Polymeric dispersant
The invention relates to a dispersant comprising a polymer obtainable by copolymerization of monomers including 5 to 80 mol % of a hydroxyalkyl acrylate phosphate and/or hydroxyalkylacrylamide phosphate (monomer 1), 0 to 20 mol % of a di(hydroxyalkyl acrylate) phosphate and/or di(hydroxyalkylacrylamide) phosphate (monomer 2) and 1 to 80 mol % of a polyalkylene glycol-containing macromonomer comprising an alkene group (monomer 3). Further disclosed is a process for preparing the polymers of the invention and the use thereof as dispersants in calcium sulphate-containing compositions. A further aspect of the invention is a process for producing shaped gypsum bodies, and also shaped gypsum bodies, more particularly gypsum plasterboards and self-levelling screeds, comprising the dispersant of the invention.
1. A dispersant comprising:
a polymer comprising as copolymerized units:
5 to 80 mol % of at least one monomer 1 of formula (1),
0 to 20 mol % of at least one monomer 2 of formula (2);
and
1 to 80 mol % of at least one monomer 3 of formula (3):
R 3 —O—(C n H 2n O) m —Z (3)
wherein
R 1 is an alkylene group having 2 to 8 carbon atoms;
Y is NR 2 ;
R 2 is a radical from the group of hydrogen, an alkyl group having 1 to 8 carbon atoms, and formula (A),
M 1 and M 2 each independently of one another are hydrogen, an ammonium compound and a mono-, di- or trivalent metal;
R 3 is hydrogen, an aliphatic hydrocarbon radical having 1 to 16 C atoms, a cycloaliphatic radical having 5 to 12 C atoms or an aryl radical having 6 to 14 C atoms, the aryl radical optionally having further substituents; n is identical or different and in each case is an integer from 2 to 3; m is an integer between 20 and 160;
Z is at least one radical selected from the group consisting of formulae (4), (5), (6) and (7):
2. The dispersant according to claim 1 , wherein the polymer comprises monomer 2.
3. The dispersant according to claim 1 , wherein the group R 1 in monomer 1 is an ethylene group.
4. The dispersant according to claim 1 , wherein the polymer comprises monomer 2 and group R 1 in both monomer 1 and monomer 2 is an ethylene group.
5. The dispersant according to claim 1 , wherein an average molecular weight of the polymer is between 15,000 and 60,000 g/mol, the molecular weight being measured by gel permeation chromatography against a PEG standard.
6. The dispersant according to claim 1 , wherein the polymer consists of copolymerized units of monomer 1 and monomer 3.
7. A process for preparing a polymer according to claim 1 , comprising: copolymerizing in an aqueous solution at least one monomer 1 of the formula (1), optionally at least one monomer 2 of the formula (2), and at least one monomer 3 of the formula (3).
8. The process according to claim 7 , wherein copolymerizing is at a temperature of is from 5 to 100° C. and a pH of is between 0.5 and 8.
9. A calcium sulphate based binder system comprising a calcium sulphate binder and the dispersant according to claim 1 .
10. A shaped gypsum body comprising gypsum and the dispersant according to claim 1 .
11. The shaped gypsum body according to claim 10 , wherein the shaped gypsum body is a gypsum plasterboard.
12. A process for producing a shaped gypsum body, comprising adding the dispersant according to claim 1 to the aqueous gypsum composition.
13. The process according to claim 12 , wherein the shaped gypsum body is a gypsum plasterboard.
14. The process according to claim 12 , wherein the shaped gypsum body is a calcium sulphate-containing self-levelling screed.