JP5249524B2 - Method for producing polytetrafluoroethylene sheet - Google Patents

Description

  The present invention relates to a method for producing a PTFE sheet and a PTFE sealing tape, which uses a dispersion of polytetrafluoroethylene (PTFE) particles as a starting material.

  PTFE has characteristics such as high chemical resistance and low dielectric constant, and has a high melting point and excellent heat resistance. Therefore, it is used in a wide range of applications mainly in the chemical and electrical fields. Further, it is widely used for mechanical applications such as a member used for a non-lubricated sliding portion by utilizing a characteristic with a small coefficient of friction and surface tension.

  One type of PTFE molded body is a sheet-shaped molded body (PTFE sheet), which can be applied to various uses depending on its shape and thickness. For example, a strip-shaped PTFE sheet having a thickness of about several tens to several hundreds of μm is suitable for use as a seal tape for ensuring the sealability of a joint of a pipe such as a water pipe or a gas pipe. The seal tape is required to have a flexibility that can easily bite into the gap of the seam, and is required to serve as both a lubrication and a seal when biting into the gap of the seam. PTFE seal tapes (hereinafter also simply referred to as “PTFE seal tapes”) have such characteristics and functions, and are widely used as raw tapes and packing materials.

On the other hand, PTFE does not dissolve in most solvents except for special solvents, and its melt viscosity is as high as about 10 ¹⁰ to 10 ¹¹ Pa · s (10 ¹¹ to 10 ¹² P) at 380 ° C. For this reason, it is difficult to apply various molding methods (extrusion molding, injection molding, etc.) used for molding a general thermoplastic resin to manufacture a PTFE molded body. In these molding methods, the melt viscosity of the resin during molding is usually about 10 ² to 10 ³ Pa · s.

  One conventional method for producing a PTFE sheet is a method in which a sintering method and a cutting method are combined. In this method, first, powdery PTFE particles (molding powder) as a starting material are preformed at room temperature (a molding aid may be added if necessary), and then the formed preform is processed. The whole is sintered (fired) by heating to a melting point (about 327 ° C.) or higher of PTFE to obtain a cylindrical PTFE block (sinter molding method). Next, the outer peripheral part of the formed block is cut (cutting method), and a PTFE sheet is obtained. According to this method, a sheet having a relatively large thickness (for example, 25 μm or more) can be obtained, but in order to efficiently manufacture the sheet, it is necessary to increase the size of the block. In order to suppress the occurrence of cracks and the like, a long time (approximately 2 to 5 days, depending on the size of the block) is required for preforming and firing. Further, it is basically a batch production method, and it is difficult to continuously produce PTFE sheets from starting materials.

  One of the other methods for producing a PTFE sheet is a paste extrusion method (fine powder method), which is a common method for producing a PTFE seal tape. In this method, a molding aid is added to fine powder and preformed into a rod shape, and then the preform is paste-extruded by an extruder, rolled with a roll before the molding aid is volatilized, and has a predetermined thickness. This sheet. And a PTFE sealing tape is obtained by removing a shaping | molding adjuvant from this sheet | seat. However, the paste extrusion method has an environmental problem because it uses an organic solvent such as oil as a molding aid, and the process of preparing the preform and the process of extruding the preform are separated. Therefore, it becomes a batch production method, and problems remain in productivity.

  For example, Japanese Patent Application Laid-Open No. 5-301267 (Patent Document 1) discloses a method of performing paste extrusion using water as a molding aid. The method disclosed in Patent Document 1 is to remove water from a slurry containing PTFE agglomerates and water to make a paste suitable for extrusion, and perform extrusion using the paste. In order to reduce the amount of water contained in the slurry, the slurry is placed in a tube having a slit or gap whose shape and width are adjusted so as to allow passage of water but prohibit passage of PTFE agglomerates. Slowly pass through. An apparatus capable of realizing such an operation is not commercially available. Therefore, if the method disclosed in Document 1 is performed, an increase in capital investment is inevitable. In order to make a slurry containing PTFE aggregates and water from a dispersion of PTFE, a step of first aggregating PTFE is indispensable. This step can be realized, for example, by adding a coagulant such as an acid to the dispersion heated to a predetermined temperature, and further stirring the dispersion with a stirrer, but this is separate from the step of removing water from the slurry. This is a major obstacle to productivity improvement.

  There is a casting method as another method for producing the PTFE sheet. In this method, a dispersion of PTFE particles (PTFE dispersion) as a starting material is applied on a support such as a metal plate, dried and fired, and then peeled from the support to obtain a PTFE sheet. According to this method, a PTFE sheet that is thinner and has no distortion can be obtained as compared with the case where the above methods are used. However, the thickness of the sheet obtained by one application, drying and firing is limited to about 20 μm in order to suppress a minute defect called a mud crack, and in order to obtain a sheet having a thickness exceeding 20 μm. It is necessary to repeat the application and baking of the dispersion several times.

  Regarding the cutting method, paste extrusion method and casting method, and other methods for producing a PTFE molded product, for example, Non-Patent Document 1 (pages 122 to 124 for paste extrusion method, pages 141 to 142 for cutting method, casting method) 130)).

Although not a method for producing a PTFE molded product, secondary particles having a particle size larger than the particles (for example, for example, by applying mechanical force to a dispersion of PTFE particles or a dispersion of a fluorinated thermoplastic resin) Methods for producing PTFE fine powders are disclosed in JP-A-2002-201217 (Patent Document 2), JP-A-6-192321 (Patent Document 3) and JP-T 2003-522230 (Patent Document 4). Has been. JP-A-47-12332 discloses a method for producing PTFE secondary particles having a particle size larger than that of the particles by applying mechanical force after wetting the PTFE particles with an aqueous solution containing a surfactant. (Patent Document 5).
Japanese Patent Laid-Open No. 5-301267 JP 2002-201217 A JP-A-6-192321 Special table 2003-522230 gazette JP 47-12332 A "Fluorine resin handbook", edited by Takaomi Satokawa, published by Nikkan Kogyo Shimbun, 1990

  As described above, in the conventional technique, it is difficult to directly and continuously produce a PTFE sheet from a starting material containing PTFE particles, and there is a limit to improvement in productivity. Accordingly, an object of the present invention is to provide a PTFE sheet manufacturing method and a PTFE sealing tape manufacturing method that are more productive than these conventional methods and can reduce the production cost.

The method for producing a PTFE sheet of the present invention comprises: (i) applying a force that allows the particles to approach or contact each other to a PTFE dispersion containing PTFE particles, a surfactant, and water as a dispersion medium. A step of forming a PTFE-containing solid containing water and the surfactant; (ii) a step of deforming the solid into a sheet; and (iii) the solid contained in the solid transformed into a sheet and a step of reducing the amount of water seen including, supplying the dispersion to the chamber or tube, by spraying the interior of the chamber or the pipe body, is a method of applying the force in the chamber or tube body .
From another aspect, the method for producing a PTFE sheet according to the present invention includes (i) a force that allows the particles to approach or come into contact with a PTFE dispersion containing PTFE particles, a surfactant, and water as a dispersion medium. A step of forming a PTFE-containing solid containing the water and the surfactant, (ii) a step of deforming the solid into a sheet, and (iii) the shape of the solid transformed into a sheet Reducing the amount of water contained in a solid material, supplying the dispersion to a chamber or tube, applying the force in the chamber or tube, and the tube having a bent portion or a constricted portion. It is a method to have.
In another aspect of the method for producing a PTFE sheet of the present invention, (i) the particles approach or come into contact with a PTFE dispersion containing PTFE particles, a surfactant, and water as a dispersion medium. By applying force, a step of forming a PTFE-containing solid containing the water and the surfactant, (ii) a step of deforming the solid into a sheet, and (iii) deforming into a sheet Reducing the amount of water contained in the solid material, and forming the solid material having substantially the same mass as the dispersion to which the force is applied.
The method for producing a PTFE sheet of the present invention as seen from another aspect is as follows. (I) The particles approach or come into contact with a PTFE dispersion containing PTFE particles, a surfactant, and water as a dispersion medium. By applying force, a step of forming a PTFE-containing solid containing the water and the surfactant, (ii) a step of deforming the solid into a sheet, and (iii) deforming into a sheet A step of reducing the amount of water contained in the solid matter, and allowing the solid matter to be deformed into a sheet by passing it through a channel having a square or slit-like cross section.

