JP4956974B2 - Conductive thermoplastic resin composition and molded article - Google Patents

Description

The present invention is excellent in electrical conductivity and mechanical properties such as bending strength, flexural modulus and impact strength, and is used for automobile parts, building materials, liquid crystal related or semiconductor related trays, etc. The present invention relates to a conductive thermoplastic resin composition that is useful as a molding material for weak electrical parts.
The present invention also relates to a conductive thermoplastic resin molded article formed by molding this conductive thermoplastic resin composition.

  Today, resin products are required to have conductivity in various fields. For example, various attempts have been made to impart conductivity in order to develop antistatic properties, electromagnetic shielding, and electrostatic coating properties. Conventionally, it is known that a conductive resin composition and a molded product can be obtained by blending carbon black with a resin. In this case, in order to obtain high conductivity, it is necessary to mix a large amount of carbon black in the resin composition. However, if a large amount of carbon black is filled in the resin, the mechanical properties of the resulting molded product will deteriorate. Is a problem.

  Therefore, in order to balance mechanical properties and conductivity, carbon is added to conductive fiber reinforced composite material (Patent Document 1) in which carbon fiber and carbon black are blended with thermoplastic resin, or fiber reinforced composite material reinforced with glass fiber. A thermoplastic resin composition excellent in electrical properties blended with black (Patent Document 2) has been proposed.

  However, these techniques are insufficient in improving mechanical properties, particularly impact strength. That is, even when carbon fiber or glass fiber is blended, rigidity and elastic modulus are improved, but impact strength is not so much improved. This is because, for example, in a method of kneading glass chopped strands as reinforcing fibers using an ordinary extruder, the fibers are cut short in the kneading process, and the fibers are further broken by injection molding. As a result, even if the rigidity and the elastic modulus can be improved, the effect of improving the impact resistance cannot be obtained.

  In Patent Document 1, an extruder having a surface processed with a screw or a cylinder is used to supply continuous carbon fibers to prevent breakage of the fibers in the kneading process, but sufficient effects are not obtained.

As disclosed in Patent Documents 1 and 2, there is a technique (Patent Document 3) that improves mechanical properties by adopting stamping molding for those mainly for injection molded products. In stamping molding, the long fiber can be filled in the molded product as it is without cutting, so that a good reinforcing effect by the long fiber can be obtained. However, stamping molding has a problem that the molding cycle is longer than that of normal injection molding, and that molding takes time.
JP-A-11-116818 Japanese Patent Publication No.51-45297 Japanese Patent Laid-Open No. 10-158443

  The present invention eliminates the above-mentioned conventional problems, obtains a sufficient reinforcing effect by blending reinforcing fibers, and enhances the effect of developing the conductivity by carbon black, thereby obtaining good conductivity with a small amount of carbon black. Thus, it is possible to provide a conductive thermoplastic resin composition capable of further improving mechanical properties, and a conductive thermoplastic resin molded article formed by molding this conductive thermoplastic resin composition. With the goal.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have made an olefin resin as a matrix resin, an organic long fiber made of a resin having polarity, and a conductive thermoplastic containing carbon black powder as a conductive filler. The present inventors have found that a resin composition can solve the above problems, and have reached the present invention.
That is, the gist of the present invention is as follows.

[1] The following components (a), (b), and (c) are used in an amount of 60 to 95% by mass of component (a) with respect to the sum of components (a) and (b). A conductive thermoplastic resin composition containing 5 to 40% by mass of the content and containing 5 to 20 parts by mass per 100 parts by mass of the component (a) is molded. A conductive thermoplastic resin composition comprising: (c) a carbon black powder containing (a) an olefin-based resin pellet; and (b) a polar resin. The organic long fiber roving is (a) impregnated with an olefinic resin, then drawn and then cut to obtain an organic long fiber-containing olefinic resin pellet, and has a volume resistivity of 10 ⁸ (Ω · conductive heat, characterized in that cm) or less is Plastic molded article.
(A) Olefin resin (b) Organic long fiber made of a resin having polarity (c) Carbon black powder as a conductive filler

[2] A conductive thermoplastic resin molded article according to [1], wherein (b) the polar resin constituting the organic long fiber has a melting point of 200 ° C. or higher.

