JPH0127018B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a binder used when molding so-called ceramics such as alumina, barium titanate, ferrite, etc., and particularly to a water-based binder for molding ceramics that does not use an organic solvent. Ceramics molding methods include dry press molding,
There are doctor blade methods, extrusion molding methods, etc., but the various binders used in these molding methods have many drawbacks. In the dry press molding method, a mold is filled with a ceramic composition that is granulated by spray drying a slurry prepared by mixing ceramic powder such as alumina with water, a lubricant, a binder, a plasticizer, etc. This is a method of press forming. As the binder used in this molding method, polyvinyl alcohol, methyl cellulose, and sodium salt of carboxymethyl cellulose are generally used. However, the granules obtained using these binders are hard, and therefore the press pressure must be increased, resulting in equipment problems such as increased die wear, shortened die life, and larger press machines. There are problems and it is also difficult to mold complex shapes. By using a plasticizer such as glycerin or polyethylene glycol in combination with a binder, it is possible to soften the granules slightly and reduce the pressing pressure, but this increases the amount of organic substances other than the binder, making it difficult to remove the binder before firing. When removing the binder, the shrinkage becomes large, causing deformation such as blistering and distortion, and cracking, and the bonding force decreases, resulting in weak mechanical strength, which is undesirable. Furthermore, during storage after molding, the plasticizer may bleed onto the surface or volatilize, causing brittleness. In addition, the Na salts of polyvinyl alcohol, methylcellulose, and carboxymethylcellulose have poor thermal decomposition properties, and carbon and carbon that cannot be decomposed or burned out in the binder removal process.
A large amount of ash containing alkali metals such as Na remains, which causes deformation such as blisters, cracks, and cracks during the firing process, causing damage to IC substrates, IC packages, etc.
When used as a dielectric or other electronic component, it causes loss of electrical properties such as electrical insulation. Furthermore, these binders have high hygroscopicity, and mechanical strength decreases due to moisture absorption after press molding, causing breakage during storage or handling before binder removal. In the doctor blade method, a slurry prepared by mixing ceramic powder with an organic solvent, a dispersant, a plasticizer, an organic solvent binder, etc. is cast onto a carrier film with a doctor blade to adjust the thickness, and then dried. This is a method of forming into a tape-shaped green sheet. Toluene, trichloroethylene, ispropyl alcohol, ethyl alcohol, etc. are used as organic solvents, but they pose problems such as the risk of explosion or fire due to ignition, odor during molding, toxicity to the human body, and pollution problems due to evaporated organic gas during drying. There are many problems. Additionally, it will be necessary to install explosion-proof equipment, waste gas treatment equipment, solvent recovery equipment, etc. Polyvinyl butyral is generally used as an organic solvent binder, but it has poor thermal decomposition properties and ash content such as carbon and sodium that remains after binder removal causes the same problems as binders for press molding.
Furthermore, a plasticizer such as a phthalate ester must be used, and the molded product becomes brittle due to breathing or volatilization of the plasticizer on the surface during storage after molding. In the extrusion molding method, ceramic powder is mixed with water, a dispersant, a lubricant, a binder, a plasticizer, etc.
