CA1112032A

CA1112032A - Filaments or fibres of polyester drawable with molecular orientation

Info

Publication number: CA1112032A
Application number: CA328,717A
Authority: CA
Inventors: Hans Stapp
Original assignee: Akzo NV
Current assignee: Akzo NV
Priority date: 1978-06-03
Filing date: 1979-05-30
Publication date: 1981-11-10
Also published as: IT7949246A0; CH631311GA3; ES481131A1; GB2022009B; IT1117772B; JPS54160817A; CH631311B; FR2427407B1; GB2022009A; FR2427407A1; ATA397379A; AT380034B; DE2824500A1

Abstract

A B S T R A C T
Filaments of polyester or fibres produced therefrom, drawable with molecular orientation and having a double refraction of from 0.004 to approximately 0.12 and an individual denier of less-than 2.5 dtex.
A process for the production such filaments is provided in which undrawn filaments are permanently plastically extended while being passed through a water bath kept at a temperature of from 93 to 100°C
and are then extended in a ratio of at least 1:3 by being spun at a take-off rate of not more than 2500 metres per minute.
Such filaments can be used in the production of bulky mixed fibre yarns and non-woven fabrics.

Description

11:12q~32 The present invention relate!s to filaments or . fibres produced therefrom of polyester, preferably : of polyethylene terephthalate, which can be drawn with molecular orientation and to a process for their productibn and to various uses of these fila-ments or fibres.
The productlon of filaments of the type in question is known for example from Swiss Patent No. 354,202. In this known process, the melt-spun undrawn filaments are passed through a watèr bath kept at temperatures-of from 70 to 100C and are : permanently plastlcally extended with a reduction in their molecular orientation. Although, according to Swiss Patent No. 354,202, the filaments are said to be extended to between I5 and 20 times their original length, the Examples show that the deniers in which the filaments are spun are so high that it is only possible to obtain individual deniers of '' ~ "' :
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lllZ~32 greater -than 2.75 den (approximately 3 dtex) with corresponding elongation. During the orien-ting drawing step which, normally, always follows elon-gation, it is only possible in this way to obtain individual deniers of more than about o.6 dtex. A
denier such as this is not fine enough for a number of new applications for synthétic filaments or fibres.
Nowadays much finer individual de!niers are required, for example, for non-woven fabrics, which in various fields of application (for example, outer clothing, synthetic shaft material, fllter aids) have to show a certain porosity in addition to low weights per square metre. Unfortunately, it has hltherto only been possible with considerable difficulty to obtain individual deniers as fine as these by spinning measures. Numerous other textile applications require fine-denier continuous yarns, if posslble also with a fibre yarn character, or fine-denier fibre yarns, -the fineness of the individual denier of the filaments -or fibres present in the yarns significantly affecting the softness in feel of the yarns and/or sheet-form materials produced therefrom.
Although there are already known processes for - producing drawn filament structures of relatively fine denier, in which matrix-fibril or matrix-filament .~ ...

