JP2019052201A - Electroconductive polyamide resin composition and molded product using the same - Google Patents

Abstract

To provide an electroconductive polyamide resin composition having excellent balance of conductivity, moldability and mechanical properties (especially impact resistance) and to provide a molded product using the same.SOLUTION: There is provided an electroconductive polyamide resin composition which comprises a polyamide resin and a conductive agent containing carbon black and a carbon milled fiber, wherein the content percentage of the carbon black is 5 to 9 wt.% and the content percentage of the carbon milled fiber is 1 to 5 wt.%. There is provided a molded product which contains the electroconductive polyamide resin composition.SELECTED DRAWING: None

Description

  The present invention relates to a conductive polyamide resin composition and a molded article using the same.

  Polyamide resins represented by nylon 6, nylon 66, and the like are widely used as clothing, industrial material fibers, or general-purpose engineering plastics because of their excellent characteristics and ease of melt molding. Moreover, in the use of parts using polyamide resin, there is a demand for conductivity for the purpose of preventing charging.

  As a method for imparting conductivity to an electrically insulating polyamide resin, it is well known to knead and disperse a conductive filler in a polyamide resin to obtain a conductive polyamide resin composition. As the conductive filler to be kneaded with the polyamide resin, ion conductive organic surfactants, metal fibers and powders, conductive metal oxide powders, carbon black, carbon fibers, graphite powder, etc. are generally used. A molded product having desired conductivity can be obtained by molding and processing the conductive polyamide resin composition melt-kneaded and dispersed therein. Among these, carbon black is widely used because high conductivity can be imparted with a relatively small addition amount.

  Patent Document 1 includes component (A): 100 parts by weight of crystalline polyamide resin, component (B): 0.05 to 30 parts by weight of a substance that lowers the crystallization temperature of component (A) by 2 ° C. or more, and component ( C): A conductive polyamide resin composition composed of 2 to 30 parts by weight of conductive carbon black having a DBP oil absorption exceeding 150 ml / 100 g is described.

JP 2005-54087 A

  However, when carbon black is added to impart conductivity to the polyamide resin, the fluidity of the polyamide resin composition is greatly reduced, and the moldability is lowered. If a general carbon fiber is used instead of carbon black, the decrease in fluidity of the polyamide resin composition can be suppressed, but the conductivity is reduced at the same addition amount as that of carbon black. When carbon black and general carbon fiber are used in an appropriate blending ratio to achieve both conductivity and moldability, the mechanical properties (especially impact resistance) of the molded product of the polyamide resin composition tend to decrease. Is seen.

  Therefore, an object of the present invention is to provide a conductive polyamide resin composition having an excellent balance of conductivity, moldability, and mechanical properties (particularly impact resistance), and a molded product using the same.

  The present invention includes a polyamide resin and a conductive agent including carbon black and carbon milled fiber, wherein the carbon black content is 5 to 9% by weight, and the carbon milled fiber content is 1 to 5% by weight. The conductive polyamide resin composition is a conductive polyamide resin composition.

  The present invention is a molded article containing the above conductive polyamide resin composition.

  ADVANTAGE OF THE INVENTION According to this invention, the electroconductive polyamide resin composition excellent in the balance of electroconductivity, moldability, and a mechanical characteristic (especially impact resistance) and a molded article using the same can be provided.

<Polyamide resin>
The polyamide resin used in the present invention is polymerized or copolymerized by a known method such as melt polymerization, solution polymerization, solid phase polymerization using a lactam, an aminocarboxylic acid, or a nylon salt composed of a diamine and a dicarboxylic acid as a raw material. Can be obtained.

  Examples of the lactam include caprolactam, enantolactam, undecane lactam, dodecane lactam, α-pyrrolidone, α-piperidone and the like. Examples of aminocarboxylic acids include 6-aminocaproic acid, 7-aminoheptanoic acid, 9-aminononanoic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid. These can use 1 type (s) or 2 or more types.

