WO1995010595A1

WO1995010595A1 - Continuous process for making high density detergent granules

Info

Publication number: WO1995010595A1
Application number: PCT/US1994/011759
Authority: WO
Inventors: Scott William Capeci; David Robert Nassano
Original assignee: The Procter & Gamble Company
Priority date: 1993-10-15
Filing date: 1994-10-14
Publication date: 1995-04-20
Also published as: CA2173108A1; JPH09503817A; CN1136824A; EP0723581A1

Abstract

A process for preparing high density detergent agglomerates having a density of at least 650 g/l is provided. The process comprising the step of continuously mixing into a moderate speed mixer/densifier the following starting detergent ingredients: (i) from about 25 % to about 50 % of a detergent surfactant; (ii) from about 20 % to about 50 % of a builder; and (iii) from about 10 % to about 40 % of a powdered material. The ratio of the builder to the powdered material is from about 1:1 to about 3.5:1. The agglomerates exiting the mixer/densifier have a density of at least 650 g/l. The process further may include one or more additional processing steps such as spraying a binder or adding a coating agent in the mixer/densifier to facilitate agglomeration. Thereafter, the agglomerates are dried to obtain high density granular detergent agglomerates which are ready for packaging as a low dosage detergent.

Description

Continuous process for making high density detergent granules

FIELD OF THE INVENTION

The present invention generally relates to a process for producing detergent agglomerates. More particularly, the invention is directed to a continuous process during which high density detergent agglomerates are produced using a single moderate speed mixer/densifier, such as a Lodige KM™ (Ploughshare) mixer. The process produces free flowing agglomerates having a density of at least 650 g 1 and are thus particularly useful in producing low dosage detergent compositions.

BACKGROUND OF THE INVENTION Recently, there has been considerable interest within the detergent industry for laundry detergents which are "compact" and therefore, have low dosage volumes. To facilitate production of these so-called low dosage detergents, many attempts have been made to produce high bulk density detergents, for example with a density of 600 g/1 or higher. The low dosage detergents are currently in high demand as they conserve resources and can be sold in small packages which are more convenient for consumers.

Generally, there are two primaiy types of processes by which detergent granules or powders can be prepared. The first type of process involves spray-drying an aqueous detergent slurry in a spray-diying tower to produce highly porous detergent granules. In the second type of process, the various detergent components are dry mixed after which they are agglomerated with a binder such as a nonionic or anionic surfactant. In both processes, the most important factors which govern the density of the resulting detergent granules are the density, porosity and surface area of the various starting materials and their respective chemical composition. These parameters, however, can only be varied within a limited range. Thus, a substantial bulk density increase can only be achieved by additional processing steps which lead to densification of the detergent granules.

There have been many attempts in the art for providing processes which increase the density of detergent granules or powders. Particular attention has been given to densification of spray-dried granules by post tower treatment. For example, Johnson et al, British patent No.

1,517,713 (Unilever) disclose a batch process in which spray-dried oι granulated detergent powders containing sodium tripolyphosphate and sodium sulfate are densified and spheronized in a Marumerizer®. This apparatus comprises a substantially horizontal, roughened, rotatable table positioned within and at the base of a substantially vertical, smooth walled cylinder. This process, however, is essentially a batch process and is therefore less suitable for the large scale production of detergent powders. More recently, attempts have been made to provide a continuous processes for increasing the density of spray dried detergent granules. Typically, such processes require a first apparatus which pulverizes or grinds the granules and a second apparatus which increases the density of the pulverized granules by agglomeration. These processes, although continuous, require two mixer/densifier apparatus to achieve the desired increase in density, thereby rendering the process more expensive and less efficient. For example, Curtis, European patent application No. 451,894 (Unilever), discloses a process for preparing high density detergent granules by using two mixers in series. In particular, the starting materials are fed into a high speed mixer/densifier after which the materials are fed into a moderate speed mixer/densifier to increase the bulk density further. Thus, Curtis initially requires a high speed mixer/densifier to pulverize the detergent granules and then a second moderate speed mixer/densifier to increase the density to the desired level.

See also Appel et al, U.S. Patent No. 5,133,924 (Lever), which discloses a similar process for preparing a high bulk density granular detergent. As with Curtis, Appel et al use a first high speed mixer for pulverizing the detergent granules and then a moderate speed mixer to increase the density of the granules by agglomeration to 650 g/1. Also, Hollingsworth et al, European Patent 351,937 (Unilever), disclose a process for preparing high bulk density (650 g/1) detergent granules by using batch mixers such as a Lodige FM™ mixer. The Hollingsworth et al process is only a batch process which does not facilitate large-scale production as currently required. While the Hollingsworth et al process provides high density detergent granules by way of a high speed, single- mixer batch process, it would be desirable to have a continuous process in which low or moderate speed mixers can be used to decrease operating costs.

However, all of the aforementioned processes are directed primarily for densϋying or otherwise processing spray dried granules. Currently, the relative amounts and types of materials subjected to spray drying processes in the production of detergent granules has been limited. For example, it has been difficult to attain high levels of surfactant in the resulting detergent composition, a feature which facilitates production of low dosage detergents. Thus, it would be desirable to have a process by which detergent compositions can be produced without having the limitations imposed by conventional spray drying techniques.

To that end, the art is also replete with disclosures of processes which entail agglomerating detergent compositions. For example, Beerse et al, U.S. Patent No. 5,108,646 (commonly assigned), relates to a process for agglomerating detergent builders by mixing zeolite and/or layered silicates in a mixer to form free flowing agglomerates. While Beerse et al suggest that their process can be used to produce detergent agglomerates, they do not provide a mechanism by which a high active surfactant paste consisting of a relatively high amount of surfactant and a low amount of liquid (e.g. water) can be agglomerated into crisp, free flowing detergent agglomerates having a density of at least 650 g/1. It would therefore be desirable to have a process for producing crisp, free flowing detergent agglomerates from a high active viscous surfactant paste. Accordingly, despite the above-described disclosures in the art, it would be desirable to have a process for continuously producing high density detergent agglomerates having a density of at least 650 g/1. Also, it would be desirable for such a process to be capable of producing crisp, free flowing detergent agglomerates from a viscous surfactant paste. Finally, it would be desirable for such a process to be more efficient and economical to facilitate large-scale production of low dosage detergents.

