JP2004204026A - Continuous production process of copolyamide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a continuous manufacturing process by which a copolyamide having stable properties is efficiently manufactured with minimal contamination. <P>SOLUTION: The continuous manufacturing process of a copolyamide comprises (1) a process 11 by which a slurry in which an aromatic dicarboxylic acid is dispersed in a molten aliphatic dicarboxylic acid is obtained, (2) an initial polymerization process 11 by which a polyamide prepolymer with a relative viscosity of 1.4-2.7 is obtained by conducting polycondensation reaction by adding a diamine containing xylylenediamine as the major ingredient to the dicarboxylic acid slurry and by increasing the degree of polymerization while removing water at a temperature not lower than the melting point of the ultimately obtained copolyamide in a water-removable batch type reaction apparatus, (3) a final polymerization process by which a copolyamide with a relative viscosity of 1.6-4.0 is obtained by introducing the prepolymer into a water-removable, self-cleaning and continuous type horizontal twin screw reactor 41 and by increasing the degree of polymerization at a temperature not lower the melting point of the ultimately obtained copolyamide. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００７８】
実施例及び比較例で得られた共重合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、優れた物性値を有する共重合ポリアミドが得られた。
【００７９】
表１において、重合時間（ｈｒ）は重合反応開始からチップ化されるまでの時間を意味し、比較例１における塩調合に要した時間は含まない。
【００８０】
また、反応容器の容量当たりの生産効率の指標として、次式による効率（％）を表１に示す。
効率（％）＝（取出ポリマー重量／仕込原料の総重量）×１００
ここで、仕込原料の総重量には、比較例１において用いられた水は含まれる。
【００８１】
比較例１では、塩形成に用いた水を反応系外へ除去するために、多大なエネルギーと時間を要した。また、反応容器の容量当たりの生産効率に劣ることも明らかである。
【００８２】
【発明の効果】
本発明によれば、キシリレンジアミンを主成分として含むジアミンと、芳香族ジカルボン酸及び炭素数６〜１２の脂肪族ジカルボン酸を含むジカルボン酸とから主として構成される共重合ポリアミドを、品質良好に生産効率良く連続製造することができる。この共重合ポリアミドは、ガスバリア性、燃料バリア性、耐溶剤性に優れ、ガソリンタンク材、飲料用ボトルをはじめとする中空成形容器、フィルム、シートなどの成形体の素材として好適に用いられる。
【図面の簡単な説明】
【図１】本発明の共重合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)：ジカルボン酸スラリー調製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 method for continuously producing a copolyamide mainly comprising a diamine containing xylylenediamine as a main component and a dicarboxylic acid containing an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid having 6 to 12 carbon atoms. This copolymerized polyamide has excellent gas barrier properties, fuel barrier properties, and solvent resistance, and is suitably used as a material for molded articles such as gasoline tank materials, beverage bottles, hollow molded containers, films, sheets, and the like.
[0002]
[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.
[0003]
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.
[0004]
For example, Japanese Patent Application Laid-Open No. Hei 8-259691 discloses a mixed diamine comprising 35 to 70 mol% of metaxylylenediamine and 30 to 65 mol% of paraxylylenediamine, 40 to 80 mol% of adipic acid and 20 to 60 of terephthalic acid. A method for producing a copolymerized polyamide by directly polymerizing a mixed dicarboxylic acid consisting of mol% is disclosed. In this method, adipic acid and terephthalic acid are made to flow at a temperature higher than the melting point of adipic acid and lower than a temperature lower by 30 ° C. than the melting point of polyamide, and the diamine is added dropwise. However, since terephthalic acid has a high melting point and is close to the decomposition point, it does not dissolve in molten adipic acid, and a uniform flow state cannot be obtained if terephthalic acid is used in an amount of 20 to 60 mol%. Therefore, good reactivity of terephthalic acid cannot be obtained, and a polyamide having a desired adipic acid / terephthalic acid copolymerization ratio cannot be obtained. Further, the polyamide into which 20 to 60 mol% of terephthalic acid has been introduced has a problem that the viscosity at the time of melting becomes very high, the fluidity is remarkably reduced at a usual molding temperature, and the productivity of molded articles is poor. There is.
[0005]
When a dicarboxylic acid component (for example, phthalic acid) having substantially no melting point or a melting point of 300 ° C. or more is copolymerized as a raw material for producing a polyamide resin, an aqueous solution of a nylon salt is prepared from a diamine acid component and a dicarboxylic acid component. Is generally formed, and polymerization is performed using the aqueous solution of nylon salt. The process for producing a polyamide resin using this aqueous solution of a nylon salt may be a batch type or a continuous type.