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systems are produced by two-component spinning tech-niques and the matrix subsequen-tly removed (for example by dissolution with a chemical solvent), .these known processes are also unsuitable for the production of filaments which can be drawn with molecular orientation, quite apart from their com-plexity and the problems involved in working with solvents.
An object of the present invention is to provide filaments of polyester and prefe~ably polyethylene terephthalate, which can be drawn with molecular orientation, from which:
(a) it is possible by molecule-orienting drawing to produce textile filaments or fibres produced therefrom whioh, as filament yarns, fibre-yarn-like filament yarns or fibre yarns can be processed into sheet-form - textiles having a particularly soft feel and an out-standing appearance, the textile data of the filament . . or fibres, i.e. their strength, elongation and 20 shrinkage, being typical of normal spun and drawn filaments or fibres;
(b) it is possible by molecule-orienting drawing and division known p~ se (e.g. cutting or tearing) to produce staple fibres which may be processed into non-wovens of particular softness and particular density, , -` ~llZ~32 in addition to which unusually low weights per square metre may be obtained;
(c) it is possible by division known per se without molecule-orienting drawing to produce fibres which by virtue of their very low crystallinity, in con-trast to fibres produced from filaments drawn with molecular orientation, are eminently suitable for use as binding fibres in the production of non-wovens without adversely affecting the softness of the non-woven;(d) it is possible to produce bulky mixed fibre yarns.
Another object of the present inv~ention is to provlde particularly fine-denier filaments or fibres produced therefrom using conventional spinning outfits and normal splnning speeds, the filaments being drawn and/or divided at relatively high w~rking speeds. In addition, drawing is intended to be carried out under the most favourable energy-distribution conditions.
According to the present invention there is provided filaments or fibres produced therefrom of polyester, which can be drawn with molecular orien-tation, and have a double refraction of from 0.004 to approximately 0.12 and an individual denier of less than 2.5 dtex.
It must be regarded as surprising to the expert - - . .: . .. ;
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~2~32 that filaments of fibres having as fine a denier as this can be produced at all and that they may even be technically further processed in such diverse forms and without difficulty to form filament-like or sheet-form textile materials having outstanding optical and feel properties. The expert was not encouraged by the prior art to approaoh the subject of deniers as fine as these in filaments or fibres which have not yet been drawn with molecular orien-tation or, in particular, to formulate any ideasconcerning the use of structures such as these.
The preferred individual denier range extends from 2.0 to 0.2 dtex, the upper limit applying to filaments which are of course intended to have an individual denier of less than 0.4 dtex after mole-' cule-orienting drawing in the usual way, and the lower limit applying to fibres (which have not been drawn with molecular orlentation) because, below this limit, staple f1bres can only be carded on special carding machines. Accordingly, filaments preferably have individual deniers of less than 2.0 dtex whilst fibres preferably have individual deniers'of greater than 0.2 dtex (up to 2.5 dtex).
' For producing filaments of particularly fine ' 25 denier and bulky mixed yarns`'~and for use as binding :

: ' ~1~;~32 fibres in the manufacture of no:n-wovens, the filaments or fibres according to the invention are characterised in particular by a molecule-orienting drawability of at least 1:2Ø
The filaments according to the invention or the fibres obtained therefrom may be produced using the first stage of the process known from Swiss Patent No.
354,202, the spun filaments having to be extended without any orientation to an individual denier of less than 2.5 dtex and preferably to an individual denier of from 2.0 to 0.2 dtex. However, a process such as this is very difficult to carry out (parti-cularly with regard to the uniformity of the structure obtained) unless the measures specified below which . describe the process according to the lnvention,are taken. ~ .
According to a further aspect of the lnvention there is provided a process`for the production of filaments of polyester, preferably of polyethylene terephthalate, which can be drawn with molecular orientation by passing melt-spun undrawn filaments through a water bath kept at temperatures of from 93 to 100C, the filaments being permanently plasti-cally extended with a reduction in their molecular orientation, wherein the filaments spun at a take-off ,, ' . .
g rate of no more than 2500 metres per minute and pre-ferably at a take-off rate of from 1000 to 2100 metres per minute are extended in a ratio of at least 1:3.0 and preferably in a ratio of at least 1:5.0 to an individual denier of less than 2.5 dtex and preferably to an individual denier of from 2.0 to 0.2 dtex.
The above-mentioned spinning take-off rates are critical. The upper limit indicated should not be exceeded because otherwise excessive orientation would occur which would result in a-lower crystallisation .
temperature so that, at temperatures in the above-mentioned range from 70 to 100C, there would be danger of crystallisation which would run contrary to the required disorientation. In the elongation of the filaments provided in àccordance with the lnvention, crystallisation and orientation are closely related to one another. The higher the temperature, the gréater the disorientation rate in relation to the further orientation which ocours during elongation. For this reason, the filaments are preferably extended in a water bath at temperatures of from 96 to 99C. On the other hand, the temperature should not be too high because otherwise crystallisation would occur.
The filaments are preferably subjected to mole-oule-orienting dr-wing lmmediatelv after elon,ation.

