EP2502981A1

EP2502981A1 - Method for producing detergent granules

Info

Publication number: EP2502981A1
Application number: EP10831629A
Authority: EP
Inventors: Kenichiro Kawamoto; Yoshinobu Imaizumi; Takashi Nakayama; Takashi Kamei; Hiroaki Warita; Masahiro Yamaguchi
Original assignee: Kao Corp
Current assignee: Kao Corp
Priority date: 2009-11-18
Filing date: 2010-11-18
Publication date: 2012-09-26
Also published as: AU2010320064B2; CN102712884B; BR112012011975A2; EP2502981A4; WO2011062236A1; JP2011127106A; CN102712884A; AU2010320064A1

Abstract

To provide a method for producing detergent particles which gives excellent yields of detergent particles having a necessary particle size, containing an anionic surfactant according to a method without including spray-drying. By using the method of the present invention, an effect such as detergent particles having a sharp particle size distribution can also be produced in excellent yields is exhibited. Having a sharper particle size distribution would also lead to exhibition of the effects that a detergent having not only improved external appearance but also excellent free flowability, and consequently excellent productivity can be efficiently obtained.

Description

TECHNICAL FIELD

The present invention relates to a method for producing detergent particles using a vessel rotary mixer, a surfactant paste containing an anionic surfactant, and a multi-fluid nozzle. Further, the present invention relates to a detergent composition containing the detergent particles.

BACKGROUND ART

In the recent years, powder detergent compositions and production methods are desired to meet the needs of economic advantages, environmental friendliness, and the like.
Various disclosures are made on powder detergents formulated with a compound of an anionic surfactant represented by the formula (1) as a surfactant, for the purposes of improvements in meeting the needs of high detergent activity capability and environmental friendliness, and the like. The above anionic surfactant is known to generally have less skin irritability and excellent biodegradability.
For example, as a production method without using spray-drying, from the viewpoint of meeting the needs of economic advantages and environmental friendliness, a method for producing a detergent composition using an anionic surfactant according to a non-spray-drying method is disclosed. Patent Publication 1 discloses a method for producing a detergent composition with a surfactant paste and dried detergent materials in a high-speed mixer/moderate speed mixer/dryer continuously. Patent Publication 2 discloses a method for producing a detergent composition with a surfactant paste and dried detergent materials in a high-speed mixer/moderate speed mixer/conditioning apparatus continuously while recirculating the fine particles.
However, in the method of Patent Publication 1, it is difficult to adjust particle sizes, and in the method of Patent Publication 2, a method of recirculating fine particles is used in order to solve to adjust particle sizes, thereby making its productivity low. Therefore, a method of obtaining detergent particles having a necessary particle size in an excellent yield in an even more simple manner is in demand.

PRIOR ART REFERENCES

PATENT PUBLICATIONS

Patent Publication 1: Japanese Unexamined Patent Publication No. Hei-10-500716
Patent Publication 2: Japanese Unexamined Patent Publication No. Hei-10-506141

SUMMARY OF THE INVENTION

MEANS TO SOLVE THE PROBLEMS

Specifically, the gist of the present invention relates to a method for producing detergent particles, including a step of mixing a surfactant paste, including
adding, to a powder of a powder detergent raw material, a surfactant paste containing the following component a) and component b):

a) an anionic surfactant represented by the following formula (1):

R-O-SO₃M (1)

wherein R is an alkyl group or alkenyl group having 10 to 18 carbon atoms, and M is an alkali metal atom or an amine; and
b) water in an amount of 25 to 70 parts by weight, based on 100 parts by weight of the above component a) using a multi-fluid nozzle, and
mixing the components with a vessel rotary mixer.

The present invention relates to the provision of a method for producing detergent particles which gives excellent yields of detergent particles having a necessary particle size, containing an anionic surfactant according to a method without including spray-drying. Further, the present invention relates to the provision of a detergent composition containing the detergent particles.
By using the method of the present invention, an effect such as detergent particles having a sharp particle size distribution can also be produced in excellent yields is exhibited. Having a sharper particle size distribution would also lead to exhibition of the effects that a detergent having not only improved external appearance but also excellent free flowability, and consequently excellent productivity can be efficiently obtained.

MODES FOR CARRYING OUT THE INVENTION

The method for producing detergent particles of the present invention is a method for producing detergent particles including the step of mixing a surfactant paste containing an anionic surfactant represented by the formula (1), and a powder of a powder detergent raw material, and one feature of the method is in that a vessel rotary mixer is used upon mixing is carried out, and that a surfactant paste containing an anionic surfactant represented by the formula (1) is added with a multi-fluid nozzle such as a two-fluid nozzle.
In general, the granulation using a vessel rotary mixer can make the powder inside the mixer homogeneously free-flowable, and further a shearing force applied to the powder is suppressed because of a mixing mechanism accompanying lifting of the particles due to rotations and sliding or cascading due to the deadweight, so that the granulation is a non-compact granulation method. In addition, since the granulation does not progress unless a paste containing an anionic surfactant represented by the formula (1) has strong adhesive property upon the contact with the powder, it is necessary that the adhesive property is exhibited upon the contact with the powder. If the paste containing an anionic surfactant represented by the formula (1) as described above is fed to a one-fluid nozzle or a pipe, which is a general feeding method for vessel rotary mixers, it is found that the fed liquid components are less likely to be homogeneously dispersed in the mixer, so that coarse particles are more likely to be formed from a large liquid lump locally generated.
In view of the above, when a paste containing an anionic surfactant represented by the formula (1) which exhibits adhesive property upon the contact with a powder is fed to a vessel rotary mixer by means of spraying using a multi-fluid nozzle such as a two-fluid nozzle, it could surprisingly be found that the powder can be formed into particles by the paste while suppressing the formation of coarse particles. This is presumably due to the fact that the paste containing the anionic surfactant as described above is previously formed into fine droplets using a multi-fluid nozzle, whereby high dispersibility of the paste containing the anionic surfactant as described above can be accomplished even within a vessel rotary mixer, so that large liquid lumps that form coarse particles are not generated. Therefore, one of the features of the present invention is also in that a paste containing an anionic surfactant as described above which exhibits adhesive property upon the contact with the powder is added to a vessel rotary mixer using a multi-fluid nozzle.
As described above, in the present invention, by using a vessel rotary mixer and a multi-fluid nozzle in a combination, an effect which cannot be expected by those detergent particles produced by each of them alone that detergent particles having a sharp particle size distribution can be produced in excellent yields is exhibited.
The mechanisms of obtaining particles having a sharp particle size distribution in high yields are presumably owing to synergistic effects such as evenly sized particles in which a shearing force applied to the powder is suppressed are obtained by using a vessel rotary mixer, and fine liquid droplets are formed with a multi-fluid nozzle and highly dispersed, whereby the aggregation caused by adhesive property of a surfactant paste containing an anionic surfactant represented by the formula (1) can be suppressed.
However, when stirring or mixing is carried out using a vessel rotary mixer, there is a disadvantage that liquid components (a surfactant paste as referred to herein) are less likely to be homogeneously dispersed in the mixer. For this reason, for example, having studied a method for supplying liquid components, a means of homogeneously dispersing liquid components is considered. For example, as a method for homogeneously dispersing liquid components, a method of achieving the formation of fine droplets of liquid components using a multi-fluid nozzle such as a two-fluid nozzle is considered. However, one of ordinary skill in the art would be less likely to arrive at the technical idea of the use of a multi-fluid nozzle for the purpose of the forming a surfactant paste having a high viscosity into fine droplets.
An embodiment of mixing in the method of the present invention is not particularly limited, so long as the embodiment involves the use of a vessel rotary mixer, and spraying of a surfactant paste containing an anionic surfactant represented by the formula (1) using a multi-fluid nozzle. An embodiment will be explained more specifically hereinbelow as one example of the method of the present invention.
In the present invention, a detergent particle means a particle containing a surfactant, a builder, or the like, and detergent particles mean to a collective member thereof. The detergent composition means a composition that contains detergent particles and separately added detergent components other than the detergent particles as desired (for example, a builder granule, a fluorescer, an enzyme, a perfume, a defoaming agent, a bleaching agent, a bleaching activator, or the like).
The term water solubility as used herein means that solubility to water at 25°C is 0.5 g/100 g or more, and the term water insolubility means that solubility to water at 25°C is less than 0.5 g/100 g.

1. Powder Detergent Raw Materials

The essential components in the present invention include powder detergent raw materials. Specifically, the powder detergent raw materials include 1) an alkalizing agent, 2) a water-soluble substance, and 3) a clay mineral, as listed hereinbelow. For these components 1) to 3), the alkalizing agents, the water-soluble substances, and the clay minerals may be used alone, or as a mixture of plural components. From the viewpoint of granulation, the powder detergent raw materials have an average particle size of preferably from 10 to 250 µm, more preferably from 50 to 200 µm, and even more preferably from 80 to 200 µm.
In addition, the average particle size of the alkalizing agent, the water-soluble substance, or the clay mineral is not particularly limited. In a case where a surfactant paste containing an anionic surfactant represented by the formula (1) is blended in a high proportion, the components may be pulverized to an average particle size of from 1 to 50 µm, from the viewpoint of improvement in yields.
The alkalizing agent includes those usable as alkalizing agents in ordinary detergent compositions, and the alkalizing agent is exemplified by sodium carbonate (for example, light ash and dense ash), sodium hydrogencarbonate, sodium silicate, potassium carbonate, calcium carbonate, and the like. The light ash is preferred, from the viewpoint of ease in handling and availability. These alkalizing agents may be used alone, or in a mixture of two or more kinds.
In a case where light ash is used as a powder detergent raw material, a surfactant-supporting ability can be even more improved by adjusting a temperature upon baking sodium bicarbonate. The baking temperature is preferably from 120° to 250°C, more preferably from 150° to 220°C, and even more preferably from 150° to 200°C, from the viewpoint of supporting ability.
The water-soluble substance includes powders usable in ordinary detergent compositions, such as sodium sulfate or sodium tripolyphosphate; porous powders prepared by drying the hydrates thereof, and the like.
The clay mineral includes clay minerals usable in ordinary detergent compositions. In a case where a clay mineral is used together with other raw materials mentioned above, mixtures thereof would be formed into particles. In a case where the clay mineral is mixed with a surfactant paste, a part of the powder detergent raw materials is dissolved by the water contained in the paste, and the bonding property resulting therefrom or the bonding property of the clay mineral is utilized in the formation of particles.
When the powder of the powder detergent raw materials and the surfactant paste are mixed, a powder raw material other than the above-mentioned powder detergent raw materials may be added as desired, and the powder raw material is added in an amount of preferably from 0 to 150 parts by weight, more preferably from 0 to 100 parts by weight, and even more preferably from 0 to 50 parts by weight, based on 100 parts by weight of the powder detergent raw material. The powder raw material includes, for example, aluminosilicates, crystalline silicates such as PREFEED (manufactured by Tokuyama Siltex), and the like. When the powder raw material is used, the powder raw material is contained in an amount of preferably 0.1% by weight or more, more preferably 1% by weight or more, and even more preferably 3% by weight or more, of the detergent particles, from the viewpoint of improvement in free flowability, suppression of bleed-out and caking, and improvement in detergency, and the powder raw material is contained in an amount of preferably 40% by weight or less, more preferably 30% by weight or less, even more preferably 20% by weight or less, and still even more preferably 10% by weight or less, of the detergent particles, from the viewpoint of rinsability and dissolubility.
Preferred examples of the powder detergent raw materials include those containing light ash and/or sodium sulfate, from the viewpoint of availability and the properties of the resulting detergent particles.

