JPH0457626B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a water-soluble organic binder used in ceramic sheet molding. One of the ceramic molding methods is a sheet molding method in which fine ceramic powder and a solvent are mixed to form a slurry, which is then drawn into a sheet using a doctor blade, for example, and then heated and dried to obtain a ceramic sheet (green sheet, green sheet). There is. Since the sheet thus obtained is then punched into a desired shape and then fired, an organic binder is used to maintain the shape during punching and firing. For example, in the conventional sheet molding method, an organic binder such as butyral resin or vinyl acetate resin is dissolved in an organic solvent such as methyl ethyl ketone, butyl acetate, ethyl acetate, toluene, or alcohol, and this is mixed with fine ceramic powder for a long period of time. A method is adopted in which the slurry is mixed to form a slurry, the air in the slurry is defoamed, and then a sheet is drawn onto a carrier film using a blade with a certain thickness, and this is heated and dried to form a ceramic sheet. ing. However, this method using organic solvents poses (1) harm to human health due to organic solvents, (2) dangers such as explosions due to the use of flammable organic solvents, and (3) dangers due to the use of expensive organic solvents. Problems arose in terms of economic efficiency. Therefore, methods have been proposed that use water-soluble organic binders such as polyvinyl alcohol and polyvinyl acetate, and water-based emulsions such as polyacrylic esters and copolymers of ethylene and organic acids as binders. However, in these proposed methods, water is used as a solvent, so although problems (1), (2), and (3) above are solved, they cannot be said to be perfect. During the long mixing stage, the presence of water tends to cause the ceramic fine powder to aggregate in the slurry, and the viscosity of the slurry deviates significantly from Newtonian flow, resulting in poor fluidity of the slurry and poor dispersibility of the ceramics, resulting in high density and smoothness. It is difficult to say that all the problems have been solved, such as the difficulty in obtaining sheets with a uniform surface. In other words, regarding ceramic sheet molding, in addition to the above issues (1), (2), and (3), (4) the surface of the ceramic sheet after drying must be smooth, (5) the molded sheet must be laminated by pressure bonding, It must have appropriate flexibility for tape winding (6) The formed sheet must be able to easily return to slurry again. However, with emulsion-type organic binders,
It is difficult to regenerate into slurry, so it is not suitable for sheet molding. Further, it is preferable to mold the molded product using a water-soluble organic binder and water as a solvent, since it is possible to reproduce the molded product. However, polymers containing carboxylic acids such as acrylic acid, which are often used as water-soluble organic binders, become water-soluble by neutralizing the carboxylic acid groups (carboxyl groups) with alkali or ammonium such as sodium hydroxide or potassium hydroxide. However, such neutralization has the disadvantage that a flexible sheet cannot be obtained. In view of the above-mentioned circumstances, an object of the present invention is to provide a water-soluble organic binder that can be used as a solvent and that can yield a high-density, flexible ceramic sheet having a smooth surface free of aggregates. . That is, the present invention provides (A) 5 to 45 mol% of at least one α,β-unsaturated carboxylic acid consisting of acrylic acid and methacrylic acid, and (B) a vinyl compound represented by the following formula () or (). A copolymer containing 95 to 55 mol% of at least one of
The present invention relates to a water-soluble ceramic binder which is neutralized with a tertiary amine whose substituents contain 6 to 9 carbon atoms in total. General formula () R ₁ : H or methyl R ₂ : C ₁ to C ₁₈ which may have a hydroxy group
Alkyl base of formula () _R3 to _R5 : H, methyl or ethyl group, n: 0
An integer of ~2, the number of carbon atoms in R ₃ + R ₄ + n R ₅ is 2
The present invention will be further explained below. The α,β-unsaturated carboxylic acid of the present invention is acrylic acid or methacrylic acid, and each alone can also be used as
They may also be mixed. One of the monomers to be copolymerized with this α,β-unsaturated carboxylic acid is a vinyl compound which is an acrylate or methacrylate represented by the above formula (1). This acrylate or methacrylate is acrylic acid or methacrylic acid and C ₁
It is an ester with ~ _C18 alcohol. Such alcohols include methanol, ethanol, isopropanol, n-propanol, sec.
- Alkane monools such as butanol, iso-butanol, n-butanol, iso-amyl alcohol, n-amyl alcohol, iso-hexyl alcohol, n-hexyl alcohol, 2-ethylhexyl alcohol, octyl alcohol, octadecyl alcohol, and ethylene glycol. ,
These include alkanediols such as 2-hydroxypropanol. These acrylates or methacrylates may be used alone or in combination. Furthermore, the monomer to be copolymerized with the above α,β-unsaturated carboxylic acid is a vinyl compound represented by the above formula (). This vinyl compound is a styrene compound such as styrene, α-methylstyrene, β-methylstyrene, α-ethylstyrene, β-ethylstyrene, α,β-dimethylstyrene, vinyltoluene, ethylstyrene, vinylxylene, or styrene with methyl It is a vinyl compound substituted with a group or an ethyl group. These vinyl compounds may be used alone or in combination. In the present invention, it is necessary that the copolymer contains 5 to 45 mol% of the α,β-unsaturated carboxylic acid. α,β-unsaturated carboxylic acid content is 5 mol%
If it is less than that, the ceramic binder will not become completely water-soluble and it will be difficult to obtain a uniform slurry, and when the ceramic sheet molded body that has been molded once is regenerated into slurry, it will not return to a uniform slurry. If it exceeds 45 mole percent, the ionicity of the ceramic binder will increase, and during long-term pulverization and mixing with the ceramic fine powder, the fine ceramic powder will aggregate, making it impossible to obtain a uniform slurry and causing a ceramic sheet molded product. flexibility is lost. The copolymer of the present invention is obtained by copolymerizing the α,β-unsaturated carboxylic acid and a vinyl compound using a polymerization initiator. For the copolymerization of these raw materials, conventional polymerization methods can be selected as appropriate, but a polymerization solvent should be used, taking into consideration the fact that the viscosity increases as the copolymerization progresses and the removal of the polymerization heat generated by copolymerization. is preferable. These solvents may be selected as appropriate, including lower alcohols such as methanol, ethanol, isopropanol, and n-propanol, acetone, methyl ethyl ketone,
