ROBUST POLYCARBOXYLATE WITH POLYALKYLENE OXIDE-BASED SACRIFICIAL SIDECHAIN LINKAGE AS MILLING AID FOR CEMENTITIOUS MATERIALS
The present invention concerns a polycarboxylate ether polymer to be used as a grinding aid during the grinding of cementitious materials, said polymer having sacrificial linkages that preferentially break inside the cement mill. The polymer can have a polycarboxylate ether structure comprising free carboxylic acid groups, neutralized carboxylic acid groups, at least one side chain A and at least one side chain B. The at least one side chain A comprises a group (AlkO) m and the at least one chain B comprises a group (AlkO) n , where AlkO represents an alkylene oxide, and m and n are integers with m<n.
1 . A polymer having a polycarboxylate ether structure comprising free carboxylic acid groups, neutralized carboxylic acid groups, at least one side chain A and at least one side chain B, wherein said at least one side chain A comprises a group (AlkO) m and said at least one chain B comprises a group (AlkO) n , wherein AlkO represents an alkylene oxide, and wherein m and n are integers with m<n.
2 . A polymer according to claim 1 , wherein AlkO is a C 2 to C 4 alkylene oxide.
3 . A polymer according to claim 1 , wherein (AlkO) m and (AlkO) n are independently chosen from the group consisting of polyethylene glycol, polypropylene glycol, polybutylene glycol, polyoxyethylene glycol, polyoxypropylene amine, and blends thereof.
4 . A polymer according to claim 1 , wherein m and n range from 2 to 120.
5 . A polymer according to claim 1 , wherein the degree of substitution of (AlkO) m is 0.01 to 0.1.
6 . A polymer according to claim 1 , wherein the degree of substitution of (AlkO) n is 0.1 to 0.4.
7 . A polymer according to claim 1 , wherein the polymer is represented by the formula (Z) below:
wherein
R 1 , R 2 , R 3 and R 4 , independently of one another, is a hydrogen atom or a methyl group.
R 5 is a hydrogen atom or C 1 to C 4 alkyl group, alkylaryl group or cycloalkyl group.
R 6 is a hydrogen atom or C 1 to C 4 alkyl group, alkylaryl group or cycloalkyl group or (AlkO) p —R 8 , wherein p is an integer ranging from 2 to 120 and R 8 is a C 1 to C 2 alkyl group.
R 7 is R 5 or is a bond to another polymer of formula (Z); providing that R 7 is at least bond to one polymer of formula (Z).
a, b, c and d represent the molar percentage of each of the monomers in the structure, and range as follows: a=25-85%; b=1-10%; c=10-40%, d=0-2%.
M, independently, is an AlkO, hydrogen, alkali, or alkaline earth metal cation, ammonium, or any other organic amine group.
8 . A polymer according to claim 1 , wherein the polymer's backbone has an averaged molecular weight between 1000 and 20000 Da, more preferably between 2500 and 15000 Da, even more preferably between 5000 and 10000 Da.
9 . A polymer according to claim 1 , wherein the polymer's molecular weight is between 10000 and 100000 Da, more preferably 15000 and 80000 Da and even more preferably between 20000 and 65000 Da.
10 . A method to use a polymer as a grinding aid during the manufacturing of cement, pozzolanic materials, or lime, that is characterized in:
a) Providing a fresh feed to a cement mill;
b) Adding a polymer according to claim 1 ;
c) Grinding the material obtained in step b) until the material reaches the final desired fineness according to the final cementitious product being produced;
d) Discharge the final product from the cement mill.
11 . The method according to claim 10 , wherein the polymer is added to the cement mill together with the fresh feed.
12 . The method according to claim 10 , wherein the polymer is added directly into the first chamber of the cement mill.
13 . The method according to claim 10 , wherein the polymer is added in an amount between 0.01 wt. % and 0.4 wt. % based on the dry weight of the cementitious material to be ground.
14 . The method according to claim 10 , wherein the residence time of the polymer inside the cement mill is between 1 and 10 minutes.
15 . The method according to claim 10 , wherein a defoamer can be added before or after the grinding process in a dosage ranging between 0.1 wt. % and 0.5 wt. %, based on the wet weight of the added polymer.