SUMMARY OF THE INVENTION The present invention meets the aforementioned needs in the art by providing a process which continuously produces high density detergent agglomerates having a density of at least 650 g/1 in a single moderate speed mixer/densifier which is horizontally positioned tc facilitate continuous processing. The process achieves the desired high density detergent agglomerates without unnecessary process parameters, such as the use of spray drying techniques, relatively high operating temperatures, and a plurality of mixer/densifiers, all of which increase manufacturing costs. As used herein, the term "agglomerates" refers to particles formed by agglomerating more porous starting detergent ingredients (particles) which typically have a smaller mean particle size than the formed agglomerates. All percentages and ratios used herein are expressed as percentages by weight (anhydrous basis) unless otherwise indicated. All viscosities referenced herein are measured at 70°C (±5°C) and at shear rates of about 10 to 100 sec^-1.

In accordance with one aspect of the invention, a process for preparing high density detergent agglomerates is provided. The process comprises the step of continuously mixing into a moderate speed mixer/densifier the following starting detergent ingredients: (i) from about 25% to about 50% of a detergent surfactant; (ii) from about 20% to about 50% of an aluminosilicate builder, and (iii) from about 10% to about 40% of an powdered material. The ratio of the builder to the powdered material is from about 1: 1 to about 3.5:1. The agglomerates exiting the mixer/densifier have a density of at least 650 g/1. The process further may include one or more additional processing steps such as spraying an additional binder or adding a coating agent in the mixer/densifier to facilitate agglomeration. Thereafter, the agglomerates are dried to obtain high density granular detergent agglomerates which are ready for packaging as a low dosage detergent. Further, the invention provides another r»" ess in which free flowing, crisp, high density detergent agglomerates are produced from a visa....-; surfactant paste among other starting detergent ingredients. This process comprises the step of continuously mixing into a moderate speed mixer/densifier the following starting detergent ingredients: (i) from about 25% to about 50% of a detergent surfactant in the form of an aqueous paste having a viscosity of from about 5,000 cps to about 100,000 cps; (ii) from about 20% to about 50% of an aluminosilicate builder, and (iii) from about 10% to about 40% of a sodium carbonate. The ratio of the aluminosilicate builder to carbonate is from about 1:1 to about 3.5:1 and the agglomerates exiting the mixer/densifier have a density of at least 650 g/1. Thereafter, the agglomerates are dried to obtain high density granular detergent agglomerates which are ready for packaging as a low dosage detergent.

Accordingly, it is an object of the present invention to provide a process for continuously producing high density detergent agglomerates with a density of at least 650 g/1 from starting detergent ingredients in a single low to moderate speed mixer/densifier. It is also an object of the invention to provide such a process which is not limited by unnecessary process parameters, such as the use of spray drying techniques or granules produced therefrom, operating temperatures, and additional mixer/densifiers so that large-scale production of low dosage detergents is more economical and efficient. These and other objects, features and attendant advantages of the present invention will become apparent to those skilled in the art from a reading of the following detailed description of the preferred embodiment and the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention is directed to a process which continuously produces high density detergent agglomerates having a density of at least 650 g/1. By using only a single moderate speed mixer/densifier, the process produces the desired high density detergent agglomerates from starting detergent ingredients without unnecessary process parameters which increase manufacturing costs and result in an undesirable detergent product. Specifically, the need for deformable, spray dried detergent granules, high operating temperatures in the mixer/densifier, and more than one mixer/densifier, all of which increase manufacturing costs, are no longer required by the present process. Generally, the present process is used in the production of low dosage detergent agglomerates from starting detergent ingredients rather than conventional "post-tower" detergent granules. By "post-tower" detergent granules, we mean those detergent granules which have been processed through a conventional spray-drying tower or similar apparatus.

The process of the invention allows for production of low dosage detergents in an environmentally conscious manner in that the use of spray drying techniques and the like which typically emit pollutants though their towers or stacks into the atmosphere is eliminated. This feature of the process invention is extremely desirable in geographic areas which are especially sensitive to emission of pollutants into the atmosphere.

Single Mixer/Densifier Process In the first step of the process, the invention entails continuously mixing into a moderate speed mixer/densifier the following starting detergent ingredients: (i) from about 25% to about 65%, preferably from about 35% to about 55% and, most preferably from about 38% to about 44%, of a detergent surfactant in an aqueous paste form; (ii) from about 20% to about 50%, preferably from about 25% to about 45% and, most preferably from about 30% to about 40% of an aluminosilicate builder, and (iii) from about 10% to about 40%, preferably from about 15% to about 30% and, most preferably from about 15% to about 25% of a powdered material. On an anhydrous basis, the surfactant component level is preferably from about 25% to about 50%. It should be understood that additional detergent ingredients may also be mixed as described herein without departing from the scope of the process invention. However, at a minimum, the detergent surfactant, aluminosilicate builder and powdered material should be continuously mixed so as to insure production of the desired free flowing, crisp detergent agglomerates. The specifics of the various essential starting detergent ingredients as well as optional detergent ingredients are described hereinafter.

Preferably, the ratio of the builder to the powdered material is from about 1:1 to about 3.5: 1, most preferably from about 2: 1 to about 3.5: 1. While the preferred builder is an aluminosilicate and the preferred powdered material is sodium carbonate, other less preferred materials as described hereinafter can be used in the process without departing from the scope of the invention. By operating the process within the aforedescribed builder/powdered material ratio parameter, detergent agglomerates having the desired properties are formed. Specifically, the detergent agglomerates exiting the mixer/densifier used herein will have a density of at least 650 g/1, more preferably from about 700 g/1 to about 800 g/1. Thereafter, the agglomerates are dried to obtain high density granular detergent agglomerates which are ready for packaging as a low dosage detergent.

