CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to U.S. App. No. 61/818,239, filed May 1, 2013, the entire contents and disclosures of which are incorporated herein.

FIELD OF THE INVENTION

[0002] The invention is directed to processes for an retrofitting existing polymer production apparatus to produce a plurality of polymer products from one continuous polymerization apparatus. In particular, the invention is directed to retrofitting existing polymer production apparatuses to produce a plurality of polymer products by allowing injection of different additives into different portions of liquid polymer using additive injection apparatuses.

BACKGROUND

[0003] A variety of polymers are known in the art which are used to make shaped articles, such as films, filament tubes, ribbons and similar shapes. The polymers, often produced in the form of solid chips, are melted and extruded into such articles. An important class of polymers includes polyamides, which are commonly used in textiles, apparel, packaging, tire reinforcement, carpets, engineering thermoplastics for molding parts for automobiles, electrical equipment, sports gear, and a wide variety of industrial applications. Aliphatic polyamides, also known as nylon, may be produced from dicarboxylic acid and diamine, such as from a salt solution of the dicarboxylic acid and the diamine. Nylon is a high performance material used in plastic and fiber applications that demand exceptional durability, heat-resistance and toughness.

[0004] However, a number of challenges have been encountered in the course of processes for making such polymers. For example, when shaped articles are produced from molten polyhexamethylene adipamide ("nylon 6,6"), the polyamide is known to decompose at the high temperatures needed to maintain the polyamide in a molten state. The decomposition causes discoloration of the extruded shaped articles and tends to have an undesirable effect on physical properties of the articles. Heat stabilizing additives added to the molten polymer have been proposed to address this issue, e.g., US Pat. No. 3,121,763.

[0005] Other additives have also been proposed for incorporation into molten polymers. U.S. Pat. No. 3,824,207 proposes injecting a pigment into a reaction mass of monomers to produce a pigmented high molecular weight polyamide. Carothers et al., U.S. Pat. No. 2,119,584, suggests adding modifying agents into a solution formed by dissolving approximately a total quantity of diamine and dicarboxylic acid required for a given quantity of polyamide in water. The modifying agents include viscosity stabilizing agents, plasticizers, delusterants, pigments and dyes.

[0006] However, challenges exist with the heretofore proposed methods of incorporating additives into polymers. For example, injection of an additive into the polyamide polymerization process upstream of the reactor may degrade the additive, as shown in WO 99/10408.

[0007] Furthermore, the introduction of the additives into various stages of the polyamide polymerization processes, particularly upstream of the polymerization reactor, may cause a significant time delay in producing a product which meets required specifications. The additives may be incorporated into the polymer products using various methods, such as physically mixing the additive with the polymerized nylon 6,6, surface-tumbling nylon 6,6 pellets with powdered additive, or physically incorporating the additive into a melt extruder.

[0008] Manufacturers have a desire to produce a variety of nylon grades from a single polymerization process and apparatus. The precursor salt solution may comprise water and hexamethylene diammonium adipate salt. The precursor salt solution may be evaporated and heated to produce a polymer. Injecting the additive package before polymerization, such as into the salt solution, evaporator or at the inlet of a continuous polymerization reactor, limits flexibility. For example, the entire resulting polymer contains the additives injected into the salt solution and thus precludes the operator from producing a plurality of polymer products. Additionally, to change the additive and polymer product, significant time is required to switch the process and produce separate salt solutions having a different additive.

[0009] Conversely, injecting additives into the effluent of a continuous polymerization process presents a number of technical problems. First, it is difficult to evenly and uniformly distribute an additive through the bulk of the polymer. Further, conventional injection valves tend to plug. Also, injection of the additive downstream of the reactor may cause additive degradation.

[0010] Hence, a need exits for a process for retrofitting an existing polymerization apparatus to allow for the production of multiple polymer products from one continuous polymerization process. SUMMARY OF THE INVENTION

[0011] In a first embodiment, the present invention is directed to a process for retrofitting a polymer production apparatus comprising: a) providing a primary manifold having two openings, a first opening for connecting to a polymerization reactor and a second opening for connecting to a primary solidifier, and a conduit for directing a liquid polymer from the polymerization reactor to the primary solidifier; b) replacing a portion of the primary manifold upstream of the second opening with a retrofit manifold having a plurality of manifold valves including a first manifold valve and a second manifold valve; c) connecting a first additive injection apparatus to the first manifold valve; d) directing a first portion of the liquid polymer from the retrofit manifold into the first additive injection apparatus; and e) injecting a first additive into the first portion of the liquid polymer to produce a first finished polymer product comprising the first additive, wherein the first additive injection apparatus comprises a secondary manifold, at least one additive injection line connected to the secondary manifold, and a polymer solidifier in fluid communication with the secondary manifold downstream of the at least one additive injection line. The retrofit manifold may comprise an opening for connecting to the primary solidifier. The retrofit manifold may comprise an opening for connecting to the polymerization reactor. The retrofitting process may further comprise at least one connector tube for securing the retrofit manifold to the primary manifold. The retrofitting process may further comprise a gasket disposed between the at least one connector tube and the primary manifold to form a substantially hermetic sealed connection between the primary manifold and the retrofit manifold. The retrofitting process may further comprise welding the retrofit manifold to the primary manifold. The retrofit manifold may have a substantially similar internal diameter as the primary manifold. Substantially all parts of the retrofit manifold may be comprised of stainless steel. The first and second manifold valves may be cross-stem injection valves, two-way valves, three-way valves, diverter valves, or combinations thereof. The plurality of manifold valves may comprise between two and ten manifold valves. The secondary manifold may comprise a pump downstream of the first manifold valve and upstream of the at least one additive injection line. The pressure of the primary manifold may be between 10 MPa and 31 MPa. The pressure within the retrofit manifold may be substantially similar to pressure within the primary manifold. The first additive may be selected from the group consisting of heat stabilizers, antifoam agents, glass fiber, lubricants, co-polymers, catalysts, flame retardants, plasticizers, impact modifiers, fillers, compounds that change ends balance, and mixtures thereof. The first additive injection apparatus may comprise between two and ten additive injection lines. The at least one additive injection line may comprise a static mixer. The first additive injection apparatus may comprise an additive injection valve for connecting the at least one additive injection line with the secondary manifold. The at least one additive injection line may be pressurized to a higher pressure than the pressure of the secondary manifold when the additive injection valve is opened. Substantially all parts of the additive injection valve and each of the first and second manifold valves may be comprised of stainless steel. The additive injection valve may be a cross-stem injection valves, two-way valves, three-way valves, diverter valves, or combinations thereof. The retrofitting process may further comprise: f) connecting a second additive injection apparatus to the second manifold valve; g) directing a second portion of the liquid polymer from the retrofit manifold into the second additive injection apparatus; and h) injecting a second additive to the second portion of the liquid polymer to produce a second finished polymer product comprising the second additive. The second additive may be selected from the group consisting of heat stabilizers, antifoam agents, glass fiber, lubricants, co-polymers, catalysts, flame retardants, plasticizers, impact modifiers, fillers, compounds that change ends balance, and mixtures thereof. The first additive may be different than the second additive. The retrofitting process may further comprise condensing a dicarboxylic acid and a diamine to form the liquid polymer. The dicarboxylic acid may be selected from the group consisting of oxalic acid, malonic acid, succinic acid, glutaric acid, pimelic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecandioic acid, maleic acid, glutaconic acid, traumatic acid, and muconic acid, 1,2- or 1,3-cyclohexane dicarboxylic acids, 1,2- or 1,3-phenylenediacetic acids, 1,2- or 1,3- cyclohexane diacetic acids, isophthalic acid, terephthalic acid, 4,4'-oxybisbenzoic acid, 4,4- benzophenone dicarboxylic acid, 2,6-napthalene dicarboxylic acid, p-t-butyl isophthalic acid and 2,5-furandicarboxylic acid, and mixtures thereof. In one embodiment, the dicarboxylic acid is adipic acid. The diamine may be selected from the group consisting of ethanol diamine, trimethylene diamine, putrescine, cadaverine, hexamethyelene diamine, 2-methyl pentamethylene diamine, heptamethylene diamine, 2-methyl hexamethylene diamine, 3-methyl hexamethylene diamine, 2,2-dimethyl pentamethylene diamine, octamethylene diamine, 2,5- dimethyl hexamethylene diamine, nonamethylene diamine, 2,2,4- and 2,4,4-trimethyl hexamethylene diamines, decamethylene diamine, 5-methylnonane diamine, isophorone diamine, undecamethylene diamine, dodecamethylene diamine, 2,2,7 ,7-tetramethyl octamethylene diamine, bis(p-aminocyclohexyl)methane, bis(aminomethyl)norbornane, C ₂ -Ci ₆ aliphatic diamine optionally substituted with one or more Q to C ₄ alkyl groups, aliphatic polyether diamines and furanic diamines, such as 2,5-bis(aminomethyl)furan, and mixtures thereof. In one embodiment, the diamine is hexamethylene diamine. In some embodiments, the dicarboxylic acid and diamine are adipic acid and hexamethylene diamine.

