JPH0543304A - Production of molded article - Google Patents

Abstract

PURPOSE:To obtain excellent unburnt molded articles free from cracks on the surface, swelling and cracks without polluting environments in a short time and to improve productivity of molded articles. CONSTITUTION:A composition for producing molded articles obtained by blending ceramics powder and/or metallic powder is molded into a desired shape by an injection molding machine or extrusion molding machine and then prepared molded articles are heated, the polyalkylene carbonate contained in the molded article is decomposed and vaporized and the ceramics powder and/or the metallic powder is sintered to produce injection molded articles or extrusion molded articles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high-performance ceramic molded body or a metal molded body, and particularly to a molded body such as a ceramic molded body or a metal molded body by plastic molding such as injection molding or extrusion molding. On how to do.

[0002]

TECHNICAL BACKGROUND AND PROBLEMS OF THE INVENTION The technology relating to the method for producing a ceramics molded body or a metal molded body is as follows.
Various proposals have hitherto been made. In particular, in recent years, an injection molding method has been attracting attention because it is possible to mass-produce a molded article having a complicated shape with high accuracy.

In order to mold a ceramic powder and / or a metal powder into a molded body by an injection molding method or an extrusion molding method, generally, a raw material for manufacturing a molded body such as a ceramic molded body or a metal molded body is injected into an injection molding machine or It was formed into a desired shape by an extrusion molding machine, and then the obtained formed body was heated to decompose and volatilize (degrease) components other than the ceramic powder or the metal powder in the raw material and further sinter.

As a raw material for producing a molded body used at this time, a mixture of ceramic powder and / or metal powder with a binder (hereinafter abbreviated as a binder) and, if necessary, a lubricant has been used. Such a binder imparts strength to a molded product obtained by injection molding or extrusion molding, and is generally classified into a water-soluble binder and a synthetic resin binder.

Water-soluble binders, namely polyvinyl alcohol, polyethylene glycol, methyl cellulose, carboxymethyl cellulose, ethyl cellulose,
Hydroxypropyl cellulose has a lower viscosity than synthetic resin binders and penetrates well between ceramic powder particles or metal powder particles, but since it has poor lubricity, it is actually diluted with water to impart lubricity. ing. However, when a product using a water-soluble binder is injection-molded or extrusion-molded, the strength of the molded body is gradually exhibited by the evaporation of water, but the strength immediately after molding is very weak and easily deformed. .. Of course, it is conceivable to reduce the amount of diluting water to improve the strength, but the fluidity decreases, and as a result, the injection (extrusion) pressure of the injection (extrusion) molding machine rises, or ceramic powder or metal powder is used. There is a problem of wear of the molding machine and accompanying contamination, and it is difficult to do in reality.

On the other hand, when a synthetic resin binder is used, a molded product having a strength superior to that of a water-soluble binder can be obtained, and therefore it is often used in injection molding and the like. However, this synthetic resin binder also has problems in decomposition and volatility at low temperature and appearance (degreasing property) of the molded body after degreasing.

That is, when a synthetic resin binder is used, it must be heated to an extremely high temperature in order to decompose the binder, and the temperature is gradually raised to improve the degreasing property. 1 time spent
There was a problem that it exceeded 00 hours and sometimes reached 300 hours.

Therefore, the inventors of the present invention used an injection-molded article or extrusion using a binder that decomposes and volatilizes rapidly and completely at a relatively low temperature, has no difference in an oxidizing atmosphere and a non-oxidizing atmosphere, and has a good degreasing property. As a result of extensive studies on a method for producing a molded body, the present invention has been completed.

[0009]

SUMMARY OF THE INVENTION That is, a method for producing an injection-molded article or an extrusion-molded article according to the present invention is a method for injection-molding a composition for producing a molded article, which comprises a ceramic powder and / or a metal powder mixed with polyalkylene carbonate. Molded into a desired shape with a machine or an extrusion molding machine, and then heating the obtained molded body to decompose and volatilize the polyalkylene carbonate contained in the molded body, and further sinter the ceramic powder and / or the metal powder. It is characterized by doing.

[0010]

DETAILED DESCRIPTION OF THE INVENTION In the method for producing an injection-molded article or an extrusion-molded article according to the present invention, a composition for producing a molded article comprising a ceramic powder and / or a metal powder mixed with polyalkylene carbonate is used. Be done.

