JP2010215682A - Method for solid state polymerization of polyamide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for solid state polymerization efficiently producing a high molecular weight polyamide having extremely high homogeneity to overcome the problems of the conventional solid state polymerization of polyamide in that, for example, a method, wherein temperature is raised to a predetermined temperature by external heat radiation and heat conduction, results in uneven heating in a solid state polymerization reactor and uneven degree of solid state polycondensation reaction and requires longer reaction time, thus generating a large amount of low molecular weight components which adhere to a wall of the solid state polymerization reactor and reduce heat conductivity, and further degrade the performance of the resulting high molecular weight polyamide and reduce productivity of bottles, fibers, films and the like. <P>SOLUTION: This solid state polymerization method includes a solid polycondensation step of polyamide carried out by directly irradiating the polyamide with microwave. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a solid phase polymerization method capable of polymerizing high quality high molecular weight polyamide in a short time. Furthermore, the present invention relates to a solid phase polymerization method for polyamide which prevents a polyamide pulverized product or a low molecular weight component generated by heating from being fused and fixed to the wall surface of the polymerization apparatus.

  Examples of the gas barrier resin not containing chlorine include polyamide resins such as nylon 6 and polymetaxylylene adipamide (hereinafter sometimes abbreviated as N-MXD6) and ethylene vinyl copolymers (hereinafter abbreviated as EVOH). Among them, polymetaxylylene adipamide is excellent in oxygen barrier properties, especially in high humidity environments and after heat sterilization treatment such as boil and retort treatment, and has high mechanical performance. Therefore, it is suitable as a food packaging material, as a multi-layer bottle or blend bottle of polyethylene terephthalate and metaxylylene adipamide, laminated with a base film such as stretched film or polyolefin, and other such as nylon 6 Used in combination with wood.

Generally, polyamides used for molding materials are molded by injection molding or the like, and are required to have high fluidity when melted, so-called low viscosity products are used. On the other hand, polyamides used for bottles, sheets, films, fibers and the like are molded by extrusion molding as well as injection molding. In extrusion molding, the fluidity at the time of melting is required to be lower than in the case of an injection-molded material, and a medium or high viscosity product is mainly used.

As the low-viscosity polyamide mainly used for injection molding materials, polyamide obtained by polycondensation in a molten state is used as it is, or further dried one is used. However, when it is mainly used for applications such as bottles, sheets, films, fibers, etc., when trying to obtain high-viscosity polyamide by polycondensation in the molten state, the general molten state in the polymerization tank is uniform with a general stirring device. In this case, sufficient stirring power for maintaining the temperature is not obtained, and a special polymerization apparatus is required. In addition, if the polycondensation reaction is continued until low viscosity, medium viscosity and high viscosity are reached, the time for maintaining the molten state (reaction time) becomes longer and the polyamide molecules are damaged (deterioration of polymer molecules due to generation of radicals, etc.). Or abnormal reactions such as non-linear molecular growth (three-dimensional polymerization) occur, resulting in increased production of gels or fish eyes, which is practically inconvenient. When a polyamide containing a large amount of gel or fish eye is used for bottles, sheets, films, fibers, etc., the rate of occurrence of defects becomes extremely high, leading to a decrease in productivity. Even if a filter that removes gels or fish eyes during the molding process is installed, complete removal is difficult, and the frequency of filter replacement increases and the continuous production time is shortened. Therefore, the gel or fish eyes in the polyamide should be as small as possible. Is desirable.

In order to obtain a high-viscosity polyamide with little gel or fish eye, it is known to perform so-called solid-phase polymerization in which a low-viscosity polyamide is obtained once by polycondensation in a molten state, followed by heat treatment in a solid-phase state. Yes. The difference in the amount of gel or fish eye produced due to the polycondensation between the molten state and the solid state is considered to be due to damage of the polyamide molecules due to the difference in reaction temperature or the difference in the frequency of occurrence of abnormal reactions. Among high-viscosity polyamides obtained by solid-phase polymerization, gels or fish eyes can be reduced compared to high-viscosity polyamides obtained by melt polymerization alone. However, in applications such as bottles, sheets, films, fibers, etc., even a small amount of gel or fish eye can significantly affect productivity, so an improved solid state polymerization method that can be further reduced is desired.

