SYSTEM OF AGITATED AUTOCLAVE

TECHNICAL FIELD The present disclosure relates to a methods and devices for cleaning and/or maintaining a venting system of an agitated autoclave during preparation of a polyamide polymer. The disclosure also relates to an agitated 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.

These chemical engineering processes can either be batch processes or continuous process, and with respect to the autoclave, there are a number of autoclaves that can be used with acceptable results. Regardless of the autoclave selected for use, clogging/plugging of venting valves and lines during venting of the autoclave can be problematic. This can be especially problematic when large volume batches are manufactured. Thus, it would be an advancement in the art to discover and utilize various techniques for maintaining the venting valves and lines during the polymer manufacturing process. SUMMARY

The disclosure herein relates to methods and devices for cleaning and/or maintaining a venting system of an agitated autoclave during preparation of a polymer, particularly a polyamide polymer such as nylon 6,6. The method includes introducing a polymerizable composition including a polyamide salt into an agitated autoclave having an agitator and a venting valve associated with a venting system, venting the agitated autoclave through a first flow path, and during at least a portion of the venting step, injecting a fluid through a second flow path into the venting valve. The venting system can include a vent line operably connected with the venting valve of the autoclave for venting the autoclave through the first flow path of the venting valve. The venting system can also include an injector associated with the venting valve and configured to inject a fluid into the venting valve through a second flow path. In one aspect, the venting system, including the venting valve, may have some pre-existing deposits in the vent line or valve. In such circumstances, application of the above method can act to clean and remove all or a portion of these deposits and prevent or reduce the formation of additional new deposits.

In another embodiment, an agitated autoclave and venting system is provided. The agitated autoclave and venting system can comprise an agitated autoclave including an agitator and a venting valve configured to vent the agitated autoclave along a first flow path, an injector associated with the venting valve and configured to inject a fluid into the venting valve along a second flow path, and an injector module adapted to control injection of the fluid from the injector into the venting valve.

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 cycle in accordance with embodiments of the present disclosure;

FIG. 2A is a schematic cross-sectional view of an agitated autoclave that is usable in accordance with embodiments of the present disclosure;

FIG. 2B is a schematic cross-sectional view of an alternative agitated autoclave that is usable in accordance with embodiments of the present disclosure; and

FIG. 3 shows a generalized flow diagram of an embodiment of an agitated autoclave with a venting system, including a fluid injector.

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 composition" or "polymerizable solution" refers to the solution that is added to an agitated autoclave in accordance with examples of the present disclosure, and that upon processing the polymerizable

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 composition begins to polymerize within the autoclave, the solution will begin to thicken into a polymer. Thus, it is difficult to delineate at what point it ceases to be a polymerizable composition compared to a thickening polymer. As a result, for convenience, the term "polymerizable solution" may be used herein to describe the composition in the autoclave regardless of its polymerization state. Additionally, the term

"solution" is not intended to describe every component in the composition, as some materials or additives may actually be dispersed in the liquid, e.g., titanium dioxide. The term "solution" is merely used for convenience as some materials will be in solution at the outset.

The term "polyamide salt" refers to the salt that is included in the polymerizable 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. Other additives can also be included in the polyamide solution, either introduced prior to the agitated autoclave, or introduced directly into the agitated autoclave. Titanium dioxide, for example, may optionally be introduced directly into the autoclave, whereas other additives, such as catalysts, anti-foaming agents, or the like, may be better suited for inclusion with the polymerizable salt prior to introducing the polymerizable composition into the agitated autoclave, though this sequence or even the presence of these or other additives is not required.

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 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.

The term "seat" or "valve seat" when used to describe a component of a valve, particularly, the venting valve, refers to a surface, generally a fixed surface on which a second moving portion of a valve rests or against which it presses. For the purposes of the present disclosure, valves in the art that can be said to have a valve seat include ball valves, butterfly valves, check valves, choke valve, diaphragm valve, gate valve, needle valve, pinch valve, plug valve, and other valves known in the art or which can readily be used or modified for use in a venting system in accordance with examples of the present disclosure.

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 agitated 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 agitator or auger per se, the method embodiments are also inherently included in such discussions, and wee versa.

