Classifications

• • 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
  • D01F1/00—General methods for the manufacture of artificial filaments or the like
  • D01F1/02—Addition of substances to the spinning solution or to the melt
  • D01F1/10—Other agents for modifying properties
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D5/00—Formation of filaments, threads, or the like
  • D01D5/42—Formation of filaments, threads, or the like by cutting films into narrow ribbons or filaments or by fibrillation of films or filaments
• • 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
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16J—PISTONS; CYLINDERS; SEALINGS
  • F16J15/00—Sealings
  • F16J15/16—Sealings between relatively-moving surfaces
  • F16J15/18—Sealings between relatively-moving surfaces with stuffing-boxes for elastic or plastic packings
  • F16J15/20—Packing materials therefor
  • F16J15/22—Packing materials therefor shaped as strands, ropes, threads, ribbons, or the like

Definitions

• T he present invention relates to a high strength expanded single molecular aligned temperature treated yarn for braiding and filter elements having a better strength, performance, durability and life and process for the manufacture of the same.
• Another object of the subject invention is that it relates to the use of these yarns in the manufacture of better performance gland packing and filter elements.
• T he other embodiment of the present invention relates to hollow core high recuperation packing for sterrn tube, rubber, stabilizer,pumps, mixers and agitators.
• the Tetra Fluoro Ethylene Polymer extruded in the form of a solid porous article resulted in poor strength.
• the conventional process comprises expanding a shaped article consisting essentially of higher crystalline poly tetra fluoroethylene made by a paste forming extrusion technique after removal of lubricant, by stretching at different rate.
• the cord extruded by this conventional method of making flat tape by calendering results in uneven expansion, due to compressing and shearing of the particle which are on the outer surface. The moment the particles on the outer surfaces are compressed and sheared, it results in the uneven expansion and dimensional variation in thickness and width of the tape.
• T he porus Tetra Fluoro Ethylene Polymer as claimed in U.S. Patent no.3,953, 566 having amorphous content exceeding about 5% and having a micro structured characterized by nodes interconnected by fibrils though having high porosity and strength needs further strength and porosity to make the shaped article having better strength and long durability.
• the properties of the fibre made in accordance with the subject invention has proved to be considerably beneficial as compared from prevoius PTFE and expanded PTFE fibres.
• a conventional porous PTFE fibre such that sold under the trademark RASTEX by W.L.Gore & Associates have performed very well where porosity, fabric finish and thickness are not critical but the improved fibre of subject invention has overcome all these criticalities.
• the objective of the present invention is accomplished by a process involving paste form product of a Tetra Fluoro Ethylene Polymer to make them both porus and stronger.
• paste forming of dispersion polymerized poly(Tetra Fluoro Ethylene Polymer ) is well known commercially.
• the steps in paste forming includes mixing the resin with a lubricant which is later removed by the process of drying .
• the unsintered product is heated above the polymers melting point causing it to sinter or coalesce into an essentially impermeable structure.
• Such paste-formed , dried unsintered shapes could be expended by stretching them in one or more directions under certain conditions but they were not found to be of desired strength and porousity.
• the PTFE paste extrusion grades are mixed with mineral oil or neptha or PTFE extrusion grade is loaded with microfine graphite powder and amorphous carbon in a special blender container where the blending or loading is carried out without shearing of particles.
• the container in which PTFE and Mineral Oil and or graphite and carbon are put in predetermined fixed quantity (for white grade no graphite and carbon) and for bettter lubricity yarn graphite and carbon in predetermined maximum percentage exceeding 50% are loaded in to the PTFE in this specialized container rotating at low RPM.
• the special blades on the sides of the container blends the mixture together uniformly with specially made bristles brush wiping them continuously without shearing of the particles.
• the PTFE extrusion grade- Teflon-GJ is mixed with MTO or Naptha and is loaded with microfine graphite powder and amorphous carbon and mixed together in predetermined quantity (for white grade no graphite and carbon) maximum percentage exceeding 50%.