[3] The conductive thermoplastic resin molded article according to [1] or [2], wherein (b) the organic long fiber is a polyester fiber and / or a polyamide fiber.

[4] A conductive thermoplastic resin molded product according to [1] to [3], wherein (a) the olefin resin is a propylene resin.

[5] The conductive thermoplastic resin molded product according to [1] to [4], wherein (b) the average fiber length of the organic long fibers is 4 mm or more.

[ 6 ] The conductive thermoplastic resin molded article according to any one of [1] to [5] , wherein the conductive thermoplastic resin composition is injection-molded.

  If the conductive thermoplastic resin composition of the present invention contains an organic long fiber composed of an olefin resin and a polar resin and carbon black powder as a conductive filler, with a good reinforcing effect by the organic long fiber, Excellent mechanical properties can be obtained, and high conductivity can be expressed with a small amount of carbon black powder due to the following effects due to organic long fibers made of a polar resin. Therefore, it is possible to further improve the mechanical characteristics by reducing the blending amount of carbon black powder.

  That is, in the conductive thermoplastic resin composition of the present invention, organic long fibers made of a resin having polarity together with carbon black powder are dispersed three-dimensionally in a resin matrix made of an olefin resin which is a nonpolar resin. However, the carbon black powder in the composition is attracted to the organic long fibers made of a polar resin and becomes localized around the organic long fibers. And, in this way, the carbon black powder is localized around the organic long fiber, so that it is higher with the blending of the same amount of carbon black powder than when the carbon black powder is simply dispersed in the olefin resin. Conductivity can be obtained.

  In addition, the organic long fiber is superior in elasticity and ductility as compared with the glass fiber and the carbon fiber, and thus is not easily damaged in the molding process. For this reason, the length of the organic long fiber is sufficiently maintained in the molded product, and an excellent reinforcing effect by the organic long fiber can be obtained.

  The conductive thermoplastic resin composition of the present invention is excellent in conductive performance and also excellent in mechanical properties such as bending strength, bending elastic modulus, impact strength, etc. It is extremely useful industrially as a molding material for weak electric parts such as trays used in liquid crystal related or semiconductor related.

  Embodiments of the conductive thermoplastic resin composition and molded product of the present invention will be described in detail below.

[(A) Olefin resin]
There is no restriction | limiting in particular as (a) olefin resin used by this invention, Various olefin resin can be used. For example, ethylene homopolymer; vinyl monomers such as propylene, 1-butene and other α-olefins, vinyl acetate, (meth) acrylic acid, (meth) acrylic acid ester, etc., mainly composed of ethylene 1 type or 2 types of ethylene-type resin, such as a copolymer with 1 type, or 2 or more types of these; Propylene homopolymer; Other alpha-olefins, such as ethylene and 1-butene which made propylene the main component Propylene-based resins such as copolymers with the above; 1-butene homopolymer; 1-butene as the main component, and other α-olefins such as ethylene, propylene, etc. Butene-based resins such as polymers; and the like. These olefin-based resins may be homopolymers or copolymers, may be random copolymers, or may be block copolymers.
In addition, said "main component" refers to what is contained in an olefin resin 50weight% or more, Preferably it is 60weight% or more.

  Among these, a propylene-based resin is preferable from the viewpoint of excellent heat resistance, and specific examples thereof include, for example, a propylene homopolymer, or a propylene-ethylene random copolymer resin mainly composed of propylene, propylene-ethylene. Examples thereof include a block copolymer resin.

  As the polymerization mode of the olefin resin, any polymerization mode may be adopted as long as a resinous material can be obtained, but a gas phase method or a solution method is particularly preferable.

  As the olefin resin, the lower limit of the melt flow rate measured at a temperature of 230 ° C. and a load of 21.18 N in accordance with JIS K7210 is preferably 0.05 g / 10 minutes, and preferably 0.1 g / 10 minutes. Is particularly preferable, and the upper limit is preferably 200 g / 10 minutes, and particularly preferably 100 g / 10 minutes. When the melt flow rate is not less than the above lower limit, the molding processability as the conductive thermoplastic resin composition tends to be improved, and the surface appearance of the obtained molded product tends to be good, whereas, at the above upper limit or less. In some cases, the mechanical strength of the conductive thermoplastic resin composition and the dispersion of organic long fibers tend to be better.

