IL37170A - Method of treating a tow - Google Patents

Description

METHOD OF TREATING A TOW BACKGROUND OP THE INVENTION A number of synthetic filaments of various types are known. These filaments are made by forcing a spinning solution through a spinnerette to form a tow of filaments. The tow is then washed and stretched and often dyed in a continuous operation.

The washing may be for the purpose of removing a spinning solvent, removing excess dye after a dyeing operation or for some other purpose. Conventionally, the tow is washed by passing it through a spray or a bath or by running it through an inclined cascade in a direction counter to the flow of water in the cascade. All of these approaches are inefficient, so that the tow must be run through the washing zone at a very low speed or the washing zone must extend a considerable length along the tow processing line. The former lowers the production rate while the latter requires the use of an excessive amount of space which might be better used for some other purpose.

The dyeing of wet spun filaments in the gel form during fiber production eliminates several processing steps necessary when the fiber is first produced and then subsequently stock dyed. The elimination of these steps .reduced the cost of the dyed fiber, so that gel state dyeing offers a real economic advantage. However, the prior art methods of continuously dyeing a freshly spun tow of filaments such as acrylonitrile have not been entirely satisfactory. Some of the problems involved in this approach are inadequate dye takeup in the limited space and contact time practical on a spinning line, poor dye uniformity on the thousands of filaments in a commercial tow, excessive dye losses and the cost and complexity of adding a continuous dyeing step into the spinning line. ·, In order to obtain best results when stretching the ' stretched while hot. The heating of the tow is usually accomplished by passing the tow over heated rolls or through a steam chamber or by other known methods. The disadvantage of most of the known methods of heating and stretching tow is that the heating operation is inefficient. Either the tow must have a long dwell time in the heating zone or excessive temperatures must be used to raise the temperature of the filaments to a point where they can be stretched. Further, it is very difficult in conventional stretching processes to heat the inner filaments of the tow to the same temperature as the outer filaments. With this in mind, one of the objects of this invention is to provide a novel and improved method of washing, dyeing and stretching a tow of filaments.

Another object of this invention is to provide a method for washing a tow of filaments in such a manner that excess dye or solvent is rapidly and efficiently . removed from the tow.

A further object of this invention is to provide a method for washing a tow of continuous filaments in such a manner that the filaments are completely washed within a very short contact time.

An additional object of this invention is to provide a method of applying a dye liquor to a tow of freshly spun filaments in such a manner that dye takeup and dye uniformity are good, dye losses are low and the filaments are dyed to the desired shade within a very short contact time.

Yet another object of this invention is to provide a method for stretching a tow of continuous filaments in such a manner that all of the filaments are stretched at substantially the same temperature. .„ The objects of this invention are achieved by passing . heated liquid transversely through the tow at a rate in excess of .a predetermined critical value, the liquid being maintained at a temperature within a predetermined range . The rate at which the heated liquid is passed to the tow must be at least as great as where x is the heated liquid flow rate in gallons per minute, t is the thickness of the stream of heated liquid, w is the width of the confined zone, h is the height of the confined zone, N is the number of filaments in the tow^4is the viscosity of the heated liquid in pounds per foot-second, aridCis the density of the heated liquid in pounds per cubic foot.

Other objects and advantages of the invention will become apparent when the following detailed description is read in conjunction with the appended drawing, in which Figure 1 is a diagrammatic cross sectional view of an apparatus useful for carrying out the process of the present invention, Figure 2 is a cross sectional view taken along line 2-2 of Figure 1 showing the cross sectional area of the confined zone in the apparatus through which the tow is passed, and Figure 3 is a diagrammatic view of a vat or discharge pan used with the Figure 1 apparatus in carrying out the process of the present invention.

