KR20100114646A - Degreasing method for powder injection moldings using super-critical carbon dioxide - Google Patents

Abstract

PURPOSE: A degreasing method for powder injection moldings using supercritical carbon dioxide is provided to eliminate binders included in powder injection moldings within a short time. CONSTITUTION: A degreasing method for powder injection moldings is characterized in that supercritical carbon dioxide is contacted to powder injection molding to extract and separate binders included in the powder injection molding. The extracting and separation process is performed under a stepwise variation of temperature or/and pressure.

Description

Degreasing Method for Powder Injection Moldings Using Super-Critical Carbon Dioxide

The present invention relates to a method for degreasing a powder injection molded body using supercritical carbon dioxide. More specifically, the present invention provides a method for degreasing a powder injection molded body for extracting and separating the binder contained in the powder injection molded body by contacting supercritical carbon dioxide to the powder injection molded body, the extraction and separation using the supercritical carbon dioxide The step relates to a powder injection molding degreasing method carried out under temperature, pressure or stepwise change of temperature and pressure.

The powder injection molding method is a new powder molding process that combines powder metallurgy technology in the metal industry and injection molding technology in the plastics industry. This process has recently been suitable for mass production of complex shaped solid products, especially for applications such as cutting tools, magnetic material parts, precious metal parts and MEMS (Micro Electro Mechanical System). The degreasing process generally refers to a process of removing a binder added to improve the flowability of fine solid powder in a molding process including a powder injection molding process.

Known degreasing methods known to date have the disadvantage of requiring a long degreasing time and a large amount of energy as shown in the following data. These known degreasing methods are described in more detail by degreasing by applying heat (hereinafter referred to as 'heat degreasing method'), degreasing by using a solvent (hereinafter referred to as 'solvent degreasing method'), and degreasing by using a catalyst. It can be roughly classified into a method of hereinafter (hereinafter referred to as 'catalyst degreasing method'). The heat degreasing method is described for the wicking method as in US Patent No. 5,028,367 and US Patent No. 4,404,166, and the solvent degreasing method is described in US Patent No. 4,197,118 and US Patent No. 4,765,950, etc. methylene chloride, acetone, and a method of using Freon, etc. as the solvent is described, as the catalyst degreasing method is US Patent No. 5,531,958 and U.S. Patent No. as described 5,073,319 arc like boron as a nitric acid, a triple (BF ₃ ) Catalysts are used.

However, the solvent degreasing method can shorten the degreasing time to some extent compared to the heat degreasing method, but there is a problem of using an organic solvent that is harmful to the environment and the human body, and has a problem for a harmful organic solvent-free formulation in the future.

In addition, the heat degreasing method takes a degreasing time of several tens of hours to several hundred hours in terms of economics and has a problem of heating the temperature to a high temperature of about 300-500 ° C.

Numerous papers and patent documents are referenced and cited throughout this specification. The disclosures of the cited papers and patent documents are incorporated herein by reference in their entirety to better understand the state of the art to which the present invention pertains and the content of the present invention.

The present inventors earnestly researched to develop a method for separating and extracting the binder contained in the powder injection molding at a lower temperature at a faster time. As a result, the present invention is included in the powder injection molding with supercritical carbon dioxide alone without cosolvents. The present invention has been accomplished by discovering that only binders, especially low molecular weight waxes, can be selectively removed under critical temperatures and critical pressures.

Accordingly, an object of the present invention is a method of degreasing a powder injection molded body for extracting and separating the binder contained in the powder injection molded body by contacting the supercritical carbon dioxide to the powder injection molded body, the extraction and separation using the supercritical carbon dioxide The step is to provide a powder injection molding degreasing method which is carried out under temperature, pressure or stepwise change of temperature and pressure.

Other objects and advantages of the present invention will become more apparent from the following detailed description of the invention, claims and drawings.

