US 3384596 A
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United States Patent Ofice 3,384,596 Patented May 21, 1968 3,384,596 PEROXY ACID BLEACHlN-G SYSTEMS John R. Moyer, Midland, Mich, assignor to The Dow Chemical Company, Midland, Mich, a corporation of Delaware No Drawing. Filed Dec. 30, 1965, Ser. No. 517,787 2 Claims. (Cl. 252--187) ABSTRACT OF THE DISCLOSURE The present invention relates to an aqueous bleaching composition which comprises an organic peroxy acid, a water soluble source of an alkaline earth metal ion, and water, said composition having a peroxy acid concentration which provides an active oxygen concentration of from about to 150 parts per million.
This invention relates to bleaching and more particularly concerns an improvement in organic peroxy acid bleaching compositions and a method of their use in bleaching operations whereby an unexpected increase in bleaching activity of organic peroxy acids is realized.
A primary object of the invention is to provide a novel system for increasing the activity of peroxy acid-containing, or, peroxy acid-producing compositions, and particularly for increasing the bleaching activity thereof.
Another object of the invention is to optimize the bleaching activity of organic peroxy acids thereby obtaining in bleaching operations brightness increases heretofore unrealized with peroxy acids alone. A related object is to provide a bleaching system and aqueous composition which does not detrimentally aifect articles bleached therein.
Other objects and advantages will become apparent from the following detailed description of the invention:
The novel aqueous bleaching composition of the present invention comprises an organic peroxy acid selected from the group consisting of metachloroperoxy-benzoic acid, monoperoxyphthalic acid, or peroxyacetic acid, a water soluble source of an alkaline earth metal ion selected from the group consisting of magnesium or calcium, and water, said aqueous bleaching composition having an alkaline pH and a peroxy acid concentration which provides an active oxygen concentration of from about 10 to 150 parts per million (p.p.m.). The aqueous bleaching composition is further characterized in that with metachloroperoxybenzoic acid either calcium or magnesium ion is employed at a metal ion/peroxy acid ratio of from about 0.5 to about 1, with monoperoxyphthalic acid magnesium ion is employed at a metal ion/peroxy acid ratio of from about 0.5 to about 2.5 and, with peroxyacetic acid calcium ion is employed at a metal ion/peroxy acid ratio of from about 0.5 to about 1.
The metal ion-to-peroxy acid ratio as used herein is based on moles of said metal ion to each acid group in the peroxy acid selected.
The improvement in activity of the peroxy acid is in general in a direct relationship to the amount of said metal ion present in the solution. Greater concentration of said metal ions, though not detrimental to the article bleached, is of diminishing value in enhancing the activity of the selected peroxy acid.
in general, the present novel process for increasing the activity of peroxy acids in aqueous solution and especially the bleaching activity of certain organic peroxy acid materials utilizing the improved composition of the present invention comprises: providing an aqueous alkaline solution of metachloroperoxybenzoic acid, monoperoxyphthalic acid, or peroxyacetic acid, and introducing thereinto a water soluble source of an alkaline earth metal ion selected from the group consisting of magnesium or calcium, said aqueous alkaline solution having an apparent pH ordinarily of about 9 and preferably about 10, and a peroxy acid concentration expressed as active oxygen of from about 10 to about 150 p.p.m., said aqueous alkaline bleaching solution containing said metal ion being characterized in that when metachloroperoxybenzoic acid is selected either calcium or magnesium ion is introduced therein in a metal ion-to-peroxy acid ratio of from about 0.5 to about 1, when monoperoxyphthalic acid is selected magnesium ion is introduced'therein in an ion-to-peroxy acid ratio of from about 0.5 to about 2.5, and when peroxyacetic acid is selected calcium ion is introduced therein in a calcium ion-to-peroxy acid ratio of from about 0.5 to about 1.
The calcium or magnesium ions are normally introduced into the peroxy acid solution as soluble inorganic salts.
In bleaching utilizing the novel aqueous composition of the present invention, a temperature within the range of from about F. to about 150 F. is ordinarily employed, but a temperature range generally limited only by said 100 F. as a minimum temperature and the boiling point of the respective bleaching solution may operably be employed. Preferably a temperature within the range of from about to about F. is used during bleaching.
The brightness increase obtained is directly related to the active oxygen concentration, i.e., greater increases are obtained at the higher active oxygen concentrations. Generally an active oxygen concentration of from about 10 to about 150 p.p.m. is employed in bleaching with peroxy acids, preferably from about 50 to about 100 p.p.m.
