JPH025706B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a raw material composition for producing high-performance ceramics, and particularly to a composition for producing ceramics suitable for plastic molding such as injection molding and extrusion molding. [Prior Art] Various techniques related to the production of ceramics have been proposed in the past. Particularly in recent years, injection molding methods, which can produce molded bodies with complex shapes in large quantities with high precision, have been attracting attention. Specifically speaking, the injection molding method involves first molding raw materials for ceramic production into a desired shape using an injection molding machine, then heating the resulting molded product to remove components other than ceramic powder or metal powder from the raw materials. Decompose and volatilize (degrease),
Ceramics are obtained by further sintering. The raw material for producing ceramics used at this time is a mixture of ceramic powder and/or metal powder with an organic binder component and, if necessary, a lubricant, a plasticizer, and the like. Particularly important here is the binder component, which imparts strength to the molded product obtained by injection molding, and is generally divided into water-soluble binders and synthetic resin binders. Water-soluble binders, such as polyvinyl alcohol, polyethylene glycol, methyl cellulose, carboxymethyl cellulose, ethyl cellulose, and hydroxypropyl cellulose, have lower viscosity than synthetic resin binders and penetrate well between ceramic powder particles, but they have poor lubricity. Therefore, it is actually diluted with water to give it lubricity. However, when a product using a water-soluble binder is injection molded, the strength of the molded product gradually develops due to evaporation of water, and there is a problem that the strength immediately after molding is very weak and easily deformed. Of course, it is possible to reduce the amount of dilution water and improve the strength, but this will reduce fluidity, resulting in an increase in the discharge pressure of the injection molding machine, and the wear and tear of the molding machine due to ceramic powder and contamination caused by it. This is difficult to implement in reality due to the following problems. On the other hand, synthetic resin binders are far superior to water-soluble binders in terms of imparting strength;
Since melting of the binder imparts fluidity to the ceramic powder, a large amount of the binder must be blended, which poses a problem in that degreasing takes a long time. Additionally, degreasing occurs when the decomposed gas generated by thermal decomposition of the binder moves from the inside of the molded object to the surface and evaporates from the surface to the outside of the molded object, but if the binder is not suitable, the decomposed gas moves. In this case, volatilization does not occur smoothly, resulting in voids such as cracks and voids inside the molded product. Therefore, when using a synthetic resin binder, it is extremely important to select a binder with good degreasing properties. [Problems to be Solved by the Invention] In view of the current situation, the present inventors have conducted repeated research on synthetic resins that can be blended with ceramic powder and/or metal powder and used as a binder component, and as a result, have arrived at the present invention. The purpose is to provide a composition for producing ceramics in which the binder component decomposes at a relatively low temperature and can be degreased without producing cracks or voids. Another object of the present invention is to provide a composition for producing ceramics that can be degreased in an extremely short time. Another object of the present invention is to provide a composition for producing ceramics that has good fluidity and is suitable for plastic molding such as injection molding and extrusion molding. Another object of the present invention is to provide a composition for producing ceramics that does not cause surface peeling even when a molded body is obtained by injection molding and then degreased and sintered. [Means for Solving the Problems] That is, the present invention consists of ceramic powder and/or metal powder and an organic binder component, and 5 to 65% by weight of the organic binder component is ethylene, vinyl acetate, and carbon monoxide. The present invention relates to a composition for producing ceramics, which is a copolymer. [Function] The terpolymer in the composition of the present invention acts as a binder, and when mixed with ceramic powder or the like, the fluidity of the resulting composition is greatly improved. As a result, a good molded product can be obtained even at low pressure during molding, and even products with complex shapes can be molded with good appearance and little internal residual strain. Furthermore, it decomposes and evaporates at relatively low temperatures without producing cracks or voids. Furthermore, as will be described later, since the components thereof are hydrocarbons and oxygen-containing hydrocarbons, the gases generated by thermal decomposition and volatilization are non-toxic and are highly safe during degreasing. The terpolymer is composed of ethylene, vinyl acetate, and carbon monoxide. Its composition ratio is ethylene: 40-80% by weight, vinyl acetate: 5-80% by weight.
60% by weight, carbon monoxide: 3 to 30% by weight, particularly preferably 56 to 76% by weight, 10 to 34% by weight, respectively.
