JPH05320708A - Binder and composition for sinterable powder injection molding - Google Patents

Abstract

(57) [Summary] [Objective] To provide a powder injection molding composition containing a binder excellent in moldability and degreasing property. [Structure] (a) An olefin polymer having one or more acid anhydride structures in the molecule of the polymer represented by the following formula 1 and /
Or copolymer 3 to 80% by weight [However, R ¹ is a hydrogen atom or a methyl group, and R ² is one kind of group selected from the group consisting of a hydrogen atom and an alkyl group having 1 to 3 carbon atoms. (C) A binder for sinterable powder injection molding, containing 20 to 80% by weight of an organic compound having a molecular weight of 2,000 or less.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a metal powder, a ceramic powder and a cermet powder (hereinafter referred to as sinterable powder).
Injection molding binders and compositions (compounds).

[0002]

2. Description of the Related Art Conventionally, a sintered product has been produced by kneading a sinterable powder and a binder (binder) and then casting, extruding,
It is manufactured by molding after firing by the rokuro method, press molding method or the like, but it is difficult to obtain a sintered product having a complicated shape by these methods. Therefore, a sinterable powder injection molding method is used as a method for obtaining a product having a more complicated shape.

The sinterable powder injection molding method is a technique used as a method for mass-producing small-sized and complicated-shaped sintered parts. In this method, first, a raw material, sinterable powder, and a binder are kneaded to obtain an injection molding raw material compound. This compound has thermoplasticity and is molded into a desired shape by an injection molding machine. This molding process is essentially the same as molding of plastic materials, and mass molding is possible. Next, unnecessary binder is removed from the obtained molded body. This process is called degreasing. The degreasing method is
It is known to heat and evaporate or flow out the binder from the molded body, to retain the molded body in a solvent to extract the binder, and to combine the two, depending on the type of binder. A degreasing method is selected. Finally, the degreased body is sintered to obtain a metal part.

The sinterable powder injection molding method is characterized in that sinterable fine powder capable of obtaining a high sinter density can be molded. Conventionally, fine powders having an average particle diameter of 10 μm or less have been difficult to mold by pressing due to problems of poor fluidity and problems of galling of molds. However, according to this method, even fine powders can be easily molded. In addition, it is possible to form a complex three-dimensional shape. Because of these advantages,
The sinterable powder injection molding method is often used for the production of pure iron parts, iron-nickel alloy parts, stainless parts, etc., and its application is expanding to magnetic materials and superhard materials.

The types of binders used in the sinterable powder injection molding method are roughly classified into thermoplastics and thermosetting resins. Considering the regeneration of sprues and runners, non-renewable thermosetting binders are used. Not used much. Examples of the components of the mainstream thermoplastic binder include thermoplastic resins, waxes, plasticizers, lubricants and the like. As a main component of the binder, the resin imparts plasticity to the raw material compound and also has strength of the molded body at room temperature. Further, in order to improve degreasing property and fluidity, wax or plasticizer which is an organic substance having a lower molecular weight than the resin is added. Known resin components include polyethylene, polypropylene, polystyrene, ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA), polymethacrylic acid alkyl ester, and polyamide.
These may be used alone or in combination of two or more. As a component having a lower molecular weight than the resin, one or more of paraffin wax, higher fatty acid, higher alcohol, higher fatty acid ester, higher fatty acid amide, phthalate ester such as diethyl phthalate, dibutyl phthalate, etc. may be used in combination. Be done. As described above, the raw material compound for sinterable powder injection molding is generally a mixture of powder and several kinds of organic substances such as resin, wax and plasticizer.

By the way, since the surface of sinterable powder such as ceramic powder or metal powder is close to hydrophilic, it has very poor wettability with a hydrophobic binder mainly composed of organic substances. Therefore, it is difficult to uniformly disperse these sinterable powders in the binder, and aggregated powders are easily generated. If agglomerated powder that is not wet with the binder is present in the compound, the compound becomes highly viscous, the moldability deteriorates, and the strength of the green molded body is drastically reduced and cracks are likely to occur. Furthermore, cracks and blisters are likely to occur during degreasing.

The formation of aggregated powder is more remarkable as the molecular weight of the binder is higher. For example, polyethylene (PE), polypropylene (PP), and polystyrene (PS) have long been used as binders for powder injection molding, but since these resins have poor wettability with sinterable powders, compound flow The properties were extremely poor, and there were problems that injection molding was difficult and the strength of the obtained molded product was low.

As a method for improving the wettability of the sinterable powder and the binder, a method of treating the surface of the sinterable powder to make it hydrophobic, and a method of adding a functional group that wets the hydrophilic surface of the sinterable powder to the binder are used. There is a method of introducing it into the component. Specific examples of the former method include silane coupling agents, titanate coupling agents (JP-B-59-41949), aluminum chelate compounds (JP-A-61-24).
2947), the surface treatment of the sinterable powder has been carried out. As a specific example of the latter, an example using a surfactant (JP-A-59-182267, JP-A-59-35).
No. 058) or a binder component having a functional group such as a carboxyl group, an ester, an amino group, a hydroxyl group or an acid anhydride that interacts with the surface of the sinterable powder, for example, an ethylene-vinyl acetate copolymer. (EVA) (JP-A-5
2-117909, JP-A-58-135173), ethylene-ethyl acrylate copolymer (EE
A) (JP-A-59-121150), a cyclopentadiene-unsaturated dicarboxylic acid anhydride copolymer or a hydrogenated product thereof (JP-A-62-12658), alphamethylstyrene-unsaturated acid anhydride. Copolymer (JP-A-63-252951), stearic acid (Japanese Patent Publication No.
6-7883), behenic acid (JP-A-2-267).
156). By using such a method, the wettability between the sinterable powder and the binder is improved, the sinterable powder is well dispersed in the binder, and it is possible to easily perform injection molding and also to obtain a good molded product. Also came to get.

[0009]

The selection of the binder is important in the sinterable powder injection molding method, but the conventional binder composition has the following problems.

When a resin such as polyethylene or polypropylene is used as the binder, it is difficult to disperse the powder because these resins have poor wettability with the sinterable powder, and the agglomerated powder remains, resulting in a uniform and good fluidity. Does not become a compound with properties. Further, even if a low-molecular component such as wax is added to improve the moldability, since the compatibility with the sinterable powder is poor, the binder and the sinterable powder are separated from each other, which causes a problem during injection molding. Furthermore, when heat degreasing is used in the degreasing step, the molded body is deformed during heating, or degreasing defects such as swelling and cracks occur.
In order to avoid such a degreasing defect, it is necessary to lengthen the degreasing time, and there is a problem that the degreasing process takes time.

Ethylene-vinyl acetate copolymer (EV
A), ethylene-ethyl acrylate copolymer (EE
A) is a resin that has a polar functional group and is well compatible with sinterable powder and is often used as a component of a binder for injection molding. When these resins are used as a binder, the compound has good moldability and excellent molded product strength. However, the content of vinyl acetate or ethyl acrylate needs to be high to some extent in order to fully exhibit its performance, which results in a low softening point. Therefore, in the degreasing process, the molded body is very likely to be deformed, and defects such as swelling are also likely to occur. Therefore, long-time degreasing is necessary to obtain a sound degreased body without defects.

