JP2015033814A - Water pressure bag - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop a water pressure bag that enables inexpensive and easy manufacture of a ceramic component, by developing an inexpensive water pressure bag free from wrinkles in a plastic film without using an expensive jig in manufacturing a ceramic green component.SOLUTION: In a water pressure bag, the four sides of two films including a front film (1) and a back film (2) are sealed. In at least one of the two films, tensile elongation is 500 percent or more both in a machine direction and in a transverse direction, and residual strain after elongation is 110 percent or less.

Description

  The present invention relates to a hydraulic bag used in an isostatic pressing method used when a green molded product is molded, pressed and fired in the manufacture of ceramic parts such as ceramic insulators and ceramic holders.

In conventional ceramic component manufacturing, ceramic dielectric material powder is mixed with a binder or the like to make a paste, solidified by injection molding or pressing, and dried. This was called a green molded product, and this green molded product was fired in a furnace to produce a final ceramic part. However, for injection molding and press molding, an expensive mold is required, and a paste containing hard ceramics is molded. The lifetime was low.
By the way, when this green molded product is in the form of a sheet, the sheet and the internal electrode are laminated and crimped, it is sandwiched from the front and back with a plastic film, and is crimped by applying heat and water pressure with hot water. It has been used in the manufacture of laminates.

  For example, in Patent Document 1, as shown in FIG. 2, a ceramic green sheet is interposed between an upper thin plate 8 and a lower thin plate 81 each having a holding hole 821 at a position corresponding to a positioning hole formed around the ceramic green sheet 7. 7, the ceramic green sheets and the upper and lower thin plates are fixed with fixing members through the positioning holes and holes, and a plurality of stacked ceramic green sheets 7 fixed to the upper and lower thin plates are sandwiched between the plastic films 10. Proposed a method for producing a green sheet laminate, comprising the steps of vacuum packing and hydrostatic pressing the ceramic green sheet 7 packed in vacuum. Further, it is also proposed to use a frame-shaped upper jig 83 and lower jig 82 as a fixing member for fixing the ceramic green sheet 7 and the upper and lower thin plates with the fixing member through the positioning holes. .

In the manufacture of such multilayer ceramic electronic parts, since the upper and lower thin plates are used and the green is held, even if the wrinkle 101 is somewhat generated in the hydraulic bag, it does not become a big problem.
However, in the case of a molded product having a non-planar shape, if the wrinkle 101 is generated to produce the shape, wrinkles are generated on the product surface as it is, or the shape is distorted and distorted. In addition to the problem that a large amount of time is required for finishing, there is a problem that the density of the molded product cannot be kept constant due to the distortion, resulting in partial variations in strength.

Patent Document 2 describes a method of manufacturing a spark plug made of ceramics by using a rubber mold, molding it by hydrostatic pressing, and firing it.
This spark plug is a hybrid type that uses a cavity core part in a normal mold and a green rubber mold in an outer part of the cavity in order to manufacture an intermediate molded green. The rubber mold part not only requires an expensive mold for making it, but also when the rubber is pressed with water pressure, the thickness of the rubber slightly affects the molded product, causing a problem that distortion tends to occur.
It is very difficult to design a green by accurately feeding back this strain to the rubber mold, so the price of the rubber mold has to be higher.
In particular, in a cavity with a partially varying thickness, the density of the thick part and thin part, and the density between the central part and the periphery are not constant, and a nest is formed in the center, resulting in a decrease in strength. Problems are likely to occur, which has become a major bottleneck in quality assurance.

JP-A-8-195326 Japanese Patent No. 4547098

  In view of the above problems, ceramic electronic parts can be manufactured easily and inexpensively by developing a hydraulic bag that is inexpensive and does not wrinkle plastic films in the manufacture of ceramic green parts. It is an object of the present invention to develop a hydraulic bag for doing so.

