JP2843189B2 - Binders and compounds for metal powder injection molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a binder and a compound for metal powder injection molding.

[0002]

2. Description of the Related Art The metal powder injection molding method is a technique used as a method for mass-producing small and complicated metal parts. In this method, first, a metal powder as a raw material and a binder are kneaded to obtain an injection molding raw material compound.
This compound has thermoplasticity and is formed into a desired shape by an injection molding machine. This molding process is essentially the same as the molding of the plastic material, and mass molding is possible. Next, unnecessary binder is removed from the obtained molded body. This step is called degreasing. The degreasing method includes a method in which the binder is heated to evaporate or flow out of the molded body,
A method of extracting a binder while holding a molded body in a solvent and a method of combining the two are known, and a degreasing method is selected according to the type of the binder. Finally, the degreased body is sintered to obtain a metal part.

[0003] The metal powder injection molding method is characterized in that a metal fine powder capable of obtaining a high sintering density can be formed. Conventionally, fine powder having an average particle size of 10 μm or less has been difficult to form by pressing due to poor fluidity and the problem of galling of a mold. However, according to this method, fine powder can be easily formed. It is possible to form even a three-dimensional complicated shape. Because of these advantages, the metal powder injection molding method is often used recently in the production of stainless steel parts and the like, and its application to magnetic materials and ultra-hard materials is expanding.

[0004] The types of binders used in the metal powder injection molding method are roughly classified into thermoplastics and thermosettings. In consideration of the regeneration of sprues, runners, etc., non-renewable thermosetting binders are often used. It has not been. The main components of the thermoplastic binder include thermoplastic resins, waxes, plasticizers, lubricants, and the like. The resin gives plasticity to the raw material compound as a main component of the binder and also gives the molded body strength at room temperature. Further, in order to improve degreasing property and fluidity, a wax or a plasticizer, which is an organic substance having a lower molecular weight than the resin, is added. Examples of the resin component include polyethylene, polypropylene, polystyrene, ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA), polyalkyl methacrylate, and polyamide.
One or more of these are used in combination. As a component having a lower molecular weight than the resin, one or a combination of two or more of paraffin wax, higher fatty acid, higher alcohol, higher fatty acid ester, higher fatty acid amide, phthalic acid ester such as diethyl phthalate and dibutyl phthalate is used. Can be As described above, the raw material compound for metal powder injection molding is generally a mixture of metal powder and several kinds of organic substances such as resin, wax, and plasticizer.

[0005]

The selection of a binder is important in the metal powder injection molding method, but the following problems have been encountered with the conventional binder composition.

When resins such as polyethylene and polypropylene are used as the binder, it is difficult to disperse the metal powder due to poor wettability with the metal, and agglomerated powder remains to provide uniform and good fluidity. It does not become the compound you have. Further, even if a low-molecular component such as wax is added to improve the moldability, troubles occur during injection molding, such as separation of the binder and the metal powder due to poor compatibility with the powder. Further, in the case where heating degreasing is used in the degreasing step, the molded body is deformed during heating, and degreasing defects such as swelling and cracks are generated. In order to avoid such a degreasing defect, it is necessary to lengthen the degreasing time, and there is a problem that the degreasing step takes time.

[0007] Ethylene-vinyl acetate copolymer (EV
A), ethylene-ethyl acrylate copolymer (EE
A) is a resin that has a functional group having polarity, is well compatible with 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 article strength. However, the content of vinyl acetate or ethylene acrylate must be large to some extent in order to exert its performance sufficiently, so that the softening point is lowered. For this reason, in the degreasing step, deformation of the molded body is very likely to occur, and defects such as swelling are likely to occur. Therefore, a long-time degreasing is necessary to obtain a sound degreasing body without defects.

Further, poly (ethylene) and poly (alkyl methacrylate) have an excellent depolymerization property, an excellent degreasing property, and are often used as a binder. However, these resins have poor wettability with metal and have problems in molding, like polyethylene and the like.

Accordingly, it has been proposed to use two or more of these resins in combination for the compound for injection molding, but each has advantages and disadvantages.
In fact, a binder showing excellent performance in both moldability and degreasing property has not yet been developed.

[0010]

As a result of studying the components and blending of the binder in order to solve the above problems, the present inventors have found that an epoxy group-containing olefin-based It has been found that when the copolymer is used, the compound is excellent in wettability with powder and good in moldability, and has little deformation of the molded body even in degreasing, and does not cause degreasing defects.