  The diamine constituting the nylon salt includes ethylene diamine, trimethylene diamine, tetramethylene diamine, pentamethylene diamine, hexamethylene diamine, heptamethylene diamine, octamethylene diamine, nonamethylene diamine, decamethylene diamine, undecamethylene diamine, Dodecamethylenediamine, tridecamethylenediamine, tetradecamethylenediamine, pentadecamethylenediamine, hexadecamethylenediamine, heptadecamethylenediamine, octadecamethylenediamine, nonadecamethylenediamine, eicosamethylenediamine, 2- / 3-methyl -1,5-pentanediamine, 2-methyl-1,8-octanediamine, 2,2,4- / 2,4,4-trimethylhexamethylenediamine, 5-methyl Aliphatic diamines such as -1,9-nonanediamine; 1,3- / 1,4-cyclohexanediamine, 1,3- / 1,4-cyclohexanedimethylamine, bis (4-aminocyclohexyl) methane, bis (4- Aminocyclohexyl) propane, bis (3-methyl-4-aminocyclohexyl) methane, bis (3-methyl-4-aminocyclohexyl) propane, 5-amino-2,2,4-trimethyl-1-cyclopentanemethylamine, Cycloaliphatic diamines such as 5-amino-1,3,3-trimethylcyclohexanemethylamine (isophoronediamine), bis (aminopropyl) piperazine, bis (aminoethyl) piperazine, norbornane dimethylamine, tricyclodecanedimethylamine; m -/ Aromatic diamines such as p-xylylenediamine Etc., and the like. These can use 1 type (s) or 2 or more types.

  On the other hand, the dicarboxylic acid constituting the nylon salt includes adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid. , Aliphatic dicarboxylic acids such as octadecanedioic acid and eicosanedioic acid; alicyclic dicarboxylic acids such as 1,3- / 1,4-cyclohexanedicarboxylic acid, dicyclohexanemethane-4,4′-dicarboxylic acid, norbornane dicarboxylic acid And aromatic dicarboxylic acids such as isophthalic acid, terephthalic acid, and 1,4- / 2,6- / 2,7-naphthalenedicarboxylic acid. These can use 1 type (s) or 2 or more types.

  In the polyamide resin, these lactams, aminocarboxylic acids, or single polymers or copolymers derived from nylon salts composed of diamines and dicarboxylic acids can be used alone or in the form of a mixture.

  Specific examples of the polyamide resin used in the present invention include polycaprolactam (polyamide 6), polyundecane lactam (polyamide 11), polydodecane lactam (polyamide 12), polyethylene adipamide (polyamide 26), polytetramethylene azide. Pamide (polyamide 46), polyhexamethylene adipamide (polyamide 66), polyhexamethylene azelamide (polyamide 69), polyhexamethylene sebamide (polyamide 610), polyhexamethylene undecamide (polyamide 611), Polyhexamethylene dodecamide (polyamide 612), polyhexamethylene terephthalamide (polyamide 6T), polyhexamethylene isophthalamide (polyamide 6I), polyhexamethylene hexahydroterephthalamide ( Polyamide 6T (H)), polynonamethylene adipamide (polyamide 96), polynonamethylene azelamide (polyamide 99), polynonamethylene sebamide (polyamide 910), polynonamethylene dodecamide (polyamide 912), poly Nonamethylene terephthalamide (Polyamide 9T), Polytrimethylhexamethylene terephthalamide (Polyamide TMHT), Polynonamethylene hexahydroterephthalamide (Polyamide 9T (H)), Polynonamethylene naphthalamide (Polyamide 9N), Polydeca Methylene adipamide (polyamide 106), polydecamethylene azelamide (polyamide 109), polydecane methylene decanamide (polyamide 1010), polydecamethylene dodecamide (polyamide 1012), polydecamethylene terephthalami (Polyamide 10T), polydecamethylene hexahydroterephthalamide (polyamide 10T (H)), polydecamemethylene naphthalamide (polyamide 10N), polydodecamethylene adipamide (polyamide 126), polydodecamethylene azelamide (polyamide 129) ), Polydodecamethylene sebacamide (polyamide 1210), polydodecamethylene dodecamide (polyamide 1212), polydodecamethylene terephthalamide (polyamide 12T), polydodecamethylene hexahydroterephthalamide (polyamide 12T (H)), Polydodecamethylene naphthalamide (polyamide 12N), polymetaxylylene adipamide (polyamide MXD6), polymetaxylylene beramide (polyamide MXD8), polymetaxylylene azelamide (polyamide) MXD9), polymetaxylylene sebacamide (polyamide MXD10), polymetaxylylene dodecamide (polyamide MXD12), polymetaxylylene terephthalamide (polyamide MXDT), polymetaxylylene isophthalamide (polyamide MXDI), polymetaxylylene Naphthalamide (polyamide MXDN), polybis (4-aminocyclohexyl) methane dodecamide (polyamide PACM12), polybis (4-aminocyclohexyl) methane terephthalamide (polyamide PACMT), polybis (4-aminocyclohexyl) methane isophthalamide ( Polyamide PACMI), polybis (3-methyl-4-aminocyclohexyl) methane dodecamide (polyamide dimethyl PACM12), polyisophorone adipamide (polyamide) IPD6), poly isophorone terephthalamide (polyamide IPDT), polyamide copolymer using these raw material monomers, and the like. These can use 1 type (s) or 2 or more types.

