JPS6046210A - Injection filtration consolidation molding method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of molding ceramics using an injection molding machine.

Ceramic injection molding has recently been attracting attention as one of the molding methods for fine ceramics or engineering ceramics. The injection molding method was originally developed for plastic materials, that is, resin materials, and has a mechanism as shown in FIG.

In other words, the raw material plastic material is pellet 1
It is charged from the inlet 4 as a liquid, and is conveyed to the screw base 5 of the injection molding machine 2 by the conveying blade 3. Then, while being conveyed to a nozzle 7 by a screw 6, it is heated by a heating section (part of a heater) 8 and becomes a melt (melt) 9, which is then injection molded into a mold 10 through the nozzle 7. Since the mold 10 is kept at a lower temperature than the melt temperature (normally room temperature) and solidifies, shape retention becomes possible, and the molding operation is completed. Therefore, it becomes possible to demold the mold and take it out as the molded body 11. The molded product thus obtained is usually accompanied by burrs at the injection hole, mold mating opening, etc., and these are removed to obtain a finished product.

In addition to using screw pressure during injection, compression pressure by a plunger or compression pressure by gas pressure may be used, but the molding principle is the same.

This is the principle of injection molding of plastics, but sometimes plastics are mixed with powder called an extender to partially improve the physical properties of the molded product or improve its aesthetic appearance. .

However, in this case (when mixing powder), there is a limit to the amount of powder mixed in, and in normal cases, the plastics to powder ratio is at most 8:2 by volume (converted to MM ratio). , approximately 57:43), and even when performing the most demanding tasks, this ratio is 7:3 by volume (approximately 44:56 by weight).
It is considered difficult to do so.

When injection molding a ceramic material, the main component of the molded body is powder, so it is desirable that the amount of powder be as large as possible. However, when injection molding a plastics-ceramics composite composition, if you rely on a side pressure molding machine, the volume ratio of plastics to powder (ceramics) should be greater than the above 7:3 (approximately 44:56 in weight ratio). It is not possible to increase the powder concentration. Even if you go as far as possible to design a powerful injection machine, the ratio will be 6.5 to 5.
(38:62 in weight) is said to be extremely difficult to achieve.

If the amount of powder exceeds this volume ratio,
The inability of the system to flow has already been theoretically proven in the rheology of suspended systems.

However, in the injection molding of ceramics, the plastic contained in the molded product must be burned off during sintering (that is, it must be turned into combustion gas and removed from the system). If as much as 65 plastics were mixed in by volume, the amount of plastics to be burned would be too large, which would be extremely disadvantageous in terms of sintering operation. It is also unfavorable from an economic point of view. moreover,
Above all, if the powder filling gap is this high (if the powder filling gap volume is small), the amount of sintering shrinkage when the powder part is sintered to form ceramics will increase, and furthermore, the final As a result, a good sintered body cannot be obtained, such as the possible sintering density being reduced. Due to these requirements, in ceramic injection molding, the plastics to powder ratio has been increased to 6 by volume.
Efforts have been made to bring the powder concentration even higher than 5:35 (weight ratio: 38:62), but the desired results have not yet been obtained. In other words, great efforts are being made to create a fluid state with a smaller amount of plastic by increasing the injection pressure, but currently it is not possible to achieve a favorable powder concentration with a volume ratio of 65:35 (weight ratio: 38:62) or higher. There are no examples of results being obtained. (In other words, if the powder concentration is higher than this, it becomes impossible to create complex shapes.

) The present invention solves the above problems, and in particular, the volume ratio of plastics to ceramics (powder) is 40:60.
(Weight ratio of approximately 18:82) was successfully obtained. (In special cases where two-stage particle size blending or three-stage particle size blending is performed on the powder side, the volume ratio is 30:70.
It was also possible to bring the weight ratio up to 12:88. ) The gist of the present invention is that in ceramic injection molding, a ceramic base is injection molded using a mold provided with a porous plate made of sintered metal or ceramic material inside, and after injection is completed, the porous plate is passed through the mold. By squeezing out a part of the medium from the object and extracting it out of the system,
The present invention is an injection overconsolidation molding method characterized by obtaining a molded product with increased powder concentration. That is, in the injection molding of the present invention, the mold temperature is equal to the melt temperature, or
The mold is kept at a temperature close to that temperature (±5℃), and the mold part is separated after injection molding is completed. Inside this mold, a filter plate (aperture plate) with a hole diameter of /1X than the powder diameter is installed. Then, by pressing this squeeze plate, the molded body kept at or near the injection molding temperature is compressed, and a part of the plastic is squeezed out through the squeeze plate to form a final molded body with an increased powder concentration. This is what you get.

