GB2086305A - An Apparatus for the Formation by Extrusion of a Fibrillated PTFE Strand - Google Patents

An Apparatus for the Formation by Extrusion of a Fibrillated PTFE Strand Download PDF

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Publication number
GB2086305A
GB2086305A GB8132842A GB8132842A GB2086305A GB 2086305 A GB2086305 A GB 2086305A GB 8132842 A GB8132842 A GB 8132842A GB 8132842 A GB8132842 A GB 8132842A GB 2086305 A GB2086305 A GB 2086305A
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GB
United Kingdom
Prior art keywords
section
strand
apparatus
cross
exit
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB8132842A
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GB2086305B (en
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Klinger AG
Original Assignee
Klinger AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to AT0537180A priority Critical patent/AT368904B/en
Application filed by Klinger AG filed Critical Klinger AG
Publication of GB2086305A publication Critical patent/GB2086305A/en
Application granted granted Critical
Publication of GB2086305B publication Critical patent/GB2086305B/en
Application status is Expired legal-status Critical

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Classifications

    • DTEXTILES; PAPER
    • D01NATURAL OR ARTIFICIAL THREADS OR FIBRES; SPINNING
    • D01FCHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F6/00Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
    • D01F6/02Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D01F6/08Monocomponent 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
    • D01F6/12Monocomponent 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
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/022Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the choice of material
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/03Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
    • B29C48/05Filamentary, e.g. strands
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25Component parts, details or accessories; Auxiliary operations
    • B29C48/30Extrusion nozzles or dies
    • DTEXTILES; PAPER
    • D01NATURAL OR ARTIFICIAL THREADS OR FIBRES; SPINNING
    • D01DMECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D5/00Formation of filaments, threads, or the like
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/03Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
    • B29C48/07Flat, e.g. panels
    • B29C48/08Flat, e.g. panels flexible, e.g. films
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29KINDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2027/00Use of polyvinylhalogenides or derivatives thereof as moulding material
    • B29K2027/12Use of polyvinylhalogenides or derivatives thereof as moulding material containing fluorine
    • B29K2027/18PTFE, i.e. polytetrafluorethene, e.g. ePTFE, i.e. expanded polytetrafluorethene

Abstract

The strand (10) is stranded from apparatus which has a first section (2) in which the PTFE material is initially stretched longitudinally to form a bar shaped strand (21), a second section (3) in which the bar shaped strand is stretched laterally to form a web shaped strand (31) and a further section (5) which comprises a converging constriction e.g. of a cross- section which may be circular, elliptical, rectangular, or square, whereby the side wall of the constriction has an inclination relative to the axis in the range of 5-20 DEG , preferably 10-15 DEG . The reduction of the cross-sectional area of the exit of section (5) relative to the cross- sectional area of the inlet amounts to at least 20%. A following strand stabilising section (6) may be provided, of a length of 5 to 20 times the longest cross-sectional dimension of the exit of section (5). <IMAGE>

Description

SPECIFICATION An Apparatus for the Formation, by Extrusion, of a Fibrillated PTFE Strand The present invention relates to an apparatus for the formation by extrusion, of a strand of fibrillated PTFE material, the strand being a semiproduct which can itself be stretched to form a porous PTFE product which has filtering and sealing applications. The apparatus has a first section in which the PTFE-material is transformed into a rectangular shaped strand by a longitudinal stretching whereafter in a second section the bar shaped strand is given the form of a web shaped strand by a lateral stretching. Due to the shearing stresses produced thereby in the PTFE-material fibrils are formed, some of which commensurate with the deforming steps extend substantially in the longitudinal direction and others of which extend substantially in the lateral direction.If such an extruded strand, after the removal of the lubricant commonly present in an extrusion process, is then stretched and thereafter sintered or simultaneously sintered, a porous PFTEproduct is produced which due to its porosity is used in filtering applications and due to the corresponding easy deformability is also used in sealing applications.

It must be noted that in many apparatuses for the extrusion of a fibrillar stock material, such as disclosed e.g. in the DE-AS 1 5 04 291, a portion of the PTFE-particles are not transformed into fibrils after having been subjected to the transformation in both sections of the apparatus.

According to that published application such is advantageous during a subsequent working of the product into non-stretched and thus non-porous formed bodies. If, however, the object is to produce a material having as fine as possible pores such non-fibrillar particles are of a disadvantage because they influence the pore size of the stretched product specifically due to their size and mutual distance.