Gels or fish eyes are generated not only when the polyamide is produced, but naturally also when melted when being molded into a molded product. Even if there is no significant difference in the amount of gel or fish eye produced after the polyamide is produced, there may be a difference when molding. One reason for this is that a slight difference in the damage to the polyamide molecules, which is not observed after production, or a difference in the frequency of occurrence of abnormal reactions was amplified in the staying part of the filter or die during the molding process. Presumed. In other words, in order to obtain a molded product with less gel or fish eye, it is necessary to design a molding device with very few staying parts, and at the same time, there is no damage or abnormal reaction at the molecular level in melt polymerization and solid phase polymerization. The production of high-quality polyamide is also essential.

By the way, when a crystalline polyamide in an amorphous state such as polymetaxylylene adipamide having a crystallinity of 13% or less is further heated beyond the glass transition temperature, the amorphous state transitions to a crystalline state. . In the amorphous state, adhesiveness rapidly develops from around the glass transition temperature, and this adhesive phenomenon is observed until crystallization occurs. Solid-phase polymerization is naturally carried out by heat transfer from a heat medium having a temperature higher than that of polyamide. At this time, if the movement of the polyamide is impaired and stays on the heat transfer surface of the inner wall of the heating device, fusion to the wall surface of the heating device is caused. Arise. Alternatively, a phenomenon of fusion between particles such as agglomeration of polyamide is observed. If the fused polyamide is crystallized as it is without collapsing, there is a problem of fixation. If solid phase polymerization is performed as it is without losing the fixed mass after crystallization, a solid phase polymer having a homogeneous degree of polymerization cannot be obtained, and gelation can cause damage and abnormal reaction of polyamide molecules due to local heating. Or the generation of fish eyes is triggered.

In order to avoid such inconvenience, the following method is generally carried out for solid-phase polymerization of polyamide.
(B) Using a batch-type heating device such as a rotating drum, heat gently in an inert gas or under reduced pressure, crystallize while avoiding fusion, and further heat to solid phase polymerization in the same device Batch method to perform. (Patent Document 1)
(B) After heating and crystallizing using a grooved stirring and heating device (preliminary crystallization treatment) under a inert gas flow, solid phase under an inert gas flow using a hopper-shaped heating device A continuous method of polymerization.
(C) A semi-continuous system in which solid-state polymerization is performed using a batch-type heating device such as a rotating drum after crystallization using a groove type stirring and heating device.

In these conventional methods, as a means for raising the temperature of the low molecular weight polyamide to a predetermined temperature, the temperature is raised to the predetermined temperature by external heat radiation and heat conduction. As the reaction degree of solid phase polycondensation becomes non-uniform and the reaction time is long, many low molecular weight components are generated, and this low molecular weight component adheres to the wall surface of the solid phase polymerization apparatus. There is a problem that the heat conduction to the polyamide during the solid phase polymerization is lowered, and the film attached to the inner wall of the apparatus is always subjected to heat, so that the film is mixed with the product pellets to increase gel or fish eye.

In addition, when the reaction time is long, yellowness increases due to oxidation of nylon pellets even under a sufficient nitrogen atmosphere, so that when used as a gas barrier material for a film or a PET bottle, an appearance problem occurs.

