JP2012241086A - Carbon fiber-reinforced thermoplastic resin composition, method for producing the composition, and injection molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon fiber-reinforced thermoplastic resin composition which has excellent conductivity and an elastic modulus in a well-balanced manner and further has satisfactory moldability.SOLUTION: The composition includes: a thermoplastic resin (A); carbon fiber (B); and conductive carbon black (C) having a dibutyl phthalate oil absorption amount of 150 ml/100 g or more. The content of the carbon fiber (B) is 35-56 mass%, the content of the conductive carbon black (C) is 4-20 mass%, and the total content of the carbon fiber (B) and the conductive carbon black (C) is 60 mass% or less.

Description

  The present invention relates to a carbon fiber reinforced thermoplastic resin composition, a method for producing the composition, and an injection-molded article comprising the composition.

Conventionally, a magnesium alloy has been frequently used for a casing of a mobile electronic device such as a mobile phone in terms of strength, specific gravity, electromagnetic wave shielding properties, and the like. However, in recent years, there has been a demand for further weight reduction of the housing, and the use of a resin instead of a magnesium alloy has been studied.
Among thermoplastic resins, aromatic polycarbonate resins are widely used in parts and casings of electric / electronic devices because they have a good balance between mechanical properties and dimensional stability. Also, in order to ensure rigidity during thin-wall molding, a thermoplastic resin may be blended with a fibrous filler such as carbon fiber or glass fiber in the thermoplastic resin, or in order to increase the conductivity of the molded product and obtain antistatic properties. In some cases, carbon fiber or conductive carbon black is blended into the glass. For example, Patent Document 1 discloses thermoplasticity in which 5 to 45 parts by weight of carbon fiber and 0.1 to 10 parts by weight of conductive carbon black are blended with 100 parts by weight of a resin component containing an aromatic polycarbonate resin. A resin composition is disclosed.

JP 2000-34408 A

  However, the thermoplastic resin composition described in Patent Document 1 has insufficient conductivity, and a molded article of this thermoplastic resin composition cannot exhibit high electromagnetic shielding properties. Further, this thermoplastic resin composition has a low elastic modulus, and is not suitable for use in a molded product that requires high rigidity such as a casing of a mobile electronic device.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a carbon fiber reinforced thermoplastic resin composition having a good balance of excellent conductivity and elastic modulus and good moldability.

The carbon fiber reinforced thermoplastic resin composition of the present invention contains a thermoplastic resin (A), carbon fiber (B), and conductive carbon black (C) having a dibutyl phthalate oil absorption of 150 ml / 100 g or more. The carbon fiber (B) content is 35 to 56% by mass, the conductive carbon black (C) content is 4 to 20% by mass, and the carbon fiber (B) and the conductive material are conductive. The total content of carbon black (C) is 60% by mass or less.
The thermoplastic resin (A) is preferably an amorphous thermoplastic resin.
The amorphous thermoplastic resin is preferably an aromatic polycarbonate resin.
The production method of the present invention is a production method of the carbon fiber reinforced thermoplastic resin composition, wherein the thermoplastic resin (A), the carbon fiber (B), and the conductive carbon black (C) are extruded. A kneading step of supplying to the machine and kneading, and in the kneading step, the carbon fiber (B) is transferred to the extruder from the downstream side of the thermoplastic resin (A) and the conductive carbon black (C). It is characterized by supplying.
The carbon fiber reinforced thermoplastic resin composition of the present invention is suitable for molding an injection molded product.

  The carbon fiber reinforced thermoplastic resin composition of the present invention has a good balance of excellent electrical conductivity and elastic modulus and good moldability.

Hereinafter, the present invention will be described in detail.
The carbon fiber reinforced thermoplastic resin composition of the present invention (hereinafter sometimes referred to as a resin composition) has a thermoplastic resin (A), carbon fiber (B), and dibutyl phthalate oil absorption of 150 ml / 100 g or more. Contains certain conductive carbon black (C).

<Resin composition>
[Thermoplastic resin (A)]
As the thermoplastic resin (A), an amorphous thermoplastic resin is preferable because of its excellent dimensional stability, and in particular, since it has a good balance between mechanical properties and dimensional stability, a dihydric phenol and a carbonate precursor are used. An aromatic polycarbonate resin obtained by reacting by a solution method or a melt method is preferably used. Hereinafter, the thermoplastic resin (A) may be referred to as component (A).

