This invention relates to the stabilization of aqueous peroxy bleach solutions, especially solutions containing active oxygen derived from sodium perborate or sodium percarbonate.

Background of the Invention

Liquid laundry products such as liquid detergents and liquid bleach formulations have become increasingly popular in the last few years. However, aqueous liquid ° detergent formulations currently available do not contain a peroxy bleach system such as is found in powdered detergents based on sodium perborate because of poor storage stability of the peroxide in the aqueous media. Although sodium perborate has been popular as a bleaching ⁵ agent for powdered detergent formulations for many years in Europe, it has only recently found acceptance in the United States as a bleach for powdered detergents. There is a need, however, for stable, concentrated water-based peroxy bleaching compositions which have a shelf life adequate to 0 provide sufficient oxidizing peroxygen bleach in a commercial product. Such concentrated solutions are

necessary so that a liquid laundry bleach, when diluted in the washing medium, will provide a concentration of active oxygen sufficient to provide adequate bleaching.

The solubility of sodium perborate in water at 520°C is 2.25% (corresponding to 0.23% active oxygen); however, it is known that the perborate solubility can be increased by use of solubilizing agents such as the alkali metal phosphates, boric acid, tartaric and citric acids as well as mineral acids, such as sulfuric acid. Although the 0 perborate content can be increased by use of such cosolutes, the problem of adequate shelf stability remains of concern.

It has been proposed that the addition of a σhelating agent or sequestrant can enhance the stability of 5 sodium perborate in aqueous formulations by removing catalytic metal ions. Examples of such chelating agents or sequestrants include salts of ethylenediamine tetraacetic acid and complex organo-phosphates, such as the alkali metal salts of amino methylenephosphonic acid as disclosed 0 in U.S. Patent Nos. 3,234,140 and 4,477,390. The pentasodiu salt of diethylenetriamine penta(methylene phosphonic) acid, which is available as DEQUEST ^® 2066 from

Monsanto Chemical Co. , is an example of such complex organo-phosphates.

Other stabilizer systems for peroxide solutions are inorganic salts of polybasic acids such as potassium polyphosphates, described in U.S. Patent 3,553,140, quaternary ammonium salts described in U.S. Patent 3,996,151, and picolinic or quinaldic acid which are described as stabilizers for organo peroxyacid bleach compositions in U.S. Patent 3,956,159.

U.S. 2,012,462 discloses stabilization of peroxide solutions by use of a mixture of a salt of pyrophosphoric acid and an aromatic amine sulphonate in which the amino nitrogen may be substituted with an alkyl or aralkyl group. It has been found, however, that this stabilizer system is not suitable for concentrated aqueous peroxy solutions based on sodium perborate.

Description of the Invention

This invention provides concentrated, stable aqueous peroxy containing bleaching compositions containing a specific class of stabilizers. Accordingly, this

invention comprises a stable, concentrated aqueous peroxygen solution comprising about 5 to 30% sodium perborate or sodium percarbonate, about 0 to 5% chelating agent, about 3 to 30% solubilizing agent, and about 0.001 to 1.0% of a water soluble salt of a stabilizing agent of a formula selected from

where Ar is phenyl or naphthyl and R is hydrogen, nitro or chloro; said percentages are by weight. The balance of the formulation is water, although other functional ingredients can be included to provide desirable properties or functions in the composition, such as for example, surfactants, builders, fragrances, activators, etc.

The peroxide providing component of the formulation is preferably sodium percarbonate or sodium perborate. The sodium perborate can be added as the

5 monohydrate or tetrahydrate or formed in situ by addition of hydrogen peroxide, boric acid or borax, and sodium hydroxide. The aqueous formulations of this invention contain about 5 to 30% sodium perborate or sodium percarbonate (ignoring the water of hydration) and preferably contain from about 8 to about 25% of the perborate or percarbonate. Although sodium peroxide and sodium percarbonate are preferred, the stabilizers of this invention may also be used to stabilize hydrogen peroxide solutions.

In order to increase the solubility of the perborate or the percarbonate in the aqueous formulation, a solubilizing agent.is included. Such solubilizing agents can be alkali metal phosphates such as sodium dihydrogen phosphate, organic acids such as citric and tartaric acids, and inorganic acids such as boric acid or sulfuric acid. The preferred solubilizing agents are the alkali metal phosphates, especially sodium dihydrogen phosphate, and boric acid.

in order to obtain a concentrated solution of the perborate or percarbonate, the solubilizing agent should be present in an amount of from about 3 to 30% by weight.

