JPH0664965A - Binder for injection molding sinterable powder and composition - Google Patents

Abstract

PURPOSE:To obtain a binder for injection molding sinterable powder and to provide a composition for injection molding sinterable powder, having excellent moldability and strength. CONSTITUTION:A binder B for injection molding powder comprises in organic compound A having <=2,000 molecular weight, containing one or more isocyanate groups in the molecule and an organic compound except the organic compound A. The binder component B comprises a thermoplastic resin and an organic compound having <=2,000 molecular weight, containing no isocyanate group, the thermoplastic resin contained in the binder B contains one or more functional groups to be reacted with isocyanate group in the molecule and the binder composition A preferably contains two or more isocyanate groups to give a binder for injection molding sinterable powder. A composition for injection molding comprises metal powder, ceramics powder and cermet powder and is treated with the binder component A and then mixed with the binder component B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding composition of ceramic powder, cermet powder or metal powder (hereinafter referred to as sinterable powder) which is excellent in moldability and shape retention during degreasing. Furthermore, the invention relates to a method for producing these powder injection molding compositions.

[0002]

2. Description of the Related Art A ceramics, cermet or metal powder injection molding method is a method in which a kneaded material (compound) of ceramics, cermet or metal fine powder and a binder is injection-molded in a mold, and the resulting molded body is debindered ( Degreasing)
It is a technology that is sintered and made into products, and is suitable for mass production of small and complex shaped ceramics, cermets or metal parts.

As a binder for sinterable powder injection molding,
Resin, wax, plasticizer, lubricant, etc. are used,
The following two points are important properties required for the binder. It can be easily injection-molded and does not cause molding defects such as cracks, deformation, voids and blister in the resulting green molded product. It can be easily degreased in a short time, and the resulting degreased body should not have degreasing defects such as cracks, deformation, and blister.

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 composed mainly 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 has a high viscosity, the moldability is deteriorated, and the strength of the green molded body is drastically reduced, and cracks are easily generated.
Furthermore, cracks and blisters easily 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 these resins have poor wettability with ceramics, cermets, or metal powders, so Liquidity is extremely poor,
There are problems that injection molding is difficult and the strength of the obtained molded product is 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. Methods of introducing it into the ingredients are known. Specific examples of the former include silane coupling agents, titanate coupling agents (Japanese Patent Publication No. 59-41949),
Aluminum chelate compound (JP-A-61-24294
No. 7), surface treatment of sinterable powder is known. As a specific example of the latter, an example using a surfactant (JP-A-59-182267, JP-A-59-3505).
No. 8), carboxyl groups, esters, amino groups,
Use of a binder component introduced with a functional group that interacts with the surface of the sinterable powder such as a hydroxyl group, for example, ethylene-
Vinyl acetate copolymer (EVA) (Japanese Patent Laid-Open No. 52-1179)
09, JP-A-58-135173), ethylene-ethyl acrylate copolymer (EEA) (JP-A-59-121150), acrylic acid-based copolymer (JP-A-02-283660). Japanese Patent Laid-Open No. 01-26
1265), ethylene-vinyl alcohol copolymer (JP-A-63-25266), stearic acid (JP-B-36-7883), behenic acid (JP-A-02-267156), and the like. ing. 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 good molding. I can also get a body.

[0007]

However, in the method of surface-treating the sinterable powder, the surface-treating agent is expensive, the number of steps for the surface-treating is increased by one, and the surface-treating agents titanium, silicon and aluminum are burned. It has the drawback that it remains in the body and adversely affects the physical properties. In addition, surfactants and higher fatty acids,
Higher alcohols exist not only in the interface between the sinterable powder and the binder, but also in the binder, and significantly lower the softening point of the binder, so that defects such as deformation and swelling are likely to occur during heating degreasing. Polymers with introduced functional groups that interact with the surface of the sinterable powder (eg EVA, EEA)
Since it has a high viscosity, it cannot penetrate into the gaps of the agglomerated powder, and the sinterable powder is difficult to disperse. The aggregated powder is stably present in the binder and causes cracks and blisters during degreasing by heating. Furthermore, whichever method is used, it takes a long time to degrease by heating so as not to deform, and if the degreasing time is shortened, it causes swelling and deformation.

