JP4151354B2 - Continuous production method of polyamide - Google Patents

Description

【００９２】
【発明の効果】
本発明によれば、品質の良好なポリアミド、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、酸素バリヤー性に優れ、色調が良好であり且つ吸水率の小さいメタキシリレンジアミンをジアミン成分とするポリアミドが連続的に製造される。このメタキシリレンジアミンを成分として含むポリアミドは、ポリエチレンテレフタレートなどの異種ポリマーの改質にも使用できる。
【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】
(1) ：原料調合工程
(2) ：アミド化工程
(21)：管状反応装置
(3) ：初期重合工程
(4) ：後期重合工程
(41)：セルフクリーニング方式の横型二軸反応装置[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a continuous process for producing a polyamide of good quality. The continuous production method of the present invention can be applied to both aliphatic polyamides and aromatic-containing polyamides, but is preferably applicable to aromatic-containing polyamides that are more difficult to produce.
[0002]
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. In particular, polyamides containing metaxylylenediamine as a diamine component can be used for films, sheets, packaging bags, bottles and the like having excellent oxygen barrier properties. The polyamide can also be used to improve the oxygen barrier properties of other polymers by blending with other polymers with low oxygen barrier properties, such as polyethylene terephthalate.
[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 a large dimensional change between water absorption / moisture absorption and drying, and also have the disadvantages that they are too soft because of their aliphatic properties, and there is a need for higher performance polyamide resins. ing. Against this background, high performance of polyamide resins has been achieved by copolymerizing aromatic dicarboxylic acids such as TPA (terephthalic acid) and IPA (isophthalic acid) with conventional aliphatic polyamides. For example, Japanese Patent Laid-Open Nos. 59-155426 and 62-156130 disclose polyamide resins copolymerized with TPA or IPA.
[0005]
However, in general, introduction of an aromatic ring into a polyamide skeleton leads to higher melting point and higher melt viscosity, and the temperature conditions during polyamide production become more severe. Generation and thermal degradation are further promoted. As a result, the gelled product is deposited in the polymerization reactor and the cleaning frequency is increased, or the gelled product is mixed into the resin, or the physical properties are deteriorated 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 manufacturing 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, for the purpose of avoiding prolonged residence at high temperatures, The initial condensate is taken out as a prepolymer and subjected to solid phase polymerization at a temperature below the melting point of the polymer to suppress thermal decomposition / deterioration. However, these are all batch-type production methods, which are not preferable in terms of production efficiency, and are likely to cause quality differences between batches.
[0007]
In JP 2001-200052 A, 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 the amidation reaction, Thus, there is disclosed a continuous process for producing a polyamide comprising a step of increasing the degree of polymerization of the polyamide while separating and removing the condensed water produced 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]
Japanese Patent Publication No. 2002-516366 discloses a continuous production method of nylon 66. According to the publication, an equimolar amount of molten dicarboxylic acid and molten diamine are mixed to form a molten reaction mixture, and the reaction mixture is passed through a reaction apparatus (static in-line mixer) that does not vent the polyamide and condensed water. Forming a first product stream containing, supplying the first product stream to an aerated tank reactor, removing condensed water and forming a second product stream containing 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 polyamide production is used as an aerated reactor, the corresponding range of viscosity that can be produced. Is narrow.
[0009]
On the other hand, due to the recent increase in interest in environmental sanitation, the aim was to obtain long-term storage stability by suppressing changes in taste, flavor, and efficacy due to oxygen in applications such as food, beverages, pharmaceuticals, and cosmetics. Oxygen barrier materials have been developed. Examples of the oxygen barrier material include polyvinyl alcohol, polyvinylidene fluoride, and polyvinylidene chloride.
[0010]
However, these materials have excellent oxygen barrier properties, but have problems with food hygiene, harmful gases during combustion, or compatibility with other materials such as polyethylene terephthalate. Furthermore, it has a drawback that its application is limited.
[0011]
Against this background, polyamides having metaxylylenediamine (MXD) as a diamine component, for example, polymetaxylylene adipamide (MXD6), which is a polyamide with adipic acid (ADA), has excellent oxygen barrier properties. Has attracted attention as a material.
[0012]
However, it is known that a polyamide using metaxylylenediamine as a raw material is a polymer that easily undergoes thermal deterioration and coloring. The reason for this is thought to be that the methylene group part of metaxylylenediamine readily generates radicals by oxygen or heat, but it has not been elucidated yet. Therefore, development of a method capable of producing a polyamide having metaxylylenediamine (MXD) as a diamine component without causing thermal deterioration or coloring is desired.
[0013]
[Problems to be solved by the invention]
An object of the present invention is to provide a continuous process for producing polyamides of good quality, especially aromatic-containing polyamides. In particular, the object of the present invention is suitable for films, sheets, packaging bags, bottles, etc. in applications such as foods, beverages, pharmaceuticals, and cosmetics, and has excellent oxygen barrier properties, good color tone, and low water absorption. An object of the present invention is to provide a continuous production method of polyamide using metaxylylenediamine as a diamine component.
