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Publication numberUS2838459 A
Publication typeGrant
Publication dateJun 10, 1958
Filing dateFeb 1, 1955
Priority dateFeb 1, 1955
Publication numberUS 2838459 A, US 2838459A, US-A-2838459, US2838459 A, US2838459A
InventorsSprout Jr Oliver S
Original AssigneePennsalt Chemicals Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Stabilization of solutions containing peroxygen compounds
US 2838459 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

United States Patent STABILIZATION OF SOLUTIONS CONTAINING PEROXYGEN COMPOUNDS Oliver S. Sprout, Jr., North Hills, Pa., assignor to Pennsalt Chemicals Corporation, Philadelphia, Pa., a corporation of Pennsylvania No Drawing. Application February 1, 1955 Serial No. 485,620

6 Claims. (Cl. 252-186) This invention relates to the stabilization of solutions containing peroxygen compounds, such as hydrogen peroxide and sodium peroxide, which may be used for the bleaching of textile fibers and fabrics, wood, wood pulp, feathers, and the like.

Bleaching solutions containing hydrogen peroxide are inherently unstable under the normal hot alkaline conditions of usage, and many stabilizing agents have been proposed in an effort to overcome excessive decomposition of the peroxide.

The present invention includes a stabilizer additive for .a solution containing an inorganic peroxygen compound such as hydrogen peroxideor sodium peroxide and an alkali-metal silicate, comprising a compound which liberates magnesium ions in alkaline aqueous solution and an alkali-metal phosphate. Also contemplated by the invention are bleaching baths stabilized by magnesium ion, alkali-metal phosphate and alkali-metal silicate, and methods of bleaching in which these materials are employed.

In accordance with the present invention, textile fibers and fabrics, feathers, wood, and wood pulp, for example, may be bleached at temperatures as high as the boiling point of the bleaching bath, and may be bleached under superatmospheric pressure if desired. Highly bleached products are produced in less time than by conventional processes while consuming small, economically attractive, quantities of peroxide.

The bleaching of cotton, silk, and synthetic fabrics has been generally accomplished heretofore by the employment of bleaching baths containing about 0.15 to 3.0%

hydrogen peroxide (100% basis) by weight of solution.

However, it has been found that up to 7% hydrogen peroxide (100% basis) may be required to bleach single strand regenerated cellulose filaments, such as viscose rayon; at ISO-160 F. in a continuous process where the bleaching stage is limited to about 30 seconds. The bleaching bath stabilizing materials of the invention can be used to stabilize baths containing up to about 7% hydrogen peroxide (100% basis) equivalent to 70 parts per liter or 2333 parts per 33.333 liters or higher, as required for viscose filament bleaching. Thus, it has been found that a solution containing 1.5% hydrogen peroxide (100% basis) can be maintained at 180 F. for seven hours with no loss of peroxide content, when stabilized according to the invention, and a solution containing 3.5% hydrogen peroxide (100% basis) under otherwise identical conditions has been found to undergo decomposition to the extent of only 17% of the original peroxide content.

Pulp from the groundwood process is often commercially bleached by the use of peroxide. Sodium or hydrogen peroxide, or their combinations, are employed as the active bleaching agents, the bleaching solutions also containing sodium silicate and Epsom salts, Sulfuric acid or caustic soda is added to the bleach liquors to obtain the desired degree of alkalinity.

The alkaline peroxide solutions are also used instead ice of chlorine-containing oxidants to bleach wood pulps from the chemical pulping processes. The peroxide bleach is usually included in the final stages of a multistage bleaching process, or it may be used alone to ob-' tain the desired product characteristics. The peroxides also find use in the bleaching of other fibrous cellulosic' materials from cotton, rags, flax straw, agricultural residues, waste paper, wood, wood chips, and the like.

The stabilizers of the invention are equally applicable to all peroxide solutions of concentration ranging from a low of about 0.25% to a high of about 7.5% (100% basis) as is disclosed in Tables 1 to 8 below. These percentage figures are equivalent to 2.5 to parts per liter or about to about 2500 parts of peroxide basis) per 33.333 liters respectively, and to all peroxide bleaching procedures regardless of the material to be bleached, its origin, the sequence of operations, or other variations within the broad class of peroxide bleaching.

By use of the stabilizers of the invention, the stability of the above described peroxide solutions in storage is improved, greater eifectiveness in bleaching action is realized, supplementary chemicals in bleach baths are significantly reduced or eliminated, and economic advantages in practical bleaching can be achieved.

The stabilizers of the invention contain specific proportions of water-soluble organic or inorganic magnesium salts, alkali-metal polyphosphate and alkali-metal silicates. Among the magnesium salts which may be used are magnesium sulfate, magnesium chloride, magnesium nitrate, and magnesium acetate either in the hydrated or anhydrous form. For example, magnesium sulfate heptahydrate, commonly known as. Epsom salts, may be employed, or any partially dehydrated magnesium sulfate containing less than 7 molecules of water of hydration per molecule of salt. Also, magnesium chloride hexahydrate may be used, or any other hydrated magnesium chloride having less than 6 molecules of water of hydration per molecule of salt. "The presence of water of hydration in the salt molecule is not important and may be compensated for when making up the stabilizer formulation. The substitution of magnesium by calcium, barium, strontium, zinc, or aluminum has not resulted in an equal reduction of peroxide decomposition. Generally, any source of magnesium ions can be employed.

Among the alkali-metal polyphosphates (conveniently referred to as polyphosphates) which may be employed are sodium tetraphosphate, sodium pyrophosphate, sodi um tripolyphosphate, sodium hexametaphosphate, potassium tetraphosphate, potassium pyrophosphate, potassium tripolyphosphate, or potassium hexametaphosphate. All of these polyphosphates may be employed on the basis of equivalent phosphorus pentoxide content with equally good results. Tri-sodium orthophosphate, or tri-potas sium orthophosphate may also be employed to impart good stability to bleaching baths, but an immediate precipitation results which may be objectionable in some applications. Thus as can be seen. from the above, the alkali metal polyphosphates are the preferred phosphate additives.

