US2700043A - Fluorescent whitening agents - Google Patents

Description

United tates FLUORESCENT WHITENING AGENTS No Drawing. Application March 26, 1953, Serial No. 344,888

8 Claims. (Cl. 260304) This invention relates to the production of novel organic compounds which are useful as whitening agents for fibrous material, such as cellulosic fibers or nylon. 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. 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, become 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 comon off-white shade of unbleached cellulosic and nylon fibers 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 removed or 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 the above two primary qualifications, an agent for the purposes of this invention should be capable of being synthesized economically from readily available materials, and should have sufficient fluorescent power (often referred to as tinctorial strength) to give the desired effect at a minimum cost. It should also have afiinity for nylon fiber and should be capable of being dispersed readily in water in the concentrations that would normally be used in the treatment of nylon or other fiber.

Now according to our invention new chemical compounds are synthesized which satisfy to an excellent degree all the aforegoing qualifications. The novel compounds of this invention are aromatic triazoles which carry in their molecule at least one and not more than two sulfamyl radicals of the group consisting of unsubtituted sulfamyl, monoalkyl sulfamyl and dialkyl sulfamyl (SO2NH2, SO2NHR and SO2NRR, respectively, R and R being alkyl radicals of not more than 4 C-atoms each). They may be defined generally by the formula .l 1. l J

wherein R represents the radical of 2-phenyl benzothiazole or a homolog thereof (e. g. the radicals obtaining ateht tion ortho to the amino group unsubstituted, but it may 2,700,043 Patented Jan. 18, 1955 benzothiazole, dehydrothio-p-toluidine and dehydrothiom-xylidine), X is a sulfamyl radical as above defined, Y is a member of the group consisting of H, sulfo and sulfamyl, the members X and Y being attached to homocyclic nuclei on opposite sides of the triazole ring.

These compounds may be synthesized by diazotizing a 2-p-aminophenyl benzothiazole compound of the group more fully defined below, coupling the diazo compound (in acid medium) to an amino-naphthalene compound of the group more fully defined below; and converting the o-amino azo dye thus obtained into a triazole by oxidation in known manner, for instance by heating in The 2-p-aminophenyl-benzothiazole compound may be selected from the group consisting of Z- -aminophenylbenzothiazole itself, dehydrothio-p-toluidine, dehydrothio-m-xylidine, and their sulfo and sulfamyl derivatives of the group above defined. The amino-naphthalene compound may be lor Z-naphthylamine having the posicarry in other positions a sulfo group or a sulfamyl radical as above defined. The two components mentioned are chosen so that at least one of them has a sulfamyl radical.

The requisite sulfamyl derivatives of the p-aminophenyl-benzothiazole compound or of the amino-napthalene, may be prepared by first acetylating the corresponding amino compound with acetic anhydride, to block the amino group; then sulfonating the compound with chlorosulfonic acid to convert it into a sulfonyl chloride. The latter is then treated with the appropriate amine (ammonia, methylamine, ethylamine, dimethylamine, etc.) to obtain the sulfonamide. Finally, hydrolysis with hot hydrochloric acid regenerates the amino group and gives the desired sulfonamide compound.

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

Example 1 240 parts (1 mol) of dehydrothio-p-toluidine was diazotized at 1015 C. in 2000 parts of dilute hydroby dropping off the NHz group from 2-p-aminophenylchloric acid with an excess of nitrous acid to give a clear solution of the diazo compound. To this was added a solution of 244 parts (1.1 mol) of 2-aminonaphthalene-6-sulfonamide in 1000 parts of water. The acidity was adjusted to slightly acid on Congo red paper by the addition of sodium acetate, and the coupling proceeded rapidly. After stirring overnight at room temperature the product was isolated by making the solution alkaline to Clayton yellow with sodium hydroxide, heating to 80 C., filtering, and washing with water.