Since polystyrene and polymethacrylic acid alkyl ester have excellent depolymerizability, they are excellent in degreasing property and are often used as a binder. However, these resins have poor wettability with the sinterable powder and, like polyethylene and the like, have a problem in molding.

Therefore, it has been proposed to use two or three or more kinds of these resins in combination in an injection molding compound, but each has advantages and disadvantages.
The reality is that no binder has yet been developed that exhibits excellent performance in terms of both moldability and degreasing property.

Furthermore, in the method of surface-treating the sinterable powder, the surface-treating agent is expensive, the number of steps of the surface-treating agent is increased by one, and the surface-treating agents titanium, silicon and aluminum remain in the sintered body, There are drawbacks such as adversely affecting physical properties. Further, the addition of a surfactant or higher fatty acid causes a decrease in the softening point of the binder, so that defects such as deformation and swelling are likely to occur during degreasing by heating. In addition, JP-A-62-1265
According to the publication No. 8, since unsaturated bonds are present in the polymer, gelation is likely to occur during kneading, the viscosity of the compound is increased, and it is difficult to recycle sprues and runners. In JP-A-63-252951, the polyalphamethylstyrene-unsaturated acid anhydride copolymer has a high softening point and a high viscosity, and therefore a large amount of a solvent such as toluene or alcohol must be used in combination. Injection molding is difficult because the density changes significantly due to volatilization and the strength is also extremely low. Furthermore, whichever method is used, it takes a long time to degrease by heating so as not to deform, and there is a drawback that swelling and deformation occur when the degreasing time is shortened.

[0015]

In order to solve the above problems, as a result of studying the components and blending of the binder, the present inventors have found that as a component of the binder for sinterable powder injection molding,
It has been found that when an olefinic copolymer containing an acid anhydride structure is used as an essential component, it has good wettability with powder, good moldability, little deformation of the molded product even in degreasing, and a degreasing defect-free compound. ..

That is, the present invention includes (a) 3 to 80% by weight of an olefin polymer and / or copolymer having at least one acid anhydride structure in the molecule of the polymer represented by the following formula 1.

[Chemical 7] [However, R ¹ is a hydrogen atom or a methyl group, and R ² is one kind of group selected from the group consisting of a hydrogen atom and an alkyl group having 1 to 3 carbon atoms. (C) A binder for powder injection molding containing 20 to 80% by weight of an organic compound having a molecular weight of 2,000 or less is provided. Further, (a) 3 to 80% by weight of an olefin-based polymer and / or copolymer having at least one acid anhydride structure in the molecule of the polymer represented by the following formula 1,

[Chemical 8] [However, R ¹ is a hydrogen atom or a methyl group, and R ² is one kind of group selected from the group consisting of a hydrogen atom and an alkyl group having 1 to 3 carbon atoms. ] (B) A binder for powder injection molding containing 70% by weight or less of a polymer and / or copolymer other than (a) above, and (c) 20 to 80% by weight of an organic compound having a molecular weight of 2,000 or less. To do. Further, (a) an olefin copolymer 3 to 8 having at least one acid anhydride structure in the molecule of the polymer represented by the following formula 2.
0% by weight,

[Chemical 9] [However, R ¹ represents a hydrogen atom or a methyl group, R ² represents a hydrogen atom, one kind of group selected from the group consisting of alkyl groups having 1 to 3 carbon atoms, and R ³ represents

[Chemical 10] (R ⁵ is a group selected from a hydrogen atom, a halogen atom, and an alkyl group having 1 to 4 carbon atoms). (C) A sinterable powder injection molding binder containing 20 to 80% by weight of an organic compound having a molecular weight of 2,000 or less is provided. Further, (a) an olefin copolymer 3 to 80 having at least one acid anhydride structure in the molecule of the polymer represented by the following formula 2.
% By weight,

[Chemical 11] [However, R ¹ represents a hydrogen atom or a methyl group, R ² represents a hydrogen atom, one kind of group selected from the group consisting of alkyl groups having 1 to 3 carbon atoms, and R ³ represents

[Chemical formula 12] (R ⁵ is a group selected from a hydrogen atom, a halogen atom, and an alkyl group having 1 to 4 carbon atoms). ] (B) Sinterable powder injection molding containing 70 wt% of an olefin polymer and / or copolymer other than (a) above, and (c) 20 to 80 wt% of an organic compound having a molecular weight of 2,000 or less. To provide a binder. In particular, (b) the olefin-based polymer and / or copolymer other than (a) above is one or two of acrylic acid ester, methacrylic acid ester, and styrene.
It is preferably a homopolymer and / or a copolymer obtained by copolymerizing one or more kinds. Further, there is provided a sinterable powder injection molding composition comprising any one of the above powder injection molding binders and a metal powder, a ceramic powder or a cermet powder. Further, the metal powder, ceramic powder or cermet powder has an average particle size of 0.01 to
A sinterable powder injection molding composition having a thickness of 1,000 μm is provided.

[0017]

The present invention will be described in more detail below. As the raw material powder that can be used for the binder of the present invention, any powder may be used as long as it is a metal powder, a ceramic powder or a cermet powder. To give an example of metal powder,
Iron, copper, titanium, tungsten, nickel, molybdenum, chromium, zinc, aluminum, zirconium, beryllium, germanium, cobalt, silicon, scandium, yttrium, lanthanide, actinide, hafnium, thorium, vanadium, tantalum, manganese, technetium, rhenium, Ruthenium, rhodium, palladium, osmium, iridium, platinum, gold, silver, cadmium, thallium, tin, lead, arsenic, antimony, bismuth, tellurium, polonium powder and alloys or mixed powders thereof, such as stainless steel, iron- Examples thereof include nickel alloys, iron-silicon alloys, iron-cobalt alloys, iron-boron alloys and iron-cobalt-vanadium alloys. As the ceramic powder, aluminum oxide, silicon oxide, zirconium oxide, titanium oxide,
Beryllium oxide, magnesium oxide, barium titanate, lead titanate, lead zirconate, lead zirconate titanate, indium oxide, barium oxide, potassium oxide, yttrium oxide, calcium oxide, strontium oxide, manganese dioxide, technetium oxide, rhenium oxide. , Cobalt oxide, nickel oxide, ruthenium oxide, lanthanum oxide, selenium oxide, scandium oxide, actinium oxide, thorium oxide, vanadium oxide, niobium oxide, tantalum oxide, molybdenum oxide, manganese oxide, tungsten oxide, rhodium oxide, cadmium oxide, oxide Oxides such as thallium, germanium oxide, tin oxide, lead oxide, antimony oxide, bismuth oxide, tellurium oxide and beryllium oxide, silicon carbide, boron carbide, aluminum carbide, tungsten carbide, Titanium, zirconium carbide, hafnium carbide, molybdenum carbide, tantalum carbide, chromium carbide, vanadium carbide, carbides such as carbon,
Nitrides such as silicon nitride, aluminum nitride, boron nitride and titanium nitride, silicides such as molybdenum silicide,
Examples thereof include sulfides such as cadmium sulfide and zinc sulfide, and borides such as titanium boride, zirconium boride, and lanthanum boride. In addition, carbonyl powder, water atomized powder, gas atomized powder, pulverized powder, and the like can be given as the powder manufacturing methods. In addition, two of these
It is also possible to use a mixed powder of at least one kind. In addition, the above-mentioned metal powder and ceramic powder, for example, silicon nitride powder / yttrium oxide / aluminum oxide powder, zirconia / yttrium oxide / magnesium oxide, silicon carbide / boron carbide / carbon black, mixed powder or alloy of alumina / magnesium oxide / silicon dioxide. Cermet powder may be used as the powder.

