JP2011011535A - Paste extrusion molding method and paste extrusion molding product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paste extrusion molding method and a paste extrusion molding product capable of effectively reducing an increase of a compression pressure even in high filler material amount.SOLUTION: A paste extrusion molding method comprises preparing a polytetrafluoroethylene composition containing polytetrafluoroethylene, a filler material and a liquid auxiliary, and conducting extrusion molding of the polytetrafluoroethylene composition, wherein the polytetrafluoroethylene composition contains 15-60 vol.% of the filler material and one or more numbers selected from a group consisting of an organic silane compound containing a hydrocarbon group having a carbon number of 3-40, an organic titanate compound and an organic aluminum compound as an agent reducing a compression pressure.

Description

  The present invention relates to a paste extrusion molding method and a paste extrusion molding, and particularly relates to reduction of extrusion pressure in paste extrusion molding.

  Polytetrafluoroethylene (PTFE) is excellent in various properties such as heat resistance, chemical resistance, electrical characteristics, non-adhesiveness, non-contamination, and low friction. For this reason, a PTFE molded object is widely utilized in various fields, such as the field | areas of sealing agents, such as a gasket and packing, for example.

  However, PTFE is inferior in wear resistance and creep resistance. For this reason, wear resistance and creep resistance are improved by adding a filler such as metal, graphite, and glass to PTFE.

  As one method for producing such a PTFE molded product, for example, a PTFE composition mixed with PTFE fine powder, a filler and a liquid auxiliary agent such as naphtha is paste extruded, and then the extruded product is rolled. There has been a method of obtaining a sheet-like PTFE molded body (for example, see Patent Document 1).

JP 2004-323717 A

  However, in the conventional paste extrusion molding method, when the filler content is high, the extrusion pressure is remarkably increased, which may make extrusion molding difficult. That is, during extrusion, the filler itself does not cause plastic deformation, but also prevents plastic deformation of PTFE. For this reason, in order to obtain a flexible continuous filler-filled PTFE molded body having strength that can withstand practical use, it is necessary to keep the filler content low.

  Therefore, a PTFE molded body (for example, a tube, rod, or sheet-shaped molded body) having excellent mechanical strength, a dense structure without large pores, and a high filler content can be produced efficiently and reliably. It was difficult to do.

  These problems become more serious as the particle size of the filler becomes smaller and the extrusion moldability is significantly impaired. The degree to which the extrusion pressure increases also depends on the extrusion mold used. For the purpose of solving these problems, for example, even if the amount of the liquid auxiliary added to the PTFE composition is increased, the pressure is remarkably increased during the extrusion, and the liquid auxiliary is used in the extrusion mold. Extruding outside makes extrusion molding difficult.

  As described above, the conventional paste extrusion molding method has a problem that the content rate of the filler cannot be increased to some extent, and a problem that the shape of the extrusion mold that can be used is limited.

  The present invention has been made in view of the above problems, and provides a paste extrusion molding method and a paste extrusion molding that can effectively reduce an increase in extrusion pressure even when the content of the filler is high. One of its purposes is to do.

  In order to solve the above problems, a paste extrusion molding method according to an embodiment of the present invention comprises preparing a polytetrafluoroethylene composition containing polytetrafluoroethylene, a filler, and a liquid auxiliary agent. A method for extruding an ethylene composition, wherein the polytetrafluoroethylene composition has a hydrocarbon group having 3 to 40 carbon atoms as an extrusion pressure reducing agent together with 15 to 60% by volume of the filler. 1 or 2 or more selected from the group which consists of an organosilane compound, an organic titanate compound, and an organic aluminate compound is characterized by the above-mentioned. ADVANTAGE OF THE INVENTION According to this invention, even if it is a case where the content rate of a filler is high, the paste extrusion molding method which can suppress effectively the increase in extrusion pressure can be provided.

  Moreover, the said hydrocarbon group is good also as not having a reactive functional group. The polytetrafluoroethylene composition may contain the organosilane compound as an extrusion pressure reducing agent. The hydrocarbon group may be an alkyl group, an aryl group, an aralkyl group, a cycloalkyl group, or an alkenyl group. In this case, the hydrocarbon group may be an alkyl group.

  A paste extrusion molded product according to an embodiment of the present invention for solving the above-mentioned problems is manufactured by the paste extrusion molding method described above. According to the present invention, it is possible to provide a paste extrusion molded body having a high filler content and excellent characteristics.

  ADVANTAGE OF THE INVENTION According to this invention, even if it is a case where the content rate of a filler is high, the paste extrusion molding method and paste extrusion molding body which can reduce the increase in extrusion pressure effectively can be provided.

It is explanatory drawing which shows the main processes contained in an example of the paste extrusion molding method which concerns on one Embodiment of this invention. It is explanatory drawing which shows the cross section about an example of the extrusion die used in the paste extrusion molding method which concerns on one Embodiment of this invention. It is explanatory drawing which shows the cross section about the other example of the extrusion die used in the paste extrusion molding method which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the result of having measured extrusion pressure in the paste extrusion molding method which concerns on one Embodiment of this invention. It is explanatory drawing which shows the other example of the result of having measured extrusion pressure in the paste extrusion molding method which concerns on one Embodiment of this invention. It is explanatory drawing which shows the other example of the result of having measured extrusion pressure in the paste extrusion molding method which concerns on one Embodiment of this invention. It is explanatory drawing which shows the other example of the result of having measured extrusion pressure in the paste extrusion molding method which concerns on one Embodiment of this invention. It is explanatory drawing which shows the other example of the result of having measured extrusion pressure in the paste extrusion molding method which concerns on one Embodiment of this invention.

