JPH0660476B2 - Method for producing inorganic sheet - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a paper-like sheet using inorganic fibers, and more particularly to a method for producing a sheet containing no particulate foreign matter contained in raw material fibers.

The inorganic sheet produced by the production method of the present invention is a heat-resistant filter material, a catalyst carrier, a heat exchanger element, a separator, a laminated plate base material, a far-infrared radiation element, an electric wire coating material, a heat-resistant fire-resistant paper, a heat-resistant insulating material for electronic industry ( Used in a wide range of applications such as printed wiring boards), heat resistant packing materials, wear resistant materials (eg brake materials, clutch materials), non-combustible building materials (eg gypsum board paper), fiber reinforced ceramic substrates, porous ceramics, etc. To be

(Prior Art) Conventional inorganic sheets include asbestos paper and glass fiber paper. Both of them have their own characteristics and were used in many applications. Asbestos is excellent in sheeting suitability and heat resistance, but since the problem of pollution was proposed, other heat resistant fibers have been demanded. Ceramic fibers such as alumina silicate and alumina have been recently put into practical use in addition to the old cotton wool, and these fibers flow out raw material melted at high temperature from a nozzle, and air or steam is discharged to the outlet. Methods such as blowing, which blows and blows away to form fibers, and spinning, which uses a centrifugal force to scatter the molten raw material that has been cast on a rotating drum to form fibers, make cotton fiber in large quantities at a lower cost. It is adopted because it is suitable for. Fibers produced by these methods have a thickness of 1 mm, such as those used for insulating boat blankets.
It is durable enough for the above moldings. However, when the inorganic fibers produced by these methods are made into a fibrous form, a part of the molten raw material does not form into a fibrous shape but solidifies in the form of particles or lumps, and is mixed in the cotton-like fibers. This is called a shot. The abundance ratio is about 10 to 60% by weight. When the inorganic fiber containing a lot of shots is used as it is to make a paper-like sheet, the wire, dryer, calender, and other parts during the making are damaged by the shot, and the pump or pipe is used. Block the road.

Since the paper made of inorganic fiber contains many shots, the surface is not smooth and cannot be adhered or applied to other materials smoothly. Since shots fall off, the impregnating solution and the impregnating solution during coating are contaminated, and printing or lamination is not possible. Even if the sheet is a folded paper sheet, the usage that makes full use of its characteristics cannot be applied, and the application is limited. There was a drawback that As a method for removing shots in inorganic fiber raw cotton, (1) JP-B-93-16908 discloses a method in which fibers are disentangled between two flash-shaped rollers, shots are separated from the fibers, and then the fibers are carried out by an air flow. (2) JP-A-54-469
No. 29 is a method of raising inorganic fibers containing shots in a vertical hollow duct at a constant speed by a carrier air flow, (3)
In JP-A-54-46928, inorganic fibers containing shots are guided by a carrier airflow to a carrier airflow introduction duct having a built-in separation device, and then guided to a vertical hollow duct for changing the carrier airflow to an upward airflow. And (4) Japanese Unexamined Patent Publication (Kokai) No. 58-208419 discloses a cotton disintegration process in which shot-containing ceramic fibers are stirred in water and separated into blocks of a certain size, and blocked fibers. A defibration process that separates the shots in the entanglement of the fibers by a device that has a stirring blade and that can generate a gentle turbulent flow. The shots and the separated fibers are collected by a net and the shots are removed. Various means such as a method for removing shots in a ceramic fiber cotton-like material by the separation and collection step and three steps have been proposed.

(Problems to be solved by the invention) However, with the methods of the conventional examples (1) and (2), fine shots taken in the entanglement of fibers cannot be separated and removed, and In the method of Example (3), the fibers are fragmented by the separation device, and in the method of Conventional Example (4), the fibers are treated from the beginning as much as they are treated in water as compared with the methods of (1) to (3). The separated shots are efficiently removed, but there is no device that applies an external force that breaks the shots connected to the tip of the fiber and breaks the shot even if it partially breaks the fiber. Since the shot connected to the tip of the fiber cannot be separated / removed because it does not exist, a particle size of 44 to 100 μ is formed.
When the paper-like sheet is made using the fiber obtained in the conventional example (4), the content is 80% by weight or more.
The present inventors have found from experiments that the thin sheet having a thickness of about 300 μm has a drawback that the shot becomes a protrusion and becomes an obstacle when printing or the like.

That is, the problem to be solved by the present invention is to break the cotton-like material containing a large amount of shots in water, or after breaking the shots connected to the fiber tip as close to the shot as possible. Then, the cut shots are efficiently separated and removed, an inorganic fiber paper stock containing almost no shots is produced, and a sheet containing almost no shots is made into paper by using this.