The method of the present invention will be explained based on the drawings. In the method of the present invention, the injection molding machine up to the nozzle is the same as that shown in FIG. 1, but the mold 10 shown in FIG. 2 is used.

The mold has a diaphragm plate 12. Heater 13. Press section 14
．． Aperture plate front and rear 15. A nozzle connection portion 16 is provided, and the shaped body 11 is first shaped along a mold maintained at or near the melt temperature. After the modeling is completed, the nozzle 7 of the injection machine is removed together with the injection machine body 2, and a stopper (not shown) is installed in its place. Further, the entire mold part is maintained at or near the melt temperature by the heater 13. As the aperture plate 12, a sintered metal or sintered ceramic slope is used which has a hole having a diameter tJ\ smaller than that of the finest powder particle in the intended compact. Next, under this condition, the piston 17 of the press shown in FIG. A portion of the plastics is squeezed out through the squeezing plate (i.e., forced separation), and a portion of the plastics equivalent to the liquid is collected at the back of the squeezing plate 12, which is removed via a discharge vibrator (not shown). is removed from the mold. When the drawing is completed, the dimensions of the molded product are determined as the final size.

By newly adding this operation after injection molding, it became possible to reduce the volume ratio of plastics to powder at the time of molding, 40:60 (weight ratio: 18:82), and improve the powder ratio. In the research conducted by the inventor using the apparatus shown in Figures 1 and 2, this ratio was the highest volume ratio of 35:65.
(weight ratio 15:85). After injection molding, a part of the molten plastic is forcibly filtered to form a shaped body, and then the position of the mold is moved and the temperature of the mold is cooled to room temperature or near room temperature. By cooling, the plastics (remaining after drawing) in the plastics/powder compounding composition solidify, so that it becomes possible to remove the mold and take out the molded body for sintering.

The molded body taken out in this way has an extremely low plastic content (the above weight ratio of 15:85 is almost the highest concentration as a theoretical value), so the strength of the sintered ceramic is You can expect something extremely high.

In the case of plastics/ceramics composite compositions, by adding a squeezing mechanism for the excess plastic part to the plastics injection molding method, it is possible to take out a molded product with a high powder concentration. This can greatly contribute to improving the performance of the molded product.

Although the plastics/ceramics composite composition has been described above, the method of the present invention can be similarly applied to ceramics/water-based and other ceramics/liquid-based compositions. That is, after injection molding of the above composition, a squeeze plate is compressed, excess liquid such as water is squeezed out from the shaped body through the squeeze plate, and a molded body with a high powder concentration that maintains sufficient shape retention can be taken out. That is, the liquid difference ΔW, which is necessary during modeling but is surplus during shape retention, is filtered and separated. As shown in Fig. 5, firstly, the raw material slurry 19 (having the optimum moisture content W1 for modeling) is injected into the casting frame 1o from the nozzle 7, but after the modeling is completed, the nozzle connection part 16 is removed and replaced with After closing with a stopper (not shown in the drawing), the piston 17 is actuated from the left to compact the liquid and discharge the excess liquid ΔW from door to door. At this time, as a means other than mechanical pressure using a piston, it is also possible to apply hydraulic or gas pressure to the shaped body to squeeze it (in this case, pressure is applied from the injection side).

Therefore, a diaphragm plate 12 is installed in advance at the tip end of the consolidation piston part 17.
The aperture plate is a perforated metal or ceramic plate made of powder sintered metal or ceramic, which has a hole diameter that allows the medium (liquid) in the slurry to pass through, but does not allow the powder to pass through. Use your body. In some cases, the shaped body 20 and the aperture plate 1
It is also possible to further improve the filtration effect by inserting a piece of paper 18 between the two. The final molded product (liquid W2) that has been squeezed out to a predetermined drawing plate position has sufficient shape retention and can be removed from the mold. In other words, the liquid difference △W, which is necessary during molding but unnecessary during shape retention, is forced; injection, filtration, and consolidation molding is made possible by performing separate steps. This will be explained more specifically.

Example 1 Alumina powder (α-A1.Os purity 99°8) was used as powder.
2% by weight), and polystyrene (weight average molecule [11,27
C) was used.

