Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
13()0361
High-strength feed yarns for sewing yarns, and process for
their preparation
The present invention relates to high-strength multifila-
ment polyester feed yarns for preparing sewing yarns and
to a process for the;r preparation.
For the purposes of the present ;nvent;on, sew;ng yarns
are multi-ply sewing yarns. The preparation of these
multi-ply yarns on an appropriate machine requires feed
yarns which are to be comprised in the present case of
continuous polyester filaments. Such sewing yarns need
10 to be of high strength, have good sewing properties, give
good seam strength, and be low-shr;nk, in order to prevent
seam distortion during washing or in the course of a ther-
mal treatment.
15 German Auslegeschrift 1,288,734 reveals that the spinning
cond;t;ons for the preparat;on of h;gh-strength yarns need
to be such that the tens;ons act;ng on the solidifying
filament are extremely low and that the resulting filament
only has a very low preor;entat;on wh;ch corresponds for
20 example to a b;refr;ngence of less than 0.003. In th;s
context, spinn;ng takeoff speeds of 600 to 80û m/m;n have
been found to be su;table.
These low outputs per sp;nn;ng jet are unsat;sfactory.
25 The obvious measure of ra;s;ng the volume throughput per
jet by ra;sing the spinn;ng takeoff speed, as for example
depicted in Figure 1 of German Offenlegungsschrift
2,207,849, does not lead to success, s;nce h;therto all
attempts at prepar;ng high-strength yarns by h;gh-speed
30 sp;nn;ng have fa;led because of the low strength and the
high extensibil;ty of such f;laments. The textile values
of filaments prepared in this way can already be found ;n
US Patent 2,604,667.
1300361
-- 2 --
German Auslegeschr;ft 2,254,998 descr;bes a process wh;ch
comprises first doubling and twisting the freshly spun
filaments and only then stretching the result;ng cord
yarn. It ;s relat;vely costly to apply a cord twist be-
5 fore stretch;ng, but in particular it is prone to break-
down. This is presumably why the process has failed to
attain practical ;mportance.
An attempt at prepar;ng high-strength polyester yarns by
10 high-speed sp;nning ;s descr;bed ;n Japanese laid open pub-
ati-on 51-53,019. The birefr;ngence of the feed yarn is
supposed to be above 0.030, and the stretch rat;o ;s sup-
posed to be at least 70X of the h;ghest poss;ble stretch
rat;o. Th;s process ;ncorporates a shr;nk stage w;th up
15 to 11X allowed shr;nkage.
The yarns thus prepared have a h;gh tensile strength w;th
values up to 7.0 g/den, and the;r hot-a;r shr;nkage at
150C ;s ;n the Examples between 0.8 and 2.7%. Desp;te
these bas;cally favorable text;le data, sew;ng yarns pre-
20 pared therefrom do not have sat;sfactory sewing proper-
t;es. Th;s shows up ;n part;cular ;n the low sew;ng
lengths of such sew;ng yarns. Presumably, the abovemen-
t;oned d;sadvantages of the polyester yarns of Japanese
patent publication 51-53,019 could be at least partly due
25 to the low molecular we;ght of these yarns. However, the
use of f;lament-form;ng polyesters hav;ng a relat;vely low
molecular we;ght ;s w;despread in the preparat;on of h;gh-
strength yarns, s;nce polyesters hav;ng a h;gher average
molecular we;ght are supposed to have a lower modulus of
30 elast;c;ty and ;n part;cular h;gh shr;nkage values. Th;s
dependence ;s ment;oned for example ;n German Auslege-
schr;ft 2,332,720 column 2 l;nes 41 to 46.
The present ;nvent;on therefore has for ;ts object the
35 preparat;on of h;gh-strength polyester feed yarns wh;ch
have a hot-a;r shr;nkage of 5 to 7% at a temperature of
200C and wh;ch can be used to obta;n sew;ng yarns hav-
;ng excellent sew;ng propert;es. Moreover, these feed
yarns should have a very h;gh strength.
13U03~.
