CONCENTRATED AQUEOUS LIQUID BLEACH COMPOSITIONS

Abstract: Concentrated aqueous liquid bleach compositions are disclosed, to be used preferably as bleach additives, containing from 30 % to 60 % by weight of a solid water-soluble peroxygen compound suspended in a liquid phase, and 0-4 % by weight of anionic surfactant.

Description: CONCENTRATED AQUEOUS LIQUID BLEACH COMPOSITIONS Technical Field The present invention relates to concentrated aqueous liquid bleach compositions, to be used preferably as bleach additives, containing from 30% to 60% of a solid water-soluble peroxygen compound suspended in a liquid phase. Background In European Patent Applications 293 040 and 294 904, have been described aqueous detergent compositions having a pH above 8 containing an anionic surfactant at conventional levels, i.e. above 5% by weight, typically from 15% to 40% by weight, and a solid, water-soluble peroxygen bleach dispersed in a specific water/solvent liquid phase. In European Patent Application 294 904 were specifically described compositions containing at least 5% anionic surfactant, at least 5% builder, and perborate bleach particles having preferably been formed by in situ recrystallization. This technology provided an answer to the long-felt need for aqueous liquid detergent compositions containing a peroxygen bleach, which are stable and efficient at the same time; indeed, attempts to formulate such compositions in the past featured non-aqueous-type executions, or hydrogen-peroxide-containing compositions, formulated at a pH around 8, where stability was acceptable but performance from the bleach was not optimal; representative of this art are : European Patent 0 086 511, granted July 2, 1986 to The Procter & Gamble Company, disclosing aqueous liquid detergent compositions having a pH below 9 and comprising organic surfactants, oxygen bleach, fatty acid and a water-soluble calcium salt. DE-OS 35 11 515, published October 17, 1985, disclosing non-aqueous liquid detergent compositions comprising sodiu perborate monohydrate and an activator for the perborate. FR 2.579.615, published October 3, 1986, disclosing similar non-aqueous compositions which further comprise catalase inhibitors. EP-A-293 040 and 294 904 are, however, representative of "dilute" liquid detergent compositions, and do not encompass compositions with a very high concentration of water-soluble peroxygen bleach. There is a need for such "concentrates", in particular for use as "bleach additives". Indeed, while bleach-containing detergent compositions have proven quite useful, there is a recognized interest for the consumer to be able to use the bleach component in an optional manner, or to use at a specific time during the wash cycle of a washing machine, depending on his specific needs or habits. Bleach additives have been developed for that purpose, and the commercially available ones are in solid form, consisting typically of sodium perborate and activator thereof, mixed as a powder. Such bleach additives in solid form suffer the disadvantage of slow dissolution, which impairs the efficiency; in addition, formation of spots on the fabrics may occur, due to very high localized concentration of the bleach. Bleach compositions based on hydrogen peroxide are well-known too, and are disclosed in e.g. EP-A-9 839; such compositions are mainly used for hard-surface cleaning applications, and are not desirable for use during the washing cycle of a washing machine. Drawbacks are low solution pH, and therefore poor efficiency, and high level of free hydrogen peroxide in the product, not desirable for consumer safety reasons. There is, therefore, a need for liquid bleach additives suitable for use in washing machine, which have no dissolution problems and which, once added to the wash medium, can be immediately effective on the fabrics; It has now been surprisingly found that aqueous liquid bleach compositions with high amounts of suspended solid peroxygen compound can be formulated, without impairing the chemical stability of the composition; it has further been discovered that unlike in the compositions of EPA 293 040 and 294 904, the amount of anionic surfactant in the present concentrated compositions must be kept under 4% by weight, since higher amounts alter the present viscosity/pourabiling characteristics of the present concentrated composition. The present invention therefore answers the above-mentioned needs, by providing concentrated aqueous liquid bleach compositions, containing