WO2004022694A1

WO2004022694A1 - Detergent particles

Info

Publication number: WO2004022694A1
Application number: PCT/JP2003/011183
Authority: WO
Inventors: Yoshinobu Imaizumi; Hiroyuki Yamashita
Original assignee: Kao Corporation
Priority date: 2002-09-06
Filing date: 2003-09-02
Publication date: 2004-03-18
Also published as: AU2003265174A1; JP2004099699A

Abstract

Detergent particles comprising a particle obtained by the step of dryneutralizing base particles comprising a water-soluble solid alkali inorganic substance (A) with a liquid acid precursor (B) of a non-soap anionic surfactant, wherein the non-soap anionic surfactant is used in an amount of 15% by weight or more of the base particles; and a fluidizing aid (C) existing on a surface of the particle, wherein the detergent particles have a 60-second dissolution ratio of 90% or more, an average particle size of from 150 to 500 µm and a bulk density of 600 g/L or less; a process for preparing detergent particles comprising the steps of (a) preparing a slurry comprising a water-soluble solid alkali inorganic substance (A), wherein the water-soluble solid alkali inorganic substance (A) is present in an amount equal to or greater than an amount equivalent for neutralizing a liquid acid precursor (B) of a non-soap anionic surfactant to be added in step (c); (b) spray-drying the slurry obtained in step (a) to give base particles; (c) adding to the base particles obtained in step (b) the liquid acid precursor (B) in an amount of 15% by weight or more of the base particles, mixing and dry-neutralizing the resulting mixture; and (d) adding a fluidizing aid (C) to the particle obtained in step (c), thereby surface-modifying the particle; and a detergent composition comprising the detergent particles as defined above. The detergent particles can be used for washing laundry items and the like.

Description

DESCRIPTION

DETERGENT PARTICLES

TECHNICAL FIELD

The present invention relates to detergent particles having medium to low bulk densities, a process for preparing the detergent particles, and a detergent composition comprising the detergent particles. More specifically, the present invention relates to detergent particles used for washing laundry items and the like, a process for preparing the detergent particles, and a detergent composition comprising the detergent particles.

BACKGROUND ART

Currently, marketed detergents can be roughly classified into high-bulk density detergents (600 g/L or more), medium- to low-bulk density detergents

(300-600 g/L), liquid detergents and the like. For instance, while high-bulk density detergents have been widely used in Japan, low- to medium-bulk density detergents have been in great demands in Asian, Oceanian and European regions. On the other hand, fast dissolubility and flowability properties are the functions required for detergents. As to the fast dissolubility, by quickly dissolving the detergent after supplying the detergent into water, the insoluble remnants or residues on clothes can be reduced, and at the same time the detergency of the composition of the detergent can be sufficiently exhibited. As to the flowability properties, by remarkably improving the powder properties of the detergent composition, there are some effects of improving user's texture and convenience of user when the detergent is used with a measuring device such as a spoon.

A dissolution ratio after 60 seconds from supplying the detergent into water at 5°C, which serves as an index for fast dissolubility, and a variance of powder dropping rate, which serves as an index for flowability properties are determined on currently marketed representative medium- to low-bulk density detergents according to the methods described in the present specification. As a result, there have not been found any medium- to low-bulk density detergents satisfying both fast dissolubility and flowability properties. As a process satisfying these functions, there has been known, for instance, a method for preparing detergent particles comprising supporting a surfactant to a spray-dried base particle, to give detergent particles comprising a detergent particle, capable of releasing a bubble of a size of one-tenth or more of the particle size from the inner portion of the particle (Japanese Patent No. 3123757 (U.S. Patent No. 6,376,453)). However, this technique is essentially a process comprising penetrating a surfactant into a base particle, and supporting the surfactant to the inner portion of the base particle to give a high-bulk density detergent, and the process is not suitable for producing a low- to medium-bulk density detergent. In addition, in order to facilitate the penetration of the surfactant into the base particle, a surfactant which is liquid at an ambient temperature is formulated in a large amount. Therefore, various high-level contrivances are necessary for completely suppressing bleed-out of the surfactant or caking.

An object of the present invention is to provide detergent particles having excellent storage stability, fast dissolubility and flowability properties, a process for preparing the detergent particles, and a detergent composition comprising the detergent particles.

These and other objects of the present invention will be apparent from the following description.

DISCLOSURE OF INVENTION

Accordingly, there are provided: [1] detergent particles comprising: a particle obtained by the step of dry-neutralizing base particles comprising a water-soluble solid alkali inorganic substance (A) with a liquid acid precursor (B) of a non-soap anionic surfactant, wherein the non-soap anionic surfactant is used in an amount of 15% by weight or more of the base particles; and a fluidizing aid (C) existing on a surface of the particle, wherein the detergent particles have a 60-second dissolution ratio of 90% or more, an average particle size of from 150 to 500 μm and a bulk density of 600 g/L or less;

[2] a process for preparing detergent particles comprising the steps of: (a): preparing a slurry comprising a water-soluble solid alkali inorganic substance (A), wherein the water-soluble solid alkali inorganic substance

(A) is present in an amount equal to or greater than an amount equivalent for neutralizing a liquid acid precursor (B) of a non-soap anionic surfactant to be added in step (c); (b): spray-drying the slurry obtained in step (a) to give base particles; (c): adding to the base particles obtained in step (b) the liquid acid precursor (B) in an amount of 15% by weight or more of the base particles, mixing and dry-neutralizing the resulting mixture; and (d): adding a fluidizing aid (C) to the particle obtained in step (c), thereby surface-modifying the particle; and [3] a detergent composition comprising the detergent particles as defined in the above [1].

BEST MODE FOR CARRYING OUT THE INVENTION

The detergent particles of the present invention, as described above, are detergent particles comprising: a particle obtained by the step of dry-neutralizing base particles comprising a water-soluble solid alkali inorganic substance (A) with a liquid acid precursor (B) of a non-soap anionic surfactant, wherein the non-soap anionic surfactant is used in an amount of 15% by weight or more of the base particles; and a fluidizing aid (C) existing on a surface of the particle, wherein the detergent particles have a 60-second dissolution ratio of 90% or more, an average particle size of from 150 to 500 μm and a bulk density of 600 g/L or less. In the present invention, the liquid acid precursor (B) of a non-soap anionic surfactant is reacted with the base particle comprising the component (A), which is a water-soluble alkalizing agent, so that the non-soap anionic surfactant is produced on the surface of the base particle, whereby the suppression of penetration of the surfactant into the inner portion of the particle can be achieved. By surface-modifying the resulting particle with a fluidizing aid, there is exhibited an effect that a medium- to low-bulk density detergent having excellent storage stability, fast dissolubility and flowability properties.

In addition, since the component (B) is added to the base particles in an amount of 15% by weight or more, the non-soap anionic surfactant produced by the above reaction can coat the surface of the base particle. Therefore, there are exhibited some excellent effects that not only an increase in the bulk density is suppressed but also the stability during storage such as bleed-out or caking is dramatically improved.

The term "detergent particle" in the present invention refers to a particle comprising a base particle, a surfactant and a builder and the like, and the term

"detergent particles" means an aggregate thereof. Also, the detergent composition means a composition comprising the detergent particles and separately added deterging components other than the detergent particles, such as fluorescers, enzymes, perfumes, defoaming agents, bleaching agents and bleaching activators.

< Composition for Base Particles >

The "base particle" constituting the detergent particle contained in the detergent particles of the present invention comprises the component (A), which is used for dry-neutralizing with the component (B), and the base particle is a particle obtained by spray-drying. An aggregate thereof is referred to as "base particles."