In recent years, a method of increasing the molecular weight in a short time by irradiating 2.45 GHz microwaves in the melt polymerization and solid phase polymerization processes of a polycondensation polymer such as polyester and polyamide is known (Patent Document 2, 3, 4). Microwaves directly act on the pulverized polyester and polyamide and water inside the pulverized material, heat generation based on dielectric relaxation, and increase the temperature of the pulverized polyester and polyamide by heat generation. Let

  However, when microwaves act on the pulverized product of polyester and polyamide, the temperature rises at a high speed. Therefore, when microwaves are continuously irradiated to the same pulverized product, the crushed product is fused and the pulverized product is melted. In addition, since the kogation of the pulverized product is generated, it is necessary to keep the pulverized product uniformly stirred. However, in the above-mentioned patent document, this is not fully considered.

Japanese Patent Laid-Open No. 08-073587 JP 2006-225591 A JP 2006-104305 A JP 2007-2087 A

An object of the present invention is to propose a solid phase polymerization method for efficiently obtaining a high molecular weight polyamide having a very high uniformity in a short time in a solid phase polymerization process of polyamide.

As a result of intensive studies to solve the above-mentioned problems, the present invention can solve the problems by irradiating microwaves to a polyamide pulverized product that has been sufficiently uniformly stirred in a polyamide solid-phase polycondensation step. The headline, the present invention has been reached.

  That is, the present invention relates to a polyamide solid phase polymerization method characterized by irradiating a polyamide resin pellet with microwaves in a stirring type solid phase polymerization apparatus.

 According to the solid phase polymerization method of the present invention, a high-quality high-molecular weight polyamide can be efficiently obtained in a short time.

  The present invention mainly relates to a method for increasing the degree of polymerization (molecular weight) by further solid-phase polymerization of a melt-polymerized polyamide. The present invention may be used to further increase the degree of polymerization of the solid phase polymerized polyamide.

  The polyamide used in the present invention was formed from a diamine component containing 70 mol% or more of xylylenediamine or bis (aminomethyl) cyclohexane and a dicarboxylic acid component containing 70 mol% or more of an aliphatic dicarboxylic acid having 4 to 20 carbon atoms. Polyamide (hereinafter sometimes referred to as “polyamide X”). Examples of xylylenediamine include metaxylylenediamine and paraxylylenediamine, with metaxylylenediamine being preferred. Examples of bis (aminomethyl) cyclohexane include 1,3-bis (aminomethyl) cyclohexane and 1,4-bis (aminomethyl) cyclohexane. Xylylenediamine and bis (aminomethyl) cyclohexane may be used in combination in a range of 70 mol% or more in total.

In the present invention, as diamines other than xylylenediamine and bis (aminomethyl) cyclohexane, aliphatic diamines such as tetramethylenediamine, pentamethylenediamine, octamethylenediamine, and nonamethylenediamine, paraphenylenediamine, metaxylylenediamine, para Although aromatic diamines, such as xylylenediamine, can be illustrated, it is not limited to these.

  Examples of the aliphatic dicarboxylic acid having 4 to 20 carbon atoms used in the present invention include succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, adipic acid, sebacic acid, undecanedioic acid, dodecanedioic acid. Examples thereof include aliphatic dicarboxylic acids such as adipic acid. In the present invention, dicarboxylic acids other than the above, for example, aromatic dicarboxylic acids such as isophthalic acid, terephthalic acid and 2,6-naphthalenedicarboxylic acid can be used within a range not exceeding 30 mol%.

The polyamide-forming compound other than the above is not particularly limited, and examples thereof include lactams such as caprolactam, valerolactam, laurolactam, and undecalactam, and aminocarboxylic acids such as 11-aminoundecanoic acid and 12-aminododecanoic acid. .

  Polyamide X used in the present invention, like other crystalline polymers having intermolecular hydrogen bonds, decreases the glass transition temperature when water is incorporated into the amorphous part, and accordingly, the crystallization start temperature decreases and the crystallization rate. Will be faster. Even if it does not contain moisture, it has an extremely fast crystallization rate (nylon 6, nylon 66, etc.), a polymer whose crystallization rate is hardly affected by moisture, a polymer with low water absorption (polyester), or no moisture However, in the case of a polymer having a glass transition temperature and a crystallization temperature close to each other, the effect of adjusting the moisture concentration is hardly recognized because the influence of the moisture is too large or too small. However, the influence of the polyamide X on the adjustment of the moisture concentration is milder than that of nylon 6 and greater than that of polyethylene terephthalate, and the effects of the present invention are remarkably exhibited. That is, when the polyamide X having a crystallinity of 13% or less is adjusted to a specific moisture concentration, the temperature range in which the stickiness due to heating is reduced and the time during which the stickiness appears is shortened. Therefore, fusion is suppressed, and as a result, no sticking occurs.

