US3696184A

US3696184A - Melt spinning

Info

Publication number: US3696184A
Application number: US44371A
Authority: US
Inventors: Joseph W Arnett Jr; David W Norwood
Original assignee: Concorde Fibers Inc
Current assignee: INTERLOOM INTERNATIONAL Inc
Priority date: 1970-06-08
Filing date: 1970-06-08
Publication date: 1972-10-03
Anticipated expiration: 1989-10-03

Abstract

In combination with melt spinning means comprising a melt spinning head arranged for extruding vertically downwardly a plurality of molten streams of a thermoplastic and a bath arranged to receive the streams from the head and to contain a liquid to quench and thereby solidify the streams to form filaments, the improvement comprising annular baffle means suspended in the bath in a position to surround the plurality of molten streams or filaments as they move substantially vertically downwardly, the baffle means comprising a plurality of radially spaced concentric annular foraminous members each having its upper edge no lower than the surface of the liquid and the lower edge of each respective member extending to a distance from the surface of the liquid greater than the corresponding distance for any other of the members of smaller diameter and lesser than the corresponding distance for any other of the members of greater diameter.

Description

United States Patent Arnett, Jr. et a1.

[54] MELT SPINNING [72] Inventors: Joseph W. Arnett, Jr., Sevema Park; David W. Nor-wood, Baltimore, both of Md.

[73] Assignee: Concorde Fibers, lnc., Columbia,

[22] Filed: June 8, 1970 [21] Appl. No.: 44,371

[52] US. Cl; ..264/178 F, 18/8 F, 264/40 [51] Int. Cl. ..D0ld 5/08 [58] Field of Search ....264/l8l, 40, 178 F, 178, 180;

18/8 B, 8 F, 8 WA, 12'IT [56] References Cited 2/ l 962 France ..264/1 78 F 5/1966 Japan ..264/178 F Primary Examiner-Jay H. Woo Attomey-Nolte and Nolte [5 7] ABSTRACT In combination with melt spinning means comprising a melt spinning head arranged for extruding vertically downwardly a plurality of molten streams of a thermoplastic and a bath arranged to receive the streams from the head and to contain a liquid to quench and thereby solidify the streams to form filaments, the improvement comprising annular baflle means suspended in the bath in a position to surround the plurality of molten streams or filaments as they move substantially vertically downwardly, the baffle means comprising a plurality of radially spaced concentric annular foraminous members each having its upper edge no lower than the surface of the liquid and the lower edge of each respective member extending to a distance from the surface of the liquid greater than the corresponding distance for any other of the members of smaller diameter and lesser than the corresponding distance for any other of the members of greater diameter.

8 Claims, 3 Drawing Figures MELT SPINNING This invention relates to an improvement in melt spinning in which a plurality of at least partially molten streams of thermoplastic is extruded into a liquid quench bath in which there is provided a baffle surrounding the streams which baffle is of novel construction for this purpose.

In a conventional form of melt spinning a thermoplastic to form filaments, a spinning head is mounted above a bath containing a quenching liquid and a plurality of closely adjacent molten streams of the thermoplastic are extruded substantially vertically downwardly from the spinning head into the quenching liquid through which they are lead substantially vertically downwardly without being diverted from this path by guide means until they have solidified into filaments having substantially non-tacky surfaces. The passage of the streams and resultant filaments into and through the liquid results in circulation and turbulence of the liquid in 'the vicinity of the streams or filaments. Specifically, friction between the thermoplastic streams or filaments and the quench liquid causes the streams or filaments to drag liquid downwardly with them which liquid circulates upwardly again, creating in additionto such circulation in the vicinity of the streams or filaments also turbulence in the vicinity of the streams or filaments. Of course, it is not intended'to limit the description of the presentinvention to any particular theory asto the circulation and turbulence of the quench liquid in the vicinity of the thermoplastic streams or filaments but, in general, it may be said that there is some sort of circulation and turbulence. This circulation and turbulence can be troublesome as it may cause the thermoplastic streams or filaments while still highly tacky to contact each other and, thus, damage one another or permanently fuse together. To

alleviate this problem, there has been proposed the use I of various annular baffles around the thermoplastic streams or filaments. The present invention provides a baffle of novel construction for this purpose which baffle is particularly effective and is also simple and economical to fabricate.

