JP4329292B2 - Method for producing polyamide prepolymer and method for producing polyamide - Google Patents

Description

【００６３】
【表２】

【００６４】
実施例１０〜１２、比較例４ （未反応カプロラクタム・オリゴマーの溶融揮発除去）
前記実施例１〜９あるいは比較例１〜３で得たポリアミドからカプロラクタム、オリゴマーを溶融揮発除去した。溶融揮発除去は、以下の条件で日本製鋼所社製３０ｍｍφベント付２軸押出機を用いて行った。・Ｌ／Ｄ＝４５．５、同方向回転、深溝タイプ、
・バレル温度：原料供給側からの温度が１６０／２４０／２５０／２６０／２６０／２６０／２６０／２５０／２５０℃
・第２、４、６ゾーンから１３３Ｐａ（1Ｔorr）で減圧脱気
・回転数２００ｒｐｍ
結果を表３に示す。その結果、本発明の方法によれば、未反応カプロラクタム含有量が０．０５重量％以下、オリゴマー含有量が０．９９重量％以下という、カプロラクタム、オリゴマーの含有量が少ないポリアミドが得られた。
【００６５】
【表３】

【００６６】
実施例１３〜１５、比較例５（未反応カプロラクタム・オリゴマーの固相揮発除去）
前記実施例１〜９あるいは比較例１〜３で得たポリアミドからカプロラクタム、オリゴマーを固相揮発除去を実施した。固相揮発除去は３Ｌ回転型減圧固相重合装置を用い、１３３Ｐａ（1Ｔorr）、１５０℃にて６時間揮発除去を行った。結果を表４に示す。その結果、未反応カプロラクタム含有量が０．０８重量％以下、オリゴマー含有量が１．１０重量％以下という、カプロラクタム、オリゴマーの含有量が少ないポリアミドが得られた。
【００６７】
【表４】

【００６８】
実施例１６，１７、比較例６（未反応カプロラクタム・オリゴマーの熱水抽出除去）
前記実施例１〜９あるいは比較例１〜３で得たポリアミドからカプロラクタム、オリゴマーを熱水抽出除去を実施した。抽出にはポリアミド樹脂の円筒状ペレット（直径約２ｍｍ、長さ約３ｍｍ）を用いた。抽出条件は以下の通り。
抽出溶媒：水
抽出浴比：ポリアミド／水＝１：２０
抽出温度：９８℃。
重合反応生成物中の未反応カプロラクタム量が０．０５重量％以下、オリゴマー量が１．０重量％以下にまで低減するために必要な抽出時間を測定した。
【００６９】
結果を表５に示す。要抽出時間の対比より、本発明の製造方法により得られたポリアミドは必要な抽出時間が短時間で済んだ。
【００７０】
【表５】

【００７１】
また、実施例１０〜１５のポリアミドを射出成形し、ハンドリング性を確認したところ、従来法によるものと遜色の無いものであった。
【００７２】
【発明の効果】
本発明の製造方法を用いることにより、未反応カプロラクタムおよびオリゴマーが低減されたポリアミドを得ることができる。本発明のポリアミドにより、熱水抽出工程の省略もしくは時間短縮が可能となり、高生産効率かつ低エネルギーコストでポリアミド樹脂を製造することができる。
【図面の簡単な説明】
【図１】実施例で用いた重合反応装置の概略図である。
【符号の説明】
１：原料貯槽
２：原料供給ポンプ
３：圧力計
４：加圧加熱処理槽
５：調圧バルブ
６：ポリアミドプレポリマー採取口
７：常圧連続重合塔[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a polyamide prepolymer produced from caprolactam as a main raw material, and a method for producing a polyamide . More specifically, when a heat treatment for a specific time is performed using caprolactam as a main raw material, a polyamide prepolymer with a very small amount of cyclic oligomer and a high degree of polymerization are reduced at the time of receiving a heat polymerization heat history for a specific time. The present invention relates to a method for producing a polyamide having unreacted caprolactam content and oligomer content with high efficiency and low energy.
[0002]
[Prior art]
Polyamide resin mainly made of caprolactam is used for textile fibers and industrial fibers by taking advantage of its excellent properties. Furthermore, it is used as an injection-molded product in the automotive, electrical and electronic fields, and mainly for food packaging applications. Also widely used as extruded film and stretched film.
[0003]
A polyamide resin mainly composed of caprolactam is usually produced by heating caprolactam in the presence of a small amount of water. This manufacturing method is a relatively simple process, and is a manufacturing method widely used in the world. The outline of the polymerization method of general-purpose polycapramide described in pages 63 to 65 of “Polyamide resin handbook” (Osamu Fukumoto, Nikkan Kogyo Shimbun) will be described below.
[0004]
Caprolactam is melted and supplied to an atmospheric polymerization tower heated to about 260 ° C., and after staying in this polymerization tower for about 10 hours, it is formed into a strand form from the bottom of the tower and discharged into a water tank to be pelletized. Since the polycapramide resin pellets thus obtained contain caprolactam monomers and oligomers generated in the polymerization equilibrium, they are then supplied to the hot water extraction tower, extracted countercurrently with hot water sent from the bottom of the tower, and then taken out from the bottom. . Since the pellet after extraction contains a large amount of water, it is dried at about 100 ° C. in a vacuum or an inert gas atmosphere.
