JP2006282475A - Composition for forming molding, degreased body, and sintered compact - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composition for forming a molding used for safely obtaining a degreased body at a low cost, to provide a degreased body produced using the composition for forming a molding and having excellent characteristics, and to provide a sintered compact. <P>SOLUTION: The composition 10 for forming a molding comprises: powder 1 mainly composed of an inorganic material; and a binder 2 containing a resin 3 decomposable by ozone. As the resin 3 decomposable by ozone, the one decomposed at about 50 to 190°C is preferable, and, specifically, the one essentially composed of an aliphatic carbonic acid ester based resin is preferable. As the binder 2, the one further comprising a second resin 4 decomposed after the decomposition of the resin 3 is preferable, and the decomposing temperature thereof is preferably about 190 to 600°C. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a molded body forming composition, a degreased body, and a sintered body.

In general, the inorganic material defatted body is obtained by forming a raw material powder (mixed powder) obtained by mixing an inorganic material powder and a binder into a molded body using various molding methods such as an injection molding method. It can obtain by heat-processing at the temperature higher than the melting temperature of this, and lower than the sintering temperature of inorganic material.
By the way, for example, the raw material powder used in the injection molding method contains a large amount of binder for the purpose of improving the fluidity during the injection molding. In order to remove the binding material, heating for a long time is required, which causes problems such as a reduction in production efficiency and deformation of the degreased body during the heat treatment.

In addition, the binder in the degreased body cannot be sufficiently removed by the heat treatment, and the binder remaining in the sintering process is vaporized to cause cracks in the sintered body.
In order to solve such problems, a composition for producing a metal degreased body (molded body) comprising a metal material powder and a binder containing a polyoxymethylene resin removed by treatment in an acid-containing atmosphere. The thing is disclosed (for example, refer patent document 1).
However, since acid is a deleterious substance in general, it is harmful to the human body, and handling thereof requires a lot of trouble such as requiring strict protective equipment.
In addition, since the acid is highly soluble in metals, it degrades the equipment, and if it is released into the atmosphere, it causes air pollution. Therefore, a large amount of cost is required to prevent them.

Japanese Patent No. 3190371

  An object of the present invention is to provide a molded body forming composition used to obtain a degreased body at low cost and safely, and a degreased body and a sintered body produced using such a molded body forming composition and having excellent characteristics. To provide a body.

Such an object is achieved by the present invention described below.
The composition for forming a molded body of the present invention is a composition for forming a molded body comprising a powder mainly composed of an inorganic material and a binder containing a resin decomposable by ozone,
It is used to obtain a degreased body by decomposing and removing at least a part of the resin by subjecting a molded body formed by molding the molded body forming composition to a degreasing treatment in an ozone-containing atmosphere. And
Thereby, a degreased body can be obtained inexpensively and safely.

In the molded body forming composition of the present invention, the content of the binder in the molded body forming composition is preferably 2 to 40 wt%.
Thereby, while being able to form a molded object with good moldability (easiness to shape | mold), the density of a molded object can be made higher and the stability of the shape of a molded object etc. can be made especially excellent. . Moreover, since the difference of the magnitude | size of a molded object and a degreased body, and what is called a shrinkage | contraction rate can be made small by this, the dimensional accuracy of a degreased body and a sintered compact can be improved.

In the molded body forming composition of the present invention, the resin is preferably one that decomposes at a temperature of 50 to 190 ° C. in an ozone-containing atmosphere.
Thereby, decomposition | disassembly and removal of resin can be performed efficiently and reliably. Moreover, it can prevent that the shape retention of a molded object falls.
In the molded article forming composition of the present invention, it is preferable that the resin contains an aliphatic carbonate-based resin as a main component.
Thereby, the aliphatic carbonate-based resin is easily decomposed when it comes into contact with ozone, and can be quickly degreased.

In the composition for forming a molded body of the present invention, the aliphatic carbonate-based resin preferably has 2 to 11 carbon atoms in the repeating unit excluding the carbonate group.
Thereby, the aliphatic carbonate ester resin can be decomposed more easily and quickly.

In the composition for forming a molded body of the present invention, it is preferable that the aliphatic carbonate-based resin does not have an unsaturated bond.
Thereby, when the aliphatic carbonate ester resin comes into contact with ozone, it becomes easier to be decomposed, and the binder can be decomposed and removed more efficiently.
In the composition for forming a molded body of the present invention, the aliphatic carbonate ester resin preferably has a weight average molecular weight of 1 to 300,000.
As a result, the melting point (softening point) and viscosity of the aliphatic carbonate ester resin are optimized, and the stability (shape retention) of the molded body can be improved.

In the composition for forming a molded body of the present invention, the content of the resin in the binder is preferably 20 wt% or more.
Thereby, the effect that resin is decomposed | disassembled and removed is acquired more reliably, and degreasing | defatting of the whole binder can be promoted more.
In the composition for forming a molded body of the present invention, the binder preferably contains a second resin that decomposes with a delay after the resin.
Thereby, resin and 2nd resin in a molded object are decomposed | disassembled in each temperature range from which a degreasing process differs. That is, by separating the degreasing step into a first degreasing step and a second degreasing step performed thereafter, the resin in the molded body and the second resin are selectively decomposed and removed (degreasing). Can do. As a result, the degree of degreasing of the molded body can be controlled, and a degreased body excellent in shape retention, that is, dimensional accuracy can be obtained easily and reliably.

In the molded article forming composition of the present invention, the second resin is preferably one that decomposes at a temperature of 190 to 600 ° C.
Thereby, decomposition | disassembly and removal of a binding material can be performed efficiently and reliably.
In the composition for forming a molded body of the present invention, the second resin is preferably one containing as a main component at least one of a polyolefin resin, a polystyrene resin, a polyvinyl resin, and an acrylic resin. .
These materials have high bonding strength in the degreased body and can reliably prevent the degreased body from being deformed. Further, these materials have high fluidity and are easily decomposed by heating, so that they can be easily degreased. As a result, a degreased body excellent in dimensional accuracy can be obtained more reliably.