The average particle size of the sinterable powder is 0.01 to 100.
A range of 0 μm, particularly 0.1 to 1000 μm can be used, but it is preferable to use a powder of 100 μm or less in view of fluidity of the compound or sinterability of the powder. A more preferable average particle size range is 0.1 to 50 μm.

The smaller the particle size of the powder, the better the flowability during injection molding and the better the sinterability, which is advantageous, but it is disadvantageous in practical use because a huge amount of energy is required to make it into a fine powder. On the other hand, when it exceeds 1,000 μm, the fluidity of the compound is deteriorated and injection molding becomes substantially impossible.

The injection molding composition of the present invention contains 2 to 100 parts by weight of the binder of the present invention per 100 parts by weight of these powders. The optimum amount of binder depends on the shape of the powder, the particle size of the powder, and the particle size distribution of the powder, so it cannot be said unequivocally, but if it is less than 2 parts by weight, the binder will be insufficient for the metal powder, and the fluidity of the compound will be low. If it exceeds 100 parts by weight, injection molding can be performed, but shape retention during degreasing cannot be maintained, which is not preferable.

The sinterable powder injection molding composition of the present invention containing metal powder, ceramic powder or cermet powder and each binder component is preferably produced by kneading, and the kneading order may be any order. .. The sinterable powder and all binder components may be kneaded at the same time, or after all the binder components are kneaded, the sinterable powder may be added and kneaded. Alternatively, the sinterable powder and the component having the binder may be kneaded first, and the remaining binder component may be added afterwards. As the kneader, a Henschel mixer, a plastomill, a pressure kneader, a Banbury mixer, a roll mill, a single screw kneader, a twin screw kneader, or the like can be used, and two or more kinds of these may be combined and kneaded.

In the present invention, the binder is an olefin (co) polymer (hereinafter referred to as an acid anhydride) having at least one acid anhydride structure in the (co) polymer molecule represented by the formula 1 or 2. A structure-containing olefin-based (co) polymer is used as an essential component. The acid anhydride structure-containing olefin (co) polymer may be a copolymer, and the mode of copolymerization may be any of random copolymerization, block copolymerization, graft copolymerization and the like.

The olefinic (co) polymer referred to in the present invention has the formula:

[Chemical 13] [However, R ¹ is a hydrogen atom or a methyl group, and R ² is one kind of group selected from the group consisting of a hydrogen atom and an alkyl group having 1 to 3 carbon atoms. ] Is a polymer represented by,
Or Equation 2:

[Chemical 14] [R ¹ is at least one group selected from a hydrogen atom and a methyl group, R ² is at least one group selected from a hydrogen atom and an alkyl group having 1 to 3 carbon atoms, and R ³ is

[Chemical 15] (R ⁵ is one or more groups selected from a hydrogen atom, a halogen atom, and a group selected from alkyl groups having 1 to 4 carbon atoms).].

Specific examples of the olefin (co) polymer represented by the formula 1 or 2 are ethylene, propylene, 1-butene, isobutene and 3-methyl-pentene-.
One or more (co) polymers selected from the group consisting of monomers such as 1,4-methyl-pentene-1, or one or more kinds selected from the group consisting of the above monomers, and vinyl acetate ,
Vinyl propionate, styrene, α-methylstyrene,
Paramethylstyrene, para-t-butylstyrene, methyl (meth) acrylate, ethyl (meth) acrylate,
Select from the group consisting of methacrylic acid esters such as n-butyl (meth) acrylate and isobutyl (meth) acrylate, and acrylic acid esters such as methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate. It is a copolymer with one or more monomers. The preferred molecular weight of this olefin-based (co) polymer is more than 2,000.

As the method for producing the olefin copolymer containing an acid anhydride structure of the present invention, there is a method of radically copolymerizing the above-mentioned monomer having an unsaturated bond and an unsaturated dicarboxylic acid anhydride. In addition to being used, a radical generator is present in the olefin homopolymer represented by Formula 1 or the olefin copolymer represented by Formula 2, and the unsaturated dicarboxylic acid anhydride is present in the presence or absence of a solvent or a dispersion medium. The method of carrying out a radical graft reaction can be mentioned below. Above all, when grafting in the molten state,
By using a melt kneader such as an extruder, a kneader or a Banbury mixer, the acid anhydride structure-containing olefin-based copolymer can be obtained in a short time by a simplified method.

Examples of unsaturated dicarboxylic acid anhydrides include:
Succinic anhydride, itaconic anhydride, glutaconic anhydride, maleic anhydride, chloromaleic anhydride, citraconic anhydride, and cis-4-cyclohexene-1,2-dicarboxylic anhydride, endo-bicyclo- (2,2,2. 1) -5
-Heptene-2,3-dicarboxylic anhydride, methyl-endo-cis-bicyclo- (2,2,1) -5-heptene-2,3-dicarboxylic anhydride, endo-bicyclo-
(2,2,1) -1,2,3,4,7,7-hexachloro-2-pentene-5,6-dicarboxylic acid anhydride and the like can be mentioned. In the present invention, one or more selected from this exemplified group can be used. Of these, maleic anhydride is preferred.

Preferred examples of the acid anhydride structure-containing olefinic (co) polymer (a) used in the present invention are maleic anhydride-modified PE, PP, ethylene-propylene copolymer, polyisobutylene, ethylene- They are butene-1 copolymer, EVA, EEA, ethylene-methyl acrylate copolymer (EMA), ethylene-methyl methacrylate copolymer (EMMA), and styrene-ethylene-butene-styrene copolymer (SEBS).

One or more unsaturated dicarboxylic acid anhydrides of the olefin (co) polymer having an acid anhydride structure in the present invention are contained in the molecule. Further, the content of the unsaturated dicarboxylic acid anhydride is preferably 0.01 to 5% by weight, more preferably 0.1 to 2% by weight.

The preferred molecular weight of the olefin-based (co) polymer containing an acid anhydride structure is about 2,000 to 500,000.
When the molecular weight is 2,000 or less, the strength of the molded product is insufficient, so that cracks are likely to occur during injection molding, and deformation occurs during degreasing. If the molecular weight exceeds 500,000, the melt viscosity becomes high and the moldability deteriorates. A more preferable molecular weight is 5
It is between 0,000 and 300,000.

