CA1064211A - Process for producing polytetrafluoroethylene products - Google Patents
Process for producing polytetrafluoroethylene productsInfo
- Publication number
- CA1064211A CA1064211A CA241,249A CA241249A CA1064211A CA 1064211 A CA1064211 A CA 1064211A CA 241249 A CA241249 A CA 241249A CA 1064211 A CA1064211 A CA 1064211A
- Authority
- CA
- Canada
- Prior art keywords
- fibrillated
- sheet
- process according
- polytetrafluoroethylene
- oriented sheet
- 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.)
- Expired
Links
Classifications
-
- 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
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Textile Engineering (AREA)
- Artificial Filaments (AREA)
- Nonwoven Fabrics (AREA)
- Spinning Methods And Devices For Manufacturing Artificial Fibers (AREA)
- Yarns And Mechanical Finishing Of Yarns Or Ropes (AREA)
- Shaping By String And By Release Of Stress In Plastics And The Like (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Fibrillated polytetrafluoroethylene (PTFE) products are produced by sintering, at a temperature of at least 600°K, a relatively thin uniaxially oriented sheet of PTFE, and mechanically disrupting the sintered oriented sheet to provide a random network of interconnecting fibrils in the form of a fibrillated tow. The fibrillated tow can be packaged, for example, by winding in a form suitable for textile processing.
Fibrillated polytetrafluoroethylene (PTFE) products are produced by sintering, at a temperature of at least 600°K, a relatively thin uniaxially oriented sheet of PTFE, and mechanically disrupting the sintered oriented sheet to provide a random network of interconnecting fibrils in the form of a fibrillated tow. The fibrillated tow can be packaged, for example, by winding in a form suitable for textile processing.
Description
' 1064Zll ; This invention relates to an improved proces~ for producing polytetrafluoroethylene products.
More particularly, the invention relates to the production of fibrillated polytetrafluoroethylene in forms ~- suitable for processing, preferably but not necessarily after twisting, into textiles, such as yarns, twisted or plaited packings or woven knitted or felted fabrics.
The term "fibrillated" (and terms derived therefrom, such as"fibrillation") have, unfortunately, been used indiscrimin-ately in the literature to designate polymeric materials whereof - the polymeric network is a random micro - porous structure, or a patterned network of largely regular-width fibrils separated by -, . . .
fine slits, or a random coarse network structure.
In this specification, the term "fibrillated" (and terms derived therefrom) is used in the second of the above ,~ senses.
In U.K. Patent Specification No. 1073741, there is .,.
` described a process for producing a fibrillated tow of a polyalkene or polyester, wherein synthetic resin is extruded to .... .
form a film which is then uniaxially oriented by stretching, -and the oriented film is longitudinally cut by means of pin ~ :
drums or lateral stretching and finally is mechanically worked (for example by twisting) to form a fibrillated tow. A slitting drum sùltable for use in this type of process is described in ~-; U.S. Patent Specification No. 3658221.
It is also known (from U.K. Patent Speciflcation No. 993,193) that uniaxially aligned unsintered polytetrafluoro~
ethylene will 'splinter'; however, under extreme stress this splintering is uncontrolled and produces an irregular microporous network. The splinters of fibres so formed are too short and irregular for textile applications and moreover will coalesce together to form a solid mass on the application of pressure.
~ .
,,~ . . ' :
,: , ~ ' `
:- ~ ~ ,; ,' . :- . , .
` 1064211 It has been determined thst if an attempt is made to sinter the splinters of f~bres, they shrlvel leading to a product which is .~; also useless for textile purposes. Furthermore it is known (from U.K. Patent Specification No. 1,355,373) that a uniaxially ; or biaxially oriented sheet of microfibrillar polytetrafluoro-ethylene may be 'amorphously locked' by the steps of hot stretching at a temperature in the range 366-600K with very high rates of stretch followed by heat treatment under restralnt above 600K.
