Classifications

• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06L—DRY-CLEANING, WASHING OR BLEACHING FIBRES, FILAMENTS, THREADS, YARNS, FABRICS, FEATHERS OR MADE-UP FIBROUS GOODS; BLEACHING LEATHER OR FURS
  • D06L4/00—Bleaching fibres, filaments, threads, yarns, fabrics, feathers or made-up fibrous goods; Bleaching leather or furs
  • D06L4/20—Bleaching fibres, filaments, threads, yarns, fabrics, feathers or made-up fibrous goods; Bleaching leather or furs using agents which contain halogen
  • D06L4/22—Bleaching fibres, filaments, threads, yarns, fabrics, feathers or made-up fibrous goods; Bleaching leather or furs using agents which contain halogen using inorganic agents
  • D06L4/24—Bleaching fibres, filaments, threads, yarns, fabrics, feathers or made-up fibrous goods; Bleaching leather or furs using agents which contain halogen using inorganic agents using chlorites or chlorine dioxide
  • D06L4/26—Bleaching fibres, filaments, threads, yarns, fabrics, feathers or made-up fibrous goods; Bleaching leather or furs using agents which contain halogen using inorganic agents using chlorites or chlorine dioxide combined with specific additives

Definitions

• an acid solution of a chlorite is commonly used to obtain maximum bleaching and the production of goods of high whiteness.
• a typical bleach bath used in textile work contains, for example, approximately one gram per liter of sodium chlorite.
• Sufficient acid is added to the bath with or without buffering to bring the pH to the desired value, generally to a pH of about 3.5 for cotton goods or about 2.5 for polyacrylonitrile fiber.
• Acetic acid is the preferred acid for achieving the pH of 3.5 and formic acid is the preferred acid for achieving the pH of 2.5.
• Phosphoric acid is also frequently used as an acidifying agent.
• Bufifer salts for example, Na HPO NaH PO or NH HF can be added.
• wetting agents which are effective under acid conditions, for example, the lgepons (salts of acylalkyl taurides) are commonly added. Bleaching baths of these compositions are commonly used at elevated temperatures, for example 180 F. to 195 F.
• the bleaching solutions generate chlorine dioxide rather rapidly, as evidenced by the development of a' yellow color in the solution and by the evolution of chlorine dioxide as a gas from the surface of the solution.
• This'generation of chlorine dioxide is objectionable in that the gas lost from the solution represents'a loss in bleaching power. It is also objectionable as a health hazard when sufficient chlorine dioxide is evolved to aflect workers deleteriously.
• Chlorine dioxide is an irritating gas and requires removal, for example, by means of hoods from the working space.
• acid chlorite solutions particularly when chlorine dioxide is being evolved in the range of pH 2 to pH 4, are corrosive to stainless steels and other metals. These metals become pitted and then corrode at a faster rate than the original highly polished surfaces.
• nitrate salts e.g., sodium nitrate
• Acetic acid has a pronounced and useful buffering action, tending to hold the pH value somewhat constant or, at least, minimizing its rise as the bleach bath is used.
• the addition of sodium nitrate or other nitrate salts to the bathdoes not interfere with the buffering action.
• a principal object of the present invention is to provide an acidic aqueous bleach bath in which the active bleaching agent is supplied in the form of a water-soluble chlorite and in which there are additionally contained novel repressers which are particularly effective in preventing the formation of chlorine dioxide in such amounts as will cause the evolution thereof from the bath as a gas and which act without interfering with the bleaching action of the bath.
• Another object of the present invention is to provide a concentrated aqueous composition suitable for addition to an acidified aqueous bleach bath to produce a buffered solution which is substantially non-corrosive to stainless steel and which contains the novel repressers.
• the active bleaching agents in the bath are supplied in the form of water-soluble metal chlorites.
• a third object of the present invention is to provide a concentrated, stable, solid composition suitable for addie liter of sodium chlorite are used, but, in some circumstances up to 20 grams per liter or more can be used. Equivalent amounts of LiCIO KClO or Ca(ClO can also be used.
