PROCESS FOR PREPARING HIGH-BULK DENSITY DETERGENT COMPOSITIONS

Abstract: A process for preparing a high-bulk density detergent composition having a bulk density of 650 g/L or more, comprising the steps of (A) blending a liquid acid precursor of an anionic surfactant with a water-soluble, alkali inorganic substance in an amount equal to or exceeding an amount necessary for neutralizing the liquid acid precursor, in a substantial absence of an alkali metal aluminosilicate, thereby neutralizing the liquid acid precursor; and (B) adding an inorganic powder to a neutralization mixture in step (A) after a point of initiation of formation of coarse grains of the neutralization mixture obtained during a course of a neutralization process in step (A) and mixing a resulting mixture; and a process for preparing a high-bulk density detergent composition having a bulk density of 650 g/L or more, comprising the steps of (a) blending a liquid acid precursor of an anionic surfactant with a water-soluble, alkali inorganic substance in an amount equal to or exceeding in an amount necessary for neutralizing the liquid acid precursor, in a substantial absence of an alkali metal aluminosilicate, thereby neutralizing the liquid acid precursor; and (b) adding an alkali metal aluminosilicate to a neutralization mixture obtained in step (a) and mixing a resulting mixture.

Description: DESCRIPTION PROCESS FOR PREPARING HIGH-BULK DENSITY DETERGENT COMPOSITIONS TECHNICAL FIELD The present invention relates to a process for preparing a high-bulk density detergent composition having excellent detergency, and a small average particle size. BACKGROUND ART Processes for preparing powder detergents having a relatively high bulk density have been remarked. Japanese Patent Laid-Open No. Hei 3-33199 discloses a method of producing a detergent composition comprising the steps of dry-neutralizing components in a high speed mixer/granulator at a temperature of 55°C or less, and thereafter adding a liquid binder thereto to carry out granulation. In addition, Japanese Patent Laid-Open No. Hei 4-363398 discloses a method of producing a detergent composition comprising the steps of dry-neutralizing components in a high speed mixer/granulator at a temperature of 55°C or more, and then adding a liquid binder thereto to cany out granulation. In the processes as represented in the above publications, there are disclosed techniques for neutralizing an acid precursor of an anionic surfactant in the presence of an alkali metal aluminosilicate. However, the present inventors have found that there arise problems that the deterioration and the aggregation of the alkali metal aluminosilicate take place by these techniques, so that the detergency of the detergent composition is lowered. In view of eliminating the above problems, an object of the present invention is to provide a process for preparing a high-bulk density detergent composition having excellent detergency, and a small average particle size. The above object and other objects of the present invention will be apparent from the following description. DISCLOSURE OF INVENTION The present invention relates to: [1] a process for preparing a high-bulk density detergent composition having a bulk density of 650 g/L or more, comprising the steps of: (A) blending a liquid acid precursor of an anionic surfactant with a water- soluble, alkali inorganic substance in an amount equal to or exceeding an amount necessary for neutralizing the liquid acid precursor, in a substantial absence of an alkali metal aluminosilicate, thereby neutralizing the liquid acid precursor; and (B) adding an inorganic powder to a neutralization mixture in step (A) after a point of initiation of formation of coarse grains of the neutralization mixture obtained during a course of a neutralization process in step (A) and mixing a resulting mixture; and [2] a process for preparing a high-bulk density detergent composition having a bulk density of 650 g/L or more, comprising the steps of: (a) blending a liquid acid precursor of an anionic surfactant with a water- soluble, alkali inorganic substance in an amount equal to or exceeding in an amount necessary for neutralizing the liquid acid precursor, in a substantial absence of an alkali metal aluminosilicate, thereby neutralizing the liquid acid precursor; and (b) adding an alkali metal aluminosilicate to a neutralization mixture obtained in step (a) and mixing a resulting mixture. BEST MODE FOR CARRYING OUT THE INVENTION The process for preparing a high-bulk density detergent composition of the present invention is roughly classified into the following two embodiments. [Embodiment 1] A process for preparing a high-bulk density detergent composition having a bulk density of 650 g/L or more, comprising the steps of: (A) blending a liquid acid precursor of an anionic surfactant with a water- soluble, alkali inorganic substance in an amount equal to or exceeding an amount necessary for neutralizing the liquid acid precursor, in a substantial absence of an alkali metal aluminosilicate, thereby neutralizing the liquid acid precursor; and (B) adding an inorganic powder to a neutralization mixture in step (A) after a point of initiation of formation of coarse grains of the neutralization mixture obtained during a course of a neutralization process in step (A) and mixing a resulting mixture. [Embodiment 2] A process for preparing a high-bulk density detergent composition having a bulk density of 650 g/L or more, comprising the steps of: (a) blending a liquid acid precursor of an anionic surfactant with a water- soluble, alkali inorganic substance in an amount equal to or exceeding in an amount necessary for neutralizing the liquid acid precursor, in a substantial absence of an alkali metal aluminosilicate, thereby neutralizing the liquid acid precursor; and (b) adding an alkali metal aluminosilicate to a neutralization mixture obtained in step (a) and mixing a resulting mixture. 1. Step (A) or Step (a) Step (A) or step (a) is a step in which essentially the same operations are carried out. The liquid acid precursor of an anionic surfactant usable in step (A) or step (a) refers to those anionic surfactants in the form of acids in a liquid or pasty state at room temperature or with heating, which are formed into salts by neutralization reaction. The liquid acid precursor of an anionic surfactant includes linear alkylbenzenesulfomc acids (LAS), α-olefϊn sulfonic acids (AOS), alkyl sulfuric acids (AS), internal olefin sulfonic acids, sulfonic acids of fatty acid esters, alkylether sulfuric acids, dialkyl sulfosuccinic acids, and the like. The liquid acid precursors may be used in a combination of two or more components. The amount of the liquid acid precursor of an anionic surfactant can be appropriately set depending upon the composition of the desired detergent composition. The amount of the liquid acid precursor of an anionic surfactant, as an anionic surfactant formed by the neutralization reaction, is preferably from 5 to 55% by weight, more preferably from 5 to 45% by weight, still more preferably from 10 to 40% by weight especially preferably from 20 to 40% by weight, of the final high-bulk density detergent composition. Incidentally, the present invention is effective also in a case where the main surfactant is supplied in another form in the detergent composition. The water-soluble, alkali inorganic substance usable in step (A) or step (a) exhibits an alkaline property which can neutralize the liquid acid precursor of an anionic surfactant. The water-soluble, alkali inorganic substance described above includes sodium carbonate, sodium hydrogencarbonate, sodium silicate, potassium carbonate, calcium carbonate, and the like. Among the water-soluble, alkali inorganic substances, preference is given to sodium carbonate because the sodium carbonate can act as a detergent builder and an alkalizing agent in the final detergent composition. Therefore, it is preferable to add the water-soluble, alkali inorganic substances in step (A) or step (a) in an amount equal to or exceeding in an amount necessary for neutralizing the liquid acid precursor of an anionic surfactant. For instance, the water-soluble, alkali inorganic substance is added in an amount of preferably from 1 to 20 times the equivalent amount required for neutralization of the liquid acid precursor of an anionic surfactant, more preferably from 2 to 