JP2003311764A - Production method for ptfe solid molded article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a production method for a PTFE solid molded article which can uniformly obtain the density and thickness of a curved surface and a complicated shape such as a rib or the like and is hard to generate the flow mark and crack of a resin. <P>SOLUTION: In the production method for a PTFE solid molded article, a mold is filled with a PTFE gelled crushed material constituted of a PTFE polymer and the PTFE gelled crushed material is pressed at a temperature higher than the melting point of the PTFE polymer to obtain the solid molded article. The PTFE polymer is a tetrafuluoroethylene homopolymer and/or a modified tetrafuluoroethylene. The mold has an uneven inner wall. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a PTFE solid molded article, and more specifically, a PTFE solid molded article capable of uniformly obtaining a complicated shape such as density and thickness and ribs by using a gelled and crushed product. The present invention relates to a body manufacturing method.

[0002]

2. Description of the Related Art Polytetrafluoroethylene [PTF
E] has excellent heat resistance, chemical resistance, etc., and therefore has a wide range of applications, and is preferably used for, for example, diaphragms. P
TFE is usually used for obtaining a solid molded body that is not a porous body.
After filling the mold with resin powder, compressing and preforming,
It is molded by a compression molding method of firing at a temperature equal to or higher than the melting point.

As a solid molded body made of PTFE, for example, a diaphragm shown in a schematic top view and a schematic sectional view of FIG. 1 has a curved surface [R portion] 11 and a rib 12, and is conventionally shown in FIG. Curved surface [R
Part] 21 and rib forming part 22 are filled with unbaked resin powder on a lower mold and covered with the upper mold, and screws and resin powder are put into the screw part forming hole at the center of the upper mold to form the screw part. After the molding die 23 is placed, the molding die 23 is pressed to be preformed, fired while being placed in the die, and then the whole die is pressed.

According to this method, when the lower die is filled with the resin powder, it is not easy to obtain a uniform thickness even if a leveling operation is performed to reduce the unevenness of the filling. Although thickness unevenness is likely to occur, there is a problem that the thickness unevenness remains as it is even when pressure is applied and the resin density becomes nonuniform.

In this method, the rib forming portion 22 of the die and the rib 12 of the molded body are also pressed by pressing the die together.
The rib 12 can be suppressed to some extent,
Is difficult to obtain a uniform shape due to uneven filling and uneven pressure,
There was a problem that a clouding phenomenon might occur.

By pressing the mold together, it is possible to suppress the waviness due to the thermal expansion of the molded body to some extent.
There is a problem that a trace of the flow of the resin is easily formed, a pearl phenomenon is likely to occur, and a crack is easily generated.

Further, this method requires considerable skill in selecting the timing of pressurization and the pressing force in the step of pressing together with the mold, and is not versatile for anyone, so that a molded product of commercial value can be obtained. There was a problem that industrial production was difficult.

In order to improve the uneven thickness due to uneven filling in the lower mold, a method has been proposed in which a non-fired non-porous resin sheet is used instead of the unfired resin powder. However, this method still requires the skill of pressing, it is difficult to obtain a rib having a uniform shape, and a flow trace of resin and a pearl phenomenon are likely to occur, and cracks are likely to remain.

[0009]

SUMMARY OF THE INVENTION In view of the above situation, it is an object of the present invention to easily obtain a curved surface density and thickness and a complicated shape such as a rib, and to prevent resin flow traces and cracks. An object of the present invention is to provide a method for producing a difficult PTFE solid molded body.

[0010]

According to the present invention, a PTFE gelled and crushed product made of a PTFE-based polymer is filled in a mold and then pressed at a temperature not lower than the melting point of the PTFE-based polymer to form a PTFE solid molded article. In the method for producing a PTFE solid molded article, the PTFE-based polymer is tetrafluoroethylene homopolymer and / or modified polytetrafluoroethylene, and the mold has irregularities on the inner wall. PTFE characterized by
It is a method for manufacturing a solid molded body. The present invention will be described in detail below.

The method for producing a PTFE solid molded article of the present invention comprises:
It is characterized by using a pulverized PTFE gel product as a raw material.