Lower ketones such as methyl-iso-butyl ketone and diethyl ketone, lower esters such as methyl acetate and ethyl acetate, and cyclic ethers such as 1,4-dioxane, 1,3-dioxane, and tetrahydrofuran, which are themselves water-soluble. This is more preferable considering the usage form of the organic binder. That is, in the case of the above water-soluble solvent, the polymerization solvent and binder are mixed completely and uniformly when mixed with the fine ceramic powder to form a slurry, so that it can be used without removing the polymerization solvent in advance. The polymerization initiator may be any commonly used so-called radical polymerization initiator. For example, ketone peroxides such as methyl ethyl ketone peroxide and methyl cyclohexanone peroxide, 1,1-bis(t-butylperoxy)cyclohexane, 2,
Peroxy ketals such as 2-bis(t-butylperoxy)butane, hydroperoxides such as t-butyl hydroperoxide and cumene hydroperoxide, di-t-butyl peroxide, t-butyl-cumyl peroxide In addition to peroxides such as oxides, dialkyl peroxides such as dikyumyl peroxide, diacyl peroxides such as acetyl peroxide and benzoyl peroxide, azobisisobutyronitrile and the like can also be used. Polymerization can be carried out at any temperature from normal temperature to 150°C, but it is industrially preferable to carry out the polymerization at a temperature below the boiling point of the polymerization solvent since there is no need for pressurization. In addition, the polymerization operation can be carried out by charging the raw materials and the solvent to be used as necessary into a polymerization reactor in advance and gradually adding the polymerization initiator, or by charging only the solvent into the polymerization reactor and gradually adding the raw materials and polymerization initiator. This can be done in the following manner. The polymerization time depends on the polymerization temperature and initiator concentration, but 6 to 30 hours is usually sufficient. A copolymer is obtained as described above and then neutralized with a tertiary amine to make it water-soluble. The amine to be treated is a tertiary amine in which the total number of carbon atoms contained in its three substituents is 6 or more and 9 or less. These amines are triethylamine,
In addition to simple alkyl amines such as diethylbutylamine and dimethylhexylamine. Those in which a hydroxyl group is introduced into an alkyl group such as hydroxyalkylamine such as triethanolamine and triisopropanolamine can also be used. The ceramic binder of the present invention can be obtained by neutralizing with these amines. If the total number of carbon atoms is less than 5, the resulting ceramic binder may have a strong amine odor and may be virtually unusable, and the ceramic sheet molded product obtained by drying may not have enough flexibility to withstand winding. do not have. When the number is 10 or more, the resulting ceramic binder has poor water solubility, making it difficult to form a uniform slurry during pulverization and mixing. It is important that the amine used for neutralization neutralizes 85 mol% or more of the carboxylic acid groups present in the resin. If more than 15 mol % of carboxylic acid groups remain, the ceramic molded product will not be completely assimilated and will not exhibit flexibility, making it unsuitable for sheet molding. Although there is no problem in using a large excess of amine in the neutralization process, there are limits to its practical use due to economic efficiency, operability, odor peculiar to amines, etc. Therefore, in practice, the amount of amine used is preferably 1.2 equivalents or less of the neutralization equivalent of the desired carboxylic acid group. Neutralization can be easily carried out by adding a predetermined amount of amine to the obtained resin solution. Normally, complete neutralization can be carried out in 30 minutes to 3 hours at the polymerization temperature. The binder of the present invention can sufficiently exhibit its performance when used alone, but it can also be used with ethylene glycol, diethylene glycol, triethylene glycol,
It is also possible to change the flexibility of the obtained ceramic sheet molded article by adding a high-boiling water-soluble polyol such as propylene glycol or glycerin as a water-soluble solubilizing agent. The present invention will be explained below with reference to Examples. In the following, all parts indicate parts by weight. Example 1 Boiling isopropyl alcohol (112.5 parts)
, n-butyl acrylate (73.1 parts), methacrylic acid (28.1 parts), styrene (11.25 parts) and peroxide (0.1 parts) (trade name Perbutyl O).
[Nippon Oil & Fats Co., Ltd.]) was added dropwise over 2 hours. After completion of the dropwise addition, stirring was continued at the same temperature for 5 hours. After cooling the reaction solution to room temperature, triethanolamine (48.7 parts) was added to neutralize it. Thereafter, isopropyl alcohol is distilled out from this solution under reduced pressure to obtain a water-soluble resin. 100 parts of alumina powder (Sumitomo Aluminum Smelting Co., Ltd.)
4 parts of the above resin and 45 parts of ion-exchanged water were added to 4 parts of the above-mentioned resin and 45 parts of ion-exchanged water, and kneaded in a ball mill for about 10 hours to form a slurry, which was then defoamed. A kneaded material sheet was made from the slurry by the doctor blade method, and after air drying this for 2 hours,
It was dried at 110°C for 2 hours to obtain a sheet with a smooth surface. This sheet was elastic enough to be punched out, and the density was measured to be 2.40. Further, 23 parts of ion-exchanged water was added to 50 parts of the sheet obtained above, and the mixture was kneaded in a ball mill for about 8 hours to form a slurry again. After defoaming treatment, a sheet was produced by the above method. This sheet also had a smooth surface and similar flexibility. The density is
It became clear in 2.38 that it was possible to play the sheet. Example 2 A water-soluble resin was obtained in the same manner as in Example 1. However, the polymerization solvent, isopropyl alcohol, was not removed, and the mixture was kneaded with alumina powder according to the following recipe. 100 parts of alumina powder 7 parts of the above resin solution (4.1 parts as resin content) and 45 parts of ion-exchanged water were kneaded in the same manner as in Example 1 to make a sheet. As in Example 1, a smooth and flexible sheet with a density of 2.39 was obtained. I got it. It was also possible to reproduce it. Examples 3-6 1,4-dioxane (112.5 parts) as polymerization solvent
A sheet was prepared in the same manner as in Example 1 using acrylic acid (23.5 parts) in place of methacrylic acid, and recycled in the same manner. In all cases, good sheets were obtained as shown in the table below.