• novel repressers employed are polyamides of the general formula:
• Ethylene diamine is a particularly preferred represser and is conveniently introduced into the bleaching bath as the dihydrochloride.
• Other amines within the scope of the formula are diethylene triamine, triethylene tetramine, tetraethylene pentamine, propylene diamine, dipropylene triamine, and other propylene homologues of these polyamines, and mixtures thereof,
• the hydrochlorides or phosphate salts of these amines are useful forms in which the amines may be obtained, handled and introduced into the bleaching bath.
• the proportions of polyamine required are suitably in the range of 10 to 1000 parts per million by weight in a bleaching bath containing about 1000 to 2000 parts by million by weight of sodium chlorite or equivalent amounts of other water-soluble chlorites. Observable effects begin at about 10 parts per million by weight of the polyamine and more than about 500 parts per million by weight appear to be of no additional advantage over somewhat smaller amounts.
• the proportion of represser is related, as described, to the chlorite content of the bleaching bath and is varied with the chlorite content, so as to maintain the proportion set forth. And, in such proportion, these polyamines are surprisingly effective in repression, particularly when compared with other nitrogen-bearing compounds and with other proposed repressers, even in the presence of known accelerators of chlorine dioxide formation. Triethylene tetrarnine, for example, represses chlorine dioxide formation, even in the presence of 2 parts per million by weight of iron, though not as well as it does in the absence of iron.
• the polyamines defined above when using the polyamines defined above in the presence of dissolved iron, there may be some loss of total efi'ective bleaching power in the bath. Ordinarily, this is not excessive unless the proportion of iron is excessive and, if iron is absent, there is substantially no loss of bleaching power.
• the products are also active bleaching agents. They reduce the formation of chloride or chlorate from the c-hlorite and thereby preserve the bleaching power of the chlorite. They do not form any colored lay-products which might interfere with bleaching textiles to high whiteness. They are stable and effective re'p'ressers at operating temperatures between room temperature and the boiling point of the solution. They are compatible with other components of the bleaching baths.
• the bleaching bath of the present invention advantageously contains conventional ingredients.
• conventional ingredients such as butters, corrosion inhibitors, wetting agents and metal ion ohelating agents.
• Suitable buffers include, for
• Equipment employed in bleaching textiles with chlorite is commonly made of stainless steel.
• the stainless steel may be combined with sheets of glass, Transite (a hard pressed, heavy board or tubing made from asbestos and Portland cement), and other inert materials.
• Transite a hard pressed, heavy board or tubing made from asbestos and Portland cement
• stainless steel may show some corrosion, sufficient to add one part per million by weight or iron to the bleach bath or a sutficient fraction of a part per million to affect the course of the bleaching adversely, e.g., by accelerating chlorine dioxide formation and evolution, by acting antagonistically toward the repressers, by introducing discoloration, and by damaging the equipment being employed.
• Nickel and cobalt which may be dissolved from the stainless steel act similarly to the iron in these regards.
• these metals may appear in the bleaching bath due to corrosion or they may be otherwise, often inadvertently, introduced. Whatever their source, they are deleterious and their introduction is to be avoided if possible. Indeed, it is preferred in the practice of this invention to take positive steps to remove such metals if they have been introduced.
• a water-soluble nitrate salt is preferably included in the bath.
• Ammonium nitrate and alkali metal and alkaline earth metal nitrates such as sodium nitrate, potassium nitrate, calcium nitrate or magnesium nitrate are preferably employed.
• a suitable proportion of up to about 0.50 mole of nitrate per mole of chlorite is used. Such proportions materially reduce corrosion and introduction of deleterious metal ions from stainless steel into the bleaching solution.
• the bleaching solution can contain, in a preferred modification of the present invention, a chelating agent which is stable with respect to the bleaching components and effective in acid solution.
• a chelating agent which is stable with respect to the bleaching components and effective in acid solution.
• the chelating agents useful in the present invention are those amines havinga plurality of hydrogen atoms of the amino group replaced by fatty carboxylic acid groups.
