Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J3/00—Processes of treating or compounding macromolecular substances
  • C08J3/12—Powdering or granulating
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
  • D01F6/02—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D01F6/08—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds from polymers of halogenated hydrocarbons
  • D01F6/12—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds from polymers of halogenated hydrocarbons from polymers of fluorinated hydrocarbons
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H13/00—Pulp or paper, comprising synthetic cellulose or non-cellulose fibres or web-forming material
  • D21H13/10—Organic non-cellulose fibres
  • D21H13/12—Organic non-cellulose fibres from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H13/14—Polyalkenes, e.g. polystyrene polyethylene
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2327/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers
  • C08J2327/02—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment
  • C08J2327/12—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
  • C08J2327/18—Homopolymers or copolymers of tetrafluoroethylene

Definitions

• the present invention relates to a polytetrafluoroethylene papermaking material excellent in pressure equalizing property, air permeability, and dust collecting property, a polytetrafluoroethylene fiber fibrous powder as a raw material thereof, a molded article made of the papermaking material, and production.
• the present invention relates to a method for producing a highly efficient polytetrafluoroethylene fibrous powder. More specifically, the present invention relates to a method for producing a polytetrafluoroethylene fibrous powder capable of obtaining a polytetrafluoroethylene paper having a smooth surface and excellent air permeability when formed.
• PTFE Polytetrafluoroethylene
• Japanese Patent Publication No. 45-8165 discloses a PTFE fibrous powder having an average fiber length of 100 to 500 m and an average shape factor of 5 or more, or a filler mixed uniformly with this.
• a method is disclosed in which a paper composition is dispersed in a liquid to form a paper stock, which is made and dried, and then the paper is peeled off from the substrate and fired.
• the PTFE fibrous powder used here is a material that strongly shears raw PTFE at high temperatures. It is obtained by crushing by applying force.
• the pulverizer itself may be heated or the powder may be heated, and it is further described that a method of pulverizing while blowing hot air is most preferable.
• a method of pulverizing while blowing hot air is most preferable.
• pulverization is performed at a temperature of about 20 to 50 ° C, but when processed at this temperature, relatively fine PTFE powder with a particle size of 5 im or less is generated, and is made of hard PTFE with low air permeability. There is a problem of becoming paper.
• the present invention has been made to overcome the above problems by clarifying the above problems, and has a uniform distribution of physical properties, and is excellent in cohesiveness, pressure equalization, air permeability, and dust collecting properties. It is an object of the present invention to provide a PTFE fibrous powder, a molded article made of the PTFE paper product, and a method for producing the PTFE fibrous powder having excellent production efficiency.
• the present invention relates to a differential scanning calorimeter performed at a heating rate of 5 ° C. per minute.
• the analysis relates to a PTFE fibrous powder having a peak area ratio on the low temperature side of the obtained endothermic curve of 88.5% or more of the total peak area.
• the PTFE fibrous powder preferably has an average fiber length of 100 to 5000 mm and an average shape factor of 5 or more.
• the specific surface area measured by the nitrogen adsorption method is preferably 4.0 m 2 Zg or more.
• the present invention also relates to a polytetrafluoroethylene papermaking product obtained by using the PTFE fibrous powder as a raw material and going through a papermaking process.
• the peak area ratio on the low-temperature side in the obtained melting endothermic curve is 88.5% or more of the total peak area.
• a method for producing a polytetrafluoroethylene fibrous powder having an average fiber length of 100 to 5,000 m and an average shape factor of 5 or more, comprising supplying a raw material polytetrafluoroethylene powder. Feeding the raw material polytetrafluoroethylene powder from the hopper to a stretching treatment tank, stretching by a stretching means, and classifying after stretching.
• the present invention relates to a method for producing a fluoroethylene fibrous powder.
• the supply of the raw material polytetrafluoroethylene powder from the hopper to the stretching treatment tank is performed by using the flow of a medium. It is preferable to remove the polytetrafluoroethylene powder having a particle size of 5.0 m or less by a classification step performed after the stretching treatment.