[0012] In a second embodiment, the present invention is directed to a process for retrofitting a polymer production apparatus comprising: a) providing a primary manifold having two openings, a first opening for connecting to a polymerization reactor and a second opening for connecting to a primary solidifier and a conduit for directing a liquid polymer from the polymerization reactor to the primary solidifier; b) replacing a portion of the primary manifold upstream of the second opening with a retrofit manifold having a plurality of manifold valves including a first manifold valve and a second manifold valve; c) connecting a first additive injection apparatus to the first manifold valve; d) directing a first portion of the liquid polymer from the retrofit manifold into the first additive injection apparatus; e) injecting a first additive into the first portion of the liquid polymer to produce a first finished polymer product comprising the first additive; f) connecting a second additive injection apparatus to the second manifold valve; g) directing a second portion of the liquid polymer from the retrofit manifold into the second additive injection apparatus; and h) injecting a second additive to the second portion of the liquid polymer to produce a second finished polymer product comprising the second additive, wherein the first and second additive injection apparatuses each comprises a secondary manifold, at least one additive injection line connected to the secondary manifold, and a polymer solidifier in fluid communication with the secondary manifold downstream of the at least one additive injection line.

[0013] In a third embodiment, the present invention is directed to a process for retrofitting a polymer production apparatus comprising: a) providing a primary manifold for directing a liquid polymer from a polymerization reactor to a primary solidifier, the primary manifold having at least one secondary manifold for injecting additives into the primary manifold upstream of the primary solidifier; b) connecting a polymer solidifier to the at least one secondary manifold; c) connecting at least one additive injection line to the at least one secondary manifold, upstream of the polymer solidifier; d) directing a first portion of the liquid polymer from the primary manifold into the at least one secondary manifold; and e) injecting a first additive to the first portion of the liquid polymer via the at least one additive injection line to produce a first finished polymer product comprising the first additive. The first additive may not injected into the primary manifold once the first portion of the liquid polymer is directed into the at least one secondary manifold. The polymer solidifier may be connected directly to the at least one secondary manifold and the polymer solidifier is not connected directly to the primary manifold. The retrofit process may further comprise a manifold valve for regulating flow of the first portion of the liquid polymer from the primary manifold into the at least one secondary manifold. The manifold valve may be a plug resistant injection valve. The manifold valve may be a cross- stem injection valve, two-way valve, three-way valve, diverter valve or combinations thereof. Substantially all parts of the manifold valve may be comprised of stainless steel. The retrofit process may further comprise repeating step c) to connect between two and ten additive injection lines to the at least one secondary manifold. The at least one additive injection line may comprise a static mixer. The retrofitting process may further comprise an additive injection valve for connecting the at least one additive injection line with the at least one secondary manifold. The additive injection valve may be a plug resistant injection valve. The additive injection valve may be a cross-stem injection valve, two-way valve, three-way valve, diverter valve, or combinations thereof. The retrofitting process may further comprise adding at least one pump in the at least one secondary manifold downstream of the manifold valve and upstream of the additive injection valve. The primary manifold may comprise a pressure controller to maintain the pressure within the primary manifold between 10 MPa and 31 MPa. The at least one secondary manifold may comprise a pressure controller to maintain the pressure within the at least one secondary manifold between 10 MPa and 28 MPa. The polymerization reactor may produce the liquid polymer by condensing a dicarboxylic acid and a diamine. The dicarboxylic acid may be selected from the group consisting of oxalic acid, malonic acid, succinic acid, glutaric acid, pimelic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecandioic acid, maleic acid, glutaconic acid, traumatic acid, and muconic acid, 1,2- or 1,3-cyclohexane dicarboxylic acids, 1,2- or 1 ,3-phenylenediacetic acids, 1,2- or 1 ,3-cyclohexane diacetic acids, isophthalic acid, terephthalic acid, 4,4'-oxybisbenzoic acid, 4,4-benzophenone dicarboxylic acid, 2,6-napthalene dicarboxylic acid, p-t-butyl isophthalic acid and 2,5-furandicarboxylic acid, and mixtures thereof. In one embodiment, the dicarboxylic acid is adipic acid. The diamine may be selected from the group consisting of ethanol diamine, trimethylene diamine, putrescine, cadaverine, hexamethyelene diamine, 2-methyl pentamethylene diamine, heptamethylene diamine, 2-methyl hexamethylene diamine, 3-methyl hexamethylene diamine, 2,2-dimethyl pentamethylene diamine, octamethylene diamine, 2,5-dimethyl hexamethylene diamine, nonamethylene diamine, 2,2,4- and 2,4,4-trimethyl hexamethylene diamines, decamethylene diamine, 5-methylnonane diamine, isophorone diamine, undecamethylene diamine, dodecamethylene diamine, 2,2,7, 7-tetramethyl octamethylene diamine, bis(p- aminocyclohexyl)methane, bis(aminomethyl)norbornane, C ₂ -Ci ₆ aliphatic diamine optionally substituted with one or more Q to C ₄ alkyl groups, aliphatic polyether diamines and furanic diamines, such as 2,5-bis(aminomethyl)furan, and mixtures thereof. In one embodiment, the diamine is hexamethylene diamine. In some embodiments, the dicarboxylic acid and the diamine are adipic acid and hexamethylene diamine. The first additive may comprise heat stabilizers, antifoam agents, glass fiber, lubricants, co-polymers, catalysts, flame retardants, plasticizers, impact modifiers, fillers, and/or compounds that change ends balance.

[0014] In a fourth embodiment, the present invention is directed to a process for retrofitting a polymer production apparatus comprising: a) providing a primary manifold for directing a liquid polymer from a polymerization reactor to a primary solidifier, the primary manifold having at least one secondary manifold for injecting additives into the primary manifold upstream of the primary solidifier; b) connecting a polymer solidifier to the at least one secondary manifold; c) connecting at least one additive injection line to the at least one secondary manifold, upstream of the polymer solidifier; d) replacing a portion of the primary manifold upstream of the primary solidifier with a retrofit manifold having a retrofit manifold valve; e) connecting a first additive injection apparatus to the retrofit manifold valve; f) directing a first portion of the liquid polymer from the primary manifold into the at least one secondary manifold; g) injecting a first additive to the first portion of the liquid polymer via the at least one additive injection line to produce a first finished polymer product comprising the first additive, the first finished polymer product is directed to the polymer solidifier; h) directing a second portion of the liquid polymer from the retrofit manifold into the first additive injection apparatus; and i) injecting a second additive into the second portion of the liquid polymer to produce a second finished polymer product comprising the second additive.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Aspects of the invention are schematically illustrated with the following figures, in which:

[0016] FIG. 1 is a conventional apparatus for making a polyamide polymer.

[0017] FIG. 2 is a schematic diagram of a polymer additive apparatus comprising two additive injection apparatuses in accordance with one embodiment of the present invention.

[0018] FIG. 3 is a schematic diagram of a polymer additive apparatus comprising three additive injection apparatuses in accordance with one embodiment of the present invention

[0019] FIG. 4 is a schematic diagram of a polymer additive apparatus of FIG. 3, in which one manifold valve to an additive injection apparatus is closed in accordance with one embodiment of the present invention.

[0020] FIG. 5 is a schematic diagram of a polymer additive apparatus having two additive injection lines in an additive injection apparatus in accordance with one embodiment of the present invention.

[0021] FIG. 6A is a sectional sideview of a cross-stem polymer valve used in accordance with an embodiment of the present invention.

[0022] FIG. 6B is a sectional sideview of a portion of the cross-stem polymer valve of FIG. 6A used in accordance with an embodiment of the present invention.

[0023] FIG. 7 is a sectional sideview of a Type I polymer valve in a position which allows flow through one outlet, used in accordance with an embodiment of the present invention.

[0024] FIG. 8 is a sectional sideview of a Type I polymer valve in a position which allows flow through two outlets, used in accordance with an embodiment of the present invention.

[0025] FIG. 9 is sectional sideview of a Type I polymer valve in a position which allows flow through one outlet, used in accordance with an embodiment of the present invention.