The resulting microfibrillar sheet may have contents of amorphous ~ 10 material varying from 2.5 to 40% depending on the temperature ! and duration of treatment.
According to the present invention, a process for . producing a fibrillated polytetrafluoroethylene product includes the steps of:-(a) providing a relatively thin uniaxially oriented sheet of polytetrafluoroethylene;
` (b) sintering the oriented sheet at a temperature -;; of at least 600K; : ~
:; .. .
(c) mechanically disrupting the sintered oriented sheet, optionally after cutting the sheet ~ to a desired width, to provide a random '~ network of interconnected fibrils in the form of a fibrillated tow; and .. ~ .
(d) packaging the fibrillated tow.
.i.. ~ :
~ The relatively thin sheet of polytetrafluoroethylene may be ~`
3 produced by extruding 3 mixture of polytetrafluoroethylene and a lubricant, and calendering the extrudate to further orient and stretch the polytetrafluoroethylene.
Sintering msy be effected by passing the sheet through an oven, or over a hotplate or heated roller in surface contact with the sheet, at a temperature in the range from , 600-673R for such a time as to completely sinter the sheet i - 2 -, --.7,--.. , .- - ~ . .
,.,. ' , ~ : - ' -. -, . , ~ ~
, ~ .
~ ,1064Zll and render it transparent. The sintering will assist in or complete, volatilisation of any lubricant used in the production of the sheet.
Following the sintering step, alignment (orientation) - may be further enhanced by hot stretching longitudinally in the -~
~., ,~ range 1.5:1 to S:l at a temperature in the range 373-523 K.
The sheet so produced possesses no micro-fibrillar structure (scanning electron micrographs) as compared with sheets produced by hot stretching followed by thermal treatment above 600 K.
The sintered aligned sheet may be fibrillated by ~; means including a pinned fibrillating roller; prior to this step, the sheet may be cut or slit into tapes of desired width.
Packaging may be effected by winding the fibrillated tow of polytetrafluoroethylene produced from steps (a), (b) and (c), onto packages suitable for further textile processing, by ,`~
means of a conventional cross-wound cheese winder or a conventional ~-twisting spindle and bobbin.
~ Preferred embodiments of the present invention will : ~, now be described by way of illustration, in the following examples. ~~
EXAMPLE 1 ~ -An oriented sheet of polytetrafluoroethylene was produced by calendering a 15 mm diameter extruded 'sausage', ; compounded by "Fluon" PTFE polymer crumb and a lubricant -~
' (paraffin oil) added at 15% by weight of the PTFE, into tape 62.5 ~m thick 125 mm wide. The tape was then passed through a gas-fired oven maintained at 670K having a residence time therein of 10 to 20 seconds so that it emerged completely sintered.
, . . .
~:i * Tr~e M~k ;
: .,: . . -106421~
The sintered tape was then water quenched and passed forward over a fibrillating roller such as that descrlbed by USP 3,658,221 emerging as a tow with "fibres" 62.5 x 200~4~m cross-section, 75 mm long for example. The tow was then twisted with for example 40 turns/m inserted to give adequate integrity for further textile processing such as rewinding, plaiting or weaving.
The sintered tape can of course be slit into narrower sections prior to fibrillating to give yarns of typical industrial textile size, e.g. a 1000 tex (g/km) yarn could be made by slit-ting the above instanced 125 mm tape into 7.5 mm wide sections and ., .
then fibrillating and twisting.
Examination of tape samples by infra-red spectro-metry showed that before sintering the ratio of amorphous to crystalline material was 1:6 and that after sintering the ratio increased to 3:2.
The density was 1.70 gmtcm3.
. .................................................................... .
.
An oriented sintered tape produced as described in Example 1 was slit into 7 sections 12 mm wide and sub~ected to hot stretching at a draw ratio of 3:1 and an air temperature ~`
of 420K for a dwell time of about 5 seconds in a hot air ,1 recirculating oven with input godet rollers slitter knives and out-put godet rollers such as is commonly employed for the hot stretching and orienting of polypropylene films. For convenience the hot stretched tapes were wound onto crosswound packages but may be fed directly to small fibrillating units and combined packaging equipment such as a ring twister.
