WO2003072876A1

WO2003072876A1 - Ceramic fiber aggregate

Info

Publication number: WO2003072876A1
Application number: PCT/JP2003/002129
Authority: WO
Inventors: Mamoru Shoji; Toshiaki Sasaki; Toshio Ito; Naoyuki Kagawa
Original assignee: Mitsubishi Chemical Functional Products, Inc.
Priority date: 2002-02-27
Filing date: 2003-02-26
Publication date: 2003-09-04

Abstract

A ceramic fiber aggregate, characterized in that it has a fiber bulkiness in the state of being dispersed in water of 140 ml/g or more and it contains shots, which mean non-fibrous particles, having a particle diameter of 45 μm or more in a content of 20 wt %. The ceramic fiber aggregate is considerably removed of shots, which are contained in a great content in a conventional ceramic fiber aggregate, while maintaining an appropriate fiber length, and thus can be suitably used for a heat-resistant packing, cushioning material and the like.

Description

Description Ceramic fiber aggregate Technical field

The present invention relates to a ceramic fiber assembly. Background art

The ceramic fiber aggregate is usually melted in a melting furnace at a temperature close to 2000 ° C at a temperature of around 2000 ° C (melting method), and then centrifuged by a rotating plate or compressed air. It is manufactured by a method that converts into fibers by cooling at once.

The ceramic fiber aggregate obtained by the melting method as described above contains a large amount of unfibrillated particles during spinning. I Dog (hereinafter referred to as shot), and its proportion is usually 50% by weight. Reach. In addition, the fiber structure becomes an amorphous amorphous glass structure because it is rapidly cooled from a molten state during fiberization. Such a ceramic fiber aggregate is inexpensive, but is inferior to a crystalline alumina fiber in heat resistance ⁵ ′, and is further reduced in performance by a large amount of shot.

By the way, there has been a description of the shot content in ceramic fibers, but the relationship between the shot content and the fiber properties has not been clarified yet. Disclosure of the invention

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a novel ceramic fiber aggregate that maintains high fiber properties and has a short shot content power of ⁵ ′.

That is, the gist of the present invention is an aggregate of ceramic fibers, is water-dispersible fiber維嵩height is 1 4 0 m 1 / g Shiyotto content and above particle diameter 4 5 _lambda m above 20% by weight or less in the ceramic fiber aggregate.

Hereinafter, the present invention will be described in detail. The ceramic fiber aggregate of the present invention is obtained by a melting method and contains alumina and silica as main components. That is, the ceramic fiber aggregate of the present invention is basically manufactured as a fiber aggregate by the above-described known melting method.

The fact that the above-mentioned alumina and silica are the main components means that their content is 80% by weight or more. That is, the ceramic fiber of the present invention in order to enhance heat resistance, a small amount of _{_{C r 2 0 3, Z r}} 0 2 or the like may be added.

The ceramic fiber aggregate of the present invention has a bulk in water of 140 m 1 / g or more and a shot content of 45 μm or more in particle diameter of 20% by weight or less. Characterized.

The value of the “bulk height of the dispersion fiber in water” described above means a value measured by the following method. That is, 3 g of ceramic fiber is refined, put into a 1 L mesis cylinder (a commercially available standard product) having a diameter of 65.5 mm, and further added with 1 L of water and sufficiently sealed to obtain a fiber. After dispersing the mixture, the mixture is allowed to stand for 30 minutes and the bulk of the precipitated fiber is measured. The value obtained by converting the bulk of the obtained fiber per unit g was defined as the bulk height of the fiber dispersed in water. The lower the value of the bulk of the dispersed fibers in water, the shorter the fibers constituting the ceramic fiber aggregate.

The content of the “shot having a particle diameter of 45 μm or more” described above means a value measured by a method in accordance with JISR-3331.

The ceramic fiber aggregate of the present invention is obtained, for example, by a melting method, and has alumina and silica as main components and an alumina-silicon weight ratio of usually 30:70 to 60:40. It can be obtained by subjecting an aggregate of ceramic fibers to a wet defibration and then performing a de-shot process.

