EP0874888B1

EP0874888B1 - Powder detergent composition for clothes washing

Info

Publication number: EP0874888B1
Application number: EP96938497A
Authority: EP
Inventors: Shu Yamaguchi; Kyoko Okada; Toshiki Nishi; Ichiro Sakamoto; Shigeru Tamura; Masaki Tsumadori
Original assignee: Kao Corp
Current assignee: Kao Corp
Priority date: 1995-11-22
Filing date: 1996-11-18
Publication date: 2003-09-03
Anticipated expiration: 2016-11-18
Also published as: DE69629833D1; KR19990071539A; WO1997019156A1; KR100258495B1; CN1109738C; DE69629833T2; TW371670B; CN1207761A; EP0874888A1

Description

TECHNICAL FIELD

The present invention relates to a powder detergent composition for clothes washing including crystalline sodium silicates capable of sufficiently showing good washing performance. More specifically, it relates to a powder detergent composition for clothes washing capable of having excellent detergency with a small standard amount of dosage thereof.

BACKGROUND ART

In general, the powder detergent compositions for clothes washing comprise three basic ingredients: surfactants as the base ingredient, metal ion capturing agents such as chelating agents and ion exchange materials, and alkalizers.
The metal ion capturing agents, such as chelating agent and ion exchange materials, have been blended in detergents for the purpose of removing the water hardness-increasing components in tap water (for instance, calcium and magnesium ions) which cause to lower the detergency in a washing system. Conventionally, tripolyphosphates have been widely used because of their low costs and easy handling in the production process. Ever since the eutrophication of closed-water systems, such as rivers, lakes and marshes, has become a social problem from the late seventies, the use of triphosphates has been decreased. Presently, the main trend is to provide detergents comprising ion exchange materials, such as crystalline aluminosilicates (zeolites) which are typically disclosed, for instance, in Japanese Patent Laid-Open No. 50-12381, the ion exchange materials being used in combination with supplementary aids, including low-molecular chelating agents, such as citrates, and polymeric builders, such as carboxylate polymers.
As for alkalizers, the tripolyphosphates acting as the chelating agents as described above also are materials having alkalizing ability, so that carbonates, such as sodium carbonate and potassium carbonate, and amorphous sodium silicates are blended as supplementary aids for alkalizers. As the mainstream of detergents shifted to phosphorus-free detergents, since the zeolites used as substitutes for the phosphorus-containing compounds have, if any, very little alkalizing ability, the alkalizers to be blended in detergents have been reconsidered. In order to provide sufficient alkalizing ability, the amounts of the alkali metal carbonates and the amorphous sodium silicates have been increased in conventional detergents.
The proportions of the carbonates and the sodium silicates added to the detergent composition vary depending upon the kinds and amounts of other builder components or the surfactant components and production methods employed. In general, although the amorphous sodium silicates have high alkalizing ability, they have high hygroscopic property and thus causing caking phenomenon in the resulting powder detergents. Therefore, presently the alkalizing ability of the detergents are maintained by using the alkali metal carbonates as the main alkalizers and by adding the sodium silicates in an amount effective to act as structure-constitution agent of the powder.
The carbonates and the amorphous silicates act to capture metal ions and allow them to precipitate when the water hardness is relatively high. From the equilibrium constant during ion exchange, it would be difficult to lower the water hardness to a level where the detergency is not substantially affected. For instance, under the water conditions in Japan where soft tap water is used, substantially no metal ion capturing capabilities are exhibited.
Recently, however, since a crystalline sodium silicate having a particular structure disclosed, for instance, in Japanese Patent Laid-Open No. 60-227895, has ion exchange capacity as well as alkalizing ability, there has been suggested a possibility that the functions of two alkalizer components conventionally used in detergents, namely ion exchange materials, such as zeolites, and sodium carbonate may be replaced with a single component of the crystalline sodium silicate. Aside from the above, because of having the industrial advantages that a starting material composition of the crystalline sodium silicate is simple and thus being able to produce at a relatively low cost, the crystalline sodium silicate is presently being paid attention as new detergent builder components.
Many patent applications have been filed concerning the formulation of crystalline sodium silicates in detergents, as disclosed in Japanese Patent Laid-Open No. 60-227895. For instance, Japanese Patent Laid-Open No. 2-178398 discloses a detergent composition comprising the above crystalline sodium silicate "SKS-6" (manufactured by Hoechst) being added to a conventional detergent system. Japanese Patent Unexamined Publication No. 6-500144 discloses a detergent comprising a crystalline sodium silicate, a zeolite, and a carboxylate polymer in particular proportions, to thereby provide a detergent which does not remain on clothes fibers. Japanese Patent Laid-Open No. 6-502199 discloses a builder composition where a zeolite and a carboxylate polymer are used in combination. Japanese Patent Unexamined Publication No. 6-505045 discloses a detergent containing no alkali metal carbonates or carboxylate polymers. Besides the above, various detergents containing crystalline sodium silicates are disclosed in Japanese Patent Laid-Open No. 1-311197, Japanese Patent Laid-Open No. 3-37298, and Japanese Patent Laid-Open No. 7-53992. In addition, the applicant of the present invention has also filed a patent application (Japanese Patent Laid-Open No. 5-10000) which teaches that excellent detergency can be obtained by using a nonionic surfactant together with the crystalline sodium silicate.
The crystalline sodium silicates disclosed in No. 60-227895 used in the above publication comprise many isomeric crystalline phases, such as δ-phase, α-phase, and β-phase. However, the remarkable improvement in detergency achieved by the optimization of the combination of the crystalline phases of the crystalline sodium silicate has not yet been studied thus far.
Accordingly, an object of the present invention is to provide a powder detergent composition for clothes washing showing excellent detergency, the powder detergent composition having good detergency with a small standard amount of dosage.
These and other objects of the present invention will be apparent from the following description.

