Chlorine-free liquid automatic dishwashing compositions

Abstract

 Liquid automatic dishwashing compositions are provided, which are free of chlorine bleach, contain a solid water-soluble peroxygen compound suspended in a liquid phase containing water and at least one water-miscible solvent; and 5% to 30% of a silicate which creates a suspending structure for the solid bleach compound.
Preferred compositions are built with a non-phosphate builder.

Description

Technical Field

[0001] The present invention relates to liquid automatic dishwashing compositions, which are free of chlorine bleach, and contain a solid water-soluble peroxygen bleach, suspended in a liquid phase;

Background

[0002] Liquid automatic dishwashing products are well-known; such products usually contain chlorine bleaches.

[0003] There is a need for liquid automatic dishwashing products which are free of chlorine bleach, for environmental reasons and in view of the strong and unpleasant odor of chlorine.

[0004] In EP-A-293 040 and 294 904 have been disclosed liquid detergent compositions containing a water-soluble peroxygen bleach, such as perborate tetrahydrate, suspended in a liquid phase consisting of water and a water-miscible organic solvent.

[0005] The compositions disclosed in said documents are intended to be used for the washing of textiles and in fact, they have an alkalinity below 2 grams NaOH/100 ml of composition.

[0006] It is well-known that dishwashing products must have a higher alkalinity, in order to function effectively; It was now been surprisingly found that the silicate can be used in liquid automatic dishwashing products, not only to provide at least partly the desired alkalinity, but also to create a suspending structure for the solid water-soluble peroxygen bleach, thus providing a remarkable physical stability to the present compositions, in addition to the chemical stability provided by the liquid phase disclosed in EP-A 293 040 and 294 904.

[0007] Silicates have been widely described as alkalinity-building ingredients of aqueous thixotropic liquid compositions used for automatic dishwashing purposes. Representative of this art is EP 315 024.

[0008] EP-A-79 646, EP-A-86 614, EP-A-203 660 and EP-A-295 021 describe liquid detergent composition containing suspended builder particles where one or more "salting-out" electrolytes, or "surfactant desolubilizing" electrolytes are used, to build structured phases with the surfactant materials; such electrolytes include, among many other substances, silicates.

[0009] Other patent documents disclosing the use of silicates in cleaning/detergent compositions of the suspendng type include GB-A-2031455, and GB-A-1342612 wherein the solid materials to be suspended include abrasives and water-insoluble phosphate builder salts, but do not encompass peroxygen bleach particles; actually, GB-A-2158453 which mentions perborate as a possible bleaching ingredient in liquid compositions of the suspending type specifically advocates that the compositions must be free of silicate, and instead must contain a carboxylic antigelling agent.

[0010] It is provided herewith liquid dishwashing compositions which are chemically and physically stable, environmentally friendly, performing at least equally as state of the art compositions and furthermore being perfectly pourable and exhibiting shear-thinning and thixothopic properties.

[0011] The composition of the invention are preferably built, with a non-phosphate builder, this latter feature completing the "environmentally friendly" character of the present composition.

Summary

[0012] Chlorine-free liquid automatic dishwashing compositions having an alkalinity of from 20 grams to 20 grams NaOH/100 ml of composition, said composition containing from 5% to 30%, preferably from 7% to 15% by weight of silicate and comprising a solid water-soluble peroxygen compound suspended in a liquid phase containing water and at least one water-miscible organic solvent. The amount of the solid water-soluble peroxygen compound being such that the amount of available oxygen provided by said peroxygen compound is from 0.5 to 3%. The compositions preferably contain from 5% to 40% of a non-phosphate builder.

Detailed Description

The alkalinity

[0013] The present compositions have an alkalinity of from 2 gram to 20 gram NaOH per 100 ml of composition, preferably from 3 gram to 10 grams NaOH per 100 ml of compositions.

[0014] The alkalinity can easily be measured as it is well known, i.e., titration of a 1% solution from initial pH to pH 9.5. The desired alkalinity is at least partly provided by the silicate described hereinbelow, which can also be used in combination with sodium or potassium carbonate.

The silicate

[0015] In order to provide (at least partly) the desired alkalinity, and to create a structure to suspend the peroxygen bleach particles, a silicate is present in the present composition, at levels of from 5% to 30%, preferably 7% to 15% of the total composition; Preferred is sodium silicate, while potassium silicate can also be used.

[0016] The silicate materials for use herein have a ratio of SiO₂ to Na₂O of from 1:1 to 4:1, preferably 1:1 (metasilicate) and 2:1.

