JP2017057112A - Surface-treated molded heat insulator and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a long-life molded heat insulator at a low cost, which could be suppressed from deterioration and powdering.SOLUTION: Provided is a method for producing a surface-treated molded heat insulator, comprising: an immersion step where at least one surface of a molded heat insulator, having a fiber felt interlaced with carbon fibers and a protective carbon layer comprising a carbonaceous material which coats surfaces of the carbon fibers in the fiber felt, is immersed in a solution of a surface coating agent comprising a synthetic resin which is carbonized by a heat treatment and a solvent which dissolves the synthetic resin to add the surface coating agent-containing solution to the molded heat insulator; and a heat treatment step where, after the immersion step, the molded heat insulator is heat treated at 1500 to 2500°C under an inert atmosphere to form a surface coating layer by carbonizing the synthetic resin.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a molded heat insulating material, and more particularly to a molded heat insulating material that has been surface-treated with a surface coating agent.

  Carbon fiber-based heat insulating materials are used in various applications because they are excellent in thermal stability and heat insulating performance and are lightweight. In particular, carbon fiber molded heat insulating material, which is carbonized by impregnating carbon fiber felt with a resin material, is excellent in shape stability and can be finely processed. Therefore, single crystal silicon pulling device, polycrystalline silicon cast furnace, metal It is used as a heat insulating material for high temperature furnaces such as ceramic sintering furnaces and vacuum evaporation furnaces.

  Since such a molded heat insulating material uses thin carbon fibers having a diameter of about 5 to 20 μm, there is a risk that the carbon fibers may be lost or powdered (dust generation) during handling or installation. If the powdered carbon fiber is released into the furnace atmosphere, the product quality may be reduced.

  Further, in a manufacturing apparatus such as single crystal or polycrystalline silicon, SiO gas is generated in a high temperature furnace, or oxygen gas is mixed as impurity gas into the manufacturing atmosphere. SiO gas and oxygen gas are highly active (reactive), and SiC is produced when the carbon fiber molded heat insulating material reacts with the SiO gas, and when the carbon fiber molded heat insulating material reacts with the oxygen gas, carbon monoxide and carbon dioxide are reacted. Carbon oxides such as carbon are produced. By these reactions, the skeletal structure composed of the carbon fibers is broken, and as a result, the heat insulating function obtained by the skeleton structure forming a large number of spaces is lowered. In addition, this deterioration particularly causes carbon fibers to be pulverized and released into the furnace atmosphere, resulting in a reduction in product quality.

  In order to solve the above problem, Patent Document 1 proposes a surface treatment technique of a molded heat insulating material that prevents the generation and deterioration of carbon fiber.

JP 2005-133033 A

The technique of Patent Document 1 is (1) a carbonized material having a carbonization rate of 40% or more, (2) scaly graphite, (3) a sticking agent, and (4) a sticking agent, and the carbonized material is dispersed or dissolved. It is a technique related to a laminate formed by applying a carbonization to the surface of a coating agent for a heat insulating material comprising a liquid agent and a carbonized molded product having a bulk density of 0.1 to 0.8 g / cm ³ and carbonizing the heat insulating coating agent. is there.

  In this technology, the carbonized material of scaly graphite (scaled graphite) or adhesive (binder) protects the carbon fiber during friction, so that powdering during handling can be suppressed, and the scaly graphite or carbonized material is carbon fiber. Since it reacts with the active gas prior to this, it is said that the deterioration of the carbon fiber can be suppressed, and thereby the deterioration of the heat insulation performance can be suppressed.

  When the present inventors diligently examined the technique according to Patent Document 1, it was found that there are the following problems.

  Scalar graphite has a highly developed graphite structure (layer structure), has a larger specific surface area than amorphous carbon, and is particularly susceptible to reaction with active gas at its edge, so that scaly graphite is oxidized unevenly. May be pulverized.

  In addition, scaly graphite contains ash due to its nature, but if this ash is mixed in the furnace, it may cause a side reaction that lowers the product performance.

  Furthermore, the coating of the coating agent containing the graphite particles has a problem that productivity is lowered because it takes time and effort.

