US2326021A - Method of brominating wool - Google Patents

Description

3, 1943- R. L. ERICSSON 2,326,021

METHOD OF BROMINATING WOOL Filed Feb. 26, 1941 I ia Z 79 /1 CSSOI'QL) Patented Aug.- 3, 1943 METHOD OF BROMINATING WOOL Ralph L. Ericsson, East Orange, N. J., assignor to Westvaco Chlorine Products Corporation, New York, N. Y., a corporation of Delaware Application February 26, 1941, Serial No. 380,749

8 Claims.

This invention or discovery relates to methods of brominating wool; and it comprises an improvement in methods of treating wool and woolen goods with relatively large amounts of bromine, often as much as 7 per cent, to lessen shrinkage and produce certain other desirable results, wherein the bromine is used in replenishing a circulating, acid, weak, aqueous bromine bath advantageously having a bromine content in the range between 0.001 and 0.05 per cent, said bath being established and maintained in circulation in contact with the wool and of substantially constant composition, the contact time being brief enough to permit passage past the wool with little depletion prior to replenishment, whereby bromination is conducted under substantially constant conditions until the necessary amount of bromine has been supplied to the wool; all as more fully hereinafter set forth and as claimed.

It is an old proposition to lessen the shrinkage of wool by bromination; by treatment of the woolen goods with bromine water. Little or no bromine is permanently taken up by the wool, and the nature of the chemical actions involved is obscure. The amount of bromine required for satisfactory results with wool is rather large, being usually taken as about 7 per cent on the dry weight of the wool; corresponding to an oxygen value of about 0.7 per cent 02.

These propositions have not passed beyond the laboratory, being found impracticable for use on a factory scale without damage to the wool. None of these propositions has been commereially successful. The action of bromine is violent and rapid. At a temperature of 70 F. bromination may be 92 per cent complete in 90 seconds; that is, 92 per cent of the free bromine in the bath disappears. In passing bromine water through a skein of yarn it is difiicult to avoid over-brominating one portion of the skein and under-brominating another, thereby changing the dyeing and other characteristics. Chlorine produces the same results as bromine as regards lessening shrinkage, but it is even more violent in its action. It is cheaper but not as easy to use in obtaining a smooth action.

What happens to woolen goods treated with bromine to reduce the shrinkage is a controversial question. The result of lessened shrinkage, however, occurs and it is a problem in the art to secure this lessened shrinkage without damage to the other physical properties of the wool.

I have found that in order to obtain constant of factors must be considered. In a general way, using low temperature and an acid pH lessens the rate of action and makes operation smoother. But I also find that it is especially desirable to use bromine solutions of low concentration, advantageously of the order of 0.001 to 0.05 per cent, and to circulate either the bath or the goods, or both, in such a way that an extremely brief time contact factor obtains. It is desirable that the bath liquid passing into and out of the wool emerge without serious depletion and that only enough bromine water be added to the circulation in replenishment to compensate for this depletion.

All other factors in the operation are held constant. Working at a temperature around 50 R, which can be reached without special refrigerating equipment, a pH of about 2 and a weak bromine water within the stated range, the main remaining variable is the time contact factor. This time contact factor is so arranged that weak bromine water contacts with the wool and is removed before complete depletion occurs. As long as the wool comes only in contact with a bromine solution having a concentration within the said range, the results are regular and smooth.

What has been said with regard to brominating is also true of chlorinating, using the stoichiometric amount of chlorine. The violent action of chlorine is moderated.

While the stated process may be applied to wool in any stage of fabrication between the yarn and piece goods, it often happens that piece goods carry dyes afiected by bromine or chlorine. In such cases the process should be applied either to yarn or to raw stock before dyeing. However, with fabrics carrying dyes not affected by bromine, etc., the treatment to render them nonshrinkable may be applied after the textile material has been dyed; even after it has been converted to a fimshed garment such as woolen stockings, Still, and particularly in the case of fabrics containing mixed colors, it is ordinarily better to apply th shrinkage-preventing process of the present invention to the undyed yarn or to the individual skeins of dyed yarn prior to knitting or weaving.

