JPH08133844A - Composition for forming ceramics - Google Patents

Abstract

PURPOSE: To obtain a composition, excellent in fluidity, formability, etc., and suitable for producing a molding according to a reactional hardening method by blending a ceramic powder with a specific organic binder and a prescribed amount of a carboxylic acid-based surfactant. CONSTITUTION: This composition for forming ceramics is obtained by mixing (A) a ceramic powder (e.g. alumina powder) with (B) a binder consisting essentially of an unsaturated polymer (e.g. an unsaturated polyester) and a cross- linking substance containing vinyl groups or acrylate groups (e.g. polyethylene glycol diacrylate) and (C) a carboxylic acid-based surfactant (e.g. an acrylic acid/ethyl methacrylate copolymer) in an amount of 0.05-5 pts. wt. based on 100 pts.wt. component (A) and, as necessary, further (D) a solvent having a higher boiling point than the reaction-initiating temperature of the unsaturated polymer in the component (B) with the cross-linking substance and ester or hydroxyl group (e.g. a phthalic acid ester). The resultant composition is filled in a forming mold, then reacted and cured to afford a molding.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a composition for molding ceramics.

[0002]

2. Description of the Related Art In recent years, not only electronic parts but also constituent parts such as devices for various chemical industries, mechanical parts such as various engines and gas turbine engines, and decorative parts such as watches and accessories are characterized by their characteristics. Ceramic parts have become widely used.

However, many of the chemical industrial equipment constituent members, various heat engine mechanical parts, decorative parts, and the like have a complicated three-dimensional structure, and ceramic materials have heat resistance and corrosion resistance as compared with metal materials. Although it has excellent characteristics such as wear resistance, it has a difficulty in workability, and it is difficult to mass-produce shaped products with complicated three-dimensional structures. It prevented the practical use of various parts.

Therefore, as a method for accurately mass-producing the above-mentioned complicated shaped products, there have been conventionally used a slurry casting method for injecting ceramic sludge into a plaster mold to obtain a ceramic compact, and a ceramic powder. An injection molding method has been adopted in which a thermoplastic compound obtained by heating and kneading a binder made of a thermoplastic material is injected into a mold at high pressure to form a ceramic molded body.

However, the sludge casting molding method is unsuitable for mass production, such as deterioration of dimensional accuracy and cracking during drying of the molded body due to wear of the molding die due to repeated use, clogging, etc. was there.

On the other hand, although the injection molding method can mass-produce various ceramic parts having a complicated shape, since the obtained molded body contains a large amount of organic binder, it has a complicated three-dimensional structure having a different wall thickness. In the product, the binder cannot be removed uniformly, cracks occur in the molded body, flow marks remain on the surface of the molded body, and the residual stress inside the molded body is large due to high-pressure injection molding. It has a drawback that it causes deterioration of body characteristics, and it is difficult to produce a ceramic molded body with high yield and high reliability.

Therefore, a reaction injection molding method in which a polymerizable monomer binder having a polyfunctional acrylate or methacrylate is used as an organic binder to be mixed with the ceramic powder and cured is disclosed in JP-A-3-502670. Has been proposed to.

[0008]

However, the organic binder used in the above-mentioned molding method is inferior in fluidity of the organic binder itself, and the composition has an acrylate or methacrylate-reactive functional group in one molecule. Since it contains at least two groups, it is extremely easy to form a polymer having a three-dimensional structure, and as a result, it easily becomes a semi-cured state (gelation) during preparation and storage. Especially, it is an oxide ceramic. Alumina (Al ₂ O ₃ ) and zirconia (ZrO
₂ ) Water attached to the surface such as ₂ ) easily turns into a semi-cured state, which deteriorates the flow characteristics and tends to cause flow marks.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to combine the advantages of conventional molding compositions such as cast molding, injection molding, tape molding, and extrusion molding, It is a ceramic molding composition that can be applied to any of them, it is hard to be in a semi-cured state during preparation and storage, and has good fluidity even at room temperature,
After filling in the mold and curing by reaction, there are no defects such as flow marks and cracks due to shrinkage, good releasability, and no cracks or deformations in the ceramic body after firing. Excellent mass production effect. Another object is to provide a ceramic molding composition.