`.
-, The tape from the crosswound package wa6 fibrlllated ~' 30 using the fibrillator section of a Mark I Laboratory Film Fibre ~ Extrusion Unit made by Plasticisers Ltd. and set to the "high"
,- - 4 -; '.
, "
.-:~ : . ': . . . ~
..... .
.. ; , flbrillation ratio. The tow so produced was of a hairy nature, i.e. a portion of the fibrils had become detached at one end from the network produced by the fibrillator, and the fibrils comprising it had the following dimensions:-Fibril Thickness 50~m Fibril Width (mean) 55~m Fibril Width (range) 20 - 140~4m Fibril Length (mean) 27~m - Fibril Length (range) 4 - 100 mm The tow was then twisted and doubled into a springy resilient yarn with the following construction and properties:-Singles tex 450 '~
Singles twist 240 t/m "Z"
Double twist 90 t/m "S"
Final tex g20 Tenacity 4.4 g/tex : .
Extension at break 40%
,: , , ~: :.
:''.................................................................. .','- ~.. -An oriented sintered tape produced as described in ;~
Example l was slit as in Example 2 and subjected to hot stretching `~.
at a draw ratio of 2:1 and an air temperature of 400K for a dwell time of about 5 seconds in the same apparatus as Example
More particularly, the invention relates to the production of fibrillated polytetrafluoroethylene in forms ~- suitable for processing, preferably but not necessarily after twisting, into textiles, such as yarns, twisted or plaited packings or woven knitted or felted fabrics.
The term "fibrillated" (and terms derived therefrom, such as"fibrillation") have, unfortunately, been used indiscrimin-ately in the literature to designate polymeric materials whereof - the polymeric network is a random micro - porous structure, or a patterned network of largely regular-width fibrils separated by -, . . .
fine slits, or a random coarse network structure.
In this specification, the term "fibrillated" (and terms derived therefrom) is used in the second of the above ,~ senses.
In U.K. Patent Specification No. 1073741, there is .,.
` described a process for producing a fibrillated tow of a polyalkene or polyester, wherein synthetic resin is extruded to .... .
form a film which is then uniaxially oriented by stretching, -and the oriented film is longitudinally cut by means of pin ~ :
drums or lateral stretching and finally is mechanically worked (for example by twisting) to form a fibrillated tow. A slitting drum sùltable for use in this type of process is described in ~-; U.S. Patent Specification No. 3658221.
It is also known (from U.K. Patent Speciflcation No. 993,193) that uniaxially aligned unsintered polytetrafluoro~
ethylene will 'splinter'; however, under extreme stress this splintering is uncontrolled and produces an irregular microporous network. The splinters of fibres so formed are too short and irregular for textile applications and moreover will coalesce together to form a solid mass on the application of pressure.
~ .
,,~ . . ' :
,: , ~ ' `
:- ~ ~ ,; ,' . :- . , .
` 1064211 It has been determined thst if an attempt is made to sinter the splinters of f~bres, they shrlvel leading to a product which is .~; also useless for textile purposes. Furthermore it is known (from U.K. Patent Specification No. 1,355,373) that a uniaxially ; or biaxially oriented sheet of microfibrillar polytetrafluoro-ethylene may be 'amorphously locked' by the steps of hot stretching at a temperature in the range 366-600K with very high rates of stretch followed by heat treatment under restralnt above 600K.
The resulting microfibrillar sheet may have contents of amorphous ~ 10 material varying from 2.5 to 40% depending on the temperature ! and duration of treatment.
According to the present invention, a process for . producing a fibrillated polytetrafluoroethylene product includes the steps of:-(a) providing a relatively thin uniaxially oriented sheet of polytetrafluoroethylene;
` (b) sintering the oriented sheet at a temperature -;; of at least 600K; : ~
:; .. .