This is a method of extrusion molding using an extrusion molding machine. Methyl cellulose, hydroxyethyl cellulose, and polyvinyl alcohol are generally used as binders, but they have poor thermal decomposition properties, and the same problems as binders for press molding occur due to ash content such as carbon and Na remaining after binder removal. . In view of the current situation, the present inventor has developed a press molding method,
As a result of extensive research to solve these problems with binders in doctor blade methods, extrusion molding methods, etc., we have developed a (meth)acrylic acid alkyl ester having an alkyl group of 1 to 20 carbon atoms and a carbon number of 1 to 4. 25-85% by weight of at least one monomer selected from the group consisting of (meth)acrylic acid alkoxyalkyl esters having alkylene groups, 10-60% by weight of vinyl acetate, and 5-60% by weight of carboxyl group-containing monomers ( However, the total amount of all monomers is 100% by weight.) It was discovered that a binder for ceramic molding obtained by copolymerizing the above-mentioned monomers satisfies these requirements, and the present invention was completed. In other words, the present invention aims to reduce press pressure, improve moldability, and moisture absorption in the press molding method; shift from a solvent-based to a safe and hygienic water-based system in the doctor blade method, and improve thermal decomposition; and improve thermal decomposition in the extrusion method. The object of the present invention is to provide a binder for use in ceramic molding that provides improved degradability and improved moldability. In the following description, (meth)acrylic acid refers to acrylic acid and/or methacrylic acid,
(Meth)acrylate shall denote acrylate and/or methacrylate. As the (meth)acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms used in the present invention, methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate acrylate,
Isobutyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-dodecyl (meth)acrylate, stearyl (meth)acrylate, etc. can be used. Examples of the (meth)acrylic acid alkoxyalkyl ester having an alkylene group having 1 to 4 carbon atoms include methoxymethyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxymethyl (meth)acrylate, ethoxyethyl (meth)acrylate, Ethoxybutyl (meth)acrylate, butoxyethyl (meth)acrylate, etc. can be used. At least one selected from the group consisting of (meth)acrylic acid alkyl esters having an alkyl group having 1 to 20 carbon atoms and (meth)acrylic acid alkoxyalkyl esters having an alkylene group having 1 to 4 carbon atoms. The seed monomers should be used in proportions ranging from 25 to 85% by weight out of 100% by weight of total copolymerized monomers. If the ratio is too low (less than 25% by weight), the thermal decomposition property will decrease, the press pressure will increase due to the hardness, and the binding strength as a binder will decrease. If the ratio exceeds 85% by weight, the hydrophilicity decreases, the amount of wetting and adsorption to ceramic powder decreases, and the binding strength as a binder decreases. Vinyl acetate is 10~10% by weight of copolymer monomer
Must be used in proportions in the range of 60% by weight.
At a small proportion of less than 10% by weight, the thermal decomposition property decreases. If the ratio exceeds 60% by weight, the binder becomes hard and press pressure increases, and the binding strength as a binder decreases. As a carboxyl group-containing monomer, (meth)
Maleic acid half esters such as acrylic acid, maleic acid, itaconic acid, monoisopropyl maleate,
Monomers having at least one carboxyl group in one molecule can be used, such as itaconic acid half ester. These carboxyl group-containing monomers may be used in an acid state, or may be partially or completely neutralized with ammonia or an organic amine. Such organic amines include monoethylamine, diethylamine, mono-n-propylamine, di-n-propylamine, mono-
Low molecular weight amines such as n-butylamine, di-n-butylamine, monoethanolamine, diethanolamine, triethanolamine, triethylenediamine, triethylenetetramine, hexamethylenediamine, hexamethylenetetramine, pyridine, piperidine, and polydimethylaminoethyl Polymer amines such as methacrylate and a condensate of alkylene dichloride and alkylene polyamine can be used. Such carboxyl group-containing monomers should be used in a proportion ranging from 5 to 60% by weight based on 100% by weight of the total copolymerized monomers. If the ratio is less than 5% by weight, the hydrophilicity decreases, the amount of wetting and adsorption to ceramic powder decreases, and the binding strength as a binder decreases. If the ratio exceeds 60% by weight, the thermal decomposition property will decrease, the press pressure will increase due to the hardness, and the binding strength as a binder will decrease. Hygroscopicity also increases. The above-mentioned (meth)acrylic acid alkyl ester and (meth)acrylic acid alkyl ester and (meth)
At least one monomer selected from the group consisting of alkoxyalkyl acrylates, vinyl acetate, and a carboxyl group-containing monomer can be used as necessary in a proportion that does not fall below the above range. Such copolymerizable monomers include 2
-Hydroxyethyl (meth)acrylate, glycerol (meth)acrylate, trimethylolpropane (meth)acrylate, pentaerythritol (meth)acrylate, glycidyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, (meth)acrylonitrile,
Acrylamide, N-methylolacrylamide, styrene, α-methylstyrene, ethylene,
Vinyl chloride etc. can be used. The polymerization method for obtaining the binder used in the ceramic molding of the present invention is not particularly limited, and conventionally known polymerization methods can be used. The binder used to form the ceramics of the present invention obtained in this way may be used as a binder as it is, or may be used after being appropriately neutralized with ammonia, the above-mentioned organic amine, or the like. The binder used in the ceramic molding of the present invention reduces press pressure, improves moldability, and
Improved hygroscopicity; The doctor blade method allows for a transition from a solvent-based to a safe and sanitary water-based system, and improved thermal decomposition; The extrusion molding method can achieve improved thermal decomposition and moldability. be. The present invention will be explained in more detail by examples.
