ELECTROCONDUCTIVE THERMOPLASTIC RESIN

Abstract

In a tumbler and the like, polypropylene pellets are blended with 1 to 5 wt % of carbon nanotubes, 10 to 30 wt % of fly ash, 10 to 20 wt % of talc and 0.3 to 1 wt % of a modifier, the resulting blend is extruded from a screw extruder while heating the blend to a melting temperature of about 160 to 260 C., to generate a strand. This strand is cooled and cut into pellets having a predetermined length. Owing to blending with fly ash, talc and a modifier, an inexpensive lightweight electroconductive thermoplastic resin excellent in dust-proofness, heat resistance and recyclability is obtained, even if the blending amount of carbon nanotubes is small.

Claims

1. An electroconductive thermoplastic resin characterized in that a crystalline thermoplastic resin is blended with 1 to 2 wt % of carbon nanotubes, 5 to 30 wt % of carbon fiber, 10 to 30 wt % of coal ash generated in a powdered coal combustion boiler, 10 to 20 wt % of an inorganic filler, and 0.3 to 1 wt % of a modifier, wherein the inorganic filler is at least one selected from the group consisting of talc, calcium silicate, aluminum silicate, bentonite, zeolite, basic magnesium carbonate, volcanic ash, natural gypsum, attapulgite, quartz powder, kaolin clay, pyrophyllite clay, cerussite, dolomite powder, mica, calcium sulfate, silicon carbide powder, magnesium oxide, titanium oxide, precipitated barium sulfate, and barite.

2. An electroconductive thermoplastic resin characterized in that a crystalline thermoplastic resin is blended with 1 to 3 wt % of carbon nanotubes, 5 to 20 wt % of carbon fiber, 10 to 30 wt % of coal ash generated in a powdered coal combustion boiler, 10 to 20 wt % of an inorganic filler, and 0.3 to 1 wt % of a modifier, wherein the inorganic filler is at least one selected from the group consisting of talc, calcium silicate, aluminum silicate, bentonite, zeolite, basic magnesium carbonate, volcanic ash, natural gypsum, attapulgite, quartz powder, kaolin clay, pyrophyllite clay, cerussite, dolomite powder, mica, calcium sulfate, silicon carbide powder, magnesium oxide, titanium oxide, precipitated barium sulfate, and barite.

3. An electroconductive thermoplastic resin characterized in that a crystalline thermoplastic resin is blended with 0.5 to 2 wt % of carbon nanotubes, 20 to 30 wt % of carbon fiber, 10 to 30 wt % of coal ash generated in a powered coal combustion boiler, 10 to 20 wt % of an inorganic filler, and 0.3 to 1 wt % of a modifier, wherein the inorganic filler is at least one selected from the group consisting of talc, calcium silicate, aluminum silicate, bentonite, zeolite, basic magnesium carbonate, volcanic ash, natural gypsum, attapulgite, quartz powder, kaolin clay, pyrophyllite clay, cerussite, dolomite powder, mica, calcium sulfate, silicon carbide powder, magnesium oxide, titanium oxide, precipitated barium sulfate, and barite.

4. The electroconductive thermoplastic resin according to claim 1, wherein said inorganic filler is talc.

5. The electroconductive thermoplastic resin according to claim 1 characterized in that the thermoplastic resin is any one of polypropylene, polyvinylidene fluoride, polyphenylene ether, polyphenylene oxide, polyamideimide, polycarbonate, polystyrene, and ABS, or a combination of two or more of them.

6. The electroconductive thermoplastic resin according to claim 2 wherein, further, 5 to 25 wt % of glass fiber and 4 to 6 wt % of a coupling agent are blended with respect to said crystalline thermoplastic resin.

7. The electroconductive thermoplastic resin according to claim 2, wherein the crystalline thermoplastic resin is blended with 2 wt % of carbon nanotubes, 10 to 20 wt % of carbon fiber, 15 wt % of coal ash generated in a powdered coal combustion boiler, 10 wt % of an inorganic filler, and 0.6 wt % of a modifier.

Description

BRIEF EXPLANATION OF DRAWINGS

[0042] FIG. 1 is a schedule table showing the component blending rate and the surface intrinsic resistance value and the like in examples and comparative examples.

[0043] FIG. 2 is a graph showing a relation between the surface intrinsic resistance value and the blending rate of carbon nanotubes.

[0044] FIG. 3 is a graph showing a relation between the surface intrinsic resistance value and the blending rate of carbon fiber.

