JPH11172146A - Conductive carbon black - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject carbon black capable of inparting a high electroconductivity to a resin when the carbon black is kneaded with the resin while keeping the sufficient processability and useful fur a hose for a solvent such as gasoline by carrying out a heat treatment of a specific furnace black in an inert gas atmosphere. SOLUTION: This carbon black is obtained by carrying out a heat treatment of a furnace black having <=20 mg/g total oxygen content before the heat treatment in an inert gas atmosphere so as to reduce 5-50%, preferably 5-30% of the total oxygen content. For example, the heat treatment is carried out in the presence of argon or the like at 200-700 deg.C for about 15 min-10 hr, and the carbon black having about 30 500 m<2> /g specific surface area, about 40-360 mL/100g DBP absorption and about 0.01-0.5% ash content is preferably used as the carbon black.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a conductive carbon black. Since the conductive carbon black of the present invention has excellent conductivity, it can be used for various applications. Specific applications include hoses for solvents such as gasoline, various connectors, door handle parts, etc., especially for these applications, suitable for imparting conductivity without loss of processability by mixing with resin. Used for

[0002]

2. Description of the Related Art Resins such as polycarbonate, polyethylene terephthalate, and nylon are generally insulative, but may be required to have conductivity depending on applications. In order to impart conductivity to these insulating resins, generally, conductive carbon black is frequently used. That is, acetylene black, Ketjen black, or the like is mainly used as such carbon black, and has advantages such as light weight and low cost as compared with metal.

[0003]

However, in a system in which these carbon blacks are blended, for example, when carbon black is blended in a polyamide resin or the like, if the blending amount of carbon black is increased to improve conductivity, Not only does the melt viscosity increase, making molding by injection molding or the like difficult, but even if molding is possible, only molded products with poor mechanical properties such as impact strength can be obtained.

[0004] More generally, when a large amount is blended in order to obtain high conductivity, 1) the viscosity becomes too high and the workability is remarkably reduced. 2) Due to the strong surface activity of carbon black, the crosslinking agent does not work effectively. 3) Even if an attempt is made to obtain higher conductivity, there may be a case where there is a physical upper limit in the compounding amount of carbon black and the obtained volume resistivity is limited.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and have found that furnace black having a total oxygen content of not more than a predetermined amount before heat treatment is heated in an inert atmosphere. 5-50% of total oxygen content by processing
The present inventors have found that reduced carbon black can impart high conductivity while maintaining sufficient workability when kneaded with a resin, and have reached the present invention. That is, the present invention is characterized in that furnace black having a total oxygen content of 20 mg / g or less before heat treatment is subjected to heat treatment in an inert atmosphere to reduce the total oxygen content by 5 to 50%. Conductive carbon black.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The conductive carbon black of the present invention has a total oxygen content of 5 to 50%, preferably 5 to 30%, obtained by subjecting furnace black having a total oxygen content of 20 mg / g or less before heat treatment to heat treatment in an inert atmosphere. % Carbon black.

Here, the inert atmosphere refers to an atmosphere in which oxygen molecules do not exist or have an extremely low composition ratio even when oxygen molecules exist. Specifically, an atmosphere composed of argon, nitrogen, carbon dioxide or the like is used. Point. Further, the heat treatment temperature is preferably from 200 ° C. to 700 ° C. At 200 ° C. or lower, oxygen functional groups are not easily desorbed, and at 700 ° C. or higher, a burning phenomenon occurs on the surface of carbon black particles and aggregates and agglomerates. May worsen. The heat treatment time depends on the temperature, but 15 minutes to 1 hour.
About 0 hours is preferable.

The carbon black used in the present invention is 19
Among the carbon blacks obtained by the oil furnace method described on page 3 of "Carbon Black Handbook (Third Edition)" issued by the Carbon Black Association of 1995, those having a total oxygen content of 20 mg / g or less. The specific surface area is about 30 to 500 m ² / g, and the DBP absorption is about 40 to 3
60 ml / 100 g, and the ash content is preferably about 0.01 to 0.5%. These physical property values do not change much before and after the heat treatment.

Usually, on the surface of the carbon black particles,
There is an oxygen functional group such as a hydroxyl group or a carbonyl group, and the amount thereof greatly changes the resistance when blended in a resin or the like.
The oxygen functional group is measured by volatile composition, the amount of hydroxyl group and carbonyl group can be quantified as CO, the amount of carboxyl group can be quantified as CO ₂ , and the total oxygen amount is an amount converted from CO and CO ₂ .

[0010] The above volatile composition is determined by adding a fixed amount of dried carbon black to a heat-resistant test tube and placing it in a 10 ^-2 mmHg
After reducing the pressure to the following, the device is placed in an electric furnace heated to 1500 ° C. and desorbed for 30 minutes. After collecting and mixing the total amount in a tank, the composition and amount of the gas are measured by gas chromatography, and the total oxygen amount is calculated from the results.

