JPH03187985A - Heat insulating material for high-temperature furnace - Google Patents

Abstract

PURPOSE:To improve radiation heat insulating performance and strength by carbonizing a phenolic resin foam, subjecting the carbonized foam to graphitization treatment and providing a carbon cellular substance having a prescribed bulk density and graphitization degree. CONSTITUTION:The aforementioned heat insulating material for high- temperature furnaces is formed from a carbon cellular substance obtained by carbonizing a phenolic resin foam and subjecting the carbonized foam to graphitization treatment. The above-mentioned carbon cellular substance has 0.05-0.15g/cm<3> bulk density and 10-50% graphitization degree. The aforementioned heat insulating material is excellent in radiation heat insulating performance, strength, etc., and used in high-temperature furnaces employed at >=2300 deg.C temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a heat insulating material used in high-temperature furnaces and the like, and more particularly, to a heat insulating material used in high-temperature furnaces used at temperatures of 2300° C. or higher, particularly 2500° C. or higher. Regarding.

TECHNICAL BACKGROUND OF THE INVENTION In high-temperature furnaces used for melting metals, firing fine ceramics, carbon products, etc., a heat insulating material is used as one of its constituent members.

For example, in recent years, attempts have been made to graphitize carbon fiber in order to increase its strength and modulus, and graphitization requires a graphitization furnace that can withstand temperatures of 2500°C or higher. It is said that

The heat insulating material used in such graphitization furnaces has conventionally been so-called molded felt, which is made by carbonizing carbon fibers hardened with pitch, furan, or phenol resin. However, this heat insulating material whose main component is carbon fiber has a problem in that it has poor ability to block radiant heat, and sufficient heat insulating performance cannot be obtained at temperatures above 2000° C., where radiant heat becomes dominant.

Therefore, a carbon porous material obtained by carbonizing a specific phenolic resin foam has been proposed as a heat insulating material with a large radiant heat blocking effect (for example, Japanese Patent Application No. 62-64084).
.

However, this heat insulating material made of porous carbon material has a heat resistance of 2300
When exposed to temperatures above ℃, it will gradually shrink, and this shrinkage will create gaps between the insulation materials, reducing insulation performance, and in extreme cases, stress will be created between the insulation materials, which may even cause cracks. Therefore, it was found that the temperature range in which it can be used as a heat insulating material for high-temperature furnaces is narrow.

As a result of intensive studies to prevent such shrinkage of the carbon porous material, the present inventors found that this shrinkage is caused by the carbon porous material being exposed to high temperatures for a long period of time and gradually becoming graphitized. Ta.

Purpose of the Invention The present invention has been made in view of the current situation, and an object of the present invention is to provide a heat insulating material for a high temperature furnace that has excellent radiation insulation performance and does not shrink due to graphitization even at high temperatures exceeding 2300°C. It is an object.

Summary of the Invention The heat insulating material for a high temperature furnace according to the present invention is a heat insulating material for a high temperature furnace that is made of a porous carbon material obtained by carbonizing and graphitizing a phenolic resin foam, and the porous carbon material is bulky. Density is 0
．． 05 to 0.15 g/cm3, and the degree of graphitization is 1
It is characterized by being 0 to 50%.

Since the heat insulating material for a high temperature furnace according to the present invention has the above-mentioned bulk density and degree of graphitization, it has excellent radiation insulation performance and hardly shrinks over time due to graphitization even when exposed to high temperatures.

Detailed Description of the Invention The carbon porous body used as a high-temperature heat insulating material in the present invention uses a specific phenolic resin foam as a raw material.

This phenol resin foam is obtained by foaming and curing a phenol resin, and a resol type phenol resin is used as such a phenol resin.

A resol type phenolic resin is obtained by reacting phenols and aldehydes in the presence of an alkali catalyst according to a known method.

Specifically, phenols include phenol, cresol, xylenol, resorcinol, and the like.

Specifically, formaldehyde, acetaldehyde, furfural, and the like are used as the aldehydes.

Specifically, the alkali catalyst is KOH.

NaOH, NH, 'NH40)I, ethanolamine, ethylenediamine, etc. are used.

