JP2011132281A - Thermoplastic resin composition and molded article of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermoplastic resin composition having good electric conductivity and a small degree of anisotropy in a molding shrinkage rate. <P>SOLUTION: The thermoplastic resin composition is prepared by mixing a thermoplastic resin, carbon nanotubes and a fibrous crystal of calcium silicate. A liquid crystal polyester resin is preferably used for the thermoplastic resin. Carbon nanotubes having a multilayer structure are preferably used for the carbon nanotubes. Aggregated particles comprising aggregates of a xonotlite crystal are preferably used as the fibrous crystal of calcium silicate. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a thermoplastic resin composition having electrical conductivity and a molded body thereof.

  In recent years, as the performance of electrical / electronic devices such as communication devices such as mobile phones and OA devices such as personal computers has increased, the operating frequency has been increased. On the other hand, an electric / electronic device that operates at a high operating frequency has electric / electronic components such as a processor and a communication cable that easily radiate high-frequency electromagnetic waves. In addition, this electromagnetic wave causes a malfunction of other nearby electric / electronic devices, and there is a concern about the influence on the human body. Therefore, electrical and electronic parts that easily radiate high-frequency electromagnetic waves are provided with a casing having electrical conductivity to shield the electromagnetic waves.

  As the casing having electrical conductivity, a metal casing is generally used, but the weight and the degree of freedom of shape are poor. Therefore, various types made of a thermoplastic resin have been studied. However, since the thermoplastic resin is generally electrically insulating, it is necessary to blend an electrically conductive filler in order to impart electrical conductivity. And as this electrically conductive filler, carbon black and carbon fiber, metal powder and metal fiber are common (for example, refer to Patent Documents 1 and 2). Since it is necessary to increase the amount, there is a problem that the moldability of the thermoplastic resin is impaired or the mechanical strength of the molded body is lowered. Therefore, carbon nanotubes have been studied as an electrically conductive filler that can provide a thermoplastic resin composition having good electrical conductivity even if the blending amount is small (see, for example, Patent Documents 3 and 4).

Japanese Patent Laid-Open No. 62-131067 JP-A-8-253671 Japanese Patent Laid-Open No. 3-74465 JP-A-8-27279

  However, a thermoplastic resin composition obtained by blending carbon nanotubes with a conventional thermoplastic resin is usually in a state where carbon nanotubes are aggregated and difficult to disperse in the thermoplastic resin. In some cases, the electrical conductivity may not always be sufficient. In addition, a thermoplastic resin composition obtained by blending carbon nanotubes with a conventional thermoplastic resin has a large anisotropy in molding shrinkage, particularly when the blended amount of carbon nanotubes is small, and the resulting molded body tends to warp. There is.

  Accordingly, an object of the present invention is to provide a thermoplastic resin composition having good electrical conductivity and low anisotropy in molding shrinkage. And it is providing the molded object which has favorable electrical conductivity and cannot warp using this thermoplastic resin composition.

  In order to achieve the above object, the present invention provides a thermoplastic resin composition comprising a thermoplastic resin, carbon nanotubes, and fibrous crystals of calcium silicate. Moreover, this invention provides the molded object formed by melt-molding the said thermoplastic resin.

  The thermoplastic resin composition of the present invention has good electrical conductivity and has a small anisotropy in molding shrinkage. Therefore, the thermoplastic resin composition has good electrical conductivity by melt molding. In addition, it is possible to obtain a molded body that is difficult to warp.

<Thermoplastic resin>
The thermoplastic resin is preferably one that can be molded at 200 to 450 ° C., and examples thereof include polyolefin, polystyrene, polyamide, halogenated vinyl resin, polyacetal, saturated polyester, polycarbonate, polyarylsulfone, polyarylketone, Examples thereof include polyphenylene ether, polyaryl ether ketone, polyether sulfone, polyphenylene sulfide, polyarylate, polyamide, liquid crystal polymer, and fluororesin. If necessary, they may be used as a polymer alloy in which two or more of them are combined. Especially, since it is excellent in heat resistance, a liquid crystal polymer, polyether sulfone, polyarylate, polyphenylene sulfide, polyamide 4/6, and polyamide 6T are preferable, and polyphenylene sulfide, polyether sulfone, and a liquid crystal polymer are more preferable.

<Polyphenylene sulfide>
Polyphenylene sulfide is typically a resin having a p- Fenirenchio group (-pC ₆ H ₄ -S-) main structural unit. As a method for producing polyphenylene sulfide, for example, a method of reacting a halogen-substituted aromatic compound with an alkali sulfide (see, for example, US Pat. No. 2,513,188, Japanese Patent Publication No. 44-27671), thiophenols as an alkali catalyst or A method in which a condensation reaction is performed in the presence of a copper salt (see, for example, US Pat. No. 3,274,165), a method in which an aromatic compound and sulfur chloride are subjected to a condensation reaction in the presence of a Lewis acid catalyst (for example, Japanese Patent Publication No. 46-27255) Reference). Examples of commercially available products of polyphenylene sulfide include those manufactured by Dainippon Ink & Chemicals, Inc.

