US 3840633 A
Description (OCR text may contain errors)
Oct. 8, 1974 ca. M. BARBE ETAL 3,840,633
PROCESS FOR THE PRODUCTION OF ORIENTATED SYNTHETIC FILA IEHTS Original Filed June 11. 1968 Bum/mks. GERARD [9 /918135 I 25km: OURT'H-kflf CLAUDE LEQMY m WM, M v- MM ATT' ENE Y5 United States Patent 3,840,633 Patented Oct. 8, 1974 Int. Cl. 1501f 3/10 US. Cl. 264-210 F 5 Claims ABSTRACT OF THE DISCLOSURE The invention provides a process for the preparation of orientated synthetic filaments wherein continuous filaments extruded from a molten mass of linear synthetic polymer, e.g. polyhexamethylene adipamide or polyethylene terephthalate, are cooled to a temperature above 50 C. and at least 5 C. above the second order transition temperature of the polymer, but not above the initial orientation temperature; positively driven at a speed above the extrusion speed; cooled from this to a lower temperature which is still not less than ambient temperature and positively driven at a still higher speed. The process is easily controllable and enables filaments of uniform and desirable tensile properties to be obtained.
This is a continuation of Ser. No. 736,229, filed June 11, 1968 and now abandoned.
This invention relates to orientated synthetic filaments and their production.
In order that filaments based upon linear synthetic polymers and obtainedby melt extrusion may have good mechanical properties, it is necessary that the polymer in these filaments should have a certain degree of crystallinity and orientation. This orientation is produced by stretching, at a temperature below the melting point of the polymer, either an already crystalline filament or an amorphous filaments. In the latter case, the orientation generally produces an incipient crystallisation.
In the processes at present most widely employed in industry, the extruded filaments are wound after cooling and subjected, in a subsequent phase, to the stretching operation, which is carried out with or without heating, depending upon the polymers and the nature of the filaments to be obtained. 1
Various single stage extrusion-stretching processes have been described, wherein the stretching may be effected by various means. For example, the extruded and solidified filaments may be taken up at a very high speed, in such manner that a sufiicient' tension is imparted to the filaments for bringing about an orientation.
v This tension necessary for the orientation may also be obtained by means of the frictional forces imparted to the filaments as they pass continuously, after extrusion, through a liquid bathof appropriate density and at appropriate temperature.
.-While these two types of processes afford various advantages, they'do not make it possible either to control accurately the. extent of stretch imparted to the filament or to obtain filaments having a high degree of orientation.
The simple combination of a conventional device for extruding the filament with cooling and of a stretching device merely makes it possible to obtain filaments of comparable quality to the filaments obtained in two separate stages. Moreover, filaments which must be hot-stretched must be. supplied with calories as in the conventional method. Whether this supply of calories be effected by passing thern'o ve'r a'he'ated surface or through an atmosphere at appropriate temperature, it results in a heating of the yarn and of the filaments which is not uniform from the centre to the periphery and consequently produces a transverse heterogeneity of the stretched yarn and filaments.
The present invention provides a new process for the production of orientated synthetic filaments, wherein continuous filaments extruded from a molten mass of linear synthetic polymer are: (a) cooled to a temperature of T which is above 50 C.,
and at least 5 C. above the second order transition temperature of the polymer, but not greater than the.
initial orientation temperature;
(b) positively driven at a speed V higher than the extrusion speed;
(c) brought to a temperature T which is between T and ambient temperature; and
(d) positively driven at a speed V which is greater than The initial orientation temperature, to which the temperature of the thread must fall before it undergoes the first positive drive is measured as follows:
A polymer in the form of a filament is extruded and wound in conventional manner after solidification; at the same time, the temperature along this filament between the spinneret and the winding point is measured by means of a temperature detector for a moving filament; the curve of this temperature is plotted as a function of the distance from the spinneret. The filament is then cut at the level of the spinneret and there is extracted from this point, a-
length equal to the distance between the spinneret and the winding point. After it has been verified that the varia tion of the cross-section of the thread over this length is identical to that existing in the course of the spinning between the spinneret and the Winding, the birefringence is measured point-by-point commencing at the end corresponding to the spinneret, and the distance from which a measurable birefringence appears is noted. By plotting the value of this distance on the temperature/distance from the spinneret curve, the initial orientation temperature T is determined.