The PTFE gelled and pulverized product is made of a PTFE-based polymer. The PTFE-based polymer is tetrafluoroethylene homopolymer [TFE homopolymer] and / or modified polytetrafluoroethylene [modified PTFE]. In the present specification, the "modified PTFE" means tetrafluoroethylene [TFE]
And a polymer obtained from the modifier. The modified P
TFE is a TFE obtained by polymerizing only tetrafluoroethylene [TFE] in a TFE homopolymer.
Which is different from the TFE homopolymer in that it does not contain a modifier.

As a modifier of the above modified PTFE, TFE is used.
It is not particularly limited as long as it can be copolymerized with, for example, perfluoroolefin such as hexafluoropropene [HFP]; chlorotrifluoroethylene [CTF]
E]; hydrofluoroolefins such as trifluoroethylene; perfluorovinyl ether and the like.

The perfluorovinyl ether is not particularly limited, and is, for example, perfluoro represented by the following general formula (I) CF ₂ ═CF—ORf (I) (wherein Rf represents a perfluoro group). An unsaturated compound etc. are mentioned. In the present specification, the “perfluoro group” means an organic group in which all hydrogen atoms bonded to carbon atoms are replaced with fluorine atoms. The perfluoro group may have ether oxygen.

Examples of the perfluorovinyl ether include perfluoro (alkyl vinyl ether) [PAVE] in which Rf represents a perfluoroalkyl group having 1 to 10 carbon atoms in the general formula (I). The carbon number of the perfluoroalkyl group is
It is preferably 1 to 5.

Examples of the perfluoroalkyl group in PAVE include a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group and a perfluorohexyl group. Perfluoropropyl groups are preferred.

As the above-mentioned perfluorovinyl ether, in the general formula (I), Rf has 4 carbon atoms.
~ 9 perfluoro (alkoxyalkyl) group, the following formula

[0018]

[Chemical 1]

(Wherein, m represents 0 or an integer of 1 to 4), or an organic group represented by the following formula:

[0020]

[Chemical 2]

(In the formula, n represents an integer of 1 to 4) and perfluoro (alkoxyalkyl vinyl ether) or perfluoro (alkyl polyoxyalkylene vinyl ether) which is an organic group. . Perfluorovinyl ether and chlorotrifluoroethylene are preferable as the modifier of the modified PTFE, and PAVE is used as the perfluorovinyl ether.
Is preferred.

The ratio (% by weight) of the modifying agent to the total amount of the modifying agent and TFE in the modified PTFE depends on the type of the modifying agent, but the modified PT obtained.
It is preferably a small amount that does not give melt flowability to FE. For example, when the perfluorovinyl ether is used as the modifier, it is usually preferably 1% by weight or less, more preferably 0.001 to 1% by weight.

As the modified PTFE, for example, one kind or two or more kinds having different number average molecular weights, copolymer compositions and the like may be used, and as the above TFE homopolymer, for example, ones having different number average molecular weights may be used. You may use 1 type (s) or 2 or more types.

The PTFE-based polymer preferably has a number average molecular weight of 2,000,000 to 20,000,000.
When the number average molecular weight is within the above range, the obtained PTFE
Physical properties such as mechanical strength of the solid molded product are improved. A more preferred lower limit is 4 million, and a more preferred upper limit is
It is 10 million.

The method for producing the above-mentioned PTFE-based polymer is not particularly limited, and conventionally known polymerization methods such as suspension polymerization, emulsion polymerization and bulk polymerization can be used, but they are industrially widely used and the like. It is preferable to use suspension polymerization or emulsion polymerization. The conditions of the above various polymerization methods are not particularly limited.

The PTFE gelled and pulverized product used in the method for producing a PTFE solid molded article of the present invention is obtained by converting the above-polymerized PTFE-based polymer obtained by various polymerization methods into PTFE powder, and gelating the PTFE powder. , Obtained by crushing. Above PT
The FE powder is one that has not been subjected to gelation described below. The above-mentioned PTFE powder is a powder of the above-mentioned PTFE-based polymer just after polymerization. The PTFE powder may be obtained by coarsely pulverizing, washing, drying and the like.