  In consideration of heat resistance, mechanical strength, transparency, economy, availability, etc. of the resulting film, polyamide resin is derived from caprolactam (caprolactam unit), hexamethylenediamine and adipic acid. It is preferably a homopolymer or copolymer composed of at least one selected from the group consisting of units (hexamethylene adipamide units) and units derived from dodecane lactam (dodecalactam units). . Specifically, polyamide 6, polyamide 12, polyamide 66, polyamide 6/66 copolymer (copolymer of polyamide 6 and polyamide 66, hereinafter the copolymer is described in the same manner), polyamide 6/69 copolymer , Polyamide 6/610 copolymer, polyamide 6/611 copolymer, polyamide 6/612 copolymer, polyamide 6/12 copolymer, polyamide 6/66/12 copolymer, polyamide 6 / 6T copolymer , Polyamide 6 / 6I copolymer, polyamide 6 / IPD6 copolymer, polyamide 6 / IPDT copolymer, polyamide 66 / 6T copolymer, polyamide 66 / 6I copolymer, polyamide 6T / 6I copolymer, polyamide It is preferably at least one selected from the group consisting of 66 / 6T / 6I copolymer and polyamide MXD6. 6, polyamide 12, polyamide 66, polyamide 6/66 copolymer, polyamide 6/12 copolymer, polyamide 6 / IPD6 copolymer, polyamide 6 / IPDT copolymer, polyamide 6/66/12 copolymer More preferably, it is at least one selected from the group consisting of: More preferably, it is at least one selected from the group consisting of polyamide 6, polyamide 6/66 copolymer, polyamide 6/12 copolymer, and polyamide 6/66/12 copolymer.

  The relative viscosity of the polyamide resin measured according to JIS K-6920 is preferably 2.0 to 5.0, and more preferably 2.5 to 4.5. When the relative viscosity of the polyamide resin is not less than the above lower limit, the resulting polyamide film has good mechanical properties. On the other hand, when the relative viscosity of the polyamide resin is not more than the above upper limit, the viscosity at the time of melting is lowered, and the film can be easily formed.

  The polyamide resin is produced by polymerizing or copolymerizing the polyamide resin raw material in the presence of amines by a known method such as melt polymerization, solution polymerization or solid phase polymerization. Alternatively, it is produced by melt-kneading in the presence of amines after polymerization. Thus, amines can be added at any stage during polymerization or at any stage during melt kneading after polymerization, but in the stage during polymerization when considering the melt stability during film formation. It is preferable to add.

  Examples of the amines include monoamines, diamines, and polyamines. In addition to amines, carboxylic acids such as monocarboxylic acid and dicarboxylic acid may be added as necessary. These amines and carboxylic acids may be added simultaneously or separately. Moreover, 1 type (s) or 2 or more types can be used for the amines and carboxylic acids illustrated below.

  Specific examples of the monoamine to be added include methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, 2-ethylhexylamine, nonylamine, decylamine, undecylamine, dodecylamine, tridecylamine , Tetradecylamine, pentadecylamine, hexadecylamine, octadecylamine, octadecyleneamine, eicosylamine, docosylamine and other aliphatic monoamines; cyclohexylamine, methylcyclohexylamine and other alicyclic monoamines; benzylamine, β- Aromatic monoamines such as phenylmethylamine; N, N-dimethylamine, N, N-diethylamine, N, N-dipropylamine, N, N-dibutylamine, N, N-dihexyl Symmetrical secondary amines such as amine, N, N-dioctylamine; N-methyl-N-ethylamine, N-methyl-N-butylamine, N-methyl-N-dodecylamine, N-methyl-N-octadecylamine, N -Hybrid secondary amines such as -ethyl-N-hexadecylamine, N-ethyl-N-octadecylamine, N-propyl-N-hexadecylamine, N-propyl-N-benzylamine and the like.