Referring now in detail to the drawin there is shown, in a more or less diagrammatic manner, an apparatus which is useful as a tow washer, a tow heater or a dye applicator in carrying out the method of the present inven-tion. The apparatus is made up of upper and lower units • i 11 and 12 which are held in a spaced relationship by. side and lower units 11 and 12 . The space 1 between the upper and lower units 11 and 12 forms a confined zone through which a tow 15 passes. The lower face 18 of the upper unit 11 and the upper face 19 of the lower unit 12 and the inner faces 20 of the side plates 13 form the confined zone through which the tow 15 passes. The cross sectional area of the confined zone is best shown in Figure 2 where h is the height or thickness of the confined zone and w is the width of the confined zone.

The cross-sectional area of the confined zone will of course be wh.

The lower unit 12 is provided with an inlet 21 through which the heated liquid is applied to the tow. The inlet 21 extends across the lower unit 12 from one of the side plates 13 to the other. The inlet 21 has a thickness of 2T, t usually being no greater than about lOh, where h is the thickness or height of the confined zone, so as to concentrate the flow of the heated liquid through the tow 15 at one location. The upper unit 11 is provided with a recess 22 which receives the heated liquid passing through the tow 15 from the inlet 21. ^ The recess 22 directs the heated liquid back through the tow at outlet locations 23 spaced from the inlet 21 in streams T T having a thickness the value of $ preferably being no greater than about lOh. The preferred value for the dimension ½ is within the range of 2h to 5h .

The heated liquid entering the inlet 21 passes through the tow 15 and is divided into substantially equal parts which pass back through the tow 15 at the outlets 23.

As shown in Figure 3 j the apparatus 10 is. mounted over a vat or discharge pan 30 containing a heated liquid 31 » ι such as water or a conventional dye liquor. Spaced pairs of uniform speed. A pump 3^ connected to the vat 30 and the inlet 21. of the apparatus 10 pumps the liquid from the vat 30 through the apparatus via the inlet 21. The liquid exiting from the apparatus 10 falls back into the vat 30 and is recirculated.

Additional liquid ma be added to the vat 30 from a supply 38 to maintain a uniform level in the vat. An overflow line 39 drains off excess liquid from the reservoir 30. Pairs of stripper bars 36 positioned in contact with the tow as shown in Figure 3 are used to prevent liquid from flowing along the tow beyond the edges of the vat 30.

The heated liquid makes one pass through the tow 15 at each of the outlet locations 23, for a total of two passes at the outlet locations. Since twice as much liquid passes through the tow at the inlet 21 as at either of the outlet loca-tions it must be considered the liquid makes a double pass, or two passes, through the tow 15' at the inlet 21. . Thus, in the apparatus shown the liquid makes four passes through the tow 15. The heating liquid can be deflected back and forth through the tow as many times as desired. At each point where the liquid passes through the tow the liquid should be flowing at a rate at least as great as as set out above.

If the liquid passes through the tow at a lower rate the process of the invention is not utilized since tow will not be heated sufficiently to stretch the tow, washing will be ineffective and very little dye will be applied to the tow.

Of course, a portion of the heated liquid will, in an apparatus such as described above, not pass completely through the tow but will travel along the voids in the tow 'to the outlet measure the liquid flow rate inside the tow an easier way of deterninlng whether the minimum critical flow rate is exceeded is 'desired. If the inlet or outlet dimensions are held within the limits set out above the flow rate into the inlet 21 can be compared with the minimum critical flow rate x = i,ooot ir~ - — to determine whether minimum critical flow rate is exceeded, without regard for actual flow rate in the tow or the fact . that 'some of the liquid will travel along voids in the tow.