A variety of silicate compounds available in liquid or solid form and varying in chemical composition are used in the stabilization action along with the magnesium ion and alkali-metal polyphosphate. I prefer to use the soluble alkali-metal silicates which are relatively cheap and readily available. For textile bleaching, one such silicate is a 42 B. sodium silicate solution having a Na O to SiO ratio of 1 to 2.5. Obviously, other sodium silicates having different Na O to SiO ratios are equally applicable. A silicate frequently used in pulp bleaching has a Na O to SiO ratio of l to 3.2.

In order to achieve the superior stabilizing action of my invention, the peroxide solutions being stabilized must contain the three components-a magnesium salt, an alkali-metal phosphate and an alkali-metal silicate in specific proportions. Thus, sufficient magnesium salt must be present to provide a concentration of at least 0.003% magnesium ion by weight. The 0.003% magnesium ion corresponds to 0.03 parts by weight per liter or 1 part for 33.333 liters. This is the concentration of magnesium ion used in Tables 2, 4 and 5. Greater amounts of magnesium salts, of course, can be used subject to the limitation that large amounts of solids, where solubilities are exceeded, would be objectionable in most bleaching operations. Preferably from 1 to 67 parts by weight of magnesium ion per 33.333 liters of solution are used, this figure corresponding to a weight concentration of from 0.003% to 0.20% magnesium ion. For every one part by weight of magnesium ion used, 1 to 5 parts of an alkali-metal phosphate must be present. The silicate preferably may vary from 8 to 1750 parts by weight for every 33.333 parts of peroxygen solution being stabilized but concentrations of from 8 to 2500 parts by weight of alkali-metal silicate per 33.333 parts by weight solution are useful in my invention.

In some applications, the materials to be bleached may contain water or moisture which would tend to unduly dilute the bleaching solutions. For such cases, strong feed solutions many times as concentrated as the bleach solution can be prepared and added to the bleach bath. The proportions of the chemicals in the feed solution are increased to compensate for any dilution effects on introduction into the bleach solution. For example, a bleach solution containing 0.27% stabilizing additive, 0.66% silicate, 0.05% caustic soda, and 0.70% H 0 (100% basis) was prepared by introducing a solution of four times this concentration, i. e., 1.08% stabilizing additive, 2.64% silicate, 0.20% caustic soda and 2.80% H 0 (100%). The strong feed solution was fed at the appropriate rate into a bleach solution through which wet cloth was passed, thereby maintaining the composition of the bleach solution at the level specified above. The bleach solution contained 0.27% stabilizing additive compound of 74% MgSO .3H O and 26% Na P O and was thus equivalent to 0.027% magnesium. The strong feed solution was four times as concentrated and contained .108% magnesium equivalent to 36 parts magnesium ion per 33.333 liters.

It is evident from the above that the overall concentration of magnesium, polyphosphate and silicate are critical; and, secondly, that the ratio of polyphosphate to magnesium is critical in securing the superior stabilizing action of my invention.

The components of the stabilizer composition may he added singly to the bleach bath or they may be added in combination. Since the alkali-metal silicate frequently used is 42 B. sodium silicate, a liquid, it is preferred to add this directly to the bleach bath, either before or after the magnesium salt and polyphosphate addition. The silicate is usually not added to mixtures of magnesium salts and polyphosphates due to formation of insoluble cement-like silicates.

It is convenient for commercial plant practice to provide the proper proportions of magnesium salt and alkali metal polyphosphate by blending the respective granular salts in the correct ratio. Such a blended mixture of magnesium salt and polyphosphate will be referred to hereafter, for convenience, as the stabilizer additive. The stabilizer additive 18 added to the bleach bath either before or after the addition of the peroxygen compound and silicate.

In batch operation, the stabilizer additive is usually added first to the water of the bleach solution, followed by the silicate, peroxygen compound and any other supplemental alkali or other material desired. This order is not essential insofar as acheivement of stabilization is concerned, however, and any other order of adding the stabilizing components can be followed, although the order first described is preferred. The bleach solution is then ready for use. Where bleaching solutions are prepared and used continuously, the stabilizer additive comprising magnesium salt and alkali-metal polyphosphate, the silicate and the peroxygen compound in dilute or concentrated form can be added concurrently to form the bleach solution.

It is also advantageous to introduce the magnesium salt and alkali-metal polyphosphate as a stabilizer additive since the polyphosphate substantially prevents the precipitation of the magnesium salt in solutions containing silicate. Thus, if a magnesium salt and silicate are introduced into the same solution, an immediate precipitate occurs. With the stabilizer additive of my invention, however, such precipitates are not formed in solutions of silicates. This is also a distinctive feature of the invention. While the exact mode of action is unknown to me, and varies with existing conditions, the polyphosphate appears to combine with the magnesium salt in a manner to prevent immediate large-scale reaction with the silicate. It is thus preferable in most cases to first dissolve the stabilizer additive in the water of the bleach bath to permit interaction of the magnesium salt and polyphosphate before introduction of the silicate. For many applications, nevertheless, such order of mixing is not essential even though the granular stabilizer additive and silicate are added to the bleach solution more or less simultaneously with development of a faint opalescense or turbidity which is not objectionable.