1. Component (A): Water-Soluble Solid Alkali Inorganic Substance The term "water-soluble solid alkali inorganic substance" of the component (A) refers to an alkali inorganic substance which is solid at an ambient temperature, and one which can be dissolved in water in an amount of 1 g or more in 100 g of water at 20°C is preferable. The water-soluble solid alkali inorganic substance is not particularly limited, and alkali metal salts, silicates and the like having hydroxyl group, carbonate group, or hydrogencarbonate group can be used. The water-soluble solid alkali inorganic substance includes, for instance, sodium hydroxide, sodium carbonate, sodium hydrogencarbonate, potassium carbonate, sodium silicate and the like. Among them, sodium carbonate is preferable as an alkalizing agent showing suitable pH buffering range in a washing liquid. Also, the formulation of sodium hydroxide is also effective from the viewpoint of the reaction rate during the dry- neutralization.

In the present invention, it is preferable that the component (A) exist in as fine state as possible in the base particles. For instance, the size of the component (A) is such that its average particle size is preferably from 0.1 to

50 μm. The state of this particle can be confirmed by direct observation with the SEM.

As to the amount of the component (A) formulated, in addition to the amount necessary from the viewpoint of detergency performance, an amount necessary for dry-neutralization with the liquid acid precursor (B) of a non-soap anionic surfactant to be mixed in step (c) must be formulated. Further, it is preferable that the reaction of the component (A) with the component (B) is accelerated on the surface of the detergent particle. Therefore, it is necessary that the amount of the component (A) is equal to or greater than the amount equivalent for neutralizing the component (B). The amount of the component (A) is preferably 4 times or more, more preferably 6 times or more, of the amount equivalent for neutralizing the component (B) from the viewpoint of accelerating the reaction on the surface.

In addition, the amount of the component (A) is preferably 10% by weight or more, more preferably 15% by weight or more, of the detergent particles from the viewpoint of detergency performance. On the other hand, the amount of the component (A) is at least the amount equivalent for neutralizing the component

(B) from the viewpoint of dry-neutralization. Therefore, the formulation amount is preferably equal to or greater than the sum of these two values. Concretely, the amount of the component (A) is preferably from 20 to

80% by weight, more preferably from 25 to 70% by weight, still more preferably from 30 to 60% by weight, from the viewpoints of reaction rate and degree of freedom in the formulation.

An essential component for the base particles in the present invention is only the water-soluble solid alkali inorganic substance (A), and other components usually used in the detergent particles can be optionally simultaneously formulated in the base particles in proper amounts, from the viewpoints of the detergency performance, the fast dissolubility and the particle strength. The other components include a chelating agent, a water-soluble inorganic salt, a (water-soluble) polymer, a surfactant, a water-insoluble excipient, other auxiliary components and the like. Among them, it is preferable that the chelating agent, the water-soluble inorganic salt and the (water-soluble) polymer are formulated. Concrete examples of these components are given hereinbelow. 2. Chelating Agent

The chelating agent can be formulated in the base particles in order to suppress the inhibition of deterging action by metal ions, and examples thereof are water-soluble chelating agents and water-insoluble chelating agents. As the amount of the chelating agent, it is desired that the amount of the chelating agent formulated in the base particle is adjusted so that the content of the chelating agent is preferably from 3 to 60% by weight, more preferably from 5 to 40% by weight, still more preferably from 10 to 40% by weight, of the detergent particles, from the viewpoint of metal ion capturing ability. A plural chelating agents can be simultaneously formulated, in which case it is desired that its total content is as specified above.

The water-soluble chelating agent is not particularly limited as long as the water-soluble chelating agent is a substance having a metal ion capturing ability, and tripolyphosphate, orthophosphate, pyrophosphate and the like can be used. Among them, tripolyphosphate is preferable, and its content is preferably 60% by weight or more, more preferably 70% by weight or more, still more preferably 80% by weight or more, of the entire water-soluble chelating agents. Also, as the counter ion, an alkali metal is preferable, and especially sodium and/or potassium is preferable. The water-insoluble chelating agent may be added to the base particles for the purposes of improving the metal ion capturing ability and enhancing the strength of the base particle. Those having an average particle size of from 0.1 to 20 μm are preferable from the viewpoint of the dispersibility in water. Preferable base materials include crystalline aluminosilicates, including, for instance, A-type zeolite, P-type zeolite, X-type zeolite and the like. The A-type zeolite is preferable from the viewpoints of the metal ion capturing ability and economic advantages.

As to the amount of the zeolite formulated, when the zeolite is formulated in a large amount, there is a possibility that the zeolite decomposes during the dry-neutralization reaction. Therefore, it is preferable that the amount of the zeolite is controlled to 10% by weight or less of the base particles. Also, for the purpose of suppressing the decomposition, the amount of zeolite formulated can be also increased by using the zeolite together with a water-soluble alkalizing agent having high dissolubility and high alkali strength, such as sodium hydroxide.

3. Water-Soluble Inorganic Salt

It is preferable that the water-soluble inorganic salt is formulated in the base particles in order to enhance the ionic strength of the washing liquid and improve the effects of sebum stain deterging and the like. The water-soluble inorganic salt is not particularly limited as long as the water-soluble inorganic salt is a substance having an excellent dissolubility and not giving worsening effect to detergency. The water-soluble inorganic salt includes, for instance, an alkali metal salt or ammonium salt having sulfate group or sulfite group, and the like. Among them, it is preferable that sodium sulfate, sodium sulfite or potassium sulfate having high degree of ionic dissociation is used as an excipient. Also, its combined use with magnesium sulfate is also effective from the viewpoint of improving the dissolution speed.

The amount of the water-soluble inorganic salt is preferably from 5 to 80% by weight, more preferably from 10 to 70% by weight, still more preferably from 20 to 60% by weight, of the base particles, from the viewpoint of the ionic strength.

4. (Water-Soluble) Polymer The water-soluble polymer may be added to the base particles for the purpose of enhancing the particle strength by adjustment of precipitation of crystals and film formation on the base particles. The water-soluble polymer includes organic polymers and inorganic polymers. For instance, the organic polymer includes carboxylate polymers, carboxymethyl cellulose, soluble starches, saccharides, polyethylene glycol and the like, and the inorganic polymer includes amorphous silicates and the like. Among them, the carboxylate polymers are preferable, among which a salt of an acrylic acid- maleic acid copolymer and a polyacrylate (Na, K, NH₄ and the like) are especially preferable. Those carboxylate polymers having a molecular weight of from 1000 to 8000 are preferable, and those having a molecular weight of 2000 or more and 10 or more carboxylate groups are more preferable. The amount of the organic polymer is preferably from 0.1 to 10% by weight, more preferably from 0.5 to 5% by weight, of the base particles.

In addition, it is preferable that the organic polymer is used together with the inorganic polymer such as amorphous silicates, from the viewpoint of enhancing the particle strength, especially No. 2 sodium silicate is preferable. The amount of the inorganic polymer is preferably 15% by weight or less, more preferably 10% by weight or less, still more preferably 5% by weight or less, of the base particles, from the viewpoint of the dissolubility. 5. Surfactant

The surfactant may be added for the purpose of controlling the bulk density. For instance, a linear sodium alkylbenzenesulfonate, a sodium alkylsulfonate, sodium ether sulfonate, sodium paratoluenesulfonate, sodium xylenesulfonate, sodium cumenesulfonate, or the like can be used. Especially, the linear sodium alkylbenzenesulfonate is preferable from the viewpoint of economic advantages.

