TW201529640A - Process for producing partially balanced acid solution with vessel having a disperser head for nylon salt production - Google Patents

Abstract

A continuous process for producing a nylon salt solution prepared using a liquid partially balanced adipic solution enriched in dicarboxylic acid, and in particular adipic acid. The liquid feed is prepared by metering dicarboxylic acid powder, based on weight, from a loss-in-weight feeder to a feeding conduit that transfers the dicarboxylic acid powder into a vessel comprising a disperser head; feeding a first feed stream of diamine to the vessel to form a dispersion comprising between 32 wt.% and 46 wt.% dicarboxylic acid, between 11 wt.% and 15 wt.% diamine, and between 39 wt.% and 57 wt.% water, and heating the dispersion at temperature between 50 DEG C and 60 DEG C to form a partially balanced adipic solution. A nylon salt solution is prepared from the liquid partially balanced adipic solution and continuously withdrawn into a storage tank. The nylon salt solution has a uniform pH and is suitable for producing nylon polymers.

Description

Method for producing a partially balanced acid solution for producing a nylon salt in a container having a disperser head Cross-reference to related applications

The present application claims priority to U.S. Application Serial No. 61/917,022, filed on Dec.

This invention relates to the manufacture of nylon salt solutions, and in particular to the manufacture of nylon salt solutions using a dispersant (including a vessel having a disperser head) using a liquid portion rich in dicarboxylic acid to equilibrate the acid solution.

Polyamines are commonly used in fabrics, garments, packaging, tire reinforcements, carpets, engineering thermoplastics for molding automotive parts, electronic equipment, sporting goods, and many industrial applications. Nylon is a high performance material for plastic and fiber applications requiring special durability, heat resistance and toughness. The aliphatic polyamine is referred to as nylon, which can be made from a salt solution of a dicarboxylic acid and a diamine. The salt solution was evaporated and then heated to cause polymerization. One of the challenges in this process is to ensure a consistent molar concentration balance of the dicarboxylic acid and the diamine in the final polyamine. For example, when nylon 6,6 is made from adipic acid (AA) and hexamethylenediamine (HMD), the inconsistent molar concentration balance adversely reduces molecular weight and may affect the dyeability of nylon. The molar concentration balance has been achieved using a batch salt process, but the batch process is not suitable for large scale industrial manufacturing. In addition, already The molar concentration balance is achieved in a continuous mode by a plurality of reactors each having a respective diamine charge during salt manufacture.

U.S. Publication No. 2010/0168375 teaches the preparation of a diamine and diacid salt solution, more specifically a concentrated solution of adipic acid hexamethylene diammonium salt, which is suitable for the manufacture of polyamines, more specifically The starting material for PA66. A salt solution having a salt concentration of 50% by weight to 80% by weight is prepared by mixing a diacid and a diamine, and an aqueous solution of a diacid/diamine molar ratio of more than 1.1 diacid and diamine is provided in the first stage, and The diacid/diamine molar ratio is adjusted to a value of 0.9 to 1.1, preferably 0.99 to 1.01, by adding a diamine in two stages, and the salt concentration by weight is fixed by adding water thereto as the case may be. Similarly, U.S. Publication No. 2012/0046439 teaches the use of two different diacids to produce a salt solution in multiple stages.

U.S. Patent No. 4,442,260 teaches a process for the manufacture of highly concentrated nylon salt solutions wherein the diamine is added in two portions, one portion is added before the water is evaporated from the maximum solubility solution and one portion is added after the water is evaporated from the maximum solubility solution.

U.S. Patent No. 4,213,884 teaches a process for the manufacture of a highly concentrated aqueous solution of a salt of a dicarboxylic acid and a diamine and a nylon precondensate produced by reacting an alkanedicarboxylic acid having 6 to 12 carbon atoms with a diamine. . A low-concentration aqueous solution containing a suitable excess of a salt of a dicarboxylic acid and a diamine which dissolves a specific dicarboxylic acid is reacted with a specific diamine in a molten state (equivalent of dissolved dicarboxylic acid), and the reaction is carried out under superatmospheric pressure and the final reaction temperature Maintain at 140 ° C to 210 ° C. Nylon was produced using the obtained solution.

U.S. Patent No. 4,131,712 teaches a process for the manufacture of high molecular weight polyamines wherein the diacid-rich component and the diamine-rich component are each separately produced in a non-stoichiometric ratio, each of which is Melting below the melting temperature of the polyamine product (and preferably below 200 ° C); then the diacid-rich component is contacted with the diamine-rich component in a liquid state at a temperature high enough to prevent solidification, And contacting in a proportion such that the total amount of the combined or uncombined diacid and diamine is as stoichiometric as possible.

Other methods of making anhydrous nylon salt solutions have been explored, such as the US Patent 5, 801, 278 and 5, 674, 974; WO 99/61510 and EP 0411790. Complex and time consuming methods have been observed to reduce production rates and have limitations for the industrial application of nylon salt solutions. For example, U.S. Patent No. 6,995,233 describes a continuous process for the manufacture of polyamines. Polyamines are of the type obtained from diacids and diamines. The process comprises the operation of continuously mixing an amine-rich end group-rich compound with an acid end group-rich compound and a polycondensation operation using the mixture. This process is related to the initial stage of the process using an aqueous solution comprising a mixture of substantially stoichiometric proportions of monomers. The mixture constituting the precursor may be anhydrous or may contain up to 10% by weight of water.

Despite efforts to improve the process of achieving the desired technical requirements, such as proper pH, molar concentration and/or salt concentration in nylon salt solutions, challenges remain. In particular, the dicarboxylic acid (and more specifically adipic acid) is a powder having a variable particle size, which results in a wide variation in bulk density and poor flow characteristics. The use of a dicarboxylic acid powder introduces another variable which makes it difficult to achieve the consistency of the target technical requirements. A volumetric feeder for dicarboxylic acid powders makes this difficulty increase.

It is necessary to use a dicarboxylic acid powder to control the improvement of the consistency of the nylon salt.

In a first embodiment, the present invention is directed to a continuous process for making a nylon salt solution comprising forming a partially balanced acid solution for storage in a liquid state at a temperature of from 50 ° C to 60 ° C, comprising the steps of: The dicarboxylic acid powder (preferably adipic acid) is metered from the weight loss feeder to the feed conduit to control the rate of change of the feed rate of the dicarboxylic acid powder based on the weight, the feed conduit transferring the dicarboxylic acid powder to contain dispersion a container of the head and feeding the first diamine feed stream to the container to form from 32% to 46% by weight dicarboxylic acid, from 11% to 15% by weight diamine and from 39% to 57% by weight water Dispersion. In one aspect, the partially balanced acid solution does not form a slurry. Further, the nylon salt solution is preferably not introduced into the container to form a dispersion. The method further comprises forming a nylon salt solution from the partially balanced acid solution to achieve a target salt concentration and a target pH, comprising the steps of: extracting from the storage dispersion Partially balancing a portion of the acid solution and introducing the portion of the partially equilibrated acid solution with the second diamine feed stream to a single continuous stirred tank reactor to form a nylon salt solution, and the nylon salt solution from a single continuous stirred tank reactor Directly and continuously pumped into the storage tank, wherein the salt concentration of the nylon salt solution is less than ±0.5% with respect to the target salt concentration and the pH of the nylon salt solution is less than ±0.04 with respect to the target pH. The target pH may be a value selected from the range of 7.200 to 7.900, preferably 7.400 to 7.705. The target salt concentration may be a value selected from the range of 50% by weight to 65% by weight, preferably 60% by weight to 65% by weight. In one aspect, the rate of change of the feed rate of the dicarboxylic acid powder to the vessel is less than ± 5%, preferably less than ± 3%. The vessel may further comprise a recycle loop having one or more in-line mixers. The method involves feeding at least two diamine streams, one fed to the vessel and one fed to a continuous stirred tank reactor. In one embodiment, the first diamine feed stream comprises from 15% to 30% by weight diamine and from 70% to 85% by weight water, and the second diamine feed stream comprises from 20% to 100% by weight two Amine and 0% by weight to 80% by weight of water. More preferably, the first diamine feed stream comprises from 20% to 30% by weight diamine and from 70% to 80% by weight water, and the second diamine feed stream comprises from 65% to 100% by weight diamine and 0% by weight to 35% by weight of water.

The invention may also relate to the program control of making a nylon salt solution. In one embodiment, the feed rates of the first diamine feed stream and the second diamine feed stream are set by creating a model comprising setting a production rate of the nylon salt solution and setting the feed rate of the dicarboxylic acid powder to The production rate is achieved and the target pH of the nylon salt solution is set. Using this model, the feed rate of the first diamine feed stream to achieve the target pH and the feed rate of the second diamine feed stream can be determined. In addition, the model can determine the adjustment of the diamine. The model can also be used to determine the feed rate of water to the vessel and reactor. The program control can further include adding a conditioned diamine feed stream upstream of the one or more pump and analyzer loops and measuring the pH of the nylon salt solution pH of the nylon salt solution in the analyzer loop. Due to changing conditions, the on-line pH measurement can be different from the target pH and can be adjusted when the pH changes. In one aspect, the sample can be removed from the analyzer loop to obtain an off-line pH measurement. In order to improve sensitivity, online The off-line pH measurements can be measured by diluting the contents of the analyzer loop to a concentration of 8 to 12% and cooling the contents of the analyzer loop to a temperature between 15 °C and 40 °C.

In a second embodiment, the present invention is directed to a continuous process for making a nylon salt solution comprising forming a partially balanced acid solution for storage in a liquid state at a temperature of from 50 ° C to 60 ° C, comprising the steps of: The dicarboxylic acid powder (preferably adipic acid) is metered from the weight loss feeder to the feed conduit to control the rate of change of the feed rate of the dicarboxylic acid powder based on the weight, the feed conduit transferring the dicarboxylic acid powder to contain dispersion a container of the head and feeding the first diamine feed stream to the container to form from 32% to 46% by weight dicarboxylic acid, from 11% to 15% by weight diamine and from 39% to 57% by weight water Dispersion. In one aspect, the partially balanced acid solution does not form a slurry. Further, the nylon salt solution is preferably not introduced into the container to form a dispersion. The method further comprises forming a nylon salt solution from the partially balanced acid solution to achieve the target salt concentration and the target pH, comprising the steps of: extracting a portion of the partially balanced acid solution from the storage dispersion and separating the portion of the partially balanced acid solution with the second The diamine feed stream is introduced together into a single continuous stirred tank reactor to form a nylon salt solution, and the nylon salt solution is continuously drawn directly from the single continuous stirred tank reactor into the storage tank. The salt concentration of the nylon salt solution is 50% by weight. Up to 65% by weight and the pH of the nylon salt solution is less than ±0.04 with respect to the target pH. The target pH may be a value selected from the range of 7.200 to 7.900, preferably 7.400 to 7.705.

In a third embodiment, the present invention is directed to a process apparatus for making a nylon salt solution comprising: a weight loss feeder including a funnel, a feed conduit, and a transfer tube for connecting the funnel to the feed conduit Wherein the funnel includes at least one external weight measuring subsystem for controlling the replenishment phase and the feeding phase, and at least one for dispensing a lower opening of the dicarboxylic acid powder at the feeding stage, wherein the at least one lower opening is located at the feed Above the pipe and wherein the feed pipe receives the dicarboxylic acid powder and transfers the dicarboxylic acid powder through the outlet via at least one rotating auger. The process apparatus further includes a container including one or more disperser heads, a first recirculation loop, and a first inlet connected to the outlet of the feed conduit And a second inlet for introducing a first diamine feed stream to form a dispersion, wherein the first recycle loop comprises an in-line mixer and a level control valve for storing the dispersion at a temperature of 50 ° C to 60 ° C a storage tank, wherein the storage tank includes a second recirculation loop connected to the level control valve to receive the dispersion from the vessel, and a continuous agitation for receiving a portion of the storage dispersion and the second diamine feed stream to produce the nylon salt solution Tank reactor.

In a fourth embodiment, the present invention is directed to a method for polymerizing a nylon salt solution comprising adipic acid and hexamethylenediamine to form nylon 6,6, comprising evaporating a nylon salt solution to form a concentrated stream, and The concentrated stream is polymerized in a second reactor to form a polyamine product. A nylon salt solution was prepared from the PBA solution as described herein. In one embodiment, a portion of the partially balanced acid solution can be introduced into the polymerization reactor.

100‧‧‧Nylon salt solution manufacturing process

102‧‧‧AA powder/pipeline

103‧‧‧Line/water

103'‧‧‧ Pipeline / Conditioning Water

104‧‧‧Line/HMD

104'‧‧‧Line/HMD

107‧‧‧Line/Adjust HMD

110‧‧‧weight loss feeder

111‧‧‧ funnel

112‧‧‧ Feeding pipeline

113‧‧‧ Controller

114‧‧‧Transportation system

115‧‧‧Supply container

116‧‧‧ Entrance

117‧‧‧ lower valve

118‧‧‧ Entrance

119‧‧‧ delivery tube

120‧‧‧Rotary feeder

122‧‧‧ sensor

123‧‧‧Rotary auger

124‧‧‧Open export

125‧‧‧Motor

127‧‧‧High level probe

128‧‧‧Low position probe

129‧‧‧Export

130‧‧‧System floor level

131‧‧‧Reactor exhaust condenser/recovery tower

132‧‧‧ water

133‧‧ ‧ bottom of the recovery tower / pipeline

134‧‧‧Exhaust gas

135‧‧‧pipeline/exhaust gas logistics

139‧‧‧Line/Quantitative AA Powder Feed

140‧‧‧Continuous Stirred Tank Reactor

141‧‧‧Recycling circuit

142‧‧‧Contacts

143‧‧‧Contacts

144‧‧‧ Pipes

145‧‧‧ entrance

146‧‧‧ entrance

147‧‧‧ Entrance

148‧‧‧ Lower exit

149‧‧‧ pump

150‧‧‧operable valve

151‧‧‧ heat exchanger

152‧‧‧Internal serpentine tube

153‧‧‧Sampling pipeline

154‧‧‧Analyzer/Online Analyzer/Online pH Meter

156‧‧‧ liquid level

157‧‧‧ mouth

158‧‧‧Agitator shaft

159‧‧‧ Impeller

160‧‧‧ blades

165‧‧‧External motor

166‧‧‧Motor drive shaft

167‧‧‧Connector

168‧‧ ‧ partition

174‧‧‧Exhaust port

184‧‧‧ storage tank

185‧‧‧Recycling circuit

186‧‧‧Internal jet mixer

187‧‧‧External injector

188‧‧‧Internal heater

189‧‧‧heater

190‧‧‧Filter

193‧‧‧Recycling circuit

194‧‧‧Internal jet mixer

195‧‧‧ storage tank

196‧‧‧Internal heater

197‧‧‧heater

199‧‧‧ pipeline

200‧‧‧polymerization process

202‧‧‧Evaporator

203‧‧‧Concentrated nylon salt

204‧‧‧Polymerization reactor/reactor

205‧‧‧ pipeline

208‧‧‧Nylon products

209‧‧‧Reactor exhaust line

211‧‧‧ signal

213‧‧‧Feed-forward signal

213'‧‧‧ signal

214‧‧‧Flower valve

214'‧‧‧ Flowmeter

215‧‧‧Feed-forward signal

215'‧‧‧ Flowmeter / Signal

216‧‧‧Flower valve

217‧‧‧Feed-forward signal/flow meter valve/pipeline/signal line

218‧‧‧Flower valve

218'‧‧‧ Flowmeter / Signal

220‧‧‧ pipeline

226‧‧‧ output

227‧‧‧Feed-forward signal

227'‧‧‧ signal

228‧‧‧Flower valve

228'‧‧‧ Flowmeter

229‧‧‧Feed-forward signal/signal pipeline

229'‧‧‧ signal

230‧‧‧Flower valve

230'‧‧‧ flowmeter

231‧‧‧Feed-forward signal

231'‧‧‧ signal

232‧‧‧Flower valve

232'‧‧‧ Flowmeter

302‧‧‧ Container

304‧‧‧Disperser head

306‧‧‧PBA solution

308‧‧‧Dispersion/PBA solution

310‧‧‧Motor

312‧‧‧ shaft

314‧‧‧Reaction mixture

316‧‧‧Liquid inlet

318‧‧‧ solid entrance

320‧‧‧Dilute HMD solution

322‧‧‧Recycling circuit

324‧‧‧Online Mixer

326‧‧‧ entrance

328‧‧‧ position control valve

The invention will be better understood in view of the accompanying non-limiting drawings in which: Figure 1 is a general flow of a nylon salt solution in accordance with an embodiment of the present invention.