[0006]
For example, in the case of a batch type, a nylon salt aqueous solution is heated under pressure in one batch type polymerization tank, and polymerization is promoted in a uniform phase while distilling out a diamine component is suppressed. After the diamine component is immobilized, the pressure of the steam in the system is gradually released, and finally the pressure is reduced to normal pressure or reduced pressure to complete the polymerization. In the case of the continuous type, two or more continuous type polymerization apparatuses each of which carries out the above steps are sequentially used, the nylon salt aqueous solution is continuously supplied to the polymerization apparatus, and the polyamide resin after the polycondensation is continuously discharged. (For example, JP-B-33-15700, JP-B-43-22874). However, these production methods require much time and a large amount of heat to remove water as a solvent, and are not economical from an industrial viewpoint. Further, since a large amount of water is used, the production efficiency per capacity of the reaction vessel is low.
[0007]
In general, the introduction of an aromatic ring into a polyamide skeleton results in a higher melting point and a higher melt viscosity, resulting in more severe temperature conditions and the like during polyamide production. 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. Therefore, it is necessary to produce a polyamide while avoiding a long residence under high temperature conditions.
[0008]
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.
[0009]
[Patent Document 1]
JP-A-59-155426
[Patent Document 2]
JP-A-62-156130
[Patent Document 3]
JP-A-8-259691
[Patent Document 4]
JP-B-33-15700
[Patent Document 5]
JP-B-43-22874
[Patent Document 6]
JP 2002-212284 A
[Patent Document 7]
JP 2002-220462 A
[Patent Document 8]
JP-A-2002-220463
[Patent Document 9]
JP-A-2002-22064
[Patent Document 10]
JP 2002-220465 A
[Patent Document 11]
JP 2002-220466 A
[0010]
[Problems to be solved by the invention]
An object of the present invention is a continuous production method of a copolyamide mainly composed of a diamine containing xylylenediamine as a main component and a dicarboxylic acid containing an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid having 6 to 12 carbon atoms. In view of the above, it is an object of the present invention to provide a continuous production method in which a copolyamide having little contamination and stable physical properties can be obtained with high production efficiency.
[0011]
[Means for Solving the Problems]
The present invention is a method for continuously producing a copolymerized polyamide from a diamine containing xylylenediamine as a main component and a dicarboxylic acid containing an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid having 6 to 12 carbon atoms,
(1) a slurry preparation step of obtaining a slurry in which an aromatic dicarboxylic acid is dispersed in a molten aliphatic dicarboxylic acid having 6 to 12 carbon atoms,
(2) Using a batch reactor capable of separating and removing water,
A diamine containing xylylenediamine as a main component is added to the dicarboxylic acid slurry, and a polycondensation reaction is performed with the molar ratio of the diamine and the dicarboxylic acid being a predetermined value. An initial polymerization step of increasing the degree of polymerization while separating and removing water to obtain a polyamide prepolymer having a relative viscosity of 1.4 to 2.7;
(3) The polyamide prepolymer is introduced into a continuous horizontal twin-screw reactor of a self-cleaning type 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 copolymerized polyamide. A continuous polymerization step of obtaining a copolymerized polyamide having a viscosity [RV] of 1.6 to 4.0.
[0012]
The present invention is (2) the method for continuously producing a copolymerized polyamide as described above, wherein a plurality of batch-type reactors are used in the initial polymerization step.
[0013]
The present invention is (3) the method for continuously producing a copolymerized polyamide as described above, wherein the average residence time in the late polymerization step is 1 to 30 minutes.
[0014]
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 produced.
[0015]
The present invention is the above-mentioned continuous production method of a copolymerized polyamide, wherein the diamine contains 70 to 100 mol% of xylylenediamine based on the diamine.
[0016]
The present invention is the above method for continuously producing a copolymerized polyamide, wherein the xylylenediamine contains 80 to 100 mol% of metaxylylenediamine based on xylylenediamine.
[0017]
In the present invention, the dicarboxylic acid contains an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid having 6 to 12 carbon atoms in a molar ratio of aromatic dicarboxylic acid / aliphatic dicarboxylic acid of 1/99 or more and less than 20/80. And a method for continuously producing the above-mentioned copolymerized polyamide.
