US3370911A - Process for rapid bleaching - Google Patents

Description

:K3-1 n 7 s R I Em @www www P19850@ XR 3937015111 Feb. 27, 1968 T. E. WESTALL. 3,370,911

PROCESS FOR RAPID BLEACHING Filed oct. 21, 1964 e sheets-sheet 1 E Q n Cz O k U M q. N n

C N 2N fg f! E' Og *L -4 om SQ N sg S S INVENTOR. ik 7/70/445 'D/So/y h/fsr/)LL Q Q BY v` bb www@ Feb. 27, 1968 T. E. WESTALL 3,370,911

PROCESS FOR RAPID BLEACHING Filed oct. 21, 1964 e sheets-sheet 2 www W l i 1 22A i @lo 5 N INVENTOR. W WOM/qfo/so/v /SSMLL v a,

Feb. 27, 1968 T. f-:.wEsTA1 1 PROCESS FOR RAPID BLEACHING G Sheets-Sheet Filed OCC. 2l, 1964 T. EWESTALL 3,370,911

PROCESS FOR RAPID BLEACHING Feb. 27, 1968 G Sheets-Sheet 4 Filed 001,. 21, 1964 R O T. N E V W Feb. 27, 1968 T. E. wEsTALL PROCESS FOR RAPID BLEACHING 6 Sheets-Sheet 5 N m7,/ ArrOfQ'YYS Filed OO. 21, 1964 Feb. 27, '1968 T. E. WESTALL 3,370,911

PROCESS FOR RAPID BLEACHING Filed oct. 21, 1964 v e sheets-sheet e i. E. 4L

EN n s 53" 5% l LO/i A a l. I ,s @Il l@ ZZ n INVENTOR. 717/0145 mso/y Misma BYMW Arrows/6X5 United States Patent 3,370,911 PROCESS FOR RAPID BLEACHING Thomas E. Westall, Marion, N.C., assignor to The American Thread Company, New York, N.Y., a corporation of New Jersey Filed Oct. 21, 1964, Ser. No. 405,430 12 Claims. (Cl. 8-111) ABSTRACT 0F THE DISCLOSURE This invention is directed to a combined and continuous mercerizng and bleaching process for yarn, which is carried out in a short period of time. The yarn moves forward continuously through the following major process steps: boiling out, mercerizng (caustic), caustic washing, steaming, bleaching, steaming, washing and finishing.

This invention relates to processes for the mercerization and bleaching of cotton yarn, and more particularly to a combined mercerization and bleaching process in which the steps of mercerization and bleaching are carried out in a single operation while a Warp of yarn is being advanced continuously.

Prior to the present invention it has been customary to mercerize and bleach yarn in separate operations. The yarn is mercerized in a continuous process, dried, and then bleached in a batch-wise operation.

Unmercerized and unbleached yarn is received in the form of spools or cones, each having a single end of yarn. These ends are brought together from a plurality of spools to form a ball of warp, in which the ends are substantially parallel. Typically, 378 ends are brought together in this manner. A plurality of warps, for example 12 to 48 warps, are passed simultaneously through the steps of the present process. The yarn is passed from the balls of warp through the mercerizng process. In mercerizng, the ends are separated from one another as they are pulled from the ball of warp so that each warp of 378 ends passes into the -mercerizing process along a horizontal plane. These warps are first passed through boiling water to remove grease and foreign matter in a step which is commonly known as boiling out. The yarn then advances into an aqueous caustic solution, which typically contains about by weight of caustic soda. Causticization is followed by a plurality of washings at various elevated temperatures. Squeeze rollers or nip rollers control the amount of liquid carried over from one treatment to the next. After the last washing cycle the warps are dried in a steam heated dryer and are piled on pallets.

Bleaching of yarn according to prior practice is carried out starting with dried mercerized yarn treated as described above. Warps of dried yarn are transferred from the pile to a bleaching tank, which is preferablyl a covered rectangular tank containing hot aqueous bleaching solution. The yarn is spread out in layers, one above the other, in the tank to afford good contact between the yarn and the bleaching solution. Various aqueous alkaline bleaching solutions can be used; a preferred bleaching solution comprises hydrogen peroxide, sodium silicate, and sodium hydroxide dissolved in water. The yarn remains in the bleaching tank several hours. Following bleaching, the yarn is transferred to a tank, then washed to remove alkali carried out by the yarn, and is then dried. The dried warp is again formed into a pile resting on a pallet.