The composition ratio is 3 to 15% by weight. If the proportion of ethylene exceeds the above range and, as a result, the proportion of other monomer components decreases, melt fluidity decreases and processability when used as a binder deteriorates. In addition, if the proportion of ethylene is less than the above range and the proportion of other components increases, the main effect as a binder, that is, imparting strength and rigidity to the molded article, will decrease, making it easier to deform, and furthermore, it will become difficult to bond with the mold. The mold releasability also deteriorates. Melt flow rate (MFR) of terpolymer
is approximately 0.1 to 3000g/10min, especially 10 to 2500g, measured according to the ASTM D 1238E method and conditions.
g/10min, more preferably 20-2000g/10min
is within the range of Furthermore, it will be obvious to those skilled in the art that the terpolymer may be modified with an unsaturated carboxylic acid or the like, if necessary. The terpolymer contains 5 to 5 in the organic binder component.
It is used in an amount of 65% by weight, preferably 10-50% by weight. If the amount is less than 5% by weight, the fluidity when mixed with ceramic powder or metal powder, that is, the melt fluidity, will deteriorate, and the degreasing property will also deteriorate. On the other hand, if the amount exceeds 65% by weight, although a good molded article can be produced without any problem in fluidity, there is a problem in that a layer that easily peels off is formed on the surface layer during degreasing and sintering. This is because a tar layer is formed on or near the surface layer during degreasing, and the gas generated when the internal organic binder components decompose and volatilize cannot escape to the outside, and is degreased or sintered while remaining near the tar layer. It is assumed that. The remainder of the organic binder component excluding the terpolymer is comprised of various known water-soluble binders, synthetic resin binders, waxes, and the like. Among these, synthetic resin binders and waxes are suitable for plastic molding. Of course, a water-soluble binder may be used depending on the purpose, and any two or three of the above three types may be used in combination. Examples of such binders include water-soluble binders such as polyvinyl alcohol, polyethylene glycol, methyl cellulose, carboxymethyl cellulose, ethyl cellulose, and hydroxypropyl cellulose, and synthetic resin binders such as ethylene-vinyl acetate copolymer, high-pressure low-density polyethylene, and linear Low density polyethylene, high density polyethylene, isotactic polypropylene, atactic polypropylene, polybutene
1, poly 4-methylpentene-1, ethylene/propylene copolymer, ethylene/butene copolymer,
Propylene/butene copolymer, polymethacrylate ester, ethylene/(meth)acrylate ester copolymer, polystyrene, styrene/butadiene copolymer, various natural rubbers, synthetic rubbers, or their modified products, i.e. Waxes such as graft-modified products of saturated carboxylic acids or derivatives thereof, halogen-modified products, etc. Candelilla wax,
Carnauba wax, wood wax, vegetable waxes such as jojoba oil, animal waxes such as beeswax, lanolin, spermaceti, montan wax, ozokerite,
Synthetic carbonization of mineral waxes such as ceresin, paraffin waxes, microcrystalline waxes, petroleum waxes such as petrolactam, fissure tropism waxes, polyethylene waxes, polypropylene waxes, poly4-methyl-1-pentene waxes, etc. Examples include hydrogen waxes, modified waxes such as montan wax derivatives, paraffin wax derivatives, and microcrystalline wax derivatives, and hydrogenated waxes such as hydrogenated castor oil and hydrogenated castor oil derivatives. These organic binder components, when used in combination with the terpolymer described above, prevent surface peeling during sintering without impairing fluidity and degreasing properties. Furthermore, by combining appropriate types, it is possible to shift the decomposition curve to the lower temperature side and promote degreasing properties. As for the organic binder component as a whole, the mixing ratio of the organic binder component to the ceramic powder and/or metal powder is 20% by volume or more, especially 35% to 35% by volume.
60% by volume, especially if the latter powder component is less than 80% by volume
40-65% by volume is preferred. In addition, here the volume is
It is calculated by dividing the weight by the density. The most preferred embodiment of the present invention is to use a system in which a wax is present in addition to the terpolymer as an organic binder component. In other words, the combined use of waxes further improves fluidity and improves degreasing properties, so compared to systems that do not use waxes, a molded product with no molding distortion can be produced at lower temperatures and pressures during injection molding. can be produced, and the time required for degreasing can also be shortened. As the waxes, the various waxes listed above can be used, but the above-mentioned effects are particularly achieved when paraffin wax and its modified products are used. The proportion of waxes in the organic binder component (including terpolymer) is at least 10% by weight and at most
It is used in an amount of 95% by weight, preferably in the range of 35 to 65% by weight. Various known ceramic powders or metal powders can be used in the present invention, and are not particularly limited, but specific examples include the following. (1) Metal powders: specifically aluminum, silicon, scandium, yttrium, lanthanide, actinide, titanium, zirconium, hafnium, thorium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, iron, manganese, technetium, rhenium, and cobalt. , nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum, copper, silver, gold, zinc, cadmium, thallium, germanium, tin, lead, arsenic, antimony, bismuth, tellurium, polonium, or alloys thereof, etc. 2) Metal oxides Specifically, oxides of the above metals or other substances such as beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, barium oxide, lanthanum oxide, potassium oxide, indium oxide, selenium oxide, etc. Furthermore, oxides containing multiple metal elements, i.e.
