JPH0667780B2 - Alumina fiber molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to an alumina fiber molded article,
In particular, the present invention relates to a molded product useful as a fireproof heat insulating material.

<Prior Art> Alumina fibers have excellent heat resistance and are widely used as fireproof heat insulating materials. Commonly used molded bodies of refractory insulation made of inorganic oxide fibers include board-shaped products called fibers or boards in which fibers are bonded with a binder, and needling by accumulating fibers. There is a non-woven product called a blanket.

However, the alumina fiber containing 65% or more of the alumina component is used as a molded body exclusively as a board or felt, and is not used as a blanket. The reason is that the alumina fiber containing 65% or more of the alumina component does not become a blanket in which the fibers are entangled with each other even if they are accumulated and needling.

Alumina fibers containing 65% or more of the alumina component are produced exclusively by a precursor fiberizing method as is well known. In this method, the aluminum compound as the main component,
A viscous solution containing a small amount of an organic polymer such as polyvinyl alcohol is spun to produce a raw fiber, and the raw fiber is then fired to be converted into an alumina fiber to produce an alumina fiber. It

A member of the present inventor produced a blanket of raw fibers by first needling the accumulated raw fibers to produce a blanket of raw fibers, and then calcining the blanket to convert the raw fibers into aluminous fibers. It has been found that a blanket of alumina fibers containing an alumina component can be manufactured (see Japanese Patent Application Nos. 58-196778 and 59-27781).

<Problems to be Solved by the Invention> The significance of the method according to the above application is that it is the first to provide a blanket of alumina fibers having a high content of alumina components. However, in the blanket manufactured by this method, the tensile strength in the thickness direction, that is, the peel strength decreases as the thickness increases, and the use thereof is severely restricted.

According to the study by the present inventors, the point that the peel strength is small is due to the fact that the fibers drawn inward from the surface by needling, that is, the fibers oriented in the thickness direction are cut in the middle of the thickness direction. it is conceivable that. That is, when the needling of the aggregate of raw fibers is carried out by the usual method, the fibers are drawn from the surface to the inside of the aggregate, so that a large number of fiber bundles exist in the thickness direction in the portion close to the surface according to the needling number. To do. However, since these fibers are cut in the middle, it is considered that the number of fibers in the thickness direction decreases from the surface to the inside, and thus the peel strength of the finally formed blanket decreases.

<Means for Solving Problems> The present inventors have studied a method of producing a blanket of alumina fibers having a large thickness and a high content of an alumina component having a large peeling strength, and as a result, reduced friction to raw fibers. It was found that a thick blanket with a large peel strength can be produced by needling after applying the agent,
The present invention has been completed.

That is, the gist of the present invention is a flat non-woven fabric formed of alumina fibers having an alumina component of 65% or more, and most of the fibers are arranged substantially parallel to the plane of the formed body, and On the plane, there are regular fiber bundles from the surface to the inside, with a thickness of 10 mm or more and a density of 0.07-
0.3g / cm ³ , tensile strength 0.5Kg / cm ³ or more, peel strength
It exists in an alumina fiber molded body characterized by being 0.5 Kg / m or more.

To explain the present invention in more detail, the fiber molding according to the present invention is substantially composed of an alumina-based fiber containing 65% or more of an alumina component. The alumina-based fiber contains zirconia and other components in addition to the alumina component. Metal oxides may be present.

The preferred aluminous fibers are those which contain from 65% to 98% alumina component with the balance consisting essentially of silica component. Alumina fibers generally have an average fiber diameter (fiber diameter in the unit of 1 μm-maximum value of fiber weight curve) of 7 μm.
In the following, the average fiber length (fiber length in 10 mm division unit-
The maximum value of the fiber weight curve) is 30 mm or more. If the average fiber diameter becomes too large, the fibers themselves become brittle and the heat insulation performance of the molded product deteriorates. In addition, when the average fiber length is shortened, the mechanical strength of the molded product is reduced. Suitable average fiber diameter and average fiber length are 5 μm or less and 50 mm or more, respectively. The abundance ratio of fibers having an average fiber diameter of 3 to 5 μm and thicker than 20 μm is substantially negligible, and the abundance ratio of fibers having an average fiber length of 50 mm or more and shorter than 10 mm is Alumina fibers such as 10% or less are particularly preferable.

