KR102275122B1 - Binder Composition for Metal Injection Molding - Google Patents

Abstract

The present invention relates to a binder composition for injection molding of metal powder, and more particularly, to enable rapid degreasing, easy setting of flow conditions in the injection process, swelling in the degreasing process, carbonization of a low molecular weight binder, and other internal defects. It relates to a binder composition for metal powder injection molding capable of minimizing defects in degreasing, etc.
The binder composition for metal powder injection molding of the present invention comprises 10 to 50 wt% of a high-viscosity polyoxymethylene polymer and 50 to 90 wt% of a low-viscosity polyoxymethylene polymer.
The binder composition for injection molding of metal powder according to the present invention contains polyoxymethylene produced by viscosity alone without adding other monomers in the polymerization process of polyoxymethylene, thereby controlling the viscosity in the polymerization process in the prior art, and in a gaseous state Compared to the technology that controls the rate of decomposition of acid, it is more economical because the manufacturing cost is lower, and compared to the technology of using other polymer resins such as polyolefin and polyamide together with polyoxymethylene, injection properties and degreasing/sintering properties are excellent. It has excellent advantages.

Description

Binder Composition for Metal Injection Molding

The present invention relates to a binder composition for injection molding of metal powder, and more particularly, to enable rapid degreasing, easy setting of flow conditions in the injection process, swelling in the degreasing process, carbonization of a low molecular weight binder, and other internal defects. It relates to a binder composition for metal powder injection molding capable of minimizing defects in degreasing, etc.

Metal Injection Molding (MIM) process is a method that combines the advantages of injection molding technology in the plastics industry and metal powder sintering technology in the powder metallurgy industry. In general metal injection molding, metal powder and resin are mixed and injection molded, and then the resin is removed from the workpiece and sintered to manufacture a product. The metal injection molding process can manufacture a three-dimensional metal workpiece, which was difficult to implement due to its complexity and precision, with high strength and precision like a sintered metal product, while using a relatively simple process like a plastic product.

Since metal products manufactured by the metal injection molding process are manufactured by a sintering method in which metal powder is combined at a high temperature, there is a disadvantage in that the relative density is low or minute cracks may occur compared to metal bulk products manufactured by the casting method.

In addition, defects such as a decrease in precision due to a change in volume due to heat applied during the process may occur. In order to prevent this type of change or defect in physical properties, it is very important to use a binder to control the spacing, distribution, fluidity, etc. between metal powders during injection.

The binder is kneaded together with the metal powder in the metal injection molding process and mainly serves to bind the metal powder particles. In addition, it is possible to increase the fluidity of the mixture to make injection advantageous, or to improve the surface properties by adjusting the spacing of the metal powder and evenly dispersing it. Accordingly, development of a binder capable of suppressing product deformation in the degreasing/sintering process and imparting high density, high strength, precise dimensional stability, and the like to a metal product after sintering is being actively developed.

In general, a binder is injected together in a mixed state with the metal powder to shape the metal powder. Thereafter, the binder should be removed in the degreasing step, and the degreasing method includes a solvent degreasing method in which a resin is dissolved in a solvent, a thermal degreasing method in which a resin is dissolved in a solvent, a catalytic degreasing method using a catalyst, and the like.

The composition of the binder for metal powder injection molding varies depending on the degreasing method. In general, the solvent degreasing method is composed of polyolefin, aliphatic wax, stearic acid, and the like. In the solvent degreasing method, solvents such as hexane and heptane must be used. These solvents are not free from fire risk, it is difficult to recycle the dissolved resin, and wastewater is generated in large amounts, which is harmful to the environment.

In addition, in the case of the thermal degreasing method, it is composed of polyolefin or polystyrene-based resin, aliphatic wax, stearic acid, and the like. Since the thermal degreasing method simply removes the binder using only heat, the process time is very long, a high operating temperature is required, and an inert gas atmosphere is required, so energy efficiency is low and uneconomical.