high amounts of solid peroxygen compound, which are stable upon storage, show excellent viscosity/pourability characteristics, and dissolve quickly and efficiently in the wash medium. The present compositions, which exhibit an alkaline pH, allow to obtain an optimal performance from the bleach component. Summary The present invention consists of aqueous liquid bleach compositions having a pH of at least 8, comprising a solid, water-soluble peroxygen compound suspended in a liquid phase containing water and at least one water-miscible organic solvent, preferably an aliphatic monoalcohol such as ethanol, characterized in. that it contains from 20% to 40%, preferably 30% to 50% by weight of the composition, of the water-soluble peroxygen compound, and that it contains 0 to 4% of anionic surfactant. Detailed Description The water-soluble solid peroxygen compound is present in the compositions herein at levels of from 30% to 60% by weight of the total composition, preferably 30% to 50% by weight. Examples of suitable water-soluble solid peroxygen compounds include the perboraues, persulfates, peroxydisulfates, perphosphates and the crystalline peroxyhydrates formed by reacting hydrogen peroxide with sodium carbonate (forming percarbonate) or urea. Preferred peroxygen bleach compounds are perborates and percarbonates. Most preferred in the present context is a perborate bleach in the form of particles having a weight-average particle diameter of from 0.5 to 20 micrometers, preferably 3 to 15 micrometers. The required small particle size can best be achieved by in-situ crystallization, typically of perborate monohydrate. In-situ crystallization encompasses processes involving dissolution and recrystallization, as in the dissolution of perborate monohydrate and subsequent formation of perborate tetrahydrate. Recrystallization may also take place by allowing perborate monohydrate to take up crystal water, whereby the monohydrate directly recrystallizes into the tetrahydrate, without dissolution step. In-situ crystallization also encompasses processes involving chemical reactions, as when sodium perborate is formed by reacting stoichiometric amounts of hydrogen peroxide and sodium metaborate or borax. The suspension system for the solid peroxygen component herein consists in a liquid phase that comprises water and a water-miscible organic solvent; This makes it possible to incorporate in the liquid detergent compositions herein a high amount of solid water-soluble peroxygen compound, while keeping the amount of available oxygen in solution below 0.5% by weight of the liquid phase, preferably below 0.1%. Less than one thenth of the total amount of peroxygen compound is dissolved in the liquid phase; the low level of available oxygen in solution is in fact critical for the stability of the system. The standard iodometric method (as described for instance in Methoden der Organischen Che ie, Houben eyl, 1953, Vo. 2, page 562) is suitable to determine the available oxygen (AVO) content of the composition. In order to ensure complete equilibration between liquid and solid phases, the compositions are to be kept after mixing for three days at room temperature before the AVO titration. Before measuring the products are thoroughly shaken in order to ensure correct sampling. For the determination of the available oxygen (AVO) in the liquid phase, samples of the compositions are centrifuged for 10 minutes at 10.000 rp . The liquid is then separated from the solid and titrated for available oxygen. It is not necessary that the organic solvent be fully miscible with water, provided that enough of the solvent mixes with the water of the composition to affect the solubility of the peroxygen compound in the described manner. Fully water-soluble solvents are preferred for use herein. The water-miscible organic solvent must, of course, be compatible with the peroxygen bleach compound at the pH that is used. Therefore, polyalcohols having vicinal hydroxy groups (e.g. 1,2-propanediol and glycerol) are less desirable when the peroxygen bleach compound is perborate. Examples of suitable water-miscible organic solvents include the lower aliphatic monoalcohols; ethers of diethylene glycol and lower monoaliphatic monoalcohols; specifically ethanol, n-propanol; iso-propanol; butanol; polyethylene glycol (e.g., PEG 150, 200, 300, 400); dipropylene glycol; hexylene glycol; methoxyethanol; ethoxyethanol; butoxyethanol; ethyldiglycolether; benzylalcohol; butoxypropanol; butoxypropoxypropanol; and