US 3437599 A
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April 8, 1969 RESIDUAL PEQOXIDE TOTAL).
W. E. HELMICK ET AL HYDROGEN PEROXIDE DECOMPOSITION CONTROL WIT ALKALINE EARTH METAL CARBONATES Filed Oct. 28. 1966 90 O H O; NaOH Nm Si0 PH [0.58
A HzOz- Na.0H-O.1% SrCO PH IO.6O O H NLOH' 0.005% 5rCO PH I055 80 E1 H 0 NwOH O-O5/o 5rCO3 PH 1 O I i 0 IO 20 3Q 40 5O INVENTOR} ATT TIME (MINUTES) NEK;
United States Patent HYDROGEN PEROXIDE DECOMPOSITION CONTROL WITH ALKALINE EARTH METAL CARBONATES William E. Helmick, Doylestown, and Blaine 0. Pray, Wadsworth, Ohio, assignors to PPG Industries, Inc., Pittsburgh, Pa., a corporation of Pennsylvania Filed Oct. 28, 1966, Ser. No. 590,324 Int. Cl. C091; 3/00 US. Cl. 252-186 6 Claims ABSTRACT OF THE DISCLOSURE Alkaline earth metal carbonates in amounts of 0.00 to 1 percent by weight are added to aqueous alkaline hydrogen peroxide containing bleaching baths to control the rate of hydrogen peroxide decomposition.
The present invention relates to hydrogen peroxide bleaching. More particularly, the invention relates to improvements in hydrogen peroxide bleaching solutions. Still more particularly the present invention relates to the controlled decomposition of aqueous, alkaline hydrogen peroxide bleaching baths.
Sodium silicate has been used to control the rate of decomposition of hydrogen peroxide in hydrogen peroxide bleaching solutions for many years. While sodium silicate represents a suitable material for this purpose, it causes difficulties during the continuous bleaching of cotton goods and/or cotton and synthetic blends. Sodium silicate tends to deposit on the surface of stainless steel processing equipment utilized in continuous bleaching ranges and these deposits build up after continuous use, thus forming a rough scaly surface on this processing equipment. When fabric passes over the scale deposits, abrasion of the fabric occurs resulting in increased processing costs due to loss of fabric. The removal of silicate deposits on steel processing equipment becomes quite diflicult and they are typically removed by recourse to grinding the stainless steel surfaces. This, in turn, requires the disassembly of parts from a continuous bleaching range and a consequent interruption of production causing additional cost. A further difficulty involved in the utilization of sodium silicate for the control of decomposition rates of hydrogen peroxide in bleaching baths involves the depositing on the surface of the fabric being processed during the bleaching operation of sodium silicate. If deposition does occur on fabric prior to dyeing of the material, crows feet or uneven dyeing results on the cloth. This deleterious effect represents an additional cost due to reprocessing of the fabric necessitated to obtain level dyeings. In some cases, the fabric is not capable of being reprocessed and is consequently ruined.
In accordance with the present invention, many of the difliculties encountered in the prior art utilization of sodium silicate for controlling the rate of decomposition of hydrogen peroxide and hydrogen peroxide bleaching solutions are overcome. Thus, the utilization of an alkaline earth metal carbonate as in alkaline hydrogen peroxide bleach solutions provides a material which does not easily form on the surface of either fabric or processing equipment in solid form. It has been found in accordance with the instant invention that the utilization of alkaline earth metal carbonates, notably barium carbonate, calcium carbonate and strontium carbonate, not only provides a controlled rate of decomposition of hydrogen peroxide utilized in hydrogen peroxide bleaching solutions, but also results in a bleaching solution which is not detrimental to processing equipment utilized in continuous steel processing equipment. Still further, any tendency for any carbonate formation on the surface of steel equipment or the fabric itself can be easily eliminated by pH control of the bleaching solution. Thus, the art is provided in accordance with the instant invention with a suitable substitute for sodium silicate in the control of decomposition of hydrogen peroxide in hydrogen peroxide bleaching solutions.
In treating bleaching baths in accordance with the teachings of the instant invention, a quantity of alkaline earth metal carbonate of from 0.005 to 1 percent by weight is typically employed. Preferably alkaline earth metal carbonate concentration is from 0.3 to 0.8 percent by weight.
In order to achieve the full benefits of the effect of the carbonates of the instant invention, it is desirable to maintain a pH in the bleaching baths of from 7 .5 to 13, preferably from 9 to 12. Maintaining pH in this range can be readily accomplished by adding quantities of alkali metal hydroxides or other soluble base to the bleaching baths as needed. It will be obvious that in some instances the use of alkali metal hydroxide for pH control may not be required. So long as the solution of H 0, containing alkaline earth metal carbonate has a pH in the aforementioned range, there is no need for additional alkali addition thereto.
In general, the alkaline earth metal carbonates of the instant invention impart to aqueous hydrogen peroxide bleaching baths a controlled decomposition of the hy drogen peroxide. Typically hydrogen peroxide bleaching solutions contain on a weight basis 0.1 to about 2 per cent H 0 by weight. Preferably, these solutions are maintained with an H 0 content of between 0.1 and 1 percent by weight. With hydrogen peroxide bleaching solutions of this concentration having a pH from 7.5 to 13 and not containing any sodium silicate, it is now possible with the instant invention to provide a controlled rate of decomposition of peroxide formerly achieved with sodium silicate using alkaline earth metal carbonate. The precise mechanism by which this decomposition occurs or why decomposition of H 0 in such bleaching solutions is controllably permitted with alkaline earth metal carbonate is not fully understood. The presence of the carbonate ions in solution may be a determining factor or it may be the presence of both the carbonate and alkaline earth metal ions in association with the peroxide that imparts the benefits. Whatever the mechanism it has been discovered that a hydrogen peroxide bleaching bath without sodium silicate can be made to controllably release oxygen from hydrogen peroxide by providing an alkaline earth metal carbonate thereto and in concentrations of between 0.005 and 1 percent by weight at an aqueous hydrogen peroxide pH of between 7.5 and 13. Since no deposition of scale on process equipment occurs, the substitution provides benefits in the over-all processing costs involved in utilizing these bleaching solutions on continuous bleaching ranges where cotton and synthetic blend fabrics are employed.