According to an aspect of the present invention, the present invention provides a method for degreasing a powder injection molded body for extracting and separating the binder contained in the powder injection molded body by contacting the supercritical carbon dioxide to the powder injection molded body, using the supercritical carbon dioxide Extracting and separating provide a powder injection molding degreasing method that is carried out under temperature, pressure or stepwisely changing temperature and pressure.

The present inventors earnestly researched to develop a method for separating and extracting the binder contained in the powder injection molding at a lower temperature at a faster time. As a result, the present invention is included in the powder injection molding with supercritical carbon dioxide alone without cosolvents. The present invention has been accomplished by discovering that only binders, especially low molecular weight waxes, can be selectively removed under critical temperatures and critical pressures.

The specification term 'powder' of the present invention means any material powder that can be used to make powder injection molded articles in the art. More specifically, the powder refers to a metal (including mono-element metals and alloys), ceramics or cermet powders in which a metal and a ceramic are mixed.

According to a preferred embodiment of the present invention, the powder means a metal or ceramic powder.

In general, supercritical fluids are very effective for extracting binders from porous materials because of their excellent permeability and transportability due to gas-like diffusion rates, and high solubility in liquid-like density. In addition, since the dissolving power changes with temperature and pressure changes, selective extraction is possible in the material.

Carbon dioxide is present in the solid state at −78.5 ° C., 1 atm (14.696 psi), as a gas at 20 ° C., 1 atm, and in the liquid state at 50 atm (734.8 psi) and 20 ° C. The term 'supercritical carbon dioxide' of the present invention refers to carbon dioxide whose density is continuously changed at 72 atm (1,058 psi) without a condensation process at 31 ° C. or higher, and the supercritical carbon dioxide is fluid like gas but has a liquid-like density. It has the property of transporting the melt while simultaneously penetrating the solid material.

The present invention is capable of degreasing binders or binders contained in powder injection moldings at flow rates of supercritical carbon dioxide (eg, flow rates of supercritical carbon dioxide above 10 l / min) that are acceptable in the art. According to a preferred embodiment of the present invention, the supercritical carbon dioxide is contacted with the powder injection molded body at a flow rate of 0.5-10 L / min. More preferably, the powder injection molded body is contacted at a flow rate of 0.8-5 L / min, most preferably 1-2 L / min.

According to a preferred embodiment of the present invention, the present invention can degrease the binder contained in the powder injection molded body having a thickness of 1 mm or more. More preferably, the present invention is able to degrease the binder contained in the powder injection molding having a thickness of 1.5-30 mm, even more preferably 2-20 mm, most preferably 3-10 mm.

As used herein, the term “binder or binder” refers to a material that imparts fluidity to the powder to be filled into a mold during injection molding and maintains a shape after cooling.

In addition, the specification term "degreasing" of the present invention means to remove the binder contained in the powder injection molding.

The binder used in the powder injection molding method is thermoplastic resins such as polyethylene, polypropylene, and polystyrene, and low molecular waxes such as paraffin wax, carnauba wax, montan wax, and Japan wax. Oils, such as edibles, water and sublimable substances are used, but are not limited thereto. According to a preferred embodiment of the present invention, the binder is a low molecular weight wax, more preferably the binder is paraffin wax or montan wax, and most preferably paraffin wax.

Low molecular waxes of the binder should be removed during the degreasing process, but polymer series such as polyethylene, polystyrene, and polypropylene should remain in the molding after degreasing to bond metal powders to maintain the shape. However, these polymer-based components are all removed during the sintering process.

According to a preferred embodiment of the present invention, the degreasing temperature for extracting and separating the binder included in the powder injection molded body using the supercritical carbon dioxide is 30-300 ° C, more preferably 35-200 ° C, and more More preferably, it is 40-100 degreeC, Most preferably, it is 40-75 degreeC. The binder extraction and separation step is carried out by changing the degreasing temperature step by step. More specifically, the step may be carried out by raising the temperature step by step from low temperature to high temperature or by decreasing step by step from high temperature to low temperature, the low temperature and high temperature may be selectively performed in any order. In the case of changing the degreasing temperature step by step in the binder extraction and separation step, the step is carried out stepwise or under a constant pressure to change the degreasing pressure described below herein.

