A dispersant comprising a polyester chain obtainable by polymerising a hydroxy carboxylic acid or lactone thereof such as E-caprolactone with a cyclic alkylene carbonate such as 5,5-dimethyltrimethylene carbonate. The dispersant may be in the form of a phosphate ester where the polyester chain is reacted with a phosphating agent such as polyphosphoric acid or the polyester chain may be attached to a polyamine or polyimine such as polyethyleneimine.
1. A dispersant which is represented by formula 4
wherein D—*—*D represents the polyamine or polyimine;
Y represents a polyoxy alkylene carbonyl chain (POAC) represented by the group T—X—(A) m (B) n — which is linked to the polyamine or polyimine via amide and/or salt linkages; and q is from 2 to 2000;
T is H or a residue of a polymerization terminating group selected from C 1-50 hydrocarbyl groups:
X is a direct bond or a divalent bridging group;
A is a residue of one or more optionally substituted C 1-50 -alkylene or C 2-50 -alkenylene hydroxycarboxylic acids or lactones thereof;
B is a residue of one or more cyclic alkylene carbonates characterized by 6 atoms in the ring portion;
m and n are positive integers: and m+n is from 2 to 200.
2. A dispersant as claimed in claim 1 wherein the weight ratio of the POAC chain represented by Y to the polyamine or polyimine is from 30:1 to 1:1.
3. A dispersant as claimed in either claim 1 or claim 2 wherein the polyimine is polyethyleneimine.
4. A process for making a dispersant as claimed in claim 1 which comprises reacting one or more hydroxycarboxylic acids or lactones thereof with one or more cyclic alkylene carbonates optionally in the presence of a polymerization terminating compound in an inert atmosphere and in the presence of an esterification catalyst at a temperature from 50 to 250° C. to form said POAC, followed by reacting with the polyamine or polyimine.
5. A composition comprising a particulate solid and a dispersant as claimed in claim 1 .
6. A composition comprising a particulate solid, an organic medium and a dispersant as claimed in claim 1 .
7. A millbase, paint or ink comprising a pigment, organic medium, film-forming resin binder and a dispersant as claimed in claim 1 .
8. A composition comprising a particulate solid, a plastic material and a dispersant as claimed in claim 1 .