JPS6270254A - Water-soluble binder for molding ceramics - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a water-soluble binder for molding ceramics.

Normally, when manufacturing ceramics, a method is used in which a green molded body is formed by mixing ceramic powder and a binder, then heated to decompose and remove the binder, and then sintered. Polyviny μa μco/&! Polymers have a strong binding force on ceramics, have high strength themselves, and are easy to handle in water systems, so they are preferably used as water-soluble binders for molding ceramics.

B. Prior Art Ceramic green molded bodies are manufactured using various methods, such as press molding, slurry casting, sheet molding, extrusion molding, and injection molding. Conventionally, among these molding methods, in various molding methods such as press molding using water as a medium, polyvinyl alcohol/l/ (hereinafter abbreviated as PVA) based polymer is water-soluble and has a high resistance to inorganic powder. It has been favorably used because it has excellent binder power, the strength of the green molded product obtained is high, and it is easy to handle, including processing (cutting, etc.) before sintering. However, since PVA is highly crystalline and hard, there is a problem in that press molding requires high press pressure. On the other hand, sheet molding requires a large amount of plasticizer, and its migration and humidity sensitivity are problematic.

C9 Problems to be Solved by the Invention The present invention uses PVA which can be used in an aqueous system as a binder for molding ceramics and whose polymer itself is flexible.
The purpose of this study is to provide a copolymer based on the present invention.

Means for Solving the D0 Problem The present inventors have developed a method that maintains the conventionally recognized excellent binding power of PVA-based polymers to inorganic solids.
As a result of intensive studies on PVA-based polymers that can be used in aqueous systems and are flexible, we have found that PVA-based polymers can be co-polymerized with vinyl esters and nonionic monomers having (meth)allyl groups that can be radically copolymerized with vinyl esters. It was discovered that the above object could be achieved by using a polyvinyl alcohol/l/l/water-soluble copolymer containing 20 to 90 mol% of vinyl alcohol units, which is obtained by saponifying a polymer, and completed the present invention. I ended up letting it happen.

That is, the present invention provides a ceramic Z molded body'! 1l-ff
A water-soluble organic binder used in U manufacturing, which is obtained by saponifying a vinyl ester and a copolymer of the vinyl ester and a nonionic monomer having a radically copolymerizable (meth)allyl group. The present invention relates to a water-soluble binder for molding ceramics, characterized in that it is composed of a polyvinyl alcohol-rho tea water-soluble copolymer containing 20 to 90% of vinyl alcohol units.

20 to 90 moles of vinyl alcohol units obtained by saponifying the vinyl ester used in the present invention and a copolymer of the vinyl ester and a nonionic monomer having a physically copolymerizable (meth)allyl group. % of polyvinyl alcohol-based water-soluble copolymers (hereinafter abbreviated as PVA-based copolymers): (1) It is water-soluble; (2) The resulting molded product has high strength and is easy to handle. (3) It is flexible; (4) The shibinder is rapidly decomposed by heating and no residual carbon is produced. is 2
000 or less, preferably 1006 or less, and 100 or more, the vinyl alcohol content is 20 to 90 mol%, preferably 40 to 90 mol%, and the content of nonionic monomer units having a (meth)allyl group is 5 mol. % to 30 mol %, preferably 2 to 20 mol %, more preferably 5 to 20 mol %, and can be used as it satisfies the above requirements.

That is, those with an average degree of polymerization exceeding 2,000 are undesirable because the viscosity of the binder aqueous solution or slurry is too high, while those with an average degree of polymerization of less than 100 are undesirable because the resulting green molded product becomes brittle. The vinyl alcohol content depends on the content of nonionic monomer units, but is 90%
If it is more than 2%, it will be too hard, and if it is less than 20%, the strength of the green molded product will be weakened, which is not preferable.

Furthermore, the content of nonionic monomer units having a K(meth)allyl group has to be balanced with the vinylalkofur content, but 3
If it exceeds 0 mol %, the strength of the green molded product will be weakened, and if it is less than 0.5 mol %, it will not be possible to have sufficient water solubility and flexibility.

On the other hand, as the vinyl ester, vinyl formate, vinyl acetate, vinyl propionate, vinyl persate, etc. can be used, but vinyl acetate is mainly used, and vinyl propionate and vinyl persate are preferably used.

