JPH0694388B2 - Injection molding ceramic composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to an injection molding ceramic composition suitable for producing a ceramic product by an injection molding method.

(Prior Art) Generally, when a ceramic product is obtained by an injection molding method,
First of all, after kneading the ceramic powder and the organic binder that is the binder to uniformly disperse the ceramic powder in the organic binder, it is made into an appropriate shape, for example, a coarsely crushed product or a pellet shape, and injection molding is performed. Use as a material (kneading process). Next, using this material, an injection molding machine is used to obtain a molded product having a desired shape by the same method as is usually used for plastic molding (molding step). After that, the organic binder is removed by a method such as thermal decomposition (debinding step),
By sintering at a suitable temperature (sintering step), a product having a desired shape having the characteristics of ceramics is manufactured.

Here, the organic binder is the homogeneity of the dispersion of the ceramic powder in the injection molding material, the fluidity of the molten material in the molding process, the strength of the obtained molded product, and the easy removal of the organic binder in the debinding process. It is an important component related to the sa (debinding property).

If the wettability of the organic binder component and the ceramic powder is poor or if the amount of the organic binder used is incorrect, it becomes difficult to uniformly disperse the ceramic powder in the organic binder, and the ceramic powder and the organic powder are not mixed in the kneading or injection molding process. It is not possible to obtain many uniform molded products because the binder components are separated or the molten molding material lacks in fluidity. Also, if the type and mixing ratio of the organic binder component is incorrect, the strength of the molded product will be significantly reduced, and the molded product will be taken out of the mold and moved to the next step.
It may be damaged during storage, or the molded product may be cracked, blistered, or deformed during the binder removal process. Furthermore, if the thermal stability of the organic binder component is poor, the organic binder component deteriorates during injection molding and a certain level of fluidity cannot be obtained, and materials such as spools and runners are reused as molding materials. Can not.

(Problems to be Solved by the Invention) Various organic substances have been conventionally used as organic binder components.

For example, in Japanese Patent Publication No. 51-29170, when atactic polypropylene (hereinafter abbreviated as APP) is used, dispersion of ceramic powder is good, and a molding ceramic composition having good fluidity, thermal stability, and appropriate strength is obtained. It has been shown to be obtained. However, APP has a defect that cracks, blisters, and deformation are likely to occur in the molded product in the debinding process.

When olefin wax, paraffin wax, etc. are used, there are few problems in the debinding process, but the wettability with the ceramic powder is poor and it is difficult to disperse the ceramic powder uniformly in the binder. There is a problem that a certain fluidity cannot be obtained because of poor performance, it is difficult to reuse materials such as spools and runners, and the strength of the obtained molded product is extremely low.

Furthermore, the acrylic polymer has good dispersibility and thermal stability of the ceramic powder, and has a small amount of heat generated during debinding.
It is characterized in that cracks, blisters, and deformation do not easily occur, but it has the drawback that the injection-molded product has low strength and is easily damaged during handling.

(Means for Solving Problems) As a result of earnest research in view of such a situation, the present inventors have found that
When an organic binder, an acrylic copolymer, and an ethylene-ethyl acrylate copolymer are used together in a specific ratio,
The inventors have found that a well-balanced ceramic composition for injection molding can be obtained without the above-mentioned drawbacks, and completed the present invention.

That is, the present invention is a composition comprising a ceramic powder (I), an acrylic polymer (II) and an ethylene-ethyl acrylate copolymer (III), wherein the acrylic polymer (II) and the ethylene-ethyl copolymer are used. A ceramic composition for injection molding, characterized in that the weight ratio (II) / (III) of the acrylate copolymer (III) is 1/4 to 20/1.

As the ceramic powder (I) used in the present invention, any known one can be used, for example, aluminum oxide,
Silicon oxide, magnesium oxide, calcium oxide, titanium oxide, zirconium oxide, mullite, cordierite, forsterite, steatite, kaolin, talc, synthetic mica, ferrite, barium titanate, silicon carbide, titanium carbide, tungsten carbide, boron carbide , Silicon nitride, boron nitride, sialon, etc., each of which may be used alone or in admixture of two or more. The amount of the ceramic powder (I) used in the ceramic composition for injection molding is usually 40 to 70% by volume, preferably 45 to 70% by volume.
The amount is 67% by volume.

The acrylic polymer (II) used as one of the organic binders in the present invention includes (meth) acrylic acid ester (a) and, if necessary, other monomer (b) copolymerizable therewith. (However, except for ethylene), a (co) polymer obtained from the above can be used alone or in admixture of two or more. Ordinarily in terms of liquidity alone or 2
The weight average molecular weight of the mixture of one or more (co) polymers is from 5000 to
200,000 is used, but 8,000 to 100,000 is preferable.

