Highly miscible polymer blends and uses thereof
Compositions comprise a highly miscible polymer blend of at least one cellulose derivative and at least one polysiloxane additive of formula [R 1 R 2 R 3 SiO 0.5 ] a [R 4 R 5 SiO] b [R 6 SiO 1.5 ] c [SiO 2 ] d , wherein the substituents R 1 , R 2 , R 3 , R 4 , R 5 and R 6 each independently represents a hydrocarbon group or a functional group selected from a hydroxyl group, an acyloxy group or an alkoxy group, and may be the same or different from each other with respect to each individual silicon atom, and 0≦a≦0.4, 0.01≦b≦0.99, 0.01≦c≦0.99, 0≦d≦0.3, under the proviso that at least one hydrocarbon group and at least one functional group are present and a+b+c+d=1. Articles such as optical films comprising such a composition exhibit improved moisture barrier properties, reduced and adjustable out of plane retardation, adjustable glass transition temperature and provide for a facile generation of hydrophilic surface properties without considerable difference of the mechanical properties compared to corresponding articles of the pure cellulose derivative. A method to prepare such optical films, which can be particularly useful as retardation or protection films for polarizing plates in liquid crystal display devices, is also provided.
1. A composition comprising a miscible blend of:
A) at least one cellulose derivative, and
B) at least one polysiloxane of the formula
[R 1 R 2 R 3 SiO 0.5 ] a [R 4 R 5 SiO] b [R 6 SiO 1.5 ] c [SiO 2 ] d
wherein the substituents R 1 , R 2 , R 3 , R 4 , R 5 and R 6 each independently represent a hydrocarbon group or a functional group selected from the group consisting of hydroxyl groups, acyloxy groups or alkoxy groups, and may be the same or different from each other with respect to each individual silicon atom, and
0≦ a≦ 0.4,
0.01≦ b≦ 0.99,
0.01≦ c≦ 0.99,
0≦ d≦ 0.3,
under the proviso that at least one hydrocarbon group and at least one functional group are present and a+b+c+d=1.
2. The composition of claim 1 , wherein the sum of b+c is in a range from 0.7 to 1 or the ratio c/b is in a range of 5:1 to 1:10.
3. The composition of claim 1 , wherein the at least one hydrocarbon group is selected from the group consisting of alkyl, cycloalkyl, aryl and aralkyl groups having 1 to 12 carbon atoms or a mixture of any of the foregoing.
4. The composition of claim 1 , wherein a single type of functional group is present, the at least one functional group being a hydroxyl group.
5. The composition of claim 1 , wherein the polysiloxane has a weight average molecular weight as measured by gel permeation chromatography using polystyrene standards in the range of 1,000 to 300,000 g/mol.
6. The composition of claim 1 , wherein the polysiloxane contains silicon-bound hydroxyl groups in an amount of 0.1 to 15 wt. % based on the total weight of the polysiloxane.
7. The composition of claim 1 , wherein the cellulose derivative is a cellulose ether.
8. The composition of claim 1 comprising the at least one polysiloxane in an amount of 0.1 to 90 wt. % and the cellulose derivative in an amount of 10 to 99.9 wt. %, each based on the total weight of solids of the composition.
9. An article comprising a composition as set forth in claim 1 .
10. A method of manufacturing an optical film comprising:
providing a solution comprising at least one cellulose derivative and at least one polysiloxane as set forth in claim 1 , and a solvent,
casting said solution onto a support, and
drying the cast film at least partially.
11. The method of claim 10 comprising stretching the at least partially dried film mechanically in at least one direction or subjecting the film to a surface treatment.