US2339837A - Dye - Google Patents

Description

Patented Jan. 25, 1944 DYE Herbert B. Charmbury, State College, Pa., asslgnor to Pennsylvania Bituminous Coal Research, Inc., Altoona, Pa..' a corporation of Pennsylvania No Drawing. Application March 25, 1941, Serial N0. 385,150

11 Claims. (Cl. 260-644) This invention relates to dyes and woodstains.

The major object of the invention is to provide dyes that are made directly from coal, and more particularly dyes capable of the direct dyeing not only of wool, silk, wood and other natural fibers of lignocellulose, protein-like or carbohydrate nature, but also of synthetic fibers, with production of dyed products which are fast under various conditions to which the dyed products may be exposed.

A further object is to provide a method of making dyes of the foregoing character directly from coal, which is cheap, easily practiced, efiicient, readily controlled, and requires no complicated, expensive or diflicultly operable apparatus.

- The invention is predicated upon my discovery that dyes may be made directly from coal by subjecting the coal to treatment with nitric acid at a temperature above room temperature to effect conversion of reactive carbonaceous constituents of the coal into reaction products capable of dyeing various kinds of fibers. Such reaction products may then be extracted from the treated coal and after separation from immiscible tarry and oily matter, if present, they are adapted for direct use for dyeing or staining purposes.

In the practice of the invention conversion of carbonaceous constituents of coal into brown dyes may be accomplished by treatment of the coal with nitric acid. Any of the coals up to, but not including, anthracites may be used for the purposes of the invention, i. e., the dyestufis made in accordance with the invention may be produced from lignites, bituminous coals, and subor semibituminous coals. Such treatment may be ,effected with the acid in either the liquid or the vapor phase. From many standpoints, however, liquid phase treatment is simpler and more readily controlled, for which reason the invention may be exemplified with detailed reference thereto.

In the practice of the preferred embodiment of the invention nitric acid and the coalare mixed at room temperature, most suitably by adding the acid to the coal. Thereupon an exothermic reaction sets in which is of such nature that artificial heating of the reaction body isunnecessary. When that reaction has died down the mixture of coal and acid is heated to complete reaction between the nitric acid and the reactive carbonaceous constituents of the coal. Such heating is necessary because, as I have discovered, without it the dyes are not produced.

The temperature attained during the treatment of the coal should not exceed the decomposition temperature of nitric acid under the conditions under which the treatment is effected, for which reason it is desirable to add the acid incrementally to the coal. It is desirable also to operate under a refluxcondenserto minimize acid losses. For most purposes I have found that the reaction is completed smoothly, satisfactorily and relatively expeditiously at atmospheric pressure by heating the reaction body on a water or steam bath, whereby decomposition of the acid does not occur, at least to any excessive or objectionable extent. If desired, the reaction might be carried out at pressures above or below atmospheric.

The proportions of acid and coal used may be varied considerably, although for economic reasons they will depend in part upon the conditions of operation. Thus, in the case of treatmentof coal with solutions of nitric acid in a container provided with a reflux condenser I have found that as the ratio of acid (sp.gr. 1.4) to coalis increased from, for example, one part by weight of each, the amount of dye produced is increased progressively until at a ratio of from'4 to 8 Ipartsof acid to 1 part of coal the yield of the desired dyestuff is apparently at a maximum so that for ordinary purposes under such conditions of operation greaterproportions of acid are of no advantage. In this range where optimum yield is obtained the lower ratios-of acid to coal, say-in the vicinity of 4 to 1 may be used by prolonging the heating as compared with the case where the higher ratios e. g., about 8 to 1, are used. Where, however, the reaction is carried on in containers freely open to the atmosphere, higher ratios of acid to coal may be necessary to obtain optimum recovery of dye. On-the other hand, in vapor phase operation using nitric acidand air the optimum ratio seems to be about two parts by weight of acidto'one part byweight of coal;

Apparently there'is nothing critical in the particle size of the coal'being treated. Tests have shown, for example, that essentially the same results are obtained with coal of one-half inch size as with coal ground to pass a ZO-mesh sieve. 7

After the reaction between the coal-and the nitric acid-hasbeen completed the excessacid is removed and the treated coal is then washed with water to remove residual acid, as by washingwith repeated changes of water.- The acidic liquors may be distilled to recover the acid, and upon evaporatin to dryness a solid product of unknown composition is recovered. The washed and treated coal is then ready for extraction .of the dyest-uif. I have found that two dyestuffs may be Thus, by extraction with certain neutral or, and preferably, acidic solvents there is recovered a brown dyestuff, and if the thus-treated coal be then extracted with alkali there is recovered another brown dyestufi. Or, if thecoal treated as described above be extracted first with alkali, all of the dyestuff of both types is recovered directly, and for many purposes such extraction is preferred.

