US3481684A - Process for refining and bleaching textile fabrics,threads and the like - Google Patents

Description

FIPSSUJ Dec. 2. 1969 YOSHIKAZU SANDO ET AL 3,481,684 1 PROCESS FOR REFINING AND BLEAGHING TEXTILE FABRICS, THREADS AND THE LIKE 2 Sheets-Sheet 1 Filed Nov. 4, 1966 INVENTOR.

YOSH/KA 2a SANOU GERU M01?! United States Patent US. Cl. 8-111 4 Claims ABSTRACT OF THE DISCLOSURE,

A continuous textilejfabric bleaching process is disclosed. The fabric is first padded with a surface active agent containing acidified chlorite solution of a pH of about between 3 to 3.51 The thus padded fabric is then heated in a steam atmosphere of about 80-85 C. in a substantially closed system, whereupon the fabric, is again passed through a heatedichlorite solution of a pH'bf about 3 to 3.5 in folded, unstretched condition in the same closed system, thereby maintaining the pH value substantially constant throughout. After washing, the fabric is padded with an alkaline hydrogen peroxide solution, heated in a steam atmosphere in a'ysubstantially closed system and passed through a hot alkaline hydrogen peroxide solution, washed and dried.

SUMMARY THE INVENTION This application is a continuation-in-part of our copending application Ser. No. 394,653, filed Sept. 1, 1964, now abandoned which, in turn, was a continuation-in-part of Ser. No. 87,209, filedj' on Feb. 6, 1961, now abandoned.

This invention relates to a novel method for rapidly refining and bleaching textile fabrics, threads andthe like, consisting of textile fibers, while dispensing with the conventional alkali boiling process.

The term textile fibers as used herein is deemed to refer to cellulose fibers, synthetic fibers, natural polyamide fibers, cotton fibers and mixtures thereof. However, since the inventive method is particularly suitable for the treatment of cotton fibers, the invention will hereinafter be described in relation to fabrics solely or essentially consisting of cotton fibers.

The conventional refining and bleaching process has hitherto been carried out substantially in such manner that cotton fabrics or the like singed and desized materials are subjected to an extended boiling in an alkaline solution, containing a substantial quantity of, for instance, caustic alkali, for scouring the material. The process is sometimes carried out under pressure. The material is then bleached by means of a hypochlorite or hydrogen peroxide. In chlorination with a hypochlorite, the fabrics and the like thus treated are finally passed through a diluted mineral acid bath and washed for final finishing.

Such conventional processing has, however, a plurality of inherent drawbacks as will be set forth hereinbelow:

Extended boiling of the fabrics and the like with use of caustic alkali and under pressure results in interruptions of the favorable continuous processing, thus sacrificing substantially the maximum attainable efficiency of the process. The process can be carried out in a continuous way, if the know J-box system is relied on. This relatively modern system requires, however, a large investment and large space, thereby preventing wider employment of the system in the industry.

On the other hand, the strong and severe refinery processing as above mentioned results in a considerable aniount of refining loss," as commonly known to those skilled in the art. The additional chlorine bleaching, when employed, sometimes causes the cellulose of the treated fabrics and the like partial l"' to turn into oxy-cellulose, which phenomenon natura ly adversely affects the desired characteristics of the products.

With regard to the treatment in the mineral acid bath, it is highly difiic'hlt to completely remove the residual acid by washing, especially when dense and thick fabrics have been treated. Dire to the presence of residual acid, if any, the fabrics andithe like will become appreciably weakened, sometimeslcausing a considerable additional loss,

Theconventibnal processing results further in severe mechanical damage to the products, due to excessivelfriction, folding and the like as encountered during the processing, resulting 'in uneven dyeing in the following drying process. The residual acid will cause disadvantageousj'provisional dyeing,}-,which may yield a color tone similar to that of the original unbleached fabric. This happens after a relatively short period of time, or when exposed to elevated temperatures. In the conventional process, uneven scouring may frequently result, which will in turn invite much trouble due to uneven dyeing or printing of the finally finished commercial products.

After extensive experimental investigations into the conventional alkali refinery processing, it was now found that the above listed drawbacks are caused by the following facts:

It is generally recognized by those skilled in the art that impurities contained in the cotton or the starting material of the fabrics and the like under consideration, essentially consist of various coloring substances, pectin substances, protein substances however small, rubber-like substances, cotton wax substantially comprising phytosterol, and fatty acids. 1"

It is natural that the above mentioned impurities must be removed as completely as possible from the treating fabrics and the like during the scouring and bleaching processing. Among these impurities, pectinand rubberlike substances, fatty acids and the like can be sufficiently removed by thefconventional alkali scouring, while phytosterol being the main component of cotton wax and amounting to about 70% of the oily and fatty substances contained in the cotton is highly difficult to remove effectively under moderate processing conditions. The reasons therefor would possibly be that phytosterol is an unsaturated higher alcohol of cyclic construction having at least an unsaturated bond and an OH-radical so that it cannot be removed effectively by means of alkali, unless a substantial quantity of phytosterol has been oxidized to the corresponding fatty acid. I

In practice, however, according to the conventional process, the alkaline processing must be carried out in a closed vessel, in order to prevent the possible transformation of cellulose into oxy-cellulose. Thus, a desirable refinery treatment in an oxidizing atmosphere or in the presence of oxidizing agent cannot be used under these operat ing conditions.