In the composition for forming a molded body of the present invention, the binder preferably contains an additive.
Thereby, the various functions which an additive has in a binder can be exhibited.
In the molded article forming composition of the present invention, the additive is preferably a dispersant for improving the dispersibility of the powder.
Thereby, powder, resin, and 2nd resin disperse | distribute more uniformly, and the degreasing | defatting body and sintered compact which are obtained have little variation in the characteristic, and become more uniform.

In the molded article forming composition of the present invention, it is preferable that the dispersant is composed mainly of a higher fatty acid.
Higher fatty acids are particularly excellent in powder dispersibility and lubricity.
In the molded article forming composition of the present invention, the higher fatty acid preferably has 16 to 30 carbon atoms.
Thereby, the composition for forming a molded body is excellent in shape retention while preventing a decrease in moldability. Further, higher fatty acids can be easily decomposed even at relatively low temperatures.

The degreased body of the present invention is obtained by molding the composition for forming a molded body of the present invention to obtain a molded body, and then subjecting the molded body to a degreasing treatment.
Thereby, the degreased body which has the outstanding characteristic is obtained.
In the degreased body of the present invention, the molding is preferably performed by an injection molding method or an extrusion molding method.
The injection molding method can easily form a molded body capable of forming a degreased body having a complicated and fine shape by selecting a molding die.
In addition, the extrusion molding method can form a molded body that can form a columnar or plate-like degreased body having a desired extruded surface shape by selecting a molding die, particularly easily and inexpensively.
The sintered body of the present invention is obtained by sintering the degreased body of the present invention.
Thereby, the sintered compact which has the outstanding characteristic is obtained.

Hereinafter, preferred embodiments of the composition for forming a molded body, degreased body and sintered body of the present invention will be described in detail.
FIG. 1 is a diagram schematically showing a molded body forming composition used in the present embodiment, and FIG. 2 is a diagram showing a method for producing a degreased body and a sintered body using the molded body forming composition shown in FIG. It is process drawing which shows embodiment.

<Composite forming composition>
First, the composition (composition for forming a molded body of the present invention) 10 used for forming a degreased body or forming a molded body that is a pre-stage of the degreased body will be described.
The composition 10 includes a powder 1 mainly composed of an inorganic material and a binder 2. Further, in the present embodiment, the binding material 2 includes the second resin 4 and the dispersant (additive) 5.

(1) Powder Powder 1 is mainly composed of an inorganic material.
Although it does not specifically limit as this inorganic material, For example, Fe, Ni, Co, Cr, Mn, Zn, Pt, Au, Ag, Cu, Pd, Al, W, Ti, V, Mo, Nb, Zr, Pr , Nd, Sm metal materials, alumina, magnesia, beryllia, zirconia, yttria, forsterite, steatite, wollastonite, mullite, cordierite, ferrite, sialon, cerium oxide oxide ceramic materials, nitriding Non-oxide ceramic materials such as silicon, aluminum nitride, boron nitride, titanium nitride, silicon carbide, boron carbide, titanium carbide, tungsten carbide, carbon materials such as graphite, nanocarbon (carbon nanotubes, fullerene, etc.) One or a combination of two or more of these Rukoto can.

As will be described later, since the composition 10 is excellent in moldability, the present invention is suitably applied when using a material in which the finally obtained sintered body has a relatively high hardness or difficult workability. Is done.
Specific examples thereof include Fe-based alloys such as SUS304, SUS316, SUS316L, SUS317, SUS329J1, SUS410, SUS430, SUS440, and SUS630, die steel, high-speed tool steel, and the like, Ti or Ti-based alloys. , W or W alloy, Co cemented carbide, Ni cermet and the like.
Also, by using a combination of two or more materials having different compositions, it is possible to obtain a sintered body having a composition that could not be produced by casting. In addition, a sintered body having a new function or multiple functions can be easily manufactured, and functions and applications of the sintered body can be expanded.

  The average particle diameter of the powder 1 is not particularly limited, but is preferably about 0.3 to 100 μm, and more preferably about 0.5 to 50 μm. When the average particle diameter of the powder 1 is a value within the above range, a degreased body (molded body) can be produced with excellent moldability (ease of molding). Moreover, the density of the degreased body can be made higher, and the characteristics such as mechanical strength and dimensional accuracy of the degreased body can be made more excellent.

In the present invention, the “average particle diameter” refers to the particle diameter of the powder distributed in a 50% cumulative volume in the particle size distribution of the target powder.
Such a powder 1 may be produced by any method. For example, when the powder 1 is made of a metal material, a liquid atomizing method such as a water atomizing method (for example, a high-speed rotating water atomizing method, Rotating liquid atomizing method, etc.), various atomizing methods such as gas atomizing method, and those obtained by chemical methods such as pulverization method, carbonyl method, reduction and the like can be used.

(2) Binder The binder 2 is a component that greatly contributes to the moldability (ease of molding) of the composition 10 and the stability of the shape of the defatted body (shape retention) in the step of obtaining a molded body to be described later. It is.
In the present invention, the binding material 2 contains a resin 3 that can be decomposed by ozone, and in the present embodiment, it contains a second resin 4 that decomposes later than the resin 3.

  Resin 3 has a property of decomposing by contact with ozone. The molded body including the resin 3 having such properties is contacted with ozone in an ozone-containing atmosphere in the first degreasing step to be described later, so that the molded body including the resin 3 is formed from the surface side of the molded body even at a relatively low temperature. Decomposition of the resin 3 proceeds toward. Therefore, as in the past, in the degreasing process, the binder in the molded body is softened due to high temperature and the molded body is deformed, or the binder that is vaporized inside the molded body is suddenly released to the outside, It is possible to reliably prevent deformation and cracks from occurring in the molded body. As a result, the resin 3 can be easily and quickly removed, that is, degreased. Thereby, while maintaining the shape-retaining property of the degreased body, the time required for the total degreasing process can be shortened and the production efficiency of the degreased body can be improved.