[0018]
The present invention is the above method for continuously producing a copolymerized polyamide, wherein the diamine is meta-xylylenediamine, the aromatic dicarboxylic acid is phthalic acid, and the aliphatic dicarboxylic acid is adipic acid.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
First, the copolymerized polyamide produced by the continuous production method of the present invention will be described. The copolymerized polyamide is mainly composed of a diamine containing xylylenediamine as a main component and a dicarboxylic acid containing an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid having 6 to 12 carbon atoms.
[0020]
The aliphatic dicarboxylic acid having 6 to 12 carbon atoms as the dicarboxylic acid component may be any as long as it can obtain a molten state, and may be adipic acid, malonic acid, succinic acid, glutaric acid, sebacic acid, pimelic acid, speric acid, Azelaic acid, undecanoic acid, undecadionic acid, dodecadionic acid, dimer acid and the like can be mentioned. One or more of these aliphatic dicarboxylic acid components can be used. In addition, an alicyclic dicarboxylic acid can also be used as long as a molten state can be obtained.
[0021]
Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, orthophthalic acid, xylylenedicarboxylic acid, and naphthalenedicarboxylic acids. One or more of these aromatic dicarboxylic acid components can be used.
[0022]
In the present invention, the molar ratio of the aromatic dicarboxylic acid to the aliphatic dicarboxylic acid having 6 to 12 carbon atoms is represented by the molar ratio of aromatic dicarboxylic acid / aliphatic dicarboxylic acid, and is not less than 1/99 and less than 20/80. Is preferred. With the molar ratio in this range, for example, a copolymerized polyamide having good performance in gas barrier properties, fuel barrier properties, and solvent resistance can be obtained. Also, at the time of production, a slurry in which an aromatic dicarboxylic acid is uniformly dispersed in a molten aliphatic dicarboxylic acid is obtained in a slurry preparation step described later, and as a result, a preferable polycondensation reaction is performed. If the amount of the aromatic dicarboxylic acid is less than the above range, the effect of adding the aromatic dicarboxylic acid is small, and it is difficult to obtain a copolymer polyamide having good physical properties. On the other hand, when the amount of the aromatic dicarboxylic acid is larger than the above range, the viscosity of the obtained copolymerized polyamide at the time of melting becomes extremely high, and the fluidity is significantly reduced at a molding temperature usually used, resulting in poor productivity. Would. In addition, even during the production, in the slurry preparation step, the amount of the insoluble aromatic dicarboxylic acid becomes too large to obtain a uniformly dispersed slurry, and a favorable polycondensation reaction is not performed. A more preferred molar ratio depends on the purpose of the copolymerized polyamide, but in particular, considering fuel barrier properties, the aromatic dicarboxylic acid / aliphatic dicarboxylic acid is 3/97 or more and less than 20/80. 5/95 or more and less than 20/80.
[0023]
The diamine component contains xylylenediamine as a main component. Examples of xylylenediamine include meta-xylylenediamine, para-xylylenediamine and the like. In the present invention, xylylenediamine is preferably contained in an amount of 70 to 100 mol% based on the diamine. Further, it is preferable to contain 80 to 100 mol% of metaxylylenediamine based on xylylenediamine. By containing xylylenediamine, particularly meta-xylylenediamine in such a ratio, a copolymerized polyamide having excellent oxygen barrier properties and low water absorption can be obtained.
[0024]
Diamine components other than the above xylylenediamine include ethylene diamine, 1-methylethyl diamine, 1,3-propylene diamine, tetramethylene diamine, pentamethylene diamine, hexamethylene diamine, heptamethylene diamine, octamethylene diamine, nonamethylene diamine, deca Aliphatic diamines such as methylenediamine, undecamethylenediamine, dodecamethylenediamine, alicyclic diamines such as cyclohexanediamine, bis- (4,4-aminohexyl) methane, paraxylylenediamine, para-bis- ( Aromatic diamines such as 2-aminoethyl) benzene are exemplified. One or two or more of these diamine components can be appropriately used in an arbitrary ratio.
[0025]
In the production of the copolymerized 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. Lactams such as ε-caprolactam and laurolactam, aminocarboxylic acids such as aminocaproic acid and aminoundecanoic acid, and aromatic aminocarboxylic acids such as para-aminomethylbenzoic acid can also be used as the copolymerization component. In particular, use of ε-caprolactam is desirable.
