JP6907843B2 - Conductive polyamide resin composition and molded products using it - Google Patents

Description

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

Polyamide resins typified by nylon 6 and nylon 66 are widely used as fibers for clothing, industrial materials, and general-purpose engineering plastics because of their excellent properties and ease of melt molding. Further, in the use of parts using polyamide resin, there is a demand for conductivity for the purpose of antistatic and the like.

As a method for imparting conductivity to an electrically insulating polyamide resin, it is well known that a conductive filler is kneaded and dispersed in a polyamide resin to obtain a conductive polyamide resin composition. As the conductive filler to be kneaded with the polyamide resin, an ionic conductive organic surfactant, metal fiber and powder, conductive metal oxide powder, carbon black, carbon fiber, graphite powder and the like are generally used, and this is used as a resin. By molding and kneading the conductive polyamide resin composition dispersed therein, a molded product having desired conductivity can be obtained. Among them, carbon black is widely used because it can impart high conductivity with a relatively small amount of addition.

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

Japanese Unexamined Patent Publication No. 2005-54087

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 general carbon fibers are used instead of carbon black, the decrease in fluidity of the polyamide resin composition can be suppressed, but the conductivity decreases with the same amount of addition as carbon black. When carbon black and general carbon fibers are used in combination at an appropriate mixing ratio to achieve both conductivity and moldability, the mechanical properties (particularly impact resistance) of the molded product of the polyamide resin composition tend to deteriorate. Can be 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 contains a polyamide resin and a conductive agent containing carbon black and carbon milled fibers, the carbon black content is 5 to 9% by weight, and the number average fiber length of the carbon milled fibers is 10 to 250 μm. This is a conductive polyamide resin composition having a carbon milled fiber content of 1 to 5% by weight.

The present invention is a molded product containing the above-mentioned conductive polyamide resin composition.

According to the present invention, it is possible 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.

<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, etc. using a nylon salt composed of lactam, aminocarboxylic acid, or diamine and dicarboxylic acid as a raw material. Obtained by

Examples of lactam include caprolactam, enantractum, undecane lactam, dodecane lactam, α-pyrrolidone, α-piperidone and the like. Examples of the aminocarboxylic acid include 6-aminocaproic acid, 7-aminoheptanoic acid, 9-aminononanoic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid and the like. These can be used alone or in combination of two or more.

Examples of the diamines constituting the nylon salt include ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, and undecamethylenediamine. Dodecamethylenediamine, tridecamethylenediamine, tetradecamethylenediamine, pentadecamethylenediamine, hexadecamethylenediamine, heptadecamethylenediamine, octadecamethylenediamine, nonadecamethylenediamine, eicosamethylenediamine, 2- / 3-methyl Aliamines such as -1,5-pentanediamine, 2-methyl-1,8-octanediamine, 2,2,4- / 2,4,4-trimethylhexamethylenediamine, 5-methyl-1,9-nonandamine Diamine; 1,3- / 1,4-cyclohexanediamine, 1,3- / 1,4-cyclohexanediamine, bis (4-aminocyclohexamethylene) methane, bis (4-aminocyclohexamethylene) 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- Alicyclic diamines such as trimethylcyclohexamethylenediamine (isophoronediamine), bis (aminopropyl) piperazine, bis (aminoethyl) piperazine, norbornanedimethylamine, tricyclodecanedimethylamine; aromatics such as m- / p-xylylenediamine Examples include family diamine. These can be used alone or in combination of two or more.

On the other hand, as the dicarboxylic acids constituting the nylon salt, adipic acid, pimelli acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid and hexadecanedioic acid , Octadecanedioic acid, aliphatic dicarboxylic acid such as eicosandioic acid; alicyclic dicarboxylic acid such as 1,3- / 1,4-cyclohexanedicarboxylic acid, dicyclohexanemethane-4,4'-dicarboxylic acid, norbornandicarboxylic acid. Examples include aromatic dicarboxylic acids such as isophthalic acid, terephthalic acid, and 1,4- / 2,6- / 2,7-naphthalenedicarboxylic acid. These can be used alone or in combination of two or more.

