EP1141219A1

EP1141219A1 - Laundry detergent bar composition

Info

Publication number: EP1141219A1
Application number: EP99902987A
Authority: EP
Inventors: Hsiang-Kuen Mao
Original assignee: Procter and Gamble Co
Current assignee: Procter and Gamble Co
Priority date: 1999-01-06
Filing date: 1999-01-06
Publication date: 2001-10-10
Also published as: WO2000040691A1; AU2311199A

Abstract

The present invention relates to a laundry detergent bar containing a linear alkyl benzene sulfonate surfactant and the balance adjunct materials. The linear alkyl benzene sulfonate surfactant has at least 30 molar % 2-phenyl isomer and less than about 5 weight % dialkyl bi-cyclic benzene sulfonate impurities.

Description

LAUNDRY DETERGENT BAR COMPOSITION

FIELD The present invention relates to laundry detergent compositions. Specifically, the present invention relates to a laundry detergent bar composition containing an anionic surfactant.

BACKGROUND In many locales, laundry detergent bars are used for cleaning clothes.. Technical developments in the field of laundry detergent bars have concerned formulating laundry detergent bars which are effective in cleaning clothes; which have acceptable sudsing characteristics in warm and cool water, and in hard and soft water; which have acceptable in-use wear rates, hardness, durability, and feel; which have low smear and rapid drying; and which have a pleasing odor and appearance. Laundry detergent bar processes are also well known in the art. Prior art disclosing laundry detergent bars and laundry detergent bar processes include: U.S. Patent 3,178,370, Okenfuss, issued April 13, 1965; and Philippine Patent 13778 to Anderson, issued September 23, 1980.

Surfactants, especially anionic surfactants, are well-known to provide detersive benefits in laundry detergent bars. Certain surfactants, such as anionic surfactants, are especially useful in laundry detergent bar compositions, as they contain a hydrophobic portion which may attach to soils, and a hydrophilic portion which hydrogen bonds to water. Thus, such surfactants can provide detersive benefits as they bind to soils, and remove them from, for example, fabrics and clothing. Typical anionic surfactants include soaps and non-soap surfactants.

Linear alkyl benzene sulfonate (LAS) is a common non-soap anionic surfactant in cleaning compositions, and especially laundry detergent bars, as it provides excellent soil removal benefits, and is widely available. Recently, greater attention has been paid to the environment by society, corporations, and governments. Thus, it has become highly desirable to increase the biodegradability of products, such as detergent compositions. LAS is a highly preferred, easily biodegradable surfactant.

To produce LAS, paraffin and benzene from, for example, crude oil, are typically combined in a catalytic process to produce linear alkyl benzene (LAB). Catalytic processes for producing LAB utilize catalysts containing aluminum chloride, hydrofluoric acid, and fluorine-containing mordenite. The LAB is sulfonated with sulfuric and/or sulfonic acid, and subsequently neutralized with an alkaline material to produce the corresponding alkaline salt of LAS, such as the sodium salt of LAS. However, in the typical LAB production process, certain less-biodegradable by-products are also produced, such as dialkyl tetralin and dialkyl indan, and/or other dialkyl bi-cyclic benzene (DBB) impurities. The DBB content in LAB typically ranges from 2% to 8%, or more. When DBB is sulfonated, it becomes a corresponding dialkyl bi-cyclic benzene sulfonate (DBBS), such as a dialkyl tetralin sulfonate or a dialkyl indan sulfonate, which is less biodegradable than the parent LAS. Due to the substantially shortened alkyl chain lengths on these impurities, they are not effective surfactants for cleaning. Accordingly, it is desirable to reduce the DBB and DBBS content of LAB and LAS, respectively. Another common issue facing formulators of laundry detergent bars is maintaining bar hardness. A laundry detergent bar formula rich in LAS is often quite soft, and not preferred by consumers. A laundry detergent bar which is too soft wears too quickly; such a laundry detergent bar is unacceptable to consumers, who interpret it as uneconomical. Thus, various bar hardening technologies are often required, which include the use of co-surfactants, structurants, soaps, fillers, and combinations thereof into the laundry detergent bar matrix.

Accordingly, the need remains for a laundry detergent bar having improved surfactancy, and increased biodegradability. There also remains a need for a laundry detergent bar which also possesses acceptable in-use wear rates, hardness, durability, rapid drying, and low smear.

SUMMARY OF THE INVENTION It has now been found that a laundry detergent bar may possess improved surfactancy and increased biodegradability. It has also been found that a laundry detergent bar may also possess acceptable in-use wear rates, hardness, durability, rapid drying, and/or low smear.

These and other features, aspects, and advantages of the present invention will become evident to those skilled in the art from a reading of the present disclosure with the appended claims.

DETAILED DESCRIPTION OF THE INVENTION In accordance with the present invention it has now surprisingly been found that the use of a specific linear alkyl benzene sulfonate surfactant may provide improved surfactancy as well as increased biodegradability. Such an linear alkyl benzene sulfonate surfactant may also possess one or more other surprising benefits when included in a laundry detergent bar, such as acceptable in-use wear rates, hardness, durability, rapid drying, and/or low smear.

All percentages, ratios and proportions herein are by weight of the laundry detergent bar, unless otherwise specified. All temperatures are in degrees Celsius (°C) unless otherwise specified. All documents cited are incorporated herein by reference.

As used herein, the term "alkyl" means a hydrocarbyl moiety which is straight or branched, saturated or unsaturated. Unless otherwise specified, alkyl moieties are preferably saturated or unsaturated with double bonds, preferably with less than two double bonds. Included in the term "alkyl" is the alkyl portion of acyl groups.