  In the conductive thermoplastic resin composition of the present invention, only one of the olefin-based resins of component (a) may be contained, or two or more kinds may be mixed and contained.

[(B) Organic long fiber made of a polar resin]
The resin constituting the organic long fiber comprising the resin having polarity (b) used in the present invention is not particularly limited as long as it has polarity, and various resins can be exemplified.
Here, the term “polar” refers to a resin that is more polar than the non-polar component (a) olefin resin.

Examples of organic long fibers made of a polar resin include, for example, polyester fibers, polyamide fibers, polyurethane fibers, polyacrylonitrile fibers, and the like.
In the conductive thermoplastic resin composition of the present invention, only one organic long fiber may be included, or two or more organic long fibers may be mixed and included.

  If the fiber diameter of the organic long fiber is too large, the Izod impact strength of the molded product is lowered. It is considered that nano-sized fibers can be used when the fiber diameter is thin, and may be very good depending on the application of the molded product. Since the fiber diameter used in this way is wide, the number of fibers used cannot be defined, but when considering the cross-sectional area of the bundle of fibers, the cross-sectional area in the direction almost perpendicular to the fibers of the pellet is usually 5-60. % Of the fiber cross-sectional area.

  By the way, when injection molding is performed using the conductive thermoplastic resin composition of the present invention, since it is performed at a molding temperature equal to or higher than the melting point of the olefin resin of component (a), the organic long fiber can be melted even by injection molding. It is preferable to use one having no temperature. That is, the melting point of the component (a) olefin resin is usually about 70 to 170 ° C., and therefore the molding temperature (referred to as the outlet temperature of the molding machine) is about 150 to 210 ° C. As the material of the organic long fiber as the component (b), a material having a melting point higher than this molding temperature by 10 ° C. or more, preferably 20 ° C. or more produces a good result.

  In addition, in the molding process, the carbon transition temperature of the material of the organic long fiber is the molding temperature so that the carbon black powder is attracted to the organic long fiber side and the conductivity improvement effect due to the localization of the carbon black powder is sufficiently obtained. Or lower (preferably lower by 5 ° C. or more). That is, if the glass transition point of the organic long fiber is lower than the molding temperature, the molecular mobility on the surface of the organic long fiber is increased during the molding process, and the carbon black powder is more likely to gather on the organic long fiber side. The specific glass transition temperature of the organic long fiber is usually preferably 150 ° C. or lower.

  (B) The organic long fiber is preferably a polyester fiber, a polyamide fiber, more preferably a PET (polyethylene terephthalate) fiber (melting point 260 ° C., glass transition temperature 67 ° C.), a PEN (polyethylene naphthalate) fiber (melting point 272). C., glass transition temperature 113.degree. C.), particularly preferably PEN fiber. That is, when polyester fiber, polyamide fiber, especially PET fiber or PEN fiber, especially PEN fiber is used, the dispersion of the fiber in the injection-molded product is good and the physical properties as the fiber are high. Goods are obtained.

  (B) The length of the organic long fiber corresponds to the length of the pellet of the composition of the present invention described later, and the average fiber length of the organic long fiber contained in the pellet made of the component (a) olefin resin is Preferably they are 4 mm-50 mm, More preferably, they are 4 mm-20 mm, Most preferably, they are 4 mm-10 mm. When the average fiber length of the organic long fibers is less than 4 mm, the effect of improving the impact strength cannot be sufficiently obtained, and when the average fiber length exceeds 50 mm, molding becomes difficult.

In the conductive thermoplastic resin composition of the present invention, the content of the organic long fiber (b) composed of a resin having polarity is such that the component (a) is based on the total amount of the component (a) and the component (b). It is essential that the component (b) is in the range of 5 to 40% by mass at 60 to 95% by mass. Preferably component (a) is 65 to 90% by mass, component (b) is 10 to 35% by mass, more preferably component (a) is 70 to 10% by mass and component (b) is 10 to 30% by mass.
When the content of (b) organic long fibers is less than the above range, the effect of improving the mechanical strength is poor, and when the content is large, the dispersion of fibers in the final molded product is deteriorated, resulting in poor product appearance. .