It can be seen that the former practice of mercerizng 3,370,911 Patented Feb. 27, 1968 rice and bleaching in separate operations involved a large number of steps. Handling of the yarn is complicated by the fact that it is necessary to take a pile of mercerized yarn, unwind it for bleaching, and then again form a pile after bleaching is concluded.

One object of this invention is to provide a continuous bleaching process.

Another object of this invention is to provide a combined mercerization and bleaching process which results in a considerable reduction in the number of steps required in order to obtain a mercerized and bleached yarn.

A further object of this invention is to provide a bleaching process which is more rapid than prior bleaching processes.

A further object of this invention is to provide an apparatus for combined mercerization and bleaching.

A still further object of this invention is to provide a novel steaming chamber for heating the yarn after it has contacted the bleaching solution and thereby make bleaching more rapid and effective.

These and other objects will be apparent from the .description which follows.

FIG. 1 is a flow sheet showing diagrammatically' the process steps of this invention;

FIG. 2A is a schematic diagram of the first part of the process;

FIG. 2B is a schematic diagram of the remainder of the process;

FIG. 3 is a side elevation of the first steam chamber;

FIG. 4 is a front section of the first steam heating chamber;

FIG. 5 is a perspective lview of a portion of the bottom wall of the first steam heating chamber, with parts broken away, showing the entrance opening for warps of yarn in detail;

FIG. 6 is a perspective view of the bleaching tank, with parts removed and parts shown in section, and with the reagent feed conduits shown diagrammatically;

FIG. 7 is a front elevational view, with parts lbroken away and parts shown in section, of the bleaching tank and second steam heating chamber;

FIG. 8 is a cross section taken along line 8-8 of FIG. 7 showing a roller in the second steam heating chamber and a clutch drive mechanism therefor in detail; and

FIG. 9 is a side sectional view of a flexible curtain seal for a steam heating chamber.

Referring now to FIG. 1, the yarn ends from a plurality of warps are brought together to form a sheet 10. The yarns in the sheet are disposed in parallel side-by-side relationship in a single plane, so that the warp from a distance has the appearance of a thin continuous tape or sheet of indefinite length.

T'he warps are passed through the entire sequence of steps illustrated in FIG. 1 at a substantially uniform velocity, for example about 2() yards per minute. The velocity may be greater or less if desired, but greater velocities require correspondingly larger apparatus in order to achieve the same residence times in each of the various steps. Minor variations in warp velocity occur at different points in the process for reasons to be hereinafter explained.

The warps of cotton yarn are first introduced into a hot water tank 11 for boiling out, i.e., removal of any grease and foreign matter which is adhering to the yarn, and are then cooled to about room temperature `in. cold water tank 12. The yarn is then immersed in a mercerization vessel 13 containing caustic soda solution. The ternheating perature and the concentration of the caustic soda solution may be the same as in conventional mercerizing procedures. For example, a typical caustic solution contains about 20% or v25% aqueous of caustic soda and is at approximately room temperature. It is understood that the temperature may be higher or lower and the concentration greater or less in accordance with usual mercerizing procedures.

The warp of yarn may be washed in dilute aqueous caustic soda in ivessel 14 after mercerization. The temperature of this wash solution is generally elevated, for example about 140 F.

The sheet of yarn after washing in caustic washing vessel 14 is heated in first steam heating chamber 15. Steaming in chamber 15 conditions the thread so that impurities therein which are diicult to bleach, such as fragments of seeds and hulls, will be bleached white. The yarn entering steaming cham-ber 15 carries with it a small amount of caustic solution, for example about 3% by weight based on the weight of yarn. The amount of caustic can be greater, up to about 6 to 8% of the weight of yarn. A small amount of caustic on the yarn as it enters steaming chamber 15 is essential for subsequent receptivity to bleaching, although the amount may vary widely while obtaining good results.

Steam is supplied to chamber 15 from a source of supply 16. The temperature in steam heating chamber 15 may be varied over wide limits. Generally the temperature is between about 180 F. and about 212 F. In a typical operation, the temperature in steam heating chamber 15 is maintained at about 190 F. to 200 F. The appropriate temperature may be maintained by the admission of either dry saturated steam or wet steam at atmospheric pressure from steam source 16. In order to prevent the temperature from going too high, cold water may be admitted as required to steam chamber 15 from cold water source 18. Addition of cold water may be necessary, for example, when forward movement of yarn through the apparatus is temporarily halted for any reason, such as splicing of yarn ends from successive warps. The yarn remains in steam heating chamber 15 about one minute at 190 to 200 F.

