JP2008106285A - Electrically-conductive fluororesin composition and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrically-conductive fluororesin composition of a thermally fusible fluororesin powder and an electrically-conductive carbon black with a stabilized electric resistance, capable of obtaining a smooth surface state of a molded product to be obtained with good accuracy, suitable for a supporting jig or a tube used for a semiconductor production apparatus, a roll or a tube for electronic office equipments, and a manufacturing method therefor. <P>SOLUTION: The composition of an electrically conductive carbon black as an acetylene black and a thermally fusible fluororesin powder as an emulsion-polymerized tetrafluoroethylene-perfluoro(alkyl vinyl ether) copolymer has two crystallization peaks at the time of being crystallized with a temperature lowering rate of 12°C/minute from a temperature not lower than the melting point of the thermally fusible fluororesin by a differential scanning calorimeter device. The ratio of the heights of the crystallization peaks (high temperature side peak/low temperature side peak) is 0.65 or more, or the ratio of the high temperature side crystallization peak area [high temperature side area/(high temperature side area + low temperature side area)] is 0.18 or more. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an improved conductive fluororesin composition and a method for producing the same. More specifically, the electrical resistance of the molded product is stable, the surface state is smoother and more accurate, and even when used in wafer holding jigs and solvent lines used in semiconductor manufacturing equipment, conductive carbon black particles The present invention relates to a conductive fluororesin composition that does not become contaminated by being released into a liquid, and a method for producing the composition by mixing conductive fine particles and fluororesin fine powder in a mixer that rotates at high speed.

  Hot-melt fluoropolymers such as tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), and tetrafluoroethylene / ethylene copolymer (ETFE) It has excellent heat resistance, chemical resistance, non-adhesiveness, etc. These fluororesins are also excellent insulating materials, but are used for holding jigs and tubes used in IC and semiconductor manufacturing equipment, or OA equipment rolls, tubes, and belt materials represented by fixing rolls such as copying machines and printers. In the case of using as, the conductivity is required.

  As a method of imparting conductivity or antistatic property to a fluororesin, a method of adding conductive fiber, conductive carbon black, graphite or the like is well known. A method of adding fullerene (C60) or carbon nanotubes is also known. In particular, PFA mixed with acetylene black as a conductive carbon black with very little impurities (Henshiel mixer) (JP-A-2-60954), melted and mixed with conductive carbon black in fluorinated PFA However, there have been proposed ones having a low electrical resistance and a small increase in melt viscosity (Japanese Patent Application Laid-Open Nos. 6-1902 and 3-38302).

  However, the fluororesin compositions according to these proposals can be used for holding jigs and tubes used in semiconductor manufacturing apparatuses that require electrical conductivity, and OA equipment rolls and tubes represented by fixing rolls such as copying machines and printers. However, it did not show satisfactory performance for use in other applications.

  That is, it is known that the electrical resistance of the conductive fluororesin composition varies greatly depending not only on the type and amount of conductive fine particles such as mixed conductive carbon black but also on the dispersion state of the conductive fine particles (Journal of Applied Polymer Science, Vol.69, P193 (1998)). However, in the mixing described in the above-mentioned publications, PFA particles and conductive carbon black are mixed with a Henschel mixer and then mixed with a melt extruder, or PFA pellets and conductive carbon black are forced by the shearing force of the extruder. Therefore, it is difficult to uniformly disperse the mixed conductive carbon black fine powder in the PFA resin.

In particular, in the conventional method in which conductive carbon black and a hot-melt fluororesin are melt-mixed with an extruder, the conductive carbon black is dispersed and the structure is destroyed simultaneously in the melt-mixing process, so that stable conductivity is controlled. It is extremely difficult. In addition, since conductive carbon black is dispersed unevenly, there is a large variation in conductivity and physical properties within or between batches, and agglomerate of carbon black that is not uniformly dispersed or a mass of undispersed fluororesin Will occur. For this reason, it was not possible to obtain a molded body that was used for a wafer holding jig or a solvent line used in a semiconductor manufacturing apparatus and that had a smooth surface state and conductive carbon black particles were not released into the liquid of the apparatus. In particular, in a conductive fluororesin composition having a high electrical resistance region (surface resistance of 10 ⁸ Ω / □ or more) with a small amount of conductive carbon black mixed, the electrical resistance of the molded article is stabilized when carbon black is dispersed unevenly. In addition, there is a risk that the insulating region may be separated from the semiconductive region.

JP-A-2-60954 Japanese Patent Laid-Open No. 6-1902 Japanese Patent Publication No. 3-38302 Journal of Applied Polymer Science, Vol.69, P193 (1998)

  Therefore, the present inventors have dispersed the conductive particles more uniformly in the fluororesin so that the electric resistance is stable, the surface state of the resulting molded body is smoother and more accurate, and the wafer used in the semiconductor manufacturing apparatus. A conductive fluororesin composition in which conductive particles are not released into the liquid of the apparatus and contaminate the apparatus even when used in a holding jig or a solvent line, and a method for producing the same were studied.

  As a result, when the fine powdery acetylene black and fluorine resin fine powder with very few impurities are mixed with a mixer using a blade rotating at high speed, it is possible to disperse the conductive carbon black in the fluororesin very uniformly. It has been found that the composition or molded body obtained by such a method exhibits a specific crystallization pattern or a specific glass transition temperature range, and the electrical resistance of the molded body is stable. Further, the molded body obtained from such a composition has a smooth surface and good accuracy, and is an OA represented by a fixing roll such as a holding jig or tube used in a semiconductor manufacturing apparatus or a copying machine or a printer. The present invention has been found to have satisfactory performance when used in applications such as equipment rolls and tubes.