Most of the alumina fibers constituting the molded body are arranged substantially parallel to the plane of the molded body. In other words, the alumina fibers are deposited almost in layers on the flat surface. The better the parallelism to the flat surface, the higher the tensile strength of the molded body.
On the other hand, the orientation of the alumina fibers in the plane parallel to the flat surface is determined by the physical properties required of the finally formed molded body. That is, the tensile strength of the molded body is large in the orientation direction of the alumina fibers and small in the direction orthogonal thereto, so that the alumina fibers may be oriented in the direction in which strength is required. When a molded product having a small anisotropy, that is, a small difference in strength depending on the pulling direction is desired, the orientation of the alumina fibers in the plane parallel to the plane of deflection may be random.

On the flat surface of the molded body, fiber bundles of alumina fibers that face inward from the surface are regularly arranged. The number is 1 cm ³
Usually, it is 3 to 20, and the larger the number is, the higher the density and peel strength of the molded article are. The fiber bundles are entangled with the alumina fibers constituting the main body of the molded product to express the mechanical strength of the molded product, particularly the peel strength. The number of aluminous fibers in one fiber bundle is generally 50 to 200. The number of fibers depends mainly on the needle used for needling the green fiber, and it is also possible to construct the fiber bundle with a number of fibers outside this range.

The molded body has a thickness of 10 mm or more. The molded article according to the present invention is characterized by having a large peel strength even with such a thickness. However, if the thickness of the molded body becomes too large, yarn breakage during needling increases, and it tends to be difficult to maintain a large peel strength. Therefore, a molded body thicker than necessary is not preferable. The general thickness of the molded product is 10 to 50 mm, preferably 15 to 3
It is 5 mm.

Molded body is 0.07-0.3g / cm ³ , preferably 0.085-0.15g
It has a density of / cm ³ . The density is related to the heat insulating performance of the fireproof heat insulating material, but in general, a molded product having a density within the above range can exhibit good heat insulating ability under various conditions.

The molded product has sufficient mechanical strength to be used as a fireproof heat insulating material. That is, the molded body has a tensile strength of at least 0.
It has a peel strength of 5 kg / cm ³ and 0.5 kg / m or more. Preferably, the molded body has a tensile strength of 1.0 kg / cm ³ or more and a peel strength of 1.0 kg / m or more. Furthermore, the compact has a size sufficient for use as a fireproof heat insulating material, that is, at least 0.27 m ³ (0.3 m × 0.9 m). Usually, it has a size of 0.6 m × 1.2 m to 0.6 m × 3.6 m.

The molded body according to the present invention is obtained by collecting raw fibers obtained by the precursor fiberizing method in a layered form, adding a lubricant to the raw fibers, and then performing needling to obtain a blanket of raw fibers, which is then constituted. It can be produced by converting raw fiber into aluminous fiber.

Production of green fiber by the precursor fiberizing method can be carried out according to a conventional method. According to the preferred method, a viscous solution mainly composed of basic aluminum chloride (AlCln (OH) _sn ) and containing silica sol and polyvinyl alcohol is placed in a high-speed air stream. A raw fiber is formed by extruding from the spinning nozzle. The thickness of raw fiber is generally several microns to ten and several microns,
The length is several centimeters to several tens of centimeters, and it is specifically determined according to the alumina fiber required for the finally formed molded body.

The raw fibers formed in the high-speed air flow are collected in a layered manner on a wire mesh arranged so as to be perpendicular to the air flow.

