JP4451176B2 - Conductive resin composition - Google Patents

Description

The present invention achieves a level of electroconductivity that can be electrostatically coated in the process of forming a large molded article such as an automobile exterior part and electrostatically coating, and maintains the same conductivity even after recycling. The present invention relates to a resin composition and an injection molded body.
The resin composition of the present invention can be used in a wide range of fields such as electric / electronic parts, OA parts, vehicle parts, machine parts, etc., and in particular, can be suitably used for automobile exterior parts capable of electrostatic coating.

Polyphenylene ether is used in a wide range of applications because it has excellent mechanical properties, electrical properties, and heat resistance, and also has excellent dimensional stability, but it is inferior in molding processability by itself. A technique for blending polyamide has been proposed (see, for example, Patent Document 1), and is currently a material used for a wide variety of applications.
Recently, the use of polyamide-polyphenylene ether alloys imparted with electrical conductivity to automotive exterior materials (fenders, door panels, etc.) capable of electrostatic coating has been rapidly advanced. Various characteristics such as conductivity, impact strength, heat resistance, fluidity and the like that can be electrostatically coated are listed as characteristics required for automobile exterior materials.

As a technique for imparting electrical conductivity to the polyamide-polyphenylene ether alloy, for example, carbon black is mainly contained in the polyamide phase, or carbon black is uniformly dispersed in the polyamide in advance and then mixed with the polyphenylene ether. A technique for reducing the surface resistance value is disclosed (for example, see Patent Document 2). In addition, techniques and products for finely and uniformly dispersing such fine powders such as carbon black in a high-viscosity substance are generally presented (for example, see Non-Patent Document 1).
However, in the above-described technology, when the runner portion of the molded product is recycled, there is a problem that the conductivity becomes worse than before recycling. Therefore, in particular, in a process of forming a large molded product such as an automobile exterior part and applying electrostatic coating, it cannot be sufficiently applied to an application requiring a level of conductivity that enables electrostatic coating. Therefore, the current situation is that the development of new technology is awaited.

Japanese Patent Publication No. 45-997 JP-A-2-201811 Chemical Technology Journal (MOL) November 1987 41-46

  The present invention achieves a level of electroconductivity that can be electrostatically coated in the process of forming a large molded article such as an automobile exterior part and electrostatically coating, and maintains the same conductivity even after recycling. It aims at providing a resin composition and a molded object.

As a result of investigations to solve the above problems, the present inventors have surprisingly found that a part of the conductive carbon black to be used is present as a secondary aggregate having an area of 8 μm ² or more, and the resin composition By producing a resin composition in which the secondary agglomerates having an area of 8 μm ² or more to the total conductive carbon black in the resin composition are 20% by weight or more, a level of conductivity capable of electrostatic coating is achieved. Further, the inventors have found that the same electrical conductivity can be maintained even after further recycling, and have reached the present invention.
That is, the present invention includes polyamide, polyphenylene ether, and conductive carbon black, and a part of the conductive carbon black exists as a secondary aggregate having an area of 8 μm ² or more, and is based on the total conductive carbon black in the resin composition. A conductive resin having a level of conductivity that can be electrostatically coated, with an abundance ratio of secondary agglomerates having an area of 8 μm ² or more, of 20% by weight or more, and that retains the same conductivity even when recycled. Relates to the composition. The present invention also relates to an injection-molded article made of the resin composition, particularly to a molded article for automobile exterior.

  The conductive resin composition of the present invention achieves excellent conductivity at a level capable of electrostatic coating, and has an effect of maintaining excellent conductivity after recycling.

The present invention will be specifically described below.
Each component constituting the conductive resin composition of the present invention will be described in detail.
Any type of polyamide that can be used in the present invention can be used as long as it has an amide bond {—NH—C (═O) —} in the polymer main chain.
In general, polyamides are obtained by ring-opening polymerization of lactams, polycondensation of diamine and dicarboxylic acid, polycondensation of aminocarboxylic acid, and the like, but are not limited thereto.
The diamines are roughly classified into aliphatic, alicyclic and aromatic diamines. Specific examples include tetramethylene diamine, hexamethylene diamine, undecamethylene diamine, dodecamethylene diamine, tridecamethylene diamine, 2, 2 , 4-trimethylhexamethylenediamine, 2,4,4-trimethylhexamethylenediamine, 5-methylnanomethylenediamine, 1,3-bisaminomethylcyclohexane, 1,4-bisaminomethylcyclohexane, m-phenylenediamine, p -Phenylenediamine, m-xylylenediamine, p-xylylenediamine and the like.

Dicarboxylic acids are roughly classified into aliphatic, alicyclic and aromatic dicarboxylic acids. Specific examples include adipic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, 1,1,3-tridecane. Examples include diacid, 1,3-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, dimer acid and the like.
Specific examples of lactams include ε-caprolactam, enantolactam, and ω-laurolactam.
Specific examples of aminocarboxylic acids include ε-aminocaproic acid, 7-aminoheptanoic acid, 8-aminooctanoic acid, 9-aminononanoic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid, and 13-aminotriic acid. Examples include decanoic acid.

In the present invention, any of copolyamides obtained by polycondensation of these lactams, diamines, dicarboxylic acids, and ω-aminocarboxylic acids alone or in a mixture of two or more types can be used.
Further, those obtained by polymerizing these lactams, diamines, dicarboxylic acids, and ω-aminocarboxylic acids up to a low molecular weight oligomer stage in a polymerization reactor and increasing the molecular weight in an extruder or the like can be suitably used.