15 times the equivalent amount required for neutralization, especially preferably from 3 to 15 times the equivalent amount required for neutralization. The water-soluble, alkali inorganic substance is preferably granular, and its average particle size is preferably 30 μm or more, more preferably from 40 to 200 μm, most preferably from 50 to 100 μm, from the viewpoints of the yield improvements and the storage stability. Here, the average particle size of the granular, water-soluble, alkali inorganic substance is evaluated based on volume, wherein the average particle size is measured by using a laser diffraction particle size distribution analyzer ("LA-700," commercially available from HORIBA Ltd.). In step (A) or step (a), the mixing operation is carried in the substantial absence of the alkali metal aluminosilicate. Here, the phrase "the substantial absence of the alkali metal aluminosilicate" refers to a case where the content of the alkali metal aluminosilicate in step (A) or step (a) is preferably 5% by weight or less, more preferably 3% by weight or less, of the neutralization mixture in step (A) or step (a). When the alkali metal aluminosilicate exists in a large amount in step (A) or step (a), the deterioration and the aggregation of the alkali metal aluminosilicate by the contact with a liquid acid precursor of an anionic surfactant in an acid form take place, so that the detergency performance in the resulting detergent composition is likely to be lowered thereby. Therefore, the above problem can be eliminated by carrying out the mixing operation under specified conditions of the substantial absence of the alkali metal aluminosilicate. Incidentally, as detailed below, Embodiment 1 also encompasses an embodiment where the addition of the alkali metal aluminosilicate of step (B) is initiated at during the course of the neutralization process of step (a), or at a point where the amount of the liquid acid precursor of an anionic surfactant added exceeds a certain level. In step (A) or step (a), besides the water-soluble, alkali inorganic substance and the liquid acid precursor of an anionic surfactant, a part or all of optional ingredients can be added. Optional ingredients which can be blended at this step include, for instance, fluorescers, pigments, anti-redeposition agents (polycarboxylate polymers, sodium salt of carboxymethyl cellulose, and the like); surfactants (fatty acids or salts thereof, linear alkylbenzenesulfonates, alkyl sulfates, and the like); diatomaceous earth, calcite, kaolin, bentonite, tripolyphosphates, sodium sulfate, sodium sulfite, and the like. In the case where a detergent composition comprising a tripolyphosphate as a main builder component is prepared, the average particle size of the tripolyphosphates is not particularly limited, and the average particle size is preferably from 1 to 30 μm, more preferably from 5 to 20 μm, still more preferably from 6 to 15 μm. From the viewpoint of inhibiting the aggregation of the detergent granules, the smaller the average particle size of the tripolyphosphate, the smaller the average particle size of the detergent granules. From the viewpoint of the productivity for preparing the detergent granules with small particle sizes on an industrial scale, the average particle size of the tripolyphosphate is preferably 1 μm or more, and from the viewpoint of inhibiting the aggregation of the detergent granules, the average particle size is preferably 30 μm or less. Here, the average particle size of the tripolyphosphate as referred to in the present specification is evaluated based on volume, wherein the average particle size is measured by using a laser diffraction particle size distribution analyzer ("LA-700," commercially available from HORIBA Ltd.). The optional ingredients which are added in step (A) or step (a) are preferably those in a granular or powdeiy state, and those prepared by pulverizing a lumpy mass, or those which are separately granulated may be used. The average particle size of the optional ingredients is preferably 200 μm or less. Incidentally, the optional ingredients may be added as an aqueous solution, paste or sluπy. However, in order to prevent excessive aggregation, when water is contained, its amount is preferably adjusted so as not to exceed the water content described below. When the above optional ingredients are added, it is preferable that the optional ingredients are previously blended with the water-soluble, alkali inorganic substance before neutralizing in step (A) or step (a). The extent of mixing is preferably such that each of the ingredients is uniformly mixed. For instance, when an agitation granulator is used, it is preferable that the operation conditions for the agitation granulator are, for instance, a mixing time period of within 5 minutes. In step (A) or step (a), water may be added for the purpose of accelerating the neutralization reaction. The amount of water added is preferably from 0.2 to 3 parts by weight, more preferably from 0.5 to 1.5 parts by weight, based on 100 parts by weight of the water-soluble, alkali inorganic substance (and in a case where optional ingredients are added, their weights on dry basis are added) in step (A) or step (a). The amount of water is preferably 0.2 parts by weight or more, from the viewpoint of initiating the neutralization reaction, and the amount is preferably 3 parts by weight or less, from the viewpoint of suppressing the aggregation of the detergent granules. Incidentally, in a case where water is contained in the components such as the liquid acid precursor of an anionic surfactant, or other water-soluble raw materials are used, or powder raw materials containing water are used, the amount of water to be added may be determined in consideration of these water contents. In addition, as a more preferable embodiment for accelerating the neutralization reaction, an aqueous alkali solution or an alkali slurry solution (hereinafter simply referred to as "alkali solution") can be preferably used in place of water mentioned above. By using the alkali solution, not only the neutralization reaction can be more accelerated as compared to the case of using water, but also the particle size of the resulting detergent granules can be made small, whereby the bulk density can be markedly increased. The alkali solution is added in an amount of preferably from 0.05 to 0.5 times the equivalent amount required for neutralization of the liquid acid precursor of an anionic surfactant, more preferably from 0.10 to 0.45 times the equivalent amount required for neutralization, especially preferably from 0.10 to 0.40 times the equivalent amount required for neutralization. From the viewpoint of initiating the neutralization reaction to obtain desired effects, the amount is preferably 0.05 times or more the equivalent amount required for neutralization, and from the viewpoint of suppressing the aggregation of the detergent granules, the amount is preferably 0.5 times or less the equivalent amount required for neutralization. Incidentally, in a case where the alkali solution has a low concentration, an excess amount of water is supplied to the mixture along with the addition of a given amount of the alkali solution, so that the aggregation of the detergent granules is likely to take place. Therefore, the concentration of the alkali solution is preferably from 20 to 50% by weight, more preferably from 30 to 50% by weight, especially preferably from 40 to 50% by weight. In addition, the kinds of the alkalizing agent used in the alkali solution include strongly alkali aqueous solutions, such as aqueous sodium hydroxide and aqueous potassium hydroxide, which can readily cause the neutralization reaction with the liquid acid precursor of an anionic surfactant. Among them, the aqueous sodium hydroxide is favorably used from the viewpoint of costs. The alkali aqueous solution more preferably has a pH of 12 or more, and it is preferable that the alkali solution is added by spraying or dropping to an extent that the alkali solution uniformly disperses when added. It is preferable that the alkali solution is added to a mixture of a water-soluble, alkali inorganic substance and other optional ingredients before blending with the liquid acid precursor of an anionic surfactant. When the neutralization reaction is carried out in step (A) or step (a), it is preferable to previously add an inorganic acid, for