On the other hand, in the case of a catalytic degreasing method in which degreasing is performed in an acid atmosphere, it is composed of polyoxymethylene and polyolefin, and may also contain wax if necessary. The catalytic degreasing method has the advantage that polyoxymethylene is well decomposed in an acid atmosphere and the degreasing rate is fast, so many companies around the world are using it. However, since different polymer resins such as polyoxymethylene and polyolefin are contained for degreasing, it is difficult to control injection conditions, and even if compatibility is good, there is a problem in that a number of defects such as swelling and internal defects occur in the final product stage.

Korean Patent Application Laid-Open No. 2016-0002964 relates to a polyoxymethylene copolymer and a thermoplastic POM composition, and discloses a method for controlling the viscosity of the polyoxymethylene copolymer. This discloses a method for preparing a binder for powder injection molding through the introduction of various monomers in the polymerization process, but there is a problem in that pre-treatment must be performed and the manufacturing cost is increased because the process is quite complicated.

Another method proposed in the above patent is described in European Patent Publication Nos. 0446708, 0444475 and 0853995, which is a binder consisting of at least two binders (one or more polymer resins and one or more wax-based materials). , which may cause compatibility problems depending on the characteristics of each binder material in the kneading step, and may become an obstacle to optimizing the injection process. In addition, since this is a binder material having a melting point difference of at least 50° C., each binder partially aggregates in the injection process, and bubbles or internal defects may appear in the final product after degreasing and sintering processes in the future. In addition, in the degreasing process or the preliminary sintering process, since a holding time is required at a specific temperature to remove each binder, it may affect the degreasing time and the sintering time. problems may arise.

Accordingly, the present inventors have made efforts to solve the above problems. As a result, when polyoxymethylene polymers having different viscosities are mixed in a specific range and used in a specific range, there is no defect in the product without polyolefin essential as a binder composition in the catalytic degreasing method. It was confirmed that the injection molding (MIM, Metal Injection Molding) process could be successfully performed, and the present invention was completed.

An object of the present invention is to provide a binder composition for injection molding of metal powder having excellent injection properties and excellent degreasing/sintering properties, and a feedstock composition for injection molding of metal powder comprising the same.

Another object of the present invention is to provide a metal injection molding method having excellent injection properties and degreasing/sintering properties.

In order to achieve the above object, the present invention provides a binder composition for injection molding metal powder comprising 10 to 50% by weight of a high-viscosity polyoxymethylene polymer and 50 to 90% by weight of a low-viscosity polyoxymethylene polymer.

In the present invention, the high-viscosity polyoxymethylene polymer has a melt flow index of 1 to 10 g/10 min when measured at a temperature of 190° C. and a load of 2.16 kg according to ASTM D1238 standard, and the low-viscosity polyoxymethylene polymer is ASTM D1238 standard It is characterized in that the melt flow index is 40 to 300 g/10 min when measured at a temperature of 190° C. and a load of 2.16 kg based on the

In the present invention, the high-viscosity or low-viscosity polyoxymethylene polymer (a) comprises an oxymethylene-(OCH ₂ )n- group as a repeating unit, and (b) oxymethylene alone, both ends of which are capped by an ester or ether group. It is a polymer or an oxymethylene-based copolymer in which oxyalkylene units having 2 to 10 carbon atoms are randomly inserted into a polymer chain composed of oxymethylene monomer units, and (c) both ends of the polymer are blocked by ester or ether groups, or ternary It is characterized in that it is a copolymer.

The present invention also provides a feedstock composition for injection molding of metal powder comprising a binder composition for injection molding of metal powder.

In the present invention, the feedstock composition for injection molding of the metal powder includes: the binder composition for injection molding of the metal powder; and (b) a sinterable powdery inorganic material selected from the group consisting of metals, metal alloys, metal carbonyls, metal oxides, metal carbides, metal nitrides, and mixtures thereof.

In the present invention, the average particle size of the powder-type inorganic material is characterized in that 1 to 20㎛.