The term "linear" as used herein, with respect to LAB and/or LAS, indicates that the alkyl portions thereof contain less than about 30%, preferably less than bout 20%, more preferably less than about 10% branched alkyl chains. The term "substantially free" as used herein indicates that the impurities contained in the laundry detergent bar of the present invention contains are insufficient to contribute positively or negatively to the cleaning effectiveness of the composition. The laundry detergent bar of the present invention preferably contains, by weight, less than about 5%, more preferably less than about 2%, and even more preferably less than about 0.5% of the indicated material. It is desirable to increase the surfactancy of, for example, LAS. Typically, LAB and the corresponding LAS contains a distribution of isomers in which the benzene moiety is attached in various positions on the hydrophobic alkyl chain. It is the hydrophobic portion of LAS which attaches to soils on. For a given alkyl chain length, the most hydrophobic alkyl chain is achieved when the benzene ring is attached to the alkyl chain at the 2-position, because this provides the longest hydrophobic "tail." Such an LAS is described as the "2-phenyl LAS" isomer and possesses improved surfactancy as compared to corresponding isomers where the benzene moiety is attached to the alkyl chain at, for example, the 3-position. Such improved surfactancy may result in improved removal of hydrophobic soils from clothing. However, the typical LAB used to form LAS contains a distribution of various LAB isomers, such as 2-phenyl LAB, 3-phenyl LAB, 4-phenyl LAB, etc.

As noted above, typical LAB is a mixture of 2-phenyl isomers, 3-phenyl isomers, etc. The general structures for these two isomers are described, below:

2-phenyl isomer 3-phenyl isomer wherein R₁ represents a linear alkyl group; typically R^ is between about 6 and about 19 carbon atoms in length (i.e., the alkyl chain, excluding the benzene group, is thus typically from about 8 to about 22 carbon atoms in length). These LAB isomers are then sulfonated to produce LAS. Accordingly, for a given alkyl chain, it is desirable to attach the benzene moiety as close to a terminal end as possible, so as to achieve the most hydrophobic isomer. A more hydrophobic isomer in turn, leads to increased surfactancy.

Recently, new LAB production processes have been disclosed which employ more selective catalysts and thus result in LAB having higher molar proportions of the 2-phenyl LAB isomer, without a corresponding increase in the DBB content. It is known that the LAS formed from such LAB has a high average level of hydrophobicity and thus improved soil removal benefits. However, it has now been recognized that the LAS described above also possesses increased crystallinity and a reduced dissolution rate, and is therefore especially useful in a laundry detergent bar. Without intending to be limited by theory, it is believed that such LAS has a high degree of molecular regularity, which in turn leads to a very uniform LAS crystal lattice when used in a solid detergent composition, such as a laundry detergent bar. The present invention also recognizes that in addition to the increased crystallinity caused by a higher proportion of 2-phenyl LAS, the reduction of DBBS impurities also increases the crystallinity and decreases the dissolution rate of solid compositions containing this LAS. Without intending to be limited by theory, it is believed that the reduction of DBBS also increases the crystallinity and reduces the dissolution rate via two mechanisms. First, it has been recognized herein that when present, DBBS impurities interfere with the regularity of the LAS crystalline lattice structure. Thus, it is believed that a reduction of the DBBS content results in an increase in the crystallinity of the LAS. Second, it has been further recognized that DBBS is an excellent hydrotrope for the corresponding linear alkyl benzene sulfonate. Thus, when the DBBS content of the LAS is reduced, the dissolution rate of the LAS is also reduced. In addition, such high crystallinity may lead to increased gel layer formation upon contact with water, which further reduces the dissolution rate of a solid composition. In most solid detergent forms, such as detergent granules, the increase in crystallinity and reduction in dissolution rate are undesirable. However, it has now surprisingly been recognized that high crystallinity and a reduced dissolution rate are highly desirable in a laundry detergent bar composition. The inclusion of such an LAS having a high proportion of 2-phenyl isomer and low levels of DBBS in a laundry detergent bar, provides significant advantages. Without intending to be limited by theory, it is believed that the increase in crystallinity increases the hardness of the laundry detergent bar. Such an increase in hardness may, for example, simultaneously decrease the in-use wear rate and increase the durability of the laundry detergent bar. As an additional benefit, the increased hardness also provides a longer-lasting laundry detergent bar. This is highly desirable as customers believe that such bars provide a better value.

While the decrease in the dissolution rate is detrimental to the performance of, for example, granular detergents, it is desirable in laundry detergent bars. If laundry detergent bar dissolves too quickly, its in-use rate is unacceptably fast for the average consumer. However, a laundry detergent bar which dissolves more slowly gives the consumer an impression of better value and economy. Furthermore, it would be expected that a decrease in the dissolution rate would correspondingly decrease the cleaning effectiveness of a laundry detergent bar. Surprisingly, the present invention may instead provide significantly enhanced cleaning. Without intending to be limited by theory, it is believed that as a detergent bar is typically rubbed directly onto clothing, and subsequently rinsed by hand, the overall performance of detergent composition is not impaired by the slower dissolution rate of the LAS. As the nature of a laundry detergent bar is to be rubbed directly onto the fabric to be washed, it is believed that any possible dissolution negatives are overcome by the greater surfactancy and cleaning ability of the LAS described herein. Additionally, the slower dissolution rate may contribute to more rapid drying of the laundry detergent bar, which in turn reduces bar smear.

An additional benefit of the present invention is that fewer, or lowered levels of, structurants, fillers, and/or co-surfactants may be required herein. This may lower the formulation cost of the laundry detergent bar, and thus provide additional value for customers. Alternatively, it allows greater flexibility in formulating laundry detergent bars with acceptable physical properties and cleaning abilities. One especially advantageous point is that a bleach, i.e., sodium perborate monohydrate or sodium percarbonate, is easier to incorporate into the laundry detergent bar of the present invention.

Accordingly, the LAS useful herein typically contains at least about 30 molar % 2-phenyl isomer, preferably at least 40 molar % 2-phenyl isomer, more preferably at least 50 molar % 2-phenyl isomer, and even more preferably at least 60 molar % 2-phenyl isomer. Such molar percentages of 2-phenyl isomers in the LAB provide the improved surfactancy and increased crystallinity desired in the present invention.

As defined herein, the "molar %" of any given isomer X in a LAB or an LAS sample may be determined by the following formula: molar % of isomer X = (moles of isomer X) / (total moles of LAB or LAS).