[0014]
[Means for Solving the Problems]
The present invention is a continuous process for producing a polyamide mainly comprising a diamine component unit and a dicarboxylic acid component unit,
(1) A raw material preparation step in which diamine and dicarboxylic acid are individually melted or a salt of amine and carboxylic acid is produced in water,
(2) an amidation step in which the prepared raw material is continuously introduced into and passed through a tubular reactor for amidation to obtain a reaction mixture containing an amidation product and condensed water;
(3) The reaction mixture is introduced into a continuous reactor capable of separating and removing water, and the degree of polymerization is increased while separating and removing water at a temperature equal to or higher than the melting point of the finally obtained polyamide to obtain a polyamide prepolymer. An initial polymerization step;
(4) The polyamide prepolymer is introduced into a continuous reactor capable of separating and removing water, and the degree of polymerization is further increased at a temperature above the melting point of the finally obtained polyamide, In the range of 1.6-4.0 A late polymerization step for obtaining a polyamide having a relative viscosity [RV],
Prior to the amidation step, an alkali metal compound and a phosphorus compound are added so that the molar ratio of alkali metal to phosphorus (alkali metal / phosphorus) is 1.2 or more and 3.5 or less. It is.
[0015]
The present invention is the above continuous process for producing a polyamide, wherein the polyamide contains metaxylylenediamine (MXD) as a diamine component, and metaxylylenediamine (MXD) is at least 70 mol% based on the diamine component. .
[0016]
The present invention is (4) the continuous production method of polyamide, wherein the continuous reaction apparatus in the late polymerization step is a horizontal reaction apparatus. The present invention is (4) the continuous production method of polyamide, wherein the continuous reaction apparatus in the late polymerization step is a self-cleaning horizontal biaxial reaction apparatus.
[0017]
The present invention is the above continuous production method of polyamide, wherein the average residence time in the late polymerization step (4) is 1 to 30 minutes.
[0019]
The present invention provides (4) the polyamide described above, wherein the relative viscosity [RV] of the polyamide is controlled by purging the inert gas, adjusting the degree of vacuum of the reactor, or a combination thereof in the late polymerization step This is a continuous production method.
[0020]
The present invention is the above-described continuous production method of polyamide, wherein (1) in the raw material preparation step, the oxygen concentration at the time of raw material preparation is 10 ppm or less.
[0021]
Further, the present invention provides the tubular reactor in the (2) amidation step, wherein L / D is 50 or more, where the inner diameter of the tube is D (mm) and the length of the tube is L (mm). The continuous production method of the polyamide.
[0022]
The present invention is the above continuous production method of polyamide, wherein the average residence time in the (2) amidation step is 10 to 120 minutes.
[0023]
In the present invention, (2) the shear rate (γ) in the amidation step is 0.1 (1 / sec) or more, and the shear stress (τ) is 1.5 × 10 ^-Five It is a continuous production method of the above-mentioned polyamide which is Pa or more.
[0024]
The present invention is the method for continuously producing a polyamide described above, wherein (2) in the amidation step, the relative viscosity [RV] of the reaction mixture is increased by 0.05 to 0.6.
[0025]
The present invention is the above continuous production method of polyamide, wherein the average residence time in the initial polymerization step (3) is 10 to 150 minutes.
[0026]
DETAILED DESCRIPTION OF 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 both aliphatic polyamides and aromatic-containing polyamides, but can be preferably applied to polyamides containing 70 mol% or more of metaxylylenediamine (MXD) as an amine component.
[0027]
It is important from the viewpoint of oxygen barrier properties and water absorption that the polyamide contains at least 70 mol% of metaxylylenediamine based on the diamine component. The smaller the amount of metaxylylenediamine, the more advantageous in terms of thermal deterioration and color tone, but 70 mol% or more is necessary from the viewpoint of oxygen barrier properties, and preferably 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 compared to aliphatic polyamides such as nylon 6 and nylon 66. However, it is also possible to further improve water absorption by copolymerizing aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid.
[0028]
In the case of copolymerizing an aromatic dicarboxylic acid, in the case of terephthalic acid, the amount is preferably 5 to 50 mol%, more preferably 5 to 40 mol% based on the dicarboxylic acid component. In the case of isophthalic acid, it is preferably 15 to 50 mol%, more preferably 20 to 40 mol% based on the dicarboxylic acid component.
[0029]
By setting the copolymerization amount of the aromatic dicarboxylic acid within the above range, a sufficient effect of improving water absorption can be expected. When the copolymerization amount exceeds the above range, the polymerization conditions become more severe due to the higher melting point and the higher melt viscosity, and this tends to cause deterioration in physical properties and color tone due to thermal decomposition.
[0030]
Desirable polyamides include hexamethylenediamine (HMDA) as another diamine component and adipic acid (ADA) as a dicarboxylic acid component, provided that the diamine component contains 70% by mole or more of metaxylylenediamine (MXD). , A polyamide composed of a combination of components arbitrarily selected from isophthalic acid (IPA), terephthalic acid (TPA), and ε-caprolactam (CLM) as a lactam component. In particular, polyamides composed of combinations of ADA-MXD, ADA-IPA-MXD, ADA-TPA-MXD, ADA-TPA-MXD-HDM, ADA-IPA-MXD-HMD, and TPA-MXD-CLM are preferable.
[0031]
In the production of the polyamide of the present invention, it is also possible to copolymerize raw materials capable of forming a polyamide other than the diamines, dicarboxylic acids and lactams as necessary from the viewpoint of performance required for the polyamide.
[0032]
Examples of the diamine component include ethylenediamine, 1-methylethyldiamine, 1,3-propylenediamine, tetramethylenediamine, pentamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine, dodeca Aliphatic diamines such as methylenediamine are exemplified, and other examples include cyclohexanediamine, bis- (4,4′-aminohexyl) methane, and paraxylylenediamine.