The amount of the surfactant is preferably 0.05% by weight or more, more preferably 0.1% by weight or more, of the base particles, from the viewpoint of controlling the bulk density. On the other hand, the amount of the surfactant is preferably 10% by weight or less, more preferably 5% by weight or less from the viewpoint of the dissolubility.

In addition, these surfactants can be added in the form of liquid acids, not neutralized form. In this case, it is preferable that the alkalizing agent is added in an amount equal to or greater than the amount equivalent for neutralizing the liquid acid, and the addition of sodium hydroxide is especially preferable.

6. Water-Insoluble Excipient

The water-insoluble excipient is not particularly limited as long as the water-insoluble excipient has excellent dispersibility in water and does not give worsening effects to detergency. The water-insoluble excipient includes, for instance, crystalline or amorphous aluminosilicates, silicon dioxide, hydrated silicic acid compound, clay compounds such as perlite and bentonite, and the like. It is preferable that the water-insoluble excipient has an average primary particle size of from 0.1 to 20 μm, from the viewpoint of the dispersibility in water. The amount of the water-insoluble excipient formulated is preferably 50% by weight or less, more preferably 30% by weight or less, of the base particles, from the viewpoints of economic advantages and the dispersibility.

7. Other Auxiliary Components

A fluorescer, a pigment, a dye or the like may be formulated in the base particles.

8. Preferable Combination Among the compositions mentioned above, it is preferable that sodium carbonate/sodium sulfate/sodium polyacrylate are used in combination, and it is more preferable that sodium carbonate/sodium sulfate/sodium polyacrylate/sodium tripolyphosphate are used in combination, from the viewpoint of precipitating a larger amount of fine crystals, thereby enhancing the particle strength.

In addition, when a base particle having a lower bulk density is prepared, it is preferable to add a surfactant to the above-mentioned combination.

The base particles used in the present invention can be obtained by spray-drying a slurry prepared by adding the above components with mixing. The water content of the slurry and the spray-drying conditions are not particularly limited.

< Composition of Detergent Particle >

The "detergent particle" contained in the detergent particles of the present invention refers to a particle obtained by dry-neutralizing base particles containing a water-soluble solid alkali inorganic substance (A) with a liquid acid precursor (B) of a non-soap anionic surfactant, and an aggregate thereof is referred to as "detergent particles."

By mixing the base particles with the liquid acid precursor of a non-soap anionic surfactant, the dry-neutralization reaction with the water-soluble solid alkali inorganic substance (A) in the base particle is generated on the particle surface, to give a detergent particle of which surface is coated with the non-soap anionic surfactant. The penetration of the surfactant into the inner portion of the base particle is suppressed by coating its surface, and the detergent particle can be adjusted to a medium- to low-bulk density without impairing its fast dissolubility/flowability properties by further surface-modifying the surface with a fluidizing aid. Also, since the base particle is coated with the non-soap anionic surfactant, the bleed-out of the surfactant to the surface and caking phenomenon caused by an inorganic salt can be suppressed, so that the storage stability is also dramatically improved.

1. Base Particles

The amount of the base particles in the detergent particles is not particularly limited. The amount of the base particles is preferably 40% by weight or more, more preferably 50% by weight or more, still more preferably

60% by weight or more, of the detergent particles, from the viewpoints of maintaining the particle size distribution and improving the dissolubility. On the other hand, the amount of the base particles is preferably 85% by weight or less, more preferably 75% by weight or less, of the detergent particles, from the viewpoint of the degree of freedom in the formulation. 2. Component (B): Liquid Acid Precursor of Non-Soap Anionic Surfactant The component (B) of the detergent particles is formulated as the liquid acid precursor of a non-soap anionic surfactant, of which a part or all of the component (B) react with the component (A) in the base particles.

The liquid acid precursor of a non-soap anionic surfactant, which is the component (B), refers to a precursor of a non-soap anionic surfactant, which has an acidic form and is liquid, and is capable of forming a salt by the neutralization reaction. Therefore, the liquid acid precursor of the non-soap anionic surfactant is not particularly limited as long as it is a precursor of a known anionic surfactant having the above-mentioned characteristics. The liquid acid precursor of a non-soap anionic surfactant includes a linear alkylbenzenesulfonic acid (LAS), α-olefinsulfonic acid (AOS), an alkylsulfuric acid (AS), an internal olefinsulfonic acid, fatty acid esters of sulfonic acid, an alkyl ether sulfuric acid, a dialkyl sulfosuccinic acid and the like. The component (B) as mentioned above may be used as a single component or in admixture of two or more components. Among them, the linear alkylbenzenesulfonic acid (LAS) is preferable from the viewpoints of economic advantages, storage stability and foaming.

The amount of the component (B) to be added to the base particles is 15% by weight or more of the base particles, and the amount of the component (B) is preferably 20% by weight or more, more preferably 25% by weight or more, from the viewpoints of the detergency and the storage stability. In addition, the amount of the component (B) is preferably 80% by weight or less, more preferably 60% by weight or less, still more preferably 40% by weight or less, from the viewpoint of suppressing the lowering of the dissolubility by the continuous layer of the neutralized product of the component (B).

Especially, in the present invention, since it is important that the surface of the base particle is substantially coated with the non-soap anionic surfactant, the specific surface area increases when the bulk density is lowered, so that the preferable amount of the component (B) also increases. The coating of the surface of the base particle with a neutralized product of the component (B) can be determined by remarkable improvements in sieve permeability in the evaluation of the caking ability described later.

3. Component (C): Fluidizing Aid

In the detergent particles of the present invention, the particle is subjected to surface modification with a fluidizing aid in order to improve the flowability and the storage stability. By carrying out the surface modification, especially there is an advantage that the flowability properties are remarkably improved, which is a feature of the present invention.

As the fluidizing aid, those known ones usually employable can be used, and sodium tripolyphosphate, a crystalline or amorphous aluminosilicate, diatomaceous earth, silica and the like can be preferably used. Among them, sodium tripolyphosphate and zeolite, each having a chelating ability, are preferable. By surface modifying the particle with a substance having a chelating ability, the chelating agent acts from the initial stage of washing, whereby improving the deterging performance. The zeolite is more preferable from the viewpoint of the flowability properties, and sodium tripolyphosphate is more preferable from the viewpoint of rinsing ability. It is desired that the particle to be used as the fluidizing aid has an average particle size of one-tenth or less that of the average particle size of the detergent . particles, from the viewpoint of coating ability.

In addition, when the amount of the fluidizing aid is too much or too little, the flowability properties are lowered. Therefore, the amount of the fluidizing aid is preferably from 2 to 20% by weight, more preferably from 5 to 15% by weight of the detergent particles.

When the zeolite is used as the fluidizing aid, it is preferable that the surface modification is carried out after the termination of the neutralization reaction from the viewpoint of suppression of the decomposition.

4. Other Components

The detergent particles of the present invention can be optionally formulated in proper amounts of the substances listed below.

(1) Inorganic Acid

When the base particles are mixed with the liquid acid precursor (B) of a non-soap anionic surfactant, an inorganic acid can be added for the purpose of reducing the adhesive property by the produced non-soap anionic surfactant. Preferable inorganic acids usable in the present invention include sulfuric acid and phosphoric acid, and a more preferable inorganic acid includes sulfuric acid.

The amount of the inorganic acid formulated is preferably from 0.3 to 1.0 mol, more preferably from 0.3 to 0.8 mol, still more preferably from 0.35 to 0.7 mol, per one mol of the component (B).

