Title of Invention

CRIMPED ACRYLIC FIBER TOW SQUEEZING APPARATUS

Abstract

57) Abstract:- A crimped acrylic fiber tow squeezing method and apparatus with which it is possible to obtain a low and stable moisture regain after squeezing and at the same time stable control of the level of the surface of a liquid in a bath in which the tow is immersed is possible. The invention provides a crimped acrylic fiber tow squeezing method wherein a crimped acrylic fiber tow is immersed in a liquid in a bath and then removed therefrom and squeezed by squeezing rollers disposed in two stages in the direction of advance of the tow and the ratio of stretching between the squeezing rollers is made between 1.00 and 1.0 and a crimped acrylic fiber tow squeezing apparatus comprising a bath for immersing a crimped acrylic fiber tow, squeezing rollers disposed in two stages for squeezing the fiber tow, means for transporting the fiber tow so that the fiber tow is immersed in the bath and then removed from the bath and squeezed by the squeezing rollers, and means for controlling the ratio of stretching between the squeezing rollers in a range between 1.00 and 1.10. PRICE: THIRTY RUPEES

Full Text

Title of the Invention CRIMPED ACRYLIUC FIBER TOW SQUEEING METHOD AND APPARATUS Background of the Invention This invention relates to a method and apparatus for squeezing a crimped acrylic fiber tow, and more particularly to a method and apparatus for squeezing a crimped acrylic fiber tow with which it is possible to obtain a low and stable moisture regain after squeezing and at the same time stable control of the level of the surface of a liquid in a bath in which the tow is immersed is possible. Acrylic fiber tow is crimped in order to put through a spinning process and to get the bulkiness of the fiber. This crimping is carried out by suitably heating and wetting the acrylic fiber tow by immersing it in hot water at 7 0 to 90°C or blowing steam directly, nipping it between two metal rollers and buckling it without damaging the fiber by pushing it into a rectangular stuffing box. The crimped acrylic fiber tow is first thermally set in a steaming vessel in saturated steam at 110 to 140°C and then goes through a rinsing process and/or a process for applying a finishing liquid for spinning, passes through a squeezing process and is dried to form a finished product. In the crimped acrylic fiber tow squeezing process, it" is desirable that the fiber tow be squeezed so that the crimp may be held at a value within product standards when the product is finished and that at the same time the moisture regain of the squeezed tow be made as low as possible and stable to accomplish a decrease in variation and a reduction of the load to be dried. This also as a result reduces the degree of liquid level variability in baths in which the tow is immersed and also enables the production line to be run with liquid surface levels stable. For the above-mentioned acrylic fiber tow squeezing process, for example [1] methods wherein squeezing is carried out in one stage (see Fig. 1 (a), (b)) and [2] methods wherein squeezing is carried out in two stages (see Fig. 2 (a), (b)) have conventionally been employed. However, with a one-stage squeezing method there has been the problem that even when the press load of an upper pressing roller is made high in order to satisfactorily reduce the moisture regain of the crimped tow not only is there a limit to how far the moisture regain can be reduced but also equipment trouble such as damage to the filaments of the tow and flaking of the roller rubber and cracking of welded parts of the roller occurs. Also, with a two-stage squeezing method, although the moisture regain can be reduced slightly further than with a one-stage squeezing method, even by taking measures such as increasing the press loads of upper pressing rollers in a range within which this will not damage the tow and changing the shapes of the pressing rollers it has still not been possible to stabilize the moisture regain at a low level. Also, in the tow squeezing methods which have been conventionally employed, because the temperature of the liquid in the bath in which the tow is immersed before being squeezed is not controlled at all, there has been the problem that the moisture regain changes during the time taken from the start of production for the temperature of the liquid in the bath to reach equilibrium at the temperature of the tow and furthermore when a finishing liquid is applied the adhesion rate of the finishing liquid fluctuates. Summary of the invention This invention was deviSed to solve such problems associated with the conventional technology, and an object of the invention is to provide a crimped acrylic fiber tow squeezing method and apparatus with which it is possible to obtain a low and stable moisture regain after squeezing and i with which stable control of the level of the surface of a liquid in a bath in which the tow is immersed is possible. The present inventors arrilved at the completion of this invention as a result of assiduous research into a method and apparatus for squeezing a crimped acrylic fiber tow using squeezing rollers disposed in two stages to achieve the above-mentioned object. That is, a squeezing method according to the invention is characterized in that a crimped acrylic fiber tow is immersed in a liquid in a bath and then removed therefrom and squeezed by squeezing rollers disposed in two stages in the direction of advance of the tow and the ratio of stretching between the squeezing rollers is made between 1.00 and 1.10. A squeezing method according to another