Process for producing epsilon-caprolactam by depolymerization of polycaprolactam (PA6)
The present invention relates to a process for producing ε-caprolactam by depolymerization of polycaprolactam (PA6) which comprises: a. contacting a composite material comprising PA6 and at least one fibrous reinforcing material with a solvent comprising at least one polyol, at a temperature in the range 130° C. 200° C. so as to obtain a solution comprising solubilized PA6 and an insoluble fraction comprising at least said fibrous reinforcing material; b. separating said insoluble fraction from said solution; c. combining said solution with a coagulation liquid comprising water to obtain a partially depolymerized coagulated PA6 dispersed in a liquid phase; d. separating said coagulated PA6 from said liquid phase; e. subjecting said coagulated PA6 separated in said phase d to further depolymerization by hydrolysis to obtain ε-caprolactam.
1 . A process for producing ε-caprolactam by depolymerization of polycaprolactam (PA6), comprising:
contacting a composite material comprising PA6 and at least one fibrous reinforcing material with a solvent comprising at least one polyol, at a temperature of 130° C. to 200° C., to obtain a solution comprising solubilized PA6 and an insoluble fraction comprising the at least one fibrous reinforcing material;
separating the insoluble fraction from the solution;
combining the solution with a coagulation liquid comprising water to obtain a partially depolymerized coagulated PA6 dispersed in a liquid phase;
separating the coagulated PA6 from the liquid phase; and
subjecting the coagulated PA6 separated from the liquid phase to further depolymerization by hydrolysis to obtain ε-caprolactam.
2 . The process according to claim 1 , wherein, when combining the solution with the coagulation liquid, the coagulation liquid has a temperature of 50° C. to 95° C.
3 . The process according to claim 1 , wherein the composite material comprises PA6 in an amount of 50% to 95% by weight with respect to a total weight of PA6 and the fibrous reinforcing material.
4 . The process according to claim 1 , wherein the composite material comprises the fibrous reinforcing material in an amount of 5% to 50% by weight with respect to a total weight of PA6 and the fibrous reinforcing material.
5 . The process according to claim 1 , wherein the solvent comprises at least one glycol.
6 . The process according to claim 5 , wherein the solvent comprises at least one selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, and butylene glycol.
7 . The process according to claim 1 , wherein contacting the composite material with the solvent comprises contacting at a temperature of 150 to 170° C.
8 . The process according to claim 1 , wherein contacting the composite material with the solvent comprises contacting at a weight ratio of the composite material to the solvent of 1:1 to 1:50.
9 . The process according to claim 1 , wherein combining the solution with the coagulation liquid comprises combining at a weight ratio of the solution to the coagulation liquid of 1:1 to 1:10.
10 . The process according to claim 1 , wherein the depolymerization by hydrolysis is carried out in the presence of at least one acid catalyst.
11 . The process according to claim 1 , wherein, when combining the solution with the coagulation liquid, the coagulation liquid has a temperature of 80° C. to 95° C.
12 . The process according to claim 1 , wherein the composite material comprises PA6 in an amount of 55% to 90% by weight with respect to a total weight of PA6 and the fibrous reinforcing material.
13 . The process according to claim 1 , wherein the composite material comprises PA6 in an amount of 60% to 85% by weight with respect to a total weight of PA6 and the fibrous reinforcing material.
14 . The process according to claim 1 , wherein the composite material comprises the fibrous reinforcing material in an amount of 10% to 45% by weight with respect to a total weight of PA6 and the fibrous reinforcing material.
15 . The process according to claim 1 , wherein the composite material comprises the fibrous reinforcing material in an amount of 15% to 40% by weight with respect to a total weight of PA6 and the fibrous reinforcing material.
16 . The process according to claim 1 , wherein contacting the composite material with the solvent comprises contacting at a weight ratio of the composite material to the solvent of 1:2 to 1:25.
17 . The process according to claim 1 , wherein combining the solution with the coagulation liquid comprises combining at a weight ratio of the solution to the coagulation liquid of 1:1 to 1.