  Divalent phenols include 2,2-bis (4-hydroxyphenyl) propane (bisphenol A), bis (4-hydroxyphenyl) methane, and 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane. And bis (4-hydroxyphenyl) sulfone. One or more of these dihydric phenols can be used, but at least bisphenol A is preferably used.

  Examples of the carbonate precursor include carbonyl hydride, carbonyl ester, haloformate, and the like. Specifically, carbonic acid diesters such as diphenyl carbonate, dinaphthyl carbonate, bis (diphenyl) carbonate, dimethyl carbonate, diethyl carbonate, and dibutyl carbonate, phosgene And dihaloformates of dihydric phenols, and one or more of these can be used. As the carbonic acid diester, diphenyl carbonate is preferred.

When phosgene is used as the carbonate precursor, the reaction is usually carried out in the presence of an acid binder and a solvent to produce an aromatic polycarbonate resin.
As the acid binder, for example, an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide, or an amine compound such as pyridine is used. As the solvent, for example, a halogenated hydrocarbon such as methylene chlorobenzene chloride is used. In order to promote the reaction, a catalyst such as a tertiary amine or a quaternary ammonium salt may be used. The reaction temperature is usually 0 to 40 ° C., and the reaction time is several minutes to 5 hours.

When carbonic acid diester is used as the carbonate precursor and aromatic polycarbonate resin is produced by transesterification, it is produced by stirring a predetermined proportion of aromatic dihydroxy component and carbonic acid diester under an inert gas atmosphere. Distilling off alcohols or phenols.
The reaction temperature in this case varies depending on the boiling point of the alcohol or phenol produced, but is usually in the range of 120 to 300 ° C. The pressure in the reaction system is reduced from the initial stage of the reaction, and the reaction is completed while distilling alcohol or phenols.
In order to accelerate the reaction, a catalyst usually used for transesterification may be used. Moreover, you may use a suitable molecular weight modifier etc. suitably.

  As the aromatic polycarbonate resin, those having a viscosity average molecular weight in the range of 10,000 to 60,000 are preferable in terms of mechanical strength and fluidity (ease of moldability), and a more preferable viscosity average molecular weight is 15 , 30,000 to 30,000.

  Examples of the amorphous thermoplastic resin include polycarbonate resins such as aromatic polycarbonate resins, polyphenylene ether (PPE), polyarylate (PAR), acrylonitrile-styrene copolymer (AS) resin, acrylonitrile-butadiene-styrene copolymer, and the like. Polymerization (ABS) resin, acrylonitrile-ethylene-styrene copolymer (AES) resin, acrylic rubber-acrylonitrile-styrene copolymer (AAS) resin, acrylonitrile-chlorinated polyethylene-styrene copolymer (ACS) resin, polystyrene (PS), Examples thereof include polyethersulfone (PES), cyclic polyolefin (COP), acrylic resin (PMMA), and the like, and one or more kinds can be used.

[Carbon fiber (B)]
As the carbon fiber (B), any of PAN (HT, IM, HM), pitch (GP, HM), and rayon can be used. From the viewpoint of mechanical strength, PAN-based carbon fiber (B ) Is preferably used. Hereinafter, the carbon fiber (B) may be referred to as the component (B).

  The fiber diameter of the carbon fiber (B) is preferably 5 to 10 μm, and more preferably 6 to 8 μm. When the fiber diameter is at least the lower limit of the above range, the surface area of the carbon fiber (B) becomes appropriate, and the moldability of the resin composition is excellent. On the other hand, when the fiber diameter is not more than the upper limit of the above range, the aspect ratio of the carbon fiber (B) is appropriate, and a sufficient reinforcing effect can be exhibited. The fiber diameter of the carbon fiber (B) can be measured with an electron microscope.