Commercially available ceramic fiber aggregates that can be subjected to the above-mentioned reforming treatment include, for example, “SC-126 Bulk” manufactured by Shin Nikka Thermal Ceramics Co., Ltd., and Toshiba Monoflux Co., Ltd. "Fiber Excel Bulk Fiber" “Isowool 126 Bulk” manufactured by Solyte Industries Co., Ltd., and “j Bulk” manufactured by Ibiden Co., Ltd.

The above commercial products have shots with an alumina / silica weight ratio of approximately 50:50, an average fiber diameter of 2-3 m, and a size of 45 ^ 111 or more according to JISR-3311. The amount is usually of the order of 50% by weight.

In addition, typical product forms of the above-mentioned commercial products include blanket and balta, but balta is preferable. In the case of a blanket, the fibers may become entangled by a heat treatment called needle punching or squeezing, and the wet defibration may not be performed sufficiently. However, it may be difficult to satisfy the physical properties specified in the present invention.

In general, commercially available ceramic fiber aggregates have a smoothing agent (hereinafter referred to as an oil agent) added to the fiber surface. Its purpose is to prevent dust from fibers and maintain the texture. Furthermore, in the case of blankets, it is added as a lubricant for punch needles during needle punching. Such an oil agent is added to the entire fiber at the stage of melt spinning. Therefore, a general blanket does not remain because the fiber is hardened by heat treatment after needle punching, but remains in the case of bulk. As the oil agent, a hydrophilic nonionic surfactant or a non-hydrophilic cationic surfactant is mainly used.

However, the above-mentioned oils have an adverse effect on the dispersibility of the fibers during wet unraveling. That is, when the oil agent is non-hydrophilic, the fibers repel water and are hardly dispersed in water. If the oil agent is hydrophilic, it foams in and further, the fibers and shots are dispersed in water, making shot separation difficult.

Therefore, in a preferred embodiment of the present invention, the ceramic fiber aggregate to be subjected to the above-described modification treatment is degreased before wet defibration. The degreasing treatment is usually performed by heat treatment at 400 to 600 ° C. If the heat treatment temperature is lower than 400 ° C, the removal of the “oil” in the fiber becomes insufficient, and if it exceeds 600 ° C, there are problems such as thermal deterioration and fusion of the fiber. Failure occurs during defibration (dispersion of fibers) Wet defibration, no. It can be carried out using a device commercially available under the name of a refiner, a stirrer, a mixer, or the like for a loop. At this time, the ratio of the fiber to water is usually 0.5 to 3% by weight, preferably 1 to 2% by weight. If the fiber concentration in the water is too high, the fibers will become entangled with each other and the dispersion of the fibers will not be successful, requiring long-term dispersion. As a result, there is a problem that the fiber length is shortened more than necessary. In addition, productivity force when the fiber concentration in the water is too ^low? Deteriorate.

Other defibration conditions are determined by the equipment used, the shot content in the resulting fiber, the yield of the fiber, the fiber length, and the like. That is, wet defibration is performed for de-short processing. In short, the separation of shots from the fibers requires that the fibers be crushed and shortened to some extent, resulting in a fiber length that is too short and conversely degrades the physical properties. Accordingly, in the present invention, the ceramic fiber aggregate is dissolved so that the bulk of the fibers dispersed in water is at least 140 ml / g and the content of the shot having a particle diameter of at least 45 μm is at most 20% by weight. The fiber conditions are appropriately selected.

The bulk of the dispersion fiber in water is preferably 200 ml / g or more, and the upper limit is not particularly limited, but it is considered that it can be up to about 700 m1 / g. On the other hand, the content of the shot having a particle diameter of 45 μm or more is preferably 10% by weight or less. The lower limit is not particularly limited, but is usually about 5% by weight because excessive de-shot processing increases the possibility of shortening the fiber length more than necessary.