The table below shows values o ^ and^P for water or an aqueous dye liquor at various temperatures 4.85 xl0"4 62.06 40 4.40 xio"4 61.95 . 45 . 4.02xl0*4 61.82 50 • . 3.69 x 10"4 61.68 . 55 3.40 xlO"4 61.54 - 60 3.15 x 10"4 61.38 65 2.92 x 10"4 61.22 70 . .2.72 x 10~¾ 61.04 75 . · · 2.55x10"4 60.86 · 80 2.39 l0"4 60.67 : - 85 2.25 l0~4 60.47 90 2.12 x 10"4 60.27 95 . - 2.01 x 10"4 60> 05 . 100 1.90 x 10"4 • · 59.83 The following examples are included to show the efficiency of this tow washing process in removing solvent from wet spun acrylonitrile filaments. Pour washers (not shown) such as described above were used in series, with the freshly spun tow entering washer A and then passing through washers B, C and D in that order. Each washer was provided with its own pan or reservoir 30 from which wash water was circulated through the washer at a rate in excess of the critical minimum flow rate as determined by the equation given above.

Fresh water was supplied to washer D from its supply 38 and the overflow line 39 of washer D was connected to feed this overflow into the pan 30 of washer C. The overflow of washer C was fed into washer B from which the overflow was fed into the pan 30 of washer A. The overflow of washer A was passed to a solvent recovery system (not shown). The fresh water supply rate, which is independent of the circulation rate in each of the washers was based on the weight of the tow passing through the washers and was varied as shown in the following examples .

The tow was spun from a 93% acrylonitrile, 7% vinyl acetate copolymer into a spin bath of 55% dimethylacetamide/^5% water at 38° C. and was led from the spin bath into washer A.

The tow entering washer A contained about 50% dimethylacetamide. The tow was made up of 80,000 filaments, 3 denier per filament.

EXAMPLE I Tow was spun at a rate of 600 pounds per hour. The values given under the headings A, B, C and D represent the amount of solvent in the tow exiting from the washers A, B, C and D, respectively.

Solvent in tow % by weight lb H20/lb tow ' A B C D 12. 5 7. 44 1. 30 0.45 • 0.25 . 3 7. 75 . 2. 35 0. 64 0.22 EXAMPLE II Tow was spun . at a rate of 735 pounds per hour. Fresh water was added to the reservoir or pan 30 of washer D at varying rates and the amount of solvent in the tow after each washer was deter¬ mined. The results are shown in the following table. 12. 5 8. 86 2. 67 0. 85 0. 34 . 8. 3 -1-1. 63 3", 38 0. 84 0. 39 The temperature of the water used for washing may ¾e ip. to 100 C. The preferred temperature for washing acrylonitrile filaments is within the range of 30s C. to 70a C.

This process may be used not only to remove solvent from a freshly spun tow but also may be used for other washing, (such as re- movel of excess dye after a dyeing process, etc. ). The washing efficiency, especially in a solvent removal process, becomes un¬ satisfactory if the flow rate through the washing zone is not maintained above the critical minimum value as set out above. . · When the process is used for dyeing, a conventional dye liquor is used. Those skilled in the art are thoroughly familiar with dyes, dye liquor concentrations, which dyes are effective with various types of man-made fibers, etc.

The dye applicator may be located at any step of the spinning process after coagulation and before drying and collapsing of the filaments. The length and dimensions of the applicator may be varied. The composition of the dye bath may be water or a solvent-water mixture with or without buffer salts, acids, retarding agents, or other materials customarily used in dyeing. Any wet spun fiber, dry spun fiber, or other swollen fiber can be dyed, provided that it is in a gel state.

- - - • EXAMPLE III " .

A 93% acrylonitrile* 7% vinyl acetate copolymer with a n of sp 0. 154 was dissolved in dimethylacetamide to form a 25% solids spinning dope. This dope was extruded through a 1 , 000 hole, 3 mil hole size Bpinnerette into a spin bath of 55% dimethylacetamide / 5% water at 38° C. The tow of gel filaments was drawn onto a godet surface at 20 feet per minute. The tow was washed free of dimethylacetamide by a 50° C. water spray during 15 wraps on this godet. The tow then passed through a dye applicator such as described above and onto a second godet also turning at 20 fpm. Tow entering the applicator had over 300% liquid carryover from the washing spray. No stretch was applied to the to in the applicator.