With this in mind, there are several different types of autoclaves that are used to prepare polymeric raw materials. One particular type of autoclave is an agitated autoclave that includes an agitation member, such as an auger, for assisting with the polymerization process. The agitator or auger assists with the process by providing salt flow mixing as well as continuous mixing of contents within the autoclave (no layered effect), controlling heat transfer, reducing vortex, drawing polymer through the autoclave, achieving higher productivity of autoclave vessels, providing a viscometer to measure relative viscosity (RV), etc.

Before discussing some of the methods and systems 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. 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 composition to the vessel, by a pressure source, by heat, etc., to a specified level. Pressure levels in this system 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 system in place, though venting levels outside of this range can also be used. During the venting of the autoclave, the venting valve can frequently become sticky or clogged/plugged by monomer, oligomer, or polymer residue that is deposited on the venting valve. These deposits can occur during a single batch cycle or following a number of batch cycles. These deposits can inhibit or completely eliminate the venting control of the autoclave, which in turn can result in a loss or reduction of control over the pressure of the autoclave. In addition to causing problems with the venting valve, deposits of these residues can also form in the vent lines which can result in the clogging/plugging of these lines. During cycles in which venting occurs, an injector can be used with the autoclave to inject a fluid, such as water, into the venting valve of the autoclave to reduce and inhibit the depositing of the monomers, oligomers, or polymers in the venting valve itself or the vent lines. Injection at the venting valve itself, and not simply in the vent line well downstream from the valve, works to inhibit and/or remove build-up of the deposits in the valve itself as well as in the vent line. Injection in the vent line well downstream from the venting valve may function to prevent the formation of deposits in the vent line itself, but may not prevent formation of deposits in the valve or valve area. Deposits in or near the valve can cause the valve to stick or become sealed shut preventing the valve from functioning properly thereby leading to the need to shut down the reactor.

Typically, the injector is configured to enter the venting valve at a different location than the typical venting fluid flow path that the valve uses to vent. In one example, a second fluid flow path can be introduced to the valve by drilling or otherwise providing a port that enters the valve at or near the valve seat, so that the valve can be injected with water, steam, or another fluid to keep the valve clean and unencumbered by deposited monomer, oligomer, or polymer.

Typically, the second fluid flow path is positioned at the vent valve immediately adjacent the valve seat, typically on the downstream, low pressure side of the valve seat. In one example, the valves are modified to inject the water or other fluid on the low pressure side right at the exit of the valve. By injecting water (or other fluids) at this location, the water provides a richer water environment in the vent lines that assists the prevention of accumulation of deposits, which in turn, assists in keeping the lines clean. Furthermore, by injecting water immediately adjacent the valve on the low pressure side, the valve that regulates pressure in the reactor is also kept free from deposits (monomer, oligomers, polymer, etc.). This can occur as the water coming through the injection port is flashed when it touches the steam from the autoclave and the hot surrounding surfaces, i.e. the valve itself and the pipe. This provides little to no chance for any deposits to stick on the surface of the valve. As precipitates tend to prefer formation at the low pressure areas, by injecting at the valve seat on the low pressure side, deposits can be minimized due to the flashed water that does not allow these deposits to precipitate in the valve. Without this injection line, there tends to be a buildup of deposits at the exit of the valve, and irregular action of the valve that regulates pressure in the autoclave can be introduced, e.g., the valve will start opening more and travel faster (fast moves up and down) to regulate pressure. Also, at times, the movement of the valve may allow for the deposits to dislocate resulting in even more sudden movements of the valve, resulting in the lifting of more monomers, oligomers, and/or polymer from the melting pool traveling through the vent line. By injecting water, steam, or other appropriate fluid at the valve seat, typically on the downstream, low pressure side, these problems can be alleviated.

In further detail, by way of one example, the water injection may have a pressure of about 1 00 psi at the point of injection. Thus, the water injection may be stopped when the autoclave pressure goes below 100 psia to prevent any water from the water injection from going back into the autoclave and create cold spots in the polymer pool, thereby resulting in casting problems when the polymer is extruded from the autoclave. Thus, one can manipulate the pressure of the injected water and continue to inject water at pressures lower than 100 psi (as long as the autoclave pressure is higher than the pressure of the water at the injection point).