Generally, the stabilizer additive of the invention contains sufficient magnesium compound to provide about 1 part by weight of magnesium, which is equivalent to about 5 parts by weight of anhydrous magnesium sulfate, and the equivalent of about 1 part by weight to 5 parts by weight of an anhydrous alkali-metal polyphosphate. The parts by weight of the components employed will be correspondingly increased when hydrated compounds are used instead of anhydrous compounds. The stabilizer additive may be formulated as a dry powder in the desired proportions, and then added to the solution to be stabilized, but if a magnesium salt and an alkali-metal polyphosphate, for example magnesium sulfate and sodium tetraphosphate, are mixed together prior to addition to the bleaching bath, a magnesium sulfate having not more than about three molecules of water of hydration per molecule of salt should be employed, instead of magnesium sulfate heptahydrate, since when magnesium sulfate heptahydrate and sodium tetraphosphate are mixed together the mass begins to set up in a few hours and a solid mass results. However, magnesium sulfate heptahydrate and an alkalimetal polyphosphate, such as sodium tetraphosphate, may be combined and stored without agglomeration it the magnesium sulfate heptahydrate is first partially dehydrated and then milled and blended with the tetraphosphate. A stabilizer additive containing about 74% by weight magnesium sulfate trihydrate, and about 26% by weight of an alkali-metal polyphosphate, such as sodium tetraphosphate, has been found to provide ex cellent results in plant usage.

Peroxide solutions for textile fabric or fiber or feather bleaching, stabilized in accordance with the invention may contain, for about each 33.333 parts of solution, a maximum of about 2500 parts by weight basis) peroxide compound selected from the group consisting of hydrogen and sodium peroxide the equivalent of about 5 parts by weight of anhydrous magnesium sulfate or anhydrous magnesium chloride, or an equivalent amount of another magnesium salt, about 1 to 5 parts by weight of alkali-metal polyphosphate, and about 8 to about 1750 parts by weight of sodium silicate.

A stabilized peroxide solution for textile fabric or fiber or feather bleaching containing, for example, 100 parts by weight of magnesium sulfate heptahydrate, or an equivalent amount of another magnesium salt, 25 parts sodium tetraphosphate, and 175 parts sodium silicate, corresponding to a concentration of 0.03%, 0.0075% and 0.0525% respectively, by weight of solution has been found ot give excellent results. The concentration of the stabilizer may be greatly increased if necessary as a result of adverse conditions, such as an increase in alkalinity or temperature of the bath. Caustic soda, soda ash, or sodium silicate may be added for the purpose of adjusting alkalinity, but satisfactory bleaching with decreased peroxide consumption has been elfected at pH values as low as 8 to 9.5. In continuous operations, the bleaching bath composition is maintained substantially constant by the introduction of feed liquor which replenishes stabilizer and peroxide lost in drag-out.

The bleaching of dark colored feathers by hot stabilized solutions of hydrogen peroxide produces feathers of a high degree of whiteness, which is unobtainable by conventional methods. For example, it has been found that dark brown goose feathers can be bleached to a full white hue by a bleaching procedure in which the feathers are immersed in an aqueous bleaching solution containing hydrogen peroxide, sodium silicate, magnesium salt, and polyphosphate in the proportions of my invention. The feathers are heated generally for several hours in the bleaching solution, after which the feathers are rinsed and dried.

In pulp bleaching, the peroxide solution should contain sufiicient magnesium compound to provide about 0.05 to 0.5 part of magnesium per 1000 parts of solution, which is equivalent to about 0.25 to 2.5 parts of anhydrous magnesium sulfate per 1000 parts of solution, about 0.05 to 2.5 parts of alkali-metal polyphosphate per 1000 parts of solution, maintaining the ratio of phosphate to magnesium at all times within the range of 1:1 to 5:1, and about 1.5 to 100 parts of sodium silicate per 1000 parts of solution. A stablizer additive containing a magnesium salt and an alkali-metal polyphosphate, such as, for example, 74% by weight magnesium sulfate trihydrate and 26% sodium tetraphosphate, may be dissolved in the water making up the bleaching solution followed by the desired amount of sodium silicate and then the peroxide, after which the bleaching liquor is ready for use. If necessary, an acid or alkali may be added to the solution to obtain the desired alkalinity. Sodium peroxide or a mixture of sodium peroxide and hydrogen peroxide is generally employed for pulp bleaching. The stabilizing compositions of the invention are equally effective for use with hydrogen peroxide, sodium peroxide, or mixtures thereof.

In employing my invention in pulp bleaching, only A water-white, iron-free sodium silicate having a Na O to SiO ratio of 1 to 2.5, containing 36.8% solids, and having a B. gravity of 42 is preferred, when a silicate is used, but silicates of other ratios, such as that having a 1 to 3.3 ratio, may also be used.

The invention will be further illustrated by reference to the following specific examples:

EXAMPLE 1 A series of experiments were performed to determine the effect of sodium silicate on the stability of hydrogen peroxide solutions. Sodium silicate, such as Philadelphia Quartz Star Brand or equivalent, having a Na O/SiO ratio of 1 to 2.5 is the most commonly used 6. stabilizer in the textile industry. Caustic soda may also be added, primarily to aid bleaching. Silicates are generally used in peroxide bleaching to assist penetration into the fibers and motes, suspend dissolved matter, and act as a detergent. A series of solutions containing 0.25% hydrogen peroxide basis), and containing various quantities of sodium silicate, were maintained at F. for the periods of time indicated in the table below. The results are as follows:

Table 1 pH H202 decomposition Percent: sodium silicate Expt. No. Percent of original decomposed Time Start End Hrs. Mins.

0.75 1.5 siL. 0.1 NaOI-I...

1 "N silicate (NarO/SiOz ratio 1/3.2) used in this run to determine whether a ditierent type of silicate would alter results.

It will be observed that the addition of sodium silicate to the peroxide solutions greatly decreased the stability thereof.

