JPH0714805B2 - Improved graphite powder, dry battery and sliding member containing the improved graphite powder - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improved graphite powder, a dry battery and a sliding member, more specifically, a conductive material for a dry battery, a sliding member,
Graphite powder having a large specific surface area, excellent shapeability, high liquid retention rate and excellent lubricity, and a dry battery and a sliding member containing the graphite powder, which are used as a raw material for producing a pencil lead or a raw material for producing silicon carbide. It is related to.

(Prior Art) Graphite powder has various aspects such as specific surface area, electric resistivity, and crystallite size, and has various uses depending on its properties.

For example, in recent years, the production of non-aqueous electrolyte batteries, that is, so-called dry batteries, has shown remarkable growth, and in these dry batteries, that is, manganese dry batteries, alkaline manganese dry batteries, silver oxide dry batteries, lithium dry batteries, etc., cylindrical, disc-shaped, or sheet-shaped products The positive electrode mixture in the shape of a sheet plays an extremely important role, and manganese dioxide, silver oxide, silver chloride, etc. are used as active materials in the positive electrode mixture depending on the type of battery, and they control electron conduction. As a conductive material, carbonaceous powder is used in most dry batteries.

However, while these various dry batteries are excellent in continuous discharge performance, high load discharge performance, storability, etc., they are required to be easily manufactured from stable and easily available raw materials. Above all, the conductive material (1) Good shapeability,
(2) Large specific surface area, (3) Desired particle size, (4) Good adhesion to active material, (5) Rich reactivity with electrolyte, (6) Characteristics such as low impurities and (7) high performance of holding a large amount of electrolyte are required.

Specifically, as a conductive material, acetylene black, which has an excellent electrolyte retention rate, is mainly used for manganese dry batteries, and it is easy to be shaped into a cylinder or a disk for alkaline manganese dry batteries, lithium dry batteries, etc. Natural flake graphite powder, which is easy to retain, has been mainly used.

Graphite is a composite material using a metal such as a copper-based iron-based material, amorphous carbon, or various resins as a binder, and is used as a bearing material, a sealing material, a gasket material, a brush material, a panda graph sanding material, or a trolley. It is used for mechanical and electrical sliding members such as wheels. The characteristics of graphite required for these sliding members include lubricity, wear resistance, mechanical strength,
It has a small coefficient of thermal expansion and chemical stability, and lubricity is especially important. However, artificial graphite powders that have been mainly used conventionally have a large friction coefficient, which is an index of lubricity, and therefore, for example, if the content of graphite powder is increased to improve the strength, the lubricity decreases. is doing.

Graphite is also used as a filling material for various plastics such as phenol, epoxy, and tetrafluoroethylene to improve the load resistance and wear resistance of plastics. However, when using conventional artificial graphite powder,
There are problems such as a large decrease in tensile strength and elongation.

Further, as the graphite powder for pencil lead raw material, natural flaky graphite powder is used for most of them because lubricity is particularly required at the time of writing, and the graphite powder used in the production of silicon carbide is more active in the reaction. Therefore, a powder having an extremely large surface area per unit weight is used.

(Problems to be Solved by the Invention) As described above, acetylene black, natural scaly graphite, and artificial graphite can be mentioned as carbonaceous substances used in various applications, but all have sufficient properties required for each application. It doesn't reach the point of satisfying.

For example, regarding the physical properties of acetylene black, JIS K-1
The first feature is that it has a large amount of hydrochloric acid absorption that shows the electrolyte retention performance, but its shapeability is inferior to that of any other conductive material. Also, natural graphite powder is excellent in shapeability because the graphite crystals are more developed and flat, but it is hard to say that it can always be obtained inexpensively and stably because it depends on imports. Further, in the case of aiming at a high performance dry battery, it is difficult to remove impurities existing between graphite crystal layers.

On the other hand, artificial carbonaceous powders are easily available as powders of stable quality, and the most distinctive feature is that impurities contained can be kept extremely low and powders of the desired particle size range can be easily obtained, but lubrication is possible. There was a problem in the properties, the amount of absorbed hydrochloric acid, the shapeability, and the like.