The content of the resin 3 in the binder 2 is preferably 20 wt% or more, more preferably 30 wt% or more, and further preferably 40 wt% or more. When the content of the resin 3 in the binder 2 is within the above range, the effect of decomposing and removing the resin 3 can be obtained more reliably, and degreasing of the entire binder 2 can be further promoted.
Such a resin 3 is not particularly limited as long as it can be decomposed by ozone, and examples thereof include aliphatic carbonate resin, polyether resin, polylactic acid resin, and the like. These can be used alone or in combination of two or more. These resins are suitably used as the resin 3 constituting the binder 2 because they have a relatively high wettability with the inorganic material powder and are sufficiently dispersed with the inorganic material powder even when kneaded for a short time.

Among these, as the resin 3, a resin mainly composed of an aliphatic carbonate resin is preferably used. This is because the aliphatic carbonate-based resin is easily decomposed when it comes into contact with ozone, and the decomposition product is vaporized and released as a gas to the outside of the degreased body (molded body), thereby enabling quick degreasing. Examples of the decomposition product include alkene oxide (for example, ethylene oxide, propene oxide, etc.), decomposition products thereof, water, carbon dioxide, and the like.
In addition, since the aliphatic carbonate ester resin has particularly high wettability with the inorganic material powder, a sufficiently uniform kneaded product can be obtained even in a short time.

Hereinafter, the aliphatic carbonate resin will be described in detail.
The aliphatic carbonate-based resin can be synthesized, for example, by reacting phosgene or a derivative thereof with an aliphatic diol in the presence of a base.
As the aliphatic carbonate-based resin used as the resin 3, the number of carbons in the repeating unit excluding the carbonate group, that is, the number of carbons existing between the carbonate groups in the resin is 2 to 2. 11 is preferred, 2-9 is more preferred, and 2-6 is even more preferred. The number of carbons means, for example, the number of m in the case of an aliphatic carbonate ester resin represented by a general formula of — ((CH ₂ ) _m —O—CO—O) _n —. When the number of carbons is within the above range, the aliphatic carbonate resin can be easily and rapidly decomposed.

  Specifically, the aliphatic carbonate ester resin as described above mainly includes, for example, alkanediol polycarbonate such as ethanediol polycarbonate, propanediol polycarbonate, butanediol polycarbonate, hexanediol polycarbonate, decanediol polycarbonate, or derivatives thereof. What is used as a component is preferable. Alkanediol polycarbonate has a particularly high decomposability and can be degreased more reliably in the first degreasing step. Therefore, the time required for the total degreasing process can be further shortened.

Moreover, as an aliphatic carbonate-type resin, what does not have an unsaturated bond is preferable. Thereby, when the aliphatic carbonate ester-based resin comes into contact with ozone, it becomes easier to be decomposed, and the binder 2 can be decomposed and removed more efficiently.
The aliphatic carbonate ester resin preferably has a weight average molecular weight of about 1 to 300,000, more preferably about 2 to 200,000. As a result, the melting point (softening point) and viscosity of the aliphatic carbonate ester resin are optimized, and the stability (shape retention) of the molded body can be improved.

  The second resin 4 decomposes later than the resin 3, that is, does not substantially decompose under the degreasing conditions for decomposing / removing the resin 3, but is decomposed / removed under a degreasing condition different from the degreasing conditions. It is. And in this embodiment, the 2nd resin 4 is decomposed | disassembled and removed by the 2nd degreasing process mentioned later. As a specific example of the second resin 4 that decomposes late with respect to the resin 3, for example, one in which the thermal decomposition temperature of the second resin 4 is higher than the melting point of the resin 3 can be cited. When the binder 2 contains the second resin 4 as described above, the resin 3 and the second resin 4 in the molded body are decomposed in different temperature regions in the degreasing process. That is, by separating the degreasing step into a first degreasing step and a second degreasing step performed thereafter, the resin 3 and the second resin 4 in the molded body are selectively decomposed and removed (degreasing). can do. As a result, the degree of degreasing of the molded body can be controlled, and a degreased body excellent in shape retention, that is, dimensional accuracy can be obtained easily and reliably.

Further, as will be described in detail later, the degreased body obtained by decomposing / removing only the resin 3 in the first degreasing step (hereinafter referred to as an intermediate degreased body) has the particles 2 of the powder 1 in the intermediate degreased body 2nd. Therefore, the hardness is not as high as that of the sintered body while having toughness as a whole. Therefore, various machining can be easily performed on the intermediate degreased body.
Although it does not specifically limit as the 2nd resin 4, It is preferable that the weight average molecular weight is about 0.1-400,000, and it is more preferable that it is about 0.4-300,000. Thereby, the effect becomes more remarkable.

  Such a second resin 4 is not particularly limited as long as it has a thermal decomposition temperature higher than the melting point of the resin 3 contained in the binder 2. For example, polyethylene, polypropylene, ethylene-vinyl acetate copolymer Polyolefin resins such as coalescence, polystyrene resins, polyvinyl alcohol, polyvinyl acetal, polyvinyl resins such as polyvinyl acetate, acrylic resins such as polymethyl methacrylate and polybutyl methacrylate, polyamide resins such as nylon, polyethylene terephthalate , Polyester resins such as polybutylene terephthalate, copolymers thereof, and the like, and one or more of these can be used in combination.

  Among these, as the 2nd resin 4, what has as a main component at least 1 sort (s) of polyolefin resin, polystyrene resin, polyvinyl resin, and acrylic resin is preferable. These materials have high bonding strength in the degreased body and can reliably prevent the degreased body from being deformed. Further, these materials have high fluidity and are easily decomposed by heating, so that they can be easily degreased. As a result, a degreased body excellent in dimensional accuracy can be obtained more reliably.

