JP2007090892A - Composite article using ptfe porous article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite body using a finely-textured PTFE porous body. <P>SOLUTION: This composite body is obtained by molding a PTFE paste article comprising ≥7 pts.wt. pore-forming agent relative to 100 pts.wt. PTFE powder, where the pore-forming agent is held in the PTFE powder by virtue of its viscous behavior, into a predetermined shape, and then removing the pore-forming agent to thereby obtain a PTFE porous article having pores, and holding the PTFE porous article in a fluororubber molded article. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a composite using a polytetrafluoroethylene (hereinafter referred to as PTFE) porous body, and particularly relates to a composite using a fine-textured PTFE porous body.

  PTFE porous body is excellent in heat resistance and chemical resistance and has excellent electrical characteristics such as relative permittivity and energy loss angle, so that it can be used as a wire covering material, a coaxial cable dielectric, a filter, a gasket, a heat insulating material, a separation membrane, It is used in many applications such as artificial blood vessels, catheters, and incubators. As a method for manufacturing such a PTFE porous body, a manufacturing method in which a mixture of PTFE powder and a binder is finely pulverized, then molded by a known method, and this molded body is fired is widely known. ing. As another manufacturing method, a manufacturing method in which pores are formed by forming a mixture of PTFE powder and a pore forming agent into a predetermined shape and then removing the pore forming agent is widely known.

For example, Patent Document 1 discloses that unfired PTFE is fired at a temperature equal to or higher than the melting point of PTFE, and the fired PTFE is pulverized to obtain a fired PTFE powder. Then, the powder is 1 g / cm ^{2 to} 800 kg / cm ² . A method is disclosed in which a porous PTFE material is produced by molding into a predetermined shape with pressure and firing again at a temperature equal to or higher than the melting point of PTFE.

  For example, Patent Document 2 includes a step of mixing PTFE powder and a binder having a melting point lower than that of PTFE and a decomposition temperature higher than that of PTFE, a step of pulverizing the mixture after gelling, There is disclosed a method for producing a porous PTFE body comprising a step of producing a preform by ram extrusion molding finely pulverized powder, and a step of firing the preform under no constraint.

  For example, Patent Document 3 discloses a method for producing a porous body by forming PTFE containing a liquid lubricant that acts as a pore-forming agent and then heating in a stretched state. Further, as a prior art, there is disclosed a method for producing a porous body by mixing PTFE and a liquid lubricant acting as a pore-forming agent and molding the mixture, and then removing the liquid lubricant. Here, examples of the liquid lubricant include naphtha, white oil, toluol, and xylol.

  In Patent Document 4, a mixture of PTFE powder with a foaming agent and a liquid lubricant acting as a pore-forming agent is formed into a predetermined shape, and the mixture is heated and foamed to produce countless fine pores. A method for producing a porous body by stretching after forming is disclosed. Here, examples of the foaming agent include azo foaming agents, hydrazide foaming agents, semicarbazide foaming agents, nitroso foaming agents, ammonium carbonate, sodium bicarbonate, and ammonium nitrite. Liquid lubricants include liquid paraffin, naphtha, white oil, toluene, xylene and the like.

  Patent Document 5 discloses that PTFE powder is mixed with a pore-forming agent that acts as a pore-forming agent, a swelling agent, and a lubricating oil, and cold-extruded to evaporate the lubricating oil and form the pores. The manufacturing method which performs sublimation or decomposition | disassembly of an agent and the said swelling agent, and sintering of PTFE one by one is disclosed. Here, examples of the lubricating oil include a mixture of aliphatic hydrocarbons. Examples of the pore forming agent include compounds such as benzene, toluene, naphthalene, benzaldehyde, aniline, and monohalogenated or polyhalogenated derivatives of these compounds. Examples of the swelling agent include azodicarbonamide, modified azodicarbonamide, 5-phenyltetrazole and derivatives thereof, or aromatic derivatives of hydrazine.

  Patent Documents 6 and 7 disclose that PTFE containing a pore-forming agent is heated and fired, and at that time, the PTFE is made porous by the action of the pore-forming agent. Here, examples of the pore-forming agent include ammonium hydrogen carbonate, ammonium carbonate, and ammonium nitrite.

  Patent Document 8 discloses a method for producing a porous body by extruding PTFE containing a foaming agent that acts as a pore-forming agent and then removing the foaming agent. Here, examples of the foaming agent include azo compounds, sodium carbonate, ammonium carbonate, hydrazine, tetrazole, benzoxazine, and semicarbazide.

JP-A-61-66730 JP-A-5-93086 Japanese Patent Publication No.42-13560 Japanese Patent Publication No.57-30059 JP 60-93709 A Japanese Patent Laid-Open No. 11-124458 JP 2001-67944 A JP-T-2004-500026

  However, in the manufacturing method for re-molding finely pulverized PTFE powder as disclosed in Patent Documents 1 and 2, not only can the pore size be coarse, but a fine textured body cannot be obtained. It is very difficult to obtain a molded body having a high rate and to control the porosity. Moreover, although continuous molding by batch-type mold molding or ram extrusion is possible, continuous molding by paste extrusion is very difficult.

