US2955017A

US2955017A - Process of flowing filamentis in laminar flow surrounded by an outer area of turbulent flow

Info

Publication number: US2955017A
Application number: US726542A
Authority: US
Inventors: Boyer Charence
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1958-04-04
Filing date: 1958-04-04
Publication date: 1960-10-04
Anticipated expiration: 1977-10-04

Description

Oct. 4, 1960 c. BOYER 2,955,017

PROCESS OF mowmc FILAMENTS IN LAMINAR FLOW SURROUNDED BY AN. OUTER AREA OF TURBULENT FLOW Filed Aug. 4, 1958 v 2 Sheets-Sheet 1 INVENTOR CLARENCE BOYER BY ya;

C. BOYER ENTS IN LAMINAR FLOW SURROU Oct. 4, 1960 2,9550] 7 NDED BY PROCESS OF FLOWING FILAM AN OUTER AREA OF TURBULENT FLOW 2 Sheets-Sheet 2 Filed Aug. 4, 1958 Ely-'2 ATTORNEY Clarence Boyer, Swarthmore, Pa., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation-of Delaware Filed Apr. 4, 1958, Ser. No. 726,542

3 Claims. (Cl. 18-54) The present invention relates to a novel and useful process for forming a filamentary structure. More particularly, it relates to an improved process for preparing fibers, filaments, ribbons, and the like at relatively high speeds. 7

One of the major problems in preparing filamentary structures by the various prior art processes is the fragility of the freshly formed thread line. Since the filament is fragile in the initial spinning stage, the filament may be easily damaged and various precautions are necessary if good quality filaments are to be obtained. This has been a serious problem in the various wet-spinning procedures in Which a polymer solution is extruded into a coagulating liquid to form filaments. Typical examples of such conventional processes are the preparation of rayon filaments by extruding viscose into a coagulating bath, the preparation of rubber filaments by extruding rubber latex into a coagulant, and the preparation of filaments of condensation elastomers by extruding solutions of the elastomers into aqueous coagulating baths. It also represents a serious problem in the so-called matrix or dispersion type of spinning process. of a relatively cheap matrix-forming material, such as sodium alginate, is added to a polymer in dispersion form.

The modified dispersion is then extruded into a setting medium for the matrix-forming material so as to form a fragile shaped article comprising a gel matrix containing immobilized discrete polymer particles. The polymer particles in the gel structure are then coalesced or fused with a coalescing solution, into filaments, fibers, etc., composed predominantly of the polymeric material but usually.

' tional viscose process, i.e., about 100 yards per minute,

it is clear that this procedure is notas attractive as it could be from a commercial standpoint. Even in those processes in which commercial speeds are obtainable, such as in the viscose process, variations or fluctuations in the bath flow direction or velocity cause filaments of poor quality to be formed.

The seriousness of this problem is reflected in'the large number of patents which have issued describing techniques and devices for minimizing this problem. Many patents have suggested the use of spinning tubes to confine the bath liquid and to minimize turbulence in the bath flow. In many instances it has been recommended that the bath flow at the same rate that the thread line is moving so that no appreciable tension will be exerted on the filament during the initial stages of formation. The use of counter-current flow or bath flowing more rapidly than In this process a small amount- Patel 111:0

the thread line has also been suggested to provide some stretching action in the bath. In such cases, however, a smooth bore tube of uniform cross section is always used.

It is an object of the present invention, therefore, to provide an improved spinning process which permits a substantial increase in spinning speeds with no damage to the filament. Another object is to provide a process which improves liquid contact withthe filament, reduces the load on the filament, allows easier stringing up and permits increasing the speed of the process. A still further object is to provide a process in which a freshly formed thread line is intimately contacted with a filamentforming liquid while being partially supported by this liquid. Other objects will become apparent from the descriptions, drawings, and the claims.

These objects are accomplished by the present invention which provides an improvement in the process of forming a filamentary structure by contacting a freshly extruded polymer with a filament-forming liquid to form a filamentary structure; the improvement which comprises flowing the filament-forming liquid concurrently continuously throughout the filamentary structure.

with the polymer as a single stream, the cross section of the concurrent stream of the filament-forming liquid having an inner area and a surrounding outer area, the said inner area surrounding the extruded polymer and being in laminar flow and the said outer area being in a state of turbulent flow which proceeds concurrently with the polymer in the form of a helix around the inner area of laminar flow.

