TECHNICAL FIELD

The present disclosure is drawn to apparatuses and methods for batch production of polyamide polymers, wherein the apparatuses and methods utilize direct injection of additives into the autoclave.

BACKGROUND Polyamide polymers, such as nylon 6,6, can be synthesized using complex chemical engineering processes on a relatively large scale. These chemical engineering processes can include steps such as a salt strike step where polyamide (e.g., nylon 6,6) salt solutions are prepared, an evaporation step where some of the water from the salt solution is evaporated off, an autoclave process where the salt solution is placed under heat and pressure for polymerization, and extrusion/cutting steps where the essentially final polymeric raw materials are formed. Other steps can also be included as understood generally by those skilled in the art.

Batch processing is often used in order to make polyamide polymers. Typically, in batch processing, additives for the batch are added in the evaporator in order to remove any excess water associated with the additive. However, this methodology can limit the number of different types of polymers that can be manufactured using the autoclaves associated with a given evaporator.

Thus, it would be an advancement in the art to increase flexibility related to producing polyamide polymers on a large scale. SUMMARY

The disclosure herein relates to apparatuses and methods for batch production of polyamide polymers utilizing additive injectors that are configured to inject additives into the autoclave. In one embodiment, an apparatus for batch production of a polyamide polymer is provided. The apparatus can include a salt strike vessel configured to produce a polyamide salt composition and an evaporator configured to reduce water content of the polyamide salt composition for producing a polymerizable polyamide composition. The apparatus can further include a first autoclave operably connected to the evaporator such that a first portion of the polymerizable polyamide composition is deliverable from the evaporator to the first autoclave, and a second autoclave operably connected to the evaporator such that a second portion of the polymerizable polyamide composition is deliverable from the evaporator to the second autoclave. A first additive injector can be associated with the first autoclave and can be configured to inject additives into the first autoclave.

In another embodiment, a method of preparing a polyamide polymer is provided. The method can include preparing a polyamide salt composition by disposing starter materials in a salt strike vessel to form a polyamide salt composition, which can be transferred into an evaporator. An additional step includes evaporating at least a portion of the water present in the polyamide salt composition to form a polymerizable polyamide composition. A first portion of the polymerizable polyamide composition can be introduced from the evaporator into a first autoclave and a second portion of the polymerizable polyamide

composition can likewise be introduced into a second autoclave. At least one additive can be injected into the first autoclave. Additionally, the method includes polymerizing the first portion of the polymerizable polyamide composition in the first autoclave to produce a first polyamide polymer and polymerizing the second portion of the polymerizable polyamide composition in the second autoclave to produce a second polyamide polymer.

Additional features and advantages of the invention will be apparent from the detailed description that follows, which illustrates, by way of example, features of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exemplary graph depicting relative plots of pressure, heat, and venting with respect to each other during a batch 5-cycle process in accordance with embodiments of the present disclosure;

FIG. 2 shows a generalized flow diagram of a polyamide polymer production process from salt strike to final pellets, including autoclaves associated with additive injectors for injection of additives directly to the autoclaves in accordance with embodiments of the present disclosure;

FIG. 3 shows a generalized flow diagram of an evaporator, a parallel group of autoclaves, and various additive injectors for injection of additives directly to the autoclaves in accordance with examples of the present disclosure;

FIG. 4 is a schematic cross-sectional view of an autoclave that is usable in the apparatuses shown in FIGS. 2 and 3 in accordance with embodiments of the present disclosure; and

FIG. 5 is a schematic cross-sectional view of an alternative autoclave that is usable in the apparatuses shown in FIGS. 2 and 3 in accordance with embodiments of the present disclosure.

It should be noted that the figures are merely exemplary of certain embodiments of the present disclosure and no limitations on the scope of the present invention are intended thereby.

DETAILED DESCRIPTION

Although the following detailed description contains many specifics for the purpose of illustration, a person of ordinary skill in the art will appreciate that many variations and alterations to the following details are within the scope of the disclosed embodiments.

Accordingly, the following embodiments are set forth without any loss of generality to, and without imposing limitations upon any claimed invention. Before the present disclosure is described in greater detail, it is to be understood that this disclosure is not limited to particular embodiments described, as these may vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of the present disclosure will be limited only by the appended claims. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

As used in this specification and the appended claims, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a vent line" includes a plurality of vent lines.