The carbon fiber (B) having such a fiber diameter can be produced, for example, by the method described in JP-A No. 2004-11030, JP-A No. 2001-214334, JP-A No. 5-261789, and the like.
As the carbon fiber (B), a commercially available product may be used. Examples of the carbon fiber having a fiber diameter in the above range include Pyrofil (registered trademark) chopped fiber TR066, TR066A, TR068, TR06U, TR06NE, TR06G (or more Besphite (registered trademark) chopped fiber HTA-C6-S, HTA-C6-SR, HTA-C6-SRS, HTA-C6-N, HTA-C6-NR, HTA-C6- NRS, HTA-C6-US, HTA-C6-UEL1, HTA-C6-UH, HTA-C6-OW, HTA-C6-E, MC HTA-C6-US; Besfite (registered trademark) filament HTA-W05K , HTA-W1K, HTA-3K, HTA-6K, HTA-12K, HTA-24K, UT500-6K, UT500-12K, UT-500-24K, UT800-24K, IM400-3K, IM400-6K, IM400-12K, IM600-6K, IM600-12K, IM600-24K, LM16-12K, HM35-12K, TM35-6K, UM40-12K, UM40-24K, UM46-12K, UM55-12K, UM63-12K, UM68-12K (above, manufactured by Toho Tenax Co., Ltd.); Trading card (registered trademark) chopped fiber T008A-003, T010-003 (Above, manufactured by Toray Industries, Inc.).

The carbon fiber (B) is preferably subjected to a surface treatment, and particularly preferably subjected to an electrolytic treatment. Examples of the surface treatment agent include an epoxy sizing agent, a urethane sizing agent, an epoxy-urentane sizing agent, a polyamide sizing agent, and an olefin sizing agent. By performing the surface treatment, the tensile strength and bending strength as the resin composition are improved.
Commercially available products may be used as the carbon fiber (B) subjected to the surface treatment, and examples include the pyrofil (registered trademark) chopped fiber manufactured by Mitsubishi Rayon. TR066 and TR066A are treated with an epoxy sizing agent, TR068 is treated with an epoxy-urentane sizing agent, TR06U is treated with a urethane sizing agent, TR06NE is treated with a polyamide sizing agent, and TR06G is water-soluble. It has been sized. Among the Besphite (registered trademark) chopped fibers manufactured by Toho Tenax, Inc., HTA-C6-S, HTA-C6-SR, HTA-C6-SRS, and HTA-C6-E are epoxy sizing. HTA-C6-N, HTA-C6-NR and HTA-C6-NRS are treated with a polyamide sizing agent, and HTA-C6-US, HTA-C6-UEL1, HTA-C6-UH, MC HTA-C6-US has been treated with a urethane sizing agent.

0.1-2.0 mm is preferable and, as for the mass mean fiber length of the carbon fiber (B) in a resin composition, 0.2-0.5 mm is more preferable. When the mass average fiber length is not less than the lower limit of the above range, a sufficient elastic modulus can be imparted to the resin composition, and when it is not more than the upper limit, moldability and appearance are excellent.
The mass average fiber length of the carbon fiber (B) in the resin composition is determined by dissolving the thermoplastic resin (A) in the resin composition in a solvent and removing the remaining carbon fiber (B) with an optical microscope. Method for obtaining: A method in which the resin composition is heated in, for example, a nitrogen atmosphere, the thermoplastic resin (A) is removed by thermal decomposition, and the remaining carbon fiber (B) is observed with an optical microscope. In the case where the thermoplastic resin (A) is an aromatic polycarbonate resin, it may be thermally decomposed by heating at 500 ° C. for 30 minutes in a nitrogen atmosphere. In addition, there are a method of obtaining the fracture surface of the resin composition by observing it with an optical microscope, a method of obtaining it by observing with an X-ray CT, and the like.

  As the carbon fiber (B), it is preferable to use non-metal coated carbon fiber whose fiber surface is not metal-coated. Since the metal-coated carbon fiber has poor affinity with the thermoplastic resin (A), it is difficult to disperse well in the resin composition, and the blending amount (content) in the resin composition must be lowered. Tend. In this regard, non-metal-coated carbon fibers can be contained in the resin composition in a large amount because they are well dispersed in the resin composition by kneading with an ordinary extruder. As a result, the resin composition can exhibit a high elastic modulus.

[Conductive carbon black (C)]
As the conductive carbon black, one having a dibutyl phthalate oil absorption of 150 ml / 100 g or more is used. Here, the dibutyl phthalate oil absorption is an index of conductivity, and the larger the value, the higher the conductivity. Dibutyl phthalate oil absorption is measured according to the method prescribed in ASTM D2414-79. By using conductive carbon black having such an oil absorption amount, an excellent conductive resin composition can be obtained. A suitable upper limit of the dibutyl phthalate oil absorption is 400 ml / 100 g. Hereinafter, conductive carbon black (C) may be referred to as component (C).

