JPS6259073B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improved method for manufacturing ceramic molded bodies, and more particularly to a method for easily manufacturing ceramic molded bodies ranging from very thin to extremely thick. Ceramic molded bodies are used as insulating materials such as multilayer wiring boards for electronic circuits, dielectric materials such as multilayer capacitors,
It is applied to piezoelectric materials such as piezoelectric buzzers.
An example of an application that has recently attracted particular attention is multilayer wiring boards made of alumina ceramics, which are used to miniaturize electronic components or circuits. Ceramic molded bodies applied in these fields are obtained by molding ceramic raw materials into rods, tapes, or thin sheets, and typical molding methods include extrusion molding and doctor blade casting. . The former extrusion molding method is a method in which ceramic raw material powder is mixed with a water-soluble polymer as a binder and water as a medium, and then molded using a high-pressure or vacuum extruder. Since it is possible to mold the ceramic raw material using the minimum amount of water necessary, it is possible to obtain a molded product that is dense and has good dimensional stability. Therefore, it is especially used in dielectric materials such as capacitors. However, in the case of ceramic tape for multilayer wiring boards used in computers, extremely thin tape of about 0.1 to 0.3 mm is required, so when using the extrusion molding method, the parts that come into contact with both ends of the mold inevitably become distorted, resulting in a uniform It is difficult to form a tape with a certain thickness. On the other hand, a method that is more widely adopted than the extrusion method is the doctor blade casting method.
This method uses polyvinyl butyral, which has a high film strength, as the binder, and requires the use of butyl alcohol or chlorethylene-based solvents as the medium, which inevitably causes problems in terms of fire safety and environmental hygiene. . This method involves pouring a slurry obtained by mixing ceramic raw material powder, a binder, and a solvent onto a carrier sheet, stretching it to a certain thickness with a doctor blade, and then peeling it off from the carrier sheet after drying to obtain a tape. be. Therefore, a tape with a wide width can be easily obtained, but due to the limited viscosity of the slurry, particle sedimentation is inevitably observed after casting.
It cannot be formed into a thick, uniform tape, and it is generally said that the maximum thickness is approximately 1.2 mm. For these reasons, there has been a strong desire in the industry to establish a method for producing ceramic molded bodies of any shape, which is water-based and has high dimensional accuracy without causing any problems in terms of fire safety or environmental hygiene. The present invention was arrived at as a result of extensive research from this point of view, and consists of 100 parts by weight of ceramic raw material powder, 1 to 10 parts by weight of a water-soluble binder, 0.5 to 10 parts by weight of sorbitan fatty acid ester as a plasticizer, and 5 parts by weight of water. This is a method for producing a ceramic molded article, characterized in that a composition comprising up to 30 parts by weight is mixed and extrusion molded and/or roll molded. Ceramic raw material powders used in the method of the present invention include alumina, barium titanate, lead zirconate titanate, zirconia, titanium oxide, silicon nitride, silicon carbide, boron nitride, and the like. As the water-soluble binder, commonly used water-soluble resins can be used, but it is particularly preferable to use water-soluble polyvinyl alcohol and water-soluble cellulose ether. Among water-soluble polyvinyl alcohols, those with a degree of saponification of polyvinyl acetate of 70 mol% or more and a degree of polymerization of 500 or less are preferable, and among water-soluble cellulose, those with a degree of methoxy group substitution of 1.3 are preferable.
~2.2 methylcellulose is preferred. Sorbitan fatty acid ester used as a plasticizer is an ester of sorbitan and a fatty acid having 6 to 18 carbon atoms, and includes monofatty acid ester, difatty acid ester,
Trifatty acid esters or mixtures thereof can be used, and those with HLB values of 9 to 12.5 show particularly good performance. Number of carbon atoms constituting sorbitan fatty acid ester is 6
~18 fatty acids include caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, 2-ethylhexanoic acid, tridecanoic acid, isostearic acid, oleic acid, linoleic acid, linolenic acid, and ricinol. There are acids etc. Sorbitan fatty acid ester is a nonionic surfactant, and adding it reduces the viscosity during mixing, making it easier to mix the ceramic raw material powder and the water-soluble binder, resulting in a uniform dispersion. It will be done. In addition, when extrusion molding is performed, thixotropy is imparted, so that it flows out easily from the mold, and distortion of the ceramic molded body at the portions that come into contact with both ends of the mold is less likely to occur. Furthermore, the mold releasability is good, and the kneaded material does not adhere to the rolling roll during tape molding, and the physical properties of the molded ceramic sheet are excellent, resulting in a sheet with good strength and flexibility. The blending ratio of sorbitan fatty acid ester as a water-soluble binder and plasticizer to the ceramic raw material powder is 1 to 10 parts by weight, preferably 3 to 8 parts by weight, of the water-soluble binder to 100 parts by weight of the ceramic raw material powder.
Parts by weight, sorbitan fatty acid ester 0.5~
10 parts by weight, preferably 3 to 6 parts by weight. Further, the amount of water added is 5 to 30 parts by weight. The optimum addition amount varies within the above range depending on the particle size and shape of the ceramic raw material powder and the type of water-soluble binder, but the apparent density of the ceramic raw material powder is large,
Also, if the viscosity of the water-soluble binder is low, the amount of water added may be reduced, while if the apparent density of the ceramic raw material powder is low or the viscosity of the water-soluble binder is high, the amount of water added may be increased. is necessary. In the production method of the present invention, it is necessary to thoroughly mix, knead, and ripen the raw material mixture. The water-soluble binder, sorbitan fatty acid ester and water may be added to the ceramic raw material powder at the same time, but the water-soluble binder dissolved in water may be added to the ceramic raw material powder before the sorbitan fatty acid ester is added. Alternatively, a method in which a water-soluble binder and a sorbitan fatty acid ester dissolved or dispersed in water is added to the ceramic raw material powder allows easy mixing and kneading of the ceramic raw material powder, and a uniform dispersion can be obtained. Since the method of the invention produces ceramic molded bodies in an aqueous system using water-soluble binders, the fire safety and environmental health problems associated with the use of organic solvents are completely avoided. When the composition of the present invention is molded by extrusion molding, a uniform ceramic molded product is obtained with less distortion of the part that contacts the mold, and when tape molding is performed using rolling rolls, the clearance between the rolls can be adjusted. Since it can be formed into a tape of any thickness with just a single step, it is also possible to easily form a tape with a thickness of 0.3 mm or less, which could only be obtained by the casting method. Moreover, due to the problem of sedimentation of ceramic raw powder particles in the casting method, the
While it is not possible to obtain tapes with a thickness exceeding mm, it is also possible to form such thick tapes. Furthermore, in the casting method, a porous tape is inevitably obtained due to the evaporation of the solvent;
In the method of the present invention, when the tape is subjected to a pre-kneading step such as extrusion molding and then roll-formed, a dense tape with high strength and good dimensional stability can be obtained. Ceramic tapes are sometimes printed with patterns before sintering, and in this case, the permeability of the printing ink becomes a problem, but in the present invention, a water-soluble polymer is used as the binder, so there is no possibility of bleeding of the printing ink. It is possible to easily perform fine printing without any stains. Next, examples of the present invention will be given. Example 1 Alumina powder (average particle size 4μ) 100 parts by weight Talc powder 6 parts by weight Clay powder 2 parts by weight Poval UMR-10H 6 parts by weight (Unitika Kasei Co., Ltd. product, degree of saponification of polyvinyl acetate 70 to 95 moles) %, polyvinyl alcohol with a degree of polymerization of 100) Plasticizer: 4 parts by weight Water: 20 parts by weight In the above composition, in addition to the sorbitan fatty acid ester, which is a nonionic surfactant used in the present invention, as a plasticizer, polyoxyethylene was added for comparison purposes. A nonionic surfactant was used. First, an aqueous solution of poval and a plasticizer dissolved in water is added to the specified amounts of alumina powder, talc powder, and clay powder, thoroughly kneaded, and passed through a vacuum extrusion molding machine to form a sheet with a thickness of 10 mm and a width of 500 mm. Extrusion molded. Table 1 shows the situation and the condition of the sheet. From Table 1, it is clear that those using sorbitan fatty acid ester as a plasticizer have excellent extrusion conditions and sheet conditions, and those using sorbitan fatty acid ester with an HLB of over ₉ are particularly excellent. After thoroughly kneading the compositions No. 1 and No. 2 in Table 1, they were put into a vacuum extrusion molding machine to a thickness of 10 mm.
The alumina tape was extruded into a sheet with a width of 500 mm and then passed between rolls with clearances of 5 mm, 2 mm, and 1 mm in order to obtain an alumina tape with a thickness of 0.2 mm. The surface condition of each tape was uniform and glossy. The ceramics obtained by firing these tapes in a reducing flame at about 1450°C were also in good condition.