Examples of the (meth) acrylic acid ester (a) used here include an n-alkyl (meth) acrylate having an alkyl group having 1 to 8 carbon atoms, isopropyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl ( (Meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2
-Hydroxy (meth) acrylate, 2-hydroxypropyl (meth) acrylate, diethylene glycol (meth) acrylate, glycidyl (meth) acrylate, aminoalkyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl methacrylate, Examples thereof include aryl (meth) acrylates, which may be used alone or in combination of two or more. Among them, n-alkyl (meth) acrylates having an alkyl group having 1 to 4 carbon atoms, isobutyl (meth) acrylate, isopropyl (meth) acrylate, and t-butyl (meth) acrylate are useful.

Examples of the other monomer (b) copolymerizable with the (meth) acrylic acid ester (a) include vinyl acetate, vinyl chloride, vinylidene chloride, butadiene, vinyl ether, styrene, methylstyrene, acrylonitrile, and methacrylonitrile. , (Meth) acrylic acid, itaconic acid, methaconic acid, citraconic acid, and the like, among which styrene, methylstyrene, and (meth) acrylic acid are useful.

Further, the ratio of the (meth) acrylic acid ester (a) to the other monomer (b) copolymerizable with the (meth) acrylic acid ester is such that the weight ratio (a) / (b) is usually 100/0 to 40 / 60, preferably 100/0
~ 60/40.

The ethylene-ethyl acrylate copolymer (hereinafter abbreviated as EEA) (III) which is another organic binder component includes a copolymer obtained from ethylene and ethyl acrylate, and usually has an ethyl acrylate content of 1 or less. ~
Although 50% by weight is used, 10 to 40% by weight is preferable. As the molecular weight of EEA, those having a weight average molecular weight of 100,000 or less are usually used, and among them, those having a weight average molecular weight of 10,000 to 70,000 are preferable in terms of strength and fluidity.

The acrylic polymer (II) and EEA (III) are used in a weight ratio (II) / (III) of 1/4 to 20/1. Among them, the strength of the molded product and debinding 1/4 to 10/1 is preferable in terms of excellent balance of properties. (II) / (III)
If the weight ratio is less than 1/4, the debinding property is lowered, cracks, blisters, and deformation are likely to occur, and if it exceeds 20/1, the strength is lowered, which are not preferable.

The composition of the present invention further comprises, if necessary, a surface treatment agent for ceramic powder, additives such as a sintering aid, a reinforcing material, an acrylic polymer (II) and EEA within a range that does not impair the effects of the present invention. Synthetic resins other than (III) can be added.

Examples of the surface modifier include vinylsilane-based, aminosilane-based, epoxysilane-based, methacrylsilane-based, and other silane-based coupling agents, monoalkoxytitanium-based agents,
Titanium-based coupling agents such as tetraalkoxytitanium-based, titanium acylate-based, titanium chelate-based, metallic soaps such as metal stearates and metal laurate, and nonionic, anionic, cationic, amphoteric surfactants Etc., and the addition amount thereof is usually 0.01 to 5 parts by weight with respect to 100 parts by weight of the ceramic powder.

Examples of the reinforcing material include inorganic or metal fibers, whiskers and the like.
Used in an amount of up to 50% by volume.

Specific examples thereof include inorganic fibers such as asbestos, rock wool, slag wool, kaolin, bauxite, kayanite, glass, fused silica, alumina / silica, magnesia, potassium titanate, alumina, zirconia, silicon carbide, silicon nitride. As the inorganic whiskers, there are whiskers made of sapphire, boron nitride, silicon nitride, aluminum nitride, beryllia, boron carbide, silicon carbide, graphite, etc., and metal fibers. As the metal whiskers, there are fibers and whiskers made of steel, stainless steel, aluminum, bronze, brass, copper, magnesium, nickel, titanium, beryllium, tungsten, molybdenum, boron and the like.

Examples of the synthetic resin include polyethylene, polypropylene, polyacrylonitrile, acrylonitrile-styrene copolymer, ethylene-vinyl acetate copolymer and the like.

In order to obtain the composition of the present invention, the ceramic powder (I), the acrylic polymer (II), the EEA (III), and additives, reinforcing agents, etc., which are optionally added, are mixed in a predetermined mixing ratio. Then, it may be melt-mixed at a temperature equal to or higher than the softening point of the organic binder by using a known kneader such as an extruder, a kneader, a high-speed mixer, or a roll. The production method is not particularly limited, but the ceramic powder (I) It is preferable to add a surface treatment agent and a sintering aid in advance and mix them.

(Effects of the Invention) The ceramic composition for injection molding of the present invention is capable of easily dispersing ceramic powder, has high fluidity, is easily excellent in strength, and can be molded into an injection-molded product that is easy to handle,
It is possible to reuse the runner and the like, and since it has excellent debinding property, it has an advantage that cracking, blistering and deformation do not occur even if debinding is performed in a relatively short time.