That is, the present invention is obtained by copolymerizing 0.1 to 30% by weight of an epoxy group-containing unsaturated monomer and 70 to 99.9% by weight of a monomer copolymerizable with the monomer. Epoxy group-containing olefin copolymer 20 to 90% by weight
Another object of the present invention is to provide a binder for metal powder injection molding which comprises an organic compound having a molecular weight lower than that of the copolymer.

The present invention also provides a metal powder injection molding compound obtained by kneading the binder with a metal powder having an average particle size of 0.1 to 1000 μm.

[0013]

The present invention will be described below in more detail. 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. For example,
Powder of iron, copper, titanium, tungsten, nickel, molybdenum, chromium, or stainless steel, Fe-Ni
Alloy powders such as a base alloy, an Fe-Si based alloy, and an Fe-Co based alloy. In addition, carbonyl powder, water atomized powder, gas atomized powder, pulverized powder and the like can be mentioned according to the method of producing the powder. Furthermore, it is also possible to use a mixed powder of two or more of these. The particle size of the powder can be in the range of 0.1 to 1000 μm,
10 from the fluidity of the compound or the sinterability of the powder
It is preferable to use a powder of 0 μm or less. A more preferable range of the particle size is 1 to 50 μm.

A compound is produced by kneading 100 parts by weight of these metal powders 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 is insufficient with respect to the metal powder, and the fluidity of the compound is poor, so that injection molding is difficult. If the amount exceeds 20 parts by weight, the injection molding can be performed but the shape cannot be maintained during degreasing. Not preferred. As a kneader, a Henschel mixer, a plast mill, a pressure kneader, a Banbury mixer, a roll mill, a single screw kneader, a twin screw kneader, or the like may be used, and kneading may be performed by combining two or more of these.

In the present invention, as a binder, an epoxy group-containing unsaturated monomer copolymerized from 0.1 to 30% by weight of an epoxy group-containing unsaturated monomer and 70 to 99.9% by weight of a copolymerizable monomer is used. An olefin copolymer is used as an essential component. The mode of copolymerization of the epoxy group-containing olefin copolymer may be any of random copolymerization, block copolymerization, and graft copolymerization.

The epoxy group-containing unsaturated monomer referred to in the present invention is represented by the general formula

[0017]

Embedded image Wherein R ₁ represents a hydrocarbon group having an olefinically unsaturated bond, and an unsaturated glycidyl ester represented by the general formula:

[0018]

Embedded image (Where, X is -CH ₂ -O- or

Embedded image And R ₂ represents a hydrocarbon group having an olefinic unsaturated bond), or an unsaturated glycidyl ether represented by the general formula:

[0019]

Embedded image (Where R ₃ is a halogen atom or a hydrocarbon group, and R ₄ represents a hydrocarbon group having an olefinically unsaturated bond).

Specific examples include glycidyl acrylate, glycidyl methacrylate, itaconic monoglycidyl ester, butenetricarboxylic acid monoglycidyl ester, butenetricarboxylic acid diglycidyl ester,
Glycidyl esters such as butenetricarboxylic acid triglycidyl ester and α-chloroallyl, maleic acid, crotonic acid, fumaric acid, or glycidyl such as vinyl glycidyl ether, allyl glycidyl ether, glycidyloxyethyl glycidyl ether, and styrene-p-glycidyl ether Ethers or p-glycidyl styrene, 3,4-epoxy-1-butene,
3,4-epoxy-3-methyl-1-butene, 3,4-
Epoxy-1-pentene, 3,4-epoxy-3-methyl-1-pentene, 5,6-epoxy-1-hexene,
And 1,2-epoxy-4-cyclohexene.

Examples of the copolymerizable monomer used in the present invention include olefins such as ethylene, propylene, isobutylene, butadiene, cyclopentadiene and isoprene, and vinyl acetate. Further, methacrylates such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, and acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate are also used. it can. In the present invention, one or more selected from the exemplified groups can be used.

As a method for producing the epoxy group-containing olefin copolymer of the present invention, a known radical copolymer is used, and a radical generator is added to an olefin homopolymer or an olefin copolymer. Examples of the method include a radical graft reaction of an epoxy group-containing unsaturated monomer in the presence or absence of a solvent or a dispersion medium. In particular, when grafting is performed in a molten state, an epoxy group-containing olefin copolymer desired in a short time can be obtained by a simplified method by using a melt kneader such as an extruder, a kneader, and a Banbury mixer.