_NaNbO3 , _SrZrO3 , _PbZrO3 , _SrTiO3 ,
_BaZrO3 , _PbTiO3 , _AgTaO3 , _BaTiO3 ,
Perovskite structures such as _LaAlO3 ,
_{MgAl2O4 , ZnAl2O4 , CoAl2O4 , NiAl2O4 ,
NiCr2O4 , FeCr2O4 , MgFe2O4 , Fe2O4 ,}
Those with spinel structure such as ZnFe ₂ O ₄ ,
_MgTiO3 , _MnTiO3 , _FeTiO3 , _CoTiO3 ,
Those with ilmenite structure such as NiTiO ₃ , ZnTiO ₃ , LiNbO ₃ , LiTaO ₃ , Ga ₃ GaO ₁₈ ,
( ₃ ) Metal carbides, specifically silicon carbide, _titanium carbide, tungsten carbide, tantalum carbide, chromium carbide, molybdenum carbide, hafnium carbide _, zirconium carbide, boron carbide, etc. , (4) Metal nitrides, specifically silicon nitride, aluminum nitride,
Boron nitride, titanium nitride, etc. (5) Metal borides, specifically titanium boride, zirconium boride, lanthanum boride, etc., (6) Surface-modified products of (1) to (5) above, specifically coupling (7) A mixture of the above (1) to (6).In the present invention, the effect is achieved regardless of the particle size of the ceramic powder or metal powder. , is particularly effective for powders with an average particle size of 100μ or less. Furthermore, from the viewpoint of homogeneity of the molded product, it is even more preferable to apply the molded product to one having an average particle size of 10 μm or less. In addition, in the present invention, various additives that are usually added to ceramic compositions, such as plasticizers, lubricants, wetting agents, peptizers,
Antistatic agents, chelating agents, foaming agents, interfacial lubricants, etc. may be added. Examples of such additives include plasticizers such as diethyl phthalate and dioctyl phthalate, fatty acids such as lauric acid, myristic acid, palmitic acid, and stearic acid, or lubricants such as esters and metal salts thereof. [Example] Preferred examples of the present invention are shown below, but the present invention is not limited to these examples unless otherwise specified, and the present invention may be modified without impairing the purpose of the present invention. Any aspect may be adopted. The details of each component used in the following examples are as follows. Tertiary copolymer a: 71% by weight of ethylene, vinyl acetate
Ethylene/vinyl acetate/carbon monoxide ternary copolymer with 26% by weight and 3% by weight of carbon monoxide. MFR=
20g/10min Tertiary copolymer b: 66% by weight of ethylene, vinyl acetate
Ethylene/vinyl acetate/carbon monoxide ternary copolymer with 24% by weight and 10% by weight of carbon monoxide. MFR=
20g/10min EVA: Ethylene/vinyl acetate copolymer, vinyl acetate content 28% by weight, MFR=150g/10min EBR: Ethylene/butene random copolymer, butene-1 content 8mol%, MFR=20g/10min PMB: Polybutyl methacrylate, Mn=40000 by GPC method PS: Polystyrene, MFR=4g/10min EEA: Ethylene/acrylic acid ester copolymer,
Ethyl acrylate content 25% by weight, MFR=275
g/10min PB: Polybutene-1, n=2000 by GPC method APP: Atactic polypropylene, n=30000 by GPC method PE: Polyethylene density 0.92 g/cm ³ , MFR=70
g/10min PBR: Propylene/butene random copolymer,
Propylene content 72 mol%, MFR=7g/
10min DOP: Dioctyl phthalate paraffin wax: mp=52-54℃ Microcrystalline wax: mp=84℃ PE wax: Viscosity average molecular weight 1000 EVA wax: Vinyl acetate content 13% by weight, GPC
n = 3500 by method EAA wax: ethylene/acrylic acid copolymer,
Acid value 40mgKOH/g, n= by GPC method
3500 Example 1 Zirconium oxide (powder A) with an average particle size of 0.3 μm to which 3 mol % of yttrium oxide was added and an organic binder were mixed in the composition ratio shown in Table 1. This mixing is done using a pressure kneader at a temperature of 140℃.
It lasted 60 minutes. After mixing, the composition was granulated to a size of 3 to 5 mm square to serve as a sample for injection molding. Subsequently, the composition was heated at a temperature of 160℃ and an injection pressure of 1200Kg/
Injection molding was carried out under the conditions of cm ² to obtain a plurality of molded bodies measuring 2 x 50 x 50 mm. The appearance and interior of any molded product were observed by fracture, and after confirming that there were no cracks on the surface or inside, the remaining molded products were degreased. For degreasing, the number of samples was 10, and the temperature was 10°C/h from 0 to 150°C, and 5 times from 150 to 500°C in an air atmosphere.
This was carried out by increasing the temperature at a rate of °C/h (required time for degreasing: 85 hours). After degreasing, complete degreasing was confirmed by measuring the weight. Next, the degreased body was observed to check for defects such as blisters and cracks on the surface. Table 1 shows the percentage of defects free, that is, the yield, and good results were obtained. Next, the obtained defatted body was heated at a heating rate of 300℃/h.
After raising the temperature to 1500°C and sintering for 120 minutes, it was left to cool in the furnace to obtain a sintered body. In addition to observing the surface of this sintered body, the sintered body was further cut at several places and the internal state was observed. As a result, it was found that a good sintered body was obtained without any defects such as surface peeling or internal cracks. Comparative Examples 1 to 2 The organic binder in Example 1 was changed to the composition ratio shown in Table 1, and the same procedure as in Example 1 was conducted. Table 1
shows the yield. Next, when the obtained degreased body was evaluated for sintering in the same manner as in Example 1, internal cracks occurred in the sample of Comparative Example 1, and a good sintered body could not be obtained. On the other hand, although peeling was observed in the surface layer of the sintered body of Comparative Example 2, no internal defects such as internal cracks were observed at all.