2 is a schematic illustration of a weight loss feeder and a container having a disperser head for use in making an AA-rich PBA solution in accordance with an embodiment of the present invention.

3 is a schematic illustration of a continuous stirred tank reactor in accordance with an embodiment of the present invention.

4 is a schematic diagram of program control in accordance with an embodiment of the present invention.

Figure 5 is a schematic illustration of a process for making nylon 6,6 in accordance with one embodiment of the present invention.

6 through 8 are graphs of feed rate change rates of adipic acid from a weight loss feeder in accordance with an embodiment of the present invention.

The terminology used herein is for the purpose of describing particular embodiments and the invention As used herein, the singular forms " It will be further understood that the term "comprising", when used in the specification, is intended to mean the presence of the features, integers, steps, operations, components and/or components, but does not exclude the presence or addition of one or more other features, integers, steps, Operations, component groups, components, and/or groups thereof.

Terms such as "including", "including", "having", "including" or "involving" and variations thereof are intended to be broad and encompass the subject matter and equivalents listed below, and additional subject matter not stated . In addition, when the composition, the component group, the processing or method steps, or any other expressions are preceded by the traditional phrase "including", "including" or "containing", it is understood that the composition also encompasses the composition, component Group, process or method step or any other expression before the narrative of the phrase "consisting essentially of", "consisting of" or "group selected from" , component group, processing or method steps or any other statement.

Where appropriate, the equivalents of the structures, materials, acts, and all components or step-plus-function elements in the claims are intended to include any structure, material, or action that is used in combination with the claimed elements. The description of the present invention has been presented for purposes of illustration and description. Many modifications and variations will be apparent to those skilled in the art without departing from the scope of the invention. The embodiment was chosen and described in order to best explain the principles of the invention Therefore, while the invention has been described in terms of the embodiments of the present invention, it will be understood that

Reference will now be made in detail to certain disclosed subject matter. It is to be understood that the scope of the invention is to be construed as being limited by the scope of the claims. To the contrary, the subject matter of the invention is intended to cover all alternatives, modifications, and equivalents, which are included within the scope of the subject matter disclosed herein.

introduction

The invention generally relates to the manufacture of nylon salt solution from a nylon salt solution of a dicarboxylic acid and a diamine. Liquid and polyamine. In particular, the present invention relates to the manufacture of a dicarboxylic acid-rich liquid partially balanced acid (PBA) solution, also known as an acid-rich feed, which is used as a feed solution for forming a nylon salt solution. A nylon salt solution that achieves a target salt concentration and/or a target pH is formed. The PBA solution was partially equilibrated and the target pH or target salt concentration of the nylon salt solution was not achieved. The PBA solution can be combined with another feed of diamine and water in a single continuous stirred tank reactor to achieve the goal of making a nylon salt solution of uniform pH. The PBA solution preferably allows the introduction of a liquid phase dicarboxylic acid into a single continuous stirred tank reactor. In one embodiment, a nylon salt solution having a uniform pH can be polymerized to form nylon 6,6. Other types of polyamines can be made depending on the starting monomer used.

In the following description, the terms adipic acid (AA) and hexamethylenediamine (HMD) will be used to denote dicarboxylic acids and diamines. When adipic acid is used, the PBA solution is a partially equilibrated adipic acid solution. However, this method also applies to other dicarboxylic acids and other diamines as indicated herein.

The dicarboxylic acid suitable for the present invention is selected from the group consisting of oxalic acid, malonic acid, succinic acid, glutaric acid, pimelic acid, adipic acid, suberic acid, azelaic acid, and azelaic acid. Acid, undecanedioic acid, dodecanedioic acid, maleic acid, glutaconic acid, callus acid, and muconic acid, 1,2- or 1,3-cyclohexanedicarboxylic acid, 1 , 2- or 1,3-benzenediacetic acid, 1,2- or 1,3-cyclohexanediacetic acid, isophthalic acid, terephthalic acid, 4,4'-oxybisbenzoic acid, 4, 4-benzophenone dicarboxylic acid, 2,6-naphthalenedicarboxylic acid, p-tert-butylisophthalic acid and 2,5-furandicarboxylic acid, and mixtures thereof. In one embodiment, the dicarboxylic acid monomer comprises at least 80% adipic acid, such as at least 95% adipic acid.

In order to produce nylon 6,6, adipic acid (AA) is most suitable for the dicarboxylic acid and is used in powder form. AA is generally obtained in pure form containing very low levels of impurities. Typical impurities include less than 60 ppm of other acids (monobasic and less dibasic), nitrogenous materials, trace metals such as iron (less than 2 ppm) and other heavy metals (less than 10 ppm or less than 5 ppm), arsenic (less than 3 ppm) and Hydrocarbon oil (less than 10 ppm or less than 5 ppm).

A diamine suitable for the present invention is selected from the group consisting of ethanol diamine, trimethylene diamine, putrescine, cadaverine, hexamethylenediamine, 2-methylpentamethylenediamine, and seven Methylenediamine, 2-methylhexamethylenediamine, 3-methylhexamethylenediamine, 2,2-dimethylpentamethylenediamine, octamethylenediamine, 2 , 5-dimethylhexamethylenediamine, nonamethylenediamine, 2,2,4- and 2,4,4-trimethylhexamethylenediamine, decamethylenediamine, 5-methylindolediamine, isophoronediamine, undecyldiamine, dodecamethylenediamine, 2,2,7,7-tetramethyloctamethylenediamine, double (Aminocyclohexyl)methane, bis(aminomethyl)norbornane, optionally C ₂ -C ₁₆ aliphatic diamine substituted by one or more C ₁ to C ₄ alkyl groups, aliphatic polyether Diamines and furan diamines (such as 2,5-bis(aminomethyl)furan), and mixtures thereof. The selected diamine may have a higher boiling point than the dicarboxylic acid, and the diamine is preferably not xylylenediamine. In one embodiment, the diamine monomer comprises at least 80% hexamethylenediamine, such as at least 95% hexamethylenediamine. Hexamethylenediamine (HMD) is most commonly used in the manufacture of nylon 6,6. The HMD is cured at a temperature of from about 40 ° C to about 42 ° C, and water is usually added to suppress this melting temperature and to simplify the treatment. Thus, the HMD can be marketed as a concentrated solution, for example from 80% to 100% or from 92% to 98% by weight.

In addition to polyamines based solely on dicarboxylic acids and diamines, it is sometimes desirable to incorporate other monomers. When added in a proportion of less than 20% by weight, for example less than 15% by weight, such monomers may be added to the nylon salt solution without departing from the invention. The monomers may include monofunctional carboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, benzoic acid, caproic acid, heptanoic acid, caprylic acid, capric acid, capric acid, undecanoic acid, lauric acid, Myristic acid, myristate oleic acid, palmitic acid, palmitoleic acid, hexadecenoic acid, stearic acid, oleic acid, elaidic acid, isooleic acid, linoleic acid, erucic acid and the like. These may also include indoleamines such as alpha-acetalamine, alpha-propionamide, beta-propionamide, gamma-butyrolactam, delta-valeramine, gamma-valerene Amines, caprolactam and similar indoleamines. These may also include lactones such as alpha-lactone, alpha-propiolactone, beta-propiolactone, gamma-butyrolactone, delta-valerolactone, gamma-valerolactone, caprolactone and Similar to lactones. These may include difunctional alcohols such as monoethylene glycol, diethylene glycol, 1,2-propylene glycol, 1,3-propanediol, dipropylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,2-pentanediol, 1,5-pentanediol, 2-ethyl-1,3-hexanediol (etohexadiol), For methane-3,8-diol, 2-methyl-2,4-pentanediol, 1,6-hexanediol, 1,7-heptanediol and 1,8-octanediol. Higher functional molecules such as glycerol, trimethylolpropane, triethanolamine and the like are also suitable. Also suitable for hydroxylamine, such as ethanolamine, diethanolamine, 3-amino-1-propanol, 1-amino-2-propanol, 4-amino-1-butanol, 3-amino-1-butene Alcohol, 2-amino-1-butanol, 4-amino-2-butanol, pentanolamine, hexanolamine and the like. It will be understood that blends of any such monomers may also be used without departing from the invention.

It is sometimes also appropriate to incorporate other additives into the polymerization process. Such additives may include heat stabilizers such as any of copper salts, potassium iodide or other antioxidants known in the art. Such additives may also include polymerization catalysts such as metal oxides, acidic compounds, metal salts of oxygenated phosphorus containing compounds or other additives known in the art. These additives may also be matting agents and color formers such as titanium dioxide, carbon black or other pigments, dyes and colorants known in the art. The additives used may also include antifoaming agents such as cerium oxide dispersions, polyoxy oxycopolymers or other antifoaming agents known in the art. Lubricating acids such as zinc stearate, stearyl erucamide, stearyl alcohol, aluminum distearate, ethyl bis-stearylamine or other polymeric lubricants known in the art may be used. . A nucleating agent may be included in the mixture, such as fumed ceria or alumina, molybdenum disulfide, talc, graphite, calcium fluoride, phenylphosphinate or other acids 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 to the polymerization process.

The present invention advantageously achieves a nylon salt solution comprising an AA/HMD salt and having a target pH. In particular, the present invention achieves a target pH using a smaller number of containers than conventional methods, and in particular, achieves a target pH in a single reactor (e.g., a single continuous stirred tank reactor (CSTR)) that forms a nylon salt solution. In the present application, a nylon salt solution is made using a vessel containing a disperser head and a single continuous stirred tank reactor that achieves a higher production rate than batch processing. In batch processing, the amount of time and capital cost required to achieve a production rate similar to continuous processing makes batch processing impractical. Target pH can be familiar with this technology Any pH selected may be selected based on the desired final polymer product. Without being bound by theory, the target may be selected from the slope of the highest inflection point of the pH curve and at a level that is optimal for the range of expected polymer products.

In some exemplary embodiments, the target pH of the nylon salt solution may range from 7.200 to 7.900, such as preferably in the range of 7.400 to 7.700. The change in the actual pH of the nylon salt solution relative to the target pH of the nylon salt solution may be less than ± 0.04, more preferably less than ± 0.03 and most preferably less than ± 0.015. Thus, for example, if the target pH is 7.500, the pH of the nylon salt solution is from 7.460 to 7.540, and more preferably from 7.470 to 7.530. For the purposes of the present invention, the rate of change of pH refers to the average change in continuous operation. This change is extremely low, less than ± 0.53%, and more preferably less than ± 0.4%, and produces a nylon salt solution having a uniform pH. A uniform nylon salt solution having a low rate of change relative to the target pH is beneficial for increasing the reliability of the polymerization process to produce a uniform high quality polymer product. A nylon salt solution having a uniform pH also allows for uniform quality feed of the polymerization process. The target pH can vary depending on the production site. In general, pH 7.620, measured at 25 ° C at a salt concentration of 9.5%, produces a nylon salt solution having a free and chemical combination of AA and HMD to AA and HMD molar ratio of 1. For the purposes of the present invention, the molar ratio varies from 0.8:1.2 depending on the target pH. Having a uniform pH also means that the molar ratio of the nylon salt solution has a correspondingly low rate of change.

In addition to the target pH, the present invention also achieves a target salt concentration. The target salt concentration can be any salt concentration selected by those skilled in the art and can be selected based on the desired final polymer product and storage considerations. The water concentration of the nylon salt solution may range from 35% to 50% by weight. The nylon salt solution may have a salt concentration of from 50% to 65% by weight, such as from 60% to 65% by weight. The rate of change of the salt concentration of the nylon salt solution is preferably extremely low, for example, less than ±0.5%, less than ±0.3%, less than ±0.2% or less than ±0.1% with respect to the target salt concentration. For the purposes of the present invention, the rate of change in salt concentration refers to the average change in continuous operation. Thus, for example, if the target salt concentration is 60%, the salt concentration of the uniform nylon salt solution is from 59.5 wt% to 60.5 wt%, preferably from 59.7 wt% to 60.3 wt% and more preferably from 59.9% wt% to 60.1 wt%. . The target salt concentration can vary depending on the production site.

The nylon salt solution can be stored in liquid form at atmospheric pressure at temperatures below 110 ° C, such as 60 ° C to 110 ° C, or 100 ° C to 105 ° C. Concentrations above 65% by weight require higher temperatures and may require pressurization to keep the nylon salt solution in a liquid, such as a homogeneous liquid. The salt concentration can affect the storage temperature and is generally effective at storing the nylon salt solution at lower temperatures and atmospheric pressures. However, lower salt concentrations undesirably increase the energy consumption of the concentrated nylon salt solution prior to polymerization.

The temperature of the nylon salt solution is controlled independently of the molar ratio of AA to HMD. Although the molar ratio and solids concentration in the nylon salt solution affect the temperature of the nylon salt solution, the method relies on a heat exchanger, a serpentine tube, and/or a jacketed CSTR process to remove heat and thereby control the temperature of the nylon salt solution. . The temperature of the nylon salt solution can be controlled to vary less than ± 1 ° C relative to the desired temperature. The temperature of the nylon salt solution is selected to be lower than the boiling point of the nylon salt solution but higher than the crystallization temperature. For example, a nylon salt solution having a solid concentration of 63% has a boiling point of from 108 ° C to 110 ° C at atmospheric pressure. Therefore, the temperature is controlled to be lower than 110 ° C, for example, lower than 108 ° C, but higher than the crystallization temperature.

The present invention uses a PBA solution to introduce AA into the nylon salt solution and the PBA solution does not achieve the target pH or target salt concentration of the nylon salt solution. Preferably, the total amount of AA required for the nylon salt solution is introduced into the PBA solution, the PBA solution achieving a low AA concentration of less than ± 5%, such as preferably less than ± 2%, less than ± 1% or less than ± 0.5%. Rate of change.

