JP2001200061A - Spherical wax particle containing powder and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide spherical wax particles which, when a raw material powder and a molding assistant containing a wax are mixed and molded, enable the powder and the assistant to be homogeneously mixed and kneaded easily in a short time and which is adaptable to a highly productive continuous kneader extruder and to provide a method for manufacturing the same. SOLUTION: Spherical wax particles containing a powder are provided, the powder being a ceramic or metal powder. In the method for manufacturing the particles, a wax melt containing the powder dispersed therein is formed into fine particles by a cool-air spray drying method with a spray dryer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to ceramics,
The present invention relates to a wax spherical granule used for powder molding of a sintered metal or the like and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, a manufacturing method has been practiced in which wax is added as a molding aid to raw material powders such as ceramic powders and metal powders, and molding is performed.

In this conventional production method, although raw material powder and wax powder as a molding aid may be dry-mixed in some cases, raw material powder such as ceramic powder and metal powder and wax granules as a molding aid are mixed for a short time. , It was difficult to dry mix uniformly. In addition, in the conventional production method, the raw material powder and the wax powder as a molding aid may be kneaded, but compared to the raw material powder such as ceramic powder and metal powder, the powder of the wax granules as the molding aid is used. Because of its low body density, it was difficult to be wound into a kneading screw and it was difficult to perform uniform kneading in a short time. As a result, application to a continuous kneading extruder with high productivity in which a kneader and an extruder are integrated has been difficult.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the various problems described above, and it is an object of the present invention to (1) add a molding aid containing a wax to a raw material powder; When mixing and molding by mixing, it is possible to easily and quickly mix and knead the raw material powder and the molding aid, and (2) to be applicable to a continuous kneading extruder with high productivity. (3) that no impurities are mixed during production; and (4) the production cost is low.

[0005]

According to the present invention, there is provided a wax spherical granule characterized by containing a powder.

In the present invention, the powder is preferably a ceramic powder or a metal powder. Preferably, the wax and the powder are in a mixed state. Further, the content of the powder is preferably from 10% by weight to 60% by weight.

In the present invention, it is preferable that a resin is contained in addition to the wax and the powder. Preferably, the resin is a thermoplastic resin. Further, the resin is preferably an ethylene / vinyl acetate copolymer.

In the present invention, the wax spherical granules are preferably 1 mm or less.

According to the present invention, there is provided a process for producing wax spherical granules, wherein a wax melt in which a powder is dispersed is atomized by a cold air spray drying method using a spray dryer.

In the production method of the present invention, the wax melt is preferably melted at a temperature of 40 ° C. or higher. Further, it is preferable that the spray system of the spray dryer is a centrifugal spray system atomizer.

[0011]

Embodiments of the present invention will be described below, but it goes without saying that the present invention is not limited to the following embodiments. The present invention is characterized in that in the wax spherical granules, the wax contains a powder. Further, they are preferably in a mixed state. As described above, since the raw material powder such as a ceramic powder or a metal powder is already contained in the wax spherical granules, when the raw material powder and the wax spherical granules are mixed, the amount of the raw material powder during dry mixing is reduced. It is easy to achieve a uniform mixing state in a very short time.
Depending on the content of the raw material powder in the wax spherical granules, the mixing with the raw material powder can be omitted, and a molded article can be produced using only the wax spherical granules.

Further, when the wax spherical granules of the present invention are uniformly kneaded as a molding aid, when the molding aid is a wax spherical granule containing ceramic powder or metal powder, the density of the spherical granules increases, and When kneading with, it is easy to get caught in the kneading screw, as a result,
Uniform kneading with the raw material powder in a short time can be performed. Further, since the molding aid is a spherical granule, it is slippery with respect to the raw material powder, so that mixing and kneading can be performed in a short time. For this reason, application to a continuous kneading extruder with high productivity becomes possible.

The powder is not limited to the main raw material powder, and may be, for example, an auxiliary raw material added to the main raw material. Further, a mixed powder of a main raw material and an auxiliary raw material may be used. Furthermore, in the case where these wax spherical granules are added to the raw material powder as a molding aid and mixed to produce a molded body, uniform dry mixing and uniform kneading of the raw material powder and the molding aid should be performed easily and in a short time. Can be.

