The present invention is concerned with coacervate fractions of builder polymers, more in particular of copolymers of acrylic acid and maleic acid, and the use of these fractions to formulate structured liquid detergent compositions.
Such structured liquids can be 'internally structured', whereby the structure is formed by primary ingredients, and/or they can be structured by secondary additives, such as certain cross-linked polyacrylates, or clays, which can be added to a composition as 'external structurants'.
Both forms of structuring are well known in the art. External structuring is usually used for the purpose of suspending solid particles and/or droplets of nonionic surfactant. Examples of externally structured liquid detergent compositions are given in EP-A-120 533.
Internal structuring is usually used to suspend particles and/or to endow properties such as consumer-preferred flow properties and/or turbid appearance. The most common suspended particulate solids are detergency builders and abrasive particles. Examples of internally structured liquids without suspended solids are given in U.S. patent 4 244 840. Examples of internally structured liquids having solid particles suspended therein are disclosed in specifications EP-A-160 342; EP-A-38 101; EP-A-104 452 and also in the aforementioned U.S. patent 4 244 840.
Two problems are commonly encountered when formulating liquids having solid suspending properties. The first is high viscosity, rendering the products difficult to pour and the second is instability, i.e. a tendency for the dispersed and aqueous phases to undergo separation of the active ingredients or sedimentation of the solid particles and/or creaming of the nonionic, upon storage at elevated or even at ambient temperatures. Thus care must always be exercised when formulating such liquids so that the nature and concentration of the active materials are selected to give the required rheological and stability properties.
It is known that incorporation of fabric-softening clays (e.g. bentonites) in liquids can give rise to unacceptably high viscosity. One approach to mitigate this disadvantage has been to also incorporate a small amount of a dissolved low molecular weight polyacrylate. This is described in GB-A-2 168 717. However, if one wishes to use such polymers for viscosity control in the widest possible range of structured liquids, then one is led on occasions to try to incorporate more and more polymer. Alternatively or additionally to this reason, there is also a desire to use increased amounts of polymers for their detergency builder properties, i.e. to counter the effects of calcium ion water hardness. This is particularly important when one wishes to substitute the polymers for conventional phosphate builders (either in whole or in part) for environmental reasons.
Unfortunately, when it is attempted to dissolve more polymer, what is then frequently found (as when trying to incorporate increased amounts of any component in a structured liquid) is an increased tendency to instability, i.e. to undergo separation of actives or sedimentation of the solid particles and/or creaming of the nonionic.
EP-A-301 882 discloses that for internally structured liquid detergent compositions, the amount of stably incorporated polymer can be increased by adjusting the composition such that only part of the polymer is in solution whilst the rest is incorporated in a stable 'non-dissolved' phase within the composition. The obtained compositions, however, are sometimes of relatively high viscosity, furthermore compositions comprising higher levels of polymer tend to be instable.
It is an object of the present invention to provide structured liquid detergent compositions which contain a builder polymer, more in particular a copolymer of acrylic acid and maleic acid, and which nonetheless are of satisfactory stability and of adequate viscosity.
Surprisingly, we have now found that this object may be achieved by incorporating the builder polymer in the composition at least partially in the form of a coacervate fraction containing said copolymer.
According to a first aspect of the invention, there is provided a coacervate fraction of a coacervate forming detergency copolymer of acrylic acid and maleic acid.
Coacervate formation is a well-known phenomenon in physical chemistry, more in particular in colloid chemistry. Basicly, coacervation is a specific way of aggregation of active materials, whereby a relatively highly concentrated dispersed phase of the active materials is obtained. Typical circumstances for the formation of such a coacervate fraction are circumstances wherein hydration of the active materials is reduced and the charge of the active materials is reduced or shielded.
One possible way of forming a coacervate fraction from a colloidal system of actives involves dehydration and neutralization of the electrical charge at the same time. When doing this, part of the actives form a coacervate fraction. Starting with a homogeneous colloidal solution, coacervation leads to phase separation. The coacervate fractions formed as a separate viscous liquid phase with a high concentration of dispersed material, which may for instance be as high as 35 % by weight. This does not exclude residual solubility of the colloid in the remaining solution. The presence of materials in coacervate form may be detected by any means well-known in the art for the detection of structure formation, suitable methods for example involve: centrifugation, preferably at high speed, chromatography, X-ray and light scattering techniques or light microscopy, each separately or in combination with one another and chemical analysis.