  This invention is made | formed in order to solve said subject, and it aims at providing the surface treatment shaping | molding heat insulating material which can suppress deterioration and powdering with high productivity.

The present invention according to a method for manufacturing a molded heat insulating material for solving the above-described problems is configured as follows.
A synthetic resin that carbonizes by heat treatment at least one surface of a molded heat insulating material having a fiber felt entangled with carbon fibers and a carbonaceous protective carbon layer covering the carbon fiber surface of the fiber felt and the synthetic resin A dipping step of adding the surface coating solution to the molded heat insulating material, and after the dipping step, the molded heat insulating material is heated at 1500 to 2500 ° C. in an inert atmosphere. And a heat treatment step of carbonizing the synthetic resin to form a surface coating layer.

  When the molded heat insulating material is immersed in the surface coating solution, the surface coating solution penetrates into the surface of the carbon fiber or protective carbon layer constituting the molded heat insulating material or the gap between the carbon fibers, and the surface coating material is formed into the molded heat insulating material. The solution is added. Thereafter, when heat treatment is performed in an inert atmosphere, the synthetic resin dissolved in the surface coating solution is carbonized and remains on the surface of the carbon fiber or the protective carbon layer and in the space between the carbon fibers, and the solvent is volatilized. By these steps, a surface coating layer made of a synthetic resin-derived carbonaceous material is formed on the surface of the carbon fiber, etc., but this layer does not contain granular components such as graphite particles, Effectively suppresses the deterioration of the molded insulation due to the atmospheric gas.

  The surface coating agent is composed of a synthetic resin and a solvent, and does not contain other components (for example, granular components such as graphite particles). For this reason, although the method of immersing a shaping | molding heat insulating material in a surface treating agent solution can be used for the addition of a surface coating agent, this method does not take time and is excellent in productivity rather than application | coating. Further, the particulate component does not remain in the surface coating layer of the molded heat insulating material to be manufactured, and the above-described problems due to the graphite particles do not occur.

  As explained above, by adopting the above manufacturing method, it is a simple method that does not require a complicated process such as coating, and a high-quality surface coating that can suppress powder fall and deterioration due to active gas A molded heat insulating material having a layer formed thereon can be produced.

  What is necessary is just to select suitably according to the use to be used, and the number of the surface of the shaping | molding heat insulating material immersed in a surface coating material solution can be made into 1 or 2 or the whole surface.

  The synthetic resin is not particularly limited, and synthetic resins that can be dissolved in a solvent and carbonized by heat treatment can be widely used. Among these, it is preferable to use polyimide. Here, when a thermosetting resin such as polyimide is used as the synthetic resin, it is preferable to perform thermosetting of the thermosetting resin soaked in the molded heat insulating material between the heat treatment step and the immersion step.

  Here, the polyimide in the present specification means a compound that has already been imidized, and does not mean a compound before imidization such as carboxylic acid dianhydride or diamine.

  Further, the volatilization of the solvent may be performed simultaneously with the heat curing or carbonization, and a step of volatilizing the solvent may be separately provided before these steps.

The viscosity of the surface coating solution is preferably 0.1 to 1 Pa · s because it easily penetrates into the voids of the molded heat insulating material and easily forms a good surface coating layer. Here, the viscosity of the surface coating solution means a value at 25 ° C. and 1 atm (1.013 × 10 ⁵ Pa).

The present invention relating to a molded heat insulating material that has been subjected to a surface treatment for solving the above-described problems is configured as follows.
In a molded heat insulating material having a fiber felt entangled with carbon fibers and a protective carbon layer made of carbon that covers the carbon fiber surface of the fiber felt, the region in the vicinity of at least one surface of the molded heat insulating material A surface coating layer is provided which covers the carbon fiber surface and the protective carbon layer surface and fills a part of the gap between the carbon fibers, and the surface coating layer is made of carbonaceous material containing no particulate component. And

  In this configuration, the surface coating layer that covers the surface of the carbon fiber and the surface of the protective carbon layer and fills a part of the gap between the carbon fibers is composed of carbon fiber and carbon fiber by reacting with the active gas first. It is possible to suppress the deterioration of the protective carbon layer that maintains the skeleton structure.