As the foaming agent for foaming the resol type phenolic resin, various conventionally known decomposition type foaming agents and evaporation type foaming agents can be used. Among these, evaporative blowing agents are preferred, and specific examples include paraffinic hydrocarbons, alcohols, ethers, halogenated hydrocarbons, etc. Among them, halogenated hydrocarbons and paraffinic blowing agents Hydrocarbons can be most preferably used.

Specifically, halogenated hydrocarbons include chloroform, carbon tetrachloride, trichloromonofluoromethane (Freon gas R11), dichloromonofluoromethane (Freon gas R11), and dichloromonofluoromethane (Freon gas R11).
21), tetrachlorodifluoroethane (same R112)
, trichlorotrifluoromethane (RII3), dichlorotetrafluoroethane (R114), dibromotrifluoroethane (R114B2), and the like are preferably used.

As the paraffinic hydrocarbon, propane, butane, pentane, hexane, cyclopenkune, cyclohexane, etc. are preferably used.

Such a blowing agent is resol type phenolic resin 100
It is preferable to use it in a proportion of 1 to 30 parts by weight.

In order to foam and cure resol type phenolic resin, a curing agent is used together with a foaming agent, and various conventionally known curing agents are selected and used according to the type of prepolymer. . Specifically, sulfuric acid,
Examples include hydrochloric acid, phosphoric acid, phenolsulfonic acid, benzenesulfonic acid, toluenesulfonic acid, metacresolsulfonic acid, resorcinolsulfonic acid, butylsulfonic acid, propylsulfonic acid, and the like.

It is usually preferable to use such a curing agent in an amount of 3 to 30 parts by weight per 100 parts by weight of the resol type phenolic resin.

The phenolic resin foam used as a raw material for the porous carbon material of the present invention includes the above-mentioned resol type phenolic resin,
Contains a curing agent and a foaming agent, but may also contain a foam stabilizer, and by selecting the amount and type of this foam stabilizer, the cell diameter and closed cell ratio of the foam can be adjusted. .

The foam stabilizer that can be used in the present invention has an HLB value of 13.
The above is preferably a so-called surfactant of 14 or more, and specifically, a block copolymerization of polyoxyethylene as a hydrophilic group and polypropylene glycol, sorbitan, castor oil, polymethylsiloxane, etc. as a hydrophobic group. I can name things. Among these, polyoxysorbitan stearate is particularly preferred. This foam stabilizer has excellent foam regulating ability, so it is possible to reduce the cell diameter of the phenolic resin foam, and therefore it is possible to carbonize and graphitize the foam. In addition to lowering the thermal conductivity of the carbon porous body obtained, the closed cell ratio of the phenolic resin foam can be made close to 0%, and subsequent carbonization and graphitization treatments can be facilitated.

Such foam stabilizers include resol type phenolic resin 100
0.1 to 10 parts by weight, preferably 1 to 3 parts by weight
It is preferable to use parts by weight.

In addition, in the present invention, other components may be added as necessary.
For example, a filler may be used in combination.

The production of phenolic resin foam from raw materials such as resol type phenolic resin, blowing agent, and hardening agent as described above involves mixing and stirring these raw materials all at once or sequentially to produce a creamy phenolic resin prepolymer. This is carried out by supplying the composition, for example, into a heat-retained mold or onto a double belt conveyor, and then foaming and curing it.

In the present invention, the bulk density of the carbon porous material is 0.05 to 0.15 g/cm in view of the balance between heat insulation performance and mechanical strength.
Limited to 3. In order to produce a carbon porous body having a bulk density in such a range, it is necessary to precisely adjust the bulk density of the phenolic resin foam as a raw material. Since the bulk density of the carbon porous body is generally slightly higher than that of the raw material phenol resin foam, the bulk density of the raw material phenol resin foam is set to be slightly lower than the bulk density of the carbon porous body. The bulk density of a phenolic resin foam depends on the type of blowing agent, the temperature of the raw material, the mold temperature, etc., and by adjusting these factors, a foam having a bulk density of 11 can be obtained.

The phenolic resin foam thus obtained can be used as it is or after being cut into a molded plate. By making the resin foam into a plate-like body in this way, it is possible to easily mass-produce the resin foam, which is preferable.