  Specific examples of the diamine to be added include ethylene diamine, trimethylene diamine, tetramethylene diamine, pentamethylene diamine, hexamethylene diamine, heptamethylene diamine, octamethylene diamine, nonamethylene diamine, decamethylene diamine, undecamethylene diamine, dodecamethylene. Diamine, Tridecamethylenediamine, Tetradecamethylenediamine, Pentadecamethylenediamine, Hexadecamethylenediamine, Heptadecamethylenediamine, Octadecamethylenediamine, Nonadecamethylenediamine, Eicosamethylenediamine, 2- / 3-methyl-1 , 5-pentanediamine, 2-methyl-1,8-octanediamine, 2,2,4- / 2,4,4-trimethyl-1,6-hexanediamine, 5-methyl-1 Aliphatic diamines such as 9-nonanediamine; 1,3- / 1,4-cyclohexanedimethylamine, bis (4-aminocyclohexyl) methane, bis (4-aminocyclohexyl) propane, bis (3-methyl-4-aminocyclohexyl) ) Methane, bis (3-methyl-4-aminocyclohexyl) propane, 5-amino-2,2,4-trimethyl-1-cyclopentanemethylamine, 5-amino-1,3,3-trimethylcyclohexanemethylamine, Examples include alicyclic diamines such as bis (aminopropyl) piperazine, bis (aminoethyl) piperazine, norbornane dimethylamine, and tricyclodecanedimethylamine; and aromatic diamines such as m- / p-xylylenediamine.

The polyamine to be added may be a compound having a plurality of primary amino groups (—NH ₂ ) and / or secondary amino groups (—NH—). For example, polyalkyleneimine, polyalkylenepolyamine, polyvinylamine, polyallylamine, etc. Is mentioned. The amino group with active hydrogen is the reaction point of the polyamine.

  The polyalkyleneimine is produced by a method of ionic polymerization of an alkyleneimine such as ethyleneimine or propyleneimine, or a method of polymerizing an alkyloxazoline and then partially hydrolyzing or completely hydrolyzing the polymer. Examples of the polyalkylene polyamine include diethylenetriamine, triethylenetetramine, pentaethylenehexamine, or a reaction product of ethylenediamine and a polyfunctional compound. Polyvinylamine can be obtained, for example, by polymerizing N-vinylformamide to poly (N-vinylformamide), and then partially or completely hydrolyzing the polymer with an acid such as hydrochloric acid. Polyallylamine is generally obtained by polymerizing a hydrochloride of an allylamine monomer and then removing hydrochloric acid. These can use 1 type (s) or 2 or more types. Among these, polyalkyleneimine is preferable.

  Examples of the polyalkyleneimine include one or more kinds of alkyleneimines having 2 to 8 carbon atoms such as ethyleneimine, propyleneimine, 1,2-butyleneimine, 2,3-butyleneimine, and 1,1-dimethylethyleneimine. Examples thereof include a homopolymer and a copolymer obtained by polymerization by a conventional method. Among these, polyethyleneimine is more preferable. A polyalkyleneimine is obtained by polymerizing an alkyleneimine as a raw material and using a branched polyalkyleneimine containing a primary amine, a secondary amine or a tertiary amine obtained by ring-opening polymerization of the alkyleneimine or an alkyloxazoline as a raw material. Either a linear polyalkyleneimine containing only a primary amine and a secondary amine obtained in this manner, or a three-dimensionally crosslinked structure may be used. Furthermore, ethylenediamine, propylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, dipropylenetriamine, tripropylenetetramine, dihexamethylenetriamine, aminopropylethylenediamine, bisaminopropylethylenediamine and the like may be included. A polyalkyleneimine is usually derived from the reactivity of an active hydrogen atom on a nitrogen atom contained therein, and in addition to a tertiary amino group, a primary amino group having an active hydrogen atom or a secondary amino group (imino Group).