[0026] FIG. 10 is a sectional sideview of a Type II polymer valve in a position which does not allow flow through the valve used in accordance with an embodiment of the present invention. [0027] FIG. 11 is a sectional sideview of a diverter polymer valve in the injection position used in accordance with an embodiment of the present invention.

[0028] FIG. 12 is a sectional sideview of a diverter polymer valve in the diverter position used in accordance with an embodiment of the present invention.

[0029] FIG. 13 is a schematic diagram of a polymerization process that may be retrofitted with a polymer additive apparatus in accordance with an embodiment of the present invention.

[0030] FIG. 14 is a schematic diagram of a polymerization process that may be retrofitted with a polymer additive apparatus in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0031] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, group of elements, components, and/or groups thereof.

[0032] Language such as "including," "comprising," "having," "containing," or "involving," and variations thereof, is intended to be broad and encompass the subject matter listed thereafter, as well as equivalents, and additional subject matter not recited. Further, whenever a composition, a group of elements, process or method steps, or any other expression is preceded by the transitional phrase "comprising," "including," or "containing," it is understood that it is also contemplated herein the same composition, group of elements, process or method steps or any other expression with transitional phrases "consisting essentially of," "consisting of," or "selected from the group consisting of," preceding the recitation of the composition, the group of elements, process or method steps or any other expression.

[0033] The corresponding structures, materials, acts and equivalents of all means or step plus function elements in the claims, if applicable, are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The embodiments described were chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated. Accordingly, while the invention has been described in terms of embodiments, those of skill in the art will recognize that the invention can be practiced with modifications and in the spirit and scope of the appended claims.

[0034] Reference will now be made in detail to certain disclosed subject matter. While the disclosed subject matter will be described in conjunction with the enumerated claims, it will be understood that they are not intended to limit the disclosed subject matter to those claims. On the contrary, the disclosed subject matter is intended to cover all alternatives, modifications, and equivalents, which can be included within the scope of the presently disclosed subject matter as defined by the claims.

Introduction

[0035] The present invention is directed to processes for retrofitting existing polymer production apparatuses with the polymer additive apparatus described herein. The present invention is also directed to a polymer additive apparatus and to a process for producing a plurality of polymer products using the polymer additive apparatus. The polymer additive apparatus is in fluid communication with a polymerization apparatus comprising a continuous polymerization reactor. The polymerization apparatus may also contain a flasher and a vessel or tank for making adjustments to the polymer, e.g., adjusting the molecular weight. The polymer additive apparatus comprises a primary manifold and at least one additive injection apparatus, e.g., at least two additive injection apparatuses. The primary manifold is a distribution line for directing the liquid polymer from a polymerization apparatus, via the polymerization reactor discharge line or flasher feed line. In one embodiment, the primary manifold distributes liquid polymer to a polymer finisher, e.g., polymer solidifier, in contact with the primary manifold. The primary manifold may comprise primary manifold valves that are used to control flow of the liquid polymer into the additive injection apparatus(es). [0036] The additive injection apparatus comprises a secondary manifold that may carry at least a portion of the liquid polymer. The secondary manifold may be in contact with at least one additive injection line for feeding an additive to the secondary manifold for combination with the liquid polymer. The process may be run continuously and has the advantage of allowing more than one polymer product to be produced from one continuous process. Generally, the process includes forming a liquid polymer, removing the liquid polymer from the polymerization apparatus, and directing at least two portions of the liquid polymer to separate additive injection apparatuses to produce different polymer products.

[0037] The present invention presents a significant improvement over the prior art because it allows productivity, yield, and rates of liquid polymer to be maximized while also allowing for tailoring of final products. For example, a liquid polyamide may be separated into portions and each portion may be combined with a different additive. A first portion may be combined with a flame retardant additive, a second portion may be combined with a pigment, and a third portion may be combined with a heat stabilizer. Thus, three polyamide products are produced from one liquid polyamide. In another example, a first portion of liquid polymer is sent from the primary manifold to a polymer finisher to form a primary finished polymer product, while another portion is sent to an additive injection apparatus to form a finished polymer product comprising an additive. Additionally, the present invention is advantageous because it reduces contamination in polymerization apparatus equipment that may be caused by buildup of the additives. Because the additives may be added after the polymer has exited the polymerization apparatus, the polymerization apparatus need not be exposed to the additives.

[0038] The present invention also includes a controlling the additive injection line pressure so that it is higher than the secondary manifold pressure when the additive valve is opened. The pressure is controlled by using appropriate injection valves which are able to prevent the polymer flow backwards into the additive injection piping when the additive flow is shut off. In the absence of pressure control, temperature may be affected and the injection valve and piping would need to be heat-traced, as a drop in temperature would solidify the polymer and plug the apparatus.

[0039] The present invention overcomes this deficiency by providing a manufacturer the flexibility of producing a plurality of polymer products with a single polymerization apparatus comprising a single polymerization reactor. The continuous polymerization reactor can produce multiple products simultaneously, or one at a time, depending on the requirements of a given plant or operator. The present invention avoids the problems associated with introduction of additives into the primary manifold. The apparatus also enables production of a polyamide meeting the product specifications for a given polyamide in a very short time, relative to the previously existing apparatuss and processes. The number of different products that can be made in a single polymerization apparatus, utilizing one polymerization reactor, combined with one or more additive injection apparatuses, is limited only by economics. The process of the present invention is also scalable to provide flexibility in delivering a variety of polymer products.

Liquid Polymer and Preparation Thereof

[0040] As discussed above, a liquid polymer is removed from a polymerization apparatus through a primary manifold. The liquid polymer removed from the polymerization apparatus may be free of additives. In another embodiment, the liquid polymer removed from the polymerization apparatus may comprise additives. However, once the liquid polymer composition is removed from the polymerization apparatus, no additives are added to the liquid polymer when it is in the primary manifold. The liquid polymer may be any polymer in a liquid form, including molten polymers, or polymers in a flowable form. For purposes of the present invention, a polymer is a liquid polymer when it is in liquid form at polymerization reactor temperature. Exemplary liquid polymers may include polyamides, polyolefins, polyurethanes, polyesters, polystyrenes, and polycarbonates. In preferred embodiments, the present invention is directed to producing polyamides.

[0041] Polyamides used in the process of the present invention may be obtained from a single monomer, or a mixture of two or more different monomers, such as dicarboxylic acids and diamines, which initially react to form poly(hexamethylene adipamide). Thus, in the case of poly(hexamethylene adipamide), the main monomers are hexamethylene diamine and adipic acid. This category of polyamides derived from two different monomers is generally manufactured using, as a starting material, a salt solution obtained by mixing a dicarboxylic acid with a diamine in a stoichiometric amount, in a solvent, such as water. In one embodiment, the molar ratio of adipic acid to hexamethylene diamine may be a ratio within the range between 0.8: 1 and 1.2: 1. The salt solution is usually concentrated by evaporating off the water. The polyamide is obtained by heating such salt solution at high temperature and pressure to evaporate off the water, while at the same time avoiding any formation of a solid phase to avoid the mixture solidifying. The relative molar amounts of the adipic acid to hexamethylene diamine may be varied depending on the desired final product.

[0042] In some embodiments, the liquid polymer may be a condensation product of a dicarboxylic acid monomer and a diamine monomer.

[0043] Dicarboxylic acids suitable for the present invention are selected from the group consisting of oxalic acid, malonic acid, succinic acid, glutaric acid, pimelic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecandioic acid, maleic acid, glutaconic acid, traumatic acid, and muconic acid, 1,2- or 1,3-cyclohexane dicarboxylic acids, 1,2- or 1,3-phenylenediacetic acids, 1,2- or 1,3-cyclohexane diacetic acids, isophthalic acid, terephthalic acid, 4,4'-oxybisbenzoic acid, 4,4-benzophenone dicarboxylic acid, 2,6-napthalene dicarboxylic acid, p-t-butyl isophthalic acid and 2,5-furandicarboxylic acid, and mixtures thereof. In one embodiment, the dicarboxylic acid monomer comprises at least 80% adipic acid, e.g., at least 95% adipic acid.

[0044] Adipic acid (AA) is the most preferred dicarboxylic acid and is used in the powder form. AA generally is available in a pure form containing very low amounts of impurities. Typical impurities include other acids (monobasic acids and lower dibasic acids), less than 60 ppm, nitrogenous materials, trace metals such as iron (less than 2 ppm) and other heavy metals (less than 10 ppm), arsenic (less than 3 ppm) and hydrocarbon oil (less than 10 ppm).