In the present invention, in addition to the above-mentioned (a) acid anhydride structure-containing olefin (co) polymer as a binder component, the acid anhydride structure-containing olefin (co) polymer of the present invention is used.
It is preferable to add a polymer other than the polymer in order to facilitate degreasing, and any polymer can be added as long as it can be degreased with heat or a solvent. Preferable examples of such a polymer include an olefin-based (co) anhydride structure-containing structure during solvent degreasing.
Those that are soluble in a solvent that does not dissolve the polymer, or those that differ in thermal decomposition temperature from the acid anhydride structure-containing olefin (co) polymer to prevent swelling and cracking due to rapid decomposition during thermal degreasing Be done.

Examples of such resins include PE and P
P, polyisobutylene, ethylene-propylene copolymer, polymethylpentene, ethylene-butene copolymer,
Styrene-ethylene-butylene-styrene copolymer, E
VA, EEA, EMA, EMMA, polyolefin such as chlorinated PE, polystyrene, poly-α-methylstyrene, styrene-acrylonitrile copolymer, styrene- (meth) acrylic acid ester copolymer, styrene-methyl (meth) Styrene resins such as acrylate copolymers, styrene-ethyl (meth) acrylate copolymers, styrene-isopropyl (meth) acrylate copolymers, styrene-n-butyl (meth) acrylate copolymers, poly (meth) acrylics Methyl acid, poly (meth) acrylate, poly (meth) acrylate, poly (meth) acrylate-n-butyl, poly (meth) acrylate isobutyl, poly (meth) acrylate-2-ethylhexyl, poly Propyl (meth) acrylate, isop (poly) methacrylate Pill, cyclohexyl poly (meth) acrylate, ethylhexyl poly (meth) acrylate, poly- (meth) acrylate-n-dodecyl, stearyl poly (meth) acrylate, methyl (meth) acrylate-butyl (meth) acrylate Copolymers, acrylic resins such as butyl methacrylate--2-ethylhexyl methacrylate copolymers, polyvinyl formal, polyvinyl butyral, polyvinyl acetoacetal, polyvinyl acetals such as polyvinyl propional, polyvinyl ether, polyvinyl butyl ether and other polyvinyl Polyethers such as ethers, polyethylene oxide, polyoxymethylene, polypropylene oxide, polytetramethylene glycol, ethylene oxide-propylene oxide copolymers, polyethylene Polyesters and polyamides such as terephthalate, polybutylene terephthalate and polyethylene sebacate, polycarbonates, polyurethanes and the like. The molecular weight of these polymers is preferably in the range of 2,000 to 500,000, more preferably 50,000 to 300,000. If the molecular weight is 2000 or less, the strength of the molded product is insufficient, so that cracks are likely to occur during molding, while if it exceeds 500000, the melt viscosity becomes high and the moldability deteriorates.

Further, preferably, a homopolymer obtained by (co) polymerizing one or more of acrylic acid ester, methacrylic acid ester, and styrene as a resin other than the acid anhydride structure-containing (co) polymer. Coalescence and / or copolymers are used. When using these resins, it is preferable to use an ethylene resin as the acid anhydride structure-containing (co) polymer. With this combination, you can easily degrease the styrene-based and acrylic-based resins from the molded product with a solvent such as toluene, chloroform, and methylene chloride.
Styrene-based and acrylic-based resins, which have a low decomposition temperature, are first decomposed, and then the ethylene-based resin is decomposed, so that it is possible to suppress the rapid generation of decomposition gas and prevent blistering and cracking during degreasing.

In the present invention, in addition to the resins (a) and (b) described above, an organic compound having a lower molecular weight than those, that is, an organic compound (c) having a molecular weight of 2,000 or less is used as the binder component. Wax, higher fatty acid, higher alcohol, higher fatty acid amide, fatty acid ester, phthalic acid ester, adipic acid ester, sebacic acid ester and the like can be used as the organic compound having a molecular weight of 2,000 or less used for the binder. Specific examples of low-molecular components that can be used include (normal) paraffin wax, microcrystalline wax, oxidized wax, petrolatum, petrolatum oxide, polyethylene wax, polypropylene wax,
Synthetic waxes such as montan wax derivatives, whale wax, Chinese wax, beeswax, wool wax, candelilla wax, wood wax, naricurie wax, sugar cane wax,
Examples include natural waxes such as ozokerite wax, ceresin, lignite wax, montan wax, carnauba wax and bee wax. The molecular weight of these waxes is preferably 300 to 2000. This is because if the molecular weight is less than 300, appropriate strength cannot be imparted to the molded product, and if the molecular weight is more than 2000, degreasing property deteriorates. Wax is most often used as a binder component because it has good compatibility with resins and is inexpensive.

The higher fatty acids include myristic acid, palmitic acid, stearic acid, lauric acid, valmotic acid,
Isostearic acid, arachidic acid, arachidonic acid, behenic acid, oleic acid, linoleic acid, linolenic acid and the like can be used. These are effective as lubricants, but if they are blended in too large an amount, the bleed-out from the molded product becomes severe and the strength of the molded product also decreases, so the compounding ratio is limited to 10% by weight or less based on the entire binder. Is preferred.

As the higher alcohols, monohydric higher alcohols such as cetyl alcohol, lauryl alcohol, ceryl alcohol, melysyl alcohol, myristyl alcohol and stearyl alcohol, and dihydric alcohols such as ethylene glycol and polyethylene glycol are used. it can.

The higher fatty acid amides include stearic acid amide, lauric acid amide, erucic acid amide, linoleic acid amide, behenic acid amide, palmitic acid amide, oleic acid amide, methylenebisstearic acid amide, ethylenebisstearic acid amide, ricinoleic acid. Examples thereof include amide, erucic acid amide, behenic acid amide, erucyl amide, hardened beef tallow amide, coconut fatty acid amide, methylenebisstearylamide, ethylenebisstearylamide, methylenebisamide and ethylenebisamide.
These amides are relatively compatible with the resin and there is no problem even if they are mixed in a large amount as compared with fatty acids and alcohols.

As the fatty acid ester, a mono- or di-ester of a C ₁₂ -C ₂₂ fatty acid with a C ₁ -C ₂₂ monohydric alcohol ester or glycols, or a mono-, di-, or triester with glycerin can be used as a binder. .. Specifically, butyl stearate, butyl laurate, octyl palmitate, isopropyl palmitate, stearic acid monoglyceride, sorbitan trioleate, cetyl palmitate, myricyl palmitate, myricyl serotinate, diethylene glycol dibenzoate, triethylene glycol. Di-2-ethylbutyrate, peanut oil, soybean oil, coconut oil, palm oil, linseed oil,
Examples include hydrogenated oil, fish oil, animal oil and the like.