In the case of copolymers of acrylic acid and maleic acid, a coacervate may be formed from an aqueous solution containing the copolymer by adding electrolyte, preferably concentrated sodium hydroxide solution, to a colloidal system of copolymer in a solvent until at a certain concentration of electrolyte material the coacervate fraction separates out, followed separating the formed coacervate fraction, for example by sedimentation or centrifugation.
By using the above method it was found that different electrolytes have a widely different coacervate-forming potential. This is illustrated in Table A below, where for certain copolymers the minimal electrolyte concentrations are given, at which formation of the coacervate fraction occurs.
A preferred method for obtaining a coacervate fraction of the copolymer involves the preparation of an aqueous solution containing from 2-20% by weight of the copolymer, adding concentrated sodium hydroxide solution to a final concentration of at least 1% (w/w) of sodium hydroxide and separating the formed coacervate fraction by sedimentation or centrifugation.
Coacervate fractions isolated by this or any other method for obtaining a similar fraction preferably contain at least 15 % by weight of the copolymer, and more preferably from 20 to 50 % by weight of the copolymer.
| COACERVATION CONCENTRATION OF ELECTROLYTES FOR ACRYLIC ACID/MALEIC ACID COPOLYMERS (5% W/V) |
| Polymer ||Mol. Weight ||40,000 ||50,000* ||70,000** |
| ||AA/MA ratio ||1/0.67 ||1/0.59 ||1/0.27 |
| Electrolyte (% w/v) |
|NaOH ||1.6 ||0.85 ||2.1 |
|KOH ||7.5 ||6.9 ||2.7 |
|NaCl || ||4.8 ||15.0 |
|NaCl (0.3% NaOH present) || || ||2.0 |
|KCl || ||> 34 || |
|Na₂SO₄ || ||> 19 || |
|Na₂SO₄ (1% NaOH present) || || ||2.0 |
|K₂SO₄ || ||> 11 || |
|STP || ||> 12 || |
|KTP || ||> 40 || |
|NWG (silicate SiO₂:Na₂O=3.3:3) || ||5.1 || |
|NWG/KOH (1:1) || ||1.4 || |
|NTA laq || ||3.4 ||10.0 |
|Na-metasilicate || ||1.3 || |
|Na-citrate (0.1% NaOH present) || || ||10.0 |
|*) Sokalan CP7 ex BASF |
|**) Sokalan CP5 ex BASF |
Coacervate fractions according to the invention advantageously comprise an aqueous base and have a pH of more than 8.0, preferably of more than 9.0, a pH of above 11.0 being especially preferred.
Preferably copolymers are used wherein the molar ratio of acrylic acid to maleic acid in the copolymer is from 1 to 10. Also preferred is the use of copolymers having molecular weight of the copolymer is at least 5,000, preferably more than 20,000, especially preferred more than 40,000. The molecular weight of the copolymer is less than 1,000,000, preferably less than 150,000, most preferred less than 100,000. Copolymers having a molecular weight from 40,000 to 100,000 are particularly preferred, especially because of their excellent builder capacity.
The coacervate fraction obtained may be used to manufacture internally or externally structured liquid detergent compositions, which may be used for dish washing or fabric washing purposes, for example.
Therefore according to a second aspect of the present invention, there is provided an externally structured liquid detergent composition comprising :
2-30% by weight of an alkaline agent,
2-60% by weight of the coacervate fraction according to the invention, and
0.1-5% by weight of a thickening agent.
For the purpose of the present invention an alkaline agent is any chemical agent suitable for use in liquid detergent compositions and capable of rendering said compositions alkaline. The alkaline agent is present in an amount of from 2% to 30% by weight, preferably 10% to 25% by weight of the total composition. Examples of suitable agents are the alkali metal hydroxides and silicates, such as alkali metal orthosilicates, metasilicates and disilicates, sodium metasilicate being preferred. Also mixtures of alkaline agents may be used, such as a combination of sodium silicate and sodium hydroxide.
The externally structured liquid detergent compositions according to the invention comprise from 2 to 30 % by weight of a coacervate fraction as defined before, preferably from 5 to 10 %.
