Polymer manufacturing method

Abstract

To provide a method for producing polyarylene sulfide that can stably produce polyarylene sulfide having a desired melt viscosity. [Solution] The present invention provides a method for producing a polymer, comprising a preparation step of preparing a mixture containing a solvent and a monomer, and a polymerization step of subjecting the mixture to a polymerization reaction, wherein in the preparation step, the monomer is supplied as a solution containing the monomer, and the concentration of the monomer-containing solution is estimated using a soft sensor.

Description

Technical Field

[0001] The present invention relates to a method for producing a polymer.

Background Art

[0002] Polymer compounds obtained by step-growth polymerization such as polyamides, polyaryl ether ketones, and polyarylene sulfides are widely used industrially. Although these polymer compounds are produced by various methods, they are generally polymerized in an organic solvent, and the monomers used for polymerization may be used in a solution state. Step-growth polymerization refers to a polymerization reaction in which monomers or polymers, particularly the functional groups possessed by monomers, react with each other to form a high-molecular-weight product. Therefore, it is known that the ratio of monomers is important in such a polymerization reaction.

[0003] For example, as a typical production method of polyarylene sulfide (hereinafter also referred to as "PAS") represented by polyphenylene sulfide (hereinafter also referred to as "PPS"), a method is known in which an alkali metal sulfide as a sulfur source is reacted with a dihaloaromatic compound in an organic polar solvent. The sulfur source may be added to the reaction system as an aqueous solution of a combination of an alkali metal hydrosulfide and an alkali metal hydroxide. Here, in the method for producing PAS, in order to obtain PAS of stable quality, it is necessary to strictly control the polymerization conditions such as the molar ratio of the sulfur source to the dihaloaromatic compound, the coexisting water content, the polymerization temperature, and the polymerization time. For example, if the molar ratio of the alkali metal sulfide to the dihaloaromatic compound falls outside the predetermined range, problems arise such that the decomposition reaction tends to proceed, or the polymerization rate is significantly slowed down. In order to solve these problems, various methods for producing PAS have been studied.

[0004] For example, Patent Document 1 discloses a method for producing PAS in which the amount of hydrogen sulfide lost due to volatilization outside the reaction system is calculated, and the molar ratio of the sulfur source and the dihalo-aromatic compound used is precisely controlled based on the calculated amount. Patent Document 2 also discloses a method for producing PAS that is highly pure and has a high molecular weight by suppressing side reactions. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2004 / 060974 [Patent Document 2] Republished Patent No. 2015 / 152032 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, in methods for producing PAS by adding a sulfur source as an aqueous solution to a reaction solution, as described in Patent Documents 1 and 2, if the concentration of the aqueous solution fluctuates, the predetermined amount of sulfur source may not be able to contribute to the reaction, causing the molar ratio of the sulfur source to the dihalo-aromatic compound to fluctuate, which may make it impossible to stably produce PAS with the desired melt viscosity. Furthermore, when purchasing a sulfur source in aqueous solution form from a supplier, while component analysis results are provided, these analysis results may be less accurate than those required during production, and concentration changes are more likely to occur if multiple lots with different sulfur source concentrations are mixed. Furthermore, phenomena resulting from such variations in monomer ratios are not limited to the production of PAS, but can occur in methods for producing sequential polymers using monomers in solution form.

[0007] The present invention has been made in view of these points, and aims to provide a method for producing polymers that can stably produce polymers having a desired melt viscosity. [Means for solving the problem]

[0008] The inventors have discovered that by calculating the concentration of monomers in an aqueous solution containing monomers in real time without chemical analysis of the aqueous solution, and by reflecting this value in the amount of material used during polymerization, it is possible to stably produce polymers with a desired melt viscosity, thus completing the present invention.

[0009] [1] A preparation step of preparing a mixture containing a solvent and a monomer, A method for producing a polymer, comprising a polymerization step of subjecting the mixture to a polymerization reaction, In the aforementioned preparation process, the monomer is supplied as a solution containing the monomer. A method for producing a polymer, comprising estimating the concentration of a solution containing the monomer using a soft sensor.

[0010] [2] The mixture contains at least two of the monomers, and in the preparation step, at least one of the monomers is supplied as a solution containing the monomer. [1] Method for producing a polymer

[0011] [3] The method for producing a polymer according to [2], further comprising determining the supply amount of at least one of the at least two monomers using the soft sensor.

[0012] [4] A method for producing a polymer according to any one of [1] to [3], wherein the solution containing the monomer comprises at least one of an aqueous alkali metal hydrosulfide solution and an aqueous alkali metal sulfide solution.

[0013] [5] The method for producing a polymer according to [4], wherein the explanatory variables of the soft sensor include at least one of the density and temperature of the alkali metal hydroxide aqueous solution and the density and temperature of the alkali metal hydroxide aqueous solution.