After steaming in first steam heating chamber 15, the yarn is washed in a dilute solution of caustic soda contained in vessel 20. This washing solution has a concen- 140 F. to 180 F. are advantageous. The concentration is preferably about 1% by weight of caustic soda in water; higher or lower concentrations may be used.

The yarn after being washed in caustic wash tank is then immersed in a bleaching solution contained in bleaching tank 22. The yarn as it enters bleaching tank 22 has a moisture content of about 80% of saturation, which corresponds to about 0.8 pound of water per pound of dry yarn. The bleaching solution may be any of the alkaline bleaching solutions known in the art. For example, the yarn may be bleached in a solution of hypochlorite in an alkaline medium. The preferred bleaching agent solution, however, is an aqueous solution of hydrogen peroxide, caustic soda, and sodium silicate. The concentration of hydrogen peroxide is generally in the range of about 2% to about 4% of the total weight of the solution. Caustic soda in concentrations ranging from about 1% to 2% of the total weight of the solution is also present. In general, the higher concentrations of caustic soda are used with the higher concentrations of hydrogen peroxide. The optimum concentration of bleaching agent can readily be determined by bleaching a sarnple of the material to be bleached. -It is lalso desirable, although not essential, to include sodium silicate in the solution. This sodium silicate may be a conventional water glass solution containing approximately 3.3 mols of SiOz 4 for each mol of NagO. The concentration of sodium silicate is preferably about 1% to about 4%, a concentration of 2% being typical.

The temperature of the solution in bleaching tank 22 may be in the range of about F. up to the boiling point of water. Preferred temperatures are about to about F. These temperatures are considerably below bleaching temperatures used heretofore with hydrogen peroxide as the bleaching agent. Generally the art has preferred to maintain the temperature at about to about F. when using an aqueous alkaline hydrogen peroxide `solution for bleaching.` Alternative ranges for the temperature of an aqueous alkaline solution of hydrogen peroxide, which contains an alkaline metal silicate, are about 110 to about 200 F. and about 110 F. to about In addition to the hydrogen peroxide, caustic soda and sodium silicate, the bleaching solution may also contain a small amount of epsom salts (magnesium sulfate), for example, about 1/2 ounce per gallon. It is also desirable to add a chelating agent. Various commercial chelating agents are quite satisfactory forthis purpose. One of these, lby way of example, diethylenetriaminepentaacetic acid, sold under the trade name Versenex 80. The epsom salt and the chelating agent are conveniently supplied as aqueous solutions containing one pound per gallon and one pint per gallon respectively.

It is necessary to replenish all constituents of the bleaching solution to make up for solution carried out on the` yarn. Replacement solutions are most advantageously supplied continuously, and in such proportions that the bleaching solution retains its original composition. For example, in the case of 18 warps of cotton yarn each y containing 378 yarn ends and passing through the bleaching tank at the rate of 20 yards per minute, make-up hydrogen peroxide may be added as a 50% aqueous solution at the rate of 15 gallons per hour. Make-up caustic soda solution and make-up sodium silicate solution may be added at the rates of y3 gallons per hour and 4 gallons per hour, respectively, from solution tanks 26 and 28, respectively. The make-up caustic solution in this case contains 50% by weight of NaOH, and the make-up silicate solution contains 81% by weight of sodium silicate having the approximate formula Na2O3.3SiO2. The flow rates and concentrations herein are merely illustrative and may be varied, depending on the desired concentrations in bleach tank 22 and the rate of liquid carry-out therefrom.

After the warp of yarn passes through the bleaching tank 22 it enters a second steam heating chamber 30. At this point the moisture content of the yarn is 100% of saturation. Steam heating chamber 30 is maintained at a temperature of about 212 F., although the temperature may be either somewhat higher or lower, as desired. Generally, the temperature in steam heating chamber 30 will be in the range of 212 to 220 F., or the temperature may be 212 to about 240 F. Live steam, preferably dry saturated steam at 212 F. and l atmosphere pressure, is introduced into steam heating chamber 30. Wet steam or superheated steam may be used if desired. The warp of yarn passes through steam heating chamber 30 in a plurality of passes so as to afford prolonged exposure to the high temperature of steam. Bleaching agent adheres to the yarn as it enters steam heating chamber 30. Most of the bleaching action takes place in steam heating chamber 30 due to the elevated temperature prevailing therein, rather than in bleaching tank 22. While the residence time of yarn` in steam heating chamber 30 may be varied within wide limits, it is generally found that bleaching times of about 4 to 6 minutes in chamber 30 are sufficient. This is considerably less than the times required for batch bleaching as previously practiced. The residence time of yarn in chamber 30 must be sufficiently long to insure proper bleaching, and at the same time must not be so long as to result in degradation of the cotton. Steam heating chamber 30 may be heated by means of an auxiliargtl heater if desired, especially if it is desired to maintain a temperature above 212 F. at one atmosphere.