[0045] Diamines suitable for the present invention are selected from the group consisting of ethanol diamine, trimefhylene diamine, putrescine, cadaverine, hexamethyelene diamine, 2- methyl pentamethylene diamine, heptamethylene diamine, 2-methyl hexamethylene diamine, 3- methyl hexamethylene diamine, 2,2-dimethyl pentamethylene diamine, octamethylene diamine, 2,5-dimethyl hexamethylene diamine, nonamethylene diamine, 2,2,4- and 2,4,4-trimethyl hexamethylene diamines, decamethylene diamine, 5-methylnonane diamine, isophorone diamine, undecamethylene diamine, dodecamethylene diamine, 2,2,7 ,7-tetramethyl octamethylene diamine, bis(p-aminocyclohexyl)methane, bis(aminomethyl)norbornane, C ₂ -Ci ₆ aliphatic diamine optionally substituted with one or more Ci to C ₄ alkyl groups, aliphatic polyether diamines and furanic diamines, such as 2,5-bis(aminomethyl)furan, and mixtures thereof. The diamine selected may have a boiling point higher than the dicarboxylic acid, and the diamine is preferably not xylylenediamine. In one embodiment, the diamine monomer comprises at least 80% hexamethylene diamine, e.g., at least 95% hexamethylene diamine. Hexamethylene diamine (HMD) is most commonly used to prepare nylon 6,6. HMD solidifies at about 42°C and water is commonly added to depress this melt temperature and ease handling. Thus, HMD is commercially available as a concentrated solution, e.g., between 80 wt.% and 100 wt.% or between 92 wt.% and 98 wt.%.

[0046] In the description below, the terms adipic acid (AA) and hexamethylene diamine (HMD) will be used to denote the dicarboxylic acid and the diamine. However, this process also applies to other dicarboxylic acids and other diamines as indicated above. Additionally, in the description below, the terms nylon 6,6 and polyamide will be used to denote the liquid polymer. However, this process also applies to other liquid polymers as indicated above.

[0047] In addition to polyamides based solely on dicarboxylic acids and diamines, it is sometimes advantageous to incorporate other monomers. When added at proportions of less than 20 wt.%, e.g. less than 15 wt.%, these monomers may be added into the nylon salt solution without departing from this invention. Such third starting material may include monofunctional carboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, benzoic acid, caproic acid, enanthic acid, octanoic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, myristic acid, myristoleic acid, palmitic acid, palmitoleic acid, sapienic acid, stearic acid, oleic acid, elaidic acid, vaccenic acid, linoleic acid, erucic acid and the like. These may also include lactams such as a-acetolactam, a-propiolactam, β-propiolactam, γ- butyrolactam, δ-valerolactam, γ-valerolactam, caprolactam and the like. These may also include lactones such as a-acetolactone, a-propiolactone, β-propiolactone, γ-butyrolactone, δ- valerolactone, γ-valerolactone, caprolactone, and such like. These may include difunctional alcohols such as monoethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, 1,2-butanediol, 1,3-butanediol, 1 ,4-butanediol, 2,3-butanediol, 1,2- pentanediol, 1,5-pentanediol, etohexadiol, p-menthane-3,8-diol, 2-methyle-2,4-pentanediol, 1,6- hexanediol, 1,7-heptanediol, and 1,8-octanediol. Higher functionality molecules such as glycerin, trimethylolpropane, triethanolamine and the like may also be useful. Suitable hydroxylamines may also be selected such as ethanolamine, diethanolamine, 3-amino-l-propanol, l-amino-2- propanol, 4-amino-l-butanol, 3-amino-l-butanol, 2-amino-l-butanol, 4-amino-2-butanol, pentanolamine, hexanaolamine, and the like. It will be understood that blends of any of these monomers may also be utilized without departing from this invention.

[0048] A wide variety of additives that may be used in embodiments of the present invention. These additives may be injected using the additive injection lines of the present invention. Preferably, this allows for the additives to be incorporated into a portion of the liquid polymer. Additives may include heat stabilizers such as copper salts, potassium iodide, or any of the other antioxidants known in the art. Such additives may also include polymerization catalysts, such as metal oxides, acidic compounds, metal salts of oxygenated phosphorous compounds or others known in the art. The additives may also be delustrants and colorants such as titanium dioxide, carbon black, or other pigments, dyes and colorants known in the art. Additives used may include antifoam agents such as silica dispersions, silicone copolymers, or other antifoams known in the art. Lubricant aids such as zinc stearate, stearylerucamide, stearyl alcohol, aluminum distearate, ethylenebisstearamide or other polymer lubricants known in the art may be used. Nucleating agents may be included in the mixtures such as fumed silica or alumina, molybdenum disulfide, talc, graphite, calcium fluoride, salts of phenylphosphinate or other aids known in the art. Other common additives known in the art such as flame retardants, plasticizers, impact modifiers, and some types of fillers may also be added into the molten imbalanced mixtures prior to solidification. It will be understood that blends of any of these additives may also be utilized without departing from the fundamentals of the embodiments disclosed herein. In one embodiment, the additives and their blends, include, without limitation, copper plasticizers, delusterants, pigments, dyes, copper-based stabilizers, pigments, including colorless pigments, glass, fiber glass, lubricants, co-polymers such as nylon 6, nylon 6,10 and nylon 6,12, catalysts, and compounds that change ends balance, e.g., amine ends. In some embodiments, the additive is provided as a master batch. In some aspects, the same additive may be injected in multiple injection lines but may be added in combination with another additive, in a different amount, or a combination thereof.

[0049] The polymer products described herein may comprise between 0.1 wt.% and 20 wt.% additive, e.g., between 0.5 wt.% and 20 wt.%, between 1 wt.% and 20 wt.%, between 1 wt.% and 15 wt.% or between 1 wt.% and 10 wt.% of the additive. Depending on the additive and the amount to be added to the portion of liquid polymer, the additive may be maintained at a temperature between 40°C and 300°C, e.g., between 50°C and 270°C, 60°C and 250°C or between 80°C and 220°C. It is understood that the amount of additive and temperature of additive are adjusted to keep the polymer flowing through the apparatus. Thus, the temperature of the additive may be less than 40°C, such as at ambient temperature. The polymer product may have a molecular weight between 10,000 and 50,000 daltons, such as between 12,000 and 45,000 daltons or between 10,000 and 20,000 daltons.

[0050] The liquid polymer may be prepared from a polymer salt solution, such as a nylon salt solution or a nylon salt that has been subjected to water removal, e.g., evaporation. The nylon salt solution may be manufactured to a target salt content and a target molar ratio of dicarboxylic acid, e.g., AA to diamine, e.g., HMD. The target molar ratio may be calculated by measuring the pH of the nylon salt solution. The nylon salt solution may be formed in a continuous stirred tank reactor (CSTR) by feeding AA powder to the CSTR and by separately feeding HMD and water, either alone or in combination, to the CSTR. The AA powder may be fed to the CSTR on a volumetric basis or a weight basis. Due to the desire for forming a nylon salt solution with low variability from the target salt content and pH, the AA powder may be metered on a weight basis using a loss-in-weight feeder. It has been found that using a loss-in-weight feeder to meter the AA powder results in a lower variability of target salt content and pH in the nylon salt solution because AA powder may vary greatly in bulk density. In an exemplary embodiment of this invention a low variable feed rate may vary by less than ±5% of the target feed rate. Acceptable loss-in-weight feeders may include Acrison Models 402/404, 403, 405, 406, and 407; Merrick Model 570; K-Tron Models KT20, T35, T60, T80, S60, SlOO, and S500; and Brabender FlexWall®Plus and FlexWall®Classic.

Polymer Additive Process

[0051] Prior art processes for preparing a polymer with an additive are shown in FIG. 1. Polymerization process 1 comprises storing a prepolymer solution, also referred to as polymer salt solution, in storage tank 5. When enough polymer salt solution is produced, or when it is otherwise desirable to form the polymer, the polymer salt solution is passed through evaporator 7 transferred via line 6 to form a polymer salt which is then transferred to polymerization reactor 20 via polymerization inlet 8. Polymer 16 is removed from reactor 20 and sent to a solidifier 18 to produce a finished polymer product 119. If desired, additive(s) could be added at two different portions of polymerization process 100. In one embodiment, additive 9 is added to storage tank 5 via line 11. In another embodiment, additive 9 is added to line 6 via line 12 as the polymer salt solution passes to polymerization reactor 20. In yet another embodiment (not shown), additive 9 is added to liquid polymer 16. In another embodiment, in addition to or instead of additive 9, additive 13 is added to liquid polymer 16 via line 14. However, each of these processes produce one polymer product when continuously producing a liquid polymer in reactor 20.