example, sulfuric acid, and the like, to the liquid acid precursor of an anionic surfactant. In the granules obtained by neutralization reaction of a powdery or granular, water-soluble, alkali inorganic substance by using the mixture prepared by previously mixing the inorganic acid with the liquid acid precursor of an anionic surfactant, since a neutralized salt derived from the inorganic acid is present more near the granular surface than in the inner portion of the granules, the resulting granules have low adhesiveness and small particle sizes, whereby the granules having a high surfactant content can be prepared without causing the aggregation of the granules. In addition, since the granules obtainable in the manner described above have a large number of micropores, the granules having a high content of liquid ingredients, such as a nonionic surfactant, can be prepared. The inorganic acid is added in an amount of preferably from 0.1 to 1.0 moles, more preferably from 0.1 to 0.8 moles, still more preferably from 0.15 to 0.75 moles, especially preferably from 0.2 to 0.7 moles, most preferably from 0.25 to 0.65 moles, per one mol of the liquid acid precursor of an anionic surfactant. It is preferable that the inorganic acid is added in an amount of 0.1 moles or more, per one mol of the liquid acid precursor, from the viewpoint of suppressing the formation of coarse grains of the detergent granules, and that the inorganic acid is added in an amount of preferably 1.0 mole or less, per one mol of the liquid acid precursor, from the viewpoint of securing the degree of freedom in the formulation composition of the concentrated detergent. In step (A) or step (a), the order of adding the liquid acid precursor of an anionic surfactant and the water-soluble, alkali inorganic substance is not particularly specified. It is preferable that the liquid acid precursor is added to the water-soluble, alkali inorganic substance. The method of adding the liquid acid precursor of an anionic surfactant may be carried out continuously or in a plurality of batches, and the plural addition means may be provided. It is preferable that the neutralization process in step (A) or step (a) is carried out by using an agitation granulator. It is preferred that the agitation granulators are equipped with agitation blades and a chopper for disintegration and dispersion (or those replaced with a functionally equivalent means). Concrete examples of the agitation granulators usable in the present invention for a batch process include Vertical Granulator (commercially available from Powrex Corp.); High-Speed Mixer (commercially available from Fukae Powtec Kogyo Corp.); Lodige Mixer (commercially available from Matsuzaka Giken Co., Ltd.); and PLOUGH SHARE Mixer (commercially available from PACIFIC MACHINERY & ENGINEERING Co., LTD.); Gericke Mixer (commercially available from Meiji Machine Co., Ltd.), and the like, and the Lodige Mixer and the PLOUGH SHARE Mixer are especially preferable. Concrete examples of the agitation granulators usable for a continuous process include continuous Lodige Mixer (moderate speed mixer: those having relatively long residence time); high-speed mixer (those having relatively short residence time) such as CB recycler (commercially available from Lodige); Turbilizer (commercially available from Hosokawa Micron Corporation); Shugi Mixer (commercially available from Powrex Corp.); Flow Jet Mixer (commercially available from Funken Powtechs, Inc.), and the like. Incidentally, in the present invention, the above mixers may be appropriately used in combination. For instance, the neutralization reaction by the blending of the water-soluble, alkali inorganic substance and other optional ingredients and the neutralization reaction by the addition of the liquid acid precursor of an anionic surfactant may be treated in different agitation granulators. It is more preferred that the agitation granulator used in the present invention is equipped with a jacket for adjusting the internal temperature of the granulator or is equipped with a nozzle for blowing a gas into the agitation granulator. Concrete examples of the more preferable agitation granulators include those mixers disclosed in Japanese Patent Laid-Open Nos. Hei 10-296064 and Hei 10-296065. In addition, in step (A) or step (a), it is preferred that the neutralization is carried out while blowing a gas into an agitation granulator. By blowing a gas into the agitation granulator, the excess water produced in the neutralization reaction can be evaporated and the resulting granular product can be cooled with the gas, to thereby inhibit the granular product from forming into a doughy mass. The gases which may be usable include an N 2 gas, air, and the like. The amount of gas blown (amount of gas flow) is not particularly limited. The gas is blown at a rate of preferably equal to or greater than 0.002 parts by weight per minute, more preferably equal to or greater than 0.02 parts by weight per minute, based on 100 parts by weight of the granular product. The mixture comprising the neutralization substance of the acid precursor of an anionic surfactant obtainable in step (A) or step (a) as described above (in step (A), however, a non-neutralized acid precursor of an anionic surfactant can be also included), and the remaining water-soluble, alkali inorganic substance and other optional ingredients (hereinafter referred to as "neutralization mixture") is in a powdery or lumpy state. Especially when a detergent containing a surfactant in a ratio exceeding 20% by weight to the final detergent composition is prepared, the detergent granules are likely to form coarse grains or become lumpy, so that it is preferable to provide a disintegration process for the purpose of obtaining a detergent composition having a small particle size. Concretely, when the content of the anionic surfactant is 30% by weight or more, of the neutralization mixture, it is preferable to provide the disintegration process. The method for disintegration may be carried out subsequently to step (A) or step (a) in the agitation granulator equipped with agitation blades and a chopper for disintegration and dispersion, or the method may be earned out by a separate disintegrator. Concrete examples of the disintegrator include Fitz Mill (commercially available from Hosokawa Micron Corporation), Speed Mill (commercially available from Okada Seiko K.K.), and the like. 2. Step (B) or step (b) 2-1. Step (B) Step (B) comprises adding an inorganic powder to a neutralization mixture in step (A) after a point of initiation of formation of coarse grains of a neutralization mixture obtained during a course of a neutralization process in step (A) and mixing a resulting mixture. By initiating the addition of the inorganic powder at this point, there can be exhibited an effect of accelerating the disintegration effect of the neutralization mixture. It is desired that the addition of the inorganic powder is initiated at any time after a point when the liquid acid precursor of an anionic surfactant is added in an amount exceeding a weight ratio of 0.25, preferably an amount exceeding a weight ratio of 0.3, to the water-soluble, alkali inorganic substance. This is because the formation of coarse grains of the neutralization mixture is initiated at this point. Further, from the viewpoint of suppressing the compactification and the formation of coarse grains of the neutralization mixture by the progress of the granulation after the termination of the neutralization, it is desired that the inorganic powder is added within a short time period from the termination of addition of an entire amount of the liquid acid precursor of an anionic surfactant, for instance, within 5 minutes. Within the above range, the disintegration of the neutralization mixture can be facilitated by initiating the addition of the inorganic powder within this range. It is desired that the inorganic powder usable in step (B) has an average particle size of 30 μm or less, preferably 20 μm or less, from the viewpoint of suppressing the aggregation of the detergent granules. Here, the average particle size of the inorganic powder is evaluated based on volume, wherein the average particle size is measured by using a laser diffraction particle size distribution analyzer ("LA-700," commercially available from HORIBA Ltd.). Examples of the inorganic powder include inorganic powdery