JPH0218349A - Binder for producing green sheet - Google Patents

Abstract

PURPOSE:To obtain the title binder giving a film having superior softness and surface smoothness and capable of being regenerated and reutilized by copolymerizing acrylic acid or a water soluble acrylate and methacrylic acid or a water soluble methacrylate with other unsatd. monomer in an aq. system to prepare an aq. resin emulsion. CONSTITUTION:The title binder is an aq. resin emulsion having -50 to +50 deg.C film forming temp. prepd. by copolymerizing <=50wt.%, in total, of 5-20wt.% acrylic acid or water soluble acrylate and 10-40wt.% methacrylic acid or water soluble methacrylate with 50-85wt.% other unsatd. monomer, preferably lower alkyl (1-6C alkyl) ester of acrylic acid in an aq. system.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a binder suitable for producing ceramic sheets by degreasing and firing green sheets.

[Prior art]

Ceramic Green 7-T has generally been produced by dissolving a binder such as butyral resin in an organic solvent such as methyl ethyl ketone, butyl acetate, or alcohol, and mixing this with fine ceramic powder for a long time to form a slurry. A method has been adopted in which air is removed and the material is formed into a sheet on a carrier film using a blade having a certain thickness, and this is heated and dried to form a green sheet (Japanese Patent Application Laid-open No. 156775/1982).

However, conventional molding methods using organic solvents have the following problems.

(1) The harm caused by organic solvents to the human body (2) There is a risk of explosions and fires when handling organic solvents (3) The material cost of organic solvents used to manufacture green sheets is high.

(4) It is necessary to make the device explosion-proof, and an organic solvent recovery device is also required, making the device expensive.

There are other problems. In order to solve these problems,
A manufacturing method using a water-soluble organic binder such as PVA has been proposed.

However, although this method has the advantage of being able to solve the above problem, the ceramic powder tends to form an agglomerated structure in the aqueous slurry during the green sheet creation stage, and the viscosity deviates significantly from the Niethonian flow, resulting in poor fluidity of the slurry. There was a problem in that the dispersibility of ceramic was poor and it was difficult to obtain green sheets with high density and a smooth surface.

On the other hand, water-soluble polymers such as PVA currently have high plasticizing efficiency and do not require plasticizers, and if a large amount of plasticizers such as glycerin are used to give green sheets flexibility, There was also the problem that the plasticizer migrating silon caused surface tackiness.

Furthermore, it has been proposed to use an aqueous emulsion consisting of an acrylic resin emulsion, an ethylene/vinyl acetate copolymer emulsion, an isobutylene polymer latex, or a mixture thereof as a binder for green sheet production (Unexamined Japanese Patent Publication No. No. 180955, 1986, Japanese Patent Publication No. 1983
-180957, 59-129277). This material has the advantage that it is highly flexible and has the disadvantage that the sheet may be cracked or chipped during the sheet secondary processing and firing process. However, the sheet-shaped molded product before firing is destroyed and cannot be recycled.

It has also been proposed to use an aqueous solution of a sodium polyacrylate copolymer salt as a ceramic binder. JP-A-59-121152 discloses (1) one or more monomers selected from acrylic acid, methacrylic acid, acrylates, or methacrylates (hereinafter referred to as monomer (1)); (10) One or more monomers selected from esters of acrylic acid or methacrylic acid and C1 to Cta monohydric alcohols or C1 to C1B polyhydric alcohols (hereinafter referred to as monomer (II)), It has been proposed to use an aqueous solution of a copolymer with molecules T20,000 to 500,000 obtained by copolymerizing at a molar ratio (monomer (I)/monomer (II)) of 99/1 to 50,150 as a ceramic binder. ing.

However, the polymer aqueous solution generally has a low solid content, a high viscosity, and has the disadvantage that it is difficult to mix sufficiently uniformly with a ceramic material because of the large influence of the molecular weight.

