Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – Heterogeneous arrangement
Reexamination Certificate
2001-09-20
2003-02-04
Ogden, Necholus (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
Heterogeneous arrangement
C510S445000, C510S446000, C510S450000, C510S457000
Reexamination Certificate
active
06514930
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a process for the production of anionic detergent particles and detergent compositions containing them. More particularly the present invention relates to a process for the production of detergent particles having a high level of anionic surfactant which involves in situ neutralisation of an acid precursor of the anionic surfactant and drying of the surfactant thereby produced.
BACKGROUND & PRIOR ART
It is known that detergent particles having high anionic surfactant levels can be prepared by processes in which acid precursors of anionic surfactants are neutralised with a neutralising agent in horizontal thin-film evaporator/drier (WO-A-96/06916, WO-A-96/06917 & WO-A-97/32002; WO-A-98/38278 & WO-A-98/40461) and the mass is granulated and dried. As used herein, the term thin-film evaporator/drier is understood to include flash-driers and scraped-surface driers as described in WO-A-96/06916, WO-A-96/06917 & WO-A-97/32002.
Basically, a thin-film evaporator/drier comprises a cylindrical chamber in which is located a coaxial shaft on which is mounted a plurality of blade-like tools. The pitch of these tools can be set to different angles along the length of the cylindrical chamber, from input end to output end. The clearance between the tips of the blade-like tools and the internal surface of the cylindrical chamber is very small, typically 5 mm or less. The cylindrical chamber comprises at least a mixing region at or towards the input end of the cylindrical chamber, a cooling region at or towards the output end of the cylindrical chamber and a drying region between the mixing and cooling regions. The drying region typically comprises one or more heating zones and the cooling region may comprise one or more cooling zones (although usually only one cooling zone. Each of the heating and cooling zones is defined by a respective jacket around the cylindrical chamber with a respective axial gap between each and through which jackets, a heating or cooling liquid, as appropriate, is pumped during operation of the process. The layering agent is “typically an aluminosilicate or a silica. The maximum amount of the layering agent dosed into the cooling region is 25% by weight of the resultant detergent particles.
Commonly, products obtained from the aforementioned process using a thin-film evaporator/drier also contain aluminosilicate detergency builder. A problem arises that the aluminosilicate interferes with the neutralisation reaction in some way. Imperfect neutralisation of the free acid form of the anionic surfactant results in one or more of the following negatives:
(i) production of oversize particles;
(ii) softer particles which are more difficult to handle and store;
(iii) the generation of heat during storage as the neutralisation reaction continues;
(iv) increased uptake of moisture upon storage, due to the hygroscopicity of many acid precursors, resulting in poor powder flow properties both of the detergent particles and of detergent compositions containing the detergent particles.
These problems are especially prevalent when neutralising linear alkyl benzene sulphonic acid (LAS acid) precursors and alkyl sulphuric acid half-esters.
WO-A-97/32002 discloses a “dry-neutralisation” process in which high anionic surfactant-content detergent particles are manufactured by contacting a pumpable acid precursor with a solid neutralising agent, such as for example sodium carbonate, in a thin-film evaporator/drier.
EP-A-555 622 describes the manufacture of detergent particles comprising anionic surfactant in which acid precursors are neutralised in a high shear mixer by a stoichiometric excess of particulate neutralising agent, preferably sodium carbonate. The neutralisation reaction is optimised by using neutralising agent of a narrowly defined particle size range, namely 50% by volume has a particle diameter of less than 5 microns. However, this reference is not specifically concerned with problems arising from incorporation of aluminosilicate and does not relate to the production of high anionic surfactant-content detergent particles or to the use of thin-film evaporator/driers.
We have now found that one or more of the aforementioned problems can be diminished or overcome by introducing at least part of the aluminosilicate between the drying region and cooling region and/or in the cooling region.
SUMMARY OF THE INVENTION
Accordingly, this invention provides a process for the production of detergent particles, the process comprising feeding an acid precursor of an anionic surfactant, a neutralising agent and aluminosilicate detergency builder into a horizontal thin-film evaporator/drier comprising a mixing region, a drying region and a cooling region, to effect neutralisation of the acid precursor, granulation, drying and cooling, to form the said detergent particles, wherein at least some of the aluminosilicate builder is fed into the thin-film evaporator/drier between the drying region and the cooling region and/or into the cooling region, provided that when all of the aluminosilicate builder is fed into the cooling region, the aluminosilicate is in an amount of more than 20% by weight of the particles exiting the cooling region. Preferably, the aluminosilicate is in an amount of more than 25% by weight of the particles exiting the cooling region.
This invention also provides detergent particles obtainable by the process.
DETAILED DESCRIPTION OF THE INVENTION
Simultaneous Neutralisation, Drying and Granulation Process in a Thin-Film Evaporator/Drier
The process is carried out in a horizontal thin-film evaporator/drier (hereinafter referred to as an “evaporator/drier”). A commercial scale machine typically comprises at least 300, preferably at least 500, more preferably at least 750, especially at least 1000 blade-like tools. The clearance between the blades and the internal wall of the chamber is suitably less than 20 mm, e.g. 15 mm or less, or even 10 mm or less. The blade tip speed in operation is suitably ≧15 ms
−1
, preferably ≧20 ms
−1
. The ratio of exposed blade length to shaft radius is preferably less than 1, e.g. less than 0.5. Preferably, the large number of blades and the pitch of the blades also means that at least 40%, for example at least 45%, and even substantially the whole chamber wall (that part along the length of the shaft which carries the blades) is scraped during operation.
Initial mixing of the components occurs in the mixing region and the neutralisation reaction is begun. Mixing and neutralisation then continue throughout the process, through the drying and cooling regions.
The anionic surfactant acid precursor (hereinafter referred to as the “acid precursor”) and neutralising agent are normally fed into the mixing region of the evaporator/drier. However, all or part of either component can be dosed into the drying region. Neutralisation occurs to form a surfactant paste, which is then converted into detergent particles by the drying and mechanical action of the evaporator/drier. The evaporator/drier exerts its drying action by forming a thin layer of material on a heated surface within the drying region.
The acid precursor is suitably fed into the evaporator/drier in a liquid phase. As acid precursors can be unstable, the neutralisation preferably occurs sufficiently rapidly and substantially completely such that thermal decomposition of the acid due to elevated temperature is minimised and desirably avoided.
The neutralising agent is introduced into the evaporator/drier as a solid particulate material. Preferably, the amount of neutralising agent with respect to the acid precursor added to the mixing region is at least in stoichiometric equality, most preferably in excess. Preferably, at least 1.25 times required for stoichiometric neutralisation is used but preferably no more than 2 times. Higher amounts of neutralising agent, e.g. no more than 5 times, no more than 4.5 times, or no more than 4 times that required for stoichiometric neutralisation can be used but these higher amounts are g
Emery William Derek
Groot Andreas Theodorus
Mitelman Rimma
Ogden Necholus
Unilever Home & Personal Care USA , division of Conopco, Inc.
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