  Particularly, polyamide resins that can be usefully used in the present invention include polyamide 6, polyamide 6,6, polyamide 4,6, polyamide 11, polyamide 12, polyamide 6,10, polyamide 6,12, polyamide 6 / 6,6. , Polyamide 6 / 6,12, polyamide 6 / MXD (m-xylylenediamine), polyamide 6, T, polyamide 6, I, polyamide 6/6, T, polyamide 6/6, I, polyamide 6,6 / 6 , T, polyamide 6,6 / 6, I, polyamide 6/6, T / 6, I, polyamide 6,6 / 6, T / 6, I, polyamide 6/12/6, T, polyamide 6,6 / 12/6, T, polyamide 6/12/6, I, polyamide 6, 6/12/6, I and the like, and polyamides obtained by copolymerizing a plurality of polyamides with an extruder or the like are also used. It is possible.

Preferred polyamides are polyamide 6, polyamide 6,6, polyamide 6 / 6,6 and mixtures thereof. More preferred is polyamide 6,6.
The number average molecular weight of the polyamide resin used in the present invention is preferably 5,000 to 100,000, more preferably 10,000 to 30,000.
The polyamide resin in the present invention is not limited to these, and may be a mixture of a plurality of polyamide resins having different molecular weights. For example, a mixture of a low molecular weight polyamide having a number average molecular weight of less than 15,000 and a high molecular weight polyamide having a number average molecular weight of 15,000 or more.
The end groups of the polyamide are involved in the reaction with the polyphenylene ether. Polyamide resins generally have amino groups and carboxyl groups as end groups. Generally, when the carboxyl group concentration increases, impact resistance decreases, fluidity improves, and conversely the amino group concentration increases. Impact resistance improves and fluidity decreases.

In the present invention, these preferred ratios are amino group / carboxyl group concentration ratios of 9/1 to 1/9, more preferably 8/2 to 1/9, still more preferably 6/4 to 1/9. is there.
The concentration of the terminal amino group is preferably at least 10 meq / kg. More preferably, it is 30 meq / kg or more.
As a method for adjusting the end groups of these polyamide resins, a known method that will be apparent to those skilled in the art can be used. For example, a method of adding diamines, dicarboxylic acids, monocarboxylic acids or the like so that a predetermined terminal concentration is obtained during polymerization of the polyamide resin, or a method of adjusting by a mixture of two or more types of polyamide resins having different terminal group ratios, etc. Is mentioned.
Also, a metal stabilizer as described in JP-A-1-163262, which is known for the purpose of improving the heat resistance stability of the polyamide resin, can be used without any problem.

Among these metal stabilizers, those that can be particularly preferably used include CuI, CuCl ₂ , copper acetate, cerium stearate, and the like. Also, alkali metal halide salts represented by potassium iodide, potassium bromide and the like can be suitably used. Of course, these may be added together.
A preferable blending amount of the metal stabilizer and / or the alkali metal halide is 0.001 to 1 part by weight with respect to 100 parts by weight of the polyamide resin as a total amount.
Furthermore, in addition to the above, known additives that can be added to the polyamide may be added in an amount of less than 10 parts by weight with respect to 100 parts by weight of the polyamide.
The polyphenylene ether that can be used in the present invention is a homopolymer and / or copolymer comprising the structural unit of the formula (1).

[Wherein O is an oxygen atom, R is independently hydrogen, halogen, primary or secondary lower alkyl, phenyl, haloalkyl, aminoalkyl, hydrocarbonoxy, or halohydrocarbonoxy (provided that At least two carbon atoms separating the halogen atom and the oxygen atom). ]

  Specific examples of the polyphenylene ether of the present invention include, for example, poly (2,6-dimethyl-1,4-phenylene ether), poly (2-methyl-6-ethyl-1,4-phenylene ether), poly (2-methyl-6-phenyl-1,4-phenylene ether), poly (2,6-dichloro-1,4-phenylene ether) and the like, and 2,6-dimethylphenol and other phenols (For example, a copolymer with 2,3,6-trimethylphenol or a copolymer with 2-methyl-6-butylphenol as described in Japanese Patent Publication No. 52-17880). Also included are polyphenylene ether copolymers.

Among these, particularly preferred polyphenylene ether is poly (2,6-dimethyl-1,4-phenylene ether), a copolymer of 2,6-dimethylphenol and 2,3,6-trimethylphenol, or a mixture thereof. It is.
The production method of the polyphenylene ether used in the present invention is not particularly limited, and known methods can be used. For example, U.S. Pat. Nos. 3,306,874, 3,306,875, 3,257,357, and Examples include the production methods described in Japanese Patent No. 3257358, JP-A-50-51197, and JP-A-63-152628.

The reduced viscosity of the polyphenylene ether that can be used in the present invention (ηsp / c: 0.5 g / dl, chloroform solution, measured at 30 ° C.) is preferably in the range of 0.15 to 0.70 dl / g, More preferably, it is the range of 0.20-0.60 dl / g, More preferably, it is the range of 0.40-0.55 dl / g.
In the present invention, even a blend of two or more polyphenylene ethers having different reduced viscosities can be used without any problem. For example, a mixture of a polyphenylene ether having a reduced viscosity of 0.45 dl / g or less and a polyphenylene ether having a reduced viscosity of 0.50 dl / g or more, a low molecular weight polyphenylene ether having a reduced viscosity of 0.40 dl / g or less, and a reduced viscosity of 0.50 dl / g or more. A mixture of polyphenylene ethers, etc., of course, is, of course, not limited to these.

In the polyphenylene ether that can be used in the present invention, the organic solvent derived from the polymerization solvent may remain in an amount of less than 5% by weight based on 100 parts by weight of the polyphenylene ether. These organic solvents resulting from the polymerization solvent are difficult to remove completely in the drying step after polymerization, and usually remain in the range of several hundred ppm to several percent. Examples of the organic solvent resulting from the polymerization solvent include one or more of toluene, xylene isomers, ethylbenzene, alcohols having 1 to 5 carbon atoms, chloroform, dichloromethane, chlorobenzene, dichlorobenzene and the like. .
In addition, the polyphenylene ether that can be used in the present invention may be a polyphenylene ether modified in whole or in part.