[0005]
Thus, since the polyamide after caprolactam polymerization contains unreacted caprolactam and an oligomer, it is thought that the hot water extraction process after superposition | polymerization is essential. This hot water extraction step requires a lot of energy, and unreacted monomers lower the productivity, so that this step is required to be omitted or shortened.
[0006]
As a means for omitting the hot water extraction step, there is a method of removing unreacted caprolactam and oligomer by treating the polymerized polyamide in a molten state under high temperature and high vacuum (US Pat. No. 3,558,567). book). However, since it is particularly difficult to remove oligomers, there are few examples applied to actual production.
[0007]
Another approach is to reduce unreacted monomers and oligomers in order to reduce the time required for the hot water extraction process. In particular, there is a demand for reduction in oligomers that have low solubility in water and are difficult to extract.
[0008]
That is, in order to omit the hot water extraction step or shorten the time, it is necessary to reduce unreacted caprolactam and oligomer after polymerization. Thus, several examples have been proposed so far for reducing unreacted caprolactam and oligomers.
[0009]
For example, Japanese Patent Application Laid-Open No. 59-164327 proposes a method in which a caprolactam prepolymer is polymerized and then further polymerized under pressure to reduce oligomers and gels.
[0010]
This method discloses a method of obtaining a polyamide polymer having a low oligomer or gel content by prepolymerizing caprolactam at 220 to 280 ° C. and then further polymerizing it at 240 to 290 ° C. under pressure. However, this method is effective for reducing the gel, but the prepolymerization step requires a relatively long time and has a large thermal history, so that the oligomer reduction effect in this step is insufficient.
[0011]
Further, Japanese Patent Publication No. 50-26594 proposes a method for reducing the oligomer amount by lowering the polymerization temperature.
[0012]
In this method, a method for producing a polyamide resin having a low cyclic oligomer content by polymerizing in a temperature range from the melting point to the melting point + 20 ° C. of the polyamide that produces caprolactam having a water content of 0.5% by weight or less is disclosed. . Here, it is shown that a polyamide having a cyclic oligomer content of 0.9% by weight was obtained, but the polymerization time was as long as 30 h, and the amount of unreacted caprolactam at that time was 15% or more. No reduction has been made. That is, there is a problem that the yield of polyamide is low and the productivity is low.
[0013]
The present inventors previously prepared a polyamide resin having a low oligomer amount by polymerizing in the presence of a dicarboxylic acid and a diamine in the presence of a dicarboxylic acid and a diamine below the melting point of the resulting polyamide in JP-A-11-343341. Has been proposed to remove caprolactam and oligomers by heating under reduced pressure, but further development of unreacted materials, polyamides with a small amount of oligomers, and a production method with high productivity of the polyamides has been demanded.
[0014]
[Problems to be solved by the invention]
As described above, in a polyamide mainly composed of caprolactam, it is obtained within a specific melt polymerization time, has a high degree of polymerization, and has a sufficiently low unreacted caprolactam content and oligomer content. Polyamide was not known. In addition, a method capable of producing a polyamide having low caprolactam content and oligomer content with high productivity has not been known so far.
[0015]
Therefore, the present inventors solved the above-mentioned problems of the prior art, obtained within a specific melt polymerization time to achieve omission of the hot water extraction step or time reduction, and have a high degree of polymerization, It is another object of the present invention to provide a polyamide having low unreacted caprolactam content and oligomer content, and a method for producing the polyamide with high productivity.
[0016]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems, a polyamide having a large amount of amino groups and a small amount of cyclic oligomers can be obtained by subjecting a caprolactam aqueous solution having a specific water content to a short heat treatment under pressure and at a specific temperature. A prepolymer is produced, and the prepolymer is polymerized under a temperature condition not exceeding the melting point of the resulting polyamide under a polymerization time of 20 hours or less, so that the degree of polymerization is sufficiently high and the unreacted caprolactam content and by-products are increased. The inventors have found that a polyamide resin having a low raw oligomer content can be produced, and reached the present invention.
[0017]
That is, the object of the present invention is to
(1) Heat treatment of caprolactam aqueous solution having a water content of 2 to 20% by weight under a sufficient pressure to prevent volatilization of water in the system at a temperature of 200 to 330 ° C. for 1 to 30 minutes. Amino group content 0.1 mmol / 1g or more, and the manufacturing method of the polyamide prepolymer whose cyclic oligomer content is 0.6 weight% or less.
(2) The method for producing a polyamide prepolymer according to (1), wherein the heat treatment is performed at 0.111 to 6.08 MPa.
(3) The method for producing a polyamide prepolymer according to (1) or (2 ), wherein the amino group content is 0.15 mmol / 1 g or more and the cyclic oligomer content is 0.4 wt% or less.
(4) A method for producing a polyamide comprising a capramide unit as a main constituent, wherein a caprolactam aqueous solution having a water content of 2 to 20% by weight is applied at a pressure of 200 to 330 ° C. under a pressure sufficient to prevent volatilization of moisture in the system. A polyamide prepolymer having an amino group content of 0.1 mmol / 1 g or more and a cyclic oligomer content of 0.6% by weight or less, obtained by heat treatment at a temperature for 1 to 30 minutes, is supplied to an atmospheric pressure polymerization apparatus and polymerized. The sulfuric acid relative viscosity is 2.0 or more, and the caprolactam content is 15% by weight or less, characterized in that the maximum temperature is polymerized within 20 hours under the temperature condition where the melting point of the obtained polyamide is + 10 ° C. or less. A method for producing a polyamide having an oligomer content of 1.8% by weight or less and a cyclic 2-tetramer content: 0.9% by weight or less.
