Process and apparatus for the mercerization of slivers

The invention relates to a method and apparatus for mercerizing a cellulosic fiber-containing sliver with an aqueous solution of caustic soda of high concentration. The sliver is transported between a belt conveyor and a press belt to hold it in place and transported in a downwardly inclined direction, then transferred from the belt conveyor onto a net conveyor having mesh openings and transported by said net conveyor such that the excessive caustic soda solution drips through the mesh openings of the net conveyor and the caustic soda is finally squeezed out of the sliver by means of squeezed rollers. The squeezed sliver material is then washed with water by transporting it to another net conveyor containing press rollers thereupon by passing the sliver between the net conveyor and press rollers located in a water-washing tub. An apparatus to effect this process also constitutes part of the present invention. The disclosed method makes it possible to mercerize a sliver containing cellulosic fibers so that it is not broken and to accomplish this mercerization in an efficient and economical manner, whereby mercerized yarns and knit fabrics can be produced which are excellent in bulkiness and softness.

The present invention relates to a method and apparatus for the 
mercerization of slivers. 
Mercerized knit products made of cotton yarns or blended yarns of cotton 
and synthetic fibers are characterized in that they have excellent luster 
and dyeability and are clear in color, in addition to their good 
dimensional stability. However, the mercerization has been heretofore 
conducted in the form of yarns or knit fabrics, so that by the strong 
shrinking action of cotton fibers resulting from the mercerization 
treatment, the hand feel of the yarns and the knit fabrics is made harsh. 
Because of this, they have a defect in that they are lacking in bulkiness 
and softness as knit materials for winter use. Also, since it is difficult 
to conduct uniform mercerization and the dyeing speed is considerably 
increased by the mercerizing treatment, and dyeing unevenness is liable to 
occur. Therefore there has been a necessity for prolonging the dyeing time 
and also there has been an increase in defective products, thereby making 
the process uneconomical. 
A method is known wherein raw cotton after removal of coarse impurities 
such as cottonseed dust, etc. is alkali-scoured, bleached, dried, 
oil-treated, fed to a blowing machine and spun (Japanese Patent 
Publication No. 6724/1980). In this known method, when mercerization is 
conducted using an aqueous caustic soda solution of high concentration in 
place of that of low concentration, the raw cotton forms hard lumps which 
make the opening of cotton fibers difficult. This renders the spinning 
process almost impossible. Even if spinning could be conducted, since a 
large quantity of short fibers are removed as waste cotton during the 
blowing step and the combing step after the above mentioned treatment, the 
caustic soda used for that waste cotton becomes useless and is uneconomic. 
Also is known a method wherein a flax sliver is continuously immersed in 
an aqueous caustic soda solution to shrink the sliver (British Pat. No. 
1,057,245). When a cotton sliver in place of the flax sliver is immersed 
into an aqueous caustic soda solution by introducing it by means of guide 
rollers, etc., since the length of the cotton fibers is shorter than that 
of the flax fibers, the cotton sliver will be broken in the solution and 
therefore it is impossible to treat it in sliver form. 
The present invention provides a method and apparatus which makes it 
possible to mercerize a sliver containing cotton fibers and/or other 
cellulosic fibers so that it is not broken, whereby there can be obtained 
mercerized yarns and knit fabrics which are excellent in bulkiness and 
softness. 
Therefore, the present invention provides a method of mercerizating a 
sliver characterized by impregnating a cellulosic fiber-containing sliver 
with an aqueous solution of caustic soda of high concentration while 
transporting the same as held between a belt conveyer and a press belt 
which contacts the upper surface of said belt conveyer, transporting said 
sliver after transferring it to a net conveyer for timing, while 
completing the reaction and dripping a part of the caustic soda solution 
through the meshes of the net conveyer, squeezing the solution out of the 
sliver by means of squeeze rollers, introducing the sliver into water, and 
washing the sliver with water while transporting the same as held between 
a net conveyer for water-washing and press rollers. 
The present invention also provides an apparatus for mercerizing a sliver 
wherein a belt conveyer having on its upper surface a press belt which 
presses it, a net conveyer for timing and water-washing tubs are arranged 
in succession, a feed opening for allowing an aqueous solution of caustic 
soda to flow onto the upper surface of said belt conveyer is provided 
above the end portion of the supply side of the belt conveyer, a net 
conveyer for water-washing and on its upper surface a plurality of press 
rollers are provided in the water-washing tubs in such a manner that the 
cellulosic fiber-containing sliver is led to said belt conveyer, a net 
conveyer for timing and water-washing net conveyer successively and said 
sliver is placed on these conveyers linearly in the transporting direction 
.