The effect of the surface coating layer increases as the amount of the surface coating layer increases, but the cost increases as the amount of the surface coating layer increases. For this reason, the bulk density of the region where the surface coating layer is formed is preferably 0.02 to 0.07 g / cm ³ larger than the bulk density of the other region of the molded heat insulating material. more preferably to ~0.06g / cm ³ greater configuration, and even more preferably from 0.04~0.05g / cm ³ greater configuration. In addition, the thickness of the region where the surface coating layer is formed is preferably 1 to 20 mm, more preferably 3 to 15 mm, and still more preferably 5 to 10 mm.

  As described above, according to the present invention, it is possible to realize a carbon fiber molded heat insulating material that can suppress deterioration of heat insulating performance at low cost.

FIG. 1 is a photomicrograph of the region where the surface coating layer of the molded heat insulating material according to Example 1 was formed. FIG. 2 is a photomicrograph of the region where the surface coating layer of the molded heat insulating material according to Example 2 was formed. FIG. 3 is a photomicrograph of the region where the surface coating layer of the molded heat insulating material according to Example 3 was formed. FIG. 4 is a photomicrograph of the molded heat insulating material according to Comparative Example 1.

(Embodiment)
The molded heat insulating material according to the present embodiment includes a fiber felt entangled with carbon fibers and a protective carbon layer made of carbonaceous material that covers the surface of the carbon fibers of the fiber felt. And the surface coating layer which fills a part of space | gap between carbon fibers while covering the carbon fiber surface and the surface of a protective carbon layer is provided in the area | region of at least one surface vicinity of a shaping | molding heat insulating material. This surface coating layer is composed of carbonaceous material that does not contain particulate components.

  In addition, the shaping | molding heat insulating material before a surface coating layer is formed is not specifically limited, A commercially available shaping | molding heat insulating material can be used. For example, what is shown below can be used as a carbon fiber and protective carbon layer which comprise a shaping | molding heat insulating material.

  The carbon fiber constituting the molded heat insulating material is not particularly limited. For example, a single or a plurality of carbon fibers such as petroleum pitch-based, polyacrylonitrile (PAN) -based, rayon-based, phenol resin-based, and cellulose-based may be used. It can be used as a mixture of seeds. Among these, it is preferable to use carbon fibers (for example, isotropic coal pitch-based, isotropic petroleum pitch-based, rayon-based, phenol resin-based carbon fibers) that are not easily graphitized by heat treatment. Further, the microscopic structure of the carbon fiber is not particularly limited, and only carbon fibers having the same shape (contracted type, linear type, cross-sectional shape, etc.) may be used, or those having different structures are mixed. May be. However, the type of carbon fiber and its microscopic structure affect the physical properties of the molded heat insulating material to be manufactured, so it is preferable to select it appropriately according to the application.

  The protective carbon layer covers the entire surface of the carbon fiber or a part of the surface of the carbon fiber. The protective carbon layer may be carbonaceous (amorphous carbon or graphitic carbon), and the amorphous carbon may be either non-graphitizable or graphitizable. The compound from which the protective carbon layer is derived is not particularly limited, but it is preferable to use a carbonized resin material that can be impregnated into the fiber felt. Such a resin material is preferably a thermosetting resin such as a phenol resin, a furan resin, a polyimide resin, or an epoxy resin. Moreover, only 1 type may be used for a thermosetting resin, and 2 or more types may be mixed and used for it.

  The surface coating layer is not particularly limited as long as it is carbonaceous (amorphous carbon or graphitic carbon), but is a carbonized product of a polyimide resin that is difficult to foam during heat treatment and easily forms a surface coating layer. Is more preferable.

  The surface coating layer is formed on the molded heat insulating material as follows. The surface coating solution (not including carbonaceous particles) in which a synthetic resin (for example, polyimide) is dissolved in a solvent (for example, N-methyl-2-pyrrolidone) has a thickness of one surface of the molded heat insulating material. A region of 5 to 10 mm is immersed for about 5 to 30 seconds, and the surface coating solution is infiltrated into this region.