In the present invention, such a phenolic resin foam is fired in a non-oxidizing or slightly oxidizing atmosphere and carbonized to form a carbon porous body.

That is, the phenolic resin foam is prepared under reduced pressure or
The firing is performed preferably at a temperature of 600° C. or higher, more preferably 900° C. or higher, in gas, H, e gas, N2 gas, halogen gas, ammonia gas, hydrogen gas, carbon oxide, or the like. By carbonizing the phenolic resin foam in this manner, a carbon porous body with excellent strength can be obtained.

Further, although there is no particular restriction on the rate of temperature increase during firing, it is preferable to increase the temperature gradually around 200 to 600°C, where decomposition of the resin generally starts.

The carbon porous body used as a high-temperature heat insulating material in the present invention is produced by further graphitizing the carbon porous body obtained in this way, and the degree of graphitization is 10 to 50%, preferably 20 to 40%. % range.

By setting the degree of graphitization of the carbon porous material within this range, it is possible to create a high-temperature insulation material that is resistant to shrinkage or warping over time when used at temperatures of 2500°C or higher, and has high strength and radiation insulation performance. Obtainable.

The degree of graphitization in the present invention is a graphitic crystal structure parameter Gd calculated from the diffraction peak of the (002) plane in an X-ray diffraction intensity curve. explain. That is, this parameter Gd is a gentle 0 diffraction peak based on the (002) plane of the X-ray diffraction intensity curve A, that is, a diffraction angle (2θ) of 18 to 32''.
The area S1 of the figure defined by the diffraction peak ■ appearing between and the baseline B of this peak ■, and (002
) A sharp peak ■ based on the surface, that is, a diffraction angle (2θ) of 1 that appears above the peak ■ between 25.5 and 26.5°
This is a value calculated from the following formula (1) from one or more peaks (1) and the area S2 of the figure defined by the peak (2), and is a value that is one of the lowest rates of graphitization of a porous carbon material.

G d-8/ (S + 82) x log(%
) ・=(+)1 Such a graphitized carbon porous body is produced by leaving a carbon porous body before graphitization at a specific temperature in an inert atmosphere for a certain period of time.

Such an inert atmosphere specifically includes N2, Ar5
It is formed in the presence of an inert gas such as He or a filler powder such as coke powder.

Further, the graphitization temperature is at least 2300°C or higher, preferably 2400°C or higher and 3000°C or lower. The graphitization treatment time is determined in consideration of the treatment temperature, and the higher the temperature, the faster the degree of graphitization progresses, so it should be shorter.

As explained above, the heat insulating material for high temperature furnace according to the present invention is
Made from phenolic resin foam, bulk density is 0.05~
Since it has a graphitization degree Gd of 0.15 g/cm3 and 10 to 40%, it has particularly excellent heat insulation performance at high temperatures, does not shrink or warp at high temperatures, and has sufficient strength as a heat insulating material. There is. Therefore, it is useful as a heat insulating material for use in furnaces that require heating at temperatures of 2,500°C or higher, for example, graphitization furnaces for producing high-strength, high-rigidity carbon fibers, for which no suitable heat-insulating materials have been available in the past. .

Effects of the Invention The heat insulating material for a high temperature furnace according to the present invention is a heat insulating material for a high temperature furnace made of a porous carbon material obtained by carbonizing and graphitizing a phenolic resin foam, and the porous carbon material is bulky. Density is 0
．． 05 to 0.15 g/cm3, and the degree of graphitization is 1
Since it is 0 to 50%, it has excellent radiation heat insulation performance and hardly causes shrinkage or warping due to graphitization even when exposed to high temperatures.

2 In addition, since it has sufficient strength as a heat insulating material, it can be used in furnaces for heating at temperatures of 2,500°C or higher, for which there were no suitable heat insulating materials, such as graphite for obtaining high strength and high rigidity carbon fibers. It is useful as a heat insulating material for chemical furnaces.

Next, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to these examples in any way as long as it does not go beyond the gist of the invention.

