JPH03262629A - Method for deep-forming fluororesin - Google Patents

Abstract

PURPOSE:To deep-form in uniform thickness without developing breakage and porousness by a method wherein fluororesin sheet, by which the recessed part of a forming mold member is covered and which is pressurized with a keep ring and heated, is fabricated as being slid on the forming mold member by suckingly discharging the air in the recessed part. CONSTITUTION:Fluororesin sheet 13, onto which a keep ring 14 is placed, is put together with a forming mold member 12 in a heating furnace so as to be heated up to the predetermined temperature. The fluororesin sheet 13, which is softened to some extent through the above-mentioned heating, is deep-formed into the predetermined shape. The said forming is performed by suckingly discharging the air in the recessed part 11 through a discharge port 15 under vacuum, which is provided at the bottom part 12a of the forming mold member 12. In this case, pressurizing force applied on the fluororesin 13 with the keep ring 14 is set so as to deep-form the fluororesin by being slid between the keep ring 14 and the top surface 10 of the forming mold member 12. As a result, the fluororesin sheet 13 deforms so as to gradually pull its surplus length part 13a in the recessed part 11.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a fluororesin deep drawing method for efficiently deep drawing a fluororesin sheet, and a method for manufacturing a fluororesin head plate using this method.

Technical background of the invention Fluororesins such as polytetrafluoroethylene (hereinafter also referred to as PTFE) have properties such as heat resistance, weather resistance, chemical resistance, mold release properties, slip properties, non-stick properties, and mechanical strength. In this respect, it has significantly superior properties compared to other synthetic resins.

Taking advantage of this property, sheet-shaped fluororesin is sometimes used as a corrosion-resistant lining material by covering the inner peripheral surfaces of pipelines, tanks, mechanical equipment, etc. that handle corrosive fluids or high-temperature fluids.

When this lining material is formed into a shape that follows the inner circumferential surface of a tank or the like, it is formed by deep drawing.
There is one disclosed in Japanese Patent No. 136,408.

In this method, as shown in FIG. 7, first, a deep-drawn riverbed-shaped container 1 consisting of a body 2 with a flange and a lid 3 with a flange is prepared. It is covered with a fluororesin sheet 5 and held between the main body 2 and the lid 3.

Then, both the flanges 2a, 3a are pressurized by suitable pressurizing means P to support the fluororesin sheet 5 so as not to move. While heating the entire container 1 at a predetermined temperature, the lid 3
Pressurized air is injected from an inlet 6 provided at the top of the fluororesin sheet 5 to gradually deform the fluororesin sheet 5 as shown by the broken line. This is what is called a habit. In order to facilitate this adjustment, the air inside the main body 2 is exhausted from an exhaust lower provided at the bottom of the main body 2 below.

In this way, the fluororesin sheet is molded into a shape that follows the inner surface of the container 1. The fluororesin sheet formed in this way is taken out from the container 1 and is adhered to the inner peripheral surface of another container to be used as a lining material.
The container itself is protected from corrosive fluids etc. that are poured into the container.

However, in such a deep drawing method, the fluororesin sheet is press-formed with the fluororesin sheet supported so as not to move during deep drawing, so the fluororesin sheet in the vicinity of this supported portion is When the material is stretched to become thinner and porous as shown in the figure, and used as a lining material, there is a drawback that the lining effect at the porous portion is reduced. For example, when a tank head plate is manufactured from a fluororesin sheet by the method described above, the fluororesin sheet at the curved portion called the knuckle is stretched and becomes porous, reducing the lining effect.

Further, in the conventional method, since the degree of processing is high, the shrinkage rate of the fluororesin sheet 5 after molding becomes large, and the variation in dimensions becomes large.

Purpose of the Invention The present invention was made in view of the above-mentioned circumstances, and the first object is to provide a fluoropolymer sheet that can be deep-drawn to form a fluororesin sheet with a uniform thickness without causing breakage or porosity. An object of the present invention is to provide a deep drawing method for resin.

A second object of the present invention is to provide a method for manufacturing a fluororesin end plate that can easily produce a lining end plate.

SUMMARY OF THE INVENTION In order to achieve the above-mentioned first object, the method for deep drawing fluororesin according to the present invention provides a method for deep drawing a fluororesin formed in a mold member for forming a rim portion of the recess by using a fluororesin sheet to cover the upper surface of a recess formed in a mold member. The fluororesin sheet on the mouth edge portion is sealed under pressure with a presser ring, and the fluororesin sheet is heated to suction and discharge the air in the recess. By doing this, the fluororesin sheet is deformed along the inner peripheral surface of the recess while being slid between the mold member and the presser ring, and the fluororesin sheet is deformed along the inner peripheral surface of the recess. The fluororesin sheet is characterized in that the fluororesin sheet is cooled while sucking the inside of the recess at the stage when the sheet is brought into close contact with the fluororesin sheet.

By molding the fluororesin sheet while sliding it in this way, the fluororesin sheet can be easily deep-drawn without making it porous.

