JPH11292636A - Binder for injection molding of inorganic powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce defects such as crazing from occurring in an inorganic sintered compact by an injection molding method and shorten the holding time in the injection molding by including a petroleum-based wax and/or a synthetic wax and a vegetable wax as a wax component constituting a binder. SOLUTION: This binder is compounded in an inorganic powder and degreased by heating thereof after injection molding and contains a thermoplastic resin, a plasticizer and a wax component. A petroleum-based wax or a synthetic wax or both are preferably compounded in a larger amount than 70 pts.wt. based on 30 pts.wt. of the vegetable wax in the wax component. The vegetable wax is preferably carnauba wax and/or rice wax. A dielectric ceramic powder capable of converting the resultant sintered compact into a dielectric such as titanium oxide, zirconium oxide or tin oxide is preferred as the inorganic powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a binder for an inorganic powder injection molding, and more particularly, to an inorganic powder which is blended with an inorganic powder to be molded by injection molding and is degreased by heating after the injection molding. The present invention relates to a binder for injection molding.

[0002]

2. Description of the Related Art Some products made of sintered bodies of inorganic powders such as ceramics and metals require complicated shapes. In order to obtain a product having such a complicated shape, plasticity is imparted by mixing a binder containing a thermoplastic resin or the like with the raw material of the inorganic powder, and a molded article is obtained by injection molding the mixture to obtain a molded article. A method has been practiced in which a molded article is heated to be degreased, and then fired at a sinterable temperature to obtain a product of an inorganic powder sintered body. This method can produce a product having a complicated shape that cannot be formed by the conventional press molding method or extrusion molding method, and is more mass-producible than the slurry casting method. It has the feature that a highly accurate product can be obtained.

As a binder used in such an injection molding method, for example, Japanese Patent Publication No. 63-50300 discloses polystyrene, polybutyl methacrylate, an ethylene-vinyl acetate copolymer, a plasticizer and a lubricant. Binder is described. Also,
No. 42682 describes a binder containing one or two kinds of ethylene-vinyl acetate copolymer and low-density polyethylene, a methacrylate copolymer, dibutyl phthalate or diethyl phthalate or stearic acid, and paraffin wax. Have been.

[0004]

However, the above-mentioned binder is used to form a box having an open side as shown in, for example, Japanese Patent Application Laid-Open No. 2-34003 and shown in FIG. In the cavity case 1, the column 2 has a shape such that it is provided continuously on the upper wall and the lower wall of the cavity case 1, or in the shape shown in FIG. If, instead, the TM-mode dielectric resonator element having such a shape as to form the prismatic column 2 is injection-molded, there is a problem that the obtained inorganic sintered body is cracked.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to reduce defects such as cracks in an inorganic sintered body obtained by firing a molded body formed by an injection molding method. It is an object of the present invention to provide a binder for inorganic powder injection molding, which can reduce the generation thereof and can shorten the pressure holding time during injection molding.

[0006]

In order to achieve the above object, the binder for inorganic powder injection molding of the present invention is blended with the inorganic powder for molding the inorganic powder by injection molding, and is heated after injection molding. A binder for inorganic powder injection molding, which is degreased by performing, comprising a thermoplastic resin, a plasticizer, and a wax component, wherein the wax component comprises a petroleum wax and / or a synthetic wax, and a vegetable wax. It is characterized by containing.

In the inorganic powder injection molding binder, the vegetable wax is preferably carnauba wax and / or rice wax. In the wax component, the vegetable wax is contained in an amount of 30 parts by weight of the vegetable wax. It is preferable that the petroleum wax and / or the synthetic wax be blended in a proportion of more than 70 parts by weight. Further, it is preferable that the inorganic powder is a dielectric ceramic powder.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The binder for inorganic powder injection molding of the present invention contains a thermoplastic resin, a plasticizer and a wax component. Examples of the thermoplastic resin include known thermoplastic resins such as polystyrene, polyethylene, polypropylene, acrylic resins such as polyacrylate and polymethacrylate, polyacetal resins, and ethylene-vinyl acetate copolymers. These may be used alone or in combination of two or more. Among them, preferred are acrylic resins and ethylene-vinyl acetate copolymers. These acrylic resins and ethylene-vinyl acetate copolymers are preferably used in combination. Is more preferred.

[0009] Examples of the plasticizer include known plasticizers such as phthalic acid ester, adipic acid ester and phosphoric acid ester. These may be used alone or in combination of two or more. Among them, phthalic acid esters are preferred. Further, as the wax component, a petroleum wax and / or a synthetic wax,
Vegetable wax. That is, the wax component used in the present invention is a combination of a petroleum wax and / or a synthetic wax and a vegetable wax. As the petroleum wax, for example, paraffin wax,
Microcrystalline wax and the like. Examples of the synthetic wax include a synthetic wax synthesized by a Fischer-Tropsch method or the like. Either one of these petroleum waxes and synthetic waxes may be used, or both may be used in combination. Furthermore, these petroleum waxes and / or
Alternatively, examples of the vegetable wax used in combination with the synthetic wax include carnauba wax and rice wax. Of these, it is preferable to use a petroleum wax and a vegetable wax in combination. As the petroleum wax, paraffin wax is preferable, and as the plant wax, carnauba wax and rice wax are preferable.