Examples of the epoxy group-containing olefin copolymers presented in the present invention include binary copolymers such as ethylene-glycidyl methacrylate copolymer and ethylene-glycidyl acrylate copolymer, and ethylene-vinyl acetate copolymer. Tertiary copolymers such as glycidyl methacrylate copolymer, ethylene-vinyl acetate-glycidyl acrylate copolymer, and ethylene-acrylate-glycidyl methacrylate copolymer are exemplified.

The content of the epoxy group-containing unsaturated monomer of the epoxy group-containing olefin copolymer in the present invention is 0.1 to 30% by weight. When the copolymerization ratio of the epoxy group-containing unsaturated monomer is less than 0.1% by weight, the strength of the interaction between the epoxy group and the surface of the metal powder is not sufficiently exhibited, and the wettability with the metal powder is poor. Become. When the copolymerization ratio of the epoxy group-containing unsaturated monomer exceeds 30% by weight, the softening point of the resin increases, the moldability deteriorates, and the resin becomes hard and brittle, so that the strength of the molded body decreases. I do. Therefore,
The content of the epoxy group-containing unsaturated monomer in the copolymer is 0.1 to 30% by weight. Further, the preferable content of unsaturated dicarboxylic anhydride is 0.3 to 20% by weight.

In the present invention, any molecular weight may be used as long as the epoxy group-containing olefin copolymer satisfies the above-mentioned conditions. However, if the molecular weight is too small, the strength of the molded article is insufficient and the molecular weight is too small. If it is large, the melting point of the resin will be high, and the viscosity at the time of melting will also be high, which will deteriorate the injection moldability of the compound. Therefore, the molecular weight is preferably from 5,000 to 300,000, and more preferably from 50,000 to 200,000.

Furthermore, in the present invention, the blending ratio of the epoxy group-containing olefin copolymer used as an essential component in the binder is 20 to 90% by weight, and the balance is a lower molecular weight component. If the blending ratio of the epoxy group-containing olefin copolymer is less than 20% by weight, the excellent binder effect of the epoxy group-containing olefin copolymer cannot be sufficiently utilized. If the compounding ratio of the epoxy group-containing olefin copolymer exceeds 90% by weight, the viscosity of the compound increases, the fluidity deteriorates, and defects such as cracks easily occur in the degreasing step. Preferably, the mixing ratio of the epoxy group-containing olefin copolymer in the binder is 30 to 80% by weight.

As the low molecular weight component used in the binder, wax, higher fatty acid, higher alcohol, higher fatty acid amide, fatty acid ester, phthalate ester, adipic ester, sebacate ester and the like can be used.
More specifically, low-molecular components that can be used include normal paraffin wax, microcrystalline wax, oxidized wax, petrolatum,
Examples include synthetic waxes such as petrolatum oxide and polyethylene wax, and natural waxes such as montan wax, carnauba wax and bee wax. The molecular weight of these waxes is preferably from 300 to 2,000. This is because if the molecular weight is less than 300, an appropriate strength cannot be imparted to the molded article, and if the molecular weight is more than 2000, the degreasing property is deteriorated. Wax is most often used as a binder component because it has good compatibility with resin and is inexpensive.

The higher fatty acids include mystyric acid, palmitic acid, stearic acid, arachidic acid, behenic acid,
Oleic acid, linoleic acid, linolenic acid and the like can be used. These have an effect as a lubricant, but if they are mixed in too much, bleed out from the molded body becomes severe and the strength of the molded body is reduced. Therefore, the blending ratio is limited to 10% by weight or less based on the whole binder. Is preferred.

As the higher alcohol, monohydric higher alcohols such as cetyl alcohol and stearin alcohol, and dihydric alcohols such as ethylene glycol and polyethylene glycol can be used.

Examples of the higher fatty acid amide include stearic acid amide, palmitic acid amide, oleic acid amide, methylenebisstearic acid amide, ethylenebisstearic acid amide and the like. These amides have relatively good compatibility with resins, and there is no problem even if they are mixed in a larger amount than fatty acids and alcohols.

As the fatty acid ester, a polyhydric alcohol ester such as a C ₁ -C ₂₂ monohydric alcohol ester or a glycol ester of a C ₁₂ -C ₂₂ fatty acid can be used as a binder. Specifically, butyl stearate, butyl laurate, octyl palmitate, isopropyl palmitate, monoglyceride stearate,
Sorbitan triolate, peanut oil, soybean oil, coconut oil,
Palm oil, linseed oil, hydrogenated oil, fish oil, animal oil, etc. are available on the market.