The pH of the treating bath should be kept below 2.0 and it is desirable to employ additions of strong acid, suchlas sulfuric acid, in establishing and maintaining the desired pH of the liquor. An unbufiered bromine solution at the point where bromination ends and the formation of hydrobromic acid has goneto a maximum has a pH in the neighborhood of 3.0. On the whole, it

reproducible results on a factory scale, a number is found that the best results are obtained at the optimum temperature of 50 F. with a consumption of ,bromine (on the wool) of about 7 per cent and a bath containingabout per cent of sulfuric acid (on the W001). W001 sotreated is rendered essentially non-shrinkabl and shows satisfactory dyeing characteristics. Direct use of this amount of bromine is dangerous. But an indirect use by the present method is safe.

It is found desirable to establish and maintain a bromination bath of considerable bulk as compared with the bulk of the wool to be treated, and to establish a rapid cyclic circulation of the bath through the wool, a portion of the circulation being diverted outside for replenishment with bromine and for removal of excess liquor.

For best results, all of the factors discussed hereinabove should be controlled in the manner described. I have found that this can be done without difficulty, and in a simple and economical manner. Control is considerably simplified by th use of a suitable mechanical device or brominator for adding the bromine to the treating solution, and I have devised an effective unit for this purpose, which is inexpensive, and which may be readily connected to any available type of apparatus in which the vbromination of the wool is to be effected. Various type of ap-' paratus are satisfactory for this purpose, and I may use, for example, a padder, a jig, a dye kettle, or a Franklin type of package unit.

Regardless of the type of apparatus used for the bromination, means for withdrawing solution from the unit and returning it thereto are easily provided. Arubber hose with suitable connections may serve for this purpose. Between the inlet and the outlet, 9. circulatory system is provided, to which my brominator is operatively connected.

A useful type of brominator is illustrated in the accompanying drawing, which illustrates more or less diagrammatically the connection of a brominator to a circulatory system of the type described. The brominator itself consists of a suitable container l0, advantageously of glass. This container need not be large, and a capacity of two or threegallons is adequate, even when large amounts of Wool or woolen goods are to be treated.

The body It] is advantageously provided. with three openings, or connections, indicated at H,

I2 and I3, One of these connections is provided with a funnel l5, or othersuitable' charging device, which is advantageously controlled by valve I6. If the container Illv is made of glass, the connection I2 is advantageously a ground glass joint. Bromine is supplied to the container body through the funnel l5 or other suitable charging device, and in practice, it is generally most convenient to introduce in this waythe amount of bromine to be employed in the treatment of any given batch of goods. For example, if 100 pounds of Wool is to be treated, the required amount,

'such as 7 pounds, of liquid bromine is charged into the body ID of the brominator. The valve I6 is then closed.

The connection I3 is provided or coupled with an elongated inlet pipe l8, adapted to discharge rises through the bromine and passes out through the connection I I. Inlet and outlet pipes are operatively attached to the inlet connection l3 and the outlet connection II, respectively; and means In operation, liquid withdrawn from a dye kettle or Franklin machine, or padder or other equipment used to brominate wool is passed through pipe 23 on its way back to the inlet of the apparatus. If the wood bromination is not effected under pressure, it is generally desirable to increase circulation, as by means of a pump 25 which draws liquid through the overflow line or outlet 26 of the wool-treating vessel (indicated diagrammaticallyat 30) and delivers it through a pipe 21 to the pipe 23.- When bromination of the wool is effected under pressure, it is generally unnecessary to employ a pump to cause the circulation, and the overflow from a Franklin machine, for example, can pass directly into pipe 23 from pipe 28. A valve 29 is provided in the pipe 23, and when this valve is open, the liquid passes directly through the pipe 23 back to the treating vessel.

When operating the brominator shown in the drawing, the first step is generally to establish circulation through the pipe 23 by either of the methods described, the valve 29 being open. At

least one of the valves 20 and 2| is initially closed.

After the brominator I0 is charged with bromine, the valves 20 and 2| are opened, and valve 29 is partially closed. This causes part of the liquid flowing through pipe 23 to flow through valve 20 and the inlet pipe Is to the bottom of the brominator I0. It then flows upwardly through the bromine, forming a bromine solution which passes through the outlet pipe and valve 2| back to the main body of liquid passing through pipe 23. This relatively strong bromine water is diluted by mixture with the liquid flowing directly through valve 29, and is further diluted when it is discharged from pipe 23 into the wool-treating vessel 30.