aspect of the invention is characterized in that a crimped acrylic fiber tow is wetted and then squeezed by squeezing rollers disposed in two stages in the direction of advance of the tow (first squeezing process) and then immersed in a bath filled with a finishing liquid and removed therefrom and squeezed by squeezing rollers disposed in two stages in the direction of advance of the tow (second squeezing process) and in the first squeezing process and the second squeezing process the ratio of stretching between the squeezing rollers is between 1.00 and 1.10. A squeezing apparatus according to the invention comprises a bath for immersing a crimped acrylic fiber tow, squeezing rollers disposed in two stages for squeezing the fiber tow, means for transporting the fiber tow so that the fiber tow is immersed in the bath and then removed from the bath and squeezed by the squeezing rollers, and means for controlling the ratio of stretching between the squeezing rollers in the range between 1.00 and 1.10. A squeezing apparatus according to another aspect of the invention comprises means for wetting a crimped acrylic fiber tow, squeezing rollers disposed in two stages for squeezing the wetted fiber tow, a finishing liquid bath for immersing the fiber tow in, squeezing rollers disposed in two stages for squeezing the immersed and removed fiber tow, means for transporting the fiber tow so that the fiber tow is wetted and then squeezed by the squeezing rollers and then immersed in the finishing liquid bath and then removed therefrom and squeezed by the squeezing rollers, and means for controlling the ratio of stretching between the squeezing rollers in the range between 1.00 and 1.10. Here, the ratio of stretching between the squeezing rollers is defined as follows: ratio of stretching = (speed of the second stage squeezing rollers)/(speed of the first stage squeezing rollers) In the invention, the ratio of stretching between the squeezing rollers disposed in two stages is as described above controlled in the range between 1.00 and 1.10. When the ratio of stretching is not controlled at all (ratio of stretching = 1.00) the drop in the moisture regain after squeezing is small, and when on the other hand the ratio of stretching is greater than 1.10 although the moisture regain can be made small the crimp is stretched and there is a likelihood of the product falling outside product standards. Considering moisture regain after squeezing and degree of decrimping and the like the optimum ratio of stretching in this invention is 1.04. In the invention, it is preferable that the temperature of the liquid in the bath be controlled to below 50°C. This is because when the liquid temperature exceeds 50°C there is a possibility that the product will fall outside the product standards. For example when the ratio of stretching between the squeezing rollers is 1.04, the optimum temperature of the liquid in the bath is 35°C. When the temperature of the liquid in the bath is higher than this the crimped fiber is stretched and when it is lower than this the fall in moisture regain after squeezing shows a tendency to become smaller. Accordingly, considering the ratio of stretching, the moisture regain after squeezing and the degree of decrimping and the like it is preferable that the bath liquid temperature be set to an optimum value below 50°C. When a crimped acrylic fiber tow is applied to an apparatus constructed as described: above, because the ratio of stretching between the squeezing rollers disposed in two stages is controlled to a value greater than 1.00, even though the filaments have the crimp they are stretched and gaps i between the filaments become few and during squeezing liquid easily leaves the inside of the tiow to the outside. As a result, it is possible to achieve a fall in moisture regain without raising the press loads of the upper squeezing rollers. Also, because the ratio of stretching between the squeezing rollers is controlled to a value below 1.10, there is no danger of the crimp is being excessively stretched and it not being possible to maintain a value within the product standards. Also, because the liquid temperature in the bath in which the tow is immersed to apply water or a finishing liquid thereto is controlled to a constant value below 50°C, the crimp is not stretched by a high temperature to outside the product standards and furthermore because the temperature in the bath can from the start of production be set to a state of substantial equilibrium with the temperature of the tow during production line running there is little fluctuation in the moisture regain after squeezing. Brief Description of the Prawinqs Figs. 1 (a) and (b) are views showing conventional one-stage squeezing apparatuses; Figs. 2 (a) and (b) are views showing conventional two-stage squeezing apparatuses; Fig. 3 is a view showing a perferred embodiment of a squeezing apparatus according to the invention; Figs. 4 (a) to (c) are views showing examples of configurations of squeezing rollers in a squeezing apparatus of the invention; Figs. 5 (a) and (b) are views illustrating a method of controlling a ratio of stretching in a squeezing apparatus of the invention; and Figs. 6 (a) and (b) are views showing another preferred embodiment of a squeezing apparatus according to the invention. Detailed Description of the Preferred Embodiments The crimped acrylic fiber tow squeezing method and apparatus of the invention will now be described using preferred embodiments thereof; however, the invention is not limited to these preferred embodiments. A preferred embodiment of a squeezing apparatus