In the de-short treatment, the shot 1 is removed from the unraveled fiber by sedimentation in water. As a separation method, a liquid cyclone, a separation method using a floating sedimentation tank, or the like can be used. In this case, the fiber concentration in the water is usually in the range of 1 to 2% by weight, preferably 0.2 to 1% by weight. If the fiber concentration is too high, shots separated from the fibers by dispersion and defibration will be mixed with the fibers and difficult to separate. What are the separation conditions? It is determined by the equipment used, the content of the shot in the fiber obtained, the yield of the fiber, and the like. The ceramic fiber aggregate modified as described above needs to be dried depending on the application. In that case, it may be dried to a suitably determined moisture content. The ceramic fiber aggregate of the present invention may be subjected to a firing treatment. The firing conditions vary depending on the type of fiber used, the type of heat treatment furnace, etc., but usually, mullite crystals are generated in the fiber at 900 to 1200 ° C (preferably 950 to 1100 ° C). The temperature is usually 5 to 5 hours (preferably about 1 hour). In the present invention, the size of the mrit crystal is measured by the Wi-son method based on X-ray diffraction, and calcined so that this value is usually 30 OA or less, preferably 20 OA or less, and more preferably 50 to 15 OA. To process.

It is preferable that the above-mentioned baking process is performed after the de-shot process. Further, in the present invention, the sheet can be processed before the firing treatment. Such sheet processing can be performed by a method in which the ceramic fiber aggregate after the de-shock treatment is processed by a paper machine, a vacuum molding machine, or the like. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to the following examples unless it exceeds the gist of the present invention. The evaluation method and the aggregate of ceramic fibers used in the following examples are as follows. The ceramic fiber aggregate was heat-treated at 600 ° C for 1 hour to remove the oil attached to the fiber surface before use.

(1) Method of preparing mat test piece by papermaking:

After dispersing the ceramic fiber 8. 3 g (0. 8 wt ^_0/0) of water 1 L, poured into the cylinder of 90 mm diameter having a net bottom, gradually withdrawn water, the lower part net The fibers were uniformly deposited on the fibers. Next, the mat was taken out from the lower net and dried at 110 ° C for 1 hour to prepare a paper-made mat having a unit area of 1300 gZm ² .

(2) Wind erosion test: The paper-cut mat was cut into 3 OmmX 5 Omm and sandwiched between two metal plates through a 5-mm spacer. Next, an air nozzle with a 5 mm hole at the tip was placed at a distance of 5 mm from the end face of the mat in the width direction (3 Omm direction). From Eanozu Le compressed air 3 kg / cm ² to the mat edge "blowing 0.5 seconds" given to 30 minutes pulsed at intervals of "stop 1.0 sec", the width direction (30 fibers eroding (in the direction of mm). Fibers that are excessively cut, shortened, and easily eroded are not suitable for heat-resistant packing and cushioning applications.

(3) Surface pressure measurement:

5 OmmX The paper mat is cut to 5 Omm, and it is applied to a compression tester (Shimadzu “IS-500”) and compressed at a compression speed of 1 mm / min. The compression density (gZc m ³ ) and the compression load (Kg). The load per unit area (kg / cm ² ) was determined by dividing the compressive load by the mat area, and the relationship between the compressive density (g / cm ³ ) and the load (kg / cm ² ) was determined. Mats that provide high surface pressure have excellent resilience and are suitable for applications such as heat-resistant packing and cushioning materials. In the case of a papermaking mat using the ceramic fiber aggregate of the present invention, the surface pressure as described above is usually about 6 kg / cm ² or more, and up to about 12 kgZ cm ² can be expected as the upper limit.

(4) Mullite crystal particle size measurement method: Measured under the conditions described in Table 1 below.

table 1

Measuring device: "RAD-2C type (software RINT2000 series)" manufactured by Rigaku Corporation Reference material: NIST Alpha Quartz

Measurement angle of reference material: 26.6, 36.5, 39.4, 40.3, 42.4

45. 8 (6 peaks)

Sample measurement angle: 26.3, 31.0, 33.3 35.3, 40.9,

42.6, 53.5, 57.6 60.7 (9 peaks) X-ray: CuK «Z40KV. ¹ 40mA, monochromator

Divergent slit (DS) / scattering slit (SS): each l d e g.

Receiving slit (R S): 0.15mm

Operation mode (FT): 0.6 sec.