The ratio of the petroleum wax and / or the synthetic wax and the vegetable wax used in combination is such that the petroleum wax and / or the synthetic wax are contained in 30 parts by weight of the vegetable wax in the wax component. It is preferable that it is blended in a proportion of more than 70 parts by weight. When the petroleum wax and / or the synthetic wax is blended in a proportion of 70 parts by weight or less, the obtained inorganic sintered body may be easily cracked.

The proportion of the thermoplastic resin, the plasticizer and the wax component is 3 to 16 parts by weight, preferably 4 to 12 parts by weight, based on 100 parts by weight of the binder for the inorganic powder injection molding. The plasticizer is 0.5 to 2 parts by weight, preferably 1 to 1.5 parts by weight, and the wax component is 1 to 12 parts by weight, preferably 2 to 6 parts by weight. In addition, the binder for inorganic powder injection molding of the present invention may contain known additives, for example, a surface modifier such as a coupling agent and the like. May be blended.

[0012] The binder for inorganic powder injection molding of the present invention obtained in this manner is used in a method for producing an inorganic sintered body obtained by firing a molded body molded by injection molding. It is blended in. Examples of the inorganic powder include known sinterable powder materials such as ceramic materials such as titanium oxide, barium titanate, zirconium oxide, and tin oxide, metal materials, alloy materials, and cermet materials. These may be used alone or in combination of two or more kinds. Preferably, a dielectric ceramic powder such as titanium oxide, zirconium oxide, tin oxide or the like, whose obtained sintered body becomes a dielectric, is used. In addition, these inorganic powders, the average particle size,
It is preferably from 0.1 to 100 μm, and more preferably from 0.5 to 10 μm. If it is smaller than 0.1 μm, it is necessary to increase the amount of binder for imparting necessary fluidity during injection molding, and it may be difficult to shorten the degreasing time. On the other hand, if it exceeds 100 μm, sintering of the molded body may be difficult.

The mixing ratio of the inorganic powder injection molding binder to the inorganic powder may be, for example, 35 to 55% by volume of the inorganic powder injection molding binder in the mixture of the inorganic powder and the inorganic powder injection molding binder. , 37-47% by volume
It is preferable that the content be contained. Next, a method for producing an inorganic sintered body by mixing an inorganic powder with a binder for injection molding of an inorganic powder, performing injection molding, and firing the mixture is described.

The compounding of the inorganic powder and the binder for the injection molding of the inorganic powder is carried out, for example, by using equipment such as a pressurized kneader which exerts a large shear stress, in a state where the binder for the inorganic powder injection molding is melted. It is preferable to carry out. By such mixing, the binder for inorganic powder injection molding is uniformly dispersed in the inorganic powder, and the mixture becomes fluid at a high temperature equal to or higher than the melting point of the binder for inorganic powder injection molding.

Next, the obtained mixture is adjusted to a predetermined size which is easy to handle. For example, for example,
A hot-cut method in which the mixture is extruded from a die having a size of, for example, about 3 mmφ while being heated, and the mixture is extruded from a die having a size of, for example, about 3 mmφ while being heated, and the cutter is cooled. And a crushing method of crushing after forming into a flat plate shape and the like.

Then, the mixture adjusted to a predetermined size is introduced into an injection molding machine. The charged mixture is sent into a heated cylinder to be in a molten state, and then injected into a mold having a predetermined shape. After the injection is completed, the inside of the mold is maintained at a predetermined pressure until a predetermined pressure holding time elapses.
Then, after the compact is cooled and solidified in the mold, the mold is opened and the compact is released from the mold. As a result, a molded article having a desired shape is obtained.

Next, the obtained molded body is degreased by heating. This degreasing is to decompose and volatilize the inorganic powder injection molding binder from the molded body by heating,
For example, a heating rate of about 2 to 10 ° C./hr, a maximum temperature of about 4
Heat at 00-600 ° C. This degreasing may be performed in an air atmosphere or an inert gas atmosphere, but is preferably performed in an air atmosphere in terms of cost.

Then, the molded body from which the binder for inorganic powder injection molding has been removed by degreasing is fired at a temperature at which sintering is possible, thereby obtaining an inorganic sintered body. In this firing, when the inorganic powder to be used is a non-oxide material, it is preferable to appropriately control the atmosphere. In addition, degreasing and baking may be performed in one continuous step. The obtained inorganic sintered body often does not particularly require post-processing, but if a large undercut or the like that cannot be processed into a mold is required, it may be appropriately applied to the obtained inorganic sintered body. Good. In addition, polishing, plating,
Surface treatment of the inorganic sintered body, such as formation of a metal film by sputtering or the like, may be appropriately performed.