These externally structured compositions further contain a structuring or thickening agent. Suitable agents are found among the alkali-stable polymers. Especially suitable are the water-soluble polymers of acrylic acid, cross-linked with about 1% of a polyallyl ether of sucrose having an average of about 5.8 allyl groups for each sucrose molecule, the polymer having a molecular weight in excess of 1,000,000. Examples of such polymers are Carbopol 934, 940 and 941. Carbopol is the Registered Trademark of B.F. Goodrich Co. Ltd, the manufacturers of these polymers. The preferred polymer is Carbopol 941. Depending on the viscosity which is desired, they may be included in the range of from 0.1% to 5% by weight, but preferably their amount varies from 0.2% to 0.8% by weight, and in particular from 0.2 to 0.6% by weight of the total composition.
Preferably, the liquid detergent composition further comprises 0.5-25% by weight of a nonionic surfactant or a mixture thereof. If a nonionic surfactant is incorporated, it is normally present in an amount of at least 0.5%, and in particular of at least 2% by weight, the amount preferably ranging from 5 to 15% by weight of the total composition.
Nonionic detergents for use in compositions of the present invention can be readily obtained commercially, such as e.g. those sold under the trade names Lutensol LF 400 to 1300 (ex BASF AG) and Plurafac RA 30 to 343 (ex Produits Chimiques Ugine-Kuhlmann).
It is especially preferred when the nonionic surfactant is an ethoxylated and propoxylated and/or butoxylated alcohol, the overall ratio in the alkylene oxide radical between the number of ethylene oxide units and the number of propylene and/or butylene oxide units being less than 9. Such nonionics are for instance described in EP-A-120 533.
The nonionic detergent can be used as sole detergent, but other detergent-active ingredients, such as e.g. the water-soluble anionic sulphate or sulphonate detergents, can be tolerated provided their amount does not exceed 5% by weight, preferably 3% by weight or even 1% by weight of the total composition.
The compositions of the invention may further contain 2% to 20%, preferably 5% to 15% by weight of an additional detergency builder. Typical examples of suitable detergency builders are the phosphate builders such as the alkali metal salts of triphosphoric acid, pyrophosphoric acid, orthophosphoric acid, polymetaphosphoric acid and mixtures thereof. Sodium and potassium triphosphates are preferred. Other suitable builders include carbonates, zeolites and organic builders such as citrates and polycarboxylates such as nitrilotriacetate, polyacrylates, polymaleinates and mixtures thereof.
According to a third aspect of the present invention, there is provided an internally structured liquid detergent composition comprising a structured phase containing detergent-active material dispersed in an aqueous phase containing dissolved electrolyte and a copolymer of acrylic acid and maleic acid in the form of a coacervate fraction according to the invention.
Preferably, more than 90% of the copolymer present in the compositions is in the form of a coacervate according to the invention.
As used herein, the term 'electrolyte' means any inorganic or organic salt which is capable of ionising in aqueous solution. The electrolyte may be dissolved in the compositions of the present invention and/or it may be present as suspended solid particles. In the great majority of cases where solid particles are suspended by an internal structure, it is necessary to have some dissolved electrolyte in order that the surfactant will exist in a structured form. Usually, the electrolyte will have another function, most often as a detergency builder, although it is possible to use electrolytes having no other role than to bring about internal structuring. Whether the composition is only internally structured and/or it contains an external structuring system, according to the particular ingredients and, sometimes, the order of mixing, it is possible to have the same electrolyte in solution and as suspended solids. Either or both of the dissolved and suspended electrolyte materials may be a single electrolyte or a mixture of different electrolytes and, in any event, can be the same or different from one another. Commonly, the electrolyte material in suspension will be the same as that in solution, being an excess of same beyond the solubility limit. It is also possible to suspend particulate solids which are functional ingredients but which are insoluble in water and therefore not electrolytes, for example insoluble abrasives such as calcite, or aluminosilicate builders.
In the widest definition the detergent active materials for use in externally structured compositions according to the present invention, may comprise one or more surfactants, and may be selected from anionic, cationic, nonionic, zwitterionic and amphoteric species, and (provided mutually compatible) mixtures thereof. For example, they may be chosen from any of the classes, sub-classes and specific materials described in "Surface Active Agents" Vol. I, by Schwartz & Perry, Interscience 1949 and "Surface Active Agents" Vol. II by Schwartz, Perry & Berch (Interscience 1958), in the current edition of "McCutcheon's Emulsifiers & Detergents" published by the McCutcheon division of Manufacturing Confectioners Company or in Tensid-Taschenburch", H. Stache, 2nd Edn., Carl Hanser Verlag, Munchen & Wien, 1981.