  In addition, as described above, the pore-forming agent disclosed in Patent Documents 3 to 8, the liquid lubricant that acts as the pore-forming agent, the foaming agent, the pore-forming agent, the expansion agent, and the lubricating oil are low. It is a liquid or powder of viscosity. Further, a pore forming agent that has been widely used conventionally is naphtha, which is also a low-viscosity liquid. When such a pore-forming agent is used, the following problems occur.

  First, when the pore-forming agent is composed only of a low-viscosity liquid, only a predetermined amount of the low-viscosity liquid is retained in the PTFE powder, and the excess part oozes out, so that the porosity exceeds 25%. It is difficult to produce a porous body. In addition, when such a porous body is completely fired, there is a problem that the pores are crushed and the porosity is reduced.

  Next, when the pore-forming agent is a powder, the portion from which the powder particles are removed becomes pores, so that the pores become coarse and the powder particles are likely to be in the form of a powder. Becomes coarse, so that it is not possible to manufacture a fine porous body. When such coarse pores exist, when external force such as bending is applied to the porous body, the mechanical strength decreases, such as stress concentration occurs in the pores and cracks and breaks occur. End up. In addition, when a large amount of powder pore former is mixed, the pressure inside the extruder increases because the tube wall resistance increases during extrusion, and the extrusion moldability deteriorates. There is.

  Next, when the pore-forming agent is a mixture of a low-viscosity liquid and powder, the case is the same as when the pore-forming agent is a powder or the pore-forming agent is a low-viscosity liquid. Problems arise. That is, since the part where the powder particles are removed becomes pores, the pores become coarse, and since the viscosity of the liquid is low, the powder particles cannot be held in a dispersed state, and the powder particles are spliced. Since the pores become coarser due to the tendency to become a shape, a fine porous body cannot be manufactured. In addition, when a large amount of a low-viscosity liquid pore-forming agent is mixed, an excessive amount oozes out. Moreover, when a large amount of a powder pore former is mixed, the tube wall resistance increases during extrusion molding, and the pressure inside the extruder increases, so the extrusion moldability deteriorates.

  Moreover, when extending | stretching like patent document 3, 4, a special apparatus is needed and since productivity increases, productivity will fall. Furthermore, in the case of stretching, it is difficult to control the porosity.

  The present invention has been made in order to solve such problems of the prior art, and an object of the present invention is to provide a composite using a fine PTFE porous body.

In order to achieve the above object, the composite according to claim 1 of the present invention contains 7 parts by weight or more of a pore forming agent with respect to 100 parts by weight of the polytetrafluoroethylene powder, and the structure is formed by the viscosity of the pore forming agent. After forming the polytetrafluoroethylene paste body in which the pore agent is held in the polytetrafluoroethylene powder into a predetermined shape, the polytetrafluoroethylene porous body having pores obtained by removing the pore former is converted into fluorine. It is characterized by being held by a rubber molded body.
A composite according to claim 2 is characterized in that, in the composite according to claim 1, the PTFE porous body and the fluororubber molded body are bonded with an adhesive.
Further, the composite according to claim 3 is the composite according to claim 1, wherein the PTFE porous body is disposed in a holding position in a state where the fluororubber molded body is unvulcanized or semi-vulcanized, and thereafter The fluororubber molded body and the PTFE porous body are integrated by heating the fluororubber molded body and the PTFE porous body to vulcanize the fluororubber molded body.
Further, the composite according to claim 4 is the composite according to claim 1, wherein grooves or protrusions are formed in the PTFE porous body, and protrusions or protrusions corresponding to the grooves or protrusions of the PTFE porous body are formed in the fluororubber molded body. Grooves are formed, and the PTFE porous body is held by the fluororubber molded body so that the grooves and projections formed in the grooves are fitted to each other.
The composite according to claim 5 is the composite according to claim 1, wherein an annular member is disposed around the PTFE porous body.
A composite according to claim 6 is the composite according to claim 1 to 5, wherein the PTFE porous body is metal-plated.

  According to the composite obtained in the present invention, it is possible to obtain a composite using a fine-textured PTFE porous body and to easily set the porosity by freely setting the mixing amount of the pore-forming agent to PTFE. It is also possible to produce a porous body having a high porosity. In addition, since the tube wall resistance is not increased, the extrusion moldability is not deteriorated during extrusion molding.