As also shown in FIG. 1 , a third cycle (Cycle 3) is defined primarily by a pressure reduction. As can be seen from the figure, some venting also can occur during Cycle 3. This venting can be accompanied by injection of fluid from the injector into the venting valve. However, it is worth noting that generally the injection of fluid during venting typically ceases when the pressure within the autoclave falls below about 100 psi. Injection of fluids into the venting valve at pressures lower than about 100 psi can result in the fluid running into the autoclave which can cause problems with the polymer process. Thus, injecting of the fluid into the venting valve is more effective for use while the venting valve is venting as a result of pressures within the agitated autoclave of 100 psi or more. 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. Furthermore, during the fourth cycle, there can be a ramping down of the agitator RPM. At the end of Cycle 4, again for nylon 6,6, the relative viscosity can be about 32 to 55 units (RV) 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.

With the above in mind, the present disclosure relates to methods of cleaning and/or maintaining a venting system of an agitated autoclave during preparation of a polymer, particularly a polyamide polymer such as nylon 6,6. The method includes introducing a polymerizable composition including a polyamide salt into an agitated autoclave having an agitator and a venting valve associated with a venting system, venting the agitated autoclave through a first flow path, and during at least a portion of the venting step, injecting a fluid through a second flow path into the venting valve. In one aspect, the venting system, including the venting valve, may have some pre-existing deposits in the vent line or valve. In such circumstances, application of the above method can act to clean and remove all or a portion of these deposits and prevent or reduce the formation of additional new deposits. Furthermore, when the injector is immediately adjacent to the valve, e.g., proximal to the seat, the cleaning/maintaining system can act to keep the valve working properly over extended periods of time.

Likewise, present disclosure also provides for an agitated autoclave and venting system. The agitated autoclave and venting system can comprise an agitated autoclave including an agitator and a venting valve configured to vent the agitated autoclave along a first flow path, an injector associated with the venting valve and configured to inject a fluid into the venting valve along a second flow path, and an injector module adapted to control injection of the fluid from the injector into the venting valve.

In one example, venting of the autoclave can be carried out after the first cycle, e.g., after a relative high pressure is achieved and maintain during the second cycle. The injection of the fluid into the venting valve can occur during substantially all of the second cycle or it can be activated and deactivated during a portion of the second cycle, if desired. Alternatively, the timing of the fluid injection can be adapted to inject in accordance with the opening and closing of the venting valve, or when venting is above a certain level (or pressure within the autoclave). In one aspect, the injection of the fluid can occur at least two times during the second cycle. The pressure during the second cycle can be typically maintained at about 230 psi to about 300 psi during the entire second cycle, thus, injecting the fluid into the venting valve during the second cycle can be beneficial. However, it is noted that that venting of the autoclave can occur during portions of a third cycle, such as shown with respect to FIG. 1 . Thus, the injection of fluid into the venting valve can also occur during these venting events as well. In embodiments of the invention, regardless of when the venting and accompanying injection of fluid occurs, the injecting of the fluid can stop following reduction in pressure within the autoclave to at or below a predetermined level, such as a level at or above about 100 psi. As mentioned, continued injection of the fluid into the venting valve when the autoclave pressure falls below 100 psi can result in the fluid travelling down into the autoclave (rather than leaving through the vent line) and having negative effects on the polymer product, though depending on the system, injecting fluid at these lower pressure levels is not necessarily precluded.

The fluid that is injected by the injector can be any fluid that can be effective in keeping the venting valve and/or vent line clean and substantially free of monomer/oligomer/polymer deposits. The fluids can be gases or liquids. In one embodiment, the fluid can be water, steam, or combinations thereof. In another embodiment, the fluid can be an aqueous solution which may include a small amount of a cleaning agent suitable for removing monomer, oligomer, or polymer deposits. In yet a further embodiment, the fluid can be water. The temperature of fluid can be ambient temperature or it can have an elevated temperature. The fluid can be sourced from any location or source. In one embodiment, the fluid can be sourced from a scrubber that is associated with the autoclave as part of a venting system. The fluid injected by the injector can be injected at an elevated pressure. In one embodiment the elevated pressure can be about 100 psig to about 200 psig. The flow rate of the fluid into the venting valve can be about 0.5 gal/min to about 5 gal/min, or alternatively, from about 2 gal/min to about 4 gal/min. Turning now to FIGS. 2A and 2B, schematic cross-sectional views of embodiments of agitated autoclaves are shown. These figures are not

necessarily drawn to scale, and do not show each and every detail that can be present in an agitated autoclave, opting instead to show schematic