[0026]
Examples of these copolymers include homopolymers such as polymetaxylylene adipamide, polymetaxylylene sebacamide, polymetaxylylene speramide, and the like, and metaxylylenediamine / adipic / isophthalic acid copolymer And a meta-xylylene / para-xylylene adipamide copolymer, a meta-xylylene / para-xylylene piperamide copolymer, and a meta-xylylene / para-xylylene azeramide copolymer.
[0027]
The relative viscosity [RV] of the copolymerized polyamide resin is in the range of 1.6 to 4.0 also from the viewpoint 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.
[0028]
The smaller the contamination (foreign matter) of the copolymerized polyamide resin, the better. When there is much contamination, the operability of the post-process is reduced or the quality is reduced.
[0029]
Next, a method for continuously producing a copolyamide 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 copolyamide of the present invention. In the example of FIG. 1, the continuous production method of the copolyamide comprises a dicarboxylic acid slurry preparation step and an initial polymerization step carried out in a batch polymerization tank (11), and a self-cleaning continuous horizontal biaxial reactor (41). In the latter stage of the polymerization.
[0030]
(Dicarboxylic acid slurry preparation step)
In this step, the aliphatic dicarboxylic acid having 6 to 12 carbon atoms is heated and melted at a temperature equal to or higher than its melting point to obtain a slurry in which the aromatic dicarboxylic acid is dispersed in the molten aliphatic dicarboxylic acid. It is preferable to melt the aliphatic dicarboxylic acid and to add the aromatic dicarboxylic acid to the molten aliphatic dicarboxylic acid because a more homogeneous slurry can be obtained.
[0031]
In the dicarboxylic acid slurry preparation step, an aliphatic dicarboxylic acid is charged and melted in a batch polymerization tank (11) also serving as a melting tank as illustrated in FIG. 1, and an aromatic dicarboxylic acid is added thereto. Good. Alternatively, the aliphatic dicarboxylic acid is charged and melted in a dedicated melting tank (not shown), and the molten aliphatic dicarboxylic acid is transferred from the melting tank to the batch polymerization tank (11), and the aromatic dicarboxylic acid is added therein. You may. Alternatively, an aliphatic dicarboxylic acid is charged and melted in a dedicated melting tank (not shown), and an aromatic dicarboxylic acid is added therein as a slurry, and the slurry is transferred to the batch polymerization tank (11) in the initial polymerization step. Is also good.
[0032]
The melting temperature of the aliphatic dicarboxylic acid is suitably not less than its melting point and not more than the melting point + 50 ° C. (temperature higher than the melting point by 50 ° C.). Setting the melting temperature to an unnecessarily high temperature is not preferable because it induces thermal decomposition and deterioration of the aliphatic 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.
[0033]
A predetermined amount of aromatic dicarboxylic acid is added to the molten aliphatic dicarboxylic acid to obtain a dicarboxylic acid slurry having a predetermined aromatic dicarboxylic acid / aliphatic dicarboxylic acid molar ratio. At this time, the above-mentioned melting temperature may be maintained.
[0034]
Further, in order to suppress the thermal oxidative decomposition and thermal decomposition of aliphatic dicarboxylic acid and aromatic dicarboxylic acid, the inside of the melting tank or the polymerization tank (11) during melting under an inert gas atmosphere, for example, under a nitrogen gas atmosphere. Preferably. 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.
[0035]
The atmospheric oxygen concentration at the time of melting the aliphatic dicarboxylic acid or preparing the slurry 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 the aliphatic dicarboxylic acid is 10 ppm or less, but when the oxygen concentration is 10 ppm or more, the obtained polyamide tends to have a strong yellow tint and degrade 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.
[0036]
In the present invention, the aliphatic 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 aliphatic dicarboxylic acid raw material is supplied to the melting tank or the polymerization tank (11). After the introduction, oxygen is removed and the atmosphere in the melting tank or the polymerization 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.
[0037]
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.
[0038]
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.
[0039]
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.
[0040]
(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 dicarboxylic acid in a slurry state to increase the degree of polymerization while separating and removing water. It is a process.
[0041]
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.
[0042]
Diamine is added to the dicarboxylic acid in a slurry state 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. In the slurry preparation step, a homogeneous dicarboxylic acid slurry is obtained, and the amidation reaction proceeds favorably for both the aliphatic dicarboxylic acid and the aromatic dicarboxylic acid.
[0043]
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 copolymerized 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 polycondensation reaction temperature in the initial polymerization step is, for example, the internal temperature is not less than the melting point (Tm) of the finally obtained copolymerized polyamide and not more than Tm + 35 ° C, preferably not more than Tm + 15 ° C, more preferably not more than Tm + 5 ° C. is there. 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.