Prior art solutions to achieve low rates of change in nylon salts have been directed to using multiple reactors to adjust the AA:HMD molar ratio and HMD concentration in the salt solution. This focus is due, at least in part, to the inherent unpredictability of AA powder feed due to the rate of change in volume density of AA powder and poor flow characteristics. When AA powder was fed into the reactor using a volumetric feeder, the rate of change in the bulk density of the AA powder was amplified. Due to the high melting temperature of AA, AA is usually supplied in powder form, which increases the difficulty of handling AA. In order to reduce the difficulty of AA powder processing, the present invention forms a liquid PBA solution containing AA. The PBA solution by combining AA powder and liquid Diamine production. The AA powder usually has an average particle diameter of from 75 to 500 μm, for example from 100 to 300 μm. The fine powder has a substantially large surface area and causes the aggregated particles to contact. The AA powder preferably contains less than 20% less than 75 μm particles, such as less than 10%. Since AA powder is typically metered in powder form based on the capacity of the reactor, variations in powder size can affect the overall packaging and density of the AA powder fed into the nylon salt reactor. These changes in overall packaging and density in turn result in a change in pH in the nylon salt solution and a change in AA to HMD molar ratio. To address this change, prior art solutions have arranged nylon salt reactors in series. See, for example, U.S. Publication Nos. 2012/0046439 and 2010/0168375. This conventional method uses the measurement of the target technology and feeds the monomer in a series reactor. However, this method requires many reactors, measurements, and adjustments, which increases cost and limits production rates. Moreover, this conventional method is more suitable for batch processing than continuous processing. Ultimately, such conventional methods cannot use models to predict pH and/or salt concentration, and therefore are more often adjusted to achieve the desired technical requirements for the nylon salt solution.

The prior art solves the effect of particle size and particle size distribution associated with feeding AA powder to nylon salt by adding AA and HMD using multiple reactors. It has been found that by varying the AA powder based on weight rather than capacity, the rate of change of the AA powder feed rate can be greatly reduced. In some aspects, the AA powder feed rate can vary by less than ± 5%, such as less than ± 3% or less than ± 1%, relative to the target AA powder feed rate. By thus stabilizing the feed, the disclosed method allows the use of a single reactor instead of a plurality of reactors in series to form a nylon salt solution of the desired technical requirements. It is difficult to control the change of the nylon salt solution relative to the target pH and target salt concentration using a single reactor operating at a continuous high production rate without stable feed to the AA powder, as the ability to adjust the monomer is limited. Stable feeding of the AA powder allows the program to control the HMD feed rate and allows the adjustment of the HMD to adjust the pH to achieve the target pH. It is contemplated that embodiments may provide a simpler design than previously disclosed by reducing the number of unit operations in processing. Thus, the disclosed method omits steps previously deemed necessary. This reduces plant emissions and reduces capital costs. The resulting nylon salt solution is then polymerizable to form the desired polyamine.

In order to achieve an acceptable yield in the manufacture of nylon salts, a continuous process can be used to produce a nylon salt solution that achieves a target pH and a target salt concentration. Batch processing will require significantly larger vessels and reactors that are not comparable to the production rates achievable with smaller continuous manufacturing equipment. In the polymerization, a nylon salt solution having a uniform pH and a salt concentration is preferably used as the starting material. A slight change can cause manufacturing quality problems, and polymerization requires additional monitoring, control, and adjustment of polymer processing.

Figure 1 provides an overview of a method of making a nylon salt solution in accordance with an embodiment of the present invention. As shown in Figure 1, the process for producing the nylon salt solution comprising 100 to 110 weight loss feeder feeding AA powder 102 to generate a directional this dispenser comprises a container 304 of the head 302 of the quantitative powder feed 139 AA. Water is passed through line 103 and the HMD is also directed via line 104 to vessel 302 to form an AA-rich PBA solution 306 , which may also be referred to as a coarse salt solution or feed solution. In one embodiment, the AA to HMD molar ratio of the PBA solution 306 is from 2:1 to 5:1, such as from 2:1 to 3:1, based on free and chemically bonded AA and HMD. The PBA solution 306 is stored in the liquid phase and does not form a slurry or solid. As discussed further below, the PBA solution 306 can be stored in the tank 184 prior to introduction to the continuous stirred tank reactor 140 . This allows for more mixing, allows storage of the AA reserve prior to formation of the nylon salt solution, and allows for the independent manufacture of the PBA solution and the nylon salt solution. The AA powder 102 is not directly introduced into the continuous stirred tank reactor 140 by using the liquid PBA solution 306 . The PBA solution 306 is transferred to a continuous stirred tank reactor 140 . In addition, water is fed via line 103' and HMD is fed via line 104' to continuous stirred tank reactor 140 . In some embodiments, lines 103' and 104' may be combined (not shown) prior to being fed into 140 .

The liquid containing the nylon salt solution is withdrawn from the reactor 140 , passed through the recycle loop 141 and returned to the reactor 140 . Additional HMD (referred to herein as conditioning HMD) may be added to the liquid from line 107 at junction 142 as needed to adjust the pH of the nylon salt. The nylon salt solution is withdrawn from the recirculation loop 141 to the conduit 144 at a junction 143 . The nylon salt solution in the conduit 144 removes impurities through the filter 190 and is collected in the storage tank 195 . Similar to the PBA solution 306 , the nylon salt solution in the storage tank 195 does not form a slurry or solid. In general, such impurities can include corrosion metals and can include impurities from monomer feeds such as AA powder 102 . The nylon salt solution is transferred via line 199 to polymerization process 200 . The nylon salt solution can be stored in storage tank 195 until polymerization is required. In some embodiments, the reservoir 195 can be delivered.

Nylon salt solution equipment

In one embodiment, the present invention is directed to a continuous process for making a nylon salt solution comprising metering dicarboxylic acid powder from a weight loss feeder to a feed conduit based on weight, the feed conduit to dicarboxylic acid powder Transferring to a vessel having a disperser head, feeding a first diamine feed stream to the vessel to form from 32% to 46% by weight dicarboxylic acid, from 11% to 15% by weight diamine and 39% by weight To a dispersion of 57% by weight of water, heating the dispersion to form a PBA solution at a temperature of 50 ° C to 60 ° C, introducing the PBA solution and the second diamine feed stream into a continuous stirred tank reactor to form a nylon salt solution, and nylon The salt solution is continuously and continuously extracted from the continuous stirred tank reactor to the storage tank, wherein the nylon salt solution comprises a salt concentration of 50 to 65 wt% and comprises a dicarboxylic acid/diamine salt having a target pH, and a feed for controlling the dicarboxylic acid powder. The rate of change of the rate changes the pH of the nylon salt solution by ±0.04 pH relative to the target pH. Preferably, the method of the invention allows the adipic acid concentration of the PBA solution to have a low rate of change of less than ± 5%, such as preferably less than ± 2%, less than ± 1%, or less than ± 0.5%.

Weight-based AA powder feeder

Figure 2 provides additional details of making AA-rich PBA solution 306 . The AA powder 102 is fed to the vessel 302 using a weight loss feeder 110 . The weight loss feeder 110 meters the AA powder 102 to produce an AA powder feed stream 139 having a low rate of change feed rate and is capable of addressing the density variation of the AA powder 102 during the feed processing. As indicated above, the bulk density and flow characteristics of the AA powder 102 can vary greatly, resulting in an imbalance in the molar ratio and a non-uniform pH in the nylon salt solution. The present invention is superior to volume feeders or other types of feeders that do not achieve a low rate of change feed rate for AA powder. For the purposes of the present invention, the low rate of change feed rate of AA powder is within ± 5% of the target feed rate of the AA powder, such as within ± 3%, within ± 2%, or within ± 1%. For the purposes of the present invention, the rate of change of the feed rate is the average change in continuous operation. Because of the low rate of change in AA powder feed rate, the feed rate of AA is stable and predictable. A low rate of change in the AA powder feed rate may allow for the formation of a PBA solution having a low rate of change in adipic acid concentration. Stable and predictable AA powder feed rates may also allow for custom diamine and water feed rates to achieve a target pH and/or target salt concentration using a single reactor. Because of the low rate of change of the AA powder feed rate relative to the target feed rate, no additional reactors are needed for blending or conditioning.

Generally, weight loss feeders 111 and 110 operate dispensing of the contents of the hopper at the feeding stage 111 to supply the charging funnel stage. Preferably, the replenishment-feeding phase cycle is sufficient to receive a feedback signal from the weight loss feeder 110 for at least 50% of the time, such as preferably at least 67% of the time. In one embodiment, the replenishment phase may be less than 20% of the total cycle time (eg, all times of the feed and replenishment phases), such as less than 10% of the total cycle time or less than 5% of the total cycle time. The replenishment phase and the full cycle phase can be determined by the production rate. In the feed phase, the contents of the funnel 111 are dispensed into a feed conduit 112 which transfers AA powder via line 139 to a continuous stirred tank reactor 140 . Additionally, during the recharge phase, the remaining AA in the funnel 111 may also be dispensed into the feed conduit 112 such that the feed conduit 112 receives a constant supply of AA powder. The weight loss feeder 110 can be adjusted using the controller 113 . The controller 113 can be a distribution control system (DCS) or a programmable logic controller (PLC) that can output a function in response to the received input. In one embodiment, there may be multiple controllers for multiple components of the system. For example, the replenishment phase can be adjusted using a PLC and the feed rate through the feed conduit 112 can be controlled using a DCS based on the target rate set in the DCS.

As shown therein, the transport system 2114 AA powder 102 is loaded into the supply vessel 115. The transport system 114 can be a mechanical or pneumatic delivery system that transfers adipic acid from a bulk bag, a lining bulk bag, a liner box container, or a funnel track automated vehicle unloading station. The mechanical transport system can include a screw or a traction chain. The pneumatic transport system can include a closed tube that delivers the AA powder 102 to the supply vessel 115 using pressurized air, vacuum air, or closed loop nitrogen. In some embodiments, the transport system 114 can provide the mechanical function of breaking the AA powder mass while loading the supply container 115 . The supply container 115 can have a cylindrical, trapezoidal, square or other suitable shape with an inlet 116 at the top. The shape having the inclined sides is suitable for helping the AA powder 102 to flow out of the supply container 115 . The upper edge of the supply container 115 can be less than 20 meters (m) above the system floor level 130 , such as preferably less than 15 meters. System floor elevation 130 refers to a flat surface on which a plurality of devices for making a nylon salt solution are placed and generally defines no flat passage on a flat surface. The system floor level can be above the entrance to the CSTR. Since the height of the supply container 115 is lower relative to the system floor level 130 , less energy is required to drive the transport system 114 and load the supply container 115 .

The supply container 115 also has a lower valve 117 that defines a lumen for holding the AA powder 102 when closed. The lower valve 117 can be a rotary feeder, a screw feeder, a rotary flow device, or a combination comprising a feeder and a valve. When the inner cavity is filled with the AA powder 102 , the lower valve 117 can remain closed. The lower valve 117 can be opened during the replenishment phase to deliver the AA powder 102 to the funnel 111 based on capacity. When the lower valve transports the AA powder to the funnel 111 , the AA powder 102 can be loaded to the supply container 115 . The lower valve 117 can include one or more baffles that form a seal when closed. In one embodiment, there may be a conveyor belt (not shown) that transfers the AA powder 102 from the supply container 115 to the funnel 111 . In other embodiments, the supply container 115 can transfer the AA powder 102 by gravity. The loading of the supply container 115 can be loaded independently of the funnel 111 .

The supply container 115 may have a larger capacity than the funnel 111 , and its capacity is preferably at least twice as large or at least three times greater. The supply container 115 should have a capacity sufficient to replenish the entire volume of the funnel 111 . The holding period of the AA powder 102 in the supply container 115 may be longer than the funnel 111 , and depending on the moisture concentration, the AA powder 102 may form a block. The block can be broken by a mechanical rotator or vibration (not shown) at the bottom of the supply container 115 .

The upper edge of the funnel 111 may be less than 15 m above the system floor elevation 130 , such as preferably less than 12 m. The funnel 111 can have a cylindrical, trapezoidal, square or other suitable shape with an inlet 118 at the top. Preferably, the inner surface of the funnel is steep to prevent AA powder bridging. In one embodiment, the angle of the inner surface is from 30 to 80, such as from 40 to 65. The inner surface can be U-shaped or V-shaped. The funnel 111 can also have a removable cover (not shown) with holes for the inlet 118 and the vent. The funnel 111 can be mounted to a delivery tube 119 that connects the funnel 111 to the feed conduit 112 . In one embodiment, the funnel 111 has an equivalent volume to maintain the desired production rate. For example, the funnel 111 can have a capacity of at least 4 tons. The maximum diameter of the delivery tube 119 is less than the largest diameter of the funnel 111 . As shown, the delivery tube 119 has a rotary feeder 120 or similar transfer device that dispenses the contents of the funnel 111 through the outlet 129 into the feed conduit 112 . Rotary feeder 120 can operate in an on/off mode or can control the rate of rotation based on changes in the desired feed rate. In other embodiments, the delivery tube 119 may not have an internal feeder mechanism. Depending on the type of weight loss feeder, the rotary feeder 120 can be replaced with an external massage paddle or vibrator that distributes the effluent of the funnel 111 into the feed conduit 112 . The outlet 129 can have a mechanical member that breaks the AA block. In another embodiment, the weight loss feeder 110 can have a dryer or dry gas purge (not shown) that removes moisture from the AA powder to prevent the AA powder from agglomerating in the funnel 111 and forming a plug.

The weight measurement subsystem 121 is coupled to the funnel 111 . The weight measurement subsystem 121 can include a plurality of weighing funnels 111 and provide a sensor 122 with a signal indicative of weight to the controller 113 . In some embodiments, there may be three inductors or four inductors. Sensor 122 may be connected to the outside of the funnel 111 of a funnel and may be any other initial weight tared apparatus 111 according to the hopper 111 and is connected to the. In another embodiment, the sensor 122 can be located below the funnel 111 . Based on the signal from the weight measurement subsystem 121 , the controller 113 controls the replenishment phase and the feed phase. The controller 113 compares the weights measured at regular intervals to determine the weight of the AA powder 102 that is dispensed to the feed conduit 112 for a period of time. Controller 113 can also control the speed of rotating auger 123 as described below.

In other embodiments, the weight measurement subsystem 121 can be located below the funnel 111 , the delivery tube 119, and the feed conduit 112 to measure the weight of material in such locations as the weight loss feeder 110 .

Feed line 112 is located below delivery tube 119 and receives AA powder 102 . In one embodiment, the feed conduit 112 can be mounted to the delivery tube 119 . The feed conduit 112 may extend substantially perpendicular to the plane of the outlet 129 of the delivery tube 119 or may extend from the plane and toward the container 302 at an angle of from 0 to 45 degrees, such as from 5 to 40 degrees. The feed conduit 112 has at least one rotating auger 123 that carries the AA powder 102 through the open outlet 124 and into the reactor 140 . The rotary auger 123 is driven by the motor 125 and may include an endless screw. A double helix configuration is also available. Motor 125 drives rotating auger 123 at a fixed or variable speed. In one embodiment, feed conduit 112 transfers AA powder 102 to vessel 302 at a low rate of change feed rate. The feed rate of AA can be adjusted depending on the production rate to be produced. This allows for the formation of a fixed AA feed rate and using the model described herein, with the feed rate of the other solution components then varying to achieve the desired salt concentration and/or pH target. The controller 113 receives the feedback signal from the weight loss feeder 110 and adjusts the speed of the rotating auger 123 . The controller 113 also adjusts the feed rate of the feed conduit 112 based on the signal from the weight measurement subsystem 121 . The command signal of the rotating auger 123 affects the motor speed (increase, maintain, or decrease) to achieve a set weight loss.