The baffle of the present inventions is in the form of a plurality of radially spaced concentric annular foraminous members each having its upper edge no lower than the surface of the liquid and the lower edge portion of each respective member extending a distance from the surface of the liquid greater than the corresponding distance for any other of the members of smaller diameter and lesser than the corresponding distance for any other of the members of greater diameter. The baffle is suspended in the quenching liquid with the group of closely mutually adjacent molten streams issuing from a spinneret in the spinning head passing concentrically through the innermost member of the baffle. It is preferred that the baffle be constituted of at least three of the members. Tl-Ie foraminous members diminish circulation and resultant turbulence of the quench liquid in the vicinity of the molten streams or tacky filaments sufficiently to essentially completely eliminate contact thereof with one another while still permitting the liquid to circulate and mix sufficiently in the vicinity of the molten streams or tacky filaments to hasten the formation of non-tacky filaments. In this respect, it should be appreciated that liquid movement in the vicinity of the molten streams or tacky filaments is desirable rather than undesirable to the extent that by preventing the formation of a relativelystagnant heated body of quench liquid in the vicinity of the molten streams or tacky filaments undue delay in the attaining of a non-tacky state is avoided.

Another factor is that motion and turbulence of the liquid tends to be greatest at the surface. In this respect, it is noted for one thing that the liquid flows most readily at the surface toward the molten streams or filaments as part of a chain effect of liquid motion which has its starting point in the frictional drag between the downwardly moving molten streams or filaments and the surrounding liquid. The reason for this phenomenon is that a hypothetical top layer of liquid is hampered in its motion by adjacent liquid only at its bottom face whereas other hypothetical layers of the liquid are hampered at both their top and bottom faces by adjacent liquid. Somewhat below the surface of the liquid, the liquid adjacent the filaments attains a more or less steady state streamlined flow which does not tend to cause the filaments to contact each other. It is found that the degree of hampering of the movement of the liquid around the molten streams or filaments may be stepped down from a maximum at the surface of the liquid and then completely eliminated when the liquid flow is adequately streamlined.

These various considerations are taken into account in the present invention. Hence, flow of the liquid is hampered by progressively fewer layers of foraminous baffle structure as the distance from the surface increases. The present invention tends to optimize the desired balance which involves on the one hand obtaining'sufiicient liquid motion in the vicinity of the molten streams or filaments to hasten the cooling thereof while on the other hand avoiding liquid motion of such magnitude or turbulence as would tend to bring the molten streams or tacky filaments into mutual contact. Hence, restriction of the motion of the liquid is applied to the greatest extent where such restriction is most important to the avoiding of excessive liquid motion and turbulence and restriction is progressively stepped down as it becomes less necessary.

The invention will now be described by reference to a specific. embodiment thereof as illustrated in the drawings, in which:

FIG. 1 is a partially schematic elevation view of a spinning head-quench bath assembly in operation and incorporating baffle means according to the invention;

FIG. 2 is an isometric view of the baffle means of FIG. 1; and

FIG. 3 is a detail, partly in section of the baffle means of FIG. 2. v

To a spinning block or head 1 through a conduit 2 is fed molten thermoplastic (FIG. 1). The molten thermoplastic is extruded or spun vertically downwardly through the multiple closely adjacent orifices of two spinnerets (not shown) in the spinning block 1. There are thus formed two sets 3 and 3' of closely adjacent molten streams of thermoplastic which subsequently are solidified to form filaments. After passing a short distance through the air, the

sets

3 and 3 enter a quench liquid 4, generally water, contained in a bath or tank 5. Suspended in the bath 5 is a baffle assembly 6 including two sets 6a and 6b of annular baffles. The bafile assembly 6 is so arranged that in their vertically downward movement the

sets

3 and 3 of molten streams or filaments pass concentrically through respective sets of baffles 6a and 6b. It will be appreciated that simple brackets or the like (not illustrated) are provided to support the baffle assembly 6 in the bath 5.

A bracket 7 interconnects the two sets 60 and 6b of baffles. Each set of bafi'les is composed of three concentrically arranged foraminous rings 8, 9, and 10 of progressively greater diameter and greater axial length (FIG. 2). Conveniently, bracket means (not shown) are provided on a wall of the bath adjacent bracket means 7 to cooperate with bracket means 7 to support the baffle assembly 6.

To facilitate such operation as threading of the apparatus during start-up, each set 6a and 6b of baffles is constructed in the form of two semi-circular units which are manually disengageable from one another along a diameter perpendicular to the long axis of the assembly 6, as illustrated in FIG. 2 with respect to the set 6b of baffles. The outer semi-circular sub-assembly is provided with solid end plates 11a and 11b and the inner semi-circular sub-assembly is provided with solid end plates 11c and 11d. Provided on respective end plates 11a and 11b are

respective hooks

13 and 13. Provided in respective end plates 11c and 11d are respective slots 12 and 12' positioned to receive hooks 13 and 13', respectively, for releasable fastening together of the two semi-circular sub-assemblies. The hook is simply received in the corresponding slot with the downwardly directed portion of the hook engaging behind the slotted end plate (FIG. 3).

