WO2014179034A1

WO2014179034A1 - Polyamide synthesis including multiple back-ends

Info

Publication number: WO2014179034A1
Application number: PCT/US2014/034106
Authority: WO
Inventors: Thomas A. Micka; Charles R. KELMAN; John P. POINSATTE; Gary R. West
Original assignee: Invista North America S.A.R.L.
Priority date: 2013-05-01
Filing date: 2014-04-15
Publication date: 2014-11-06
Also published as: CN110938205A; CN104130399A; TW201502163A

Abstract

The present invention relates to methods, systems, and apparatus for synthesizing a polyamide and including multiple back-ends. The method can be a method of synthesizing a polyamide, including evaporating a mixture comprising an oligomer formed from a linear dicarboxylic acid and a linear diamine sufficient to remove at least some water from the mixture, to provide a pre-finished mixture. The method can include splitting the pre-finished mixture into at least a first pre-finished mixture and a second pre-finished mixture. The method can include finishing the first pre-finished mixture in a first finisher, to provide a first finished mixture comprising a first polyamide. The method can include finishing the second pre-finished mixture in a second finisher, to provide a second finished mixture comprising a second polyamide.

Description

POLYAMIDE SYNTHESIS INCLUDING MULTIPLE BACK-ENDS

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application Serial No. 61/818,169, filed May 1, 2013, the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND OF THE INVENTION

[0002] Polyamides have useful properties such as extreme durability and strength that makes them useful in a variety of settings. Polyamides such as nylons, aramids, and sodium poly(aspartate) are commonly used in, for example, carpet, airbags, machine parts, apparel, ropes, and hoses. Nylon 6,6, a silky thermoplastic material, is one of the most commonly used polyamides. Nylon 6,6' s long molecular chains and dense structure qualifies it as a premium nylon fiber, which exhibits high mechanical strength, rigidity, and stability under heat.

[0003] Polyamides are commercially synthesized in large-scale production facilities. For example, nylon 6,6 can be synthesized by allowing

hexamethylenediamine and adipic acid to undergo a condensation reaction, forming amide linkages and releasing water. In a series of components including an evaporator, reactor, a flasher, and a finisher, heat is applied to the reaction mixture and water is gradually removed to drive the equilibrium toward the polyamide, until the polymers reach the desired range of lengths. Then, the molten nylon 6,6 is extruded into pellets which can be spun into fibers or processed into other shapes.

[0004] Current methods and apparatus for manufacture of polyamides experience certain problems. Certain components of the back-end of the process, such as the finisher, the flasher, or the reactor, can only be economically built to a certain size. Thus, the size of the back-end of the process limits the size of the entire process. When any component in the back-end requires shut down for maintenance, which can be a difficult and burdensome procedure, the entire production process must be shut down. In addition, most methods and apparatuses for synthesis of polyamides can only make type of polyamide, for example a polyamide having a single range of relative viscosities. Also, the process can either be batch or continuous, but not both. As explained herein, the present invention can provide solutions to these problems.

SUMMARY OF THE INVENTION

[0005] The present invention provides a method of synthesizing a polyamide. The method can include evaporating a mixture including an oligomer formed from a linear dicarboxylic acid and a linear diamine. The evaporation can be sufficient to remove at least some water from the mixture. The evaporation can provide a pre-finished mixture. The method can include splitting the pre-finished mixture into at least a first pre-finished mixture and a second pre-finished mixture. The method can include finishing the first pre-finished mixture in a first finisher, to provide a first finished mixture including a first polyamide. The method can include finishing the second pre-finished mixture in a second finisher, to provide a second finished mixture including a second polyamide.

[0006] The present invention provides a system for synthesizing a polyamide. The system can include an evaporator configured to remove at least some water from a mixture including an oligomer formed from a linear dicarboxylic acid and a linear diamine. In some embodiments the system has a separate salt strike, while in other embodiments the salt strike and the evaporator are combined. The evaporator can provide a pre-finished mixture. The system can include a splitter configured to split the pre-finished mixture into at least a first pre-finished mixture and a second pre-finished mixture. The system can include a first finisher configured to finish the first pre-finished mixture. The first finisher can provide a first finished mixture including a first polyamide. The system includes a second finisher configured to finish the second pre-finished mixture. The second finisher can provide a second finished mixture including a second polyamide.

[0007] The present invention provides an apparatus for synthesizing a polyamide. The apparatus can include an evaporator configured to remove at least some water from a mixture including an oligomer formed from a linear dicarboxylic acid and a linear diamine. The evaporator can provide a pre-finished mixture. The apparatus can include a splitter configured to split the pre-finished mixture into at least a first pre-finished mixture and a second pre-finished mixture. The apparatus can include a first finisher configured to finish the first pre-finished mixture. The first finisher can provide a first finished mixture including a first polyamide. The apparatus can include a second finisher configured to finish the second pre-finished mixture. The second finisher can provide a second finished mixture including a second polyamide.

[0008] The present invention can provide advantages over other methods, systems, and apparatus for making polyamides, at least some of which are unexpected. For example, certain components of the back-end of a conventional process, such as the finisher, the flasher, or the reactor, can only be economically built to a certain size. When the system is built to a larger size, the cost of the reactor, the finisher, or the flasher can become prohibitively high. When the system is built to a larger size, the cost of operating the finisher can unexpectedly become higher, and the finisher can be less efficient, due to the exponentially larger torque experienced when stirring large quantities of viscous polymer, and the

correspondingly strong forces upon the finisher agitator/scraper can make the finisher in particular exponentially expensive at larger scales. In addition, the limits of larger scale stirring in the finisher can make the finisher less effective, requiring a slower throughput to remove the desired amount of water, despite the larger size. Thus, the size of the back-end of the process can limit the size of the entire process. However, the present invention can provides a method or apparatus having multiple back-ends, such as two or more back-ends. Therefore, the present invention can avoid the capacity bottleneck caused by the back-ends of most other processes. In various embodiments, surprisingly, the multiple back ends can provide more economical equipment cost and more economical run- time cost, while providing a higher overall throughput, as compared to a system or method lacking multiple back ends. [0009] Most methods and apparatuses for synthesis of polyamides can only make type of polyamide, for example a polyamide having a single range of relative viscosities. However, the present invention can provide a method or apparatus having multiple back-ends wherein at least two different types of polyamides are generated, for example one polyamide having one range of relative viscosities, and another polyamide having another range of relative viscosities. Most methods and apparatuses for synthesis of polyamides can either be continuous or batch, but not both. However, the present invention can provide a method or apparatus having multiple back ends including at least one batch back-end such as an autoclave and at least one continuous back-end including a finisher.

[0010] In most methods and apparatuses for synthesis of polyamides, when any component in the back-end requires shut down for maintenance, which can be a difficult and burdensome procedure, the entire production process must be shut down. The present invention provides a method or apparatus having multiple back ends, such that one side of the back-end of the process can be shut down while the other sides continue to run. Therefore, shutting down the entire back-end of the process can be avoided, allowing the production facility to continue to operate even when aspects of a single back end require maintenance, and avoiding tedious shut down procedures.

BRIEF DESCRIPTION OF THE FIGURES

[0011] The drawings, which are not necessarily drawn to scale, illustrate generally, by way of example, but not by way of limitation, the present invention.

[0012] FIG. 1 illustrates a method of making a polyamide, according to one example.

FIG. 2 illustrates a method of making a polyamide, according to one

FIG. 3 illustrates a method of making a polyamide, according to one

[0015] FIG. 4 illustrates a method of making a polyamide, according to one example.

[0016] FIG. 5 illustrates a method of making a polyamide, according to one example

[0017] FIG. 6 illustrates a method of making a polyamide, according to one example.

[0018] FIG. 7 illustrates a system or apparatus for making a polyamide, according to one example.

[0019] FIG. 8 illustrates a system or apparatus for making a polyamide, according to one example.

[0020] FIG. 9 illustrates a system or apparatus for making a polyamide, according to one example.

[0021] FIG. 10 illustrates a system or apparatus for making a polyamide, according to one example.

[0022] FIG. 11 illustrates a system or apparatus for making a polyamide, according to one example.

[0023] FIG. 12 illustrates a system or apparatus for making a polyamide, according to one example. DETAILED DESCRIPTION OF THE INVENTION

[0024] Reference will now be made in detail to certain examples of the disclosed subject matter. While the disclosed subject matter will be described in conjunction with the enumerated claims, it will be understood that the exemplified subject matter is not intended to limit the claims to the disclosed subject matter.

[0025] Values expressed in a range format should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a range of "about 0.1% to about 5%" or "about 0.1% to 5%" should be interpreted to include not just about 0.1% to about 5%, but also the individual values (e.g., 1%, 2%, 3%, and 4%) and the sub-ranges (e.g., 0.1% to 0.5%, 1.1% to 2.2%, 3.3% to 4.4%) within the indicated range. The statement "about X to Y" has the same meaning as "about X to about Y," unless indicated otherwise. Likewise, the statement "about X, Y, or about Z" has the same meaning as "about X, about Y, or about Z," unless indicated otherwise.

[0026] In this document, the terms "a," "an," or "the" are used to include one or more than one unless the context clearly dictates otherwise. The term "or" is used to refer to a nonexclusive "or" unless otherwise indicated. In addition, it is to be understood that the phraseology or terminology employed herein, and not otherwise defined, is for the purpose of description only and not of limitation. Any use of section headings is intended to aid reading of the document and is not to be interpreted as limiting; information that is relevant to a section heading may occur within or outside of that particular section. Furthermore, all publications, patents, and patent documents referred to in this document are incorporated by reference herein in their entirety, as though individually incorporated by reference. In the event of inconsistent usages between this document and those documents so incorporated by reference, the usage in the incorporated reference should be considered supplementary to that of this document; for irreconcilable

inconsistencies, the usage in this document controls.

[0027] In the methods of manufacturing described herein, the steps can be carried out in any order without departing from the principles of the invention, except when a temporal or operational sequence is explicitly recited. Furthermore, specified steps can be carried out concurrently unless explicit claim language recites that they be carried out separately. For example, a claimed step of doing X and a claimed step of doing Y can be conducted simultaneously within a single operation, and the resulting process will fall within the literal scope of the claimed process.

[0028] The term "about" as used herein can allow for a degree of variability in a value or range, for example, within 10%, within 5%, or within 1% of a stated value or of a stated limit of a range. [0029] The term "substantially" as used herein refers to a majority of, or mostly, as in at least about 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.99%, or at least about 99.999% or more.

[0030] The term "oligomer" as used herein refers to a molecule having an intermediate relative molecular mass, the structure of which essentially includes a small plurality of units derived, actually or conceptually, from molecules of lower relative molecular mass. A molecule having an intermediate relative mass can be a molecule that has properties that vary with the removal of one or a few of the units. The variation in the properties that results from the removal of the one of more units can be a significant variation.