[0008]

The present inventors have found that the wettability with the sinterable powder is good, the injection moldability is also good, cracks, swelling and deformation do not easily occur during degreasing, and the physical properties of the sintered body are improved. As a result of diligent search for a composition (compound) that does not have an adverse effect, the inventors have found that the object can be achieved by treating the surface of the sinterable powder with an isocyanate compound, and have reached the present invention.

That is, the present invention provides (A) a molecular weight of 200.
Provided is a binder for sinterable powder injection molding, which comprises an organic compound having 0 or less and one or more isocyanate groups in the molecule, and (B) an organic compound other than (A).

Further, there is provided a sinterable powder injection molding binder in which the binder component (B) contains a thermoplastic resin having a molecular weight of 2000 or more.

The binder component (B) also provides a sinterable powder injection molding binder containing an organic compound having a molecular weight of 2000 or less, which does not contain an isocyanate group, and a thermoplastic resin.

The thermoplastic resin contained in the binder component (B) has at least one functional group that reacts with an isocyanate group in the molecule, and the binder component (A) is
Provided is a sinterable powder injection molding binder having two or more isocyanate groups.

The binder component (A) is 0.01
10 to 10 parts by weight of the binder component (B) is 2 to 100
A binder for sinterable powder injection molding, which is part by weight, is provided.

Also provided is a sinterable powder injection molding composition comprising a sinterable powder injection molding binder and a metal powder, a ceramics powder or a cermet powder.

The metal powder, ceramic powder or cermet powder has an average particle size of 0.1 to 1000 μm.
Which is a sinterable powder injection molding composition.

A composition for sinterable powder injection molding, characterized in that the metal powder, ceramic powder or cermet powder is treated with the binder component (A) and then the binder component (B) is mixed. A method for manufacturing the same is provided.

As the ceramics, cermet or metal powder used in the present invention, all known ones can be used.
Specific examples include ceramics such as aluminum oxide, silicon oxide, zirconium oxide, titanium oxide, beryllium oxide, magnesium oxide, niobium oxide,
Tantalum oxide, molybdenum oxide, manganese oxide, tungsten oxide, vanadium oxide, technetium oxide, rhenium oxide, cobalt oxide, nickel oxide, ruthenium oxide, rhodium oxide, cadmium oxide, thallium oxide, germanium oxide, tin oxide, lead oxide, antimony oxide ,
Bismuth oxide, tellurium oxide, indium oxide, barium oxide, gallium oxide, yttrium oxide, calcium oxide, strontium oxide, lanthanum oxide, selenium oxide,
Scandium oxide, actinium oxide, thorium oxide,
Hafnium oxide, chromium oxide, palladium oxide, osmium oxide, zinc oxide, iron oxide, lead titanate, barium titanate, lead zirconate, strontium zirconate, lead zirconate titanate, magnesium titanate, manganese titanate, titanate. Iron, cobalt titanate, nickel titanate, silicon carbide, boron carbide, aluminum carbide,
Tungsten carbide, titanium carbide, zirconium carbide, hafnium carbide, molybdenum carbide, tantalum carbide, chromium carbide, vanadium carbide, silicon nitride, aluminum nitride, boron nitride, titanium nitride, titanium boride, zirconium boride, lanthanum boride, and 2 silicate Examples thereof include molybdenum chloride, cadmium sulfide, zinc sulfide, and a mixture of two or more thereof. Examples of the metal powder include iron, nickel, aluminum, copper, titanium, zirconium, zinc,
Chromium, molybdenum, tungsten, beryllium, germanium, cobalt, silicon, scandium, yttrium, lanthanide, actinide, hafnium, thorium, vanadium, tantalum, manganese, technetium,
Rhenium, ruthenium, iridium, rhodium, palladium, osmium, indium, platinum, gold, silver, cadmium, thallium, tin, lead, arsenic, antimony, bismuth, tellurium, polonium and their alloys or mixed powders such as iron-nickel, Examples thereof include stainless steel, iron-silicon, iron-boron, iron-cobalt, and iron-cobalt-vanadium. As cermets, tungsten carbide powder / cobalt powder, aluminum oxide powder / aluminum powder, iron powder / silicon powder, iron Examples include powders / boron powders, metal powders / ceramics powders such as silicon nitride powders / yttrium oxide powders / aluminum oxide powders, alloys of the above ceramics and metals such as metal powders / nonmetal powders, or mixed powders. .