It is readily possible to ascertain the proper setting of the valves 20, 2| and 29 to cause the desired flow of liquid through the body IU of the brominating vessel. Thus, if it is desired to subject the wool to a twenty-minute treatment under substantially uniform conditions with a total of say 7 per cent of bromine, one or both of the valves 20 and 2| is set in such a manner that the amount of aqueous liquid passing through the brominatorwill dissolve and carry forward all of the bromine in the desired time. This setting is readily ascertained. To prolong the treatment for say thirty minutes, it is merely necessary to close one or both of the valves 20 and 2| slightly. In any case, after the valves have been set in accordance with the desired rate, the brominator requires no further attention.

It is often convenient to mount the brominator H), with or without the pump 25, on a movable truck provided with hose connections adapted to connect with the apparatus in which wool is to be treated. It is frequently desirable to brominate wool in the same vessel in which it is to be dyed, and a portable brominator of the type described may be used successively with several dye kettles or other treating units. It is immaterial if varying amounts of wool are to be treated in each of the units, since the required amount of bromine for any amount of wool may be charged into the vessel I0. After setting'the valves inaccordance with the amount of bromine to be employed and the time in Which it is to be dissolved, no further attention is necessary.

.In a useful embodiment of the invention, 200 pounds of woolen yarn in four-inch skeins or spools was treated in a Franklin-type machine.

was filled with water at a temperature of approximately 50 F., and circulation of the water was started. Ten pounds of concentrated sulfuric acid per cent on the weight of the wool) were added to the circulating water. A brominator of the type described hereinabove was connected to the circulating system and charged with 14 pounds of liquid bromine ('7 per cent on the weight of the wool). The valves on the brominator were given a previously determined setting such that the amount of circulating water by-passed through the brominator dissolved all of the bromine in 40 minutes. During this time, the concentration of bromine in the liquid contacting the wool remained between 0.01 and 0.03 per cent; that is, the relative movement of the bath and the wool was at such a rate that the bromine content was never depleted below 0.01 per cent, and replenishment, due to the action of the brominator, was at substantially the same rate as the depletion. The total amount of bromine was therefore applied ,at a substantially constant concentration. Also, the acidity of the solution remained constantly at a pH below 2, and the temperature of the solution did not vary more than 5 F. during the treatment.

The wool treated in this manner was thoroughly washed with water, and then with sodium carbonate solution to remove retained acid. Tests of various skeins of this wool showed that its physical properties were not adversely affected by bromination. The wool dyed uniformly and wasfound to be substantially free from shrinkage during dyeing, washing, padding and other conventional treatments.

This operation involves a standard pH and a standard temperature; and the one variable is the time contact factor. Conditions of circulation are so arranged that a weak bromine water with the stated concentration range goes into contact with the wool and is removed while it still contain available bromine. The critical matter is thus the speed of circulation of the liquor or of the wool, or both, so as to obtain this result.

In similar operations, it has also been determined that piece goods may be brominated satisfactorily, and without injury, by observing the precautions described hereinabove. One feature of this invention is that the brominating process is applicable to substantially all types of woolen goods.

While the invention has been described with special reference to bromination, it has been found that useful results are also obtained when the stoichiometrically equivalent amount of chlorine is substituted for bromine, provided that the rate of reaction of the chlorine is controlled, as described hereinabove, by regulation of the temperature, acidity and concentration of the solution, and of the time of contact between the woolen goods and the solution.

As noted, low temperatures tend to reduce the violence and speed of halogenating reactions, and are desirable for that reason. For example, the rate of reaction (e. g., bromine disappearance) is substantially reduced, if the temperature of the treating bath is reduced from 70 F. to 60 F., other conditions remaining the same. The rate of reaction is still further reduced by lowering the temperature to 50 F., and I generally prefer to operate at temperatures in this range. Temperatures of about 50 F. may generally be obtained without artificial refrigeration, and such temperatures assist materially in controlling the reactions.

- tageous.

The acidity of the treating bath is also an important factor, and for the best results, the pH of the bath should be below 2. This acidity tends to restrain the development of hydrobromic acid in the solution, and for this and other reasons, makes it possible to obtain better results. This low pH can only be obtained with strong acids, of which sulfuric acid is generally most advan- In practice, I usually find it advantageous to acidify the treating bath with an amount of sulfuric acid corresponding to about 5 per cent of the weight of the Wool to be treated, although the acid content is not highly critical.