[0052] The inventive polymerization process 101 is shown in FIGS. 2, 3 and 4 and includes polymer additive apparatus 102. Polymerization process 101 comprises polymer salt storage tank 105, evaporator 107, transfer line 106, polymerization reactor 120, and polymer inlet 108. Polymerization inlet 108, which comprises polymer salt and any monomer added to adjust the stoichiometry of the polymer salt, feeds the polymer salt to polymerization reactor 120. The polymer salt may optionally comprise additives as discussed above. The polymer salt is polymerized in a condensation reaction in continuous polymerization reactor 120 to form polymer 116. Polymer 116 is removed from polymerization reactor 120 into primary manifold 121, passes through pump 115 and enters polymer additive apparatus 102. Prior to exiting polymerization reactor 120, polymer 116 may be fed to a flasher (not shown) and/or to a vessel for adjusting the molecular weight of the polymer (not shown). The vessel may comprise a mixing basket and screw pump. The vessel may be horizontal or vertical, and may be operated under vacuum. Polymer additive apparatus 102 comprises primary manifold 121, primary manifold pump 115, polymer solidifier 118, and primary manifold valves 122 and 123. Polymer additive apparatus 102 also comprises at least one, e.g., at least two additive injection apparatuses. As shown in FIG. 2, two additive injection apparatuses, comprising secondary manifolds 125 and 135, secondary manifold pumps 126 and 136, additive injection storage tanks 127 and 137, additive injection lines 128 and 138, additive injection pumps 129 and 139, additive injection valves 130 and 140, and polymer solidifiers 133, 143 are in fluid communication with primary manifold 121. Finished polymer products 161, 162, and 119 are then removed from polymer solidifiers 133, 143 and 118. Although one pump, valve and injection lines are shown in FIGS. 2, 3, and 4, there may be additional pumps, valves and injection lines, as well as temperature controllers and sensors, pressure controllers and sensors, and optional static mixers.

[0053] The present invention allows for the production of a plurality of polymer products. The present invention also allows for efficient additive injection apparatus modification and/or replacement. In conventional processes, to switch from a first additive to a second additive and produce polymer product with the second additive, the process may take between 3 and 12 hours. The time requirement is due to the physical switching of equipment (additive storage tanks), to removing all liquid polymer comprising the first additive, to adding the second additive, and to producing a polymer product comprising the desired amount of second additive. The present process advantageously switches a first additive to a second additive and produces a polymer product comprising the desired amount of second additive within 1 hour, e.g., within 30 minutes, within 15 minutes, within 5 minutes, or within 1 minute.

[0054] In some embodiments, finished polymer product 119 may be substantially free of additive. In some embodiments, finished polymer product 119 may be substantially free of the additive in additive injection storage tank 127 and/or in additive storage tank 137. The additive in additive injection storage tank 127 may be a different additive than the additive in additive storage tank 137. Additionally, more than one additive may be stored in each additive storage tank as an additive mixture. Each finished polymer product 161, 162, and 119 may be a different finished polymer product.

[0055] Polymer 116 flows through primary manifold 121 and the secondary manifolds 125 and 135 at a temperature sufficient to maintain the polymer in the liquid form. In some embodiments, for a polyamide, the temperature of the liquid polymer may range between 265 °C and 300°C. In primary manifold 121, the pressure may be between 10 and 31 megapascals (MPa). The pressure in each secondary manifold may be equal to or less than the pressure in the primary manifold, e.g., between 10 MPa and 31 MPa, or between 10 MPa and 28 MPa. The primary and secondary manifolds may be jacketed or otherwise heated or insulated to maintain the temperature of the primary and secondary manifolds required to keep the polymer in liquid form. Additionally, the primary and secondary manifolds may each comprise a temperature controller to measure the temperature of the liquid polymer and adjust the temperature if needed. The primary and secondary manifolds may also each comprise pressure controllers to measure and adjust the pressure of the liquid polymer.

[0056] Primary manifold valves 122 and 123, when opened as shown in FIG. 2, provide fluid communication between primary manifold 121 and secondary manifolds 125 and 135. The internal diameter of primary manifold 121 may be equal to or greater than the internal diameter of secondary manifolds 125 and 135. In some embodiments, the internal diameter of the secondary manifolds relative to the internal diameter of primary manifold 121 may be used to control flow and pressure of the liquid polymer in the secondary manifolds.

[0057] Although primary manifold 121 is shown with a 90° angle in the manifold, primary manifold 121 may be a straight pipe, curved pipe, or bent pipe from continuous polymerization reactor 120 or may be angled at any suitable angle from continuous polymerization reactor 120.

[0058] The primary and secondary manifolds may have a circular, elliptical, rectangular or any other suitable cross-section, depending on requirements of each installation and process In one embodiment, a primary manifold may be a cylindrical pipe The internal diameter of primary manifold 121 may vary between 25 millimeters (mm) and 650 mm, e.g., between 50 mm and 300 mm or between 50 mm and 200 mm. The internal diameter of secondary manifolds 125 and 135 may vary between 25 mm and 300 mm, e.g., between 50 mm and 250 mm or between 50 mm and 150 mm. For the primary or secondary manifolds, "internal diameter" means the longest internal diameter of a cross-section of the primary or secondary manifolds, regardless of the shape of the manifolds. Primary manifold 121 may be comprised of a corrosion-resistant material that limits dissolution of iron into the polymer. Examples include austenitic stainless steel, such as 304, 304L, 316 and 316L. Secondary manifolds 125 and 135 may be comprised of materials similar to the materials used for the primary manifold. Although secondary manifolds 125 and 135 are shown at a 90° angle to primary manifold 121, they may be bent, curved or may be angled at any suitable angle from primary manifold 121. Additionally, although secondary manifolds 125 and 135 are shown in parallel and from the same side of primary manifold 121, they can be on opposite sides of primary manifold 121 or otherwise arranged.

[0059] Each secondary manifold and additive injection line may optionally be equipped with one or more static mixers (not shown) to assure uniform mixing. Exemplary static mixers are further described in Perry, Robert H., and Don W. Green. Perry's Chemical Engineers' Handbook. 7 th ed. New York: McGraw-Hill, 1997: 18-25 to 18-34, hereby incorporated by reference.

[0060] The additive injection storage tanks may be used to store additive supplies in the form of pure liquids, pure solids which are melted, liquid master batches or solid master batches. As needed, each additive storage tank may include a suitable apparatus for maintaining the additive supply vessel at required temperature. In some embodiments, the additive is stored at an elevated temperature substantially the same as the temperature of the liquid polymer when it passes into the secondary manifold. For example, if liquid polymer 116 is at a temperature of 300°C when it enters secondary manifold 125, additive storage tank 127 may be maintained at a temperature of approximately 300°C, using a heating apparatus. The additive storage tank may be capable of maintaining and adjusting temperature using jacketing with heat transfer tubing, an electrical trace heating, cloth heating, jacket apparatuses, band heaters, or electric heat tracing. If heat transfer tubing is used, a suitable heat transfer fluid such as a mixture of biphenyl and diphenyl oxide (sold by the Dow Chemical Company under the tradename DOWTHERM® A) can be used. These apparatuses may also be used to jacket and/or heat the primary and secondary manifolds, as well as the primary manifold valves and the additive injection valves.

[0061] In other embodiments, the temperature of additive in the additive injection line may range between 40°C and 300°C. The temperature of the additive may be selected based on the amount of additive that is added to the liquid polymer. For example, if the finished polymer product will comprise 0.1 wt.% additive, the effect of additive temperature on the liquid polymer will be minimal and the additive may be injected into the secondary manifold at a different temperature, e.g., lower, than the temperature of the liquid polymer in the secondary manifold.

[0062] Additive injection lines 128 and 138 are pressurized to provide additive that is at a higher pressure than liquid polymer 131 and 141. This helps to improve mixing of the additive with the liquid polymer and to prevent the additive from flowing back toward additive storage. When beginning to use the polymer additive apparatus 102, the additive injection lines are brought to a target pressure prior to opening the additive injection valves. Next, the primary manifold valve is opened, allowing liquid polymer to flow through the secondary manifold. The additive injection valve is then opened and additive is pumped through the valve into the secondary manifold. The pressure of the liquid polymer in the secondary manifold may range between 10 MPa and 31 MPa. In some embodiments, the additive injection line pressure may be at least 2 to 10% greater than the liquid polymer pressure in the secondary manifold.