(2) Aqueous Alkali Solution For the purpose of accelerating the dry-neutralization reaction, an aqueous alkali solution can be added to the base particles as a reaction initiator. The amount of the aqueous alkali solution added is preferably from 0.05 to 0.5 times the amount equivalent for neutralizing the liquid acid precursor (B) of the non- soap anionic surfactant, more preferably from 0.10 to 0.45 times the amount equivalent for neutralizing the liquid acid precursor, especially preferably from 0.15 to 0.4 times the amount equivalent for neutralizing the liquid acid precursor. The amount of the aqueous alkali solution is preferably 0.05 times or more of the amount equivalent for neutralizing the liquid acid precursor, from the viewpoint of initiating the neutralization reaction to give desired effects, and is preferably

0.5 times or less of the amount equivalent for neutralizing the liquid acid precursor, from the viewpoint of suppressing the aggregation of the detergent particle. The concentration of the aqueous alkali solution is not particularly limited. In order to suppress the dissolution of the base particles, the concentration of the aqueous alkali solution is preferably from 20 to 50% by weight, more preferably from 30 to 50% by weight, still more preferably from 40 to 50% by weight.

The kind of the aqueous alkali solution is not particularly limited. The aqueous alkali solution includes, for instance, aqueous strong-alkali solutions which easily cause neutralization reactions with the liquid acid precursor (B) of a non-soap anionic surfactant, such as an aqueous sodium hydroxide and an aqueous potassium hydroxide. Among them, the aqueous sodium hydroxide is preferred from the viewpoint of economic advantages. In addition, it is more preferable that the aqueous alkali solution has a pH of 12 or more. (3) Water-Soluble Solid Alkali Inorganic Substance (A)

For the purpose of accelerating the dry-neutralization reaction, the above- mentioned water-soluble solid alkali inorganic substance (A) can be added in a solid state as a reaction initiator. It is preferable that the component (A) is added as powder which is as fine as possible from the viewpoint of the reactivity, and it is more preferable that the component (A) is used together with the aqueous alkali solution.

The amount of the component (A) is preferably equal to or greater than the amount equivalent for neutralizing the non-soap anionic surfactant, from the viewpoint of maintaining the particle size distribution.

(4) Surfactant

A surfactant which is liquid at an ambient temperature may be added, from the viewpoint of improving the detergency, within the range so as not to affect the storage stability and the flowability properties and not to increase the bulk density to be equal to or greater than the desired level. The surfactant includes, for instance, nonionic surfactants, such as polyoxyalkylene alkyl(8 to 20 carbon atoms) ethers, alkyl polyglycosides, polyoxyalkylene alkyl(8 to 20 carbon atoms) phenyl ethers, polyoxyalkylene sorbitan fatty acid(8 to 22 carbon atoms) esters, polyoxyalkylene glycol fatty acid(8 to 22 carbon atoms) esters, polyoxyethylene polyoxypropylene block polymers, and the like.

The amount of these surfactants which are liquid at an ambient temperature is preferably 10% by weight or less, more preferably 5% by weight or less, most preferably 3% by weight or less, of the detergent particles, from the viewpoints of suppression of bleed-out and foaming. < Detergent Composition >

The detergent composition comprises separately added detergent components other than the detergent particles (for instance, fluorescers, enzymes, perfumes, defoaming agents, bleaching agents, bleaching activators, and the like).

In this case, it is preferable that the detergent composition comprises the detergent particles according to the present invention in an amount of preferably 50% by weight or more, more preferably 60% by weight or more, still more preferably 80% by weight or more. Since the detergent composition has the above constitution, a detergent composition having medium- to low bulk density and excellent storage stability, fast dissolubility and flowability properties can be provided.

< Preparation Process > The process for preparing detergent particles of the present invention is characterized in that the process comprises the steps of: (a): preparing a slurry comprising a water-soluble solid alkali inorganic substance (A), wherein the water-soluble solid alkali inorganic substance

(A) is present in an amount equal to or greater than an amount equivalent for neutralizing a liquid acid precursor (B) of a non-soap anionic surfactant to be added in step (c); (b): spray-drying the slurry obtained in step (a) to give base particles; (c): adding to the base particles obtained in step (b) the liquid acid precursor

(B) in an amount of 15% by weight or more of the base particles, mixing and dry-neutralizing the resulting mixture; and (d): adding a fluidizing aid (C) to the particle obtained in step (c), thereby surface-modifying the particle.

Since the process for preparing detergent particles of the present invention comprises the above steps (a) to (d), there is an advantage that a medium- to low- bulk density detergent having excellent storage stability, fast dissolubility and flowability properties can be provided.

The steps (a) to (d) will be described in detail hereinbelow.

1. Step (a)

The conditions for the preparation of the slurry are not particularly limited as long as the base particle satisfy the above-described composition. In order to improve the particle strength of the base particle, it is desired to employ a preparation process which allows the precipitation of fine crystals in the slurry in a large amount. The process therefor is given hereinbelow. The fine crystal as referred to herein includes not only the crystal containing the water-soluble solid alkali inorganic substance (A) but also the crystal not containing an alkali, such as the crystal of sodium tripolyphosphate or the crystal of sodium sulfate.

(1) Precipitation of Crystals in Slurry

The dissolved water-soluble inorganic substance is precipitated by controlling the solubility of the component (A). The precipitated crystal may be solely form a crystal or form a complex salt with another component. In this case, it is preferable that the solubility is controlled by adding other water- soluble components in order to produce fine crystals. In addition, the addition of the polymer is also effective as a crystal-controlling agent in order to suppress the crystal from growing larger.

(2) Pulverization in Slurry The crystals can be made finer by pulverizing coarse grains derived from raw materials, crystals of a complex salt reacted in coarse grain state and crystals of largely grown complex salt by the precipitation, with a wet-type pulverizer. By combining these processes, the water-soluble alkali solid inorganic substance can be formulated in the base particles in the form of fine particles. In order to sufficiently exhibit the reactivity in the base particles, the size of the fine particles is such that their average particle size in the slurry is preferably 50 μm or less, more preferably 30 μm or less, still more preferably 20 μm or less.

The water content of the slurry is preferably 60% by weight or less, more preferably 55% by weight or less, from the viewpoint of the precipitation of the crystals. On the other hand, the water content of the slurry is preferably 40% by weight or more, more preferably 45% by weight or more, from the viewpoint of easy handling.

The preparation temperature of the slurry is preferably 30°C or higher, more preferably 40°C or higher, from the viewpoint of the solubility. On the other hand, the preparation temperature of the slurry is preferably 80°C or lower, more preferably 70°C or lower, from the viewpoint of the thermal stability.

In addition, the order of the addition of each of the components during the preparation of the slurry greatly affects the precipitation of the crystals. The order of the formulation for the preferable composition mentioned above is, for instance, the order of the formulation mentioned below. sodium tripolyphosphate → sodium sulfate → sodium polyacrylate → sodium carbonate sodium sulfate → sodium tripolyphosphate → sodium polyacrylate → sodium carbonate sodium tripolyphosphate → sodium carbonate → sodium polyacrylate → sodium sulfate

Besides the above, the fine crystals can be precipitated in a large amount by a process such as a process comprising making the temperature difference (ΔT) between the slurry and the jacket larger, or a process comprising applying a shearing force to the slurry with a line mill or the like during the preparation and/or after the preparation of the slurry.

