AU2010331312B2 - Process for producing detergent particles - Google Patents

Abstract

Disclosed is a process for producing detergent particles which comprises the step (B) of mixing an anionic-surfactant paste with an alkyl glyceryl ether to prepare an anionic-surfactant composition and the step (C) of mixing the anionic-surfactant composition prepared in the step (B) with base granules having an oil absorption of 0.2 mL/g or more to prepare the detergent particles. Use of the process produces the effect that detergent particles which are inhibited from agglomerating and have a narrow particle diameter distribution, high solubility, and a high cleaning effect can be produced without requiring a drying step for water removal after the anionic-surfactant composition is mixed with the base granules having an oil absorption of 0.2 mL/g or more. By inhibiting particle agglomeration and imparting a narrow particle size distribution, a detergent having not only an improved appearance but also excellent solubility can be obtained. Furthermore, the content of coarse particles in the detergent particles to be produced can be made low regardless of differences in the content of coarse particles in the base granules.

Description

1 DESCRIPTION TITLE OF THE INVENTION: PROCESS FOR PRODUCING DETERGENT PARTICLES 5 TECHNICAL FIELD [0001] The present invention relates to a method for producing detergent particles, and detergent particles obtained by the method. 10 BACKGROUND ART [0002] One of the methods for producing detergent particles includes a production method including the step of mixing a powdery substance and a liquid surfactant composition. Among them, various methods in which an anionic surfactant is used in a paste-like state have been so far disclosed. 15 [0003] For example, Patent Publication 1 discloses a method for producing a granular detergent composition including oil-absorbing a paste of an alkyl ether sulfate to silica or a silicate, granulating the mixture, and drying the granules. While the method as described above has an advantage that an anionic surfactant can be blended in a higher proportion, an oil 20 absorbing carrier such as silica or a silicate is necessary, in order to facilitate the production of the granular detergent composition as described above, and further a drying step is necessitated in order to remove a water content contained the above-mentioned paste after the granulating step. [0004] In addition, Patent Publication 2 discloses a production method 25 including mixing a base particle produced by spray-drying, the base 2 particle containing a water-soluble inorganic salt and having a supporting ability of 20 mL / 100 g or more, and a paste of an alkyl sulfate, and subjecting the mixture to surface modification. However, in the case of the production method as described above, large amounts of aggregates are 5 formed, and there is also yet dissatisfaction from the viewpoint of the degree of particle growth. In addition, although this problem is somewhat improved by adding a polyoxyethylene alkyl ether, the polyoxyethylene alkyl ether needs to be blended in a large amount so that there is yet dissatisfaction, from the viewpoint of compositional flexibility. 10 PRIOR ART REFERENCES PATENT PUBLICATIONS [0005] Patent Publication 1: WO 00/31223 Patent Publication 2: Japanese Patent Laid-Open No. 2006-137925 15 SUMMARY OF THE INVENTION MEANS TO SOLVE THE PROBLEMS [0006] Specifically, the present invention relates to: [1] a method for producing detergent particles, including the following 20 steps of: step (B): mixing an anionic surfactant paste and an alkyl glyceryl ether to prepare an anionic surfactant composition; and step (C): mixing the anionic surfactant composition prepared in the step (B) and base particles having an oil-absorbing ability of 25 0.2 mL/g or more to prepare detergent particles; and 3 [2] detergent particles obtained by the method as defined in the above [1]. [0007] The present invention relates to a method for producing detergent particles in which a drying step is unnecessary even when a surfactant 5 composition having a high water content is used, the detergent particles having suppressed particle growth, a sharp particle size distribution and excellent powder properties such as dissolubility. [0008] By using the method for producing detergent particles of the present invention, some effects are exhibited such as detergent particles having a 10 suppressed particle growth, a sharp particle size distribution, and a high dissolubility, and further higher detergency effects can also be produced, without necessitating a drying step of removing a water content after the mixing of an anionic surfactant composition and base particles having an oil-absorbing ability of 0.2 mL/g or more. By having a suppressed particle 15 growth and a sharper particle size distribution, a detergent having not only improved external appearance but also excellent dissolubility can be obtained. Further, the coarse particle percentage of the produced detergent particles can be suppressed, irrespective of differences in coarse particle percentage of the base particles. 20 MODES FOR CARRYING OUT THE INVENTION [0009] One of the major features of the method for producing detergent particles of the present invention, as mentioned above, is in that the method includes the steps of: 25 step (B): mixing an anionic surfactant paste and an alkyl 4 glyceryl ether to prepare an anionic surfactant composition; and step (C): mixing the anionic surfactant composition prepared in the step (B) and base particles having an oil-absorbing ability of 0.2 mL/g or more to prepare detergent particles. 5 The method of the present invention will be explained more specifically hereinbelow. [0010] < step (B) > The step (B) is a step of mixing an anionic surfactant paste and an alkyl glyceryl ether to prepare an anionic surfactant composition. The 10 anionic surfactant paste as used herein refers to a mixture of an anionic surfactant and water. The water is contained in an amount of preferably from 15 to 50% by weight, more preferably from 25 to 45% by weight, and even more preferably from 25 to 40% by weight, of the anionic surfactant paste. Incidentally, the % indications in the contents and the 15 blending amounts of each of the components as used herein are in % by weight, unless specified otherwise. [0011] As the anionic surfactant usable in this step, generally, those usable in laundry detergents, vegetable and dishwashing detergents, hair and skin detergents, and the like can be used. The anionic surfactant includes, for 20 example, salts of alkyl sulfuric esters, salts of polyoxyethylene alkyl sulfuric esters, salts of a-sulfofatty acid esters, a-olefinsulfonates, alkyl or hydroxyalkyl ether carbonates, N-acylated taurine, N-acylated methyltaurine, N-acylated glycine, N-acylated aspartate, N-acylated sarcosine, N-acylated glutaminate, salts of higher fatty acids, 25 alkylbenzenesulfonates, alkyl sulfates, salts of monoalkyl phosphoric 5 esters, salts of alkylamide ether sulfuric esters, salts of fatty acid monoglyceride sulfuric esters and alkyliminodicarboxylates and the like. The anionic surfactants can be used alone, or in combination of plural kinds. 5 [0012] Among the anionic surfactants, preferred anionic surfactants are alkyl sulfates, salts of alkyl sulfuric esters, salts of a-sulfofatty acid esters, c-olefinsulfonates, and salts of polyoxyethylene alkyl sulfuric esters, and the like. The alkyl sulfates are more preferred, from the viewpoint of obtaining remarkable effects. 10 [0013] The anionic surfactant 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 anionic surfactant composition prepared in this step. [0014] The alkyl glyceryl ether usable in this step can be represented by the 15 following general formula (3):

