JPS61159488A - Production of lightweight hollow sphere pitch - Google Patents

Abstract

PURPOSE:To produce the title hollow sphere having the desired particle size distribution in high yields, by molding a mixture of pitch and a low-boiling org. solvent, crushing the molding and expanding it by heating. CONSTITUTION:A solvent-contg. pitch powder obtd. by mixing pitch having a softening point of 80-320 deg.C with a low-boiling org. solvent (e.g. toluene) as a blowing agent, is molded under a pressure of 50kg/cm<2> or above. The molding is crushed by an atomizer to adjust the particle size, and the crushed material is instantaneously heated at a temp. of not lower than the b.p. of said solvent to expand it, thus obtaining lightweight hollow pitch sphere having a density of 0.05-0.7g/cm<3>. EFFECT:Particle size distribution is uniform and composite materials such as heat-resistant material and nuclear reactor material having excellent packing rate, rigidity and strength can be obtd.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for manufacturing lightweight pitch hollow spheres that have a wide range of uses such as heat insulating materials and raw materials for various composite materials, and can be used as raw materials for carbon micro hollow bodies. It is something.

<Conventional technology and its problems> Pitch micro hollow bodies can be used as is 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 by undergoing infusibility and carbonization treatments. . The range of applications for carbon microhollow bodies is wide-ranging.For example, their properties such as heat resistance, chemical resistance, electrical conductivity, and lightness are utilized to create insulation materials, reactor materials for nuclear reactors, materials for conductive plastics,
It can be used as a raw material for composite materials with metals and inorganic materials, and as a material for molding compounds.

Japanese Patent Publication No. 49-30253 is a typical method for obtaining pitch-based carbon microhollow bodies.

In this method, so-called solvent-containing pitch mixed with a low-boiling point organic solvent is stirred at high speed in pressurized water to form solvent-containing pitch spheres, which are then subjected to rapid heating, infusibility, and carbonization treatment to obtain carbon micro hollow bodies. However, this method did not yield large particles, and had many drawbacks, such as the tendency for small particles to fuse together due to electrostatic attraction during rapid heating. . Furthermore, this method is extremely complicated and expensive, and has not been widely used despite having many excellent features.

According to a method in which the amount of the low boiling point organic solvent mixed with the pitch is adjusted appropriately to increase the viscosity of the solvent-containing pinch to the extent that it can be crushed at room temperature, the pinch is crushed and rapidly heated.
It is possible to obtain pitch hollow spheres and carbon microhollow bodies of 0.01II to 0.05 mn+. Although this method is industrially superior, it is unavoidable that fine powder with a particle size smaller than the desired size is produced when the solvent-containing pitch is crushed. No decline was avoided.

<Object of the Invention> The object of the present invention is to effectively utilize solvent-containing pitch particles with a small particle size and to improve the yield of pinched hollow spheres having a desired particle size distribution in an extremely easy manner. It is an object of the present invention to provide a method for manufacturing a lightweight pitch hollow body.

<Structure of the Invention> The present invention includes a blending step of mixing pitch with a low-boiling organic solvent as a blowing agent, a particle size adjustment step of molding the solvent-containing pitch fine powder, and then re-pulverizing it, and then adding the low-boiling point organic solvent to the pitch. The present invention provides a method for manufacturing lightweight pitch hollow spheres, which comprises a foaming step of foaming by instantaneously heating at a temperature higher than the boiling point.

The present invention will be explained in more detail below.

In the method of the present invention, coal or petroleum-based pinch is used as the raw material. The softening starting point of the pitch needs to be higher than the boiling point of the low boiling point organic solvent used as the blowing agent, but it is particularly preferable to use one in the range of 80 to 320°C. What is the softening starting point of the pitch here? , is the temperature at which the pitch starts to flow when a pressure of 10 kg/cm2 is applied using a normal flow tester. Pitches with a softening start point lower than 80'0 tend to cause mutual fusion during the foaming process,
Furthermore, the infusibility treatment is extremely difficult, which is not preferable. In addition, if the softening start point is higher than 320° C., it is difficult to mix uniformly with a low boiling point organic solvent, and a desired pinch hollow body cannot be obtained in one foaming process.

The blowing agent used in the present invention is a low-boiling organic solvent that is compatible with pitch, and it is preferable that the difference between the molecular weight of the pitch used as a raw material and the molecular weight of the organic solvent is larger.

The content of the solvent used as a blowing agent.