  In general, it is extremely difficult to examine whether the conductive carbon black in the conductive fluororesin is uniformly dispersed or not. Although it is possible to observe the carbon black dispersed in the conductive fluororesin composition directly with a scanning electron microscope (SEM) or a transmission electron microscope (TEM), the observation magnification is high, so it is very local. It is difficult to examine the dispersion state of carbon black in the entire sample.

  However, in the conductive fluororesin composition in which the acetylene black and the heat-meltable fluororesin fine powder are mixed with a mixer using a blade that rotates at high speed, the present inventors have found that the fine powder of acetylene black finely dispersed in the fluororesin is fluorine. It acts as a nucleating agent during resin crystallization, and the dispersion state of conductive carbon black in the conductive fluororesin is easily evaluated by comparing the ratio of crystallization by nucleation and crystallization by crystal growth from the nucleus. I found out that I can do it. In addition, the fine particles of acetylene black finely and uniformly dispersed in the fluororesin facilitate the movement of the molecular chain in the amorphous region of the fluororesin (lowering the glass transition temperature). It was found that the dispersion state of conductive carbon black in the conductive fluororesin can be easily evaluated by comparing the glass transition temperatures of the fluororesin.

  Accordingly, an object of the present invention is to solve the problems in the above-described conventional technology, to stabilize the electric resistance, to obtain a smooth and accurate surface state of the obtained molded body, and to provide a holding jig used in a semiconductor manufacturing apparatus. It is an object of the present invention to provide a conductive fluororesin composition exhibiting satisfactory performance when used in applications such as tubes, OA equipment rolls such as copiers and printers, and fixing rolls such as printers.

  That is, the present invention is a composition comprising a conductive carbon black which is acetylene black and a heat-meltable fluororesin powder which is a copolymer of tetrafluoroethylene and perfluoro (alkyl vinyl ether) obtained by emulsion polymerization, When crystallized at a temperature drop rate of 12 ° C./min from a temperature equal to or higher than the melting point of the heat-meltable fluororesin in a DSC apparatus, the ratio of the crystallization peak height (high-temperature side peak) / Low temperature side peak) is 0.65 or more and / or the ratio of the high temperature side crystallization peak area [high temperature side peak area / (high temperature side peak area + low temperature side peak area)] is 0.18 or more. It is related with the conductive fluororesin composition characterized by these.

  According to the present invention, the electrical resistance is stable, the surface of the resulting molded body is smoother and more accurate, and is representative of fixing jigs and tubes used in semiconductor manufacturing equipment, and fixing rolls such as copying machines and printers. Provided is a conductive fluororesin composition that exhibits satisfactory performance when used in applications such as OA equipment rolls and tubes.

  The conductive fluororesin composition of the present invention comprises a conductive carbon black and a heat-meltable fluororesin powder, and exhibits a specific crystallization pattern in a DSC apparatus or has a specific glass transition temperature by a dynamic viscoelasticity measuring apparatus. Indicates the range.

  Here, the heat-meltable fluororesin is a tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer (hereinafter referred to as PFA). In the copolymer of tetrafluoroethylene and perfluoro (alkyl vinyl ether), it is preferable to use a copolymer having a perfluoro (alkyl vinyl ether) content of 1 to 10% by weight, particularly about 3 to 8% by weight. The alkyl group of perfluoro (alkyl vinyl ether) preferably has 1 to 5 carbon atoms, particularly 1 to 3 carbon atoms.

  There is no particular limitation on the melt viscosity or molecular weight of these heat-meltable fluororesins, but the viscosity of the mixture becomes high by mixing conductive carbon black. Therefore, for the purpose of injection molding, the melt at 372 ° C. and 5000 g load is used. When expressed in terms of an index, it is preferable to use a product of about 10 to 50 g / 10 minutes.

  The conductive carbon black used in the present invention is acetylene black, and pulverized acetylene black with very few impurities is preferable. When fine powdered acetylene black is mixed with a heat-melting fluororesin fine powder having an average particle size of 10 μm or less with a mixer using a blade rotating at high speed, the acetylene black particles are more uniformly and finely divided into the heat-meltable fluororesin fine powder. To be distributed. Therefore, the surface state of the resulting molded body is smoother and more accurate than those obtained by mixing other conductive carbon black, and even when used in wafer holding jigs or solvent lines used in semiconductor manufacturing equipment, the conductive particles remain in the equipment. A conductive fluororesin composition that does not contaminate the device by not being released into the liquid is obtained. Moreover, the electroconductive fluororesin composition suitable for uses, such as OA equipment rolls and tubes represented by fixing rolls such as printers that require a very smooth surface, can be obtained.

  The blending amount of the conductive carbon black varies depending on the intended level of conductivity, but is preferably about 1 to 15% by weight, particularly about 5 to 10% by weight in the composition.

  The conductive fluororesin composition of the present invention has two crystallization peaks when crystallized at a rate of temperature decrease of 12 ° C./min from a temperature equal to or higher than the melting point of the heat-meltable fluororesin in a DSC apparatus, The ratio of the height of the crystallization peak (high temperature side peak / low temperature side peak) is 0.65 or more, preferably 0.70 to 1.20 and / or the ratio of the high temperature side crystallization peak area [high temperature side peak Area / (high temperature side peak area + low temperature side peak area)] is 0.18 or more, preferably in the range of 0.20 to 0.35. In the conductive fluororesin composition of the present invention showing such a crystallization pattern, the conductive carbon black is very uniformly dispersed in the heat-meltable fluororesin, so that the electric resistance is stable and the surface of the resulting molded body Smoother and more accurate, can be used for applications such as holding jigs and tubes used in semiconductor manufacturing equipment, and OA equipment rolls and tubes typified by fixing rolls such as copying machines and printers. .

