JP2006037001A - Electrode made from thermoplastic resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode made from a thermoplastic resin, equipped with a high electroconductivity, molding processability and mass production property jointly. <P>SOLUTION: This electrode made from the thermoplastic resin is characterized by containing 10-50 wt.% electroconductive fiber having 0.35-2 mm weight-average fiber length. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a thermoplastic resin electrode having high conductivity, moldability and mass productivity.

  In general, metal is used for the electrode, but if it rusts in the presence of water, the conductivity will decrease, and the degree of freedom of the shape of the molded product will be low, leading to increased costs. It is being considered.

  In order to apply the resin material to the electrode, it is necessary to impart conductivity. In order to impart conductivity to the resin material, a method of adding a highly conductive material such as a metal or carbon fiber or filler to the matrix resin is generally used, and in recent years, improvement by nanotechnology has been actively studied.

  For example, a highly conductive resin molded article formed by molding a resin composition containing a thermoplastic resin and fine carbon fibers having an average fiber diameter of 100 nm or less is disclosed (Patent Document 1). In this technique, fine carbon fibers are aggregated to some extent and dispersed in a matrix resin to form a continuous network, whereby high conductivity can be obtained. Further, it is disclosed that carbon fibers such as carbon nanotubes are dispersed in a matrix and used as a highly conductive member in which the tip of the carbon fiber protrudes on a molding surface and as an electrode element that emits electrons. (Patent Document 2).

However, in these techniques, as described in the examples, the conductivity of the molded product is larger than 10 ⁻¹ Ω · m, which is insufficient for use as an electrode.

  In addition, a conductive member such as an electrode made of a conductive curable resin composition made of a curable resin having a specific viscosity and a carbonaceous material and a cured product thereof is disclosed (Patent Document 3). Further, a rod-shaped electrode material made of a long-fiber carbon fiber oriented along the axial direction and a matrix resin is disclosed (Patent Document 4). According to these methods, although high conductivity can be obtained, like a metal material, the degree of freedom of shape of a molded product is low, and further, molding processing is difficult, so that it is inferior in mass productivity and disadvantageous in cost.

As described above, there has been a strong demand for the development of an electrode having high conductivity, moldability, and mass productivity.
JP 2004-35826 A JP 2004-107534 A JP 2003-268249 A JP 7-11466 A

  An object of the present invention is to provide an electrode having high conductivity, molding processability, and mass productivity in view of the background of the conventional technology.

  That is, the present invention provides a thermoplastic resin electrode characterized by containing 10 to 100 parts by weight of conductive fibers having a weight average fiber length of 0.35 to 2 mm with respect to 100 parts by weight of a thermoplastic resin. .

  According to the present invention, it is possible to provide an electrode having high conductivity, molding processability, and mass productivity.

  Hereinafter, the present invention will be specifically described.

  The electrode of the present invention is based on a thermoplastic resin. Thereby, it is possible to obtain rust prevention, molding processability and mass productivity superior to those of metals.

  The thermoplastic resin needs to contain 10 to 100 parts by weight of conductive fibers with respect to 100 parts by weight of the thermoplastic resin in order to impart conductivity of the electrode. If the amount is less than 10 parts by weight, sufficient conductivity cannot be imparted to the electrode. If the amount exceeds 100 parts by weight, there is a problem because the fluidity during molding decreases.

  As the conductive fiber, for example, a fiber exhibiting conductivity alone such as carbon fiber, metal fiber (stainless steel fiber, copper fiber, etc.) can be employed.

  Insulating fiber (organic fiber such as aramid fiber, PBO fiber, polyphenylene sulfide fiber, polyester fiber, acrylic fiber, nylon fiber, polyethylene fiber, etc., inorganic fiber such as glass fiber, silicon carbide fiber, silicon nitride fiber, etc.) Alternatively, a fiber in which a conductive material (metal, metal oxide, carbon, etc.) is coated on a conductive fiber (metal fiber, carbon fiber) can also be used. The conductor can be coated by plating (electrolytic or electroless), CVD, PVD, ion plating, vapor deposition, etc., and can be coated with a metal such as nickel, ytterbium, gold, silver, or copper. .

  These may be used alone or in combination of two or more. Among these, carbon fiber excellent in the balance of mechanical properties, conductivity, and specific gravity is preferable.

