CN1116402C - Preparation of Silica-Containing Low Density Detergent Agglomerates - Google Patents

Abstract

A process for continuously producing low density detergent agglomerates is provided. The method comprises the following steps: agglomerating a detergent surfactant paste and dry starting detergent material in a high speed mixer to obtain detergent agglomerates, wherein the dry starting detergent material comprises silica material; and (b) drying the detergent agglomerates to form a detergent composition having a density of less than about 500 g/l.

Description

Preparation of Silica-Containing Low Density Detergent Agglomerates

field of invention

The present invention generally relates to a process for the preparation of low density detergent compositions. More specifically, the present invention relates to the preparation of low density detergent agglomerates by feeding a surfactant slurry and dry detergent starting material comprising silica material into a high speed mixer followed by a drying unit Methods. The process produces a free-flowing, low-density detergent composition that can be sold commercially as a conventional non-compacted detergent composition or used as an admixture in a low-volume, "compacted" detergent product .

Background of the invention

Recently, there has been considerable interest in laundry detergents which are "compact" and thus have low dosage volumes in the detergent industry. In order to facilitate the production of these so called low usage detergents, much effort has been made to prepare high bulk density detergents eg with a density of 600 g/l or more. This low-use detergent is currently in great demand as it saves resources and can be sold in small packages, which is more convenient for consumers. However, the extent to which modern detergent products need to be "compact" in nature remains unresolved. In fact, many consumers, especially in developing countries, still prefer higher usage levels in their respective laundering operations. Thus, within the technical field of production of modern detergent compositions there is a need for flexibility in the final density of the final composition.

Generally, there are two main types of methods of making detergent granules or powders. The first type of process involves spray drying an aqueous detergent slurry in a spray drying tower to produce highly porous detergent granules. In the second type of process, the various detergent ingredients are dry blended after agglomeration using a binder such as a nonionic or anionic surfactant. In both types of processes, the most important factors controlling the density of the resulting detergent granules are the density, shape, porosity and surface area of the various starting materials and their respective chemical compositions. However, these parameters are varied only within limited limits. Thus, substantial bulk density flexibility can only be achieved through additional processing steps that result in a lower density of the detergent granules.

Numerous efforts have been made in the art to provide means of increasing the density of detergent granules or powders. Particular attention has been paid to the densification of spray-dried granules by post tower treatment. For example, one attempt involved a batch process of densifying and pelletizing spray-dried or granulated detergent powders containing sodium tripolyphosphate and sodium sulfate in a Marumerizer(R). The apparatus comprises a substantially horizontal, roughened, rotatable table disposed at the bottom of a substantially vertical, smooth-walled cylinder. However, this process is primarily a batch process and thus not very suitable for large-scale production of detergent powders. More recently, other attempts have been made to provide a continuous process for increasing the density of "back tower" or spray dried detergent granules. These methods generally require a first means to grind or grind the particles and a second means to increase the density of the ground particles by agglomeration. These methods, while treating or densifying the "back tower" or spray-dried granules to achieve the desired density increase, do not provide a method with the flexibility to provide lower density granules.

Furthermore, all of the above methods primarily involve densification or otherwise processing of the spray-dried granules. Currently, there are limitations on the relative amounts and types of raw materials that can be subjected to the spray drying process in the production of detergent granules. For example, it has been difficult to achieve high levels of surfactants in the resulting detergent compositions, a feature that would encourage detergents to be produced in a more efficient manner. Thus, it would be desirable to have a process by which detergent compositions can be prepared without the constraints imposed by conventional spray drying techniques.

For this reason, the art is also replete with disclosures of methods of agglomerating detergent compositions. For example, many attempts have been made to agglomerate detergent builders by mixing zeolites and/or layered silicates in a mixer to form free-flowing agglomerates. While these attempts suggest that their methods can be used to prepare detergent agglomerates, they fail to provide that starting detergent materials in the form of pastes, liquids, and dry materials can be efficiently agglomerated into crisp, free-flowing, low- Mechanism of density of detergent agglomerates.

Thus, there remains a need in the art for a process for the continuous production of a low density detergent composition directly from starting detergent ingredients. Furthermore, there is a need for such methods to be more efficient, flexible and economical for large scale production of low and high usage detergents.

