PROCESS FOR POLYMERIZING CYCLIC OLIGOMERS OF POLYAMIDES
A process tear production of high molecular weight polyamide polymers, such as 6/66 copolymers, using a reactant stream that includes at least one lactam and cyclic oligomers. The stream is reacted with at least one diamine at an elevated temperature ring-open the cyclic oligomers to produce amide pre-polymers that are end-capped with amine groups. The pre-polymers are then reacted with at least one diacid at an elevated temperature to form polyamide 6/66 copolymers. The cyclic oligomers may be formed as by-products during standard polymerization of polyamide polymers from monomers such as caprolactam, hexamethylene diamine and adipic acid.
1 . A process for production of polyamide 6/66 copolymer, comprising the steps of:
providing a reactant stream comprising at least one lactam and cyclic oligomers;
reacting the reactant stream with at least one diamine to ring-open the at least one lactam and the cyclic oligomers to produce amide pre-polymers, the amide pre-polymers including amine end groups; and
subsequently reacting the amide pre-polymers with at least one diacid to form polyamide 6/66 copolymer.
2 . The process of claim 1 , wherein in the providing step, the reactant stream includes at least 10 wt. % cyclic oligomers, based on the total weight of the reactant stream.
3 . The process of claim 1 , wherein in the first reacting step, between 0.5 and 20 wt. % of the at least one diamine is used, based on the total weight of the reactant stream.
4 . The process of claim 1 , wherein in the second reacting step, a stoichiometric amount in the form of a 1:1 molar ratio of the at least one diacid is used relative to the amount of diamine used in the first reacting step.
5 . The process of claim 1 , wherein in the second reacting step, a ratio of diacid to diamine used in the first reacting step is from 0.8:1 to 1.2:1.
6 . The process of claim 1 , wherein the cyclic oligomers include caprolactam dimers and C3-C9 analogs.
7 . The process of claim 1 , wherein the at least one lactam comprises caprolactam.
8 . The process of claim 1 , wherein the at least one diamine comprises hexamethylene diamine.
9 . The process of claim 1 , wherein the at least one diacid comprises adipic acid.
10 . The process of claim 1 , wherein the first reacting step is conducted at an elevated temperature of between 220° C. and 280° C.
11 . The process of claim 1 , wherein the second reacting step is conducted at an elevated temperature of between 220° C. and 280° C.
12 . The process of claim 1 , wherein the polyamide 6/66 copolymer has a relative viscosity (RV) between 2.0 and 4.5 as determined by ISO 307:2007.
13 . The process of claim 1 , wherein the polyamide 6/66 copolymer has a formic acid viscosity (FAV) between 30 and 150 as determined by ASTM D-789-07.
14 . A process for production of polyamide 6/66 copolymer, comprising the steps of:
producing a primary polyamide polymer including a by-product composition including at least one lactam and cyclic oligomers;
separating the by-product composition from the primary polyamide polymer;
reacting the by-product composition with at least one diamine to ring-open the at least one lactam and the cyclic oligomers to produce amide pre-polymers, the amide pre-polymers including amine end groups; and
reacting the amide pre-polymers with at least one diacid to form a polyamide 6/66 copolymer.
15 . The process of claim 14 , wherein in the first reacting step, the by-product composition includes at least 15 wt. % cyclic oligomers.
16 . The process of claim 14 , wherein in the first reacting step, between 0.5 and 20 wt. % of the at least one diamine is used.
17 . The process of claim 14 , wherein in the second reacting step, a stoichiometric amount in the form of a 1:1 molar ratio of the at least one diacid is used relative to the amount of diamine used in the first reacting step.
18 . The process of claim 14 , wherein in the second reacting step, a ratio of diacid to diamine used in the first reacting step is from 0.8:1 to 1.2:1.
19 . The process of claim 14 , wherein the secondary polyamide 6/66 copolymer has a relative viscosity (RV) between 2.0 and 4.5 as determined by ISO 307:2007 and a formic acid viscosity (FAV) between 30 and 150 as determined by ASTM D:789-07.
20 . The process of claim 14 , wherein the first reacting step is conducted at an elevated temperature of between 230° C. and 280° C., and the second reacting step is conducted at an elevated temperature of between 230° C. and 280° C.