(Means for Solving the Problems) As a result of intensive studies by the present inventors in order to solve the above problems, as a result, the inorganic fiber cotton material containing a large amount of shots was unwound in water, or The present invention has been completed by finding that the inorganic fiber and the shot can be cut later by applying a mechanical shearing force, and then the shot can be efficiently removed by passing through a device that applies a centrifugal force.

The method of the present invention will be described below.

To disintegrate the inorganic fiber cotton-like material containing shots in water, add water and the inorganic fiber cotton-like material to a high-speed mixer or pulper and stir to form an aqueous dispersion. In this case, it is preferable that the solid content concentration is not too low, and about 4 to 7% is appropriate. A paper making machine such as the above pulper is suitable for the defibration, but the invention is not limited thereto, and a tank may be combined with a suitable stirring mechanism. At the time of dispersion, as a dispersion auxiliary agent, a surfactant, a spinnable polymer, that is, a plant-based sticky agent such as thighs, kneading, a synthetic polymer such as polyethylene oxide, polyacrylate, polyacrylamide, polyphosphoric acid, polyphosphorus An inorganic dispersant such as an acid salt may be added.

Then mechanical shear is applied to the dispersion. The mechanical shearing force is most preferably applied so that it breaks from the part of the neck of the shot that is connected to the fiber tip, so that the fiber is not cut unnecessarily. This is because the inorganic fiber sheet is advantageous in strength as the fiber length is longer. However, in the case where the fiber length is distributed in the range of several mm to several tens of mm, such as ceramic fiber, it is better to arrange the average fiber length in the range of 5 to 15 mm in order to improve the sheet strength in terms of paper-making property. From the aspect, it is desirable because it can be separated. As a method of applying mechanical shearing force, for example, needle-like, comb-like,
A rotating body having a toothed or plate-shaped convex body and a plane or tooth,
It is added by passing through the gap with a stationary body having plate-shaped convex bodies so that the dispersion is temporarily compressed and then opened. The strength of the shearing force is adjusted by the rotation speed of the rotating body or the width of the gap between the rotating body and the stationary body.

Examples of the device for applying mechanical shearing force include, but are not limited to, paper machines such as beaters, refiners, top finers, Jordan, and pulpers. These paper-making machines are originally used to hit, grind, and cut cellulose pulp to fibrillate it. However, since the inorganic fibers and shots used in the present invention have high hardness, they are If the gap of the stationary body is made too narrow, the surface of the rotating body and the stationary body will be abraded so much that a proper gap is required. Since inorganic fibers are more rigid and easier to break than cellulose pulp, they can be broken at the neck of a shot simply by compressing them. Therefore, it is not necessary to bring the rotating body and the stationary body close to each other. The shot neck, which is connected to the tip of the inorganic fiber, is thicker than the fiber portion, and when the fiber shear force is applied, it is most likely to break in the vicinity where the shot neck becomes a fiber. . These devices are similar in appearance to the conventional example (3), but in the conventional example (3), the fiber is directly struck, and the fiber is cut at unnecessary points to make the fiber into pieces. It is fundamentally different from the method of the invention. The solid content concentration of the water dispersion when passing through this device is appropriately about 4 to 7% when the above-mentioned defibration is performed. If the concentration is too low, the shearing force cannot be effectively applied, which makes it difficult to cut the shot.

Efficient separation and removal of the cut shots is achieved by passing a water dispersion of the inorganic fibers containing the cut shots through a device that applies a centrifugal force. An apparatus used for this purpose is, for example, a papermaking centrifugal separator. This is used to remove dust from paper-making samples, and is capable of allowing the water flow of the stock material to swirl and separating foreign matter with different specific gravities by centrifugal force. Dispersion is pressed in the tangential direction of the upper part of a slender cylinder with a tapered lower part to generate centrifugal force, the substances to be removed are discharged from the lower orifice, and the selected components are taken out from the upper part. The treatment by the separation device is performed once or twice or more depending on the type of fiber, the content of shots in the fibrils, the size of shots, the concentration, and the dispersion state.

The shot-containing fiber used in the present invention may be made of any material as long as it is produced by the probing method or the spinning method. Examples thereof include high alumina fibers such as mullite fibers, alumina silica fibers, silica fibers, other ceramic fibers, mineral wool and mineral wool.