The shape and particle size of these sinterable powders are not particularly limited, but a spherical particle size of 0.01 to 1000 μm, preferably 0.1 to 50 μm. The smaller the particle diameter of the sinterable powder, the better the fluidity 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 the fine powder. Also, 1000 μm
If it exceeds, the fluidity of the compound deteriorates and injection molding becomes substantially impossible.

The binder component (A) used in the present invention has a molecular weight of 200 having at least one isocyanate group in the molecule.
Specific examples of 0 or less organic compounds (hereinafter referred to as isocyanate compounds) include C _{1 to} C ₈ lower alkyl isocyanates, C _{10 to} C ₁₈ aliphatic hydrocarbon isocyanates, monocyclic or Isocyanates of condensed ring aromatic hydrocarbons, in addition, those carbon atoms are halogen, C ₁ -C
Isocyanate having a substituent such as ₆ lower alkyl group, especially methyl isocyanate, ethyl isocyanate, n-propyl isocyanate, isopropyl isocyanate, n-butyl ester isocyanate, n-heptyl isocyanate, octadecyl Isocyanate, Phenyl Isocyanate, Chlorophenyl Isocyanate,
Monoisocyanate compounds such as dichlorophenyl isocyanate, further, paraphenylene diisocyanate, tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, dianisidine diisocyanate, orthoxylylene diisocyanate, tetramethylene diisocyanate , Metaxylylene diisocyanate, 1,5-naphthalene diisocyanate, hexamethylene diisocyanate, dodecamethylene diisocyanate, dimeryl diisocyanate, trans vinylene diisocyanate, N, N'-di (p-isocyanate Natophenyl) carbodiimide, tolylene diisocyanate 2
N, N '-(4,4'-dimethyl-3,3', which is a monomer
-Diphenyldiisocyanato) urezion, N, N'-
Di (3-isocyanato-4-methylphenyl) urezion, 2,6-diisocyanatomethylcaproate, cyclobutane-1,3-diisocyanate, cyclohexane-1,3-diisocyanate, cyclohexane-1,4
-Diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, 1,4-bis (isocyanatomethyl) cyclohexane, dicyclohexylmethane diisocyanate, 1,3-bis (2-isocyanato-2-propyl) benzene , 1,4-bis (2-isocyanato-2)
-Propyl) benzene, 1-isocyanato-3,3,5
-Trimethyl-5-isocyanatomethylcyclohexane and other diisocyanate compounds, triphenylmethane triisocyanate and tolylene diisocyanate trimer 4,4 ', 4 "-trimethyl-3,3', 3" −
Triisocyanato-2,4,6-triphenyl _{cyanurate, OCN- (CH 2) 6 -N} [CNH (CH 2) 6
NCO] ₂ ,

[Chemical 1] Examples thereof include triisocyanate compounds such as tris (4-phenylisocyanato) thiophosphate, polymethylene polyphenyl polyisocyanate, and the like.

The isocyanate compound having a molecular weight of 2,000 or less quickly penetrates into the gaps of the agglomerated powder during kneading with the sinterable powder to disperse the sinterable powder and react with hydroxyl groups on the surface of the sinterable powder. The surface is made hydrophobic and the wettability with the binder is improved. However, the molecular weight is 2,000
An isocyanate compound having a viscosity of more than 10% is not preferable because the viscosity of the compound becomes high and the dispersion of the agglomerated powder does not proceed easily.

The binder component (B) used in the present invention includes:
It includes thermoplastic resins, thermosetting resins, waxes, plasticizers, lubricants and the like.