mixtures thereof. Preferred solvents include ethanol; iso-propanol, l-methoxy2-propanol and butyldiglycolether. A preferred solvent system is ethanol. Although the presence or absence of other ingredients plays a role, the amount of available oxygen in solution is largely determined by the ratio water:organic solvent. It is not necessary however to use more organic solvent than is needed to keep the amount of available oxygen in solution below 0.5%, preferably below 0.1%. In practical terms, the ratio water:organic solvent is, for most systems, in the range from 0:1 to 1:3, preferably from 5:1 to 1:2. The present liquid bleach compositions exhibit a pH (1% solution in distilled water) of at least 8, preferably of at least 9, more preferably at least 9.5. The alkaline pH allows to get a good bleaching action of the peroxygen compound, particularly when the peroxygen is a perborate. The compositions herein preferably contain a nonionic or cationic surfactant, or a mixture thereof, at total levels of from 1 to 6%. The nonionic surfactants are conventionally produced by condensing ethylene oxide with a hydrocarbon having a reactive hydrogen atom, e.g., a hydroxyl, carboxyl, or amido group, in the presence of an acidic or basic catalyst, and include compounds having the general formula R (CH 2 CH2θ) n H wherein R represents the hydrophobic moiety, A represents the group carrying the reactive hydrogen atom and n represents the average number of ethylene oxide moieties. R typically contains from about 8 to 22 carbon atoms. They can also be formed by the condensation of propylene oxide with a lower molecular weight compound, n usually varies from about 2 to about 24. The hydrophobic moiety oi the nonionic compound is preferably a primary or secondary, straight or branched, aliphatic alcohol having from about 8 to about 24, preferably from about 12 to about 20 carbon atoms. A more complete disclosure of suitable nonionic surfactants can be found in U.S. Patent 4,111,855. Mixtures of nonionic surfactants can be desirable. A preferred class of nonionic ethoxylates is represented by the condensation product of a fatty alcohol having from 12 to 15 carbon atoms and from about 4 to 10 moles of ethylene oxide per mole of fatty alcohol. Suitable species of this class of ethoxylates include : the condensation product of C 12 ~ i5 oxo-alcohols and 7 moles of ethylene oxide per mole of alcohol; the condensation product of narrow cut C 14 -C 15 oxo-alcohols and 7 or 9 moles of ethylene oxide per mole of fatty(oxo)alcohol; the condensation product of a narrow cut 12~ c 13 fatty(oxo)alcohol and 6,5 moles of ethylene oxide per mole of fatty alcohol; and the condensation products of a C 1Q -C 14 coconut fatty alcohol with a degree of ethoxylation (moles EO/mole fatty alcohol) in the range from 5 to 8. The fatty oxo alcohols while mainly linear can have, depending upon the processing conditions and raw material olefins, a certain degree of branching, particularly short chain such as methyl branching. A degree of branching in the range from 15% to 50% (weight %) is frequently found in commercial oxo alcohols. Preferred nonionic ethoxylated components can also be represented by a mixture of 2 separately ethoxylated nonionic surfactants having a different degree of ethoxylation. For example, the nonionic ethoxylate surfactant containing from 3 to 7 moles of ethylene oxide per mole of hydrophobic moiety and a second ethoxylated species having from 8 to 14 moles of ethylene oxide per mole of hydrophobic moiety. A preferred nonionic ethoxylated mixute contains a lower ethoxylate which is the condensation product of a C 12 ~ c i5 oxo-alcohol, with up to 50% (wt) branching, and from about 3 to 7 moles of ethylene oxide per mole of fatty oxo-alcohol, and a higher ethoxylate which is the condensation product of a c 16~ c 19 oχo ~ a lcohol with more than 50% (wt) branching and from about 8 to 14 moles of ethylene oxide per mole of branched oxo-alcohol. Examples of suitable cationic surfactants include quaternary ammonium compounds of the formula R 1 R2R 3 R N + ~, wherein R- j^ is C 12 -C 2u alkyl or hydroxyalkyl; R 2 is C- j _-C 4 alkyl or C 1 2~ c 20 alkyl or hydroxyalkyl or C 1 -C 4 hydroxyalkyl; R 3 and R 4 are each C 1 -C alkyl or hydroxyalkyl, or Cg-C 8 aryl or alkylaryl; and X~ is halogen. Preferred are mono-long chain quaternary ammonium compounds (i.e., compounds of the above formula wheren R is C- j _-C 4 alkyl or hydroxyalkyl) . The compositions