builders and fine granular components generally usable in detergent compositions. Concrete examples thereof include alkali metal aluminosilicates, tripolyphosphates, crystalline silicates, sodium sulfate, calcite, diatomaceous earth, silica, and the like. The inorganic powders may be used in combination of two or more kinds. Among these inorganic powders, from the viewpoint of the disintegration efficiency, the alkali metal aluminosilicate is especially preferable. The alkali metal aluminosilicate may be either amorphous or crystalline, and those having a metal ion capturing ability as a detergent aid are preferable, and especially those generally so-called "synthetic zeolite" in the field of detergent are preferable. The alkali metal aluminosilicate has an average particle size of preferably from 1 to 30 μm, more preferably from 10 μm or less. Especially in step (B), in a case where the alkali metal aluminosilicate is added, it is preferable that the alkali metal aluminosilicate is added at any point after the termination of the addition of an entire amount of the liquid acid precursor of an anionic surfactant, preferably after any point between a point where the agitation granulator is operated for additional 30 seconds or more, more preferably 1 minute or more, and a point up to 5 minutes from the termination of addition of an entire amount of the liquid acid precursor of an anionic surfactant. By operating the agitation granulator after the termination of the addition of the liquid acid precursor, the neutralization reaction can be favorably completed. According to the above process, since the liquid acid precursor of an anionic surfactant is already neutralized, its deterioration and aggregation would not take place even if the alkali metal aluminosilicate were added. Therefore, the lowering of the detergency performance of the resulting detergent composition can be suppressed, so that there can be sufficiently exhibited an effect by the addition of the alkali metal aluminosilicate, namely the effect of improving the metal ion capturing ability and the supporting ability of the liquid ingredients. 2-2. Step (b) Step (b) comprises adding an alkali metal aluminosilicate to a neutralization mixture obtained in step (a) and mixing a resulting mixture. The neutralization mixture obtained in step (a) referred to herein is a mixture in which an entire amount of the liquid acid precursor of an anionic surfactant is added, and it is preferable those in which the neutralization is terminated. In addition, the alkali metal aluminosilicate usable in step (b) may be the same ones as those of step (B). In step (b), it is preferable that the addition of the alkali metal aluminosilicate is initiated in step (b) at any time within 5 minutes from the teirnination of the addition of an entire amount of the liquid acid precursor of an anionic surfactant, from the viewpoint of suppressing the compactification and the formation of coarse grains of the neutralization mixture by the progress of the granulation after the termination of the neutralization process. Especially, it is preferable that the alkali metal aluminosilicate is added at any point after the termination of the addition of an entire amount of the liquid acid precursor of an anionic surfactant, preferably after any point between a point where the agitation granulator is operated for additional 30 seconds or more, more preferably 1 minute or more, and a point up to 5 minutes from the termination of the addition of an entire amount of the liquid acid precursor of an anionic surfactant. By operating the agitation granulator after the termination of the addition of the liquid acid precursor, the neutralization reaction can be favorably completed. According to the above process, since the liquid acid precursor of an anionic surfactant is already neutralized, its deterioration and aggregation would not take place even if the alkali metal aluminosilicate were added. Therefore, the lowering of the detergency performance of the resulting detergent composition can be suppressed, so that there can be sufficiently exhibited an effect by the addition of the alkali metal aluminosilicate, namely the effect of improving the metal ion capturing ability and the supporting ability of the liquid ingredients. 2-3. Others The amount of the inorganic powder usable in step (B) or the alkali metal aluminosilicate usable in step (b) is preferably from 5 to 50% by weight, more preferably from 8 to 40% by weight, especially preferably from 10 to 36% by weight, of the high-bulk density detergent composition, which is the final product. From the viewpoint of suppressing the aggregation of the neutralization mixture, the amount is preferably 5% by weight or more, and from the viewpoint of securing the degree of compositional freedom of the resulting detergent composition, the amount is preferably 50% by weight or less. In addition, a method of adding an inorganic powder or alkali metal aluminosilicate includes adding it at once or in a plurality of divided portions. Embodiments for adding in a plurality of divided portions include (i) an embodiment of adding an inorganic powder or alkali metal aluminosilicate for the pmpose of facilitating disintegration when the neutralization mixture obtained in step (A) or step (a) is formed into coarse grains or lumpy masses (addition as a disintegration aid); (ii) an embodiment of adding an inorganic powder or alkali metal aluminosilicate for the purpose of adjusting the granulation property when adding the liquid binder described below (addition as a granulation adjustment agent); and (iii) an embodiment of adding an inorganic powder or alkali metal aluminosilicate before the surface modification of the finally obtained detergent granules (addition as a surface modifier). In step (B) or step (b), from the viewpoints of the reduction of fine powder and the improvements in the detergency and the metal ion capturing ability, it is desirable to formulate a liquid binder. According to the process of the present invention, the neutralization mixture can be made to have a small particle size, so that greater amounts of the liquid binder can be formulated. The term "liquid binder" in the present invention refers to a substance imparting a property of increasing the bulk density of the detergent composition by collectively assembling the granules by the formulation of the liquid binder. The liquid binder includes, for instance, optional liquid ingredients in the detergent composition such as water, liquid nonionic surfactants, aqueous solutions of water-soluble polymers (polyethylene glycols, acrylic acid-maleic acid copolymers, and the like), and fatty acids. These liquid binders may be used in combination of two or more kinds, and embodiments of such addition methods include (1) adding after previously mixing two or more liquid binders; (2) simultaneously adding each of the liquid binders; and (3) alternately adding each of the liquid binders. In any of these methods, from the viewpoints of cost reduction, it is preferable to use water in combination. The amount of the liquid binder formulated is preferably 20 parts by weight or less, more preferably 15 parts by weight or less, based on 100 parts by weight of the neutralization mixture, from the viewpoint of suppressing the aggregation of the detergent composition. The method of adding the liquid binder may be carried out continuously or in a plurality of batches. It is preferable that the liquid binder is added to the neutralization mixture obtained in step (A) or step (a) before or after the addition of the inorganic powder. By the addition of the liquid binder at this stage, the adhesiveness of the granular surface by the liquid binder can be reduced, whereby the granulation can be suppressed. In the process of the present invention, besides adding a part of or all of optional ingredients in step (A) or step (a), the optional ingredients can also be formulated in step (B) or step (b). Especially when the above aqueous solution of the water-soluble polymer is used, it is preferable to add the aqueous solution in step (B) or step (b) rather than in step (A) or step (a), from the viewpoint of granulation property. In this case, the inorganic powder can be added in plural batches as shown in the above embodiments (i) to (iii), so that the granulation property is not greatly affected by the water content carried by the