Examples of thermoplastic resins include PE, low density polyethylene (LDPE), PP, polyisobutylene,
Ethylene-propylene copolymer, ethylene-butene copolymer, polymethylpentene-1, ethylene-methylpentene-1 copolymer, styrene-ethylene-butylene-styrene copolymer, ethylene-vinyl acetate copolymer (EV
A), ethylene-acrylic acid copolymer (EAA), EE
A, polyolefins such as ethylene-methyl (meth) acrylate copolymer, chlorinated PE, ethylene-carbon monoxide copolymer, polystyrene (PS), poly-α-methylstyrene, styrene-acrylonitrile copolymer, Styrene-based resins such as styrene- (meth) acrylic acid ester copolymers and styrene-butadiene copolymers, methyl poly (meth) acrylate, ethyl poly (meth) acrylate, propyl poly (meth) acrylate, poly ( Butyl (meth) acrylate, 2-ethylhexyl poly (meth) acrylate, -n-octyl poly (meth) acrylate,
Acrylic resins such as methyl (meth) acrylate-butyl (meth) acrylate copolymer, butyl methacrylate-2-hydroxyethyl methacrylate, methacrylic acid-2-ethylhexyl copolymer, polyvinyl formal,
Polyvinyl butyral, polyvinyl acetoacetal,
Polyvinyl acetals such as polyvinyl propional, polyvinyl ethers such as polyvinyl ether and polyvinyl butyl ether, polyethylene oxide, polyoxymethylene, polypropylene oxide, polytetramethylene glycol, polyethers such as ethylene oxide-propylene oxide copolymers, polyethylene terephthalate Polyesters such as polybutylene terephthalate and polyethylene sebacate, polycarbonates such as polyethylene carbonate and polypropylene carbonate, polyamides and polyurethanes.

A preferred example of the thermosetting resin is urea resin,
Melamine resin, epoxy resin, phenol resin, unsaturated polyester resin, xylene resin, diallyl phthalate resin, aniline resin, furan resin, polyurethane resin,
Examples thereof include alkylbenzene resins, guanamine resins, silicone resins and the like.

Paraffin wax,
Synthetic wax such as microcrystalline wax, oxidized wax, petrolatum, petrolatum oxide, polyethylene wax, polypropylene wax, montan wax derivative, whale wax, tuna wax, beeswax, wool wax, candelilla wax, carnauba wax, wood wax, Natural waxes such as naricurie wax, sugar cane wax, montan wax, ozokerite wax, ceresin, and lignite wax are mentioned.

The plasticizers and lubricants are higher fatty acids, higher alcohols, higher fatty acid amides, fatty acid esters, dibasic acid esters and the like. Specifically, higher fatty acids include stearic acid, lauric acid, valmotic acid, isostearic acid. , Behenic acid, myristic acid, oleic acid, linoleic acid, linolenic acid, palmitic acid, arachidonic acid, arachidic acid, and higher fatty acid amide,
Oleic acid amide, stearic acid amide, lauric acid amide, ricinoleic acid amide, erucic acid amide, behenic acid amide, palmitic acid amide, erucylamide, hardened tallow fatty acid amide, coconut fatty acid amide, methylenebisstearylamide, ethylenebisstearylamide, methylene Examples thereof include bisamide and ethylenebisamide. Examples of the fatty acid ester include C _{12 to} C ₂₂ fatty acids and C
Examples thereof include esters with _{1 to} C ₂₂ monohydric alcohols, monoesters with glycols, diesters, and mono-, di-, and triesters with glycerin. Specific examples include butyl stearate, butyl laurate, and octyl palmi. Tate, isopropyl palmitate, cetyl palmitate, myricyl palmitate, myricyl serotinate, stearic acid monoglyceride, diethylene glycol dibenzoate, triethylene glycol di-2-ethylbutyrate, sorbitan trioleate, peanut oil,
Soybean oil, coconut oil, palm oil, linseed oil, fish oil, animal oil,
Hydrogenated oil etc. can be mentioned.