  Due to the fine texture of the PTFE porous body, the following effects can be obtained. First, since the pores are fine and uniform, and there are no coarse pores, the stress is dispersed even when an external force such as bending is applied, and cracks and breaks do not easily occur and the mechanical strength is excellent. In addition, when used for a heat insulating material, since the pores are fine, heat transfer by radiation, which is one element of heat conduction, can be reduced. Further, when used for a sealing material such as a gasket, the surface smoothness is improved, so that the sealing property can be improved. Further, when used for an insulator such as a wire coating, the dielectric breakdown strength can be improved. Also, when used in dielectric applications such as coaxial cables, the dielectric constant differs between the pores and the part where PTFE is present, so if the pores are coarse and non-uniform, the signal delay time will be uneven in the part. However, if the pores are fine and uniform, such unevenness can be prevented.

Moreover, the following effects can be acquired by making a PTFE porous body into a high porosity. First, since the specific gravity of the entire porous body can be reduced, it is possible to meet the demand for weight reduction. Moreover, when using it for the use of a heat insulating material, since the content of the air with low heat conductivity will increase, the heat insulation effect can be improved. Further, when used in a filter application, since the number of conduction paths increases, the life until clogging can be extended. When used in dielectric applications, the effective relative permittivity (ε _e ) of the porous body is determined by the relative permittivity (ε _A ) and porosity (V) of PTFE,
ε _e = ε _A ^1-V
Therefore, the effective relative dielectric constant can be lowered. The signal delay time (τ) is determined by the effective relative dielectric constant (ε _e ) of the porous body.
τ = 3.33561√ε _e (ns / m)
Therefore, the signal delay time can be reduced by setting the porosity to be high.

  As an aspect of the pore forming agent mixed with the PTFE powder for PTFE paste used in the composite of the present invention, one having viscosity can be mentioned. There are various cases in which the pore-forming agent develops viscosity. For example, the pore-forming agent component partially melts to develop viscosity, and the pore-forming agent itself is a viscous material whose composition can be deformed. A case, a case where the pore-forming agent is colloid, that is, a case where a solid is dispersed in a liquid and develops viscosity may be considered.

  As the pore-forming agent having viscosity, when mixing PTFE powder and pore-forming agent, and molding a mixture of PTFE powder and pore-forming agent into a predetermined shape, the viscosity in the environmental condition is 5 mPa -The thing containing the viscous body more than s is mentioned. The viscosity of the viscous material can be measured using, for example, a rotational viscometer. At this time, measurement conditions may be set in consideration of environmental conditions such as temperature and pressure during mixing and molding.

  If it contains such a viscous material, the pore-forming agent easily changes its shape by applying pressure and flows, and easily and evenly enters between powder particles such as PTFE powder. Furthermore, once it permeates, it is held by its viscosity. Once these pore-forming agents are held between the powder particles, unlike the case where a low-viscosity fluid such as naphtha or toluene is used as it is as a pore-forming agent, pressure is applied when forming into a predetermined shape. However, it does not occur that only the pore-forming agent oozes out and the PTFE powder and the pore-forming agent are separated. In addition, powder particles can be prevented from agglomerating and becoming a spatter, and such fine particles can be dispersed and held, so that fine and uniform pores can be formed. Can do. When a plurality of components are mixed and used as the pore-forming agent, each component constituting the pore-forming agent may be a powder or a low-viscosity liquid when present alone. In short, it is only necessary to contain a viscous material in a state where the components constituting the pore-forming agent are mixed.

  In addition, if the pore-forming agent is a viscous material having the above-mentioned specific viscosity, pores due to the shape of the powder particles will not be generated, and therefore finer and more uniform pores can be formed. preferable.

  In addition, it is preferable that the pore forming agent has a property of being vaporized by heating in air, since it is easy to vaporize and remove the pore forming agent by heating. When removing the pore-forming agent by evaporating it, for example, compared to removing the pore-forming agent by thermal decomposition, it is less likely to leave a residue of the pore-forming agent in PTFE, preventing the residue from adversely affecting various electrical properties. can do. As such a pore-forming agent having a property of being vaporized by heating in air, for example, if it has a boiling point of 300 ° C. or less, a special apparatus is not required, and it can be easily produced by a commonly used heating furnace. It is preferable because the pore agent can be removed. If the pore forming agent has a boiling point of 300 ° C. or lower, the pore forming agent is removed at a temperature lower than the PTFE firing temperature (370 to 400 ° C.). Can prevent accidents.

  As a preferable pore-forming agent that satisfies the above conditions, for example, those having terpenes as the main component can be used. Examples of terpenes include camphor, menthol, camphene, borneol and the like. Among these, it is preferable that at least one selected from camphor and menthol is a main component.

  An organic solvent may be used as a component of the pore-forming agent so that the pore-forming agent contains a viscous material having a specific viscosity. For example, menthol and camphor are solid substances at room temperature, but can be made into a viscous material having a specific viscosity by mixing with an organic solvent. Moreover, since the viscosity of the pore-forming agent can be adjusted by the mixing amount of the organic solvent, depending on the mixing amount of the pore-forming agent to the PTFE powder, the molding method when molding the mixture of the PTFE powder and the pore-forming agent, etc. The mixing amount of the organic solvent can be appropriately set.