[(C) Carbon black powder]
Examples of (c) carbon black powder as the conductive filler include furnace black, acetylene black, thermal black, and channel black. Among these, highly conductive acetylene black and furnace black, which can provide conductivity when added in a small amount, are preferable.
In the conductive thermoplastic resin composition of the present invention, the carbon black powder of component (c) may contain only one of them, or two or more of them may be mixed and contained.

When (c) DBP oil absorption of the carbon black powder is less than 50 cm ^3/100 g, because the conductivity even when a large amount of carbon black added is hardly expressed, DBP oil absorption of the carbon black powder 50 cm ^3/100 g or more It is preferable that it is 100 cm < ³ > / 100g or more especially.

  It is essential that the content of the component (c) in the conductive thermoplastic resin composition of the present invention is 5 to 20 parts by mass per 100 parts by mass of the component (a). Preferably, the component (c) is 5 to 15 parts by mass, more preferably 5 to 10 parts by mass per 100 parts by mass of the component (a). When the component (c) is less than 5 parts by mass per 100 parts by mass of the component (a), the necessary conductivity cannot be obtained, and when it exceeds 20 parts by mass, the mechanical properties are significantly deteriorated.

In addition, the volume specific resistance value required as the conductive material targeted by the present invention indicates 10 ⁸ (Ω · cm) or less. In general, a conductive material of 10 ⁸ (Ω · cm) or less, 10 ⁴ (Ω · cm) or more is called an antistatic material, and 10 ⁴ (Ω · cm) or less, 10 ⁰ (Ω · cm) or more. Is referred to as a conductive material, and 10 ⁰ (Ω · cm) or less is referred to as a highly conductive material. For example 10 ⁸ in automotive parts (Ω · cm) or less, 10 ⁴ (Ω · cm) or more antistatic material region, 10 ⁴ in the electrode material (Ω · cm) or less, 10 ⁰ (Ω · cm) or higher The conductive material region is generally required.

[Other ingredients]
The conductive thermoplastic resin composition of the present invention contains the above-mentioned components (a), (b) and (c) as essential components, but is further thermoplastic as long as the effects of the present invention are not impaired. You may contain components, such as resin, rubber | gum, an additive, a filler. However, the conductive thermoplastic resin composition of the present invention preferably contains 50 mass% or more of the essential components (a) to (c), and preferably contains 80 mass% or more. Particularly preferred.

  Examples of the additive include an antioxidant, a heat stabilizer, a light stabilizer, an ultraviolet absorber, a neutralizer, a lubricant, an antifogging agent, an antiblocking agent, a dispersant, a flame retardant, a colorant, and a heat agent. The various additives etc. which are normally used for a plastic resin can be mentioned.

  Among these, examples of the antioxidant include monophenol type, bisphenol type, tri- or higher polyphenol type, thiobisphenol type, naphthylamine type, diphenylamine type, and phenylenediamine type. Among these, monophenol-based, bisphenol-based, tri- or higher polyphenol-based, and thiobisphenol-based antioxidants are preferable because of their high antioxidant effects. When using antioxidant, it is 0.01-5 mass% normally with respect to the total amount of component (a)-(c), Preferably 0.05-3 mass% is used. If the antioxidant is above the above lower limit, the antioxidant effect due to the use of the antioxidant is more easily expressed effectively, and if it is below the above upper limit, an effect commensurate with the amount of use is obtained and economical. In addition, there is little risk of coloration.

  Examples of the filler include talc, mica, silica, titania, calcium carbonate, and various fillers usually used for thermoplastic resins.

[Method for Producing Conductive Thermoplastic Resin Composition]
The conductive thermoplastic resin composition of the present invention is obtained by impregnating an organic long fiber roving composed of a resin having polarity with an olefin-based resin, followed by pultrusion, and then preferably 4 mm to 50 mm, more preferably 4 mm to 20 mm, Particularly preferably, it can be produced by cutting to 4 mm to 10 mm and pelletizing.

