Hydrophilic vinylidene fluoride polymers

Abstract

The present invention pertains to a process for the manufacture of a grafted fluorinated polymer comprising at least one grafted side chain comprising one or more glycosidic recurring units [polymer (F)], said process comprising polymerizing: vinylidene fluoride (VDF), optionally, one or more other fluorinated monomers [monomers (F)], and optionally, one or more (meth)acrylic monomers [monomers (MA)],
in the presence of at least one polysaccharide derivative [derivative (P)], said polysaccharide derivative having a dynamic viscosity of less than 15 mPas, as measured according to ASTM D445 at 20 C. in an aqueous solution at a concentration of 2% by weight,
and by further providing novel polymers (F) as defined above.

Claims

1. A process for the manufacture of a grafted fluorinated polymer comprising at least one grafted side chain comprising one or more glycosidic recurring units [polymer (F)], said process comprising polymerizing: vinylidene fluoride (VDF), optionally, one or more other fluorinated monomers, and optionally, one or more (meth)acrylic monomers, in the presence of at least one polysaccharide derivative, said polysaccharide derivative having a dynamic viscosity of at most 12 mPas, as measured according to ASTM D445 at 20 C. in an aqueous solution at a concentration of 2% by weight.

2. The process of claim 1, wherein the polysaccharide derivative comprises as recurring units glycosidic units selected from the group consisting of D-glucopyranosides linked to each other by glycosidic bonds.

3. The process of claim 1, wherein the polysaccharide derivative is selected from the group consisting of cellulose derivatives comprising as recurring units -D-glucopyranosides of formula (III-b) linked to each other by -glycosidic bonds, wherein OR.sub.b is a -glycosidic bond, R.sub.b is a glycosidic unit and R, equal to or different from each other, represent a hydrogen atom or a hydrocarbon group: ##STR00008##

4. The process of claim 1, wherein the polysaccharide derivative has a dynamic viscosity comprised between 2 and 10 mPas, as measured according to ASTM D445 at 20 C. in an aqueous solution at a concentration of 2% by weight.

5. The process of claim 1, wherein one or more suspension stabilizers are used.

6. A fluorinated polymer [polymer (F)] comprising: a main chain comprising recurring units derived from vinylidene fluoride (VDF), optionally, recurring units derived from one or more other fluorinated monomersand, optionally, recurring units derived from one or more (meth)acrylic monomers, and at least one side chain grafted to said main chain, said grafted side chain comprising one or more glycosidic recurring units.

7. The polymer of claim 6, comprising at least 40 ppm of hydrogen atoms of one or more glycosidic recurring units in at least one grafted side chain of polymer (F) with respect to the total amount of hydrogen atoms of VDF recurring units in the main chain of polymer (F).

8. The polymer of claim 6, wherein at least one side chain comprises one or more -D-glucopyranosides of formula (III-b) ##STR00009## wherein OR.sub.b is a -glycosidic bond, R.sub.b is a glycosidic unit and R, equal to or different from each other, represent a hydrogen atom or a hydrocarbon group and wherein the -D-glucopyranosides of formula (III-b) are linked to each other by -glycosidic bonds.

9. A composition comprising the polymer of claim 6 and at least one VDF polymer.

10. A hydrophilic membrane comprising the polymer of claim 6 or the composition of claim 9.

11. The polymer of claim 7, comprising at least 50 ppm of hydrogen atoms of one or more glycosidic recurring units in at least one grafted side chain of polymer (F) with respect to the total amount of hydrogen atoms of VDF recurring units in the main chain of polymer (F).

12. The polymer of claim 7, comprising at least 60 ppm of hydrogen atoms of one or more glycosidic recurring units in at least one grafted side chain of polymer (F) with respect to the total amount of hydrogen atoms of VDF recurring units in the main chain of polymer (F).