-- 3
It has now been found that such feed yarns can be obtained
in a modified high-speed spinning process provided that,
unlike the teaching of the state of the art, the filament-
form;ng polyesters used have a high average molecular
S we;ght corresponding to a h;gh relative viscos;ty of above
2Ø
This relative viscosity is determined on solutions of 1 9
of polymer ;n 100 ml of dichloroacet;c ac;d at 25C by
means of capillary viscometers. It is surprising that
10 such high-speed filaments hav;ng h;gh molecular we;ght are
su;table at all for prepar;ng sewing yarns. ~y rais;ng
the sp;nning speed and the windup speed and because of the
attendant preorientation of the filaments, the strength of
the filaments obtained is reduced even after a correspond-
15 ing additional stretching, as was to be expected from theteaching of German Auslegungsschrift 1,288,734. However,
such feed yarns with markedly reduced tens;le strength
surpr;s;ngly show a smaller loss of strength after the
doubl;ng process and an appropr;ate dyeing; the strength
20 ut;l;zat;on of the dyed multi-ply yarn ;s sign;f;cantly
better than in the case of corresponding multi-ply yarns
from material spun at low speed. In particular, however,
after processing into a sewing yarn the yarns according to
the invention have an unexpectedly h;gh seam strength and
25 unexpectedly improved processing properties. The measure
used here ;s the so-called sew;ng length.
The process accord;ng to the ;nvent;on compr;ses a high-
speed spin of h;gh-molecular polyesters where;n measures
30 known per se, such as, for example, heating of the jet,
are to be used to obtain ideally no reduct;on of the mole-
cular weight dur;ng sp;nning. The stabilizat;on tempera-
ture of 225C and below makes ;t poss;ble to prepare the
yarns according to the ;nvent;on on convent;onal stretch-
35 ;ng apparatus. The stretch rat;o needs of course to beadapted to the higher preorientation of the feed yarns.
The advantages wh;ch are obta;nable through us;ng the feed
yarns according to the invent;on are most read;ly apparent
from the Examples. In the Examples, var;ous feed yarns
13G0361
were used and processed by doubllng ;nto sewing yarns.
The quant;t;es var;ed ;n the Examples were the average
molecular weight of the f;lament-form;ng polyester and the
preorientat;on, ;.e. the w;ndup speed of the f;laments
dur;ng sp;nn;ng.
In th;s descr;pt;on the preor;entat;on ;s expressed ;n
terms of the b;refr;ngence of the f;laments. The refer-
ence extension (D45), i.e. the extension wh;ch is
measured under 45 cN/tex, ;s used as a measure of the
elast;c;ty of the f;laments. Unl;ke the ;n;t;al modulus,
the reference extens;on ;s additionally also affected by
the possible presence of a "shr;nkage saddle" ;n the
stress-stra;n d;agram. The stress-stra;n d;agram of ther-
momechan;cally fully shrunk f;laments shows to a lesser
or h;gher degree after a customary steep r;se a marked
extens;on of the mater;al even at reLat;vely low tens;le
stresses. It ;s only at h;gher extens;on values that the
curve r;ses further and then ends up at poss;bly s;m;lar
values as the correspond;ng but unshrunk mater;al. In
the case of a fully shrunk mater;al, however, the elonga-
t;on at break value ;s at any rate s;gn;f;cantly h;gher.
The hot-air shrinkage S200 or S180 was determ;ned ;n
accordance with DIN 53,866 at temperatures of 200 or
180C.
The sew;ng propert;es were determ;ned by means of a spec;-
ally developed test method for which patent protect;on ;s
being sought in an application of the same priority date. The
measured variable used is a sewing test by means of an in-
dustr;al sewing machine under standard;zed cond;t;ons.
The length of the seam produced perm;ts ;nferences about
the su;tab;lity of a sew;ng yarn.