R-OCH

2

-CHOH-CH

2 OH (3) wherein R is a linear or branched, alkyl group or alkenyl group having 1 to 24 carbon atoms, or a cycloalkyl group having 3 to 8 carbon atoms. [0015] By using an anionic surfactant composition obtained by mixing this 20 alkyl glyceryl ether and an anionic surfactant paste, detergent particles containing smaller amounts of aggregates and having a small degree of particle growth can be obtained. [0016] In the general formula (3), R is a linear or branched, alkyl group or alkenyl group having 1 to 24 carbon atoms, or a cycloalkyl group having 3 25 to 8 carbon atoms, preferably a linear or branched, alkyl group having 6 to 6 18 carbon atoms, and more preferably an alkyl group having 8 to 12 carbon atoms. Specifically, R includes linear alkyl groups, such as a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a 5 pentadecyl group, a hexadecyl group, a heptadecyl group, and an octadecyl group; branched alkyl groups, such as a 2-ethylhexyl group, a 2 methylheptyl group, a 2-methylnonyl group, a 2-octyldecyl group, a 3,5,5 trimethylhexyl group, an isodecyl group, and an isostearyl group; and alkenyl groups such as an oleyl group. 10 [0017] The alkyl glyceryl ether in this step is blended in an amount of preferably from 10 to 40 parts by weight, more preferably from 15 to 40 parts by weight, and even more preferably from 20 to 40 parts by weight, based on 100 parts by weight of the anionic surfactant in the anionic surfactant paste. The alkyl glyceryl ether is blended in an amount of 15 preferably 10 parts by weight or more, from the viewpoint of the degree of particle growth of the detergent particles of the present invention, and the alkyl glyceryl ether is blended in an amount of preferably 40 parts by weight or less, from the viewpoint of the effective content of an anionic surfactant which can be supported to the base particles, and the cost of the 20 alkyl glyceryl ether. [0018] The anionic surfactant composition in this step can be prepared by mixing a given amount of an anionic surfactant paste and a given amount of an alkyl glyceryl ether. Components other than these components may be added as occasion demands. 25 [0019] The viscosity of the anionic surfactant composition of this step is 7 not particularly limited, and when the viscosity of the surfactant composition is measured with MCR300 (manufactured by PHYSICA Messtechnik GmbH) under conditions of a temperature of 50C and a shearing rate of 10[1/s], the viscosity is preferably within the range of 5 from 0.01 to 20 Pa-s, and more preferably within the range of from 0.05 to 15 Pa-s, from the viewpoint of handling ability in the step of mixing the anionic surfactant composition with the base particles to prepare detergent particles. [0020] Specific procedures for preparing an anionic surfactant composition 10 include, for example, the procedures of mixing a given amount of an anionic surfactant paste and a given amount of an alkyl glyceryl ether. Components other than these components may be added, as occasion demands. As mixers to be used, those mixers which are generally used in the field of detergents can be used, and as the conditions upon mixing, the 15 conditions generally employed in the field of detergents can be employed. [0021] < step (C) > The step (C) is a step of mixing the anionic surfactant composition prepared in the above step (B) and base particles having an oil-absorbing ability of 0.2 mL/g or more to prepare detergent particles. 20 [0022] The base particles usable in the step (C) include particles capable of supporting a surfactant. More specifically, the base particles include the following spray-dried base particles (a) and non-spray-dried base particles (b). [0023] [Preparation of Spray-Dried Base Particles (a): step (A-1)] 25 The spray-dried base particles (a) are particles obtained by spray- 8 drying a slurry containing a water-soluble inorganic salt. For example, the spray-dried base particles (a) can be prepared by spray-drying a slurry containing the following components. [0024] The water-soluble inorganic salt is not particularly limited, and, for 5 example, sodium carbonate, potassium carbonate, sodium sulfate, sodium sulfite, sodium chloride, or the like is a preferred water-soluble inorganic salt. The water-soluble inorganic salts can be used alone or in a combination of plural kinds. [0025] In addition to the water-soluble inorganic salt, the components as 10 mentioned below can be further used. The components include, for example, builders generally usable in laundry detergents, for example metal ion sequestering agents such as zeolite, citrates, and sodium tripolyphosphate, and components having both metal ion sequestering ability and alkalizing ability such as crystalline silicates; re-deposition 15 preventing agents such as acrylic acid polymers, acrylic acid-maleic acid copolymers and carboxymethyl cellulose; fluorescent brighteners, and the like. [0026] The water content in the slurry is not particularly limited, and, for example, it is preferable that the water content is from 40 to 60% by 20 weight of the slurry. Conditions upon spray-drying the slurry, such as temperature, spray-drying apparatus, spraying method, drying method and the like, may be known conditions, and the conditions are not particularly limited. By employing the raw materials and conditions as mentioned above, base particles having a given oil-absorbing ability can be obtained. 25 [0027] [Physical Properties of Spray-Dried Base Particles (a)] 9 The spray-dried base particles (a) have an oil-absorbing ability of preferably 0.2 mL/g or more, and more preferably 0.3 mL/g or more. In addition, The preferred upper limit of the oil-absorbing ability is 0.7 mL/g or less. In this range, the aggregation of the spray-dried base particles (a) 5 themselves is suppressed, which in turn favorably suppresses particle growth of the particles in the detergent particles. Accordingly, the spray dried base particles (a) have an oil-absorbing ability of preferably from 0.2 to 0.7 mL/g, and more preferably from 0.3 to 0.7 mL/g, from the same viewpoint as mentioned above. 10 [0028] The method for measuring an oil-absorbing ability of the spray dried base particles (a) is as follows. A cylindrical mixing vessel of an inner diameter of about 5 cm and a height of about 15 cm which is equipped with agitation blades in the inner portion thereof is charged with 100 g of a sample (the spray-dried base particles (a)). With stirring the 15 agitation blades at 350 r/min, linseed oil at 25*C is supplied into the vessel at a rate of about 10 mL/min, and changes in the agitation torque with time are measured. The oil-absorbing ability (mL/g) is defined as an amount of linseed oil supplied when the agitation torque reaches the highest level. [0029] The spray-dried base particles (a) have a bulk density of preferably 20 from 200 to 1,000 g/L, more preferably from 300 to 1,000 g/L, even more preferably from 400 to 1,000 g/L, and even more preferably from 500 to 800 g/L. In the present specification, the bulk density of the spray-dried base particles (a) is measured by a method as prescribed in JIS K3362, unless specified otherwise. 25 [0030] The spray-dried base particles (a) have an average particle size of 10 preferably from 140 to 600 [Am, more preferably from 150 to 500 [tm, and even more preferably from 180 to 300 [tm. In the present specification, the average particle size of the detergent particles, the base particles or the like is obtained in the following manner using sieves as prescribed in JIS Z 5 8801, unless specified otherwise. [0031] For example, nine-step sieves having sieve openings of 2,000 [tm, 1,400 [im, 1,000 [tm, 710 [tm, 500 [tm, 355 jim, 250 jim, 180 [tm, and 125 Rm and a receiving tray are used, and attached to a rotating and tapping shaker machine (manufactured by Kabushiki Kaisha Tanaka 10 Kagaku Kikai Seizosho, tapping: 156 times/min, rolling: 290 times/min). A 100 g sample is vibrated for 10 minutes to sieve the sample, and the mass base frequency on the receiving tray and under each sieve in the order of the receiving tray and sieves having sieve openings of 125 jm, 180 ptm, 250 jim, 355 jim, 500 ptm, 710 [tm, 1,000 jim, 1,400 jim, and 15 2,000 jim is then accumulated. Supposing that a first sieve opening at which cumulative mass base frequency is 50% or more is defined as xj [tm and a sieve opening of a sieve one step smaller than that is defined as xj, 1 [tm, and that the cumulative mass base frequency from the receiving tray to the sieve xj stm is defined as Qj%, and the cumulative mass base 20 frequency from the receiving tray to the sieve xj, 1 jim is defined as Qj,1%, the average particle size Xa can be obtained by the formulas (A) and (B). [0032] Xa = 10' (A) z = logioxj+1 + (logioxj - logioxj,1) x (50 - Qj+ 1 )/(Qj - Qj,1 (B) 25 [0033] The water content of the spray-dried base particles (a) is measured 11 in accordance with an infrared moisture meter method as described below. Specifically, a 3 g sample (the spray-dried base particles (a)) is weighed and placed on a weighing dish of a known weight, and the sample is heated for 3 minutes with an infrared moisture meter (manufactured by Kett 5 Kagaku Kenkyujo K.K.; infrared lamp: 185 W) and dried. After drying, the weights of the sample dish and the dry sample are measured. The difference in weights of the sample dish before and after drying and the weight of the dry sample is divided by the amount of the sample taken, and the quotient is multiplied by a factor of 100, to calculate an amount of 10 water content (%) of the sample. [0034] The water-soluble inorganic salt in the spray-dried base particles (a) is contained in an amount of preferably from 40 to 90% by weight, more preferably from 50 to 90% by weight, and even more preferably from 55 to 90% by weight, of the particles (a), from the viewpoint of detergency and 15 handling ability of the slurry before spray-drying. [0035] [Preparation of Non-Spray-Dried Base Particles (b): step (A-2)] The non-spray-dried base particles (b) are particles obtained by adding a binder to a detergent powder raw material having an oil absorbing ability of 0.4 mL/g or more in a vessel rotary mixer with a 20 multi-fluid nozzle, and forming the mixture into particles. The detergent powder raw material includes, for example, powder raw materials given hereinbelow (referred to as "powder raw material (a)"). [0036] Examples of the powder raw material (a) include soda ash, for example, light ash or soda ash, prepared by baking sodium bicarbonate, 25 sodium sulfate, a porous powder prepared by drying a hydrate of sodium 12 tripolyphosphate, a clay mineral powder, and the like. Light ash is preferred, from the viewpoint of easiness in handling and easy availability. The powder raw material (a) may be used alone or together with plural kinds of components. The powder raw material (a) has fine micropores 5 having sizes of 10 [im or less in an inner portion of the powder, and a surfactant can be supported to the micropores. [0037] The clay mineral powder as mentioned above includes, for example, talc, pyrophyllites, smectites such as saponite, hectorite, sauconite, stevensite, montmorillonite, beidellite and nontronite, vermiculites, micas 10 such as phlogopite, biotite, zinnwaldite, muscovite, paragonite, celadonite and glauconite, chlorites such as clinochlore, chamosite, nimite, pennantite, sudoite and donbassite, brittle micas such as clintonite and margarite, thulite, serpentine minerals such as antigorite, lizardite, chrysotile, amesite, cronstedtite, berthierine, greenalite and garnierite, kaolin minerals such as 15 kaolinite, dickite, nacrite and halloysite, and the like. [0038] The powder raw material (a), excluding the clay mineral powder, has an average particle size of preferably from 10 to 250 jim, more preferably from 50 to 200 Rm, and even more preferably from 80 to 200 [tm, from the viewpoint of the formation of particles. Also, the clay 20 mineral powder has a particle size of preferably from 10 to 100 sm, more preferably 50 jim or less, and even more preferably 30 ptm or less. In addition, it is preferable that the powder raw material (a) is a water-soluble substance, from the viewpoint of dissolubility. [0039] The oil-absorbing ability of the powder raw material (a) usable in 25 this step is a value determined by the following evaluation method.