optional ingredients into the neutralization mixture. In the process of the present invention, it is preferable to provide a surface-modifying step as shown in the above embodiment (iii). The surface modification step can be also carried out by using the inorganic powder such as an alkali metal aluminosilicate. By adding the inorganic powder to detergent granules in which the granulation is proceeded to a certain extent and surface- coating the detergent granules, the powder properties such as anti-caking property and flowability can be improved. It is desired that the amount of the surface modifier is from 2 to 15% by weight, preferably from 4 to 12% by weight, of the detergent composition after the surface modification. Incidentally, in the present invention, in a case where other volatile compounds or thermally sensitive optional ingredients are added, such components may be added after at a point where at least the first batch of the inorganic powder or alkali metal aluminosilicate is added in step (B) or step (b) in the present invention, and the particle sizes are evenly sized, or these components may be after-blended by mixing the granules finally treated with a surface-coating agent by using a mixer such as a rotary mixer. The high-bulk density detergent composition obtained by the process of the present invention may be used as ingredients for constituting other detergent compositions. In addition, the process of the present invention can be earned out by a continuous process. In this case, step (A) or step (a) can be carried out using, for instance, a high-speed mixer such as CB recycler, and thereafter, step (B) or step (b) can be carried out using, for instance, a moderate-speed mixer such as continuous Lodige Mixer. According to the process described above, a high-bulk density detergent composition comprising a granular mixture having a bulk density of 650 g/L or more, the detergent composition having excellent detergency and a small average particle size, can be obtained. It is more preferable that the high-bulk density detergent composition obtained by the process of the present invention has the following properties. Average particle size: Measured by vibrating a sample with each of standard sieves according to JIS Z 8801 for 5 minutes, and thereafter determining from a weight percentage depending upon the size openings of the sieves. The average particle size is preferably 700 μm or less, more preferably 650 μm or less. Bulk density: Preferably from 650 to 950 g/L, more preferably from 700 to 900 g/L. Here, in the present specification, the bulk density is measured by a method according to JIS K 3362. Flowability: The flowability of the detergent composition in the present specification is expressed as flow time which is defined as a time period required for dropping 100 mL of a powdery detergent composition from a hopper used in the determination of the bulk density according to JIS K 3362. The flow time is preferably 8 seconds or shorter, more preferably 7 seconds or shorter. Detergency: The detergency is expressed a relative detergency ratio. The relative detergency ratio is preferably 0.95 or more, more preferably 0.98 or more. The more the relative detergency ratio approximates 1, the less the affect of the process to individual ingredients. Incidentally, in the present invention, the relative detergency ratio is obtained as follows. First, a detergent composition to be tested is dissolved in water, to give an aqueous solution of the detergent composition. This solution is refened to as "test detergent aqueous solution." Next, an aqueous solution having the same composition as the test detergent aqueous solution is obtained by adding and mixing the individual ingredients constituting the detergent composition with water. This aqueous solution is refened to as "control detergent aqueous solution." The detergency of the test detergent aqueous solution and the detergency of the control detergent aqueous solution are obtained by the following detergency test. Thereafter, the relative detergency ratio is obtained by: Detergency of Relative Test Detergent „ Aqueous Solution Detergency = - r- 1 - 7 Ratio Detergency of Control Detergent Aqueous Solution <Detergency of Detergent> (Preparation of Artificial Stained Cloth) An artificially stained cloth is prepared by smearing an artificial soil solution having the composition shown in Table 1 to a cloth. The smearing of the artificial soil solution to a cloth is carried out in accordance with Japanese Patent Laid-Open No. 7-270395 wherein the artificial soil solution was printed on a cloth by a gravure staining machine equipped with a gravure roll coater. The conditions for smearing the artificial soil solution to a cloth to prepare an artificially stained cloth are a cell capacity of a gravure roll of 58 cm /cm , 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. Table 1 Laurie Acid 0.44% by weight Myristic Acid 3.09% by weight Pentadecanoic Acid 2.31% by weight Palmitic Acid 6.18% by weight 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 Squalene 6.53% by weight Lecithin, from 1.94% by weight Egg White Kanuma Red Clay 8.11 by weight Carbon Black 0.01 by weight Tap Water Balance (Detergent Conditions and Evaluation Method) Five pieces of the artificially stained cloths of 10 cm x 10 cm prepared above are placed in one liter of an aqueous solution for measurement detergent or that of control detergent and washed with turgotometer at 100 rotations/min. The washing conditions are concretely as follows: the washing time: 10 minutes, the detergent concentration: 0.083% by weight; water hardness: 5°DH; water temperature: 20°C; rinsing: with tap water for 5 minutes. The detergency was evaluated by measuring the reflectance at 550 nm of the original cloth before staining and those of the stained cloth before and after washing by an automatic recording colorimeter (manufactured by SHIMADZU CORPORATION), and the detergency (%) was calculated by the following equation. The average value determined of 5 pieces was expressed as the detergency (%). Reflectance Reflectance After - Before Detergency _ Washing Washing x lOO (%) Reflectance Reflectance of Original - Before Cloth Washing In the subsequent Examples, as the zeolite, there was used Zeolite 4A (manufactured by Tosoh Corporation); as the nonionic surfactant, there was used a polyoxyethylene alkyl ether (prepared by adding ethylene oxide in an average of 8 moles to a primary alcohol of which alkyl moiety has 12 to 14 carbon atoms (average being 12.8)); as a fatty acid, there was used palmitic acid; and as the acrylic acid-maleic acid copolymer, there was used one having a weight-average molecular weight of about 70000 as determined by gel permeation method using a polyethylene glycol as a standard. Example 1 A detergent composition having a composition shown in Table 2 was prepared in an amount of 35 kg for each unit, using a Lodige Mixer "FKM-130D" (manufactured by Matsubo Co., Ltd.). This mixer was equipped with agitator blades; a shearing device conesponding to a chopper for disintegration and dispersion; and a jacket for adjusting the temperature within the mixer. The operations were carried out as follows. <Powder Blending> Solid ingredients, comprising 13.19 parts by weight of sodium carbonate ("LIGHT ASH," manufactured by Central Glass Co., Ltd.; average particle size: 56.1 μm), and 0.11 parts by weight of a fluorescer, were blended for one minute with the above Lodige Mixer under the conditions of a rotational speed of agitator blades of 130 rotations/min (peripheral speed: 3.4 m/s) and a rotational speed of a shearing device of 2850 rotations/min (peripheral speed: 27 m/s). <Neutralization> While the mixer was operated under the same conditions as above, 9.40 parts of by weight of a linear alkylbenzenesulfomc acid (LAS; molecular weight: 322) was added to the mixer in 4 minutes. During this stage, the ingredients were cooled by allowing water at 25°C to flow through the mixer jacket. During the addition of the LAS, the temperature inside the mixer rose to 75°C in the highest. After the addition of the LAS, the mixer was continuously operated under the same conditions for 5 minutes to complete the neutralization reaction and the granulation operation. In addition, from immediately after the initiation of addition of the LAS, the aeration within the mixer (300 L/min) was earned out. <Addition of