  Examples of the organic solvent include hydrocarbons such as liquid paraffin, naphtha, white oil, and kerosene, aromatic hydrocarbons such as toluene and xylene, alcohols, ketones, esters, and the like. Among them, it is preferable to use a petroleum solvent such as naphtha because of its permeability to PTFE. However, when PTFE is fired, it is usually fired at a temperature of about 370 to 400 ° C., so there is a risk of ignition if the solvent remains up to a high temperature during firing, and the solvent is completely evaporated before firing. Therefore, the boiling point of the organic solvent is preferably 300 ° C. or lower.

  In addition, when both camphor and menthol are contained, since they are liquefied by mixing them, it is possible to obtain a viscous material having a specific viscosity without an organic solvent. Of course, an organic solvent may be added to the mixture of camphor and menthol.

  The pore former as described above is mixed in an amount of 7 parts by weight or more with respect to 100 parts by weight of the PTFE powder. When the mixing amount of the pore-forming agent is less than 7 parts by weight, a sufficient amount of pores cannot be obtained even if the pore-forming agent is removed. In particular, when PTFE is baked, even if pores remain slightly, they are all crushed and no pores remain at all.

  Further, as another aspect of the pore-forming agent mixed with the PTFE powder, the above-mentioned terpenes such as camphor may be used as a powder as it is. Since terpenes such as camphor have the flexibility to be easily plastically deformed, even if they are used as a pore-forming agent in a powder that does not contain a viscous material, It will penetrate evenly and be held, and then it will be held in a state of plastic deformation. Therefore, a PTFE porous body in which fine and uniform pores are formed can be obtained with a PTFE paste body mixed with such a pore-forming agent. Of course, the terpenes may be in a viscous state instead of powder.

  The pore former as described above and PTFE powder are mixed by stirring with a tumbler or the like to obtain a PTFE paste body. At this time, the porosity can be easily controlled by changing the mixing amount of the pore-forming agent. In addition, when mixing and using a plurality of components as a pore-forming agent, if each component constituting the pore-forming agent is mixed in advance, the pore-forming agent becomes homogeneous. Although it can be prepared, each component constituting the pore former may be separately added to the PTFE powder, and then mixed together by stirring or the like.

  Further, as another aspect of the PTFE paste body, there is one in which PTFE powder and powder or a viscous pore former are mixed so as to form particles. Thus, if the PTFE powder and the pore-forming agent are mixed so as to be integrated particles, even if the pore-forming agent is a powder, the pores are not as in Patent Documents 2 to 7 described above. Since it does not become coarse, a fine textured PTFE porous body can be obtained. Further, the tube wall resistance is not increased and the extrusion moldability is also improved. Here, “integrated particles” means that the particles of PTFE powder and the pore-forming agent are hardly observed as separate particles and are not easily separated into the respective particles. .

  As described above, when the PTFE powder and the pore former are mixed so as to be integrated particles, the pore former is not particularly limited. For example, the above-mentioned terpenes, naphthalene, aniline, benzoic acid, ammonium hydrogen carbonate, ammonium carbonate, ammonium nitrite and the like can be mentioned. Among these, it is difficult to leave a residue as long as it vaporizes below the firing temperature of PTFE powder. Therefore, it is preferable. Furthermore, the above-mentioned terpenes, particularly camphor, are particularly preferred because they are not only difficult to leave a residue but also easily integrated with PTFE powder. Of course, an organic solvent as described above may be mixed with these pore formers.

  As a method of mixing so that the PTFE powder and the pore forming agent become integrated particles, after mixing the PTFE powder and the pore forming agent, or while mixing, the shear stress between the PTFE powder and the pore forming agent. The method of integrating by adding is mentioned. Specifically, for example, the PTFE powder and the pore former are kneaded and integrated with a roll or the like, and then pulverized into a fine powder, or the PTFE powder and the pore former with a high-speed rotating blade such as a mixer. And integration by applying a shear stress between the two. Of these, the latter is preferable because integration and pulverization can be performed in the same process. In addition, when adding the above-mentioned organic solvent etc., you may add before integrating, and may add after integrating. Alternatively, a part of the amount may be added before integration, and the rest may be added after integration.

  By forming the PTFE paste body into a predetermined shape and removing the pore-forming agent, pores are provided in the PTFE, and a PTFE porous body is produced. In forming the PTFE paste body, it can be formed by various generally known forming methods. For example, a bulk material may be formed by molding or the like, or a film material may be formed by rolling or the like. Furthermore, since tube wall resistance does not increase, extrusion molding can also be performed. Therefore, a conductor may be formed by coating on a conductor by extrusion molding. Moreover, as a method for removing the pore-forming agent, it is preferable to vaporize the pore-forming agent by heating for the convenience of equipment, but it is also conceivable to vaporize the pore-forming agent by reducing the pressure.