herein may also contain anionic surfactants; however, it has been found that anionic surfactants, if used at levels above 4% by weight, could give problems with respect to the viscosity/pourability characteristics of the present compositions. Accordingly, anionic surfactants, if used, are present at levels up to 4% by weight, preferably up to 1% by weight. Synthetic anionic surfactants, can be represented by the general formula R-^SO ^ ^M wherein R 1 represents a hydrocarbon group selected from the group consisting of straight or branched alkyl radicals containing from about 8 to about 24 carbon atoms and alkyl phenyl radicals containing from about 9 to about 15 carbon atoms in the alkyl group. M is a salt forming cation which typically is selected from the group consisting of sodium, potassium, ammonium, and mixtures thereof. A preferred synthetic anionic surfactant is a water-soluble salt of an alkylbenzene sulfonic acid containing from 9 to 15 carbon atoms in the alkyl group. Another preferred synthetic anionic surfactant is a water-soluble salt of an alkyl sulfate or an alkyl polyethoxylate ether sulfate wherein the alkyl group contains from about 8 to about 24, preferably from about 10 to about 20, preferably from about 1 to about 12 ethoxy groups. Other suitable anionic surfactants are disclosed in U.S. Patent 4,170,565, Flesher et al., issued October 9, 1979. The present compositions may contain a builder, preferably no more than 4% of the total composition. If present, such builder can consist of the inorganic or organic types already described in the art; Examples of inorganic builders include the phosphourus-based builders, e.g., sodium tripolyphosphate, sodium pyrophosphate, and aluminosilicates (zeolites) . Examples of organic builders are represented by polyacids such as citric acid, nitrilotriacetic acid, and mixtures of tartrate monosuccinate with tartrate disuccinate. Preferred builders for use herein are citric acid and alk(en)yl-substituted succinic acid compounds, wherein alk(en)yl contains from 10 to 16 carbon atoms. An examples of this group of compounds is dodecenyl succinic acid. Polymeric carboxylate builders inclusive of polyacrylates, polyhydroxy acrylates and polyacrylates/polymaleates copolymers can also be used. The compositions herein may also contain further additives at levels of from 0.05% to 2%. These additives include polyaminocarboxylates such as ethylenediaminotetracetic acid, diethylenetriamino-pentacetic acid, ethylenediamino disuccinic acid or the water-soluble alkali metals thereof. Other additives include organo-phosphonic acids; particularly preferred are ethylenediamino tetramethylenephosphonic acid, diethylenetria ino pentamethylenephosphonic acid and aminotrimethylenephosphonic acid, hydroxyethylidene diphosphonic acid. Bleach stabilizers such as ascorbic acid, dipicolinic acid, sodium stannates and 8-hydroxyquinoline can also be included in these compositions, at levels between 0.01 and 1%. The compositions herein can contain a series of further optional ingredients which are mostly used in additive levels, usually below about 5%. Examples of the like additives include : enzymes and enzymatic stabilizing agents, opacifiers, agents to improve the machine compatibility in relation to enamel-coated surfaces, bactericides, dyes, perfumes, brighteners and the like. Suitable enzymes include the detergent proteases, amylases, lipases and cellulases. Preferred enzymatic stabilizing agents for use herein are salts of formic acid or acetic acid, e.g. sodium formate and sodium acetate. Use of the Compositions The present compositions are mainly intended to be used as bleach additives, in the washing cycle of washing machines, on top of conventional granular or liquid detergent compositions. Typically, said bleach additives will be added to the wash medium, separately from the detergent composition, at a time chosen by the consumer or predetermined by washing-machine manufacturers, preferably at the beginning of the wash cycle. The use of the concentrated bleach compositions of the present invention as bleach-additives in the wash cycle of a washing machine, is the preferred one; however, other uses can be contemplated, such as pretreatment product for heavily-soiled fabrics, or soaking product; the use as bleach additive is not necessarily limited to the washine-machine context, and the compositions of the present invention can be used in combination with bleach-compatible handwash compositions. The