  Examples of the carbon fiber include polyacrylonitrile (PAN), pitch-based, cellulose-based, vapor-grown carbon fiber by hydrocarbon, graphite fiber, etc. Among them, mechanical properties such as strength and elastic modulus, etc. A PAN-based carbon fiber having an excellent balance is preferred.

  The weight average fiber length of the conductive fibers needs to be 0.35 to 2 mm. If it is less than 0.35 mm, the conductivity is insufficient. The thickness of 0.5 mm or more is preferable because excellent electromagnetic shielding properties and mechanical strength can be obtained. As for the upper limit, the longer one is more preferable from the viewpoint of conductivity. However, in the present thermoplastic resin molding technique, 2 mm is the limit due to the shear stress at the time of molding.

The weight average fiber length Lw is based on the fiber length Li of each fiber and the weight Wi.
Lw = Σ (Wi × Li) / ΣWi
In the case where the fiber diameter and density are constant, Ni represents the number of fibers having a fiber length Li,
Lw = Σ (Ni × Li ² ) / Σ (Ni × Li)
Can be measured as In addition, in order to obtain a sample for measuring the weight average fiber length of fibers in the thermoplastic resin, use a solvent that dissolves the thermoplastic resin without dissolving the fibers, sufficiently dissolve the thermoplastic resin component, and filter. The fibers may be separated by

  Examples of the thermoplastic resin used as a base in the present invention include polyamide, modified polyphenylene ether (PPE), polyacetal (POM), polyphenylene sulfide (PPS), liquid crystal polyester, polyethylene terephthalate, polybutylene terephthalate, and polycyclohexane dimethyl terephthalate. , Polyarylate, polycarbonate, polystyrene (PS), styrene resin such as HIPS, ABS, AES, AAS, acrylic resin such as polymethyl methacrylate (PMMA), polyolefin such as vinyl chloride, polyethylene, polypropylene, modified polyolefin, phenol Examples thereof include resins and phenoxy resins. Also, ethylene / propylene copolymer, ethylene / 1-butene copolymer, ethylene / propylene / diene copolymer, ethylene / carbon monoxide / diene copolymer, ethylene / ethyl (meth) acrylate copolymer, Various types such as ethylene / glycidyl (meth) acrylate, ethylene / vinyl acetate / glycidyl (meth) acrylate copolymer, polyether ester elastomer, polyether ether elastomer, polyether ester amide elastomer, polyester amide elastomer, polyester ester elastomer Examples include elastomers. Among these, one type may be used alone, or two or more types may be used in combination.

  From the viewpoint of electrode strength, chemical resistance, and abrasion resistance, PPS, polyamide, polyester, and polyacetal are preferable. Among them, polyamide having excellent balance of mechanical properties such as strength and abrasion resistance, surface appearance quality, and economic efficiency is preferable. More preferred.

  Examples of polyamides include nylon 6, nylon 66, nylon 6 / nylon 66 copolymer, nylon XD6, nylon MXD6, nylon 6T / 6I, nylon 66 / 6I, and nylon 6/66 / 6I copolymer. . Among them, nylon 6, nylon 66, nylon MXD6, and nylon 6/66 / 6I can obtain high fluidity at the time of molding, can suppress shrinkage and sink after molding, and are excellent in high moldability and appearance quality. preferable. Among these, polyamides may be used alone or in combination of two or more.

These polyamides preferably have a relative viscosity ηr of 1.5 to 2.5 from the viewpoint of fluidity during molding. Especially preferably, it is the range of 1.8-2.4.
The relative viscosity ηr can be measured at 25 ° C. using an Ostwald viscometer by dissolving 1 g of a thermoplastic resin in 100 mL of 98% sulfuric acid (98% sulfuric acid method). In order to measure the relative viscosity ηr of the thermoplastic resin, it can be measured after sufficiently dissolving the thermoplastic resin in a solvent capable of dissolving it and separating the thermoplastic resin by filtration. (The thermoplastic resin content of the electrode is determined from the content of other components (conductive fiber, conductive filler).)
The electrode of the present invention may further contain a conductive filler in order to impart conductivity. Examples of the conductive filler that can be used include carbon black, amorphous carbon powder, natural graphite powder, artificial graphite powder, expanded graphite powder, pitch microbeads, metal powder, and the like. Among these, carbon black is preferable from the viewpoint of improving conductivity.