The second order transition temperature of the polymer T is measured for the purpose of the invention on a mois peratures for the various polymers concerned being well known.
It is well known that the speed of extrusion is a function of the cross-section of the extrusion orifices, of their number and of the rate of flow of molten polymer. It does 1 not constitute a critical characteristic of the invention and.
may vary within very wide limits.
The cooling of the filaments to a temperature at most equal to the initial orientation temperature T is influenced by a number of factors, and notably by: the count of the filaments, their speed of travel, the temperature of the atmosphere through which the filaments pass, and the length of the zone traversed.
The means by which the cooling of the thread can be most readily controlled is the temperature of the atmos phere through which it passes. The other factors, i.e.1
count, speed of the filaments and length of the zone through which they pass, are generally determined by technological requirements and considerations of production.
An atmosphere at ambient temperature may be employed without disadvantage, as also a gas at higher temperature, but the latter is at most equal to T When the filaments have been cooled to a temperature T, as defined above, they are positively driven at a speed V above the extrusion speed V The upper limit of the ratio V zV is determined essentially 'by the rheological parameters of the polymer.
The filaments are thereafter cooled to the temperature T This temperature T is preferably a few degrees lower than T It is generally made lower than T notably in the case of condensation polymers.
The length of this second cooling zone and the temperature of the atmosphere obtaining in this zone are the two factors which can be most readily varied for operating under the characteristic temperature conditions of the process according to the invention.
fit is preferable to neutralise the static electricity on the filaments and this can be done, while cooling them, by passing them through a solution which simultaneously cools them and provides them with a coating of antistatic agent.
After having reached the temperature T the filaments are driven at a speed V higher than V The ratio V :V is chosen as a function of the extent of stretch which it is desired to impart to the filaments. It is generally between 321 and 6:1.
The time for which the filaments are kept in the orientation zone at temperatures above T influences the degree of crystallinity of the filaments.
-An additional crystallisation may optionally be produced by thermal treatment of the orientated yarn. This thermal treatment may be carried out in various ways: after the filaments have reached the temperature T they may again be brought to a temperature above T either continuously or in the course of a separate operation. The thermal treatment may be carried out under conditions such that the yarn contracts, retains its length or undergoes re-stretching.
The process according to the invention is applicable notably to: condensation polymers such as polyamides and copolyamides obtained by condensation of diacids and diamines, e.g. polyhexamethylene adipamide, or aminoacids, e.g. polyundecanamide, or by polymerisation of lactams, e.g. polycapronamide; polyesters such as polyethylene terephthalate and copolyesters comprising at least 75% of ethylene terephthalate units in the chain; and to addition polymers such as polypropylene.
For carrying out the process of the invention it is desirable that the means employed to drive the filaments at the speed V should not suddenly change the temperature of the filaments at this point.
Preferably, rollers maintained at the same temperature as the filaments are employed. However, the temperature of the rollers employed influences the properties of the filaments, and more particularly the contraction properties, and it may be desirable to utilise this factor in the preparation of filaments having particular character istics.
The preferred means for driving the filaments at the speed V: are also rollers which may be either at the temperature T or at a higher temperature, depending on whether or not it is desired to subject the filaments to a thermal treatment at this point.
In the process of the invention, the dynamometric properties of the threads which it is desired to obtain can be precisely controlled, and products having high regularity of count and a good structural homogeneity can be continuously prepared.
