JP2004204027A - Continuous production process of polyamide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a continuous production process of a polyamide by which the polyamide with a minimal contamination is efficiently produced while hardly causing gelation. <P>SOLUTION: This continuous production process of the polyamide comprises (1) a process 11 to melt a dicarboxylic acid, (2) an initial polymerization process by which a polyamide prepolymer with a relative viscosity of 1.4-2.7 is obtained by conducting polycondensation reaction by adding a molten diamine 12 at a specific molar ratio of the diamine to the dicarboxylic acid and by increasing the degree of polymerization while removing water at a temperature not lower than the melting point of the ultimately obtained polyamide in a water-removable batch type reaction apparatus 11, (3) a final polymerization process by which the polyamide with a desired relative viscosity [RV] is obtained by introducing the polyamide prepolymer into a water-removable, self-cleaning and continuous type vertical biaxial reaction apparatus 41 and by increasing the degree of polymerization at a temperature not lower than the melting point of the ultimately obtained polyamide. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００７７】
実施例及び比較例で得られたポリアミド及びポリアミドプレポリマーの特性を表１に示す。いずれの実施例１〜２においても、操作は良好であり、コンタミネーションが非常に抑制され、ゲル化発生までの熱処理時間も長い優れたポリアミドが得られた。
【００７８】
比較例１のポリアミド樹脂中には、実施例１のポリアミド樹脂に比べ、より多くのコンタミネーションが見られ、また、ゲル化発生までの熱処理時間も短かった。
【００７９】
【発明の効果】
本発明によれば、生産効率に優れ、ゲル化が起こりにくく且つコンタミネーション（黒色異物）の少ないポリアミドが得られるポリアミドの連続製造方法、とりわけ芳香族含有ポリアミドの連続製造方法が提供される。本発明の方法では、食品、飲料品、医薬品、化粧品などの用途における、フィルム、シート、包装袋、ボトル等に好適な、強度に優れ、色調が良好であり且つ吸水率の小さい芳香族含有ポリアミドが連続的に製造される。
【図面の簡単な説明】
【図１】本発明のポリアミドの連続製造方法の概略工程を示すフロー図である。
【符号の説明】
(11)：ジカルボン酸溶融槽及び初期重合用回分式重合槽
(12)：ジアミン添加装置
(41)：後期重合用セルフクリーニング方式の横型二軸反応装置
(15)：溶融保持槽
(19)：三方バルブ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a continuous method for producing polyamide with good quality and improved production efficiency. More specifically, the present invention relates to a method in which a diamine in a molten state is continuously or intermittently added to a dicarboxylic acid in a molten state, or a dicarboxylic acid in a molten state is continuously or intermittently added to a diamine in a molten state. And a method for continuously producing a polyamide by direct polymerization reaction. The continuous polyamide production method of the present invention can be applied to both aliphatic polyamides and aromatic-containing polyamides, but can be preferably applied to aromatic-containing polyamides whose production conditions are more difficult.
[0002]
A polyamide having an aromatic ring is excellent in mechanical strength and dimensional stability, and can be preferably used for films, sheets, packaging bags, bottles, engineering plastics, fibers and the like.
[0003]
[Prior art]
Polyamide resins are widely used in applications such as films, sheets, packaging bags, engineering plastics, and fibers because of their excellent physical and mechanical properties.
[0004]
Conventionally, aliphatic polyamides such as nylon 6 and nylon 66 have been mainly used for these applications. However, aliphatic polyamides generally have the disadvantage that the dimensional change between water absorption / moisture absorption and drying is large, and the elastic modulus is too small and soft because of aliphaticity. ing. Against this background, high performance polyamide resins have been achieved by copolymerizing aromatic dicarboxylic acids such as TPA (terephthalic acid) and IPA (isophthalic acid) with conventional aliphatic polyamides. For example, JP-A-59-155426 and JP-A-62-156130 disclose a polyamide resin obtained by copolymerizing TPA or IPA.
[0005]
However, generally, the introduction of an aromatic ring into the polyamide skeleton increases the melting point and the melt viscosity, and the temperature conditions during polyamide production become more severe. And thermal degradation are further promoted. As a result, a gelled substance accumulates in the polymerization reactor to increase the frequency of cleaning, or the gelled substance is mixed into the resin, and physical properties are reduced due to thermal deterioration, so that a high-quality polyamide resin cannot be obtained.
[0006]
The main cause is that the polyamide resin stays for a long time under high temperature conditions, and various production methods have been proposed to avoid this. For example, according to the production methods disclosed in JP-A-60-206828, JP-A-2-187427, and JP-A-8-170895, once, for the purpose of avoiding long-term stagnation at high temperatures, The initial condensate is taken out as a prepolymer, which is subjected to solid-state polymerization at a temperature lower than the melting point of the polymer to suppress thermal decomposition and deterioration. However, these are all batch-type production methods, which are not preferable in terms of production efficiency, and are likely to cause a difference in quality between batches.
[0007]
Japanese Patent Application Laid-Open No. 2001-200502 discloses a process in which a slurry comprising a diamine containing xylylenediamine and a dicarboxylic acid is continuously supplied to a twin-screw extruder without a vent and heated to advance an amidation reaction. And a step of increasing the degree of polymerization of the polyamide while separating and removing condensed water generated by the amidation reaction in a vented single-screw extruder. However, according to the examples, the molecular weight of the obtained polyamide is as small as about 3000 to 5000.