As an aqueous resin emulsion for ceramic binders similar to the present invention, JP-A-60-122768 discloses a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms and an alkylene having 1 to 4 carbon atoms. At least one heptamine selected from the group consisting of (meth)acrylic acid alkoxyalkyl esters having groups 4
0 to 95 in and carboxyl group-containing monomer 5 to 60
1! t% and 0 to 55 monomers copolymerizable with these (however, the total of all monomers is 100 monomers).

) has been proposed for use in ceramic molding.

However, when examining the examples in this publication, there are no examples in which alkrylic acid and methacrylic acid are used in combination, and no consideration is given to recycling the binder.

When acrylic acid is used alone as the carboxyl group-containing monomer, the water-soluble ammonium acrylate base cannot be incorporated into the resulting emulsion carbon copolymer particles (water-soluble). Although it can be recycled, its strength is weak and the strength of the resulting Nana-mix product is fragile. When backpressure methacrylic acid is used alone, the emulsion has poor dispersibility and is difficult to recycle.

[Problem to be solved by the invention]

The present invention provides a binder for producing green sheets that is recyclable and provides a highly flexible film. Ceramics manufactured using this No. 9 Ingu have good strength. [Specific Means for Solving the Problem] In the present invention, the Cal. Acrylic acid and methacrylic acid are used together in a specific ratio as xyl group-containing monomers, and the resulting emulsion copolymer is neutralized with ammonia, etc., and is present on the particle surface of the copolymer and is water-soluble. shows,
This objective is achieved by equipping the copolymer particles of the emulsion with an acrylic acid base that contributes to recycling and a methacrylic acid group that is incorporated into the interior of the copolymer particles and contributes to improving the strength of ceramics.

(a) Component Niacrylic acid or its water-soluble salt 5 to 20 kqb (b) Component: Methacryl IR or its water-bathable ring 1O to 40! Component (e): Other unsaturated monomers] Aqueous resin emulsion obtained by copolymerizing the above components (a), (b) and (c) for producing a desired green sheet The present invention provides a binder for producing a green sheet, in which the film forming temperature of the emulsion is 150°C to +50°C.

This resin aqueous emulsion for binders is made by combining acrylic acid, methacrylic acid and other unsaturated monomers with ammonium persulfate, azobisisobutyronitrile, etc. in water or a mixture of water and water-soluble alcohol. The copolymer emulsion obtained by radical polymerization at a temperature of 60 to 120° C. in the presence of a polymerization initiator is treated with ammonia, organic amines, alkali metal hydroxide salt (NaOH), etc.

The number average molecular weight of the resin in the aqueous emulsion is from 2.500 to 2.500.
300,000 is preferred b0 Other unsaturated monomers include (meth)acrylic acid alkyl esters having an alkyl group having 1 to 8 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, Isopropyl (
meth)acrylate), n-butyl(meth)acrylate, isobutyl(meth)acrylate, cyclohexyl(
In addition to meth)acrylate, 2-ethylhexyl methacrylate, etc., hydrophilic monomers such as diallyl phthalate, 2-hydroxyethyl acrylate, acrylamide, methacrylamide, styrene, methyl methacrylate, methyl acrylate, ethyl acrylate, acrylic T-butyl acid, acrylonitrile, maleic anhydride, N-methylolacrylamide, etc. can be used. The type and amount of vinyl monomer used is determined so that the resulting liquid will form an emulsion.

In addition to ammonia, caustic soda, and caustic potash, organic amines may be used for neutralization.

Examples of organic amines include monoethylamine, diethylamine, 7-n-propylamine, so-n-zorobylamine, mohe'-butylamine, di-n-butylamine, monoethanolamine, jetanolamine, triethanolamine, triethylenediamine, and triethanolamine. Low-molecular amines such as ethylenetetramine, hexamethylene diamine, hexamethylenetetramine, pyricine, and piperidine, and high-molecular amines such as polydimethylaminoethyl methacrylate and a condensate of alkylene dichloride and fullkylene polyamine can be used.

These bases, which neutralize acrylic acid and methacrylic acid, have no limitations when used in ceramics, such as pottery, scissors, cutlery, etc., but in applications where conductivity is disliked, such as insulators and ICs, they are used when burning green sheets. Ammonia and organic amines that disappear are preferred, and caustic soda and caustic potash, which leave metal residue on the ceramic product when the green sheet is burned, are not preferred.