Phthalates, adipates,
Sebacic acid esters and the like are generally used as plasticizers for plastics, but they also have excellent properties as binders for sinterable powder injection molding. Specifically, dimethyl phthalate, diethyl phthalate, dibutyl phthalate (DBP), diheptyl phthalate, di-n-octyl phthalate, di2-ethylhexyl phthalate (DOP), dinonyl phthalate, diisononyl phthalate, Didecyl phthalate, diisodecyl phthalate, diundecyl phthalate, dilauryl phthalate, butylbenzyl phthalate, octylbenzyl phthalate, butyloctyl phthalate, dibasic acid esters such as dibutyl adipate, di-n-hexyl adipate, Adipic acid di2-
Ethylhexyl, Didecyl adipate, Diisodecyl adipate, Octyldecyl adipate, Dibutyldiglycol adipate, Di-2-ethylbutyl azelate, Di-2-ethylhexyl azelate, Dibutyl sebacate, Di2-ethylhexyl sebacate, Sebacate Examples thereof include butylbenzyl, dioctyl sebacate, dibutyl maleate, di-2-ethylhexyl maleate, and dibutyl fumarate. Furthermore, triethylene phosphate, tributyl phosphate, trioctyl phosphate, phosphate esters such as triphenyl phosphate, triethyl borate, tributyl borate, borate esters such as trioctyl borate, calcium stearate, magnesium stearate, Higher fatty acid salts such as aluminum stearate can also be used.

The molecular weight of the compound (c) is 2,000 or less, preferably 300 to 1,000. If the molecular weight is less than 300, it becomes difficult to impart appropriate strength to the molded product. If the molecular weight exceeds 1,000, moldability and degreasing property deteriorate, and if it exceeds 2,000, precision molding is performed. This is because it is impossible to mold the product, the degreasing time becomes extremely long, and it becomes impossible to efficiently manufacture the precision component having a complicated shape, which is the object of the present invention, with high accuracy.
The compound (c) is compounded in the range of 20 to 80% by weight.
When the compounding ratio of the low molecular weight component is less than 20% by weight, the compound has poor fluidity and moldability and is not preferable, and when the compounding ratio exceeds 80% by weight, degreasing becomes difficult, which is not preferable.

The acid anhydride structure-containing olefin (co) polymer in the present invention is contained in the binder in an amount of 3 to 80% by weight. When it is less than 3% by weight, the powder surface cannot be sufficiently covered with the olefin (co) polymer, and the wettability between the powder and the binder is not improved. As a result, defects such as low strength of the molded body and easy cracking, deformation during degreasing, and swelling and cracking occur. If it exceeds 80% by weight, the compound viscosity becomes high, the moldability is deteriorated, and cracks and blister defects are likely to occur during degreasing.

The olefin (co) polymers other than the acid anhydride structure-containing olefin (co) polymer in the present invention are
In order to shorten the degreasing time, it is better to be contained in the binder, and the content is 70% by weight or less. If it exceeds 70% by weight, the compound viscosity becomes high, the moldability is deteriorated, and cracks and blister defects are likely to occur during degreasing.

Of the resin components (a) and (b),
The preferable blending ratio in the binder is an amount capable of sufficiently covering the powder surface with the acid anhydride structure-containing olefin-based (co) polymer, that is, 10 to 70% by weight, and other olefin-based (co) polymers The polymer is 10 to 60% by weight, the sum of the former and the latter resin components is 20 to 70% by weight, and the balance is (c) an organic compound having a molecular weight of 2,000 or less.

Further, additives such as an antioxidant, a flow agent, and a surfactant may be added to the powder injection molding composition of the present invention as appropriate.

In order to avoid defects such as sagging and swelling during the degreasing step, it is preferable to blend two or more kinds of components (c) having different boiling points. This is because defects during the degreasing process occur when low-molecular components are removed at a temperature lower than the temperature at which the resin decomposes. Therefore, in order to avoid these defects, the low-molecular components of (c) are removed. This is because it is better to mix two or more kinds of the above to make a wide temperature range for removing.

The method for kneading the sinterable powder and the binder of the present invention is not limited, and a Henschel mixer, a Banbury mixer, a kneader, a roll mill, a single screw extruder, 2
Any material that can knead the binder and the powder, such as an axial screw extruder, can be used.

The compound obtained by kneading the binder of the present invention and the sinterable powder is crushed or granulated to obtain a molding material. A general injection molding machine for thermoplastics can be used as the injection molding machine. Injection molding is carried out at an injection temperature in the range of 100 ° C to 250 ° C. However, if the injection temperature is too high, the binder component will be significantly deteriorated and the moldability and degreasing property of the recycled material will change. The range of 100 ° C to 180 ° C is preferable.

Degreasing can be performed by either a heat degreasing method or a solvent extraction method. In the case of the heat degreasing method, it is preferable to carry out in a stream of nitrogen, argon, hydrogen or the like, or to remove the binder under reduced pressure. The rate of temperature increase depends on the thickness of the molded product, but the temperature is raised in the range of 10 ° C / h to 100 ° C / h. The maximum temperature for degreasing is preferably 450 ° C to 800 ° C. If the maximum degreasing temperature is lower than 450 ° C., the resin components (a) and (b) cannot be decomposed and removed efficiently, which is not preferable.
Further, even if the temperature is raised to 800 ° C. or higher, the decomposition and removal rates of the resin components of (a) and (b) do not change so much, and conversely the degreasing time is extended.

In the case of the solvent extraction method, one or more low molecular weight components other than the acid anhydride structure-containing olefin (co) polymer are extracted and removed from the molded product with a solvent, and then heated and degreased. Then, the remaining binder component is removed. When solvent degreasing is used, the compound (c) is preferably soluble in a solvent that does not dissolve the resin component (a).

The sintering step may be carried out subsequently in the same furnace after the degreasing step is completed, or may be carried out in a different furnace after taking out the degreased body from the degreasing furnace. Sintering is from 800 ℃ to 2,0
The sintering is carried out at a temperature of 00 ° C. for 10 minutes to 6 hours. The sintering conditions and the sintering atmosphere are appropriately selected and determined according to the material of the sinterable powder used and the powder characteristics.

Next, the features of the binder and compound of the present invention will be described.

As will be described later in Examples, EVA, EE
Compared to those conventionally used as a binder for A, polyethylene, polypropylene, polystyrene, acrylic resin, etc., the resin containing the acid anhydride of the present invention has an organic substance that cannot be washed off with hot toluene on the powder surface and carbon. Converted to amount, 0.02% to 0.08 in the case of metal powder
%, And in the case of ceramic powder, it is 0.4 to 0.55% higher.
The interaction between the hydrophilic powder and the resin component in the binder is considered to be van der Waals force in the case of PE, PP, PS having no functional group, and EVA, EEA having a functional group,
In the case of acrylic resin, hydrogen bonds are considered, but these bonds are weak bonds that are washed away with hot toluene. However, in the binder composition of the present invention, the polymer is fixed to the powder surface by a strong bond that cannot be cut with hot toluene. Perhaps the acid anhydride part reacts with the hydroxyl group on the surface of the sinterable powder to form a strong bond such as a covalent bond, and as a result, a polymer is grafted on the surface of the sinterable powder. Be done. The characteristics of the present invention are considered to be due to the graft polymer firmly fixed to the surface of the sinterable powder. That is, the unsaturated dicarboxylic acid anhydride forms a hydrogen bond with the hydroxyl group on the powder surface like the conventionally used ethylene-vinyl acetate copolymer (EVA) and ethylene-ethyl acrylate copolymer (EEA). Instead, it seems that they are more firmly fixed by a covalent bond as in Formula 3.