Preferably, when sodium dihydrogen phosphate or boric acid are used as the solubilizing agent, from about 10 to 20% by weight is included in the solution. When citric acid and tartaric acid are used, they are preferably added as the sodium salt and are present in the range of from about 15 to 25% by weight of the formulation. Sulfuric acid can be used as a cosolute in an amount corresponding to about 2 to 10% H ₂ SO _d in the formulation.

The use of a chelating or sequestering agent is optional but preferred to give optimum stability at high concentrations of perborate or percarbonate. Suitable chelating agents are the well known sequestrants, ethylenediamine tetraacetic acid (sodium salt) and trisodium nitrilotriacetate (NTA) . The preferred chelating agents are the complex organo aminophosphonic acid derivatives such as described in U.S. Patents 3,234,140 and

4,477,390. A preferred agent is the pentasodium salt of diethylenetriamine penta(methylene phosphonic acid) which is sold as DEQUEST ^® 2066 (25% active on free acid basis). The formulations of this invention can contain up to about

5% by weight of the chelating agent with a preferred amount being in the range of from about 0.05% to 0.5% by weight, on an active free acid basis.

The components of the compositions of this invention are dissolved in water, which may be either deionized water or tap water, deionized water being preferred. The formulations are prepared by merely dissolving the components in water (deionized or tap water) which has been heated slightly, such as to about 40°C. The order of addition is not critical, although it appears that there may be some advantages in the sequential, step-wise addition of solubilizing agent followed by perborate. The resultant solution is stirred until all the components are dissolved or nearly dissolved. It has been noted that some of the stabilizing agents have limited water solubility and, as a result, a slight turbidity of the formulated solution may be observed. However, this slight turbidity does not detract from the utility of the formulation as a source for active oxygen in laundry solutions.

It is believed that the stabilizing agents act as free radical inhibitors to deactivate deleterious free radicals as well as to help remove catalytic metal ions. The latter may be present in liquid bleach solutions and act to catalyze the loss of peroxide from the solutions. However, this invention is not to be considered to be limited to any specific theory on ^" Itow the ^stabilizing

agents work.

As pointed out above, the stabilizing agents of the formulations of this invention comprise a water soluble salt of a compound of a formula selected from

in which Ar is phenyl or naphthyl and R is hydrogen, nitro or chloro. Representative examples of compounds embraced by the above formulae are: diphenylamine-4-sulfonic acid diphenylamine-3-sulfonic acid

4-nitrodiphenylamine-4'-sulfonic acid N-phenyl-2-aminonaphthalene-5-sulfonic acid 3-chlorodiphenylamine-4'-sulfonic acid 4-chlorodiphenylamine-4'-sulfonic acid

4-nitrodiphenylamine-3-'sulfonic acid 2-nitrodiphenylamine-4'-sulfonic acid N-(4-nitrophenyl)-2-aminonaphthalene-5- sulfonic acid

N-(3-chlorophenyl)-2-aminonaphthalene-5- sulfonic acid

4-nitrodiphenylamine-2'-sulfonic acid carbazole-3-sulfonic acid carbazole-4-sulfonic acid

The salts are the water-soluble alkali metal and alkaline earth metal salts such as the sodium, potassium, barium, and calcium salts.

The stabilizing agents according to this invention are commercially available, or can be readily prepared. For example, sodium diphenylamine-4-sulfonate may be obtained from Aldrich Chemical Company and the chloro substituted diphenylamine sulfonic acids can be prepared by sulfonation of the corresponding chloro- substituted diphenylamine with chlorosulfonic acid. The nitro- substituted derivatives are prepared by a displacement reaction between the corresponding fluoro-nitrobenzene and an anilinesulfonic acid salt in the presence of magnesium

oxide according to the procedure of Lantz et al. , Bull. Soc. Chi Fr.. 311 (1956).

Carbazole may also be sulfonated with chloro- sulfonic acid, such as by the procedure described by Sumpter et al., Heterocyclic Compounds. Vol. 8, Pages 81- 82, (1954).