• Particularly useful members of this group include ethylene diamine tetra-acetic acid, hydroxyethyl-ethylene diamine triacetic acid, iminodiacetic acid, nitrilo-triacetic acid, symmetrical ethylene-diamine diacetic ajcidand their salts, generally alkali metal salts, such as sodium salts.
• citric, --maleic,-rlac.tic andtartaric acid and salts of citric acid and tartaric acid for example, alkali metal salts such as sodium citrate and sodium potassium tartrate.
• alkali metal salts such as sodium citrate and sodium potassium tartrate.
• These chelating agents are effective at the pH used in acidified chlorite bleaching baths to the action of iron and other metal ions, such as nickel and cobalt, in engendering the formation of chlorine dioxide. Ordinarily, about 5 to50 parts per million by weight, based on the solution'are satisfactory.
• these aqueous compositions include from about 0.1 and 20 grams per liter of sodium chlorite or equivalent weights of other water-soluble chlorites, are given a pH within the range of 2 to 7, and contain at least one polyamine of the formula NH, (CH CHR NH H in an amount sufficient to prevent the evolution of chlorine dioxide gas from the bath but insuflicicnt in amount to destroy the bleaching potential of the chlorite.
• R in the formula is selected from the group consisting of H and methyl and n is aninteger from 1 to 4.
• polyamines are present in proportions of about to 1000 parts per million by weight in baths containing about 1000 to 2000 parts per' million by weight of sodium chlorite or equivalent amounts of other chlorites.
• solutions can also contain an alkali metal or an alkaline earth metal nitrate in an amount of up to 0.50 mole of nitrate per mole of chlorite to serve as a corrosion inhibitor and suitable amounts of buffering agents, wetting agents and chelating agents.
• aqueous concentrates within the ambit of the present invention differ from the bleaching baths discussed above in that they contain neither water-soluble chlorite nor acid. They contain an alkali metal or alkaline earth metal nitrate such as sodium nitrate, potassium nitrate, lithium nitrate or calcium nitrate and they contain a polyamine of the type previously discussed. Advantageously, they also contain a chelating agent.
• the proportion of each component in the mixture is adjusted to provide a composition which, when introduced into an acidified chlorite solution, provides a bleaching bath which is substantially non-corrosive to stainless steel, suitably repressed'with respect to chlorine dioxide formation and still efiective under normal bleaching operation conditions. To this end, the following composition is generally suitable:
• Component Percent by weight Nitrate 32 Polyamine 5-15 Chelating agent 3-10 Water Balance Where particularly low temperatures may be encountered, it is preferable to use about 30 percent by weight of the nitrate component to lower the freezing point. Where the nitrate is an alkaline earth metal nitrate, it is preferable to use about 8 to 10 percent by weight of the chelating agent to obtain clear concentrates.
• non-aqueous components of the concentrates of the invention are all readily soluble in water inthe recited proportions to form clear, stable solutions of a pH of about 11 to 12.
• the concentrates themselves freeze only below 0 F. and are easily prepared, stored,
• a bleaching bath which is effective, stable, substantially non-corrosive and does not generate obnoxious quantities, of chlorine dioxide.
• Suitable proportions are about 0.5 to 1.3 grams of the concentrate per gram of a commercial bleaching product containing from 80 to 84 percent by weight of sodium chlorite or an equivalent amount of another" water-soluble chlorite used in bleaching baths. Smaller proportions may protect only inadequately and greater amounts slow the bleaching process, although they do not impair the bleaching capacity of the bath.
• the concentrated aqueous compositions of the present invention are completely soluble in water and are effective represser s, especially at a pH of 2 to 3, without destroying bleaching power.
• the solid compositions within the scope of the present invention differ from the bleaching baths discussed above in that they contain neither water-soluble chlorite, acid nor water. They contain an alkali metal nitrate such as sodium nitrate, potassium nitrate or lithium nitrate, but generally, they do not contain alkaline earth metal nitrates because of their hygroscopic nature. They contain a polyamine of the above noted formula, preferably in the form of a hydrochloride or phosphate salt. They also contain a buffering agent.