Suitable nonionic surfactants include, in particular, the reaction products of compounds having a hydrophobic group and a reactive hydrogen atom, for example aliphatic alcohols, acids, amides or alkyl phenols with alkylene oxides, especially ethylene oxide either alone or with propylene oxide. Specific nonionic detergent compounds are alkyl (C₆-C₁₈) primary or secondary linear or branched alcohols with ethylene oxide, and products made by condensation of ethylene oxide with the reaction products of propylene oxide and ethylenediamine. Other so-called nonionic detergent compounds include long chain tertiary amine oxides, long chain tertiary phospine oxides and dialkyl sulphoxides.
Suitable anionic surfactants are usually water-soluble alkali metal salts of organic sulphates and sulphonates having alkyl radicals containing from about 8 to about 22 carbon atoms, the term alkyl being used to include the alkyl portion of higher acyl radicals. Examples of suitable synthetic anionic detergent compounds are sodium and potassium alkyl sulphates, especially those obtained by sulphating higher (C₈-C₁₈) alcohols produced for example from tallow or coconut oil, sodium and potassium alkyl (C₉-C₂₀) benzene sulphonates, particularly sodium linear secondary alkyl (C₁₀-C₁₅) benzene sulphonates; sodium alkyl glyceryl ether sulphates, especially those ethers of the higher alcohols derived from tallow or coconut oil and synthetic alcohols derived from petroleum; sodium coconut oil fatty monoglyceride sulphates and sulphonates; sodium and potassium salts of sulphuric acid esters of higher (C₈-C₁₈) fatty alcohol-alkylene oxide, particularly ethylene oxide, reaction products; the reaction products of fatty acids such as coconut fatty acids esterified with isethionic acid and neutralised with sodium hydroxide; sodium and potassium salts of fatty acid amides of methyl taurine; alkane monosulphonates such as those derived by reacting alpha-olefins (C₈-C₂₀) with sodium bisulphite and those derived from reacting paraffins with SO₂ and Cl₂ and then hydrolysing with a base to produce a random sulponate; and olefin sulphonates, which term is used to describe the material made by reacting olefins, particularly C₁₀-C20 alpha-olefins, with SO₃ and then neutralising and hydrolysing the reaction product. The preferred anionic detergent compounds are sodium (C₁₁-C1₅) alkyl benzene sulphonates and sodium (C₁₆-C₁₈) alkyl sulphates.
It is also possible, and sometimes preferred, to include an alkali metal salt of a fatty acid, especially a soap of an acid having from 12 to 18 carbon atoms, for example oleic acid, ricinoleic acid, and fatty acids derived from castor oil, rapeseed oil, groundnut oil, coconut oil, palmkernel oil or mixtures thereof. The sodium or potassium soaps of these acids can be used.
For active structured compositions the only restriction on the total amount of detergent active material and electrolyte is that together they must result in formation of an aqueous lamellar dispersion.
The liquid detergent compositions of the invention may further contain any of the adjuvants normally used in fabric-washing detergent compositions, e.g. sequestering agents such as ethylene diamine tetra-acetate and diethylene tetramine methylene phosphoric acid; soil-suspending and anti-redeposition agents such as carboxymethylcellulose, polyvinyl pyrrolidone and the maleic anhydride/vinylmethyl ether copolymer; fluorescent agents; hydrotropes; conditioning agents; lather boosters; perfumes, germicides and colorants.
Further, the addition of lather-depressors such as liquid polysiloxane anti-foam compounds; alkali-stable enzymes; bleaches, such as e.g. sodium sulphite, and potassium dichlorocyanurate, may be necessary or desirable to formulate a complete heavy-duty detergent composition suitable for use in machine washing operations. These ingredients can be employed in the liquid detergent without the risk of undue decomposition during storage, especially if a proper protective coating is applied.
Compositions of the present invention normally have viscosities within the range of 0.3 to 3.0 Pa.s (at 20°C and 21 sec⁻¹), in particular within the range of 0.5 to 2.0 Pa.s and preferably within the range of 0.6-1.2 Pa.s.
Externally structured compositions of the present invention are especially advantageous having pH-values within the high alkaline region, in particular values equal to or above 11, but preferred are pH-values above 12 or even above 13. Internally structured compositions preferably have a pH of between 7.0 and 11.0.
COMPARATIVE EXAMPLES 1-3
The invention will be further illustrated in the following examples. All percentages used therein are by weight unless otherwise specified.