  According to the present invention, a PTFE-containing solid material that can be formed into a sheet can be obtained directly from a dispersion of PTFE particles. That is, it is possible to continuously produce a PTFE sheet or a PTFE sealing tape from a dispersion liquid as a starting material. Therefore, the production method of the present invention is superior in productivity to the conventional method of producing a PTFE sheet, and it is not necessary to use an organic solvent as a molding aid, and the environmental load is small.

  In the production method of the present invention, a PTFE-containing solid material (hereinafter, also simply referred to as “solid material”) including water as a dispersion medium and a surfactant can be formed (step (i)). As apparent from the manufacturing method, this solid is an aggregate formed by binding PTFE particles. Such a solid cannot be obtained as an intermediate product in the conventional method for producing a PTFE molded product. For example, as in the production method of the present invention, in the casting method using a dispersion of PTFE particles as a starting material, water is removed by drying in a state where the PTFE particles are dispersed, so that water and a surfactant are included. A solid is not formed.

  The solid formed in the step (i) is formed by binding PTFE particles to such an extent that the applied shape is maintained (has self-shape retention), and the shape can be deformed (deformation). It is a solid substance that contains water to the extent that it has properties. This solid matter can basically be deformed into an arbitrary shape until it is dried or fired, and after being transformed into a sheet (step (ii)), the amount of water contained in the solid matter after transformation (Step (iii)), a PTFE sheet can be obtained. The solid material is also characterized by a large range that can be deformed without breaking.

  Such a solid cannot be obtained as an intermediate product even in the conventional method for producing secondary particles as disclosed in Patent Documents 2 to 5. In the methods disclosed in Patent Documents 2 to 4, although a mechanical force is applied to the dispersion liquid of fluorinated thermoplastic resin particles or the dispersion liquid of PTFE particles, which is a starting material, the solid matter is formed. No power is applied. In the method disclosed in Patent Document 5, the starting material is not even a dispersion of PTFE particles, and for this reason, of course, no force is applied to form the solid matter.

  For example, in the method of Patent Document 3, a solidified phase (concentrated slurry) that can be diluted with water is obtained (described in paragraph No. [0008] of Document 3), but the solid formed in step (i) Cannot be diluted with water. It can be said that the solid matter is formed by binding PTFE particles to such an extent that they do not disperse in water.

  Further, for example, in the methods of Patent Documents 2 to 4, a mechanical force (for example, a force for precipitating PTFE particles in a dispersion) is applied to a dispersion of fluorinated thermoplastic resin particles or a dispersion of PTFE particles. The particle aggregate is dried to obtain secondary particles. In the method of Patent Document 5, the PTFE particles are wetted with an aqueous solution containing a surfactant and then dried by applying mechanical force. To obtain secondary particles. On the other hand, even if the solid formed in step (i) is dried to remove water, it does not return to the particles again. It can be said that the solid matter is formed by binding the PTFE particles to each other to such an extent that repartitioning due to a decrease in the amount of water contained therein does not occur.

  The reason why such a solid can be obtained by the step (i) is not necessarily clear, but probably a structure in which the PTFE phase and the aqueous phase are mixed with each other is formed by the action of the surfactant in the dispersion. This is probably because of this. Although elucidation of the detailed structure of the solid material requires further investigation, a mechanism that the self-shape retention property of the solid material is manifested by the PTFE phase formed by joining the PTFE particles to each other to some extent is considered. . In some cases, a stronger binding structure may be formed between the PTFE particles, or a part of the PTFE particles may be fibrillated to form a PTFE network structure. In addition, a mechanism in which the deformability of the solid material is expressed by the presence of a stable aqueous phase via a surfactant between the hydrophobic PTFE phase is conceivable.

  Hereinafter, step (i), (ii) and (iii) will be described in detail.

In the step (i), a method for applying a force that allows the PTFE particles to approach or come into contact with each other in the dispersion is not particularly limited. For example, the following method may be used.
Method A: Method of supplying the dispersion liquid to the chamber and applying the force in the chamber Method B: Method of applying the force by spraying the dispersion liquid onto the target Method C: Dispersing the dispersion liquid The method of applying the said force by making it contact with the barrier which arrange | positions in the barrier which disturbs the flow of a dispersion liquid.

  In Method A, the pressure generated in the chamber as the dispersion is supplied can be used as a force for bringing the PTFE particles closer to or in contact with each other. Further, as will be described later, a tube body (first tube body) that discharges the solid material formed in the chamber, or a flow path (for example, a T-die) that deforms the solid material formed in the chamber into a sheet shape. ) Can be connected to the chamber.

  Specifically, in Method A, the dispersion liquid supplied to the chamber may be sprayed in the chamber (Method A1) or passed through a constriction provided in the chamber (Method A2).

  In the method A1, the dispersion may be sprayed, for example, toward the inner wall of the chamber or a member disposed in the chamber. When the dispersion collides with the inner wall or member, a force is applied so that the PTFE particles approach or come into contact with each other.

  In the method A1, the PTFE particles can collide with each other depending on the structure and shape of the chamber, the injection condition of the dispersion liquid, and the like. It is also possible to apply a force that causes the PTFE particles to approach or come into contact with each other by colliding the dispersion and the solid formed in the chamber. The dispersion is sprayed onto the solid formed in the chamber. As a result, solids are continuously formed.

  The dispersion liquid may be ejected from a nozzle having an ejection port, and the structure and shape of the nozzle, for example, the shape of the ejection port can be freely set.

  Similarly, in the method B, the dispersion may be ejected from a nozzle having an ejection port. In addition, although the target in the method B can be set freely, in order to suppress scattering of the injected dispersion liquid and increase the ratio of the amount of the obtained solid matter to the amount of the injected dispersion liquid, the target is disposed. A higher degree of sealing of the space is preferable.

  The injection pressure of the dispersion may be set freely depending on the content of PTFE particles in the dispersion, the content of the surfactant, the shape of the chamber, the internal volume, etc., but if the injection pressure is too low, It may be difficult to obtain.

  According to the knowledge of the present inventors, the formation of solids is started immediately by setting a relatively high injection pressure in the initial stage of injection, and once solids are generated in the chamber, lower injection is performed. Solid matter can be stably formed even under pressure. Thus, the spray pressure of the dispersion liquid can be made different between the time when the formation of the solid is started and the time when the solid is continuously generated after a certain time has elapsed from the start. Specifically, the former injection pressure can be increased and the latter injection pressure can be decreased, so that useless energy is not consumed. However, such a high injection pressure is not necessarily indispensable for formation of a solid substance.

  In the method A2, the shape of the constriction part through which the dispersion liquid passes is not particularly limited, and may be, for example, a slit shape. As the dispersion passes through the slit, a force is applied that causes the PTFE particles to approach or contact each other.

  The above-mentioned force may be applied to the dispersion liquid by supplying the dispersion liquid to the chamber via two or more supply paths and causing the dispersion liquid supplied from the two or more supply paths to collide with each other in the chamber. (Method A3). In the method A3, PTFE particles can be collided with each other depending on the structure and shape of the chamber, the colliding method, and the like.

  In order to cause the dispersion liquid to collide with each other in the chamber, for example, the dispersion liquid may be sprayed from a nozzle disposed at each end of the two or more supply paths. At this time, by disposing at least two nozzles in the chamber so that the respective injection directions intersect, the dispersions can collide with each other more efficiently.

  Also in the method A3, as in the above method, it is possible to apply a force such that the PTFE particles approach or come into contact with each other by colliding the dispersion and the solid matter formed in the chamber. For example, in the initial stage of forming a solid material, the dispersions ejected from two or more nozzles may collide with each other to promote the formation of the solid material. And once a solid substance is formed, you may spray a dispersion liquid toward the solid substance. By doing in this way, it can transfer to continuous production of a solid substance smoothly.

