US569680A - Electrolytic process of bleaching and refining - Google Patents

Description

B. S. & L. L. 'SUMMERS ELEGTROLYTIO PROCESS or BLBAGHING AND REPINING. 4No:15.69.680.

Patented Oct. 20,l 1896.;

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BERTRAND S. SUMMERS AND LELAND L. SUMMERS, OF CHICAGO, ILLINOIS.

ELECTROLYTIC PROCESS OF BLEACHING AND REFINING.

SPECIFICATION forming part of Letters Patent No. 569,680, dated October 20, 1896.

Application filed November 29, 1895. Serial No. 570,394. (No specimens) To @ZZ 'Lz/'7mm it may concer/L.-

Be it known that we, BERTRAND S. SUM- MERS and LELAND L. SUMMEES, citizens of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in Elcctrolytic Bleaching and Refining Processes, (Case No. 2,) of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

Our invention relates to an electrolytic bleaching and refining process, the object of our invention being to provide an improved method of bleaching and rening various fibers and materials employed in the arts without impairin g the strength of the materials, and, furthermore, to provide an improved process of degumming, bleaching, and

refining the vegetable fiber known in the arts as ramie or chinagrass Various substances have been chemically employed heretofore for bleaching purposes, most notably chlorin, sulfur, and the caustics; but these processes of bleaching are not satisfactory, as the bleaching agents thereof are so active that unless certain precautionary measures be adopted, entailing time and labor, the action is such as to affect the strength of many fibers or materials, either by producing immediate disintegration or by so impairing the strength that after a short lapse of time the fibers fall to pieces.

XVe have discovered that certain chemical agents, such as the commercial hydrates, will, when electrolyzed, yield bleaching agents at the positive pole in a solution giving an alkaline reaction at the positive pole. The presence of the alkaline solution at the positive pole results in a very effective bleaching action, which, however, with certain fibers may produce a destructive action, and to prevent this certain agents may be used, which, however, may cause the production ofa reaction at the positive pole neutral or even acid in character, as, for instance, when a fluoride is added to the bath. TVe have employed sodium fluoride, potassium fluoride, and cryolite. By varying the strength of the current a reaction, resulting in either an acid or an alkaline solution at the positive pole, may be produced, and this result is obtained even when the quantity of fiuoride is small as compared with the quantity of hydrate. In practice the quantity of each and the strength of the current are so proportioned as to maintain theA -acid reaction at the positive pole.

le have successfully employed various of the alkaline hydrates for bleaching purposes after the manner of our invention,v but in practice preferably employ sodium hydrate upon the material to be bleached, and to pre-v vent this we add a fluoride to the bath, as above described.

The solution of the hydrate is placed inthe electrolytic cell and the positive and negative electrodes are immersed in the solution, the material to be bleached being immersed in the solution in the vicinity of the positive pole. A porous partition or diaphragm is interposed between the two electrodes, which for best results should be non-permeable to diffusive action, while readily pervious to the electrolytic action. The solutions resulting from the electrolytic action are thus confined to their respective poles, and the solution present at the negative pole is thus prevented from coming in contact with the material to be bleached, and thereby diminishing the desired electrochemical action upon the material to be bleached, which is immersed in the solution at the positive pole. The bleaching process as thus practiced is very active, and the time during which the material is subjected to the bleaching process must be carefully determined, as too long a subjection to the bleaching process may affect the material. We have discovered, however, that if a iiuoride solution be added to the hydrate bath the tendency to affect the strength of the material on extended or continued subjection of the material to the bleaching process is removed, the fluoride possessing the property of counteracting the destructive effect of the bleaching agents. The quantity of the fluoride need not be great and maybe determined for the particular material to be bleached by experiment.

The process, as above described, is adapted for the bleaching of any of the materials, such IOO as pulps, cloths, theanimal and vegetable fibers, and, in fact, any of they substances that are usually bleached in the arts, and is particularly applicable to those materials the fibers of which are easily attacked and are either destroyed or impaired by such bleaching agents as are commonly used in the arts.

We are aware that caustic potash and caustic soda have been employed for chemically bleaching materials, the`bleaching being due to the direct chemical action of the hydrate on the coloring-matter; but by the present electrolytic process itis not the hydrate in itself that effects the bleaching process, but the products liberated therefrom by the electrolytic action, and we find that the same hydrates have a very different effect when employed for electrolytic bleaching from that which they have when employed for chemical bleaching.

l/Ve find our process particularly adapted to the preparation of the fibers of'k ramie or china grass, which possess a remarkable strength when properly prepared, but which -are very susceptible to the action of bleaching agents and are readily weaken ed thereby. Some bleaching agents have the effect of immediately destroying the fibers, while others so im pair them in strength that after the lapse of a short time they disintegrate and fall to pieces.