First, powder and plastics were mixed at a volume ratio of 30:70 (weight ratio: 59:41), and the mixture was placed in a compression test container 21 of the apparatus shown in FIG. The upper punch 22 was inserted into this, and while the upper punch 22 was kept in contact with the raw material surface, the heater 23 was operated from the outside to raise the temperature. As it heats up, the pestle sinks a little due to its own weight, but at this time the entire device is placed in a vacuum container (
(not shown) and tested.

When the thermometer 25 at the center of the bottom mold 24 reached the softening point of polystyrene, 127° C., compression pressure was applied from the top of the upper punch 22 to press. After the molded body was compressed to a certain volume by pressing, the pressurization was continued under heating for a certain period of time (determined by the size of the molded body).

After that, once cooled to room temperature, a porous squeeze bottom plate 12 made of forest material similar to the porous squeeze plate shown in FIG.
' was attached to the bottom of the compression test container as shown in FIG. This porous drawing bottom plate 12' is molded only from the same alumina powder used in the test, and has an earthenware-like structure (open pore structure: the same powder is used and fired to an earthenware-like structure), so the porous passages that it has are The diameter of the powder material can be made smaller than the smallest diameter of the powder material. Therefore, the pore diameter of the porous plate is smaller than that of the raw powder, and the passage of the powder is not allowed. This passageway allows only melt polystyrene to pass through. The temperature ft25 and the distance piece 26 are placed under the throttle bottom plate, and the melt polystyrene squeezed out under the throttle base plate is stored in the lower cavity 27G.

The entire container was kept at the same temperature as during the modeling in Figure 3 (
In this case as well, the measurement was made at the center position of the drawing bottom plate at the bottom), and then the upper punch 22 was inserted and drawing pressure was applied from above.

The molding pressure in Fig. 3 was 50 kg 7 cm Q, but the squeezing pressure was lower than this and was able to squeeze sufficiently at 19 to 23 kg/cm. Just to be sure, the molding pressure was increased again to the initial molding pressure (50 kg 7 cm'').

The measurement specifications are as follows.

Model size (before squeezing) = 50φX 57. ．． 3 m
Concentration of plastics in the molded body: Weight ratio: 41% (volume ratio: 70%) Next, when the molded body was made into a squeezed body, the dimensions were measured and the result was 50φ×37-3 mm. When calculating the amount of polystyrene squeezed out from this result, it corresponds to 35 of the initial 70 amounts of polystyrene being squeezed out. Converting this to the concentration ratio after squeezing, it is 46 volume ratio (
This corresponds to an increase in the solids concentration to 74% by weight). The sample before squeezing and the sample after squeezing were fired under the same firing conditions to form ceramics (temperature raised to 1,650°C over 3 hours, ffl, held at 1,650°C for another hour). Twenty test pieces for strength measurement were cut out from each of these samples, and a bending test (3-point bending strength) was performed, and the average value of the 20 pieces was determined. A molded body of the same sample powder (At, Os powder) by T (IP (high temperature isostatic compression molding)) was similarly fired and subjected to a bending test.The results are shown in Table 1 below.

Table 1 From this table, it can be seen that the improvement rate in the case of the present invention [case (■)] is extremely high. Also 1, HI
We were able to prove that it was comparable to the P molded product.

Example 2 An injection molding machine was used to inject an Al, 03 powder/polystyrene composite sample (mixing ratio: powder concentration: 30% by volume) as a raw material. The specifications of the injection molding machine used are as follows.

1N Small pressure 2000 kg up to 7cm'' Cylinder temperature 110℃ ・Injection temperature 127℃ Mold temperature 127℃ Screw rotation speed 6Orpm Injection pressure 1300kg /an 2 Maximum injection speed
The shape obtained by molding 7 times for 16 sec is cylindrical and has a size of 50φ×50 mm.

In this case, the difference from ordinary injection molding is that the mold temperature is adjusted to the injection temperature. For squeezing, a squeezing device shown in FIG. 2 is installed in the mold in advance.
Excess polystyrene was squeezed out using the method described in the text.

After squeezing is completed, reduce the pressure to 50 kg 7 cm 11
raised to.

The sample taken without squeezing and the sample squeezed by the method of the present invention were made into ceramics under the same conditions as in Example 1. From these, 20 samples for strength measurement were cut out, and the 3-point bending strength was measured. The results are shown in Table 2.