According to a preferred embodiment of the present invention, the degreasing pressure for extracting and separating the binder included in the powder injection molding using the supercritical carbon dioxide is 50-500 bar, more preferably the degreasing pressure is 80-400 bar, even more preferably the degreasing pressure is 100-130 bar, and most preferably the degreasing pressure is 130-250 bar. In addition, since the step change method of the degreasing pressure is the same as the step change method of the degreasing temperature, the common content between the two is omitted in order to avoid excessive complexity of the present specification.

The term 'bar and Pa' of the present specification means a unit of pressure, 10 bar is expressed in the following examples and claims of the present invention by cross-converting with each other in 1 MPa.

The present invention can be used with or without a cosolvent when separating and extracting the binder included in the powder injection molding using supercritical carbon dioxide. According to a preferred embodiment of the present invention, the present invention is a cosolvent, for example methanol, ethanol, propane, isopropanol, benzoyl alcohol when separating and extracting the binder included in the powder injection molding using supercritical carbon dioxide It is characterized by not using alcohols, monoethanolamine, diethanolamine, triethanolamine, carbon tetrachloride, acetone, methyl ethyl ketone, tetrahydrofuran, and the like.

According to a preferred embodiment of the present invention, the powder injection molding degreasing method of the present invention is characterized in that the supercritical carbon dioxide is in contact with the powder injection molding for 1-50 hours. More preferably, supercritical carbon dioxide is contacted with the powder injection molded body for 5-45 hours, even more preferably 10-40 hours, and most preferably 12-38 hours.

Conventional degreasing process uses a method of supercritical fluid degreasing, heating degreasing or solvent extraction under fixed conditions, but these methods have a limitation in that they can be efficiently applied only to injection moldings having a relatively thin thickness of about 1-3 mm. As a result, when a supercritical degreasing process of fixed conditions applied to a powder injection molded product having a thickness of 1-3 mm is applied to a powder injection molded product having a thickness of 3 mm or more, the powder injection molded body is deformed and the efficiency is very low even if it is degreased. It becomes very difficult to use in the degreasing process.

In comparison, the present invention makes it possible to effectively degrease the binder contained in the powder injection molded body of 1 mm or more in a faster time at a much lower temperature than the prior art by making a step change in temperature, pressure or temperature and pressure. In addition, the present invention is able to mass produce a large amount of powder injection molded body with very high energy efficiency due to the low temperature and short degreasing process time.

According to a preferred embodiment of the present invention, the present invention degreases at least 50% by weight of the binder contained in the powder injection molding. More preferably, the present invention degreases at least 70% by weight of the binder contained in the powder injection molding, and even more preferably, the present invention degreases at least 80% by weight of the binder contained in the powder injection molding. Even more preferably, the present invention degreases at least 90% by weight of the binder contained in the powder injection molding, and most preferably, the present invention degreases the binder contained in the powder injection molding at 100% by weight.

As used herein, the term 'wt%' refers to the weight of the low molecular weight waxes degreased based on the total amount of the low molecular weight waxes (eg, paraffin wax) included in the powder injection molding as a percentage.

The features and advantages of the present invention are summarized as follows:

(Iii) The present invention provides a method of degreasing a powder injection molded body in which a supercritical carbon dioxide is contacted with a powder injection molded body to extract and separate a binder contained in the powder injection molded body, wherein the extraction and separation using the supercritical carbon dioxide is performed. The step provides a powder injection molding degreasing method which is carried out under temperature, pressure or step change of temperature and pressure.

(Ii) The present invention has a significant value in terms of energy efficiency by degreasing at a lower temperature than the conventional heat degreasing method or solvent degreasing method as a technology for removing only low molecular wax components in moldings. The binder contained in can be degreased.

