Copolymers having gem-bisphosphonate groupings

1. A method of maintaining workability of hydraulic binders comprising adding to said hydraulic binders an admixture comprising a copolymer comprising a main hydrocarbon chain and side groups, wherein the side groups comprise carboxylic groups, polyoxyalkylate groups and gem-bisphosphonate groups, wherein the copolymer has an average molar mass between 10,000 and 110,000 (Mw) as determined by size exclusion chromatography in equivalent of standard polyoxyethylene, wherein:

the carboxylic groups of the copolymer fit the formula (III) below:

—C(O)—O—R d   (III)

 wherein:

R d represents H or a C 1 -C 12 alkyl, aryl, alkylaryl or arylalkyl group or an alkali metal, alkaline earth metal or ammonium cation; and

the gem-bisphosphonate side groups:

fit the formula (IA) below:

wherein:

L represents a group —NR 4 — for binding to a carboxylic group of the main chain wherein R 4 is a hydrogen or a C 1 -C 6 alkyl group;

X is a C 1 -C 20 alkylene spacer group, optionally substituted;

R1 are, independently of each other, H; or a cation; and

R2 is a hydrogen atom, a hydroxyl group or a C 1 -C 10 alkyl group; or

is a result of a grafting with 1-hydroxyethylene-1,1-bisphosphonic acid (HEDP) to carboxylic group of the main chain.

2. The method according to claim 1 , wherein the polyoxyalkylate side groups of the copolymer are bound to the main chain through an ester, ether or amide bond.

3. The method according to claim 1 , wherein the gem bisphosphonate groups of the copolymer is a result of a grafting with a compound selected from the group consisting of 1-hydroxy-3-amino-propylene-1,1-bisphosphonic acid (AHP) and 1-hydroxy-4-amino-butylene-1,1-bisphosphonic acid (BHP) to carboxylic group of the main chain.

4. The method according to claim 1 , wherein the polyoxyalkylate groups of the copolymer are of the formula (II) below:

—R e —Z-A  (II)

wherein:

R e is a C 1 -C 12 alkylene group, a C═O group or is absent; and

Z is an oxygen atom or a group N—R 4 , wherein R 4 is a hydrogen or a C 1 -C 6 alkyl group; and

A is a group of formula (QO)n-R 3 wherein:

Q represents an alkylene group with 2 to 4 carbon atoms or a mixture of these alkylene groups;

n is an integer varying from 1 to 500; and

R 3 represents a hydrogen atom or a C 1 -C 12 alkyl, aryl, alkylaryl or arylalkyl group.

5. The method according to claim 1 , wherein the carboxylic groups of the copolymer fit the formula (III) below:

—C(O)—O—R d   (III)

wherein:

R d represents H.

6. The method according to claim 1 , wherein admixture is in a solvent comprising 1 to 50% by weight of copolymer based on the total weight of the admixture.

7. The method according to claim 1 , wherein the copolymer comprises from 2 to 10% in number of gem-bisphosphonate side groups.

8. The method according to claim 1 , wherein the gem-bisphosphonate groups of the copolymer are of formula (IA), X being a C 1 -C 6 alkylene group.

9. The method according to claim 1 , wherein the gem bisphosphonate groups of the copolymer are of formula (IA), R 1 being a hydrogen atom or an alkali metal, earth alkaline metal or ammonium cation.

10. The method according to claim 1 , wherein the gem bisphosphonate groups are of formula (IA), R 2 being a hydroxyl group.

11. The method according to claim 1 , wherein in the bisphophonate group of formula (IA), R1 is a hydrogen.

12. The method according to claim 1 , wherein in the bisphophonate group of formula (IA), R1 is an alkali metal, an alkaline earth metal, or an ammonium cation.

13. The method according to claim 4 , wherein, in the polyoxyalkylate groups of the copolymer of formula (II), A is a group of formula (QO)n-R 3 wherein R 3 is a methyl.

14. The method according to claim 6 , wherein the solution comprises 10 to 30% by weight of copolymer based on the total weight of the admixture.