[Polyalkylene carbonate] The polyalkylene carbonate used in the present invention serves as a binder for ceramic powder or metal powder. The surprising properties of polyalkylene carbonate are, first of all, its excellent affinity with ceramic powder or metal powder. As a result, even if a large amount of ceramic powder or metal powder is mixed, the kneading property is good, and since air or the like is not entrained in the obtained composition for forming a molded body, a space is not generated. There is no foaming and the density of the obtained ceramic molded body or metal molded body does not decrease. The second characteristic of the polyalkylene carbonate used in the present invention is its excellent thermal decomposability. More specifically, even under an oxidizing atmosphere (for example, in air) and a non-oxidizing atmosphere (for example, in nitrogen), the thermal decomposition is rapid in a low temperature region. And this characteristic is fully exhibited even if it is a composition with ceramic powder or metal powder. These characteristics are characteristics that are not found in aromatic polycarbonate even if they are the same polycarbonates.

The polyalkylene carbonate used in the present invention is, for example, at least one carbon dioxide (C) of an alkylene oxide such as ethylene oxide, propylene oxide, butene oxide and cyclohexene oxide.
It is obtained by copolymerizing O2) with an organozinc catalyst. The obtained copolymer is a chain polymer, but it may contain alkylene groups and carbonate groups alternately, or the alkylene groups may form a chain by an ether bond.

It will be apparent to those skilled in the art that it may be modified with an unsaturated carboxylic acid or the like if necessary. The molecular weight of the polyalkylene carbonate used in the present invention is usually 10,000 to 100,000 in Mn, and most is about 20,000 to 50,000. In the present invention, basically any polyalkylene carbonate can be used, but a lower one having an alkylene group having about 2 to 6 carbon atoms is particularly preferable, and specifically, polyethylene carbonate and polypropylene carbonate are preferable. Used.

[Ceramic powder or metal powder] In the present invention, various known ceramic powders or metal powders can be used and are not particularly limited, but specific examples are as follows. It is illustrated. (1) Metal powder Specifically, aluminum, silicon, scandium, yttrium, lanthanide, actinide, titanium, zirconium, hafnium, thorium, vanadium, niobium,
Tantalum, chromium, molybdenum, tungsten, iron, manganese, technetium, rhenium, 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, as oxides of the above metals or others, beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, barium oxide, Lanthanum oxide, gallium oxide, indium oxide, selenium oxide, and other oxides containing a plurality of metal elements, that is, Na
NbO ₃ , SrZrO ₃ , PbZrO ₃ , SrTiO
₃ , BaZrO ₃ , PbTiO ₃ , AgTaO ₃ , Ba
Perovskite structure such as TiO ₃ , LaAO ₃ , MgA ₂ O ₄ , ZnA ₂ O ₄ , CoA ₂ O ₄ , Ni
A ₂ O ₄ , NiCr ₂ O ₄ , FeCr ₂ O ₄ , MgFe ₂
O _4, Fe ₂ O _4, those having a spinel structure such as _{ZnFe 2 O 4, MgTiO 3,} MnTiO 3, FeTiO 3,
CoTiO ₃ , NiTiO ₃ , LiNbO ₃ , LiTa
Of ilmenite structure such as O ₃ , Gd ₃ GaO 18,
Garnet structure such as Y3 Fe5 O8, etc. (3) Metal carbides, specifically silicon carbide, titanium carbide, tantalum carbide, chromium carbide, molybdenum, hafnium carbide, zirconium carbide, boron carbide, etc. (4) Metal nitride Material Specifically, silicon nitride, aluminum nitride, boron nitride, titanium nitride, etc. (5) Metal boride Specifically, titanium boride, zirconium boride, lanthanum boride, etc. (6) Above (1) to ( Surface-modified product of 5) Specifically, those surface-treated with a coupling agent, a surfactant, a polymerizable monomer, etc. (7) The mixture of (1) to (6) above.

In the present invention, the effect is exhibited regardless of the particle size of the ceramic powder or metal powder used, but it is particularly effective to use a powder having an average particle size of 100 or less. Furthermore, it is even more preferable to apply the obtained molded product to those having an average particle size of 40 or less in terms of homogeneity.

In the present invention, when a composition for producing a molded body is prepared, the above polyalkylene carbonate and ceramic powder and / or metal powder are used. The ceramic powder and / or metal is used. The powder and the polyalkylene carbonate are ceramic powder and / or
Alternatively, the polyalkylene carbonate is usually used in an amount of 5 to 40 parts by weight, particularly 10 to 3 parts by weight, based on 100 parts by weight of the metal powder.
It is preferably blended in an amount of 0 part by weight.

Further, in the present invention, various additives, such as a plasticizer, a lubricant, a wetting agent, a peptizer, an antistatic agent, which are compounded in a usual composition for producing a molded article, within a range not impairing the purpose thereof, A chelating agent, a foaming agent, a surfactant and the like may be added.