EXAMPLE 2 Table 2 pH H202 decomposition Percent Not P4013 Percent Time Parts 1 Start End original decomposed Hrs. M ins.

1 Based on 0.03% MgSO4.7H2O=1 part, 0.007591, NaoP4On=ll25 part, 0.0525% silicate=L75 parts.

These experiments show that when .0075 to 0.015% of Na P O are added to peroxide solutions containing 0.03% MgSO .7H O and 0.0525 sodium silicate effective peroxide stabilization is obtained (Nos. 4, 5 and 6); but that when larger amounts of Na P O are used Without increasing the other components little effective stabilization is obtained (Nos. 1, 2 and 3).

EXAMPLE 3 A series of experiments were performed to ascertain the eifect of various combinations of stabilizing ingredients on peroxide stability. The ingredients were added to peroxide solutions containing 0.25% by weight hydrogen peroxide 100% basis) and these solutions were maintained at 180 F. for the periods of time indicated. The results are as follows:

Table 3 pH H2O: decomposition Percent Expt. Solution eonstitucon- Percent Time No. ents) stituof out Start. End original decom- .l'lrs. Mins.

posed 1.-. 112010111 5,0 5.9 72.8 1 2 Sodium sil eatonn 0.0525 10.2 10.2 99.2 0 20 3 Mg'SO4-7H2O 0.03 6.0 5.0 80.0 2 30 4.- NaePioia 0.0375 8.8 7.5 76.5 24 i3 5. klfialIzign 8.8075 8.2 7.2 94.3 24 0 1110 4 1:1 375 0 nhf p s 8 }7.0 0.0 01.5 24 10 "a- 4 l3 .0075 7 l i gi 8837 }0.8 '3 89.7 24 0 is 4 1:1 8 Sodium silicatcnu 0.0525 24 (0.03% IMgSO4.7H2O=1 part, 0.053751% NaaP4O13=L25 part8, 0.0525% sihcatc =1.75 parts.)

Table 3 shows that the stability of a peroxide solution (No. 1) is quite poor since major decomposition occurs in an hour at 180 F. Addition of sodium silicate as indicated actually accelerates decomposition (No. 2), while addition of Epsom salt to a peroxide solution (No. 3) has very little stabilizing effect. The stability of peroxide solutions containing sodium tetraphosphate in several proportions (Nos. 4 and 5) or sodium tetraphosphate with Epsom salt (Nos. 6 and 7) or silicate (No. 8) is somewhat improved since a little peroxide (about 1-40%) remains after heatingfor 24 hours. The degree of stabilization achieved is of such a minor degree, however, that these solutions would have no value as commercial bleach baths. On the other hand, in accordance with my invention, solutions containing critical proportions of Epsom salt, sodium tetraphosphate and silicate suffered only from about 10% to 50% decomposition, on heating 24 hours at 180 F. as is shown by Table 2, Nos. 4, 5 and 6.

EXAMPLE 4 To ascertain the effect of substituting various phosphates in the stabilizing formulation, various constituents were added to 0.25% by weight hydrogen peroxide solutions (100% basis) in quantities sufiicient to provide the same quantity of P 0 as would be normally supplied by 0.0075% by weight sodium tetraphosphate in solution. All solutions contained 0.03% by weight magnesium suifate heptahydrate and 0.0525 by weight sodium silicate in addition to the other constituents. The results are as follows:

07HzO=i part, 0.00759}; NHOP4013=025 part, 0.0525% sodium silicate=1.75 parts.)

Insofar as stability is concerned, any of the above polyphosphates can be employed with success. It was also found that although the solution of magnesium sulfate and tri-sodium orthophosphate had excellent stability a precipitate was produced which would be disadvantageous in practice (No. 4).

8 1 EXAMPLE 5 A series of tests were performed to ascertain the effect of substituting other cations for magnesium ions, and

5 various constituents were added to 0.25% hydrogen peroxide solutions (100% basis) in quantities suflicient to provide an amount of cation chemically equivalent to Mg++ in solutions containing 0.03% by weight magnesium sulfate heptahydrate. All solutions contained 10 0.0075 by weight sodium tetraphosphate and 0.0525 by weight sodium silicate in addition to the constituents shown. The results are as follows:

Table 5 pH H202 decomposition Percent Expt. Cation constituent con- Percent Time N o. stituont of Start End original decomposed Hrs. Mins.

lVIgClzfiI-IzO. 0. 2 s. 3 10. 4 24 0 0.5 0.7 08.6 4 25 0.7 as 98.0 a5 0.7 9.8 98.0 5 45 8.7 7.8 42.0 24 10 7. 1 o. 0 57. s 21 10 0. 4 7. 0 12 0 2:5 5',

(0.03% MgSO .7I'l2O=l part, 0.00757 N11nl1O ;--0.25 part, 0.0525% sodium silicatc=1.75 parts.)

From the above it will be seen that Ca Ba++, Sr++,

Zn++, and Al do not give stability equivalent to Mg, and that magnesium chloride may replace magnesium sulfate with equivalent efficacy.