The terminology process to form a filamentary structure is used to describe the conventional processes, such as the ones hereinbefore mentioned. It thus includes the conventional wet-spinning and the matrix type of spinning procedures. The term a filamentary structure is used to designate a structure which is long as compared to its width or cross section, such as a filament, fiber, ribbon or the like. The term freshly extruded is used to signify that the polymer has recently come from the extrusion orifice and that it has not as yet been completely changed to a structure in which the final polymer runs continuously throughout the structure. The term filament-forming is used to describe a liquid which causes the polymer to solidify or coalesce so that it is distributed The filament-forming liquid may thus be either a coagulating or a coalescing liquid for in each case it causes the polymer to be continuous through the structure. The terms laminar flow and turbulent flow are given their conventional meaning as in hydraulics. The term laminar flow thus means streamline or viscous flow whereas the term turbulent" means that the flow is non-laminar or in a state of turbulence.

The desired flow of the present invention is obtained by the use of a novel enclosure which imparts this how pattern to the filament-forming liquid. One type of enclosure for achieving this flow is a non-round or elliptical tube twisted lengthwise about its axis, the turns being in the same or in alternately opposed directions. Such a non-circular cross section can be given to a tube by indenting the tube, by creasing the tube, by partially flattening the tube to an oval shape, by the proper molding or extruding of the tube, etc., or by a combination of these or other operations. Each of these tubes has an inner periphery which is non-uniform. A liquid which would normally pass through the tube in laminar flow is thus given'an outer area of tubulence. The preferred tubes employed in this invention are those which have an oval or elliptical cross section with a maximum internal free passageway of about 1 inch, a length of from about 1 to about 16 feet and a twist of from about i 1 to about 10 turns per foot.

In the accompanying drawings which illustrate preferred embodiments of the invention,

Figure 1 is a diagrammatical flow sheet of this invention as applied to the matrix or dispersion type of spinning process;

' Figure 2' is. a diagrammatical flow sheet of this invention as applied to the coagulation type of spinning process; and

Figure 3 is a plain view of one enclosure which may be used in the practice of this invention.

In Figure 1, a dispersion of the synthetic polymer particles is prepared by polymerizing the monomer in an aqueous medium containing anemulsifying agent. This dispersion is stored in tank 1. A quantity of an aqueous solution containing the matrix-forming material, such as a one percent by Weight solution of sodium alginate is prepared and stored in tank 2. The contents of both tanks are then mixed in a mixer 3 to form a modified dispersion. The mixture is pumped by pump 4 through a filter 5, then through the orifices of spinneret 6 into the coagulating or setting medium 7, to form the filaments 8. The filaments comprising the gel matrix containing immobilized discrete particles of polymer are converged over roll 9 and led through funnel 10 into the coalescing tube (twists not shown) 11. The coalescing liquid is fedinto trough 12 through tube 13. An overflow tube 14 allows a constant head to be maintained in trough 12. After several feet of concurrent travel through tube 11, the coalescing liquid and filament are led into trough 15 containing additional coalescing liquid. The filament then passes over the edge of trough 15 into trough 16 which contains wash water. After being washed, the filament is led under roll 17 to the Windup 18.

In Figure 2, a solution of the polymer from supply pipe 20 is extruded through spinneret 22 into a coagulating bath 29 maintained at a constant head in tank 30 by means of an adjustable overflow 21. The extruded polymer proceeds through twisted tube 23 along with the coagulating liquid 29 into trough 19, which contains additional coagulating liquid 29'.- The trough 19 is equipped with an adjustableoverflow pipe 24 to control the liquid level in the trough. The filament upon emerging from the coagulating liquid 29 in trough 19 is carried over a guide roll 25 around wash rolls 26 into wash water 28 to windup 27.

Figure 3 is a detailed illustration of a section of one of the tubes used in the process of the present invention. The tube is noncircula-r in cross section and is twisted about its axis to provide a spiral pattern.

The invention is illustrated by the following examples which are cited to illustrate the invention but are not intended to limit it in any manner. Unless otherwise stated, all percentages mentioned in the specification are by weight. When tubes are employed in the following examples, the differential (hydrostatic) head: between 'the two baths connected by the tube is maintained at about 4 inches.