On the other hand, it is possible to radically copolymerize with vinyl ester (meth)
Specific examples of the nonionic monomer having an aryl group include (meth)allyl alcohol-(meth)allyl acetate, dimethylallyl alcohol allyl acetone, allyl ethyl ether/allyl grindyl ether, etc.
Among them, (meth)allyl alcohol, (meth)allyl acetate, and dimethylallyl-alco-ρ are more preferred, and (meth)allyl acetate μ is most preferably used.

However, one or more other radically copolymerizable monomers may be used in combination without departing from the spirit of the present invention. Specifically, α-olefins such as ethylene, propylene, and 1-butene, methyl (meth)acrylate, (
(meth)acrylic acid esters such as ethyl meth)acrylate and butyl (meth)acrylate, nonionic monomers such as (meth)acrylamide, N,N-dimethylacrylamide, N-vinylpyrrolidone, or (meth)acrylates; Acrylic acid (including salts), itaconic acid (including salts), maleic acid (including salts), fumaric acid (including salts), maleic anhydride, 2-acrylamidopropanesulfonic acid (including i), ( meta)allylsulfonic acid (including salts), (
Examples include ionic monomers such as meth)acrylamidopropyltrimethylammonium chloride and the like. These copolymerizable monomers may be used alone or in combination of two or more of them copolymerized with vinyl ester. Particularly from the viewpoint of water solubility, it is preferable to use less than 0.5 mol% of an ionic monomer.

In addition, the water solubility of a PVA-based copolymer as used in the present invention refers to a state in which the PVA-based copolymer is completely dissolved or dispersed when dissolved in water at a concentration of 1% at 25°C. say something The average degree of polymerization (P) is a value calculated by measuring [η] of the polyvinyl ester copolymer before saponification in acetone at 30°C.

The present invention is characterized in that the above-mentioned PVA-based copolymer is used as a water-soluble binder for molding ceramics, but it may also be used in combination with a deflocculant, a lubricant, etc.

As the deflocculant, commonly used deflocculants can be used.

For example, inorganic deflocculants include sodium phosphate, caustic soda,
Examples of organic peptizers include amines, pyridine, piperidine, metal salts or ammonium salts of polyacrylic acid, metal salts or ammonium salts of copolymers of styrene or isobutyne and maleic anhydride, and polyquine ethylene nonylphenol such as sodium citrate. Aether etc. are destroyed. On the other hand, lubricants that are commonly used include natural waxes such as beeswax and Japanese wax, paraffin wax, microcrystalline wax, synthetic waxes such as low-molecular polyethylene and its derivatives, stearic acid,
Examples include fatty acids such as lauric acid, metal salts of fatty acids such as magnesium stearate and sium stearate, fatty acid amides such as oleic acid amide and stearic acid amide, and polyethylene glycol, and these may be in the form of an aqueous dispersion.

Further, other organic binders or plasticizers may be used in combination with the PVA copolymer of the present invention within a range that does not impair the effects of the present invention. As the organic binder, water-based emulsions of water-soluble polymers and hydrophobic polymers, which are usually used in ceramic molding, can be used in combination.

Moreover, any commonly used plasticizer may be used.

For example, polyhydric alcohols such as ethylene glycol, propylene glycol, glycerin, mannitol, and sorbitol, derivatives thereof, and esters such as diethyl phthalate can be used.

Ceramic powders to which the PVA-based copolymer of the present invention can be applied include powders of metal or nonmetal oxides or nonoxides that can be used in ceramic production.

Further, these powders may have a single composition, or may be used singly or in the form of a compound. The constituent elements of the metal oxide or non-oxide may be either a single element or a plurality of cations or anions, and additives may be added to improve the properties of the oxide or non-oxide. Systems containing the above can also be used in the present invention.

Specifically, Li%, Bs, Mg, B, Aj?
, Si, Cu, Ca, Br, Ba, Zn,
Cd%Ga, "%"), actinide, Ti, Zr, Hf, B11V, Nb, T
a, WSMn.