according to the invention is shown in Fig. 3. In the apparatus shown in Fig. 3, a crimped acrylic fiber tow 1 passes around rollers 2 and 3a into a liquid in a bath, passes around a roller 3b and out of the liquid in the bath and is then squeezed by first stage squeezing rollers 4a, 4b and second stage squeezing rollers 5a, 5b; this movement of the tow is effected by a first stage driving squeezing roller 4b and a second stage driving squeezing roller 5b. As the method by which the tow is immersed in the liquid in the bath, besides using the two rollers 3a and 3b it is also possible to employ a method wherein the tow is immersed in the bath by one roller 3c as shown with a broken line in Fig. 3. The liquid in the bath is usually rinsing water or a finishing liquid for spinning; the level of the liquid is high enough if the whole surface of the tow is immersed, and normally is slightly below the centers of the rollers 3a, 3b (for example the level 7 of Fig. 3). In this invention it is preferable that the temperature of the liquid in the bath be controlled to a constant value below 50°C, and as the method for doing this for example a method wherein a tubular heat exchanger mounted inside the bath or a heat exchanger provided outside the bath is used to keep the temperature of the liquid supplied to the bath constant is employed. However, in this case, it is necessary for both heating and cooling control to be possible. In the apparatus shown in Fig. 3 the upper rollers 4a and 5a of the first stage squeezing rollers and the second stage squeezing rollers move up and down and exert loads on the respective lower rollers 4b and 5b to squeeze the tow; liquid squeezed out of the tow by the first stage squeezing rollers 4a, 4b and the second stage squeezing rollers 5a, 5b drops back into the bath 6. In this invention the ration of stretching between the first stage squeezing rollers 4a, 4b and the second stage squeezing rollers 5a, 5b is controlled to the range between 1.00 and 1.10, and as the method for doing this for example methods shown in Figs. 5 (a) and (b) can be employed. In the method shown in Fig. 5(a) the first stage squeezing rollers are driven by one motor, a driving force is transmitted from this motor to the second stage squeezing rollers by a shaft and a gearbox and by suitably varying the gear ratio and adjusting the speeds of the first and second stage squeezing rollers a desired ratio of stretching can be obtained. In this case the adjustment of the difference in speed between the squeezing rollers can be achieved using a continuously variable transmission function provided in the gearbox. In the method shown in Fig. 5(b), the first stage squeezing rollers and the second stage squeezing rollers are each driven by a different motor and a desired ratio of stretching is obtained by the speeds of the first and second stage squeezing rollers being adjusted by means of inverters connected to the motors. In the invention there are no restrictions on the shapes, dimensions or configurations of the squeezing rollers as long as they can squeeze a tow with two stages of squeezing rollers, and besides the two stages of squeezing rollers shown in Fig. 3 for example the arrangements shown in Figs. 4 (a), (b) and (c) can also be employed. The apparatus shown in Fig. 4 (a) is the same as that shown in Fig. 3 but that the upper squeezing roller of the first stage has been changed to two small rollers, and these small rollers move up and down and exert a load on the lower roller to squeeze the tow. The apparatuses of Fig. 4 (b) and Fig. 4 (c) are the same as the apparatuses of Fig. 3 and Fig. 4 (a) but that an additional roller is interposed between the first and second stage squeezing rollers. The interposed roller may be driven or not driven, but when it is driven it must be driven at the same speed as the second stage squeezing rollers. Another preferred embodiment of the invention is shown in Figs. 6 (a) and (b). In the apparatus shown in Figs. 6 (a) and (b), a crimped acrylic tow is first wetted and then squeezed in a first squeezing process and is then dipped in a finishing liquid bath and squeezed again in ■ a second squeezing process, and the ratio of stretching between the squeezing rollers of the squeezing processes is controlled to the range between 1.00 and 1.10. The main difference between the apparatuses of Figs. 6 (a) and (b) is the wetting process: the wetting method in Fig. 6 (a) is dipping in a liquid in a bath and in Fig. 6 (b) wetting is carried out by spraying. In these apparatuses also, for the same reasons as discussed above the liquid temperatures in the baths are preferably controlled to constant values below 50°C. (Test Example) A crimped acrylic fiber tow was applied to the squeezing apparatus shown in Fig. 3, and for the different ratios of stretching and liquid temperatures shown in Table 2 moisture regain, moisture regain fluctuation, degree of decrimping and degree of liquid level variability in the bath after squeezing under the test conditions given below were measured. For comparison with the apparatus of the invention, the test was also carried out on a one-stage squeezing apparatus (Fig. 1 (a)) and a two-stage squeezing apparatus (Fig. 2 (a)) under the same conditions as with the apparatus of the invention but without controlling the ratio of stretching and the bath liquid temperature. Test Conditions [1] press load per 1cm of tow width: lOOkg/cm [2] tow transport speed: lOOm/min [3] acrylic fiber tow: denifer of the filament 5, total denier 1,500,000 [4] liquid in bath: water [5] room temperature: 20°C The methods by which