JPH0617277B2 - Heat resistant ceramic sheet - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat-resistant ceramic sheet used by being applied to a heating surface such as a heating tube or a heating plate.

(Prior Art) Conventionally, a heat-resistant sheet of a formula formed by compounding and molding inorganic fibers made of ceramic fibers and glass fibers having a fiber diameter of 1 μm or more, natural or synthetic fibers, and an organic binder has been disclosed in patent publications. . Further, there is also known an inorganic heat-resistant ceramic sheet of a type in which inorganic fibers made of ceramic fibers and glass fibers having a fiber diameter of 1 μm or more are bound with an organic binder without blending natural or synthetic fibers.

(Problems to be Solved by the Invention) The heat-resistant sheet of the type in which the fibers are bound to each other by the above-mentioned known organic binder is convenient to obtain as a thin and tough sheet of 5 mm or less, but it has a relatively high tensile strength. , Mechanical strength such as folding endurance is small, the organic binder is burned down in the process of use due to heating and heating, the strength at that time is significantly reduced, the entire sheet becomes brittle, and a little vibration or It causes cracks, defects, and drops due to impact, and it is not suitable for use as a heat-resistant sheet mainly composed of ceramic fiber, which is originally high heat resistance, at a low temperature of about 500 to 600 ° C. Have inconvenience.

(Means for Solving Problems) The present invention provides a relatively small improvement in mechanical strength at room temperature, which is a drawback of the conventional heat-resistant ceramic sheet, and at the same time, excellent mechanical strength even after the organic binder is burned out. Provided is a highly reliable heat-resistant ceramic sheet that can be maintained, wherein the inorganic heat-resistant ceramic sheet is a type in which inorganic fibers composed of ceramic fibers and glass fibers are bound with an organic binder, wherein the ceramic sheet has a fiber length of 10 to 15 mm
50-95% by weight of ceramic fiber, low-softening fiber that softens at 350-600 ° C, medium-softening fiber that softens at 600-800 ° C, 800
It consists of a mixture of at least a medium-softening fiber and 50 to 5% by weight of glass fiber of the highly-softening fiber among the highly-softening fiber softening at a temperature of not less than 0 ° C, and all or part of the glass fiber has a fiber diameter of 1 μm.
It is characterized by being composed of short fibers of m or less.

(Function) The above-mentioned heat-resistant ceramic sheet of the present invention has a function of binding the fibers with an organic binder and particularly a fiber diameter of 1 at room temperature.
Due to the good entanglement and binding of fine short fibers of μm or less and ceramic fibers, extremely high mechanical strength can be obtained.
When the thickness is 5 mm or less, a tough and thin paper-like ceramic sheet is provided.

Further, for example, when the pipe is wrapped around a heat pump and used for encapsulation, and the heating temperature of the pipe rises to 450 ° C. or higher and the organic binder is burned out, the fiber diameter is 1 μm or less, generally 0.5 μm or less. Since the entanglement and binding due to the short fibers having a small fiber diameter (the fiber length is about 1000 to 5000 times the fiber diameter) is extremely large, the sheet does not become brittle, and high mechanical strength can be maintained.

In this case, when the short fibers include low-softening fibers that soften at 350 to 600 ° C., they are softened at this temperature to further strengthen the entanglement with the ceramic fibers, and the machine at the time of burning out the organic binder. It also serves as a heat-resistant ceramic sheet with excellent stability, which brings about an increase in mechanical strength.

(Example) Next, the Example of this invention is described in full detail.

As the ceramic fiber, the composition ratio of Al ₂ O ₃ and SiO ₂ is selected according to the required heat resistance such as 47:53, 56:44, and the fiber diameter is 1 to 10 μm, average 3 μm, and fiber length. Ten
It is common to use the one having about 15 mm.

The glass fiber blended with this is made of soda glass, phosphate glass, borate glass, solder glass, soda lime silicate, alkali-free glass (E glass), quartz glass, etc. Use a fibrous material. The softening degree is in the range of about 350 ° C. to 1200 ° C. depending on the kind of the material, which is appropriately selected and used. In this case, according to the present invention, in particular, the fiber diameter is 1 μm.
The following thin glass short fibers make up all or part of the glass fibers incorporated in the ceramic fibers.