In other embodiments, the feed conduit 112 described herein can be of any equivalent controllable feeder type, such as a belt feeder, a compartment feeder, a plate feeder, a vibratory feeder, and the like. Feed line 112 may also include a damper (not shown). Additionally, feed conduit 112 may have one or more ports (not shown) for injecting nitrogen to remove oxygen.

The funnel 111 can also include a high level probe 127 and a low level probe 128 . It should be understood that for convenience, one high level probe and low level probe are shown, but multiple probes may be present. The probe can be used in conjunction with the weight measurement subsystem 121 . For the purposes of the present invention, the probes can be point level indicators or volume proximity sensors. The position of the high level probe 127 and the low level probe 128 can be adjusted within the funnel 111 . The high level probe 127 is located near the top of the funnel 111 . When the high level probe 127 detects the material in the funnel 111 , the replenishment phase is complete and the feed phase begins. In contrast, the low level probe 128 is located below the high level probe 127 and near the bottom of the funnel 111 . The position of the low level probe 128 may allow for a sufficient amount of AA powder 102 to be dispensed during the replenishment phase. The replenishment phase begins when the low level probe 128 detects that the funnel 111 has no material at its location. As mentioned above, the feed can continue during the replenishment phase.

The AA solid can be an etchant. The weight loss feeder 110 can be constructed of corrosion resistant materials such as austenitic stainless steel or, for example, 304, 304L, 316, and 316L, or other suitable corrosion resistant materials to provide an economical interface between equipment life and capital cost. A feasible balance. In addition, corrosion-resistant materials prevent corrosion contamination of the product. Other corrosion resistant materials are preferably more resistant to AA attack than carbon steel. High concentrations (eg, greater than 65%) of HMD are not corrosive to carbon steel, and thus carbon steel can be used to store concentrated HMD, while stainless steel can be used to store relatively dilute concentrations of HMD.

While an exemplary weight loss feeder 110 has been shown, other acceptable weight loss feeders may include Acrison Models 402/404, 403, 405, 406, and 407; Merrick Model 570; K-Tron Models KT20, T35. , T60, T80, S60, S100 and S500; and Brabender FlexWall ^TM Plus and FlexWall ^TM Classic. The acceptable weight loss feeder 110 should be capable of achieving a feed rate sufficient for continuous industrial operation. For example, the feed rate can be at least 500 Kg/h, such as at least 1000 Kg/h, at least 5,000 Kg/h, or at least 10,000 Kg/h. Embodiments of the invention may also use higher feed rates.

Container with disperser head

When the AA powder is dissolved, the present invention forms a homogeneous mixture with the HMD and water in the form of a PBA solution. Water is beneficial to help dissolve AA because HMD is not sufficient to dissolve AA powder. Water is also beneficial in reducing the freezing point of the resulting mixture. Adipic acid has low solubility in water, and Therefore, a much higher storage temperature is required in the absence of HMD.

Returning to the container 302 , in one embodiment, the container 302 can operate as a batch or continuous high shear mixer. Essentially all of the AA required for the nylon salt solution passes through the vessel 302 and thus does not require dissolution of the AA powder in the continuous stirred tank reactor 140 . The vessel 302 produces an AA-rich dispersion 308 and it can be pumped to the continuous stirred tank reactor 140 in the form of a PBA solution 306 . Advantageously, this improves to the AA feed consistency of reactor 140 and significantly increases the storage capacity of the adipic acid treatment. For example, together with the liquid PBA solution 306 , the AA powder 102 can be stored in a bin (not shown) that is 15 m (eg, better 10 m) from the floor level 130 . Therefore, it is easier to load the bin.

The vessel 302 can be a mixing chamber, mixing tank or mixing tank having one or more disperser heads 304 , such as a continuous stirred tank reactor. Preferably, the disperser head provides an improved cycle to form a dispersion as compared to a rotor-stator mixer. Container 302 is preferably used to disperse AA powder 102 into liquid HMD 104 and water 105 .

Each of the disperser heads 304 is coupled to the motor 310 via a shaft 312 . The motor 310 speed can be adjusted as needed to thoroughly mix the reaction mixture. The disperser head 304 can be secured to the shaft 312 and held below the level of liquid in the container 302 . In some embodiments, the disperser head 304 can be removed from the shaft 312 to allow for opening and/or switching between the disperser heads. Suitable disperser heads are described in U.S. Patent No. 5,407,271, the disclosure of which is incorporated herein by reference. The reactants are added to the contents of vessel 302 to form a reactant mixture 314 . The disperser head 304 provides high shear mixing to form a dispersion comprising a homogeneous mixture. The size and shape of the disperser head 304 can vary. In one embodiment, the reactant mixture 314 is drawn into the interior of the disperser head 304 and mechanically torn by the impeller blades or teeth. Mechanical tears can be provided on the top and bottom of the disperser head 304 . The reactants are drawn to the top and bottom of the disperser head 304 to form a high velocity countercurrent stream that converges in the interior cavity to create a high degree of turbulence and hydraulic shear. The centrifugal force presses the contents through the opening in the side of the disperser head 304 . The edges of the opening can be sharpened to provide further mechanical shear. The combination of high velocity emissions and reactant mixture 314 provides additional hydraulic shear and circulation.

In an alternate embodiment, the shaft 312 can include one or more mixing blades (not shown) to further aid mixing.

Container 302 may also have one or more ports (not shown) for injecting nitrogen to remove oxygen. If a nitrogen blanket is used, the humidity of the nitrogen gas charged to the port is preferably lower than the air surrounding the processing unit. For example, dry nitrogen can be used.

Heating is required to keep the AA powder dissolved in water in a liquid state because AA has low solubility in water. In one embodiment, one or more heaters may be provided in the recirculation loop 322 . The amount of heat necessary to maintain a liquid state can vary with the water concentration. The present invention uses HMD and water to further aid in the dissolution of AA and the formation of a PBA solution 306 comprising a mixture that can be stored at low temperatures. Advantageously, the lower temperature of the mixture reduces the extra energy typically used to prevent slurry formation. In one embodiment, the PBA solution 306 can be maintained as a homogeneous solution at a temperature of from 50 °C to 60 °C, such as from 55 °C to 60 °C. The mixture can be in the form of a slurry for a limited period of time until the acid has completely dissolved in time, at which point the mixture will become a clear homogeneous solution. The composition and temperature conditions are set such that the initial slurry is not a slurry but is converted to a clear homogeneous solution. The AA dissolution time depends on variables such as mixing energy, temperature, and the like.

In one embodiment, water 103 and HMD 104 may be fed to vessel 302 via liquid inlet 316 and AA powder 102 metered by weight loss feeder 110 is passed through solids inlet 318 . Liquid inlet 316 and solid inlet 318 can be on top of vessel 302 . For the purposes of the present invention, at least 80% of the water required to form a nylon salt solution having a desired salt concentration of 50 to 65%, and more preferably at least 90% of the desired water can be introduced directly into the vessel 302 . In general, the feed may be adjusted 103 'form (e.g., the second portion of water) additional water as shown in Figure 3 to the reactor vent condenser 131 or reactor 140, to achieve the desired concentration. The HMD 104 fed to the container 302 can be from 10% to 60% of the HMD required to form the nylon salt solution, such as from 25% to 45% of the desired HMD. The HMD 104 fed to the container 302 may be anhydrous or may contain 0% to 20% by weight water. The temperature of the HMD 104 fed to the vessel 302 may be sufficient to prevent the HMD from solidifying and is typically greater than 40 °C, such as or greater than 45 °C. Water can be added at ambient temperature to form a dilute HMD solution 320 having a temperature above 40 °C, such as or above 45 °C. In one embodiment, the dilute HMD solution 320 comprises 15% to 30% by weight HMD, and 70% to 85% by weight water, more preferably 20% to 30% by weight HMD and 70% to 80% by weight water, And can be fed to the container 302 .

In one embodiment, the AA powder is dispersed and dissolved in the vessel 302 in the presence of fresh HMD and water due to the high shear mixing formed by the disperser head 304 . Therefore, the salt solution from the reactor 140 , the storage tank 184 or the storage tank 195 is not fed into the vessel 302 to dissolve the AA powder. Recycling of the salt solution reduces processing capacity by up to 50%.

Container 302 forms a homogeneous dispersion 308 . The composition of the dispersion may vary and generally comprises from 32% to 46% by weight of AA, from 11% to 15% by weight of HMD, and from 39% to 57% by weight of water, and more preferably from 40% to 46% by weight of AA, 13 Weight% to 15% by weight HMD, and 41% to 47% by weight water. In one embodiment, the AA weight in the PBA solution is at least twice the weight of the HMD in the PBA solution. In one embodiment, dispersion 308 comprises from 25% to 50% balanced salt, such as hexamethylene diammonium adipate, and 15% to 40% free adipic acid. The solids concentration of dispersion 308 can be less than 60%. Solid concentrations include balanced salts and free AA. In general, the dispersion does not contain any free HMD and all of the HMD fed to the vessel 302 is chemically combined with the equilibrium salt. The PBA solution 306 has the same composition and solids concentration as the dispersion 308 .

In one embodiment, reactant mixture 314 can be continuously recycled in loop 322 . To further assist in dispersing and grinding the AA powder, the loop 322 can include an in-line mixer 324 for continuous processing of the dispersion 308 . Online mixer 324 can be a high shear mixer and a disperser. The reactant mixture 314 enters through inlet 326 and is sheared by internal mechanical stators, impellers, and blades to form a homogeneous mixture. There may be multiple mechanical stages that form shearing action. For example, the reactant mixture 314 can be sheared by rotating the vanes and into the stator, at which time the reactant mixture 314 is sheared as it passes through the slots in the stator. Dispersion 308 can be advanced to storage tank 184 by means of level control valve 328 . A portion of the dispersion 308 can also be recycled to the vessel 302 . In some embodiments, external heating or cooling in circuit 322 can be used to adjust the temperature of vessel 302 . In order to maintain a homogeneous solution free of suspended crystals, the temperature of the contents of loop 322 and vessel 302 should preferably be above 50 °C, such as 50 °C to 60 °C or 55 °C to 60 °C. The temperature can be controlled by adjusting the flow through circuit 322 and/or by adjusting the vapor or hot water to the recirculation loop heater.

In one embodiment, the liquid feed through the liquid inlet 326 may be above atmospheric pressure upon entering the in-line mixer 324 and form a low pressure zone (below atmospheric pressure) that creates a negative pressure. Although an in-line mixer 324 is shown in FIG. 2 , in some embodiments, there may be multiple in-line mixers arranged in parallel or in series. Suitable commercially available in-line mixer may comprise Admix DYNASHEAR ^TM mixer, QUADRO YTRON ^TM mixer, INOXPA ^TM-line mixer ME 4100, IKA ^TM Works mixer, GERICKE ^TM mixer, YSTRAL ^TM mixer and SILVERSON ^TM mixer.

In some embodiments, a pump such as a centrifugal pump or a positive displacement pump may be provided in circuit 322 to provide further mixing of reactant mixture 314 . A pump (not shown) can be used in addition to the in-line mixer 324 , or if the disperser head 304 is used for adequate mixing, the pump can be used independently of the in-line mixer 324 .

In one embodiment, the recirculation loop 322 is not connected to any analyzer that directly measures the pH or salt concentration of the dispersion 308 . In some embodiments, mass flow meters can be used to measure density and temperature, and to infer pH. In addition, no monomer is added to the recycle loop 322 in response to the pH measurement to adjust the pH.

As shown in FIG. 2, 308 dispersion into the storage tank 184 through a recirculation loop 185. As shown, the recirculation loop is returned to the lower portion of the storage tank by one or more internal jet mixers 186 , such as injectors. In one embodiment, the internal jet mixer 186 can be located 0.3 to 1.5 m, preferably 0.5 to 1 m from the bottom of the storage tank 184 . One or more jet mixers 186 can be used to blend or mix the dispersion into storage tank 184 . The PBA solution 306 can be withdrawn from the recycle loop 185 as needed and fed to the continuous stirred tank reactor 140 .

In some embodiments, the in-line mixer 324 can have a pressure differential of less than 200 kPa, such as less than 170 kPa or less than 100 kPa. The use of dispersion 308 as the power flow for injection mixer 186 in storage tank 184 may require a relatively high pressure of 175 to 350 kPa. In order to increase the pressure of the dispersion 308 through the level control valve 328 , an external injector 187 may be present at the intersection of the dispersion 308 and the recirculation loop 185 . Recirculation loop 185 acts as a power flow to the external injector, providing boost to dispersion 308 . In another embodiment, a booster pump (not shown) may be used in place of the jet mixer along the disperser discharge to the storage tank 184 .

In one embodiment, the recirculation loop 185 is not connected to any direct analyzer that measures or samples the stored dispersion (i.e., PBA solution 306 ). Due to the enrichment of AA, the PBA solution 306, such as the nylon salt solution described below, is more acidic and less sensitive to compositional differences. Therefore, the PBA solution 306 is not adjusted in response to the pH measurement of the liquid in the reservoir 184 . Providing a stable feed of AA powder with low variations allows for adequate control of the PBA solution without the need to monitor and control the contents of storage tank 184 .

The storage tank 184 can have a capacity of up to 5 days of PBA solution reserve, and more preferably up to 3 days of reserve. Although one storage tank 184 is shown , it should be understood that a plurality of storage tanks can be used to hold sufficient reserves. This allows the container 302 to be operated independently to dissolve the adipic acid, and the resulting dispersion 308 can be stored prior to forming the nylon salt solution. The storage tank 184 can be maintained under an inert atmosphere (such as a nitrogen atmosphere) at or slightly above atmospheric pressure. Storage tank 184 may have an exhaust port 174 of the exhaust gas is removed.

The storage tank 184 can be maintained at a temperature of from 50 ° C to 60 ° C, preferably from 55 ° C to 60 ° C. Advantageously, lower storage temperatures increase operating efficiency, reduce salt degradation and reduce energy consumption. For example, the PBA solution is not directly stored in the continuous stirred tank reactor 140 to provide storage for 2 to 8 hours, and the storage of the PBA solution from the storage tank 184 (which can be held for 3 to 5 days) is an advantage of the present invention. . This reduction is interrupted by the PBA solution feed loss to the continuous stirred tank reactor 140 . An internal heater 188 can be present in the reservoir 184 . Additionally, the recirculation loop 185 can have one or more heaters 189 that supply heat to the storage tank 184 . The vapor or hot water flow rate to the internal heater 188 or one or more heaters 189 can be adjusted to maintain the desired temperature of the storage tank 184 .

In one embodiment, the pH of the PBA solution 306 in the storage tank 184 is not directly measured or adjusted by adding monomer to the PBA solution 306 and/or storage tank 184 . In one embodiment, the pH of the PBA solution 306 need not be measured prior to introducing the PBA solution 306 to the continuous stirred tank reactor 140 . In some embodiments that may be present, supplemental pH measurements may be used.

