JPH0510444A - Manufacture of diaphragm made of fluorocarbon resin - Google Patents

Abstract

PURPOSE:To provide an industrial method of obtaining a diaphragm made of good-quality fluorocarbon resin in a stable way. CONSTITUTION:A primary metal mold 1 to be used in this case is provided with a cavity S of T-shape cross section with a cylindrical cavity S2 disposed vertically from the center part of a disk-shape cavity S1. A movable fitting 5 with a piece 6 is set into the cylindrical cavity S2, and fluorocarbon resin powder 3o is filled into the cavity S. Rams L1, L2 are then driven in the compressing direction from both upper and lower parts to press the powder 3o in the cavity S from both upper and lower parts. A preliminary molded body 3a is thus formed. This preliminary molded body 3a is burned in a furnace to obtain a burned body 3b. The burned body 3b is then mounted in a secondary metal mold 2 to form a heat treated body 3c which is subjected to high temperature pressing and then quenching to obtain a diaphragm 3d.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for industrially producing a diaphragm made of a fluororesin.

[0002]

2. Description of the Related Art A diaphragm is a disc-shaped valve as shown in FIG. 6 which will be described later, and has a ring-shaped collar portion (4a) serving as a peripheral region.
And a curved belly portion (4b) surrounded by the collar portion (4a). In the case of a diaphragm made of fluorocarbon resin, a ring-shaped rib (4c) is formed at the boundary between the two, and this ring-shaped rib (4c) serves as a seal portion in actual use. In the diametrical direction of the ring-shaped rib (4c), one or several diametrical ribs (4d) may be formed, and a movable metal fitting (5) is embedded in the center of the abdomen (4b). ing.

When the collar portion (4a) is fixed to the fluid passage and the movable metal fitting (5) is operated from the outside to reversely deform the abdomen portion (4b) in the dorsal-ventral direction, the passage is opened and closed. It

As described above, since the diaphragm opens and closes the flow path by inverting the abdomen (4b) in the dorsoventral direction, it is required to have flexibility, flexibility and toughness. Chemical resistance is also required when handling corrosive fluids.

Since the diaphragm made of fluorine resin has excellent chemical resistance, flexibility and durability, it is suitable for use in handling corrosive fluids. In addition to the case where the entire diaphragm is made of a fluororesin, a fluororesin film may be provided on the surface of the base material and the side that comes into contact with the corrosive fluid may be made of a fluororesin film. Examples of literatures that describe the latter include, for example, Japanese Utility Model Publication No. 48-49453, Japanese Utility Model Publication No. 60-43764, and “Plastic Materials Course”.
[6], Fluororesin, Published by Nikkan Kogyo Shimbun, 1981 1
Issued on March 30, the first edition, 5 prints, 108 pages ".

A diaphragm which is entirely made of a fluorine-based resin is typically manufactured by the following procedure. This conventional method will be described below with reference to FIG.

1. First, the fluorine resin powder in the mold (1 ') is charged. The mold (1 ') is a cylindrical frame mold (11'), a dish-shaped lower mold (12 '), an upper mold (1) with a hole facing the lower mold (12').
3 ') and a tubular bush (14') fitted in the hole of the upper mold (13 '). Charge is frame type (11 ')
Insert the fluororesin powder into the lower mold (12 ') inserted in and insert the upper mold (13') into the lower mold (12 ').
Fluorine resin powder is additionally charged from the 3 ') hole and pushed in with the pushing jig, and then the movable metal fitting (5) is attached to the piece (6).
Set it on the powder from the hole of the upper mold (13), and then add the fluororesin powder and push it in with the pressing jig to push the bush (14 ') into the hole of the upper mold (13'). Set to.

2. After the above charging is completed, the upper die (13 ') and the lower die (12') are pressed from above and below by the pressing means (7), (7). As a result, the fluororesin powder in the mold (1 ') is compressed to form a relatively brittle preform.

3. Thereafter, the pressure is released and the mold (1 ') and the heating furnace (8)
And is heated to a temperature higher than the melting temperature of the fluororesin for a predetermined time and fired.

4. After completion of firing, the mold (1 ') is taken out of the heating furnace (8), put into a water tank (9) in a pressed state, and cooled under pressure with water.