(5) The method for producing a polyamide as described in (4 ), wherein the maximum polymerization temperature is not higher than the melting point of the obtained polyamide.
(6) A method for producing a polyamide comprising a capramide unit as a main constituent, wherein a caprolactam aqueous solution having a water content of 2 to 20% by weight is applied at a pressure of 200 to 330 ° C. under a sufficient pressure to prevent evaporation of moisture in the system. A polyamide prepolymer having an amino group content of 0.1 mmol / 1 g or more and a cyclic oligomer content of 0.6% by weight or less, and 5 mol% or less based on the caprolactam obtained by heat treatment at a temperature for 1 to 30 minutes. At least one additive selected from dicarboxylic acids, diamines, and salts thereof is supplied to an atmospheric pressure polymerization apparatus, and the maximum polymerization temperature is the melting point of the resulting polyamide + 10 ° C. or less. The relative viscosity of sulfuric acid is 2.0 or more and the caprolactam content is 15% by weight or less, and the oligomer content is 1. Wt% or less, the total of the cyclic 2-4 mer content: 0.9 manufacturing method of weight percent of the polyamide.
(7) The method for producing a polyamide as described in (6 ), wherein the maximum polymerization temperature is not higher than the melting point of the obtained polyamide.
(8) The method for producing a polyamide according to (6) or (7 ), wherein the additive is a salt of a dicarboxylic acid and a diamine.
(9) The method for producing a polyamide according to (8) , wherein the salt of the dicarboxylic acid and the diamine is a salt derived from an aliphatic and / or aromatic dicarboxylic acid and an aliphatic diamine.
(10) The method for producing a polyamide according to (9 ), wherein the dicarboxylic acid constituting the salt of the dicarboxylic acid and the diamine is adipic acid and / or terephthalic acid, and the diamine is hexamethylenediamine.
(11) The method for producing a polyamide according to any one of (4) to (10), wherein a heat treatment is performed at 0.111 to 6.08 MPa when a polyamide prepolymer is obtained.
(12) The method for producing a polyamide as described in any one of (4) to (11), wherein the moisture content of the polyamide prepolymer when supplied to the atmospheric pressure polymerization apparatus is 4% by weight or less.
(13) The method for producing a polyamide as described in any one of (4) to (12) , wherein the prepolymer is flushed at the upper part of the atmospheric pressure polymerization apparatus and moisture is removed by evaporation before supplying the polyamide prepolymer to the atmospheric pressure polymerization apparatus.
(14) The method for producing a polyamide according to any one of (4) to (13) , wherein the atmospheric pressure polymerization apparatus is a continuous atmospheric pressure polymerization apparatus.
Can be achieved.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
The polyamide prepolymer referred to in the present invention is a composition obtained by the following heat treatment of a polyamide raw material, and refers to a mixture comprising a polyamide chain oligomer, a cyclic oligomer, and an unreacted raw material.
[0019]
Caprolactam is mainly used as the raw material for the polyamide used in the polyamide prepolymer or the polyamide production method of the present invention, but one or more other lactams and derivatives thereof are used in the polyamide as long as the object of the invention is not impaired. You may use together and use in the range which does not exceed 20 mol% of the whole raw material. If it exceeds 20 mol%, the crystallinity of the resulting polyamide polymer may be lowered.
[0020]
Specific examples of such combined lactams and derivatives thereof include valerolactam, enantolactam, capryllactam, undecalactam, laurolactam, etc. Among these, laurolactam, aminocaproic acid, aminoundecanoic acid, aminododecane Acid is preferred.
[0021]
In the method for producing a polyamide prepolymer of the present invention, an aqueous caprolactam solution is prepared. The lower limit of the water content at this time is 2% by weight, preferably 2.4% by weight, particularly preferably 3% by weight, based on the total amount. The upper limit of the moisture content is 20% by weight, preferably 17% by weight, particularly preferably 15% by weight, based on the total amount. If the water content is outside the range of 2 to 20% by weight, the amount of oligomer in the polyamide prepolymer increases until the necessary amino group amount is obtained, and the object of the present invention cannot be achieved.
[0022]
The method for producing the polyamide prepolymer of the present invention requires heat treatment at 200 to 330 ° C. for 1 to 30 minutes under pressure.
[0023]
The pressure at this time is not particularly limited as long as it is sufficient to prevent the evaporation of moisture in the system, but it is 0.111 to 6.08 MPa (1.1 to 60 atm, 1.14 to 62.00 kg / cm 2). ) Is preferable, and 0.152 to 5.065 MPa (1.5 to 50 atm, 1.55 to 51.67 kg / cm 2) is more preferable. Under a pressure of less than 0.111 MPa, the amino group production efficiency during prepolymerization is reduced, so that the amount of oligomer in the polyamide prepolymer increases until the necessary amino group amount is obtained, while 6.08 MPa. If it exceeds, the productivity and economy will be inferior.
[0024]
The processing temperature when preparing the polyamide prepolymer of the present invention is in the range of 200-330 ° C. The lower limit of the treatment temperature is preferably 205 ° C, particularly preferably 210 ° C, and most preferably 250 ° C. The upper limit of the treatment temperature is preferably 325 ° C, particularly preferably 320 ° C, and most preferably 315 ° C. If the temperature is less than 200 ° C., the content of the cyclic oligomer is large when the necessary amino group content is obtained.