It is well known in the art to determine compositional parameters of conventional LAB and LAS. See, for example Surfactant Science Series, Volume 40, Chapter 7 and Surfactant Science Series, Volume 73, Chapter 7. Typically this is done by GC and/or GC-mass spectroscopy for the alkyl benzenes and HPLC for the alkyl benzene sulfonates or sulfonic acids; ¹³C NMR is also commonly used. Another common practice is desulfonation. This permits GC and/or GC-mass spectroscopy to be used, since desulfonation converts the sulfonates or sulfonic acids to the alkyl benzenes which are tractable by such methods. A preferred method is to prepare LAB sample solution at 100 mg/ml concentration by dissolving 0.5 g of LAB sample in 5 ml of n-hexane. 1 μL of this solution is then injected into a GC/MS equipped with an ionization detector. The resulting chromatogram is analyzed based on the MS results. The minor peaks in-between all linear alkyl benzene species are summarized and calculated as the sum of the DBB impurities, including dialkyl tetralins and dialkyl indans. Specifically, the GC/MS instrument suitable for such analysis can be HP 5890 II GC/HP 5971 MSD (ANI-59). The GC/FID system can be HP 5890 II GC (ANI- 61). A GC column of Rtx-5MS, Restek (GC-C-116) and a pre-column of 0.25 mm ID 5 m length with helium at 50 kPa as the carrier gas. For mass identifications, the column is kept at 100 °C for 1 minute then increased to 180 °C at 2 °C/min. The FIC is operated at 70 eV. The mass scan was done in between 50 to 500 m/z at 3 scans/sec. The sample injection was done with a splitter at a ratio of 100 to 1. For quantitation of species by GC/FID, the system can be operated at 120 kPa helium carrier gas with all other parameters staying the same.

The DBB impurities are formed in the LAB production process when a single alkyl chain interacts with the same benzene ring twice. Typical dialkyl bi- cyclic benzene impurities have the following structures:

Dialkyl Tetralin Dialkyl Indan where R₂ and R₃ are alkyl chains of at least 1 carbon atom each; e.g., for dialkyl tetralin, R₂ + R₃ + 2 = from about 8 to about 22 carbon atoms, for dialkyl indan, R₂ + R₃ + 3 = from about 8 to about 22 carbon atoms, etc. Because such impurities and their sulfonated counterparts are significantly less biodegradable than, for example, LAB and LAS, it is desirable to reduce the DBBS content to as low a level as possible. Also, as recognized herein, such a reduction in the DBBS content of the LAS further enhances the crystallinity of the LAS. Therefore, the LAS useful herein contains, by weight of the LAS, less than about 5 weight % DBBS impurities, preferably less than about 3 weight % DBBS impurities, more preferably less than about 2 weight % DBBS impurities, and even more preferably less than about 1 weight % DBBS impurities. In a highly preferred embodiment, the LAS herein is substantially free of DBBS impurities. In a more preferred embodiment of the present invention, the LAS herein contains, by weight of the LAS, less than about 2.5 weight % dialkyl tetralin sulfonate impurities, preferably less than about 1.3 weight % dialkyl tetralin sulfonate impurities, and more preferably less than about 0.5 weight % dialkyl tetralin sulfonate impurities. The weight % of DBBS impurities such as dialkyl tetralin sulfonates and dialkyl indan sulfonates may be determined by methods such as those described above (e.g., GC or HPLC) for characterizing LAB and/or LAS.

Processes for forming LAB having a high proportion of 2-phenyl isomer and a "low" DBB content are described, for example, in U.S. Patent 5,196,574 to Kocal, issued Mar 23, 1993; U.S. Patent 5,770,782 to Knifton et al., issued June 23, 1998;, and U.S. Patent 5,777,187 to Knifton et al., issued July 7, 1998. The LAB useful herein is also available as DETAL® LAS from Petresa Corporation, of Ville de Becancour, Canada; from Universal Oil Products Company, of Des Plaines, Illinois, U.S.A.; and Huntsman Petrochemical Corporation, of Austin, Texas, U.S.A. For further information about LAB production processes, please see "Recent Advances in the Production of Detergent Olefins and Linear Alkylbenzenes" by Vora et al., published in Tenside Surfactants, Detergents, vol. 28, pp. 287-294, 1991 , and "Science and Technology in Catalysis 1994" by T. Imai et al., published in Studies in Surface Science and Catalysis, vol. 92, pp. 339-342, 1995.

Generally, the laundry detergent bars herein typically comprise from about 1% to about 99%, preferably from about 5% to about 50%, and more preferably from about 5% to about 25% LAS as described herein, by weight of the laundry detergent bar. It is also desirable that the LAS useful herein has from about 8 to about 22, preferably from about 8 to about 18, and more preferably from about 10 to about 16 carbon atoms in the alkyl group, for example, the C₁₀.₁₆ linear alkyl benzene sulfonates. The LAS suitable for use herein includes the water-soluble salts, preferably the alkali metal, ammonium and alkylolammonium salts of organic sulfuric reaction products having in their molecular structure an alkyl group containing from about 8 to about 22 carbon atoms, as described above, and a sulfonic acid group. The alkali metal salts, particularly the sodium salts, the potassium salts, or mixtures thereof are preferred.

In an embodiment of the present invention, an effective amount of an added hydrotrope may be provided and added to the LAS described herein, or a laundry detergent bar containing the LAS described herein. The "added hydrotrope" herein is a hydrotrope which is deliberately added to the LAB, linear alkyl benzene acid active, LAS, and/or a composition containing the LAS, and is not intended to include those hydrotropes which are present solely as by- products of the LAB production process. However, if a compound is present as a by-product, and additional amounts of this same compound are added to the LAB, linear alkyl benzene acid active, LAS, and/or a composition containing the LAS as a hydrotrope, then these additional amounts added would be considered an "added hydrotrope" herein. Of course, it is highly preferred that any added hydrotrope be biodegradable, preferably at least as biodegradable as the LAS parent compound.