【table】

[Table] Example 2 Lead zirconate titanate powder 100 parts by weight Metrose SM-4000 3 parts by weight (Methylcellulose, product of Shin-Etsu Chemical Co., Ltd.) Plasticizer 2 parts by weight Water 10 parts by weight In the above composition, plasticizer The same nonionic surfactant as in Example 1 was used. An aqueous solution of methyl cellulose and a plasticizer was added to a specified amount of lead zirconate titanate powder, thoroughly kneaded, and then extruded into a rod shape using a flow tester. Table 2 shows the extrusion conditions and rod conditions. From Table 2, it is clear that the products using sorbitan fatty acid ester as a plasticizer are excellent in both the extrusion condition and the rod condition, and it is clear that the products using sorbitan fatty acid _ester as a plasticizer are particularly excellent. After thoroughly kneading the compositions No. 10 and No. 11 in Table 2, they were put into a vacuum extrusion molding machine to a thickness of 10 mm.
The tape was extruded into a sheet with a width of 500 mm and a width of 500 mm, and then passed between rolls that were sequentially tightened with clearances of 5 mm, 2 mm, and 1 mm, to finally obtain a lead zirconate titanate ceramic tape with a thickness of 0.3 mm. The surface condition of each tape was uniform and glossy. The ceramics obtained by firing these tapes in a reducing flame at about 1450°C were also in good condition.

【table】

【table】

Claims (1)

[Claims] 1. A composition consisting of 100 parts by weight of ceramic raw powder, 1 to 10 parts by weight of a water-soluble binder, 0.5 to 10 parts by weight of sorbitan fatty acid ester as a plasticizer, and 5 to 30 parts by weight of water, A method for producing a ceramic molded body, characterized by extrusion molding and/or roll molding. 2. The method for producing a ceramic molded article according to claim 1, wherein the water-soluble binder is water-soluble polyvinyl alcohol or water-soluble cellulose ether. 3. The method for producing a ceramic molded article according to claim 2, wherein the water-soluble polyvinyl alcohol has a degree of saponification of polyvinyl acetate of 70 mol% or more and a degree of polymerization of 500 or less. 4. The method for producing a ceramic molded article according to claim 2, wherein the water-soluble cellulose ether is methyl cellulose with a degree of methoxy group substitution of 1.3 to 2.2. 5. The method for producing a ceramic molded article according to claim 1, wherein the sorbitan fatty acid ester is an ester of sorbitan and a fatty acid having 6 to 18 carbon atoms. 6 HLB with sorbitan fatty acid ester from 9 to 12.5
6. The method for producing a ceramic molded article according to claim 1 or 5, wherein the ceramic molded article has a value.