in dB (unit: dB) representing an attenuation amount of the flat plate having a thickness of 1 mm when the flat plate is irradiated with an electromagnetic wave of 1 GHz.
[0052]
Since it has high rigidity due to carbon fiber, the bending stiffness at a plate thickness of 6 mm is in the range of 8 to 40 GPa according to ASTM D 790 standard (distance between spans L / plate thickness D = 16), preferably 10 GPa. It is good to use as a molded product in the range of -30 GPa, particularly preferably in the range of 15-25 GPa.
[0053]
Since the thermoplastic resin composition and the pellets for injection molding of the present invention have both thin moldability (fluidity during molding) and conductivity, it is possible to make the wall thickness smaller than conventional molded products, Most preferably, it is used as a thin molded product having a thickness in the range of 0.3 to 4 mm. More preferably, it is used as a thin molded product having a thickness of 0.5 to 3 mm, more preferably 0.6 to 2 mm, so that the effects of the present invention can be more exhibited. Particularly preferably, it is used as a thin-walled molded product having a wall thickness of 0.7 to 1.6 mm. Here, the thickness of the molded product refers to the thickness of a flat portion of the molded product excluding protrusions such as a rib portion and a boss portion.
[0054]
The present invention has determined that when a carbon fiber having such characteristics is used, it is possible to provide a conductive resin composition having both specific high conductivity and thin-wall moldability (particularly fluidity during molding). Things. That is, a carbon fiber having a specific range of bulk resistance and ILSS and strand tensile modulus by a measurement method described later in the Examples section achieves an excellent effect of simultaneously satisfying the high conductivity and thin-wall moldability. It was found that. The bulk resistance, the ILSS and the strand tensile modulus can be easily and accurately selected without measuring various properties of the carbon fiber, and are therefore extremely significant from an industrial viewpoint.
[0055]
The above-mentioned molded article of the present invention is particularly preferably a polyamide molded article whose matrix is a polyamide resin.
[0056]
Examples of the use of the molded article in the present invention include members for electronic and electric devices, which are required to have moldability and mechanical properties (particularly rigidity) in a thin molded article. Since the molded article of the present invention can achieve high rigidity, light weight, electromagnetic wave shielding properties, and the like, it is effective for uses such as housings of portable electronic and electric devices. More specifically, it is preferred for housings for large displays, notebook computers, portable telephones, PHS, PDAs (portable information terminals such as electronic notebooks), video cameras, digital still cameras, portable radio cassette players, and the like. used.
[0057]
In addition, because of its high conductivity, it is possible to impart antistatic / discharge properties by adding a small amount of carbon fiber, and members requiring such properties, for example, IC trays, baskets for transporting silicon wafers, etc. It is also useful for adaptation.
[0058]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following Examples do not limit the present invention, and changes and implementations that do not depart from the gist of the preceding and following descriptions are all within the technical scope of the present invention. Is included.
[0059]
The evaluation items and the method for the present invention are described below. Table 1 summarizes the results of the various measurements.
(1) Bulk resistance measurement of carbon fiber aggregate
50 g of short carbon fiber cut into a length of 6 mm is divided into 20 equal parts in a cylindrical container having an inner diameter of 55 mm made of a copper plate, and the carbon fibers divided into 20 equal parts are sequentially shaken down into a cylindrical container, Next, a copper plate having an outer diameter of 47 mm was lowered from above as a pressure plate, a load of 50 N was applied to the carbon fiber aggregate, the resistance value between the two copper plates was measured while sandwiching and compressing, and the value 2 minutes after the start of the measurement was read. . A sample was taken three times for the same lot of carbon fiber, and the average value of the results measured for each sample was taken as the measured value. Using a digital multimeter (R6581 manufactured by Advantest) as a measuring device, the measurement was performed in an environment where the resistance between the copper plate electrodes was 0.001Ω, the ambient temperature was 23 ° C., and the relative humidity was 50%. The cylindrical container used was a container made of glass and having an insulating property.
(2) ILSS measurement
A carbon fiber bundle wound up to a predetermined thickness was placed in a mold, and 100 parts of an epoxy resin (Japan Epoxy Resin Co., trade name: Epicoat 828) and 3 parts of boron trifluoride / monomethylamine as a curing agent were mixed. The resin was poured into a mold and cured at 170 ° C. for 1 hour while being deaerated, and the cured product taken out of the mold was further heat-treated at 170 ° C. for 2 hours. This was cut in the length direction to prepare a test piece having a width of 5.9 mm, a thickness of 2.5 mm, a length of 190 mm and a carbon fiber volume content of 60 vol%. The length and volume content of the test piece used were the values actually measured. This test piece was evaluated by a measuring method according to ASTM D2344 (unit is MPa).