• the amount of energy applied to the polytetrafluoroethylene powder from the stretching means during the stretching process is preferably 10 to 200 kcalZkg.
• the present invention relates to a molded article obtained from the PTFE paper product.
• BRIEF DESCRIPTION OF THE FIGURES Figure 1 shows an example of a melting endothermic curve obtained by analyzing PTF powder with a differential scanning calorimeter, and two peak curves obtained by separating the peaks of the melting endothermic curve.
• Fig. 1 shows an example of a melting endothermic curve (hereinafter also referred to as a DSC curve) obtained by analyzing PTFE powder with a differential scanning calorimeter (solid line), and two peak curves obtained by separating the peaks of the DSC curve. (Broken line).
• a DSC curve melting endothermic curve obtained by analyzing PTFE powder with a differential scanning calorimeter
• Differential scanning calorimeter measurement of PTFE fine powder with normal molecular weight shows that there is a double peak or a clear shoulder from around 337 to around 340 ° C as shown in Fig. 1.
• a single peak is observed. This is due to the release of the first (lower temperature) peak (or shoulder) due to the release of the micro-Brownian motion of molecules that have been unraveled during the polymerization process of PTFE, and the micro-Brownian motion of the molecules that have not progressed during the polymerization process.
• the molecular weight of PTFE molecules is much larger than that of general-purpose molten resins, it may be more energy stable to organize them with a single molecular chain than to organize them as a group.
• the molecules are present in a state where the binding force from the surroundings is relatively small, so that the conformational stabilization of one molecular chain is likely to occur.
• some molecules are organized by interference from external forces such as shear force and intermolecular force.
• the disintegration of molecules progresses further, and the more fusion between tissues occurs, the more the molded product with excellent cohesion and shape can be obtained.
• the stress is transmitted uniformly, and the pressure is excellent.
• the disentanglement of the molecular chains may have occurred during the temperature rise.However, if only the thermal disentanglement operation was used, it would be difficult to achieve uniform control of the disassembly, and some excess heat would be applied. In such a case, there is a problem that the site is firmly organized and loses the adhesion to other tissues. To avoid this, it is preferable to use unraveling by external force and unraveling by heat at the same time.
• the peak area in the melting endothermic curve obtained by the differential scanning calorimeter is directly proportional to the calorific value, and is proportional to the number of molecules in a generally accepted range. Therefore, as shown in Figure 1, two pins When a DSC curve with a single peak or peak is separated into two normal or other distribution curves, as shown by the dashed lines, the molecule whose peak area on the cold side is unraveled And the area of the peak (P H ) on the high temperature side can be considered to be proportional to the number of undissociated molecules, so that the ratio of the dissociated PTFE molecules is It can be evaluated by the ratio of the area of the low-temperature side peak (P L ) to the total peak area in the melting endothermic curve obtained by the differential scanning calorimeter.
• a double peak or a single peak with a distinct shoulder can be mathematically understood as a composite curve with three or more multiple normal distributions, but since it has two vertices, it has two normal distributions or Separation as a distribution curve similar to this is considered sufficiently valid, and reasonable results have been obtained in the study of the present invention.
• the composite absorption peak can usually be separated by approximation using a Gaussian-Lorentian type curve.
• the degree of divergence is smaller, and this method is also used in the computational software attached to many commercially available analytical instruments.
• the basic peak position is determined by giving the two apparent vertices found in the PTFE powder as a raw material as initial values and performing approximation without any restriction.
• the basic peak positions obtained in this way are 339.14 ° «0 and 33.43.01, and based on this, the linear and half-value widths are not limited, and only the peak temperature is the initial value. From this, the composite curve was separated into two by approximation with the range limited to 0.6 to 0.7 or less, and the peak area was determined. In this study, we tried to reduce the time required for convergence of values. For this purpose, information on the raw material powder was used, but it can also be obtained directly from the melting curve of the fibrous powder.
