Chemistry of inorganic compounds – Zeolite – Organic compound used to form zeolite
Reexamination Certificate
2002-08-09
2004-08-10
Sample, David (Department: 1755)
Chemistry of inorganic compounds
Zeolite
Organic compound used to form zeolite
C423S716000, C423SDIG002, C510S507000, C510S532000
Reexamination Certificate
active
06773693
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a fine zeolite particle, a process for preparing the same, and a detergent composition comprising the fine zeolite particle.
BACKGROUND ART
Zeolites are crystalline aluminosilicates, which can be classified into various crystal structures such as A-type, X-type and Y-type by the arrangements of SiO
4
tetrahedrons and AlO
4
tetrahedrons. The zeolites have an even pore size depending upon the crystal structures, thereby exhibiting a molecular sieve function. For the reason, the zeolites have been used for adsorbents, catalysts (carriers) and the like. In addition, since the zeolites have cationic exchange abilities, they have been utilized as detergent builders, agents for waste water treatment, and the like.
The functions of the zeolites greatly depend on the crystal structure and the composition of the zeolite. For instance, the smaller the Si/Al molar ratio of the zeolite, the larger the cationic exchange capacity, and theoretically an A-type zeolite of which Si/Al is 1 is most excellent. Therefore, the A-type zeolites having a high cationic exchange theoretical capacity have been mainly used as detergent builders.
Further, as detergent builders, there are especially needed zeolites excellent in not only the calcium ion exchange capacity but also the calcium ion exchange rate. This is because when calcium ions in water especially at an initial stage of washing can be captured in large amounts, the detergency performance is improved. Since the calcium ion exchange rate of the zeolite is determined by a collision probability of the calcium exchange site of the zeolite with the calcium ions in water, the smaller the primary particle size of the zeolite, the higher the calcium ion exchange rate of the zeolite.
In view of above, various proposals for preparing A-type zeolites having a very small primary particle size have been so far made. For instance, Japanese Patent Laid-Open No. Sho 54-81200 discloses a process for preparing a fine A-type zeolite particle comprising carrying out the reaction in the co-existence of an organic acid such as formic acid or acetic acid in a reaction mixture. However, in this process, the resulting zeolite particle only has a primary particle size of at least 0.5 &mgr;m. On the other hand, Japanese Patent Laid-Open No. Hei 1-153514 discloses a process for preparing a fine A-type zeolite particle having a maximal particle size of 0.4 &mgr;m or less, comprising forming a zeolite nucleus at a temperature of 40° C. or less. However, even in this process, the formed A-type zeolite particle has a primary particle size of at least 0.2 &mgr;m.
Meanwhile, a largest defect of the zeolite builder is in that zeolite makes water turbid due to its water insolubility. In view of this problem, there has been proposed to reduce turbidity of the zeolite by making an aggregate particle size of the zeolite small to a size of equal to or less than a wavelength of visible light (0.4 &mgr;m) [Okumura,
Nendo Kagaku
27, 21 (1987)]. In other words, the turbidity of the washing water is reduced with making the aggregate particle size smaller, and when the aggregate particle size is 0.4 &mgr;m or less, the washing water (zeolite concentration: 0.013% by weight) becomes almost transparent. However, when the A-type zeolite of which aggregate particle size is made very fine to the order of submicron size is made into a powdery state, the powder then re-aggregates to undesirably form a large aggregate. Also, it is very difficult to carry out solid-liquid separation for the zeolite by means of filtration or concentration. Therefore, the zeolite has been actually fed to the detergent raw material in a slurry state. At this time, the existence of Al ions in the slurry (unreacted compounds of the zeolite raw materials or zeolite-eluted products) could be a factor of lowering the detergency performance. Therefore, the Al ion concentration in the slurry must be controlled to a low level.
Generally, the aggregate particle size of A-type zeolite is made smaller by means of vigorous stirring, pulverization or the like. For instance, as disclosed in Japanese Patent Laid-Open No. Hei 9-67117, an aggregate particle size and a primary particle size are made smaller to the order of submicron size by mechanical pulverization. However, when an A-type zeolite having a large primary particle size is subjected to pulverization treatment, the cationic exchange abilities, i.e. the cationic exchange capacity and the cationic exchange rate, are undesirably lowered due to the crystallinity degradation caused by the disintegration of primary crystals of the A-type zeolite and the deterioration of the primary particle size distribution. In addition, in a water-based liquid of the zeolite after the pulverization treatment, ions of zeolite-constituting elements, i.e. Al, Si, and Na, especially Al, tend to be easily eluted in water, by the mechanochemical reaction of the zeolite particle surface. Therefore, when the zeolite is used for a detergent composition, there also arises a problem that the detergency performance of the composition is lowered.
In order to suppress the generation of the problems due to the process of making the aggregate particle size of the zeolite smaller, the disintegration of the zeolite primary crystals by the process of making the size fine must be avoided. In order to avoid the disintegration, it is desired that the primary particle size of A-type zeolite before pulverization is equal to or less than the aggregate particle size of the zeolite after pulverization. Concretely, when the average aggregate particle size is made smaller to a size of 0.4 &mgr;m or less, the average primary particle size is generally 0.1 &mgr;m or less. On the basis of this fact, it is considered to be desirable that the average primary particle size of A-type zeolite before pulverization is 0.1 &mgr;m or less in order to suppress the generation of the problems mentioned above and to make the zeolite particle smaller by pulverizing the particle until the particle has an average aggregate particle size (0.4 &mgr;m or less) which gives almost transparent washing water (zeolite concentration: 0.013% by weight). In addition, as long as a zeolite has the average primary particle size mentioned above, a desired average aggregate particle size could be obtained without subjecting the zeolite to pulverization treatment. However, as mentioned above, there are no examples of a process for preparing a fine A-type zeolite particle having an average primary particle size of 0.1 &mgr;m or less without carrying out pulverization treatment or the like after the reaction for preparing the zeolite.
An object of the present invention is to provide a fine A-type zeolite particle having an average primary particle size of 0.1 &mgr;m or less and a variation coefficient of 90% or less, and excellent in the cationic exchange capacity, and giving small amounts of Al eluted in water and little water turbidity in a water-based liquid, a process for preparing the fine A-type zeolite particle, and a detergent composition comprising the fine A-type zeolite particle (hereinafter simply referred to as “fine zeolite particle or fine zeolite particles”), which is very excellent in the detergency and the rinsing performance.
These and other objects of the present invention will be apparent from the following description.
DISCLOSURE OF INVENTION
According to the present invention, there is provided:
(1) A fine A-type zeolite particle having an average primary particle size of 0.1 &mgr;m or less and a variation coefficient of 90% or less, wherein a ratio of a peak area above a background level to all peak area in the range of 2&thgr;=20° to 40° in a powder X-ray diffraction spectrum of said fine A-type zeolite particle is 30% or more;
(2) a process for preparing the fine A-type zeolite particle of item (1) above, comprising reacting a silica source with an aluminum source in the presence of an organic compound having an oxygen-containing functional group and a molecular w
Hosokawa Hiroji
Oki Kazuo
Birch & Stewart Kolasch & Birch, LLP
Kao Corporation
Sample David
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