[0044]
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).
[0045]
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.
[0046]
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.
[0047]
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.
[0048]
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.
[0049]
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.
[0050]
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.
[0051]
(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 copolymerized polyamide. To obtain a copolymerized polyamide having a relative viscosity [RV] of
[0052]
As a continuous reaction device in the latter polymerization step, a self-cleaning horizontal twin-screw reaction device (41) is used.
[0053]
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.
[0054]
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 type horizontal twin-screw reactor, the clearance between the blades changes depending on the size of the device, but the inner volume of the reactor is 0.15 m. ^Three In this case, the clearance between the wings is preferably less than 50 mm, more preferably less than 20 mm, very preferably less than 10 mm.
[0055]
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 device, the inner volume of the reactor is 0.15 m. ^Three In this case, the clearance between the wing and the inner wall is preferably less than 15 mm, more preferably less than 10 mm, very preferably less than 5 mm.
[0056]
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.
[0057]
The reaction conditions in the latter polymerization step vary depending on the type of the copolymerized polyamide and the desired relative viscosity [RV], but the resin temperature is from the melting point (Tm) to Tm + 80 ° C of the copolymerized polyamide, preferably from the melting point to Tm + 70 ° C or less. . 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.
[0058]
The average residence time in the continuous reactor varies depending on the type of the copolymerized polyamide, the desired relative viscosity [RV], the degree of vacuum, the addition of an acid anhydride compound described below, the purge of an inert gas described later, and the like. It is preferably for about 30 minutes. If the average residence time is less than 1 minute, it is difficult to obtain a copolymerized polyamide having an [RV] in the range of 1.6 to 4.0. Conversely, if the average residence time exceeds 30 minutes, continuous polymerization of the polymer will occur. It is necessary to reduce the amount of supply to the apparatus, resulting in a significant decrease in productivity. A desirable average residence time is 1.5 to 25 minutes, more preferably 2 to 20 minutes.
[0059]
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. .
[0060]
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.
[0061]
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.
[0062]
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.
[0063]
A desirable control method of [RV] for a polyamide containing adipic acid / phthalic acid / meta-xylylenediamine 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.
[0064]
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.
[0065]
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.
[0066]
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.
[0067]
【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.
[0068]
(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.
[0069]
[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.
[0070]
3.40 kg of adipic acid 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 was purged with nitrogen. The mixture was heated under stirring while flowing a small amount of nitrogen, and the temperature was raised to 170 ° C. to melt adipic acid. Then, while stirring the molten adipic acid, 0.68 kg of terephthalic acid was added to form a slurry. Next, 3.74 kg of meta-xylylenediamine was continuously dropped from the dropping tank (12) under normal pressure over 3 hours. 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.
[0071]
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. The RV of the obtained polyamide prepolymer was 1.85. 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.
[0072]
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, cooled with water, and granulated to continuously obtain copolymerized polyamide resin chips. The RV of the obtained copolymerized polyamide resin was 2.25.
[0073]
[Example 2]
The same reaction apparatus as in Example 1 was used.
3.80 kg of adipic acid was charged into a 20-liter stainless steel reaction vessel (11) equipped with a stirrer, a nitrogen gas introduction pipe, a pressure reducing valve, a 1.3 MPa steam introduction pipe, and a diamine dropping tank, and the atmosphere was replaced with nitrogen. The mixture was heated under stirring while flowing a small amount of nitrogen, and the temperature was raised to 170 ° C. to melt adipic acid. Then, while stirring the molten adipic acid, 0.23 kg of terephthalic acid was added to form a slurry. Next, 3.73 kg of meta-xylylenediamine was continuously dropped from the dropping tank (12) under normal pressure over 3 hours. 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.
[0074]
Subsequent steps were performed in the same manner as in Example 1. The RV of the obtained polyamide prepolymer was 1.76, and the RV of the obtained copolyamide resin was 2.15.
[0075]
[Comparative Example 1]
The same reactor as in Example 1 was used, but the production was carried out by a salt forming method.