  After that, by heat-treating at 1000 to 2500 ° C. under an inert atmosphere to carbonize the synthetic resin, the surface coating layer made of the carbonized product of the synthetic resin becomes the surface of the carbon fiber, the surface of the protective carbon layer, and the carbon. It is formed in a part of the space between the fibers. Here, when the synthetic resin is a thermosetting resin, the thermosetting resin is thermally cured by heating to a temperature higher than the curing temperature of the thermosetting resin before carbonization. The solvent is volatilized and removed during heat treatment or thermosetting.

  Here, the carbonization referred to in this specification means a broad meaning including graphitization. For example, when heat treatment is performed at a temperature of 2000 ° C. or more, it is considered that the graphite structure of the surface coating layer is developed. In the present invention, the carbonaceous material constituting the surface coating layer is amorphous carbon, graphitic carbon. Either of these may be used.

  The invention is explained in more detail on the basis of examples.

Example 1
(Production of surface coating agent)
Surface coating agent solution by adding N-methyl-2-pyrrolidone as a solvent to polyimide Rika Coat SN-20 (viscosity 13.9 Pa · s) manufactured by Shin Nippon Rika Co., Ltd. so that the viscosity becomes 1 Pa · s. Was made. The viscosity of the surface coating solution was measured at 25 ° C. and 1 atm in accordance with JIS Z 8803.

A molded heat insulating material (DON-1000-H manufactured by Osaka Gas Chemical Co., Ltd., bulk density 0.16 g / cm ³ ) was cut into 100 mm (length) × 100 mm (width) × 40 mm (thickness). One surface of this molded heat insulating material was immersed in the surface coating solution for 10 seconds so that an area of 5 mm from the surface was immersed in the liquid, and then slowly pulled up.

  This surface coating agent-added molded heat insulating material is heat-treated at 500 ° C. for 1 hour under an inert atmosphere to thermally cure the polyimide resin and volatilize and remove N-methyl-2-pyrrolidone, and then 5 ° C. at 2000 ° C. under an inert atmosphere. The molded heat insulating material according to Example 1 was produced by heat treating for a time to carbonize the polyimide resin.

(Comparative Example 1)
Comparison was made by cutting a molded heat insulating material (Don-1000, manufactured by Osaka Gas Chemical Co., Ltd., bulk density 0.16 g / cm ³ ) into 100 mm (vertical) x 100 mm (horizontal) x 40 mm (thickness) without surface treatment The molded heat insulating material according to Example 1 was obtained.

(Powder falling test)
The molded heat insulating materials according to Example 1 and Comparative Example 1 produced as described above were cut into 10 cm squares to produce test pieces. Sandpaper # 500 was placed on the surface of this test piece, and a metal weight was placed on the sandpaper so that a load of 15 gf / cm ² was applied. After that, the sandpaper was pulled 10 cm at 2 cm / sec, and the weight change (reduction) before and after the test was measured. The weight change per 1 cm ² of the surface of the test piece was 0.023 mg in Example 1 and 0.047 mg in Comparative Example 1.

  The change in weight in the powder falling test is considered to be due to the pulverization and desorption (dust generation) of the constituent material of the molded heat insulating material due to the friction when pulling the sandpaper.

  From the above, it can be seen that dusting due to friction can be suppressed by performing the surface treatment.

(Example 2)
The molded heat insulating material according to Example 2 was obtained in the same manner as in Example 1 except that the addition amount of N-methyl-2-pyrrolidone was changed so that the viscosity of the surface coating solution was 0.1 Pa · s. Produced.

(Example 3)
A molded heat insulating material according to Example 3 was produced in the same manner as in Example 1 except that the addition amount of N-methyl-2-pyrrolidone was changed so that the viscosity of the surface coating solution was 10 Pa · s. .

  The mass before and after forming the surface coating layer of the molded heat insulating material according to Examples 1 to 3 was measured (2 points in each Example), and the amount of change in the bulk density of the region where the surface coating layer was formed (the coating amount by the surface coating material solution) ) Was calculated. The results are shown in Table 1 below. In Table 1 below, the numerical value outside the parentheses of the coating amount represents an average value, and the numerical value within the parentheses represents an actual measurement value.