2. Step (b) The conditions for spray-drying the slurry obtained in the step (a) are not particularly limited, as long as the substances formulated in the slurry are not substantially affected, and spray-drying conditions generally carried out can be employable.

The spray-drying temperature is preferably from 150° to 300°C, more preferably from 170° to 250°C, from the viewpoints of improving the drying efficiency and suppressing the decomposition. On the other hand, as the device for carrying out spray-drying, a usually known spray-drying tower can be used.

It is preferable that the exhaust air temperature of the spray-drying tower is adjusted to 80° to 130°C. During the spray-drying in the present invention, it is preferable that the base particle having a relatively small particle size is obtained with a sharp particle size distribution. In order to obtain such a base particle, it is important to select the nozzle type and its spraying pressure. For instance, the above- mentioned object can be achieved by using a single-fluid high-pressure nozzle.

3. Step (c)

The step (c) comprises adding and mixing the base particles obtained in step (b) with the liquid acid precursor (B) of a non-soap anionic surfactant, so that the amount of the liquid acid precursor (B) of a non-soap anionic surfactant is 15% by weight or more of the base particles, to dry-neutralize the components

(A) and (B) to give a particle. It is preferable that the component (B) is mixed as homogeneously as possible with the base particles.

As the process for adding the component (B), it is preferable that the component (B) is mixed as homogeneously as possible by spraying the component (B) with a nozzle. The temperature at which the component (B) is added is preferably from 40° to 80°C, more preferably from 50° to 70°C, from the viewpoint of the flowability.

The dry-neutralization temperature is preferably the higher the better, from the viewpoint of accelerating the reaction, and the dry-neutralization temperature is preferably from 60° to 80°C. On the other hand, the dry- neutralization temperature is the lower the better from the viewpoints of delaying the reaction, and extending the mixed state with the liquid acid, thereby uniformly coating the surface of the particle, and the dry-neutralization temperature is preferably from 20° to 40°C. Also, during the dry-neutralization, the aggregation of the detergent particles is likely to be generated because the component (B) becomes more viscous by the neutralization. A process for suppressing the aggregation includes a process comprising allowing air draft during the neutralization reaction, thereby lowering the adhesive property of the surface of the surfactant. Also, it is also effective to add an inorganic acid to the component (B), thereby forming an inorganic salt at the same time as the formation of the surfactant.

On the other hand, in order to accelerate the dry neutralization, the aqueous alkali solution or the water-soluble solid alkali inorganic substance (A) can be added to the base particles before the addition of the liquid acid. In the step (c), it is preferable that the shearing force during the neutralization is reduced as much as possible in order to suppress the disintegration of the base particle during the dry neutralization. A process for reducing shearing force during the neutralization includes a process comprising lowering the mixing speed by the mixing mechanism, or a process comprising lowering a shearing force by a cutting mechanism such as a chopper. The process comprising lowering a shearing force by a cutting mechanism is preferable from the viewpoint of the mixing property. The mixer which does not have a cutting mechanism includes, for instance, Ribbon Mixer, Nauta Mixer and the like. Even in a case where a device equipped with a cutting mechanism, such as Lodige Mixer or High-Speed Mixer, is used, the disintegration of the base particles can be suppressed by reducing a shearing force with a low-speed rotation of the chopper or not using the cutting mechanism.

4. Step (d) The step comprising surface-modifying with a fluidizing aid (step (d)) is carried out in order to further improve the flowability properties and the storage stability of the detergent particle of which surface obtained in step (c) is coated with the non-soap anionic surfactant.

The conditions for the surface modification are not particularly limited, and it is preferable that the fluidizing aid is distributed on the surface of the detergent particle as uniformly as possible.

The temperature in the device for surface modification is not particularly limited. It is preferable that the surface modification is carried out with cooling from the viewpoint of solidifying the surfactant. The device for surface modification is preferably a device which can give a strong agitating power and shearing power at the same time, and modify the surface uniformly. As the device described above, a Lδdige Mixer and High- Speed Mixer are suitably used.

The properties of the base particles and the detergent particles of the present invention, and the methods for determining the properties thereof will be described hereinbelow.

< Properties of Base Particles >

The functions required for the base particles in the present invention include, in addition to the bulk density necessary to manufacture medium- to low-bulk density detergents, (i) being fast-dissoluble, (ii) retaining the component (A) in an amount sufficient to complete the reaction with the surfactant on its surface in the dry-neutralization step, (iii) having a particle strength equal to or greater than a given level in order to suppress disintegration of particles in the dry neutralization step, and the like. Therefore, it is preferable that the base particles satisfy the following properties.

The bulk density of the base particles is preferably the same as, or slightly lower than, that of the detergent particles, and it is desired that the bulk density is lower than the desired bulk density by 0 to 150 g/L or so. Specifically, the bulk density is preferably from 150 to 600 g/L, more preferably from 300 to 500 g/L.

The base particles have an average particle size of preferably from 150 to 400 μm, more preferably from 200 to 300 μm, from the viewpoints of the external appearance, the reactivity and the flowability.

The base particles have a particle strength of preferably 100 kg/cm or more, more preferably 200 kg/cm or more, from the viewpoint of suppression of the disintegration during the dry-neutralization step.

The base particles have a water content of preferably 10% by weight or less, more preferably 5% by weight or less, still more preferably 3% by weight or less, from the viewpoints of easy handling and the storage stability.

< Properties of Detergent Particles >

One of the features of the detergent particles in the present invention resides in that the base particles are coated with the component (B) by dry- neutralization, and thereafter the obtained particle is subjected to surface modification with a fluidizing aid. Therefore, the properties of the detergent particles are greatly affected by the properties of the base particles, and the desired detergent particles can be obtained by using the above-mentioned base particles.

Specifically, the detergent particles have an average particle size of from 150 to 500 μm, preferably from 180 to 300 μm, from the viewpoints of easy handling and the external appearance.

Also, the detergent particles have a bulk density of 600 g/L or less, preferably from 150 to 600 g/L, more preferably from 300 to 500 g/L.

The detergent particles have a water content of preferably 10% by weight or less, more preferably 5% by weight or less, still more preferably 3% by weight or less, from the viewpoint of the storage stability.

Among the detergent particles having these properties, preferable are detergent particles comprising a detergent particle in which the size of the above- mentioned base particle is retained. Here, the retention of the shape of the base particle is evaluated by the degree of particle growth of the detergent particle.

The degree of particle growth is preferably from 0.7 to 1.6, more preferably from 0.9 to 1.4. The degree of particle growth can be determined by the following equation:

_{n f} Average Particle Size of _p °. ₁ _ Final Detergent Particles , Average Particle Size of

Base Particles

The "final detergent particles" refer to particles obtained by further subjecting the detergent particles obtained by dry neutralization to surface modification.

The detergent particles of the present invention comprise a detergent particle (bubble-releasing particle) capable of releasing a bubble having a size of 1/10 or more of the particle size of the detergent particle from the inner portion of the particle in a process where the detergent particle is dissolved in water. In a process where the detergent particle is dissolved in water, the detergent particle firstly releases a bubble having a given size from the inner portion of the particle when a small amount of water is allowed to enter into the inner portion of the particle, and subsequently the particle itself undergoes disintegration (self- disintegration of the particle) by allowing a large amount of water to enter into the inner portion of the particle. Therefore, not only the dissolution takes place from a portion near the surface, but also the dissolution and the disintegration of the particle take place from the inner portion of the particle.