As described below, the use of vessel 302 to form a PBA solution not only reduces the number of series salt reactors, but the PBA solution advantageously increases the adipic acid reserve in the process and carries a portion of the target salt reserve at a significantly lower temperature in the form of a semi-finished product to reduce salt. Degradation, improving the AA feed consistency of the continuous stirred tank reactor 140 , and eliminating the individual batch PBA facilities in the form of the final modified additive of the polymerizer.

reactor

In one embodiment of the present invention, as shown in Figure 3, a single continuous stirred PBA solution 306 from producing a nylon salt solution tank reactor 140. The continuous stirred tank reactor 140 forms a sufficient turbulence for the manufacture of a homogeneous nylon salt solution. For the purposes of the present invention, "continuous stirred tank reactor" means one reactor and does not include multiple reactors. In addition, a single reactor does not include vessel 302 . The present invention enables a uniform nylon salt solution to be achieved in a single container without the need for multiple cascaded containers as used in conventional methods. Suitable continuous stirred tank reactors are single vessel reactors, such as non-cascade reactors. Advantageously, this reduces capital investment in the manufacture of nylon salt solutions on an industrial scale. When used in combination with the weight loss feeders described herein, the continuous stirred tank reactor is capable of achieving a uniform nylon salt solution that achieves the target pH and target salt concentration.

The nylon salt solution is withdrawn from reactor 140 and transferred directly to storage tank 195 . The subsequently introduced monomer (AA or HMD) is not introduced into the nylon salt solution between the extraction from the continuous stirred tank reactor 140 and into the storage tank 195 . More specifically, the nylon salt solution is withdrawn from the recycle loop 141 in line 144 and no monomer is added to line 144 . In one aspect, the conduit 144 does not have an inlet for introducing additional monomers, which may include dicarboxylic acids and/or diamines. Therefore, the pH of the nylon salt solution is not further adjusted by introducing additional monomer into the conduit, and in particular is not adjusted by the addition of additional HMD. Additional mixing and filtration of the nylon salt solution may be present as needed, but the monomer is only fed to a single continuous stirred tank reactor as described herein. Thus, the disclosed method avoids the need for multiple vessels and a continuous pH measurement and adjustment step that was previously required to maintain a stable stoichiometric balance between AA and HMD to make nylon 6,6.

The continuous stirred tank reactor 140 can have a height to diameter ratio of from 1 to 6, such as from 2 to 5. Reactor 140 may be constructed from a material selected from the group consisting of: Hastelloy C, aluminum and austenitic stainless steels (such as 304, 304L, 316, and 316L), or other suitable corrosion resistant materials to provide An economically viable balance between equipment life and capital costs. The material can be selected by considering the temperature in the continuous stirred tank reactor 140 . The residence time in the continuous stirred tank reactor 140 can vary depending on the size and feed rate, and is typically less than 45 minutes, such as less than 25 minutes. Liquid is drawn into the recirculation loop 141 in the lower outlet 148 and a nylon salt solution is drawn in the conduit 144 .

In general, suitable continuous stirred tank reactors include at least one monomer inlet for introducing HMD and/or water and an inlet for introducing a PBA solution. The inlet is directed to the top of the reactor. In some embodiments, the monomer is dropped into the liquid. In other embodiments, a liquid level probe tube can be used to feed the monomer at the liquid level. There may be multiple inlets for introducing each monomer in the reaction medium. 3 is shown in FIG exemplary reactor 140. When a PBA solution is used, the remaining AA of the nylon salt solution is preferably fed to the vessel 302 to form a PBA solution 306 . Thus, the continuous stirred tank reactor 140 preferably has a PBA inlet 145 and an HMD inlet 146 and does not introduce solids into the continuous stirred tank reactor 140 . The HMD may be in the form of pure HMD 104' or an aqueous solution comprising 20% to 100% by weight of HMD (for example, 65% to 100% by weight), and 0% to 80% by weight of water (for example, 0% to 20% by weight) Form introduction. The HMD 104' fed to the continuous stirred tank reactor 140 can be from 20% to 70% of the HMD required to form the nylon salt solution, such as from 30% to 55% of the desired HMD. The HMD 104' can be introduced through an inlet 146 that is adjacent to the inlet 145 of the PBA solution 306 . Because the tolerance of the salt concentration is not as stringent as the pH, water can be introduced at a number of locations, such as through inlets 145 and/or 146 and/or by pump 149 as described herein. Depending on the situation, there may be an inlet 147 for the individual introduction of water. Water can also be introduced through the reactor recovery column 131 . In some aspects, recovery column 131 is an exhaust condenser. Since most of the water is introduced with the PBA solution 306 , a small amount of water may be required to achieve the desired salt concentration.

The liquid in reactor 140 is continuously drawn and passed through a recirculation loop 141 . Recirculation loop 141 may include one or more pumps 149 . Recirculation loop 141 may also include temperature control equipment (eg, serpentine tubes, jackets or equipment containing heat exchangers), temperature measuring equipment, and controllers. The temperature control device controls the temperature of the nylon salt solution in the recirculation loop 141 to prevent the nylon salt solution from boiling or slurrying. When additional HMD is introduced via line 107 (e.g., conditioning HMD), it is preferred to introduce HMD upstream of one or more pumps 149 at junction 142 and upstream of any pH or salt concentration analyzer. As further discussed herein, the conditioning HMD 107 can contain from 1% to 20% of the HMD required to form the nylon salt solution, such as from 1% to 10% of the desired HMD. Contact 142 can be a feed port for recirculation loop 141 . In addition to recirculating the liquid, pump 149 is also used as a secondary mixer. The pump can be used to introduce a regulated HMD into the recirculation loop 141 and mix and adjust the HMD with the liquid drawn from the reactor. The pump can be selected from the following groups: vane pumps, piston pumps, flexure pumps, multi-leaf pumps, gear pumps, ring piston pumps and screw pumps. In some embodiments, the pump 149 is located at the junction 142 . In other embodiments, pump 149 is located downstream of junction 142 but before junction 143 , as shown. Secondary mixing is preferably performed after all HMDs have been added (including the addition of conditioning HMD via line 107 ) and prior to any analysis or extraction to storage tank 195 . In an alternate embodiment, one or more static mixers (not shown) may be placed downstream of the pump 149 in the recirculation loop 141 . An exemplary static mixer is further described in Perry, Robert H. and Don W. Green. Perry's Chemical Engineers' Handbook. 7th ed. New York: McGraw-Hill, 1997: 18-25 to 18-34, which is incorporated by reference. The way is incorporated in this article.

At junction 143 , the nylon salt solution can be drawn into conduit 144 . The residence time in the conduit 144 can vary depending on the location of the storage tank 195 and the filter 190 , and is typically less than 600 seconds, such as less than 400 seconds. In one embodiment, valve 150 can be operated to control the pressure of the nylon salt solution. Although a valve is shown, it should be understood that additional valves may be used in the recirculation loop 141 . No monomer (e.g., AA or HMD) is introduced downstream of junction 143 or in conduit 144 . In addition, no monomer is introduced into the storage tank 195 under normal operating conditions.

The recirculation loop 141 may also include a heat exchanger 151 for regulating the temperature of the liquid in the reactor 140 . The temperature can be adjusted by using a temperature controller (not shown) in the reactor 140 or at the outlet of the continuous stirred tank reactor 140 (not shown). The liquid temperature can be adjusted using an internal heat exchanger such as a serpentine tube or jacket controller (not shown). The heat exchanger 151 can be supplied with cooling water that maintains a freezing point higher than a salt of a predetermined concentration. In one embodiment, the heat exchanger can be an indirect shell and tube heat exchanger, a spiral or plate and frame heat exchanger, or a reboiler for recovering heat from the reactor 140 . The temperature in reactor 140 is maintained in the range of 60 ° C to 110 ° C to prevent slurry formation and crystal formation. As the water concentration increases, the temperature of the solution is lowered. In addition, the temperature in reactor 140 is kept low to prevent oxidation of the HMD. A nitrogen blanket can also be provided to prevent oxidation of the HMD.

As shown in Figure 3, in one embodiment, the reactor 140 has an internal serpentine tube 152, which can be fed to the coolant temperature of the reactor was adjusted to the temperature 60 ℃ deg.] C to 110 of. In another embodiment, the reactor 140 can also be jacketed with a coolant (not shown). The internal serpentine tube can also regulate the temperature by recovering the heat generated by the reaction.

In addition to the temperature controller, reactor 140 may also have an atmospheric venting port in the presence of an exhaust condenser to maintain atmospheric pressure within reactor 140 . The pressure controller can have internal and/or external pressure sensors.

In one embodiment, a sampling line 153 for measuring the pH and/or salt concentration of the nylon salt may also be present. The sampling line 153 can be in fluid communication with the recirculation loop 141 and preferably receive a fixed flow to minimize the effects of flow on the analyzer. In one aspect, the sampling line 153 can extract less than 1% and more preferably less than 0.5% of the nylon salt solution in the recirculation loop 141 . One or more analyzers 154 may be present in the sampling line 153 . In some embodiments, the sampling line 153 can include a filter (not shown). In another embodiment, the sampling line 153 may contain a suitable heating or cooling device, such as a heat exchanger, to control the temperature of the sample stream. Similarly, sampling line 153 can include a watering line (not shown) that adds water to the sample stream to adjust the concentration. If water is added to the sample stream, the water can be deionized water. The water fed through the sampling line 153 is calculated to maintain the target salt concentration and other feeds of water can be adjusted. Analyzer 154 can include an on-line analyzer for instant measurement. Depending on the type of sampling, the test portion can be returned to reactor 140 via line 155 or discharged. The sampling line 153 can be returned via the recirculation loop 141 . Alternatively, sampling line 153 is returned to reactor 140 at various locations.

The continuous stirred tank reactor 140 remains at least 50% full, such as at least 60% full of liquid level 156 . The liquid level is chosen to be sufficient to submerge the CSTR vanes and thus prevent foaming of the nylon salt solution. Nitrogen or another inlet gas may be introduced via port 157 to the headspace above level 156 .

The agitator shaft 158 can have one or more impellers 159 such as a mixing paddle, a spiral belt, an anchor, a helical impeller, and/or a turbine. Axial flow impellers are preferred for mixing AA and HMD because such impellers tend to prevent solid particles from settling at the bottom of reactor 140 . In other embodiments, the impeller can be a flat blade radial turbine having a plurality of blades equally spaced along the disk. The entire agitator shaft 158 can have from 2 to 10 impellers, such as 2 to 4 impellers. 160 on the impeller blades 159 may be straight, curved, concave, convex, angled or pitch. The number of vanes 160 can vary from 2 to 20, such as from 2 to 10. The blade 160 may also have a stabilizer (not shown) or a scraper (not shown) as needed.

The agitator shaft 158 can have one or more impellers 159 such as a mixing paddle, a spiral belt, an anchor, a helical impeller, and/or a turbine. Axial flow impellers are preferred for mixing AA and HMD because such impellers tend to prevent solid particles from settling at the bottom of reactor 140 . In other embodiments, the impeller can be a flat blade radial turbine having a plurality of blades equally spaced along the disk. The entire agitator shaft 158 can have from 2 to 10 impellers, such as 2 to 4 impellers. The impeller blades 159,160 may be straight, curved, concave, convex, angled, or inclined. The number of vanes 160 can vary from 2 to 20, such as from 2 to 10. The blade 160 may also have a stabilizer (not shown) or a scraper (not shown) as needed.

In an exemplary embodiment, the agitator shaft can be a three pitch turbine assembly. In this type of assembly, the agitator shaft 159 includes at least one upper pitch blade turbine (not shown) and at least one lower pitch blade turbine (not shown). In a three-pitch turbine assembly, the inclined surface of the upper pitch blade turbine is preferably offset from the inclined surface of the lower pitch blade turbine.

Multiple agitator shafts with different types of impellers, such as spirals and anchors, can also be used. In addition, side suspension stirrer shafts can be used, especially those with marine impellers.

The agitator shaft 158 is driven by an external motor 165 that can mix liquid at 50 to 500 rpm, such as 50 to 300 rpm. The agitator shaft 158 can be movably mounted to the motor drive shaft 166 at the connector 167 . The speed of movement can vary, but the speed should generally be sufficient to maintain the full surface area of the solid particles in contact with the liquid phase, ensuring the highest availability of interfacial area for mass transfer in the solid-liquid.

Reactor 140 may also include one or more separators 168 for mixing and preventing the formation of a stagnant zone. The number of separators 168 can vary from 2 to 20, such as from 2 to 10, and is evenly spaced around the circumference of the reactor 140 . The separator 168 can be mounted to the inner wall of the reactor 140 . In general, a vertical partition 168 is used , but a curved partition can also be used. The separator 168 can extend above the liquid level 156 in the reactor 140 .

In one embodiment, reactor 140 includes an exhaust port through which exhaust gas is removed via line 135 and a recovery column 131 for returning condensable HMD to reactor 140 . Water 132 can be fed to recovery column 131 and recovered at bottom 133 of recovery column 131 . Water is fed at the lowest rate to maintain the efficiency of the recovery column 131 , and the amount of water is calculated to maintain the target salt concentration and other feeds of water can be adjusted. Exhaust gas 134 may condense to recover any water and monomer exhaust gases and may be returned via line 133 . Non-condensable gases, including nitrogen and air, may be removed as an off-gas stream 135 . When the recovery column 131 is an exhaust condenser, the recovery column 131 can be used to recover exhaust gas and remove non-condensable gases.

Although an exemplary continuous stirred tank reactor is shown, other acceptable continuous stirred tank reactors can be used.

Nylon salt solution storage

As shown in FIG. 3, when the nylon salt solution is formed, which is fed into the storage tank 195, the nylon salt solution may be held therein until needed for polymerization. In some embodiments, storage tank 195 can include a recycle loop 193 that recycles a nylon salt solution. Internal jet mixer 194 can be used to maintain circulation within storage tank 195 . In one embodiment, the internal jet mixer 194 can be located 0.3 to 1.5 m, preferably 0.5 to 1 m from the bottom of the storage tank 195 . Further, in some embodiments, at least a portion of the nylon salt solution can be returned to the reactor 140 to prevent the processing line from solidifying and/or correcting the desired change in the nylon salt solution or target pH and/or target salt solution in the event of system reversal. Any unused nylon salt solution of polymerization process 200 can also be returned to storage tank 195 .

Storage tank 195 may be constructed of corrosion resistant materials such as austenitic stainless steels such as 304, 304L, 316, and 316L, or other suitable corrosion resistant materials to provide an economically viable balance between equipment life and capital cost. The storage tank 195 may include one or more storage tanks depending on the size of the storage tank and the volume of the nylon salt solution to be stored. In some embodiments, the nylon salt solution is stored in at least two storage tanks, such as at least three storage tanks, at least four storage tanks, or at least five storage tanks. The storage tank 195 can be maintained at a temperature above the freezing point of the solution, such as at a temperature of from 60 °C to 110 °C. For a nylon salt solution having a salt concentration of 60% by weight to 65% by weight, the temperature can be maintained at 100 ° C to 110 ° C. An internal heater 196 can be present in the reservoir. Additionally, the recirculation loop may have one or more heaters 197 that supply heat to the storage tank. For example, the storage tank can have a reserve of up to 5 days of nylon salt solution, and more preferably up to 3 days of reserve capacity. The storage tank can be maintained under a nitrogen atmosphere at atmospheric pressure or slightly above atmospheric pressure.