The aggregate preferably has a weight of 10 to 100 g / m ² , especially 20 to 50 g. Next, after adding about 1 to 3% of a lubricant to the aggregate, the aggregates are stacked and needling is performed to obtain a blanket of raw fiber. As the lubricant, an ester of a higher fatty acid such as lauric acid, palmitic acid, stearic acid or the like diluted with a hydrocarbon solvent such as mineral oil about 10 times is used. The lubricant should be applied to the whole raw fiber as evenly as possible.
Needling is performed from both sides of the blanket according to a conventional method. The needling number is generally 3 to 20 shots / cm ² , and generally, the higher the number of shots, the higher the bulk density and peel strength of the finally obtained molded product. For example, when the bulk density of the molded body is desired to be 0.1 g / cm ³ , the number of needling strokes is suitably 3 to 10 strokes / cm ² . Due to the needling, the raw fiber bundles are regularly arranged on the blanket surface from the surface toward the inside. Needling is preferably performed using a needle having a diameter as small as possible, as long as the strength of the needle allows. If the diameter of the needle is large, the chances of cutting the raw fiber by the needle increase, and at the same time, the traces of the needle remain as holes in the finally produced molded body, which may reduce the heat insulating performance of the molded body. The size of the fiber bundle formed by needling depends on the hook provided on the needle. Generally, the number of fibers constituting one fiber bundle is 50 to 200. The speed at which the needle penetrates into the raw fiber during needling is preferably as small as possible, as productivity permits. If this speed is too high, the raw fiber placed in the raw fiber by being pulled by the needle will be cut midway, and the peel strength of the finally formed molded article will decrease. Needle speed is usually 0.5 ~
The range is 10 cm / sec, preferably 2-5 cm / sec.

Raw fiber shrinks when fired and its bulk density increases, so
The bulk density and thickness of the raw fiber blanket may be set in consideration of the shrinkage rate due to firing based on the bulk density and thickness required for the molded product. For example, when a molded body of 0.1 g / cm ² is desired, the raw fiber blanket may be produced by reducing the thickness by 20% and increasing the bulk density by 20% (raw fiber blanket). For the details of the production method of the above, refer to "Inorganic fiber blanket production method" filed by the applicant on July 16, 1985). The green fiber blanket is then fired above 1100 ° C. to convert the green fibers into aluminous fibers. The final temperature of calcination depends on the composition of the alumina fiber and the desired physical properties.

Firing up to 300 ° C over 2 hours and then 3
The temperature is raised at a rate of about 2 ° C / minute between 00 and 500 ° C, and then 50
The temperature is raised from 0 ° C to the final temperature at about 5 ° C / minute, and the final temperature is increased to 30 ° C.
It is suitable to hold for about a minute. If the rate of temperature increase between 300 and 500 ° C. is too high, the mechanical strength of the obtained molded article decreases (for the relationship between the firing conditions and the strength of the alumina fiber produced, dated July 19, 1985). The details are described in "Method for producing inorganic oxide fiber" filed by the present applicant.

<Example> 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.

In this specification, the tensile strength and the peel strength are values measured by the following methods.

Method of measuring tensile strength Two test pieces (a, b) having a width of 50 mm and a length of 150 mm are cut out from the center of the molded body in a method orthogonal to each other.

Both ends in the length direction of the test piece are fixed to a strength tester, and the maximum load (Kg) is measured by pulling vertically. The distance between the quantity fixed ends is 100 mm and the pulling speed is 30 mm / min.

From the measured value (Kg) obtained above, the tensile strength is calculated by the following formula.

A = thickness of test piece: cm B = specific gravity of test piece Peel strength measuring method Two test pieces (a, b) having a width of 50 mm and a length of 100 mm are orthogonal to each other from the center of the molded body. Cut out into. Bake one end in the length direction of the test piece at a position of 1/2 in the thickness direction 3
Peel off 0 mm, fix both ends to a strength tester, pull up and down at 10 mm / min, and measure the maximum load (kg) at that time. The peel strength is calculated from the measured value (kg) by the following formula.