The main object of the invention is to provide a novel scouring and bleaching process, wherein the hitherto employed disadvantageous alkali boiling treatment can be completely dispensed with.

Another object is to provide a novel process of the kind referred to above which is simple and rapid in its operation, yet provides a considerably higher efficiency as compared with that obtainable with the comparable conventional process.

Still another object of the invention is to provide a continuous process of the kind referred to above, according to which superior, permanently and evenly scoured and bleached products can be obtained.

According to the present invention, cotton or cottoncontaining fabrics or the like singed and desized materials are subjected to a series of processing steps which allows the fabrics to be treated in a continuous manner with resultant high throughputs and reduced processing periods. Highly efficient continuous operations are obtained without sacrifice in uniformity of the refining and bleaching results. The combination of steam 'jtreating followed by solution heat treating in a closed system (closed vessel) reduces loss of reagent and increases gas density (C10 in the case of the chlorite treatment), thereby providing more efficient treatment.

More particularly, the cotton-containing fabric i first padded with a chlorite solution havinga pH of 3 to 3.5, the pH being maintained by the used of suitable acids such as hydrochloric, acetic, formic, sulfuric, etc. The solution also contains a surface active agent, preferably an anionic activator of the alkyl-aryl sulfonic acid series. Commercially available products of this type include Scourol-95 and Lavenpon-TH, among others well known in the art. After squeezing to a fixed pick-up rate, suchas 100%, the cotton material is then subjected to heating with steam at 80 to 85 C. while moving in a closed sysem for a relatively short period of time such as 15 to 20 minutes, and passed through'a hot, preferably boiling, solution of chlorite having a,pH of 3 to 3.5 and containing the above surface active agent (having normally essentially the same composition as the initial chlorite impregnating bath and which can be a portion thereof). Due to the steam heating step, temperatures of chlorite treatment are of the order of 80 to 85 C. The steam heated material is in contact .'-with the chlorite bath in a closed vessel, to wit the system used for the steam. heating step, for a relatively short time, e.g. 1 to 15, preferably 5 to 10, minutes, the material then passing in continuous fashion to one or mofe water washing stages.

The combination of the steaming treatment with the r solution heating treatment prevents lack of uniformity while permitting continuous and accelerated treatment.

Aniimportant feature for the success of the invention is that the fabric is folded in the closed system and passes through the second bleaching bath in folded unstretched condition.

Thereafter, the bleached fabric is then preferably treated with an alkaline solution of hydrogen peroxide in a similar manner, i.e., first padded with reactant, steam treated and then solution treated, the latter steps preferably being effected in a closed system (vessel). Accordingly, after washing the chlorite-treated fabric with water, it is padded with an alkaline hydrogen peroxide solution (pH of about 9 to 11, especially 10); squeezed to a fixed pick-up rate; and steam heated in a closed system for a relatively short period, "eg. for about 10 to minutes, at a temperature of the order of 85 to 90 C. The heated fabric may then be passed through a heated solution of the alkaline peroxide having the foregoing pH and composition (in much the same manner as described relative to the chlorite treatment). The peroxide solution is normally in the same closed vessel as the steam treatment and at temperatures of about 85 to 90 C., the fabric having a relatively short residence'time in the peroxide bath, e.g. 1 to 10 minutes. The material is thus simultaneously dechlorinated and dewaxed. It may then be washed and dried and a bleached cotton product recovered.

The novel process as mentioned above is based on the following additional factors and observations:

It is natural that, for bleaching purposes only, the conventional chlorite bleaching without employment of alkali boiling would sufiice. With such measure, however, oily and wax substances contained in the material cannot substantially be removed, so that the desired wettability is not obtainable. After testing a number of surface active agents to be added to the chlorite solution, it was now found that with the use of penetrating detergents substantially consisting of anionic activators of the alkylaryl sulfonic acid series, desired wettability of the material to be treated, successful removal of neps therefrom, and increased whiteness of the treated products can be realized. With such means, however, the dewaxing effects are rather insufficient, so that other suitable measures must be relied upon.

As such additional measure, hydrogen peroxide treatment known per se was additionally introduced, and it was found that this introduction was employable with highly superior results, bringing about enough dechlorination, sufficiently permanent whiteness, together with a considerable degree of dewaxing. It suffices for this purpose to employ such treatment by means of a relatively lower concentration of the peroxide such as less than .5% calculated on H 0 and during a relatively short period, such as for 10 to 15 minutes. The results are normally such that the residual quantity of fat amounts to 0.2 to 0.24% in comparison with the initial fat content of about 0.6 to 0.7% of the material fabrics, coupled with highly superior wetting speed of the products. In connection with the latter, it was found that for realization of sufiiciently wetted condition of highly close and thick fabrics, it needed only a short period of such treatment amounting to less than unit second.

