STABLE SUSPENSION OF PIGMENTS IN AQUEOUS HYPOCHLORITE BLEACH COMPOSITIONS

Abstract: Aqueous hypochlorite laundry bleach compositions con­ taining a suspension of a bleach stable (e.g., Ultramarine Blue) pigment, optical brightener 4,4′-bis(4-phenyl-2H-1,2,3-­ triazol-2-yl)-2,2′-stilbenedisulfonate, and a certain alkylaryl sulfonate surfactant. Preferred compositions contain a bleach stable organic material having a density of from 0.8 to 1.05 g/cc, which organic material is preferably a perfume.

Description: FIELD OF THE INVENTION The invention pertains to an aqueous hypochlorite laundry bleach product which contains suspended pigments, and to the process for making same. BACKGROUND ART "The conventional method of transferring optical brighteners or bluing agents to fabric is by adding the optical brighteners or bluing agents to the wash water along with the detergent. Generally, optical brighteners and bluing agents are not present in bleach, particularly liquid bleach, since the liquid bleach has a strong tendency to oxidize and destroy the dyes with concurrent reduction in bleaching strength. Alternative approaches involving addition of bleach stable inorganic pigments to liquid hypochlorite bleach to effect bluing have also been unsuccessful generally because the pigment particles have a tendency to settle out of suspension." Quoted from GB 2,100,307A, December 22, 1982 (The Clorox Co.) German Patent Document DE-C-2849225, originally published May 23rd 1979, discloses a colored liquid hypochlorite bleach composition primarily designed for cleaning lavatory pans. The composition contains Ultramarine Blue (UMB) suspended in a flocculate, which is preferably made by reacting a soap or synthetic surfactant with calcium ions. Such a composition which contains a calcium floc is undesirable for laundry cleaning because the calcium floc will deposit on the fabric. (Also, a linear alkylbenzene sulfonate (LAS)/hypochlorite floc alone will not support an effective amount of Ultramarine Blue pigment at an LAS level desirable for an aqueous laundry bleach composition.) This patent does not teach the essential optical brightener of the present invention. The state of the art as defined under Article 54(3) EPC also includes EP-A-0142883 published on May 29 1985. This document discloses aqueous hypochlorite bleach compositions containing from 0.025% to 0.2% of 4, 4' bis (4 phenyl-2H-1,2,3, triazol-2-yl)-2, 2' stilbene disulfonic acid, from 0.05% to 2% of a bleach stable alkyl aryl sulfonate surfactant, form 0% to 0.5% of a bleach stable organic oil and a bleach stable pigment such as Ultramarine Blue. It is an object of the present invention to provide a process for preparing a superior aqueous hypochlorite laundry bleach with suspended inorganic pigments, without calcium soap or the like. SUMMARY OF THE INVENTION According to the present invention there is provided a process for making an aqueous bleach composition comprising (a) from 3% to 8% by weight of the composition of sodium hypochlorite; (b) from 0.01% to 0.3% by weight of the composition of a bleach stable pigment selected from Ultramarine Blue and 3,3'-dichloro indanthrone;. (c) a bleach-stable anionic sulfonate surfactant; (d) from 0% to 0.5% by weight of the composition of a bleach-stable organic oil having a density of from 0.8 to 1.05g/ml; and (e) at least 80% by weight of the composition of water. wherein the process comprises the steps of: 1) preparing an aqueous system containing said pigment, said surfactant, and, where present, said bleach-stable organic oil, together with an optical brightener having the formula: or the alkali metal salts thereof; said optical brightener being added in an amount so as to provide from 0.025% to 0.2% by weight thereof in the bleach composition, said surfactant being selected from alkylaryl sulfonates having the formulas: wherein R₁ is a C₈-C₂₀ alkyl group, R₂ and R₃ are C₁₀-C₁₆ alkyl groups. M is alkali metal and n is 0 or 1; said pigment being uniformly dispersed in said aqueous system; 2) adding slowly, and with low shear mixing, to the system of Step 1, a sufficient amount of aqueous sodium hypochlorite to produce the bleach composition. DETAILED DESCRIPTION OF THE INVENTION In accordance with the present Invention it has been found that the bleach stable pigment selected from 3,3¹-dichloro indanthrone and Ultramarine Blue, Na₇Al₆Si₆O₂₄S₂ can be stably dispersed in an aqueous sodium hypochlorite laundry bleach containing LAS and a special optical brightener. The pigment is mixed with the LAS/optical brightener before they are salted out as a fine dispersion The blue pigment particles settle very slowly. When settling does occur, the settled layer of particles is very loose and occupies a substantial volume of the composition. The settled particles can be readily redispersed throughout the composition by gentle shaking of the bottle or other container from which the composition is to be dispensed. If an organic oil such as perfume is included in the