JP2691384B2 - Additives for ceramics molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic molding additive used in an aqueous system.

[0002]

2. Description of the Related Art Conventionally, a polyvinyl butyral resin having a specific degree of polymerization has been used as a binder in the production of ceramics green sheets, and a solvent such as an organic compound such as an alcohol, a ketone, a halogen-containing compound or an aromatic compound. It was necessary to use a large amount of solvent. Therefore, there are various problems such as explosion and flame due to ignition, toxic effect on human body, and pollution problem due to evaporated organic solvent gas during drying. To solve these problems, polyvinyl alcohol, water-soluble polyvinyl acetate, water-soluble polyurethane, water-soluble acrylic resin, etc. have been proposed as binders. And, usually, when these water-soluble binders are used in the production of green sheets, poor dispersion of the ceramic powder occurs,
In order to sufficiently disperse the ceramic powder, a step called initial dispersion is provided using a dispersant. Further, although the combination of the dispersant and the binder has an important influence on the slurry properties and the raw sheet formability during sheet forming, a combination of acrylic resins having different molecular weights (Japanese Patent Laid-Open No. 63-147853), A combination of polyvinyl butyral resins having different degrees of polymerization (Japanese Patent Laid-Open No. 64-42)
Although a combination of a solvent-based binder and a dispersant such as 357) has been proposed, an aqueous one has not yet been proposed.

[0003]

DISCLOSURE OF THE INVENTION According to the present invention, by combining an aqueous binder and a dispersant, a ceramic green sheet having excellent slurry characteristics, excellent moldability of ceramics, high density and a smooth ceramic surface can be obtained. The purpose is to provide an additive for use.

[0004]

The present invention is a copolymer containing a specific monomer as one copolymerization component and containing a specific amount thereof, and an aqueous binder having a large weight-average molecular weight, and also the specific monomer. It was made based on the finding that the above-mentioned problems can be efficiently achieved by combining a copolymer containing one specific copolymerization component and a specific amount and having a small weight average molecular weight.

That is, in the present invention, a carboxyl group-containing unsaturated monomer or a sulfonic acid group-containing unsaturated monomer 0.1
˜20% by weight and the balance of other copolymerizable monomers and an aqueous binder having an average molecular weight of 55,000 to 2,000,000, and a carboxyl group-containing unsaturated monomer or a sulfonic acid group-containing unsaturated monomer 10 to 50% by weight. And the balance of other copolymerizable monomers are 1,000.
Disclosed is an additive for ceramics molding, which is characterized by being combined with up to 50,000 dispersants.

Examples of the carboxyl group-containing unsaturated monomer (A) used in the present invention include unsaturated carboxylic acids such as acrylic acid and methacrylic acid, unsaturated dibasic carboxylic acids such as maleic acid, itaconic acid and fumaric acid, and half thereof. Ester can be given. Of these, acrylic acid and methacrylic acid are particularly preferable. As the sulfo group-containing unsaturated monomer (B), vinyl sulfonic acid, allyl sulfonic acid, methacryl sulfonic acid, 2-acrylamido-2-
Methyl propane sulfonic acid, styrene sulfonic acid, α-
Methyl styrene sulfonic acid, vinyl toluene sulfonic acid, etc. are mentioned. 2-acrylamide-2 of these
-Methylpropanesulfonic acid and vinylsulfonic acid are preferred.

As the monomer copolymerizable with the unsaturated monomer containing a carboxyl group or the unsaturated monomer containing a sulfo group, a (C) alkyl group having a carbon number of 1 to 8 is a (meth) acrylic acid alkyl ester, (D). ) (Meth) acrylic acid alkoxyalkyl ester having an alkylene group having 1 to 4 carbon atoms, (E) a monomer represented by the following general formula

[0008]

Embedded image

(Wherein R ₁ is hydrogen or a methyl group, R ₂ is hydrogen, an alkyl group having 1 to 4 carbon atoms or a phenyl group, and n is 2 or more). These can be used as one kind or as a mixture of two or more kinds. Here, as the (meth) acrylic acid alkyl ester having an alkyl group having 1 to 8 carbon atoms of the monomer (C), for example, methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n- Butyl (meth) acrylate, isobutyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and the like, and (meth) acrylic having an alkylene group having 1 to 4 carbon atoms in the monomer (D). As the acid alkoxyalkyl ester,
For example, methoxymethyl (meth) acrylate, methoxyethyl (meth) acrylate, n-butoxymethyl (meth) acrylate, n-butoxyethyl (meth) acrylate, ethoxymethyl (meth) acrylate, ethoxyethyl (meth) acrylate, ethoxybutyl. Examples thereof include (meth) acrylate. Here, examples of the alkoxy group include those having 1 to 4 carbon atoms.

