CS241455B2 - Method of fabric strip mercerizing containing cellulose by means of liquid ammonia and equipment for performance of this method - Google Patents

Abstract

To achieve the desired processing results cellulose fabrics with no ammonia their shrinkage increases and decreases according to the invention, the length of the fabric path the belt in the ammonia zone depending on on changes in the web tension. The device according to the invention comprises a tank (23) for ammonia and coated roller (62), between which are a series of fixed rollers (54, 55) and movable rollers (56, 57), and a voltage controller (16). The voltage controller (16) contains a flexible constraining member (79) that is connected with the web (11) and compressed and stretched by the tension of this fabric belt (11), and with lever (L), controlling the lowering and lifting of the movable rollers (56, 57) in the opposite direction to change the tension of the web (11).

Description

In order to achieve the desired results of treating the cellulosic webs with ammonia without much shrinkage, according to the invention, the length of the web of the web in the ammonia zone increases and decreases depending on the variations in the web tension.

The apparatus according to the invention comprises an ammonia tank (23) and a coated roller (62), including a series of fixed rollers (54, 55) and movable rollers (56, 57), and a voltage controller (16). The tension controller (16) comprises a yielding limiting member (79) which is coupled to the fabric belt (11) and compressed and expanded by the tension of the fabric belt (11), and the lever (L) controlling lowering and lifting of the movable rollers. 56, 57) in the opposite direction to change the tension of the fabric web (11).

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The present invention relates to a process for mercerizing a web of cellulose-containing fabric with liquid ammonia for 0.6 to 0.9 seconds without causing substantial shrinkage, wherein the web of cellulose-containing fabric is continuously passed through a processing zone to treat liquid ammonia and remove unreacted liquid ammonia. in which zone the fabric belt is exposed to liquid ammonia to which the cellulosic content of said fabric belt reacts and the unreacted liquid ammonia is removed from the fabric belt.

The invention further relates to an apparatus for carrying out the method, comprising a chamber in which the fabric web is exposed to liquid ammonia for a limited period of time, and wherein a liquid ammonia tank is provided for impregnating the fabric web; ammonia from said fabric belt and a device for defining the path of the fabric belt through the ammonia removal device.

Many fabrics are commonly exposed to aqueous sodium hydroxide solutions to mercerize their fibers. The fibers thus swell and the existing ones become more porous and accessible, thus increasing affinity for dyes, flame retardants, resins, etc. However, sodium hydroxide solutions break down many fibers, so they need to be impregnated with a less active substance that can achieve good mercerization results without fiber degradation. Alkaline merceration also results in the need for thorough scrubbing to remove the base, and this scrubbing has proven to be a disadvantage. For various reasons, furthermore, for basic merceration or materials for workwear, it is also desirable. Imines ammonia has been used to pre-wash my fibers and has also been used (as described in U.S. Patent Nos. 4,511,591 and 3,347,963) to provide more compliant cellulosic fibers for shaping. US Pat. No. 1,963,572 and US Pat. No. 1,998,551, however, did not achieve favorable results According to US Pat. No. 3,560,140, the yarns and yarns were treated with liquid ammonia and then stretched to increase their strength.

For cellulose fabrics treated with liquid ammonia according to U.S. Pat. No. 3,406,006, there was excessive shrinkage of fabrics.

According to US Pat. No. 3,664,158, fabrics were treated with liquid ammonia and subjected to transverse stress shrinkage. However, this attempt to limit the shrinkage of fabrics during treatment with liquid ammonia has been unsuccessful. Inducing and controlling such tensions has proven impractical, especially when processing knitted goods. Also for woven goods, the stresses required to limit shrinkage to 2% were not fully feasible and the problem was further complicated by seams in fabrics. It has been difficult to maintain fabric widths, both for shrinkage by liquid ammonia and because warp tension increases the width loss. In the processes used hitherto, stretching has proved unsatisfactory to reduce shrinkage in the treatment of cellulosic fabrics with liquid ammonia.

The consequence of this is that although liquid ammonia has been shown to be suitable for mercerizing cellulosic fabrics (especially fabrics for work clothes and corduroy suits), liquid ammonia mercerization until the present invention has not found true industrial use.

According to MS. U.S. Pat. No. 152,359, it has been found that upon contact of cellulose fibers with liquid ammonia, the fibers initially swell radially and become porous without substantial shrinkage, and soon thereafter the fibers begin to shrink longitudinally.