  As the carbon black, for example, furnace black, acetylene black, thermal black, channel black, and the like can be employed. One of these may be used alone, or two or more may be used in combination. Of these, furnace black is preferable from the viewpoints of price, conductivity, and the like.

  As content of the conductive filler of an electrode, it is preferable to set it as 1-65 weight part with respect to 100 weight part of thermoplastic resins. When the amount is less than 1 part by weight, the effect of adding the conductive filler is not exhibited, and when the amount exceeds 65 parts by weight, the fluidity during molding deteriorates.

  Moreover, you may add an inorganic filler and an additive to a resin composition in the range which does not impair the objective of this invention according to the characteristic requested | required.

  Examples of the inorganic filler include glass fiber, glass powder, glass bead, aramid fiber, alumina fiber, aramid fiber, silicon carbide fiber, ceramic fiber, asbestos fiber, gypsum fiber, layered silicate (montmorillonite, beidellite, nontronite, Smectite clay minerals such as saponite, hectorite, saconite, vermiculite, various clay minerals such as halloysite, kanemite, kenyanite, zirconium phosphate, titanium phosphate, Li-type fluorine teniolite, Na-type fluorine teniolite, Na-type tetrasilicon fluorine mica, Li Swellable synthetic mica such as type tetrasilicon fluorine mica), calcined clay, talc, silica, magnesium oxide, titanium oxide, calcium silicate, wollastonite, zeolite, serinite, kaolin, bentonite, alumina Recoating, mica, titanium oxide, potassium titanate, calcium carbonate, magnesium carbonate, zinc carbonate, hydrotalcite, iron oxide, ferrite, iron hydroxide, and the like boron nitride.

  The inorganic fillers as described above may be used alone or in combination of two or more. Moreover, as the shape, powder shape, flake shape, fiber shape, whisker balloon shape, or the like can be adopted.

  Additives include crystal nucleating agents, ultraviolet absorbers, antioxidants, vibration control agents, antibacterial agents, insect repellents, deodorants, coloring inhibitors, heat stabilizers, mold release agents, antistatic agents, plasticizers, lubricants , Colorants, pigments, dyes, foaming agents, antifoaming agents, coupling agents, flame retardants and the like.

In the electrode of the present invention, the volume resistivity of the resin composition is preferably 10 ⁻⁵ to 10 ⁻³ Ω · m. More preferably, it is 10 ^<-5 > ^-10 <^{-4> (} omega ^| ohm) * m. If it has conductivity of 10 ⁻³ Ω · m or less, it can be suitably used as an electrode. The lower volume resistivity is more preferable, but the lower limit is set to 10 ⁻⁵ Ω · m because the limit that can be achieved by the thermoplastic resin electrode is 10 ⁻⁵ Ω · m.

  Here, the volume resistivity is a value measured according to the IEC 60093 standard. IEC stands for International Electrotechnical Commission, and IEC 60093 standard conforms to JIS K7194 standard. Such volume resistivity can be achieved by appropriately adopting conductive fibers or auxiliary conductive fillers as described above.

  As a method for producing the thermoplastic resin electrode of the present invention, from the viewpoint of productivity and mass productivity, it is preferable to prepare a pellet of a thermoplastic resin composition and use it for molding.

  As a method for producing pellets of a thermoplastic resin composition, a method of melting and kneading each essential component and optional additives at once, a method of melting and kneading a part of the components, and adding the remaining components from the middle, components It is possible to adopt a method of melting and kneading a part of the pellets in advance to form pellets once again and melt-kneading the remaining components again, a method of melting and kneading specific components separately to form a plurality of pellets, and blending them. .

  For melt kneading, it is preferable to use an apparatus capable of performing mechanical shearing in a molten state, such as a single screw extruder, a twin screw extruder, or a kneader. As a preferred embodiment of the melt-kneading apparatus, a vent port may be provided in order to remove moisture and low-molecular-weight volatile components generated during melt-kneading. Further, a plurality of hopper ports may be provided so that components can be added during the melt kneading.

  In addition, when carbon fiber is used as the conductive fiber and this is melt-kneaded with a thermoplastic resin, etc., the temperature of the cylinder to which mechanical shearing is applied (except for the vicinity of the raw material supply part) is the thermoplasticity of the resin composition. The melting point of the resin (preferably the flow starting point in the case of an amorphous resin such as modified PPE or polyarylate) is preferably 10 ° C. or higher. By doing so, excessive breakage of the carbon fiber due to shearing can be prevented. Other means for preventing excessive breakage of the carbon fiber include avoiding the shape of the screw that is subject to strong shearing, increasing the groove depth of the screw, and increasing the die diameter.