representations of features particularly relevant to the present disclosure. Thus, an agitated autoclave 10 can include an autoclave vessel 20 and an agitator or auger 30 in this example. The vessel includes a vessel wall 22, which is typically a cladded vessel wall, and the vessel wall and/or other structures are adapted to support one or more type of heating components 24, 26. In this example, external jacket heating components are shown at 24 and internal heating components are shown at 26. FIG. 2A shows the internal heating component near the vessel wall, whereas FIG. 2B shows the internal heating component nearer the agitator or auger. Also shown in FIG. 2B is a pair of refresher bars 18 that work with the central agitator or auger to refresh the polymer. Essentially, the agitator works to move the polymer upward along a center portion, and the pair of refresher bars are used to refresh the molten polymer by removing the polymer from the side wall surfaces as the molten polymer is churned. This arrangement can improve the heat transfer within the system, and can reduce the height of the vortex caused by the agitation.

The external jacket heating components can be used to raise the temperature and pressure of the polymerizable 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 28. The valve is not shown, but this is the location where polymer prepared in the autoclave is extruded for further processing.

With respect to a specific agitation process described herein, in the configuration shown, the agitator or auger 30 will bring the polymerizable composition (or polymer as it forms) upward toward a central region of the autoclave vessel 20 and downward toward the vessel wall 22 in the flow pattern 32 shown in FIG. 2A. A similar flow pattern will be present in the autoclave shown in FIG. 2B, except that the refresher bars 18 will provide additional refreshing agitation near the vessel wall 22. In either case, when the auger is agitating, the auger can be moving at an RPM level sufficient to cause at least some mixing of the polymerizable composition or polymer in accordance with the pattern shown. For example, the auger or agitator can be spinning within the agitated autoclave at up to 100 RPM, but is normally set to a speed of 5 RPM to 90 RPM, or from 70 RPM to 90 RPM, for example. RPM levels outside this range can also be used, as would be appreciated by one skilled in the art.

An inlet valve 44 and can be used to adding the polymerizable

composition, other additives, or gasses to increase the pressure within the autoclave vessel. Typically, pressure is modulated within the vessel by

introduction of the polymerizable composition and modulation of the heating profile. Furthermore, a venting system is also present, which includes an autoclave venting valve 46, a vent line 48, and an injector 92. The venting system is present for venting gases from the autoclave vessel, through the venting valve, and into the vent line 48 in order to reduce or maintain the pressure of the autoclave. It is noteworthy that any type valve known in the art can be used for the venting valve or any of the other valves discussed herein. Furthermore, it is also noted that irrespective of the description and shown location of these inlets and valves, etc., these or other ports can be used differently than shown for any purpose designed by the user, as would be appreciated by one skilled in the art. As previously described, during a second cycle of the polymerization process within the autoclave, the pressure is brought to a relative high pressure and maintained substantially constant during the cycle though a combination of increasing heat coupled with venting of the autoclave. For example, the pressure during the second cycle can be maintained at from about 230 psi to about 300 psi during the entire second cycle, though pressure profiles outside of this range may also useable in some embodiments. Generally, the second cycle can last from 10 to 45 minutes although variations of duration can be adjusted. As mentioned, the venting system of the autoclave further includes an injector that is associated with the venting valve and configured to inject a fluid into the venting valve. Although not shown in FIGS. 2A and 2B, but detailed further in FIG. 3, the injector can be connected to a source of fluid for injection into the venting valve. The injector can be configured to inject the fluid immediately adjacent to the seat of the venting valve, and in one example, at the seat or even slightly upstream or downstream from the seat as it relates to the flow (first flow path) of venting gasses. In one embodiment, the injector can be disposed such that the fluid is injected through a side wall of the venting valve (along a second fluid flow path) onto or proximal to the seat of the venting valve. Thus, in one example, the first flow path can be defined as the flow path from the interior of the autoclave, through the venting valve, and into the vent line 48. The second flow path can be defined as the flow path from the injector, through the venting valve, and into the vent line. In this arrangement, the first flow path and the second flow path are different, but become joined within the venting valve or the venting 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 FIGS. 2A and 2B, the autoclave can include a controller 50, which can include various modules 60, 70, 80, 90 and can be used to automatically carry out the general functions or process steps of the agitated autoclave. For example, the heating component(s) 24, 26 can be controlled by a heating module 60. The pressure of the autoclave can be controlled utilizing the pressure control module 70 which can control the inlet valve 44 and the venting valve 46 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. The venting system, including the venting valve 46 and the injector 92 can be controlled by a venting module 80 and an injector module 90, respectively. The venting and injector modules can be programmed to inject the fluid into the venting valve when the venting valve is opened and the autoclave is at a predetermined pressure of at least 100 psi, for example. The modules can work together to cycle the system in a manner to cause predictable batch polymerization of the polymerizable composition. Thus, FIG. 1 illustrates an example where the heating module, pressure control module, and venting module, work together to achieve acceptable polymerization results. Additionally, and in accordance with the present disclosure, the injector module can also be used with these other modules to assist with prevention of clogging/plugging or encumbering the venting valve or the vent lines with monomer, oligomer, and/or polymer deposits. Other benefits include the ability to process the batch faster; thus, increasing productivity.

