US3313001A - Melt spinning apparatus - Google Patents

Description

A ril 11, 1967 T. G. FlNZEL ET AL MELT SPINNING APPARATUS Filed Sept. 24, 1965 INVENTORS.

THERON G.'FINZEL 8\ KENNETH M. M LELLAN ATTORNEY United States Patent Ofifice 3,313,001 MELT SPINNING APPARATUS Theron G. Finzel, Westlake, and Kenneth M. McLellan, Mentor, Ohio, assignors to Midland-Ross Corporation, Cleveland, Dhio, a corporation of Ohio Filed Sept. 24, 1965, Ser. No. 490,023 3 Claims. (Cl. 18-8) This invention relates to an improvement in melt spinning apparatus. More particularly, the improvement is directed to a protective melt spinning shroud about a spinneret controlling quenching of the threads in the area of initial draw.

Thermoplastic yarn is spun generally vertically downwardly in a protected atmosphere. The general area is guarded against uncontrolled gas currents and temperature changes by a blow box. Advantageously additionally each spinneret itself is generally provided with an individual protective shroud, surrounding it against premature chilling and possible coalescence of the still delicate threads. The spinneret protecting shroud may not only shield the partly molten filaments from any local air disturbances, the slightest of which can effect coalescence but, more importantly, it preheats and controls quenching air in the area of the spinneret.

It is of particular importance in the spinning of thermoplastic fibers to avoid too early quenching or filament hardening by circulating cooling gases at the moment of filament formation, generally in the initial distance from the spinneret face to a few inches away. In that distance the very important initial stretch in the issuing yarn is effected. Generally, under normal conditions initial orientation is on an as spun basis determined by the specific melt and its rate of extrusion, spinning speed being related to orientation rate. Where, however, the temperature of the atmosphere about the issuing yarns is raised, as by a shroud about the spinneret, the lower is the as spun orientation. This initial stretch, properly handled, will provide, during subsequent stretching, a yarn of uniform denier of about maximum strength. Advantageously, this invention provides a protective cell or shroud secured to the spinning head about a spinneret where circulation of the quenching or attempering gas or air is controlled and where such quenching air or gas is advantageously preheated by the issuing yarn or extra heating means before it contacts the filaments, desirably prolonging their molten state when initial stretch is effected. Initial draw stretch is carried out thus while fibers are only partially solidified causing a minimum amount of orientation at the point of take-up. The provision of a protective shroud advantageously, then, gradually quenches the issuing melt spun threads prolonging their melt elasticity for an extent of time permitting the drawing apparatus to desirably impart the important, controlled, initial draw stretch. When initially properly imparted, the yarn is in a more advantageous condition for a subsequent cold stretch, yielding uniform diameters and maximum strength. The quench providing and control apparatus is generally applicable to spun fibers from organic compounds as the polyamides, polyesters and polyethers and derivatives of these compounds. Yarns spun from these thermoplasts must be successfully drawn in order that their optimum mechanical properties be brought out.

The invention is more particularly shown and described in the accompanying drawing where:

FIGURE 1 represents a protective spinneret cell, in section, secured to a partially shown spinning head;

FIGURE 2 is a plan view of the protective spinneret cell taken across line 22 of FIGURE 1;

FIGURE 3 is an exploded view, in perspective, of the spinneret protective cell of FIGURE 2; and

FIGURE 4 is a modification of the base of the cell of FIGURE 2.

In FIGURE 1, a melt spun yarn 10 is shown extruding from a spinneret 11 positioned in and being part of a partially shown spinning head 12. The yarn 10 is spun vertically downward where, upon travel through a regulated atmosphere for a required distance, it is subsequently led onto and about a drawing roller 30 thence to a collecting station (not shown). The drawing roller 30 desirably rotates at a speed which will impart a desired initial stretch to the issuing yarn 10, all other conditions being met, which yarn will be eventually stretched a matter of about four or five times. It is important that the emerging yarn 10 be protected for subsequent best results in its mechanical properties as it issues from the spinneret face for an important distance from the face of the spinneret from too rapid cooling or displacement by local air currents or cooling gases which would alfect its initial drawing and subsequent stretching.