[0031] The term "solvent" as used herein refers to a liquid that can dissolve a solid, liquid, or gas. Nonlimiting examples of solvents are silicones, organic compounds, water, alcohols, ionic liquids, and supercritical fluids.

[0032] The term "room temperature" as used herein refers to a temperature of about 15 °C to 28 °C.

[0033] The term "polymer" as used herein can include a copolymer.

[0034] The term "relative viscosity" (RV) as used herein refers to the ratio of solution and solvent viscosities measured in a capillary viscometer at 25° C. In one example, RV by ASTM D789-06 is the ratio of viscosity (in centipoises) at 25°C of 8.4% by weight solution of the polyamide in 90% formic acid (90% by weight formic acid and 10% by weight water) to the viscosity (in centipoises) at 25°C of 90% formic acid alone.

[0035] The present invention relates to methods, systems, and apparatus for synthesizing a polyamide and including multiple back-ends.

Method of synthesizing a polyamide.

[0036] The present invention provides a method of synthesizing a polyamide, such as the method illustrated in FIG. 1. The method 100 can include evaporating 110 a mixture 101 including an oligomer formed from a linear dicarboxylic acid and a linear diamine. The evaporation can be sufficient to remove at least some water from the mixture. The evaporation 110 can provide a pre- finished mixture 111. The method can include splitting 150 the pre-finished mixture 111 into at least a first pre-finished mixture 151 and a second pre-finished mixture 152. The method can include finishing the first pre-finished mixture 151 in a first finisher 190, to provide a first finished mixture 191 including a first polyamide. The method can include finishing the second pre-finished mixture 152 in a second finisher 195, to provide a second finished mixture 196 including a second polyamide.

[0037] Each unit (e.g., the salt strike, evaporator, flasher, or finisher) can have any suitable size, such as about 100 L to about 5,000,000 L, about 500 L to about 1,000,000 L, or about 100 L or less, or about 200L, 300, 400, 500, 600, 700, 800, 900, 1,000, 1,500, 2,000, 2,500, 5,000, 10,000, 25,000, 50,000, 100,000, 500,000, 1,000,000, or about 5,000,000 L or more. Each unit can have any suitable flow rate into or out of the unit, such as about 10 L/min to about 100,000 L/min, about 20 L to about 1,000 L/min, or about 10 L/min or less, or about 20 L/min, 30, 40, 50, 60, 70, 80, 90, 100, 125, 150, 175, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900, 1,000, 1,500, 2,000, 2,500, 5,000, 10,000, 50,000, or about 100,000 L/min or more.

[0038] The method can include evaporating a mixture including an oligomer formed from a linear dicarboxylic acid and a linear diamine. The oligomer formed from the linear dicarboxylic acid and the linear diamine can be a polyamide salt, such as a nylon salt formed by the combination of adipic acid and hexamethylene diamine. The oligomer can include a combination of a single molecule of diacid with a single molecule of diamine, such as a hexamethylene diammonium adipate. The oligomer can be the product of one or more than one molecule of diacid with one or more than one molecule of diamine. The mixture including the oligomer can also include unreacted diamine and unreacted diacid. The mixture including the oligomer can include oligomers of various length in any suitable proportion.

[0039] The evaporation of the mixture including the oligomer can be sufficient to remove at least some water from the mixture. In any step described herein, when the removal of water is described, the removal of water can be at least one of water that was originally present in the mixture, water that is generated by the reaction of diacid with diamine to form an amide, water that is generated by the reaction of diacid or diamine with an oligomer to form an amide, and water that is generated by the reaction of one oligomer with another to form an amide. In some examples, the evaporating can remove sufficient water such that the material exiting the evaporator is any suitable wt water, such as about 5-50 wt water, or about 25-35 wt% water, or about 25 wt% or less, 26 wt%, 27, 28, 29, 30, 31, 32, 33, 34 wt or about 35 wt or more water. The evaporating can elevate the temperature of the reaction mixture to any suitable temperature, such as a temperature of about 100-230 °C, or 100-150 °C, or about 100 °C or less, or about 110 °C, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220 °C, or about 230 °C or more.

[0040] The method can include splitting the pre-finished mixture into at least a first pre-finished mixture and a second pre-finished mixture. The splitting can be any suitable splitting, in any suitable proportion. For example, the first pre- finished mixture can include about 1-99 wt , or about 20-80 wt , or about 40-60 wt of the pre-finished mixture, or about 0.001 wt of the pre-finished mixture or less, or about 0.01 wt%, 0.1, 1, 10, 20, 30, 40, 45, 50, 55, 60, 70, 80, 90, 99, 99.9, 99.99 wt , or about 99.999 wt or more of the pre-finished mixture. For example, the second-pre-finished mixture can include about 1-99 wt , or about 20-80 wt , or about 40-60 wt of the pre-finished mixture, or about 0.001 wt of the pre- finished mixture or less, or about 0.01 wt%, 0.1, 1, 10, 20, 30, 40, 45, 50, 55, 60, 70, 80, 90, 99, 99.9, 99.99 wt%, or about 99.999 wt% or more of the pre-finished mixture. Reacting can occur in the process prior to the splitting. Reacting and flashing can occur in the process prior to the splitting. Reacting can occur in the process after the splitting. Reacting and flashing can occur in the process after the splitting. Finishing occurs in the process after the splitting.

[0041] The method can include finishing the first pre-finished mixture in a first finisher, to provide a first finished mixture including a first polyamide. The method can include finishing the second pre-finished mixture in a second finisher, to provide a second finished mixture including a second polyamide. The finishing can be any suitable finishing. In some examples, the finishing can remove sufficient water from the pre-finished mixture to drive the reaction forward the final amount necessary to achieve a desired relative viscosity. The finishing in the first finisher can be the same as the finishing in the second finisher. The finishing in the first finisher can be different from the finishing in the second finisher. The finishing can occur in an autoclave, such as can be used to generate polyamide in a batch process. The finishing can occur in a continuous finisher which continuously heats, stirs, and removes water from the pre-finished mixture. In some examples, the finishing can remove sufficient water such that the material exiting the finisher is any suitable wt% water, such as about 0.000,1 wt% to 2 wt%, 0.001 to 1 wt%, or about 0.01 to 1 wt%, or about 0.000,1 wt% or less, or about 0.001 wt%, 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.2, 1.4, 1.6, 1.8 wt%, or about 2 wt% or more water. The finishing can elevate the temperature of the reaction mixture to any suitable temperature, such as a temperature of about 150-400 °C, or about 250-350 °C, or about 250-310 °C, or about 200 °C or less, or about 210 °C, 220, 230, 240, 250, 260, 265, 270, 275, 280, 285, 290, 295, 300, 305, 310, 320, 330, 340 °C, or about 350 °C or more.

[0042] The finishing of the first pre-finished mixture in the first finisher and the finishing of the second pre-finished mixture in the second finisher can occur at least partially simultaneously. The finishing of the first pre-finished mixture in the first finisher and the finishing of the second pre-finished mixture in the second finisher can occur substantially simultaneously, e.g., the finishing of the first pre- finished mixture in the first finisher and the finishing of the second pre-finished mixture in the second finisher can temporally overlap about 50% of the total finishing time in the first finisher or the second finisher, or about 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.99%, or about 99.999% or more.

[0043] The first finished mixture can have a relative viscosity that is substantially the same as a relative viscosity of the second finished mixture. The first polyamide can be substantially the same as the second polyamide. The first finished mixture can have a different relative viscosity than a relative viscosity of the second finished mixture. The first finished mixture and the second finished mixture each independently can have a relative viscosity of about 15-70. The first finished mixture can have a relative viscosity of about 15-70 and the second finished mixture has a relative viscosity of about 15-70. The first polyamide can be different from the second polyamide. The first finished mixture can have a relative viscosity of about 30-50, 35-40, or about 38 and the second finished mixture has a relative viscosity of about 30-50, 35-55, or about 45.

[0044] The method can be a continuous method for making polyamide, a batch method for making polyamide, or a combination thereof. The method can further include, prior to the evaporating, mixing the linear dicarboxylic acid and the linear diamine, to provide the mixture including the oligomer.

[0045] The method can include reacting prior to the splitting. For example, the evaporating can provide an evaporated mixture, and the method can include reacting the evaporated mixture in a reactor so as to remove at least some water therefrom, to provide the pre-finished mixture. The reacting can be any suitable reacting, such that the reacting heats the mixture and removes water therefrom, pushing the equilibrium further toward the polyamide. The reacting can be performed in a tubular reactor. The reacting can be performed in a distillative reactor. The reacting can form a mixture having about 0.000,1 wt to 20 wt , 0.001 to 15 wt%, or about 0.01 to 15 wt%, or about 0.000,1 wt% or less, or about 0.001 wt%, 0.01, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.2, 1.4, 1.6, 1.8, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 wt%, or about 20 wt or more. The reacting can elevate the temperature of the reaction mixture to any suitable temperature, such as about 150-400 °C, or about 250-350 °C, or about 250-310 °C, or about 200 °C or less, or about 210 °C, 220, 230, 240, 250, 260, 265, 270, 275, 280, 285, 290, 295, 300, 305, 310, 320, 330, 340 °C, or about 350 °C or more. [0046] FIG. 2 illustrates a method of making a polyamide. The present invention provides a method 200 of synthesizing a polyamide. The method can include evaporating 210 a mixture 201 including an oligomer formed from a linear dicarboxylic acid and a linear diamine. The evaporation can be sufficient to remove at least some water from the mixture. The evaporating 210 can provide an evaporated mixture 211. The method can include reacting 220 the evaporated mixture 211 in a reactor to remove at least some water therefrom. The reacting 220 can provide a pre-finished mixture 221. The method can include splitting 250 the pre-finished mixture 221 into at least a first pre-finished mixture 251 and a second pre-finished mixture 252. The method can include finishing 290 the first pre- finished mixture 251 in a first finisher, to provide a first finished mixture 291 including a first polyamide. The method can include finishing 295 the second pre- finished mixture 252 in a second finisher, to provide a second finished mixture 296 including a second polyamide.