[0014] [6] The method for producing a polymer according to [5], wherein the explanatory variable further comprises at least one of the following: the number of days elapsed since use of a flow meter installed in a storage tank for an aqueous solution containing a sulfur source, the ambient temperature, and the flow rate of the aqueous solution containing a sulfur source. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a method for producing polymers that can stably produce polymers having a desired melt viscosity. [Modes for carrying out the invention]

[0016] The following describes specific embodiments of the present invention in detail. The present invention is not limited to the following embodiments, and can be modified as appropriate without altering the essence of the invention. In this specification, a numerical range represented by "~" means a range that includes the numbers written before and after "~" as the lower and upper limits, and "A~B" means A or greater and B or less.

[0017] [Method for producing polymers] A polymer manufacturing method according to one embodiment of the present invention is a polymer manufacturing method comprising a preparation step of preparing a mixture containing a solvent and a monomer, and a polymerization step of subjecting the mixture to a polymerization reaction. Furthermore, the polymer manufacturing method may also include a dehydration step, a cooling step, a post-treatment step, etc., similar to general manufacturing methods (see, for example, Japanese Patent Publication No. 61-7332, Japanese Patent Publication No. 2004-244619, Japanese Patent Publication No. 9-286861, etc.). The steps of the present invention will be described in detail below, using the manufacturing method of PAS as an example.

[0018] <Dehydration process> In a polymer production method according to one embodiment of the present invention, if the reaction system is such that the polymerization reaction is inhibited by water, it is preferable to include a dehydration step. The dehydration step is a step in which, before the charging step, at least a portion of the water-containing distillate is discharged from the system containing a mixture (described later) containing a solvent and a monomer. In PAS, the polymerization reaction between the sulfur source contained in the monomer-containing mixture and the dihalo-aromatic compound is affected by the amount of water present in the polymerization reaction system, such as being promoted or inhibited. Therefore, it is preferable to reduce the amount of water in the polymerization reaction system before the charging step so that the amount of water does not inhibit the polymerization reaction.

[0019] The dehydration step is preferably performed by heating under an inert gas atmosphere. The water to be dehydrated in the dehydration step refers to water contained in each raw material charged in the dehydration step, the aqueous medium of the aqueous mixture, water by-produced by the reaction between the respective raw materials, and the like.

[0020] The heating temperature in the dehydration step is not particularly limited, and is preferably 300°C or lower, more preferably from 100 to 250°C.

[0021] In the dehydration step, dehydration is carried out until the water content falls within a predetermined range. That is, in the dehydration step, it is desirable to perform dehydration until the water content in the charged mixture (described later) is 0.5 to 2.4 mol relative to 1.0 mol of the charged sulfur source. If the water content becomes too low in the dehydration step, water may be added in the charging step to adjust to the desired water content.

[0022] <Charging Step> The charging step is a step of preparing a mixture containing a solvent and monomers (hereinafter also referred to as "charged mixture"). The mixture preferably contains at least two types of monomers, and at least one of these monomers is supplied as a solution containing the aforementioned monomer. In the method for producing PAS, the charging step is a step of preparing a mixture containing a solvent, and a sulfur source and a dihaloaromatic compound as monomers, and a solution containing at least one of an alkali metal sulfide and an alkali metal hydrosulfide as the sulfur source is supplied. The dihaloaromatic compound may be supplied in the form of a solution, or may be heated to a temperature equal to or higher than its melting point and supplied in a liquid form. From the viewpoint of increasing the production amount per batch, it is preferable that the dihaloaromatic compound is heated to a temperature equal to or higher than its melting point and supplied in a liquid form. The amount contained in the charged mixture is referred to as "charged amount", and the amount of the sulfur source in the charged mixture is also referred to as "charged sulfur source".

[0023] Examples of the sulfur source include alkali metal sulfides and alkali metal hydrosulfides, and alkali metal hydrosulfides are preferred. Examples of alkali metal sulfides include lithium sulfide, sodium sulfide, potassium sulfide, rubidium sulfide, and cesium sulfide. Examples of alkali metal hydroxylated compounds include lithium hydroxylide, sodium hydroxylide, potassium hydroxylide, rubidium hydroxylide, and cesium hydroxylide. The sulfur source may be used alone or in combination of two or more types.

[0024] Furthermore, the sulfur source can be handled in either an aqueous slurry or an aqueous solution, for example, but from the viewpoint of handling characteristics such as metering and transportability, it is preferable that it be in the form of an aqueous solution.

[0025] Examples of dihalo-aromatic compounds include o-dihalobenzene, m-dihalobenzene, p-dihalobenzene, dihalotoluene, dihalonaphthalene, methoxy-dihalobenzene, dihalobiphenyl, dihalobenzoic acid, dihalodiphenyl ether, dihalodiphenyl sulfone, dihalodiphenyl sulfoxide, and dihalodiphenyl ketone. The two or more halogen atoms in the dihalo-aromatic compound may be the same or different. Note that halogen atoms refer to fluorine, chlorine, bromine, and iodine atoms. Among these, p-dihalobenzene is more preferred from the viewpoint of availability and reactivity, and p-dichlorobenzene is even more preferred. Dihalo-aromatic compounds may be used individually or in combination of two or more.

[0026] The amount of dihalo-aromatic compound added is preferably 0.90 to 1.50 moles, and more preferably 0.95 to 1.05 moles, per mole of sulfur source added. When the amount of dihalo-aromatic compound used is within the above range, decomposition reactions are less likely to occur, and stable polymerization reactions can be easily carried out, making it easier to produce high molecular weight polymers.