The modified polyphenylene ether here means at least one carbon-carbon double bond or triple bond and at least one carboxylic acid group, acid anhydride group, amino group, hydroxyl group, or glycidyl in the molecular structure. The polyphenylene ether modified with at least one modifying compound having a group.
The method for producing the modified polyphenylene ether includes (1) a modified compound without melting the polyphenylene ether at a temperature in the range of 100 ° C. or higher in the presence or absence of a radical initiator and lower than the glass transition temperature of the polyphenylene ether. (2) A method in which polyphenylene ether and a modifying compound are melt-kneaded and reacted at a temperature in the range of the glass transition temperature of polyphenylene ether to 360 ° C. in the presence or absence of a radical initiator, ( 3) A method of reacting a polyphenylene ether and a modifying compound in a solution at a temperature lower than the glass transition temperature of the polyphenylene ether in the presence or absence of a radical initiator may be mentioned. , (1) and (2) are preferred.

Next, at least one modified compound having at least one carbon-carbon double bond or triple bond and at least one carboxylic acid group, acid anhydride group, amino group, hydroxyl group, or glycidyl group in the molecular structure Will be described in detail.
Examples of modified compounds having a carbon-carbon double bond, a carboxylic acid group, and an acid anhydride group in the molecule include maleic acid, fumaric acid, chloromaleic acid, cis-4-cyclohexene-1,2-dicarboxylic acid, and these And acid anhydrides. Fumaric acid, maleic acid, and maleic anhydride are particularly preferable, and fumaric acid and maleic anhydride are particularly preferable.
In addition, one in which one or two of the carboxyl groups of the unsaturated dicarboxylic acid is an ester can be used.

Examples of the modified compound having both a carbon-carbon double bond and a glycidyl group in the molecule include allyl glycidyl ether, glycidyl acrylate, glycidyl methacrylate, and epoxidized natural fats and oils.
Among these, glycidyl acrylate and glycidyl methacrylate are particularly preferable.
Examples of the modified compound having both a carbon-carbon double bond and a hydroxyl group in the molecule include general formulas C _n H _2n-3 such as allyl alcohol, 4-penten-1-ol, and 1,4-pentadien-3-ol. Examples thereof include unsaturated alcohols of OH (n is a positive integer), general alcohols such as C _n H _2n-5 OH, C _n H _2n-7 OH (n is a positive integer), and the like.

The above-described modifying compounds may be used alone or in combination of two or more.
The amount of the modifying compound added when producing the modified polyphenylene ether is preferably from 0.1 to 10 parts by weight, more preferably from 0.3 to 5 parts by weight, based on 100 parts by weight of the polyphenylene ether.
A preferable amount of the radical initiator in producing the polyphenylene ether modified with the radical initiator is 0.001 to 1 part by weight with respect to 100 parts by weight of the polyphenylene ether.

The addition rate of the modifying compound in the modified polyphenylene ether is preferably 0.01 to 5% by weight. More preferably, it is 0.1 to 3% by weight.
In the modified polyphenylene ether, an unreacted modified compound and / or a polymer of the modified compound may remain.
In order to reduce the amount of the modified compound and / or polymer of the modified compound remaining in the modified polyphenylene ether, an amide bond and / or an amide bond and / or Alternatively, a compound having an amino group may be added.

The compound having an amide bond here is a compound having an amide bond {—NH—C (═O) —} structure in the molecular structure, and the compound having an amino group has a {—NH ₂ } structure at the terminal. It is a compound which has this. Specific examples of these compounds include aliphatic amines such as octylamine, nonylamine, tetramethylenediamine, hexamethylenediamine, aniline, m-phenylenediamine, p-phenylenediamine, m-xylylenediamine, p-xylylenediamine. Aromatic amines such as the above, reactants of the above amines with carboxylic acid, dicarboxylic acid and the like, lactams such as ε-caprolactam, and polyamide resins, but are not limited thereto.
A preferable addition amount when adding the compound having an amide bond or an amino group is 0.001 part by weight or more and less than 5 parts by weight with respect to 100 parts by weight of the polyphenylene ether. Preferably they are 0.01 weight part or more and less than 1 weight part, More preferably, they are 0.01 weight part or more and less than 0.1 weight part.

Next, the conductive carbon black that can be used in the present invention will be described.
The conductive carbon black that can be used in the present invention preferably has a dibutyl phthalate (DBP) oil absorption of 250 ml / 100 g or more, more preferably has a DBP oil absorption of 300 ml / 100 g or more, more preferably 350 ml / 100 g or more. Black. The DBP oil absorption referred to here is a value measured by a method defined in ASTM D2414.
The conductive carbon black that can be used in the present invention preferably has a BET surface area of 200 cm ² / g or more, and more preferably 400 cm ² / g or more. Examples of commercially available products include Ketjen Black International's Ketjen Black EC and Ketjen Black EC-600JD.

Further, the conductive carbon black may be used in the form of granules as it is, and may be melt-mixed with the thermoplastic resin, or may be previously pulverized and powdered and melt-mixed with the thermoplastic resin.
A preferable amount of the conductive carbon black is 0.2 to 5 parts by weight when the amount of all components excluding the conductive carbon black is 100 parts by weight. More preferably, it is 0.2-3 weight part, More preferably, it is 0.5-2.5 weight part, and it is excellent in the balance of an impact property, fluidity | liquidity, and electroconductivity.