A slight elongation of the yarn, usually about 0.5%, takes place as the yarn passes through steaming chamber 30. To maintain the yarn taut, it is necessary to increase the speed of the yarn in an amount proportional to the amount of elongation. Thus the exit velocity of the yarn as it leaves steaming chamber30 is about 0.5% greater than the entrance velocity. In the typical case already mentioned where the entrance velocity is 20 yards per minute, the exit velocity is 20.1 yards per minute.

After steaming in chamber 30, the yarn is washed by passage through a plurality of wash tanks. Typically the wash'tanks include one or more water wash tanks 32 followed by an acid wash tank 34 in which the yarn is passed through a dilute aqueous acid solution of a suitable acid such as acetic acid. The yarn after acid washing may be contacted with a bluing solution in bluing tank 36, or processed in such other finishing operations as desired. After any desired bluing and finishing are performed, the warp of yarn is conveyed to a drier, where the yarn is dried. The yarn ends may then be separated and each individual thread may be wound to form a package as desired.

The apparatus for carrying out the above described process will now be described14 in greater detail with reference to FIGS. 2 to 8`. Referring first of all to FIGS. '2A and 2B, the apparatus includes boiling-out tank 1l, cold water tank 12, mercerization tank 13, caustic wash tank 14, first steam treating chamber 15, second caustic wash tank 20, bleaching tank 22, second steam treating chamber 30, water wash tank 32, acid wash tank 34, and bluing tank 36. The warps of yarn pass through the elements of the apparatus in the order named, first entering boilingout tank 11 and finally passing outward from bluing tank 36 to a drier (not shown).

Each of the tanks ll, 12, 13, 14, 20, 32 and 34 includes a plurality of rollers 42 immersed beneath the liquid surface of the tank, and a plurality of rollers 44 above the liquid surface of the tank. The warp of yarn passes alternately between submerged rollers 42 and overhead rollers 44, so that the yarn passes alternately in and` out of the solutions contained in each tank. A pair of pinch rolls 46 including a fixed lower roll 46a and an upper roll 46b movable toward or away from lower roll 46a in response to diaphragm actuator 48 is provided for each of the tanks to control the amount of liquid carryover from that tank to the next tank in the series. Pinch rolls 46 may be preset to any desired roll pressure which in turn controls the amount of liquid carried over to the next tank. Diaphragm actuator 48, which may be biased to a constant predetermined pressure by suitable fluid means such as air, maintains the pair of pinch rolls at the desired operating pressure. Each set of pinch rolls 46 is controlled by a separate diaphragm actuator 48. The lower roll 46a in each set of rolls 46 is motor driven and the upper roll 46b is an idler.

Boiling-out tank 11, cold water tank 12, mercerization tank 13, and first caustic wash tank 14 may be included in a single housing 49 if desired. Successive tanks in housing 49 are separated by partitions 50.v Similarly, in FIG. 2B, which is a continuation of FIG. 2A, water wash tank 32, acid wash tank 34, and bluing tank 36 may be included in a single housing 5l separated by partitions 52.

Referring now to FIGS. 3 and 4, steam heating chamber 15 is preferably in the shape of a rectangular prism, and includes a plurality of idler rolls over which the yarn passes. Preferably these rolls are disposed in upper and lower rows 53 and 54 respectively. The yarn is introduced into steam heating chamber 15 through slot 56 in the bottow wall 58, as may be seen best in FIG. 5. The entering yarn passes upwardly over the first of the upper rolls 53, thence downwardly over the first of the lower rolls 54, thence back and forth alternately over rolls 53 and 54, and finally passes downwardly through exit opening in bottom wall 58. A.l conduit 61 is provided for', the introduction of steam into heating chamber 14. n

' Bleaching tank 22, which is best seen in FIG. 6, is. preferably in the form of a rectangular box, made of sheet metal, and having an open top. The tank 22`has exterior side walls 62 and a bottom wall 64 of sheet metal. A plurality of rollers 66 are provided in tank 22 beneathfthe liquid surface for carrying the warp through the tank. Two pairs of diaphragm-actuated power driven pinch rolls 67, each including a fixed driven lower roll 67a and a vertically movable upper idler roll 67b controlled by diaphragm actuator 67e and additional idler rollers 68, are located in the air space above bleaching tank 22 (see FIG. 2A). The warp passes alternately over a roller66 in bleaching tank 22 and a roller 68 above the bleaching tank, so that the yarn has a plurality of passes in and out of the bleaching tank 22. The interior Wall '.70 of bleaching tank 22 is made of sheet metal and has'a plurality of upstanding ridges 71 between adjacent rollers 66. The wall 72 is disposed close to rollers 66 so as to minimize the volume of solution required in bleachingtank 22. The space between wall 70 and side wall 62 and bottom wall 64 constitutes a cooling water shell 74. Cooling water is introduced into shell 74 by inlet 76 and removed through cooling water outlet 78.

