JP2016172941A - Additive comprising pitch-based carbon fiber, and resin composition and molding comprising the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an additive comprising pitch-based carbon fibers with a small average fiber diameter, and a resin composition and a molding comprising the additive.SOLUTION: The additive comprises the following (1a)-(1b): (1a) pitch-based carbon fibers using an isotropic pitch as a carbon precursor and having an average fiber diameter of 10 μm or less or (1b) pitch-based carbon fibers using an isotropic pitch as a carbon precursor, having an average fiber diameter of 10 μm or less, and containing boron 6-1000 massppm.SELECTED DRAWING: None

Description

  The present invention relates to an additive composed of pitch-based carbon fiber, and a resin composition and a molded article containing the additive.

  The carbon fiber generally refers to a fiber-like material made by pyrolysis of an organic material and substantially composed of carbon. This carbon fiber has both (A) the structure, structure and characteristics as a carbon material that is a constituent element, and (B) the characteristics due to the fiber form. Therefore, features such as good heat resistance, chemical stability, electrical / thermal conductivity, low thermal expansion, low density, friction / wear characteristics, X-ray permeability, electromagnetic wave shielding, biocompatibility, flexibility, etc. It is also possible to add adsorption performance. Known carbon fibers include pitch-based carbon fibers and PAN-based carbon fibers (polyacrylonitrile-based carbon fibers). Pitch-based carbon fibers are carbon fibers that are manufactured using pitches such as distillation residues of heavy oil derived from petroleum or coal as raw materials, and are broadly divided into isotropic pitch-based carbon fibers and anisotropic pitch-based carbon fibers. Examples thereof include carbon fibers (mesophase pitch-based carbon fibers).

  An isotropic pitch-based carbon fiber is obtained by firing pitch fibers obtained by spinning an isotropic pitch that is optically isotropic (in other words, molecules or groups of molecules are randomly oriented). Carbon fiber. This isotropic pitch-based carbon fiber is generally called a general-purpose carbon fiber and can be manufactured at a relatively low cost. In addition, isotropic pitch-based carbon fibers are superior in performance to improve slidability, although mechanical strength and elastic modulus are not high as compared with anisotropic pitch-based carbon fibers and PAN-based carbon fibers. For this reason, isotropic pitch-based carbon fibers are widely used as additives for resins (synthetic resins, etc.) (for example, Non-Patent Document 1).

  A method for producing an isotropic pitch-based carbon fiber is described in Patent Document 1 below, for example. Patent Document 1 includes (i) a step of spinning a melt pitch by a vortex method, (ii) a step of insolubilization (infusibilization), and (iii) a step of carbonization. A method is disclosed in which a melt pitch is caused to flow out from an outflow nozzle after a swirl flow is applied thereto. Patent Document 2 discloses a resin composition for a sliding component comprising carbon fiber, bronze powder, and a fluorine-containing resin that can be melt-processed.

JP-A-6-235123 Patent No. 3410487

Carbon Glossary (October 5, 2000, 1st edition, 1st edition, Agne Jofusha) p.261-262

  By the way, an isotropic pitch-based carbon fiber having a small average fiber diameter (average fiber diameter, which is the diameter of the carbon fiber) is used as a lubricant for a sliding material (also referred to as a sliding member) formed from a resin. When (added), (a) improved moldability during resin molding, (b) reduced wear of the mating material during sliding of the molded product, (c) the number of fillers per unit volume of the carbon fiber is Increases in the sliding characteristics of the molded product and (d) a reduction in the dropout of the carbon fibers in the molded product can be considered.

  From the above viewpoint, development of an isotropic pitch-based carbon fiber having a smaller average fiber diameter is desired.

  However, an isotropic pitch-based carbon fiber has an average fiber diameter of about 12 to 18 μm, and an isotropic pitch-based carbon fiber having an average fiber diameter of 10 μm or less has not been obtained yet.

  For example, a method is conceivable in which a pitch fiber having a small fiber diameter is first produced by spinning by a centrifugal method, and then the pitch fiber having a small diameter is made infusible and carbonized. However, it is extremely difficult to obtain fine pitch fibers by spinning by a centrifugal method from the viewpoint of spinning energy. Even if it is possible to produce pitch fibers with a small fiber diameter to obtain an isotropic pitch-based carbon fiber having an average fiber diameter of 10 μm or less, the pitch fibers stick to each other when infusible in the next step. May harden or burn. Moreover, even if the method of producing a pitch fiber having a small diameter by performing spinning by the vortex method described in Patent Document 1, the above infusibility problem is still not solved.

  On the other hand, it is also conceivable that an isotropic pitch-based carbon fiber having an average fiber diameter larger than 10 μm is once obtained, and the carbon fiber is subjected to a treatment for reducing the average fiber diameter in the next step. However, Non-Patent Document 1 describes an isotropic pitch-based carbon fiber having “isotropic structure and no significant change in structure and material mechanical properties even when heat-treated to a high temperature”. Therefore, it has been considered that the average fiber diameter of the carbon fibers cannot be designed and controlled by high-temperature heat treatment of the isotropic pitch-based carbon fibers.

  On the other hand, it is also conceivable to use PAN-based carbon fibers or anisotropic carbon fibers in place of the isotropic pitch-based carbon fibers. This is because PAN-based carbon fibers and anisotropic carbon fibers having an average fiber diameter of 10 μm or less are easily available. However, since the PAN-based carbon fiber and anisotropic carbon fiber are too hard, there is a risk of damaging the mating material or scraping off the film formed on the surface of the mating material when formed into a molded product. There is.

  An object of the present invention is to provide an additive comprising an isotropic pitch-based carbon fiber having a small average fiber diameter under the above-described conventional techniques and problems. Another object of the present invention is to provide a resin composition and a molded product using such an additive.

  As a result of intensive studies to solve the above problems, the present inventors have found that an isotropic pitch-based carbon fiber having an average fiber diameter of 10 μm or less can be obtained according to a specific method, and It has been found that it can be used as an isotropic pitch-based carbon fiber additive (especially an additive for resins). As a result of further studies, the present inventors have completed the present invention.

That is, this invention relates to the following resin composition and its molded article.
Item 1. The following (1a):
(1a) An additive comprising pitch-based carbon fibers having an isotropic pitch as a carbon precursor and an average fiber diameter of 10 μm or less.
Item 2. The pitch-based peak height of a band of Raman spectrum of 1560～1610Cm ^-1 obtained peak band of the Raman spectrum of 1320～1370Cm ^-1 obtained from the side of the carbon fiber and the height I _D from the side surface of the carbon fiber I is the ratio of _G I _D / I _G is 0.3 to 1.5, additive according to claim 1.
Item 3. The following (1b):
(1b) An additive comprising pitch-based carbon fibers having an isotropic pitch as a carbon precursor and an average fiber diameter of 10 μm or less and containing 6 to 1000 massppm of boron.
Item 4. The crystallite size La in the a-axis direction of the graphite crystal obtained from the X-ray diffraction method of the pitch-based carbon fiber is 100 nm or more, and
The crystallite size Lc in the c-axis direction of the graphite crystal obtained from the (004) diffraction line of the pitch-based carbon fiber X-ray diffraction method is 100 nm or more.
Item 4. The additive according to Item 3.
Item 5. A peak height I _D of the band of the pitch-based Raman spectra of 1320～1370Cm ^-1 obtained from the side of the carbon fiber, the peak of the band 1560～1610Cm ^-1 of a Raman spectrum obtained from the side of the pitch-based carbon fibers is the ratio of the height I _G I _D / I _G is additive according to which 0.3 to 1.0, claim 3 or 4.
Item 6. Item 6. The additive according to any one of Items 1 to 5, which is an additive for resin.
Item 7. Item 6. The additive according to Item 5, wherein the resin is a tetrafluoroethylene resin.
Item 8. Item 6. A resin composition comprising the additive according to any one of Items 1 to 5 and a resin component.
Item 9. Item 9. The resin composition according to Item 8, wherein the resin component is a tetrafluoroethylene resin.
Item 10. Item 10. The resin composition according to item 8 or 9, wherein the content of the resin component is 50% by mass or more of the entire resin composition.
Item 11. Item 10. A molded product obtained by molding the resin composition according to any one of Items 8 to 10.

  The additive of the present invention is characterized by comprising the pitch-based carbon fiber (1a) or (1b).

  Since the additive of the present invention having the characteristics is formed of pitch-based carbon fibers and has a small average fiber diameter, it has excellent moldability at the time of molding mixed with other materials (for example, resin components), and other materials ( For example, when a resin composition mixed with a resin component) is made into a molded product and slid, the wear of the other material is reduced, and when the resin composition mixed with the other material (eg resin component) is used as a molded product (1a) or (1b) can increase the number of packings per unit volume of the pitch-based carbon fiber, resulting in excellent sliding characteristics and cost reduction, and other materials (for example, resin components) When the resin composition mixed with) is used as a molded product, it is possible to reduce the dropout of the pitch-based carbon fiber of (1a) or (1b), and as a result, it can be expected to improve the production yield of the molded product. .

