JP2010253755A - Extrusion mold for polytetrafluoroethylene particle-containing material, extruder for polytetrafluoroethylene particle-containing material, method of producing polytetrafluoroethylene sheet-like product, method of producing polytetrafluoroethylene porous sheet-like product, method of producing polytetrafluoroethylene sheet-like baked product, method of producing polytetrafluoroethylene porous sheet-like baked product, and polytetrafluoroethylene sheet-like baked product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an extrusion mold for a PTFE particle-containing material which improves the effect for suppressing variation in strength in the direction perpendicular to the extrusion direction and the stretching strength, while maintaining the thickness accuracy, and can produce a wide width PTFE sheet-like baked product. <P>SOLUTION: The extrusion mold includes a female mold 1 and a male mold 2, the female mold has a hollow internal space, passing therethrough in the vertical direction, and a tapered space formed at the lower part of the internal space, and the male mold has a cylindrical lower part and a tapered shaped distal part. A radial expansion part extending from the upper part to the lower part along the distal part of the male mold and a flow passage for pressing a material having a tubular part extending along the cylindrical lower part of the male mold are provided between the female mold and the male mold by coaxially disposing the male mold in the lower part of the internal space of the female mold so that the distal part of the male mold is directed toward the upper part of the hollow internal space, and the outer wall surface of the distal part of the male mold faces the inner wall surface of the female mold forming the tapered space. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an extrusion mold for polytetrafluoroethylene (hereinafter, appropriately referred to as PTFE) particle-containing material, an extruder for PTFE particle-containing material, a method for producing a PTFE sheet, and a method for producing a PTFE porous sheet The present invention relates to a method for producing a PTFE sheet-like fired product, a method for producing a PTFE porous sheet-like fired product, and a PTFE sheet-like fired product.

  PTFE resin extruded products are used in various fields as tube materials, electric wire materials, and the like. In particular, after extruding PTFE resin, it is further uniaxially stretched in the extrusion direction, or a porous sheet obtained by stretching sequentially or simultaneously in the biaxial direction (extrusion direction and direction perpendicular to the extrusion direction) The object has a structure in which fibrils (linear molecular bundles drawn by the folding crystal being unwound by stretching) diffuse radially from the nodes due to the folded crystals, and there are many vacancies defined by the fibrils and the nodes. It is known that the PTFE sheet-like material having the porous structure is used as a clothing material such as ski wear, a filter material for an air filter, or the like by taking advantage of its characteristics. The porous PTFE sheet is used in various applications such as sealing materials such as seal tapes and gaskets, and it is desired that a wide PTFE porous sheet can be produced.

  Since the PTFE sheet material subjected to the stretching treatment can adopt various stretching conditions when its width is wide and stable, it has a great merit in adjusting the cost and physical properties of the PTFE porous sheet material. Obtainable.

  The PTFE sheet-like material having a wide tape shape subjected to the stretching treatment is currently produced by roll rolling, but the PTFE sheet-like material has a width of 150 mm or 300 mm due to equipment restrictions of roll rolling. There are many, most of them are 400 mm wide or less. The reason why the width of the PTEE sheet is limited is that, in roll rolling, when trying to obtain a wide width, there can be a difference in physical properties between the end portion in the width direction and the center portion. Can be mentioned. As another reason, in roll rolling, it is necessary to make the force with which the roll pulls the PTFE sheet-like material larger than the force that crushes the PTFE sheet-like material and widens the width, but it is limited by the capability of the apparatus to be used. Can be mentioned.

  As shown in FIG. 7, an extrusion mold for producing a PTFE sheet-like material used for producing such a PTFE porous sheet-like material has an internal space 104 of a female die 101 as a male die 102 in the longitudinal direction. In this extrusion mold 103, a constriction of the female mold is known in which a conical enlarged portion 108 whose vertical cross-sectional diameter with respect to the diameter gradually increases in the pressing direction of the material is arranged coaxially with the female mold 101. In the internal space 104 on the outlet side from the portion 151, the inner wall surface of the female die 101 and the conical enlarged portion 108 of the male die 102 are opposed to each other, and the material radially extends diagonally downward between the female die and the male die. A pressing channel 111 is formed (see, for example, Patent Document 1).

  In this extrusion mold 103, a mixture of PTFE powder and a lubricant is injected as a molding material from the inlet side of the internal space 104, pressed, and tubular (tubular) from the material pressing flow path 111 below the molding mold 103. After the molded product is discharged, the obtained molded product is cut in the axial direction (discharge direction), and a PTFE sheet having a porous structure is produced by subjecting the obtained PTFE sheet material to stretching treatment.

  In the extrusion mold 103 shown in FIG. 7, the PTFE particles are oriented in the vertical direction by the pressure in the outlet direction in the material pressing flow path 111, and the particles are also spread in the horizontal direction and oriented in the horizontal direction. Will adhere to each other. For this reason, when the extrusion mold 103 shown in FIG. 7 is used, the PTFE particles are oriented in the direction perpendicular to the extrusion direction simultaneously with the extrusion direction by pressing from the inlet side. It is said that the tensile strength in the direction perpendicular to the extrusion direction can be improved and the variation in the stretching strength in the direction perpendicular to the extrusion direction can be suppressed.

Japanese Patent Laid-Open No. 10-128827

  However, when the extrusion mold 103 shown in FIG. 7 is used, the physical property improvement effect (orientation improvement effect) of the pressed product in the direction perpendicular to the extrusion direction obtained by passing through the material pressing flow path 111 is shown in FIG. The larger the inner diameter enlargement ratio b / a defined using the cross-sectional diameter b of the male outlet and the cross-sectional diameter a of the male inlet shown in FIG. In order to further increase the inner diameter enlargement ratio, if an attempt is made to reduce the cross-sectional diameter a of the male inlet, the mandrel (mandrel) 100 becomes smaller in diameter so that the male mold 102 cannot be supported sufficiently in a straight line. In order to increase the ratio, if the cross-sectional diameter b of the lower part of the male mold is increased, not only the weight of the male mold becomes excessive, but it becomes difficult to uniformly and easily add the raw material, or the mold holding facility is large. Turned into Ukoto was found. For this reason, in the extrusion mold 103 shown in FIG. 7, the strength of the obtained extruded product in the direction perpendicular to the extrusion direction is not sufficiently improved, and it is difficult to obtain a wide PTFE sheet.

  Further, the extrusion mold 103 shown in FIG. 7 employs a configuration in which the male mold 102 is fixed by a mandrel (mandrel) 100 from the material inlet side, so that the inner diameter enlargement ratio is increased in order to widen the PTFE sheet. When the pressure is increased, the pressure received by the male mold 102 from the inlet becomes too large, and the central axis of the male mold 102 is shifted or inclined, so that the material pressure formed between the female mold 101 and the male mold 102 is increased. It has been found that it is difficult to keep the width of the flow path 111 constant, uneven thickness occurs in the obtained press-molded product, and it is difficult to obtain practically sufficient thickness accuracy.