The hydrogen peroxide bleaching per so has been known to be accompanied by dewaxing effects to a more or less degree. Although the theoretical mechanism of the processing has not yet been enough clarified, but the considerable results have been determined and acknowledged empirically by those skilled in the art for a long time.

According to our recognition based on a number of practical experiments, when phytosterol is subjected to oxidation, its double bond is possibly transferred into two OH-radicals which are, when further oxidized, converted into ketone and then further info a COOH radical.

Thus, when textile fabrics are, according to the invention, subjected to oxidation in, the presence of chlorite, followed by the further oxidation by means of hydrogen peroxide, a substantial quantity of phytosterol contained therein is transferred into the; corresponding fatty acid which, together with another fatty acid contained, saponified by the influence of alkalinity of sodium silicate added in the course of the peroxide; bleaching stage to soap, which is finally dissolved and removed.

In this case, a colloidal state of the added sodium silicate serves considerably for emulsifying the fatty acids and thus effectively accelerates the desired removal of the latter. From the foregoing, it will be noted that the combined bleaching processing according to the invention will provide superior results in connection with effective refining and bleaching of cotton and the like fabrics or threads."

The aforemc ntioned figures of 0.2 to 0.24% of residual fat, being obta. nable according to this invention, are comparable to those attainable by the elaborate conventional Kier bleaching process, as enlisted in the following Tables I and II.

Addition of special surface active agents to the sodium chlorite bath contributes to promote the desired impregnation of the liquid bath into the material under treatment, resulting in even action of NaOCl throughout the material, thereby effective removal of neps, increased whiteness of the material and some degree of dewaxing therefrom being attained, coupled with stronger penetrating power provided by the absorbed agents, which will improve the wettability by water, thus advantageously influencing the dyeing process to be followed.

When the process accordingto the invention is carried into effect with use of non-tension system, the products can be given non-shrink effects, indeed, without employment of mechanical treatment for this purpose as otherwise necessary, for instance, in the case of Sanforizing process- I It is natural that the process according to this invention is not limited to the treatment of cotton fabrics, and: thus it can be well adapted to that of cotton threads, mixedly spun or mixedly woven fabrics including chemical orsynthetic fibers with cotton.

Now certain comparative data of the products obtained by the novel process with those attainable by the iconventional Kier refinery process shall be given in the following Tables I and II. In this'case, the treated materials were canvas cloths which were comparatively thin and thick, respectively. The treatment according to thenovel process was such that a solution containing 3% by weight of sodium chlorite was activated by means of a suitable quantity] of formic acid, making its pH 3 to 3.5, 0.5% of Scourol-95 was added to the solution which was then padded io the material after singeing and desizing thereof and squeezed to a take-up of about 100%. The thus treated i naterial is then subjected to treatment at elevated temperatures between 80 and 85 C. for about 15 3:9 20 minutes} washed with water; bleached with a diluted hydrogen peroxide bath having a peroxide concentration of about 0.3% H 0 relative to the dry weight of the material fabrics and being adjusted the pH to by adding a corresponding quantity of sodium silicate, at elevated temperatures between 85 and 90 C. for about minutes; and finally again washed with water.

TABLET-TREATED MATERIAL: THIN CANVAS CLOTH TABLE I I.TREATED MATERIAL: THICK CANVAS CLOTH According to Processinvention Whitenessbbtained 97. 4 Residual fat, relative to initial figure of 0 3% based on dry weight or material percent 0. 171

Submerging time period necessary for sinking below 0 9 water level by gravity, sec

In order successfully to carry out the inventive procedure it is essential that the pH value of the two chlorite baths or solutions with which the fabric comes into contact is between about 3 to 3.5 and that this pH value is maintained throughout the treatment. Further, it is an important feaure of the present invention that the steaming of the fabric and the second chlorite treating Step are carried out-in the same closed system for reasons which will become clear from the following.

With a view to bleaching and/ or refining cotton fabrics in a continuous manner, it has previously been suggested to make use of steam heating methods. According to these prior art methods, the textile fabric is first padded with a solution containing the necessary ingredients or reactents and is then conveyed to a. closed type of reactor, wherein the padded fabric is heated to the desired temperature by a jet of steam. The fabric is maintained at an elevated temperature for an appreciable length of time and the fabric is squeezed or compacted to such an extent that the largest possible amount of fabric can be introduced into the reactor space. The compacted fabric is then continuously drawn out from the reactor. This prior art method has several serious drawbacks which will be briefly discussed:

(1) It has been observed that the pH of the chlorite solution has a tendency to rise rather rapidly which, of course, is highly undesired. While, of course, the fluctuations in the pH value are to a certain extent dependent on the chemicals employed to activate the NaClO or the like chlorite and the temperature and the period of treatment, a change or flu ctuation of the pH value generally cannot be avoided in the prior art methods. In the tables below, a few experimental results have been tabulated. These results were obtained by activating NaClO by means of formic or acetic acid. In arriving at these results, two samples of twilled cotton flannelette contaminated by cotton seed refuse to a considerable extent were steamed, desized by means of an enzymatic agent, and then padded with an aqueous solution containing NaOH in an amount of. 2.5%, calculated the initial weight of the cloth. 0.3% of an anion-type of surfactant was added to the bath. The fabric was soaked in the solution, squeezed to a pick-up rate of aboujt100%, then refined by Steam heating under exclusion of air at about 100 C. for sixty minutes, washed with cold water and completely neutralized by dilute aqueous formic acid. The fabric was then thoroughly washed again with cold water and padded with an aqueous solution containing 2.0% of NaClO calculated on the initial weight of the sample cloth. The pH was adjusted to 3.0 in Experiment A and to 3.5 in Experiment B. This was done by adding formic acid. The fabric was then squeezed again to a pick-up rate of about 100%, steam-heated under exclusion of air at C. for 15 minutes (A) and for 30 minutes (B). The fabric was then cooled and the pH was measured.

No'rE.Wl1iteness of the refined fabric was estimated as 55 by means of Sbimazu automatical spectrophotometer.

It will thus be noted that the pH value rose considerably during the treatment. This rise of the pH value is very detrimental from a practical point of view, because it has been experimentally confirmed that in apH range above 4.5, the decomposition of NaClO and other chlorites and hence the progress of the bleaching slows down significantly even if the temperature is raised to a higher value. Therefore, it is important to make sure that the pH value stays at a value below 4.5 and, in accordance with the present invention, it has been ascertained that superior results are obtained by maintaining the pH value at between about 3 toi 3.5. Since the decomposition of the NaClO slows down 'at higher pH values, bleaching in the higher pH range therefore takes place in much slower and less effective manner. This disadvantage makes itself particularly felt in continuous processes since the bleaching bath after a relatively short time will not exihibit sufficient bleaching efi'ect. Further, of course, the economics of the process suffer and substantial losses of reactants are suifered.

In respect to the change of the pH value in a steam atmosphere, it has been established that there is very little difference as to whether formic acid or acetic acid is used as activator. To indicate this, a few data are reproduced hereinbelow which have been taken from Silvrite News published by Nippon Inc. These data reflect experimental results obtained in a manner similar to that described hereinabove, namely by padding samples of cotton materialwhich previously had been desized and refined by caustic alkali-with solutions containing NaClO at various concentrations as indicated in the following Table IV. These solutions had an initial pH value of 3.5 by activation caused by the addition of acetic acid or formic acid. The impregnated cotton material was then squeezed to a pickup rate of The samples were then placed in weighing bottles with the stoppers or caps of the bottles tightly closed and the material was then bleached in a thermostatically controlled atmosphere of 100 C. for 1 /2 hours,

TABLE IV Residual NaClOz NaOlOz No. (percent) Acid Final pH (percent) whiteness 0.5 Acetic 76.0 79.3 80.9 68.0 81.1 81.2 54.0

Reference is also had to experimental results published by Hodogaya Kagaku Kenkyusho. These results were obtained by adjusting a liquid system containing 4% of NaClO with formic acid to obtain a pH value of 3.0. Small portions of the solution, to wit cubic centimeters, were then heated in the open atmosphere at 90 C. in the absence of any substance susceptible to bleaching. The decomposition rate was determined at intervals in respect to each of the portions which were strongly agitated during the heating. The results obtained indicate that the decomposition rate after minutes is about 80% while after 60 minutes the decomposition rate has risen to about 94%. Not much weight, however, should be given to these experiments since the operational conditions of the experiments were quite different and distinct from those prevailing in the present process.

In conclusion, therefore, the conventional prior art steam heating processes are not suitable for effectively causing a bleaching of the fabric since a rise of the pH value in the chlorite solution with resulting drop of chiciency of the bleaching cannot be avoided. If steps are to be taken to reactivate the chlorite solution to a sufiicient extent, the continuity of the process is interrupted.

(2) Fabrics which are treated in the conventional manner cannot be dyed evenly after the bleaching process. This will become apparent from the following:

In the conventional steam-heating processes, even highly hydrophobic textile fabrics, like textile fabrics consisting of synthetic fibers, are introduced into a saturator with normal moisture cdntent. The fabrics are impregnated in the saturator with the chemical solution and withdrawn from the saturator with a slightly higher moisture content, which usuallyj amounts to about to 30% calculated on the original weight of the fabric. This, of course, is disadvantageous in respect to fabrics having high hydrophobicity and the fabric therefore has to be heated by a blast of raw steam to a relatively high temperature of 90 C. or more. Due to the considerable amounts of condensation water which are formed during the steam treatment and which may amount to about 20% of the fabric weight, the' liquid is considerably dilutedand the chemicals contained in the liquid therefore will not properly react in uniform manner with and on the fabric. Further, the steam has a tendency to carry away and remove substantial amounts of the reagents from the solution. For this reason, the reagents have to be used in considerable excess over the theoretical amount which, in turn, results in unequal distribution of the chemicals over the fabric surfaces which, in turn, causes uneven dyeing of the finished product. This disadvantages cannot successfully be overcome in the prior art processes.