In the present invention, the binder composition for injection molding of the metal powder is 20 to 80% by volume, and the inorganic powder is 20 to 80% by volume.

In the present invention, the feedstock composition for metal powder injection molding further comprises an additive selected from the group consisting of a lubricant and a dispersant.

The present invention also comprises the steps of obtaining a green part by injection molding the feedstock composition for injection molding of the metal powder; removing a binder for metal powder injection molding from the green part to obtain a brown part; and sintering the brown part to manufacture a metal product.

In the present invention, the removal of the binder for injection molding of the metal powder is characterized in that it is performed for 0.1 to 30 hours at 50 to 140 ℃ in an acid atmosphere.

The binder composition for injection molding of metal powder according to the present invention contains polyoxymethylene produced by viscosity alone without adding other monomers in the polymerization process of polyoxymethylene, thereby controlling the viscosity in the polymerization process in the prior art, and in a gaseous state Compared to the technology that controls the rate of decomposition of acid, it is more economical because the manufacturing cost is lower, and compared to the technology of using other polymer resins such as polyolefin and polyamide together with polyoxymethylene, injection properties and degreasing/sintering properties are excellent. It has excellent advantages.

1 is an explanatory diagram of a typical metal injection molding process.

In the present invention, when polyoxymethylene polymers having different viscosities are mixed and used in a specific range, the MIM (Metal Injection Molding) process is performed without defects in the product without polyolefin, which is essentially used as a binder composition in the catalyst degreasing method. We wanted to confirm that it could be done successfully.

In the present invention, a binder composition for metal powder injection molding was prepared by applying high-viscosity and low-viscosity polyoxymethylene by using polyoxymethylene produced for each viscosity without adding other monomers in the polymerization process of polyoxymethylene. Next, a powdery inorganic material is added to the prepared binder composition for injection molding of metal powder and kneaded to prepare a feedstock composition for injection molding of metal powder, injection molding this to obtain a green part, and degreasing it to obtain a brown part. By sintering, a metal product was finally manufactured. As a result of evaluating the physical properties of intermediates and final products produced in each manufacturing step, the kneading properties of the feedstock, the injection properties of the metal workpiece (brown part), the degreasing property of the metal workpiece (brown part) after degreasing, and after sintering It was confirmed that both the sintering characteristics and quality of the metal products were excellent.

Accordingly, in one aspect, the present invention relates to a binder composition for injection molding of metal powder comprising 10 to 50% by weight of a high-viscosity polyoxymethylene polymer and 50 to 90% by weight of a low-viscosity polyoxymethylene polymer.

In the present invention, when the content of the high-viscosity polyoxymethylene polymer is less than 10% by weight, it is not possible to control the rate of decomposition in the acid in gaseous state, so that poor degreasing may occur, and when it exceeds 50% by weight, the viscosity is increased There is a problem that the injection molding process is difficult.

The high-viscosity polyoxymethylene polymer has a melt flow index of 1 to 10 g/10min when measured at a temperature of 190° C. and a load of 2.16 kg according to ASTM D1238 standard, and the low-viscosity polyoxymethylene polymer has a temperature of 190 according to ASTM D1238 standard. It is characterized in that the melt flow index is 40 to 300g/10min when measured at ℃ 2.16kg load.

In the present invention, if the melt flow index of the high-viscosity polyoxymethylene polymer is less than 1 g/10 min, the injection speed should be basically increased when injecting small and complex shapes. It can be difficult to eject the speed and product. Therefore, injection failure may occur, and mixing with the powder may not be uniform, and the product may collapse in the degreasing and sintering process.

In addition, if the melt flow index of the high-viscosity polyoxymethylene polymer is more than 10 g/10 min, the polymer that can serve as a desired support during degreasing may be decomposed, and the product may collapse in the degreasing and sintering process.