[0047] The method can include flashing after the splitting. For example, the splitting of the pre-finished mixture can include splitting the pre-finished mixture into a first pre-flashed mixture and a second pre-flashed mixture. The method can also include flashing the first pre-flashed mixture in a first flasher to provide the first pre-finished mixture, and flashing the second pre-flashed mixture in a second flasher to provide the second pre-finished mixture. The flashing of the first pre- flashed mixture in the first flasher and the flashing of the second pre-flashed mixture in the second flasher can be at least partially simultaneous, or can be substantially simultaneous. The flashing can be any suitable flashing that includes heating the reaction mixture and removing at least some water therefrom to push the equilibrium toward the polyamide. In some example, the material exiting the flasher can have any suitable amount of water, such as about 0.000,1 wt to 2 wt , 0.001 to 1 wt , or about 0.01 to 1 wt , or about 0.000,1 wt or less, or about 0.001 wt%, 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.2, 1.4, 1.6, 1.8 wt , or about 2 wt or more. In some examples, the flasher can elevate the temperature of the reaction mixture to about 150-400 °C, or about 250-350 °C, or about 250-310 °C, or about 200 °C or less, or about 210 °C, 220, 230, 240, 250, 260, 265, 270, 275, 280, 285, 290, 295, 300, 305, 310, 320, 330, 340 °C, or about 350 °C or more.

[0048] FIG. 3 illustrates a method of making a polyamide. The present invention provides a method 300 of synthesizing a polyamide. The method can include evaporating 310 a mixture 301 including an oligomer formed from a linear dicarboxylic acid and a linear diamine. The evaporation can be sufficient to remove at least some water from the mixture. The evaporating 310 can provide a pre- finished mixture 311. The method can include splitting 350 the pre-finished mixture 311 into at least a first pre-flashed mixture 351 and a second pre-flashed mixture 352. The method can include flashing 360 the first pre-flashed mixture 351 in a first flasher, to provide a first pre-finished mixture 361. The method can include flashing 365 the second pre-flashed mixture 352 in a second flasher, to provide a second pre-finished mixture 366. The method can include finishing 390 the first pre-finished mixture 361 in a first finisher, to provide a first finished mixture 391 including a first polyamide. The method can include finishing 395 the second pre-finished mixture 366 in a second finisher, to provide a second finished mixture 396 including a second polyamide.

[0049] The method can include reacting and flashing prior to splitting. For example, evaporating can provide an evaporated mixture. The method can include reacting the evaporated mixture in a reactor so as to remove at least some water therefrom, to provide a pre-flashed mixture. The method can also include flashing the pre-flashed mixture in a flasher so as to remove at least some water therefrom, to provide the pre-finished mixture.

[0050] FIG. 4 illustrates a method of making a polyamide. The present invention provides a method 400 of synthesizing a polyamide. The method can include evaporating 410 a mixture 401 including an oligomer formed from a linear dicarboxylic acid and a linear diamine. The evaporation can be sufficient to remove at least some water from the mixture. The evaporating 410 can provide an evaporated mixture 411. The method can include reacting 420 the evaporated mixture 411 in a reactor so as to remove at least some water therefrom. The reacting 420 can provide a pre-flashed mixture 421. The method can include flashing 430 the pre-flashed mixture 421 in a flasher so as to remove at least some water therefrom, to provide a pre-finished mixture 431. The method can include splitting 450 the pre-finished mixture 431 into at least a first pre-finished mixture 451 and a second pre-finished mixture 452. The method can include finishing 490 the first pre-finished mixture 451 in a first finisher, to provide a first finished mixture 491 including a first polyamide. The method can include finishing 495 the second pre-finished mixture 452 in a second finisher, to provide a second finished mixture 496 including a second polyamide.

[0051] The method can include reacting after the splitting. For example, the method can include the splitting of the pre-finished mixture can include splitting the pre-finished mixture into a first pre-reacted mixture and a second pre-reacted mixture. The method can include reacting the first pre-reacted mixture in a first reactor to provide the first pre-finished mixture. The method can also include reacting the second pre-reacted mixture in a second reactor to provide the second pre-finished mixture. The reacting of the first pre-reacted mixture in the first reactor and the reacting of the second pre-reacted mixture in the second reactor can be at least partially simultaneous, or can be substantially simultaneous.

[0052] FIG. 5 illustrates a method of making a polyamide. The present invention provides a method 500 of synthesizing a polyamide. The method can include evaporating 510 a mixture 501 including an oligomer formed from a linear dicarboxylic acid and a linear diamine. The evaporation can be sufficient to remove at least some water from the mixture. The evaporating 510 can provide a pre- finished mixture 511. The method can include splitting 550 the pre-finished mixture 511 into at least a first pre-reacted mixture 551 and a second pre-reacted mixture 552. The method can include reacting 560 the first pre-reacted mixture 551 in a first reactor, to provide a first pre-finished mixture 561. The method can include reacting 565 the second pre-reacted mixture 552 in a second reactor, to provide a second pre-finished mixture 566. The method can include finishing 590 the first pre-finished mixture 561 in a first finisher, to provide a first finished mixture 591 including a first polyamide. The method can include finishing 595 the second pre-finished mixture 566 in a second finisher, to provide a second finished mixture 596 including a second polyamide.

[0053] The method can include reacting, flashing, and finishing after the splitting. For example, the splitting of the pre-finished mixture can include splitting the pre-finished mixture into a first pre-reacted mixture and a second pre-reacted mixture. The method can include reacting the first pre-reacted mixture in a first reactor to provide a first pre-flashed mixture. The method can include reacting the second pre-reacted mixture in a second reactor to provide a second pre-flashed mixture. The method can include flashing the first pre-flashed mixture in a first flasher to provide the first pre-finished mixture. The method can also include flashing the second pre-flashed mixture in a second flasher to provide the second pre-finished mixture. The reacting of the first pre-reacted mixture in the first reactor and the reacting of the second pre-reacted mixture in the second reactor can be at least partially simultaneous or substantially simultaneous. The flashing of the first pre-flashed mixture in the first flasher and the flashing of the second pre-flashed mixture in the second flasher can be at least partially simultaneous or substantially simultaneous.

[0054] FIG. 6 illustrates a method of making a polyamide. The present invention provides a method 600 of synthesizing a polyamide. The method can include evaporating 601 a mixture 601 including an oligomer formed from a linear dicarboxylic acid and a linear diamine. The evaporation can be sufficient to remove at least some water from the mixture. The evaporating 610 can provide a pre- finished mixture 611. The method can include splitting 650 the pre-finished mixture 611 into at least a first pre-reacted mixture 651 and a second pre-reacted mixture 652. The method can include reacting 660 the first pre-reacted mixture 651 in a first reactor to provide a first pre-flashed mixture 661. The method can include reacting 665 the second pre-reacted mixture 652 in a second reactor to provide a second pre-flashed mixture 666. The method can include flashing 670 the first pre- flashed mixture 661 in a first flasher to provide a first pre-finished mixture 671. The method can include flashing 675 the second pre-flashed mixture 666 in a second flasher to provide a second pre-finished mixture 676. The method can include finishing 690 the first pre-finished mixture 671 in a first finisher, to provide a first finished mixture 691 including a first polyamide. The method can include finishing 695 the second pre-finished mixture 676 in a second finisher, to provide a second finished mixture 696 including a second polyamide.

System for synthesizing a polyamide.

[0055] The present invention provides a system for synthesizing a polyamide, such as the system shown in FIG. 7. The system 1100 can include an evaporator 1110 configured to remove at least some water from a mixture 1101 including an oligomer formed from a linear dicarboxylic acid and a linear diamine. The evaporator 1110 can provide a pre-finished mixture 1111. The system can include a splitter 1150 configured to split the pre-finished mixture 1111 into at least a first pre-finished mixture 1151 and a second pre-finished mixture 1152. The system can include a first finisher 1190 configured to finish the first pre-finished mixture 1151. The first finisher 1190 can provide a first finished mixture 1191 including a first polyamide. The system includes a second finisher 1195 configured to finish the second pre-finished mixture 1152. The second finisher 1195 can provide a second finished mixture 1196 including a second polyamide.

Apparatus for synthesizing a polyamide.

[0056] The present invention provides an apparatus for synthesizing a polyamide, such as the apparatus illustrated in FIG. 7. The apparatus 1100 can include an evaporator 1110 configured to remove at least some water from a mixture 1101 including an oligomer formed from a linear dicarboxylic acid and a linear diamine. The evaporator 1110 can provide a pre-finished mixture 1111. The apparatus can include a splitter 1150 configured to split the pre-finished mixture 1111 into at least a first pre-finished mixture 1151 and a second pre-finished mixture 1152. The apparatus can include a first finisher 1190 configured to finish the first pre-finished mixture 1151. The first finisher 1190 can provide a first finished mixture 1191 including a first polyamide. The apparatus can include a second finisher 1195 configured to finish the second pre-finished mixture 1152. The second finisher 1195 can provide a second finished mixture 1196 including a second polyamide.

[0057] The apparatus can include an evaporator configured to remove at least some water from a mixture including an oligomer formed from a linear dicarboxylic acid and a linear diamine. The evaporator can be any suitable evaporator, such that the evaporator removes at least some water from the mixture. In some examples, the evaporator can remove sufficient water such that the material exiting the evaporator is any suitable wt water, such as about 60-80 wt water, or about 65-75 wt water, or about 70 wt water.

[0058] The apparatus can include a splitter configured to split the pre- finished mixture into at least a first pre-finished mixture and a second pre-finished mixture. The splitter can be any suitable splitter, such as a Y-fitting or a T-fitting, or a valve, optionally in combination with a suitable pump. The first pre-finished mixture and the second pre-finished mixture can be any suitable wt of the pre- finished mixture and can elevate the temperature of the reaction mixture to any suitable temperature, as described herein. A reactor can occur in the process prior to the splitting. A reacting and a flasher can occur in the process prior to the splitting. Reacting can occur in the process after the splitting. Reacting and flashing can occur in the process after the splitting. Finishing occurs in the process after the splitting.

[0059] The apparatus can include a first finisher configured to finish the first pre-finished mixture. The first finisher can provide a first finished mixture including a first polyamide. The apparatus can include a second finisher configured to finish the second pre-finished mixture. The second finisher can provide a second finished mixture including a second polyamide. The finishers can be any suitable finishers, such that the finishers can remove sufficient water from the pre-finished mixture to drive the reaction forward the final amount necessary to achieve a desired relative viscosity. The first finisher is configured to finish the first pre- finished mixture and the second finisher is configured to finish the second pre- finished mixture at least partially simultaneously, or substantially simultaneously. The first finisher can be the same as the second finisher. The first finisher can be different from the second finisher. The finisher can be an autoclave, such as can be used to generate polyamide in a batch process. The finisher can be a continuous finisher which continuously heats, stirs, and removes water from the pre-finished mixture. The first finisher and the second finisher can each independently produce a finished mixture having any suitable relative viscosity, the same or different, as described herein.

[0060] The apparatus can be configured to make polyamide in a continuous fashion, a batch fashion, or a combination thereof. The apparatus can include a mixer configured to mix the linear dicarboxylic acid and the linear diamine, to provide the mixture including the oligomer.