[0008]
JP-T-2002-516366 discloses a continuous production method of nylon 66. According to the publication, an equimolar amount of a melted dicarboxylic acid and a melted diamine are mixed to form a melted reaction mixture, and the reaction mixture is passed through a reactor (static in-line mixer) that does not ventilate the polyamide and condensed water. To form a first product stream comprising: supplying a first product stream to a vented tank reactor to remove condensed water to form a second product stream comprising polyamide. . However, the polyamide obtained by the production method of the same publication has a relatively low molecular weight, and when a reaction vessel conventionally used in the production of polyamide is used as an aerated reactor, the corresponding range of the viscosity that can be produced is used. Is narrow.
[0009]
Furthermore, JP-A-2002-212284, JP-A-2002-220462, JP-A-2002-220463, JP-A-2002-220465, JP-A-2002-220465, and JP-A-2002-220466. Discloses a method for continuously producing a polyamide containing xylylenediamine using a horizontal twin-screw mixer. A horizontal twin-screw mixer is advantageous as a reactor because it has excellent surface renewability. However, the twin-screw agitating mixer used in the examples of the above publication has an L / D of 25, and is a special specification that is extremely long compared to a normal horizontal reactor, so that it is an advanced method for manufacturing the apparatus. It has the disadvantage of requiring technology and being expensive. This is disadvantageous in view of actual industrial use.
[0010]
[Patent Document 1]
JP-A-59-155426 [Patent Document 2]
JP-A-62-156130 [Patent Document 3]
JP-A-60-206828 [Patent Document 4]
JP-A-2-187427 [Patent Document 5]
JP-A-8-170895 [Patent Document 6]
Japanese Patent Application Laid-Open No. 2001-200052 [Patent Document 7]
JP-T-2002-516366 [Patent Document 8]
JP 2002-212284 A [Patent Document 9]
Japanese Patent Application Laid-Open No. 2002-220462 [Patent Document 10]
JP 2002-220463 A [Patent Document 11]
Japanese Patent Application Laid-Open No. 2002-220564 [Patent Document 12]
JP 2002-220465 A [Patent Document 13]
JP, 2002-220466, A
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide a continuous method for producing a polyamide, which is excellent in production efficiency, is less likely to cause gelation and has less contamination (black foreign matter), and particularly a continuous method for producing an aromatic-containing polyamide. . In particular, the object of the present invention is to provide a film, sheet, packaging bag, bottle, etc., in applications such as foods, beverages, pharmaceuticals, cosmetics, etc., which has excellent strength, good color tone, and low water absorption. It is to provide a continuous manufacturing method.
[0012]
[Means for Solving the Problems]
The present invention is a continuous method for producing a polyamide mainly comprising a diamine component unit and a dicarboxylic acid component unit,
(1) a dicarboxylic acid melting step of melting a dicarboxylic acid,
(2) Using a batch reactor capable of separating and removing water,
To the dicarboxylic acid in the molten state, the diamine in the molten state is added continuously or intermittently, or to the diamine in the molten state, the dicarboxylic acid in the molten state is added continuously or intermittently,
A polycondensation reaction is carried out with the molar ratio of diamine and dicarboxylic acid being a predetermined value, and the degree of polymerization is increased while separating and removing water at a temperature not lower than the melting point of the finally obtained polyamide, and the relative viscosity is 1.4 to 2.7. An initial polymerization step of obtaining a polyamide prepolymer of
(3) The polyamide prepolymer is introduced into a self-cleaning continuous horizontal twin-screw reactor capable of separating and removing water, and the degree of polymerization is further increased at a temperature equal to or higher than the melting point of the finally obtained polyamide to obtain a desired relative degree. And a late polymerization step for obtaining a polyamide having a viscosity [RV].
[0013]
The present invention is (2) the method for continuous production of polyamide described above, wherein a plurality of batch reactors are used in the initial polymerization step.
[0014]
The present invention is (3) the above continuous method for producing a polyamide, wherein the average residence time in the late polymerization step is 1 to 30 minutes.
[0015]
The present invention is (3) the continuous method for producing a polyamide, wherein the relative viscosity [RV] of the polyamide obtained in the latter polymerization step is in the range of 1.6 to 4.0.
[0016]
The present invention provides (3) purging an inert gas, adjusting the degree of vacuum of a reactor, adding an acid anhydride compound, or using a combination thereof in the latter polymerization step to thereby increase the relative viscosity of the polyamide [ RV] is continuously controlled.
[0017]
The present invention is the continuous method for producing a polyamide as described above, wherein the polyamide contains metaxylylenediamine (MXD) as a diamine component, and the metaxylylenediamine (MXD) is at least 70 mol% based on the diamine component. .
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
First, the polyamide produced by the continuous production method of the present invention will be described.
The continuous production method of the present invention can be applied to any of an aliphatic polyamide such as nylon 66 and an aromatic-containing polyamide, but can be preferably applied to a polyamide containing 70 mol% or more of metaxylylenediamine (MXD) as an amine component. .
[0019]
It is important that the polyamide contains 70 mol% or more of metaxylylenediamine based on the diamine component in terms of oxygen barrier properties and water absorption. The smaller the amount of meta-xylylenediamine, the more advantageous in terms of thermal deterioration and color tone, but from the viewpoint of oxygen barrier properties, 70 mol% or more is required, and desirably 75 mol% or more. On the other hand, from the viewpoint of water absorption, since MXD itself has an aromatic ring, the water absorption is small and advantageous as compared with aliphatic polyamides such as nylon 6 and nylon 66.