A belt conveyer 1 arranged in an upper position is composed of an 
impermeable sheet made of rubber, synthetic resin or the like, and is 
provided in an inclined manner so that the front of its advancing 
direction (the direction of the arrow mark P) is lowered. Above the end 
portion of its supply side, there are provided letting-off rollers 2,2 and 
a feed opening 3 for causing an aqueous solution of caustic soda to flow 
down onto the upper surface of the belt conveyer 1. On the upper surface 
of the central part of the belt conveyer 1, an endless press belt 4 
composed of a similar impermeable sheet as mentioned above is caused to 
travel while being pressed down. Below this belt conveyer 1, a first net 
conveyer 5 and a second net conveyer 6 for timing made of synthetic fibers 
such as polyvinyl chloride fibers, glass fibers or stainless steel are 
provided in zigzag form, each inclined downward. On the letting-off side 
of the second net conveyer 6, a pair of upper and lower squeeze rollers 
7a, 7b are provided. Below the end part of the letting-off side of this 
second net conveyer, there are provided in sequential order a first 
water-washing tub 8 and a second water-washing tub 9. Inside the first 
water-washing tub 8 and the second water-washing tub 9, there are provided 
a net conveyer 10 for water-washing composed of fibers or wires similar to 
those of said net conveyers 5 and 6 and a plurality of press rollers 11 
pressed on its upper surface, respectively. Furthermore, there are 
provided above the second water-washing tub, a plurality of water-jetting 
nozzles 12 and at the upper part before and after the second water-washing 
tub, letting-off rollers 13, respectively. Below the second net conveyer 6 
for timing, a trough 14 for collecting the solution and a tub 15 of the 
caustic soda solution connected thereto are arranged. The solution feed 
opening 3 is connected to this solution tub 15 through a solution feed 
pipe 16 and a pump 17. 
When a sliver A is fed on the belt conveyer 1 by the rollers 2,2 and a high 
concentration aqueous caustic soda solution (14-24%) is fed to the sliver 
A from the solution feed opening 3, the sliver A is transported while 
being held between the belt conveyer 1 and the press belt 4. During this 
time, the sliver A is impregnated with the caustic soda solution and 
swells. The sliver A is then transferred to the net conveyers 5,6 and is 
caused to travel. During this time, the reaction is completed and an 
excess quantity of the caustic soda solution is caused to drip through the 
meshes of the net conveyers 5,6, and further squeezed out of the sliver A 
by the squeeze rollers 7a, 7b. Thereafter, the sliver A is introduced into 
the first and second water-washing tubs 8, 9 where it is washed with 
water. The sliver A is then transported to an acid treating step (not 
shown) and an oiling step. 
The sliver A includes a carded sliver spun from raw cotton through a 
blowing machine and a carding engine, a combed sliver further spun through 
a comber, etc. which is a non-twisted fiber assembly in band form or in 
rope form. The silver A used in this invention may be either a sliver 
composed solely of cellulosic fibers such as cotton, flax, polynosic 
rayon, etc. or a sliver composed of a mixture of cellulosic fibers with 
synthetic fibers such as polyester fibers, polyamide fibers, etc. 
By setting the travelling speed of the belt conveyer 1 and the peripheral 
speed of the letting-off rollers 2, 2 at an equal rate, the sliver A can 
be placed linearly without meandering or being placed one over another, 
and a plurality of such slivers can be placed in parallel. The sliver A is 
immersed in the high concentration aqueous caustic soda solution in such a 
state that it is pressed from above on the conveyer belt 1 by the press 
belt 4. Accordingly, the fiber arrangement in the sliver A is not 
disordered by the swelling caused by the impregnation. Since the belt 
conveyer 1 is composed of an impermeable sheet and is inclined below 
forward in the travelling direction, the caustic soda solution flows along 
the sliver A and is absorbed to said sliver without loss. In order to 
prevent the fiber arrangement of the sliver A from being disordered by the 
caustic soda solution which is caused to flow down through the solution 
feed opening 3, the feed opening 3 is preferably set near the press belt 4 
with the end of the opening being set upward at a low height, to overflow 
the caustic soda solution gently from this low position. 
The net conveyers 5, 6 below the belt conveyer 1 are driven at a speed 
substantially the same speed as the belt conveyer 1, and the sliver A 
swollen by the impregnation with the caustic soda solution is placed 
linearly on the net conveyers 5, 6. The net conveyers 5, 6 have a large 
number of meshes over the whole surface, and when the sliver A is placed 
on the conveyers 5, 6, an excess quantity of the caustic soda solution 
contained in the sliver A drips or flows down below through the meshes. 
Accordingly, the fibers does not substantially float or move in the sliver 
A, so that the fiber arrangement is not disordered while the sliver A is 
transported by the net conveyers 5, 6 and squeezed between the squeeze 
rollers 7a, 7b. The caustic soda solution which has flowed down below is 
collected in the solution tub 15 through the solution collecting trough 14 
and thereafter it is sent again to the solution feed opening through the 
solution feed pipe 16 and the pump 17. 