[0061] The apparatus can include a reactor prior to the splitter. For example, the evaporator can provide an evaporated mixture. The apparatus can include a reactor configured to remove at least some water from the evaporated mixture to provide the pre-finished mixture. The reactor can be any suitable reactor, such that the reactor heats the mixture and removes water therefrom, pushing the equilibrium further toward the polyamide. The reactor can be a tubular reactor. The reactor can be a distillative reactor.

[0062] FIG. 8 illustrates a system or apparatus for making a polyamide. The present invention provides an apparatus 1200 for synthesizing a polyamide. The apparatus 1200 can include an evaporator 1210 configured to remove at least some water from a mixture 1201 including an oligomer formed from a linear dicarboxylic acid and a linear diamine. The evaporator 1210 can provide an evaporated mixture 1211. The apparatus can include a reactor 1220 configured to remove at least some water from the evaporated mixture 1211. The reactor 1220 can provide a pre- finished mixture 1221. The apparatus can include a splitter 1250 configured to split the pre-finished mixture 1221 into at least a first pre-finished mixture 1251 and a second pre-finished mixture 1252. The apparatus can include a first finisher 1290 configured to finish the first pre-finished mixture 1251. The first finisher 1290 can provide a first finished mixture 1291 including a first polyamide. The apparatus can include a second finisher 1295 configured to finish the second pre-finished mixture 1252. The second finisher 1295 can provide a second finished mixture 1296 including a second polyamide.

[0063] The apparatus can include a flasher after the splitter. For example, the splitter can be configured to split the pre-finished mixture into at least a first pre- flashed mixture and a second pre-flashed mixture. The apparatus can include a first flasher configured to flash the first pre-flashed mixture to provide the first pre- finished mixture. The apparatus can also include a second flasher configured to flash the second pre-flashed mixture to provide the second pre-finished mixture. The first flasher can be configured to flash the first pre-flashed mixture and the second flasher can be configured to flash the second pre-flashed mixture at least partially simultaneously or substantially simultaneously. The flasher can be any suitable flasher that heats the reaction mixture and removing at least some water therefrom to push the equilibrium toward the polyamide, to generate a suitable flashed mixture as described herein.

[0064] FIG. 9 illustrates a system or apparatus for making a polyamide. The present invention provides an apparatus 1300 for synthesizing a polyamide. The apparatus can include an evaporator 1310 configured to remove at least some water from a mixture 1301 including an oligomer formed from a linear dicarboxylic acid and a linear diamine. The evaporator 1310 can provide a pre-finished mixture 1311. The apparatus can include a splitter 1350 configured to split the pre-finished mixture 1311 into at least a first pre-flashed mixture 1351 and a second pre-flashed mixture 1352. The apparatus can include a first flasher 1360 configured to flash the first pre-flashed mixture 1351. The first flasher can provide a first pre-finished mixture 1361. The apparatus can include a second flasher 1365 configured to flash the second pre-flashed mixture 1352. The second flasher 1365 provides a second pre-finished mixture 1366. The apparatus can include a first finisher 1390 configured to finish the first pre-finished mixture 1361. The first finisher 1390 can provide a first finished mixture 1391 including a first polyamide. The apparatus can include a second finisher 1395 configured to finish the second pre-finished mixture 1366. The second finisher 1395 can provide a second finished mixture 1396 including a second polyamide.

[0065] The apparatus can include a reactor and a flasher prior to the splitter.

For example, the evaporator can provide an evaporated mixture. The apparatus can further include a reactor configured to react the evaporated mixture to remove at least some water therefrom, to provide a pre-flashed mixture. The apparatus can also include a flasher configured to flash the pre-flashed mixture to remove at least some water therefrom, to provide the pre-finished mixture.

[0066] FIG. 10 illustrates a system or apparatus for making a polyamide.

The present invention provides an apparatus 1400 for synthesizing a polyamide. The apparatus can include an evaporator 1410 configured to remove at least some water from a mixture 1401 including an oligomer formed from a linear dicarboxylic acid and a linear diamine. The evaporator 1410 can provide an evaporated mixture 1411. The apparatus can include a reactor 1420 configured to react the evaporated mixture 1411 to remove at least some water therefrom. The reactor 1420 can provide a pre-flashed mixture 1421. The apparatus can include a flasher 1430 configured to flash the pre-flashed mixture 1421 to remove at least some water therefrom. The flasher 1430 can provide a pre-finished mixture 1431. The apparatus can include a splitter 1450 configured to split the pre-finished mixture 1431 into at least a first pre-finished mixture 1451 and a second pre-finished mixture 1452. The apparatus can include a first finisher 1490 configured to finish the first pre-finished mixture 1451. The first finisher 1490 can provide a first finished mixture 1491 including a first polyamide. The apparatus can include a second finisher 1495 configured to finish the second pre-finished mixture 1452. The second finisher 1495 can provide a second finished mixture 1496 including a second polyamide. [0067] The apparatus can include reactors after the splitter. For example, the splitter can be configured to split the pre-finished mixture into a first pre-reacted mixture and a second pre-reacted mixture. The apparatus can further include a first reactor configured to react the first pre-reacted mixture to provide the first pre- finished mixture. The apparatus can also further include a second reactor configured to react the second pre-reacted mixture to provide the second pre- finished mixture. At least one of the first and second reactor can be a tubular reactor or a distillative reactor. The first reactor is configured to react the first pre- reacted mixture and the second reactor can be configured to react the second pre- reacted mixture at least partially simultaneously or substantially simultaneously.

[0068] FIG. 11 illustrates a system or apparatus for making a polyamide.

The present invention provides an apparatus 1500 for synthesizing a polyamide. The apparatus can include an evaporator 1510 configured to remove at least some water from a mixture 1501 including an oligomer formed from a linear dicarboxylic acid and a linear diamine. The evaporator 1510 can provide a pre-finished mixture 1511. The apparatus can include a splitter 1550 configured to split the pre-finished mixture 1511 into at least a first pre-reacted mixture 1551 and a second pre-reacted mixture 1552. The apparatus can include a first reactor 1560 configured to react the first pre-reacted mixture 1551. The first reactor 1560 can provide a first pre- finished mixture 1561. The apparatus can include a second reactor 1565 configured to react the second pre-reacted mixture 1552. The second reactor 1565 can provide a second pre-finished mixture 1566. The apparatus can include a first finisher 1590 configured to finish the first pre-finished mixture 1561. The first finisher 1590 can provide a first finished mixture 1591 including a first polyamide. The apparatus can include a second finisher 1595 configured to finish the second pre-finished mixture 1566. The second finisher 1595 can provide a second finished mixture 1596 including a second polyamide.

[0069] The apparatus can include reactors and flashers after the splitting.

For example, the splitter can be configured to split the pre-finished mixture into at least a first pre-reacted mixture and a second pre-reacted mixture. The apparatus can include a first reactor configured to react the first pre-reacted mixture to provide a first pre-flashed mixture. The apparatus can include a second reactor configured to react the second pre-reacted mixture to provide a second pre-flashed mixture. The apparatus can include a first flasher configured to flash the first pre-flashed mixture to provide the first pre-finished mixture. The apparatus can include a second flasher configured to flash the second pre-flashed mixture to provide the second pre-finished mixture. The first reactor can be configured to react the first pre-reacted mixture and the second reactor can be configured to react the second pre-reacted mixture at least partially simultaneously or substantially simultaneously. The first flasher can be configured to flash the first pre-flashed mixture and the second flasher can be configured to flash the second pre-flashed mixture at least partially simultaneously or substantially simultaneously.

[0070] FIG. 12 illustrates a system or apparatus for making a polyamide.

The present invention provides an apparatus 1600 for synthesizing a polyamide. The apparatus can include an evaporator 1610 configured to remove at least some water from a mixture 1601 including an oligomer formed from a linear dicarboxylic acid and a linear diamine. The evaporator 1610 can provide a pre-finished mixture 1611. The apparatus can include a splitter 1650 configured to split the pre-finished mixture 1611 into at least a first pre-reacted mixture 1651 and a second pre-reacted mixture 1652. The apparatus can include a first reactor 1660 configured to react the first pre-reacted mixture 1651. The first reactor 1660 can provide a first pre-flashed mixture 1661. The apparatus can include a second reactor 1665 configured to react the second pre-reacted mixture 1652. The second reactor 1665 can provide a second pre-flashed mixture 1666. The apparatus can include a first flasher 1670 configured to flash the first pre-flashed mixture 1661. The first flasher 1670 can provide a first pre-finished mixture 1671. The apparatus can include a second flasher 1675 configured to flash the second pre-flashed mixture 1666. The second flasher 1675 can provide a second pre-finished mixture 1676. The apparatus can include a first finisher 1690 configured to finish the first pre-finished mixture 1671. The first finisher 1690 can provide a first finished mixture 1691 including a first polyamide. The apparatus can include a second finisher 1695 configured to finish the second pre-finished mixture 1676. The second finisher 1695 can provide a second finished mixture 1696 including a second polyamide. Polyamide

[0071] The polyamide made by the method, system, or apparatus can be any suitable polyamide. The polyamide can be synthesized from a linear dicarboxylic acid and a linear diamine or from an oligomer formed from a linear dicarboxylic acid and a linear diamine. The polyamide can be nylon 6, nylon 7, nylon 11, nylon 12, nylon 6,6, nylon 6,9; nylon 6,10, nylon 6,12, or copolymers thereof.

[0072] The dicarboxylic acid can be any suitable dicarboxylic acid. The dicarboxylic acid can have has the structure HOC(0)-R¹-C(0)OH, wherein R¹ is a C1-C15 alkylene group, such as a methylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, or decylene group. The dicarboxylic acid can be adipic acid (e.g., R¹ = butylene).

[0073] The diamine can be any suitable diamine. The diamine can have the structure H₂N-R 2 -NH₂, wherein R 2 is a C1-C15 alkylene group, such as a methylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, or decylene group. The diamine can be hexamethylenediamine, (e.g., R = butylene).

Examples

[0074] The present invention can be better understood by reference to the following examples which are offered by way of illustration. The present invention is not limited to the examples given herein.

[0075] Throughout the Examples, X represents the same cost. Throughout the Examples, Z represents the same cost. Comparative Example la. Continuous process with no multiple back-ends.