It is noteworthy that all metal ions and, in fact, even all alkaline earth metal ions do not operate to activate or increase the bleaching potential of the aforesaid peroxy acids. For example, the transition metal ions, iron, nickel, copper, mercury and cobalt actually serve to decrease the brightness of articles bleached by peroxy acids. Similarly, the alkali metal ions or the alkaline earth metal ions other than calcium and magnesium are not operable to any significant extent in the present invention.
The presence of the calcium or magnesium metal ions in the indicated ratio with the peroxy acid in the solution unexpectedly and very significantly enhances and increases the bleaching activity of the particular peroxy acid specified providing a powerful oxidizing solution, thereby obtaining unusually high brightness increases in fabric articles bleached therein.
The amount of water employed in the composition is that amount necessary to provide the aforesaid concentration of active oxygen in the solution. The pH of the bleaching solutions of the present invention are adjusted to an alkaline pH by eg the addition of caustic, etc.
The present invention distinguishes from methods concerning the stabilization of bleaching compositions. For example, though magnesium sulfate in bleach baths containing hydrogen peroxide serves to stabilize said baths by e.g., minimizing decomposition, neither calcium nor magnesium ions enhance the bleaching activity of hydrogen peroxide-containing solutions. In addition, as is shown in the following examples, neither magnesium nor calcium ion is effective to increase the bleaching activity of all peroxy acids, contrary to what might be expected if the ion were acting or being employed as a stabilizer.
The following examples serve to further illustrate the present invention but are not to be construed as limiting the invention thereto.
For purposes of the following examples and in order to make relative quantitative brightness determinations, a brightness (reflectance) value of zero (0) was assigned 3 1.0 a piece of unbleached muslin which had been washed in a 2.0 gram solution of a hOusehold detergent called Tide. All brightness readings in the following examples were obtained using a Hunter Photovolt Reflectometer with a green tri-stimulus lilter.
Example I Five by five (5 x 5") inch squares of unbleached muslin (brightness of were bleached in a solution at l30 F. and pH of 9.8 containing 2 grams of Tide detergent and 0.254 gram of 85% pure metachloroperoxybenzoic acid, corresponding to 20 parts per million (p.p.m.) active oxygen. The reflectance of the muslin bleached in the metachloroperoxybenzoie acid was determined to be 65.
Two identical solutions to that above were prepared. Calcium nitrate (Ca(NO -4H O) was added to one and magnesium sulfate (MgSO -4H O) to the other in a molar amount equal to that of the meiaehloroperoxybenzoic acid. Unbleached muslin squares were then exposed to each solution at 130 F. for about 10 minutes, rinsed, dried and then tested for brightness. Brightness increases of 11 and 6 points respectively on the scale defined above, were obtained over the brightness of muslin bleached in the detergent-metachloroperoxybenzoic acid solution not containing said calcium or magnesium values.
Example 11 Four bleaching baths were prepared. Each contained one liter of tap water and 2.0 grams of Tide detergent. Three contained sufficient metachloroperoxybenzoic acid to give 50 ppm. active oxygen. To one of these three baths, no additional chemicals were added. To a second was added a solution of magnesium sulfate sufficient to give one mole of magnesium ion per acid group in the metachloroperoxybenzoic acid. To the third bath was added a solution of calcium nitrate, in the same molar proportion with the peroxy acid. Each bath was maintained at 130 F. and adjusted to pH 9.8 by addition of NaOH solution.
A inch square of unbleached cotton muslin was agitated in each bath for minutes and then rinsed and dried. The reflectance of the cloth was measured with the Hunter Photovolt Refiectometer. The reflectance of the unbleached muslin was set at zero and that of the muslin bleached in 50 ppm. active oxygen as metachloroperoxybenzoic acid alone was established at 39. The bleaching results obtained by introduction of the aforesaid calcium and magnesium ions are given in Table I below.
From the figures in Table I it can be seen that the present invention provides outstanding brightness increases over the brightness obtained with metachloropcroxybenzoic acid alone.
Example III The tests set forth in Example II were repeated but at a temperature of 100 F. The increase in brightness (reflectance) obtained is presented in Table II below:
Example IV Similarly as in Example I unbleached muslin squares were bleached in a solution containing 2.0 grams of Tide detergent and an equal molar mixture of sodium perborate and phthalic anhydride (which react in aqueous solution to form monoperoxyphthalic acid) for about 10 minutes at F. The solution was adjusted to a pH of 9.8 and contained about 50 ppm. active oxygen. The brightness obtained was 20 as determined on the scale wherein the brightness of unbleached muslin was about 0.