In an application filed by Bertrand S. Summers and Charles O. Boring November 4,-

1895, Serial No. 567,847, an electrolytic process of removing the gums and cementing material from the fibers of ramie and other vegetable fibers is described, according to which process the fibers are subjected to the action of a fiuoride bath.

We find that` by the employment ofthe bleaching process of the present invention in connection with the degumming process of the above-mentioned application a better product can be secured than by the employment of the said degumming process alone. In practicing the invention we may first subject the ramie fibers to the hydrate bath,

which also has the property of removing a large proportion of the gum Vor cementing material, the fibers being thus separated and bleached. After the fibers have been subjected to the hydrate bath they may be removed and immersed in the fluoride bath and the process completed. It is preferable when the invention is thus practiced in separate baths to place a small quantity of the fluoride solution in the hydrate bath in order that the fibers may not be impaired in strength by the action of the bleaching agents.

When the fibers are removed from the hydrate bath, it will be found that they are somewhat harsh, and not soft and delicate, as is desirable. After placing in the fiuoride bath, however, the harshness will be found to be completely removed, the fluoride bath, when employed with the hydrate bath, serving to refine the fibers, either by the further and complete removal of the gum or cementing material 'or by the removal of the silica or other substances which may remain in the fibers.

Instead of employing separate hydrate and uoride baths the two may be combined, and instead of adding only sufficient fluoride solution to the hydrate bath to prevent the destruction of the fibers during the bleaching process a sufficientquantity of the fluoride may be added to eect the complete refining and softening of the fibers, the complete process of degumming, bleaching, and refining the fibers being thus effected in the single bath. XVe prefer, however, to employ separate hydrate and fluoride baths, as better results are obtained thereby.

We have illustrated the apparatus for practicing our invention in the accompanying drawings, in which- Figure l is a view of an experimental apparatus which we have employed for bleaching purposes. Fig. 2 is a view of apparatus which we have employed for the refining process. Fig. 3 is a view of apparatus as designed for practical use.

Like letters refer to like parts in the several figures.

Within a jar or retaining vessel ct is supported a porous vcup b. Within the cup b, having an opening b3 in the bottom to lower the electrical resistance of the bath and to maintain the level of the liquid the same upon the inside and the outside of the cup, is supported a partition h', beneath which is the positive electrode c, the negative electrode CZ being immersed in the solution upon the eX- terior of the porous cup. The positive and negative electrodes are connected with a source of electricity e, and the electrodes are immersed in the bleaching solution, in practice a solution of sodium hydrate. terial to be bleached is supported upon the shelf Z9 or maintained in an immersed position in any convenient manner in the solution within the porous cup. Vhen current is passed through the cell, the bleaching agents are liberated at the positive pole, and thus come in contact with and act upon the material to be bleached.

In Fig. 2 we have illustrated a cell similar in all structural details to that illustrated in Fig. l, and this cell may be employed for the refining process, a liuoride bath being provided in the cell, to the action of which the fibers are subjected.

In Fig. 3 we have illustrated a vat ct', divided into two compartments by a porous partition b2, the positive electrode c being in the form of a large plate occupying a horizontal position, upon which the material to be bleached may be laid or in the vicinity of which it may be suspended. A number of negative electrodes d d are provided upon IOO IIO

the opposite side of the partition b2, the elec- Having described our invention, what we claim as new, and desire to secure by Letters Patent, is-

l. The herein-described method of bleaching, which consists in immersing the material to be bleached in the region of the positive pole in an electrolytic bath containing a hydrate and a fluoride, passing a current of electricity through said bath, and isolating the chemical agents passing to the positive pole which come in contact With the material to be bleached from the agents passing to the negative pole, substantially as described.

2. The herein-described method of bleaching by which the deleterious effects of the bleaching agent are prevented, which consists in immersing the material to be bleached in an electrolytic bath containing a fluoride and a materia-l yielding a bleaching agent when electrolyzed, and passing a current of electricity through saidl bath, whereby the fluoride acts to prevent deleterious action upon the material being bleached, substantially as described.

3. The herein-described process of degumming, bleaching and refining vegetable fibers iniiuence of a bath con taining sodium hydrate and a small quantity of a fluoride, passing a current of electricity through said bath, and then subjecting the iibers to the influence of a fluoride bath, and passing a current of electricity through said bath; substantially as described.

In Witness whereof we hereunto subscribe our names this 22d day of November, A. D.

BERTRAND S. SUMMERS. LELAND L. SUMMERS.

lVitnesses:

W. CLYDE JoNns, GEORGE L. GRAGG.

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