US3135811A

US3135811A - Process and apparatus for uniformly cooling melt-spun filaments

Info

Publication number: US3135811A
Application number: US152089A
Authority: US
Inventors: Barnett Thomas Rosslyn; Warner Harold Edward
Original assignee: Imperial Chemical Industries Ltd
Current assignee: Imperial Chemical Industries Ltd
Priority date: 1960-11-18
Filing date: 1961-11-13
Publication date: 1964-06-02
Anticipated expiration: 1981-06-02
Also published as: GB938056A; DE1278684B; FR1313873A; NL271547A; ES272106A1

Description

June 2, 1964 T. R. BARNETT ETAL 3,135,811 PROCESS AND APPARATUS FOR UNIFORMLY COOLING MELT-SPUN FILAMENTS Filed Nov. 13. 1961 7 1 24 I I ,20 1 2Z\ 4 25 3&5.

INVENTOR8 7740/1/73 ZZBJ/P/YJrr 649x040 f. Wax/vii ATTORNEYS United States Patent 3,135,811 PROCESS AND APPARATUS FOR UNIFORMLY COOLING MELT-SPUN FILAMENTS Thomas Rosslyn Barnett and Harold Edward Warner, Harrogate, England, assignors to Imperial Chemical Industries Limited, London, England, a corporation of Great Britain Filed Nov. 13, 1961, Ser. No. 152,089 Claims priority, application Great Britain Nov. 18, 1960 6 Claims. (Cl. 264-176) are cooled has a pronounced effect on their properties and it is generally accepted that some form of imposed quench is required if uniformity in the cooling of filaments is to be achieved.

Known forms of quench include liquid baths or jets and flowing gases. An example of a gas flow quench is disclosed in British Patent 533,304 in which is claimed a process for the spinning of molten organic filamentforming compositions which comprises passing a cooling medium with a substantially straight line flow across the spun structure while the latter is being transformed from the molten to the solid state. The preferred cooling medium is a stream of air.

The type of quench disclosed in British Patent Number 533,304, although widely used by manufacturers of melt spun filaments, possesses inherent faults which adversely affect the quality of the filaments. Thus, the flow of air passing across the curtain of extruding filaments has a non-uniform quenching effect because the air is heated in its passage over the filaments. A second disadvantage arises because the filaments nearest to the quench outlet deflect the air stream downwards so that subsequent filaments are cooled at diflering distances below the spinneret.

We have found that when operating gas flow quenches, similar to those illustrated in British Patent 533,304, little improvement was obtained in the variability of the filament denier compared with the use of no imposed quench, i.e. natural cooling conditions.

It is an object of our invention to provide a quenching system for melt spun filaments whereby the difficulties outlined above are very much reduced. This and other objects and advantages will be understood from the following discussion and detailed description taken with the drawings in which:

FIGURE 1 is a schematic elevational view of a meltspinning system including an apparatus for directing a radial stream of quenching fluid past the melt-spun filaments;

FIGURE 2 is a longitudinal sectional view, on an enlarged scale, of the quenching apparatus of FIGURE 1;

FIGURE 3 is a bottom view of the apparatus of FIG- URE 2; and

FIGURE 4 is a view, partly in section, taken on the line 44 of FIGURE 1.

7 According to our invention, we provide a melt spinning process of the type wherein a molten synthetic polymer is extruded downwards through a filter pack and multi-hole spinneret or spinnerets and the filaments are cooled by a stream of gas whilst they are being stretched characterised in that the filaments are uniformly retention when using non-circular holes.

3,135,811 Patented June}, 1964 ice cooled by a stream of gas which is directed radially outwards from a region substantially in the centre of the array of filaments. Preferably the stream of gas flows horizontally outwards from a vertical cylindrical surface located substantially below the centre of a single spinneret in which the holes are symmetrically arranged in a circle or concentric circles. It will, however, be understood that our invention includes the case where the filaments emanate from a multiplicity of spinnerets, for example two spinnerets, fitted into a single pack, each providing a number of holes arranged in crescent or semi-circular formation(s) so that the eventual disposition of the filaments approximates to a cylinder or concentric cylinders within which the quench device is located. The preferred cooling gas is air at ordinary temperatures. By the technique of our invention several advantages are obtained over metheds using uni-directional flow.

One important advantage is that the mean distance between the filaments tends to increase as a result of the radial air flow, whereas in the case of a uni-directional air stream there is often a tendency for filaments to be blown into one another.