EXAMPLE 6 quantities of sodium hydroxides were added to 0.25% by weight hydrogen peroxide solutions (100% basis) containing 0.03% magnesium sulfate heptahydrate (1 part) and 0.0525% by weight sodium silicate (1.75 parts), the solutions being maintained at 180 F. for the do periods of t1me 1nd1cated. The results are as follows:

Table 6 5O N3aP40|3 NaOH pH H202 Decomposition Percent Expt. oiOrigi- Time No. Percent Parts Percent Parts Start End nai De- C0111- posed None None None None 9.0 7.8 6.4 23 None None 0.015 0.5 9.9 0.7 14.0 23 55 0.0075 0.25 0.015 0.5 10.0 9.8 17. 0 21 0 0.015 0.5 0.015 0.5 10.1 9.9 30.8 23 55 0.0375 1.25 0.015 0.5 10.3 9.9 72.8 23 55 None None 0.03 1 10.4 10.2 16.0 2:; 55 0.0075 0.25 0. 03 1 10.5 10.3 34.4 24 5 0.015 0.5 0.03 1 10.4 10.3 00.0 23 55 0.0375 1.25 0.03 1 10.4 10.4 84.0 23 55 None None 0.00 2 10.0 10.8 33.0 24 0 0.0075 0.25 0.00 2 10.0 11.1 72.8 24 5 0.015 0.5 0.06 2 10.6 10.0 00.4 24 5 0.0375 1.25 0.06 2 10.8 10.8 72.8 24 0 EXAMPLE 7 A series of experiments were performed in which increased quantities of stabilizer were used with increased caustic concentrations. The solutions to which the constituents were added were 0.'25% by weight hydrogen peroxide solutions (100% basis) maintained at 180 F[ The results are as follows:

.those from the hypochlorite bleach. Under the explora tory conditions employed in these trials, the use of solutions containing about 3% hydrogen peroxide before the Table 7 MgSOMHgO Sodium silicate NauPtOn PH 11202 decomposition Efipt. NaOH, Percent Time percent of Percent Parts Percent Parts Percent Parts Start End original decom- Hrs. Mins.

posed At equal ingredient concentration, use Of 0.25 part sodium tetraphosphate is superior to 1.25 parts. At a given sodium hydroxide content, the use of 0.25 part sodium tetraphosphate permits the use of reduced amounts of stabilizing chemicals. If the sodium hydroxide content of the bath increases, as might happen in use, stabilization may be controlled to some extent by increasing the stabilizer concentration at 0.25 part sodium tetraphosphate.

EXAMPLE 8 A series of experiments were performed to determine whether continuously generated and processed rayon filaments might .be satisfactorily bleached by the use of hydrogen peroxide instead of sodium hypochlorite. The filaments are continuously generated and formed into a loose. yarn which then progresses successively through the following stages: acid, water-wash, sulfide, wash, bleach, acid, wash, soap, and dry. Twenty seconds are normally allowed for bleaching, or about two inches on the machine.

Peroxide bleaching solution was first used in place of the usual hypochlorite bleach without subsequent washing and soaping. Increases were then made in the peroxide. The washing and soaping stages were next respectively reintroduced into the cycle. The peroxide bleaching solution was then added after soaping and before drying with subsequent reductions in strength of the heater gave most satisfactory results. The influence of temperature on the speed of the bleaching reaction is of considerable importance and elevated temperatures perrnit reduction in bleaching time as well as reduction in peroxide content of the bleach solution. Thus, use of solutions containing 6.6% hydrogen peroxide was required for satisfactory bleaching when washing and soaping were omitted and the normal machine distance of about two inches for bleaching was lengthened to about fourteen inches including drying (Run No. 2). However, solution strength requirements were reduced to only 3.3% hydrogen peroxide when. the bleach was added after soaping and immediately before the heater, where warm air at about 180 F. dried the yarn on the last few inches of the machine (Run No. 7).

EXAMPLE 9 A series of plant runs were performed on various types of fabrics in which kier-boiled and washed cloth was pulled from a storage pit in succession through a washer,

a saturator filled with hot water, a squeezer, first and second U-shaped tubes containing heated bleach solution, a final squeezer, and out to a washer. The cloth speed was 110 yards per minute through the U-tubes while the washers were operated intermittently at 225 yards per minute. pits to the first U-tube, and in one run the second U-tube contained only a small amount of bleach solution and peroxide bleaching solution. The results are as follows: was operated essentially dry. In another series of Table 8 SUMMARY OF PROCEDURES AND RESULTS FOR CONTINUOUS RAYON YARN BLEAOHING Percent Bleaching Residual Bun Bleaching solution Bleaching solution solution Further process Results H509 No. used added temp., operations F. yarn basis 1 0.5% av. OhNaOOl. Bleaching stage... Control .4% H 0. Not as well bleached as No. 1, NaOOl.

do- Alter soap, before heater.

About as good as No. 1, N 21001 White not as good as No. 3.-. Still poorer bleach than N o. 4

harsh.

All peroxide bleach solutions contained 0.12% stabilizer additive and 0.44% sodium silicate.

The stabilizer additive employed consisted of 74% by weight magnesium sulfate trihydrate and 26% by weight sodium tetraphosphate. Continuously produced rayon yarn was bleached with stabilized solutions of hydrogen peroxideto-yield products which appeared as white as 7!! follows:

bleaches, the bleaching solution used in one days operation was held over for use the second day. Feed liquor addition was made to maintain the peroxide strength of the bleaching solutions in the U'tubes. The results are as In two instances passage was directly from the Table 9 I SUMMARY OF BLEACHIN G CONDITIONS AND RESULTS FOR STABILIZED HIGH TEMPERATURE CONTINUOUS PEROX IDE BLEAOHING Cloth Pro-treatment 1st U-tube Single Double Bleach Temp., Time. Type Yards Pounds wash, no wash, soln. F. mins. pH range Feed preheat preheat soln.