Spanner members 140 and 14b lend additional rigidity to the outer semi-circular baffle sub-assemblies. Spanner 15 functions similarly with respect to the subassembly composed of the inner semi-circular baffle sub-assemblies and bracket 7 and also functions to rigidly fasten to one another the respective inner semicircular sub-assemblies.

The following is noted as a typical but non-limiting example of the relative dimensions involved. Each set 3 and 3' of filaments is 6% inches in diameter. Baffles 8, 9, and are respectively 8 inches, 10 inches, and 12 inches in diameter and respectively 2% inches, 5 inches and 6% inches in axial length and are positioned with their top edges about 1/4 inch above the liquid surface in the bath. The baffles 8, 9 and 10 are each constituted of expanded metal having /;-inch openings separated by one-fourth inch.

While the invention has been described be reference to a specific embodiment thereof, it is to be understood that such description is not intended as a limitation upon the scope of the invention as defined by the appended claims.

What is claimed is:

I. In a method of producing filaments of a thermoplastic in which the thermoplastic is extruded substantially vertically downwardly in the form of a plurality of closely mutually adjacent molten streams into a liquid quench bath from a location vertically spaced above the surface of the bath and passed substantially vertically downwardly through the liquid at least until I trudin the filaments into a zone in the bath in which circula ion and turbulence of the liquid in the bath due to passage therethrough of the filaments is diminished whereby any tendency of the molten streams or the resultant filaments while still substantially tacky to be brought into mutual contact by circulation or turbulence of the liquid is diminished, the zone extending downwardly from the surface of the bath, surrounding the plurality of molten streams of filaments and being defined by a plurality of radially spaced concentric annular foraminous members each having its upper edge no lower than the surface of the liquid and the lower edge portion of each respective member extending a distance from the surface of the liquid greater than the corresponding distance for any other of said members of smaller diameter and lesser than the corresponding distance for any other of said members of greater diameter.

2. A method according to claim 1, wherein said thermoplastic is a synthetic resin of the type which can be solidified by cooling and which tends when extruded as hot liquid, to form tacky filaments.

3. A method according to claim 1, wherein said bath is of aqueous type.

4. In combination with melt spinning means comprising a melt spinning head arranged for extruding vertically downwardly a plurality of molten streams of a thermoplastic and a bath arranged to receive the streams from the head and to contain a liquid to quench and thereby solidify the streams to form filaments, the head being vertically spaced above the surface of the liquid, the improvement comprising annular baffle means suspended in the bath in a position to surround the plurality of molten streams or filaments as they move substantially vertically downwardly, said baffle means comprising a plurality of radially spaced concentric annular foraminous members each having its upper edge no lower then the surface of the liquid and the lower edge portion of each respective member extending a distance from the surface of the liquid greater than the corresponding distance for any other of said members of smaller diameter and lesser than the corresponding distance for any other of said members of greater diameter.

5. Apparatus according to claim 4, wherein the innermost one of said members is outwardly spaced from said plurality of streams by a fraction of the diameter of said plurality of streams.

6. Apparatus according to claim 5, wherein outer ones of said members are outwardly spaced from said innermost one by distances approximately similar to said fraction of said diameter.

7. Apparatus according to claim 5, wherein said innermost member extends a distance below said surface approximately one-half said diameter.

8. Apparatus according to claim 7, wherein the outermost one of said members extends a distance below said surface approximately equal to said diameter.

Claims

1. In a method of producing filaments of a thermoplastic in which the thermoplastic is extruded substantially vertically downwardly in the form of a plurality of closely mutually adjacent molten streams into a liquid quench bath from a location vertically spaced above the surface of the bath and passed substantially vertically downwardly through the liquid at least until the molten streams have solidified to form substantially non-tacky filaments, the improvement comprising extruding the filaments into a zone in the bath in which circulation and turbulence of the liquid in the bath due to passage thErethrough of the filaments is diminished whereby any tendency of the molten streams or the resultant filaments while still substantially tacky to be brought into mutual contact by circulation or turbulence of the liquid is diminished, the zone extending downwardly from the surface of the bath, surrounding the plurality of molten streams of filaments and being defined by a plurality of radially spaced concentric annular foraminous members each having its upper edge no lower than the surface of the liquid and the lower edge portion of each respective member extending a distance from the surface of the liquid greater than the corresponding distance for any other of said members of smaller diameter and lesser than the corresponding distance for any other of said members of greater diameter.

3. A method according to claim 1, wherein said bath is of aqueous type.