The conductive resin composition of the present invention can be obtained by melt-kneading polyamide, polyphenylene ether and conductive carbon black.
What is important in the present invention is that a part of the conductive carbon black is present as a secondary aggregate, and the abundance ratio of the secondary aggregate is 20% of the total conductive carbon black in the conductive resin composition. It is more than weight%. The abundance ratio of the secondary aggregate is preferably 20% by weight or more and 80% by weight or less, and more preferably 20% by weight or more and 50% by weight or less.

  The size and abundance ratio of the secondary aggregate of conductive carbon black in the present invention are measured by the method described below. Specifically, using a reflection optical microscope (PME3: manufactured by Olympus Corporation), the dispersion state of carbon black on the smooth surface of the observation sample was observed at a magnification of 100 times and photographed. Furthermore, the photographed reflection micrograph was converted into a digital image with a scanner (CC-600PX: manufactured by Epson Corporation). The capture resolution was 400 dpi. The area fraction occupied by the black phase (secondary aggregate of carbon black) observed in the field of view of the obtained digital image is automatically calculated using image processing software (Image-Pro PLUS Ver4.0J: manufactured by MEDIA CYBERNETCS). Analysis by measurement. In order to eliminate human factors, analysis conditions and procedures at the time of measurement were performed as follows.

(1) Filter: Median (impulse noise removal, intensity: 3 × 3 pixels, frequency: 2 times)
(2) Filter: flattening (object width 20 pixels, background: bright)
(3) Area fraction measurement conditions: area is 8 μm ² or more (corresponding to an average diameter of 3 μm or more: 7.06 μm ^{2 for} a circle with a diameter of 3 μm), and ellipse major axis ratio (diameter passing through the center of gravity is measured in 2 ° increments) The ratio of the major axis to the minor axis diameter) is 2 or less (to eliminate mess when cutting samples that are difficult to distinguish from elongated secondary aggregates), and the brightness range (256th floor color) In the histogram display, the hue range on the black side of the grayish white phase (polyamide-polyphenylene ether phase) was detected as an extraction target. In addition, the oval major / minor axis ratio which is not automatically counted as described above is larger than 2, and a large black phase which can be clearly judged as a secondary aggregate is manually traced around the black phase and added to the result. In addition, if there was a small mess when cutting the sample that could not be removed by the filter, it was manually deleted.

By the above method, the area fraction occupied by the secondary aggregate that is the black phase in the field of view was calculated, and the average value of 10 photographs (total field of view 10 mm ² ) was determined. Here, since it generally holds that the volume fraction occupied by the secondary aggregate is equal to the area fraction appearing on the cut surface, the area fraction was replaced with the volume fraction. Next, by using a true specific gravity of carbon black of 1.8 and a specific gravity of resin of 1.1, the volume fraction is converted into a weight fraction, whereby the weight fraction of the secondary aggregate having an area of 8 μm ² or more is obtained. Calculated. By dividing the weight fraction of the secondary aggregate by the weight fraction (charge amount) of the total carbon black, the existence ratio of the secondary aggregate having an area of 8 μm ² or more with respect to the total carbon black in the resin was calculated.

In the present invention, the conductive carbon black can be added in the form of a conductive masterbatch obtained by melt-kneading polyamide and conductive carbon black.
The conductive resin composition of the present invention may be blended with a styrenic thermoplastic resin as long as it is less than 50 parts by weight with respect to 100 parts by weight of the total of polyamide and polyphenylene ether. Examples of the styrenic thermoplastic resin in the present invention include homopolystyrene, rubber-modified polystyrene (HIPS), styrene-acrylonitrile copolymer (AS resin), styrene-rubbery polymer-acrylonitrile copolymer (ABS resin), and the like. Can be mentioned.
Further, known additives that can be added to polyphenylene ether may be added in an amount of less than 10 parts by weight based on 100 parts by weight of polyphenylene ether.
Moreover, you may mix | blend the impact improving material with the conductive resin composition of this invention.

The impact modifier that can be used in the conductive resin composition of the present invention is an aromatic vinyl compound composed of a polymer block mainly composed of an aromatic vinyl compound and a polymer block mainly composed of a conjugated diene compound. It is at least one selected from the group consisting of a conjugated diene compound block copolymer, a hydrogenated product thereof, and an ethylene-α-olefin copolymer.
Specific examples of the aromatic vinyl compound that can be used in the aromatic vinyl compound-conjugated diene compound block copolymer in the present invention include styrene, α-methylstyrene, vinyltoluene, and the like. More than one kind of compound is used, and styrene is particularly preferable among them.

Specific examples of the conjugated diene compound include butadiene, isoprene, piperylene, 1,3-pentadiene, etc., and one or more compounds selected from these are used, and among them, butadiene, isoprene and combinations thereof. Is preferred.
The microstructure of the soft segment portion of the conjugated diene compound of the block copolymer is preferably 1,2-vinyl content or the total amount of 1,2-vinyl content and 3,4-vinyl content of 5-80%, 10 to 50% is preferable, and 10 to 40% is most preferable.
In the block copolymer of the present invention, the polymer block A mainly composed of an aromatic vinyl compound and the polymer block B mainly composed of a conjugated diene compound are represented by AB type, ABA type, AB type. A block copolymer having a bond type selected from the -A-B type is preferable. Of course, a mixture thereof may be used.
Among these, the ABA type and the ABBA type are more preferable. Of course, these may be a mixture.

  The block copolymer of an aromatic vinyl compound and a conjugated diene compound that can be used in the conductive resin composition of the present invention is more preferably a hydrogenated block copolymer. The hydrogenated block copolymer is an aliphatic double bond of a polymer block mainly composed of a conjugated diene compound by subjecting the block copolymer of the aromatic vinyl compound and the conjugated diene compound to a hydrogenation treatment. Is controlled in the range of more than 0 and 100%. A preferable hydrogenation rate of the hydrogenated block copolymer is 50% or more, more preferably 80% or more, and most preferably 98% or more.

