TWI669330B - Shot material composition for metal injection molding,molded article and preparing method thereof - Google Patents

Abstract

The present invention provides a metal injection molding shot composition comprising metal powder containing copper, cobalt or a combination thereof, a binder as a carrier of the shot composition, and a passivation layer coated on the metal powder and having the following Silane shown in structural formula (1),

Description

Metal injection molding injection material composition, molding body and preparation method thereof

The invention relates to a metal injection molding injection composition, a molded body, and a preparation method thereof, and particularly to a metal injection molding injection composition, a molded body, and a preparation method thereof that can use nitric acid as a catalyst for acid removal.

Metal Injection Molding (MIM) is a technology that combines powder metallurgy and injection molding. Because the MIM process is suitable for manufacturing parts with complex shapes, high precision and high performance materials, it is widely used in the manufacturing of automotive parts, electronic parts, medical components, machinery industry, daily necessities and other fields.

The MIM process mainly includes mixing, kneading, heating, and granulating processes to obtain metal powder and a binder to obtain an injection molding composition, and injection molding into a green embryo by a mold such as an injection molding machine, and then After debinding to remove the binding agent, the temperature is raised and sintered to obtain an injection molded body. Among them, since the degreasing step is used to ensure the quality of the subsequent sintered product, the degreasing step is one of the key steps of MIM.

The degreasing steps currently used in industry can be roughly divided into thermal debinding (thermal debinding) method and catalytic debinding (catalytic debinding) method. The thermal degreasing method uses the method of heating to make the binding agent Cracking, and using an inert medium to remove the cracked binder, thermal degreasing method has the advantage of simple process, however, it is limited by conditions such as heating rate and holding time. The catalyst degreasing method, also known as the acid degreasing method, uses the case where polyacetal is used as a binding agent, and a strong acid gas is introduced to carry out a catalyst reaction that decomposes polyacetal into formaldehyde. The acid degreasing method has the advantages of excellent product quality and a shorter time for carrying out the catalytic reaction. However, when the metal powder contains copper and / or cobalt, nitric acid causes the metal powder to oxidize and produce nitrate, which greatly reduces the degreasing efficiency. Therefore, there is still a need to provide a shot composition that can be quickly degreased by the acid degreasing method when the metal powder contains copper and / or cobalt.

In view of the above problems, the object of the present invention is to provide a metal injection molding injection composition, a molded body and a preparation method thereof, using silane coated on the metal powder as a passivation layer to overcome the inability to use acid degreasing method in the MIM field To prepare alloys containing cobalt and / or copper to further improve the problems caused by the above-mentioned conventional techniques.

According to the object of the present invention, there is provided a metal injection molding shot composition comprising: a metal powder containing copper, cobalt or a combination thereof, a binder as a carrier of the shot composition, and coating on the metal powder as a passivation Layer, and its structure is the silane shown in the structural formula (1) below, Among them, Y is a protecting group and does not react with nitric acid; R is selected from H, substituted or unsubstituted C ₁ -C ₃₀ alkyl, substituted or unsubstituted C ₁ -C ₃₀ heteroalkyl, substituted or Unsubstituted C ₃ -C ₃₀ cycloalkyl, substituted or unsubstituted C ₂ -C ₃₀ heterocycloalkyl, substituted or unsubstituted C ₂ -C ₃₀ alkenyl, substituted or unsubstituted C ₃ -C ₃₀ cycloalkenyl, substituted or unsubstituted C ₂ -C ₃₀ heterocycloalkenyl, substituted or unsubstituted C ₆ -C ₆₀ aryl, and substituted or unsubstituted C ₁ -C ₆₀ hetero Aryl; wherein, OR dehydrates with water molecules adsorbed on the surface of the metal powder.

Preferably, the weight ratio of metal powder to silane is 100: 1 to 400: 1.

Preferably, Y is selected from substituted or unsubstituted long carbon chain alkyl.

Preferably, the binder contains at least one of polyoxymethylene, polyene and wax.