Example I is then passed over a wheel into a coalescing bath containing calcium thiocyanate at 103 C. In this bath the filament is passed through a 4.5 foot straight bore smooth-walled inch internal diameter glass tube at a rate of 30 y.p.m. The filaments are washed and wound up at 33-40 y.p.m. These filaments cannot be drawn more than about 8X. Portions of these filaments drawn 7 in water heated at 100 C. have the following properties:' tenacity-:43 .g.p.d., elongation =24%, and initial modulus=35 g.p-.d.

No improvement is noted it a flexible tube is used in place of the glass tube and the filamentpassed through this tube arranged in a spiral pattern. For example, the dispersion described in the first paragraph is extruded through a 40 hole- 3 mil spinneret into a 5% calcium chloride bath, and. then passed over a wheel into a coalescing bath containing '6570% of calcium thiocya nate heated to 102 C. In this bath the filament is passed at approximately 29 y.p.m. through 6 feet of 0.75" inch internal. diameter flexible plastic tubing arranged in the form of a coil and then Washed. Portions of these filaments drawn 7X in water heated at 100 C. have the following properties: tenacity=3.7 g.p.d., elongation-=31%, and initial modulus=39 g.p-.d.

The following data show the advantage of the tube design of this invention. A 4.5 feet, 0.75 inch internal diameter stainless steel tube is flattened to an oval shape and twisted approximately 3 turns/ft. A 40% disperslot: (550 grams) of polyacrylonitrile is mixed with 515 grams of a 1% sodium algina-te solution containing 0.5% of sodium lauryl sulfate. Filaments are prepared hy extruding (using the apparatus of Figure 1) at approximately 50 y.p'.m. and coagulating as described in the-preceding two paragraphs. The coagulated gel filament is then passed over a wheel into a calcium thiocyanate solution heated at 110 C. The coagulated gel filament is passed along with this solution through the'twisted stainless steel tube where coalescence occurs. The filaments are then washed and wound. The c0- aiiesced' filaments can be drawn as much as 22x. The following table shows the properties obtained at various draw ratios:

w r Tenacity Elonga Initial Draw Ratio (g.p. l.)- tion Modulus Denier y (percent) (g.p.d.)

Example 11 lPoh/(tetramethylene oxide) glycol (124.5 grams=0.12 mol) having a molecular weight of 1035 is reacted with 10.50 grams (0.06 mol.) of 4-methyl-m-phcnylene diisocya-nate by stirring in an anhydrous atmosphere for 3 hours at. steam bath temperatures. To this dimer with hydroxyl ends is added without cooling 30.0 grams f (0.12 mol.) of methylene bis(4-phenylisocyanate) dis material as determined by evaporation of a portion. 7 I

into an aqueous coagulating bath containing 5% by weight of calcium chloride. The coagulated gel filament 0.32 grid. and an elongation of 418%.

solved in-dry methylene chloride and the mixture allowed to react. for 1 hour at steam bath temperatures. Thefdimer iwith isocyanate ends is allowed to cool and 400- grarnsof N,N-dimethylformamide added. To this solution is added 3.0 grams (0.06 mol) of hydrazine hydrate dissolved in 26 grams of N,Ndlimethyl-formamide. The resulting polymer solution, which contains approximately 28% -solids, is diluted with N,N-dimethylformamide to produce a spinning solution containing about 20% solids. i

The solution is extruded throu gh a 20 mil single hole spinneret into varyingaqueous baths heated at C. A filament formed at arate. of approximately 50 y.p.m. by extruding into water-is found to have a tenacity of By changing the coagulationbath to one containing 50% by weight ofi N,N-dimethylformamide, filaments can be obtained from this solution which have a tenacity of 0.56 g.p.d; and an elongation of 570%. This represents greatly improved physical properties, because the tenacity has been markedly increased with an accompanying increase in elongation. The improvement in properties is attributed to the presence of the N,Ndimethylformamide in the spinning baths, which causes slower coagulation and the formation of a more desirable structure.

