JPH0689369B2 - Binder composition for injection molding - Google Patents

Description

TECHNICAL FIELD The present invention relates to a binder composition for injection molding, and more specifically, to a binder composition for injection molding excellent in physical properties such as moldability, degreasing property and sinterability. .

[Conventional technology]

Injection molding of metal powder such as iron and alloy or ceramic powder is generally performed as follows. A compound is prepared by adding a binder to the above-mentioned metal powder or ceramic powder, injection molding the compound with an injection molding machine, and then removing the binder from the molded product (degreasing).
After that, the degreased molded product is sintered to obtain a product.

At this time, the binder added to the metal powder or the ceramic powder is required to have the following properties.

(1) The compound to which the binder is added can be molded by an injection molding machine.

(2) The molded product injection-molded using the above compound has such strength that it is not damaged until the sintering step.

(3) Degreasing of the molded product is easy (the degreasing time is short and the degreasing temperature is low).

(4) It has a strength such that the degreased molded product is not damaged.

(5) The sinterability of the molded product is good (a small dimensional change, large strength, and high-density product can be obtained).

Conventionally, as a binder of this type, as described in JP-A-59-121150 and JP-A-59-121151, a thermoplastic resin or wax has been used.

[Problems to be Solved by the Invention]

However, the conventionally used binder was satisfactory in the performance of the above (1), but was still unsatisfactory in other performances. For example, when a conventional binder containing a wax or a thermoplastic resin as a main component was used, degreasing took tens of hours or more. If the degreasing process takes a long time in this way, only a small molded product can be produced, and during degreasing, the product is likely to be swollen, cracked or damaged, and it is difficult to obtain a good product. Further, when the thermoplastic resin was not used, the moldability was poor and there was a practical problem.

Therefore, an object of the present invention is to provide a binder composition for injection molding which satisfies all of the above performances required as a binder, that is, has excellent physical properties such as moldability, degreasing property and sinterability. .

[Means for solving problems]

The present invention has the above-mentioned object of having an average molecular weight of 7,000 to 26,000.
One or two or more selected from the group consisting of natural wax, synthetic wax, fatty acid, esters, metal soap and water, which contains polyoxyethylene-polyoxypropylene condensate-based polyether which is A composition containing a compound as an auxiliary component, which is achieved by a binder composition for injection molding which is solid at room temperature and has a pour point of 40 to 100 ° C.

Hereinafter, the binder composition for injection molding of the present invention will be described in detail.

Polyoxyethylene-polyoxypropylene condensate-based polyether which is the main component of the binder composition for injection molding of the present invention, ethylene glycol, propylene glycol, polyhydric alcohols such as glycerin and polyvalent amines such as ethylenediamine, It can be obtained by condensing ethylene oxide and propylene oxide, and its average molecular weight is 7,000 to 26,000. If the average molecular weight is less than 7,000, moldability tends to be impaired,
If it is super, stability may be a problem.

Further, the polyoxyethylene-polyoxypropylene condensate-based polyether has an ethylene oxide content of 60 to
90% by weight is preferred. Ethylene oxide content of 60
If it is less than wt%, moldability and releasability may be impaired, and if it exceeds 90 wt%, stability may be impaired.

Examples of the preferred polyoxyethylene-polyoxypropylene condensate-based polyether include Pluronic (registered trademark) surfactant manufactured by Asahi Denka Co., Ltd. and Tetronic (registered trademark) surfactant manufactured by Asahi Denka Co., Ltd.

The binder composition for injection molding of the present invention contains the above-mentioned polyoxyethylene-polyoxypropylene condensate-based polyether as a main component, and is a group consisting of natural wax, synthetic wax, fatty acid, esters, metal soap and water. One or more compounds selected from the above are contained as subcomponents.

The subcomponent is the main component polyoxyethylene-
It is preferable to add 10 to 100 parts by weight to 100 parts by weight of the polyoxypropylene condensate-based polyether. Further, the obtained binder composition for injection molding of the present invention needs to be blended so as to be solid at room temperature and have a pour point of 40 to 100 ° C. That is, when the binder composition for injection molding is solid at room temperature, it is easy to pelletize and knead the kneaded product after kneading with metal powder, etc. If the point is 40 to 100 ° C, 1
Molding at temperatures below 00 ° C is possible.

In particular, the binder composition for injection molding of the present invention using water as an accessory component can easily adjust the viscosity of the binder without the need for a polymer resin and is excellent in the effect of debinding (degreasing).

Examples of the natural wax used as an auxiliary component in the present invention include plant waxes such as carnauba wax and candelilla wax, and mineral waxes such as ceresin and montan wax, and the synthetic waxes include amine amides. Wax, paraffin wax,
Microcrystalline wax, polyethylene wax, polypropylene wax, etc. are also included. Examples of the above-mentioned fatty acid used as an auxiliary component in the present invention include stearic acid, palmitic acid, oleic acid, saturated fatty acids having 4 to 30 carbon atoms and unsaturated fatty acids. Fatty acids can be used as well as other natural fatty acids such as coconut oil fatty acids.