The air flow from a conventional cross flow unit applies a side thrust to the filaments and this is a useful property since it reduces filament vibration which is likely to cause coalescence and denier variability. When using a radial flow system this thrust is not constant, the radial air velocity being inversely proportional to the radius. At the velocities used the drag force exerted on the filament is approximately proportional to (velocity) Thus the thrust varies as 1/ (radius) and the system is highly damped. This is an important advantage of this flow system and enables filament vibration to be reduced to very low levels.

A further advantage resulting from the use of the radial outflow method of cooling is that a more uniform treatment of the individual filaments is obtained. A large number of holes can be accommodated, e.g. in concentric circles, around the cooling device and suitably staggered so that each filament receives a fresh supply of cooling gas and the gas reaching the remote filaments has not been appreciably deflected by the preceding ones. By placing the gas source inside the filament curtain as outlined, a more effective use is made of a given area available for spinneret holes, without having to blow gas past many filaments in a row, than by any other method.

It has been found when the source of the radial outflow gas is a vertical cylinder that cylinder lengths between three and twenty inches, preferably between six and ten inches, are suitable for our purpose. In general the length of quench required increases with spun filament denier and the number of filaments being cooled. With up to about 50 holes at spun filament deniers up to about 10 a cylinder some six inches in length has proved adequate. For larger numbers of holes, e.g. 200 to 1,000 as commonly used in the production of staple tows, or for higher filament deniers e.g. 10 to 50 denier per filament, such as are required in industrial yarns a longer quench unit, preferably of at least 10 inches, is desirable. The distance from the spinneret at which quench begins is important in that cooling must be sufliciently rapid to prevent coalescence and to ensure shape Good results are obtained with a vertical cylindrical device when the cooling air first strikes the filaments at a distance of /2 to 2 /2 from the spinneret. The rate of gas flow required is dependent on several factors such as number of filaments, filament denier, rate of extrusion and angle of the gas flow to the filaments. In the spinning of textile and industrial yarns using a radial outflow a polymer pump '12, a polymer filter 14, a spinneret 16 gas quench substantially at right angles to the filaments a mean velocity at the filaments between 25 and 200' feet per minute has proved satisfactory.

We also provide a melt spinning apparatus of the type comprising a means'foi' forwarding polymer to a melt- 5 ing zone, a pump or, pumps for forwarding said molten polymer to a, filter and multihole spinneret or spinnerets and a quench source, positioned centrally below the spinneret'or spinnerets to provide a uniform stream of gas around the filaments characterised in that the quenching means comprises. a hollow porous container into which a gas is introduced under pressure. Referring to FIGURE 1 there is shown schematically a melt-spinning system which includes a polymer forwarding means 10,

and a yarn-collecting means 18 disposed below the spinneret 16. A quenching apparatus 20, constructed in ac- 'cordance with the principles of' the present invention, and receiving a stream of air through a pipe 21 is disposed below the spinneret 16 at the center of a pattern of extrusion orifices 17.

As shown in FIGURES 2 and 3,.the quenching apparatus 20 includes a vertical cylinder 22 of sintered bronze sealed at thetop end with a closure fitting 24 and provided with an inlet fitting 26 at the bottom. A solid cone-shaped rod 28, with its convergent end at the bottom extends axially along the whole length of the cylinder 22 and is secured at its ends to the fittings 24an'd 26. 'As seen in FIGURE 4 the cylinder 22 is disposed along the axis of the spinneret16 so that all the fila- 30 ments emerging from the orifices'17 will be swept with a radial flow of cooling air.

The construction of our quench is not restricted to sintered bronze; other porous materials 'may be used, for example, porous earthenware or perforated metal sheets or tubes. The cone-shaped inner member may also take other forms such as a plurality of steel mesh disks mounted on an axial rod at substantially equal intervals, the disks increasing in diameter away from the inlet fittings of the porous cylinder. The container com- 40 -an air entry at the other.

A prising the quench need not be strictly of cylindrical section but'may for example be in the shape of a cone.