  In the method C, the dispersion may be supplied to, for example, a tubular body (second tubular body) having the barrier, and the above force may be applied in the tubular body. When the dispersion liquid passes through the barrier disposed in the flow path (second tube), the flow of the dispersion liquid is disturbed, or the dispersion liquid partially stays in the dispersion liquid. A pressure imbalance occurs and a force is applied that causes the PTFE particles to approach or contact each other.

  The barrier may be, for example, a plate-like member arranged to narrow the flow path inside the second tubular body. The barrier can also be formed by bending the second tube or partially reducing its inner diameter. That is, the barrier may be a bent portion or a narrowed portion of the second tubular body. In this case, Method C can be said to be a method in which the dispersion liquid is supplied to the second tubular body having the bent portion or the narrowed portion, and a force is applied so that the PTFE particles approach or come into contact with each other in the bent portion or the narrowed portion. .

  When supplying the dispersion liquid to the second tube body, the dispersion liquid may be supplied by being sprayed from a nozzle. In this case, the force can be efficiently applied to the PTFE particles. The nozzle used for spraying may be the same as in method A1, and the spray pressure of the dispersion liquid can be freely set depending on the content of PTFE particles in the dispersion, the content of surfactant, the shape of the second tubular body, and the like. That's fine.

  In Method C, the PTFE particles can collide with each other depending on the structure and shape of the second tubular body, the supply condition of the dispersion, and the like. It is also possible to apply a force that the PTFE particles approach or come into contact with each other by colliding the dispersion and the solid matter formed in the second tube.

  The shape, the inner diameter, the length of the second tubular body, the shapes of the bent portion and the narrowed portion, etc. are not particularly limited.

  Method A1 to A3, Method B, and Method C are examples of a method of applying a force for the PTFE particles contained in the dispersion to approach or contact each other to the dispersion of the PTFE particles. It is not limited to the case where the method shown in the example is used.

  The configuration of the chamber for applying the force to the dispersion liquid including the shape and the internal volume is not particularly limited, but a commercially available device (for example, an optimizer manufactured by Sugino Machine) may be applied. The optimizer is originally an atomizing / dispersing device that pulverizes and atomizes various materials such as pigments, fillers, and catalysts. The application for obtaining PTFE particle-containing solids was discovered by the present inventors. is there.

  An example of the chamber is shown in FIG. The chamber 1A shown in FIG. 1 has a substantially conical shape in which the inner space 2 is cut off at the periphery near the bottom surface, and a pair of nozzles 3a and 3b for injecting a dispersion liquid are provided on the periphery. The injection port is arranged so as to face the internal space 2. The nozzles 3a and 3b are in a positional relationship where the respective injection directions 4a and 4b intersect each other. The dispersion liquid can be supplied from the supply port 7 to the nozzles 3a and 3b via supply paths 6a and 6b formed inside the structure 5 of the chamber 1A. In the vicinity of the apex of the substantially conical internal space 2, a discharge port 8 is formed for discharging solid matter formed in the chamber 1 </ b> A (inside the internal space 2). The shape of the discharge port 8 is not particularly limited, and may be, for example, a circular shape.

  In the chamber 1A shown in FIG. 1, the pressurized dispersion liquid is supplied to the nozzles 3a and 3b via the supply port 7 and the supply paths 6a and 6b, so that the dispersion liquid is injected into the internal space 2 and collides with each other. (Method A3 can be realized). In addition, by using the chamber 1A having the same structure, the number of nozzles to be arranged is one, or by controlling the injection directions 4a and 4b of the nozzles 3a and 3b, the dispersion liquid is injected into the internal space 2, It can be made to collide with the inner wall (wall surface of the inner space 2) of the chamber 1A (method A1 can be realized). It is preferable that the injection directions of the nozzles 3a and 3b are variable because such operations can be performed freely.

  The chamber 1A may have a structure that allows the internal space 2 to be a pressurized atmosphere. That is, the chamber 1A may be capable of forming a solid in an atmosphere at a pressure higher than atmospheric pressure. For this purpose, for example, a pressure adjusting mechanism for adjusting the pressure in the internal space 2 may be provided in the chamber 1A. By pressurizing the inside of the chamber 1A, the force that the PTFE particles approach or come into contact with each other can be more efficiently applied to the dispersion. Even when the pressure adjusting mechanism is not provided, the cross-sectional area of the discharge port 8 and the length and number of pipes connected to the discharge port 8 are appropriately adjusted, and the dispersion liquid from the nozzles 3a and 3b is adjusted. If the injection pressure is used, the inside of the chamber 1A can be made a pressurized atmosphere. The same applies to chambers 1B to 1E shown in FIGS.

  A method for supplying the pressurized dispersion liquid to the nozzles 3 a and 3 b is not particularly limited. For example, the dispersion liquid pressurized by a high-pressure pump may be supplied from the supply port 7. Using the chamber 1B as shown in FIG. 2, the dispersion and the water pressurized by the pump (pressurized water) are supplied to the mixing valve 9 provided immediately before the nozzles 3a and 3b via mutually different supply paths. And after mixing both with the mixing valve 9, you may supply to nozzle 3a, 3b. In the chamber 1B shown in FIG. 2, the pressurized water is supplied to the mixing valve 9 via the supply port 7 and the supply paths 6a and 6b, and the dispersion is supplied to the mixing valve 9 via the supply ports 17a and 17b and the supply paths 16a and 16b. .

  Another example of the chamber is shown in FIG. In the chamber 1C shown in FIG. 3, a freely rotatable sphere 10 is disposed at one end of the internal space 2, and a nozzle 3 for injecting the dispersion liquid is disposed at the other end thereof. Are arranged so as to face the internal space 2. The nozzle 3 and the sphere 10 are in a positional relationship where the injection direction 4 of the nozzle 3 intersects the sphere 10. The dispersion liquid can be supplied to the nozzle 3 from the supply port 7 via the supply path 6 formed inside the structure 5 of the chamber 1C. On the wall surface between the nozzle 3 and the sphere 10 in the internal space 2, a discharge port 8 is formed for discharging solid matter formed in the chamber 1 (inside the internal space 2).

  In the chamber 1C shown in FIG. 3, by supplying the pressurized dispersion liquid to the nozzle 3 via the supply port 7 and the supply path 6, the dispersion liquid is sprayed into the internal space 2 and arranged in the chamber 1C. It can be made to collide with the spherical body 10 which is the member (method A1 is realizable). At this time, by disposing the nozzle 3 and the sphere 10 so that the injection direction 4 of the nozzle 3 deviates from the center of the sphere 10, the sphere 10 can be rotated by the dispersion liquid injection, and the chamber 1C due to the collision of the dispersion liquid Internal wear can be suppressed.

  The sphere 10 is preferably made of a material that does not deform due to the collision of the dispersion liquid. For example, the sphere 10 may be made of ceramic, metal (preferably alloys having high hardness), diamond, or the like.

  Another example of the chamber is shown in FIG. In the chamber 1 </ b> D shown in FIG. 4, a pair of cores 12 a and 12 b are accommodated inside a cylindrical outer peripheral body 11. Each of the cores 12a and 12b has a shape in which a truncated cone is joined to one end surface of the cylindrical body, and the upper surfaces 13a and 13b of the truncated cones in each of the cores are spaced apart by a certain distance d. It arrange | positions so that it may mutually oppose. The central axes of the outer peripheral body 11 and the cores 12a and 12b are substantially the same. A supply port 7 for supplying the dispersion liquid is formed at one end of the outer peripheral body 11. The outer diameter of the core 12 a close to the supply port 7 is smaller than the inner diameter of the outer peripheral body 11 and is far from the supply port 7. The outer diameter of the child 12 b is the same as the inner diameter of the outer peripheral body 11. Further, the core 12 b is formed with a discharge path 14 that passes from the center of the upper surface 13 b to the inside of the core 12 b and communicates with the outside of the chamber 1. The core 12a is supported by the outer peripheral body 11 via a support member (not shown).