In addition, examples of the above-mentioned esters used as an accessory component in the present invention include butyl stearate, oleyl oleate, stearic acid monoglyceride, coconut oil fatty acid methyl ester, and sorbitan ester.

Examples of the metal soap used as an accessory component in the present invention include calcium salts, magnesium salts, aluminum salts and other metal salts of fatty acids such as stearic acid, palmitic acid and oleic acid.

When producing an injection molding compound using the injection molding binder composition of the present invention, the metal powder is a ceramic powder containing the injection molding binder composition of 80 to 150.
It is preferable to add and knead at 0 ° C., and the amount to be added may be increased or decreased according to the particle size distribution of the metal powder or ceramic powder to be used, according to a conventional method.

Examples of the metal powder to which the binder composition for injection molding of the present invention is added include metal silicon powder, iron or iron alloy powder such as high-speed steel, titanium-based, tungsten-based, superalloy powder such as boron-based, and magnetic. Examples include various metal powders such as material powders, and the ceramic powders include
Examples include various ceramic powders such as silicon nitride powder, silicon carbide powder, alumina powder, zirconia powder, and sialon powder (silicon nitride-alumina system). Cermet powder obtained by mixing metal powder and ceramic powder can also be used, and if necessary, two or more kinds of the above-mentioned various metal powders and various ceramic powders can be appropriately mixed and used.

Injection molding, degreasing and sintering of the compound to which the binder composition for injection molding of the present invention is added can be performed in the same manner as in the case of the conventional compound of this type.

According to the binder composition for injection molding of the present invention described above, degreasing of about 50% or more is possible at a degreasing temperature of 300 ° C. and a degreasing time of 3 hours, and usually 10 to 15 hours or less, depending on the shape of the molded article. It is possible to degrease almost completely in about 5 hours.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples of the present invention.

Example 1 (1) Production of compound 100 parts of alloy powder (SUS304L, average particle size 20 μm) (parts by weight; the same applies hereinafter) 12.10 parts of binder composition for injection molding having the composition shown in Table 1 below [addition amount composition The product / (powder + composition) = 10.8%] was added and kneaded with a kneader at a temperature of 60 to 90 ° C. for 40 minutes to sufficiently fluidize the kneaded product. Then, the flowing kneaded product was pelletized by applying a pelletizer, and the pellet was cooled to room temperature.

(2) Injection molding Using the above pellets, using a screw type injection molding machine, the cylinder temperature was set to 60 ° C for the measuring part, 55 ° C for the compressing part and 50 ° C for the supplying part, and the mold temperature was set to room temperature. The back pressure, injection speed, holding pressure, etc. were adjusted by a conventional method and molded to obtain a molded product. The obtained molded product is a JIS tensile type dumbbell (tensile part width 10 mm, thickness 5 mm, length 30 mm, total length 80 mm including grip part).

(3) Degreasing The above molded product was heated to 400 ° C at a rate of 100 ° C / 1 hour, and
Degreasing was performed by holding at 0 ° C for 2 hours (total degreasing time: 6 hours). The results are as follows.

Weight of molded product before degreasing 28.79g (0.119) Weight of molded product after degreasing 25.69g (0.125) Reduction 10.78g (0.018) Degreasing rate 99.81% Weight is the average value of 8 molded products. The values in parentheses are standard deviation values.

(4) Sintering The degreased molded product was sintered by a conventional method. The physical properties of the obtained sintered product are as follows.

Relative density 96% Tensile strength 48kgf / cm ² Hardness (HRB) 68 Example 2 (1) Production of compound 100 parts of iron powder (average particle size 15 to 16 microns) and an injection molding binder having the composition shown in Table 1 below. 9.6 parts of composition
Composition / (powder + composition) = 8.8%] was added and kneaded with a mixer at a temperature of 60 to 90 ° C. to sufficiently fluidize the kneaded product. Then, the kneaded product was cooled to give granules.

(2) Injection molding A molded article (JI
S tension type damper) was obtained.

(3) Degreasing The above molded product is heated at 250 ° C at a rate of 100 ° C / hour for 25 hours.
Degreasing was performed by holding at 0 ° C for 2 hours (synthetic degreasing time: 4.5 hours). The degreasing rate was 99.8%.

(4) Sintering The degreased molded product was sintered by a conventional method. The physical properties of the obtained sintered product are as follows.