Preferably, the mean residence time of the various starting detergent ingredients in the low or moderate speed mixer/densifier is preferably in range from about 0.5 minutes to about 15 minutes, most preferably the residence time is about 1 to about 5 minutes. In this way, the density of the resulting detergent agglomerates is at the desired level.

After undergoing the process in accordance with the invention, the particle porosity of the resulting detergent agglomerates is preferably in a range from about 5% to about 20%, more preferably at about 10%. As those skilled in the art will readily appreciate, a low porosity detergent agglomerate provides a dense or low dosage detergent product, to which the present process is primarily directed. In addition, an attribute of dense or densified detergent agglomerates is the relative particle size. The present process typically provides agglomerates having a mean particle size of from about 400 microns to about 700 microns, and more preferably from about 450 microns to about 500 microns. As used herein, the phrase "mean particle size" refers to individual agglomerates and not individual particles or detergent granules. The combination of the above- referenced porosity and particle size, results in agglomerates having density values of 650 g/1 and higher. Such a feature is especially useful in the production of low dosage laundry detergents as well as other granular compositions such as dishwashing compositions.

In another step of the present process, the agglomerates are conditioned by either drying or adding a coating agent to improve flowability after they exit the moderate speed mixer/densifier to obtain the high density granular detergent agglomerates produced by the process which are in shippable or packagable form. Those skilled in the art will appreciate that a wide variety of methods may be used to dry as well as cool the exiting agglomerates without departing from the scope of the invention. By way of example, apparatus such as a fluidized bed can be used for drying while an airlift can be used for cooling should it be necessary. Since the moderate speed mixer/densifier can be operated at relatively low temperatures, the need for cooling apparatus is not required by the present process, which thereby further reduces manufacturing costs of the final product.

The particular moderate speed mixer/densifier used in the present process should include pulverizing or grinding and agglomeration tools so that both techniques can be carried forth simultaneously in a single mixer. To that end, it has been found that the first processing step can be successfully completed, under the process parameters described herein, in a Lodige KM™ (Ploughshare) 600 mixer or similar brand mixer. These types of mixers essentially consist of a horizontal, hollow static cylinder having a centrally mounted rotating shaft around which several plough-shaped blades are attached. Preferably, the shaft rotates at a speed of from about 15 φm to about 140 φm, more preferably from about 80 φm to about 120 φm. The grinding or pulverizing is accomplished by cutters, generally smaller in size than the rotating shaft, which preferably operate at about 3600 φm. Other mixers similar in nature which are suitable for use in the process include the Lodige Ploughshare™ mixer and the Drais® K-T 160 mixer.

In accordance with the present process, the moderate speed mixer/densifier preferably imparts a requisite amount of energy to form the desired agglomerates. More particularly, the moderate speed mixer/densifier imparts from about 5 χ 10 ^ erg/kg to about 2 x 10^ erg/kg at a rate of from about 3 x 10⁸ erg/kg-sec to about 3 x 10⁹ erg/kg-sec to form free flowing high density detergent agglomerates. The energy input and rate of input can be determined by calculations from power readings to the moderate speed mixer/densifier with and without granules, residence time of the granules in the mixer/densifier, and the mass of the granules in the mixer/densifier. Such calculations are clearly within the scope of the skilled artisan. Use of higher energy levels and/or rates of energy input will require lower levels of binder or possibly lead to over agglomeration of the granules, thereby producing a doughy mass. However, the use of lower energy levels and/or rates of energy input tend to result in fine powders in the form of light, fluffy agglomerates not having the desired physical properties and/or broad particle size distribution. If the agglomerates produced by the present process are used as a component of a granular composition, the actual size of the agglomerates is preferably selected to match the size of the primary component particles of the composition to minimize product segregation.

Optional Process Steps The process can comprises the step of spraying an additional binder in the mixer/densifier used in the agglomeration step to facilitate production of the desired detergent agglomerates. A binder is added for purposes of enhancing agglomeration by providing a "binding" or "sticking" agent for the detergent components. The binder is preferably selected from the group consisting of water, anionic surfactants, nonionic surfactants, polyethylene glycol, polyvinyl pyrrolidone polyacrylates, citric acid and mixtures thereof. Other suitable binder materials including those listed herein are described in Beerse et al, U.S. Patent No. 5,108,646 (Procter & Gamble Co.), the disclosure of which is incoφorated herein by reference.

Another optional processing step includes continuously adding a coating agent such as zeolites and fumed silica to the mixer/densifier to facilitate free flowability of the resulting detergent agglomerates and to prevent over agglomeration. In addition, the detergent starting materials can be fed into a pre-mixer, such as a Lodige CB mixer or a twin-screw extruder, prior to entering in the mixer/densifier described herein. This step, although optional, does indeed facilitate agglomeration. Other optional steps contemplated by the present process include additional conditioning of the detergent agglomerates by subjecting the agglomerates to additional drying and/or addition of coating agents to improve flowability after they exit the mixer/densifier used in agglomeration. This furthers enhances the condition of the detergent agglomerates for use as an additive or to place them in shippable or packagable form. Those skilled in the art will appreciate that a wide variety of methods may be used for additional drying as well as cooling the exiting detergent agglomerates without departing from the scope of the invention. As mentioned earlier, apparatus such as a fluidized bed can be used for drying while an airlift can be used for cooling should it be necessary.

Powdered Material _JjUt

As used herein, the phrase "powdered material" refers to a material in the form of fine grains, generally having a particle size within a range of from about 2 microns to about 700, more typically from about 50 microns to about 100 microns. The preferred powdered material used in the process is added in an optimum ratio with the aluminosilicate builder so as to provide structure and integrity in the resulting detergent agglomerates. Thus, the resulting detergent agglomerates produced according to the process are "crisp" agglomerates as they are commonly referred to by those skilled in the art. Furthermore, the powdered material can, and preferably does, add alkalinity to the detergent mixture, a condition necessary for optimum cleaning performance.