[0052]

[Chemical 16] Further, the acid anhydride structure-containing olefin system (co) of the present invention
Since the polymer is an olefin-based polymer, it has a low melt viscosity, easily penetrates into the gaps of the agglomerated sinterable powder, promotes powder dispersion, and at the same time grafts on the surface of the sinterable powder.

It is disclosed in JP-A-59-182266 and JP-A-57-38896 that a resin containing an unsaturated dicarboxylic acid anhydride can be used as a binder for sinterable powder molding. However, these do not focus on the interaction with the sinterable powder as described above, the molding material is a slurry such as used in the doctor blade method, and the properties of the sinterable powder injection molding compound are Are different. The present invention presents a resin obtained by copolymerizing an unsaturated dicarboxylic acid anhydride based on the above-mentioned principle as a binder for sinterable powder injection molding, and is completely novel.

On the other hand, acid anhydride-modified styrenic resins such as acid anhydride-modified polyalphamethylstyrene or styrene-maleic anhydride copolymers disclosed in JP-A-63-252951, JP-A-62- Since the acid anhydride-modified resin disclosed in Japanese Patent No. 12658 has a high melt viscosity, a large amount of a solvent or a plasticizer is required to obtain a compound viscosity capable of obtaining a good molded product. For this reason, the strength of the molded product is reduced, and the molded product is swollen and deformed during degreasing. Further, since the acid anhydride-modified thermoplastic resin of the present invention does not have an ethylenic unsaturated bond which is present in the acid anhydride-modified resin disclosed in JP-A-62-12658, the viscosity and the like during kneading or recycling of molded articles Stable quality is maintained with little change in physical properties.

This will be described more specifically. The dispersibility of the sinterable powder during kneading, the fluidity of the compound, and the strength of the compact are greatly affected by the wetting of the surface of the sinterable powder and the binder, that is, the strength of interaction. The chemical covalent bond is one of the strongest bonds, and the acid anhydride structure-containing olefin-based (co) polymer according to the present invention is an unsaturated dicarboxylic acid anhydride capable of covalently bonding with a hydroxyl group on the surface of the sinterable powder. Since it is a resin obtained by copolymerizing the products, it seems that it became a binder with excellent performance for sinterable powder injection molding.

That is, when the acid anhydride structure-containing olefinic (co) polymer of the present invention is used as a binder component, the sinterable powder is very well dispersed at the time of kneading, and a uniform raw material compound is obtained in a short time. In addition, the fluidity is not deteriorated due to the remaining aggregated powder, and the amount of the binder is small. Further, the wetting with the sinterable powder has a high strength of the molded body due to the strong covalent bond, the crack of the molded body is eliminated, and the deformation in handling is small. Even when degreasing, since the acid anhydride structure-containing olefin-based (co) polymer and the powder are well wetted, there are few degreasing defects, and there is almost no deformation of the molded body compared to the binder used conventionally,
Degreasing defects such as blisters, voids and cracks do not occur. Further, since the interface between the sinterable powder and the binder is firmly fixed, the strength of the molded body is high, and cracking and deformation during molding and during transportation of the molded product are small.

In the present invention, one of poly (meth) acrylic acid ester, polystyrene, and styrene- (meth) acrylic acid ester copolymer together with the above-mentioned olefinic (co) polymer having an acid anhydride structure as a binder component, or Mix two or more. Since these polymers and copolymers are excellent in depolymerization, the occurrence of degreasing defects at the resin decomposition and removal temperature is suppressed.

When only an olefin (co) polymer having an acid anhydride structure is used as a resin component, the resin is decomposed and removed. 3
In the temperature range of 00 ° C or higher, the degreased body may have defects such as cracks and surface peeling. This is because there is only one resin component and the decomposition starts rapidly at a certain temperature. Thermal decomposition of polyethylene, polypropylene, ethylene-based copolymers, propylene-based copolymers, etc.
While it rapidly starts from 400 ° C. by random cleavage, poly (meth) acrylic acid ester, polystyrene,
Styrene- (meth) acrylic acid ester copolymer is 30
Decomposes gradually from 0 ° C to 350 ° C by depolymerization. Therefore, in the present invention, these resins are blended to increase the resin decomposition temperature and suppress degreasing defects. This makes it possible to set the temperature rise during degreasing faster,
The degreasing time can be shortened.

Furthermore, when an ethylene (co) polymer or a propylene (co) polymer is used as the acid anhydride structure-containing olefin (co) polymer, when the molded article has a thin wall, for example, at the stage of the molded article. Although cracks easily occur, this can also be improved by blending a poly (meth) acrylic acid ester, polystyrene, and a styrene- (meth) acrylic acid ester copolymer. In particular, if a plasticizer such as phthalic acid ester or adipic acid ester is used as the low molecular weight component, the fluidity is improved and the moldability is remarkably improved.

However, since the poly (meth) acrylic acid ester, polystyrene, and styrene- (meth) acrylic acid ester copolymer do not wet well with the sinterable powder, the acid anhydride structure-containing olefin-based copolymer The blending ratio is preferably 70% or less so as not to impair the effect.

In the present invention, a component having a lower molecular weight than the resin components (a) and (b) described above is added as another binder component. This is because it is difficult to degrease the binder only with the resin component, but it also has the meaning of further improving the fluidity during molding.

As described above, the present invention has been found as a result of improving the moldability and degreasing property while making the best use of the performance of the acid anhydride structure-containing olefin (co) polymer. It is much better than anything.

[0063]

EXAMPLES The present invention will be specifically described below based on examples. First, raw materials and evaluation methods used in the examples will be described. 1) Binder raw material Table 1 shows the raw material monomer components of the resin used as the binder raw material, the copolymerization ratio (wt%) and the average molecular weight thereof. The paraffin wax used had an average molecular weight of 380. Other components include dibutyl phthalate (DB
P), dioctyl phthalate (DOP), stearic acid, stearyl alcohol, and behenic acid amide were used. 2) Amount of organic substances bonded to metal powder, ceramics powder and cermet powder The binder was removed from the crushed compound with a Soxhlet extractor using toluene, and the amount of carbon in the separated powder was measured. This difference between the carbon amount and the carbon amount of the raw material powder before kneading (powder carbon increase amount) is due to the resin that is not removed from the powder by toluene, and the strength of interaction between the binder and the powder is evaluated depending on the difference. can do. 3) Degreasing test The compound was injection-molded into a trapezoidal test piece having a flat portion 1 and supporting portions 2 and 2 having a thickness of 4 mm shown in FIG. The test piece was heated from normal temperature to 250 ° C. under reduced pressure in 12 hours and kept at 250 ° C. for 1 hour. Thereafter, nitrogen was introduced, and thereafter, the temperature was raised to 500 ° C. in a nitrogen stream in 1 hour, and the temperature was maintained for 1 hour and then cooled. FIG. 2 is a cross-sectional view showing the molded body before degreasing (a) and the molded body after degreasing (degreased body (b)), and the deformation at the center of the flat surface portion 1 of the molded body before and after the degreasing process as the degreasing deformation amount. The quantity was measured. The amount of deformation is the amount of deformation due to its own weight during degreasing. Further, the degreased body was observed for the presence of degreasing defects such as swelling and cracks. (Invention Examples 1 to 7 and Comparative Examples 1 to 5) Water atomized stainless steel powder having an average particle size of 9.5 μm was used as the metal powder, and injection molding compounds were prepared according to the formulations shown in Tables 2 and 3. The amount of the binder added was all 9.8 parts by weight with respect to 100 parts by weight of the stainless steel powder.