4.66 kg of water was charged into a jacketed 20 L stainless steel reaction vessel (11) equipped with a stirrer, a nitrogen gas introduction pipe, a pressure reducing valve, a 1.3 MPa steam introduction pipe and a diamine dropping tank, and then meta-xylylenediamine 1.52 kg, 1.38 kg of adipic acid and 0.28 kg of terephthalic acid were respectively charged, and the internal temperature was raised to 135 ° C. to prepare a completely dissolved salt aqueous solution. Next, the mixture was heated in a sealed state, and the temperature was raised to 190 ° C. with stirring. At this time, the internal pressure was 1.0 MPa, and the temperature raising time required 1 hour. Next, the amidation reaction was allowed to proceed for 5 hours while maintaining the above temperature to remove water. Thereafter, pressure release was started, and the mixture was stirred for 10 minutes after the pressure reached 0.3 MPa to perform initial polymerization to obtain a polyamide prepolymer. The RV of the obtained polyamide prepolymer was 1.90. 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.
[0076]
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, cooled with water, and granulated to obtain copolymerized polyamide resin chips. The RV of the obtained copolymerized polyamide resin was 2.31.
[0077]
[Table 1]

[0078]
Table 1 shows the properties of the copolymerized polyamide and the polyamide prepolymer obtained in Examples and Comparative Examples. In each of Examples 1 and 2, the operation was good, and a copolymerized polyamide having excellent physical property values was obtained.
[0079]
In Table 1, the polymerization time (hr) means the time from the start of the polymerization reaction to chipping, and does not include the time required for salt preparation in Comparative Example 1.
[0080]
Table 1 shows the efficiency (%) according to the following equation as an index of the production efficiency per capacity of the reaction vessel.
Efficiency (%) = (weight of polymer removed / total weight of raw material) × 100
Here, the total weight of the raw materials includes water used in Comparative Example 1.
[0081]
In Comparative Example 1, a large amount of energy and time were required to remove water used for salt formation to the outside of the reaction system. It is also clear that the production efficiency per capacity of the reaction vessel is poor.
[0082]
【The invention's effect】
According to the present invention, a copolyamide mainly composed of a diamine containing xylylenediamine as a main component and a dicarboxylic acid containing an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid having 6 to 12 carbon atoms, in good quality. Continuous production can be performed with good production efficiency. This copolymerized polyamide has excellent gas barrier properties, fuel barrier properties, and solvent resistance, and is suitably used as a material for molded articles such as gasoline tank materials, beverage bottles, hollow molded containers, films, sheets, and the like.
[Brief description of the drawings]
FIG. 1 is a flowchart showing a schematic process of a continuous production method of a copolyamide of the present invention.
[Explanation of symbols]
(11): Dicarboxylic acid slurry preparation 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 (7)

A method for continuously producing a copolyamide from a diamine containing xylylenediamine as a main component and a dicarboxylic acid containing an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid having 6 to 12 carbon atoms,
(1) a slurry preparation step of obtaining a slurry in which an aromatic dicarboxylic acid is dispersed in a molten aliphatic dicarboxylic acid having 6 to 12 carbon atoms,
(2) Using a batch reactor capable of separating and removing water,
A diamine containing xylylenediamine as a main component is added to the dicarboxylic acid slurry, and a polycondensation reaction is performed with the molar ratio of the diamine and the dicarboxylic acid being a predetermined value. An initial polymerization step of increasing the degree of polymerization while separating and removing water to obtain a polyamide prepolymer having a relative viscosity of 1.4 to 2.7;
(3) The polyamide prepolymer is introduced into a continuous horizontal twin-screw reactor of a self-cleaning type 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 copolymerized polyamide. A continuous polymerization step of obtaining a copolymerized polyamide having a viscosity [RV] of 1.6 to 4.0. (2) The method for continuously producing a copolymerized polyamide according to claim 1, wherein a plurality of batch type reactors are used in the initial polymerization step. (3) The method for continuously producing a copolyamide according to claim 1 or 2, wherein the average residence time in the latter polymerization step is 1 to 30 minutes. (3) The relative viscosity [RV] of the polyamide is controlled 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. A method for continuously producing the copolymerized polyamide according to any one of claims 1 to 3. The method for continuously producing a copolyamide according to any one of claims 1 to 4, wherein the diamine contains 70 to 100 mol% of xylylenediamine based on the diamine. The method for continuously producing a copolymerized polyamide according to any one of claims 1 to 5, wherein the xylylenediamine contains 80 to 100 mol% of metaxylylenediamine based on xylylenediamine. The dicarboxylic acid contains an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid having 6 to 12 carbon atoms in a molar ratio of aromatic dicarboxylic acid / aliphatic dicarboxylic acid of 1/99 or more and less than 20/80. 7. A continuous production method of the copolymerized polyamide according to any one of the above-mentioned items.

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