5. Finally, the mold (1 ') is disassembled to obtain a product diaphragm.

It is also known to manufacture a diaphragm by automatic compression molding (see "Fluorine Resin Handbook,
Published by Nikkan Kogyo Shimbun, date of issue: November 30, 1990
(See Figure II.1.59, page 109). This is because the mold cavity is automatically filled with a certain amount of fluororesin powder, and at the same time, the ram is lowered from above to compress it, and in the latter half of the compression process, the lower ram is raised to perform double-pressing. After pressing and holding for a certain period of time, the pressure is released and the preform is extruded. The preform thus obtained is placed in a heating furnace and fired.

[0013]

However, in the production of the diaphragm by the conventional method described above, since the product diaphragm is made at once from the fluorine-based resin powder which is the charge raw material, the fluorine for the mold is not formed. Even a slight non-uniformity in the filling of the system resin has a direct effect on the quality of the diaphragm. Further, since the firing is performed only once, it is difficult to obtain uniform density and uniform crystallinity.

As a result, the produced diaphragm is likely to have a decrease in transparency due to excessive crystallization, and in particular, the thick ring-shaped rib (4c) and the embedded portion (4e) of the movable metal fitting (5). ) The transparency is likely to be reduced in the vicinity. Such a low-transparency part may not function as a valve when a diaphragm is actually used, and a minute crack is generated by repeated deformation in the dorsoventral direction, and the crack expands to cause fluid leakage. Disappear.

As described above, since it is difficult to stably obtain a high-quality diaphragm by the conventional method, it is the actual situation that the defective rate of the product reaches several tens of percent even if it is a skilled person. Is requested.

Under the circumstances, the present invention has an object to provide an industrial method capable of stably obtaining a high quality fluororesin diaphragm.

[0017]

[Means for Solving the Problems] A method for manufacturing a fluororesin diaphragm of the present invention is a cross-sectional view in which a cylindrical cavity (S2) is arranged vertically from the center of a disk-shaped cavity (S1). Set the movable metal fitting (5) with the piece (6) in the cylindrical cavity (S2) of the primary mold (1) having the T-shaped cavity (S), and then in the cavity (S). After filling the fluororesin powder (3o) in the above, by driving the rams (L1), (L2) from both the upper and lower sides in the compression direction and pressing the powder (3o) in the cavity (S) both sides. , Step A to form a preform (3a) slightly thicker than a predetermined thickness, the preform of Step A
Step (B), in which (3a) is taken out from the primary mold (1) and is fed into the furnace and fired at a temperature higher than the melting point to obtain a fired body (3b), It is attached to a secondary mold (2) with a
Step C, which is c), and the heat-treated body (3c) of Step C are used as a secondary mold.
The method is characterized in that, while being mounted in (2), it is subjected to high-temperature pressing, and then rapidly cooled to obtain a diaphragm (3d) in step D.

The present invention will be described in detail below.

Examples of the fluorine-based resin powder (3o) include polytetrafluoroethylene, tetrafluoroethylene / hexafluoropropylene copolymer, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, polychlorotrifluoroethylene, polyfluorine. Vinylidene,
Powders of polyvinyl fluoride, ethylene / tetrafluoroethylene copolymer, ethylene / chlorotrifluoroethylene copolymer and the like are used. Among them, polytetrafluoroethylene (PTFE) and tetrafluoroethylene / hexafluoropropylene copolymer are used. A powder such as a polymer (FEP) or a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA) is preferably used.

The step A is a step of filling the primary mold (1) described below with the fluororesin powder (3o) and pressurizing it to obtain a preform (3a) slightly thicker than a predetermined thickness. (See Figure 1)

Here, the primary mold (1) is a T-shaped cavity in a sectional view in which a cylindrical cavity (S2) is arranged vertically from the center of the disk-shaped cavity (S1).
The one having (S) is used.

A piece (6) is placed in the cylindrical cavity (S2) described above.
Set the movable bracket (5) with the
Fluorine resin powder (3o) is filled in (S). Then, the rams (L1) and (L2) are driven from both the upper and lower sides in the compression direction to press the powder (3o) in the cavity (S) both sides. Ram's (L1),
To drive (L2), drive the ram (L1) on the disk-shaped cavity (S1) side first, and then drive the ram (L2) on the cylindrical cavity (S2) side.
The method of driving 2) is often adopted, but the ram (L1),
(L2) may be driven simultaneously, or the ram (L2) may be driven first.