Background technique

The following references relate to densified spray-dried granules: Appel et al., U.S. Patent 5,133,924 (Lever); Appel et al., U.S. Patent 5,164,108 (Lever); Bortolotti et al., U.S. Patent 5,160,657 (Lever); Johnson et al., UK Patent 1,517,713 (Unilever); and European Patent Application 451,894 by Curtis. The following references relate to the preparation of detergents by agglomeration: Beerse et al. U.S. Patent 5,108,646 (Procter &Gamble); Capeci et al. U.S. Patent 5,366,652 (Procter &Gamble); Hollingsworth et al. European Patent Application 351,937 (Unilever); and Swatling US Patent 5,205,958 to et al.

Summary of the invention

The present invention fulfills the aforementioned need in the art by providing a process for the preparation of low density (less than about 500 g/l) detergent compositions directly from starting components such as surfactant pastes and dry detergent components . The dry component comprises silica material which is ultimately agglomerated such that it forms part of or is within the agglomerate particle itself rather than "coating" on the outer surface of the agglomerate. Surprisingly, this provides a low density agglomerate composition with improved physical properties. The method does not use the conventional spray-drying towers in use today and is therefore more efficient, economical and flexible with respect to the variety of detergent compositions which can be prepared by the method. Furthermore, the method is more environmentally friendly because it does not use a spray drying tower, which typically emits particulates and volatile organic compounds into the atmosphere.

As used herein, the term "agglomerate" refers to particles formed by agglomerating detergent particles having an average particle size generally smaller than the agglomerates formed. All percentages used herein are expressed as "% by weight" unless otherwise specified. All viscosities described herein are measured at 70°C at a shear rate of about 10 to 50 sec ^-1 , preferably 25 sec ^-1 . All documents cited herein are hereby incorporated by reference.

According to one aspect of the present invention there is provided a process for the preparation of low density detergent agglomerates having a density of less than about 500 g/l. The method comprises the steps of: (a) agglomerating detergent surfactant slurry and dry starting detergent material in a high speed mixer to obtain detergent agglomerates, wherein the dry starting detergent material comprises dioxide a silicon material; and (b) drying the detergent agglomerates to form a detergent composition having a density of less than about 500 g/l.

In another aspect of the present invention, there is provided another process for the preparation of low density detergent agglomerates having a density of less than about 500 g/l. The method comprises the steps of: (a) agglomerating a detergent surfactant slurry and dry starting detergent material in a high speed mixer to obtain detergent agglomerates, wherein the dry starting detergent material comprises fumed silica material; (b) mixing the detergent agglomerates in a medium speed mixer to further agglomerate the detergent agglomerates; and (c) drying the detergent agglomerates to form densities less than A low density detergent composition of about 500 g/l. Also provided is a low density detergent composition prepared by any of the method embodiments described herein.

It is thus an object of the present invention to provide a process for the continuous preparation of low density detergent compositions directly from starting detergent ingredients. Yet another object of the present invention is to provide a more efficient, flexible and economical process for large scale production of low and high volume detergents. These and other objects, features and attendant advantages of the present invention will be apparent to those skilled in the art from a reading of the following detailed description of the preferred embodiments and the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention relates to a process for the preparation of free flowing low density detergent agglomerates having a density of less than about 500 g/l, preferably from about 350 g/l to about 500 g/l. The process prepares low density detergent agglomerates from a highly viscous surfactant slurry having a relatively high water content, typically at least about 10%. In general, the process of the invention is used in the production of normal detergents as opposed to low usage detergents, whereby the resulting detergent agglomerates can be used as detergents or as detergent additives. It should be understood that the methods described herein can be continuous or batch, depending on the desired application.

method

In the first step of the process, the starting detergent material is fed into a mixer for agglomeration. In order to obtain the desired density below 500 g/l, the agglomeration step is carried out initially in a high speed mixer, optionally followed by an optional medium speed mixer if further agglomeration is desired. The starting detergent material preferably comprises a highly viscous surfactant paste and dry detergent material, the components of which are more fully described hereinafter. The starting detergent material is agglomerated in the presence of a silica material as described more fully below to produce agglomerated particles having the desired low density. To this end, the process preferably mixes from about 1% to about 20%, more preferably from about 3% to about 10%, most preferably from about 3% to about 5%, by weight of the silica material into the high speed mixer. As detailed hereinafter, the nature and composition of the added or starting detergent materials and optional additive ingredients may vary.