The dissolution behavior described above can be confirmed by a digital microscope or optical microscope as a phenomenon in which a bubble having a size of 1/10 or more, preferably 1/5 or more, more preferably 1/4 or more, still more preferably 1/3 or more, of the particle size of the particle (hereinafter referred to as "bubble having a given size") is released in the case where the bubble-releasing detergent particle is dissolved in water. In the case where the bubble-releasing detergent particle is dissolved in water with a stand-still state, the bubble having a given size is generated preferably within 120 seconds, more preferably within 60 seconds, still more preferably within 45 seconds.

< Methods for Evaluation of Properties >

The methods for determining the properties of the above-mentioned base particles or detergent particles are described below.

1. Bulk Density

The bulk density is measured by a method according to JIS K 3362.

2. Average Particle Size The average particle size is measured by vibrating a sample for 5 minutes using standard sieves (sieve-openings: 2000 to 125 μm,) according to JIS Z 8801, and thereafter calculating the median size from a weight percentage depending upon the size openings of the sieves.

3. Particle Strength

The method for measuring the particle strength is as follows. A cylindrical vessel of an inner diameter of 3 cm and a height of 8 cm is charged with 20 g of a sample, and the sample-containing vessel (manufactured by TSUTSUI RIKAGAKU KIKAI CO., LTD., "Model TVP1" tapping-type close-packed bulk density measurement device; tapping conditions: period

36 times/minute, free fall from a height of 60 mm) is tapped for 30 times. The sample height (an initial sample height) at that time is measured. Thereafter, an entire upper surface of the sample kept in the vessel is pressed at a rate of 10 mm/min with a pressing machine to take measurements for a load-displacement curve. The slope of the linear portion at a displacement rate of 5% or less is multiplied by an initial sample height, and the resulting product is divided by a pressed area, to give a quotient which is defined as the particle strength.

4. Average Particle Size of Fine Particles As to the fine particles in the slurry, the average particle size can be determined by using, for instance, an FBRM system (manufactured by

MET LER TOLEDO) without diluting the slurry.

When the FBRM system is used, 1 L of a slurry to be determined is supplied in a 1-L plastic cup, and a probe is inserted therein at an angle of 40 to 45° to the liquid surface and placed so that a determining surface of the probe does not appear above the liquid surface. Next, the slurry is agitated at 250 r.p.m. using a propeller having a diameter of 6 cm, and the determination is made after confirming the determining surface of the probe is in the slurry. Incidentally, the plastic cup is kept in a water bath so as to have the same temperature as that the preparation temperature for the slurry.

< Method for Evaluating Qualities > 1. Fast Dissolubility

As the index for the fast dissolubility of the detergent particles in the present invention, there can be employed the 60-seconds dissolution ratio of the detergent particles. The dissolution ratio is 90% or more, preferably 95% or more, from the viewpoint of the fast dissolubility. Incidentally, the fast dissolubility of the detergent composition can also be evaluated in the same manner. The 60-seconds dissolution ratio of the detergent particles is calculated by the method described below.

A 1-L beaker (a cylindrical form having an inner diameter of 105 mm and a height of 150 mm, for instance, a 1-L glass beaker manufactured by Iwaki Glass Co., Ltd.) is charged with 1 L of hard water cooled to 5°C and having a water hardness corresponding to 71.2 mg CaC0₃/L (a molar ratio of Ca/Mg: 7/3).

With keeping the water temperature constant at 5°C with a water bath, water is stirred with a stirring bar [length: 35 mm and diameter: 8 mm, for instance, Model "TEFLON SA" (MARUGATA-HOSOGATA), manufactured by ADVANTEC] at a rotational speed (800 r.p.m.), such that a depth of swirling to the water depth is about 1/3. The detergent particles which are accurately sample-reduced and weighed so as to be 1.0000 g ± 0.0010 g are supplied and dispersed in water with stirring, and stirring is continued. After 60 seconds from supplying the particles, a liquid dispersion of the detergent particles in the beaker is filtered with a standard sieve (diameter: 100 mm) having a sieve-opening of 74 μm as defined by JIS Z 8801 of a known weight. Thereafter, water- containing detergent particles remaining on the sieve are collected in an open vessel of a known weight together with the sieve. Incidentally, the operation time from the start of filtration to collection of the sieve is set at 10 sec ± 2 sec. The insoluble remnants of the collected detergent particles are dried for one hour in an electric dryer heated to 105°C. Thereafter, the dried insoluble remnants are cooled by keeping in a desiccator with a silica gel (25°C) for 30 minutes. After cooling the insoluble remnants, a total weight of the dried insoluble remnants of the detergent, the sieve and the collected vessel is measured, and the dissolution ratio (%) of the detergent particles is calculated by Equation (1): Dissolution Ratio (%) = {1 - (T/S)} x 100 (1) wherein S is a weight (g) of the detergent particles supplied; and T is a dry weight (g) of insoluble remnants of the detergent particles remaining on the sieve when an aqueous solution prepared under the above stirring conditions is filtered with the sieve (drying conditions: maintaining at a temperature of 105°C for 1 hour, and thereafter maintaining for 30 minutes in a desiccator (25°C) containing silica gel).

2. Flowability Properties

The flowability properties of the detergent particles of the present invention can be evaluated by a variance of powder dropping rate (V) as an index. The variance of powder dropping rate (V) is preferably 2.0 or less, more preferably 1.5 or less, still more preferably 1.0 or less, especially preferably 0.8 or less, from the viewpoint of particle size property. Incidentally, the variance of powder dropping rate of the detergent composition can also be evaluated in the same manner.

The variance of the powder dropping rate (V) can be measured as described below.

When the experiment for measuring powder flowability properties is carried out by using a "measuring device for powder flowability properties" as disclosed in Japanese Patent Laid-Open No. 2000-171377, the dropping rate v

(θ) (%/deg.) at a slanted angle θ (°) of the holding member is determined, and variance of the v value against the θ, in which the dropping ratio Y(θ) of the sample powder falls between 1% and 99%, is calculated. This variance is defined as the variance of the powder dropping rate (V). The method for using the "measuring device for powder flowability properties" is as follows.

A cascading portion is provided in the holding member such that the cascading portion has a height of 20 cm from a receiver of the weight measurement device, and then an angle θ of the holding member is set at 0°. Next, a measurement sample is poured to a cascading portion in a sufficient amount using a funnel from a height of 10 cm above the cascading portion, and thereafter a sample filled over the brim of the cascading portion is removed by gentle leveling. The holding member is rotated at an angular velocity of 6° per one second, until the angle θ of the holding member is changed from 0° to 180°. During this period, the measurement of the dropped weight of the sample is taken every 1/80 seconds with a weight measurement device, and the θ and the dropped weight at an instant time are sequentially recorded.

Based on the results obtained by the above-mentioned method, in order to reduce an aberration of the measuring device, the dropping ratio and the dropping rate at a slant θ of the holding member are obtained by carrying out the following data processing.

The dropping ratio (%) at an angle θ is defined by a ratio of a dropped weight at an angle θ to an entire weight of the measurement sample, wherein the dropped weight at an angle θ is an average value of measurement values of the dropped weights of a total of 40 points from an angle of (θ - 3)° to an angle θ.

The dropping rate at an angle θ is defined as a value (%/deg.) of a slope of a straight line obtained by plotting an angle as abscissa and the dropping ratio (%) described above as coordinate for a total of 19 points from angles (θ - 0.675)° to (θ + 0.675)°, and obtaining the slope of a straight line by using least square method.

3. CaJking Property (Storage Stability)

The detergent particles have a caking property as evaluated by sieve permeability. The sieve permeability is preferably 90% or more, more preferably 95% or more. The testing method for caking property is as follows.

