JPS62101B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an inorganic material sheet having sinterability. Conventional methods for manufacturing ceramics include direct methods such as hot pressing, melt casting, gas cracking, and forging, in which raw materials (powder) → molding → sintering are performed in one operation, and dry pressing, extrusion, and casting. , injection molding, doctor blade,
Indirect methods such as rubber presses were used. Industrially, indirect methods are the mainstream, but the doctor blade method is particularly preferred because it has high thickness accuracy and can yield thin sheets. The characteristics required of these molded sheets (green tapes) are (1) uniform tape thickness (2) uniform composition (3) good dimensional stability (4) appropriate flexibility (5) It is easily thermally decomposed and leaves no ash. In order to satisfy these required properties, various solvents, binders, plasticizers, peptizers, wetting agents, etc. have been studied. However, this method requires expensive materials such as polyvinyl butyral as a binder, and the use of solvents poses various operational difficulties. is required. Several methods have been proposed from this point of view, one of which is to replace cellulose pulp with a degree of substitution of 0.02~
Water content 200-100ml CSF after cationic denaturation to 0.04
There are two methods, such as a method of making paper using a conventional paper-making method using beaten pulp and inorganic powder (Japanese Patent Application Laid-Open No. 56-63099), and a method of using pulp pre-impregnated with a flocculant (Japanese Patent Application Laid-Open No. 56-167407). The former requires a process of cationizing the pulp in advance, and it is difficult to manufacture sheets containing a large amount of inorganic powder when the water content of the pulp is 100 to 200 c.c. (JIS method). The drawback was that high-quality ceramics could not be manufactured. As a result of intensive research from the viewpoint of the physical form of organic fibers and the space factor of inorganic substances, the present inventors found that if the space factor of all inorganic substances in the sheet is 25% or more, the water content of the fiber suspension is It was discovered that an extremely good ceramic can be obtained from an inorganic material sheet consisting of 3 to 20% by weight of organic fibers of 100 to 400 c.c./0.3g at a concentration of 0.03% by weight, leading to the completion of the present invention. Generally, in order for an inorganic material sheet to have homogeneous sinterability, the space factor of the inorganic material before firing is important. The space factor of the constituent material can be calculated based on the following formula from the density of the sheet before firing and the density of each component. Space factor of inorganic material Vi=P/Pixw Space factor of organic material Vo=P-PiVi/Po Space factor of voids Va=1-(Vi+Vo) However, P: Density of raw molded sheet Vi: Inorganic space factor Productivity Vo: Organic content 〃 Va: Voids 〃 Pi: Inorganic content ideal density after sintering Po: Organic content average density xw: Inorganic content weight ratio Here, the organic content average density (Po) is the pulp component and binder resin. It means the average density of
Calculated using the formula below. Po=P ₁ P ₂ (x ₁ + x ₂ )/P ₁ x ₂ + P ₂ x ₁ P ₁ : Pulp fiber density P ₂ : Binder resin density x ₁ : Pulp weight density x ₂ : Binder resin weight ratio Inorganic matter When manufacturing ceramics by sintering a sheet, if the inorganic space factor is low, a uniform sintered body cannot be obtained and the sintered state may be low density, distorted, or in extreme cases. Sometimes they are not fired as a whole and end up in pieces. Therefore, the higher the inorganic space fraction, the more desirable. FIG. 1 shows the relationship between the sintering temperature and the inorganic space factor of the green sheet during normal sintering of alumina. The shaded area is a region that can be sintered, but from the viewpoint of dimensional accuracy and economical efficiency, the inorganic space factor of the green sheet must be 25% or more, preferably 40% or more. It was confirmed that for other sinterable materials, the inorganic space factor of the raw sheet required to obtain a good sintered body is about the same as that of alumina. The weight ratio of the inorganic material powder required to achieve the above inorganic volume ratio varies slightly depending on its true specific gravity, but is approximately 70
% or more from various experimental results. Particularly when attempting to sinter high-density inorganic materials with high specific gravity, 90% by weight or more, preferably 95% by weight.
It was also found that a higher inorganic content ratio is required. It is not only extremely difficult to produce sheets with such a high mineral content using ordinary wood pulp raw materials (600 to 100 c.c. CSF), but even if it were possible, This is undesirable from the viewpoint of smoothness because the pulp disappears after consolidating and remains in the form of a pipe with a diameter of 10 μm. The inventors of the present invention have fully grasped the current situation and have conducted intensive research to create an inorganic material sheet in which the inorganic material powder is sufficiently fixed, which can be made using a general paper machine, and which has good sinterability after firing. I ended up getting it. The organic fibers used in the present invention include:
Examples include vegetable fibers such as hardwood pulp, softwood pulp, and cotton linters, and synthetic fibers such as acrylic fibers, polyester fibers, polypropylene fibers, and rayon fibers. Among these, fibers that can be made into fine fibrils are suitable for the present invention. In this respect, acrylic fibers and rayon fibers are particularly suitable among synthetic fibers in addition to vegetable fibers. Moreover, some of these fibers can also be replaced with inorganic fibers. As a method of measuring freeness, the Canadian standard freeness defined in JISP8121 is generally known.
The fine fibrillable organic fibers used in the present invention have extremely low freeness values;
Since freeness cannot be displayed properly, the freeness measurement method shown below (hereinafter referred to as freeness H method or simply H) is used.
law) was adopted. Freeness H method Using a Canadian standard freeness tester specified in JISP8121, test the brass sieve plate at the bottom of the filter tube.
Concentration of disintegrated pulp after changing to 50 mesh wire mesh
Except for changing 0.3% to 0.03%, the freeness measurement procedure is exactly the same as the JIS method, and the measured value is converted to H
It was defined as legal freeness. This H method reflects the state of fine fibrillation well and can be said to be a suitable method for indicating the degree of fibrillation of fibers necessary for the present invention. Using this method, we investigated the relationship between the water content of various fiber materials and the fixing properties of inorganic powders, and found that the water content suitable for fixing is approximately 400 c.c. or less using the H method. . When the inorganic substance powder is a ferroelectric substance, it exhibits good fixing properties even without the use of a fixing aid due to the high polarity of the material itself, but in the case of a general paraelectric substance, a fixing agent is required. In this case, high fixing properties can be obtained by using a nonionic polymeric fixing agent, a cationic polymeric fixing agent, or a combination of both. The above-mentioned beaten fine fibers alone have low aqueous properties and are difficult to make into paper, but after fixing the inorganic substance powder, the aqueous properties greatly improve as they form micro flocs.
The ability to make paper is a completely unexpected result, and the economic effect on papermaking is also great. In addition, in order to improve the peelability from the twin wire and the strength of the wet paper, it is possible to add a very small amount of relatively coarsely beaten fibers within a range that does not affect the smoothness after firing to further improve the papermaking properties. do not have. These relatively coarse fiber raw materials act as a support for fine fibers on which inorganic powder particles are fixed, so if it is less than 0.5% by weight, the effect is difficult to appear, but if it is more than 10% by weight, papermaking properties are good, but , sinterability during firing tends to deteriorate. However, when the coarse fiber raw material is a fibrous inorganic material, good papermaking properties and a high inorganic fraction can be obtained. The above-mentioned constituent raw materials are used as the main materials, binder resin is added as needed, and after the sheet is formed through the papermaking process, it is dried using a normal dryer process. It becomes possible to increase the volume ratio of objects to 30% or more. In this case, the pressure of the hot pressure roll is preferably 20 to 100 kg/cm, and if a binder resin is used, the temperature of the roll is preferably at least the softening temperature of the binder. This will be explained in detail below using examples. Example 1 The inorganic powder is alumina powder (for example, true specific gravity
3.93, α-alumina powder with an average particle diameter of 0.83 μm), and unbleached softwood pulp of various degrees of beating (200 to 400 c.c. according to the water test H method) as the organic fiber to create sheets. Fixability of alumina powder,
Sinterability etc. were confirmed. An emulsion type acrylic resin was added as a binder. After mixing these raw materials in the proportions shown in Table 1, 0.1% by weight of a nonionic polymer fixing agent was added to the raw material slurry (4% concentration) as a fixing agent, and the alumina powder and binder resin were mixed into pulp fibers. This was fixed on the surface and paper was made using a conventional wet cylinder Yankee paper machine at a speed of 3 m/min. The paper drying sheet was made highly dense and highly smooth using a super calender at a linear pressure of 30 kg/cm and a temperature of 120°C. The obtained inorganic material sheet was sintered in an electric furnace at a firing temperature of 1600°C, and the uniformity of the sheet after firing was evaluated.
The surface smoothness was examined and the sinterability was evaluated. Table 2 shows the properties of sheets using pulps with various degrees of beating. Incidentally, the inorganic content fixing rate was determined by measuring the added weight and the weight after firing.