[0033]
Dicarboxylic acid components include malonic acid, succinic acid, glutaric acid, sebacic acid, pimelic acid, speric acid, azelaic acid, undecanoic acid, undecadioic acid, dodecadioic acid, dimer acid and other aliphatic dicarboxylic acids, 1,4-cyclohexane Examples thereof include dicarboxylic acid, paraxylylene dicarboxylic acid, metaxylylene dicarboxylic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid and the like.
[0034]
In addition to the diamine and dicarboxylic acid components, lactams such as laurolactam, aminocaproic acid, and aminoundecanoic acid, and aminocarboxylic acids can also be used as the copolymerization component.
[0035]
The relative viscosity [RV] of the polyamide resin is in the range of 1.6 to 4.0 from the viewpoint of physical and mechanical properties and operational stability of the obtained molded article. And When [RV] is less than 1.6, the obtained molded product is not only inferior in mechanical properties, but also causes vent-up, makes it difficult to take out a polymer strand, and causes cracking during chip formation. The effect tends to increase. On the other hand, when [RV] exceeds 4.0, the melt viscosity becomes high and the molding conditions become more severe, so that there is a tendency that it is difficult to obtain a molded product of stable quality. Product physical properties that meet the required effort cannot be expected. In order to achieve a high [RV] exceeding 4.0, it is necessary to increase the purge amount of the inert gas or to apply a high degree of vacuum, which leads to operational instability such as cost increase and vent up. Absent. More desirable [RV] is 1.9 to 3.8.
[0036]
The smaller the value of the color tone [Co-b] of the polyamide resin, the less yellowish the color tone means. If [Co-b] is generally in the range of -3 to 3, there is no problem as a product. When [Co-b] is less than -3, the difference in color tone obtained is out of the visible range and is not meaningful compared to the labor required to achieve it. On the other hand, when [Co-b] exceeds 3, yellowishness increases, and even if it becomes a product, the deterioration of the color tone is clearly visible. Desirable [Co-b] is in the range of -2.5 to 2.8.
[0037]
The water absorption rate of the polyamide resin is an index indicating the degree of dimensional change of the molded body between the time of drying and the time of moisture absorption. Since a dimensional change will become large if a water absorption is high, it is so desirable that a water absorption is small. The water absorption is desirably 7% or less, and more desirably 6.7% or less. Since the lower the water absorption rate, the better the dimensional stability, the lower limit of the water absorption rate is not particularly defined. However, it is technically difficult to obtain a polyamide having a water absorption rate of 3.5% or less due to the inherent properties of the polyamide.
[0038]
Next, the continuous manufacturing method of the polyamide of this invention is demonstrated, referring FIG. FIG. 1 is a flowchart showing the schematic steps of the continuous production method for polyamide of the present invention. In FIG. 1, the polyamide continuous production method includes a raw material preparation step (1), an amidation step (2), an initial polymerization step (3), and a late polymerization step (4).
[0039]
Raw material preparation process
In the raw material preparation step, diamine and dicarboxylic acid are individually melted, and each molten monomer is directly supplied to the amidation step. A salt of amine and carboxylic acid is formed in water, and an aqueous salt solution is prepared. There is a method of supplying to the amidation step.
[0040]
1. Direct supply of molten monomer
The raw material preparation equipment consists of a dicarboxylic acid melting tank (11), its molten liquid storage tank (12) and supply pump (15), and a diamine melting tank (13), its molten liquid storage tank (14) and supply. It consists mainly of a pump (16). FIG. 1 illustrates this case.
[0041]
The melting temperature and storage temperature of the dicarboxylic acid are suitably not lower than the melting point and not higher than the melting point + 50 ° C. (temperature higher by 50 ° C. than the melting point). Making the melting temperature and storage temperature higher than necessary is undesirable because it induces thermal decomposition and deterioration of the raw material. On the other hand, if the temperature is too low, non-uniform melting occurs, and the raw material supply accuracy to the amidation process deteriorates, which is not preferable. Desirable melting temperature and storage temperature are melting point + 5 ° C. or higher and melting point + 25 ° C. or lower. The same applies to diamines, and the melting temperature and storage temperature of diamines are suitably higher than the melting point and lower than melting point + 50 ° C., and preferably higher than melting point + 5 ° C. and higher than melting point + 25 ° C.
[0042]
For any of the dicarboxylic acids and diamines, it is preferable to place the melting tank and the storage tank at the time of raw material preparation in an inert gas atmosphere, for example, a nitrogen gas atmosphere, in order to suppress thermal oxidative decomposition and thermal decomposition. At this time, it is preferable to place in an inert gas atmosphere under pressure of 0.05 to 0.8 MPa, desirably 0.1 to 0.6 MPa, in order to prevent mixing of outside air.
[0043]
In the raw material preparation step, an alkali metal and a phosphorus compound are used as a polymerization catalyst for the purpose of suppressing the decomposition of the polyamide, and the dicarboxylic acid is adjusted so that the molar ratio of alkali metal to phosphorus (alkali metal / phosphorus) is 1.2 or more and 3.5 or less. Add to the acid bath or diamine bath. Usually, it is good to add to the melting tank of dicarboxylic acid.