  Hereinafter, an embodiment of the present invention will be described. Note that the present invention is not limited to this embodiment.

  A paste extrusion molding method according to the present embodiment (hereinafter referred to as “the present method”) is a method of preparing a polytetrafluoroethylene composition containing polytetrafluoroethylene, a filler, and a liquid auxiliary agent. A method for extruding an ethylene composition, wherein the polytetrafluoroethylene composition has a hydrocarbon group having 3 to 40 carbon atoms as an extrusion pressure reducing agent together with 15 to 60% by volume of the filler. 1 or 2 or more selected from the group which consists of an organic silane compound, an organic titanate compound, and an organic aluminate compound is contained.

  That is, in this method, for example, as shown in FIG. 1, a first step S1 for preparing a polytetrafluoroethylene composition containing an extrusion pressure reducing agent (hereinafter referred to as “PTFE composition”), and the PTFE concerned. And a second step S2 for performing paste extrusion molding of the composition.

  In the first step S1, first, at least polytetrafluoroethylene (hereinafter referred to as “PTFE”), a filler, a liquid auxiliary agent, and an extrusion pressure reducing agent are prepared as raw materials for the PTFE composition.

  PTFE is not particularly limited as long as it can be used for paste extrusion molding. For example, PTFE fine powder can be preferably used. The PTFE fine powder is obtained by coagulating and drying an aqueous dispersion (PTFE dispersion) of PTFE fine particles (for example, PTFE fine particles having an average particle diameter of 0.1 to 0.5 μm) obtained by emulsion polymerization of tetrafluoroethylene. This is a fine powder of PTFE produced by The average particle diameter of the PTFE powder is, for example, 200 to 1000 μm.

  As PTFE, pure PTFE made of a homopolymer obtained by polymerizing only tetrafluoroethylene can be used, or modified PTFE which is a copolymer containing a small amount of other monomers can also be used. That is, in emulsion polymerization for producing PTFE fine powder, pure PTFE can be obtained using only tetrafluoroethylene as a monomer, or other than tetrafluoroethylene and a small amount (for example, 0.1% by weight or less). It is also possible to obtain a modified PTFE by copolymerizing with the above monomer. As a component to be copolymerized with tetrafluoroethylene, for example, one or both of hexafluoropropylene and perfluoropropyl vinyl ether can be used.

  The filler is not particularly limited as long as it improves predetermined characteristics such as wear resistance and creep resistance of PTFE. That is, as the filler, a particulate or fibrous inorganic filler or organic filler can be used.

  As the inorganic filler, for example, silica, feldspar, silica, alumina, bronze, mica, talc, talc, white carbon, graphite, glass fiber, carbon fiber, carbon black, titanium oxide, iron oxide, silicon nitride, carbon nitride, One or two of aluminum nitride, aluminum silicate, calcium silicate, zirconium carbide, silicon carbide, calcium carbonate, barium sulfate, molybdenum disulfide, kaolin, clay, mica, glass beans, glass balloon, carbon, coke, graphite, activated carbon More than seeds can be used. As an organic filler, 1 type (s) or 2 or more types can be used among a polyimide resin, aromatic polyester, and polyphenylene sulfide, for example. Further, one or more of these inorganic fillers can be used in combination with one or more of the organic fillers.

  The liquid auxiliary agent is not particularly limited as long as it is a solvent that easily wets PTFE, facilitates plastic deformation of the PTFE, and can be easily removed after extrusion. That is, as the liquid auxiliary agent, for example, organic liquid auxiliary agents such as aliphatic saturated hydrocarbons, aromatic hydrocarbons, alcohols and the like can be used.

  Specifically, as the organic liquid auxiliary agent, for example, petroleum solvents such as solvent naphtha, white oil, petroleum ether, and alcohol solvents such as methanol, ethanol, isopropyl alcohol, ethylene glycol, glycerin can be used. .

  In addition, as the liquid auxiliary agent, for example, an aqueous auxiliary agent such as water can be used, but those containing an organic liquid auxiliary agent as a main component are preferable. That is, for example, a liquid auxiliary containing 80% by weight or more, preferably 90% by weight or more, more preferably 98% by weight or more of the organic liquid auxiliary in the total solvent can be preferably used.

  As an extrusion pressure reducing agent, 1 or 2 or more selected from the group which consists of an organic silane compound which has a C3-C40 hydrocarbon group, an organic titanate compound, or an organic aluminate compound can be used. That is, any one or more of organic silane compounds, organic titanate compounds, and organic aluminate compounds can be used as long as they have one or more hydrocarbon chains having 3 to 40 carbon atoms.

  Carbon number of this hydrocarbon group becomes like this. Preferably it is 6-30, More preferably, it is 10-30, Most preferably, it is 12-24. The hydrocarbon group is, for example, an aliphatic hydrocarbon group or an aromatic hydrocarbon group having a carbon number in the above range. More specifically, this hydrocarbon group is, for example, an alkyl group, an aryl group, an aralkyl group, a cycloalkyl group, or an alkenyl group.