The term "polymerizable polyamide composition" refers to the solution or slurry that is added to an agitated autoclave in accordance with examples of the present disclosure, and that upon processing the polymerizable polyamide composition within the autoclave under certain heat and pressure profiles, a polymer can be formed that may be extruded or otherwise harvested for further use. It is noted, however, that as the polymerizable polyamide composition begins to polymerize within the autoclave, the composition will begin to thicken into a polymer. Thus, it is difficult to delineate at what point it ceases to be a polymerizable polyamide composition compared to a thickening polymer. As a result, for convenience, the term "polymerizable polyamide composition" may be used herein to describe the composition in the autoclave regardless of its polymerization state.

The term "polyamide salt" refers to the salt that is included in the polymerizable polyamide composition (optionally along with other additives) that provides the basic polymerizable material for forming the polyamide polymer. If the polyamide polymer is nylon 6,6, for example, then the salt can be prepared from a condensation reaction between adipic acid and hexamethylene diamine. A "polyamide salt composition" refers to a composition produced in a salt strike that includes a polyamide salt and a portion of water. Other additives can also be included in the polyamide salt composition, either introduced prior to the agitated autoclave, or, as described herein, the additives can be introduced directly into the autoclave. The term "additive injector" or "injector" generally refers to all or part of a component or collection of components that act to deliver an additive to an autoclave. This is disguisable with apparatuses for introducing additives into the evaporator, which are not included in this definition. The additive injector can be said to include a variety of elements including, but not limited to, an additive reservoir where the additive can be stored prior to delivery to an autoclave, delivery lines that carry the additive to an autoclave, and/or a port that allows passage of the additive directly into the autoclave or other inlet means that delivers the additive to the autoclave. A valve can be present on the additive injector, or the autoclave, as would be appreciated by one skilled in the art.

The term "cycle" refers to the stages of a batch polymerization process as defined primarily by the pressure profile within the agitated autoclave. A first cycle (Cycle 1 ) occurs at the beginning of the batch process while the pressure is being increased from a low press to a relative high pressure. A second cycle (Cycle 2) occurs as the relative high pressure is maintained for a period of time, typically assisted by pressure venting. A third cycle (Cycle 3) occurs as the relative high pressure is reduced back to a low pressure (which can optionally be an even lower pressure than the initial low pressure as per the use of a vacuum). A fourth cycle (Cycle 4) occurs as the (vacuum) low pressure is maintained for a period of time. A fifth cycle (Cycle 5) occurs as the prepared polymer in the autoclave is being extruded by increased pressure from the agitated autoclave vessel.

The terms "relative high pressure" refer to pressures within a batch process where the pressure is at essentially its highest level. Thus, the pressure is "high" relative to the other pressure levels during the batch cycle process. For example, an initial low pressure can be increased to a relative high pressure during Cycle 2. In considering a pressure profile of a 5 cycle batch, when the pressure is at or about the highest pressure of a batch process profile, the "relative high pressure" has been reached. In some of the examples shown herein, a relative high pressure of about 230 to 300 psi is shown, though other pressure profiles may provide a relative high pressure outside of this range.

The term "agitating" refers to the state of the agitator while it is functioning at a level sufficient to cause at least some polymerizable polyamide composition or resultant polymer mixing. In one example, the agitator can be an auger that is spinning within the agitated autoclave at up to 100 RPM, but can range from 5 RPM to 90 RPM, for example. Not all autoclaves include an agitator, so this definition is relevant to only agitated autoclaves (as shown in FIG. 4), and not non-agitated autoclaves (as shown in FIG. 5).

In this disclosure, "comprises," "comprising," "containing" and "having" and the like can have the meaning ascribed to them in U.S. Patent law and can mean "includes," "including," and the like, and are generally interpreted to be open ended terms. The term "consisting of" is a closed term, and includes only the devices, methods, compositions, components, structures, steps, or the like specifically listed, and that which is in accordance with U.S. Patent law.