[0020]
Desirable polyamides include hexamethylenediamine (HMD) as another diamine component and adipic acid (ADA) as a dicarboxylic acid component, provided that at least 70 mol% of metaxylylenediamine (MXD) is contained as a diamine component. And polyamides composed of
[0021]
As the diamine component, ethylenediamine, 1-methylethyldiamine, 1,3-propylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine (HMD), heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine , Undecamethylenediamine, dodecamethylenediamine, and other aliphatic diamines, and in addition, cyclohexanediamine, bis- (4,4-aminohexyl) methane, paraxylylenediamine, and the like. One or more of these diamine components can be used.
[0022]
Any dicarboxylic acid component may be used as long as a molten state can be obtained, and adipic acid (ADA), malonic acid, succinic acid, glutaric acid, sebacic acid, pimelic acid, speric acid, azelaic acid, undecanoic acid, undecadioic acid, Examples thereof include aliphatic dicarboxylic acids such as dodecadionic acid and dimer acid, 1,4-cyclohexanedicarboxylic acid, and 4,4-diphenyldicarboxylic acid. One or more of these dicarboxylic acid components can be used.
[0023]
In the production of the polyamide of the present invention, a raw material capable of forming a polyamide other than the above-mentioned diamines and dicarboxylic acids can be copolymerized as necessary in view of the performance required for the polyamide. For example, lactams such as caprolactam, valerolactam, laurolactam, undecalactam, aminocaproic acid and aminoundecanoic acid, and aminocarboxylic acids such as 11-aminoundecanoic acid and 12-aminododecanoic acid can also be used as the copolymerization component.
[0024]
The relative viscosity [RV] of the polyamide resin is desirably in the range of 1.6 to 4.0 from the viewpoints of physical and mechanical properties of the obtained molded article and operation stability. When the [RV] is less than 1.6, the obtained molded product is not only inferior in mechanical properties, but also becomes bent up, it is difficult to take out the strand of the polymer, and cracks occur at the time of chipping. The effect tends to be greater. Conversely, when [RV] is more than 4.0, the melt viscosity becomes high and the molding conditions become more severe, so that it becomes difficult to obtain a molded product of stable quality. It is not possible to expect the physical properties of the product to match the required labor. Further, in order to achieve a high [RV] exceeding 4.0, it is necessary to increase the amount of inert gas purge or to apply a high degree of vacuum, which leads to instability of operation such as cost increase and vent up, which is preferable. Absent. More desirable [RV] is 1.9 to 3.8.
[0025]
The less contamination (foreign matter) of the polyamide resin, the better. When there is much contamination, the operability of the post-process is reduced or the quality is reduced.
[0026]
Next, the continuous production method of the polyamide of the present invention will be described with reference to FIG. FIG. 1 is a flowchart showing a schematic process of a continuous production method of a polyamide of the present invention. In the example of FIG. 1, the continuous production method of the polyamide is performed in a dicarboxylic acid melting step and an initial polymerization step performed in a batch polymerization tank (11), and a self-cleaning continuous horizontal biaxial reactor (41). Including a late polymerization step.
[0027]
(Dicarboxylic acid melting step)
In the dicarboxylic acid melting step, the dicarboxylic acid may be charged and melted in a batch polymerization tank (11) also serving as a melting tank as illustrated in FIG. 1, or the dicarboxylic acid may be charged in a dedicated melting tank (not shown). The charged and melted dicarboxylic acid may be transferred from the melting tank to the batch polymerization tank (11).
[0028]
The melting temperature of the dicarboxylic acid is suitably not less than its melting point and not more than the melting point + 50 ° C. (a temperature 50 ° C. higher than the melting point). Making the melting temperature higher than necessary undesirably induces thermal decomposition and deterioration of the dicarboxylic acid. Conversely, if the temperature is too low, it is not preferable because the melt becomes uneven. A desirable melting temperature is not less than the melting point + 5 ° C and not more than the melting point + 25 ° C.
[0029]
Further, in order to suppress the thermal oxidative decomposition or thermal decomposition of dicarboxylic acid, it is preferable to place the inside of the melting tank or the polymerization tank (11) during melting under an inert gas atmosphere, for example, a nitrogen gas atmosphere. At this time, it is preferable to place it in an inert gas atmosphere under a pressure of 0.05 to 0.8 MPa, preferably 0.1 to 0.6 MPa, from the viewpoint of preventing the outside air from being mixed.
[0030]
The atmospheric oxygen concentration at the time of melting the dicarboxylic acid greatly affects the color tone of the obtained polyamide. In particular, this tendency is remarkable for polyamides using meta-xylylenediamine as a raw material. There is no problem if the oxygen concentration in the atmosphere at the time of melting of the dicarboxylic acid is 10 ppm or less. However, when the oxygen concentration is 10 ppm or more, the obtained polyamide tends to have a strong yellow tint and deteriorate the quality of the product. On the other hand, the lower limit of the oxygen concentration is not particularly defined, but is, for example, 0.05 ppm or more. In the production of polyamide, there is no problem that the oxygen concentration is less than 0.05 ppm, but in order to achieve less than 0.05 ppm, the oxygen removal step becomes unnecessarily complicated, and the color tone and other There is almost no effect on the physical properties of the material. A desirable range of the oxygen concentration is 0.05 ppm or more and 9 ppm or less, and more preferably 0.05 ppm or more and 8 ppm or less.