  Polyamide X is a crystalline polyamide in which a clear endothermic peak due to melting is confirmed in DSC measurement (differential scanning calorimetry), and the degree of crystallinity after solid-phase polymerization reaches 20% or more. The crystallinity of polyamide X obtained by polycondensation in the molten state is preferably 13% or less. Polyamide is generally granulated in a water-cooled tank after polymerization, and the crystallinity at that time is 13% or less. In the present invention, the degree of crystallinity can be determined from the amount of heat of crystal melting in DSC measurement.

  The relative viscosity of the polyamide X used in the present invention is preferably 1.83 or more and 2.28 or less, more preferably 1.87 or more and 2.24 or less. By setting the relative viscosity to 1.83 or more, it is possible to maintain an appropriate viscosity in a molten state, it becomes easy to form a strand when taken out from the polymerization tank, and workability can be kept good. On the other hand, when the relative viscosity is 2.28 or less, the molten state in the polymerization tank can be kept uniform, and a polyamide having a uniform degree of polymerization can be obtained. Furthermore, it is possible to prevent the polyamide molecules from being damaged as the heat history in the molten state increases, and to suppress abnormal reactions such as non-linear molecular growth.

  The terminal group balance of polyamide X, that is, the balance between the terminal carboxyl group concentration and the terminal amino group concentration is such that the terminal carboxyl group concentration is higher than the terminal amino group concentration, and the difference is 8 μeq / g or more and 82 μeq / g or less. preferable. When the difference is zero, the amide group formation rate is the fastest, so that it is generally expected that the polymerization time in the molten state and the solid phase is the shortest and the damage to the polyamide molecule is minimized. However, as a result of investigation, in the polyamide X used in the present invention, when the difference is less than 8 μeq / g, in other words, if the terminal amino group concentration is excessive than the concentration defined in the present invention, An increase in viscosity was observed that was attributed to reactions other than the amide group formation reaction. This is presumed to be due to non-linear molecular growth and is the main cause of gels or fish eyes. In addition, by setting the difference to 82 μeq / g or less, the amide group generation rate can be maintained at a practical rate, the polymerization time in the melted state and the solid phase can be prevented from becoming considerably long, and the polyamide molecule Damage can be prevented and the occurrence of gel or fish eye can be reduced. That is, in order to obtain polyamide X with less gel or fish eye, it has been found that there exists an optimum end group balance range not disclosed so far.

  The polyamide X having the above characteristics is produced by a polycondensation method in which at least one step proceeds in a molten state. For example, a method in which an aqueous solution of a nylon salt of metaxylylenediamine and adipic acid is heated under pressure and polycondensed directly in a molten state while removing water and condensed water, and metaxylylenediamine is directly converted into molten adipic acid. In addition, it is produced by a method such as polycondensation under normal pressure. The polymerization conditions are not particularly limited, and the above properties, particularly relative viscosity, can be selected by appropriately selecting the raw material compound charge ratio, polymerization catalyst, polymerization temperature, and polymerization time based on knowledge generally known in the polymer production field. And polyamide X having end group balance can be produced.

The moisture concentration is preferably 0.2% by mass or more of polyamide X for the purpose of preventing sticking, and is preferably 0.3% by weight or more for the purpose of preventing fusion as well as preventing sticking. Considering the dehydration operation in the drying step and the solid phase polymerization step after crystallization, 0.3 to 5% by mass is preferable.