Phenylnaphthylamines can be sulfonated with fuming sulfuric acid, such as according to the procedure of Lesser, Chem. Ber. 27, 2363 (1894) and German Patent 70349 (1892), as well as with chlorosulfonic acid.

The alkali metal and alkaline earth metal salts are readily prepared by reaction of the phenylamine-aryl sulfonic acids with the corresponding alkali metal or alkaline earth metal hydroxides or carbonates.

The following examples illustrate the preparation of representative stabilizing agents of this invention.

EXAMPLE I

The procedure of R. Lantz and P. Obelliance (Bull. Soc. Che . Fr. , 311, 1956) was followed. A mixture of 6.80 grams of 4-fluoronitrobenzene, 6.92 grams of sulfanilic acid and 4.0 grams of magnesium oxide was prepared in 28 ml. of water containing 3.08 grams of 51.9% sodium hydroxide solution. Heating in a sealed Pyrex tube for 14.5 hours at 167-172°C gave a dark amber solution plus solids. Unreacted 4-fluoronitrobenzene was removed by steam distillation and the residue evaporated to dryness in a vacuum. Sodium hydroxide solution (40 ml of 0.25 N) was added and the solids removed by filtration. The filtrate was acidified with concentrated HC1, evaporated to dryness in vacuum, and the residue extracted with boiling ethyl alcohol followed by removal of solids by filtration. The ethanolic filtrate was evaporated to dryness in a vacuum, the residual solids redissolved in 25 ml. of water, adjusted to pH 8 with 10% aqueous sodium carbonate solution and evaporated to dryness in vacuum. Crystallization from 9:1 ethanol: water solution gave golden crystals whose proton nuclear magnetic resonance pattern showed two AB

quartets ato'7:02 and 8:00 ppm (J= 9Hz, nitrated ring) and at cf 7.10 and 7.57 ppm (J=8Hz, sulfonated ring). A thin layer chromatogram (TLC) on silica gel G using acetone/chloroform/glacial acetic acid/water in a volume ratio of 8:8:4:1 showed a single spot at R _e 0.35.

EXAMPLE II

4-Nitrodipn«τιγi»mine-3 ^/ -Sulfonic Acid, sod-jnm salt

4-Nitrodiphenylamine-3'-sulfonic acid sodium salt was prepared from metanilic acid by the procedure of Example I, but a simplified workup was used in which the product was crystallized directly from 0.5 N sodium hydroxide solution after the steam distillation step. The resulting 5.55 grams of orange crystals gave a proton NMR pattern consistent with the desired structure.

EXAMPLE III

4-Nitrodiph^τιyi«mine-2*-Sulfonic Acid. Sodium a t-

4-Nitrodiphenylamine-2 ^/ -sulfonic acid sodium salt was prepared from aniline-2-sulfonic acid by the procedure

of Example II to give beautiful yellow crystals whose proton NMR spectrum was consistent with this structure and which showed a strong TLC spot at R _s 0.67 plus a faint impurity at R _t 0.55.

EXAMPLE IV

3-Chlorodiphenylamine-4 -sulfonic acid sodium salt was prepared by adding a solution of 2.86 grams of chlorosul onic acid in 25 ml. of 1,2-dichlorobenzene dropwise over 15 minutes to an ice-cooled, stirred solution of 5.0g. of 3-chlorodiphenylamine in 25 ml. of 1,2- dichlorobenzene. After warming to room temperature, the mixture was heated near reflux for 4 hours and then cooled. Extraction with 10% sodium carbonate solution gave a solution which was treated with sodium chloride to give a crude solid. Crystallization of the latter from 60:40 ethanol-isopropanol gave an initial fraction of inorganic salts followed by a product from the filtrate which showed proton NMR peaks at0^8.60 ppm (NH) , multiplets at 7.63 and 7.15, plus two aromatic proton peaks at lower field than seen in the starting material. A TLC gave an impurity at

R _£ 0.37, product at R _f 0.72, and some unreacted starting material at R _f 0.92.