  Here, the high temperature side crystallization peak is a crystallization peak associated with nucleation based on the nucleating agent effect of the conductive carbon black fine powder, and the low temperature side crystallization peak is a normal crystal growth peak. When are uniformly dispersed, two peaks appear.

  In the conductive fluororesin composition of the present invention, the glass transition temperature (Tg (composite)) measured by a dynamic viscoelasticity measuring device is that of a pure fluororesin not mixed with conductive carbon black (Tg (neat)) is 3 ° C. or more, preferably 3 to 10 ° C. lower. Similarly, those exhibiting such a glass transition temperature range also have conductive carbon black dispersed extremely uniformly in the heat-meltable fluororesin, so that the electric resistance is stable and the surface state of the resulting molded product is more It is smooth and accurate, and can be used for applications such as holding jigs and tubes used in semiconductor manufacturing apparatuses, OA equipment rolls and tubes typified by fixing rolls such as copying machines and printers.

  Here, the glass transition temperature (α-transition temperature) is a peak temperature of tan δ measured by a dynamic viscoelasticity measuring apparatus (Rheometric Scientific, ARES). In a heat-melting fluororesin, in the amorphous region of the fluororesin This is the temperature at which partial movement of a molecular chain (Micro-Brown movement) begins (Polymer Vol.42, P5453 (2001)).

  The conductive fluororesin composition having the crystallization pattern or the conductive fluororesin composition within the glass transition temperature range rotates at high speed a heat-meltable fluororesin fine powder having an average particle size of 10 μm or less and conductive carbon black. In a mixer using a blade, it can be obtained by mixing at a peripheral speed of 35 m / sec or more. The heat-meltable fluororesin fine powder having the above particle size is preferably separated from the aqueous medium by mechanical stirring after the electrolysis substance is added to the hot-melt fluororesin aqueous dispersion to aggregate the fluororesin fine particles and dried. Obtained by

  As the above-mentioned hot-melt fluororesin aqueous dispersion, an aqueous dispersion obtained by emulsion polymerization is preferable. Usually, 1-75 wt.% Of the hot-melt fluororesin colloidal particles having an average particle size of about 0.2 μm in water. What is contained in about% is preferably used.

Electrolytic substances used for the purpose of agglomerating colloidal fine particles of an aqueous dispersion of a heat-meltable fluororesin include HCl soluble in water, H ₂ SO ₄ , HNO ₃ , H ₃ PO ₄ , and Na ₂ SO _4. , MgCl ₂ , CaCl ₂ , sodium formate, potassium acetate, ammonium carbonate, H ₂ CO ₃ and other inorganic or organic compounds. Among these, it is preferable to use a compound that can be volatilized in the subsequent drying step of the heat-meltable fluororesin fine powder, such as HCl, HNO ₃ , H ₂ CO _{3 and the} like.

  These electrolytic substances are preferably used in an amount of 1 to 15% by weight, particularly 1.5 to 10% by weight, based on the weight of the heat-meltable fluororesin. It is preferably added in the form of an aqueous solution. When the amount of the electrolytic substance used is too small, it takes a long time to form aggregated particles of the heat-meltable fluororesin, so that productivity is lowered. Increasing the amount used more than necessary does not affect the formation of aggregated particles of a heat-meltable fluororesin, but is not preferable because it is not economical and requires time for the washing process.

  The apparatus for forming the agglomerated particles of the heat-meltable fluororesin is not particularly limited, but stirring means that can maintain a peripheral speed of about 4 m / second or more, such as propeller blades, turbine blades, paddle blades, paddle blades A device including a horseshoe-shaped wing, a spiral wing, and the like and drainage means is preferable.

  By adding a predetermined amount of the hot-melt fluororesin aqueous dispersion and electrolyte in such an apparatus and stirring, the colloidal fine particles of the hot-melt fluororesin aggregate to form aggregated particles that are separated from the aqueous medium. Ascend and float. At this time, the stirring speed is preferably maintained at about 4 m / second or more. That is, when the stirring speed is too slow, it takes a long time for the hot-melt fluororesin to aggregate, and it becomes difficult for moisture to be discharged from the hot-melt fluororesin aggregate particles. Stirring is performed until the agglomerated particles are separated from the aqueous medium.

  The heat-meltable fluororesin agglomerated particles are dried at a temperature not higher than the melting point of the heat-meltable fluororesin after discharging the aqueous medium and washing with water as necessary. The average particle diameter of the heat-meltable fluororesin fine powder thus obtained is usually 10 μm or less. Further, each fluororesin fine powder has a small cohesive force between particles, and is suitable for crushing and pulverizing.