4.75 168 40 7.8-8.2 1 1 2.85 163 26 7. 5-8. 3 7 2 4.75 173 40 6. 7-7. 8 a 1 4.75 2.85 161 24 8. 0-9. 2 9 3 e2 167 6.8-8.0 3 2.3.? 164 20 7. 8-3. a 1 3 Cloth 2nd U-tube Percent Whiteness H 01 Bleach (100%) house conwash Acceptance 'lype Yards Pounds Bleach soln. Tom Time, pH Feed sumed 1st U 2nd U F mins. range soln. cloth basis 4.75 yd. None-. Acceptable. 2.85 yd. do 4.75 yd. ..do. Do. 4.75 yd. Do. 2.85 yd. .do.. Do. 4.75 yd. Do. 2.85 yd. do Do. 4.75 yd. 8 oz. duck 2.85 yd. jeans None 1 Composition of bleach solutions: 1. 0.12% stabilizer additive, 0.22% silicate, 0.25% H20; (100%). 2. 0.12% stabilizer additive, 0.44% silicate, 0.25%

H 0: (100%). 3. Residual liquor from previous days runs-as #2. 4

0.12% stabilizer additive, 0.44% silicate, 0.35% H20 (100 2 7 Composition of feed solutions: 1. 0.36% stabilizer additive, 0.66% silicate, 1.16% H10: (100%). 2. 0.36% stabilizer additive 0.66% silicate, 1.58% H10, (100%). 3. 0.36% stabilizer additive, 1.32% silicate, 1.68% H 0, (100%).

The stabilizer additive consisted of 74% by weight stabilizer additive, 0.66% by weight sodium silicate,

magnesium sulfate trihydrate, and 26% by weight sodium tetraphosphate.

The pH values of 7-8.5 attained in all the runs were well below the values of 10.5, or higher, commonly employed for cotton bleaching and constitute a distinctive feature of the process.

EXAMPLE 10 tory and was not improved by reducing the temperature of the steam chamber from about 212 F. to 190 F. A second run using 0.2% NaOH in a similar saturator solution produced worse results than the first run.

To provide for more effective stabilization of peroxide during steaming, the stabilizer additive was increased to provide a saturator solution containing 0.18% by weight 0.04% by weight caustic, and 0.70% by weight hydrogen peroxide 100%). Bleaching and mote removal essentially equivalent to results from the regular plant procedure were obtained. Better stability was shown by the 40 peroxide content of cloth leaving the steamer which was about twice as great as from the initial run.

The amount of stabilizer additive was then increased to give still further stabilizing action, the saturator solution containing 0.27% by Weight stabilizer additive, 0.66%

by weight sodium silicate, 0.05% caustic soda, and 0.70% by weight hydrogen peroxide (100%). improved stabilizing action and also presented an opportunity to reduce the quantity of peroxide in the satu-. rator solution for reasons of economy since the residual, peroxide found was higher than necessary. Bleaching and mote removal were at least as good as by the regular procedure for a variety of cloth including 1.90 and 2.35 yards per pound twill, and 2.85 yards per pound jeans. The bleach being stabilized in accordance with my invention appeared to impart a more desirable blue-white tint in the bleached goods than the customary pink hue. The results are as follows:

This indicated Table 10 APPLICATION OF STABILIZER ADDITIVEPEROXIDE SATURATOR SOLUTION IN CONVEYOR STEAMER Saturator solution Percent Percent H O; Percent Cloth Yards Pounds Stabii- 202 (100%) whiteacceptabilityv izer Addi- Percent Percent (100%) consumed ness tive silicate caustic cloth basis 2.00 yd./lb. twill Regular 0. 71 Mote removal acceptable but not completely satisfactory. 0.70 0.46 84.7 Bleaching and mote removal unsatisfactory. 0. 0. 51 83. 3 Do. 0. 70 0. 46 lleas: equivallentt 1to reglrlar proceidure. h eas equiva en 0 regu ar proce ure wit gig ggfigifit: 28g respect to bleaching and mote removal. Z yd'llb. 2' 384 0. 70 0.81 Blue white tmt Do 6,000 Dn 62 90. 0 Acceptable. Poplin-- .70 89.7 Do.

1 Regular silicate content in saturator solution is 0.88% by weight. All saturator solutions derived from teed solutions at 400% the saturator con centration.

13 It should be noted that in these runs no cooling water was used to reduce the temperature of the cloth coming from the caustic stage hot water washer into the peroxide 14 It is evident that the most extreme decomposition was exhibited by bleaching solution No. l, which is the typical mill formula. Solutions 2, 3 and 4, employing the saturator. Saturator temperatures as high as 130 F. stabilizing composition of my invention, all provided betwere observed. This was in contrast to usual operations ter stabilization than the commercial solution. The stawhere a cold water spray on the cloth is normal pracbility of these solutions increased with increased stablizer tice to prevent undue decomposition of the peroxide satadditive (3 and 4). urator solution. Bleach solutions stabilized in accordance with my invention showed no instability even though EXAMPLE 12 operating conditions occasionally necessitated holding the Equal weights of semi-bleached. flax pulp were further bath idle for some time or permitted the entrance of unbleached by treatment with solutions made up as dedue amounts of alkali. scribed in Example 11. Bleaching was performed at a The normal saturator solution contained 0.88% by 5% pulp consistency with oxidant suflicient to provide weight sodium silicate while the largest amount of silithe equivalent of 2% sodium peroxide on the pulp basis. cate used in the system when stabilized in accordance 5 Bleaching was continued for twenty-three hours at room with my invention amounted to 0.66% silicate or 75% temperature to observe any long-term decomposition cfof that normally employed. fects, after which the pulp was warmed to 120 F., held EXAMPLE 1 about an additional hour and then washed. The white- A series of bleach solution compositions were made g fi g g i Peroxide consumpnon are up, one of which was the typical mill formula used in ta u ate mt e ta 6 e wood pulp bleaching, and the other three employing my Table 12 stabilizer additive consisting of 74% by weight magnesium sulfate trihydrate and 26% by weight sodium tetraphosphate. These solution were stored at 100 F. and Bleach solution 1 2 3 iit iiii their oxidizing power was periodically determined. The compositions of the various solutions are tabulated in Percent equivalent Nstot consumed- 0.90 1.07 1.08 the table below in relation to their loss of oxidizing Whlteness(Mgo=100 power with time. (It may be noted that some sulfuric acid was employed in making up these solutions to pro- The yp mill fel'lnula (bleach Solution vide the desired free soda to silica ratio; however, with yielded pulp of the lowest whiteness and its actual peroxsome silicates that have a Na O to SiO ratio of 1/3.2, i consumption s also H the residual the addition of sulfuric acid may not be required.) peroxide remaining in the p p would be lost in the The results are a follow tralization or washing treatments which commonly fol- Table 11 low peroxide bleaching. The pulps which were bleached with solutions containing the stabilizer additives of my invention (Nos. 2 and 3) had significantly higher white- Bleach solution composition N0 Parts/1'00) Parts ness in the products than did the mill formula. For