  By adjusting the positions of the cores 12a and 12b and appropriately controlling the value of the distance d, the gap 15 between the upper surfaces 13a and 13b can be made into a slit-like constriction, and a pressurized dispersion liquid is supplied. By supplying to the chamber 1D from the port 7, the dispersion liquid can be passed through the narrowed portion (gap 15) disposed in the chamber (method A2 can be realized). The dispersion liquid passes through the gap 15 and then flows into the discharge path 14 and is discharged from the discharge port 8 of the chamber 1 as PTFE-containing solid matter.

  The pressure of the dispersion to be supplied (supply pressure) may be freely set depending on the shape and inner volume of the chamber, the size of the interval d, the amount of the dispersion to be supplied, etc. If the supply pressure is too low, It may be difficult to obtain things.

  In the chambers 1A to 1D shown in FIGS. 1 to 4, a tube (first tube) is connected to the discharge port 8, and solid matter is brought into contact with the entire inner wall of the tube from the connected tube. It is preferable to discharge. When the solid matter discharged from the discharge port 8 passes through the first tubular body, it is possible to further apply a force for approaching or contacting the PTFE particles with each other. A solid having improved properties can be obtained.

  Further, from such a solid material, a PTFE sheet with improved mechanical properties such as strength can be formed. For example, by selecting the shape, inner diameter, length, etc. of the first tube, the MD after drying A PTFE sheet having a tensile strength in the direction (flow direction: in this case, the direction of discharging from the tube) of about 0.5 MPa or more and a tensile strength in the TD direction of about 1 MPa or more can be obtained. As a cause of improving the strength of the solid material and the sheet, it is considered that a skin layer in which the PTFE particles are more firmly bonded to each other is formed on the surface of the solid material and the sheet by the passage of the first tubular body. It is also conceivable that a shearing force is generated inside the solid due to the frictional force generated between the first tubular body and the surface of the solid, and further binding and joining of the PTFE particles are promoted. In order to discharge the solid matter while making contact with the entire inner wall of the tube, the shape and diameter of the discharge port 8, the shape, inner diameter, length, and the like of the tube may be selected.

  The shape, inner diameter, length, and the like of the first tubular body to be connected are not particularly limited, and can be freely set according to the shape and inner volume of the chamber 1, the amount of the dispersion liquid supplied to the chamber 1, and the like. Basically, the longer the tubular body, the better the self-shape retention property and mechanical properties of the obtained solid matter tend to be improved. Therefore, it is preferable that the length of the tubular body is larger than the minimum inner diameter of the tubular body. As an example, when the processing speed of the dispersion is about 0.1 to 0.5 L / min, the inner diameter of the tube connected to the chambers 1A to 1D is in the range of about 1 mm to 10 mm, and the length of the tube is 1 mm to 5000 mm. A range of the degree may be used. In the chamber 1 </ b> D shown in FIG. 4, depending on the shape of the discharge path 14, the discharge path 14 can also serve as the tube body.

  In order to apply force to the solid more efficiently, it is preferable that the minimum inner diameter of the first tubular body is equal to or smaller than the diameter of the discharge port 8. Further, it may be a tubular body whose inner diameter gradually changes as it moves away from the discharge port 8 (that is, the inner surface is tapered). In this case, it is preferable that the inner diameter gradually decreases as it moves away from the discharge port 8.

  Another example of the chamber is shown in FIG. A chamber 1E shown in FIG. 5 includes a structure 5 (chamber body) in which the nozzle 3 is disposed, and a pipe 18 having one end connected to the structure 5 and the other end forming a discharge port 8 for the dispersion. I have. The pipe 18 can be a bent pipe 18 (specifically, an L-shaped pipe). The ejection direction 4 of the nozzle 3 is adjusted so that the dispersion liquid ejected from the nozzle collides with the inner wall surface of the bent tube 18, more specifically, the inner wall surface of the bent portion 18 a of the bent tube 18.

  As shown in FIG. 6, by injecting the dispersion liquid P into the bent portion 18a of the bent tube 18, the production of the solid material 19 starts in the bent portion 18a (step S1). Then, by continuing to inject the dispersion P onto the solid 19 that has started to be generated at the bent portion 18a, the solid 19 gradually grows and fills the inside of the bent tube 18 (step S2). Eventually, the solid 19 is discharged from the outlet 8 of the bent tube 18 to the outside of the chamber 1E (step S3).

  The injection direction 4 of the nozzle 3 is not limited to the above. For example, the injection direction of the nozzle 3 may be adjusted so that the injected dispersion liquid collides with the inner wall surface 5p of the structure 5. In that case, the inner wall surface 5p of the structure 5 is preferably a tapered surface that is smoothly inclined toward the connection portion between the nozzle 3 and the structure 5. By doing in this way, the solid substance formed in the structure 5 can be smoothly moved to the bent tube 18.

  The temperature of the chambers 1A to 1E described in FIGS. 1 to 5 and the temperature of the dispersion liquid supplied to the chambers 1A to 1E (treatment temperature) are usually in the range of 0 ° C. to 100 ° C. The range of 80 ° C is preferable, and the range of 25 ° C to 50 ° C is more preferable. In order to keep the processing temperature within the above temperature range, the chambers 1A to 1E may be provided with a cooling mechanism or a heating mechanism as necessary. In particular, in the case of a chamber for injecting the dispersion liquid into the internal space 2, it is preferable to provide a cooling mechanism because the temperature of the system rises due to the injection.

  In step (i), a solid can be continuously obtained by continuously applying the above force to the dispersion. That is, solids can be formed not by batch production but by continuous production. For example, the dispersion may be continuously supplied to the chambers 1A to 1E shown in FIGS. 1 to 5 and the solid matter may be continuously discharged from the chambers. Further, for example, the dispersion may be continuously supplied to the second tube used in Method C, and the solid matter may be continuously discharged from the tube.

  In this case, if the chamber or tube has a structure other than the supply port and the discharge port, there is no opening through which substances enter and exit, and the mass of the dispersion supplied to the chamber or tube and the chamber or tube are discharged from the chamber or tube. The mass of the PTFE-containing solid material can be made substantially the same. In such an initial stage of continuous production, liquid may be discharged from the chamber or the like, probably because sufficient force is not applied to the dispersion. However, once the initial stage is reached and a stable state in which a sufficient force is applied to the dispersion is achieved, the entire amount of the dispersion is then changed to a PTFE-containing solid. Thereafter, except for a small amount of water lost by evaporation from the discharged PTFE-containing solid material, the supplied dispersion and the obtained PTFE-containing solid material have the same mass. As described above, according to the production method of the present invention, substantially all of the liquid phase raw material (dispersion) containing the solid content can be changed to a solid phase single phase intermediate (PTFE-containing solid). it can.

  The solid material obtained by the step (i), for example, the solid material discharged from the discharge port 8 shown in FIGS. 1 to 5 or the second tubular body used in the method C can be deformed. The shape of deformation and the method of deforming the solid are not particularly limited, and for example, a string-like solid is obtained by passing the first tubular body, and a sheet-like solid is obtained by passing the slit. be able to. Alternatively, the solid material may be passed through various dies (die) used for extrusion molding, and by selecting the shape of the die, it is possible to obtain a solid material having various shapes such as a string shape and a sheet shape. it can. For example, the solid material deformed into a string shape or a sheet shape may be further deformed by stretching, rolling, or the like.

  According to step (i), the degree of freedom of the shape of the obtained solid can be increased, for example, the minimum thickness of the obtained solid is 20 μm or more, depending on the production conditions, exceeds 20 μm, 1 mm or more, or It can be 2 cm or more. Conversely, the maximum thickness of the obtained solid material can be 5 cm or less. In addition, the thickness of a solid substance shows the diameter, for example, when a solid substance is a string form, and the thickness when a solid substance is a sheet form.

  The minimum thickness and the maximum thickness of the obtained solid matter are the diameter of the discharge port 8, the (minimum) inner diameter of the first tube connected to the discharge port 8, the (minimum) inner diameter of the second tube, It can be controlled by selecting a die shape or the like for deforming the solid material. For example, by connecting a first tubular body having a minimum inner diameter exceeding 20 μm to the discharge port 8, a solid material having a maximum thickness (maximum diameter) exceeding 20 μm can be obtained.