The invention provides an apparatus which produces tighter interlaced fibrils and accordingly finer pores at a comparatively same stretching rate which is specifically advantageous for a filtering duty. It has been now recognized that this is achieved in apparatuses of the kind mentioned above which comprise as a final section a converging constriction, preferably a frustoconical constriction converging at all sides, having an inclination of the constricting walls relative to the axis of 5-20#, preferably 10-1 50 whereby the reduction of the cross-sectional area of the exit compared with the cross-sectional area of the inlet amounts to at least 20%.The resistance component produced at such a reduction of the cross-sectional area of the strand extends due to the mentioned inclination acting on all sides of the converging walls of the constriction inclining and relative to the direction of material flow through the apparatus that no additional orientation in the longitudinal as well as lateral direction is produced and acts rather onto the existing fibrils in the form of an inclined force in the sense of a tighter interlacing.

The end section designed in accordance with the present invention as a conically converging constriction in order to reduce the crosssection area of the strand does not only produce the above described additional interlacing of existing lateral and longitudinal fibrils but forms from the possibly present PTFE-particles additional fibrils resulting from a given design of the conical constriction so that these PTFE-particles will be completely eliminated, too. Accordingly, after the stretching a uniformly porous final product, having tightly interlaced fibrils, is produced whereby its pore size is considerably reduced in comparison with the known porous products.

Dependent from the prevailing dimensions of the inventive extruder it may be possible in some instances that the stock material exiting out of the conical constriction comprises a fibrillar surface and/or a larger cross-sectional area than such of the constriction proper. In order to avoid such the final section can be shaped in accordance with a further preferred embodiment such that said conical constriction proceeds smoothly into a stabilizing section having a length which is about five to twenty times larger than the longest diagonal line of the cross-section of the exit of the conical constriction.

The present invention will be more fully understood by reference to the following detailed description thereof when read in conjunction with the attached drawing, wherein the single figure shows schematically a preferred embodiment of the invention.

Referring now to the single figure there is shown schematically a piston cylinder device 1, a first shaping section 2 having a cylindrical rectangular cross-sectional shape 21, a second shaping section 3 having flattened cross-sectional shape 31 at its exit, a third shaping section 4 having a cross-sectional shape 41 at its exit, a further shaping section 5 having a cross-sectional shape 51 at its exist described further below and a stabilizing section 6. The direction of the flow of the material is identified by arrow 10. Also shown is a first heating section 7 and a second heating section 8 and finally a stretching section 9.

A known apparatus is a so-called cord extruder. In such an apparatus a mixture consisting of PTFE (polytetrafluoroethylene) and lubricant are compressed in cylinder 1 having a diameter of 60 millimeters and thereafter shaped in the first section 2 of the apparatus by longitudinal stretching to about 800% to a bar shaped strand having the shape 21. In the subsequent second shaping section 3 of the apparatus the strand is shaped by a lateral stretching to about 600% to a web having a shape 31 and a cross-sectional area of 4.5 square centimeters.Because the final product of this known apparatus is a circular shaped strand 51, the second shaping section 3 is followed by a third section of the apparatus 4 in which the width of the strand is reduced and its thickness continuously increased until a circular exit opening of 15 millimeters diameter is reached~ shape 41. This section (of the known apparatus forming the prior art) follows the second section 3 and its lateral cross section is not described in detail.

If a mixture is used for the extrusion process which has been pretreated, namely a mixture consisting of PTFE (Fluor CD 123) and 25 weight parts of a lubricant (Shellsol E) the strand of about 15 millimeters leaving the apparatus is treated for 25 minutes at 1400C in order to expel the lubricant such as indicated by the first heating section 7. Thereafter, the strand is heated up to 2000C (second heating section 8) and thereafter stretched by 600% by means of two stretching rollers located at a distance of 3.25 meters from each other and a stretching speed of 8.66% per second. The subsequent sintering produces a porous strand; this strand comprises unchanged PTFE-particles which are interconnected by fibrils.

The void spaces defined by these fibrils and the unchanged PTFE-partic [ es form pores corresponding in length to the distance of the unchanged particles and in width to the distance of adjacent fibres. These pores have a length of about 35,um (1377.95x10-6 inches) and a width of 2-4 ym (78.74x 10-6 inches~157.48 10-6 inches).

The above description relates to a known apparatus. According to the embodiment of the present invention now being described there is provided a tapered, converging section 5 which is inclined relative to the direction of material flow by an angle of inclination of 100 and which has a length of 7 millimeters. Where the extruded strand is to take the form of a strip, the third section 4 may be dispensed with so that the second section 3 is followed by the tapered, converging section 5. Where the extruded strand is to take the form of a cord, the third section 4 is retained and this leads to the tapered converging section 5. Accordingly, an exiting strand is produced which has been reduced by the taper from 15 millimeters (i.e. the diameter on exiting from section 4) to a diameter of about 12.5 millimeters. Accordingly, the cross-section area of the strand has been reduced by about 30%.This handling of the material leads to a product which does not contain any unchanged PTFE-particles and comprises rather-viewed in a plane-a netlike structure in which the pores have a length of in the range of 0.1-5#um (3.937x 10 inches~ 196.85x10-6 inches) and a width in the range of 0.001 -0.05#um (0.003937 xl 10~6 inches~ 1.9685x 10~6 inches).