In the present specification, the above "gelling" means
This means performing heat treatment on the PTFE powder.
The heat treatment in the gelation is preferably performed to such an extent that the individual particles of the PTFE powder are fused and the whole is in a state of being integrally bonded with a weak bonding force. Above P
The fusion of the particles of the TFE powder to each other does not necessarily have to be completely performed on all the particles, and may be in a so-called semi-gelled state. In the present specification, the above "gelling"
Is a state in which the heat treatment of each particle of the above PTFE powder is completely performed on all the particles, “complete gelation”
And "semi-gelling", which is a state of being performed on some particles or a part of one particle.

As the heat treatment in the gelation, it is preferable to heat for 1 minute to 5 hours at a temperature not lower than the melting point of the PTFE polymer and not higher than the decomposition start temperature of the PTFE polymer. .
More preferably, 10 minutes to 3 at 300 to 390 ° C.
Time, and more preferably at 350 to 380 ° C. for 1 to 2 hours.

The above heat treatment is preferably performed in an inert atmosphere or air. The gelation may include a step of cooling to a temperature below the melting point of the PTFE-based polymer after the heat treatment, and in this case, cooling is preferably slow cooling.

As a result of the gelation, the polymer chains in the individual particles of the PTFE powder increase in momentum and become entangled with each other, and as a result, the individual particles have hardness, tend to shrink in a small size and dense structure. In addition, since it has the characteristic that it has good fluidity, it can be suitably used for the method for producing a PTFE solid molded article of the present invention after pulverization described later.

The above-mentioned PTFE powder is gelled and then further pulverized. The gelled PTFE obtained by the pulverization
The powder can have a small average particle size and a narrow particle size distribution. In the present specification, the "pulverization" after the gelation means that the gelled PTFE powder is fused and integrated with each other into individual particles,
This means crushing this lump into a desired size using a rotary blade crusher or the like.

The PTFE gelled and pulverized product preferably has an average particle size of 5 to 1000 μm.
When the average particle size is within the above range, after the PTFE gelled and pulverized product is filled in a mold as described below, a void is generated between the particles of the PTFE gelled and pulverized product before the main molding pressure is applied. Can be made. A more preferable lower limit is 2
It is 0 μm, and a more preferable upper limit is 250 μm.

The PTFE gelled and pulverized product is preferably classified to have a uniform particle size distribution. When the particle diameters are not uniform, during the preforming pressurization described below and the main molding pressurization described below,
The pressure may be unevenly applied, resulting in uneven thickness.

The method for producing a PTFE solid molded article of the present invention is as follows:
The above-mentioned PTFE gelled and crushed product is filled in a mold. The mold has irregularities on the inner wall. The unevenness may be any shape of unevenness, for example, a cross section having a key shape or a semicircular shape as shown in the schematic diagram of FIG. 3, a combination of a key shape and a semicircular shape, and the like. Is mentioned.

The above-mentioned unevenness is generally understood to be a shape consisting of a concave portion and a convex portion, but at first glance, even if it can be understood that a concave portion is formed without forming a convex portion, a shape other than the concave portion is formed. The part should be called a convex part when viewed from the concave part.
At first glance, even if it may be understood that the convex portion is formed without forming the concave portion, the portion other than the convex portion is a concave portion when viewed from the convex portion. Therefore, in the present specification, the above-mentioned "unevenness" is generally understood to be composed of a concave portion and a convex portion, what can be regarded as a concave portion formed without forming a convex portion, and a seemingly concave portion. It is a concept that includes what can be understood as forming a convex portion without doing.

The method for producing a PTFE solid molded article of the present invention is as follows:
When the unevenness of the mold is a rib forming portion and / or a curved surface, it can be suitably applied. In this specification,
The above-mentioned "rib forming part" is a part of the inner wall surface of the mold, and is for forming a ridge-shaped projection on the surface of the PTFE solid molded product manufactured by the method for manufacturing a PTFE solid molded product of the present invention. Means a groove-shaped recess. The rib forming portion is not particularly limited, and examples thereof include a rib forming portion of a diaphragm molding die described later. In the present specification, the above-mentioned “curved surface” means, among the inner wall surfaces of the mold whose cross-sectional shape is drawn as a curve when the mold placed so as to fill the PTFE gelled pulverized product is cut in the vertical direction, It means a portion that does not correspond to the rib forming portion. The curved surface is not particularly limited, and examples thereof include a round surface [R portion] of a diaphragm molding die described later.