[0010]

A ceramic molding composition of the present invention is a composition in which a ceramic powder is mixed with an unsaturated polymer and a binder whose main component is a crosslinked binder containing a vinyl group or an acrylate group. The composition contains 0.05 to 5 parts by weight of a carboxylic acid-based surfactant with respect to 100 parts by weight of ceramic powder, and is used to obtain a ceramic molded body by reactively curing the binder during molding. is there.

In particular, it is preferable that the carboxylic acid type surfactant is contained in a ratio of 0.1 to 2 parts by weight with respect to 100 parts by weight of the ceramic powder, and the composition is at least non-existent. It is more desirable to contain a solvent having an ester group or a hydroxyl group having a boiling point higher than the temperature generated by the reaction curing of the saturated polymer and the crosslinked body.

The unsaturated polymer of the present invention is a condensate of a polyfunctional acid and a polyfunctional alcohol, and is a polymer compound having an unsaturated double bond in the molecule, such as unsaturated polyester or The unsaturated polyepoxy and polydiene polymers are applicable.

Among them, unsaturated polyester is preferable from the viewpoint of thermal decomposability and polymerization reactivity, and the content thereof is ceramic powder 10 in order to prevent the viscosity from becoming high.
It is preferably 0.5 parts by weight or more with respect to 0 parts by weight, and 35 parts by weight or less from the viewpoint of reaction curing, and 1 to 20 parts by weight is most preferable from the viewpoint of easy handling of the molded body. .

Further, the crosslinked body containing a vinyl group or an acrylate group of the present invention may be a crosslinked body containing one or more vinyl groups or acrylate groups in one molecule.

For example, as the cross-linked binder containing a vinyl group, alkyldivinyl such as ethyldivinylether, propyldivinylether, neopentanedivinyl, di (pentaneerythrivinylether) hexane, tri (methylvinylether) propane, bisphenol A.
Examples thereof include divinyl ether.

Further, the cross-linked binder containing an acrylate group is an alkyl diacrylate such as propyl diacrylate or neopentane diacrylate, di (pentane erythriacrylate) hexane, tri (methyl acrylate) propane, diethylene oxide diacrylate, etc. Can be mentioned.

Particularly, diethylene oxide-diacrylate is most suitable as the cross-linked product.

In order to maintain the fluidity and moldability of the mixture, it is desirable that the content thereof should not be high in viscosity, and should be 0.5 parts by weight or more based on 100 parts by weight of the ceramic powder. From the viewpoint of shrinkage of the molded product due to the condensation reaction, it is preferably 35 parts by weight or less, and particularly preferably 1 to 20 parts by weight.

The vinyl group or acrylate group is a functional group for radical polymerization, specifically, vinyl group, acrylate group, methacrylate group,
Examples thereof include an ethacrylate group.

On the other hand, the carboxylic acid type surfactant which is an essential component of the present invention includes an acrylic acid type polymer, and the acrylic acid type polymer shown here means an acrylic acid, methacrylic acid or ethacrylic acid monomer. May be copolymerized in the polymer, specifically, acrylic acid / methacrylic acid ester copolymer, methacrylic acid / ethacrylic acid ester, acrylic acid / ethacrylic acid copolymer, and further vinyl. You may copolymerize alcohol, vinyl acetate, and vinyl chloride.

The copolymerization amount of acrylic acid, methacrylic acid and ethacrylic acid contained in the copolymer is preferably 1 mol% or more and 50 mol% or less from the viewpoint of dispersion efficiency.

If the content of the carboxylic acid type surfactant is less than 0.05 parts by weight with respect to 100 parts by weight of the ceramic powder, the flow characteristics of the composition will be poor and flow marks will be generated. If it exceeds 5 parts by weight, the reactivity becomes poor and the strength of the molded article decreases, so that it is in the range of 0.05 to 5 parts by weight, and most preferably 0.1 to 2 parts by weight.