[0031]
In the present invention, the dicarboxylic acid raw material is supplied to the melting tank or the polymerization tank (11) in which oxygen has been removed in advance and the oxygen concentration is 10 ppm or less, or the dicarboxylic acid raw material is supplied to the melting tank or the polymerization tank (11), and then the oxygen is added. Is removed and the atmosphere in the melting tank is set to an oxygen concentration of 10 ppm or less, or both may be used in combination. This may be selected in terms of facilities or operation. When melting is performed using a melting tank, the atmosphere in the polymerization tank (11) is also preferably set to an oxygen concentration of 10 ppm or less.
[0032]
As a method for removing oxygen, there are a vacuum substitution method, a pressure substitution method, and a combination thereof. The degree of vacuum or the degree of pressurization applied to the substitution and the number of substitutions may be selected under conditions that are most efficient for achieving the desired oxygen concentration.
[0033]
In the dicarboxylic acid melting step, it is also possible to add an alkali metal compound or a phosphorus compound to the melting tank or the polymerization tank (11) as a polymerization catalyst for the purpose of suppressing the decomposition of the polyamide.
[0034]
The alkali metal compound used is a lithium compound, a sodium compound, a potassium compound or the like, and a sodium compound is most preferred. Further, as the phosphorus compound, phosphoric acid, phosphorous acid, hypophosphorous acid, pyrophosphoric acid, metaphosphoric acid, polyphosphoric acid and salts thereof are used.
[0035]
(Initial polymerization step)
In the initial polymerization step, in the example of FIG. 1, in a batch polymerization tank (11), a diamine in a molten state is continuously or intermittently added to a dicarboxylic acid in a molten state to increase the degree of polymerization while separating and removing water. It is a process. Alternatively, in a batch polymerization tank, a step of adding a dicarboxylic acid in a molten state to a diamine in a molten state continuously or intermittently to increase the degree of polymerization while separating and removing water may be employed. Diamines are usually liquid at room temperature, and often take the form shown in FIG.
[0036]
The polymerization tank (11) is provided with a diamine addition device (12), a water separation and removal device (13), a nitrogen gas introduction pipe (14), and the like.
[0037]
The diamine is added to the molten dicarboxylic acid in the polymerization tank (11) from the addition device (12). The addition of the diamine may be performed continuously or intermittently, and is performed so that the molar ratio between the diamine and the dicarboxylic acid becomes a predetermined value. At the time of addition, the dicarboxylic acid is desirably at a temperature of 160 ° C. or higher, which is a temperature at which the amidation reaction substantially proceeds, and the oligomer and / or low-molecular-weight polyamide produced as an intermediate is in a molten state. It is desirable that the temperature be maintained at a temperature at which the entire reaction system can maintain a uniform fluidized state.
[0038]
During the addition of the diamine, the temperature of the reaction mixture is gradually raised to a predetermined polycondensation reaction temperature not lower than the melting point (Tm) of the finally obtained polyamide. Since the rate of temperature rise depends on the heat of amidation reaction, the latent heat of evaporation of condensed water, the heat of supply, and the like, the rate of addition of the diamine component is appropriately adjusted. The internal temperature of the polycondensation reaction temperature in the initial polymerization step is, for example, not less than the melting point (Tm) of the finally obtained polyamide and not more than Tm + 35 ° C., preferably not more than Tm + 15 ° C., and more preferably not more than Tm + 5 ° C. If the reaction temperature is out of the above range, the ultimate degree of polymerization is undesirably low, or thermal degradation or productivity decreases. During the addition of the diamine, the pressure is not particularly limited, but a pressure equal to or higher than normal pressure is desirable for fixing the diamine component.
[0039]
After completion of the addition of the diamine, it is desirable to maintain the inside of the polymerization tank at a normal pressure or higher for a predetermined time, for example, 5 minutes or longer, preferably 10 minutes or longer. At the initial stage of the addition of the diamine, the carboxyl group is present in a considerable excess with respect to the diamine, and the reaction rate of the diamine, that is, the immobilization rate is extremely high. However, at the end of the addition, a considerable amount of the carboxyl group has been consumed, and the immobilization speed of the diamine component becomes extremely slow as compared with the initial stage of the addition. In addition, the increase in the degree of polymerization lowers the stirring efficiency of the reaction mixture, which is more disadvantageous for immobilizing the diamine. After the addition of the diamine is completed, the diamine is fixed by maintaining the pressure at normal pressure or higher for a predetermined time, and the molar balance of the preparation is accurately reflected on the molar balance of the polyamide. The condensed water generated by the polymerization is distilled out of the reaction system by the separation and removal device (13).
[0040]
In the initial polymerization step, the degree of polymerization is increased by the above polymerization reaction to obtain a polyamide prepolymer having a relative viscosity of 1.4 to 2.7. If the relative viscosity of the prepolymer is less than 1.4, a long residence time is required in order to obtain a polyamide having a desired relative viscosity [RV] in the latter polymerization step, which causes thermal degradation and coloring of the polyamide. In addition, it is necessary to increase the size of the equipment in the latter polymerization step, which is inferior in economy. On the other hand, if the relative viscosity of the prepolymer exceeds 2.7, an extremely long residence time is required in the initial polymerization step, and furthermore, the viscosity is high and uniform stirring and mixing are insufficient. It becomes. The lower limit of the relative viscosity of the prepolymer obtained in the initial polymerization step is preferably 1.45 or more, and the upper limit is preferably 2.3 or less, more preferably 2.1 or less.