• the PTFE fibrous powder of the present invention was subjected to differential scanning calorimetry analysis at a heating rate of 5 ° C per minute, and the peak area on the low temperature side of the obtained melting endothermic curve was 88.5% of the total peak area. It is preferably 92.0% or more and 99.5% or less. If the low-temperature side peak area is less than 88.5% of the total peak area, the cohesive force tends to be insufficient and the molded article tends to lose its shape, and the obtained paper tends to have poor cushioning properties. is there. As already mentioned, when the peak area on the low temperature side is too large, that is, when two peaks (or shoulders) are not observed, it is often impossible to obtain a desirable state of molding the paper.
• the specific surface area of the raw material greatly affects its cohesion, that is, the mechanical properties of the molded product.
• the specific surface area of the PTFE fibrous powder may be 4.0 m 2 / g or more. More preferably, it is not less than 5.0 m 2 Zg and not more than 8.5 m 2 Zg.
• the specific surface area is a value measured by a nitrogen adsorption method.
• the fibrous powder is likely to be densely packed, resulting in a large weight per unit area of the paper, resulting in low air permeability and a tendency to hardly exhibit cushioning properties. .
• the raw material powder has a fibrous shape.
• the shape factor can indicate that the raw material is fibrous.
• amorphous powders exhibiting cohesive strength as paper show cohesive strength but may not be fibrous in view factor.
• the fibrous state means that all or a part thereof is stretched by an external force and can exhibit anisotropy in physical properties.
• the raw material PTFE used in the present invention may be a homopolymer of tetrafluoroethylene (hereinafter abbreviated as TFE), or 95 to 100 mol% of TFE, and the formula (I):
• R f is a fluorine-containing alkyl group having 1 to 3 carbon atoms
• fluoroolefin represented by the formula (I) examples include perfluoroolefins such as hexafluoropropylene (hereinafter abbreviated as HFP).
• fluorine-containing (alkyl vinyl ether) represented by the formula (II) examples include perfluoro (methyl vinyl ether) (hereinafter abbreviated as PMVE), perfluoro (ethyl vinyl ether) (hereinafter abbreviated as PEVE), and perfluoro. (Propyl vinyl ether) (hereinafter abbreviated as PPVE).
• the raw material PTFE powder used in the present invention can be obtained by polymerization using a polymerization initiator in the presence of a water-soluble fluorinated dispersant.
• a polymerization initiator include persulfates and organic peroxides
• the chain transfer agent include hydrogen and hydrocarbons such as propane, and water-soluble compounds such as ethanol.
• the raw material PTFE powder thus obtained preferably has an average particle size of 5 to 2000 m. If the average particle size is less than 5 zzm, the paper will be hard and have low air permeability due to the large amount of fine powder after treatment. If the average particle size exceeds 2 OO Om, coarse powder will remain after the treatment, resulting in a paper with a rough surface.
• the PTFE fibrous powder of the present invention can be produced by the following production method using, for example, an apparatus having a raw material hopper, a stretching tank, and a classification device.
• the raw material PTFE powder is charged from a supply machine into a raw material hopper,
• the raw material PTFE powder is supplied from the hopper to the stretching tank.
• the supply of the raw PTFE powder to the drawing tank may be performed by dropping under its own weight, or may be performed mechanically depending on the form of the raw PTFE powder, but the shape of the obtained PTFE fibrous powder is completely controlled.
• the stretching treatment tank is provided with stretching means (details will be described later).
• Use fibrous powder when processing the raw material PTFE powder, it is preferable to control the amount of energy applied to the PTFE powder during the process to control the degree of unraveling of the PTFE fibrous powder.
• the raw material PTFE powder In the step of supplying the raw material PTFE powder from the raw material hopper to the stretching tank, if a material having a small particle size is used, it hardens in the hopper, and it becomes difficult to drop and supply the PTFE powder by its own weight. In that case, a liquid such as water can be forcibly supplied to the stretching tank as a medium.
• a liquid medium When the obtained PTFE fiber powder is stored without immediately sending it to the papermaking process, it is not preferable to use a liquid medium, so supply the raw PTFE powder using a gas such as dry air as the medium. be able to. However, it is not preferable because it may affect the movement of the rotating body in the stretching tank or the discharge of the stretched raw PTFE powder.