When the melt flow index of the low-viscosity polyoxymethylene polymer is less than 40 g/10 min, the overall viscosity of the composition obtained by kneading the high-viscosity and low-viscosity polyoxymethylene is lowered, so a high injection pressure is required, and as a result, a product of a small and complex shape is injected. There are difficulties. In addition, when the melt flow index exceeds 300 g/10 min, it is a low molecular weight polymer, so it may be easy to establish injection process conditions, but the product may collapse due to rapid decomposition during degreasing.

In the present invention, the high-viscosity or low-viscosity polyoxymethylene polymer (a) comprises an oxymethylene-(OCH ₂ )n- group as a repeating unit, and (b) oxymethylene alone, both ends of which are capped by an ester or ether group. It is a polymer or an oxymethylene-based copolymer in which oxyalkylene units having 2 to 10 carbon atoms are randomly inserted into a polymer chain composed of oxymethylene monomer units, and (c) both ends of the polymer are blocked by ester or ether groups, or ternary It is characterized in that it is a copolymer.

In another aspect, the present invention relates to a feedstock composition for injection molding of a metal powder comprising the binder composition for injection molding of a metal powder.

The feedstock composition for injection molding of the metal powder includes (a) the binder composition for injection molding of the metal powder; and (b) a sinterable powdery inorganic material selected from the group consisting of metals, metal alloys, metal carbonyls, metal oxides, metal carbides, metal nitrides, and mixtures thereof.

Examples of metals that may be present in powder form include stainless, aluminum, iron, in particular iron carbonyl powder, chromium, cobalt, copper, nickel, silicon, titanium and tungsten. Examples of powdered metal alloys include high- or low-alloy steels and metal alloys based on aluminum, iron, titanium, copper, nickel, tungsten or cobalt. These are already finished alloys, for example, superalloys such as IN713C, GMR 235 and IN 100, and powders of alloys known from magnet technology using the main constituents Nd-Fe-B and Sm-Co, and individual alloy constituents. of both powder mixtures. Metal powders, metal alloy powders and metal carbonyl powders, metal oxides, metal carbides, metal nitrides may also be used in the mixture.

Suitable inorganic powders also _{include oxide ceramic powders such as Al 2} O ₃ , ZrO ₂ , Y ₂ O ₃ , as well as non-oxide ceramic powders such as SiC, Si ₃ N ₄ , and further complex oxide powders such as _{NiZnFe 2} O _{4 ,} and also inorganic color pigments such as _{CoAl 2} O _{4 .}

It is preferable that the average particle size of the powdery inorganic material is 1 to 20 μm.

The binder composition for injection molding of the metal powder is preferably contained in an amount of 20 to 80% by volume, and the inorganic material in the powder form is included in an amount of 20 to 80% by volume.

When the binder composition for injection molding is less than 20% by volume, there is a problem in mixing characteristics in kneading and injection, and when it exceeds 80% by volume, there is a problem that there is no value of process characteristics as a metal powder injection molding process.

In the present invention, the feedstock composition for metal powder injection molding may further include an additive selected from the group consisting of a lubricant and a dispersant.

The lubricant is distributed so that the powdery inorganic material is uniformly and evenly spaced in the metal powder injection molding binder to improve dimensional stability after sintering, and includes stearic acid, ethylene oxide, diethanolamine, and glycerin. , sorbitol (Sorbitol), behenic acid (Behenic Acid) and the like may be exemplified, but is not limited thereto.

The dispersing agent may use a dispersing agent commonly used, stearic acid, Zinc-Stearate, Calcium-Stearate, and the like may be exemplified, but is not limited thereto.

Preferably, the lubricant and the dispersant are included in an amount of 3% by volume or less with respect to 100% by volume of the total metal powder injection molding feedstock composition.

In another aspect, the present invention comprises the steps of: obtaining a green part by injection molding the feedstock composition for injection molding of the metal powder; removing a binder for metal powder injection molding from the green part to obtain a brown part; and sintering the brown part to manufacture a metal product.