(Iii) The present invention can selectively remove only binders, particularly low molecular weight waxes, contained in the powder injection molding with supercritical carbon dioxide without cosolvents under critical temperature and critical pressure.

(Iii) In addition, the present invention is applicable to a powder injection molded body having a thickness of 3 mm or more, and when commercialized, it is possible to produce a very high value-added product, and thus the possibility of having high commercial and commercial effects. Have

Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood by those skilled in the art that these embodiments are only for describing the present invention in more detail and that the scope of the present invention is not limited by these embodiments in accordance with the gist of the present invention .

Example

Optimum variable condition setting

In order to determine the degreasing condition of the powder injection molding without deformation, experiments were carried out on disk specimens injection-molded with ceramic powder. For 1 mm and 2 mm disk samples, the temperature was between 40-75 ℃ and 100 bar-300 bar. In general, the extraction speed tended to be shorter as the temperature and pressure were higher. However, when the thickness of the ceramic powder injection molded product was 3 mm or more, deformation occurred at a temperature of 65 ° C. and a pressure of 170 bar or more. That is, when the thickness of the ceramic powder injection molded body was 3 mm or more, it was necessary to change the conditions because the deformation occurred in the powder injection molded body when the pressure and temperature conditions applied to the 1-2 mm powder injection molded body were applied as they are. As a result of lowering the experimental conditions, no abnormality occurred at the conditions of 65 ° C. and 150 bar pressure. Based on these results, the pressure and temperature initial conditions for the 6 mm thick ceramic powder injection molded sample were basically set to 65 ° C. and 150 bar or less.

Degreasing conditions for metal powder injection moldings with a thickness of 5 mm were also identified. Generally, metal injection moldings withstand higher conditions than ceramic injection moldings, but deformation occurs when the temperature is 75 ° C at a pressure of 250 bar. . Therefore, as a result of lowering the experimental conditions, degreasing was performed without any abnormality at a temperature of 50 ° C. and a pressure of 250 bar. Based on this result, the initial degreasing condition for the metal powder injection molded product having a thickness of 5 mm or more was set to a temperature of 50 ° C. and a pressure of 250 bar, and then a degreasing process was performed while gradually increasing the temperature and pressure conditions.

Example 1 Variable Conditions Debinding First Process for Ceramic Nozzle Samples

CO _{2 was added} to a 6 mm ceramic nozzle sample at an average flow rate of 2 L / min and a variable condition debinding process was conducted continuously for a total of 38 hours. That is, 12 hours at 40 ° C. and 13 Mpa, 12 hours at 45 ° C. and 15 MPa, 6 hours at 50 ° C. and 15 MPa, 6 hours at 55 ° C. and 20 MPa, and 60 hours and 20 MPa The experiment was carried out for 2 hours continuously.

^a) 1 MPa = 10 bar

^b) % by weight based on the total amount of paraffin wax contained in the ceramic powder injection molding.

As a result, in each step 15% by weight, 15% by weight, 20% by weight, 20% by weight and 15% by weight of paraffin wax binders were removed, totaling at least 85% by weight of paraffin wax binders (Table 1).

Example 2 Variable Condition Debinding Second Process for Ceramic Nozzle Samples

CO _{2 was added} to a 6 mm ceramic nozzle sample at an average flow rate of 2 L / min and a variable condition debinding process was conducted continuously for a total of 35 hours. That is, 12 hours at 40 ° C. and 13 Mpa, 12 hours at 45 ° C. and 15 MPa, 6 hours at 50 ° C. and 20 MPa, 3 hours at 55 ° C. and 20 MPa, and 60 hours and 25 MPa. The experiment was carried out for 2 hours continuously.

^a) 1 MPa = 10 bar

^b) % by weight based on the total amount of paraffin wax contained in the ceramic powder injection molding.

As a result, in each step 15% by weight, 15% by weight, 25% by weight, 15% by weight and 13% by weight of paraffin wax binders were removed, totaling at least 83% by weight of paraffin wax binders (Table 2).