Phthalates, adipic esters,
Sebacate and the like are generally used as plasticizers for plastics, but also have excellent performance as a binder for metal powder injection molding. Specifically, diethyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dinonyl phthalate, diisononyl phthalate, didecyl phthalate, didecyl phthalate,
Diundecyl phthalate, butyl benzyl phthalate, octyl benzyl phthalate, butyl octyl phthalate, dibutyl adipate, di-2-ethylhexyl adipate, didecyl adipate, diisodecyl adipate, octyl dale adipate, dibutyl sebacate, dibutyl sebacate , Di-2-ethylhexyl sebacate, butylbenzyl sebacate and the like.

The binder for injection molding according to the present invention comprises 20 to 90% by weight of an epoxy group-containing olefin-based copolymer, and the remainder comprises one or more of the above-mentioned organic compounds of low molecular weight organic compounds and is an organic mixture. is there.

In order to avoid defects such as sagging and swelling during the degreasing step, it is preferable to mix two or more low molecular components having different boiling points. This is because defects during the degreasing step occur when low-molecular components are removed at a temperature lower than the temperature at which the resin decomposes, so that two or more low-molecular components are used to avoid those defects. This is because it is better to widen the temperature range for blending and removing.

The compound obtained by kneading the binder of the present invention and the metal powder is pulverized or granulated to obtain a molding material. As the injection molding machine, a general injection molding machine for thermoplastics can be used. Injection temperature is injection temperature 1
When the injection temperature is too high, the deterioration of the binder component becomes remarkable, and the moldability of the recycled material,
Injection temperature is preferably 10 because it causes a change in degreasing property.
The range of 0 ° C to 180 ° C is good.

For degreasing, any of a heating degreasing method and a solvent extraction method can be used. In the case of the heat degreasing method, it is preferable to carry out the method in a stream of nitrogen, argon, hydrogen or the like, or to remove the binder under reduced pressure. The rate of temperature rise depends on the thickness of the molded body, but the temperature is raised in the range of 10 ° C / h to 100 ° C / h. The maximum temperature of degreasing is preferably about 450 ° C to 800 ° C. If the maximum temperature of degreasing is less than 450 ° C., the epoxy group-containing olefin copolymer is not efficiently decomposed and removed, which is not preferable. Even if the temperature is raised to 800 ° C. or more, the decomposition of the epoxy group-containing olefin copolymer is not performed. The removal rate does not change much,
Conversely, it only extends the degreasing time.

In the case of the solvent extraction method, one of the low molecular components other than the epoxy group-containing olefin copolymer is removed from the molded product.
The seed or two or more kinds are extracted and removed with a solvent, and thereafter, heat degreasing is performed to remove the remaining binder components.

The sintering step may be performed in the same furnace after the degreasing step, or may be performed in a different furnace after removing the degreased body from the degreasing furnace. Sintering is 800 ° C ~ 200
The sintering is carried out at a temperature of 0 ° C. for 10 minutes to 6 hours, and these sintering conditions and sintering atmosphere are appropriately selected and determined according to the material and powder characteristics of the metal powder to be used.

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

As described later in the embodiments, EVA, EE
A, compared to those conventionally used as binders such as polyethylene, polypropylene, polystyrene, and acrylic resin, the copolymer containing an epoxy group has a residual carbon content of the metal powder after separation with a solvent of 0.05% to 0%. .15%
Many. This is considered that the surface of the metal powder and the resin are firmly bonded by the covalent bond caused by the epoxy group. That is, glycidyl methacrylate or glycidyl acrylate forms a hydrogen bond with a hydroxyl group on the surface of a metal powder like an ethylene-vinyl acetate copolymer (EVA) or an ethylene-ethyl acrylate copolymer (EEA) as conventionally used. Rather, it is believed that the covalent bond described below creates a stronger bond.

[0041]

Embedded image

It has been found that a resin containing an epoxy group can be used as a binder for ceramic molding.
82266 and JP-A-57-38896. However, these do not focus on the interaction with the metal powder as described above, and the molding material is also in a slurry form used for a doctor blade method or the like, and has different properties from the metal powder injection molding compound. is there.
The present invention proposes a resin obtained by copolymerizing an epoxy group-containing unsaturated monomer based on the above-described principle as a binder for metal powder injection molding, and is completely novel.