[0045] FIG. 4 is a graph showing a relation between the heat resistant temperature and the blending rate of carbon fiber.

[0046] FIG. 5 is a graph showing a relation between the specific gravity and the blending rate of carbon fiber.

[0047] FIG. 6 is a table showing the blending rate of fly ash and the measured data of the surface intrinsic resistance value.

[0048] FIG. 7 is a table showing the blending rate of talc and the measured data of the surface intrinsic resistance value.

[0049] FIG. 8 is a table showing the blending rate of a modifier and the measured data of the surface intrinsic resistance value.

[0050] FIG. 9 is a graph showing a relation between the surface intrinsic resistance value and the blending rate of fly ash.

[0051] FIG. 10 is a graph showing a relation between the surface intrinsic resistance value and the blending rate of talc.

[0052] FIG. 11 is a graph showing a relation between the surface intrinsic resistance value and the blending rate of a modifier.

[0053] FIG. 12 is a table showing properties in the ease of blending glass fiber.

BEST MODES FOR CARRYING OUT THE INVENTION

[0054] For obtaining the electroconductive thermoplastic resin according to the present invention, for example, in a tumbler and the like, 58 wt % or pellets of polypropylene as a crystalline thermoplastic resin (for example, Sun Allomer PM900A manufactured by Sun Allomer Ltd.) are blended with 2 wt % of carbon nanotubes (for example, vapor grown carbon fiber VGCF (registered trademark)X manufactured by Showa Denko K.K.: fiber diameter 15 nm, fiber lengths 3 nm), 15 wt % of carbon fiber (for example, T300B-12000 manufactured by Toray Industries Inc.), 15 wt % of fly ash having a particle size of 10 to 30 m (for example, article manufactured by J Power/EPDC), 10 wt % of talc having a bulk specific volume of 0.9 to 1.2 ml/g (for example, MS-P manufactured by Nippon Talc Co., Ltd.) and 0.6 wt % of a modifier (for example, Excel T-95 manufactured by Kao Corporation).

[0055] This blend is extruded from a screw extruder while heating the blend to a melting temperature of about 160 to 260 C., to generate a strand. This strand is cooled while moving on a conveyor. The surface-cooled strand is cut into pellets having a predetermined length by a rotary cutter. For making detachment from the screw extruder easy, a lubricant (for example, ca-st manufactured by Nitto Kasei Co., Ltd.) and an antioxidant (for example, AO-60 manufactured by ADEKA Corporation) are blended each in an amount of 0.1 wt %.

[0056] The surface intrinsic resistance value of the above-described pellets was measured by a surface resistivity tester (Lorester AP manufactured by Mitsubishi Petrochemical Co., Ltd.) to find the value 10.sup.6. The heat resistant temperature of the above-described pellets was measured according to JIS K7191 PlasticsDetermination of temperature of deflection under load to find a value of 150 C. Further, the above-described pellets had a specific gravity of 1.193, smaller by about 5% as compared with those obtained by using an amorphous resin according to conventional technologies (see, patent document 2).

EXAMPLES

[0057] Examples and comparative examples of the electroconductive thermoplastic resin according to the present invention will be shown. Components constituting this electroconductive thermoplastic resin are as described below. That is, pellets of polypropylene SunAllomer PM900A manufactured by SunAllomer Ltd. as a crystalline thermoplastic resin, vapor grown carbon fiber VGCF (registered trademark)X (fiber diameter 15 nm, fiber length 8 nm) manufactured by Showa Denko K.K. as carbon nanotubes, T300B-12000 manufactured by Toray Industries Inc. as carbon fiber, fly ash having an average particle size of 10 to 30 m manufactured by J Power/EPDC as coal ash, MS-P manufactured by Nippon Talc Co., Ltd. as talc, Excel T-95 manufactured by Kao Corporation as a modifier, ca-st manufactured by Nitto Kasei Co., Ltd. as a lubricant, and AO-60 manufactured by ADEKA Corporation as an antioxidant were used.

[0058] The above-described components were blended in a tumbler and the like, the resultant blend was extruded from a screw extruder while heating the blend to a melting temperature of about 160 to 260 C., to generate a strand, and this strand was cooled while moving on a conveyor. The surface-cooled strand was cut by a rotary cutter to make pallets. The pellets were injection-molded, to fabricate a sample in the form of a plate.

