CN105463347B - A kind of preparation method of powder injection forming binding agent and feeding - Google Patents

Abstract

The invention discloses a method for preparing a binder and feeding material for powder injection molding. The preparation of the binder includes the following steps: (1) Weighing the powder according to the mass ratio of 1:5~20:0.1~0.6 Carbon nanotubes, paraffin and oleic acid, heat the paraffin to melt, add carbon nanotubes and oleic acid, keep the temperature at 80~85°C, ultrasonically stir for 0.5~1.5h to disperse the carbon nanotubes evenly; then cool rapidly To solidify, obtain composite solid paraffin; (2) chop the obtained composite solid paraffin, by mass parts, add 30～40 parts of chopped composite solid paraffin into mixer, add 12-18 parts of medium density after mixing Polyethylene, after the medium density polyethylene is dissolved, add 2-3 parts of surfactant, and then knead to obtain the binder. The invention can use a low molecular weight binder that is easy to come out, which can realize stable and uniform dispersion of carbon nanotubes in the metal matrix composite material, can inhibit the growth of crystal grains, effectively inhibit the shrinkage of volume, and obtain a highly dense composite Material.

Description

A kind of preparation method of binder and feeding material for powder injection molding

technical field

The invention relates to a preparation method of a binder and a feeding material for powder injection molding.

Background technique

With its unique structure and properties, carbon nanotubes are expected to become the most promising reinforcement phase for composite materials. In the process of preparing carbon nanotube-reinforced metal matrix composites, the dispersion of carbon nanotubes in the matrix and the compatibility of the two phases are two key issues. Because carbon nanotubes, like carbon fibers, are not wetted with most metals, it is difficult to form a firm bonding interface between carbon nanotubes and the metal matrix, thereby affecting the performance of the carbon nanotube reinforcement effect. Using a relatively simple mixing method such as mechanical or solvent, the difference in size and specific gravity between the two will lead to the aggregation and segregation of carbon nanotubes is difficult to avoid; modifying carbon nanotubes, such as Cu, Ni, etc. Surface coating, but because the diameter is only nanoscale, it is difficult to achieve uniform and dense metal layer plating on the surface, and it is even more difficult to ensure continuous and dense coating layer in large-scale plating. In order to overcome this problem, some new composite methods have been proposed. Korean scientists functionalized carbon nanotubes, used the liquid phase to composite with copper ions, and used plasma flame sintering after reduction. The Young's modulus was doubled. . Our research group has also made a big breakthrough in solving this problem, using the electrostatic assembly method to pre-synthesize micron-sized carbon nanotube-copper composite particles through the liquid phase. The carbon nanotubes are "locked" in the composite particles, which can greatly reduce the segregation during the sintering process; as the original powder, it is hot-pressed in a mold, and then hot-rolled to obtain a block with uniform distribution of carbon nanotubes Material. It is not difficult to see that these methods have carried out functional modification on carbon nanotubes, and have good wettability with the matrix. However. It is a tedious task to functionalize carbon nanotubes with nanoscale size. Generally, it needs to undergo ordinary acid washing and purification before further chemical or physical modification, which is expensive and time-consuming, and it is difficult to achieve large-scale production.

Using the infiltration method to prepare carbon nanotube-reinforced metal matrix composites is also a technical path that people have explored. The idea is to disperse the carbon reinforcement in organic matter in advance, and obtain a porous preform with a three-dimensional network skeleton structure of carbon nanotubes through heat treatment. The hot molten metal is pressed into the carbon reinforcement preform. The dispersion and uniform distribution of carbon nanotubes in the composite material obtained by this method is easier to solve, and the volume content of carbon nanotubes can also reach more than 20%, but this method requires high wettability of the two phases. The penetration of liquid metal is difficult to fully and completely, there are many holes, and the density is difficult to increase.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for preparing the binder and its feeding materials required for the preparation of carbon nanotube reinforced metal matrix composite materials by powder injection molding method in view of the defects existing in the prior art. This binder uses medium-density polyethylene as a polymer with a high viscosity as a mixing medium, and is fully dispersed and mixed with carbon nanotubes in advance. With the help of shearing and stretching when the polymer melt flows, carbon nanotubes And metal powder is uniformly dispersed and anchored in a wide range.

One of the technical solutions of the present invention is to provide a method for preparing a binder for powder injection molding, comprising the following steps:

(1) Weigh carbon nanotubes, paraffin and oleic acid according to the mass ratio of 1:5~20:0.1~0.6, heat the paraffin to melt, add carbon nanotubes and oleic acid, and keep the temperature at 80~85 Ultrasound and stir for 0.5~1.5h at ℃ to disperse the carbon nanotubes evenly; then cool rapidly until solidified to obtain composite solid paraffin;

(2) The obtained composite solid paraffin is chopped, and 30 to 40 parts of chopped composite solid paraffin are added to the mixer in parts by mass. After mixing, 12 to 18 parts of medium density polyethylene are added, and the medium density polyethylene Add 2~3 parts of surfactant after ethylene is dissolved, and then knead to obtain binder.