<Polyethersulfone>
Polyether sulfones include those obtained by polycondensation of a dihydric phenol compound and a dihalodiphenyl compound in an organic solvent in the presence of an alkali metal compound, or an alkali metal disalt of a dihydric phenol compound and a dihalo. Those obtained by polycondensation with a diphenyl compound are preferably used.

  The organic solvent is preferably an organic polar solvent. Examples thereof include sulfoxide solvents such as dimethyl sulfoxide, amide solvents such as N, N-dimethylformamide and N, N-dimethylacetamide, N-methyl-2- Pyrrolidone solvents such as pyrrolidone and N-vinyl-2-pyrrolidone, piperidone solvents such as N-methyl-2-piperidone, 2-imidazolinone solvents such as 1,3-dimethyl-2-imidazolidinone, hexamethyl Examples thereof include diphenyl compounds such as phosphoramide, γ-butyrolactone, sulfolane, diphenyl ether, and diphenyl sulfone. If necessary, two or more of them may be mixed and used. Among them, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, dimethylsulfone, diphenylsulfone, dimethylsulfoxide, dimethylformamide, hexamethylphosphoramide, γ-butyrolactone, sulfolane, 1,3-dioxolane and 1,3 At least one selected from the group consisting of -dimethyl-2-imidazolidinone is preferably used.

  Examples of the alkali metal compound include alkali metal carbonates, alkali metal hydroxides, alkali metal hydrides, alkali metal alkoxides, and the like. Of these, anhydrous alkali metal carbonates such as potassium carbonate and sodium carbonate are preferred.

  Examples of the dihydric phenol compound include hydroquinone, catechol, resorcin, 4,4′-biphenol, 2,2-bis (4-hydroxyphenyl) propane, and 2,2-bis (4-hydroxyphenyl) methane. Bis (4-hydroxyphenyl) alkanes such as 2,2-bis (4-hydroxyphenyl) ethane, dihydroxydiphenyl sulfones such as 4,4′-dihydroxydiphenylsulfone, dihydroxy such as 4,4′-dihydroxydiphenyl ether Diphenyl ethers, wherein at least one of the hydrogen atoms of the benzene ring of these compounds is a lower alkyl group such as a methyl group, an ethyl group or a propyl group, a lower alkoxy group such as a methoxy group, an ethoxy group or a propyloxy group, a chlorine atom, a bromine With halogen atoms such as atoms and fluorine atoms Those can be mentioned which formed by conversion, may be used in combination of two or more of them as required. Of these, hydroquinone, 4,4′-biphenol, 2,2-bis (4-hydroxyphenylpropane), 4,4′-dihydroxydiphenyl ether, and 4,4′-dihydroxydiphenylsulfone are preferable from the viewpoint of price and availability. Bisphenol represented by the following formula (1) is more preferred, and 4,4′-dihydroxydiphenylsulfone is more preferred.

(In the formula, Y represents a direct bond, —SO ₂ —, —C (CH ₃ ) ₂ — or —O—).

  As the dihalodiphenyl compound, typically, a dihalodiphenyl compound having a sulfone group, for example, dihalodiphenyl sulfones such as 4,4′-dichlorodiphenyl sulfone and 4,4′-difluorodiphenyl sulfone, , 4-bis (4-chlorophenylsulfonyl) benzene, bis (halogenophenylsulfonyl) benzenes such as 1,4-bis (4-fluorophenylsulfonyl) benzene, 4,4′-bis (4-chlorophenylsulfonyl) Bis (halogenophenylsulfonyl) biphenyls such as biphenyl and 4,4′-bis (4-fluorophenylsulfonyl) biphenyl may be mentioned, and two or more of them may be mixed and used as necessary. Among these, dihalodiphenyl sulfones are preferable because they are easily available, and 4,4′-dichlorodiphenyl sulfone and 4,4′-difluorodiphenyl sulfone are more preferable. More preferred is 4′-dichlorodiphenyl sulfone.

  The polyethersulfone is preferably polycondensed using a dihydric phenol compound and a dihalodiphenylsulfone compound in substantially equimolar amounts. In order to adjust the molecular weight, it may be obtained by using a dihydric phenol compound from an equimolar amount to a slight excess amount. Similarly, it may be obtained by adding a small amount of a monohalodiphenyl compound or a monohydric phenol compound to the polymerization solution in order to adjust the molecular weight.

  The polycondensation reaction temperature for obtaining polyethersulfone is preferably 140 to 340 ° C. If the reaction temperature is too high, the decomposition reaction of the product polymer proceeds, so that high-purity polyethersulfone cannot be obtained. If the reaction temperature is too low, a useful high molecular weight polymer cannot be obtained. . As the polyether sulfone, those having a weight average molecular weight of 50,000 to 200,000 in terms of polystyrene are preferred.