Perhaps even more important than the temperature and acidity of the bath is its halogen concentration. The concentration has a marked effect on the rate of reaction, and dilute solutions react much more slowly than strong solutions. I have found that it is generally desirable to maintain the concentration of the treating solution at about 0.001 to 0.05 per centby weight when using bromine, and it is especially important that the concentration be maintained substantially constant. Since the rate of absorption (or reaction) depends partially on the concentration of the solution, it is clear that completely uniform halogenation can only be obtained when there is no concentration differential in the fluid passing through the wool. However, a concentration differential of zero can only be obtained when the absorption or removal of halogen is also zero. This, of course, could not produce the desired results. However, the amount of absorption and the concentration differential can, in practice, he kept at a minimum so that the results are substantially those theoretically obtainable under perfect conditions. I find that if the solution coming into contact with the wool, and that leaving the wool, both have concentrations within a narrow range, such as the stated range from 0.001 to 0.05 per cent for bromine, the concentration differential is negligible for practical purposes, and uniform results are obtained.

I have also found that, even with dilute solutions, it is necessary to control the time of contact between the wool and the liquid in order to obtain uniform results. This is done by circulating the bath or the woolen goods, or sometimes both, in such a way that an extremely brief time contact factor obtains. As noted, it is highly desirable that the bath liquid pass through the wool without serious depletion; and I find that this result-is best effected by using low concentrations and rapid circulation. Between successive contacts with the wool, the solution is made up to the desired concentration, advantageously by adding only sufficient halogen, preferably in solution, to compensate for the slight depletion during contact with the wool. One feature of this invention is therefore the cyclic recirculation of a dilute bath through a stage in which a very small amount of halogen is removed or absorbed during contact with wool, and through a stage in which its halogen content is replenished. Another feature of the invention is the employment of a solution which at any one time contains far less than the total amount of halogen to be employed in the treatment. For example, if the complete treatment involves the use of 7 per cent bromine on the wool, the maximum concentration of the solution during the treatment may be 1 per cent on the wool, or may be considerably less than 1 per cent.

What I claimis: 1. The process of treating wool to lessen shrinkage without forfeiture 'ofother physical and chemical properties, which comprises effecting contact between the wool and an aqueous solution of a halogen selected from the class consisting of bromine and chlorine, said solution containing available halogen in a concentration equivalent to a bromine concentration in the range between 0.001 to 0.05 per cent and having an acidity corresponding to a pH below about 2 while maintaining the solution at a temperature below 70 F., at which halogenation occurs, and removing the solution from contact with the wool while the solution still contains available halogen in the stated range.

f 2. The process of treating wool to lessen shrinkage without forfeiture of other physical and chemical properties, which comprises effecting contact between the wool and an aqueous solution of a halogen selected from the class consisting of bromine and chlorine, said solution containing available halogen in a concentration equivalent to a bromine concentration in the range between 0.001 to 0.05 per cent and having an acidity corresponding to a pH below about 2 while maintaining the solution at a temperature approximating 50 F., and removing the solution from contact with the wool while the solution still contains available halogen in the stated range.

3. The process as defined in claim 1, wherein treatment is continued until the total amount the replenished solution is again brought into contact with the wool and removed therefrom while having a halogen concentration within the stated range.

5. The process of treating wool to lessen shrinkage without forfeiture of other physical and chemical properties, which comprises efiecting contact between the wool and an aqueous solution of bromine, said solution having a bromine concentration in the range between 0.001 and 0.05 per cent and having an acidity corresponding to a pH below about 2 while maintaining the solution at a temperature below 70 F. at which bromination occurs, and removing the solution from contact with the wool while the solution still contains available halogen in the stated range.

6. The process of treating wool to lessen shrinkage without forfeiture of other physical and chemical properties, which comprises efiecting contact between the wool and an aqueous solution of bromine, said solution having a bromine concentration in the range between 0.001 and 0.05 per cent and having an acidity corresponding to a pH below about 2 while maintaining the solution at a temperature approximating 50 F., and removing the solution from contact with the wool while the solution still contains available bromine in the stated range.

7. The process as defined in claim 5, wherein treatment is continued until the total amount of bromine taken up is approximately '7 per cent on the weight of the wool.

8. The process as defined in claim 5, wherein the solution is re-utilized by passing the removed solution through an intermediate stage at which its bromine content is replenished and wherein the replenished solution is again brought into contact with the wool and removed therefrom while having a bromine concentration within the stated range.

RALPH L ERICSSON.

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