US2433661A

US2433661A - Method of bleaching

Info

Publication number: US2433661A
Application number: US472053A
Authority: US
Inventors: Clifford A Hampel
Original assignee: Mathieson Alkali Works Inc
Current assignee: Mathieson Alkali Works Inc
Priority date: 1943-01-11
Filing date: 1943-01-11
Publication date: 1947-12-30
Anticipated expiration: 1964-12-30

Description

; iiii-ciiiaib i Stab FIP83U9 XR 2s453166l.

UNITED STATES ATENT" OFFICE METHOD OF BLEACHING Clifford A. Hampel, Painesville, Ohio, assignorto The Mathieson'Alkali Works, Inc., New York, N. Y.., a corporation of, Virginia No Drawing. Application January 1 1, 1943,

Serial No. 472,053

9 Claims. (Cl. 8-109) This invention relates to an improved process for eifecting color improvement or bleaching of non-cellulosic organic materials. The invention is applicable to' the treatment of a Wide variety of such materials including the following: Carbohydrates such as sugar and starch; synthetics such as acetate rayon and nylon; sponges: walnut shells; resins, such as shellac; oils, fats, waxes, soaps and the like and fatty acids, such as oleic acid .or red oil. 10

The application: of my present invention to the bleaching of cellulosicmaterials is described and claimed in my co-pending application, Serial No. 412,438, filed September 26-, 1941, granted July 18, 1944 as Patent No. 2,353,823, of which my present application is in part a continuation.

In accordance with the process of my present invention, the material to be bleached is subjected to the simultaneous action of a chlorite and a persulfate in the presence of water. Advantage- 29 ously, the material being treated is admixed with the chlorite and a persulfate in aqueous solution, the pH of the solution during the bleaching operation generally being maintained at not less than about 7.

The term persulfate is employed herein and in the appended claims to designate a salt of persulfuric acid, i. e. HzSzOs. The use of'persulfates of the alkali metals and alkaline earth metals, especially sodium persulfate, NazSzOa, and 30 potassium persulfate, K2S2Os, has been found particularly desirable.

Various methods have heretofore been proposed for the bleaching of organic materials. Many of such methods have involved the use of acids and other strong chemicals which have a tendency to injure the material being bleached or require very careful, critical control to avoid such injury.

Many of these previously proposed bleaching 4Q methods, especially those involving the use of acid solutions, tend to char or cause an undesirable reaction between the organic material and the acid constituent of the solution and are not applicable to the treatment of many materials can economically be lkaline'oisifbstantfdfiy neutral aqueous solution in the presence of a: persulfate, as hereinafter more fully described.

The function of the persulfate in my improved bleaching process appears to be that of activat- 'ing the chlorite rather than a direct action upon the organic material itself. Thus activated, the chlorites,'or reaction products thereof, are enabled to effect the bleaching of the organic mate-. rial either in-an alkaline or substantially neutralenvironment.

Chlorites useful inmy. process are those suffie ciently soluble in water to provide an adequate concentration toeffect the desired bleaching. When the bleaching requirement is'relatively-low, less soluble chlorites. may be used. However, for most purposes, I prefer the chlorites 0f the alkali and alkaline earth metals, such as sodium chlorite, NaClOz, and calcium chlorite, Qa(Cl O Temperatures and concentrations are a ct usually critical and may be varied over a wide range. Increasing the temperatures has generaally been found to increase the rate ofbleaching, Also, the ratio of chlorite to persulfate may be widely varied. However, a molar ratio of chlorite to persulfate of about 2:1 has been found generally useful.

The optimum operating conditions, with respect to temperature, concentration and ratio of chlorite to persulfate, are to a considerable extent interdependent and' will vary with the, particular material being bleached, the degree of bleaching required, the length of the period of treatment and, to some extent, with the particular chlorite and persulfate employed.

The temperature best suited for-a particular operation will, to a considerable extent, depend upon the nature of the materialbeing treated. Ordinary room temperature may frequently be employed with advantage but higher temperatures are usually desirable when treating material normallysolid where it is desired to eifect the melting or'solution thereof. Temperatures at which the material being treated becomes unstable or at which the material is deleteriously affected are to be avoided.

