JP2924051B2 - Highly durable coating agent for carbonaceous molded insulation - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a highly durable coating agent for a carbonaceous molded heat insulating material used for a high-temperature furnace in a non-oxidizing atmosphere.

(Prior art) Carbon materials do not wear out even at a high temperature of 2500 ° C or higher in a non-oxidizing atmosphere and maintain high strength. For example, carbon fibers are made of carbonizable polymer compounds such as phenolic resin. As a binder, molded into an arbitrary shape, and further carbonized and graphitized, the obtained carbonaceous molded body has excellent heat insulation, durability, and shape retention for high-temperature furnaces used in a non-oxidizing atmosphere. It can be suitably used as a heat insulating material.

However, in actual furnace operation, although it varies depending on the furnace application, vapors of metals and inorganic compounds are generated, and a small amount of air enters from outside the furnace. Since the furnace must be opened to the atmosphere at high temperatures, it is not possible to completely prevent the wear of the carbonaceous molded heat insulating material. When the powders, grains, pieces, etc. come off or fall off, and the object to be treated is likely to be contaminated, the carbonaceous molded heat insulating material is replaced. Conventional techniques for preventing and reducing wear and the accompanying phenomena include, for example, carbon fiber woven fabric, a method of attaching a flexible graphite sheet to the surface of a heat insulating material, and a method mainly using graphite powder and a carbonizable polymer compound. A method has been adopted in which a coating agent is applied to the surface of a heat insulating material, carbonized and graphitized to convert the coating film into a dense graphite film. In particular, the latter method is generally used frequently because it is easy to construct and the shape of the heat insulating material does not matter.

(Problems to be Solved by the Invention) However, even if a dense graphite film is formed on the surface of the heat insulating material by applying a coating agent, the life of the heat insulating material itself is prolonged, but the effect is not sufficient. There is a demand for the development of a coating agent capable of forming a graphite film having excellent durability.

(Means for Solving the Problems) Accordingly, the present inventors have conducted intensive studies to solve the problems, and as a result, as a graphite powder in the coating agent, the graphite powder has an ash content of 2% or less. The present inventors have found that the problem can be solved by using natural or artificial graphite and making the particle size of the graphite powder substantially 20 μm or more, and reached the present invention. That is, an object of the present invention is to obtain a coating agent which forms a graphitic film which is significantly more durable than conventional products, and an object of the present invention is to provide a carbonizable polymer compound and a carbonizable polymer. In a coating agent for a carbonaceous molded heat insulating material comprising a solvent of a compound and graphite powder, the graphite powder is earth-like natural or artificial graphite having an ash content of 2% or less,
This is achieved by a highly durable coating agent for a carbonaceous molded heat insulating material, which is substantially a graphite powder having a particle size of 20 μm or more.

 Hereinafter, the present invention will be described in detail.

The coating agent for a carbonaceous molded heat insulating material according to the present invention basically comprises a carbonizable polymer compound, a solvent of the carbonizable polymer compound, and graphite powder, but may further include carbon fiber powder and the like.

 Hereinafter, each component will be described specifically.

The carbonizable polymer compound used in the present invention refers to a substance that is liquid or soluble in a solvent at normal temperature, and that can be converted to a carbonized product in a high yield when heat-treated in a non-oxidizing atmosphere. . Specific examples of such a substance include thermosetting resins such as phenolic resins and furan resins, and lime-based and petroleum-based tars and pitches. In consideration of the above, a thermosetting resin is preferable, and the use of a phenol resin is particularly preferable. The solvent of the carbonizable polymer compound is a solvent that sufficiently dissolves the above-described carbonizable polymer compound and has a viscosity that does not hinder the dispersion of the graphite powder and, if necessary, the carbon fiber powder and the like in the liquid. At room temperature.
Further, it is a substance having an appropriate boiling point such that it does not volatilize rapidly when the coating agent is applied, but can be easily volatilized by light heating or the like after the application. Specific substances include, for example, alcohols such as methanol, ethanol, propanol and butanol, benzene,
Toluene, quinoline, xylene, hydrocarbons such as hexane, other ethers, esters, halogenated hydrocarbons, compounds such as water can be mentioned, when using a phenol resin as a carbonizable polymer compound The use of alcohols is preferred.