(3) In the prior art methods, an exceedingly uneconomical use of the bleaching agent takes place. By con trast, in the present process the bleaching agent is fully utilized in a most economical manner. This is so because the steam heating is carried out in a closed system which also contains the second bleaching bath, the fabric being folded in the closed system into a pile of multiple unstretched layers. The fabric which enters the closed system as a continuous web thus is formed into a folded or stacked unit which is formed by the fabric in relaxed or unstretched condition. This condition of the fabric lends itself particularly for successful bleaching in an economical manner, since the.fabric is treated in the absence of any tension. This condition of the fabric is particularly advantageous for the subsequent cooking or steeping step because the feel of the fabric is improved thereby. Since C10 gas evolves in the closed system in which the steaming step takes place, a very favorable distribution pattern of the gas is obtained. If the steam heating and the bleaching are carried out in two .different reaction vessels, an uneven bleaching is bound to occur. This is so because the amount of C10 gas which penetrates to the inner regions of the folded fabric} unit is normally not equal to the amount of gas reaching the outer or marginal regions of the unit. The gas, of course, has a tendency to escape through the narrow spaces between the individual layers of the pile of the molded fabric and through the space between the pileand the wall of the reactor. This is so because the gas will attempt to escape through the passages offering least resistance. This, of course, results in uneven or speckled bleaching. By contrast, if the procedure is carried out in'a single closed system, the presence of the steam which has thoroughly soaked and permeated the fabric pile overcomes this disadvantage so that all areas of the fabric pile are substantially equally penetrated by the'chlorite gas. The steam thus acts also as a carrier medium.

Generally, experience has demonstrated that the combined' steam heating chlorite treatment in a single closed system overcomes many of the problems which are known to those skilled in the art of bleaching fabrics.

The advantages of the present invention may therefore be summarized as follows:

(1) Since the fabric is subjected to the steaming and bleaching treatment in an untensioned, folded condition, the feel of the fabric is considerably improved. The residual contraction rate is very small. In fact, in many instances, a residual shrinkage of only about 02% has been established. 1

(2) Even in the event that the pH value should slightly rise during the bleaching treatment, thu's resulting in a decrease of the bleaching activity, the bleaching solution is again readily reactivated during the {cooking step so that residual NaClO is entirely decomposed and the bleaching efliciency is again raised to its maximum value'. This can be accomplished without interrupting the continuity of the process.

(3) Even in the event that the amount of bleaching gas passing through the fabric in the closed system above the bleaching liquor should be somewhat uneven due to improper folding or the like, this can 'readily be rectified in the subsequent cooking step.

(4) Excellent whiteness of the fabric is obtained.

As previously stated, it is an essential feature of this invention that the pH of the NaClO bleaching liquor should be in the range of about 3.0 to 3.5 and should be maintained within this range during the bleaching procedure. At pH values below 3.0, the decomposition of the NaClO advances very rapidly. For this reason, it is extremely difiicult to store and preserve the bleaching agent in the form of a stock solution. Furthermore, at low pH values, it is difficult to control the gas evolution in the closed system and excessive amounts of C10 gas are generated which render control of the bleaching procedure extremely difficult. Furthermore, since the thermal decomposition in the closed. system proceeds very rapidly at low pH values, considerable amounts of the chlorite gas have a tendency tolescape, thus resulting in losses or requiring complicated recovery systems. Moreover, if the gas concentration in the system is too high, the fabric may be damaged. "For all these reasons, it is disadvantageous to proceed at a pH value of less than 3.0. As previously stated, pH; values higher than 3.5 are also undesired because the decomposition of the NaClO proceeds very slowly and hence the bleaching action is decreased and bleaching thus takes place at a slow pace. Moreover, an appreciable 9 amount of NaClO remains undecomposed within the liquid. For all these reasons and particularly since a continuous. procedure is intended, the desirable pH range is 3 to 3.5.

It should also be pointed out that in the indicated pH range, the chlorite has a tendency oxidatively to decompose and thereby to solublize any starch which may still be presenton the fabric. Furthermore, in the indicated range cotton seed refuse is effectively removed. More over, the subsequent high temperature treatment and the treatment with alkaline hydrogen peroxide solution is more effective if the pH value of the chlorite solution is in the indicated range. This is so because it has been found that grease removal is facilitated in this manner.

Various further and more specific objects, features and advantages of the invention will appear from the description below, taken in connection with the accompanying drawings illustrating by way of example a preferred embodiment of a plant adapted to carry out the process according to the invention.