Alkali Metal Aluminosilicate> At a point where the neutralization reaction and granulation process were completed, a zeolite (5.00 parts by weight) having an average particle size of 4 μm was added, while the mixer was operated under the same conditions as above, and mixing was carried out for 5 minutes. <Addition of Liquid Ingredients and Surface Modification> While the mixer was operated under the same conditions as above, the nonionic surfactant (0.98 parts by weight) was added to the mixer and blended for one minute. Next, a zeolite (2.00 parts by weight) having an average particle size of 4 μm was added thereto, and blended for additional 5 minutes. Thereafter, a 40% by weight aqueous solution of acrylic acid-maleic acid copolymer (effective ingredient: 1.49 parts by weight) was added to the mixer, and the ingredients were blended for 1 minute and 30 seconds. Subsequently, the resulting mixture was subjected to a surface modification treatment by adding the zeolite (3.50 parts by weight) having an average particle size of 4 μm to the mixer as a surface modifier, and operating the mixer for additional one minute. The granules of the resulting detergent composition had an average particle size of 640 μm, a bulk density of 795 g/L, and a flowability of 7.1 seconds, whereby showing excellent powder properties. In addition, the granules had a relative ratio for the detergency rate of 0.998, whereby showing excellent detergency. <After-Blending> Using a rotary mixer, an enzyme (0.18 parts by weight) and the detergent composition obtained above were mixed, and a perfume (0.07 parts by weight) was further sprayed thereto, to give a final powder of the high-bulk density detergent composition. Example 2 A detergent composition having a composition shown in Table 2 was prepared in an amount of 35 kg for each unit, using a Lodige Mixer "FKM-130D" (manufactured by Matsubo Co., Ltd.). This mixer basically had the same construction as that described in Example 1. The operations were carried out as follows. <Powder Blending> Solid ingredients, comprising 12.88 parts by weight of sodium carbonate (the same "LIGHT ASH" as in Example 1), and 0.11 parts by weight of a fluorescer, were blended for one minute with the above Lodige Mixer under the same conditions as in Example 1. <Neutralization> While the mixer was operated under the same conditions as above, a mixture comprising 9.40 parts of by weight of the LAS and 0.84 parts by weight of 98% sulfuric acid was added to the mixer in 4 minutes. During this stage, the ingredients were cooled by allowing water at 25°C to flow through the mixer jacket. During the addition of the mixture, the temperature inside the mixer rose to 80°C in the highest. After the addition of the mixture, the mixer was continuously operated under the same conditions for 5 minutes to complete the neutralization reaction and the granulation operation. In addition, from immediately after the initiation of addition of the mixture, the aeration within the mixer (300 L/min) was carried out. <Addition of Alkali Metal Aluminosilicate> In the same manner as in Example 1, a zeolite (5.00 parts by weight) having an average particle size of 4 μm was added, and mixing was carried out for 5 minutes. <Addition of Liquid Ingredients and Surface Modification> In the same manner as in Example 1, the nonionic surfactant (0.98 parts by weight), the zeolite (2.00 parts by weight) having an average particle size of 4 μm, and the 40% by weight aqueous solution of acrylic acid-maleic acid copolymer (effective ingredient: 1.49 parts by weight) were added to the mixer, and the ingredients were blended. Subsequently, the resulting mixture was subjected to the same surface modification treatment as in Example 1. The granules of the resulting detergent composition had an average particle size of 565 μm, a bulk density of 776 g/L, and a flowability of 7.3 seconds, whereby showing excellent powder properties. In addition, the granules had a relative ratio for the detergency rate of 0.988, whereby showing excellent detergency. <After-Blending> In the same manner as in Example 1, the enzyme and the perfume were added thereto, to give a final powder of the high-bulk density detergent composition. Example 3 A detergent composition was obtained by using the same composition and the operations as employed in Example 2, except for changing the amount of LIGHT ASH used to 12.73 parts by weight, adding 0.23 parts by weight of a 48%o by weight aqueous NaOH solution as a reaction initiating agent before neutralization to the mixture of LIGHT ASH and a fluorescer, and thereafter adding a process for blending for 1 minute and 30 seconds under the same conditions as those for the process of powder blending. The granules of the resulting detergent composition had an average particle size of 550 μm, a bulk density of 780 g/L, and a flowability of 7.3 seconds, whereby showing excellent powder properties. In addition, the granules had a relative ratio for the detergency rate of 0.990, whereby showing excellent detergency. <After-Blending> In the same manner as in Example 1, the enzyme and the perfume were added thereto, to give a final powder of the high-bulk density detergent composition. Example 4 A detergent composition having a composition shown in Table 2 was prepared in an amount of 35 kg for each unit, using a Lodige Mixer "FKM-130D" (manufactured by Matsubo Co., Ltd.). This mixer basically had the same construction as that described in Example 1. The operations were carried out as follows. <Powder Blending> Solid ingredients, comprising 12.22 parts by weight of sodium carbonate (the same "LIGHT ASH" as in Example 1), and 0.11 parts by weight of a fluorescer, were blended for one minute with the above Lodige Mixer under the same conditions as in Example 1. <Neutralization> While the mixer was operated under the same conditions as above, a mixture comprising 7.39 parts of by weight of the LAS and 0.87 parts by weight of 98% sulfuric acid was added to the mixer in 4 minutes. During this stage, the ingredients were cooled by allowing water at 25°C to flow through the mixer jacket. During the addition of the mixture, the temperature inside the mixer rose to 75°C in the highest. After the addition of the mixture, the mixer was continuously operated under the same conditions for 5 minutes to complete the neutralization reaction and the granulation operation. In addition, from immediately after the initiation of addition of the mixture, the aeration within the mixer (300 L/min) was carried out. Subsequently, 0.97 parts by weight of a fatty acid was added in 30 seconds, and thereafter, the ingredients were mixed for one minute. <Addition of Alkali Metal Aluminosilicate> In the same manner as in Example 1, a zeolite (6.05 parts by weight) having an average particle size of 4 μm was added, and mixing was canied out for 5 minutes. <Addition of Liquid Ingredients and Surface Modification> In the same manner as in Example 1, the nonionic surfactant (1.51 parts by weight), the zeolite (2.00 parts by weight) having an average particle size of 4 μm, and the 40% by weight aqueous solution of acrylic acid-maleic acid copolymer (effective ingredient: 1.49 parts by weight) were added to the mixer, and the ingredients were blended. Subsequently, the resulting mixture was subjected to the same surface modification treatment as in Example 1. The granules of the resulting detergent composition had an average particle size of 510 μm, a bulk density of 778 g/L, and a flowability of 6.5 seconds, whereby showing excellent powder properties. In addition, the granules had a relative ratio for the detergency rate of 0.988, whereby showing excellent detergency. <After-Blending> In the same manner as in Example 1, the enzyme and the perfume were added thereto, to give a final powder of the high-bulk density detergent composition. Example 5 A detergent composition having a composition shown in Table 2 was prepared in an amount of 35 kg for each unit, using a Lodige Mixer "FKM-130D" (manufactured by Matsubo Co., Ltd.). This mixer basically had the same construction as that described in Example 1. The operations were canied out as follows. <Powder Blending> Solid ingredients, comprising 11.00 parts by weight of sodium carbonate (the same "LIGHT ASH" as in Example 1), and 0.11 parts by weight of a fluorescer, were blended for one minute with the above Lodige Mixer under the same conditions