[0063] In some embodiments, as shown in FIGS. 3 and 4, polymer additive apparatus 102 comprises three valves 122, 123 and 124, that, when opened, provide fluid communication between primary manifold 121 and secondary manifolds 125, 135 and 145. It is understood that polymer additive apparatus 102 may comprise more than three valves and additive injection apparatuses, e.g., more than four, more than five, or more than six, depending on the number of polymer products are desired to be produced by the apparatus. In some embodiments, polymer additive apparatus 102 comprises from three to ten additive injection apparatuses. Secondary manifold 145 comprises secondary manifold pump 146, additive injection storage tank 147, additive injection line 148, additive injection pump 149, additive injection valve 150, polymer solidifier 153, and finished polymer product 164.

[0064] In FIG. 2, primary manifold valves 122 and 123 are shown in an open position, e.g., fully open or partially open to allow flow through the valve, and additive injection valves 130 and 140 are shown in open position. Therefore, liquid polymer 116 flows through primary manifold 121 to secondary manifolds 125 and 135 and to polymer solidifier 118. Additionally, because additive injection valves 130 and 140 are shown in the open position, and additive is flowing from additive storage tanks 127 and 137 into the secondary manifolds 125 and 135.

[0065] In FIG. 3, primary manifold valves 122, 123 and 124 are shown in an open position and additive injection valves 130, 140 and 150 are shown in an open position. Therefore, liquid polymer 116 flows through primary manifold 121. At least a portion of liquid polymer 116 flows into secondary manifolds 125, 135, and 145. At least a portion of liquid polymer 116 flows into polymer solidifier 118. Additionally, additive injection valves 130, 140 and 150 are shown in the open position, and therefore additive is flowing from additive storage tanks 127, 137 and 147 into the secondary manifolds. The liquid polymers with additive 132, 142, and 152 are then fed through secondary manifolds 125, 135 and 145 to polymer solidifiers 133, 143 and 153.

[0066] In FIG. 4, primary manifold valves 122 and 123 are shown in an open position and additive injection valves 130 and 140 are shown in an open position. Primary manifold valve 124 and additive injection valve 150 are shown in the closed position. Therefore, liquid polymer 116 flows through primary manifold 121. At least a portion of liquid polymer 116 flows into secondary manifolds 125 and 135, but not into secondary manifold 145. Additionally, additive injection valves 130 and 140 are shown in the open position, and therefore additive is flowing from additive storage tanks 127 and 137 into secondary manifolds 125 and 135. The liquid polymers with additive 132, and 142 are then fed through secondary manifolds 125 and 135 to polymer solidifiers 133 and 143.

[0067] In FIG. 5, secondary manifold 145 contains a second additive storage tank 157, a second additive injection line 158, a second additive injection pump 159, and a second additive injection valve 160. The additive in additive storage tank 157 is different than the additive in additive storage tank 147. Although two different additive storage tanks are shown in secondary manifold 145, it is understood that any and/or all of the secondary manifolds may have more than one additive injection line, along with the additive pump, valve and other elements needed to operate the additive injection line. Primary manifold valves 122, 123 and 124 are shown in an open position and additive injection valves 130, 140 and 150 are shown in an open position. Therefore, liquid polymer 116 flows through primary manifold 121. At least a portion of liquid polymer 116 flows into secondary manifolds 125, 135, and 145. At least a portion of liquid polymer 116 flows into polymer solidifier 118. Additionally, additive injection valves 130, 140, 150 and 160 are shown in the open position, and therefore additive is flowing from additive storage tanks 127, 137, 147 and 157 into the secondary manifolds. The liquid polymers with additive 132, 142, and 152 are then fed through secondary manifolds 125, 135 and 145 to polymer solidifiers 133, 143 and 153.

[0068] Primary manifold pump 115 and secondary manifold pumps 126, 136 and 146 may be a pump selected from the group consisting of vane pumps, piston pumps, flexible member pumps, lobe pumps, gear pumps, centrifugal pumps, circumferential piston pumps, and screw pumps.

[0069] Primary manifold valves 122, 123, and 124 and additive injection valves 130, 140, 150 and 160 may include plug resistance injection valves, such as a cross-stem injection valve, schematically illustrated in FIGS. 6A and 6B, Type I and/or Type II polymer valves schematically illustrated in FIGS. 7, 8, 9 and 10, and a diverter valve schematically illustrated in FIGS. 11 and 12. Although the function of each valve is described as if it is an additive injection valve, each valve may also function as a primary manifold valve, allowing flow of liquid polymer into the secondary manifold when open or blocking flow when closed. [0070] As shown in FIGS. 6A and 6B, a cross-stem injection valve comprises a valve body 213, a handle 201, packing housing 207, injection port 205 through which a portion of the liquid polymer flows through the secondary manifold, and a pipe assembly 210 including a threaded stem 209. The pipe assembly 210 includes a supply line 204 through which the additive is transferred to the valve. The pipe assembly 210 is inserted into the bottom of the valve at position 208. The pipe assembly 210 includes a check valve 203 which allows flow only in one direction. Pipe connector 202 connects two pipes. The packing 207 is kept in place by the nut and bolt assembly 211, 212 to prevent leakage.

[0071] As shown in FIG. 7, a Type I polymer valve, also referred to as a two-way valve, allows flow of liquid polymer into the valve in void area 219 and then allows for one of two ports to be open. Type I polymer valve has an inlet port 214 and an outlet port 218, and a plug 217. Inlet port 214, when open, allows additive to flow into the secondary manifold. The outlet port 218 allows additive plus liquid polymer to flow through the secondary manifold. The plug 217 rotates to keep one port always open (partially or fully) and the other closed. In FIG. 7, port 218 is open and port 214 is closed. No additive may be injected through port 214 and liquid polymer is flowing through the valve. As shown, the valve is jacketed. Heat is delivered to the valve via port 216. Vent 215 may be connected to a vacuum to remove non-condensable gases. Drain pipe 220 removes condensate and any other liquids. The Type I polymer valve may also be used as a primary manifold valve to allow flow of the liquid polymer from the primary manifold to the secondary manifold.

[0072] As shown in FIGS. 8, 9 and 10, a Type II polymer valve, also referred to as a three-way valve, allows flow of the liquid polymer into the valve at void area 219 and then allows for either i) both ports 214 and 218 to be open (FIG. 8), ii) port 218 to be open and port 214 to be closed (FIG. 9), or iii) both ports 214 and 218 to be closed (FIG. 10). The Type II polymer valve may be used as a primary manifold valve to allow flow of the liquid polymer from the primary manifold to the secondary manifold.

[0073] A diverter valve is shown in FIGS. 11 and 12. A diverter valve allows for an injection position, as shown in FIG. 11, where the liquid polymer flows through void area 219, perpendicular to the plane of additive injection. Additive may flow through inlet 214. As shown in FIG. 12, inlet 214 may be diverted to diverter line 221 by mechanical means. The diverter valve may be used as a primary manifold valve or an additive injection valve.

[0074] Each of the valves described herein and all of the parts thereof may be plug resistant and comprised of stainless steel.

[0075] Polymer solidifiers 133, 143, 153 and 118 may comprise wet spinners, dry spinners, melt spinners, extrusion spinners, direct spinners, gel spinners, electro spinners, or pelletizers. Each of polymer solidifiers 133, 143, 153 and 118 may be a different polymer solidifier, depending on the final desired polymer product. Each polymer may be a fiber grade polymer and/or may be subsequently divided into substantially solid chips, e.g., flakes or pellets.

Retrofit of Prior Art Polymerization Processes

[0076] The present invention is directed to retrofit processes for reconfiguring existing polymerization processes to use a polymer additive apparatus described herein. Prior art polymerization process 3 is shown in FIG. 13. This process introduces a prepolymer or polymer salt via inlet 8 to polymerization reactor 20. A liquid polymer 16 is withdrawn from polymerization reactor 20 into primary manifold 21, which acts as a conduit for directing the liquid polymer from polymerization reactor 20 to polymer solidifier 18. In polymerization process 3, primary manifold 21 is the only manifold present in the process. Primary manifold 21 has two openings: an opening for connecting to a discharge line from polymerization reactor 20 and an opening for connecting to polymer solidifier 18. Optionally, polymerization process 3 may comprise a pump 15. Prior to prepolymer or polymer salt entering inlet 8, prior art polymerization process 3 may comprise additional steps and equipment to prepare the prepolymer or polymer salt for polymerization. These steps may include salt formation reactors, evaporators, prepolymerization reactors, prepolymer/gas separation, flashers, and the like. As shown in FIG. 13, polymerization process 3 does not add additives to the liquid polymer once it exits polymerization reactor 20. The liquid polymer 16 flows through primary manifold 21 to polymer solidifier 18 and a finished polymer product 19 is recovered.