In FIG. 1, the plant is shown in somewhat diagrammatic manner, which is adapted to treatment'of textile fabrics in a continuous way for its scouring and bleaching, while treatment of threads is preferred to carry out in batch system;

FIG. 2 depicts a schematic representation of the process steps employed.

Now, referring to the drawings, the material cloth comprising cotton to a larger or smaller degree, and having been singed and desized is passed around a swivel tension bar 1 and a guide roller 2 in succession and fed through an electro operated cross guider 3 into a first washing vessel-4, wherein it is washed. The washed material advances then through a curved expander 5 to a first squeezing mangle 6 for sequeezing to a sufficient degree. The squeezed material is fed into a. chlorite impregnatingvessel 7, which containsa body of bleaching liquid comprising a solution of sodium chlorite, being activated to the pH 3 to 3.5 by adding thereto a suitable acid, such as formic acid or the like, and including further active surface agents such as those specified hereinabove.

The material thus sufiiciently impregnated with the above bleaching liquid during passage on a plurality of feed and press rollers 8-9 arranged within the vessel 7, is then passed through a second squeezing mangle 10, thereby the material being squeezed to about 100% pick-= up relative to the dry weight thereof. The squeezed material is fed into a closed type first reaction tower 15, 16, 18 wherein it is first subjected to heating by means of steam streams issuing from a number of nozzles 11 and then passed over a plurality of feed rollers 12 to a couple of swing rollers 13 and thence to a swingingly folding plate 14 for folding the fabric. The thus swingingly fed fabric is fed downwardly in folded condition onto several stages of roller couples arranged within the middle portion of the tower 16, each forming a rotatable reception table 17, on which the fed material is stuck provisionally and then fed downwardly after a certain dwell period onto the next adjoining reception table, said material being finally passed into a boiling bleaching bath contained within the lower portion of the tower 18. The constitution of the bath is just the same as that contained in the impregnating vessel 7 already described. The developed gases may be discharged as at 21. The scoured and bleached material is drawn out from the side of the lower part 18 of the tower before settling on the bottom of lower part 18 after passing on several guide bars 19 and led through a liquid seal 20 into a first rear washing vessel 22. The material is guided over several guide and take-up rollers 23-24 and squeezed by a mangle 26 after passage through a pneumatic cross guider and the like. The material is then passed further through second, third. and fourth washing vessels 22-22"', having mangles 27-29. The construction and arrangement of each of these vessels are similar to those of the first vessel denoted by 22 as representative and clear from the draw ing. The material thus cleaned is then transferred into a dechlorizer impregnating vessel 30, which contains a body of diluted hydrogen ,jperoxide having the, already mentioned specific concentration, and after having been sufficiently and evenly impregnated with the liquid, and sub-= jected to suitable squeezing by a mangle, fed into a dechlorizing tower 31, which has a similar construction and arrangement to thoseiof the first mentioned tower. Thus, the detailed description of the operating mode in the second tower may be dispensed with for simplicity. In this way, the material finally treated with the boiling alkaline peroxide solution contained within the lower part of the second tower 31 for vbleaching and dechlorizing, is then led through a plurality of washing vessels 32-36 for enough cleaning and dried finally by passage through dryer 37, thus providing thefinal products satisfactorily scoured and bleached. Incidentally, treatments within the first and second towers arecarried out at elevated temperatures of to C. and the operation of turnable tables 17 is brought into effect intermittently by automatic drive means (not shown).Dwellings of the material on the turnable tables will contribute to provide enough and even scouting and bleaching or dechlorizing effects upon the material under treatment.

Several numerical Q'examples of the process according to the invention willbe given hereinbelow for still further better understanding thereof:

- EXAMPLE 1 Cotton broad or G-poplin, singed and desized, is passed through the aforementioned plant, firstly for enough impregnation of the following liquid mixture by padding:

Sodium chlorite a- 25 kgs.

Scourol- 0.5-0.3 kg.

Water lit.

Formic acid Suitable quantity for adjusting pH to 3-3.5.

The padded material is squeezed in the plant to a 100% pick-up. If the material to be padded is yet wet after desizing, the concentration of the above mixture must be correspondingly adjusted in consideration of the contained aqueous moisture.

The thus impregnated material is treated in a steam atimosphere within the. first reaction tower of the plant at a temperature ranging from 80 to 85 C. for about 20 minutes. After passing through the second hot chlorite bath located at the bottom of the tower (having substantially the composition indicated above) for a period of about 5 minutes, it is then washed with water, and then padded again while wet with a liquid containing 1.5% of 35% hydrogen peroxide by weight relative to the liquid, together with a suitable quantity of sodium silicate for adjusting the pH value to about 10. The liquid may preferably contain a suitable quantity of alkali, such as causic soda, in order to avoid the possible hydrolysis of the silicate. The thus padded material is then mangled to 100% pick-up, heat treated at temperatures between 85 and 90 C. for about 15 minutes in the sealed reaction tower, washed and dried.