[0044]
The alkali metal compound used is a lithium compound, a sodium compound, a potassium compound or the like, and a sodium compound is most preferable. As the phosphorus compound, phosphoric acid, phosphorous acid, hypophosphorous acid, pyrophosphoric acid, metaphosphoric acid, polyphosphoric acid and salts thereof are used. In addition, both the alkali metal compound and the phosphorus compound must be used. If the alkali metal / phosphorus molar ratio is within the above range, one compound such as an alkali metal phosphate is used. You may use only.
[0045]
When the alkali metal / phosphorus molar ratio exceeds 3.5, the amidation reaction is slowed and the productivity is deteriorated. Conversely, when the molar ratio is less than 1.2, the reaction rate increases, but side reactions other than the amidation reaction increase and the quality of the polyamide deteriorates. A desirable alkali metal / phosphorus molar ratio is 1.3 or more and 3.4 or less, and more desirably 1.4 or more and 3.3 or less. The amount of the phosphorus compound used is preferably in the range of 10 to 600 ppm (weight), more preferably in the range of 20 to 400 ppm (weight) with respect to the product polyamide. The amount of the alkali metal compound to be used is selected so as to satisfy the above molar ratio in the case of such a phosphorus compound amount.
[0046]
The dicarboxylic acid and the diamine thus prepared are individually supplied to the amidation step by the respective raw material supply pumps and mixed at the inlet of the amidation step. At this time, the supply accuracy of both raw materials to the amidation process is important, and it is important that the accuracy of the raw material supply pump is within 2%, and more preferably within 1.5%. If the supply accuracy is outside the above range, the polymerization reaction of the polyamide is greatly affected, making it difficult to control the reaction after the amidation step, and adverse effects on operability such as venting up and clogging of the condenser are also large. In some cases, the desired degree of polymerization may not be reached. As the material supply pump, it is desirable to use a plunger pump.
[0047]
2. Salt formation method
The salt forming method is advantageous for producing a polyamide using a dicarboxylic acid having no melting point such as terephthalic acid or isophthalic acid as a raw material. The raw material preparation equipment mainly consists of a salt formation tank, a storage tank of the obtained salt aqueous solution, and a supply pump.
[0048]
The salt formation tank is an equipment for uniformly mixing dicarboxylic acid, diamine, lactam, aminocarboxylic acid and the like, which are polyamide raw materials, in water to form an aminocarboxylate solution. In this salt formation step, the molar ratio of amino group to carboxyl group can be arbitrarily adjusted according to the desired product properties. However, if the amino group / carboxyl group is deviated more than 1 (molar ratio), the desired polyamide [RV] cannot be obtained. This is not preferable.
[0049]
At the time of preparing the raw material, an alkali metal and a phosphorus compound are used for the purpose of suppressing the decomposition of the polyamide and as a polymerization catalyst so that the molar ratio of alkali metal to phosphorus (alkali metal / phosphorus) is 1.2 or more and 3.5 or less. Add to the forming tank. The kind and amount of the alkali metal compound and phosphorus compound used, the preferred molar ratio of alkali metal / phosphorus, and the like are as described in the method for directly supplying the molten monomer.
[0050]
The salt concentration of the aminocarboxylate salt produced in the salt forming step varies depending on the type of polyamide and is not particularly limited, but it is generally preferably 30 to 90% by weight. If the salt concentration exceeds 90% by weight, the salt may precipitate due to slight fluctuations in temperature and clog the piping. Also, since the solubility of the salt needs to be increased, the equipment must be of high temperature and high pressure resistance. This is disadvantageous in terms of cost. On the other hand, when the salt concentration is less than 30% by weight, not only is the amount of water evaporated after the initial polymerization step increased, which is disadvantageous in terms of energy, but also causes an increase in cost due to a decrease in productivity. A desirable salt concentration is 35 to 85% by weight.
[0051]
The conditions in the salt forming step vary depending on the type of polyamide and the salt concentration, but in general, the temperature is in the range of 60 to 180 ° C., and the pressure is in the range of 0 to 1 MPa. When the temperature exceeds 180 ° C., or when the pressure exceeds 1 MPa, the equipment has a high temperature and high pressure resistance specification, so that the equipment cost increases, which is disadvantageous. Conversely, when the temperature is less than 60 ° C. or the pressure is less than 0 MPa, it not only causes trouble such as clogging of piping due to salt precipitation, but also makes it difficult to increase the salt concentration. It will cause a decline. Desirable conditions are a temperature of 70 to 170 ° C. and a pressure of 0.05 to 0.8 MPa, more preferably 75 to 165 ° C. and 0.1 to 0.6 MPa.
[0052]
The salt solution storage tank basically has no problem unless salt is precipitated, and the conditions of the salt formation step can be applied as they are.
[0053]
The salt aqueous solution thus prepared is continuously supplied to the amidation step by a supply pump. The feed pump used here must be excellent in quantitativeness. The fluctuation in the supply amount is a process fluctuation in the amidation process, and as a result, an unstable quality polyamide having a large relative viscosity [RV] deviation is obtained. In this sense, it is recommended to use a plunger pump with excellent quantitativeness as the supply pump.