According to this patent, the fabrics are immersed in liquid ammonia and then liquid ammonia is quickly removed from the fabrics (from about 0.6 to 9.0 seconds and preferably within 1.8 seconds at 3.6 seconds) before the fibers of the fabrics. they have the opportunity to shrink in any significant way.

According to this publication and all other publications mentioned above, the length of the belt path and the speed of the belt are determined empirically before starting the actual processing.

However, it has been found that during the treatment with ammonia, the fabric web, by reaction with liquid ammonia, slightly increases or decreases its tension towards the length of the web. In the event that variations are not accurately detected and no adjustment is made, the belt may be over-treated or under-chemically treated.

The purpose of the invention is to control the shrinkage (especially of knitted articles) in liquid ammonia merceration, to provide a device of the above type comprising means for controlling the speed of the fabric and controlling the length of the fabric path between the liquid ammonia impregnation and the start of ammonia removal. voltage, so that mechanical requirements for equipment are simplified, and reducing voltage to a minimum also reduces equipment requirements.

Another object of the present invention is to use a device of the proposed type with a small volume for fabric processing, so that the necessary start and stop periods are kept to a minimum length and to create a device of the proposed type which is economical in both assembly and operation and otherwise well suited for its supposed function.

The device is designed for processing of cellulose fabrics on an industrial scale. In order to be able to carry out this treatment, it is necessary for the device to be able to process large quantities of fabrics with consistent and uniform results in a safe manner. Furthermore, it is important that the machine is able to process a wide range of fabrics, light and heavy, low and high cellulose, sparse or knitted, densely woven or knitted, and the like.

The method according to the invention consists in increasing and decreasing the path length of the fabric belt in the ammonia treatment zone as a function of variations in the tension of the fabric belt. '

In order to carry out the method according to the invention, the apparatus of the type mentioned above is adapted so that, between the ammonia tank and the coated roll, the web of travel comprises a series of fixed rollers and rollers which are movable relative to the fixed rollers.

The invention achieves the new and higher effect that the web of fabric is reproducibly treated chemically in exactly the desired manner regardless of its condition prior to processing.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is explained in more detail with reference to the accompanying drawings, in which FIG. 1 is a vertical section through an apparatus for carrying out mercerization of cellulosic fabrics with liquid ammonia; FIG. 2 is a plan view of the apparatus of FIG. Fig. 4 shows the relationship between the shrinkage and the time of liquid ammonia exposure in the warp direction at different stresses for the cotton fabric; Fig. 5 shows the relationship between the shrinkage and the time exposure of liquid ammonia in the weft direction at Fig. 6 shows the dependence of the color number on the exposure time of liquid ammonia for the cotton fabric.

When the cellulose fiber is immersed in liquid ammonia, the cellulose swells similarly as when the cellulose fiber is immersed in an aqueous solution of sodium hydroxide to achieve mercerization. The typical bobble shape of the cellulosic fiber becomes more cylindrical and the walls of the fiber become thicker. In this state, the fiber is more accessible to dyes, flame retardants, resins, and the like.

If the cellulose fibers are spun into yarns and these yarns are woven into fabrics, and these are then immersed in liquid ammonia, there will be considerable shrinkage in the longitudinal direction. For most industrial fabrics, shrinkage is asymmetrical and greater shrinkage occurs in the warp direction than in the weft direction. Giant. 4 shows a warp shrinkage diagram as a function of the time of exposure to liquid ammonia at various stresses to which the warp is exposed in the case of a cotton fabric. The load curves, 4.52 kp to 0.452 kp were determined empirically and corresponding to stresses of 178 kPa to 17.8 kPa.

The top curve is an extrapolated shrinkage estimate that would occur without load. The reason why the no-load curve was not determined experimentally is that when the unstretched fabric is inserted into liquid ammonia, it wrinkles strongly and is therefore extremely difficult to determine its shrinkage. It can be concluded from FIG. 4 that shrinkage can be reduced by stretching the fabric. A similar effect is seen in FIG. 5, graphically depicting the shrinkage as a function of liquid ammonia exposure time for various weft stresses. Obviously, the shrinkage in the weft direction is much less sensitive to the stress and duration of exposure to liquid ammonia than in the warp direction, which is advantageous since tensioning in the weft direction is difficult. It should be noted, however, that in general the curves of Figs. 4 and 5 are of a similar nature, indicating that similar means of shrinkage control can be used in the weft direction.