  When the hydrocarbon group is an alkyl group, the hydrocarbon group is a linear alkyl group or a branched alkyl group having a carbon number in the above range. Moreover, these hydrocarbon groups may have a substituent. That is, for example, it may be connected to another group via a functional group such as an ester group or an ether group.

  The hydrocarbon group can be, for example, a hydrocarbon group having no reactive functional group. That is, the hydrocarbon group can be, for example, a hydrocarbon group having no amino group, epoxy group, sulfide group or mercapto group, and preferably an amino group, epoxy group, sulfide group, mercapto group, vinyl group, allyl group. It can be a hydrocarbon group having no group or methacryl group.

  The hydrocarbon group can be, for example, an alkyl group having no reactive functional group, an aryl group, an aralkyl group, a cycloalkyl group, or an alkenyl group, and preferably an alkyl group having no reactive functional group. , An aryl group, an aralkyl group, or a cycloalkyl group.

  The organosilane compound can have one, two or three hydrocarbon groups as described above. The organosilane compound can be, for example, a compound represented by the following general formula (I).

  Here, in the general formula (I), one, two or three of R1 to R4 have 3 to 40 carbon atoms, preferably 6 to 35 carbon atoms, more preferably 10 to 30 carbon atoms, and particularly preferably 12 to 12 carbon atoms. 24 hydrocarbon groups. When two or three of R1 to R4 are hydrocarbon groups, these may be the same or different.

  Further, among R1 to R4, those other than the hydrocarbon group having 3 to 40 carbon atoms described above are a hydrocarbon group or a halogen group having 10 or less carbon atoms and smaller carbon number than the hydrocarbon group. is there. The hydrocarbon group having a small carbon number is, for example, an alkoxy group, an alkyl group, a vinyl group, a halogen group, or an aminoalkyl group. Further, the carbon number of the hydrocarbon group having a small carbon number is preferably 4 or less, more preferably 3 or less, and particularly preferably 2 or less.

  The organic silane compound has, for example, a so-called silane coupling agent having one, two, or three hydrocarbon groups having 3 to 40 carbon atoms as hydrocarbon groups other than hydrolyzing groups such as alkoxy groups or the like. An organosilane compound having a similar molecular structure can be obtained.

  That is, this organosilane compound can be, for example, a compound represented by the following general formula (II).

  Here, in the general formula (II), n is an integer of 3 to 40, preferably 6 to 35, more preferably 10 to 30, particularly preferably 12 to 24, m is 1, 2 or 3. OR independently represents an alkoxy group having 1 to 10 carbon atoms and smaller than the carbon number of the alkyl group.

  That is, in this case, the organic silane compound can be an alkylalkoxysilane such as an alkyltrialkoxysilane, a dialkyldialkoxysilane, or a trialkylalkoxysilane.

  The PTFE composition can also contain other components. That is, for example, the PTFE composition can contain other resins as long as the characteristics based on PTFE and the filler are not impaired. As this resin, for example, other fluororesin, polyimide, and aromatic polyamide can be used.

  As other fluororesin, for example, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA) or tetrafluoroethylene / hexafluoropropylene copolymer (FEP) can be used. The content of the other fluororesin can be, for example, 0 to 40 parts by weight, preferably 0 to 20 parts by weight with respect to 100 parts by weight of PTFE.

  In the first step S1, a PTFE composition having a filler content of 15 to 60% by volume is prepared from these raw materials. Furthermore, the content rate of this filler can be 15-50 volume%, for example, and can be 15-40 volume%.

  Moreover, the content rate of the filler in a PTFE composition can be 25 to 80 weight%, for example, can be 25 to 70 weight%, and can be 25 to 60 weight%.

  Moreover, the content rate of PTFE in a PTFE composition can be 2 to 60 weight%, for example, can be 10 to 60 weight%, and can be 20 to 60 weight%.

  Moreover, the content rate of the liquid adjuvant in a PTFE composition can be 15-40 weight%, for example, and can be 16-25 weight%.

  The content of the extrusion pressure reducing agent in the PTFE composition can be, for example, 0.02 to 10% by weight, 0.08 to 10% by weight, and 0.2 to 10% by weight. And can be 0.2 to 8% by weight, and can be 0.5 to 6% by weight.

  The PTFE composition in the first step S1 can be prepared by mixing the above-described raw materials. The order of mixing the components is not particularly limited. For example, it is preferable to first treat the filler with an extrusion pressure reducing agent, and then mix the treated filler with PTFE.

  That is, first, a treatment solution containing an extrusion pressure reducing agent is prepared. The treatment solution can be prepared, for example, by dissolving the extrusion pressure reducing agent in a predetermined solvent. The solvent is not particularly limited as long as it can dissolve the extrusion pressure reducing agent and can be evaporated after the treatment. For example, ethanol, toluene, isopropyl alcohol, and acetone can be used.

  Next, the treatment solution and the filler are mixed. That is, for example, the treatment solution is added to the dried filler, and these are uniformly mixed by an operation such as stirring. Thus, by sufficiently wetting the surface of the filler particles or fibers with the treatment solution, the extrusion pressure reducing agent can be effectively adsorbed on the surface. Further, the solvent is evaporated from the mixture of the filler and the treatment solution and dried. As a result, the surface of the filler particles or fibers can be effectively coated with the extrusion pressure reducing agent.