In spite of the fact that melt spinning heads and the entire associated apparatus are enclosed against changes in the temperature of a spin room atmosphere and especially against air currents tending to shift the delicate threads, there is need of further additional protection of the issuing tender filaments. There exists the area of temperature change in the atmosphere right about the spinning head, and particularly about each spinneret in the spinning head. The immediate area about the spinneret is very sensitiveit ranges for a short distance measured in millimeters to inches below the spinneret face depending upon the rate of filament extrusion. This distance is considered important since in this distance the molten polymeric resin forced through the holes of the spinneret 11 becomes solidified into filaments meanwhile, within a few millimeters of the spinneret face, it is being initially stretched a desired predetermined amount. The filaments solidify so very quickly upon emergence into the atmosphere due to the cooling effect of the outside air that the atmosphere thereabouts must be controlled to delay the quick solidification or poor yarn will result.

Generally, whatever air or gas quenches the spinneret face 11 and yarn 10 is usually blown in at a controlled rate at right angles to the issuing filaments in the area encompassing several spin heads. Upon emergence the yarns solidify immediately. During this brief solidifying period or interval an initial stretching also takes place, the initial draw down or stretch between the velocity of the melt at the jet 11 and the pull of the draw reel 30 may be up to 50 and perhaps to or more. It is clear, therefore, that to control a predetermined optimum draw down, control of the temperature during the first few inches of filament travel must be had and it is thus highly important. The flow of attempered air or gas must be such to keep the filaments in a soft or semimolten stage for a longer period during which the most advantageous initial stretch can be effected without causing undue orientation. Obviously, if the filaments are chilled too rapidly by the surrounding air they will not stretch properly in subsequent stretching operations where they will most often break.

It has been found that a spinneret protecting shroud having an induced air pumping action by the spun threads comprising one duct within another and positioned against the spinning head and spaced about the spinneret provides an efiicient control of attempered quenching air. The protective shroud 15 of FIGURE 1 comprises an outer shell 16 and an inner shell 14, the outer shell being adapted to be secured against the face of the spinning head 12, surrounding and being spaced about the spinneret 11 face. The mounting is flush against the spin head 12 to keep out any outside currents from reaching the spinneret face 11. It may be secured to the spin head Patented Apr. 11, 1967 3. '12 by side extensions 17 through screws 18 turned into spin head 12. The inner shell 14 is spaced at least about inch from the outer shell 16 and spacedly supported therein by nut and bolt combinations 22, the spacing being maintained by intervening circular spacer washers 21.

It is to be noted that the inner shell 14 of the cell 15 is positioned so that its top is lower than the top of the shell 16. Since the top of the shell 16 generally is about flush with the spin head and/or the spinneret face, the lowered position of the top of the inner shell 14, below the spinneret face a distance of about A to inch, permits an inflow of air from between the shells already prewarmed. Where both shells are of the same length, the inner shell is thence positioned lower to extend below the outer shell; the'inner shell extension being such so as to catch and redirect air being transversely supplied in the spin housing. This spacing is advantageous in that such air from without the outer shell 16 is directed to flow within the space between the two shells meanwhile being attempered by a surrounding resistance heater 25 where found necessary. Generally by the time any air flows into and through the interior of the shell 14 to and about and with the downward traveling yarn, it is brought up in temperature. Where the increase in temperature of attempering air by natural exchange of heat is not sufi'lcient then a heating means 25 can be used.

Any drawn air from within the blow box area is pulled into the space between the walls of the shells 14 and 16 brought up therein in temperature prior to flow in and about the face of the spinneret being redirected downwardly by the yarn effecting a pumping action giving a more uniform and gradual cooling of the filaments resulting in a more uniform filament structure during the draw down and, subsequently, for a more uniform yarn for after stretching operations. The flow of the filaments rushing through the duct forms a pumping action which carries the air downwardly, and outside air upwardly through the cell walls making an efficient circulation of desirably attempered air about the extruding filaments permitting higher draw down spinning speeds and maintaining a high degree of uniformity after subsequent stretching.