However, despite the fact that the ultimate properties are better, the filament initially formed when this bath is used is actually much weaker. Consequently, in order to maintain spinning continuity, it is necessary to reduce the spinning speed materially. Spinning continuity can be maintained at a satisfactory level using spinning speeds of 50 y.p.m. with this bath while still retaining the desirable level of properties (e.g., filaments with a tenacity of approximately 0.5 g.-p.d. and an elongation of approximately 600%) only by using the twisted tube of the preceding example in the spinning bath as shown in Figure 2. The use of a twisted tube made of a transparent material shows that the running filament stays in the center of the twisted tube and does not come in contact with the Walls. Further tests show that flow contains a central area of laminar flow (through which the filaments pass) and an outer area of turbulence adjacent the wall of the twisted tube.

Example [11 A polymer with an inherent viscosity of approximately 1.62 in sulfuric acid is prepared from m-phenylene diamine and isophthaloyl chloride. A portion of this polymer is dissolved in N,N-dimethylacetamide to produce a solution. containing approximately 19.5% of the polymer and 4.5% by weight of calcium chloride (based on polymer weight). This solution is heated to 60 C. and extruded through a 100 hole 3 mil spinneret into a bath maintained at 60 C. which contains a mixture of 35% by weight of N,Ndimethylacetamide, 20% of calcium chloride, and 45% by weight of water. After passing through approximately yards of this bath at a rate of 18 yards per minute, the filament is transferred to a bath of Water at room temperature. After passing through approximately 18 yards of this bath at the same speed, the filaments are collected on a bobbin. 'The filaments are drawn approximately 1.5 X while passing through these baths. They are subsequently after-drawn bypassing through steam and over a hot-plate to produce a filament which has had a total draw of approxi- I Following is a comparison of the properties of the filaments obtained by these two different processes:

. Tenacity Elouga- Initial Denier (g.p.d.) tion Modulus (percent) (g.p.d.)

control; 2. 4 2.8 42 5e Tube-Spun 2. 5 4. 5 40 67 This example demonstrates that the use of the twisted tube results in the formation of filaments with substant-ially superior properties even when higher spinning speeds are used. The following example shows that the properties are more divergent when equal spinning speeds are used. 1

'6 Example IV The polymer used in the preceding example is dissolved to form a solution of the same composition. The

spinning conditions are identical with those described in Tenacity Elonga- Initial Denier (g.p.d.) tion Modulus (percent) (g.p.d.)

Control 4. 1 1. 7 24 42 Tube 2. 2 4. 4 31 76 The use of the special enclosure permits one to at least double, and in some cases more than quadruple, the rate of spinning without increasing the number of breaks in the thread line. While a tube of one particular designhas been demonstrated in the examples, any enclosure which imparts the desired flow to the coalescing bath as it flows concurrently with the filaments can be used. 1

Another advantage of the special enclosure, of the present invention is the fact that string-up trouble is practically eliminated when spinning is initiated. In the prior art, when tubes were used, the freshly spun filament was led into the tube where it often became tangled .to such an extent that the tube became partially or totally obstructed and spinning had to be restarted. When employing the process of the present invention, however,

the freshly spun filament is carried through the tube with substantially no tangling of the filament or plugging of the tube passageway. 1

Many types of materials may be used for preparing the tubes employed in the present invention. For example, ordinary glass and plastic tubing may be used. The flow.characteristics in tubes of metal or plastic or glass can-be modified by pressing dimples or rings into the outside surface to form irregularities on the inner surface. The tube may also be made uneven by corrugating or sand blasting. The tubing can also be made from elastomeric materials, which can, if desired, be distorted or made uneven by applying an irregular outer cover prior to vulcanization, or by using an irregular curing mold.

As mentioned earlier, the process of this invention is useful when utilized in the preparation of rubber threads from latices. The usual processes for preparing rubber threads in this manner are well known in the art. Latices from natural rubber or synthetic polymer latices prepared by emulsion polymerization may be used. The stabilized emulsions are extruded through suitable orifices into a coagulating bath. Acetic acid has been suggested as a suitable coagulant. The freshly formed thread line is very weak and very gentle handling is required. The process of this invention is well suited to the handling of this thread line during its formative stages. The apparatus is also well suited to the processing of highly elastic filaments from condensation elastomers. This is a conventional wet-spinning process in which solutions of the elastomers are extruded into a coagulating bath. Typical condensation elastomers are those in which a low molecular weight polymer with active hydrogen ends, such as a polyester of a polyether glycol, is reacted with a diisocyanate and this isocyanate-terminatedlow molecular weight polymer is chain-extended with a difunctional active hydrogen compound. As is true in the case of the addition elastomers, the freshly formed filaments tend to be quite weak. These filaments increase in strength upon further treatment in the bath, but very low spinning speeds must be used until coalescence is sufliciently complete to permit more rapid processing. The use of the flow of the present invention eliminates contact with the walls of the tube. This factonin conjunction with the concurrent 'bathflow made possible by the use of this tube,'reduces the tension on the filaments and permitsspinning speedstobe increased from approximately 30 y.p.m. to approximately 100 y.p.m.

