GB2237279A - Heat treatment of plastics extrudate - Google Patents

Heat treatment of plastics extrudate Download PDF

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Publication number
GB2237279A
GB2237279A GB8921775A GB8921775A GB2237279A GB 2237279 A GB2237279 A GB 2237279A GB 8921775 A GB8921775 A GB 8921775A GB 8921775 A GB8921775 A GB 8921775A GB 2237279 A GB2237279 A GB 2237279A
Authority
GB
United Kingdom
Prior art keywords
heat treatment
extrudate
sintering
ptfe
heat
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.)
Withdrawn
Application number
GB8921775A
Other versions
GB8921775D0 (en
Inventor
John Richard Murphy
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.)
VACTITE Ltd
Associated Electrical Industries Ltd
Original Assignee
VACTITE Ltd
Associated Electrical Industries Ltd
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
Application filed by VACTITE Ltd, Associated Electrical Industries Ltd filed Critical VACTITE Ltd
Priority to GB8921775A priority Critical patent/GB2237279A/en
Publication of GB8921775D0 publication Critical patent/GB8921775D0/en
Publication of GB2237279A publication Critical patent/GB2237279A/en
Withdrawn legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
    • B29C35/02—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
    • B29C35/08—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation
    • B29C35/10—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation for articles of indefinite length
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/022—Extrusion 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/03—Extrusion 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
    • B29C48/06—Rod-shaped
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/03—Extrusion 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
    • B29C48/09—Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/88—Thermal treatment of the stream of extruded material, e.g. cooling
    • B29C48/91—Heating, e.g. for cross linking
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2791/00—Shaping characteristics in general
    • B29C2791/004—Shaping under special conditions
    • B29C2791/008—Using vibrations during moulding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING 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
    • B29K2027/00—Use of polyvinylhalogenides or derivatives thereof as moulding material
    • B29K2027/12—Use of polyvinylhalogenides or derivatives thereof as moulding material containing fluorine
    • B29K2027/18—PTFE, i.e. polytetrafluorethene, e.g. ePTFE, i.e. expanded polytetrafluorethene

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Oral & Maxillofacial Surgery (AREA)
  • Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)

Abstract

A method of sintering a crystalline polymer extrudate, comprising irradiating it with ultrasound to heat it to above its crystalline melting point. Preferably, the polymer is PTFE.

Description

Heat treatment of plastics extrudate This invention relates to the heat treatment of elongate, extruded material of crystalline polymer, and is particuarly useful in the so-called sintering of extruded PTFE (polytetrafluorethylene).
It is known that PTFE mixed with a processing aid may be extruded to form an elongate, semi-porous extrudate, and that it requires subsequent heat treatment, known as sintering, before it can be used e.g. as insulation or as a gasket or valve.
When heated, the PTFE loses the processing aid by evaporation, and once the polymer is at or above the crystalline melting point (about 330 C) then the molecules are relatively mobile; however, because of their exceedingly great length they never become truly mobile. They are able, nevertheless, to assume a preferred low energy position (a crystalline form) within the limits of their entanglement. During the heating process, the microscopic fibres formed during the extrusion process are made to coalesce.
For example it is common practice to heat articles made of unsintered PTFE to above the crystalline melting point without flow or other deformation occurring, because of the highly entangled nature of the network.
The sintering of hollow tubing of extruded PTFE for use as wire insulation is currently done in large ovens, through which the coated wire or hollow tubing passes. The speed of the extrusion process can be no greater than the time needed for heat from the elements of the sintering oven to reach the internal surfaces of the tube or wire insulation.
The purpose of the invention is to increase the production speed of heat-treated plastics extrudate such as PTFE wire insulation, Accordingly, the invention provides a method of sintering a crystalline polymer extrudate, comprising irradiating it with ultrasound to heat it to above its crystalline melting point.
By way of example, an ultrasonic radiation transducer is mounted in line with the extruder, either in the place of, or in addition to, the conventional sintering ovens.

Claims (2)

1. A method of sintering a crystalline polymer extrudate, comprising irradiating it with ultrasound to heat it above its crystalline melting point.
2. A method according to Claim 1, in which the polymer comprises PTFE.
GB8921775A 1989-09-27 1989-09-27 Heat treatment of plastics extrudate Withdrawn GB2237279A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB8921775A GB2237279A (en) 1989-09-27 1989-09-27 Heat treatment of plastics extrudate

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB8921775A GB2237279A (en) 1989-09-27 1989-09-27 Heat treatment of plastics extrudate

Publications (2)

Publication Number Publication Date
GB8921775D0 GB8921775D0 (en) 1989-11-08
GB2237279A true GB2237279A (en) 1991-05-01

Family

ID=10663670

Family Applications (1)

Application Number Title Priority Date Filing Date
GB8921775A Withdrawn GB2237279A (en) 1989-09-27 1989-09-27 Heat treatment of plastics extrudate

Country Status (1)

Country Link
GB (1) GB2237279A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5746856A (en) * 1992-04-10 1998-05-05 W. L. Gore & Associates, Inc. Method of ultrasonically welding articles of porous polytetrafluoroethylene

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1009654A (en) * 1962-08-17 1965-11-10 Union Carbide Corp Improved method and apparatus for processing thermoplastics
EP0004542A2 (en) * 1978-04-06 1979-10-17 Conoco Phillips Company Rapid phase transformation for polybutene-1
DE3617902A1 (en) * 1986-05-28 1987-12-03 Jurij Anatolevic Lapickij Process for the modification of polyethylene

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1009654A (en) * 1962-08-17 1965-11-10 Union Carbide Corp Improved method and apparatus for processing thermoplastics
EP0004542A2 (en) * 1978-04-06 1979-10-17 Conoco Phillips Company Rapid phase transformation for polybutene-1
DE3617902A1 (en) * 1986-05-28 1987-12-03 Jurij Anatolevic Lapickij Process for the modification of polyethylene

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5746856A (en) * 1992-04-10 1998-05-05 W. L. Gore & Associates, Inc. Method of ultrasonically welding articles of porous polytetrafluoroethylene

Also Published As

Publication number Publication date
GB8921775D0 (en) 1989-11-08

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Legal Events

Date Code Title Description
730A Proceeding under section 30 patents act 1977
WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)