2 is a magnified photograph of a pitch-based carbon fiber of Example 1. FIG. 4 is a magnified photograph of a pitch-based carbon fiber of Example 3. FIG. 4 is a magnified photograph of a pitch-based carbon fiber of Comparative Example 2. 2 is an X-ray diffraction pattern of pitch-based carbon fibers of Example 1, Example 3, and Comparative Example 2. FIG. 4A shows the first embodiment, FIG. 4B shows the third embodiment, and FIG. 4C shows the second comparative example. It is a Raman spectrum figure of Example 1 (side surface of a fiber), Example 3 (side surface of a fiber), Comparative example 2 (side surface of a fiber), and Comparative example 3 (anisotropic carbon fiber) (side surface). As a reference, the Raman spectrum of natural graphite (basal surface of scaly graphite) is also shown. The schematic diagram of the Atchison furnace used in the production example is shown.

<< 1. Additives >>
The additive of the present invention includes the following (1a):
(1a) Pitch-based carbon fiber having an isotropic pitch as a carbon precursor and an average fiber diameter of 10 μm or less, or (1b) An average fiber diameter having an isotropic pitch as a carbon precursor is 10 μm or less, and boron It consists of pitch-based carbon fiber containing 6-1000 massppm.

  The additive of the present invention having the characteristics is expected to be excellent in moldability at the time of molding mixed with another material (for example, resin component). The reason is that since the average fiber diameter of the pitch-based carbon fiber (1a) or (1b) is small (thin), for example, during the granulation, the pitch-based carbon fiber of (1a) or (1b) is another material. This is considered to be because it becomes easy to be taken in (for example, a resin component) and becomes familiar with the other material (for example, a resin component).

  Further, the additive of the present invention having the characteristics described above is used when the molded product (for example, a sliding material) obtained by molding a resin composition mixed with another material (for example, a resin component) is slid. It is expected to reduce wear and tear.

  Further, the additive of the present invention having the characteristics described above is the pitch-based carbon fiber of (1a) or (1b) because the average fiber diameter of the pitch-based carbon fiber of (1a) or (1b) is small (thin) The number of fillers per unit volume can be increased, and as a result, when a resin composition mixed with other materials (for example, resin components) is used as a molded product, it has excellent sliding characteristics and can lead to cost reduction. Be expected.

  Further, the additive of the present invention having the characteristics described above is the pitch-based carbon fiber of (1a) or (1b) in a molded product obtained by molding a resin composition mixed with another material (for example, resin component). It is expected that dropout can be reduced, and as a result, production yield of molded products can be improved (troubles caused by molded products can be reduced).

  Since the pitch-based carbon fiber (1a) or (1b) has high graphite crystallinity, for example, a resin molded product obtained by using a tetrafluoroethylene resin as a main component as a resin component is particularly excellent in lubricity. It is expected that it can be used as a moving material.

Further, in the additive of the present invention, pitch-based carbon fibers are obtained from the peak height I _D and the carbon fiber sides of the band of the Raman spectrum of 1320～1370Cm ^-1 obtained from the side of the pitch-based carbon fiber Raman It is preferable that I _D / I _G that is a ratio of peak height I _G of the band of 1560 to 1610 cm ^{−1 in} the spectrum is 0.3 to 1.5. This is expected to give better sliding characteristics.

(1a) or (1b) Pitch-based carbon fiber having an average fiber diameter of 10 μm or less with an isotropic pitch as a carbon precursor The additive of the present invention has an average fiber diameter of 10 μm with an isotropic pitch as a carbon precursor. It consists of the following pitch-based carbon fibers (in the above and below, also referred to as (1a) or (1b) carbon fiber or (1a) or (1b) pitch-based carbon fiber).

  The pitch-based carbon fiber (1a) or (1b) is a carbon fiber having an isotropic pitch as a carbon precursor, and is an isotropic pitch-based carbon fiber. Here, the pitch-based carbon fiber is a carbon fiber manufactured using a pitch described later as a raw material. An isotropic pitch-based carbon fiber is a carbon fiber when the pitch is isotropic. Isotropic means that it is optically isotropic and molecules or groups of molecules are randomly oriented. A carbon precursor refers to a series of carbonized intermediates in a stage prior to the intended final carbon product. The carbon precursor in the present invention is an isotropic pitch, and the final carbon product is the pitch-based carbon fiber (isotropic pitch-based carbon fiber) of (1a) or (1b).

  Pitch, which is a carbon precursor, refers to liquid tar obtained during dry distillation of wood, coal, etc., bitumen obtained from oil sand, oil obtained by dry distillation of oil shale, residual oil obtained by distillation of crude oil, petroleum fraction It is solid at room temperature obtained by heat treatment and polymerization of tar and the like produced by cracking. Specific examples include (a) coal pitch, (b) petroleum pitch, and (c) synthetic pitch obtained by polymerizing aromatic compounds such as naphthalene. Pitch is a mixture of a myriad of condensed polycyclic aromatic compounds chemically. Examples of the coal-based pitch obtained using coal as a raw material include pitch obtained by heat treatment of coal tar generated from a coke oven.

  The isotropic pitch in the present invention is not particularly limited, but coal-based isotropic pitch (isotropic pitch obtained using coal as a raw material) is preferable.

  The softening point of the isotropic pitch is not particularly limited, and can be appropriately set according to the spinning method in the pitch-based carbon fiber production method described later.

  The pitch-based carbon fiber (1a) or (1b) is obtained by obtaining a precursor fiber from an isotropic pitch that is a carbon precursor (raw material) and then heat-treating the precursor fiber. The method for producing the pitch-based carbon fiber (1a) or (1b) will be described later.

The average fiber diameter of the pitch-based carbon fiber of (1a) or (1b) is as follows (i) to (iii):
(i) The pitch-based carbon fiber of (1) is magnified 1000 times using a magnifying glass and an image analyzer,
(ii) Next, the pitch-based carbon fiber of (1) above is arbitrarily selected 10 points, the fiber diameter of the 10 points is measured,
(iii) Finally, the average value of the 10 fiber diameters obtained in (ii) above is calculated.
It was decided by doing.

  The pitch-based carbon fiber (1a) or (1b) has an average fiber diameter of 10 μm or less, preferably less than 10 μm, and more preferably 9 μm or less. The lower limit value of the average fiber diameter is preferably 6 μm. When the average fiber diameter of the pitch-based carbon fibers (1a) or (1b) is 6 μm or more, the pitch-based carbon fibers are not easily crushed and can be more suitably used for various applications such as a lubricant for sliding materials.

  The average fiber length of the pitch-based carbon fiber (1a) or (1b) is not particularly limited. For example, when the pitch-based carbon fiber (1a) or (1b) is a milled fiber, the average fiber length is preferably about 0.04 to 3 mm, and the pitch-based carbon fiber (1a) or (1b) is a chopped fiber. The average fiber length is preferably about 3 to 10 mm. When the pitch-based carbon fiber of (1a) or (1b) is a mat fiber, the mat fiber has a length of several centimeters to several tens of centimeters and a set of short fibers having a certain width. The concept of average fiber length is not particularly required. Here, the average fiber length means an average length in a direction perpendicular to the fiber diameter. The method for measuring the average fiber length is the same as the method for measuring the average fiber diameter except that the fiber length is used instead of the fiber diameter.

  The average aspect ratio of the pitch-based carbon fiber (1a) or (1b) is not particularly limited. For example, when the pitch-based carbon fiber of (1a) or (1b) is a milled fiber, the average aspect ratio is preferably 4 to 500, and the pitch-based carbon fiber of (1a) or (1b) is a chopped fiber. In some cases, the average aspect ratio is preferably 300-1700. Here, the average aspect ratio means an average value of the ratio (= L / R) of the fiber diameter R and the fiber length L. The method for measuring the average aspect ratio is the same as the method for measuring the average fiber diameter except that the ratio L / R is used instead of the fiber diameter R.

  In the pitch-based carbon fiber (1a) or (1b), the crystallite size La in the a-axis direction of the graphite crystal obtained from the X-ray diffraction method is 100 nm or more, and (004 ) The crystallite size Lc in the c-axis direction of the graphite crystal obtained from the diffraction line is preferably 100 nm or more. When the La and Lc of the pitch-based carbon fiber of (1a) or (1b) are in the above ranges, the pitch-based carbon fiber of (1a) or (1b) is a pitch-based carbon having a more developed graphite structure. Means fiber.