• the main embodiment of the invention resides in the improved process for the manufacture of tapes having uniform dimension of thickness and width giving better strength and durability.
• the embodiment of the invention resides in extracting yarns from the collapsed and silted hollow tubes by means of conventional yarns separating means, treating the individual tow and winding them to make a versatile, durable and high strength yarns by temperature stretching the slitted tape and then separating the yarns. The temperature stretch is again applied which is used for braiding purposes giving better strength and durability
• the increase in strength of the polymer matrix is dependent upon the strength of the extruded material before expansion, the degree of crystallinity of the polymer, the rate and temperature at which the expansion is performed and amorphous locking. When all these factors are employed to maximize the strength of the material the high tensile stength and porosity is obtained.
• the hollow tube of the subject invention extruded with a predetermined diameter and thickness not only obviates the disadvantageous inherent in the conventional extruded solid cord but gives an extra strength due to the homogenous alignment of PTFE along with the pariphery.
• the wall thickness and diameter of the tube is predetermined keeping in view the ingredients, extrusion pressure.
• the optimum configuration is achieved by having a wall thickness of the extruded tube from 0.5mm to 5mm diameter and the diameter of the hollow core to be 1mm to 15mm.
• the PTFE paste extrusion grade is mixed with mineral oil or neptha or PTFE extrusion grade is loaded with microfine graphite powder and amorphous carbon in a special blender container where the blending or loading is carried out without shearing of particles.
• the container in which PTFE and Mineral Oil and or graphite and carbon are put in predetermined fixed quantity (for white grade no graphite and carbon) and for bettter lubricity yarn graphite and carbon in predetermined maximum percentage exceeding 50%, are loaded in to the PTFE in this specialized container rotating at low RPM.
• the special blades on the sides of the container blends the mixture together uniformly with specially made brush having bristles wiping them continously without shearing of the particles.
• the hollow core packing is designed keeping in view the very aspect of deformation and reformation.
• the concept of the hollow core packing is designed and custom built for each application.
• the measurement of runout , type of fluid, gas required to be sealed against the temperature and pressure are the parameters required to design the core and the covering braid depending upon particular application.
• the holow core takes care of the excessive runout without damaging the braid due to constant deforming and reforming as in the case of an ordinary packing.
• the rubber core used should have the required chemical resistance against the media and the temperature resistance.
• the round hole inside the square tube is designed keeping in view the amount of run out i.e. if the runout of the shaft is 6mm, the inner hole should be minimum 4 to 6mm thick.
• the rubber should have minimum of 40 to 80 shore hardness. Since, the minimum wall thickness required is 4 to 6mm.
• the rubber core may be made of silicone, viton, ethylene, propylene, nitrile, neoprne, butyl rubber etc. or a combination of any of them best suited to resist the temperature and the chemicals inside the equipment.
• the outer braiding can be either, the one which is disclosed above or the combination of Fluoro polymer, PTFE or Graphite/PTFE only or Fluoro polymer, PTFE or graphite/PTFE reinforced with kevlar fibre, carbon fibre, glass fibre or nylon fibre , the same have been disclosed in detail in the U.S. Patent application No. 09/100,066 dated June 19,1998 corresponding to Indian Patent Application Number 276/BOM/97.
• Figure 1 relates to the conventional packing showing the distribution of gland follower load
• Figure 2 relates to the graph of conventional packing showing that the maximum pressure on the gland packing is near the gland follower
• Figure 3 relates to the cross-section view of the developed hollow core high recuperation packing
• Figure 4 relates to the uniform gland load distribution
• the PTFE extrusion grade paste or PTFE extrusion grade paste loaded with microfine graphite powder of size 150-220 microns.
• the PTFE paste extrusion grade either alone or with graphite powder are put into a round transparent container and 10-40 % by weight mineral spirit or oil or neptha is added.