The process of this invention is particularly well adapted to the processing of the relatively weak freshly formed filaments obtained by extruding dispersions of water-insoluble synthetic linear polymers in a solution of a matrix-forming material. This process has been referred to earlier and Will be described in detail in the following'sections. The following advantageshave been observed when the process of this invention is applied to the preparation of filaments by this r'riethod:'"

(:1) No dragging or snagging of'the'filaments on'the walls of the tube. e I

(2) Better coalescence of the'polyiner particles embedded in the matrix.

(3) Filaments are obtained which are more readily drawable and can be drawn to a final lengthwhich is a much higher percentage of the original length than is possible without the use of this tube.

(4) Yarn obtained is free of loops.

(5) Much'highe'r spinning'speeds are possible.

(6) Fewer interruptions in the spinning'process due to filament breakage.

(.7) Permits use of baths which would otherwise be impractical because of the weak thread line'de'veloped.

As illustrated by the examples, attemptsto' use a'nun modified cylindrical tube, or even a cylindrical tube arranged to form a spiral passage, does not provide comparable results. The filaments tend to hang up on the Walls of the tube and breakage of the thread line results when speeds substantially above about 30 yards per minute are tried when preparing filaments from polymer dispersions. Despite the fact that the turbulence, along with the laminar flow, Within-the tube would appear to represent a harsher treatment for the filaments, the results-demonstrate-that thereverse is actually true. I

The preparation of filaments from polymer particles dispersed in a'solution of a matrix-'formingmaterial is a recently developed process which has not been described extensively in the literature. Accordingly, it 'will'be described in more detail than the other spinningprocesses well-known in the art which maybe improved by the use of this invention. In general, the dispersion spinning process may be used to prepare films and fibers of waterinso'luble synthetic linear polymershaving. amolecul'ar weight of 10,000or higher. Someof the many polymers that can be used'include: acrylonitrile polymers and copolymers; polyacrylic and polymet-hacrylic esters, such as poly(methyl methac-rylate); poly(vinyl chloride) and copolymers of vinyi chloride with vinylesters, acrylonitrile, vinylidene chioride, and the like; copolymers of vinyl compounds with conjugated dienes such as butadiene; 'vinylidene chloride polymers; polyethylene; polytetrafluoroethylene; polychlorotrifluoroethylene; poly('viny1 acetate); partially hydrolyzed poly.('vinyl esters) poly (methyl winyl ketone); polyvinyl ethers; chlorosulforiated polyethylene; poly(vinyl carba'zole); poly(vinyl acetals) poly- Jamides, such as poly(hexamethylene adipamide),poly(N- :methoxymethylhexamethylene adipamide) polytethylene :sebacamide), polyQmethylene bis-[p-cyclohexylene] adipamide); polysulfonamides; polyureas, such'as -poly(tetramethylene urea); polyurethanes, such asthose' prepared from piperazine; polyesters, such as, poly (e'thylene ter ephthalate), and elastic copolyesters, such asthose prepared from a mixture of aromatic and aliphatic dib'asic acids and a suitable. glycol pdlyesteramidesppolytliiolesters; 'poly'sulfones; polyethers; cellulose 'derivatives, such as cellulose acetate, and many others. Copolyrners of all types can be used as wel-l as' the vhor'ntzrpoflyiners listed;

The term copolyrner is intended-"to include an types, such 'as random, alternating, segmented or block, and graft oopolymers. The polymer particles may even be cross linked, providing the degree or tightness of oress linkin'g is not suflicient to prevent the coalescence required to produce the desired structure. a

The matrix-forming materials useful in the invention comprise cationic or anionic polymeric electrolytes or neutral or non-ionic polymeric materials which are soluble in the dispersion ofthe fiber-forming polymer and which can be shaped in aqueous or non-aqueous media. Suitable anionic polymer materials contain a plurality of acidic groups, such as carboxyl, su1fonic and/erphosphoric or other acid groups. Specific polymers and classes of polymers Whichare applicable -as anionic matrix-forming materials iii this process include the following: alginates, carboxyalkylcelluloses, carb'oxy'rnethylhydroxyethylcellulose's, viscose, polyacrylates, 'polymethacrylates, and the like. In most cases the monovalent alkali metal salts of the anionicpolymeric electrolytes are more soluble in Water and are preferred.