The o-aminoazo dye intermediate thus obtained was oxidized to the triazole 1by refluxing for 3 hours with 500 parts .(2 mols) of cupric sulfate (CuSOrSHzO) in an excess of aqueous ammonia. The mixture was made acid to Congo red paper with hydrochloric acid and filtered hot. The solid product was slurried in water, vmade alkaline to Clayton yellow paper with sodium hydroxide, and treated with an excess (positive test on fiavanthrone paper) of sodium hydrosulfite for 16 hrs. at 70 C. The slurry was then made acid with hydrochloric acid and filtered. The product was crystallized from aqueous dimethyl formamide .and dried.

When applied from an aqueous bath to cotton or nylon at 33 p. p. m. (based on fabric), the product gave a .fabric which appeared considerably whiter in daylight than the untreated fabric. The atfinity for cotton and nylon was about equal, with a somewhat lower afiinity for cellulose acetate.

Example 2 342 parts ,(1 mol) of dehydrothiop-toluidine sodium sulfonate was dissolved in water. An excess of hydrochloric acid was added and the amine was diazotized at 10l5 C. in the usual manner by the addition of sodium nitrite. The diazo was then coupled to 2-aminonaphthalene-6-sulfonamide and the dye isolated in the same manner as Example 1.

The azo dye thus obtained was oxidized by refluxing with ammoniacal cupric sulfate as in Example 1. The alkaline reaction mass was filtered and the cake was slurried in water, made acid to Congo red paper with hydrochloric acid. This slurry was heated to 8090 C. to dissolve all copper salts and filtered hot. The cake was washed with water until acid-free and dried. The final product is believed to have the structure Cotton cloth treated in water with 84 p. p. m. of this whitening .of the .cotton and nylon with a lesser whitening efiect on the acetate fabri Example 4 Example 5 3-1.9 parts (0.1 mol) of the sulfonamide of dehydro- 0 thio-p-toluidine was diazotized at 0-5 C. in dilute hydrochloric acid and the resulting diazo was coupled with 15.7 parts (0.11 mol) of Z-aminonaphthalene in the usual manner. The resulting dye was oxidized to the triazole by refluxing for 4-0 hrs. with 50 parts of cupric sulfate (CuSO45I-IzO) dissolved in a mixture of 185 parts of pyridine and 125 parts of water. The oxidation product was precipitated by drowning in 2000 parts of 10% sulfuric acid. The final product was filtered off, washed with water, dried and crystallized from ethylene glycol monoethyl ether. It was a pale yellow powder, soluble in alcoholic solvents with bright blue fluorescence. This product, when applied on cotton and nylon, gives a very strong bluish fluorescence.

Example 6 31.9 parts (0.1 mol) of the sulfonamide of dehydrothio-p-toluidine was diazotized at 05 C. in dilute hydrochloric acid and the resulting diazo was coupled 9 to Z-aminonaphthalene-6-sulfonic acid in the usual manner. The resulting dye was oxidized as described in Example 1. The oxidation mixture was filtered hot and the triazole isolated from the filtrate by salting out with sodium chloride, filtering, washing the product with 10% NaCl solution and drying. It was a cream colored powder, soluble in water with bright bluish fluorescence. The end product is believed to have the formula compound fluoresced brightly in ultraviolet light and appeared much whiter in daylight than untreated cloth.

Example 3 334 parts (1. mol) of the N-methyl sulfonamide oi' SOzNHz When appliedto cotton, nylon and celluloseacetate fabti'cs at '80 p. p. m. this agent caused considerable This compound applied on cotton and nylon gives very strong bluish fluorescence.

Similar compounds may be prepared by coupling the diazotized dehydrothio-p-toluidine-sulfonic acid, -sulfonamide, or -N-alkyl-sulfonamides to naphthionic acid (1-aminonaphthalenet-sulfonic acid), to Laurents acid (l-aminonaphthalene-S-sulfonic acid), or to the correspending sulfonamide or N-alkylsulfonamides of these acids, e. g. 1-aminonaphthalene4-N,N-dimethylsulfonamide or Z-aminonaphthaiene-S (or 6)-N,Ndirnethylsulfonamide, and oxidizing the resulting o-arninoazo dye as in the aforegoing examples. a

in place of dehydrothio-p-toluidine and the sulfonic acids and sulfonamides thereof named in the examples, other derivatives of the same class may be used, for instance Z-(p-aniinophenyl)-6-methyl benzothiazole-7-N,N- dimethylsulfonamide; also, dehydrothio-m-xylidine and 2-(p-aminophenyl)-benzothiazole, as well as their sulfo and sulfamyl derivatives may be used with similar results.