The pressure in step A is usually 100 to 350 kg.
It is about f / cm ² , preferably about 150 to 300 kgf / cm ² . By this pressurizing operation, the volume of the fluororesin powder (3o) becomes a fraction (for example, about 1/3). The conditions are set so that the thickness of the obtained preform (3a) is, for example, about 5 to 30% thicker than the thickness of the product diaphragm (3d). The pressurizing operation in step A is usually performed at room temperature.

In step B, the preform (3a) obtained in step A is taken out from the primary mold (1), supplied into a furnace and fired at a temperature higher than the melting point to obtain a fired body (3b). .. This firing is performed at a temperature higher than the melting point of the fluororesin powder (3o). For example, when polytetrafluoroethylene (melting point 327 ° C) is used as the fluorine-based resin powder (3o),
The firing temperature is preferably set to about 360 to 380 ° C.

In step C, the fired body (3b) obtained in step B is mounted on a secondary mold (2) having a ring-shaped recess, and heat-treated to a temperature higher than the melting point to form a heat-treated body (3c). It is a process. (See Figure 3)

The calcined body (3b) obtained in the step B can be cooled and stocked before being used in the step C, so that the production efficiency can be improved.

The secondary mold (2) used in the step C is usually composed of a frame mold (21), a lower mold (22) and an upper mold (23). Lower mold
A ring-shaped recess (2a) is provided on the mold surface of (22), and the lower mold (2
The mold surface of 2) is provided with one or more diametrical recesses (2b).

The heating temperature in step C is, for example, in the case of polytetrafluoroethylene, its melting point (327
It is desirable that the temperature is set to about 360 to 380 ° C., which is a temperature higher than (° C.). In step C, no pressure is applied.

Step D is a step in which the heat-treated body (3c) of step C is pressed at a high temperature in a state where it is attached to the secondary mold (2) and then rapidly cooled to obtain the diaphragm (3d). (See Figure 4)

The pressing in this case is carried out before the temperature of the heat-treated body (3c) has cooled to below its melting point. The pressing pressure is usually set to about 50 to 100 kgf / cm ² . Due to this high-temperature pressing operation, excess wall thickness is removed by the annular recess (2) of the lower mold (22).
a), and further gathered in the diametrical recess (2b), the ring-shaped rib (4
c) and further diametrical ribs (4d) are formed.

In this state, the press body is rapidly cooled. This quenching operation is performed with water, while the press body is still attached to the secondary mold (2).
It is made by charging into a refrigerant such as liquid nitrogen.
By this rapid cooling operation, crystallization is kept to a minimum. In order to improve the quenching effect, it is preferable to use an aluminum mold having a high thermal conductivity as the secondary mold (2).

After the quenching operation is completed, the secondary mold (2) is disassembled and the target diaphragm (3d) is taken out.

[0033]

In the present invention, the preform (3
a) is obtained, the fired body (3b) is obtained by the step B, and the step C
Thus, the heat-treated body (3c) is obtained, and in step D, the diaphragm (3d) is obtained.

In step A, a T-shaped cavity
Set the movable metal fitting (5) with the piece (6) in the cylindrical cavity (S2) of the primary mold (1) having (S), and then set the fluororesin powder in the cavity (S). After filling (3o),
Since the rams (L1) and (L2) are driven in the compression direction from both the top and bottom to push the powder (3o) in the cavity (S) both sides, the powder (3o) The filling operation can be performed all at once on the embedded part (4e) of the movable metal fitting (5), and also from the embedded part (4e) of the thick movable metal fitting (5) to the abdomen (4b). Homogeneity is obtained even in the boundary region.

After the firing step B, the fired body (3
After mounting b) in the secondary mold (2) with a ring-shaped recess and heat-treating it to form a heat-treated body (3c), press it at a high temperature and
Since it is cooled rapidly to obtain the diaphragm (3d),
With this high temperature press, excess wall thickness is skillfully collected in the ring-shaped recess (2a) and diametrical recess (2b) of the lower mold (22) to form precise ring-shaped ribs (4c) and diametrical ribs (4d). To be done.

[0036]

EXAMPLES The present invention will be further described with reference to examples.

FIG. 1 is an explanatory view of the step A, (a) shows a state where the fluorine-containing resin powder (3o) is filled in the primary mold (1),
(B) shows the state when the preform (3a) is formed by pressing.