  In addition, when shape | molding a PTFE paste body or after shape | molding, a skin layer can be formed in a PTFE porous body by applying a shear stress to the surface. As a specific mode for forming the skin layer, for example, molding by the above-described extrusion molding may be mentioned.

  Note that the PTFE porous body used in the composite of the present invention may be used as an unfired PTFE porous body after removing the pore-forming agent by a heat treatment at about 200 ° C. and thereafter without firing. Further, after removing the pore-forming agent, further baking at 370 ° C. or more may be performed and used as a completely fired PTFE. Moreover, it is good also as a PTFE porous body with which unbaking and complete baking were mixed by adjusting baking temperature. In addition, you may add an extending | stretching process further to these PTFE porous bodies.

  Even if the PTFE porous body thus obtained is completely fired and non-stretched, it can have a porosity of 5% or more, an average pore diameter of 300 μm or less, and a hardness of less than A95. Such a PTFE porous body can be suitably used, for example, as a dielectric of a coaxial cable having an excellent relative dielectric constant or a bulk filter. In particular, if the average pore size is 100 μm or less, as a filter for the purpose of separating gas (air, water vapor, etc.) and liquid (water, etc.), or gas (air, water vapor, etc.) and solid (powder, etc.), This is preferable because it exhibits a high filter function. Further, by increasing the mixing amount of the pore-forming agent, for example, a PTFE porous body having a porosity of 80% or more can be obtained.

  Further, the porous PTFE material obtained as described above can also control the pore state. For example, when the porosity is 5% or more and less than 40%, the porous material is mainly independent pores, and the porosity is 40% or more and 50%. If the ratio is less than 50%, both the independent pores and the continuous pores are included, and if the porosity is 50% or more, the independent pores are mainly used.

  The PTFE porous body obtained as described above is held in a fluororubber molded body to form a composite. Thus, since the composite body which hold | maintained the PTFE porous body in the fluororubber molded object can be used in a high temperature environment, it can be used suitably for the grommet with a filter used for an oxygen sensor etc., for example. .

  Specific examples of the complex include those shown in FIG. FIG. 25 shows the PTFE porous body 1 held in the through hole of the fluororubber molded body 2 formed into a shape having a through hole. At this time, an adhesive may be applied to the fluororubber molded body 2 and / or the PTFE porous body 1 to bond the fluororubber molded body 2 and the PTFE porous body 1 together. Examples of the adhesive include a fluororubber adhesive, a silane solution, a titanate solution, and an aluminate solution. Further, the PTFE porous body 1 is disposed in the through-hole of the fluororubber molded body 2 in a state in which the fluororubber molded body 2 is unvulcanized or semi-vulcanized, and thereafter, the fluororubber molded body 2 and the PTFE porous body 1 are disposed The fluororubber molded body 2 and the PTFE porous body 1 may be integrated by heating and vulcanizing the fluororubber molded body 2. Alternatively, the PTFE porous body 1 may be disposed at a predetermined position, and fluoro rubber is molded around the PTFE porous body 1 by injection molding or the like, so that the PTFE porous body 1 is held by the fluoro rubber molded body 2.

  Another specific example of the complex is as shown in FIG. 26, for example. FIG. 26 shows a PTFE porous body 1 held in a through hole of a fluororubber molded body 2 formed into a shape having a through hole. A groove 11 is formed on the side surface of the PTFE porous body 1 to form a fluororubber. Protrusions 12 are formed in the through holes of the molded body 2 and the grooves 11 and the protrusions 12 are fitted. Thereby, the PTFE porous body 1 does not come off from the fluororubber molded body 2 and can be reliably held. Of course, a protrusion may be formed on the side surface of the PTFE porous body 1 and a groove may be formed in the through hole of the fluororubber molded body 2. Also, there is no limitation on the shape of the grooves and protrusions, and a shape that is easy to fit and difficult to remove may be selected as appropriate.

  Another specific example of the composite is shown in FIG. 27, for example. FIG. 27 shows a PTFE porous body 1 held in a through hole of a fluororubber molded body 2 formed into a shape having a through hole. An annular member 3 is fixedly disposed around the PTFE porous body 1. Has been. Thus, since the annular member 3 is fixedly disposed around the PTFE porous body 1, the PTFE porous body 1 does not come out of the fluororubber molded body 2 and can be reliably held. The shape of the annular member 3 is not limited. For example, a cylindrical shape or a coil shape may be used, or a plurality of annular members 3 may be used. Further, if the annular member 3 is made of metal, the annular member 3 can be fixedly disposed by caulking or the like so that there is no gap between the porous PTFE body 1 and the fluororubber is easily bonded to the metal material. Since it has the property, the gap between the fluororubber molded body 2 and the annular member 3 can be easily eliminated.