The content of powder such as ceramic powder or metal powder contained in the granules of the present invention is 10% by weight.
It is preferably at least 60% by weight. When the content of the powder is less than 10% by weight, the powder density of the wax granules is low, and when kneading with the raw material powder, it becomes difficult for the wax granules to be spread into the kneading screw, and the uniform kneading time increases. Conversely, if the content of the powder exceeds 60% by weight, the viscosity of the wax melt containing the powder increases, and smooth fluidity cannot be ensured, so that it is difficult to produce wax granules by a spray dryer. In view of the production of wax granules, the powder content is more preferably 50% by weight or less.

In the present invention, it is preferable that a resin is contained in addition to the wax and the powder. When a molded article is produced by using the spherical granules of the present invention as a molding aid, plasticity during molding is ensured, and the strength of the molded article increases according to the content of the resin, so that deformation can be prevented.

In the present invention, the resin to be used can be appropriately changed depending on the application target, but a thermoplastic resin is preferable from the viewpoint of compatibility with the wax, and particularly, an ethylene / vinyl acetate copolymer (abbreviation: EVA) It is preferred that

Further, the spherical granules of the present invention preferably have a particle size of 1 mm or less. Reducing the particle size of the granules in this manner is more preferable for the above-described uniform mixing and uniform kneading.

Next, a method for producing the wax spherical granules in the present invention will be described. Weigh a predetermined amount of raw powder such as wax and ceramic powder or metal powder,
After melting the wax, the raw material powder is added to the melt and mixed and stirred to disperse the raw material powder in the wax melt. Next, the mixed melt is put into a feed tank and stored with stirring in the tank. The feed mixture feeds the molten mixture in the feed tank to the atomizer via the feed pipe. The molten mixture is sprayed from the atomizer into the spray dryer main body to produce wax granules containing powder.

When a resin is added to the wax, a predetermined amount of each of the wax and the resin is weighed and melt-mixed. In order to develop fluidity, the melting temperature of the wax and the resin is preferably 40 ° C. or higher, more preferably 80 ° C. or higher. The raw material powder is added to the mixed melt of the wax and the resin, and the mixture is stirred and dispersed in the mixed melt of the wax and the resin. Hereinafter, the step of producing the wax granules by spraying the mixture into the spray dryer main body is as described above. When mixing the wax and the powder, if necessary, an auxiliary agent such as a coupling agent, a lubricant, or a dispersant is added and mixed.

When a resin is added, the resin used is preferably a resin having a melting point of 200 ° C. or less. Mixing and melting of the wax and the resin can be performed at a temperature of 200 ° C. or lower, which is preferable in that oxidation deterioration due to overheating of the wax is prevented, and an increase in oil content and a change in hue can be suppressed. As a matter of course, after mixing the wax and the powder, the mixture may be heated to a temperature higher than the melting temperature of the wax and melted to obtain a mixed melt.

Further, controlling the temperature of the supply system of the molten mixture, which includes a feed tank, a feed pump, a feed pipe, an atomizer, and the like so as to be equal to or higher than the melting point of the molten mixture, ensures smooth fluidity of the molten mixture,
Necessary for preventing coagulation. Further, it is necessary to control the ambient temperature of the spray dryer main body (cooling chamber) to a temperature below the freezing point of the molten mixture.

The atomizer may be either a centrifugal spray method or a nozzle spray method, but the centrifugal spray method is preferable in terms of atomizing the granules to be produced, preventing clogging of the spraying section, and stably spraying for a long time. The production conditions such as the atomizer rotation speed during the centrifugal spraying, the atomizer temperature, and the supply speed of the molten mixture are appropriately set in accordance with the ratio of wax to resin and the mixing ratio of powder such as ceramic powder or metal powder.