The pitch-based carbon fiber (1a) or (1b), a Raman spectrum obtained from the peak height I _D and the carbon fiber sides of the band of the Raman spectrum of 1320～1370Cm ^-1 obtained from the side of the carbon fiber I _D / I _G , which is the ratio of the peak height I _G of the band of 1560 to 1610 cm ⁻¹ , is preferably 0.3 to 1.0, particularly 0.4 to 0.7. When the I _D / I _G of the pitch-based carbon fiber of (1a) or (1b) is in the above range, (a) three-dimensional regularity of graphite, and (b) optical isotropy (ie, It also has the property of a molecule or a group of molecules (lamellar) oriented randomly. Here, in other words, the properties (a) and (b) can be said to have an isotropic structure and high graphite crystallinity. When such a pitch-based carbon fiber is contained together with a resin component to be described later to constitute a resin composition, it has excellent lubricity due to high graphite crystallinity and has an isotropic structure. Gives moderate elasticity and strength. Therefore, the pitch-based carbon fiber (1a) or (1b) in which the I _D / I _G is in the above range is a preferred embodiment in the present invention. Such an embodiment is easily achieved by containing boron in an amount of 6 to 1000 massppm.

  The pitch-based carbon fiber (1a) preferably has a low boron content in order to maintain the shape of the carbon fiber. Boron is doped in the form of a substitutional solid solution on the graphite hexagonal mesh surface, and is known as a very strong graphitization catalyst, but carbon fiber is present in the presence of a large amount of boron (11.7 mass%) at about 2600 ° C. It has been reported that the interface between crystallites constituting the carbon fiber disappears upon heat treatment, and the shape of the carbon fiber cannot be maintained (T. Sogabe et al., J. Mater. Sci. Vol. 31, p. 6469-6476). In the above case, the concentration of boron present in the solid solution is estimated to be around 1 mass% from the BC phase diagram. From such a viewpoint, the boron concentration in the pitch-based carbon fiber of the present invention is preferably less than 0.0006 mass% (less than 6 massppm), and more preferably 0.0001 to 0.0005 mass% (1 to 5 massppm). The amount of boron in the pitch-based carbon fiber (1a) is measured by ICP-AES (luminescence method) after ashing a sample of about 50 to 100 g, dissolving the ash with an acid. In addition, carbon materials such as artificial graphite and carbon fiber produced from petroleum or coal-derived carbon precursors usually contain about 1 to 4 mass ppm of boron as an impurity.

The pitch-based carbon fiber (1b) contains 6 to 1000 massppm of boron, and is (a) a carbon fiber having a developed graphite structure, and (b) optical isotropy. It also has the property of nature (that is, the property of molecules or groups of molecules (lamellar) randomly oriented). Here, in other words, the properties (a) and (b) can be said to have an isotropic structure and high graphite crystallinity. When such a pitch-based carbon fiber is contained together with a resin component to be described later to constitute a resin composition, it has excellent lubricity due to high graphite crystallinity and has an isotropic structure. Gives moderate elasticity and strength. Therefore, the pitch-based carbon fiber (1b) in which the I _D / I _G is in the above range is a preferred embodiment in the present invention.

  On the other hand, anisotropic pitch-based carbon fibers have an anisotropic structure (that is, a structure in which crystallites are highly arranged), so that the elasticity and strength are too high. For this reason, the resin molded product containing the anisotropic pitch-based carbon fiber damages the counterpart material or scrapes off the film formed on the surface of the counterpart material, resulting in poor sliding characteristics.

  The pitch-based carbon fiber (1a) or (1b) may be subjected to a pulverization process, a cutting process, or the like depending on the intended use under the condition that the average fiber diameter is maintained at 10 μm or less. By this operation, the shape of the pitch-based carbon fiber (1a) or (1b) can be appropriately changed.

  The pulverization method is not particularly limited. For example, the carbon fiber can be pulverized using a jet mill, a hammer mill, a pin mill, or the like.

  The cutting method is not particularly limited. For example, the carbon fiber can be cut using a roving cutter, a guillotine cutter, a cross cutter, a low-speed shear type screen pulverizer, or the like.

  Such a pitch-based carbon fiber of (1a) or (1b) maintains the fluidity of the resulting resin composition, for example, when mixed with a resin, and a film suitable for stabilizing wear friction is formed on the surface of the resin component. The effect by carbon fiber, such as the improvement of a sliding characteristic formed, can be expressed. For this reason, the additive comprising the pitch-based carbon fiber (1a) or (1b) is particularly preferably used as an additive for a resin.

< Method for producing pitch-based carbon fiber (1a) >
The production method of the pitch-based carbon fiber (1a) (or the method of reducing the average fiber diameter of the pitch-based carbon fiber (1a)) is a pitch-based carbon having an isotropic pitch as a carbon precursor. A method for producing pitch-based carbon fibers that are fibers and have an average fiber diameter of 10 μm or less, wherein the carbon fiber precursor fibers obtained using the isotropic pitch as a raw material are heat-treated at 2800 to 3000 ° C. By having the process to do, it is obtained suitably.

< Method for producing pitch-based carbon fiber (1b) >
The method for producing the pitch-based carbon fiber (1b) (or the method for reducing the average fiber diameter of the pitch-based carbon fiber (1b)) can be obtained by using an isotropic pitch as a carbon precursor and an average fiber diameter. Is a pitch-based carbon fiber manufacturing method containing 10 to 1000 massppm of boron, and the precursor fiber of the carbon fiber obtained using the isotropic pitch as a raw material, in an atmosphere containing boron It can be suitably obtained by having a heat treatment step of heat treatment at 2800 to 3000 ° C.

  The pitch-based carbon fiber (1b) is doped with boron in order to further enhance the graphite crystallinity. As described above, since it is difficult to maintain the shape of the carbon fiber when boron is contained in a large amount, the boron concentration in the pitch-based carbon fiber of (1b) is 0.0006 to 0.1 mass% (6 to 1000 massppm), preferably 0.001 to 0.05 mass% (10 to 500 massppm). The amount of boron in the pitch-based carbon fiber (1b) is measured by ICP-AES (luminescence method) after ashing a sample of about 50 to 100 g, dissolving the ash in acid.

  In addition, carbon materials such as artificial graphite and carbon fiber produced from petroleum or coal-derived carbon precursors usually contain about 1 to 4 mass ppm of boron as an impurity.

[(1a) or (1b) pitch-based carbon fiber precursor fiber]
In the method for producing a pitch-based carbon fiber of (1a) or (1b), the precursor of the pitch-based carbon fiber of (1a) or (1b) is used as a raw material (hereinafter referred to as (1a) or (1b) The pitch-based carbon fiber precursor is simply referred to as “precursor fiber”).

  The precursor fiber is a carbon fiber obtained using isotropic pitch as a raw material. That is, the precursor fiber is an isotropic pitch-based carbon fiber, similar to the pitch-based carbon fiber of (1a) or (1b).

  The average fiber diameter of the precursor fiber is larger than 10 μm. The method for measuring the average fiber diameter is the same as the above-described method for measuring the average fiber diameter of the pitch-based carbon fibers (1a) or (1b). The average fiber diameter of the precursor fibers is preferably 11 to 14 μm. When the preferable average fiber diameter of the precursor fibers is within the above range, pitch-based carbon fibers having an average fiber diameter of 10 μm or less can be efficiently produced in the heat treatment step described later.

  The average fiber length of the precursor fibers is not particularly limited, and any of mat fibers, milled fibers, chop fibers, and the like can be used. For example, when the precursor fiber is a milled fiber, the average fiber length is preferably about 0.04 to 3 mm, and when the precursor fiber is a chop fiber, the average fiber length is preferably about 3 to 10 mm. When the precursor fiber is a mat fiber, the mat fiber is an aggregate of short fibers having a length of several centimeters to several tens of centimeters and having a certain width, and the concept of average fiber length Is not particularly required. Here, the average fiber length means an average value of lengths in a direction perpendicular to the fiber diameter of the precursor fiber. The method for measuring the average fiber length is the same as the method for measuring the average fiber length of the pitch-based carbon fibers (1a) or (1b) described above. Since the pitch-based carbon fiber (1a) or (1b) as the final product is used as a chop fiber or a milled fiber, the precursor fiber is also preferably a chop fiber or a milled fiber. When the precursor fiber is chopped fiber or milled fiber, there is an advantage that it can be easily packed in a container to be described later when heating in a heating furnace (a larger amount can be packed in the container).

  The average aspect ratio of the precursor fiber is not particularly limited. For example, when the precursor fiber is a milled fiber, the average aspect ratio is preferably 3 to 270, and when the precursor fiber is a chop fiber, the average aspect ratio is preferably 210 to 910. The method for measuring the aspect ratio is that of the precursor fiber except that the ratio of the precursor fiber diameter R ′ to the precursor fiber length L ′ (= L ′ / R ′) is used instead of the precursor fiber diameter R ′. This is the same as the method for measuring the average fiber diameter.

A commercial item can be used for the precursor fiber. As a specific example of a commercial product,
・ Donakabo chops (product number: S-231, S-232) manufactured by Osaka Gas Chemical Co., Ltd.
・ Donakabo Mildo (product number: S-2404N, S-249K, S-241, S-242, S-243, S-244, S-246, S-247, SC-244, manufactured by Osaka Gas Chemical Co., Ltd. , SG-249, SG-241),
・ Carbon fiber mat (product number: S-210) manufactured by Osaka Gas Chemical Co., Ltd.
Etc.