[0054]
3. Oxygen concentration during raw material preparation
The atmospheric oxygen concentration at the time of raw material preparation greatly affects the color tone of the resulting polyamide. In particular, this tendency is remarkable for polyamides using metaxylylenediamine as a raw material. There is no problem if the atmospheric oxygen concentration at the time of raw material preparation is 10 ppm or less, but when the oxygen concentration is 10 ppm or more, the yellowness of the obtained polyamide tends to be strong and the quality of the product tends to deteriorate. 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 process becomes more complicated than necessary, and the color tone and other There is almost no effect on the physical properties. A desirable oxygen concentration range is 0.05 ppm or more and 9 ppm or less, and more desirably 0.05 ppm or more and 8 ppm or less.
[0055]
In the present invention, the raw material is supplied to a mixing tank (melting tank or raw material salt forming tank) in which oxygen is previously removed and the oxygen concentration is 10 ppm or less, or the raw material is charged into the mixing tank (melting tank or raw material salt forming tank). Oxygen is removed later, the atmosphere in the mixing tank is adjusted to an oxygen concentration of 10 ppm or less, or both may be used in combination. This may be selected in terms of equipment or operation. Moreover, it is also preferable that the atmosphere in a storage tank shall be 10 ppm or less of oxygen concentration.
[0056]
As a method for removing oxygen, there are a vacuum replacement method, a pressure replacement method, or a combination thereof. The degree of vacuum or pressure applied to the substitution and the number of substitutions may be selected under the most efficient conditions for achieving the desired oxygen concentration.
[0057]
Amidation process
In the amidation step, the raw material prepared in the raw material preparation step is continuously introduced into and passed through the tubular reactor (21) to perform polycondensation amidation, and a reaction that includes an amidation product with a low polymerization degree and condensed water. A mixture is obtained. In the tubular reactor (21), water is not separated and removed.
[0058]
When the raw material preparation step is a direct supply method of molten monomer, the molten dicarboxylic acid and the molten diamine are separately supplied by respective raw material supply pumps (15) and (16), and the inlet of the tubular reactor (21) ( Mixed in 22).
[0059]
The tubular reactor (21) preferably has an L / D of 50 or more, where the inner diameter of the tube is D (mm) and the length of the tube is L (mm). The tubular reactor has advantages such as no need for liquid level control due to its structure, high plug flow properties, excellent pressure resistance, and low equipment costs. When L / D is less than 50, when L is small, the residence time of the reaction mixture flow is shortened, and the degree of increase in relative viscosity [RV] is small. On the other hand, when D is large, plug flow properties are small and the residence time is low. A time distribution is created and the desired function is not performed. The upper limit of L / D is not particularly defined, but is about 3000 in consideration of the residence time and the degree of increase in relative viscosity [RV]. L / D is more preferably 60 or more for the lower limit, further preferably 80 or more, more preferably 2000 or less for the upper limit, and further preferably 1000 or less. Further, L is preferably 3 m or more for the lower limit, more preferably 5 m or more, and preferably 50 m or less, more preferably 30 m or less for the upper limit.
[0060]
The reaction conditions in the tubular reactor (21) vary depending on the structure of the polyamide and the desired degree of polymerization. For example, the internal temperature is 110 to 310 ° C., the internal pressure is 0 to 5 MPa, and the average residence time of the reaction mixture in the tube The time is 10 to 120 minutes. The degree of polymerization of the amidation product can be controlled by the internal temperature, internal pressure and average residence time.
[0061]
When the average residence time is shorter than 10 minutes, the degree of polymerization of the amidation product having a low degree of polymerization is lowered, and as a result, entrainment, vent-up, and the like are likely to occur in the post-process, resulting in unstable operation. On the other hand, when the average residence time is longer than 120 minutes, amidation reaches equilibrium, and the rise in [RV] reaches a peak, while thermal deterioration proceeds, which is not preferable. A desirable average residence time is 12 to 110 minutes, and more desirably 15 to 100 minutes. The average residence time can be controlled by adjusting the inner diameter D of the tube of the tubular reactor, the length L of the tube, or changing the raw material supply amount.
[0062]
The relative viscosity [RV] of the reaction mixture is increased by 0.05 to 0.6 at the inlet (22) and the outlet (23) of the tubular reactor (21) by the polycondensation reaction in the amidation step. It is preferable. When the increase in [RV] is less than 0.05, the degree of polymerization of the amidation product is low, as in the case where the residence time is short, and therefore, entrainment, vent-up, and the like are likely to occur in the subsequent process, leading to unstable operation. On the other hand, when the increase in [RV] is greater than 0.6, thermal degradation tends to proceed due to the influence of coexisting condensed water (in the case of a salt forming method, water used for salt formation and condensed water). In addition, a reaction mixture having an excessively high viscosity causes piping blockage, which may adversely affect the operation. A desirable range of increase in [RV] in the amidation step is 0.15 to 0.5, and more desirably 0.2 to 0.4.
[0063]
In order to guarantee the plug flow property in the amidation step, the shear rate (γ) is 0.1 (1 / sec) or more and the shear stress (τ) is 1.5 × 10. ^-Five It is preferable that it is Pa or more. If either one of the shear rate and the shear stress is lower than the above value, the residence time distribution of the reaction mixture may be widened, and the polyamide may be colored or may cause process fluctuations. Desirable shear rate (γ) is 0.3 or more, and shear stress (τ) is 2.0 × 10 ^-Five Pa or higher. These upper limits are not particularly defined, but are usually a shear rate (γ) of 100 (1 / sec) or less and a shear stress (τ) of 3 × 10. ^-2 Pa or less.