  The hydraulic bag according to claim 1 of the present invention is a hydraulic bag that seals the four sides of two front and back films, and the tensile elongation of at least one of the films is 500% or more in both the vertical and horizontal directions, and after being pulled. The hydraulic bag is characterized by having a residual strain of 110% or less.

  The hydraulic bag according to claim 2 of the present invention is the hydraulic bag according to claim 1, wherein at least one of the two front and back films is formed of urethane resin.

  The hydraulic bag of the present invention is a hydraulic bag for producing ceramic green at a low cost without using a rubber mold, and improves workability and does not cause wrinkles on the film. It is possible to produce a stable product that is less prone to occur. In addition, since the hydraulic bags as products can be produced in a large amount at a low cost, it is possible to perform firing without removing the product from the hydraulic bags as it is with ceramic green as it is. Therefore, the ceramic green can be moved and produced without touching the ceramic green, so that there is an advantage that the green is not damaged and the productivity is high.

It is sectional drawing of the Example which showed the usage pattern which shape | molded green with the hydraulic bag of this invention. It is sectional drawing which shows the Example of the ceramic green sheet laminated | stacked by the conventional hydraulic bag. It is a cross-sectional conceptual diagram of the hydrostatic press which pressurizes using the hydraulic bag of this invention. Cross-sectional view before forming green of the embodiment using the hydraulic bag of the present invention, cross-sectional view of the state of forming the green, cross-sectional view of the embodiment of firing the green, and before forming the green FIG. 3 is an enlarged view of the inner part of the green, an enlarged view of the inner part of the green, and an enlarged view of the inner part of the fired product. It is sectional drawing which shows the process of manufacturing the cavity of the surface film which uses vacuum-pressure forming and uses the hydraulic bag of this invention. It is sectional drawing which shows the process of vacuum-forming and manufacturing the core of the back film which uses the hydraulic bag of this invention. It is sectional drawing which shows the state which put together after forming a front film and a back film, and forms the cavity.

Hereinafter, the usage form of the conventional hydraulic bag and the embodiment in the hydraulic bag of this invention are demonstrated in detail using figures.
FIG. 1 is a sectional view of an embodiment using a hydraulic bag of the present invention.
The front-side film 1 and the back-side film 2 are manufactured so as to have the shape of the product by molding the shapes of the mold and the core, respectively, and the ceramic green material 3 between the front-side film 1 and the back-side film 2. Is sandwiched.
The ceramic green material 3 is a mixed powder in which a ceramic component is bonded to a ceramic component and a binder based on a resin component that sublimes when fired at a high temperature.
The ceramic green material 3 is weighed in advance according to the shape and inserted into the cavity of the surface film 1.
Further, the back film 2 is positioned and inserted into the front film 1 and is vibrated with ultrasonic waves or the like so that the core portion of the back film 2 completely enters the ceramic green material 3.
Then, the ceramic green material 3 between the front film 1 and the back film 2 is also degassed, and in this state, the cavity periphery 41 of the front film 1 and the back film 2 is fused.

FIG. 3 shows a state in which a hydrostatic bag in which the degassed ceramic green material 3 is sandwiched between the front film 1 and the back film 2 is placed in the hydrostatic press 6 and pressurized and heated.
The working space of the hydrostatic press 6 is usually a cylindrical container, and has a structure in which one disk-shaped pressing plate 61 at both ends is pressed to apply pressure to the inside.
Since the interior of the hydrostatic press 6 is filled with a liquid 62 such as water, according to Pascal's principle, the fluid in the sealed container per unit area received at a certain point regardless of the shape of the container. Since the pressure is transmitted as it is to all other parts of the fluid, the hydraulic bag applies pressure uniformly from all directions.
In addition, the water or liquid filled in the hydrostatic press is heated to a temperature equal to or higher than the softening point of a resin component called a binder. Therefore, in the ceramic green material 3, a resin component called a binder is melted or softened to give fluidity to the ceramic powder, the gap between the powders is reduced, and the ceramics and the resin component are completely adhered to each other. And come together.
The pressure at this time is as high as possible as long as the hydraulic bag is not damaged. Further, the temperature of the liquid injected into the working space to be heated needs to be higher than the softening point of the binder, but it is necessary not to exceed the boiling point. However, since the boiling temperature rises in a high pressure state, the heatable temperature can be changed depending on the pressure used.