Preferably, the powdered material is selected from the group consisting of carbonates, sulfates, carbonate/sulfate complexes, phosphates, polyethylene glycol and mixtures thereof. The preferred powdered material, as briefly mentioned, is sodium carbonate which has been found to facilitate agglomeration especially well. While not intending to be limiting, specific suitable powdered materials include powdered tripolyphosphate, powdered tetrasodium pyrophosphate, powdered citrate, powdered sodium carbonate, powdered potassium carbonate, and powdered sodium sulfate.

Detergent Surfactant The detergent surfactant used in the process can be in liquid, powdered or paste form. Typically, when the surfactant is in the form of a paste, it is an aqueous viscous paste. This so- called viscous surfactant paste has a viscosity of from about 5,000 cps to about 100,000 cps, more preferably from about 10,000 cps to about 80,000 cps, and contains at least about 10% water, more preferably at least about 16% water. As mentioned previously, the viscosity is measured at 70°C and at shear rates of about 10 to 100 sec.^*-'. Furthermore, the surfactant paste, if used, preferably comprises a detersive surfactant in the amounts specified previously and the balance water and other conventional detergent ingredients. The surfactant itself, upon use alone or in the form of a viscous surfactant paste, is preferably selected from anionic, nonionic, zwitterionic, ampholytic and cationic classes and compatible mixtures thereof. Detergent surfactants useful herein are described in U.S. Patent 3,664,961, Norris, issued May 23, 1972, and in U.S. Patent 3,919,678, Laughlin et al., issued December 30, 1975, both of which are incorporated herein by reference. Useful cationic surfactants also include those described in U.S. Patent 4,222,905, Cockrell, issued September 16, 1980, and in U.S. Patent 4,239,659, Muφhy, issued December 16, 1980, both of which are also incorporated herein by reference. Of the surfactants, anionics and nonionics are preferred and anionics are most preferred.

The following are representative examples of detergent surfactants useful in the present surfactant paste. Water-soluble salts of the higher fatty acids, i.e., "soaps", are useful anionic surfactants in the compositions herein. This includes alkali metal soaps such as the sodium, potassium, ammonium, and alkylolammonium salts of higher fatty acids containing from about 8 to about 24 carbon atoms, and preferably from about 12 to about 18 carbon atoms. Soaps can be made by direct saponification of fats and oils or by the neutralization of free fatty acids. Particularly useful are the sodium and potassium salts of the mixtures of fatty acids derived from coconut oil and tallow, i.e., sodium or potassium tallow and coconut soap.

Additional anionic surfactants which suitable for use herein include 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 10 to about 20 carbon atoms and a sulfonic acid or sulfuric acid ester group. (Included in the term "alkyl" is the alkyl portion of acyl groups.) Examples of this group of synthetic surfactants are the sodium and potassium alkyl sulfates, especially those obtained by sulfating the higher alcohols (C_{g ι}g carbon atoms) such as those produced by reducing the glycerides of tallow or coconut oil; and the sodium and potassium alkylbenzene sulfonates in which the alkyl group contains from about 9 to about 15 carbon atoms, in straight chain or branched chain configuration, e.g., those of the type described in U.S. Patents 2,220,099 and 2,477,383. Especially valuable are linear straight chain alkylbenzene sulfonates in which the average number of carbon atoms in the alkyl group is from about 11 to 13, abbreviated as Cu_i3 LAS.

Other anionic surfactants suitable for use herein are the sodium alkyl glyceryl ether sulfonates, especially those ethers of higher alcohols derived from tallow and coconut oil; sodium coconut oil fatty acid monoglyceride sulfonates and sulfates; sodium or potassium of ethylene oxide per molecule and wherein the alkyl groups contain from about 8 to about 12 carbon atoms; and sodium or potassium salts of alkyl ethylene oxide ether sulfates containing about 1 to about 10 units of ethylene oxide per molecule and wherein the alkyl group contains from about 10 to about 20 carbon atoms.

In addition, suitable anionic surfactants include the water-soluble salts of esters of alpha-sulfonated fatty acids containing from about 6 to 20 carbon atoms in the fatty acid group and from about 1 to 10 carbon atoms in the ester group; water-soluble salts of 2-acyloxyalkane-l-sulfonic acids containing from about 2 to 9 carbon atoms in the acyl group and from about 9 to about 23 carbon atoms in the alkane moiety; water-soluble salts of olefin and paraffin sulfonates containing from about 12 to 20 carbon atoms; and beta-alkyloxy alkane sulfonates containing from about 1 to 3 carbon atoms in the alkyl group and from about 8 to 20 carbon atoms in the alkane moiety.

Preferred anionic surfactants are C . _Q linear alkylbenzene sulfonate and C _{n 0} alkyl lU-lo 10-18 sulfate. If desired, low moisture (less than about 25% water) alkyl sulfate paste can be the sole ingredient in the surfactant paste. Most preferred are C._ft ._ alkyl sulfates, linear or branched, and any of primary, secondary or tertiary. A preferred embodiment of the present invention is wherein the surfactant paste comprises from about 20% to about 40% of a mixture of sodium C _n linear alkylbenzene sulfonate and sodium C._ . , alkyl sulfate in a weight ratio of " ^,ut 2:1 to 1:2. Another preferred embodiment of the detergent composition includes a mixt ; of C_jo-i_β alkyl sulfate and C^Q-18 -^^ ethoxy sulfate in a weight ratio of about 80:20. Water-soluble nonionic surfactants are also useful in the instant invention. Such nonionic materials include compounds produced by the condensation of alkylene oxide groups (hydrophilic in nature) with an organic hydrophobic compound, which may be aliphatic or alkyl aromatic in nature. The length of the polyoxyalkylene group which is condensed with any particular hydrophobic group can be readily adjusted to yield a water-soluble compound having the desired degree of balance between hydrophilic and hydrophobic elements.