  Further, the PTFE porous body 1 may be subjected to a surface treatment for the purpose of bonding the fluororubber molded body 2 and the PTFE porous body 1 without a gap. Examples of the surface treatment include discharge treatment using corona discharge or plasma discharge, radiation treatment, UV treatment, laser treatment, flame treatment, and formation of a metal plating layer. Among these, as described above, the fluororubber has the property of easily adhering to a metal material, and therefore it is preferable to form a metal plating layer. Examples of the method for forming the metal plating layer include plating with a metal colloid solution, plating with vacuum deposition, plating with molten metal, electrolytic plating, and the like, and may be appropriately selected from these. May be combined.

  The above has shown an aspect in which the PTFE porous body used in the composite of the present invention is used as a filter. For example, the above PTFE porous body is coated on a conductor to form an insulated wire (lead wire). May be held in a fluororubber molded body to form a grommet with a lead wire.

  Examples of the PTFE porous material used in the composite of the present invention and comparative examples will be described below.

Examples 1-12
Naphtha, camphor and menthol were mixed in the weight parts shown in Table 1, and ground on a mortar to obtain a pore-forming agent containing a viscous material. A PTFE paste body obtained by mixing 100 parts by weight of the pore former and PTFE powder is put into a cylindrical mold having an inner diameter of 4 mm, compression molded at about 40 kgf / cm ² for 30 seconds, taken out, and heated at 250 ° C. for 10 minutes. Then, the pore-forming agent was vaporized and removed, followed by heating and baking at 400 ° C. for about 10 minutes to prepare a sample piece.

Example 13
Naphtha, camphor (powder), and PTFE powder were mixed in parts by weight shown in Table 2 to obtain a PTFE paste. This PTFE paste body is put into a cylindrical mold having an inner diameter of 7 mm and temporarily compression-molded at about 40 kgf / cm ² for 30 seconds, and then a cylinder having an outer diameter of 7 mm and an inner diameter of 4 mm is pushed into the mold to form a cylindrical shape having an outer diameter of about 4 mm. The molded body was extruded. The molded body was heat-treated at 250 ° C. for 10 minutes to vaporize and remove the pore-forming agent, and then heat-fired at 400 ° C. for about 10 minutes to produce a sample piece.

Examples 14-19
Naphtha, camphor (powder), and PTFE powder were mixed in parts by weight shown in Table 2, and integrated with a mixer having a rotary blade for about 3 minutes to obtain a PTFE paste. This PTFE paste body was put into a cylindrical mold having an inner diameter of 7 mm and temporarily compression molded at about 40 kgf / cm ² for 30 seconds, and then a cylinder having an outer diameter of 7 mm and an inner diameter of 4 mm was pushed into the mold and the outer diameter was increased. A cylindrical shaped body of about 4 mm was extruded. The molded body was heat-treated at 250 ° C. for 10 minutes to vaporize and remove the pore-forming agent, and then heat-fired at 400 ° C. for about 10 minutes to produce a sample piece.

Comparative Examples 1-3
Ammonium hydrogen carbonate, naphtha, and PTFE powder ground and pulverized in a mortar were mixed in parts by weight shown in Table 3, and a sample piece was produced from this mixture by the same method as in the first embodiment.

Comparative Examples 4 and 5
Naphtha and PTFE powder were mixed in parts by weight shown in Table 3, and a sample piece was produced from this mixture by the same method as in the first embodiment.

Comparative Example 6
The PTFE powder was heat treated at about 360 ° C. and fired, and then pulverized with a pulverizer to prepare a powder having an average particle size of about 100 μm. Further, the sample was press-molded at 370 ° C. to prepare a cylindrical sample piece having a diameter of 2 mm and a length of 15.6 mm.

Here, the porosity and the pore state of the sample pieces according to Examples 1 to 12 of the present invention are shown in Table 1, the porosity and the pore state of the sample pieces according to Examples 13 to 19 of the present invention are shown in Table 2, and Comparative Example 1 Table 3 shows the porosity and porosity of the sample pieces according to -6. In addition, the porosity is a sample piece produced by the same method as in Example 1 except that the pore-forming agent is not mixed.
Porosity = 100− (specific gravity of sample piece / specific gravity of index sample piece) × 100
It was calculated by the following formula. Moreover, the pore state observed the surface which cut the sample piece with the knife with the microscope. 1 to 19 are photographs showing the pore states of the sample pieces according to Examples 1 to 19, FIGS. 20 to 22 are photographs showing the pore states of the sample pieces according to Comparative Examples 1 to 3, and FIG. 23 is a comparison. 6 is a photograph showing the pore state of a sample piece according to Example 6. FIG.