2. Surfactant Paste

An essential component in the present invention includes a surfactant paste. In the present invention, a surfactant paste is added to powder detergent raw materials, and the powder detergent raw materials are formed into particles using a vessel rotary mixer, thereby producing detergent particles.

[Component for Surfactant Paste]

The anionic surfactant in the surfactant paste used in the present invention is an anionic surfactant represented by the formula (1):

R-O-SO₃M,

wherein R is an alkyl group or alkenyl group having 10 to 18 carbon atoms, and preferably 12 to 16 carbon atoms, M is an alkali metal atom such as Na or K, or an amine such as monoethanolamine or diethanolamine. M is preferably Na or K, from the viewpoint of improvement in detergency of the detergent composition.

[Physical Properties of Surfactant Paste]

A surfactant paste refers to one containing an anionic surfactant represented by the formula (1) (referred to "component a)" in the present specification) and a given amount of water. In an operable temperature region of the surfactant composition, it is desired that the surfactant paste has a temperature range satisfying that the surfactant paste has a viscosity of preferably 10 Pa•s or less, and more preferably 5 Pa•s or less, from the viewpoint of handling property upon the production. As the operable temperature region described above, it is preferable that the temperature range mentioned above exists preferably up to 70°C, and more preferably up to 60°C, from the viewpoint of stability of the surfactant paste. Here, the viscosity is determined with a coaxial double cylindrical rotary viscometer (manufactured by HAAKE, sensor: SV-DIN) at a shearing rate of 50 [1/s].
The surfactant paste greatly varies in viscosity depending upon the water content. For example, a surfactant paste can be prepared by neutralizing the component a), an acid precursor, with an alkali compound, and in that case, it is preferable that a water content of the alkali compound used is adjusted, so that a surfactant paste having a desired water content, in other words, a desired viscosity, can be prepared. It is generally known that when a surfactant paste contains water in an amount of from 25 to 70 parts by weight, based on 100 parts by weight of the component a), i.e. water content of the surfactant composition being from about 20 to about 40%, the viscosity is lowered, thereby making its handling easy. In the present invention, it is preferable to use a surfactant composition of which amount of water is adjusted within this range. The amount of water in the surfactant paste is in the range of from 25 to 70 parts by weight, preferably from 30 to 65 parts by weight, and more preferably from 35 to 65 parts by weight, based on 100 parts by weight of the component a), from the viewpoint of handling.
In addition, since the component a), the acid precursor, is very unstable and more likely to be degraded, it is preferable that the surfactant paste is prepared so that the degradation can be suppressed. The method of preparation is not particularly limited, and a known method can be used. For example, the production may be carried out by removing heat of neutralization with a heat exchanger or the like using a loop reactor, while cautiously temperature-controlling the acid precursor and the surfactant paste. A temperature range during the production is preferably from 30° to 60°C, and a temperature range for storage after the production is preferably 60°C or lower. In addition, the surfactant composition may be used by optionally elevating the temperature upon use.
In addition, it is preferable that the resulting anionic surfactant paste has excess degree of alkalinity, from the viewpoint of suppressing degradation.
In addition, the surfactant paste may contain an unreacted alcohol or an unreacted polyoxyethylene alkyl ether upon the production of the acid precursor of the component a), sodium sulfate, which is a by-product formed during the neutralization reaction, or a pH buffering agent, which can be added during the neutralization reaction, a decolorizing agent, or the like.
Here, the component a) is contained in an amount in the range of preferably from 10 to 55% by weight, more preferably from 10 to 45% by weight, even more preferably from 15 to 40% by weight, and still even more preferably from 15 to 40% by weight, of the detergent particles obtainable in the present invention, from the viewpoint of detergency and dissolubility.
In the surfactant paste, the component a) as the surfactant can be used alone, or can also be used in combination with the following surfactant. In a case of a combined use, a surfactant may be previously mixed with a surfactant paste containing the component a), or each of those surfactants may be added separately. Here, when combined with the following surfactant, the following surfactant is contained in an amount of preferably from 1 to 70 parts by weight, more preferably from 2 to 50 parts by weight, even more preferably from 3 to 30 parts by weight, and even still more preferably from 5 to 15 parts by weight, based on 100 parts by weight of the component a). In addition, when the following surfactant is used in combination, the component a) is contained in an amount of preferably from 40 to 80% by weight, more preferably from 45 to 75% by weight, and even more preferably from 50 to 70% by weight, of the surfactant paste.
For example, a nonionic surfactant can be mixed or separately added thereto. In a case where a nonionic surfactant having a melting point of 30°C or lower is used, it is preferable to use the nonionic surfactant together with a water-soluble nonionic organic compound having a melting point of from 45° to 100°C and a molecular weight of from 1,000 to 30,000, the water-soluble nonionic organic compound having an action of elevating a melting point of a surfactant (hereinafter referred to as a "melting-point elevating agent"), or an aqueous solution thereof. Here, the melting-point elevating agent which can be used in the present invention includes, for example, polyethylene glycols, polypropylene glycols, polyoxyethylene alkyl ethers, Pluronic nonionic surfactants, and the like. Also, an amphoteric surfactant or a cationic surfactant can be used together, depending upon the purposes.
For example, an anionic surfactant other than the component a) can be mixed or separately added thereto. The anionic surfactant includes a polyoxyethylene alkyl ether sulfate or an alkylbenzenesulfonate, a salt of an α-sulfofatty acid ester, and a secondary alkanesulfonate. In addition, the anionic surfactant, such as a polyoxyethylene alkyl ether sulfate or an alkylbenzenesulfonate, may be contained in an amount of preferably from 0 to 10% by weight, more preferably from 0 to 5% by weight, and even more preferably from 0 to 3% by weight, of the detergent particles, from the viewpoint of improving dispersibility of the detergent particles in low-temperature water. In addition, the anionic surfactant is contained in an amount of preferably 0.1% by weight or more, more preferably 1% by weight or more, and even more preferably 3% by weight or more, from the viewpoint of improving detergency, and the anionic surfactant is contained in an amount of preferably 10% by weight or less, more preferably 8% by weight or less, and even more preferably 5% by weight or less, from the viewpoint of improvement in yields of detergent.
Further, in order to obtain defoaming effects, a fatty acid salt can be used together therewith.
The nonionic surfactant is not particularly limited, and it is preferable that the nonionic surfactant is, for example, a polyoxyalkylene alkyl ether prepared by adding an alkylene oxide to an alcohol having 10 to 14 carbon atoms in an amount of from 6 to 22 mol, from the viewpoint of detergency.
The nonionic surfactant is contained in the detergent particles in an amount of preferably from 0 to 10% by weight, more preferably from 0 to 5% by weight, and even more preferably from 0 to 3% by weight, of the detergent particles, from the viewpoint of improving detergency, improving anti-caking property, and suppressing the choking upon formation of powder dusts. In addition, the nonionic surfactant is contained in an amount of preferably 0.1% by weight or more, more preferably 1% by weight or more, and even more preferably 3% by weight or more, from the viewpoint of improving detergency, and the nonionic surfactant is contained in an amount of preferably 10% by weight or less, more preferably 8% by weight or less, and even more preferably 5% by weight or less, from the viewpoint of improvement in yields of detergent.

3. Polymer

The detergent particles in the present invention can be used together with a water-soluble cellulose derivative, a saccharide, and a carboxylate polymer, or an inorganic polymer such as amorphous silicate, from the viewpoint of detergency and a binder effect for formation of particles, and a salt of acrylic acid-maleic acid copolymer and a salt of polyacrylic acid are more preferred. The salt is preferably a sodium salt, a potassium salt, or an ammonium salt. Here, the carboxylate polymer has a weight-average molecular weight of preferably from 1,000 to 100,000, and more preferably from 2,000 to 80,000.

4. Other Components

The detergent particles in the present invention can be properly blended with a substance other than those listed in the above 1 to 3, as occasion demands. The timing of addition of other components is not particularly limited.

- Chelating Agent (Metal Sequestering Agent)

The chelating agent can be blended for the purpose of suppressing the inhibition of detergent action by metal ions. A water-soluble chelating agent is not particularly limited, so long as the chelating agent is a substance that holds a metal ion sequestering ability, and a crystalline silicate, a tripolyphosphate, an orthophosphate, a pyrophosphate, or the like can be used. A water-insoluble chelating agent is preferably particles that have an average particle size of from 0.1 to 20 µm, from the viewpoint of dispersibility in water, including crystalline aluminosilicates, and, for example, A-type zeolite, P-type zeolite, X-type zeolite, or the like can be used.

- Water-Soluble Inorganic Salt

It is preferable that a water-soluble inorganic salt is added, for the purpose of enhancing an ionic strength of a washing liquid, and improving an effect such as sebum dirt washing.

- Water-Insoluble Excipient

The water-insoluble excipient is not particularly limited, so long as the water-insoluble excipient is a substance that has favorable dispersibility in water and does not give a disadvantageous influence on detergency. The water-insoluble excipient preferably has an average primary particle size of from 0.1 to 20 µm, from the viewpoint of dispersibility in water.

- Other Auxiliary Components

Other auxiliary components include fluorescers, pigments, dyes, and the like.
Here, the average particle size of the above components can be measured in accordance with the methods described in the Measurement Methods of Physical Properties described later.

< Method for Producing Detergent Particles >

The method for producing detergent particles of the present invention is a method including the step of mixing a surfactant paste, including adding a surfactant paste to a powder of a powder detergent raw material and mixing the components, and the detergent particles are prepared through the steps.