It has been surprisingly found that by including silica in the agglomerates, rather than using it as a coating agent, low density agglomerates can be formed. This is contrary to what was expected since using silica as a coating or release agent to deposit it on the outer surface of the agglomerate particles will increase or increase the density. However, as demonstrated by the present process invention, the silica within the agglomerate particles reduces the density, which is desirable for making low density agglomerated compositions. While not wishing to be bound by theory, it is believed that silica, when subjected to agglomeration with surfactant and subsequent drying step, forms hollow "finger-like" structures within individual agglomerate particles, thereby increasing the The internal void space in the particle. Of course, this results in looser agglomerates with relatively low density.

Other essential steps in the process include, if optionally used, the step of drying the agglomerates exiting the high speed mixer or the medium speed mixer. This can be accomplished with a variety of devices including, but not limited to, fluid bed dryers. The drying step enhances the free-flowing properties of the agglomerates and promotes the "loose" or "loose" physical characteristics of the resulting agglomerates. Therefore, sufficient drying is necessary to obtain the desired low density agglomerates. In this regard, the drying temperature in whichever drying device is used is preferably from about 50°C to about 300°C, more preferably from about 80°C to about 250°C, most preferably from about 100°C to about 250°C.

Preferably, the average residence time of the starting detergent material in a high speed mixer (e.g., Lodige Recycler CB30 or other similar equipment) is from about 2 to 45 seconds, and in an optional low or medium speed mixer (e.g., Lodige The residence time in the Recycler KM 300 "Ploughshare" or other similar equipment) is about 0.5 to 15 minutes.

Detergent agglomerates prepared by the present process preferably have a surfactant content of from about 20% to about 55%, more preferably from about 35% to about 55%, most preferably from about 45% to about 55%. The resulting detergent agglomerates prepared according to the process of the present invention preferably have a particle porosity of from about 5% to about 50%, more preferably about 25%. Additionally, one characteristic of densified or densified agglomerates is relative particle size. The average particle size of the detergent agglomerates provided by the present process is generally from about 250 microns to about 1000 microns, more preferably from about 400 microns to about 600 microns. The phrase "average particle size" as used herein refers to individual agglomerates rather than individual particles or detergent granules. The above combination of porosity and particle size results in agglomerates having density values below 500 g/l. This feature is particularly useful in the production of laundry detergents with varying usage levels, as well as other granular compositions such as dishwashing compositions.

optional method steps

In an optional step of the process, the detergent agglomerates exiting the fluid bed dryer are further conditioned by cooling the agglomerates in a fluid bed cooler or similar device well known in the art. Another optional process step includes adding a coating agent to improve flow and/or minimize over-agglomeration of the detergent composition at one or more of the following locations of the process: (1) The coating agent can be added at Add directly behind the fluidized bed cooler; (2) The coating agent can be added between the fluidized bed dryer and the fluidized bed cooler; (3) The coating agent can be added between the fluidized bed dryer and the medium speed mixer and/or (4) The coating agent can be added directly to the medium speed mixer and fluidized bed. The coating agent is preferably selected from aluminosilicates, silicates, carbonates and mixtures thereof. The coating agent not only enhances the free-flowing properties of the resulting detergent composition, which is desired by consumers because it allows easy scooping of the detergent during use, but also serves to control Agglomeration, especially when added directly to the optional medium speed mixer. As known to those skilled in the art, over-agglomeration can lead to very undesirable flow properties and aesthetics of the final detergent product.

Optionally, the method may include the step of spraying an additional binder into either or both of the mixer or fluid bed dryer. Binders are added to enhance agglomeration by providing a "binding" or "sticking" agent to the detergent ingredients. The binder is preferably selected from water, anionic surfactants, nonionic surfactants, polyethylene glycol, polyvinylpyrrolidone, polyacrylates, citric acid and mixtures thereof. Other suitable adhesive materials, including those listed here, are described in U.S. Patent 5,108,646 (Procter & Gamble Company) to Beerse et al., the disclosure of which is incorporated herein by reference.

Other optional steps contemplated by the process include screening oversized detergent agglomerates in a screening device which may take various forms including, but not limited to, those required for finished detergent products. Regular sieves selected for particle size. Other optional steps include conditioning the detergent agglomerates by subjecting the agglomerates to additional drying in one of the drying units described above.