(a) Component acrylate is 5! If it is less than it*, it is difficult to recycle the binder. If the total amount is 20m, the strength of the ceramic will be weakened.

If the methacrylate of component (b) is less than 10% by weight, the strength of the ceramic will be weak, and if it exceeds 40% by weight, it will be difficult to recycle.

When the sum of components (,) and (b) exceeds 50 times, there are disadvantages such as a decrease in binding strength as a binder and a decrease in thermal decomposition during green sheet sintering.

If necessary, the binder may contain plasticizers such as dibutyl 7 tallate and octyl 7 tallate, surfactants, antifoaming agents, dispersants, emulsifiers, wetting agents, water-soluble poly 1, oligomers, etc. .

The blending amount of the binder is 2 to 25 parts by weight in terms of solid content per 100 parts by weight of the fine ceramic powder. Zffif
If it is less than t part, cracks tend to occur in the ceramic green sheet, and if it exceeds 251 parts, the ceramic green sheet will have many pores and a high-density ceramic will be obtained.

Preferably 3 to 20 parts by weight, more preferably 4 to 15 parts by weight
Parts by weight.

The slurry composition for ceramic green sheets is usually obtained by mixing the binder, ceramic raw material fine powder, and other ingredients in a Gale mill or the like.

The ceramic fine powder used in the present invention is alumina, magnesia, zirconia, beryllia, doria, spinel,
General inorganic compounds such as steatite, titanium oxide, barium titanate, borides, nitrides, silicides, and carbides can be mentioned, and if they are used for ceramics,
There are no particular restrictions.

Ceramic green sheets are manufactured by applying the aqueous slurry composition for ceramic green sheets onto a polyester tape using a doctor blade or the like and drying the tape at a temperature of 50 to 100°C.

Ceramic green sheets using the binder of the present invention have excellent surface smoothness and flexibility, and the dried sheets can be melted and reused. In addition, since no organic solvent is used in the manufacturing process, there are no problems such as environmental pollution or recovery of dangerous organic solvents such as explosion, and there are great economic advantages.

[Examples, etc.]

Example 1 of manufacturing emulsion
The temperature was raised to , and while stirring, the following solutions a and b were added over 2 hours, and the reaction was completed by further stirring at the same temperature for 10 minutes. Then, after cooling to room temperature, - was reduced to 8 with ammonia. Adjust the viscosity at 20℃ to 3 centipoise, and the resin solid content to 5.
An aqueous resin emulsion of No. 01 was obtained.

Example 2 (for comparison) Stirrer, thermometer, cooling tube, nitrogen introduction tube, mixed monomer,
Nanano J equipped with a dropping funnel and a polymerization initiator dropping funnel
? In a rubble flask, add 150 parts of distilled water and polyoxyethylene nonylphenyl ether (HLB) as an emulsifier.
18.2,? Three parts of E-Oseki K (Tens) were charged, and nitrogen was introduced through the nitrogen introduction tube to create a nitrogen atmosphere inside the flask. Next, a mixture of 20 parts of n-butyl 7-acrylate, 40 parts of 2-ethoxyethyl acrylate, and 40 parts of methacrylic acid was charged into the mixing monomer dropping funnel, and 20 parts of a 5-preferential ammonium sulfate aqueous solution was charged into the polymerization initiator dropping funnel. I prepared it. Next, while adjusting the internal temperature of the flask to 95°C, the mixed monomers and polymerization initiator were added dropwise over 2 hours each, heated at 95°C for an additional 30 minutes, cooled, and added with aqueous ammonia to pE (7.0K1.+4 sections). A water-based ceramic molding binder having a solid content concentration of 20 was obtained.

Production example of water-soluble polymer (for comparison) 2g equipped with reflux condenser, thermometer, stirring bar, nitrogen inlet tube
A flask was charged with 20 parts of distilled water and 150 parts by weight of acrylic acid. Aqueous ammonia was gradually added while stirring and cooling to prepare an aqueous solution of ammonium acrylate.