  In addition, as a specific example of the 2nd resin 4 decomposed | disassembled late with respect to the other resin 3, the 2nd resin 4 is a thing which can be decomposed | disassembled by an ultraviolet-ray, and an ultraviolet irradiation process is carried out in the 2nd degreasing process mentioned later. Examples include those that decompose when applied, and those that allow the second resin 4 to be decomposed by an acid, and those that decompose when brought into contact with an acid-containing atmosphere in the second degreasing step.

As shown in FIG. 1, the dispersant (additive) 5 adheres around the powder 1 and has a function of improving the dispersibility of the powder 1 in the composition 10. That is, when the composition 10 contains a dispersant, the powder 1, the resin 3 and the second resin 4 are more uniformly dispersed, and the obtained degreased body and sintered body have less variation in characteristics. , Become more uniform.
Moreover, the dispersing agent 5 has a function as a lubricant, that is, a function of improving the fluidity of the composition 10 in the molded body forming step described later. Thereby, the filling property in the molding die can be improved, and a molded body having a uniform density can be obtained.

The dispersant 5 is preferably decomposed and removed together with the second resin 4 in the second degreasing step. Thereby, an additive can be decomposed | disassembled and removed, without having a bad influence on the shape retention property and dimensional accuracy of a degreased body.
Here, as an additive, a lubricant, a plasticizer, antioxidant, etc. are mentioned, for example, These can be used 1 type or in combination of 2 or more types. By adding these, the binder 2 can exhibit various functions of the additive.

  As the dispersant 5, for example, stearic acid, distearic acid, tristearic acid, linolenic acid, octanoic acid, oleic acid, palmitic acid, higher fatty acids such as naphthenic acid or metal salts thereof, polyacrylic acid, polymethacrylic acid, Nonionic organic dispersion such as polymaleic acid, acrylic acid-maleic acid copolymer, anionic organic dispersing agent such as polystyrene sulfonic acid, cationic organic dispersing agent such as quaternary ammonium salt, polyvinyl alcohol, carboxymethyl cellulose, polyethylene glycol And inorganic dispersants such as tricalcium phosphate. These can also be used as a lubricant.

Among these, the dispersant 5 is preferably one having a higher fatty acid as a main component. The higher fatty acid is particularly excellent in the dispersibility and lubricity of the powder 1.
Further, the higher fatty acid preferably has 16 to 30 carbon atoms, and more preferably 16 to 24 carbon atoms. When the number of carbon atoms of the higher fatty acid is within the above range, the composition 10 has excellent shape retention while preventing deterioration of moldability. Further, when the carbon number is within the above range, the higher fatty acid can be easily decomposed even at a relatively low temperature.
Moreover, by adding a plasticizer as an additive, the binder 2 can give the composition 10 flexibility, and can facilitate molding in a molded body forming step described later.

Examples of the plasticizer include phthalic acid esters (eg, DOP, DEP, DBP), adipic acid esters, trimellitic acid esters, sebacic acid esters, and the like.
Moreover, the oxidation of the resin 3 contained in the binder 2 can be prevented by adding an antioxidant as an additive.
Examples of the antioxidant include hindered phenol-based antioxidants and hydrazine-based antioxidants.
The form of the binder 2 is not particularly limited, and may be any form. Examples thereof include powder, liquid, and gel.

  Moreover, the content rate of the binder 2 in the composition 10 is not particularly limited, but is preferably about 2 to 40 wt%, and more preferably about 5 to 30 wt%. When the content of the binder 2 is within the above range, a molded body can be formed with good moldability, the density of the molded body is higher, and the shape stability of the molded body is particularly excellent. Can be. Moreover, since the difference of the magnitude | size of a molded object and a degreased body, and what is called a shrinkage | contraction rate can be made small by this, the dimensional accuracy of a degreased body and a sintered compact can be improved.

The composition 10 containing each component as described above can be prepared, for example, by mixing powders corresponding to each component. The mixing of each component may be performed in any atmosphere, but in a non-oxidizing atmosphere such as under vacuum or reduced pressure (for example, 3 kPa or less) or in an inert gas such as nitrogen gas, argon gas, helium gas, etc. Preferably it is carried out in the middle. Thereby, especially the oxidation of a metal material contained in the composition 10 can be prevented.
Moreover, you may knead | mix etc. after mixing as needed. Thereby, for example, since the bulk density of the composition 10 is increased and the uniformity of the composition is also improved, the molded body can be obtained as a higher density and higher uniformity, and the dimensional accuracy of the degreased body and the sintered body Will also improve.

  The composition 10 can be kneaded using various kneaders such as a pressure or double-arm kneader, a roll kneader, a Banbury kneader, a single-screw or twin-screw extruder, etc. It is preferable to use a pressure kneader type kneader. Since the pressure kneader-type kneader can apply a high pressure to the composition 10, the composition 10 including the high-hardness powder 1 and the composition 10 having a high viscosity can be more reliably kneaded.

The kneading conditions vary depending on various conditions such as the composition and particle size of the powder 1 to be used, the composition of the binder 2 and the blending amount thereof. For example, kneading temperature: about 70 to 200 ° C., kneading time: It can be about 15 to 210 minutes. The atmosphere for kneading may be any atmosphere as in the case of the mixing, but it may be in vacuum or under reduced pressure (for example, 3 kPa or less), or an inert gas such as nitrogen gas, argon gas, helium gas, etc. It is preferably carried out in a non-oxidizing atmosphere as described above. Thereby, like the above-mentioned, the oxidation of especially a metal material contained in the composition 10 can be prevented.
Moreover, the obtained kneaded material (compound) is grind | pulverized as needed and is made into a pellet (small lump). The particle size of the pellet is, for example, about 1 to 10 mm.
The kneaded product can be pelletized using a pulverizer such as a pelletizer.

<Production of degreased body and sintered body>
[A] Molded body forming step Next, the kneaded product obtained above or pellets granulated from the kneaded product is molded into a predetermined shape to obtain a molded body 20 as shown in FIG.
The molded body 20 can be formed by various molding methods such as an injection molding method, an extrusion molding method, a compression molding method (press molding method), and a calendar molding method. For example, the molding pressure in the compression molding method is preferably about 5 to 100 MPa.