The inner wall surface of the mold may have the rib forming portion and / or the curved surface, and further may have a flat surface. In the present specification, the above-mentioned “flat surface” refers to, among the inner wall surfaces of the mold whose cross-sectional shape is drawn as a straight line when the mold placed to fill the PTFE gelled and crushed product is cut in the vertical direction, It means a portion that does not correspond to the rib forming portion.

The unevenness of the mold comprises the rib forming portion and the curved surface, the rib forming portion, the curved surface and the flat surface, the rib forming portion and the flat surface, and the curved surface and the flat surface. It may be any of those having only the rib forming portion and those having only the curved surface.

The above-mentioned mold is not particularly limited, and various molds and the like according to the purpose can be mentioned, and examples thereof include a mold for diaphragm formation. The above-mentioned diaphragm forming die is not particularly limited, and for example, as shown in the schematic perspective view of FIG. 4, a lower die 414 usually composed of a curved surface 411, a flat surface 412 and a rib forming portion 413; a curved surface 415, a flat surface. 416 and through hole 417, an upper mold 418; a square cylinder 419; a plurality of diaphragm mold parts such as a screw part molding mold 420, and the screw 421 is the through hole 4
Set from 17 as shown.

A preferable lower limit of the groove width of the rib forming portion 413 of the lower die 414 is 0.5 mm, and a preferable upper limit of the groove depth is 3 mm. In particular, when the diameter of the curved surface 511 of the lower mold 514 is large, the preferable upper limit of the groove depth may be 3 mm. The preferable lower limit of the diameter of the curved surface 411 of the lower mold 414 is 20 mm, the preferable upper limit of the diameter is 400 mm, and the more preferable upper limit is
It is 300 mm. The preferable lower limit of the depth of the curved surface 411 of the lower mold 414 is 2 mm, and the more preferable lower limit is 3 mm.
The preferable upper limit is 50 mm, and the more preferable upper limit is 40 mm.

The method for producing a PTFE solid molded article of the present invention is as follows:
The above-mentioned mold is filled with the above-mentioned PTFE gelled and pulverized product. When the PTFE gelled and pulverized product is filled in the die, it is usually required that the PTFE gelled and pulverized product is first placed on the die so as to be as uniform as possible. During the filling, it is preferable to reduce the filling unevenness as much as possible, and for that reason, it is preferable to perform a leveling operation. In the present specification, the above-mentioned "filling" means putting resin powder in a mold and performing a leveling operation as desired. The above-mentioned filling is one in which pre-pressing pressure described later is not performed. The above-mentioned work is the
After filling the FE gel crushed product into a mold,
This is a work of smoothing the surface of the above-mentioned layer so that the thickness of the layer made of the gelled and pulverized product is as uniform as possible. The above-mentioned break-in work can be performed, for example, by applying the above-mentioned slight vibration or impact.

In the present specification, the "filling unevenness" means non-uniformity of the amount of resin powder on the mold, which occurs when the mold is filled with resin powder such as PTFE gel pulverized product. The "non-uniformity" of the uneven filling means that the amount of the resin powder on any part of the inner wall surface of the mold and the amount of the resin powder on the other part of the inner wall surface of the mold are equal to each other. , It is different when converted to the amount per unit area. If the packing density of the resin powder is the same, the above-mentioned filling unevenness appears as thickness unevenness in which the thickness is non-uniform. In the present specification, the above-mentioned "filling unevenness" is conceptually distinguished from non-uniformity in the density and thickness of the PTFE gelled and pulverized product after pre-pressing and pressurization, which will be described later, and after press-molding, which will be described later. .

The method for producing a PTFE solid molded article of the present invention is as follows:
After the PTFE gelled and pulverized product is filled in the mold, pre-molding may be carried out if desired before heating at a temperature equal to or higher than the melting point described later. It is preferable not to perform preforming in order to increase the number of voids. In the present specification, the above-mentioned "preforming" means applying a pressure to the PTFE gelled and pulverized product filled in the mold before heating at a temperature equal to or higher than the melting point described later. The above-mentioned preforming is usually carried out at room temperature, and it is preferable to carry out pressure application to such an extent as to leave voids between the particles of the PTFE gelled and pulverized product produced during filling. In the present specification, the application of pressure during the preforming may be referred to as preforming pressing.