DISCLOSURE OF THE INVENTION

As a result of intense research in view of the above objects, the present inventors have found that the compositional weight ratios of the isomeric crystalline phases of the crystalline sodium silicates are affected by baking conditions such as temperature and time, and that the detergency is greatly differed by the combination of the isomeric crystalline phases which have the same detergent composition, and that such a difference in detergency becomes notably apparent particularly when a large amount of the crystalline sodium silicates is added. Also, the present inventors have found after intensive study that the ion exchange speed and thus the speed for decreasing the level of the water hardness are affected by the composition ratios of the crystalline phases of the crystalline sodium silicates, and that the ion exchange speed affects the detergency of the resulting detergent composition when the crystalline sodium silicates are added in large amounts. Further, by combinably using the metal ion capturing agents other than the crystalline. sodium silicates and the surfactants in particular proportions, the present inventors have been able to develop a powder detergent composition having a remarkably good detergency even when the standard amount of dosage of the detergent composition is small. The present invention has been completed based upon these findings.
In one aspect, the present invention is concerned with a powder detergent composition for clothes washing having a bulk density of 0.50 g/mL or more, comprising 5% by weight or more of a crystalline sodium silicate represented by the following general formula (1): Na₂O • xSiO₂ • yH₂O wherein x and y each stands for a molar number, wherein x is from 1.5 to 2.2, and y is from 0 to 5,
wherein the crystalline sodium silicate has an average particle size of from 1 to 100 µm and comprises crystalline phases of a δ-phase, an α-phase, and a β-phase, wherein the compositional weight ratios of the α-phase, the β-phase, and the 6-phase satisfy all of the following relationships: 0.085 ≤ α/(α + β + δ) ≤ 0.15; 0.01 ≤ β/(α + β + δ) ≤ 0.10; and 0.80 ≤ δ/(α + β + δ) ≤ 0.90, wherein said average particle size is a median diameter obtained from a particle size distribution determined by a laser scattering particle size analyser, and wherein said compositional weight ratio is obtained by determining the intensity of the main diffraction peak for each of the crystalline phases as measured by a powder X-ray diffraction, these main diffraction peaks being assigned to the following d values:

α-crystalline phase d=3.31 ± 0.04Å

β-crystalline phase d=4.15 ± 0.04Å

δ-crystalline phase d=3.95 ± 0.04Å

and calculating the proportion of the crystalline phases by the following equation:

α-crystalline phase I_3.31;

β-crystalline phase 4.33 x I_4.15; and

δ-crystalline phase I_3.95 - (1.33 x I_4.15),

wherein I_3.31, I_4.15, and I_3.95 each stands for an intensity at the above d value for the respective crystalline phases.
In a preferred embodiment, the powder detergent composition comprises the following components:
A) one or more surfactant components;
B) a crystalline sodium silicate as defined above;
and
C) one or more metal ion capturing agents other than component B,