[Other components (D)]
In addition to the thermoplastic resin (A), carbon fiber (B), and conductive carbon black (C), the resin composition may contain other components (D) as necessary.
Examples of other components (D) include antioxidants, metal deactivators, nucleating agents, mold release agents, lubricants, antistatic agents, light stabilizers, ultraviolet absorbers, glass fibers, inorganic fillers, and impact resistance. Various resin additives such as a property modifier, a melt tension improver, and a flame retardant can be used. Hereinafter, the other component (D) may be referred to as the component (D).

[Content of each component]
The content of each component in the resin composition is such that (A) component is 24-61 mass%, (B) component is 35-56 mass%, (C) component is 4-20 mass%, and The total content of the component (B) and the component (C) is 60% by mass or less. Moreover, (D) component becomes like this. Preferably it is the range of 15 mass% or less.
Within such a range, it is possible to produce a resin composition having a good balance of electrical conductivity and elastic modulus and also having moldability, and molded articles such as injection molded articles formed from the resin composition are excellent. It has high electromagnetic shielding properties based on electrical conductivity and sufficient rigidity based on high elastic modulus.
Here, when the component (B) is less than the lower limit of the above range, the elastic modulus and conductivity of the resin composition decrease, and when the upper limit of the above range is exceeded, the resin composition is inferior in moldability, It becomes brittle. When the component (C) is less than the lower limit of the above range, the conductivity of the resin composition is reduced, and when the component exceeds the upper limit of the above range, the moldability of the resin composition is inferior. Moreover, when the total content of (B) component and (C) component exceeds the said range, the moldability of a resin composition will be inferior.

<Method for producing resin composition>
The above-described resin composition is obtained by kneading the component (A), the component (B), the component (C), and the component (D) blended as necessary with an extruder such as a co-directional twin-screw extruder. It can manufacture by doing (kneading process). And in this kneading | mixing process, it is preferable to supply (B) component (carbon fiber (B)) to an extruder from the downstream rather than (A) component and (C) component. Thereby, excessive breakage in the extruder of the carbon fiber (B) supplied to the extruder is suppressed, and the mass average fiber length of the carbon fiber (B) in the resin composition is within the above-described range, that is, preferably It can be controlled to 0.1 to 2.0 mm, more preferably 0.2 to 0.5 mm. Specifically, components other than the carbon fiber (B) among the components are supplied from the main feeder to the extruder, melted and kneaded, and then carbon fiber (B) from the side feeder located downstream from the main feeder. And a side feed method for supplying.
In addition, the mass average fiber length of the carbon fiber (B) in the resin composition appropriately controls the feed method of the carbon fiber (B) to the extruder, as well as the screw rotation speed, the extrusion amount (discharge amount). ) And the like can be adjusted by appropriately controlling the kneading conditions.

  Moreover, in order to control the mass average fiber length of the carbon fiber (B) in the resin composition within the above range, the carbon fiber (B) has a fiber length of 2 to 20 mm in the total fiber length. It is preferable to prepare the resin composition by using the fiber (B) and subjecting it to a kneading step. When the carbon fiber (B) has a fiber length within the above range, the carbon fiber is controlled in the resin composition while controlling the mass average fiber length of the carbon fiber (B) within the above range. (B) can be dispersed well and the resin composition can exhibit a sufficient elastic modulus.

  As such a carbon fiber (B), what is marketed as a chopped fiber can be used. For example, in the case of a PAN-based carbon fiber, “Pyrofil (registered trademark) (chop)” manufactured by Mitsubishi Rayon Co., Ltd., “ Torayca (registered trademark) chop ", Toho Tenax Co., Ltd." Besfight (registered trademark) (chop) ", and the like. Examples of pitch-based carbon fibers include "DIALEAD (registered trademark)" manufactured by Mitsubishi Plastics, "DonaCarbo (registered trademark) (chop)" manufactured by Osaka Gas Chemical Company, and "Kureka (registered trademark) chop" manufactured by Kureha Chemical. It is done.

<Molded product>
As described above, the above resin composition has excellent conductivity and elastic modulus in a well-balanced manner and has good moldability. Therefore, by molding this by injection molding or the like, it has excellent conductivity. A molded product having both high electromagnetic shielding properties based on the surface and sufficient rigidity based on a high elastic modulus can be obtained. Specifically, by molding the above resin composition, it is possible to obtain a molded product having a surface resistance value of 50Ω or less, and further 20Ω or less. In a molded product having such a surface resistance value, energization by surface contact is possible, and electrostatic shielding is possible.
Examples of molded products include injection-molded products, and uses of such applications that require electromagnetic shielding and rigidity, such as parts for electrical and electronic equipment such as mobile phones, personal computers, OA equipment, AV equipment, and various home appliances. And housing.

