JPH0788616B2 - Method for manufacturing inorganic fiber molded body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention has a high tensile strength suitable for a fireproof heat insulating material provided inside an industrial heating furnace or the like widely used in steel, ceramics, chemical plants and the like, This is a method for producing a high-bulk density inorganic fiber molded body.

[Conventional technology]

As a heat-resistant material for an industrial heating furnace, a molded product of an amorphous ceramic fiber containing 40 to 60% by weight of alumina (hereinafter referred to as "%") and 40 to 60% of silica and having a bulk density of 0.09 or more has been widely used. However, the maximum operating temperature of these ceramic fiber molded articles is 1200 ° C, and for use in industrial heating furnaces used at higher temperatures, 70-90% alumina in recent years,
So-called crystalline alumina fibers with 5-30% silica have been developed.

However, since the crystalline alumina fiber has weaker strength than the amorphous ceramic fiber, the needle punching method used for molding the ceramic fiber easily causes the fibers to be shattered, and it is difficult to obtain a strong molded product. Atsuta

For this reason, in the case of crystalline alumina fiber, after deflocculating the alumina fiber once in water, it is molded with an organic sizing agent such as cornstarch and an inorganic binder such as silica sol to form a felt, and a molded body with a bulk density of 0.09 or more. Was being manufactured. However, in this method, the length of the fiber is cut to a few mm during molding, so there is little entanglement between the fibers, and the tensile strength is 50 ~
In addition to the decrease to 100 g / cm ^2, there is a drawback that the manufacturing cost becomes high due to the wet process.

On the other hand, as an attempt to use the fiber in its original long state, a method of needle-punching an alumina fiber laminate with an organic non-woven fabric as a reinforcing material to obtain mats (JP-A-60-1104).
No. 39 gazette) has been proposed, but the phenomenon in which alumina fibers are shattered during needle punch molding also occurs, and when the organic nonwoven fabric is burned out at high temperature, the bulk density before firing is
Even with a molded body of 0.1, the density of the alumina fiber mat is significantly reduced, such as the bulk density being 0.06 or less, and the tensile strength is 50%.
It fell to ~ 100 g / cm ² and was not sufficient.

As a method for solving this drawback, JP-A-60-88162 and JP-A-60-252717 disclose a method of needle punching a precursor laminate of alumina fibers before firing, and then firing to obtain a blanket. Is proposed. This method is said to be capable of obtaining a blanket having higher strength than the conventional method. However, even in this method, in order to perform needle-punching, an expensive fiber treatment agent or a needle-punching machine is required, and when the needle is broken during the needle-punching treatment, metal needles are mixed in the product. Atsuta

[Problems to be solved by the invention]

As described above, it has been difficult to manufacture a mat-shaped molded product of crystalline alumina fibers having high heat resistance and high temperature strength without using an expensive fiber treating agent or a special device.

[Means for solving problems]

The present invention, by a firing treatment, a precursor fiber laminate obtained by spinning a viscous liquid obtained by adding a water-soluble organic polymer to a fiber composition aqueous solution that gives a metal oxide, has a steam pressure of 10 to 100 mmHg.
The method for producing an inorganic fiber molded body is characterized in that the inorganic fiber molded body is subjected to a humidification treatment at 1, then pressure-molded, and then fired at 1100-1400 ° C.

The present invention will be specifically described below.

The precursor fiber used in the present invention is obtained by spinning a metal salt solution having a high viscosity by adding a water-soluble organic polymer.
The spinning solution is prepared by adding polyvinyl alcohol, an aqueous solution of a water-soluble organic polymer such as polyethylene oxide to an aqueous solution of aluminum oxychloride containing colloidal silica or a water-soluble metal salt such as magnesium or zirconium, and then concentrating under reduced pressure. can get.

A precursor fiber can be obtained by spinning the spinning solution thus obtained by a commonly used spinning method such as an extrusion method or a centrifugal method. For example, in the case of the centrifugal method, a spinning solution of 5 to 20 poise is supplied to the surface of a rotating disk having an opening in the center, and after spinning, it is drawn by a high-speed air flow and dried to become a precursor fiber. . In this case, the precursor fiber is sufficiently dried to prevent the fiber from adhering to the wall of the spinning device or forming a droplet.

The precursor fiber thus dried has a water content of 3% or less and does not adhere to each other. Humidity of the precursor is
It can be suitably carried out by a method such as holding in a humidified atmosphere in the range of 10 to 100 mmHg, preferably 14 to 50 mmHg for 1 to 30 minutes, or passing the humidified air through the precursor fiber laminate layer. The moisture content of the precursor after humidification is in the range of 3-12%,
The case of about 4 to 8% is most suitable for the pressure treatment. When the water vapor pressure is less than 10 mmHg, it takes a long time to sufficiently humidify the precursor fiber, which is not practical, and when it exceeds 100 mmHg, the surface of the precursor fiber laminate is excessively humidified and the fiber It is not preferable because the shape of the laminate is broken and the surface of the laminate is stretched after firing.

The moisturized precursor can be pressure-molded by an ordinary pressing machine having a plate shape, a roll shape, a belt shape or the like. The molding pressure depends on the moisture content of the precursor laminate and the bulk density after pressure molding, but a very small pressure of 100 kg / m ² or less is sufficient, and the bulk density of the precursor fiber laminate is 0.06 g / cm ³ or more. And pressure molding.