The present invention is not limited to these examples. In addition, all parts in the examples indicate parts by weight, and all percentages indicate weight %. Example 1 (Synthesis of binder) In a separable flask equipped with a stirrer, a thermometer, a cooling tube, a nitrogen introduction tube, a mixing monomer dropping funnel, and a polymerization initiator dropping funnel, 150 parts of distilled water and polyoxyethylene nonylphate as an emulsifier were added. Three parts of enyl ether (HLB18.2, manufactured by Kao Soap Co., Ltd.) was charged, and nitrogen was introduced from the nitrogen introduction tube to create a nitrogen atmosphere inside the flask. Next, 30 parts of ethyl acrylate, 45 parts of vinyl acetate,
Prepare 100 parts of mixed monomer of 25 parts of methacrylic acid,
20 parts of a 2% aqueous t-butylhydroperoxy solution was charged into the polymerization initiator dropping funnel. While adjusting the internal temperature of the flask to 80℃, the mixed monomer and polymerization initiator were added dropwise over 2 hours, heated at 80℃ for 1 hour, cooled, and adjusted to pH 8.0 with aqueous ammonia until the solid content concentration was 35. % water-based binder used for ceramic molding was obtained. The ash content and Na content of this binder were measured and the results are shown in Table 1. The ash content was determined by placing the dried binder in a platinum crucible, incinerating it in an electric furnace at 650° C. in an air atmosphere for 2 hours, and measuring its weight. The Na content was measured by dissolving a part of the above ash with mineral acid and using an atomic absorption spectrophotometer. Example 2 (Molding of ceramics) 100 parts of alumina (AL-160SG, purity 99.0%, average particle size 0.4μ, manufactured by Showa Light Metal Co., Ltd.), 40 parts of distilled water,
Dispersant (Aquarik NL, Nippon Shokubai Chemical Co., Ltd.)
0.2 parts of ammonium polyacrylate (M.D., Ammonium Polyacrylate) and 20 parts of the aqueous binder used for 35% ceramic molding obtained in Example 1 were mixed in a ball mill for 24 hours, and the resulting slurry was spray-dried to form granules with an average particle size of 100μ. I got it. The granules were filled into a mold and pressed at press pressures of 500Kg/cm ² , 1000Kg/cm ² , and 1500Kg/cm ² to a thickness of 3 mm, width of 10 mm, and length of 30 mm.
A molded product of mm was obtained. The releasability from the mold and the surface smoothness of the molded product were good. The green density, bending strength, and hygroscopicity of these molded articles were measured, and the results are shown in Table 1. The bending strength was measured using an Instron strength testing machine model 1102 at a span width of 20 mm and a head speed of 0.5 cm/min. The evaluation of hygroscopicity was based on the weight increase rate after humidifying a molded product obtained at a press pressure of 1000 kg/cm ² at 20°C and 65% relative humidity for 24 hours, and the weight increase rate after humidifying the molded product at 20°C and 95% relative humidity for 24 hours.