[Method for producing precursor fiber]
The method for producing the precursor fiber is not particularly limited, but the following steps:
(i) Step 1 of spinning isotropic pitch (carbon precursor),
(ii) Step 2 of infusibilizing the spinning (pitch fiber) obtained in Step 1;
(iii) Step 3 of carbonizing the infusible fiber (infusible pitch fiber) obtained in Step 2;
It is preferable to produce the precursor fiber by a production method including: Hereinafter, each step will be described.

(Process 1 (spinning))
In step 1, isotropic pitch (carbon precursor) is spun. By this step 1, spinning (pitch fiber) is obtained.

  The isotropic pitch is the same as that described above for the isotropic pitch. A preferable isotropic pitch is also the same as that described above for the isotropic pitch, and a coal-based isotropic pitch is preferable. The softening point of the isotropic pitch is not particularly limited, and can be appropriately set depending on the spinning method.

  The spinning method is not particularly limited, and examples thereof include melt spinning. Specific melt spinning methods include vortex spinning, spunbond spinning, and centrifugal spinning. Moreover, the temperature at the time of melt spinning is not particularly limited as long as the isotropic pitch melts. Also, other spinning conditions such as the shape of the nozzle and the spinning speed are not particularly limited, and can be set as appropriate according to the intended use. Note that the vortex spinning is a method in which a hot gas jet stream is blown onto a molten pitch yarn discharged from a nozzle to efficiently draw. In this spinning method, irregularly curved spinning (pitch fibers) can be obtained.

  In the step 1, when the pitch fiber is obtained by melt spinning, the pitch fiber is not a continuous fiber, and for example, a short fiber having a length of several centimeters to several tens of centimeters and a certain width is obtained.

(Process 2 (infusibilization process))
In step 2, the spinning (pitch fiber) is infusibilized. By this step 2, an infusible fiber is obtained. Infusibilization treatment is generally heat curing by oxidative dehydrocyclization or condensation so that the fiber shape can be maintained by subsequent carbonization (carbonization) after giving the fiber shape to the carbon precursor. It refers to the processing to be sex. In this step, by performing the infusibilization treatment, oxygen is introduced into the pitch fiber and stabilized by cross-linking with oxygen.

  The method for infusibilization is not particularly limited. For example, hot air is applied to the pitch fibers.

  The atmosphere during the infusibilization treatment is an oxygen-containing atmosphere. As the introduction of oxygen, in addition to air, a gaseous oxidant such as nitrogen oxide or sulfur oxide may be used.

  The temperature during the infusibilization process is not particularly limited. For example, it can be heated to around the spinning temperature.

  Other conditions for the infusibilization treatment (for example, the rate of temperature rise, the retention time for the infusibilization treatment, etc.) are not particularly limited, and can be set as appropriate according to the intended use.

(Process 3 (carbonization treatment))
In step 3, the infusible fiber is carbonized. By this step 3, a precursor fiber is obtained. Carbonization treatment (carbonization treatment) refers to a treatment that releases elements other than carbon to produce a solid with a high carbon content.

  The temperature during the carbonization treatment is not particularly limited. For example, heat treatment is preferably performed at about 700 to 1000 ° C.

  The atmosphere during the carbonization treatment is preferably a non-oxidizing gas atmosphere, and more preferably a nitrogen gas atmosphere.

  Other carbonization treatment conditions (for example, the rate of temperature rise, the retention time of the carbonization treatment, etc.) are not particularly limited, and can be appropriately set according to the intended use.

(Other processes)
After the carbonization treatment, the precursor fiber is obtained. In general, the precursor fiber is often in the form of a mat. After the precursor fiber is obtained, if necessary, the precursor fiber may be subjected to preliminary graphitization treatment, cutting treatment, pulverization treatment, and the like. In the cutting process and the pulverizing process, the shape of the precursor fiber can be appropriately changed.

  In general, graphitization is a process in which non-graphitic carbon is converted into graphitic carbon having a three-dimensional regular structure of graphite by developing its laminated structure mainly by physical changes by heat treatment at about 1500 ° C or higher. Say. Here, the temperature during the preliminary graphitization treatment is preferably 1500 to 2400 ° C.

  The pulverization method is not particularly limited. For example, the precursor fiber can be pulverized using a jet mill, a hammer mill, a pin mill, or the like.

  The cutting method is not particularly limited. For example, the precursor fibers can be cut using a roving cutter, a guillotine cutter, a cross cutter, a low-speed shear type screen grinder, or the like.

[Heat treatment step for precursor fiber in the case of pitch-based carbon fiber (1a)]
The pitch-based carbon fiber production method (1a) can be suitably obtained by heat-treating the precursor fiber at 2800 to 3000 ° C. By heat-treating the precursor fiber at 2800 to 3000 ° C., the average fiber diameter of the precursor fiber as a raw material is reduced, and as a result, pitch-based carbon fibers having an average fiber diameter of 10 μm or less are obtained. The reason why the average fiber diameter is reduced is considered to be that the entire carbon fiber is thermally contracted due to the development of the graphite structure in the precursor fiber.

  The heating method in the heat treatment step is not particularly limited. For example, energization resistance heating, induction heating and the like can be mentioned. Examples of the energization resistance heating include a method using each heating furnace such as an Atchison furnace (Acheson-type graphitization furnace), an LWG furnace (direct energization graphitization furnace), a tubular resistance furnace, or the like. Examples of induction heating include methods such as susceptor heating of a graphite case by high-frequency induced current and direct heat generation of an object to be heated. The furnace used when performing heat treatment by energization resistance heating is not particularly limited, and a furnace having a specification capable of heat treating a carbon material can be used.

  The Atchison furnace is an indirect energization method using resistance heat generation of packing coke, and finally the object to be heated itself generates resistance heat. A rectangular furnace made of refractory bricks is filled with a product to be heat-treated (for example, precursor fibers, containers containing precursor fibers, etc.) with packing coke, and the outer periphery thereof is further insulated with a heat shielding lining. The packing coke packed around the product to be heat-treated is energized in the furnace length direction to increase the temperature. The LWG furnace is a direct energization type furnace that directly energizes the product to be heat-treated and heat-treats with its resistance heat. The packing coke around the heat-treated product serves as an antioxidant and a heat insulating material. The heat treatment is preferably a heat treatment using an Atchison furnace or an LWG furnace.

  There are no particular limitations on the method for placing the precursor fibers when performing the heat treatment step. For example, when heat treatment is performed using a heating furnace, (a) precursor fibers (mats, chops, milled fibers, etc.) may be placed directly in the heating furnace, and (b) precursor fibers are The container may be put (contained) in a container, then the container may be covered and sealed, and then the container may be placed in a heating furnace. Among them, in order to prevent a material to be packed in a heating furnace (for example, powder such as packing coke) from being mixed with the precursor fiber, the embodiment of (b), that is, a sealed container, It is preferable to place the container in which the precursor fiber is present in a heating furnace. In this case, the container is preferably made of graphite.

  The atmosphere of the precursor fiber in the heat treatment step is preferably a self-generated gas atmosphere or a hydrocarbon gas atmosphere, and more preferably a self-generated gas atmosphere. Here, the self-generated gas atmosphere is, for example, heat-treated in the mode (b) (that is, the precursor fiber is put in a container and sealed, and the container is heat-treated), whereby the inside of the container is precursor. It refers to an atmosphere filled with gas generated from body fibers, contains a large amount of hydrocarbon gas components, and contains trace amounts of oxygen. Since both the self-generated gas atmosphere and the hydrocarbon gas atmosphere have a large amount of hydrocarbon gas components, the precursor fibers are likely to shrink and the crystallinity of graphite is likely to increase. In particular, the self-generated gas atmosphere is a preferred embodiment because it causes shrinkage of the precursor fiber while removing the non-crystalline portion in the precursor fiber with the trace amount of oxygen and increases the crystallinity of graphite. In the case of performing the heat treatment in the mode (b), the atmosphere in the heating furnace is not particularly limited, but it is preferable not to flow an inert gas such as nitrogen gas or argon gas into the furnace.

  The pressure during the heat treatment step is not particularly limited. Moreover, the time of the heat treatment step is not particularly limited. For example, the heat treatment step is preferably held for 1 hour or longer, more preferably 5 hours or longer.

[Heat treatment step for precursor fiber in the case of pitch-based carbon fiber (1b)]
In the method for producing the pitch-based carbon fiber of (1b), in addition to the heat treatment step for the precursor fiber in the case of the pitch-based carbon fiber of (1a), the precursor fiber is 2800 to 3000 ° C. in an atmosphere containing boron. It has the heat processing process which heat-processes by.