Bleaching tank 22 also includes a cylindrical .sleeve 80 defining a mixing chamber near one end of the tank. In the water inlet pipe 82 for the introduction of make-upY or process water, a second inlet pipe 84 for the introduction ofcaustic soda and sodium silicate solutions, and a third inlet pipe 86 for the introduction of hydrogen'peroxide solution, lead to the mixing chamber contained in sleeve 80. The caustic soda solution is conveyed ito` mixing chamber through suitable piping 88 from=castic soda tank 26, and sodium silicate solution is conveyed to mixing chamber 80 through piping 90 from sodium silicate tank 28. Piping 88 and 90 come together at mixing funnel 91 which feeds mixed caustic and silicate solutions into mixing chamber 80 through .pipe 84. For convenience, the caustic soda tank 26 and the sodium silicate tank28 may be included in a single housing 92 which includes an internal partition 94 separating tanks 26 and 28.'.H-ydrogen peroxide is introduced through piping 96 into inlet pipe 86 and thence into mixing chamber 80.

Bleaching tank 22 includes a recirculation system which comprises an outlet pipe 98 leading from tank 22 a`short distance below mixing chamber 80, a recirculation'pump 100, and a main 102 having a plurality of inlets Vy10411, 104b, 104e` and 104d leading to spaced points at the bottom of bleaching tank 22. Preferably these inlets lead into individual sections of the bleaching tank 22 whichV are separated by the convolutions in wall 72. Main 102 also serves as a drain when it is desired to empty the bleaching tank 22 of bleaching solution. Ordinarily during operation of bleaching tank 22, it is not necessary to remove' any liquid therefrom, since a substantial volume of liquid is carried out of bleaching tank 22 by the yarn. The makeup caustic soda, sodium silicate, hydrogen` peroxide and water introduced into mixing chamber 80 and thence into bleaching tank 22 make up for losses of liquid which are carried out by the yarn. According to a typical embodiment, the make-up water volume is 15 gallons per-ihour, and the volumes of caustic soda solution, sodium silicate solution, and hydrogen peroxide solution are 3"-gallons per hour, 4 gallons per hour, and 15 gallons per hour, respectively. The recirculation pump 100 in this same ernbodiment should be able to handle liquid volumes of l0 gallons lper minute. Of course, it is understood thatill of these figures are merely illustrative, and the size `of: the bleaching tank, which is determined by the size of theE apparatus as a whole, may be varied at will. f -1 The feed lines 88, and 96 for caustic, sodiumsilicate, and hydrogen peroxide, respectively, contain pumps 110, 112 and 114, respectively, which are driven by a gang drive from a single alternating Current motor 116; A

switch 118 is placed in AC line 120 leading to motor 116 so that pumps 110, 112 and 114 will ordinarily be shut down in the event that the driven rolls in mercerizer 13 are stopped. To this end, switch 118 is controlled by a solenoid 122. Energzation of solenoid 122 is controlled by lpower line 124 which includes a normally open relay 126 which is closed whenever the motor to the powerdriven rolls 46a in pinch rolls 46 are in use, and a manually operated override relay 128 for permitting energization of solenoid 122 when the power-driven rolls 46a are shut down. When the pinch rolls 46a are in operation, relay 126 is closed and relay 128 open, causing solenoid 122 to be energized. When these rolls are shut down, both relays 126 and 128 are open unless relay 128 is manually closed. In this way pumps 110, 112 and 114 are automatically shut down when the mercerizer pinch rolls are not in operation, unless relay 128 is manually closed in order to permit override operation.

The water supplied to pipe 82 is controlled by a diaphragm-operated valve 130 wherein control of the diaphragm is effected by an air supply 132 under pressure. This air supply is controlled by a solenoid valve 134 which is in parallel with solenoid 122 in power line 124. Thus, when pinch rolls 46 above the mercerizer 13 are in operation, Ipower line 124 is energized, valve 134 is opened, supplying air through line 132 to the diaphragm in valve 130 and thus causing valve 130 to be opening for the admission of process water. Likewise, process water is shut olf 4when driven rolls 46a are shut down.