[0041]
In the present invention, in the initial polymerization step, it is preferable to use a plurality of, for example, two batch polymerization tanks (11) in parallel (the example in FIG. 1). While continuously transferring the polyamide prepolymer obtained in one batch polymerization tank (11) to the late polymerization step by a gear pump (18), the polyamide prepolymer was transferred in the other batch polymerization tank (11). Prepare. When the continuous transfer of the prepolymer from one polymerization tank (11) is completed, the continuous transfer of the prepolymer is switched to the other polymerization tank (11) by opening and closing the three-way valve (19). In this way, a continuous production method that exceeds the amount of the prepolymer when one batch polymerization tank (11) is used is achieved.
[0042]
When the transfer of the prepolymer is switched between the polymerization tanks (11) using a plurality of batch polymerization tanks (11) in this manner, the degree of polymerization (relative viscosity) of the polyamide prepolymer between the polymerization tanks (11) is reduced. Need to make no difference. To this end, as shown in FIG. 1, a melt holding layer (15) is provided downstream of the polymerization tank (11), and the polyamide prepolymer obtained in the polymerization tank (11) is mixed with the melt holding layer (15). ), And is preferably maintained under certain conditions. The melt holding layer (15) is provided with a water separation / removal device (16), a steam introduction pipe (17), and the like. By transferring the polyamide prepolymer from the polymerization tank (11) to the melt holding layer (15) and maintaining the gas phase in the holding layer (15) at a predetermined pressure with steam, a change in the degree of polymerization can be suppressed. The water vapor used for holding pressure suppresses the progress of the polymerization reaction by utilizing the amidation equilibrium reaction. If the water vapor pressure is too low, the polymerization proceeds and the degree of polymerization increases. The polymerization proceeds and the degree of polymerization decreases.
[0043]
An appropriate water vapor pressure at which the degree of polymerization does not change depends on the monomer composition ratio, the molar balance between diamine and dicarboxylic acid, the degree of polymerization, the equilibrium constant, the temperature, and the like, but can be appropriately determined by experimental trial. For example, when a prepolymer having a molar balance of 1.000 ± 0.01 is held in the melt holding layer (15) at a temperature of 250 to 260 ° C. and a pressure of 0.25 to 0.35 MPa, the degree of polymerization becomes It can be kept below 100.
[0044]
As an index of a change in the degree of polymerization when the pressure is maintained with steam, it is preferable to suppress the change in the relative viscosity of the polyamide prepolymer to within ± 0.2. If the change in the relative viscosity exceeds ± 0.2, the degree of polymerization (relative viscosity) of the finally obtained product is greatly changed, which is not preferable. By adjusting the reaction conditions (temperature, pressure, residence time) in the late polymerization step, it is also possible to absorb fluctuations in the degree of polymerization of the prepolymer, but from the viewpoint of continuous production, it is not possible to change the reaction conditions during production. Not realistic.
[0045]
If the same function as the above-mentioned holding layer (15) is provided in the polymerization tank (11), the melt holding layer (15) may not be provided downstream of the polymerization tank (11). In this case, the polyamide prepolymer obtained in the polymerization tank (11) is directly and continuously transferred to a late polymerization step.
[0046]
(Late polymerization step)
In the late polymerization step, the polyamide prepolymer from the initial polymerization step is introduced into a continuous reaction apparatus capable of separating and removing water, and the degree of polymerization is further increased at a temperature equal to or higher than the melting point of the finally obtained polyamide to obtain a desired relative degree. A polyamide having a viscosity [RV] is obtained.
[0047]
As a continuous reaction device in the latter polymerization step, a self-cleaning horizontal twin-screw reaction device (41) is used.
[0048]
A twin-screw extruder may be used as a continuous reaction device in the latter polymerization step. The twin-screw extruder has good reaction efficiency and has a certain degree of self-cleaning function. However, in the twin-screw extruder, not only the entire inside of the apparatus cannot be kept under vacuum, but also a low melt viscosity material is liable to cause vent up. In addition, there is a problem that temperature control is difficult due to high shearing force, and the degree of freedom of residence time is limited. In order to further increase the residence time, there are disadvantages such as an increase in the size of the apparatus and an increase in equipment costs.
[0049]
Therefore, in the present invention, a self-cleaning horizontal twin-screw reactor (41) is used as the continuous reactor. For example, it is preferable to use SCR manufactured by Mitsubishi Heavy Industries. In the self-cleaning type horizontal twin-screw reaction device (41), two parallel drive shafts are formed in a state where the blades (rotors) are superposed with a slight gap with a twist, and two parallel drive shafts are formed. The drive shaft is rotated in the same direction. The smaller the clearance between the wings, the greater the cleaning effect between the wings. In a self-cleaning horizontal biaxial reactor, the clearance between the blades varies depending on the size of the device. When the inner volume of the reactor is about 0.15 m ³ , the clearance between the blades is preferably 50 mm. Hereinafter, it is more desirably 20 mm or less, and most desirably 10 mm or less.