<Liquid crystal polymer>
A liquid crystal polymer refers to a polymer that exhibits optical anisotropy when melted and forms an anisotropic melt at a temperature of 450 ° C. or lower. This optical anisotropy can be confirmed by a normal polarization inspection method using an orthogonal polarizer. The liquid crystal polymer has a long and narrow molecular shape, a flat and highly rigid molecular chain along the long chain of the molecule (this highly rigid molecular chain is usually referred to as a “mesogen group”). The mesogenic group may be contained in either one or both of the polymer main chain and the side chain. However, if it is desired that the resulting molded product has higher heat resistance, the mesogenic group is added to the polymer main chain. Those having the following are preferred.

  Examples of liquid crystal polymers include liquid crystal polyesters, liquid crystal polyester amides, liquid crystal polyester ethers, liquid crystal polyester carbonates, liquid crystal polyester imides, and liquid crystal polyamides, among which liquid crystal polyesters, Liquid crystal polyester amide and liquid crystal polyamide are preferable, and liquid crystal polyester and liquid crystal polyester amide are preferable in that a molded article having a lower water absorption can be obtained.

  As a suitable liquid crystal polymer, the liquid crystal polyester shown by the following (A1)-(A6) is mentioned, You may use it in combination of 2 or more types as needed.

(A1): A liquid crystal polyester composed of repeating units represented by the following formula (i).
(A2): A liquid crystal polyester comprising a repeating unit represented by the following formula (ii) and a repeating unit represented by the following formula (iii).
(A3): A liquid crystal polyester comprising a repeating unit represented by the following formula (i), a repeating unit represented by the following formula (ii), and a repeating unit represented by the following formula (iii).
(A4): A liquid crystal polyester amide or liquid crystal polyamide obtained by replacing part or all of the repeating units represented by the following formula (i) in the above (A1) with repeating units represented by the following formula (iv).
(A5): In the above (A2), part or all of the repeating unit represented by the following formula (iii) is represented by the repeating unit represented by the following formula (v) and / or the following formula (vi). Liquid crystal polyester amide or liquid crystal polyamide replaced with a repeating unit.
(A6): In the above (A3), some or all of the repeating units represented by the following formula (iii) are represented by the repeating units represented by the following formula (v) and / or the following formula (vi). Liquid crystalline polyester amides that are replaced with repeating units.

—O—Ar ¹ —CO— (i)
-CO-Ar ² -CO- (ii)
-O-Ar ³ -O- (iii)
—NH—Ar ⁴ —CO— (iv)
—O—Ar ⁵ —NH— (v)
—NH—Ar ⁶ —NH— (vi)

(In the formula, Ar ¹ and Ar ⁴ each independently represents a 1,4-phenylene group, a 2,6-naphthalenediyl group, or a 4,4′-biphenylylene group. Ar ² , Ar ³ , Ar ⁵ and Ar ⁶ each independently represents a 1,4-phenylene group, a 2,6-naphthalenediyl group, a 1,3-phenylene group, or a 4,4′-biphenylylene group, and Ar ¹ , Ar ² , Ar ³ , (The hydrogen atom in the group represented by Ar ⁴ , Ar ⁵ or Ar ⁶ may be independently substituted with a halogen atom, an alkyl group or an aryl group.)

  The repeating unit (i) is a repeating unit derived from an aromatic hydroxycarboxylic acid, and examples of the aromatic hydroxycarboxylic acid include 4-hydroxybenzoic acid, 3-hydroxybenzoic acid, and 6-hydroxy-2-naphthoic acid. Acid, 7-hydroxy-2-naphthoic acid, 6-hydroxy-1-naphthoic acid, 4′-hydroxybiphenyl-4-carboxylic acid, part of the hydrogen atoms on the aromatic ring in these aromatic hydroxycarboxylic acids or Examples thereof include aromatic hydroxycarboxylic acids that are all substituted with an alkyl group, an aryl group or a halogen atom.

  The repeating unit (ii) is a repeating unit derived from an aromatic dicarboxylic acid. Examples of the aromatic dicarboxylic acid include terephthalic acid, phthalic acid, 4,4′-diphenyldicarboxylic acid, and 2,6-naphthalenedicarboxylic acid. Examples include acids, isophthalic acids, and aromatic dicarboxylic acids in which some or all of the hydrogen atoms on the aromatic ring in these aromatic dicarboxylic acids are substituted with alkyl groups, aryl groups, or halogen atoms.

  The repeating unit (iii) is a repeating unit derived from an aromatic diol, and examples of the aromatic diol include hydroquinone, resorcin, naphthalene-2,6-diol, 4,4′-biphenylenediol, 3,3 '-Biphenylenediol, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenylsulfone, some or all of the hydrogen atoms on the aromatic ring in these aromatic diols are alkyl groups, aryl groups or halogen atoms And aromatic diols substituted with.