Suitable nonionic surfactants include the polyethylene oxide condensates of alkyl phenols, e.g., the condensation products of alkyl phenols having an alkyl group containing from about 6 to 15 carbon atoms, in either a straight chain or branched chain configuration, with from about 3 to 12 moles of ethylene oxide per mole of alkyl phenol. Included are the water-soluble and water-dispersible condensation products of aliphatic alcohols containing from 8 to 22 carbon atoms, in either straight chain or branched configuration, with from 3 to 12 moles of ethylene oxide per mole of alcohol.

An additional group of nonionics suitable for use herein are semi-polar nonionic surfactants which include water-soluble amine oxides containing one alkyl moiety of from abut 10 to 18 carbon atoms and two moieties selected from the group of alkyl and hydroxyalkyl moieties of from about 1 to about 3 carbon atoms; water-soluble phosphine oxides containing one alkyl moiety of about 10 to 18 carbon atoms and two moieties selected from the group consisting of alkyl groups and hydroxyalkyl groups containing from about 1 to 3 carbon atoms; and water-soluble sulfoxides containing one alkyl moiety of from about 10 to 18 carbon atoms and a moiety selected from the group consisting of alkyl and hydroxyalkyl moieties of from about 1 to 3 carbon atoms.

Preferred nonionic surfactants are of the formula R (OC,H .) OH, wherein R is a

2 4 n

C_{] f)}-C.₆ alkyl group or a C₈-C. , alkyl phenyl group, and n is from 3 to about 80. Particularly preferred are condensation products of C..-C. , alcohols with from about 5 to about 20 moles of ethylene oxide per mole of alcohol, e.g., C..-C.. alcohol condensed with about 6.5 moles of ethylene oxide per mole of alcohol.

Additional suitable nonionic surfactants include polyhydroxy fatty acid amides of the formula

O R,

II I

R— C— N— Z wherein R is a C9.17 alkyl or alkenyl, R_j is a methyl group and Z is glycityl derived from a reduced sugar or alkoxylated derivative thereof. Examples are N-methyl N-1-deoxyglucityl cocoamide and N- methyl N-1-deoxyglucityl oleamide. Processes for making polyhydroxy fatty acid amides are known and can be found in Wilson, U.S. Patent No. 2,965,576 and Schwartz, U.S. Patent No. 2,703,798, the disclosures of which are incorporated herein by reference.

Ampholytic surfactants include derivatives of aliphatic or aliphatic derivatives of heterocyclic secondary and tertiary amines in which the aliphatic moiety can be straight chain or branched and wherein one of the aliphatic substituents contains from about 8 to 18 carbon atoms and at least one aliphatic substituent contains an anionic water-solubilizing group. Zwitterionic surfactants include derivatives of aliphatic, quaternary, ammonium, phosphonium, and sulfonium compounds in which one of the aliphatic substituents contains from about 8 to 18 carbon atoms.

Cationic surfactants can also be included in the present invention. Cationic surfactants comprise a wide variety of compounds characterized by one or more organic hydrophobic groups in the cation and generally by a quaternary nitrogen associated with an acid radical. Pentavalent nitrogen ring compounds are also considered quaternary nitrogen compounds. Suitable anions are halides, methyl sulfate and hydroxide. Tertiary amines can have characteristics similar to cationic surfactants at washing solution pH values less than about 8.5. A more complete disclosure of these and other cationic surfactants useful herein can be found in U.S. Patent 4,228,044, Cambre, issued October 14, 1980, incorporated herein by reference.

Cationic surfactants are often used in detergent compositions to provide fabric softening and/or antistatic benefits. Antistatic agents which provide some softening benefit and which are preferred herein are the quaternary ammonium salts described in U.S. Patent 3,936,537, Baskerville, Jr. et al., issued February 3, 1976, the disclosure of which is incorporated herein by reference. The starting detergent surfactant ingredient can also be a secondary (2,3) alkyl sulfate surfactant as described herein. For the convenience of those skilled in the art, the following, discussion of the secondary (2,3) alkyl sulfates used herein will be distinguished from conventional alkyl sulfate surfactants where appropriate. Conventional primary alkyl sulfate surfactants have the general formula

ROS03-M+ wherein R is typically a linear C10-C20 hydrocarbyl group and M is a water-solubilizing cation. Branched-chain primary alkyl sulfate surfactants (i.e., branched-chain "PAS") having 10-20 carbon atoms are also known; see, for example, European Patent Application 439,316, Smith et al, filed 21.01.91, the disclosure of which is incorporated herein by reference.

Conventional secondary alkyl sulfate surfactants are those materials which have the sulfate moiety distributed randomly along the hydrocarbyl "backbone" of the molecule. Such materials may be depicted by the structure

CH₃(CH₂)_n(CHOS0₃-M⁺)(CH2)_mCH3 wherein m and n are integers of 2 or greater and the sum of m + n is typically about 9 to 17, and M is a water-solubilizing cation.

By contrast with the above, the selected secondary (2,3) alkyl sulfate surfactant sjd herein comprise structures of formulas A and B -_?.:

(A) CH₃(CH₂)_x(CHOS0₃-M⁺) CH₃ and (B) CH₃(CH₂)_y(CH0S03-M⁺)CH2CH3 for the 2 -sulfate and 3-sulfate, respectively. Mixtures of the 2- and 3-sulfate can be used herein. In formulas A and B, x and (y+l) are, respectively, integers >f at least about 6, and can range from about 7 to about 20, preferably about 10 to about 16. M is a cation, such as an alkali metal, ammonium, alkanolammonium, alkaline earth metal, or the like. Sodium is typical for use as M to prepare the water-soluble (2,3) alkyl sulfates, but ethanolammonium, diethanolammonium, triethanolammonium, potassium, ammonium, and the like, can also be used.

The physical/chemical properties of the foregoing types of alkyl sulfate surfactants are unexpectedly different, one from another, in several aspects v - are important to formulators of various types of detergent compositions, for example, the primary alkyl sulfates can disadvantageously interact with, and even be precipitated by, metal cations such as calcium and magnesium. Thus, water hardness can negatively affect the primary alkyl sulfates to a greater extent than the secondary (2,3) alkyl sulfates herein. Accordingly, the secondary (2,3) alkyl sulfates have now been found to be preferred for use in the presence of calcium ions and under conditions of high water hardness, or in the so-called "under-built" situation which can occur when nonphosphate builders are employed.