Such an effective amount of an added hydrotrope may, for example, ease processing. In such an embodiment, the "effective amount" of added hydrotrope useful herein is preferably at least about 0.1%, more preferably from about 1% to about 25%, and even more preferably from about 1 % to about 10%, by weight of the LAS. However, in certain cases, as where a very crystalline or slow- dissolving laundry detergent bar is desired, the hydrotrope may reduce the effects of the LAS described herein. Thus, in an especially preferred embodiment, the laundry detergent bar is substantially free of added hydrotrope. The added hydrotrope useful herein may be either branched, linear, aromatic, or a mixture thereof. Linear added hydrotropes having an attached aromatic moiety are preferred herein. The added hydrotrope precursor includes non-sulfonatable added hydrotropes and sulfonatable added hydrotropes having sulfonatable functional groups, such as an alkyl benzene, an olefin (e.g., an alpha olefin or an internal olefin) with at least one carbon-carbon double bond, a methyl or ethyl ester of a carboxylic acid, an alkyl alcohol, and mixtures thereof. The alkyls and alkyl benzenes useful herein as added hydrotrope precursors typically contain from about 1 to about 8 carbon atoms in their alkyl chains, while the olefins, methyl esters, and alkyl alcohols typically contain less than or equal to about 10 carbon atoms therein. Nonlimiting examples of the preferred added hydrotrope include the alkali metal and ammonium salts, preferably the sodium, potassium, ammonium, and magnesium salts of the above compounds. Specifically, the added hydrotrope useful herein includes a paraffin sulfonate, an alkyl benzene sulfonate, an olefin sulfonate, a methyl or ethyl ester sulfonate, an alkyl sulphate, non-sulfonated added hydrotropes, and mixtures thereof. Non- sulfonated added hydrotropes useful herein include octanol ethoxylates, hexanol ethoxylates, ethylhexanol ethoxylates, secondary alcohol ethoxylates, octanol monoglyceride, hexanol monoglyceride, ethylhexanol glyceride, octyl glycoside or di-glycosides, octanoic mono-amine glucose amide, hexanoic mono-amine glycose amide, and mixtures thereof.

Nonlimiting examples of preferred sulfonatable added hydrotropes useful herein include toluene sulfonate, xylene sulfonate, cumene sulfonate, olefin sulfonates, methyl ester sulfonates, alcohol sulfates, and mixtures thereof. If present, the added hydrotrope or its precursor may be added at any stage of the laundry detergent bar process, for example, prior to an LAB sulfonation step, or after addition of the LAS. Preferably, the added hydrotrope or its precursor is added to the LAB and homogenized therewith. The homogenized mixture is then sulfonated, and neutralized to form an LAS surfactant paste, which is further processed into a laundry detergent bar. Such added hydrotropes are commonly available from, for example,

Rutgers Organics Corp. in U.S.A.; Albright & Wilson Corporation, of U.K.; and Marchon Corporation, of France or Italy. Their precursors, i.e. toluene, xylene, cumene, etc., are widely available from companies such as Basis Petroleum; Exxon; Texaco of Houston, Texas, U. S. A.; Petroquimica Uniao Sa of San Paulo, Brazil; Fina Oil of Dallas, Texas, U. S. A.; etc.

The laundry detergent bar of the present invention contains a linear alkyl benzene sulfonate surfactant as described herein, and the balance adjunct materials. Typical adjunct materials useful herein include a bleach, a builder, a chelating agent, an enzyme, a filler, other surfactants, a soil suspension agent, a structurant, and mixtures thereof.

The bleach useful herein is typically a bleach precursor product, but may include an actual bleach, such as, for example, a hypochlorite bleach. Typically, a bleach precursor product containing an active oxygen source is provided herein. The active oxygen source useful herein includes compounds which form available peroxyacid oxygen when exposed to a bleach activator, an alkalinity source, and moisture. An active oxygen source can be hydrophilic, hydrophobic, or both. The active oxygen source useful in the present invention can be any of the oxidizing agents known for laundry, hard surface cleaning, automatic dishwashing, or denture cleaning purposes, including oxygen. A preferred active oxygen source of the peroxygen type includes hydrogen peroxide, inorganic per- compounds, inorganic peroxohydrates, organic peroxohydrates, and mixtures thereof; a more preferred active oxygen source includes hydrogen peroxide, perborate, percarbonate, and mixtures thereof. If present, an active oxygen source will typically be at a level of from about 1% to about 30%, more typically from about 5% to about 20%, of the laundry detergent bar.

When commingled with the active oxygen source, the bleach activator product leads to production of available peroxyacid oxygen. A bleach activator may comprise an alkalinity source, either alone, or in conjunction with amides, imides, esters, anhydrides, and mixtures thereof. Usually, at least one substituted or unsubstituted acyl moiety is present, covalently connected to a leaving group as in the structure R-C(O)-L. The atom in the leaving group connecting to the peracid-forming acyl moiety R(C)O- is most typically O or N. A bleach activator can have non-charged, positively or negatively charged peracid- forming moieties and/or noncharged, positively or negatively charged leaving groups. One or more peracid-forming moieties or leaving-groups can be present.

A preferred class of bleach activator includes the esters, including acyl phenol sulfonates, acyl alkyl phenol sulfonates or acyl oxybenzenesulfonates

(OBS leaving-group); the acyl-amides; the quaternary ammonium substituted peroxyacid precursors including the cationic nitriles, and mixtures thereof. A preferred hydrophobic bleach activator includes sodium nonanoyloxybenzene sulfonate (NOBS or SNOBS), sodium decanoyloxybenzene sulfonate (DOBS), sodium dodecanoiyloxybenzene sulfonate (LOBS), sodium nonanoyloxybenzene carboxylate (NOBA), sodium nonanoyloxybenzene carboxylate (DOBA), sodium dodecanoyloxybenzene carboxylate (LOBA), substituted amide types described in detail hereinafter, and the bleach activators related to certain imidoperacid bleaches. Another suitable bleach activator includes sodium-4-benzoyloxy benzene sulfonate (SBOBS); sodium-1-methyl-2-benzoyloxy benzene-4- sulphonate; sodium-4-methyl-3-benzoyloxy benzoate; trimethyl ammonium toluyloxy-benzene sulfonate; sodium 3,5,5-trimethyl hexanoyloxybenzene sulfonate (STHOBS), and mixtures thereof. A preferred bleach activator includes N,N,N'N'-tetraacetyl ethylene diamine (TAED) or any of its close relatives including the triacetyl or other unsymmetrical derivatives, and mixtures thereof. TAED and the acetylated carbohydrates such as glucose pentaacetate and tetraacetyl xylose are preferred. Builders may optionally be included in the laundry detergent bars herein to assist in controlling mineral hardness. Builders are typically used in fabric laundering compositions to assist in the removal of particulate soils. Laundry detergent bars typically contain from about 3% to about 60%, preferably from about 5% to about 50%, more preferably from about 10% to about 30% builder, by weight of the final composition.