"Consisting essentially of or "consists essentially" or the like, when applied to devices, methods, compositions, components, structures, steps, or the like encompassed by the present disclosure, refers to elements like those disclosed herein, but which may contain additional structural groups, composition components, method steps, etc. Such additional devices, methods, compositions, components, structures, steps, or the like, etc., however, do not materially affect the basic and novel characteristic(s) of the devices, compositions, methods, etc., compared to those of the corresponding devices, compositions, methods, etc., disclosed herein. In further detail, "consisting essentially of or "consists essentially" or the like, when applied to devices, methods, compositions, components, structures, steps, or the like encompassed by the present disclosure have the meaning ascribed in U.S. Patent law and the term is open- ended, allowing for the presence of more than that which is recited so long as basic or novel characteristics of that which is recited is not changed by the presence of more than that which is recited, but excludes prior art embodiments. When using an open ended term, like "comprising" or "including," it is understood that direct support should be afforded also to "consisting essentially of language as well as "consisting of language as if stated explicitly.

Phrases such as "suitable to provide," "sufficient to cause," or "sufficient to yield," or the like, in the context of methods of synthesis, refers to reaction conditions related to time, temperature, solvent, reactant concentrations, and the like, that are within ordinary skill for an experimenter to vary to provide a useful quantity or yield of a reaction product. It is not necessary that the desired reaction product be the only reaction product or that the starting materials be entirely consumed, provided the desired reaction product can be isolated or otherwise further used.

It should be noted that ratios, concentrations, amounts, and other numerical data may be expressed herein in a range format. It is to be understood that such a range format is used for convenience and brevity, and thus, 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 includes "about 'x' to about 'y'". To illustrate, a concentration range of "about 0.1 % to about 5%" should be interpreted to include not only the explicitly recited concentration of about 0.1 wt% to about 5 wt%, but also include individual concentrations (e.g., 1 %, 2%, 3%, and 4%) and the sub-ranges (e.g., 0.5%, 1.1 %, 2.2%, 3.3%, and 4.4%) within the indicated range. In an

embodiment, the term "about" can include traditional rounding according to significant figures of the numerical value. In addition, the phrase "about 'x' to 'y " includes "about 'x' to about 'y'".

The term "about" as used herein, when referring to a numerical value or range, allows for a degree of variability in the value or range, for example, within 10%, or, in one aspect within 5%, of a stated value or of a stated limit of a range.

Where features or aspects of the disclosure are described in terms of a list or a Markush group, those skilled in the art will recognize that the disclosure is also thereby described in terms of any individual member or subgroup of members of the Markush group. For example, if X is described as selected from the group consisting of bromine, chlorine, and iodine, claims for X being bromine and claims for X being bromine and chlorine are fully described as if listed individually. For example, where features or aspects of the disclosure are described in terms of such lists, those skilled in the art will recognize that the disclosure is also thereby described in terms of any combination of individual members or subgroups of members of list or Markush group. Thus, if X is described as selected from the group consisting of bromine, chlorine, and iodine, and Y is described as selected from the group consisting of methyl, ethyl, and propyl, claims for X being bromine and Y being methyl are fully described and supported.

As used herein, all percent compositions are given as weight-percentages, unless otherwise stated. When solutions of components are referred to, percentages refer to weight-percentages of the composition including solvent (e.g., water) unless otherwise indicated.

As used herein, all molecular weights (Mw) of polymers are weight- average molecular weights, unless otherwise specified.

As will be apparent to those of skill in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein has discrete components and features that may be readily separated from or combined with the features of any of the other several embodiments without departing from the scope or spirit of the present disclosure. Any recited method can be carried out in the order of events recited or in any other order that is logically possible.

It is noted in the present disclosure that when describing the autoclaves or methods, individual or separate descriptions are considered applicable to one another, whether or not explicitly discussed in the context of a particular example or embodiment. For example, in discussing a particular vent per se from a specific device, the method embodiments are also inherently included in such discussions, and vice versa.

