Stable suspension of pigments in aqueous hypochlorite bleach compositions

Abstract

 Aqueous hypochlorite laundry bleach compositions containing 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

[0001] The invention pertains to an aqueous hypochlorite laundry bleach product which contains suspended pigments, and to the process for making same.

BACKGROUND ART

[0002] "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.)

[0003] U.S. Pat. No. 4,271,030, Brierley et al., issued June 2, 1981, 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 '030 patent does not . teach the essential optical brightener of the present invention.

[0004] It is an object of the present invention to prepare a superior aqueous hypochlorite laundry bleach with suspended inorganic pigments, without calcium soap or the like.

SUMMARY OF THE INVENTION

[0005] The present invention is directed to the formulation of aqueous sodium hypochlorite laundry bleach compositions containing a dispersion of bleach stable inorganic pigment, an optical brightener and LAS (linear alkylbenzene sulfonate). The preferred compositions comprise a uniform mixture of from 3% to 8% sodium hypochlorite, from 0.01% to 0.3% of the Ultramarine Blue pigment, from - 0.025% to 0.2% of the optical brightener 4,4'-bis(4-phenyl-2H-1,2,3-triazol-2-yl)-2,2'- stilbenedisulfonate, from 0.05% to 2% of a certain alkylaryl sulfonate surfactants, and preferably from 0.01% to 0.5% of a bleach stable organic oil, and at least 80% water.

DETAILED DESCRIPTION OF THE INVENTION

[0006] in accordance with the present invention it has been found that the bleach stable pigment selected from the group consisting of chlorinated indanthrone (and its equivalents) and Ultramarine Blue, Na₇Al₆Si₆O₂₄S₂ (and its equivalents), can be stably dispersed in an aqueous sodium hypochlorite laundry bleach containing LAS and a special optical brightener. The pigment can be mixed with the LAS/optical brightener before they are salted out as a fine dispersion or it can be mixed into the LAS/optical brightener/hypochlorite. 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.

[0007] All percentages herein are "by weight" unless specified otherwise.

[0008] The compositions of the invention comprise:

(a) from 3% to .8% sodium hypochlorite;

(b) from 0.01% to 0.3% (preferably 0.01% to 0.1%) of the pigment selected from the group consisting of Ultramarine Blue Na₇Al₆Si₆O₂₄S₂ and its equivalents, and chlorinated indanthrone (3,3'-dichloroindanthrone) and its equivalents;

(c) from 0.025% to 0.2% of the optical brightener, optical brightener 4,4'-bis(4-phenyl-2H-1,2,3-triazol-2-yl)-2,2'-stilbenedisulfonic acid (or its alkali metal salts)

(d) from 0.05% to 2% of a surfactant selected from the group consisting of alkylaryl sulfonates having the formulas:

and

wherein R₁ is a Ca-C20 alkyl group, R₂ and R₃ are C₆-C₁₆ alkyl groups, M is alkali metal and n is 0 or 1; and

(e) at least 80% water;

wherein the pigment is suspended in the composition in the form of dispersed particles.

[0009] The composition of this invention prepared by either admixing the pigments prior to or after mixing the brightener/surfactant solution with the aqueous sodium hypochlorite.

Sodium Hypochlorite

[0010] Typically, sodium hypochlorite is commercially available in aqueous solutions having a concentration of from about 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.

[0011] Sodium hypochlorite is present in the compositions of the invention at levels of from 3% to 8%, preferably from 4% to 6%.

Pigments

[0012] A preferred pigment used in this invention is Ultramarine Blue. It is sold as "C.I. Pigment Blue 29; C.l. 77007". It is a blue pigment occurring naturally as the mineral iapis lazuti. 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.

[0013] "it is used as a pigment in calico printing, wallpaper, mottied 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 microns and Grade 5151 has a particle size range of 0.3-1.3 microns.

[0014] Another preferred pigment is C.l. 69825 and is known under the names of C.l. Vat Blue 6 and C.l. Pigment Blue 64. They have the following chemical formula.

This C.I. 69825 pigment is available from Crompton ε Knowles Corporation under the name Intravat Blue.

[0015] The pigment is present in the composition of this invention at levels of from 0.01% to 0.3%, preferably from 0.02% to 0.05% and more broadly 0.01% to 0.1%.

Brightener

[0016] The brightener used in the compositions herein is 4,4- bis(4-phenyl-2H-1,2,3-triazol-2-yl)-2,2'-stilbenedisulfonic said, its alkali metal (e.g., sodium or potassium) salts. The structure of the sodium salt is: .

[0017] This optical brightener is available from Mobay Chemical Corporation, a subsidiary of Bayer AG, under the name Phorwite® CNA.

[0018] The optical brightener is present in the compositions of the invention at levels of from 0.025% to 0.2%, preferably from 0.05% to 0.075%.

Surfactant

[0019] 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.

[0020] Surfactants of Formula 1 are called alkytbenzene 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.

[0021] Surfactants of Formula 2 are alkyl diphenyloxide sulfonates and are available under the Dowfax® name from Dow Chemical Company.

[0022] 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%.

[0023] 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

[0024] Preferred compositions contain an organic oil which has a density of from 0.8 to 1.05. Preferably, the oils are present in the compositions of the invention 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, cyclo- pentadecanolide, p-tertiarybutyl cyclohexyl acetate, tetrahydro- mycenol, 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.

[0025] When organic oils are used in the compositions herein they are mixed into the pigment, brightener and surfactant solution prior to the addition of aqueous sodium hypochlorite to the solution.

[0026] The preferred bleach stable organic oils are selected from the group consisting of:

(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.

[0027] A preferred embodiment of the present invention is where 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:

[0028] 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.