Useful inorganic or phosphate-containing detergent builders include, but are not limited to, the alkali metal, ammonium and alkanolammonium salts of polyphosphates (exemplified by the tripolyphosphates, pyrophosphates, and glassy polymeric meta-phosphates), phosphonates, phytic acid, silicates, carbonates (including bicarbonates and sesquicarbonates), sulphates, and aluminosilicates such as zeolites. However, non-phosphate builders are required in some locales. Importantly, the compositions herein function surprisingly well even in the presence of the so-called "weak" builders (as compared with phosphates) such as citrate, or in the so-called "underbuilt" situation that may occur with zeolite or layered silicate builders. Specific examples of a non- phosphate builder, such as inorganic detergency builders, include the water soluble inorganic carbonate and bicarbonate salts. The alkali metal (e.g., sodium and potassium) carbonates and bicarbonates are particularly useful herein. Other specifically preferred examples of a builder useful herein include polycarboxylates. Especially preferred as builders herein are co-polymers of acrylic acid and maleic acid. Accordingly, in a preferred embodiment, the laundry detergent bar of the present invention is substantially free of phosphate.

The optional chelating agent may be one or more iron and/or manganese chelating agents. Such chelating agents can be selected from the group consisting of amino carboxylates, amino phosphonates, polyfunctionally- substituted aromatic chelating agents and mixtures therein, all as hereinafter defined. Without intending to be bound by theory, it is believed that the benefit of these materials is due in part to their exceptional ability to remove iron and manganese ions from washing solutions by formation of soluble chelates. Amino carboxylates useful as optional chelating agents include ethylenediaminetetrace- tates, N-hydroxyethylethylenediaminetriacetates, nitrilotriacetates, ethylenediamine tetraproprionates, triethylenetetraaminehexacetates, diethylene- triaminepentaacetates, and ethanoldiglycines, alkali metal, ammonium, and substituted ammonium salts therein and mixtures therein. Amino phosphonates are also suitable for use as chelating agents when at least low levels of total phosphorus are permitted in the laundry detergent bar, and include ethylenediaminetetrakis (methylenephosphonates) as DEQUEST. Preferred, these amino phosphonates to not contain alkyl or alkenyl groups with more than about 6 carbon atoms. Polyfunctionally-substituted aromatic chelating agents are also useful in the compositions herein. See U.S. Patent 3,812,044, issued May 21 , 1974, to Connor et al. Preferred compounds of this type in acid form are dihydroxydisulfobenzenes such as 1 ,2-dihydroxy-3,5-disulfobenzene. A preferred biodegradable chelator for use herein is ethylenediamine disuccinate ("EDDS"), especially the [S,S] isomer as described in U.S. Patent 4,704,233, November 3, 1987, to Hartman and Perkins.

If present, these chelating agents will generally comprise from about 0.1% to about 15% by weight of the laundry detergent bar. More preferably, if utilized, the chelating agents will comprise from about 0.1% to about 3.0% by weight of the laundry detergent bar. An enzyme may also be useful herein for a variety of purposes, including removal of protein-based, carbohydrate-based, or triglyceride-based stains from substrates, for the prevention of refugee dye transfer in fabric laundering, and for fabric restoration. A suitable enzyme herein includes an amylase, a cellulase, a cutinase, a lipase, a peroxidase, a protease, and mixtures thereof of any suitable origin, such as vegetable, animal, bacterial, fungal and yeast origin. Preferred selections are influenced by factors such as pH-activity and/or stability optima, thermostability, and stability to active detergents, builders and the like. In this respect bacterial or fungal enzymes are preferred, such as bacterial amylases and proteases, and fungal cellulases. In practical terms for current commercial preparations, typical amounts are up to about 5 mg by weight, more typically 0.01 mg to 3 mg, of active enzyme per gram of the laundry detergent bar. Stated otherwise, the laundry detergent bars herein will typically comprise, by weight of the final bar, from about 0.001 % to about 5%, preferably from about 0.01% to about 1% of a commercial enzyme preparation. Protease enzymes are usually present in such commercial preparations at levels sufficient to provide from 0.005 to 0.1 Anson units (AU) of activity per gram of the laundry detergent bar.

An amylase useful herein includes, for example, -amylases described in GB 1 ,296,839 to Outtrup H, et al., published November 22, 1972 to Novo Industries A S of Denmark (hereinafter, "Novo"); RAPIDASE® from International Bio-Synthetics, Inc.; TERMAMYL® from Novo; and FUNGAMYL® from Novo.

Cellulases usable herein include both bacterial and fungal types, preferably having a pH optimum between 5 and 9.5. U.S. 4,435,307 to Barbesgoard, et al., March 6, 1984, discloses suitable fungal cellulases from Humicola insolens or Humicola strain DSM1800 or a cellulase 212-producing fungus belonging to the genus Aeromonas, and cellulase extracted from the hepatopancreas of a marine mollusk, Dolabella Auricula Solander. Suitable cellulases are also disclosed in GB-B-2,075,028 to Barbesgaar, et al., issued March 28, 1984; GB-B-2,095,275 to Murata, et al., issued August 7, 1985 and DE-OS-2,247,832 to Horikoshi and Ikeda, issued June 27 1974. CAREZYME® and CELLUZYME® (Novo) are especially useful. See also WO 91/17243 to Hagen, et al., published November 14, 1991.