FIG. 2 is an explanatory view of step B, in which the heating furnace (8) is used.
The figure shows a state in which the preform (3a) is supplied and fired into a fired body (3b).

FIG. 3 is an explanatory view of the process C, in which the secondary mold is used.
(2) shows a state in which the fired body (3b) is mounted inside and the heat treated body (3c) is obtained.

FIG. 4 is an explanatory view of the step D, (a) shows a state in which the heat-treated body (3c) in the secondary mold (2) is hot-pressed into a high-temperature pressed body, (b) Shows the state when the secondary mold (2) after hot pressing is put into the water tank (9) and rapidly cooled.

In FIG. 5, the secondary mold (2) after quenching is disassembled,
It shows a state when the diaphragm (3d) is taken out.

FIG. 6 shows the diaphragm (3d). (A) is a plan view of the diaphragm (3d), (b) is a bottom view thereof, and (c) is a front view thereof.

A commercially available polytetrafluoroethylene powder was used as the fluorine-based resin powder (3o), and the diaphragm (3d) was manufactured according to the following steps A to D.

Two types of dies were used: an iron primary die (1) used in step A and an aluminum secondary die (2) used in steps C and D.

Of these, the primary mold (1) is a mold for obtaining the original shape of the diaphragm, and the disk-shaped cavity (S1)
Cylindrical cavity (S2) vertically from the center of
A frame die (11) having a T-shaped cavity (S) in a sectional view, a ram (L1) fitted in the disc-shaped cavity (S1) of the frame die (11), and the frame die (11) ) Is provided with a ram (L2) fitted in the cylindrical cavity (S2).

The secondary mold (2) is composed of a frame mold (21), a lower mold (22) and an upper mold (23). The lower die (22) is provided with a ring-shaped recess (2a) having a width of 4 mm, and a diametrical recess (2b) having a width of 4 mm is provided so as to cross the ring-shaped recess (2a).

Step A As shown in FIG. 1, a movable metal fitting with a piece (6) in a cylindrical cavity (S2) of the cavity (S) of the primary mold (1).
(5) was set. After filling the cavity (S) with a certain amount of fluororesin powder (3o), first lower the ram (L1) from the upper side to the lower side, and then move the ram (L2) from the lower side to the upper side. Raise the powder (3o) in the cavity (S)
Pressed both. The pressing pressure was 212 kgf / cm ^2, and this state was continued for about 1 minute before releasing the pressure. As a result, the preform (3a) was formed.

Step B This preform (3a) is taken out from the primary mold (1) and
It was charged into the heating furnace (8) as described above and baked at a temperature of 375 ° C. Since the fired body (3b) was obtained by this, the heating furnace (8)
It was taken out and left to cool.

Step C As shown in FIG. 3, the fired body (3b) obtained above is mounted on the secondary mold (2) and placed in the heating furnace (8) without applying a pressure. Heat treated. The heating temperature was set to 375 ° C.
As a result, the heat-treated product (3c) was obtained.

Step D Next, as shown in FIG. 4, while the heat-treated body (3c) of Step C is attached to the secondary die (2), it is pressed at a pressure of 190 kgf / cm ^{2 and} the secondary die is pressed. The mold (2) was put into the water in the water tank (9) and quenched.

After the quenching operation described above, the secondary mold (2) was placed in a water tank.
Take out from the (9) and release the pressure, and as shown in Fig. 5, the secondary mold (2)
Was disassembled and the diaphragm (3d) was taken out.

As a result, as shown in FIG. 6, the ring-shaped rib (4c)
And a diaphragm (3d) with diametrical ribs (4d) was obtained. This diaphragm (3d) has a collar (4
a) and the curved abdomen (4b) surrounded by it,
A ring-shaped rib (4c) is formed at the boundary between the collar portion (4a) and the abdomen (4b), and the diametrical rib (4c) is also formed in the diameter direction of the ring-shaped rib (4c).
d) is formed. The product diaphragm is obtained by punching out the bolt holes (4f) in the collar portion (4a).

A large number of diaphragms were manufactured by the above-mentioned method, but none of the diaphragms had whitened parts, and no cracks were observed even after repeated inversion deformation in the dorsoventral direction.