  Further, in order to make the pitch-based carbon fiber of the present invention contain boron at 6 mass ppm or more, it is preferable to cover a graphite powder or the like around a graphite powder doped with a predetermined amount of boron. Specifically, the pitch-based carbon fiber of the present invention is 0.02 to 0.04 mass% or less (200 to 400 massppm) by surrounding (covering) the graphite container with graphite powder doped with about 1 mass% boron. ) Can be included. In order to further increase the boron content in the pitch-based carbon fiber of the present invention, the boron doping amount of the graphite powder covering the graphite container may be further increased. On the other hand, in order to reduce the boron content in the pitch-based carbon fiber of the present invention, a container such as a graphite container is placed in another container such as a graphite container, and the gap between the two containers is filled with graphite powder. That's fine. In order to further reduce the boron content in the pitch-based carbon fiber of the present invention, a container such as a graphite container is placed in another container such as a graphite container, and the gap between the two containers is filled with graphite powder. Furthermore, it is preferable to put in a container such as another graphite container and fill the gap with graphite powder. Thereby, it is possible to adjust the boron dope amount in the pitch-based carbon fiber of the present invention to a desired amount within a range of about 0.0006 to 0.1 mass% (6 to 1000 massppm).

≪2. Resin composition >>
The resin composition of the present invention contains the pitch-based carbon fiber (1a) or (1b) and a resin component.

  In the resin composition of the present invention, the content of the pitch-based carbon fiber (1a) or (1b) is not particularly limited, but is preferably 3 to 45% by mass with respect to the resin composition. When the content of the pitch-based carbon fiber (1a) or (1b) is within the above range, the fluidity of the composition is maintained, and a film suitable for stabilizing wear friction is formed on the surface of the counterpart material. It is expected that the effects of carbon fiber such as improvement of dynamic characteristics will be expressed.

  In particular, in a resin composition having tetrafluoroethylene resin (PTFE) as a main component, first, powdery PTFE and the pitch-based carbon fiber (1a) or (1b) are mixed with pitch-based carbon. The fiber content is preferably 50% by mass or less, particularly preferably 3 to 35% by mass. More preferably, it is 5-12 mass%. If the blending amount of the pitch-based carbon fiber is less than this, the effect due to the carbon fiber is hardly expressed, and if it is more than that, the fluidity is inhibited and it becomes difficult to obtain a homogeneous composition.

(2) Resin component The resin component is not particularly limited, and may be a synthetic resin, a natural resin, or the like. As the resin component, a synthetic resin is preferable. In addition, a resin component can be used 1 type or in combination of 2 or more types.

  The synthetic resin is not particularly limited and may be a thermosetting resin, a thermoplastic resin, or the like.

  As a thermosetting resin, a phenol resin, a furan resin, an epoxy resin etc. are mentioned, for example.

  Examples of thermoplastic resins include polyphenylene sulfide resin (PPS), polyimide resin (PI), polyamideimide resin (PAI), polyamide resin (PA), polyetheretherketone resin (PEEK), polysulfone resin (PSF), polyester Resin (eg, polyethylene terephthalate resin (PET), polybutylene terephthalate resin (PBT), etc.), polyolefin resin (eg, polyethylene resin (PE), polypropylene resin (PP), etc.), various vinyl polymers (polyvinyl chloride resin, Polyvinyl acetate resin, polyvinylidene chloride resin, polyvinyl alcohol resin, polyvinyl acetal resin, etc.), fluorine resin, acrylonitrile-butadiene-styrene resin (ABS), polystyrene resin (PS), acrylic resin, polyphenylene ether resin (PPE), Polycarbonate resin (PC), polyacetal resin (POM), and urethane resins.

  Examples of the fluororesin include PTFE (tetrafluoroethylene resin, polytetrafluoroethylene), FEP (tetrafluoroethylene / hexafluoropropylene copolymer, tetrafluoroethylene / hexafluoropropylene copolymer), and PFA. (Perfluoroalkoxy fluororesin, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer), PCTFE (polychlorotrifluoroethylene), ETFE (ethylene / tetrafluoroethylene copolymer), ECTFE (ethylene / chlorotrifluoroethylene) Copolymer), PVDF (polyvinylidene fluoride), THV (tetrafluoroethylene / hexafluoropropylene / vinylidene fluoride copolymer), PVF (polyvinyl fluoride, polyvinyl fluoride) and the like.

Among them, when using PTFE as the resin component of the resin composition, graphite crystalline (d ₀₀₂ such surface spacing, La, a crystallite size such Lc) is preferably used a carbon fiber to some extent developed.

That is, for example, graphite powder may be added to increase the lubricity in sliding members mainly composed of PTFE, but the addition of graphite powder is thought to tend to lower the mechanical strength of the sliding members. ing. Therefore, it is considered preferable to add carbon fibers having graphite crystallinity close to graphite powder. On the other hand, the anisotropic pitch-based carbon fiber has very high graphite crystallinity, but has high crystallinity and high elasticity and high strength. Such a carbon fiber is not preferable because it damages the counterpart material, and scrapes off the film formed on the surface of the counterpart material, resulting in poor sliding characteristics. Therefore, isotropic pitch-based carbon fiber for use in the present invention is a Raman spectrum obtained with the peak height I _D of the band of the Raman spectrum of 1320～1370Cm ^-1 resulting from side to side of the carbon fiber 1560～1610Cm ^- peak ¹ of the band which is the ratio of the height I _G I _D / I _G is a carbon fiber is 0.3 to 1.5. Since the G band is a peak due to graphite crystallinity, (I _D / I _G ) is not so large and is preferably 1.0 or less. The reason _why (I _D / I _G ) is 0.3 or more is considered to be that if the value is smaller than that, the orientation is high and the anisotropy becomes too high and the lubricating performance is impaired.

  The content of the resin component in the resin composition varies depending on the type and use of the synthetic resin, but is preferably 50% by mass or more based on the entire resin composition. For example, in the PTFE resin composition, the content of the resin component is 65 to 97% by weight, more preferably 88 to 95% by weight. When the content of the resin component is within the above range, it can be expected that the fluidity of the composition is maintained and good sliding characteristics and the like are obtained.

(3) Other Components The resin composition of the present invention may contain various additives in addition to the pitch-based carbon fiber (1a) or (1b) and the resin component (2). Examples of the additive include a lubricant, a reinforcing material, a filler, and a metal powder.

  Examples of the lubricant include artificial graphite, natural graphite, and molybdenum disulfide. When the lubricant is contained, the content is not particularly limited, but 1 to 30% by mass of the resin composition of the present invention is preferable.

  Examples of the reinforcing material include glass fiber and aramid fiber. When the reinforcing material is contained, the content is not particularly limited, but 1 to 30% by mass of the resin composition of the present invention is preferable.

  Examples of the filler include talc and glass beads. When the filler is contained, the content is not particularly limited, but 1 to 30% by mass of the resin composition of the present invention is preferable.

  Examples of the metal powder include copper powder, brass powder and bronze powder. When the metal powder is contained, the content is not particularly limited, but 1 to 10% by mass of the resin composition of the present invention is preferable.

Method for Producing Resin Composition The method for producing the resin composition of the present invention is not particularly limited as long as it contains the pitch-based carbon fiber (1a) or (1b) and the resin component (2).

  The method of mixing the pitch-based carbon fiber (1a) or (1b) and the resin component (2) (and the component when the other components are used) is not particularly limited, but is used. What is necessary is just to select the well-known method suitable for the kind of resin component. For example, for thermoplastic resins such as PPS, a method of kneading the respective components using a twin screw extruder while setting the cylinder temperature to the melting temperature of the resin component (2) can be mentioned. In this case, a pellet-shaped resin composition is obtained after kneading by a twin screw extruder. In addition, it does not specifically limit about the shape of the said pellet-shaped resin composition, a magnitude | size, etc.

  In addition, as a method of mixing the pitch-based carbon fiber of (1a) or (1b) and the resin component of (2) (and the component when the other components are used), the above components are mixed. The method of uniformly mixing using a sill mixer is mentioned, Furthermore, the method of preforming the said mixed resin composition, pressing suitably using normal temperature or a hot press machine is also mentioned. In this case, the preformed product can be used as a resin composition. The shape, size, etc. of the preformed resin composition are not particularly limited. Moreover, although it does not specifically limit about normal temperature or the temperature and pressure in a hot press machine, What is necessary is just to select the well-known method suitable for the kind of resin component to be used.

For example, in the production of a PTFE resin composition, it is preferable to perform uniform molding using a Hensyl mixer and pre-molding while pressing at a pressure of about 40 to 100 kg / cm ² using a room temperature press.

≪3. Molded product formed by molding resin composition >>
The molded article of the present invention has the following (1a) and (2):
(1a) pitch-based carbon fiber having an average fiber diameter of 10 μm or less using an isotropic pitch as a carbon precursor, and
(2) resin component,
A resin composition containing is molded.

Further, the molded article of the present invention in another aspect is the following (1b) and (2):
(1b) A pitch-based carbon fiber having an average fiber diameter of 10 μm or less with an isotropic pitch as a carbon precursor and containing 6 to 1000 massppm of boron
(2) resin component,
A resin composition containing is molded.