The rate of cooling water supplied into shell 74 is controlled by a temperature controller 136 which is responsive to the temperature of solution in bleaching tank 22. Controller 136 operates a valve 138 in the cooling water supply line 140, leaving the cooling water inlet 76 in accordance with the bleaching tank solution temperature.

The structure of the second steam heating chamber 30 is best shown in FIG. 7. Steam heating chamber 30 is generally rectangular in shape, having housing side wal-ls 140 including access doors 142 in at least one of said walls for permitting access to the interior, a bottom wall 144, a -top wall 146, and an inlet chute 148 adjacent one end wall for the admission of the continuously traveling warp of yarn. Inlet chute 148 preferably extends below bottom wall 144 and includes a pair of rubber or plastic flaps 149 (see FIG. 9) and an idler roller 150 for directing the warp of yarn from a horizontal direction to an upward vertical direction. A plurality of plate heaters 149 having steam heating coils (not shown) and mounted on the inside walls of chamber 30 permit superheating of the steam therein. Steam heating chamber 30 includes a plurality of rolls for conveying the warp of yarn through the chamber. This plurality of rolls includes a plurality of driven rol-ls 152 arranged in a row adjacent the top wall 146, and a plurality of idler rolls 154 arranged in a second row adjacent bottom wall 144. The chamber 30 also includes an exit opening 156 for the warp of yar-n leaving chamber 30.

The speed of the yarn increases by a slight amount, usually about 0.5%, as it passes through chamber 30. Since the yarn must be maintained taut at all times in chamber 30 without slip between the yarn and driven rolls 152, it is necessary to drive rolls 152 at different speeds so that each roll travels at the same speed as that of the yarn passing thereover. To this end, a clutch drive mechanism 158, illustrated in FIG. 8, is provided.

Referring now to FIG. 8, roll 152 has a pair of shaft portions 160 and `162 progressively smaller diameter and integral and concentric with roll 1'52. Shaft 162 is driven by a chain drive mechanism (not shown) through sprocket 163 and sleeve 164 welded thereto and surrounding shaft 162. Bearing 166 is interposed between sleeve 164 and shaft 162. The clutch mechanism also includes a washer 168 having ange 170 thereon. Washer 168 is maintained in driving relationship with shaft 160 by means of dowel pin 172. A pair of axially displaced thrust washers 174 and 176 are disposed at either end of sleeve 164. Thrust washer 174 bears against washer 168 so as to transmit motion from sleeve 164 to washer 168 and thence to shaft 160. A retaining sleeve 178 is located axially outwardly from sleeve 164 and bea-rs against washer 176. Key 179 on shaft 162 and a mating keyway in sleeve 178 cause sleeve 178 and shaft 162 to rotate as a unit. A spring-pressed washer 184 holds the entire clutch drive mechanism 158 in place. Shaft 162 has a internally screwth-readed bore 180 at its outer end which receives externally screw-threaded bolt 182. The assembly includes washer 184 which is spring-pressed against retaining sleeve 178 by compression spring 186. -It will thus be apparent that roll 1'52, shafts 160 and 162, and retaining sleeve 178 all rotate as a unit, but that sleeve 164 may rotate at a different speed from the rest of the unit. This provides a friction drive transmitting power from sprocket 163 to roller 152, permitting shaft 162 to slip with respect to sleeve 164. The amount of slip between sleeve 164 and shaft 162 is controlled by turning screw 182. In this way the axial pressure between sleeve 164 and thrust washers 174 and 176 may be varied depending on the amount of slip desired.

Referring again to PIG. 2B, hot water wash tank 32 is partitioned by partition 187 to provide a pair of side-byside wash tanks 32a and 32b. Water is withdrawn from the bottom of tank 32a via conduit 188 near the end of tank 32a where warp 10 of yarn first enters the tank. This water is recirculated by pump 189 through heater 190 and header 191 to sprays 192 and 193, which direct hot water against the yarn 10 to wash the same.

A second recirculation pump 194 withdraws hot wash water Ifrom the bottoms of tanks 32a and 32b via conduit 196 an-d returns the water through conduit 198 and header 200 to sprays 202 and 204 which direct water against yarn 10. Water is also withdrawn from tank 32b through line 205 by reci-rculation pump 206 and returned through conduit 208 to spray 209 which directs hot water against warp 10 of yarn.