Table 2 It has been demonstrated that the method of the present invention improves the strength of ceramic molded bodies, and that the value has been increased to correspond to I (IP molded body).

Example 3 Zirconia powder (ultra fine powder, average particle size of 0.5 μm or less, purity 95.8%) was used. Water was used as a medium, and an acrylonitrile aqueous solution was used as a dispersion aid. (The soil was prepared so that the amount after addition was within 0.2% of the powder.) The base material was poured into the mold structure shown in FIG. 5 and molded. At the time of injection, the liquid content was 10% by weight (25% by volume).
%)Met. After modeling, the squeezing piston was operated to squeeze out excess moisture in the shaped object (in this case, 15% of the above 25% by volume of excess moisture ΔW could be squeezed out). In this case, the liquid content of the final model was 43% by weight (12% by volume), so the initial liquid It(
25% by volume), 15% by volume was to be squeezed out. This liquid content (4.3% by weight, 12% by volume) had good shape retention and could be demolded.

[Brief explanation of drawings]

Figure 1 is a vertical cross-sectional view showing the schematic structure of an injection molding machine;
The figure shows a vertical cross-sectional view of a mold section equipped with a squeezing mechanism according to the method of the present invention, FIGS. 3 and 4 are vertical cross-sectional views of the molding apparatus used in Example 1, and FIG. FIG. 2 is a longitudinal cross-sectional view of a liquid-based filtration compaction molding device. 1...Synthetic resin pellets. 2...Injection molding machine body. 6...Screw, 7...Nozzle. 10...Mold (casting frame). 12... Aperture plate, 12'... Aperture bottom plate. 13...Part of the heater, 14...Press part. 15... Rear part of the aperture plate, 16... Nozzle connection part. 17...piston, 18...1 paper. 21... Compression test container, 22. -1. Upper pestle. 23...Heater, 24...Bottom mold. 25...Thermometer. 26... Distance piece. Patent applicant Kaoru Umeya Patent attorney Keiji Matsunaga Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 14 1J 1 Do I (j IB IJ Do IJ
Let +! 9 Procedural amendment October 21, 1980 Director of the Patent Office Kazuo Wakasugi 1. Indication of the case 1981 Patent Application No. 154148 2. Name of the invention Injection 5. Filtration consolidation molding method 3. Person making the amendment Related: Patent Applicants: Number of inventions to be increased by the amendment ＼ 7, Column 8 of “Claims” and “Detailed Description of the Invention” of the specification subject to the amendment, Contents of the amendment ( 1) As per appended claims (2) Detailed Description of the Invention 1, Specification, page 9, line 10 "...As explained, j and "method of the present invention...1.
Add the following sentence between...]. "For example, it can also be applied to ceramic solid compositions consisting of solids and ceramic powders, such as paraffin, which become liquid under heating and can be burned at high temperatures and volatilized outside the system, just like plastics. In addition, ``2, p. 10, line 7, ``...pressure is applied'' is corrected to ``...it is also possible to apply pressure.'' 3. Specification, page 14, line 3 “HIP (AI, C) 3 powder)”
・” to “・・・・・・(A120.Powder) HI P,,”
, , ,J is corrected. Above 2P Claim 1 In ceramic injection molding, a ceramic base is injection molded using a mold provided with a porous plate made of sintered metal or ceramic material inside, and after injection is completed, the porous plate is An injection filtration compaction molding method characterized in that a molded product with increased powder concentration is obtained by squeezing out a part of the medium from the molded body and extracting it out of the system. 2. The injection filtration compaction molding method according to claim 1, wherein the ceramic base is a plastics-ceramics composite composition. a The ceramic base is powder/liquid type or powder/
The injection 5 filtration compaction molding method according to claim 1, which is a solid composite composition.

Claims (1)

[Claims] 1. In ceramic injection molding, a ceramic base is injection molded using a mold provided with a porous plate made of sintered metal or ceramic material inside, and after injection is completed, the mold is molded through the porous plate. , an injection 5 filtration compaction molding method characterized in that a molded article with increased powder concentration is obtained by squeezing out a part of the medium from the shaped body and extracting it out of the system. 2. The injection-filtration compaction molding method according to claim 1, wherein the ceramic base is a plastics-ceramics composite composition. (a) The injection filtration compaction molding method according to claim 1, wherein the ceramic base is a powder/liquid composite composition.