The kneading was performed with a pressure kneader. After heating the pressure kneader to 140 ° C., the binder component was added and melted, the metal powder was gradually added and the whole amount was added and kneaded for 1 hour, and then the kneaded material was crushed to obtain a raw material compound for injection molding. .. The obtained raw materials were subjected to the measurement of the amount of organic substances bound to the powder and the degreasing test by the method described above. The results are also shown in Tables 2 and 3.

Inventive Examples 1 to 3 use ethylene-maleic anhydride-modified PE having a copolymerization ratio of maleic anhydride according to the present invention of 3% by weight as a binder, and
Polystyrene is blended in No. 2 and polybutylmethacrylate is blended in Inventive Example 3. Paraffin wax, stearic acid, dibutyl phthalate (DB
P) is blended to form a binder. Since the respective compounding ratios were also appropriate, the molded articles obtained by injection molding of these compounds were sound, and the appearance of the degreased body was not swollen or found defects such as cracks. Further, the amount of deformation of the degreased body is also very small. Inventive Example 4 is an example in which maleic anhydride-modified EVA and polystyrene are used, and Inventive Example 5 is an example in which maleic anhydride-modified EEA and polybutyl methacrylate are used as binders. These examples also use an olefin copolymer containing an acid anhydride structure as a binder, and since it also contains polystyrene or polybutylmethacrylate, it was a binder excellent in moldability and degreasing property. Inventive Examples 6 and 7 are formulation examples in which stearyl alcohol, behenic acid amide, dioctyl phthalate (DOP) and the like were used as the low-molecular component, and these are also very excellent in moldability and degreasing property.

Comparative Examples 1 and 2 are maleic anhydride-modified PEs having the same maleic anhydride copolymerization ratio of 3% by weight as in the invention examples.
However, in Comparative Example 1, since the compounding ratio was 2% by weight and less than 3% by weight, maleic anhydride-modified P was used.
The excellent binder effect of E was not exhibited and the molded body was brittle and cracked. Further, in Comparative Example 2, the total compounding ratio of paraffin wax, stearic acid, and DBP, which are organic compounds having a molecular weight of 2000 or less, is 15% by weight and less than 20% by weight, resulting in poor fluidity and insufficient filling during molding and degreasing. The body was greatly deformed.

Comparative Examples 3 to 5 are the binders conventionally used as the binder, which are blended with EVA (ethylene-vinyl acetate copolymer), EEA (ethylene-ethyl acrylate copolymer) and PE (polyethylene). It was used. Comparative Examples 8 and 9 are EVA and EE, respectively.
A is used as a resin component. These had excellent fluidity, sound molded bodies, and good moldability. However, both were swollen and denatured during degreasing. Comparative Example 5 is a PE-wax-stearic acid binder. Those using this binder were brittle and cracked in the molded product, and a good molded product could not be obtained.

Regarding the increase amount of powder carbon, EVA,
Increase in powder carbon due to EEA and PE is 0.01-
While it is 0.03% (Comparative Examples 3 to 5), the residual carbon amount of the separated powders of Invention Examples 1 to 7 using the acid anhydride structure-containing copolymer is 0.06 to 0.09%. It is high, and it can be seen that the binding between the binder and the powder is strong. As described above, it is considered that this is due to the bond between the powder surface and maleic anhydride as shown in Formula 3, which is a concrete proof that the resin presented by the present invention becomes a binder excellent in wettability with powder. ..

(Invention Example 8 and Comparative Examples 6 and 7) Table 4 shows examples of blending of a binder for solvent extraction. The powder used was the same as in Invention Examples 1 to 7, and kneading conditions and injection molding were performed in the same manner as in Invention Examples 1 to 7. For degreasing, the injection-molded body was held in normal heptane for 4 hours, then taken out and subjected to heat degreasing. In the heating degreasing, the temperature was raised from room temperature to 500 ° C. in 6 hours in a nitrogen stream, the temperature was maintained for 1 hour and then cooled.

Inventive Example 8 is one in which a binder was blended using a maleic anhydride-modified PP having a maleic anhydride content of 3% by weight. The molded body obtained by molding this compound had good filling and no cracking. The degreased body (solvent degreased body) obtained by holding this in normal heptane for 4 hours showed no defects, and the appearance of the heated degreased body was also good. Comparative Example 6 is a binder for solvent degreasing in which polyethylene and hydrogenated palm oil are blended, and Comparative Example 7 uses polypropylene in place of polyethylene. The compounds of these comparative examples had poor moldability and cracked the molded product. Furthermore, the solvent degreased body was very brittle and cracked during handling during charging into the degreasing furnace.

[0071]

[Table 1]

[0072]

[Table 2]

[0073]

[Table 3]

[0074]

[Table 4]

(Invention Examples 9 to 10 and Comparative Examples 8 to 12) Table 5
A ceramic powder injection molding compound was produced using the binder having the composition shown in. First, after heating the pressure kneader to 140 ° C., 12 parts by weight of the binder is charged and melted, and 94% by weight of silicon nitride powder having an average particle diameter of 1.0 μm and 3% by weight of yttrium oxide powder having an average particle diameter of 0.4 μm. %, And 100 parts by weight of a mixed powder of 3% by weight of aluminum oxide powder having an average particle size of 0.3 μm was gradually added. After all the powder was added and kneaded for 1 hour, the kneaded product was taken out, cooled and pulverized. The amount of organic substances bound to the powder and the degreasing test were conducted by the above-mentioned method. The results are shown in Table 5.

In Comparative Example 8, the wettability between the powder and the binder was poor, and the powder and the binder separated during injection molding, and molding was impossible. When EVA and EEA were used (Comparative Examples 9 and 10), good molded products were obtained, but blistering occurred during degreasing and significant deformation occurred. However, as shown in Inventive Examples 9 and 10, when a resin containing an acid anhydride structure was used, the moldability was good,
The degreased body had no defects such as swelling and cracks, and the degreasing deformation was small. Further, the increased amount of powdered carbon was 0.48 to 0.57 in Invention Examples 9 and 10 using a resin containing an acid anhydride structure.
It was found that the wetting of the powder and the binder was good, which was as high as wt%. In the invention examples 9 and 10 and the comparative examples 8 to 10, the injection molding temperature was optimally 150 ° C., but in the comparative example 11, 1
The optimum temperature was 80 ° C. and 200 ° C. in Comparative Example 12. Further, in both Comparative Examples 11 and 12, cracks and swelling were remarkable in the degreased body.