  In the present invention, fine particles of the heat-meltable fluororesin fine powder and conductive carbon black, preferably acetylene black, thus obtained are mixed with each other by a blade rotating at high speed. As a mixer using a high-speed rotating blade for mixing such fluororesin fine powder and conductive carbon black, commercially available products include, for example, “Cutter Mixer” manufactured by Aikosha Seisakusho or “Eirich Intensive Mixer” manufactured by Nihon Eirich. is there. This high-speed rotary mixer is capable of pulverizing and mixing the heat-meltable fluororesin fine powder and conductive carbon black particles while the cutter knife or blade rotates at a high speed of 3000 rpm or higher. The mixing ability or the dispersion state of conductive carbon black is different from that of a normal Henschel mixer. Accordingly, the mixing conditions in the high-speed rotary mixer are preferably such that the cutter knife or blade is in the range of 1500 rpm or more or a circumferential speed of 35 m / second or more, particularly 3000 to 20000 rpm or a circumferential speed of 70 to 115 m / second. Moreover, it is preferable to perform the said mixing so that the average particle diameter of the powder composition obtained may be set to about 0.5-8 micrometers, Preferably it is about 1-6 micrometers.

  The feature of the heat-meltable fluororesin composition filled with acetylene black mixed by the high-speed rotary mixer, particularly the cutter mixer, is that the acetylene black particles are uniformly dispersed in the heat-meltable fluororesin fine powder. The acetylene black fine powder finely dispersed in the heat-meltable fluororesin fine powder becomes a nucleating agent when the fluororesin is crystallized. In order for a crystalline polymer to crystallize from a melt, it is known that nuclei are first generated and crystals (or spherulites) grow from the nuclei. Also for the purpose of refining crystals in fluororesins, metal sulfates (Japanese Patent Laid-Open No. 49-5153) are used for polychlorotrifluoroethylene, and alkali metal salts (Japanese Patent Laid-Open No. 49-17015) are used for polyvinylidene fluoride. Inorganic and organic cyclic compounds (Japanese Patent Laid-Open No. 48-33983) are available. However, since acetylene black particularly suitable for mixing in the present invention has a nucleation effect larger than the nucleating agent described in the above publication, nucleation and crystal growth are also measured by crystallization process measurement using a differential scanning calorimeter (DSC). The greater the crystallization peak, the greater the heat of crystallization during the nucleation process.

  Since the acetylene black fine powder dispersed in the hot-melt fluororesin becomes a nucleating agent for the hot-melt fluororesin, for example, PFA, the more uniformly the acetylene black fine powder is dispersed, the more frequently the nucleation occurs. There is a correlation between the dispersion state of black and the heat of crystallization due to nucleation. The more the heat of crystallization due to nucleation, the better the dispersion state of acetylene black. As a result, the surface state of the resulting molded body is smoother and more accurate than the mixture of other conductive carbon blacks. Even if it is used for a wafer holding jig or a solvent line to be used, a conductive fluororesin powder composition that does not contaminate the device can be obtained because the conductive particles are not released into the liquid of the device. In addition, since a molded body obtained from a conductive fluororesin powder composition in which acetylene black is more uniformly dispersed has little change in electrical resistance between molded bodies or between molded bodies, the heat of crystallization due to nucleation determined by DSC. Of the total crystallization heat (area ratio A / (A + B) in FIG. 1) or the ratio of the heights of two crystallization peaks (the ratio of the heights H1 and H2 of the two crystallization peaks in FIG. 1) It is possible to evaluate the dispersion state and electrical resistance stability of acetylene black.

  In the measurement of the crystallization heat in the nucleation process by DSC, the crystallization rate (cooling rate) from the melt is important. If the crystallization rate is too high, the peak of nucleation (high temperature side peak, FIG. 1A) and crystal growth (low temperature side peak near the normal fluorination resin crystallization peak temperature, B in FIG. 1) If the nucleation peak and the crystal growth peak are too slow, it becomes difficult to distinguish the boundary between the peaks. Therefore, in order to evaluate the dispersion state of the conductive carbon black in the heat-meltable fluororesin powder composition, although depending on the crystallinity or crystallinity of the heat-meltable fluororesin, the crystallization rate is the nucleation rate. It must be 8-25 ° C./min at which two peaks of crystal growth can be separated, and a range of 10-15 ° C./min is preferable.

  Since acetylene black plays a role of a nucleating agent in the initial stage of crystallization of a heat-melting fluororesin, crystallization occurs at a temperature higher than that of pure heat-melting fluororesin (A in FIG. 1). When acetylene black is finished, acetylene black interferes with the crystal growth process of the heat-melting fluororesin, and therefore the crystal growth rate of the conductive fluororesin composition is slower than that of pure heat-melting fluororesin (the crystal growth is wide). It occurs in the temperature range, and the width of the crystallization curve due to crystal growth becomes wider). Therefore, if the acetylene black is not uniformly dispersed in the heat-meltable fluororesin, the proportion of pure heat-meltable fluororesin that is not disturbed by the acetylene black increases, so the crystallization peak height during the crystal growth process is high. (H2 in FIG. 1B) also becomes higher (crystal growth occurs in a narrow temperature range, and the width of the crystallization curve by crystal growth becomes narrower). When mixed in the same amount, acetylene black has a higher heat of crystallization due to nucleation of conductive fluororesin than other conductive carbon blacks, and the height of the crystallization peak due to crystal growth becomes lower. Acetylene black is also preferable from the viewpoint of dispersibility of black.