practical purposes, the peroxide consumption using solu- 1 2 3 4 tion No. 3 was not appreciably greater than No. 1, especially in View of the increased whiteness. 26$ 1% ti i %i) MgSO Nos. 0 5 0 5 2 7 Epsomss mtsoinnorit:21:33: 0.5 None None None EXAMPLE 13 57.4 3.25 28.9 17.4 A Series of experiments Were conducted to test e 3Zl%xiita%?ftt5a;x:::: it at 02 8:2 om of the e i the Hydrogenperoxide,50% 9.8 9.8 9.8 9.8 blhzers for sodium peroxide solutions 1n bleaching gp ig ggg pg pggegg 3 g roundwood-sulfite pulp mixtures. Thestabilizer addiprgsggdsag 1 9 24 7 18 4 11 6 6 3 tive employed consisted of 74% by weight magnesium 7 g at suulfate trihydrate and 26% by weight sodium tetraphosphate. The results are as follows:

Table 13 Bleaching solution, percent Residual NaaOipH Whiteness Bleach normal strength Stabilizer number Notes additive Epsom Silicate Minutes Percent Start End Hunter Points Blank salts original increase 1 Control..- 100 None 125 10.0 10.3 9.2 75.0 7.4 07.0 0- d 100 50 None 18. 0 10. 2 9. 0 74. 0 5. 3 09. a 2 None 50 100 20.0 10.3 9.1 75.5 7.9 07.0 None 50 100 13.8 8.7 7.4 72.4 2.9 09.5 (=0. None 50 100 90 13.2 10.4 9.0 75.4 5.9 09.5 None 50 None 120 19.4 10.0 8.9 75.4 0.1 09.3

1 Solution adjusted to pH 10 by additional amount 2 Solution adjusted to free alkalinity present in mill 3 Used MgSOtJHgO equal to MgSOt.3HtO 1'11 stabilizer additive and substituted NasPao o for NasP O in stabilizer additive on basis of equal P405 content.

Normal solution contained (parts/1,000 parts of solution):

14.8 parts sulfuric acid per 1,000 parts of solution.

bleach by use of only 12.5 parts sulfuric acid per 1,000 parts of solution.

It will be seen from the above table that when the stabilizer additive of the invention is employed, it can be substituted for all of the Epsom salts commonly used in mill bleach formulations, and for one-half of the sodium silicate contained in the regular mill bleach solution. Also, in bleach No. an equivalent weight of magnesium sulfate heptahydrate was substituted for magnesium sulfate trihydrate in the stabilizer additive and sodium tripolyphosphate was substituted for sodium tetraphosphate. The bleaching results produced by this stabilizer additive were equivalent to those produced using magnesium sulfate trihydrate and sodium tetraphosphate.

EXAMPLE 14 A peroxide feather bleaching bath was made up in which sufiicient stabilizer additive, containing 74% by weight magnesium sulfate trihydrate and 26% by weight sodium tetraphosphate, was added to 100 gallons of water to produce a solution containing 0.12% by weight stabilizer additive. The stabilizer additive was added as a dry powder and, after it became dissolved, a liquid-type sodium silicate was added to the bath in an amount equivalent to 3.75 pounds of sodium silicate per 100 gallons of solution, producing a concentration of 0.44% by weight sodium silicate in the solution. The sodium silicate had a density of 42% B. Containing 10.5% Na O and 26.3% SiO by weight, in a ratio of l to 2.5. Hydrogen peroxide was then added to the bath in an amount equivalent to 20.5 pounds of 130 volume strength hydrogen peroxide per 100 gallons of solution, producing a concentration in the bath of 0.86% hydrogen peroxide (100% basis) by weight. The pH of this solution was 9.7.

The bleach bath was then heated to a temperature of 190 F. and dark brown goose feathers were added thereto. After ermitting the bath to stand for 65 minutes, the temperature had decreased to 140 F. and the pH to 8.4. The bath was then heated so that after another hour the temperature had again reached 190 F. At the expiration of an additional 20 minutes, no further bleaching was observed.

The feathers were removed from the bleach bath, rinsed in water, and dried by exposure to a moving air stream, followed by storage in an oven at 140 F. The feathers had lost their original dark brown color and were a satisfactory full white.

A peroxide feather bleaching bath having substantially the same composition as that above, except that the stabilizer additive was omitted, failed to produce significant bleaching of feathers and was unstable when heated to 120 F.

EXAMPLE A series of bleaching solutions were prepared in order to ascertain the effect of the stabilizer additive of the invention on wood bleaching solutions. The solutions were prepared as follows:

Solution No. 1 represents a typical bleach used in the commercial bleaching of mahogany veneer. Solution No. 2 contained a stabilizer additive of the invention instead of sodium silicate, and solution No. 3 employed no caustic soda but contained a stabilizer additive of the invention and sodium silicate, the latter being employed to supply alkalinity. The stabilizer additive contained 74% magnesium sulfate trihydrate and 26% sodium tetraphosphate.