Further, the carbon nanotubes have a diameter of 10-30 nm and a length of 5-50 μm.

Further, the surfactant is stearic acid, butyl stearate and/or octyl stearate.

Further, the specific process of the step (2) is as follows: chop the obtained composite solid paraffin, and add 30 to 40 parts of the chopped composite solid paraffin into the mixing machine in parts by mass, at a speed of 25 to 30r/ min, and the temperature is 80~85°C for 20~40min; adjust the temperature of the mixer to 140~150°C, add 15 parts of medium density polyethylene, and adjust the speed to 40 after the medium density polyethylene is dissolved. ~50r/min, add 2.5 parts of surfactant, knead for 40~80min to get binder.

Another technical solution of the present invention is to provide a method for preparing feedstock for powder injection molding. The binder obtained by the above preparation method is mixed with metal powder, and then extruded and granulated to obtain the feedstock.

Further, the metal powder is spherical and has a particle size of 0.5-3 μm.

Further, the metal powder is copper powder or nickel powder.

Further, the mass ratio of the binder to the metal powder is 1:4~6.

Further, the mixing temperature of the binder and the metal powder is 150-160°C, and the extrusion temperature is 175-185°C.

The beneficial effect of the invention is that the invention can realize stable and uniform dispersion of the carbon nanotubes in the metal matrix composite material. The introduction of carbon nanotubes into the binder system will make full use of the polymer as the main component of the binder, which is beneficial to the dispersion and anchoring of carbon nanotubes, and the advantages of high densification obtained by injection molding. At the same time, the addition of carbon nanotubes can not only improve the mechanical strength of the binder system, but also increase the viscosity of the binder system, and the carbon nanotubes in the network structure will further improve Effectively inhibit volume shrinkage. In addition, the presence of carbon nanotubes allows us to choose lower molecular weight medium-density polyethylene to meet the requirements of binder shape retention and fluidity, without using high-density polyethylene used in traditional binders, but Low molecular weight medium density polyethylene is easier to come out in the subsequent degreasing process. It is also worth mentioning that the presence of high-strength and high-toughness carbon nanotubes can not only reduce the volume shrinkage during the debinding process, but also inhibit the growth of grains in the subsequent sintering process, which is very beneficial to the density and performance. improvement.

Description of drawings

Fig. 1 represents the scanning electron micrograph of the feeding material that embodiment 1 obtains.

detailed description

Example 1: Weigh 2g of carbon nanotubes (with a diameter of 10-30nm and a length of 5-50μm) with 32.5g of paraffin and 1g of oleic acid and heat to 80°C to be in a molten state. Under the action of ultrasonic dispersion, stir and mix for 1 h. When the mixed solution becomes roughly uniform and roughly black, take it out quickly until it solidifies, and chop the obtained composite solid paraffin.

Add the above-mentioned chopped paraffin into the kneader whose temperature has been raised to 80°C, and knead for 30 min at the speed of 30 r/min. Adjust the temperature of the mixer to 145°C, add 15g of medium-density polyethylene, and knead for 60 minutes while keeping the speed constant. After the medium-density polyethylene is roughly dissolved, adjust the speed to 45r/min, and add 2.5g of surface active agent, mixed for 1 hour in a kneader to obtain a binder;

Next, 250 g of copper powder (0.5 µm in diameter) was added to the above binder. Raise the mixing temperature to 155°C, keep the stirring speed at 45r/min, and mix for 1.5h. The obtained compound was put into a twin-screw extruder, and the extrusion temperature was set at 180° C. for extrusion granulation to obtain feed.

The feed sample preparation that above-mentioned preparation method obtains is carried out scanning electron microscope analysis, and its electron microscope photo is as shown in Figure 1, finds out from Figure 1, feed is spherical particle, and carbon nanotube is very evenly distributed in the particle, It shows that this technical route can well realize the uniform composite of carbon nanotubes and copper powder.

Example 2: Weigh 6g of carbon nanotubes (with a diameter of 10-30nm and a length of 5-50μm) with 32.5g of paraffin and 1g of oleic acid and heat to 80°C to be in a molten state. Under the action of ultrasonic dispersion, stir and mix for 1 h. When the mixed solution becomes roughly uniform and roughly black, take it out quickly until it solidifies, and chop the obtained composite solid paraffin.