13. The polymer of claim 6, wherein the glycosidic recurring units comprise one or more OH groups that have been converted into ether groups of formula OR, wherein R is selected from the group consisting of CH.sub.2CH(OH)CH.sub.3, CH.sub.2CH(OCH.sub.3)CH.sub.3 and (CH.sub.2CH(CH.sub.3)O).sub.xCH.sub.2CH(CH.sub.3)OH, wherein x is an integer of at least 1.

14. The process of claim 1, wherein the polysaccharide derivative has a dynamic viscosity of at most 6 mPas, as measured according to ASTM D445 at 20 C. in an aqueous solution at a concentration of 2% by weight.

15. The process of claim 1, wherein the glycosidic recurring units comprise one or more OH groups that have been converted into ether groups of formula OR, wherein R is selected from the group consisting of CH.sub.2CH(OH)CH.sub.3, CH.sub.2CH(OCH.sub.3)CH.sub.3 and (CH.sub.2CH(CH.sub.3)O).sub.xCH.sub.2CH(CH.sub.3)OH, wherein x is an integer of at least 1.

Description

EXAMPLES 1-3

(1) Manufacture of Polymer (F)

(2) In a 4 liter reactor equipped with an impeller running at a speed of 880 rpm were subsequently introduced 2050 g of demineralized water, METHOCEL K3 cellulose ether and, optionally, METHOCEL K100 in the amounts as detailed in Table 1 here below.

(3) The reactor was then repeatedly evacuated and purged with nitrogen (1 bar) while maintaining the temperature at 14 C. Then, 24.5 g of diethylcarbonate/kg of VDF fed, 1 g/kg of VDF fed of a 75% by weight solution of tert-amyl perpivalate radical initiator in isododecane and 1346 g of VDF were introduced into the reactor. The reactor was then gradually heated until the set-point temperature of 52 C. was attained, which corresponded to a pressure of 120 bar. The pressure was kept constantly equal to 120 bar during the whole polymerization run by feeding water. After conversion of about 80-90% of the VDF, the polymerization was stopped by degassing the suspension until reaching atmospheric pressure. The polymer was then collected by filtration, washed with demineralized water and oven-dried at 50 C.

(4) A polymer was obtained having an intrinsic viscosity of 0.15 l/g at 25 C. in dimethylformamide and a particle size of about 100-120 m (D50).

COMPARATIVE EXAMPLE 1

(5) Manufacture of VDF Homopolymer

(6) The same procedure as detailed in Examples 1 to 3 according to the invention was followed but without using a polysaccharide derivative having a dynamic viscosity of less than 15 mPas, as measured according to ASTM D445 at 20 C. in an aqueous solution at a concentration of 2% by weight (see Table 1 here below).

(7) The amounts of METHOCEL K3 cellulose ether and, optionally, of METHOCEL K100 suspension stabilizer fed to the polymerization reactor are reported in Table 1 here below:

(8) TABLE-US-00001 TABLE 1 METHOCEL K3 METHOCEL K100 Run [g/Kg VDF fed] [g/Kg VDF fed] Example 1 0.5 0.4 Example 2 2.5 Example 3 5.0 Comparative 0.4 Example 1

(9) The results of the hydrophilicity tests as detailed above are reported in Table 2 here below:

(10) TABLE-US-00002 TABLE 2 H.sub.grafted glycosidic units/ H.sub.VDF polymer Bottom phase Top phase Run [ppm] [% by weight] [% by weight] Example 1 69 ppm 66% 34% Example 2 139 ppm 94% 6% Example 3 252 ppm 87% 13% Comparative 36% 64% Example1

(11) Data shown in Table 2 here above demonstrated that the polymer obtained by the process of the invention is successfully grafted with one or more glycosidic recurring units in an amount of advantageously at least 40 ppm, preferably at least 50 ppm, more preferably at least 60 ppm of hydrogen atoms with respect to the total amount of hydrogen atoms of VDF recurring units in the main chain of polymer (F), even at low levels of glycosidic recurring units grafted to VDF polymer main chain, so that the polymer so obtained successfully exhibits the targeted hydrophilic surface properties, while maintaining outstanding mechanical and thermal stability typical of PVDF.