The fiber dispersion liquid from which the shots have been removed by the shot removing means of the present invention is directly produced into paper, or other fibers such as glass fibers, asbestos, zirconia fibers, boron fibers, inorganic fibers such as metal fibers and carbon fibers, or silica. Stone, silica sand, diatomaceous earth, kibushi clay, frog grain clay, kaolin, bauxite, mica, clay-like mica (serisite, illite), vermiculite, bentonite, zeolite, phosphate rock, diaspore, giipsite, acid clay,
Natural minerals such as porcelain stone, wax stone, feldspar, limestone, wollastonite, gypsum, dolomite, magnesite, talc, and metal hydroxides such as aluminum hydroxide, magnesium hydroxide, ferric hydroxide. , And hydrates of various oxides such as calcium silicate hydrates such as tobermonite and xonotlite, calcium aluminate hydrates and calcium sulfoaluminate hydrates, or alumina, silica, magnesia, calcia, zirconia, Thorium, beryllia, titanium oxide, spinel, synthetic cordierite, synthetic mullite, synthetic zeolite, synthetic calcium carbonate, calcium phosphate, and various other carbides (TiC, ZrC, HfC, VC, Ta)
C, NbC, WC, B ₄ C, SiC, etc., nitrides (TiN, VN, NbN, T)
aN, HfN, AbN, BN, Si ₃ N _4, etc.), lithium oxide, ferrous oxide, ferric oxide, lead oxide, zinc oxide, nickel oxide,
Manganese dioxide, cupric oxide, cobalt oxide, vanadium oxide, barium carbonate, barium sulfate, manganese carbonate,
Metal titanate (potassium titanate, calcium titanate, sodium titanate, barium titanate, strontium titanate, magnesium titanate, etc.), graphite,
Activated carbon, powder of metal such as molybdenum, tungsten, copper, aluminum, tin, zinc, lead, or powder of artificial inorganic material such as various inorganic pigments, or fibrous material, needle crystal (whisker), scale crystal, flake shape Products, hollow products, and further, those obtained by crushing fibrous products having an average fiber length of 1 mm or more into powder or fine fibrous materials, or aramid fibers, aramid resin frebrids, novoloid fibers, flame resistant fibers (carbon fibers Precursor), synthetic fiber such as polyester, polyamide, rayon, natural fiber such as cotton, linter, hemp, pulp such as wood, fine powder of organic synthetic polymer, polyacrylamide Resin starch, PVA, CMC, chaotic starch, acrylic resin emulsion, vinyl resin emulsion, synthetic rubber latte Binding agents such as camphor, paper strengthening agent, a melamine resin, a polyamide polyamine epichlorohydrin resin, wet strength agents such as polyimine resin, was blended as necessary material selected from sizing agents, papermaking. Papermaking is performed by a wet papermaking method or a method similar thereto.

The wet papermaking method or a method similar thereto means, for example, flowing an aqueous dispersion liquid over an excess medium such as a band-shaped, circular-shaped, or rectangular-shaped over-mesh, over-cloth or over-plate so as to have a uniform thickness. It is a general term for a method of forming a sheet-like material by passing it through an operation such as a natural overpressure or an overpressure reduction after being or after being caught by these excess media. The sheet material thus obtained is peeled from the excess medium and then dried, or dried and then peeled to be a sheet through a drying step. As a method of continuously forming these sheets, there are conventionally known wet paper machines such as a fourdrinier type, a cylinder type, a short mesh type, a cylinder former type, and an inclined wire type.

If necessary, this sheet material may be impregnated or coated, printed, embossed, corrugated, honeycombed, laminated with other materials, or cut into appropriate sizes. Secondary processing can be performed by folding, bending, or pasting. Further, if necessary, the organic matter may be removed by heating and baking at a temperature of 400 ° C. or higher. Further, it may be sintered at a temperature of 700 ° C. or higher to obtain a ceramic material.

The sheet produced in this manner is a sheet having almost no unevenness due to shots even when the fiber raw material forming shots is used by the method of the present invention and 10% or more of the stock is used after the shots are removed. In particular, the effect is remarkable when the thickness of the sheet is 0.3 mm or less.

(Function) The fiber containing shot has the same material in the fiber portion and the shot portion, and there is no difference in true specific gravity. For example, in the case of cellulose pulp, since the true specific gravity is about 1 and the foreign matter such as sand is about 2.5 to 3, it is easy to separate the foreign matter by the centrifugal action. However, in the case of shot-containing fibers, there is no difference in the material and the fact that the fibers can be separated and removed in the same way as the foreign matter of the pulp despite the simple morphology of the fibers is not due to the difference in specific gravity, but can be actually separated. It must be considered that the reason for the separation was that the shots and the fibers could be separated due to the difference in flow resistance due to the difference in morphology, which is an unexpected effect. It is also unexpected that the equipment for wood pulp, which has a low specific gravity, could be used as it was.

