JPH05116119A - Production of injection molding composition - Google Patents

Abstract

PURPOSE:To produce an injection molding composition low in viscosity, reducing the generation of an abrasion phenomenon in the member of a kneading device and capable of performing the uniformizing treatment of kneaded matter within a short time by kneading one or more kinds of powdery raw materials selected from a metal powder, an alloy powder and a ceramics powder with two or more kinds of binders. CONSTITUTION:In a method for producing an injection molding composition by kneading one or more kinds of powdery raw materials selected from a metal powder, an alloy powder and a ceramics powder with two or more kinds of binders, a binder resin with a particle size of 3mm or less is used as the binder resin added to the raw material powder and the working temp. at the time of kneading treatment is held to a temp. range from the m.p. of the binder composition to be used to below the evaporation temp. thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preparing an injection molding composition used for producing a metal or ceramics sintered product by an injection molding sintering method.

[0002]

2. Description of the Related Art An injection molding composition is prepared by kneading one or more raw material powders selected from metal, alloy and ceramic powders with a plurality of binders. After injection molding using it, the method of manufacturing a sintered product by repeating debinding process and sintering process is
In particular, it has been widely used since it is suitable for obtaining a product having a three-dimensionally complicated shape.

In this case, in order to knead the raw material powder and the binder, the raw material powder and the binder are simultaneously added to a pressure type kneader to start the kneading process, or only the binder is completely heated and melted in advance. However, a method of advancing the kneading process while gradually adding the raw material powder is adopted.

[0004]

However, since the injection molding composition contains a large amount of raw material powder,
Even if the same raw material is kneaded under the same conditions, it is not easy to make the composition uniform, and the viscosity of the injection molding composition that is made varies, and on the other hand, the molding accuracy of the injection molded body becomes poor. As a result, it causes a problem that the quality of the finished product lacks uniformity, and on the other hand, it is inevitable that the kneading work for a long time is unavoidable. Inevitably, impurities were continuously mixed in the kneaded product.

The present invention solves the above problems and provides an injection molding composition obtained by kneading one or more raw material powders selected from metal, alloy and ceramic powders and a plurality of binders. An object of the present invention is to disclose a method for preparing an injection molding composition which has a low viscosity, causes little wear phenomenon in a member of a kneading device, and allows a kneaded product to be homogenized in a short time.

[0006]

[Means for Solving the Problems] As a means for solving the above problems, the present invention comprises kneading one or more raw material powders selected from metal, alloy, and ceramic powders and a plurality of binders. In the method for preparing a composition for injection molding, the binder resin added to the raw material powder has a particle size of 3 m.
A method for adjusting an injection molding composition in which a binder resin of m or less is used and the working temperature during the kneading process is kept in a temperature range which is higher than the melting point of the binder composition used but lower than the evaporation temperature is used. Disclose.

The raw material powders used in the present invention are based on various metal powders, alloy powders, metal oxide powders, and ceramics powders, so that they can meet the requirements of the final product. It is used in the physical condition.

The binder used in combination with the raw material powder is mixed in the raw material powder for the purpose of facilitating a smooth work when the raw material powder is injection molded, and its composition is the injection molding work. A lubricant that sometimes affects the fluidity of the kneaded material and a binder resin that affects the shape retention of the injection-molded molded product are used in combination.

As the lubricant, waxes such as paraffin wax having a low molecular weight and low melting point, microcrystalline wax, low molecular weight polyethylene wax, modified wax and montan ester wax are used.

As the binder resin, polymers such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-acrylate copolymer and polystyrene, which have high molecular weight, boiling point and viscosity, are used.

The above-mentioned lubricant and binder resin used in the present invention are used in a weight ratio of lubricant 1 to binder resin 4 to lubricant 4 to binder resin 1 in a weight ratio. The ratio of the binder resin 3 to the lubricant 1 to the binder resin 1 to the lubricant 3 is a preferable ratio.

As the composition of the binder, a dispersant or a surface active agent may be further used, if necessary, for the purpose of improving the wettability of the raw material powder and the binder resin so that both are uniformly dispersed in the kneaded product. As the dispersant and surfactant, saturated fatty acids and unsaturated fatty acids such as stearic acid and oleic acid are used, and the addition ratio thereof is 100 parts by weight with respect to the total amount of the binder resin and the lubricant. It is used at 0.5 to 5 parts by weight.

The blending ratio of the binder to the raw material powder is 75 to 95% by weight of the raw material powder and 2 parts of the binder.
It is used in a proportion of 5 to 5% by weight.

[0014]

In the present invention, the particle size of the binder resin mixed in the raw material powder when kneading the kneaded product is specified to be 3 mm or less. Four
In the present invention, this is defined to be 3 mm or less for ˜15 mm, because the binder resin particles used in the kneading step themselves are composed of innumerable molecular chains and are mixed with the raw material powder. In this case, it is important to separate these molecular chains one by one and then carry out the kneading process, and the uniform kneading process is possible only after the separated molecular chains are coated on the individual particles of the raw material powder. When the particle size of the binder resin exceeds 3 mm, it becomes difficult to mix the raw material powder and the binder resin uniformly even when the binder resin melts, and the binder resin on the particle surface of the raw material powder is Since the coating tends to lack uniformity, the composition of the kneaded product also lacks uniformity, resulting in instability in the quality of the product obtained in the injection molding process. To come.