The method for producing a PTFE solid molded article of the present invention is as follows:
It is characterized in that the above-mentioned PTFE gelled and pulverized product made of a PTFE-based polymer is filled in the mold and then pressurized at a temperature equal to or higher than the melting point of the PTFE-based polymer. In the present specification, pressurization at a temperature equal to or higher than the melting point of the PTFE-based polymer is sometimes referred to as “main molding pressurization”. In the present specification, the above-mentioned “preforming pressure” means
It is conceptually distinguished from the above-mentioned main molding pressurization in that it is performed prior to heating at a temperature equal to or higher than the melting point of the PTFE-based polymer.

When two or more kinds of the PTFE homopolymer and the modified PTFE are used as the PTFE-based polymer, the temperature above the melting point of the above-mentioned PTFE-based polymer is higher than the highest melting point of one kind among them. It is preferably temperature. The melting point of the PTFE-based polymer is usually 310 to 340 ° C., though it depends on the number average molecular weight and, in the case of modified PTFE, the copolymer composition. In the present specification, the “melting point of the PTFE-based polymer” means the melting point of the gelled PTFE-based polymer for obtaining the above-mentioned PTFE gelled and pulverized product. Above PTF
The temperature above the melting point of the E-based polymer is usually the above-mentioned PTFE.
It is selected within a temperature range below the decomposition temperature of the base polymer.

The method of raising the temperature to the melting point of the above PTFE-based polymer or above is not particularly limited, and a method of heating using a calcining device such as a hot air circulation furnace having a uniform temperature distribution is generally mentioned. In the present specification, the heating for raising the temperature to the melting point of the PTFE-based polymer or higher is sometimes referred to as “calcining”. The firing is conceptually distinguished from the heating in the heat treatment for gelation in that the heating target is different. The time required for the above firing is usually 10 per 1 mm of the thickness of the PTFE solid molded article which is empirically desired.
-30 minutes is preferable, but the baking time may be appropriately lengthened in consideration of the heat capacity of the mold.

It is preferable that the main molding pressurization is performed by applying a pressure of 10 to 35 MPa.
By performing the above-mentioned main molding pressurization by applying a pressure within the above range, the particles of the PTFE gelled and pulverized product flow by utilizing the voids between the particles, and the irregularities of the mold, particularly the corners of the concave parts of the mold. You can get in. When the unevenness of the mold is a rib forming portion and / or a curved surface, PT especially on a curved surface
The FE gelled and pulverized product has a uniform density and thickness, and the particles of the PTFE gelled and pulverized product can be made to penetrate into every corner of the rib forming portion. A more preferable lower limit is 15 MPa, and a more preferable upper limit is 30 MPa.
It is MPa.

The above-mentioned step of forming and pressurizing may be carried out in parallel with the step of firing in the firing apparatus, but normally, from the point that existing equipment can be used, it is carried out from the firing apparatus and transferred to a press machine. Is preferred. The above-mentioned main molding pressurization usually depends on the pressure to be applied, but is usually empirically set at a pressure within the above range.
It is preferably performed for 10 minutes.

After the main molding pressurization at a temperature equal to or higher than the melting point of the above-mentioned PTFE-based polymer, it is usually cooled. In applications such as diaphragms where flex fatigue resistance is required, the crystallinity is preferably low, so that water cooling is usually preferred.

The method for producing a PTFE solid molded article of the present invention is as follows:
As described above, the present invention is characterized in that a PTFE solid molded article is obtained by performing main molding and pressurization at a temperature equal to or higher than the melting point of the PTFE polymer. In the present specification, the “PTFE solid molded product” means a molded product in which the particles of the PTFE gelled and pulverized product are fused or fused and densely packed.

The PTFE solid molded body has a specific gravity of 1.8.
It is preferable that it exceeds. The specific gravity is preferably less than 2.5 within the above range. The specific gravity can be adjusted by adjusting the magnitude of the pressure applied in the steps of the preforming pressure and the main molding pressure. A more preferable upper limit is 2.2.

The method for producing a PTFE solid molded article of the present invention is as follows:
Even if there is some irregularity in filling during filling, it is possible to obtain a PTFE solid molded article in which the amount of the above PTFE gelled and pulverized product is made uniform over the entire mold by suppressing the influence of irregularity in filling by the above-mentioned main molding pressurization. to enable. It is considered that the above-mentioned preforming pressurization, which is performed if desired, also contributes to making the density and thickness of the PTFE gelled and pulverized product in the mold uniform.