(3) Crystal size of carbon fiber
(A) When the carbon fiber is in the form of a filament
A carbon fiber was cut into a length of 4 cm, 20 mg was weighed, and a prism was prepared with a mold (length 3 cm, width 1 mm, depth 1 mm) and a collodion-alcohol solution to prepare a measurement sample.
[0060]
(B) When the carbon fiber length is around 10 mm
5 mg of carbon fiber was weighed, and a prism was prepared using a mold (length: 3 cm, width: 1 mm, depth: 1 mm) and a collodion-alcohol solution to prepare a measurement sample.
[0061]
It was measured under the following conditions by a transmission method and a wide-angle X-ray diffraction method.
[0062]

Analysis method: From the half width of the peak of the plane index (002) obtained by the transmission method, the crystal size was determined using Scherrer's formula below.
[0063]
L (hkl) = Kλ / β₀COSθ_B
L (hkl): average size in the direction perpendicular to the microcrystal (hkl) plane
K: 1.0
λ: X-ray wavelength
β₀: (Β_E ²-Β₁ ²)^1/2
β_E: Apparent half width (measured value)
β₁: 1.05 × 10^-2rad (equipment constant)
θ_B: Bragg angle
(4) Average single fiber diameter Df of carbon fiber
It was calculated by the following equation.
[0064]
Df = [(W × 4) / (N × ρf × 100 × 3.14)]^1/2× 10000
Df: average single fiber diameter (μm)
W: Weight of fiber bundle per meter (g)
N: Number of filaments in fiber bundle (number)
ρf: specific gravity of fiber
The average single fiber diameter Df of the carbon fibers was also measured by the following method. This method is a method of observing a cross section of a carbon fiber in a molded article and obtaining the same.
[0065]
A shape (circular, elliptical, or a shape in which a part of the shape was cut out) from which a short diameter could be determined was selected from the cross sections of 100 randomly extracted fibers, and the diameter (μm) was calculated as follows. .
[0066]
Df = average value of Ds
Df: average single fiber diameter (μm)
Ds: short diameter (μm)
(5) ESCA (O / C) measurement of carbon fiber surface
The measurement was performed using X-ray photoelectron spectroscopy (ESCA-750, manufactured by Shimadzu Corporation).
[0067]
(A) First, carbon fibers from which a sizing agent or the like has been removed with a solvent are spread and arranged on a copper sample support, the photoelectron escape angle is set to 90 °, and MgKα1 and 2 are used as X-ray sources. Is 1.3 × 10^-6Pa (1 × 10^-8Torr).
[0068]
(B) As a correction of the peak due to the charging during the measurement, C_1SKinetic energy value of the main peak of B. E. FIG. To 284.6 eV. C_1SThe peak area is determined by drawing a linear base line in the range of 282 to 296 eV. O_1SThe peak area is determined by drawing a linear baseline in the range of 528 to 540 eV.
[0069]
(C) Here, the surface oxygen concentration (O / C)_1SPeak area and C_1SFrom the ratio of the peak areas, it is calculated as an atomic ratio using a sensitivity correction value unique to the apparatus.
(6) Volume specific electric resistance VR
A test piece having a width of 12.7 mm, a length of 65 mm and a thickness of 2 mm, which was injection-molded with a fan gate, was subjected to measurement in a completely dry state (water content: 0.1% or less). First, a conductive paste (Dotite manufactured by Fujikura Kasei Co., Ltd.) is applied to the width × thickness surface having two surfaces, and the conductive paste is sufficiently dried. The value is measured with a digital multimeter (manufactured by FLUKE). The value obtained by subtracting the contact resistance of the measuring instrument and the jig from the electric resistance value was multiplied by the area of the conductive paste applied surface, and then the value was divided by the length of the test piece to obtain a volume specific electric resistance value. (Unit is Ω · cm). The injection molding was performed at a cylinder temperature of 280 ° C. and a mold temperature of 70 ° C.
(7) Flexural rigidity E
The bending rigidity was evaluated according to the ASTM D 790 standard (distance between spans L / plate thickness D = 16) (unit: GPa). The test specimens used were 6 mm thick and had a moisture content of 0.1% or less. The injection molding was performed at a cylinder temperature of 280 ° C. and a mold temperature of 70 ° C.
(8) Izod impact without notch
Evaluated by IZOD impact strength without mold notch conforming to ASTM No. 256 standard (unit is kJ / m²). The test specimens used were 3 mm thick and had a moisture content of 0.1% or less. The injection molding was performed at a cylinder temperature of 280 ° C. and a mold temperature of 70 ° C.