  The molded product of the present invention having the characteristics is expected to reduce wear on the counterpart material when sliding. In addition, the molded product of the present invention having the characteristics described above has a small (thin) average fiber diameter of the pitch-based carbon fiber of (1a) or (1b), so the pitch-based carbon fiber of (1a) or (1b) It is expected that the number of fillers per unit volume can be increased, resulting in excellent sliding characteristics and cost reduction.

  In addition, the molded product of the present invention having the above characteristics can reduce the dropping of the pitch-based carbon fiber of (1a) or (1b), and as a result, improves the production yield (reduces troubles caused by the molded product). ) Can be expected.

  Since the pitch-based carbon fiber of (1b) has high graphite crystallinity, a resin molded product obtained by using a tetrafluoroethylene resin as a main component as a resin component is used as a sliding material particularly excellent in lubricity. be able to.

  Specifically, the molded product (also referred to as a molded product or a molded product) of the present invention is subjected to heating, room temperature or hot pressing, injection molding, extrusion molding, or the like for the resin composition described in the above item 2. Can be obtained.

  Examples of the molded article of the present invention include sliding materials for automobiles, home appliances, various industrial equipment, O-rings, joint seals, bearings, bearing retainers, tubes, hoses, rods, sheets, and the like.

  Hereinafter, the present invention will be specifically described with reference to Examples, Comparative Examples, Production Examples, Comparative Production Examples and the like. However, the present invention is not limited to the embodiment (or production example).

Example A
Below, the Example (Example A) of the additive which consists of an isotropic pitch-type carbon fiber mat (mat fiber) of Examples 1-5 is described. First, a coal-based isotropic pitch (carbon precursor) is used as a starting material, and the isotropic pitch is spun (spun) by a vortex method. Next, an infusibilization treatment is performed on the pitch fiber obtained by the treatment in an air (atmosphere) atmosphere. Next, the infusible fiber (infusible pitch fiber) obtained by the above-described treatment is subjected to a heat treatment at 900 to 1000 ° C. in an inert gas atmosphere to perform a carbonization treatment. The spinning treatment, infusibilization treatment, and carbonization treatment are performed continuously.

  As a result, the isotropic pitch-based carbon fiber mat that is the raw material of Examples 1 and 2 is obtained. This technique is also shown in Reinforced Plastics (1998) Vol. 34, No. 3, p.89-93.

Example 1 (mat fiber)
Isotropic pitch-based carbon fiber mat (precursor fiber, trade name: S-210 (described in the DONACARBO (registered trademark) catalog), Osaka Gas Chemical Co., Ltd., average fiber diameter 13 μm) 5 graphite containers (A cylinder with an inner diameter of 150 mm and an inner height of 160 mm), and a graphite lid was placed on the container. The weight of the isotropic pitch-based carbon fiber mat put in one graphite container was 82 g. These five graphite containers were placed in a resistance heating furnace and heat-treated at a temperature and time of 2000 ° C. for 2 hours. Argon gas was allowed to flow into the resistance furnace. Of the mat after heat treatment at 2000 ° C., 306 g was placed in a graphite container (a cylinder with an inner diameter of 240 mm and an inner height of 310 mm), and a graphite lid was placed on the container. Next, the container containing the carbon fiber mat was placed in an Atchison furnace and heated to about 2900 ° C. (2800 to 3000 ° C.) (heat treatment). By this heat treatment, an additive (particularly an additive for resin) made of the pitch-based carbon fiber (isotropic pitch-based carbon fiber) of Example 1 was obtained.

  The heat treatment has a temperature atmosphere of 2800 to 3000 ° C. for at least 5 hours. During the heat treatment, the atmosphere made of the carbon fiber mat (self-generated gas) was generated in the graphite container. That is, the heat treatment was performed in a self-generated gas atmosphere.

  Chop fibers and milled fibers can be obtained by pulverizing the pitch-based carbon fibers (mat fibers) of Example 1 obtained by the heat treatment.

Example 2 (matte fiber)
Isotropic pitch-based carbon fiber mat (precursor fiber, trade name: S-210 (described in the DONACARBO (registered trademark) catalog), Osaka Gas Chemical Co., Ltd., average fiber diameter 13 μm) 125 g of graphite container ( It was a cylinder with an inner diameter of 160 mm and an inner height of 230 mm, and was placed in an internal volume of 4622 cm ³ ), and the above-mentioned container was covered with graphite. The graphite container was surrounded by graphite powder doped with about 1 mass% (10000 massppm) boron. Since boron easily diffuses at a high temperature, boron penetrates into the carbon fiber from the open pores and gaps of the graphite container containing the isotropic pitch-based carbon fiber mat by the heat treatment described later. Next, the container containing the carbon fiber mat was placed in an Atchison furnace and heated to about 2900 ° C. (2800 to 3000 ° C.) (heat treatment). By this heat treatment, an additive (particularly an additive for resin) made of the pitch-based carbon fiber (isotropic pitch-based carbon fiber) of Example 2 was obtained.

  The heat treatment has a temperature atmosphere of 2800 to 3000 ° C. for at least 5 hours. During the heat treatment, the atmosphere made of the carbon fiber mat (self-generated gas) was generated in the graphite container. That is, the heat treatment was performed in a self-generated gas atmosphere.

  In addition, the additive (especially for resin) made of chopped fiber or milled fiber is obtained by pulverizing the additive (particularly additive for resin) made of pitch-based carbon fiber (mat fiber) of Example 2 obtained by the heat treatment. Additive).

Example 3 (milled fiber)
An isotropic pitch-based carbon fiber mat (trade name: S-210 (described in the DONACARBO (registered trademark) catalog), Osaka Gas Chemical Co., Ltd., average fiber diameter: 13 μm) was prepared. Next, the carbon fiber mat was pulverized with a pulverizer to obtain milled carbon fibers (precursor fibers, average fiber length: about 0.11 mm (about 110 μm)) (hereinafter also referred to as milled fibers). 302 g of the milled fiber was placed in a graphite container (inner diameter: 50 mm, inner height: 90 mm cylinder, inner volume: 177 cm ³ ), and the container was covered with a graphite lid. The graphite container was surrounded by graphite powder doped with about 1 mass% (10000 massppm) boron. Since boron easily diffuses at a high temperature, boron penetrates into the carbon fiber from the open pores and gaps of the graphite container containing the isotropic pitch-based carbon fiber mat by the heat treatment described later. Next, the vessel containing the milled fiber was placed in an Atchison furnace and heated to about 2900 ° C. (2800 to 3000 ° C.) (heat treatment). By this heat treatment, an additive (particularly an additive for resin) made of the pitch-based carbon fiber (isotropic pitch-based carbon fiber) of Example 3 was obtained.

  The heat treatment has a temperature atmosphere of 2800 to 3000 ° C. for at least 5 hours. During the heat treatment, the atmosphere made of the carbon fiber mat (self-generated gas) was generated in the graphite container. That is, the heat treatment was performed in a self-generated gas atmosphere.

Example 4 (milled fiber)
In Example 3, the milled fiber was placed in the graphite container, and the graphite container was placed in another larger graphite container (inner diameter 160 mm, inner height 140 mm cylinder). The same treatment was performed except that the gap was filled with graphite powder. Thereby, compared with Example 3, the additive (especially additive for resin) which consists of pitch-type carbon fiber (isotropic pitch-type carbon fiber) which reduced the boron dope amount of pitch-type carbon fiber was obtained.

Example 5 (milled fiber)
In Example 4, the milled fiber was placed in the graphite container, and the graphite container was placed in another larger graphite container (inner diameter: 160 mm, inner height: 140 mm cylinder). Were filled with graphite powder, and these two containers were placed in another larger graphite container (a cylinder with an inner diameter of 240 mm and an inner height of 245 mm), and the gap between the containers was filled with graphite powder. The process was performed in the same manner except that. Thereby, compared with Example 3 and 4, the additive (especially additive for resin) which consists of pitch type carbon fiber (isotropic pitch type carbon fiber) which reduced the boron dope amount of pitch type carbon fiber is obtained. It was.

Comparative Example 1 (mat fiber)
Isotropic pitch-based carbon fiber mat (precursor fiber, trade name: S-210 (described in the DONACARBO (registered trademark) catalog), Osaka Gas Chemical Co., Ltd., average fiber diameter 13 μm) 82 g is graphite container ( The cylinder was covered with a graphite lid with an inner diameter of 150 mm and an inner height of 160 mm. The graphite container was placed in a resistance heating furnace, and heat treatment was performed at a temperature and time of 2400 ° C. for 2 hours. Argon gas was allowed to flow into the resistance furnace. Thereby, the additive (especially additive for resin) which consists of the pitch-type carbon fiber of the comparative example 1 was obtained.