[Table] Examples 7 to 11 Organic binders were synthesized in the same manner as in Example 1 using the reaction solvents, α, β-unsaturated carboxylic acids, and vinyl compounds shown in Table 1, and ceramic sheets were evaluated. In both cases, recyclable smooth and flexible sheets were obtained.

[Table] Examples 12 to 16 and Comparative Examples 1 to 2 A mixture of n-butyl acrylate, methacrylic acid, and azobisisobutyronitrile (0.1 part) as a polymerization initiator was added to boiling isopropyl alcohol (100 parts). It was added dropwise over a period of 2 hours.
After the completion of the dropwise addition, the mixture was stirred at the same temperature for 5 hours, and the reaction solution was heated to room temperature, and triethanolamine was added for neutralization. Using the thus obtained resin solution, sheets were evaluated in the same manner as in Example 2. The results are shown in Table 2.

[Table] Examples 17 to 19 Copolymerization was carried out in the same manner as in Example 15, various amine treatments were carried out, and the resulting resin solution was used in Example 2.
A ceramic sheet was prepared in the same manner as in .

[Table] Sum.
Examples 20 to 22, Comparative Example 3 Copolymerization was performed in the same manner as in Example 15, triethanolamine treatment was performed, and the resin solution was used in the same manner as in Example 2 to prepare sheets.

【table】

Claims (1)

[Scope of Claims] 1(A) 5 to 45 mol% of at least one α,β-unsaturated carboxylic acid consisting of acrylic acid and methacrylic acid, and (B) the following general formula () or () R ₁ : H or methyl R ₂ : C ₁ to C ₁₈ which may have a hydroxy group
alkyl group of _R3 to _R5 : H, methyl or ethyl group,
and a copolymer containing 95 to 55 mol% of at least one vinyl compound having a total number of carbon atoms of 2 or less, where n is an integer of 0 to 2, and a carboxyl compound contained in the copolymer. A water-soluble ceramic binder characterized in that at least 85% by mole of the groups are neutralized with a tertiary amine whose three substituents have a total of 6 to 9 carbon atoms. 2. The water-soluble ceramic binder according to claim 1, wherein the vinyl compound of the general formula () is styrene, α-methylstyrene, or vinyltoluene. 3. The water-soluble ceramic bond according to any one of claims 1 and 2, wherein the tertiary amine is triethylamine, dimethylhexylamine, triethanolamine, or triisopropanolamine. agent.