The ;ndustr;al sew;ng mach;ne used was suppl;ed by Pfaff
with a needle of metr;c count 90; sew;ng took place w;th
a double lock st;tch sett;ng of 5 stitches per centimeter
and, in the standard case, at a sew;ng speed of 4,000
stitches per m;nute. The tens;on on the top thread ;s
175 to 180 cN, and the bottom thread ;s ;n th;s test a
13(~03f~1
good sew;ng thread ;n cotton. The tens;on on the bottom
thread ;s set such that the loops disappear ;n the fabr;c
mater;al tsat;sfactory seam appearance). The mater;al
sewn ;s a 5-fold layer of cotton tw;ll hav;ng a we;ght per
un;t area of 185 g/m2 and 95 warp and 50 weft threads
per cent;meter. A standard weave for workwear from the
f;rm of Nadler & Sohn, Augsburg, Art;cle No. 13960-80/2,
dyed dark blue w;th Hydron Blue and sanfor;zed, was used.
The measured value, namely "sew;ng length", indicates the
length of the seam in centimeters unt;l thread breakage
and ;s a mean value from 10 sews per test bobb;n. The
test procedure ;s term;nated when a measurement g;ves a
sew;ng length of greater than 1,000 cm, s;nce from exper;-
ence sew;ng lengths of above 1,000 cm under these cond;-
t;ons are certa;nly ;nd;cat;ve of very good sewingproperties.
It is possible to make the sewing test more severe. In
the more severe sew;ng test, the abovement;oned cond;t;ons
are ma;ntained, except that the top thread now has a ten-
sion of 220 cN and the number of stitches is 5,000
stitches/minute.
The seam strength is a further parameter for assess;ng the
propert;es of sew;ng yarns. It ;s determ;ned by us;ng an
;ndustr;al sew;ng mach;ne, for example from Pfaff.
Mach;ne sett;ng: lock st;tch 5 st;tches per centimeter
of seam length, 4,000 stitches/m;nute. The top and bottom
threads are ;dent;cal ;n th;s test and compr;se the test
sample. The thread tens;on sett;ng is optimized for good
seam appearance, and sewing takes place on a twofold
layer of cotton twi~l. The cotton tw;ll used was the same
mater;al as used ;n the sew;ng length determ;nat;on. The
seam strength ;s the max;mum tens;le force of a 5 cm w;de
str;p. This tens;le force ;s determ;ned ;n a tens;le
tester us;ng an operat;ng speed of 10 cm per m;nute. The
value found ;s converted to the ;nd;v;dual thread.
The propert;es of sew;ng yarns can also be character;zed
~3(~036~
by means of the "number of rotations of an abrading
knife", wh;ch were determ;ned by means of a mod;f;ed abra-
s;on tester from the firm of Zweigle bearing the des;gna-
t;on G 550 S, the rotat;ng test body having a hard-metal
section abras;ve str;p. In each measurement, 20 yarn
loops are placed on the ;nstrument and each is we;ghted
w;th such a we;ght that the yarn tens;on ;s 0.135 cN/dtex.
The variable determined in each case is the number of
abras;on revolut;ons wh;ch ;s necessary for abrad;ng
through one of the 20 test loops used.
The follow;ng Examples are ;ntended to ;llustrate the ;n-
vent;on ;n more detail. Parts and percentages are by
we;ght, unless otherw;se stated.
Examples
The f;laments were spun by melt;ng su;table polyethylene
terephthalate mater;als ;n an extruder. If the polyester
materials were of h;gh viscos;ty, the sp;n pack temperature
was mainta;ned at 290C, but the jet temperature at
315C. In contrast, the spinning of lower-viscosity
mater1al was effected at a spin pack and jet temperature
of 295C. The jets used in either case had 32 holes.
After cooling down in the spinning cell the filaments were
treated with a spin finish and then wound up at 800 or
1,000 m per minute or, in accordance with the ;nvent;on,
at for example 3,000 m per m;nute.