[0027] The solvent is not particularly limited, and any organic polar solvent commonly used in the production of PAS can be used, such as organic amide solvents.

[0028] Examples of organic amide solvents include amide compounds such as N,N-dimethylformamide and N,N-dimethylacetamide; aliphatic cyclic amide compounds such as N-methyl-ε-caprolactam, N-methyl-2-pyrrolidone, and N-cyclohexyl-2-pyrrolidone; N,N-dialkylimidazolidinone compounds such as 1,3-dialkyl-2-imidazolidinone; tetraalkylurea compounds such as tetramethylurea; and hexaalkylphosphate triamide compounds such as hexamethylphosphate triamide. Among these, aliphatic cyclic amide compounds are preferred from the viewpoint of availability and handling, and N-methyl-2-pyrrolidone is more preferred. Organic amide solvents may be used alone or in combination of two or more.

[0029] From the viewpoint of the efficiency of the polymerization reaction, the amount of organic polar solvent used is preferably 1 to 30 moles, and more preferably 3 to 15 moles, per mole of sulfur source used.

[0030] Furthermore, if a dehydration process is performed before the mashing process, alkali metal hydroxides and water can be added to the mixture remaining in the system after the dehydration process during the mashing process, as needed.

[0031] Furthermore, the number of moles of alkali metal hydroxide is calculated based on the number of moles of alkali metal hydroxide added as needed during the initial preparation process, the number of moles of alkali metal hydroxide added as needed during the dehydration process, and the number of moles of alkali metal hydroxide generated in conjunction with the production of hydrogen sulfide during the dehydration process. If the sulfur source contains alkali metal sulfides, the number of moles of alkali metal hydroxide per mole of sulfur source shall be calculated including the number of moles of alkali metal sulfides. If hydrogen sulfide is used as the sulfur source, the number of moles of alkali metal hydroxide per mole of sulfur source shall be calculated including the number of moles of alkali metal sulfides produced. However, the number of moles of alkali metal hydroxide added for other purposes, for example, when an organic carboxylic acid metal salt is used as a phase separating agent in combination with an organic carboxylic acid and an alkali metal hydroxide, shall not be included in the number of moles of alkali metal hydroxide per mole of sulfur source. Furthermore, if, for any reason, at least one acid selected from the group consisting of inorganic acids and organic acids is used, the number of moles of alkali metal hydroxide required to neutralize the above at least one acid shall not be included in the number of moles of alkali metal hydroxide per mole of sulfur source.

[0032] (Estimation of monomer-containing solution concentration using a soft sensor) The amount of monomer-containing solution supplied during the preparation process is determined by estimating the concentration of at least one of at least two monomers in the solution using a soft sensor. Therefore, it is not used to estimate the monomer concentration in the gas phase or other monomers contained outside the solution. The soft sensor is not particularly limited, but for example, analysis software such as SAS Release 9.4 (SAS Institute Inc., Cary, NC, USA) can be used.

[0033] A soft sensor is a method that mathematically calculates the relationship between target state variables based on the values ​​of variables that are relatively easy to measure (hereinafter also referred to as "explanatory variables"). Soft sensors are useful as a means of predicting the status of state variables from explanatory variables when it is difficult to directly measure state variables in the work process.

[0034] Linear multiple regression equations are used for soft sensors, and the coefficient values ​​that make up the model equation are usually obtained using statistical analysis such as multiple regression analysis using the least squares method or PLS regression. Multiple regression analysis is preferred when determining continuous variables.

[0035] The explanatory variables may include at least one of the following: the density and temperature of the alkali metal hydroxide aqueous solution as a sulfur source contained in the monomer-containing solution, and the density and temperature of the alkali metal hydroxide aqueous solution.

[0036] Furthermore, in addition to the density and temperature values ​​of the aqueous solution mentioned above, at least one of the following may also be used as explanatory variables: the number of days since the use of the flow meter installed in the storage tank for the aqueous solution containing the sulfur source (hereinafter also referred to as "number of days since use"), the ambient temperature (referring to the average temperature for 24 hours prior to fermentation), and the flow rate of the aqueous solution containing the sulfur source. Here, "flow rate of the aqueous solution containing the sulfur source" refers to at least one of the flow rate when the aqueous solution containing the sulfur source is circulated within the storage tank, and the flow rate when it is transferred from the storage tank to the tank where the fermentation process is carried out.

[0037] The concentration of the aqueous solution of the sulfur source using the above explanatory variables can be expressed, for example, by the following equation (I). Concentration of an aqueous solution [%] = aA + bB + cC + dD + eE ... (I)

[0038] In formula (I), A is the density (kg / m³) of an alkali metal sulfide aqueous solution and / or alkali metal sulfide aqueous solution. 3 Equation (I) shows the following: B is the temperature (°C) of the alkali metal water sulfide aqueous solution and / or alkali metal sulfide aqueous solution, C is the number of days (days) since the flow meter installed in the storage tank of the sulfur source aqueous solution was put into use, D is the ambient temperature (average temperature (°C) for the 24 hours before brewing), E is the flow rate (t / h) of the sulfur source aqueous solution, and a to e are coefficients. Note that A to E in equation (I) are values ​​obtained by measurement.

