JP2002194636A - Polytetrafluoroethylene twisted yarn - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polytetrafluoroethylene(PTFE) twisted yarn to be made thin, having high mechanical strength without heat fixing treatment at over the melting point of PTFE. SOLUTION: This PTFE twisted yarn is a PTFE final-twist yarn obtained by final twist of two first-twist yarns or more, wherein the first-twist yarn is such as to be obtained by first twist of a hot-stretched ribbon-shape biscuit- bake PTFE film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a high strength twisted yarn made of polytetrafluoroethylene (PTFE). This twist yarn is useful as a material for various woven or knitted fabrics.

[0002]

2. Description of the Related Art Yarns made from PTFE include:
(1) An aqueous dispersion obtained by dispersing emulsion polymerized particles of PTFE with a dispersant is coagulated in an acidic bath to produce a continuous fiber, which is produced by an emulsion spinning method. However, this yarn has the inherent disadvantage that carbonaceous residues such as dispersants are present in the fiber. (2) PTF
There is one produced by heating and stretching a thin extruded bead obtained by paste extrusion of an E emulsion polymerization powder. However, in order to increase the strength of this yarn, it is necessary to use PTF after stretching.
It is necessary to heat set (heat set) at a temperature equal to or higher than the melting point of E (JP-B-56-45773). (3) PTF
An unfired PTFE tape obtained by subjecting an E emulsion polymerization powder to paste extrusion molding is cut into a ribbon shape, and this is manufactured by heating and stretching the ribbon. However, this yarn also needs to be heat-set at a temperature higher than the melting point of PTFE after stretching in order to increase the strength. (4) Unfired PTFE tape obtained by paste extrusion of PTFE emulsion polymerization powder
There is also a baked tape manufactured by heat-treating at a temperature equal to or higher than the melting point of FE or a baked tape manufactured by skiving from a PTFE fired block, cut into a ribbon shape, and then heated and stretched. However, this yarn can stretch the fired PTFE ribbon only at a draw ratio of about 10 to 15 times, and a thin yarn cannot be obtained.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a PTFE twisted yarn which can be reduced in size and has a high strength without heat-setting at a temperature higher than the melting point of PTFE.

[0004]

That is, the present invention is a PTFE twisted yarn in which two or more twisted yarns are twisted, and the ribbon-shaped semi-fired PTFE in which the twisted yarn is hot-drawn. The present invention relates to a PTFE twisted yarn which is a twisted yarn obtained by twisting a film.

[0005] Semi-fired PTFE for the primary twist yarn used
As the film, heat-stretched ribbon-shaped semi-fired PT
A hot stretched split film obtained by splitting the FE film may be used, or a ribbon-like semi-baked PTF
A hot stretched split film obtained by splitting an E film and then hot stretching may be used.

[0006] Furthermore, the ribbon-like semi-baked PTFE film used for the ply-twisted yarn may be heat-set, though not essential. As the heat setting treatment, the ribbon-shaped hot stretched film may be subjected to tension at a temperature not lower than the melting point of the PTFE and lower than the melting point before twisting the ribbon-shaped hot stretched film, or the ribbon-shaped hot stretched film may be subjected to PTFE before twisting. It may be performed while applying tension at a temperature higher than the melting point. The former gives a semi-fired yarn and the latter gives a fired yarn.

The twisted yarn of the present invention has a thickness of 100 to 3
000 denier and tensile strength of 2 g / denier or more can be provided.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION As a ribbon-shaped semi-baked PTFE film used in the present invention, an unfired PTFE tape obtained by paste extrusion of a PTFE emulsion polymerization powder is used. (° C.) or less and a heat treatment (semi-sintering treatment) at a temperature not lower than the melting point of baked PTFE (usually 327 ° C. ± 5 ° C.) and cut into a ribbon.

[0009] The PTFE may be a homopolymer of tetrafluoroethylene or a modified PTFE modified with another monomer as long as it can maintain the property that it cannot be melt-processed.