Moreover, even after processing, the range of change in shrinkage rate becomes smaller, and the variation in dimensions of the resulting molded product becomes smaller. Therefore, the sheet after this molding can be used satisfactorily as, for example, a lining material.

In addition, in order to achieve the above-mentioned second object, the method for manufacturing a fluororesin end plate according to the present invention is such that the upper surface of the recess formed in the end plate mold is covered with a fluororesin sheet at a predetermined edge portion of the recess. The fluororesin sheet on the mouth edge portion is sealed under pressure with a presser ring, and the fluororesin sheet is heated to suction and discharge the air in the recess. The resin sheet is deformed along the inner peripheral surface of the recess while being slid between the mirror plate mold and the holding ring, and when the fluororesin sheet is in close contact along the inner peripheral surface of the recess, The present invention is characterized in that the fluororesin sheet is cooled while sucking the inside of the recess.

In this way, the fluororesin sheet is deformed while sliding, so when manufacturing a fluororesin end plate, there will be no damage at the knuckle, and the shrinkage rate will change less even after processing. Therefore, the variation in dimensions of the resulting end plate is also reduced.

DETAILED DESCRIPTION OF THE INVENTION The present invention will now be described in more detail based on examples.

FIGS. 1 to 3 are sectional views of essential parts showing the process order of a method for deep drawing a fluororesin according to an embodiment of the present invention.

In order to deep-draw a fluororesin sheet, first, as shown in FIG. 1, a mold is used which has a flat upper surface 10 and a recess 11 having a predetermined depth d and diameter approximately in the center. A mold, which is the member 12, is prepared.

Concave portion 11 and lip portion 11a of this mold member 12
is covered with a fluororesin sheet 13, and this fluororesin sheet 13 may have a low crystallinity or a high crystallinity, but it is more preferable to use a low crystallinity sheet. It is desirable to do so. This is because a fluororesin sheet with a low crystallinity has a higher elongation rate. In order to obtain a fluororesin sheet with a low crystallinity, the cut sheet may be gelled and then rapidly cooled.

The outer peripheral portion of the fluororesin sheet 13 has an extra length portion 13 that protrudes from the mouth edge portion 11a of the recess 11 by a predetermined distance a.
It is preferable to allow the formation of a.

Next, as shown in FIG. 2, this fluororesin sheet 13
Place the presser ring 14 on top. This presser ring 14 is for pressurizing and sealing between the fluororesin sheet 13 and the upper surface 10 of the mold member 12.

Then, in order to heat the fluororesin sheet 13 to a predetermined temperature, it is placed in, for example, a heating furnace together with the mold member 12 for heating. Alternatively, only the fluororesin sheet is heated from the top surface of the sheet.

This heating temperature is preferably below the melting point of the fluororesin sheet and higher than the temperature at which it is actually used, and this heating brings the fluororesin sheet 13 into a state where it can be easily deformed. The heating temperature may be determined, for example, if the fluororesin sheet 13 is made of PTFE? If so, it is preferably about 300''C.

The fluororesin sheet 13, which has been softened to some extent by this heating, is deep drawn into a predetermined shape.

This molding is performed by vacuum suction to exhaust the air in the recess 11 through an outlet 15 provided at the bottom 12a of the mold member 12 for molding. This step is a step in which the fluororesin sheet 13 is subjected to a so-called shaping process.

During this vacuum suction, since the presser ring 14 seals between the upper surface 10 of the mold member 2 and the fluororesin sheet 13, the suction force effectively acts on the deformation of the fluororesin sheet 13. , fluororesin sheet) 13,
It is gradually deformed as shown by the broken line in FIG.

In this case, the pressing force applied to the fluororesin sheet 13 by the presser ring 14 is such that the fluororesin sheet is deep-drawn while sliding between the presser ring 14 and the upper surface 1o of the mold member 12. The pressing force is set to a level that seals between the fluororesin sheet 13 and the fluororesin sheet 13.

For this reason, the fluororesin sheet 13 deforms while its extra length portion 13a is gradually drawn into the recess 11. Therefore, even in areas where tensile deformation is large, such as near the mouth edge, the fluororesin sheet 13 can be molded without unevenly varying in thickness.

Note that this pressing force is adjusted by the tightening force of the attachment means that attaches the presser ring 14 to the mold member 12 for molding.

Here, if a fluororesin sheet 13 with a low crystallinity is used for molding, although the permeation resistance is inferior to that with a high crystallinity, the elongation rate is large and the fluororesin sheet 13 can be formed without forming porosity. As shown in FIG. 3, the sheet can be formed into a shape along the inner peripheral surface of the recess 11 with a substantially uniform thickness.

Once the fluororesin sheet 13 is in complete contact with the inner circumferential surface of the recess 11 in this manner, the fluororesin sheet 13 is cooled to maintain this shape. At that time, the presser ring 14 is attached to the flange portion 12b of the mold member 12 for molding.
, 12b is further tightened (retightened) using a predetermined tightening means,
It is preferable to perform cooling while performing vacuum suction. However, in the present invention, it is not always necessary to perform additional tightening.