【table】

【table】

[Table] Example 2 As the organic fiber, unbleached softwood pulp beaten to 200 c.c. by H method was used, and as the inorganic powder, α-alumina powder of the same type as in Example 1 was used. A sheet with an inorganic ratio was created. The fixing method and paper making method were all the same as in Example 1. Table 3 shows the raw material blending ratios of various blending ratios and their characteristics.

[Table] Example 3 As Experiment No. 1, the same α-alumina powder as in Example 1 was used, and the organic fibers were acrylic fibers and beaten cashmilon fibers of H method 200 c.c., and low beaten cashmilon fibers of JIS method 300 c.c. Paper was made by blending pulp and other materials to create sheets. Experiment No. 2 used H method 200c.c. acrylic fiber/beaten cashmilon fiber as the organic fiber, and Experiment No. 3 used H method.
Sheets were prepared in the same manner as in Example 1 using 200 c.c. of beaten rayon fibers. In Experiment No. 4, paper was made and sheets were made in exactly the same manner as in Example 1, except that a part of the alumina powder was replaced with alumina fiber. Table 4 below shows the blending ratio and sheet properties. As shown in Table 4, the sheets of Experiments No. 1 to No. 4 all had good sinterability.

【table】

[Table] Example 4 As the organic fiber, unbleached softwood pulp beaten to 200 c.c. by water test method H was used, and as the inorganic powder, barium titanate powder with an average particle size of 2 μm was used. Table 5 below shows blending examples and sinterability. The paper was made under the same conditions as in Example 1.

【table】

【table】 [Brief explanation of the drawing]

FIG. 1 shows the relationship between the sintering temperature and the inorganic space factor of the green sheet during normal sintering of alumina. The shaded area is the area that can be fired.

Claims (1)

[Scope of Claims] 1. An inorganic material sheet produced by a wet papermaking method using inorganic particles and organic fibers as main raw materials, (1) using plant fibers and/or synthetic fibers capable of forming fine fibrils as the organic fibers ( 2) The space factor of all inorganic particles in the sheet is 25%
The above is preferably 40% or more, and (3) the organic fiber has a water filtration degree of 100 to 400 c.c. when measured at a concentration of 0.03% by weight.
An inorganic material sheet characterized by containing % by weight.