Other optional steps in the process include recycling oversized and undersized agglomerates as described in Capeci et al., U.S. Patent Nos. 5,489,392 and 5,516,448 (Procter & Gamble). Also, as described in Capeci et al., U.S. Patent Nos. 5,366,652 and 5,486,303 (Procter & Gamble), steps involving anhydrous materials are added at selected points in the process. Optionally, the agglomerates exiting the moderate speed mixer can be dried using a spray drying tower as described in Capeci et al., U.S. Patent 5,496,487 (Procter & Gamble).

Another optional step of the process is conditioning the resulting detergent agglomerates by various means including spraying and/or admixing other conventional detergent ingredients. For example, the finishing step includes spraying fragrances, brighteners and enzymes onto the finished agglomerate to obtain a more finished detergent composition. These techniques and components are well known in the art.

Detergent Surfactant Paste

The detergent surfactant paste used in the present process is preferably in the form of an aqueous viscous paste, although other forms are also contemplated by the present invention. Such so-called viscous surfactant pastes have a viscosity of from about 5000 cps to about 100000 cps, more preferably from about 10000 cps to about 80000 cps, and contain at least about 10% water, more preferably at least about 20% water. Viscosity is measured at 70°C and a shear rate of about 10-100 sec ^-1 . Furthermore, the surfactant paste, if used, preferably contains the previously specified amount of detersive surfactant and a balance of water and other conventional detergent ingredients.

The surfactant itself in the viscous surfactant paste is preferably selected from anionic, nonionic, zwitterionic, amphoteric and cationic surfactants and compatible mixtures thereof . Detergent surfactants useful in the present invention are described in U.S. Patent 3,664,961, Norris, issued May 23, 1972, and U.S. Patent 3,919,678, Laughlin et al., issued December 30, 1975, both of which are incorporated herein as refer to. Useful cationic surfactants also include those described in US Patent 4,222,905, Cockrell, issued September 16, 1980, and US Patent 4,239,659, Murphy, issued December 16, 1980, both of which are incorporated herein by reference. Of these surfactants, anionic surfactants and nonionic surfactants are preferred, and anionic surfactants are most preferred.

Non-limiting examples of preferred anionic surfactants useful in surfactant pastes include conventional C ₁₁ -C ₁₈ alkylbenzene sulfonates ("LAS"), primary branched and random C ₁₀ -C ₂₀ Alkyl sulfate (“AS”), C ₁₀ of the formula CH ₃ (CH ₂ ) _x (CHOSO ₃ ⁻ M ⁺ ) CH ₃ and CH ₃ (CH ₂ ) _y (CHOSO ₃ ⁻ M ⁺ ) CH ₂ CH ₃ -C ₁₈ secondary (2,3) alkyl sulfate, wherein 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, and C ₁₀ -C ₁₈ alkyl alkoxy sulfates ("AE _x S"; especially EO 1-7 ethoxy sulfates).

Optionally, other exemplary surfactants useful in the slurries of the present invention include C ₁₀ -C ₁₈ alkyl alkoxy carboxylates (especially EO 1-5 ethoxy carboxylates), C ₁₀ - C ₁₈ glyceryl ethers, C ₁₀ -C ₁₈ alkyl polyglycosides and their corresponding sulfated polyglycosides, and C ₁₂ -C ₁₈ α-sulfonated fatty acid esters. If desired, conventional nonionic and amphoteric surfactants such as C ₁₂ -C ₁₈ alkyl ethoxylates ("AE ”) and C ₆ -C ₁₂ alkylphenol alkoxylates (especially ethoxylates and mixed ethoxy/propoxy), C ₁₂ -C ₁₈ betaines and sultaines, C ₁₀ - C ₁₈ amine oxides and more. C ₁₀ -C ₁₈ N-alkyl polyhydroxy fatty acid amides are also useful. Typical examples include C ₁₂ -C ₁₈ N-methyl glucamides. See WO 9,206,154. Other sugar-derived surfactants include N-alkoxy polyhydroxy fatty acid amides such as C ₁₀ -C ₁₈ N-(3-methoxypropyl) glucamide. N-propyl to N-hexyl C ₁₂ -C ₁₈ glucamides are available for low sudsing. C ₁₀ -C ₂₀ conventional soaps can also be used. If high sudsing is desired, branched C ₁₀ -C ₁₆ soaps can be used. Mixtures of anionic and nonionic surfactants are especially useful. Other conventionally useful surfactants are listed in standard textbooks.

dry detergent material

The starting dry detergent material of the process preferably comprises a silica material. Silica is a highly dispersed amorphous silica that is commercially available in many forms. The bulk density of the silica is most typically from 50 g/l to 120 g/l. The specific surface area of the particles ranges from 25 m2/g to 800 m2/g. The surface of silica particles can be chemically modified to change their properties with respect to water. For example, silica particles can be treated with organosilanes to render the particles primarily hydrophobic. Silicas that are hydrophobic in nature have been found to work extremely well in the present method invention; however, hydrophilic silicas are also useful in the present method. Additionally, diatomaceous earth materials may be used in combination with or as a substitute for the silica mentioned herein.