  Further, the treated filler is mixed with PTFE. That is, the filler previously coated with the extrusion pressure reducing agent and dried and the dried PTFE fine powder are mixed. In this way, a dry mixed powder in which the filler and the PTFE fine powder are uniformly dispersed is prepared.

  And this mixed powder and a liquid adjuvant are mixed, and a PTFE composition is finally prepared. That is, the liquid auxiliary is added while stirring the mixed powder. In this way, the surface of the filler particles or fibers and the surface of the PTFE powder particles can be sufficiently wetted with the liquid auxiliary. Further, the mixture of the filler, PTFE powder, and liquid auxiliary agent is held for a predetermined time so that they are sufficiently adapted (so-called aging is performed). In the first step S1, a PTFE composition is thus prepared using PTFE, a filler, a liquid auxiliary, and an extrusion pressure reducing agent as raw materials.

  In preparing the PTFE composition, when the extrusion pressure reducing agent, the filler, the PTFE fine powder, and the liquid auxiliary are mixed at once, for example, when the solubility of the extrusion pressure reducing agent in the liquid auxiliary is small. In some cases, the extrusion pressure reducing agent may be unevenly present locally, the solubility of the extrusion pressure reducing agent in the liquid auxiliary agent is large, and the affinity between the liquid auxiliary agent and PTFE fine powder is high. If it is high, the extrusion pressure reducing agent is unevenly distributed in the liquid auxiliary agent unevenly distributed on the particle surface of the PTFE fine powder, and in any case, it is difficult to uniformly distribute the extrusion pressure reducing agent in the mixture. Become.

  On the other hand, as described above, the extrusion pressure reducing agent is uniformly distributed in advance on the surface of the filler, and then the filler treated with the extrusion pressure reducing agent, PTFE fine powder and liquid auxiliary agent, , Even if the filler content is high as in the PTFE composition according to the present invention, the extrusion pressure reducing agent is uniformly dispersed between the particles or fibers of the filler, The frictional resistance between the particles or fibers can be effectively reduced, and as a result, the paste extrusion pressure can be effectively reduced and stabilized.

  In the subsequent second step S2, paste extrusion molding is performed using the PTFE composition prepared in the first step S1 as described above. In the second step S2, first, preforming is performed. That is, a PTFE composition is molded into a preform having a shape corresponding to the mold using a mold having a predetermined shape.

  Next, the preform is filled into a paste extruder equipped with an extrusion die having a predetermined shape. Then, the paste extruder is operated to extrude the PTFE composition from the extrusion mold at high pressure. In addition, extrusion can be performed at the temperature of 20-80 degreeC, for example, and can also be performed at normal temperature.

  Thus, a PTFE extruded product having a shape corresponding to the discharge port of the extrusion mold can be obtained. The shape of the PTFE extrudate is a shape corresponding to the extrusion mold, and can be, for example, a tube shape (cylindrical shape), a rod shape (rod shape), or a sheet shape.

  2 and 3 show a cross section of an example of an extrusion die used for the paste extrusion. In addition, the direction which the arrow X shown in FIG.2 and FIG.3 points is an extrusion direction.

  The mold 10 shown in FIG. 2 includes a cylinder 20 and a die 30 attached to the downstream end of the cylinder 20 in the extrusion direction. A cylinder channel 21 through which the PTFE composition passes is formed inside the cylinder 20.

  Inside the die 30, a taper-shaped reduced flow path 31 extending while reducing the diameter from the upstream end in the extrusion direction to a midway portion, and a discharge flow path 32 extending from the midway portion to the downstream end in the extrusion direction with a constant diameter. And are formed.

  3 includes a cylinder 50, a die 60 attached to the downstream end of the cylinder 50 in the extrusion direction, and a mandrel 70 inserted into the downstream side portion of the die 60 in the extrusion direction. I have. A cylinder channel 51 through which the PTFE composition passes is formed inside the cylinder 50.

  Inside the die 60 is a tapered reduced flow passage 61 extending from the upstream end in the extrusion direction to the midway portion while reducing the diameter, and a tapered discharge flow extending from the midway portion to the downstream end while increasing the diameter again. A path 62 is formed.

  A tapered mandrel 70 extending concentrically from the middle part of the die 60 to the downstream end while concentrating the diameter is disposed concentrically inside the discharge flow path 62 corresponding to the tapered shape. That is, the discharge flow path 62 is formed as a space sandwiched between the die 60 and the mandrel 70.

  In the dice 60 shown in FIG. 3, a double pipe structure in which the mandrel 70 is inserted into the discharge flow path 62 is formed. Therefore, the inner surface area of the discharge flow path 62, that is, the die 60 and the PTFE composition Is larger than the inner surface area of the downstream end of the reduced flow path 61.

  As described above, in the die 60 in which the inner surface area of the discharge channel 62 is larger than the inner surface area of the downstream end of the reduced channel 61, as shown in FIG. The extrusion pressure is likely to increase compared to the die 30 having a constant inner surface area in the flow path 32. 3 shows the case where the diameters of the discharge flow path 62 and the mandrel 70 expand in the extrusion direction. For example, even if the diameters are constant, the inner surface area is reduced due to the double structure. Increase.