13 [0040] Specifically, a 30 to 35 g sample (powder raw material (a)) 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, 5 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. 10 [0041] Here, the upper limit of the oil-absorbing ability of the powder raw material (a) is not particularly limited, and it is desired that the upper limit of the oil-absorbing ability is, for example, 1.0 mL/g or less. [0042] The powder raw material (a) in the non-spray-drying base particles (b) is contained in an amount of preferably from 40 to 95% by weight, 15 more preferably from 45 to 90% by weight, even more preferably from 50 to 85% by weight, and even more preferably from 50 to 80% by weight, of the particles (b), from the viewpoint of oil-absorbing ability. [0043] The powder raw material (a) may be used alone as a detergent raw material, or used in plural kinds. 20 [0044] Non-spray-dried base particles (b) can be obtained by further using other components as mentioned below, in addition to the powder raw material (a). Specifically, other components include builders, re deposition preventing agents and fluorescent brighteners, and the like, which are generally usable in laundry detergents, mentioned in the 25 explanation of the spray-dried base particles (a).

14 [0045] As a method for formation of particles (granulation method) usable in this step, a method including granulating a detergent powder raw material and a binder in a vessel rotary mixer is employed. It is preferable that the vessel rotary mixer is a rotary drum mixer or a pan mixer. The 5 rotary drum mixer is not particularly limited, so long as the treatment is carried out while rotating a drum-shaped cylinder, and, in addition to a horizontal or slightly slanted rotary drum mixer, a conical rotary drum granulator (mixer), a multi-stage conical rotary drum granulator (mixer) or the like can be also used. These apparatuses can be used in any one of 10 batch process or continuous process. [0046] Specifically, the binder to be added includes, for example, polyethylene glycols, polypropylene glycols, polyoxyethylene alkyl ethers and derivatives thereof, polyvinyl alcohols and derivatives thereof, water soluble cellulose derivatives (derivatives thereof including ether 15 compounds, and the like), organic polymers such as carboxylate polymers, starch, and saccharides, inorganic polymers such as amorphous silicate; higher fatty acids; alkylbenzenesulfonic acids; general surfactants as described in Shuchi Kanyo Gijutsu Shu and the like. The water-soluble cellulose derivatives, the saccharides, and the carboxylate polymers are 20 preferred, and salts of acrylic acid-maleic acid copolymers, and salts of polyacrylic acids are more preferred, from the viewpoint of bonding property and detergency. The salt is preferably a sodium salt, a potassium salt, or an ammonium salt. Here, the weight-average molecular weight of the carboxylate polymer is preferably from 1,000 to 100,000, and more 25 preferably from 2,000 to 80,000.

15 [0047] The binder may be added in the form of an aqueous solution. The concentration of the binder when added in the form of an aqueous solution is not particularly limited. Since the particle sizes upon the formation of particles of the non-spray-dried base particles (b) are greatly affected by 5 the volume of the binder, the concentration may be determined from the amount of the necessary binder and the particle sizes of the desired particles. For example, it is preferable that the concentration of the component of the binder when added in the form of an aqueous solution is from 20 to 80% by weight. 10 [0048] The binder is added with a multi-fluid nozzle. By using the nozzle, fine liquid droplets of the binder can be formed to allow dispersibility. The multi-fluid nozzle refers to a nozzle that allows to flow a liquid and a gas for forming fine droplets, such as the air or nitrogen, in independent pathways, to communicate to a portion in the vicinity of a tip end portion 15 of the nozzle, and mixing and forming fine droplets. As the multi-fluid nozzle, a two-fluid nozzle, a three-fluid nozzle, a four-fluid nozzle, or the like can be used. In addition, a mixing section of the binder 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 20 mixing type where the mixing is carried out in the external of a tip end portion of the nozzle. [0049] The multi-fluid nozzle mentioned above includes 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 25 mixing type two-fluid nozzles manufactured by Spraying Systems Japan 16 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. [0050] For example, in a case where a two-fluid nozzle is used, it is 5 preferable to, for example, supply the binder under the following conditions. The adjustment of the flow rate for gas for forming fine droplets can be easily carried out by adjusting a gas spraying pressure of forming fine droplets. The gas spraying pressure of forming fine droplets is preferably 0.1 MPa (gauge pressure) or more, from the viewpoint of 10 dispersibility of the binder, and the gas spraying pressure is preferably 1.0 MPa (gauge pressure) or less, from the viewpoint of loads on the facilities. In addition, the spraying pressure for the binder is not particularly limited, and the spraying pressure is, for example, preferably 1.0 MPa or less, from the viewpoint of loads on the facilities. 15 [0051] The binder in the non-spray-dried base particles (b) is contained in an amount of preferably from 1 to 50% by weight, more preferably from 5 to 45% by weight, even more preferably from 8 to 40% by weight, and even more preferably from 10 to 35% by weight, of the non-spray-dried base particles (b), from the viewpoint of bonding property and oil 20 absorbing ability. [0052] [Physical Properties of Non-Spray-Dried Base Particles (b)] The non-spray-dried base particles (b) are, for example, a group of particles having a structure in which the powder raw material (a) is loosely aggregated. In that case, the particles have two supporting sites: 25 (1) large voids between the particles, and (2) small voids within the 17 powder raw material (a) having sizes of 10 [tm or less, or between layers. By adjusting the two supporting sites, the non-spray-dried base particles (b) having a desired supporting ability can be obtained. [0053] The non-spray-dried base particles (b) have an oil-absorbing ability 5 of 0.2 mL/g or more, preferably 0.3 mL/g or more, and more preferably 0.4 mL/g or more. On the other hand, the non-spray-dried base particles have an oil-absorbing ability of preferably 0.7 mL/g or less. When the oil absorbing ability is within the above range, the aggregation of the non spray-dried base particles (b) themselves is suppressed, so that the degree 10 of particle growth of the particles of the detergent particles can be desirably suppressed. Accordingly, the non-spray-dried base particles (b) have an oil-absorbing ability of preferably from 0.2 to 0.7 mL/g, and more preferably from 0.3 to 0.7 mL/g , from the same viewpoint as above. The method for measuring an oil-absorbing ability of the non-spray-dried base 15 particles (b) is the same as the method for measuring an oil-absorbing ability of the spray-dried base particles (a). [0054] The non-spray-dried base particles (b) have a bulk density of preferably from 200 to 1,000 g/L, more preferably from 300 to 1,000 g/L, even more preferably from 400 to 550 g/L, and still even more preferably 20 from 400 to 500 g/L, from the viewpoint of securing supporting capacity of a surfactant composition and from the viewpoint of securing a high bulk density after supporting a surfactant composition. In the present specification, the method for measuring a bulk density of the non-spray dried base particles (b) is the same as the method for measuring a bulk 25 density of the spray-dried base particles (a).