Moreover, the solubility of the primary alkyl sulfates is not as great as the secondary (2,3) alkyl sulfates. Hence, the formulation of high-active surfactant particles has now been found to be simpler and more effective with the secondary (2,3) alkyl sulfates than with the primary alkyl sulfates. Thus, in addition to compatibility with enzymes, the secondary (2,3) alkyl sulfates are exceptionally easy to formulate as heavy-duty granular laundry detergents.

With regard to the random secondary alkyl sulfates (i.e., secondary alkyl sulfates with the sulfate group at positions such as the 4, 5, 6, 7, etc. secondary carbon atoms), such materials tend to be tacky solids or, more generally, pastes. Thus, the random alkyl sulfates do not afford the processing advantages associated with the solid secondary (2,3) alkyl sulfates when formulating detergent granules. Moreover, the secondary (2,3) alkyl sulfates herein provide better sudsing than the random mixtures. It is preferred that the secondary (2,3) alkyl sulfates be substantially free (i.e., contain less than about 20%, more preferably less than about 10%, most preferably less than about 5%) of such random secondary alkyl sulfates.

One additional advantage of the secondary (2,3) alkyl sulfate surfactants herein over other positional or "random" alkyl sulfate isomers is in regard to the improved benefits afforded by said secondary (2,3) alkyl sulfates with respect to soil redeposition in the context of fabric laundering operations. As is well-known to users, laundry detergents loosen soils from fabrics being washed and suspend the soils in the aqueous laundry liquor. However, as is well-known to detergent formulators, some portion of the suspended soil can be redeposited back onto the fabrics. Thus, some redistribution and redeposition of the soil onto all fabrics in the load being washed can occur. This, of course, in undesirable and can lead to the phenomenon known as fabric "greying". (As a simple test of the redeposition characteristics of any given laundry detergent formulation, unsoiled white "tracer" cloths can be included with the soiled fabrics being laundered. At the end of the laundering operation the extent to which the white tracers deviate from their initial degree of whiteness can be measured photometrically or estimated visually by skilled observers. The more the tracers' whiteness is retained, the less soil redeposition has occurred.) The preparation of the secondary (2,3) alkyl sulfates of the type useful herein can be carried out by the addition of H₂Sθ4 to olefins. A typical synthesis using α-olefins and sulfuric acid is disclosed in U.S. Patent 3,234,258, Morris, or in U.S. Patent 5,075,041, Lutz, granted December 24, 1991, both of which are incorporated herein by reference. The synthesis, conducted in solvents which afford the secondary (2,3) alkyl sulfates on cooling, yields products which, when purified to remove the unreacted materials, randomly sulfated materials, unsulfated by-products such as C \Q and higher alcohols, secondary olefin sulfonates, and the like, are typically 90+% pure mixtures of 2- and 3-sulfated materials (up to 10% sodium sulfate is typically present) and are white, non-tacky, apparently crystalline, solids. Some 2,3-disulfates may also be present, but generally comprise no more than 5% of the mixture of secondary (2,3) alkyl mono-sulfates. Such materials are available as under the name "DAN", e.g., "DAN 200" from Shell Oil Company.

If increased solubility of the "crystalline" secondary (2,3) alkyl sulfate surfactants is desired, the formulator may wish to employ mixtures of such surfactants having a mixture of alkyl chain lengths. Thus, a mixture of C^-Cj alkyl chains will provide an increase in solubility over a secondary (2,3) alkyl sulfate wherein the alkyl chain is, say, entirely C^. The solubility c^c he secondaiy (2,3) alkyl sulfates can also be enhanced by the addition thereto of other surfacL~..s such as the material which decreases the crystallinity of the secondary (2,3) alkyl sulfates. Such crystallinity-interrupting materials are typically effective at levels of 20%, or less, of the secondary (2,3) alkyl sulfate.

Aluminosilicate Builder The starting detergent ingredients of the present process also comprise a detergent aluminosilicate builder which are referenced as aluminosilicate ion exchange materials. The aluminosilicate ion exchange materials used herein as a detergent builder preferably have both a high calcium ion exchange capacity and a high exchange rate. Without intending to be limited by ieory, it is believed that such high calcium ion exchange rate and capacity are a function of several interrelated factors which derive from the method by which the aluminosilicate ion exchange material is produced. In that regard, the aluminosilicate ion exchange materials used herein are preferably produced in accordance with Corkill et al, U.S. Patent No. 4,605,509 (Procter & Gamble), the disclosure of which is incorporated herein by reference.

Preferably, the aluminosilicate ion exchange material is in "sodium" form since the potassium and hydrogen forms of the instant aluminosilicate do not exhibit the as high of an ex: nge rate and capacity as provided by the sodium form. Additionally, the aluminosilicate ion exchange material preferably is in overdried form so as to facilitate production of crisp detergent agglomerates as described herein. The aluminosilicate ion exchange materials used herein preferably have particle size diameters which optimize their effectiveness as deterg Guilders. The term "particle size diameter" as used herein represents the average particle size diame of a given aluminosilicate ion exchange material as determined by conventional analytical techniques, such as microscopic determination and scanning electron microscope (SEM). The preferred particle size diameter of the aluminosilicate is from about 0.1 micron to about 10 microns, more preferably from about 0.5 microns to about 9 microns. Most preferably, the particle size diameter is from about 1 microns to about 8 microns. Preferably, the aluminosilicate ion exchange material has the formula Na_z[(A10₂)_z.(Si0₂)y]xH₂0 wherein z and y are integers of at least 6, the molar ratio of z to y is from about 1 to about 5 and x is from about 10 to about 264. More preferably, the aluminosilicate has the formula

Na₁₂[(A10₂)₁₂.(Si0₂)ι₂]xH₂0 wherein x is from about 20 to about 30, preferably about 27. These preferred aluminosilicates are available commercially, for example under designations Zeolite A, Zeolite B and Zeolite X. Alternatively, naturally-occurring or synthetically derived aluminosilicate ion exchange materials suitable for use herein can be made as described in Krummel et al, U.S. Patent No. 3,985,669, the disclosure of which is incorporated herein by reference. The aluminosilicates used herein are further characterized by their ion exchange capacity which is at least about 200 mg equivalent of CaCθ3 hardness/gram, calculated on an anhydrous basis, and which is preferably in a range from about 300 to 352 mg equivalent of CaC03 hardness/gram. Additionally, the instant aluminosilicate ion exchange materials are still further characterized by their calcium ion exchange rate which is at least about 2 grains Ca⁺⁺/gallon/minute/-gram/gallon, and more preferably in a range from about 2 grains Ca^"H"/gallon/minute/-gram/gallon to about 6 grains Ca^/gallon/minuteZ-gram/gallon .