This will be described more specifically. Wetting of the surface of the metal powder with the binder, that is, the strength of the interaction, greatly affects the dispersibility of the metal powder during kneading, the fluidity of the compound, and the strength of the compact. The chemical covalent bond is
One of the strongest bonds, a resin obtained by copolymerizing an epoxy group-containing unsaturated monomer that can covalently bond with the hydroxyl group on the surface of the metal powder, that is, the epoxy group-containing olefin copolymer according to the present invention has very high performance It is a good binder for metal powder injection molding.

That is, when the olefin-based copolymer containing an epoxy group is used as a binder component, the metal powder can be dispersed very well during kneading, and a uniform raw material compound can be obtained. There is no deterioration and the amount of binder is small. Furthermore, the wetness with the powder is high due to the strong covalent bond, so that the strength of the compact is high, cracks in the compact are eliminated, and deformation during handling is small.

In the present invention, a component having a lower molecular weight than the epoxy group-containing olefin copolymer described above is added as another binder component. This is because it is difficult to degrease the binder with one component, but it also has the meaning of further improving the fluidity during molding. As the low-molecular component, the above-mentioned wax, plasticizer and the like can be used. Even at the time of degreasing, the wetness between the epoxy group-containing olefin copolymer and the powder is good, so there are few degreasing defects, and conventionally, there is almost no deformation of the molded body, compared to the binder used,
No degreasing defects such as blisters, voids and cracks occur.

[0046]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments. (Example) Water atomized stainless steel powder having an average particle size of 9.5 μm and a tap density of 3.8 g / cc was used as metal powder.
Compounds for injection molding were prepared with the formulations shown in Table 1. The amount of the binder added was 9.8 parts by weight based on 100 parts by weight of the stainless steel powder. Table 2 shows the raw material monomer components of the epoxy group-containing olefin copolymer used as the binder and the copolymerization ratio (% by weight).

The kneading was performed with a pressure kneader. After heating the pressure kneader to 140 ° C., the binder component was charged and melted, the metal powder was gradually charged, and the whole amount was charged and kneaded for 1 hour. The kneaded product was pulverized to obtain a raw material compound for injection molding. . The viscosity of the obtained raw material at a temperature of 150 ° C. and a shear rate of 1000 s ⁻¹ was measured to evaluate the fluidity during injection molding. Further, the binder was removed from the pulverized compound with a Soxhlet extractor using toluene, and the carbon content of the separated powder was measured. The difference between the carbon content and the carbon content of the raw material powder before kneading (residual carbon content) is due to the resin that is not removed from the powder by toluene. be able to. Table 3 shows the measurement results. Next, the prepared compound was injection molded into a test piece as shown in FIG.

For degreasing, the molded body was placed as shown in FIG. 1, and the temperature was raised from room temperature to 500 ° C. for 25 hours in a nitrogen stream, and the temperature was maintained for 1 hour, followed by cooling.

The appearance of the degreased body such as swelling and cracks was observed, and the amount of deformation due to its own weight during degreasing was measured. Here, the deformation amount is the difference between the height of the molded body and the height of the degreased body shown in FIG. Table 1 also shows the observation results and the amount of deformation of the degreased body.

In Invention Examples 1 to 3, an ethylene-glycidyl methacrylate copolymer having a copolymerization ratio of glycidyl methacrylate according to the present invention of 5% by weight was used as a binder, and paraffin wax, stearic acid, dibutyl as low molecular components were used. The binder is obtained by blending phthalate (DBP). Since the compounding ratio of the resin to the binder is appropriate at 40% by weight to 80% by weight, molded articles obtained by injection molding these compounds are sound, and the appearance of the degreased body is not swollen, and no defects such as cracks are found. Was. Furthermore, the amount of deformation of the degreased body is very small. Inventive Example 4 is an example using an ethylene-glycidyl acrylate copolymer, and Inventive Example 5 is an example using an ethylene-vinyl acetate-glycidyl methacrylate copolymer as a binder. These resins also contained glycidyl methacrylate or glycidyl acrylate, and their copolymerization ratio was appropriate, so that they were good binders. Inventive Examples 6 and 7 are formulation examples using stearyl alcohol, behenic acid amide, dioctyl phthalate (DOP) and the like as low molecular components, and these are also very excellent in both moldability and degreasing properties.