Example 3: Variable Condition Debinding Third Process for Ceramic Nozzle Samples

An average flow rate of CO ₂ was applied to the 6 mm ceramic nozzle sample at 2 L / min, and the variable condition debinding process was conducted continuously for a total of 36 hours. That is, 12 hours at 40 ° C. and 13 Mpa, 12 hours at 45 ° C. and 15 MPa, 6 hours at 50 ° C. and 20 MPa, 3 hours at 55 ° C. and 20 MPa, and 60 hours and 25 MPa. The experiment was continued for 3 hours.

^a) 1 MPa = 10 bar

^b) % by weight based on the total amount of paraffin wax contained in the ceramic powder injection molding.

As a result, in each step 15% by weight, 15% by weight, 25% by weight, 15% by weight and 15% by weight of paraffin wax binders were removed, totaling at least 85% by weight of paraffin wax binders (Table 3).

Example 4 Variable Conditions Debinding First Process for Metal Powder Injection Molded Parts

The average flow rate of CO ₂ was applied to the 5 mm metal powder injection molded body at 1 L / min, and the variable condition debinding process was continuously performed for a total of 12 hours. That is, 2 hours at 50 ° C and 25 Mpa, 2 hours at 50 ° C and 25 MPa, 2 hours at 50 ° C and 25 MPa, 2 hours at 55 ° C and 25 MPa, 2 hours at 65 ° C and 25 MPa The experiments were conducted continuously for 2 hours at 75 ° C. and 25 MPa.

^a) 1 MPa = 10 bar

^b) % by weight based on the total amount of paraffin wax contained in the ceramic powder injection molding.

As a result, at each step 40% by weight, 20% by weight, 10% by weight, 10% by weight, 7% by weight and 5% by weight of paraffin wax binders were removed, totaling at least 92% by weight of paraffin wax binders ( Table 4).

Example 5 Variable Conditions Debinding Second Process for Metal Powder Injection Molded Parts

The average flow rate of CO ₂ was applied to the 5 mm metal powder injection molded body at 1 L / min, and the variable condition debinding process was continuously performed for a total of 12 hours. That is, 2 hours at 50 ° C and 25 Mpa, 2 hours at 50 ° C and 25 MPa, 2 hours at 55 ° C and 25 MPa, 2 hours at 60 ° C and 25 MPa, 2 hours at 65 ° C and 25 MPa The experiments were conducted continuously for 2 hours at 75 ° C. and 25 MPa.

^a) 1 MPa = 10 bar

^b) % by weight based on the total amount of paraffin wax contained in the ceramic powder injection molding.

As a result, at each step 40% by weight, 20% by weight, 15% by weight, 10% by weight, 7% by weight and 3% by weight of paraffin wax binders were removed, totaling at least 95% by weight of paraffin wax binders ( Table 5).

Example 6 Variable Conditions Debinding Third Process for Metal Powder Injection Molded Parts

The average flow rate of CO ₂ was applied to the 5 mm metal powder injection molded body at 1 L / min, and the variable condition debinding process was continuously performed for a total of 12 hours. 2 hours at 50 ° C and 25 MPa, 2 hours at 50 ° C and 25 MPa, 2 hours at 50 ° C and 25 MPa, 2 hours at 65 ° C and 25 MPa, 2 hours at 75 ° C and 25 MPa The experiments were conducted continuously for 2 hours at 75 ° C. and 25 MPa.

^a) 1 MPa = 10 bar

^b) % by weight based on the total amount of paraffin wax contained in the ceramic powder injection molding.

As a result, at each step 40% by weight, 20% by weight, 10% by weight, 17% by weight, 10% by weight and 3% by weight of paraffin wax binders were removed and a total of nearly 100% paraffin wax binders were removed. Table 6 and FIG. 16.

