The valve member according to one embodiment of the present disclosure is a resin formed product having a crosslinked ethylene-tetrafluoroethylene copolymer as a main component, and having a crosslinking density of 85.0 mol/m.sup.3 or more calculated from a storage modulus at 300° C.

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.

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.

The present invention pertains to a method for producing a copolymer of ethylene and an allyl monomer having a polar group represented by general formula (1), or a copolymer of ethylene, an allyl monomer having a polar group represented by general formula (1), and other monomers, wherein the copolymer is produced in the presence of a boron compound having a boron-hydrogen bond or a boron-carbon bond (for example, a compound represented by general formula (2)) by using a metal complex represented by general formula (C1) as a polymerization catalyst (the symbols in the formulas are as described in the description). According to the present invention, a copolymer of ethylene and an allyl monomer can be efficiently produced with high catalytic activity, wherein the copolymer has a polar group and can be used in various applications. ##STR00001##

The present invention pertains to a method for producing a copolymer of ethylene and an allyl monomer having a polar group represented by general formula (1), or a copolymer of ethylene, an allyl monomer having a polar group represented by general formula (1), and other monomers, wherein the copolymer is produced in the presence of a boron compound having a boron-hydrogen bond or a boron-carbon bond (for example, a compound represented by general formula (2)) by using a metal complex represented by general formula (C1) as a polymerization catalyst (the symbols in the formulas are as described in the description). According to the present invention, a copolymer of ethylene and an allyl monomer can be efficiently produced with high catalytic activity, wherein the copolymer has a polar group and can be used in various applications. ##STR00001##

The present invention pertains to a method for producing a copolymer of ethylene and an allyl monomer having a polar group represented by general formula (1), or a copolymer of ethylene, an allyl monomer having a polar group represented by general formula (1), and other monomers, wherein the copolymer is produced in the presence of a boron compound having a boron-hydrogen bond or a boron-carbon bond (for example, a compound represented by general formula (2)) by using a metal complex represented by general formula (C1) as a polymerization catalyst (the symbols in the formulas are as described in the description). According to the present invention, a copolymer of ethylene and an allyl monomer can be efficiently produced with high catalytic activity, wherein the copolymer has a polar group and can be used in various applications. ##STR00001##

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.

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.

The present invention relates to a method for preparing a catalyst, and in particular provides a method for preparing a catalyst suitable for the polymerisation of ethylene and/or propylene, said catalyst comprising a compound of yttrium, neodymium or scandium supported on a silica support, and wherein the method comprises: a) Treating a silica support by heating at a temperature of at least 550° C., b) Contacting the treated silica support with a complex of the following formula: D.sub.mMX.sup.1X.sup.2R wherein M is selected from Y, Sc and Nd, R is a hydrocarbyl group, X.sup.1 and X.sup.2 are anionic groups, D is a neutral donor group, and m is 0 or greater.