Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – For cleaning a specific substrate or removing a specific...
Reexamination Certificate
1998-04-28
2002-01-01
Gupta, Yogendra N. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
For cleaning a specific substrate or removing a specific...
C510S356000, C510S438000, C510S441000, C510S442000, C510S444000, C510S511000
Reexamination Certificate
active
06335313
ABSTRACT:
TECHNICAL FIELD
The present invention relates to detergent granules having an excellent degree of whiteness and a granular detergent composition. More particularly, the present invention relates to detergent granules containing a nonionic surfactant and a crystalline alkali metal silicate and having an excellent degree of whiteness, and a granular detergent composition containing the above detergent granules.
BACKGROUND ART
In detergents, for the purpose of improving their washing performance, builders for capturing water hardness-increasing components (for instance, Ca
2+
, Mg
2+
, and the like) which are present in tap water and builders for maintaining the alkalinity of the washing liquid are formulated aside from the surfactants. Ever since the eutrophication of rivers, lakes and marshes has become a social problem, zeolites have more frequently been used to act as the builders for capturing water hardness-increasing components in place of phosphorus compounds (tripolyphosphates and the like). Also, as for the alkali builders, carbonates and amorphous silicates have been usually used.
In recent years, crystalline alkali metal silicates which have a water hardness component-capturing function as well as an alkalizing-buffering function, which shows buffering ability as well as alkalizing ability, have been known to be used as detergent builders (Japanese Patent Examined Publication No. Hei 1-41116). Moreover, the crystalline alkali metal silicates not only are known as multi-functional builders, possessing both the alkalizing ability and the cationic exchange capacity, but also have a property wherein the crystalline alkali metal silicates are gradually dissolved after being released in the natural environment. Having the properties mentioned above, the crystalline alkali metal silicates have been markedly noted as excellent builders with a relatively small load to the environment. In particular, it has been known that in the case where these crystalline alkali metal silicates are used in combination with the nonionic surfactant, the resulting composition has excellent detergency against fatty acid stains (Japanese Patent Laid-Open Nos. Hei 6-10000 and Hei 6-116600).
Although the crystalline alkali metal silicates described above are water-soluble, they are only partially dissolved in a short time period such as the length of the washing time, so that there arise such problems that the crystalline alkali metal silicates adhere and remain on clothes as granules. In order to eliminate this problem, it is preferred to formulate crystalline alkali metal silicates which are powdered to have an average particle size of several dozens &mgr;m or less.
In addition, it has been unavoidable that the resulting detergent granules have a grayish color in cases where the crystalline alkali metal silicates and the nonionic surfactant are formulated in one granule, even though the crystalline alkali metal silicate powder obtained by powdering has a whitish color. This tendency is more remarkably noted in an industrial scale powdering, such as pulverization and milling, wherein a large amount of powdering treatment is required in a short period of time. Conventionally, it has also been known to blend a nonionic surfactant with a zeolite, an oil-absorbing carrier, or a carbonate in one granule (Japanese Patent Laid-Open Nos. Hei 4-339898 and Hei 5-5100). The detergent granules of such blends have excellent whitish color, and the “graying phenomenon” described above is a unique phenomenon occurring only in the cases where the crystalline alkali metal silicates and the nonionic surfactant are used in combination in one granule.
In general, it is needless of say that the whitish color powders are preferred as detergents. Since the detergents obtained by blending the crystalline alkali metal silicates and the nonionic surfactant in one granule have hues of grayish color, the commercial values of the detergents are drastically lowered regardless of having high detergency performance in the detergents.
Accordingly, objects of the present invention are to provide detergent granules which have remarkable improvements in hue and also have an excellent degree of whiteness and thus have high commercial values, and a granular detergent composition containing the above detergent granules.
These and other objects of the present invention will be apparent from the following description.
DISCLOSURE OF THE INVENTION
As a result intensive of research, the present inventors have found that in the detergent granules comprising the crystalline alkali metal silicates and the nonionic surfactants, the unique graying phenomenon mentioned above is ascribed to the fact that the difference in the refractive indices between the crystalline alkali metal silicates and the nonionic surfactants is small, and particularly that the graying phenomenon is greatly affected by the iron content mingled in the processes up to the preparation of the crystalline alkali metal silicate powders.
The present inventors have found that owing to the small difference in the refractive indices between the crystalline alkali metal silicates and the nonionic surfactants, an irregular reflection at the interface is substantially suppressed by the fact that the crystalline alkali metal silicates are coated by the nonionic surfactants, so that the resulting detergent granules have excellent transparency. In addition, the crystalline alkali metal silicates are usually obtained as baked products of block forms or masses of sizes of about several cm or more. In order to use the baked products as starting materials for detergent granules, a process of finely graining the baked products, which may be carried out previously or during the processes of producing the detergent granules, is unavoidable as mentioned above. By the additional finely graining process, the iron components are mingled during the finely graining process (powdering process) of the crystalline alkali metal silicate in addition to the iron components mixed in the starting materials for baking (water glass starting materials and alkali source, such as NaOH). Small amounts of the iron components mentioned above mingled therein give causation for greatly affecting the hue of the detergent granules. Although there is a possibility of the coloration under the same principle as conventionally used builders (such as zeolites and carbonates), since the crystalline alkali metal silicate is in the form of quite a rigid solid as compared to the conventional builders, the iron components are liable to be mingled in the finely graining process. In addition, the difference in the refractive indices with the nonionic surfactant becomes small, thereby resulting in the unique graying phenomenon in the cases where the crystalline alkali metal silicate and the nonionic surfactant are blended in one granule.
Moreover, the present inventors have found that the mingling of the iron components in the production process of the detergent granules can be remarkably inhibited by selecting starting materials with as little Fe content as possible and by using crystalline alkali metal silicate with a contrivance in the powdering method, so that the desired object mentioned above of the present invention can be achieved. The present invention has been completed based upon these findings.
Specifically, the present invention is in essence concerned with the following:
(1) In the detergent granules comprising 10% by weight or more of a nonionic surfactant and 1% by weight or more of a crystalline alkali metal silicate having an average particle size of from 1 to 60 &mgr;m, the detergent granules characterized in that a proportion of the nonionic surfactant to the crystalline alkali metal silicate is in a weight ratio of from 20/1 to 1/20, and that the iron content calculated as Fe in the crystalline alkali metal silicate is 140 ppm or less;
(2) The detergent granules described in item (1) above, characterized in that the nonionic surfactant is a polyoxyethylene alkyl ether;
(3) The detergent granules descr
Kasai Katsuhiko
Nakamae Taiji
Takaya Hitoshi
Tsukahara Itsuro
Yamaguchi Shu
Birch & Stewart Kolasch & Birch, LLP
Gupta Yogendra N.
Kao Corporation
Mruk Brian P.
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