  On the other hand, in order to obtain a wide PTFE sheet without increasing the inner diameter enlargement ratio, if both the cross-sectional diameter a and the cross-sectional diameter b shown in FIG. It becomes difficult to throw in or the weight of the mold increases in proportion to the cube of the diameter, so that the weight increase becomes significant and the mold holding equipment becomes large.

  Under such circumstances, the present invention, in the obtained extruded product, sufficiently increases the strength in the direction perpendicular to the extrusion direction while maintaining the thickness accuracy at a practically sufficient level, and the direction perpendicular to the extrusion direction. It is a first object of the present invention to provide an extrusion mold for a PTFE particle-containing material that can improve the strength variation suppressing effect and can produce a wide PTFE sheet. The second object of the present invention is to provide a PTFE particle-containing material extrusion molding machine having the above extrusion mold, and the production of a PTFE sheet using the above extrusion molding machine. A third object is to provide a method, and a fourth object is to provide a method for producing a PTFE porous sheet from the PTFE sheet. Furthermore, the present invention has a fifth object to provide a method for producing a PTFE sheet-like fired product, and a sixth object to provide a method for producing a PTFE porous sheet-like fired product. The seventh object is to provide goods.

  In order to solve the above technical problem, the present inventors have conducted intensive studies. As a result, an extrusion mold for PTFE particle-containing material having a female mold and a male mold, the female mold penetrates in the vertical direction. A hollow space having a hollow inner space, a tapered space in which the vertical cross-sectional diameter with respect to the vertical direction gradually decreases is formed in the middle portion from the lower portion to the upper portion of the inner space. And a tapered tip portion in which the vertical cross-sectional diameter with respect to the vertical direction gradually decreases from the columnar lower portion to the upper direction, so that the male tip portion faces the upper portion of the hollow internal space. The male mold is disposed coaxially with the female mold at the lower portion of the female mold inner space so that the outer wall surface of the tip of the male mold faces the female inner wall surface forming the tapered space. The tip of the male mold is inserted between the female mold and the male mold. An extrusion mold for a PTFE particle-containing material is obtained by providing a material pressing flow path having a radially enlarged portion extending from the upper portion to the lower portion along the portion and a tubular portion extending along the male cylindrical lower portion. Based on these findings, it has been found that the first object can be achieved by the mold, and that the second to seventh objects can be achieved by using the extrusion mold. The present invention has been completed.

That is, the present invention
(1) An extrusion mold for a PTFE particle-containing material having a female mold and a male mold,
The female mold has a hollow internal space penetrating in the vertical direction, and a tapered space in which the vertical cross-sectional diameter with respect to the vertical direction is gradually reduced is formed in the middle part from the lower part to the upper part of the internal space. Become
The male mold has a cylindrical lower part, and a tapered tip part in which the vertical cross-sectional diameter with respect to the vertical direction from the cylindrical lower part to the upper part gradually decreases,
The male mold so that the male mold tip faces the upper part of the hollow internal space, and the male mold tip outer wall faces the female mold wall that forms the tapered space. Is arranged coaxially with the female mold at the lower part of the internal space of the female mold,
Provided between the female mold and the male mold is a material pressing flow path having a radially enlarged portion extending from the upper portion to the lower portion along the male tip portion and a tubular portion extending along the male cylindrical lower portion. An extrusion mold for a PTFE particle-containing material,
(2) In the narrowest part of the tapered space, a circumference that bisects the material inflow area formed in a direction perpendicular to the vertical direction of the tapered space is defined as the narrowest part cross-sectional area average circumference, When the circumference that bisects the material outlet area formed in the direction perpendicular to the vertical direction of the tapered space at the lower end portion of the material pressing flow path is defined as the outlet portion cross-sectional area average circumference,
The extrusion mold for the PTFE particle-containing material according to the above (1), wherein the ratio of the length of the outlet cross-sectional area average circumference to the length of the narrowest cross-sectional area average circumference is 5 or more,
(3) The extrusion mold for the PTFE particle-containing material according to (1) or (2), wherein an internal angle of a tapered tip end portion is 80 ° or less in a horizontal section with respect to the vertical direction of the male mold,
(4) An PTFE particle-containing material extrusion molding machine comprising the PTFE particle-containing material extrusion mold according to any one of (1) to (3) above,
(5) Using the PTFE particle-containing material extrusion molding machine described in (4) above,
By supplying and pressing the PTFE particle-containing material into the internal space of the female mold constituting the extrusion mold, the tubular preform is discharged from the lower end of the material pressing flow path,
A method for producing a PTFE sheet, characterized by producing a sheet by cutting the obtained tubular preform in the axial direction;
(6) The method for producing a PTFE sheet-like product according to (5), wherein the tubular molded product is further subjected to a rolling process in the extrusion direction after cutting.
(7) Using the PTFE particle-containing material extrusion molding machine described in (4) above,
By supplying and pressing the PTFE particle-containing material into the internal space of the female mold constituting the extrusion mold, the tubular preform is discharged from the lower end of the material pressing flow path,
After the obtained tubular preform is cut in the axial direction, it is further uniaxially stretched in the extrusion direction or biaxially stretched in the direction perpendicular to the extrusion direction and the extrusion direction. ,
(8) Using the PTFE particle-containing material extrusion molding machine described in (4) above,
By supplying and pressing the PTFE particle-containing material into the internal space of the female mold constituting the extrusion mold, the tubular preform is discharged from the lower end of the material pressing flow path,
A method for producing a PTFE sheet-like fired product, characterized in that the obtained tubular preform is cut in the axial direction and then fired.
(9) Using the PTFE particle-containing material extrusion molding machine described in (4) above,
By supplying and pressing the PTFE particle-containing material into the internal space of the female mold constituting the extrusion mold, the tubular preform is discharged from the lower end of the material pressing flow path,
After the obtained tubular preform is cut in the axial direction, the obtained cut product is further uniaxially stretched in the extrusion direction, or biaxially stretched in the extrusion direction and the direction perpendicular to the extrusion direction, and fired. A method for producing a PTFE porous sheet-like fired product, characterized by:
(10) PTFE sheet-like fired product characterized in that the tensile strength in the longitudinal direction and the direction perpendicular to the longitudinal direction is 35 to 70 MPa,
Is to provide.