  Furthermore, in the die 60 shown in FIG. 3, the inner surface area of the discharge flow path 62 increases in the extrusion direction. Thus, in the die 60 in which the inner surface area of the discharge channel 62 increases in the extrusion direction, as shown in FIG. 2, the extrusion pressure is higher than that of the die 30 in which the inner surface area of the discharge channel 32 is constant. Is likely to rise.

  In this regard, the PTFE composition used in the present method contains an extrusion pressure reducing agent as described above, so that the extrusion pressure is reduced even when the mold 40 having the die 60 as shown in FIG. 3 is used. Can be effectively reduced.

  Although the mechanism by which the extrusion pressure reducing effect is obtained by using this extrusion pressure reducing agent is not clear, for example, the extrusion pressure reducing agent is easy to form micelles in solution based on its molecular structure, and molecular chains are likely to line up. . This structure in which molecular chains are arranged is considered to be slippery to each other. The molecules of the extrusion pressure reducing agent having such a structure are dispersed in the vicinity of the surface of the filler particles or fibers, and enter between the particles or fibers to form a molecular film in which molecular chains are arranged. By forming, friction between the filler particles or fibers and between the filler particles or fibers and the PTFE particles is effectively reduced (that is, the filler and PTFE are slippery). Is possible).

  Further, in paste extrusion molding of a PTFE composition containing conventional PTFE and a filler, it has been considered important to uniformly distribute PTFE and the filler. Based on this idea, for example, a dispersion (dispersion) obtained by dispersing PTFE fine particles having an average particle size of 0.5 μm obtained in emulsion polymerization in water, and a filler similarly dispersed in water. And a hydrocarbon group having a small number of carbons so that the filler and the PTFE can be mixed well. Attempts have been made to add organosilane compounds having the following:

  In contrast, in this method, unlike such conventional methods, it is possible to use a fine powder of PTFE when mixing the filler and PTFE. For example, PTFE fine particles are dispersed in water. There is no need to use the PTFE dispersion, and a complicated process of finely dispersing the filler in water, mixing, agglomerating, filtering, collecting and drying can be omitted. That is, the extrusion pressure can be effectively reduced only by uniformly distributing the extrusion pressure reducing agent on the surface of the filler.

  The method may further include a step of processing the PTFE extrudate obtained by the paste extrusion described above into a predetermined shape. That is, in this case, for example, by rolling the PTFE extrudate using a predetermined rolling roll, the shape can be changed to a desired sheet shape.

  Moreover, this method is good also as including the process of baking the above-mentioned PTFE extrudate. That is, in this case, after the PTFE extrudate obtained by extrusion is processed as it is or by rolling or the like, it is fired by holding it at a predetermined high temperature for a predetermined time. In this way, a sintered body of the PTFE extrudate can be obtained. The firing temperature can be, for example, a temperature not lower than the melting point of PTFE and lower than the decomposition point.

  According to such a method, even when the content of the filler in the PTFE composition is high, an increase in the extrusion pressure can be effectively reduced. And the paste extrusion molding which concerns on this embodiment (henceforth "this molding") can be manufactured efficiently and reliably by this method.

  The content rate of the filler in this molded object is as high as 25-98 volume% corresponding to the PTFE composition used for the manufacture. And although the content rate of a filler is high in this way, as mentioned above, it manufactures by effectively reducing the pressure at the time of paste extrusion.

  In particular, when a mold 40 as shown in FIG. 3 is used, it has been difficult to achieve good paste extrusion due to a significant increase in extrusion pressure. It is possible to efficiently and reliably manufacture the molded body having high strength and having a uniform structure peculiar to the PTFE molded body and having a high filler content.

  Next, specific examples according to the present embodiment will be described.

  As PTFE, PTFE fine powder (Fullon (registered trademark) CD145, manufactured by Asahi Glass Co., Ltd.) was used. As the filler, silica stone powder (bird roof silica stone No. 20, manufactured by Mares Co., Ltd.), which is an inorganic filler, was used. As the liquid auxiliary agent, an isoparaffin solvent (Isopar M, manufactured by ExxonMobil Corp.) which is an organic liquid auxiliary agent was used.

[Filler + Organosilane compound]
As the organic silane compound, three types of alkyltriethoxysilanes having different alkyl group carbon atoms, that is, methyltriethoxysilane having 1 carbon atom, hexyltriethoxysilane having 6 carbon atoms, octadecyl having 18 carbon atoms Triethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.) was prepared.

  Then, 1 part by weight of this alkyltriethoxysilane was dissolved in ethanol to prepare a treatment solution (weight ratio of alkyltriethoxysilane: ethanol = 1: 6). The treatment solution was then mixed with 40 parts by weight of filler powder to prepare a mixture of these. During the mixing, the treatment solution was added little by little to the filler powder while stirring.

  Thereafter, the mixture was stirred at room temperature to evaporate ethanol, and further dried by maintaining at 80 ° C. for 5 to 12 hours. Next, 59 parts by weight of PTFE fine powder was added to the dried mixture and mixed thoroughly with a mixer to prepare a dry mixed powder of filler powder treated with alkyltriethoxysilane and PTFE fine powder.