FIGURE 2 represents, in plan, the construction of the shroud 15 adapted to provide a desirably controlled quenching by air improving draw down and after stretching. As shown, the shroud 15 is generally rectangular in shape following the contour of a spinneret 11. The inner shell 14 of the shroud 15 is maintained in a spaced relation from the outer shell 16 by spacer washers 21 kept in position by the stud-bolt 22 combination. In assembly, the nut and bolt combination 22 can be inserted from the inside or from the outside as desired. Air flow obstructions within the inner portion of the shell 14 are desirably minimized so as not to effect a straight downward flow of air along with the yarn 10. Wherever the shells 14, 16 are joined to form the shroud 15 a smooth surface is advantageous and it can be had by resort to spot welding, riveting or countersinking of bolt heads. The extending arms 17 on opposite sides of the shell 16 can be secured to the shell by any desirable method, general- 1y by bolts. 'The inner shell 14 of the shroud 15 is provided with a lip 23 extending slightly outwardly in the direction of the horizontal air flow supply within the blow box of the spinning chamber of the entire apparatus. The lip 23 helps in picking up transversely flowing air and directing it into the space between the shells 14, 16 toward and about and down with the drawn filaments of the thread 10. It has been found that the inner shell may be positioned from about A to of an inch below the spinneret face and the efficiency of the final draw down of the spun yarn is not greatly afiected. Where the inner shell 14 is positioned closer to the spinneret face so as to limit the inflow of quenching air or away from the spinneret face to increase it, the initial draw is disturbed and subsequent final draws become more erratic and the uniformity of final stretch is disturbed. The length of the shroud 15 is based on the rate of spinning and the degree of preheated air desired to prolong yarn elasticity. It has been noted that the longer the shroud the longer the time the filaments are exposed to the heated atmosphere, and thus the as spun orientation is lowered, or delayed. Empirical positioning can readily determine the best inner shell position from the spinneret face to provide for amount of flow and a gradual cooling of the filaments yielding an initial draw giving a yarn that finally draws well and at optimum strength.

Should a greater quantity or volume of quenching gas, heated or otherwise, air or other than air, be required to maintain yarn plasticity for a longer initial period due to increased initial takeup or for some other operational reason the base of the shroud 15 can be sealed as shown in FIGURE 4 and needed additional gas pumped in. As shown, the lower shroud portion in FIGURE 4 comprising the ends of elements 14 and 16 is enclosed, as at 31, in a sealing relation. At about the base there is positioned an inlet 32 for heated gas, as nitrogen, under pressure. Also, within the sealed portion there is a circumferential weir 33 intended to straighten out the gas flow upwardly within the shroud walls. Several inlets 32 can be provided about the shroud base 15 for a greater supply of quenching gas.

What is claimed is:

1. A melt spinning head including a shroud about a spinneret in said head and said spinneret extending into said shroud, said shroud comprising at least two generally coextensive elements one within the other and spaced from each other, the outer element being secured in gas tight sealing relationship with the spinning head and the inner element being spaced from said head permitting a flow of attempering gases over its edge, means securing said inner element in a spaced relation to said outer element the space between said elements being adapted to admit and direct attempering gases therethrough then reversely downwardly along with spun filaments, and access means for introduction of said attempering gases at about the base of the outer element.

2. The spinneret shroud of claim 1 where the inner element is supported by the outer element and its lower edge extends below that of said outer element forming the spaced gas access means.

3. The spinneret shroud of claim 1 where the lower ends of the shroud elements are joined in sealing relationship, and attempering gas supply means are positioned Within the base area of the outer shroud element.

References Cited by the Examiner UNITED STATES PATENTS 2,252,684 8/1941 Babcock 18-8 2,514,189 7/1950 Spencer et al. 18-8 X 3,053,611 9/1962 Griehl 18-8 X 3,061,874 11/1962 Lees 188 3,067,458 12/ 1962 Dauchert 188 X FOREIGN PATENTS 661,542 3/1929 France. 731,478 6/1955 Great Britain.

OTHER REFERENCES Ser. No. 362,260, Egger et al. (A.P.C.), published Apr, 27, 1943. V I

WILLIAM J. STEPHENSON, Primary Examiner,

Claims (1)

1. A MELT SPINNING HEAD INCLUDING A SHROUD ABOUT A SPINNERET IN SAID HEAD AND SAID SPINNERET EXTENDING INTO SAID SHROUD, SAID SHROUD COMPRISING AT LEAST TWO GENERALLY COEXTENSIVE ELEMENTS ONE WITHIN THE OTHER AND SPACED FROM EACH OTHER, THE OUTER ELEMENT BEING SECURED IN GAS TIGHT SEALING RELATIONSHIP WITH THE SPINNING HEAD AND THE INNER ELEMENT BEING SPACED FROM SAID HEAD PERMITTING A FLOW OF ATTEMPERING GASES OVER ITS EDGE, MEANS SECURING SAID INNER ELEMENT IN A SPACED RELATION TO SAID OUTER ELEMENT THE SPACE BETWEEN SAID ELEMENTS BEING ADAPTED TO ADMIT AND DIRECT ATTEMPERING GASES THERETHROUGH THEN REVERSELY DOWNWARDLY ALONG WITH SPUN FILAMENTS, AND ACCESS MEANS FOR INTRODUCTION OF SAID ATTEMPERING GASES AT ABOUT THE BASE OF THE OUTER ELEMENT.

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