1. Step of Mixing Surfactant Paste

The step includes the steps of adding, to a powder of a powder detergent raw material, a surfactant paste containing an anionic surfactant represented by the formula (1) and water, and mixing these components with a vessel rotary mixer, thereby preparing detergent particles.
The surfactant paste to be mixed in this step is in an amount of preferably from 25 to 200 parts by weight, more preferably from 25 to 180 parts by weight, even more preferably from 25 to 160 parts by weight, still even more preferably from 25 to 100 parts by weight, especially preferably from 30 to 90 parts by weight, and especially more preferably from 35 to 85 parts by weight, based on 100 parts by weight of the powder detergent raw material. The surfactant paste is in an amount of preferably 25 parts by weight or more, from the viewpoint of detergency, and the surfactant paste is in an amount of preferably 200 parts by weight or less, more preferably 180 parts by weight or less, even more preferably 160 parts by weight or less, and still even more preferably 100 parts by weight or less, from the viewpoint of yields of detergent and dissolubility.
The vessel rotary mixer usable in this step may be any apparatus neither giving a strong shear to particles nor densifying them. For example, even in a vertical or horizontal mixer equipped with a main blade and a disintegration blade that can inherently give a high shearing force, the mixer can be utilized in the production of the particles of the present invention by setting a rotational speed or a Froude number as defined below to a low value, thereby controlling densification. In other words, the vessel rotary mixer as used herein encompasses a mixer which can be operated by lowering a shearing force with setting or the like of operating conditions, even if the mixer is capable of giving a high shearing force to the particles.
As the vessel rotary mixer, a pan mixer and a rotary drum mixer, in which the formation of particles progresses with the rotation of the body of the mixer, are preferred, from the viewpoint of easiness in formation of particles and improvement in supporting ability. These apparatuses can be used in both methods of a batch process and continuous process. Here, it is preferable that the low-shearing mixer is provided with baffles for assisting mixing in the pan or the rotary drum, from the viewpoint of powder miscibility and liquid-solid miscibility.
Also, from the viewpoint of allowing the powder to homogeneously free-flow, and further securing a mixing mechanism of lifting-up of the particles according to rotations and sliding or cascading the powder due to the deadweight of the particles, in order to use a mixer as a vessel rotary mixer, the mixer is set to have a Froude number of preferably 1.0 or less, more preferably 0.8 or less, even more preferably 0.6 or less, and still even more preferably 0.4 or less, as defined in the following formula.
$Froude number : Fr = V^{2} / (R \times g)$

wherein V: peripheral speed [m/s],
R: a radius [m] from the center of rotation to the circumference of the rotated object, and
g: a gravitational acceleration rate [m/s²].
The mixer is set to have a Froude number of preferably 0.001 or more, more preferably 0.005 or more, even more preferably 0.01 or more, and still even more preferably 0.05 or more, from the viewpoint of homogeneously adding a surfactant paste to a mixed powder.
Here, it is supposed that in a vertical or horizontal mixer equipped with a main blade and a disintegration blade, the values of the main shaft are used for V and R, and that in a pan mixer or a rotary drum mixer in which the formation of particles is progressed by the rotation of the body of the mixer, the values of the body of the mixer are used for V and R. In addition, in a pan mixer equipped with a disintegration blade, it is supposed that the values for disintegration blade are used for V and R.
The rotation time for the mixer is not particularly limited, and, for example, it is preferable that the rotation time is 0 to 10 minutes after addition of a surfactant paste.
In the present invention, it is preferable that a surfactant paste is added while homogenously dispersing. As a method for serving this purpose, there is a method of forming fine droplets by using a multi-fluid nozzle.
The multi-fluid nozzle refers to a nozzle that allows to flow a liquid component and a gas for formation fine droplets, such as the air or nitrogen, in independent pathways, to communicate to a portion in the vicinity of a tip end portion of the nozzle, and mixing and forming fine droplets, and a two-fluid nozzle, a three-fluid nozzle, a four-fluid nozzle, or the like can be used therefor. In addition, a mixing section of the liquid component and the gas for forming fine droplets may be any one of an internal mixing type where the mixing is carried out within a tip end portion of the nozzle, or an external mixing type where the mixing is carried out in the external of a tip end portion of the nozzle.
In the present invention, it is preferred to add a liquid component by using a multi-fluid nozzle to form fine liquid droplets, and it is more preferred to use a two-fluid nozzle. The multi-fluid nozzle mentioned above includes, for example, internal mixing type two-fluid nozzles manufactured by Spraying Systems Japan K.K., Kyoritsu Gokin Co., Ltd., H. IKEUCHI Co., Ltd., and the like; external mixing type two-fluid nozzles manufactured by Spraying Systems Japan K.K., Kyoritsu Gokin Co., Ltd., Atomax Co., Ltd., and the like; external mixing four-fluid nozzles manufactured by fujisaki electric co., ltd., and the like.
In a case where a two-fluid nozzle is used, for example, it is preferable to feed the above-mentioned paste under the following conditions. For example, an air spraying pressure for forming fine droplets of from 0.05 to 0.7 MPa is preferred.
In the present invention, it is preferable to use an external mixing-type two-fluid nozzle, from the viewpoint of formation of fine liquid droplets of a high-viscosity surfactant paste used in the present invention, and prevention of clogging of the surfactant paste at tip ends of the nozzles.
As a result of intensive studies on the influences of the differences in liquid droplet sizes on the yield of the detergent particles obtained and the amount of coarse particles, the above-mentioned paste has a liquid droplet size in an average particle size of preferably from 1 to 300 µm, more preferably from 1 to 200 µm, and even more preferably from 1 to 150 µm, from the viewpoint of yields.
In addition, when it is desired to increase a rate of adding the above-mentioned paste, it is effective to use a plural number of these multi-fluid nozzles, thereby increasing the rate of addition, while maintaining the formation of fine liquid droplets.
By using the method as described above, homogeneous dispersion is made possible even in the above-mentioned paste having a high viscosity, so that detergent particles having an improved yield and a sharp particle size distribution are obtained.
Here, the average particle size of the liquid droplet size of the surfactant paste is calculated on a volume basis, which is a value measured using a laser diffraction particle size distribution analyzer Spraytec (manufactured by Malvern Instruments Ltd.).

< Physical Properties of Detergent Particles >

According to the method of the present invention, detergent particles having given properties can be obtained. The detergent particles obtained by the method of the present invention are also embraced by the present invention. The preferred physical properties of the detergent particles according to the present invention are as follows.
The bulk density is preferably 400 g/L or more, more preferably from 450 to 1,000 g/L, even more preferably from 450 to 950 g/L, and still even more preferably from 500 to 900 g/L. The average particle size of preferably from 150 to 800 µm, more preferably from 180 to 700 µm, and even more preferably from 200 to 500 µm.
Here, the bulk density and the average particle size mentioned above can be measured in accordance with the Measurement Methods of Physical Properties described later.
In addition, as an index of the preferred particle size distribution of the detergent particles according to the present invention, Rosin-Rammler number (R-R number in the table) can be used. In the calculation for the Rosin-Rammler number, the following formula is used.
$\log (\log (100 / R (Dp))) = nlog (Dp) + \log (β)$

R (Dp): a cumulative percentage [%] of powder having particle sizes of Dp µm or more;
Dp: a particle size [µm];
n: a Rosin-Rammler number; and
β: a particle size distribution coefficient.

The larger the Rosin-Rammler number n, the sharper the particle size distribution. n is preferably 1.5 or more, more preferably 1.7 or more, even more preferably 1.9 or more, and still even more preferably 2.0 or more, from the viewpoint of aesthetic appreciation of the detergent particles.
An yield of preferred particle sizes of the detergent particles according to the present invention, as expressed by a proportion of the particles having a sieve opening of from 125 to 1000 µm, is preferably 70% or more, more preferably 75% or more, even more preferably 80% or more, still even more preferably 85% or more, especially preferably 87% or more, and especially more preferably 90% or more.
As the amount of water of the detergent particles according to the present invention, the smaller the amount of water, the more preferred, from the viewpoint of a high blending ratio of the component a). Specifically, in a case where an amount of water in the detergent particles is measured with an infrared moisture meter, the amount of water is preferably 20% by weight or less, more preferably 15% by weight or less, even more preferably 10% by weight or less, and still even more preferably 5% by weight or less.
The oil-absorbing ability of the detergent particles according to the present invention is measured as an oil-absorbing ability after excluding particles having a sieve opening of 2000 µm or more. Preferably, the oil-absorbing ability is preferably 0.15 mL/g or more, more preferably 0.2 mL/g or more, even more preferably 0.3 mL/g or more, and still even more preferably 0.4 mL/g or more, from the viewpoint of increasing an allowable range of the amount of the liquid detergent raw material blended in the step of absorbing a liquid detergent raw material. It is considered that a relatively high oil-absorbing ability of the detergent particles in the present invention is accomplished by formation of particles with a vessel rotary mixer mentioned above.
In addition, the oil-absorbing ability of the detergent particles according to the present invention can be optionally adjusted by adjusting the amount of the surfactant paste blended in the step of mixing a surfactant paste with the amount of the liquid detergent raw material blended in the step of oil-absorbing a liquid detergent raw material, because the smaller the amount of the surfactant paste blended in the step of mixing a surfactant paste, the higher the oil-absorbing ability.
A preferred method for obtaining detergent particles may further optionally include a step of oil-absorbing a liquid detergent raw material or a surface-modifying step or a drying step as detailed below.

2. Optional Production Steps

Step of oil-absorbing a liquid detergent raw material: A step includes mixing detergent particles obtained by the step of mixing a surfactant paste, and a liquid detergent raw material such as the above-mentioned nonionic surfactant or the above-mentioned polymer.
Surface-modifying step: A step includes surface-modifying detergent particles obtained by the step of mixing a surfactant paste or the step of oil-absorbing a liquid detergent raw material with a surface coating agent. Here, in the surface-modifying step, disintegration may be progressed concurrently.
Drying step: A step includes drying detergent particles obtained in the step of mixing a surfactant paste, the step of oil-absorbing a liquid detergent raw material or the surface-modifying step.