The thus obtained inorganic sintered body has few defects such as cracks, and can secure a high yield rate in production. Also, during injection molding,
Since a compact without sinking can be obtained in a short dwell time, the molding cycle can be shortened, and the manufacturing cost can be reduced.

[0020]

The present invention will be described below in detail with reference to examples and comparative examples. 1) Manufacture of inorganic sintered body Each powder of titanium oxide, zirconium oxide, and tin oxide is mixed in such a ratio as to obtain an electrical property as a dielectric after sintering, so that fine powder is obtained. It was pulverized to prepare an inorganic powder.

Next, the obtained inorganic powder was mixed with the inorganic powder injection-molding binders of Examples 1 to 7 and Comparative Examples 1 and 2 each having the composition shown in Table 1 by adding the inorganic powder and the inorganic powder injection-molding binder. Were mixed so that the proportion of the binder for inorganic powder injection molding was 40% by volume, respectively, to prepare mixtures corresponding to Examples 1 to 7 and Comparative Examples 1 and 2. Then, each mixture was mixed at 150 ° C. for 60 minutes under a pressure of 5 kg / cm ² using a pressurized kneader, and then formed into a cylindrical shape of about 3 mmφ × 5 mm by a hot cut method using an extrusion granulator. Granules were each prepared.

Each of the obtained granules is put into a horizontal injection molding machine, and a cavity case 1 made of a box with one side open, such as a TM mode dielectric resonator element shown in FIG.
, So that the column 2 has a shape continuously provided on the upper wall and the lower wall of the cavity case 1.
Each was injection molded. The injection molding conditions at this time are as follows:
Nozzle temperature 170-200 ° C, injection pressure 1000-15
It was 00 kgf / cm ² . In Examples 1 to 7 in which carnauba wax or rice wax was blended as a wax component, a molded product without sink was obtained in 5 seconds. However, paraffin wax was used as a wax component. In Comparative Example 1 alone or Comparative Example 2 containing stearic acid, it took 15 seconds to obtain a molded product without sink marks.

Each of the obtained molded bodies was heated at a rate of 2 ° C./h.
r, after degreasing under the condition of a maximum temperature of 500 ° C., subsequently, a heating rate of 120 ° C./hr, a maximum temperature of 1300 to 14
By firing at 00 ° C. for 4 hours, dielectric ceramic sintered bodies as inorganic sintered bodies were obtained.

[0024]

[Table 1]

2) Evaluation of dielectric ceramic sintered bodies Each of the obtained dielectric ceramic sintered bodies was examined for the occurrence of cracks. Table 1 shows the results. In addition,
The crack occurrence rate and non-defective rate are the number of units where cracks have occurred by appearance inspection and destructive inspection of the sintered body,
It is a value obtained by dividing the number of units in which no defect such as cracks was observed by the number of inspected units.

As is evident from Table 1, Examples 1 to 7 in which carnauba wax or rice wax was blended as the wax component were significantly different from Comparative Example 1 in which only paraffin wax was blended as the wax component. Shows a high non-defective rate. In Comparative Example 2 in which stearic acid was blended, cracks had already occurred on the surface of the molded body in the degreasing step, and the cavity case was greatly deformed in the sintered body.

Examples 1 to 3 in which carnauba wax or rice wax is blended as a wax component
7. In 7, the paraffin wax in the wax component is 7
Examples 1, 2, 3, containing more than 0% by weight
In 5, 6, and 7, a good product rate of 85% or more was obtained.

[0028]

As described above, by blending the binder for inorganic powder injection molding of the present invention with the inorganic powder and performing injection molding, it is possible to obtain a molded body without sinking in a short dwell time during injection molding. Can be. Therefore, the molding cycle can be shortened, and the manufacturing cost can be reduced.

The inorganic sintered body obtained by firing has few defects such as cracks, and can secure a high yield rate in production.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a TM mode dielectric resonator element of interest to the present invention.

[Explanation of symbols]

 1 cavity case 2 pillar

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 91/06 C08L 101/00 101/00 C04B 35/00 X

Claims (4)

[Claims] 1. A binder for inorganic powder injection molding, which is blended with said inorganic powder to form said inorganic powder by injection molding, and degreased by heating after injection molding, comprising: a thermoplastic resin, a plasticizer. And a wax component, wherein the wax component contains a petroleum-based wax and / or a synthetic wax and a vegetable-based wax. 2. The binder for inorganic powder injection molding according to claim 1, wherein the vegetable wax is carnauba wax and / or rice wax. 3. The wax component according to claim 1, wherein the petroleum wax and / or the synthetic wax is blended in an amount of more than 70 parts by weight with respect to 30 parts by weight of the vegetable wax. 3. The binder for inorganic powder injection molding according to 1.). 4. The binder for injection molding of an inorganic powder according to claim 1, wherein the inorganic powder is a dielectric ceramic powder.