JPS6183239A - Preparation of minute hollow pitch - Google Patents

Abstract

PURPOSE:To yield minute hollow pitch inexpensively, by a process wherein solvent-contg. pitch mixed with a low-boiling org. solvent as a foaming agent is heated under pressure in a hermetic pressure vessel and dispersed into a gaseous or liq. phase to cool and solidify. CONSTITUTION:Coal or petroleum pitch is mixed with 3-30wt% low boiling org. solvent (e.g., benzene, toluene) as a foaming agent. Then, said solvent-contg. pitch is put into a hermetic pressure vessel and melted by applying pressure and heat. The melt is sprayed from the vessel through a nozzle, etc. into a gas phase or dispersed into a liq. phase such as water to cool and solidify, thus yielding the intended minute hollow pitch. The resulting pitch can be converted into minute hollow carbon by rendering it infusible or carbonization and calcination, and said pitch as prepd. can also be used as a heat insulator or a raw material of composites with metals, plastics, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for manufacturing pitch micro hollow bodies, which have a wide range of uses such as heat insulating materials and raw materials for composite materials.

<Prior art and its problems> Pitch micro hollow bodies can be used as they are for a wide range of applications such as heat insulating materials and raw materials for composite materials, but they can be made into carbon micro hollow bodies through infusibility and carbonization processes. The range of applications for carbon microhollow bodies is wide-ranging.For example, by taking advantage of their heat resistance, chemical resistance, conductivity, and other properties, they can be used as insulation materials, reactor materials for nuclear reactors, materials for conductive plastics, metals, and inorganic materials. It can be used as a composite material etc.

Conventionally, methods for obtaining pitch-based carbon micro hollow bodies include, for example, Japanese Patent Publication No. 49-30253 and Japanese Patent Publication No. 50-2983.
7, Special Publication No. 54-10948 is known.

The method disclosed in Japanese Patent Publication No. 49-30253 involves forming solvent-containing pitch spheres by high-speed stirring in pressurized water, and then obtaining micro hollow carbon bodies by subjecting them to rapid heating, infusibility, and carbonization treatment. This method does not yield large grains, and even the method of Japanese Patent Publication No. 0-29837 only yields extremely limited grains. In addition, both require a step of volatilizing a special additive, ie, a hollowing step, to effect hollowing, which makes the manufacturing process extremely complicated.

In the method disclosed in Japanese Patent Publication No. 54-10948, the manufacturing conditions were very complicated and the operation was difficult, and the product obtained also had various drawbacks such as cracks in the surface shell.

Carbon microhollow bodies are carbon materials with various characteristics, but as mentioned above, they are extremely expensive due to the complexity of the manufacturing method and other factors, so they have not been widely used.

<Object of the Invention> The object of the present invention is to overcome all the drawbacks of the conventional products as described above, and to provide a new method for manufacturing pitch micro hollow bodies having a wide range of particle size distributions at low cost using an extremely easy method. Another object of the present invention is to provide a method for producing pitch hollow spheres, which are raw materials for carbon microhollow bodies.

<Structure of the Invention> The present invention involves heating a solvent-containing pitch mixed with a low boiling point organic solvent as a blowing agent to a molten state by heating it under pressure in a pressure-tight airtight container, and then dispersing it into a gas phase or a liquid phase and cooling it to solidify it. The present invention provides a method for manufacturing a pitch micro hollow body, which is characterized by:

Hereinafter, the method for manufacturing a pitch fine hollow body of the present invention will be explained in detail.

The method of the present invention uses coal-based or petroleum-based pitch as a raw material. It is necessary to use a pitch whose softening starting point is higher than the boiling point of the low-boiling organic solvent used as the blowing agent.
Particularly preferred is a temperature range of 100 to 320°C. The softening starting point of the pitch here is the temperature at which the pitch starts to flow when a pressure of 100 kg/Cf112 is applied using a normal flow tester. Pitch whose softening start point is lower than 100° C. is difficult to melt and mold into a spherical shape, and furthermore, it is extremely difficult to perform infusibility treatment, which is not preferable.

Pitch whose softening start point is higher than 320° C. is difficult to mix uniformly with a low boiling point organic solvent, and the desired hollow spheres cannot be obtained in the process of melt-molding into spheres.

The low-boiling organic solvent used as a blowing agent must be compatible with the pitch, and the larger the difference between the softening starting point of the raw material pitch and the boiling point of the blowing agent, the better. Representative examples of these include benzene, toluene, xylene, and mixtures thereof.

The amount of blowing agent added to the pitch varies depending on the pitch's softening point, molecular weight distribution, spray temperature, etc.
Normally, if the amount of the blowing agent is in the range of 3 to 30 wt%, pitch hollow spheres can be obtained sufficiently. If the amount of the blowing agent is less than 3 wt%, it is difficult to obtain the desired hollow spheres, and the amount of the blowing agent is 30w.
If the content exceeds t%, the viscosity of so-called solvent-containing pitch, which is a mixture of pitch and a low-boiling organic solvent, decreases, making it difficult to obtain a single spherical pitch.