• a PTFE fibrous powder having an average fiber length of 100 to 500; m and an average shape factor of 5 or more can be produced very efficiently.
• the stretching treatment temperature preferably utilizes the frictional heat during stretching. This tends to make it easier to fibrillate and to obtain powder having a relatively stable fiber length. Therefore, it is preferable that the stretching means performs a stretching process using a frictional force.
• a stretching means includes, for example, a hammer mill and a screen mill, and is preferably an apparatus capable of applying a shearing force in one direction only by a rotating body to stretch the raw material powder.
• the amount of energy applied to the PTFE powder from the stretching means during the stretching process is 10 to 200 kcal Zkg, it is possible to prevent the generation of PTFE aggregates.
• the PTFE paper made from the PTFE fibrous powder obtained in this way has much entanglement between the fibrous powders, and is locally excellent in cushioning properties accompanied by heat fusion between the powders. Papermaking can be obtained.
• the amount of energy added to the PTFE powder from the stretching means is less than 10 kca 1 Zkg, short fibrous powders increase and sufficient physical entanglement cannot be obtained.
• the amount of energy applied to the PTFE powder from the stretching means during the stretching process can be defined by the amount of energy given to the stretching means.
• the amount of energy given to the stretching means is the amount of energy per 1 kg of the PTFE powder required to maintain the number of revolutions of the stretching when the PTFE powder is stretched by the stretching means. It can be obtained from the difference between the current values of When using a medium to supply the raw material to the stretching tank, the amount of heat to be applied must be calculated based on the room temperature of 40 ° C or less, including the amount of heat given from the temperature difference with the medium.
• the raw material PTFE powder is processed, and then classified using a classifier.
• the average fiber length is preferably from 100 to 4000. If the average fiber length is less than 100 zm, a part of the average fiber length will fall off from the net-like base material during papermaking, causing pinholes. On the other hand, if the average fiber length exceeds 5000 m, it will be difficult to produce paper with a uniform thickness because the fiber length is long.
• the classification device include a classification screen and the like, and a device capable of separating powder at a predetermined size as a boundary is preferable.
• removing the PTFE fibrous powder having a particle size of 5 m or less is preferable in that the air permeability of the PTFE paper made using the powder is improved, and the PTFE is excellent in flexibility and cushioning property. Further, it is preferable to remove the PTFE fibrous powder having a particle size of lOzm or less.
• the particle size is measured using a laser diffraction type particle size distribution analyzer HELO S & RODOS system (manufactured by SYMPATEC) while dispersing the PTFE fiber powder with 3 bar compressed air.
• Particle size refers to 50% particle size.
• the average view factor of the PTFE fibrous powder is preferably 5 or more, more preferably 10 or more.
• the upper limit of the average view factor is not particularly limited, but is preferably 1000 or less.
• the average form factor is obtained by dividing the fiber length by the fiber width. When the average form factor is less than 5, the paper is difficult to peel off from the net-like base material after firing, resulting in a poorly finished paper having poor surface smoothness and appearance (fluffing, distortion).
• the PTFE fibrous powder thus obtained can be paper-made by the following method.
• the PTFE fibrous powder is uniformly dispersed in water or the like with a dispersant. And is considered as stock.
• an organic polymer reinforced fiber, an inorganic filler and the like may be added to the stock.
• the stock is formed on a substrate such as a net. After that, it is dried and fired to obtain PTFE paper.
• a filter having a larger area can be installed without backing, thereby reducing the size of the filter unit.
• the thickness of the PTFE paper obtained by papermaking depends on the intended use, but is preferably 0.02 mm or more and 8.00 mm or less, more preferably 0.05 mmL3 ⁇ 4 and 6.0 mm or less. More preferably, it is more than 0.10 mm and less than 4.00 mm. When the thickness is less than 0.02 mm, the trapping capacity tends to be insufficient when used as a filler. If the thickness is greater than 8.0 mm, the paper material will creep under its own weight, and the uniformity of the basis weight tends to be impaired.