These block copolymers can be used without any problem as a mixture of a non-hydrogenated block copolymer and a hydrogenated block copolymer.
As the block copolymer used in the conductive resin composition of the present invention, it is desirable to use a mixture of a low molecular weight block copolymer and a high molecular weight block copolymer. Specifically, it is a mixture of a low molecular weight block copolymer having a number average molecular weight of less than 120,000 and a high molecular weight block copolymer having a number average molecular weight of 120,000 or more.
More preferably, it is a mixture of a low molecular weight block copolymer having a number average molecular weight of less than 100,000 and a high molecular weight block copolymer having a number average molecular weight of 200,000 or more.

The number average molecular weight referred to in the present invention is measured with an ultraviolet spectroscopic detector [UV-41: Showa Denko KK] using a gel permeation chromatography measuring device [GPC SYSTEM21: Showa Denko KK]. And the number average molecular weight in terms of standard polystyrene. The measurement conditions are as follows.
(Measurement condition)
Solvent: Chloroform Temperature: 40 ° C
Column: Sample side (KG, K-800RL, K-800R)
Reference side (K-805L x 2)
Flow rate: 10 ml / min Measurement wavelength: 254 nm
Pressure: 15-17 kg / cm ²
At this time, a low molecular weight component due to catalyst deactivation during polymerization may be detected. In this case, the low molecular weight component is not included in the molecular weight calculation. Usually, the calculated correct molecular weight distribution (weight average molecular weight / number average molecular weight) is in the range of 1.0 to 1.2.

The weight ratio of these low molecular weight block copolymer and high molecular weight block copolymer is low molecular weight block copolymer / high molecular weight block copolymer = 95/5 to 5/95. Preferably it is 90/10-10/90.
Further, as a low molecular weight block copolymer, heat resistance is improved by using a block copolymer in which the number average molecular weight of one polymer block mainly composed of an aromatic vinyl compound is 20,000 or more. Additional effects can be obtained.
The number average molecular weight of one polymer block mainly composed of an aromatic vinyl compound can be obtained by the following equation using the number average molecular weight of the block copolymer described above.
Mn (a) = {Mn × a / (a + b)} / N
[In the above formula, Mn (a) is the number average molecular weight of one polymer block mainly composed of an aromatic vinyl compound, Mn is the number average molecular weight of the block copolymer, and a is all of the block copolymers. % By weight of polymer block based on aromatic vinyl compound, b is weight% of polymer block based on all conjugated diene compounds in the block copolymer, and N is aromatic in block copolymer It represents the number of polymer blocks mainly composed of vinyl compounds. ]

In the present invention, a preferred range of the content of the polymer block mainly composed of the aromatic vinyl compound of the low molecular weight block copolymer is 55% by weight or more and less than 90% by weight. Since the heat resistance can be improved by using a block copolymer having an aromatic vinyl polymer block within this range as the low molecular weight block copolymer, it can be used more suitably.
Furthermore, in the present invention, a low molecular weight block copolymer, a block copolymer containing a polymer block mainly composed of an aromatic vinyl compound in an amount of 55 wt% or more and less than 90 wt%, and an aromatic vinyl compound By using a mixture with a block copolymer containing the main polymer block in an amount of 20 wt% or more and less than 55 wt%, the fluidity can be improved.

Moreover, what mixed previously the oil which has a paraffin as a main component may be used in the block copolymer used for the conductive resin composition of this invention. The processability of the resin composition can be improved by mixing oil mainly composed of paraffin in advance. In this case, the preferred amount of oil mainly composed of paraffin is 1 to 70 parts by weight with respect to 100 parts by weight of the block copolymer. When 70 parts by weight or more is mixed, the handleability is poor.
The oil mainly composed of paraffin here is a mixture of a hydrocarbon compound having a weight average molecular weight of 500 to 10,000, which is a combination of an aromatic ring-containing compound, a naphthene ring-containing compound, and a paraffinic compound. Yes, the paraffinic compound content is 50% by weight or more. More preferably, the paraffinic compound is 50 to 90% by weight, the naphthene ring-containing compound is 10 to 40% by weight, and the aromatic ring-containing compound is 5% by weight or less.

These oils mainly composed of paraffin are commercially available, and examples thereof include PW380 manufactured by Idemitsu Kosan Co., Ltd.
These block copolymers of aromatic vinyl compound-conjugated diene compound are different in bond type, different in aromatic vinyl compound type, different in conjugated diene compound type, unless otherwise contrary to the spirit of the present invention, Used with a mixture of 2-bond vinyl content or 1,2-bond vinyl content different from 3,4-bond vinyl content, different aromatic vinyl compound component content, or different hydrogenation rate It doesn't matter.

As the ethylene-α-olefin copolymer that can be used in the conductive resin composition of the present invention, an ethylene-α-olefin copolymer described in JP-A-2001-302911 can be used. .
Moreover, the impact improving material used for the conductive resin composition of the present invention may be an impact improving material modified in whole or in part.
As used herein, a modified impact modifier is at least one carbon-carbon double bond or triple bond and at least one carboxylic acid group, acid anhydride group, amino group, hydroxyl group in the molecular structure, or It refers to an impact modifier modified with at least one modifying compound having a glycidyl group.