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitative of the present invention, and wherein:
Figure 1 is a graph of a calibration curve showing the relationship between the logarithm of the calcium ion concentration and the voltage; and
Figure 2 is a graph showing the relationships between the amount of the CaCl₂ aqueous solution added dropwise and the calcium ion concentration.
The reference numerals in Figure 2 are as follows:
A is an intersection of the extension of the linear portion of Line Q with the abscissa (horizontal axis); P shows the data of the blank solution (buffer solution without using the chelating agent); and Q shows the data for the chelating agent-containing buffer solution.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is concerned with a powder detergent composition for clothes washing having a bulk density of 0.50 g/mL or more, comprising 5% by weight or more of a crystalline sodium silicate represented by the following general formula (1): Na₂O • xSiO₂ • yH₂O wherein x and y each stands for a molar number, wherein x is from 1.5 to 2.2, and y is from 0 to 5,
wherein the crystalline sodium silicate has an average particle size of from 1 to 100 µm and comprises crystalline phases of a δ-phase, an α-phase, and a β-phase, wherein the compositional weight ratios of the α-phase, the β-phase, and the δ-phase satisfy all of the following relationships: 0.085 ≤ α/(α + β + δ) ≤ 0.15; 0.01 ≤ β/(α + β + δ) ≤ 0.10; and 0.80 ≤ δ/(α + β + δ) ≤ 0.90.
In the present invention, since α, β, and δ satisfy the above relationships, good ion exchange speed of the crystalline sodium silicate can be obtained.
The crystalline sodium silicates satisfying the above crystalline phase relationships are contained in an amount of 5% by weight or more, preferably from 10 to 60% by weight. In particular, from the aspect of achieving excellent detergency, a particular preference is given to the following compositions depending upon the water hardness of the water for washing used.
1) In the case of using water for washing having a water hardness of from 2 to 6°DH, 20 to 50% by weight of the crystalline sodium silicate in the entire composition;
2) In the case of using water for washing having a water hardness of from 6 to 10°DH, 10 to 45% by weight of the crystalline sodium silicate in the entire composition; and
3) In the case of using water for washing having a water hardness of from 10 to 20°DH, 5 to 30% by weight of the crystalline sodium silicate in the entire composition.
When the content of the crystalline sodium silicate is 5% by weight or more, a high detergency can be obtained.
The average particle size of the crystalline sodium silicate is usually from 1 to 100 µm, preferably from 10 to 50 µm. The average particle size of the crystalline sodium silicate is preferably 1 µm or more from the viewpoint of preventing elevation of hygroscopic property. Also, the average particle size is preferably 100 µm or less, from the viewpoint of ion exchange speed. Incidentally, the average particle size referred herein is a median diameter obtained from a particle size distribution.
The crystalline sodium silicate having the average particle size and the particle size distribution described above is prepared by pulverizing using pulverization devices, such as vibration mills, hammer mills, ball-mills, and roller mills.
As disclosed in Japanese Patent Laid-Open No. 60-227895, α-, β-, and δ-phases are crystalline phases characteristic for the crystalline sodium silicate. The crystalline sodium silicate may also include many other crystalline phases, and it is preferred in the present invention that the NS-phase is mixed therein, to thereby further improving the detergency. In addition, the total amount of the δ-phase, the α-phase, the β-phase, and the NS-phase is preferably substantially 100% by weight of the entire crystalline phase of the crystalline sodium silicate. In the general formula (1), it is preferred that x is from 1.7 to 1.9 and y is zero (0).
A method for producing the above crystalline sodium silicates is carried out by a method similar to that disclosed in Japanese Patent Laid-Open No. 60-227895, wherein the crystalline sodium silicates may be generally produced by baking glassy amorphous sodium silicate at a temperature of from 200 to 1000°C. Details of the production method is disclosed in "Phys. Chem. Glasses, 7, pp.127-138 (1966), and Z. Kristallogr., 129, pp.396-404(1969)." In the present invention, the crystalline sodium silicates having a suitable crystalline phase construction can be easily prepared by baking a water glass or the dried product thereof whose composition is previously adjusted. The baking temperature is preferably from 500 to 900°C, more preferably from 650 to 780°C. In particular, from the aspect of controlling the growth of the β-phase, the baking temperature is preferably 680 to 750°C. The baking temperature is preferably equal to or higher than 500°C, from the aspect of having sufficient progress in crystallization. In addition, the baking temperature is preferably equal to or lower than 900°C, from the aspect of preventing the start of melting. This is because once the melting is started, the crystallinity is lowered, thereby making it difficult to achieve good detergency.
The crystalline phases can be identified as α-, β-, δ-, and NS-phases by a powder X-ray diffraction measurement by collating the obtained data with the diffraction data (PDF-Nos. 22-1397, 24-1123, 22-1396, and 16-818) listed in powder diffraction data file (PDF) published by Joint Committee of Powder Diffraction Standard (JCPDS). Also, the intensity of the main diffraction peak of each of the crystalline phases is calculated to measure and confirm the proportion (compositional weight ratio) in the entire crystalline phases.
The crystalline sodium silicates have good ion exchange capacity and alkalizing ability as mentioned above. Therefore, a possibility of replacing zeolites and carbonates with a single component of the crystalline sodium silicates has been conventionally suggested. As discussed in BACKGROUND ART section of the present invention, Japanese Patent Unexamined Publication No. 6-505045 discloses a detergent containing no carbonates or no carboxylate polymers, and Japanese Patent Laid-Open No. 7-53992 disclose a detergent system containing a crystalline sodium silicate, the detergent used in a standard amount of dosage of from 14 to 21 g/30 liters. In these prior art techniques, a part or whole of the builder components, such as zeolites and sodium carbonate, is simply replaced with the crystalline sodium silicate. However, when these methods are studied by actually replacing the builder components, sufficient detergency cannot be obtained in cases where the standard amount of dosage per cycle is reduced. The reasons for not being able to achieve a good detergency are as follows.
In conventional detergents, the mainstream of the technical idea has been to make the oily components in dirt soluble by surfactants. Specifically, sebum dirt stains ascribed to human bodies, the most typical dirt stains adhered to clothes (most likely to be observed on collars and sleeves), are taken as examples. The sebum dirt stains contain oily components, such as free fatty acids and glycerides, with a high content of 70% by weight or more (Ichiro KASHIWA et al., "Yukagaku," 19, 1095 (1969)). The oily components lock carbon and dirt in dust and peeled keratin, so that the resulting substance is observed as dirt stains. In order to wash off the sebum dirt stains, conventionally, detergents are designed based on a washing mechanism mainly by making these oily components soluble with micelle of surfactants, thereby detaching carbon, dirt, and keratin from clothes. This technical idea has been widely established among those of ordinary skill in the art, and even when the conventional detergents are shifted to compact detergents, substantially no changes have taken place in the surfactant concentration in the washing liquid. This fact is described in "Dictionary for Detergents and Washing," Haruhiko OKUYAMA et al., p. 428, 1990, First Edition, Asakura Publishing Company Limited, which shows that there are substantially no changes in concentrations in the washing liquid for components other than sodium sulfate.
The technical idea of blending zeolites and alkalizers, such as sodium carbonate, in the detergent composition is based on these washing principles. Here, the surfactant concentration in the washing liquid has to be made high in order to achieve high detergency, so that the surfactant is blended as the major component in the detergent composition. In such detergents, the surfactant concentration is set by considering the amount of the detergent added to the washing liquid.
Therefore, the present inventors have started their study by reconsidering the detergent composition, and an extremely interesting observation has been made for clothes washing in a simple washing system. Specifically, while intensively studying the effects on washing of the pH and the water hardness of the washing liquid, the present inventors have made the following findings.
(i) Higher the pH and the lower the water hardness, the dependency of the detergency on the surfactant concentration is lessened, so that good detergency can be achieved.
(ii) In the case of a high pH but a high water hardness, the detergency is drastically lowered even at a high pH.
(iii)In the case of washing solely with a composition containing a surfactant but containing no alkalizers, the dependency of the detergency on the water hardness is sufficient small when compared to systems containing alkalizers, even though the detergency at low water hardness is low.
From these results, the present inventors have paid attention to the relationship between the washing liquid and the dirt stains.
As discussed above, the sebum dirt stains which are the most typical dirt stains adhered to clothes contain free fatty acids and glycerides, and the dirt stains are presumably a mixture of these organic materials with carbon, dirt, or peeled keratin. In the case of a high pH, while the content of the fatty acids increases by hydrolysis of glycerides, the reaction of the fatty acids with alkali metals to form salts also proceeds. The alkali metal salts of the fatty acids are soaps, so that the freeing speed of the dirt stains in the washing liquid becomes notably faster. However, this reaction is a competitive reaction with calcium ions, magnesium ions, etc. in the hard water. Since the alkali metal salts of fatty acids form a scum by carrying out ion-exchange reaction with calcium and magnesium, the dirt stains are solidified without being freed from the interface of clothes in the case where the water hardness is high, which results in causing difficulty in stain removal. In particular, the scum-formation rate is extremely faster with the alkali metal salts than that with the fatty acid (unneutralized product).
In other words, in a system where the water hardness-increasing components are not completely removed, the higher the pH of the system, the faster the scum-formation rate, thereby making it more difficult to remove the dirt stains. Since the crystalline sodium silicates have sufficiently a high level of alkalizing ability comparative to those of the conventional alkalizers, such as sodium carbonate, the scum is more liable to be formed by the actions of calcium ions or magnesium ions, thereby requiring an even lower water hardness.
Therefore, the present inventors have found the following concerning the compositional requirements for reducing the standard amount of dosage. Specifically, in addition to blending sodium silicate for the purpose of maintaining a high alkalizing ability, the metal ion capturing agents other than the crystalline sodium silicate are needed for the purpose of further lowering the water hardness of the washing liquid. In addition, the present inventors have found that the surfactant concentration in the washing liquid at such low water hardness and high pH can be notably lowered, and also found that a particular weight ratio between the surfactants, the crystalline sodium silicates, and the metal ion capturing agents for achieving such a low surfactant concentration serves to lower the standard amount of dosage of the resulting detergent composition without deterring its detergency.
Accordingly, the preferred powder detergent composition for clothes washing, from the aspect of its detergency, comprises the following components:
A) one or more surfactant components;
B) a crystalline sodium silicate as defined above; and
C) one or more metal ion capturing agents other than component B,