2-1. Step of Oil-Absorbing Liquid Detergent Raw Material

This step is an optional step including mixing detergent particles obtained in the step of mixing a surfactant paste and a liquid detergent raw material, thereby making it possible to support the liquid detergent raw material to the detergent particles.
In the step of oil-absorbing a liquid detergent raw material, at least detergent particles obtained in the step of mixing a surfactant paste may be used. In other words, in this step, other particles having an ability of supporting a surfactant, for example, particles obtained by other methods such as spray-drying may be used together therewith.
The proportion of the detergent particles in the step of oil-absorbing a liquid detergent raw material is preferably 50% by weight or more, more preferably 70% by weight or more, and even more preferably 90% by weight or more, of 100% by weight of the particles to which the liquid detergent raw material is added, from the viewpoint of detergency and oil-absorbing ability.
The above method includes a method of mixing the components in a vessel rotary mixer in which the detergent particles are produced. Also, the method includes, for example, a method including mixing detergent particles and a liquid detergent raw material by using a mixer for a batch process or a continuous process. Here, in a case of carrying out according to a batch process, as a method of supplying to a mixer, there can be employed such a method as (1) a method including previously supplying detergent particles, and thereafter adding thereto a liquid detergent raw material; (2) a method including repeatedly supplying detergent particles and a liquid detergent raw material in the mixer in small amounts at a time; (3) a method including repeatedly supplying a part of detergent particles in a mixer, and thereafter supplying the remaining detergent particles and a liquid detergent raw material in the mixer in small amounts at a time, and the like.
In the addition of the liquid detergent raw material to the detergent particles, the larger the amount of the liquid detergent raw material blended, the more important the rate of addition. Specifically, it is preferable that a rate of adding a liquid detergent raw material is equal to or lower than a rate of absorbing oil in the detergent particles. By carrying out addition of the liquid detergent raw material at a rate of addition as mentioned above, oil absorption of the liquid detergent raw material can be made possible even to an inner portion of the detergent particles, whereby consequently the aggregation of the detergent particles due to adhesive property of the liquid detergent raw material can be suppressed, so that the particle size distribution of the resulting detergent particles can be made sharp. For example, when a surfactant paste used in the present invention is added, the liquid detergent raw material has a specific rate of addition of preferably 35 parts by weight/minute or lower, more preferably 20 parts by weight/minute or lower, even more preferably 10 parts by weight/minute or lower, and still even more preferably 7.5 parts by weight/minute or lower, based on 100 parts by weight of the detergent particles.
In addition, the liquid detergent raw material includes, for example, optional liquid components usable in ordinary detergent compositions, such as the above-mentioned nonionic surfactants, the water-soluble polymers (polyethylene glycol, sodium polyacrylate, acrylic acid-maleic acid polymers, and the like), fatty acids, and the like. The liquid component may be used as one component alone or in a combination of two or more components. As the liquid component, the component may be added as a liquid, or the component may be added in the form of an aqueous solution or dispersion. The liquid detergent raw material is used in an amount of preferably 0.1 parts by weight or more, more preferably 1 part by weight or more, and even more preferably 3 parts by weight, based on 100 parts by weight of the detergent particles, from the viewpoint of improvement in detergency, and the liquid detergent raw material is used in an amount of preferably 30 parts by weight or less, more preferably 20 parts by weight or less, and even more preferably 10 parts by weight or less, from the viewpoint of suppression of aggregation between particles of the detergent particle contained in the detergent particles, fast dissolubility, and suppression of bleed-out property and caking property.
Preferable mixers specifically include, in addition to the above-mentioned vessel rotary mixers, as follows. In a case of mixing by a batch process, those of (1) to (3) are preferable: (1) Henschel Mixer (manufactured by Mitsui Miike Machinery Co., Ltd.); High-Speed Mixer (Fukae Powtec Corp.); Vertical Granulator (manufactured by Powrex Corp.); Lödige Mixer (manufactured by Matsuzaka Giken Co., Ltd.); PLOUGH SHARE Mixer (manufactured by PACIFIC MACHINERY & ENGINEERING Co., LTD.); mixers disclosed in Japanese Patent Laid-Open No. Hei-10-296064 , mixers disclosed in Japanese Patent Laid-Open No. Hei-10-296065 , and the like; (2) Ribbon Mixer (manufactured by Nichiwa Kikai Kogyo K.K.); Batch Kneader (manufactured by Satake Kagaku Kikai Kogyo K.K.); Ribocone (manufactured by K.K. Okawahara Seisakusho), and the like; (3) Nauta Mixer (manufactured by Hosokawa Micron Corp.), SV Mixer (Shinko Pantec Co., Ltd.), and the like. Among the above-mentioned mixers, preferable are, in addition to the above-mentioned vessel rotary mixers, Lödige Mixer, PLOUGH SHARE Mixer, and the mixers disclosed in Japanese Patent Laid-Open No. Hei-10-296064 , mixers disclosed in Japanese Patent Laid-Open No. Hei-10-296065 , and the like. By using the above mixers, since the surface-modifying step described below can be carried out by the same mixer, these mixers are preferable, from the viewpoint of simplification of equipments. Among them, the mixers disclosed in Japanese Patent Laid-Open No. Hei-10-296064 and the mixers disclosed in Japanese Patent Laid-Open No. Hei-10-296065 are preferable, because the moisture and temperature of the mixture can be regulated by ventilation, whereby the disintegration of the detergent particles can be suppressed. In addition, mixers, such as Nauta Mixer, SV Mixer and Ribbon Mixer, which are capable of mixing powders and liquids without applying a strong shearing force, are preferable, from the viewpoint that the disintegration of the detergent particles can be suppressed.
Also, the detergent particles and a liquid detergent raw material may be mixed by using a continuous process-type mixer. Also, the continuous process-type mixer other than those listed above includes Flexo Mix (manufactured by Powrex Corp.), Turbulizer (manufactured by Hosokawa Micron Corporation), and the like.
It is preferable that the temperature within the mixer in this step is adjusted so that the degradation of the anionic surfactant in the detergent particle can be suppressed, and the temperature range during the production is preferably from 30° to 60°C, and the storage temperature range after the production is preferably 60°C or lower.
The mixing time in a batch process and the average residence time in the mixing in a continuous process for obtaining the suitable detergent particles are preferably from 1 to 30 minutes, more preferably from 2 to 25 minutes, and even more preferably from 3 to 20 minutes.
In the step of oil-absorbing a liquid detergent raw material, the mixing of the detergent particles and a liquid detergent raw material may be carried out under ventilation. More specifically, in the step of oil-absorbing a liquid detergent raw material, the ventilation includes the procedures of blowing a gas such as the air into a mixing vessel of a mixer during addition and/or during mixing of each of the raw materials. By carrying out the procedures, detergent particles can further support a liquid detergent raw material so that the resulting detergent particles contain a liquid detergent raw material in a higher blending ratio.
The reasons why the effects as described above are exhibited are deduced to be due to the fact that by carrying out the procedures, water in the anionic surfactant paste and other liquid detergent raw materials existing on the surface of the detergent particles is removed. As a result, the adhesive property of the detergent particles is reduced, thereby suppressing the aggregation of the detergent particles, leading to a sharp particle size distribution of the resulting detergent particles.
The blowing conditions are, for example, such that a gas to be blown in is at a temperature of preferably from 10° to 65°C, more preferably from 30° to 60°C, and even more preferably from 50° to 60°C.
The blowing amount is preferably from 1 to 15 parts by weight/min, more preferably from 2 to 10 parts by weight/min, and even more preferably from 3 to 8 parts by weight/min, based on 100 parts by weight of the detergent particles.
A powdery builder can also be added before adding a liquid detergent raw material, simultaneously with adding a liquid detergent raw material, in the course of adding a liquid detergent raw material, or after adding a liquid detergent raw material. By adding the above component, the particle size of the detergent particles can be controlled, and an improvement in detergency can be achieved. Incidentally, the term "powdery builder" as referred to herein refers to an agent in a powdery form for enhancing detergency other than surfactants, concretely, including base materials showing metal ion sequestering ability, such as zeolite and citrates; base materials showing alkalizing ability, such as sodium carbonate and potassium carbonate; base materials having both metal ion sequestering ability and alkalizing ability, such as crystalline silicates; other base materials enhancing ionic strength, such as sodium sulfate; and the like.
Here, as crystalline silicates, crystalline silicates described in Japanese Patent Laid-Open No. Hei-5-279013 , column 3, line 17 (those prepared by a process comprising calcinating and crystallizing at a temperature of from 500° to 1,000°C being preferable); Japanese Patent Laid-Open No. Hei-7-89712 , column 2, line 45; and Japanese Patent Laid-Open No. Sho-60-227895 , page 2, lower right column, line 18 (the silicates in Table 2 being preferable) can be used as preferred powdery builders. Here, the alkali metal silicates having an SiO₂/M₂O ratio, wherein M is an alkali metal, of from 0.5 to 3.2, preferably from 1.5 to 2.6, are more favorably used.
The amount of the powdery builder used is preferably from 0 to 12 parts by weight, and more preferably from 0 to 6 parts by weight, based on 100 parts by weight of the detergent particles. When the amount of the above component used is in the above range, it is excellent in dissolubility.
Further, subsequent to the step of oil-absorbing a liquid detergent raw material, it is preferable to add a surface-modifying step including surface-modifying the detergent particles.

2-2. Surface-Modifying Step

This step is an optional step, including modifying the particle surface of the detergent particles obtained in the step of mixing a surfactant paste or in the step of oil-absorbing a liquid detergent raw material. For this purpose, the embodiments for addition may include the surface-modifying step including adding various surface coating agents such as (1) fine powder, and (2) a liquid material given hereinbelow. The number of times for the surface-modifying step may be one or more times.
The free flowability and the anti-caking property of the detergent particles are likely to be improved by modifying the particle surface of the detergent particles with a surface coating agent. Therefore, it is preferable to provide a surface-modifying step in the method of the present invention. The apparatuses to be used in the surface-modifying step include those equipped with both agitation blades and disintegration blades as preferred apparatuses, among the mixers exemplified in the step of oil-absorbing a liquid detergent raw material. Each of the surface coating agents will be explained below.

(1) Fine Powder

As the fine powder, it is preferable that the average particle size of its primary particle is preferably 10 µm or less, and more preferably from 0.1 to 10 µm. When the particle size is in the above range, it is favorable from the viewpoints of the improvement in the coating ratio of the particle surface of the detergent particles, and improvements in free flowability and anti-caking property of the detergent particles. The average particle size of the fine powder is measured by a method utilizing light scattering by, for instance, a particle analyzer (manufactured by Horiba, LTD.), or it may be measured by a microscopic observation or the like. Further, it is preferable that the fine powder has a high ion exchange capacity or a high alkalizing ability from the viewpoint of detergency. The fine powder may be constituted by one component, or the fine powder may be constituted by plural components.
The fine powder is desirably aluminosilicates, which may be in any of crystalline or amorphous forms. Besides the aluminosilicates, fine powders of sodium sulfate, calcium silicate, silicon dioxide, bentonite, talc, clay, amorphous silica derivatives, crystalline silicates, and the like are preferable. In addition, a metal soap of which primary particles have an average particle size of from 0.1 to 10 µm, a powdery surfactant (for instance, an alkyl sulfate, or the like), or a water-soluble organic salt can be also similarly used. In addition, when a crystalline silicate is used, it is preferably used in a mixture with fine powder other than the crystalline silicate for the purpose of preventing deterioration owing to aggregation of the crystalline silicates by moisture absorption and carbon dioxide absorption, and the like.
The amount of the fine powder used is preferably from 0 to 40 parts by weight, more preferably from 0.5 to 40 parts by weight, even more preferably from 1 to 30 parts by weight, and still even more preferably from 2 to 20 parts by weight, based on 100 parts by weight of the detergent particles. When the amount of the fine powder used is in the above range, the free flowability is improved, thereby giving a good sense of feel to consumers. The amount of the fine powder is preferably 0.1 parts by weight or more, more preferably 0.5 parts by weight or more, even more preferably 1 part by weight or more, still even more preferably 2 parts by weight or more, and even more preferably 3 parts by weight or more, from the viewpoint of improvement in free flowability and suppression in bleed-out property and caking property, and the amount of the fine powder is preferably 40 parts by weight or less, more preferably 30 parts by weight or less, even more preferably 20 parts by weight or less, and still even more preferably 10 parts by weight or less, from the viewpoint of improvements in rinsability and free flowability.