Optional Detergent Components The starting or entering detergent components in the present process can also include any number of additional ingredients. These include other detergency builders, bleaches, bleach activators, suds boosters or suds suppressors, anti-tarnish and anticorrosion agents, soil suspending agents, soil release agents, germicides, pH adjusting agents, non-builder alkalinity sources, chelating agents, smectite clays, enzymes, enzyme-stabilizing agents and perfumes. See U.S. Patent 3,936,537, issued February 3, 1976 to Baskerville, Jr. et al., incorporated herein by reference. Other builders can be generally selected from the various water-soluble, alkali metal, ammonium or substituted ammonium phosphates, polyphosphates, phosphonates, polyphosphonates, carbonates, borates, polyhydroxy sulfonates, polyacetates, carboxylates, and polycarboxylates. Preferred are the alkali metal, especially sodium, salts of the above. Preferred for use herein are the phosphates, carbonates, _]0-.„ fatty acids, polycarboxylates, and mixtures thereof. More preferred are sodium tripolyphosphate, tetrasodium pyrophosphate, citrate, tartrate mono- and di-succinates, and mixtures thereof (see below).

In comparison with amoφhous sodium silicates, crystalline layered sodium silicates exhibit a clearly increased calcium and magnesium ion exchange capacity. In addition, the layered sodium silicates prefer magnesium ions over calcium ions, a feature necessary to insure that substantially all of the "hardness" is removed from the wash water. These crystalline layered sodium silicates, however, are generally more expensive than amoφhous silicates as well as other builders. Accordingly, in order to provide an economically feasible laundry detergent, the proportion of crystalline layered sodium silicates used must be determined judiciously.

The crystalline layered sodium silicates suitable for use herein preferably have the formula NaMSi_x0_2x+i.yH₂0 wherein M is sodium or hydrogen, x is from about 1.9 to about 4 and y is from about 0 to about 20. More preferably, the crystalline layered sodium silicate has the formula

NaMSi₂0₅.yH₂0 wherein M is sodium or hydrogen, and y is from about 0 to about 20. These and other crystalline layered sodium silicates are discussed in Corkill et al, U.S. Patent No. 4,605,509, previously incorporated herein by reference. Specific examples of inorganic phosphate builders are sodium and potassium tripolyphosphate, pyrophosphate, polymeric metaphosphate having a degree of polymerization of from about 6 to 21, and orthophosphates. Examples of polyphosphonate builders are the sodium and potassium salts of ethylene diphosphonic acid, the sodium and potassium salts of ethane 1-hydroxy-l, 1 -diphosphonic acid and the sodium and potassium salts of ethane,

1,1,2-triphosphonic acid. Other phosphorus builder compounds are disclosed in U.S. Patents 3,159,581; 3,213,030; 3,422,021; 3,422,137; 3,400,176 and 3,400,148, all of which are incorporated herein by reference.

Examples of nonphosphorus, inorganic builders are tetraborate decahydrate and silicates having a weight ratio of SiO. to alkali metal oxide of from about 0.5 to about 4.0, preferably from about 1.0 to about 2.4. Water-soluble, nonphosphorus organic builders useful herein include the various alkali metal, ammonium and substituted ammonium polyacetates, carboxylates, polycarboxylates and polyhydroxy sulfonates. Examples of polyacetate and polycarboxylate builders are the sodium, potassium, lithium, ammonium ar... substituted ammonium salts of ethylene diamine tetraacetic acid, nitrilotriacetic acid, oxydisuccinic acid, mellitic acid, benzene polycarboxylic acids, and citric acid.

Polymeric polycarboxylate builders are set forth in U.S. Patent 3,308,067, Diehl, issued March 7, 19 the disclosure of which is incorporated herein by reference. Such materials include the water-soluble salts of homo- and copolymers of aliphatic carboxylic acids such as maleic acid, itaconic acid, mesaconic acid, rumaric acid, aconitic acid, citraconic acid and methylenemalonic acid. Some of these materials are useful as the water-soluble anionic polymer as hereinafter described, but only if in intimate admixture with the non-soap anionic surfactant.

Other suitable polycarboxylates for use herein are the polyacetal carboxylates described in U.S. Patent 4,144,226, issued March 13, 1979 to Crutchfield et al, and U.S. Patent 4,246,495, issued March 27, 1979 to Crutchfield et al, both of which are incorporated herein by reference.

These polyacetal carboxylates can be prepared by bringing together under polymerization conditions an ester of glyoxylic acid and a polymerization initiator. The resulting polyacetal carboxylate ester is then attached to chemically stable end groups to stabilize the polyacetal carboxylate against rapid depolymerization in alkaline solution, converted to the corresponding salt, and added to a detergent composition. Particularly preferred polycarboxylate builders are the ether carboxylate builder compositions comprising a combination of tartrate monosuccinate and tartrate disuccinate described in U.S. Patent 4,663,071, Bush et al., issued May 5, 1987, the disclosure of which is incorporated herein by reference.