Graphite powder is a powder of a substance having a so-called graphite structure, which is a layered structure of a benzene ring network surface, and the graphite powder is earth-like natural or artificial graphite.
And artificial graphite obtained by heat treatment at a high temperature of 00 ° C. or higher.

The graphite powder used in the present invention is substantially graphite powder having a particle size of 20 μm or more, and the content of fine powder having a particle size of less than 20 μm should be generally 8% or less, preferably 5% or less.
Here, the term "substantially the particle size" means that the shape of the graphite powder is various and is not necessarily a perfect round particle shape. In many cases, the shortest diameter is 20 μm or less, and the long diameter is 20 μm or more.
Since it is difficult to separate at the boundary of m, it means that it is 20 μm or more at the place where it is separated by industrial means such as sieving or sedimentation velocity difference class. A more preferred particle size is substantially 30 μm or more. On the other hand, the upper limit of the particle size is not particularly specified, and is easily determined by the ease of dispersion during preparation of the coating agent, the ease of application, the roughness of the coating film surface, etc., but is generally 200 μm.
m or less is suitable.

In the graphite powder used in the present invention, it is preferable that a component represented as ash such as an inorganic compound is small, and specifically, a graphite powder having an ash content of 2% or less, particularly preferably 1% or less is used. desirable.

Further, in the coating agent of the present invention, the above-mentioned ~
Other components can be used, if necessary, other than
For example, carbon fiber powder, etc. prevent and reduce large cracks due to carbonization and graphitization shrinkage and peeling of the coating film when carbonizing and graphitizing after applying the coating agent to the heat insulating material. It is added in order to As the carbon fiber, those derived from any of the raw materials such as pitch-based and PAN-based can be used, but in order to achieve the purpose of addition, at least 1000 ° C., preferably 2000 ° C.
It is desirable to use one that has been subjected to the above heat treatment.
Further, it is desirable that the fiber diameter is 25 μm or less, preferably 15 μm or less, and the fiber length is 5 mm or less, preferably 1 mm or less.

In the present invention, for 100 parts by weight of graphite powder,
50 to 300 parts by weight of the carbonizable polymer compound, preferably 100
Add up to 200 parts by weight. Further, carbon fiber powder or the like may be blended in an amount of 20 parts by weight or less, preferably 5 to 15 parts by weight. The amount of the solvent of the carbonizable polymer compound is determined by the ease of dispersing the graphite powder and the carbon fiber powder and the ease of application, and is not particularly limited, but is usually a carbonizable polymer. It is in the range of 100 to 400 parts by weight based on 100 parts by weight of the compound.

The components are sufficiently mixed to uniformly disperse graphite powder, carbon fiber powder, and the like. When used after being left after blending, it is desirable to carry out stirring and mixing to perform uniform dispersion. Even if the prepared coating agent is roasted by the flame of a burner, it can be made into a graphite film which can sufficiently withstand practical use.

(Examples) Hereinafter, the present invention will be described in more detail with reference to Examples.
The present invention is not limited to the embodiments unless it exceeds the gist.

Example 1 Earth-like natural graphite powder in which the ratio of powder having a particle size of 20 to 40 μm is 40%, the ratio of powder having a particle size of 40 to 100 μm is 45%, and the ratio of powder having a particle size of 100 μm or more is 10%. (Ash content 1 wt% or less) Resole type phenol resin 115 parts by weight, 100 parts by weight, 2400 ℃
12.5 parts by weight of a carbon fiber powder obtained by cutting a pitch-based carbon fiber having a fiber diameter of 10 μm treated to 1 mm into a length of 1 mm, and 400 parts by weight of ethanol were added, and sufficiently stirred and mixed to obtain a coating agent.