(2) Liquid Materials

The liquid materials include water-soluble polymers, fatty acids, and the like, which can be added in the form of aqueous solutions and molten states. The liquid materials may be constituted by one component, or the liquid materials may be constituted by plural components.

(2-1) Water-Soluble Polymer

The water-soluble polymer includes carboxymethyl celluloses, polyethylene glycols, polycarboxylates such as sodium polyacrylate and copolymers of acrylic acid and maleic acid or salts thereof, and the like. The amount of the water-soluble polymer used is preferably from 0 to 10 parts by weight, more preferably from 0 to 8 parts by weight, and even more preferably from 0 to 6 parts by weight, based on 100 parts by weight of the detergent particles. When the amount of the water-soluble polymer used is in the above range, the detergent particles exhibiting excellent dissolubility and excellent free flowability and anti-caking properties can be obtained.

(2-2) Fatty Acid

The fatty acid includes, for instance, fatty acids having 10 to 22 carbon atoms, and the like. The amount of the fatty acid used is preferably from 0 to 5 parts by weight, and more preferably from 0 to 3 parts by weight, based on 100 parts by weight of the detergent particles. In a case of a fatty acid in a solid state at ordinary temperature, it is preferable that the fatty acid is heated to a temperature exhibiting free flowability, and then supplied to the detergent particles by spraying.

2-3. Drying Step

In this step, the procedures of drying the resulting detergent particles may be further carried out. By carrying out the above procedures, water derived from a surfactant paste or the like can be removed from the detergent particles.
This step is an optional step including drying the detergent particles obtained in the step of mixing a surfactant paste, the step of oil-absorbing a liquid detergent raw material, or the surface-modifying step. By removing water, the content of an active agent component in the detergent particles can be improved.
A drying method that does not give a strong shearing force as much as possible is preferred, from the viewpoint of suppressing the disintegration of the detergent particles. For example, in a batch process, the drying method includes a method including placing the particles in a vessel, and drying the particles with an electric dryer or a hot air dryer; a method including drying with a batch-type fluidized bed; or the like. In a continuous process, the drying method employs a fluidized bed, a rotary dryer, a steam tube dryer, or the like.
The drying temperature is preferably from 40° to 110°C, more preferably from 50° to 100°C, and even more preferably from 60° to 90°C, from the viewpoint of the suppression of degradation of the component a) and the drying speed.

< Detergent Composition >

The detergent composition of the present invention is a composition containing the detergent particles described above, and the composition further comprises separately added detergent components other than the detergent particles (for instance, builder particles, fluorescers, enzymes, perfumes, defoaming agents, bleaching agents, bleaching activators, and the like).
The detergent particles are contained in an amount of preferably 50% by weight or more, more preferably 60% by weight or more, even more preferably 70% by weight or more, and still even more preferably from 80 to 100% by weight, of the detergent composition, from the viewpoint of detergency.
The detergent components other than the detergent particles are contained in an amount of preferably 50% by weight or less, more preferably 40% by weight or less, even more preferably 30% by weight or less, and still even more preferably 20% by weight or less, of the detergent composition.

< Method for Producing Detergent Composition >

The method for producing a detergent composition is not particularly limited, and the method includes, for example, a method of mixing the detergent particles and separately added detergent components. Since the detergent composition obtained in the manner described above contains a detergent particle having a high content of the component a), sufficient detergent effects can be exhibited even with a small amount. The application of such a detergent composition is not particularly limited, as long as it is applied to powder detergent, including, for example, laundry powder detergents, detergents for automatic dishwashers, and the like.

< Measurement Methods of Physical Properties >

1. Bulk Density

Bulk density is measured in accordance with a method prescribed in JIS K 3362. Here, in the present invention, the bulk density of the detergent particles is considered to be a bulk density after excluding particles having sizes of 2,000 µm or more.

2. Average Particle Size

Average particle sizes are determined in accordance with the following two methods.

(1) For those having an average particle size of 125 µm or more, an average particle size is obtained by vibrating particles for 5 minutes using standard sieves of JIS Z 8801-1 (sieve openings from 2,000 to 125 µm), and calculating a median size from weight percentages according to the sizes of the sieve openings. More specifically, nine-step sieves having sieve openings of 125 µm, 180 µm, 250 µm, 355 µm, 500 µm, 710 µm, 1,000 µm, 1,400 µm, and 2,000 µm and a receiving tray are used, and the sieves are stacked on the receiving tray in the order beginning from those sieves having smaller sieve openings, and 100 g of particles are added from above the uppermost sieve having a size of 2,000 µm, and a lid is placed over the particles, and attached to a rotating and tapping shaker machine (manufactured by HEIKO SEISAKUSHO, tapping: 156 times/min, rolling: 290 times/min). The particles are vibrated for 5 minutes, and thereafter the weights of the particles remaining on each of the sieves and the receiving tray are measured, and weight proportions (%) of the particles on each sieve are calculated. The weight proportions of the particles in the order beginning from the receiving tray to those sieves having smaller sieve openings are cumulated, and a particle size at which a total is 50% is defined as an average particle size.

(2) Here, as to those products having an average particle size of 80 µm or more and less than 125 µm, similar measurements are carried out using 12-step sieves having sieve openings of 45 µm, 63 µm, 90 µm, 125 µm, 180 µm, 250 µm, 355 µm, 500 µm, 710 µm, 1,000 µm, 1,400 µm, and 2,000 µm, and a receiving tray, and an average particle size is calculated.
(3) As to those having an average particle size of less than 80 µm, a laser diffraction/scattering type particle size analyzer LA-920 (manufactured by Horiba, LTD.) is used, and particles are dispersed in a solvent that does not dissolve the particles, and a median size measured is defined as an average particle size.
Here, the average particle size of the detergent particles is considered to be an average particle size of the entire particles.

3. Rosin-Rammler Number

The Rosin-Rammler number is the number as defined above. In the present specification, the number is specifically obtained in the following manner. The weights of the particles remaining on each of the sieves and the receiving tray are measured in accordance with a method similar to that of the measurement of the above average particle size to calculate the weight proportions of the particles (cumulative proportion R(Dp) [µm]) on each sieve (opening Dp [µm]). Moreover, a slope n of a least square approximation linear line when plotting log(log(100/R(Dp))) against each of logDp is defined as the Rosin-Rammler number.

4. Water (Content)

Water content is measured in accordance with an infrared moisture meter method. Specifically, a 3 g sample is weighed and placed on a weighing dish of a known weight, and the sample is heated at 105°C with an infrared moisture meter (FD-240, manufactured by Kett Kagaku Kenkyujo K.K.). A time point at which there is not weight change for 30 seconds is defined as a termination of drying. Thereafter, a water content is calculated from the weight after drying and the weight before drying.

5. Free Flowability

A flow time is defined as a time period required for flowing 100 mL of powder from a hopper used in a measurement of bulk density as prescribed in JIS K 3362. The free flowability as expressed by the flow time is preferably 10 seconds or less, more preferably 8 seconds or less, and even more preferably 7 seconds or less.
Here, in the present invention, the free flowability of the detergent particles is considered to be flowability after excluding particles having sizes of 2,000 µm or more.

< Evaluation Methods for Qualities >

1. Oil-Absorbing Ability

A 30 to 35 g powder is supplied into an absorption amount measurement apparatus (S410, manufactured by ASAHISOUKEN), and driving blades are rotated at 200 r/m. To this powder a liquid nonionic surfactant (EMULGEN 108, manufactured by Kao Corporation) is added dropwise at a liquid feeding rate of 4 mL/min, and a point that reaches a maximum torque is probed thoroughly. The amount of the liquid at a point satisfying 70% of the torque of this maximum torque is divided by an amount of the powder supplied, and the resultant value is defined as an oil-absorbing ability.
Here, in the present invention, the oil-absorbing ability of the detergent particles is considered to be oil-absorbing ability after excluding particles having sizes of 2,000 µm or more.

2. Yield of Detergent

The yield of detergent in the present invention is expressed by a weight proportion of detergent particles having sizes between 125 and 1,000 µm of the detergent particles obtained.

EXAMPLES

The following examples further describe and demonstrate embodiments of the present invention. The examples are given solely for the purposes of illustration and are not to be construed as limitations of the present invention. In the following Examples and the like, the following raw materials were used, unless specified otherwise.

Light Ash: Average particle size: 100 µm (manufactured by Central Glass Co., Ltd., oil-absorbing ability: 0.45 mL/g, water content: 2% by weight)
Pulverized Light Ash: Average particle size: 8 µm (product obtained by pulverizing the above-mentioned Light Ash)
Sodium Sulfate: Average particle size: 200 µm, "Neutral Anhydrous Sodium Sulfate" manufactured by SHIKOKU CHEMICALS CORPORATION
Pulverized Sodium Sulfate: Average particle size: 10 µm (product obtained by pulverizing the above-mentioned Sodium Sulfate)
Zeolite: Average particle size: 3.5 µm, manufactured by Zeobuilder

In the following Examples and the like, as a vessel rotary mixer, a 75-L rotary drum mixer (ϕ 40 cm x L 60 cm) having baffles was used. As a two-fluid nozzle, a product manufactured by Atomax Co., Ltd. under the model number of BN90 was used. Also, as a one-fluid nozzle, a product manufactured by Spraying Systems Japan K.K. under the model number of UNIJET8003 was used, and as a thin pipe nozzle, a nozzle having a pipe opening size of 8.1 mm.
The present invention will be further explained on the basis of the following Examples.

Example 1

A surfactant paste containing an anionic surfactant (R-OSO₃Na, C12/C14/C16 = 64/24/12 (weight ratio); water content: 33% by weight; viscosity at 60°C: about 2 Pa•s or less, hereinafter referred to as "Composition A") was heated to 60°C. Next, 5.6 kg of Light Ash was stirred in the rotary drum mixer (rotational speed: 30 r/m, Froude number: 0.2) having baffles. After stirring the components for 10 seconds, 25 parts by weight of the above Composition A was added thereto, based on 100 parts by weight of the above Light Ash, in 6.5 minutes as liquid droplets having a diameter of about 130 µm with the two-fluid nozzle (air spraying pressure for forming fine droplets: 0.3 MPa). After the addition, the components were continued mixing for 3 minutes, and formed into particles, and Detergent Particles 1 were then discharged from the rotary drum mixer.
The resulting Detergent Particles 1 had a water content of 6.9%, an average particle size of 221 µm, a Rosin-Rammler number of 2.05, an yield of detergent of 94.6%, a bulk density of 543 g/L, a free flowability of 6.4 s, and an oil-absorbing ability of 0.40 mL/g.