detergent compositions to be used in combination with the present bleach additives should be bleach-compatible; preferably the present liquid aqueous bleach additives will be used in combination with bleach-compatible liquid detergent compositions. A typical bleach-compatible liquid detergent composition has the following formula : Ingredients Com osition wt * Diethylene triamine pentamethylene phosphonic acid Examples The following liquid aqueous concentrated bleach compositions are prepared : Ingredients Composition wt% II III IV Viscosity (cps) NOT 4000 1500 2600 2700 at 60 rpm POURABLE * Diethylene triamine pentamethylene phosphonic acid The above compositions were prepared according to the following method : The solvent(s) and the phosphonic acid are dissolved in water and the pH is adjusted to about 8 with sodium hydroxide. The surfactant(s) , if present, are then added and, if needed, the pH is adjusted back to 8 with sodium hydroxide. The sodium perborate monohydrate is then added under stirring, at room temperature; it recrystallizes to perborate tetrahydrate within a few hours of stirring. The recrystallization process can be speeded up by adding, prior to the perborate, some seed crystals of sodium perborate tetrahydrate of small particle size (5-10 microns) . In practice this is best done by adding a small percentage (less than 10%, typically around 5%) of the finished composition of this patent. Bleach-containing dilute aqueous detergent compositions (such as described in EP-A-293 040 and EP-A-294 904) can also be used as seeding compositions. After the recrystallization is completed, minor ingredients such as dyes, perfumes etc. are added. The composition can also be prepared by reacting in situ hydrogen peroxide and sodium metaborate (or borax) . In this case sodium metaborate powder is added to the solvent(s)/surfactant(s) solution; then an aqueous solution of hydrogen peroxide is added. Sodium perborate tetrahydrate crystallizes from the solution, and then the product is completed as described above. Composition A is prepared for comparative purposes, to show the criticality of the anionic surfactant level. Composition A appears to be non pourable. The compositions of Examples I to IV show perfectly acceptable viscosity characteristics, and have excellent stability behaviour upon storage

Claims: CLAIMS 1. An aqueous liquid bleach composition having a pH of at least 8, comprising a solid, water-soluble peroxygen compound suspended in a liquid phase containing water and at least one water-miscible organic solvent, characterized in. that it contains from 30% to 60%, by weight of the composition, of the water-soluble peroxygen compound, and that it contains from 0 to 4% by weight of anionic surfactant. 2. A composition according to claim 1, wherein the water-miscible organic solvent is an aliphatic monoalcohol. 3. A composition according to claim 2, wherein the water-miscible solvent is ethanol, and is present in a water:ethanol ratio of from 8:1 to 1:3. 4. A composition according to claims 1-3, wherein the water-soluble peroxygen compound is present at levels of from 30-50% by weight. 5. A composition according to claims 1-4 wherein the solid, water-soluble peroxygen compound is a perborate tetrahydrate. 6. A composition according to claim 5 wherein the perborate tetrahydrate is in the form of particles having a weight-average particle diameter of from 0.5 micrometer to 20 micrometer. -Ϊ9-- 7. A composition according to claim 6, wherein the perborate tetrahydrate particles have been formed by recrystallization of a perborate monohydrate. 8. A composition according to claims 1-4, wherein the solid, water-soluble peroxygen compound is a percarbonate. 9. A composition according to any one of the preceding claims having a pH of at least 9. 10. A composition .according to any of the preceding claims which contains from 1 to 6% by weight of a nonionic or cationic surfactant, or mixture thereof. 11. A composition according to any of the preceding claims which contains from 0 to 1% by weight of anionic surfactant. 12. The use of the composition of claims 1-11 as a bleach additive for a detergent composition. 13. The use according to claim 12 wherein said detergent composition is a bleach-compatible liquid detergent composition.

Inventors: DEBUZZACCARINI FRANCESCO, DEBUZZACCARINI, FRANCESCO
Applicants: PROCTER & GAMBLE, THE PROCTER & GAMBLE COMPANY
Application year: 1990
Main classification: C11D3
IPC codes: C01B15, C11D3, C11D7, D06L3