Before discussing some of the methods and apparatuses of the present disclosure, it can be useful to understand a generalized plot of the pressure, temperature, and venting of an autoclave in one embodiment of a five cycle process for the production of a polymer. FIG. 1 shows a generalized plot of the pressure, temperature, and venting over a five cycle process. Specifically, a first cycle (Cycle 1 ) occurs at the beginning of the batch process while the pressure is being increased from a low pressure to a relative high pressure. A second cycle (Cycle 2) occurs as the relative high pressure is maintained for a period of time. Thus, as the temperature rises, thus inherently increasing pressure, the pressure can actually be maintained at the relative high pressure by venting the autoclave, as shown by the venting profile of FIG. 1 in Cycle 2. A third cycle (Cycle 3) occurs as the relative high pressure is reduced to an even lower pressure than initially present, which can be in some examples, reduced to vacuum levels for a fourth cycle (Cycle 4), which in this example, occurs as the lower (vacuum) pressure is maintained for a period of time. It is noted that vacuum pressure is not required, but is shown in this example by way of example only. A fifth cycle (Cycle 5) occurs as the pressure is increased again for the purpose of extruding the polymer from the agitated autoclave vessel.

A more detailed description of an embodiment of a five cycle process for preparing a polymer, such as shown in FIG. 1 is described below. In preparation for starting the polymer preparation process, a salt solution can brought into the agitated autoclave from an evaporator at from 80 wt% to 84 wt% concentration levels. During a first cycle (Cycle 1 ), the pressure can be increased by introducing the polymerizable polyamide composition to the vessel, by a pressure source, by heat, etc., to a specified level. Pressure levels in this apparatus can range from vacuum pressures to about 300 psi. Typically, during much or all of Cycle 1 , there is little to no venting of the autoclave, as one objective is to increase the pressure of the vessel.

In a second cycle (Cycle 2), the pressure is held substantially constant at a relative high pressure, e.g., from 230 psi to 300 psi. As the temperature of the autoclave increases the pressure is maintained substantially constant at the relative high pressure by venting the autoclave, including in some embodiments, maximum venting. In this specific example, maximum venting is shown at 2000 kg/hr (venting range from 0 to 2000 kg/hr), but it is noted that maximum venting may be at levels ranging from 1500 to 2500 kg/hr, for example, depending on the apparatus in place, though venting levels outside of this range can also be used.

As also shown in FIG. 1 , a third cycle (Cycle 3) is defined primarily by a pressure reduction. At the end of Cycle 3, with specific reference again to nylon 6,6, the relative viscosity can be about 16 to 20 units and the water concentration can be about 0.002 to 0.006 gr/gr, for example.

A fourth cycle (Cycle 4) can be characterized by an even lower pressure than initially present at the beginning of the autoclave process, and can be achieved using vacuum pressure. At the end of Cycle 4, again for nylon 6,6, the relative viscosity can be about 32 to 40 units and the water content can be about 0.001 to 0.004 gr/gr. A fifth cycle (Cycle 5) can be characterized as the casting or extrusion cycle where the polymer that is formed is extruded and pelleted for further use. Additional steps after extrusion are typically carried out, as would be understood by one skilled in the art. It is noted that these cycle descriptions are for example purposes only, and many other cyclic profiles are effective for use with the apparatuses and methods of the present disclosure.

With the above in mind, the present disclosure relates to relates to apparatuses and methods for batch production of polyamide polymers utilizing additive injectors that are configured to inject additives into the autoclave. In one embodiment, an apparatus for batch production of a polyamide polymer is provided. The apparatus can include a salt strike vessel configured to produce a polyamide salt composition. The apparatus can also include an evaporator configured to receive the polyamide salt composition and reduce its water content to produce a polymerizable polyamide composition. The apparatus can further include a first autoclave operably connected to the evaporator such that a first portion of the polymerizable polyamide composition is deliverable from the evaporator to the first autoclave, and a second autoclave operably connected to the evaporator such that a second portion of the polymerizable polyamide composition is deliverable from the evaporator to the second autoclave. The first additive injector can be associated with the first autoclave and can be configured to inject additives into the first autoclave. Optionally, the second autoclave can include a second additive injector. Also optionally, the first and/or second autoclave can include additional or supplemental additive injectors. Still further, the apparatus may include third, fourth, fifth, etc., autoclaves that are fed from the same evaporator, each having from 0 to multiple additive injectors associated therewith.