[0023]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

(Examples 1 to 8, Comparative Examples 1 and 2) Paraffin wax, microcrystalline wax, EVA
Using (resin), oleic acid and cordierite powder, wax spherical granules containing cordierite powder were produced by a spray dryer. The material melting temperature at the time of the spray drier was set to an appropriate temperature for each material in consideration of the material composition (ratio of EVA) and the amount of cordierite powder added. Whether spherical granules could be produced by a cold air spray drying method using a spray dryer and the average particle size of the obtained spherical granules were evaluated. Table 1 shows the results.

[0025]

[Table 1]

Further, the wax spherical granules containing the cordierite powder obtained in each of the Examples and Comparative Examples and the cordierite raw material powder were dry-mixed and kneaded at 100 ° C. Incidentally, a wax component containing a resin is 22% by weight,
The cordierite raw material was prepared to be 78% by weight.

The time required for uniformly kneading the cordierite raw material powder and the wax granules was evaluated. Table 1 shows the results. The kneading conditions such as the total input weight to the kneader, the number of revolutions of the kneading screw, the material temperature and the like were the same in all of the examples and comparative examples.

Also, at a kneading time of 10 minutes, five samples (3 g each) of the kneaded material were randomly taken, and the apparent viscosity was measured using a flow tester under appropriate temperature conditions.
The time when the apparent viscosity of the five samples became ± 10% was defined as the time during which uniform kneading was possible.

A description will be given of a flow tester evaluated for uniform kneading. A flow tester is an apparatus that measures the melting characteristics and flowability of a thermoplastic material, a thermosetting material, and the like. This time, using a flow tester, the sampled kneaded material was heated to give plasticity, and a load was applied from the top of the kneaded material so that the kneaded material was passed through the narrow tube, and the apparent speed from the passage of a predetermined amount of the kneaded material was observed. The viscosity was calculated and determined. This time, the degree of uniform kneading was evaluated based on the variation in apparent viscosity calculated by this measurement method.

Next, it was evaluated whether or not each of the examples and comparative examples can be applied to a continuous kneading extruder. Table 1 shows the results. The shape of the extruded product was a honeycomb shape, and the honeycomb molded body was extruded under appropriate molding conditions in consideration of the material composition (the ratio of EVA) and the like. In each of Examples and Comparative Examples, the wax component containing the resin was 22% by weight and the cordierite raw material was 78% by weight.
Were measured by separate feeders so as to obtain a continuous kneading extruder. Wax spherical granules and cordierite raw material powder are smoothly caught in the kneading screw,
It was visually observed and evaluated whether or not the honeycomb formed body was uniformly mixed and kneaded and extruded without any problem.

Example 1 In Example 1, paraffin wax, microcrystalline wax (manufactured by Nippon Seiwa Co., Ltd.), EVA (manufactured by Mitsui Dupont Chemical Co., Ltd.),
As shown in Table 1, oleic acid and cordierite raw material powder were blended so that the cordierite raw material powder was contained at 5% by weight, then mixed and melted, and sprayed into a spray dryer by a centrifugal spray method to obtain fine particles. An example in which granules were produced is shown. A spherical granule in which the wax and cordierite raw material powder were in a homogeneously mixed state and had an average particle size of 0.07 mm was obtained.

Next, when the fine granules obtained in Example 1 were mixed and kneaded with the cordierite raw material powder, the time required to reach a uniform kneading state was as short as 40 minutes. However, an attempt to produce a honeycomb formed body by a continuous kneading extruder using the fine granules obtained in Example 1 and the cordierite raw material powder did not give good results. The reason is that the powder density of the obtained wax granules is low, and it is difficult for the wax granules to be smoothly caught in the kneading screw.

When the content of the cordierite raw material powder in the wax spherical granules is small, the production of the wax spherical granules is possible, and the effect of shortening the uniform kneading time of the wax spherical granules and the raw material powder can be obtained. It was considered difficult to apply to a continuous kneading extruder.

(Examples 2 to 5) Examples 2 to 5 show examples in which the content of cordierite raw material powder was sequentially increased to 60% by weight as shown in Table 1. In each of the examples, it was possible to produce wax spherical granules, and the average particle diameter of the wax spherical granules tended to increase as the content of the cordierite raw material powder increased. The time required for uniformly kneading the wax spherical granules and the cordierite raw material powder was reduced to 30 to 10 minutes as the content of the cordierite raw material powder increased. Furthermore, when a honeycomb formed body was manufactured by a continuous kneading extruder using the wax spherical granules and the cordierite raw material powder, a good honeycomb formed body was obtained without any problem.