Exposing the cellulose fabric to liquid ammonia can result in undesirable shrinkage, but also produces mercerizing effects. The result of fiber swelling during mercerization is an increase in cellulose accessibility by becoming more porous and therefore more reactive. The practical benefit of this increased accessibility is greater dye affinity, increased affinity for resins, and the like, which (along with other similarly obtained benefits) are commonly associated with mercerization in aqueous sodium hydroxide solution.

The test for determining the degree of merceration is based on the fact that the mercerized cotton absorbs more barium hydroxide than the unmerged, so that barium hydroxide can be used to quantify the degree of merceration. When using this assay, it is important that no other barium ion-absorbing materials, such as finishes or other fibers, are present. Carefully washed and cleaned samples of the mercerized fiber (and the unmerged control element) were immersed for 2 hours in a 10 ml 0.25 N barium hydroxide bath at 21 ° C. 10 ml of each solution is then titrated with 0.1 N hydrochloric acid. The mercerized fiber sample absorbs more barium hydroxide than the control sample. The amount of barium hydroxide remaining in the solution will be lower and therefore the amount of hydrochloric acid required for neutralization will be lower. The amount of hydrochloric acid required for neutralization becomes a quantitative measure of the barium absorbed. The ratio of barium hydroxide absorbed by the cerium sample to the amount absorbed by the unmercerated sample, multiplied by 100, gives a bar number. Values from 100 to 105 indicate that the material was not mercerized. A number above 150 indicates essentially complete merceration. Intermediate values usually indicate incomplete reaction or poor mercerization bath.

Typically, the mercerized samples should have a barium number of 150 to 160 so that they can be considered correctly mercerized. FIG. 6 is a graphical representation of the sum of barium numbers obtained from materials exposed to liquid ammonia for various times as a closed curve. Assuming that a representative curve of the respective data lies in the center of the envelope curve, the middle dashed curve between coordinates represents an approximation for 0 to 30 seconds.

Since the tests were carried out on samples of cotton fabric that are extremely large in comparison to their yarn size, the loose samples indeed show average activity for all of their yarns and hence for the fibers in these samples.

When comparing cotton fibers exposed to liquid ammonia with non-exposed control fibers, there is a marked difference in degree of swelling (merceration effect). This indicator, together with the steep slope of the barium numbers curve in relation to the liquid ammonia exposure time in Fig. 6, led to a conclusion that was then empirically proven that satisfactory merceration can be achieved without undesirable shrinkage, assuming the liquid ammonia exposure time on the cellulosic fabric. sufficiently shortened.

1, 2 and 3 show the most preferred arrangement of the apparatus for carrying out the method according to the invention.

The cellulosic fabric web 11 is continuously moved by the liquid ammonia treatment chamber 12 in which the immersion trough 13, the bending roller 14, the pair of pressure rollers 15, the voltage regulator 16, the delay roller assembly 17, and the dryer 18 are located. a seal 19 around the cylinder 21 and below the insertion cylinder 22 into the tank 23 for liquid ammonia in the trough 13. In the trough 13, near its upper edge, a float 24 is connected via an arm 25 to a switch 26. The switch 26 is connected to a solenoid 27 which controls The valve 29 feeds the immersion chute 13 through the conduit 31 passing through the housing 32 that surrounds the chamber 12 in the conduit 29. In normal operation, the manual valve 33 is opened and another manual valve 34 is closed. Upon closing, the valve 33 in line 29 is closed and the valve 34 in line 31 is open. If the ammonia in the trough 13 is to be replaced quickly, the contents of the trough 13 can be quickly emptied through the valve 35 on the pipe 36 into a cup 37 which is provided with a heating coil 38 to vaporize ammonia from the tray 37 and the vent pipe 41. to a suitable incineration or recovery plant (not shown). The immersion chute 13 can be raised or lowered (as indicated by dashed lines in FIG. 1) to control the dipping of the fabric web 11 into the combustion ammonia tank 23.

In order to prevent the ammonia from escaping outwards, it is desirable to maintain a slight vacuum in the chamber 12. For this purpose, the vent pipe 41 is connected to a suitable suction device (not shown). The housing 32 is sheathed with insulating material 42 interposed between the inner lining 43 and the outer lining 44. The inlet seal 19 and the outlet seal 45 each comprise pairs of members, each pair comprising a resilient member 46 and an opposing rigid member 47. In both seals 19 and 45 the fabric web 11 is inserted between the resilient member 46 and the fixed member 47 of each pair, and the spaces between the two pairs are evacuated by conduits 48 and 49.