The effect of removing the shots by the centrifugal separator used in the present invention was created by taking the amount of the dispersion liquid before and after the removal corresponding to 2 g of the dispersoid, and making the handsheet by the handsheet making method of JIS P 8209. While observing the sheet with a magnifying glass such as a microscope, the shot portion can be taken out with tweezers and the weight can be measured to calculate the separation efficiency. The shot content before separation of 50% or more can be reduced to 10% or less by the method of the present invention.

(Examples) Hereinafter, the present invention will be specifically described with reference to Examples.

Example 1 and Comparative Example 1 A ceramic fiber having a shot content of raw cotton of 54% (alumina / silica fiber: alumina 52%, silica 48).
%) In a water with a high speed mixer at a concentration of 5%,
The gap between the fly bar (rotating teeth) and the cret (stationary teeth) was put into a beater adjusted so that the gap between the teeth was not ground, and the mixture was circulated for about 30 minutes. Then the concentration is 1%
Diluted into paper dusters (centrifugal type) and then passed the stock to a sheet with a dry weight of 2 g by the JIS P 8209 handsheet sheet making method. Take a shot with tweezers with a magnifying glass and measure the weight and length. Then, the shot content and the average fiber length were determined.

Separately, the raw material, the cotton breaking method, the centrifugal separation method, and the hand-making method were made in exactly the same manner, and a sheet having a dry weight of 2 g was prepared using a paper material that did not pass through the beater, and the shot content and the average fiber length were measured in the same manner. The results are shown in Table 1 as Comparative Example 1.

In Example 1, most of the shots were removed, and the average fiber length was also an appropriate length for making paper, whereas in Comparative Example 1, a considerable number of shots were still included, and the average length was also average. The fiber length was too long, and it was difficult to form a uniform fabric in terms of paper formability.

Example 2 and Comparative Example 2 Using the stock materials of Example 1 and Comparative Example 1, the solid content was 10 respectively.
A sheet having a basis weight of 50 g / m ² was prepared by adding 2 parts by weight of a polyacrylamide type paper strengthening agent to 0 part by weight and making a handsheet according to JIS P 8209. The physical properties and appearance of each are shown in Table 2. (The sheet using the paper material of Comparative Example 1 is referred to as Comparative Example 2) Example 3 Mineral wool having a shot content of 58% and water were put into a pulper and dispersed at a concentration of 6%, and after passing through a refiner, the gaps between the teeth of a refiner were adjusted so that the fibers were not crushed, and then the concentration was reached. Was diluted to 2% with water, and then passed through a paper dust remover (centrifugal separation type). When the shot content and the average fiber length of this paper material were measured by the same method as in Example 1, the shot content was 9.8% and the average fiber length was 8 mm. Furthermore, for 100 parts by weight of the solid content of the stock, SBR
3 parts by weight of latex and 2 parts by weight of sulfuric acid band were added, and a 0.2 mm thick sheet was continuously produced by a rotoformer.
The physical properties of this sheet were as shown in Table 3, and it was possible to use it as a non-combustible paper for building materials.

Example 4 The aromatic aramid resin was added to 100 parts by weight of the solid content of the treated ceramic fiber which was passed through the same treatment steps as in Example 1, narrowed the gap between the flybar of the beater and the klet, and enhanced the centrifugal separation ability. 5 of fibrid fiber
1 part by weight and 2 parts by weight of polyamide polyamine epichlorohydrin resin were mixed and dispersed in water, and then a sheet having a thickness of 0.08 mm was produced using an inclined wire mesh paper machine. This sheet contained almost no shots and was usable as a printed wiring board. At this time, the shot content contained in the ceramic fiber was 5% or less when measured by the same method as in Example 1.

(Effect) As described above, by removing the shots of the inorganic fibers by the method of the present invention, it was possible to fabricate a sheet having a good texture and texture.

Claims (1)

[Claims] 1. A wet papermaking method in which an inorganic fiber cotton-like material having spherical particles (shots) at the tips of inorganic fibers fiberized by a blowing method or a spinning method from a heat-melted raw material is dispersed in water. When forming a sheet by a method according to it, while breaking the inorganic fiber cotton-like material in water or after applying mechanical shearing force, the inorganic fiber and the shot are cut, and then the shot is cut. A method for manufacturing an inorganic sheet, which comprises removing the inorganic sheet by passing it through a device that exerts a centrifugal force.