The width of the ribbon-like semi-baked PTFE film is usually 2 to 20 mm, preferably 4 to 12 mm.
The thickness is usually 5-300 μm, preferably 5-150 μm
It is. If it is too wide or too thick, the cross-sectional shape after twisting will not be circular and will not be easily coherent even if a subsequent drawing treatment (for example, 50 times) is performed, which is not suitable for processed yarn. If it is too narrow or too thin, it tends to break during stretching.

The ribbon-like semi-baked PTFE film is stretched under heating. Stretching is usually about 250-320 ° C
Conventional methods such as a method of stretching between two rolls heated at different rotation speeds and a method of performing acceleration while sliding on an arcuate hot plate heated to about 250 to 320 ° C. can be adopted. The draw ratio is 10 times or more, and the draw ratio is as high as possible in order to reduce the fiber diameter of the twisted yarn, preferably 20 times or more, and it is possible to draw up to about 60 times. The width of the semi-baked PTFE ribbon after stretching is 1 to 10 m
m, especially 1.5 to 5 mm, and a thickness of 1 to 100 μm
m, particularly preferably 1 to 50 μm. If the width is too wide or too thick, the rigidity becomes a yarn.
Those having a width smaller than 0.5 mm or a thickness smaller than 1 μm are difficult to manufacture.

In the present invention, the ribbon-like semi-baked PTFE film for the twisted yarn is a hot stretched split film obtained by splitting a hot stretched ribbon-like semi-baked PTFE film, or a ribbon-like semi-baked PTFE film.
A hot stretched split film obtained by splitting an E film and then hot stretching may be used. Splitting is preferably performed after stretching, since it is easy to split.

When this hot stretched split film is used, the flexibility and strength of the twisted yarn can be further increased.

The splitting method may be a conventional method, for example, in the stretched or stretched direction, semi-baked PTFE.
A method of passing a film between at least one pair of needle blade rolls to form a network structure (WO96 / 00807 pamphlet) can be exemplified. In addition, JP-A-58-1806
The method described in JP-A-21 or JP-B-53-23413 may be employed.

[0015] Although not an essential treatment in the present invention, as described above, semi-fired PTFE for a twisted yarn is used.
The film may be subjected to a heat setting treatment.

The heat setting is performed while applying tension to the ribbon-shaped heat-stretched film before twisting. as a result,
The heat shrinkage of the ply-twisted yarn and the ply-twisted yarn can be effectively prevented. When the temperature of the heat setting treatment is not less than the stretching temperature of PTFE and less than the melting point, semi-baked PTFE
It becomes E yarn, and if it is performed at a temperature equal to or higher than the melting point of PTFE, it becomes fired PTFE yarn.

The thus obtained semi-fired PTFE stretched ribbon is sent to a twisting machine and is twisted. An ordinary method is adopted as the bottom twisting method, for example, Z twisting is adopted. The number of twists may be appropriately determined depending on the required denier strength, elongation, and the like, but is preferably 50 / m or more from the viewpoint of low untwisting.

The fiber diameter of the obtained twisted yarn is usually 50
１1500 denier, preferably 100 好 ま し く 1000 denier. If it is too thick, twisting becomes difficult, and it becomes a rigid twisted yarn. Those thinner than 50 denier are difficult to manufacture.

Although this twisting improves the strength of the stretched ribbon having a strength of less than 2 g / denier, the twisted yarn alone does not yet have sufficient strength.

Therefore, the upper twist is performed using two or more lower twist yarns. As the twisting method, a usual method is adopted, and for example, S twisting or Z twisting is suitable. In addition, a twisting method different from the lower twisting method is employed in order to prevent the return of twisting. In particular, it is a general twisting method that the bottom twist is Z twist and the upper twist is S twist.