[0025]
The processing time for preparing the polyamide prepolymer of the present invention is 1 to 30 minutes. The upper limit is preferably 25 minutes or less, particularly preferably 20 minutes or less. This is because the cyclic oligomer content in the reaction product increases when the reaction time exceeds 30 minutes, and the amino group content fluctuates below 1 minute, making it difficult to control the degree of polymerization of the polyamide in the polymerization step.
[0026]
The polyamide prepolymer of the present invention thus obtained has an amino group content of 0.1 mmol / 1 g or more in the prepolymer. Furthermore, it is preferably 0.15 mmol / 1g or more, particularly preferably 0.2 mmol / 1g or more. This is because when the amount is less than 0.1 mmol / 1 g, the oligomer content in the polyamide increases when the polyamide is produced from the obtained polyamide prepolymer. Although there is no upper limit to the amount of amino groups, a range of 1.0 mmol / g or less is usually employed in terms of productivity. Moreover, cyclic oligomer content in a prepolymer is 0.6 weight% or less. Preferably it is 0.4 weight% or less, Most preferably, it is 0.3 weight% or less. This is because when the amount exceeds 0.6% by weight, the oligomer content in the polyamide polymer increases when the polyamide polymer is produced from the obtained polyamide prepolymer. Although there is no restriction | limiting in particular in the minimum of this cyclic oligomer content, Usually, it is 0.01 weight%.
[0027]
When the polyamide of the present invention is produced by melt polymerization within 20 hours, the relative viscosity of sulfuric acid is 2.0 or more, the unreacted caprolactam content is 15 wt% or less, the oligomer content is 1.8 wt% or less, and the cyclic amount is 2 to 4 amounts. It is necessary to have a total body content of 0.9% by weight or less, and by satisfying this requirement, it becomes possible to produce high-quality polyamide with high productivity. .
[0028]
The sulfuric acid relative viscosity of the polyamide of the present invention is 2.0 or more as the relative viscosity at 25 ° C. of a 98% sulfuric acid solution having a sample concentration of 0.01 g / mL. Furthermore, it is preferably 2.05 to 7.0, particularly preferably 2.1 to 6.5, and most preferably 2.15 to 6.0. When the relative viscosity is less than 2.0, the mechanical properties are not sufficiently developed. When the relative viscosity exceeds 8.0, the melt viscosity is too high and molding becomes difficult.
[0029]
In the polyamide of the present invention, the unreacted caprolactam content in the finally obtained polyamide is 15% by weight or less, preferably 13% by weight or less, and more preferably 11% by weight or less. If it exceeds 15% by weight, the time and energy required for the hot water extraction step will increase. The lower limit of caprolactam content is not limited, but is usually about 3% by weight.
[0030]
In the polyamide of the present invention, the oligomer content in the finally obtained polyamide is 1.8% by weight or less. Preferably it is 1.5 weight% or less, More preferably, it is 1.3 weight% or less. If it exceeds 1.8% by weight, the time required for the hot water extraction step increases, and the content of the oligomer after caprolactam and oligomer volatilization removal increases. The lower limit of the oligomer content is not limited, but is usually about 0.6% by weight.
[0031]
In the polyamide of the present invention, the total cyclic 2-tetramer content in the finally obtained polyamide is 0.9% by weight or less. Preferably it is 0.85 weight% or less, More preferably, it is 0.8 weight% or less. If it exceeds 0.9% by weight, the time required for the hot water extraction step will increase, and the content of the oligomer after volatilization removal of caprolactam and oligomer will increase. Although there is no restriction | limiting in the total of cyclic | annular 2-4 tetramer content, Usually, it is about 0.2 weight%.
[0032]
In the method for producing a polyamide of the present invention, at the start of polymerization, caprolactam can be further added to the polyamide prepolymer for polymerization. The additional amount of caprolactam is not particularly limited as long as the amino group content in the raw material composition composed of the polyamide prepolymer and the additional caprolactam is 0.1 mmol / 1 g or more.
[0033]
In the polyamide production method of the present invention, at least one additive selected from 5 mol% or less of dicarboxylic acid, diamine, and salts thereof with respect to caprolactam in the raw material before heat treatment is added to the atmospheric pressure polymerization apparatus. It can be fed and polymerized. By adding the additive, the required polymerization time can be further shortened and the oligomer content in the polyamide polymer can be further reduced. However, the addition amount is preferably 4 mol% or less, more preferably 3 mol% or less. If the additive amount exceeds 5 mol%, the melting point and crystallinity of the polyamide polymer obtained may be lowered, and the moldability and physical properties of the molded product may be lowered.
[0034]
Dicarboxylic acids constituting the additive include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassic acid, tetradecanediic acid. Acids, aliphatic dicarboxylic acids such as pentadecanedioic acid, octadecanedioic acid, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, etc. Can be mentioned.
[0035]
Examples of the diamine constituting the additive include 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, 1,12-diaminododecane, 1,13-diaminotridecane, 1,14-diaminotetradecane, 1,15-diaminopentadecane, 1,16-diaminohexadecane, Aliphatic diamines such as 1,17-diaminoheptadecane, 1,18-diaminooctadecane, 1,19-diaminononadecane, 1,20-diaminoeicosane, diethylaminopropylamine, cyclohexanediamine, bis- (4-aminohexyl) ) Alicyclic diamines such as methane, xylylene diamine And aromatic diamines such as emissions and the like.