To an identical solution was added 2 moles of per mole of the phthalic anhydride and like squares of unbleached muslin were contacted with the solution for 10 minutes at 130 F. A total brightness measurement of 30 points was obtained, representing a significant brightness increase of 10 points over that obtained with the monoperoxyphthalic acid solution containing no magnesium sulfate.
Example V The effect of increasing amounts of MgSO -7H O in bleaching unbleached muslin squares with m-chloroperoxybenzoic acid to give an active oxygen concentration of 50 ppm. was determined in a series of experiments at 130 F. in which the moles of magnesium ion (introduced as MgSO per acid group in the metachloroperoxybenzoic acid was varied. The results of these tests are given in Table III below:
TABLE III Molar Ratio of Mg++ ion-to-aeid group Total 7 Total Uain Brightness 0 (control) 1 .2 73 77 Example VI The effect of increasing amounts of MgSO -7H O in treating unbleached muslin squares with monoperoxyphthalic acid was determined in a series of experiments in which the moles of the Mg++ io-n, introduced as MgSO to the acid groups in the acid was varied. The test conditions of temperature, time and pH are those of the Example IV. The results are given in Table IV below.
TABLE IV Molar ratio: Total brightness 0 (control) 20 0.25 (control) 18 Table IV shows that with respect to monoperoxyphthalic acid, increases in brightness are obtained by increasing the moles of Mg ion to the acid at least to about 2.5, whereas at a ratio of less than about, e.g., 0.25 no increase in brightness is provided over that obtained with the mono peroxyphthalic acid alone.
Example VII Squares of unbleached muslin fabric (brightness at 0) were bleached for minutes in a bleaching solution comprising 2.0 grams of Tide detergent in one liter of tap water at a temperature of 130 F. To this was added sufiicient peroxyacetic acid to give 100 p.p.m. active oxygen and aqueous sodium hydroxide to adjust the pH to 10. The brightness of the muslin obtained from bleaching in this manner was 45.
Two identical bleaching baths were prepared. To one was added a solution of calcium nitrate in a mole quantity equal to the number of acid groups in the peroxyacetic acid. To the other bath, as a comparative or control example was added a similar amount of magnesium sulfate.
The brightness of the muslin after bleaching in the calcium nitrate-containing solution was about 58, whereas, the brightness of the muslin after bleaching in the magnesium sulfate-containing solution was about 46, this being substantially the same as for the peroxyacetic acid alone.
This example illustrates the outstanding increases in brightness obtained by the introduction of calcium ion to peroxyacetic acid, while essentially no bleaching improvement is obtained by the introduction of magnesium ion to peroxyacetic acid.
Similarly as in the foregoing examples, other combinations and concentrations of metal ions and peroxyacids maybe employed in solution to optimize or increase the activity over that of the peroxyacid alone.
The present novel invention may be modified and changed without departing from the spirit or scope thereof, and it is understood the invention is only limited as defined in the appended claims.
1. An aqueous bleaching composition consisting essentially of an organic peroxy acid selected from the group consisting of metachloroperoxybenzoic acid, monoperoxyphthalic acid, or peroxyacetic acid, a water soluble salt of an alkaline earth metal ion selected from the group consisting of magnesium or calcium, and water, said aqueous bleaching composition having an alkaline pH and a peroxy acid concentration which provides an active oxygen concentration of from about 10 to 150 parts per million, said aqueous bleaching composition being further characterized in that with metachloroperoxybenzoic acid an alkaline earth metal ion selected from the group consisting of magnesium or calcium is employed at a metal ion to peroxy acid ratio of from about 0.5 to about 1.0, with monoperoxyphthalic acid magnesium ion is employed at a metal ion to peroxy acid ratio of from about 0.5 to about 2.5, and with peroxyacetic acid calcium ion is employed at a metal ion to peroxy acid ratio of from about 0.5 to about 1.
2. The aqueous bleaching composition of claim 1 wherein said composition has a pH of at least about 9.
References Cited UNITED STATES PATENTS 2,254,434 9/1941 Lind et al 252 X 3,075,921 1/1963 Brecklehurst et al. 252186 X 3,156,654 11/1964 Konecny 252-186 X LEON D. ROSDOL, Primary Examiner.
I. GLUCK, Assistant Examiner.