.4 manner by immersion in a 3 percent by weight sodium hydroxide containing 0.1 percent by weight Sandopan D.T.C. The cloth was padded to a 100 percent pickup of solution, steamed for one hour at 212 F., washed with water and dried.
The dried cloth was then padded to 100 percent pickup of solution with the various bleach baths listed in Table 1. Each sample after pickup of the bleaching solution was steamed for various times as indicated in Table I and at 212 F., washed, dried and subjected to measurement of its reflectance. The results of these runs are shown in Table I.
TABLE I Securing Steam Bleaching Steam Reflectance 1 Run No. time time pH NaOH SrC 03 (min.) H202 NaOH NazSlOa SrC 03 (min) Blue Green (percent) (percent) (35%) (percent) (percent) (percent) (percent) (percent) 1 Measured on a Hunter multipurpose reflectometer.
tion to time. Also shown is a plot of the same residual peroxide as a percent of the total peroxide in the starting aqueous solution of peroxide with sodium silicate as the stabilizer.
The following example details the method employed to obtain the plots of FIGURE 1.
EXAMPLE I All decomposition studies were made by utilizing a five neck reaction flask of one liter capacity mounted in a constant temperature oil bath. The flask was equipped with stirrers passed in through one of the necks. A thermometer was inserted into the flask through another neck and two of the remaining three necks were filled with ground glass stoppers to serve as sample parts. The remaining neck was fitted with a set of condensers in tandem, both condensers being water cooled.
All solutions were prepared by adding all ingredients except the hydrogen peroxide to deionized water. When the solution of the ingredients for each run was effected the solution was placed in the flask and the temperature of the solution elevated by the oil bath to 95 C. When the temperature was lined out at 95 C. the hydrogen peroxide was added by pipette volumetrically. When the addition was complete, 1 minute was allowed for thorough mixing. A 10 milliliter sample was taken by volumetric pipette and called the zero sample time. Additional samples were then taken at 3, 6, 9, 12, 15, 30, 45 and 60 minutes. The peroxide content of the samples was then determined by volumetric method using a permanganate titrated similar to the test outlined on pages 553 and 554 of Schumb et al., Hydrogen Peroxide, 1955, Reinhold Publishing Corp., N.Y.
EXAMPLE II In all experiments 80 by 80 count cotton print cloth was used to test bleaching effectiveness. The fabric was scoured in caustic before bleaching in the conventional As will be readily appreciated from the above table, the use of alkaline earth metal carbonate, notably strontium carbonate, produces adequate bleaching of cloth and compares favorably with sodium silicate containing peroxide bleaching baths.
While the above examples show the utilization of strontium carbonate, barium and calcium carbonates can also be employed. When used both barium and calcium have been found to be effective in producing a control on the decomposition of hydrogen peroxide bleach baths while permitting such baths to perform effectively in the bleaching of cloth, particularly cotton cloth and blends of cotton and synthetics such as polyurethane, nylon, orlon and the like.
In utilizing the alkaline earth metal carbonates it is an important consideration that substantially pure chemicals (99.99 percent purity) be employed. Thus, reagent grade material is preferred and was employed in all the above examples.
Further, while the invention has been described with particular reference to the use of hydrogen peroxide bleaching baths, it is of course to be understood that it can also be employed in peroxide bleach baths prepared from inorganic and organic peroxides such as sodium peroxide, benzoyl peroxide and complex peroxy hydrates such as are described in US. Patent 3,140,149.
While the invention has been described with reference to certain specific examples, it is not intended to be so limited except insofar as appears in the accompanying claims.
What is claimed is:
1. An aqueous alkaline hydrogen peroxide containing bleaching solution containing a concentration of from 0.005 to 1 percent by weight of an alkaline earth metal carbonate sufiicient to control the rate of decomposition of the hydrogen peroxide wherein the pH is from 7.5 to 13.
5 2. The bleaching bath of claim 1 wherein the alkaline earth metal carbonate is strontium carbonate.
3. The bleaching bath of claim 1 wherein the alkaline earth metal carbonate is calcium carbonate.
4. The bleaching 'bath of claim 1 wherein the alkaline 5 6 References Cited UNITED STATES PATENTS 5/1916 Schaidhauf 252-186 1/1958 Feldmann 252-186 X LEON D. ROSDOL, Primary Examiner. I. GLUCK, Assistant Examiner.
US. Cl. X.R.
U.S. DEPARTMENT OF COMMERCE PATENT OFFICE Washington, 0.6. 20231 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,437 ,599 April 8 196' William E. Helmick et a1.
It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:
Column 5, line 9, "earth carbonate" should read earth metal carbonate Signed and sealed this 7th day of April 1970.
WILLIAM E. SCHUYLER, J
Edward M. Fletcher, Jr.
Commissioner of Patent Attesting Officer