[0039] Here, a represents a coefficient calculated from a multiple regression analysis in which the density of the alkali metal water sulfide aqueous solution and / or alkali metal sulfide aqueous solution is set as the explanatory variable; b represents a coefficient calculated from a multiple regression analysis in which the temperature of the alkali metal water sulfide aqueous solution and / or alkali metal sulfide aqueous solution is set as the explanatory variable; c represents a coefficient calculated from a multiple regression analysis in which the number of days elapsed since use is set as the explanatory variable; d represents a coefficient calculated from a multiple regression analysis in which the ambient temperature is set as the explanatory variable; and e represents a coefficient calculated from a multiple regression analysis in which the flow rate of the aqueous solution containing a sulfur source is set as the explanatory variable. Note that the coefficients a to e are values ​​that change depending on the combination of explanatory variables.

[0040] The number of data points required for multiple regression analysis is determined appropriately depending on the combination of explanatory and dependent variables used, the required estimation accuracy, etc. When applying these multiple regression analyses to the PAS manufacturing method, the dependent variable is the concentration of the aqueous solution of the sulfur source. Furthermore, if temperature or density is measured using multiple measuring instruments, the results obtained from any one of the instruments may be used, or the arithmetic mean obtained from multiple measurement results may be used.

[0041] In one embodiment of the present invention, formula (I) preferably includes at least A and B as explanatory variables, more preferably includes at least one of C, D, and E in addition to A and B, even more preferably includes A, B, C, and / or D, and particularly preferably includes A, B, C, and D.

[0042] Because aqueous solutions containing sulfur sources are basic, they tend to degrade measuring instruments such as flow meters. Therefore, by further including C as an explanatory variable in equation (I), the degradation state of the flow meter can be taken into account, and the accuracy of estimating the sulfur source concentration can be further improved.

[0043] Furthermore, since storage tanks for aqueous solutions are generally installed outdoors, the temperature of the aqueous solution is easily affected by the ambient temperature. On the other hand, because the temperature of the aqueous solution does not quickly follow changes in ambient temperature, the difference between the temperature of the aqueous solution in the storage tank and the ambient temperature can be large depending on the timing of the measurement. Therefore, by including D (average temperature for 24 hours before preparation) as an explanatory variable in equation (I), the accuracy of estimating the concentration of the sulfur source can be further improved. In addition, industrial flow meters that can simultaneously measure temperature and density are often used, such as Coriolis flow meters. Coriolis flowmeters utilize the vibration frequency of the tubes that make up the flowmeter, and this vibration frequency can be affected by temperature. When using such a flowmeter, changes in ambient temperature may affect the measurement results such as flow rate and temperature measured by the Coriolis flowmeter. Therefore, by further including D as an explanatory variable, the accuracy of estimating the aqueous solution concentration can be improved compared to when only A and B are included as explanatory variables. Furthermore, by including D as an explanatory variable, it is possible to confirm the required supply amount of the monomer-containing solution over a wide temperature range from cold regions to warm regions (for example, -7°C to 37°C), thereby enabling a stable supply of the solution.

[0044] Aqueous solutions containing sulfur sources are sometimes circulated within a tank or transferred between tanks using a pump that discharges a fixed volume. In this case, since the mass per unit volume changes when the purity or density of the aqueous solution changes, accuracy can be improved by using E as an explanatory variable. Furthermore, while the temperature and density used as explanatory variables may be taken from flow meter values, in this case, the flow rate value can also be used as an indicator of flow meter degradation, so it is considered that E can be used as an explanatory variable.

[0045] In one embodiment of the present invention, as described above, the soft sensor predicts from explanatory variables to estimate the concentration of monomers in the monomer-containing solution during the preparation process. Therefore, the state quantities of monomers (specifically, at least one of the alkali metal hydroxide aqueous solution and alkali metal sulfide aqueous solution, which are sulfur sources) during the preparation process and polymerization reaction can be predicted, and the supply amount of monomers (sulfur source and / or dihalo-aromatic compound) can be adjusted as appropriate according to the state quantities. At this time, the difference between the estimated concentration of the sulfur source obtained from the soft sensor and the actual concentration is preferably ±0.35% or less, and more preferably ±0.20% or less. This makes it possible to reduce the range of variation in the melt viscosity of the obtained PAS, specifically PPS (for example, by about ±5%), and thus enable the stable production of PPS having the desired melt viscosity.

[0046] The melt viscosity of PPS can be measured, for example, using a Capillograph 1-C manufactured by Toyo Seiki Co., Ltd.

[0047] [Adjusting monomer supply] In the PAS manufacturing method, the supply amounts of dihalo-aromatic compounds, alkali metal hydroxides, and solvents may be determined based on the sulfur source. Therefore, the monomer whose supply amount is determined after estimating the concentration of the monomer-containing solution using the soft sensor described above may be the monomer-containing solution, or the monomer itself in solid or molten liquid form. Specifically, the monomer whose supply amount is determined after estimating the concentration of the aqueous solution containing the sulfur source may be the sulfur source, a dihalo-aromatic compound, or a combination thereof. In addition, the supply amounts of additives other than monomers and / or solvents may be determined. Examples include alkali metal hydroxides and organic amide solvents.