Cationicpoly'meric electrolytes suitable as matrix-forming materials coritain'a plurality of basic groups. These are usually amino and/ or quaternary ammonium groups. Examples of useful cationic polymeric electrolytes are polyvinylpyridine, diethylamin'omethyl methacrylate polymer, hydrolyzed copolymers of vinyl acetate and vinyl pyridine, N-yinylphthalimide, N vinylsuccinimide, and other vinyl-substituted amino and masked amino polymers.

- Neutral polymers which may he used as matrix-forming materials include methylcellulo'se, hydroxyethylcellulose, cellulose acetate, urea-formaldehyde and melamine-formaldehyde resins, cyanoethylcellulose, poly(vinyl alcohol) and polyacrylamide.

Only small amounts of matrix-forming material are required to provide a definite advantage over 'none at all. The quantity used ranges from 0:10% to 10% by weight of the dispersion, with'0.25' to 5% being preferred. The specific quantity preferred varies with'the matrix material.

The setting or immobilizing medium maybe any liquid or vapor capable of precipitating or gelling the matriX- forming material. This includes air and vapors such as volatile strong acids, e.g., hydrogen chloride. Also useful are various other compounds and/ or mixtures in liquid or vapor form, such as water miscible organic compounds and aqueous solutions of solid, liquid, or gaseous inorganic and/or organic compounds. Preferably, aqueous solutions are used'which contain a lowconcentrationteg, O.540% by weight of. the aqueous solution) of an electrolyte or a non-electrolyte. Typi'cal' useful non-eleet'rolytes are water-miscible'org'anio liquids, such as alcohols, ketones, or glycols. High or low temperatures maybe used in coagulating baths to develop the desired precipitating qualities of the particular setting agent being used.

When aqucousbaths are used, the anionic and cationic matrix-forming materials will generally be terms into shaped articles through 'gelation as a result of chemical action on the materials hy the coagulating bath. Aqueous solutions of polyvalent'i'iietal salts are particularly useful as precipitants when an anionic matrix-forming material is used. Whena neutral, water-soluble polymeric material is used, physical gelling action of the coagulating 7 bath will most likely be involved.

The choice of matrix-forming material depends to some extent on the water-insoluble dispersed polymer. 7 It 'is' Water-soluble salts are preferred as coalescing solutions and include preferably metal salts of inorganic acids. These salts should be sufiiciently soluble in water to yield 10% solutions and, preferably 30% solutions. Furthermore, concentrated aqueous solutions of the salt being used should be capable of dissolving the polymer being processed at. some temperature up to the boiling point of the salt solution, for example, from C. to 175 C., and generally from 20 C. to 120 C. Coalescence can also be achieved by the use of organic coalescing agents. Organic compounds which are to be used should, preferably, be capable of dissolving the polymers at a temperature below their boiling points. However, temperatures higher than the boiling point of the liquid may be used for conducting the process in the vapor phase or under pressure. In practice, any coalescing agent need only exert a solvent action on the polymer that can be regulated to achieve the desired fusing of the discrete polymer particles.

It is possible to extrude the polymer dispersion into a liquid medium which will precipitate the matrix-forming material and will also exert solvent action on the polymer particles in the precipitated matrix. In this case, the special enclosure would be used in the single bath system to protect the filaments during the combined coagulation and coalescence.

In coalescing the polymer particles room temperatures or lower can be used, but it is generally preferred that the coalescing bath be heated, since less time is needed. For example, temperatures of the order of 30-175 C. may be employed momentarily in transforming the semirigid shaped article to a transparent, coherent film or fiber. Low time consumption is preferred in continuous processes and it is advantageous that the coalescence step consume only a few seconds or less. The use of the flow pattern of this invention is particularly useful in this step of the dispersion spinning process.