• the container in which PTFE and Mineral Oil and or graphite and carbon are put in predetermined fixed quantity (for white grade no graphite and carbon) and for bettter lubricity yarn graphite and carbon in predetermined maximum percentage exceeding 50% are loaded in to the PTFE in the specialized container rotating at low RPM.
• the special blades on the sides of the container blends the mixture together uniformly with specially made brush having bristles wiping them continously without shearing of the particles.
• Normally PTFE paste extrusion grade does not accept more than 15% loading of carbon.
• the extra loading of graphite for lubrisity is possible only due to this innovative specialized technique.
• the said homogenous mixture is loaded in a hydraulic barrel for extrusion under a presssure of 20-500kgs.
• the extruder is provided with the proper die having a predetermined diameter for extruding a hollow tube having the desired diameter and wall thickness.
• the pre-determind diameter and wall thickness of hollow tube plays a very important and significant roll in determining the overall strength of the end product.
• the hollow tube thus obtained is then immediately collapsed and slited to the required size and wound on different bobbins.
• the slited and collapsed tube is further treated to a high temperature by feeding it through a temperature zone of 50-300°C where the stretching and expanding is carried out about 20% to 1000%).
• the treated tape are then cooled by passing through water at an ambient temperature and dried preferably in an open atmosphere.
• the dried tape or tow is further passed through rollers covered with lubricants such as micro fined graphites mobindinum di- sulphide and the like.
• the tapes thus softened has uniform dimension of thickness and width and is then used for braiding.
• FIG 1 shows the conventional gland packing where the shaft (2) is having the conventional gland packing (3).
• the load of the packing (3) is minimum while the load on the packing (4) is maximum which can be seen by compression (4).
• Such distribution of load has been shown in the graph as depicted in figure 2 which indicates that the load on gland packing (3) is just 10% while at the gland packing (4) it is maximum of 100%) thus causing wear of shaft as well as packing itself.
• the Figure 3 is depicting the cross-section view of the hollow core high recuperation packing which comprises an inner hollow square core (6) made of rubber having an inner hole (5).
• the size of the inner hole (5) is determined by the size of the packing to consider the required amount of run out or sag of shaft of the equipment.
• the inner hole (5) is generally 2mm to 24mm.
• the wall thickness of square hollow core made of rubber is 2.5mm to 20mm which should be minimum 15% to 20% or more the actual gland packing size.
• the rubber square hollow core is having the braiding of reinforced yarns (7) which is generally synthetic fibre enveloped with PTFE or Graphite/PTFE.
• the braiding (7) varies from 2mm to 6mm. This braiding is also dependent on the size of the packing.
• Figure 4 depicts the uniform load distribution, which is not acquired by the conventional gland packing as shown in figure 2.
• EXAMPLE 1 A process for the manufacture of a high strength, single molecular aligned temperature treated yarn for braiding and filter elements wherein :-
• the PTFE extrusion grade paste mixed with 12-38% by weight with microfine graphite powder of size 155-200 microns.
• the PTFE extrusion grade paste with graphite powder are put into a round transparent container and 18-32% by weight mineral spirit is added,, rotating at low RPM of 22-58 RPM for 3 1/2 .-5 3 4 hours and put in a specialized container for loading of graphite into PTFE without shearing of
• PTFE particles by rotating at 20-60 RPM for 3-6 hours.
• the said homogenous mixture is loaded in a hydraulic barrel for extrusion under a presssure of 25-480kgs.
• the extruder is provided with the proper die having a pre-determined diameter for extruding a hollow tube having the desired diameter and wall thickness.
• the hollow tube thus obtained is then immediately collapsed and slited to the required size and wound on different bobbins.
• the slited and collapsed tube is further treated to a high temperature by feeding it through a temperature zone of 55-305°C where the stretching and expanding is carried out about 30% to 1010%).
• the treated tape are then cooled by passing through water at an ambient temperature and dried in an open atmosphere.
• the dried tape or tow is further passed through rollers covered with lubricants such as micro fined graphites molybdenum di- sulphide.
• the tapes thus softened has uniform dimension of thickness and width and is then used for braiding.
• EXAMPLE-2 A process for the manufacture of a high strength, single molecular aligned temperature treated yarn for braiding and filter elements wherein:-
