JPH0553746B2 - - Google Patents

Description

[Detailed description of the invention]

Object of the Invention The present invention relates to a method for producing a calcium silicate plate by a papermaking method, and more specifically, a method for producing a calcium silicate plate by combining secondary particles (spherical agglomerates) of calcium silicate crystals and a specific flocculant. Regarding. Prior Art Calcium silicate plates are nonflammable, lightweight, and have excellent workability, so demand has been increasing in recent years. When producing a calcium silicate plate, a paper forming method is generally used as the forming method due to its high productivity. However, conventionally, calcium silicate plates formed using the paper-making method require high-temperature, high-pressure steam curing in an autoclave after paper-making. Due to the problem of having to use it for a long time and the low reactivity when autoclaved after molding, most of the products are mainly composed of tobermorite crystals, which have low heat resistance, and xonotrite crystals, which have high heat resistance, are used. It is difficult to obtain the main component,
It wasn't even manufactured. On the other hand, in Japanese Patent Publication No. 48-40896, spherical agglomerates made of needle-shaped xonotrite crystals (herein, these agglomerates are referred to as secondary particles) are mixed with wood fibers,
A method has been proposed in which this is formed by a papermaking method and then hot pressed. This method uses a raw material with unique properties called xonotlite crystal secondary particles.
This method makes it possible to manufacture wood fiber boards with excellent non-combustibility, but this method has the problem that reducing the amount of wood fiber to further improve the non-combustibility results in a decrease in strength and productivity. The dot was hot. Structure of the Invention The present invention is an improvement on the conventional method for manufacturing calcium silicate plates using a papermaking method using calcium silicate crystal secondary particles, and produces calcium silicate plates that are lightweight, have high strength, and are highly nonflammable. It can be manufactured with good productivity. The present invention uses 0.05 to 1.0 parts by weight of a cationic flocculant and 0.01 to 0.01 to 1.0 parts by weight of an anionic flocculant or nonionic flocculant to 100 parts by weight of solids in an aqueous slurry containing calcium silicate crystal secondary particles and wood fibers.
After adding 1.0 parts by weight within a range where the total amount of both does not exceed 1.5 parts by weight, the slurry is made into a paper,
The present invention relates to a method for producing a calcium silicate plate, characterized in that the obtained sheets are laminated and dried after pressure molding, or dried simultaneously with pressure molding. The secondary particles of calcium silicate crystals used in the present invention are disclosed in, for example, Japanese Patent Publication No. 53-12526 and Japanese Patent Application Laid-open No. 53-12526.
It can be manufactured by the method of No. 146997. That is,
It can be produced by heating a silicic acid raw material and a lime raw material under pressure while stirring in an autoclave to cause a hydrothermal synthesis reaction. Further, it is preferable that the secondary particles obtained in this way are crystals mainly composed of xonotlite from the viewpoint of heat resistance, and the secondary particles of xonotlite crystals have a CaO/SiO ₂ molar ratio of the silicic acid raw material and the lime raw material. Usually 0.8
~1.3, and the water vapor pressure during the hydrothermal synthesis reaction is usually 8 Kg/cm ² or more. As the silicic acid raw material and the lime raw material, any conventionally known raw materials can be used. In the present invention, an aqueous slurry containing the secondary particles and the fibers is prepared by adding wood fibers to the aqueous slurry of the calcium silicate crystal secondary particles. As the wood fiber, for example, wood pulp, waste paper pulp, notkas, etc. can be used. The content of the wood fibers is generally about 2 to 10% by weight based on the solid content of the aqueous slurry containing the calcium silicate crystal secondary particles and the wood fibers.
If the content exceeds 10% by weight, the nonflammability tends to decrease, and if the content is less than 2% by weight, the strength of the sheet tends to decrease and paper making becomes difficult, which is not preferable. In the present invention, the use of wood fibers improves paper formability and improves the strength of the resulting molded plate, but if necessary, inorganic fibers such as glass fibers, vinylon fibers, popipropylene fibers,
Synthetic fibers such as polyamide fibers may be used in combination as appropriate. Glass fibers and vinylon fibers contribute to improving the strength of the obtained molded plate, and polypropylene fibers and polyamide fibers contribute to improving the impact resistance of the obtained molded plate. The solid content concentration of the aqueous slurry containing the above secondary particles of calcium silicate crystals and wood fibers is usually
It is preferable to adjust the amount to about 0.2 to 3% by weight for paper making. In the present invention, papermaking is carried out after adding specific amounts of a cationic flocculant and an anionic flocculant or a nonionic flocculant to the aqueous slurry containing the calcium silicate crystal secondary particles and wood fibers obtained above. It is mandatory that This addition improves the freeness of the solid content in the slurry, allowing efficient papermaking. The amount of the cationic flocculant added is based on 100 parts by weight of the solid content in the above slurry.