Further, a binder other than the polymer of the present invention may be used in combination, and in some cases, water may be used in combination. Examples of such additives include diethyl phthalate, plasticizers such as dioctyl phthalate, lauric acid,
There are fatty acids such as myristic acid, palmitic acid and stearic acid, or their lubricants such as esters, metal salts and hydrocarbon waxes, and binders that can be used in combination include polyethylene, polypropylene, polybutane,
Poly (meth) acrylate, polystyrene, ethylene / vinyl acetate copolymer or low molecular weight products thereof,
There are various natural waxes.

Particularly, it is preferable to use a plasticizer and / or a lubricant together because the fluidity is improved. These are preferably mixed in an amount of up to 5 parts by weight with respect to 100 parts by weight of ceramic powder and / or metal powder.

When other synthetic resin binders are used in combination, it is preferable to add up to 40 parts by weight, especially up to 30 parts by weight. [Production of Injection-Molded Article or Extruded-Molded Article] In the present invention, in addition to ceramic powder and / or metal powder and polyethylene carbonate, a plasticizer such as dioctyl phthalate and a lubricant such as stearic acid are added if necessary. If necessary, the composition for producing a molded body thus obtained is kneaded under heating. When kneading in this way, a pressure type kneader can be used. Then, the obtained kneaded product may be crushed into small pieces if necessary.

In the present invention, the composition for producing a molded body as described above is molded into a desired shape using an injection molding machine or an extrusion molding machine. Next, the obtained molded body is heated to decompose and volatilize (degrease) the polyalkylene carbonate contained in the molded body. In this way, the unbaked injection-molded article and extrusion-molded article (also referred to as degreased article) obtained by decomposing and volatilizing (defatting) the polyalkylene carbonate contained in the article do not have deformation, cracks, or swelling.

In the present invention, the ceramic powder and / or the metal powder constituting such a degreased compact is then sintered according to a conventional method. In this way, a desired injection-molded article or extruded article that has been fired is obtained.

[0023]

EXAMPLES The contents of the present invention will be described below with reference to suitable examples, but the present invention is not limited to these examples unless otherwise specified.

In the following Examples and Comparative Examples, the process up to the production of the unfired injection-molded body or the extrusion-molded body was described. However, the step of firing the unfired injection-molded body or the extrusion-molded body Regarding the above, it was performed according to a conventional method.

[0025]

Example 1 As a ceramic powder, 25 parts by weight of polyethylene carbonate (Mn: 41000), 2 parts by weight of dioctyl phthalate and 2 parts by weight of stearic acid were mixed and kneaded with 100 parts by weight of alumina powder (average particle size 0.6 μ). The kneading was performed using a pressure kneader at 140 ° C. for 1 hour, and the obtained kneaded product was crushed into small pieces having a diameter of 3 to 5 mm. Injection pressure 1000kg using a commercially available injection molding machine
/ Cm ² , temperature of 150 ° C, mold temperature of 50 ° C, a plate-like test piece having a thickness of 5 mm, a width of 10 mm and a length of 50 mm was obtained.

This molded body is heated at room temperature in an electric furnace in an air atmosphere.
The temperature is raised to 100 ° C at a heating rate of 30 ° C / hour,
The temperature was raised up to 350 ° C. at 5 ° C./hour, and degreasing was performed in about 53 hours.

After degreasing, the molded body did not deform, and neither crack nor swelling was observed.

[0028]

Example 2 25 parts by weight of polypropylene carbonate (Mn: 21500), 2.5 parts by weight of dioctyl phthalate and 2.5 parts by weight of stearic acid were mixed with 100 parts by weight of the alumina powder of Example 1 and kneaded. The kneading was performed using a pressure kneader at 150 ° C. for 1 hour, and the obtained kneaded product was crushed into small pieces having a diameter of 3 to 5 mm.

The molding temperature for molding the plate-shaped test piece is 16
A test piece was obtained in the same manner as in Example 1 except that the temperature was 0 ° C. This molded body (test piece) was heated in an air atmosphere from room temperature to 110 ° C. at a heating rate of 30 ° C./hour, and 1
The temperature was raised from 10 to 350 ° C at 5 ° C / hour, and degreasing was performed in about 51 hours.

The molded body after degreasing did not deform, and neither crack nor swelling was observed.

[0031]

Example 3 12 parts by weight of polyethylene carbonate and 8 parts by weight of ethylene-vinyl acetate copolymer, and 2 parts by weight of dioctyl phthalate and stearic acid were added to 100 parts by weight of the alumina powder of Example 1. A test piece was obtained by injection molding in the same manner as in Example 1 except for the above.

