Functionalized halogenated polymers for microencapsulation
View Patent ↗The present invention is directed to a novel reactive protective colloid system suitable for stabilizing an electrophoretic display in which a halogenated solvent, particularly a fluorinated, more particularly a perfluorinated, solvent, or a mixture thereof, is used as the dielectric solvent.
1. A microencapsulation process for preparing pigment microcapsules, which process comprises:
(a) forming an internal phase which comprises pigment particles dispersed in a reactive monomer or oligomer and optionally a fugitive solvent;
(b) forming a continuous phase which comprises a reactive protective colloid of Formula (I):
R-[Q-L-(A)m]n (I)
wherein m and n are independently natural numbers which are ≧1;
Q is a linking moiety and L is a linking group; Q and L together is a linking chain;
A is a reactive functional group;
R is represented by the following formula:
wherein the open and not designated substituent positions on the main chain are independently selected from the group consisting of hydrogen, halogen, alkyl, aryl, alkylaryl, fluoroalkyl, fluoroaryl, fluoroalkylaryl, —COOR 1 , —CONR 1 R 2 , and substituted derivatives thereof, wherein R 1 and R 2 are independently hydrogen, alkyl, aryl, alkylaryl, fluoroalkyl, fluoroaryl, fluoroalkylaryl or fluorinated polyether;
Z 1 , Z 2 , and Z 3 are independently oxygen or absent;
a, b and c are the weight fractions of the corresponding repeating units and are independently in the range of 0-1 with their sum no greater than 1, and
R comprises at least 20 wt % of fluorine;
(c) emulsifying said internal phase into said continuous phase to cause interfacial reaction between the reactive monomer or oligomer in said internal phase and the reactive protective colloid in said continuous phase; and
(d) forming pigment microcapsules each comprising a hard shell and pigment particles, wherein said hard shell is around the pigment particles.
2. The microencapsulation process of claim 1 , wherein said fugitive solvent in the internal phase is a fugitive solvent having a boiling point less than 150° C. at 1 atm.
3. The microencapsulation process of claim 2 wherein said fugitive solvent in the internal phase is a fugitive solvent having a boiling point less than 100° C. at 1 atm.
4. The microencapsulation process of claim 1 wherein said continuous phase further comprises a fluorinated solvent selected from the group consisting of perfluoroalkanes, perfluoalkylbenzenes, perfluoro-tert-amines and fluoropolymers.
5. The microencapsulation process of claim 4 wherein said fluoropolymer is perfluoropolyether, poly(perfluoroalkyl acrylate) or poly(perfluoroalkyl methacrylate).
6. The microencapsulation process of claim 1 wherein said interfacial reaction is accomplished through one of the following pairings: amine/isocyanate, amine/thioisocyanate, amine/anhydride, amine/acid chloride, aminekhloroformate, amine/epoxide, alcohol/isocyanate, alcohol/thioisocyanate, thiol/isocyanate, thiol/thioisocyanate, carbodiimide/epoxide or alcohol/silyl.
7. The microencapsulation process of claim 1 wherein the internal phase is further hardened by solvent evaporation, in-situ radical, ring-opening, condensation polymerization, condensation crosslinkling, or a combination thereof.
8. The microencapsulation process of claim 1 wherein said continuous phase further comprises a second reactive monomer or oligomer.
9. The microencapsulation process of claim 8 wherein said second reactive monomer or oligomer is a polyfunctional amine.
10. The microencapsulation process of claim 8 wherein said second reactive monomer or oligomer is tris-(2-aminoethyl)amine.
11. The microencapsulation process of claim 8 wherein said second reactive monomer or oligomer is an (1:1) precondensate product of tris-(2-aminoethyl)amine and CF 3 CF 2 CF 2 COOCH 3 .
12. The microencapsulation process of claim 1 wherein m and n are independently 1 to 10.
13. The microencapsulation process of claim 1 wherein m and n are independently 2 to 6.
14. The microencapsulation process of claim 1 wherein the linking moiety Q is ether, thioether, amide, imide, urea, thiourea, urethane, thiourethane, ester, carbonate, imine, amine or a derivative thereof.
15. The microencapsulation process of claim 14 wherein said linking moiety is amide.
16. The microencapsulation process of claim 14 wherein said linking moiety is urethane.
17. The microencapsulation process of claim 1 wherein R comprises at least 50 wt % of fluorine.
18. The microencapsulation process of claim 1 wherein A is an amino or an isocyanate group.
19. The microencapsulation process of claim 18 wherein m is ≧2.
20. The microencapsulation process of claim 19 wherein m is 2.
21. The microencapsulation process of claim 1 wherein the open and not designated substituent positions on the main chain is substituted with one or more fluorine atoms or trifluoromethyl groups, Z 1 is oxygen, Z 3 is absent, a is 0.8-0.995, b is 0, and c is 0.005-0.2.
22. The microencapsulation process of claim 21 wherein A is —NH 2 group, m is 2 and -Q-L- is a linking chain with an amide linking moiety.
23. The microencapsulation process of claim 1 wherein the open and not designated substituent positions on the main chain is substituted with one or more fluorine atoms or trifluoromethyl groups, Z 1 is oxygen, Z 2 is absent, c is 0, a is 0.8 to 0.995, and b is 0.005 to 0.2.
24. The microencapsulation process of claim 23 wherein A is isocyanate group, m is 2 and -Q-L- is a linking chain with an urethane or urea linking moiety.