US2702296A - Fluorescent whitening agents - Google Patents

Description

FLUORESCENT WHITENING AGENTS Mario Francesco Sartori, Monroe Park, Del., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware N Drawing. Application June 19, 1953, Serial No. 362,945

9 Claims. (Cl. 260-3431) This invention relates to the production of novel organic compounds which are useful as whitening agents for fibrous material such as textiles or paper. It is an object of this invention to produce compounds of the above general nature, but which are characterized further by bleach fastness and by correct shade of fluorescence. A further object is the production of whitening agents of the above class which are adapted for use on cellulosic fiber as well as on the hydrophobic fibers such as cellulose acetate, nylon, polyacrylonitrile fibers and polyethylene-terephthalate fibers. Additional objects and achievements of this invention will appear as the description proceeds.

The art of whitening or brightening textile fiber and paper is of relatively recent development. It has been found that fibrous materials which normally have a dull, yellowish cast when in the white, unbleached state, hecome whiter and brighter if treated with agents which fluoresce under ultraviolet light. Presumably the action of the ultraviolet rays present in ordinary daylight is suflicient to excite these agents upon the fiber to emit fluorescence which overcomes the undesirable tinge of color in the unbleached fiber. Best results are obtained when the shade of fluorescence is complementary to that of the unbleached fiber, so that the colors will cancel out each other. Since the most common off-white shade of unbleached cellulosic fiber is yellowish, the most desirable shade in a fluorescent is blue.

Another very important demand developed by the trade is bleach fastness. Inasmuch as the aforementioned fluorescent agents are-generally incorporated into soap and synthetic detergents, which are packaged and marketed for household use, and inasmuch as in household practice laundered articles are often subjected to bleaching with various agents, for instance hypochlorites, it is essential that the fluorescent transferred from the detergent to the fiber shall not be destroyed by the action of bleach. Unfortunately, most of the fluorescent agents now on the market, and having the desirable blue shade, are weak in respect to this qualification of bleach resistance.

In addition to theabove two primary qualifications, a practical whitening agent should have good light-fastness, should be capable of being synthesized economically from readily available materials, and should have sufiicient fluorescent power (often referred to as tinctorial strength) to give the desired effect at a minimum cost. It must also have afiinity for the fiber that is to be treated gndhshould have good exhaust qualities from an aqueous Now according to my invention new chemical compounds are synthesized which have good afiinity for cellulosic and hydrophobic fibers and produce thereon a desirable blue fluorescence, fast to light and to bleach. My novel compounds may be designated generically as 3p-benzamidophenyhcoumarins which bear in the benzamido nucleus groups of substituents selected from the group of combinations consisting of one, two or three lower alkoxy radicals such as methoxy or ethoxy; one methoxy and one methyl radical; a methylene dioxy radical OC attached to two adjacent C- atoms. Accordingly, the novel family of compounds of this invention may be expressed by the general formula 2,702,296 Patented Feb. 15, 1955 wherein R is a phenyl radical bearing one, two or three lower alkoxy radicals, one methyl and one methoxy radical, or a methylene dioxy radical.

These compounds may be synthesized by several optional methods, for instance:

A. By condensing 3-p-aminophenyl-coumarin with a benzoyl chloride bearing methoxy groups or other substituents from the above specified combinations. The condensation is preferably carried out in pyridine or in hydrocarbon solvent containing a tertiary organic base, and the further details of procedure, including recovery may follow in general the teachings of Lubs et al., U. S. P. 2,497,130.

B. By condensing S-p-aminophenyl-coumarin with a benzoic acid having methoxy groups or other substituents of the groups above indicated. The reaction mass in this case necessarily includes an acid halogenating agent, such as phosphorus trichloride or oxyehloride, and the reaction is preferably carried out in pyridine or in a combination of a hydrocarbon solvent and a tertiary organic base, following in general the details of Lubs et al., U. S. P. 2,497,131.