(Example) Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. The parts in the examples are parts by weight.

Example 1 100 parts of aluminum oxide and an acrylic polymer (36 parts of methyl methacrylate, 54 parts of butyl methacrylate, 7 parts of ethyl acrylate and 3 parts of acrylic acid, 9.3 parts by weight average molecular weight of 25,000), EEA (acrylic acid Ethyl content 18% by weight, weight average molecular weight 58000) 2.2 parts, polystyrene 8.8
Part, 1.2 parts of dibutyl phthalate and 1.0 part of stearic acid are added, and the mixture is kneaded at 130 ° C. for 30 minutes by a pressure type double-arm kneader, cooled, pelletized to about 3 mm, and a ceramic composition for injection molding containing 55% by volume of aluminum oxide. Got
When this composition was observed with a 100 × optical microscope, no agglomerated particles were found and the dispersion of the ceramic powder was good.

This was injection-molded under the conditions of a heating cylinder temperature of 150 ° C and an injection pressure of 600 kg / cm ² , and the plate-shaped molding (width 50 mm, length 90
mm, thickness 3.6 mm and 2 mm) and a rod-shaped molded body (4 × 4 × 60 mm) shown in FIG.

Three-point bending test (span spacing)
Bending strength is 155k when 30mm, weighting speed 1mm / min)
It was g / cm ² .

Next, these molded bodies were heated to 500 ° C. at a rate of 20 ° C./hr to remove the binder. Then, it was held at 1700 ° C. for 1 hour and sintered to obtain a good aluminum oxide sintered body.

Example 2 8 parts of an acrylic polymer (composed of 40 parts of butyl methacrylate, 20 parts of butyl acrylate and 40 parts of styrene and having a weight average molecular weight of 90000) based on 100 parts of aluminum oxide, EEA
(Ethyl acrylate content 25% by weight, weight average molecular weight 29
000) 3 parts, dioctyl adipate 1.5 parts, stearic acid
A ceramics composition for injection molding containing 65% by volume of aluminum oxide was obtained in the same manner as in Example 1 except that 1.0 part and 1.0 part of polyethylene wax were used. Similar to the composition of Example 1, this composition had good ceramic dispersion.

This was injection-molded under the conditions of a heating cylinder temperature of 160 ° C. and an injection pressure of 800 kg / cm ² to obtain a molded product having a shape shown in FIGS. 1 and 2. The bending strength of the molded body shown in FIG. 2 was 140 kg / cm ² . Next, these molded bodies are heated to 500 ° C at a rate of 25 ° C / hr to completely remove the binder, and then held at 1700 ° C for 1 hour and sintered to obtain a good aluminum oxide sintered body. Obtained.

Example 3 The molded product obtained in Example 1 and its molding waste (spool, runner, etc.) were roughly crushed to obtain a ceramic composition for injection molding. A good aluminum oxide sintered body was obtained in the same manner as in Example 1 except that this was used. Further, during injection molding, the molding ceramic composition was allowed to stay in a heating cylinder at 170 ° C. for 8 hours, but the moldability did not change, and a good molded product was obtained.

Example 4 A good aluminum oxide sintered body was obtained in the same manner as in Example 3 except that the molded product obtained in Example 2 and the molding waste thereof were used.

Example 5 9 parts of an acrylic polymer (50 parts of methyl methacrylate and 50 parts of butyl methacrylate, weight average molecular weight 8500) in 100 parts of aluminum oxide, EEA (ethyl acrylate content 35% by weight, weight average molecular weight 56000) ) Add 9 parts, styrene 4.5 parts, dioctyl phthalate 2 parts, aluminum stearate 1 part, and pressurize with a double-arm kneader.
The mixture was kneaded at 130 ° C. for 30 minutes, cooled and pelletized to obtain a ceramic composition for injection molding containing 51% by volume of aluminum oxide. Similar to the composition of Example 1, this composition had good ceramic dispersion.

This was injection-molded under the conditions of a heating cylinder temperature of 140 ° C. and an injection pressure of 700 kg / cm ² to obtain a molded product having a shape shown in FIGS. 1 and 2. The bending strength of the molded body shown in FIG. 2 was 160 kg / cm ² .

Next, these molded bodies were heated to 500 ° C. at a rate of 15 ° C./hr to remove the binder, and then held at 1650 ° C. for 1 hour and sintered to obtain a good aluminum oxide sintered body.