EXAMPLE V

Carbazole-3-Sulfonic Acid, Sodium Sait-

A solution of 3.50 grams of chlorosulfonic acid in 20 ml. of chloroform was added dropwise over 30 minutes to a stirred, cooled solution of 5.0g. of carbazole in 200 ml. of chloroform. After the addition was completed, the mixture was refluxed for 2 hours, cooled, and 100 ml. of ιo% Na ₂ C0 ₃ solution added. The chloroform layer was separated, washed twice with 50 ml. of the Na ₂ C0 ₃ solutions, and the combined aqueous solutions filtered. Addition of sodium chloride gave a white solid which was removed by filtration and crystallized from aqueous ethanol. The white, crystalline product showed a proton NMR spectrum with NH near 11 ppm plus a complex aromatic region with peaks at lower field than seen in the starting carbazole itself. Comparison of this spectrum with the spectra of other carbazole-3-sulfonates (J. Cislo and A. Hopfringer, Tenside Detergents _r 13., No. 5, 253-9 (1976)) showed them to be very similar. The TLC had a strong

product spot at R _£ 0.47 plus an impurity at 0.28.

EXAMPLE VI

N-Phenyl-2-Aminonaphthalene-5-Sulfonic Acid. So ftφn Salt-

The sulfonation of N-phenyl-2-naphthylamine was carried out using the procedure of R. Lesser, Chem. Ber. , 27. 2363 (1894). To 80.2 g. of stirred 100% H ₂ S0 _Λ was added, with cooling to 20°C, 20.0 g. of N-phenyl-2- naphthylamine. When most of the solids had dissolved, the solution (under a drying tube) was put in a bath at 45°C overnight. The resulting solution was poured into 250 ml. of ice water with vigorous stirring and the resulting mixture heated to boiling. After cooling, the solids were removed by filtration, washed with water, triturated with 160 ml. of 0.518N. sodium hydroxide solution, filtered, and the solids crystallized from hot, aqueous ethanol to give beautiful white flakes. The TLC showed a strong spot at R _f 0.44 with faint impurities at R _t 0.014-0.18. Titration for sulfonate using a solution of diisobutylphenoxyethoxyethyl dimethyl benzylammonium chloride monohydrate (Hyamine ^® 1622 from Rohm and Haas) by the procedure reported in Anionic Surfactants-Chemical Analysis , Vol. 8 of "Surfactant

Science Series", J. Cross, Ed., p. 228 (1977) gave an equivalent weight of 322.9, compared with 325.4 calculated for the sodium salt of N-phenyl-2-naphthylamine-5-sulfonic acid.

EXAMPLE V I

N-Phenyl-2-Amiπonaphthlene-8-Sulfonic Acid, u salt-.

The sodium hydroxide solution (filtrate) from Example VI above was treated with an equal volume of saturated sodium chloride solution. The resulting precipitate was removed by filtration and air dried to give 16.6g. of buff-colored solids. Recrystallization from 25 ml. of hot water gave the 8-isomer, whose proton NMR spectrum showed peaks at 6.87 and 6.77 ppm. (2H); 6.31, 6.18, and 6.00 (3H); plus two peaks at 5.53 and 5.60 (7H), consistent with the structure of isomer B reported by Lesser to be the sodium salt of N-phenyl-2- aminonaphthalene-8-sulfonic acid (Chem. Ber. , 27 , 2363 (1894)). A TLC showed a strong blue fluorescent spot at R _£ 0.50 plus faint impurities at R _£ 0.10 and 0.33.

EXAMPLE VIII

ni hg»nγl mjne-4-Sulfonic Acid, Potassium Salt

To a solution of 4.00 g. (0.0148 mole) of sodium diphenylamine-4-sulfonate in 30 ml. of 0.5152 N HC1 solution (0.01546 mole) was added potassium hydroxide (0.174 g.) and a total of 8 g. KC1, in increments, with warming af er each 2 g. increment to dissolve the KC1. Standing gave off-white plates which were isolated by filtration, washed twice with a small amount of ice water (some product dissolved) and dried to give 0.82 g. white solids. A small amount of buff-white material was also recovered from the filtrate.

EXAMPLE IX

Diphenγ ?»i"«-4-Sulfonic Acid, Calci sai-h

To a solution of 4.00 g. (0.0148 mole) of sodium diphenylamine-4-sulfonate in 30 ml. of 0.5152 N HC1 solution (0.01546 mole) was added calcium hydroxide (1.15 g; 0.0155 mole). The mixture was heated to give a thick slurry which was cooled and filtered. The solids were water washed and dried to give 2.70 g. of white solids.