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In this case, it is particularly important to ensure that the temperature of the filaments entering the drawing zone from the elonga-tion zone is kept at around 70C in order to obtain neck-free drawing.
Drawing may readily be carried out in a single stage.
The drawing rate should preferably amount to between 80 and 200 metres per minute.
~ In thls connection, it is also preferred to draw the filaments to an individual denier of less than 0.5 dte~ and preferably to an individual denier of less than 0.3 dtex.
- These filaments are particularly suitable for the production of filament yarns, fibre-yarn-like filament yarns or, after conversion into staple fibres, for the production of fibre yarns.
Fo~ producing staple fibres intended for the production of non-wovens, the filaments are preferably flrst drawn to an individual denier of from 0.ll5 to 0.3 dtex, subsequently crimped and converted into fibres.
For producing binding fibres-for non-woven fabrios, the filaments are crimped and converted into fibres immediately after elongation.
The process is preferably carried out by running the filaments into the water bath with a denier density ~LllZ~32 of at least 50,000 dtex cm of entry width.
For numerous app-lications, the filaments may have a cross-section differing from the circular form.
For the produotion of non-wovens, it is preferred to use filaments or fibres ob~ained therefrom which have a rectangular cross-section with a ratio of the longer side to the shorter side of from 1.5:1 to 5:1.
The invention also relates to the use of the filaments according to the invention which can be drawn with molecular orientation for the production of filaments drawn with molecular orientation having an individual denier of less than 0.5 dtex and pre-ferably less than 0.3 dtex.
The invention also relates -to the use of corres-ponding fibres in conjunction with fibres drawn withmolecular orientation for the production of bulky mixed-fibre yarns.
Finally, the invention relates to the use of fibres according to the invention in conjunction with fibres drawn with molecular-orientation for the pro-duction of a non-woven fabric.
The lnvention is described in more de-tail in the following with reference to the accompanying drawing.
Filamcnts run off from a spinning nozzle at a rate of no more than 2500 metres per minute and in the ~ ,:

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t32 form of bobbins 1, but preferably in the form of tows

2 in cans 3, are subjected to the process according to the invention. In the case of tows 2 in cans 3, the first roller system 4 (in this case in the form of a duo) is preferably covered with a denier density of at least 50,000 dtex per cm of entry width. The filaments are.drawn through a water bath 6 over guide rollers 7 to 10 by a second roller system 5 (in this case in the form of a qinitet). The water has a .10 temperature in the range from 93 to 100C and preferably in the range from 96 to 99~C. The higher the tem-perature, the more quickly the filaments are heated, the flatter their SS-curve and the more quickly draLting is completed (the filaments may be drafted to 15 or 20 times their original length, as known ~_r se) On account of the very low degree of crys-tallisation of the starting material, disorientation still takes place in the above mentioned temperature range, occurring more quickly than the elongation-induce.d orientation.on account of the relatively slow elongation. Accordingly, the level of orientation and, as a measure thereof, the double refractlon of the filaments decrease. The rollers of the second roller system 5 are preferably operated at a surface speed of up to about 50 metres per minute, whilst the ~3 Z

rollers of the first roller sytem 4 are operated at a - surface speed of from about 3.5 to 15 metres per minute.
The residence time of the filaments in the water bath 6,is generally less than 1 minute, a residence time of less than 20 seconds being su~ficient in most cases. The drafting of the filaments (diameter re-duction) generally begins about 15 to 40 cm behind the-point of entry.
After leaving the second roller system 5, the filaments should have a double refraction which is lower than it was before entry into the first roller system 4. It amounts to between about 0.004 and about 0.012. In addition, the filaments have an individual denier of less than 2.5 dtex and preferably from 2.0 to 0.2 dtex. The filaments are still capable of being drawn with full molecular orientation and have substantially the same low crystallinity as the starting filaments.
Filaments with these properties may be run off from one of the rollers of the roller system 5 and delivered to-a further processing stage "Wl" where the filaments are crimped in a stuffer box and sub-sequently converted into staple fibres.' By virtue of their relatively low melting and'softening tem-perature, the crimped, undrawn fibres,are eminently .