  The number of nitrogen atoms in the polyalkyleneimine is not particularly limited, but is preferably 4 to 3,000, more preferably 8 to 1,500, and still more preferably 11 to 500. The number average molecular weight of the polyalkyleneimine is preferably from 100 to 20,000, more preferably from 200 to 10,000, and further preferably from 500 to 8,000.

  On the other hand, as carboxylic acids to be added, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, capric acid, pelargonic acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, myristic acid, Aliphatic monocarboxylic acids such as palmitic acid, stearic acid, oleic acid, linoleic acid, arachidic acid, behenic acid and erucic acid; alicyclic monocarboxylic acids such as cyclohexanecarboxylic acid and methylcyclohexanecarboxylic acid, benzoic acid and toluic acid , Aromatic monocarboxylic acids such as ethylbenzoic acid and phenylacetic acid; malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, hexadecanedioic acid , Hexadecenedioic acid, octadecadioic acid, octadecenedioic acid, ray Sandioic acid, eicosenedioic acid, docosandioic acid, diglycolic acid, aliphatic dicarboxylic acids such as 2,2,4- / 2,4,4-trimethyladipic acid; 1,4-cyclohexanedicarboxylic acid, norbornane dicarboxylic acid Cycloaliphatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, m- / p-xylylene dicarboxylic acid, 1,4- / 2,6- / 2,7-naphthalenedicarboxylic acid and other aromatic dicarboxylic acids Etc.

  Therefore, it is preferable to add a diamine and / or polyamine at the time of polymerization without reducing the productivity at the time of polyamide resin production. It is more preferable to add at least one selected.

  Further, the polyamide resin may be a mixture of two or more kinds of polyamide resins having different terminal group concentrations. In this case, the terminal amino group concentration and the terminal group carboxyl concentration of the polyamide resin mixture are determined by the terminal amino group concentration, the terminal carboxyl group concentration and the blending ratio of the polyamide resin constituting the mixture.

  For the polyamide resin, the amount of water extraction measured according to the method for measuring the content of low molecular weight substances specified in JIS K-6920 is preferably 1.0% or less, and preferably 0.5% or less. It is more preferable. When the amount of water extraction exceeds the above value, the oligomer component is remarkably attached to the vicinity of the die, and appearance defects are liable to occur due to the generation of die lines and fish eyes caused by these attachments. Furthermore, the polyamide resin has a higher hygroscopicity than the olefin resin, and if a hygroscopic material is used, an oligomer is generated when the raw material is melt-extruded, resulting in difficulty in film production. It is preferable that the moisture content is 0.1% by mass or less after drying.

<Conductive agent>
The conductive agent used in the present invention contains at least carbon black and carbon milled fiber.

  As carbon black, acetylene black obtained by incomplete combustion of acetylene gas, furnace black, oil black, naphthalene black, thermal black, lamp black, channel black, manufactured by furnace type incomplete combustion using crude oil as a raw material, Examples thereof include roll black and disc black. Among them, acetylene black or furnace black is preferable, furnace black is more preferable, and ketjen black classified as the furnace black is further preferable. The carbon black may be surface-treated with a surface treatment agent such as titanate, aluminum or silane. Carbon black can use 1 type (s) or 2 or more types.

  Ketjen black is a carbon black having a hollow structure and a porous structure whose surface is activated, and can impart high conductivity with a small amount of addition than general carbon black. Is. Commercially available products of Ketjen Black include EC300J, ECP, EC600JD, and ECP600JD (trade name) manufactured by Lion Specialty Chemicals.

The average particle size of carbon black is preferably 500 nm or less, more preferably 5 to 100 nm, and even more preferably 10 to 70 nm. Surface area of the carbon black (BET method) is preferably ^{10 m} 2 / g or more, more preferably 300 meters ² / g or more, further preferably 500 to 1500 ² / g. The DBP oil absorption (measured according to ASTM D-2414) of carbon black is preferably 50 ml / 100 g or more, more preferably 100 ml / 100 g or more, and further preferably 300 ml / 100 g or more. The ash content of carbon black is preferably 0.5% by mass or less, and more preferably 0.3% by mass or less. The volatile content of carbon black is preferably less than 1.0% by mass.