Among such various molding methods, the molded body 20 is preferably formed by an injection molding method or an extrusion molding method.
In the injection molding method, a kneaded product or pellets are used for injection molding by an injection molding machine to form a molded body 20 having a desired shape and size. In this case, it is possible to easily form a molded body 20 having a complicated and fine shape by selecting a molding die.

The molding conditions of the injection molding vary depending on various conditions such as the composition and particle size of the powder 1 to be used, the composition of the binder 2 and the blending amount thereof. For example, the material temperature is preferably 80 to About 200 ° C. and the injection pressure are preferably about ^{2 to} 15 MPa (20 to 150 kgf / cm ² ).
In the extrusion molding method, a kneaded product or pellets are used for extrusion molding by an extruder and cut into a desired length to form the molded body 20. In this case, the columnar or plate-like molded body 20 having a desired extruded surface shape can be formed particularly easily and inexpensively by selecting a molding die.

The molding conditions for extrusion molding vary depending on various conditions such as the composition and particle size of the powder 1 to be used, the composition of the binder 2 and the blending amount thereof. For example, the material temperature is preferably 80 to About 200 ° C., and the extrusion pressure is preferably about 1 to 10 MPa (10 to 100 kgf / cm ² ).
In addition, the shape dimension of the molded body 20 to be formed is determined in consideration of the shrinkage of the molded body 20 in each subsequent degreasing process and sintering process.

[B] First degreasing step The molded body 20 obtained in the molded body forming step is exposed to an atmosphere containing ozone, whereby the resin 3 is decomposed and removed from the molded body 20, and is shown in FIG. Such a molded body 30 is obtained.
When the resin 3 comes into contact with ozone, the decomposition product becomes a gas and is easily and quickly removed (degreased) from the molded body 20. Thereby, the time required for the total degreasing process can be shortened while maintaining the shape retention. In addition, since ozone does not have corrosive properties, there is no risk of causing corrosion or the like of the equipment that performs the first degreasing process, and there is an advantage that the maintenance and management of the equipment is easy.

  At this time, the decomposition product of the resin 3 is released from the inside of the molded body 20 to the outside. Accordingly, an extremely small flow path 31 is formed in the trace of the decomposition product in the molded body 30. . This flow path 31 can be a flow path when the decomposition product of the binding material 2 composed of the second resin 4 and the additive is released in the second degreasing step described later. Accordingly, the second resin 4 and the additive can thereby be decomposed and removed more efficiently.

In addition, since this flow path 31 disappears in a sintering process to be described later or only remains as a fine pore, there is a problem that the aesthetic appearance of the obtained sintered body is lowered or the mechanical strength is lowered. Very unlikely to occur.
The atmosphere for performing the first degreasing step only needs to contain ozone. As a composition other than ozone, for example, air, an oxidizing gas such as oxygen, an inert gas such as nitrogen, helium, and argon, Or you may contain the mixed gas containing these 1 type, or 2 or more types. Among these, the atmosphere preferably contains an inert gas other than ozone, and more preferably contains an inert gas containing nitrogen as a main component. Since the inert gas has poor reactivity with the constituent material of the powder 1, it prevents the powder 1 from being altered or deteriorated due to an unintended chemical reaction or the like.

  The ozone concentration in the atmosphere is preferably about 50 to 10000 ppm, more preferably about 80 to 8000 ppm, and further preferably about 100 to 5000 ppm. When the ozone concentration is a value within the above range, the resin 3 can be decomposed and removed efficiently and reliably. Even if the ozone concentration exceeds the upper limit, further increase in the efficiency of decomposition of the resin 3 by ozone cannot be expected.

Moreover, it is preferable to degrease such an atmosphere containing ozone while supplying a new gas around the molded body 20 and discharging a decomposition product of the resin 3. Thereby, the density | concentration of the decomposition gas discharge | released from the molded object 20 with the progress of degreasing | defatting around the molded object 20 can prevent that the efficiency of decomposition | disassembly of the resin 3 by ozone falls.
At this time, the flow rate of the gas supplied is suitably set depending on the volume of the equipment performing the degreasing is not particularly limited, and is preferably about 1-30 m 3 / ^h, is about 3 to 20 m 3 / ^h Is more preferable.

  Moreover, it is preferable that the temperature of such an atmosphere is about 50-190 degreeC in an ozone containing atmosphere, and it is more preferable that it is about 70-170 degreeC. When the temperature of the atmosphere is a value within the above range, the resin 3 can be decomposed and removed efficiently and reliably. Moreover, since it can avoid that the resin 3 softens by this, it can prevent that the shape retention property of the molded object 30 falls. As a result, it can prevent more reliably that the dimensional accuracy of a degreased body and a sintered compact falls.

The first degreasing time is appropriately set according to the content of the resin 3, the temperature of the atmosphere, and the like, and is not particularly limited, but is preferably about 1 to 30 hours, preferably about 3 to 20 hours. Is more preferable. Thereby, the resin 3 can be decomposed and removed efficiently and reliably.
In addition, you may perform a process process after a 1st degreasing process as needed.
As described above, various machining processes can be easily performed on the intermediate degreased body obtained by decomposing and removing only the resin 3 in the first degreasing step. The processing step for this intermediate degreased body is suitably applied to materials composed of materials that are difficult to work with sintered bodies, such as high-hardness metal materials such as W and Mo, brittle materials such as ceramics, etc. Is done.

[C] Second degreasing step The molded body 30 degreased in the first degreasing step is heated to heat the second resin 4 and the additive (for example, the dispersant 5) out of the molded body 30. 5 is obtained by decomposing and removing the binding material 2 ′.
The binding material 2 ′ decomposed by heating is discharged to the outside of the molded body 30 through the small flow path 31 formed in the first degreasing step, and is easily and quickly degreased. Thereby, since it is possible to prevent a large amount of the binding material 2 ′ from remaining in the molded body 30, it is possible to prevent the resulting degreased body 40 from being deformed, cracked, etc., and to ensure the total degreasing process. The time required can be shortened. As a result, a degreased body 40 and a sintered body that are excellent in dimensional accuracy, mechanical strength, and the like can be obtained.