[0017] The silicate herein also provides desriable shear-thinning and thixotropic properties to the present compositions.

The water-soluble solid peroxygen compound :

[0018] The compositions herein are free of chlorine-bleach. Instead, they contain a solid water-soluble peroxygen compound.

[0019] The water-soluble solid peroxygen compound is present in the compositions herein at levels such that the amount of available oxygen provided by said peroxygen compound is from 0.5% to 3%.

[0020] Examples of suitable water-soluble solid peroxygen compounds include the perborates, 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.

[0021] Perborate tetrahydrates are especially preferred, and are present at levels of from 5% to 30% by weight of the total composition.

[0022] Most preferred in the present context is a perborate tetrahydrate bleach in the form of particles having a weight-average particle diameter of from 0.5 to 20 micrometers, preferably 3 to 15 micrometers.

[0023] The required small particles size can best be achieved by in-situ crystallization, typically of perborate monohydrate.

[0024] 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.

[0025] 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 liquid phase

[0026] The suspension system for the solid peroxygen component herein consists in a liquid phase that comprises water and a water-miscible organic solvent;

[0027] This makes it possible to incorporate in the liquid detergent compositions herein an 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 fifth by weight 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.

[0028] The standard iodometric method (as described for instance in Methoden der Organischen Chemie, Houben Weyl, 1953, Vo. 2, page 562) is suitable to determine the available oxygen (AVO) content of the composition.

[0029] 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.

[0030] For the determination of the available oxygen (AVO) in the liquid phase, samples of the compositions are centrifuged for 10 minutes at 10.000 rpm. The liquid is then separated from the solid and titrated for available oxygen.

[0031] 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.

[0032] 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.

[0033] 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, 1-methoxy2-propanol and butyldiglycolether. A preferred solvent system is ethanol.

[0034] 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%.

[0035] 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.

[0036] The present liquid compositions are formulated at a pH of from 9.5 to 12.5, preferably from 10 to 11.5. The alkaline pH allows to get a good bleaching action of the peroxygen compound, particularly when the peroxygen is a perborate.

Optional ingredients

[0037] The present compositions may contain a series of ingredients which, while being optional, are often desirable.

[0038] First of all, it is highly preferred that the present compositions contain a builder :

[0039] The present compositions can contain from 5% to 40% of a builder which is non-phosphate material; inorganic builders useful in the present compositions include aluminosilicates (zeolites), while organic builders include polyacids such as citric acid, nitrilotriacetic acid, certain alk(en)yl-substituted succinic acid/anhydride compounds, and mixtures of tartrate monosuccinate with tartrate disuccinate. Polymeric carboxylate builders inclusive of polyacrylates, polyhydroxy acrylates and polyacrylates/polymaleates copolymers can also be used. Iminodiacetic acid derivatives such as N-glyceryl imino N,N diacetic acid, (N(-2-hydroxypropyl)imino N,N-diacetic acid are also suitable as builders. Preferred builders for use herein are citric acid and alk(en)yl-substituted succinic acid/anhydride compounds, wherein alk(en)yl contains from 10 to 16 carbon atoms and mixtures thereof. An example of this group of compounds is dodecenyl succinic acid/anhydride, especially preferred for the present compositions are mixtures of dodecenyl succinic/anhydride and citric acid, at ratios of dodecenyl succinic acid/anhydride to citric acid of from 2:1 to 1:1.

[0040] It is also preferred that the present compositions contain a surface-active agent, at levels of from 1% to 10% by weight of the total composition;

[0041] Said surface-active agents are preferably nonionic surfactants :

[0042] 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 RA(CH₂CH₂O)_nH 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.

[0043] The hydrophobic moiety of 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.

[0044] 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.

[0045] Suitable species of this class of ethoxylates include : the condensation product of C₁₂-C₁₅ oxo-alcohols and 7 moles of ethylene oxide per mole of alcohol; the condensation product of narrow cut C₁₄-C₁₅ oxo-alcohols and 7 or 9 moles of ethylene oxide per mole of fatty(oxo)alcohol; the condensation product of a narrow cut C₁₂-C₁₃ fatty(oxo)alcohol and 6,5 moles of ethylene oxide per mole of fatty alcohol; and the condensation products of a C₁₀-C₁₄ 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.

[0046] A degree of branching in the range from 15% to 50% (weight %) is frequently found in commercial oxo alcohols.