On the other hand, in the ceramic molding composition of the present invention, a solvent may be optionally used in order to further improve the dispersibility of the ceramic powder, and the solvent may be an organic solvent of the ceramic molding composition of the present invention. The solvent is not particularly limited as long as it is compatible with the additive, but a solvent having an ester group or a hydroxyl group having a boiling point of at least the temperature generated by the reaction curing of the unsaturated polymer and the crosslinked body is more preferable.

The reaction production temperature mentioned here is not the polymerization initiation temperature but the temperature of the molded body when the inside of the molded body during curing generates heat due to radical polymerization of unsaturated groups.

As the solvent having an ester group, for example, an aromatic solvent such as phthalic acid ester or an ester such as acetic acid ester or glyceride can be used.
Among them, phthalic acid ester is the most suitable solvent because of its compatibility with unsaturated polymers.

On the other hand, examples of the solvent having a hydroxyl group include higher alcohols such as hexanol, octanol, decanol, and oxyalcohol. Among them, octanol is most suitable because of its compatibility with the unsaturated polymer.

In addition, it is desirable that the content of the solvent is low in the composition from the viewpoint of moldability, and the content is 0.1 part by weight or more based on 100 parts by weight of the ceramic powder. Good and, in order to increase the strength of the molded body and maintain the shape-retaining property, 35 parts by weight or less is more preferable, and in particular, from the viewpoint of easy handling of the molded body,
Most preferably, it is 1 to 20 parts by weight.

The solvent is 0.1% by a known method.
It is desirable to perform a dehydration treatment up to the following, and two or more kinds may be used in combination so that the ceramic molded body is slowly volatilized.

The binder of the present invention may contain other organic additives such as a curing catalyst called a curing reaction accelerator or a polymerization initiator, a dispersant and the like.

[0030]

According to the ceramic molding composition of the present invention, the composition comprises a binder mainly composed of an unsaturated polymer and a cross-linking bond containing a vinyl group or an acrylate group, and a carboxylic acid surfactant as a ceramic. Since 0.05 to 5 parts by weight is contained with respect to 100 parts by weight of the powder, the surfactant is oriented on the particle surface of the ceramic powder to improve the fluidity and lower the viscosity of the composition. Further, if a solvent having an ester group or a hydroxyl group is further contained, it becomes possible to inject the thermoplastic resin into the molding die at a lower pressure.

Further, since the above-mentioned surfactant absorbs H ₂ O molecules on the surface of the ceramic particles, it is considered that the composition is prevented from becoming a semi-cured state.

Further, since the above composition is polymerized and crosslinked and cured even in a state where it contains a solvent having an ester group or a hydroxyl group having a boiling point of at least the reaction formation temperature of the unsaturated polymer and the crosslinked product, the composition is crosslinked during debinding. Before the binder was thermally decomposed, a solvent having a low boiling point or a low thermal decomposition temperature is volatilized in advance to form a volatilization hole, so that when the hardened binder is thermally decomposed, a decomposition gas passes through the volatilization hole. Volatilizes and facilitates binder removal.

[0033]

EXAMPLES The ceramic molding composition of the present invention will be described in detail below with reference to examples.

The ceramic molding composition of the present invention is a mixture of a ceramic powder and an unsaturated polymer and a binder whose main component is a crosslinked binder containing a vinyl group or an acrylate group, and the mixture contains 100 parts by weight of the ceramic powder. A carboxylic acid-based surfactant is contained in an amount of 0.05 to 5 parts by weight per part, and the composition is used to obtain a ceramic molded body by reaction-curing in a mold after filling. The carboxylic acid surfactant is a ceramic powder 1
0.1 to 2 parts by weight with respect to 00 parts by weight, or the composition is a solvent having an ester group or a hydroxyl group having a boiling point of at least the reaction formation temperature of the unsaturated polymer and the cross-linked product. Is more preferable.