EXAMPLE X

Dipheny3amine-4-Sulfonic Acid. Barium sal

To a solution of 4.00 g. (0.0148 mole) of sodium diphenylamine-4-sulfonate in 30 ml. of 0.5152 N HC1 solution (0.01546 mole) was added barium hydroxide (2.65 g; 0.0155 mole). The resultant thick slurry was diluted with 50 ml. of deionized water, stirred and heated to boil, and barium chloride dihydrate (2.0 g.) added. The solution was cooled, filtered, the solids washed with water, air dried, and then dried at 50°C, to give 6.44 g. of white solid.

The following examples illustrate peroxygen compositions containing the stabilizing agents of this invention. EXAMPLE XI

Five solutions were prepared by dissolving

32.00g. of sodium perborate tetrahydrate and 41.00g. of sodium dihydrogen phosphate monohydrate in lOOg. of tap water (corresponding to 9.84% NaB0 ₃ and 20.6% NaH ₂ P0 ₄ ). The sodium salt of diphenylamine-4-sulfonic acid (DPλS) was

added in the amounts of 0, 0.0017, 0.0087, 0.0346 and 0.173 grams to give final solutions containing 0 to 1005 ppm of the stabilizing agent. The solutions were kept in a constant temperature bath at 30°C and samples removed weekly for titration with 0.1N KMn0 ₄ solution to determine the active oxygen content. The active oxygen lost as a percentage of the initial value then was calculated. These results are shown in Table I.

TABLE I Stability of Sodium Perborate/Dihydrogen

Phosphate Solutions with 0-1005 ppm DPAS at 30°C Active Oxvσen Lost

It is seen that excellent stabilization was achieved at 1005 ppm. of the DPAS stabilizer and that significant activity was observed at only 10 ppm.

EXAMPLE XII

Four solutions were prepared by dissolving 28.2g. of sodium perborate tetrahydrate, 28.2g of boric acid, and l.OOg. of DEQUEST 2066 (30% pentasodium salt of diethylenetriamine penta(methylene phosphonic acid) in aqueous solution) in lOOg. of tap water. This corresponds to 9.52% NaB0 ₃ , 17.9% H ₃ B0 ₃ and 1588 ppm. diethylenetriamine penta(methylene phosphonic acid) . To each of three solutions was added 0.0787g. (500 ppm.) of the indicated stabilizing agent. The fourth solution, containing no stabilizer, was included as a control.

The four solutions were held at 45°C for 14 days and the active oxygen content determined at the indicated intervals. The results are given in Table II. TABLE II

Stability of Sodium Perborate/Boric Acid Solutions at 45°C ve O

DPAS Diphenylamine-4-sulfonic acid, sodium salt. Cmpd. I 4-Nitrodiphenylamine-4 -sulfonic acid, sodium salt. Cmpd. II 4-Nitrodiphenylamine-3 -sulfonic acid, sodium salt.

These data show that, even in solutions already stabilized by a sequestrant (DEQUEST) , the stabilizing agents of this invention impart significantly more stability.

EXAMPLE XIJI

Aqueous solutions were prepared containing 33.3g. (10.6% NaB0 ₃ ) of sodium perborate tetrahydrate, 33.3g. (17.4% NaH ₂ P0 ₄ ) of sodium dihydrogen phosphate monohydrate, and 0.167g. (1000 ppm.) of various additives in lOOg. of deionized water. These solutions were maintained at 45°C in a constant temperature bath for 14 days, with samples taken periodically for active oxygen analysis by potassium permanganate titration. The stability test results are set forth in Table III.

TABLE III

Stability Test Data for Sodium Perborate/Sodium Dihydrogen Phosphate Solutions at 45°C.

Percent Active Oxygen Lost Days

11 14

14.4 82.7 98.2 99.7 0.8 10.6 59.6 79.9 0.4 9.7 54.8 77.0 0.7 11.4 55.4 77.0 0.0 17.5 34.2 42.5 0.4 43.7 87.1 95.4 2.4 18.50 63.4 85.6 0.0 7.0 18.8 30.4 0.0 7.2 17.2 25.2 0.0 8.2 19.3 31.2 1.3 19.1 65.0 82.6 0.0 7.9 21.4 42.3

14.0 81.6 97.4 99.1

Diphenylamine-4-sulfonic acid, sodium salt.