As mentioned above, it is effective to keep the amount of the anionic flocculant or nonionic flocculant at about 0.05 to 1.0 parts by weight, and the total amount of both does not exceed about 1.5 parts by weight. This is necessary from the standpoint of papermaking. In the present invention, the effect obtained by using such a specific flocculant in combination is that the secondary particles and wood fibers are
By coagulating with a cationic flocculant and an anionic flocculant, or a cationic flocculant and a nonionic flocculant, it is possible to form a stable floc, thereby increasing the freeness of the solid content in the slurry. Seem. Further, when adding a flocculant, it is preferable to first add a cationic flocculant, and then add an anionic flocculant or a nonionic flocculant. That is, when a specific amount of cationic flocculant is added to the slurry, the ζ potential (interfacial potential) in the slurry and on the surface of the solid content is increased to form aggregates that are not decomposed even by stirring, and then the specific By adding an amount of an anionic flocculant or a specified amount of a nonionic flocculant, the above-mentioned aggregates can be agglomerated to obtain a slurry having large and stable flocs. Furthermore, according to experiments conducted by the present inventors, when a cationic flocculant, an anionic flocculant, or a nonionic flocculant is used alone, the flocculation in the slurry is insufficient even if the amounts of these agents are increased. There is a lot of leakage during paper making (poor freeness), resulting in poor paper making properties. The flocculant used in the present invention preferably has a molecular weight of about tens of thousands for cationic flocculants.
The anionic flocculant and nonionic flocculant preferably have a molecular weight of approximately several million to ten million. Further, the anionic flocculant preferably has an ionic strength of 1.5 meq/g or less. Here, the ionic strength is determined as follows. That is, after adding a certain amount of methyl glycol chitic acid (cationic reagent) to an aqueous solution of an anionic flocculant, the pH of the aqueous solution is adjusted to 10.0, and then toluidine blue is added as an indicator. Then, the neutralization equivalent is determined by titration with an aqueous polyvinyl potassium sulfate solution (anionic reagent), and the value obtained by the following formula is taken as the ionic strength. Ionic strength (meq/g) =
Neutralization equivalent/solid content of anionic flocculant Specific examples of the cationic flocculant include flocculants such as polyethyleneimine, dialkylamine/epichlorohydrin polycondensate, and modified polyamidoamine/epichlorohydrin. Specific examples of anionic flocculants include ammonium polyacrylate, polyacrylates such as sodium polyacrylate, and acrylamide/acrylic acid copolymers. Furthermore, specific examples of nonionic flocculants include polyacrylamide, polyethylene oxide, and the like. The slurry to which the flocculant has been added is made into paper using a normal paper making method, the resulting sheets are laminated to a required thickness, cut with a cutter, and then pressure-formed to a predetermined thickness and dried. Furthermore, if pressure forming and drying are performed simultaneously using a hot press or the like, the strength of the plate can be improved and the cost of drying fuel can be reduced, which is advantageous. Effects of the Invention According to the method of the present invention, there is no dropout of the molding material during papermaking, and the water time is short, resulting in excellent productivity.Furthermore, the molded plate obtained by this method has a bulk density of, for example, 0.6. It has a high bending strength of 100Kg/cm2 or ^more at ~0.7g/ ^cm3 ,
Furthermore, it has the feature of being nonflammable. EXAMPLES Hereinafter, the present invention will be described in more detail with reference to production examples and examples. In each example, "parts" and "%" indicate "parts by weight" and "% by weight," respectively, unless otherwise specified. Production example: 49 parts quicklime and silica powder slaked with warm water at approximately 85℃
51 parts (CaO/SiO ₂ molar ratio 1.0) was prepared as a raw material slurry by adjusting the amount of water so that the amount of water was 12 times the solid content, and subjected to a hydrothermal synthesis reaction under stirring at a pressure of 15 kg/cm ² for 4 hours. An aqueous slurry of secondary particles of xonotrite crystals was obtained. Example 1 8 parts of kraft pulp (produced in Canada), 2 parts of glass fiber, and water were added to 90 parts (solid content) of the aqueous slurry of secondary xonotlite crystal particles obtained in the production example to make a slurry with a solid concentration of 2%. I mixed it. A cationic flocculant [“Polymaster R-
607 (dimethylamine/epichlorohydrin polycondensate with a molecular weight of approximately 25,000, manufactured by Hakuto Kagaku Co., Ltd.)], an anionic flocculant [``Polymaster R-623S'' (with a molecular weight of approximately 7 million) was added. Acrylamide/acrylic acid copolymer, ionic strength 1.1meq/
(manufactured by Hakuto Kagaku Co., Ltd.)] and further diluted with water to adjust the liquid volume to 5% and the solid content concentration to 0.6%. Freeness was evaluated using a tapping standard machine. The results are shown in Table 1. However, the evaluation was performed using the following method. (1) Molding material falling out from the wire mesh: Visually inspect. (2) Strength of the sheet: Pinch the sheet after papermaking with your fingers and lift it.
Evaluate according to the following criteria. ○: It does not break even if you pick it up and shake it. ×; The sheet breaks when lifted and shaken. (3) Filtration time: Measure the time from the start of filtration until the water on the mat disappears.