Comparative Example 2 (milled fiber)
An isotropic pitch-based carbon fiber mat (trade name: S-210 (described in the DONACARBO (registered trademark) catalog), Osaka Gas Chemical Co., Ltd., average fiber diameter: 13 μm) was prepared. Next, the carbon fiber mat was pulverized with a pulverizer to obtain milled carbon fibers (precursor fibers, average fiber length: about 0.11 mm (about 110 μm)) (hereinafter also referred to as milled fibers). 302 g of the milled fiber was placed in a graphite container (inner diameter 50 mm, inner height 90 mm cylinder), and the container was covered with a graphite lid. The graphite container was placed in a resistance heating furnace, and heat treatment was performed at a temperature and time of 2400 ° C. for 2 hours. Argon gas was allowed to flow into the resistance furnace. This obtained the additive (especially resin additive) which consists of the pitch-type carbon fiber of the comparative example 2. FIG.

Comparative Example 3 (anisotropic pitch-based carbon fiber)
Simply, anisotropic pitch-based carbon fibers (average fiber diameter: 11 μm, average fiber length: 0.20 mm) were prepared.

<Analysis 1: Measurement of average fiber diameter>
The average fiber diameter of the additive (especially additive for resin) which consists of each pitch-type carbon fiber obtained by the Example and the comparative example was measured. Specifically, the measurement was performed by performing the following steps (i) to (iii).
(i) Each pitch-based carbon fiber obtained in Examples and Comparative Examples was magnified 1000 times using a Hirox magnifier and an image analyzer.
(ii) Next, 10 points of each pitch-based carbon fiber were arbitrarily selected, and the fiber diameters of the 10 points were measured.
(iii) Finally, by calculating the average value of the 10 fiber diameters obtained in (ii) above, the average fiber diameter of each pitch-based carbon fiber was determined.
The average fiber diameter of the additive (especially resin additive) consisting of each pitch-based carbon fiber measured is as follows:
-Average fiber diameter of pitch-based carbon fiber of Example 1: 5.9 μm
-Average fiber diameter of pitch-based carbon fiber of Example 2: 8.7 μm
-Average fiber diameter of pitch-based carbon fiber of Example 3: 8.7 μm
-Average fiber diameter of pitch-based carbon fiber of Example 4: 7.2 μm
-Average fiber diameter of pitch-based carbon fiber of Example 5: 8.5 μm
-Average fiber diameter of pitch-based carbon fiber of Comparative Example 1: 13.4 μm
-Average fiber diameter of pitch-based carbon fiber of Comparative Example 2: 13.2 μm
-Average fiber diameter of pitch-based carbon fiber of Comparative Example 3: 11 μm
Magnifying glass photograph of pitch-based carbon fiber of Example 1: FIG.
Magnifying glass photograph of pitch-based carbon fiber of Example 3: FIG.
Magnifying mirror photo of pitch-based carbon fiber of Comparative Example 2: FIG.
It is.

<Analysis 2: Measurement of boron doping amount>
The boron dope amount of an additive (particularly an additive for resin) made of each pitch-based carbon fiber obtained in Examples and Comparative Examples was measured. Specifically, the quantitative analysis of boron doped in the carbon fiber additive (especially resin additive) obtained in the examples and comparative examples is carried out by ashing about 50 samples and then dissolving the ash with acid. And ICP-AES (luminescence method).

The boron doping amount of the additive (particularly resin additive) made of each pitch-based carbon fiber was measured as follows:
-Boron doping amount of pitch-based carbon fiber of Example 1: None- Boron doping amount of pitch-based carbon fiber of Example 2: 300 massppm
-Boron doping amount of pitch-based carbon fiber of Example 3: 300 massppm
-Boron doping amount of pitch-based carbon fiber of Example 4: 40 massppm
-Boron doping amount of pitch-based carbon fiber of Example 5: 6 massppm
-Boron doping amount of pitch-based carbon fiber of Comparative Example 1: None-Boron doping amount of pitch-based carbon fiber of Comparative Example 2: None-Boron doping amount of pitch-based carbon fiber of Comparative Example 3: None

<Analysis 3: X-ray diffraction measurement>
By performing X-ray diffraction measurement on each pitch-based carbon fiber of Example 1, Example 3 and Comparative Example 2, X-ray diffraction of an additive (particularly an additive for resin) composed of each of the pitch-based carbon fibers. A figure was obtained (Figure 4). The above X-ray diffraction pattern uses Si as the standard substance, and the lattice constant and crystal size of carbon materials using the X-ray diffractometer established by the Japan Science and Technology Act (Japan Society for the Promotion of Science 117th round round robin test) This method was obtained in accordance with a method prescribed for general matters in the case of measurement. The central figure in FIG. 4 (FIG. 4A) is an X-ray diffraction pattern of an additive (particularly an additive for resin) made of pitch-based carbon fiber of Example 1, and the upper figure in FIG. 4 (FIG. 4). (b)) is an X-ray diffraction pattern of an additive (particularly an additive for resin) made of pitch-based carbon fiber of Example 3, and the lower figure of FIG. 4 (FIG. 4 (c)) is Comparative Example 2. 2 is an X-ray diffraction pattern of an additive (particularly an additive for resin) made of a pitch-based carbon fiber. Next, the lattice constant and crystal size (also referred to as crystallite size or crystallite size) of an additive (particularly an additive for resin) made of pitch-based carbon fiber of Example 2 were measured using Carbon Analyzer Version 4.10D. And analyzed. This technique is also shown in, for example, Hiroyuki Fujimoto, Carbon No. 206 (2003) p1-6.

  As shown in the figure of FIG. 4 (b), the 002 diffraction line peak was clearly recognized in the additive (particularly the additive for resin) made of the pitch-based carbon fiber of Example 3. Further, as shown in the lower figure of FIG. 4 (c), the additive made of pitch-based carbon fiber of Comparative Example 2 (particularly, the additive for resin) does not clearly show the peak of the 002 diffraction line. Only broad diffraction lines were observed.

  The analysis results of the additive (particularly resin additive) made of the pitch-based carbon fiber of Example 1 are shown below.

The d ₀₀₂ (plane spacing of the 002 plane) obtained from the 004 diffraction line in the additive (particularly an additive for resin) made of the pitch-based carbon fiber of Example 1 was 0.3386 nm (= 3.386 mm). The crystallite size Lc in the c-axis direction obtained from the 002 diffraction line was 14 nm, and the crystallite size Lc in the c-axis direction obtained from the 004 diffraction line was 10 nm or less. The crystallite size La in the a-axis direction was 10 nm or less.

D ₀₀₂ obtained from the 004 diffraction line in the additive (particularly an additive for resin) made of the pitch-based carbon fiber of Comparative Example 2 was 0.3424 nm (= 3.424 mm). The crystallite size Lc in the c-axis direction obtained from the 002 diffraction line and the 004 diffraction line was both estimated to be 10 nm or less. The crystallite size La in the a-axis direction was also estimated to be 10 nm or less.

  The additive (especially an additive for resin) made of pitch-based carbon fiber of Example 1 is heat-treated at a high temperature of 2800 to 3000 ° C., so the interplanar spacing is small, the graphite crystal structure is developed, and the crystallinity is It was recognized that it was high. However, it was observed that the crystallites were not well developed.

  Moreover, the X-ray-diffraction measurement was similarly performed in Examples 4-5. The analysis results of additives (particularly additives for resins) made of pitch-based carbon fibers of Examples 3 to 5 are shown below.

D ₀₀₂ (plane spacing of the 002 plane) obtained from the 004 diffraction line was Example 3: 0.3355 nm (= 3.355 mm), and Examples 4 and 5: 0.3356 nm (= 3.356 mm).

  The crystallite size Lc in the c-axis direction obtained from the 002 diffraction line was Example 3: 69 nm, Example 4: 100 nm or more, and Example 5: 92 nm.

  The crystallite size Lc in the c-axis direction obtained from the 004 diffraction line was 100 nm or more in all of Examples 3 to 5.

  The crystallite size La in the a-axis direction was 100 nm or more in all of Examples 3 to 5.

L ₁₁₂ obtained from 112 diffraction lines was Example 3: 15 nm, Example 4: 22 nm, and Example 5: 11 nm. This value indicates a three-dimensional regularity.

From the analysis results of the additive (particularly resin additive) comprising the pitch-based carbon fibers of Examples 3 to 5, the additive (particularly resin additive) comprising the pitch-based carbon fibers of Examples 3 to 5 is graphite. It was found that the crystal structure was developed. In particular, the value of d ₀₀₂ (.3355 and 0.3356 nm) was close to the value (0.3354 nm) of d ₀₀₂ in the single crystal of graphite. It was also observed that crystallites were developed.

  The analysis results of the pitch-based carbon fiber of Comparative Example 2 are shown below.

D ₀₀₂ obtained from the 004 diffraction line was 0.3424 nm (= 3.424 mm). The crystallite size Lc in the c-axis direction obtained from the 002 diffraction line and the 004 diffraction line was both estimated to be 10 nm or less. The crystallite size La in the a-axis direction was also estimated to be 10 nm or less. It is recognized that the graphite crystal structure is not developed.