Remarks

Based on the test results of the disk specimens, the experiments were carried out by setting various degreasing conditions of a nozzle sample with a thickness of 6 mm and the paraffin wax melted at a temperature above 55-60 ℃, which is the melting point of paraffin wax. Cracks were observed in the sample even at low pressures. This is because a large amount of paraffin wax binders in the sample are pulled out at once, resulting in deformation of the sample because of the strong capillary force. Here, it was found that it is important to set the initial degreasing temperature and pressure very low so that degreasing occurs at a slow rate so that the paraffin wax binder does not rush out and the paraffin wax does not melt to create a condition in which capillary forces do not occur. Under these conditions, if half of the paraffin wax binder was removed without cracking in the sample, the paraffin wax binder was more easily released than the initial state. In this state, the pressure and temperature conditions were increased stepwise to remove the remaining paraffin wax binder, thereby obtaining a complete sample without any abnormality. In order to apply the fixed degreasing process without the variable condition degreasing process, the temperature and pressure conditions have to be very low, but it takes a long time to apply to the actual process. Therefore, a variable condition debinding process was required to remove the half of the binder by increasing the pressure and temperature to a small width and then to remove the residual binder by increasing the pressure and the temperature to a great extent. The binder removed was about 90% of the total weight of the paraffin wax binder. When the solvent extraction method was applied, the sample could be deformed due to deformation, and the degreasing efficiency of the deformed sample was only 20% of the paraffin wax binder removed after 12 hours of degreasing. In contrast, the variable condition degreasing process yielded very breakthrough results.

In the case of a metal injection molded body having a thickness of 5 mm, when the conventional solvent extraction method was applied, only about 30% of the binder was removed as a result of degreasing for 8 hours. Therefore, a variable condition degreasing process using supercritical carbon dioxide was applied, and very high efficiency of nearly 100% of the paraffin wax binder was obtained for 12 hours.

The nozzle sample that has undergone the degreasing process using the above supercritical carbon dioxide as a solvent becomes a finished product after the heat treatment and the sintering process.

This result shows that, in the case of the thick powder injection molding, the conventional method such as heating degreasing or solvent extraction, including the supercritical degreasing process under fixed conditions, may cause deformation of the powder injection molding, and even if degreasing, The results are quite dramatic, as they are very far apart and very difficult to use in actual degreasing processes. Commercially available products to which the degreasing process is currently applied are ceramic injection moldings having a thickness of about 1 mm, such as bulbs used in metal halide lamps, and are extremely valuable when supercritical degreasing methods are commercialized for such thick powder injection moldings. It is possible to produce high-quality products, which can be said to be a research result that is highly effective not only for technical aspects but also for commercial use.

Having described the specific part of the present invention in detail, it is apparent to those skilled in the art that the specific technology is merely a preferred embodiment, and the scope of the present invention is not limited thereto. Thus, the substantial scope of the present invention will be defined by the appended claims and equivalents thereof.

1 is a result of degreasing the ceramic injection molded body having a thickness of 3 mm for 300 hours under a pressure of 150 bar and a temperature of 65 ° C. at an average flow rate of carbon dioxide of 1 L / min. 90% of the binder contained in the 3 mm thick ceramic injection molded body was degreased.

FIG. 2 shows a 3 mm thick ceramic injection molded product in which cracking occurred as a result of performing a degreasing process for 1 hour at a pressure of 170 bar and a temperature of 65 ° C. with an average flow rate of carbon dioxide of 1 L / min. Image.

3 is an image of a 3 mm-thick ceramic injection molded body having cracks as a result of performing a degreasing process for 1 hour at a pressure of 200 bar and a temperature of 65 ° C. at an average flow rate of carbon dioxide of 1 L / min.

FIG. 4 is an image of a 3 mm thick ceramic injection molded body having cracks as a result of performing a degreasing process for 1 hour at a pressure of 250 bar and a temperature of 75 ° C. at an average flow rate of carbon dioxide of 1 L / min.

FIG. 5 is a front image of a 6 mm thick ceramic injection molded body subjected to a degreasing process by solvent extraction for 12 hours at a temperature of 30 ° C. FIG. It was degreased at 30 ° C. for 12 hours, and 19% by weight of paraffin wax was degreased relative to the total weight of the paraffin wax binder included in the molded body.