N-Phenyl-2-aminonaphthalene-5-sulfonic acid, sodium salt.

N-Phenyl-2-aminonaphthalene-8-sulfonic acid, sodium salt

Carbazole-3-sulfonic acid, sodium salt. 4-Nitrodiphenylamine-4'-sulfonic acid, sodium salt.

Cmpd. Ill 4-Nitrodiphenylamine-2'-sulfonic acid, sodium salt.

Cmpd. II 4-Nitrodiphenylamine-3 ^/ -sulfonic acid, sodium salt. The data shows that sodium 4-nitrodiphenyl- amine-4 '-sulfonate (Cmpd. I) is a preferred stabilizer in deionized water. Although Cmpd. VII showed improved stability compared with the control after 6 and 11 days, the activity dropped off at 14 days.

EXAMPLE XIV

Aqueous solutions were prepared containing 33.3g. of sodium perborate tetrahydrate and 33.3g. of sodium dihydrogen phosphate monohydrate in lOOg. of tap water. The sodium salt of diphenylamine-4-sulfonic acid (DPAS, 1001 ppm.) was added to one solution and 0.188g. (1127 ppm.) of 3-chlorodiphenylamine-4 ^/ -sulfonic acid, sodium salt (Cmpd. IV) to the other. After 14 days at 45°C, 77.5% of the initial active oxygen had been lost from the DPAS solution and 54.1% from the solution containing Cmpd. IV.

EXAMPLE XV

Seven solutions were prepared in deionized water as in Example XIII, and the barium, calcium, and potassium salts of diphenylamine-4-sulfonic acid tested as stabilizers with and without diethylenetriamine penta(raethylene phosphonic acid) (DTPA) chelating agent present. The results of active oxygen analyses over a 14 day period at 45°C are given in Table IV.

TABLE IV

Stability of Sodium Perborate/Dihydrogen Phosphate Solutions* at 5°C

% Active Oxygen Lost Days

10.64% NaB0 ₃ and 17.39% NaH ₂ P0 _Λ in deionized water.

These data clearly show that the potassium, calcium, and barium salts all are effective stabilizers, alone and in combination with the sequestrant.

EXAMPLE XVI

5 Boric Acid (14.0g.) and sodium percarbonate

(2Na ₂ C0 ₃ 3H ₂ 0 ₂ , 85%, 14.Og.) were dissolved in lOOg. of deionized water, in portions, with about one-third of the boric acid added first and dissolved followed by one-third of the percarbonate. This was repeated until all of the

10 boric acid and sodium percarbonate had been dissolved to give solutions containing 10.9% boric acid and 9.3% sodium percarbonate. To the solutions were added 1654 ppm. DTPA chelating agent and 1001 ppm. of the indicated additives. The results of following the loss of active oxygen over a

15 14 day period at 45°C are given in Table V.

TABLE V

Stability of Sodium Percarbonate/Boric Acid Solutions at 45°C

Percent Active Oxygen Lost Days

ne-4-sulfonic acid, sodium salt. Cmpd. I 4 -N itrodiphenyl amine- 4 ' -sul f onic ac i d , sodium salt.

EXAMPLE XVII

Test solutions were prepared by dissolving 25.Og. of sodium perborate tetrahydrate and 1220 ppm. of pentasodium diethylenetriamine penta(methylene phosphonic acid) (as DEQUEST 2066) in lOOg. of IN sulfuric acid solution in tap water to give 10.58% NaB0 ₃ , 3.9% H ₂ S0 ₄ and 1220 ppm. of the DTPA chelating agent. Stabilizing agents were added as indicated and controls (with and without the DTPA) were included. The active oxygen content of these

solutions was monitored for 14 days while maintained at

45°C in a constant temperature bath. The active oxygen losses are reported in Table VI.

TABLE VI

Stability of PBS4/H ₂ SO _d Solutions. 45°C.

Percent Active x en t Stabilizer

Additive ^* ppm

None -

DPAS 504

Cmpd. I 584 Cmpd. Ill 584

Control (No DTPA)

*

DPAS Diphenylamine-4-sulfonic acid, Na salt.

Cmpd. I 4-Nitrodiphenylamine-4'-sulfonic acid, Na salt.

Cmpd. Ill 4-Nitrodiphenylamine-2 ^/ -sulfonic acid, Na salt.