  The method for producing the modified impact modifier is as follows: (1) In the presence or absence of a radical initiator, the impact modifier and the modifying compound at a temperature in the range of the softening point temperature of the impact modifier to 250 ° C. or less. (2) a method of reacting an impact modifier and a modifying compound in a solution at a temperature below the softening point of the impact modifier in the presence or absence of a radical initiator, and (3) Examples include a method in which the impact modifier and the modifying compound are reacted without melting at a temperature below the softening point of the impact modifier in the presence or absence of a radical initiator, and any of these methods may be used. The method (1) is preferable, and the method (1) is most preferably performed in the presence of a radical initiator.

At least one modification having at least one carbon-carbon double bond or triple bond and at least one carboxylic acid group, acid anhydride group, amino group, hydroxyl group, or glycidyl group in the molecular structure referred to herein. As the compound, the same modified compounds described for the modified polyphenylene ether can be used.
The preferred quantitative ratio of polyamide, polyphenylene ether and impact modifier in the conductive resin composition of the present invention is 30 to 70 parts by weight of polyamide and 20 to 50 parts by weight of polyphenylene ether when the total of these three components is 100 parts by weight. The impact modifier is in the range of 5 to 30 parts by weight. More preferably, it is within the range of 40 to 60 parts by weight of polyamide, 30 to 40 parts by weight of polyphenylene ether, and 5 to 15 parts by weight of impact modifier.

Moreover, you may add a compatibilizing agent to the conductive resin composition of this invention in the case of manufacture of a composition. The main purpose of using the compatibilizer is to improve the physical properties of the polyamide-polyphenylene ether mixture. The compatibilizing agent that can be used in the present invention refers to a polyfunctional compound that interacts with polyphenylene ether, polyamide, or both.
In any case, it is desirable that the resulting polyamide-polyphenylene ether mixture exhibits improved compatibility.
Examples of the compatibilizer that can be used in the conductive resin composition of the present invention are described in detail in JP-A-8-48869 and JP-A-9-124926, and these known phases are described. All the solubilizers can be used and can be used in combination.

Among these various compatibilizers, examples of particularly suitable compatibilizers include maleic acid, maleic anhydride, and citric acid.
A preferable amount of the compatibilizing agent that can be used in the conductive resin composition of the present invention is 0.1 to 20 parts by weight, more preferably 0.1 to 100 parts by weight of a mixture of polyamide and polyphenylene ether. -10 parts by weight.
In the present invention, an inorganic filler may be added.
Examples of the inorganic filler that can be used in the present invention include talc, kaolin, zonotlite, wollastonite, titanium oxide, potassium titanate, glass fiber, etc. Among them, wollastonite can be preferably used.

The wollastonite that can be used in the present invention is a product obtained by purifying, grinding and classifying a natural mineral containing calcium silicate as a component. Artificially synthesized materials can also be used. The size of wollastonite is preferably one having an average particle diameter of 2 to 9 μm and an aspect ratio of 5 or more, more preferably an average particle diameter of 3 to 7 μm and an aspect ratio of 5 or more, and further preferably an average particle diameter of 3 to 3. 7 μm and an aspect ratio of 8 or more.
Further, the wollastonite of the present invention preferably has a weight loss at 1000 ° C. of 1.5% by weight or less.

In addition, these wollastonites have higher fatty acids or their derivatives and derivatives such as salts (eg, stearic acid, oleic acid, palmitic acid, magnesium stearate, calcium stearate, aluminum stearate, stearic acid) as surface treatment agents. Amide, stearic acid ethyl ester, etc.) and coupling agents (for example, silane, titanate, aluminum, zirconium, etc.) can be used if necessary. The amount used is preferably 0.05 to 5% by weight based on wollastonite.
The preferred amount ratio of these wollastonites is 2 to 80 parts by weight based on 100 parts by weight of the total of polyamide, polyphenylene ether and impact modifier. More preferably, it is 2-70 weight part, More preferably, it is 5-60 weight part.
In the present invention, in addition to the above-described components, additional components may be added as necessary within a range not impairing the effects of the present invention.

Examples of additional components are listed below.
Other thermoplastic resins such as polyester and polyolefin, known adhesion improvers to increase the affinity between the inorganic filler and the resin, flame retardants (halogenated resins, silicone flame retardants, magnesium hydroxide, hydroxylation Aluminum, organophosphate compounds, ammonium polyphosphate, red phosphorus, etc.) Fluoropolymers exhibiting dripping prevention effects, plasticizers (oil, low molecular weight polyolefins, polyethylene glycols, fatty acid esters, etc.), and difficulties such as antimony trioxide Conductivity-imparting materials such as combustion aids, carbon black for coloring, carbon fibers, carbon nanotubes, carbon nanofibers, antistatic agents, various peroxides, zinc oxide, zinc sulfide, antioxidants, UV absorbers, light stability Agents.

The specific addition amount of these components is the range which does not exceed 100 weight part in total with respect to 100 weight part of total amounts of polyamide, polyphenylene ether, and an impact modifier.
Specific processing machines for obtaining the conductive resin composition of the present invention include, for example, a single screw extruder, a twin screw extruder, a roll, a kneader, a Brabender plastograph, a Banbury mixer, etc. A twin screw extruder is preferable, and a twin screw extruder having an upstream supply port and one or more downstream supply ports is most preferable.
The melt kneading temperature at this time is not particularly limited, but the conditions under which a suitable composition can be usually obtained can be arbitrarily selected from 240 to 360 ° C.

  As a preferable method for producing a conductive resin composition of the present invention, a twin screw extruder having an upstream supply port and a downstream supply port is used, and an impact modifier and polyphenylene ether are supplied from the upstream supply port and melt kneaded. After that, a method of supplying and melting and kneading polyamide and a conductive masterbatch from the downstream supply port, an upstream supply port and two or more downstream supply ports (among the downstream supply ports, the upstream side is the downstream side). (1) Supplying an impact modifier and polyphenylene ether from the upstream supply port, melt-kneading, and then downstream Examples include a method in which polyamide is supplied from the first side supply port and melt-kneaded, conductive carbon black is supplied from the second downstream supply port, and further melt-kneaded.

