Vinylidene fluoride polymer polymerization
The present invention pertains to a vinylidene fluoride polymer, to a process for manufacturing said vinylidene fluoride polymer and to an article comprising said vinylidene fluoride polymer.
1 . A vinylidene fluoride polymer comprising more than 50% moles of recurring units derived from the polymerization of vinylidene fluoride monomer, said polymer (VDF) being characterized by having a size distribution with a D50 value higher than 250 microns.
2 . The vinylidene fluoride polymer of claim 1 , wherein the flowability of the polymer (VDF) is less than 50 seconds per 50 g with 5 minutes of manual shaking according to ASTM D 1895.
3 . A composition comprising at least one polymer (VDF) according to claim 1 .
4 . An article comprising the at least one polymer (VDF) according to the composition (C) according to claim 3 .
5 . The article according to claim 4 that is a component for secondary batteries.
6 . The article according to claim 4 that is a hydrophilic membrane.
7 . A process for manufacturing a vinylidene fluoride polymer in aqueous suspension, said process comprising polymerizing vinylidene fluoride monomer (VDF monomer) from a polymerization reaction mixture comprising:
A) at least a non-ionic suspending agent present in the polymerization reaction mixture in an amount of from 0.01 to 2 g per kg of VDF monomer; and
B) at least an ionic carboxyalkyl cellulose.
8 . The process according to claim 7 , wherein the non-ionic suspending agent is a polymer containing hydroxyl groups selected from the group consisting of:
a) polysaccharide derivatives;
b) partially hydrolysed polyvinylalcohol (PVAs); and
c) alkylene oxide polymers (PAOs).
9 . The process according to claim 8 , wherein the polysaccharide derivative is a carbohydrate comprising recurring β-D-glucopyranosides units of formula (I), linked to each other by β-glycosidic bonds:
wherein
each R′, equal to or different from any other at each occurrence, represents a hydrogen atom, a C 1 -C 8 hydrocarbon group or a C 2 -C 8 hydroxyalkyl group.
10 . The process according to claim 9 , wherein the carbohydrate comprising recurring β-D-glucopyranosides units of formula (I) is hydroxyethyl methylcellulose or 2-hydroxypropyl methylcellulose.
11 . The process according to claim 8 , wherein the partially hydrolysed polyvinylalcohol (PVA) is as an aqueous composition of partially hydrolyzed polyvinyl acetate and polyvinyl alcohol having a degree of hydrolysis of at least 80%.
12 . The process according to claim 8 , wherein the alkylene oxide polymer (PAO) is a polyethylene glycol having formula (IIb):
HO—(CH 2 CH 2 O) n —H (IIb)
wherein n is an integer from 1000 to 200000.
13 . The process according to claim 7 , wherein the ionic carboxyalkyl cellulose B) is present in the polymerization reaction mixture in an amount of from 0.05 to 10 g per kg of VDF monomer.
14 . The process according to claim 7 , wherein the amount of the at least an ionic carboxyalkyl cellulose B) is higher than that of the non-ionic suspending agent A).
15 . The process according to claim 7 , wherein the amount of the at least one ionic carboxyalkyl cellulose B) in the polymerization reaction mixture is higher than 0.5 g per kg of VDF monomer and the amount of the at least one non-ionic suspending agent A) is lower than 0.3 g per kg of VDF monomer.
16 . A vinylidene fluoride polymer obtained by the process according to claim 7 , wherein the flowability of the polymer (VDF) is less than 50 seconds per 50 g with 5 minutes of manual shaking according to ASTM D 1895.