  The characteristics of the conductive fluororesin composition filled with the conductive carbon black mixed by the high-speed rotary mixer, particularly the cutter mixer, is also that the conductive carbon black particles are uniformly dispersed in the heat-meltable fluororesin fine powder. Therefore, the glass transition temperature of the conductive fluororesin composition is lower than that of pure fluororesin not containing conductive carbon black. As described above, the glass transition temperature of the fluororesin represents the temperature at which partial molecular motion starts in the amorphous region. However, in the conductive fluororesin composition according to the prior art, the conductive carbon black is uniformly dispersed. Therefore, the glass transition temperature of the conductive fluororesin composition is almost the same as the glass transition temperature of pure fluororesin. However, in the conductive fluororesin composition of the present invention, the conductive carbon black is fine and very uniformly dispersed, so that the molecular motion of the fluororesin in the amorphous region is a pure resin that does not contain the conductive carbon black. It appears to occur at a lower temperature (lower glass transition temperature). Accordingly, there is a correlation between the dispersion state of the conductive carbon black dispersed in the conductive fluororesin composition, particularly the fine powder of acetylene black, and the glass transition temperature. The more uniformly the acetylene black fine powder is dispersed, the lower the glass transition temperature of the conductive fluororesin composition (the molecular motion of the fluororesin chain starts in a lower temperature range).

  In the conductive fluororesin powder composition of the present invention, additives can be arbitrarily blended. Additives can be blended when mixing with the mixer. Such additives include powders or fibers of glass, graphite, alumina, mica, silicon carbide, boron nitride, titanium oxide, bismuth oxide, iron oxide, bronze, gold, silver, copper, nickel, stainless steel, molybdenum disulfide, etc. For example, powdery powder can be exemplified. Further, nanomaterials such as fullerene (C60) and carbon nanotubes which have recently been mass-produced and are commercially available can also be added as additives.

  In addition, the conductive fluororesin powder composition of the present invention obtained by mixing with a mixer using a high-speed rotating blade under specific conditions is formed into pellets through an ordinary melt extruder, and then extrusion molding, injection molding, transfer molding, Melt forming such as melt spinning can be performed. Of course, the conductive fluororesin powder composition that is not pelletized as described above is directly used as a molding raw material, or the powder composition is hardened and melt-molded with a compactor to improve the bite of the powder composition with a molding machine hopper. You can also. Furthermore, the conductive fluororesin powder composition obtained in the present invention can be granulated and used as a powder molding or coating material.

  The types of molded products that are finally produced are molding materials for various molded products such as hoses, tubes, containers for the transport of flammable substances that require antistatics, and fixing roll surfaces for copiers that require electrical conductivity control. Can be used as Furthermore, since it is intended for any molded body that requires electrical conductivity, there is no particular limitation in the present invention. For example, tubes, sheets, rods, fibers, packings, semiconductor manufacturing related There are conductive jigs.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. The tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer (PFA) is a tetrafluoroethylene / perfluoropropyl vinyl ether (alkyl group having 3 carbon atoms, PPVE) copolymer (hereinafter referred to as PFA-C3). And tetrafluoroethylene / perfluoroethyl vinyl ether (alkyl group having 2 carbon atoms, PEVE) copolymer (hereinafter referred to as PFA-C2), the crystallization temperature, heat of crystallization of the conductive fluororesin powder composition, Measurement of the dispersion state of carbon black, average particle diameter, glass transition temperature of the compression molded sheet, and surface resistance, surface smoothness, and carbon black release (desorption) of the extruded thin tube were performed by the following methods. .

  (A) Crystallization temperature, heat of crystallization: A differential scanning calorimeter DSC7 manufactured by PerkinElmer was used. The sample is heated to 360 ° C. at 10 ° C./min and held at 360 ° C. for 5 minutes to completely melt the crystal, and then cooled to 200 ° C. at a constant rate (12 ° C./min). The crystallization peak temperature on the low temperature side was determined from the crystallization curve as the crystallization temperature, and the crystallization heat was determined from the peak area (J / g). One crystallization peak appears in the sample mixed with fluorocarbon resin alone or conductive carbon black other than acetylene black, but in the sample mixed with acetylene black, acetylene black acts as a nucleating agent for PFA, Two crystallization peaks appear: a peak (A in FIG. 1) and a low temperature side peak due to crystal growth (B in FIG. 1, appearing near the crystallization peak temperature of a normal fluororesin).

  (B) Dispersion state of carbon black: Since there is a correlation between the dispersion state of acetylene black and the heat of crystallization due to nucleation, all crystals of the heat of crystallization due to nucleation (area A in FIG. 1) determined by DSC The ratio to the heat of formation (area A + area B in FIG. 1) and the ratio of the height of the crystallization peak due to nucleation (height H1 in FIG. 1) and the peak height due to crystal growth (height H2 in FIG. 1) The dispersion state of acetylene black was evaluated. In the evaluation of the dispersion state of carbon black, the heat of crystallization and the height of the crystallization peak obtained from the crystallization peak when the sample was crystallized by DSC at 12 ° C./min were used. When the DSC crystallization curve did not have two crystallization peaks, the right side was regarded as crystallization by nucleation and the left side as crystal growth based on the inflection point appearing around 294 ° C. (in this case) The distance from the baseline to the inflection point was considered as H1).

  (C) Average particle diameter: average particle diameter of PFA fine powder obtained by agglomeration and granulation of fluororesin aqueous dispersion and conductive fluororesin powder composition pulverized and mixed with impact shear mixer (cutter mixer) Was measured with a laser diffraction particle size distribution analyzer (Sympatec GmbH. HEROS & RODOS).