Step width: 0.01 °

Measurement method: Wi 1 s 0 n method

(5) TMA (thermo-mechanical analysis) measures the thickness reduction rate of the load condition by way: papermaking mat cut into small pieces, but such gives a constant load of 1 kg / cm ² in TMA al, from a stable point, 10 ° The temperature was raised to 1 130 ° C at C / min and maintained for 9 Q minutes. Under these conditions, the amount of reduction (AL) relative to the initial thickness (L) was determined, and the reduction rate (%) was measured using AL / LX100. A mat with a small reduction rate has good durability at high temperatures, and is suitable for heat resistance, heat sink, and cushioning. In the case of a papermaking mat using the ceramic aggregate of the present invention, the above reduction rate is usually 40% or less, preferably 30% or less, and the lower limit can be expected to about 15%. Table 2

Examples and comparative examples

40 g of a test fiber aggregate ((F) in Table 2) was added to 4.0 L of water and dispersed to form a 1% by weight slurry, and the slurry was mixed with a commercially available mixer (Model 34BL22 manufactured by Waring Co.) to 7800 The dispersion was further dispersed by rpm and dispersed for 2 minutes.

Then, the mixture was transferred to a 10 L beaker, and a commercially available stirrer (“Model Z-1200”, manufactured by Tokyo Rika Kikai Co., Ltd., equipped with 6 vertical stirring blades of 10 Oiran) was stirred at 75 rpm and dispersed for 15 minutes. After that, 20 LZ min. Of running water was given with stirring to overflow, and the fiber content was recovered to obtain a fiber aggregate. In addition, various fiber aggregates were obtained by changing the rotation speed of the mixer and the dispersion concentration of the fibers. Each of the obtained fiber aggregates was evaluated as described above. Table 3 shows the evaluation results. Table 3

(*: Wet defibration (without de-shot processing)) As shown in Table 3, the results of the compression surface pressure and wind erosion test of the ceramic fiber aggregate of the present invention shown in each example were superior to those of the alumina fiber aggregate shown in Reference Examples 1 and 2. I understand.

Test example 1

The fiber assembly (papermaking mat) obtained in Example 3 above was subjected to a heat treatment to test the high temperature properties. Table 4 shows the results. Mullite crystal grains were detected in the paper-made mat that had been heat-treated above 950 ° C, and the heat resistance by TMA was greatly improved. In particular, in the case of a paper-made mat having a crystal grain size of 15 OA or less, the fiber did not deteriorate due to the heat treatment, and a high surface pressure could be maintained.

Table 4

Industrial applicability

According to the present invention, a short fiber contained in a large amount of fibers while maintaining an appropriate fiber length is provided. By removing the fibers, it is possible to obtain a ceramic fiber aggregate having significantly improved physical properties. Such a ceramic fiber aggregate is relatively inexpensive and, moreover, covers an intermediate temperature region between alumina fiber and ceramic fiber, so that it is suitable for applications such as heat-resistant packing and cushioning materials. As a specific example of such a use, a gripping material for a catalytic converter of a vehicle exhaust gas purification device is exemplified.

Claims

The scope of the claims

1. An aggregate of ceramic fibers having a bulk in water dispersed fiber of at least 140 m 1 g and a particle diameter of 45; Characteristic ceramic fiber aggregate.

2. The aggregate according to 1, wherein the mullite crystal particle size of the ceramic fiber is 200 A or less.

3. The aggregate according to 1, wherein the bulk of the fibers dispersed in water is 200 m 1 / g or more.

4. The aggregate according to 1, wherein the content of the shot having a particle size of more than 45 m is 10% by weight or less.

5. The aggregate according to 1, wherein the content of alumina and silica in the ceramic fiber is 80% by weight or more, and the weight ratio of alumina to silica is 30:70 to 60:40.

6. The aggregate according to 1, obtained by subjecting the aggregate of ceramic fibers to wet defibration and then performing a deshort treatment.

7. The aggregate according to 6, wherein the aggregate of ceramic fibers is degreased before wet defibration.

8. The aggregate according to 6, wherein the aggregate of ceramic fibers is subjected to a baking treatment.

9. The aggregate according to 8, wherein the ceramic fiber aggregate is fired after the de-shot processing.

10. The aggregate according to item 8, wherein the aggregate of ceramic fibers is subjected to sheet processing before firing.

11. The assembly according to 8, wherein the firing temperature is 900 to 1200 ° C.