• Disodium phosphate is the preferred butler, but sodium dihydrogen phosphate, polyphosphates, e.g., tetrasodiumpyrophosphate and sodium tripolyphosphate, as well as ammonium bifluoride and sodium acetate, can be employed. These buffers tend to hold the pH constant when chlorine dioxide is formed according to the equation:
• compositions also contain chelating agents of the type discussed above.
• the proportion of each component in the mixture is adjusted to provide a com position which, when introduced into an acidified chlorite solution, provides a bleach bath which is non-corrosive to stainless steel, suitably repressed with respect to chlorine dioxide formation and still efiective in bleaching under normal operating conditions.
• the following composition is generally suitable:
• composition of the present invention is readily soluble in water and is an effective represser, particularly at a pH of 2 to 3, without being destructive of bleaching power.
• the solid compositions when dissolved in suitable proportions in an acidified chlorite solution, yield a bleaching bath which is effective, stable, substantially non-corrosive and does not generate obnoxious quantities of chlorine dioxide.
• Suitable proportions are about 0.5 to 1.0 gram of the solid per gram of a commercial bleaching product containing 80 percent by weight sodium chlorite used in the bleaching bath. Smaller proportions may protect only inadequately and greater amounts slow the bleaching process, although they do not impair the bleaching capacity of the bath. Larger proportions of nitrate in the composition are accommodated by decreasing the proportion of bufier. When the nitrate is in the 45 to 55 weight percent range, the proportion is reduced to about 0.5 gram per gram of sodium chlorite product, maintaining the molar ratio of nitrate to chlorite below about 0.50/1 in the bleach bath.
• Example XII A bleaching bath was made up containing 0.925 gram per liter of a commercial bleaching product containing 80 weight percent NaCl equivalent to 1200 parts per million of available chlorine. Eight milliliters of 56 weight percent aqueous acetic acid and 0.5 gram of caustic soda were added per liter to adjust the pH to 3. Then 0.5 gram per liter of Igepon T-77 wetting agent was dissolved in the solution. To separate portions of this solution were added various proportions of ethylene diamine dihydrochloride and to another portion none was added. The solutions were heated to 86 C.
• Example XIII This example shows the eifectiveness of one of the polyamines in repressing chlorine dioxide formation in the presence of 'iron using ethylene diamine tetra-acetic acid as chelating agent.
• a bleaching bath was made up containing 0.925 gram per liter of a commercial product containing 80 weight percent NaClO equivalent to 1200 parts per million of available chlorine. Eight milliliters of 56 percent aqueous acetic acid and 0.5 gram of caustic soda were added per liter to adjust the pH to 3. Then 0.5 gram per liter of Igepon T-77 wetting agent was dissolved in the solution. To separate portions of this solution were added various proportions of ethylenediamine dihydrochloride, ferric chloride and ethylenediamine tetra-acetic acid with suitable blanks. The solutions were heated to 86 C.
• Example XIV This example shows the additional use of sodium. niirate in the bleach baths of the present invention.