As a result of an in-depth study to solve the above problems, the inventors of the present invention, graphite, by using a roll mill or the like, by crushing mainly with a shearing force parallel to the carbon mesh plane of the crystallite,
The surface area per unit weight (hereinafter referred to as "specific surface area") is dramatically increased, and the shapeability and pressure-resisting force after shaping (referred to as pseudo-collective force)
Further, they have found that the liquid retention rate increases, the lubricity improves, the electrical resistance decreases, and the physical properties are changed.

That is, the object of the present invention is a graphite powder and a continuous discharge performance exhibiting properties equal to or higher than those of natural flake graphite in terms of electric resistance, specific surface area, shapeability, pseudo-collection force, liquid retention rate, lubricity, etc. ,
An industrial advantage is to provide a dry battery excellent in high-load discharge performance, storage stability, and the like, and a sliding member excellent in lubricity and antifriction.

(Means for Solving the Problem) The object of the present invention is, however, to improve graphite powder and artificial graphite powder obtained by pulverizing artificial graphite powder by a roll mill mainly by shearing force parallel to the carbon mesh plane of the graphite. It is easily achieved by a dry battery containing a powder as a conductive material, and a sliding member containing the improved graphite powder.

(Operation) Hereinafter, the present invention will be described in detail.

The improved graphite powder of the present invention is characterized in that it is produced by crushing graphite mainly while applying a shearing force parallel to a carbon mesh plane of a crystallite of the graphite, and the dry battery and sliding member of the present invention are It is characterized by containing the improved graphite powder produced as described above as a conductive material or a lubricant.

Graphite is a plate-shaped crystal in which microcrystals formed by stacking carbon net planes are aligned in the same direction, and the plate surface of the plate-shaped crystal and the direction of the carbon net plane coincide with each other.

Therefore, for example, when graphite is crushed using a roll mill, the graphite is necessarily wound into the gap between the rolls so that the plane of the carbon mesh coincides with the tangent plane of the peripheral surface of the roll, and at this time, even if there is a slight gap between the rolls. If there is a difference in speed, a strong shear force parallel to the plane of the carbon mesh will be applied.

Such a crushing method in which a strong shearing force parallel to the plane of the carbon mesh is applied, and the crushing is performed mainly by the contribution of the shearing force, other than the ball mill, especially a vibrating ball mill, a stamp mill,
A disk vibration mill is more preferable, and a rod mill is more preferable, and an Ong mill is a device that pulverizes only by shearing force in principle, but it is also very preferable, but in consideration of ease of operation, productivity, etc. In this case, a roll mill is most preferable as the crushing device used in the present invention.

In the case of pulverizing with a roll mill, the greater the difference in peripheral speed between the two rolls for pulverizing graphite, the greater the shearing force. As a result, the specific surface area of the resulting improved graphite powder is large and the electrical resistance is small. It is suitable that the ratio of the peripheral speed of the rolls of the book is 1: 1.2 or more, more preferably 1: 2 or more, and most preferably 1: 3 or more. However, since graphite is not always wound into a roll at an angle such that the tangential plane of the roll peripheral surface and the carbon mesh plane completely coincide with each other, even if there is no difference in the peripheral speed of the two rolls, the carbon mesh A strong shearing force parallel to the plane is applied, and in this case, the contribution to the crushing is greater than the pressure of the roll, and the shearing force has a significant effect in improving various properties such as specific surface area and electric resistance.

Whatever the carbonaceous powder is used, it is preferable that there are few impurities mixed. In the case of a dry battery, the presence of impurities causes polarization and self-discharge, resulting in a shorter battery life. Further, in the case of a pencil lead material, especially when a metal is mixed, the lubricity is impaired, and in the case of silicon carbide production, the production of silicon carbide is hindered. Cu, N especially for dry batteries
Heavy metals such as i, Co, Fe, Sb, As, Mo and V pose a problem.
The following table shows an example of the analysis results of various carbonaceous powders.

As the graphite powder used as the raw material of the present invention, artificial graphite is used for the above reason.

Further, the crushing device used in the present invention is preferably devised to avoid mixing of metal into graphite, and a normal steel roll may be used. In the case of graphite powder for pencil lead raw material, it is not preferable that a metal is mixed, so a chromium-plated steel roll, more preferably a stainless steel roll, further preferably a chilled layer is provided on the surface by quenching. Steel rolls, most preferably ceramic rolls, are preferably used to prevent metal contamination.