  Carbon milled fiber is obtained by pulverizing carbon fiber (carbon fiber), and although the fiber length is shorter than general carbon fiber or carbon chopped fiber obtained by cutting carbon fiber short, it still has the shape of the fiber. Is maintained. Examples of the carbon fiber used as a raw material for the carbon milled fiber include PAN-based carbon fiber, pitch-based carbon fiber, and phenol-based carbon fiber. Commercially available carbon milled fibers include MLD-30, MLD300 (trade name) manufactured by Toray, CFMP-30X, CFMP-150X, CFMP-300X (trade name) manufactured by Nippon Polymer Sangyo, and Mitsubishi Rayon. DIALEAD K6371M, DIALEAD K223HM (above, trade name), Nippon Graphite Fiber XN-100-05M, XN-100-15M, HC-600-10M, HC-600-15M, XN-P9C-10M, XN-P9C-15MX (trade name) is mentioned. One type or two or more types of carbon milled fibers can be used.

  The number average fiber length of the carbon milled fiber is preferably 10 to 250 μm, more preferably 30 to 200 μm, and further preferably 50 to 100 μm. The number average fiber diameter of the carbon milled fiber is usually 3 to 15 μm.

  The tensile strength of the carbon milled fiber is preferably 1500 to 5000 MPa, more preferably 1800 to 4200 MPa, and particularly preferably 2200 to 4000 MPa.

  The weight ratio of carbon black to carbon milled fiber is preferably 9: 1 to 5: 5, and more preferably 8: 2 to 6: 4.

  The conductive agent may be composed of only carbon black and carbon milled fiber, but may contain a conductive material other than carbon black and carbon milled fiber. The conductive material may be granular, flaky, or fibrous. Examples of the granular conductive material include graphite and metal particles. Examples of the conductive material of the flakes include aluminum flakes, nickel flakes, and nickel-coated mica. Examples of the fibrous conductive material include carbon fibers other than carbon milled fibers, carbon-coated ceramic fibers, carbon whiskers, carbon nanotubes and other carbon-containing fibers; aluminum fibers, copper fibers, brass fibers, stainless steel fibers, and the like. It is done. 1 type (s) or 2 or more types can be used for an electroconductive material. The proportion of the conductive material other than carbon black and carbon milled fiber contained in the conductive agent can be in a range not exceeding 10% by weight, for example.

<Conductive polyamide resin composition>
The conductive polyamide resin composition of the present invention contains the aforementioned polyamide resin and the aforementioned conductive agent. That is, the conductive polyamide resin composition of the present invention includes at least a polyamide resin, carbon black, and carbon milled fiber.

  When carbon black is added to impart conductivity to the polyamide resin, the fluidity of the polyamide resin composition is greatly lowered, and the moldability is lowered. If a general carbon fiber is used instead of carbon black, the decrease in fluidity of the polyamide resin composition can be suppressed, but the conductivity is reduced at the same addition amount as that of carbon black. When carbon black and general carbon fiber are used in an appropriate blending ratio to achieve both conductivity and moldability, the mechanical properties of the molded article of the polyamide resin composition tend to be reduced. However, when carbon milled fiber is used instead of general carbon fiber, it is possible to suppress the deterioration of the mechanical properties of the molded product of the polyamide resin composition, and the conductivity, moldability, and mechanical properties (especially impact resistance) are reduced. The conductive polyamide resin composition has an excellent balance of the property.

  However, the carbon black content in the conductive polyamide resin composition needs to be 5 to 9% by weight. When the carbon black content is less than 5% by weight, the polyamide resin cannot be provided with a desired conductivity. When the content of carbon black exceeds 9% by weight, a decrease in fluidity of the polyamide resin composition cannot be suppressed. The content of carbon black in the conductive polyamide resin composition is preferably 6 to 8% by weight.

  Moreover, the content rate of the carbon milled fiber in a conductive polyamide resin composition needs to be 1 to 5 weight%. When the content of the carbon milled fiber is less than 1% by weight, a decrease in fluidity of the polyamide resin composition cannot be suppressed. When the content of the carbon milled fiber exceeds 5% by weight, the desired conductivity cannot be imparted to the polyamide resin. The content of carbon milled fiber in the conductive polyamide resin composition is preferably 2 to 4% by weight.