FIG. 3 shows a generalized flow diagram of an embodiment of an agitated autoclave 100 with a venting system, including a fluid injector 190 and a venting valve 1 10, in accordance with examples of the present disclosure. As can be seen in the figure, the autoclave and venting valve are associated with a venting system, the venting system including a scrubber 120, a pump 130, and the aforementioned injector. As shown in the flow diagram, the injector can include a check valve 170 that prevents the backflow of fluids from the venting valve into the injector, a restrictive orifice 160 configured to maintain fluid flow at a desired flow rate, and a block valve 150 that is configured to activate flow of the fluid from the injector. In some embodiments, it can be useful to include manual valves 140, 180 at one or both ends of the injector in order to allow for ease in maintenance or replacement.

As also shown in FIG. 3, the venting valve 1 10 is connected to a scrubber 120 that is located downstream from the venting valve. Such a fluid connection can be through the presence of a vent line (not shown). It is noted that the arrows shown in FIG. 3 can represent fluid lines or pipes, as would be appreciated by one skilled in the art. The scrubber can be any type known in the art. Although not shown, the scrubber can be operably connected to the venting valve of a plurality of autoclaves, each of which having their own injector. In certain embodiments, the fluid (e.g. water and/or steam) from the scrubber can be recycled from the scrubber and pumped by a pump 130 back to the injector 190. The pump can function to pressurize the fluid in the injector.

It is noteworthy that the methods and agitated autoclave and associated venting systems can provide several advantages as compared to similar methods or autoclave venting systems that do not include the injector described herein. For example, the inclusion of the injector significantly reduces the

clogging/plugging or inhibiting of the proper function of the venting valve and/or the associated vent lines of the venting system. This allows for less downtime that is required to clean or otherwise maintain the venting valve and vent lines. For example, each clog/plug in a vent line or venting valve can cost about 5 days of lose time and a lost production of thousands of kilograms of polymer.

Additionally, the use of the injector in the agitated autoclave can allow for larger batch sizes in the autoclave, which larger batches leave less head space in the autoclave. Typically reduced head space distances between the top of the polymer material and the autoclave can result in increased problems with clogging or inhibiting of function of the venting valve and/or vent lines.

Furthermore, the use of the injector allows for the placement of the scrubber of the venting system at a distance that is further from the autoclave which in turn allows for a single common scrubber to be used on a plurality of autoclaves simultaneously. The use of a single common scrubber for multiple autoclaves reduces cost associated with manufacturing and allows for more efficient use of space within a manufacturing facility.

Turning now to example polymers that can be prepared using the methods and devices 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 3000 Kg, and can be cycled during the batch within the autoclave at from about 100 to about 360 minutes, or even more. In one aspect, the cycle duration can be about 100 minutes to about 180 minutes. In another aspect, the cycle duration can be about 100 minutes to about 160 minutes. In another aspect, the cycle duration can be less than about 155 minutes. In still a further aspect, the cycle duration can be about 100 minutes to about 155 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.

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 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. 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 salt solution is introduced into an evaporator to remove a portion of the water prior to introduction into the agitated autoclave as described herein. This solution, referred to herein as the polymerizable composition, can include the nylon 6,6 salt, as well as other additives, such as anti-foaming agents, catalysts, antioxidant stabilizers, antimicrobial additives, optical brighteners, acid-dyable polymer, acid dyes or other dyes, or the like, as is generally known in the art. If the objective is to whiten the product, titanium dioxide can also be included, but is usually added directly to the autoclave to avoid agglomeration. When prepared for polymerization in the autoclave, the polyamide salt, such as nylon 6,6 salt, can be present in the polymerizable composition in an amount ranging from about 50 wt% to 95 wt%, for example.