  In step (ii) in the production method of the present invention, the PTFE-containing solid material is deformed into a sheet shape. The method for transforming the solid material into a sheet shape is not particularly limited, and for example, the solid material may be transformed into a sheet shape by passing it through a channel having a square or slit-like cross section. In this case, a sheet-like solid having a cross-sectional shape corresponding to the cross-sectional shape of the flow path (hereinafter also referred to as “sheet-like solid”) can be obtained. Here, the cross-sectional shape of the flow path means a cross section in a direction orthogonal to the traveling direction of the solid matter.

  The cross-sectional shape of the flow path is not particularly limited as long as it is a square shape or a slit shape, and may be appropriately set according to the width and thickness of the PTFE sheet to be finally obtained. Moreover, as long as a sheet-like solid is obtained by passage through the flow path, a portion whose cross-sectional shape is not square or slit-like may exist in the middle of the flow path. Moreover, the method of deform | transforming into a sheet form by rolling solid substance, such as letting a solid substance pass between 1 or more pairs of rotating rolls, can also be employ | adopted suitably.

  A slit die (T die) can be used as a specific means for obtaining a sheet-like solid. In this case, the solid material formed in the step (i) may be transformed into a sheet shape by passing through the slit die as the flow path.

  FIG. 7 is a schematic diagram of a PTFE sheet manufacturing apparatus in which a die for deforming a solid material into a sheet is mounted in a chamber. The PTFE sheet manufacturing apparatus 100 includes the chamber 1E described with reference to FIG. 5 and a slit die 20 attached to the discharge port 8 of the chamber 1E. Instead of the chamber 1E, the chambers 1A to 1D described with reference to FIGS. 1 to 4 may be employed. When the chambers 1A to 1D are employed, the slit die 20 may be directly connected to the chamber, or the chamber and the slit die 20 may be connected via a relay member such as a pipe.

  According to the apparatus 100 shown in FIG. 7, the solid material formed by the bent tube 18 (or the structure 5) of the chamber 1 </ b> E is sent to the slit die 20 (T die) via the discharge port 8. The solid material that has passed through the slit die 20 is deformed into a sheet shape. The sheet-like solid material thus obtained is excellent in mechanical properties such as strength and easy to handle. Therefore, the conveyance can be automated, and the mechanical properties when this sheet-like solid is dried to obtain a PTFE sheet are excellent. The reason why the strength of the sheet-like solid material is improved is not necessarily clear, but when passing through the bending tube 18 or the slit die 20, a shearing force acts on the solid material, and the PTFE particles are more firmly bonded to the surface of the solid material. This is probably because a bonded skin layer is formed or because deformation or fibrillation is promoted between the PTFE particles due to deformation.

  In addition, according to the manufacturing method using the apparatus 100 of FIG. 7, the solids are immediately deformed into a sheet while the solids are formed by continuously applying the force that the PTFE particles approach or contact each other to the dispersion. Can be made. That is, not a batch production method but a continuous production method. Further, depending on the configuration of the chamber 1E and / or the slit die 20, the mass of the dispersion supplied to the chamber 1E and the mass of the sheet-like solid matter discharged from the slit die 20 are made substantially the same. Can do.

  The slit die may be connected to the second tube used in Method C.

  That is, in step (ii), the solid material formed in step (i) is transformed into a sheet by passing it through a channel having a square or slit-like cross section connected to a chamber or a tubular body. May be.

  At this time, depending on the configuration of the chamber or pipe body and the flow path, the dispersion can be continuously supplied to the chamber or the pipe body, and the solid material deformed into a sheet can be continuously discharged from the flow path. In some cases, solids having substantially the same mass as the dispersion supplied to the chamber or tube can be discharged from the flow path.

  In the step (iii), the method for reducing the amount of water contained in the sheet-like solid is not particularly limited, and for example, the sheet-like solid may be dried. Examples of the drying method include heat drying and air drying. When the sheet-like solid is dried by heat drying, the conditions may be appropriately set according to the thickness of the sheet-like solid. For example, the temperature of the sheet-like solid is raised to about 50 ° C to 200 ° C. What is necessary is just to hold | maintain several seconds-about 1 hour.

  The PTFE sheet obtained through the step (iii) (drying step) may be used as it is as a final product, or after the drying step, steps such as rolling and stretching may be further performed as necessary. That is, the step of rolling and / or stretching the sheet-like solid material with reduced water content may be further performed after step (iii).

  The rolling process is a process in which a PTFE sheet is passed between a pair of rotating rolls and formed into a predetermined thickness. The stretching process is a process of stretching the PTFE sheet in a uniaxial direction or a biaxial direction at a predetermined magnification. Both processes are processes for adjusting the PTFE sheet obtained through the drying process to the specifications required for the final product (for example, thickness, apparent density, mechanical strength, etc.), and are performed simultaneously with the drying process. You can also

  Moreover, you may bake by heating the PTFE sheet which passed through the drying process or the process of rolling and / or extending | stretching to the temperature beyond melting | fusing point of PTFE as needed. That is, you may further implement the process of baking the sheet-like solid substance in which content of water was reduced after process (iii). Similarly to the rolling and stretching steps, the firing step is a step of adjusting the PTFE sheet obtained through the drying step to have specifications required as a final product.

  The specific method of the firing step is not particularly limited. For example, the temperature of the melting point of PTFE or higher (about 327 ° C. to 400 ° C., preferably 360 ° C.) while moving the sheet-like solid material after the drying step in the electric furnace. (C ° -380 ° C.). What is necessary is just to set the temperature and time of a heating suitably according to the thickness etc. of a sheet-like solid substance.

  According to the production method of the present invention, for example, a PTFE sheet having a minimum thickness of 20 μm or more, exceeding 20 μm, or 1 mm or more, or 2 cm or more depending on the production conditions of the solid in step (i). it can.

  In the production method of the present invention, the PTFE sheet obtained by steps (i) to (iii) may be a PTFE seal tape. In order to obtain the seal tape, for example, in the step (ii), the solid material may be deformed into a shape necessary for the seal tape (for example, a strip shape or a thickness suitable for the seal tape). Further, for example, after step (iii), a rolling and / or stretching step or a shape processing step may be performed so as to obtain a shape necessary as a seal tape. In step (ii), in order to deform the solid material so as to have a shape necessary as a seal tape, for example, the slit width of the slit die 20 shown in FIG. 7 may be adjusted.

  According to the method of the present invention, a PTFE seal tape having a thickness of, for example, 0.05 mm to 10 mm (preferably 0.08 mm to 5 mm) can be manufactured with high productivity. When performing a rolling process or a drawing process after the process (iii), a thickness of 0.2 mm to 20 mm (preferably in the process (ii) so as not to cause insufficient thickness of the PTFE seal tape to be produced) You may prepare the sheet-like solid substance of 0.5 mm-10 mm).

  The PTFE dispersion which is a starting material in the production method of the present invention will be described.

  The content of PTFE particles in the dispersion is not particularly limited, but in order to obtain a solid having an excellent balance between self-shape retention and deformability, for example, the lower limit may be 40% by mass or more, and 40% by mass. %, More preferably more than 45% by mass, and even more preferably in the order of 50% by mass or more and 55% by mass or more. Moreover, the upper limit of the content rate of the PTFE particles in the dispersion may be, for example, 70% by mass or less, and more preferably 65% by mass or less, for the same reason as described above. Although depending on the method and conditions for applying force to the dispersion, basically, as the content of PTFE particles in the dispersion increases, the self-shape retention of the resulting solid improves, and the content of PTFE particles As the value becomes smaller, the deformability of the obtained solid matter tends to be improved.

  When the PTFE seal tape is formed by the production method of the present invention, the content of PTFE particles in the dispersion is preferably in the range of 40% by mass to 70% by mass from the viewpoint of the apparent density when the seal tape is formed. The range of mass% to 65 mass% is more preferable, and the range of 55 mass% to 65 mass% is more preferable.

  The average particle size of the PTFE particles is usually in the range of 0.05 μm to 40 μm, preferably in the range of 0.05 μm to 4 μm, more preferably in the range of 0.1 to 1 μm, and further in the range of 0.2 μm to 1 μm. preferable.