Oxides, carbides, nitrides such as Fe, Co, Ni, etc.
Examples include borides and sulfides. Furthermore, if we classify specific oxide powders containing multiple metal elements, which are usually called double oxides, based on their crystal structures, we find that NaNbO3, S r Zr O3,
PbZrO3, 5rTi03, BaZrO3, PbTi
O3, BaTiO3, etc. have a spinel structure, such as MgAJ204, ZnAgzO+, C0AJ? 20
4. N1AlzO4, MgFe2O4, etc. have an ilmenite structure, such as MgTi 03, MnTi
Examples of O3, FeTi 03, etc. that have a garnet structure include GdGa5O12, Y3 Fe 5012, etc.

Among these ceramic powders, P" used in the present invention for oxide powders, particularly metal oxide powders for producing electronic materials, magnetic materials, optical materials, high-temperature materials, etc.
/A type copolymers are preferably used.

The PVA-based copolymer of the present invention can also be suitably used as a precursor that can be converted into a metal or non-metal oxide or non-oxide by heat treatment at a high temperature after sheet forming. Examples of the precursors include metal or nonmetal alcoholades, hydroxide sol obtained by hydrolysis from them, silica sol obtained from water glass, basic metal chloride salts, sulfuric acid, nitric acid, etc. Examples include metal salts such as formic acid and acetic acid.

The PVA-based copolymer of the present invention can be used in a solid content of 0.2 to 20 parts by weight, preferably 1 to 15 parts by weight, based on 100 parts by weight of the ceramic powder.

Further, the PVA-based copolymer of the present invention is usually handled as an aqueous solution, but it can also be handled as a powder that is added to an aqueous slurry of ceramics.

The PVA copolymer of the present invention is suitably used in various molding methods for ceramics using water as a medium, such as press molding, slurry casting, sheet molding, and extrusion molding.

Effects of E1 and Effects of the Invention The present invention provides P, which can be used in an aqueous system as a binder for molding ceramics and whose polymer itself is flexible.
Regarding the VA copolymer, as mentioned above (as the PVA copolymer, the content of nonionic monomer units having a (meth)allyl group is 0.5 mol% or more and 30 mol% or less). PV with an average degree of polymerization of 2000 or less and 100 or more and a vinyl alcohol content of 20 mol% or more and 90 mol% or less
The purpose could only be achieved by using the A-based copolymer. Surprisingly, the PVA-based copolymer of the present invention exhibits remarkable effects in various molding methods as described below.

Since the PVA-based copolymer of the present invention is flexible, (1) in press molding of ceramics, molded products with high strength, high density, or complex shapes can be obtained at low plain pressure; (2) sheets In molding, a flexible molded body can be obtained with the addition of a small amount or no plasticizer. (3) In all molding methods, the molded body obtained is highly tough and easy to handle or process before sintering. It has the following characteristics.

EXAMPLES The present invention will be explained in detail below with reference to Examples, but the present invention is not limited to these Examples.

In addition, "part" or "%" in the examples means "part by weight" [wt% J] unless otherwise specified.

1125 parts of vinyl acetate (hereinafter abbreviated as V A c), 7 parts of acetic acid! 150 parts of J/l/ (hereinafter abbreviated as AAc) and 1570 parts of methanol were placed in a reaction vessel, and the inside was sufficiently replaced with nitrogen.The outside temperature was raised to 650°C, and when the inside temperature reached 60°C, 2.2'-azobis was added. 19.5 parts of isobutyronitrile was added to initiate polymerization. After 5 hours, when the polymerization rate reached 70%, it was cooled to stop the polymerization. Subsequently, remaining VA c, , AA e were removed under reduced pressure while adding methanol to obtain a methanol solution of the (VAc-AAc) copolymer. A part of this polymer was taken out, purified twice by reprecipitation using an acetone-n-hexane system, and measured by NMR, and the AAc content was found to be 10.2 mol%. Further, [η] was measured at 30° C. in acetone to determine the degree of polymerization, which was 256. Subsequently, a portion of the methanol solution of the (VAe-AAc) copolymer was removed to give a concentration of 60% (N
aOH)/(VAc+AAc)~0.0060.4
Saponification was carried out at 0°C to obtain a polyvinyl alcohol copolymer. After thoroughly washing and purifying this polyvinyl alcohol copolymer with a mixed solvent of methiacetate/l//methanol=70,730 (weight), the vinyl alcohol content was determined by NMR and found to be 60.5 mol%.

The polyvinyl ester copolymer obtained in this example will be referred to as Polymer 1, and the polyvinyl alcohol copolymer obtained by saponifying this will be referred to as Polymer IA.