This was done by measuring the weight increase rate when humidified for a period of time. Comparative Example 1 A molded product was obtained in the same manner as in Example 2 except that 7 parts of polyvinyl alcohol (GL-05, manufactured by Nippon Gosei Kagaku Co., Ltd.) was used as a binder for 100 parts of alumina (AL-160SG). The green density, bending strength, and hygroscopicity of the molded products were measured. In addition, the ash content and sodium content of polyvinyl alcohol were also measured. The ash Na content is considerably higher than that of the ceramic molding binder of Example 1. Furthermore, the pressing pressure had to be higher than in Example 2 to obtain the same green density. Furthermore, the bending strength was low and the hygroscopicity was high at the same green density. These results are shown in Table 1. Comparative Example 2 Polymerization and molding were carried out in the same manner as in Examples 1 and 2, except that 100 parts of a mixed monomer consisting of 15 parts of ethyl acrylate, 20 parts of vinyl acetate, and 65 parts of methacrylic acid were used, and the resulting binder was The ash content, sodium content, green density, bending strength, and hygroscopicity of the molded products were measured, and the results are shown in Table 1. Compared to Example 1, the ash content was higher, the hygroscopicity was higher, the pressing pressure was higher, and the bending strength was lower. Example 3 (Synthesis of binder) Polymerization was carried out using the same apparatus as in Example 1. First, add 100 parts of distilled water and ammonium salt of polyoxyethylene sulfate (Hitenol N) to a flask.
-08, 2 parts (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) were prepared. Next, 20 parts of n-dodecyl methacrylate, 30 parts of n-butyl acrylate,
100 parts of a mixed monomer consisting of 10 parts of 2-methoxyethyl acrylate, 20 parts of vinyl acetate, 10 parts of methacrylic acid, and 10 parts of acrylic acid were charged, and 20 parts of a 2% t-butyl hydroperoxide aqueous solution was charged into the polymerization initiator dropping funnel. is. While adjusting the internal temperature of the flask to 80°C, the mixed monomer and polymerization initiator were added dropwise over 2 hours each, heated at 80°C for 1 hour, cooled, and adjusted to pH 8.0 with aqueous ammonia to reduce the solid content concentration. A water-based binder used for 45% ceramic molding was obtained. The ash content of this binder and
The Na content is shown in Table 2. Example 4 (Molding of ceramics) 100 parts of alumina (AL-160SG), 40 parts of distilled water,
0.2 parts of the dispersant (Aquarik NL) and 30 parts of the aqueous binder used for 45% ceramic molding obtained in Example 3 were mixed in a ball mill for 24 hours, and the resulting slurry was defoamed under reduced pressure and then spread on silicone coated release paper to a thickness. Casting was done at 1.5m/m. Next, the mixture was heated from 60°C to 120°C at a heating rate of 1°C/min, and dried to a moisture content of 0.1% or less to produce a flexible tape-shaped green sheet.
The green density and tensile properties of the sheet were measured. The tensile properties were determined by punching out the sheet into dumbbell size 3 (JISK6301), pulling it at a pulling speed of 0.5 cm/min, and measuring the elongation and strength at break. These results are shown in Table 2. Comparative Example 3 100 parts of alumina (AL-160SG), 13.5 parts of polyvinyl butyral (3000K, manufactured by Denki Kagaku Kogyo Co., Ltd.) as a binder, 5 parts of n-octyl phthalate as a plasticizer, 0.5 parts of glyceryl triolate as a dispersant, and a solvent. 40 parts of trichlorethylene and 20 parts of ethyl alcohol were mixed in a ball mill for 24 hours, a green sheet was prepared in the same manner as in Example 4, and the green density and tensile properties were measured. The ash and sodium contents of polyvinyl butyral were also measured. These results are shown in Table 2. Both the ash content and the sodium content were considerably higher than those of the binder used for ceramic molding in Example 3. Comparative Example 4 Same as Example 3 except that 100 parts of a mixed monomer consisting of 23 parts of n-dodecyl methacrylate, 35 parts of n-butyl acrylate, 15 parts of 2-methoxyethyl acrylate, 25 parts of vinyl acetate, and 2 parts of acrylic acid was used. Polymerize with aqueous ammonia and adjust the pH
I adjusted it to 8.0 and got the binder. An attempt was made to obtain a green sheet using this binder in the same manner as in Example 4, but cracks appeared in the sheet due to drying. Example 5 (Synthesis of binder) Polymerization was carried out using the same apparatus as in Example 1. Add 20 n-butyl acrylate to the mixing monomer dropping funnel.