[0059] The surface intrinsic resistance value of the above-described sample was measured by a surface resistivity tester (Lorester AP manufactured by Mitsubishi Petrochemical Co., Ltd.). The heat resistant temperature was measured according to JIS K7191 PlasticsDetermination of temperature of deflection under load. Further, the specific gravity was measured using an automatic specific gravity measuring instrument D-8 manufactured by Toyo Seiki Co., Ltd.

[0060] FIG. 1 shows the blending rates (wt %) of carbon nanotubes and carbon fiber and the measured results of the surface intrinsic resistance value (), the heat resistant temperature ( C.) and the specific gravity, of the above-described sample. The blending rates of other components were 15 wt % of fly ash, 10 wt % of talc, 0.6 wt % of a modifier, 0.1 wt % of a separating agent and 0.1 wt % of antioxidant.

[0061] In Examples 1 to 5 shown in FIG. 1, the blending rate of carbon nanotubes (CNT) was changed from 1 to 5 wt % without blending carbon fiber. In Comparative Example 2, the blending rate of carbon nanotubes was set at 7 wt % without blending carbon fiber. FIG. 2 shows a relation between the surface intrinsic resistance value () and the blending rate of carbon nanotubes, for Examples 1 to 5 and Comparative Example 2. As shown in FIG. 2, it could be confirmed that an intended surface intrinsic resistance value of 10.sup.4 to 10.sup.11 can be attained by blending carbon nanotubes in an amount of as small as 1 to 5 wt % even if carbon fiber is not blended.

[0062] In Examples 6 to 30 and Comparative Example 1 shown in FIG. 1, carbon fiber is mixed, and the blending rate of this carbon fiber is changed from 5 to 30 wt % and the blending rate of carbon nanotubes is changed from 0.5 to 4 wt %. FIG. 3 shows a relation between the surface intrinsic resistance value () and the blending rate of carbon nanotubes, for Examples 1 to 30 and Comparative Example 1. As shown in FIG. 3, it could be confirmed that an intended surface intrinsic resistance value of 10.sup.4 to 10.sup.11 can be attained by blending carbon nanotubes in an amount of as extremely small as 1 to 2 wt % when 5 to 30 wt % of carbon fiber is blended.

[0063] As shown in FIG. 3, it could be confirmed that an intended surface intrinsic resistance value of 10.sup.11 to 10.sup.4 can be attained by blending 1 to 3 wt % of carbon nanotubes when the blending rate of carbon fiber is in the range of 5 to 20 wt %. Further, it could be confirmed that an intended surface intrinsic resistance value of 10.sup.4 to 10.sup.11 can be attained by blending 0.5 to 2 wt % of carbon nanotubes when the blending rate of carbon fiber is in the range of 20 to 30 wt %.

[0064] FIG. 4 shows a relation between the heat resistant temperature and the blending rate of carbon fiber, for the cases of measurement of the heat resistant temperature among Examples 1 to 30. That is, FIG. 4 shows a relation between the heat resistant temperature and the blending rate of carbon fiber when the blending rate of carbon nanotubes is set at 2, 3 and 5 wt % when the blending rate of carbon fiber is in the range of 0 to 30 wt %. As shown in FIG. 4, when carbon fiber is not blended, the heat resistant temperature is about 130 C., however, the heat resistant temperature rises when the blending rate of carbon fiber increases. That is, it could be confirmed that when the blending rate of carbon fiber is 5 wt % or more, the heat resistant temperature rises to 140 C. or higher, and when the blending rate of carbon fiber is 15 wt % or more, the heat resistant temperature rises to 150 C. or higher. Since the heat resistant temperature rises approximately linearly when the blending rate of carbon fiber is in the range of 5 to 20 wt %, it can be expected that the heat resistant temperature further rises when the blending rate of carbon fiber is in the range of 20 to 30 wt %.

[0065] FIG. 5 shows a relation between the specific gravity and the blending rate of carbon fiber in the cases of measurement of the specific gravity among Examples 1 to 30. That is, FIG. 5 shows a relation between the specific gravity and the blending rate of carbon fiber when the blending rate of carbon nanotubes is set at 2, 3 and 5 wt % when the blending rate of carbon fiber is in the range of 0 to 30 wt %. As shown in FIG. 5, when carbon fiber is not blended, the specific gravity is as low as about 1.10, and the specific gravity increases approximately linearly when the blending rate of carbon fiber increases.