Returning to the second additive injector, this injector can likewise be configured to inject one or more additives into the second autoclave. When each autoclave in the apparatus includes a distinct associated additive injector, in some embodiments the additive injectors can be such that the first additive injector injects a first additive into the first autoclave while the second additive injector injects a second additive into the second autoclave. Thus, the additives being injected into the autoclaves of the apparatus are different, resulting in polyamide polymers having different chemical and/or physical properties. In some embodiments, the first additive injector and second additive injector may be configured to inject identical additives into their respective autoclaves, however the amounts or concentrations of the additives injected into the autoclaves by the respective additive injectors can be different so as to yield distinctive polyamide polymers as well.

In some embodiments, a single additive injector can be used on each autoclave to inject two or more additive additives, either simultaneously or in series. However, in other embodiments, one or more of the autoclaves in an apparatus can have a second, third, forth, etc., additive injector (e.g. a

supplemental additive injectors). When multiple injectors are associated with a single autoclave, the injectors can inject single additives or can inject

combinations or mixtures of additives. In one embodiment, each of the

autoclaves (or at least two autoclaves) in the apparatus has two or more additive injectors associated therewith.

As also briefly mentioned, the apparatuses of the present disclosure can include a third or even other additional autoclaves that are operably connected to the same evaporator. In one embodiment, the apparatus can include a third autoclave operably connected to the evaporator such that a third portion of the polymerizable polyamide composition is deliverable from the evaporator to the third autoclave. In such an embodiment, one or both of the second autoclave and the third autoclave can have an additive injector that is associated thereto.

The additives injected by the additive injectors of the present apparatus can be selected from any additives known in the art to be useful in the processing or preparation of polyamide polymers. Non-limiting examples of additives that can be injected utilizing the additive injectors include copper-acetate, anti-foaming agents, catalysts, antioxidant stabilizers, antimicrobials, optical brighteners, acid- dyable polymer, acid dyes, base dyes, metalized dyes, or combinations.

If a catalyst is the additive, the catalyst can be added such that it is present in the polymerizable polyamide in an amount ranging from 10 ppm to 1 ,000 ppm by weight. In another aspect, the catalyst can be present in an amount ranging from 10 ppm to 100 ppm by weight. The catalyst can include, without limitation, phosphoric acid, phosphorous acid, hypophosphoric acid

arylphosphonic acids, arylphosphinic acids, salts thereof, and mixtures thereof. In one embodiment, the catalyst can be sodium hypophosphite, manganese hypophosphite sodium phenylphosphinate, sodium phenylphosphonate, potassium phenylphosphinate, potassium phenylphosphonate,

hexamethylenediammonium bis-phenylphosphinate, potassium tolylphosphinate, or mixtures thereof. In one aspect, the catalyst can be sodium hypophosphite.

The polyamide compositions prepared in accordance with embodiments disclosed herein can be improved in whiteness appearance through the addition of an optical brightener additive, such as titanium dioxide. Such polyamides can exhibit a permanent whiteness improvement and can retain this whiteness improvement through operations such as heat setting. In one embodiment, the optical brightener can be present in the polymerizable polyamide in an amount ranging from 0.01 wt% to 1 wt%. In one embodiment, when used, the additive ΤΊΟ2 can be injected into the autoclave during the second cycle of the

polymerization in the autoclave. In another embodiment, the ΤΊΟ2 can be injected into the autoclave when the autoclave is at a temperature of at least about 230°C or more. It has been discovered that injection of the ΤΊΟ2 at temperatures lower than 230°C can result in coagulate leading to poor quality polyamide polymer. In another embodiment, the ΤΊΟ2 can be added prior to the beginning of the third cycle.

In one aspect, the ΤΊΟ2 additive used can be in a slurry form and can be injected directly into the autoclave using an additive injector. The total flow of T1O2 slurry injected into the autoclave can be measured and controlled such that the agitation (when present) of the polymerizable polyamide composition prevents coagulation of the T1O2 particles. In one embodiment, the flow rate of the T1O2 slurry can be below about 400 gr/sec slurry for a slurry having a 38% T1O2 concentration. In some embodiments, it can be desirable to utilize an injector having a dip-pipe in order to reduce the incidence of the T1O2 coming into contact with the inner walls of the autoclave. Following injection of the T1O2, the additive injector can be flushed with DM-water in order to prevent fouling of the T1O2 slurry in the dip type. As mentioned, using the apparatuses of the present disclosure, one amount of concentration of T1O2 can be added to one autoclave, and another amount or concentration of TiC^ can be added to another autoclave, thereby producing two distinct polymer compositions from a single salt strike- and evaporator-prepared composition. In further detail, if the additive is an anti-foaming additive, it can be present in the polymerizable polyamide composition in an amount ranging from 1 ppm to 500 ppm by weight. Examples of anti-foaming agents are well known in the art and are not listed herein.