The short glass fiber has a fiber length of about 1000 to 5000 of the fiber diameter.
Those with doubles are commonly used. When one part of the glass fibers to be blended is composed of the glass short fibers, about 95 to 40% by weight of glass short fibers, a fiber diameter of 5 to 20 μm, and a fiber length of 5
A mixture of thick glass filaments of about 13 mm and about 5 to 60% by weight is used. By mixing these long fibers, the flexibility of the entire sheet is improved. Particularly, the fiber diameter is 7 to 9 μm and the fiber length is
When 40 to 60% by weight of 10 to 13 mm long fibers are mixed, it acts as a reinforcing core material for the entire sheet. As a glass fiber to be blended, a low softening fiber that softens at 350 to 600 ° C,
A mixture of three types of medium-softening fibers that soften at 600 to 800 ° C. and a high-softening fiber that softens at 800 ° C. or more, and a mixture of two types of medium-softening fibers and high-softening fibers are used. 350-6
Instead of the softening fiber at 00 ° C, a low-softening inorganic powder that softens at 350 to 600 ° C may be used. For example, when three kinds of low-softening fiber, medium-softening fiber and high-softening fiber are mixed, the blending ratio is 17% by weight, 50% by weight and 33% by weight, respectively, and the medium-softening fiber and the high-softening fiber are respectively. When two kinds of fibers are mixed, they are 67% by weight and 33% by weight, respectively. In this case, as the glass fibers, all of the short fibers are used, or one part of the short fibers is changed to the above long fibers up to about half the amount thereof. According to the present invention, in particular, by incorporating short fibers having a fiber diameter of 1 μm or less, for example, an average fiber diameter of 0.5 μm into ceramic fibers in an amount of about 5 to 50% by weight, the tensile strength and folding endurance of the entire ceramic sheet can be improved. , Conventional fiber diameter of 1 μm or more, usually 1 to 5 μm, average fiber diameter of 3
It was confirmed that the temperature can be significantly increased from room temperature to high temperature as compared with a ceramic sheet in which approximately the same amount of μm is mixed with the ceramic fiber. In this case, when a low-softening fiber that softens at 350 to 600 ° C. is included when the organic binder burns out, the fiber is softened and the entangled binding with the ceramic fiber is further strengthened to secure a tough ceramic sheet. Therefore, it is possible to reliably prevent the conventional ceramic sheet from being fragile, cracked, or dropped due to burning of the organic binder. When the ceramic sheet is heated to 600 ℃ or more during use, it should be treated with medium softened fiber of 600 to 800 ℃ and 800 ℃ to 1 ℃.
Since the binding to the ceramic fibers is increased by softening the softening fibers at 200 ° C. respectively, it is advantageous to provide a ceramic sheet having further increased mechanical strength.

The compounding ratio of the glass fiber to the ceramic fiber can be approximately equal to the ceramic fiber, that is, up to about 50% by weight. If the content is higher than this, the properties as a highly heat-resistant ceramic sheet at 1000 ° C or higher, that is, the heat resistance deteriorates.

In particular, when obtaining a very thin, tough and flexible ceramic paper of 0.5 mm or less, the glass fiber content is 20
A range of up to 30% by weight is preferred.

The organic binder is added to these inorganic fibers in an amount of 5% by weight. Addition of 5% by weight or more increases the strength of the sheet at room temperature, but especially for sheets with a thickness of 0.5 mm or less, the strength at a temperature of 600 ° C or higher after the organic binder is burned off is drastically reduced and Causes problems.

In addition, it is desirable to add the organic binder in an amount of 5% by weight or less in consideration of the relationship that harmful gas is generated when burned out. As the organic binder, phenol resin,
A commonly used one such as a thermosetting resin such as a urea resin is selected and used.

The ceramic sheet is preferably manufactured by a wet method using a paper machine. That is, the above-mentioned ceramic fibers and a maximum of approximately the same amount of thin glass short fibers having a fiber diameter of 1 μm or less alone or a mixed glass fiber in which, for example, the glass short fibers and thick glass long fibers are mixed in a ratio of 60:40. An organic binder of 5% by weight or less with respect to these fibers was well disintegrated and mixed with a pulper, and then the paper was made into a predetermined thickness by means of a cylinder paper machine, dehydrated and fitted, and a ceramic having a thickness of 5 mm or less. Get the papermaking. In particular, in order to create a thickness of 0.5 mm or less, short fibers having a fiber diameter of 0.4 to 0.6 μm alone or 60 to 40% by weight of the short fibers and 40 to 60% by weight of long fibers having a fiber diameter of 6 to 9 μm are mixed. In this case, the organic binder is 5 for the ceramic fiber and the glass fiber.
Generally, even if not added by weight, 2-3% by weight,
It is advantageous that a ceramic sheet having a sufficiently large mechanical strength can be obtained from room temperature to high temperature, and in this case, the degree of decrease in strength due to burning of the organic binder is reduced and the generation of harmful gas is also reduced. When the amount of the organic binder is reduced, it is preferable to increase the mixing amount of the short fibers of the present invention accordingly and prevent the reduction of the sheet strength at room temperature or when the organic binder is burned out.

Next, more specific examples will be described in detail together with comparative examples.

Example 1 Ceramic fiber (Al ₂ O ₃ : SiO ₂ = 56: 44, softening point 1400
C)) with an average fiber diameter of 0.5 μm, a fiber length of 2.5 mm, and a softening point of about 650 ° C., 20 parts by weight of glass short fibers, and a softening point of about 1100 ° C. with a softening point of about 1100 ° C. 2 parts by weight of the thermosetting resin binder with respect to the total amount of the ceramic fiber and the glass fiber are added to the mixture of 1 part by weight and the mixture is disintegrated and mixed by a pulper, and the paper is dried and dried by a usual method.
A tough, flexible, paper-like ceramic sheet having a thickness of 0.5 mm was obtained.