18 [0055] The non-spray-dried base particles (b) have an average particle size of preferably from 140 to 600 [tm, more preferably from 150 to 500 im, and even more preferably 200 to 500 [m. [0056] The non-spray-dried base particles (b) have a water content of 5 preferably 30% by weight or less, more preferably 20% by weight or less, and even more preferably 15% by weight or less, from the viewpoint of handling ability and oil-absorbing ability. The method for measuring a water content of the non-spray-dried base particles (b) is the same as the method for measuring a water content of the spray-dried base particles (a). 10 [0057] [Method for Mixing Anionic Surfactant Composition and Base Particles] The ratio of the two components when mixing an anionic surfactant composition and base particles are not particularly limited, so long as the two components can be homogeneously mixed. For example, the ratio is 15 such that an anionic surfactant composition is preferably from 5 to 100 parts by weight, more preferably from 10 to 90 parts by weight, even more preferably from 20 to 70 parts by weight, and even more preferably from 25 to 50 parts by weight, based on 100 parts by weight of the base particles. An anionic surfactant composition is preferably 5 parts by 20 weight or more, more preferably 10 parts by weight or more, preferably 20 parts by weight or more, preferably 25 parts by weight or more, based on 100 parts by weight of the particles, from the viewpoint of detergency. An anionic surfactant composition is preferably 100 parts by weight or less, more preferably 90 parts by weight or less, even more preferably 70 parts 25 by weight or less, and still even more preferably 50 parts by weight or less, 19 based on 100 parts by weight of the particles, from the viewpoint of compositional flexibility, dissolubility and the like. [0058] As the mixing conditions in step (C), mixing conditions may be selected such that the base particles substantially maintain their shapes, i.e., 5 the particles do not undergo disintegration. For example, mixing may be carried out manually with a spatula or the like when mixed in small amounts. Alternatively, in the case where mixing is carried out with a mixer equipped with agitation blades, in an embodiment where mixing blades for the agitation blades equipped in the mixer have a paddle shape, 10 the agitation blades have a Froude number of preferably from 0.5 to 8.0, more preferably from 0.8 to 4.0, and even more preferably from 0.5 to 2.0, from the viewpoint of the suppression of the disintegration of the base particles and from the viewpoint of mixing efficiency. In addition, in an embodiment where the mixing blades have a screw shape, the agitation 15 blades have a Froude number of preferably from 0.1 to 4.0, and more preferably from 0.15 to 2.0. Also, in an embodiment where the mixing blades have a ribbon shape, the agitation blades have a Froude number of preferably from 0.05 to 4.0, and more preferably from 0.1 to 2.0. [0059] In addition, the Froude number defined in the present specification is 20 calculated by the following formula: Froude Number = V2/(R x g), wherein V is a peripheral speed [m/s] at a tip end of the agitation blades, R is a rotating radius [m] of the agitation blades, and g is a gravitational acceleration rate [m/s 2 1. 25 [0060] In the step (C), other powder raw material than the base particles 20 can also be blended as desired. The other powder raw material is blended in an amount of preferably 30 parts by weight or less, based on 100 parts by weight of the base particles, from the viewpoint of dissolubility. [0061] The other powder raw material than the base particles as mentioned 5 - in this step refers to a detergency enhancing agent or an oil-absorbing agent, which is in a powdery form at an ambient temperature. Specifically, the other powder raw material includes 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 10 materials having both metal ion sequestering ability and alkalizing ability, such as crystalline silicates; amorphous silicas or amorphous aluminosilicates, having high oil-absorbing ability but low metal ion sequestering ability; and the like. By using the powder raw material together with the base particles as desired, a high blending ratio of the 15 anionic surfactant composition and the reduction in the adhesion of the mixture in the mixer can be accomplished, and the improvement in detergency can be achieved. The powder raw materials can also be used alone or in combination of plural kinds. [0062] After mixing an anionic surfactant composition and base particles, 20 the surface of the base particles may be coated by adding to the mixture a polyethylene glycol (PEG) and/or a fatty acid and/or a soap water in an amount of preferably 1 to 10 parts by weight, based on 100 parts by weight of the base particles. By this coating, the anti-caking property of the detergent particles is desirably improved. Further, by adding a PEG and/or 25 a fatty acid and/or a soap water thereto, the detergent particles can be 21 suppressed from being aggregated, and the dispersibility can be enhanced, upon dissolving the detergent particles, whereby consequently the dissolubility of the detergent particles can be desirably improved. [0063] Also, the detergent particles obtained by the present invention may 5 contain a nonionic surfactant. The nonionic surfactant may be oil absorbed or supported to the base particles before and/or after the step (C), or the nonionic surfactant may be mixed with an anionic surfactant composition used in the step (B) to oil-absorb or support concurrently with the anionic surfactant composition. It is preferable that the nonionic 10 surfactant is oil-absorbed and supported before the step (C) from the viewpoint of suppressing caking caused by bleed-out of the nonionic surfactant. In addition, the nonionic surfactant in the detergent particles is contained in an amount of preferably 20% by weight or less, and more preferably 15% by weight or less, of the detergent particles, from the 15 viewpoint of suppressing caking caused by bleed-out. Also, the nonionic surfactant is contained in an amount of preferably 5% by weight or more, and more preferably 10% by weight or more, from the viewpoint of detergency. [0064] The kinds of the surfactants are not particularly limited, and, for 20 example, nonionic surfactants listed in Shuchi Kanyo Gijutsu Shu (Laundry Powder Detergents), published by the Japan Patent Office can be used. [0065] In addition, it is preferable that the temperature within the mixer during mixing is a temperature capable of efficiently mixing an anionic 25 surfactant composition and base particles, while substantially suppressing 22 the disintegration of the base particles. For example, the temperature is preferably a temperature equal to or higher than a pour point of an anionic surfactant composition mixed therewith, more preferably a temperature of a pour point plus 10*C or more, and even more preferably a temperature of 5 a pour point plus 20*C or more. Also, the mixing time during mixing is preferably from 2 to 20 minutes or so, and more preferably 2 to 10 minutes or so. The adjustment of the temperature within the mixer can be carried out by allowing cold water or warm water to flow through a jacket or the like. For this purpose, it is preferable that an apparatus used in the mixing 10 is one that has a structure equipped with a jacket. [0066] The method for mixing an anionic surfactant composition and base particles is carried out in a batch process or a continuous process. In a case where the mixing is carried out in a batch process, it is preferable that a mixer is previously charged with base particles, and an anionic surfactant 15 composition is added thereto. The temperature of the anionic surfactant composition to be supplied is preferably 70"C or lower, and more preferably 60*C or lower, from the viewpoint of stability of the anionic surfactant composition. [0067] In the case where mixing is carried out in a batch process, the mixer 20 is not particularly limited, as long as a mixer is one generally usable for mixing in a batch process. The mixers are, for example, (1) a mixer of which mixing blades have a paddle shape, including a mixer in which blending of powders is carried out by having an agitating shaft within a mixing vessel and attaching agitating blades on the agitating shaft: for 25 example, Henschel Mixer (manufactured by Mitsui Miike Machinery Co., 23 Ltd.), High-Speed Mixer (manufactured by Fukae Powtec Corp.), Vertical Granulator (manufactured by Powrex Corp.), L6dige Mixer (manufactured by MATSUBO CORPORATION), PLOUGH SHARE Mixer (manufactured by PACIFIC MACHINERY & ENGINEERING Co., 5 LTD.), TSK-MTI Mixer (manufactured by Tsukishima Kikai CO., LTD.) and a mixer described in JP-A-Hei-10-296064 or JP-A-Hei-10-296065, and the like; (2) a mixer of which mixing blades have a shape of a ribbon type, including a mixer in which blending is carried out by rotating spiral ribbon blades in a non-rotatable vessel which is cylindrical, semi 10 cylindrical, or conical: Ribbon Mixer (manufactured by Nichiwa Kikai Kogyo K.K.), Batch Kneader (manufactured by Satake Kagaku Kikai Kogyo K.K.), Ribocone (manufactured by Daijun Seisakusho), Julia Mixer (manufactured by TOKUJU CORPORATION), and the like; (3) a mixer of which mixing blades have a screw shape, including a mixer in which 15 blending is carried out by revolving a screw along a conical vessel, with autorotation centering about a rotating shaft arranged parallel to the vessel wall: for example, Nauta Mixer (manufactured by Hosokawa Micron Corp.), SV Mixer (manufactured by Shinko Pantec Co., Ltd.), and the like. [0068] In addition, in a case where mixing is carried out in a continuous 20 process, the mixer is not particularly limited, as long as a continuous mixer which is generally used for a continuous mixing is used. For example, the base particles and the surfactant composition may be mixed by using a continuous-type mixer among the above-mentioned mixers. [0069] < Surface Modification > 25 It is desired that the detergent particles obtained in the step (C) are 24 further subjected to surface modification. By carrying out the surface modification, detergent particles having more improved free-flowability and anti-caking property can be obtained. When the surface modification is carried out, it is preferable to use a fine powder. In a case where a fine 5 powder is used, the surface modification can be carried out by mixing the detergent particles obtained in the step (C) and a fine powder under given conditions. [0070] The fine powder is not particularly limited, and a fine powder of which primary particles have an average particle size of 20 [tm or less is 10 preferable, from the viewpoint of improving the coating ratio of the detergent particles, and improving free-flowability and anti-caking property of the detergent particles. The average particle size is determined by a method utilizing light scattering, for example, a particle analyzer (manufactured by HORIBA, LTD.), or by a microscopic observation. 15 [0071] Specific examples of the fine powder include, for example, inorganic fine powders such as silicate compounds such as crystalline silicate compounds, aluminosilicates, calcium silicate, silicon dioxide, bentonite, sodium tripolyphosphate, talc, clay, and amorphous silica derivatives; and a metal soap of which primary particles have an average 20 particle size of 20 Rm or less. The fine powders can be used alone or in a combination of plural kinds. Further, it is preferable that a fine powder has a high ion exchanging ability and an alkalizing ability, from the viewpoint of detergency. Among them, the preferred fine powders are silicate compounds such as crystalline silicate compounds and 25 aluminosilicates.

