Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – Heterogeneous arrangement
Reexamination Certificate
2000-06-30
2001-09-25
Douyon, Lorna M. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
Heterogeneous arrangement
C510S276000, C510S443000, C510S444000, C510S452000, C008S137000
Reexamination Certificate
active
06294512
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to improving the dissolution of a granular detergent composition, especially in cold temperature laundering solutions (i.e., less than about 30° C.). More particularly, the detergent composition contains particles having optimally selected physical properties, such as particle size, particle density and concentration of detergent ingredients, for achieving improved dissolution performance.
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. These 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. Unfortunately, such low dosage or “compact” detergent products experience dissolution problems, especially in cold temperature laundering solutions (i.e., less than about 30° C.). More specifically, poor dissolution results in the formation of “clumps” which appear as solid white masses remaining in the washing machine or on the laundered clothes after conventional washing cycles. These “clumps” are especially prevalent under cold temperature washing conditions and/or when the order of addition to the washing machine is laundry detergent first, clothes second and water last (commonly known as the “Reverse Order Of Addition” or “ROOA”). Similarly, this clumping phenomenon can contribute to the incomplete dispensing of detergent in washing machines equipped with dispenser drawers or in other dispensing devices, such as a granulet. In this case, the undesired result is undissolved detergent residue in the dispensing device.
It has been found that the cause of the aforementioned dissolution problem is associated with the “bridging” of a “gel-like” substance between surfactant-containing particles to form undesirable “clumps.” The gel-like substance responsible for the undesirable “bridging” of particles into “clumps” originates from the partial dissolution of surfactant in the aqueous laundering solutions, wherein such partial dissolution causes the formation of a highly viscous surfactant phase or paste which binds or otherwise “bridges” other surfactant-containing particles together into “clumps.” This undesirable dissolution phenomena is commonly referred to as “lump-gel” formation. In addition to the viscous surfactant “bridging” effect, inorganic salts have a tendency to hydrate which can also cause “bridging” of particles which linked together via hydration. In particular, inorganic salts hydrate with one another to form a cage structure which exhibits poor dissolution and ultimately ends up as a “clump” after the washing cycle. It would therefore be desirable to have a detergent composition which does not experience the dissolution problems identified above so as to result in improved cleaning performance.
The prior art is replete with disclosures addressing the dissolution problems associated with granular detergent compositions. For example, the prior art suggests limiting the use and manner of inorganic salts which can cause clumps via the “bridging” of hydrated salts during the laundering cycle. Specific ratios of selected inorganic salts are contemplated so as to minimize dissolution problems. Such a solution, however, constricts the formulation and process flexibility which are necessary for current commercialization of large-scale detergent products. Various other mechanisms have been suggested by the prior art, all of which involve formulation alteration, and thereby reduce formulation flexibility. As a consequence, it would therefore be desirable to have a detergent composition having improved dissolution without significantly inhibiting formulation flexibility.
Accordingly, despite the disclosures in the prior art discussed previously, it would be desirable to have a detergent composition which exhibits improved cleaning performance. Also, it would be desirable to have such a detergent composition which exhibits such improved dissolution without significantly inhibiting formulation flexibility.
SUMMARY OF THE INVENTION
The invention meets the needs above by providing a detergent composition which has improved dissolution in laundering solutions, especially in solutions kept at cold temperatures (i.e., less than about 30° C.). A combination of optimally selected physical properties of various particulate detergent ingredients in a detergent composition is used to achieve improved dissolution performance. Specifically, the detergent composition comprises from about 1% to about 50%, based on the total number of discrete particles in the composition, of substantially “sticky particles” with certain composition, size and density specifications. The substantially sticky particles contain at least about 15%, by weight of the sticky particles, of a “substantially sticky surfactant.” In addition, the substantially sticky particles have a geometric mean particle diameter size of from about 300 microns to about 700 microns with a geometric standard deviation of less than about 1.8, and a bulk density of at least about 450 g/l. Additionally, the composition includes at least about 35%, based on the total number of discrete particles in the admixture composition, of substantially non-sticky particles having a geometric mean particle diameter size of from about 200 microns to about 500 microns with a geometric standard deviation of greater than about 1.2 and a bulk density of less than about 850 g/l. The substantially non-sticky particles may include inorganic fillers, builders, “substantially non-sticky surfactants” and other ingredients. Typically, the non-sticky particles will have a substantially low to nil (i.e., less than about 10% on a weight basis) concentration of sticky surfactants. The total amount of surfactants, including both sticky and non-sticky surfactants, in the composition is at least about 15% by weight of the composition.
With the aforementioned optimally selected particulate concentrations, respective particle densities, particle sizes and particle size ranges as measured by geometric mean and geometric standard deviation statistics, the composition unexpectedly exhibits superior dispersion and dissolution in cold temperature laundering solutions. A method of laundering clothes comprising the steps of contacting soiled clothes with an effective amount of a detergent composition according to compositions described herein in an aqueous washing solution is also provided.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention provides a detergent composition which exhibits improved dispersion and dissolution in aqueous laundering solutions. It has been found that by optimally selecting physical properties of various particles contained in granular detergent compositions, the dissolution can be improved. As mentioned previously, typical detergent formulations that dissolve in aqueous laundering solutions form highly viscous surfactant phase or paste which binds or otherwise “bridges” other surfactant-containing particles together into “clumps” ultimately causing “lump-gel” formation.
As used herein, the phrase “discrete particles” means individual particles, agglomerates or granules which can be identified via a scanning electron microscope as discrete units of mass. For each type of particle component in an admixture, the discrete particles of that type have the same or substantially similar composition regardless of whether the particles are in contact with other particles. For agglomerated components, the agglomerates themselves are considered as discrete particles and each discrete particle may be comprised of a composite of smaller primary particles and binder compositions.
As used herein, the phrase “geometric mean particle diameter” means the geometric mass average diameter of a set
Mort, III Paul R
Norwood Kevin Todd
Douyon Lorna M.
Dressman Marianne
Miller Steven W.
The Procter & Gamble & Company
William Zerby Kim
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