  Furthermore, a PTFE composition for extrusion molding was prepared by uniformly mixing 20 parts by weight of an organic liquid auxiliary with the dry mixed powder. That is, a PTFE composition containing 49.2% by weight of PTFE, 33.3% by weight of a filler, 16.7% by weight of an organic liquid auxiliary, and 0.8% by weight of an organic silane compound was prepared. The filler content was 22.1% by volume.

[Comparative Example 1]
Instead of the above-mentioned organosilane compound, synthetic smectite (Lucentite, Corp Chemical Co., Ltd.) or synthetic mica (Somasif, Corp Chemical Co., Ltd.) is used at the same blending ratio, and PTFE for extrusion molding is performed in the same procedure. A composition was prepared.

  Moreover, the PTFE composition for extrusion molding was prepared without using the above-mentioned additive. That is, first, a dry mixed powder was prepared by sufficiently mixing 60 parts by weight of the dried PTFE fine powder and 40 parts by weight of the dried filler powder with a mixer. Next, an PTFE composition for extrusion molding was prepared by uniformly mixing 20 parts by weight of an organic liquid auxiliary agent with the dry mixed powder.

  Moreover, the PTFE composition for extrusion molding which does not contain filler powder was similarly prepared. That is, 99 parts by weight of PTFE fine powder, 1 part by weight of any of the above-mentioned additives, and 20 parts by weight of an organic liquid auxiliary agent are uniformly mixed to obtain a PTFE composition for extrusion molding that does not contain a filler powder. A product was prepared.

  Further, by uniformly mixing 100 parts by weight of PTFE fine powder and 20 parts by weight of an organic liquid auxiliary agent, a PTFE composition for extrusion molding containing no filler powder was prepared without using an additive.

[Measurement of extrusion pressure]
Paste extrusion molding of the PTFE composition obtained as described above was performed. That is, a rod-shaped preform having an outer diameter of 30 mm was molded by compressing the PTFE composition at a pressure of 0.8 MPa using a predetermined mold.

  Subsequently, this preform was filled in a paste extruder, and paste extrusion was performed at room temperature. And the pressure at the time of this extrusion was measured using the pressure measuring device (Tensilon, A & D Co., Ltd.).

  The paste extrusion molding corresponds to the first mold (hereinafter referred to as “mold (I)”) corresponding to the mold 10 shown in FIG. 2 and the mold 40 shown in FIG. A second mold (hereinafter referred to as “mold (II)”) was used.

  That is, as the mold (I), a die having a cylinder 20 having an inner diameter Ds of 30 mm, a reduction channel 31 having a taper angle θd of 60 °, and a discharge channel 32 having a constant inner diameter Dd of 2 mm. 30 was used.

  Further, as the mold (II), the cylinder 50 having an inner diameter Ds of 30 mm, the reduction channel 61 having a taper angle θd of 90 °, the inner diameter Dd1 at the upstream end, and the inner diameter Dd2 at the downstream end are each 2 mm. And a die 60 having a discharge flow path 62 of 37 mm and a mandrel 70 having a taper angle θm of 50 ° were used.

  In the discharge flow path 62, the distance (clearance) between the inner surface of the die 60 and the inner surface of the mandrel 70 was 2.0 mm. In the paste extrusion molding using the mold 10, the extrusion speed was 50 mm / min, and in the paste extrusion molding using the mold 40, the extrusion speed was 5 mm / min.

  In FIG. 4, the result of having measured extrusion pressure (MPa) in paste extrusion molding of each PTFE composition of Example 1 and Comparative Example 1 is shown. As shown in FIG. 4, in the extrusion molding using the mold (I), when the PTFE composition did not contain a filler, there was no significant difference in extrusion pressure depending on the presence or absence of additives. .

  In contrast, when the PTFE composition contained a filler, the extrusion pressure was reduced by using the additive. In particular, when an alkyltriethoxysilane having 18 carbon atoms was used, the extrusion pressure could be significantly reduced.

  Further, as shown in FIG. 4, in the extrusion molding using the mold (II), even when the PTFE composition does not contain a filler, the extrusion pressure is reduced by using alkyltriethoxysilane. I was able to.

  In contrast, when the PTFE composition contained a filler, the extrusion pressure was reduced by using the additive. In particular, when an alkyltriethoxysilane having 6 and 18 carbon atoms was used, the extrusion pressure could be significantly reduced. Especially, the fall of the extrusion pressure when using C18 alkyltriethoxysilane was conspicuous.

  As in Example 1 above, PTFE fine powder was used as PTFE, silica stone powder was used as the filler, and isoparaffinic solvent was used as the liquid auxiliary.

[Filler + Organosilane compound]
As an organic silane compound, three types of alkyltriethoxysilanes having different alkyl group carbon atoms, that is, methyltriethoxysilane having 1 carbon atom, hexyltrimethoxysilane having 6 carbon atoms, octadecyl having 18 carbon atoms Triethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.) was prepared.

  Next, three kinds of treatment solutions having different concentrations were prepared for each alkyltrialkoxysilane by the same procedure as in Example 1 described above, and the filler was treated and dried using the treatment solutions. . Then, a PTFE composition was prepared by the same procedure as in Example 1 as shown in FIG.

[Comparative Example 2]
In the same manner as in Example 1 described above, a PTFE composition for extrusion molding was prepared using synthetic smectite or synthetic mica instead of alkyltrialkoxysilane. Moreover, as shown in FIG. 5, the PTFE composition for extrusion molding was prepared, without using the above-mentioned additive.