The unsaturated polymer is generally obtained from a saturated dibasic acid, a polyhydric alcohol and an unsaturated dibasic acid by a known production method, but the raw materials thereof are not particularly limited.

Concretely, orthophthalic acid, isophthalic acid, phthalic anhydride, succinic acid, diadipic acid, sebacic acid, entmethylenetetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, chlorendic acid or maleic acid and pyrrylene are added. 1. Saturated dibasic acids such as adducts of ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, neopentyl glycol, hydrogenated bisphenol A or ethylene oxide or propylene oxide adduct of bisphenol A, 1.3 butanediol, 1. By heating a polyhydric alcohol such as 4-butanediol or 1.6 hexanediol, and an unsaturated dibasic acid such as maleic anhydride, fumaric acid or itaconic acid to about 160 to 240 ° C. It is those, and the like.

In addition, 12 hydroxystearic acid, 12
A molecule having a monobasic acid such as hydroxylinoleic acid and a monohydroxyl group may be copolymerized as a simple substance or with the above basic acid and alcohol.

The molecular weight of these high molecular weight polymers is preferably 1,000,000 or less for the purpose of reducing the viscosity and improving the fluidity of the ceramic molding composition, but in order not to increase the solidification shrinkage during molding. Since a molecular weight of 10,000 or more is preferable, the molecular weight is suitably 10,000 to 1,000,000.

Further, as the solvent that can be used in the ceramic molding composition of the present invention, in addition to those mentioned above, for example, straight chain alkyls such as hexane, nonane, decane and octadecane, and formic acid, Carboxylic acids such as acetic acid and valeric acid, esters such as methyl acetate, ethyl acetate and propyl formate, polyvalent esters such as glycerite and methyl oxalate, or various solvents such as higher alcohols can be used.

In order to uniformly remove the binder after molding, a solvent having an ester group or a hydroxyl group having a boiling point of at least the curing temperature of the unsaturated polymer may be used.
Several solvents having different boiling points or evaporation coefficients may be arbitrarily mixed and used, and a mixture of linear alkyl solvents and higher alcohols can be preferably used.

In the ceramic molding composition of the present invention, a curing catalyst called a curing reaction accelerator or a polymerization initiator, and other organic additives such as a dispersant can be optionally used.

Examples of the curing catalyst include organic peroxides and azo compounds, such as ketone peroxides, peroxyketals, peroxyesters, hydroperoxides, peroxide carbonates, tertiary butyl peroxy 2-ethylhexanoate. And organic peroxides such as bis (4 tert-butylcyclohexyl) peroxydicarbonate and dicumyl peroxide, and azo compounds such as azobis and ciobutyronitrile.

The addition amount of the curing catalyst, which is the curing reaction accelerator or the polymerization initiator, cannot be unconditionally determined because the required pot life time and the reaction rate of the unsaturated compound and the monomer vary depending on the molding method. Usually, 0.01 to 0.5 parts by weight is preferable with respect to 100 parts by weight of the organic component.

On the other hand, the ceramic powder to which the present invention can be applied includes not only oxide-based ceramics such as alumina, zirconia, mullite and glass, but also non-oxide-based ceramics such as silicon nitride, aluminum nitride and silicon carbide. Therefore, any dependency due to the difference in the raw material powder is not recognized, and any ceramic can be used at any mixing ratio.

Further, as a sintering aid, for example, a raw material powder containing alumina (Al ₂ O ₃ ) as a main component is silica (S
iO ₂ ), calcia (CaO), yttria (Y ₂ O)
₃ ), magnesia (MgO), etc., and zirconia (ZrO
₂ ) Yttria (Y
₂ O ₃ ), a stabilizer such as silicon nitride (Si ₃ N ₄ )
Rare earth element oxides may be added to the raw material powder containing as a main component, and boron (B) and carbon (C) may be added to the raw material powder containing silicon carbide (SiC) as a main component. For the purpose of improving or improving electric characteristics, it is possible to add a refractory metal such as molybdenum (Mo) or tungsten (W).