FIG. 6 is a front image of a 6 mm thick ceramic injection molded body subjected to a degreasing process by solvent extraction for 12 hours at a temperature of 30 ° C. FIG. It was degreased at 30 ° C. for 12 hours, and 20% by weight of paraffin wax was degreased relative to the total weight of the paraffin wax binder included in the molded body.

FIG. 7 is a bottom image of two 6 mm thick ceramic injection moldings subjected to a degreasing process with solvent extraction for 12 hours at a temperature of 30 ° C. FIG.

8 is an image of a broken 6 mm thick ceramic injection molded body degreased at a pressure of 250 bar and a temperature of 75 ° C. with an average flow rate of carbon dioxide of 2 l / min.

9 is an image of a broken 6 mm thick ceramic injection molded body degreased at a pressure of 250 bar and a temperature of 75 ° C. with an average flow rate of carbon dioxide of 2 l / min.

10 is an image of a broken 6 mm thick ceramic injection molded body degreased at a pressure of 150 bar and a temperature of 55 ° C. with an average flow rate of carbon dioxide of 2 l / min.

11 is an image of a broken 6 mm thick ceramic injection molded body degreased at a pressure of 150 bar and a temperature of 55 ° C. with an average flow rate of carbon dioxide of 2 l / min.

12 is a front image of a complete nozzle sample degreased under the continuously variable process conditions of Example 1 of the present invention.

FIG. 13 is a bottom image of a complete nozzle sample degreased under the continuously variable process conditions of Example 1 of the present invention.

FIG. 14 is a front image of a 5 mm thick metal powder injection molded body having a mean flow rate of carbon dioxide of 1 L / min and cracked when degreased at a pressure of 250 bar and a temperature of 75 ° C. FIG.

FIG. 15 is a front image of a broken 5 mm thick metal powder injection molded body degreased at a pressure of 250 bar and a temperature of 75 ° C. with an average flow rate of carbon dioxide of 1 L / min.

FIG. 16 is a front image of a complete metal powder injection molding degreased under the continuously variable process conditions of Inventive Example 4. FIG.

Claims (13)

In the degreasing method of a powder injection molded body in which a supercritical carbon dioxide is contacted with a powder injection molded body to extract and separate a binder contained in the powder injection molded body, the step of extracting and separating using the supercritical carbon dioxide may be performed by using a temperature, pressure or A method of degreasing a powder injection molded body, characterized in that it is carried out under a stepwise change in temperature and pressure. The powder injection molding degreasing method according to claim 1, wherein the powder is a metal or ceramic powder. The powder injection molding degreasing method according to claim 1, wherein the powder injection molding has a thickness of 1 mm or more. 2. The powder injection molding degreasing method according to claim 1, wherein the binder is a low molecular weight wax. 5. The powder injection molding degreasing method according to claim 4, wherein the wax is paraffin. 2. The powder injection molding degreasing method according to claim 1, wherein the supercritical carbon dioxide is brought into contact with the powder injection molding at a flow rate of 0.5-10 L / min. 2. The powder injection molding degreasing method according to claim 1, wherein the temperature is 30-300 deg. 8. The powder injection molding degreasing method according to claim 7, wherein the temperature is gradually changed from low temperature to high temperature. The method of claim 1 wherein the pressure is 50-500 bar.  The powder injection molding degreasing method according to claim 9, wherein the pressure is gradually changed from low pressure to high pressure. The powder injection molding degreasing method according to claim 1, wherein the method does not use a cosolvent when separating and extracting the binder using supercritical carbon dioxide. 12. The method for degreasing the powder injection molded body according to claim 1, wherein the method comprises contacting the powder injection molded body with supercritical carbon dioxide for 1 to 50 hours. The method for degreasing the powder injection molded body according to claim 1, wherein the degreasing method degreases at least 50% by weight of the binder contained in the powder injection molded body.

Images