The atmosphere for performing the second degreasing step is not particularly limited, but is an atmosphere, an oxidizing atmosphere such as oxygen, a reducing atmosphere such as hydrogen or carbon monoxide, an inert atmosphere such as nitrogen, helium, or argon, A reduced pressure atmosphere (vacuum) and the like can be mentioned.
Moreover, it is preferable that the temperature of atmosphere is about 190-600 degreeC, and it is more preferable that it is about 250-550 degreeC. When the temperature of the atmosphere is a value within the above range, the binder 2 ′ can be decomposed and removed efficiently and reliably. On the other hand, when the temperature of the atmosphere is less than the lower limit, the efficiency of decomposition / removal of the binder 2 ′ may be reduced. Further, even if the temperature of the atmosphere exceeds the upper limit, the decomposition rate of the binding material 2 ′ is hardly improved, so that it is not efficient.

The second degreasing time is appropriately set according to the composition and content of the binder 2 ′, the temperature of the atmosphere, etc., and is not particularly limited, but is preferably about 0.5 to 10 hours. More preferably, it is about ˜5 hours. Thereby, decomposition | disassembly and removal (defatting) of binding material 2 'can be performed efficiently and reliably.
The first degreasing step and the second degreasing step may be performed independently, but are preferably performed continuously. Thereby, the residual stress which arises in the inside of the molded object 30 with the temperature rise and temperature fall of the molded object 30 can be reduced more.
Moreover, what is necessary is just to perform a 2nd degreasing process as needed, for example, when the 2nd resin 4 and an additive are not contained in the composition 10, it can also be abbreviate | omitted. In this case, the degreased body 40 can be obtained only through the first degreasing step.

[D] Sintering Step The degreased body 40 obtained in the second degreasing step is sintered. Thereby, the powder 1 in the degreased body 40 is diffused mutually at the interface between those in contact with each other, grows into grains, and becomes crystal grains. As a result, a sintered body 50 as shown in FIG. 6 which is dense as a whole, that is, high density and low porosity is obtained.

Although the sintering temperature in the sintering step is slightly different depending on the composition of the powder 1, for example, it is preferably about 1000 to 1800 ° C, more preferably about 1100 to 1700 ° C. When the sintering temperature is a value within the above range, diffusion of the powder 1 and grain growth are optimized, and a sintered body 50 having excellent characteristics (mechanical strength, dimensional accuracy, appearance, etc.) can be obtained. it can.
Note that the sintering temperature in the sintering step may vary (increase or decrease) over time within or outside the above-described range.

The sintering time is preferably about 0.5 to 7 hours, and more preferably about 1 to 4 hours.
The atmosphere in which the sintering step is performed is appropriately selected depending on the composition of the inorganic material constituting the powder 1 and is not particularly limited. However, the atmosphere is an oxidizing atmosphere such as oxygen or oxygen, such as hydrogen or carbon monoxide. Examples thereof include a reducing atmosphere, an inert atmosphere such as nitrogen, helium, and argon, a reduced-pressure atmosphere obtained by reducing each of these atmospheres, and a pressurized atmosphere obtained by applying pressure.

As a specific example, when the inorganic material which comprises the powder 1 is a metal material, it is preferable that the atmosphere which performs a sintering process is a pressure-reduced inert atmosphere. Thereby, deterioration of the characteristic of the sintered compact 50 accompanying the oxidation of a metal material can be prevented more reliably.
In this case, the pressure of the vacuum inert atmosphere is not particularly limited, but is preferably 3 kPa (22.5 Torr) or less, more preferably 2 kPa (15 Torr) or less.

When the inorganic material is an oxide ceramic material, the atmosphere in which the sintering process is performed is preferably an oxidizing atmosphere. Thereby, the sintered compact 50 can be obtained, without the characteristic of an oxide type ceramic material changing.
When the inorganic material is a non-oxide ceramic material, the atmosphere in which the sintering process is performed is preferably an inert atmosphere. Thereby, the characteristic deterioration of the sintered compact 50 accompanying the oxidation of a non-oxide type ceramic material can be prevented easily and reliably. Furthermore, the effect can be obtained in a shorter time by sintering in a pressurized inert atmosphere.

In this case, the pressure of the pressurized inert atmosphere is not particularly limited, but is preferably about 110 to 1500 kPa, and more preferably about 200 to 1000 kPa.
Note that the atmosphere in which the sintering process is performed may change during the process. For example, a reduced-pressure atmosphere of about 3 kPa can be set first, and the inert atmosphere as described above can be switched on the way.
The sintering process may be performed in two stages or more. Thereby, the efficiency of sintering of the powder 1 is improved, and sintering can be performed in a shorter sintering time.

Moreover, it is preferable to perform a sintering process continuously with the above-mentioned 2nd degreasing process. Thereby, the 2nd degreasing process can serve as a pre-sintering process, can preheat the degreased body 40, and can sinter powder 1 more certainly.
As mentioned above, although preferred embodiment of this invention was described, this invention is not limited to this.
For example, in this embodiment, the binding material 2 contains the second resin 4 and the dispersant 5, but these may be added as necessary and can be omitted.

Next, specific examples of the present invention will be described.
1. Production of molded body In the following, a predetermined number of molded bodies of each example were produced.
(Sample No. 1)
SUS316L powder produced by the water atomization method and butanediol polycarbonate (weight average molecular weight: 50,000) were mixed and kneaded with a pressure kneader (kneader) under the following kneading conditions.
The average particle size of the SUS316L powder was 10 μm.
The mixing ratio of the powder and the binder was 93: 7 by weight.