After leaving the dye applicator the tow made 10 wraps on a second godet, dipping into a water bath each time. This wash bath removed free dye from the tow.

Three doffs were spun as described below with variations in dye application. Doff 1 employed the process of this invention utilizing an applicator such as described above. Doffs 2 and 3 were dyed during immersion in a conventional dip bath with the bath flow countercurrent to tow movement. In all cases the aqueous dye liquor was recirculated from a separate dye tank. A commercial basic · · dye, Sevron Red GL, C. I. Basic Red 18, was used for all three doffs.

* The dye liquor was aqueous and had a temperature of 60° C.

The cross -sectional area of the tow passageway, or confined zone, through the applicator was 0. 00875 square inches (3 /32" by 3/32 "). The dimension'f irefer to Figure 1) was 9 /32 ". The critical minimum flow rate of dye liquor through the applicator 10 at 60° C. was Q .0 ¾allons per minute, in accordance with the equation: x = . ooot T ^ where . b y t is 9 /32 " w is 3/32" h is 3/32 " N is 1000 Actual dye liquor flow rate through the applicator was 0. 21 gallons per minute, in excess of the critical minimum of 0. 045 gallons per minute.

The dye bath was made fresh for each doff and analyzed. After the tow was completely strung up on the spinning line the dye bath circula tion was started. No dye makeup was added during spinning, so that the dye bath concentration, decreased. Dyeing lasted 20 minutes on each doff. At the end of this time dye bath circulation was stopped. The final concentration and dye concentration in the wash bath were then determined. The dye pickup on the last portion of dyed fiber was also determined by dissolving the fiber in solvent. All dye determinations were made by absorption measurements on a Cary Model 14 Spectrophotometer in a well known manner. The tow was evaluated visually for dyeing uniformity.

Doff 3 This Conventional Conventional Dye Applicator Invention Dip Bath Dip Bath Immersion Length, inches 26 40 40 Dye Bath Temperature, β C 60 60 60 Circulation Rate, gal/min 0.21 0.21 0.21 Dye Bath Concentration Original, % . 041 .040 .244 After 20 minutes, % .015 . 034 .213 Decrease . 026 . 006 . 031 Dye on Fiber, % by wt.

End of 20 minutes . 68 .23 1. 11 Dye on Fibe Pickup Ratio: 45. 3 6. 7 5. 2 Dye in Dye Bath Dye Lost in Wash Bath After 20 Minutes, gms . 002 . 0012 . 01 Tow Color Uniformity Good Streaky Streaky Two indicators of dyeing effectiveness are the decrease in dye bath concentration during 20 minutes dyeing and the dye pickup ratio at a specified time.. Both show that the process of this invention gave much higher dye pickup even though the conventional dip baths were 54% longer. A comparison of Doffs 1 and 2 where the initial dye bath con- centrations were equal shows 4. 3 times as large a decrease in dye bath concentration with this invention. The dye pickup ratio was 6-8 times higher with this invention.

Dye pickup in the dip bath application can be increased by going to the higher dye bath concentration as in Doff 3 but dye losses will be Increased proportionately as shown. • · · · . ·· _ The process of this invention gave a very uniformly dyed tow with no filament-to-filament color differences. In contrast, both doffs dye in the conventional dip bath were quite streaky.

EXAMPLE IV Twelve parts of a 50% acrylonitrile/50% methyl vinyl pyridine copolymer was blended with 88 parts of a 95% acrylonitrile / 5% vinyl acetate copolymer. The resulting polymer blend was dissolved in " dimethylacetamide to form an 18% solids spinning dope. The methyl -vinyl pyridine provided amino groups making this polymer dyeable with acid dyes.

This dope was spun into fiber and the tow dyed in accordance with Doff 1 of Example I except that the tow contained only 250 filaments. The critical minimum dye liquor flow rate, with a tow of 250 filaments, waso . 023 gallons per minute. Actual dye liquor flow rate was 0. 21 gallons per minute. No stretch was applied to the tow in the applicator.