The polymerizable polyamide compositions, in accordance with

embodiments of the present disclosure, can be inherently acid dyeable, but may also be rendered into a basic dyeing form by modifying these polymers or copolymers with a cationic dye copolymerized in the polymer. This modification makes compositions particularly receptive to coloration with base dyes.

Accordingly, in some embodiments the additive added can be an acid dye, a base dye, or a metalized dye.

Some additives that can be utilized in the apparatuses and methods disclosed herein can be unstable when stored over long periods of time or can become unstable when they are exposed to other compositions or additives. For example, cupric acetate is an additive that can be used in the apparatuses and methods disclosed herein. Typically, cupric acetate can be added to the autoclave during the first cycle of the polymerization process. However, solutions of copper acetate are known to be unstable over time as copper acetate can react into copper oxide in the presence of water. The addition of low

concentrations of acetic acid to the cupric acetate solution can help stabilize the copper acetate additive.

As mentioned, the polyamide polymers prepared in accordance with examples of the present disclosure can be nylon-type polyamides, such as nylon 6,6. A polymerizable polyamide composition used to form nylon 6,6 polymer, for example, can be prepared initially using a salt strike process where adipic acid and hexamethylene diamine reacted in a salt strike configured for these starting components. Water present in this composition, either introduced as a solvent to carry the reactants or by the condensation reaction of the adipic acid and the hexamethylene diamine, can be removed when the polyamide salt composition is introduced into an evaporator to remove a portion of the water prior to

introduction into the autoclave as described herein. This composition, referred to herein as the polymerizable polyamide composition, can include the nylon 6,6 salt, in some embodiments, some additive can also be included in the compositions prepared in the salt strike or evaporator, though whatever additives are included at or before the evaporator step should be additives that can commonly be present in all autoclaves being fed by the evaporator. In other words, only additives in common between batches ran in parallel should be added prior to the autoclave step.

In addition to the above described apparatuses, a method of preparing a polyamide polymer is also provided. The method can include preparing a polyamide salt composition by disposing starter materials in a salt strike vessel. The polyamide salt composition can be transferred into an evaporator where the step of evaporating at least a portion of water present in the polyamide salt composition is carried out to form a polymerizable polyamide composition. A first portion of the polymerizable polyamide composition can be introduced from the evaporator into a first autoclave and a second portion of the polymerizable polyamide composition can be introduced from the evaporator into a second autoclave. At least one additive can be injected into the first autoclave, thus making the polymer formed from the two autoclaves at least minimally different. Additionally, the method includes polymerizing the first portion of the

polymerizable polyamide composition in the first autoclave to produce a first polyamide polymer and polymerizing the second portion of the polymerizable polyamide composition in the second autoclave to produce a second polyamide polymer.

In one embodiment, the method can further comprise disposing one or more additives in the evaporator to form part of the polymerizable polyamide composition. As described above, the processes for preparing the polyamide polymers can include a multi-cycle polymerization that occurs within each autoclave. In one embodiment, the polymerizing in the autoclaves can includes a first cycle, a second cycle, and a third cycle, the first cycle comprising increasing the pressure within the autoclave from a low pressure to a relative high pressure, the second cycle comprising increasing the temperature within the autoclave and maintaining the pressure in the autoclave at a relative high pressure, and the third cycle comprising reducing the temperature and pressure within the autoclave. Depending on the additive and the desired polymer, the timing of the injection can vary. In one embodiment, the injection of one or more of the additives can occur during the first cycle of the above described polymerization. In another embodiment, the injection of one or more additive can occur during the second cycle of the above described polymerization.

Turning now to example polymers that can be prepared using the methods and apparatuses described herein, one can consider the preparation of polyamide polymers, and in particular nylon 6,6. A typical batch size in accordance with examples of the present disclosure can be from about 1000 Kg to about 1500 Kg, and can be cycled during the batch within the autoclave at from about 100 to 120 minutes. Batch sizes and timing outside of these ranges can also be used, depending on equipment and polymer choices, or other considerations within the knowledge of one skilled in the relevant arts.