Bleaching agents and activators are described in U.S. Patent 4,412,934, Chung et al., issued November 1, 1983, and in U.S. Patent 4,483,781, Hartman, issued November 20, 1984, both of which are incorporated herein by reference. Chelating agents are also described in U.S. Patent 4,663,071, Bush et al., from Column 17, line 54 through Column 18, line 68, incorporated herein by reference. Suds modifiers are also optional ingredients and are described in U.S. Patents 3,933,672, issued January 20, 1976 to Bartoletta et al., and 4,136,045, issued January 23, 1979 to Gault et al., both incorporated herein by reference.

Suitable smectite clays for use herein are described in U.S. Patent 4,762,645, Tucker et al, issued August 9, 1988, Column 6, line 3 through Column 7, line 24, incorporated herein by reference. Suitable additional detergency builders for use herein are enumerated in the Baskerville patent, Column 13, line 54 through Column 16, line 16, and in U.S. Patent 4,663,071, Bush et al, issued May 5, 1987, both incorporated herein by reference.

In order to make the present invention more readily understood, reference is made to the following examples, which are intended to be illustrative only and not intended to be limiting in scope.

EXAMPLE I This Example illustrates the process of the invention which produces free flowing, crisp, high density detergent agglomerates. Several feed streams of various detergent starting ingredients are continuously fed, at a rate of 660 kg/hr, into a Lodige KM™ (Ploughshare) 600 mixer/densifier, which is a horizontally-positioned moderate speed mixer/densifier. The rotational speed of the shaft in the mixer/densifier is about 100 φm and the rotational speed of the cutters is about 3600 φm. The relative proportion of each starting detergent ingredient in the total feed stream fed into the mixer/densifier (the phrase "total feed stream" meaning the aggregate of all the individual feed streams being fed into the mixer/densifier) is presented in Table I below:

TABLE I Component % Weight of Total Feed

C45 alkyl ethoxylate sulfate (EO 0.6) 29.1

Aluminosilicate 34.4 Sodium carbonate 17.5

Polyethylene glycol (MW 4000) 1.3

Misc. (water, perfume, etc.) 16.7

100.0 The starting detergent ingredients are continuously passed through a Lodige CB 30 pre- mixer and then into a Lodige KM™ (Ploughshare) 600 mixer/densifier, their mean residence time in the mixer/densifier is about 2-3 minutes. A water binder is continuously fed into the Lodige KM™ 600 mixer/densifier to aid in the agglomeration process. The agglomerates from the mixer/densifier are dried in a conventional fluidized bed dryer after they exit the Lodige KM™ 600 mixer/densifier to obtain the high density granular detergent agglomerates produced by the process. The density of the resulting detergent agglomerates is 796 g/1 and the mean particle size is 613 microns.

EXAMPLE II This Example also illustrates the process of the invention and incorporates the parameters of Example I. Accordingly, several feed streams of various detergent starting ingredients are continuously fed, at a rate of 660 kg/hr, into a Lodige KM™ (Ploughshare) 600 mixer/densifier, which is a horizontally-positioned moderate speed mixer/densifier. The rotational speed of the shaft in the mixer/densifier is about 100 φm and the rotational speed of the cutters is about 3600 φm. The relative proportion of each starting detergent ingredient in the total feed stream fed into the mixer/densifier is presented in Table IT below:

TABLE π Component % Weight of Total ieed C45 alkyl ethoxylate sulfate (EO 0.6, 29.1

Aluminosilicate 45.0

Sodium carbonate 15.1

Polyethylene glycol (MW 4000) 1.3

Misc. (water, perfume, etc.) 2^5 100.0

While the starting detergent ingredients are continuously passed into a Lodige KM™ (Ploughshare) 600 mixer/densifier, their mean residence time in the mixer/densifier is about 2-3 minutes. A water binder is continuously fed into the Lodige KM™ 600 mixer/densifier to aid in the agglomeration process. The agglomerates from the mixer/densifier are dried in a conventional fluidized bed dryer after they exit the Lodige KM™ 600 mixer/densifier to obtain the high density granular detergent agglomerates produced by the process. The density of the resulting detergent agglomerates is 700 g/1 and a mean particle size of 550 microns.

Having thus described the invention in detail, it will be obvious to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is described in the specification.

Claims

What is Claimed is

1 A process for continuously preparing high density detergent agglomerates characterized by the steps of

(a) continuously mixing into a moderate speed mixer/densifier. 5 (i) from 25% to 50% of a detergent surfactant,

(ii) from 20% to 50% of an aluminosilicate builder, and (iii) from 10% to 40% of an powdered material, wherein the ratio of said builder to said powdered material is from 1 : 1 to 3.5: 1, said moderate speed mixer/densifier is operated such that agglomerates having a density of at least 650 g/1 lυ are produced, and

(b) drying said agglomerates to obtain said high density detergent agglomerates

2. A process according to claim 1 wherein the mean residence time of said

15 detergent surfactant, said builder and said powdered material in said mixer/densifier is in range from 0.5 minutes to 15 minutes.

3. A process according to any of claims 1-2 further characterizing the step of continuously spraying a binder material into said mixer/densifier.

20

4. A process according to any of claims 1-3 wherein said binder is selected from the group characterized by water, anionic surfactants, nonionic surfactants, polyethylene glycol, polyvinyl pyrrolidone, polyacrylates, citric acid and mixtures thereof.

25

5. A process according to any of claims 1-4 wherein said mixing step is further characterized by mixing a crystalline layered silicate builder in said mixer/densifier.

6. A process according to any of claims 1-5 wherein said powdered material is 30 sodium carbonate.

7. A process according to any of claims 1-6 further characterized by the step of adding a coating agent in said moderate speed mixer/densifier to enhance free flowability of said agglomerates. 35

8 A process according to any of claims 1-7 wherein said detergent surfactant is alkyl ethoxylate sulfate in the form of an aqueous paste having a viscosity of from 5,000 cps to 100,000 cps

9. A process according to any of claims 1-8 wherein said detergent surfactant is selected from the group characterized by anionic, nonionic, zwitterionic, ampholytic and cationic surfactants and mixtures thereof.

10. A process according to any of claims 1-9 wherein said detergent surfactant is secondary (2,3) alkyl sulfate