[0076] In a continuous nylon 6,6 manufacturing process, adipic acid and hexamethylenediamine are combined in an approximately equimolar ratio in water to form an aqueous mixture containing nylon 6,6 salt and having about 50 wt water. The aqueous salt is transferred to an evaporator at approximately 105 L/min. The evaporator heats the aqueous salt to about 125-135 °C (130 °C) and removes water from the heated aqueous salt, bringing the water concentration to about 30 wt . The evaporated salt mixture is transferred to a tubular reactor at

approximately 75 L/min. The reactor raises the temperature of the evaporated salt mixture to about 218-250 °C (235 °C), allowing the reactor to further remove water from the heated evaporated salt mixture, bringing the water concentration to about 10 wt , and causing the salt to further polymerize. The reacted mixture is transferred to a flasher at approximately 60 L/min. The flasher heats the reacted mixture to about 270-290 °C (285 °C) to further remove water from the reacted mixture, bringing the water concentration to about 0.5 wt , and causing the reacted mixture to further polymerize. The flashed mixture, having a relative viscosity of about 13, is transferred to a finisher at approximately 54 L/min. In the transfer piping between the flasher and the finisher, the polymer mixture maintains a temperature of about 285 °C. The finisher subjects the polymeric mixture to a vacuum to further remove water, bringing the water concentration to about 0.1 wt and the relative viscosity to about 60, such that the polyamide achieves a suitable final range of degree of polymerization before transferring the finished polymeric mixture to an extruder and a pelletizer at about 54 L/min.

[0077] The salt strike has a volume of about 4,000 L, costs about Z to purchase and build into the system, and costs about X/h to operate. The evaporator has a volume of about 4,000 L, costs about 3*Z to purchase and build into the system, and costs about 4*X/h to operate. The reactor has a volume of about 1,500 L, costs about 5*Z to purchase and build into the system, and costs about 4*X/h to operate. The flasher has a volume of about 2,500 L, costs about 5*Z to purchase and build into the system, and costs about 4*X/h to operate. The finisher has a volume of about 3,000 L, costs about 5*Z to purchase and build into the system, and costs about 4*X/h to operate.

Comparative Example lb. Continuous process with no multiple back-ends, two times the size of Example la.

[0078] The process described in Example la is followed, using a system that includes units that are about twice the size and that handle twice the flow rate.

[0079] The salt strike delivers material to the evaporator at about 210 L/min, has a volume of about 8,000 L, costs about 2*Z to purchase and build into the system, and costs about 2*X/h to operate. The evaporator delivers material to the reactor at about 150 L/min, has a volume of about 8,000 L, costs about 6*Z to purchase and build into the system, and costs about 8*X/h to operate. The reactor delivers material into the flasher at about 120 L/min, has a volume of about 3,000 L, costs about 10*Z to purchase and build into the system, and costs about 8*X/h to operate. The flasher delivers material into the finisher at about 118 L/min, has a volume of about 5,000 L, costs about 10*Z to purchase and build into the system, and costs about 8*X/h to operate. The finisher delivers material to the

extruder/pelletizer at about 118 L/min, has a volume of about 6,000 L, costs about 10*Z to purchase and build into the system, and costs about 8*X/h to operate.

[0080] The system generates twice as much product in a given time as the system of Example la. The components each cost twice as much to purchase and build into the system, and each component of the system costs twice as much to operate. Comparative Example lc. Continuous process with no multiple back-ends, three times the size of Example la.

[0081] The process described in Example la is followed, using a system that includes units that are about three times the size and that handle three times the flow rate. [0082] The salt strike delivers material into the evaporator at about 315

L/min, has a volume of about 12,000 L, costs about 3*Z to purchase and build into the system, and costs about 3*X/h to operate. The evaporator delivers material into the reactor at about 225 L/min, has a volume of about 12,000 L, costs about 9*Z to purchase and build into the system, and costs about 12*X/h to operate. The reactor delivers material into the flasher at about 180 L/min, has a volume of about 4,500 L, costs about 15*Z to purchase and build into the system, and costs about 12*X/h to operate. The flasher delivers material into the finisher at about 177 L/min, has a volume of about 7,500 L, costs about 15*Z to purchase and build into the system, and costs about 12*X/h to operate. The finisher delivers material to the

extruder/pelletizer at about 177 L/min, has a volume of about 9,000 L, costs about 30*Z to purchase and build into the system, and costs about 24*X/h to operate.

[0083] The system generates three times as much product in a given time as the system of Example la. The components each cost three times as much to purchase and build into the system, except for the finisher which costs six times more, and each component of the system costs three times as much to operate, except for the finisher which costs six times more. Comparative Example Id. Continuous process with no multiple back-ends, five times the size of Example la.

[0084] The process described in Example la is followed, using a system that includes units that are about five times the size and that handle five times the flow rate.

[0085] The salt strike delivers material into the evaporator at about 525

L/min, has a volume of about 20,000 L, costs about 5*Z to purchase and build into the system, and costs about 5*X/h to operate. The evaporator delivers material into the reactor at about 375 L/min, has a volume of about 20,000 L, costs about 15*Z to purchase and build into the system, and costs about 20*X/h to operate. The reactor delivers material into the flasher at about 300 L/min, has a volume of about 7,500 L, costs about 25*Z to purchase and build into the system, and costs about 20*X/h to operate. The flasher delivers material into the finisher at about 295 L/min, has a volume of about 12,500 L, costs about 25*Z to purchase and build into the system, and costs about 20*X/h to operate. The finisher delivers material to the

extruder/pelletizer at about 295 L/min, has a volume of about 15,000 L, costs about 2,500*Z to purchase and build into the system, and costs about 500*X/h to operate.

[0086] The system generates 5 times as much product in a given time as the system of Example la; however, the finisher is less efficient at the larger size, causing the wt water in the product to be 0.2 wt , which is unsatisfactory. Flow rates from the flasher are reduced to 236 L/min to produce product have 0.1 wt water, limiting the overall flow rates of the entire system. The components each cost five times as much to purchase and build into the system, except the finisher which costs five-hundred times more, and each component of the system costs five times as much to operate, except the finisher which costs 125 times more.

Comparative Example le. Continuous example with no multiple back-ends, 10 times the size of Example la.

[0087] The process described in Example la is followed, using a system that includes units that are about ten times the size and that handle ten times the flow rate.

[0088] The salt strike delivers material into the evaporator at about 1,050

L/min, has a volume of about 40,000 L, costs about 10*Z to purchase and build into the system, and costs about 10*X/h to operate. The evaporator delivers material into the reactor at about 750 L/min, has a volume of about 40,000 L, costs about 30*Z to purchase and build into the system, and costs about 40*X/h to operate. The reactor delivers material into the flasher at about 600 L/min, has a volume of about 15,000 L, costs about 50*Z to purchase and build into the system, and costs about 40*X/h to operate. The flasher delivers material into the finisher at about 590 L/min, has a volume of about 25,000 L, costs about 50*Z to purchase and build into the system, and costs about 40*X/h to operate. The finisher delivers material to the extruder/pelletizer at about 590 L/min, has a volume of about 30,000 L, costs about 20,000*Z to purchase and build into the system, and costs about 8,000*X/h to operate.

[0089] The system generates ten times as much product in a given time as the system of Example la; however, the finisher is less efficient at the large size, and the wt water of the product is 0.5 wt . The flow rate of material exiting the finisher is reduced to 295 L/min to produce product having a wt water of 0.1, limiting the overall capacity of the system. The components each cost ten times as much to purchase and build into the system, except the finisher which costs 4,000 times more. The components each cost ten times more to operate, except the finisher which costs 2,000 times more.

Comparative Example 2a. Batch process with single autoclave.

[0090] In a batch nylon 6,6 manufacturing process, adipic acid and hexamethylenediamine are combined in an approximately equimolar ratio in water to form an aqueous mixture containing nylon 6,6 salt and having about 50 wt water. The aqueous salt is transferred to an autoclave at approximately 105 L/min until the autoclave contains about 6,000 L of material. The autoclave heats the aqueous salt to about 270-290 °C (285 °C) and polymerizes and removes water from the heated aqueous salt, with a residence time of 1 h, bringing the water concentration to about 0.1 wt and the viscosity to about 60, such that the polyamide achieves a suitable final range of degree of polymerization before transferring the finished polymeric mixture to an extruder and a pelletizer.

[0091] The salt strike has a volume of about 4,000 L, costs about Z to purchase and build into the system, and costs about X/h to operate. The autoclave has a volume of about 15,000 L, costs about 25*Z to purchase and build into the system, and costs about 8*X/h to operate. Comparative Example 2b. Batch process with single autoclave, two times the size of Example 2a.

[0092] The process described in Example 2a is followed, using a system that includes units that are about two times the size.

[0093] The salt strike delivers material into the autoclave at about 210

L/min, has a volume of about 8,000 L, costs about 2*Z to purchase and build into the system, and costs about 2*X/h to operate. The autoclave has a volume of about 30,000 L, costs about 50*Z to purchase and build into the system, and costs about 16*X/h to operate.

[0094] The system generates twice as much product in a given time as the system of Example 2a. The components each cost twice as much to purchase and build into the system, and each component of the system costs twice as much to operate. Comparative Example 2c. Batch process with single autoclave, three times the size of Example 2a.

[0095] The process described in Example 2a is followed, using a system that includes units that are about three times the size.

[0096] The salt strike delivers material into the autoclave at about 315 L/min, has a volume of about 12,000 L, costs about 3*Z to purchase and build into the system, and costs about 3*X/h to operate. The autoclave has a volume of about 45,000 L, costs about 150*Z to purchase and build into the system, and costs about 40*X/h to operate.

[0097] The system generates three times as much product in a given time as the system of Example 2a. The salt strike costs three times as much to purchase and build into the system, and the autoclave costs six times as much to purchase and build into the system. The salt strike costs three times more to operate, and the autoclave costs six times more to operate. Comparative Example 2d. Batch process with single autoclave, five times the size of Example 2a.

[0098] The process described in Example 2a is followed, using a system that includes units that are about five times the size.

[0099] The salt strike delivers material into the autoclave at about 525

L/min, has a volume of about 20,000 L, costs about 5*Z to purchase and build into the system, and costs about 5*Z/h to operate. The autoclave has a volume of about 75,000 L, costs about 500*Z to purchase and build into the system, and costs about 80*X/h to operate.

[00100] The system generates five times as much product in a given time as the system of Example 2a; however, the larger batch reactor is less efficient, such that the product generated has 2 wt water. To bring the wt water to 0.1 , the residence time in the autoclave is extended to 1.5 h. The salt strike costs five times more to purchase and build into the system. The autoclave costs twenty times more to purchase and build into the system. The salt strike costs five times more to operate. The autoclave costs ten times more to operate.

Comparative Example 2e. Batch process with single autoclave, ten times the size of Example 2a.

[00101] The process described in Example 2a is followed, using a system that includes units that are about ten times the size.

[00102] The salt strike delivers material into the autoclave at about 1,050

L/min, has a volume of about 40,000 L, costs about 10*Z to purchase and build into the system, and costs about 10*X/h to operate. The autoclave has a volume of about 150,000 L, costs about 12,500*Z to purchase and build into the system, and costs about 2,000*X/h to operate.