formulation, the blue composition is very stable and very little settling occurs. All percentages herein are "by weight" unless specified otherwise. Sodium Hypochlorite Typically, sodium hypochlorite is commercially available in aqueous solutions having a concentration of from 5% to about 15%. These solutions typically contain an amount of sodium chloride about equal, (on a mole basis) to the amount of sodium hypochlorite. In making the compositions of the present invention it is generally desirable to add sodium hypochlorite solution to a pigment/brightener/surfactant solution in volumes such that the volume of sodium hypochlorite will be from about 0.4 to about 8 times the volume of the pigment/brightener/surfactant solution. Accordingly, the aqueous sodium hypochlorite source chosen for preparing a composition of the invention should be one which has a sodium hypochlorite concentration such that it can be mixed with the aqueous pigment/brightener/surfactant solution within these volume proportions to produce the desired amounts of sodium hypochlorite, pigment, brightener and surfactant in the finished product. Sodium hypochlorite is present in the compositions of the invention at levels of from 3% to 8%, preferably from 4% to 6%. Pigments A preferred pigment used in this invention is Ultramarine Blue. It is sold as "C.I. Pigment Blue 29; C.I. 77007". It is a blue pigment occurring naturally as the mineral lapis lazuli. It is made by igniting a mixture of kaolin, Na₂CO₃ (or Na₂SO₄), S and carbon. The resulting product is believed to have the formula Na₇Al₆Si₆O₂₄S₂. It is insoluble in water and readily decomposed by acids, even carbonic acid, with liberation of H₂S. "It is used as a pigment in calico printing, wallpaper, mottled soap; bluing in laundry use; for coloring tiles, cement, rubber, but is now largely replaced by coal tar dyes." The Merck index , 9th Ed. Ultramarine Blue is available from Whittaker, Clark & Daniels, Inc. Grade 5017 has a particle size range of 0.2-3.0 µm and Grade 5151 has a particle size range of 0.3-1.3 µm. Another preferred pigment is C.I. 69825 and is known under the names of C.I. Vat Blue 6 and C.I. Pigment Blue 64. They have the following chemical formula. This C.I. 69825 pigment is available from Crompton & Knowles Corporation under the name Intravat Blue. The pigment is present in the composition of this invention at levels of from 0.01% to 0.3%, preferably from 0.01% to 0.1% and more preferably from 0.02% to 0.05%. Brightener The brightener used in the compositions made by the process of the invention herein is 4,4'-bis(4-phenyl-2H-1,2,3-triazol-2-yl)-2,2'-stilbenedisulfonic acid, or its alkali metal (e.g. sodium or potassium) salts. The structure of the sodium salt is: This optical brightener is available from Mobay Chemical Corporation, a subsidiary of Bayer AG, under the name Phorwite® CNA. The optical brightener is present at levels of from 0.025% to 0.2%, preferably from 0.05% to 0.075%. Surfactant The surfactants used in the present invention are alkylaryl sulfonates of the following formulas: wherein R₁ is an alkyl group of from 8 to 20 (preferably 11 to 13) carbon atoms, R₂ and R₃ are alkyl groups of 6 to 16 (preferably 10-12) carbon atoms and M is an alkali metal, e.g., sodium or potassium, and n is 0 or 1. Surfactants of Formula 1 are called alkylbenzene sulfonates and are available under various tradenames, e.g., Calsoft® L-60, F-90 and L-40 from Pilot Chemical Company, and Naccanol® 35SL and 90F from Stephan Chemical Company. Surfactants of Formula 2 are alkyl diphenyloxide sulfonates and are available under the Dowfax® name from Dow Chemical Company. The surfactants are present in the compositions herein at levels of from 0.05% to 2.0%, preferably from 0.2% to 1.0%. In aqueous laundry bleach products a most preferred range is from 0.2% to 0.5%. The presence of surfactant in the compositions of the invention has been found to be essential to creating dispersed particles of brightener having a small particle size. If surfactant is not used, the particles are much larger. These larger particles have the appearance of curd and render the product less appealing from an aesthetic standpoint. The UMB pigment will settle quickly if only surfactant or only brightener is used. The surfactant/brightener dispersion must be present for a uniform UMB bleach in the practice of this invention. Organic Oils Preferred processes in acordance with the invention employ an organic oil which has a density of from 0.8 to 1.05 g/cm³. Preferably, the oil is present at levels of from 0.01% to 0.5%, preferably from 0.05% to 0.3%. Preferred oils are perfume materials which have a high degree of stability to sodium hypochlorite. Some preferred materials for use as perfume ingredients in the compositions herein are patchouli oil, cyclopentadecanolide, p-tertiarybutyl cyclohexyl acetate, tetrahydromycenol, tetrahydrolinalool, phenylacetaldehyde dimethylacetal, methylphenyl carbinol, and mixtures thereof. Another preferred