Aluminum was dissolved in hydrochloric acid to form basic aluminum chloride [AlCl _n (OH) _sn ], and silica sol was added to this to prepare a solution containing an aluminum component and a silicon component.

After concentrating this, an aqueous solution of polyvinyl alcohol was added thereto to give an alumina-silica content of about 30 (weight)%, (Al ₂ O ₃ : SiO ₂ = 72: 28 (weight ratio)) a viscosity of about 2
A raw material solution of 500 CP was obtained.

This raw material solution is extruded into a high-speed air stream from a spinning nozzle and spun, and raw fibers that fly along with the air stream are collected by a rotating wire net arranged perpendicular to the air stream, and the diameter is about 4 to 6 μm and the length is about 6 μm. About 30 g / m ² of thin raw fiber aggregate consisting of 50-200 mm raw fiber was obtained. About 30 m / Kg of a lubricant was applied to this, and 80 layers were laminated and needling. As a lubricant, 1 part by weight of higher fatty acid ester is added to mineral oil 9
What was melt | dissolved in the weight part was used. The number of needling strokes was 5 strokes / cm ² , and the obtained raw fiber blanket was vertical,
The horizontal size is 2000 x 650 mm, the thickness is about 30 mm, and the bulk density is about
It was 0.08 g / cm ³ .

Place this in a furnace maintained at a temperature of about 300 ° C. 2
It was kept for 300 hours to 300 ° C. Next, the ambient temperature is 300 to 550 ° C., 2 ° C./min, 550 to 125
The temperature was successively raised at 5 ° C./min between 0 ° C. and kept at 1250 ° C. for 30 minutes to complete the firing.

The obtained alumina fiber molded body has a fiber diameter of 3 to 4 μ,
Thickness is about 25 mm, bulk density is about 0.1 g / cm ² , and tensile strength is 1.
The peel strength was ² kg / cm ² , and the peel strength was 1.3 kg / m.

The tensile strength and the peel strength were measured using an electric measurement control type universal testing machine Autograph IS-500 manufactured by Shimadzu Corporation.

The number of fibers in one fiber bundle was about 70 to 130.

[Brief description of drawings]

 The figure is an illustration of a method for measuring peel strength. (1) Test piece, (2) Test piece fixture

Front page continued (72) Inventor Shoji Mamoru 1 Fukuda-cho, Joetsu City, Niigata Prefecture Kasei Naoetsu Naoetsu Factory (56) References JP-A-60-88162 (JP, A)

Claims (6)

[Claims] 1. A flat non-woven fabric comprising an alumina fiber having an alumina content of 65% or more, and most of the fibers are arranged substantially parallel to the plane of the plane of the molded body. Has regular fiber bundles from the surface to the inside, and has a thickness of 10 mm or more, a density of 0.07 to 0.3 g / cm ³ , a tensile strength of 0.5 Kg / cm ³ or more, and a peel strength of 0.5 Kg / m. The above is an alumina fibrous molded article characterized by the above. 2. A thickness of 15 to 35 mm and a density of 0.085 to 0.15.
The alumina fiber molded body according to claim 1, which is g / cm ³ . 3. The alumina fiber according to claim 1, wherein the alumina fiber is composed of 65% or more of an alumina component and the balance substantially consisting of a silica component. Molded body. 4. A fiber bundle, which is regularly present on the flat surface from the surface toward the inside, is the same as the fiber of the main body, and is arranged by needling. Alumina fiber molded article according to any one of claims 1 to 3. 5. The alumina-based fiber having an average fiber diameter of 7 μm or less and an average fiber length of 30 mm or more, as claimed in any one of claims 1 to 4.
Alumina fiber molded article according to any one of items. 6. The alumina fiber molded product according to any one of claims 1 to 5, wherein the area of the flat surface of the molded product is 0.27 m ² or more.