(c) mechanically disrupting the sintered oriented sheet, optionally after cutting the sheet ~ to a desired width, to provide a random '~ network of interconnected fibrils in the form of a fibrillated tow; and .. ~ .
(d) packaging the fibrillated tow.
.i.. ~ :
~ The relatively thin sheet of polytetrafluoroethylene may be ~`
3 produced by extruding 3 mixture of polytetrafluoroethylene and a lubricant, and calendering the extrudate to further orient and stretch the polytetrafluoroethylene.
Sintering msy be effected by passing the sheet through an oven, or over a hotplate or heated roller in surface contact with the sheet, at a temperature in the range from , 600-673R for such a time as to completely sinter the sheet i - 2 -, --.7,--.. , .- - ~ . .
,.,. ' , ~ : - ' -. -, . , ~ ~
, ~ .
~ ,1064Zll and render it transparent. The sintering will assist in or complete, volatilisation of any lubricant used in the production of the sheet.
Following the sintering step, alignment (orientation) - may be further enhanced by hot stretching longitudinally in the -~
~., ,~ range 1.5:1 to S:l at a temperature in the range 373-523 K.
The sheet so produced possesses no micro-fibrillar structure (scanning electron micrographs) as compared with sheets produced by hot stretching followed by thermal treatment above 600 K.
The sintered aligned sheet may be fibrillated by ~; means including a pinned fibrillating roller; prior to this step, the sheet may be cut or slit into tapes of desired width.
Packaging may be effected by winding the fibrillated tow of polytetrafluoroethylene produced from steps (a), (b) and (c), onto packages suitable for further textile processing, by ,`~
means of a conventional cross-wound cheese winder or a conventional ~-twisting spindle and bobbin.
~ Preferred embodiments of the present invention will : ~, now be described by way of illustration, in the following examples. ~~
EXAMPLE 1 ~ -An oriented sheet of polytetrafluoroethylene was produced by calendering a 15 mm diameter extruded 'sausage', ; compounded by "Fluon" PTFE polymer crumb and a lubricant -~
' (paraffin oil) added at 15% by weight of the PTFE, into tape 62.5 ~m thick 125 mm wide. The tape was then passed through a gas-fired oven maintained at 670K having a residence time therein of 10 to 20 seconds so that it emerged completely sintered.
, . . .
~:i * Tr~e M~k ;
: .,: . . -106421~
The sintered tape was then water quenched and passed forward over a fibrillating roller such as that descrlbed by USP 3,658,221 emerging as a tow with "fibres" 62.5 x 200~4~m cross-section, 75 mm long for example. The tow was then twisted with for example 40 turns/m inserted to give adequate integrity for further textile processing such as rewinding, plaiting or weaving.
The sintered tape can of course be slit into narrower sections prior to fibrillating to give yarns of typical industrial textile size, e.g. a 1000 tex (g/km) yarn could be made by slit-ting the above instanced 125 mm tape into 7.5 mm wide sections and ., .
then fibrillating and twisting.
Examination of tape samples by infra-red spectro-metry showed that before sintering the ratio of amorphous to crystalline material was 1:6 and that after sintering the ratio increased to 3:2.
The density was 1.70 gmtcm3.
. .................................................................... .
.
An oriented sintered tape produced as described in Example 1 was slit into 7 sections 12 mm wide and sub~ected to hot stretching at a draw ratio of 3:1 and an air temperature ~`
of 420K for a dwell time of about 5 seconds in a hot air ,1 recirculating oven with input godet rollers slitter knives and out-put godet rollers such as is commonly employed for the hot stretching and orienting of polypropylene films. For convenience the hot stretched tapes were wound onto crosswound packages but may be fed directly to small fibrillating units and combined packaging equipment such as a ring twister.
`.
-, The tape from the crosswound package wa6 fibrlllated ~' 30 using the fibrillator section of a Mark I Laboratory Film Fibre ~ Extrusion Unit made by Plasticisers Ltd. and set to the "high"
,- - 4 -; '.