[00103] The system generates ten times as much product in a given time as the system of Example 2a; however, the autoclave is less efficient at the larger size, generating product having 0.5 wt water. To generate 0.1 wt water, the residence time in the autoclave is extended to 5 h. The salt strike costs ten times more to purchase and build into the system. The autoclave costs 500 times more to purchase and build into the system. The salt strike costs ten times more to operate. The autoclave costs 250 times more to operate. Example 3a. Continuous process with multiple finishers.

[00104] The process described in Example la is followed, using a system that includes units that are about three times the size and that handle three times the flow rate, like Example lc. However, instead of the single finisher of Example lc, two parallel finishers are used, with the flow from the flasher being split evenly between the finishers.

[00105] The salt strike delivers material into the evaporator at about 315

L/min, has a volume of about 12,000 L, costs about 3*Z to purchase and build into the system, and costs about 3*X/h to operate. The evaporator delivers material into the reactor at about 225 L/min, has a volume of about 12,000 L, costs about 9*Z to purchase and build into the system, and costs about 12*X/h to operate. The reactor delivers material into the flasher at about 180 L/min, has a volume of about 4,500 L, costs about 15*Z to purchase and build into the system, and costs about 12*X/h to operate. The flasher delivers material into the finishers at about 177 L/min, has a volume of about 7,500 L, costs about 15*Z to purchase and build into the system, and costs about 12-X/h to operate. Each of the finishers delivers material to the extruder/pelletizer at about 89 L/min, has a volume of about 4,500 L, costs about 7.5*Z to purchase and build into the system, and costs about 6*X/h to operate.

[00106] The system generates three times as much product in a given time as the system of Example la. The components each cost three times as much to purchase and build into the system, including each finisher, as contrasted with

Example lc, although the total cost of the finishers is the same. The components each cost three times as much to operate, including the finisher, as contrasted with Example lc, although the total cost of operating the finishers is the same. Example 3b. Continuous process with multiple finishers.

[00107] The process of Example 3 is followed, except one finisher is configured to produce polymer having a relative viscosity of about 60, and the other finisher is configured to polymer having a relative viscosity of about 50.

Example 4. Continuous process with multiple finishers.

[00108] The process described in Example la is followed, using a system that includes units that are about five times the size and that handle five times the flow rate, like Example Id. However, instead of the single finisher of Example Id, three parallel finishers are used, with the flow from the flasher being split evenly between the finishers.

[00109] The salt strike delivers material into the evaporator at about 525

L/min, has a volume of about 20,000 L, costs about 5*Z to purchase and build into the system, and costs about 5*X/h to operate. The evaporator delivers material into the reactor at about 375 L/min, has a volume of about 20,000 L, costs about 15*Z to purchase and build into the system, and costs about 20*X/h to operate. The reactor delivers material into the flasher at about 300 L/min, has a volume of about 7,500 L, costs about 25*Z to purchase and build into the system, and costs about 20*X/h to operate. The flasher delivers material into the finishers at about 295 L/min, has a volume of about 12,500 L, costs about 25*Z to purchase and build into the system, and costs about 20*X/h to operate. Each of the finishers delivers material to the extruder/pelletizer at about 100 L/min, has a volume of about 5,100 L, costs about 8.5*Z to purchase and build into the system, and costs about 6.8*X/h to operate.

[00110] The system generates five times as much product in a given time as the system of Example la. The components each cost five times as much to purchase and build into the system, except for the flashers which each cost about 1.7 times as much, as contrasted with the finisher of Example Id which cost 500 times more. The components each cost five times as much to operate, except for the flashers which each cost about 1.7 times more. The product produced has a wt water of 0.1%; the capacity and throughput of the system is not limited by inefficiencies of a larger flasher as with Example Id.

Example 5a. Continuous process with multiple finishers.

[00111] The process described in Example la is followed, using a system that includes units that are about ten times the size and that handle ten times the flow rate, like Example le. However, instead of the single finisher of Example le, five parallel finishers are used, with the flow from the flasher being split evenly between the finishers.

[00112] The salt strike delivers material into the evaporator at about 1,050

L/min, has a volume of about 40,000 L, costs about 10*Y to purchase and build into the system, and costs about 10*X/h to operate. The evaporator delivers material into the reactor at about 750 L/min, has a volume of about 40,000 L, costs about 30*Y to purchase and build into the system, and costs about 40*X/h to operate. The reactor delivers material into the flasher at about 600 L/min, has a volume of about 15,000 L, costs about 50*Z to purchase and build into the system, and costs about 40*X/h to operate. The flasher delivers material into the finishers at about 590 L/min, has a volume of about 25,000 L, costs about 50*Z to purchase and build into the system, and costs about 40*X/h to operate. Each of the finishers delivers material to the extruder/pelletizer at about 118 L/min, has a volume of about 6,000 L, costs about 10*Z to purchase and build into the system, and costs about 8*X/h to operate.

[00113] The system generates ten times as much product in a given time as the system of Example la. The components each cost ten times as much to purchase and build into the system, except for the finishers which each cost two times as much, as contrasted with the finisher of Example le which cost 4,000 times more. The components each cost ten times more to operate, except for the finishers which each cost about two times more as contrasted with finisher of Example le costing 2,000 times more to operate. The product produced has a wt% water of 0.1%; the capacity and throughput of the system is not limited by inefficiencies of a larger flasher as with Example le.

Example 5b. Continuous process with multiple finishers and multiple flashers.

[00114] The process described in Example la is followed, using a system that includes units that are about ten times the size and that handle ten times the flow rate, like Example le. However, instead of the single finisher and the single flasher of Example le, two parallel flashers are used, and five parallel finishers are used, with the flow from the flasher being split evenly between the flashers and the finishers.

[00115] The salt strike delivers material into the evaporator at about 1,050

L/min, has a volume of about 40,000 L, costs about 10*Z to purchase and build into the system, and costs about 10*X/h to operate. The evaporator delivers material into the reactor at about 750 L/min, has a volume of about 40,000 L, costs about 30*Z to purchase and build into the system, and costs about 30*X/h to operate. The reactor delivers material into the flashers at about 600 L/min, has a volume of about 15,000 L, costs about 50*Z to purchase and build into the system, and costs about 40*X/h to operate. Each of the flashers delivers material into the finishers at about 295 L/min, has a volume of about 12,500 L, costs about 20*Z to purchase and build into the system, and costs about 20*X/h to operate. Each of the finishers delivers material to the extruder/pelletizer at about 118 L/min, has a volume of about 6,000 L, costs about 10*Z to purchase and build into the system, and costs about 8*X/h to operate.

[00116] The system generates ten times as much product in a given time as the system of Example la. The components each cost ten times as much to purchase and build into the system, except for 1) the finishers which each cost two times as much, as contrasted with the finisher of Example le which cost 4,000 times more, and 2) the flashers, which each cost five times as much, as contrasted with Example le, although the total cost of flashers is the same. The components each cost ten times more to operate, except for 1) the finishers which each cost about two times more as contrasted with the finisher of Example le costing 2,000 times more to operate, and 2) the flashers, which each cost five times as much, as contrasted with Example le, although the total cost of operating the flashers is the same. The product produced has a wt water of 0.1%; the capacity and throughput of the system is not limited by inefficiencies of a larger flasher as with Example le. When a finisher or flasher goes offline for maintenance, the system can continue to produce product.

Example 5c. Continuous process with multiple finishers, multiple flashers, and multiple reactors.

[00117] The process described in Example la is followed, using a system that includes units that are about ten times the size and that handle ten times the flow rate, like Example le. However, instead of the single reactor, finisher, and flasher of Example le, two parallel reactors are used, two parallel flashers are used, and five parallel finishers are used, with the flow from the flasher being split evenly between the reactors, flashers, and the finishers.

[00118] The salt strike delivers material into the evaporator at about 1,050

L/min, has a volume of about 40,000 L, costs about 10*Z to purchase and build into the system, and costs about 10*X/h to operate. The evaporator delivers material into the reactor at about 750 L/min, has a volume of about 40,000 L, costs about 30*Z to purchase and build into the system, and costs about 40*X/h to operate. Each of the reactors delivers material into the flashers at about 300 L/min, has a volume of about 7,500 L, costs about 25*Z to purchase and build into the system, and costs about 20*X/h to operate. Each of the flashers delivers material into the finishers at about 295 L/min, has a volume of about 12,500 L, costs about 25*Z to purchase and build into the system, and costs about 20*X/h to operate. Each of the finishers delivers material to the extruder/pelletizer at about 118 L/min, has a volume of about 6,000 L, costs about 10*Z to purchase and build into the system, and costs about 8*X/h to operate. [00119] The system generates ten times as much product in a given time as the system of Example la. The components each cost ten times as much to purchase and build into the system, except for 1) the finishers which each cost two times as much, as contrasted with the finisher of Example le which cost 4,000 times more, 2) the flashers, which each cost five times as much, as contrasted with Example le, although the total cost of flashers is the same, and 3) the reactors, which each cost five times as much, as contrasted with Example le, although the total cost of reactors is the same. The components each cost ten times more to operate, except for 1) the finishers which each cost about two times more as contrasted with the finisher of Example le finisher costing 2,000 times more to operate, 2) the flashers, which each cost five times as much, as contrasted with Example le, although the total cost of operating the flashers is the same, and 3) the reactors, which each cost five times as much, as contrasted with Example le, although the total cost of operating the reactors I the same. The product produced has a wt water of 0.1%; the capacity and throughput of the system is not limited by inefficiencies of a larger flasher as with Example le. When a reactor, finisher, or flasher needs to go offline for maintenance, the system can continue to produce product. Example 6a. Batch process with multiple autoclaves.

[00120] The process described in Example 2a is followed, using a system that includes units that are about three times the size and that handle three times the flow rate, like Example 2c. However, instead of the single autoclave of Example 2c, two parallel autoclaves are used, with the flow from the flasher being split evenly between the finishers.

[00121] The salt strike delivers material into the autoclaves at about 315

L/min, has a volume of about 12,000 L, costs about 3*Z to purchase and build into the system, and costs about 3*X/h to operate. Each autoclave has a volume of about 22,500 L, costs about 37.5*Z to purchase and build into the system, and costs about 12*X/h to operate. [00122] The system generates three times as much product in a given time as the system of Example 2a. The components each cost three times as much to purchase and build into the system, and each component of the system costs three times as much to operate, as constrasted with the autoclave of Example 2c which costs six times more to purchase and to operate, although the total cost of purchasing and operation is the same.

Example 6b. Batch process with multiple autoclaves.

[00123] The procedure of Example 6a is followed, except one autoclave is configured to produce product having a relative viscosity of about 50, and the other autoclave is configured to produce product having a relative viscosity of about 60.