as in Example 1. <Neutralization> While the mixer was operated under the same conditions as above, a mixture comprising 11.76 parts of by weight of the LAS and 1.05 parts by weight of 98% sulfuric acid was added to the mixer in 5 minutes. During this stage, the ingredients were cooled by allowing water at 25°C to flow through the mixer jacket. During the addition of the mixture, the temperature inside the mixer rose to 85°C in the highest. After the addition of the mixture, the mixer was continuously operated under the same conditions for 4 minutes to complete the neutralization reaction and the granulation operation. In addition, from immediately after the initiation of addition of the mixture, the aeration within the mixer (300 L/min) was carried out. <Addition and Disintegration of Alkali Metal Aluminosilicate> While the mixer was operated under the same conditions as above, a zeolite (5.00 parts by weight) having an average particle size of 4 μm was added as a disintegration aid, and mixing was canied out for 5 minutes. Thereafter, the mixture was disintegrated using a Fitz Mill (manufactured by Hosokawa Micron Corporation). <Addition of Liquid Ingredients and Surface Modification> While the disintegrated mixture was stirred in the above Lodige Mixer under the same conditions as above, the nonionic surfactant (0.70 parts by weight) was added to the mixer and blended for one minute. Next, a zeolite (2.00 parts by weight) having an average particle size of 4 μm was added thereto, and blended for additional 5 minutes. Thereafter, a 40% by weight aqueous solution of acrylic acid-maleic acid copolymer (effective ingredient: 1.49 parts by weight) was added to the mixer, and the ingredients were blended for 1 minute and 30 seconds. Subsequently, the resulting mixture was subjected to the same surface modification treatment as in Example 1. The granules of the resulting detergent composition had an average particle size of 560 μm, a bulk density of 780 g/L, and a flowability of 7.4 seconds, whereby showing excellent powder properties. In addition, the granules had a relative ratio for the detergency rate of 0.994, whereby showing excellent detergency. <After-Blending> In the same manner as in Example 1, the enzyme and the perfume were added thereto, to give a final powder of the high-bulk density detergent composition. Comparative Example 1 A detergent composition having a composition shown in Table 2 was prepared in an amount of 35 kg for each unit, using a Lodige Mixer "FKM-130D" (manufactured by Matsubo Co., Ltd.). This mixer basically had the same construction as that described in Example 1. The operations were carried out as follows. <Powder Blending> Solid ingredients, comprising 13.19 parts by weight of sodium carbonate (the same "LIGHT ASH" as in Example 1), 7.00 parts by weight of a zeolite having an average particle size of 4 μm, and 0.11 parts by weight of a fluorescer, were blended for one minute with the above Lodige Mixer under the same conditions as in Example 1. <Neutralization> While the mixer was operated under the same conditions as above, 9.40 parts of by weight of the LAS was added to the mixer in 4 minutes. During this stage, the ingredients were cooled by allowing water at 25°C to flow through the mixer jacket. During the addition of the LAS, the temperature inside the mixer rose to 75°C in the highest. After the addition of the LAS, the mixer was continuously operated under the same conditions for 5 minutes to complete the neutralization reaction and the granulation operation. In addition, from immediately after the initiation of addition of the LAS, the aeration within the mixer (300 L/min) was carried out. <Addition of Liquid Ingredients and Surface Modification> While the mixer was operated under the same conditions as above, the nonionic surfactant (0.98 parts by weight) was added to the mixer and blended for one minute, and thereafter a 40% by weight aqueous solution of acrylic acid- maleic acid copolymer (effective ingredient: 1.49 parts by weight) was added to the mixer, and the ingredients were blended for 1 minute and 30 seconds. Subsequently, the resulting mixture was subjected to the same surface modification treatment as in Example 1. The granules of the resulting detergent composition had an average particle size of 650 μm, a bulk density of 770 g/L, and a flowability of 6.9 seconds, whereby showing excellent powder properties. However, the granules had a relative ratio for the detergency rate of 0.902, whereby showing notably poorer detergency. <After-Blending> In the same manner as in Example 1, the enzyme and the perfume were added thereto, to give a final powder of the detergent composition. Table 2 Example No. Comp. Ex. No. 1 2 j 4 5 1 Composition (% by weight) LAS-Na 28.00 28.00 28.00 22.00 35.00 28.00 Soap 0.00 0.00 0.00 3.00 0.00 0.00 Zeolite 30.00 30.00 30.00 33.00 30.00 30.00 Sodium 33.00 29.50 29.50 28.00 22.30 33.00 Carbonate Sodium Sulfate 0.50 4.00 4.00 4.00 5.00 0.50 Copolymer* 1.70 1.70 1.70 1.70 1.70 1.70 Nonionic** 2.80 2.80 2.80 4.30 2.00 2.80 Fluorescer 0.30 0.30 0.30 0.30 0.30 0.30 Enzyme 0.50 0.50 0.50 0.50 0.50 0.50 Perfume 0.20 0.20 0.20 0.20 0.20 0.20 Water 3.00 3.00 3.00 3.00 3.00 3.00 Total 100.00 100.00 100.00 100.00 100.00 100.00 *. Acrylic acid-maleic acid copolymer. **: Nonionic surfactant. Examples 6 to 8 and Comparative Example 2 A detergent composition having a composition shown in Table 3 was prepared in an amount of 35 kg for each unit, using a Lodige Mixer "FKM-130D" (manufactured by Matsubo Co., Ltd.). This mixer basically had the same construction as that described in Example 1. The operations were carried out as follows (the amount of each raw material formulated in each step is shown in Table 4). <Powder Blending> Solid ingredients, comprising sodium carbonate ("LIGHT ASH," manufactured by Central Glass Co., Ltd.; average particle size: 56.1 μm), sodium tripolyphosphate (STPP; average particle size: 11.2 μm), and a fluorescer, were blended for one minute with the above Lodige Mixer under the conditions of a rotational speed of agitator blades of 130 rotations/min (peripheral speed: 3.4 m s) and a rotational speed of a shearing device of 2850 rotations/min (peripheral speed: 27 m s). <Addition of Reaction Initiating Agent> A 48%o by weight of NaOH aqueous solution was added to the contents in the mixer as a reaction initiating agent, and the blending was canied out for 1 minute and 30 seconds under the same conditions as above. <Neutralization> While the mixer was operated under the same conditions as above, a mixture comprising 9.40 parts of by weight of the LAS and 0.84 parts by weight of 98%> sulfuric acid was added to the mixer in 4 minutes. During this stage, the ingredients were cooled by allowing water at 25 °C to flow through the mixer jacket. During the addition of the mixture, the temperature inside the mixer rose to 75°C in the highest. In addition, from immediately after the initiation of addition of the mixture, the aeration within the mixer (300 L/min) was canied out. <Blending of Inorganic Powder > An inorganic powder (1.75 parts by weight) was added to the resulting neutralized mixture, and the mixer was continuously operated under the same conditions as above for 4 minutes and 30 seconds. <Addition of Liquid Ingredients and Surface Modifιcation> While the mixer was operated under the same conditions as above, the nonionic surfactant (0.98 parts by weight) was added to the mixer and blended for one minute. Next, a zeolite (2.00 parts by weight) having an average particle size of 4 μm was added thereto, and blended for additional 5 minutes. Thereafter, a 40% by weight aqueous solution of acrylic acid-maleic acid copolymer was added to the mixer, and the ingredients were blended for 1 minute and 30 seconds. Subsequently, the resulting mixture was subjected to a surface modification treatment by adding the zeolite (2.20 parts by weight) having an average particle size of 4 μm to the mixer as a surface modifier, and operating the mixer for additional one minute. <After-Blending> In the same manner as in Example 1, the enzyme and the perfume were added thereto, to give a final powder of the high-bulk density granular detergent composition. Here, in Example 6 or 7, after 30 seconds from the termination of addition of the LAS, STPP or zeolite (1.75 parts by weight) was added as an inorganic powder. In addition, in Example 8, the addition