25 [0072] The amount of the fine powder used is preferably from 0.5 to 40.0 parts by weight, and more preferably from 1 to 30 parts by weight, based on 100 parts by weight of the base particles, from the viewpoint of free-flowability and feel of use. 5 [0073] As the mixing conditions in the surface modification, the mixing conditions capable of substantially maintaining the form of the base particles supporting the anionic surfactant composition may be selected. For example, mixing may be carried out manually with a spatula or the like when mixing in small amounts, or mixing may be carried out using a 10 mixer equipped with both agitation blades and disintegration blades. When the mixer is used, the agitation blades provided in the mixer have a Froude number of preferably 10 or less, and more preferably 7 or less, from the viewpoint of the suppression of the disintegration of the base particles. The agitation blades have a Froude number of preferably 2 or 15 more, and more preferably 3 or more, from the viewpoint of efficiency in mixing with the fine powder and efficiency in dispersion with the fine powder. Further, the disintegration blades have a Froude number of preferably 8,000 or less, and more preferably 5,000 or less, from the viewpoint of efficiency in mixing with the fine powder and dispersion with 20 the fine powder. When the Froude numbers are within the above range, detergent particles having excellent free-flowability can be obtained. [0074] Preferred mixers in this step include mixers equipped with both the agitation blades and the disintegration blades among the mixers usable in the step (C). In addition, by carrying out the step (C) and the surface 25 modification using separate mixers, the temperature-control of the mixed 26 substances is facilitated. For example, when a non-heat-resistant component such as perfume or an enzyme is added during the course or after the termination of the surface modification, it is preferable that the subject mixture is temperature-controlled during the surface modification. 5 The temperature-control can be accomplished by the setting of a jacket temperature or ventilation. In order to efficiently transport the detergent particles obtained in the step (C) to the apparatus for surface modification, also a preferred embodiment is adding a part of a fine powder to the detergent particles at the termination of the step (C). 10 [0075] < Detergent Particles > The detergent particles can be obtained in accordance with the method of the present invention as described above. [0076] [Physical Properties of Detergent Particles] In the present invention, the detergent particles are not particularly 15 limited, and the detergent particles preferably refer to detergent particles produced by using base particles as cores, the group of detergent particles each featuring that one detergent particle has substantially one base particle as a core is preferred. [0077] As an index showing the feature as described above of the detergent 20 particles, a degree of particle growth defined by the following formula (1): Degree of Average Particle Size of Particle Detergent Particles Growth Average Particle Size of Base Particles can be used. Specifically, the detergent particles have a degree of particle 27 growth of preferably 1.25 or less, more preferably 1.20 or less, and even more preferably 1.15 or less. The lower limit of the degree of particle growth is not particularly limited, and the lower limit is preferably 1.0 or more. Accordingly, the degree of particle growth is preferably from 1.0 to 5 1.25, more preferably from 1.0 to 1.20, and even more preferably from 1.0 to 1.15, from the viewpoint of suppressing aggregation of the detergent particles. [0078] Since the aggregation between the detergent particles is suppressed, the detergent particles of the present invention have some advantages such 10 as an amount of particles formed having a size outside the desired particle size range (aggregated particles) is even smaller, the detergent particles have excellent dissolubility, and the detergent particles have a sharp particle size distribution. [0079] The detergent particles of the present invention have an average 15 particle size of preferably 150 stm or more, more preferably in the range of from 150 to 500 stm, and even more preferably in the range of from 180 to 350 ptm. [0080] The coarse particle percentage as used herein is defined by % by weight of a proportion of particles having sizes of 500 pim or more 20 occupying the base particles or the detergent particles. Specifically, the detergent particles or the base particles in the present invention have a coarse particle percentage of preferably 35% by weight or less, preferably 25% 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 25 weight or less.