Removal of the coalescing agent from the shaped polymer is readily accomplished by washing. In washing multifilaments it is generally preferred that cold water be used. The resulting structure may then be aftertreated with boiling water, and, if desired, stretched to orient the molecules to effect improvement in physical properties. On the other hand, the coalesced structure may be atleast partially oriented by drawing prior to the washing step.

In addition to water, matrix-forming material, and polymer, the dispersion used for producing this shaped article can contain dispersing agents, plasticizers, pigments, non-solvent salts, dyes, clay, silica, alcohol, acetone, and similar materials. Alternatively, these materials may be incorporated in the coagulating bath, in the coalescing bath, or in separate baths or combinations thereof. These substances may or may not appear in the shaped article. If desired, the coagulated articles may be passed through a bath between the coagulating and coalescing media for washing, filling, plasticization,

and the like, prior to coalescing. After coalescing, the.

shaped article may be treated with a suitable finishing agent to enhance its usefulness or to facilitate subsequent processing.

The filaments which are produced in accordance with the present invention are useful in filter cloths, conventional textile fabrics, industrial fabrics, elastomeric fabrics and the like.

Many modifications will be apparent to those skilled in the art from the reading of the above without a departure from the inventive concept.

What isclaimed is:

1. In a process of forming a filamentary structure by contacting a freshly extruded polymer with a filamentforming liquid to form a filamentary structure; the improvement which comprises flowing the filament-forming liquid concurrently with the polymer as a single stream, the cross section of the concurrent stream of the filamentforrning liquid having an inner area and a surrounding outer area, the said inner area surrounding the extruded polymer and being in laminar flow and the said outer area being in a state of turbulent fiow which proceeds concurrently with the polymer in the form of a helix around the inner area of laminar flow.

2. In a process of forming a filamentary structure by contacting a freshly extruded polymer, the said polymer being present as particles which are immobilized in a gel matrix, with a coalescing liquid to coalesce the polymer particles into a filamentary structure; the improvement which comprises flowing the coalescing liquid concurrently with the polymer as a single stream, the cross section of the concurrent stream of the coalescing liquid having an inner area and a surrounding outer area, the said innerarea surrounding the extruded polymer and being in laminar flow and the said outer area being in a state of turbulent flow which proceeds concurrently with the polymer in the form of a helix around the inner area of laminar flow.

3. In a process of forming a filamentary structure by contacting a freshly extruded polymer solution with a coagulating liquid to coagulate the polymer into a filamentary structure; the improvement which comprises flowing the coagulating liquid concurrently with the polymer as a single stream, the cross section of the concurrent stream of the coagulating liquid having an inner area and a surrounding outer area, the said inner area surrounding the extruded polymer and being in laminar flow and the said outer area being in a state of turbulent flow which proceeds concurrently with the polymer in the form of a helix around the inner area of laminar flow.

References Cited in the file of this patent UNITED STATES PATENTS 827,434 Friedrich July 31, 1906 1,619,768 Schubert Mar. 1, 1927 2,402,846 Ryan June 25, 1946 FOREIGN PATENTS 293,977 Great Britain July 19, 1928 UNITED STATES PATENT OFFICE CERTIFICATE OF "CORRECTION Patent No, 2., 955 o17 October 4 1960 I Clarence Boyer- Q It is hereby certified that error appears in the printed specification of the above numbered patent requiri ng correction and that the said Letters Patent should read as corrected belo Column 4 lines 64 and 65 for N,N-dimethyl-for'mamide" read N N-dimethylformamide column 6 line 67 4 for "of" read or Signed and sealed this 11th day of April 1961,

(SE/AL) Attest: ERNEST w. syvmER a v ARTHUR W. CROCKER Attesting Officer Acting Commissioner of Patents

Claims

1. IN A PROCESS OF FORMING A FILAMENTARY STRUCTURE BY CONTACTING A FRESLY EXTRUDED POLYMER WITH A FILAMENTFORMING TO FORM A FILAMENTARY STRUCTURE, THE IMPROVEMENT WHICH COMPRISES FLOWING THE FILAMENT-FORMING LIQUID CONCURRENTLY WITH THE POLYMER AS A SINGLE STREAM, THE CROSS SECTION OF THE CONCURRENT STREAM OF THE FILAMENTFORMING LIQUID HAVING AN INNER AREA AND A SURROUNDING