  According to the present invention, an extrusion mold having a hollow internal space penetrating in the vertical direction is adopted, and the male mold constituting the extrusion mold is suspended from the upper part of the internal space of the female mold by the mandrel. Instead, the male mold is placed in the lower part of the inner space so that the outer wall surface of the male mold tip and the female inner wall surface in the tapered inner space face each other. By arranging and supporting from below, it is possible to increase the circumference of the outlet, and it is possible to use a thick and rigid support, and the thickness accuracy of the resulting extruded product is maintained at a practically sufficient level. can do. In addition, a male mold having a cylindrical lower part and a tapered tip part having a vertical cross-sectional diameter gradually decreasing from the lower part to the upper part in the upper direction is used. The extrusion direction by increasing the difference between the length of the outlet cross-sectional area average circumference at the bottom of the male mold and the length of the narrowest cross-sectional area average circumference at the top of the male mold Highly oriented in the direction perpendicular to the extrusion direction, the strength of the resulting extruded product in the direction perpendicular to the extrusion direction is sufficiently improved, and the effect of suppressing variation in the stretching strength in the direction perpendicular to the extrusion direction is achieved. While improving, the extrusion mold for PTFE particle containing materials which can manufacture a wide PTFE sheet-like material can be provided.

  Furthermore, according to the present invention, an PTFE particle-containing material extrusion molding machine characterized by comprising the above-mentioned extrusion mold, and a method for producing a PTFE sheet-like product using the extrusion molding machine A PTFE porous sheet-like product manufacturing method, a PTFE sheet-like fired product manufacturing method, a PTFE porous sheet-like fired product manufacturing method, and a PTFE sheet-like fired product can be provided.

It is a figure which shows the one aspect | mode of the extrusion mold of this invention. It is a figure which shows the one aspect | mode of the extrusion mold of this invention. It is a figure which shows the one aspect | mode of the extrusion mold of this invention. It is a figure explaining the calculation method of ratio of the outlet part cross-sectional area average circumference with respect to the narrowest part cross-sectional area average circumference in the extrusion mold of this invention. It is a figure explaining the internal angle of the taper-shaped front-end | tip part of the male type | mold which comprises the extrusion mold of this invention. It is a figure which shows the one aspect | mode of the extruder of this invention. It is a figure explaining the conventional extrusion mold.

  First, the extrusion mold for PTFE particle-containing material of the present invention will be described.

  The extrusion mold for PTFE particle-containing material of the present invention is an extrusion mold for PTFE particle-containing material having a female mold and a male mold, and the female mold has a hollow internal space penetrating in the vertical direction. A tapered space in which the vertical cross-sectional diameter with respect to the vertical direction gradually decreases is formed in the middle portion from the lower portion to the upper portion of the internal space, and the male mold has a cylindrical lower portion and the cylindrical lower portion. A taper-shaped tip portion whose vertical cross-sectional diameter with respect to the up-down direction gradually decreases in the upper direction, and the tip portion of the male mold faces the upper portion of the hollow internal space, and the tip of the male mold By arranging the male mold coaxially with the female mold at the lower part of the inner space of the female mold so that the outer wall surface faces the female mold inner wall surface forming the tapered space, the female mold and the male mold Between the mold and the top along the tip of the male mold And it is characterized in that formed by providing a material pressing channel having a tubular portion extending along the cylindrical lower portion of the radial expansion part and the male extending downwardly.

  Hereinafter, an embodiment of an extrusion mold of the present invention will be described based on the drawings.

  FIG. 1 is a schematic cross-sectional view showing one embodiment of the extrusion mold of the present invention, and FIG. 2 is a schematic cross-sectional view showing another embodiment of the extrusion mold of the present invention.

  The extrusion mold 3 shown in FIGS. 1 and 2 has a female mold 1 and a male mold 2. The female mold 1 has an upper and lower portion in a middle part (longitudinal middle part) from the lower part to the upper part. A hollow internal space 4 penetrating in the vertical direction is provided, in which a tapered space 52 in which the vertical cross-sectional diameter with respect to the direction gradually decreases is formed.

  The extrusion mold shown in FIG. 1 and the extrusion mold shown in FIG. 2 differ from each other in whether or not the constricted portion 51 is provided in the middle portion in the longitudinal direction of the internal space 4 of the female mold 1. Since the points are common, the extrusion mold of the present invention will be described below mainly based on the embodiment shown in FIGS.

  As shown in FIGS. 1 and 2, the extrusion mold 3 of the present invention is formed with a tapered space 52 in the middle in the longitudinal direction from the lower part to the upper part of the internal space 4 of the female mold 1.

  As shown in FIGS. 1 and 2, the male mold 2 constituting the extrusion mold 3 of the present invention has a columnar lower portion 6 and a tapered shape in which the vertical sectional diameter with respect to the vertical direction gradually decreases from the lower portion 6 in the upper direction. And a distal end portion 7.

  The overall shape of the internal space 4 of the female mold 1 is preferably substantially cylindrical, and the dimensions of the internal space 4 of the female mold 1 and the dimensions of the male mold 2 depend on the amount of molding material to be pressed, etc. It can be determined as appropriate.

  As shown in FIGS. 1 and 2, the distal end portion 7 of the male mold 2 faces the upper portion of the hollow internal space 4 (the upper side of FIGS. 1 and 2 which is the material pressing side) and the distal end portion. The male mold 2 is placed below the inner space 4 (lower part in the pressing direction of the molding material) so that the outer wall surface 8 of the female mold 7 and the female mold inner wall surface 9 forming the tapered space 52 face each other. Coaxially arranged.

  By adopting such a configuration, a male tapered tip (in the direction from the upper side to the lower side in FIGS. 1 and 2) between the female mold 1 and the male mold 2 in the extrusion direction of the molding material ( A radially enlarged portion 11 extending from the central axis side of the male mold 2 to the outside of the male mold 2 and a tubular section 12 extending along the male lower section 6 are formed along the outer wall surface 8) of the tapered tip portion. A material pressing channel 11 is provided.

  1 and 2, the upper end of the distal end of the male mold 2 protrudes from the narrowest portion of the tapered space 52, but the upper end of the distal end of the male mold 2 does not necessarily protrude from the narrowest portion of the tapered space 52. As shown in FIG. 3, it may be arranged so as not to protrude from the narrowest portion.

  The extrusion mold for PTFE particle-containing material according to the present invention has the circumference that bisects the material inflow area formed in the direction perpendicular to the vertical direction of the tapered space at the narrowest portion of the tapered space. The cross-sectional area of the outlet portion is defined as the circumference that divides the material outlet area formed in the direction perpendicular to the up-down direction of the tapered space into two equal parts at the lower end portion of the material pressing flow path. The ratio of the length of the cross-sectional area average circumference to the length of the cross-sectional area average circumference of the narrowest part (the length of the cross-sectional area average circumference of the outlet / the average cross-sectional area of the narrowest part) The length) is preferably 5 or more.