In the polyamide resin, these monopolymers or copolymers derived from lactam, aminocarboxylic acid, or nylon salt composed of diamine and dicarboxylic acid can be used alone or in the form of a mixture, respectively.

Specific examples of the polyamide resin used in the present invention include polycaprolactam (polyamide 6), polyundecanelactam (polyamide 11), polydodecanelactam (polyamide 12), polyethylene adipamide (polyamide 26), and polytetramethylene adhi. Pamide (polyamide 46), polyhexamethylene adipamide (polyamide 66), polyhexamethylene azelamide (polyamide 69), polyhexamethylene sebacamide (polyamide 610), polyhexamethylene undecamide (polyamide 611), Polyhexamethylene dodecamide (polyamide 612), polyhexamethylene terephthalamide (polyamide 6T), polyhexamethylene isophthalamide (polyamide 6I), polyhexamethylene hexahydroterephthalamide (polyamide 6T (H)), polynonamethylene azi. Pamide (polyamide 96), polynonamethylene azelamide (polyamide 99), polynonamethylene sebacamide (polyamide 910), polynonamethylene dodecamide (polyamide 912), polynonamethylene terephthalamide (polyamide 9T), poly Trimethylhexamethylene terephthalamide (polyamide TMHT), polynonamethylene hexahydroterephthalamide (polyamide 9T (H)), polynonamethylene naphthalamide (polyamide 9N), polydecamethylene adipamide (polyamide 106), polydeca Methylene azelamide (polyamide 109), polydecamethylene decamide (polyamide 1010), polydecamethylene dodecamide (polyamide 1012), polydecamethylene terephthalamide (polyamide 10T), polydecamethylene hexahydroterephthalamide (polyamide 10T) (H)), Polydecamethylene 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), polymethoxylylen adipamide (Polyamide MXD6), Polymethoxylylence veramide (Polyamide MXD8), Polymethoxylylene azelamide (Polyami) Do MXD9), polymethoxylylene sevacamido (polyamide MXD10), polymethoxylylend decamide (polyamide MXD12), polymethoxylylene terephthalamide (polyamide MXDT), polymethoxylylene isophthalamide (polyamide MXDI), polymethoxylylene Naphthalamide (polyamide MXDN), polybis (4-aminocyclohexyl) methadodecamide (polyamide PACM12), polybis (4-aminocyclohexyl) methaneterephthalamide (polyamide PACMT), polybis (4-aminocyclohexyl) methaneisophthalamide (polyamide PACMT) Polyamide PACMI), polybis (3-methyl-4-aminocyclohexyl) methadodecamide (polyamide dimethyl PACM12), polyisophorone adipamide (polyamide IPD6), polyisophorone terephthalamide (polyamide IPDT) and their raw material monomers are used. Examples thereof include the polyamide copolymer used. These can be used alone or in combination of two or more.

Considering the heat resistance, mechanical strength, transparency, economy, availability, etc. of the obtained film, the polyamide resin is derived from caprolactam-derived units (caprolactam units), hexamethylenediamine and adipic acid. It is preferably a homopolymer or copolymer composed of at least one selected from the group consisting of units to be (hexamethylene adipamide units) and units derived from dodecantactam (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, and is preferably polyamide 6, polyamide 12, polyamide 66, polyamide 6/66 copolymer, and polyamide 6/12 copolymer. , Polyamide 6 / IPD6 copolymer, Polyamide 6 / IPDT copolymer, Polyamide 6/66/12 copolymer, at least one selected from the group. It is more preferable that 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 at least the above lower limit value, the mechanical properties of the obtained polyamide film are good. On the other hand, when the relative viscosity of the polyamide resin is not more than the above upper limit value, the viscosity at the time of melting becomes low, and the film can be easily molded.