1 is an explanatory diagram of a typical metal injection molding process. The metal injection molding method of the present invention is similar to the conventional metal injection molding process of FIG. 1, but is characterized by using the feedstock composition for injection molding of the metal powder.

Injection molding can be carried out using a conventional screw and ram injection molding machine, generally a mold having a temperature of 160 to 250° C. and a temperature of 30 to 250° C. at a pressure of 300 to 2,000 bar. can be done in

The green part obtained by injection molding should be subjected to a degreasing reaction to remove the metal powder binder for injection molding, and the present invention is characterized in that it is carried out at 50 to 150° C. in an acid atmosphere for 0.1 to 30 hours. It is preferable that the acid for forming the acid atmosphere is already in gaseous form at room temperature, or an inorganic acid capable of at least evaporation at the processing temperature is used. The acid may be exemplified by hydrohalic acid, nitric acid, and the like, but is not limited thereto.

The brown part produced after the degreasing reaction is finally made into a metal product through a sintering process, and the sintering is preferably performed at a temperature of 600 to 2000° C., which is a typical condition.

[Example]

Hereinafter, the present invention will be described in more detail through examples. These examples are only for illustrating the present invention, and it will be apparent to those of ordinary skill in the art that the scope of the present invention is not to be construed as being limited by these examples.

Examples 1-24 and Comparative Examples 1-12: Preparation of feedstock composition for injection molding of metal powder

The composition of Tables 1 to 4 below was put in a mixer and kneaded to prepare a feedstock.

Category (vol%) Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 Comparative Example 3 powdered
inorganic substances 55 55 55 55 20 80 55 55 55 Polyoxymethylene Polymer (MFI: 1) 20 15 10 4 40 10 30 0 7.5 Polyoxymethylene Polymer (MFI:40) 20 25 30 36 40 10 0 30 7.5 additive 5 5 5 5 0 0 5 5 30 polyolefin 0 0 0 0 0 0 10 10 0

Category (vol%) Example 7 Example 8 Example 9 Example 10 Example 11 Example 12 Comparative Example 4 Comparative Example 5 Comparative Example 6 powdered
inorganic substances 55 55 55 55 20 80 55 55 55 Polyoxymethylene Polymer (MFI: 1) 20 15 10 4 40 10 30 0 7.5 Polyoxymethylene Polymer (MFI:300) 20 25 30 36 40 10 0 30 7.5 additive 5 5 5 5 0 0 5 5 30 polyolefin 0 0 0 0 0 0 10 10 0

Category (vol%) Example 13 Example 14 Example 15 Example 16 Example 17 Example 18 Comparative Example 7 Comparative Example 8 Comparative Example 9 powdered
inorganic substances 55 55 55 55 20 80 55 55 55 Polyoxymethylene Polymer (MFI:10) 20 15 10 4 40 10 30 0 7.5 Polyoxymethylene Polymer (MFI:40) 20 25 30 36 40 10 0 30 7.5 additive 5 5 5 5 0 0 5 5 30 polyolefin 0 0 0 0 0 0 10 10 0

Category (vol%) Example 19 Example 20 Example 21 Example 22 Example 23 Example 24 Comparative Example 10 Comparative Example 11 Comparative Example 12 powdered
inorganic substances 55 55 55 55 20 80 55 55 55 Polyoxymethylene Polymer (MFI:10) 20 15 10 4 40 10 30 0 7.5 Polyoxymethylene Polymer (MFI:300) 20 25 30 36 40 10 0 30 7.5 additive 5 5 5 5 0 0 5 5 30 polyolefin 0 0 0 0 0 0 10 10 0

* Powdered inorganic material: Atmix, STS-316L D50 8㎛

* Polyoxymethylene polymer (high viscosity): Kolon Plastics developed material (melt flow index 1)

* Polyoxymethylene polymer (high viscosity): Kolon Plastic K300 (melt flow index 10)

* Polyoxymethylene polymer (low viscosity): Kolon Plastic K900 (melt flow index 40)

* Polyoxymethylene polymer (low viscosity): Kolon Plastics developed material (melt flow index 300)

* Additives: carnauba wax and stearic acid (mixing ratio = 1:1 volume ratio)

* Polyolefin: Lotte Chemical_UL814

Experimental Example 1: Manufacturing of metal products

(1) Manufacture of injection-molded body

The injection pressure of the feedstock prepared in Examples and Comparative Examples was fixed at 1,500 bar, and the mold was fixed at 120° C. to prepare an injection body (green part).