According to the purpose of the present invention, there is also provided a method for preparing a molded body, which comprises: mixing the above-mentioned shot composition; injection molding into a green embryo; degreasing the green embryo, degreasing includes using a catalyst at a first temperature Acid degreasing and thermal degreasing at a second temperature; and sintering and obtaining a molded body.

Preferably, the catalyst is nitric acid.

Preferably, the first temperature is between 100 ° C and 130 ° C.

Preferably, the second temperature is between 550 ° C and 850 ° C.

According to the purpose of the present invention, there is also provided a molded body produced by the above method.

The metal injection molding injection composition, molded body and preparation method thereof of the present invention have the following advantages:

(1) The silane system of the present invention is a dual-function coating, which may have a passivation layer, so that the metal injection molding composition after mixing and granulation can not react with nitric acid in the subsequent acid degreasing process, The cobalt and / or copper contained in the shot composition can avoid the oxidation energy, and also has the borrowing By adjusting the polarity of the shot composition, the mutual solubility between the metal powder and the binding agent is increased to improve the dispersibility function.

(2) Since the silane of the metal injection molding injection composition of the present invention is added during the mixing and granulation process, the use of the injection composition of the present invention does not need to significantly change the original metal injection molding process, only It can be used by replacing the original shot composition with the shot composition of the present invention, so it can be degreased using an acid degreasing method that can react quickly without increasing the cost, so it can increase the yield and reduce manufacturing cost.

S10 ~ S40‧‧‧Step

FIG. 1 is a schematic flow chart of the method for preparing a molded body of the present invention.

In order to make the above purpose, technical features and benefits after actual implementation easier for those with ordinary knowledge in the art to understand, it will be described in more detail in the following with examples and drawings.

Refer to FIG. 1, which is a schematic flow chart of the method for preparing a molded body of the present invention.

In step S10, the shot composition is kneaded. The kneading process may include a process known to those with ordinary knowledge in the technical field such as mixing and granulation.

The shot composition may include metal powder, binder and silane. The metal powder may include copper and / or cobalt, that is, the metal powder may be any alloy powder including copper and / or cobalt. The binder is used as a carrier for the shot composition. The binder may include at least one of polyacetal, polyene, and wax. Preferably, the binding agent may be polyoxymethylene (POM) and / or polyethylene (PE).

Silane can be coated on the metal powder as a passivation layer, and its structure is shown in the following structural formula (1), Among them, Y is a protecting group and does not react with nitric acid; R is selected from H, substituted or unsubstituted alkyl groups containing 1-30 carbon atoms, substituted or unsubstituted hetero groups containing 1-30 carbon atoms Alkyl, substituted or unsubstituted cycloalkyl containing 3-30 carbon atoms, substituted or unsubstituted heterocyclic alkyl containing 2-30 carbon atoms, substituted or unsubstituted 2-30 containing Alkenyl group with 3 carbon atoms, substituted or unsubstituted cycloalkenyl group with 3-30 carbon atoms, substituted or unsubstituted heterocyclic alkenyl group with 2-30 carbon atoms, substituted or unsubstituted Aryl groups containing 6-60 carbon atoms, and substituted or unsubstituted heteroaryl groups containing 1-60 carbon atoms.

Among them, the heteroalkyl group refers to an alkyl group including S, P, O, and N. Heterocycloalkyl refers to cycloalkyl containing S, P, O, N. Heterocyclenyl refers to a cycloalkenyl group containing S, P, O, N. Heteroaryl refers to an aryl group containing S, P, O, N.