40 g of this coating agent on one side of a board of carbon fiber insulation material (density 0.2 g / cm ³ ) of 20 × 20 cm in size and 4 cm in thickness,
The brush was applied so as to have a uniform thickness. Then this one
After heat treatment at 220 ° C for 1 hour to remove the solvent and harden the phenolic resin, carbonize to 1000 ° C in a nitrogen atmosphere,
Graphitization was further performed up to 2000 ° C. in an argon atmosphere.

This heat insulating material was set in the opening of the electric furnace with a size of 18 × 18 cm with the coating film inside the furnace, heated at 700 ° C while sending 5 l / min of air into the furnace, and the coating film disappeared It was 25 hours when the time until the surface of the heat insulating material appeared (oxidation resistance consumption time) was examined.

Comparative Example 1 Natural graphite powder having a maximum particle size of 15 μm and an average particle size of 4.5 μm (ash content: 1 wt%)
The following was used in place of the natural graphite powder of Example 1 except that the mixture was mixed at a weight ratio of 4: 1 to prepare a coating agent in the same compounding ratio as in Example 1. This coating agent was applied to a carbon fiber heat insulating board under the same conditions as in Comparative Example 1, carbonized and graphitized, and the oxidation resistance consumption time was determined to be 13 hours.

Comparative Example 2 Ratio of powder having a particle size of 10 to 60 μm is 75 to 90%, and 60 to 100 μm.
The ratio of powder having a particle size of m is 5 to 20%, and the ratio of powder having a particle size of 100 μm or more is 5% or less. Resin 115
12.5 parts by weight of carbon fiber powder obtained by cutting a pitch-based carbon fiber having a fiber diameter of 10 μm,
Parts by weight and 350 parts by weight of ethanol were added and sufficiently stirred and mixed to obtain a coating agent. This coating material is a 20 x 20 cm, 4 cm thick carbon fiber insulation (density
0.2 g / cm ³ ) of 20 g was applied to one side of the board, and then the same treatment as in Comparative Example 1 was performed to obtain a heat insulating material having a dense graphite coating film. This heat insulating material is placed in a large-scale graphitizing furnace for carbon material production using induction heating, and is repeatedly operated at 1700 to 2400 ° C in an argon atmosphere until the coating film disappears and the heat insulating material surface appears. The number of times was 49 times. The natural graphite powder used here was 40
The mixture was sieved with a 0-mesh (opening 37 μm, JIS) sieve to obtain an 84% sieve. When the particle size distribution of the 16% under the sieve was examined by the sedimentation separation method, 9% of the total natural graphite powder was analyzed.
% Was less than 20 μm.

Example 2 The coating agent was the same as in Comparative Example 2 except that the natural graphite powder used in Comparative Example 2 was sieved with a 400-mesh (opening 37 μm, JIS standard) sieve, and only the natural graphite powder was used on the screen. Was prepared. This coating agent was applied to a carbon fiber insulation board under the same conditions as in Comparative Example 2, carbonized and graphitized, and placed in a large graphitizing furnace together with the coating insulation material produced in Comparative Example 2, and the number of operations required It was 78 times when it was examined whether the coating film had disappeared and the surface of the heat insulating material appeared.

(Effect of the Invention) A dense graphitic film obtained by applying, carbonizing, and graphitizing the coating agent of the present invention has a remarkably improved durability as compared with that obtained from a conventional coating agent, and is useful for insulating materials. It makes a significant contribution to extending the time to exchange.

Claims (2)

(57) [Claims] 1. A coating material for a carbonaceous molded heat insulating material comprising a carbonizable polymer compound, a solvent of the carbonizable polymer compound and graphite powder, wherein the graphite powder has an ash content of 2% or less in the form of a natural or artificial soil. A highly durable coating material for carbonaceous molded heat insulating material, which is graphite and is a graphite powder having a particle diameter of substantially 20 μm or more. 2. The coating agent according to claim 1, wherein the carbonizable polymer compound is a resol type phenol resin.