  Further, as another embodiment employing the carbon fiber, the continuous carbon fiber is passed through the molten thermoplastic resin so that the surface of the carbon fiber is coated with the thermoplastic resin, and the obtained strand is cooled to a predetermined state. It is also preferable to obtain long fiber pellets containing carbon fibers by cutting into lengths. According to the method for producing the pellet, a long fiber pellet in which conductive fibers substantially the same as the length of the pellet are arranged in the longitudinal direction of the pellet is obtained. When forming electrodes from long fiber pellets, carbon fiber breaks due to shear during molding, so it is better to set the cut length of the pellets (ie, the fiber length in the pellets) according to the desired fiber length in the molded product. In order to obtain 0.35 to 2 mm in the molded product as described above, the long fiber pellet is preferably 3 mm to 15 mm, more preferably 5 to 10 mm.

  The electrode of the present invention can be obtained by molding the resin composition thus obtained by a method such as injection molding, extrusion molding or compression molding. In particular, the injection molding has high productivity and is suitable for a molded product having a complicated shape and a thin molded product.

  In injection molding, in consideration of the following points, it is more preferable to suppress excessive breakage of carbon fibers. That is, preferable trends in molding conditions include lower back pressure, slower injection speed, slower screw rotation speed, and larger nozzle diameter in the injection molding machine, and screw groove depth. These include deepening, reducing the taper angle, reducing the compression ratio, and increasing the sprue diameter, runner diameter, and gate diameter in the molding die.

  The following examples illustrate the present invention more specifically.

[Measurement and evaluation method]
(1) Relative viscosity ηr of thermoplastic resin
1 g of thermoplastic resin was dissolved in 100 mL of 98% sulfuric acid and measured at 25 ° C. using an Ostwald viscometer.

(2) Molding lower limit pressure The molding lower limit pressure when a square plate of 100 mm x 100 mm x 3 mm was produced by injection molding was measured. The lower the molding lower limit pressure, the easier the molding and the better the moldability and mass productivity. Under these conditions, molding is difficult at a value greater than 150 kgf / cm ² .

(3) Volume resistivity A square plate of 100 mm × 100 mm × 3 mm was produced by injection molding, and the volume resistivity was measured according to IEC 60093 standard. The smaller the resistance value, the better the conductivity. The resin material used for the electrode of the present invention is preferably less than 10 ⁻³ Ω · m, and more preferably less than 10 ⁻⁴ Ω · m.

(4) Electrode Resistance An electrode having a shape as shown in FIG. 1 was injection molded, and the resistance value between the upper surface and the lower surface was measured with a general tester. The smaller the resistance value, the better the conductivity. In order to use it for an electrode, a resistance value of less than 140Ω is required, and less than 100Ω is more preferable.

(5) Weight average fiber length About 0.5 g was cut out from a part of the produced electrode, immersed in 100 cc of formic acid and left for 12 hours. After confirming that the components such as the resin were dissolved, the fibers were filtered using a paper filter. The fibers obtained through filtration were observed with a microscope, the fiber lengths of 400 randomly extracted fibers were measured, and calculated using the following formula under the assumption that the fiber diameter and density were constant. .
Lw = Σ (Ni × Li ² ) / Σ (Ni × Li)
Here, Lw is the weight average fiber length, Li is the fiber length, and Ni is the number of fibers having the fiber length Li.

(6) Comprehensive evaluation It judged comprehensively from the said moldability and electroconductivity (resistivity), and evaluated in three steps in order of *, (circle), (double-circle) from the worse one. ○ and ◎ are levels that can be used for electrodes.

[material]
The components used in each example and comparative example are as follows.

(Thermoplastic resin)
A-1: Nylon 6 resin (ηr = 2.4)
A-2: Nylon 66 resin (ηr = 2.2)
(Conductive fiber)
B-1: Long carbon fiber (Toray Industries, Inc. trading card T700SC-12K)
B-2: Short carbon fiber (Chopped trading card TS-12 manufactured by Toray Industries, Inc.)
(Conductivity imparting agent)
C-1: Carbon black (Mitsubishi Chemical Corporation 3050B)
[Example 1]
The entire amount of the material A-1 is extruded in a single-screw extruder in a sufficiently kneaded state in a crosshead die attached to the tip thereof, and at the same time, the yarn of the long carbon fiber B-1 is also put in the crosshead die. By continuously supplying, the melted thermoplastic resin or the like was coated on the surface of the long carbon fiber B-1.