(2) Degreasing the molded product

Nitric acid was added to the injection body (green part) and degreased for 6 hours in an acid atmosphere at 120° C. to prepare a metal degreasing body (brown part).

(3) Sintering of metal workpieces

A metal degreasing body (brown part) was sintered at 1250° C., H ₂ and N ₂ mixed gas atmosphere at a temperature increase rate of 2° C./min per minute to prepare a metal product having a diameter of about 10×20 mm and a weight of 20 to 30 g.

Experimental Example 2: Evaluation for each process

Examples 1-24, Comparative Examples 1-12, and Experimental Example 1 kneading characteristics of the feedstock prepared in each manufacturing step, the injection characteristics of the metal work body (brown part), degreasing the metal work body (brown part) after degreasing Characteristics, sintering characteristics and quality of metal products after sintering were evaluated, and the results are shown in Tables 5-8.

by process
test results Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 Comparative Example 3 kneading characteristics ○ ○ ◎ ◎ ◎ △ Ⅹ ◎ Ⅹ Injection characteristics △ ○ ◎ ◎ ◎ △ △ △ Ⅹ Degreasing properties ◎ ◎ ◎ ◎ ◎ ◎ △ Ⅹ Ⅹ Sintering Characteristics ○ ◎ ◎ ○ ○ ◎ ○ △ △ quality inspection ○ ◎ ◎ ○ ○ ○ ○ ○ Ⅹ

by process
test results Example 7 Example 8 Example 9 Example 10 Example 11 Example 12 Comparative Example 4 Comparative Example 5 Comparative Example 6 kneading characteristics ○ ○ ◎ ◎ ◎ △ Ⅹ ◎ Ⅹ Injection characteristics ○ ○ ◎ ◎ ◎ ○ △ △ Ⅹ Degreasing properties ◎ ◎ ◎ ◎ ◎ ◎ ○ Ⅹ Ⅹ Sintering Characteristics ○ ◎ ◎ ○ ○ ◎ ○ △ △ quality inspection ○ ◎ ◎ ○ ○ ○ ○ ○ Ⅹ

by process
test results Example 13 Example 14 Example 15 Example 16 Example 17 Example 18 Comparative Example 7 Comparative Example 8 Comparative Example 9 kneading characteristics ○ ○ ◎ ◎ ◎ △ Ⅹ ◎ Ⅹ Injection characteristics ○ ○ ◎ ◎ ◎ ○ Ⅹ ○ Ⅹ Degreasing properties ◎ ◎ ◎ ◎ ◎ ◎ ○ Ⅹ Ⅹ Sintering Characteristics ◎ ◎ ◎ ○ ○ ◎ ○ Ⅹ △ quality inspection ○ ◎ ◎ ○ ○ ○ ○ ○ Ⅹ

by process
test results Example 19 Example 20 Example 21 Example 22 Example 23 Example 24 Comparative Example 10 Comparative Example 11 Comparative Example 12 kneading characteristics ○ ○ ◎ ◎ ◎ ○ Ⅹ ◎ Ⅹ Injection characteristics ○ ○ ◎ ◎ ◎ ○ △ △ Ⅹ Degreasing properties ◎ ◎ ◎ ◎ ◎ ◎ ○ Ⅹ Ⅹ Sintering Characteristics ○ ◎ ◎ ○ ○ ◎ ○ △ △ quality inspection ○ ◎ ◎ ○ ○ ○ ○ ○ Ⅹ