Shaped property, liquid retention, considering improved lubricity, the improved graphite powder produced by the present invention has a specific surface area of 50 m ² / g or more, more preferably 80 m ² / g or more, liquid retention of 15 ml / 5 g or more, and more preferably. Is 18 ml / 5 g or more, the friction coefficient (the polynomial formula) as an index showing lubricity is 0.24 or less, preferably 0.22 or less, and the crystallite size Lc which is one index of the graphite crystal is 1200 Å or less and more preferably 800 Å It is necessary to manufacture as follows.

Furthermore, in the case of the present invention, it is also possible to add one or more kinds of a dry type, an extremely small amount of a dispersant or a surfactant, etc., which is added to graphite at all, or a wet method. is there. By adding a dispersant together with graphite as a raw material, a new fracture surface is generated, and at the same time, the dispersant or the like can be fixed on the surface of graphite by a mechanochemical phenomenon to improve the wettability, which is extremely convenient.

It is not clear why the specific surface area increases dramatically when a shearing force is applied parallel to the carbon mesh plane of graphite, the liquid retention rate increases, Lc decreases, and lubricity improves. However, as the crushing time became longer, the overall blackness in X-ray diffraction gradually increased, but the diffraction lines did not spread significantly and appeared sharply, so the size of each crystallite did not decrease. It is understood that amorphization occurs due to three-dimensional miniaturization.

More specifically, when a shearing force parallel to the plane of the carbon net is applied, the crystallites of carbon open the wall along the plane of the net and at the same time strain occurs in the crystal, so that the lattice constant Co of the crystal becomes slightly large. It was confirmed by X-ray diffraction that the crystallite size Lc decreased. Therefore, the true specific gravity decreases and the particle size decreases, resulting in a large increase in the specific surface area and the liquid retention rate. However, it is considered that the lubricity is improved because the size of each crystallite is not reduced.

Using the improved graphite powder of the present invention as a conductive material, various dry batteries can be obtained by a conventional method. Namely manganese batteries,
Alkali-manganese dry batteries, silver oxide dry batteries, lithium dry batteries and the like can obtain various improvements in performance described below.

First, when the improved graphite powder of the present invention is used as a conductive material for a positive electrode mixture of a dry battery, for example, when 1/2 of acetylene black is replaced, according to JIS K-1469, the electrical resistivity is 0.26Ω.
・ It can be reduced from cm to 0.08Ω ・ cm, and the conductivity can be greatly improved. Further, since the improved graphite powder of the present invention has a high specific surface area, an electrolytic solution holding capacity comparable to that of acetylene black can be obtained, and since the packing density is large, the volume ratio of the conductive material is 80 or less when the conventional is 100. Can
It is possible to significantly increase the filling amount of the positive electrode active material.

In addition, in this type of battery, during high temperature storage, the water in the positive electrode mixture evaporates, albeit little by little, causing the upper part of the molded positive electrode mixture to shrink, creating a gap between the mixture and the separator, and causing a discharge reaction. Although the area may be reduced, the generation can be reduced by using the improved graphite powder of the present invention.

Furthermore, the improved graphite powder of the present invention can be used to prepare a composite material with non-carbonaceous carbons, resins or metals by a conventional method to prepare a sliding member for machinery or electricity. The sliding members for machines include bearing materials, sealing materials, vanes, gaskets as fixed sealing materials, and the like, while the sliding members for electric use include brush materials, plates for pantographs, trolley wheels, and the like. The sliding member of the present invention has sufficiently improved properties such as lubrication, mold release, wear and friction. For example, 10 to 40% of the improved graphite powder of the present invention is added to a copper-based and iron-based sintered material. It can also be used as a seal material or sliding bearing in places where oil cannot be supplied. The improved graphite powder is also very useful as a raw material for a carbon member for a fuel cell and a carbon raw material for a release agent.

(Examples) Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded.

Example 1 The electrical resistivity of the improved graphite powders A and B and other samples obtained by pulverizing a highly graphitized coal-based artificial graphite powder in a roll mill 10 times or 5 times, respectively, is shown in Table 1. The electric resistance of the improved graphite powder A, acetylene black, and a carbonaceous powder obtained by mixing the both were measured, and the results shown in Table 2 were obtained. The electrical resistivity was measured according to the JIS K-1469 test method.