[Measurement of extrusion pressure]
Paste extrusion molding of the PTFE composition obtained as described above was performed. That is, according to the same procedure as in Example 1 above, a preformed PTFE composition was molded, and then paste extrusion was performed. And the pressure at the time of this extrusion was measured using the pressure measuring device. In addition, the above-mentioned metal mold | die (I) was used for extrusion.

  In FIG. 5, the result of having measured extrusion pressure (MPa) in paste extrusion molding of each PTFE composition of Example 2 and Comparative Example 2 is shown. As shown in FIG. 5, when synthetic smectite, synthetic mica, and alkyltrialkoxysilane having 1 carbon were used, there was no significant difference in extrusion pressure as compared with the case where no additive was contained.

  On the other hand, when the alkyltrialkoxysilane having 6 or 18 carbon atoms was used, the extrusion pressure could be effectively reduced as compared with the case where no additive was contained.

  As in Example 1 above, PTFE fine powder was used as PTFE, silica stone powder was used as the filler, and isoparaffinic solvent was used as the liquid auxiliary.

[Filler + Organosilane compound]
As the organosilane compound, three alkyltrialkoxysilanes in which the alkyl group has different carbon numbers and the alkyl group has no reactive functional group, that is, propyltrimethoxysilane having 3 carbon atoms, 8 carbon atoms N-octyltriethoxysilane and 12-carbon n-dodecyltriethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.) were prepared.

  Subsequently, according to the procedure similar to the above-mentioned Example 1, three types of treatment solutions were prepared for each alkyltrialkoxysilane, and the filler was treated and dried using the treatment solutions. Then, a PTFE composition similar to that in Example 1 was prepared by the same procedure as in Example 1 described above.

[Comparative Example 3]
Instead of the above alkyltrialkoxysilane, an PTFE composition for extrusion molding was prepared using three types of organosilane compounds in which the alkyl groups had different carbon numbers and the alkyl groups had reactive functional groups. That is, as the organic silane compound, two kinds of γ-aminoalkyltrimethoxysilane (3-aminopropyltrimethoxysilane having 3 carbon atoms and having an amino group, or 3- (5 carbon atoms having an amino group) ( 2-Aminoethylamino) propyltrimethoxysilane) or 3-glycidyloxypropyltrimethoxysilane (Tokyo Kasei Kogyo Co., Ltd.) having 6 carbon atoms and having an epoxy group was used. Prepared. Moreover, the PTFE composition for extrusion which does not use an additive and the PTFE composition for extrusion which does not contain a filler powder and an additive were also prepared in the same manner as in Comparative Example 1 described above.

[Measurement of extrusion pressure]
Paste extrusion molding of the PTFE composition obtained as described above was performed. That is, according to the same procedure as in Example 1 above, a preformed PTFE composition was molded, and then paste extrusion was performed. And the pressure at the time of this extrusion was measured using the pressure measuring device. In addition, the above-mentioned metal mold | die (II) was used for extrusion. The extrusion speed was 5 mm / min.

  In FIG. 6, the result of having measured extrusion pressure (MPa) in paste extrusion molding of each PTFE composition of Example 3 and Comparative Example 3 is shown. As shown in FIG. 6, when γ-aminoalkyltrimethoxysilane or 3-glycidyloxypropyltrimethoxysilane having a reactive functional group (amino group or epoxy group) is used, no additive is used. The extrusion pressure increased.

  On the other hand, when the alkyltrialkoxysilane having no reactive functional group was used, the extrusion pressure could be effectively reduced as compared with the case where no additive was used. In particular, the decrease in extrusion pressure when using an alkyltrialkoxysilane having 12 carbon atoms was significant, and the extrusion pressure was even lower than when no fillers and additives were used.

  As PTFE, instead of PTFE fine powder (Fluon (registered trademark) CD145, manufactured by Asahi Glass Co., Ltd.) used in Example 1 described above, PFA micro powder (Teflon (registered trademark) MP-101, PTFE / PFA fine powder added with Mitsui DuPont Fluorochemical Co., Ltd.) was used. This PTFE / PFA fine powder contained 90% by weight of PTFE fine powder and 10% by weight of PFA micropowder. Further, silica powder was used as the filler, and isoparaffinic solvent was used as the liquid auxiliary.

[Filler + Organosilane compound]
As the extrusion pressure reducing agent, alkyltriethoxysilane (octadecyltriethoxysilane) having 18 carbon atoms used in Example 1 was used. And according to the procedure similar to the above-mentioned Example 1, the processing solution of the alkyltriethoxysilane was prepared, the filler was processed using the processing solution, and it was made to dry. Then, a PTFE composition for extrusion molding was prepared by the same procedure as in Example 1 described above.

[Comparative Example 4]
Moreover, the PTFE composition for extrusion molding was prepared without using the above-mentioned extrusion pressure reducing agent. That is, first, 60 parts by weight of PTFE / PFA fine powder (PTFE: PFA = 90: 10 (weight ratio)) prepared as described above and 40 parts by weight of the dried filler powder are sufficiently mixed with a mixer. Thus, a dry mixed powder was prepared. Next, an PTFE composition for extrusion molding was prepared by uniformly mixing 20 parts by weight of an organic liquid auxiliary agent with the dry mixed powder.