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~112~32 suitable for use as binding fibres -for the production o-f non-wovens and, by virtue o-f their high shrinkage capacity, for the production of bulky fibre mïxed yarns.
However, the extended filaments may also be con-tinuously delivered -from the second roller system 5 to a third roller system 11 (in this case in the form of a quintet) which operates at a speed of 80 to 200 metres per minute and subjects the filaments to molecule-orienting drawing. As a result of this treatment, the filaments acqulre normal textile properties (elongatlon, strength, shrinkage), but unusually low individual deniers of less than 0.5 dtex and preferably less than 0.3 dtex, Individual deniers of less than 0.1 dtex can be obtained without di-fficulty. The filaments are then delivered to a further process1ng stage "W2"
where they may either be crimped in a stuffer box and converted into staple fibres, as in "Wl", or simply wound into packages or otherwise textured and subseq~ently - wound into packages, the texturing treatment comprising 2Q for example the formation of loops and proj-ecting fibre ends (production of fibre-yarn-like yarn).
EXAM~'LE

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A tow 300,Q00 dtex thick of polyethylene tere-phthalate filaments w~ic-h have been spun at a rate of 2~ 1300 metres per mi~nute and whlch have a double refraction . . .
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' ~112g~32 of 0.0090 and individual denier of 6 . 5 dtex, is delivered from cans to a first roller system consisting of three rollers driven at a peripheral speed of 5 . 5 metres per minute. The filaments are passed through 5 a 2 ~ 5 metres long water bath kept at a temperature of 97C. They are run off by a second roller system at 38 . 5 metres per minute and are permanently extended in the water bath with a reductio~ in their degree of orientation. The filaments now have a double re-fraction of only 0.0080, their individual denier having been reduced to 0.8 dtex. The filaments have a strength of approximately 10 cN/tex and,an elongation of 280%. As filaments or staple fibres, they are suitable for use as binding fibres for non-woven , 15 fabrics.
~: .
" E~MPLE 2 A tow corresponding to ~xample 1 is extended , between the first and second rolle,r systems as des-cribed in that Example. The filaments are then deIivered with a temperature of about 75 to 85C to a continuously adjoining drawing zone from which they are run off by a third roller system at 100 metres per , minute. The filament now have a denler of~0.45 dtex, - , a strength of 40 cN/tex, an elongation of 25% and a 25 shrinkage in hot air at 190C of 8%. The filaments ~1~2! 32 are suitable for the productlon of very fine fibre yarns (for example havlng a count of 160).

A tow 1750 dtex thick of polyethylene tere-, phthalate fila~ments, which have been spun at a rate of 1000 metres per minute and which have a double refraction of 0.0078 and an individual denier of 7.5 dtex, is delivered from cans to a!first roller system consi'sting of three rol,lers driven at a peripheral ,10 speed of 5 metres per minute. The filaments are passed through a 2.5 metres long water bath kept at a temperature of 98C. They'are run off by a second roller system at 35 metres per minute and are per-manently extended in the water bath with a reduction in their degree of orientation. The filaments now have a double refraction o~f only 0.0068, their in-dividual denier having been reduced to 1.1 dtex. The filaments are delivered with a temperature of about , 75 to 85C to the continuously adjoining drawing zone ' - 20 from which they run off by a third roller system at ~ ' - 87.5 metres per minute. The filaments,now have a' 'denier of approximately 0.4 dtex, a strength of 35 c~/tex, an elongation of approximatèly 30% and a shrinkage ln hot air at 190C of approximately 10%.
The filaments,are sultab~le'for the production of special plush fab~ics.