  (D) Glass transition temperature: A dynamic viscoelasticity measuring device (ARES) manufactured by Rheometric Scientific was used. The conductive fluororesin powder composition was pelletized by a twin-screw extruder, and a test piece having a length of 45 mm, a width of 12.5 mm, and a thickness of 1.3 mm was prepared therefrom by compression molding. Using this test piece, the temperature dependence of tan δ from −50 ° C. to + 150 ° C. at a frequency of 1 Hz and a heating rate of 5 ° C./min in a torsion mode (Tortion Rectangular Kit) of a dynamic viscoelasticity measuring device (ARES). Sex was measured. The glass transition temperature was determined from the peak temperature of the tan δ curve.

(E) Surface resistance: A tube having a thickness of 50 μm or 100 μm and an inner diameter of 40 mm was prepared from the above pellets using a 30 mmφ single screw extruder, and an HR100 probe was applied to the obtained tube surface using a surface resistance measuring machine (HIRESTA IP) manufactured by Mitsubishi Oil Corporation. The value displayed on the indicator when 10 V (DC) was applied for 10 seconds after contact was made the surface resistance value (Ω / □) (according to JIS K6911). This measurement limit is 9 × 10 ¹² Ω / □, and when it exceeds 9 × 10 ¹² Ω / □ and measurement is impossible, “> 10 ¹³ ” is displayed. In the measurement, arbitrary five points were measured, and the average value was used as a measured value (Table 2). For samples with high surface resistance (Table 3), the resistance value may exceed the measurement limit, so the maximum value, minimum value, and average value thereof were taken as measurement values (if measurement became impossible, the value was Excluding the average value).

  (F) Surface smoothness: The surface of the tube sample was measured with a stylus-type surface roughness shape measuring instrument (manufactured by TOKYO SEIMITU, SURFCOM 575A-3D). The measured values were measured at five arbitrary locations, and the average value was taken as the measured value.

  (G) Carbon black releasability (removability): After putting the above tube sample in hydrochloric acid solution for 24 hours, apply white filter paper to the surface of the washed sample and rub the surface with a fingertip from the top of the filter paper. The degree of carbon black release was evaluated by comparing the degree of transfer to filter paper. The case where the carbon black did not slightly adhere to the filter paper was indicated by a circle, the case where the carbon black was slightly transferred and adhered to the white filter paper was indicated by a Δ, and the case where the adhesion was visually observed was indicated by x.

[Example 1]
60 kg of 30 wt% PFA-C3 aqueous dispersion (average particle size 0.2 μm, melting point 309 ° C., PPVE = 3.5 wt%) obtained by emulsion polymerization was mixed with a downflow propeller type 6 bladed stirring shaft And 500 g of 60% nitric acid was added while stirring at 300 rpm. The mixture was further stirred at 300 rpm for 10 minutes, and the aqueous dispersion was agglomerated, and then stirred at 450 rpm for 20 minutes to float and float the PFA-C3 aggregated particles on the aqueous layer, thereby separating from the aqueous layer.

  The aqueous layer was discharged from the agitation tank, and then water was added to the agitation tank to wash the PFA-C3 aggregated particles, and then a stainless steel screen (aperture 100 to 150 μm) was passed through. The PFA-C3 aggregated particles remaining on the screen were dried at 160 ° C. for 24 hours to obtain PFA-C3 fine powder. The average particle size of the obtained PFA-C3 fine powder was 2 to 6 μm.

  An impact shearing type mixer (cutter mixer, manufactured by Aikosha Seisakusho Co., Ltd., AC) in which 14 kg of this PFA-C3 fine powder and 1.05 kg of acetylene black (manufactured by Denki Kagaku Kogyo) are cutter-shaped. -200S) and pulverized and mixed at 3600 rpm (circumferential speed 75.3 m / sec) for 10 minutes to obtain a conductive fluororesin powder composition. The average particle size of the obtained conductive fluororesin powder composition was 5 μm. In addition, Table 1 shows the crystallization process measurement result by DSC of the obtained conductive fluororesin powder composition.

[Example 2]
A conductive fluororesin powder composition was prepared in the same procedure as in Example 1 except that the pulverization / mixing time in the cutter mixer was 20 minutes. The results are shown in Table 1. In addition, Table 1 shows the crystallization measurement result of the powder composition by DSC. Moreover, the DSC crystallization curve of a conductive fluororesin powder composition is shown in FIG.

[Example 3]
A conductive fluororesin powder composition was prepared in the same procedure as in Example 1 except that the pulverization / mixing time in the cutter mixer was 30 minutes. The results are shown in Table 1. In addition, Table 1 shows the crystallization measurement result of the powder composition by DSC.

[Example 4]
A conductive fluororesin powder composition was prepared in the same procedure as in Example 1 except that the pulverization / mixing time in the cutter mixer was 40 minutes. The results are shown in Table 1. Table 1 shows the measurement results of the conductive fluororesin powder composition by DSC.

[Comparative Example 1]
A conductive fluororesin powder composition was prepared in the same procedure as in Example 1 except that the pulverization / mixing time in the cutter mixer was 5 minutes. The results are shown in Table 1. In addition, Table 1 shows the crystallization measurement result of the powder composition by DSC.

[Comparative Example 2]
In place of the PFA-C3 fine powder, 60 kg of 30 wt% PFA-C3 aqueous dispersion obtained by emulsion polymerization is placed in a stirring tank (100 liters) having a downflow type propeller type 6-blade stirring shaft and drainage means. Then, after adding 500 g of 60% nitric acid while stirring at 300 rpm (circumferential speed 4.7 m / sec), the mixture was further stirred at 300 rpm for 10 minutes to aggregate the aqueous dispersion, and then water-soluble hydrofluorocarbon HFC43-10 was added. The same procedure as in Example 1 except that PFA-C3 agglomerated particles having an average particle diameter of 200 μm obtained by stirring for 20 minutes and solvent granulation were used, and the pulverization / mixing time in the cutter mixer was changed to 20 minutes. A conductive fluororesin powder composition was prepared. The DSC measurement results and crystallization curve of the powder composition are shown in Table 1 and FIG.