[0036]
The additive is preferably a salt of a dicarboxylic acid and a diamine, more preferably a salt derived from an aliphatic and / or aromatic dicarboxylic acid and an aliphatic diamine, and most preferably an adipic acid and hexamethylene. Salts derived from diamines and / or salts derived from terephthalic acid and hexamethylenediamine.
[0037]
There is no restriction | limiting in particular in the method of supplying the said additive to an atmospheric pressure polymerization apparatus. A granular solid may be added to the polymerization apparatus, or may be dissolved in a solvent such as water and added as a solution.
[0038]
In the method for producing a polyamide of the present invention, the obtained reaction product is preferably polymerized under normal pressure.
In the method for producing a polyamide of the present invention, the polymerization apparatus to be used is not particularly limited, and an apparatus generally used for polymerization of caprolactam can be used. Specific examples include liquid phase polymerization apparatuses such as a continuous atmospheric polymerization apparatus and a batch polymerization apparatus. Of these, a continuous atmospheric polymerization apparatus is preferred from the viewpoint of productivity.
[0039]
In the method for producing a polyamide of the present invention, the polymerization is carried out under a temperature condition in which the maximum polymerization temperature is the melting point of the obtained polyamide + 10 ° C. or less, preferably the melting point or less. If the melting point of the polyamide at which the highest temperature is obtained during the polymerization exceeds + 10 ° C., the oligomer content increases, and if the polymerization temperature is too low, the time required for the polymerization becomes long and the production efficiency decreases. Therefore, the polymerization temperature is preferably in the range of 160 to 232 ° C, more preferably in the range of 170 to 222 ° C, and particularly preferably in the range of 180 to 220 ° C. The melting point is determined by using a differential scanning calorimeter (DSC) with a heating rate of 20 ° C./min using a sample obtained by removing caprolactam, oligomers, and the like from the obtained polyamide by hot water extraction and then cooling the polyamide. Defined as peak top temperature of endothermic peak based on measured crystal melting.
[0040]
If the above conditions are satisfied, the polymerization temperature profile can be arbitrarily set according to a conventional method.
In the polyamide production method of the present invention, the polymerization time is within 20 hours, preferably within 18 hours, and more preferably within 16 hours. If it exceeds 20 hours, the practical value is reduced in terms of production efficiency.
[0041]
In the method for producing a polyamide of the present invention, the water content when supplied to the atmospheric polymerization apparatus is not limited, but is preferably 4% by weight or less. If the amount exceeds 4% by weight, a large amount of heat is required for heating when producing the polyamide, and the productivity is lowered.
[0042]
In the method for producing a polyamide polymer of the present invention, when the polyamide prepolymer obtained by heat treatment under pressure is supplied to an atmospheric pressure polymerization apparatus, the reaction product after heat treatment under pressure is flushed to the upper part of the atmospheric pressure polymerization apparatus to remove moisture. It is preferable to remove the transpiration. By removing the water by transpiration, the amount of heat required for heating when producing the polyamide can be reduced and the polymerization temperature can be easily controlled.
[0043]
In the method for producing a polyamide polymer of the present invention, caprolactam and oligomer may be removed from the obtained polyamide by hot water extraction, or may be removed by volatilization by heating under reduced pressure, or heated under reduced pressure. After removing caprolactam and oligomer, hot water extraction may be further performed.
[0044]
The volatilization removal of caprolactam and oligomer by heating under reduced pressure may be performed in a solid phase or in a molten state after the polymerization reaction product is made into a solid such as a pellet. Volatile removal in the molten state may be performed by making the polymerization reaction product a solid such as pellets, and then performing melting / depressurization heating with an extruder / thin film evaporator, etc. The reaction product may be directly supplied to an extruder, a thin film evaporator or the like.
[0045]
Moreover, in the volatilization removal by heating under reduced pressure of caprolactam and oligomer, the degree of polymerization of polyamide can be adjusted to a suitable value according to the application.
[0046]
The polyamide obtained by the method for producing a polyamide of the present invention has a temperature lower than the melting point of the polyamide and a reduced pressure so that a suitable viscosity can be obtained for applications where the polyamide is required to have a high viscosity such as extrusion molding. It is preferable to adjust to a desired degree of polymerization by solid-phase decompression treatment under heat treatment.
[0047]
In the method for producing a polyamide of the present invention, the terminal can be blocked with a carboxylic acid compound as necessary. When end-capping is performed by adding a monocarboxylic acid, the end group concentration of the obtained polyamide resin is lower than when no end-blocking agent is used. On the other hand, when end-capping with dicarboxylic acid, the total amount of terminal groups does not change, but the ratio of amino terminal groups to carboxyl terminal groups can be changed. Specific examples of the carboxylic acid compound include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, myristic acid, palmitic acid, Aliphatic monocarboxylic acids such as stearic acid, oleic acid, linoleic acid and arachidic acid, cycloaliphatic monocarboxylic acids such as cyclohexanecarboxylic acid and methylcyclohexanecarboxylic acid, benzoic acid, toluic acid, ethylbenzoic acid, phenylacetic acid Aromatic monocarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassic acid, tetradecanedioic acid Aliphatic dica, such as pentadecanedioic acid, octadecanedioic acid Bon acid, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, and aromatic dicarboxylic acids such as naphthalene dicarboxylic acid.