(9) Average fiber length lw
For the calculation, at least 400 or more carbon fiber filaments are arbitrarily extracted from the molded article, and the length is measured with an optical microscope or a scanning electron microscope to a unit of 1 μm, and the following formula (1) or It was calculated using equation (2). Here, lw is the average fiber length, Wi is the weight of the carbon fiber having the length li, and Ni is the number of carbon fibers having the length li.
[0070]
lw = {(Wi × li) / {Wi}... (1)
Equation (1) can be expressed as equation (2) for a carbon fiber having a constant diameter.
[0071]
lw = Σ (Ni × li²) / Σ (Ni × li) ... (2)
In the present invention, as a method of removing components other than carbon fibers when measuring lw, only the components other than carbon fibers are dissolved, and the contained carbon fibers are immersed in a solvent or the like that does not dissolve the molded article for a certain time, After sufficiently dissolving the components other than the carbon fiber, a method of separating from the carbon fiber by filtration or the like was employed.
[0072]
Examples 1a to 1d
Using a copolymer consisting of 99.4 mol% of acrylonitrile and 0.6 mol% of methacrylic acid, an acrylic fiber having 1 d of single fiber denier and 24,000 filaments was obtained by a dry-wet spinning method. The obtained fiber bundle is heated in air at 240 to 280 ° C. at a draw ratio of 1.05 to convert it into oxidized fiber, and then heated at 300 to 1800 ° C. in a nitrogen atmosphere at a draw ratio of 1.00. It was calcined to obtain a carbon fiber. Further, the carbon fiber is subjected to electrolytic treatment with a 0.1 mol / l aqueous sulfuric acid solution at a current of 2 to 10 coulombs / g, and alcohol-soluble nylon (Amilan CM4000, manufactured by Toray Industries, Inc.) is applied as a sizing agent. I let it. The sizing agent was applied by passing a carbon fiber bundle through a 1% methanol solution of CM4000 and then drying to remove methanol. The adhesion amount was 0.5%. The carbon fiber thus obtained had a strand strength of 4500 MPa, an elastic modulus of 270 GPa, a fiber cross-sectional diameter of 7 μm, and a crystal size of 2.3 nm.
[0073]
Table 1 shows the results of the bulk resistance measured by cutting the carbon fiber into 6 mm with the ILSS and the cutter.
[0074]
The carbon fibers were continuously treated while running at a speed of 30 m / min.
[0075]
On a roll heated at 130 ° C., a terpene phenol polymer (adduct of monocyclic monoterpene phenol and phenol, YP902 manufactured by Yasuhara Chemical Co., Ltd., weight average molecular weight 460) is continuously applied to the carbon fiber, and further 180 ° C. Ironing was performed in a heated atmosphere to impregnate the polymer into the carbon fiber bundle.
[0076]
A nylon resin pellet (Amilan CM1001１００ηr = about 2.35 manufactured by Toray Industries, Inc.) is extruded by a single screw extruder while being sufficiently kneaded into a crosshead die attached to the tip of the pellet, and at the same time, the polymer is impregnated. The continuous yarns of the carbon fibers thus obtained were also continuously supplied into the crosshead die to obtain a strand in which the carbon fibers impregnated with the polymer were covered with a nylon resin. Further, the obtained resin strand was cut into a length of 7 mm with a cutter to obtain a long fiber pellet.
[0077]
The obtained long fiber pellets and nylon resin pellets are dry-blended so that the carbon fiber content in the molded article after drying is 27% by weight, and dried in vacuum at 80 ° C. for 5 hours or more. The samples were subjected to injection molding in the tests described in (1) to (9). Table 1 shows the results.
[0078]
Example 2
Carbon fibers were obtained in the same manner as in Example 1 except that the acrylic fiber bundle of Example 1 was fired at 300 to 1300 ° C. in a nitrogen atmosphere, and the amount of electrolytic electricity was 2 coulombs / g. The carbon fiber thus obtained had a strand strength of 4900 MPa, an elastic modulus of 230 MPa, a fiber cross-sectional diameter of 7 μm, and a crystal size of 1.7 nm.
[0079]
The bulk resistance and ILSS of the carbon fiber were measured in the same manner as in Example 1. Further, long fiber pellets were obtained in the same manner as in Example 1, and injection molding was performed in the same manner as in Example 1 to evaluate. Table 1 shows the results.
[0080]
Example 3
Using a copolymer consisting of 99.4 mol% of acrylonitrile and 0.6 mol% of methacrylic acid, an acrylic fiber having a single fiber denier of 0.8 d and a filament number of 24,000 was obtained by a dry-wet spinning method. The obtained fiber bundle is heated in air at 240 to 280 ° C. at a draw ratio of 1.05 to convert it into oxidized fiber, and then heated at 300 to 2100 ° C. in a nitrogen atmosphere at a draw ratio of 1.03. It was calcined to obtain a carbon fiber. Further, the carbon fiber was subjected to an electrolytic treatment with a 0.1 mol / l aqueous solution of sulfuric acid at a current of 10 coulomb / g, and a sizing agent was applied in the same manner as in Example 1a. The carbon fiber thus obtained had a strand strength of 4500 MPa, an elastic modulus of 360 GPa, a fiber cross-sectional diameter of about 5.3 μm, and a crystal size of 2.8 nm.