Referring first to direct alkaline extraction, there may be. used an aqueous solution of an alkali, for instance sodium hydroxide or potassium hydroxide. Ammonium hydroxideis,ihowever unsatisfactory, unless it is very .dilute, ,e. g. about 0.1 normal. Very dilute solutions of other alkalies sufice, and they are preferred for reasons which will appear hereinafter. The extraction may be carried out at room temperature although it is hastened by moderate heating, preferably not beyond about 100 C. The most satisfactory results appear to be had by extraction below about 50 0. Complete extraction of dy from the treated coal will depend upon the volume of solution and the alkali concentration, but multiple extractions with fresh lots of'the alkali solution are desirable, the separate extracts being combined, if desired, for "further treatment.

The alkaline extracts are of brown color, the exact shade depending upon the concentration of dye taken up from the coal. "If th alkali solution usedfor extraction is-sufficiently dilute, say "0.1 normal, the extracts may be used for dyeing. But if concentrated alkalies are used the extracts are useless as dyeing agents 'because they con'tainimmiscible tarry and oily matter which prevents the attainment o'fsa'tisfactory dyeing, and particularly is this the case as the extraction temperaure is raised above room temperature. I have discovered, however, that if such solutions be freed "from the immiscible tarry and oily matter, they, or solutions of the solid dyestuif recovered therefrom, may then "be used directly for satisfactory dyeing of wool, silk, such artificially produced fibers as :those sold under the trade-mark Nylon, and other fibers of generally similar nature. To this end the tarry and oily matter, when present, may beremoved from the alkaline solution in various ways, as by filtering the solution or by the use of selective solvents which will remove the tars and oils butin which the dye is insoluble. Satisfactory separation can be effected also in simple and inexpensive fashion by steam distillation.

The solutions, freed from tarry and oily matter when present, maybe used for direct dyeing. Where it is desirable to have the material in solid form, however, the solutions maybe evaporated to dryness thus producinga soluble .solid which may be redissolved in water to produce dyeing solutions, but when this is done the dye bath should contain sodium sulfate or other equivalent salt the use of which .is understood in the dyeing indutsry. As intimated above, the exact color produced will depend upon the concentration of the solution, whether it be the original or dilute solution of alkaline extract or a solution made from the dried productobtained by evaporation thereof.

In addition to the reason -pointed :out above, thexuse of very dilute solutions .of alkali and-of relatively low extraction temperatures are desirable also because the possibility of damaging the fabric by alkali is minimized. However, where the separation from tarry matterl-ls not iorganic acidic agents.

objectionable, concentrated alkaline extracts may be diluted to avoid damage to the fabric.

As pointed out above, one type of dyestuif may be removed from the treated coal by extracting it first with certain neutral or acidic solvents, and this material appears to be different from that obtained by extracting the treated coal with alkali solutions, although both are brown dyes.

.Neutral extracting solvents may be used for this purpose, but preferably there are used Aqueous solutions of inorganic .acids, such as hydrochloric acid, appear to offer little or no advantage over water, which might be used, astaneutral solvent, but which is not advantageous because the solubility of the dye in it is low and large volumes are needed. Aqueoussolutions of organic acids such as acetic, benzoic and phthalic acids have a considerable solvent effect on the dye, while certain organic acids such as glacial acetic acid appear to give the best results. Other organic acidic materials that may be used are phenol, resorcinol and the like.

Various methods of carrying out the extraction are applicable. It has been found that the use of a standard type of extraction apparatus, such as the 'Soxhlet, gives satisfactory results. The extraction may also be effected simply by agitatinga mixture of treated coal and solvent. In this case it is usually desirable to heat the mixture to the boilingtemperature of the solvent,

since the solubility of the dye increases with increasing temperature.