FIGS. 4-1 and FIGS. 4-2 are ceramic green materials 3 placed in a cavity formed larger than the molded product between the front film 1 and the back film 2 before being heated and pressed by an isostatic press. It is a state.
There are gaps between the ceramic powders 31 of the ceramic green material 3 and the binder 32, and the binder is blended in an amount smaller than the gap.
FIGS. 4-3 and 4-4 show the state of the ceramic green 5 which is heated and pressurized by an isostatic press and has a shape.
There is a binder 32 between the ceramic powder 31 and the ceramic powder 31, which serves as an adhesive and adheres. The binder 32 moves as much as the pressure is applied, but the pressure is uniformly applied inside the hydrostatic press, the pressure is evenly compressed, the size is slightly reduced, the ceramic powder 31, the ceramic powder 31, and the ceramic powder. It adheres between 31 and the binder 32, and although it is somewhat brittle in this state, it is molded into a firm shape.
Although this ceramic green 5 is in a state of being in a hydraulic bag, it is placed in a higher-temperature firing furnace as it is and fired at a high temperature.
When the ceramic green 5 is heated at a high temperature for a long time and fired, a resin component called a binder 32 between the ceramic powder and the ceramic powder is gradually vaporized or decomposed into a gas and evaporated. It disappears between the ceramic powder 31.
The ceramic powders 31 that have been heated to a high temperature without the binder 32 start to come into close contact with each other along the crystal arrangement, and the shape of the joining portion between the ceramic powders 31 changes, FIGS. As shown in FIG. 4-6, the gaps between the ceramic powders 31 are reduced, and the shape remains as it is, but the ceramic sintered product 51 is completed by being reduced as a whole.
Naturally, since the hydraulic bag is made of a resin component, it melts at the beginning of the firing step, melts and vaporizes.
Of course, when the ceramic green 5 is molded, the shape has a certain hardness, so the hydraulic bag may be cut off before firing.

5-1, FIG. 5-2, and FIG. 5-3 are schematic views illustrating the shape of the surface film 1 of the hydraulic bag.
The surface film can also be obtained by vacuum forming, but when vacuum / pressure forming is performed, the formability is further increased and a film close to a sphere can be formed.
In FIG. 5A, the periphery of the surface film 1 is fixed by the frame 11. Furthermore, the processed surface of the surface film 1 is heated by the heater 12, and the temperature is adjusted to be higher than the softening point and lower than the melting point. Depending on the material of the surface film 1, it may be stretched at room temperature, so that heating may not be necessary.
In FIG. 5-2, the front film 1 heated to the softening point or more and easily stretched is placed on the front mold model 13 fixed to the suction plate 14 together with the frame 11, and the compressed air cover is formed while the front film 1 is not cooled. 15 is moved to the periphery of the frame 11 to block outside air.
From the suction hole 141 provided in the suction plate 14, air between the front mold model 13 or the suction plate 14 and the inside of the front film 1 is sucked by a vacuum pump.
Further, the compressed air is uniformly pressurized with pressurized air from the compressed air holes 151 provided in the compressed air cover 15 to the front side of the front film 1.
Thus, the front film 1 has a ceramic green outer shape due to the pressure difference between the front and back surfaces. At this time, it is preferable that alignment with the back film 2 can be easily performed by providing a plurality of concave and convex portions or around the molded shape.
In FIG. 5, a step is provided around the molded shape to correspond to the figure, but a protrusion and a recess may be provided at two or more locations.