of STPP, an inorganic powder was canied out during the course of the neutralization process, and the mixture was continued to be blended for 5 minutes after termination of the addition of the LAS. Incidentally, the addition of STPP was canied out at a point where a weight ratio of the LAS added to sodium carbonate reached 0.6. In Comparative Example 2, the mixture was blended for 5 minutes after the termination of the addition of LAS, without adding an inorganic powder during the course of the neutralization process or immediately after the neutralization process. The properties of each of the resulting high-density detergent composition are shown in Table 5. Table 3 Example No. Comp. Ex. No. 6 7 8 9 2 Composition (% by weight) LAS-Na 28.00 28.00 28.00 28.00 28.00 Zeolite 12.00 17.00 12.00 12.00 12.00 STPP 20.00 15.00 20.00 20.00 20.00 Sodium Carbonate 27.50 27.50 27.50 28.80 27.50 Sodium Sulfate 4.00 4.00 4.00 4.00 4.00 Copolymer* 1.70 1.70 1.70 1.70 1.70 Nonionic** 2.80 2.80 2.80 - 2.80 Fluorescer 0.30 0.30 0.30 0.30 0.30 Enzyme 0.50 0.50 0.50 0.50 0.50 Perfume 0.20 0.20 0.20 0.20 0.20 Water 3.00 3.00 3.00 4.50 3.00 Total 100.00 100.00 100.00 100.00 100.00 *: Acrylic acid-maleic acid copolymer. **: Nonionic surfactant. Table 4 Composition Example No. Comp. (parts by weight) Ex. No. 6 7 8 9 2 <Powder Blending> Sodium Carbonate 12.03 12.03 12.03 12.48 12.03 Sodium Tripolyphosphate 5.25 5.25 5.25 5.25 7.00 Fluorescer 0.11 0.11 0.11 0.11 0.11 <Addition of Reaction Initiating Agent> 48% by weight NaOH 0.23 0.23 0.23 0.23 0.23 <Neutralization> Linear Alkylbenzene9.40 9.40 9.40 9.40 9.40 sulfomc Acid (LAS) 98%o Sulfuric Acid (Amount 0.84 0.84 0.84 0.84 0.84 of Air Flow [L/min]) 300 300 300 300 300 <Blending of Inorganic Powder> Sodium Tripolyphosphate 1.75 - 1.75 - - Zeolite - 1.75 - 3.75 - <Addition of Liquid Ingredients and Surface Modification> Nonionic Surfactant 0.98 0.98 0.98 - 0.98 Zeolite 2.00 2.00 2.00 - 2.00 Water - - - 0.53 - Acrylic Acid-Maleic Acid 1.49 1.49 1.49 1.49 1.49 Copolymer (Effective Ingredient) Zeolite for Surface 2.20 2.20 2.20 2.20 2.20 Modification <After-Blending> Enzyme 0.18 0.18 0.18 0.18 0.18 Perfume 0.07 0.07 0.07 0.07 0.07 Table 5 Example No. Comp. Ex. No. 6 7 8 9 2 Final Average Particle Size 460 457 474 450 547 (μm) Average Particle Size 465 458 460 453 440 (μm) Immediately After Acid Addition Bulk Density (g/L) 753 756 764 755 783 Flowability (sec) 6.5 6.5 6.5 6.4 6.7 Ratio of Relative 0.997 0.988 0.996 0.996 0.997 Detergency It is clear from the above results of Table 5 that by adding an inorganic powder during the course or immediately after the neutralization process, the granular growth from the termination of the neutralization process can be suppressed, and consequently, there can be obtained a high-bulk density detergent composition not only having excellent detergency but also comprising granules having a small average particle size. Example 9 A detergent composition having a composition shown in Table 3 was prepared in an amount of 35 kg for each unit, using a Lodige Mixer "FKM-130D" (manufactured by Matsubo Co., Ltd.). This mixer basically had the same construction as that described in Example 1. The operations were carried out as follows (the amount of each raw material formulated in each step is shown in Table 4). <Powder Blending> Solid ingredients, comprising sodium carbonate (the same LIGHT ASH as in Example 1), sodium tripolyphosphate (the same STPP as in Example 6), and a fluorescer, were blended for one minute with the above Lodige Mixer under the same conditions as in Example 1. <Neutralization> While the mixer was operated under the same conditions as in Example 1, a mixture comprising 9.40 parts of by weight of the LAS and 0.84 parts by weight of 98% sulfuric acid was added to the mixer in 4 minutes. During this stage, the ingredients were cooled by allowing water at 25°C to flow through the mixer jacket. During the addition of the mixture, the temperature inside the mixer rose to 80°C in the highest. After the completion of the addition of the mixture, the mixer was continuously operated under the same conditions for 30 seconds to complete the neutralization reaction and the granulation operation. In addition, from immediately after the initiation of addition of the mixture, the aeration within the mixer (300 L/min) was canied out. <Addition of Alkali Metal Aluminosilicate> Zeolite (3.75 parts by weight) was added to the resulting neutralized mixture, and the mixer was continuously operated under the same conditions as above for 4 minutes and 30 seconds. <Addition of Liquid Ingredients and Surface Modification> While the mixer was operated under the same conditions as in Example 1, a mixture comprising a 40% by weight aqueous solution of acrylic acid-maleic acid copolymer and water was added to the mixer and blended for 1 minute and 30 seconds. Subsequently, the resulting mixture was subjected to a surface modification treatment in the same manner as in Example 1. <After-Blending> In the same manner as in Example 1, the enzyme and the perfume were added thereto, to give a final powder of the high-bulk density granular detergent composition. The properties of the resulting high-bulk density detergent composition are shown in Table 5. It is clear from Table 5 that a high-bulk density detergent composition having excellent detergency and a small average particle size can be obtained. INDUSTRIAL APPLICABILITY According to the process of the present invention, a high-bulk density detergent composition having excellent detergency and a small average particle size can be obtained.

Claims: CLAIMS 1. A process for preparing a high-bulk density detergent composition having a bulk density of 650 g/L or more, comprising the steps of: (A) blending a liquid acid precursor of an anionic surfactant with a water- soluble, alkali inorganic substance in an amount equal to or exceeding an amount necessaiy for neutralizing the liquid acid precursor, in a substantial absence of an alkali metal aluminosilicate, thereby neutralizing the liquid acid precursor; and (B) adding an inorganic powder to a neutralization mixture in step (A) after a point of initiation of formation of coarse grains of the neutralization mixture obtained during a course of a neutralization process in step (A) and mixing a resulting mixture. 2. The process according to claim 1, wherein the addition of the inorganic powder is initiated in step (B) at any time between a point when the liquid acid precursor of an anionic surfactant is added in an amount exceeding a weight ratio of 0.25 to the water-soluble, alkali inorganic substance and a point up to 5 minutes from termination of addition of an entire amount of the liquid acid precursor. 3. The process according to claim 1 or 2, wherein the average particle size of the inorganic powder is 30 μm or less. 4. The process according to any one of claims 1 to 3, wherein the inorganic powder is an alkali metal aluminosilicate. 5. The process according to claim 4, wherein the addition of the alkali metal aluminosilicate is initiated in step (B) at any time within 5 minutes from tennination of addition of an entire amount of the liquid acid precursor of an anionic surfactant. 6. A process for preparing a high-bulk density detergent composition having a bulk density of 650 g/L or more, comprising the steps of: (a) blending a liquid acid precursor of an anionic surfactant with a water- soluble, alkali inorganic substance in an amount equal to or exceeding in an amount necessary for neutralizing the liquid acid precursor, in a substantial absence of an alkali metal aluminosilicate, thereby neutralizing the liquid acid precursor; and (b) adding an alkali metal aluminosilicate to a neutralization mixture obtained in step (a) and mixing a resulting mixture. 7. The process according to claim 6, wherein the addition of the alkali metal aluminosilicate is initiated in step (b) at any time within 5 minutes from tennination of addition of an entire amount of the liquid acid precursor of an anionic surfactant.

Inventors: NITTA HIDEICHI, SAITO JUN, SAKATA YUSHI, YAMASHITA HIROYUKI, NITTA, HIDEICHI, SAITO, JUN, SAKATA, YUSHI, YAMASHITA, HIROYUKI
Applicants: KAO CORP, NITTA HIDEICHI, SAITO JUN, SAKATA YUSHI, YAMASHITA HIROYUKI, KAO CORPORATION, NITTA, HIDEICHI, SAITO, JUN, SAKATA, YUSHI, YAMASHITA, HIROYUKI
Application year: 2000
Main classification: C11D11
IPC codes: C11D3, C11D11, C11D17