In one embodiment, Y of the silane is a substituted or unsubstituted long carbon chain alkyl. In one embodiment, the silane selected in the present invention is dissolved in a solvent for dilution to increase the dispersibility and facilitate the subsequent coating process. Since the boiling point of the higher alcohol is too high, the solvent may be a lower alcohol. The lower alcohol includes but is not limited to absolute ethanol, isopropanol and the like. The coating method includes but is not limited to spray coating. The coating method may be any method known to those having ordinary knowledge in the technical field. Since the lower alcohol is used for dilution and then the coating process is continued, it can be improved by heating Heating energy is used to produce dehydration reaction, and at the same time, lower alcohol used to increase dispersibility is removed by raising the temperature. Among them, the heating time may be 0.5 to 2 hr. Preferably, the heating temperature may be a temperature greater than 100 ° C. for the purpose of removing by-products and solvents of the dehydration reaction including water vapor. In addition, since the heating temperature can be greater than 100 ° C, even silanes with a higher carbon number can also produce dehydration reactions.

In an embodiment, the silane may include but is not limited to silanes represented by the following chemical formulas: H ₂ NC ₃ H ₆ -Si (OC ₂ H ₅ ) ₃ , H ₂ NC ₂ H ₄ NHC ₃ H ₆ -Si (OCH ₃ ) ₃ , H ₂ NC ₂ H ₄ NHC ₃ H ₆ -Si (OH) ₃ , C ₆ H ₅ -CH ₂ -NHC ₂ H ₄ NHC ₃ H ₆ -Si (OCH ₃ ) ₃ , H ₂ C = CH ( CH ₃ ) C (O) OC ₃ H ₆ -Si (OCH ₃ ) ₃ , H ₂ C = CH-C ₆ H ₄ -CH ₂ -NHC ₂ H ₄ NHC ₃ H ₆ -Si (OCH ₃ ) ₃ , H ₂ C = CH-Si- (OC ₂ H ₄ OCH ₃ ) ₃ , ClC ₃ H ₆ -Si (OCH ₃ ) ₃ , CH ₂ (O) CHCH ₂ OC ₃ H ₆ -Si (OCH ₃ ) ₃ , H ₂ C = CH-Si (OC ₂ H ₅ ) ₃ , CH ₂ (O) CHCH ₂ OC ₃ H ₆ -Si (CH ₃ ) (OC ₂ H ₅ ) ₂ , C ₆ H ₅ -Si (OCH ₃ ) ₃ , HS (CH ₂ ) ₃ Si (OCH ₃ ) ₃ , H ₂ C = CH-Si (OCH ₃ ) ₃ , CH ₃ -Si (OCH ₃ ) ₃ , C ₆ H ₁₃ -Si (OCH ₃ ) ₃ , C ₈ H ₁₇ Si (OC ₂ H ₅ ) ₃ , C ₈ H ₁₇ Si (OCH ₃ ) ₃ , C ₃ H ₇ Si (OCH ₃ ) ₃ , C ₃ H ₇ Si (OC ₂ H ₅ ) ₃ , (CH ₃ ) ₃ C-Si (OCH ₃ ) ₃ , (CH ₃ ) ₃ C-Si (OC ₂ H ₅ ) ₃ , ((CH ₃ ) ₃ Si) ₂ NH, Si (OC ₂ H ₅ ) ₄ , (CH ₃ O ) ₃ SiCH = CH ₂ , (C ₂ H ₅ O) ₃ SiCH = CH ₂ , (C ₂ H ₅ O) ₄ Si, (CH ₃ O) ₃ SiCH ₃ , (C ₂ H ₅ O) ₃ SiCH ₃ , (C ₂ H ₅ O) ₂ Si (CH ₃ ) ₂ , (CH ₃ ) ₃ SiNHSi (CH ₃ ) ₃ , (CH ₃ O) ₃ SiC ₆ H ₁₃ , (C ₂ H ₅ O) ₃ SiC ₆ H ₁₃ 、 (CH ₃ O) ₃ SiC ₁₀ H ₂₁ 、 (C ₂ H ₅ O ) ₃ SiCH = CH ₂ 、 (CH ₃ OC ₂ H ₄ O) ₃ SiCH = CH ₂ 、 (CH ₃ O ₃ ) SiCH = CH ₂ 、 (CH ₃ CO ₂ ) ₃ SiCH = CH ₂ 、 (CH ₃ O) ₃ SiC ₃ H ₆ N = C = O, (CH ₃ O) ₂ Si (CH ₃ ) ₂ , (C ₂ H ₅ O) Si (CH ₃ ) ₃ , (CH ₃ O) ₃ SiC ₁₆ H ₃₃ , bis -triethoxysilylpropyldisulfidosilane (TESPD) or bis-triethoxysilylpropyltetrasulfidosilane (TESPT).