This molded body (test piece) was heated in an air furnace from room temperature to 80 ° C. at a temperature raising rate of 30 ° C./hour, and was heated from 80 to 400 ° C. under the condition of 5 ° C./hour. Let it warm
It was degreased for about 66 hours.

No crack or swelling was observed in the molded product after degreasing.

[0034]

Example 4 As 100 parts by weight of silicon carbide powder (average particle size 0.4 μ) as ceramic powder, 15 parts by weight of polyethylene carbonate and 10 parts by weight of polystyrene, and 2 parts by weight of dioctyl phthalate and stearic acid were each mixed, Kneaded

This kneaded product was injection-molded according to Example 1, and degreasing was performed in a nitrogen atmosphere under the same temperature rising pattern as in Example 3. The molded body after degreasing did not deform, and neither crack nor swelling was observed.

[0036]

Example 5 As a ceramic powder, 2 parts of polyethylene carbonate was added to 100 parts by weight of the alumina powder of Example 1.
5 parts by weight were prepared and kneaded by heating. The obtained kneaded product was molded into a round bar having a diameter of 8 mm at 150 ° C. using an extruder.

This molded body was cut into a length of 100 mm and degreased under the same conditions as in Example 1. The molded body after degreasing did not deform, and neither crack nor swelling was observed.

[0038]

Comparative Example 1 As a ceramic powder, 100 parts by weight of the alumina powder of Example 1 was added to ethylene-vinyl acetate copolymer 16
After adding parts by weight and heating and kneading according to Example 1, a test piece obtained by injection molding is heated in an electric furnace from room temperature to 80 ° C at a heating rate of 30 ° C / hour from room temperature to 80 ° C. Let's 80 ~
The temperature was raised up to 400 ° C. under the condition of 2 ° C./hour, and degreasing was performed in about 162 hours.

Despite the longer degreasing time compared to Example 1, cracks and swelling were observed in the molded article after degreasing.

[0040]

[Comparative Example 2] As a ceramic powder, 100 parts by weight of the alumina powder of Example 1 was added to ethylene-vinyl acetate copolymer 16
By weight, 2 parts by weight of dioctyl phthalate and 2 parts by weight of stearic acid were prepared and kneaded by heating. And Comparative Example 1
The test piece obtained by injection molding was degreased in the same manner as above, but the molded product was distorted, and cracks and swelling were observed.

[0041]

Comparative Example 3 25 parts by weight of aromatic polycarbonate, 2 parts by weight of dioctyl phthalate and 2 parts by weight of stearic acid were mixed and kneaded with 100 parts by weight of alumina powder (average particle size: 0.6 μ) as a ceramic powder. The kneading was performed using a pressure kneader at 150 ° C. for 1 hour, and the obtained kneaded product was crushed into small pieces having a diameter of 3 to 5 mm.

Injection pressure of 100 using a commercially available injection molding machine
A plate-like test piece having a thickness of 5 mm, a width of 10 mm and a length of 50 mm was obtained under the conditions of 0 kg / cm ² , a temperature of 150 ° C. and a mold temperature of 50 ° C.

This molded body (plate-shaped test piece) was heated in an air furnace from room temperature to 100 ° C. at a heating rate of 30 ° C. /
The temperature was raised for 100 hours to 100 to 500 ° C. at 5 ° C./hour, and degreasing was performed for about 83 hours.

Cracks and swelling were observed in the molded body after degreasing.

[0045]

EFFECTS OF THE INVENTION (1) In the composition for producing a molded product used in the present invention, polyalkylene carbonate decomposes extremely rapidly in a low temperature region, and decomposed gas (main component is
Carbon dioxide and water) are also non-toxic. Therefore, according to the method for producing a molded article of the present invention, the environment is not polluted.

(2) In addition, after pyrolyzing the polyalkylene carbonate in the composition for producing a molded body, the unfired molded body such as the unfired ceramic molded body or metal molded body has a surface crack. Baking and cracking do not occur, and when this unfired molded body is fired, a fired body with excellent performance is obtained.

(3) In addition to the above-mentioned effects, the composition used for producing a molded product has a good kneading property, and when it is used for plastic molding such as injection molding or extrusion molding, the time required for the degreasing step is shortened. , Productivity is improved.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C08L 69/00 LPU 8416-4J

Claims (1)

[Claims] 1. A composition for producing a molded body, which comprises a ceramic powder and / or a metal powder mixed with polyalkylene carbonate, is molded into a desired shape by an injection molding machine or an extrusion molding machine, and then the obtained molding is carried out. A method for producing an injection molded body or an extrusion molded body, which comprises heating a body to decompose and volatilize polyalkylene carbonate contained in the molded body and further sinter the ceramic powder and / or the metal powder.