The requisite 3-p-aminophenyl-coumarin employed as initial material for the above synthesis may be prepared by reducing the corresponding 3-nitro-compounds, and the latter in turn may be prepared by optional, known methods, for instance:

A. By coupling diazotized p-nitroaniline, with coumarin, in the presence of cupric chloride. Further details on this process are given by Meerwein in Jour. fiir pragtische Chemie, vol. 152, p. 254 (1939).

B. By condensing salicylaldehyde with p-nitrophenylacetic acid, according to Walter, Jour. fiir prakt. Chemie, vol. 61, p. 186 (1900).

Without limiting this invention, the following examples are given to illustrate my preferred mode of operation. Parts mentioned are by weight.

Part I.Preparation of initial material B-(p-nitrophenyl) coumarin was prepared from diazotized p-nitroaniline and coumarin, according to the aforementioned method of Meerwein (J. pr. Chem. 152, 254). The nitro group was then reduced as follows:

To a boiling suspension of 4.5 parts of 3-(p-nitro phenyl)coumarin in parts of ethyl alcohol, a solution of 22 parts of stannous chloride in 30 parts of concentrated hydrochloric acid was added at the boil. The mixture was refluxed for 3 hours, then cooled and filtered. The precipitate was dissolved in water; the obtained solution was saturated with hydrogen sulfide and then filtered. The filtrate was made alkaline with sodium carbonate. The obtained yellow precipitate was filtered off and crystallized from ethyl alcohol. Bright yellow crystals of 3-p-aminophenyl-coumarin were obtained, melting at -182 C. and soluble in ethyl alcohol with yellow fluorescence.

Part II.-Preparation of the whitening agents Example 1.-A suspension of 1.1 parts of 3-p-aminophgnyl-coumarin, h0.9 part of m-methoxy benzoic acid an 0.7 part of p 0s h ous oxychlgride in 1 arts of pyridintfivasmefi'fixe for mftwo room temperature, the mixture was drowned in water, made alkaline with 10% caustic and filtered. The crude product was crystallized from ethyl alcohol. White crystals were obtained, melting at 216 C. and soluble in ethyl alcohol with bluish fluorescence. This product is believed to be 3-p-(3-methoxybenzamido)phenylcoumarin, of the formula Example 2.A solution of 23.7 parts of 3-p-aminophenyl coumarin and 18.7 parts of p-anisoyl chloride in 142 parts of pyridine was refluxed for one hour. After cooling to room temperature, the mixture was drowned in water and filtered. The product was recrystallized from ethyl alcohol, yielding white crystals, which melted at 231 C. and dissolved in ethyl alcohol with bright bluish fluorescence. These crystals are believed to be 3-p-(4-methoxybenzamido)-phenyl-coumarin.

Following the procedure of Example 1, but replacing the 0.9 part of m-methoxy-benzoic acid by equivalent amounts of the acids indicated below, the following additional compounds were synthesized:

Compound No.2

3. 3-p-(2-methoxybenzamido) phenyl coumarin (from o-methoxy-benzoic acid).

4. 3-p-(3-methyl 4 methoxybenzamido) phenylco%n)1arin (from 3-methyl 4 methoxy-benzoic acr 5. 3-p-(2,4-dimethoxybenzamido) phenyl-coumarin (from 2,4-dimethoxy-benzoic acid).

6. 3-p-(3,4-dimethoxybenzamido)-phenyl coumarin (from 3,4-dimethoxy-benzoic acid).

7. 3-p-(2,5-dimethoxybenzamido)-phenyl coumarin (from 2,5-dimethoxy-benzoic acid).

8. 3-p-(2,4-diethoxybenzamido) phenyl coumarin (from 2,4-diethoxy-benzoic acid).

9. 3-p-(2,4,5-trimethoxybenzamido) phenyl-coumarin (from 2,4,5-tr'imethoxy-benzoic acid).