In an embodiment, the silane may include but is not limited to silane as shown in the following structural formula:

Due to the large surface area of the metal powder, under normal operation, the surface of the metal powder will adsorb water molecules, and the OR on the silane can be dehydrated with the water molecules under heating conditions, thereby effectively coating and bonding to the metal powder on.

In one embodiment, the flow of the dehydration reaction may be as shown in the following reaction formula (1).

Among them, silane undergoes hydrolysis first and then reacts with a metal having OH groups on the surface to form a hydrogen bond, and then undergoes dehydration condensation reaction by heating to transform the hydrogen bond with lower interaction force into a stronger interaction Chemical bond.

In step S20, injection molding is performed into a green embryo. The injection molding process may include a process known to those skilled in the art. The mold for injection molding may be a sphere, a regular polyhedron, an irregular polyhedron, etc., an irregular polyhedron containing a curved surface, and the like.

In step S30, the green embryo is degreased. Degreasing involves acid degreasing at a first temperature and thermal degreasing at a second temperature using a catalyst. The catalyst may be any acid catalyst known to those of ordinary skill in the art. Preferably, the catalyst may be nitric acid or oxalic acid. More preferably, the catalyst may be nitric acid. The second temperature may be greater than the first temperature to complete the degreasing step by increasing the temperature. Preferably, the first temperature may be between 100 ° C and 130 ° C; more preferably, the first temperature may be between 110 ° C and 120 ° C. Preferably, the second temperature may be between 550 ° C and 850 ° C; more preferably, the second temperature may be between 600 ° C and 800 ° C.

Step S40, sintering and obtaining a molded body. The sintering process may be any process known to those skilled in the art.

In Example 1, a comparison of the metal injection molding shot composition is made, and a copper-cobalt alloy is selected as the metal powder, wherein the copper content may be 88 to 94% or the cobalt content may be 88 to 94%. Nitric acid is used as a catalyst, and POM is used as a binding agent for nitric acid. The composition of the binding agent is 60 to 80 wt% POM, 2 to 5 wt% high-density polyethylene (HDPE), and 2 to 5 wt% via maleic acid. Maleic anhydride modified low-density polyethylene (OREVAC ^® 18302N, density 0.912g / cm ³ ), 2 to 6wt% stearic acid (SA, Stearic Acid), 4 to 20wt% brown Montan wax and 1 to 5 wt% ethylene-vinyl acetate copolymer (EVA). At the same time, in order to match nitric acid, silane is also used as a dual-function coating. In addition to being used as a passivation layer of copper-cobalt alloys, silanes with long carbon chains and POM have better miscibility due to their similar mutual solubility. The mutual solubility is better, and the dispersibility is improved accordingly, the result is better.

In Example 2, following the above, the remaining conditions are the same as in Example 1, and comparison is made for metal powders containing different amounts of silane. The weight ratio of metal powder to silane is 100: 1 to 400: 1. However, when the metal powder content is too low, the metal powder is a limited amount of reagents, and silane is an excessive reagent, and excess silane causes a waste of cost; conversely, when the metal powder content is too high, part of the metal powder cannot be completely coated with silane Therefore, in the subsequent degreasing process, the oxidation problem of cobalt and / or copper alloy cannot be used in the conventional acid degreasing process.

Following the above, the remaining conditions are the same as in Example 1 and Example 2, and the comparison of different MIM processes is performed. Among them, the selected mixing granulation process, metal injection molding process and sintering process can be any process known to those skilled in the art.