The tensile strength of this ceramic sheet at room temperature is 2.2 kg / 2.
It has a width of 5 mm. This was placed in a heating furnace and heated to measure the strength at about 550 ° C. at which the organic binder was completely burned out, and the tensile strength of 1.5 kg / 25 mm width was maintained. After burning 800
It improved to 1.8kg / 25mm width at the time of ℃, and maintained 1.8Kg at the final heating time of 1.200 ℃. For comparison, all the short fibers of Example 1 were replaced with all-quality glass fibers having an average fiber diameter of 3 μm, that is, 30 parts by weight were compounded.
When a ceramic sheet was prepared in the same manner as above, the tensile strength at room temperature was only 0.8 kg / 25 mm width. When this was placed in a heating furnace and tested for heat resistance, the strength when the organic binder was completely burned down fell below 0.1 Kg / 25 mm width, weakened, and damaged and cracked just by touching with a finger. Occurred.

Example 2 In Example 1, except that 20 parts by weight of glass short fibers having a softening point of about 650 ° C. was mixed in an amount of 15 parts by weight, and 5 parts by weight of a low-softening glass fiber that was softened at 400 to 500 ° C. was mixed. A ceramic sheet was prepared in the same manner as in Example 1. As a result, when the tensile strength was measured, the tensile strength at room temperature was 2.2 kg / 25 mm as in Example 1. When a heat resistance test was conducted by heating the same in the same manner as described above, the strength was 2 Kg / 25 mm width, which was larger than that of Example 1, at about 550 ° C. when the organic binder was completely burned out. 800 ℃ after that, 1
The strength at 200 ° C maintained 1.8 kg / mm25 width and 1.8 kg / mm25 width, respectively.

When the folding endurance of Examples 1 and 2 was measured at room temperature,
They had 9 times / 100g and 10 times / 100g, respectively.

Example 3 Instead of 10 parts by weight of glass short fibers having a softening point of 1100 ° C., a softening point
10 long glass fibers with a fiber diameter of 7 μm and a fiber length of 10 mm at 840 ° C
A ceramic sheet was prepared in the same manner as in Example 1 except that the parts by weight were compounded.

The tensile strength was 1.8, 1.1, 1.4 and 1.4 kg / 25 mm width at room temperature, 500 ° C, 800 ° C, 1000 ° C and 1200 ° C, respectively, and the folding endurance was improved to 12 times / 100g.

(Effect of the Invention) As described above, according to the present invention, the ceramic fiber 50 to
95% by weight consists of low-softening fibers, medium-softening fibers, high-softening fibers at least medium-softening fibers and high-softening fibers,
Glass short fibers having a fiber diameter of 1 μm or less alone or 50 to 5% by weight of glass fibers mixed with the glass short fibers and glass long fibers are mixed, a small amount of an organic binder is mixed with these inorganic fibers, and a ceramic sheet is produced by papermaking or the like. In particular, the mechanical strength of the sheet can be significantly increased at room temperature or when the organic binder is burned out, and even when it is wound around a heat pipe or the like, it is 1 μm or more and usually 1 to 5 μm as a conventional glass fiber. As in the case of an organic binder binding-type ceramic sheet containing a range of fiber diameters, there is no risk of cracking, dropping, or destruction of the sheet due to weakening when the organic binder is burned, and slight vibration or impact. It is possible to improve the practicability as a heat-resistant ceramic sheet with good stability, and in particular, we propose heat-resistant ceramic paper with a wall thickness of 0.5 mm or less. It has the effect of being able to serve.

Claims (4)

[Claims] 1. An inorganic heat-resistant ceramic sheet of the formula in which inorganic fibers composed of ceramic fibers and glass fibers are bound with an organic binder, wherein the ceramic sheet has a fiber length.
10 ~ 15mm ceramic fiber 50 ~ 95wt% and 350 ~ 600 ℃
Low softening fiber that softens at 600 ° C, medium softening fiber that softens at 600 to 800 ° C, high softening fiber that softens at 800 ° C or higher, and at least medium softening fiber, and glass fiber of 50% to 5% by weight of highly softening fiber And a heat-resistant ceramic sheet characterized in that all or part of the glass fiber is composed of short fibers having a fiber diameter of 1 μm or less. 2. A ceramic fiber and an organic binder of 5% by weight or less based on the total amount of the glass fiber are mixed to have a thickness of 5 mm.
The heat-resistant ceramic sheet according to claim 1, which is formed into the following sheet. 3. The heat-resistant ceramic sheet according to claim 1, wherein the glass fibers are all short fibers having a fiber diameter of 1 μm or less and a fiber length of 0.1 to 5 mm. 4. The glass fiber comprises about 95 to 40% by weight of short fibers having a fiber diameter of 1 μm or less and a fiber length of 0.1 to 5 mm, and a fiber diameter of 5.
A heat-resistant ceramic sheet according to claim 1, which is composed of about 5 to 60% by weight of long fibers having a fiber length of -20 µm and a fiber length of 5 to 13 mm.