JPH09170992A - Manufacture of carbon black molded object and its density managing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable efficient density measurement, by examining the relation between the molding density and the volume resistivity of carbon black, and applying the relation to the production management of carbon black molded object. SOLUTION: The density management method manages the density of a carbon black molded object by measuring the resistance value. In the manufacturing method, when the molded object is obtained by pressure-molding carbon black powder, the density of the molded object is obtained during the pressure molding or after molding, by measuring the volume resistivity or the volume resistance value of the molded object in a mold. Thereby the resistances of all molded objects are measured during press molding of carbon black or just after the molding, and the densities of molded objects can be simply and speedily measured. The volume resistivity can be stably measured almost without being affected by the temperature and the humidity of measuring atmosphere.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for efficiently controlling the density of carbon black moldings.

[0002]

2. Description of the Related Art Carbon black is a powder which generally has an extremely low bulk density of about 0.1 g / cc. Therefore, there is a problem that packaging cost, storage cost, and transportation cost are high, and dust is generated at the time of use to deteriorate the use environment. In order to solve such a problem, a dry granulation product or a wet granulation product called a bead product is usually used. The beaded product has a bulk density of 0.3 to 0.5 g / cc, which is considerably higher than that of untreated carbon black. However, the effects of suppressing dust generation during weighing and preventing pulverization of granulated products during transportation were not sufficient. Further, the granulation deteriorates the dispersibility in a varnish or a resin, which is a raw material of a paint or an ink, so that a bead product cannot be used in some cases.

To solve these problems, for example, Japanese Unexamined Patent Publication No. Hei 6
According to Japanese Patent Laid-Open No. 122111, a carbon black powder is subjected to a pressure reduction treatment in a closed molding container, and then the pressure in the container is restored to normal pressure to obtain a molded body. Further, in British Patent 551862, degassing of carbon black, lamp black and the like is described in German Patent 1302382.
Describes a device for increasing the density by pressing.

[0004]

However, in all of these conventional techniques, reduction in transportation cost and ink
In order to obtain the density of a molded product, which is an important factor for the dispersibility of paints and the like in varnish, a method of calculating from the weight-volume ratio of the molded product is used. Although this method is possible in the laboratory, it is not an efficient method for measuring all the products when a large amount of carbon black is produced.

A basic study on the relationship between the density and the resistivity of a carbon black molded body is given by Andries Voet and William.
Whitten Jr. et al. (Rubber Worl
d 1963, August P.33-P.36), only the physical analysis of the correlation of these physical properties is done.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present inventors investigated the relationship between the molding density and volume resistivity of carbon black, and applied this to the production control of carbon black moldings. The present invention has been accomplished by finding that efficient density measurement can be performed. That is, the present invention provides a method for controlling the density of a carbon black molded body, characterized in that the density of the carbon black molded body is managed by measuring its resistance value, and when a molded body is obtained by press-molding carbon black powder. The method for producing a carbon black molded body is characterized in that the density of the molded body is obtained by measuring the volume resistivity or the volume resistance value of the molded body in the mold during or after pressure molding.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
First, the carbon black used in the present invention may be any fine carbon powder such as carbon black manufactured by the furnace method, lamp black, and acetylene black. Further, these carbon black powders may be post-treated with various oxidizing agents or granulated.

The carbon black molding method is not particularly limited, but preferably the density of the resulting molded body is 0.2 to
1.2 g / cc, particularly preferably 0.5-1.0 g / c
It is desirable to perform pressure molding as much as possible, because the compact and the dispersibility of the resulting molded product are particularly well balanced. As a pressing method, carbon black may be charged into a mold and a press machine may be used to pressurize.

As a mold to be used, any mold may be used as long as it has a strength capable of withstanding the applied pressure at the time of molding. For example, as a metal mold, SUS304,
Stainless steel molds such as SUS316 and super steels such as tungsten carbide can be used. Also, resin molds include polytetrafluoroethylene (PTFE), polytrifluorochloroethylene (PCTEF), polytetrafluoroethylene.
Fluorine resin such as propylene hexafluoride (FEP) (trademark:
"Teflon") molds, plastics such as nylon, polyethylene, polycarbonate, phenolic resins, and the like, FRP such as CFRP and GFRP as composite materials, and alumina, zirconia, mullite, etc. as ceramic molds.

As the press machine, a hydraulic mechanical press machine,
Any press molding machine such as a hydraulic hand press machine, a mechanical press machine, an air cylinder type press machine or the like can be used as long as it can perform pressure molding. Thus, a carbon black molded body is obtained, and the density is measured by the following method during or after molding of this molded body.

As a place for measuring the resistance value of the molded body,
It may be in the mold at the time of molding, for example, a circular or polygonal side surface of a cylinder or a piston surface that slides to press and solidify carbon black, or may be taken out from the mold used for molding. Further, when the measuring electrode is installed inside the molding die, at any timing from immediately after the pressure applied for molding reaches a predetermined pressure to immediately before taking out the molded body from the mold. Good.