[0064]
Initial polymerization process
In the initial polymerization step, the reaction mixture containing the amidation product having a low degree of polymerization from the amidation step and condensed water is introduced into a continuous reaction apparatus capable of separating and removing water, and finally the polyamide obtained. While separating and removing water at a temperature equal to or higher than the melting point, the degree of polymerization is increased to obtain a polyamide prepolymer.
[0065]
In the initial polymerization step, equipment such as a vertical stirring tank and a centrifugal thin film evaporator can be applied, but a vertical stirring tank (31) in which the reaction conditions are easily controlled can be preferably used. The vertical stirring tank (31) continuously receives the reaction mixture from the amidation process outlet (23) and is equipped with a water separation / removal device (32), and continuously removes the polyamide prepolymer from its bottom (33). It is configured to discharge.
[0066]
The reaction conditions in the initial polymerization step are, for example, that the internal temperature is not lower than the melting point (Tm) of the finally obtained polyamide and not higher than Tm + 90 ° C., the internal pressure is 0 to 5 MPa, and the average residence time is 10 to 150 minutes. Desirable reaction conditions are an internal temperature of not less than the melting point (Tm) of the polyamide and Tm + 80 ° C., an internal pressure of 0 to 4 MPa, an average residence time of 15 to 140 minutes, and a more desirable reaction condition is that the internal temperature is a polyamide. The melting point (Tm) is Tm + 70 ° C., the internal pressure is 0 to 3.5 MPa, and the average residence time is 20 to 130 minutes. If the reaction condition is out of the above range, it is not preferable that the degree of polymerization reached is too low, or that heat deterioration and productivity decrease. The degree of polymerization of the polyamide prepolymer can be controlled by the internal temperature, internal pressure and average residence time.
[0067]
Late polymerization process
In the late polymerization step, the polyamide prepolymer from the initial polymerization step is introduced into a continuous reactor capable of separating and removing water, and the degree of polymerization is further increased at a temperature above the melting point of the finally obtained polyamide. In the range of 1.6-4.0 A polyamide having the desired relative viscosity [RV] is obtained.
[0068]
As the continuous reaction apparatus in the late polymerization step, a single screw extruder or a twin screw extruder can be used. A twin screw extruder is generally recommended because of its good reaction efficiency and a certain degree of self-cleaning function. However, the twin-screw extruder can not only make the entire apparatus under vacuum, but also tends to vent up with a low melt viscosity product. 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. Furthermore, in order to increase the residence time, there are disadvantages such as an increase in the size of the apparatus and an increase in equipment costs.
[0069]
Therefore, it is preferable to use a self-cleaning horizontal biaxial reactor (41), for example, an SCR manufactured by Mitsubishi Heavy Industries, as the continuous reactor. In the self-cleaning horizontal biaxial reactor (41), the blades (rotors) are twisted and overlapped with a slight gap to form two parallel drive shafts, and the two parallel drive shafts The drive shaft is rotated in the same direction. Since the clearance between the blade and the inner wall is smaller than that of a general horizontal biaxial reactor, the cleaning effect of the inner wall is brought about as the drive shaft rotates. This is the same for the 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 slight gap between the blades and the two parallel drive shafts are in the same direction. , The cleaning effect between the blades is further increased. Since the self-cleaning effect brings about an improvement in quality due to a reduction in scale adhesion and a reduction in contamination, it is suitably used for the production of polyamides that are susceptible to thermal degradation during the reaction. Furthermore, unlike the twin-screw extruder, the entire apparatus can be kept under vacuum, so that vacuum can be applied even to low melt viscosity products, heat generation due to shearing force is small, and residence time is relatively short. It has the advantage of being long, having a high applicability to viscosity fluctuations and flow rate fluctuations, and having a large productionable viscosity range. Furthermore, in terms of equipment, it has the advantage that it can be made more compact and cheaper than the twin-screw extruder.
[0070]
The reaction conditions for the late polymerization step vary depending on the type of polyamide and the desired relative viscosity [RV], but the resin temperature is not less than the melting point (Tm) of the polyamide and not more than Tm + 80 ° C., preferably not less than the melting point and not more than Tm + 70 ° C. When the resin temperature is Tm + 80 ° C. or higher, the deterioration of the polyamide is easily accelerated, resulting in deterioration of physical properties and coloring. On the other hand, at Tm or less, there is a risk that the polyamide solidifies and causes damage to the reaction apparatus.
[0071]
The average residence time in the continuous reaction apparatus varies depending on the type of polyamide, the desired relative viscosity [RV], the degree of vacuum, the addition of an acid anhydride compound described later, the purging of an inert gas described later, and the like. Minutes are preferred. If the average residence time is less than 1 minute, it is difficult to obtain a polyamide having [RV] in the range of 1.6 to 4.0. Conversely, if the average residence time exceeds 30 minutes, the polymer is continuously reacted. Therefore, it is necessary to reduce the supply amount of the material, and the productivity is significantly reduced. A desirable average residence time is 1.5 to 25 minutes, more desirably 2 to 20 minutes.
[0072]
Unlike the twin screw extruder, the screw speed (rpm) of the reactor SCR has little influence on the polymerization reaction and the average residence time, and may be selected as appropriate, but generally 20 rpm to 150 rpm is applied. .
[0073]
Controlling the relative viscosity [RV] is an important function in the late polymerization process.
There are (1) inert gas purge, (2) vacuum degree, and (3) inert gas purge and vacuum degree as control methods of [RV]. Each method will be described below.