The sliver A let-off from the second net conveyer 6 is then introduced into 
the first water-washing tub 8. Since the sliver is placed linearly on the 
water-washing net conveyer 10 and is transported while being pressed from 
above by the press rollers 11, the sliver A is prevented from floating up 
and is washed with water without being broken, with most of the caustic 
soda solution in the sliver A being removed. In this case, since the 
sliver A let-off from the second conveyer 6 is very weak in strength, the 
water in the first water-washing tub 8 desirably does not substantially 
flow. The sliver A is then transported while being held between the net 
conveyer 10 and the press rollers 11 in the second water-washing tub 9, 
and during this time the sliver A is washed with water jetted from the 
nozzles 12. At this time, since the sliver A has been remarkably shrunk by 
the water-washing in the first water-washing tub 8 and has become 
stronger, it is not broken by the shower washing. 
By subjecting the sliver A to acid treatment, water-washing and oiling 
treatment subsequently to the shower washing, the mercerization is 
finished. Since the strength of the sliver A has been elevated, the above 
treatments including acid treatment can be carried out either by a 
conveyer system or roller system. The sliver A after being oiled is dried 
and is sent to the spinning process where it is spun. At this time, since 
the fiber arrangement is maintained in parallel without being disordered, 
the sliver A can be easily spun into yarns. Also, since the sliver A 
shrunk by mercerization is oiled and dried and then fed to a drawing 
frame, fly frame and ring frame successively and opened, the yarn thus 
obtained have the same degree of bulkiness and softness as the usual 
non-mercerized spun yarns, and in addition it has luster which is not seen 
in the usual spun yarns. Since the mercerized sliver A has been elevated 
in strength as mentioned above, the sliver can be package-dyed by an 
Obermayer dyeing machine or continuously dyed by padders and when oiled 
and dried and thereafter can be spun in the same way as mentioned above. 
In this case, even if dyeing unevenness may occur due to an increase in 
dyeing speed, the dyeing unevenness will be eliminated by the doubling of 
slivers in the drawing step. Also, it is possible to produce grandrelle 
yarns by blending different color slivers in the drawing step. 
In the above-mentioned mode of practice of the present invention, it is 
possible to omit the second net conveyer 6 by elongating the length of the 
first net conveyer 5. In this case, it is possible to provide the first 
net conveyer 5 at a position from below to the right of the end of the 
belt conveyer 1, and it is also possible to provide it horizontally 
without being inclined. Also, it is possible to omit the nozzles 12 by 
filling the second water-washing tub 9 with water in the same way as in 
the first water-washing tub 8. Naturally, the number of the sliver A 
placed on the belt conveyer 1 may be either one or a plural number. 
In the following the invention will be explained more concretely by way of 
Example. 
EXAMPLE 
A sliver A composed solely of cotton fibers and obtained from a comber was 
mercerized by the apparatus of the drawing explained above. The sliver A 
was placed linearly on the belt conveyer 1 which is travelling at a speed 
of 6 m/min. An aqueous caustic soda solution of 18.degree. C. having a 
concentration of 18.7% was dropped on the sliver, which was treated on the 
belt conveyer 1, the first net conveyer 5 and the second net conveyer 6, 
each for 10 seconds. The sliver was then washed with water in the first 
water-washing tub 8 and the second water-washing tub 9, each for 15 
seconds. Thereafter, the sliver was neutralized for 10 seconds with an 
aqueous solution of acetic acid having a concentration of 5 g/l, washed 
with running water for 30 seconds and dehydrated with squeeze rollers, to 
finish the mercerizing treatment. After oiling and drying, the sliver was 
spun into a 40-count (English type cotton count) cotton yarn. With this 
cotton yarn, a circular rib fabric for underwear was knitted by a 19-gauge 
circular rib fabric machine. On the other hand, a 40-count (English type 
cotton count) cotton yarn was spun by the usual spinning process and was 
knitted into a similar circular rib fabric as mentioned above. Thereafter, 
the fabric was mercerized to obtain a circular rib fabric for underwear 
(Comparison Example). Luster and hand feel were evaluated for the circular 
rib fabrics of Example and Comparison Example. It was found that the hand 
feel of Example fabric was soft and warm while that of Comparison Example 
was harsh and cool. But there was no substantial difference between them 
in luster and the clearness of color. Undershirts were produced from these 
fabrics of Example and Comparison Example, and wearing tests were 
conducted. The undershirt of Example was soft to the skin and had a warm 
feel in comparison with that of Comparison Example, and gave a good 
wearing feel as an underwear. 
As explained hereinabove, the yarn produced according to the present 
invention has a soft hand feel in comparison with the conventional 
mercerized yarn, and moreover has good luster and clear color development 
as a mercerized yarn. Especially, when used for knit fabrics, the yarn can 
produce a new commercial product which has not been obtained heretofore.