A tow of polyethylene terephthalate filaments with an individual denier of 6.7 dtex spun at a rate of 1365 metres per.minute is permanently.extended between the first two rollers systems in a 2.5 metres long water bath kept at 97C. The second roller system operates at 38.5 metres per min~te. The filaments are then continuously delivered to the third roller system operating at 100 metres per minute where they are subjected to molecule-orienting drawing in a ratio of 1:2.6. The properties (individual denier, strength, elongation) of the extended filaments obtained with different extenslon ratios and orthe subsequently drawn filaments are shown in Table 1.
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Example Extension Extended filaments No ratio . Individual Strength Elongation denier dtex c/Ntex %
~ .
4a 1 : 3 1.93 9.3 264 .
4b 1 : 4 1.60 9.3 245 .
4c 1 : 5 1.20 10.7 234 4d 1 : 6 0,97 ! 10.8 214 4e 1 : 7 0.88 9.9 212 /If 1 : 8 10.78 9.9 214 .
,~ ' ~ ' .
TABLE 1 (Continued) No l Drawn filaments (1:2.6) . ¦ Individual Strength Elongation ¦ denier dtex c/Ntex %
: ' : .
4a 0.77 30.2 44 4b 0.60 32.8 33 4c 0,46 33.1 29 4d 0.40 32.3 22 4e 0.38 29.7 21 4f 0.37 29.9 18 ' -:

This Example is intended to demonstrate the in-fluence of the temperature of` the,water bath. The filaments extended were spun at a rate of 2000 metres 5 per minute (degree of crystallisation 6. 7%~ double refraction 0.0147), a) Water bath temperature 85C
TAB LE II
. , Extension Double Degree of ratio refraction crystallisation .
, . ~ 1: 1,5 0.0148 4.8 ' . , 1: 2.0 0,0325 .9.3 1 : 2.5 0.1520 29.8 1: 3.0 ' 0.170 3.5' .
1: 3.5 ' 0.176 . 3.5 ,' '. ' .
Table II shows that, even with minimal extension, the double,refraction increases with a rapid increase 20 in the degree OI crystallisatlon.
b) Water bath temperature 90C

TABLE III

Extension- Double Degree of . ratio refract'ion, crystallisation ' 1: 1,5 ' 0.0114 - 4,9 1: 2.0 0.0156 ' 5.7 1: 2.5 0.0180 5.2 .
1: 3.0 0.169 ' 30.8 .

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Table III shows that, at a water bath temperature of 90C and with minimal extension ratios, the double refraction decreases slightly but, in the technically interesting range, increases considerably in the same way as the degree of crystallisation, so that molecule-orienting drawing after elongation is only possible to a minimal extent.
c) Water bath temperature 97C !
: TABLE IV
. . ' Extension Double Degree of ratio refractlon crystallisation 1 : 1,5 0.0068 4.0 . 1 : 2.0 0.0062 1.4 1 : 2.5 0.0085 2.4 . 1 : 3.0 0.0075 . 3.6 . 1 : 3.5 0.0075 3.6 1 : 4.0 o.oo69 4.5 . 1 : 4.5 0.0073 4.5 1 : 5.0 0.0074 4.8 1 : 5.5 ~0.0088 4.0 ' . . .
Table IV shows that, in the temperature range according tQ the invention, an extension o-f more than 1:3.) is possible with a reduction in double refraction and degree of crystallisation.

3L 112t~32 In order to demonstrate the critical significance of the spinning rate, a tow of -filaments spun at 2500 metres per minute lS first extended. The starting material has a double refraction of 0,0224 and a degree o-f crystallisation of 7.5%. The results are set out in Table V. It can be seen that filaments which have been spun at 2500 metres per minute can only be extended in a ratio of 1:1.5 without significant molecular orlentation occurring. Extension in a ratio of only 1:2.0 is su-fflcien-t to produce a considerable increase in double refraction and degree of crystallisation.
In this case, it lS no longer a question of extension, but rater of drawing.