Examples of the dibasic acid ester include phthalic acid ester, adipic acid ester, sebacic acid ester, azelaic acid ester, maleic acid ester, fumaric acid ester, and the like, specifically, dimethyl phthalate, diethyl phthalate, and phthalic acid. Dibutyl (DBP), diheptyl phthalate, di-n-octyl phthalate, di-2-ethylhexyl phthalate (DOP), diisononyl phthalate, didecyl phthalate, diisodecyl phthalate, diundecyl phthalate, dilauryl phthalate, phthalic acid Dicyclohexyl, butylbenzyl phthalate, octylbenzyl phthalate, butyloctyl phthalate, dibutyl maleate, di-2-ethylhexyl maleate, dibutyl fumarate,
Butyl adipate, di-n-hexyl adipate, di-2-ethylhexyl adipate, didecyl adipate,
Diisodecyl adipate, octyldecyl adipate,
Dibutyl diglycol adipate, Azelaic acid di-2
-Ethylbutyl, di-2-ethylhexyl azelate, dibutyl sebacate, di-2-ethylhexyl sebacate, and dioctyl sebacate can be mentioned.
Examples of higher alcohols include cetyl alcohol, ceryl alcohol, melysyl alcohol, stearyl alcohol, myristyl alcohol, and lauryl alcohol. Furthermore, phosphates such as triethyl phosphate, tributyl phosphate, trioctyl phosphate, triphenyl phosphate and the like, borate esters such as triethyl borate, tributyl borate, trioctyl borate, calcium stearate, magnesium stearate, stearin Higher fatty acid salts such as aluminum acid salts can also be used.

The binder component (B) used in the present invention preferably contains a thermoplastic resin. The thermoplastic resin imparts an appropriate strength to the green molded body and functions to prevent the molded body from being deformed even when degreasing. A more preferable composition of the component (B) is a combination of an organic compound containing no isocyanate group and having a molecular weight of 2,000 or less and a thermoplastic resin.

A molecular weight of 2,0 containing no isocyanate group
The organic compound of 00 or less is called the above-mentioned wax, plasticizer or lubricant, and has a function of lowering the viscosity of the composition to improve moldability and a function of being easily degreased by a solvent or heat. Have both.

A molecular weight of 2,0 containing no isocyanate group
The preferred molecular weight of the organic compound of 00 or less is 300 to 1,
It is 000. If the molecular weight is 300 or less, it becomes difficult to impart appropriate strength to the molded product,
If the molecular weight exceeds 1,000, the moldability and degreasing property deteriorate, and if it exceeds 2,000, it is impossible to mold a precision molded product, and the degreasing time becomes extremely long. This is because it becomes difficult to produce the precision parts with high precision and efficiency. The preferred molecular weight of the thermoplastic resin is 2,000 to 500,000, more preferably 50,000 to 300,000. 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. Molecular weight 500,00
If it exceeds 0, the melt viscosity becomes high and the moldability deteriorates.

The composition of the binder (B) is such that two or more kinds of resins having different thermal decomposition behaviors, such as a combination of an ethylene resin and an acrylic resin, are used as the thermoplastic resin so as not to be rapidly degreased during heat degreasing. As the organic compound having a molecular weight of 2,000 or less, it is preferable to use two or more compounds having different boiling points in combination. Rapid degreasing causes swelling,
It causes cracks and deformation. When solvent degreasing is used, it is preferable that at least one thermoplastic resin is insoluble in the solvent and the other thermoplastic resin and the organic compound having a molecular weight of 2,000 or less are soluble in the solvent.

In the present invention, a di-, tri-, or polyisocyanate compound is used as the binder component (A), and a thermoplastic resin having at least one functional group that reacts with an isocyanate group in the molecule as the binder component (B). It is preferable to use in combination because the deformation of the molded body is reduced during degreasing by heating. One isocyanate group of the isocyanate compound reacts with the hydroxyl group on the surface of the sinterable powder to form a covalent bond, and the other isocyanate group reacts with the functional group of the thermoplastic resin to form a bond and sinter. It seems that the polymer is grafted on the surface of the crystalline powder. Examples of the thermoplastic resin having a functional group that reacts with an isocyanate group include ethylene-vinyl alcohol copolymer, partially saponified EVA, ethylene- (meth) acrylic acid copolymer, ethylene-maleic anhydride copolymer, and propylene. -Maleic anhydride copolymer, styrene-maleic anhydride copolymer, styrene-
Paraaminostyrene copolymer, styrene-paravinylphenol copolymer, styrene- (meth) acrylic acid copolymer, styrene-2-hydroxyethylmethacrylate copolymer, methylmethacrylate-2-hydroxyethylmethacrylate copolymer, etc. Can be mentioned.