Fresh water supplied lthrough conduit 210 is heated in two-stage heater 212 by overow water from tank 32a, which is piped to heater 212 through pipeline 214. The hot water is further heated in a second two-stage heater 216 to about 190 F., and .then is piped to hot w-ater spray 218 which directs hot water against yarn 10. Spray 218 has an alternative hot water supply conduit 220.

-In addition to the aforedescribed recirculation systems, tanks 32a and 32b also have drain conduits 221 and 222 respectively.

Acid w-ash tank 34 has a recirculation system for washing the yarn with dilute aqueous acid. This system includes withdrawal conduit 224 leading from the bottom of tank 34, pump 226, re'tu-rn line 228 having heater 230 therein, and acid spray nozzle 232 at the end of return line 228 directing dilute acid against warp 10. Acid wash tank 34 also has a drain conduit 234.

Chemical treat-ment tank 36 for supplying bluing or other desired finishing chemical, is divided into two separate compartments 36a and 36b by partition 235. This tank has a trough 236 on one end partition 52 in compartment 36a for adding bluing or other finishing chemical. This chemical is mixed in trough 236 with solution from tank 36. The resulting solution is withdrawn from trough 236 by recirculating pump 238, which reintroduces the solution linto compartment 36b via line 240 after heating in heater 242. Drain conduits 244 and 246 lead from the bottom of compartments 36a and 36b respectively.

After finishing in tank 36, yarn 10 is withdrawn for drying.

Example 1 A warp of yarn is made up by bringing 378 ends of cotton yarn together after the yarns have been individually passed through a llame to remove lint and fuzz. The yarn ends are broughttogether in sidc-by-side parallel relationship with all of the yarn ends lying in a single phase. Eighteen warps made in this manner are continuously advanced in parallel side-by-side relationship through the sequence of steps illustrated in FIG. 1 of the drawing, using the apparatus shown in FIG. 2. The velocity of the yarn is 20 yards per minute throughout the process from the beginning until the yarn reaches steam heating chamber 30. The velocity increases to about 20.1 yards per minute in steam heating chamber 30, and remains at this level throughout the remainder of the process.

The sheet of yarn 10 is li-rst contacted with boiling water in boiling-out tank l1 toremove grease and impurities. The yarn is then cooled to about room temperature in cold water tank 12, and is then passed into mercerizing tank 13 containing an aqueous 23% caustic soda solution at room temperature. The yarn is then washed in caustic wash tank 14 containing an aqueous solution of 7% to 9% by weight of caustic soda. The pressure of rolls 46 through which the warp of yarn is passed after it leaves caustic wash tank 13 is set so that the yarn contains 3% by weight of caustic solution as it enters first steaming chamber 15. The yarn passes through steaming chamber l in a plurality of passes. Wet steam is continuously supplied to steaming chamber 15, and the temperature in that chamber is maintained at 190 F. to 200 F. The residence time of yarn in steaming chamber 14 is approximately one minute. The yarn is then passed through a second caustic wash solution in tank 20. This caustic wash solution also contains 1% by weight of caustic soda and is at a temperature of 140 F. to 180 F.

After caustic washing in tank 20, the yarn enters bleaching tank 22. The yam is contacted in bleaching tank 22 with a bleaching solution containing 4% by weight of hydrogen peroxide, 1% by weight of caustic soda, 2% by weight of sodium silicate (water glass, Na2O3.3SiO2), le ounce per gallon of epsom salts (magnesium sulfate), and l/z ounce per gallon of diethylenetriaminepentaacetic acid chelating agent (Versenex 80). The temperature in bleaching tank 22 is 120 F. Makeup solutions are continuously supplied to bleaching tank 22 from hydrogen peroxide storage tank 24 containing 50% aqueous hydrogen peroxide, caustic soda tank 26 containing 50% by weight of caustic soda, sodium silicate solution tank 28 containing 81% lby weight of sodium silicate (water glass) having the approximate formula Na2O-3.3SiO2, epsom salts make-up tank containingl pound of epsom salts per gallon of water, and chelating agent make-up tank containing 1 pint of Versenex 80 per gallon of water. The liow rates of these make-up solutions in gallons per hour are as follows:

The total amount of make-up solution is approximately equal to the amount of solution carried out by the yarn.

From bleaching tank 22 the yarn goes to second steaming chamber 30. Dry saturated steam is introduced into this chamber at 212 F. and 1 atmosphere, and the steam is superheated to about 218 F. by means of steam heaters within chamber 30. The speed of the yarn as it enters is 20 yards per minute. The yarn passes alternately up and down through a number of passes in chamber 30, and is kept under tension at all times. Due to the tension and the high temperature in chamber 30, the velocity increases by about 0.5% to 20.1yards-perminute at the exit. The yarn passes alternately over a driven roll 152 and an idler roll 154. The roll speed of driven rolls 152 progressively increases as the warp of yarn advances through chamber 30,

so that 'there is no slip between the yarn and any of the 10 rolls. The residencetime of yarn in chamber 30 is approximately 5 minutes.