The process according to the invention affords the possibility of stretching very uniformly the various filaments of a multi-filament product, since the distance between the spinneret and the first driving rollers may be sufficiently low for the filaments to be disposed on this roller without difliculty and stretched in the form of a tow rather than assembled in compact form, so that all the filaments undergo exactly the same extent of stretch.
On the other hand a regular stretch could not be effected if the filaments were driven at the speed V before being cooled to a temperature not greater than T because under these conditions the fibres would adhere to the driving rollers. On the other hands, if the filaments were cooled to a temperature below T they would slip on the rollers and it would no longer be possible to effect a regular stretch.
In the following examples, which illustrate the invention, the tenacity and the elongation are measured on the Instron dynamometer, the contraction is measured on skeins after remaining in hot air at 150 C. for 30 minutes, the value of the modulus is given by the slope of the tangent to the origin of the dynamometric curve corresponding to a specimen of a length of 50 cm. and to a break time of 20 to 30 seconds and the birefringence is measured on filaments without tension.
EXAMPLES 1-2 A polyhexamethylene adipamide having a relative viscosity of 36 measured at 25 C. on an 8.4% by weight solution in formic acid has a transition point of the second order at 50 C. and its intial orientation temperature is C.
This polymer is extruded at 292 C. through a spinneret having 23 holes of a diameter of 0.34 mm.
The extruded filaments pass through a calm atmosphere maintained at ambient temperature.
When these filaments have reached a temperature of 75 C., i.e. at a distance of 54 cm. from the spinneret, they are driven at 295 m./min. by a supply system consisting of 2 rollers heated at 75 C. and rotating in opposite directions, which are diagrammatically illustrated at 1 and 2 in the accompanying FIG. 1.
The filaments thereafter pass through a zone 65 cm. long, in which a calm atmosphere at ambient temperature also obtains and in which they are cooled to this temperature. They are then driven by a stretching roller 3 associated with an idler 4 maintained at 25 C. Disposed in the passage of the filaments between the stretching roller 3 and the idler 4 is a batching device 5. The filaments are thereafter wound in known manner. The following results are obtained for 'various degrees of stretch:
EXAMPLES 3-4 A polyamide identical to that of Example 1 is extruded under the same conditions with a rate of flow of 0.36 g./min. per hole, and then orientated under the conditions set out in the following table:
Example 3 4 Distance between spinneret and supply roller, cm 55 47 Temperature of the filaments at the level of the supply rollers, C 55 65 Temperature of the supply rollers, C 55 65 Peripheral velocity of the supply rollers, m./nu'n 300 300 Distance between the supply and stretching rollers, cm 60 70 Peripheral velocity of the stretching rollers, m./min 1, 260 1, 200 Temperature of the filaments at the level of the supply rollers, C 25 25 Count:
dtmr 73 73 d- 66 70 Tenacity:
gJtex 43. 2 37. 8 g./d 4. 8 4. 2, Elongation, percent 35. 5 37. 6 Modulus: g./d 30 27 g./tex 270* 248 Contraction, percent 5.9
These tests show that, in the temperature range between 55 and 65 C., the temperature of the thread at the level of the supply rollers only slightly affects the strength and the elongation, which are above all influenced by the value of the extent of stretch.
On the other hand, if the filaments are cooled to a temperature of 45 C. before being passed over supply rollers at the same temperature, a regular stretch is no longer possible: slipping occurs on the supply rollers and the degree of stretch cannot be maintained at a constant value.
If the temperature of the filaments at the supply rollers is above 100 C., the filaments stick together and to the rollers: the stretching cannot be eflFected under good conditions.
EXAMPLE 5-10 A polyhexamethylene adipamide identical to that of Example 2 is extruded under the same conditions. When the filaments have reached a temperature of 60 C., i.e. at 51 cm. from the spinneret, they are driven at 300 m./ min. by supply rollers maintained at 60 C.
