Agglomeration of high active pastes to form surfactant granules

Details Agglomeration of high active pastes to form surfactant granules Agglomeration of high active pastes to form surfactant granules

1993-10-12

1996-02-27

Lieberman, Paul

Compositions

Dust suppressants for bulk materials, or processes of...

252174, 252135, C11D 1100, C11D 1706

Patent

active

054945992

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to a process for preparing compositions comprising condensed detergent granules.


BACKGROUND OF THE INVENTION

Granular detergent compositions have so far been principally prepared by spray drying. In the spray drying process the detergent components, such as surfactants and builders, are mixed with as much as 35-50% water to form a slurry. The slurry obtained is heated and spray dried, which is expensive. A good agglomeration process, however, could be less expensive.
Spray drying requires 30-40 wt. % of the water to be removed. The equipment used to produce spray dry is expensive. The granule obtained has good solubility but a low bulk density, so the packing volume is large. Also, the flow properties of the granule obtained by spray drying are adversely affected by large surface irregularities, and thus the granulate has a poor appearance. There are other known disadvantages in preparing granular detergents by spray drying.
There are many prior art nonspray-drying processes which produce detergent granules. They have drawbacks as well. Most require more than one mixer and a separate granulation operation. Others require use of the acid form of the surfactant to work. Some others require high temperatures which degrade the starting materials. High active surfactant paste is avoided in these processes because of its stickiness.
EP-A-0 345 090, published Dec. 6, 1989, discloses a process for manufacturing particulate detergent compositions comprising contacting detergent acid with neutralizing agents and providing particulates by contacting the detergent acid with a particulate neutralizing agent or detergent salt with carrier in an absorption zone.
EP-A-0 349 201, published Jan. 3, 1990, discloses a process for preparing condensed detergent granules by finely dispersing dry detergent builders and a high active surfactant put into a uniform dough which is subsequently chilled and granulated using fine dispersion to form uniform, free flowing granular particles.
EP-0 390 251, published Oct. 3, 1990, discloses a process for the continuous preparation of a granular detergent or composition comprising steps of treating, firstly, particulate starting material of detergent surfactant and builders in a high-spead mixer, secondly in a moderate-speed granulator/densifier and thirdly in a drying/cooling apparatus, with the addition of powder in the second or between the first and second step to reduce the amount of oversize particles.
A. Davidsohn and B. M. Mildwidsky, Synthetic Detergents, John Wiley & Sons 6th edition, 1978, discloses general detergency teachings, including the manufacturing of finished detergent products.
High shear and cold mixing processes per se are known, but they require an extra grinding step or some other action. E.g., some use a dry neutralization technique of mixing an acid form of the surfactant with sodium carbonate. See U.S. Pat. No. 4,515,707, Brooks, issued May 7, 1985; Japanese laid-open Appln. No. 183540/1983, Kao Soap Co., Ltd., filed Sept. 30, 1983; and Japanese Sho. 61-118500, Lion K. K., Jun. 5, 1986. Typically, excess carbonate is required (2-20 molar excess) to assure reasonable conversion of the surfactant acids. Excess carbonate adversely drives up the wash water pH to the very alkaline range which can be undesirable, particularly for some low-phosphate formulas.
The use of a surfactant acid generally requires immediate use or cool temperature storage, for highly reactive acids such as the alkyl sulfate acids are subject to degradation unless cooled, they tend to undergo hydrolysis during storage, forming free sulfuric acid and alcohol. In practical terms, such prior art processes require close-coupling of surfactant acid production with granulation which requires an additional capital investment.
A second route, well known in the field and described in the patent literature, is the in-situ neutralisation of the anionic surfactant acid with caustic solutions (e.g. 50% NaOH) or caustic powders (e.g. Na.sub.2 CO.sub.3) r

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