The yarn upon leaving second steaming chamber 30 is washed with hot water at 190 F. in water wash tanks 32 and 32a, and then is contacted with dilute aqueous acetic acid at a temperature of about 140 F. to 160 F. in acid wash tank 34'.l After. acid washing, the yarn is contacted with a bluing agent in bluing tank 36, which is maintained at 160 F. From vbluing tank 36 the yarn passes through a drier. After drying, the yarn is taken up on a pallet.

Example 2 The process of Example 1 is repeated except that the concentration of hydrogen peroxide in bleaching tank 22 is 2V: The ow rate of hydrogen peroxide from storage tank 24 to bleaching tank 22 is about 9.5 gallons per hour.

While one embodiment of the invention has been shown and described herein it is to be understood that changes and additions may be made by those skilled in the art without departing from the scope and spirit of the invention.

I claim:

l. A process for rapid bleaching of cotton yarn which comprises the steps of forming a warp of yarn, contacting said warp with an aqueous caustic alkaline solution, steaming the causticized yarn, contacting said yarn with a bleaching agent in an alkaline medium, steaming the yarn with bleaching agent adhering thereto, and neutralizing the excess alkali adhering to said yarn with dilute aqueous acid.

2. A process for continuously mercerizing and bleaching cotton yarn which comprises the steps of forming a warp of yarn ends, and, while said warp is continuously advancing, contacting said warp with an aqueoust caustic alkaline solution, steaming said warp, contacting said warp with an aqueous alkaline solution of a lbleaching agent, steaming the warp with ble-aching agent adhering thereto, and neutralizing the alkali adhering to said yarn with dilute aqueous acid.

3. A process for continuously mercerizing and bleaching cotton yarn which comprises the steps of forming a Warp of yarn ends, and, while said warp is continuously advancing, boiling out the warp to remove foreign inatter, contacting said warp with an aqueous caustic alkaline solution, steaming said warp, washing the warp in aqueous caustic alkali, contacting said warp with an aqueous alkaline solution of a bleaching agent, steaming the warp lwith bleaching agent adhering thereto, and neutralizing the alkali adhering to said yarn with dilute aqueous acid.`

4. A process according to claim 3 wherein the first-mentioned steaming is carried out at a temperature of about 180 to 212 F. l

5. A process according to claim 3 wherein the second mentioned steaming is carried out at a temperature of g about 212 F.

6. A process according to claim 3 wherein the bleaching agent is hydrogen peroxide.

7. The process according to claim 6 wherein theaqueous alkaline solution of hydrogen peroxide also contains sodium silicate. 'p

8. A process according to claim 7 wherein the temperature of said aqueous alkaline solution of hydrogen peroxide is about to about 120 F.

9. A process according to claim 7 wherein the temperature of said aqueous alkaline solution of hydrogen peroxide is about 110 to about 160 F.

10. In a process for mercerization and bleaching of cotton yarn wherein a warp of said yarn is contacted with an aqueous caustic solution, the improvement comprising the Asteps of,

(a) steaming said warp at a temperature below the boiling point of water subsequent to contacting of said yarn with said caustic solution,

(b) contacting said warp with a Ibleaching agent while alkali adheres to the yarn, f'

(c) steaming the warp after contact with said bleaching 1l 12 -agent at a temperature not less than the boiling References Cited P011 0f Water ald UNITED STATES PATENTS (d) washing the warp with acid to remove alkali adhering to said warp. 11. The process of claim 3, wherein said warp ad- 5 vances at a substantially uniform velocity.

12. The process of claim 10, in which the warp is passed LEON D' ROSDOL Primary Exammer' through each of said steps at a substantially uniform M. WEINBLA'IT, Assistant Examiner. velocity.

1,630,786 5/1927 Conrad 8-101 3,280,039 10/ 1966 Smolens 252-103 X UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3,370,911 February 27, 1968 Thomas E. Westall ppears in the above numbered pat- It is hereby certified that error a aid Letters Patent should read as ent requiring correction and that the s corrected below.

l Column 7, line 27, for "opening" read opened column 9 line 3, for "phase" read plane Signed and sealed this 6th day of May 1969.

(SEAL) Attest: Edward M. Fletcher, Jr. W2(

Attesting Officer d Commissioner of Patents

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