Though the hydrogen ion concentration of my improved bleaching solution may be varied over a considerable range, a decided acid condi: tion of the solution is generally to be avoided, as previously noted. Where the material being treated has an acid reaction, I have found it usually desirable. to employ a buffer to maintain the solution substantially neutral, 1. e., about pH 7, or on the alkaline side. The use of a buffer having the characteristics and in sufficient quan- V 3 tity to maintain the solution at a pH of about 7 is generally desirable in the treatment of material such as oils and waxes. In the bleaching of soap, a higher pH is usually desirable and no buffer need be employed.

Generally satisfactory results have been obtained where the pH is maintained at about '7 or higher, for instance Within the range of about '7 to about 11. While solutions having a pH slightly lower than '7 may be used in the treatment'of acid materials such as fatty acids and of various other materials with good results, a pH substantially on the acid side should generally be avoided.

Alkali metal phosphates such as the monosodium and disodium orthophosphates have been found to be particularly advantageous buffers for the purpose of the present invention, though other buffers may be used with advantage. I have found that in the presence of such phosphates the consumption of chlorite in the bleaching operation is materially reduced. In some instances a saving of 50% of chlorite has been eiiected by the use of these phosphates, in conjunction with the other constituents of my bleaching solution previously noted.

As applied to the bleaching of oils, fats, waxes, soaps and the like, my invention is particularly useful in the treatment of either natural or synthetic materials of this type, including uneaponifiable petroleum waxes and saponifiable oils and waxes such as beeswax, carnauba wax, candelilla wax, corn oil and soya bean oil. It is especially applicable to the bleaching of soaps and similar alkaline reacting materials.

The consumer market of sugar requires a highly bleached product. Also, in numerous commercial uses of starch, current trade requirements necessitate bleaching and the attainment of a high degree of whiteness while at the same time precluding any substantial chemical reaction with the starch. By my improved process, sugars and starches may be bleached without deleteriously affecting the product or imparting thereto objectionable tastes or odors.

It will be recognized that in a strictly scientific sense there are a great variety of so-called sponges. Some of these are composed of hard, calcareous or siliceous substances. However, the familiar bath sponges which are the remains of marine animals belonging to species of the genera Euspongia and Hippspongia are made up of horny fibers closely resembling silk in composition. It is to the bleaching of the familiar bath sponges which the present invention relates.

In their natural state these sponges are of a dark color and unattractive appearance. The desirability of bleaching sponges to improve their appearance and salability has heretofore been recognized. Though sponges have been bleached to a greater or less degree, such color improvement has generally been accomplished at the expense of durability of the sponge if excessive bleaching is effected.

By my improved bleaching method, the sponges may be bleached to an exceptionally high degree with no substantial tendering or weakening of their fiber structure so that their normal resistance to tearing apart in use is not substantially impaired.

The bleaching of starch, in accordance with my present invention, is with advantage effected by subjecting the starch to the action of the chlorite and the persulfate while in aqueous suspension. The bleaching of sugar, oils, fats, waxes, soaps, shellac, fatty acid and the like is with advantage effected by treating the material while in a liquid condition, 1. e. either molten or in aqueous solution, depending upon the characteristics of the particular material being treated.

For example, such materials, either molten or in aqueous solution, may be admixed with the chlorite in the presence of water and the persulfate thereafter added or the material to be treated may be admixed with the persulfate in the presence of water and the chlorite added to this mixture. The resultant mixture is maintained at a temperature usually ranging from room temperature to about 100 C., for a period of time sufiicient to effect the desired bleaching and is thereafter'cooled and separated.

" I In the bleachinggof soap, for instance, the soap may be melted by heating in water, the soap solution admixed with an aqueous chlorite solution and the desired amount of persulfate there- Example I 118 parts of crude reddish brown colored shellac was dissolved in 11.8 parts of soda ash and 1,000 parts of water by boiling for about 15 minutes. The solution was then passed through a coarse screen to remove foreign matter. To 100 parts of this solution there was added 20 parts of an aqueous sodium chlorite solution containing 50 grams per liter of available chlorine and 20 parts of a sodium persulfate solution containing 50 grams per liter of sodium persulfate. The solution was permitted to stand for one hour at a temperature of 40 C. At the beginning of this period the pH of the solution was 8.1, and at the end thereof the pH had dropped to 6.85. Thereafter the shellac was precipitated by dilution to about 8 volumes with water at C. and acidification with 5% H2SO4 until the mixture was just acid to litmus. The precipitated shellac was filtered, washed and spread on trays to dry at a temperature of about 40-45 C. The resulting shellac was a very desirable light cream color.