  The repeating unit (iv) unit is a repeating unit derived from an aromatic aminocarboxylic acid, and examples of the aromatic aminocarboxylic acid include 4-aminobenzoic acid, 3-aminobenzoic acid, 6-amino-2- Examples include naphthoic acid and aromatic aminocarboxylic acids in which some or all of the hydrogen atoms on the aromatic ring in these aromatic aminocarboxylic acids are substituted with alkyl groups, aryl groups or halogen atoms.

  The repeating unit (v) is a repeating unit derived from an aromatic amine having a hydroxyl group. Examples of the aromatic amine having a hydroxyl group include 4-aminophenol, 3-aminophenol, 4-amino-1 -Naphthol, 4-amino-4'-hydroxydiphenyl, part or all of the hydrogen atoms on the aromatic ring in the aromatic amine having a hydroxyl group are substituted with an alkyl group, an aryl group or a halogen atom Aromatic hydroxyamines may be mentioned.

  The repeating unit (vi) unit is a structural unit derived from an aromatic diamine. Examples of the aromatic diamine include 1,4-phenylenediamine, 1,3-phenylenediamine, and aromatic rings in these aromatic diamines. An aromatic diamine in which a part or all of the above hydrogen atoms are substituted with an alkyl group, an aryl group or a halogen atom is exemplified.

  Here, when it illustrates about the substituent which repeating unit (i)-(vi) has, as an alkyl group, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a tert- butyl group, a hexyl group, a cyclohexyl group An octyl group and a decyl group are mentioned, The carbon number is usually 1-10, a linear form may be sufficient, a branched form may be sufficient and an alicyclic form may be sufficient. Moreover, as an aryl group, a phenyl group and a naphthyl group are mentioned, The carbon number is 6-10 normally. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

  Among the liquid crystal polymers described above, a liquid crystal polyester selected from the group of (A1) to (A3) is preferable in that a molded product having more excellent heat resistance and dimensional stability can be obtained, and (A1) or (A3) Liquid crystal polyester is more preferable, and liquid crystal polyester (A3) is more preferable.

  As described above, the liquid crystalline polyester (A1) is composed of the repeating unit (i), and preferably has a plurality of types of repeating units (i). The reason is that it has an excellent balance between heat resistance and moldability.

  The liquid crystalline polyester (A3) has a repeating unit (i), a repeating unit (ii) and a repeating unit (iii), and the content of the repeating unit (i) when the total of these is 100 mol%. Is 30 to 80 mol%, the content of the repeating unit (ii) is preferably 10 to 35 mol%, and the content of the repeating unit (iii) is preferably 10 to 35 mol%. The molar ratio of the repeating unit (ii) to the repeating unit (iii) is 0.9 / 1.0 to 1.0 / 0.9, expressed as repeating unit (ii) / repeating unit (iii). It is preferable that the number of carboxyl groups and hydroxyl groups capable of forming an ester bond is equal when 1.0 / 1.0, that is, substantially equimolar, in producing a liquid crystalline polyester. The resulting liquid crystalline polyester can be made high in molecular weight, which is advantageous in obtaining a molded article having more excellent heat resistance.

  Here, when there are too few repeating units (i) and there are too many repeating units (ii) and / or repeating units (iii), the obtained polyester tends to hardly exhibit liquid crystallinity. On the other hand, when there are too many repeating units (i) and there are too few repeating units (ii) and / or repeating units (iii), the liquid crystalline polyester obtained will become difficult to melt | dissolve and there exists a tendency for a moldability to fall.

  The content of the repeating unit (i) is more preferably 40 to 70 mol%, further preferably 45 to 65 mol%. Further, the content of the repeating unit (ii) and the repeating unit (iii) is more preferably 15 to 30 mol%, and further preferably 17.5 to 27.5 mol%, respectively.

  In order to obtain the liquid crystal polyester of (A1) or (A3), raw material monomers for deriving the liquid crystal polyester, that is, a plurality of types of aromatic hydroxycarboxylic acids, or aromatic hydroxycarboxylic acids, aromatic dicarboxylic acids and aromatics The diol can be obtained by polymerizing by a known means. In particular, from the viewpoint of ease of production of the liquid crystalline polyester, it is preferable to produce the liquid crystalline polyester after previously converting the raw material monomer into an ester-forming derivative.

  Here, the ester-forming derivative has a group that promotes the ester formation reaction. In the case of a raw material monomer having a carboxyl group in the molecule, for example, the carboxyl group is converted into a haloformyl group or an acyloxycarbonyl group. And those obtained by converting the carboxyl group into an alkoxycarbonyl group with a lower alcohol. Moreover, in the case of the raw material monomer which has a hydroxyl group in a molecule | numerator, what converted this hydroxyl group into the acyloxy group by lower carboxylic acid is mentioned, for example.

  In the production of liquid crystal polyesters using such ester-forming derivatives, an ester-forming derivative in which the hydroxyl group of aromatic hydroxycarboxylic acid and aromatic diol is converted to an acyloxy group by a lower carboxylic acid is used. It was the way. This acylation is usually performed by reacting a compound having a hydroxyl group with acetic anhydride. A liquid crystal polyester can be obtained by subjecting such an ester-forming derivative to deacetic acid polymerization with an aromatic dicarboxylic acid.