Composition Preparation

[0029] The compositions of the invention are preferably prepared by the following steps:

1. Preparing an aqueous solution containing from 0.01% to 0.3% UMB pigment, from 0.05% to 0.4% of the brightener; from 0.1% to 4% of the surfactant; and from 0% to 1.0% bleach stable perfume or organic oil. The pigment is added last. Alternatively, the pigment is added at the end of or during Step 2.

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% UMB pigment, from 0.025% to _. 0.2% brightener; from 0.05% to 2% surfactant; and from 0% to 0.5% perfume or oil.

[0030] 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.

[0031] 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.

[0032] In the compositions made in accordance with this invention, the particles of pigmentlbrightenerlsurfactant 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.

[0033] 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., HCI or NaOH).

[0034] The invention will be illustrated by the following examples.

EXAMPLE I

[0035] A composition consisting of:

[0036] ^*The perfume has a density of about 1.03 g/cc and contains about about 15% 2,6-dimethyloctan-2-ol, about 15% of 3,7-dimethyloctan-3-ol and balance made of one or more components listed in Table A.

[0037] 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 rpm. 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% NaOCI content) were gradually added to the brightenerlsur- factant/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 11

[0038] Same as Example 1, except that the pigment was added to the system after the hypochtorite was added to the perfumel brightenerlsurfactant solution. A homogeneous blue product was formed which also remained stable for several days.

EXAMPLE III

[0039] A composition consisting of:

[0040] The procedure for making the composition of Example III was the same as that of Example 1, except that in Example III 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.

[0041] This example shows that it is not possible to get a stable suspension of the pigment in a bleach composition by surfactant alone.

EXAMPLE IV

[0042] Compositions were made consisting of:

[0043] 

[0044] The procedure was to dissolve the surfactant in water first and then add an 11% solution of calcium chloride slowly and with gentle stirring. Bleach was added next, again slowly and with gentle stirring. A 10% dispersion of UMB in water was then added and stirred to distribute the pigment uniformly in the composition. 500 ml of Compositions A and B were stored in 500 ml graduated glass cylinders. Within an hour, almost the entire pigment had settled down, in both cases.

EXAMPLE V

[0045] Compositions were made consisting of:

[0046] The procedure was the same as described in Example I, except that in Example V the UMB was added as a 10% dispersion in water after the brightener/surfactant dispersion was formed by the addition of NaOCI. 500 ml of Compositions A and B were stored in 500 ml graduated glass cylinders. The pigment was uniformly suspended throughout the composition and did not settle down.

EXAMPLE VI

[0047] A composition consisting of:

[0048] 

[0049] The pigment was added after precipitation of the brightener and surfactant. Pigment levels were varied from 0.02% to 0.1% to get different shades of blue color. In all cases, the pigment was dispersed uniformly throughout the composition and had excellent physical stability for several days. There was also good chemical stability as evidenced by the retention of color and % NaOCI.

[0050] Alternatively, it is possible to mix the pigment in the brightener/surfactant mixture before the bleach is added.

EXAMPLE VII

[0051] A composition consisting of:

[0052] An intense blue color was obtained immediately after the pigment was mixed with NaOCI. However, the pigment settled down entirely overnight.

EXAMPLE VIII

[0053] A composition consisting of:

[0054] The surfactant was precipitated first by addition of the bleach. The pigment was then stirred into the surfactant/pre- cipitate/bleach mixture. An intense blue coloration was obtained immediately after mixing with the pigment, but the pigment settled down entirely overnight. Example VIII shows that it is not possible to get a stable suspension of the pigment in a bleach composition by surfactant alone.

Claims

1. An aqueous bleach composition comprising

(a) from 3% to 8% sodium hypochlorite;

(b) from 0.01% to 0.3% of a bleach stable pigment selected from the group consisting of Ultramarine Blue, chlorinated indanthrone and their equivalents: and

(c) at least 80% water,

characterized in that it further comprises

(d) from 0.025% to 0.2% of an optical brightener having the formula :

or the alkali metal salts thereof;

(e) from 0.05% to about 2% of a surfactant selected from the group consisting of alkylaryl sulfonates having the formulas:

and

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; and

(f) from 0% to 0.5% of a bleach stable organic oil having a density of 0.8 to about 1.05 g/cc;

wherein the pigment is uniformly dispersed in an aqueous system of said brightener and said surfactant; and wherein the said composition is made by a process comprising the steps of:

1. preparing an aqueous system containing said pigment, said optical brightener,. said surfactant, and said bleach stable organic oil;

2. adding slowly, and with low shear mixing, to the system 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% of pigment, from 0.025% to 0.2% optical brightener, from 0.05% to 2% surfactant, and from 0% to 0.5% of said bleach stable organic oil.

2. The composition of Claim 1 wherein said organic oil is added to the aqueous system of Step 1 after the surfactant and brightener have been mixed.

3. The composition of Claim 1 or 2 wherein the amount of pigment in the finished composition is from 0.01% to 0.1%.

4. The composition of any of the preceding claims wherein the amount of sodium hypochlorite in the finished composition is from 4% to 6%.

5. The composition of any of the preceding claims wherein the amount of optical brightener in the finished composition is from 0.05% to 0.075%.

6. The composition of any of the preceding claims wherein the amount of surfactant in the finished composition is from 0.2% to 1%.

7. The composition of any of the preceding claims wherein the amount of organic oil in the finished composition is from 0.05% to 0.3%.

8. The composition of any of the preceding claims which is made by a process comprising the steps of :

1. preparing an aqueous system containing said optical brightener, said surfactant, and said bleach stable organic oil;

2. adding slowly, and with low shear mixing, to the system of Step 1, a sufficient amount of aqueous sodium hypochlorite to produce the desired composition.