Here, the crystalline sodium silicate has the average particle size, the compositional weight ratio of the crystalline phases, and the composition as described above, and their suitable ranges are also given above.
The crystalline sodium silicate having the compositional weight ratio of the crystalline phases as mentioned above have fast ion exchange speed, so that the speed for lowering the water hardness of the washing liquid is fast, thereby being particularly suitably useful for the detergent composition of the present invention having a notably small standard amount of dosage. In the above detergent composition, excellent detergency can be achieved even when the standard amount of dosage is smaller than that of the conventional detergents.
The standard amount of dosage of the detergents greatly differs throughout the world. This is due to the differences in the water hardness of tap water in each of the countries. For instance, while the tap water has a water hardness of usually around 4°DH in Japan, the tap water having a water hardness of not less than 6°DH in the U.S., and that exceeding 10°DH in European countries is used for the water for washing. Therefore, since the required absolute amount of the metal ion capturing agents varies, the standard amount of dosage would need to be adjusted accordingly. While the amount of the metal ion capturing agent in the present invention varies depending upon the water hardness, the surfactant concentration in the washing liquid remains substantially the same, and the standard amount of dosage becomes smaller than the that of conventional detergents.
Particularly, in cases where the initial water hardness differs in each of the washing liquids, the standard amounts of dosage expressed as detergent concentrations for achieving good detergency are as follows:
1) As for the washing liquid having a water hardness of 2 to 6°DH, in a case where the weight ratio of component B to component C is B/C = 3/1 to 3/7, the standard amount of dosage is from 0.33 to 0.67 g/L, preferably from 0.33 to 0.50 g/L.
2) As for the washing liquid having a water hardness of 6 to 10°DH, in a case where the weight ratio of component B to component C is B/C = 4/3 to 1/6, the standard amount of dosage is from 0.50 to 1.20 g/L, preferably from 0.50 to 1.00 g/L.
3) As for the washing liquid having a water hardness of 10 to 20°DH, in a case where the weight ratio of component B to component C is B/C = 1/1 to 1/15, the standard amount of dosage is of from 0.80 to 2.50 g/L, preferably from 1.00 to 2.00 g/L.
Each of the detergent components blended in the powder detergent composition of the present invention will be explained below. Incidentally, component B is as described above.

A) Surfactant

The surfactants usable in the present invention are not particularly limited, and any ones generally used for detergents are used, in which a nonionic surfactant is preferably contained in an amount of from 50 to 100% by weight, more preferably from 65 to 100% by weight, of the entire surfactant. Specifically, they may be one or more surfactants selected from the group consisting of nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants, each being exemplified below. For instance, the surfactants can be chosen such that the surfactants of the same kind are chosen, as in the case where a plurality of the nonionic surfactants are chosen. Alternatively, the surfactants of the different kinds are chosen, as in the case where the anionic surfactant and the nonionic surfactant are respectively chosen. In addition, from the aspect of detergency, a preference is given to the surfactant component comprising a polyoxyethylene alkyl ether-type nonionic surfactant in an amount of 50% by weight or more.
Examples of the nonionic surfactants are as follows:
Polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, polyoxyethylene fatty acid esters, polyoxyethylene alkyl ether fatty acid esters, polyoxyethylene polyoxypropylene alkyl ethers, polyoxyethylene castor oils, polyoxyethylene alkylamines, glycerol fatty acid esters, higher fatty acid alkanolamides, alkylglucosides, alkylglucosamides, and alkylamine oxides.
Among the nonionic surfactants, a preference is given to polyoxyethylene alkyl ethers which are ethylene oxide adducts whose alkyl moieties are ascribed to linear or branched, primary or secondary alcohols, each having 10 to 18 carbon atoms, and whose ethylene oxide moieties have an average molar number of 5 to 15, and more preferably polyoxyethylene alkyl ethers which are ethylene oxide adducts whose alkyl moieties are ascribed to linear or branched, primary or secondary alcohols, each having 12 to 14 carbon atoms, and whose ethylene oxide moieties have an average molar number of 6 to 10.
Examples of the anionic surfactants include alkylbenzenesulfonates, alkyl or alkenyl ether sulfates, alkyl or alkenyl sulfates, α-olefinsulfonates, α-sulfofatty acid salts, α-sulfofatty acid ester salts, alkyl or alkenyl ether carboxylates, amino acid-type surfactants, and N-acyl amino acid-type surfactants, with a preference given to alkylbenzenesulfonates, alkyl or alkenyl ether sulfates, and alkyl or alkenyl sulfates.
Examples of the cationic surfactants include quaternary ammonium salts, such as alkyl trimethylamine salts. Examples of the amphoteric surfactants include carboxy-type and sulfobetaine-type amphoteric surfactants.
The surfactant content is preferably from 1 to 45% by weight, and the surfactant content is particularly in the following ranges, depending on the types of water for washing used.
1) In the case where the water for washing having a water hardness of 2 to 6°DH, the surfactant content is particularly preferably from 12 to 30% by weight;
2) In the case where the water for washing having a water hardness of 6 to 10°DH, the surfactant content is particularly preferably from 8 to 25% by weight; and
3) In the case where the water for washing having a water hardness of 10 to 20°DH, the surfactant content is particularly preferably from 5 to 20% by weight.
Since the powder detergent composition for clothes washing of the present invention has the above compositions, when the detergent composition is added to the water for washing so as to provide a surfactant concentration in the washing liquid of from 0.07 to 0.17 g/L, the standard amount of dosage of the detergent composition for achieving sufficient detergency can be reduced to an amount which is notably smaller than the standard amount of dosage needed for the conventional detergents.