Silica is typically prepared industrially by one of two techniques: either by precipitation (ie, precipitated silica) or by high temperature flame hydrolysis (ie, fumed silica). Both precipitated silica and fumed silica are useful in the present process invention. Precipitated silicas typically have agglomerate sizes ranging from 3 microns to 100 microns, while fumed silicas prepared by flame hydrolysis typically have particles that are substantially spherical and have an average particle size ranging from about 7 nanometers to about 40 nanometers. Fumed silicas having an average particle size of from about 7 nanometers to about 25 nanometers are preferred herein. Exemplary commercially available silicas useful in the present method invention include those supplied by Degussa AG (Germany) known as Aerosil ^™ , Aerosil ^™ R927 being particularly preferred. Most preferred are hydrophobic, fumed silicas having a surface area of at least about 110 square meters per gram and an average particle size of 16 nanometers.

Dry detergent materials also preferably include an aluminosilicate detergent builder known as aluminosilicate ion exchange material. The aluminosilicate ion exchange materials useful herein as detergent builders preferably have a high calcium ion exchange capacity and a high exchange rate. Without being bound by theory, it is believed that this high calcium ion exchange rate and capacity is a function of several interrelated factors resulting from the method of producing the aluminosilicate ion exchange material. In that regard, the aluminosilicate ion exchange materials used herein are preferably prepared according to Corkill et al., U.S. Patent 4,605,509 (Procter & Gamble), the disclosure of which is incorporated herein by reference.

Preferably, the aluminosilicate ion exchange material is in the "sodium" form, since the potassium and hydrogen forms of this aluminosilicate exhibit exchange rates and capacities not as high as those provided by the sodium form. Additionally, to facilitate the production of the crisp detergent agglomerates described herein, the aluminosilicate ion exchange material is preferably in an overdried form. The aluminosilicate ion exchange materials used herein preferably have a particle size that optimizes their effectiveness as detergent builders. The term "particle size" as used herein means the average particle size of a given aluminosilicate ion exchange material as determined by conventional analytical techniques such as microscopic measurements and scanning electron microscopy (SEM). The preferred particle size 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 is from about 1 micron to about 8 microns.

Preferably, the aluminosilicate ion exchange material has the formula

Na _z [(AlO ₂ ) _z ·(SiO ₂ ) _y ]xH ₂ O 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

Na ₁₂ [(AlO ₂ ) ₁₂ ·(SiO ₂ ) ₁₂ ]xH ₂ O, wherein x is about 20 to about 30, preferably about 27. These preferred aluminosilicates are available commercially, for example under the names Zeolite A, Zeolite B and Zeolite X. Alternatively, naturally occurring or synthetically derived aluminosilicate ion exchange materials useful herein can be prepared as described in Krummel et al., US Patent 3,985,669, the disclosure of which is incorporated herein by reference.

The aluminosilicates used herein are also characterized by their ion exchange capacity on an anhydrous basis of at least about 200 meq _CaCO hardness per gram, and preferably between about 300 and 352 meq _CaCO hardness/gram. gram. In addition, the aluminosilicate ion exchange materials are further characterized in that they have a calcium ion exchange rate of at least about 2 grains Ca ⁺⁺ /gallon/min/- grams/gallon, more preferably about 2 grains Ca ^{++ +} /gallon/min/-gram/gallon ~ about 6 grains Ca ⁺⁺ /gallon/min/-gram/gallon.

One particularly preferred group of dry detergent materials is selected from the group consisting of aluminosilicates, crystalline layered silicates, sodium carbonate and mixtures thereof.

detergent additive components

The starting dry detergent material in the process may include additional detergent components, and/or any of these additional components may be incorporated into the detergent composition in subsequent steps of the process. These additive components include other builders, bleaches, bleach activators, suds boosters or suds suppressors, antitarnish and preservatives, soil suspending agents, soil release agents, bactericides, pH regulators, non-builders Lotion Alkaline Source, Chelating Agent, Smectite Clay, Enzyme, Enzyme Stabilizer and Perfume. See US Patent 3,936,537, issued February 3, 1976 to Baskerville, Jr. et al., incorporated herein by reference.