the moisture regain the degree of decrimping and the degree of liquid level variability were measured in this test example were as follows: Measuring Methods . • moisture regain (X), moisture regain fluctuation (R) i Squeezed tow was sampled by cutting to a suitable length with scissors and the tow weight (Wl) was measured. This tow was then put in a dryer and the liquid adhered to the tow evaporated and the tow weight (W2) when the tow was absolutely dry (moisture regain 0%) was measured. These measurements were carried out five times under the same conditions and values of the moisture regain (X) after squeezing and the moisture regain fluctuation (R) were calculated using the following formulae: X(%) = (Wl-W2)/W2 X 100 R(%) = (maximum value of X) - (minimum value of X) • degree of decrimping Crimped acrylic tow sampled by cutting tow on the squeezing process entry side and on the squeezing process exit side with scissors developed the crimp by drying off-line while reproducing the heat history undergone by tow during drying processing on-line, and degrees of crimping (a, (3) (%) of each samples of tow as finished products were measured. Values of "the degree of decrimping were calculated using the following formula: degree of decrimping Initial crimping and set conditions were set so that i when the degree of decrimping exceeds 20% the product is i outside product standards and if |the degree of decrimping is within 20% the product is within the crimping standards irrespective of its level. • degree of liquid level variability The difference between the maximum value (%) and the minimum value (%) of the liquid surface level shown over in an eight hour period by a value indicated continuously by liquid surface level detecting device mounted in the bath in which the tow was immersed was made the degree of liquid level variability (%). The measured results of moisture regain after squeezing, moisture regain fluctuation, degree of decrimping and liquid surface level fluctuations obtained for the conventional example and the apparatus of the invention are shown in Table 1 and Table 2. As can be seen from Table 1, with the conventional one-stage squeezing apparatus the moisture regain and the degree of liquid level variability were both high and in particular because the liquid surface fluctuation was large the liquid in the bath sometimes overflowed. With the conventional two-stage squeezing apparatus the moisture regain and the degree of liquid level variability were both slightly lower than with the one-stage squeezing apparatus but still were not satisfactory. With the apparatus according to the invention, as can be seen from Table 2 the moisture regain, the moisture regain fluctuation and the degree of liquid level variability were all markedly lower than with the conventional apparatuses and furthermore when the ratio of stretching and the liquid temperature in the bath were controlled to ' within predetermined ranges the degree of decrimping was well within the range of the product standards. Because in this invention a tow is squeezed with a ratio of stretching kept in the range between 1.00 and 1.10, a low and stable moisture regain of the squeezed tow can be obtained without the crimp being excessively extended and as a result the cost of drying the squeezed tow can be reduced and also fluctuation in the level of the surface of the liquid in the bath in which the tow is immersed can be reduced. When a bath is filled with a finishing liquid and a crimped tow is squeezed after being dipped in the finishing liquid, because a stable moisture regain can be obtained as described above, fluctuations in finishing liquid adhesion rate can be reduced and an improvement in product quality can be obtained. Also, because in the invention the temperature of the liquid in the bath in which the tow is dipped is controlled to a constant value below 50°C, the degree of decrimping does not fall outside the product standards and furthermore fluctuations in moisture regain occurring in the time it takes the temperature of the liquid in the bath to reach equilibrium can be reduced. WE CLAIM 1. A crimped acrylic fiber tow squeezing apparatus comprising a bath for immersing a crimped acrylic fiber tow, a first set of squeezing rollors disposed in two stages for squeezing the fiber tow, means for transporting the fiber tow so that the fiber tow is immersed in the bath and then removed from the bath and squeezed by the squeezing rollers, and means for controlling the ratio of stretching between the squeezing rollers in a range between 1.00 and 1.10. 2. The crimped acrylic fiber tow squeezing apparatus according to claim I comprises means for wetting a crimped acrylic fiber tow, a second set of squeezing rollers disposed in two stages for squeezing the wetted fiber tow before the crimped acrylic fiber tow is immersed in the said bath. 3. The crimped acrylic fiber tow squeezing apparatus according to claims 1 or 2 wherein controlling means is provided for controlling the temperature of the liquid in the both to a constant value below 5OoC. 4. A crimped acrylic fiber tow squeezing apparatus substantially as herein described with reference to figures 3 to 6 of the accompanying - drawings.

Documents:

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1519-mas-1995 abstract.pdf

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1519-mas-1995 correspondence-others.pdf

1519-mas-1995 correspondence-po.pdf

1519-mas-1995 description (complete).pdf

1519-mas-1995 drawings.pdf

1519-mas-1995 form-1.pdf

1519-mas-1995 form-26.pdf

1519-mas-1995 form-4.pdf

1519-mas-1995 petition.pdf