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(11) | EP 0 233 689 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Aqueous zeolite dispersion |
| (57) An aqueous zeolite dispersion comprising 40% to 55% by weight, in terms of anhydride,
of fine zeolite and 0.00l% to 0.l% by weight of a lipopolysaccharide produced by a
microorganism belonging to sp. Acineto bactor. |
BACKGROUND OF THE INVENTION
l. Field of the Invention
2. Description of the Related Art
[0002] It is well-known in the art that zeolites have an excellent ion exchange capability, adsorption capability, and other capabilities and, therefore, are industrially utilized as, for example, a detergent builder. Zeolites are generally produced in the form of an aqueous dispersion by a hydrothermal reaction, and are often handled as an aqueous dispersion from the viewpoints of transportation and handling. For example, granulated detergents for garments (e.g., clothes and fabrics) are produced by first preparing a detergent slurry, followed by spray drying. However, since it is difficult to uniformly disperse fine powdery zeolites in an aqueous detergent slurry, preferably an aqueous zeolite dispersion is prepared before mixing with a detergent slurry.
[0003] An aqueous zeolite dispersion, however, is unstable because of the difference in the specific gravities of water and the zeolite. Therefore, the zeolite separates and settles in the aqueous dispersion when the aqueous dispersion is stored.
[0004] Various attempts have been made to stabilize the aqueous zeolite dispersion. For example, Japanese Unexamined Patent Publication (Kokai) No. 5l-9l898 proposes that alkyl phospate esters, slightly water-soluble nonionic surfactants, and sulfonate anionic surfactants be added to the aqueous zeolite dispersions, and Japanese Unexamined Patent Publication (Kokai) No. 54-l55200 proposes that water-soluble nonionic surfactants and compatible salts (e.g., inorganic sodium salts) be combined and added to the aqueous zeolite dispersions. However, these proposals still do not satisfy the stability requirements for a long term storage of the aqueous dispersion, or provide satisfactory handling properties.
SUMMARY OF THE INVENTION
[0005] Accordingly, the objects of the present invention are to eliminate the above-mentioned disadvantages of the prior art and to provide an aqueous zeolite dispersion having an excellent fluidity and good storage stability.
[0006] Other objects and advantages of the present invention will be apparent from the following description.
[0007] In accordance with the present invention, there is provided an aqueous zeolite dispersion comprising 40% to 55% by weight, in terms of anhydride, of fine zeolite and 0.00l% to 0.l% by weight of a lipopolysaccharide produced by a microorganism belonging to sp. Acineto bactor.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0008] The zeolites usable in the present invention include natural and synthetic zeolites. Examples of the synthetic zeolites are type-A, type-X, and type-Y. Of these zeolites, the use of type-A zeolite is preferable from the builder standpoint. The average particle size of the zeolite is preferably 0.l to l0 µm, more preferably 0.5 to 5 µm, and the zeolite is formulated into the aqueous dispersion at a content of 40% to 55% by weight, preferably 44% to 50% by weight. A zeolite content of less than 40% by weight is not economically preferable. For example, since the solid content of a conventional detergent slurry is generally 35% to 40% by weight, the water content in the detergent slurry is increased, when an aqueous zeolite dispersion having a low solid concentration is added, and therefore, the spray drying load is unpreferably increased. When the zeolite content is more than 55% by weight, it is difficult to treat the aqueous dispersion.
[0009] The lipopolysaccharides prepared from microorganisms belonging to sp. Acineto bactor are so-called biosurfactants, which are available from, for example, Petroferm (U.S.A.) under the trade name of "Emulsan". "Emulsan" is an extracellular microbiological protein associated with lipopolysaccharides, which is produced by a microorganism belonging to sp. Acineto bactor (deposited as ATCC No. 3l0l2).
[0010] Examples of such lipopolysaccharides are α-Emulsans (i.e., Neoemulsans), which are produced when mainly ethanol is used as a carbon source, and β-Emulsans (i.e., Protoemulsans), which are obtained when mainly crude oil or hexadecane is used as a carbon source.
[0011] According to the present invention, the lipopolysaccharides produced by a microorganism belonging to sp. Acineto bactor are formulated into the aqueous zeolite dispersion in an amount of 0.00l% to 0.l% by weight, preferably 0.005% to 0.06% by weight. When the content of the lipopolysaccharide is less than 0.00l% by weight, the stability of the resultant zeolite dispersion is reduced. On the other hand, when the content of the lipopolysaccharide is more than 0.l% by weight, handling of the resultant aqueous zeolite dispersion becomes difficult because the viscosity of the dispersion is increased and the fluidity thereof is reduced.
[0012] The aqueous zeolite dispersion according to the present invention may optionally contain any conventional optional detergent ingredients (e.g., anionic surfactant, sodium sulfate, sodium carbonate, sodium citrate, sodium silicate) unless the stability of the dispersion is adversely affected.
[0013] According to the present invention, the aqueous zeolite dispersion having a high fluidity even at a low temperature and an excellent storage stability, can be advantageously obtained by adding thereto the lipopolysaccharides produced by a microorganism belonging to sp. Acineto bactor.
Examples
[0014] The present invention will now be further illustrated by, but is by no means limited to, the following Examples, wherein all parts and percentages are expressed on a weight basis unless otherwise noted.
[0015] Aqueous zeolite dispersions (i.e., sample Nos. l to 5 in Table l) having the following formulations were prepared.
[0016] The viscosity of the resultant aqueous zeolite dispersion was determined and the settling stability of the resultant aqueous zeolite dispersion was evaluated after storage, by a stability test.
(l) Viscosity
[0019] The viscosity was determined at 20 r.p.m. at a temperature of 25°C by using a B-type viscometer (i.e., a Brookfield type visometer).
(2) Settling stability
[0020] A sample dispersion was taken in a glass bottle. The bottle was sealed and was allowed to stand at a temperature of 25°C. Thus, the stability after one day was determined. The upper clear transparency layer in the bottle was visually evaluated, and the lower settled gel product was determined in terms of % by volume, as follows. That is, a glass plate having a diameter of 5 mm was quietly and vertically placed in the lower settled gel product layer from the top of the glass bottle. When the glass plate came to the settled gel product, the length of the glass plate was determined. The volume percentage based on the total volume was calculated from the length of the glass plate.
[0021] The storage stability was good when the volume percentage of the upper layer was 30% by volume or less, and when the volume percentage of the lower layer was l% or less after storage for 9 days. The results were evaluated in terms of the number of days for which the dispersion was maintained.
1. An aqueous zeolite dispersion characterized by comprising 40% to 55% by weight,
in terms of anhydride, of fine zeolite and 0.00l% to 0.l% by weight of a lipopolysaccharide
produced by a microorganism belonging to sp. Acineto bactor.
2. An aqueous zeolite dispersion as claimed in claim l, wherein a content of the zeolite
is 44% to 50% by weight.
3. An aqueous zeolite dispersion as claimed in claim l, wherein a content of the lipopolysaccharide
is 0.005% to 0.06% by weight.
4. An aqueous zeolite dispersion as claimed in claim l, wherein an average particle
size of the zeolite is 0.l to l0 µm.
5. An aqueous zeolite dispersion as claimed in claim l, wherein the lipopolysaccharide
is Emulsan.