Other builders may generally be selected from various water-soluble alkali metal, ammonium or substituted ammonium phosphates, polyphosphates, phosphonates, polyphosphonates, carbonates, borates, polyhydroxysulfonates , polyacetates, carboxylates and polycarboxylates. Alkali metal salts, especially sodium salts, of the aforementioned substances are preferred. Preferred for use herein are phosphates, carbonates, _C10-18 fatty acids, polycarboxylates and mixtures thereof. More preferred are sodium tripolyphosphate, tetrasodium pyrophosphate, citrates, tartrate mono- and disuccinates and mixtures thereof (see below).

Compared with amorphous sodium silicate, crystalline layered sodium silicate shows significantly enhanced calcium and magnesium ion exchange capacity. In addition, layered sodium silicates favor magnesium ions over calcium ions, a property that is necessary to ensure that substantially all "hardness" is removed from the wash water. However, these crystalline layered sodium silicates are generally more expensive than amorphous silicates and other builders. Therefore, in order to provide an economically viable laundry detergent, the proportion of crystalline layered sodium silicate used must be properly determined.

Crystalline layered sodium silicates suitable for use herein preferably have the formula

_{NaMSixO2x + 1.yH2O} 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

NaMSi ₂ O ₅ .yH ₂ O wherein M is sodium or hydrogen, and y is about 0 to about 20. These and other crystalline layered sodium silicates are described in US Patent 4,605,509 to Corkill et al., previously incorporated herein by reference.

Specific examples of inorganic phosphate builders are sodium and potassium tripolyphosphates, pyrophosphates, polymeric metaphosphates having a degree of polymerization of about 6-21, 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-1,1-diphosphonic acid, ethane-1,1, Sodium and potassium salts of 2-triphosphonic acid. Other phosphorus builder compounds are disclosed in US Patent Nos. 3,159,581; 3,213,030; 3,422,021; 3,422,137; 3,400,176 and 3,400,148, all incorporated herein by reference.

Examples of non-phosphorous inorganic builders are tetraborate decahydrate and silicates having a weight ratio of _SiO2 to alkali metal oxide of from about 0.5 to about 4.0, preferably from about 1.0 to about 2.4. Water-soluble non-phosphorus organic builders suitable for use herein include the various alkali metal, ammonium and substituted ammonium polyacetates, carboxylates, polycarboxylates and polyhydroxy sulfonates. Examples of polyacetate and polycarboxylate builders are sodium, potassium, lithium, ethylenediaminetetraacetic acid, nitrilotriacetic acid, oxydisuccinic acid, mellitic acid, benzene polycarboxylic acid and citric acid. , ammonium and substituted ammonium salts.

Polymeric polycarboxylate builders are set forth in US Patent 3,308,067, Diehl, issued March 7, 1967, the disclosure of which is incorporated herein by reference. These materials include the water-soluble salts of homopolymers and copolymers of aliphatic carboxylic acids such as maleic, itaconic, mesaconic, fumaric, aconitic, citraconic and methylenemalonic acids. Some of these materials are useful as the water-soluble anionic polymers described below, but only in intimate blends with non-soap anionic surfactants.

Other suitable polycarboxylates for use in the present invention are the polyacetal carboxylates described in U.S. Patent 4,144,226, Crutchfield et al., issued March 13, 1979, and Crutchfield et al., issued March 27, 1979. in US Patent 4,246,495, 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. Then, the resulting polyacetal carboxylate is attached to a chemically stable end group to stabilize the polyacetal carboxylate so as not to depolymerize rapidly in an alkaline solution, convert it into the corresponding salt, and add to in detergent compositions. Particularly preferred polycarboxylate builders are ether carboxylate builder compositions comprising a mixture of tartrate monosuccinate and tartrate disuccinate described in Bush et al., issued May 5, 1987. in US Patent 4,663,071, the disclosure of which is incorporated herein by reference.