  The ratio is more preferably 7 or more, and still more preferably 10 or more. In the extrusion mold for the PTFE particle-containing material of the present invention, the above ratio is 5 or more, so that, at the time of extrusion molding, the stretch strength after the firing treatment in the direction perpendicular to the extrusion direction of the obtained extrusion molding is obtained. Thus, a wide sheet-like molded product can be produced.

  As described above, in the extrusion mold for PTFE particle-containing material of the present invention, the upper end of the male mold may or may not protrude from the narrowest part of the tapered space. For this reason, in the case where the upper end portion of the male mold 2 does not protrude from the narrowest portion of the tapered space, the male upper section diameter a as shown in FIG. 7 cannot be defined. It becomes impossible to define the inner diameter enlargement ratio b / a defined by the sectional diameter a of the upper part of the mold and the sectional diameter b of the lower part of the male mold. Further, the inner diameter enlargement ratio does not sufficiently consider the average enlargement ratio, the minimum enlargement ratio, the maximum enlargement ratio, and the like, and is considered insufficient as a description of the enlargement ratio.

  Therefore, in the extrusion mold of the present invention, the ratio of the length of the outlet cross-sectional area average circumference to the length of the narrowest cross-sectional area average circumference shown below (the length of the outlet cross-sectional area average circumference / The average circumference of the narrowest section cross-sectional area) is defined, and this is replaced by the inner diameter enlargement ratio, so that the circumferential length in the direction perpendicular to the extrusion direction of the material is between the narrowest section cross section and the outlet section cross section. It is possible to give a ratio of increasing the size, that is, a calculated value of orientation in the width direction of the sheet-like material (direction perpendicular to the extrusion direction). That is, according to the ratio of the length of the cross-sectional area average circumference of the outlet portion to the length of the cross-sectional area average circumference of the narrowest part, the average of the enlargement ratio, the volume average value considering the minimum enlargement ratio, the maximum enlargement ratio, etc. By controlling the ratio, the orientation of the sheet material in the width direction (direction perpendicular to the extrusion direction) can be controlled within a desired range.

As shown in FIG. 4, in the narrowest part of the tapered space 52, when the radius of the outer periphery of the material pressing flow path 11 is W and the radius of the inner periphery is X, it is perpendicular to the vertical direction of the inner space 4. The material inflow area formed in is defined by πW ² −πX ² . In addition, when the circumference that divides the material inflow area into two is the narrowest section cross-sectional area average circumference, and the radius of the narrowest section cross-sectional area average circumference is c, the following formula (I) is established. Will do.
πW ² −πX ² = 2 (πc ² −πX ² ) (I)
When formula (I) is summarized with respect to radius c, the following formula (II) is obtained.
c = ((W ² + X ² ) ^0.5 ) / (2 ^0.5 ) (II)

Further, as shown in FIG. 4, at the outlet portion of the material pressing channel 11, when the radius of the outer periphery of the channel is Y and the radius of the inner periphery is Z, it is perpendicular to the vertical direction of the internal space 4. The material exit area to be formed is defined by πY ² −πZ ² . Further, when the circumference that divides the material outlet area into two equal parts is defined as the outlet section cross-sectional area average circumference, if the radius of the outlet section cross-sectional area average circumference is d, the following formula (III) holds: become.
πY ² −πZ ² = 2 (πd ² −πZ ² ) (III)
Summarizing the formula (III) with respect to the radius d, the following formula (IV) is obtained.
d = ((Y ² + Z ² ) ^0.5 ) / (2 ^0.5 ) (IV)

Since the length of the narrowest section cross-sectional area average circumference derived from the radius c is 2πc and the outlet section cross-sectional area average circumference derived from the radius d is 2πd, the narrowest section cross-sectional area average circumference is 2πd / 2πc, which is the ratio of the length of the cross-sectional area average circumference of the outlet portion relative to the length (the length of the cross-sectional area average circumference of the outlet portion / the length of the cross-sectional area average circumference of the narrowest portion), From (IV), it can be expressed as the following formula (V).
2πd / 2πc = ((Y ² + Z ² ) ^0.5 ) / ((W ² + X ² ) ^0.5 ) (V)

In the extrusion mold of the present invention, when the upper end of the male mold 2 is not protruded from the narrowest portion of the tapered space 52 as shown in FIG. 3, in the narrowest portion of the tapered space 52. Since the radius X can be regarded as 0, the following formula (V ′) is derived from the above formula (V).
2πd / 2πc = ((Y ² + Z ² ) ^0.5 ) / W (V ′)

  Therefore, in the extrusion mold of the present invention, as shown in FIG. 1 and FIG. 2, the case where the top end of the male mold 2 protrudes from the narrowest portion of the tapered space 52 is also shown in FIG. As shown, even when the top end of the male mold 2 does not protrude from the narrowest part of the tapered space 52, the cross-sectional area average of the narrowest part is obtained by the above formula (V) or formula (V ′). The ratio 2πd / 2πc of the outlet section cross-sectional area average circumference length to the circumference length can be obtained. Further, FIG. 4 discloses an extrusion mold having a constricted portion 51. However, even in an extrusion mold having no constricted portion 51 as shown in FIG. A ratio 2πd / 2πc of the length of the cross-sectional area average circumference to the length of the cross-sectional area average circumference can be obtained.

  Ratio of the length of the outlet cross-sectional area average circumference to the length of the narrowest cross-sectional area average circumference (length of the outlet cross-sectional area average circumference / length of the narrowest cross-sectional area average circumference) 2πd To increase / 2πc, there are a method of increasing the length 2πd of the outlet cross-sectional area average circumference and a method of decreasing the length 2πc of the narrowest cross-sectional area average circumference, but only the former method Accordingly, since the male mold 2 becomes unnecessarily large and heavy, and the inner angle α of the tip 7 of the male mold 2 described later increases, it is preferable to first increase 2πd / 2πc by the latter method. .

  Specifically, the top of the tip 7 of the male mold 2 is positioned at the narrowest part of the tapered space 52 shown in FIGS. 1 and 2 (the part where the inner wall of the female mold 1 protrudes most toward the internal space 4). Or lower than that (below the narrowest portion of the tapered space 52 in FIGS. 1 and 2), that is, by setting X = 0, the narrowest portion cross-sectional area average circumference 2πc Can be reduced.

  The flow path width (flow path width of the material) from the narrowest part of the material pressing flow path toward the outlet part may be appropriately determined according to the thickness of the extruded product to be obtained. It is preferable that it is 1 mm-10 mm. As shown in FIG. 1 and the like, in the extrusion mold of the present invention, the width of the material pressing flow path is preferably narrowed from the narrowest portion toward the outlet portion. By adopting such a configuration, the strength of the obtained extruded product (PTFE sheet-like product) in the direction perpendicular to the extrusion direction is sufficiently improved, and the effect of suppressing variation in the stretching strength in the direction perpendicular to the extrusion direction is achieved. Can be improved.