[Comparative Example 3]
Conductive fluororesin powder composition in the same procedure as in Example 1 except that 0.49 kg of ketjen black (Ketjen black EC) was used instead of acetylene black and the pulverization and mixing time in the cutter mixer was 20 minutes. A product was made. Since ketjen black has a more developed structure than acetylene black, the mixing amount was reduced to 0.49 kg. The results are shown in Table 1 and FIG.

  From the results shown in Table 1, the longer the pulverization / mixing time in the cutter mixer, the crystallization heat by nucleation (area A in FIG. 1) obtained by DSC or the total crystallization heat of crystallization heat by nucleation ( The ratio with respect to area A + area B) in FIG. 1 increases, and the ratio between the height of the crystallization peak due to nucleation and the height of the peak due to crystal growth (H1 / H2) also increases. Therefore, there is a correlation between the dispersion state of acetylene black and the heat of crystallization by nucleation determined by DSC, and the larger the ratio of the heat of crystallization by nucleation to the total heat of crystallization (area A + area B in FIG. 1) or As the ratio between the crystallization peak due to nucleation and the peak height due to crystal growth (H1 / H2) is larger, acetylene black is more uniformly and finely dispersed in the PFA-C3 fine powder (Examples 1 to 4).

  From the results shown in Table 1 and FIG. 1, instead of PFA-C3 fine powder having an average particle diameter of 2 to 6 μm obtained by solventless granulation by high speed stirring, an average particle diameter of 200 μm obtained by solvent granulation is used. The sample using the PFA-C3 agglomerated particles of (Comparative Example 2) has a poor dispersion state of acetylene black, so the ratio of the crystallization heat due to nucleation, the crystallization peak due to nucleation, and the peak height due to crystal growth ( H1 / H2) becomes smaller.

  Further, in the sample using ketjen black (Comparative Example 3) instead of acetylene black, crystallization peak due to nucleation does not appear because ketjen black has no nucleation effect. Further, in any sample, the crystallization peak temperature due to crystal growth (the peak of area B in FIG. 1) hardly changes, suggesting that area A in FIG. 1 is crystallization due to nucleation. .

  The conductive fluororesin powder compositions obtained in Examples and Comparative Examples were extruded with a twin screw extruder (Toyo Seiki Seisakusho, Labo Plato Mill 30C150) at 370 ° C. and 20 rpm to prepare pellets, and then thickened with a 30 mm single screw extruder. A tube having a thickness of 50 μm and an inner diameter of 40 mm was prepared. The evaluation results of the obtained tube are shown in Table 2.

  From the results shown in Table 2, the conductive fluororesin tube formed using the conductive fluororesin powder composition of the present invention is a conductive fluororesin tube using another conductive fluororesin powder composition (comparison). Compared with Examples 1-3), since conductive carbon black is uniformly dispersed, the change in surface resistance is small and the surface smoothness is excellent. Moreover, the electroconductive fluororesin composition which does not contaminate an apparatus because electroconductive particle does not isolate | separate in a solution is made.

[Examples 5 to 7, Comparative Example 4, Reference Example 1]
PFA-C3 fine powder and acetylene black obtained in the same manner as in Example 1 were mixed at 3600 rpm at the mixing ratio and mixing time shown in Table 3 using the same cutter mixer as in Example 1, and the conductive fluororesin powder composition I got a thing. The obtained conductive fluororesin powder composition was pelletized using a lab plast mill, and then compression molded to prepare a sheet-like test piece, and the glass transition temperature was measured. For comparison, a sheet-like test piece was prepared by compression molding from PFA-C3 in the same manner, and its glass transition temperature was determined. Further, from the above pellets, an extruded tube having a thickness of 100 μm and an inner diameter of 40 mm was formed using a 30 mm uniaxial extruder and evaluated. The results are shown in Table 3.

[Comparative Example 5]
Except that a Henschel mixer was used in place of the cutter mixer, a conductive fluororesin composition pellet was prepared by the same procedure as in Example 7 (mixing time 30 minutes), and then a sheet-like test piece and a tube were prepared and evaluated. Went. The results are shown in Table 3.

[Comparative Example 6]
Instead of the PFA-C3 dry fine powder used in Examples 5 to 7, 60 kg of the 30 wt% PFA-C3 aqueous dispersion used in these examples was mixed with a downflow propeller type 6-bladed stirring shaft and drainage means. Was added to a stirring tank (100 L) having a water content of 500% of 60% nitric acid while stirring at 300 rpm. Further, the mixture was stirred at 300 rpm for 10 minutes, and after the aqueous dispersion was agglomerated, PFA-C3 agglomerated particles having an average particle diameter of 200 μm obtained by adding water-soluble hydrofluorocarbon HFC43-10 and solvent granulation were used. After preparing the pellets of the conductive fluororesin composition by the same procedure as in Example 6 (mixing time is 20 minutes), sheet-like test pieces and tubes were prepared and evaluated. The results are shown in Table 3.