C) Metal Ion Capturing Agents Other Than Crystalline Sodium Silicates

The metal ion capturing agents other than the crystalline sodium silicates in the present invention are preferably those having a calcium ion capturing capacity of 200 CaCO₃ mg/g or more.
A particular preference is given to the metal ion capturing agents containing a carboxylate polymer in an amount of 10% by weight or more. Examples of the above carboxylate polymer include polymers or copolymers, each having repeating units represented by the general formula (2):
wherein X₁ stands for a methyl group, a hydrogen atom, or a COOX₃ group; X₂ stands for a methyl group, a hydrogen atom, or a hydroxyl group; X₃ stands for a hydrogen atom, an alkali metal ion, an alkaline earth metal ion, an ammonium ion, or 2-hydroxyethylammonium ion.
In the general formula (2), examples of the alkali metal ions include Na, K, and Li ions, and examples of the alkaline earth metal ions include Ca and Mg ions.
Examples of the polymers or copolymers usable in the present invention include those obtainable by polymerization reactions of acrylic acid, (anhydrous) maleic acid, methacrylic acid, α-hydroxyacrylic acid, crotonic acid, isocrotonic acid, and salts thereof; copolymerization reactions of each of the monomers; or copolymerization reactions of the above monomers with other polymerizable monomers. Here, examples of the other polymerizable monomers used in copolymerization reaction include aconitic acid, itaconic acid, citraconic acid, fumaric acid, vinyl phosphonic acid, sulfonated maleic acid, diisobutylene, styrene, methyl vinyl ether, ethylene, propylene, isobutylene, pentene, butadiene, isoprene, vinyl acetate (vinyl alcohols in cases where hydrolysis takes place after copolymerization), and acrylic acid ester, without particularly being limited thereto. Incidentally, the polymerization reactions are not particularly limited, and any of the conventionally known methods may be employed.
Also, polyacetal carboxylic acid polymers such as polyglyoxylic acids disclosed in Japanese Patent Laid-Open No. 54-52196 are also usable for the polymers in the present invention.
In the present invention, the above polymers and copolymers preferably have a weight-average molecular weight of from 800 to 1,000,000, more preferably from 5,000 to 200,000.
Also, in the case of copolymers, although the copolymerization ratios between the repeating units of the general formula (2) and other polymerizable monomers are not particularly limited, a preference is given to copolymerization ratios of the repeating units of general formula (2)/other polymerizable monomer = 1/100 to 90/10.
In the present invention, the above polymer or copolymer is contained in the entire composition in an amount of preferably from 1 to 50% by weight, more preferably from 2 to 30% by weight, particularly from 5 to 15% by weight.
In addition, even more preferred example of the C) metal ion capturing agent comprises:
C-i) the carboxylate polymer mentioned above having a Ca ion capturing capacity of 200 CaCO₃ mg/g or more; and
C-ii)an aluminosilicate having an ion exchange capacity of 200 CaCO₃ mg/g or more and having the following formula (3): x"(M₂O)•Al₂O₃•y"(SiO₂)•w" (H₂O), wherein M stands for an alkali metal, such as sodium or potassium; x", y", and w" each stands for a molar number of each component; and generally, x" is from 0.7 to 1.5; y" is from 0.8 to 6.0; and w" is from 0 to 20,
wherein the weight ratio of (C-i) component to (C-ii) component is (C-i)/(C-ii) = 1/20 to 4/1, preferably 1/9 to 4/1, and wherein the total amount of (C-i) and (C-ii) components preferably occupies 70 to 100% by weight in the entire C) metal ion capturing agent. The aluminosilicates mentioned above may be crystalline or amorphous, and among the crystalline aluminosilicates, a particular preference is given to those having the following general formula: Na₂O•Al₂O₃•ySiO₂•wH₂O, wherein y is a number of from 1.8 to 3.0; and w is a number of from 1 to 6.
As for the crystalline aluminosilicates (zeolites), synthetic zeolites having an average, primary particle size of from 0.1 to 10 µm, which are typically exemplified by A-type zeolite, X-type zeolite, and P-type zeolite, are suitably used. The zeolites may be used in the forms of powder, a zeolite slurry, or dried particles comprising zeolite agglomerates obtained by drying the slurry. The zeolites of the above forms may also be used in combination.
The above crystalline aluminosilicates are obtainable by conventional methods. For instance, methods disclosed in Japanese Patent Laid-Open Nos. 50-12381 and 51-12805 may be employed.
On the other hand, the amorphous aluminosilicates represented by the same general formula as the above crystalline aluminosilicate are also obtainable by conventional methods. For instance, the amorphous aluminosilicates are prepared by adding an aqueous solution of a low-alkali alkali metal aluminate having a molar ratio of M₂O to Al₂O₃ (M standing for an alkali metal) of M₂O/Al₂O₃ = 1.0 to 2.0 and a molar ratio of H₂O to M₂O of H₂O/M₂O = 6.0 to 500 to an aqueous solution of an alkali metal silicate having a molar ratio of SiO₂ to M₂O of SiO₂/M₂O = 1.0 to 4.0 and a molar ratio of H₂O to M₂O of H₂O/M₂O = 12 to 200 under vigorous stirring at usually 15 to 60°C, preferably 30 to 50°C.
The intended product may be advantageously obtained by heat-treating a white slurry of precipitates thus formed at 70 to 100°C, preferably 90 to 100°C, for usually 10 minutes or more and 10 hours or less, preferably 5 hours or less, followed by filtration, washing and drying. Here, the addition method may comprise adding the aqueous solution of an alkali metal silicate to the aqueous solution of a low-alkali alkali metal aluminate.
By this method, the oil-absorbing amorphous aluminosilicate carrier having an ion exchange capacity of 100 CaCO₃ mg/g or more and an oil-absorbing capacity of 80 ml/100 g or more can be easily obtained (see Japanese Patent Laid-Open Nos. 62-191417 and 62-191419).
Examples of other metal ion capturing agents include aminotri(methylenephosphonic acid), 1-hydroxyethylidene-1,1-diphosphonic acid, ethylenediaminetetra(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), and salts thereof; salts of phosphonocarboxylic acids, such as salts of 2-phosphonobutane-1,2-dicarboxylic acid; amino acid salts, such as salts of aspartic acid and salts of glutamic acid; aminopolyacetates, such as nitrilotriacetates and ethylenediaminetetraacetates.
Examples of other components which may be added to the detergent composition in the present invention, used as alkalizers besides the crystalline sodium silicates, include various compounds including alkali metal salts such as alkali metal carbonates and alkali metal sulfites, and organic amines, such as alkanolamines.
In addition, color-fading preventives and recontamination preventives generally used for detergent compositions, including non-dissociating polymers such as polyethylene glycols, polyvinyl alcohols, and polyvinyl pyrrolidones; organic acid salt builders, such as diglycolates and oxycarboxylates; and carboxymethyl cellulose may be optionally used.
Besides the above, the following components may be also contained in the detergent composition of the present invention. Specifically, the detergent composition of the present invention may contain one or more components selected from enzymes, such as protease, lipase, cellulase, and amylase; caking preventives, such as lower alkylbenzenesulfonates whose alkyl moieties have about 1 to 4 carbon atoms, sulfosuccinates, talc, and calcium silicates; antioxidants, such as tert-butylhydroxytoluene, and distyrenated cresol; bleaching agents, such as sodium percarbonate; bleaching activators, such as tetraacetylethylenediamine; fluorescent dyes; blueing agents; and perfume, without being particularly limited thereto, to give compositions suitable for their purposes. In the powder detergent composition of the present invention where the standard amount of dosage is small, the total amount of component A, component B, and component C is preferably from 70 to 100% by weight, more preferably from 80 to 100% by weight. The total amount of component A, component B, and component C is preferably 70% by weight or more from the aspect of reducing the standard amount of dosage of the resulting detergent composition.
The detergent compositions of the present invention containing each of the components described above may be produced by any of the conventionally known methods without particular limitation. The powder detergent composition of the present invention has a bulk density of 0.50 g/mL or more, preferably 0.65 to 1.20 g/mL. Examples of the methods for producing high-bulk density detergents include the methods disclosed in Japanese Patent Laid-Open Nos. 61-69897, 61-69899, 61-69900, and 5-209200.
The present invention will be more specifically explained of the following working examples, without intending to restrict the scope of the present invention thereto.
The physical properties of products obtained in Examples and Comparative Examples are measured by the following methods.