The process of our invention has proved of considerable value in spinning synthetic polymers including polyesters, copolyesters, polyamides, copolyamides, polyolefines and copolyolefines, In particular the adoption of the radial outflow quench technique has greatly facilitated the spinning of materials having low melt viscosity such as high melting copolyesters of .terephthalic acid of intrinsic viscosity 05 which yield filaments and fibres having useful nonepilling properties and enhanced dye-,atfinity. In some instances radial outflow quench has enabled the production of filaments of low denier which could otherwise not have been spun successfully because'of. coalescence and variations'in filament denier. The following examples, which illustrate "but do not limit our invention, describe the spinning of typicalsyn-v thetic polymers using radial outflow quench. The gen eral spinning procedure which provided the tubulated data involved melting the polymer by means of a screw melter and pumping metered quantities of molten polyiner through a sand filter and spinneret or spinnerets. The extruded filaments were then quenched under the conditions indicated and wound-up at the appropriate rate for the required denier. The spinneret temperatures used were as follows:

, C. Poly(ethylene terephthalate) 280-290 Poly(ethylene terephthalate/sebacate) 250-255 'Isotactic' polypropylene 270-280 Poly(hexamethylene adipamide) 270-280 The radial outflow quench devicein the tabulated ex periments comprised a cylinder made of porous sinteredbronze about .1 in diameter closed at one end and having The cylinder was placed in a vertical position in the centre of the filament array. at the desired distance below the spinneret or spinnerets. A cylinder of length 10" was used in all experimentsexcept numbers 4, 5, 6 and 9 Where the length was 6". i

T able-Quench Experiments .Spinneret Quench 4 Denier V N P 1 Wind-51p f rfier tDisfiair Melan air o. o ymer spee aance ow ve oeit Yarn 'ro ertes No. of Hole shape and Hole arrangement (ftz/miu.) ment Type from rate, at filap p 1 j 7 holes size sptucu. ft./ merits,

neret, min. ftJmin.

inch (a) (1') v 1 Polyethylene 508 Round, 0.009 Equally'in 4 con- 2, 700 5 Radial 1 60 65 Denier O.V.

terephthalate' dia. centric circles, outflow 10%; (intrinsic vismean diameter Cross flow. 1 60 65 20%. cosity 0.67). 4.0. 21%. 2 do 336 do Equally in 3 eon- 1,800 10 Radial 1 40 8%.

. centric circles, outflow mean diameter do 1 1 100 110 6%. 4.1". Cross 1 40 45 18%;

. flow I 18 3 do 981 Round, 0.008 Equally in 9 con- 1, 830 5 Radial 1 15%;. vdia. centric circles, V outflow.

mse an diameter Would not spin. 4.1;. do '36 Round, 0.009 In one circle. 3, 800 7 do-- %-2% 12 50 O.V. 1.0-1 .4%.

' p dia. diameter 2". 2.0%. 5 do 36 Y shaped arm, do 4,000 7. Radial 1 6 25 1.2%. p length 0.02; outflow width, 0.005. V O. 1% 12 50 1.2%. p 3.3. 6 do 24 Round, 0.02 do 4,000 7 Radial 1 12 50 0.9g; V dia. a I 7 outflow 1.9 7; Polyethylene 508 Round, 0.009 Equally in 4 con- 2, 200 5 Radial 1% 50 55 8%? terephthalate dia. centric circles, outflow (intrinsic vismean diameter 18%. cosity 0.60). a p 4.0. V 8--.; do 250 cr ciform. Eq lly in 5 con- 2, 200 10 Radial 1% Shape factor '0.035/0.004. I centrie circles, outflow O.V. 5%; j

. mean diameter 7 Cross section i 3.75. lderu'er O.V.

15%. Shape factor Denier C V 6 Table-Continued Spinneret Quench Denier Wind-up per Dis- Air Mean air No. Polymer speed fllatance flow velocity Yarn properties No. 0! Hole shape and Hole arrangement (it/min.) ment Type from rate, at filaholes size spincu. ft./ ments, neret, min. ItJmin.

inch

9 Polyethylene 2 x 48 Round, 0.009 In twin packs. 4,300 7 Radial 1 18 Denier C V terephthalate dia. Each spinneret outflow. 1.1%. (intrinsic viscontains three 3.0%. cosity 0.60). rows of holes in crescent formation. Mean distance from centre, 1.1".

10.-- Ethylene ter- 448 Round, 0.009 Equally in 4 con- 2, 700 5 Radial 1 8%.

ephthalate/ dia. centric circles, outflow. sebacate 94:6 mean diameter Would not spin copolymer 4.0. due to coales- (intrinsic viscence. cosity 0.47).