[Example 8, Reference Example 2]
The same procedure as in Example 6 except that 30% by weight PFA-C2 aqueous dispersion (average particle size 0.2 μm, melting point 290 ° C., PEVE = 7.1% by weight) was used instead of the PFA-C3 aqueous dispersion ( After preparing the conductive fluororesin composition pellets at a mixing time of 20 minutes, sheet-like test pieces and tubes were prepared and evaluated. For comparison, a sheet-like test piece was prepared by compression molding from PFA-C2 in the same manner, and its glass transition temperature was determined. The results are shown in Table 3.

  From the results shown in Table 3, the glass transition temperature of the conductive fluororesin composition becomes lower than that of a single PFA as the heat-meltable fluororesin powder and acetylene black are mixed longer with a cutter mixer. Therefore, there is a correlation between the dispersion state of acetylene black and the glass transition temperature obtained with a dynamic viscoelasticity measuring device. The lower the glass transition temperature of the conductive fluororesin composition, the more uniformly and finely disperses acetylene black in PFA. (Examples 5 to 7). In the example (Example 8) in which PFA-C2 was used instead of PFA-C3, the glass transition temperature of the conductive fluororesin composition was 5 ° C. lower than that in the case where acetylene black was not added.

  On the other hand, the sample (Comparative Example 5) mixed using a Henschel mixer instead of the cutter mixer has a poor dispersion state of acetylene black, and therefore the glass transition temperature is almost the same as when acetylene black is not added.

  Moreover, instead of using a fluororesin dry fine powder having a small average particle diameter, a sample (Comparative Example 6) mixed with a cutter mixer using PFA-C3 aggregated particles having an average particle diameter of 200 μm obtained by a solvent granulation method is Since the particle diameter of PFA-C3 agglomerated particles is large, the dispersion state of acetylene black is poor even when mixed with a cutter mixer, so the glass transition temperature is the same as when acetylene black is not added.

  From the tube physical properties shown in Table 3, conductive fluororesin tubes (Examples 5 to 8) molded using the conductive fluororesin composition of the present invention were molded using other conductive fluororesin compositions. Since the acetylene black is more uniformly dispersed than the conductive fluororesin tubes (Comparative Examples 5 to 6), the variation in surface resistance of the tube molded body is small, and the surface smoothness is excellent.

  In Comparative Example 4, since the mixing time is short, the decrease in glass transition temperature is only 2 ° C., the variation in the surface resistance of the tube is large, and the surface smoothness is also poor compared to those in Examples 5-8. .

  In the conductive fluororesin composition of the present invention, the conductive carbon black is more uniformly dispersed in the heat-meltable fluororesin. Therefore, the molded product obtained from the conductive fluorocarbon resin can be obtained even in a high electrical resistance region that has been considered difficult until now. A conductive fluororesin composition article that exhibits stable electrical resistance, and has a smoother and more accurate surface state can be produced. Moreover, even if it uses for the wafer holding jig and solvent line which are used for a semiconductor manufacturing apparatus, the electroconductive fluororesin composition article which does not contaminate an apparatus can be manufactured because an electroconductive particle does not detach | leave in the liquid of an apparatus. Furthermore, since there is a correlation between the dispersion state of conductive carbon black and the crystallization curve obtained by DSC, the dispersion state of conductive carbon black can be easily evaluated using the DSC analysis method proposed in the present invention. Can do. In addition, since there is a correlation between the dispersion state of conductive carbon black and the glass transition temperature obtained with a dynamic viscoelasticity measuring device, the comparison between the glass transition temperatures of the conductive fluororesin composition and the single fluororesin Easily evaluate the dispersion state of carbon black

  Furthermore, the mixer using the blade rotating at high speed used in the present invention mixes the conductive carbon black and the fluororesin fine powder well, so the conductive carbon black and the hot melt melt regardless of the melt viscosity of the hot melt fluororesin. The conductive fluororesin composition in which the conductive fluororesin fine powder is uniformly dispersed can be produced.

  In addition, the composition of the present invention can be melt-molded such as extrusion molding, injection molding, transfer molding, and melt spinning, and finally the type of molded product to be manufactured is any molding that requires electrical conductivity. The body can be manufactured, and is not particularly limited by the present invention. Examples thereof include tubes, sheets, rods, fibers, packings, and semiconductor manufacturing related conductive jigs.

It is a DSC crystallization peak of a conductive fluororesin composition.

Explanation of symbols

A: Crystallization peak accompanying nucleation of fluororesin B: Crystallization peak accompanying crystal growth of fluororesin H1: Height of crystallization peak accompanying nucleation of fluororesin H2: Crystallization accompanying crystal growth of fluororesin Peak height

Claims (3)

A composition comprising conductive carbon black, which is acetylene black, and a heat-meltable fluororesin powder, which is a copolymer of tetrafluoroethylene and perfluoro (alkyl vinyl ether) obtained by emulsion polymerization, in the DSC apparatus, the heat There are two crystallization peaks when crystallized at a temperature drop rate of 12 ° C./min from a temperature above the melting point of the meltable fluororesin, and the ratio of the crystallization peak heights (high temperature side peak / low temperature side peak) Is 0.65 or more and / or the ratio of the high temperature side crystallization peak area [high temperature side peak area / (high temperature side peak area + low temperature side peak area)] is 0.18 or more. Fluororesin composition. The conductive fluororesin composition according to claim 1, wherein the high temperature side crystallization peak is a crystallization peak accompanying nucleation, and the low temperature side crystallization peak is a normal crystal growth peak. 3. The conductive fluororesin composition according to claim 1, wherein the conductive carbon black is contained in an amount of 5 to 10% by weight.

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