As the monomer (E), in the general formula, n is preferably 2-40, more preferably 4-2.
5 Specific examples of the monomer of component (E) include phenoxy polyethylene glycol (n = 2 or 6) mono (meth) acrylate, methoxy polyethylene glycol (n = 2,3,4,9 or 23) (meth) acrylate, polyethylene glycol. (N = 2, 4, 9 or 2
3) Mono (meth) acrylate and the like can be mentioned.

Further, as other copolymerizable monomers, (meth) acrylonitrile, acrylamide, N-
Methylolacrylamide, styrene, α-methylstyrene, ethylene, vinyl chloride, vinyl acetate, N-vinylpyrrolidone, hydroxyethyl (meth) acrylate,
A hydroxyl group-containing monomer such as hydroxymethyl (meth) acrylate can be used.

The aqueous binder used in the present invention contains the above-mentioned monomers (A) and / or (B) in an amount of 0.1 to 20% by weight (hereinafter abbreviated as "%"), preferably 0.1 to 15% by weight. Polymerizable monomer (monomer (C), (D), (E), etc.)
Of 99.9 to 80%, preferably 99.9 to 85%, and the weight average molecular weight (Mw) of the copolymer is 55,000 to 2,000,000, preferably 55,000 to 150%.
10,000, and more preferably 100,000 to 1,000,000. They are,
It can be easily measured using a standard substance by gel permeation chromatography.

Further, the salt of the above copolymer is produced by neutralizing a part or all of the carboxylic acid or sulfonic acid groups in the copolymer with ammonia or an organic amine and adjusting the pH to 6 to 10. Is preferred. The organic amine is, for example, OH such as monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, N-methylethanolamine, dimethylaminopropanol and the like.
Examples thereof include a group-containing organic amine and morpholine, but are not limited thereto.

Therefore, as long as the above conditions are satisfied, the method for producing the aqueous solution of the aqueous binder of the present invention can be carried out by a known polymerization method without any limitation, preferably emulsion polymerization or solution polymerization. As the water-based binder, either Elmagion or an aqueous polymer solution containing an aqueous solvent or removing the aqueous solvent may be used.

Among the water-based binders, the water-soluble binder is 0.1 to 20.0% of monomer (A) and / or (B), and 50.0% of monomer (C) and / or (D). ~ 99.9% and monomer (E) 0.1
A copolymer or a salt thereof whose essential component is ˜50.0% is preferable. Among the water-based binders, the emulsion-based binder includes 0.1 to 20.0% of monomers (A) and / or (B) and 80.0 to 99.9 of monomers (C) and / or (D). A copolymer containing 100% as an essential component or a salt thereof is preferable.

The dispersant used in combination with the aqueous binder is 10 to 50 of the above-mentioned monomers (A) and / or (B).
%, Preferably 10 to 45% and other copolymerizable monomers (monomers (C), (D), (E), etc.) 90 to 50
%, Preferably 90-55%, and the Mw of the copolymer is 1,000-50,000, preferably
It is 3,000 to 30,000. Further, like the aqueous binder, it is preferable to neutralize a part or all of the carboxylic acid groups and sulfonic acid groups in the copolymer with ammonia or amine. The dispersant thus produced is water-soluble.
Of these, the monomers (A) and / or (B) 10.
0-50.0%, monomer (C) and / or (D) 5
0.0-90.0% and monomer (E) 0-50.0%
A copolymer or a salt thereof containing as an essential component is preferable.