Add the above-mentioned chopped paraffin into the kneader whose temperature has been raised to 80°C, and knead for 30 min at the speed of 30 r/min. Adjust the temperature of the mixer to 145°C, add 15g of medium-density polyethylene, and knead for 60 minutes while keeping the speed constant. After the medium-density polyethylene is roughly dissolved, adjust the speed to 45r/min, and add 2.5g of surface active agent, mixed for 1 hour in a kneader to obtain a binder;

Next, 300 g of copper powder (2 microns in diameter) was added to the above binder. Raise the mixing temperature to 155°C, keep the stirring speed at 45r/min, and mix for 1.5h. The obtained compound was put into a twin-screw extruder, and the extrusion temperature was set at 180° C. for extrusion granulation to obtain feed.

Example 3: Weigh 4g of carbon nanotubes (10-30nm in diameter, 5-50μm in length), 32.5g of paraffin wax and 1g of oleic acid and heat to 80°C to be in a molten state. Under the action of ultrasonic dispersion, stir and mix for 1 h. When the mixed solution becomes roughly uniform and roughly black, take it out quickly until it solidifies, and chop the obtained composite solid paraffin.

Add the above-mentioned chopped paraffin into the kneader whose temperature has been raised to 80°C, and knead for 30 min at the speed of 30 r/min. Adjust the temperature of the mixer to 145°C, add 15g of medium-density polyethylene, and mix for 60 minutes while keeping the speed constant. After the medium-density polyethylene is roughly dissolved, adjust the speed to 45r/min, and add 2.5g of surface active agent, mixed for 1 hour in a kneader to obtain a binder;

Next, 300 g of copper powder (2 microns in diameter) was added to the above binder. Raise the mixing temperature to 155°C, keep the stirring speed at 45r/min, and mix for 1.5h. The obtained compound was put into a twin-screw extruder, and the extrusion temperature was set at 180° C. for extrusion granulation to obtain feed.

Claims (9)

1. a kind of preparation method of powder injection forming binding agent, it is characterised in that comprise the following steps：

(1) CNT, paraffin and oleic acid are weighed respectively for the ︰ 0.1 ~ 0.6 of 1 ︰ 5 ~ 20 ratio in mass ratio, by heating paraffin extremely CNT and oleic acid are added after melting, ultrasound and 0.5 ~ 1.5h of stirring, make CNT under the conditions of keeping temperature is 80 ~ 85 DEG C It is uniformly dispersed；Then it is rapidly cooled to solidify, obtains composite solid paraffin；

(2) obtained composite solid paraffin is shredded, by mass parts, the composite solid paraffin of 30 ~ 40 parts of choppings is added and is kneaded Machine, after mixing, 12-18 part medium density polyethylenes are added, 2 ~ 3 parts of surfactants are added after medium density polyethylene dissolving, then Through being kneaded, binding agent is obtained.

2. preparation method as claimed in claim 1, it is characterised in that a diameter of 10 ~ 30nm of the CNT, length are 5 ~50μm。

3. preparation method as claimed in claim 1, it is characterised in that described surfactant is stearic acid, stearic acid fourth Ester and/or octyl stearate.

4. preparation method as claimed in claim 1, it is characterised in that the detailed process of the step (2) is as follows：By what is obtained Composite solid paraffin is shredded, and by mass parts, the composite solid paraffin of 30 ~ 40 parts of choppings is added into kneading machine, rotating speed be 25 ~ 30r/min, temperature are kneaded 20 ~ 40min under the conditions of being 80 ~ 85 DEG C；After the temperature of kneading machine is adjusted into 140 ~ 150 DEG C, 15 are added Part medium density polyethylene, rotating speed is adjusted to 40 ~ 50r/min after medium density polyethylene dissolving, adds 2.5 parts of surfactants, 40 ~ 80min is kneaded, obtains binding agent.

5. a kind of preparation method of powder injection forming feeding, it is characterised in that by the preparation of any one of claim 1 ~ 4 The binding agent that method obtains is kneaded with metal dust, then extruded granulation, obtains feeding.

6. preparation method as claimed in claim 5, it is characterised in that the metal dust is spherical, and particle diameter is 0.5 ~ 3 μm.

7. preparation method as claimed in claim 5, it is characterised in that the metal dust is copper powder or nickel powder.

8. preparation method as claimed in claim 5, it is characterised in that the mass ratio of the binding agent and metal dust be 1 ︰ 4 ~ 6。

9. preparation method as claimed in claim 5, it is characterised in that the temperature that the binding agent is kneaded with metal dust is 150 ~ 160 DEG C, the temperature of the extrusion is 175 ~ 185 DEG C.