Comparative Examples 1 and 2 use the same ethylene-glycidyl methacrylate copolymer in which the copolymerization ratio of glycidyl methacrylate is 5% by weight. Since the mixing ratio was less than 10% by weight and less than 20% by weight, the excellent binder effect of the ethylene-glycidyl methacrylate copolymer was not exhibited, and the molded article was brittle and cracked. Further, in Comparative Example 2, since the compounding ratio of the resin was 95% by weight or more than 90% by weight, the fluidity was poor and insufficient filling occurred during molding, and the degreased body was greatly deformed. In Comparative Example 3, an ethylene-glycidyl methacrylate copolymer was used. However, since the copolymerization ratio was 0.05% by weight, the effect of glycidyl methacrylate did not appear, and a defect in which a molded product was cracked occurred. . In Comparative Example 4, the glycidyl methacrylate copolymerization ratio of the ethylene-glycidyl methacrylate copolymer was as high as 40% by weight, the softening point was high, and the molded article was cracked. Comparative Example 5 is an example in which a resin containing 0.05% by weight of glycidyl methacrylate in an ethylene-vinyl acetate copolymer was used. However, since the content of glycidyl methacrylate was insufficient, this compound had a degreasing property. It was bad.

In Comparative Examples 6 to 8, EVA (ethylene-vinyl acetate copolymer), EEA (ethylene-ethyl acrylate copolymer), and LDPE (low-density polyethylene) which were conventionally used as binders were blended. It uses a binder. Comparative Examples 6 and 7 are E
VA and EEA were used as resin components. These were excellent in fluidity, the molded body was sound, and the moldability was good. However, in the degreasing, both swelled and caused dripping. Comparative Example 8 is an LDPE-wax-stearic acid-based binder. The one using this binder was brittle, and cracks occurred in the molded body, and a good molded body could not be obtained.

Table 3 shows the carbon content of the powder obtained by removing the binder from the raw material compound and separating it. EVA, EEA, L
While the residual carbon content due to DPE is 0.05 to 0.08% (Comparative Examples 6 to 8), the separation powders of Invention Examples 1 to 7 using the acid anhydride-containing olefin copolymer were used. The residual carbon content is as high as 0.1 to 0.18%, which indicates that the binding between the binder and the powder is strong. As described above, this is considered to be due to the bonding of the epoxy group to the surface of the powder as shown in Formula 1, and it is a specific proof that the resin presented by the present invention is a binder excellent in powder and wettability.

Table 4 shows examples of the blending of the binder for solvent extraction. The powder used was the same as in Invention Examples 1 to 7, and kneading and injection molding were performed in the same manner as in Invention Examples 1 to 7. For degreasing, the injection molded body was kept 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. for 6 hours in a nitrogen stream, and the temperature was maintained for 1 hour, followed by cooling.

Inventive Example 8 is one in which an ethylene-glycidyl methacrylate copolymer having a copolymerization ratio of glycidyl methacrylate of 5% by weight was blended. The molding obtained by molding this compound was well filled and did not crack. The degreased body (solvent degreased body) which was kept in normanheptane for 4 hours did not show any defect, and the appearance of the pressure degreased body was good. Comparative Example 9 is a solvent degreasing binder containing polyethylene and hydrogenated palm oil. Comparative Example 1
0 indicates that polypropylene was used instead of polyethylene. The compounds of these comparative examples had poor moldability and cracks occurred in the molded articles. Furthermore, the solvent degreased body was very fragile and broke during handling when charged into the degreasing furnace. As described above, the binder using the epoxy group-containing olefin copolymer according to the present invention has excellent moldability and degreasing properties.

[0056]

[Table 1]

[0057]

[Table 2]

[0058]

[0059]

[0060]

[0061]

[0062]

By using the binder according to the present invention, the moldability and degreasing property of the compound are greatly improved, and the productivity of manufacturing parts by the metal powder injection molding method is greatly improved.

[Brief description of the drawings]

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

FIGS. 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.

Claims (2)

(57) [Claims] 1. An unsaturated monomer having an epoxy group of 0.1 to 30.
% By weight, and 70 to 9 of a monomer copolymerizable with the monomer.
A binder for metal powder injection molding comprising 20 to 90% by weight of an epoxy group-containing olefin-based copolymer obtained by copolymerizing 9.9% by weight with an organic compound having a lower molecular weight than the copolymer. 2. The method according to claim 1, wherein the binder has an average particle size of 0.1.
A metal powder injection molding compound which is kneaded with a metal powder of 1 to 1000 μm.