<Kneading conditions>
-Kneading temperature: 200 ° C
・ Kneading time: 0.75 hours ・ Atmosphere: Nitrogen gas Next, this kneaded product is pulverized to form pellets having an average particle diameter of 3 mm, and the pellets are used for injection with an injection molding machine under the following molding conditions. Molding was repeated until sample no. 1 molded body was produced.
In addition, the molded object was shape | molded in the cube shape of 15x15x15 mm. Moreover, this molded object has a through-hole with an internal diameter of 5 mm in the center part of the two opposing surfaces.

<Molding conditions>
-Material temperature: 210 ° C
・ Injection pressure: 10.8 MPa (110 kgf / cm ² )
(Sample Nos. 2-11, 20)
Except for changing the composition and the mixing ratio of the binder, the mixing ratio of the powder and the binder, and the kneading conditions as shown in Table 1, the sample No. In the same manner as in sample 1, sample no. Each molded body of 2-11 and 20 was produced.

(Sample Nos. 12-15)
The sample No. was changed except that the powder was changed to zirconia powder and the composition and mixing ratio of the binder, the mixing ratio of the powder and binder, and the kneading conditions were changed as shown in Table 1, respectively. In the same manner as in sample 1, sample no. 12-15 molded bodies were produced.
As the zirconia powder, one having an average particle diameter of 0.6 μm and containing 5.3 wt% yttria was used.

(Sample Nos. 16-19)
The sample No. was changed except that the powder was changed to silicon nitride powder and the composition and mixing ratio of the binder, the mixing ratio of the powder and the binder, and the kneading conditions were changed as shown in Table 1, respectively. In the same manner as in sample 1, sample no. 16-19 molded bodies were produced.
The silicon nitride powder used had an average particle size of 0.6 μm and contained 4 wt% yttria and 4 wt% cerium oxide.

2. Preparation of degreased body and sintered body (Example 1)
Next, sample no. The 1st degreasing | defatting was performed with respect to the molded object of 1 by the degreasing | defatting conditions shown below in a degreasing furnace, and the degreased body was obtained.
<Degreasing conditions>
・ Degreasing temperature: 150 ° C
・ Degreasing time: 20 hours ・ Atmosphere: Nitrogen gas ・ Ozone concentration: 20 ppm
Next, the obtained degreased body was sintered in a firing furnace under the following sintering conditions to obtain a sintered body.

<Sintering conditions>
・ Sintering temperature: 1360 ° C
・ Sintering time: 3 hours ・ Atmosphere composition: Argon (reduced pressure atmosphere)
・ Atmospheric pressure: 1.3 kPa
(Examples 2 to 25, Comparative Examples 1 and 2)
Sample No. of molded article to be used The degreasing conditions were obtained in the same manner as in Example 1 except that the degreasing conditions were as shown in Table 2 and the sintering conditions were as shown in Table 3, respectively. Obtained.

3. Evaluation 3-1. Evaluation of fluidity of kneaded material Sample No. About each kneaded material of 1-20, the fluidity | liquidity of the kneaded material was evaluated.
The fluidity of the kneaded material was evaluated by a method of measuring the viscosity of the kneaded material at the material temperature of the molding conditions (specified in JIS K 7199). The conditions for measuring viscosity are shown below.

<Viscosity measurement conditions>
Viscometer: Capillograph (manufactured by Toyo Seiki Seisakusho, model number: D-1)
・ Measurement temperature: 210 [℃]
・ Shear rate: 1000 [/ sec]
Next, the measured viscosity was evaluated according to the following criteria.
○: Less than 500 Pa · s (5000 poise) ×: 500 Pa · s (5000 poise) or more

3-2. Evaluation of aesthetic appearance of molded product Sample No. About each molded object of 1-20, the aesthetic appearance of the molded object was evaluated.
The evaluation of the aesthetic appearance of the molded body was performed by a method of visually observing each molded body. The evaluation was performed according to the following criteria.
◎: No number of molding defects ○: Defect in less than 1% △: Defect in 1% or more but less than 5% ×: Defect in 5% or more 3-1 and 3-2 are shown in Table 1 Shown in

As is apparent from Table 1, sample No. which is a composition for forming a molded product corresponding to the present invention. Each of the kneaded materials 1 to 19 had high fluidity despite kneading for a relatively short time. In addition, since such a kneaded product is uniformly filled in an injection mold, each of the obtained molded articles has a low defect rate (defective rate) of less than 1% and a good aesthetic appearance. .
Among them, the molded product containing butanediol polycarbonate (aliphatic carbonate resin) showed a particularly excellent aesthetic appearance even though it was kneaded for a short time.
In addition, the higher the content of butanediol polycarbonate, the more the kneaded product showed sufficient fluidity even when kneaded for a shorter time, and the molded product showed an excellent aesthetic appearance.
On the other hand, sample No. which is a composition for forming a molded body corresponding to the comparative example. No. 20 kneaded product had low fluidity, and defects of about several percent were observed in the appearance of the obtained molded body.

3-3. Evaluation of Weight Reduction Rate For Examples 1 to 13 and Comparative Example 1, the weight reduction rate in the first degreasing was measured. Moreover, about Examples 14-25 and the comparative example 2, the weight decreasing rate in 1st degreasing and 2nd degreasing was measured, respectively.
The weight reduction rate was measured by measuring the weight of the molded body using an electronic balance before and after each degreasing and calculating the ratio of the reduced weight.
Moreover, about each Example and each comparative example, the total of each weight decreasing rate of 1st degreasing and 2nd degreasing was computed.
The results are shown in Table 2.

As is clear from Table 2, the first degreasing and the second degreasing in each example have a difference depending on the composition of the inorganic material, but the weight reduction rate increases, and the degreasing process totals 97% or more of the binder. Was removed. This shows that degreasing is reliably performed even though the degreasing temperature of the first degreasing is 150 ° C. and a relatively low temperature.
Further, in the first degreasing step and the second degreasing step of each example, the resin having ozone decomposability has been decomposed and removed in a relatively short degreasing time, which is necessary depending on the composition of the binder. Total time was also shortened.