As a method for adjusting the water concentration, there is a method in which the polyamide X particles are preliminarily absorbed or absorbed by using the water absorption of the polyamide X so as to obtain a target water concentration and then supplied to the polymerization apparatus. In addition, a method of adjusting the water concentration by charging ice, water, or steam together with the polyamide X particles in a heating device may be used. At this time, excessive water that is not absorbed by the polyamide may be present in the polymerization apparatus. The present invention is not limited to these methods for adjusting the water concentration.

After adjusting the water concentration, polyamide X is solid-phase polymerized. In the present invention, the solid phase polymerization is preferably carried out in a two-stage process.

The first step is a pretreatment step until the crystallinity of polyamide X reaches at least 15%. In the first step, crystallization is promoted by moisture and fusion is suppressed. Therefore, the decompression operation should be avoided to prevent the water inside the polymerization apparatus from being easily dissipated outside the apparatus. Also, the reduced pressure state is not preferable in order to make heat conduction in this temperature range advantageous and reach the solid phase polymerization temperature in a short time. The inside of the polymerization apparatus may be normal pressure or pressurized, but if the structure is such that the water added to adjust the moisture concentration is not easily dissipated outside the apparatus, the pressurization is particularly effective. do not need. Moreover, it is not necessary to suppress the heat medium temperature on the heat transfer surface of the polymerization apparatus in order to avoid fusion, and it can be set equal to the target maximum heat medium temperature.

As described above, since the pressure is not reduced in the first step, the contact between the polyamide X and oxygen is unavoidable, and deterioration due to oxygen tends to occur. In order to avoid this, it is necessary to keep the oxygen concentration in the atmosphere inside the heating device low. Therefore, the oxygen concentration inside the polymerization apparatus is preferably 5% by volume or less. More preferably, it is 1 volume% or less, and 0.1 volume% or less is especially preferable. For the same reason, the pellet temperature of polyamide X is kept at 60 ° C. or higher and 160 ° C. or lower.

The second step is a step in which the polyamide X is dried and solid-phase polymerized after the crystallinity reaches at least 15% in the first step. In the second step, the inside of the polymerization apparatus is kept in a reduced pressure state in order to positively remove the water adhering to the polyamide X and the condensed water produced by polycondensation, and further avoid deterioration due to oxygen. The pressure at this time is preferably 500 Torr or less, more preferably 100 Torr or less, and particularly preferably 30 Torr or less. In order to avoid fusion, the temperature of polyamide X is preferably 15 ° C. or more lower than the melting point, more preferably 210 ° C. or less.

In any of the above steps, the maximum temperature of the heat transfer surface of the polymerization apparatus when the polyamide X is heated is preferably 120 ° C. or higher and 230 ° C. or lower. In the case of a polyamide X copolymer, the maximum temperature is adjusted according to the melting point. By setting the temperature to 120 ° C. or higher, it is possible to prevent the time required for the entire process from becoming considerably long. By setting the temperature to 230 ° C. or lower, it can be avoided that the melting point of the polyamide X is approached. The occurrence of fusion can be prevented.

The reaction time in the second step is not particularly limited, but the balance between the terminal carboxyl group concentration and the terminal amino group concentration of the polyamide X solid phase polymer obtained by the above-described method is such that the terminal carboxyl group concentration is higher than the terminal amino group. The difference is desirably 8 μeq / g or more and 82 μeq / g or less. The reason is the same as described above. Furthermore, it is preferable that the reaction time is sufficient for the relative viscosity of the polyamide solid phase polymer of the present invention to be 2.30 or more and 4.20 or less. If the above 4.20 is considerably exceeded, the polymerization time in the solid phase becomes long even if the end group balance is within the above range. Time can be within a practical range, damage to the polyamide molecule can be reduced, and reactions other than the usual amide group formation reaction can be suppressed.