[Table] Table 1 shows that according to the present invention, by using a specific amount of a cationic flocculant and a specific amount of an anionic flocculant in an aqueous slurry containing calcium silicate crystal secondary particles and wood fibers, freeness is improved. It is clear that calcium silicate plates can be manufactured with high productivity. Example 2 The same aqueous slurry as used in Example 1 was mixed with a predetermined amount of the aqueous slurry of xonotlite crystal secondary particles obtained in Production Example, kraft pulp, and glass fiber to form a slurry with a solid content concentration of 2.0%. A material slurry was prepared by adding 0.1 part of each of the cationic flocculant and the same anionic flocculant used in Example 1 to 100 parts of solid content. Using this material slurry, a thin sheet was formed using a tapping test machine, and the sheets were laminated and then pressure-formed using a hot press and dried at the same time to obtain a calcium silicate plate with a thickness of 6 mm. . Table 2 shows the blending ratio and the measurement results of physical properties.

【table】

[Table] Example 3 Using a material slurry adjusted to the blending ratio of Example 2-1 or 2-2, papermaking was carried out using a circular mesh papermaking machine to create a thin sheet. After the sheets were laminated, they were pressure-formed using a hot press and simultaneously dried to produce molded plates with thicknesses of about 6 mm and about 9 mm. The physical properties of the obtained product were investigated in the same manner as in Example 2 and were as shown in Table 3.

【table】

[Table] Example 4 In Example 1, a nonionic flocculant ["Polymaster R-620" (polyacrylamide with a molecular weight of about 6 million, manufactured by Hakuto Chemical Co., Ltd.) was used instead of the anionic flocculant.
The freeness was evaluated in the same manner as in Example 1, except that a sample (manufactured by J.D. Co., Ltd.) was used. The results are shown in Table 4.

【table】

[Table]
Table 4 shows that according to the present invention, by using a specific amount of a cationic flocculant and a specific amount of a nonionic flocculant in an aqueous slurry containing calcium silicate crystal secondary particles and wood fibers, the freeness is significantly improved. It is clear that calcium silicate plates can be manufactured with good productivity.

[Claims]

1 5 to 50 volume % of partially stabilized zirconia with an average particle size of 0.1 to 1.0 μm; 3 to 40 volume % of silicon carbide whiskers with a diameter of 1 μm or less and an aspect ratio of 3 to 200 (however, the total of this silicon carbide whisker and the zirconia is (55% by volume or less); High strength, high hardness alumina-zirconia-silicon carbide composite sintered body, the remainder of which is substantially composed of alumina. 2. 5-50% by volume of partially stabilized zirconia powder with an average particle size of 0.1-1.0 μm; 3-40% by volume of silicon carbide whiskers with a diameter of 1 μm or less and an aspect ratio of 3-200.
(However, the total of the silicon carbide whiskers and the zirconia powder is 55% by volume or less); The mixed powder, the remainder of which is essentially alumina powder, is molded, and this molded body is sintered at a temperature within the range of 1400 to 1700°C. A method for producing a high-strength, high-hardness alumina-zirconia-silicon carbide composite sintered body by sintering or pressure sintering.