The conductive resin composition of the present invention thus obtained can be molded as molded parts of various parts by various conventionally known methods such as injection molding.
These various parts include, for example, IC tray materials, chassis of various disk players, electrical / electronic parts such as cabinets, OA parts and machine parts such as various computers and peripheral devices, motorcycle cowls, and automobile fenders. , Door panel, front panel, rear panel, rocker panel, rear bumper panel, back door garnish, emblem garnish, fuel inlet panel, over fender, outer door handle, door mirror housing, bonnette air intake, bumper, bumper guard, roof rail, Various aero parts such as roof rail legs, pillars, pillar covers, wheel covers, spoilers, exterior parts such as various malls and emblems, instrument panels , It can be suitably used for interior parts typified by console box, trims and the like.
Among these, it can be suitably used for exterior parts of automobiles to be electrostatically coated, in particular, automobile exterior parts that pass through a drying process of an electrodeposition paint together with a steel sheet, and in particular, can be suitably used for automobile fenders.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to what was shown by this Example.
(Raw materials used)
The raw materials used in Examples and the like are as follows.
(1) Polyamide (hereinafter abbreviated as PA)
Polyamide 66 (hereinafter abbreviated as PA66)
Number average molecular weight = 14,000
Terminal amino group concentration = 30 milliequivalents / kg
Terminal carboxyl group concentration = 100 milliequivalent / kg
(2) Polyphenylene ether (hereinafter abbreviated as PPE)
Poly (2,6-dimethyl-1,4-phenylene ether)
Reduced viscosity: 0.52 dl / g
(0.5 g / dl, chloroform solution, 30 ° C. measurement)
(3) Conductive carbon black Conductive carbon black (hereinafter abbreviated as KB)
Product name: Ketjen Black EC-600JD (Ketjen Black International)

(4) Block copolymer (4-1) Polystyrene-hydrogenated polybutadiene-polystyrene (hereinafter abbreviated as SEBS-1)
Number average molecular weight = 246,000
Total content of styrene components = 33%
(4-2) Polystyrene-hydrogenated polybutadiene-polystyrene (hereinafter abbreviated as SEBS-2)
Number average molecular weight = 113,000
Total content of styrene components = 60%
(5) Compatibilizer Maleic anhydride (Mitsubishi Chemical Corporation) (hereinafter abbreviated as MAH)
(Measuring method)
Hereinafter, a method for measuring the abundance ratio of conductive carbon black secondary aggregates (hereinafter abbreviated as “secondary aggregate abundance ratio”) and conductivity (volume resistivity) will be described.

<Secondary aggregate abundance ratio>
The obtained resin composition pellets were molded as a dumbbell bar as described in ISO 294 using a Toshiba IS-80EPN molding machine (cylinder temperature set at 280 ° C. and mold temperature set at 80 ° C.). The obtained molded product was fixed to an ultramicrotome (ULTRACUT S: manufactured by REICHERT-NISSEI), and an edge surface of about 2 × 3 mm was roughly cut out from the sample surface layer using a glass knife, and then further edged using a diamond knife. The surface was cut out to obtain an observation sample having a smooth surface.
Using a reflection optical microscope (PME3: manufactured by Olympus Corporation), the dispersion state of carbon black on the smooth surface of the observation sample was observed at a magnification of 100 times and photographed. Furthermore, the photographed reflection micrograph was converted into a digital image with a scanner (CC-600PX: manufactured by Epson Corporation). The capture resolution was 400 dpi. The area fraction occupied by the black phase (secondary aggregate of carbon black) observed in the field of view of the obtained digital image is automatically determined using image processing software (Image-Pro PLUS Ver4.0J: manufactured by MEDIA CYBERNETCS). Analysis by measurement. In order to eliminate human factors, analysis conditions and procedures at the time of measurement were performed as follows.

(1) Filter: Median (impulse noise removal, intensity: 3 × 3 pixels, frequency: 2 times)
(2) Filter: flattening (object width 20 pixels, background: bright)
(3) Area fraction measurement conditions: area is 8 μm ² or more (corresponding to an average diameter of 3 μm or more: 7.06 μm ^{2 for} a circle with a diameter of 3 μm), and ellipse major axis ratio (diameter passing through the center of gravity is measured in 2 ° increments) The ratio of the major axis to the minor axis diameter) is 2 or less (to eliminate mess when cutting samples that are difficult to distinguish from elongated secondary aggregates), and the brightness range (256th floor color) In the histogram display, the hue range on the black side of the grayish white phase (polyamide-polyphenylene ether phase) was detected as an extraction target. In addition, the oval major / minor axis ratio which is not automatically counted as described above is larger than 2, and a large black phase which can be clearly judged as a secondary aggregate is manually traced around the black phase and added to the result. In addition, if there was a small mess when cutting the sample that could not be removed by the filter, it was manually deleted.

By the above method, the area fraction occupied by the secondary aggregate that is the black phase in the field of view was calculated, and the average value of 10 photographs (total field of view 10 mm ² ) was determined. Here, since it generally holds that the volume fraction occupied by the secondary aggregate is equal to the area fraction appearing on the cut surface, the area fraction was replaced with the volume fraction. Next, by using a true specific gravity of carbon black of 1.8 and a specific gravity of resin of 1.1, the volume fraction is converted into a weight fraction, whereby the weight fraction of the secondary aggregate having an area of 8 μm ² or more is obtained. Calculated. By dividing the weight fraction of the secondary aggregate by the weight fraction (charge amount) of the total carbon black, the existence ratio of the secondary aggregate having an area of 8 μm ² or more with respect to the total carbon black in the resin was calculated.