[0048] <Polymerization process> In one embodiment of the present invention, the polymerization step is a step of heating a mixture containing a solvent and a monomer to initiate a polymerization reaction and produce a polymer. The polymerization step may include a pre-polymerization step, a phase separation agent addition step, and a post-polymerization step.

[0049] (Pre-polymerization step, phase separation agent addition step, and post-polymerization step) The pre-polymerization step involves supplying the preparation mixture prepared in the initial preparation step, then heating it to initiate the polymerization reaction and produce a prepolymer. The phase separation agent addition step is the step of adding a phase separation agent. The phase separation agent addition step may be performed in the preparation step before the polymerization reaction, or it may be performed after the preceding polymerization step. The subsequent polymerization step is a step to continue the polymerization reaction when a phase separation agent addition step is performed after the preceding polymerization step. The mixture heated in the preceding and subsequent polymerization steps, the mixture to which the phase separation agent is added in the phase separation agent addition step, and the mixture separated in the phase separation agent addition step are collectively referred to as the "reaction mixture."

[0050] To obtain high molecular weight PAS, the polymerization reaction is preferably carried out in two or more stages. Specifically, a preliminary polymerization step and a subsequent polymerization step in which the polymerization reaction is continued in the presence of a phase separating agent are performed. The phase separating agent is added to the reaction mixture in a phase separating agent addition step that is provided between the preliminary polymerization step and the subsequent polymerization step.

[0051] In the pre-polymerization and post-polymerization processes, it is preferable to carry out the polymerization reaction under heating at 170-300°C from the viewpoint of polymerization reaction efficiency, and more preferably at 180-290°C from the viewpoint of suppressing side reactions and decomposition reactions. Furthermore, the polymerization temperature in the pre-polymerization process is preferably 180-265°C from the viewpoint of suppressing side reactions and decomposition reactions. The polymerization temperature may be raised or lowered in stages or continuously as needed, or it may be maintained at a constant temperature.

[0052] In the subsequent polymerization step, the reaction system containing the prepolymer produced in the preceding polymerization step and a phase-separating agent is heated to continue the polymerization reaction in a phase-separated state. The polymerization temperature in the subsequent polymerization step is generally preferably higher than that of the preceding polymerization step. The polymerization temperature in the subsequent polymerization step is preferably 240 to 290°C, and more preferably 255 to 275°C. By using these temperature conditions, the decomposition of the produced PAS and organic amide solvent is suppressed, and high molecular weight PAS can be obtained.

[0053] The presence of a phase-separating agent causes the polymerization reaction system (reaction mixture) to separate into a polymer-concentrated phase (a phase with a high polymer concentration in the organic amide solvent) and a polymer-dilute phase (a phase with a low polymer concentration in the organic amide solvent). Phase separation may also be induced during the subsequent polymerization process by adjusting the timing of the addition of the phase-separating agent or the polymerization temperature.

[0054] Water is preferred as the phase separation agent because it readily forms a good phase separation state. Other phase separation agents may be used in the phase separation agent addition step. When using a phase separation agent other than water, it may be used alone, but it is preferable to use it together with water.

[0055] As the phase separation agent, those commonly used in the production of PAS can be used, and include at least one selected from the group consisting of water, metal organic carboxylic acid salts (for example, alkali metal salts of aliphatic carboxylic acids such as sodium acetate, or alkaline earth metal salts of aromatic carboxylic acids), metal organic sulfonic acid salts, alkali metal halides, alkaline earth metal halides, alkali metal phosphates, alcohols, and nonpolar solvents. Furthermore, if the phase separation step is performed after the preceding polymerization step, it is preferable to include water in the phase separation agent, as this facilitates the formation of a good phase separation state.

[0056] The amount of phase separation agent used varies depending on the type of phase separation agent used, but it is preferably 0.01 to 20 moles per 1 kg of organic polar solvent. Furthermore, when water is used as the phase separation agent, the amount of water used is preferably 2 to 10 moles per mole of sulfur source, and more preferably 2.2 to 5 moles.

[0057] The polymerization reactions in the pre- and post-polymerization steps may be carried out in batches or continuously. For example, the polymerization reaction can be carried out continuously by simultaneously supplying an organic polar solvent, a sulfur source, and a dihalo-aromatic compound, generating PAS by the reaction of the sulfur source and the dihalo-aromatic compound in the organic polar solvent, and recovering the reaction mixture containing PAS.

[0058] (cooling process) The cooling step is a step in which the reaction mixture described above is cooled after the polymerization step. The specific operations in the cooling step are as described in, for example, Japanese Patent Publication No. 6062924.