The sinterable powder injection molding binder of the present invention comprises an organic compound (A) 0.01 to 10 having a molecular weight of 2000 or less and having one or more isocyanate groups in the molecule.
It is preferable to knead 2 parts by weight to 2 parts by weight of the organic compound (B) other than (A) to produce it. The optimum amounts of the binder components (A) and (B) are different depending on the shape of the sinterable powder, the particle size of the powder, and the particle size distribution.
If the binder component (A) is less than 0.01 parts by weight, it is difficult to cover the entire surface of the sinterable powder with the isocyanate compound, and the wettability between the sinterable powder and the organic component is not sufficiently improved. If the amount exceeds 10 parts by weight, the amount exceeds the amount necessary for improving the wettability of the sinterable powder and is unnecessarily present in the binder, which may cause gelation during kneading and may cause a softening point of the molded product. It lowers and causes deformation during degreasing. If the amount of the binder component (B) is less than 2 parts by weight with respect to 100 parts by weight of the sinterable powder, the binder cannot fill the gaps between the powders, resulting in poor fluidity of the compound, which makes injection molding difficult. On the other hand, if the amount exceeds 100 parts by weight, the fluidity is improved and the injection molding can be easily performed, but the shape cannot be maintained during degreasing, which is not preferable.

The most preferable compositions of the isocyanate compound (A) which is the binder component of the present invention and the organic compound (B) other than (A) are the following two. 1. (1) Mono-, di-, tri-, or polyisocyanate compound as component (A) (2) Two or more thermoplastic resins as component (B) (3) Two or more molecular weight 300 as component (B) ~ 100
Organic compound of 0. 2. (1) Component (A) is a di-, tri-, or polyisocyanate compound (2) Component (B) has at least one functional group that reacts with an isocyanate group to form a bond. Two or more types of thermoplastic resins in which a plastic resin is essential (3) Two or more types of molecular weight 300 to 100 as the component (B)
The composition of organic compound 1 of 0 is thin and easy to degrease. Therefore, the composition of 2 is thick and does not deform during degreasing because of its injection molding property because the injection moldability is more important than the degreasing deformation. It is most suitable for parts with required shapes.

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

The powder injection molding composition (compound) of the present invention is preferably produced by kneading 100 parts by weight of the sinterable powder with 3 to 20 parts by weight of the binder of the present invention. If the amount is less than 3 parts by weight, the binder cannot fill the gaps between the sinterable powders, resulting in poor fluidity of the compound and making injection molding difficult. On the other hand, if the amount exceeds 20 parts by weight, the fluidity is improved and injection molding can be easily performed, but it is not preferable because the shape cannot be maintained during degreasing.

The composition for injecting a sinterable powder of the present invention can be produced by a usual kneading method. However, after the surface of the sinterable powder is surface-treated with the component (A), the component (B) is added. Is preferably added. Specifically, a binder component (A) which is liquid at a kneading temperature of room temperature to 100 ° C. and a sinterable powder are first kneaded, or a binder component (B) which becomes liquid at the kneading temperature, such as DOP or DBP, is an isocyanate. After the compound is dissolved and kneaded with the sinterable powder to sufficiently disperse the powder and improve the wettability of the surface, the remaining binder component is added.

There is no limitation on the kneading method of the sinterable powder injection molding composition of the present invention, and it is possible to sinter with a binder such as a Henschel mixer, a Banbury mixer, a kneader, a roll mill, a single screw extruder or a twin screw extruder. Any material can be used as long as it can knead the powdery powder. The kneaded composition is ground or granulated to obtain a molding material.

As a method of injection molding the composition of the present invention, a general injection molding machine for thermoplastics can be used. The injection molding temperature is preferably 100 to 250 ° C, more preferably 100 to 180 ° C. When the molding temperature is too high, the deterioration of the binder component becomes remarkable,
This is not preferable because it causes changes in the moldability and degreasing property of the recycled material.

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 at 10 to 100 ° C./h. The maximum degreasing temperature is preferably 450 to 600 ° C. If the temperature is lower than 450 ° C, the thermoplastic resin component cannot be efficiently decomposed and removed, which is not preferable, and even if the temperature is raised to 600 ° C or higher, the decomposition and removal rate of the resin component becomes constant.

In the case of the solvent extraction method, only a specific binder component is extracted and removed from the molded body, and thereafter, heat degreasing is performed to remove the remaining binder component.