After soaking in liquid ammonia in the dip trough 13, the web 11 is conveyed to a bending roll 14 which expands and smoothes the web 11 before passing between the pressure rollers 15. Excess liquid ammonia removed from the web 11 (by the operation of the pressure rollers anyway) as well as the operation of the bending roll 14) is trapped by the downflow trough 52 into the immersion trough 13. From the press rolls 15, the fabric web 11 is conveyed to the roll 53 and then through a series of rollers including fixed rolls 54 and 55 alternated with movable rolls 56 and 57. This row of rollers forms a delay system 17. The movable rollers 56 and 57 move vertically, as discussed in more detail below, to control the length of the path of the fabric belt 11 between the time it is impregnated in the immersion trough 13 and the time when liquid ammonia removal begins. drying the fabric web 11. Delays In the assembly 17, the fabric web 11 is conveyed through the roller 59 to the heated coated dryer 18, being guided on the tread 61 around the coated roller 62. The tread 61 is endless and circulated by the rollers 63 around the heated drum S4. The fabric web 11 exits the dryer 18 through the discharge rollers 65 and exits through the outlet seal 45 from the chamber 12. Water spraying and re-drying can then also be carried out to remove any residual ammonia remaining in the fabric.

Giant. 3 shows the connection between the movable rollers 56 and 57 and the voltage controller 16. The movable rollers 56 and 57 are rotatably mounted between a pair of vertically movable support members 66, only one of which can be seen in FIG. 3. In a sleeve 68 secured to the rear of the support member 66, a villa shaft 67 is screwed in, rotating the shaft 67 in one direction causes downward movement of the support member 66 causing shortening of the tread pattern 11 and decreasing its tension, while rotation of the shaft 87 in the opposite direction causes upward movement of the support member 66 so the path of the fabric web 11 is extended and its tension is increased. A bevel gear 69 is attached to one end of the shaft 67 and engages with a bevel gear 71. The gear 71 is connected to the output motor shaft 72 of the reciprocating motor M. The motor M is of a well known design and is of the type in which it is the direction of rotation of the motor is determined by the direction of current flow through the armature or field winding.

Between the motor M and the voltage regulator 1S, switching members are provided for starting the motor M and controlling the direction of rotation of the motor M and depending on the degree of tension of the fabric belt 11 so that the movable rollers 56 and 57 are raised or lowered automatically and maintain this tension within the prescribed range. The switching members comprise a two-pole two-way switch having a pair of fixed contacts 73 and 74 connected to one motor terminal M and a pair of fixed contacts 75 and 76 connected to the other motor terminal M. A movable contact 77 is movably mounted between contacts 73 and 75. as well as between the contacts 74 and 76, a movable contact 78 is movably mounted to make electrical contact with said fixed contacts.

The movable contact 77 is connected to the positive voltage source and the movable contact 78 is connected to the negative voltage source by a pair of rigid conductive bars. The conductive bars are rotatably mounted to allow the movable contacts 77 and 78 to pivot into contact with the fixed contacts. The lever L pivotally connects the conductive rods to each other and is connected to the bearing housing of the voltage controller 16 at its center. In such a design, variations in tension in the fabric web 11 result in compression or expansion of the yielding limiting member 79 accompanied by a corresponding downward movement of the bearing housing; up. If the tension of the fabric belt 11 exceeds a certain value, the yielding limiting member 79 is sufficiently compressed causing the lever L to move and move the movable contacts 77 and 78 downwardly in contact with the fixed contacts 75 and 74, thereby turning the motor M on. -a induces a current flow in the direction of arrow 1i, causing the motor M to rotate in a direction causing lowering of the carrier member 66. Lowering of the carrier member 66 causes lowering of the movable rollers 56 and 57, thereby correspondingly reducing the tension of the fabric web 11, and this continues until the voltage drops to a prescribed range, the limiting member 79 opening enough to cause the movable contacts 77 and 78 to be disengaged from the fixed contacts 75 and 74, and the motor M is then switched off.