[0059] (Post-processing and recovery processes) The PAS produced by the method described above is usually recovered through a post-treatment and recovery process. The post-treatment and recovery processes can be carried out by conventional methods. For example, by cooling the reaction mixture after the subsequent polymerization process, a slurry containing granular polymer products can be obtained. The cooled product slurry can be filtered, either directly or diluted with water, and then washed and filtered repeatedly before drying to recover the PAS.

[0060] By generating granular PAS using the method described above, the granular PAS can be separated from the reaction solution, for example, by sieving using a screen. This allows for easy separation of PAS from by-products and oligomers. The granular PAS may also be sieved while the product slurry is still at a high temperature. Specifically, the granular PAS separated by a 100-mesh screen (mesh opening diameter 150 μm) (sometimes referred to as "100-mesh on") can be recovered as a product.

[0061] A method for producing a polymer according to one embodiment of the present invention may include the steps of: measuring the temperature and density of a solution containing a monomer; estimating the monomer concentration in the monomer-containing solution; and determining the amount of at least one monomer to be used in the production of the polymer from the estimated monomer concentration. The production of PAS may include the steps of: measuring the temperature and density of an aqueous alkali metal hydrosulfide solution and / or an aqueous alkali metal sulfide solution as a sulfur source; estimating the sulfur source concentration of the aqueous solution containing the sulfur source; and determining the supply amount of at least one of monomers, additives other than monomers, and organic polar solvents from the estimated sulfur source concentration. The supply amount determined from the estimated sulfur source concentration is preferably a monomer, and more preferably a dihalo-aromatic compound. Determining the supply amount of monomer makes it easy to adjust the production amount per batch while producing PAS that satisfies the desired melt viscosity. Furthermore, in the step of measuring the temperature and density of the monomer-containing solution, it is preferable to further measure at least one of the following: the number of days elapsed since use, the ambient temperature, and the flow rate of the monomer-containing solution, and it is even more preferable to measure the ambient temperature.

[0062] The polymer production method according to one embodiment of the present invention is not limited to the production of PAS, but can be broadly used in the production of sequential polymers using solution monomers. In the case of producing PAS, it is preferable that the production is of PPS.

[0063] Furthermore, the polymer manufacturing method in one embodiment of the present invention is particularly useful in industrial production because it can stably produce polymers (e.g., PAS) having a desired melt viscosity, especially in large-scale production facilities and factories. [Examples]

[0064] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0065] [Verification of model learning] (1) Model learning The following data was input into a soft sensor to estimate the concentration of a monomer-containing solution, and a model was trained (multiple regression analysis). It was confirmed that all of the explanatory variables listed below had a strong correlation with the concentration of the NaSH aqueous solution. • Target variable: Concentration (mass%) of sodium hydrogen sulfide (NaSH) aqueous solution • Explanatory variable: Density of NaSH aqueous solution obtained from Coriolis flow meter (kg / m³) 3 ) Temperature of NaSH aqueous solution obtained from a Coriolis flow meter (°C) Flow rate (t / h) of NaSH aqueous solution obtained from a Coriolis flow meter. Number of days since the Coriolis flow meter was put into use. Outside temperature (average temperature for the 24 hours prior to preparation) (°C) • Study period: Term 1 (7 months), Term 2 (10 months), Term 3 (11 months) • Analysis software: SAS Release 9.4 (SAS Institute Inc., Cary, NC, USA)

[0066] (2) Model Verification [Model 1] Model learning (multiple regression analysis) was used to apply data for the fourth period (5 months) and validate Model 1. The model equation is given by equation (1) below, and the residual variance was calculated from equation (2) below. Note that the adjustment R in Table 1 2 The variable is a measure used to evaluate the prediction accuracy of model equation (1) below, taking into account the explanatory variables included in model equation (1). A value closer to 1 indicates higher model performance. The residual variance is a measure used to evaluate the magnitude of the error in model equation (1) below. A value closer to 0 indicates higher model performance. The verification results in Table 1 are values ​​calculated from the observed and predicted values ​​using regression analysis. <Model formula> Concentration of NaSH solution [mass %] = [K1 × density of NaSH solution (average)] + [K2 × temperature of NaSH solution (average)] + [K3 × number of days elapsed since use] - Y1···(1) In the above model equation (1), K1, K2, and K3 represent coefficients calculated from a multiple regression analysis using the concentration (mass%) of the NaSH aqueous solution as the dependent variable and the explanatory variables listed in Table 1, while Y1 is the value corresponding to the intercept of the multiple regression analysis. Note that the density and temperature of the NaSH aqueous solution in Table 1 are the arithmetic mean of values ​​obtained from multiple devices, and the number of days elapsed indicates the number of days elapsed since the Coriolis flow meter was put into use. <Residual variance> Residual variance = Residual sum of squares / (Np-1) (2) N: Number of data points, p: Number of explanatory variables Sum of squared residuals: (Actual value - Predicted value) 2 Total

[0067] [Table 1]

[0068] The model's performance was evaluated by randomly selecting 50 data points from all data from periods 1 to 3, calculating predicted values ​​from the model equation, and then calculating the residual variance from the difference between the predicted and actual values. This process was repeated 10,000 times, and the mean residual variance and 95% confidence interval were calculated. The results of the performance evaluation for Model 1, shown in Table 1, revealed that the mean residual variance was 0.023, and the 95% confidence interval was 0.016 to 0.029. Therefore, it can be inferred that even if the same process is repeated multiple times, the residual variance will fall within the range of 0.016 to 0.029 with 95% probability, confirming the high reliability of the model.