Moreover, about the sample piece of Examples 13-18 and the comparative example 6, it measured about the air flow rate, the water flow rate, and the hardness. The air flow rate is measured by wrapping the sample piece with a sealing tape to prevent leakage from the side, then covering the tube, applying an air pressure of 0.5 kgf / cm ² from one side of the sample piece, and replacing the permeated air with the water displacement method. The volume collected in the graduated cylinder and stored in the unit time was measured. The amount of water flow is also wrapped with a seal tape to prevent leakage from the side, then covered with a tube, applied with a water pressure of 0.5 kgf / cm ² from one side of the sample piece, and the permeated water is collected in a graduated cylinder. The volume accumulated within the unit time was measured. The hardness was measured with a durometer A hardness meter according to JIS K6253 (ISO7619). The measurement results of the air flow rate, the water flow rate, and the hardness are shown together in Tables 2 and 3.

  Further, the sample pieces according to Examples 1 to 19 and the sample pieces according to Comparative Examples 1 to 6 were subjected to differential scanning calorimetry (DSC) by the transition heat measurement method of JIS K7122 plastic, and the crystal melting obtained thereby. An endothermic peak was confirmed in the curve. According to this DSC, since any sample piece has a peak around 320 to 330 ° C. characteristic of fully fired PTFE, it becomes fully fired PTFE by heating and firing at 400 ° C. for 10 minutes. It can be confirmed. FIG. 24 shows the crystal melting curve of Example 1.

  In this example, Examples 1 to 12 using a pore-forming agent containing a viscous material, Example 13 using a pore-forming agent of a specific powder, and a powder pore-forming agent and PTFE powder were integrated. In any of Examples 14 to 19 in which the particles were made into particles, the porosity could be arbitrarily changed depending on the blending amount of the pore-forming agent. Further, it was confirmed that in all Examples, the pore state was fine and uniform, and the PTFE porous material 1 was fine regardless of the porosity. In this example, a porosity of 3.8% to 81.0% was prepared. Of course, a porosity of less than 3.8% or a porosity of more than 81.0% was used. It is also possible to produce it.

  Moreover, since Examples 13-19 were formed by extrusion molding and shear stress was applied to the cylindrical side surface portion, it was confirmed that a skin layer was formed on the side surface portion.

  In Comparative Examples 1 to 3 using powdered ammonium hydrogen carbonate as a pore-forming agent, the porosity could be arbitrarily changed depending on the amount of the pore-forming agent. However, in Comparative Example 1 where the porosity is relatively low at 36.2%, several slightly coarse pores 2 are seen and the texture is slightly rough, and Comparative Examples 2 and 69. with a porosity of 51%. In Comparative Example 3 of 1%, a large number of coarse pores 2 were observed, and it was very difficult to say that the texture was fine.

  About Comparative Examples 4 and 5 using only naphtha which is a low-viscosity liquid as a pore-forming agent, since Comparative Example 4 had a small amount of pore-forming agent, the pores were crushed by the heat-firing treatment, and the porosity was low It was 0%. In Comparative Example 5 in which the amount of the pore-forming agent was increased as compared with Comparative Example 4, naphtha as the pore-forming agent oozed out when the mixture was formed, and only the pore-forming agent in the same amount as Comparative Example 4 was PTFE. Since it was not held between the particles of the powder, the porosity was 0% as in Comparative Example 4.

  Looking at the test results of the air flow rate and the water flow rate, Example 13, which does not form particles in which the PTFE powder and the powder pore forming agent are integrated, has a very large air flow rate, but also has a large water flow rate. ing. On the other hand, Examples 14-18 which made the particle | grains which integrated PTFE powder and the powder pore-former can obtain favorable air flow by controlling a porosity, and the water flow is large. The result is very few. This is because the pore diameter of Example 13 was slightly larger than the pore diameters of Examples 14-18. In Comparative Example 6, since the pore diameter is large but a high porosity is not obtained, the air flow rate is very small.

  As described above, according to Examples 1 to 12, since the pore-forming agent contains a viscous material, a finely textured PTFE porous material having fine and uniform pores can be obtained regardless of the porosity. . Moreover, the porosity can be easily controlled by setting the mixing amount of the pore-forming agent. In addition, since the viscosity of the pore forming agent itself can be changed depending on the ratio of the blending components, it is possible to have good moldability.

  Further, according to Example 13, since the pore-forming agent is made of a specific powder (terpenes), a finely textured PTFE porous body having relatively fine and uniform pores can be obtained. In addition, the porosity can be easily controlled by setting the mixing amount of the pore-forming agent. Further, according to Example 13, since the slightly larger pores are uniformly formed as described above, the amount of air flow becomes very large, which makes the filter extremely useful as a gas-solid separation filter.

  Further, according to Examples 14 to 19, since the pore-forming agent is a particle obtained by integrating a powder pore-forming agent and PTFE powder, it has fine and uniform pores regardless of the porosity. A finely textured PTFE porous body can be obtained. Moreover, the porosity can be easily controlled by setting the mixing amount of the pore-forming agent. Moreover, according to Examples 14-18, since there are much ventilation | gas_flowing amount and very little water-flowing amount, it becomes a very useful thing as a filter for gas-liquid separation.