[0054]

EFFECTS OF THE INVENTION In the present invention, since the process A is devised, the filling operation of the fluororesin powder (3o) is performed all at once on the embedded portion (4e) of the movable metal fitting (5). In addition, it is possible to obtain homogeneity even in the boundary region from the embedded portion (4e) to the abdomen (4b) of the thick movable metal fitting (5).

In step B, the fired body (3b) can be prepared and stored, which is advantageous in production planning.

Then, in steps C and D, the excess wall thickness is skillfully collected in the ring-shaped recess (2a) and the diametrical recess (2b) of the lower die (22) by the high temperature press, and the precise ring-shaped rib (4c ) And the diametrical ribs (4d) are formed, and moreover, by the quenching operation, the ring-shaped ribs (4c) and the diametrical ribs (4c) are thickened.
d), too much crystallization does not occur even in the movable fitting embedded portion (4e).

As a result, the obtained diaphragm has a uniform density and low crystallinity and is of very good quality, and cracks do not occur even when it is repeatedly deformed in the dorsoventral direction during use.

Further, according to the present invention, the defective rate of the product is significantly reduced without requiring a high degree of skill, so that a reliable production plan can be established and the product cost can be reduced.

As described above, according to the present invention, a high-quality fluororesin diaphragm can be stably manufactured industrially.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a process A, in which (a) is a primary mold (1).
The inside is filled with the fluororesin powder (3o), and (b) shows the state when the preform (3a) is formed by pressing.

FIG. 2 is an explanatory diagram of step B, showing a state when a preform (3a) is supplied into the heating furnace (8) and fired to form a fired body (3b).

FIG. 3 is an explanatory diagram of step C, showing a state in which a fired body (3b) is mounted in the secondary mold (2) to form a heat-treated body (3c).

FIG. 4 is an explanatory view of step D, in which (a) is a secondary mold (2).
The state when the heat-treated body (3c) in the inside is hot pressed into a hot pressed body, (b) is when the secondary mold (2) after hot pressing is put into the water tank (9) and rapidly cooled It shows the state of.

FIG. 5 shows a state in which the secondary mold (2) after quenching is disassembled and the diaphragm (3d) is taken out.

FIG. 6 shows a diaphragm (3d), (a)
Is a plan view of the diaphragm (3d), (b) is its bottom view,
(C) is a front view thereof.

FIG. 7 is a process drawing showing an example of a conventional diaphragm manufacturing method.

[Explanation of symbols]

(1) ... primary mold, (11) ... frame mold, (S) ... T-shaped cavity, (S1) ... disk-shaped cavity, (S2) ... cylindrical cavity, (L1), (L2) ... Ram, (2) ... Secondary mold, (21) ... Frame mold, (22) ... Lower mold, (23) ... Upper mold, (2a) ... Ring recess, (2b) ... Diameter recess, (3o) ) ... Fluorine-based resin powder, (3a) ... Preform, (3b) ... Fired body, (3c) ... Heat treated body, (3d) ... Diaphragm, (4a) ... Collar part, (4b) ... Abdominal part, (4c) ... annular rib, (4d) ... diametrical rib, (4e) ... movable metal fitting embedded portion, (4f) ... bolt hole, (5) ... movable metal fitting, (6) ... bridge, (7) ... Pressing means, (8) ... heating furnace, (9) ... water tank, (1 ') ... mold, (11') ... frame mold, (12 ') ... lower mold, (13') ... upper mold, (14 ') ...
bush

Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location // B29K 27:12 B29L 31:38 4F

Claims (1)

Claims: 1. A T-shaped cavity (S) in a sectional view in which a cylindrical cavity (S2) is arranged vertically from the center of a disk-shaped cavity (S1). Movable bracket (5) with piece (6) in the cylindrical cavity (S2) of the primary mold (1)
Set, then fill the cavity (S) with fluororesin powder (3o), then press the ram (L
1), (L2) are driven to push the powder (3o) in the cavity (S) in both directions to form a preform (3a) slightly thicker than a predetermined thickness. Remove the body (3a) from the primary mold (1),
Fired body (3b) that is fed into the furnace and fired at a temperature higher than the melting point
Step B for obtaining the step B, the secondary die (2) with a ring-shaped recess for the fired body (3b) obtained in the step B
And heat-treating it to a temperature higher than the melting point to form the heat-treated body (3c), and the heat-treated body (3c) of the step C is attached to the secondary mold (2) and pressed at high temperature. And a step D of rapidly cooling to obtain the diaphragm (3d).