• the surface smoothness of the PTFE paper obtained by papermaking is preferably 10.5 m or less, more preferably 10.0 m or less. If the surface smoothness is larger than 10.5 m, it tends to fluff and dust during handling.
• the surface smoothness is an arithmetic average roughness measured by a stylus type surface roughness meter, as described later.
• the air permeability of the PTFE paper obtained by making the paper depends on the use of the PTFE paper, but 5.5 sec / cm ⁇ ) ⁇ 30 OmL or more, 14.0 sec cZcm ⁇ i ) ⁇ 30 OmL or less, more preferably 6.0 sec / cm (i) * 300 mL or more, and 13.0 sec / c ⁇ ⁇ 300 mL or less. If the value of the air permeability is less than 5.5 se ⁇ / ⁇ -300 ml, the collection efficiency of the fill tends to be inferior, and the value of the air permeability is 14.0 se ⁇ / ⁇ - If it is larger than 30 OmL, the processing capacity tends to be poor. As described later, the air permeability is required for 30 OmL of air to pass through a 1 cm (f) orifice using a Gurley tester. Measured time.
• the paper product of the present invention is not only used in a so-called paper form, but also processed into a cubic shape and used as a molded product.
• a plate-like material having irregularities such as an exterior plate is obtained.
• it when it is fixed in a cylindrical shape, it can be used as a belt-shaped cushion material or a filter.
• the PTFE molded article of the present invention can be applied to more various uses. For example, to provide high dimensional stability such as high strength that cannot be exhibited by a molded product of PTFE alone, such as resistance to riff, it is possible to mix and mold with powders of aramide, fiber, fibrid, etc. Good. Abrasion resistance can be expected to be improved by mixing with fibers and fibers made of polyvinyl thiazole.
• the fibrous powder of the present invention Even if the molded product obtained from the mixture with other materials has a shape such as a columnar or rectangular parallelepiped, if the fibrous powder of the present invention is used, a relatively dry dispersing method can be used to obtain a relatively dispersible material. Good complexes are obtained. Dry mixing is easy, but wet mixing may be used if necessary. It is also possible to obtain mixed paper products based on these findings.
• the melting point of the mating partner material is preferably 200 or more, more preferably 220 ° C. or more, so as not to impair the high heat resistance of PTFE.
• the component does not necessarily need to be organic, and one or more mating materials should be appropriately selected according to the purpose.
• Examples of these include fibers such as polyparaphenylenebenzoxazole, liquid crystalline polyester, aramide pulp, glass, and carbon, but the present invention is not limited to these examples.
• the melting point is a value determined by the DSC method.
• the mating material used in the composite has high heat resistance, but it always has high heat resistance depending on applications that do not particularly require heat resistance. No need. For example, if it is desired to improve the strength of the paper while maintaining the charging characteristics of PTFE, it is possible to select a cut material of acrylic fiber, fibrid, etc. as the mating material.
• Polyamide, polyester, polyolefin, etc. can also be selected as mating materials for bulky paper materials to expand.
• the paper product of the present invention can be applied to various uses owing to its excellent heat resistance, but in some cases, it can be used as a more suitable one by forming the above-mentioned composite paper product.
• a core material for compression molding it is possible to prevent the occurrence of abrasion at the edge of the sheet stamping molded product and the die, and it is possible to ensure excellent releasability continuously.
• a filter medium it can not only electrostatically collect dust, but also exhibit durability against strong acids and strong alkalis and filterability at high temperatures. If it is used as a wire wrapping covering material, it has pores inside, so it can exhibit more excellent insulation properties and can also be expected to have properties as a heat insulating layer.
• the PTFE fibrous powder is in a very bulky state, it is very easy to mix with other materials in a dry state, and thus it is suitable as a raw material for a composite molded product.
