Process of making a dispersion of stabilized particles

Details Process of making a dispersion of stabilized particles Process of making a dispersion of stabilized particles

1998-06-30

2001-01-09

Henderson, Christopher (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Processes of preparing a desired or intentional composition...

C510S276000

Reexamination Certificate

active

06172136

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the formation of polymeric particles (ie particles having an external surface of organic polymer) which give improved stability when dispersed in a liquid detergent concentrate.
2. Description of the Related Art
Processes are described in PCT/GB96/03233 for forming particulate compositions comprising particles having a hydrophilic core within a shell comprising a membrane comprising an association product of (a) an interfacial condensation (IFC) product formed in a non-aqueous liquid by reaction between a first IFC reactant having at least two first condensation groups and the second IFC reactant having at least two second condensation groups and (b) an amphipathic polymeric stabiliser which will concentrate at the interface between oil and water and which has recurring hydrophobic groups and recurring reactive hydrophilic groups which associate with the second condensation groups. After formation in the non-aqueous liquid, the particles are then dispersed in liquid electrolyte.
It is explained in that application that the association may comprise a condensation reaction and, in particular, condensation may occur when the stabiliser is a copolymer of an ethylenically unsaturated carboxylic anhydride such as maleic anhydride and the second condensation groups are amino groups. It is also explained, however, that the association preferably comprises forming an internal, ring-formed salt between the adjacent carboxylic groups of a stabiliser formed from a monomer such as malcic acid or maleic anhydride with an IFC reactant which is a polyamine.
We have found that the best performance is generally achieved when the formation of the IFC shell does depend on 35 the use of a polycarboxylic stabiliser which is in hydrolysed acid form rather than anhydride form, and this is probably due to the fact that internal salt formation occurs and. that covalent reaction between the amine and the carboxylic acid groups does not occur during normal processing.
We have also found that when particles are made in this way, the resultant particles sometimes have less dispersion-stability than is desirable, especially when they are subsequently dispersed in an aqueous electrolyte solution (such as a liquid detergent concentrate) We have found that, when developing these unpublished processes, it is difficult simultaneously to optimise the shell formation and the stability of the particles in the final liquid dispersion. We believe that this may arise because of there being different requirements for optimum shell formation and for optimum stability. In particular, we believe that optimum shell formation may often be promoted by some degree of ionic association between the stabiliser and IFC reactant groups, but we believe that materials which are optimum for undergoing this ionic association may give less satisfactory stability in the final dispersion. Conversely, materials which may give optimum stability in the final dispersion appear to give less adequate shell formation.
Our object, arising out of this unpublished work, is to try to obtain a better combination of properties during manufacture and during long term storage in the electrolyte.
Different types of dispersions are known from, for instance, GB-A-1,198,052, GB-A-1,231,614, GB-A-1,268,692, GB-A-2,207,681, AU-A-455,165, U.S. Pat. No. 3,580,880, U.S. Pat. No. 3,875,262, EP-A-707,018 and EP-A-719,085.
BRIEF SUMMARY OF THE INVENTION
According to the invention, we provide a process for making a dispersion in liquid electrolyte of particles having a size below 30 &mgr;m, the process comprising forming a dispersion in a first liquid of particles which have a size of below 30 &mgr;m and which have a core containing a detergent active ingredient and a shell which has been formed by interfacial condensation and which has an outer surface which includes reactive groups, and covalently reacting a reactive stabiliser material with some of the reactive groups and thereby forming a dispersion of the particles with the stabiliser material covalently bonded on to the outer surface of the shell of the particles, and dispersing the resultant self-stabilised particles into the liquid electrolyte.
DETAILED DESCRIPTION OF THE INVENTION
The dispersion is substantially stable and the particles may be self-stabilising, as explained below. The aqueous electrolyte is usually a concentrate which contains anionic or cationic surfactant as electrolyte, and the concentrate is usually a liquid detergent concentrate: It usually contains at least 0.5%, preferably at least 3%, most preferably at least 5% by weight electrolyte. It is usually an aqueous liquid electrolyte.
By saying that we covalently react the stabiliser material with some of the reactive groups, we mean that there is sufficient covalent bonding between the stabiliser material and the reactive groups to ensure that the stabiliser is attached to the particles by sufficient covalent bonding to hold the stabiliser material in place despite reasonable changes in the continuous phase in which the particles may be dispersed. For instance the stabiliser material should remain in place, and give a stabilising effect, even though the continuous phase may change from a first liquid which is non-aqueous, predominantly hydrocarbon, liquid to a relatively high electrolyte liquid, such as a detergent concentrate. There can additionally be some ionic bonding or other forms of association but there must be sufficient covalent bonding to dominate the performance of the particles when the continuous phase is changed.
The number of reactive groups which remain unreacted after covalently reacting the stabiliser material on to the particles is often unimportant but in practice there will always be some reactive groups that do not react covalently with the stabiliser. For instance some of the reactive groups will be prevented from reacting because of steric hindrance between the stabilizer and the particle surface. Some of the reactive groups will be prevented from reacting covalently because they may react in another manner, for instance forming an ionic complex. In practice some of the reactive groups may remain unreacted because there is a stoichiometric excess of reactive groups on the polymer particles over groups on the stabiliser that can react with them.
The invention is preferably applied to the production of particles which have a size at least 90% by weight below 30 &mgr;m, preferably below 10 or 20 &mgr;m and which are preferably to be provided as a substantially stable dispersion in a liquid detergent concentrate. The invention reduces or eliminates the risk of the particles sedimenting and/or aggregating, both at low concentrations (.e.g, down to 0.1% by weight) and at higher concentrations (e.g., 5% or even much higher such as 30% or 50% in some liquids used for introducing the particles into the detergent concentrate).
Thus, by the invention, a substantially stable dispersion of the particles may be formed in a first liquid (usually a non-aqueous liquid) and then these particles may be dispersed into the liquid detergent concentrate or other electrolyte, and the dispersion would have been less stable in this if the covalent bonding of the invention had not been applied. In particular, by the invention the dispersion in the liquid detergent concentrate is preferably more stable than if the same stabiliser material is simply mixed into the final dispersion of particles in the second liquid, without the covalent reaction. Generally the covalent reaction is conducted in the first (usually non-aqueous) liquid and the resultant self-stabilised particles are dispersed in the second liquid. However if desired the first non-aqueous liquid may be exchanged with another non-aqueous liquid or some other liquid such as a surfactant before the covalent reaction or even before adding the reactive stabiliser.
The change of the continuous phase from the first liquid to another liquid, and in particular to the detergent or other electrolyte concentrate

Affiliated with

Also associated with

Rating

Process of making a dispersion of stabilized particles 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 of making a dispersion of stabilized particles, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process of making a dispersion of stabilized particles will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2556810