If a catalyst is added, the catalyst can be present in the polymerizable polyamide composition 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, 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 addition, these polymerizable polyamides may contain an antioxidant stabilizer or an antimicrobial additive as is known in the art. Additionally, the polymerizable composition may contain an anti-foaming additive. In one embodiment, the anti-foaming additive can be present in the polymerizable composition in an amount ranging from 1 ppm to 500 ppm by weight.

The polymerizable 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.

As a further note, 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. EXAMPLES

Example 1 - Autoclave with Traditional Cycling

A commercial autoclave with capacity to produce 1000 to 1300 kg of nylon-6,6 per cycle is charged with an aqueous solution of adipic acid and hexamethylene diamine. Temperature is raised from 150 °C to 280 °C. The commercial autoclave is equipped with a pressure control valve emptying into a vent line. When the pressure of the autoclave reaches about 300 psia, the control valve opens sufficiently to maintain the pressure at 300 psia. Both the water of the solution and the water evolved by the condensation reaction of adipic acid and hexmethylene diamine are controllably released from the autoclave through the control valve into the vent line. As the pressure drops across the control valve and the vent line, water containing at least minor amounts of solids (diamine, adipic acid, and very small amounts of short chain Nylon-6,6 polymeric material) condenses on the inner wall of the vent line and at least a portion of the solids precipitates to form a tenacious deposit on the inner wall, and can also be deposited in some circumstances at or near the valve seat.

Example 2 - Comparative Plugging Rates - Long Cycle Times

Example 1 is repeated with varying cycle times. At long cycle times greater than 360 minutes, the rate of solids deposition within the vent line is low. Cycle times are progressively shortened, and the rate of plugging per unit time increases. Moderate plugging is observed in the vent line at cycle time of 180 minutes. It is noted that plugging can also occur at or near the valve, e.g., valve seat, under similar conditions as well.

Example 3 - Comparative Plugging Rates - Moderate Cycle Times

The polymerization cycle of Example 1 is repeated at 182 minutes, and then progressively shortened to 153 minutes. The problem (plugged vent lines) becomes progressively worse with higher production rates. Significant solids deposition is observed during the 153 minute cycle. This accumulation represents a production rate-limiting technical problem, because further reduction in cycle time triggers more solids deposition and plugs the vent line over a shorter period of time.

Example 4 - Increased Production and Shorter Cycle Times

The polymerization cycle of Example 1 is repeated at the 153 min cycle time. Vent line plugging proves a persistent problem, with 0.7 vent lines plugging per month per autoclave. This plugging rate causes economic loss in four ways. First, the plugging limits overall polymer production (number of batches per month) because it takes significant amounts of time to clean the vent lines (1 -2 days with the autoclave being off-line), and in many cases the autoclave itself needs to be overhauled (5-10 days of the autoclave being off-line) because a plugged vent line can freeze the nylon-6,6 polymer in the autoclave. Second, the last few batches prior to complete pluggage of the vent line have to be downgraded due to the off-standard diamine loss that takes place during the cylces. Third, maintenance costs increase as full-time mechanics are required to be added to each shift to clean out the plugged vent lines. Forth, it can cause increase in the overall cost per ton of polymer due to the inability to operate the autoclaves at shorter cycle times, which reduces the amount of total polymer produced.

Example 5 - Fluid Injection to Clean/Maintain Vent Lines and/or Valve Function

The polymerization cycle of Example 1 is repeated, except that water is injected into the vent lines. Almost immediately, a significant improvement in the pressure drop is observed through the vent lines. In a first set of autoclaves, the vent lines are not mechanically cleaned prior to the installation of the water injection, yet the pressure drop becomes lower with water injection. Vent lines that are inspected show clearly that they are cleaner, although experience indicated that these vent lines should have been dirtier, building up deposits. This shows clearly that the water injection helps to keep the vent lines clean, and even can act to clean vent lines with accumulated deposits prior to the introduction of water injection.

In spite of the fact that not all the vent lines are cleaned prior to the introduction of water injection, in the first 30 days after the introduction of water injection in all claves, only one plugged vent line is observed. Thus, the rate of the problem drops from 0.7 plugged vent lines per month per clave to 0.05 plugged vent line per month per clave. After the first 30 days, the problem of plugged vent lines is virtually eliminated and the area vent line clogs only occur in extreme cases of external problems, e.g., power failures.

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.