As a check, the shellac wastested with the same concentration of sodium persulfate and of sodium chlorite alone. The latter bleached the shellac only slightly, and the persulfate bleached it not at all.

Example II .A stock solution was prepared by dissolving 500 grams of brown sugarin water and making up the solution to ,1 liter. To cc. of this stock solution there was added 20 cc. of a solution of sodium chlorite containing 50 grams per liter of available chlorine and 20 cc. of a solution containing 50 grams per liter of sodium persulfate. The solution was buffered at a pHof 8 by the presence of a phosphate buffer and allowed to stand for one hour at 40" C. At the end of this period the pH had dropped to 6.85 and the solution was substantially colorless, Control tests using sodium chlorite and sodium persulfate alone under the same conditions caused no bleaching whatever.

W038 REiERENQE ageaeei A: 10 gram sample ofacetaterayon fabric was immersed for two-hours in. 200 cc. of an'aqueous solution at 40 0. containing 0.4:gram of available chlorine as sodium chlorite and 0.4 gram of sodium; persulfate; the; pH of the solution being about 8. Thereafter the fabric was removed, rinsed and dried',. ,and.,the brightness thereof found to be considerably improved.

ExampleIV 50 parts of crude corn oil was heated in a boiling water bath to a temperature of about 100 C. and agitated by the passage of steam therethrough. 10 parts of anaqneous solution containing 0.5.part of available chlorine as sodium chlorite and 0.3 part of sodium persulfate were then added, and the steamingc'ontinued for one hour' the' pHof the solution being maintained at about neutral. At the endoflthis period the available chlorine had been consumed. and the oil was separated and drawn. on. The resulting oil product was found to be bleached to an excellent light color, almost water white.

Example: V

50 parts of a deep yellow cottonseed oil was treated by the same procedure of. the preceding example and the resultant oil was similarly bleached, though it'did'not separate as readily as did the corn oilof thepreceding example.

Example VI 50 parts of dark colored beeswax was melted in a boiling water bath and agitated by the passage of steam therethrou'gh. An aqueous sodium chlorite solution containing 05 part of available chlorine in 10 parts of solution was addedto the melted wax and this was followed by the addition of 0.5 part of sodium persulfate in 10 parts of water, about 10% of the sodium persulfate solution being added at 5-minute intervals. After one hOur of steaming at a temperature of about 100 C. and a pH of about '7, the available chlorine was completely consumed and the wax then sep arated. On cooling, the wax Was found to be of a very good white color. Steaming of the dark colored wax for 2 hours in the absence of the chlorite and sodium persulfate had no effect on the color.

Example VII 200 parts of yellow laundry soap was melted in a boiling water bath and agitated by the passage of steam therethrough as before. 3 parts of available chlorine as sodium chlorite in about 45 parts of aqueous solution was then added followed by 5 parts of an aqueous solution containing'0.6 part of sodium persulfate at 10-minute intervals until parts of the solution had been added. After steaming for five hours at a temperature of about 100 C. and a pH of about 9.3, all available chlorine had been consumed. The soap was then salted out, separated and poured into molds to set. By this treatment. the soap product was bleached to a very light color.

Ewample VIII To 25 parts of crude cornstarch having a greenish tint suspended in 200 parts of water and buffered at a pH of 8, there was added 20 parts of an aqueous sodium chlorite solution containing 1 part of available chlorine as sodium chlorite and 1 part of sodium persulfate in 20 parts of water. The mixture was maintained at a temperature of 6 50. 0;: for one: hour, and: at the end ofthis'period thestarch was filtered: and washed. The product was of a fine white. color, entirely free from any undesirable tint.

Example IX Example X To 50 parts of red oil (oleic acid) heated in a boiling. water bath to a temperature of about (EL-and agitated by'the passage of steam therethrough, there was added 1 part of available chlorineassodium chlorite in 10 parts of aqueous solution. An aqueous solution containing 1 part of sodium persulfate in 10 parts of solution was prepared, and. one-tenth of this solution was added at 5-minute intervals until the total had been added. After the final addition, about one hour of-s-teaming was required to utilize all the available chlorine. At the end of this period, the fatty acidwas separated and was found to be. of a very pale yellow color.