As the polymerization apparatus used in the solid phase polymerization of the present invention, a batch polymerization apparatus that is excellent in airtightness and highly capable of interrupting the contact between polyamide X and oxygen by a batch or continuous polymerization apparatus is preferable. A rotary drum type heating device called a tumble dryer, a conical dryer, a rotary dryer, etc. and a conical type and a cylindrical type polymerization device with rotary blades inside called a Nauta mixer can be suitably used. It is not limited. In particular, a dispersion type mixing polymerization apparatus composed of a cylindrical vessel and a mixing blade attached to a rotating shaft is suitable for irradiating microwaves, and is suitable for Proshare mixer manufactured by Taiheiyo Kiko Co., Ltd. Good apex granulator is good.

The operating conditions of the batch polymerization apparatus, that is, the moving speed of the polyamide resin pellets in the apparatus is arbitrarily selected within a range where the polyamide resin pellets are uniformly heated, and it is necessary to provide a particularly high moving speed for the purpose of preventing fusion. Absent. Since the movement speed of the polyamide resin pellets depends on the filling rate and the stirring speed, in order for the polyamide resin pellets to receive uniform heating, it is necessary to increase the stirring speed if the filling ratio is high, and the filling rate can be lowered. If so, the stirring speed can be reduced. For example, in the case of a rotating drum, when the filling rate is less than 40%, a rotational speed of 0.5 rpm to 30 rpm is preferable, and when the filling amount is 40% or more, 2 rpm to 60 rpm is preferable. However, as described above, the operating conditions are not particularly limited as long as the polyamide resin pellets are uniformly heated. In particular, in the case of a dispersion type mixing polymerization apparatus composed of a cylindrical vessel and a mixing blade attached to a rotating shaft, the mixing rate may be 40% or more and 90% or less because of excellent dispersion mixing properties. Is preferably 0.1 m / s to 10 m / s, and in particular, 5 m / s or less is optimal in order not to damage the polyamide resin pellets.

  The microwave irradiated in the present invention can be generated by a microwave generator such as a magnetron, and refers to an electromagnetic wave having a frequency of 0.3 GHz to 30 GHz. 2.45 GHz used in commercially available microwave ovens can be obtained. The solid phase polymerization apparatus is preferably made of a material that does not absorb or reflect microwaves. In addition, since microwaves adversely affect the human body, it is necessary to prevent leakage of microwaves.

  It is preferable to adjust the irradiation amount of the microwave irradiated in the present invention in accordance with the heating rate of the polyamide resin pellets in the apparatus, and it may be continuous irradiation or intermittent irradiation. In addition, it is not necessary to use only microwaves in the entire process of the solid phase polymerization process. In combination with a heat medium, the first half of polymerization uses microwaves, and the second half of polymerization uses only a heat medium. good. In addition, since the dew condensation of a polymerization apparatus can be prevented by using together with a heat medium, it is preferable to also use a heat medium together. Furthermore, microwave irradiation may be performed not only from one place in the polymerization apparatus but also from several places in view of the capacity and efficiency of the polymerization apparatus.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. In addition, the measurement for evaluation in this invention was based on the following method.
(A) 1 g of a relative viscosity pellet was precisely weighed and dissolved in 100 cc of 96% sulfuric acid at 20-30 ° C. with stirring. After complete dissolution, 5 cc of the solution was quickly taken into a Cannon-Fenceke viscometer and allowed to stand in a thermostatic bath at 25 ° C. ± 0.03 ° C. for 10 minutes, and then the drop time (t) was measured. The drop time (t0) of 96% sulfuric acid itself was also measured in the same manner. The relative viscosity was obtained from the measured values of t and t0 by the formula (D).
Formula (D) Relative viscosity = t / t0
(B) Water concentration (ppm)
Using 1 g of pellets, Hiranuma Sangyo Co., Ltd., Hiranuma Trace Moisture Titrator (AQ-2000), the amount of water was quantified under the vaporization conditions at the melting point temperature for 30 minutes to determine the water concentration.
(C) A fisheye number pellet of the film is melt-extruded at 260 ° C. from a single-screw extruder (PTM-25 manufactured by Plastics Engineering Laboratory), and a single-layer unstretched film having a thickness of 50 μm is produced by a T-die-cooling roll method. The number of fish eyes of this film was measured with an in-line fish eye inspection machine. As the fish eye inspection machine, GX70W manufactured by Meiling Erie was used.