10. 3-p-piperonylamido-phenyl-coumarin (from 3,4-

methylenedioxy-benzoic acid):

COOH

The products of all the examples hereinabove exhibit the property of fluorescence under ultraviolet light, and are suitable as whitening agents for the purposes aforementioned. When applied to the hydrophobic fibers or cotton from a hot aqueous bath, preferably in the presence of a soap or detergent, they impart to the fibers a bluishwhite fluorescence which is outstanding when viewed under ultraviolet light.

The products are also related to each otherin other physical properties, and their C, H and N analyses agreed well with those calculated from their formulas.

Cotton and cellulose acetate fabrics were treated in aqueous baths containing commercial detergents (Tide, Surf) and various compounds from the above examples, and were then tested for afi'inity, tinctorial strength (i. e., strength of the fluorescent effect produced upon a standard weight of the fabric by a standard weight of the compound being tested), bleach fastness and light fastness (fadcometer exposure). Control samples of the same fabrics were tested simultaneously for each compound under similar conditions, except that no fluorescent agent was added to the aqueous detergent bath for treating the control. Finally, for the sake of exhaustive comparison, other samples of the corresponding fabrics were treated with S-p-acetamido-phenylcoumarin, 3 p benzamido phenyl coumarin (unsubstituted), and other known compounds of the coumarin series.

The results showed that the unsubstituted benzamido phenyl coumarin has very poor afiinity for both cotton and hydrophobic fiber; the acetamido compound is better in this respect, but has poor fastness to bleach; some of the other known coumarin derivatives (e. g., 7-diethylamino-4-methyl-coumarin) are fugitive to light; whereas the novel compounds of this invention possess an admirable combination of these desirable practical properties, namely tinctorial strength, bleach fastness and light fastness.

The mentioned combination of desirable properties makes my novel compounds excellently suitable for the whitening of textile fiber. They may, however, be used also for various other purposes where fluorescence or absorption of ultraviolet light is desirable, for instance to achieve fluorescent effects in costumes or stage settings, to achieve novel effects on photographic paper, as ultraviolet filters when impregnated on cellulosic films which are used for wrapping materials, etc.

wherein R is a phenyl radical carrying from one to three lower alkoxy radicals.

3. 3-p-(2,4-dimethoxy benzamido)-phenyl coumarin.

4. 3-p-(3,4-dimethoxy 'benzamido)-phenyl coumarin.

5. 3-p-(4-methoxy benzamido)-phenyl coumarin.

6. 3-p-(3-methoxy benzamido)-phenyl coumarin.

7. 3-p-(3-methyl-4-methoxy benzamido)-phenyl coumarm. 1

8. A process for preparing a fluorescent coumarin compound which comprises reacting in pyridine 3-paminophenyl coumarin with an aroyl chloride of the formula RCOC1 wherein R is a phenyl nucleus hearing substituents selected from the following group of combinations: one lower alkoxy radical, two lower alkoxy radicals, three lower alkoxy radicals, one methoxy and one methyl radical, and a methylene dioxy radical attached to two adjacent C-atoms.

9. A process as in claim 8, the aroyl chloride being formed in situ from the corresponding carboxy acid and an acid halogenating agent.

Axelrad Feb. 8, 1944 Hoefle et al. Apr. 6, 1954 OTHER REFERENCES I. prakt. chem. 152, p. 241 (1939). Biochem. J. 45, p. 535 (1949).

Claims (1)

1. A 3-P-BENZAMIDO-PHENYL-COUMARIN BEARING IN THE BENZAMIDO NUCLEUS A GROUP OF SUBSTITUENTS SELECTED FROM THE FOLLOWING GROUP OF COMBINATIONS: ONE LOWER ALKOXY RADICAL, TWO LOWER ALKOXY RADICALS, THREE LOWER ALKOXY RADICALS, ONE METHOXY AND ONE METHYL RADICAL, AND A METHYLENE DIOXY RADICAL ATTACHED TO TWO ADJACENT CATOMS.