Among them, to degrease the raw embryos, first of all, acid degreasing is performed using nitric acid with a concentration of 70 to 90 wt%. Among them, the nitrogen flow rate is 400 to 1000 nL / hr, the temperature is 120 to 170 ° C., the degreasing rate is 0.5 to 2.5 mm / hr, and the acid degreasing duration is 0.5 to 6 hr. The main purpose of acid degreasing is to remove POM quickly. The higher the nitric acid concentration, the faster the acid degreasing efficiency. The higher the inert gas displacement rate, the lower the concentration of the intermediate product produced by acid degreasing, so the higher the nitric acid concentration on the surface of the embryo reaction, so the higher the nitrogen degreasing efficiency, the higher the acid degreasing efficiency.

Among them, the thermal degreasing is continued. Among them, the thermal degreasing temperature is 600 to 800 ° C., and the thermal degreasing duration is 0.5 to 16 hr. The main purpose of thermal degreasing is to remove the silane as a protective function to facilitate the subsequent sintering process. At the same time, the green embryos after acid degreasing are likely to produce binder residues, which can also be removed by heat degreasing.

In summary, in addition to the metal injection molding composition, molded body and preparation method of the invention, the composition of the metal injection molding injection composition can be adjusted according to different usage requirements, and more importantly, the package of the invention Metal injection molding injection composition can overcome the unusable in the field of MIM The problem of preparing an alloy containing cobalt and / or copper by acid degreasing method, and can accelerate the production rate without significantly changing the original process to achieve the purpose of reducing costs.

The above is only exemplary, and not restrictive. Any equivalent modifications or changes made without departing from the spirit and scope of the present invention should be included in the scope of the patent application.

Claims (9)

A metal injection molding shot composition comprising: a metal powder comprising copper, cobalt or a combination thereof, and the copper content or cobalt content of the metal powder is 88 to 94% of the metal powder; a binding agent is used as the The carrier of the shot composition; and a silane coated on the metal powder as a passivation layer, the structure of which is shown in the following structural formula (1):

Among them, Y is a protecting group and does not react with nitric acid; R is selected from H, substituted or unsubstituted C ₁ -C ₃₀ alkyl, substituted or unsubstituted C ₁ -C ₃₀ heteroalkyl, substituted or Unsubstituted C ₃ -C ₃₀ cycloalkyl, substituted or unsubstituted C ₂ -C ₃₀ heterocycloalkyl, substituted or unsubstituted C ₂ -C ₃₀ alkenyl, substituted or unsubstituted C ₃ -C ₃₀ cycloalkenyl, substituted or unsubstituted C ₂ -C ₃₀ heterocycloalkenyl, substituted or unsubstituted C ₆ -C ₆₀ aryl, and substituted or unsubstituted C ₁ -C ₆₀ hetero Aryl; wherein OR dehydrates water molecules adsorbed on the surface of the metal powder. The shot composition as described in item 1 of the patent application range, wherein the weight ratio of the metal powder to the silane is 100: 1 to 400: 1. The shot composition as described in item 1 of the scope of patent application, wherein Y is selected from substituted or unsubstituted long carbon chain alkyl. The shot composition as described in item 1 of the patent application range, wherein the binding agent comprises at least one of polyacetal, polyene and wax. A method for preparing a molded body, comprising: kneading the injection composition as described in any one of claims 1 to 4; injection molding to form a green embryo; defatting the green embryo, including Using a catalyst for acid degreasing at a first temperature and thermal degreasing at a second temperature; and sintering and obtaining the shaped body. The method as described in item 5 of the patent application scope, wherein the catalyst is nitric acid. The method as described in item 5 of the patent application range, wherein the first temperature is between 100 ° C and 130 ° C. The method as described in item 5 of the patent application range, wherein the second temperature is between 550 ° C and 850 ° C. A molded body produced by the method described in any one of items 5 to 8 of the patent application.