[0077] Prior art polymerization process 3 may be retrofitted with a polymer additive apparatus by modifying primary manifold 21. The retrofit process may comprise replacing a portion of primary manifold 121 upstream of the opening for connecting to polymer solidifier 18 with a retrofit manifold. The retrofit manifold may be added by cutting primary manifold 21 at desired locations 71 and 72 and welding retrofit manifold into primary manifold 21. It is understood that these locations may be selected based on existing primary manifold 21 location, length, and process configuration. The retrofit manifold comprises a plurality of manifold valves including a first manifold valve and a second manifold valve. In some embodiments, the retrofit manifold may comprise between two and ten manifold valves. The retrofit manifold may comprise at least one connector tube for securing the retrofit manifold to primary manifold 21. The connector tube may be a compression fitting, threaded connector tube, bore connector, luer integral lock ring, etc. A gasket may be disposed between the at least one connector tube and primary manifold 21 to form a substantially hermetically sealed connection between primary manifold 21 and the retrofit manifold. Additionally, the retrofit manifold may be secured to the primary manifold using nuts, bolts, screws, or other connection means.

[0078] The retrofit manifold may have a substantially similar, or equal shape and internal diameter as primary manifold 21. Substantially all parts of the retrofit manifold, manifold valves, and additive injection valves may be comprised of stainless steel, e.g., austenitic stainless steel, such as 304, 304L, 316 and 316L. The manifold valves may be the primary manifold valves described herein, including cross-stem injection valves, two-way valves, three-way valves, diverter valves, or combinations thereof. The pressure and temperature of the liquid polymer within the retrofit manifold are substantially the same as the temperature and pressure within primary manifold 21, e.g., a temperature between 65°C and 300°C and a pressure between 10 MPa and 31 MPa

[0079] The retrofit process may further comprise connecting a first additive injection apparatus to the first manifold valve, directing a first portion of the liquid polymer from the retrofit valve into the first additive injection apparatus, and injecting a first additive into the first portion of the liquid polymer to produce a first finished polymer product comprising additive. As shown in FIGS. 2, 3, 4 and 5, the first additive injection apparatus comprises secondary manifold 125, secondary manifold pump 126, additive injection storage tank 127, additive injection line 128, additive injection pump 129, additive injection valve 130, and polymer solidifier 133 in fluid communication with secondary manifold 125 downstream of additive injection line 128. The additive in additive injection storage tank 127 may be selected from the group consisting of antifoam agents, lubricant aids, nucleating agents, flame retardants, plasticizers, impact modifiers, fiber glass, copper-based stabilizers, lubricants, delusterants, co-polymers, catalysts, compounds that chance ends balance, and mixtures thereof. Additional additives may include pigments and dyes. Additive injection line 128 may further comprise a static mixer (not shown). Finished polymer products 161 and 119 are then removed from polymer solidifiers 133 and 118. Each finished polymer product 161 and 119 may be a different finished polymer product.

[0080] The retrofit process may further comprise connecting a second additive injection apparatus to the second manifold valve, directing a second portion of the liquid polymer from the retrofit manifold into the second additive injection apparatus, and injecting a second additive to the second portion of liquid polymer to produce a second finished polymer product comprising the second additive. As shown in FIGS. 2, 3, 4 and 5, the second additive injection apparatus comprises secondary manifold 135, secondary manifold pump 136, additive injection storage tank 137, additive injection line 138, additive injection pump 139, additive injection valve 140, and polymer solidifier 143 in fluid communication with secondary manifold 135 downstream of additive injection line 128. The additive in additive injection storage tank 137 may be selected from the group consisting of heat stabilizers, antifoam agents, glass fiber, lubricants, copolymers, catalysts, flame retardants, plasticizers, impact modifiers, fillers, compounds that change ends balance, and mixtures thereof. In one embodiment, the additive in the first additive injection apparatus is different than the additive in the second additive injection apparatus. Additive injection line 138 may further comprise a static mixer (not shown). Finished polymer products 161, 162 and 119 are then removed from polymer solidifiers 133, 143 and 118. Each finished polymer product 161, 162 and 119 may be a different finished polymer product.

[0081] The retrofit process may further comprise adding or modifying pump 15 of FIGS. 13 and 14. If pump 15 is not present, it may be added. If the materials of the pump are insufficient for use with a desired liquid polymer, or if the pump is not the type of pump desired, pump 15 may be replaced with pump 115 as described herein. Generally, pump 115 may be a vane pump, piston pump, flexible member pump, lobe pump, gear pump, centrifugal pump, circumferential piston pump, or screw pump.

[0082] As shown in FIG. 14, prior art polymerization process 4 is similar to that of prior art polymerization process 3, except that prior art polymerization process 4 comprises a secondary manifold 25 for injecting additive from additive storage tank 27, through secondary manifold 25 to the liquid polymer in primary manifold 21. Primary manifold 21 optionally comprises a valve 22 that may be opened or closed to control the flow of additive from secondary manifold 25 into primary manifold 21. Secondary manifold 25 optionally comprises pump 26.

[0083] Prior art polymerization process 4 may be retrofitted with a polymer additive apparatus by modifying primary manifold 21 and secondary manifold 25. The retrofit process may comprise connecting a polymer solidifier to secondary manifold 25, and connecting at least one additive injection line to secondary manifold 25 upstream of the polymer solidifier, now referred to as the primary polymer solidifier. The retrofit process may further comprise directing a first portion of the liquid polymer from the primary manifold into secondary manifold 25, and injecting a first additive to the first portion of the liquid polymer via the at least one additive injection line. The liquid polymer comprising additive may then be directed to the additive polymer solidifier to produce a first finished polymer comprising the first additive. The additive polymer solidifier may be connected directly to the secondary manifold. The additive polymer solidifier in contact with the secondary manifold is therefore not connected to primary manifold 21. In the retrofit process, once the portion of liquid polymer flows into the secondary manifold, the process has been retrofitted and the first additive is no longer injected into primary manifold 21 but instead flows into secondary manifold 25 and into the additive polymer solidifier. It is understood that although prior art polymerization process 4 shows only one secondary manifold 125, if additional secondary manifolds are present, each may be retrofitted as described herein.

[0084] If primary manifold 21 in prior art polymerization process 4 did not comprise a manifold valve or if the valve is insufficient for use in the retrofit polymerization process, the valve may be added or replaced. Suitable valves and materials for the valves are described herein. Additionally, suitable materials for the additive injection lines are described herein. If secondary manifold 25 in prior art polymerization process 4 did not comprise pump 26, the pump may be added.

[0085] The additive injection line, additive injection storage tanks, valves, pumps and static mixers are added as described herein. Further, more than one additive injection line may be added to secondary manifold 125, e.g., from two to ten additive injection lines and respective additive storage tanks, valves, pumps and static mixers. [0086] The retrofit of prior art polymerization process 4 may further comprise retrofitting primary manifold 21 with one additive injection apparatuses, to produce a apparatus as shown in FIG. 2, or retrofitting primary manifold 21 with two additive injection apparatuses to produce a apparatus as shown in FIGS. 3 and 4. As described for the retrofit of prior art polymerization process 3, the retrofit process for adding the additive injection apparatus(s) comprises replacing a portion of the primary manifold upstream of the polymer solidifier with a retrofit manifold having a retrofit manifold valve, connecting an additive injection apparatus to the retrofit manifold valve, and directing a portion of the liquid polymer from the primary manifold into the additive injection apparatus to produce a finished polymer product.

EXAMPLES

Example 1

[0087] A continuous polymerization product is produced comprising nylon 6,6. The continuous polymerization product flows through a primary manifold at a temperature between 265°C and 300°C and at a pressure between 10 MPa and 31 MPa. The primary manifold is in fluid communication with two secondary manifolds via two primary manifold valves. Each primary manifold valve is opened to allow a portion of liquid polymer to flow through each secondary manifold at a temperature between 265°C and 300°C and at a pressure between 10 MPa and 31 MPa. Each secondary manifold is in fluid communication with a different additive injection line. Each additive injection line is in fluid communication with an additive source. To prepare a Nylon 6,6 polymer comprising additive, the additive is introduced from an additive storage tank to the additive injection line. Pressure of the additive in additive injection line is built to at least the pressure of the liquid polymer flowing through the secondary manifold. Temperature of the additive in the additive injection line may range between 40°C and 300°C. The additive injection valve is then opened. A target finished polymer product is set and to achieve this target, a value within the range between 0.1 wt.% and 20 wt.% additive is allowed to flow through the additive injection valve to be combined with the liquid polymer in the secondary manifold.