Liquid carryover of the tow entering the dye applicator was 380%, An acid dye, Scarlet 4RA, C. I. Acid Red 18, No. 16255, was used for this run. The dye liquor was prepared using sodium formate and form a a Sam le f t e d e uor and fiber were taken simultaneously at the end of the run for dye analysis.

Dye Liquor Temperature: 50e C Circulation Rate: 0.21 gallons per minute Percent Dye in Dye Liquor: .052 Percent Dye on Fiber: 1. 53 τ>· i ' * T> 1. 53 _ Q1 · " Pickup Ratio: . 0 n5g2 = 31 The color uniformity of this tow was very good.

EXAMPLE V A polyacrylonitrile polymer was dissolved in dimethyls ul-.-foxide to form a 20% solids dope. This dope was spun into fiber and a tow made up of 250 filaments, was as in Example II. · Another basic dyestuff, Astrazon Yellow 7GLL was used for this sample. Pickup results are shown below.

Dye Bath Temperature: 50° C.

Circulation Rate: 0. 2.1 gal/min.

% Dye on Fiber: 2. 53 % Dye in Bath: 0. 97 Pickup Ratio: . = 26 Polyacrylonitrile fibers are known to be very difficult to dye in conventional stock dyeing. With the process of this invention EXAMPLE VI A modacrylic polymer containing 10. 9% vinyl bromide, 18. 3% vinylidene chloride, 1. 65% sodium p-sulfophenyl methylallyl ether, 1% styrene, and 67.2% acrylonitrile was prepared. This polymer, with an n sp of 0. 15, was dissolved in dimethylacetamide to form a 23% • .* · ·■ solids spinning dope. The dope was spim into fiber using conditions similar to Example II, except that the cascade stretch, which oriented the fiber, was only 4X.

In this case the dye applicator was located after the boiling water cascade stretch rather than before as in the prior examples.

The tow was consequently moving at 78 fpm durin dyeing but the reduced contact time was counterbalanced by the reduction in filament size and increase in surface area. Another basic dyestuff Deorlene Blue 5G was used for this example. Samples of dye bath and fiber were taken simultaneously and analyzed for dye.

Liquid carryover of this tow entering the dye applicator from the cascade was 246%. In this case the tow was allowed to · relax 2. 5% in the dye applicator.

Dye Bath Temperature: .. . 60* C.

. „ Number of Filaments: 250 Actual Circulation Rate: " " .0.21 gal/min.

Aqueous Dye Bath Concentration, %: . 0294 Dye on Fiber, %: 1. 26 Pickup Ratio: 43 · · ■ ί Tow Color Uniformity: Good The process of this invention is effective after fiber orientation.

EXAMPLE VII A 93% acrylonitrile-7% vinyl acetate copolymer with an ngp of 0. 154 was dissolved in dimethylacetamide to form a 25% solids spinning dope. The dope was extruded into a spin bath containing 55% dimethylacetamide /45% water to form a tow of 1 , 000 filaments and drawn onto a godet at 17. 5 fpm.

This tow was passed directly into the dye applicator described in Example I without washing to remove the solvent, dimethylacetamide. The dye liquor had the same solvent composition as the spin bath. Tow entering the dye applicator had over 250% liquid carryover. After leaving the dye applicator the tow was washed to remove solvent, then stretched, and treated as in Example I. The basic dyestuff, Sevron Red GL, C. I. Basic Red 18, was dissolved in the solvent /water dye liquor. A series of simultaneous dye liquor and fiber samples were taken during three hours spinning, with no additional dye being added to the system during the three hour run.

Dye Liquor Temperature: 38° C.

Circulation Rate: 0.21 gal/min.