The resistance value is measured by the two-terminal method, the four-terminal method and the four-terminal method.
There are probe method, van der Pauw method, etc.
The probe method is most suitable for measuring the density of the carbon black molded body according to the present invention because it can be measured simply by pressing the electrode needle against the sample. Generally, there is a "resistance value" as an expression that represents electric resistance. However, the resistance value depends on the shape such as the length and cross-sectional area of the sample. Therefore, it is preferable to use "volume resistivity" as an index of specific resistance, which does not depend on the shape of the sample, as an index of density control. The volume resistivity can be obtained by arithmetically processing the result measured by the 4-terminal method.

Carbon black was filled in a slidable mold and pressed to mold the carbon black. The volume resistivity of this molded body was measured using the four-point probe method. Hereinafter, the present invention will be described in more detail with reference to Examples.

[0014]

Example 1 The physical properties of carbon black used as an example of the present invention are shown in Table 1.

[0015]

[Table 1]

The press machine is 37t manufactured by Oji Machine Industry Co., Ltd.
on 4-column single-acting hydraulic press (ram diameter 152.4 mm)
, And the mold is made of SUS304 (inner method 70m
m × 70 mm, height 40 mm, manufactured by Mitsubishi Kasei Engineering Co., Ltd. was used. A die was set in the lower punch portion of the die, and 50 g of carbon black powder (manufactured by Mitsubishi Chemical Corporation: "# 45" and "MA8" were used) was used.
Prepared each. The upper punch was inserted into the die and set in the press. A carbon black molded body was obtained by press molding at a predetermined pressure. The density of this molded body was measured.

The density was measured by measuring the length, width and thickness of the rectangular parallelepiped with a caliper and calculating the volume (cc) of the molded body from the measured values. In addition, the weight (g) of the molded product was measured with an electronic direct-reading type balance. The density (g / cc) of the molded body was calculated from the weight and volume of these molded bodies. The volume resistivity of each molded body was measured using the PS-type probe (1.5 mm between electrode pins, 4
Mitsubishi Chemical Corporation's "Loresta A.
P. It was measured using the.

The results are shown in Table 2.

[0019]

[Table 2]

Further, in order to clarify the relationship between the volume resistivity and the density of the molded body, the relationship between the volume resistivity and the molding density shown in Table 2 is shown in FIG. As is clear from this result, there is a clear correlation between the volume resistivity and the density of the molded body,
By measuring the volume resistivity, the density of the molded body can be easily controlled.

(Temperature dependence of volume resistivity) MA8 19
The molded body molded at a pressure of 0 kgf / cm ² was placed in a small environment tester manufactured by Tabai Co., Ltd., the humidity was set to 50% and the temperature was set to the predetermined values shown in Table 3 and held for 1 hour. The volume resistivity of this molded body was measured by using a PS type probe (between electrode pins 1.
The measurement was performed using "Loresta AP" manufactured by Mitsubishi Chemical Co., Ltd., which was attached with 5 mm, 4 tubes in series.

The measurement results are shown in Table 3 and FIG.

[0023]

[Table 3]

(Humidity dependence of volume resistivity) MA8 19
The molded body molded at a pressure of 0 kgf / cm ² was placed in a small environment tester manufactured by Tabai Co., Ltd., the temperature was set to 25 ° C., the humidity was set to a predetermined value shown in Table 4, and the sample was held for 1 hour. The volume resistivity of this molded body was measured by using a PS type probe (between electrode pins 1.
The measurement was performed using "Loresta AP" manufactured by Mitsubishi Chemical Co., Ltd., which was attached with 5 mm, 4 tubes in series.

The measurement results are shown in Table 4 and FIG.

[0026]

[Table 4]

[0027]

According to the present invention, the resistance of all molded products can be measured during or immediately after press molding of carbon black, and the density of the molded products can be measured easily and speedily. Further, the volume resistivity can be measured stably without being affected by the temperature and humidity of the measurement atmosphere.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the volume resistivity and the molding density of the carbon black molded body obtained in Example 1.

FIG. 2 is a graph showing the temperature dependence of the volume resistivity of the carbon black molded body obtained in Example 1.

FIG. 3 is a diagram showing the humidity dependence of the volume resistivity of the carbon black molded body obtained in Example 1.

Claims (7)

[Claims] 1. A method for controlling the density of a carbon black molded body, which comprises managing the density of the carbon black molded body by measuring its resistance value. 2. The carbon black molding has a density of 0.2.
The density control method for a carbon black molded body according to claim 1, wherein the density is 1.2 g / cc. 3. The method for controlling the density of a carbon black molded body according to claim 1, wherein the resistance value is volume resistivity. . 4. When the carbon black powder is pressure-molded to obtain a molded body, the density of the molded body is obtained by measuring the volume resistivity of the molded body in the mold during or after pressure molding. And a method for producing a carbon black molded body. 5. The density of the carbon black molding is 0.2.
It is-1.2 g / cc, The manufacturing method of the carbon black molded object of Claim 4 characterized by the above-mentioned. 6. The method for controlling the density of a carbon black molded body according to claim 1, wherein the resistance value is measured by a 4-probe method. 7. The method for producing a carbon black molded article according to claim 4, wherein the resistance value is measured by a 4-probe method.