Although it varies depending on the type of pitch used as a raw material and the density of the desired pitch hollow spheres, it is extremely important to add a foaming agent so that the viscosity is such that it can be pulverized in the pulverization process.

<Specific Structure of the Invention> It is extremely important to mix the raw material pitch and the blowing agent in a sufficiently uniform manner. Insufficient mixing will not only cause non-uniform foaming in the foaming process, but also make it difficult for the fine powder to contain the necessary amount of foaming agent for foaming. In order to obtain the desired pinched hollow spheres, it is necessary to grind the solvent-containing pitch obtained in the above step to an appropriate particle size, but since the generation of fine powder is unavoidable, the yield of the desired pinched hollow spheres is unavoidably reduced.

In the present invention, it has been discovered that solvent-containing pitch particles of the required particle size can be obtained by an extremely easy method of re-molding these fine powders. Molding of fine powder can be carried out using ordinary molds and pressure equipment. The pressurizing pressure is required to be 50 kg/cm2 or more, although it varies depending on the particle size of the fine powder. If it is lower than 50 kg/cm2, the fine powders will not coagulate sufficiently, and large-sized solvent-containing pitch particles will not be obtained upon re-pulverization.

The molded product can be easily pulverized into solvent-containing pitch particles of the required particle size using an ordinary atomizer or the like. As mentioned above,
By repeatedly molding and re-pulverizing the fine powder, it is possible to improve the yield of pitch hollow spheres having a desired particle size range.

In the foaming step, pitch hollow spheres can be obtained by instantaneously heating the solvent-containing pitch particles at a temperature higher than the boiling point of the foaming agent used. In addition, by appropriately selecting the foaming temperature conditions, the porosity of the pinch hollow spheres can be adjusted to: A
It is possible to produce products that are knotty and have a bulk density in the range of 0.05 to 0.7 g/c++3.

The pitch hollow spheres obtained as described above are infusible,
It can be easily made into carbon micro hollow bodies by carbonization treatment, but it can also be used as is.

Due to its various properties such as lightness, heat insulation, and uniformity of particle size distribution, it can be used as a raw material for various composite materials with a high filling rate and high strength.

Example: Pitch with a softening starting point of 216°C was used as a raw material, and 600 g of this pitch and 70 g of toluene were mixed in an internal volume of 1 with a stirring blade.
After the mixture was placed in an autoclave and the inside was sufficiently replaced with N2 gas, the temperature was raised to 150°C over 30 minutes, and the mixture was kept at that temperature for 2 hours while stirring at 500 r, p, m. When the solvent-containing pitch produced in this way was pulverized with an atomizer, 71% of the particles were 20 to 60 mesh.
, 29% of particles with a size of 60 menshies or less were obtained. Take out 150g of these particles with an inner diameter of 80 mesh or less.
The particles were placed in a tamφ mold and held for 5 minutes while applying a pressure of t00 kg/c layer 2 to mold the particles.

When the obtained molded body was pulverized using an atomizer, 67% of the particles were 20 to 60 meshes, and 33% of the particles were 60 meshes or less. When the particles of 20 to 60 meshes obtained after remolding were instantaneously heated and foamed at 230'O, pitch hollow spheres containing 24% of particles of 9 to 20 meshes and 76% of particles of 20 to 60 meshes were obtained. The bulk density of pitch hollow spheres with a particle size distribution of 20 to 60 mesh is Q, 13g.
/c,c.

In the above process, when the same treatment was performed on the products that were not molded, 74% of the hollow bodies had a pitch of 20 to 60 meshes, and 26% had a pitch of 60 meshes or less. Figure 1 shows the particle size distribution of the pitch hollow body before and after molding.

From the above, it can be seen that pitch hollow spheres with a uniform particle size distribution can be manufactured by adding a molding process.

<Effect of the invention> In the present invention, by molding fine powder.

Since it has become possible to selectively produce pitch hollow spheres with a uniform particle size, which was difficult to obtain using conventional methods, it has become possible to mass-produce pitch hollow spheres with a desired particle size. A uniform particle size distribution greatly contributes to a high filling rate and improved rigidity and strength during composite material production.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the particle size distribution of the pitch hollow body before and after molding. FfG, 1 j

Claims (1)

[Claims] A blending process in which pitch is mixed with a low-boiling organic solvent as a blowing agent, a particle size adjustment process in which the solvent-containing pitch fine powder is molded and then re-pulverized, and then instantaneously heated at a temperature above the boiling point of the low-boiling organic solvent. A method for manufacturing a lightweight pitch hollow sphere, comprising a foaming step of performing foaming.