[0048]
In addition, as a method for adding a terminal blocking agent, a method of simultaneously charging raw materials such as caprolactam at the initial stage of the heat treatment of the polyamide prepolymer, a method of adding in the middle of the heat treatment, a method of adding after the heat treatment and before introducing the atmospheric pressure polymerization apparatus, A method of adding a polyamide resin when removing unreacted caprolactam and oligomer in a molten state is employed. The terminal blocking agent may be added as it is, or may be added after dissolving in a small amount of solvent.
[0049]
In the production method of the present invention, for example, an antioxidant or a heat stabilizer (hindered phenol type, hydroquinone type, phosphite type and substituted products thereof, copper halide, iodine compound, etc.), weathering agent ( Resorcinol, salicylate, benzotriazole, benzophenone, hindered amine, etc.), release agents and lubricants (fatty alcohol, aliphatic amide, aliphatic bisamide, bisurea, polyethylene wax, etc.), pigments (cadmium sulfide, phthalocyanine) , Carbon black, etc.), dyes (nigrosine, aniline black, etc.), crystal nucleating agents (talc, silica, kaolin, clay, etc.), plasticizers (octyl p-oxybenzoate, N-butylbenzenesulfonamide, etc.), antistatic Agent (alkyl sulfate type anionic antistatic agent, Quaternary ammonium salt type cationic antistatic agent, nonionic antistatic agent such as polyoxyethylene sorbitan monostearate, betaine amphoteric antistatic agent, etc.), flame retardant (melamine cyanurate, magnesium hydroxide, aluminum hydroxide) Such as hydroxide, ammonium polyphosphate, brominated polystyrene, brominated polyphenylene oxide, brominated polycarbonate, brominated epoxy resin or a combination of these brominated flame retardants and antimony trioxide), filler (graphite, sulfuric acid) Barium, magnesium sulfate, calcium carbonate, magnesium carbonate, antimony oxide, titanium oxide, aluminum oxide, zinc oxide, iron oxide, zinc sulfide, zinc, lead, nickel, aluminum, copper, iron, stainless steel, glass fiber, carbon fiber, aramid Fiber, ben Particles, fibers, needles, platy fillers such as knight, montmorillonite, synthetic mica), other polymers (other polyamides, polyethylene, polypropylene, polyester, polycarbonate, polyphenylene ether, polyphenylene sulfide, liquid crystal polymer, polysulfone) , Polyethersulfone, ABS resin, SAN resin, polystyrene, etc.) can be added at any time.
[0050]
The polyamide obtained by the production method of the present invention can be formed into a molded product by an ordinary molding method as in the case of conventional polyamide. There is no restriction | limiting in particular about a shaping | molding method, Well-known shaping | molding methods, such as injection molding, extrusion molding, blow molding, and press molding, can be utilized. The molded product referred to here includes shaped products such as fibers, films, sheets, tubes, monofilaments, etc. in addition to molded products in a narrow sense such as injection molding.
[0051]
【Example】
Hereinafter, the present invention will be specifically described with reference to examples. The analysis and measurement described in Examples and Comparative Examples were performed according to the following methods.
[0052]
(1) Amino acid content in polyamide prepolymer About 0.2 g of the substance to be measured is precisely weighed and dissolved in 25 cc of a phenol / ethanol mixed solvent (83.5: 16.5, volume ratio), and then 0.02N hydrochloric acid aqueous solution. Was titrated using.
[0053]
(2) Cyclic oligomer content in polyamide prepolymer The material to be measured is pulverized, passed through JIS standard sieve 24mesh, 124mesh is not passed, and the powder of the material to be measured is collected. Extraction was performed using a Soxhlet extractor for 3 hours, and cyclic oligomers contained in the extract were quantified using a high performance liquid chromatograph. In the following examples, cyclic oligomers of 7-mer or higher were not detected. The measurement conditions are as follows.
High performance liquid chromatograph: Waters 600E
Column: GL Sciences ODS-3
Detector: Waters 484 Tunable Absorbance Detector
Detection wavelength: 254 nm
Injection volume: 10 μl
Solvent: methanol / water (The composition of methanol / water was a gradient analysis of 20: 80 → 80: 20)
Flow rate: 1 ml / min.
[0054]
(3) Water content of polyamide prepolymer Measured using Hiranuma trace moisture measuring device AQ-6.
[0055]
(4) Caprolactam content in polyamide Polyamide was pulverized, passed through JIS standard sieve 24 mesh, 124 mesh collected non-passed polyamide powder, about 20 g of the powder was Soxhlet extracted with 200 ml of methanol for 3 hours, The caprolactam contained in was quantified using a high performance liquid chromatograph. The measurement conditions are as follows.
High performance liquid chromatograph: Waters 600E
Column: GL Sciences ODS-3
Detector: Waters 484 Tunable Absorbance Detector
Detection wavelength: 254 nm
Injection volume: 10 μl
Solvent: methanol / water (20:80 (volume ratio))
Flow rate: 1 ml / min.
[0056]
(5) Polyamide content of cyclic 2- to 4-mer in polyamide was pulverized, passed through JIS standard sieve 24mesh, 124mesh collected non-passed polyamide powder, and about 20g of the powder was extracted with 200ml of methanol for 3 hours with Soxhray extraction. Then, cyclic 2-tetramer content contained in the extract was quantified using a high performance liquid chromatograph. The measurement conditions are as follows.