[Table] * However, surface peeling occurred after sintering.
As can be seen from these results, when a terpolymer is used in combination, moldability and degreasing properties are good despite the large amount of organic binder components and other organic substances. Further, in cases where the terpolymer was used alone, the surface layer sometimes peeled off after sintering. Examples 2 to 6, Comparative Examples 3 to 6 Aluminum oxide with an average particle size of 0.6 μm (powder B)
and an organic binder were mixed in the composition ratio shown in Table 2. This mixing was carried out using a pressure kneader at 120
℃ temperature for 30 minutes. After mixing, the composition was granulated to a size of 3 to 5 mm square to serve as a sample for injection molding. Subsequently, the composition was heated at a temperature of 120℃ and an injection pressure of 1000Kg/
Injection molding was carried out under conditions of cm ² to obtain a molded article of 8 x 10 x 40 mm. This molded body was degreased and evaluated in the same manner as in Example 1, and the yield was determined. Table 2 shows the yield at this time.
As shown in Figure 2, the composition containing the terpolymer showed good results, whereas the composition not containing the terpolymer had poor yield.

[Table] Examples 7 to 9, Comparative Examples 7 to 8 89% by weight of silicon nitride with an average particle size of 0.3 μm, 7% by weight of yttrium oxide, 4% by weight of aluminum oxide
An organic binder was mixed into the powder (powder C) in the proportions shown in Table 3. Mixing was performed at 120° C. for 60 minutes using a pressure kneader. After mixing,
Since the composition is used as a sample for injection molding, 3 to 5
It was granulated to the size of mm square. Subsequently, the composition was heated at a temperature of 120℃ and an injection pressure of 800Kg/cm ²
The mixture was injection molded to obtain a molded product measuring 4 x 5 x 40 mm. This molded body is heated in a nitrogen atmosphere from 0 to 150℃/h.
Degreasing was carried out at a temperature increase rate of 20°C/h and 10°C/h from 150 to 600°C/h. This defatted product was evaluated in the same manner as in Example 1 to determine the yield. The yields at this time are shown in Table 3, and while the composition containing the terpolymer showed good results, the yield of the composition not containing the terpolymer was poor.