(Invention Examples 11 to 13 and Comparative Examples 13 to 17)
Invention Examples 9 and 1 except that the binder composition shown in Table 6 was used.
Kneading, pulverization, injection molding, and degreasing test were performed in the same manner as in No. 0.
The results are shown in Table 6. Comparative Example 13 uses a resin containing an acid anhydride structure as a binder component, but the compounding ratio is 1
Since it was less than 3% by weight and less than 3% by weight, cracks occurred in the molded body. In Comparative Examples 14 and 15, the molecular weight is 200.
Paraffin wax, which is an organic compound of 0 or less, DB
The total compounding ratio of P and DOP is 10% by weight, 15% by weight and 2
Since it was 0% by weight or less, the moldability was poor and the deformation during degreasing was remarkable. In Comparative Example 16, the degreasing property was poor because the compounding ratio of the components having a molecular weight of 2000 or less was 85% by weight and 80% by weight or more. In Comparative Example 17 using a polyethylene wax having a molecular weight of 3000, the degreased body was swollen and cracked and was significantly deformed. On the other hand, invention examples 11 to 1
In No. 3, both moldability and degreasing property were good, and deformation during degreasing was small.

(Invention Example 14) Maleic anhydride-modified PP /
Hydrogenated linseed oil / DBP = 50/30/20 (weight ratio)
Kneading, pulverization, and injection molding were performed in the same manner as in Inventive Example 9 except that the binder having the composition ratio of 1. was used. The molded body was dipped in heptane for 12 hours to extract most of the plasticizer, and then vacuum dried for 30 minutes. The dried molded body was heated in a nitrogen stream from room temperature to 500 ° C. in 4 hours, kept at 500 ° C. for 1 hour and then cooled. The appearance of the molded body, the appearance of the solvent degreased body, and the appearance of the thermally degreased body were good without any defects, and the deformation was 10
It was as small as μm. Then, the degreased body was placed under argon gas for 2
The temperature was raised at 00 ° C./hour, and the temperature was kept at 1,800 ° C. for 6 hours for sintering. The density of the sintered body was 98% of the theoretical value, and the appearance was excellent.

(Comparative Example 18) The same procedure as in Example 17 was carried out except that PP was used instead of the maleic anhydride-modified PP, but some of the molded articles were cracked during injection molding, and cracked during thermal degreasing. Occurs and the deformation is 3,500
It was as large as μm.

(Invention Examples 15 to 17) A binder comprising 33% by weight of maleic anhydride-modified EEA, 22% by weight of PBMA, 20% by weight of paraffin wax (mp 55 ° C.) and 25% by weight of DBP was used. Using the ceramic powder and the amount of binder shown in Table 7, kneading in the same manner as in Inventive Example 9,
Molded and degreased. The degreased body was heated at a temperature of 200 ° C./hour from room temperature in an argon stream and sintered at the temperature and time shown in Table 7. In each case, a good sintered product without defects was obtained.

[0081]

[Table 5]

[0082]

[Table 6]

[0083]

[Table 7]

[0084]

INDUSTRIAL APPLICABILITY The present invention uses a binder component, metal powder,
A composition for sinterable powder injection molding in which an interface between a metal powder, a ceramic powder or a cermet powder and a binder is strongly adhered because an acid anhydride-modified thermoplastic resin that firmly adheres to a ceramic powder or a cermet powder is used. was gotten. Therefore, the sinterable powder injection molding composition of the present invention has good moldability, in addition to manufacturing advantages such as short degreasing time, and high strength, cracks during molding,
With the advantage that deformation, blistering, and cracking during degreasing can be dramatically reduced, complex precision parts can be efficiently produced with high-precision dimensions.

[Brief description of drawings]

FIG. 1 is a diagram showing dimensions of a test piece manufactured in an example.

2A and 2B are diagrams illustrating measurement of a deformation amount, in which FIG. 2A is a molded body and FIG. 2B is a degreased body.

[Explanation of symbols]

 1 Flat part 2 Support part

Claims (7)

[Claims] (A) 3 to 80% by weight of an olefin polymer and / or copolymer having at least one acid anhydride structure in the molecule of a polymer represented by the following formula 1, [However, R ¹ is a hydrogen atom or a methyl group, and R ² is one kind of group selected from the group consisting of a hydrogen atom and an alkyl group having 1 to 3 carbon atoms. (C) A binder for sinterable powder injection molding, which contains 20 to 80% by weight of an organic compound having a molecular weight of 2,000 or less. (A) 3 to 80% by weight of an olefin polymer and / or copolymer having at least one acid anhydride structure in the molecule of the polymer represented by the following formula 1, and [However, R ¹ is a hydrogen atom or a methyl group, and R ² is one kind of group selected from the group consisting of a hydrogen atom and an alkyl group having 1 to 3 carbon atoms. ] (B) 70% by weight or less of a polymer and / or copolymer other than (a) above, and (c) a powder injection characterized by containing 20 to 80% by weight of an organic compound having a molecular weight of 2,000 or less. Binder for molding. 3. An olefinic copolymer 3 having (a) one or more acid anhydride structures in the molecule of the polymer represented by the following formula 2.
~ 80% by weight, and [Wherein R ¹ represents a hydrogen atom or a methyl group, R ² represents a hydrogen atom, one kind of group selected from the group consisting of alkyl groups having 1 to 3 carbon atoms, and R ³ represents (R ⁵ is a group selected from a hydrogen atom, a halogen atom, and an alkyl group having 1 to 4 carbon atoms). (C) A binder for sinterable powder injection molding, which contains 20 to 80% by weight of an organic compound having a molecular weight of 2,000 or less. (A) Olefin-based copolymer 3 having at least one acid anhydride structure in the molecule of the polymer represented by the following formula (2):
~ 80% by weight, and [Wherein R ¹ represents a hydrogen atom or a methyl group, R ² represents one group selected from the group consisting of a hydrogen atom and an alkyl group having 1 to 3 carbon atoms, and R ³ represents (R ⁵ is a group selected from a hydrogen atom, a halogen atom, and an alkyl group having 1 to 4 carbon atoms). ] (B) 70% by weight of an olefin-based polymer and / or copolymer other than (a) above, and (c) 20-80% by weight of an organic compound having a molecular weight of 2,000 or less. Binder for binding powder injection molding. 5. The (b) the olefin polymer and / or copolymer other than the above (a) is a copolymer of one or more of acrylic acid ester, methacrylic acid ester, and styrene. Homopolymer and /
Alternatively, the binder for powder injection molding according to claim 2 or 4, which is a copolymer. 6. A sinterable powder injection molding composition comprising the powder injection molding binder according to any one of claims 1 to 5 and a metal powder, a ceramic powder or a cermet powder. 7. The sinterable powder injection molding composition according to claim 6, wherein the metal powder, the ceramic powder or the cermet powder has an average particle diameter of 0.01 to 1,000 μm.