[0074]
While the inert gas purge accelerates the polymerization reaction, [RV] can be controlled by adjusting the purge amount. The inert gas purge is performed from an inert gas purge port (42). The purge amount of the inert gas varies depending on the desired polymerization conditions such as [RV] and temperature, but the amount is desirably 0.005 to 10 L per 1 kg of the polymer. When the purge amount exceeds 10 L / kg, the amount of inert gas used becomes excessive due to the promoting action of the polymerization reaction, which causes a cost increase. A more desirable purge amount is 0.005 to 9.5 L / kg, and further desirably 0.01 to 9 L / kg. Further, when a desired RV can be obtained without performing an inert gas purge, it is possible not to perform the purge (that is, the purge amount: 10 L / kg). The inert gas is not particularly limited as long as it is inert to the polyamide formation reaction, but nitrogen gas is advantageous in terms of safety and cost.
[0075]
Also, the polymerization reaction can be accelerated by the degree of vacuum, and the reaction rate can be controlled. Perform 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 accelerated by removing generated water. The degree of vacuum applied in the late polymerization step is 150 to 1200 hPa, although it varies depending on the desired [RV] and polymerization conditions. When the pressure is less than 150 hPa, in the latter polymerization step, the polymer is vented up, the piping is clogged, and stable operability cannot be expected. On the other hand, when it exceeds 1200 hPa, the effect of the degree of vacuum is not so much, the speed of reaching the desired [RV] is slowed down, and the productivity is lowered. In some cases, the desired [RV] may not be reached. A desirable degree of vacuum is 200 to 1100 hPa, and more desirably 250 to 1050 hPa.
[0076]
A desirable control method of [RV] in a polyamide mainly composed of ADA-MXD is a combination of an inert gas purge and a degree of vacuum. The advantage of this method is that it is easy to produce an inert gas or a high [RV] polyamide that cannot be achieved by a vacuum degree alone, and purging of the inert gas under a constant degree of vacuum control of [RV]. This is 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.
[0077]
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. When the inert gas purge amount is less than 0.005 L / kg, or when 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 the vacuum level is less than 200 hPa, the amount of inert gas used increases, resulting in a cost increase, and the polymerization rate is slowed to produce. This causes disadvantages such as decreased sex.
[0078]
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 done through the addition port (44). Since the terminal amino group of the polymer is blocked by the addition of the acid anhydride compound, it is considered 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, and HOPA is desirable from the viewpoint of the color tone of the polyamide. The amount of the acid anhydride compound added is not particularly limited depending on the desired [RV], but it is usually 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 the venting-up factor is caused, resulting in poor operation stability. Further, the unreacted acid anhydride compound remains in the polymer and causes deterioration of the quality of the polyamide.
[0079]
【Example】
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.
[0080]
[Parameter measurement]
1. Relative viscosity [RV]
0.25 g of polyamide resin was dissolved in 25 ml of 96% sulfuric acid and measured with an Ostwald viscosity tube.
[0081]
2. Color [Co-b]
10 g of polyamide resin chips were uniformly filled in the cell and measured with a color meter model 1001DP manufactured by Nippon Denshoku Industries Co., Ltd.
[0082]
[Example 1]
25 kg of powdered adipic acid (ADA), 13.7 g of sodium acetate, and 28.4 g of sodium phosphinate monohydrate were supplied to the melting tank (11), and metaxylylenediamine ( (MXD) 18 kg was fed. Subsequently, each of the melting tank (11) and the melting tank (13) was maintained at a vacuum degree of 40 hPa for 5 minutes and then brought to normal pressure with nitrogen gas. After the same operation was repeated three times, ADA was heated to 180 ° C. and MXD was heated to 60 ° C. at a nitrogen pressure of 0.2 MPa to obtain molten liquids. Subsequently, ADA was transferred to the storage tank (12) and MXD was transferred to the storage tank (14).
[0083]
The ADA and MXD molten raw materials are respectively fed at 4.75 kg / hr and 4.42 kg / hr with plunger pumps (15) and (16), respectively, in the amidation step tubular reactor (L / D = 780) (21) Quantitative supply to. The reaction conditions in the amidation step were an internal temperature of 180 ° C. at the inlet (22), an internal temperature of 255 ° C. at the outlet (23), an internal pressure of 0.7 MPa, and an average residence time of 30 minutes.
[0084]
The reaction mixture that had undergone the amidation step was supplied to a vertical stirring tank (31) of the initial polymerization step that was set under stirring conditions of an internal temperature of 255 ° C., an internal pressure of 0.7 MPa, and 30 rpm. It was allowed to stay for a minute, and at the same time, condensed water was distilled off. Subsequently, the reaction product after the initial polymerization step was supplied to the SCR (41) set under the conditions of a reaction temperature of 255 ° C., a vacuum of 1013 hPa, a nitrogen gas purge amount of 0.3 L / kg, and a screw rotation speed of 50 rpm, for 10 minutes. Thus, a polyamide resin having [RV] of 2.07 and [Co-b] of 0.4 was obtained.
[0085]
[Example 2]
The same procedure as in Example 1 was performed except that the amount of sodium acetate added was changed so that the Na / P molar ratio was 1.75. A polyamide resin having [RV] of 2.00 and [Co-b] of 0.5 was obtained.