The additive for ceramics molding of the present invention may be a combination of the above binder and dispersant in an arbitrary ratio. Specifically, it can be used as an amount suitable for the following green sheet manufacturing method. When a ceramic molded body is manufactured using the ceramic molding additive obtained by the present invention, the ceramic powder 100 is used.
Solid content of binder is 0.3 to 25.0 with respect to weight%
%, Preferably 0.5 to 20.0% by weight. The dispersant is used in a solid content of 0.05 to 5.0% by weight, preferably 0.1 to 2.0% by weight. At this time, the water content of the aqueous slurry is 20 to 70%, preferably 25 to 50%.
%. Typical target ceramic powders are oxide-based or composite oxide-based ceramics such as alumina, zirconia, magnesia, beryllia, titanium oxide, barium titanate, lead zirconate titanate, PLZT, and ferrite-manganese. Examples thereof include powder and non-oxide ceramic powder such as silicon carbide and sialon. If necessary, a water-soluble plasticizer (for example,
A molding aid other than a binder and a dispersant such as polyethylene glycol, glycerin) and a defoaming agent may be used in combination.

[0018]

Since the additive for ceramics molding of the present invention is a combination of an aqueous binder obtained by copolymerizing a specific anionic group monomer and a dispersant, it is excellent in dispersion stability of the ceramics aqueous slurry and can be dispersed with the binder. Since the compatibility of the agent is good, the ceramic green sheet is excellent in moldability, and a ceramic compact having a high density and a smooth surface can be obtained. Further, since the green sheet as the molded body has a small amount of moisture absorption, it is less affected by humidity, and the ceramic molded body can be provided with flexibility and strength equivalent to those of the solvent-based binder.

The ceramic molding additive of the present invention can be applied to press molding and cast molding of ceramics. Next, the present invention will be described with reference to examples.

[0020]

Example Alumina having an average particle size of 1.5 μm (AL-45
1: Showa Denko) 200 g of the dispersant, antifoaming agent (Lion PL-71L) and water shown in Table 1 were added, and the mixture was dispersed and mixed by a ball mill for about 14 hours, then a binder was added and dispersed for 1 hour. Mixed. The resulting alumina slurry is dehydrated at the same time by removing internal bubbles by degassing under reduced pressure,
The slurry viscosity was adjusted to be 1 to 50,000 cP. After that, the thickness is 1.2 on the mylar sheet by the doctor blade method.
Sheet molding was performed with a setting of mm. This was dried with a hot air dryer at 45 ° C. for 2 hours and 120 ° C. for 1 hour to obtain a raw sheet. At that time, the water content of the slurry, the viscosity, the formability of the green sheet, the surface state, and the density were evaluated. Incidentally, instead of the above-mentioned alumina, alumina having an average particle size of 0.6 μm (AL-160S
G-1: Showa Denko) was used in the same manner to obtain a raw sheet, and its performance was evaluated. Table 2 shows the results. Various performances were evaluated as follows.

[Slurry characteristics] Alumina slurry is added to BH
Viscosity at 50 rpm and 1 rpm with a type viscometer. If the ratio of viscosity at 1 rpm / viscosity at 50 rpm is less than 3, Newtonian, and if the ratio is 3 or more, thixotropy. I decided. [Moldability] ◯: The sheet was easily peeled from the Mylar sheet, and a sheet without cracks was obtained.

Δ: A sheet with some cracks was obtained. X: The sheet was not cracked due to cracking. [Surface Condition] ◯: The surface of the green sheet is smooth and has no agglomerates. Δ: There are aggregates on the surface of the green sheet.

X: A molded body of agglomerates whose surface of the green sheet is rough. The copolymer of No. 2 is the following polymer (N in Table 1
O.1 polymer). Also, No 11 ~ 1
The dispersant of 5 was polymerized by changing the solvent from ethanol to IPA.

Method for producing No. 1 polymer Ethanol was added to a 3 liter flask equipped with a stirrer, a thermometer, a reflux condenser, a dropping funnel and a gas introduction tube.
0 g was charged and the temperature was raised to 80 ° C. under a nitrogen gas stream. Then, 50 g of 2-acrylamido-2-methylpropanesulfonic acid, 750 g of a mixture of methyl acrylate and butyl acrylate (3: 1 by weight ratio), 200 g of a monomer mixture solution of methoxypolyethylene glycol (n = 9) methacrylate and azobis- After adding an aqueous polymerization initiator solution of 2.5 g of 2-amidine propane (W-50, Wako Pure Chemical Industries, Ltd.) and 180 g of water, the temperature was kept for 1 hour to complete the polymerization. The obtained copolymer was neutralized with aqueous ammonia. Further, ethanol was distilled off to produce an aqueous solution type binder.