Cutinase enzymes suitable for use herein are described in WO 88/09367A to Kolattukudy, et al., published December 1 , 1988. Suitable lipase enzymes for detergent usage include those produced by microorganisms of the Pseudomonas group, such as Pseudomonas stutzeri ATCC 19.154, as disclosed in GB 1 ,372,034 to Dijk and Berg, published October 30, 1974. See also lipases in Japanese Patent Application 53-20487 to Inugai, published February 24, 1978. This lipase is available from Amano Pharmaceutical Co., Ltd., Nagoya, Japan, under the trade name Lipase P "Amano," or "Amano-P." Other suitable commercial lipases include Amano-CES, lipases ex Chromobacter viscosum, e.g. Chromobacter viscosum var. lipolyticum NRRLB 3673 from Toyo Jozo Co., Tagata, Japan; Chromobacter viscosum lipases from U.S. Biochemical Corp., U.S.A. and Disoynth Co., the Netherlands, and lipases ex Pseudomonas gladioli. LIPOLASE®, from Novo, is a preferred lipase for use herein. LIPOLASE® is derived from Humicola lanuginosa, see also EP 341 ,947 to Cornelissen, et al., issued August 31 , 1994. Lipase and amylase variants stabilized against peroxidase enzymes are described in WO 94/14951 to Halkier, et al., published July 7, 1994 A to Novo. See also WO 92/05249 to Clausen, et al., published April 2, 1992. Peroxidase enzymes may be used in combination with oxygen sources, e.g., percarbonate, perborate, hydrogen peroxide, etc., for "solution bleaching" or prevention of transfer of dyes or pigments removed from substrates during the wash to other substrates present in the wash solution. Known peroxidases include horseradish peroxidase, ligninase, and haloperoxidases such as chloro- or bromo-peroxidase. Peroxidase-containing detergent compositions are disclosed in WO 89/09813 A to Damhus, et al., published October 19, 1989.

A suitable example of a protease is a subtilisin, which is obtained from particular strains of B. subtilis and β. licheniformis. One suitable protease is obtained from a strain of Bacillus, having maximum activity throughout the pH range of 8-12, developed and sold as ESPERASE® by Novo. Other examples of a suitable protease includes ALCALASE® and SAVINASE® from Novo and MAXATASE® from International Bio-Synthetics, Inc., the Netherlands; as well as Protease A and Protease B as disclosed in EP 130,756 A to Bott, published January 9, 1985. An especially preferred protease, referred to as "Protease D," as described in U.S. Patent 5,679,630 to A. Baeck, et al, issued October 21 , 1997, entitled "Protease-Containing Cleaning Compositions," and U.S. Patent 5,677,272 to C. Ghosh, et al, issued October 14, 1997, entitled "Bleaching Compositions Comprising Protease Enzymes." Commercially-available enzymes are typically available as an enzyme prill, an enzyme marume, a high-shear granule, or even an already-coated granule. Any of these enzyme forms may be coated by the improved encapsulation coating described herein. For example, a preferred embodiment comprises an enzyme prill which contains an enzyme. Preferred examples of commercially- available enzymes useful herein include SAVINASE®, sold by Novo Corporation, Maxacal sold by Gist-brocades, Opticlean sold by Solvay-lnterox, Co, and Enzoguard sold by Genencor.

Fillers useful herein include water-soluble and water-insoluble fillers known in the art, such as the alkali and alkali earth metals salts of carbonate, sulphate, and mixtures thereof. Fillers also include minerals, such as talc, bentonite, and hydrated magnesium silicate-containing minerals, where the silicate is mixed with other minerals, e.g., old mother rocks such as dolomite. Sodium sulfate is a well-known filler useful herein. It may be a by-product of the surfactant sulfation and sulfonation processes, or it can be added separately. As noted above, the laundry detergent bars of the present invention may require lower amounts of filler, or may not require a filler at all. Filler materials are typically used, if included, at levels up to 40%, preferably from about 5% to about 25%.

Other surfactants may also be included herein in addition to the linear alkyl benzene sulfonate described herein. Preferably the laundry detergent bar comprises at least about 0.01% of an other surfactant; more preferably at least about 0.1%; more preferably at least about 1 %; more preferably still, from about

1% to about 55%.

Preferred other surfactants are cationic surfactants, nonionic surfactants, ampholytic surfactants, zwitterionic surfactants, other anionic surfactants, and mixtures thereof, further described herein below. Nonlimiting examples of other surfactants useful in the laundry detergent bar include, the primary, branched-chain and random C-10-C20 alkyl sulfates, the C10-C18 secondary

(2,3) alkyl sulfates of the formula CH₃(CH₂)_x(CHOSO3^"M⁺) CH3 and CH3 (CH2)_y(CHOSθ3^_M⁺) CH2CH3 where x and (y + 1) are integers of at least about

7, preferably at least about 9, and M is a water-solubilizing cation, especially sodium, unsaturated sulfates such as oleyl sulfate, the C-|o-C-|8 ^a'ky' alkoxy sulfates (especially EO 1-7 ethoxy sulfates), C-I Q-CI S alkyl alkoxy carboxylates (especially the EO 1-5 ethoxycarboxylates), the C-ιo-18 glycerol ethers, the C-10-C18 alkyl polyglycosides and their corresponding sulfated polyglycosides, and C12-C18 alpha-sulfonated fatty acid esters. If desired, the conventional nonionic and amphoteric surfactants such as the C-12-C18 alkyl ethoxylates including the so-called narrow peaked alkyl ethoxylates and Cø-C^ alkyl phenol alkoxylates (especially ethoxylates and mixed ethoxy/propoxy), C12-C18 betaines and sulfobetaines, C-10-C18 amine oxides, and the like, can also be included in the overall compositions. The C10-C18 N-alkyl polyhydroxy fatty acid amides can also be used. Typical examples include the C12-C-I8 N- methylglucamides. See WO 92/06154 to Cook, et al., published April 16,1992.

Other sugar-derived surfactants include the N-alkoxy polyhydroxy fatty acid amides, such as C<|Q-Ci8 N-(3-methoxypropyl) glucamide. The N-propyl through N-hexyl C12-C18 glucamides can be used for low sudsing. C10-C20 conventional soaps may also be used. If high sudsing is desired, the branched- chain C-10-C16 soaps may be used. Mixtures of anionic and nonionic surfactants are especially useful. Coconut fatty alcohol sulfate is an anionic surfactant which is especially useful in combination with the LAS described herein. Other conventional useful surfactants are listed in standard texts, and are useful herein as well.