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 800-22
The sintering is carried out at 00 ° C. for 10 minutes to 6 hours, and the sintering conditions and the sintering atmosphere are appropriately selected and determined according to the material, shape, particle size, particle size distribution of the powder used.

[0042]

EXAMPLES The present invention will be specifically described below with reference to examples, but first, the evaluation methods used in the examples will be described.

(Physical property evaluation method) 1) Amount of organic substance bound to sinterable powder: The binder was extracted and removed from the ground compound by a Soxhlet extractor using a toluene solvent. The sinterable powder from which the binder was removed was dried and then subjected to quantitative carbon analysis. In addition,
The extraction time was sufficient until the carbon content reached a constant value. This difference between the carbon content and the carbon content of the raw material powder before kneading is due to the polymer that is firmly fixed to the surface of the sinterable powder that cannot be extracted with hot toluene. The strength of the powder interaction can be evaluated.

2) Degreasing test: A plate having a thickness of 4 mm shown in FIG. 1 was molded into a trapezoid having a plane portion 1 and supporting portions 2 and 2 to obtain an injection molded test piece (molded body). The shape of the other parts is shown in FIG.
As shown in. This test piece was heated from normal temperature to 250 ° C. under reduced pressure in 12 hours and kept at 250 ° C. for 1 hour. Then, nitrogen was introduced, 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 amount of the degreased body is measured at the center of the flat surface portion 1 of the molded body before and after the degreasing step. The amount of deformation was measured. This amount of deformation is the amount of deformation due to its own weight during degreasing.

Example 1 A 0.5 liter pressure kneader was heated to 140 ° C., and then 2500 g of water atomized stainless steel powder (average particle size 9.5 μm) was added. Next, a mixed solution of 15 g of octadecyl isocyanate and 35 g of dibutyl phthalate (DBP) was added and kneaded at 50 ° C. for 10 minutes. Next, low density polyethylene (LDPE) 62.5
g, 62.5 g of polystyrene (PS) and 75 g of paraffin wax (melting point 60 ° C.) were added, and the mixture was further kneaded for 1 hour. The kneaded product was taken out, cooled, pulverized, and then injection-molded to obtain a test piece shown in FIG. Molding was easy, and good molded products without defects were obtained. The molded product is heated from room temperature to 250 ° C under reduced pressure in 12 hours and then heated at 250 ° C for 1 hour.
Held for hours. After that, nitrogen is introduced and 500 in a nitrogen stream.
The temperature was raised to 0 ° C. in 1 hour, and the temperature was maintained for 1 hour and then cooled.
The degreasing deformation amount is a difference in height between the molded body and the degreasing body shown in FIG. 2, and is deformed by its own weight during degreasing. The degreased body did not swell or crack at all, but slightly deformed. The results are shown in Table 1.

(Example 2) The same procedure as in Example 1 was carried out except that LDPE was replaced with ethylene-vinyl acetate copolymer (EVA) (vinyl acetate content 20% by weight). Molding was easy, and neither the molded body nor the degreased body had swelling and cracks, but the degreased body was slightly deformed. The results are shown in Table 1.

Example 3 In place of octadecyl isocyanate, hexamethylene diisocyanate was used, and LDP was used.
Instead of E, ethylene-acrylic acid copolymer (EAA)
Example 1 except using (acrylic acid content 6% by weight)
It carried out similarly to. Molding was easy, and neither the molded body nor the degreased body had defects such as swelling and cracks, and the degreased body hardly deformed. The results are shown in Table 1.

Example 4 Instead of octadecyl isocyanate

[Chemical 2] In place of PS, butyl-2-hydroxyethyl methacrylate copolymer (BMA-HEMA)
The same procedure as in Example 1 was carried out except that the content of 2-hydroxyethyl methacrylate was 5% by weight. Molding was easy, and neither the molded body nor the degreased body had defects such as swelling and cracks, and the degreased body hardly deformed. The results are shown in Table 1.

Comparative Example 1 DBP50 was used instead of the mixed solution of 15 g of octadecyl isocyanate and 35 g of DBP.
The same procedure as in Example 1 was carried out except that g was used, but powder and binder were separated in the cylinder during injection molding, and molding could not be performed. The results are shown in Table 1.