<Analysis 4: Measurement of I _D / I _G in Raman spectrum >
Example 1 (fiber side face), Example 3 and Comparative Examples 2 and 3, each additive comprising the pitch-based carbon fiber (especially an additive for resin) is subjected to Raman spectroscopic measurement, and Raman spectrum (Raman scattering). Spectrum) was obtained (FIG. 5). For Raman spectroscopic measurement, a Raman spectrometer (Raman DXR microscope) manufactured by Thermo Fisher Scientific Co., Ltd. was used. The conditions were laser light output: 2 mW and laser light wavelength: 532 nm. Further, the laser beam was narrowed down with an aperture of 25 μm slit, and measurement was performed using an objective lens having a magnification of 50 times. Raman spectra, band peak height of around 1360 cm ^-1 called the D band and the peak height I _D band (1320~1370cm ^-1), 1580cm ^-1 around (1560~1610cm ^-1) called G band The ratio to I _G (ie, I _D / I _G ) was determined. As for the above I _D / I _G , (i) I _D / I _G from the side surface of the carbon fiber was determined.

Here, I _G is the intensity of the relatively sharp G band associated with the complete graphite structure, and I _D is the intensity of the broad D band corresponding to the increased disturbance of the structure. In other words, I _D / I _G is a value that represents the ratio of the edges and grain boundaries of the graphite crystal, and the larger the I _D / I _G value, the more edges, and the graphite structure is disturbed. . Each _ID / _IG value in the additive (especially additive for resin) which consists of the pitch-type carbon fiber of Examples 1-5 and Comparative Examples 1-3 is as follows:
-I _D / I _G value of the additive (particularly resin additive) comprising the pitch-based carbon fiber of Example 1: 0.45
-I _D / I _G value of additive (especially resin additive) comprising the pitch-based carbon fiber of Example 2: 0.53
I _D / I _G value, a third embodiment of the pitch-based additives consisting of carbon fiber (particularly a resin additive) 0.40
-I _D / I _G value of additive (especially resin additive) comprising the pitch-based carbon fiber of Example 4: 0.42
-I _D / I _G value of additive (especially resin additive) comprising the pitch-based carbon fiber of Example 5: 0.43
-I _D / I _G value of an additive (particularly an additive for resin) comprising the pitch-based carbon fiber of Comparative Example 1: 1.15
-I _D / I _G value of an additive (particularly an additive for resin) comprising the pitch-based carbon fiber of Comparative Example 2: 1.15
I _D / I _G value of Comparative Example 3 of the pitch-based additive consisting of carbon fiber (particularly a resin additive): 0.11
-(Reference) I _D / I _{G of} natural graphite (basal surface side of scaly graphite): 0.1 or less.

The additive (especially additive for resin) which consists of the pitch-type carbon fiber of Examples 1-5 is a crystal surface more than the additive (especially additive for resin) which consists of the pitch-type carbon fiber of Comparative Examples 1-2. There are few edges and defects. Therefore, it was also found in Analysis 3 that the additives (particularly additives for resin) composed of the pitch-based carbon fibers of Examples 1 to 5 have a more developed graphite structure. However, the I _D / I _G values of the additives (particularly additives for resins) made of the pitch-based carbon fibers of Examples 1 to 5 are 0.40 to 0.53, which is a large value compared to natural graphite. That is, it can be considered that there are many edges and crystal defects for the crystallite sizes La and Lc showing large values. In summary, the additives (particularly additives for resin) made of the pitch-based carbon fibers of Examples 1 to 5 are the following (a) and (b):
(a) three-dimensional regularity of graphite;
(b) optical isotropy (i.e., the property that molecules or groups of molecules are randomly oriented);
It can be said that it has both.

Further, the additive (particularly an additive for resin) made of pitch-based carbon fiber of Comparative Example 3 has high graphite crystallinity, and the I _D / I _G value obtained from the side surface of the carbon fiber is as low as (0.11). It was. Moreover, the additive (especially additive for resin) which consists of the pitch-type carbon fiber of the comparative example 3 is characterized by the crystallite being highly oriented.

<Analysis 5: Apparent density measurement>
Apparent density measurement was performed on the additives (particularly additives for resin) made of the pitch-based carbon fibers of Examples 1 and 2 and Comparative Example 1. Specifically, the apparent density of the additive (especially an additive for resin) made of each pitch-based carbon fiber was measured by a gas substitution method. As a measuring apparatus, a dry automatic densimeter Accupic 1330-03 manufactured by Micromeritics was used. The gas used for the measurement was helium gas, and the temperature was 25 ° C.

The apparent density is a value obtained by dividing the mass of the sample by the volume obtained by removing the open pores (pores) from the external volume of the sample. In this case, the open pores (pores) are considered to be pores (pores) through which helium gas penetrates. The measurement results are as follows:
-Apparent density of the pitch-based carbon fiber of Example 1: 1.55 g / cm ³
-Apparent density of the pitch-based carbon fiber of Example 2: 1.71 g / cm ³
-Apparent density of the pitch-based carbon fiber of Comparative Example 1: 1.62 g / cm ³
Shown in

<Analysis 6: Consideration of sliding characteristics of PTFE molded article>
The sliding characteristics of the PTFE molded body will be considered as follows.

  9% by mass of a tetrafluoroethylene resin (polyflon produced by Daikin Industries, Ltd.) and 10% by mass of milled fiber of anisotropic pitch-based carbon fiber of Comparative Example 3 were prepared.

  Next, the tetrafluoroethylene resin and the milled fiber were mixed with a Hensyl mixer (rotation speed 1200 rpm, 2 minutes). This obtained the resin composition.

Next, this resin composition was preformed by pressing at room temperature to obtain a flat plate having a length of 125 mm × width of 125 mm × thickness of 3 mm. This flat plate was further heated at a temperature of about 350 ° C. to obtain a molded product. The density of the molded product was 2.2 g / cm ³ .

  Each of the molded products was cut into a length of 30 mm, a width of 30 mm, and a thickness of 3 mm to obtain a sliding test specimen. Next, a sliding test was performed on the test piece in accordance with the JIS K7218A method using a friction wear tester MODEL EMF-III-F manufactured by A & D Co., Ltd. Specifically, the limit PV value was measured. The point at which the wear amount suddenly increased was defined as the limit PV value.

The test environment, test conditions, and measurement results are as follows:
・ Test environment: 23 ℃ ± 2 ℃, 50% RH ± 5% RH
・ Test conditions: Speed 1m / s, initial load 50N, load step 50N / min
It is.

  The limit PV value of this PTFE molded product was 1000 kPa · m / s.

  From this fact, the limit PV value in the same test becomes 2000 to 4000 kPa · m / s or more by using the additive (especially resin additive) made of the pitch-based carbon fiber of the present invention. There is expected.

1 Atchison furnace 2 Packing coke 3 Processed material 4 Heat insulation layer (powder)
5 Brick 6 Water-cooled jacket 7 Busbar (copper)
8 Graphite electrode

Claims (11)

The following (1a):
(1a) An additive comprising pitch-based carbon fibers having an isotropic pitch as a carbon precursor and an average fiber diameter of 10 μm or less. The pitch-based peak height of a band of Raman spectrum of 1560～1610Cm ^-1 obtained peak band of the Raman spectrum of 1320～1370Cm ^-1 obtained from the side of the carbon fiber and the height I _D from the side surface of the carbon fiber I is the ratio of _G I _D / I _G is 0.3 to 1.5, the additive of claim 1. The following (1b):
(1b) An additive comprising pitch-based carbon fibers having an isotropic pitch as a carbon precursor and an average fiber diameter of 10 μm or less and containing 6 to 1000 massppm of boron. The crystallite size La in the a-axis direction of the graphite crystal obtained from the X-ray diffraction method of the pitch-based carbon fiber is 100 nm or more, and
The crystallite size Lc in the c-axis direction of the graphite crystal obtained from the (004) diffraction line of the pitch-based carbon fiber X-ray diffraction method is 100 nm or more.
The additive according to claim 3. A peak height I _D of the band of the pitch-based Raman spectra of 1320～1370Cm ^-1 obtained from the side of the carbon fiber, the peak of the band 1560～1610Cm ^-1 of a Raman spectrum obtained from the side of the pitch-based carbon fibers it is the ratio of the height I _G I _D / I _G is from 0.3 to 1.0, the additive according to claim 3 or 4. The additive according to any one of claims 1 to 5, which is an additive for resin. The additive according to claim 5, wherein the resin is a tetrafluoroethylene resin. The resin composition containing the additive in any one of Claims 1-5, and a resin component. The resin composition according to claim 8, wherein the resin component is a tetrafluoroethylene resin. The resin composition according to claim 8 or 9, wherein the content of the resin component is 50% by mass or more of the entire resin composition. The molded product formed by shape | molding the resin composition in any one of Claims 8-10.