Disclosed is a method for preparing an EVA copolymer with a high ethylene content by solution polymerization under a low to a medium pressure. The method comprises the following steps: initiating with a free radical initiator(s), a copolymerization reaction between ethylene and vinyl acetate in a solvent in a reactor under a low to a medium pressure to obtain the EVA copolymer; and continuing to add ethylene during the reaction to maintain the low to medium pressure, wherein the low to medium pressure is 1-101 MPa, and a ratio of a mass of the vinyl acetate to a mass of the initially added ethylene is (1:1) to (1:20). The amount of ethylene incorporated in the EVA copolymer prepared according to the method is ≥ 50 wt%, and the EVA copolymer has properties equivalent to those of an EVA copolymer obtained by bulk polymerization at high temperature under high pressure.

A binder for a secondary battery includes a copolymer having a first repeating unit, a second repeating unit, and a third repeating unit. A ratio of a number of the first repeating unit (A) and a sum of a number of the second repeating unit and a number of the third repeating unit (B) is 90:10 to 52:48. A ratio of the number of the second repeating unit and the number of the third repeating unit is 67:33 to 1:99. A weight average molecular weight of the copolymer is 225,000 to 2,000,000.

A binder for a secondary battery includes a copolymer having a first repeating unit, a second repeating unit, and a third repeating unit. A ratio of a number of the first repeating unit (A) and a sum of a number of the second repeating unit and a number of the third repeating unit (B) is 90:10 to 52:48. A ratio of the number of the second repeating unit and the number of the third repeating unit is 67:33 to 1:99. A weight average molecular weight of the copolymer is 225,000 to 2,000,000.

It is provided a process for producing an ethylene copolymer comprising compressing ethylene monomer at a certain pressure; adding a fresh comonomer in liquid form and, optionally, a fresh modifier in liquid form at a certain pressure to the compressed ethylene monomer; introducing the resulting compressed mixture into an autoclave reactor having a first reaction zone and at least one more reaction zone, the first reaction zone having a volume that is greater than 50% of the total reactor volume, and, optionally, at least one additional reactor; adding at least one free radical initiator in order to start a polymerization reaction; and separating the ethylene copolymer from the reaction mixture; wherein all the compressed ethylene monomer or the compressed mixture are introduced into the first reaction zone of the autoclave reactor, and wherein the compressed mixture is introduced into the autoclave reactor and, optionally, into the at least one additional reactor at a temperature from −20° C. to 70° C.

It is provided a process for producing an ethylene copolymer comprising compressing ethylene monomer at a certain pressure; adding a fresh comonomer in liquid form and, optionally, a fresh modifier in liquid form at a certain pressure to the compressed ethylene monomer; introducing the resulting compressed mixture into an autoclave reactor having a first reaction zone and at least one more reaction zone, the first reaction zone having a volume that is greater than 50% of the total reactor volume, and, optionally, at least one additional reactor; adding at least one free radical initiator in order to start a polymerization reaction; and separating the ethylene copolymer from the reaction mixture; wherein all the compressed ethylene monomer or the compressed mixture are introduced into the first reaction zone of the autoclave reactor, and wherein the compressed mixture is introduced into the autoclave reactor and, optionally, into the at least one additional reactor at a temperature from −20° C. to 70° C.

A vinyl alcohol copolymer, wherein the vinyl alcohol copolymer includes a vinyl alcohol unit and a constituent unit derived from an unsaturated monomer (A), the unsaturated monomer (A) is at least one selected from the group consisting of an unsaturated carboxylic acid, a salt thereof, an anhydride thereof, and an alkyl ester thereof, a content of the constituent unit derived from the unsaturated monomer (A) with respect to total constituent units of the vinyl alcohol copolymer is 1.00 mol % or more and 5.00 mol % or less, and 70 mol % or more of the constituent unit derived from the unsaturated monomer (A) forms a lactone ring structure.

A resin composition comprises: a modified vinyl alcohol-based polymer (A) containing from 1 to 20 mol % of a structural unit represented by a formula (1) below; and a layered inorganic compound (B). Such a resin composition is excellent in water vapor barrier properties, recyclability, and productivity during coating.

##STR00001##

A resin composition comprises: a modified vinyl alcohol-based polymer (A) containing from 1 to 20 mol % of a structural unit represented by a formula (1) below; and a layered inorganic compound (B). Such a resin composition is excellent in water vapor barrier properties, recyclability, and productivity during coating.

##STR00001##

A PVA excellent in resistance to melting at high temperature is provided. The polyvinyl alcohol-based polymer is a saponificated product of a homopolymer composed of a vinyl ester monomer, a copolymer of a vinyl ester monomer and a monofunctional monomer other than the vinyl ester, a copolymer of a vinyl ester monomer and a polyfunctional monomer, or a copolymer of a vinyl ester monomer, a monofunctional monomer other than vinyl ester, and a polyfunctional monomer has a particle size of 50 nm or more at a cumulative frequency of 50% in particle size distribution by dynamic light scattering measurement of a 0.4 mass % aqueous solution of the polyvinyl alcohol-based polymer at 25° C.

A PVA excellent in resistance to melting at high temperature is provided. The polyvinyl alcohol-based polymer is a saponificated product of a homopolymer composed of a vinyl ester monomer, a copolymer of a vinyl ester monomer and a monofunctional monomer other than the vinyl ester, a copolymer of a vinyl ester monomer and a polyfunctional monomer, or a copolymer of a vinyl ester monomer, a monofunctional monomer other than vinyl ester, and a polyfunctional monomer has a particle size of 50 nm or more at a cumulative frequency of 50% in particle size distribution by dynamic light scattering measurement of a 0.4 mass % aqueous solution of the polyvinyl alcohol-based polymer at 25° C.