Example 7. Batch process with multiple autoclaves.

[00124] The process described in Example 2a is followed, using a system that includes units that are about five times the size and that handle five times the flow rate, like Example 2d. However, instead of the single autoclave of Example 2d, three parallel autoclaves are used, with the flow from the flasher being split evenly between the finishers.

[00125] The salt strike delivers material into the autoclave at about 525 L/min, has a volume of about 20,000 L, costs about 5*Z to purchase and build into the system, and costs about 5*X/h to operate. The autoclaves each have a volume of about 25,500 L, cost about 42.5*Z to purchase and build into the system, and cost about 13.6*X/h to operate.

[00126] The system generates five times as much product in a given time as the system of Example 2a. The salt strike costs five times more to purchase and build into the system, and five times more to operate. The autoclaves each cost 1.7 times the amount to purchase and build into the system, as contrasted with the autoclave of Example 2d costing twenty times more. The autoclaves each cost 1.7 times the amount to operate, as contrasted with the autoclave of Example 2d costing ten times more to operate. Unlike Example 2d, the multiple autoclaves produce product having a wt water of 0.1 wt without limiting the capacity of the salt strike.

Example 8. Batch process with multiple autoclaves.

[00127] The process described in Example 2a is followed, using a system that includes units that are about ten times the size and that handle ten times the flow rate, like Example 2e. However, instead of the single autoclave of Example 2e, five parallel autoclaves are used, with the flow from the flasher being split evenly between the finishers.

[00128] The salt strike delivers material into the autoclave at about 1,050

L/min, has a volume of about 40,000 L, costs about 10*Z to purchase and build into the system, and costs about 10*X/h to operate. The autoclave has a volume of about 75,000 L, costs about 125*Z to purchase and build into the system, and costs about 40*X/h to operate.

[00129] The system generates ten times as much product in a given time as the system of Example 2a. The salt strike costs ten times more to purchase and build into the system, and to operate. The autoclaves each cost two times as much to purchase and build into the system, as contrasted with Example 2e, with autoclaves costing 500 times more to purchase and build into the system. The autoclaves each cost two times as much to operate, as contrasted with Example 2e, with autoclaves costing 250 times as much to operate. Unlike Example 2e, the multiple autoclaves produce product having a wt water of 0.1 wt without limiting the capacity of the salt strike. [00130] The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention that in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. Modification and variation of the concepts herein disclosed may be resorted to by those of ordinary skill in the art, and that such modifications and variations are considered to be within the scope of this invention as defined by the appended claims.

Additional Statements.

[00131] The present invention provides for the following statements, the numbering of which is not to be construed as designating levels of importance:

[00132] Statement 1 provides a method of synthesizing a polyamide, the method comprising: evaporating a mixture comprising an oligomer formed from a linear dicarboxylic acid and a linear diamine sufficient to remove at least some water from the mixture, to provide a pre-finished mixture; splitting the pre-finished mixture into at least a first pre-finished mixture and a second pre-finished mixture; finishing the first pre-finished mixture in a first finisher, to provide a first finished mixture comprising a first polyamide; and finishing the second pre-finished mixture in a second finisher, to provide a second finished mixture comprising a second polyamide.

[00133] Statement 2 provides the method of Statement 1, wherein the finishing of the first pre-finished mixture in the first finisher and the finishing of the second pre-finished mixture in the second finisher occurs at least partially simultaneously.

[00134] Statement 3 provides the method of any one of Statements 1-2, wherein the finishing of the first pre-finished mixture in the first finisher and the finishing of the second pre-finished mixture in the second finisher occurs substantially simultaneously.

[00135] Statement 4 provides the method of any one of Statements 1-3, wherein the first finished mixture has a relative viscosity that is substantially the same as a relative viscosity of the second finished mixture.

[00136] Statement 5 provides the method of any one of Statements 1-4, wherein the first polyamide is substantially the same as the second polyamide. [00137] Statement 6 provides the method of any one of Statements 1-5, wherein the first finished mixture has a different relative viscosity than a relative viscosity of the second finished mixture.

[00138] Statement 7 provides the method of any one of Statements 1-6, wherein the first finished mixture and the second finished mixture each

independently have a relative viscosity of about 15-70.

[00139] Statement 8 provides the method of any one of Statements 1-7, wherein the first finished mixture has a relative viscosity of about 15-70 and the second finished mixture has a relative viscosity of about 15-70.

[00140] Statement 9 provides the method of any one of Statements 1-8, wherein the first finished mixture has a relative viscosity of about 30-50 and the second finished mixture has a relative viscosity of about 30-50.

[00141] Statement 10 provides the method of any one of Statements 1-9, wherein the first polyamide is different from the second polyamide.

[00142] Statement 11 provides the method of any one of Statements 1-10, wherein the evaporating provides an evaporated mixture, further comprising reacting the evaporated mixture in a reactor so as to remove at least some water therefrom, to provide the pre-finished mixture.

[00143] Statement 12 provides the method of Statement 11, wherein the reactor comprises a tubular reactor.

[00144] Statement 13 provides the method of Statement 11, wherein the reactor comprises a distillative reactor.

[00145] Statement 14 provides the method of any one of Statements 11-13, wherein the splitting of the pre-finished mixture comprises splitting the pre-finished mixture into at least a first pre-flashed mixture and a second pre-flashed mixture; flashing the first pre-flashed mixture in a first flasher to provide the first pre- finished mixture; and flashing the second pre-flashed mixture in a second flasher to provide the second pre-finished mixture. [00146] Statement 15 provides the method of Statement 14, wherein the flashing of the first pre-flashed mixture in the first flasher and the flashing of the second pre-flashed mixture in the second flasher is at least partially simultaneous.

[00147] Statement 16 provides the method of any one of Statements 1-15, wherein the evaporating provides an evaporated mixture, further comprising reacting the evaporated mixture in a reactor so as to remove at least some water therefrom, to provide a pre-flashed mixture; and flashing the pre-flashed mixture in a flasher so as to remove at least some water therefrom, to provide the pre-finished mixture.

[00148] Statement 17 provides the method of any one of Statements 1-16, wherein the splitting of the pre-finished mixture comprises splitting the pre-finished mixture into at least a first pre-reacted mixture and a second pre-reacted mixture; reacting the first pre-reacted mixture in a first reactor to provide the first pre- finished mixture; and reacting the second pre-reacted mixture in a second reactor to provide the second pre-finished mixture.

[00149] Statement 18 provides the method of Statement 17, wherein at least one of the first and second reactor comprises a tubular reactor.

[00150] Statement 19 provides the method of any one of Statements 17-18, wherein at least one of the first and second reactor comprises a distillative reactor.

[00151] Statement 20 provides the method of any one of Statements 17-19, wherein the reacting of the first pre-reacted mixture in the first reactor and the reacting of the second pre-reacted mixture in the second reactor is at least partially simultaneous.

[00152] Statement 21 provides the method of any one of Statements 1-20, wherein the splitting of the pre-finished mixture comprises splitting the pre-finished mixture into at least a first pre-reacted mixture and a second pre-reacted mixture; reacting the first pre-reacted mixture in a first reactor to provide a first pre-flashed mixture; reacting the second pre-reacted mixture in a second reactor to provide a second pre-flashed mixture; flashing the first pre-flashed mixture in a first flasher to provide the first pre-finished mixture; and flashing the second pre-flashed mixture in a second flasher to provide the second pre-finished mixture.

[00153] Statement 22 provides the method of Statement 21, wherein the reacting of the first pre-reacted mixture in the first reactor and the reacting of the second pre-reacted mixture in the second reactor is at least partially simultaneous.

[00154] Statement 23 provides the method of any one of Statements 21-22, wherein the flashing of the first pre-flashed mixture in the first flasher and the flashing of the second pre-flashed mixture in the second flasher is at least partially simultaneous.

[00155] Statement 24 provides the method of any one of Statements 1-23, wherein the finisher comprises an autoclave.

[00156] Statement 25 provides the method of any one of Statements 1-24, wherein the method is a continuous method for making polyamide.

[00157] Statement 26 provides the method of any one of Statements 1-25, wherein the method is a batch method for making polyamide.

[00158] Statement 27 provides the method of any one of Statements 1-26, comprising mixing the linear dicarboxylic acid and the linear diamine, to provide the mixture comprising the oligomer.

[00159] Statement 28 provides the method of any one of Statements 1-27, wherein the dicarboxylic acid has the structure HOC(0)-R¹-C(0)OH, wherein R¹ is a C1-C15 alkylene group.

[00160] Statement 29 provides the method of Statement 28, wherein the dicarboxylic acid is adipic acid.

[00161] Statement 30 provides the method of any one of Statements 27-29, wherein the diamine has the structure H₂N-R 2 -NH₂, wherein R 2 is a C1-C15 alkylene group.

[00162] Statement 31 provides the method of Statement 30, wherein the diamine is hexamethylenediamine.

[00163] Statement 32 provides the method of any one of Statements 27-31, wherein the polyamide is nylon 6,6. [00164] Statement 33 provides a system for synthesizing a polyamide, the system comprising: an evaporator configured to remove at least some water from a mixture comprising an oligomer formed from a linear dicarboxylic acid and a linear diamine, to provide a pre-finished mixture; a splitter configured to split the pre- finished mixture into at least a first pre-finished mixture and a second pre-finished mixture; a first finisher configured to finish the first pre-finished mixture to provide a first finished mixture comprising a first polyamide; and a second finisher configured to finish the second pre-finished mixture to provide a second finished mixture comprising a second polyamide.

[00165] Statement 34 provides an apparatus for synthesizing a polyamide, the apparatus comprising: an evaporator configured to remove at least some water from a mixture comprising an oligomer formed from a linear dicarboxylic acid and a linear diamine, to provide a pre-finished mixture; a splitter configured to split the pre-finished mixture into at least a first pre-finished mixture and a second pre- finished mixture; a first finisher configured to finish the first pre-finished mixture to provide a first finished mixture comprising a first polyamide; and a second finisher configured to finish the second pre-finished mixture to provide a second finished mixture comprising a second polyamide.

[00166] Statement 35 provides the apparatus of Statement 34, wherein the first finisher is configured to finish the first pre-finished mixture and the second finisher is configured to finish the second pre-finished mixture at least partially simultaneously.

[00167] Statement 36 provides the apparatus of any one of Statements 34-35, wherein the first finisher is configured to finish the first pre-finished mixture and the second finisher is configured to finish the second pre-finished mixture substantially simultaneously.

[00168] Statement 37 provides the apparatus of any one of Statements 34-36, wherein the first finished mixture has a relative viscosity that is substantially the same as a relative viscosity of the second finished mixture. [00169] Statement 38 provides the apparatus of any one of Statements 34-37, wherein the first polyamide is substantially the same as the second polyamide.