[0050]
The self-cleaning type horizontal twin-screw reactor has a smaller clearance between the blades and the inner wall as compared with a general horizontal twin-screw reactor, so that the rotation of the drive shaft provides an inner wall cleaning effect. Although the clearance between the wing and the inner wall varies depending on the size of the apparatus, when the inner volume of the reactor is about 0.15 m ³ , the clearance between the wing and the inner wall is preferably 15 mm or less, more preferably 10 mm or less, and most preferably. Is 5 mm or less.
[0051]
The fact that the clearance between the wing and the inner wall is small is the same for a twin-screw extruder. However, compared to a twin-screw extruder where there is a considerable gap between the blades and the drive shaft rotates in the opposite direction, the SCR has only a small gap between the blades and the two parallel drive shafts are in the same direction. , The cleaning effect between the blades is further increased. The self-cleaning effect brings about a reduction in scale adhesion and an improvement in quality due to a reduction in contamination. Furthermore, unlike a twin-screw extruder, it is possible to apply vacuum to low melt viscosity materials because the entire device can be kept under vacuum. It has the advantage of being long, having high applicability to viscosity fluctuations and flow rate fluctuations, and having a large producible viscosity range. Further, in terms of equipment, there is an advantage that the size can be reduced and the cost is low as compared with the twin-screw extruder.
[0052]
The reaction conditions in the latter polymerization step differ depending on the type of polyamide and the desired relative viscosity [RV], but the resin temperature is from the melting point (Tm) of the polyamide to Tm + 80 ° C, preferably from the melting point to Tm + 70 ° C. When the resin temperature is Tm + 80 ° C. or higher, the deterioration of the polyamide is easily accelerated, which causes deterioration in physical properties and coloring. Conversely, below Tm, there is a danger that the polyamide solidifies and damages the reactor.
[0053]
The average residence time in the continuous reactor varies depending on the type of polyamide, desired relative viscosity [RV], degree of vacuum, addition of an acid anhydride compound described below, purging of an inert gas described later, and the like. Minutes. If the average residence time is less than 1 minute, it is difficult to obtain a polyamide having an [RV] in the range of 1.6 to 4.0. , It is necessary to reduce the supply amount, which causes a significant decrease in productivity. A desirable average residence time is 1.5 to 25 minutes, more preferably 2 to 20 minutes.
[0054]
Unlike the twin screw extruder, the screw rotation speed (rpm) of the reactor SCR has a small effect on the polymerization reaction and the average residence time, and may be appropriately selected, but generally 20 rpm to 150 rpm is applied. .
[0055]
An important function in the late polymerization step is control of the relative viscosity [RV].
Control methods for [RV] include (1) purge of inert gas, (2) vacuum degree, and (3) combination of inert gas purge and vacuum degree. Hereinafter, each method will be described.
[0056]
While the inert gas purge promotes the polymerization reaction, [RV] can be controlled by adjusting the purge amount. The inert gas purge is performed from the inert gas purge port (42). The amount of inert gas purge varies depending on desired polymerization conditions such as [RV] and temperature, but the amount is preferably 0.005 to 10 L per kg of polymer. If the purge amount exceeds 10 L / kg, the amount of inert gas used becomes excessive due to the action of accelerating the polymerization reaction, which causes a cost increase. A more desirable purge amount is 0.005 to 9.5 L / kg, and still more preferably 0.01 to 9 L / kg. Further, when a desired RV can be obtained without performing the inert gas purge, the purge may not be performed (that is, the purge amount: 10 L / kg). Any inert gas may be used as long as it is inert to the polyamide production reaction, but nitrogen gas is advantageous in terms of safety and cost.
[0057]
The polymerization reaction can be promoted by controlling the degree of vacuum, and the reaction rate can be controlled. This is performed through the vacuum port (43). The polyamide formation reaction is a condensation reaction between a carboxylic acid and an amine, and the polymerization reaction is promoted by removing generated water. The degree of vacuum applied in the latter polymerization step varies depending on the desired [RV] and polymerization conditions, but is 150 to 1200 hPa. When the pressure is less than 150 hPa, in the latter polymerization step, the polymer vents up, clogs the piping, and cannot expect stable operability. On the other hand, when the pressure exceeds 1200 hPa, the effect of the degree of vacuum is not so great, the speed of reaching the desired [RV] is slowed, and the productivity is reduced. In some cases, the desired [RV] is not reached. Desirable degree of vacuum is 200-1100 hPa, and more desirably 250-1050 hPa.
[0058]
A desirable control method of [RV] in polyamide using ADA-MXD as a main raw material is a combination of inert gas purging and vacuum. The advantage of this method is that it is easy to produce an inert gas or a polyamide having a high [RV] which cannot be achieved by a vacuum degree alone. It becomes possible by adjusting the amount, or conversely, by adjusting the degree of vacuum when the amount of inert gas is constant, there is an advantage that [RV] control can be performed more flexibly.
[0059]
Desirable conditions are an inert gas purge amount of 0.005 to 9.5 L / kg and a degree of vacuum of 200 to 1150 hPa, more preferably 0.01 to 9 L / kg and 250 to 1100 hPa. If the purge amount of the inert gas is less than 0.005 L / kg, or if the degree of vacuum exceeds 1150 hPa, the polymerization rate becomes slow. Conversely, if the inert gas purge amount exceeds 9.5 L / kg or if the degree of vacuum is less than 200 hPa, the amount of inert gas used increases, resulting in a cost increase factor. Disadvantages such as a decrease in performance.