  Furthermore, in the extrusion mold of the present invention, as shown in FIG. 5, the internal angle α of the tip of the tapered tip portion is preferably 80 ° or less and 60 ° or less in the horizontal cross section with respect to the vertical direction of the male die 2. It is more preferable that the angle is 55 ° or less. When the internal angle α is more than 80 °, the pressing force increases excessively during the extrusion molding of the PTFE particle-containing material, and not only the pressure loss increases, but also the narrowest part cutting as in the extrusion mold of the present invention. For molds with a large ratio of outlet cross-sectional area average circumference length to area average circumference length (exit cross-sectional area average circumference length / narrowest section cross-sectional area average circumference length) , A single flow of the molding material (a phenomenon in which the PTFE particle-containing material does not flow uniformly through the entire material pressing flow path) is likely to occur. In addition, if the internal angle α of the tapered tip end is too small, the entire molding equipment becomes too large, or the amount of material retention increases and the yield decreases each time the molding is switched. Is preferably 15 ° or more, more preferably 25 ° or more, and further preferably 30 ° or more.

  The molding material used in the extrusion mold of the present invention is a PTFE particle-containing material. The PTFE particle-containing material is not particularly limited as long as it contains PTFE particles. For example, Fullon CD-123, CD145 (Asahi ICI Fluoropolymers), Polyflon F-104 (Daikin Industries), Examples thereof include those marketed as PTFE extrusion resins such as Teflon (registered trademark) 6J (Mitsui / Dupont Fluoro Chemical).

  It is preferable that the molding material usually contains a lubricant used at the time of pressing. As the lubricant, the surface of PTFE can be wetted, and after extrusion to obtain a sheet-like material, evaporation, extraction, etc. It is preferable that it can be removed by this method. For example, in addition to hydrocarbon oils such as liquid paraffin, naphtha, white oil, toluene, and xylene, alcohols, ketones, esters, and mixtures of two or more of these can be mentioned. The amount of the lubricant added to the PTFE particles is appropriately determined depending on the PTFE particles, the type of the lubricant, and the like, but the lubricant is preferably about 5 to 50 parts by weight with respect to 100 parts by weight of the PTFE particles. .

  In the extrusion mold for PTFE particle-containing material of the present invention, as shown in FIGS. 1 and 2, the male mold 2 constituting the extrusion mold 3 is suspended from the upper part in the internal space 4 of the female mold 1 by a mandrel. Instead, by disposing the male mold 2 below the inner space 4 of the female mold 1, that is, the outer wall surface 8 of the male tip 7 and the female inner wall surface 9 forming the tapered space 52 face each other. As described above, by disposing the male mold 2 in the lower part of the internal space 4, the deviation and inclination of the central axis of the male mold 2 that occurs during pressing are suppressed, and the thickness accuracy of the obtained extruded product is brought to a practically sufficient level. Can be maintained. The male mold 2 has a cylindrical lower portion 6 and a tapered tip portion 7 formed by gradually decreasing the vertical cross-sectional diameter in the vertical direction from the lower portion to the upper direction. The male mold is arranged so as to face the upper part of the space 4 (the pressing side of the molding material), the cross-sectional area average circumference at the narrowest part of the material pressing flow path is reduced, and the cross-sectional area average circumference with respect to the narrowest part is reduced. By increasing the ratio of the cross-sectional area average circumference of the outlet portion, the strength of the obtained extruded product in the direction perpendicular to the extrusion direction can be sufficiently improved, and the effect of suppressing variation in the stretching strength in the same direction can be improved. .

Next, the extruder for PTFE particle-containing material of the present invention will be described.
The PTFE particle-containing material extrusion molding machine of the present invention is characterized by comprising the PTFE particle-containing material extrusion mold of the present invention.

  Examples of the extrusion mold for PTFE particle-containing material and the PTFE particle-containing material used in the extruder for PTFE particle-containing material of the present invention include the same ones as described above.

  FIG. 6 illustrates a PTFE particle-containing material extruder 14 having the PTFE particle-containing material extrusion die 3 of the present invention. As shown in the drawing, the PTFE particle-containing material extrusion molding machine 14 of the present invention, together with the PTFE particle-containing material extrusion molding die 3 of the present invention, is a cutter 15 that cuts the pressing rod 13 and the extrusion molding 16 in the axial direction. It is preferable that it has.

  Next, the manufacturing method of the PTFE sheet material of this invention is demonstrated.

  The method for producing a PTFE sheet-like material of the present invention is to supply and press the PTFE particle-containing material into the internal space of the female mold constituting the extrusion mold using the PTFE particle-containing material extrusion molding machine of the present invention. The tubular preform is discharged from the lower end portion of the material pressing flow path, and then the obtained tubular preform is cut in the axial direction to produce a sheet-like material. .

  Examples of the PTFE particle-containing material extrusion molding machine and the PTFE particle-containing material used in the method for producing a PTFE sheet-like material of the present invention include the same ones as described above.

  In the method for producing a PTFE sheet of the present invention, for example, a molding material obtained by mixing PTFE particles and a lubricant in an arbitrary ratio is used as a female mold constituting the extrusion mold 3 shown in FIG. The tubular preform is discharged from the outlet of the material pressing flow path at the lower end of the extrusion mold 3 by pressing with the pressure rod 13 after being put into the inner space of the extrusion mold 3. The desired sheet 16 can be obtained by cutting in the axial direction (extrusion direction) 15.

In the method for producing a PTFE sheet of the present invention, the pressure applied to the molding material in the extrusion mold 3 for PTFE particle-containing material is preferably 30 to 500 kg / cm ² .

  Moreover, in the method for producing a PTFE sheet material of the present invention, as a method of cutting the obtained tubular material in the axial direction (extrusion direction) to form a sheet, one part of the tubular material is cut in the axial direction. The sheet may be opened to form a sheet, or the tubular material may be crushed and both ends thereof may be cut in the axial direction to form two sheets.

  Moreover, in the manufacturing method of the PTFE sheet-like material of the present invention, after cutting the tubular molded product, the cut product may be further rolled in the extrusion direction.

  The rolling treatment is preferably performed so that the thickness after rolling is 1/10 to 9/10 of the thickness before rolling, and the thickness after rolling is 2/10 to 7/10 of the thickness before rolling. It is more preferable to carry out.