Turning now to FIG. 2, a generalized flow diagram of the production process of multiple polyamide polymers is shown. The process begins with the formation of a polyamide salt composition in a salt strike or salt strike vessel 102. The polyamide salt composition can then be transferred into an evaporator 104 where at least a portion of the water present in the polyamide salt composition is removed, resulting in a polymerizable polyamide composition. As shown in FIG. 2, a single evaporator can function to provide the polymerizable polyamide composition for a plurality of autoclaves 105, 106, 107. The autoclaves can be agitated autoclaves, such as autoclave 107 with an agitator 1 16, or can be non- agitated, such as autoclaves 105 and 106, or any combination thereof. The autoclaves in the example apparatus are shown as being associated with an additive injector 1 14 that is configured to inject an additive into the associated autoclaves 105 and 106. It is noteworthy that not all autoclaves are required to be associated with the additive injector of the apparatus. Following polymerization of the polymerizable polyamide composition, the polyamide polymer can be cast and cut utilizing casting and cutting equipment 108 and optionally blended utilizing blending equipment 1 10 to yield a final polyamide polymer 1 12. It is noted that with this apparatus, three different polyamide polymers can be prepared. The polymer prepared in autoclave 105 might include an additive that is injected at a first concentration. The polymer prepared in autoclave 106 might include the same additive as injected in autoclave 105, but may be injected at a greater concentration into autoclave 106 (e.g., controlled by valves or timing profiles allowing different concentrations to be introduced into each autoclave). The polymer prepared in autoclave 107 would not include any of the additive, and thus, would likewise be of a different composition.

FIG. 3 shows an additional generalized flow diagram of an evaporator 204 (salt strike vessel not shown in this example) as it flows polymerizable polyamide composition in parallel to autoclaves 205, 206, 207. Here, a plurality of additive injectors 208, 210, 212, and 214 are also included for injection of additives directly to the autoclaves. As set forth in the present disclosure, the embodiment shows an apparatus in which a single evaporator serves to provide polymerizable polyamide composition to a plurality of autoclaves. Each of the autoclaves is associated with an additive injector that is only associated with a single autoclave. For example, additive injector 208 is associated with autoclave 205 and is not associated with any other autoclave. Likewise, additive injector 210 is only associated only with autoclave 206 while additive injector 212 is only associated with autoclave 207. Conversely, additive injector 214 is associated with each of the autoclaves 205, 206, and 207. This general flow diagram is exemplary of various combinations of additive injector and autoclave

configurations that can be arranged. In some embodiments, it can be beneficial to have additive injectors that are configured to deliver additive to a plurality of autoclaves while in other embodiments, an additive injector can be configured to inject into a single or select group of autoclaves. It is noted that though the autoclaves shown in FIG. 3 are shown as including the optional agitator 216, the use of an agitated autoclave is not required.

FIG. 4 shows a schematic cross-sectional view of an embodiment of an autoclave. This figure is not necessarily drawn to scale, and does not show each and every detail that can be present in an autoclave, opting instead to show schematic representations of features particularly relevant to the present disclosure. Thus, an autoclave 410 can include an autoclave vessel 420 defined by a vessel wall 424. Furthermore, the autoclave can optionally be an agitated autoclave and include any type of agitator 416 known in the art. The vessel includes one or more type of heating components 426a, 426b. In this example, external jacket heating components are shown at 426a and internal heating components are shown at 426b. It is noted that the internal heating components can be present in either or both locations shown. In one example, the internal heating components are positioned nearer the agitator (as shown in phantom lines), to provide appropriate heat near the agitator. In this example, there may also be room near the exterior vessel wall 424 for a pair of wall scrapers (not shown) which act to remove the polymer from close contact with the vessel wall as the polymer is moved through the vessel. The external jacket heating components can be used to raise the temperature and pressure of the

polymerizable polyamide composition or polymer contained within the vessel, and the internal heating components in particular can be used for the additional purpose of preventing polymer from becoming adhered to an interior surface of the vessel wall. It is noted that the interior heating components are shown schematically in cross-section, but it is understood that any shape or

configuration of interior heating components could be used. It is also noted that the heating components can be configured or adapted to carry any fluid known in the art for providing heat to autoclaves, including gases and/or liquids.