  From Table 1 above, it can be seen that as the viscosity of the surface coating agent solution increases, the coating amount by the surface coating material solution tends to decrease. Moreover, in Example 3 with the largest viscosity, it turns out that the variation in a coating amount is large. From this result, it can be seen that the surface coating layer containing a sufficient amount of carbonaceous material can be stably formed as the viscosity of the surface coating solution decreases.

  The microscope picture of the area | region in which the surface coating layer of the shaping | molding heat insulating material which concerns on Examples 1-3 was formed is shown in FIGS. 1-3, and the microscope picture of the shaping | molding heat insulating material which concerns on the comparative example 1 is shown in FIG. Here, in FIG. 4 where the surface coating layer does not exist, a large number of fibers (carbon fibers) 1 exist while holding a large number of voids (voids between fibers), and the surface of the fibers 1 and the fibers 1. It turns out that the protective carbon layer 2 which covers the fiber 1 exists in the mutual contact vicinity. Further, the inside (back) fibers 1 and the protective carbon layer 2 can be seen from these gaps, and there are many areas that are voids to the back (areas where no fibers or the like exist in the in-focus range).

  On the other hand, in FIGS. 1 to 3 where the surface coating layer exists, the region that is a void to the back is greatly reduced as compared with FIG. 4, and instead the planar layer 3 that fills between the fibers is increased. I understand that. That is, it can be confirmed that the planar layer 3 is the surface coating layer 3 and the surface coating layer 3 covers the surface of the carbon fiber 1 or the protective carbon layer and fills a part of the gap between the fibers 1. . Moreover, it turns out that the planar layer 3 derived from the surface coating layer 3 is increasing as the coating amount of the surface coating layer increases. From the above, it is considered that as the viscosity of the surface coating solution decreases, the surface coating solution easily penetrates into the gaps between the fibers 1, so that the coating amount increases.

  As described above, according to the present invention, a long-life molded heat insulating material that can suppress deterioration and pulverization can be realized by a simple surface coating treatment, and therefore, its industrial applicability is great.

1 Carbon fiber (fiber)
2 Protective carbon layer 3 Surface coating layer (planar layer)

Claims (6)

A synthetic resin that carbonizes by heat treatment at least one surface of a molded heat insulating material having a fiber felt entangled with carbon fibers and a carbonaceous protective carbon layer covering the carbon fiber surface of the fiber felt and the synthetic resin Dipping in a surface coating solution comprising a solvent that dissolves, and adding the surface coating solution to the molded insulation,
After the immersion step, a heat treatment step of heat-treating the molded heat insulating material at 1500 to 2500 ° C. in an inert atmosphere, carbonizing the synthetic resin, and forming a surface coating layer;
A method for producing a surface-treated molded heat insulating material having The synthetic resin is polyimide,
The method further comprises a thermosetting step for thermosetting the polyimide after the dipping step and before the heat treatment step.
The manufacturing method of the shaping | molding heat insulating material of Claim 1 characterized by the above-mentioned. The viscosity of the surface coating agent solution is 0.1 to 1 Pa · s.
The manufacturing method of the shaping | molding heat insulating material of Claim 1 or 2 characterized by the above-mentioned. In a molded heat insulating material having a fiber felt entangled with carbon fibers, and a protective carbon layer made of carbon that covers the carbon fiber surface of the fiber felt,
In the region in the vicinity of at least one surface of the molded heat insulating material, a surface coating layer that covers the carbon fiber surface and the protective carbon layer surface and fills a part of the gap between the carbon fibers is provided,
The surface coating layer is made of carbonaceous material containing no particulate component,
A molded insulation characterized by that. The bulk density of the region where the surface coating layer is formed is 0.02 to 0.07 g / cm ³ larger than the bulk density of other regions of the molded heat insulating material,
The molded heat insulating material according to claim 4. The thickness of the region where the surface coating layer is formed is 1 to 20 mm.
The molded heat insulating material according to claim 4 or 5, characterized by the above.