  Here, the method of impregnating the olefin resin is not particularly limited, and a method of heating the organic long fiber roving to a temperature higher than the melting point of the resin after passing through the resin powder fluidized bed (Japanese Patent Publication No. 52-3985). A method of impregnating an organic long fiber roving with a molten olefin resin using a crosshead die (JP-A-62-260625, JP-A-63-132036, JP-A-63-264326, JP-A-1-208118); Any method may be used, such as a method in which polyolefin resin fibers are used and roving of the organic long fibers is simultaneously focused and then heated to a temperature higher than the melting point of the resin (Japanese Patent Laid-Open No. 61-118235).

  Since the fiber length of the organic long fiber in the conductive thermoplastic resin composition of the present invention is equal to the pellet length manufactured in this way, the conductive length is adjusted by adjusting the cut length in the manufacture of the pellet. The fiber length of the organic long fiber in the thermoplastic resin composition can be controlled.

  When producing the above pellets, the olefin resin impregnated into the organic long fiber is an olefin resin blended with carbon black powder, so that the organic long fiber and carbon black that are the conductive thermoplastic resin composition of the present invention are used. Olefin-based resin pellets containing powder can be obtained. In this case, carbon black powder and olefin resin are kneaded with an extruder, the die of the extruder is replaced with a crosshead die, and organic long fibers made of a polar resin are impregnated, and pultrusion molding is performed. Just do it.

  Further, in the present invention, carbon black powder and organic long fibers made of a resin having polarity are separately blended into an olefin-based resin, and each is made into a master batch. You may dry blend.

That is, the conductive thermoplastic resin composition of the present invention is
(1) Olefin resin pellets containing organic long fibers and carbon black powder
(2) Olefin resin pellets containing organic long fibers
(3) Among the olefin resin pellets containing carbon black powder, (1) only, a mixture of (2) and (3), a mixture of (1) and (2) and / or (3), or It is further provided as a mixture of olefin-based resin pellets containing neither organic long fibers nor carbon black powder.

[Method for Molding Conductive Thermoplastic Resin Composition]
The conductive thermoplastic resin composition of the present invention can be molded using various general molding machines having a screw plasticizing mechanism.
The conductive thermoplastic resin composition of the present invention uses an organic long fiber that is difficult to break even if the screw is strongly kneaded as the reinforcing fiber, so that the efficiency is improved by using a molding machine with relatively strong kneading of the screw. Injection molding can be performed. More specifically, using a high-kneading type screw containing subflight or dull mage, etc., it can be molded by a method such as molding after applying back pressure and low screw speed over time. preferable.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.
The materials and evaluation methods used in the examples and comparative examples are as follows.

[Materials used]
Component (a-1): Propylene homopolymer resin (“SA06A” manufactured by Nippon Polypro Co., Ltd.)
Melt flow rate 60 g / 10 min (230 ° C., 21.2 N load))
Component (b-1): PET fiber (“P900M BHT1670T250” manufactured by Teijin, average
(Fiber diameter 25μm)
Component (b-2): PEN fiber (manufactured by Teijin "Q900N BHT1670T250", average
(Fiber diameter 25μm)
Component (c-1): Carbon black powder (Ketjen Black E “Ketjen Black E”
C ", DBP oil absorption of 360cm ³ / 100g)
Ingredient (x-1): Carbon fiber ("Torayca" manufactured by Toray)

[Evaluation methods]
<Bending elastic modulus>
The obtained thickness 1/8 inch × 1/2 inch wide × length: 5.0 inches bar by molding, was measured under the following conditions in compliance with ASTM-D-790 method.
Test speed: 2 mm / min
Distance between fulcrums: 100mm

<Izod impact strength>
For those cutting thickness 1/8 inch × 1/2 inch wide × obtained by molding a length: 5.0 inch bar half length 2.5 inches, conforming to ASTM-D-256 method The measurement was performed under the following conditions.
Notch rotation speed: 400rpm
Notch feed speed: 120 mm / min
Hammer capacity: 60kgf · cm

<Volume resistivity>
Both ends of the resulting thick 1/8 inch × 1/2 inch wide × length: 5.0 inches bar by molding cut was adjusted to 10 cm, coated with a conductive paste to the end face was cut, volume resistivity measurement A sample was used. About this sample, resistance value was measured using the digital multimeter (made by Yokogawa M & C Co., Ltd.), and the volume specific resistance value was calculated | required by calculation with the following formula from the obtained measured value.
Volume resistivity = (measured value / sample bar length) x cross-sectional area

<appearance>
The surface of a flat plate of 80 mm × 100 mm × 2.0 mm thickness obtained by molding was visually observed and evaluated according to the following criteria.
○: The fiber dispersion is the best, the bundle of unopened fibers is hardly visible, and the flat plate surface is smooth.
(Triangle | delta): The bundle | flux of the fiber which is not opened is seen for a while, and a flat surface has a slight unevenness.
X: Many bundles of unopened fibers are seen, and the flat plate surface is rough.