The number of the primary twist yarns used for the primary twist is as follows:
It may be appropriately selected depending on the desired denier, total strength, purpose of use of the processed yarn, and the like, but usually 2 to 3 fibers. The number of twists may be appropriately determined depending on the productivity and the like, but is preferably 50 / m or more from the viewpoint of low untwisting and 800 / m or less from the viewpoint of not generating kink. Further, it is preferable that the number of twists of the lower twist is larger than the number of twists of the upper twist, since kink does not occur during weaving.

The fiber diameter of the obtained twisted yarn is usually 10
The range of 0 to 3000 denier, preferably 200 to 2500 denier is preferable from the viewpoint of processing into sewing thread, woven thread and the like. If it is too thick, it will be a rigid twisted yarn, and it will be difficult to process such as weaving. If it is too thin, the strength will be insufficient. The twisted yarn (twisted yarn) can have a strength of 2 g / denier or more, particularly 3 to 6 g / denier.

[0023]

EXAMPLES Next, the twisted yarn of the present invention will be described in accordance with examples, but the present invention is not limited to these examples.

EXAMPLE An unfired PTFE film was prepared from a PTFE fine powder produced by an emulsion polymerization method by a paste extrusion method.
Passing through a salt bath heated to 340 ° C. for 45 seconds, semi-baked P
A TFE film (width 160 mm, thickness 100 μm) was obtained. This semi-baked PTFE film has a crystal conversion rate of 0.6.
(Calculated from the value measured with a differential operation calorimeter), specific gravity 2.2
It was.

This semi-baked PTFE film is cut into a ribbon having a width of 8 mm, stretched 30 times on a circular arc hot plate heated to 330 ° C., and stretched to about 575 denier.
An FE ribbon (untwisted yarn) was produced. The strength of this untwisted yarn was 0.5 g / denier.

In the present invention, the strength (tensile strength) of the yarn was measured at a tensile speed of 100 mm / min according to JIS L1069-1995.

The non-twisted yarn is subjected to 400 /
A sub-twisted yarn was produced by Z-twisting with a twist number of m.

[0028] Two of the obtained sub-twisted yarns were used and twisted by S twisting at a twist number of 200 / m using a twisting machine. This twisted yarn had a fiber diameter of 1270 denier and the strength was as high as 3.7 g / denier.

[0029]

According to the present invention, it is possible to reduce the size of the PT
A PTFE twisted yarn having high strength can be provided without performing a heat-setting treatment at a temperature equal to or higher than the melting point of FE.

Claims (5)

[Claims] 1. A polytetrafluoroethylene twisted yarn obtained by twisting two or more twisted yarns, wherein the twisted yarn is placed on a heat-stretched ribbon-shaped semi-baked polytetrafluoroethylene film. Polytetrafluoroethylene twisted yarn, which is a twisted yarn obtained by twisting. 2. A hot-stretched split film obtained by splitting a hot-stretched ribbon-like semi-fired polytetrafluoroethylene film, or a ribbon-like half-fired polytetrafluoroethylene film for a ply-twisted yarn. The twisted yarn according to claim 1, which is a hot-stretched split film obtained by splitting a fired polytetrafluoroethylene film and then hot-stretching. 3. A ribbon-shaped half obtained by heat-setting the ribbon-shaped hot-stretched film while applying tension at a temperature in a range from a stretching temperature of a polytetrafluoroethylene to a melting point before the twist-stretching of the ribbon-shaped hot-stretched film. 3. The twisted yarn according to claim 1, wherein the twisted yarn is produced using a fired polytetrafluoroethylene stretched film. 4. A ribbon-like fired polytetrafluoroethylene stretched film obtained by heat-setting the ribbon-like hot stretched film while applying tension at a temperature not lower than the melting point of polytetrafluoroethylene before twist-twisting the ribbon-like hot stretched film. 3. The twisted yarn according to claim 1, wherein the twisted yarn is produced using a film. 5. The twisted yarn according to claim 1, having a thickness of 100 to 3000 denier and a tensile strength of 2 g / denier or more.