JPH0453994B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Technical Field of the Invention The present invention utilizes the various characteristics of the whiskers by integrally molding microfibrous crystals, so-called whiskers, in a single layer or multilayer form by simple aqueous papermaking. Concerning providing undamaged sheets.

(B) Prior art Whiskers are expected to have excellent chemical resistance, heat resistance, and stable chemical properties, as well as physical properties such as excellent tensile strength and bullet yield, so whiskers can be used to strengthen various composite materials. It is well known that early industrialization is expected for use in wood and heat-resistant materials.

When whiskers are used as reinforcing materials in various composite materials, their properties as composite reinforcement materials can only be utilized if they are uniformly dispersed in the matrix, but this uniform dispersion is not easy. Therefore, if a sheet made of uniformly dispersed whiskers is obtained, it becomes possible to easily form a composite material using it.

However, such whiskers are extremely small in shape, for example, whiskers made of silicon dioxide or silicon carbide are extremely fine with a fiber diameter of less than 0.5 μm and a length of less than 300 μm, so it is difficult to make a sheet of the whisker alone. However, even after being made into a Yoshiba molded sheet, the sheet itself has no mechanical strength due to its handling, making it difficult to put it into practical use. Furthermore, whiskers are not only extremely small in size compared to glass fibers or carbon fibers, but also have extremely low dispersibility, making it difficult to uniformly form whiskers into a sheet. In the past, for example, such sheets were made by mixing whiskers made of silicon carbide or silicon titanide with an organic solvent such as acetone, as shown in Japanese Patent Publication No. 58-502193, etc., and spreading the mixture thinly on aluminum foil. You can see an example where the whiskers are applied and dried and integrated, but the whiskers are just attached to the aluminum foil, and the sheet itself lacks the holding ability, so it is still not practical in terms of workability. The sheet has not yet been formed. Apart from this, it is also possible to form a sheet by adding a conventional binder such as a water-soluble resin, but such a method alone is unsatisfactory.

Therefore, it is desirable to form these whiskers into sheets for the purpose of making the material more versatile.

(C) Purpose of the Invention The purpose of the present invention is to provide a window layer or laminated sheet of a whisker sheet that is easy to handle, can embody the attributes of whiskers at high yield and low cost, and can have any thickness and density. It is in. Other objects of the invention will become apparent from the description below.

(D) Structure of the Invention The object of the present invention is to stir whiskers at high speed to form a dispersed slurry, and to obtain a slurry with a freeness of 100mlcsf.
This is achieved by a method for producing mixed paper, in which an aqueous composition to which a slurry containing a fibrous material of less than 10% is added and mixed is integrally formed into paper. That is, the idea is to add a natural or synthetic fibrous material to the whiskers and obtain a sheet by a normal papermaking method. The fibrous material to be combined here is required to have a good shape and properties in order to function as a whisker holding material, and in order to form a uniform sheet, a fibrous material with a Canadian Standard Freeness (CSF) of less than 100 ml is used. Such a fibrous material satisfies the above-mentioned numerical values, is natural or synthetic, and its shape is not particularly limited. Further, the amount of the fibrous material to be combined can be arbitrarily selected depending on the degree of porosity or densification of the desired sheet, but from the viewpoint of sheet forming ability, less than 20 parts per 100 parts of whisker is sufficient. More preferably, in order to embody the attributes of whiskers, a value of 5 to 10% can also satisfy sufficient handling characteristics. The gist of the present invention is to combine fibrous materials as fine as possible, that is, with low water content, in order to achieve more preferable compatibility with whiskers. It has a small surface area and lacks the ability to promote fine whiskers on its surface, resulting in no dispersion ability, making it difficult to form a desired sheet. Therefore, in order to enhance the whisker supplementation ability, it is necessary to keep the water level below 100ml.
Further, during such paper making, a well-known retention agent can be used in combination so that fine whiskers can be easily peeled off from the wire during paper making.

The whiskers used in the present invention include the aforementioned silicon titanium and silicon carbide alumina, as well as substantially any inorganic compound that satisfies the shape of a fibrous crystal. This does not include powder materials. On the other hand, fibrous materials include natural fibers such as cellulose fibers, regenerated cellulose fibers, and cellulose acetate, fibers made of aromatic polyamide as synthetic fibers, fibers made of nitrogen-containing polyheterocyclic compounds, and fibers made of polyphenylene oxide ( It is possible to use one type or a combination of two or more types selected from polyarylene), aromatic polyester, aliphatic polyester, etc.

In a preferred embodiment of the present invention, thermal conductivity,
In combination with a highly heat-resistant fibrous material, for example, an aromatic polyamide fibrous material is advantageous in that any sheet obtained from it can be applied to printed circuit boards and various industrial materials.