The ceramic powder having a particle size of several tens of microns to submicrons can be used, but the ceramic powder can be pulverized simultaneously with mixing the ceramic molding composition of the present invention, Furthermore, a part or all of each component of the ceramic molding composition of the present invention,
It is also possible to obtain a ceramic molding composition of the present invention by mixing and pulverizing an excess solvent and then pulverizing and removing the excess solvent by a known method.

In order to improve the wettability of the powder, the ceramic powder is surface-treated with a coupling agent such as a silane coupling agent, a titanate coupling agent, an aluminate coupling agent, and an acetyl alcohol compound. It is also possible to perform surface modification using an agent, and a titanate coupling agent having an excellent reaction rate is particularly preferable.

Next, in order to evaluate the ceramic molding composition of the present invention, a composition containing α-alumina (Al ₂ O ₃ ) and zirconia (ZrO ₂ ) as main components and the above-mentioned known sintering aid was added and mixed. As oxide-based ceramic powder, silicon nitride (Si ₃ N ₄ ) and aluminum nitride (AlN)
For the ceramic molding for evaluation by adding and mixing the above-mentioned known sintering aid as non-oxide type ceramic powder, and adding and mixing the binder composition as shown in Table 1 in various ratios. A composition was prepared. The types of each binder shown in Table 1 are the same as the substance names shown in Table 2.

Sample No. 1 containing no cross-linked product containing vinyl group or acrylate group, Sample No. 2 containing no surfactant, and Sample Nos. 21 and 22 containing surfactant other than carboxylic acid group were used. It was used as a comparative example.

[0050]

[Table 1]

[0051]

[Table 2]

First, the above-mentioned ceramic molding composition for evaluation was prepared by adding a sintering aid to each ceramic powder, wet-mixing the mixture, and drying the mixture to obtain a sized ceramic powder.
The binders shown in Table 1 are added and mixed by stirring for 12 hours.

Although a ceramic molding composition was prepared by adding ceramic powder to the solution here, the method of adding the ceramic powder is not particularly limited, and it is known that the composition finally becomes uniform. Various means of can be used.

Next, in order to prevent air bubbles from remaining in the ceramic molded body, the ceramic molding composition is sufficiently defoamed with a vacuum device or the like.
An antifoaming agent, a defoaming agent, etc. can be added, and after sufficient stirring, the same defoaming treatment may be used together.

Thereafter, the ceramic molding composition was added to
A cylinder with a height of 50 mm and a diameter of 35 mm has a maximum thickness of 5 mm,
Four straight blades having a length of 30 mm are poured into a simple radial type rotor forming mold provided so as to be orthogonal to each other, and after filling, the forming mold is heated and kept at a temperature of less than 100 ° C. for a predetermined time to react. After curing, the ceramic molded body was taken out of the molding die.

The material of the molding die is not particularly limited as long as it is suitable for various reaction curing methods described below.
For example, in the case of reaction curing, any material can be used as long as it can withstand heating, and specifically, a metal type, a resin type, or the like can be used. Therefore, it is possible to apply a surface treatment such as Teflon coating.

Further, in the case of the above-mentioned reaction curing, a heated molding die can be filled with a ceramic molding composition.

Further, as the reaction curing method, in addition to the reaction curing method, an ultraviolet curing method or an X-ray curing method can be used. The reaction curing method is suitable for a product having a complicated shape, and the ultraviolet curing or X The wire curing method is suitable for products with thin wall thickness.

10 ceramic molded bodies each thus obtained
The appearance of each piece is visually inspected, the presence of defects such as flow marks on the surface of the molded product, and the filling property up to the corners of the molding die are investigated to evaluate the moldability. If not observed, ○ 1 out of 10 shows defective or defective filling △: 1 or more out of 10 both defective and defective filling, or 2 or more defective Also, the case where any of the poor filling was recognized was marked with x.