Further, during kneading of the kneaded product, mechanical shearing force is applied to the container and the device, so that in the kneading device, a wear phenomenon occurs in a portion in contact with the raw material powder. When the kneading process takes a long time, the number of peeling pieces generated from the kneading machine increases, and the purity of the kneaded product gradually decreases. Since it becomes easier, it is preferable to shorten the kneading time of the raw material powder and the binder as much as possible.From this point as well, the ease of kneading according to the present invention in the kneading treatment greatly contributes to the improvement of the quality of the kneaded product. Can be said to be

Further, in the present invention, the processing temperature in the case of processing the kneaded product in the kneading step is defined as a temperature range which is higher than the melting point of the binder and lower than the evaporation temperature.
In the kneading step of the present invention, the treatment temperature when treating the kneaded product is defined as the melting point of the binder or higher. This is because it is difficult to create a film, and as a result it becomes impossible to uniformly knead the raw material powder and the binder, and it is included in the raw material powder only by heating above the melting point of the binder. This is because water is removed, and as a result, particles that have aggregated are easily dispersed uniformly.

On the contrary, in the present invention, the treatment temperature for treating the kneaded material is regulated within the temperature range which is lower than the evaporation temperature of the binder. However, in the kneading step of the present invention, the kneaded material is treated. The treatment temperature is defined as less than the evaporation temperature of the binder.When the treatment temperature of the kneaded material is heated to the evaporation temperature of the binder or higher, the binder composition is changed only with the evaporation phenomenon of the binder. Not only this, but the fluidity of the kneaded product is reduced due to this effect, and when the degree of progress further increases, carbonization of the binder progresses and carbon becomes scattered in the kneaded product, resulting in the kneaded product. This is because the purity of is reduced.

[0018]

EXAMPLES Details of examples of the present invention will be described below.

Example 1 After heating 4550 g of copper powder having an average particle diameter of 18 microns to 130 ° C., the average particle diameter was 0.5.
180 g of low-density polyethylene having a melting point of 110 mm and a melting point of 57 ° C. and paraffin wax 2 having a melting point of 57 ° C.
A kneaded product obtained by adding 70 g and performing a kneading process until the kneaded product becomes uniform while maintaining the working temperature at 150 ° C. and confirming the uniform state of the kneaded product and then continuing the kneading process for another 20 minutes. Was taken out of the system, and the kneaded product taken out of the system was 40
After air-cooling to ℃, pulverize, measure the viscosity of the pulverized kneaded product when the extrusion speed is 500 mm / min using a capillary rheometer, and the extrusion temperature is 100 ° C. As a means for confirming the contamination of the kneaded material due to abrasion, a chemical analysis for the Fe content was performed, and further, using the above-mentioned pulverized kneaded material, the thickness was 4 mm, the width was 7 mm, and the long Is 40
As a result of continuously injecting 50 rectangular parallelepiped shaped bodies having a size of 10 mm and investigating the variation of the weight and shape of the shaped body, the Fe content of the shaped body was 20 ppm and the viscosity was 1
60 poise, with a standard deviation of 0.
0035 and the standard deviation for the thickness is 0.002
It was 0, and the standard deviation of the width was 0.0018, which confirmed that the quality was stable.

(Example 2) The measurement was carried out in the same manner as in Example 1 except that the particle size of the low density polyethylene was 2.5 mm. The result was that the Fe content of the molded body was 25 ppm and the viscosity was 180 poise. , The standard deviation for product weight is 0.0038 and the standard deviation for thickness is 0.0
It was 027, and the standard deviation of the width was 0.0024, which confirmed that the quality was stable.

(Example 3) The raw material powder was 4250 g of 0.3 micron zirconia powder, and 375 g of montan ester wax having a melting point of 75 ° C. was added to this raw material powder.
And oleic acid (75 g) having a melting point of 15 ° C. are added, and the melting point is 155 ° C. and the particle size is 1.0 m.
The result of measurement in the same manner as in Example 1 except that 300 g of polypropylene (m) was added and the mixture was kneaded at 170 ° C. showed that the Fe content of the molded product was 15 ppm and the viscosity was 130.
Poise, standard deviation of product weight is 0.00
40, the standard deviation for the thickness was 0.0022, and the standard deviation for the width was 0.0020, which confirmed that the quality was stable.

[0022]

[Comparative example]

(Comparative Example 1) The result of measurement in the same manner as in Example 1 except that the particle size of the low density polyethylene was 5 mm is F of the molded product.
The e content is 38 ppm, the viscosity is 280 poise, the standard deviation for product weight is 0.0048, the standard deviation for thickness is 0.0042, and the standard deviation for width is 0.0051. However, it was confirmed that there was a large variation and that the product quality was not stable.

(Comparative Example 2) The measurement was carried out in the same manner as in Example 3 except that the particle size of the low density polyethylene was 4 mm. The result was that the Fe content of the molded product was 39 ppm and the viscosity was 24.
0 poise and standard deviation of product weight is 0.0
058 with a standard deviation of 0.0048 for thickness
It was confirmed that the standard deviation of the width was 0.0059, showing a large variation and lacking in stability of product quality.

The above measurement results are summarized in Table 1.

[0025]

[Table 1]

As can be seen from the measurement results shown in Table 1, when the present invention was carried out, it became clear that injection molded sintered products could be supplied to the market with stable quality.

[0027]

According to the practice of the present invention, it is clear that an injection molded sintered product having excellent workability, low viscosity, and stable quality can be supplied to the market, and the progress of abrasion of the kneading device can be reduced. From a certain point, there is a great contribution to the industry using such products.

Claims (1)

[Claims] 1. A method for preparing an injection molding composition by kneading one or more raw material powders selected from metal, alloy and ceramic powders and a plurality of binders.
A binder resin having a particle size of 3 mm or less is used as the binder resin added to the raw material powder, and the working temperature during the kneading process is higher than the melting point of the binder composition used but lower than the evaporation temperature. A method for preparing an injection molding composition, characterized in that the composition is kept in a temperature range.