EXAMPLE 2 Raw flannelet, sized or desized, as the case may be, is passed through the aforementioned plant, firstly for enough impregnation of the following liquid mixture by padding:

Sodium chlorite 25 kgs.

Lavepon-TH, H/ C 0.5-0.3 kg.

Water 100 lit.

Formic acid suitable quantity for adjusting pH to 3-3.5.

The padded material is squeezed in the plant to a 100% pick-up. The thus impregnated material is treated in the presence of steam within the first reaction tower of the plant at a temperature between 80'and 85 C. for about 15 minutes. After passing through the second boiling chlorite bath of essentially the composition indicated above for a period of about 5 minutes, it is then washed with water and thereafter padded while wet with a liquid containing about 1.5% of 35% hydrogen peroxide by weight relative to the liquid, added with a suitable quantity of sodium silicate for adjusting the pH value to about 10. The thus padded material is then mangled to a 100% pick-up, heat treated at temperatures between 85 and 90 C. for about 15 minutes in the second reaction tower washed and dried.

EXAMPLE 3 Raw corduroy, while grey without desizing, is bleached substantially in the same manner as set forth in Example 2 wherein, however, the concentration of the sodium ehlorite is adjusted to 1.5-2.0%.*In this way, equally superior results are attained.

EXAMPLE 4 A previously signed fabric is subjected to the following successive steps:

(I) Simultaneous desizing and refinining (in this step the fabric is maintained in an extended unfolded state) Percent Sodium hydroxide 1.5-2.5 An alkali salt or an ester of Carosacid 1-2 An anion type of surface active agent as detergent -3 .5

the percentage being based upon the starting weight of the fabric. The fabric is then squeezed to a pick-up rate of about 100%, conveyed into a closed type of reaction tower and folded therein and' subjected to steam heating for a period of 20-45 minutes atabout 100 C. Thereafter, the fabric is conducted into a second tank arranged in the lower part of said reaction tower and communicating with the tower space. The tank holds a solution of the aforementioned chemicals at a concentration of about fiaof that in the first tank-4hr." addition of chemicals to the tank content is performed only once at the start. The fabric is subjected in this solution to a temperature of about 90-l00 C. for a period of 5-10 minutes. Then, the fabric is drawn out from the tank, washed, brought to neutral reaction, again washed and squeezed.

(II) Bleaching by ehlorite After finishing the desizing and refining step of I above, the fabric is fed into a saturator containing a solution which is prepared so as to contain:

Percent Sodium ehlorite (as 85% solution) 1.0-1.5 An anionic or nonionic surface active agent or a mixture of both 0.1-0.3

the percentage being based upon the starting weight of the fabric, and adjusted to a pH of approximately 3-3.5 by the addition of formic acid or another organic acid. The fabric is then squeezed to a pick-up rate of about 100% and steam heated at 75-90".C, for -25 minutes in a reaction tower of the same construction as employed in the step I, the heating time being variable according to the kind of fibers constituting the fabric. After transferring into a tank in the 'bottom of the tower space and containing a solution of the abovementioned chemicals at a concentration of /s-% of that in the saturator and stepping in this solution at about 90100 C. for 5-10 m nutes, the fabric is drawn out from the tank, washed and squeezed (in some cases, it is possible to finish both the teps of washing and squeezing in a total period as short as 5-6 minutes).

(III) Treatment with hydrogen peroxide The object of this step is to obtain various effects such as dechlorination, further increases of bleaching effect, securing of permanent whiteness and higher-degree of grease removal (degree of refining). Thus, the fabric emanating from the process step II above is fed into a saturator containing a solution of Hydrogen peroxide (as 35% solution) percent 0.3-0.5 Sodium hydroxide g./l 0.06-0.1 Sodium 'metasilicate (water glass) g./l 0.3-0.5

the percentage being based on the starting weight of the fabric, and having a pH adjusted to about 11. After squeezing to a pick-up of about 100%, the fabric is steam heated at about C. for 15-20 minutes in the aforesaid reaction'tower, cooked therein at a temperature of about C. for 5-10 minutes in a hot solution containing the abovementioned chemicals at a concentration of /s% of that in the saturator and then washed and dried. (Also as regards this process step, it is possible in certain circum stances to finish both steps of washing and drying in a total period as short as 5-6 minutes.)