※ Characteristic evaluation method

1) Kneading Characteristics: Rheological behavior, Viscosity

2) Injection characteristics: exterior inspection of molded parts, X-ray internal non-destructive inspection

3) Degreasing properties: Degreasing body external inspection, X-ray internal non-destructive inspection

4) Sintering Characteristics: Density Measurement

5) Quality inspection: hardness of sintered compact, X-ray internal non-destructive inspection

※ Marking method: Very good - ◎, Good - ○, Normal - △, Poor - X

From Tables 5 to 8, Examples 1-24 showed average to very good kneading properties, injection properties, degreasing properties, sintering properties and quality, but Comparative Examples 1, 4, 7, and 10 using only high-viscosity polyoxymethylene polymer had kneading properties. This was poor, and Comparative Examples 2, 5, 8, and 11 using only low-viscosity polyoxymethylene polymer had poor degreasing properties, and Comparative Examples 3, 6, 9, and 12 with low content of powdered inorganic material and polyoxymethylene polymer. It was found that the kneading, injection and degreasing properties were poor, and thus the quality was also poor.

As the specific parts of the present invention have been described in detail above, for those of ordinary skill in the art, it is clear that these specific descriptions are only preferred embodiments, and the scope of the present invention is not limited thereby. will be. Accordingly, it is intended that the substantial scope of the present invention be defined by the appended claims and their equivalents.

Claims (10)

10 to 50% by weight of a high-viscosity polyoxymethylene polymer and 50 to 90% by weight of a low-viscosity polyoxymethylene polymer;
The high-viscosity polyoxymethylene polymer has a melt flow index of 1 to 10 g/10min when measured at a temperature of 190° C. and a load of 2.16 kg according to ASTM D1238 standard, and the low-viscosity polyoxymethylene polymer has a temperature of 190 according to ASTM D1238 standard. A binder composition for metal powder injection molding, characterized in that the melt flow index is 40 to 300 g/10 min when measured at ℃ 2.16 kg load.
delete The oxymethylene according to claim 1, wherein the high or low viscosity polyoxymethylene polymer (a) comprises oxymethylene -(OCH ₂ )n- groups as repeating units, and (b) oxymethylene capped at both ends by ester or ether groups. It is a homopolymer or an oxymethylene-based copolymer in which oxyalkylene units having 2 to 10 carbon atoms are randomly inserted into a polymer chain composed of oxymethylene monomer units, and (c) both ends of the polymer are blocked by ester or ether groups, or A binder composition for metal powder injection molding, characterized in that it is a terpolymer.
A feedstock composition for metal powder injection molding comprising the binder composition for metal powder injection molding according to claim 1 or 3.
5. The method of claim 4, wherein the feedstock composition for injection molding of the metal powder is
(a) the binder composition for metal powder injection molding of claim 1 or 3; and
(b) a feedstock for metal powder injection molding, comprising a sinterable powdery inorganic material selected from the group consisting of metals, metal alloys, metal carbonyls, metal oxides, metal carbides, metal nitrides and mixtures thereof composition.
[Claim 6] The feedstock composition for injection molding of metal powder according to claim 5, wherein the average particle size of the powdery inorganic material is 1 to 20 μm.
[Claim 6] The feedstock composition for injection molding of metal powder according to claim 5, wherein the binder composition for injection molding of the metal powder is contained in an amount of 20 to 80% by volume, and the inorganic material is in an amount of 20 to 80% by volume.
The feedstock composition for injection molding of metal powder according to claim 5, wherein the feedstock composition for injection molding of metal powder further comprises an additive selected from the group consisting of lubricants and dispersants.
Obtaining a green part by injection molding the feedstock composition for injection molding of the metal powder of claim 4; removing a binder for metal powder injection molding from the green part to obtain a brown part; and sintering the brown part to manufacture a metal product.
The metal injection molding method according to claim 9, wherein the removal of the binder for injection molding of the metal powder is performed at 50 to 140° C. in an acid atmosphere for 0.1 to 30 hours.

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