  The content of the surfactant in the dispersion is not particularly limited, but is preferably in the range of 0.01% by mass to 15% by mass in order to obtain a solid having an excellent balance between self-shape retention and deformability. More preferably in the order of 0.1 mass% to 10 mass%, 1 mass% to 9 mass%, 1.5 mass% to 9 mass%, and 2 mass% to 7 mass%. If the content of the surfactant is within a preferable range, it becomes easy to obtain a PTFE-containing solid while suppressing the separation of the PTFE phase and the aqueous phase.

  The type of the surfactant is not particularly limited. For example, an anionic surfactant such as a carboxylate having a hydrocarbon skeleton, a nonionic surfactant such as a fluorosurfactant, a silicone surfactant, and the like. Use it. From the viewpoint of the stability of the dispersion, it is preferable to use a nonionic surfactant such as polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether, polyoxyethylene glyceride, polyoxyethylene alkylphenyl ether.

  When a surfactant that decomposes at a temperature near the melting point of PTFE is used, the surfactant is decomposed when the obtained solid is fired, and the amount of surfactant remaining in the PTFE sheet after the firing process is determined. Can be reduced.

  A commercially available PTFE dispersion may be used as the dispersion. Commercially available PTFE dispersions include, for example, AD series such as AD938, AD911, AD912, AD1, AD639, and AD936 manufactured by Asahi Glass Co. (former: Asahi Glass Fluoropolymers), D1, D2, D3 manufactured by Daikin Industries, Ltd. A series may be used. These commercially available PTFE dispersions usually contain a surfactant.

  The dispersion may contain substances other than PTFE particles, water, and a surfactant, for example, a filler. When the dispersion contains a filler, a PTFE sheet in which the filler is dispersed can be obtained by drying the sheet-like solid.

  The kind of filler is not specifically limited, For example, a powder form or a fibrous thing can be used, An inorganic substance may be sufficient and an organic substance may be sufficient. In general, inorganic materials such as glass, carbon, metal, and ceramic are often used. For example, as an example of characteristics required for PTFE seal tape, there are electrical conductivity and thermal conductivity. From the viewpoint of improving the electrical conductivity of the seal tape to be formed, carbon black, carbon fiber, graphite powder, etc. It is preferable to add conductive carbon to the dispersion, and from the viewpoint of improving thermal conductivity, for example, boron nitride or the like is preferably added to the dispersion.

  When the dispersion includes a filler, it is preferable to uniformly disperse the filler in the dispersion in advance. When the chamber 1B shown in FIG. 2 is used, the dispersion liquid and water in which the filler is dispersed may be mixed in the mixing valve 9.

  The filler content in the dispersion is usually 50% by mass or less, preferably 30% by mass or less. If the filler content is excessive, it may be difficult to form a solid.

  As described above, according to the production method of the present invention, a PTFE sheet or a PTFE seal tape can be obtained continuously without requiring any pretreatment such as coagulating powder from the PTFE dispersion. Therefore, the production method of the present invention is more excellent in productivity than the conventional production method based on the batch method. Further, since continuous production is possible, a long PTFE sheet or PTFE seal tape can be easily produced. Moreover, since the manufacturing method of this invention can be implemented with a very simple apparatus, it is possible to significantly reduce the facility cost as compared with the prior art.

  Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to the examples shown below.

Example 1
In Example 1, the dispersion is a commercially available PTFE dispersion, AD938 manufactured by Asahi Glass Co., Ltd. (PTFE particle content: 60 mass%, surfactant content: 3 mass%, PTFE particle average particle size: 0.3 μm) A sheet-like solid was formed using the chamber 1A shown in FIG. 1, and the formed solid was dried and fired to produce a PTFE sheet.

The volume of the internal space 2 of the chamber 1A (the internal volume of the chamber 1A) was 200 cm ^3, and a pair of nozzles 3a and 3b having circular injection ports (0.25 mmφ) were arranged in the chamber. The nozzle 3a, 3b was arrange | positioned so that the injection direction 4a, 4b of each nozzle may cross | intersect in the part in which the injection opening in the front-end | tip of a nozzle was formed. A tube body (first tube body) having an inner diameter of 10 mm and a length of 1000 mm having a circular cross section was connected to the discharge port 8 (circular, diameter 10 mm).

  The dispersion liquid was supplied to such a chamber 1A, the injection pressure was set to 200 MPa, and the dispersion liquid was injected from the nozzles 3a and 3b. The amount of the dispersion supplied was about 3 L / min, the temperature of the dispersion supplied to the chamber 1A (treatment temperature) was 25 ° C., and the chamber 1A was not particularly heated.

  A few seconds after the injection, the string-like (columnar) PTFE-containing solid matter is discharged from the tip of the tube, and the discharged solid matter contains water and a surfactant and is not supported by the support itself. It was possible to keep the shape of.

  Subsequently, a T die (die width 320 μm) for forming a solid material into a sheet shape is connected to the end surface of the tubular body opposite to the end surface connected to the discharge port 8. The dispersion was sprayed from 3a and 3b. The dispersion liquid is continuously supplied to the chamber 1A, and an aluminum foil is disposed under the discharge port of the T die as a support that continuously receives the sheet-like solid material discharged from the die. Was moved at a speed of 2 m / min.

  A few seconds after the injection, a solid material (width 5 cm, thickness 500 μm) formed into a sheet shape is continuously discharged from the die onto the aluminum foil, and the discharged solid material contains water and a surfactant. In addition, it was possible to maintain its own shape without the aluminum foil as a support. Subsequently, the obtained solid was dried at 90 ° C. for 15 minutes and then baked at 370 ° C. for 10 minutes. As a result, a PTFE sheet having a uniform thickness without occurrence of cracks (thickness 350 μm) was gotten.

  The same test was conducted with the nozzle orifice diameter in the range of 0.05 mmφ to 0.5 mmφ, the injection pressure in the range of 100 MPa to 300 MPa, and the dispersion supply amount in the range of 0.3 L / min to 30 L / min. The same PTFE sheet could be produced by changing each of them.

(Reference Example 1)
In Reference Example 1, AD938 manufactured by Asahi Glass Co., Ltd. was used as the dispersion, a string-like solid was formed using the chamber 1D shown in FIG. 4, the formed solid was dried and fired, and a string-like PTFE molded product was obtained. Was made.

The internal volume of the chamber 1D was 200 cm ^3, and the interval d between the slit-like narrow portions was adjusted to 0.1 mm by adjusting the positions of the cores 12a and 12b. A tube body (first tube body) having an inner diameter of 1.6 mm and a length of 200 mm having a circular cross section was connected to the discharge port 8 (circular, diameter: 10 mm).

  The dispersion liquid pressurized to 245 MPa was supplied to such a chamber 1D. The supply amount of the dispersion was about 0.5 L / min, the temperature was 25 ° C., and the chamber 1 was not particularly heated.

  A few seconds after the start of the supply of the dispersion, a string-like (columnar) PTFE-containing solid is discharged from the tip of the tube, and the discharged solid contains water and a surfactant. It was possible to keep its own shape without support by.

  Subsequently, the obtained solid was dried at 90 ° C. for 30 minutes and then baked at 370 ° C. for 20 minutes. As a result, a string-like (columnar) PTFE molded body (diameter 1 having no cracks) was generated. 0.7 mm) was obtained.

  The same test was performed by changing the supply pressure of the dispersion liquid in the range of 100 MPa to 300 MPa and the interval d in the range of 1 μm to 1 mm. As a result, similar PTFE molded bodies could be produced.

(Reference Example 2)
In Reference Example 2, Asahi Glass Co., Ltd. AD938 was used for the dispersion, and a string-like PTFE solid was formed using the tube (second tube) 21 shown in FIG. The tube body 21 has an L-shaped bent portion 23 in the vicinity of one end portion 22 as a barrier that hinders the flow of the dispersion liquid. The inner diameter of the tube body 21 was 10 mm, the length was 200 mm, and the position of the bent portion 23 was 30 mm from one end 22 of the tube body 21.