An open-top box having dimensions of 10.2 cm in length, 6.2 cm in width, and 4 cm in height is made out of a filter paper (No. 2, manufactured by ADVANTEC) by stapling the filter paper at four corners. A total weight of 15 g + 250 g of an acrylic resin plate and a lead plate (or an iron plate) are placed on the box charged with a 50 g sample. The box is allowed to stand in a thermostat kept at a temperature of 30°C and a humidity of 80%, and the caking state after 7 days or 1 month is evaluated.

The evaluation is made by calculating the sieve permeability as follows. < Sieve Permeability >

A sample obtained after the test is gently placed on a sieve (sieve opening: 4760 μm, as defined by JIS Z 8801), and the weight of the powder passing through the sieve is measured. The sieve permeability based on the sample obtained after the test is calculated.

Weight (g) of Powder

Sieve _ Passing Through Sieve _{ι n}„

Permeability (%) ^~ Weight (g) of Whole Sample

4. Bleed-out Property

As to the bleed-out property of the detergent particles, it is preferable when the evaluation by the following test methods is preferably 2 rank or better, more preferably 1 rank. The testing method for bleed-out property is as follows:

Bleed-out state of a surfactant is visually examined at bottom (side not contacting with powder) of the vessel made of the filter paper after the caking test. The evaluation of the bleed-out property is made based on the area of wetted portion occupying the bottom in the following 1 to 5 ranks. Incidentally, the state for each rank is as follows:

Rank 1: not wetted;

Rank 2: about 1/4 of the bottom area being wetted;

Rank 3: about 1/2 the bottom area being wetted; Rank 4: about 3/4 of the bottom area being wetted; and Rank 5: the entire bottom area being wetted.

As described above, since the detergent particles of the present invention are excellent in the storage stability, the fast dissolubility and the flowability properties, the detergent particles can be suitably used for laundry detergent compositions.

As is seen from the above, preferred embodiments of the present invention include the followings: (1) detergent particles comprising: a particle obtained by the step of dry-neutralizing base particles comprising a water-soluble solid alkali inorganic substance (A) with a liquid acid precursor (B) of a non-soap anionic surfactant, wherein the non-soap anionic surfactant is used in an amount of 15% by weight or more of the base particles; and a fluidizing aid (C) existing on a surface of the particle, wherein the detergent particles have a 60-second dissolution ratio of 90% or more, an average particle size of from 150 to 500 μm and a bulk density of 600 g/L or less; (2) the detergent particles according to the above (1), wherein a sieve permeability is 90% or more;

(3) the detergent particles according to the above (1) or (2), wherein the particle strength of the base particle is 100 kg/cm² or more;

(4) the detergent particles according to any one of the above (1) to (3), wherein the surfactant contained is liquid at an ambient temperature; (5) a process for preparing detergent particles comprising the steps of: (a): preparing a slurry comprising a water-soluble solid alkali inorganic substance (A), wherein the water-soluble solid alkali inorganic substance

(B) in an amount of 15% by weight or more of the base particles, mixing and dry-neutralizing the resulting mixture; and

(d): adding a fluidizing aid (C) to the particle obtained in step (c), thereby surface-modifying the particle; and

(6) a detergent composition comprising the detergent particles as defined in any of the above (1) to (4).

Example 1

Preparation of Base Particles>

Base particles were prepared by the following procedures. The amount 492.3 kg of water was added to a 1 m³-mixing vessel having agitation impellers. After the water temperature reached 55°C, 128.9 kg of sodium tripolyphosphate and 185.6 kg of sodium sulfate were sequentially added thereto. The temperature of the jacket was set at 45 °C. After agitating the mixture for 10 minutes, 12.9 kg of a 40% by weight-aqueous sodium polyacrylate solution and 180.4 kg of sodium carbonate were added thereto, and the resulting mixture was then agitated for 60 minutes, with pulverizing under circulation in a line mill, to give a homogeneous slurry. The final temperature of this slurry was 50°C. In addition, the water content of this slurry was 50% by weight. Incidentally, the average particle size of fine particles present in the slurry was determined using an FBRM system. As a result, the average particle size was 25 μm. This slurry was sprayed at a spraying pressure of 35 kg/cm with a pressure spray nozzle arranged near the top of a spray-drying tower. A high- temperature gas fed to the spray-drying tower was supplied at a temperature of 240°C to the bottom of the tower and exhausted at a temperature of 107°C from the top of the tower. The composition and the properties of the resulting base particles are shown in Table 1. Incidentally, the base particle was directly observed with an SEM. As a result, fine particles were present in the base particle.

Preparation of Detergent Particles> The amount 3.0 kg of the base particles obtained by the above-mentioned procedures were supplied into Lδdige Mixer (manufactured by Matsuzaka Giken Co., Ltd.; capacity: 20 L; equipped with a jacket), and the rotation of a main shaft was started at 70 r.p.m., without rotating a chopper. Incidentally, hot water at 80°C was allowed to flow through the jacket at 10 L/minute. A mixed solution of 0.6 kg of an acidic form of LAS (liquid acid precursor of an anionic surfactant) and 0.06 kg of sulfuric acid, which was temperature-controlled to 60°C, was supplied into the above mixer in 1 minute, and the components were then mixed and agitated for 4 minutes to carry out a dry-neutralization reaction (the amount of the alkali in the base particles: 10.6 times the amount equivalent for neutralizing the anionic surfactant, 6.4 times the amount equivalent for neutralization by the acid).

Subsequently, 0.51 kg of a zeolite A-type was added thereto, and thereafter a surface modification was carried out with rotating the main shaft at 150 r.p.m. and the chopper at 3600 r.p.m., to give detergent particles. The composition and the properties of the resulting detergent particles are shown in

Table 2. Incidentally, the degree of particle growth of the resulting detergent particles was 1.2.

The resulting detergent particles were particles which satisfied both the fast dissolubility and the flowability properties and had a low caking property. Incidentally, when the detergent particles were dissolved in water, it could be confirmed by a digital microscope/optical microscope that bubbles having a size of 1/10 or more of the particle size of the particles were released within 45 seconds.

Example 2

Preparation of Base Particles>

Base particles were prepared by the following procedures. The amount

440.5 kg of water was added to a 1 m -mixing vessel having agitation impellers. After the water temperature reached 55°C, 127.6 kg of sodium tripolyphosphate and 206.6 kg of sodium sulfate were sequentially added thereto. The temperature of the jacket was set at 45°C. After agitating the mixture for

10 minutes, 25.5 kg of a 40% by weight-aqueous sodium polyacrylate solution,

127.6 kg of sodium carbonate, 63.8 kg of No. 2 Sodium Silicate (40% by weight- aqueous solution), and 8.5 kg of 30% by weight-aqueous-LAS-Na were added thereto. Thereafter, the components were agitated for 60 minutes, with pulverizing under circulation in a line mill, to give a homogeneous slurry. The final temperature of this slurry was 50°C. In addition, the water content of this slurry was 50% by weight. Incidentally, the average particle size of fine particles present in the slurry was determined using an FBRM system. As a result, the average particle size was 27 μm.

This slurry was sprayed at a spraying pressure of 35 kg/cm² with a pressure spray nozzle arranged near the top of a spray-drying tower. A high- temperature gas fed to the spray-drying tower was supplied at a temperature of 240°C to the bottom of the tower and exhausted at a temperature of 110°C from the top of the tower. The composition and the properties of the resulting base particles are shown in Table 1. The base particle was directly observed with an SEM. As a result, fine particles was present in the base particle.