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

Examples of the amines include monoamines, diamines, polyamines and the like. In addition to amines, carboxylic acids such as monocarboxylic acids and dicarboxylic acids may be added, if necessary. These amines and carboxylic acids may be added at the same time or separately. Further, as the amines and carboxylic acids exemplified below, one kind or two or more kinds can be used.

Specific examples of the monoamine to be added include methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, 2-ethylhexylamine, nonylamine, decylamine, undecylamine, dodecylamine and 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-dihexylamine, N, N-dioctyl Symmetrical secondary amines such as amines; N-methyl-N-ethylamine, N-methyl-N-butylamine, N-methyl-N-dodecylamine, N-methyl-N-octadecylamine, N-ethyl-N-hexadecyl Examples thereof include mixed secondary amines such as amines, N-ethyl-N-octadecylamines, N-propyl-N-hexadecylamines and N-propyl-N-benzylamines.

Specific examples of the diamine to be added include ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine, and dodecamethylene. Diamine, Tridecamethylenediamine, Hexamethylenediamine, Pentadecamethylenediamine, Hexamethylenediamine, Hexamethylenediamine, Octadecamethylenediamine, Nonadecamethylenediamine, Eikosamethylenediamine, 2- / 3-Methyl-1 , 5-Pentanediamine, 2-methyl-1,8-octanediamine, 2,2,4- / 2,4,4-trimethyl-1,6-hexanediamine, 5-methyl-1,9-nonandamine, etc. Aliphatic diamine; 1,3- / 1,4-cyclohexanediamine, bis (4-aminocyclohexamethylene) methane, bis (4-aminocyclohexamethylene) propane, bis (3-methyl-4-aminocyclohexamethylene) methane, bis ( 3-Methyl-4-aminocyclohexamethylene) propane, 5-amino-2,2,4-trimethyl-1-cyclopentanemethylamine, 5-amino-1,3,3-trimethylcyclohexanemethylamine, bis (aminopropyl) Examples thereof include alicyclic diamines such as piperazine, bis (aminoethyl) piperazine, norbornandimethylamine 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 and the like. Can be mentioned. The amino group with active hydrogen is the reaction site for polyamines.

Polyalkyleneimine is produced by a method of ion-polymerizing an alkyleneimine such as ethyleneimine or propyleneimine, or a method of polymerizing an alkyloxazoline and then partially or completely hydrolyzing the polymer. Examples of the polyalkylene polyamine include diethylenetriamine, triethylenetetramine, pentaethylenehexamine, and a reaction product of ethylenediamine and a polyfunctional compound. Polyvinylamine can be obtained, for example, by polymerizing N-vinylformamide to obtain 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 salt of an allylamine monomer and then removing hydrochloric acid. These can be used alone or in combination of two or more. Among these, polyalkyleneimine is preferable.

As the polyalkyleneimine, one or more of 2 to 8 alkyleneimines having 2 to 8 carbon atoms such as ethyleneimine, propyleneimine, 1,2-butyleneimine, 2,3-butyleneimine, and 1,1-dimethylethyleneimine can be used. Examples thereof include homopolymers and copolymers obtained by polymerization by a conventional method. Among these, polyethyleneimine is more preferable. Polyalkyleneimine is obtained by ring-opening polymerization of alkyleneimine as a raw material, and branched polyalkyleneimine containing primary amine, secondary amine and tertiary amine, or alkyloxazoline as a raw material, which is polymerized. It may be either a linear polyalkyleneimine containing only the primary amine and the secondary amine obtained above, or a three-dimensionally crosslinked structure. Further, it may contain ethylenediamine, propylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, dipropylenetriamine, tripropylenetetramine, dihexamethylenetriamine, aminopropylethylenediamine, bisaminopropylethylenediamine and the like. Polyalkyleneimines are usually derived from the reactivity of active hydrogen atoms on the contained nitrogen atoms, and in addition to tertiary amino groups, primary amino groups and secondary amino groups (imino) having active hydrogen atoms. 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 even more preferably 11 to 500. The number average molecular weight of polyalkyleneimine is preferably 100 to 20,000, more preferably 200 to 10,000, and even more preferably 500 to 8,000.