It will be clear from the foregoing that according to the invention, a novel scouring and bleaching process is provided which mainly comprises substantially: a first treating step of material, normally singed and desized, being directly subjected to the action of a solution of alkali salt of chlorous acid which has been activated by addition thereto of a suitable quantity of a different acid, at relatively higher temperatures for a relatively short period, said solution further including anion activator belonging to alk'yl-aryl sulfonic acid series, as main component of additives serving as penetrating detergents, and a second treating step of the thus treated material being subjected to the action of a hydrogen peroxide solution for a relatively short period. According to the invention, it will be now clear that the several following advantages are realized:

At first, the novel process dispenses with the conventional elaborate alkali boiling process and provides nevertheless a simple and ideal scouring and bleaching process having an amazingly improved efiiciency. While according to the conventional process the successful scouring and bleaching after desizing amounts normally in its duration to 15-16 hours, only 20-30 minutes will sufiice according to the novel process according to the invention, yet with equal or rather superior results. Although several grave disadvantages are, as already described, inherent to the conventional process relying mainly upon the alkali boiling, not only at least equal results in connection with the wettability by water and the whiteness of the finished products are obtained according to the invention, but also rather superior results from the viewpoint of the durability of whiteness, the durability against elevated temperatures, and the strength of the treated products, the scouring and bleaching losses, the possible deteriora tions and adverse effects, the frictional and folded damages, strips and other mechanical defects caused on and in the treated products are realized by the present novel process.

Whilea preferred embodiment of the novel process, as well as several numerical examples thereof, have been described in detail hereinabove, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention as reci ed. in t e ppended claims.

What is claimed is:

1. In a continuous textile fabric bleaching process, wherein the fabric is first padded with an acidified aqueous chlorite solution containing minor amounts of anionic surface active agent, is then heated and after washing is thereafter subjected to the action ofv an alkaline aqueous solution of hydrogen peroxide, the improvement which comprises that the fabric in the recited sequence is:

(a) padded with a surface active agent containing acidified chlorite solution having a pH of about between 3 to 3.5;

(b) heated for a period of about 15 to 20 minutes in a steam atmosphere at a temperature of about 80 to 85 C. in a substantially closed system;

(c) passed through a hot chlorite solution of a pH of about between 3 to 3.5 in folded, unstretched condition in said closed system;

(d) washed;

(e) padded with an alkaline hydrogen peroxide solution;

(f) heated for about to minutes at a temperature of about between 85 to 90 C. in a steam atmosphere in a substantially closed system;

(g) passed through a hot alkaline hydrogen peroxide solution; and

(h) washed and dried.

2. The process of claim 1, wherein said hot chlorite solution and fabric are contacted in said closed system at a temeprature of about 80 to 85 C. for a period of 1 to 15 minutes.

3. Ina continuous textile fabric bleaching process, wherein the fabric is first padded with an acidified aqueous chlorite solution containing minor amounts of anionic surface active agent, is then heatedand after washing is thereafter subjected to the action of an alkaline aqueous solution of hydrogen peroxide, the improvement which comprises that the fabric in the recited sequence is:

(a) padded with a surface active agent containing acidified chlorite solution having a pH of about be tween 3 to 3.5;

(b) squeezed to a fixed pick-up rate;

(c) heated for a period of about 15 to minutes in a steam atmosphere at a temperature of about 80 to 85 C. in a substantially closed system;

(d) folded;

(e) passed through a hot chlorite solution in un stretched condition at a temperature of 80 to 85 C. fora period of 1 to 15 minutes in said closed system, said hot chlorite solution having a pH of about 3 to 3.5;

(f) washed;

(g) padded with an alkaline hydrogen peroxide solu= tion having a pH of 9 to 11;

(h) squeezed to a fixed pick-up rate;

(i) heated for about 10 to 15 minutes at a temperature of about between 85 to 90 C. in a steam atmosphere in a substantially closed system;

(j) passed through a hot alkaline hydrogen peroxide solution having a pH of 9 to 11 for 1 to 10 minutes; and

(k) washed and dried.

4. In a continuous textile fabric bleaching process, wherein the fabric is first padded with an acidified aque ous chlorite solution containing minor amounts of anionic surface active agent, is then heated and after Washing is thereafter subjected to the action of an alkaline aqueous solution of hydrogen peroxide, the improvement which comprises that the fabric in the recited sequence is:

(a) padded with a surface active agent containing acidified chlorite solution having a pH of about be tween 3 to 3.5;

(b) squeezed;

(c) heated in unstretched condition for a period of about 15 to 20 minutes in a steam atmosphere at a temperature of about to C. in a substantially closed system;

((1) passed through a hot chlorite solution in unstretched and folded condition at a temperature of 80 to 85 C for a period of 1 to 15 minutes in the same closed system as step (c), while maintaining the pH of said hot chlorite solution at a value of about 3 to 3.5 While the fabric is passed therethrough;

(e) washed;

(f) padded with an alkaline hydrogen peroxide solu tion having a pH of 9 to 11;

(g) squeezed;

(h) heated for about 10 to 15 minutes at a temperature of about between 85 to C. in a steam atmosphere in a substantially closed system;

(i) passed through a hot alkaline hydrogen peroxide solution having a pH of 9 to 11 for 1 to 10 minutes; and

(j) washed and dried.

' References Cited UNITED STATES PATENTS 7/1964 Syan et al. tttttttt 8-108.5

OTHER REFERENCES MAYER WEINBLAIT, Primary Examiner US. Cl. X.R.

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