In a typical test, 25 grains of treated, washed and dried coal was-extracted in a Soxhlet apparatus with .300 cc. of glacial acetic acid during a-period of approximately 72 hours when extraction'was complete. The extracted material was freed from acetic acid by evaporation over a steam bath. The dye thus obtained weighed '4.5;:grams.

The dye Droduced'in this "manner is, after removal of the solvent, a dark brown solid which is somewhat soluble in water. Aqueous solutions of this dye are, .as "in the case of the dyes alkali extracted as described'above, capable of dyeing silk, wool and other fibers brown, the exact shade depending on the concentration. This acid-soluble dye gives lighter shades for the same concentrations than the alkali-soluble dyes described hereinabove, and when celanese and ny lonare dyed with it the dyed fabrics exhibit a fluorescent effect.

The extract after being filtered is optically void in sufiiciently dilute solution, thus showing that "the'dye is in'true solution. Although the exact nature of the reaction by which the reactiveconstituents of coal are converted to dyes is not known, th absorption spectra of solutions produced in accordance with the invention indicates the presence of a carbon-nitrogen linkage in the dye, and analysis by appropriate methods has shown that the dye material containshydroxy and carboxyl groups. The nitrogen content of the treated coal is substantially greater than that of the original coal. Also, the

conditions: as the composition of the coal treated,

the concentration :of nitric acid or other nitrating and oxidizing agent, the temperature and time of reaction, and the like. Under the conditions outlined above, however, it is ordinarily possible to dissolve about 70 to 90 per cent by weight of the coal treated. If the inert constituents of coal, chiefly fusain, mineral matter and water be disregarded it appears that substantially 100 per cent of the coal is converted into the soluble matter.

As an example of actual practice, there was used an upper Freeport coal whose proximate analysis was 7.28 per cent of ash, 31.67 per cent of volatile matter, 1.38 per cent of sulfur, and 0.67 per cent of water, and whose ultimate analysis was 80.59 per cent of carbon, 5.17 per cent of hydrogen, 1.38 per cent of sulfur, 1.35 per cent of nitrogen, and the balance essentially oxygen. This coal contained about 3.5 to 4 per cent of fusain. 100 grams of the coal, ground to pass a 20-mesh sieve, was placed in a 3 litre flask provided with a reflux condenser. A total of 800 grams of ordinary concentrated nitric acid (sp. gr. 1.4) was added in small amounts at a time, the rate of addition being such as to keep the temperature of the mass below the decomposition temperature of the acid without resort to artificial cooling. After about 400 grams of the acid had been added the reaction subsided to a point such that the flask with its condenser attached was placed on a steam bath on which it was heated thereafter, and the balance of the acid was added gradually. About three hours was consumed in addition of the acid. The flask and its contents were then heated for one hour longer, after which heating was discontinued. One hour later the contents of the flask were filtered through a fiber glass mat, and the coal retained on the mat was then washed with distilled water until the runnings were neutral to litmus. The washed and treated coal was then air dried, after analysis showed 109 grams of mositure-free coal. As thus dried the coal was ready for extraction. Ten grams of the dried material were placed with 100 cc. of 1 per cent sodium hydroxide solution in a glass container and shaken at room temperature for about 15 minutes. The material was then centrifuged and the supernatent liquid was separated from the deposited solid. By repeating such extraction twice substantially all of the dyestuff was removed.