Examples 6 to 8 In Examples 6 to 8, as shown in Table 1, the content of cordierite raw material powder was fixed at 30% by weight, and the content of resin was 0 to 54% by weight. Are shown below. In each of the examples, it was possible to produce wax spherical granules. In addition, the time required for uniformly kneading the wax spherical granules and the cordierite raw material powder was as short as 20 minutes. Furthermore, when a honeycomb formed body was manufactured by a continuous kneading extruder using the wax spherical granules and the cordierite raw material powder, a good honeycomb formed body was obtained without any problem.

(Comparative Example 1) In Comparative Example 1, as shown in Table 1, a material having a material composition containing only paraffin wax, microcrystalline wax, EVA and oleic acid without spraying cordierite raw material powder was sprayed. The example which manufactured the wax granule by the dryer is shown. Although the production of wax granules was possible, using the wax granules and kneading the cordierite raw material powder with the same method and conditions as in Examples 1 to 8, the time required for uniform kneading was as long as 70 minutes. Cost. Furthermore, when the production of a honeycomb formed body was attempted using a continuous kneading extruder using the wax granules and the cordierite raw material powder, a good honeycomb formed body could not be extruded.

Comparative Example 2 Comparative Example 2 shows an example in which cordierite raw material powder was added at 70% by weight as shown in Table 1. Wax spherical granules were not obtained by the spray dryer, and fibrous ones were obtained. When the powder content in the wax is extremely large, the conditions for producing the wax spherical granules by a spray dryer are changed, for example, by setting the mixed melt supply system from the feed tank to the atomizer to high temperature and high pressure, It seems necessary to take measures such as ensuring the fluidity of the mixed melt smoothly.

[0038]

As described above, the present invention is a wax spherical granule containing a powder such as a ceramic powder or a metal powder, and thus is suitably applied to powder molding of a ceramic, a sintered metal or the like. Especially when used in addition to the raw material powder,
The effect is obtained that uniform mixing and kneading can be easily and in a short time.

Furthermore, since the method for producing the spherical granules melts and mixes the wax and the powder, and then produces the fine granules by a cold air spray drying method using a spray dryer, the mixing of the wax and the powder is uniform. In addition, impurities are prevented from being mixed during manufacturing, and the manufacturing process and time can be reduced. Therefore, it is considered that the manufacturing cost is low. Furthermore,
Since the wax spherical granules containing the powder are used as a molding aid, the density of the wax spherical granules is high, the wax spherical granules are easily entangled in the kneading screw in the kneading machine, and are uniformly kneaded with the raw material powder in a short time. Therefore, the present invention can be applied to a high productivity continuous kneading extruder or the like in which a kneader and an extruder are integrated.

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Claims (12)

[Claims] 1. Wax spherical granules characterized by containing a powder. 2. The powder according to claim 1, wherein said powder is a ceramic powder.
3. The wax spherical granules according to 1.). 3. The wax spherical granules according to claim 1, wherein said powder is a metal powder. 4. The wax spherical granules according to claim 1, wherein the wax and the powder are in a mixed state. 5. The wax spherical granule according to claim 1, wherein the content of the powder is 10% by weight or more and 60% by weight or less. 6. The wax spherical granule according to claim 1, which contains a resin. 7. The wax spherical granules according to claim 6, wherein said resin is a thermoplastic resin. 8. The wax spherical granules according to claim 6, wherein the resin is an ethylene / vinyl acetate copolymer. 9. The wax spherical granules according to claim 1, wherein the wax granules are 1 mm or less. 10. A method for producing wax spherical granules, wherein the wax melt in which the powder is dispersed is atomized by a cold air spray drying method using a spray dryer. 11. The method according to claim 10, wherein the wax melt is at a temperature of 40 ° C. or higher. 12. The method for producing wax spherical granules according to claim 10, wherein the spray system of the spray dryer is a centrifugal spray system atomizer.