• a bleaching bath was made up containing 0.925 gram per liter of a commercial productcontaining 80 weight percent NaClO The pH was brought to 3 by the addition of acetic acid and 0.5 gram per liter of Igepon T- 77 wetting agent was added. Two portions of this solution were used as blanks. To each of two other portions were added 100 parts per million by weight of ethylenediamine dihydrochloride, 50 ppm. by weight of Versene (ethylene diamine tetra-acetic acid sodium salt) and 360 p.p.m. by weight of sodium nitrate. Swatches of a polyethylene terephthalate fiber-coton cloth weighing 15 grams were introduced into each solution, including the blanks and they were then stirred at C. for one hour. The swatches were removed and the brightness determined for comparison with the original brightness of 60.0. The following data were obtained:
• Example XV intervals spectrophotometrically. A blank was run without the propylenediamine and the following results were obtained:
• Example XVII A solution containing 860 parts per million by weight of sodium chlorite was buffered at pH 3 by adding an acetic acid-sodium acetate buffer. A portion of this solution was used as a blank. To the remainder of the solution was added 500 parts per million by Weight of triethylene tetramine. A portion of this solution was used in test No. 1. To the remainder of the solution was added 2 parts per million by weight of ferric chloride. A portion of this solution was used in test No. 2. To the remainder of the solution was added 400 parts per million by weight of citric acid. This solution was used in test No. 3. 'Each of the test solutions was maintained 12 at 88 C. for 30 minutes, removing samples from time to time and determining the parts per million by weight of chlorine dioxide. The total content of chlorine dioxide and dissolved sodium chlorite was determined 'in' the final sample. The following results were obtained:
• Example XIX An aqueous concentrate of the following composition l 14 were removed, rinsed, dried, ironed and the brightness again measured. The following results were obtained:
• a bleach bath was prepared by dissolving 0.9 gram Example XXI P li of this and g P liter of a 9- A concentrate of the following composition was premel'mal Product FQIltalIllllg l Naclo: 111 pared by dissolving the following components in water water. The addition of milllhters of 56 percent acem h propel-Hons mdlcated; tic acid per liter of solution brought the pH to 3.0. A swatch of a polyethylene terephthalate fiber-cotton was 20 O t P t b introduced into a solution having a solution/cloth weight omponen $51211: y ratio of 30/1 and the mixture was stirred at 85 C.
• a bleach bath was. prepared by dissolving, 1.0 gram per liter of 94 weight 'percentcalcium chlorite in water.
• Example XXIV The following solid composition was prepared :v
• a bleach bath was prepared by dissolving one gram per liter of a commercial product containing 80 weight percent NaClO and one gram per liter of the above composition in water. Formic acid was added to bring the pH to 2.5 and the solution was heated to 85 C. It was stirred and maintained at that temperature for one hour in contact with swatches of a polyethylene terephthalate fiber-cotton cloth (solution to cloth weight ratio, 30/1) and with a test piece of type 316 stainless steel. Chlorine dioxide content of the solution was determined from time to time and at the end of one hour the swatch was-re moved, rinsed, dried, ironed and the brightness determined using a Photovolt brightness meter with a tristimulus green filter (original brightness, 60.0). A'blank was run omitting the'solid'repressor' compositionofthe-- Nitrogen was bubbled 1-6 present invention and the following comparative results were obtained:
• Example XXV A bleach bath was prepared; by dissolving one: per. liter of 'a commercial product containing 80 weight.
• Example XXVI A bleach bath was prepared by dissolving one gram per liter of 'a commercial product containing 80 weight percent Nac1o,', ferric chloride to provide 3 parts per million by weight of dissolved iron per liter and one gram per'liter' of the solid composition of Example" XXIV. Acetic acid was added to bring the pH to 3. A swatch of a polyacrylonitrile fiber cloth was added (solution to cloth weight ratio, 30/1) and the mixture was stirred at 85 C. for one hourwith a type 316 stainless steel stirrer. The cloth had an original brightness of 83 measured using a Photovolt brightness meter with a tristimulus green filter. Chlorine dioxide content of the solution was determinedon samples removed at intervals. At the end of one hour, the cloths were removed, rinsed, dried, ironed and the brightness determined asbefore. A blank w'asrun omittingthe' solid repressor composition of the present invention. The-following results were obtained:
• Example XXVII A bleach bath was prepared by dissolving one gram perliter of a commercial product containing 80 weight percent NaCIO ferric chloride to provide 3 parts per million by Weight of dissolved iron per liter and one gram per liter of the solid composition of Example XXIV. A mixture of two volumes. of concentrated nitric acid and one volume of glacial acetic acid was added to bring the pH of the solution to 2.5. Swatches of polyacrylonitrile fiber-cloth were added (solution to cloth ratio, 30/1) and the mixture was stirred at 85 C. for one hour. The cloth had an original brightness of 83 measured using a Photovolt brightness meter with a tristimulus green filter. Chlorine dioxide content of the solution was determined on samples removed at intervals. At the end of one hour, the cloths were removed, rinsed, dried, ironed and the brightness determined as before. A blank was run omitting the solid represser composition of the present invention. The following results were obtained:
• Example XX VIII The following solid composition was, prepared by mixing the finely ground components:
• a bleach, solution was prepared by dissolving in-water at 60 C., 17.2 grams of the above composition and 17.2 grams of a commercial product containing 80 weight percent NaClO to make each liter of solution. Thesolution was acidified to pH 3.8 by the addition of acetic acid. To one portion of the solution was added several swatches of cotton cloth using a solution to cloth weight ratio of 9:1. Another portion was tested without cloth. A third solution contained 17.2 grams per liter of a commercial product containing 80 weight percent NaClO acidified with acetic acid to pH 3.8, but containing no represser composition or cloth. All three solutions were maintained at 60 C. for 45 minutes. A stream of nitrogen was passed over each solution at 200 milliliters per minute.