  Examples of the method for producing the liquid crystal polyester using the ester-forming derivative include the method described in JP-A-61-69866 for the liquid crystal polyester (A1), and the method for producing the liquid crystal polyester (A3), for example. The method described in Japanese Unexamined Patent Publication No. 2002-146003 can be applied. That is, a monomer corresponding to the repeating unit (i), the repeating unit (ii) and the repeating unit (iii) is mixed, acylated with acetic anhydride to form an ester-forming derivative, and then a raw material containing the ester-forming derivative Liquid crystal polyester can be obtained by melt polymerizing the monomer.

  Here, in the case of aiming at a molded article having further excellent heat resistance, it is preferable to use the liquid crystalline polyester obtained by the melt polymerization as a prepolymer, and to further increase the molecular weight of the prepolymer. For this, it is advantageous to use solid-state polymerization. This solid phase polymerization can be performed by pulverizing the prepolymer into a powder and heating the powder. According to this solid phase polymerization, the polymerization proceeds further, and the molecular weight can be increased.

  In order to make the prepolymer into a powder, for example, the prepolymer may be cooled and solidified and then pulverized. The average particle size of the powder obtained by pulverization is preferably 0.05 to 3 mm, and more preferably 0.05 to 1.5 mm, because higher molecular weight of the liquid crystal polyester is further promoted. . In addition, since the average particle size is 0.1 to 1.0 mm, since sintering between particles does not occur, the operability of solid phase polymerization tends to be good, and the liquid crystalline polyester can be efficiently used. It is more preferable because high molecular weight is promoted. In addition, the average particle diameter of a prepolymer is calculated | required by external appearance observation.

  In a suitable solid phase polymerization, first, the temperature is raised from room temperature to a temperature that is 20 ° C. lower than the flow initiation temperature of the prepolymer. The temperature raising time at this time is preferably within one hour from the viewpoint of shortening the reaction time. Next, the temperature is raised from a temperature 20 ° C. or more lower than the flow start temperature of the prepolymer to a temperature of 280 ° C. or more. The temperature increase is preferably performed at a temperature increase rate of 0.3 ° C./min or less, and more preferably performed at a temperature increase rate of 0.1 to 0.15 ° C./min. When the rate of temperature rise is 0.3 ° C./min or less, sintering between the particles of the powder is less likely to occur, and a higher molecular weight liquid crystal polyester can be produced.

  In order to further increase the molecular weight of the liquid crystalline polyester, it is preferable to react at a temperature of usually 280 ° C. or higher, preferably 280 ° C. to 400 ° C. for 30 minutes or longer in the final step of the solid phase polymerization. In particular, from the viewpoint of improving the thermal stability of the liquid crystalline polyester, it is preferable to react at 280 to 350 ° C. for 30 minutes to 30 hours, and more preferably at 285 to 340 ° C. for 30 minutes to 20 hours. Such heating conditions can be optimized as appropriate depending on the type of raw material monomer used in the production of the liquid crystalline polyester.

  The liquid crystalline polyester (A3) obtained by performing the solid phase polymerization can achieve a sufficiently high molecular weight, and a molded product excellent in heat resistance can be obtained. Preferably, it is a liquid crystal polyester having a flow start temperature of 280 ° C. or higher, and the flow start temperature is more preferably 280 to 390 ° C.

The flow start temperature is a capillary rheometer equipped with a die having an inner diameter of 1 mm and a length of 10 mm, and the liquid crystalline polyester is heated at a rate of temperature rise of 4 ° C./min under a load of 9.8 MPa (100 kg / cm ² ). This means a temperature at which the melt viscosity shows 4800 Pa · s (48000 poise) when extruding from a nozzle, and the flow start temperature is an index representing the molecular weight of a liquid crystal polyester known in the art (Naoyuki Koide, (Refer to "Liquid Crystalline Polymer Synthesis / Molding / Application-", pages 95-105, CMC, issued June 5, 1987). As an apparatus for measuring the flow start temperature, for example, a flow characteristic evaluation apparatus “Flow Tester CFT-500D” manufactured by Shimadzu Corporation is used.

  As described above, the liquid crystal polyester (A1) or (A3) particularly suitable as the liquid crystal polymer has been described. However, other liquid crystal polymers such as the liquid crystal polyesters (A2) and (A4) to (A6) are also as described above. It can be easily produced by a production method using an ester-forming derivative.

<Carbon nanotube>
The carbon nanotube is preferably obtained by, for example, a vapor phase growth method, an arc discharge method, or a laser evaporation method, and has a multilayer structure. Further, the number average fiber diameter of the carbon nanotubes is preferably 5 to 20 nm, and more preferably 5 to 15 nm. If the number average fiber diameter of the carbon nanotubes is too small, the carbon nanotubes are bulky and difficult to mold, which is not preferable. On the other hand, if the number average fiber diameter of the carbon nanotubes is too large, it is difficult to obtain desired conductivity, which is not preferable. Moreover, it is preferable that the average aspect ratio (number average fiber length / number average fiber diameter) of the carbon nanotube is 100 or more, since the excellent conductivity is easily exhibited.