[0086]
[Comparative Example 1]
The same procedure as in Example 1 was performed except that the amount of sodium acetate added was changed so that the Na / P molar ratio was 4. A polyamide resin having [RV] of 1.64 and [Co-b] of 0.7 was obtained. Since the Na / P molar ratio was too high, the reaction rate was decreased, and [RV] was smaller than that in Example 1.
[0087]
[Comparative Example 2]
25 kg of powdered adipic acid (ADA) and 28.4 g of sodium phosphinate monohydrate were supplied to the melting tank (11), and 18 kg of metaxylylenediamine (MXD) was supplied to the melting tank (13). Subsequently, each of the melting tank (11) and the melting tank (13) was maintained at a vacuum degree of 40 hPa for 5 minutes and then brought to normal pressure with nitrogen gas. After the same operation was repeated three times, ADA was heated to 180 ° C. and MXD was heated to 60 ° C. at a nitrogen pressure of 0.2 MPa to obtain molten liquids. Subsequently, ADA was transferred to the storage tank (12) and MXD was transferred to the storage tank (14).
[0088]
The ADA and MXD molten raw materials are respectively fed at 4.75 kg / hr and 4.42 kg / hr by a plunger pump (15) and (16), respectively, and an amidation step tubular reactor (L / D = 780) (21) Quantitative supply to. The reaction conditions in the amidation step were an internal temperature of 180 ° C. at the inlet (22), an internal temperature of 255 ° C. at the outlet (23), an internal pressure of 0.7 MPa, and an average residence time of 30 minutes.
[0089]
The reaction mixture that had undergone the amidation step was supplied to a vertical stirring tank (31) in the initial polymerization step that was set under the conditions of stirring at an internal temperature of 255 ° C., an internal pressure of 0.7 MPa, and 30 rpm. It was allowed to stay for a minute, and at the same time, condensed water was distilled off. Subsequently, the reaction product after the initial polymerization step was supplied to the SCR (41) set under the conditions of a reaction temperature of 255 ° C., a vacuum degree of 1013 hPa, a nitrogen gas purge amount of 0.3 L / kg, and a screw rotation speed of 50 rpm, for 10 minutes. A polymer was obtained with an average residence time of. However, the obtained polymer was so gelled that it could not be chipped. Moreover, when it melt | dissolved in the sulfuric acid for [RV] measurement, the insoluble matter precipitated.
[0090]
Table 1 shows the production conditions of the above polyamide and the properties of the obtained polyamide. In any of the examples, the operation was good, and a polyamide having excellent physical property values was obtained.
[0091]
[Table 1]

[0092]
【The invention's effect】
According to the present invention, there is provided a continuous process for producing a high-quality polyamide, particularly an aromatic-containing polyamide. The method of the present invention is suitable for films, sheets, packaging bags, bottles, etc. in applications such as foods, beverages, pharmaceuticals and cosmetics, and has excellent oxygen barrier properties, good color tone and low water absorption. Polyamide having range amine as a diamine component is continuously produced. The polyamide containing metaxylylenediamine as a component can also be used to modify different polymers such as polyethylene terephthalate.
[Brief description of the drawings]
FIG. 1 is a flow diagram showing schematic steps of a continuous production method for polyamide of the present invention.
[Explanation of symbols]
(1): Raw material preparation process
(2): Amidation process
(21): Tubular reactor
(3): Initial polymerization process
(4): Late polymerization process
(41): Self-cleaning horizontal biaxial reactor

Claims (6)

A process for continuously producing a polyamide mainly comprising a diamine component unit and a dicarboxylic acid component unit,
(1) A raw material preparation step in which diamine and dicarboxylic acid are individually melted or a salt of amine and carboxylic acid is produced in water,
(2) an amidation step in which the prepared raw material is continuously introduced into and passed through a tubular reactor for amidation to obtain a reaction mixture containing an amidation product and condensed water;
(3) The reaction mixture is introduced into a continuous reactor capable of separating and removing water, and the degree of polymerization is increased while separating and removing water at a temperature equal to or higher than the melting point of the finally obtained polyamide to obtain a polyamide prepolymer. An initial polymerization step;
(4) The polyamide prepolymer is introduced into a continuous 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, in the range of 1.6 to 4.0. A late polymerization step for obtaining a polyamide having a relative viscosity [RV],
Prior to the amidation step, an alkali metal compound and a phosphorus compound are added so that the molar ratio of alkali metal to phosphorus (alkali metal / phosphorus) is 1.2 or more and 3.5 or less. .   The method for continuously producing a polyamide according to claim 1, wherein the polyamide contains metaxylylenediamine (MXD) as a diamine component, and metaxylylenediamine (MXD) is at least 70 mol% based on the diamine component.   (4) The continuous production method of polyamide according to claim 1 or 2, wherein the continuous reaction apparatus in the late polymerization step is a self-cleaning horizontal biaxial reaction apparatus.   (4) The continuous production method of polyamide according to any one of claims 1 to 3, wherein an average residence time in the late polymerization step is 1 to 30 minutes. (4) in the later polymerization stage, purging the inert gas, to adjust the degree of vacuum of the reactor, or by a combination thereof, to control the relative viscosity of the polyamide [RV], of claims 1-4 The continuous manufacturing method of the polyamide of any one of these. (1) The continuous production method of polyamide according to any one of claims 1 to 5 , wherein in the raw material preparation step, the atmospheric oxygen concentration at the time of raw material preparation is 10 ppm or less.

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