The present invention relates to a method for preparing a polyamide resin, comprising the steps of: (a) preparing a polyamide polymer by anionically polymerizing a monomer including 2-pyrrolidone; (b) refining an unreacted monomer and a catalyst in the polyamide polymer with water; (c) pH-controlling through an ion exchange of the refined water; and (d) recovering the unreacted monomer by concentrating the pH-controlled water.

The present invention relates to a method for preparing a polyamide resin, comprising the steps of: (a) preparing a polyamide polymer by anionically polymerizing a monomer including 2-pyrrolidone; (b) refining an unreacted monomer and a catalyst in the polyamide polymer with water; (c) pH-controlling through an ion exchange of the refined water; and (d) recovering the unreacted monomer by concentrating the pH-controlled water.

To provide a method for producing a polymer, which contains: bringing a ring-opening polymerizable monomer containing an amide bond, and a compressive fluid into contact with each other to melt or dissolve the ring-opening polymerizable monomer containing an amide bond, followed by allowing the ring-opening polymerizable monomer containing an amide bond to react through ring-opening polymerization in the presence of a basic organic metal catalyst and a cocatalyst, to thereby obtain a polymer product.

To provide a method for producing a polymer, which contains: bringing a ring-opening polymerizable monomer containing an amide bond, and a compressive fluid into contact with each other to melt or dissolve the ring-opening polymerizable monomer containing an amide bond, followed by allowing the ring-opening polymerizable monomer containing an amide bond to react through ring-opening polymerization in the presence of a basic organic metal catalyst and a cocatalyst, to thereby obtain a polymer product.

A polyamide comprises a plurality of amide units forming a polymer chain, and an alkyl substituent on the amide group. The polyamide has a substitution of the amide units in an amount of between about 0.1% to about 10% of the amide units in the polymer chain. A method of forming a polyamide composition includes providing a that includes a plurality of amide groups in a backbone structure of the polyamide, and modifying a portion of the plurality of amide groups in the backbone structure with one or more alkyl substituents to form the polyamide composition. The polyamide has a substitution of the amide units in an amount of between about 0.1% to about 10% of the amide units in the backbone.

A polyamide comprises a plurality of amide units forming a polymer chain, and an alkyl substituent on the amide group. The polyamide has a substitution of the amide units in an amount of between about 0.1% to about 10% of the amide units in the polymer chain. A method of forming a polyamide composition includes providing a that includes a plurality of amide groups in a backbone structure of the polyamide, and modifying a portion of the plurality of amide groups in the backbone structure with one or more alkyl substituents to form the polyamide composition. The polyamide has a substitution of the amide units in an amount of between about 0.1% to about 10% of the amide units in the backbone.

Provided is an ester-amide multi-block copolymer represented by formula (1), which comprises a block containing a polyester and a block containing a polyamide obtained through ring opening polymerization of a cyclic lactam. (R1 and R2 each denote a hydrogen atom or a substituent group-containing alkyl chain having 1-20 carbon atoms, and R3 denotes a hydrogen atom or a substituent group-containing alkyl chain having 1-10 carbon atoms. In addition, R4 is an aromatic hydrocarbon chain that does, or does not, contain a heteroatom or an aliphatic hydrocarbon chain that does, or does not, contain a hetero atom. Y is NH, O or S. Furthermore, m denotes an integer between 1 and 60, n denotes an integer between 1 and 120, 1 denotes an integer between 2 and 100, and x denotes an integer between 1 and 11).

Provided is a polyamide resin, which is a copolymer of a biodegradable polyamide, such as polyamide 2 to polyamide 4, and another polyamide, the polyamide resin having enhanced biodegradability. The polyamide resin contains a structural unit represented by Formula (1) and another polyamide structural unit, and a difference between a degree of randomness determined based on a proportion of each structural unit as determined by .sup.1H-NMR measurement when structural units are assumed to have an ideal random sequence and a degree of randomness determined based on a proportion of carbonyl carbon of an amide group linking different structural units with respect to a total peak integrated value for carbonyl carbon as determined by .sup.13C-NMR measurement is 0.10 or less, where in Formula (1), x is an integer of 1 or greater and 3 or less.

##STR00001##

Provided is a polyamide resin, which is a copolymer of a biodegradable polyamide, such as polyamide 2 to polyamide 4, and another polyamide, the polyamide resin having enhanced biodegradability. The polyamide resin contains a structural unit represented by Formula (1) and another polyamide structural unit, and a difference between a degree of randomness determined based on a proportion of each structural unit as determined by .sup.1H-NMR measurement when structural units are assumed to have an ideal random sequence and a degree of randomness determined based on a proportion of carbonyl carbon of an amide group linking different structural units with respect to a total peak integrated value for carbonyl carbon as determined by .sup.13C-NMR measurement is 0.10 or less, where in Formula (1), x is an integer of 1 or greater and 3 or less.

##STR00001##

Polyamide fine particles include a polymer or a copolymer including a repeating structure unit represented by Formula (1) as a main component, wherein a ratio (r/A.sub.BET) of a porosity r occupying a particle surface and a BET specific surface area A.sub.BET that is a specific surface area of the particle surface measured by a BET method is 6.0 or more and 100.0 or less: ##STR00001##
wherein x is an integer of 2 or more and 3 or less.