  Examples of commercially available carbon nanotubes include “VGCF-X”, Nanocyl S., manufactured by Showa Denko K.K. A. “NC7000” manufactured by Bayer Holding Co., Ltd. and “baytubes C150P” manufactured by Bayer Holding Co., Ltd. may be mentioned.

<Fibrous crystals of calcium silicate>
Examples of the calcium silicate fibrous crystals include tobermorite (Ca ₅ Si ₆ O ₁₆ (OH) ₂ .4H ₂ O) crystals, wollastonite (CaO.SiO ₂ ) crystals, and zonotolite (CaO.SiO ₂ ). ₂ · H ₂ O) crystals. Of these, crystals of zonotolite are preferable. As the crystals of wollastonite, those having a number average fiber length of about 6 to 25 μm are available from Sakai Chemical Co., Ltd. and Nagase Chemspec Co., Ltd., for example. Moreover, as a crystal of zonotlite, for example, those having a number average fiber length of about 10 to 20 μm are available from Ube Materials Co., Ltd.

  The fibrous crystal of calcium silicate preferably has a number average fiber length of 0.1 to 10 μm, a number average fiber diameter of preferably 10 nm to 1 μm, and more preferably 50 to 600 nm. Calcium silicate fibrous crystals having a number average fiber length and a number average fiber diameter in these predetermined ranges are preferred because of their good affinity with thermoplastic resins.

  The number average fiber length and the number average fiber diameter of the calcium silicate fibrous crystals are prepared by dispersing the fibrous crystals in methanol, preparing a dispersion, spreading the dispersion on a glass slide, After evaporation, a micrograph is taken at a measurement magnification of 2000 using a scanning electron microscope, and the fiber length of about 100 fibrous crystals is measured from the photograph, and the measured values are number averaged. Similarly, it is obtained by measuring the fiber diameter of about 100 fibrous crystals and averaging the measured values.

  The fibrous crystals of calcium silicate are preferably in the state of aggregated particles formed by agglomerating them, in other words, in the state of secondary particles formed by aggregation of the fibrous crystals. Agglomerated particles formed by agglomeration of tobermorite crystals, for example, as disclosed in JP-A-6-40715, lime milk, crystalline silicic acid raw material and water are mixed to obtain a raw slurry, It is obtained by carrying out a hydrothermal synthesis reaction while heating and stirring the raw slurry. A method for producing aggregated particles formed by agglomerating wollastonite crystals is disclosed, for example, in JP-A-53-146997. Moreover, as an example of a commercial product of aggregated particles formed by agglomerating zonotolite crystals, “Zonotolite Powder XK” (volume average particle diameter 30 μm) or “Zonotolite Powder XJ” (volume average particle diameter 22 μm) manufactured by Nippon Insulation Co., Ltd. ) And the like. The volume average particle diameter of the aggregated particles can be obtained by laser diffraction particle size distribution measurement.

  The shape of the aggregated particles may be spherical or substantially spherical, may be irregular, or may have irregularities on a part of the surface thereof. The aggregated particles preferably have a volume average particle size of 1 to 100 μm, more preferably 10 to 50 μm, because the miscibility becomes better when melt-kneaded with the thermoplastic resin. More preferably, it is 20-40 micrometers. For example, when the fibrous crystals are aggregated by the above-described method and the obtained aggregated particles do not have a desired volume average particle diameter, the desired volume average particle diameter can be adjusted by classification.

<Other ingredients>
The thermoplastic resin composition of the present invention may contain components other than the thermoplastic resin, carbon nanotubes, and fibrous crystals of calcium silicate as necessary. Examples thereof include glass fiber, silica alumina. Fibrous reinforcing agents such as fibers, alumina fibers and carbon fibers; acicular reinforcing agents such as aluminum borate whiskers and potassium titanate whiskers; inorganic fillers such as glass beads, talc, mica, graphite, wollastonite and dolomite; Mold release improvers such as fluororesins and metal soaps; Colorants such as dyes and pigments; Antioxidants; Thermal stabilizers; Ultraviolet absorbers; Surfactants, and two or more of them if necessary May be used in combination. It is also possible to use additives having an external lubricant effect such as higher fatty acids, higher fatty acid esters, higher fatty acid metal salts, fluorocarbon surfactants and the like.

<Thermoplastic resin composition>
The thermoplastic resin composition of the present invention can be obtained by mixing a thermoplastic resin, a carbon nanotube, a fibrous crystal of calcium silicate, and other components used as necessary. In terms of cost, it is preferable to obtain these components by melt-kneading, and it is more preferable to obtain them by extrusion-melt-kneading to obtain pellets. Moreover, before melt-kneading, these components may be mixed using, for example, a Henschel mixer or a tumbler.