  Such a tube body 21 and a nozzle 25 (having a circular injection port (0.15 mmφ)) arranged at the end of the dispersion liquid supply path 26 are disposed on the central axis of the tube body 21. Then, after arranging each other so that the distance between the other end 24 of the tube 21 and the nozzle 25 is 5 mm (see FIG. 8), the spray pressure is set to 160 MPa, and the dispersion liquid is supplied from the nozzle 25 to the inside of the tube 21. Was sprayed. The amount of the dispersion supplied to the nozzle 25 was about 0.5 L / min, the temperature of the dispersion was 25 ° C., and the tube 21 was not particularly heated.

  A few seconds after the start of injection, the string-like PTFE-containing solid matter is discharged from the end 22 of the tube body 21, and the discharged solid matter contains water and a surfactant and is not supported by the support itself. It was possible to keep the shape of.

  When the same experiment was performed by changing the spray pressure of the dispersion, the same PTFE-containing solid material could be obtained even when the spray pressure was 200 MPa and 245 MPa.

  The same experiment was conducted by changing the content of PTFE particles in the dispersion, and the same PTFE-containing solid matter could be obtained even when the content was 54 mass% and 48 mass%. .

(Reference Example 3)
In Reference Example 3, AD938 manufactured by Asahi Glass Co., Ltd. was used as the dispersion, and a string-like PTFE solid was formed using the tube (second tube) 31 shown in FIG. The tubular body 31 has a T-shaped bent portion 27 in the vicinity of one end portion 22 as a barrier that hinders the flow of the dispersion liquid. The inner diameter of the tube 31 is 10 mm, the length (the length from one end 22 to the other end 24) is 200 mm, and the position of the bent portion 27 is 30 mm from the one end 22 of the tube 31. .

  Such a pipe body 31 and a nozzle 25 (having a circular injection port (0.15 mmφ)) arranged at the end of the dispersion liquid supply path 26 are located on the central axis of the pipe body 31. Then, after arranging each other so that the distance between the other end 24 of the tube 31 and the nozzle 25 becomes 5 mm (see FIG. 9), the spray pressure is set to 245 MPa, and the dispersion liquid is discharged from the nozzle 25 into the tube 31. Was sprayed. The amount of the dispersion supplied to the nozzle 25 was about 0.5 L / min, the temperature of the dispersion was 25 ° C., and the tube 31 was not particularly heated.

  A few seconds after the start of injection, the string-like PTFE-containing solid matter is discharged from the end portion 22 of the tubular body 31, and the discharged solid matter contains water and a surfactant, and is not supported by the support itself. It was possible to keep the shape of. At this time, the string-like PTFE-containing solid matter was not discharged from the end portion 28 that constitutes the “T-shaped” open end portion together with the end portion 22. When the above injection was performed a plurality of times, in each case, the string-like PTFE-containing solid matter was discharged only from either one of the end 22 or the end 28.

  When the same experiment was performed by changing the spray pressure of the dispersion, the same PTFE-containing solid material could be obtained even when the spray pressure was 200 MPa.

  The same experiment was conducted by changing the content of PTFE particles in the dispersion, and the same PTFE-containing solid matter could be obtained even when the content was 54 mass% and 48 mass%. .

(Reference Example 4)
In Reference Example 4, a string-like PTFE solid was formed using AD938 manufactured by Asahi Glass Co., Ltd. as the dispersion and using the tube (second tube) 41 shown in FIG. The tube body 41 has a constricted portion 29 having an inner diameter changed at a central portion in the length direction as a barrier that hinders the flow of the dispersion liquid. The length of the tube 41 was 400 mm, the inner diameter in the range of 200 mm from one end 22 was 2 mm, and the inner diameter in the range of 200 nm from the other end was 10 mm. That is, in the tubular body 41, the inner diameter changes from 10 mm to 2 mm at the narrowed portion 29.

  Such a pipe body 41 and a nozzle 25 (having a circular injection port (0.15 mmφ)) arranged at the end of the dispersion liquid supply path 26 are arranged on the central axis of the pipe body 41. Then, after arranging them so that the distance between the end 24 of the tube body 41 having an inner diameter of 10 mm and the nozzle 25 is 5 mm (see FIG. 10), the spray pressure is set to 245 MPa, and the dispersion liquid is discharged from the nozzle 25 to the tube body. 41 was injected into the interior. The amount of the dispersion supplied to the nozzle 25 was about 0.5 L / min, the temperature of the dispersion was 25 ° C., and the tube 41 was not particularly heated.

  Several seconds after the start of injection, the string-like PTFE-containing solid matter is discharged from the end portion 22 of the tube body 41. The discharged solid matter contains water and a surfactant and is not supported by the support itself. It was possible to keep the shape of.

  When the same experiment was performed by changing the spray pressure of the dispersion, the same PTFE-containing solid material could be obtained even when the spray pressure was 200 MPa.

  The same experiment was conducted by changing the content of PTFE particles in the dispersion, and the same PTFE-containing solid matter could be obtained even when the content was 54 mass% and 48 mass%. .

(Example 2)
When the sheet-like solid before drying obtained in Example 1 was left standing in water, the solid remained in its shape before being put into water after 365 days. Was.

  Moreover, after drying the sheet-like solid before drying obtained in Example 1 at 90 ° C. for 15 minutes, the sieve was vibrated on a sieve of 1 μm mesh, but a particulate object was obtained. I couldn't.

(Example 3)
In Example 3, as a dispersion which is a starting material, a commercially available PTFE dispersion D-2 manufactured by Daikin (PTFE particle content 60 mass%, surfactant content 6 mass%) was used. A string-like PTFE-containing solid material was formed using the chamber 1E shown in FIG. 5, and the solid material was rolled and dried to produce a PTFE seal tape.

The volume of the internal space 2 of the chamber 1E (the internal volume of the chamber 1E) was 30 cm ^3, and the nozzle 3 having a circular injection port (0.25 mmφ) was disposed in the chamber. As the bending tube 18, a cylindrical L-shaped tube (inner diameter φ18 mm, length 200 mm (bending portion 18 a is substantially in the center)) was used.

  The dispersion liquid was supplied to such a chamber 1E, the spray pressure was set to 230 MPa, and the dispersion liquid was sprayed from the nozzle 3. The spray amount of the dispersion was about 0.5 liter / min. The temperature of the dispersion used was 23 ° C., and the temperature of the chamber 1E was not particularly controlled.

  About 20 seconds after the start of injection, a string-like solid (outer diameter 20 mm) began to be discharged from the tip of the bent tube 18. By analysis, it was confirmed that the solid matter contained water and a surfactant.

  Next, the obtained string-like solid was rolled between two metal rolls heated to 60 ° C. three times while changing the roll interval to obtain a sheet-like solid having a thickness of 0.13 mm. . This sheet-like solid was dried for 3 minutes in a drying furnace having an atmospheric temperature of 150 ° C. to obtain a PTFE seal tape (thickness: 100 μm).

Example 4
A slit die 20 (slit width 100 mm, gap 2 mm) as shown in FIG. 7 was attached to the chamber 1E used in Example 3, and the dispersion was sprayed under the same conditions as in Example 3. And the sheet-like solid substance discharged | emitted from the front-end | tip of the slit die 20 was collect | recovered. After passing this sheet-like solid substance between two metal rolls heated to 60 ° C. and adjusting the thickness to 0.15 mm, in a drying furnace with an atmospheric temperature of 150 ° C., two pairs of speed differences were doubled. The film was dried while being stretched twice in the length direction with a roll to obtain a PTFE seal tape.