A soil suspending agent may also be used herein. One such soil suspending agent is an acrylic/maleic copolymer, commercially available as Sokolan®, from BASF Corp. Other soil suspending agents include polyethylene glycols having a molecular weight of about 400 to 10,000, and ethoxylated mono- and polyamines, and quaternary salts thereof. A highly preferred soil suspending agent is a water-soluble salt of carboxymethylcellulose and carboxyhydroxymethylcellulose. The soil suspending agent may be used at a level up to about 5%, preferably about 0.1 % to about 1%, by weight of the laundry detergent bar

The laundry detergent bars of the present invention may also contain structurants to increase the hardness of the bar, reduce smear, etc. Such structurants are known in the art, and include, for example, water-insoluble matrices, silicates, calcium oxides, sodium swelling clays, polyvinyl alcohol- borate complexes, gelling agents such as cross linked polyacrylates, and mixtures thereof.

Other adjunct materials useful in cleaning compositions and detergent compositions may also be useful herein, including other active ingredients such as carriers, processing aids, suds supressors, suds boosters, dyes, pigments, perfumes, perfume derivatives, dye transfer inhibitors, optical brighteners, clay soil removal agents, dispersants, alkalinity sources, soil suspension polymers, anti-redeposition polymers, etc.

Bar Processing

The laundry detergent bars of the present invention may be processed in conventional soap or detergent bar making equipment with some of all of the following key equipment: blender/mixer, mill or refining plodder, two-stage vacuum plodder, logo printer/cutter, cooling tunnel and wrapper. The preferred mixer type to be used is a high shear mixer. Suitable equipment can include: Sigma (single arm or double arms) blender, manufactured by Mazzoni; Winkworth RT 25 series, manufactured by Winkworth Machinery Ltd., Berkshire, U.K.; Eirich, series RV, manufactured by Gustau Eirich Hardheim, Germany; Lodige, series FM for batch mixing; series Baud KM for continuous mixing, manufactured by Lodige Machinenbau GmbH. Other types of suitable mixers for this application are Twin Screw Extruders, supplied by APV Bakes (CP series), Werner and Pfleiderer (continua series). Preferably, more than one mixer is used herein.

In a preferred process, the raw materials are mixed in the blender. An acid active, such as a linear alkyl benzene sulfonic acid corresponding to the LAS described herein, is preferably premixed with an added hydrotrope, if present, and then reacted with alkaline inorganic salts such as a builder, to complete neutralization. The amount of alkaline inorganic salt is at least sufficient to completely neutralize the acid active. In an alternate process, a pre- neutralized LAS surfactant as described herein is added in the blender. Other adjunct materials are then added to the mixture, such as coconut fatty alkyl sulfate. If present, the added hydrotrope may also be added at this point. Some of the adjunct materials may be present in the mixer when the LAS is added thereto. Alternatively, the adjunct materials may be added thereafter. The composition is then mixed to homogeneity. The mixing can take from one minute to one hour, with the usual mixing time being from about two to twenty minutes. The blender mix is charged to a surge tank. The product is conveyed from the surge tank to the mill, or refining plodder via a multi-worm conveyor, and further processed to form a laundry detergent bar. A preferred mixed LAS/alkyl sulfate laundry detergent bar composition is made by the following method: The raw materials are first mixed in a blender. Sodium carbonate and pre-neutralized coconut fatty alkyl sulfate is mixed for about 1-2 minutes. This is followed by the addition of a linear alkyl benzene acid active corresponding to the LAS described herein. This acid active is then completely neutralized by the sodium carbonate in the seat of the blender. (Sodium carbonate should be present in at least a stoichiometric amount sufficient to neutralize the acid active.) Sodium tripolyphosphate may also be present, or may be added after the acid is completely neutralized. Once the neutralization reaction is completed, an optional chelant, if present is added, followed by any other surfactants, and any other adjunct materials. The mixing may take from one minute to one hour, with the usual mixing time being from about 5 to about 10 minutes. As one of the last ingredients, bleach and enzymes are added to the mixture and then mixed for an additional one to five minutes. The blender mix is charged to a surge tank. The product is conveyed from the surge tank to the mill or refining plodder via a multi-worm conveyor. After milling or preliminary plodding, the product is then conveyed to a two-stage vacuum plodder, operating at high vacuum, e.g. 600 to 740 mm of mercury vacuum, so that entrapped air is removed. The product is extruded and cut to the desired bar length, and printed with the product brand name. The printed bar can be cooled, for example in a cooling tunnel, before it is wrapped, cased, and sent to storage. This laundry detergent bar is substantially free of an added hydrotrope.

Bar Physical Properties Laundry detergent bars of the present invention possess acceptable physical properties such as hardness, a smooth feel, rapid drying, and acceptable in-use properties.

A preferred method to measure the hardness of the solid composition is to measure the penetration of a needle through the surface under a standard weight, for 5 seconds using a cone penetrometer. One such penetrometer is made by Associated Instrument Manufacturers India Pvt. Ltd. (Model number AIM 512). The weight of the rod and the cone is 149 grams and an additional 50 gram weight is placed on the cone. The penetration reading of a fresh, acceptable laundry bar will typically be about 35-50 (1/10 mm) immediately after plodding. Acceptable laundry bars aged about 3 days at ambient conditions will typically have a bar penetration reading of about 5-25 (1/10 mm).

Yet another physical property of consumer relevance is the rate of drying of the bar after usage and storage under high humidity conditions. A preferred method to measure this property is to place a bar with dimensions of 75mm x 55mm with one of its large flat surface in contact with about 20 ml of water in a petri dish for 2 hours and then scraping the gel formed. This procedure is repeated for a second cycle except that the gel is not scraped off from the bar surface after the second contact with water. The bar is then stored under 30 degrees C and 88% Relative Humidity for 24 hours and then the bar surface which was exposed to the water is graded for dryness on a 1-5 grading scale by experienced operators as illustrated below:

Dryness Grade Physical state of the bar surface

1 very wet, very soft, melting, soft core

2 wet, soft gel, hard core 3 somewhat dry (moist), feels soft 4 somewhat dry ( moist), feels hard

5 completely dry, hard

For good consumer acceptance, the desired dryness grade is typically between 3.5-5.0. Preferred bars of the present invention have a dryness grade within this range.