Bleach and activators are described in US Patent 4,412,934, Chung et al., issued November 1, 1983, and US Patent 4,483,781, Hartman, issued November 20, 1984, both of which are incorporated herein by reference. Chelating agents are also described in US Patent 4,663,071 to Bush et al. at column 17, line 54 through column 18, line 68, incorporated herein by reference. Foam regulators are also optional components and are described in U.S. Patent 3,933,672, issued January 20, 1976 to Bartoletta et al., and in U.S. Patent 4,136,045, issued January 23, 1979 to Gault et al., incorporated herein Both are used as reference.

Smectite clays suitable for use herein are described in US Patent 4,762,645, Tucker et al., issued August 9, 1988, column 6, line 3 through column 7, line 24, incorporated herein by reference. Additional detergent builders suitable for use herein are listed in the Baskerville patent at Column 13, line 54 through Column 16, line 16, and in U.S. Patent 4,663,071 to Bush et al., issued May 5, 1987, incorporated herein by two or as a reference.

In order that the present invention may be more readily understood, reference is made to the following examples, which are given by way of illustration and not limitation of scope.

Example I-IV

These examples illustrate a batchwise embodiment of the process of the invention. Low density agglomerated detergent compositions were prepared using a laboratory tilt-a-pin mixer (commercially available from Processall). A kind of powder mixture is first loaded into the mixer, i.e. sodium carbonate (made through an air classifier mill (Air Classifier Mill) with an average particle size of 5-40 microns), light-density granular sodium tripolyphosphate (commercially produced by FMC Corporation) provided, referred to as "STPP" in the present invention), type A zeolite (commercially provided by Ethyl Corporation, hereinafter referred to as "zeolite A"), and fumed silica (provided by Cabot Corporation under the trade name M-5 Cab- o-sil ^™ commercially available), except that Example IV did not use these or any fumed silica materials. A surfactant slurry containing sodium linear alkylbenzene sulfonate (referred to herein as "LAS") surfactant (75% by weight) and a balance of water was then added to the powder mixture while the mixer was operating at 700 rpm For about 15 seconds, until discrete granules form in the mixer. The composition of the agglomerates formed is described in Table I below.

Table I

(% by weight) Component I II III LAS 30.0 30.0 30.0 Sodium carbonate (soda ash) 36.0 36.0 34.0 STPP 29.0 29.0 29.0 Zeolite A 2.0 0.0 0.0 Fumed silica 3.0 5.0 7.0

                                                                                                                     

Unexpectedly, the bulk density of the resulting agglomerates of Examples I, II and II was lower than 500 g/l, all of which were produced by a process involving silica within the scope of the present process invention .

Having thus described the invention in detail, it will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention, and the invention should not be construed as being limited to the description in this specification.

Claims (11)

1. A method for preparing a low-density detergent composition, comprising the steps of: (a) agglomerating a detergent surfactant slurry having a viscosity of 5,000-100,000 cps and at least 10% water and dry starting detergent material in a high speed mixer to obtain detergent agglomerates, wherein said dry starting detergent material comprises silica material; and (b) drying said detergent agglomerates to form said detergent composition having a density of less than about 500 g/l. 2. The method according to claim 1, wherein said detergent composition has a density of about 350 g/l to about 500 g/l 3. The method of claim 1 wherein said dry starting material comprises a builder selected from the group consisting of aluminosilicates, crystalline layered silicates, sodium carbonate and mixtures thereof. 4. The method of claim 1, wherein said silica material is fumed silica. 5. The method of claim 1, wherein said silica material is hydrophobic silica. 6. The method according to claim 1, wherein said silica material is hydrophilic silica. 7. The method according to claim 1, wherein said surfactant slurry has a viscosity of from about 5,000 cps to about 100,000 cps. 8. The method of claim 1 wherein said silica material is precipitated silica. 9. The method according to claim 1, further comprising mixing said detergent agglomerates to further agglomerate said detergent agglomerates after said agglomerating step and before said drying step in a moderate speed mixer. Steps for detergent agglomerates. 10. The method of claim 1, wherein said dry starting material comprises diatomaceous earth material. 11. A method of preparing a low density detergent composition comprising the steps of: (a) agglomerating a detergent surfactant slurry having a viscosity of 5,000-100,000 cps and at least 10% water and dry starting detergent material in a high speed mixer to obtain detergent agglomerates, wherein the dry starting detergent material comprises a fumed silica material; (b) mixing said detergent agglomerates in a medium speed mixer to further agglomerate said detergent agglomerates; and (c) drying said detergent agglomerates to form said low density detergent composition having a density of less than about 500 g/l.