By means of the taper of the final section 5 a substantial decrease of the pore-size is achieved whereby the specific gravity of the product remains unchanged.

In some instances it may be possible that the strand leaving the final section 5 tends to swell and thus to comprise finally a cross-sectional area, which is larger than the final cross-sectional area of the taper of the final section 5. In order to avoid such the final section 5 is followed by a stabilizing section 6 having a length which is about five to twenty times larger than the longest diagonal line of the lateral cross-section of the exit of the final section 5. Where this final section 5 is of circular section, the stabilizing section has a length which is about five to twenty times the exit diameter of the final section 5, but neither final section 5 nor stabilizing section 6 need be circular. They may, for example be of elliptical, rectangular or square cross section.

Claims (5)

Claims
1. An apparatus for the formation, by extrusion, of a fibrillated strand, which extruded strand is stretchable to provide a porous strand of a polytetrafluorethylene material, which apparatus includes a first section for shaping the PTFE material by longitudinal stretching into a barshaped strand, a second section for shaping said strand by lateral stretching into a web-shaped strand, and a further section comprising a converging constriction with an inclination of the construction walls relative to its axis in the range of about 5--200 whereby the reduction of the exit cross-sectional area relative to the inlet crosssectional area amounts to at least 20%.
2. The apparatus of Claim 1, including an intermediate section disposed between the said second and further sections for reducing the width and increasing the thickness of the strand.
3. The apparatus of Claim 1 or Claim 2 wherein said inclination is in the range of about 10--150.
4. The apparatus of Claim 1, Claim 2 or Claim 3 wherein said further section proceeds subsequent to said converging constriction smoothly into a stabilizing section having a length which is about five to twenty times larger than the longest diagonal line of the lateral cross-section of the said further section at the exit thereof.
5. An apparatus according to any one of the preceding claims substantially as herein described with reference to and as illustrated in the accompanying drawings.
GB8132842A 1980-10-31 1981-10-30 An apparatus for the formation by extrusion of a fibrillated ptfe strand Expired GB2086305B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT0537180A AT368904B (en) 1980-10-31 1980-10-31 Plodder to produce a fibrillated precursor of polytetrafluoroethylene [Thylen

Publications (2)

Publication Number Publication Date
GB2086305A true GB2086305A (en) 1982-05-12
GB2086305B GB2086305B (en) 1984-05-02

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Family Applications (1)

Application Number Title Priority Date Filing Date
GB8132842A Expired GB2086305B (en) 1980-10-31 1981-10-30 An apparatus for the formation by extrusion of a fibrillated ptfe strand

Country Status (3)

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AT (1) AT368904B (en)
DE (1) DE3140755A1 (en)
GB (1) GB2086305B (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4908516A (en) * 1986-05-23 1990-03-13 West Michael A Apparatus and process for checking the authenticity of an article having a magnetic storage information means
US5026513A (en) * 1987-10-19 1991-06-25 W. L. Gore & Associates, Inc. Process for making rapidly recoverable PTFE
US5308664A (en) * 1987-10-19 1994-05-03 W. L. Gore & Associates, Inc. Rapidly recoverable PTFE and process therefore
EP0644037A1 (en) * 1993-09-22 1995-03-22 COMPAGNIE PLASTIC OMNIUM Société Anonyme dite: Hollow article made from a fluororesin, process of manufacture and extruder for carrying out the process

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4129881C2 (en) * 1991-09-09 1994-03-31 Gerhard Dr Ing Frey Plastic profile self-reinforcing

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4908516A (en) * 1986-05-23 1990-03-13 West Michael A Apparatus and process for checking the authenticity of an article having a magnetic storage information means
US5026513A (en) * 1987-10-19 1991-06-25 W. L. Gore & Associates, Inc. Process for making rapidly recoverable PTFE
US5308664A (en) * 1987-10-19 1994-05-03 W. L. Gore & Associates, Inc. Rapidly recoverable PTFE and process therefore
EP0644037A1 (en) * 1993-09-22 1995-03-22 COMPAGNIE PLASTIC OMNIUM Société Anonyme dite: Hollow article made from a fluororesin, process of manufacture and extruder for carrying out the process
FR2710286A1 (en) * 1993-09-22 1995-03-31 Plastic Omnium Cie hollow body fluororesin, process for its manufacture and extrusion press for carrying the method Óoeuvre.
US5518676A (en) * 1993-09-22 1996-05-21 Compagnie Plastic Omnium Process and extrusion press for making hollow body made of fluoro resin

Also Published As

Publication number Publication date
ATA537180A (en) 1982-04-15
GB2086305B (en) 1984-05-02
DE3140755A1 (en) 1982-05-27
AT368904B (en) 1982-11-25

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