The foregoing example illustrates the use of a ratio of 8 parts of acid to 1 of coal. The ability to use lower ratios by extending the heating time appears from the following example. Twentyfive grams of the same coal, ground to pass a 20-mesh sieve, were placed in a 1-liter flask provided with a reflux condenser. To the coal there was added cc. of C. P. concentrated nitric acid (sp. gr. 1.4) every five minutes until a total of 72 cc. of acid had been added. This represents an acid to coal ratio of 4:1, in other words, a total of 100.8 grams of acid. After 60 cc. of the acid had been added to the coal, the flask was subjected to the heat of a steam bath, and heating of the acid-coal mixture was continued for 3 hours. After the heating had been discontinued for minutes the solution was filtered using a fiber glass mat as a filter bed. The treated coal was then washed with distilled water until the residual acid was removed; this required about 1 liter of distilled water. The washed and treated coal was then dried overnight in an oven at 105 C., and after cooling it was found to weigh 28.3 grams. Three grams of this treated, washed and dried coal were then added to cc. of 0.1N NaOI-I in small portions at a time and with constant stirring. The NaOH solution became dark brown in color. After the addition of the coal to the solution was completed and stirring had continued for about 5 minutes, the solution was poured into a centrifuging bottle. To the beaker that still contained some undissolved residue was added 100 cc. of distilled water and after stirring this was poured into the same centrifuging bottle with the above solution. 1 The bottle containing the total solution was then placed in the shaker for 5 minutes and finally centrifuged for 10 minutes. After this the solution was separated from the undissolved treated coal by filtration, divided into two parts and used directly as a dye for silk and wool. This yielded a light brown color on the fibers. The undissolved coal was washed until the washings were colorless, dried for several hours in an ovenat 0., cooled in a desiccator and found to Weight 0.7 gram.

Dyes made as described hereinabove produce pleasing shades of brown depending, as stated, upon the concentration of the solution, and also upon the time and temperature of the bath and the material being dyed. By actual test I have found that the dyed products possess satisfactory resistance to various deteriorating influences. Thus, tested by standard procedures wool and silk fabrics dyed with dyes made according to the invention are fast to water, and washing, at least at temperatures up to about 100 C., to crocking, and to perspiration. Also, they are apparently resistant to wide variations of acidity and alkalinity, being resistant to water varying in pH from 4 to 10. The color is, however, bleached by chlorine and other bleaching agents.

Various modifications are permissible, of course. Thus, although the invention has been described with reference to the use of nitric acid, it will be understood that any agent or combination of agents productive of nitration and oxidation may be used.

The term bituminous coals as used in the claims includes suband semi-bituminous coals. as indicated above.

According to the provisions of the patent statutes, I have explained the principle and method of practicing my invention and have described what I now consider to represent its best embodiments. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

I claim:

1. That method of making a dye from bituminous coals which comprises treating the coal with nitric acid at a temperature above room temperature but below the decomposition temperature of said acid, and then extracting the treated coal to recover brown dyestufi.

2. That method of making a dye from bituminous coals which comprises treating the coal with nitric acid at a temperature above room temperature but below the decomposition temperature of said acid, washing the treated coal to remove residual acid, and then extracting the treated coal with a solvent for brown dyestui'l produced thereby.

3. A method according to claim 2, said acid being used in an amount varying from about 1 part by weight per part of coal to 8 parts by weight per part of coal.

4. That method of making a dye from bitumie. That method of making a dye from bituminous coals which comprises treating the coal with nitric acid solution at room temperature and thereby causing an exothermic reaction to be initiated, permitting said reaction to proceed at room temperature and then heating the mixture at a temperature not over about 100 C. to complete the action of said acid upon the coal, then washing the treated coal to remove residual acid, and then extracting brown dyestufi from the washed coal.

'7. A method according to claim 6, said acid being used in an amount from about one to about eight parts by weight per one part by weight of coal, and being added in small amounts at a time.

8. That method of making a dye from bituminous coals which comprises mixin the coal with nitric acid solution at room temperature and thereby causing an exothermic reaction to be initiated, permitting said reaction to proceed at froom temperatureand then heating the mixture -at.a temperature not over about 100 C. to complete the action of the acid upon the coal, then washing the treated coal to remove residual acid, and extracting the washed coal with an organic acidicmaterial and thereby recovering a brown dye solution.

9. A method according to claim '7, said material being glacial acetic acid.

10. That method of making a dye from bituminous coals which comprises treating one part by weight of coal with air and nitric acid in the vapor phase :at a temperature at which said acid reacts with reactive constituents of the coal, washing the treated coal to remove residual acid, and extracting the Washed coal to recover solution of brown dyestuff.

11. The method of making a dye from bituminous coals which comprises mixing time part'by weight of coal with up to about eight parts by weight of nitric acid added in small amounts, heating the mixture at a temperature below the decomposition temperature of said acid after initial exothermic reaction has abated to complete the reaction, washing the treated coal to remove residual acid, extracting the washed coal with an organic acidic material to recover solution of dye stuff, then extracting a further amount of dyestuff with an aqueoussolution of alkali.

HERBERT B. CHARMBURY.