Hereinafter, the present invention will be described specifically by way of examples. In the following description, “parts” and “%” mean “parts by mass” and “% by mass”.
[Examples 1 to 4, Comparative Examples 1 to 6]
Each component shown in Table 1 was kneaded using a same-direction twin-screw extruder (manufactured by Ikegai Co., Ltd .: PCM-30) to produce a resin composition. In addition, (A) component, (C) component, and (D) component were supplied to the extruder from the main feeder, and (B) component was supplied from the side feeder installed in C5 part downstream from the main feeder. (Side feed method). The kneading conditions are as follows.
Cylinder temperature C1: 280 ° C, C2-C8: 300 ° C
Screw formation: One with kneading zones at each upstream and downstream of the side feeder.
Screw rotation speed: 200rpm
Discharge rate: 10kg / h

Next, a dumbbell-shaped test piece was molded from the pelletized resin composition under the conditions of cylinder temperature: 300 ° C. and mold temperature: 80 ° C. using an IS55 injection molding machine manufactured by Toshiba Machine.
The molded test piece was cut out as necessary, and conditioned for 1 day in a thermostatic chamber at 23 ° C., and then evaluated for physical properties (1) to (3) shown below.
(1) Specific gravity: According to ISO 1183.
(2) Flexural modulus: according to ISO178.
(3) Surface resistance value: The resistance of the narrow portion at the center of the dumbbell test piece was measured with a Fluke 189 digital multimeter.

Each component used is as follows.
(A) Component: Aromatic polycarbonate resin, trade name “Novalex 7022PJ”, manufactured by Mitsubishi Engineering Plastics, viscosity average molecular weight 21000
(B) Component: Carbon fiber: “Pyrofil (registered trademark) chop TR06U”, manufactured by Mitsubishi Rayon Co., Ltd., fiber length 6 mm
Component (C): Conductive carbon black, trade name “Conductex 975”, manufactured by Colombian Carbon Co., Dibutyl phthalate oil absorption 165 ml / 100 g
Component (D): lubricant, trade name “Licowax PE520” (manufactured by Clariant, polyethylene wax)

As shown in Table 1, according to each Example, the resin composition could be injection-molded without any problem, and an injection-molded product having an excellent bending elastic modulus and a low surface resistance value in a good balance could be obtained. In addition, the resin composition of each example had an appropriate specific gravity and was excellent in lightness.
On the other hand, in Comparative Example 1 with a small amount of carbon fiber (B) and Comparative Example 2 with a small amount of conductive carbon black (C), a certain degree of conductivity was obtained, but it was not sufficient as compared with the Examples. In addition, when the conductive carbon black (C) of Comparative Examples 3 to 5 was not used, high conductivity was not obtained even when the content of the carbon fiber (B) was increased. When the carbon fiber (B) of Comparative Example 6 was not used, the bending elastic modulus, bending strength, and conductivity were insufficient.

Claims (5)

A thermoplastic resin (A);
Carbon fiber (B),
Containing conductive carbon black (C) having a dibutyl phthalate oil absorption of 150 ml / 100 g or more,
The carbon fiber (B) content is 35 to 56% by mass, the conductive carbon black (C) content is 4 to 20% by mass, and the carbon fiber (B) and the conductive carbon. A carbon fiber reinforced thermoplastic resin composition, wherein the total content of black (C) is 60% by mass or less.   The carbon fiber reinforced thermoplastic resin composition according to claim 1, wherein the thermoplastic resin (A) is an amorphous thermoplastic resin.   The carbon fiber reinforced thermoplastic resin composition according to claim 2, wherein the amorphous thermoplastic resin is an aromatic polycarbonate resin. A method for producing a carbon fiber reinforced thermoplastic resin composition according to any one of claims 1 to 3,
Supplying the thermoplastic resin (A), the carbon fiber (B), and the conductive carbon black (C) to an extruder and kneading the mixture;
In the kneading step, the carbon fiber (B) is supplied to the extruder from the downstream side of the thermoplastic resin (A) and the conductive carbon black (C), and the carbon fiber reinforced thermoplastic resin composition is produced. Method.   An injection molded article comprising the carbon fiber reinforced thermoplastic resin composition according to any one of claims 1 to 3.