  In the method for producing a PTFE sheet of the present invention, the lubricant is usually removed from the cut product thus obtained. The removal of the lubricant may be performed with the cut pieces as they are, or after the cut pieces are rolled with a pair of rolls and further thinned in order to increase the degree of alignment of PTFE particles. Good. The removal of the lubricant is preferably carried out by a conventional heating method or extraction method or a combination thereof.

  In the method for producing a PTFE sheet-like material of the present invention, a PTFE sheet-like material having a wide width and high thickness accuracy and having an arbitrary width and thickness can be obtained. In the method for producing a PTFE sheet material of the present invention, for example, a PTFE sheet material having a width of 150 to 2000 mm and a thickness of 1 to 25 mm can be obtained.

  In the method for producing a PTFE sheet of the present invention, an extrusion mold that can increase the ratio of the length of the cross-sectional area average circumference of the outlet portion / the length of the cross-sectional area average circumference of the narrowest portion is used during extrusion molding. Thus, the PTFE particles are highly uniformly oriented in the extrusion direction and in the direction perpendicular to the extrusion direction. For this reason, the PTFE sheet material obtained by the method for producing a PTFE sheet material of the present invention has a high strength in two directions because the PTFE resin raw material is oriented in two longitudinal and lateral directions of the sheet.

  Next, the manufacturing method of the PTFE porous sheet-like material of this invention is demonstrated.

  The method for producing a PTFE porous sheet-like material of the present invention uses the extruder for PTFE particle-containing material of the present invention to supply the PTFE particle-containing material to the internal space of the female mold constituting the extrusion mold, and press The tubular preform is discharged from the lower end of the material pressing flow path, and then the obtained tubular preform is cut in the axial direction, and then the obtained cut product is uniaxially stretched in the extrusion direction. Or a biaxial stretching process in a direction perpendicular to the extrusion direction and the extrusion direction.

  Examples of the PTFE particle-containing material extruder and the PTFE particle-containing material used in the method for producing a PTFE porous sheet according to the present invention include the same ones as described above, and also include PTFE particles. After the material is supplied and pressed, the specific aspect of cutting the obtained tubular preform in the axial direction is the same as that described in the description of the method for producing the PTFE sheet of the present invention. Can be mentioned.

  In the method for producing a porous PTFE sheet of the present invention, after cutting the tubular preform, the obtained PTFE sheet is uniaxially stretched in the extrusion direction, or is perpendicular to the extrusion direction and the extrusion direction. Biaxial stretching treatment in the direction.

  As a specific aspect of the method for producing the PTFE porous sheet material of the present invention, for example, in the extruder shown in FIG. 6, after obtaining the sheet material 16 by the method described above, the sheet material 16 is stretched. Examples thereof include a method in which the apparatus 17 performs a uniaxial stretching process in the extrusion direction or a biaxial stretching process in the extrusion direction and a direction perpendicular to the extrusion direction.

  Examples of the stretching treatment method include known methods.

  The area ratio of the stretching treatment is usually from 10 to 15000% and suitably from about 50 to 10000% based on the size of the PTFE sheet.

Porous PTFE sheet obtained by the process of the present invention is appropriate that a density of 0.05 to 1.0 g / cm ^3, more to be 0.1 to 0.5 g / cm ³ Is appropriate.

  In the method for producing a porous PTFE sheet of the present invention, the PTFE sheet to be stretched is oriented in the extrusion direction and in the direction perpendicular to the extrusion direction with respect to the PTFE particles, as described above. Since the treatment for highly uniform orientation is performed, the PTFE sheet-like material is oriented in two vertical and horizontal directions of the PTFE sheet and has high strength in both directions. For this reason, the PTFE sheet material is uniaxially stretched in the extrusion direction, so that the PTFE particles in the sheet are finely and highly highly fiberized, and as a result, the PTFE sheet becomes highly porous for stretching. Can be suitably performed.

  Moreover, it becomes possible to extend | stretch fully to a desired grade by performing biaxial extending | stretching process, ie, the extending | stretching process to the direction perpendicular | vertical to an extrusion direction, sequentially or simultaneously as needed.

  In the method for producing a PTFE porous sheet according to the present invention, a PTFE porous sheet having a desired dimension is easily produced from a PTFE sheet having a wide width and high thickness accuracy and having an arbitrary width and thickness. be able to.

  Next, a method for producing the PTFE sheet-like fired product of the present invention will be described.

  The method for producing a PTFE sheet-like fired product of the present invention uses the extruder for PTFE particle-containing material of the present invention to supply the polytetrafluoroethylene particle-containing material to the internal space of the female mold constituting the extrusion mold. The tubular preform is discharged from the lower end of the material pressing flow path by pressing, and then the obtained tubular preform is cut in the axial direction and then fired. is there.

  In the method for producing a PTFE sheet-like fired product of the present invention, examples of the PTFE particle-containing material extruder and the PTFE particle-containing material that can be used include the same ones as described above.

  Further, in the method for producing a PTFE sheet-like fired product of the present invention, the steps from supplying the PTFE particle-containing material to the PTFE particle-containing material extrusion molding machine and then cutting the tubular preform in the axial direction are the present invention. This is the same as the method for producing a PTFE sheet-like material, and is different from the invention for the method for producing a PTFE sheet-like material of the present invention only in that the obtained cut product is further subjected to a firing treatment.

  It is preferable that the heating temperature at the time of a baking process is 300-380 degreeC, and it is more preferable that it is 320-360 degreeC. The firing time is preferably 10 minutes to 24 hours. The firing atmosphere is not particularly limited and can be performed in air. The baking treatment can be performed using a known baking apparatus or the like.

  By the baking treatment, a PTFE sheet-like fired product having an improved tensile strength compared to the PTFE sheet-like material can be obtained. The PTFE sheet-like fired product obtained by the method of the present invention has, for example, a tensile strength in the direction perpendicular to the extrusion direction and the extrusion direction of 35 to 70 MPa.

  In the method for producing a PTFE sheet-like fired product of the present invention, a PTFE sheet-like fired product having a desired dimension can be easily produced from a PTFE sheet-like product having a wide and high thickness accuracy and having an arbitrary width and thickness. it can.

  Next, the manufacturing method of the PTFE porous sheet-like fired product of the present invention will be described.

  The method for producing a PTFE porous sheet-like fired product of the present invention uses the extruder for PTFE particle-containing material of the present invention to supply the PTFE particle-containing material to the internal space of the female mold constituting the extrusion mold, The tubular preform is discharged from the lower end of the material pressing channel by pressing, and then the obtained tubular preform is cut in the axial direction, and then further uniaxially stretched in the extrusion direction, or A biaxial stretching process is performed in a direction perpendicular to the extrusion direction and the extrusion direction, and a baking process is performed.

  Examples of the PTFE particle-containing material extrusion molding machine and the PTFE particle-containing material used in the method for producing a PTFE porous sheet-like fired material according to the present invention include the same methods as those for producing the PTFE sheet-like material according to the present invention. Can do.