After having passed through a calm atmosphere over a distance of 60 cm., maintained at ambient temperature, the filaments are driven by stretching rollers under the conditions indicated in the following table, in which the characteristics of the filaments obtained are also indicated:
Example 5 6 7 8 9 10 Speed of the Stretching rollers,
m. min 600 750 900 1, 050 1, 200
perature of the stretching 18. 9 27 29. 7 37. 8 46 g./d 1.5 2.1 3 3.3 4.2 5.1 Elongation, percent.-. 266 165 106 66 42 28. Contraction, percent. 1. 6 0. 6 1. 2 1. 9 3. 4 5. 5 Modulus of elasticity' g./tex 77. 4 116 172 215 306 g./d 8. 6 12.9 19. 1 24 27. 6 Birefringence 0. 025 0. 041 0. 048 0. 051 0. 053 0. 057
"It will be seen from these examples that it is possible to obtain by the process of the invention polyamide filaments having high elongation and low contraction. Filaments stretched by conventional methods and having characteristics of tenacity and elongation substantially identical to those of Examples 5 to 8 have substantially higher contrac tions of the order of 8l2%.
It is found that in the process of the invention the tenacity and the elongation of the filaments vary continuously as a function of the extent of stretch, while the values of the contraction pass through a minimum.
EXAMPLE 1 1 A copolyamide obtained from 95 parts by weight of hexamethylene diamine adipate and 5% by weight of caprolactam, having a relative viscosity of 36, is extruded through a spinneret having 23 holes of a diameter of 0.34 mm. at a rate of flow of 0.36 g./min./hole. At 55 cm. from the spinneret, when the filaments have reached a temperature of 55 0., they are driven at 300 m./min. by a system of supply rollers maintained at 55 C. After having travelled 60 cm. through a calm atmosphere maintained at ambient temperature, the filaments are driven at 1380 m./min. by a system of stretching rollers at 25 C.
The filaments obtained have a count of 69 d./tex (62 d.), a tenacity of 45 g./tex (5 g./d.), an elongation of 24.7% and a contraction of 8%.
EXAMPLES 12-13 Polyethylene terephthalate having an intrinsic viscosity of 0.67 has a transition point of the second order at a temperature T of 70 C. and an initial orientation at a temperature T of 130 C.
This polymer is extruded at 285 C. through a spinneret having 30 holes of a diameter of 0.34 mm. in an atmosphere maintained at ambient temperature.
At 53 cm. from the spinneret, the filaments have reached a temperature of C. and are driven at 300 m./min. by a system of supply rollers maintained at 90 C. After having travelled a distance of l m. through an atmosphere maintained at ambient temperature and having been passed over a batching device, the filaments, which have reached a temperature of 25 C., are driven at 1500 m./ min. by a system of stretching rollers heated at the temperature indicated in the following table, in which the properties of the filaments obtained are also set out:
Example 12 13 Temperature of the stretching rollers, C 150 170 Count:
g./tex 41. 5 41. 5 g./d 4. 6 4. 6 Elongation, percent 20 19 Modulus:
g./tex 1, 080 950 g. d 104 Contraction, percent 12 9. 7
It will be seen from these examples that when the temperature of the stretching rollers increases, the tenacity and the elongation of the filaments are only slightly modified, while the modulus and the contraction decrease.
EXAMPLE l4 Filaments of polyethylene terephthalate which have reached a temperature of 25 C., and which have been extruded under the same conditions as in Example 13 and are driven at 280 m./ min. by a system of supply rollers maintained at 90 C., are passed over a first train of stretching rollers maintained at 200 C. and rotating at a peripheral velocity of 1400 m./min. The filaments are thereafter continuously conducted to a second train of stretching rollers maintained at 25 C., which is situated at 30 cm. from the first stretching train and which drives these filaments at 1680 m./min.
The yarn obtained, of 150 d./tex d.), 30filaments, has a tenacity of 60.3 g./tex (6.7 g./d.), an elongation of 9% and a contraction of 13.5%; its modulus is 1080 g./ tex (120 g./d.).