Then, the fluororesin sheet 13 molded into substantially the same shape as the recess 11 is taken out from the mold member 12. After this removal, it can also be used as a lining material, for example, by applying an adhesive or the like to the inner peripheral surface of the metal container. Alternatively, it is also possible to use the fluororesin sheet 13 itself shaped in this way as a container.

The method of the present invention can be applied to the production of various molded parts that must be deep drawn using a fluororesin sheet.

For example, it can be applied to a method of manufacturing a fluororesin end plate as shown in FIG. 5.6. In addition, in Figures 5 and 6, 1st to 3rd
The same members as those shown in the figures are given the same reference numerals.

In the embodiment shown in FIGS. 5 and 6, a mirror plate mold 12a is used as the above-mentioned mold member 12 to manufacture a fluororesin lining mirror plate.

In the case of this embodiment as well, the fluororesin sheet can be deformed while sliding as in the previous method, and the knuckle portion 19
No breakage occurs during molding, the molding work becomes easier, the range of change in shrinkage rate after molding becomes smaller, dimensional variations become smaller, and products with good dimensional accuracy can be easily obtained. The fluororesin end plate thus obtained is joined to the body 17 similarly formed on a cylinder made of fluororesin, as shown in FIG.
Used as lining material.

The fluororesin sheet 13 used in the present invention is not particularly limited, but has a thickness of 1 to 4 mm, particularly 2.5 to 3 mm.
5 mm is preferred. Further, the extra length does not need to be such that the end of the fluororesin sheet 13 is present on the flange 11a of the mold or the mouth edge of the end plate during molding.
It may be dimensioned to cover the entire top of the flange portion 11a and the like.

Furthermore, the material of the fluororesin sheet 13 mentioned above is as follows:
Not limited to PTFH, for example, PFA which is a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether, FEP which is a copolymer of tetrafluoroethylene and hexafluoropropylene, or tetrafluoroethylene and hexafluoropropylene EPE, which is a copolymer of and perfluoroalkyl vinyl ether
It may also be a fluororesin.

As described in detail, according to the present invention, the concave portion of a mold member for molding is covered with a fluororesin sheet, and the air in the concave portion is suctioned and discharged while being heated while being pressurized by a presser ring. Since the fluororesin sheet is molded while being slid on the mold member, it is possible to deep draw the sheet to a uniform thickness without causing breakage or porosity. In addition, the shrinkage rate after molding is small, making it possible to obtain molded products with excellent dimensional accuracy. Therefore, such a molded article can be particularly suitably used as a lining material.

In addition, by using such a deep drawing method for fluororesin, it is possible to manufacture a fluororesin head plate that does not break or become porous at the knuckle, and is also easy to form, and the range of change in shrinkage rate is small. It is possible to easily obtain a small size with small variation in dimensions.

[Brief explanation of drawings]

Figures 1 to 3 are sectional views of main parts showing the process of deep drawing of fluororesin according to an embodiment of the present invention in order of process, Figure 4 is a sectional view of the lining material, and Figures 5 and 6 are sectional views of the method of the present invention. FIG. 7 is a sectional view of the main part showing another embodiment, FIG. 7 is a sectional view of the main part showing the conventional method, and FIG. 8 is an enlarged sectional view of the main part of FIG. 7. 10... Upper surface, 11... Recessed part, 1, 1 a
... Mouth rim portion, 12... Molding mold member, 13...
-Fluororesin sheet, 13a... extra length, 14... presser ring.

Claims (1)

[Scope of Claims] 1) Cover the upper surface of the recess formed in the mold member with a fluororesin sheet so that a predetermined extra length is left at the rim of the recess, and remove the fluorine resin on the rim of the recess. The resin sheet is pressurized and sealed by a presser ring, the fluororesin sheet is heated, and the air in the recesses is sucked and discharged, so that the fluororesin sheet is held between the mold member and the presser ring. The fluororesin sheet is deformed along the inner peripheral surface of the recess while being slid, and when the fluororesin sheet is in close contact with the inner peripheral surface of the recess, the fluororesin sheet is cooled while sucking the inside of the recess. A deep drawing method for fluororesin. 2) Cover the upper surface of the recess formed in the mirror plate mold with a fluororesin sheet so that a predetermined extra length is left at the edge of the recess, and press the fluororesin sheet on the edge of the recess with a presser ring. At the same time as pressure sealing, the fluororesin sheet is heated and the air in the recess is suctioned and discharged, whereby the fluororesin sheet is slid between the mirror plate mold and the presser ring and the inner periphery of the recess is heated. The fluororesin sheet is deformed along a surface, and when the fluororesin sheet is in close contact with the inner peripheral surface of the recess, the fluororesin sheet is cooled while sucking the inside of the recess. A method for manufacturing a resin mirror plate.