• the weight fraction of PTFE is less than 2%, the properties of PTFE will not be sufficiently exhibited, and if it exceeds 98%, the effect of adding components other than PTFE will be sufficient. Can not be obtained. Therefore, the weight fraction of components other than PTFE contained in the mixed molded product is preferably from 2 to 98%, more preferably from 4 to 96%, and still more preferably from 5 to 95%.
• the powder is measured with an electron microscope, and the obtained length in the fiber direction of 200 points or more is the value obtained by arithmetic averaging. In the measurement, those with a length of 80 tim or less shall not be measured.
• the powder is measured with an electron microscope, and the length in the fiber direction obtained is divided by the width of the fiber. The following shall not be measured.
• the standard sample is a specially-made paper whose compression work X 100 (%) is 60%.
• the measurement was performed using RPC-220 manufactured by Seiko Instruments Inc. at a heating rate of 5 ° CZ for a sample amount of 3 mg. JIS—K7123 was referenced.
• a differential scanning calorimeter analysis was performed at a heating rate of 5 ° C / min, and the obtained DSC curve was separated into two peak curves using a Gaussian-Lorentian type curve, and the area of the low-temperature side peak was calculated. Divide by peak area to calculate peak area ratio.
• the PTFE paper is measured using a dial gauge H type (pressurized 200 g or less).
• the specific surface area of the powder was evaluated by the nitrogen adsorption method using Biosorb manufactured by Yuasa Ionics Co., Ltd. in a standard accessory cell.
• tensile strength (tensile strength) Using a Tensilon STA-1 150 manufactured by Orientec Co., Ltd., a sample having a width of 15 mm was measured at a distance between chucks of 100 mm and a tensile speed of 20 OmmZ, and tensile strength was calculated by the following conversion formula.
• a polymer obtained by emulsion polymerization of 100 mol% of tetrafluoroethylene was used as a raw material PTFE powder (average particle size: 570 ⁇ m).
• the obtained raw material PTFE powder was fed into a hopper by a feeder.
• the PTFE powder was supplied to a stretching tank equipped with a rotary blade (tank inner diameter: 16 Om ⁇ ) and stretched while appropriately assisting with dry air.
• the grinding capacity was 10-15 kgZ hours.
• the results of calculating the amount of energy applied to the raw material powder at this time are as shown in Table 1.
• the lower surface of the stretching tank is partially meshed, so that only small pieces of a certain size are allowed to exit the stretching tank. This was treated with a standard classification sieve to remove powder of 5 m or less.
• a PTFE fibrous powder was obtained in the same manner as in Example 1 except that the raw PTFE powder was supplied to the stretching tank with hot air at the temperature shown in Table 2 and stretched.
• the obtained PTFE fibrous powder had the average fiber length, average shape coefficient, peak area ratio, and specific surface area shown in Table 2, respectively.
• Example 2 papermaking was performed in the same manner as in Example 1 to obtain PTFE paper having a thickness of 0.47 to 0.51 mm.
• the surface smoothness, air permeability, cushioning property, and tensile strength of the obtained PTFE paper were as shown in Table 2.
• the PTFE paper obtained in Comparative Example 1 has remarkably poor air permeability, and is not at all suitable for filter use.
• any of the PTFE papers was frayed at the time of cutting and was inferior in dimensional retention of the cut portion. Table 2
• a mixed paper product was obtained in the same manner as in Example 1, except that 2 parts by weight of aramide pulp (manufactured by Toray Industries, Inc., Kepler pulp) was added to 8 parts by weight of the PTF E fibrous powder during wet papermaking.
• the coefficient of linear thermal expansion from room temperature to 250 ° C. was measured and found to be 0.5 ppm, indicating that it exhibited excellent hot dimensional stability.
• a PTFE paper product having a uniform physical property distribution and excellent in cohesiveness, surface smoothness, pressure equalization, air permeability, dust collecting property, electrical properties, and mechanical properties.
• a PTFE fibrous powder having an average fiber length of 100 to 500 Atm and an average shape factor of 5 or more.

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• 2004
  • 2004-02-05 CN CNB2004800014615A patent/CN100374485C/zh not_active Expired - Fee Related
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