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An attempt to extend a bundle of filaments spun at 3500 metres per minute without orientation was un-successful. Molecule-orie~ting drawing was always observed.
TABLE V

Example Water Extension Double Degree of No. bath ratio refrac- crystalli-tempera- tion sation ture C ~ %

6a 85~ 1:1.5 0.0214 8.1 6b 85C 1:2.0 0.1384 29.2 6c 90C 1:1.5 0.0242 7.8 6d 90C 1:2.0 0.1349 31.2 6e 97C 1:1,5 0,0131 8.6 6f 97C 1:2.0 0.1331 33.8 .

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Filaments or fibres produced therefrom of poly-ester, which can be drawn with molecular orientation, and have a double refraction of from 0.004 to approximately 0.12 and an individual denier of less than 2.5 dtex.

2. Filaments or fibres as claimed in claim 1, pro-duced from polyethylene terephthalate.

3. Filaments or fibres as claimed in claim 1, having an individual denier of from 2.0 to 0.2 dtex.

4. Filaments or fibres as claimed in claim 1, having a molecule-orienting drawability of at least 1:2Ø

5. A process for the production of filaments of poly-ester, which can be drawn with molecular orientation in the usual way by passing melt-spun, undrawn filaments through a water bath kept at temperatures of from 93 to 100°C, the filaments being permanently plastically extended with a reduction in their molecular orientation, wherein the filaments spun at a take-off rate of no more than 2500 metres per minute are extended in a ratio of at least 1:3.0 to an individual denier of less than 2.5 dtex.

6. A process as claimed in Claim 5, for the pro-duction of filaments of polyethylene terephthalate.

7. A process as claimed in Claim 5 or 6, wherein the take-off rate is in the range of from 1000 to 2100 metres per minute.

8. A process as claimed in Claim 5 or 6, wherein the filaments are extended in a ratio of at least 1:5Ø

9. A process as claimed in Claim 5 or 6, wherein the filaments are extended to an individual denier in the range of from 2.0 to 0.2 dtex.

10. A process as claimed in Claim 5 or 6, wherein the water temperature lies between 96 and 99°C.

11. A process as claimed in Claim 5, wherein immediately after extension, the filaments are sub-jected to molecule-orienting drawing.

12. A process as claimed in Claim 11, wherein the drawing speed is in the range of from 80 to 200 metres per minute.

13. A process as claimed in Claim 11, wherein the filaments are drawn to an individual denier of less than 0.5 dtex.

14. A process as claimed in Claim 13, wherein the filaments are drawn to an individual denier of less than 0.3 dtex.

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15. A process as claimed in Claim 11, 12 or 13, wherein the filaments are drawn to an individual denier of from 0.45 to 0.3 dtex, subsequently crimped and con-verted into fibres.

16. A process as claimed in Claim 5 or 6, wherein the filaments are crimped and converted into fibres immediately after extension.

17. A process as claimed in Claims 5 or 6, wherein the filaments enter the water bath with a denier density of at least 50,000 dtex per cm of entry width.

18. A process as claimed in Claim 5, wherein the filaments have a cross section differing from the circular form.

19. A process as claimed in Claim 18, wherein the cross section is rectangular, the ratio of the longer side to the shorter side of the rectangle being from 1.5:1 to 5:1.

20. A process for the production of filaments as claimed in Claim l, drawn with molecular orientation having an individual denier of less than 0.5 dtex.

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21. A process as claimed in Claim 20, wherein the filaments are drawn to have an individual denier of less than 0.3 dtex.

22. Filaments or fibres as claimed in claim 2, having an individual denier of from 2.0 to 0.2 dtex.

23. Bulky mixed-fibre yarns comprising fibres as claimed in claim 1, 2 or 3, in conjunction with fibres drawn with molecular orientation.

24. Bulky mixed-fibre yarns comprising fibres as claimed in claim 4 or 22, in conjunction with fibres drawn with molecular orientation.

25. A non-woven fabric comprising fibres as claimed in claim 1, 2 or 3, in conjunction with fibres drawn with molecular orientation.

26. A non-woven fabric comprising fibres as claimed in claim 4 or 22, in conjunction with fibres drawn with molecular orientation.