28 [0081] One of the features of the present invention is in that the coarse particle percentage of the detergent particles produced does not greatly increase, even when base particles having a relatively high coarse particle percentage were used. This feature can be clearly shown by "differences 5 in increase of coarse particle percentage of the detergent particles" defined hereinbelow. In the present specification, the differences in increase of coarse particle percentage of the detergent particles as referred to herein are defined as a value obtained by subtracting a coarse particle percentage of the base particles from a coarse particle percentage of the detergent 10 particles. Specifically, the detergent particles of the present invention preferably have even smaller differences in increase of coarse particle percentage, for example, the detergent particles have differences in increase of coarse particle percentage of preferably 15% by weight or less, and more preferably 10% by weight or less. 15 [0082] The detergent particles have a bulk density of preferably from 300 to 2,000 g/L, more preferably from 500 to 1,500 g/L, and even more preferably from 600 to 1,000 g/L. The method for measuring a bulk density of the detergent particles is the same as the method for measuring a bulk density of the spray-dried base particles (a). 20 [0083] The detergent particles obtainable by the method of the present invention having the constitution as described above are, as mentioned above, detergent particles having suppressed particle growth and a sharp particle size distribution, so that the detergent particles have not only improved external appearance but also excellent dissolubility. 25 [0084] As an index for dissolubility in the present invention, a 60-seconds 29 dissolution ratio of the detergent particles can be used. The detergent particles have a 60-seconds dissolution ratio of preferably 80% or more, and more preferably 90% or more. [0085] The 60-seconds dissolution ratio of the detergent particles is 5 calculated by a method described below. A 1-liter beaker (a cylindrical form having an inner diameter of 105 mm and a height of 150 mm, for example, a 1-liter beaker manufactured by Iwaki Glass Co., Ltd.) is charged with 1-liter of hard water cooled to 5*C, the hard water being equivalent to 71.2 mg 10 CaCO 3 /liter (a molar ratio of Ca/Mg: 7/3). With keeping the water temperature constant at 5*C with a water bath, water is stirred with a stirring bar (length: 35 mm and diameter: 8 mm, for example, Model "TEFLON SA" (MARUGATA-HOSOGATA), manufactured by ADVANTEC) at a rotational speed (800 r/m), such that a depth of swirling 15 to the water depth is about 1/3. The detergent particles which are accurately sample-reduced and weighed so as to be 1.0000 g ± 0.0010 g are supplied and dispersed in water with stirring, and stirring is continued. After 60 seconds from supplying the particles, a liquid dispersion of the detergent particles in the beaker is filtered with a standard sieve (diameter: 20 100 mm) having a sieve-opening of 74 stm as defined by JIS Z 8801 of a known weight. Thereafter, water-containing detergent particles remaining on the sieve are collected in an open vessel of a known weight together with the sieve. Incidentally, the operation time from the start of filtration to collection of the sieve is set at 10 sec ± 2 sec. The insoluble remnants 25 of the collected detergent particles are dried for one hour in an electric 30 dryer heated to 105*C. Thereafter, the dried insoluble remnants are cooled by keeping in a desiccator with a silica gel (25'C) for 30 minutes. After cooling the insoluble remnants, a total weight of the dried insoluble remnants of the detergent, the sieve and the collecting vessel is measured, 5 and the dissolution ratio (%) of the detergent particles is calculated by the formula (4): [0086] Dissolution Ratio (%) = {1 - (T/S)} x 100 (4) wherein S is a weight (g) of the detergent particles supplied; and T is a dry weight (g) of insoluble remnants of the detergent particles 10 remaining on the sieve when an aqueous solution prepared under the above stirring conditions is filtered with the sieve. [0087] In addition, the detergent particles of the present invention have excellent detergency. As the index of detergency in the present specification, the following method is used unless specified otherwise. 15 [0088] (Preparation of Artificially Soiled Cloth) An artificially soiled cloth is prepared by smearing an artificial soil solution having the composition shown below on a cloth. The smearing of the artificial soil solution on a cloth is carried out by printing the artificial soil solution on a cloth with a gravure roll coater. The step of preparing an 20 artificially soiled cloth including smearing an artificial soil solution on a cloth is carried out under the conditions of a cell capacity of a gravure roll of 58 cm3/cm2 , a coating speed of 1.0 m/min, a drying temperature of 100*C, and a drying time of one minute. As to the cloths, #2003 calico (manufactured by Tanigashira Shoten) is used. 25 [0089] [Composition of Artificial Soil Solution] 31 Lauric Acid: 0.44% by weight Myristic Acid: 3.09% by weight Pentadecanoic Acid: 2.31% by weight Palmitic Acid: 6.18% by weight 5 Heptadecanoic Acid: 0.44% by weight Stearic Acid: 1.57% by weight Oleic Acid: 7.75% by weight Triolein: 13.06% by weight n-Hexadecyl Palmitate: 2.18% by weight 10 Squalene: 6.53% by weight Liquid Crystals of Lecithin, from Egg White: 1.94% by weight Kanuma Red Clay: 8.11% by weight Carbon Black: 0.01% by weight Tap Water: Balance 15 [0090] (Detergent Conditions) Washing is carried out in a concentration of detergent particles of 0.0667% by weight using Terg-O-Tometer at a rotational speed of 85 r/m, a washing time of 10 minutes, a temperature of 20*C, and 4*DH water used (Ca/Mg = 3/1). Usually, the hardness components of the water for 20 washing are represented by Ca + and Mg2+, wherein a weight ratio thereof is Ca/Mg = (60 to 85)/(40 to 15) or so. Here, as a model water, one having Ca/Mg = 3/1 is used. 4*DH refers to the hardness when an equimolar amount of Mg ions are replaced by Ca. [0091] (Calculation of Detergency Ratio) 25 The reflectance at 550 mum of the original cloth and those of the 32 soiled cloths before and after washing are measured with a self-recording colorimeter (manufactured by Shimadzu Corporation), and the detergency ratio D (%) is calculated in accordance with the following equation. The higher the detergency ratio, the more excellent the detergent particles. 5 D = (L2 - Ll) / (LO - L1) x 100 wherein LO: Reflectance of original cloth; Li: Reflectance of soiled cloth before washing; and L2: Reflectance of soiled cloth after washing. 10 EXAMPLES [0092] The present invention will be further described on the basis of the following Examples and the like. 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 15 components were used, unless specified otherwise. [0093] Sodium Polyacrylate: weight-average molecular weight: 10,000 (manufactured by Kao Corporation); Zeolite: Zeobuilder (4A type, manufactured by Zeobuilder; median size: 3.0 lim) 20 Clay Mineral Powder: Laundrosil DGA Powder; oil-absorbing ability: 0.44 mL/g (manufactured by Siid-Chemie) Light Ash: Average particle size: 100 [tm; oil-absorbing ability 0.45 mL/g (manufactured by Central Glass Co., Ltd.) Sodium Alkyl Sulfate: a product of which alkyl group has the 25 number of carbon atoms of C12 : C14 : C16 = 67:28:5 (weight ratio) 33 Crystalline Silicate: PREFEED Granules (manufactured by Tokuyama Siltex) Polyoxyethylene Alkyl Ether: EMULGEN 106KH (manufactured by Kao Corporation) 5 [0094] Production Example 1: Production of Spray-Dried Base Particles (a) Spray-dried base particles (a) were prepared in accordance with the following procedures. <step (A-1) > To a 1-m 3 mixing vessel having agitation blades was added 405 kg 10 of water, and after a water temperature reached 55*C, 110 kg of sodium sulfate, 123 kg of sodium carbonate, and 4.4 kg of sodium sulfite were added to this mixing vessel. After stirring the components for 10 minutes, 137 kg of a 40% by weight aqueous sodium polyacrylate solution (the content of active ingredient being 40% by weight) was added to this 15 mixing vessel. After stirring the components for additional 10 minutes, 37 kg of sodium chloride and 120 kg of Zeolite were added to this mixing vessel, and the mixture was stirred for another 30 minutes, to provide a homogeneous slurry. A final temperature of this slurry was 58'C. [0095] This slurry was sprayed from a pressure spray nozzle arranged near 20 the top of the spray-drying tower at a spraying pressure of 2.5 MPa, to produce spray-dried base particles (a). A high-temperature gas supplied to the spray-drying tower was supplied from a bottom part of the tower at 235"C, and exhausted from a top of the tower at 119*C. The spray-dried base particles (a) obtained had a water content of 0.15% by weight. 25 [0096] The physical properties of the spray-dried base particles (a) obtained 34 were an average particle size of 257 tm, a bulk density of 538 g/L, a coarse particle percentage of 0.2% by weight, and an oil-absorbing ability of 0.45 mL/g. [0097] Production Example 2: Production of Non-Spray-Dried Base 5 Particles (b-i) Non-spray-dried base particles (b-1) were prepared in accordance with the following procedures. < step (A-2) > As powder raw materials (a), 2.1 kg of a clay mineral powder and 10 4.2 kg of Light Ash were mixed in a 75-L rotary drum mixer (< 40 cm x L 60 cm, rotational speed: 30 r/m, Froude number: 0.2) having baffles. After mixing the components for 2 minutes, 3.8 kg of a 25% by weight aqueous sodium polyacrylate solution (the content of active ingredient being 25% by weight) was added to the mixer with a two-fluid 15 nozzle (manufactured by Spraying Systems Japan K.K.; a spraying pressure for a binder: 0.15 MPa; air spraying pressure for forming fine droplets: 0.3 MPa, both being gauge pressures) over 5 minutes. After the addition, the components were further mixed, the formation of particles was carried out for 3 minutes, and the particles obtained were then 20 discharged from the rotary drum mixer. Next, the particles were dried with an electric dryer at 200*C over 3 hours. The particles after drying (non-spray-dried base particles (b-1)) had a water content of 1.3% by weight. [0098] The physical properties of the non-spray-dried base particles (b-1) 25 obtained were an average particle size of 289 [tm, a bulk density of 511 g/L, 35 a coarse particle percentage of 12.2% by weight, and an oil-absorbing ability of 0.51 mL/g. [0099] Production Example 3: Production of Non-Spray-Dried Base Particles (b-2) 5 Non-spray-dried base particles (b-2) were prepared in accordance with the following procedures. < step (A-2) > As a powder raw material (a), 4.55 kg of Light Ash was mixed in a 75-L rotary drum mixer ($ 40 cm x L 60 cm, rotational speed: 30 r/m, 10 Froude number: 0.2) having baffles. After mixing the components for 2 minutes, 2.45 kg of a 40% by weight aqueous sodium polyacrylate solution (the content of active ingredient being 40% by weight) was added to the mixer with a two-fluid nozzle (manufactured by Atomax Co., Ltd.; a spraying pressure for a binder: 0.15 MPa; air spraying pressure for forming 15 fine droplets: 0.3 MPa, both being gauge pressures) over 3.7 minutes. After the addition, the components were further mixed, the formation of particles was carried out for 3 minutes, and the particles obtained were then discharged from the rotary drum mixer. Next, the particles were dried with an electric dryer at 200*C over 3 hours. The particles after drying 20 (non-spray-dried base particles (b-2)) had a water content of 1.8% by weight. [0100] The physical properties of the non-spray-dried base particles (b-2) obtained were an average particle size of 270 [tm, a bulk density of 484 g/L, a coarse particle percentage of 20.4% by weight, and an oil-absorbing 25 ability of 0.52 mL/g.