Method for producing No. 3 polymer In a 3 liter separable flask equipped with a stirrer, a thermometer, a reflux condenser, a dropping funnel and a gas introduction tube,
Azobis (4cyanovaleric acid) (Wako Pure Chemical Industries, Ltd. V-50
1) An aqueous solution of a polymerization initiator dissolved in 2.5 g and 180 g of water, 5.0 g of acrylic acid, 495 g of butyl acrylate, 10% of a monomer mixture of 500 g of butyl methacrylate, and 3.5 g of ammonia water (28%). A 10% amount of a neutralizing agent aqueous solution dissolved in 50 g of water and 120 g of an emulsifier (SANYO KASEI KOGYO CO., LTD. EMELINOL STA-16: 30% active ingredient) were charged, and the temperature was raised to 80 ° C. under a nitrogen gas stream. After about 1 hour, the contents became milky white with sufficient emulsification and the internal temperature was 8
After confirming that the temperature was 0 ° C., the remaining amount of the monomer mixed liquid and the neutralizing agent aqueous solution were added. After that, the mixture was kept warm for 2 hours to complete the polymerization, cooled to room temperature and filtered through a nylon mesh to produce an emulsion-based aqueous binder.

The weight average molecular weight of the binder obtained by the above method is tetrahydrofuran as a solvent,
And it measured by the gel permeation chromatography using polystyrene as a standard substance. The weight average molecular weights of the polymers No. 1 to 3 and Nos. 11 to 15 of the present invention are 250,000, 150,000, 1,000,000 and 5,000, respectively.
10,000, 15,000, 10,000 and 20,000.

Table-1 No Binder Dispersant Monomer Composition Amount (%) Monomer Composition Amount (%) 1 2-Acrylamido-2-8 Acrylic Acid / Acrylic 0.2 Methyl Propane Sulfonate Methyl Acid / Butyl Acrylate / (Polymer No. 11) = Methoxypolyethylene 30/70 Recall (n = 9) Methacrylate (Polymer No. 1) = 5/55/20/20 Ammonia neutralized aqueous solution binder 2 Acrylic acid / Acrylic 12 Acrylic acid / Acrylic 0.7 acid Methyl / Acrylic acid Methyl butyl / Methoxy poly (Polymer No12) = Ethylene glycol (15/85 n = 9) Methacrylate (Polymer No2) = 2.5 / 57.5 / 20/20 Ammonia neutralized aqueous solution binder

3 acrylic acid / acrylic 8 acrylic acid / acrylic 0.4 butyl butyl / ethyl methacrylate butyl (Polymer No13) = (Polymer No3) = 40/60 0.5 / 49.5 / 50 Emulsion Water-based Binder 4 Polymer No2 12 Acrylic acid / Acrylic 0.7 Methyl acid (Polymer No14) = 60/40 5 Polymer No3 8 Acrylic acid / Acrylic 0.4 Methyl acid (Polymer No15) = 75/25 * In Nos. 1, 3 and 5 above, alumina As AL45-
1 and No. 2 and 4 used AL160SG-1.

Table-2 No Slurry Final Slurry Raw Sheet Moisture Content (%) Characteristic Formability Surface Condition Density 1 22.3 Newtonian 〇 〇 2.42 2 34.8 Newtonian 〇 〇 2.50 3 23.5 New Tonian 〇 〇 2.39 4 62.6 Thixotropy × × 2.27 5 34.6 Thixotropy × △ 2.25

Claims (1)

(57) [Claims] 1. An aqueous system having an average molecular weight of 55,000 to 2,000,000, which is composed of a copolymer of 0.1 to 20% by weight of a carboxyl group-containing unsaturated monomer or a sulfonic acid group-containing unsaturated monomer and the balance of other copolymerizable monomers. A combination of a binder and a dispersant having an average molecular weight of 1,000 to 50,000, which is a copolymer of 10 to 50% by weight of a carboxyl group-containing unsaturated monomer or a sulfonic acid group-containing unsaturated monomer and the balance of other copolymerizable monomers. An additive for forming ceramics, which is characterized in that