JP2811224B2 - Manufacturing method of alumina fiber blanket - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a blanket made of crystalline alumina fibers.

[Conventional technology]

One of the refractory heat insulating materials used in high-temperature furnaces and the like is a blanket made of inorganic fibers, but it is not easy to manufacture inorganic fibers made of ceramic fibers having good heat resistance. This is because the ceramic fibers are generally rigid and hard to cause entanglement, and are fragile and easily broken when trying to cause entanglement by needle punching. Such properties are particularly remarkable in crystalline alumina fibers, and it is difficult to utilize the excellent heat resistance in a blanket state.

One means for solving the above problem is disclosed in Japanese Patent Application Laid-Open No. 60-8816.
It is disclosed in Japanese Patent Publication No. 2 (1993) -195, in which a needle-punching treatment is applied to a layer of still-soft unfired fibers obtained by a precursor fiberization method, and then firing is performed. However, the unsintered precursor fibers are flexible but have low strength and are easily cut by needle punching, so that the effect of needle punching tends to be insufficient when it comes to the final product.

Also, since the unfired precursor fibers do not have water resistance, the lubricant to be attached to the fibers to lower the coefficient of friction in needle-punching the blanket-like aggregate of the precursor fibers must be non-aqueous. No
No. 17060). However, non-aqueous lubricants require special treatment equipment, and the lubricants themselves are expensive.

[Problems to be solved by the invention]

Therefore, an object of the present invention is to make it possible to use a water-based lubricant which is easy to handle as a lubricant, to ensure the effect of needle punching, to produce an alumina fibrous blanket which is less likely to cause delamination and has excellent physical properties. It is an object of the present invention to provide a method that can be manufactured efficiently.

[Means for solving the problem]

The blanket manufacturing method of the present invention, which succeeded in achieving the above object, produces a fleece of alumina fiber precursor fibers by spinning a fiber-forming solution of an aluminum compound, collecting the fleece and drying it. The fleece of the precursor fiber is fired in a temperature range where substantially no crystalline alumina is generated from the aluminum compound in the precursor fiber, an aqueous lubricant is attached to the fired fleece, and then any of the following processes The fleece is laminated to a thickness required for blanket production, and the resulting lubricant-treated fleece laminate is needle-punched, and then fired at a high temperature until the fibers constituting the fleece produce crystalline alumina fibers. It is characterized by the following.

This production method has been completed based on the following new findings by the present inventors. That is, once a step of firing at a relatively low temperature in the process of firing the precursor fiber to produce the crystalline alumina fiber, the low-temperature fired fiber obtained there is already sufficiently water-resistant, It is much stronger than fibers, and more flexible than those fired at high temperatures to produce sufficient crystalline alumina. Since it has water resistance, an aqueous lubricant can be used as the lubricant, so that a so-called dipping method and many other methods can be adopted for attaching the lubricant to the fiber, so that uniform lubricant treatment can be easily performed. it can. As described above, the low-temperature fired fiber has properties extremely suitable for performing the needle punching treatment.

In the case of producing an alumina fiber blanket by the production method of the present invention, the step of producing a precursor fiber from a solution of an aluminum compound can be performed by any method with reference to a known method. Usually, preferred raw aluminum compounds are aluminum oxychloride, basic aluminum acetate, basic aluminum lactate and the like. As a silica source to be added in a small amount thereto, silica sol, tetraethyl silicate and the like are suitable. As an organic polymer added to give a fiber forming property to the aluminum compound solution, polyvinyl alcohol, polyethylene glycol, polyacrylamide, or the like can be used. The solutions of the above-mentioned various raw materials are concentrated to prepare a spinning solution having a viscosity of about 1 to 500 poise, and fiberized by a spinning method such as a centrifugal method or a blowing method.

When the formed precursor fibers are received by a conveyor running directly below the spinning device, a fleece of precursor fibers, that is, a thin sheet-like aggregate is obtained. After drying, it is fired in an oxidizing atmosphere to decompose organic substances and aluminum compounds in the precursor fibers. In this firing, firing in a normal aluminum fiber manufacturing process can produce crystalline alumina.
Although it is performed at around 1000 ℃, lower temperature,
It is preferably carried out at a temperature of about 400 ° C. to 800 ° C. so as not to substantially form crystalline alumina.

An oil agent / lubricating agent for lowering the friction coefficient between the needle and the fiber in the needle punching process is attached to the obtained low-temperature fired fleece. The amount of the lubricant attached is about 0.5 to 5% by weight as a solid based on the low-temperature fired fleece. Since the precursor fiber is a water-resistant low-temperature fired fiber, an emulsion obtained by emulsifying a higher alcohol, a paraffinic mineral oil, or the like in water with various surfactants can be used as the lubricant. Also, the treatment can be carried out by any method such as a method of spraying the lubricant on the fleece and a method of dipping the fleece in the lubricant diluent.

A suitable number of anti-friction treated fleece
The thickness is required to produce the desired blanket.

The lamination of the fleece may be performed before the low-temperature firing, or after the firing, and before the lubricant treatment.

Thereafter, the fleece laminate is needle-punched at a density of about 1 to 60 times / cm ² .

Laminated product after needle punching is about 800 ~ 1300 ℃
To convert the fibers into crystalline alumina fibers.

〔Example〕

Aluminum oxychloride aqueous solution (solid concentration 50%, Al ₂
The O ₃ reduced concentration 23%) 1000ml, 20% silica sol 520 ml, 6
A 700% aqueous solution of polyvinyl alcohol was added, and the mixture was concentrated at 40 ° C. under reduced pressure to obtain a spinning stock solution having a viscosity of 30 poise. The spinning solution was spun, collected, and dried by a centrifugal method to obtain a precursor fiber fleece. This was baked in air at 600 ° C. for 15 minutes. The obtained low-temperature fired fiber fleece was immersed in a lubricant (aqueous emulsion of paraffinic mineral oil), dehydrated, and dried to adhere a 2% by weight of the fleece to the lubricant.

Next, 10 pieces of the processed fleece are stacked, and the obtained laminate is needle-punched 30 times / cm ² with a needle punch machine, and then baked at 1250 ° C. for 20 minutes to form a blanket made of crystalline alumina fibers. Obtained. The product has a bulk density of 0.12
g / cm ³ , the tensile strength was 1.4 kg / cm ² , and the peel strength was 15 g / cm ² .

〔The invention's effect〕

As described above, in the present invention, a treatment with an aqueous lubricant and a needle punching process are performed when the material becomes water resistant by low-temperature firing and has the most suitable physical properties for the needle punching process. It is safer than the method, the lubricant is cheaper, the processing equipment is simpler, and it is advantageous in many points, and the fiber breakage due to needle punching is less. Thereby, not only the needle punching treatment is facilitated, but also the treatment effect is enhanced, and a blanket which is less likely to cause delamination and has excellent shape stability and strength can be easily manufactured at low cost.

Claims (1)

(57) [Claims] A fiber-forming solution of an aluminum compound is spun, collected in a fleece form, and dried to produce a fleece of alumina fiber precursor fiber, and the fleece of the precursor fiber is converted into aluminum in the precursor fiber. Firing in a temperature range in which crystalline alumina does not substantially occur from the compound,
A water-based lubricant is applied to the fired fleece, and then the fleece is laminated to the thickness required for blanket production in the above or any of the above steps, and the obtained lubricant-treated fleece laminate is needle-punched. A method for producing a blanket made of alumina fiber, which comprises firing at a high temperature until a crystalline alumina fiber is formed from the fiber constituting the fleece.