36 [0101] Examples 1 to 6 < step (B) > To an anionic surfactant paste composed of 75% by weight of sodium alkyl sulfate and 25% by weight of water was added a mixture 5 composed of 90% by weight of isodecyl glyceryl ether and 10% by weight of water in an amount of 20 parts by weight (Example 1), 30 parts by weight (Example 2) or 40 parts by weight (Example 3), or a mixture composed of 90% by weight of 2-ethylhexyl glyceryl ether and 10% by weight of water in an amount of 20 parts by weight (Example 4), 30 parts 10 by weight (Example 5) or 40 parts by weight (Example 6), each mixture being based on 100 parts by weight of the sodium alkyl sulfate. The components were mixed at a temperature of 60"C for one minute, to provide an anionic surfactant composition. [0102] Viscosities of the anionic surfactant compositions of Examples 1 15 and 4 were measured with MCR300 (manufactured by PHYSICA Messtechnik GmbH) at a temperature of 50*C and a shearing rate of 10 [1/s]. As a result, the viscosities were 12.2 Pa-s (Example 1) and 10.1 Pa-s (Example 4). [0103] < step (C) > 20 Based on 100 parts by weight (50 g) of the spray-dried base particles (a) produced in Production Example 1, an anionic surfactant composition prepared in the step (B) was mixed in an amount of 33.9 parts by weight (Example 1 or 4), 36.1 parts by weight (Example 2 or 5), or 38.3 parts by weight (Example 3 or 6) with a spatula over 10 minutes, to 25 provide each of the mixtures. The mixture obtained was observed, and as 37 a result, the presence of a liquid was not found in any of the mixtures, and the mixtures were formed into particles without aggregates. [0104] Each of the formed particles obtained by the above procedures was added to a plastic bag containing 4.2 parts by weight of a crystalline 5 silicate and 23.1 parts by weight of zeolite, based on 100 parts by weight of the spray-dried base particles (a). This plastic bag was shaken upwards and downwards 30 times, to carry out the surface modification of the formed particles (mixture), to provide each of the detergent particles. [0105] Comparative Example 1 10 < step (C) > Based on 100 parts by weight (50 g) of the spray-dried base particles (a) produced in Production Example 1, 29.5 parts by weight of an anionic surfactant paste composed of 75% by weight of the sodium alkyl sulfate and 25% by weight of water was added, and the components were 15 mixed with a spatula over 10 minutes, to provide a mixture. The mixture obtained was observed. As a result, although the presence of liquid was not found, aggregates were observed in large amounts. [0106] The formed particles obtained by the above procedures were added to a plastic bag containing 4.2 parts by weight of a crystalline silicate and 20 23.1 parts by weight of zeolite, based on 100 parts by weight of the spray dried base particles (a). This plastic bag was shaken upwards and downwards 30 times, to carry out the surface modification of the formed particles (mixture), to provide detergent particles. [0107] Comparative Example 2 25 < step (B) > 38 To a mixture composed of 75% by weight of the sodium alkyl sulfate and 25% by weight of water was added Polyoxyethylene Alkyl Ether in an amount of 25 parts by weight, based on 100 parts by weight of the sodium alkyl sulfate, and the components were mixed at a temperature 5 of 60'C for one minute, to provide an anionic surfactant composition. Viscosity of the anionic surfactant composition obtained was measured with MCR300 (manufactured by PHYSICA Messtechnik GmbH) at a temperature of 50*C and a shearing rate of 10 [1/s]. As a result, the viscosity was 11.2 Pa-s. 10 [0108} < step (C) > Based on 100 parts by weight (50 g) of the spray-dried base particles (a) produced in Production Example 1, 35.0 parts by weight of an anionic surfactant composition prepared in the step (B) was added, and the components were mixed with a spatula over 10 minutes, to provide a 15 mixture. The mixture obtained was observed. As a result, although the presence of liquid was not found, aggregates were observed in large amounts. [0109] The mixture obtained by the above procedures was added to a plastic bag containing 4.2 parts by weight of a crystalline silicate and 23.1 20 parts by weight of zeolite, based on 100 parts by weight of the spray-dried base particles (a). This plastic bag was shaken upwards and downwards 30 times, to carry out the surface modification of the formed particles (mixture), to provide detergent particles. [0110] The physical properties and the like of the detergent particles 25 obtained in Examples 1 to 6 and Comparative Examples 1 and 2 are shown 39 in Table 1. [0111] [Table 1] 5~C- N.f -4 C -: .*Dj r! - 0 N;1 CD Q.~ 2 ~ 00 ~ ~ N N '00 00'~ 00 . d~-d d4 C - - ~- '.o -" m 00 0 0 e~m -4 . . - ~- cc - N .~ -~~-4*~~ ~ -6~ ~ -. 0 0 -~ . 0 cc r~ M N 00 V) 4)o .4. .- 0 0 4 Z E 0 . 4) * 0 ~0 0.~Co 40 [0112] Examples 7 to 10 < step (B) > To an anionic surfactant paste composed of 75% by weight of the sodium alkyl sulfate and 25% by weight of water was added a mixture 5 composed of 90% by weight of isodecyl glyceryl ether and 10% by weight of water, in an amount of 20 parts by weight (Example 8) or 30 parts by weight (Example 7), or a mixture composed of 90% by weight of 2 ethylhexyl glyceryl ether and 10% by weight of water, in an amount of 20 parts by weight (Example 9 or 10), each mixture being based on 100 parts 10 by weight of the sodium alkyl sulfate, and the components were mixed at a temperature of 60*C for one minute, to provide an anionic surfactant composition. [0113] < step (C) > Based on 100 parts by weight (50 g) of the non-spray-dried base 15 particles (b-1) or (b-2) produced in Production Example 2 or 3, an anionic surfactant composition prepared in the step (B) was added in an amount of 36.1 parts by weight (Example 7), 36.2 parts by weight (Example 8 or 9), or 50.7 parts by weight (Example 10), and the components were mixed with a spatula over 10 minutes, to provide each of the mixtures. The 20 mixtures obtained were observed. As a result, the presence of a liquid was not found in any of the mixtures, and the mixtures were formed into particles without aggregates. [0114] Each of the formed particles obtained by the above procedures was added to a plastic bag containing 4.2 parts by weight of a crystalline 25 silicate and 23.1 parts by weight of zeolite, based on 100 parts by weight 41 of the non-spray-dried base particles (b-1) or (b-2). This plastic bag was shaken upwards and downwards 30 times, to carry out the surface modification of the formed particles (mixture), to provide each of the detergent particles. 5 [0115] Comparative Examples 3 to 5 < step (C) > Based on 100 parts by weight (50 g) of the non-spray-dried base particles (b-1) or (b-2) produced in Production Example 2 or 3, an anionic surfactant paste composed of 75% by weight of the sodium alkyl sulfate 10 and 25% by weight of water was added in an amount of 29.5 parts by weight (Comparative Example 3), 31.5 parts by weight (Comparative Example 4), or 44.1 parts by weight (Comparative Example 5), and the components were mixed with a spatula over 10 minutes, to provide each of the mixtures. The mixtures obtained were observed. As a result, although 15 the presence of liquid was not found, aggregates were observed in large amounts. [0116] Each of the formed particles obtained by the above procedures was added to a plastic bag containing 4.2 parts by weight of a crystalline silicate and 23.1 parts by weight of zeolite, based on 100 parts by weight 20 of the non-spray-dried base particles (b-1) or (b-2). This plastic bag was shaken upwards and downwards 30 times, to carry out the surface modification of the formed particles (mixture), to provide each of the detergent particles. [0117] The physical properties and the like of the detergent particles 25 obtained in Examples 7 to 10 and Comparative Examples 3 to 5 are shown 42 in Table 2. [Table 2] 0.0 E -; - C! 0. C (1) 0 q cq CD x ON0 'Z1 (NJ~~c C9 m... N - N C-4 tf->- CV r C CI \0 -4.. cq \Cle': .0 "1 0'. -0 -:3 N 10 M : * "T MU ' V "0~c 00 0. 0 0 r. CV r- c m