FIG. 6 shows a process of manufacturing the core shape of the back film 2 by vacuum forming.
As for the simple shape, after the film is heated, it is sucked with the vacuum forming die 21 and formed. Of course, pressing the film partially with the plug 22 to equalize the thickness is the same as in normal vacuum forming.
Also, if the shape is a complicated shape that cannot be obtained by vacuum forming or a shape with a tight gradient is required, the back film 2 can also be manufactured by vacuum / pressure forming like the front film 1. It doesn't matter.

FIG. 7 shows a state in which the front film 1 formed in the mold shape and the back film 2 formed in the core shape are fitted to the convex portions 16 and the concave portions 23 provided around the ceramic green shape. .
A space provided between the front film 1 and the back film 2 becomes a cavity 4 in which the ceramic green 5 is molded.

The front film 1 and the back film 2 used in the hydraulic bag of the present invention are preferably materials that can be stretched as much as possible.
In molding like a ceramic cap made of ceramics, it is required that the ceramic cap can be molded so as to rise rapidly from the surface to be fused.
Therefore, the inventor tested various films and tested specifications necessary for the front film and the back film. As a result, in both the film flow direction and the direction perpendicular to the flow, the tensile elongation is 500% or more and the residual strain in the state where the tensile elongation of 200% or more is applied is 110% or less. And found that this standard is necessary.
And as such a film, it discovered that urethane with a thickness of 50 micrometer applied.
In particular, when a film bonded with an adhesive is used for forming the front film 1 or the back film 2, if the tensile elongation exceeds 120%, delamination occurs or distortion occurs. Problem occurs.
Moreover, when the shaping | molding residual distortion of the surface film 1 or the back film 2 exceeds 110 percent, it may deform | transform by the residual distortion at the time of shaping | molding of ceramic green.
In order to produce this urethane film, it is manufactured by a method of calendar molding or cast molding using a polyethylene film or the like.

Examples of the present invention and comparative examples will be described below.
Table 1 shows the hydraulic bags of the present invention and the structures of the films used in Examples and Comparative Examples. In Comparative Example 1, an adhesive was applied between a stretched polyamide film and a linear low-density polyethylene film, and bonded together with a dry laminating machine.
In Comparative Example 2, a stretched polypropylene film and a linear low-density polyethylene film are directly bonded to each other by molten polyethylene using an extruder laminating machine.
Comparative Example 3 and Comparative Example 4 are each extruded as a single film.

表１で示した実施例、比較例用フィルムで、縦・横共１２０ｍｍの大きさに用意した評価用フィルムを使用し、図５で示したセラミックスキャップの表側キャビ形状のモデル型１３を使用して成形した。
また、その実施例、比較例のフィルムを流れ方向と流れに直角の幅方向に、１５ｍｍ幅で切断した短冊を用意し、それぞれ、７０℃で引張り試験を実施し、引張伸度を測定し、評価した。

Using the evaluation film prepared in the size of 120 mm in both the vertical and horizontal directions in the example and comparative film shown in Table 1, the model mold 13 having the front side of the ceramic cap shown in FIG. 5 is used. And molded.
In addition, strips obtained by cutting the films of the examples and comparative examples in the flow direction and the width direction perpendicular to the flow in a width of 15 mm were prepared, respectively, a tensile test was performed at 70 ° C., and the tensile elongation was measured. evaluated.

また、その評価の中で、良かった実施例、比較例４について、引張り長さと残留歪の違いを確認した。

Further, in the evaluation, the difference between the tensile length and the residual strain was confirmed for the good example and the comparative example 4.