(1) Ion Capturing Capacity

The ion capturing capacities of ion exchange materials and chelating agents are measured by the following methods. Incidentally, the ion capturing capacity of the metal ion capturing agents is shown in Table 1 by CEC (calcium ion exchange capacity) as in the same manner as that of the crystalline sodium silicates. In addition, the DH water hardness is measured by ion coupling plasma method (ICP method). In the table, Crystalline Sodium Silicates A and B and Crystalline Aluminosilicates are ion exchange materials, and Acrylic Acid/Maleic Acid Copolymer and Sodium Polyacrylate are chelating agents.

Ion Exchange Material

The amount 0.1 g of an ion exchange material is accurately weighed and added to 100 ml of a calcium chloride aqueous solution (500 ppm concentration, when calculated as CaCO₃), followed by stirring at 25°C for 60 minutes. Thereafter, the mixture is filtered using a membrane filter (made of nitrocellulose; manufactured by Advantech) with 0.2 µm pore size. The amount 10 ml of the filtrate is assayed for Ca content by an EDTA titration, and the calcium ion exchange capacity (cationic exchange capacity) of the ion exchange material is calculated from the titer.

Chelating Agent

The calcium ion capturing capacity of the chelating agent is measured by the following method using a calcium ion electrode. Incidentally, the solution used herein is prepared with the following buffer solution:
Buffer: 0.1 M-NH₄Cl-NH₄OH solution (pH 10.0)

(i) Preparation of Calibration Curve

A standard calcium ion solution is prepared and voltage readings are taken to prepare a calibration curve showing the relationships between the logarithm of the calcium ion concentration and the voltage, as shown in Figure 1.

(ii) Measurement of Calcium Ion Capturing Capacity

About 0.1 g of a chelating agent is weighed, and a 100 ml volumetric flask is charged with the chelating agent. The volumetric flask is filled up to a volume of 100 ml with the above buffer solution. A CaCl₂ aqueous solution (pH 10.0) having a calcium ion concentration of 20,000 ppm calculated as CaCO₃ is added dropwise from a burette in an amount of 0.1 to 0.2 ml to the volumetric flask for making each voltage reading. In addition, the buffer solution without containing the chelating agent is also subjected to the same dropwise treatment. This solution is called a "blank solution." Thus, a calcium ion concentration is calculated from the calibration curve given in Figure 1 by taking a voltage reading. The relationship between the amount of the CaCl₂ solution added dropwise and the calcium ion concentration is shown in a graph (Figure 2). In Figure 2, Line P shows the data of the blank solution (buffer solution without using the chelating agent), and Line Q shows the data for the chelating agent-containing buffer solution. The point where the extension of the linear portion of Line Q intersects with the abscissa (horizontal axis) is called "A." The calcium ion capturing capacity of the chelating agent is obtained from the calcium ion concentration at "A" of the blank solution.

(2) Average Particle Size and Particle Size Distribution of Crystalline Sodium Silicates

The average particle size and the particle size distribution are measured by using a laser scattering particle size distribution analyzer. Specifically, about 200 ml of ethanol is poured into a measurement cell of a laser scattering particle size distribution analyzer ("LA-700," manufactured by HORIBA Ltd.), and about 0.5 to 5 mg of the crystalline sodium silicate is suspended in ethanol. Next, while subjecting the obtained ethanol suspension to ultrasonic wave irradiation, the mixture is agitated for one minute, to thereby sufficiently disperse the crystalline sodium silicate. Thereafter, the resulting mixture is subjected to an He-Ne laser beam (632.8 nm) irradiation to measure diffraction/scattering patterns. The particle size distribution is obtained from the diffraction/scattering patterns. The analysis is made based on the combined theories of Fraunhofer diffraction theory and Mie scattering theory. The particle size distribution of the suspended particles in the liquid is measured within the size range of from 0.04 to 262 µm. The average particle size is a median diameter of the particle size distribution.

(3) X-ray Diffraction Measurement

A sample powder pulverized to a size of 75-µm sieve-pass is subjected to X-ray diffraction measurement by packing the sample powder in a glass folder and using a powder X-ray diffractometer (RAD-C system, manufactured by Rigaku Industrial Corporation). Here, Cu is used as a target, and a single Kα beam is taken out from X-ray beams having an acceleration voltage of 40 kV, an electric current of 80 mA and a wavelength of 1.5407Å by means of a monochrometer made of a pyrolitic graphite. The measurement is taken by -2 scanning at a sweeping speed of 5°/minute in a diffraction angle range 2 of from 10 to 40°. The resulting diffraction profile is subjected to smoothing (at 15 smoothing points) and background removal, and then the diffraction intensity of each of the peaks is obtained.
The main diffraction peaks for each of the α-crystalline phase, the β-crystalline phase, and the δ-crystalline phase are respectively assigned to have the following d values:

α-crystalline phase d=3.31 ± 0.04Å

β-crystalline phase d=4.15 ± 0.04Å

δ-crystalline phase d=3.95 ± 0.04Å
From the intensities of each peak, the proportions of the crystalline phases are calculated. Here, the proportion of the crystalline phases is calculated by the following equation:

α-crystalline phase I_3.31;

β-crystalline phase 4.33 x I_4.15; and

δ-crystalline phase I_3.95 - (1.33 x I_4.15)

wherein I_3.31, I_4.15, and I_3.95 each stands for an intensity at the above d value for the respective crystalline phases.

Preparation Example 1 (Crystalline Sodium Silicate A)

An alkaline solution was prepared by adding 40.4 parts by weight of sodium hydroxide to 500 parts by weight of No. 3 sodium silicate (Na₂O = 9.9% by weight; SiO₂ = 29.6% by weight). A given amount of the alkaline solution was transferred into a nickel crucible and baked in the air at a temperature of 720°C for five hours, to allow crystallization. The obtained baked product was pulverized to a size of 75 µm sieve-pass using a mortar, to give powder of Crystalline Sodium Silicate A. The relative proportions of the crystalline phases of the resulting powder were measured by X-ray diffraction, and they were found to be as follows: α-crystalline phase = 0.09, β-crystalline phase = 0.04, and δ-crystalline phase = 0.87. Here, in the general formula (1), x and y were as follows: x = 1.9 and y = 0. The average particle size of Crystalline Sodium Silicate A was 30.6 µm.

Preparation Example 2 (Crystalline Sodium Silicate B)

An alkaline solution was prepared by adding 40.4 parts by weight of sodium hydroxide to 500 parts by weight of No. 3 sodium silicate (Na₂O = 9.9% by weight; SiO₂ = 29.6% by weight). A given amount of the alkaline solution was transferred into a nickel crucible and baked in the air at a temperature of 650°C for 7 hours, to allow crystallization. The obtained baked product was pulverized to a size of 75 µm sieve-pass using a mortar, to give powder of Crystalline Sodium Silicate B. The relative proportions of the crystalline phases of the resulting powder were measured by X-ray diffraction, and they were found to be as follows: α-crystalline phase = 0.07, β-crystalline phase = 0.21, and δ-crystalline phase = 0.72. Here, in the general formula (1), x and y were as follows: x = 1.9 and y = 0. The average particle size of Crystalline Sodium Silicate B was 29.8 µm.