In some embodiments, the nylon salt solution can be filtered to remove impurities prior to entering the storage tank 195 . The nylon salt solution can be filtered through at least one filter 190 , such as at least two filters or at least three filters. The filters 190 can be arranged in series or in parallel. Suitable filters may include membrane filters comprising polypropylene, cellulose, cotton and/or glass fibers. In some embodiments, the filter can have a pore size of 1 to 20 μm, such as 2 to 10 μm. The filter can also be an ultrafiltration filter, a microfiltration unit, a nanofiltration filter or an activated carbon filter.

Adjust HMD

As indicated in the above description, the equivalent amount of HMD required to form the nylon salt is introduced into the different portions in at least three positions to form a nylon salt solution. The first portion was added to form a PBA solution. Additionally, the feed rate of the HMD portion added to the vessel can be fixed to provide the requisite amount of HMD to dissolve the AA powder. The second and third portions are added to the CSTR to form a nylon salt solution. In order to use a continuous stirred tank reactor and form a uniform nylon salt solution, the nylon salt solution is drawn from the reactor into the pipeline and then no HMD is added after the storage tank. The HMD acts as a recirculation loop that regulates the introduction of HMD into the vessel, the continuous stirred tank reactor, and the continuous stirred tank reactor. To use a single continuous stirred tank reactor and form a uniform nylon salt solution, the nylon salt solution is drawn from reactor 140 into line 144 , and then no HMD is added after storage tank 195 . May be further improved by the control as shown in FIG via line 3107 at point 142 into HMD adjusted relative to the target technical requirements (e.g., certain pH) of the variance. The conditioning HMD is typically the smallest portion of the added HMD and is used as a fine tuning control for the pH of the nylon salt solution because the use of a smaller valve has a higher control over small changes in flow compared to the primary HMD feed. Adjusting the feed rate or flow rate of the primary HMD is the second preferred method of controlling the pH of the nylon salt solution because of the delay between the primary HMD adjustment and the pH measurement. Furthermore, since the HMD is adjusted to be the smallest portion of the HMD added to the CSTR, the HMD is adjusted to more precisely adjust the pH of the nylon salt solution and the pH analyzer provides near instantaneous feedback. The adjustment of HMD is added upstream of the pH measurement to reduce the delay in the addition of a pH action measurement that modulates the HMD. The water feed rate can also be adjusted to control the solids concentration in the nylon salt solution as the adjustment of the HMD is adjusted. These adjustments can be set by the controller and can be monitored by a refractometer in the sampling line 153 described herein.

The conditioning HMD 107 can be combined with the nylon salt solution prior to entering the conduit 144 . Without being bound by theory, the HMD 107 can react with any remaining free AA in the nylon salt solution. Additionally, the addition of conditioning HMD 107 can be used to adjust the pH of the nylon salt solution as described above.

In one embodiment, the present invention is directed to metering a PBA solution 306 to a continuous stirred tank reactor 140 ; separately introducing an aqueous solution comprising a first portion of HMD 104' and water 103' to a continuous stirred tank reactor 140 to form a nylon salt The solution; and a second portion of HMD (e.g., conditioning HMD) is introduced into the nylon salt solution via line 107 . The first portion of HMD 104' and water 103' can be combined to form an aqueous HMD feed. The conditioning HMD 107 can be added to the nylon salt solution at the junction 142 in the recirculation loop 141 . The regulated HMD 107 is continuously fed into the recirculation loop 141 at a feed rate that allows adjustment of the flow of the HMD 107 within a range flow (e.g., 20 to 60%, 40 to 50%, or about 50%) through the valve. Medium range flow refers to maintaining continuous flow through the valve to prevent loss of control.

To achieve the target pH at a low rate of change, the method involves forming a PBA solution 306 using a weight loss feeder 110 to provide a constant feed rate of AA powder 102 , and adjusting the HMD and water feed rates in response to program control. Advantageously, a high production rate can be achieved by continuous processing. When the salt production rate is varied, the HMD feed rate is also adjusted proportionally because the AA feed rate changes at discrete intervals. The feed rate of the HMD can be adjusted by varying the feed rate of the HMD fed to the reactor 140 or as the feed rate for adjusting the HMD fed HMD. In a preferred embodiment, the feed rate of the HMD 107 can be adjusted and the feed rate of the HMD 104' and/or the feed rate of the HMD aqueous feed can be constant for a given salt production rate. In an alternate embodiment, the feed rate of the regulated HMD 107 can be set to a constant rate and, if necessary, the feed rate of the HMD 104' and/or the feed rate of the HMD aqueous feed can be adjusted to achieve a target pH and/or salt concentration. . In other embodiments, the HMD 104' can be adjusted and the feed rate of the HMD 107 and/or the feed rate of the HMD aqueous feed can be adjusted to achieve a target pH and/or salt concentration.

The conditioning HMD 107 can have the same HMD source as the HMD 104' . The HMD 104' can comprise from 80% to 99%, such as from 90% to 99%, of the total HMD in the nylon salt solution. The HMD 107 can be adjusted to be from 1% to 20%, for example from 1% to 10%, of the total HMD in the nylon salt solution. The ratio of HMD 104' to adjusted HMD 107 can be adjusted depending on the target pH and target salt concentration. As described herein, the ratio of HMD 104' to adjusted HMD 107 can be set by a model for the total HMD feed rate.

The conditioning HMD can have the same source as the HMD used for the vessel and the continuous stirred tank reactor. The HMD may be supplied in pure HMD form, for example in the form of an aqueous solution comprising at least 99.5% by weight HMD, such as 100% HMD and anhydrous, or may comprise 80% to 99.5% by weight HMD. The HMD 107 was fed into the nylon salt solution as pure HMD or as an aqueous HMD solution. When the HMD 107 is adjusted to be an aqueous HMD solution, the aqueous solution that modulates the HMD 107 may comprise from 50% to 99% by weight HMD, such as from 60% to 95% by weight HMD or from 70% to 90% by weight HMD. As with the aqueous solution of HMD 104' , the amount of water can be adjusted based on the desired salt concentration of the HMD source and the nylon salt solution. Advantageously, the HMD concentration of the HMD 107 is adjusted from 90% to 100% by weight to increase the effect on pH control while minimizing the effect of adjusting the HMD 107 in salt concentration control.

The regulated HMD 107 is added to the nylon salt solution upstream of pump 149 and sampling line 153 in a recirculation loop. The pH of the nylon salt solution in the recycle loop 141 can be measured using an analyzer 154 in the sample line 153 after the second portion of the HMD 107 is added. This allows for a small delay between adjusting the pH and pH measurement by adjusting the feed rate of the HMD 107 . No additional AA is added to the recirculation loop 141 . The HMD is not added to the recirculation loop 141 except for the adjustment of the HMD 107 . A second portion of HMD 107 is added upstream of the pH measurement to allow pH measurement including the second portion of HMD 107 .

Unlike the prior art methods shown in U.S. Patent Publication No. 2010/0168375 and U.S. Patent No. 4,233,234, no adjustment of HMD is added after pH measurement. The addition of HMD after pH measurement creates a large delay in measuring the effect of the added HMD on pH, since the added HMD must pass through the reactor before being measured. Therefore, the addition of HMD in this manner may undershoot or overshoot the target pH, making such processing inefficient due to constant pursuit of the target pH. Advantageously, the present invention adds a regulated HMD upstream of the pH measurement such that the effect of regulating the HMD is addressed with a small delay and the problem of undershoot or overshoot target pH is avoided. In addition, the present invention constantly feeds the regulated HMD 107 because the valve remains at a medium range flow.

Program control

As described herein, a polyammonium salt solution (e.g., a nylon salt solution) is produced in a continuous process in a prior art process, and a rate of change can be present in the target technical requirements (including pH and salt concentration) in the nylon salt solution. This rate of change in the target technical requirements is caused, at least in part, by the unpredictable and fluctuating AA powder feed rate. These unpredictability and fluctuations make program control difficult because the process must be constantly monitored and adjusted downstream of the initial reactor prior to storage. Therefore, a single reactor operating continuously may not be able to effectively solve the unpredictable and fluctuating AA powder feed rate. Conventionally, in order to address this unpredictability and fluctuations, a number of reactors, mixers, and multiple reactant feed locations (especially for the addition of HMD) are used to make a nylon salt solution having the desired technical requirements. The ability to adjust the nylon salt solution in multiple reactors is removed using a continuous stirred tank reactor in accordance with the present invention. However, an improved procedure can be achieved by leveling the rate of change of the AA powder feed (ie, a variation of less than ± 5%) by forming a PBA solution using a weight loss feeder and forming a nylon salt solution using the PBA solution as the AA source. control. In one aspect, the present invention achieves a nylon salt solution having a target pH and salt concentration using model-based feedforward control with or without feedback.

Feedforward control

The reaction model can be made based on the desired nylon salt solution production rate prior to the start of continuous processing of the nylon salt solution. Based on this production rate, the AA powder feed rate was set, followed by the target pH and target salt concentration. The HMD feed rate and water feed rate are then stoichiometrically calculated to achieve the target pH and target salt concentration. The HMD feed rate includes the HMD forming the PBA solution, the primary HMD to the reactor, and the regulated HMD. The water feed rate includes all of the water fed into the vessel and reactor 140 . It should be understood that the target pH reflects the target molar ratio of AA to HMD. In other embodiments, additional features may be added to the model including, but not limited to, reaction temperature and reaction pressure. This model is used to set feedforward control of the HMD and/or water feed rate to the vessel and continuous stirred tank reactor. In some embodiments, the model can also be used to set feed forward control of the PBA solution to a continuous stirred tank reactor.

In some aspects, the model is made by inputting the feed rate of the AA powder provided by the weight loss feeder described herein. The model can also be set to the HMD feed rate of the vessel to achieve the desired mixture. For a given production rate, the feed rate of AA should be constant. The weight loss feeder can contain discontinuous control as described herein to produce an AA powder feed rate with a low rate of change. The AA powder feed rate from the weight loss feeder can be provided to the model continuously, semi-continuously, or at discrete intervals (e.g., every 5 minutes, every 30 minutes, or every hour). In other aspects, the model can set the HMD feed rate and water feed rate once the AA powder feed rate is set because of the low rate of change of the AA powder feed rate. These feed rates are set by the model to achieve the target pH and target salt concentration.

The model can be a dynamic model and can be adjusted by feedback signals from online and offline analyzers. For example, if a change in production rate, pH, or salt concentration is desired, the model can be adjusted. The model can be stored in the memory of the controller, such as a programmable logic controller (PLC) controller, a distributed control system (DCS) controller, or a proportional-integral-derivative (PID) controller. In one embodiment, a PID controller with a feedback signal can be used to resolve errors in model calculations and flow measurements.

Feedforward control itself previously had a low rate of change for formation relative to target technology requirements The nylon salt solution is not practical because the volumetric feeder cannot be used to accurately predict the AA powder feed rate. This is due, at least in part, to the change in the AA powder feed rate caused by the use of a volumetric feeder. Because of the rate of change of AA powder feed, a model that controls the ratio of AA to HMD cannot be produced. Thus, with regard to feedforward control, such conventional methods may use feedback control and therefore require frequent adjustments or will be batch processing. However, when the AA powder is metered by weight to a vessel having a disperser head, the feedforward control is sufficient to continuously manufacture a nylon salt solution having a low rate of change relative to the target specification.

Accordingly, in one embodiment, the present invention is directed to a method for controlling the manufacture of a nylon salt solution comprising producing a model for a target feed rate for AA powder to produce a PBA solution, and subsequently producing a target salt concentration and/or Or a nylon salt solution of the target pH. As indicated above, the target salt concentration can be a value selected from the range of 50% to 65% by weight, such as 60% to 65% by weight. The target pH may be a value selected from the range of 7.200 to 7.900, such as 7.400 to 7.705. The method can further comprise introducing the HMD to the vessel at a first feed rate and introducing the water at a second feed rate, wherein the first and/or second feed rate is based on a model for the PBA solution. The method can further comprise introducing the PBA solution separately at a third feed rate into the continuous stirred tank reactor, wherein the third feed rate is based on a model for the nylon salt solution. The method can further comprise introducing the HMD into the continuous stirred tank reactor at a fourth feed rate and introducing the water at a fifth feed rate, wherein the fourth and/or fifth feed rate is based on a target feed to the AA powder. Model of rate. The HMD and PBA solutions react to form a nylon salt solution which can then be continuously drawn directly from the continuous stirred tank reactor to the storage tank. The nylon salt solution can then be stored for future polymerization. Regardless of the selected target salt concentration or pH, the actual technical requirements of the nylon salt solution have a low rate of change relative to the target count requirement, such as less than 0.53% rate of change, such as less than 0.4%, less than 0.3%, or less than 0.1%.

In order to further illustrate the process control program of the present invention, it shows a schematic diagram in FIG. 4. For simplicity, Figure 4 excludes multiple pumps, recirculation loops, and heaters. Several flow meters (such as coriolis mass flow meters, positive displacement flow meters, electromagnetic flow meters, and turbine flow meters) for measuring flow through the system are shown in FIG . In some embodiments, the flow meter may also be capable of measuring temperature and/or density. The output of the flow meter can be input to the controller 113 continuously or at regular intervals. Preferably, at least one flow meter is present upstream of each flow meter valve. In some embodiments, the flow meter and flow meter valve can be provided integrally and together in a compact package. Although one controller is shown, in some embodiments, there may be multiple controllers. As shown in FIG. 4, AA powder fed via line 102 to produce a weight loss of quantitative feeder 110 139 AA powder feed. The controller 113 sends a signal 211 to the rotary auger 123 . Using the model, the HMD and water feed feed rate models can be stored in the controller 113 . As described above, the weight loss feeder 110 adjusts the rate of change of the AA powder to provide a quantitative AA powder feed 139 having a low rate of change relative to the target feed rate. For example, the weight loss feeder 110 can use the feedback loop from the weight measurement subsystem 121 to adjust the speed of the rotating auger 123 .

The controller 113 sends a feedforward signal 213 to the flow meter valve 214 to regulate the flow of water 103 into the vessel 302 . Similarly, controller 113 sends feed forward signal 215 to flow meter valve 216 to regulate the flow of HMD 104 entering container 302 . These feedforward signals are set by the model to achieve a target pH, a target AA to HMD ratio, and/or a target salt concentration. The HMD and water can be combined into an aqueous HMD solution and fed to the vessel 302 .

