Process for preparing fluid detergent compositions

Details Process for preparing fluid detergent compositions Process for preparing fluid detergent compositions

2001-04-12

2003-12-09

Boyer, Charles (Department: 1751)

Cleaning compositions for solid surfaces, auxiliary compositions

Cleaning compositions or processes of preparing

Solid, shaped macroscopic article or structure

C510S290000, C510S357000, C510S444000, C510S426000, C510S435000, C510S509000, C510S536000

Reexamination Certificate

active

06660708

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a process for preparing fluid detergent compositions comprising an anionic surfactant. More particularly, it relates to a process for the continuous preparation of a fluid detergent composition comprising an anionic surfactant, formed by neutralisation of its anionic surfactant acid precursor, and an nonionic surfactant.
BACKGROUND OF THE INVENTION
In the manufacture of detergent compositions containing anionic surfactants, the anionic surfactants are often manufactured via and supplied in their acid form. There are several reasons for this, including the fact that certain anionic surfactants, for example linear alkylbenzene sulphonates, are much easier to handle, store and transport in their acid form as compared with the neutralised form. The anionic surfactant acid precursors are then converted into their corresponding surfactant salts by neutralisation with either aqueous or dry neutralising agents.
One of the most common pieces of plant set up for carrying out neutralisation of anionic surfactant acid precursors is a loop reactor. The anionic surfactant acid precursor, neutralising agent and other diluents/buffers are injected into the loop reactor, usually at a common point, and blended by an in-line mixer present in the loop. The heat of neutralisation is typically removed by a pipe bundle heat exchanger in the loop.
An inherent problem with neutralisation reactions is how to deal with the large amount of heat generated. Overheating (i.e. “hot-spots”) and the long residence time can lead to discoloration of the product. Loop reactors address the problem of overheating by only removing a small fraction of the product flow, for example 5-10%, from the loop, whilst the recirculating mixture, generally in the form of a paste, acts as a heat sink, preventing a large rise in temperature at the injection point. This method of operation means that neutralisation in a loop reaction is a highly inefficient process.
Many fully neutralised anionic surfactants tend to become highly viscous pastes which are difficult to handle. For this reason, neutralisation is very often carried out in the presence of other liquid detergent components such as nonionic surfactants. However, there is a problem with discoloration of the anionic
onionic surfactant mixture as a result of the anionic surfactant acid precursor reacting with the nonionic surfactant. It is therefore desirable that the time over which the anionic surfactant acid precursor, prior to neutralisation, is in contact with the nonionic surfactant is short. The very design and operation of neutralisation loop reactors means that any nonionic surfactant is going to be in contact with anionic surfactant acid precursor for a considerable period of time as it recirculates in the loop and more acid is added to be neutralised.
Finally, the start-up (i.e. up to the point where a “steady-state” recirculation is achieved) and the shut-down procedures for neutralisation in a loop reactor are long and time-consuming, with the material being produced during these procedures being outside of specification.
There was therefore a need for the development of a simple process for neutralising an anionic surfactant acid precursor, in particular in the presence of a nonionic surfactant, which:
(i) does not involve a recirculation loop;
(ii) is relatively quick;
(iii) effectively inhibits the generation of hot-spots;
(iv) is efficient in terms of start-up and shut-down;
(v) avoids the production of outside of specification material at start-up and shut-down, and
(vi) ensures full neutralisation of the anionic surfactant acid precursor.
PRIOR ART
EP 507 402 (Unilever) describes a process for preparing a liquid surfactant composition comprising anionic surfactant, nonionic surfactant and having a relatively low water content, wherein essentially equimolar amounts of neutralising agent and liquid anionic surfactant acid precursor are blended simultaneously with the nonionic surfactant. The surfactant mixtures can be prepared in a batch process in which equimolar amounts of the anionic precursor and neutralising agent are added to a reaction vessel containing the required amount of nonionic surfactant. Alternatively, and preferably, the process is carried out continuously in a loop reactor. The liquid surfactant compositions may additionally contain a fatty acid, and may be applied in a process for making high bulk density granular detergent compositions having a high active detergent level, as disclosed by EP 367 339 (Unilever).
WO93/23520 (Henkel) describes a method for preparing anionic surfactant containing granular washing compositions comprising (i) partially or completely neutralising one or more anionic surfactant acid precursors with an inorganic or organic neutralising agent to produce an anionic-containing mixture which is flowable/pumpable up to at least 20° C., and (ii) mixing and granulating the anionic-containing mixture with a particulate material in a mixer. For partial neutralisation in step (i), the level neutralisation in step (i) is preferably from 20-40%. The anionic surfactant acid precursor is preferably mixed with a nonionic surfactant in step (i).
Surprisingly, we have now found that a fluid detergent product comprising an anionic surfactant can be prepared in a simple continuous process without the need for a loop reactor by passing the anionic surfactant acid precursor through at least two mixers in series, an initial portion of neutralising agent being fed to the first mixer and further neutralising agent being fed to the subsequent mixer or mixers to complete neutralisation. It is essential, in order for the process to work efficiently, that the process mixture be cooled after addition of the initial portion of neutralising agent and before further neutralising agent is added, and, that the temperature of the mixture be maintained at a level which allows the mixture to be readily pumpable.
Thus the present invention allows fluid detergent products containing anionic surfactant to be prepared from anionic surfactant acid precursors in a simple single pass process. This is far more efficient than a loop reactor operation and has relatively short start-up and shut-down times. In addition, if nonionic surfactant is present during the neutralisation reaction, the present invention ensures it is not exposed to the anionic surfactant acid precursor for too long a period.
DEFINITION OF THE INVENTION
In a first aspect, this invention provides a continuous process for the preparation of a fluid detergent product containing an anionic surfactant, comprising mixing an initial liquid component comprising the anionic surfactant acid precursor with sufficient neutralising agent to substantially complete neutralisation of the anionic surfactant acid precursor characterised in that:
(i) the initial liquid component is fed to a first mixing device with sufficient initial neutralising agent to neutralise 25-75 wt % of the anionic surfactant acid precursor, and
(ii) the partially neutralised process stream from step (i) is fed through one or more subsequent mixing devices with sufficient further neutralising agent to substantially complete neutralisation by the time the process stream exits the final mixing device, wherein the process stream comprising the initial neutralising agent is actively cooled by a cooling means prior to the addition of any further neutralising agent, and the initial liquid component and process stream are kept at a temperature above the pumpable temperature at all times during the process.
DETAILED DESCRIPTION OF THE INVENTION
Definitions
The “pumpable temperature” as herein defined is the temperature at which a fluid exhibits a viscosity of 1 Pa.s at 50 s
−1
. In other words, fluids are considered readily pumpable if they have a viscosity of no greater than 1 Pa.s at a shear rate of 50 s
−1
at the temperature of pumping. Fluids of higher viscosity may still in principle be pumpable, but an upper limit of 1 Pa.s at a shear rate of 50 s
−1
is us

Affiliated with

Also associated with

Rating

Process for preparing fluid detergent compositions does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Process for preparing fluid detergent compositions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for preparing fluid detergent compositions will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3137227