[0069] [Models 2-4] Models 2-4 were evaluated using multiple regression analysis in the same manner as Model 1. The model equations are shown in (3)-(5) below, and the residual variance was calculated from equation (2) above. In model equation (3), K4, and in model equations (3) and (4), K5 represent coefficients calculated from multiple regression analysis using the concentration (%) of the NaSH aqueous solution as the dependent variable and the explanatory variables listed in Table 2. In model equations (2)-(4), Y2-Y4 represent values ​​corresponding to the intercept of the multiple regression analysis. The verification results in Table 2 are values ​​calculated from measured and predicted values ​​through regression analysis. <Model formula> (Model 2) Concentration of NaSH solution [mass %] = [K1 × density of NaSH solution (average)] + [K2 × temperature of NaSH solution (average)] - Y2...(3) (Model 3) Concentration of NaSH solution [mass %] = [K1 × Density of NaSH solution (average)] + [K2 × Temperature of NaSH solution (average)] + [K4 × Flow rate of NaSH solution (t / h)] + [K5 × Ambient temperature (°C)] - Y3...(4) (Model 4) Concentration of NaSH solution [mass %] = [K1 × density of NaSH solution (average)] + [K2 × temperature of NaSH solution (average)] + [K5 × ambient temperature (°C)] - Y4···(5)

[0070] [Table 2]

[0071] [Production of polyarylene sulfide] (Method for measuring melt viscosity) The melt viscosity of 20g of dry polymer was measured using a Capillograph 1-C (manufactured by Toyo Seiki Co., Ltd.). Measurement conditions • Capillary: Flat die, 1mm diameter x 10mm length ·Set temperature: 310℃ • Measurement method: The polymer sample is introduced into the instrument and held for 5 minutes, then the shear rate is 1216 sec. -1Measured in Pa·s

[0072] (Iodine oxidation titration method) The concentration of NaSH in an aqueous sodium hydrosulfide (NaSH) solution, which is the sulfur source, was measured using an automatic titrator COM-A19S (manufactured by HIRANUMA Corporation).

[0073] [Reference example] (Analysis of sodium hydrosulfide aqueous solution concentration) A NaSH aqueous solution used in the production of PPS was sampled, and its concentration was measured by iodine oxidation titration, revealing a concentration of 48.82% by mass.

[0074] (Dehydration process) An aqueous NaSH solution was used as the sulfur source. This NaSH solution, along with a 49.22% by mass aqueous sodium hydroxide (NaOH) solution and N-methylpyrrolidone (NMP), were added to the reaction vessel. After purging the inside of the reaction vessel with an inert gas, the temperature was gradually raised to 194°C over approximately 4 hours to distill off the water. In this operation, the compositions of water, NMP, and NaOH in the vessel after distillation were H2O / NaSH = 1.50 mol / mol, NMP / NaSH = 379 g / mol, and NaOH / NaSH = 1.062 mol / mol, relative to the NaSH present in the vessel.

[0075] (Preparation process) p-dichlorobenzene (p-DCB) was added to the can after the dehydration process, with a ratio of p-DCB / NaSH = 1.074 mol / mol based on the NaSH present in the can. Hereafter, these will also be referred to as the "compound mixture".

[0076] (Polymerization process) Polymerization was carried out by stirring the initial mixture and gradually increasing the temperature to 260°C over 2.5 hours. Then, water was added, using the NaSH present in the container after the dehydration step as a reference, to achieve a H2O / NaSH ratio of 2.57 mol / mol. The temperature was then increased to 265°C, and polymerization was continued for another 2 hours. After the polymerization reaction was complete, the reaction mixture was cooled to room temperature and then passed through a 100-mesh (150 μm opening) screen for solid-liquid separation. The polymer on the screen was washed with acetone, water, and an aqueous acetic acid solution, and then the polymer was dried. The melt viscosity of the dried polymer was measured to be 25 Pa·s.

[0077] [Example 1] The concentration of the NaSH aqueous solution used in the preparation in the reference example was calculated using a soft sensor on the same day as the implementation of the reference example, with the density of the NaSH aqueous solution obtained from the Coriolis flow meter used in the preparation and the temperature of the NaSH aqueous solution as explanatory variables. The concentration was 48.65 mass%, and the concentration error was calculated using the following formula (II) to be 0.17 mass%. Next, seven days after the implementation date of the reference example, the concentration of the NaSH aqueous solution was calculated using a soft sensor and was found to be 48.27% by mass. The amount of NaSH aqueous solution added was adjusted so that, in weight ratio, it was 48.82 / 48.27 times the amount added in the reference example, so that the number of moles of NaSH added during polymerization was the same as in the reference example. Polymerization was carried out in the same manner as in the reference example, except for the above changes. The melt viscosity of the polymer produced by this polymerization reaction was 25 Pa·s. Concentration error [mass%] = Concentration of NaSH aqueous solution determined by iodine oxidation titration [mass%] - Concentration of NaSH aqueous solution estimated by soft sensor [mass%] ... (II)