The firing is performed at 1000 to 1400 ° C, preferably 1200 to 1350 ° C. If the temperature is less than 1000 ° C, the strength of the fiber is insufficient, and
Reheat shrinkage at 1500 ° C is large and it is not suitable for practical use as a fireproof heat insulating fiber molding. Further, even if heated above 1400 ° C, the performance of the fiber is not particularly improved, and the strength is rather lowered, which is not economical.

As described above, according to the present invention, after the dried precursor fiber laminate is humidified again under specific conditions, the precursor fibers are partially adhered by pressure molding, and the density of the precursor fibers is increased by firing as it is. It is possible to obtain a mat-shaped molded product having high flexibility.

〔Example〕

Example 1 (Test No. 1) Colloidal silica (Snowtex Nissan Chemical) was added to the aluminum oxychloride aqueous solution at a ratio such that the composition after firing was 80% alumina and 20% silica, and then a 10% polyvinyl alcohol aqueous solution (Dencapovar) was added. (B-17 used) is added to the total amount of alumina and silica in a proportion such that polyvinyl alcohol is 8%, and a concentrated aqueous solution having a viscosity of 15 poise is used as a spinning stock solution, and a rotating disk having an opening in the center. Was spun to obtain a precursor fiber laminate having a bulk density of 0.04 g / cm ³ .

This precursor laminate is 20 ℃, relative temperature 80% steam partial pressure 14mm
After keeping it in a constant temperature and constant temperature tank of Hg for 5 minutes to moisturize, pressurize and compress with a force of 50 kg / m ² for 1 minute in the direction in which the fibers are laminated to form a bulk density.
A precursor press-molded body of 0.07 g / cm ³ was obtained.

This molded body is fired in a tunnel furnace with a temperature gradient from room temperature to a maximum of 1300 ° C so that it can be kept at room temperature to 800 ° C for 30 minutes, 800 ° C to 1300 ° C for 15 minutes, and 1300 ° C for 10 minutes. Got the body

The bulk density of the fired body was 0.095 g / cm ³ and the tensile strength was 500 g / cm ² .

Examples 2 to 4 (Test Nos. 2 to 4) The precursor used in Example 1 was treated while changing humidification conditions, pressurization conditions, and firing temperatures as shown in the table, and a bulk density of 0.085 or more,
A fired body having a tensile strength of 460 g / m ² or more was obtained.

Comparative Example 1 (Test No5) The precursor having a bulk density of 0.04 g / cm ³ obtained in Example 1 was not subjected to a humidification treatment, and was compressed under a pressure of 50 kg / m ² for 1 minute to obtain 0.052 g / cm ^2.
A precursor compact of cm ³ was obtained. This compact was fired under the same conditions as in Example 1. The bulk density of the fired body is 0.058 g / cm ³ ,
The tensile strength was insufficient at 200 g / cm ³ .

Comparative Example 2 (Test No. 6) The precursor having a bulk density of 0.04 g / cm ³ obtained in Example 1 was humidified at a steam partial pressure of 8 mmHg for 20 minutes and then molded at a pressure of 50 kg / m ² under the conditions of Example 1. It was baked in. The bulk density of the fired product is 0.
The strength was low, as low as 072 g / cm ³ .

Comparative Example 3 (Test No. 7) The same precursor obtained in Example 1 was humidified at a steam partial pressure of 102 mmHg for 1 minute, and thereafter pressure-calcined as in Example 1. Both the bulk specific gravity and the tensile strength were good, but a part of the surface of the precursor was excessively humidified, and the surface of the fired body was stretched and lacked in flexibility.

Comparative Example 4 (Test Nos. 8 and 9) Wet pressure molding was performed under substantially the same conditions as in 2 test Nos. 3 and 4 of Example 1, and the firing temperature was changed to 800 ° C and 1400 ° C. Although the sintered body had a good density, the tensile strength was insufficient.

The bulk density and the tensile strength of the fired body were measured as follows.

Bulk Density A 100 mm test piece was cut out from the sample, and the weight, width, length and thickness of the section were measured to calculate the bulk density. Since the thickness is recoverable, it was measured according to JIS R-3131.

Tensile strength A sample with a shape of 50 (width) x 300 (length) mm was cut out from the sample and the tensile strength in the 300 mm length direction was measured using a tensile tester (Toyo Baldwin UTM-4-100 type). Measured. The thickness of the test piece was measured by JIS R-3331 before cutting the sample. The cross-sectional area of the test body was calculated using this value.

〔The invention's effect〕

According to the method of the present invention, without using special equipment or expensive auxiliary agent, without destroying the precursor fiber, it has sufficient tensile strength to be used as a refractory heat insulating material, and has an appropriate flexibility. It is possible to easily and economically obtain a molded product such as a fiber mat that the user has.

Claims (1)

[Claims] 1. A precursor fiber laminate obtained by spinning a viscous liquid obtained by adding a water-soluble organic polymer to an aqueous fiber composition solution which gives a metal oxide by a firing treatment, has a water vapor pressure of 10 to 100 m.
1100 ~ 1400 after humidifying with mHg and then pressure molding
A method for producing an inorganic fiber molded body, which comprises firing at ° C.