Doff Dye Liquor Dye on Pickup . Dye Concentration, % Fiber, % Ratio Uniformity 1 . 041 0.92 22 Good 2 . 022 0. 50 23 Good 3 .01 0.27 27 . Good . 005 0. 13 26 Good .003 0. 07 23 Good 6 . 0018 0. 04 · 22 . Good The effectiveness of this process in a solvent -water dyeing system is apparent. Also, all samples were uniformly clyed even at these very light shades. ' EXAMPLE VIII A terpolymer of 7. % vinyl acetate, 2. 4% vinyl bromide and 91. 2% acrylonitrile with an ng^ of 0. 15 was dissolved in dimethyl - acetamide to form a 25% solids spinning dope. This dope was extruded through a 60 hole, 5 mil hole size spinnerette into a 60% dimethyl- acetamide /40% H20 spin bath at 30° C. The 60 filament tow was drawn onto a godet at 17. 5 fpm, washed with water during 15 wraps on this godet and passed directly into the dve applicator. Liquid carryover into the dye bath under these conditions was over 230% based on dry fiber.

From the dye applicator the tow passed to a second godet whose speed was varied. The tow also' dipped into a neutralization bath of 0. 5% NaHCOg underneath this godet. The tow was then stretched 6. OX in a boiling water cascade, finish applied, and the tow dried, crimped, and relaxed as customary in the spinning process. Final !denier per filament in this case was 15. 0.

Six doffs were spun with variations in dye bath temperature and stretch in the dye. bath. Sevron Red GL dyestuff was used for these experiments. Results are tabulated below. Fresh dye liquor was prepared before each doff and no dye was added during the 10 minute run time.

Doff 1. 2 3 4 Prewash Temperature, ° C. 45 45 45 45 Dye Bath Temperature, * C. 54 61 70 80 Circulation Rate, gal/min 0.21 0. 21 0. 21 0.21 Dye Liquor Concentration: • Original .0230 . 0234 .0230 . 0248 After 10 minutes . 0200 . 0200 . 0192 . 0238 Decrease . 0030 . 0034 . .0038 . 0010 Dye. Zone Stretch 1 1 1. 1 Color Uniformity Good Good Good Good These results show that good dye pickup and uniformity can be obtained with the dye liquor temperature equal to or higher than the prewash temperature. Dye pickup increases with increasing dye liquor temperature up to 70° C. but decreases above 80° C. .

: . In the following examples an apparatus such as that described" above was used for carrying out the process of the invention with the exception that the apparatus was made larger to accommodate larger tows.* The confined passageway through the apparatus, had a width, w. of 4. 0" and a height, h of 11 /64". The thickness, 2* of the stream of dye liquor impinging on the tow at the inlet 21 was 1 1 /8", while the dimension t was 9 /16". A conventional dye liquor well known to those skilled in the art was used. Critical minimum flow rate of dye liquor through the tow was determined in accordance with the equation set out above.

EXAMPLE IX In order to determine dyeing efficiency on acrylonitrile fibers at various temperatures runs were made at various tempera¬ tures under the conditions set forth below. The dyeing was carried out on freshly spun filaments in gel state prior to drying and collapsing.

Conditions Polymer Composition 93 percent acrylonitrile •7 percent vinyl acetate Polymer n . sp 0. 16 Polymer solvent -solids dimethylacetamide -25% Spin bath temperature 35° C.

Stretch in applicator Spin bath composition 55% dimethylacetamide / .45% water 50 60 18 70 27 80 27 90 27 1 10000 2 277 The following example illustrates the use of the process in. stretching the tow.

EXAMPLE X A 93$ acrylonitrile , 1% vinyl acetate copolymer was spun into a spin bath made up of .55? dlmethylacetamide and ^5% water. The tow formed was made up of 40,000 filaments, 3 denier pier filament. The tow was withdrawn from the spin bath, washed to remove dlmethylacetamide and then passed through an apparatus such as that described above. Water at a temperature of 100°C. was circulated through the apparatus at a rate in excess of the critical minimum flow rate as determined by the equation set out above. The tow was fed into the stretch zone at 26.5 feet per minute and withdrawn at 132.5 feet per minute, giving a stretch ration of 5 to 1. No broken filaments were observed.