Relative density 93% Tensile strength 16kgf / cm ² Example 3 Ceramics powder (fine ceramics, alumina AL16
0SG) 2.0 parts of 100 parts of binder composition for injection molding in the proportions shown in Table 1 below [addition amount composition / (powder + composition) = 1
6.7%] and kneaded with a mixer at a temperature of 90 to 110 ° C. to sufficiently fluidize the kneaded product.

(2) Injection molding Using the above kneaded product, a screw type injection molding machine was used to set the cylinder temperature to 70 ° C for the measuring part, 80 ° C for the compressed product and 90 ° C for the supplying part, and the mold temperature to room temperature. The number, back pressure, injection speed, holding pressure, etc. were adjusted by a conventional method and molded to obtain a molded product. The obtained molded product is 40 mm × 60 mm ×
It is a 1.5 mm plate.

(3) Degreasing The above molded product was heated to 100 ° C over 60 minutes, and then 20 ° C /
The temperature was raised to 300 ° C at a rate of 1 hour, and the temperature was kept at 300 ° C for 2 hours for degreasing (total degreasing time: 13 hours). The degreasing rate was 90%.

Further, the above-mentioned molded product was heated to 100 ° C over 60 minutes, then heated to 300 ° C at a rate of 50 ° C / 1 hour, and held at 300 ° C for 2 hours to be degreased (total degreasing time: 7 time). Degreasing rate is 85-
It was 90%.

Example 4 Ceramic powder (fine ceramic zirconia,
To 100 parts of a specific gravity of 6.27 and an average particle size of 0.02 mm, 22.3 parts of an injection molding binder composition having the composition shown in the following Table 1 [addition amount composition / (powder + composition) = 18.3%] was added with a pressure kneader. The mixture was kneaded at a temperature of 90 ° C. and a rotation speed of 30 rpm for 40 minutes.

(2) Injection molding Using the above kneaded product, in a screw type injection molding machine, the cylinder temperature was set to 70 ° C. for both the measuring section, the compression section and the supply section, and the mold temperature was set to room temperature. The pressure, injection speed, holding pressure, etc. are adjusted by a conventional method, and the nozzle is
A molded product was obtained by molding using 10R (for EP). The obtained molded product is a plate-shaped product having a size of 50.0 mm × 50.0 mm × 4.0 mm.

(3) Degreasing The above molded product was heated to 100 ° C over 60 minutes, and then 20 ° C /
The temperature was raised to 300 ° C. at a rate of 1 hour, and further raised to 400 ° C. at a rate of 50 ° C./hour to degrease (total degreasing time: 13 hours).
The degreasing rate was 88%.

(4) Sintering The degreased molded product is heated to 1500 ° C over 15 hours to 1500
The temperature was maintained at 2 ° C. for 2 hours to sinter in air. The degreasing rate of the sintered product was 94.4%. Examples 5 to 9 and Comparative Example 1 Molded articles were prepared in the same manner as in Example 1 except that the binder composition for injection molding having the composition shown in Table 1 below was used. It was made. The degreasing rate of the molded product is as shown in Table 1 below.

Reference example 1 Ceramics powder (fine ceramics, alumina AL16
0SG) 100 parts, polybutyl methacrylate 9.86 parts, ethylene vinyl acetate copolymer 4.23 parts, stearic acid 3.16 parts and dibutyl phthalate 1.61 parts as a degreasing example of a molded article molded from room temperature to 80 ° C over 30 minutes Up to 80 ~
There is an example in which the temperature was raised to 380 ° C at a rate of 5 ° C / hour and kept at 380 ° C for 2 hours (total degreasing time 62.3 hours). Further, conventionally, it takes about 1 to 2 days to degrease the metal powder (iron-based).

〔The invention's effect〕

The binder composition for injection molding of the present invention has excellent physical properties such as moldability, degreasing property, and sinterability.

Front Page Continuation (72) Inventor Hideo Hachimori 7-35 Higashiohisa, Arakawa-ku, Tokyo ADEKA FINE CHEMICAL CO., LTD. (56) Reference JP-A-61-34101 (JP, A) JP-A-64- 11908 (JP, A) JP-A-63-11562 (JP, A)

Claims (3)

[Claims] 1. A polyoxyethylene-polyoxypropylene condensate-based polyether having an average molecular weight of 7,000 to 26,000 as a main component, and containing natural wax, synthetic wax, fatty acid, esters, metal soap and water. A binder composition for injection molding, which is a composition containing one or more kinds of compounds selected from the group consisting of as a subcomponent and which is solid at room temperature and has a pour point of 40 to 100 ° C. 2. A polyoxyethylene-polyoxypropylene condensate-based polyether having an ethylene oxide content of 60.
The binder composition for injection molding according to claim 1, wherein the binder composition is about 90% by weight. 3. The content of the subcomponent is polyoxyethylene-
The binder composition for injection molding according to claim 1, which is 10 to 100 parts by weight based on 100 parts by weight of the polyoxypropylene condensate-based polyether.