[0081]
The bulk resistance and ILSS were measured in the same manner as in Example 1. Further, long fiber pellets were obtained in the same manner as in Example 1, and injection molding was performed in the same manner as in Example 1 to evaluate. Table 1 shows the results.
[0082]
Comparative Example 1
Example 1 was carried out in the same manner as in Example 1 except that the treatment was performed without passing the current for the electrolytic treatment. Table 1 shows the results.
[0083]
Comparative Example 2
Example 1 was carried out in the same manner as in Example 1 except that the current of the electrolytic treatment was 12 coulombs. Table 1 shows the results of the above examples and comparative examples.
[0084]
[Table 1]

[0085]
From the results in Table 1, it can be seen that Examples 1a to 3 in which the bulk resistance is within the range of 1 to 8 Ω are more stable than those of Comparative Examples 1 to 2 in which the conductivity is higher than that of Comparative Examples 1 and 2. And the impact and rigidity are stable and high. Therefore, its superiority is clear.
[0086]
【The invention's effect】
According to the present invention, it is possible to provide a fiber-reinforced thermoplastic resin composition exhibiting high electrical conductivity and mechanical properties, and a molded product thereof. Such a resin composition and a molded product thereof can be suitably used particularly in a wide range of industrial fields requiring the above-described properties, particularly for housings of electronic devices and the like.

Claims (13)

A carbon fiber aggregate 50 g cut to a length of 6 mm was packed in a cylindrical container under the following conditions, and a measurement of the electrical resistance value of the carbon fiber aggregate compressed by applying a load of 50 N from above was started. A carbon fiber, wherein the bulk electric resistance value after 2 minutes is in the range of 1.0 to 8.0Ω.
Cylindrical container: Insulating cylindrical container having a bottom part made of a copper plate and having an inner diameter of 55 mm Method of charging carbon fiber into cylindrical container: 50 g of carbon fiber cut to 6 mm is divided into 20 equal parts, which are sequentially charged into the cylindrical container I do.
Compression method: The carbon fiber assembly in the container is compressed from above with a copper disk having an outer diameter of 47 mm as a pressure plate. The carbon fiber according to claim 1, wherein an interlayer shear strength (ILSS) measured under the following conditions is in a range of 60 to 85 MPa.
Molding condition:
・ Resin: Epoxy resin Epicoat 828, curing agent Boron trifluoride monomethylamine ・ Carbon fiber volume content: 60 vol%
Curing condition: After heating at 170 ° C. for 1 hour, after-curing is heated at 170 ° C. for 2 hours Measurement condition: According to ASTM D2344 The crystal size of the carbon fiber measured by the wide-angle X-ray diffraction method is in the range of 1.6 to 4.5 nm, and the O / C measured by ESCA is in the range of 0.02 to 0.2. The carbon fiber according to claim 1, wherein the average single fiber diameter is in a range of 3 to 15 μm. The carbon fiber according to any one of claims 1 to 3, wherein the strand is an acrylic carbon fiber having a tensile elastic modulus in a range of 230 to 400 GPa. The carbon fiber for a thermoplastic resin composition according to any one of claims 1 to 4, wherein the fiber length has a length in a range of 1 to 15 mm. A thermoplastic resin composition comprising at least a thermoplastic resin and the carbon fiber according to any one of claims 1 to 4. The thermoplastic resin composition according to claim 6, wherein the carbon fiber is contained in the thermoplastic resin composition in a range of 10 to 60% by weight. A long-fiber pellet comprising the thermoplastic resin composition according to claim 6. At least, a composite containing a thermoplastic resin polymer having a lower melt viscosity than the carbon fiber and the thermoplastic resin, and the thermoplastic resin are arranged so as to be in direct contact with each other. 8. The long fiber pellet according to 8. The long fiber pellet according to claim 9, wherein the thermoplastic resin is arranged so as to cover the periphery of the composite. The long fiber pellet according to any one of claims 8 to 10, wherein the carbon fiber is constituted by a carbon fiber bundle having a number of filaments in the range of 3,000 to 150,000. An injection-molded product obtained by injection-molding a pellet containing at least the long fiber pellet according to any one of claims 8 to 11. The injection molded article according to claim 12, wherein the weight average fiber length lw of the carbon fiber is in a range of 0.25 to 1 mm.