The following externally structured liquid detergent formulations were prepared by adding the ingredients in the given order. The copolymer was a copolymer of acrylic acid and maleic acid sold by BASF under the trade name CP7, in the form of a 40 % by weight solution in water. The amounts indicated below are in % by weight.
| || Examples |
| || 1 || 2 || 3 |
|NaOH ||20 ||20 ||20 |
|STP (N-hexa) ||12.5 ||12.5 ||12.5 |
|Carbopol 941 ||0.5 ||0.6 ||0.7 |
|Copolymer ||7.5 ||7.5 ||7.5 |
|Water ||- Balance - |
|The liquids had the following physical properties : |
|Before addition of copolymer : |
|S(kPa.s, 10⁻⁵s⁻¹, 25°C) ||15 ||46 ||125 |
|After addition of copolymer : |
|S(kPa.s, 10⁻⁵s⁻¹, 25°C) ||0.8 ||1.8 ||2.3 |
|Viscosity(mPa.s, 21s⁻¹, 25°C) ||1630 ||2145 ||2860 |
|Stability ||only a few days at 37°C |
It can be seen that the instability observed of liquid detergent compositions containing high amounts of copolymer cannot effectively be compensated by increasing the amount of externally structuring agent (Carbopol). Moreover, the viscosity at 21 s⁻¹ increases to unacceptable levels.
The following externally structured liquid detergent products were prepared whereby the amounts are given in % by weight.
| || Example |
| || 4 || 5 || 6 |
|NaOH ||20.0 ||20.0 ||20.0 |
|STP ||2.5 ||2.5 ||2.5 |
|Carbopol 941 ||0.50 ||0.55 ||0.60 |
|Copolymer ||7.5 ||7.5 ||7.5 |
|Water ||- Balance - || |
The copolymer was again CP7 ex BASF. In these Examples it was added in the form of a coacervate fraction which was prepared from an aqueous solution containing 22.8 % by weight sodium hydroxide, 8.6 % CP7 and 68.6 % water. This solution was allowed to stand for one day and then the bottom layer was separated and used.
The physical properties of the compositions were:
| || Examples |
| || 4 || 5 || 6 |
|Viscosity(mPa.s, 21s⁻¹, 25°C) ||1500 ||1600 ||2200 |
|Stability at 20°C (months) ||> 3 ||> 3 ||> 3 |
|Stability at 37°C (months) ||< 1 ||< 1 ||< 3 |
|S(kPa.s, 10⁻⁵s⁻¹, 25°C) ||16 ||18 ||42 |
The addition of the copolymer in the form of its coacervate leads to a markedly increased stability.
The following components were mixed to form an internally structured liquid detergent product. The amounts are given in % by weight.
|Water ||52.8 |
|Glycerol ||7.3 |
|Borax ||6.3 |
|NaOH ||1.8 |
|Citric acid ||1.7 |
|Zeolite A4 ||16.7 |
|Marlon AS3 ||7.1 |
|LES ||4.2 |
|Synperonic A3 ||2.7 |
In the above, Marlon AS3 is dodecyl benzene sulphonic acid, LES is lauryl ether sulphate (about 3 EO), and Synperonic A3 is an ethoxylated C13-C15 fatty alcohol having 3 EO moieties. To 480 g of this product, various amounts were added of an acrylic acid/maleic acid copolymer sold by BASF under the trade name Sokalan CP5. The copolymer was added in the form of its coacervate, which was prepared by isolation of the bottom fraction which separates as a bottom layer after storage of the following composition for one day (the percentages are % by weight).
|Water ||72.0 % |
|Glycerol ||10.1 % |
|Borax ||8.6 % |
|NaOH ||1.8 % |
|Citric acid ||2.3 % |
|Copolymer (CP5) ||5.2 % |
The coacervate contained approximately 33% by weight of the copolymer. After the addition, the viscosity and stability of the product were investigated.
| Example ||grams of coacervate added ||final conc. copolymer ||viscosity (mPa.s, 21s⁻¹, 25°C) |
|7 ||0 ||0 ||1530 |
|8 ||4.9 ||0.3 ||1180 |
|9 ||10.0 ||0.7 ||990 |
|10 ||20.4 ||1.3 ||650 |
|11 ||42.6 ||2.7 ||460 |
|12 ||66.7 ||4.0 ||390 |
|13 ||93.2 ||5.6 ||300 |
The pH of the liquids was 8.7. In all cases, the stability after storage for three weeks at room temperature was good, showing less than 2% phase separation.