XI Example I was repeated using water temperatures of 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 102°C, 10i»oC, 106°C. and 108°C. in order to determine the temperature range in which stretching of the tow could be accomplished. The tempera-tures above 100°C. were accomplished by constructing the apparatus in such a manner that the heated water made 20 passes through the tow in order to obtain a sufficient back pressure to raise the temperature of the water above 100°C. It was found that, in order to obtain a 4x stretch the temperature of the water had to be at least 80°C. Preferably, the water temperature is maintained at a value above 90°C.

It is not necessary that the heating fluid be water when stretching the tow. For examples, the heated fluid may be ethylene glycol, polyethylene glycol or other high boiling alcohols. The advantage ,of using one of these liquids is that temperatures higher than 100°C. can easily be utilized. 37170/2 EXAMPLE A number of rune were made usi g filament of different chemical eorapoeitlon wherein the filaments were washed with water containing a finish for the purpose of applying the finish to the filaments* Fiber types included in these rone were polyvinyl chloride* polyester* nylon and rayon* ell well known to those skilled in the art* The washing fluid wae 98$ water and 2$ of a conventional finish* at a teaperattsre of 100°C* In addition to being washed, the filaments were stretched* The confined eone had the following dimensionst w*3A6*i h- 3A6"t end T-9/16 with an overall length of 8% The number of filaments in each bundle of filaments passing through the confined zone wae such that the minimum critical flow rate varied up to approximately 0*1 allon per minute for the different fibers* The actual flow rate through the confined zone wae 1*8 gallons per minute* The following table shows the conditions under which these runs were made* Approximately 1$ of the finish* baaed on the weight of the fiber* wae applied to the fiber in each washing run* hie process may be need not only to remove solvent from a freshly spua tow but also may be need for other washing such ae application of a dye or finish or removal of excess dye after a dyeing process, etc* The washing un efficiency becomes/satisfactory if the flow rate through the washing atone le not amaintained above the critical minimum^ value ae eet out above* Preferably, the flow rate le at least three tines the niniflBim rate and may be man* timee as great ae the minimum rate* The minimum dwell or contact time of the to* in the confined stone (i.e., the length of time that a given point on the tow requires to pass through the fluid in the confined gone) varies slightly with the washing operation* For example* if it is desired to

Claims (8)

14-53-001V15/16 WHAT IS CLAIMED IS: artificial

1. A process for treating a tow of/filaments with a liquid characterized by (1) advancing the tow through a confined zone and (2) forcing the liquid through the tow in the confined zone at a flow rate at least as great as X where wherein X is the liquid flow rate in gallons/ minute t is the thickness of the liquid w is the width of the confined zone h is the height of the confined zone N is the number of filaments J* is the viscosity of the liquid in pounds/foot-second is the density of the liquid in pounds/cubic foot

2. The process of claim 1 characterized in that the liquid is a dye liquor at a temperature within the range of 30°C to 100°C and the filaments are in the gel state.

3· The process of claim 1 characterized in that the liquid is water at a temperature of at least 80°C and the tow is stretched at least about 4 X.

4. The process of claim 1 characterized in that the liquid is water at a temperature of from about 30°C to 70°C.

5. The process of claim 1 characterized in that the ow is composed of acrylonitrile filaments.

6. The process of claim 1 characterized in that the ow is composed of modacrylic filaments. 14-53-0011/15/16

7» The process of claim 2 characterized in that the dye liquor forced through the tow is deflected to pass back through the tow at a plurality of locations along the tow.

8. The process of claim 1 characterized in that the liquid is ethylene glycol. C P. O. Box 33116 , Tel-Aviv Attorneys for Applicant