15 parts of 2-ethoxyethyl acrylate, 25 parts of vinyl acetate, and 40 parts of methacrylic acid were charged, and 20 parts of a 5% ammonium persulfate aqueous solution was charged into the polymerization initiator dropping funnel. Next, while adjusting the internal temperature of the flask to 95℃, the mixed monomer and polymerization initiator were added dropwise over 2 hours each, heated at 95℃ for another 30 minutes, cooled, and adjusted to pH 7.0 with aqueous ammonia to solidify. An aqueous binder used for ceramic molding with a concentration of 20% was obtained. Example 6 (Molding of ceramics) 100 parts of barium titanate (KYORIX A, manufactured by Kyoritsu Nitugyo Genryo Co., Ltd.), 40 parts of distilled water, 0.2 parts of dispersant (Aquarik NL), 2 parts of stearic acid as a lubricant, and Example 15 parts of the aqueous binder used for ceramic molding with a concentration of 20% obtained in step 5 was mixed with a universal mixer (Model 5DMV, manufactured by Sanei Seisakusho). Next, the mixture was extruded into a rod shape with a diameter of about 5 mm using a container kneader (manufactured by Kurimoto Iron Works). The obtained extrusion molded product was heated from 60°C to 120°C at a heating rate of 1°C/min, and further heated at 120°C for 30 minutes to dry to a water content of 0.1% or less. After drying, cut it and polish the top and bottom circular planes with sandpaper to a length of 10 mm.
It was made into a cylinder shape of mm, and the crushing strength in the longitudinal direction was measured. The results are shown in Table 3. The crushing strength was measured using a Honya type hardness meter (manufactured by Kiya Seisakusho). Comparative Example 5 Extrusion molding was carried out in the same manner as in Example 6 using 3 parts of methyl cellulose (Marporose M-600, manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.) as a binder to 100 parts of barium titanate (KYORIX A). The crushing strength was then measured. The ash and sodium contents of methylcellulose were also measured, and the results are shown in Table 3. Compared to the binder used for ceramic molding in Example 5, both ash and sodium content were higher. Comparative Example 6 Polymerization was carried out in the same manner as in Example 5, except that 100 parts of a mixed monomer consisting of 10 parts of n-butyl acrylate, 10 parts of 2-ethoxyethyl acrylate, 5 parts of vinyl acetate, 73 parts of styrene, and 2 parts of methacrylic acid was used. The pH was adjusted to 7.0 with aqueous ammonia and used for extrusion molding. In addition, the ash content of this binder, Na
The compressive strength of the molded product was measured. The result is the third
Shown in the table. The crushing strength was lower than that of Example 6.

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Claims (1)

[Claims] 1 (Meth)acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms and having 1 to 20 carbon atoms
25 to 85% by weight of at least one monomer selected from the group consisting of (meth)acrylic acid alkoxyalkyl esters having four alkylene groups, 10 to 60% by weight of vinyl acetate, and 5 to 60% by weight of a carboxyl group-containing monomer. (However, the total of all monomers is
It is 100% by weight. ) is a binder used for ceramic molding obtained by copolymerizing with.