In such a preferred embodiment,
Aromatic polyamide fibrous material (fibrid) disclosed in No. 5732 etc. is mixed with whiskers at the above-mentioned compounding ratio, and after paper making, heating or heat pressure is applied near the softening point of the fibrous material to achieve good bonding strength. This is an excellent method because it increases the mechanical strength of the sheet. In this way, whiskers and fibrous materials can be made by dispersing them simultaneously or separately to obtain a single sheet or a laminate (so-called sheet combination), and then monolayering or laminating them in a wet state. When whiskers are tightly entangled, it is difficult to disperse them, so when dispersing them uniformly, it is necessary to use a dispersion medium such as glass or sand to achieve sufficient dispersion through means such as high-speed stirring. The desired dispersion is obtained by adding the desired dispersion.

These whisker sheets of the present invention may be made using a conventional paper making method, such as a Fourdrinier machine, a circular paper machine, or a combination machine combining these machines, and an inclined paper machine capable of layer paper making can be used.

Example 1 10 parts of polymetaphenylene isophthalamide (logarithmic viscosity in sulfuric acid 1.5) was dissolved in 90 parts of N,N-dimethylacetamide containing 5 parts of Licl, and the solution was stirred at high speed. A pulp-like object was obtained by introducing the mixture into an aqueous glycerin solution in a homomixer. This is Canadian Standard Freeness (CSF)
was 80ml. Add 10 parts of silicon dioxide whiskers (average fiber length 100μ, diameter 0.5μ) to 500 parts of water,
A whisker dispersion slurry was prepared using a homomixer (manufactured by Tokushu Kika Kogyo). Next, 100 parts of a slurry containing 1 part of the above pulp-like material as a solid content was added to this slurry and mixed to obtain a uniform dispersion. Then, the paper was made by hand according to the usual method.30
A sheet of g/m ² was obtained. The obtained sheet has whiskers evenly dispersed, has a tensile strength of 0.20 kg/25 mm, and has excellent handling workability. The ash content of the sheet was 90.2%.

Example 2 A dispersion slurry of whiskers and pulp-like material was obtained in the same manner as in Example 1. Next, 30 parts of a 0.01% aqueous solution of a high molecular weight cationic polyacrylamide, Percoll 57 (manufactured by Allied Colloids), was added to this slurry and mixed. Make paper by hand according to the usual method, 30
A sheet of g/m ² was obtained. The texture of the sheet was that the whiskers were a little agglomerated and it was a little fluffy, but the tensile strength of the sheet was the same as in Example 1. Moreover, the ash content was 90.6%.

Example 3 NBKP was beaten and the beating degree was csf500ml, csf350ml,
200ml and 80ml of pulp slurry were obtained. 10 parts of silicon carbide whiskers (average fiber length 40 μm, diameter 0.2 μm) were added to 500 parts of water and dispersed at 6000 rpm using a homogenizer (Nippon Seiki Seisakusho) to obtain 4 uniformly dispersed slurries of whiskers. To this slurry, 1.5 g of each pulp slurry having a pulp solid content of which the beating degree had been changed was mixed to obtain four types of slurries. Then 0.01 of Percoll 57 for each
% solution in 30 parts portions at a time, and hand papermaking was performed using this slurry. In hand-making, a slurry is collected using an 80-mesh wire, and after dehydration, the felt or paper is brought into close contact with a wet sheet on the wire and pressed to transfer the slurry to the felt or paper.
When using pulp with a beating degree of 200 ml or more, the wet paper could not be transferred from the wire. In contrast to this
Transfer was possible only when using 80 ml of pulp, and subsequent press-drying was carried out without any problems, and 40 ml of pulp was used.
A sheet of g/m ² was obtained. This sheet was easy to handle.

Example 4 Silicon carbide whiskers (average fiber length 10μ, diameter
0.1μ) was used in the same manner as in Example 1 to obtain 500 parts of a whisker dispersion slurry. Next, 100 parts of a slurry containing pulp with a solid content of 1 part is added, and anionic polyacrylamide (Star Gum A-
15; manufactured by Seiko Kagaku) was added and mixed with stirring.
Further, 0.5 part of cationic polyacrylamide (Polystron 619; manufactured by Arakawa Chemical) was added and mixed with stirring. Using this slurry, hand paper is made by a conventional method,
A sheet of 50 g/m ² was obtained. The resulting sheet had a tensile strength of 0.6 kg/25 mm and was easy to operate. In addition, the whiskers were uniformly dispersed in the sheet.

Claims (1)

[Claims] 1. A method for producing a whisker sheet, which comprises integrally forming an aqueous composition in which whiskers are dispersed into a slurry and a fibrous material-containing slurry having a freeness of less than 100 mlcsf is added to the slurry.