High performance liquid chromatograph: Waters 600E
Column: GL Sciences ODS-3
Detector: Waters 484 Tunable Absorbance Detector
Detection wavelength: 254 nm
Injection volume: 10 μl
Solvent: methanol / water (20:80 (volume ratio))
Flow rate: 1 ml / min.
[0057]
(6) Oligomer content in polyamide.
[0058]
The polymerization reaction product is pulverized, JIS standard sieve 24mesh passes, 124mesh non-passable polyamide powder is collected, about 20 g of the powder is Soxhlet extracted with 200 ml of methanol for 3 hours, and caprolactam contained in the extract is After quantifying by the method, the residue was obtained by evaporating to dryness with an evaporator and further vacuum-drying at 80 ° C. for 8 hours to obtain the oligomer content.
[0059]
(7) Sulfuric acid relative viscosity (ηr)
Measurement was performed using an Ostwald viscometer at a concentration of 0.01 g / ml in 25% sulfuric acid in 98% sulfuric acid.
[0060]
Reference example (preparation of raw materials used)
Caprolactam was prepared by melting a special grade of Tokyo Chemical Industry Co., Ltd. and drying with molecular sieve. Hexamethylenediamine, terephthalic acid, and adipic acid were used as they were as special grades from Tokyo Chemical Industry Co., Ltd. The adipic acid / hexamethylene diamine salt and terephthalic acid / hexamethylene diamine salt used in the Examples and Comparative Examples were equimolar amounts of the above diamine and dicarboxylic acid, and then cooled in hot water, and the precipitated crystals were filtered. It vacuum-dried at 80 degreeC / 8 hours.
[0061]
Examples 1-9, Comparative Examples 1-3 (heat treatment and normal pressure continuous polymerization)
Heat treatment and normal pressure continuous polymerization were performed using the apparatus shown in FIG. The caprolactam aqueous solution having the composition described in Table 1 and Table 2 is charged into the raw material storage tank 1, and then supplied to the pressurized heat treatment tank 4 using the raw material supply pump 2 having the pressurization meter 3, and the conditions described in Table 1 and Table 2 The heat treatment was performed continuously under. Next, each of the obtained polyamide prepolymers was supplied to an atmospheric pressure continuous polymerization tower 7, and polymerization was performed under the conditions described in Tables 1 and 2 to obtain a polyamide as a polymerization reaction product. If necessary, various additives were added in powder form from the top of the polymerization tower. The pressure during the pressure heating treatment was controlled by the opening of the pressure regulating valve 5 in the middle of the flow path. In the analysis of the prepolymer, a sample was collected from the polyamide prepolymer sampling port 6 before being supplied to the atmospheric pressure continuous polymerization tower 7 and used for the analysis. The results are shown in Tables 1 and 2. As can be seen from a comparison between Examples 1 to 9 and Comparative Examples 1 to 3, the polyamide polymer obtained by the production method of the present invention had a small amount of unreacted caprolactam and an amount of oligomer, and the amount of oligomer was greatly reduced. . Moreover, the amount of oligomers was further reduced by adding a nylon salt to the top of the polymerization tower.
[0062]
[Table 1]

[0063]
[Table 2]

[0064]
Examples 10-12, comparative example 4 (melting volatilization removal of unreacted caprolactam oligomer)
Caprolactam and oligomers were melted and volatilized from the polyamides obtained in Examples 1 to 9 or Comparative Examples 1 to 3. Melt volatilization removal was performed using a 30 mmφ vented twin screw extruder manufactured by Nippon Steel Works under the following conditions.・ L / D = 45.5, same direction rotation, deep groove type,
Barrel temperature: Temperature from the raw material supply side is 160/240/250/260/260/260/260/250/250 ° C.
・ Depressurized degassing at 2 Pa, 1st and 6th zones at 133 Pa (1 Torr) ・ Rotation speed 200 rpm
The results are shown in Table 3. As a result, according to the method of the present invention, a polyamide having a low caprolactam and oligomer content in which the unreacted caprolactam content was 0.05% by weight or less and the oligomer content was 0.99% by weight or less was obtained.
[0065]
[Table 3]

[0066]
Examples 13 to 15 and Comparative Example 5 (solid phase volatilization removal of unreacted caprolactam oligomer)
From the polyamides obtained in Examples 1 to 9 or Comparative Examples 1 to 3, caprolactam and oligomers were subjected to solid phase volatilization removal. The solid phase volatilization removal was performed by using a 3 L rotary vacuum solid phase polymerization apparatus at 133 Pa (1 Torr) and 150 ° C. for 6 hours. The results are shown in Table 4. As a result, a polyamide having a low caprolactam and oligomer content in which the unreacted caprolactam content was 0.08% by weight or less and the oligomer content was 1.10% by weight or less was obtained.
[0067]
[Table 4]

[0068]
Examples 16, 17 and Comparative Example 6 (Hot water extraction removal of unreacted caprolactam oligomer)
Caprolactam and oligomer were removed from the polyamide obtained in Examples 1 to 9 or Comparative Examples 1 to 3 by hot water extraction. For extraction, a cylindrical pellet of polyamide resin (diameter: about 2 mm, length: about 3 mm) was used. The extraction conditions are as follows.