Upon standing a few minutes, solution No. 1 proved so unstable that violent bubbling occurred, with the result that most of the solution boiled out of the container. Only a negligible amount of bubbling occurred with solutions No. 2 and No. 3, and substantially all the peroxide of these solutions was found to have been retained, upon analysis of the solutions on the following day. Mahogany veneer bleached with solutions No. 1 and No. 2, immediately after preparation of the solutions and before substantial decomposition of solution No. 1 occurred, was bleached equally well, with the bleaching effect of solution No. 3 being somewhat inferior.

It will be obvious to those skilled in the art that many modifications may be made within the scope of the present invention without departing from the spirit thereof and the invention includes all such modifications.

This application is a continuation-in-part of my application Serial No. 382,217 filed September 24, 1953, now abandoned.

Having thus described my invention, I claim:

1. A stabilized peroxide solution containing for each 33,333 parts of solution a maximum of about 2,500 parts by weight basis) of a peroxide compound selected from the group consisting of hydrogen and sodium peroxide, about 8 parts to about 2,500 parts by weight of an alkali-metal silicate, anhydrous and hydrated magnesium salts selected from the group consisting of magnesium sulfate, magnesium chloride, magnesium nitrate and magnesium acetate in a quantity suificient to provide at least about 1 to 67 parts by weight of magnesium, and for each 1 part of magnesium, about 1 part to 5 parts by weight of an alkali metal polyphosphate.

2. A stabilized peroxide solution containing for each 33,333 parts of solution a maximum of about 2,500 parts by weight 100% basis) of a peroxide compound selected from the group consisting of hydrogen and sodium peroxide, about 8 parts to about 2,500 parts by weight of alkali-metal silicate, anhydrous and hydrated magnesium salts selected from the group consisting of magnesium sulfate, magnesium chloride, magnesium nitrate and magnesium acetate in a quantity sufiicient to provide 1 to 67 parts by weight of magnesium, and for each 1 part by weight of magnesium about 1 part to 5 parts by weight of a compound selected from the group consisting of sodium tetraphosphate, sodium tripolyphosphate, sodium pyrophosphate, sodium hexametaphosphate, potassium tetraphosphate, potassium tripolyphosphate, potassium pyrophosphate, and potassium hexametaphosphate.

3. A stabilized peroxide solution containing for each 33,333 parts of solution a maximum of about 2,500 parts by weight (100% basis) of a peroxide compound selected from the group consisting of hydrogen and sodium peroxide, about 8 parts to about 1,750 parts by weight of sodium silicate, about 2.5 parts by weight of sodium tetraphosphate, and anhydrous and hydrated magnesium salts selected from the group consisting of magnesium sulfate, magnesium chloride, magnesium nitrate and magnesium acetate in a quantity sufficient to provide about 1 part by weight of magnesium.

4. A stabilized peroxide solution containing for each 33,333 parts of solution a maximum of about 2,500 parts by weight (100% basis) of a peroxide compound selected from the group consisting of hydrogen and sodium peroxide, about 8 parts to about 1,750 parts by weight of sodium silicate, about 2.5 parts by weight of sodium tripolyphosphate, and anhydrous and hydrated magnesium salts selected from the group consisting of magnesium sulfate, magnesium chloride, magnesium nitrate and magnesium acetate in a quantity sufficient to provide about 1 part by weight of magnesium.

5. A stabilized peroxide solution containing for each 33,333 parts of solution a maximum of about 2,500 parts by weight (100% basis) of a peroxide compound selected from the group consisting of hydrogen and sodium peroxide, about 8 to 2,500 parts by weight of alkalimetal silicate, about 1 to 335 parts by weight of an alkali metal polyphosphate, and anhydrous and hydrated magnesium salts selected from the group consisting of magnesium sulfate, magnesium chloride, magnesium nitrate and magnesium acetate in a quantity suflicient to provide about 1 to 67 parts by weight of magnesium while maintaining the ratio of alkali-metal polyphosphate to magnesium within the range of 1 to 1 to 5 to l.

6. A method of bleaching textile fabrics, feathers and wood fiber which comprises subjecting the fabrics to the action of a peroxide bath containing for each 33,333 parts of solution not in excess of about 2,500 parts by weight of hydrogen peroxide (100% basis), about 8 parts to about 2,500 parts by weight of an alkalimetal silicate, anhydrous and hydrated magnesium salts selected from the group consisting of magnesium sulfate, magnesium chloride, magnesium nitrate and magnesium acetate in a quantity sufficient to provide 1 to 67 parts by weight of magnesium and, for each 1 part of magnesium, about 1 part to 5 parts by weight of an alkali metal polyphosphate, while maintaining the pH within the range of 7 to 14.

References Cited in the file of this patent UNITED STATES PATENTS 1,181,409 Schaidhauf May 2, 1916 1,758,920 Baum May 20, 1930 2,004,809 Gilbert et a1. June 11, 1935 2,027,838 Reichert Jan. 14, 1936 2,037,566 Durgin Apr. 14, 1936 2,121,952 Colonius June 28, 1938 2,141,189 Lind Dec. 27, 1938 2,160,391 Reichert et al. May 30, 1939 2,164,146 Reuss et al June 27, 1939 2,191,431 Kautfmann Feb. 20, 1940 2,220,682 Kauffmann et al Nov. 5, 1940 2,333,916 Campbell et al. Nov. 9, 1943 2,366,740 McEwen Jan. 9, 1945 2,706,178 Young Apr. 12, 1956

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Classifications
U.S. Classification252/186.29, 8/111, 252/186.32, 162/78, 252/186.28
International ClassificationC01B15/00, D06L3/00, D06L3/02, C01B15/037, C11D3/39
Cooperative ClassificationC01B15/037, D06L3/021, C11D3/3937
European ClassificationC11D3/39B4, D06L3/02B, C01B15/037