organic oil is linear alkyl benzene (LAB) having alkyl chains of from 10 to 14 carbon atoms. When organic oils are used in the process of the invention they are mixed into the pigment, brightener and surfactant solution prior to the addition of aqueous sodium hypochlorite to the solution. The preferred bleach stable organic oils are selected from (A) C₆-C₂₀ aliphatic tertiary alcohols having the following molecular structures: wherein R₁₁ is a C₃-C₁₇ straight chain, branched or cyclic saturated alkyl group and R₁₂ and R₁₃ are C₁-C₁₂ straight chain or branched saturated alkyl groups; (B) C₆-C₂₀ aliphatic esters having the following molecular structures: wherein R₁₄ is a C₁-C₁₈ straight chain, branched or cyclic saturated alkyl group and R₁₅ is a C₁-C₁₈ straight chain, branched or cyclic saturated alkyl group; (C) C₆-C₂₀ aromatic esters and diesters having the following molecular structures: wherein R₁₆ and R₁₇ are C₁-C₁₂ straight chain, branched, or cyclic saturated alkyl groups, and c is 0 or 1; (D) C₆-C₂₀ lactones having the structure: wherein R₁₈ is a C₁-C₁₆ straight chain or branched saturated alkyl group; and B is a hydrogen atom or C₁-C₁₆ straight chain or branched saturated alkyl group; (E) C₆-C₂₀ acetals and C₆-C₂₀ ketals having the following molecular structures: wherein R₁₉ is a C₃-C₁₆ straight chain, branched or cyclic saturated alkyl group or is a benzyl, alkyl-benzyl, dialkylbenzyl, 2-phenylethyl, or naphthyl group; and R₂₀ and R₂₁ are separate C₁-C₁₂ straight chain or branched saturated alkyl chains or together complete a five membered ring by contributing two saturated carbon atoms and may or may not contain an alkyl substituent, and A is a hydrogen atom or a C₁-C₈ straight chain or branched saturated alkyl group; (F) and mixtures thereof. In a preferred embodiment of the present invention some or all of the organic oil materials are also perfume ingredients. For example, the following organic oil materials can also be used as perfume ingredients: If organic oil usage is toward the upper end of the usage range (i.e., 0.3% to 0.5%) then it is usually necessary to use an amount of surfactant which is also at the higher end of the 0.05% to 2% surfactant usage range hereinbefore disclosed. The process of the invention comprises 1. Preparing an aqueous solution containing the pigment, the brightener; the surfactant; and, where present, the bleach stable perfume or organic oil. The pigment is added last. 2. Adding slowly, and with low shear mixing, to the solution of Step 1, a sufficient amount of aqueous sodium hypochlorite to produce a final composition comprising from 3% to 8% sodium hypochlorite, from 0.01% to 0.3% pigment, from 0.025% to 0.2% brightener; from 0.05% to 2% surfactant; and from 0% to 0.5% perfume or oil. The aqueous solution of Step 1 is preferably prepared with deionized water. This minimizes the presence of heavy metal ions, which tend to cause decomposition of sodium hypochlorite. At the higher end of the brightener concentration ranges, heating of the solution may be necessary to get all of the brightener into solution. The organic oil (if used) is added after the surfactant has been added. Higher levels of oil generally require surfactant usage to be at the high end of the above stated concentration range. When adding concentrated sodium hypochlorite to the aqueous composition of Step 1 the hypochlorite should be added slowly and with gentle mixing. The rate of addition should be sufficiently slow to allow maintenance of substantial uniformity of hypochlorite throughout the system, notwithstanding the gentle mixing. As the hypochlorite is added, brightener and surfactant will be salted out as a fine dispersion. Mixing should be gentle throughout the addition of the hypochlorite. High shear mixing and other forms of mixing which produce a high degree of agitation should be avoided since they will lead to formation of larger particles which have poor suspension properties in the solution. The dispersion is best described as loose aggregates of very small brightener and surfactant particles. The insoluble UMB is uniformly dispersed in the system and thereby provides uniform color. In the compositions made in accordance with this invention, the particles of pigment/brightener/surfactant will typically remain more or less homogeneously suspended in the compositions for at least fifteen minutes, and in most cases an hour or more. The length of time depends on the amount of pigment present. A smaller amount can remain suspended for days. Even after the composition eventually becomes nonhomogeneous, most of the particles do not settle to the bottom of the composition, but remain suspended in the bottom one third to two thirds of the composition volume. With a very minor amount of agitation (such as by inverting a bottle and returning it to its upright position) a homogeneous composition is quickly restored. When an organic oil is used the pigment is stably suspended for days. Thus, the present invention provides compositions