Examples of the invention are set forth hereinafter by way of illustration and are not intended to be in any way limiting of the invention.

In the Examples herein, the following definitions apply: C_X._Y LAS: LAS as described herein, containing an average of from x to y carbon atoms in the alkyl chain. NaCFAS: Sodium coconut fatty alcohol sulfate STPP: Sodium tripolyphosphate

EXAMPLE 1

The following laundry detergent bars are prepared according to the present invention.

All proportions above are by weight of the laundry detergent bar. indicates linear alkyl benzene sulfonate surfactant having about 50 molar % 2-phenyl LAS and about 2 weight % dialkyl tetralin sulfonate impurities. indicates linear alkyl benzene sulfonate surfactant having about 70 molar % 2-phenyl LAS and about 1 weight % dialkyl tetralin sulfonate impurities. indicates linear alkyl benzene sulfonate surfactant having about 30 molar % 2-phenyl LAS and about 2 weight % dialkyl tetralin sulfonate impurities. ^t indicates linear alkyl benzene sulfonate surfactant having about 80 molar % 2-phenyl LAS and about 1 weight % dialkyl tetralin sulfonate impurities, and less than about 0.5 weight % dialkyl tetralin sulfonate impurities.

* indicates linear alkyl benzene sulfonate surfactant having about 35 molar % 2-phenyl LAS and about 2 weight % dialkyl tetralin sulfonate impurities.

All of the above compositions possess excellent surfactancy and a high level of biodegradability. Furthermore, all the above examples possess acceptable in-use wear rates, hardness, durability, rapid drying, and/or low smear.

EXAMPLE 2

Synthetic detergent bars are prepared as described below. Process scale up is obvious to those skilled in the art.

Using a blender, 16.2 g soda ash, 16.6 g coconut fatty alcohol sulfate sodium salt 80% active, 1.2 g zeolite 4A are added first. 6.2 g DETAL® linear alkyl benzene acid active, (i.e., LAB + sulfuric acid mixture; 98% active with an average carbon chain length of 11.8, 2-phenyl content of 50%, dialkyl bi-cyclic benzene sulfonate impurities of 2 weight %), is added onto this bed of solids, and neutralized for 4 minutes. Batch temperature is controlled at or below 65 °C.

1 g of a chelant, diethylene triamine pentaphophonate sodium salt, and 1 g coconut fatty alcohol are then added, and mixed for 1 minute. Fillers (18.2 g calcium carbonate and 5 g sodium sulfate fine particles) are added, and mixed for 1 minute.

Other minor additives, i.e., about 0.7 g titanium dioxide, 1 g polyacrylate/ maleic copolymer (50% active), 0.2 g soil release polymer, and 2 g coconut fatty acid monoethanol amide, are then added, and mixed for 30 seconds. 0.05 g brightener 49, in powder form, is then added followed by other polymers. The paste-like mixture is then mixed for 1 minute.

The batch is cooled to around 50 °C, and relatively unstable ingredients are added. Unstable ingredients include: 4.5 g sodium perborate monohydrate, 0.1 g SAVINASE® 4T, 0.05 g zinc phthalocyanine sulfonate are added, and briefly mixed. The final mix is then pressed in a mold to form the bar.

The above synthetic detergent bar composition possesses excellent surfactancy and a high level of biodegradability. Furthermore, the above example possesses acceptable in-use wear rates, hardness, durability, rapid drying, and/or low smear.

Claims

WHAT IS CLAIMED IS:

1. A laundry detergent bar comprising:

A. a linear alkyl benzene sulfonate surfactant comprising: i. at least about 30 molar % 2-phenyl isomer; and ii. less than about 5 weight % dialkyl bi-cyclic benzene sulfonate impurities; and

B. the balance adjunct materials.

2. A laundry detergent bar according to Claim 1 , wherein the linear alkyl benzene sulfonate surfactant comprises less than about 3 weight % dialkyl bi-cyclic benzene sulfonate impurities.

3. A laundry detergent bar according to Claim 1 , wherein the laundry detergent bar is substantially free of added hydrotropes.

4. A laundry detergent bar according to Claim 1 , further comprising an adjunct material selected from a bleach, a builder, a chelating agent, an enzyme, a filler, other surfactants, a soil suspension agent, a structurant, and mixtures thereof.

5. A laundry detergent bar according to Claim 1 , wherein the laundry detergent bar is substantially free of phosphate.

6. A laundry detergent bar according to Claim 1 , wherein the linear alkyl benzene sulfonate surfactant comprises at least 40 molar % 2-phenyl isomer.

7. A laundry detergent bar according to Claim 1 , wherein the linear alkyl benzene sulfonate surfactant comprises less than about 2.5 weight % dialkyl tetralin sulfonate impurities.

8. A laundry detergent bar according to Claim 4 wherein the bleach is selected from a bleach precursor product, an actual bleach, and combinations thereof.

9. A laundry detergent bar according to Claim 4 wherein the enzyme is selected from the group consisting of an amylase, a cellulase, a cutinase, a lipase, a peroxidase, a protease, and mixtures thereof.

10. A laundry detergent bar comprising:

A. from 5% to about 50% of a linear alkyl benzene sulfonate surfactant comprising: i. at least about 30 molar % 2-phenyl isomer; and ii. less than about 3 weight % dialkyl bi-cyclic benzene sulfonate impurities; and

B. at least about 0.01% of an other surfactant selected from the group consisting of cationic surfactants, nonionic surfactants, ampholytic surfactants, zwitterionic surfactants, other anionic surfactants, and mixtures thereof;

C. from about 1 % to about 99% builder;

D. from about 0.001% to about 5% of an enzyme; and

E. the balance adjunct materials, wherein the laundry detergent bar is substantially free of added hydrotropes.