[0088] The liquid polymer with additive is then fed to a polymer solidifier to spin or pelletize the polymer and a finished polymer product is recovered. Additionally, at least a portion of liquid polymer is sent to a polymer solidifier in fluid communication with the primary manifold and a finished nylon 6,6 polymer is recovered. Therefore, at least two different finished nylon 6,6 polymer are thus removed from the apparatus. The time between providing the additive source to the additive injection line and removing the nylon 6,6 polymer comprising additive to target additive content is less than 1 hour.

Example 2

[0089] A continuous polymerization product is produced as in Example 1 and additives are added as in Example 1. The primary manifold is in contact with three secondary manifolds, each connected to a different additive injection line. The solidifier in contact with the primary manifold is blocked, resulting in no final polymer product from that solidifier. A first additive comprising delusterant is injected through a first additive injection line into the first secondary manifold and combined with liquid polymer to form a polymer product. A second additive comprising fiber glass is injected through a second additive injection line into a second secondary manifold and combined with liquid polymer to form a polymer product. The additive injection valve connecting the third additive injection line and the third secondary manifold is closed. Each product is fed through the polymer solidifier in contact with the respective secondary manifold to produce the final polymer product. The process therefore produces three polymer products from one continuous polymerization process: polymer product A with delusterant, polymer product B with fiber glass, and polymer product C with no additive. Because there is no flowback of additive or liquid polymer from the respective secondary manifolds into the primary manifold, polymer products A and C are free of fiber glass and polymer product B is free of delusterant.

Example 3

[0090] A continuous polymerization product is produced as in Example 1 and additives are added as in Example 1. The primary manifold is in contact with three secondary manifolds, each connected to a different additive injection line. A first additive comprising 20 meq/kg amine ends is injected through a first additive injection line into the first secondary manifold and combined with liquid polymer to form a polymer product. A second additive comprising 40 meq/kg amine ends is injected through a second additive injection line into a second secondary manifold and combined with liquid polymer to form a polymer product. A third additive comprising 60 meq/kg amine ends is injected through a third additive injection line into a third secondary manifold and combined with liquid polymer to form a polymer product. Each product is fed through the polymer solidifier in contact with the respective secondary manifold to produce the final polymer product. The process therefore produces three polymer products from one continuous polymerization process: each with different amine ends content and thus each with a different dyeability. Dyes and/or pigments may be added to the polymer products downstream or by an end user.

Example 4

[0091] A continuous polymerization product is produced as in Example 1 and additives are added as in Example 1, the primary manifold is in contact with three secondary manifolds, each connected to a different additive injection line. A first additive comprising nylon 6 is injected through a first additive injection line into the first secondary manifold and combined with liquid polymer to form a polymer product. A second additive comprising nylon 6,12 is injected through a second additive injection line into a second secondary manifold and combined with liquid polymer to form a polymer product. A third additive comprising nylon 6,10 is injected through a third additive injection line into a third secondary manifold and combined with liquid polymer to form a polymer product. Each product is fed through the polymer solidifier in contact with the respective secondary manifold to produce the final polymer product. The process therefore produces three polymer products from one continuous polymerization process, each with a different final polymer.

Example 5

[0092] A continuous polymerization product is produced as in Example 1 and additives are added as in Example 1. The primary manifold is in contact with three secondary manifolds, each connected to a different additive injection line. A first additive comprising a lubricant is injected through a first additive injection line into the first secondary manifold and combined with liquid polymer to form a polymer product. A second additive comprising a copper-based stabilizer package is injected through a second additive injection line into a second secondary manifold and combined with liquid polymer to form a polymer product. A third additive comprising a flame retardant is injected through a third additive injection line into a third secondary manifold and combined with liquid polymer to form a polymer product. Each product is fed through the polymer solidifier in contact with the respective secondary manifold to produce the final polymer product. The process therefore produces three polymer products from one continuous polymerization process: polymer product A comprising lubricant, polymer product B comprising a copper-based stabilizer package, and polymer product C comprising flame retardant.

Example 6

[0093] A continuous polymerization product is produced as in Example 1 and additives are added as in Example 1. The primary manifold is in contact with three secondary manifolds, each connected to a different additive injection line. A first additive comprising a first amount of nylon 6 is injected through a first additive injection line into the first secondary manifold and combined with liquid polymer to form a polymer product. A second additive comprising a second amount of nylon 6, which is different than the first amount, is injected through a second additive injection line into a second secondary manifold and combined with liquid polymer to form a polymer product. A third additive comprising a third amount of nylon 6, which is different than the first or second amount of nylon 6 is injected through a third additive injection line into a third secondary manifold and combined with liquid polymer to form a polymer product. Each product is fed through the polymer solidifier in contact with the respective secondary manifold to produce the final polymer product. The process therefore produces three polymer products from one continuous polymerization process, each containing a different amount of nylon 6.

Comparative Example A

[0094] A continuous polymerization product is produced comprising nylon 6,6 with an additive at a temperature between 265°C and 300°C and at a pressure between 10 MPa and 31 MPa. Prior to entering the polymerization reactor, a nylon salt solution is formed. The nylon salt solution is then sent to an evaporator to remove water and then to a polymerization reactor. An additive is added to the nylon salt solution prior to the solution being sent to the evaporator. A target finished polymer product is set and to achieve this target, a value within the range between 0.1 wt.% and 20 wt.% additive is added to the nylon salt solution. The time between providing the additive to the nylon salt solution and removing a nylon 6,6 polymer comprising additive to target additive content is between 8 and 12 hours. If a second polymer product with a different additive than the first polymer product was desired, the polymerization apparatus is taken offline and cleaned to remove any build up of additive from the evaporator, polymerization reactor, conduit between the evaporator and reactor, and from the reactor discharge line. An additional 8 to 12 hours are then required after the cleaning to produce a second polymer product that meets target specifications.

Comparative Example B

[0095] A continuous polymerization product is produced comprising nylon 6,6 with an additive at a temperature between 265 °C and 300°C and at a pressure between 10 MPa and 31 MPa. Prior to entering the evaporator to remove water, and prior to entering the polymerization reactor, a nylon salt solution is formed. The nylon salt solution is then sent to a storage tank for storage until needed. A target finished polymer product is set and to achieve this target, a value within the range between 0.1 wt.% and 20 wt.% additive is added to the nylon salt solution in the storage tank. The time between providing the additive to the nylon salt solution in the storage tank and removing a nylon 6,6 polymer comprising additive to target additive content is between 8 and 12 hours. If a second polymer product with a different additive than the first polymer product was desired, the polymerization apparatus is taken off-line and cleaned to remove any build up of additive from the storage tank, evaporator, polymerization reactor, conduit between the storage tank and evaporator, conduit between the evaporator and reactor, and from the reactor discharge line. An additional 8 to 12 hours are then required after the cleaning to produce a second polymer product that meets target specifications.

Comparative Example C

[0096] A continuous polymerization product is produced comprising nylon 6,6. The continuous polymerization product flows through a primary manifold at a temperature between 265°C and 300°C and at a pressure between 10 MPa and 31 MPa. The primary manifold is in fluid communication with an additive injection line. A target finished polymer product is set and to achieve this target, a value within the range between 0.1 wt.% and 20 wt.% additive is allowed to flow through the additive injection line to be combined with the liquid polymer in the primary manifold. The time between providing the additive to the primary manifold in the storage tank and removing a nylon 6,6 polymer comprising additive to target additive content is between 3 and 6 hours. If a second polymer product with a different additive than the first polymer product was desired, the polymerization apparatus is taken off-line and the primary manifold is cleaned to remove any build up of additive from the primary manifold. An additional 3 to 6 hours are then required after the cleaning to produce a second polymer product that meets target specifications.

[0097] While the invention has been described in detail, modifications within the spirit and scope of the invention will be readily apparent to those skilled in the art. All publications and references discussed above are incorporated herein by reference. In addition, it should be understood that aspects of the invention and portions of various embodiments and various features recited may be combined or interchanged either in whole or in part. In the foregoing descriptions of the various embodiments, those embodiments which refer to another embodiment may be appropriately combined with other embodiments as will be appreciated by one skilled in the art. Furthermore, those skilled in the art will appreciate that the foregoing description is by way of example only, and is not intended to limit the invention.