11 do 252 do Equally in 3 con- 2, 700 10 Radial y -2y 18%.

centric circles, outflow. ing a n diameter Would not spin. 12-.. do 238 Y shaped arm, In 4 circles, mean 2, 200 10 Radial 1 10% (triangular length 0.015; diameter 3.6. outflow. flls. width 0.0045. 10% (shape variable). 13 clo 250 Oruciiorm In 5 concentric 2, 200 8 Radial 2% 70 85 Denier G.V. 9%

0.035/0.004. circles, mean outflow. (circular yarn).

diameter 3.75.

14- lsotactic poly- 85 Round, 0.015 In 2 circles mean 1, 000 50 Radial 1% 6%.

propylene dia. diameter 3.6. outflow. (melt index 13% (some coal- 23.2 g.). escence). 15 d 85 --do -do 1,000 37 Radial 1% 40 50 2.5%.

1 outflow.

16. 05 nylon (rela- 508 Round, 0.009" Equally 1n 4 con- 2, 200 5 Denier O.V.

tive viscosity dia. centric circles, 15%.

34.). inggn diameter 27%.

17-.. do 252 do Equally in 4 con- 1,800 10 Radial 1% 30 35 11%.

centric circles, outflow. mean diameter 22%. 3.6.

l8 66 nylon (rela- 36 Round, 0.013 One circle clia- 2,800 7 5 Radial 1 13 55 0.8%.

tive viscosity dia. meter outflow. 7

Norns:

(1) The quench distances from spinneret quoted are those distances below the spinneret at which air first came into contact with the filaments. (2) The air flow rate is the total volume of gas per unit of time passing through the quench device.

(3) Coeflicients of variation (C.V.) are percentage estimates of the average range of denier and shape factor respectively.

(-1) Intrinsic viscosity measurements were made at 8% (wt.) concentration in ortho-chlorophenol at 25 C.

(5) The relative viscosity of 66 nylon was measured at 8.4% (wt.) concentration in 90% formic acid at 25 C.

(6) The melt index of isotactic polypropylene is the amount in grams extruded in 10 minutes at 0. through orifice 0.08 25" in diameter and 0.316 long under a load oi 10 kgrn.

What we claim is:

l. A melt-spinning process of the type wherein a molten synthetic polymer is extruded downwards through a filter pack and at least one multihole spinneret and wound upon a yarn collecting means characterized in that the filaments are uniformly cooled by a stream of gas which is directed radially outwards from a vertical cylindrical surface located substantially in the center of an array of filaments emanating from the spinneret and at a distance from the spinncrct such that the cooling gas first contacts the filament at a distance between 0.5 and 2.5 inches from the spinneret.

2. A melt-spinning process according to claim 17 wherein the cooling gas is distributed with a mean velocity of 25-200 feet per minute from a hollow porous cylinder closed at one end and having an inlet for the cooling gas at the other end.

3. A melt-spinning process according to claim 2 wherein the hollow cylinder is fitted inside with a tapered metal cone increasing in diameter away from the gas inlet.

4. A melt-spinning process according to claim 1 wherein the denier per filament of the spun filaments as collected is between 5 and 50.

5. A melt-spinning head having means defining a plurality of downwardly facing spinning orifices, said orifices 50 being disposed in a generally circular pattern; a vertically 55 cylinder being sealed at the top and provided with a gas inlet at the bottom; a tapered solid cone within said cylinder and extending along a substantial length thereof, said cone increasing in diameter away from the gas inlet; and means for delivering cooling gas to the gas inlet.

60 6. Apparatus as in claim 5 wherein said cylinder is constructed of sintered bronze and is between 3 and 20 inches in length.

References Cited in the file of this patent 65 UNITED STATES PATENTS 2,730,758 Morrell ct al. Jan. 17, 1956 FOREIGN PATENTS 572,083 Canada Mar. 10, 1959

Claims

1. A MELT-SPINNING PROCESS OF THE TYPE WHEREIN A MOLTEN SYNTHETIC POLYMER IS EXTRUDED DOWNWARDS THROUGH A FILTER PACK AND AT LEAST ONE MULTIHOLE SPINNERET AND WOUND UPON A YARN COLLECTING MEANS CHARACTERIZED IN THAT THE FILAMENTS ARE UNIFORMLY COOLED BY A STREAM OF GAS WHICH IS DIRECTED RADIALLY OUTWARDS FROM A VERTICAL CYLINDRICAL SURFACE LOCATED SUBSDTANTIALLY IN THE CENTER OF AN ARRAY OF FILAMENTS EMANATING FROM THE SPINNERET AND AT A DISTANCE FROM