[0078] [Example 2] Polymerization was carried out in the same manner as in Example 1, except that the density of the NaSH aqueous solution obtained from the Coriolis flow meter used in the preparation, the temperature of the NaSH aqueous solution, and the number of days elapsed since the Coriolis flow meter was used were used as explanatory variables for the soft sensor used, and the density of the NaSH aqueous solution was calculated. The concentration error of the NaSH aqueous solution concentration calculated on the same day as the implementation of the reference example was 0.26 mass%, and the melt viscosity of the polymer produced by the polymerization reaction 7 days after the implementation of the reference example was 25 Pa·s.

[0079] [Example 3] Polymerization was carried out in the same manner as in Example 1, except that the explanatory variables of the soft sensor used were changed to the density of the NaSH aqueous solution, the temperature of the NaSH aqueous solution, the flow rate of the NaSH aqueous solution, and the ambient temperature, all obtained from a Coriolis flow meter used in the preparation. The concentration error of the NaSH aqueous solution concentration calculated on the same day as the implementation of the reference example was 0.01 mass%, and the melt viscosity of the polymer produced by the polymerization reaction 7 days after the implementation of the reference example was 25 Pa·s. The ambient temperature refers to the average temperature for the 24 hours prior to the preparation.

[0080] [Example 4] Polymerization was carried out in the same manner as in Example 1, except that the explanatory variables of the soft sensor used were changed to the density of the NaSH aqueous solution obtained from the Coriolis flow meter used in the preparation, the temperature of the NaSH aqueous solution, and the ambient temperature. The concentration error of the NaSH aqueous solution concentration calculated on the same day as the implementation of the reference example was 0.14 mass%, and the melt viscosity of the polymer produced by the polymerization reaction 7 days after the implementation of the reference example was 25 Pa·s.

[0081] [Comparative Example 1] Seven days after the implementation of the reference example, polymerization was carried out using the same preparation and mixing ratio as in the reference example. The melt viscosity of the polymer produced by this polymerization reaction was 27 Pa·s. Immediately after this polymerization reaction, an aqueous NaSH solution was sampled and its concentration was measured by iodine oxidation titration, and it was found to be 48.45% by mass.

[0082] The reason why the melt viscosity of the polymer in the comparative example differs from that of the reference example is thought to be because the purity of the NaSH aqueous solution fluctuated during the 7 days that elapsed.

[0083] Table 3 shows the reference examples and concentration estimation results for Examples 1-4 on the same day, and Table 4 shows the results for Examples 1-4 and Comparative Example 1. Note that the "density, temperature, and flow rate" listed in the explanatory variables column in Tables 3 and 4 refer to the density (kg / m³) of the NaSH aqueous solution. 3 ), temperature (°C), and flow rate (t / h) are indicated. "Elapsed days" refers to the number of days the Coriolis flow meter has been in use, and "Outside temperature" refers to the average temperature (°C) for the 24 hours prior to brewing.

[0084] [Table 3]

[0085] [Table 4]

[0086] Based on the results of Examples 1-4 and Comparative Example 1, it was confirmed that the concentration (state quantity) of the monomer-containing solution (an aqueous solution containing at least one of alkali metal sulfide and alkali metal hydrosulfide as a sulfur source) during the preparation process and polymerization reaction can be predicted, and that the range of variation in melt viscosity can be reduced by appropriately adjusting the amount of monomer supplied in accordance with the state quantity. [Industrial applicability]

[0087] The present invention provides a method for producing polyarylene sulfide that enables stable production of polyarylene sulfide by determining the amount of sulfur source supplied in a monomer-containing mixture using a soft sensor.

Claims

1. A preparation step for preparing a mixture containing a solvent and a monomer, A method for producing a polymer, comprising a polymerization step of subjecting the mixture to a polymerization reaction, In the aforementioned preparation process, the monomer is supplied as a solution containing the monomer. The concentration of the solution containing the monomer is estimated using a soft sensor. A method for producing polymers.

2. The mixture contains at least two monomers, In the preparation step, at least one of the two monomers is supplied as a solution containing the monomer. A method for producing a polymer according to claim 1.

3. Furthermore, the method for producing a polymer according to claim 2, wherein the supply amount of at least one of the at least two monomers is determined using the soft sensor.

4. The method for producing a polymer according to claim 1 or 2, wherein the solution containing the monomer comprises at least one of an aqueous alkali metal hydrosulfide solution and an aqueous alkali metal sulfide solution.

5. The method for producing a polymer according to claim 4, wherein the explanatory variable of the soft sensor includes at least one of the density and temperature of the alkali metal sulfide aqueous solution, and the density and temperature of the alkali metal sulfide aqueous solution.

6. The method for producing a polymer according to claim 5, wherein the explanatory variable further includes at least one of the following: the number of days elapsed since use of a flow meter installed in a storage tank for an aqueous solution containing a sulfur source, the ambient temperature, and the flow rate of the aqueous solution containing a sulfur source.

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