Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – Heterogeneous arrangement
Reexamination Certificate
2000-04-10
2001-09-25
Douyon, Lorna M. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
Heterogeneous arrangement
C510S469000, C510S495000, C510S496000, C510S498000, C510S501000, C510S503000, C510S504000, C510S506000
Reexamination Certificate
active
06294513
ABSTRACT:
FIELD OF THE INVENTION
The present invention is generally directed to a process for making high density detergent compositions from a high active surfactant paste and other detergent ingredients. More particularly, the invention is directed to a process for producing a high density detergent composition in the form of agglomerates in which the stability and shelf life of a high active surfactant paste containing mid-chain branched primary alkyl sulfate surfactant is unexpectedly improved and maintained. This process is especially useful in the production of modern compact granular detergent compositions which typically require higher levels of active detersive surfactants.
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 650 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.
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, various detergent components are mixed after which they are agglomerated with a nonionic or anionic detergent paste that also serves as the binder for the agglomerated particle itself. In both processes, the most important factors which govern the density of the resulting detergent granules are the density, porosity and surface area of the various starting materials and their respective chemical composition. These parameters, however, can only be varied within a limited range. Thus, a substantial bulk density increase can only be achieved by additional processing steps which lead to densification of the detergent granules or via build-up agglomeration processes.
The art is replete with processes directed to agglomeration for producing 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. Yet another example involves a starting detergent material in the form of highly active, viscoelastic surfactant paste which is agglomerated with dry powders such as aluminosilicates and carbonates into crisp, free flowing, highly dense detergent agglomerates. However, a wide variety of problems have been encountered with handling high active, highly viscoelastic surfactant pastes which are used to produce high density, high active detergent agglomerates suitable for modem low dosage detergent products. Specifically, such high active surfactant pastes are extremely sensitive to environmental and operating equipment parameters, all of which make the pastes difficult to transport, store and process when producing detergent agglomerates.
Typically, surfactant pastes are manufactured by a process in which fatty alcohol is sulfated, and thereafter, neutralized with an alkaline material (e.g. sodium hydroxide). This is an extremely delicate process, especially when used to produce high active surfactant pastes predominantly (greater than 60% by weight) containing the active surfactant and only a relatively minor amount of water and adjuncts. The resulting high active surfactant pastes are extremely sensitive to their environment, for example, high temperature zones or “hot spots” in the equipment (pipes, valves, storage tanks and the like) to which it is exposed as well as any contaminants having a pH of less than 7 which make their way into the paste. In the event that the high active surfactant paste is exposed to one or more of these environmental factors, such high active pastes have a tendency to undergo a hydrolysis reaction, wherein the surfactant reverts back to its alcohol form. This hydrolysis reaction is an autocatalytic reaction in that a by-product is an acid which continues to react with any remaining surfactant. This threat of hydrolysis particularly exacerbates the environmental sensitivity of high surfactant pastes and renders them difficult to keep stable over periods of time (e.g. 2-7 days) necessary for large-scale commercial manufacture of modem compact laundry detergents. It should be understood that even hydrolysis of 1% by weight of the surfactant paste can have major financial consequences in large-scale commercial manufacturing of detergent products.
Typical prior art attempts in this area involved immediately forming surfactant particles after the paste was manufactured. However, this requires “on-site” particle forming equipment or requires the surfactant-making equipment to be housed in or near the detergent manufacturing facility. Currently, detergent-making and surfactant paste-making industries have become separated both physically as well as from a commercial standpoint, a trend which is only increasing. Thus, it would be desirable to have a high active surfactant paste which remains stable over longer periods of time so as to enable the surfactant-making operation to be located farther away from the detergent-making facility which is more representative of the current commercial environment.
Yet another challenge with the use of such high active surfactant pastes involves their rheological properties in that they must have a low enough viscosity to be pumped in and out of transport trucks or trains and in and out of storage tanks at the detergent manufacturing facility. Any significant temperature changes may lead to undesirable gelling or solidification of the surfactant paste causing increases in manufacturing expenses and time. Note, however, that different rheological properties of the surfactant paste may result upon reheating.
Also in that regard, additional ingredients such as carbonates which are included so as to maintain the storage and transport stability of the surfactant paste before it is processed has the effect of increasing the viscoelasticity of the high active surfactant paste, therefore rendering it very difficult to process. The difficulty in processing arises due to a change in the viscoelasticity of the surfactant paste which requires relatively expensive high-pressure pumps, larger pipe lines and shorter transport distances to be implemented into the detergent-making process. As a consequence, it would be desirable to have a process in which the storage stability of the paste is maintained without sacrificing its processability.
Accordingly, despite the above-mentioned disclosures in the art, there remains a need for a process for producing an agglomerated detergent composition from a high active surfactant paste which is sufficiently stable during transportation and storage for sufficient periods of time so as to enable large-scale commercial manufacture of modem compact detergent compositions. Also, there remains a need for such a process which is inexpensive and can be easily incorporated into large-scale production facilities for low dosage or compact detergents.
BACKGROUND ART
The following references are directed to surfactant pastes: Aouad et al, WO 93/18123 (Procter & Gamble); Aouad et al, WO 92/18602 (Procter & Gamble); Aouad et al, EP 508,543 (Procter & Gamble); Mueller et al, U.S. Pat. No. 5,152,932; Strauss et al, U.S. Pat. No. 5,080,848 (Procter & Gamble); Ofosu-Asante et al, U.S. Pat. No. 5,066,425 (Procter & Gamble); Jolicoeur et al, U.S. Pat. No. 5,045,238 (Procter & Gamble); and Van Zorn et al, EP 504,986 (Shell). 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 prod
Culver Gayle Elizabeth
Jensen Michael Chris
Douyon Lorna M.
Dressman Marianne
Miller Steven W.
The Procter & Gamble & Company
William Zerby Kim
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