EXAMPLE XVIII

Test solutions were prepared by dissolving 40.Og. of sodium hydrogen (+) tartrate and 40.Og. of sodium perborate tetrahydrate in lOOg. of tap water to give 11.82%

NaB0 ₃ and 22.23% sodium hydrogen (+) tartrate. Tetrasodium ethylenediamine tetraacetate (EDTA) was added and 500 ppm.

of sodium diphenylamine-4-sulfonate added as a stabilizer. The solutions were maintained at 30°C. and the active oxygen content was determined as a function of time for each of the solutions. The results are shown in Table VII.

TABLE VII Stability of PBS4/Na H(+)Tartrate Solutions

Percent Active Oxygen Lost

EDTA DPAS** Days m" 14

* As free acid

** Sodium diphenylamine-4-sulfonate.

EXAMPLE XIX

Three solutions were prepared containing 33.3g. of sodium perborate tetrahydrate and 33.33g. of sodium dihydrogen phosphate monohydrate in tap water. The first

solution had no additives and lOOg. of tap water, the second contained 99.7g. of water plus 0.285g. of tetrasodium ethylenedia inetetraacetate dihydrate (EDTA) (1201 ppm. as free acid) and the third solution had a combination of 0.285g. of EDTA plus 0.167g. of sodium diphenylamine-4-sulfonate in 99.5g. of water. After aging for 14 days at 45°C, the solutions had lost 98.8, 91.4 and 72.4%, respectively, of their initial active oxygen content.

EXAMPLE XX

Three solutions were prepared containing 28.1g. each of sodium perborate tetrahydrate and of boric acid. The first solution (no additive) was prepared in lOOg. of tap water, the second in 99.7g. of water with 0.285g. of EDTA (1281 ppm as free acid), and the third in 99.5g. of water with a combination of 0.285g. of EDTA and 0.167g. of sodium diphenylamine-4-sulfonate. After aging at 45°C. for 14 days, the solutions had lost 81.1, 31.5 and 25.5%, respectively, of their initial active oxygen content.

EXAMPLE XXI

Comparative Test

In a comparative test, aqueous solutions containing 10.6% NaB0 ₃ and 17.4% NaH ₂ P0 ₄ in deionized water were prepared. Various stabilizing agents were added at a level of 1000 ppm. and the solutions maintained at 45°C. for 14 days. Samples were taken periodically for active oxygen analysis by potassium permanganate titration. Included in the test were two N-aralkyl substituted compounds (A and B) which are embraced by the generic formula of U.S. Patent 2,012,462. The results are set forth in Table VIII.

10

Cmpd. A N-benzyl-N-ethyl-4-sulfanilic acid, sodium salt

Cmpd. B N-benzyl-4-sulfanilic acid, sodium salt

DPAS Diphenylamine-4-sulfonic acid, sodium salt

15 cmpd. I 4-nitrodiphenylamine-4'-sulfonic acid, sodium salt

Cmpd. II 4-nitrodiphenylamine-3'-sulfonic acid, sodium salt

Cmpd. VI N-phenyl-2-aminonaphthalene-5-sulfonic ²⁰ acid, sodium salt

It is clear that the stabilizing agents of this invention are far superior to the N-benzyl substituted compounds disclosed by U.S. Patent 2,012,462.

EXAMPLE XXII

Hydrogen Peroxide/Boric Acid Solutions

Three solutions were prepared containing 20.0% of boric acid and sufficient 30% hydrogen peroxide plus aqueous sodium hydroxide to give a solution in tap water with a pH of 6.3 and an initial active oxygen content of 2.15%. One solution (no additives) served as a control, the second contained 1248 ppm. of diethylenetriamine penta(methylene phosphonic acid) (DTPA) , and the third had a combination of 1248 ppm. of DTPA plus 503 ppm. of sodium diphenylamine-4-sulfonate. After 14 days at 45°C, the solutions had lost 86.2, 33.8 and 28.3%, respectively, of their initial active oxygen content. Thus the DPAS (sodium diphenylamine-4-sulfonate) imparted additional stabilization over that provided by the DTPA sequestrant.

Various changes and modifications of the invention can be made and, to the extent that such variations incorporate the spirit of this invention, they are intended to be included within the scope of the appended claims.