Vinyl alcohol-vinyl acetate copolymer
The present invention provides a vinyl alcohol-vinyl acetate copolymer having excellent solubility and a method for producing a vinyl alcohol-vinyl acetate copolymer. Provided is a vinyl alcohol-vinyl acetate copolymer including a unit of vinyl alcohol and a unit of vinyl acetate, the vinyl alcohol-vinyl acetate copolymer having a randomness value R of 0.5 or higher, the randomness value R being obtained using the following equation (1): R = 1 L A + 1 L O ( 1 ) where L O represents a mean chain length of the unit of vinyl alcohol and L A represents a mean chain length of the unit of vinyl acetate.
1. A method for producing a vinyl alcohol-vinyl acetate copolymer comprising a unit of vinyl alcohol and a unit of vinyl acetate, wherein the vinyl alcohol-vinyl acetate copolymer has a randomness value R of 0.5 or higher, and wherein the randomness value R is obtained using the following equation (1):
R
=
1
L
A
+
1
L
O
(
1
)
where L O represents a mean chain length of the unit of vinyl alcohol and L A represents a mean chain length of the unit of vinyl acetate,
the method comprising the step of:
transesterification of polyvinyl acetate or a raw material vinyl alcohol-vinyl acetate copolymer using a dianionic zincate complex represented by the following formula (2):
t -Bu n R 4-n ZnM m (2)
where n represents an integer of 1 to 4, m represents 1 or 2, Rs may be the same as or different from one another when n represents 1 or 2 and each represent a C1-C8 alkyl, alkenyl, aryl, or arylalkyl group, and M represents lithium or magnesium.
2. The method for producing the vinyl alcohol-vinyl acetate copolymer according to claim 1 ,
wherein the dianionic zincate complex is dilithium tetra-t-butylzincate.
3. The method for producing the vinyl alcohol-vinyl acetate copolymer according to claim 1 ,
wherein the transesterification is performed in a homogeneous system.
4. The method for producing the vinyl alcohol-vinyl acetate copolymer according to claim 1 ,
wherein the transesterification is performed in a heterogeneous system.
5. The method for producing the vinyl alcohol-vinyl acetate copolymer according to claim 1 ,
wherein the vinyl alcohol-vinyl acetate copolymer has a mean chain length L O of the unit of vinyl alcohol of 1 or longer.
6. The method for producing the vinyl alcohol-vinyl acetate copolymer according to claim 1 ,
wherein the vinyl alcohol-vinyl acetate copolymer has a mean chain length L A of the unit of vinyl acetate of 1 or longer.
7. The method for producing the vinyl alcohol-vinyl acetate copolymer according to claim 1 ,
wherein the vinyl alcohol-vinyl acetate copolymer comprises the unit of vinyl alcohol in an amount of 0.2 to 99.8 mol %.
8. The method for producing the vinyl alcohol-vinyl acetate copolymer according to claim 2 ,
wherein the vinyl alcohol-vinyl acetate copolymer has a mean chain length L O of the unit of vinyl alcohol of 1 or longer.
9. The method for producing the vinyl alcohol-vinyl acetate copolymer according to claim 2 ,
wherein the vinyl alcohol-vinyl acetate copolymer has a mean chain length L A of the unit of vinyl acetate of 1 or longer.
10. The method for producing the vinyl alcohol-vinyl acetate copolymer according to claim 2 ,
wherein the vinyl alcohol-vinyl acetate copolymer comprises the unit of vinyl alcohol in an amount of 0.2 to 99.8 mol %.