On the other hand, as the carboxylic acids to be added, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, capric acid, capric acid, pelargonic acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, myristoleic acid, Adicyclic monocarboxylic acids such as palmitic acid, stearic acid, oleic acid, linoleic acid, araquinic acid, behenic acid and erucic acid; alicyclic monocarboxylic acids such as cyclohexanecarboxylic acid and methylcyclohexanecarboxylic acid, benzoic acid and toluic acid. , Ethylbenzoic acid, aromatic monocarboxylic acids such as phenylacetic acid; malonic acid, succinic acid, glutaric acid, adipic acid, pimelliic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, hexadecadioic acid , Hexadecenodic acid, Octadecadioic acid, Octadecenoic acid, Eikosandioic acid, Eikosendioic acid, Docosandioic acid, Diglycolic acid, 2,2,4- / 2,4,4-trimethyladiponic acid and other aliphatic dicarboxylic acids Acids; alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid and norbornandicarboxylic acid; terephthalic acid, isophthalic acid, phthalic acid, m- / p-xylylene dicarboxylic acid, 1,4- / 2,6- / Examples thereof include aromatic dicarboxylic acids such as 2,7-naphthalenedicarboxylic acid.

Therefore, it is preferable to add diamine and / or polyamine at the time of polymerization without reducing the productivity at the time of producing the polyamide resin, and from the viewpoint of suppressing gel generation, it is more than the group consisting of aliphatic diamines, alicyclic diamines, and polyamines. 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 thereof of the polyamide resin constituting the mixture.

For the polyamide resin, the water extraction amount 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, preferably 0.5% or less. Is more preferable. When the amount of water extracted exceeds the above value, the oligomer component adheres remarkably to the vicinity of the die, and the appearance is likely to be deteriorated due to the generation of die lines and fish eyes due to these deposits. Further, the polyamide resin has a higher hygroscopicity than the olefin resin, and if a hygroscopic resin is used, hydrolysis occurs when the raw material is melt-extruded, so that oligomers are generated, which makes it difficult to produce a film. It is preferably dried and has a water content of 0.1% by mass or less.

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

Carbon black includes acetylene black, which is obtained by incomplete combustion of acetylene gas, furnace black, oil black, naphthaline black, thermal black, lamp black, and channel black, which are produced by furnace-type incomplete combustion using crude oil as a raw material. Examples include roll black and disc black. Among them, acetylene black or furnace black is preferable, furnace black is more preferable, and Ketjen black classified into the furnace black is further preferable. The carbon black may be surface-treated with a surface treatment agent such as titanate-based, aluminum-based, or silane-based. One type or two or more types of carbon black can be used.

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 smaller amount of addition than general carbon black. It is a thing. Examples of commercially available products of Ketjen Black include EC300J, ECP, EC600JD, and ECP600JD (hereinafter, trade names) 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 of carbon black (measured according to ASTM D-2414) 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 crushing carbon fiber (carbon fiber), and although it has a shorter fiber length than general carbon fiber and carbon chopped fiber obtained by cutting carbon fiber into short pieces, it still has the shape of the fiber. It is something that is maintained. Examples of carbon fibers used as raw materials for carbon milled fibers include PAN-based carbon fibers, pitch-based carbon fibers, and phenol-based carbon fibers. Commercially available carbon milled fibers include Toray's MLD-30, MLD300 (above, trade name), Nippon Polymer Industry's CFMP-30X, CFMP-150X, CFMP-300X (above, trade name), 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, Examples thereof include XN-P9C-15MX (hereinafter referred to as a trade name). One kind or two or more kinds of carbon milled fibers can be used.