The spin packages obtained were then presented to so-
called three-godet machines, for example to an SZ 26 from
the firm of Barmag. The multif;lament yarns are drawn
there from the spin package and are looped for example 6
t;mes around a first godet where they are heated to the
stretching temperature of customar;ly 87C and are then
passed on to a second hot godet at the stabil;zation tem-
perature. Between the first and second godet is the
stretching zone. The stretch ratio used is dependent on
the preorientation of the filaments. The ;nd;v;dual
1300361
-- 7 --
f;gures are g;ven ;n the Table below. After the stab;l;-
zat;on godet, around wh;ch the yarn passes for example 10
times, the yarn is passed to a third godet wh;ch is custo-
marily not heated. Between the second and the third godet
the yarn material can be relaxed. The stretched yarns are
subsequently wound up on cops. Under these conditions the
yarn material has only rece;ved protective torque of about
10 turns per meter. Operat;ng speed when using SZ 26
mach;nes: 610 m/m;n. The yarn mater;al thus obta;ned
10 represents the feed yarns for the preparat;on of a sew;ng
yarn.
The feed yarns need to be rewound onto feed packages. To
test their propert;es they are then used to feed a LEZZENI
15 twisting/plying/twisting mach;ne of the TBR type. Th;s
mach;ne operates at a speed of 10 m/m;n and produces a
three-ply yarn wh;ch ;s des;gnated 138 dtex f 32 S 840 x
3 Z 540.
The multi-ply yarns obta;ned were subjected to an HT dye-
20 ing at 135C for 120 m;nutes. The dyed yarn was subse-
quently tested for ;ts text;le propert;es and ;n part;cu-
lar for ;ts suitabil;ty as a sewing yarn. The measured
values obtained are reproduced in the following Table.
13~0361
- 8 -
Example No. 1 Z 3
(Comparison) (Comparison)
Relative viscosity of threads 2.03 2.03 1.93
Sp;n speed m/min3000 800 1000
~;refr;ngence x10 3 44 ~10 ~lO
Stretch;ng temperature C 78 78 78
Stretch rat;o 1 . 2.0 4.84 4.75
Stabilization (set) t~era~C 220 225 225
Relaxation % 5.2 7.4 9.2
Values of feed yarns
Denier dtex 138 120 138
Maximum tensile force cN 769 817 965
Tenacity cN/tex 55 68 69
Elongation at break % 19 21 17
Loop strength cN/tex 46 43 40
Reference extension D45 % 9.4 13 3 10.6
Heat shrinkage S 2007~ . 6.0 8.8 6.0
V2 lues of dyed yarns
Maximum tensile forcecN 2250 2280 2560
Tenacity cN/tex 50 60 57
Elongation at break % 24 20 20
Loop strength ^N/t ex 38 42 35
Reference extension D45 96 14.7 l 9 3 15.3
Heat shrinkage S180 g 1.9 1.4 2.8
Strength utiLization % 97 93 88
(efficiency)
Seam strength cN/tex 29 ~ 25
Sew;ng length, standard load cm ~1000 ~ 1000 640
Sew;ng length, h;gh load cm >1000 77 81
130Q36~
_ 9 _
The Table of the Examples reveals that the feed yarns
prepared according to the invention ;n Example 1 have
markedly lower strength than those which are in accordance
with the state of the art, i.e. in particular those of
Example 3. But it is not only the strength values of the
feed yarns but also the multi-ply yarns prepared therefrom
and then dyed which still have a lower tenacity than the
state of the art. However, it is noteworthy that in the
case of the yarns according to the invention the decrease of
10 the strength values is lower than for the state of the art
material. That is particularly clear from considering the
strength utilization, which is calculated as follows:
Maximum tensile force of the dyed
Strength multi-ply yarn
15 utilization = ----------------------------------
(efficiency) 3 x maximum tensile force of the
feed yarns.
The difference in strength utilization of 97% in the case
20 of the yarns according to the invention compared with 88X
of the state of the art material is remarkable. It is
even more remarkable, however, that the sewing yarns pre-
pared from feed yarns which are in accordance with the
invention have a better seam strength, but in particular
25 a signiflcantly improved sewing length, in particular
under tougher conditions. This surprising improved fit-
ness for purpose was in no way foreseeable and could not
in particular be inferred from the values of the feed
yarns or indeed from the physical values of the sewing
3û yarns prepared therefrom.