Production Example 1
[Preparation of Melt Polymerized Polyamide (Polyamide 1)]
Into a jacketed reactor equipped with a stirrer, a condenser, a cooler, a thermometer, a dripping tank, and a nitrogen gas introduction tube, adipic acid was charged, and after sufficient nitrogen substitution, the temperature was further raised to 170 ° C under a nitrogen stream. After heating to bring the adipic acid into a molten state, metaxylylenediamine was added dropwise with stirring. During this time, the internal temperature was continuously raised to 245 ° C., and the water distilled with the addition of metaxylylenediamine was removed out of the system through a condenser and a cooler. After the completion of the dropwise addition of metaxylylenediamine, the internal temperature was continuously raised to 255 ° C., and the reaction was continued for 15 minutes. Thereafter, the internal pressure of the reaction system was continuously reduced to 600 mmHg over 10 minutes, and then the reaction was continued for 40 minutes. During this time, the reaction temperature was continuously raised to 260 ° C. After completion of the reaction, the inside of the reaction vessel was pressurized with nitrogen gas at a pressure of 0.2 MPa, the polymer was taken out as a strand from the nozzle at the bottom of the reaction vessel, and was cooled after water cooling to obtain a pellet-shaped polymer (polyamide 1). The polyamide 1 obtained had a relative viscosity of 2.1 and a melting point of 237 ° C.

Example 1
[Solid phase polymerization of polyamide 1]
20 kg of polyamide 1 consists of a 2.45 GHz microwave irradiation device and its waveguide, and is charged in a stainless steel 50 L capacity rotating drum type polymerization device that can also flow a heat medium, while continuously irradiating microwaves at 3 KW, Rotated at 5 rpm. The atmosphere in the reaction system was raised from room temperature to 140 ° C. under a small nitrogen flow. When the internal temperature of the reaction system reached 140 ° C, the pressure was reduced to 1 Torr or less, and the internal temperature was further increased to 180 ° C. From the time when the system temperature reached 180 ° C., the solid state polymerization reaction was continued at the same temperature. After completion of the reaction, the pressure reduction was terminated, the system temperature was lowered under a nitrogen stream, and the pellets were taken out when the temperature reached 60 ° C. (polyamide 2). The total reaction time was 145 minutes. The obtained polyamide 2 has no welding or burnt between pellets, has a relative viscosity of 2.65, a melting point of 237 ° C., a glass transition point of 85 ° C., a water concentration of 205 ppm, and a fish eye number of 200. there were.

Comparative Example 1
[Solid phase polymerization of polyamide 1]
20 kg of polyamide 1 was charged in a stainless steel 50 L capacity rotating drum type polymerization heating apparatus and rotated at 5 rpm. The atmosphere in the reaction system was raised from room temperature to 140 ° C. under a small nitrogen flow. When the internal temperature of the reaction system reached 140 ° C, the pressure was reduced to 1 Torr or less, and the internal temperature was further increased to 180 ° C. From the time when the system temperature reached 180 ° C., the solid state polymerization reaction was continued at the same temperature. After completion of the reaction, the pressure reduction was terminated, the system temperature was lowered under a nitrogen stream, and the pellets were taken out when the temperature reached 60 ° C. (polyamide 3). The total reaction time was 300 minutes. Polyamide 3 obtained had a relative viscosity of 2.62, a melting point of 237 ° C., a glass transition point of 85 ° C., a moisture concentration of 432 ppm, and a fish eye number of 600.