  The content of the carbon nanotube is preferably 1 to 10 parts by weight, and preferably 1 to 6 parts by weight with respect to 100 parts by weight of the total content of the thermoplastic resin, the carbon nanotube and the calcium silicate fibrous crystal. Is more preferably 1 to 5 parts by weight. When the content of the carbon nanotube is in such a range, the balance between electric conductivity and moldability is good and advantageous.

  The content of the calcium silicate fibrous crystal is preferably 1 to 5 parts by weight with respect to 100 parts by weight of the total content of the thermoplastic resin, the carbon nanotube and the calcium silicate fibrous crystal. The amount is more preferably 4 parts by weight, and still more preferably 1 to 3 parts by weight. When the content of the calcium silicate fibrous crystal is in such a range, the balance between electrical conductivity and low anisotropy of molding shrinkage is good and advantageous.

<Molded body>
Examples of the method for molding the thermoplastic resin composition of the present invention include injection molding, extrusion molding, transfer molding, blow molding, press molding, injection press molding, and extrusion injection molding. The above may be combined. Among these, for the production of electric / electronic parts used as parts of electric / electronic devices, melt molding such as injection molding or extrusion injection molding is preferable, and injection molding is more preferable.

  Injection molding is performed by melting the thermoplastic resin composition of the present invention using an injection molding machine (for example, “hydraulic horizontal molding machine PS40E5ASE type” manufactured by Nissei Plastic Industry Co., Ltd.). Can be performed by heating into a mold having a desired cavity shape, heated to a suitable temperature. The temperature at which the thermoplastic resin composition is heated and melted for injection is Tp ′ + 10 (° C.) or more and Tp ′ + 50 (° C.) or less based on the flow start temperature Tp ′ (° C.) of the thermoplastic resin composition used. It is preferable to make it. Moreover, the temperature of a metal mold | die is normally selected from the range of room temperature-180 (degreeC) from the point of the cooling rate and productivity of a thermoplastic resin composition.

The molded body thus obtained preferably has a volume resistivity value of 10 ¹² Ωcm or less. The ratio of the molding shrinkage ratio in the direction perpendicular to the flow direction to the molding shrinkage ratio in the flow direction of the thermoplastic resin composition during melt molding is preferably 5 or less.

  The molded body obtained in this way can be applied to various uses, but it is suitably used as a surface-mounted component, particularly by taking advantage of its electrical conductivity. Examples of such surface mount components include housings for electric / electronic components, choke coils, and connectors. A molded body formed by molding the thermoplastic resin composition of the present invention is extremely useful when used as a surface-mounted component because it is expected to absorb electronic noise. Further, it is useful when used as a tray used in a semiconductor manufacturing process because it is expected to prevent dust due to static electricity.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

  As the carbon nanotube, “VGCF-X” (number average fiber diameter: 15 μm, number average aspect ratio: 200) manufactured by Showa Denko KK, which is a multi-walled carbon nanotube, was used.

“Zonotolite powder XK” manufactured by Nippon Insulation Co., Ltd., which is an aggregated particle formed by agglomerating zonotlite crystals as fibrous crystals of calcium silicate (volume average particle diameter (laser diffraction method): 30 μm, packing density (JIS) K1464): 0.084 g / cc, oil absorption (JIS K5101): 492 ml / 100 g, specific surface area (BET method): 56 m ² / g).

  As the glass fiber, “chopped glass fiber CS03JAPX-1” (number average fiber diameter: 10 μm, number average fiber length: 3 mm) manufactured by Asahi Fiber Glass Co., Ltd. was used.

Production Example 1 (Production of liquid crystal polyester)
To a reactor equipped with a stirrer, a torque meter, a nitrogen gas inlet tube, a thermometer and a reflux condenser, 994.5 g (7.2 mol) of parahydroxybenzoic acid, 446.9 g of 4,4′-dihydroxybiphenyl (2 4 mol), 299.0 g (1.8 mol) of terephthalic acid, 99.7 g (0.6 mol) of isophthalic acid, and 1347.6 g (13.2 mol) of acetic anhydride, and the reactor was sufficiently filled with nitrogen. After replacing with gas, the temperature was raised to 150 ° C. over 30 minutes under a nitrogen gas stream, and the mixture was refluxed for 1 hour while maintaining the temperature. Thereafter, the temperature was raised to 320 ° C. over 2 hours and 50 minutes while distilling off distilling by-product acetic acid and unreacted acetic anhydride, and the prepolymer was obtained at the point where the increase in torque was observed. The obtained prepolymer was cooled to room temperature and pulverized with a coarse pulverizer to obtain a powder. The powder was heated from room temperature to 250 ° C. over 1 hour in a nitrogen atmosphere, heated from 250 ° C. to 285 ° C. over 5 hours, and held at that temperature for 3 hours to perform solid-state polymerization. It was. The liquid crystal polyester obtained by cooling had a flow start temperature of 327 ° C.