Preparation Example 3 (Amorphous Aluminosilicate)

Sodium carbonate was dissolved in ion-exchanged water, to prepare an aqueous solution with 6% by weight concentration. 132 g of the above aqueous solution and 38.28 g of a sodium aluminate aqueous solution (conc. 50% by weight) were placed in a 1000-ml capacity reaction vessel equipped with baffles. 201.4 g of a solution of No. 3 Water Glass diluted with twice the amount of water were added dropwise to the above mixed solution by under strong agitation at a temperature of 40°C over a period of 20 minutes. Here, the reaction speed was optimized by adjusting a pH of the reaction system to a pH of 10.5 by blowing CO₂ gas thereinto. Thereafter, the reaction system was heated up to a temperature of 50°C and stirred at 50°C for 30 minutes. Subsequently, an excess alkali was neutralized by adjusting a pH of the reaction system to a pH of 9.0 by blowing CO₂ gas thereinto. The obtained neutralized slurry was filtered under a reduced pressure using a filter paper (No. 5C, manufactured by Toyo Roshi Kaisha, Ltd.). The filtered cake was rinsed with water in an amount of 1000-folds, and the rinsed cake was filtered and dried under the conditions of 105°C, 300 Torr, and 10 hours. The residual portion was dried under the same conditions as the above without giving any further rinsing treatments. Further, the dried cake was broken into particles, to give an amorphous aluminosilicate powder. Incidentally, the sodium aluminate aqueous solution was prepared by the steps of adding and mixing 243 g of Al(OH)₃ and 298.7 g of a 48% by weight NaOH aqueous solution in a 1000 ml-capacity four-necked flask, heating the mixture to a temperature of 110°C with stirring, and maintaining the temperature of 110°C for 30 minutes, to dissolve the components.
From the results of atomic absorption spectrophotometry and plasma emission spectrochemical analysis, the resulting amorphous aluminosilicate had the following composition: Al₂O₃ = 29.6% by weight; SiO₂ = 52.4% by weight; and Na₂O = 18.0% by weight (1.0 Na₂O • Al₂O₃ • 3.10 SiO₂). In addition, the calcium ion capturing capacity was 185 CaCO₃ mg/g, and the oil-absorbing capacity was 285 ml/100 g. The content of the microporous capacity having a microporous diameter of less than 0.1 µm was 9.4% by volume in the entire micropores, and the content of the microporous capacity having a microporous diameter of not less than 0.1 µm and not more than 2.0 µm was 76.3% by volume in the entire micropores. The water content was 11.2% by weight.

Examples 1 and 2 and Comparative Examples 1 and 2

Given amounts of the aqueous components, including such components as, sodium alkyl sulfate (AS-Na), an acrylic acid-maleic acid copolymer, sodium polyacrylate, sodium sulfite, sodium sulfate, and sodium salt of tallow fatty acid, and one-half the given amount of the crystalline aluminosilicate were added and prepared as an aqueous slurry of 50% by weight solid content. After spray-drying the slurry, obtained granules and the remaining of the given amounts of powder starting materials, such as amorphous aluminosilicate and Crystalline Sodium Silicate A or B, were supplied into Lödige Mixer (agitation and tumbling granulator, manufactured by Matsuzaka Giken Co., Ltd.; capacity: 20 liters; equipped with a jacket), to initiate agitation. Hot water at 40°C was supplied into the jacket. The granulation was carried out after a given amount of the polyoxyalkylene alkyl ether previously heated to 70°C was supplied to the mixer. Further, one-third of the given amount of the crystalline aluminosilicate was added to the above mixture, and the obtained mixture was subjected to granulation (surface-improvement step). Thereafter, the resulting granules were dry-blended with one-sixth the given amount of crystalline aluminosilicate and a given amount of enzymes, to give a powder detergent having a low water content as listed in Table 1. The bulk density and the average particle size are shown in Table 1.

Test Example 1

Detergent Compositions obtained in Examples and Comparative Examples mentioned above were used to carry out a detergency test under the following conditions:

Preparation of Artificially Stained Cloth

A sheet of cloth (#2003 calico, manufactured by Tanigashira Shoten) was stained with an artificial staining liquid having the following compositions. The artificially stained cloth was produced by printing the artificial staining liquid on the sheet of cloth by an engravure staining machine equipped with an engravure roll coater. The process for staining the cloth with the artificial staining liquid to prepare an artificially stained cloth was 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 period of time of one minute.

Composition of Artificial Staining Liquid
Lauric 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
Egg white lecithin crystalline liquid	1.94% by weight
Kanuma sekigyoku soil	8.11% by weight
Carbon black	0.01% by weight
Tap water	Balance

Washing Conditions

Washing of the above-mentioned artificially stained cloth with 4°DH water (Ca/Mg = 3/1) is carried out by using turgometer at a rotational speed of 100 rpm, at a temperature of 20°C for 10 minutes, and washing was carried out with two different standard amounts of dosage (detergent concentration) at 0.67 g/L and 0.50 g/L. Here, the typical water hardness-increasing components (namely minerals) in the water for washing are Ca²⁺ and Mg²⁺. The ratio of Ca²⁺ to Mg²⁺ is generally within the range of Ca/Mg = 60/40 to 85/15. Here, a model sample of water has Ca/Mg of 3/1. The unit "°DH" refers to a water hardness which was calculated by replacing Mg ions with equimolar amounts of Ca ions.

Calculation of Detergency

Reflectivities of the original cloth and those of the stained cloth before and after washing were measured at a wavelength of 550 nm by means of an automatic recording colorimeter (manufactured by Shimadzu Corporation). The detergency D (%) was calculated by the following equation. The results thereof are also shown in Table 1. D = (L2 - L1)(L0 - L1) × 100(%), wherein

L₀:: Reflectivity of the original cloth;
L₁:: Reflectivity of the stained cloth before washing; and
L₂:: Reflectivity of the stained cloth after washing.