, "
.-:~ : . ': . . . ~
..... .
.. ; , flbrillation ratio. The tow so produced was of a hairy nature, i.e. a portion of the fibrils had become detached at one end from the network produced by the fibrillator, and the fibrils comprising it had the following dimensions:-Fibril Thickness 50~m Fibril Width (mean) 55~m Fibril Width (range) 20 - 140~4m Fibril Length (mean) 27~m - Fibril Length (range) 4 - 100 mm The tow was then twisted and doubled into a springy resilient yarn with the following construction and properties:-Singles tex 450 '~
Singles twist 240 t/m "Z"
Double twist 90 t/m "S"
Final tex g20 Tenacity 4.4 g/tex : .
Extension at break 40%
,: , , ~: :.
:''.................................................................. .','- ~.. -An oriented sintered tape produced as described in ;~
Example l was slit as in Example 2 and subjected to hot stretching `~.
at a draw ratio of 2:1 and an air temperature of 400K for a dwell time of about 5 seconds in the same apparatus as Example
2. The hot stretched tape was fibrillated on the same apparatus as Example 2 but set to the "low" fibrillation ratio.
The resultant tow whilst containing very many fibrils of 20~4m x 50~ x 10 mm long also contained unfibrillated sections up to 1 mm wide and was less hairy than Example 2.
;~ The invention as exemplified above obviates or ,, .
mitigates the high cost of methods employing dispersion technology.
A macrofibrillated network of fully sintered PTFE fibres, capable of recovery after compression, can be obtained. Such products are useful as plaited packings, filter media, and in composite -.~
bearing material, inter alia.
:',"
The resultant tow whilst containing very many fibrils of 20~4m x 50~ x 10 mm long also contained unfibrillated sections up to 1 mm wide and was less hairy than Example 2.
;~ The invention as exemplified above obviates or ,, .
mitigates the high cost of methods employing dispersion technology.
A macrofibrillated network of fully sintered PTFE fibres, capable of recovery after compression, can be obtained. Such products are useful as plaited packings, filter media, and in composite -.~
bearing material, inter alia.
:',"
Claims (11)
1. A process for producing a fibrillated polytetrafluoro-ethylene product, including the steps of:
(a) providing a relatively thin uniaxially oriented sheet of polytetrafluoroethylene;
(b) sintering the oriented sheet at a temperature of at least 600°K;
(c) mechanically disrupting the sintered oriented sheet, to provide a random network of inter-connected fibrils in the form of a fibrillated tow; and (d) packaging the fibrillated tow.
(a) providing a relatively thin uniaxially oriented sheet of polytetrafluoroethylene;
(b) sintering the oriented sheet at a temperature of at least 600°K;
(c) mechanically disrupting the sintered oriented sheet, to provide a random network of inter-connected fibrils in the form of a fibrillated tow; and (d) packaging the fibrillated tow.
2. A process according to claim 1, wherein the relatively thin sheet is one produced by extruding a mixture of polytetra-fluoroethylene and a lubricant and calendering the extrudate to orient and stretch the polytetrafluoroethylene.
3. A process according to claim 1, wherein the sintering is effected by heating means selected from the group consisting of ovens, hotplates and heated rollers, operated at a temperature in the range from 600°K to 673°K for such time as to completely sinter the sheet and render it transparent.
4. A process according to claim 1, wherein, following sintering, the sheet is stretched longitudinally in the range 1.5:1 to 5:1 at a temperature of from 373° to 523°K.
5. A process according to claim 1 wherein the sintered oriented sheet is mechanically disrupted by means including a pinned fibrillating roller.
6. A process according to claim 1 wherein packaging is effected by winding the tow onto packages suitable for textile processing, by means of a cross-wound cheese winder or twisting spindle and bobbin system.
7. A process according to claim 1 wherein the sintered oriented sheet is water-quenched prior to being mechanically disrupted.