The mechanism by which the method for producing a PTFE solid molded article of the present invention has such an excellent effect is not clear, but it is considered as follows. That is, since the above-mentioned PTFE gelled and pulverized product has undergone gelation, each particle is hard and has a spherical shape or a shape close to a spherical shape.
Even when the main molding and pressurization is performed at a temperature equal to or higher than the melting point of the FE-based polymer, unlike the conventional unsintered powder, it is hard to be crushed in place and has fluidity. On the other hand, the above P filled on the mold
There are voids generated during filling between the particles of the TFE gelled and ground product. Therefore, at the location P ¹ where the PTFE gelled and pulverized product was thickly present due to uneven filling, the internal pressure is increased by the main molding pressurization, but some of the particles at the location P ¹ move due to the adjacent voids. can do. As a result, when the internal pressure at the point P ¹ decreases and becomes lower than the internal pressure at the other points P ² , while the main molding pressurization continues,
Some of the particles at the above-mentioned location P ² move to locations such as the above-mentioned location P ¹ where the internal pressure is lower.

The movement of the particles having the high internal pressure to the points having the low internal pressure is repeatedly performed everywhere in the mold to fill the voids between the particles and the density of the PTFE gelled and ground product. And the thickness becomes uniform. When the mold has a recess having a complicated shape such as a rib-forming portion, the movement of the particles proceeds while entering every corner of the recess.
Macroscopically, the movement of particles is a flow of particles from a thickly filled portion to a thinly filled portion. The flow of particles stops when the density and thickness of the PTFE gelled and pulverized product in the mold become uniform, and the fusion of the particles whose surfaces are softened by the pressurization at a temperature equal to or higher than the melting point begins to proceed. As a result, PT that suppresses the effect of uneven filling
It is considered that an FE solid molded body can be obtained.

The method for producing a PTFE solid molded article of the present invention is as follows:
Since the particles of the above-mentioned PTFE gelled and pulverized product enter into a portion such as a concave portion in the unevenness of the inner wall of the mold which is conventionally hard to enter, a mold having an uneven shape such as a rib forming part is formed. Even if it is used, it can be said that this is a method for obtaining a PTFE solid molded product having a uniform unevenness. Further, according to the method for producing a PTFE solid molded article of the present invention, a portion other than the rib forming portion in the mold, for example, a curved surface P
It can be said that this is a method in which the density and thickness of the TFE gelled and pulverized product are made uniform as a whole and cracks are less likely to occur in the obtained PTFE solid molded article.

When the mold is a diaphragm mold, the density and thickness of the PTFE gel crushed product are uniform in the R part of the mold, and the PTFE gel crushed product is also formed in the rib forming portion of the mold. Since the particles of (3) enter every corner, it is possible to obtain a rib having a uniform shape.

The method for producing a PTFE solid molded article of the present invention is as follows.
Further, it is a method of directly molding the above-mentioned PTFE gelled and crushed product, and in the above-mentioned PTFE gelled and crushed product, the concave portion of the mold can be inserted into, for example, a relatively deep dent. There are a wide variety of molds that can be applied. Moreover, since a PTFE gelled and pulverized product that has been subjected to heat treatment at a melting point or above is used, there is little generation of corrosive gas in the process of heating above the melting point temperature, and unfired PTFE powder is used as a raw material as it is. It can be said that this is a method capable of improving the durability of the mold as compared with

The method for producing a PTFE solid molded article of the present invention is as follows:
In this way, the PTFE gelled and crushed product having a curved surface has a uniform density and thickness, and the PTFE and the like have a uniform complex shape such as ribs.
Since a solid molded body can be easily obtained without requiring skill, it can be preferably used when a solid molded body having a curved surface and / or a complicated shape is obtained.
Such solid molded body is not particularly limited, and examples thereof include oil seals, gland packings, mechanical seals, lip packings, squeeze packings, boots, dust covers, accumulators, gaskets, diaphragms, etc. Is preferred.