In particular, when the ratio of the ozone decomposable resin in the binder and the ozone concentration in the first degreasing atmosphere is high, the decomposition efficiency of the whole binder is improved, so that the processing time can be greatly shortened. .
On the other hand, in each comparative example, although heating was performed for a long time, it could not be sufficiently degreased, and the removal rate of the binder in the total degreasing process was less than 90%. This is presumed to be because the first degreasing step was performed at a relatively low temperature, and the decomposition did not proceed sufficiently in the case of a resin having no ozone decomposability.

3-4. Evaluation of Density of Sintered Body The density of each sintered body obtained in each example and each comparative example was measured. In addition, the measurement of the density was performed about 100 pieces by the Archimedes method (specified in JIS Z 2505), and the average value was used as the measurement value.
Next, the relative density of the sintered body was calculated from each measured value. In calculating the relative density, a relative standard (theoretical density) is set for each composition of each inorganic material, SUS316L is 7.98 g / cm ³ , zirconia is 6.07 g / cm ³ , and silicon nitride is 3.30 g / cm ^3. It was.

3-5. Evaluation of Dimensions of Sintered Body For the sintered bodies obtained in the respective Examples and Comparative Examples, the dimensions in the width direction were measured, and the variation in the dimensions was calculated. The dimensions were measured for 100 pieces using a micrometer, and the variation was calculated.
Next, the roundness of the center hole was measured for each sintered body. The roundness was measured using a three-dimensional measuring device (manufactured by Mitutoyo Corporation, model number: FT805), and the average value was defined as roundness.
In addition, since the sintered body of Comparative Example 1 had almost all cracks, the density and dimensions could not be measured.

3-6. Evaluation of Aesthetic Appearance of Sintered Body The aesthetic appearance of each sintered body obtained in each Example and each Comparative Example was evaluated. Evaluation was performed according to the following criteria.
A: There are no scratches or cracks (including microcracks). O: There are some scratches or cracks (including microcracks). Δ: Many scratches or cracks (including microcracks). Table 3 shows the evaluation results of 3-4, 3-5, and 3-6.

As is clear from Table 3, the sintered bodies obtained in each example had a relative density of 90% or more, and were sintered reliably and became a dense body with low porosity. . Moreover, since the sintered body obtained in each Example performed the first degreasing process at a relatively low temperature and prevented the shape retention of the degreased body from being deteriorated due to the softening of the binder, the dimensional accuracy was relatively high. It was good.
Furthermore, all of the sintered bodies obtained in each Example were excellent in aesthetic appearance without any defects such as scratches and cracks.
On the other hand, the sintered body obtained in each comparative example had a low relative density of less than 90% and a low dimensional accuracy.
In addition, almost all the cracks were confirmed in the sintered body obtained in Comparative Example 1. This is presumed to have occurred when the binder that could not be removed in the degreasing process rapidly decomposed during sintering.

It is a figure which shows typically the composition for molded object formation used by this embodiment. It is process drawing which shows embodiment of the method of manufacturing a degreased body and a sintered compact using the composition for molded object formation shown in FIG. It is a figure which shows typically the longitudinal cross-section of the molded object obtained using the composition for molded object formation of this embodiment. It is a figure which shows typically the longitudinal cross-section of the molded object obtained using the composition for molded object formation of this embodiment. It is a figure which shows typically the longitudinal cross-section of the degreased body of this embodiment. It is a figure which shows typically the longitudinal cross-section of the sintered compact of this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Powder 2, 2 '... Binder 3 ... Resin 4 ... 2nd resin 5 ... Dispersant 10 ... Composition 20, 30 ... Molded body 31 ... Flow path 40 ... Degreased body 50 …… Sintered body A, B, C, D …… Process

Claims (18)

A composition for forming a molded body comprising a powder mainly composed of an inorganic material and a binder containing a resin decomposable by ozone,
It is used to obtain a degreased body by decomposing and removing at least a part of the resin by subjecting a molded body formed by molding the molded body forming composition to a degreasing treatment in an ozone-containing atmosphere. A composition for forming a molded body.   The composition for forming a molded body according to claim 1, wherein the content of the binder in the composition for forming a molded body is 2 to 40 wt%.   The said resin decomposes | disassembles at the temperature of 50-190 degreeC in ozone containing atmosphere, The composition for molded object formation of Claim 1 or 2.   The composition for forming a molded body according to any one of claims 1 to 3, wherein the resin contains an aliphatic carbonate ester resin as a main component.   The composition for forming a molded body according to claim 4, wherein the aliphatic carbonate-based resin has 2 to 11 carbon atoms in the repeating unit excluding the carbonate group.   The composition for forming a molded body according to claim 4 or 5, wherein the aliphatic carbonate-based resin does not have an unsaturated bond.   The composition for forming a molded body according to any one of claims 4 to 6, wherein the aliphatic carbonate ester resin has a weight average molecular weight of 1 to 300,000.   The composition for forming a molded body according to any one of claims 1 to 7, wherein a content of the resin in the binder is 20 wt% or more.   The composition for forming a molded body according to any one of claims 1 to 8, wherein the binder contains a second resin that decomposes with a delay after the resin.   The composition for forming a molded body according to claim 9, wherein the second resin is decomposed at a temperature of 190 to 600C.   The composition for forming a molded body according to claim 9 or 10, wherein the second resin is mainly composed of at least one of a polyolefin resin, a polystyrene resin, a polyvinyl resin, and an acrylic resin. .   The composition for forming a molded body according to claim 1, wherein the binder contains an additive.   The composition for forming a molded body according to claim 12, wherein the additive is a dispersant for improving dispersibility of the powder.   The composition for forming a molded body according to claim 13, wherein the dispersant is mainly composed of a higher fatty acid.   The composition for forming a molded body according to claim 14, wherein the higher fatty acid has 16 to 30 carbon atoms.   A degreased body obtained by molding the composition for forming a molded body according to claim 1 to obtain a molded body, and then subjecting the molded body to a degreasing treatment.   The degreased body according to claim 16, wherein the molding is performed by an injection molding method or an extrusion molding method. A sintered body obtained by sintering the degreased body according to claim 16 or 17.

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