[Production example]
<Production Example 1: Production of long fiber-containing olefin resin pellet>
Component (a-1) A propylene homopolymer resin and the long fiber component shown in Table 1 were mixed into the twin-screw extruder (JSW “TEX30”, L / D = 42, Drawing was performed using a cylinder diameter of 30 mm, a cylinder temperature of 190 to 220 ° C., and a cross die head temperature of 220 ° C. to produce long fiber reinforced polyolefin resin pellets (components A-1 to 7, X-1). The pellet length was adjusted to 8 mm.

<Production Example 2: Production of carbon master batch>
A predetermined amount of the component (a-1) propylene homopolymer resin and the component (c-1) carbon black powder are twin-screw extruder (“TEX30” manufactured by JSW, L / D = 42, cylinder diameter 30 mm, cylinder temperature: 160 to 240 ° C.) to prepare a carbon master batch (component C, carbon black powder content 20 mass%).

[Examples and Comparative Examples]
<Examples 1-4, Comparative Examples 3-6>
Each of the long fiber-containing polyolefin resin pellets with the material composition shown in Table 2 is dry blended with a carbon masterbatch (component C) and then subjected to an injection molding machine. , and at a screw rotation number 50 rpm, and 80 mm × 100 mm × thickness 2.0mm flat, thickness 1/8 inch × 1/2 inch wide × length: 5.0 inch bars were molded respectively.
Table 2 shows the evaluation results of the molded products.

<Comparative Examples 1 and 2>
Component (a-1) not impregnated with organic long fibers (a-1) Propylene homopolymer resin and carbon masterbatch component C were dry blended with the material composition shown in Table 2 and then subjected to an injection molding machine. Molding and evaluation were performed in the same manner as in Example 1 except that molding was performed at a mold temperature of 40 ° C., a back pressure of 10 kg, and a screw rotation speed of 50 rpm, and the results are shown in Table 2.

  From Table 2, it can be seen that according to the present invention, a molded product having excellent electrical conductivity, excellent mechanical properties such as flexural modulus and impact strength, and good molded product appearance can be obtained.

Claims (6)

In the following components (a), (b) and (c), the content of the component (a) with respect to the sum of the components (a) and (b) is 60 to 95% by mass, and the content of the component (b) is The conductive thermoplastic resin composition is contained so as to be 5 to 40% by mass and the content of the component (c) is 5 to 20 parts by mass per 100 parts by mass of the component (a). A conductive thermoplastic resin molded article,
The conductive thermoplastic resin composition comprises (a) olefinic resin roving (a) olefinic resin pellets containing carbon black powder, and (b) organic long fibers made of a resin having polarity. Including olefin resin pellets containing organic long fibers obtained by impregnation, pultrusion, and then cutting,
A conductive thermoplastic resin molded article having a volume resistivity of 10 ⁸ (Ω · cm) or less .
(A) Olefin resin (b) Organic long fiber made of a resin having polarity (c) Carbon black powder as a conductive filler 2. The conductive thermoplastic resin molded article according to claim 1, wherein (b) a resin having polarity constituting the organic long fiber has a melting point of 200 ° C. or higher. 3. The conductive thermoplastic resin molded article according to claim 1, wherein (b) the organic long fiber is a polyester fiber and / or a polyamide fiber. The conductive thermoplastic resin molded article according to any one of claims 1 to 3, wherein (a) the olefin resin is a propylene resin. The conductive thermoplastic resin molded article according to any one of claims 1 to 4, wherein (b) an average fiber length of the organic long fibers is 4 mm or more. 6. The conductive thermoplastic resin molded article according to claim 1 , wherein the conductive thermoplastic resin composition is injection-molded.