Next, the properties of the PTFE seal tapes obtained in Examples 3 and 4 were examined by the following measurements according to JIS K 6885 (2005) “Unsealed Tetrafluoride Ethylene Resin Tape (Green Tape)”. The results are shown in Table 1 below. In addition, in the lower column of Table 1, JIS standard type 1 and type 2 are shown.
(1) Thickness (mm)
Measurement was performed using a dial gauge (contact surface: diameter 10 mm, load 1 N).
(2) Apparent density (g / cm ³ )
Each size and mass of the test piece was measured, and the apparent density was calculated from the following (Formula 1).
ρ = m / (l × b × d) (Formula 1)
ρ: Apparent density (g / cm ³ )
l: Length of test piece (cm)
b: Width of test piece (cm)
d: Test piece thickness (cm)
m: Mass of the test piece (g)
(3) Tensile strength (MPa) and elongation (%)
A test piece is collected at a length of about 20 cm, and marked lines with an interval of 50 mm are attached to the center of the test piece. Using a Tensilon-type tensile tester, the test is conducted under the condition of a pulling speed of 200 mm / min, the maximum load until cutting and the marked line interval when starting to break are measured, the tensile strength from the following (Formula 2), the following The elongation was calculated from (Formula 3).
T = F / (b × d) (Formula 2)
T: Tensile strength (MPa)
F: Maximum load until cutting (N)
b: Width of test piece (mm)
d: Test piece thickness (mm)
E = 100 × (l ₂ −l ₁ ) / l ₁ (Equation 3)
E: Elongation (%)
l ₁ : Mark interval (mm) before test of test piece
l ₂ : Marking interval when starting to cut (mm)

  As shown in Table 1, the PTFE seal tapes of Examples 3 and 4 all satisfied two JIS standards.

(Comparative example)
In the comparative example, AD938 manufactured by Asahi Glass Co., Ltd. was used as the dispersion, and an attempt was made to produce a PTFE sheet having a thickness of 300 μm by a casting method.

  The dispersion was applied to the surface of the aluminum substrate (application thickness: 600 μm), and the whole was dried at 120 ° C. for 15 minutes and then baked at 380 ° C. for 10 minutes. As a result, sheet-like PTFE was formed on the substrate. The formed PTFE had innumerable cracks and could not be peeled off from the substrate in the form of a sheet.

  ADVANTAGE OF THE INVENTION According to this invention, the novel manufacturing method of the PTFE sheet and PTFE sealing tape which use the dispersion liquid of PTFE particle | grains as a starting material can be provided. According to the production method of the present invention, a PTFE sheet and a PTFE seal tape can be produced with high productivity.

It is a schematic diagram which shows an example of the chamber which can be used for the manufacturing method of this invention. It is a schematic diagram which shows another example of the chamber which can be used for the manufacturing method of this invention. It is a schematic diagram which shows another example of the chamber which can be used for the manufacturing method of this invention. It is a schematic diagram which shows another example of the chamber which can be used for the manufacturing method of this invention. It is a schematic diagram which shows an example different from the above of the chamber which can be used for the manufacturing method of this invention. It is a schematic diagram which shows a mode that a PTFE containing solid substance produces | generates in the chamber shown in FIG. It is a schematic diagram which shows an example of the implementation apparatus which can implement the manufacturing method of this invention with which the die | dye for deform | transforming a PTFE containing solid substance into a sheet form was mounted | worn in the chamber. It is a schematic diagram for demonstrating the formation method of the 2nd tubular body used for the reference example, and the PTFE containing solid substance by the said 2nd tubular body. It is a schematic diagram for demonstrating the formation method of the 2nd tubular body used for the reference example, and the PTFE containing solid substance by the said 2nd tubular body. It is a schematic diagram for demonstrating the formation method of the 2nd tubular body used for the reference example, and the PTFE containing solid substance by the said 2nd tubular body.

Explanation of symbols

1A, 1B, 1C, 1D, 1E Chamber 2 Internal space 3, 3a, 3b Nozzle 4, 4a, 4b Injection direction 5 Structure 6, 6a, 6b Supply path 7 Supply port 8 Discharge port 9 Mixing valve 10 Sphere 11 Outer body 12a, 12b Core 13a, 13b Upper surface 14 Discharge path 15 Gap 16a, 16b Supply path 17a, 17b Supply port 18 Bent pipe 18a Bent part 19 Solid material 20 Slit die 21 Tubular body (second tubular body)
22 End portion 23 Bending portion 24 End portion 25 Nozzle 26 Supply path 27 Bending portion 28 End portion 29 Constriction portion 31 Tubular body (second tubular body)
41 Tube (second tube)
P dispersion

Claims (14)

(I) Applying a force for the particles to approach or come into contact with each other to a polytetrafluoroethylene dispersion containing polytetrafluoroethylene particles, a surfactant, and water as a dispersion medium. Forming a polytetrafluoroethylene-containing solid containing the active agent;
(Ii) transforming the solid into a sheet;
A step of reducing the amount of the water contained in the solid material deformed into (iii) a sheet-like, only including,
A method for producing a polytetrafluoroethylene sheet, wherein the dispersion is supplied to a chamber or a tube, sprayed into the chamber or the tube, and the force is applied in the chamber or the tube . The method for producing a polytetrafluoroethylene sheet according to claim 1 , wherein the dispersion is sprayed from a nozzle. (I) Applying a force for the particles to approach or come into contact with each other to a polytetrafluoroethylene dispersion containing polytetrafluoroethylene particles, a surfactant, and water as a dispersion medium. Forming a polytetrafluoroethylene-containing solid containing the active agent;
(Ii) transforming the solid into a sheet;
(Iii) reducing the amount of the water contained in the solid material deformed into a sheet,
Supplying the dispersion to a chamber or tube, applying the force in the chamber or tube;
The pipe body is that having a bent portion or the narrowed portion, Po Li tetrafluoroethylene sheet manufacturing method of. (I) Applying a force for the particles to approach or come into contact with each other to a polytetrafluoroethylene dispersion containing polytetrafluoroethylene particles, a surfactant, and water as a dispersion medium. Forming a polytetrafluoroethylene-containing solid containing the active agent;
(Ii) transforming the solid into a sheet;
(Iii) reducing the amount of the water contained in the solid material deformed into a sheet,
You form the solid The dispersion substantially the same mass plus the force, Po Li tetrafluoroethylene sheet manufacturing method of. (I) Applying a force for the particles to approach or come into contact with each other to a polytetrafluoroethylene dispersion containing polytetrafluoroethylene particles, a surfactant, and water as a dispersion medium. Forming a polytetrafluoroethylene-containing solid containing the active agent;
(Ii) transforming the solid into a sheet;
(Iii) reducing the amount of the water contained in the solid material deformed into a sheet,
It said solid angular or Ru deformed into a sheet form by passing it through a channel having a slit-shaped cross section, Po Li tetrafluoroethylene sheet manufacturing method of. Extent the particles imparted shape is maintained is by forming wear, and claim 1 to form the solid material in which the shape formed by encapsulating the water to the extent that deformable, 3, 4 or 5. A method for producing a polytetrafluoroethylene sheet according to 5 . The method for producing a polytetrafluoroethylene sheet according to claim 1 , 3, 4, or 5 , wherein the solid matter formed by binding the particles to such an extent that they are not dispersed in water is formed. The method for producing a polytetrafluoroethylene sheet according to claim 1 , 3, 4, or 5 , wherein the solid material is formed by binding the particles to such an extent that re-particulation does not occur due to a decrease in the amount of water contained. . The method for producing a polytetrafluoroethylene sheet according to claim 1, 3 or 4, wherein the solid is rolled into a sheet shape.
The method for producing a polytetrafluoroethylene sheet according to claim 1 , 3, 4 or 5 , wherein the dispersion further contains a filler. The method for producing a polytetrafluoroethylene sheet according to claim 1 , 3, 4, or 5 , wherein the solid matter deformed into a sheet shape is dried to reduce the amount of the water contained in the solid matter. The polytetrafluoroethylene sheet according to claim 1 , 3, 4, or 5 , wherein the step of rolling and / or stretching the solid material having a reduced water content is further performed after the step (iii). Manufacturing method. The solids content of the water is reduced, the firing by heating to a temperature above the melting point of polytetrafluoroethylene, claim 1, further embodiment will be after the step (iii), 3, 4 or 5. A method for producing a polytetrafluoroethylene sheet according to 5 . The method for producing a polytetrafluoroethylene sheet according to claim 1 , 3, 4 or 5 , wherein the polytetrafluoroethylene sheet obtained by the steps (i) to (iii) is a polytetrafluoroethylene sealing tape.

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