実施例の評価結果は、成形性、生産性が高く、引張伸度が大きく、フィルム成形の流れ方向と幅方向と引張伸度も均一で、自然な伸びが観測され、実際の成形でも良好なセラミックスの成形と焼成ができた。
比較例の評価結果は、接着剤でドライラミネーションした比較例１と、エクストルーダーラミネートした比較例２は、どちらも、延伸フィルムを使用しているので、フィルムが形状に追従できず、引張方向の向きにおける違いがひずみとなって、しわが入り、バリ、形状のムラ、グリーンの成形不良による収率の低下が著しくなり、仕上げ工程に時間が掛かる問題も発生した。
特に接着剤で貼り合わせた比較例１では、引張伸度が１２０パーセントを越えると、層間剥離を発生したり、歪みが生じてしまう問題が発生した。

The evaluation results of the examples show that the moldability and productivity are high, the tensile elongation is large, the film forming flow direction, the width direction and the tensile elongation are uniform, natural elongation is observed, and the actual forming is also good. Ceramics could be molded and fired.
The evaluation results of the comparative examples are that both Comparative Example 1 dry-laminated with an adhesive and Comparative Example 2 laminated with an extruder use a stretched film, so the film cannot follow the shape, and the tensile direction Differences in orientation became distortions, wrinkles, burrs, uneven shape, and a significant decrease in yield due to poor green molding, resulting in the problem that the finishing process took time.
In particular, in Comparative Example 1 bonded with an adhesive, when the tensile elongation exceeded 120 percent, problems such as delamination or distortion occurred.

In addition, the ionomer resin film of Comparative Example 3 has remarkably different tensile elongations in the film forming flow direction and the width direction, and therefore, the problem of partial wrinkles and pinholes are likely to occur. There were many molding defects.
Furthermore, although the ethylene-methyl methacrylate copolymer film of Comparative Example 4 had good moldability, it was easy to generate pinholes, and when the ceramic green material 3 was inserted and hydrostatically pressed, the remaining residue There was a problem of deformation due to distortion.
When the residual strain is 110% or more, this deformation problem occurs. In fact, it is considered that the ethylene-methyl methacrylate copolymer film of Comparative Example 4 cannot be pulled by 180% or more. It was judged to be inappropriate for such molding.

The hydraulic bag of the present invention is as described above, and is a hydraulic bag that can be stably fired into ceramics by performing ceramic green molding with a hydrostatic pressure press using the molded hydraulic bag. When this hydraulic bag is used, it is not possible to mold ceramics with large dimensions, but because it can be quickly produced using an inexpensive model mold, the equipment cost is low, the productivity is high, the occurrence of defects is low, and early start-up is possible. It is a possible hydraulic bag.
Further, depending on the shape, there is only one expensive urethane film, and the simple and nearly flat shape portion can also use the inexpensive films of Comparative Examples 1 to 4 and can respond flexibly to the advantages of the present invention. It is.

1 ..... front film 10 ..... plastic film 101 ..... wrinkle 11 ..... frame 12 ... · Heater 13 ······ Cavity-shaped model 14 ·····························································・ ・ ・ ・ ・ ・ ・ Pressurized hole 16 ・ ・ ・ ・ ・ ・ ・ ・ Projection 2 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Back film 21 ・ ・ ・ ・ ・ ・ ・ ・ Vacuum mold 22 ・ ・ ・... Plug 23 ......... Recess 3 ... Ceramic green material 31 ... Ceramic powder 32 ... Binder 4 · · · · · · Around the cavity 5 · · · · · · ceramic green 51 · · · · · · fired ceramics 6 · · ·・ ・ Hydrostatic press 61 ・ ・ ・ ・ ・ ・ ・ ・ Press plate 62 ・ ・ ・ ・ ・ ・ ・ ・ Liquid 7 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Ceramic green sheet 8 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・Upper thin plate 81 ... Lower thin plate 82 ... Lower jig 821 ... Holding hole 83 ... Upper jig

Claims (2)

  In a hydraulic bag that seals four sides of two front and back films, the tensile elongation of at least one of the films is 500% or more in both the machine direction and the transverse direction, and the residual strain after stretching is 110% or less. A hydraulic bag.   The hydraulic bag according to claim 1, wherein at least one of the two front and back films is made of urethane resin.

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