<Volume resistivity>
The obtained resin composition pellets were molded as a dumbbell bar as described in ISO 294 using a Toshiba IS-80EPN molding machine (cylinder temperature set at 280 ° C. and mold temperature set at 80 ° C.). Both ends of this test piece were broken to obtain a portion having a uniform cross-sectional area of 10 × 4 mm and a length of about 70 mm and having fractured surfaces at both ends. Silver paint is applied to the fractured surfaces at both ends, and the volume resistivity between both fractured surfaces is measured using a digital ultrahigh resistance / microammeter [R8340A: manufactured by Advantest] at an applied voltage of 250V. Was calculated. The measurement was performed on five different test specimens, and the volume average was defined as the addition average.

<Surface roughness of the pellet (Ra)>
Based on JIS B 0601, the center line average roughness (Ra) of the pellet side horizontal portion of the master batch was measured using a surface roughness meter Surfcom 579A (manufactured by Tokyo Seimitsu Co., Ltd.). As measurement conditions, a standard probe (diamond, tip R5 μm) was used for the stylus, and the stylus travel speed was 0.3 mm / second, the measurement length was 2.5 mm, and the cutoff value was 0.8 mm. The average value of 10 measurement points was calculated.

<Low temperature impact test>
The obtained resin composition pellets were molded into a 90 mm × 50 mm flat plate with a thickness of 2.5 mm using a Toshiba IS-80EPN molding machine (cylinder temperature set to 280 ° C. and mold temperature set to 80 ° C.). The obtained molded piece was allowed to cool in a thermostatic bath at −30 ° C. for at least 2 hours. The cooled molded piece was taken out of the thermostat and measured immediately. For the measurement, a falling weight graphic impact tester (manufactured by Toyo Seiki Co., Ltd.) was used. A holder diameter of 40 mm, a striker diameter of 12.7 mm, and a striker weight of 6.5 kg was used. Energy was measured.

[Comparative Example 1, Examples 1-2]
Using a twin screw extruder [ZSK-25: manufactured by Werner & Frederer (Germany)] having one feed port on the upstream side and one feed port on the downstream side, a weight of 90 wt. Part of polyamide 66 and 10 parts by weight of conductive carbon black were melt-kneaded to prepare master batches (hereinafter abbreviated as PA66 / KB-MB1, PA66 / KB-MB2, PA66 / KB-MB3). Here, the screw configuration, the screw rotation speed, the discharge amount, and the like were adjusted so that the center line average roughness (Ra) of the pellet side surface horizontal portion was 0.25 to 1.18. Further, using the above twin screw extruder, under conditions set at a cylinder temperature of 300 ° C., polyphenylene ether and a block copolymer are supplied from the upstream supply port and melt-kneaded, and then the polyamide 66 is supplied from the downstream supply port. A conductive master batch (PA66 / KB-MB1) was supplied to prepare resin composition pellets made of polyamide 66, polyphenylene ether, and conductive carbon black. The obtained resin composition pellets were molded, and the secondary aggregate abundance ratio and volume resistivity were measured. Furthermore, the resin composition pellets were supplied from the upstream supply port and repelleted under the conditions set at a cylinder temperature of 300 ° C. using the above twin screw extruder, and then molded and measured for volume resistivity ( Volume resistivity after recycling). Each physical property value is shown together with the composition in Table 1.
From Table 1, it is possible to achieve high conductivity by the presence of secondary aggregates of conductive carbon black in the resin composition, and the same conductivity can be maintained even after recycling. Was possible.

[Example 3]
An automobile fender was molded using the conductive resin composition of Example 1. At this time, the secondary aggregate abundance ratio was 28%. The obtained automobile fender was subjected to electrostatic coating through an automobile painting process including a drying process of the electrodeposition paint. As a result, the amount of thermal deformation was extremely small and the electrostatic coating was satisfactory.

  The conductive resin composition of the present invention and the molded body made of the conductive resin composition can be used in a wide range of fields such as electric / electronic parts, OA parts, vehicle parts, machine parts, etc. It can be suitably used for paintable automobile exterior parts, particularly automobile fenders.

Claims (9)

Polyamide, a resin composition comprising a polyphenylene ether and conductive carbon black, observed total 10 mm ² field of view of 100 times using a reflection method optical microscope a resin composition as a molded body created under the conditions described in ISO294 when the part of the conductive carbon black is present as an area 8 [mu] m ² or more secondary aggregates, and the presence ratio of an area 8 [mu] m ² or more secondary aggregates all conductive carbon black in the resin composition On the other hand, the conductive resin composition is 20% by weight or more. To the presence ratio of the entire conductive carbon black secondary agglomerates of the surface product 8 [mu] m ² or more electrically conductive carbon black, conductive according to claim 1, characterized in that at least 20% by weight 80% by weight Resin composition. To the presence ratio of the entire conductive carbon black surface product 8 [mu] m ² or more conductive carbon blacks in the secondary aggregate, according to claim 1 or 2, characterized in that 20% by weight to 50% by weight Conductive resin composition. The amount of the conductive carbon black is 0.2 to 5 parts by weight with respect to a total of 100 parts by weight of all components excluding the conductive carbon black. Conductive resin composition. The conductive resin composition in any one of Claims 1-4. The conductive resin composition according to any one of claims 1 to 5, wherein the conductive resin composition is for automobile exteriors subjected to electrostatic coating after passing through a drying step of an electrodeposition paint together with a steel plate. An injection-molded article comprising the conductive resin composition according to any one of claims 1 to 6. The molded object for motor vehicle exterior which consists of a conductive resin composition in any one of Claims 1-6. An automobile fender comprising the conductive resin composition according to claim 1.