The number average fiber length of the carbon milled fibers is preferably 10 to 250 μm, more preferably 30 to 200 μm, and even more preferably 50 to 100 μm. The number average fiber diameter of the carbon milled fibers 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 consist only of 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; and metal fibers such as aluminum fibers, copper fibers, brass fibers and stainless fibers. Be done. One kind or two or more kinds of conductive materials can be used. The ratio of the conductive material other than carbon black and carbon milled fiber contained in the conductive agent can be in the range not exceeding, for example, 10% by weight.

<Conductive polyamide resin composition>
The conductive polyamide resin composition of the present invention contains the above-mentioned polyamide resin and the above-mentioned conductive agent. That is, the conductive polyamide resin composition of the present invention contains 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 reduced, and the moldability is lowered. If general carbon fibers are used instead of carbon black, the decrease in fluidity of the polyamide resin composition can be suppressed, but the conductivity decreases with the same amount of addition as carbon black. When carbon black and general carbon fibers are used in combination at an appropriate blending ratio to achieve both conductivity and moldability, the mechanical properties of the molded product of the polyamide resin composition tend to deteriorate. However, when carbon milled fiber is used instead of general carbon fiber, deterioration of mechanical properties of the molded product of the polyamide resin composition can be suppressed, and conductivity, moldability, and mechanical properties (particularly impact resistance) can be suppressed. A conductive polyamide resin composition having an excellent balance of properties).

However, the content of carbon black in the conductive polyamide resin composition needs to be 5 to 9% by weight. When the content of carbon black is less than 5% by weight, the desired conductivity cannot be imparted to the polyamide resin. When the content of carbon black exceeds 9% by weight, the 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.

Further, the content of the carbon milled fiber in the conductive polyamide resin composition needs to be 1 to 5% by weight. When the content of the carbon milled fiber is less than 1% by weight, the decrease in the fluidity of the polyamide resin composition cannot be suppressed. If 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 fibers 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 the desired conductivity to the polyamide resin. By setting the content of the conductive agent to 20% by weight or less, it becomes easy to suppress a decrease in the fluidity of the polyamide resin composition. The content of the conductive agent in the conductive polyamide resin composition is more preferably 7 to 15% by weight.

The volume resistivity of the conductive polyamide resin composition of the present invention, which is an index of conductivity, is preferably as small as possible, but preferably ^{less than 1 × 10 5} Ω · cm, and less than 1 × 10 ⁴ Ω · cm. More preferably, it 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. The volume resistivity can be measured by the method described in Examples described later.

The L / T flow length, which is an index of the moldability of the conductive polyamide resin composition of the present invention, is preferably as large as possible, preferably 64 mm or more, more preferably 68 mm or more, and 72 mm or more. It is more preferably 76 mm or more, and particularly preferably 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 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, is preferably 16 kJ / m ² or more, at 17 kJ / m ² or more It is more preferably 18 kJ / m ² or more, and ^{particularly preferably 19 kJ / m 2} or more. The Charpy impact strength (without 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 Examples described later.

<Molded product>
The molded product of the present invention contains the above-mentioned conductive polyamide resin composition, and more specifically, the above-mentioned conductive polyamide resin composition is molded.

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

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

As an example and a comparative example of the present invention, a conductive polyamide resin composition was produced by the method shown below and evaluated as shown below. The results are shown in Table 1.