  In addition, by uniformly mixing 100 parts by weight of the above-mentioned PTFE / PFA fine powder and 20 parts by weight of an organic liquid auxiliary agent, a PTFE composition for extrusion molding containing no filler powder and an extrusion pressure reducing agent was also prepared. .

[Measurement of extrusion pressure]
Paste extrusion molding of the PTFE compositions of Example 4 and Comparative Example 4 obtained as described above was performed. That is, according to the same procedure as in Example 1 above, a preformed PTFE composition was molded, and then paste extrusion was performed. And the pressure at the time of this extrusion was measured using the pressure measuring device. In addition, the above-mentioned metal mold | die (II) was used for extrusion. The extrusion speed was 5 mm / min.

  In FIG. 7, the result of having measured extrusion pressure (MPa) in paste extrusion molding of each PTFE composition of Example 4 and Comparative Example 4 is shown. As shown in FIG. 7, by using alkyltriethoxysilane having 18 carbon atoms, the extrusion pressure could be remarkably reduced as compared with the case where no additive (extrusion pressure reducing agent) was used.

  As in Example 1 above, PTFE fine powder was used as PTFE, and isoparaffinic solvent was used as the liquid auxiliary. On the other hand, alumina powder (A-42-2, manufactured by Showa Denko KK) was used as the filler instead of silica powder.

[Filler + Organosilane compound]
As the extrusion pressure reducing agent, alkyltriethoxysilane (octadecyltriethoxysilane) having 18 carbon atoms used in Example 1 was used.

  Then, 1 part by weight of this alkyltriethoxysilane was dissolved in ethanol to prepare a treatment solution (weight ratio of alkyltriethoxysilane: ethanol = 1: 6). The treatment solution was then mixed with 52 parts by weight of filler powder to prepare a mixture of these. During the mixing, the treatment solution was added little by little to the filler powder while stirring.

  Thereafter, ethanol was evaporated while stirring the mixture at room temperature, and the mixture was further dried by maintaining at 70 ° C. for 12 hours. Next, 48 parts by weight of PTFE fine powder was added to the dried mixture and mixed thoroughly with a mixer to prepare a dry mixed powder of filler powder treated with alkyltriethoxysilane and PTFE fine powder.

  Furthermore, a PTFE composition for extrusion molding was prepared by uniformly mixing 20 parts by weight of an organic liquid auxiliary with the dry mixed powder. That is, a PTFE composition containing 39.5% by weight of PTFE, 42.7% by weight of a filler, 17.0% by weight of an organic liquid auxiliary, and 0.8% by weight of an organic silane compound was prepared. The filler content was 21.2% by volume.

[Comparative Example 5]
Moreover, the PTFE composition for extrusion molding was prepared without using the above-mentioned extrusion pressure reducing agent. That is, first, a dry mixed powder was prepared by thoroughly mixing 48 parts by weight of PTFE fine powder and 52 parts by weight of a dried filler powder with a mixer. Next, an PTFE composition for extrusion molding was prepared by uniformly mixing 20 parts by weight of an organic liquid auxiliary agent with the dry mixed powder.

[Measurement of extrusion pressure]
Paste extrusion molding of the PTFE compositions of Example 5 and Comparative Example 5 obtained as described above was performed. That is, according to the same procedure as in Example 1 above, a preformed PTFE composition was molded, and then paste extrusion was performed. And the pressure at the time of this extrusion was measured using the pressure measuring device. In addition, the above-mentioned metal mold | die (II) was used for extrusion. The extrusion speed was 5 mm / min.

  In FIG. 8, the result of having measured extrusion pressure (MPa) in paste extrusion molding of each PTFE composition of Example 5 and Comparative Example 5 is shown. As shown in FIG. 8, by using alkyltriethoxysilane having 18 carbon atoms, the extrusion pressure could be remarkably reduced as compared with the case where no additive (extrusion pressure reducing agent) was used.

10, 40 mold, 20, 50 cylinder, 21, 51 cylinder flow path, 30, 60 dies, 31, 61 reduced flow path, 32, 62 discharge flow path, 70 mandrels.

Claims (6)

A method of preparing a polytetrafluoroethylene composition containing polytetrafluoroethylene, a filler, and a liquid auxiliary, and extruding the polytetrafluoroethylene composition,
The polytetrafluoroethylene composition is composed of an organic silane compound having 3 to 40 carbon atoms, an organic titanate compound, and an organic aluminate compound as an extrusion pressure reducing agent together with 15 to 60% by volume of the filler. A paste extrusion molding method comprising one or more selected from the group consisting of: The paste extrusion method according to claim 1, wherein the hydrocarbon group does not have a reactive functional group. The paste extrusion molding method according to claim 1 or 2, wherein the polytetrafluoroethylene composition contains the organosilane compound as an extrusion pressure reducing agent. The paste extrusion molding method according to any one of claims 1 to 3, wherein the hydrocarbon group is an alkyl group, an aryl group, an aralkyl group, a cycloalkyl group, or an alkenyl group. The paste extrusion molding method according to claim 4, wherein the hydrocarbon group is an alkyl group. A paste extrusion molded article produced by the paste extrusion molding method according to any one of claims 1 to 5.

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