  According to the present invention, in particular, a composite using a finely textured PTFE porous material can be obtained, and the porosity of the PTFE porous material can be easily controlled. Such a PTFE porous body can be suitably used for many applications such as a wire coating material, a coaxial cable dielectric, a filter, a gasket, a heat insulating material, a separation membrane, an artificial blood vessel, a catheter, and an incubator. it can. In addition, a composite in which such a PTFE porous body is held in a fluororubber molded body can be used in a high-temperature environment, and can be suitably used, for example, in a grommet with a filter used for an oxygen sensor. It is.

It is a figure showing Example 1, and is a figure which shows the pore state of a PTFE porous body. It is a figure showing Example 2, and is a figure which shows the pore state of a PTFE porous body. It is a figure showing Example 3, and is a figure which shows the pore state of a PTFE porous body. It is a figure showing Example 4, and is a figure which shows the pore state of a PTFE porous body. It is a figure showing Example 5, and is a figure which shows the pore state of a PTFE porous body. It is a figure showing Example 6, and is a figure which shows the pore state of a PTFE porous body. It is a figure showing Example 7, and is a figure which shows the pore state of a PTFE porous body. It is a figure showing Example 8, and is a figure which shows the pore state of a PTFE porous body. It is a figure showing Example 9, and is a figure which shows the pore state of a PTFE porous body. It is a figure showing Example 10, and is a figure which shows the pore state of a PTFE porous body. It is a figure showing Example 11, and is a figure which shows the pore state of a PTFE porous body. It is a figure showing Example 12, and is a figure which shows the pore state of a PTFE porous body. It is a figure showing Example 13, and is a figure which shows the pore state of a PTFE porous body. It is a figure showing Example 14, and is a figure which shows the pore state of a PTFE porous body. It is a figure showing Example 15, and is a figure which shows the pore state of a PTFE porous body. It is a figure showing Example 16, and is a figure which shows the pore state of a PTFE porous body. It is a figure showing Example 17, and is a figure which shows the pore state of a PTFE porous body. It is a figure showing Example 18, and is a figure which shows the pore state of a PTFE porous body. It is a figure showing Example 19, and is a figure which shows the pore state of a PTFE porous body. It is a figure showing the comparative example 1, and is a figure which shows the pore state of a PTFE porous body. It is a figure showing the comparative example 2, and is a figure which shows the pore state of a PTFE porous body. It is a figure showing the comparative example 3, and is a figure which shows the pore state of a PTFE porous body. It is a figure showing the comparative example 6, and is a figure which shows the pore state of a PTFE porous body. 2 is a diagram showing a crystal melting curve by differential scanning calorimetry (DSC) of Example 1. FIG. It is a figure which shows the composite_body | complex which hold | maintained the PTFE porous body in the fluororubber molded object, (A) is a perspective view, (B) is bb 'sectional drawing in (A). It is a figure which shows the composite_body | complex which hold | maintained the PTFE porous body in the fluororubber molded object, (A) is a perspective view, (B) is bb 'sectional drawing in (A). It is a figure which shows the composite_body | complex which hold | maintained the PTFE porous body in the fluororubber molded object, (A) is a perspective view, (B) is bb 'sectional drawing in (A).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 PTFE porous body 1a Coarse pore 2 Fluoro rubber molding 3 Ring member

Claims (6)

  Polytetrafluoroethylene paste containing 7 parts by weight or more of a pore-forming agent with respect to 100 parts by weight of the polytetrafluoroethylene powder, and the pore-forming agent held by the polytetrafluoroethylene powder due to the viscosity of the pore-forming agent A composite comprising a porous polytetrafluoroethylene body having pores obtained by removing the pore-forming agent after the body is molded into a predetermined shape, and held in a fluororubber molded body.   The composite according to claim 1, wherein the polytetrafluoroethylene porous body and the fluororubber molded body are bonded with an adhesive.   With the fluororubber molded body unvulcanized or semi-vulcanized, the polytetrafluoroethylene porous body is placed at a holding position, and then the fluororubber molded body and the polytetrafluoroethylene porous body are heated. 2. The composite according to claim 1, wherein the fluororubber molded body and the polytetrafluoroethylene porous body are integrated by vulcanizing the fluororubber molded body.   Grooves or protrusions are formed in the polytetrafluoroethylene porous body, and protrusions or grooves corresponding to the grooves or protrusions of the polytetrafluoroethylene porous body are formed in the fluororubber molded body. 2. The composite according to claim 1, wherein the polytetrafluoroethylene porous body is held by the fluororubber molded body so as to be fitted together.   The composite according to claim 1, wherein an annular member is disposed around the polytetrafluoroethylene porous body.   6. The composite according to claim 1, wherein the polytetrafluoroethylene porous body is metal-plated.