Example 2
[Solid phase polymerization of polyamide 1]
Polyamide 1 20kg 2.45GHz microwave irradiation device and its waveguide, 50L capacity dispersion type mixing polymerization device consisting of stainless steel cylindrical container that can also flow heat medium and mixing blade attached to the rotating shaft And rotated at 0.5 m / s while continuously irradiating microwaves at 3 KW. The atmosphere in the reaction system was raised from room temperature to 140 ° C. under a small nitrogen flow. When the internal temperature of the reaction system reached 140 ° C, the pressure was reduced to 1 Torr or less, and the internal temperature was further increased to 180 ° C. From the time when the system temperature reached 180 ° C., the solid state polymerization reaction was continued at the same temperature. After completion of the reaction, the pressure reduction was terminated, the system temperature was lowered under a nitrogen stream, and the pellet was taken out when the temperature reached 60 ° C. (polyamide 4). The total reaction time was 140 minutes. The obtained polyamide 4 has no welding or burnt between pellets, has a relative viscosity of 2.70, a melting point of 237 ° C., a glass transition point of 85 ° C., a moisture concentration of 205 ppm, and a fish eye number of 200. Met.

Comparative Example 2
[Solid phase polymerization of polyamide 1]
20 kg of polyamide 1 was charged into a 50 L capacity dispersion type mixing polymerization apparatus composed of a stainless steel cylindrical container capable of flowing a high-temperature heat medium and a mixing blade attached to a rotating shaft, and rotated at 0.5 m / s. The atmosphere in the reaction system was raised from room temperature to 140 ° C. under a small nitrogen flow. When the reaction system temperature reached 140 ° C., the pressure was reduced to 1 Torr or less, and the system temperature was further increased to 180 ° C. in 40 minutes. From the time when the system temperature reached 180 ° C., the solid state polymerization reaction was continued at the same temperature for 180 minutes. After completion of the reaction, the pressure reduction was terminated, the system temperature was lowered under a nitrogen stream, and the pellet was taken out when the temperature reached 60 ° C. (polyamide 5). The total reaction time was 300 minutes. Polyamide 5 obtained had a relative viscosity of 2.62, a melting point of 237 ° C., a glass transition point of 85 ° C., a moisture concentration of 700 ppm, and a fisheye number of 650.

Comparative Example 3
[Solid phase polymerization of polyamide 1]
The same procedure as in Example 2 was performed except that the stirring blade was stopped and stirring was not performed. When the internal temperature rose to 110 ° C., the temperature of the polyamide resin pellets partially melted beyond the melting point due to local irradiation of microwaves.

  In the solid phase polymerization according to the present invention, a high-quality high-molecular weight polyamide can be efficiently obtained in a short period of time and without the occurrence of fusion between polyamides or kogation, as compared with conventional solid-phase polymerization. it can. Because it is possible to obtain a given high molecular weight polyamide in a short heat treatment time, the occurrence of low molecular weight components is extremely low, and the number of fish eyes during production of films such as food packaging can be suppressed, resulting in productivity. Can be greatly improved, and the effect is great.

Claims (5)

  A method for solid-phase polymerization of polyamide, comprising irradiating a polyamide resin pellet with microwaves in a stirring type solid-phase polymerization apparatus.   The polyamide is a polyamide formed from a diamine component containing 70 mol% or more of xylylenediamine or bis (aminomethyl) cyclohexane and a dicarboxylic acid component containing 70 mol% or more of an aliphatic dicarboxylic acid having 4 to 20 carbon atoms. The solid phase polymerization method according to claim 1.   The solid phase polymerization method according to claim 1 or 2, wherein a microwave and a heat medium are used in combination as a heat source of the stirring type solid phase polymerization apparatus.   The solid phase polymerization method according to any one of claims 1 to 3, wherein the stirring type solid phase polymerization apparatus is a batch type.   The solid phase polymerization method according to any one of claims 1 to 4, wherein the stirring type solid phase polymerization apparatus is a dispersion type mixing polymerization apparatus including a cylindrical vessel and a mixing blade attached to a rotating shaft.