The carbon black of the present invention is suitable for being kneaded with a resin to be used as a conductive composition, but the kneading method is not particularly limited, and a material obtained by dry blending with a Henschel mixer or the like is used. A method of continuously kneading with a shaft or a twin-screw kneader to form pellets can be employed. In preparing the resin composition, various additives such as a reinforcing filler, a heat resistance improver, a flame retardant, and a foaming agent may be optionally added in addition to the resin and the carbon black of the present invention. As such materials, usually, fumed silica, precipitated silica, reinforcing fillers such as diatomaceous earth, aluminum oxide, mica, clay, zinc carbonate, glass beads, polydimethylsiloxane, alkenyl group-containing polysiloxane,
Examples thereof include polysilsesquioxane.

[0012]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the scope of the invention. (Example 1) Specific surface area 28 m ² / g, DBP absorption 13
500 g of furnace method carbon black having a volatile content shown in Table 1 with 0 ml / 100 g and ash content of 0.06%
Was placed in a cylindrical SUS kiln having a diameter of 30 cm and a length of 50 cm, and rotated at 10 rpm.

As an inert atmosphere, CO ₂ gas was used. C
O ₂ gas was inserted at a rate of 10 liters / minute from the center of the kiln, and heating was started after the entire area of the kiln was completely replaced with CO ₂ . Heating was performed for 60 minutes using an electric furnace covering the entire kiln while controlling the temperature of the carbon black to be 350 ° C. ± 5 ° C.

The physical properties of the obtained carbon black are shown in Table 1. Using this carbon black,
A molded article made of the conductive nylon resin composition was manufactured.
Nylon 6 manufactured by Mitsubishi Engineering-Plastics Corporation
Resin, product name “Novamid 1020” 73%, Example 1
22% carbon black manufactured by Toray Industries, Inc., and N-n-butylbenzenesulfonamide manufactured by Toray Co., Ltd., trade name “BBS
A "5%, and mixed with a Henschel mixer (1000 rpm)
m) for 10 minutes.

[0015] The resulting mixture was screwed to a diameter of 35 mmφ.
Kneading part temperature 275 ° C, resin temperature 270 ° C, feed 4 kg / H
The resulting strand was water-cooled and cut with a pelletizer to produce a pellet. After the pellets were dried at 70 ° C. × 12 HR in a vacuum dryer, the cylinder temperature was adjusted to 2 using an injection molding machine (trade name “J75ED” manufactured by Nippon Steel Corporation).
80 ° C, Mold temperature 80 ° C, Screw rotation speed 120rpm
m and injection pressure of 1039 kg / m ² . There was no particular problem in injection molding, and a molded article having a desired shape and sufficient conductivity could be easily obtained. (Example 2) Specific surface area 133 m ² / g, DBP absorption 1
Table 1 shows the physical properties of the carbon black obtained by subjecting a furnace-process carbon black having a volatile composition shown in Table 1 to a heat treatment of 16 ml / 100 g and an ash content of 0.03% in exactly the same manner as in Example 1. Using the obtained carbon black, a molded article made of the conductive nylon resin composition was produced in exactly the same manner as in Example 1. There was no particular problem in the injection molding, and the molded article had sufficient conductivity in a desired shape. A molded product was easily obtained. (Comparative Example 1) The furnace method carbon black subjected to the heat treatment in Example 1 was used without heat treatment,
When a molded article made of the conductive nylon resin composition was manufactured in exactly the same manner as in Example 1, the viscosity of the resin composition was too high at the time of molding, and the molded article could not be formed into a desired shape. Also,
The volume resistivity of the molded product was also higher than that of the example. (Comparative Example 2) Table 1 shows the physical properties of carbon black obtained in exactly the same manner as in Example 1 except that air was charged at 10 L / min instead of CO ₂ gas during the heat treatment. Using the obtained carbon black, a molded article made of the conductive nylon resin composition was produced in exactly the same manner as in Example 1, and the viscosity of the resin composition was too high at the time of molding, and the molded article could not be molded into a desired shape. Was. Further, the volume resistivity of the molded product was significantly higher than that of the example. (Comparative Example 3) Table 1 shows the physical properties of carbon black obtained in exactly the same manner as in Example 1 except that the heat treatment was performed at 800 ° C for 1 hour. Using the obtained carbon black, a molded product made of the conductive nylon resin composition was produced in exactly the same manner as in Example 1, and the volume resistivity of the molded product was larger than that of the example. (Comparative Example 4) Specific surface area 225 m ² / g, DBP absorption 1
Table 1 shows the physical properties of carbon black obtained by subjecting a furnace-process carbon black having a volatile composition shown in Table 1 to a heat treatment of 61 ml / 100 g and an ash content of 0.65% in exactly the same manner as in Example 1. Using the obtained carbon black, a molded product made of the conductive nylon resin composition was produced in exactly the same manner as in Example 1, and the volume resistivity of the molded product was significantly higher than that of the example.

[0016]

The conductive carbon black of the present invention is a carbon black capable of imparting sufficient conductivity while maintaining processability when kneaded with a resin. It is suitable as a material that can give a molded product.

[0017]

[Table 1]

Claims (3)

[Claims] 1. Furnace black having a total oxygen content of 20 mg / g or less before heat treatment is heat-treated in an inert atmosphere to reduce the total oxygen content by 5 to 50%. Conductive carbon black. 2. The heat treatment reduces the total oxygen content to 5 to 3
2. The conductive carbon black according to claim 1, wherein the carbon black is reduced by 0%. 3. The conductive carbon black according to claim 1, which is used for kneading a resin.