Examples 1 and 2 and Comparative Examples 1 and 2
The liquid crystal polyester, carbon nanotubes, calcium silicate fibrous crystals and glass fibers obtained in Production Example 1 were mixed in the same weighted biaxial extruder ("PCM-30HS" manufactured by Ikekai Tekko Co., Ltd.) in the weight ratio shown in Table 1. ) And kneaded at 340 ° C. to obtain a pellet-shaped thermoplastic resin composition. The obtained thermoplastic resin composition was injection molded at a cylinder temperature of 350 ° C., a mold temperature of 130 ° C., and an injection rate of 30 cm ³ / s using an injection molding machine (“PS40E5ASE type” manufactured by Nissei Plastic Industry Co., Ltd.). A molded body 1 (64 mm × 64 mm × 1 mm) and a molded body 2 (64 mm × 64 mm × 3 mm) were obtained.
The volume specific resistance value and molding shrinkage ratio of the molded body thus obtained were determined. The results are shown in Table 1.

  About the molded object 1, based on ASTMD257, volume specific resistance was measured using "SM-10E type super insulation meter" manufactured by Toa Denpa Kogyo Co., Ltd., and the results are shown in Table 1.

  For the molded body 2, the molding shrinkage in the flow direction (MD) of the thermoplastic resin composition during injection molding and the molding shrinkage in the direction perpendicular to the flow direction (TD) are measured, and the value of the ratio of the latter to the former Was determined as the anisotropy of the molding shrinkage, and the results are shown in Table 1.

Claims (16)

  A thermoplastic resin composition comprising a thermoplastic resin, carbon nanotubes, and fibrous crystals of calcium silicate.   The thermoplastic resin composition according to claim 1, wherein the thermoplastic resin is a liquid crystal polyester resin. The liquid crystalline polyester resin is at least one liquid crystalline polyester selected from the group consisting of a liquid crystalline polyester resin represented by the following (A1), a liquid crystalline polyester resin represented by the following (A2), and a liquid crystalline polyester resin represented by the following (A3). The thermoplastic resin composition according to claim 2, which is a resin.
(A1): A liquid crystal polyester resin comprising a repeating unit represented by the following formula (i).
(A2): A liquid crystal polyester resin comprising a repeating unit represented by the following formula (ii) and a repeating unit represented by the following formula (iii).
(A3): A liquid crystal polyester resin comprising a repeating unit represented by the following formula (i), a repeating unit represented by the following formula (ii), and a repeating unit represented by the following formula (iii).
—O—Ar ¹ —CO— (i)
-CO-Ar ² -CO- (ii)
-O-Ar ³ -O- (iii)
(In the formula, Ar ¹ represents a 1,4-phenylene group, a 2,6-naphthalenediyl group, or a 4,4′-biphenylylene group. Ar ² and Ar ³ are each independently a 1,4-phenylene group. 2,6-naphthalenediyl group, 1,3-phenylene group or 4,4′-biphenylylene group, and the hydrogen atoms in the groups represented by Ar ¹ , Ar ² or Ar ³ are independent of each other. And may be substituted with a halogen atom, an alkyl group or an aryl group.   The thermoplastic resin composition according to claim 1, wherein the thermoplastic resin is a polyethersulfone resin. The polyethersulfone resin is a resin obtained by polycondensation of a compound represented by the following formula (1) and a compound represented by the following formula (2) in the presence of an alkali metal compound in an organic solvent. The thermoplastic resin composition according to claim 4.

(In the formula, Y represents a direct bond, —SO ₂ —, —C (CH ₃ ) ₂ — or —O—).

The thermoplastic resin composition according to claim 5, wherein Y is —SO ₂ —.   The thermoplastic resin composition according to claim 1, wherein the carbon nanotube is a carbon nanotube having a multilayer structure.   The number average fiber diameter of the said carbon nanotube is 5-20 nm, The thermoplastic resin composition in any one of Claims 1-7.   The thermoplastic resin composition according to claim 1, wherein the number average aspect ratio of the carbon nanotube is 100 or more.   The thermoplastic resin composition according to any one of claims 1 to 9, comprising the fibrous crystals as aggregated particles formed by aggregation.   The thermoplastic resin composition according to any one of claims 1 to 10, wherein the fibrous crystal is a zonotlite crystal.   The content of the carbon nanotube is 1 to 10 parts by weight with respect to 100 parts by weight of the total content of the thermoplastic resin, the carbon nanotube, and the fibrous crystal. Thermoplastic resin composition.   The content of the fibrous crystal is 1 to 5 parts by weight with respect to 100 parts by weight of the total content of the thermoplastic resin, the carbon nanotube, and the fibrous crystal. Thermoplastic resin composition.   The molded object formed by melt-molding the thermoplastic resin composition in any one of Claims 1-13. The molded product according to claim 14, wherein the volume resistivity is 10 ¹² Ωcm or less.   The molded product according to claim 15 or 16, wherein a ratio of a molding shrinkage rate in a direction perpendicular to the flow direction to a molding shrinkage rate in the flow direction of the thermoplastic resin composition during melt molding is 5 or less.