Polymers 2 (2A) to 4 (4A) were prepared in the same manner as in this example.
I got it. Details of polymers 2 (2A) to 4 (4A) are shown in Table 1.
Shown below.

Example 1 100 parts of alumina (99.5% purity), 50 parts of water, and 0.2 parts of a polyacrylic acid ammonium salt peptizer were placed in a ball mill, and after dispersing for 900 hours, Polymer I was added as a binder.
Two parts of the solid content of the aqueous solution of A were added and mixed uniformly. Granules (particle size: 100±20 μm) were prepared from this slurry, and molded into a rectangular parallelepiped with a width of 20 m, a length of 100 μm, and a thickness of IOm using a mold (both 1 and 2 were on/J). Table of evaluation results
Shown in 2.

Examples 2 to 4 Molded articles were obtained in the same manner as in Example except that Polymers 2A to 4 were used instead of the binder in Example 1. The evaluation results are shown in Table-2.

Comparative Example] ~3 Example 1 except that polymers 5A to 6A or polyvinyl acetate emulsion were used instead of the binder of Example 1.
A molded product was obtained in the same manner as above. The evaluation results are shown in Table-2.

Table 2 (**) Workability was evaluated by drilling holes with a drill and evaluating the difficulty level.

○; Processing is easy. Δ: Difficult to process.

X: Very difficult to process.

Example 5 Fine powder type high purity alumina (average particle size 0.6μ, Al
2O5 content 99.9%) 100 parts, deionized treated water 25
peptizer (Dai Kogyo Seiyaku Sefu 700-14) 0.7
After 5 parts were placed in a ball mill and dispersed for 24 hours, 4 parts of a 25% aqueous solution of Polymer IA (solid content: 10 parts) was added as a binder and thoroughly kneaded to obtain an aqueous slip.

Air bubbles in the slip were removed using a vacuum degassing device to obtain a homogeneous slip. A green sheet with a thickness of 400 μm was produced by drawing the sheet onto a polyester sheet using a blade having a predetermined gap and drying with hot air at a temperature of 85° C. for 5 minutes and then at 120° C. for 5 minutes.

The aqueous glue had good fluidity, and the obtained green sheet had good visibility and elasticity, was strong and easy to handle, and had a smooth surface without cracks. Table of evaluation results
Shown in 3.

Examples 6 to 8 Green sheets were obtained in the same manner as in Example 5, except that Polymers 2A to 4A were used instead of the binder in Example 5.

The evaluation results are shown in Table-3.

Comparative Examples 4 to 5 Green sheets were obtained in the same manner as in Example 5, except that Polymers 5A to 6A were used instead of the binder in Example 5. The evaluation results are shown in Table-3.

Table-3 (*) Evaluation method of green sheet flexibility.

The judgment was based on whether or not it would not open when wrapped around a stick with a diameter of 5 kaku.

0 Very flexible. ○: Flexible. △: Insufficient flexibility and easy to break. ×: Poor flexibility.

(**) Evaluation method for cracks during drying.

Judging by the amount of cracks generated in the green sheet under the molding and drying conditions of Example 5: ○: No cracks were generated. △: A few cracks occur. ×: Multiple cracks occur.

Claims (5)

[Claims] (1) The vinyl alcohol unit content is 20 to 90 mol%, obtained by saponifying a vinyl ester and a copolymer of the vinyl ester and a nonionic monomer having a radically copolymerizable (meth)allyl group. A water-soluble binder for molding ceramics, characterized by comprising a polyvinyl alcohol-based water-soluble copolymer. (2) The water-soluble binder for molding ceramics according to claim 1, wherein the vinyl ester is vinyl acetate. (3) The water-soluble binder for molding ceramics according to claim 1, wherein the nonionic monomer having a (meth)allyl group is (meth)allyl acetate. (4) The content of nonionic monomer units having a (meth)allyl group in the water-soluble polyvinyl alcohol copolymer is 0.
．． The water-soluble binder for ceramic molding according to claim 1, wherein the content is 5 to 30 mol%. (5) The content of nonionic monomer units having (meth)allyl groups in the water-soluble polyvinyl alcohol copolymer is 2
The water-soluble binder for ceramic molding according to claim 4, wherein the content is 20 mol %.