In another embodiment, the controller 113 sends a feedforward signal 227 to the flow meter valve 228 to regulate the feed rate of the PBA solution 306 into the continuous stirred tank reactor 140 . When the storage tank 184 is not in use, the flow meter valve 228 must be set according to the production rate of the vessel 302 , which may limit the reserve. These feedforward signals are set by the model to achieve the target pH and target salt concentration. Because feedforward signals 213 and 215 are used for HMD and water to container 302 , it is not necessary to obtain any on-line or off-line measurements of PBA solution 302 . In order to supply a sufficient amount of HMD and water to form the desired nylon salt solution, the DCS controller 113 can be based on the feed rate of the PBA solution 306 to the continuous stirred tank reactor 140 based on the HMD and water fed to the continuous stirred tank reactor 140 . Individual feedforward signals. Feed forward signal 229 may be based on a target feed rate of PBA solution 306 , and feed forward signal 229 may control flow meter valve 230 to supply remaining HMD 104' to continuous stirred tank reactor 140 . In addition, there is a feed signal 217 to the flow meter valve 218 to regulate the flow of the regulated HMD 107 entering the recirculation loop 141 . The model can determine the relative amount of HMD fed to the HMD 104 to the vessel 302 , the primary HMD 104', and the regulated HMD 107 feed. The controller 113 also sends a feed forward signal 231, valve 232 may be controlled to supply a flow meter to a continuous stirred tank reactor 140 water regulator 103 '. The conditioning water 103' may be supplied directly to the continuous stirred tank reactor 140 or supplied through an exhaust line. The feedforward signal 217 and the feedforward signal 229 are adjusted to ensure a medium range output flow to the flow meter valve 217 that regulates the HMD 107 . In one embodiment, the model may establish a feed rate that is sent by the feed forward signal 217 to the flow meter valve 218 to ensure that the constant flow (ie, medium range flow) of the regulated HMD 107 is maintained.

Secondary program control

In addition to using feed forward control based on prior modeling outside, as shown in FIG. 4, the control program may include a program control as a feedback signal of the two to achieve the target pH and the target salt concentration. These feedback signals can be measured from the flow meter and on-line analyzer 154 , which are used to adjust the HMD and water feed, preferably to adjust the HMD and water feed. The line analyzer 154 can include a pH probe, a refractometer, and combinations thereof. The pH probe and refractometer can be connected in series or in parallel.

As shown in Figure 4, the method uses line analyzer 154 (e.g. pH meter line 154) to generate a feedback signal, measuring pH in the recirculation loop 141 nylon salt solution. To facilitate on-line measurement of the pH of the nylon solution, a nylon salt solution is continuously withdrawn from the reactor and at least a portion of the nylon salt solution is directed to a recycle loop 141 and a sample line 153 . The recirculation loop 141 can include a flow meter (not shown) and a flow meter valve. In another embodiment, the recirculation loop 141 can include a pressure controller (not shown) to control the flow of the nylon salt solution. The flow rate of the nylon salt solution through the recirculation loop 141 is preferably constant. The sampling line 153 contains components for pH measurement (such as a pH meter) and/or components for salt concentration measurement (such as a refractometer). In one embodiment, the pH of at least a portion of the nylon salt solution is measured under reactor conditions without any dilution or cooling. At least a portion of the nylon salt solution is then returned to reactor 140 either directly or via vent condenser 131 . The nylon salt solution can displace the water fed into the vent condenser when at least a portion of the nylon salt solution is returned to the reactor via the vent condenser 131 . The sampling line 153 may also include a cooler (not shown) for cooling the nylon salt solution and a temperature sensor (not shown) for measuring the temperature prior to pH measurement. In some embodiments, the nylon salt solution is cooled to a target temperature prior to pH measurement. This target temperature can be a target that is in the range of 5 ° C to 10 ° C colder than the nylon salt solution exiting the reactor 140 . The change in temperature relative to the target temperature can be less than ± 1 ° C, such as less than ± 0.5 ° C. A temperature sensor (not shown) may be present upstream of the pH measurement to monitor the temperature of the nylon salt solution.

The on-line pH meter 154 then provides an output 226 to the controller 113 . This output 226 sends the pH value measured by the on-line pH meter 154 to the controller 113 . The rate of change of the pH of the nylon salt solution during continuous processing was determined using an on-line pH meter 154 . In other words, the on-line pH meter 154 can measure a different pH than the target pH, but when the measured pH changes, the controller 113 adjusts the monomer feed. In a preferred embodiment, the pH of the nylon salt solution varies by less than ± 0.04, such as less than ± 0.03 or less than ± 0.015. Since the on-line pH measurement is offset, the on-line pH measurement is used to measure the pH change rate rather than the absolute pH. This is at least in part because the feed control is allowed before the target pH is set. The change in the process can be detected by using an on-line pH meter to determine if the pH has changed. Using secondary control, a change in pH can result in a corresponding adjustment of at least one of the feed rates sent to flow meter valves 218 and 230 via signal lines 217 and 229 , respectively. In one aspect, when the PBA solution 306 is fed to the reactor 140 in a constant amount, it is preferred to adjust the feed rate of the HMD and water to the reactor 140 rather than to the feed of the vessel 302 that produces the PBA solution. rate. To provide responsive pH adjustment, a signal adjustment adjustment HMD 107 is sent to valve 218 via line 217 . The amount of adjustment made to adjust HMD 107 can be resolved by metering valve 230 correspondingly changing HMD 104' . The HMD adjusted to container 302 was preferably 104 times as this would affect the PBA solution. This adjustment is responsive and should not be able to return to the feed rate set by the feedforward control once the pH change is not displayed. These adjustments to adjust the HMD 107 can also affect the salt concentration of the nylon salt solution. These salt concentration changes can be controlled by adjusting the water by signal 231 of flow meter valve 232 .

Since the processing to form the nylon salt solution is continuous, the pH measurement in the on-line pH meter 154 can be obtained instantaneously (e.g., continuously) or almost instantaneously. In some embodiments, pH measurements are taken every 60 minutes, such as every 45 minutes, every 30 minutes, every 15 minutes, or every 5 minutes. The pH meter can have an accuracy of within ±0.05, such as ±0.02.

Depending on the adjustments required for feedback, the model can also be independently adjusted to the HMD and water of vessel 302 and reactor 140 using secondary control. This is especially advantageous when there is a tendency to cause a long-term adjustment to adjust the pH of the HMD 107 .

In addition to feedback from the on-line pH meter 154 , the flow meters 214' , 215' , 218' , 228' , 230' and/or 232' may be signaled 213' , 215' , 218' , 227' , 229', respectively. And/or 231' provides information or mass flow rate to controller 113 . This information from the flow meter can be used to maintain the overall production rate.

Prior art methods for measuring the pH of a nylon salt solution using a pH probe have been disclosed. See U.S. Patent No. 4,233,234 and U.S. Publication No. 2010/0168375. However, each of these prior art methods measures the pH of the nylon salt solution followed by the addition of additional diamines and/or acids to adjust the pH. The effect of additional diamines and/or acids is determined until additional diamines and/or acids are incorporated into the reactor and are again extracted for measurement. This method results in "chasing" the pH and forming a non-reactive program control that may overshoot or undershoot the target pH.

In the present invention, as shown in FIG. 4, adjusting pH meter line upstream of the preferred feed HMD 107. Thus, the HMD in the HMD 107 is adjusted to combine with the nylon salt solution in the reactor recycle loop and the pH of the nylon salt solution is measured before the recycle through the reactor 140 .

Secondary program control with online laboratory measurement

As described above, the pH measurement from the secondary program control does not have to reflect the target pH, but is used to interpret the pH change. In order to improve the sensitivity of the pH measurement, the secondary program control may also involve measuring the pH of the nylon salt solution under laboratory control. Without being bound by theory, the pH improvement accuracy of the nylon salt solution is measured under laboratory conditions because the sensitivity of the pH measurement near the inflection point is increased under the reduced concentration and temperature conditions. This allows for the detection of small pH changes that are not noticeable under the reaction conditions. For the purposes of the present invention, laboratory conditions refer to the measurement of a nylon salt solution sample at a temperature of from 15 ° C to 40 ° C, for example from 20 ° C to 35 ° C or 25 ° C, ± 0.2 ° C. The nylon salt solution sample measured under laboratory conditions may have a salt concentration of 8 to 12%, such as 9.5%. This pH measurement under laboratory conditions is performed by diluting and cooling the nylon salt solution line in the sampling line 153 .

As shown in FIG. 4, for convenience in the nylon line was measured under the laboratory conditions of pH, extracted from the reactor continuously and the nylon salt solution at least part of the nylon salt solution (e.g., less than 1%) directed to the recirculation loop 141 And sampling line 153 . Sampling line 153 contains components for pH measurement under laboratory conditions. The sampling line 153 may also include a cooler (not shown) to cool the nylon salt solution. In other embodiments, this cooler can be omitted. The temperature and concentration of the nylon salt solution in the sampling line 153 can be adjusted by adding water via line 220 . This water is a small fraction of the overall water feed rate explained by the model. Water is added in an amount sufficient to achieve the desired temperature and concentration of the diluted nylon salt solution sample for pH measurement and at the temperature at which the target is achieved. Further cooling of the diluted sample can be included. The pH of at least a portion of the nylon salt solution is obtained under laboratory conditions, and then at least a portion of the nylon salt solution is returned to reactor 140 as described herein. The on-line pH meter 154 then provides an output 226 to the controller 113 .

The rate of change of the pH of the nylon salt solution was measured using an on-line pH meter 154 as described above. In a preferred embodiment, the pH of the nylon salt solution varies by less than ± 0.04, such as less than ± 0.03 or less than ± 0.015. Similar to the pH measurement under the reaction conditions, since the on-line pH measurement is offset, the pH change rate is measured using the on-line pH measurement under laboratory conditions instead of the target pH. This is at least in part because the feed control is allowed before the target pH is set. The change in the process can be detected by using an on-line pH meter to determine if the pH has changed. Similar to the secondary program control, the feed rate can be adjusted by sending signals to lines 217 and 229 of flow meter valves 218 and 230 . These adjustments can also affect the salt concentration of the nylon salt solution. These salt concentration changes can be controlled by adjusting the water via signal 231 to flow meter valve 232 .

Since the process for forming the nylon salt solution is continuous, the pH measurement in the on-line pH meter 154 can be obtained instantaneously (e.g., continuously) or almost instantaneously. In some embodiments, pH measurements are taken every 60 minutes, such as every 45 minutes, every 30 minutes, every 15 minutes, or every 5 minutes. The pH measuring member should have an accuracy of ±0.05, such as ±0.03 or ±0.01.

Three-level program control

Although the feed before use as shown in FIG. 4 and a feedback control signal may help reduce the rate of change of the technical requirements of the nylon salt solution, but further analysis (pH, especially off-line analysis) is carried out under laboratory conditions can be used to detect homogeneous nylon salt solution Sex. Off-line program control under such laboratory conditions is referred to as three-level program control, which may include pH and/or salt concentration measurements. In one embodiment, the pH of the nylon salt solution can be measured off-line under laboratory conditions to determine if the target pH is achieved. Off-line pH measurement also detects any instrument problems or deviations that can be adjusted. In another embodiment, the nylon salt solution pH measured offline under laboratory conditions can also be used to adjust to signal lines 217 and 229 of flow meter valves 218 and 230 . Off-line pH measurements under laboratory conditions can have the ability to measure a pH within ±0.01.

As used herein, laboratory conditions refer to the measurement of a nylon salt solution sample at 15 to 40 °C, such as 20 to 35 °C or 25 °C, ± 0.2 °C, such as ± 0.2 °C. The concentration of the nylon salt solution sample measured under laboratory conditions may range from 8 to 12%, such as 9.5%. To achieve this temperature and concentration, the sample of the nylon salt solution removed from the recirculation loop can be diluted and cooled with water. A sample of the diluted nylon salt solution can be cooled using a temperature bath. Samples can be taken as needed, such as every 4 to 6 hours, daily or weekly. In the case of system reversal, samples can be taken more frequently, such as every hour. In general, offline analyzers can be used to resolve meter deviations in online analyzers. For example, if the target pH is 7.500, the on-line analyzer can report a pH of 7.400, while the off-line analyzer reports a pH of 7.500 indicating the on-line pH analyzer meter deviation. in In one aspect, an exponentially weighted moving average automatic deviation line analyzer can be used each time an offline measurement is taken. In some aspects, the output of the off-line analyzer is used to correct any deviation or offset of the line analyzer. In other aspects, the inline analyzer is uncorrected, but the offset or bias is monitored by an off-line analyzer. In this aspect, the pH change is determined by an on-line analyzer, such as in addition to a preset acceptable rate of change.

In another embodiment, an off-line analyzer can be used to measure the target salt concentration of the nylon salt solution. Off-line salt concentration measurements can also detect any instrument problems or deviations that can be adjusted. When multiple refraction timings are used, each refractometer can be independently biased.

Nylon polymerization

The nylon salt solution described herein can be directed to a polymerization process 200 for forming polyamines (especially nylon 6,6). Nylon salt solution may be from a continuous stirred tank reactor 140 is sent directly to the polymerization process or 200 may be first stored in the storage tank 195 and then sent to the polymerization process 200, as shown in FIG.

The nylon salt solution of the present invention has a uniform pH which improves the polymerization process efficiency of the polyamide. The uniform pH of the nylon salt solution provides a reliable starting material for the manufacture of a variety of polyamide products. This greatly improves the reliability of the polymer product. In general, the polymerization process comprises evaporating water from a nylon salt solution to concentrate the nylon salt solution and concentrating the concentrated nylon salt to form a polyamine product. One or more evaporators 202 can be used. The water may be evaporated under vacuum or pressure to remove at least 75% water in the nylon salt solution, and more preferably at least 95% water in the nylon salt solution. The concentrated nylon salt 203 may contain 0 to 20% by weight of water. It can be concentrated by batch processing or continuous processing. Additional AA and/or HMD may be added to polymerization reactor 204 depending on the final polymerization product desired. In some embodiments, the additive can be combined with the polyamidamine product.

For the purposes of the present invention, it is suitable for the polyamine product to be at least 85% carbon chain aliphatic between the guanamine groups.

When transferred from the storage tank 195 to the evaporator 202 , the nylon salt solution can be maintained at a temperature above its melting point. This prevents pipeline fouling. In some embodiments, the vapor captured from evaporator 202 can be used to maintain temperature. In other embodiments, heated cooling water can also be used.

The polymerization can be carried out in a single stage reactor or a multistage condensation reactor 204 . Different nylon products 208 can be made by adding additional monomer (AA or HMD, but preferably HMD) via line 205 . In one embodiment, a portion of the PBA solution 308 can be introduced to the reactor 204 to produce a different nylon product 208 . Reactor 204 can include a stirrer for mixing nylon salts. Reactor 204 can also use a thermal transfer media jacket to adjust the temperature. The condensation reaction in the reactor 204 may be carried out in an inert atmosphere of nitrogen and can be added to the reactor 204. The polymerization temperature may vary depending on the starting dicarboxylic acid and the diamine, but is generally higher than the melting temperature of the nylon salt, and more preferably at least 10 ° C higher than the melting temperature. For example, a nylon salt comprising a hexamethylene diammonium adipate salt has a melting temperature in the range of from 165 °C to 190 °C. Thus, the condensation reaction can be carried out at a reactor temperature of from 165 ° C to 350 ° C, for example from 190 ° C to 300 ° C. The condensation reaction can be carried out under atmospheric pressure or under a pressurized atmosphere. The nylon product 208 was removed from the reactor as a free flowing solid product.

Water produced during the condensation reaction can be removed from the reactor vent line 209 as a vapor stream. The vapor stream can be a condensed and vapor monomer (such as a diamine), and the vapor stream that escapes with the water can be returned to the reactor.