  The content of the conductive agent in the conductive polyamide resin composition is preferably 5 to 20% by weight. By setting the content of the conductive agent to 5% by weight or more, it becomes easy to impart a desired conductivity to the polyamide resin. It becomes easy to suppress the fall of the fluidity | liquidity of a polyamide resin composition because the content rate of a electrically conductive agent shall be 20 weight% or less. The content of the conductive agent in the conductive polyamide resin composition is more preferably 7 to 15% by weight.

The volume resistivity serving as an index of conductivity of the conductive polyamide resin composition of the present invention is preferably as small as possible, but is preferably less than 1 × 10 ⁵ Ω · cm, and less than 1 × 10 ⁴ Ω · cm. Is more preferably less than 1 × 10 ³ Ω · cm, and particularly preferably less than 1 × 10 ² Ω · cm. The volume resistivity of the conductive polyamide resin composition of the present invention is usually 1 × 10 ⁻¹ Ω · cm or more. In addition, volume resistivity can be measured by the method described in the Example mentioned later.

  The L / T flow length as an index of moldability of the conductive polyamide resin composition of the present invention is preferably as large as possible, but is preferably 64 mm or more, more preferably 68 mm or more, and 72 mm or more. More preferably, it is 76 mm or more. The L / T flow length of the conductive polyamide resin composition of the present invention is usually 90 mm or less. The L / T flow length of the conductive polyamide resin composition can be measured by the method described in the examples described later.

Charpy impact strength an impact resistance of an indicator of the conductive polyamide resin composition of the present invention (unnotched) is as large as possible is preferred, it is preferably 16 kJ / m ² or more, at 17 kJ / m ² or more More preferably, it is more preferably 18 kJ / m ² or more, and particularly preferably 19 kJ / m ² or more. The Charpy impact strength (no notch) of the conductive polyamide resin composition of the present invention is usually 22 kJ / m ² or less. The Charpy impact strength (without notch) can be measured by the method described in the examples described later.

<Molded product>
The molded article of the present invention includes the above-described conductive polyamide resin composition, and more specifically, is formed by molding the above-described conductive polyamide resin composition.

  As a method for molding the conductive polyamide resin composition, injection is performed such that the polyamide resin, the conductive agent and other optional components are blended in advance, or the polyamide resin, the conductive agent and other optional components are charged in the middle of the molding machine. All known molding methods applicable to polyamide resin compositions such as extrusion, hollow, press, roll, foaming, vacuum / compression, stretching, etc. are possible, and these molding methods can be used for films, sheets, molded products, fibers, etc. Can be processed.

  Molded articles using the conductive polyamide resin composition include various molded articles, sheets, films, pipes, tubes, monofilaments, fibers, containers, etc. for which molded articles of the conventional polyamide resin composition have been used. It can be used for a wide range of applications such as related equipment, optical equipment, electrical / electronic equipment, information / communication equipment, precision equipment, civil engineering / building supplies, medical supplies, and household goods. In particular, it is useful for applications such as automobiles and electrical / electronic devices.

  As examples and comparative examples of the present invention, conductive polyamide resin compositions were produced by the following methods, and the following evaluations were performed. The results are shown in Table 1.

<Example 1>
90 parts by weight of polycaprolactam (PA6, manufactured by Ube Industries, trade name: 1013B), 8 parts by weight of ketjen black (KB, manufactured by Mitsubishi Chemical, trade name: 3400B), and carbon milled fiber (CMF, manufactured by Mitsubishi Rayon, trade name) : DIALEAD K6371M, number average fiber length: 50 μm, tensile strength: 2600 MPa) 2 parts by weight were mixed. The obtained mixture was melt-kneaded using a biaxial kneader with a cylinder diameter of 40 mm at a cylinder setting temperature of 260 ° C., extruded into a strand, cooled in a water bath, and then pelletized with a polyamide resin composition using a pelletizer. Was made. And the test piece which performs electroconductivity evaluation and impact resistance evaluation mentioned later was obtained by carrying out injection molding of the obtained polyamide resin composition pellets as appropriate.

<Example 2>
Except that the amount of ketjen black was changed to 6 parts by weight and the amount of carbon milled fiber was changed to 4 parts by weight, the pellets of the conductive polyamide resin composition and various tests were performed in the same manner as in Example 1. I got a piece.