EXAMPLE 15 The polyhexamethylene adipamide filament of Example 10 is re-stretched to 1.4 times its length, at m./min., lfgopas sing it over a cold finger and a plate heated at The resultant filament has a tenacity of 74 g./tex (8.2 g./d.), an elongation of 12.6%, a modulus of 414 g./tex (46 g./d.) and a contraction of 4.7%.
This test shows that the process according to the invention makes it possible to obtain polyamide filament of very high modulus and low contraction.
EXAMPLE 16 A polyethylene terephthalate identical to that employed in Example 12 is extruded and the filaments obtained are driven under the conditions described in the said Example 12. These filaments are thereafter passed over a system of stretching rollers maintained at 25 C. and rotating at a peripheral velocity of 1500 m./min.
The filament obtained is re-stretched to 1.3 times its length, at 130 m./min., by passing it over a finger maintained at 90 C. and a plate heated at 230 C. There is finally obtained a filament having a tenacity of 74 g./tex 8.27 g./d.), an elongation of 6.5% and a contraction of What is claimed is: p V
1. A process for the production of oriented continuous filaments of polyesters or polyamides' of fiber-forming molecular weight by spinning the polymer and orienting the resulting filament by stretching in which the'spinning and stretching are carried out as a single continuous process, which comprises as a series of successive steps, one following immediately on one another in the following order:
(a) extruding as continuous filaments the molten polymer into an atmosphere at substantially the ambient temperature; 1
(b) cooling the filaments so formed directly to a temperature T between 55 and 130 C. which is (i) above 55 C., (ii) at least C. above the second order transition temperature of the polymer, and (iii) not higher than the maximum temperature at which stretching fiaments of the polymer orients them;
(c) positively forwarding the filaments when they have reached the said temperature T at a speed V higher than the extrusion speed, whereby the freshly extruded filaments are attenuated without being substantially oriented;
(d) cooling the filaments further to a temperature T below 75 C. which is alsobetween T and the ambient temperature, by causing them to continue to travel through an atmosphere at the ambient temperature; and
(e) positively forwarding the filaments While they are at the said temperature T at a speed V which is greater than V the ratio V2/V1 being from 3:1 to 6: 1, whereby the filaments so produced are oriented.
2. Process according to claim 1, wherein filaments of polyhexamethylene adipamide are made, the temperature T is between 55 and 100 C., the temperature T is between 55 C. and the ambient temperature, and the filaments are forwarded in steps (c) and (e) by means of rotating surfaces whose temperatures are T and T respectively.
3. Process according to claim 1, wherein filaments of polyethylene terephthalate are made, the temperature T is between and C., the temperature T is between 75 C. and the ambient temperature, and the filaments are forwarded in steps (c) and (e) by means of rotating surfaces whose temperatures are T and T respectively.
4. Process according to claim 2, wherein the temperature T is the ambient temperature.
5. Process according to claim 3, wherein the temperature T is the ambient temperature.
References Cited UNITED STATES PATENTS 3,400,192 9/1968 Hartmann et al. 264-290 T 3,414,646 12/1968 Pitzl 264-290 T 3,448,186 6/1969 Nicita et al. 264-210 Z 3,452,131 6/1969 Geerdes et al. 264-210 Z 3,452,132 6/1969 Pitzl 264-210Z 3,511,905 5/1970 Martin 264-210 Z 3,002,804 10/1961 Kilran 260-210 F 3,199,281 8/1965 Maerov et a1 264-103 3,256,258 6/1966 Herrman 260-937 3,361,859 1/1968 Cenzato 264-210 F 3,379,810 4/1968 Ono et al. 264-210-F 3,454,998 7/1969 Satterwhite 28-1 2,734,794 2/1956 Calton 264-210 F 3,549,743 12/1970 Riordon 264-210 F JAY H. WOO, Primary Examiner US. Cl. X.R. 264-290