  The obtained strand was subsequently cooled online and then cut online to a length of 7 mm with a cutter to form a pellet for molding.

  The obtained pellets were dried under vacuum at 80 ° C. for 5 hours or more, then subjected to injection molding of test pieces and electrodes, and using a J350E2-SP type injection molding machine manufactured by Nippon Steel Works, Ltd., 100 mm × 100 mm A 3 mm square plate and an electrode model molded product as shown in FIG. 1 were molded. Such an electrode model molded product has a shape of an upper surface φ10 mm, a lower surface φ20 mm, and a height 30 mm. The injection molding conditions were a cylinder temperature of 280 ° C., a mold temperature of 70 ° C., a cooling time of 30 seconds, and an injection speed of 70%.

[Examples 2-6, Comparative Examples 1, 2, 4]
With the composition ratios shown in Tables 1 and 2, the entire amount of thermoplastic resin and conductive filler was extruded with a single screw extruder in a sufficiently kneaded state in a crosshead die attached to the tip of the thermoplastic resin and conductive filler. The yarn of carbon fiber B-1 was also continuously fed into the crosshead die so that the molten thermoplastic resin or the like was coated on the surface of the yarn of long carbon fiber B-1.

  The obtained strand was subsequently cooled online and then cut online to a length of 7 mm with a cutter to form a pellet for molding.

  The obtained pellets were dried under vacuum at 80 ° C. for 5 hours or more, and thereafter, square plates and electrode model molded products were formed in the same manner as in Example 1.

[Comparative Examples 3 and 5]
Using a twin screw extruder (TEX30α manufactured by Nippon Steel Works) at a composition ratio as shown in Tables 1 and 2, the entire amount of materials A-1 and C-1 was supplied from the main feeder, and then material B -2 was fed from the side feeder and compounded. The cylinder temperature and the die temperature were set to 270 ° C., and the screw rotation speed was set to 200 rpm. Moreover, the decompression vent part was provided between the side feed part and the die, and the screw shape was arranged for full flight after the side feed.

  The obtained strand was continuously cooled online and then formed into pellets for molding with a cutter online.

  The obtained pellets were dried under vacuum at 80 ° C. for 5 hours or more, and thereafter, square plates and electrode model molded products were formed in the same manner as in Example 1.

  The compositions and evaluation results of Examples 1 to 6 and Comparative Examples 1 to 5 are shown in Tables 1 and 2.

As shown in Tables 1 and 2, Examples 1 to 6 had a good molding lower limit pressure of the square plate and an electrode resistance value of less than 130Ω. Moreover, the weight average fiber length of these electrodes was in the range of 0.44 to 0.48 mm. On the other hand, Comparative Examples 1, 3, and 5 have large volume resistance values and electrode resistance values, and cannot be used as electrodes. Further, Comparative Examples 2 and 4 are inferior in moldability because the square plate cannot be molded.

It is a schematic perspective view of an electrode model molded product.

Explanation of symbols

1: Electrode model molded product L1: Upper disc diameter L2: Lower plate diameter H1: Height

Claims (7)

A thermoplastic resin electrode, comprising 10 to 100 parts by weight of conductive fibers having a weight average fiber length of 0.35 to 2 mm with respect to 100 parts by weight of the thermoplastic resin. The thermoplastic resin electrode according to claim 1, comprising 1 to 65 parts by weight of a conductive filler other than conductive fibers. The thermoplastic resin electrode according to claim 1 or 2, which is obtained by molding a long fiber pellet in which conductive fibers substantially the same as the length of the pellet are arranged in the longitudinal direction of the pellet. The thermoplastic resin electrode according to any one of claims 1 to 3, wherein the conductive fiber is a carbon fiber. The volume resistivity is in the range of 10 ⁻⁵ to 10 ⁻³ Ω · m, and the thermoplastic resin electrode according to claim 1. The thermoplastic resin electrode according to any one of claims 1 to 5, wherein the thermoplastic resin is one or a mixture of two or more selected from polyamide, polyester, polyphenylene oxide, and polyacetal. The thermoplastic resin electrode according to any one of claims 1 to 5, wherein the thermoplastic resin is polyamide.

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