Subsequent processing, such as extrusion, spinning, drawing or tensile deformation, can be carried out to produce the polyamine product. The polyamine product can be selected from the group consisting of nylon 4,6; nylon 6,6; nylon 6,9; nylon 6,10; nylon 6,12; nylon 11; and nylon 12. Additionally, the polyamine product can be a copolymer such as nylon 6/6,6.

The following non-limiting examples describe the methods of the invention.

Example 1

By means of bulk bag unloading, lining bulk bag unloading, lining box container unloading or funnel track automatic car unloading station, transport system by means of mechanical (ie screw, traction chain) or pneumatic (ie high pressure air, vacuum air or closed loop nitrogen) Transfer AA powder from the unloading system to Supply container.

The supply vessel was transferred to a weight loss (L-I-W) feeder as needed and adjusted by the PLC based on the low and high levels of the selected L-I-W funnel. The supply container meters the AA powder by means of a screw conveyor or a rotary feeder at a rate sufficient to allow filling of the LIW at a maximum time interval equal to half and preferably less than half of the minimum LIW discharge time from the high level to the low level of the LIW box. The feeder funnel receives feedback of the LIW feeder feed rate for at least 67% of the time.

The LIW feeder system PLC adjusts the LIW feeder screw speed to maintain the feed rate (as measured from the LIW feeder funnel load meter) at the feed rate target feed received from the distributed control system (DCS) .

As shown in FIG. 6, by feeding the adipic acid weight loss feeder feed rate change rate over 48 hours of continuous feeding period of time with the feed rate of the rate of change of less than ± 5%. As shown in Figure 7, after the material feed rate is the rate of change of the period of 48 hours can be less than ± 3%. As shown in FIG. 8, after the material feed rate is the rate of change of the period of 18 hours can be less than ± 1%. The use of a weight loss feeder for adipic acid improves feed rate change rate performance by eliminating interference with the adipic acid feed rate using a volumetric feeder.

Example 2

A partially equilibrated adipic acid (PBA) solution was made as follows.

This AA powder feed is supplied from an L-I-W feeder to a vessel containing a disperser head, in this case a continuous stirred tank reactor. The disperser head was continuously blended with the reactant mixture of AA powder and dilute HMD solution to produce a PBA solution having 43.3% AA, 14.2% HMD, and 42.5% deionized water. The vessel also has an external in-line mixer for additional grinding of the reactant mixture and recycling back to the disperser CSTR. The partially equilibrated adipic acid solution had a solids concentration of 57.5 wt% and contained 25.4 wt% free AA.

The DCS model is used to determine the DCS setting of the L-I-W AA feed rate based on the PBA solution feed rate fed to the continuous stirred tank reactor (CSTR) and/or the target reserve content of the PBA storage. Fixed point.

A dilute HMD solution was produced as follows. The HMD solution (98%) was supplied to the vessel from a pressure controlled HMD storage recirculating head. Using Coriolis mass flow meter measurements and DCS input values, the DCS regulates the HMD feed stream flow rate to the PBA vessel to precisely control the ratio of AA to HMD in the reactant mixture. For the 63% salt concentration target, the HMD charge of the 41.2% container of the HMD charge for the process was added to the PBA vessel. The HMD solution is fed at a temperature greater than 45 °C.

Deionized water was mixed with the HMD solution to form a dilute HMD solution to the PBA vessel. The water is supplied from the pressure-controlled deionized water supply head. Using Coriolis mass flow meter measurements and DCS input values, the DCS regulates the flow rate of the deionized water feed stream flowing to the vessel to precisely control the aqueous solution concentration of AA and HMD in the reactant mixture. For the 63% salt concentration target, the PBA solution feed has a minimum of 56.75% solids (43.25% water) to allow for minimal deionized water injection and concentration adjustment adjustment of the reactor vent condenser. Water is fed at a temperature close to an ambient temperature of 20 ° C to 30 ° C.

The PBA vessel also has an external in-line mixer for mixing the reactant mixture and recycling the dispersion back to the PBA vessel, and feeding the dispersion forward to the storage tank.

When the head capacity of the in-line mixer is limited to less than the pressure required to discharge the dispersion directly into the subsequent tank, the in-line mixer is pump-assisted or in-line jetted into the recirculation loop of the storage tank in the form of an incoming stream. Device. The recirculating liquid of the storage tank is used as a power flow for the in-line injector.

The PBA solution temperature is raised to a minimum of 50 ° C, preferably 55 ° C to 60 ° C, using a storage vessel recirculation loop heat exchanger, maintaining the PBA as a homogeneous solution free of suspended crystals. The junction of the dispersion from the vessel and storage tank cycle is installed upstream of the recirculation loop heat exchanger in the form of a simple tee with a pressurized pump feed or an in-line injector with a vessel feed to ensure blending The stream reaches the minimum desired temperature before entering the storage container.

Control PBA storage recycle stream recirculation rate for recirculation line injectors and storage The tank's hybrid injector provides sufficient power flow rate. The tank mixing ejector will be located 0.2 to 1.5 m from the bottom of the tank, for example preferably 0.5 to 1 m, to ensure complete dispersion of the dispersion with the contents of the tank. The storage tank temperature will be adjusted to 50 ° C to 60 ° C, preferably 55 ° C to 60 ° C, by adjusting the vapor flow rate to the recycle line heat exchanger.

Example 3

A nylon salt solution was obtained which achieved a target salt concentration of 63% concentration and a target pH of 7.500. The PBA solution produced in Example 2 was used as a source of adipic acid for the nylon salt solution.

The DCS uses the DCS model to provide a target feed rate for the PBA solution to the salt CSTR, which is based on the polymerizer production rate and the target salt reserve level and adjusts the target at configurable intervals. The PBA solution feed rate was measured by means of a Coriolis mass flow meter and controlled according to the target in the DCS.

The DCS uses a feed forward ratio control loop to control the feed rate of the remaining HMD based on the target PBA feed rate. Adjust the set point of the DCS residual HMD ratio flow controller to maintain the output of the regulated HMD valve in the middle range, ensuring that the valve remains in the control range. For the 63% salt target, the remaining HMD charge is typically 48.8% to 56.8% for the processed HMD charge and is about 90 to 98% HMD when combined with the PBA solution fed to the HMD component.

The pH is continuously measured by an excess pH meter in the filtered temperature and flow control sample recirculation loop supplied by the reactor recirculation pump. Using the pH input of the continuously compared online pH measurement pair selected by the DCS, the DCS adjustment adjusts the feed rate of the HMD to maintain the pH at the target set point in the DCS. For the 63% salt target, the HMD charge was adjusted to be about 2 to 10% of the total HMD charge for the process.

Based on a statistical basic algorithm, adjust the pH controller setpoint using pH analysis of samples taken at discrete intervals downstream of the reactor and adjusted to 9.5% concentration and 25 °C to achieve maximum acid/amine balance as a function of pH. Sensitivity, or continuous dilution/regulation of the product from the reactor product or, preferably, from the subsequent storage vessel, to 9.5% by continuous input The pH of the on-line analyzer at 25 °C adjusts the set point of the pH controller.

The conditioned HMD is injected into the main reactor recirculation loop pump head to achieve the fastest reaction time for the pH meter and to ensure that the reactor product is adjusted to the target value in the shortest amount of time. The pump is used to blend the HMD with the reactor salt product to ensure a uniform solution for each of the pH meter and concentration meter.

The reactor concentration was continuously measured by an excess refractometer in the same filtered temperature and flow control sample recirculation loop supplied by the reactor recirculation pump. Using the concentration input of the continuously compared online concentration measurement pairs selected by the DCS, the DCS adjustment adjusts the feed rate of the deionized water to maintain the concentration at the target set point in the DCS. For the 63% salt target, the conditioning water charge is from 1 to 5%, preferably about 3%, of the total water charge of the process.

The reactor product is continuously fed to the storage tank by means of the level control of the CSTR, and the reactor product is further blended in the storage tank to be supplied to the polymerization apparatus. This transfer includes at least one stack of filter cartridge-type filter housings arranged in parallel that are designed for an initial cleaning pressure drop of up to 34.5 kPa (5 psig) at a maximum instantaneous salt solution transfer rate to storage. Filter cartridge removal efficiency using synthetic fiber depth or folded membrane cartridges is a minimum rating of 10 μm absolute, or a nominal nominal value of 1 μm when using a cotton fiber wound filter cartridge. The filter selection is based on a minimum of 110 °C rated operating temperature.

It is preferred to use a tank mixing ejector located 0.5 to 1 m from the bottom of the tank to continuously recycle the brine solution through the salt storage tank to more quickly switch the contents of the tank to maximize blending efficiency.

For a 63% salt concentration, the salt storage tank temperature was adjusted between 100 °C and 105 °C by adjusting the vapor flow rate of the recycle line heat exchanger. The salt in the storage tank has a uniform pH of 7.500 and is less than ±0.0135 from the target pH.

Comparison example A

The mixture was made from Example 1 of U.S. Patent No. 6,995,233. A concentrated HMD aqueous solution having a concentration of water equal to 10% and having AA powder is continuously fed to the first stirring reaction A mixture of 81% AA monomer and 19% diamine monomer was obtained in a weight ratio. This mixture may contain a small amount of water, for example about 7% by weight relative to the AA/HMD mixture. The mixture was maintained at a temperature of about 126 ° C to prevent crystallization.

Compare example B

The model and method follow Examples 1-3, but the HMD is not fed into the container. The partially equilibrated adipic acid solution from the storage tank contained 49.7 wt% adipic acid and 50.3 wt% water and must be maintained at a temperature above 85 °C to prevent solidification.

Comparative example C

The model and method were in accordance with Examples 1-3, but no water was fed into the container. It is not possible to feed only AA and HMD into the container because the container does not dissolve AA in the absence of water. This product will have a high viscosity and will be easy to handle only at much higher temperatures.

Comparison example D

The model and method were in accordance with Examples 1-3, but a volumetric feeder was used instead of the L-I-W feeder to feed the AA powder to the vessel. The pH of the nylon salt solution varies by more than 0.1 pH units relative to the target pH. Poor pH control can result in significantly higher freezing points, which would require higher processing temperatures to prevent crystallization risks.

Comparative example E

The model and method were in accordance with Examples 1-3, but no conditioning water was fed into the reactor. The salt concentration in the nylon salt solution increased from 63% to 63.707%, which requires a higher storage temperature, such as 3.5 ° C to 4 ° C, prior to polymerization. At atmospheric pressure, the increased storage temperature is closer to the boiling temperature of the nylon salt solution. In order to compensate for the increased salt concentration, the concentration of the partially equilibrated adipic acid solution is lowered, and since there is no adjustment of the water adjustment, it is more difficult to achieve a uniform concentration.

Although the present invention has been described in detail, modifications in the spirit and scope of the invention will be apparent to those skilled in the art. All publications and references mentioned above are incorporated herein by reference. In addition, it is to be understood that the aspects of the invention and the various embodiments of the invention and the various features may be combined or interchanged in whole or in part. If you are familiar with this technology, It is to be understood that in the foregoing description of the various embodiments, the embodiments of the other embodiments may be appropriately combined with other embodiments. In addition, those skilled in the art will understand that the foregoing description is by way of example only and is not intended to limit the invention.

100‧‧‧Nylon salt solution manufacturing process

102‧‧‧AA powder/pipeline

103‧‧‧Line/water

103'‧‧‧ Pipeline / Conditioning Water

104‧‧‧Line/HMD

104'‧‧‧Line/HMD

107‧‧‧Line/Adjust HMD

110‧‧‧weight loss feeder

139‧‧‧Line/Quantitative AA Powder Feed

140‧‧‧Continuous Stirred Tank Reactor

141‧‧‧Recycling circuit

142‧‧‧Contacts

143‧‧‧Contacts

144‧‧‧ Pipes

184‧‧‧ storage tank

190‧‧‧Filter

195‧‧‧ storage tank

199‧‧‧ pipeline

200‧‧‧polymerization process

302‧‧‧ Container

304‧‧‧Disperser head

306‧‧‧PBA solution

Claims (15)

A continuous process for the manufacture of a nylon salt solution comprising: a) forming a partially balanced acid solution stored in a liquid state at a temperature of from 50 ° C to 60 ° C, comprising the steps of: 1) by weight-based dicarboxylic acid powder Controlling the rate of change of the feed rate of the dicarboxylic acid powder from a weight loss feeder that transfers the dicarboxylic acid powder to a vessel containing the disperser head; and 2) The first diamine feed stream is fed to the vessel to form a dispersion comprising 32% to 46% by weight dicarboxylic acid, 11% to 15% by weight diamine, and 39% to 57% by weight water; b) forming the nylon salt solution from the partially balanced acid solution to achieve the target salt concentration and the target pH, comprising the steps of: 1) extracting a portion of the partially balanced acid solution from the storage dispersion and balancing the portion of the acid solution Partially introduced into the single continuous stirred tank reactor together with the second diamine feed stream to form the nylon salt solution; and 2) continuously extracting the nylon salt solution directly from the single continuous stirred tank reactor into the storage tank, Where the nylon salt solution is The concentration of the target with respect to the variation of less than ± 0.5% salt concentration and the pH of the nylon salt solution with respect to the target is less than the pH change ± 0.04. The method of claim 1, wherein the rate of change of the feed rate of the dicarboxylic acid powder is less than ± 5%. The method of claim 1, wherein the container further comprises a recirculation loop having one or more in-line mixers. The method of claim 1, wherein the nylon salt solution is not introduced into the container to form the dispersion. The method of claim 1, wherein the portion of the equilibrium acid solution does not form a slurry. The method of claim 1, wherein the target pH is a value selected from the range of 7.200 to 7.900. The method of claim 1, wherein the target salt concentration is a value selected from the range of 50% by weight to 65% by weight. The method of claim 1, wherein the first diamine feed stream comprises from 15% to 30% by weight diamine and from 70% to 85% by weight water. The method of claim 1, wherein the second diamine feed stream comprises from 20% to 95% by weight diamine and from 5% to 80% by weight water. The method of claim 1, wherein the feed rates of the first diamine feed stream and the second diamine feed stream are set by: a) producing a model comprising: i. setting the nylon salt a production rate of the solution; ii. setting a dicarboxylic acid powder feed rate to achieve the production rate; and iii. setting a target pH of the nylon salt solution; and b) using the model to determine the first two to achieve the target pH The feed rate of the amine feed stream and the feed rate of the second diamine feed stream. The method of claim 10, wherein the nylon salt solution is adjusted by adding a conditioning diamine feed stream upstream of one or more pumps and analyzer circuits and measuring the pH of the nylon salt solution in the analyzer circuit. pH. The method of claim 11, further comprising removing the sample from the analyzer loop to obtain an off-line pH measurement. The method of claim 11, wherein the content of the analyzer circuit is diluted to a concentration of 8 to 12% and the contents of the analyzer circuit are cooled to 15 ° C to 40 ° C to measure the content. The pH measurement in the analyzer circuit. The method of claim 13, wherein the pH measurement is different from the target pH. A method for polymerizing a nylon salt solution of claim 1 to form nylon 6,6 comprising evaporating the nylon salt solution to form a concentrated stream, and polymerizing the concentrated stream in a second reactor to form a polyamine product .