[0047] 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 mixture contains a lower ethoxylate which is the condensation product of a C₁₂-C₁₅ 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 C₁₆-C₁₉ oxo-alcohol with more than 50% (wt) branching and from about 8 to 14 moles of ethylene oxide per mole of branched oxo-alcohol.

[0048] The composition herein may, however, also contain other types of surfactant, like anionic or cationic surfactants, possibly in combination with the nonionic surfactants described above.

[0049] Synthetic anionic surfactants can be represented by the general formula R¹SO³M wherein R¹ 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 19 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.

[0050] 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.

[0051] Examples of suitable cationic surfactants include quaternary ammonium compounds of the formula R₁R₂R₃R₄N⁺X⁻, wherein R₁ is C₁₂-C₂₀ alkyl or hydroxyalkyl; R₂ is C₁-C₄ alkyl or C₁₂-C₂₀ alkyl or hydroxyalkyl or C₁-C₄ hydroxyalkyl; R₃ and R₄ are each C₁-C₄ alkyl or hydroxyalkyl, or C₆-C₈ aryl or alkylaryl; and X⁻ is halogen. Preferred are mono-long chain quaternary ammonium compounds (i.e., compounds of the above formula wheren R₂ is C₁-C₄ alkyl or hydroxyalkyl).

[0052] Detergent enzymes can be used in the present composition. Suitable enzymes include the detergent proteases, amylases, lipases and cellulases;
Enzymatic stabilizing agents for use herein include the salts of formic acid, e.g. sodium formate, but also the salts of higher carboxylic acids, such as sodium acetate, and mixtures of above species.

[0053] The total amount of enzymatic stabilizing agent typically ranges from 0.5 to 5%.

[0054] The present compositions may also contain relatively small amounts of :
- Bleach stabilizers such as following organo-phosphonic acids :
- ethylenediamino tetramethylenephosphonic acid, hexamethylenediamino tetramethylenephosphonic acid, diethylenetriamino pentamethylenephosphonic acid, amino-trimethylenephosphonic acid, hydroxyethylidene 1,1 diphosphonic acid and mixtures thereof.
- Other bleach stabilizers such as ascorbic acid, dipicolinic acid, sodium stannates and 8-hydroxyquinoline.
- polyaminocarboxylates such as ethylene­diaminotetracetic acid, diethylenetriaminopentacetic acid, ethylenediamino disuccinic acid or the water-soluble alkali metals thereof.
- Silicone suds regulants
- Sodium peroxide to adjust to the desired pH
- opacifiers, bactericides, dyes, perfumes, etc...

[0055] The following compositions illustrate the present invention :

[0056] The compositions of example I to IV are pourable, show no phase separation after storage (3 weeks), and feature a remaining percentage of initial aVO of 90%, after 3 weeks.

[0057] The compositions of example I to IV perform equally well vs. commercially available dishwashing products containing chlorine bleach.

Claims

1. A chlorine-free liquid automatic dishwashing composition having an alkalinity of from 2 grams to 20 grams NaOH/100 ml of composition, said composition containing from 5% to 30% by weight of silicate and comprising a solid water-soluble peroxygen compound suspended in a liquid phase containing water and at least one water-miscible organic solvent; the amount of the solid water-soluble peroxygen compound being such that the amount of available oxygen provided by said peroxygen compound is from 0.5% to 3%.

2. A liquid detergent composition according to claim 1, wherein the water-miscible organic solvent is an aliphatic monoalcohol.

3. A liquid detergent composition according to claim 2 wherein the water-miscible organic solvent is ethanol, and the water:ethanol ratio of from 8:1 to 1:3, preferably 5:1 to 1:2.

4. A liquid detergent composition according to claims 1-3, wherein the solid, water-soluble peroxygen compound is perborate tetrahydrate, and present at levels of from 5% to 30% by weight of the total composition.

5. A composition according to claim 4 wherein the perborate tetrahydrate bleach is in the form of particles having a weight-average particle diameter of from 0.5 micrometer to 20 micrometer.

6. A composition according to claim 5 wherein the perborate tetrahydrate particles have been formed by recrystallization of a perborate monohydrate.

7. A composition according to claims 1-3, wherein the solid, water-soluble peroxygen compound is a percarbonate.

8. A composition according to claims 1-7, containing from 7% to 15% of silicate.

9. A composition according to claims 1-8, having an alkalinity of from 3 grams to 10 grams NaOH/100 ml of composition.

10. A composition according to claims 1-9, which contains from 5% to 40% of a builder selected from dodecenyl succinic acid, citric acid, iminodiacetic acid derivatives, and mixtures thereof.