Furthermore, at the bottom end of the autoclave vessel is an extrusion valve opening 432. The valve is not shown, but this is the location where polymer prepared in the autoclave is extruded for further processing.

Various ports 428 are shown at a top of the autoclave vessel, which can be used for any number of purposes, including as an inlet port to introduce the polymerizable polyamide composition, inject additives, introduce gasses to the vessel, etc. Typically, pressure is modulated within the vessel by introduction of the polymerizable polyamide composition and modulation of the heating profile. However, in accordance with examples of the present disclosure, one or more of the ports 428 can be used as part of an additive 440 described herein. The additive injectors are shown as injecting additives through a wall of autoclave, thus, additive(s) directly added to the autoclave. Furthermore, a venting valve 430 is also shown for venting pressure from the autoclave.

FIG. 5 shows an additional schematic cross-sectional view of an embodiment of an autoclave. As with the autoclave shown in FIG. 4, the autoclave 510 includes an autoclave wall 524 which defines the autoclave vessel 520, and includes one or more type of heating components 526a, 526b, a venting valve 430, and an extrusion valve opening 532. This example is not an agitated autoclave as shown in FIG. 4, and thus an additional central pipe or line 542 is present that can be used to introduce fluids or additives, or vent gases, depending on how the engineer decides to rig the autoclave. Uniquely as compared the additive injectors of FIG. 4, the embodiment shown in FIG. 5 includes an inlet port 528 that is associated with the autoclave via the pipe or line, which can be used in conjunction with an additive injector 540 to introduce additives into the autoclave. Thus, an additive injector can introduce additives indirectly by using an existing inlet line.

In further detail regarding the autoclave, in some embodiments, one or more of the mechanisms of the autoclave can be automated. For example, as shown in FIG. 5, the autoclave can include a process controller 550, which can include various modules 560, 570, 580, 590 and can be used to automatically carry out the general functions or process steps of the autoclave. For example, the heating component(s) 526a, 526b can be controlled by a heating module 560. The pressure and inlet of polymerizable polyamide composition into the autoclave can be controlled utilizing the pressure/inlet control module 570 which can control the inlet port/valve 542 and the venting valve 530 of the autoclave. It is noted that pressure can also be controlled, e.g., increased, by increasing heat within the autoclave. Thus, the pressure control module can alternatively control the heating components as well. Similarly, an additive injector module 580 can operate to control the additive injector 540, thereby controlling the timing, amount, specific additive, and/or flow rate of an additive introduced into the autoclave. Thus, FIG. 1 illustrates an example where the various modules together to achieve acceptable polymerization results. It is noted, however, that other modules 590 can also be included that act together with those shown to cycle the apparatus in a manner to cause predictable batch polymerization of the polymerizable polyamide composition. For example, if an agitator is used, and agitation module can be used to control the agitator, etc.

Some of the functional units described in this specification have been labeled as "modules," in order to more particularly emphasize their

implementation independence. For example, a "module" may be implemented as a hardware circuit comprising custom VLSI circuits or gate arrays, off-the-shelf semiconductors such as logic chips, transistors, or other discrete components. A module may also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices or the like. Modules may also be implemented in software for execution by various types of processors. An identified module of executable code may, for instance, comprise one or more blocks of computer instructions, which may be organized as an object, procedure, or function. Nevertheless, the executables of an identified module need not be physically located together, but may comprise disparate instructions stored in different locations which comprise the module and achieve the stated purpose for the module when joined logically together.

Indeed, a module of executable code may be a single instruction, or many instructions, and may even be distributed over several different code segments, among different programs, and across several memory devices. Similarly, operational data may be identified and illustrated herein within modules, and may be embodied in any suitable form and organized within any suitable type of data structure. The operational data may be collected as a single data set, or may be distributed over different locations including over different storage devices. The modules may be passive or active, including agents operable to perform desired functions.

Although the subject matter has been described in language specific to structural features and/or operations, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features and operations described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims. Numerous modifications and alternative arrangements can be devised without departing from the spirit and scope of the described technology.