Example 2

Composition A was heated to 60°C. Next, 4.9 kg of Light Ash was stirred in the rotary drum mixer (rotational speed: 30 r/m, Froude number: 0.2) having baffles. After stirring the components for 10 seconds, 43 parts by weight of the above Composition A was added thereto, based on 100 parts by weight of the above Light Ash, in 9.8 minutes as liquid droplets having a diameter of about 130 µm with the two-fluid nozzle (air spraying pressure for forming fine droplets: 0.3 MPa). After the addition, the components were continued mixing for 3 minutes, and formed into particles, and Detergent Particles 2 were then discharged from the rotary drum mixer.
The resulting Detergent Particles 2 had a water content of 9.1%, an average particle size of 318 µm, a Rosin-Rammler number of 2.79, an yield of detergent of 98.9%, a bulk density of 550 g/L, a free flowability of 6.1 s, and an oil-absorbing ability of 0.36 mL/g.

Example 3

Composition A was heated to 60°C. Next, 4.2 kg of Light Ash was stirred in the rotary drum mixer (rotational speed: 30 r/m, Froude number: 0.2) having baffles. After stirring the components for 10 seconds, 67 parts by weight of the above Composition A was added thereto, based on 100 parts by weight of the above Light Ash, in 13 minutes as liquid droplets having a diameter of about 130 µm with the two-fluid nozzle (air spraying pressure for forming fine droplets: 0.3 MPa). After the addition, the components were continued mixing for 3 minutes, and formed into particles, and Detergent Particles 3 were then discharged from the rotary drum mixer.
The resulting Detergent Particles 3 had a water content of 11.1 %, an average particle size of 416 µm, a Rosin-Rammler number of 2.44, an yield of detergent of 98.9%, a bulk density of 624 g/L, a free flowability of 5.8 s, and an oil-absorbing ability of 0.26 mL/g.

Example 4

Composition A was heated to 60°C. Next, 3.5 kg of Light Ash was stirred in the rotary drum mixer (rotational speed: 30 r/m, Froude number: 0.2) having baffles. After stirring the components for 10 seconds, 100 parts by weight of the above Composition A was added thereto, based on 100 parts by weight of the above Light Ash, in 16.3 minutes as liquid droplets having a diameter of about 130 µm with the two-fluid nozzle (air spraying pressure for forming fine droplets: 0.3 MPa). After the addition, the components were continued mixing for 3 minutes, and formed into particles, and Detergent Particles 4 were then discharged from the rotary drum mixer.
The resulting Detergent Particles 4 had a water content of 14.8%, an average particle size of 678 µm, a Rosin-Rammler number of 2.49, an yield of detergent of 87.4%, a bulk density of 636 g/L, a free flowability of 6.9 s, and an oil-absorbing ability of 0.13 mL/g.

Example 5

Detergent particles were obtained in the same manner as in Example 1, and the detergent particles were dried at 105 °C for 2 hours with an electric dryer, to discharge Detergent Particles 5.
The resulting Detergent Particles 5 had a water content of 1.1%, an average particle size of 208 µm, a Rosin-Rammler number of 1.73, an yield of detergent of 87.7%, a bulk density of 522 g/L, a free flowability of 7.1 s, and an oil-absorbing ability of 0.43 mL/g.

Example 6

Detergent particles were obtained in the same manner as in Example 2, and the detergent particles were dried at 105°C for 2 hours with an electric dryer, to discharge Detergent Particles 6.
The resulting Detergent Particles 6 had a water content of 1.4%, an average particle size of 272 µm, a Rosin-Rammler number of 1.98, an yield of detergent of 90.9%, a bulk density of 519 g/L, a free flowability of 6.5 s, and an oil-absorbing ability of 0.42 mL/g.

Example 7

Detergent particles were obtained in the same manner as in Example 3, and the detergent particles were dried at 105°C for 2 hours with an electric dryer, to discharge Detergent Particles 7.
The resulting Detergent Particles 7 had a water content of 2.1%, an average particle size of 442 µm, a Rosin-Rammler number of 2.29, an yield of detergent of 98.1%, a bulk density of 573 g/L, a free flowability of 6.1 s, and an oil-absorbing ability of 0.33 mL/g.

Example 8

Detergent particles were obtained in the same manner as in Example 4, and the detergent particles were dried at 105°C for 2 hours with an electric dryer, to discharge Detergent Particles 8.
The resulting Detergent Particles 8 had a water content of 1.7%, an average particle size of 651 µm, a Rosin-Rammler number of 2.04, an yield of detergent of 98.7%, a bulk density of 579 g/L, a free flowability of 6.6 s, and an oil-absorbing ability of 0.15 mL/g.

Comparative Example 1

Composition A was heated to 60°C. Next, 26 kg of Light Ash was stirred in a Lödige mixer FKM-130D (manufactured by Matsubo Co., Ltd.). Here, a hot water at 60°C was allowed to flow through a jacket. After stirring for 10 seconds under the conditions of a rotational speed of agitation blade of 115 r/m, a Froude number of 3.7, and a rotational speed of a chopper of 3600 r/m, 25 parts by weight of the above Composition A, based on 100 parts by weight of the above Light Ash, was added in 7 minutes with the thin pipe nozzle. After the addition, the components were continued mixing for 3 minutes, and formed into particles, and Detergent Particles 9 were then discharged from the Lödige mixer.
The resulting Detergent Particles 9 had a water content of 6.6%, an average particle size of 128 µm, a Rosin-Rammler number of 0.85, an yield of detergent of 50.3%, a bulk density of 739 g/L, and a free flowability which is undeterminable.

Comparative Example 2

Composition A was heated to 60°C. Next, 22.8 kg of Light Ash was stirred in a Lödige mixer FKM-130D (manufactured by Matsubo Co., Ltd.). Here, a hot water at 60°C was allowed to flow through a jacket. After stirring for 10 seconds under the conditions of a rotational speed of agitation blade of 115 r/m, a Froude number of 3.7, and a rotational speed of a chopper of 3600 r/m, 43 parts by weight of the above Composition A, based on 100 parts by weight of the above Light Ash, was added in 10.5 minutes with the thin pipe nozzle. After the addition, the components were continued mixing for 3 minutes, and formed into particles, and Detergent Particles 10 were then discharged from the Lödige mixer.
The resulting Detergent Particles 10 had a water content of 10.0%, an average particle size of 219 µm, a Rosin-Rammler number of 1.16, an yield of detergent of 85.5%, a bulk density of 720 g/L, a free flowability of 6.1 s, and an oil-absorbing ability of 0.18 mL/g.

Comparative Example 3

Composition A was heated to 60°C. Next, 19.5 kg of Light Ash was stirred in a Lödige mixer FKM-130D (manufactured by Matsubo Co., Ltd.). Here, a hot water at 60°C was allowed to flow through a jacket. After stirring for 10 seconds under the conditions of a rotational speed of agitation blade of 115 r/m, a Froude number of 3.7, and a rotational speed of a chopper of 3600 r/m, 67 parts by weight of the above Composition A, based on 100 parts by weight of the above Light Ash, was added in 14.1 minutes with the thin pipe nozzle. After the addition, the components were continued mixing for 3 minutes, and formed into particles, and Detergent Particles 11 were then discharged from the Lödige mixer.
The resulting Detergent Particles 11 had a water content of 12.1%, formation of coarse particles to an extent that an average particle size was undeterminable, a Rosin-Rammler number of 1.65, an yield of detergent of 4.8%, a bulk density of 798 g/L, and a free flowability of 8.2 s.

Comparative Example 4

Composition A was heated to 60°C. Next, 5.6 kg of Light Ash was stirred in the rotary drum mixer (rotational speed: 30 r/m, Froude number: 0.2) having baffles. After stirring the components for 10 seconds, 25 parts by weight of the above Composition A was added thereto, based on 100 parts by weight of the above Light Ash, in 2.2 minutes with the one-fluid nozzle. After the addition, the components were continued mixing for 3 minutes, and formed into particles, and Detergent Particles 12 were then discharged from the rotary drum mixer.
The resulting Detergent Particles 12 had a water content of 5.1%, an average particle size of 148 µm, a Rosin-Rammler number of 0.77, an yield of detergent of 55.9%, a bulk density of 656 g/L, and a free flowability of 9.5 s.

Comparative Example 5

Composition A was heated to 60°C. Next, 4.9 kg of Light Ash was stirred in the rotary drum mixer (rotational speed: 30 r/m, Froude number: 0.2) having baffles. After stirring the components for 10 seconds, 43 parts by weight of the above Composition A was added thereto, based on 100 parts by weight of the above Light Ash, in 3.3 minutes with the one-fluid nozzle. After the addition, the components were continued mixing for 3 minutes, and formed into particles, and Detergent Particles 13 were then discharged from the rotary drum mixer.
The resulting Detergent Particles 13 had a water content of 10.9%, an average particle size of 502 µm, a Rosin-Rammler number of 1.25, an yield of detergent of 69.5%, a bulk density of 642 g/L, a free flowability of 6.4 s, and an oil-absorbing ability of 0.33 mL/g.

Comparative Example 6

Composition A was heated to 60°C. Next, 4.2 kg of Light Ash was stirred in the rotary drum mixer (rotational speed: 30 r/m, Froude number: 0.2) having baffles. After stirring the components for 10 seconds, 67 parts by weight of the above Composition A was added thereto, based on 100 parts by weight of the above Light Ash, in 4.4 minutes with the one-fluid nozzle. After the addition, the components were continued mixing for 3 minutes, and formed into particles, and Detergent Particles 14 were then discharged from the rotary drum mixer.
The resulting Detergent Particles 14 had a water content of 13.9%, an average particle size of 983 µm, a Rosin-Rammler number of 1.46, an yield of detergent of 48.7%, a bulk density of 784 g/L, and a free flowability of 7.2 s.

Example 9

A surfactant paste containing an anionic surfactant (R-OSO₃Na, C12/C14/C16 = 64/24/12 (weight ratio); water content: 30% by weight; viscosity at 60°C: about 2 Pa•s or less, hereinafter referred to as "Composition B") was heated to 55°C. Next, 1.73 kg of Pulverized Light Ash and 1.63 kg of Sodium Sulfate were stirred in the rotary drum mixer (rotational speed: 30 r/m, Froude number: 0.2) having baffles. After stirring the components for 10 seconds, 81 parts by weight of the above Composition B was added thereto, based on 100 parts by weight of the above powder detergent raw materials, in 13.3 minutes as liquid droplets having a diameter of about 130 µm with the two-fluid nozzle (air spraying pressure for forming fine droplets: 0.3 MPa). After the addition, the components were continued mixing for one minute, and formed into particles. Thereafter, 15 parts by weight of Zeolite was added, based on 100 parts by weight of the detergent particles obtained, and the components were mixed for an additional one minute, and Detergent Particles 15 then discharged from the rotary drum mixer.
The resulting Detergent Particles 15 had a water content of 11.0%, an average particle size of 406 µm, a Rosin-Rammler number of 2.05, an yield of detergent of 93.9%, a bulk density of 712 g/L, a free flowability of 6.9 s, and an oil-absorbing ability of 0.16 mL/g.