[Table] Examples 10 to 12, Comparative Examples 9 to 10 Silicon nitride (powder D) with an average particle size of 0.6 μm containing 1% by weight of boron carbide was treated in the same manner as in Example 1 at the composition ratio shown in Table 4. The mixture was mixed and granulated to obtain a composition. This composition was heated at a temperature of 140℃ and an injection pressure of 1000℃.
Injection molding was carried out under the conditions of Kg/cm ² to obtain a molded product of 12×16×14 mm. This molded body was heated at 0 to 150℃ in a nitrogen atmosphere.
The temperature was raised at a rate of 5°C/h from 150 to 600°C, and 3°C/h from 150 to 600°C for degreasing. The yield of the obtained defatted product was determined in the same manner as in Example 1. The yields are shown in Table 4, and while the composition containing the terpolymer showed good results, the yield of the composition not containing the terpolymer was poor.

[Table] Examples 13 to 14, Comparative Example 11 Table 5 was added to metallic silicon (powder E) with an average particle size of 1 μm.
Mixing and mixing in the same manner as in Example 1 at the composition ratio shown in
It was granulated to obtain a composition. Next, the composition was 40mmφ
5mmφ with an extruder at 140℃ and a speed of 0.5m/min
It was formed into a round bar. This round bar was cut into a length of 20 cm and degreased in a nitrogen atmosphere from 0 to 600°C at a heating rate of 10°C/h. We observed the appearance and interior of the degreased body, and found that the composition containing the terpolymer yielded a good degreased body, whereas the composition not containing the terpolymer yielded a round bar. A crack occurred in the center along the longitudinal direction.

【table】

[Table] Example 15 5×10 alumina powder with an average particle size of 0.6 μm was prepared in the same manner as in Example 1 using the composition ratio shown in the table below.
A molded body of ×40 mm was obtained. This molded body was degreased at a heating rate of 5° C./h, and the weight loss curve at this time was measured. The results are shown in Figure 1. Incidentally, the weight reduction rate in the figure was determined with the total weight of the organic binder component or other organic matter as 100.

【table】

[Table] As you can see from Figure 1, terpolymer and
In the case of the present invention C using EVA, the thermal decomposition curve is shifted to the lower temperature side than when each is used alone. Therefore, the time required for degreasing can be shortened, and the amount of heat required for degreasing can also be reduced. Example 16 The same procedure as Example 15 was carried out except that the composition shown in the table below was used. The results are shown in Figure 2.

【table】

〔Effect of the invention〕

As described above, the composition for producing ceramics of the present invention has excellent melt flowability, and can produce molded articles with no molding distortion and good appearance at low temperatures and low pressures. Can be degreased at low temperatures, reducing degreasing time. Decomposition and volatilization during degreasing are appropriate, and no voids or cracks are generated. No layer peeling occurs during degreasing and sintering. It exerts various effects such as.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are diagrams showing thermal decomposition curves.

Claims (1)

[Claims] 1. Consists of ceramic powder and/or metal powder and an organic binder component, and 5 to 65% by weight of the organic binder component is an ethylene/vinyl acetate/carbon monoxide ternary copolymer. A characterized composition for producing ceramics. 2. The ratio of the ceramic powder and/or metal powder to the organic binder component is 40 to 80% by volume,
The composition for producing ceramics according to claim 1, wherein the latter is 20 to 60% by volume. 3 The composition ratio of the ternary copolymer is ethylene: 40 to 80
3. The composition for producing ceramics according to claim 1 or 2, wherein the composition contains vinyl acetate: 5 to 60% by weight, and carbon monoxide: 3 to 30% by weight. 4. The method according to any one of claims 1 to 3, wherein the remainder of the organic binder component excluding the ethylene/vinyl acetate/carbon monoxide ternary copolymer contains at least waxes. Composition for producing ceramics. 5. The composition for producing ceramics according to claim 4, wherein the wax is paraffin wax. 6 Waxes are organic binder components of 10 to 95
The composition for producing ceramics according to claim 4 or 5, which is % by weight. 7. The composition for producing ceramics according to any one of claims 1 to 6, which further contains a lubricant and/or a plasticizer.