<Comparative Example 1>
The pellets and various test pieces of the conductive polyamide resin composition were obtained in the same manner as in Example 1 except that the amount of ketjen black was changed to 10 parts by weight and no carbon milled fiber was added.

<Comparative example 2>
Except that the amount of ketjen black was changed to 4 parts by weight and the amount of carbon milled fiber was changed to 6 parts by weight, in the same manner as in Example 1, pellets of the conductive polyamide resin composition and various tests I got a piece.

<Comparative Example 3>
Except that ketjen black was not blended and the blended amount of the carbon milled fiber was changed to 10 parts by weight, pellets and various test pieces of the conductive polyamide resin composition were obtained in the same manner as in Example 1.

<Comparative example 4>
The conductive polyamide resin composition was the same as in Example 1 except that carbon fiber (CF, manufactured by Mitsubishi Rayon, trade name: Pyrofil TR06NEB4J, number average fiber length: 290 μm) was used instead of carbon milled fiber. Pellets and various test pieces were obtained.

<Comparative Example 5>
The conductive polyamide resin composition was the same as in Example 2 except that carbon fiber (CF, manufactured by Mitsubishi Rayon, trade name: Pyrofil TR06NEB4J, number average fiber length: 290 μm) was used instead of carbon milled fiber. Pellets and various test pieces were obtained.

<Comparative Example 6>
The conductive polyamide resin composition was the same as in Comparative Example 3 except that carbon fiber (CF, manufactured by Mitsubishi Rayon, trade name: Pyrofil TR06NEB4J, number average fiber length: 290 μm) was used instead of carbon milled fiber. Pellets and various test pieces were obtained.

<Electrical conductivity evaluation>
Tested by a four-terminal method using a low resistivity meter (trade name: Loresta GP, manufactured by Mitsubishi Chemical) in accordance with JIS K7194 as an index of conductivity of the conductive polyamide resin compositions produced in Examples and Comparative Examples The volume resistivity of the pieces was measured. And the electroconductivity of the conductive polyamide resin composition was evaluated according to the following criteria.
◎: Volume resistivity is less than 1 × 10 ² Ω · cm ○: Volume resistivity is 1 × 10 ² Ω · cm or more and less than 1 × 10 ⁵ Ω · cm ×: Volume resistivity is 1 × 10 ⁵ Ω · cm or more

<Formability evaluation>
The L / T flow length of the polyamide resin composition pellets was measured as an index of moldability of the conductive polyamide resin compositions produced in the examples and comparative examples. Specifically, an injection molding machine (product name: PS40E, manufactured by Nissei Plastic Industry Co., Ltd.) equipped with a bar flow mold having a cavity thickness of 1 mm and a width of 15 mm was used. Pellets were injection molded under molding conditions of 50 MPa, injection speed 38 mm / sec, injection time 4 seconds, and cooling time 15 seconds. And the moldability of the conductive polyamide resin composition was evaluated according to the following criteria.
◎: L / T flow length is 80 mm or more ○: L / T flow length is 70 mm or more and less than 80 mm ×: L / T flow length is less than 70 mm

<Impact resistance evaluation>
The Charpy impact strength (no notch) of the test piece was measured according to ISO 179 as an index of impact resistance of the conductive polyamide resin compositions produced in Examples and Comparative Examples. And the impact resistance of the conductive polyamide resin composition was evaluated according to the following criteria.
○: Charpy impact strength (no notch) is 16 kJ / m ² or more ×: Charpy impact strength (no notch) is less than 16 kJ / m ²

  As described above, the conductive polyamide resin compositions (Examples 1 and 2) of the present invention were excellent in the balance between conductivity, moldability, and impact resistance.

Claims (5)

A polyamide resin;
A conductive agent including carbon black and carbon milled fiber,
The carbon black content is 5 to 9% by weight,
A conductive polyamide resin composition having a carbon milled fiber content of 1 to 5% by weight. The conductive polyamide resin composition according to claim 1, wherein a weight ratio of the carbon black to the carbon milled fiber is 9: 1 to 5: 5. The conductive polyamide resin composition according to claim 1, wherein the carbon black is ketjen black. The conductive polyamide resin composition according to any one of claims 1 to 3, wherein the number average fiber length of the carbon milled fiber is 10 to 250 µm.   The molded article containing the conductive polyamide resin composition of any one of Claims 1-4.