Plastic and nonmetallic article shaping or treating: processes – Forming articles by uniting randomly associated particles – Agitating to form larger particles
Reexamination Certificate
2000-01-14
2002-08-27
Vargot, Mathieu D. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Forming articles by uniting randomly associated particles
Agitating to form larger particles
C264S121000, C264S122000, C264SDIG005, C510S444000
Reexamination Certificate
active
06440342
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to a process for producing a low density detergent composition. More particularly, the invention is directed to a process during which low density detergent agglomerates are produced by feeding a surfactant paste or liquid acid precursor of anionic surfactant and dry starting detergent material sequentially into two high speed mixers followed by a fluid bed dryer which has an optimally selected nozzle height for spraying on a binder. The process produces a free flowing, low density detergent composition which can be commercially sold as a conventional non-compact detergent composition or used as an admix in a low dosage, “compact” detergent product.
BACKGROUND OF THE INVENTION
Recently, there has been considerable interest within the detergent industry for laundry detergents which are “compact” and therefore, have low dosage volumes. To facilitate production of these so-called low dosage detergents, many attempts have been made to produce high bulk density detergents, for example with a density of 600 g/l or higher. The low dosage detergents are currently in high demand as they conserve resources and can be sold in small packages which are more convenient for consumers. However. the extent to which modern detergent products need to be “compact” in nature remains unsettled. In fact, many consumers, especially in developing countries, continue to prefer a higher dosage levels in their respective laundering operations. Consequently, there is a need in the art of producing modem detergent compositions for flexibility in the ultimate density of the final composition.
Generally, there are two primary types of processes by which detergent granules or powders can be prepared. The first type of process involves spray-drying an aqueous detergent slurry in a spray-drying tower to produce highly porous detergent granules. In the second type of process, the various detergent components are dry mixed after which they are agglomerated with a binder such as a nonionic or anionic surfactant. In both processes, the most important factors which govern the density of the resulting detergent granules are the density, porosity and surface area, shape of the various starting materials and their respective chemical composition. These parameters, however, can only be varied within a limited range. Thus, flexibility in the substantial bulk density can only be achieved by additional processing steps which lead to lower density of the detergent granules.
There have been many attempts in the art for providing processes which increase the density of detergent granules or powders. Particular attention has been given to densification of spray-dried granules by post tower treatment. For example, one attempt involves a batch process in which spray-dried or granulated detergent powders containing sodium tripolyphosphate and sodium sulfate are densified and spheronized in a Marumerizer®. This apparatus comprises a substantially horizontal, roughened, rotatable table positioned within and at the base of a substantially vertical, smooth walled cylinder. This process, however, is essentially a batch process and is therefore less suitable for the large scale production of detergent powders. More recently, other attempts have been made to provide continuous processes for increasing the density of “post-tower” or spray dried detergent granules. Typically, such processes require a first apparatus which pulverizes or grinds the granules and a second apparatus which increases the density of the pulverized granules by agglomeration. While these processes achieve the desired increase in density by treating or densifying “post tower” or spray dried granules, they do not provide a process which has the flexibility of providing lower density granules.
Moreover, all of the aforementioned processes are directed primarily for densifying or otherwise processing spray dried granules. Currently, the relative amounts and types of materials subjected to spray drying processes in the production of detergent granules has been limited. For example, it has been difficult to attain high levels of surfactant in the resulting detergent composition, a feature which facilitates production of detergents in a more efficient manner. Thus, it would be desirable to have a process by which detergent compositions can be produced without having the limitations imposed by conventional spray drying techniques.
To that end, the art is also replete with disclosures of processes which entail agglomerating detergent compositions. For example, attempts have been made to agglomerate detergent builders by mixing zeolite and/or layered silicates in a mixer to form free flowing agglomerates. While such attempts suggest that their process can be used to produce detergent agglomerates, they do not provide a mechanism by which conventional starting detergent materials in the form of surfactant pastes or precursors thereof, liquids and dry materials can be effectively agglomerated into crisp, free flowing detergent agglomerates having low densities rather than high densities. In the past, attempts at producing such low density agglomerates involves a nonconventional detergent ingredient which is typically expensive, thereby adding to the cost of the detergent product. One such example of this involves a process of agglomerating with inorganic double salts such as Burkeite to produce the desired low density agglomerates.
Accordingly, there remains a need in the art to have a process for producing a low density detergent composition directly from starting detergent ingredients without the need for relatively expensive specialty ingredients. Also, there remains a need for such a process which is more efficient, flexible and economical to facilitate large-scale production of detergents of low as well as high dosage levels.
BACKGROUND ART
The following references are directed to densifying spray-dried granules: Appel et al. U.S. Pat. No. 5,133,924 (Lever); Bortolotti et al, U.S. Pat. No. 5,160,657 (Lever): Johnson et al, British patent No. 1,517,713 (Unilever); and Curtis, European Patent Application 451,894. The following references are directed to producing detergents by agglomeration: Beerse et al, U.S. Pat. No.5,108,646 (Procter & Gamble); Capeci et al. U.S. Pat. No. 5,366,652 (Procter & Gamble); Hollingsworth et al, European Patent Application 351,937 (Unilever); and Swatling et al, U.S. Pat. No. 5,205,958. The following references are directed to inorganic double salts: Evans et al, U.S. Pat. No. 4,820,441 (Lever); Evans et al, U.S. Pat. No.4,818,424 (Lever); Atkinson et al, U.S. Pat. No. 4,900,466 (Lever); France et al, U.S. Pat. No. 5,576,285 (Procter & Gamble); and Dhalewadika et al, PCT WO 96/04359 (Unilever).
SUMMARY OF THE INVENTION
The present invention meets the aforementioned needs in the art by providing a process which produces a low density (below about 600 g/l) detergent composition directly from a surfactant paste and dry starting detergent ingredients. In essence, the process involves agglomerating the starting detergent ingredients in a high speed mixer followed by a second high speed mixer. Thereafter, the agglomerates formed in the high speed mixers are agglomerated and dried in a fluid bed dryer in which a liquid binder is sprayed onto the agglomerates from one or more nozzles at a selected height from the distribution plate of the fluid bed dryer. The process does not use the conventional spray drying towers currently used and is therefore more efficient, economical and flexible with regard to the variety of detergent compositions which can be produced in the process. Moreover, the process is more amenable to environmental concerns in that it does not use spray drying towers which typically emit particulates and volatile organic compounds into the atmosphere.
As used herein, the term “agglomerates” refers to particles formed by agglomerating detergent granules or particles which typically have a smaller median particle size than the formed agglomerates. By “median particle size”, i
Bolam Brian M.
Miller Steven W.
The Procter & Gamble & Company
Vargot Mathieu D.
William Zerby Kim
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