[0059]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Example 1 Diaphragm molding using PTFE gelled and crushed product Granulated ungelled product of PTFE (trade name: New Polyflon M-111, manufactured by Daikin Industries, Ltd.) was heat-treated at a melting point or higher, crushed, classified, and averaged particles Adjusted to a diameter of 71 μm, PTF
An E-gelled pulverized product was obtained. As the die, a die for forming a diaphragm (made of SUS304) having an inner diameter of the R portion of 52.15 mm as shown in the schematic perspective view of FIG. 2 was used. First, a PTFE molding gel pulverized product was filled in a diaphragm molding die and baked at 360 ° C. for 1 hour. Then, it was transferred to a press and a water pressure was applied immediately after applying a pressure of 30 MPa to obtain a PTFE solid molded body. The obtained PTFE solid molded product was taken out of the mold and observed for appearance, and in particular, cracks, flow patterns due to the generation of wrinkles, rib deformation, rib displacement, etc. were not observed. The dimensions of the obtained PTFE solid molded article are 0.4 mm in thickness and R
The diameter of the part was 51 mm, and the shrinkage ratio of the diameter of the R part was 2.2% with respect to the inner diameter of the mold. The specific gravity of the obtained PTFE solid molded body was 2.15.

The obtained PTFE solid molded product is smaller than the mold in terms of the size of the molded product, but by using a PTFE gelled pulverized product having a higher fluidity than the powder of the conventional method, The step of filling the mold with the PTFE gelled pulverized product was facilitated, and it became possible to perform molding with one press of main molding after firing without preliminary molding. The rib of the obtained diaphragm was similar to the shape of the rib forming portion of the mold.

[0061]

EFFECTS OF THE INVENTION The method for producing a PTFE solid molded article according to the present invention has the above-mentioned constitution, and therefore it is easy to uniformly obtain the density and thickness of the curved surface and the complicated shape such as ribs.
EPT that does not easily generate flow marks or cracks in gelled pulverized products
A solid FE molding can be obtained.

[0062]

[Brief description of drawings]

FIG. 1 is a schematic top view and a schematic cross-sectional view showing an example of a diaphragm.

FIG. 2 is a schematic cross-sectional view showing an example of a diaphragm molding die.

FIG. 3 is a schematic diagram showing an example of a cross-sectional shape of irregularities that the mold has on the inner wall surface.

FIG. 4 is a schematic cross-sectional view showing an example of a diaphragm molding die.

[Explanation of symbols]

11 curved surface 12 ribs 21,411,415 curved surface 22,413 Rib forming part 23 Mold for screw part molding 412, 416 plane (lower mold) 414 Lower mold 417 through hole 418 Upper mold 419 square cylinder 420 Mold for screw part molding 421 screw

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shuji Tagashi             Daiichi Nishiichitsuya 1-1, Settsu City, Osaka Prefecture             Yodogawa Manufacturing Co., Ltd. F-term (reference) 3J045 AA14 BA03 CA01 CA05 DA01                       EA01                 4F204 AA17 AA17J AC04 AH15                       AR03 FA01 FB01 FF01 FN15                       FQ15

Claims (7)

[Claims] 1. A PTFE solid molded article obtained by filling a mold with a PTFE gelled and pulverized product comprising a PTFE polymer and then pressurizing at a temperature not lower than the melting point of the PTFE polymer to obtain a PTFE solid molded article. A method for producing a body, wherein the PTFE-based polymer is a tetrafluoroethylene homopolymer and / or a modified polytetrafluoroethylene, and the mold has an unevenness on an inner wall thereof. Molded body manufacturing method. 2. The method for producing a PTFE solid molded article according to claim 1, wherein the pressurization is performed by applying a pressure of 10 to 35 MPa. 3. The method for producing a PTFE solid molded article according to claim 1, wherein the PTFE solid molded article has a specific gravity of more than 1.8. 4. The method for producing a PTFE solid molded article according to claim 3, wherein the specific gravity is more than 1.8 and less than 2.5. 5. The method for producing a PTFE solid molded product according to claim 1, wherein the PTFE gelled and pulverized product has an average particle size of 5 to 1000 μm. 6. The method for producing a PTFE solid molded article according to claim 1, wherein the unevenness of the mold is a rib forming portion and / or a curved surface. 7. The method for producing a PTFE solid molded article according to claim 1, 2, 3, 4, 5, or 6, wherein the PTFE solid molded article is a diaphragm.