CL

126~ . u L 0 -M L-uVC CV 7)c I 0o (j).~c w)_C ~ : ) .2 73 "m - c) 0 0 .0 r- , I = -* * 0 LLc"V C 0 -0 u C)0 0.C 0 43 [0118] Table 1 summarized the results using the spray-dried base particles (a). It can be seen from Table 1 that the detergent particles obtained in Examples 1 to 6 are excellent in all of coarse particle percentage, differences in increase of coarse particle percentage, degree of 5 particle growth, dissolubility, and detergency, as compared to those of Comparative Examples 1 and 2, and from the observation results of the detergent particles obtained that detergent particles containing smaller amounts of aggregates can be produced according to the method of the present invention. From the comparison between Examples 1 to 6 and 10 Comparative Example 2, it could be seen that intended effects are not exhibited by simply mixing a nonionic surfactant (polyoxyethylene alkyl ether in Comparative Example 2) and an anionic surfactant paste, and that the intended effects are exhibited for the first time by using an alkyl glyceryl ether as defined in the present invention. 15 [0119] Further, Table 2 summarized the results of using the non-spray-dried base particles (b-1) or (b-2). It can be seen from Table 2 that the detergent particles obtained in Examples 7 to 10 are excellent in all of coarse particle percentage, differences in increase of coarse particle percentage, degree of particle growth, dissolubility, and detergency, as compared to those of 20 Comparative Examples 3 to 5, and from the observation results of the detergent particles obtained that detergent particles containing smaller amounts of aggregates can be produced according to the method of the present invention. Further, although the non-spray-dried base particles (b-1) or (b-2) were likely to have a higher coarse particle percentage than 25 that of the spray-dried base particles (a), even in cases where those of (b- C \NRPortbI\DCC\RXS\4544i63_1.DOC-8I/IW2012 -44 1) or (b-2) were used, it could be seen that differences in increase of coarse particle percentage of the detergent particles are small. It was shown from the above that according to the method of the present invention detergent particles having suppressed increase of coarse particle percentage can be produced, irrespective of the differences in the coarse particle percentages of the base particles used. INDUSTRIAL APPLICABILITY [01201 Since the detergent particles of the present invention have a sharp particle size distribution, a smaller amount of aggregates, and excellent dissolubility, the detergent particles can be suitably used in the production of, for example, laundry powder detergents, detergents for dishwashers, and the like. 101211 The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates. 101221 Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

Claims (21)

1. A method for producing detergent particles, comprising the following steps of: step (B): mixing an anionic surfactant paste and an alkyl glyceryl ether to prepare an anionic surfactant composition; and step (C): mixing the anionic surfactant composition prepared in the step (B) and base particles having an oil-absorbing ability of 0.2 mL/g or more to prepare detergent particles.

2. The method according to claim 1, wherein the detergent particles produced have a degree of particle growth defined by the following formula (1): Average Particle Size of Degree of Detergent Particles Particle = (1) Growth Average Particle Size of Base Particles of 1.25 or less.

3. The method according to claim I or 2, wherein the alkyl glyceryl ether is mixed in an amount of from 10 to 40 parts by weight, based on 100 parts by weight of the anionic surfactant in the anionic surfactant paste.

4. The method according to any one of claims I to 3, wherein the anionic surfactant composition is mixed in an amount of from 5 to 100 parts by weight, based on 100 parts by weight of the base particles.

5. The method according to any one of claims I to 4, wherein the base particles are base particles prepared by either one of the following step: step (A-I): spray-drying a slurry comprising a water-soluble inorganic salt, to obtain base particles, or step (A-2): adding a binder to a detergent powder raw material having an C-NRPonbIl\DCC\RXS\4544563 DOC-8/16/2012 -46 oil-absorbing ability of 0.4 mL/g or more in a vessel rotary mixer with a multi fluid nozzle to form particles, to obtain base particles.

6. The method according to claim 5, wherein the water-soluble inorganic salt is one or more members selected from the group consisting of sodium carbonate, potassium carbonate, sodium sulfate, sodium sulfite, and sodium chloride, in the step (A-1).

7. The method according to claim 5 or 6, wherein the water content in the slurry is from 40 to 60% by weight of the slurry, in the step (A-1).

8. The method according to any one of claims 5 to 7, wherein the detergent powder raw material is one or more members selected from the group consisting of soda ash, sodium sulfate, a porous powder prepared by drying a hydrate of sodium tripolyphosphate, and a clay mineral powder, in the step (A-2).

9. The method according to any one of claims 5 to 8, wherein the vessel rotary mixer is a rotary drum mixer or a pan mixer, in the step (A-2).

10. The method according to any one of claims 5 to 9, wherein the binder is one or more members selected from the group consisting of water-soluble cellulose derivatives, saccharides, and carboxylate polymers, in the step (A-2).

11. The method according to any one of claims 1 to 10, wherein the anionic surfactant is an anionic surfactant represented by the following formula (2): R-O-SO 3 M (2) wherein R is an alkyl group or alkenyl group having 10 to 18 carbon atoms; and M is an alkali metal atom or amine.

12. The method according to any one of claims I to 11, wherein the alkyl glyceryl ether is represented by the following general formula (3): C:\NRPortbl\DCC\RXSu4563_l.DOC-WI620(,12 -47 R-OCH 2 -CHOH-CH 2 OH (3) wherein R is a linear or branched, alkyl group or alkenyl group having I to 24 carbon atoms, or a cycloalkyl group having 3 to 8 carbon atoms.

13. The method according to any one of claims 1 to 11, wherein the alkyl glyceryl ether is isodecyl glyceryl ether and/or 2-ethylhexyl glyceryl ether.

14. The method according to any one of claims I to 13, wherein water is contained in an amount of from 15 to 50% by weight of the anionic surfactant paste.

15. The method according to any one of claims 1 to 14, wherein the anionic surfactant is contained in an amount of from 40 to 80% by weight of the anionic surfactant composition.

16. The method according to any one of claims 1 to 15, wherein the anionic surfactant composition has a viscosity (at 50'C) of from 0.01 to 20 Pa-s.

17. The method according to any one of claims I to 16, wherein the base particles have an oil-absorbing ability of 0.7 mL/g or less.

18. The method according to any one of claims I to 17, wherein the base particles have an average particle size of from 140 to 600 Rm.

19. The method according to any one of claims 5 to 18, wherein the detergent powder raw material has an oil-absorbing ability of 1.0 mL/g or less.

20. Detergent particles obtained by the method as defined in any one of claims I to 19.

21. A method according to claim 1 substantially as hereinbefore described with reference to any one of the Examples.