  Further, in the method for producing a PTFE porous sheet-like fired product of the present invention, after the PTFE particle-containing material is supplied to the PTFE particle-containing material extrusion molding machine, the process until the tubular preform is cut in the axial direction, After the tubular preform is cut in the axial direction, the method for further uniaxial stretching treatment or biaxial stretching treatment is the same as the method for producing the PTFE porous sheet according to the present invention, and is uniaxial stretching treatment or biaxial stretching treatment. Only the point which carries out a baking process with a process is different from the manufacturing method of the PTFE porous sheet-like material of this invention.

  The firing treatment may be performed on the cut product of the tubular preform before performing the uniaxial stretching process or the biaxial stretching process, or the cut product of the tubular preform may be uniaxially stretched or biaxially stretched. It may be carried out after the cutting, or may be carried out at the same time while drawing a cut product of the tubular preform.

  It is preferable that the heating temperature at the time of a baking process is 300-380 degreeC, and it is more preferable that it is 320-360 degreeC. The firing time is preferably 10 minutes to 24 hours. The firing atmosphere is not particularly limited and can be performed in air. The baking treatment can be performed using a known baking apparatus or the like.

  In the method for producing a PTFE porous sheet-like fired product of the present invention, a PTFE porous sheet-like fired product having a desired dimension can be easily obtained from a PTFE sheet-like product having a wide width and high thickness accuracy and having an arbitrary width and thickness. Can be produced.

  Next, the PTFE sheet-like fired product of the present invention will be described.

  The PTFE sheet-like fired product of the present invention is characterized in that the tensile strength in the longitudinal direction and the direction perpendicular to the longitudinal direction is 35 to 70 MPa.

  The PTFE sheet-like fired product of the present invention can be produced by the method for producing a PTFE sheet-like fired product of the present invention. In the obtained PTFE sheet-like fired product, the tensile strength in the longitudinal direction and the direction perpendicular to the longitudinal direction are both 35 to 70 MPa. In the method for producing a PTFE sheet-like fired product of the present invention, a tubular preform After being cut in the axial direction, it may be rolled to a desired level and then fired.

  EXAMPLES Next, although an Example demonstrates this invention further, this invention is not limited at all by this Example.

(Example 1 to Example 3) (Production Example of PTFE Sheet)
Sheet-like materials were manufactured using three extrusion molds 14 having the apparatus configuration as shown in FIG.

  As shown in FIG. 4, the extrusion mold 14 has a female mold 1 having a constricted portion 51 and a male mold 3, and the upper end of the distal end portion 7 of the male mold 3 is used for manufacturing a sheet-like material. A sheet-like material was manufactured using three devices having different positions (the inner angle of the top of the tapered tip of the male mold 3 was 50 °).

  That is, the ratio of the length of the outlet cross-sectional area average circumference to the length of the narrowest cross-sectional area average circumference (the length of the outlet cross-sectional area average circumference / the length of the narrowest cross-sectional area average circumference) And an extrusion mold having a ratio of the length of the cross-sectional area average circumference of the exit portion to the length of the cross-sectional area average circumference of the narrowest part of 15.6 (Example 1). Example 2) and an extrusion molding machine each having an extrusion mold (Example 3) in which the ratio of the length of the cross-sectional area average circumference of the outlet portion to the length of the cross-sectional area average circumference of the narrowest part is 22.1 14 was used to produce a sheet.

  First, 83 parts by weight of PTFE fine powder (trade name “Fullon CD145”, manufactured by Asahi Glass Co., Ltd.) and 17 parts by weight of a lubricant (Isopar M, manufactured by ExxonMobil) were uniformly mixed to obtain a molding material. .

  As shown in FIG. 6, this molding material is put into the internal space of the female mold 1 constituting the extrusion mold and pressed with a pressing bar 13 to obtain a tubular preform, and this tubular The preform was cut in the axial direction (extrusion direction) with a cutter 15 to form a sheet, and the lubricant was removed by drying at 180 ° C. for 16 hours to obtain a PTFE sheet.

  Table 1 shows the width and thickness of the obtained sheet.

  Further, for the obtained PTFE sheet-like material, the tensile strength in the machine direction (extrusion direction) and the tensile strength and elongation in the transverse direction (direction perpendicular to the extrusion direction), and the ratio of the tensile strength in the machine direction and the transverse direction. Table 2 shows the results of measurement using a tensile strength tester (Tensilon, manufactured by Toyo Baldwin).

(Examples 4 to 5) (Production example of PTFE sheet-like fired product)
The sheet-like material obtained in Example 2 (the length of the outlet section cross-sectional area average circumference / the narrowest section cross-sectional area average circumference made of an extrusion mold having a length of 15.6) and Example 3 The sheet-like material obtained in the above (the length of the cross-sectional area average circumference of the outlet part / the length of the cross-sectional area average circumference of the narrowest part produced by an extrusion mold having a length of 22.1) is further 3 mm thick stainless steel. The steel plate (SUS plate) was sandwiched and held at 360 ° C. for 3 hours for firing treatment.

  Table 3 shows the width and thickness of the obtained PTFE sheet-like fired product.

  The obtained PTFE sheet-like fired product has a tensile strength in the machine direction (extrusion direction) and a tensile strength and elongation in the transverse direction (direction perpendicular to the extrusion direction), and the tensile strength in the machine direction and the transverse direction. Table 4 shows the results of measuring the ratio using a tensile strength tester (Tensilon, manufactured by Toyo Baldwin).

(Examples 6 to 7) (Production example of PTFE sheet-like fired product)
The sheet-like material obtained in Example 2 (the length of the outlet section cross-sectional area average circumference / the narrowest section cross-sectional area average circumference made of an extrusion mold having a length of 15.6) and Example 3 The sheet-like material obtained in the above (produced with an extrusion mold having an outlet cross-sectional area average circumference length / narrowest-section cross-sectional area average circumference length of 22.1) is further longitudinally (with a roll) After being rolled in the extrusion direction) to a thickness of about ¼, it was sandwiched between stainless steel plates (SUS plates) having a thickness of 3 mm and held at 360 ° C. for 3 hours for firing treatment.

  Table 5 shows the width and thickness of the obtained PTFE sheet-like fired product.

  The obtained PTFE sheet-like fired product has a tensile strength in the machine direction (extrusion direction) and a tensile strength and elongation in the transverse direction (direction perpendicular to the extrusion direction), and the tensile strength in the machine direction and the transverse direction. Table 6 shows the results obtained by measuring the ratio using a tensile strength tester (Tensilon, manufactured by Toyo Baldwin).