Example 10

Composition B was heated to 55°C. Next, 1.73 kg of Light Ash and 1.63 kg of Pulverized Sodium Sulfate were stirred in the rotary drum mixer (rotational speed: 30 r/m, Froude number: 0.2) having baffles. After stirring the components for 10 seconds, 81 parts by weight of the above Composition B was added thereto, based on 100 parts by weight of the above powder detergent raw materials, in 13.3 minutes as liquid droplets having a diameter of about 130 µm with the two-fluid nozzle (air spraying pressure for forming fine droplets: 0.3 MPa). After the addition, the components were continued mixing for one minute, and formed into particles. Thereafter, 15 parts by weight of Zeolite was added, based on 100 parts by weight of the detergent particles obtained, and the components were mixed for an additional one minute, and Detergent Particles 16 then discharged from the rotary drum mixer.
The resulting Detergent Particles 16 had a water content of 13.9%, an average particle size of 447 µm, a Rosin-Rammler number of 2.17, an yield of detergent of 95.5%, a bulk density of 629 g/L, a free flowability of 6.9 s, and an oil-absorbing ability of 0.18 mL/g.

Example 11

Composition B was heated to 60°C. Next, 2.8 kg of Pulverized Light Ash was stirred in the rotary drum mixer (rotational speed: 30 r/m, Froude number: 0.2) having baffles. After stirring the components for 10 seconds, 150 parts by weight of the above Composition B was added thereto, based on 100 parts by weight of the above powder detergent raw materials, in 20.6 minutes as liquid droplets having a diameter of about 130 µm with the two-fluid nozzle (air spraying pressure for forming fine droplets: 0.3 MPa). After the addition, the components were continued mixing for 1 minute, and formed into particles, and Detergent Particles 17 were then discharged from the rotary drum mixer.
The resulting Detergent Particles 17 had a water content of 16.1 %, an average particle size of 395 µm, a Rosin-Rammler number of 1.76, an yield of detergent of 92.8%, a bulk density of 555 g/L, a free flowability of 6.1 s, and an oil-absorbing ability of 0.47 mL/g.

Example 12

The amount 92.4 parts by weight of Composition B and 7.6 parts by weight of polyoxyethylene lauryl ether (EO(21 mol) adduct) were mixed (the mixture hereinafter referred to as "Composition C"), and the mixture was heated to 55°C. Next, 4.2 kg of Light Ash was stirred in the rotary drum mixer (rotational speed: 30 r/m, Froude number: 0.2) having baffles. After stirring the components for 10 seconds, 67 parts by weight of the above Composition C was added thereto, based on 100 parts by weight of the above powder detergent raw materials, in 15.1 minutes with the two-fluid nozzle (air spraying pressure for forming fine droplets: 0.3 MPa). After the addition, the components were continued mixing for 1 minute, and formed into particles, and Detergent Particles 18 were then discharged from the rotary drum mixer.
The resulting Detergent Particles 18 had a water content of 11.3%, an average particle size of 480 µm, a Rosin-Rammler number of 1.52, an yield of detergent of 79.7%, a bulk density of 590 g/L, a free flowability of 6.3 s, and an oil-absorbing ability of 0.29 mL/g.

Example 13

Composition C was heated to 55°C. Next, 3.15 kg of Pulverized Light Ash was stirred in the rotary drum mixer (rotational speed: 30 r/m, Froude number: 0.2) having baffles. After stirring the components for 10 seconds, 122 parts by weight of the above Composition C was added thereto, based on 100 parts by weight of the above powder detergent raw materials, in 18.9 minutes with the two-fluid nozzle (air spraying pressure for forming fine droplets: 0.3 MPa). After the addition, the components were continued mixing for 1 minute, and formed into particles, and Detergent Particles 19 were then discharged from the rotary drum mixer.
The resulting Detergent Particles 19 had a water content of 14.2%, an average particle size of 698 µm, a Rosin-Rammler number of 2.37, an yield of detergent of 72.5%, a bulk density of 684 g/L, a free flowability of 6.6 s, and an oil-absorbing ability of 0.17 mL/g.

Example 14

Ninety-three parts by weight of Composition B and 7 parts by weight of sodium polyoxyethylene lauryl ether sulfate (manufactured by Kao Corporation, EMULGEN 270J) were mixed (the mixture hereinafter referred to as "Composition D"), and the mixture was heated to 55°C. Next, 4.2 kg of Light Ash was stirred in the rotary drum mixer (rotational speed: 30 r/m, Froude number: 0.2) having baffles. After stirring the components for 10 seconds, 67 parts by weight of the above Composition D was added thereto, based on 100 parts by weight of the above powder detergent raw materials, in 14.6 minutes with the two-fluid nozzle (air spraying pressure for forming fine droplets: 0.3 MPa). After the addition, the components were continued mixing for 1 minute, and formed into particles, and Detergent Particles 20 were then discharged from the rotary drum mixer.
The resulting Detergent Particles 20 had a water content of 16.5%, an average particle size of 431 µm, a Rosin-Rammler number of 2.22, an yield of detergent of 93.9%, a bulk density of 622 g/L, a free flowability of 6.4 s, and an oil-absorbing ability of 0.56 mL/g.

Example 15

Composition D was heated to 55°C. Next, 3.5 kg of Pulverized Light Ash was stirred in the rotary drum mixer (rotational speed: 30 r/m, Froude number: 0.2) having baffles. After stirring the components for 10 seconds, 100 parts by weight of the above Composition D was added thereto, based on 100 parts by weight of the above powder detergent raw materials, in 18.2 minutes with the two-fluid nozzle (air spraying pressure for forming fine droplets: 0.3 MPa). After the addition, the components were continued mixing for 1 minute, and formed into particles, and Detergent Particles 21 were then discharged from the rotary drum mixer.
The resulting Detergent Particles 21 had a water content of 16.0%, an average particle size of 408 µm, a Rosin-Rammler number of 1.87, an yield of detergent of 92.4%, a bulk density of 642 g/L, a free flowability of 6.1 s, and an oil-absorbing ability of 0.24 mL/g.

Example 16

Composition B was heated to 60°C. Next, 4.2 kg of Sodium Sulfate was stirred in the rotary drum mixer (rotational speed: 30 r/m, Froude number: 0.2) having baffles. After stirring the components for 10 seconds, 67 parts by weight of the above Composition B was added thereto, based on 100 parts by weight of the above powder detergent raw materials, in 14.5 minutes with the two-fluid nozzle (air spraying pressure for forming fine droplets: 0.3 MPa). After the addition, the components were continued mixing for 1 minute, and formed into particles, and Detergent Particles 22 were then discharged from the rotary drum mixer.
The resulting Detergent Particles 22 had a water content of 9.6%, an average particle size of 411 µm, a Rosin-Rammler number of 2.15, an yield of detergent of 95.4%, a bulk density of 796 g/L, a free flowability of 6.2 s, and an oil-absorbing ability of 0.25 mL/g.

Example 17

Detergent particles 17 obtained in Example 11 were supplied in a 500-mL beaker in an amount of 100 g. Five parts by weight of polyoxyethylene lauryl ether (EO(21 mol) adduct, hereinafter referred to as "Composition E") was added thereto, based on 100 parts by weight of the above detergent particles, and the components were mixed manually using a spatula, to allow the detergent particles to oil-absorb to the above composition. Thereafter, the detergent particles obtained were supplied into a bag, 5 parts by weight of Zeolite was added thereto, based on 100 parts by weight of the above detergent particles, and the components were mixed 20 times, to provide Detergent Particles 23.
The resulting Detergent Particles 23 had an average particle size of 440 µm, a Rosin-Rammler number of 1.88, an yield of detergent of 86.2%, a bulk density of 515 g/L, and a free flowability of 6.4 s.

Example 18

Detergent particles 17 obtained in Example 11 were supplied in a 500-mL beaker in an amount of 100 g. Ten parts by weight of Composition E was added thereto, based on 100 parts by weight of the above detergent particles, and the components were mixed manually using a stirring rod, to allow the detergent particles to oil-absorb to the above composition. Thereafter, 10 parts by weight of Zeolite was added thereto, based on 100 parts by weight of the above detergent particles obtained, and the components were further mixed, to provide Detergent Particles 24.
The resulting Detergent Particles 24 had an average particle size of 590 µm, a Rosin-Rammler number of 2.96, an yield of detergent of 90.2%, a bulk density of 640 g/L, and a free flowability of 6.8 s

Comparative Example 7

A surfactant paste containing an anionic surfactant (R-OSO₃Na, C12/C14/C16 = 64/24/12 (weight ratio); water content: 70% by weight, hereinafter referred to as "Composition F") was heated to 60°C. The state of the paste at 60°C was very high in free flowability. Next, 3.85 kg of Light Ash was stirred in the rotary drum mixer (rotational speed: 30 r/m, Froude number: 0.2) having baffles. After stirring the components for 10 seconds, 82 parts by weight of the above Composition F was added thereto, based on 100 parts by weight of the above powder detergent raw materials, in 14.6 minutes with the two-fluid nozzle (air spraying pressure for forming fine droplets: 0.3 MPa). After the addition, the components were continued mixing for 3 minutes, and formed into particles, and Detergent Particles 25 were then discharged from the rotary drum mixer.
The resulting Detergent Particles 25 were formed into coarse particles, so that evaluations could not be carried out.

Comparative Example 8

A polyoxyethylene lauryl ether (EMULGEN 106, manufactured by Kao Corporation, hereinafter referred to as "Composition G") was heated to 60°C. Composition G at 60°C was in a liquid state. Next, 4.93 kg of Light Ash was stirred in the rotary drum mixer (rotational speed: 30 r/m, Froude number: 0.2) having baffles. After stirring the components for 10 seconds, 35 parts by weight of the above Composition G was added thereto, based on 100 parts by weight of the above powder detergent raw materials, in 9.4 minutes with the two-fluid nozzle (air spraying pressure for forming fine droplets: 0.3 MPa). After the addition, the components were continued mixing for one minute, and formed into particles. Thereafter, 5 parts by weight of Zeolite was added thereto, based on 100 parts by weight of the above detergent particles obtained. After the addition, and the components were continued mixing for one minute. Detergent Particles 26 were then discharged from the rotary drum mixer.
The resulting Detergent Particles 26 had high adhesive property, so that evaluations could not be carried out.