Further, the presence or absence of defects such as chipping and cracks in the corners of the molded product caused by insufficient strength of the molded product at the time of mold release was visually inspected in the same manner as described above.
The releasability was evaluated by assigning Δ as a defect in which only one defect was observed and x as a defect in which two or more defects were observed.

Next, when the ceramic molded body for evaluation is an oxide-based ceramic, in the air, and when it is a non-oxide-based ceramic, in a non-oxidizing atmosphere such as nitrogen gas, up to 500 ° C. After heating to remove the binder,
In order to evaluate the ease of debinding, carbon remaining in the debinding body was quantified as CO _{2 by} an infrared absorption method by a combustion method, and a carbon residual rate was calculated.

Based on the above results, the most desirable binder composition was evaluated as ◯, the desirable binder composition was evaluated as Δ, and the undesired binder composition was evaluated as x. The above results are shown in Table 3.

[0063]

[Table 3]

As is clear from the above results, the sample Nos. 1, 2, 21, 22 which are comparative examples and the sample Nos. 3 and 12 which are not claimed in the present invention do not plasticize, flow marks or defective filling. Etc., or a molded product is cracked due to poor releasability, the carbon residual ratio after debinding is increased, and a stable molded product cannot be obtained. On the other hand, it can be seen that the molded body using the ceramic molding composition of the present invention is a stable molded body.

As the ceramic molding composition of the present invention, a radial type turbo rotor having silicon nitride powder as a main component and having a complicated three-dimensional structure, a maximum diameter of about 50 mm and a minimum blade thickness of about 1 mm was molded. However, even the tip of a thin blade is fully filled, there are no defects such as flow marks on the surface of the molded product, and it is extremely easy to release from a complicated mold without chipping or cracking in the molded product. You can
It was confirmed that the binder removal property was also good.

Furthermore, when the molded body of the radial type turbo rotor was fired in a nitrogen gas atmosphere, no cracks or deformations were found in the obtained sintered body.

The present invention is not limited to the above-described embodiments.

[0068]

As described above, the ceramic molding composition of the present invention comprises a ceramic powder used for reaction-curing to obtain a ceramic molded body and a cross-linking bond of an unsaturated polymer containing a vinyl group or an acrylate group. Since the mixture of the binder containing the body as the main component contains 0.05 to 5 parts by weight of the carboxylic acid type surfactant with respect to 100 parts by weight of the ceramic powder, the fluidity is extremely good even at room temperature and the moldability is high. Good, surface defects and poor filling are eliminated, there is no crack due to shrinkage after filling in the mold and reaction curing, and there are no chips or cracks during mold release, and it is extremely easy to remove the binder ceramic molding. You can get the body.

Moreover, since the ceramic molding composition of the present invention can be applied to any of the conventional cast molding method, injection molding method, extrusion molding method, etc., it can be used for molding all ceramic parts. For example, not only electronic parts, but also gas turbines, turbo rotors, artificial joints, etc. having complicated three-dimensional structures, parts for large-scale semiconductor manufacturing equipment and various other components, or thin articles and watches of simple shapes, accessories, etc. It is also suitable as a decorative component, etc., and can provide a ceramic molding composition having an excellent mass production effect.

Claims (3)

[Claims] 1. A molding is obtained by filling a mixture of a binder containing an unsaturated polymer and a cross-linking body containing a vinyl group or an acrylate group as a main component and a ceramic powder in a molding die and then curing the mixture by reaction curing. The composition is used in an amount of 0.05 to 100 parts by weight of ceramic powder.
A ceramic molding composition comprising 5 parts by weight of a carboxylic acid surfactant. 2. The ceramic molding composition according to claim 1, wherein the carboxylic acid surfactant is 0.1 to 2 parts by weight with respect to 100 parts by weight of the ceramic powder. 3. The ceramic according to claim 1, wherein the composition contains at least a solvent having an ester group or a hydroxyl group having a boiling point not lower than the reaction formation temperature of the unsaturated polymer and the crosslinked body. Molding composition.