• the PTFE extrusion grade paste is put into a round transparent container and 18-32%) by weight mineral oil is added, rotaitng at low RPM for 3-4 hours and put in a specialized container for loading of graphite into PTFE without shearing of PTFE particles by rotating at 25-60 RPM for 3-6 hours.
• the said homogenous mixture is loaded in a hydraulic barrel for extrusion under a presssure of 35-540kgs.
• the extruder is provided with the proper die having a pre-determined diameter for extruding a hollow tube having the desired diameter and wall thickness. The hollow tube thus obtained is then immediately collapsed and slited to the required size and wound on different bobbins.
• the slited and collapsed tube is further treated to a high temperature by feeding it through a temperature zone of 60-295 °C where the stretching and expanding is carried out about 30%o to 1010%.
• Stretching the said tape for single axis molecular aligned of the fibers of the said tape dipping the said single axis molecular aligned tape in mineral oil/ light paraffin oil or heavily lubricating oil or mixture thereof. It is then calendered through a set of rollers to obtain the thickness of 0.55mm to 0.006mm.
• the calendered tape is further passed through a temperature zone of 350-420°C for a period of 4 seconds -6 minutes in an inert atmosphere.
• the treated tape are then cooled by passing through water at an ambient temperature and dried in an open atmosphere.
• the dried tape or tow is further passed through rollers covered with lubricants such as micro fined graphites molybdenum di- sulphide.
• the tapes thus softened has uniform dimension of thickness and width and is then used for braiding.
• EXAMPLE 3 A process for the manufacture of a high strength, single molecular aligned temperature treated yarn for braiding and filter elements wherein,
• the PTFE extrusion grade paste is put into a round transparent container and 18-32%)
• neptha 1/2 by weight neptha is added, rotating at low RPM of 25-60 RPM for 3-4 hours and put in a specialized container for loading of graphite into PTFE without shearing of PTFE particles by rotating at 20-60 RPM for 3-6 hours.
• the said homogenous mixture is loaded in a hydraulic barrel for extrusion under a presssure of 35-540kgs.
• the extruder is provided with the proper die having a pre-determined diameter for extruding a hollow tube having the desired diameter and wall thickness.
• the hollow tube thus obtained is then immediately collapsed and silted to the fibrous mass, which may then be slitted into strands by slitting means.
• the strands are further treated to a high temperature by feeding it through a temperature zone of 60-295 °C where the stretching and expanding is carried out about 30%) to 1010%). Stretching the said strands and dipping the said single axis molecular aligned tape in mineral oil/ light paraffin oil or heavily lubricating oil or mixture thereof. It is then calendered through a set of rollers to obtain the thickness of 0.55mm to 0.006mm. The calendered tape is further passed through a temperature zone of 350-420°C for a period of 4 seconds -6 minutes in an inert atmosphere. Once the such sheets are formed they are further sent to a set of cutting means for expansion in the longitudinal directions.
• the width of the fibre can be controlled by several process known in the art of expanding PTFE.
• the subject invention has proved to be more advantageous as the subject invention resulted in the manufacture of high strength of even dimension yarns for braiding and filter elements.
• the inventive fibre has a smoother surface than the conventional fibres, which resulted very beneficial as having less chances of fibrillation and thus providing superior release properties when woven into a sheet.
• the improved processing steps of the present invention create a fibre that has a number of improved properties,including more uniform dimensions along its length, improved compressibility and handling along with easy high quality uniform processing.
• the subject invention has provided the use of these yarns in the manufacture of better performance gland packing and filter elements as compared to commercially available conventional yarns.

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• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Sealing Devices (AREA)
• Braiding, Manufacturing Of Bobbin-Net Or Lace, And Manufacturing Of Nets By Knotting (AREA)

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Cited By (7)

Citations (3)

• 1998
  • 1998-05-20 IN IN318BO1998 patent/IN190482B/en unknown
  • 1998-12-29 WO PCT/IN1998/000001 patent/WO1999060191A1/en active Application Filing

Patent Citations (3)

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