The sulfonic acid compounds given in the above examples have been isolated as the sodium salts of the sulfonic acids. By using potassium hydroxide and po tassium salts in lieu of sodium hydroxide and sodium salts, throughout, the products may be obtained as potassium sulfonates. Isolation as the free sulfonic acids can beeffected by acidification of-the condensation mass,

and the products thus obtained may be reacted with ammonium hydroxide or any suitable organic or inorganic base, to yield the corresponding salt.

The novel compounds hereinabove described, have been subjected by us to various tests to determine their bleach fastness, light fastness and wash fastness and showed that the novel compounds compare favorably in respect to these qualities with the best fluorescents which are now on the market.

In addition to being applied to textile fibers directly from a dye bath or to paper stock by addition to the beater, our novel compounds may be incorporated into soap and synthetic detergents. They may also be used 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.

We claim as our invention:

1. An aromatic triazole compound of the general formula F l X-| N: J Y

wherein R represents the 4'-radical of a compound selected from the group consisting of Z-phenyl benzothiazole and its lower homologs, X is a sulfamyl radical of the group consisting of unsubstituted sulfamyl, lower monoalkyl sulfamyl and lower dialkyl sulfamyl, Y is a member of the group consisting of hydrogen, sulfo and sulfamyl, the members X and Y being attached to homocyclic nuclei on opposite sides of the triazole ring.

2. An aromatic triazole compound of the formula f i =Q wherein R is the 4-radical of 2-phenyl-6-methyl-benzothiazole carrying an N-methyl-sulfonamide group in the benzo nucleus, while Q is the 1,2-radical of naphthalene- 6-sulfonamide.

3. An aromatic triazole compound of the formula R-N-N wherein R is the 4'-radical of 2-phenyl-6-methyl-benzothiazole carrying a sulfonamide group in the benzo nucleus, while Q is a naphthalene radical attached in the l,2-positions.

4. An aromatic triazole compound of the formula R-N-lfil l=Q wherein R is the 4'-radical of 2-phenyl-6-methyl-benzothiazole carrying an N-methyl-sulfonamide group in the benzo nucleus, while Q is the 1,2-radical of naphthalene- 6-sulfonic acid. 4

5. An aromatic triazole compound of the formula RNN I II =Q wherein R is the 4-radical of sulfonated 2-phenyl-6- methylbenzothiazole, while Q is the 1,2-radical of naphthalene-6-sulfonamide.

6. An aromatic triazole compound of the formula fi N=Q wherein R is the 4'-radical of 2-phenyl-6-methyl-benzothiazole, while Q is the 1,2-radical of naphthalene-6-sulfonamide.

7. The process of producing a fluorescent agent of bluish fluorescence, which comprises diazotizing a paminophenyl-benzothiazole of the group consisting of paminophenyl-benzothiazole, its lower homologs, and its sulfo and sulfamyl derivatives, coupling the diazo compound thus formed to an aminonaphthalene of the group consisting of l-aminonaphthalene, Z-aminonaphthalene and their sulfo and sulfamyl derivatives which are not substituted in position ortho to the amino group, the selection of said components from said groups being such that the resulting ortho-aminoazo compound will possess at least one sulfamyl radical, and then oxidizing said1 ortho-aminoazo compound to the corresponding triazo e.

8. A process as in claim 7, the oxidation being effected by heating the compound in an aqueous solution of ammoniacal cupric sulfate.

References Cited in the file of this patent UNITED STATES PATENTS 2,410,619 Allen et al. Nov. 5, 1946

Claims (1)

1. AN AROMATIC TRIAZOLE COMPOUND OF THE GENERAL FORMULA