Comparative Example 2 DBP50 was used instead of the mixed solution of 15 g of octadecyl isocyanate and 35 g of DBP.
Example 2 was repeated except that g was used. Although the molding was easy and a good molded product was obtained, swelling and cracks occurred in the degreased body, and the deformation was remarkable. The results are shown in Table 1.

(Comparative Example 3) DBP5 was used instead of a mixed solution of 15 g of hexamethylene diisocyanate and 35 g of DBP.
Example 3 was repeated except that 0 g was used. Although the molding was easy and a good molded product was obtained, the defatted body had a large number of swellings and the deformation was remarkable. The results are shown in Table 1.

(Comparative Example 4)

[Chemical 3] Instead of the mixture of 15g and 35g of DBP, DBP50
The same procedure as in Example 4 was carried out except that g was used, but the compound had a high viscosity and could not be molded into a perfect shape.

(Examples 5 to 7) 0.5 parts by weight of hexamethylene diisocyanate was added to 100 parts by weight of the ceramic mixed powder shown in Table 2, and the same EVA as used in Example 2 was used.
2.5 parts by weight of BMA-H as used in Example 4
2.5 parts by weight of EMA, paraffin wax (melting point 55
C.) 3.0 parts by weight and DBP 2.0 parts by weight were added, and the mixture was kneaded with a pressure kneader at 140 ° C. for 1 hour. After that, the kneaded material was pulverized, molded and degreased in the same manner as in Example 1.
Both were easily injection-molded, and neither the molded body nor the degreased body had defects such as swelling and cracks, and almost no deformation. The results are shown in Table 2.

Comparative Examples 5 to 7 The same procedure as in Example 5 was carried out except that hexamethylene diisocyanate was not added.
In each case, molding was easy and the appearance of the molded product was good, but the degreased body swelled and cracked, and the deformation was remarkable.

[0055]

[Table 1]

[0056]

[Table 2]

[0057]

The present invention uses an isocyanate compound that firmly adheres to ceramic powder, cermet powder or metal powder as a component of the binder for sinterable powder injection molding. Has improved binders and even compounds. Furthermore, by using a compound having two or more isocyanate groups and a thermoplastic resin having a functional group that reacts with the isocyanate group in combination, sinterability injection in which the interface between the sinterable powder and the binder is strongly fixed A molding binder and compound was obtained. For this reason, the compound of the present invention has good moldability, in addition to manufacturing advantages such as short degreasing time and the like, because of its high strength, cracking during molding, deformation during deformation or degreasing, swelling, cracking It has the advantage of drastically reducing the generation, and precision parts with complicated shapes can now be efficiently produced with highly precise dimensions.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view of a molded body (a) and a degreased body (b) for explaining the measurement of the amount of deformation.

[Explanation of symbols]

 1 plane part 2 support part

Claims (8)

[Claims] 1. Sinterability characterized by containing (A) an organic compound having a molecular weight of 2000 or less and having one or more isocyanate groups in the molecule, and (B) an organic compound other than (A) above. Binder for powder injection molding. 2. The binder component (B) has a molecular weight of 200.
The sinterable powder injection molding binder according to claim 1, containing 0 or more thermoplastic resins. 3. The binder for sinterable powder injection molding according to claim 1, wherein the binder component (B) contains an organic compound having a molecular weight of 2000 or less, which does not contain an isocyanate group, and a thermoplastic resin. 4. The thermoplastic resin contained in the binder component (B) has at least one functional group that reacts with an isocyanate group in the molecule, and the binder component (A) has at least two functional groups. The binder for sinterable powder injection molding according to claim 2 or 3, which has an isocyanate group. 5. The binder component (A) is 0.01 to 10
The sinterable powder injection molding binder according to claim 1, wherein the binder component (B) is 2 to 100 parts by weight. 6. A composition for sinterable powder injection molding, comprising the binder for sinterable powder injection molding according to claim 1 and a metal powder, a ceramic powder or a cermet powder. object. 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 size of 0.1 to 1000 μm. 8. The firing according to claim 6, wherein the metal powder, the ceramic powder or the cermet powder is treated with the binder component (A) and then the binder component (B) is mixed. A method for producing a binding powder injection molding composition.