• the chlorine dioxide was absorbed from the gas stream in acidified potassium iodide solution and the liberated iodine was titrated at the end of 45 minutes using standard sodium thiosulfate solution.
• the sweepgas from the solution without represser contained 25 parts per million of chlorine dioxide, while the sweepgas from the solutions containing the represser composition contained only 5.1 and 4.1 parts per million of chlorine dioxide from the solutions with and without cloth, respectively.
• Example XXIX A composition was prepared by mixing 6 grams of ethylene diamine with 30 grams of sodium dihydrogen phosphate monohydrate.
• the mixture was moistened with one milliliter of water and stirring was continued while the mixture heated to 98 C. On cooling, the composition was ground and further mixed with. 19 grams of disodium phosphate and 5 grams of ethylene diamine tetra-acetic acid sodium salt. The mixture was reground and then combined with 40 grams of sodium nitrate, ground again. The resulting powder was stable, odorless and suitable for use in acid chlorite solutions.
• Example XXX A bleach bath was prepared by dissolving one gram per liter of 94 percent calcium chlorite and one gram per liter of the solid composition of Example XXIV in water. Acetic acid was added to bring the pH to 3.5. The solution was heated to C. and stirred for one hour. A stream of nitrogen sweeping over the surface at 200 cc./min. swept all chlorine dioxide released into a trap containing aqueous potassium iodide. At the end of one hour the chlorine dioxide dissolved in the solution, the chlorine dioxide swept off, and the total available chlorine in the solution were determined. A blank was run omitting the composition of this invention and the following comparative data were obtained:
• composition of this invention in an amount sufiicient to prevent the evolution of chlorine dioxide gas from the bath but insuflicient in amount to destroy the bleaching power of the chlorite, R being selected from the group consisting of hydrogen and methyl and n being an integer from 1 to 4.
• V wherein the polyamine is triethylene tetramine.
• aqueous acidic bleaching bath of claim 1 in which the pH range is from 2 to 4.
• the aqueous concentrate of claim 12 wherein the compound selected from the group consisting of alkali 15.
• the aqueous concentrate of claim 12 wherein the chela ting agent is ethylene diamine tetra-acetic acid.
• a 16 The aqueous concentrate of claim'12 wherein the compound selected from the group of .alkali metal nitrates and alkaline earth metal nitrates issodium nitrate,
• the polyamine is ethylene diamine and the chelating
• th chelating agent is ethylene diamine tetraacetic acid.
• chlorite being a water-soluble metal chlorite selected from the group consisting of alkali metal chlorites and alkaline earth metal chlorites, the method of repressing the generation of chlorine dioxide in the bath which comprises including in the bath at least one polyamine of the formula pH range of from 2 to 4.

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• Chemical & Material Sciences (AREA)
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  • BE BE578918D patent/BE578918A/xx unknown
• 1958
  • 1958-06-11 US US741216A patent/US2988514A/en not_active Expired - Lifetime
• 1959
  • 1959-05-29 GB GB18414/59A patent/GB898305A/en not_active Expired
  • 1959-06-09 FR FR796982A patent/FR1228602A/fr not_active Expired
  • 1959-06-10 DE DES63399A patent/DE1209095B/de active Pending

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