[00170] Statement 39 provides the apparatus of any one of Statements 34-38, wherein the first finished mixture has a different relative viscosity than a relative viscosity of the second finished mixture.

[00171] Statement 40 provides the apparatus of any one of Statements 34-39, wherein the first finished mixture and the second finished mixture each

independently have a relative viscosity of about 15-70.

[00172] Statement 41 provides the apparatus of any one of Statements 34-40, wherein the first finished mixture has a relative viscosity of about 30-50 and the second finished mixture has a relative viscosity of about 30-50.

[00173] Statement 42 provides the apparatus of any one of Statements 34-41, wherein the first finished mixture has a relative viscosity of about 30-50 and the second finished mixture has a relative viscosity of about 30-50.

[00174] Statement 43 provides the apparatus of any one of Statements 34-42, wherein the first polyamide is different from the second polyamide.

[00175] Statement 44 provides the apparatus of any one of Statements 34-43, wherein the evaporator provides an evaporated mixture, wherein the apparatus further comprises a reactor configured to remove at least some water from the evaporated mixture to provide the pre-finished mixture.

[00176] Statement 45 provides the apparatus of Statement 44, wherein the reactor comprises a tubular reactor.

[00177] Statement 46 provides the apparatus of Statement 44, wherein the reactor comprises a distillative reactor.

[00178] Statement 47 provides the apparatus of any one of Statements 44-46, wherein the splitter is configured to split the pre-finished mixture into at least a first pre-flashed mixture and a second pre-flashed mixture, wherein the apparatus further comprises a first flasher configured to flash the first pre-flashed mixture to provide the first pre-finished mixture; and a second flasher configured to flash the second pre-flashed mixture to provide the second pre-finished mixture. [00179] Statement 48 provides the apparatus of Statement 47, wherein the first flasher is configured to flash the first pre-flashed mixture and the second flasher is configured to flash the second pre-flashed mixture at least partially simultaneously.

[00180] Statement 49 provides the apparatus of any one of Statements 47-48, wherein the first flasher is configured to flash the first pre-flashed mixture and the second flasher is configured to flash the second pre-flashed mixture substantially simultaneously.

[00181] Statement 50 provides the apparatus of any one of Statements 34-49, wherein the evaporator provides an evaporated mixture, wherein the apparatus further comprises a reactor configured to react the evaporated mixture to remove at least some water therefrom, to provide a pre-flashed mixture; and a flasher configured to flash the pre-flashed mixture to remove at least some water therefrom, to provide the pre-finished mixture.

[00182] Statement 51 provides the apparatus of any one of Statements 34-50, wherein the splitter is configured to split the pre-finished mixture into a first pre- reacted mixture and a second pre-reacted mixture, wherein the apparatus further comprises a first reactor configured to react the first pre-reacted mixture to provide the first pre-finished mixture; and a second reactor configured to react the second pre-reacted mixture to provide the second pre-finished mixture.

[00183] Statement 52 provides the apparatus of Statement 51, wherein at least one of the first and second reactor comprises a tubular reactor.

[00184] Statement 53 provides the apparatus of Statement 51, wherein at least one of the first and second reactor comprises a distillative reactor.

[00185] Statement 54 provides the apparatus of any one of Statements 51-53, wherein the first reactor is configured to react the first pre-reacted mixture and the second reactor is configured to react the second pre-reacted mixture at least partially simultaneously.

[00186] Statement 55 provides the apparatus of any one of Statements 51-54, wherein the first reactor is configured to react the first pre-reacted mixture and the second reactor is configured to react the second pre-reacted mixture substantially simultaneously.

[00187] Statement 56 provides the apparatus of any one of Statements 34-55, wherein the splitter is configured to split the pre-finished mixture into at least a first pre-reacted mixture and a second pre-reacted mixture, wherein the apparatus further comprises a first reactor configured to react the first pre-reacted mixture to provide a first pre-flashed mixture; a second reactor configured to react the second pre- reacted mixture to provide a second pre-flashed mixture; a first flasher configured to flash the first pre-flashed mixture to provide the first pre-finished mixture; and a second flasher configured to flash the second pre-flashed mixture to provide the second pre-finished mixture.

[00188] Statement 57 provides the apparatus of Statement 56, wherein the first reactor is configured to react the first pre-reacted mixture and the second reactor is configured to react the second pre-reacted mixture at least partially simultaneously.

[00189] Statement 58 provides the apparatus of any one of Statements 56-57, wherein the first reactor is configured to react the first pre-reacted mixture and the second reactor is configured to react the second pre-reacted mixture at substantially simultaneously.

[00190] Statement 59 provides the apparatus of any one of Statements 56-58, wherein the first flasher is configured to flash the first pre-flashed mixture and the second flasher is configured to flash the second pre-flashed mixture at least partially simultaneously.

[00191] Statement 60 provides the apparatus of any one of Statements 34-59, wherein the finisher comprises an autoclave.

[00192] Statement 61 provides the apparatus of any one of Statements 34-60, wherein the apparatus is configured to make polyamide in a continuous fashion.

[00193] Statement 62 provides the apparatus of any one of Statements 34-61, wherein the apparatus is configured to make polyamide in a batch fashion. [00194] Statement 63 provides the apparatus of any one of Statements 34-62, comprising a mixer configured to mix the linear dicarboxylic acid and the linear diamine, to provide the mixture comprising the oligomer.

[00195] Statement 64 provides the apparatus of any one of Statements 34-63, wherein the dicarboxylic acid has the structure HOC(0)-R¹-C(0)OH, wherein R¹ is a C1-C15 alkylene group.

[00196] Statement 65 provides the apparatus of Statement 64, wherein the dicarboxylic acid is adipic acid.

[00197] Statement 66 provides the apparatus of any one of Statements 34-65, wherein the diamine has the structure H₂N-R 2 -NH₂, wherein R 2 is a C1-C15 alkylene group.

[00198] Statement 67 provides the apparatus of Statement 66, wherein the diamine is hexamethylenediamine.

[00199] Statement 68 provides the apparatus of any one of Statements 34-67, wherein the polyamide is nylon 6,6.

[00200] Statement 69 provides the apparatus or method of any one or any combination of Statements 1-68 optionally configured such that all elements or options recited are available to use or select from.

Claims

CLAIMS What is claimed is:

1. A method of synthesizing a polyamide, the method comprising:

evaporating a mixture comprising an oligomer formed from a linear dicarboxylic acid and a linear diamine sufficient to remove at least some water from the mixture, to provide a pre-finished mixture;

splitting the pre-finished mixture into at least a first pre-finished mixture and a second pre-finished mixture;

finishing the first pre-finished mixture in a first finisher, to provide a first finished mixture comprising a first polyamide; and

finishing the second pre-finished mixture in a second finisher, to provide a second finished mixture comprising a second polyamide.

2. The method of claim 1, wherein the finishing of the first pre-finished mixture in the first finisher and the finishing of the second pre-finished mixture in the second finisher occurs at least partially simultaneously.

3. The method of any one of claims 1-2, wherein the first finished mixture has a relative viscosity that is substantially the same as a relative viscosity of the second finished mixture.

4. The method of any one of claims 1-3, wherein the first polyamide is substantially the same as the second polyamide.

5. The method of any one of claims 1-4, wherein the first finished mixture has a different relative viscosity than a relative viscosity of the second finished mixture.

6. The method of any one of claims 1-5, wherein the first finished mixture and the second finished mixture each independently have a relative viscosity of about

15-70.

7. The method of any one of claims 1-6, wherein the first finished mixture has a relative viscosity of about 15-70 and the second finished mixture has a relative viscosity of about 15-70.

8. The method of any one of claims 1-7, wherein the first polyamide is different from the second polyamide.

9. The method of any one of claims 1-8, wherein the evaporating provides an evaporated mixture, further comprising

reacting the evaporated mixture in a reactor so as to remove at least some water therefrom, to provide the pre-finished mixture.

10. The method of claim 9, wherein the splitting of the pre-finished mixture comprises

splitting the pre-finished mixture into at least a first pre-flashed mixture and a second pre-flashed mixture;

flashing the first pre-flashed mixture in a first flasher to provide the first pre- finished mixture; and

flashing the second pre-flashed mixture in a second flasher to provide the second pre-finished mixture.

11. The method of claim 10, wherein the flashing of the first pre-flashed mixture in the first flasher and the flashing of the second pre-flashed mixture in the second flasher is at least partially simultaneous.

12. The method of any one of claims 1-11, wherein the evaporating provides an evaporated mixture, further comprising

reacting the evaporated mixture in a reactor so as to remove at least some water therefrom, to provide a pre-flashed mixture; and

flashing the pre-flashed mixture in a flasher so as to remove at least some water therefrom, to provide the pre-finished mixture.

13. The method of any one of claims 1-12, wherein the splitting of the pre- finished mixture comprises

splitting the pre-finished mixture into at least a first pre-reacted mixture and a second pre-reacted mixture;

reacting the first pre-reacted mixture in a first reactor to provide the first pre- finished mixture; and

reacting the second pre-reacted mixture in a second reactor to provide the second pre-finished mixture.

14. The method of claim 13, wherein the reacting of the first pre-reacted mixture in the first reactor and the reacting of the second pre-reacted mixture in the second reactor is at least partially simultaneous.

15. The method of any one of claims 1-14, wherein the splitting of the pre- finished mixture comprises

reacting the first pre-reacted mixture in a first reactor to provide a first pre- flashed mixture;

reacting the second pre-reacted mixture in a second reactor to provide a second pre-flashed mixture;

16. The method of claim 15, wherein the reacting of the first pre-reacted mixture in the first reactor and the reacting of the second pre-reacted mixture in the second reactor is at least partially simultaneous.

17. The method of any one of claims 15-16, wherein the flashing of the first pre- flashed mixture in the first flasher and the flashing of the second pre-flashed mixture in the second flasher is at least partially simultaneous.

18. The method of any one of claims 1-17, wherein the finisher comprises an autoclave.

19. A system for synthesizing a polyamide, the system comprising:

an evaporator configured to remove at least some water from a mixture comprising an oligomer formed from a linear dicarboxylic acid and a linear diamine, to provide a pre-finished mixture;

a splitter configured to split the pre-finished mixture into at least a first pre- finished mixture and a second pre-finished mixture;

a first finisher configured to finish the first pre-finished mixture to provide a first finished mixture comprising a first polyamide; and

a second finisher configured to finish the second pre-finished mixture to provide a second finished mixture comprising a second polyamide.

20. An apparatus for synthesizing a polyamide, the apparatus comprising: an evaporator configured to remove at least some water from a mixture comprising an oligomer formed from a linear dicarboxylic acid and a linear diamine, to provide a pre-finished mixture;