Example 6 100 parts of aluminum oxide and 15 parts of an acrylic polymer (50 parts of methyl methacrylate, 20 parts of glycidyl methacrylate, 10 parts of isobutyl acrylate and 20 parts of styrene, weight average molecular weight 20000), EEA (acrylic acid Ethyl content 18% by weight, weight average molecular weight 62000) 1.5 parts, dioctyl phthalate 1.5 parts, stearic acid 1.0 part, and kneading with a pressure type double-arm kneader, and injection molding containing 60% by volume of aluminum oxide as a pellet shape. A ceramic material for materials was obtained.

This was injection-molded under the conditions of a heating cylinder temperature of 160 ° C. and an injection pressure of 600 kg / cm ² to obtain a molded product having the shape shown in FIG. The bending strength of this molded product was 140 kg / cm ² . Next, this molded body is
The temperature was raised to 00 ° C. at a rate of 25 ° C./hr, the binder was removed, and then the mixture was held at 1700 ° C. for 1 hour and sintered to obtain a good aluminum oxide sintered body.

Example 7 Ceramic powder 51 in the same manner as in Example 1 except that 100 parts of yttria solid solution zirconium oxide, 9 parts of the same acrylic polymer as in Example 1, 3 parts of EEA, 3 parts of dibutyl phthalate, and 3 parts of stearic acid were used. A ceramic composition for injection molding containing volume% was obtained. As for the dispersibility of this composition, the dispersion of the ceramics was good as in Example 1.

This was injection-molded under the conditions of a heating cylinder temperature of 160 ° C. and an injection pressure of 800 kg / cm ² to obtain a molded product having the shape shown in FIG. The bending strength of this molded product was 140 kg / cm ² . This molded body is 500 ℃
The temperature was raised at a rate of 15 ° C./hr to remove the binder, and the mixture was held at 1500 ° C. for 1 hour and sintered to obtain a good aluminum oxide sintered body.

Comparative Example 1 EEA was omitted and the amount of acrylic polymer used was 16.5.
A molded body shown in FIG. 2 was obtained in the same manner as in Example 6 except that the parts were changed, and the bending strength of this molded body was as small as 115 kg / cm ² .

Then, when the plate-shaped molded body shown in FIG. 1 was injection-molded in the same manner, the strength of the molded body was low, and therefore cracking occurred at the time of protrusion for releasing from the mold, and a good molded body could not be obtained.

Comparative Example 2 Eliminate the use of acrylic polymer and set the amount of EEA to 16.5.
1 and 2 were obtained in the same manner as in Example 6 except that the parts were changed, and then the binder was removed by raising the temperature to 500 ° C. at a rate of 25 ° C./hr. Cracks and blisters were formed on the body, and a satisfactory debinder product was not obtained.

Comparative Example 3 A ceramic composition for injection molding containing 65% by volume of aluminum oxide was obtained in the same manner as in Example 2 except that the use of the acrylic polymer was omitted and the amount of EEA used was changed to 11 parts. When this composition was observed with a 100 × optical microscope, many agglomerated particles were found and the dispersion of the ceramic powder was poor. This is carried out in the same manner as in Example 1, and FIG.
The molded product shown in (1) was injection molded, but the fluidity was poor and only a short shot molded product was obtained.

Comparative Example 4 Paraffin wax (melting point: 1 with respect to 100 parts of aluminum oxide)
A ceramic composition for injection molding containing 60% by volume of aluminum oxide was obtained in the same manner as in Example 5 except that 14 parts of 35 ° F.), 1 part of dibutyl phthalate and 2 parts of stearic acid were used. When this composition was observed with a 100 × optical microscope, many agglomerated particles were found and the dispersion of the ceramic powder was poor.

Heating cylinder temperature 140 ° C. This, the plate-shaped molded body shown in Figure 1 under conditions of injection pressure 800 kg / cm ² was injection-molded, due to the low strength of the molded body was damaged during projecting for the release However, a good molded product could not be obtained.

Further, when this molding ceramic composition was retained in a heating cylinder at 170 ° C. for 8 hours and then injection-molded, the fluidity was lowered and only a short-shot molding was obtained.

Comparative Example 5 A molded body shown in FIG. 1 was obtained in the same manner as in Example 1 except that APP 15 parts, dioctyl adipate 1.0 part and stearic acid 1.0 part were used with respect to 100 parts of aluminum oxide, and then debinding was performed. Cracking and blistering occurred in all the samples, and a satisfactory debindered product was not obtained.

[Brief description of drawings]

1 and 2 are perspective views of a molded body obtained by injection molding a ceramic composition for injection molding.

Claims (1)

[Claims] 1. A ceramic powder (I), an acrylic polymer (II) and an ethylene-ethyl acrylate copolymer (II
I), which is an acrylic polymer (II) and an ethylene-ethyl acrylate copolymer (II
A ceramic composition for injection molding, wherein the weight ratio (II) / (III) of I) is 1/4 to 20/1.