Incidentally, the abbreviations and materials shown in Table 1 are as follows:

AS-Na :: Sodium alkyl sulfate, 12 carbon atoms;
Sodium salt of fatty acid:: sodium salts of tallow fatty acids, 14 to 18 carbon atoms;
Polyoxyethylene alkyl ether:: alkyl moieties having 12 to 14 carbon atoms and being ascribed to "DOBANOL 23" (manufactured by Mitsubishi Petrochemical Co., Ltd.), ethylene oxide moieties having an average molar number of 8.
Acrylic acid-maleic acid copolymer:: "SOKALAN CP5," (manufactured by BASF Aktiengesellschaft), a copolymer made of acrylic acid monomers and maleic acid monomers, weight-average molecular weight of 70,000;
Sodium polyacrylate:: a polymer of sodium acrylate, average molecular weight of 10,000;
Crystalline aluminosilicate:: "4A-Type ZEOLITE" (manufactured by Zeobuilder K.K.), having an average particle size of 3 µm; and
Enzymes:: A mixture of 0.5% by weight of "CELLULASE K" disclosed in Japanese Patent Laid-Open No. 63-264699; 1.0% by weight of "API-21" (manufactured by Showa Denko K.K.); and 0.5% by weight of "LIPOLASE 100T" manufactured by NOVO Nordisk Bioindustry LTD.

Composition (% by weight)	C E C	Exmaples	Comparative Examples
		1	2	1	2
Component A
A S - N a (C12)		0.00	7.50	0.00	7.50
Sodium salt of fatty acid		3.50	3.50	3.50	3.50
Polyoxyethylene alkyl ether (C12-14)		17.00	20.00	17.00	20.00
Component B
Crystalline Sodium Silicate A	246	40.00	20.00	0.00	0.00
Crystalline Sodium Silicate B	191	0.00	0.00	40.00	20.00
Component C
Acrylic Acid/Maleic Acid Copolymer	380	5.00	0.00	5.00	0.00
Sodium Polyacrylate	220	0.00	3.00	0.00	3.00
Crystalline Aluminosilicate	280	18.00	18.50	18.00	18.50
Amorphous Aluminosilicate		10.00	12.50	10.00	12.50
Sodium Sulfate		2.50	6.50	2.50	6.50
Sodium Sulfite		1.00	1.50	1.00	1.50
Enzymes		1.50	3.00	1.50	3.00
Water Content		1.50	4.00	1.50	4.00
Total Amount		100.00	100.00	100.00	100.00
Total Amount of Components A, B, and C		83.50	72.50	83.50	72.50
Properties of the Resulting Granules
Average Particle Size (µm)		403	469	394	481
Bulk Density (g/L)		762	745	758	740
Detergency (%) at a tested detergent concentration of 0.67 g/L		70.8	63.9	66.9	59.8
Detergency (%) at a tested detergent concentration of 0.50 g/L		63.5	44.6	59.1	40.5
C E C : Calcium Ion Exchange Capacity (CaCO₃) mg/g)

As is clear from Table 1, when the detergency of the detergent compositions comprising crystalline sodium silicates having the same composition but different compositional ratio in the isomeric crystalline phases are compared with each other, the powder detergent compositions of the present invention have an improvement in detergency by about 4% for each detergent concentration, which is acknowledged to be notably superior by one of ordinary skill in the art.

INDUSTRIAL APPLICABILITY

The powder detergent composition of the present invention exhibits excellent detergency for clothes owing to its high ion exchanging speed because the crystalline phases of the crystalline sodium silicate is adjusted to have particular compositional ratios.
Moreover, the powder detergent composition of the present invention exhibits notable reduction in the standard amount of dosage owing to the fact that the metal ion capturing agent other than the crystalline sodium silicate and the surfactant in a particular weight ratio are combinably used, in addition to the crystalline sodium silicate comprising crystalline phases adjusted to have particular compositional ratios.
The present invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.

Claims

A powder detergent composition for clothes washing having a bulk density of 0.50 g/mL or more, comprising 5% by weight or more of a crystalline sodium silicate represented by the following general formula (1): Na₂O • xSiO₂ • yH₂O wherein x and y each stands for a molar number, wherein x is from 1.5 to 2.2, and y is from 0 to 5,
wherein said crystalline sodium silicate has an average particle size of from 1 to 100 µm and comprises crystalline phases of a δ-phase, an α-phase, and a β-phase, wherein the compositional weight ratios of the α-phase, the β-phase, and the δ-phase satisfy all of the following relationships: 0.085 ≤ α/(α + β + δ) ≤ 0.15; 0.01 ≤ β/(α + β + δ) ≤ 0.10; and 0.80 ≤ δ/(α + β + δ) ≤ 0.90, wherein said average particle size is a median diameter obtained from a particle size distribution determined by a laser scattering particle size analyser, and wherein said compositional weight ratio is obtained by determining the intensity of the main diffraction peak for each of the crystalline phases as measured by a powder X-ray diffraction, these main diffraction peaks being assigned to the following d values: α-crystalline phase d=3.31 ± 0.04Å β-crystalline phase d=4.15 ± 0.04Å δ-crystalline phase d=3.95 ± 0.04Å

and calculating the proportion of the crystalline phases by the following equation: α-crystalline phase I_3.31; β-crystalline phase 4.33 x I_4.15; and δ-crystalline phase I_3.95 - (1.33 x I_4.15),

wherein I_3.31, I_4.15, and I_3.95 each stands for an intensity at the above d value for the respective crystalline phases.
The powder detergent composition according to claim 1, comprising the following components:

A) one or more surfactant components;

B) a crystalline alkali metal silicate as defined in claim 1; and

C) metal ion capturing agents other than component B,

wherein a total amount of component A, component B, and component C is from 70 to 100% by weight of the entire powder detergent composition, and wherein the weight ratio of component B to component A is B/A = 9/1 to 9/11, and
wherein the weight ratio of component B to component C is B/C = 4/1 to 1/15.
The powder detergent composition according to claim 2, wherein the weight ratio of component B to component A is B/A = 9/1 to 1/1, and wherein the weight ratio of component B to component C is B/C = 3/1 to 1/15.
The powder detergent composition according to claim 2 or 3, wherein 50% by weight or more of said component A is polyoxyethylene alkyl ethers.
The powder detergent composition according to any one of claims 1 to 4, wherein a standard amount of dosage of said powder detergent composition is from 0.33 to 0.67 g/L in the water for washing having a water hardness of 2 to 6°DH in a case where the weight ratio of component B to component C is B/C = 3/1 to 3/7.
The powder detergent composition according to any one of claims 1 to 4, wherein a standard amount of dosage of said powder detergent composition is from 0.50 to 1.20 g/L in the water for washing having a water hardness of 6 to 10°DH in a case where the weight ratio of component B to component C is B/C = 4/3 to 1/6.
The powder detergent composition according to any one of claims 1 to 4, wherein a standard amount of dosage of said powder detergent composition is from 0.80 to 2.50 g/L in the water for washing having a water hardness of 10 to 20°DH in a case where the weight ratio of component B to component C is B/C = 1/1 to 1/15.
The powder detergent composition according to any one of claims 1 to 7, wherein the powder detergent composition has a bulk density of from 0.65 to 1.20 g/mL.