A similar event occurs when the tension of the web 11 drops below a certain amount, except that in this case the limiting member 79 expands, causing upward movement of the movable contacts 77 and 78 into respective contact with the fixed contacts 73 and 76, thereby The motor M turns on and generates a current flow in the direction of the arrow i2, causing the motor M to rotate in the other direction, thereby raising the movable rollers 56 and 57 to increase the tension of the fabric web accordingly.

The speed of the fabric web 11 may be suitably controlled by controlling the speed of the dryer 18 or preferably the pressure rollers 15.

The mixture of ammonia gas and air in the chamber 12 during normal operation contains above 90% by volume of ammonia. The 90% by volume ammonia gas lies well above the explosive or flammable limits of the ammonia gas / air mixture. When the device is started, the chamber 12 is filled with air and much of this air must be removed or removed from the chamber 12 and replaced with ammonia gas. Conversely, when the device is stopped, ammonia must be removed from chamber 12. Since air-ammonia gas mixtures in a zone in which ammonia gas accounts for about 15-25% of the volume of the mixture, they are explosive (when sufficient heat is supplied to the mixture or if the mixture is ignited) care should be taken to minimize the risk to this species.

It will be apparent to those skilled in the art of fabric processing that the preferred embodiment of the invention can be varied within wide limits without departing from the spirit of the invention as defined by the present invention. For example, other methods of supplying ammonia (such as by spraying), other types of dryers, and other systems (for speed control and tension adjustment) may be used.

Figure 4 shows the relationship between liquid ammonia exposure time and warp shrinkage at different stresses for the cotton fabric, the upper curve representing the stress-free state and the following curves representing the stress of 17.8 kP-a, 45.6 kPa, 0 kPa, 134.6 kPa and 178 kPa. The vertical axis shows the percentage of shrinkage and the horizontal axis the time in seconds.

Giant. 5 shows a similar dependence in the weft direction, with the upper curve expressing the stress at 40.5 kPa and the curves following 35.6 kPa and 99.0 kPa.

Giant. 6 shows the relationship between the time of liquid ammonia exposure and the barium number for 100% cotton fabric, where the vertical axis shows the barium number and the horizontal axis the time in seconds. The range between 150 and 160 for the barium number represents the area acceptable for merceration.

Claims (6)

SUBJECT CLAIMS 1. A method of mercerizing a web of cellulose-containing fabric with liquid ammonia for a period of from 0.6 to 0.9 seconds without inducing a substantial amount of ammonia. shrinking, wherein a cellulose-containing web of tissue is continuously passed through a processing zone for treating liquid ammonia and removing unreacted liquid ammonia from the web, and characterized in that the shrinkage of the web is controlled by decreasing and increasing its path in the ammonia environment - on the belt tension. 2. The method of claim 1, wherein the path of the web is sinusoidal. 3. Apparatus for carrying out the method of item 1, comprising an impregnation chamber in which a liquid ammonia tank is provided, a heated cylinder with a coating to remove unreacted ammonia from the fabric belt, and a device for defining the fabric belt path of the tanks with the ammonia removal device. characterized in that, between the ammonia tank (23) and the coated cylinder (62), the track comprises a series of fixed cylinders (54, 55) and cylinders (56, 57) which are vertically movable relative to the rigid cylinders (54, 55) and coupled to the belt tension controller (16) for feedback. Device according to claim 3, characterized in that the movable rollers (58, 57) are rotatably mounted between a pair of vertically movable carrier members (66) rotatably mounted on a threaded shaft (67) connected to a gear (69, 71). connected to the shaft (72) of the gate motor (M), between which and the voltage controller (16) there is a two-pole two-way switch with a pair of fixed contacts (73, 74j) connected to one motor terminal (M) 76, connected to the second motor terminal (M), the fixed contacts (73, 74, 75, 76) being connected to the motor terminals (Mj by movable contacts (77, 78) connected to each other by a lever (L) connected to the bearing the tension controller housing (16) of the fabric belt (11). Device according to Claims 2 and 3, characterized in that the voltage regulator (16) comprises a yielding limiting member (79j) which is connected to the fabric web (11) and compressed and expanded by the tension of the fabric web (11), and one with a lever (Lj, controlling lowering and lifting of the movable rollers (56, 57) in the opposite direction to the grain tension of the fabric web (11). Device according to Claims 3 to 5, characterized in that the tension controller (16) is positioned with respect to the direction of travel of the web (11) in front of the fixed rollers (54, 55) and the movable rollers (56, 57).