[0060]
On the other hand, when it is desired to suppress the polymerization reaction, the polymerization reaction can be controlled by adding an acid anhydride compound. This is performed through the addition port (44). It is considered that the addition of the acid anhydride compound blocks the terminal amino group of the polymer, so that the polymerization reaction can be suppressed. Examples of the acid anhydride compound that can be used include hexahydrophthalic anhydride (HOPA), phthalic anhydride, trimetic anhydride, pyromellitic anhydride, succinic anhydride, and the like. The use of HOPA is desirable from the viewpoint of the color tone of the polyamide. The amount of the acid anhydride compound to be added is not particularly limited depending on the desired [RV], but usually is preferably 150 meq / kg or less per 1 kg of the polymer. When the addition amount exceeds 150 meq / kg, the polymerization rate becomes slow or a vent-up factor is caused, resulting in poor operation stability. In addition, unreacted acid anhydride compounds remain in the polymer and cause deterioration of polyamide quality.
[0061]
The control method of [RV] is not limited to the above method, and addition of an alkali metal compound and various conventionally known means can be performed.
[0062]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In addition, the evaluation method of the characteristic value of the polyamide resin used in the Example is as follows.
[0063]
(1) Relative viscosity [RV]
0.25 g of a polyamide resin was dissolved in 25 ml of 96% sulfuric acid, and measured with an Ostwald viscometer.
[0064]
(2) Contamination chip-shaped polyamide resin (500 g) was placed on a white plate so as not to overlap, and the presence or absence of black foreign matter in the chips was visually observed. The ratio of the number of chips to be performed was determined. It was determined based on the following criteria.
：: small ×: large
(3) Heat treatment time until gelation occurred As an index of the difficulty of gelation of the obtained polyamide resin, the heat treatment time (Hr) until gelation occurred was determined by the following operation. The longer the heat treatment time (Hr) until the gelation occurs, the less the gelation occurs, and the less the contamination by insoluble and infusible foreign matter.
[0066]
A polyamide resin sample (3 g) dried under reduced pressure at 100 ° C. for 24 hours was placed in a test tube with a branch having an internal volume of about 20 ml, and vacuum nitrogen replacement was performed three times. Then, while flowing nitrogen gas at 30 ml / min into the test tube, It was immersed in an oil bath at a constant temperature of 260 ° C. to perform heat treatment. At a lapse of a predetermined time (x hours) from the start of the heat treatment, a sample of the heat-treated resin was sampled, and 0.25 g of the sample was dissolved in 25 ml of 96% sulfuric acid. Whether or not an object was generated was visually observed. This observation was performed for various predetermined times (x hours). The shortest time of the heat treatment time (x hours) of the sample in which the insoluble matter was generated was defined as the heat treatment time (Hr) until gelation occurred.
[0067]
[Example 1]
In this example, two reactors (11) for the initial polymerization are arranged in parallel, and the polyamide prepolymer from the reactor (11) is alternately supplied to the SCR reactor for the late polymerization by switching the three-way valve (19). did. No melt retention layer (15) was provided.
[0068]
4 kg of adipic acid (ADA) was charged into a 20-liter stainless steel reaction vessel (11) equipped with a stirrer, a nitrogen gas introduction pipe, a pressure reduction control valve, a 1.3 MPa steam introduction pipe, and a diamine dropping tank, and purged with nitrogen. Further, the mixture was heated with stirring while flowing a small amount of nitrogen, and the temperature was raised to 170 ° C. to melt adipic acid. Then, 3.73 kg of meta-xylylenediamine (MXD) was continuously dropped from the dropping tank (12) under normal pressure over 3 hours while stirring the molten adipic acid. During this time, the internal temperature was continuously raised to 250 ° C. Water distilled off together with meta-xylylenediamine was removed from the reaction system.
[0069]
After completion of the dropping of meta-xylylenediamine, the mixture was stirred for 20 minutes while increasing the temperature at a rate of 0.2 ° C./min under normal pressure to promote immobilization of meta-xylylenediamine and perform initial polymerization. Thereafter, steam of 1.3 MPa was introduced into the reactor, and the pressure in the gas phase was adjusted to 0.3 MPa by a pressure control valve. After a lapse of 10 minutes after the pressure reached 0.3 MPa, the discharge of the polyamide was started to obtain a polyamide prepolymer. At this time, the stirring was continued, the pressure in the gas phase was maintained at 0.3 MPa, and the internal temperature was further maintained at 255 ° C. ± 1 ° C.
[0070]
The prepolymer was supplied to an SCR (41) set at a reaction temperature of 255 ° C., a degree of vacuum of 1013 hPa, a nitrogen gas purge amount of 1.13 L / kg, and a screw rotation speed of 50 rpm. The supply of the prepolymer to the SCR (41) was performed alternately from the two reaction vessels (11). After elapse of an average residence time of 10 minutes in the SCR (41), the polyamide was continuously discharged as strands, water-cooled and granulated to obtain polyamide resin chips.
[0071]
[Example 2]
The same reaction apparatus as in Example 1 was used. A stainless steel reaction vessel (11) was charged with 4 kg of adipic acid (ADA), purged with nitrogen, and further heated with stirring while flowing a small amount of nitrogen, and heated to 170 ° C. to melt adipic acid. Next, 3.1 kg of hexamethylenediamine (HMD) was dropped from the dropping tank (12) continuously at normal pressure over 3 hours while stirring the molten adipic acid. During this time, the internal temperature was continuously raised to 255 ° C. Water distilled off together with hexamethylenediamine was removed from the reaction system.