As shown in Tables 1 and 2, the improved graphite powder produced by the present invention has an extremely low electric resistivity required for a conductive material, and is effective not only when used alone but also when used in a mixture with acetylene black. .

Example 2 Various physical properties of graphite powder and other carbonaceous powders obtained by pulverizing a highly graphitized coal-based artificial graphite powder in a roll mill for 0 to 10 times were obtained, and the results shown in Table 3 were obtained. .

In the case of this embodiment, a strong type three-roll mill was used.

The roll mill used in Examples 1 and 2 had a diameter of 16
Strong type 3 with 3 inch chilled casting rolls
In this roll mill, the number of rotations of each roll is 100 times /
Minute (peripheral speed 127m / min), 300 times / minute, 900 times / minute.

Example 3 The same carbonaceous powder used in Example 2 was filled in a cylindrical container having a diameter of d20 mm and a height of 200 mm, a load of 3 ton was applied from the top, the load was removed, and a disk-shaped molded product was obtained. Took out. At this time, the thickness H of the carbonaceous powder when a load was applied and the thickness l of the carbonaceous powder after removing the load were measured.

Subsequently, a force was applied vertically to the molded disc from the side, the force P required to break the disc was measured, and 2P / πdl was calculated as an index of the pseudo-aggregation force. In addition, the specific gravity of the disk was also measured. The results are shown in Table 4.

Example 4 As an electric sliding member, graphite powder obtained by grinding the artificial graphite powder used in Example 1 over a roll mill 15 times, or 80 parts of conventional artificial graphite powder and 20 parts of phenol resin were blended. The physical properties of the product produced by molding and heat treatment at 1000 ° C. were measured, and the results shown in Table 5 were obtained.

As shown in Table 5, when the improved graphite powder produced according to the present invention is used, the bulk specific gravity and bending strength are improved, the specific resistivity is significantly reduced, and the electric sliding member is improved as compared with the conventional artificial graphite powder. Shows extremely good physical properties.

Example 5 As a sliding member for machinery, a product prepared by blending the same improved graphite powder as that used in Example 4 in a tetrafluoroethylene resin (PTFE) at different content ratios was manufactured, and its physical properties were measured, The results shown in Table 6 were obtained.

As shown in Table 6, when the improved graphite powder is used, tensile strength, elongation, compressive strength, friction coefficient, wear rate and all other physical properties are improved, and it shows good properties as a sliding member for machinery. ing.

(Effects of the Invention) According to the present invention, the properties of the graphite powder can be improved very easily, and the improved graphite powder obtained has a large specific surface area, liquid retention rate and pseudo-collection power, and has good shapeability and lubricity. It is excellent in electrical resistance and has a small friction coefficient, and can be suitably used for applications such as conductive materials for dry batteries, sliding members, pencil leads, and production of silicon carbide. Further, if artificial graphite is used as a raw material, impurities, particularly impurities of metals are very small and graphite showing performance equal to or higher than natural flake graphite can be easily and stably produced,
The dry battery of the present invention containing such improved graphite powder exhibits excellent characteristics such as easy manufacture and long life, and the sliding member of the present invention also has excellent lubricity, releasability, wear resistance, abrasion resistance, etc. The characteristics are sufficiently improved, and both provide a great industrial benefit.

Continuation of the front page (56) References JP-A-3-50110 (JP, A) JP-A-2-167808 (JP, A) JP-B-37-10977 (JP, B1)

Claims (3)

[Claims] 1. A specific surface area obtained by crushing artificial graphite powder with a roll mill is 50 m ² / g or more, and a liquid retention rate is 15 ml / 5 g or more,
Friction coefficient is 0.24 or less and graphite crystallite size Lc is 1200
Å Improved graphite powder with the following characteristics. 2. The artificial graphite powder is pulverized by a roll mill to have a specific surface area of 50 m ² / g or more and a liquid retention rate of 15 ml / 5 g or more,
Friction coefficient is 0.24 or less and graphite crystallite size Lc is 1200
Å Dry battery containing improved graphite powder with the following characteristics as a conductive material. 3. The artificial graphite powder is pulverized by a roll mill to have a specific surface area of 50 m ² / g or more and a liquid retention rate of 15 ml / 5 g or more,
Friction coefficient is 0.24 or less and graphite crystallite size Lc is 1200
Å A sliding member containing improved graphite powder with the following characteristics.