[0066] In view of the relation with the heat resistant temperature shown in FIG. 4 described above, it could be confirmed that a heat resistant temperature of 140 to 150 C. can be obtained while suppressing the specific gravity at 1.1 to 1.2 when the blending rate of carbon fiber is 5 to 15 wt %. When the blending rate of carbon fiber is increased to 15 to 30 wt %, it can be expected that a heat resistant temperature of 150 to 160 C. is obtained while suppressing the specific gravity at 1.2 to 1.3.

[0067] FIGS. 6, 7 and 8 show the results of measurement of the surface intrinsic resistance value when the blending rates of fly ash, talc and a modifier as other components are changed. In all cases, the blending rate of carbon nanotubes is set at a constant value of 2 wt % and carbon fiber is not blended.

[0068] FIG. 9 shows a relation between the surface intrinsic resistance value and the blending rate of fly ash. That is, it could be confirmed that when the blending rate of fly ash is 10 wt % or less, the surface intrinsic resistance value increases drastically, while when the blending rate of fly ash is in the range of 1 to 30 wt %, the surface intrinsic resistance value is converged in a narrow range of 10.sup.4 to 10.sup.5. FIG. 10 shows a relation between the surface intrinsic resistance value and the blending rate of talc. That is, it could be confirmed that when the blending rate of talc is 10 wt % or lower, the surface intrinsic resistance value increases drastically, while when the blending rate of talc is in the range of 10 to 20 wt %, the surface intrinsic resistance value is converged to approximately 10.sup.4.

[0069] FIG. 11 shows a relation between the surface intrinsic resistance value and the blending rate of a modifier. That is, it could be confirmed that when the blending rate of a modifier is 0.3 wt % or less, the surface intrinsic resistance value is as high as 10.sup.9 or more, while when the blending rate is in the range of 0.3 to 0.6 wt %, the surface intrinsic resistance value lowers to 10.sup.4 to 10.sup.9 and when the blending rate is in the range of 0.6 to 1.0 wt %, the surface intrinsic resistance value is converged to approximately 10.sup.4.

[0070] According to the above described results, it could be confirmed that when fly ash, talc or a modifier is blended, each of them is capable of lowering the surface intrinsic resistance value significantly, and in a predetermined range of the blending rate, the influence on the surface intrinsic resistance value converges to an approximately constant level.

[0071] FIG. 12 shows the properties of an electroconductive thermoplastic resin for two examples of blending glass fiber (test number: TRF-106KTG15 and TRF-106ASG15) for suppressing generation of warpage. Components constituting this electroconductive thermoplastic resin are as shown below. That is, pellets of polypropylene SunAllomer PM900A manufactured by Sun Allomer Ltd. as a crystalline thermoplastic resin, vapor grown carbon fiber VGCF (registered trademark)-X (fiber diameter 15 nm, fiber length 3 nm) manufactured by Showa Denko K.K. as carbon nanotubes, fly ash having an average particle size of 10 to 30 m manufactured by J Power/EPDC as coal ash, kaolin clay Burgess NO. 30 manufactured by U.S. Burgess Pigment Company as an inorganic filler, TP69A (average fiber length: 3.3 mm, average fiber diameter: 13.5) manufactured by Owens Corning Corporation as glass fiber, ADTEX ER320P manufactured by Japan Polychem Corporation as a coupling agent and Excel T-95 manufactured by Kao Corporation as a modifier were used. The baseline of warpage was determined to 0.5 mm or less, and the temperature at which warpage generated could be maintained at 0.5 mm or less was measured.

[0072] As shown in the test number TRF-106KTG15 in FIG. 12, it was clarified that when 15 wt % of glass fiber and 5 wt % of a coupling agent are blended, the baseline of warpage of 0.5 mm or less is satisfied even at a sufficiently high temperature of 152 C. As shown in the test number TRF-106ASG15 in FIG. 12, it was clarified that when 10 wt % of acetylene black is blended, the temperature satisfying the baseline of warpage of 0.5 mm or less can be maintained at a high level of 155 C. even if the blending rate of carbon nanotubes is as small as 1 wt %.

INDUSTRIAL APPLICABILITY

[0073] Since an inexpensive lightweight electroconductive thermoplastic resin excellent in dust-proofness, heat resistance and recyclability can be provided, the present invention can be utilized widely in industries regarding thermoplastic resins, particularly industries regarding packaging containers, conveying trays and the like for semiconductor devices, optical lenses and the like.