[0072]
After the completion of the dropping of hexamethylenediamine, the mixture was stirred for 20 minutes while raising the temperature at a rate of 0.2 ° C./min under normal pressure to perform initial polymerization. Thereafter, steam of 1.3 MPa was introduced into the reactor, and the pressure in the gas phase was adjusted to 0.3 MPa by a pressure control valve. After a lapse of 10 minutes after the pressure reached 0.3 MPa, the discharge of the polyamide was started to obtain a polyamide prepolymer. At this time, stirring was continued, the pressure in the gas phase was maintained at 0.3 MPa, and the internal temperature was further maintained at 270 ° C. ± 1 ° C.
[0073]
The prepolymer was supplied to the SCR (41) set at a reaction temperature of 270 ° C., a degree of vacuum of 1013 hPa, a nitrogen gas purge amount of 1.13 L / kg, and a screw rotation speed of 50 rpm. The supply of the prepolymer to the SCR (41) was performed alternately from the two reaction vessels (11). After elapse of an average residence time of 10 minutes in the SCR (41), the polyamide was continuously discharged as strands, water-cooled and granulated to obtain polyamide resin chips.
[0074]
[Comparative Example 1]
As the late polymerization reactor, a 20 L stainless steel reactor equipped with a jacket was used instead of the SCR reactor of Example 1.
[0075]
Melting and initial polymerization steps until a polyamide prepolymer was obtained were performed in the same manner as in Example 1. The polyamide prepolymer obtained in the initial polymerization step was supplied to a jacketed 20 L stainless steel reaction vessel. The supply of the prepolymer to the stainless steel reaction vessel was performed alternately from the two prepolymerization reaction vessels (11). The late-stage polymerization reaction temperature is 255 ° C., the degree of vacuum is 800 hPa, the polymerization reaction is further advanced under stirring, and after elapse of an average residence time of 20 minutes, the polyamide is continuously discharged as strands, cooled with water, granulated, and subjected to polyamide resin chips. Got.
[0076]
[Table 1]

[0077]
Table 1 shows the properties of the polyamide and the polyamide prepolymer obtained in Examples and Comparative Examples. In each of Examples 1 and 2, the operation was good, contamination was extremely suppressed, and an excellent polyamide having a long heat treatment time until gelation occurred was obtained.
[0078]
In the polyamide resin of Comparative Example 1, more contamination was observed than in the polyamide resin of Example 1, and the heat treatment time until gelation occurred was also shorter.
[0079]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the continuous production method of the polyamide which is excellent in production efficiency, hardly causes gelation, and has few contaminations (black foreign substances) is obtained, especially the continuous production method of the aromatic-containing polyamide is provided. In the method of the present invention, an aromatic-containing polyamide having excellent strength, good color tone, and low water absorption, suitable for films, sheets, packaging bags, bottles, etc. in applications such as foods, beverages, pharmaceuticals, and cosmetics. Are manufactured continuously.
[Brief description of the drawings]
FIG. 1 is a flowchart showing a schematic process of a continuous production method of a polyamide of the present invention.
[Explanation of symbols]
(11): Dicarboxylic acid melting tank and batch polymerization tank for initial polymerization
(12): Diamine addition equipment
(41): Self-cleaning horizontal twin-screw reactor for late polymerization
(15): Melt holding tank
(19): Three-way valve

Claims (6)

A continuous method for producing a polyamide mainly containing a diamine component unit and a dicarboxylic acid component unit,
(1) a dicarboxylic acid melting step of melting a dicarboxylic acid,
(2) Using a batch reactor capable of separating and removing water,
To the dicarboxylic acid in the molten state, the diamine in the molten state is added continuously or intermittently, or to the diamine in the molten state, the dicarboxylic acid in the molten state is added continuously or intermittently,
A polycondensation reaction is carried out with the molar ratio of diamine and dicarboxylic acid being a predetermined value, and the degree of polymerization is increased while separating and removing water at a temperature not lower than the melting point of the finally obtained polyamide, and the relative viscosity is 1.4 to 2.7. An initial polymerization step of obtaining a polyamide prepolymer of
(3) The polyamide prepolymer is introduced into a self-cleaning continuous horizontal twin-screw reactor capable of separating and removing water, and the degree of polymerization is further increased at a temperature equal to or higher than the melting point of the finally obtained polyamide to obtain a desired relative degree. A continuous polymerization step of obtaining a polyamide having a viscosity [RV]. (2) The continuous production method of polyamide according to claim 1, wherein a plurality of batch-type reactors are used in the initial polymerization step. (3) The continuous production method of polyamide according to claim 1 or 2, wherein the average residence time in the latter polymerization step is 1 to 30 minutes. (3) The continuous method for producing a polyamide according to any one of claims 1 to 3, wherein the relative viscosity [RV] of the polyamide obtained in the latter polymerization step is in the range of 1.6 to 4.0. (3) Controlling the relative viscosity [RV] of the polyamide by purging the inert gas, adjusting the degree of vacuum of the reactor, adding an acid anhydride compound, or a combination thereof in the latter polymerization step. The continuous production method of the polyamide according to any one of claims 1 to 4. The polyamide according to any one of claims 1 to 5, wherein the polyamide comprises metaxylylenediamine (MXD) as a diamine component, and the metaxylylenediamine (MXD) is at least 70 mol% based on the diamine component. A continuous method for producing the above-mentioned polyamide.

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