8. A fibrillated polytetrafluoroethylene product produced by a process as defined in claim 1.
9. A fibrillated polytetrafluoroethylene product as defined in claim 8 having a ratio of amorphous to crystalline material of about 3:2.
10. A fibrillated polytetrafluoroethylene product as defined in claim 8 having a fibril width in the range 20 to 140µm and a fibril length of from 4 to 100 mm.
11. A process according to claim 1, wherein the sintered oriented sheet is cut to a desired width before being mechanically disrupted.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB5390774A GB1531720A (en) | 1974-12-13 | 1974-12-13 | Process for producing polytetrafluoroethylene products |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1064211A true CA1064211A (en) | 1979-10-16 |
Family
ID=10469367
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA241,249A Expired CA1064211A (en) | 1974-12-13 | 1975-12-08 | Process for producing polytetrafluoroethylene products |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS5858442B2 (en) |
| CA (1) | CA1064211A (en) |
| DE (1) | DE2556130A1 (en) |
| FR (1) | FR2294259A1 (en) |
| GB (1) | GB1531720A (en) |
| IT (1) | IT1052570B (en) |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5880197A (en) * | 1981-11-04 | 1983-05-14 | Toshiba Corp | Rom test system |
| US4646766A (en) * | 1982-10-01 | 1987-03-03 | Johnson & Johnson | Dental tape |
| GB2128133B (en) * | 1982-10-01 | 1986-05-21 | Johnson & Johnson | Fibrillatable dental floss tape |
| JPS59187615A (en) * | 1983-04-01 | 1984-10-24 | Kureha Chem Ind Co Ltd | Ultrafine tetrafluoroethylene copolymer fiber and production thereof |
| JPH01100731U (en) * | 1987-12-25 | 1989-07-06 | ||
| ATE175248T1 (en) * | 1993-04-05 | 1999-01-15 | Daikin Ind Ltd | POLYTETRAFLUORETHYLENE FIBER, COTTON-LIKE MATERIAL CONTAINING SUCH FIBER, AND METHOD FOR THE PRODUCTION THEREOF |
| JP3743007B2 (en) * | 1994-06-30 | 2006-02-08 | ダイキン工業株式会社 | Bulky polytetrafluoroethylene long fibers and split yarns, process for producing them, process for producing cotton-like materials using them, and filter cloth for collecting dust |
| US5912077A (en) * | 1994-10-04 | 1999-06-15 | Daikin Industries, Ltd. | Cotton-like mixed materials, non-woven fabrics obtained therefrom and process for production thereof |
| EP1439247B1 (en) * | 2003-01-20 | 2009-12-09 | Yeu Ming Tai Chemical Industrial Co., Ltd. | Polytetrafluoroethylene fiber and method for manufacturing the same |
| US7346961B2 (en) * | 2004-09-08 | 2008-03-25 | Toray Fluorofibers (America), Inc. | Fiber having increased filament separation and method of making same |
| JP5364461B2 (en) * | 2009-06-17 | 2013-12-11 | 宇明泰化工股▲ふん▼有限公司 | Polytetrafluoroethylene twisted yarn and method for producing the same |
-
1974
- 1974-12-13 GB GB5390774A patent/GB1531720A/en not_active Expired
-
1975
- 1975-12-08 CA CA241,249A patent/CA1064211A/en not_active Expired
- 1975-12-11 FR FR7537906A patent/FR2294259A1/en active Granted
- 1975-12-12 IT IT5266375A patent/IT1052570B/en active
- 1975-12-12 DE DE19752556130 patent/DE2556130A1/en not_active Withdrawn
- 1975-12-12 JP JP14830975A patent/JPS5858442B2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB1531720A (en) | 1978-11-08 |
| IT1052570B (en) | 1981-07-20 |
| JPS5184931A (en) | 1976-07-24 |
| FR2294259A1 (en) | 1976-07-09 |
| FR2294259B1 (en) | 1978-05-12 |
| DE2556130A1 (en) | 1976-06-24 |
| JPS5858442B2 (en) | 1983-12-26 |
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