whereby consistent dosages of a combination of sodium hypochlorite, pigment and optical brightener in a concentrated aqueous medium can be easily obtained. For best chemical stability, the compositions herein should have a pH above 12, preferably about 12.5. The pH of the composition should be tested after preparation is complete. If needed, pH adjustment can be made with acid or base (e.g., HCl or NaOH). The invention will be illustrated by the following examples. EXAMPLE I A composition consisting of: Ingredient Wt. % Ultramarine Blue 0.02 Brightener 0.05 Surfactant (NaLAS) 0.25 Perfume 0.15 NaOCl (∼13%) 44.25 Water to 100.00 1600 g of the sample were made. 0.80 g of brightener (Phorwite CNA®, Mobay Chemical Corp.) was taken in 530 ml hot (∼65°C) water in a 1-liter flask. The mixture was stirred moderately with a magnetic stirrer-cum-hot plate. 4.44 g of NaLAS surfactant (Calsoft F-90, 90% active having an average alkyl chain of 12 carbon atoms, Pilot Chemical Co.) were added and the brightener completely went into solution. The mixture was transferred into a 2-liter beaker with baffles and 354 ml cold water were added. The mixture (∼40°C) was then stirred by an electrical stirrer at ∼400 rev/min. A bleach stable organic oil perfume (2.4 g) and then Ultramarine Blue (0.32 g, grade 5017, Whittaker, Clark & Daniels, Inc.) were added and the mixture was stirred for 30 minutes. 708 g of bleach solution (∼13% NaOCl content) were gradually added to the brightener/surfactant/perfume/pigment mixture over a 20 minute period. The brightener and surfactant were salted out and were dispersed uniformly throughout the vessel. 500 ml of this bleach composition were taken in a graduated 500 ml glass cylinder for settling studies. The pH of the final composition was determined to be 12.57 at 24°C. After 7 days of storage at ambient conditions, there was only 2% settling. The pigment was uniformly dispersed in 98% of the composition volume providing a uniform coloration. EXAMPLE II (comparative) A composition consisting of: Ingredient Wt. % Ultramarine Blue 0.02 Surfactant (NaLAS) 0.25 NaOCl (∼13%) 44.25 Water to 100.00 The procedure for making the composition of Example II was the same as that of Example I, except that in Example II the brightener and perfume were not included. The surfactant was precipitated by addition of the bleach solution. The pigment was gently stirred into the surfactant precipitate. The pigment settled down entirely within about 3 hours. This example shows that it is not possible to get a stable suspension of the pigment in a bleach composition by surfactant alone.

Claims: A process for making an aqueous bleach composition comprising (a) from 3% to 8% by weight of the composition of sodium hypochlorite; (b) from 0.01% to 0.3% by weight of the composition of a bleach stable pigment selected from Ultramarine Blue and 3,3'-dichloro indanthrone;. (c) a bleach-stable anionic sulfonate surfactant; (d) from 0% to 0.5% by weight of the composition of a bleach-stable organic oil having a density of from 0.8 to 1.05g/ml; and (e) at least 80% by weight of the composition of water. characterized in that the process comprises the steps of: 1) preparing an aqueous system containing said pigment, said surfactant, and, where present, said bleach-stable organic oil, together with an optical brightener having the formula: or the alkali metal salts thereof; said optical brightener being added in an amount so as to provide from 0.025% to 0.2% by weight thereof in the bleach composition, said surfactant being selected from alkylaryl sulfonates having the formulas: wherein R₁ is a C₈-C₂₀ alkyl group, R₂ and R₃ are C₁₀-C₁₆ alkyl groups, M is alkali metal and n is 0 or 1; said pigment being uniformly dispersed in said aqueous system; 2) adding slowly, and with low shear mixing, to the system of Step 1, a sufficient amount of aqueous sodium hypochlorite to produce the bleach composition. A process according to Claim 1 wherein said organic oil is added to the aqueous system of Step 1 after the surfactant and brightener have been mixed and before the addition of the pigment. A process according to either one of Claims 1 or 2 wherein the amount of pigment in the finished composition is from 0.01% to 0.1% by weight. A process according to any of the preceding claims wherein the amount of sodium hypochlorite in the finished composition is from 4% to 6% by weight. A process according to any of the preceding claims wherein the amount of optical brightener in the finished composition is from 0.05% to 0.075% by weight. A process according to any of the preceding claims wherein the amount of surfactant in the finished composition is from 0.2% to 1% by weight. A process according to any of the preceding claims wherein the amount of organic oil in the finished composition is from 0.05% to 0.35% by weight.

Inventors: BAIER, KATHLEEN GRIESHOP, NAYAR, BALA CHANDRAN
Applicants: THE PROCTER & GAMBLE COMPANY
Application year: 1985
Main classification: C11D3
IPC codes: C11D3