Provided are a method for producing a polyamide including an amide-based molecular weight controller and a polyamide produced thereby, wherein the amide-based molecular weight controller may easily control the molecular weight of the polyamide to have a narrow molecular weight distribution so as to prevent an increase in the molecular weight due to a basic intermediate produced in anionic polymerization and a side reaction generated under a high-temperature polymerization condition.

Provided is a polyamide composition including a linear and high molecular weight polyamide and having a low residual monomer content. The composition includes a polyamide having a site formed of repeating structural units having at least one alkylene group and at least one amide bond, each of the at least one alkylene group having a carbon number of 1 to 3, the polyamide having a linear structure with a weight average molecular weight of 200000 or greater, and the content of the included raw material monomer, which is a raw material of the structural units, being less than 1000 ppm.

The present invention provides a method for producing a polyamide with controlled activator addition, and a polyamide produced thereby, the method allowing a polymerization conversion rate and a polydispersity index (PDI) to be enhanced by controlling the addition of an activator so as to prevent a gelation phenomenon that occurs during anionic polymerization.

The present invention provides a method for producing a polyamide with controlled activator addition, and a polyamide produced thereby, the method allowing a polymerization conversion rate and a polydispersity index (PDI) to be enhanced by controlling the addition of an activator so as to prevent a gelation phenomenon that occurs during anionic polymerization.

Provided is a method for preparing a polyamide by an anionic polymerization reaction, wherein lactam, and based on 100 parts by weight of the entire lactam, 0.01 parts by weight to 20 parts by weight of an alkali metal as an initiator, 0.3 parts by weight to 10 parts by weight of a molecular weight controller, and 0.002 parts by weight to 1.0 part by weight of carbon dioxide as an activator may be included.

Provided is a method for preparing a polyamide by an anionic polymerization reaction, wherein lactam, and based on 100 parts by weight of the entire lactam, 0.01 parts by weight to 20 parts by weight of an alkali metal as an initiator, 0.3 parts by weight to 10 parts by weight of a molecular weight controller, and 0.002 parts by weight to 1.0 part by weight of carbon dioxide as an activator may be included.

The present invention is to provide a spherical polyamide fine particle having smooth sliding properties and causing a low degree of environmental pollution. The polyamide fine particle according to the present invention includes: a polyamide including a repetition of a structural unit having at least one alkylene group and at least one amide bond, each of the at least one alkylene group having from 1 to 5 carbon atoms, wherein the polyamide fine particle has a sphericity of 80 or greater.

The present invention is to provide a spherical polyamide fine particle having smooth sliding properties and causing a low degree of environmental pollution. The polyamide fine particle according to the present invention includes: a polyamide including a repetition of a structural unit having at least one alkylene group and at least one amide bond, each of the at least one alkylene group having from 1 to 5 carbon atoms, wherein the polyamide fine particle has a sphericity of 80 or greater.

A system for manufacturing a thermoplastic prepreg includes a double belt mechanism that is configured to compress a fiber mat, web, or mesh that is passed through the double belt mechanism, a resin applicator that is configured to apply monomers or oligomers to the fiber mat, web, or mesh, and a curing oven that is configured to effect polymerization of the monomers or oligomers and thereby form the thermoplastic polymer as the fiber mat, web, or mesh is moved through the curing oven. The double belt mechanism compresses the fiber mat, web, or mesh and the applied monomers or oligomers as the fiber mat, web, or mesh is passed through the curing oven so that the monomers or oligomers fully saturate the fiber mat, web, or mesh. Upon polymerization of the monomers or oligomers, the fiber mat, web, or mesh is fully impregnated with the thermoplastic polymer.

The present specification provides a composition for interfacial polymerization of polyamide including at least one of an amine compound and an acyl halide compound; a surfactant; and a compound represented by Chemical Formula 1, and a method for preparing a reverse osmosis membrane using the same.