Examples of methods for melt-molding the solvent-containing pitch into a spherical shape include spraying it from a nozzle into a gas phase from inside a pressurized and heated container, and dropping it from a perforated plate. All of these methods are industrially excellent, but the method of spraying from a nozzle into the gas phase in particular allows pitch hollow spheres with a relatively wide particle size distribution to be obtained.

However, the method of melt-molding into a spherical shape is not limited to these methods, and a method of dispersing it in a liquid phase (for example, water) may also be used.

The manufacturing process of the carbon microhollow body of the present invention will be described in detail.

First, it is necessary to mix the raw material pitch and the low boiling point organic solvent as a blowing agent sufficiently uniformly. If the mixing is insufficient, the expansion and degassing effects of the low-boiling organic solvent cannot be expected sufficiently in the next step of melting and molding the solvent-containing pitch, and the desired pitch hollow spheres cannot be obtained. Mixing is accomplished by stirring for 20 to 150 minutes in a pressurized inert gas atmosphere at between 100 and 250<0>C.

In the melt-molding process of the solvent-containing pitch, as described above, the method of spraying from a heated and pressurized container into the gas phase using a nozzle, the method of dropping it from a perforated plate, etc. can be used.

In this case, a liquid such as water or a gas such as air can also be used as the refrigerant. Here, it is necessary to melt the solvent-containing pitch in an airtight pressure-resistant container so that the low-boiling point organic solvent contained in the solvent-containing pitch does not evaporate.

The particle size of the pitch hollow spheres obtained is determined by the type of nozzle, the pressure applied, the surface tension of the pitch, etc.

The mechanism by which hollowing occurs in the melt-molding process of solvent-containing pitch will be explained using as an example a method of spraying with a nozzle into the gas phase.

Solvent-containing pitch sprayed into the gas phase becomes spheroidized due to the pitch's surface tension. On the other hand, the low boiling point organic solvent is heated under pressure in an airtight container, so most of it exists in a liquid state, but when it is sprayed into the gas phase at high temperature, it is simultaneously vaporized and causes volumetric expansion. It is believed that hollowing is achieved through a mechanism in which the low-boiling point organic solvent evaporates within the spheroidized solvent-containing pitch, causing volumetric expansion as described above, and finally breaking through the surface shell and being extracted to the outside. It will be done.

The pitch micro hollow bodies obtained as described above can be easily made into carbon micro hollow bodies by infusibility and carbonization firing treatment, but they can also be used as is by taking advantage of their light weight, heat insulating properties, etc. Therefore, it is used in a wide range of applications as a heat insulating material and as a raw material for composite materials with metals, plastics, etc.

Practical example Hereinafter, the present invention will be specifically explained with reference to examples.

Pitch with a softening starting point of 172°C and a benzene insoluble content of 63% was used as a raw material. 2400 g of this pitch and 240 g of toluene were charged into an autoclave with an internal volume of 3 cm equipped with a stirring blade, and after the interior was sufficiently replaced with nitrogen gas, the pitch was heated to 150°C. Heat to A for 30 minutes, then keep at that temperature for 2 hours until heated to 600℃.
Stirring was performed at r, p, m. The solvent-containing pitch thus produced contained 8.1 wt% toluene.

The mixture was transferred to a pressure-resistant container with an internal volume of 3 cm kept at an internal temperature of 240°C and melted, and then heated at a nitrogen gas pressure of 5 kg/c
Pitch micro hollow bodies were obtained by spraying into the gas phase under pressure. The particle size distribution of the obtained pitch micro hollow bodies is shown in FIG. It can be seen from this figure that a micropitch hollow body with a wide pitch distribution was obtained. FIG. 2 shows a cross-sectional photograph of the pitch micro hollow body. From this figure, it can be seen that there are countless pores that are thought to be degassing holes for toluene, a low-boiling organic solvent.

The average particle size of the obtained pitch micro hollow bodies is 1l100IL
, the bulk density is 0. There was an IEl g/cm3.

<Effects of the Invention> Conventionally, when a special additive was added to obtain a carbon microhollow body, an independent step of volatilizing it was required.

However, in the present invention, since granulation and hollowing are performed in one process, it is thought that this greatly contributes to a reduction in the total number of man-hours and, by extension, to a reduction in the manufacturing cost of the pitch micro hollow body. Furthermore, if it becomes possible to manufacture pitch micro hollow bodies or pitch micro hollow bodies at low cost, it is thought that they will be used in a very wide range of fields.

[Brief explanation of drawings]

Fig. 1 is a graph showing the particle size distribution of the pitch micro hollow bodies obtained in the example, and Fig. 2 is a photograph showing the structure of the particles, which is 70 times larger than the cross section of the pitch micro hollow bodies obtained in the example. It's a photo. FIo, 1; fJ7 Takeshi (mm)

Claims (1)

[Claims] A pitch micro-hollow characterized in that a solvent-containing pitch mixed with a low-boiling organic solvent as a blowing agent is heated under pressure in a pressure-resistant airtight container to a molten state, then dispersed in a gas phase or liquid phase, and cooled and solidified. How the body is manufactured.