(Examples 8 to 10) (Production Examples of PTFE Porous Sheet and PTFE Porous Sheet Firing)
Sheet-like material obtained in Example 1 (produced with an extrusion mold having an outlet cross-sectional area average circumference length / the narrowest part cross-sectional area average circumference length of 7.6), Example 2 The sheet-like material obtained in the above (obtained with an extrusion mold having an outlet cross-sectional area average circumference length / the narrowest cross-sectional area average circumference length of 15.6) and obtained in Example 3 The sheet-like material (the length of the outlet section cross-sectional area average circumference / the narrowest section cross-sectional area average circumference made of an extrusion mold having a length of 22.1) is further longitudinally (extruded direction) with a roll. After being rolled to a thickness of about 1/4, the film was stretched 600% in the longitudinal direction (extrusion direction) and simultaneously fired at 340 ° C. to obtain a PTFE porous sheet-like fired product.

  When the PTFE porous sheet-like fired product was observed with a scanning electron microscope, it could be confirmed that it had a porous structure. Table 7 shows the width and thickness of the obtained PTFE sheet-like fired product.

  The obtained PTFE sheet-like fired product has a tensile strength in the machine direction (extrusion direction) and a tensile strength and elongation in the transverse direction (direction perpendicular to the extrusion direction), and the tensile strength in the machine direction and the transverse direction. Table 8 shows the results of measuring the ratio using a tensile strength tester (Tensilon, manufactured by Toyo Baldwin).

  According to the present invention, while maintaining the thickness accuracy of the obtained PTFE sheet at a practically sufficient level, the strength in the direction perpendicular to the extrusion direction is sufficiently improved, and the variation in stretching strength in the same direction is suppressed. In addition, it is possible to provide an extrusion mold for a PTFE particle-containing material capable of producing a wide PTFE sheet.

  Moreover, according to the present invention, the PTFE particle-containing material extrusion molding machine having the extrusion mold, the PTFE sheet-like production method using the extrusion machine, and the PTFE porous sheet-like production method A method for producing a PTFE sheet-like fired product, a method for producing a PTFE porous sheet-like product, and a PTFE sheet-like fired product can be provided.

DESCRIPTION OF SYMBOLS 1,101 Female mold 2,102 Male mold 3,103 Extrusion mold 4,104 Internal space 51,151 Constricted part 52 Tapered space 6 Cylindrical lower part 7 Tapered tip part 8 Tip part outer wall surface 9 Female mold inner wall surface 10 Axes 11, 111 Radial enlargement part 12 Tubular part 13 Press bar 14 Extruder 15 Cutter 16 Extrusion 17 Stretching device 100 Mandrel 108 Conical enlargement part

Claims (10)

An extrusion mold for polytetrafluoroethylene particle-containing material having a female mold and a male mold,
The female mold has a hollow internal space penetrating in the vertical direction, and a tapered space in which the vertical cross-sectional diameter with respect to the vertical direction is gradually reduced is formed in the middle part from the lower part to the upper part of the internal space. Become
The male mold has a cylindrical lower part, and a tapered tip part in which the vertical cross-sectional diameter with respect to the vertical direction from the cylindrical lower part to the upper part gradually decreases,
The male mold so that the male mold tip faces the upper part of the hollow internal space, and the male mold tip outer wall faces the female mold wall that forms the tapered space. Is arranged coaxially with the female mold at the lower part of the internal space of the female mold,
Provided between the female mold and the male mold is a material pressing flow path having a radially enlarged portion extending from the upper portion to the lower portion along the male tip portion and a tubular portion extending along the male cylindrical lower portion. An extrusion mold for polytetrafluoroethylene particle-containing material. In the narrowest part of the tapered space, the circumference that bisects the material inflow area formed in a direction perpendicular to the vertical direction of the tapered space is defined as the narrowest part cross-sectional area average circumference, and the material pressing When the circumference that bisects the material outlet area formed in the direction perpendicular to the vertical direction of the tapered space at the lower end of the flow path is defined as the outlet section cross-sectional area average circumference,
The extrusion mold for a polytetrafluoroethylene particle-containing material according to claim 1, wherein the ratio of the length of the cross-sectional area average circumference to the length of the cross-sectional area average circumference of the narrowest part is 5 or more.   3. The extrusion mold for polytetrafluoroethylene particle-containing material according to claim 1, wherein an inner angle of the top of the tapered tip portion is 80 ° or less in a horizontal section with respect to the vertical direction of the male mold.   An extrusion molding machine for polytetrafluoroethylene particle-containing material comprising the extrusion mold for polytetrafluoroethylene particle-containing material according to any one of claims 1 to 3. Using the polytetrafluoroethylene particle-containing material extruder according to claim 4,
By supplying and pressing the polytetrafluoroethylene particle-containing material into the internal space of the female mold constituting the extrusion mold, the tubular preform is discharged from the lower end of the material pressing flow path,
A method for producing a polytetrafluoroethylene sheet material, characterized in that a sheet material is produced by cutting the obtained tubular preform in the axial direction.   The method for producing a polytetrafluoroethylene sheet-like product according to claim 5, wherein after the tubular molded product is cut, a rolling process is further performed in the extrusion direction. Using the polytetrafluoroethylene particle-containing material extruder according to claim 4,
By supplying and pressing the polytetrafluoroethylene particle-containing material into the internal space of the female mold constituting the extrusion mold, the tubular preform is discharged from the lower end of the material pressing flow path,
After the obtained tubular preform is cut in the axial direction, it is further subjected to uniaxial stretching in the extrusion direction or biaxial stretching in the direction perpendicular to the extrusion direction and the extrusion direction. A method for producing a porous sheet. Using the polytetrafluoroethylene particle-containing material extruder according to claim 4,
By supplying and pressing the polytetrafluoroethylene particle-containing material into the internal space of the female mold constituting the extrusion mold, the tubular preform is discharged from the lower end of the material pressing flow path,
A method for producing a polytetrafluoroethylene sheet-like fired product, wherein the obtained tubular preform is cut in the axial direction and then fired. Using the polytetrafluoroethylene particle-containing material extruder according to claim 4,
By supplying and pressing the polytetrafluoroethylene particle-containing material into the internal space of the female mold constituting the extrusion mold, the tubular preform is discharged from the lower end of the material pressing flow path,
After the obtained tubular preform is cut in the axial direction, the obtained cut product is further uniaxially stretched in the extrusion direction or biaxially stretched in the direction perpendicular to the extrusion direction and the extrusion direction and fired. The manufacturing method of the polytetrafluoroethylene porous sheet-like baked product characterized by processing.   A polytetrafluoroethylene sheet-like fired product having a tensile strength in the longitudinal direction and a direction perpendicular to the longitudinal direction of 35 to 70 MPa.

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