By my improved process a high degree: of bleaching may thus be accomplished with econ- .om-y in time andchemi-cals while avoiding deleteriously affecting the material being treated and the'necessity of critical control of time, temperature and concentration heretofore required to avoid injuring the material.

I claim:

1. In the bleaching of non-cellulosic organic materials, the improvement which comprises subjecting the material to be bleached to the action of an aqueous, substantially non-acidic solution containing a compound selected from the group consisting of chlorites of alkali metals and alka-" line earth metals and a compound selected from the group consisting of persulfates of alkali metals and alkaline earth metals.

2. In the bleaching of non-cellulosic organic materials, the improvement which comprises subjecting the material to be bleached to the action of an aqueous solution containing a compound selected from the group consisting of chlorites of alkali metals and alkaline earth metals and a compound selectedfrom the group consisting of persulfates of alkali metals and alkaline earth metals at a pH of about 7-11.

3. In the bleaching of non-cellulosic organic materials, the improvement which comprises admixing the material to be bleached with a compound selected from the group consisting of chlorites of alkali metals and alkaline earth metals and a compound selected from the group consisting of persulfates of alkali metals and alkaline earth metals in the presence of Water at a pH of about 7-11.

4. In the bleaching of non-cellulosic organic materials, the improvement which comprises admixing the material to be bleached with a compound selected from the group consisting of chlo rites of alkali metals and alkaline earth metals and a compound selected from the group consisting of persulfates of alkali metals and alkaline earth metals in the presenceof Water, and main- EARCH RUQl taining the hydrogen ion concentration of the mixture at a pH of about 7-11 by the presence of an alkali metal phosphate buffer.

5. In the bleaching of non-cellulosic carbohydrates, the improvement which comprises subjecting the carbohydrate to the action of an aqueous solution containing a compound selected from the group consisting of the chlorites of alkali metals and alkaline earth metals and a compound selected from the group consisting of persulfates of alkali metals and alkaline earth metals at a pH of about 7-11.

6. In the bleaching of starch, the improvement which comprises subjecting the starch to the action of an aqueous solution having a pH of about 7-11 and containing a compound selected from the group consisting of chlorites of alkali metals and alkaline earth metals and an alkali metal persulfate.

7. In the bleaching of starch, the improvement which comprises subjecting the starch in aqueous suspension to the action of an aqueous solution have a pH of about 8 and containing a compound selected from the group consisting of chlorites of alkali metals and alkaline earth metals and an alkali metal persulfate for a period of about one hour at a temperature of about 50 0., about part of available chlorine as the chlorite and about A; part of the persulfate being used per part of starch by weight.

8. In the bleaching of sugar, the improvement which comprises subjecting the sugar in aqueous solutionto the action of an aqueous solution containing a compound selected from the group consisting of chlorites of alkali metals and alkaline earth metals and a compound selected from the group consisting of persulfates of alkali metals and alkaline earth metals at a pH not less than about 7.

9. In the bleaching of sponges, the improvement which comprises subjecting the sponges to the action of an aqueous solution containing a compound selected from the group consisting of chlorites of alkali metals and alkaline earth metals and a compound selected from the group consisting of persulfates of alkali metals and alkaline earth metals at a pH of about 7-11.

CLIFFORD A. HAMPEL.

REFERENCES CITED The following references are of record in the file of this patent:

. UNITED STATES PATENTS Number; A Name Date 1,880,046 Richter Sept. 27, 1932 2,265,033 Fryer Dec. 2, 1941 1,501,553 Bochter July 15, 1924. 2,020,437 Smith Nov. 12, 1935 1,750,657 Adolph Mar. 18, 1930 2,107,297 Kauffmann Feb. 8,11938 2,145,062 Taylor Jan; 24,1939 2,100,496 Taylor Nov. 30, 1937 2,203,212 Casciani June 4,1940 2,120,678 Parsons June 14, 1938 2,343,048 V Eble Feb. 29, 1944 1. 2,307,684 Kauffman Jan. 5, 1943 2,173,041 Muller Sept. 12, 1939 698,632 Cerf Apr, 29, 1902 FOREIGN PATENTS Number Country Date 1,414 Great Britain 1 1878 479,965 Great Britain Feb. 15, 1938 OTHER REFERENCES White et al., Ind. and Eng. Chem, July 1942, pp. 782-792.