Extraction solvent: water extraction bath ratio: polyamide / water = 1: 20
Extraction temperature: 98 ° C.
The extraction time required to reduce the amount of unreacted caprolactam in the polymerization reaction product to 0.05% by weight or less and the amount of oligomer to 1.0% by weight or less was measured.
[0069]
The results are shown in Table 5. From the comparison of the extraction time required, the polyamide obtained by the production method of the present invention required a short extraction time.
[0070]
[Table 5]

[0071]
Moreover, when the polyamide of Examples 10-15 was injection-molded and the handling property was confirmed, it was inferior to that by the conventional method.
[0072]
【The invention's effect】
By using the production method of the present invention, a polyamide with reduced unreacted caprolactam and oligomers can be obtained. With the polyamide of the present invention, the hot water extraction step can be omitted or the time can be shortened, and a polyamide resin can be produced with high production efficiency and low energy cost.
[Brief description of the drawings]
FIG. 1 is a schematic view of a polymerization reaction apparatus used in Examples.
[Explanation of symbols]
1: Raw material storage tank 2: Raw material supply pump 3: Pressure gauge 4: Pressure heat treatment tank 5: Pressure regulating valve 6: Polyamide prepolymer sampling port 7: Normal pressure continuous polymerization tower

Claims (14)

A caprolactam aqueous solution having a water content of 2 to 20% by weight is heat-treated at a temperature of 200 to 330 ° C. for 1 to 30 minutes under a pressure sufficient to prevent volatilization of moisture in the system . Amino group content 0.1 mmol / 1 g or more And the manufacturing method of the polyamide prepolymer whose cyclic oligomer content is 0.6 weight% or less. The manufacturing method of the polyamide prepolymer of Claim 1 which heat-processes at 0.111-6.08MPa. The method for producing a polyamide prepolymer according to claim 1 or 2 , wherein the amino group content is 0.15 mmol / 1 g or more and the cyclic oligomer content is 0.4 wt% or less. A method for producing a polyamide comprising a capramide unit as a main constituent, wherein a caprolactam aqueous solution having a water content of 2 to 20% by weight is applied at a temperature of 200 to 330 ° C. under a pressure sufficient to prevent volatilization of water in the system. A polyamide prepolymer having an amino group content of 0.1 mmol / 1 g or more and a cyclic oligomer content of 0.6% by weight or less, obtained by heat treatment for 30 minutes, is supplied to an atmospheric pressure polymerization apparatus, and the maximum polymerization temperature is obtained. Polymerization within 20 hours under a temperature condition where the value is the melting point of the obtained polyamide + 10 ° C. or less, sulfuric acid relative viscosity is 2.0 or more, caprolactam content is 15% by weight or less, oligomer content Is 1.8% by weight or less, and the total cyclic 2-tetramer content is 0.9% by weight or less. The method for producing a polyamide according to claim 4, wherein the maximum polymerization temperature is not higher than the melting point of the obtained polyamide. A method for producing a polyamide comprising a capramide unit as a main constituent, wherein a caprolactam aqueous solution having a water content of 2 to 20% by weight is applied at a temperature of 200 to 330 ° C. under a pressure sufficient to prevent volatilization of water in the system. A polyamide prepolymer having an amino group content of 0.1 mmol / 1 g or more and a cyclic oligomer content of 0.6 wt% or less, and a dicarboxylic acid of 5 mol% or less based on the caprolactam obtained by heat treatment for ˜30 minutes At least one additive selected from diamine, diamine, and salts thereof is supplied to an atmospheric pressure polymerization apparatus, and the maximum polymerization temperature is 20 ° C. under a melting point of the obtained polyamide + 10 ° C. or less. The relative viscosity of sulfuric acid is 2.0 or more, caprolactam content is 15 wt% or less, oligomer content is 1.8 wt% Hereinafter, the sum of the cyclic 2-4 mer content: 0.9 manufacturing method of weight percent of the polyamide. The method for producing a polyamide according to claim 6, wherein the maximum polymerization temperature is not higher than the melting point of the obtained polyamide. The method for producing a polyamide according to claim 6 or 7, wherein the additive is a salt of a dicarboxylic acid and a diamine. The method for producing a polyamide according to claim 8 , wherein the salt of the dicarboxylic acid and the diamine is a salt derived from an aliphatic and / or aromatic dicarboxylic acid and an aliphatic diamine. The method for producing a polyamide according to claim 9, wherein the dicarboxylic acid constituting the salt of the dicarboxylic acid and the diamine is adipic acid and / or terephthalic acid, and the diamine is hexamethylenediamine. The method for producing a polyamide according to any one of claims 4 to 10, wherein the polyamide prepolymer is subjected to a heat treatment at 0.111 to 6.08 MPa. The method for producing a polyamide according to any one of claims 4 to 11 , wherein the moisture content of the polyamide prepolymer when fed to the atmospheric pressure polymerization apparatus is 4% by weight or less. The method for producing a polyamide according to any one of claims 4 to 12 , wherein the prepolymer is flushed at an upper portion of the atmospheric pressure polymerization apparatus before the supply of the atmospheric pressure polymerization apparatus of the polyamide prepolymer to evaporate and remove moisture. The method for producing a polyamide according to any one of claims 4 to 13 , wherein the atmospheric pressure polymerization apparatus is a continuous atmospheric pressure polymerization apparatus.

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