<Preparation of Detergent Particles> The amount 3.0 kg of the base particles obtained by the above-mentioned procedures were supplied into Lόdige Mixer (manufactured by Matsuzaka Giken Co., Ltd.; capacity: 20 L; equipped with a jacket), and the rotation of a main shaft was started at 70 r.p.m., without rotating a chopper. Incidentally, hot water at 80°C was allowed to flow through the jacket at 10 L/minute. The amount 0.75 kg of an acidic form of LAS, which was temperature-controlled to 60°C, was supplied thereinto in 1 minute, and the components were then mixed and agitated for 4 minutes to carry out a dry-neutralization reaction (the amount of the alkali in the base particles: 6.1 times the amount equivalent for neutralizing the anionic surfactant). Subsequently, 0.60 kg of a zeolite A-type was added, and thereafter a surface modification was carried out with rotating the main shaft at 150 r.p.m. and the chopper at 3600 r.p.m., to give detergent particles. The composition and the properties of the resulting detergent particles are shown in Table 2. Incidentally, the degree of particle growth of the resulting detergent particles was 1.1.

Example 3

Preparation of Base Particles> Base particles were prepared by the following procedures. The amount

450.7 kg of water was added to a 1 m³-mixing vessel having agitation impellers. After the water temperature reached 55°C, 199.0 kg of sodium sulfate, and 127.6 kg of sodium tripolyphosphate were sequentially added thereto. The temperature of the jacket was set at 45°C. After agitating the mixture for 10 minutes, 12.8 kg of a 40% by weight-aqueous sodium polyacrylate solution and 127.6 kg of sodium carbonate were added thereto, and the resulting mixture was then agitated for 60 minutes, with pulverizing under circulation in a line mill. Thereafter, 63.8 kg of No. 2 Sodium Silicate (40% by weight-aqueous solution), and 34.0 kg of 30% by weight-aqueous LAS-Na were added thereto, and further agitated for 60 minutes, with pulverizing under circulation in a line mill, to give a homogeneous slurry. The final temperature of this slurry was 52°C. In addition, the water content of this slurry was 51% by weight. Incidentally, the average particle size of fine particles present in the slurry was determined using an FBRM system. As a result, the average particle size was 24 μm. This slurry was sprayed at a spraying pressure of 35 kg/cm² with a pressure spray nozzle arranged near the top of a spray-drying tower. A high- temperature gas fed to the spray-drying tower was supplied at a temperature of 242°C to the bottom of the tower and exhausted at a temperature of 112°C from the top of the tower. The composition and the properties of the resulting base particles are shown in Table 1. The base particle was directly observed with an

SEM. As a result, fine particles were present in the base particle.

Preparation of Detergent Particles>

Thirty kilograms of the base particles obtained by the above-mentioned procedures were supplied into Ribbon Mixer (manufactured by Fuji Paudal Co.,

Ltd.; whole capacity: 90 L; equipped with a jacket), and the rotation was initiated at a rotational speed of 67 rpm, with a Froude number of 0.85. Incidentally, hot water at 80°C was allowed to flow through the jacket at 10 L/minute. The amount 6.0 kg of an acidic form of LAS, which was temperature-controlled to 60°C, was supplied thereinto in 1 minute, and the components were then mixed and agitated for 5 minutes to carry out a dry-neutralization reaction (the amount of the alkali in the base particles: 7.6 times the amount equivalent for neutralizing the anionic surfactant).

Subsequently, 2.5 kg of the above mixture and 0.35 kg of a zeolite A-type were supplied into Lδdige Mixer (manufactured by Matsuzaka Giken Co., Ltd.; capacity: 20 L; equipped with a jacket), and thereafter a surface modification was carried out with rotating the main shaft at 150 r.p.m. and the chopper at 3600 r.p.m., to give detergent particles. The composition and the properties of the resulting detergent particles are shown in Table 2. Incidentally, the degree of particle growth of the resulting detergent particles was 0.9.

Comparative Examples

The marketed detergents (A to E) having intermediate or low bulk densities were evaluated for the fast dissolubility and the flowability properties.

The evaluation results are shown in Table 3. None of the detergents could satisfy all of the fast dissolubility, the excellent flowability properties and the excellent storage stability at the same time.

Table 1

Example 1 Example 2 Example 3

Composition of

Base Particles (% bv weight

Component (A)

Sodium Carbonate 35 25 25

Others

Sodium Tripolyphosphate 25 25 25

Sodium Sulfate 36 40.5 40

LAS-Na 0 0.5 2

Sodium Polyacrylate 1 2 1

No. 2 Sodium Silicate 0 5 5

Water 3 2 2

Properties of Base Particles

Bulk Density [g/L] 575 400 270

Average Particle Size [μm] 278 284 275

Particle Strength [g/cm²] 240 160 102

Table 2

Example 1 Example 2 Example 3

Composition of Detergent Particles

(parts bv weight

Base Particles 100 100 100

Component (B)

LAS-Acid Type Liquid Acid 20 25 20

Precursor

Others

Sulfuric Acid 2 0 0

Component (O

Zeolite A-type 17 20 17

Properties of Detergent Particles

Bulk Density [g/L] 587 460 406

Average Particle Size [μm] 336 310 251

60-seconds Dissolution Rate [%] 96 97 99

Variance of Powder Dropping 0.3 0.9 0.7

Rate [-]

Sieve Permeability [%] 100 100 100

(after 7 days)

Bleed-out Property [-] 1 1 1

Table 3

Bulk Density 60-Seconds Variance Sieve

[g/L] Dissolution of Powder Permeability

Rate Dropping (after 7 days)

[ ] Rate [-1 r%ι

Example 1 587 96 0.3 100

Example 2 460 97 0.9 100

Example 3 406 99 0.7 100

Comp. Ex. Marketed 436 64 1.1 70 Detergent A

Marketed 426 82 1.4 84 Detergent B

Marketed 357 71 3.4 - Detergent C

Marketed 334 82 0.6 - Detergent D

Marketed 497 94 2.1 — Detergent E

INDUSTRIAL APPLICABILITY

Since the detergent particles of the present invention are excellent in the storage stability, the fast dissolubility and the flowability properties, there is exhibited an effect that detergent compositions which are suitably used for detergent composition for clothes can be obtained by using the above detergent particles. The detergent particles can be used for washing laundry items and the like.

Claims

1. Detergent particles comprising: a particle obtained by the step of dry-neutralizing base particles comprising a water-soluble solid alkali inorganic substance (A) with a liquid acid precursor (B) of a non-soap anionic surfactant, wherein the non-soap anionic surfactant is used in an amount of 15% by weight or more of the base particles; and a fluidizing aid (C) existing on a surface of the particle, wherein the detergent particles have a 60-second dissolution ratio of 90% or more, an average particle size of from 150 to 500 μm and a bulk density of 600 g/L or less.

2. A process for preparing detergent particles comprising the steps of: (a): preparing a slurry comprising a water-soluble solid alkali inorganic substance (A), wherein the water-soluble solid alkali inorganic substance

(A) is present in an amount equal to or greater than an amount equivalent for neutralizing a liquid acid precursor (B) of a non-soap anionic surfactant to be added in step (c); (b): spray-drying the slurry obtained in step (a) to give base particles;

(c): adding to the base particles obtained in step (b) the liquid acid precursor

(d): adding a fluidizing aid (C) to the particle obtained in step (c), thereby surface-modifying the particle.

3. A detergent composition comprising the detergent particles as defined in claim 1.