Example 100 parts by weight of Luzol, 10 parts by weight of para-toluenesulfonic acid as a hardening agent, and 6 parts by weight of chlorofluorocarbon gas (olefin 123) as a blowing agent were sufficiently stirred with a high-speed mixer, and the mixture was poured into a wooden mold. After closing the lid, 8
By leaving it in an air oven at 0℃ for 30 minutes,
Height 50cm.

Width 500111% Height 5cm, Bulk density 0.08g/cm
A plate-shaped phenolic resin foam of No. 3 was obtained.

This molded plate was placed in a Matsufuru furnace and heated under a nitrogen atmosphere at a temperature increase rate of 60°C/hour to a temperature of 800°C, then held at the same temperature for 2 hours, and then cooled to produce a carbon porous body. .

The porous carbon material obtained by the above method was placed in a graphite tray, the tray was placed in a resistance heating furnace, and after replacing the inside of the furnace with N2 atmosphere, the temperature was raised to a temperature of 2600°C at a rate of 3°C/min. ,
The same temperature was maintained for 5 hours, and then the porous carbon material was left in the furnace, cooled, and then taken out.

The physical properties and performance of the carbon porous material obtained by the above method were evaluated by the following method.

Thermal conductivity: The thermal conductivity was calculated by calculating 91 by measuring the total reflux heat amount of a plate with a thickness of 30 mm and a diameter of 300 mm using the flat plate comparison method at an upstream temperature of 2500°C and a downstream temperature of 50°C.

Compressive strength: Measured based on JISK.

Degree of graphitization: Rotating anode cathode type X-ray diffraction system manufactured by Rigaku Corporation ■
Using e-rotorflex RU800, 50kV, 3
Measurement was performed using a reflection method under the following measurement conditions: 00mASCuk α-ray (λ-1, 5418A), slit width of 1/2″, 0.15mm, scanning speed of 1°/min, and full scale of 800 cps.

Heat shrinkage: A plate-shaped carbon porous body measuring 200 x 200 x 500 m was left in a furnace at 2500° C. in an N2 atmosphere, and after 50 hours it was measured by the \'' method to determine the dimensional shrinkage rate (%).

The results are shown in Table 1.

Examples 2 to 4 Carbon porous bodies were produced in the same manner as in Example 1, except that the treatment temperature and time in the graphitization treatment were changed as shown in Table 1, and the physical properties of the obtained carbon porous bodies were measured. did.

The results are shown in Table 1.

Comparative Example 1 A carbon porous body was produced in the same manner as in Example 1 except that the graphitization treatment was not performed, and the physical properties of the obtained carbon porous body were measured.

The results are shown in Table 1.

Comparative Examples 2 to 3 5 Carbon porous bodies were produced in the same manner as in Example 1, except that the treatment temperature and time in the graphitization treatment were changed as shown in Table 1, and the physical properties of the obtained carbon porous bodies were It was measured.

The results are shown in Table 1.

Example 5 The procedure was the same as in Example 1 except that the foaming ratio of the raw material phenolic resin foam was changed as shown in Table 1, and the bulk density was 0.
A porous carbon material having a weight of 0.6 g/cm3 was obtained, and the physical properties of this porous carbon material were measured in the same manner as in Example 1. , the results are shown in Table 2.

Comparative Examples 4 to 5 The foaming ratio of the raw material phenolic resin foam was changed as shown in Table 2, and the bulk density was 0.20 g/i in the same manner as in Example 1.
, and a carbon porous body of 0.04 g/cm3 was obtained. The physical properties of this carbon porous body were measured in the same manner as in Example 1.

The results are shown in Table 2.

6 table 1 1q - 8

[Brief explanation of drawings]

FIG. 1 is a graph showing an example of the X-ray diffraction intensity curve of the carbon porous material of the present invention. ■...Gentle peak ■...Sharp peak B...Baseline

Claims (1)

[Claims] A heat insulating material for a high temperature furnace comprising a carbon porous body obtained by carbonizing and graphitizing a phenolic resin foam, wherein the carbon porous body has a bulk density of 0.05 to 0.0. 15g/cm^3, and the degree of graphitization is 10-5
A heat insulating material for high-temperature furnaces, characterized in that it is 0%.