Next, parts by weight of methyl methacrylate, parts by weight of isozorobyl alcohol, and 5 parts by weight of 2-mercaptoethanol were charged and mixed uniformly. The temperature was adjusted to 40°C, and nitrogen was started to be blown into the reactor through the nitrogen inlet tube.

Next, 0.1 of 2,2 azobis(amidinopropane) hydrochloride
5 parts by weight were dissolved in 10 parts by weight of water and added. After an induction period of approximately 20 minutes, an exotherm was observed and polymerization began. During the polymerization period, stirring, cooling, and nitrogen blowing were continued, and the temperature was maintained at 60℃.
The temperature was maintained at ±5°C. Heating starts from 3 hours after the start of polymerization.
Aging was performed at 0° C. for 1 hour, and then, cyisoglobil alcohol was distilled off under reduced pressure. The obtained copolymer is water-soluble, has a molecular weight of 200,000.20°C, and a viscosity of a 20% aqueous solution of 3.1! It was pH.

Examples 4 to 6 In Example 1, the amount of monomers blended was changed to obtain emulsions or water-soluble polymers shown in Table 1.

Example 1 To 241.6 parts of the binder obtained in Example 1, 1 part of alumina powder was added.
,000 parts, pendylstyl phthalate as a plasticizer)
(BBP), 5 parts of polyoxyethylene octylphenyl ether (FFL lubricant) of HLB 17, and 200 parts of water were mixed to prepare an aqueous slurry composition for ceramic green sheets.

This composition was put in an equivalent amount of porcelain gall having a diameter of 1 in a porcelain mill, and kneaded for 2 days.

It was defoamed using a vacuum defoaming device to obtain a homogeneous slurry.

After adjusting the viscosity appropriately, this was cast onto a polyester film to a dry film thickness of 0.1 to 0.5 cm to produce a green sheet. The obtained sheet was highly flexible, elastic, strong, easy to handle, and had a smooth surface.

When the green sheet was fired at 1600° C., porcelain was obtained which was comparable to the conventional method.

The green sheet before firing was evaluated by the following method.

The results are shown in Table 1.

Evaluation method Flexibility: When the green sheet was wrapped around a glass rod with a diameter of 10 m, cracks at the curved portion were observed.

0 No cracks. ×There are cracks.

Re-dissolution time The green sheet was immersed in 5 times a day of water and stirred, and the re-dispersion time was measured. When the dispersion was filtered using a 150-mesh wire mesh, the time required for complete dispersion until nothing remained on the wire mesh was defined as the redissolution time.

05 minutes or more, ×5 minutes or more Surface tackiness: Evaluated by touch with fingers.

Evaluation criteria O- No stickiness at all.

Δ- Slightly sticky feet.

× - Very sticky.

Porcelain strength When 20 pieces of porcelain were dropped from a height of 1 inch onto a polyvinyl chloride floor, the number of pieces broken was investigated.

0-0 to 3 pieces Δ-4 to 8 pieces Ceramic green sheets were obtained.

The results are shown in Table IK.

still, The amount of each component is shown in parts by weight of solid content.

(Margin below)

Claims (1)

[Scope of Claims] 1) Component (a): 5 to 20% by weight of acrylic acid or its water-soluble salt (b) Component: 10 to 40% by weight of methacrylic acid or its water-soluble salt (c) Component: Other non-acrylic acid 50-85% by weight of saturated monomers. [However, the sum of components (a) and (b) is 50% by weight or less.] For manufacturing green sheets made of an aqueous resin emulsion obtained by copolymerizing components (A), (b), and (c) above. A binder for producing a green sheet, wherein the emulsion has a film forming temperature of -50°C to +50°C. 2) The binder according to claim 1, wherein the water-soluble salts of component (a) and component (b) are ammonium salts. 3) Component (c) is acrylic acid lower alkyl ester (
The binder according to claim 1, wherein the alkyl group has 1 to 6 carbon atoms.