<Example 1>
90 parts by weight of polycaprolactam (PA6, Ube Industries, product name: 1013B), 8 parts by weight of Ketjen Black (KB, Mitsubishi Chemical, product name: 3400B), and carbon milled fiber (CMF, Mitsubishi Rayon, product name) : Dialead K6371M, number average fiber length: 50 μm, tensile strength: 2600 MPa) 2 parts by weight were mixed. The obtained mixture is melt-kneaded using a twin-screw kneader having a cylinder diameter of 40 mm under the condition of a cylinder set temperature of 260 ° C., extruded into strands, cooled in a water tank, and then pellets of the polyamide resin composition using a pelletizer. Was produced. Then, the pellets of the obtained polyamide resin composition were appropriately injection-molded to obtain test pieces for conducting conductivity evaluation and impact resistance evaluation, which will be described later.

<Example 2>
Pellets and various tests of the conductive polyamide resin composition were carried out in the same manner as in Example 1 except that the blending amount of Ketjen Black was changed to 6 parts by weight and the blending amount of carbon milled fiber was changed to 4 parts by weight. I got a piece.

<Comparative example 1>
Pellets of the conductive polyamide resin composition and various test pieces were obtained in the same manner as in Example 1 except that the blending amount of Ketjen Black was changed to 10 parts by weight and carbon milled fiber was not blended.

<Comparative example 2>
Pellets and various tests of the conductive polyamide resin composition were carried out in the same manner as in Example 1 except that the blending amount of Ketjen Black was changed to 4 parts by weight and the blending amount of carbon milled fiber was changed to 6 parts by weight. I got a piece.

<Comparative example 3>
Pellets of the conductive polyamide resin composition and various test pieces were obtained in the same manner as in Example 1 except that the amount of carbon milled fiber compounded was changed to 10 parts by weight without blending Ketjen Black.

<Comparative example 4>
A conductive polyamide resin composition similar to 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>
A conductive polyamide resin composition similar to 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>
A conductive polyamide resin composition similar to 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.

<Evaluation of conductivity>
Tested by the four-terminal method using a low resistivity meter (manufactured by Mitsubishi Chemical Co., Ltd., trade name: Loresta GP) conforming to JIS K7194 as an index of conductivity of the conductive polyamide resin compositions produced in Examples and Comparative Examples. The volume resistivity of the piece was measured. Then, the conductivity of the conductive polyamide resin composition was evaluated according to the following criteria.
⊚: Volume resistivity ^{less than 1 × 10 2} Ω · cm ○: Volume resistivity less than 1 × 10 ² Ω · cm 1 × 10 ⁵ Ω · cm ×: Volume resistivity less than 1 × 10 ⁵ Ω · cm

<Evaluation of moldability>
The L / T flow length of the pellets of the polyamide resin composition was measured as an index of the moldability of the conductive polyamide resin compositions produced in Examples and Comparative Examples. Specifically, an injection molding machine (manufactured by Nissei Resin Industry Co., Ltd., trade name: PS40E) equipped with a bar flow mold having a cavity thickness of 1 mm and a width of 15 mm is used, and the cylinder temperature is 260 ° C, the mold temperature is 80 ° C, and the injection pressure is high. The pellets were injection molded under the molding conditions of 50 MPa, an injection speed of 38 mm / sec, an injection time of 4 seconds, and a cooling time of 15 seconds. Then, 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 (without notch) of the test piece was measured according to ISO179 as an index of the impact resistance of the conductive polyamide resin compositions produced in Examples and Comparative Examples. Then, the impact resistance of the conductive polyamide resin composition was evaluated according to the following criteria.
◯: Charpy impact strength (without notch) is 16 kJ / m ² or more ×: Charpy impact strength (without notch) is less than ^{16 kJ / m 2.}

As described above, the conductive polyamide resin composition of the present invention (Examples 1 and 2) had an excellent balance of conductivity, moldability, and impact resistance.

Claims (4)

Polyamide resin and
Containing with conductive agents including carbon black and carbon milled fiber,
The carbon black content is 5-9% by weight.
The carbon milled fiber has a number average fiber length of 10 to 250 μm.
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 the 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 or 2, wherein the carbon black is Ketjen black. A molded product containing the conductive polyamide resin composition according to any one of claims 1 to 3.