Comparative Example 9

Composition G was heated to 60°C. Next, 4.93 kg of Light Ash was stirred in the rotary drum mixer (rotational speed: 30 r/m, Froude number: 0.2) having baffles. After stirring the components for 10 seconds, 35 parts by weight of the above Composition G was added thereto, based on 100 parts by weight of the above powder detergent raw materials, in 9.4 minutes with the two-fluid nozzle (air spraying pressure for forming fine droplets: 0.3 MPa). After the addition, the components were continued mixing for 1 minute, and formed into particles. Thereafter, 30 parts by weight of Zeolite was added thereto, based on 100 parts by weight of the above detergent particles obtained, and the components were further mixed for one minute, and Detergent Particles 27 were then discharged from the rotary drum mixer.
The resulting Detergent Particles 27 had a water content of 2.8%, an average particle size of 138 µm, a Rosin-Rammler number of 1.0, an yield of detergent of 59.4%, a bulk density of 698 g/L, and a free flowability of 12.1 s.
Conditions and results of Examples and Comparatives Examples given above are shown in the following tables.

[Table 1]

Table-1

	Ex.1	Ex. 2	Ex. 3	Ex. 4	Ex. 5	Ex. 6	Ex.7	Ex. 8
Detergent Particles No.	1	2	3	4	5	6	7	8
Kinds of Mixers		Vessel Rotary Mixer				Vessel Rotary Mixer
Kinds of Nozzles		Two-Fluid Nozzle				Two-Fluid Nozzle
Drying Step		Not Conducted				Conducted

Components
Amount of Light Ash	[Parts by Weight]	100	100	100	100	100	100	100	100
Surfactant Composition A	[Parts by Weight]	25	43	67	100	25	43	67	100

Physical Properties of Detergent Particles
Average Particle Size	[µm]	221	318	416	678	208	272	442	651
Product of 1000 µm or More	[%]	0.1	0.0	0.6	12.3	0.0	0.0	0.6	0.0
Product of Less Than 125 µm	[%]	5.3	1.1	0.6	0.2	12.3	9.1	1.3	1.3
R-R Number	[-]	2.05	2.79	2.44	2.49	1.73	1.98	2.29	2.04
Yield of Detergent	[%]	94.6	98.9	98.9	87.4	87.7	90.9	98.1	98.7
Water Content	[%]	6.9	9.1	11.1	14.8	1.1	1.4	2.1	1.7
2000 µm-Sieve Pass Product
Bulk Density	[g/L]	543	550	624	636	522	519	573	579
Free Flowability	[s]	6.4	6.1	5.8	6.9	7.1	6.5	6.1	6.6
Oil-Absorbing Ability	[mL/g]	0.40	0.36	0.26	0.13	0.43	0.42	0.33	0.15

[Table 2]

Table-2

	Comp. Ex.1	Comp. Ex. 2	Comp. Ex. 3	Comp. Ex. 4	Comp. Ex. 5	Comp. Ex. 6
Detergent Particles No.	9	10	11	12	13	14
Kinds of Mixers	Lödiger Mixer			Vessel Rotary Mixer
Kinds of Nozzles	Thin Pipe Nozzle			One-Fluid Nozzle
Drying Step	Not Conducted			Not Conducted

Components
Amount of Light Ash	[Parts by Weight]	100	100	100	100	100	100
Surfactant Composition A	[Parts by Weight]	25	43	67	25	43	67

Physical Properties of Detergent Particles
Average Particle Size	[µm]	128	219	×	148	502	983
Product of 1000 µm or More	[%]	1.8	4.4	95.0	3.6	23.1	49.3
Product of Less Than 125 µm	[%]	47.9	10.1	0.2	40.6	7.4	2.1
R-R Number	[-]	0.85	1.16	1.65	0.77	1.25	1.46
Yield of Detergent	[%]	50.3	85.5	4.8	55.9	69.5	48.7
Water Content	[%]	6.6	10.0	12.1	5.1	10.9	13.9
2000 µm-Sieve Pass Product
Bulk Density	[g/L]	739	720	798	656	642	784
Free Flowability	[s]	×	6.1	8.2	9.5	6.4	7.2
Oil-Absorbing Ability	[mL/g]	-	0.18	-	-	0.33	-

[Table 3]

[Table 4]

Table-4

			Ex. 17	Ex. 18
Detergent Particles No.			23	24
Components
Detergent Particles 17
	Amount of Detergent Particles	[Parts by Weight]	100	100
Surfactant
	Surfactant Composition E	[Parts by Weight]	5	10
Surface-Modifying Agent
	Zeolite	[Parts by Weight]	5	10

Physical Properties of Detergent Particles
Average Particle Size	[µm]	440	590
Product of 1000 µm or More	[%]	12.5	9.6
Product of Less Than 125 µm	[%]	1.3	0.2
R-R Number	[-]	1.88	2.96
Yield of Detergent	[%]	86.2	90.2
2000 µm-Sieve Pass Product
Bulk Density	[g/L]	515	640
Free Flowability	[s]	6.4	6.8

[Table 5]

Table-5

	Comp. Ex.7	Comp. Ex.8	Comp. Ex. 9
Detergent Particles No.	25	26	27
Kinds of Mixers	Vessel Rotary Mixer
Kinds of Nozzles	Two-Fluid Nozzle
Drying Step	Not Conducted	Not Conducted	Not Conducted

Components
Amount of Powder Detergent Raw Materials
Light Ash	[Parts by Weight]	100	100	100

Amount of Surfactant Paste
Surfactant Composition F	[Parts by Weight]	82	-	-
Surfactant Composition G	[Parts by Weight]	-	35	35

Surface-Moditying Agent
Zeolite	[Parts by Weight]	0	5	30

Physical Properties of Detergent Particles
Average Particle Size	[µm]	×	×	138
Product of 1000 µm or More	[%]	×	×	0.8
Product of Less Than 125 µm	[%]	×	×	39,8
R-R Number	[-]	×	×	1.00
Yield of Detergent	[%]	×	×	59.4
Water Content	[%]	×	×	2.8
2000 µm-Sieve Pass Product
Bulk Density	[g/L]	×	×	698
Free Flowability	[s]	×	×	12.1

In the tables, the phrase "Product of 1000 µm or More" refers to a proportion of particles having sizes of 1000 µm or more in the entire detergent particles (% by weight), and the phrase "Product of Less Than 125 µm" refers to a proportion of particles having sizes of less than 125 µm of the entire detergent particles (% by weight). In addition, in Tables 3 to 5, the amount of zeolite is an amount where the amount of the detergent particles after the step of mixing a surfactant paste is assumed to be 100 parts by weight.
It was clarified from Examples 1 to 8 that detergent particles having a sharp particle size distribution can be obtained with an excellent yield by mixing a powder detergent raw material and a surfactant paste containing an anionic surfactant represented by the formula (1), obtained according to the present invention.
In addition, it was clarified from the comparisons made between Examples 1 to 4 and Comparative Examples 1 to 3 that the detergent particles have a broad particle size distribution and lowered yield of detergent by using a mixer other than the vessel rotary mixer, and adding a surfactant paste containing an anionic surfactant represented by the formula (1) with a one-fluid nozzle and mixing the components.
Also, it was clarified from the comparisons made between Examples 1 to 4 and Comparative Examples 4 to 6 that even in cases where the vessel rotary mixer was used, the detergent particles have a broad particle size distribution and lowered yield of detergent by adding a surfactant paste containing an anionic surfactant represented by the formula (1) with a one-fluid nozzle and mixing the components.
It could be seen from Examples 9 and 10 that even in cases where plural components were used as powder detergent raw materials, detergent particles having favorable properties can be produced. It could be seen from Example 16 that even in a case where the powder detergent raw material is sodium sulfate, but not light ash, detergent particles having favorable properties can be produced. It could be seen from Examples 11 and 13 that even in cases where the weight of the surfactant paste exceeds the weight of the powder detergent raw material, detergent particles having favorable properties can be produced. Further, as shown in Examples 12 to 15 in which Surfactant Composition C or D was used, even in cases where a surfactant paste containing, in addition to the anionic surfactant as defined in the formula (1), a nonionic surfactant or an anionic surfactant other than the anionic surfactant as defined in the formula (1) was used, detergent particles having favorable properties can be produced.
Further, as shown in Examples 17 and 18, it could be seen that desired detergent particles can be obtained by mixing the detergent particles obtained after a step of mixing a surfactant paste, and a liquid detergent raw material.
On the other hand, it could be seen that even when a rotary drum mixer or a two-fluid nozzle was used, the desired detergent particles cannot be produced in some cases. Only products that were so poor in properties that could not be evaluated as detergent particles could be obtained in a case where the amount of water in a surfactant paste is too large as in Comparative Example 7, or a case where a surfactant in a surfactant paste is a nonionic surfactant, and an anionic surfactant as defined in the formula (1) is not contained therein as in Comparative Example 8. As in Comparative Example 9, even when zeolite is added in a large amount in Comparative Example 8, the properties of the resulting detergent particles did not satisfy the desired range.

INDUSTRIAL APPLICABILITY

According to the present invention, detergent particles having a sharp particle size distribution and having a necessary particle size can be produced in excellent yields by using a surfactant paste containing anionic surfactant. The detergent particles can be used as constituents for, for example, laundry powder detergents, detergents for automatic dishwashers, and the like.

Claims

A method for producing detergent particles, comprising a step of mixing a surfactant paste, comprising
adding, to a powder of a powder detergent raw material, a surfactant paste comprising the following component a) and component b):
a) an anionic surfactant represented by the following formula (1):

R-O-SO₃M (1)

wherein R is an alkyl group or alkenyl group having 10 to 18 carbon atoms, and M is an alkali metal atom or an amine; and

b) water in an amount of 25 to 70 parts by weight, based on 100 parts by weight of the above component a)
using a multi-fluid nozzle, and
mixing the components with a vessel rotary mixer.
The method according to claim 1, wherein the multi-fluid nozzle is a two-fluid nozzle.
The method according to claim 1 or 2, wherein the powder detergent raw material has an average particle size of from 10 to 250 µm.
The method according to any one of claims 1 to 3, wherein the powder detergent raw material is a powder detergent raw material comprising light ash and/or sodium sulfate.
The method according to any one of claims 1 to 4, wherein the surfactant paste is mixed in an amount of from 25 to 200 parts by weight, based on 100 parts by weight of the powder detergent raw material.
The method according to any one of claims 1 to 5, further comprising the step of mixing the detergent particles obtained in the step of mixing a surfactant paste, and a liquid detergent raw material.
The method according to any one of claims 1 to 6, further comprising the step of drying the detergent particles.
Detergent particles obtained by the method as defined in any one of claims 1 to 7.
A detergent composition comprising detergent particles obtained by the method as defined in any one of claims 1 to 7.