JP2003002966A - Polyamide resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyamide resin, especially a polyamide resin whose gelation is suppressed. SOLUTION: In the polyamide resin, >=70 mol. % of a diamine component is m-xylylenediamine and the total contents of tertiary nitrogen comprising nitrogen based on imino compounds and nitrogen based on tertiary amides is <=0.5 mol. % with respect to the total nitrogen content based on secondary amides.

Description

Description: TECHNICAL FIELD The present invention relates to a polyamide resin,
In particular, it relates to a polyamide resin in which gelation is suppressed. [0002] Various oxygen-barrier materials have been developed for the purpose of suppressing long-term storage stability by suppressing changes in taste, flavor, and efficacy due to oxygen in foods, beverages, pharmaceuticals, cosmetics, and the like. . Examples of such an oxygen barrier material include polyamide, polyvinyl alcohol, polyvinylidene fluoride, and polyvinylidene chloride. [0003] In particular, for example, poly-m-xylylenediamine (hereinafter may be abbreviated as MXD) and adipic acid (hereinafter may be abbreviated as AA) may be used.
m, such as m-xylylene adipamide (MXD-6)
-A polyamide containing xylylenediamine (MXD) as a diamine component has been attracting attention as a material having excellent oxygen barrier properties. [0004] However, polyamides containing MXD as a diamine component have the disadvantage that they tend to gel. This gelled substance is deposited on the polymerization kettle during the production of the polyamide resin and causes soiling of the kettle. The only way to clean the polymerization kettle is to open and clean the kettle, and the time and cost required for cleaning cannot be ignored in terms of cost and the like. In addition, dirt on the kettle becomes insoluble / infusible foreign matter and mixes with the polyamide resin product,
The quality of a molded article obtained from the polyamide resin is reduced. For the purpose of solving the above problems, Japanese Patent Publication No. Sho 51
No. 24297, Japanese Patent Publication No. 51-25065,
JP-B-51-25066, JP-B-51-4190
No. 6 discloses a method of adding a phosphorus compound such as sodium hypophosphite and an alkali metal compound such as sodium hydroxide during the production of polyamide. However,
Although these methods have some effect in suppressing gelation,
The degree of inhibition of gelation is low and is not a fundamental solution. As described above, there are many proposals aimed at suppressing the gelation of polyamide, but at present there is no definitive method. SUMMARY OF THE INVENTION An object of the present invention is to provide a polyamide resin which suppresses gelling and has oxygen barrier properties. According to the present invention, there is provided a diamine component wherein at least 70 mol% of the diamine component is m-xylylenediamine, and a total of nitrogen based on an imino compound and nitrogen based on a tertiary amide is used. A polyamide resin characterized in that the content of tertiary nitrogen represented by a molar ratio (mol%) to nitrogen based on tertiary amide is 0.5 mol% or less. DETAILED DESCRIPTION OF THE INVENTION In the polyamide resin of the present invention, 70% by mole or more of the diamine component constituting the polyamide is m-.
It must be xylylenediamine (MXD). If the MXD is less than 70 mol% of the diamine components constituting the polyamide, the oxygen barrier properties are significantly reduced. Preferably, among the diamine components constituting the polyamide, M
The XD is preferably at least 75 mol%, more preferably at least 80 mol%. The components constituting the polyamide resin of the present invention are not particularly limited as long as MXD is at least 70 mol% of the diamine components. The components of the polyamide resin of the present invention include MXD and adipic acid (AA). M obtained from
-Xylylene adipamide (MXD-6), m-xylylene sebacamide (MXD-10) obtained from MXD and sebacic acid (hereinafter sometimes abbreviated as SA), M
M-Xylylene isophthalamide (MXD-I) obtained from XD and isophthalic acid (hereinafter sometimes abbreviated as IPA) is preferred. Further, a copolymer polyamide obtained from MXD and an acid component obtained by combining two or three kinds selected from the above-mentioned AA, SA and IPA at an arbitrary ratio is also preferable. As the diamine component constituting the polyamide resin of the present invention, a diamine other than MXD can be used in an amount of less than 30 mol% of the diamine component. As such a diamine, for example, ethylenediamine, 1-
Methylethylenediamine, 1,3-propylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine,
Aliphatic diamines such as decamethylenediamine, undecamethylenediamine, dodecamethylenediamine, cyclohexanediamine, bis- (4,4′-aminohexyl)
Examples include alicyclic diamines such as methane, and aromatic diamines such as paraxylylenediamine. These can be used in combination of two or more kinds in any ratio. Among the above diamine components, hexamethylenediamine and paraxylylenediamine are preferred. As the acid component constituting the polyamide resin of the present invention, in addition to the above-mentioned AA, SA and IPA, malonic acid, succinic acid, glutaric acid, pimelic acid, stearic acid, azelaic acid, undecanoic acid, undecadioic acid, Aliphatic dicarboxylic acids such as dodecanedioic acid and dimer acid, 1,4-
Alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid,
Aromatic dicarboxylic acids such as terephthalic acid, phthalic acid, xylylenedicarboxylic acid, and naphthalenedicarboxylic acid can be used. These can be used in combination of two or more kinds in any ratio. Further, in addition to the above-mentioned diamine component and acid component, lactams such as ε-caprolactam and laurolactam, and aminocarboxylic acids such as aminocaproic acid and aminoundecanoic acid can also be used as the copolymerization component. When used as a copolymer component, ε-caprolactam is preferred. The tertiary nitrogen content of the polyamide resin of the present invention must be 0.5 mol% or less. In the present invention, the “tertiary nitrogen content” refers to the sum of the nitrogen content based on the imino compound and the nitrogen content based on the tertiary amide. In the present invention, the “tertiary nitrogen content” is represented by a molar ratio (mol%) to nitrogen based on the secondary amide.
Although it is difficult to reduce the tertiary nitrogen content to 0%, the lower the tertiary nitrogen content, the smaller the molecular weight dependency on gelation, and a stable polyamide resin is obtained. The quality of the formed body is also improved. When the content of tertiary nitrogen exceeds 0.5 mol%,
Gelation occurs even in a low molecular weight region, which not only deteriorates the quality of the polyamide resin and a molded article formed from the polyamide resin, but also promotes fouling of the reaction vessel. The content of tertiary nitrogen is preferably 0.48 mol% or less, more preferably 0.45 mol% or less. The method for obtaining the polyamide resin of the present invention is not particularly limited, and it can be obtained by a method similar to the production method in Examples described later. Specifically, as a method for reducing the content of tertiary nitrogen to 0.5 mol% or less, for example, a method in which the conditions at the time of production are set as specific conditions, as described later, may be mentioned. One of the methods for reducing the content of tertiary nitrogen to 0.5 mol% or less is as follows:
A method of increasing the concentration of an aqueous solution of an aminocarboxylate (hereinafter sometimes abbreviated as salt concentration) in a raw material preparation step (in the case of a batch method) or in an amidation step (in a case of a continuous step method). Is preferably used. By increasing the salt concentration (reducing the amount of the water solvent), gelation of the polyamide resin is suppressed. The reason is, for example, that according to Polymer Chemistry 25 318 (1968), a hydrogen cation acts as a catalyst for the reaction of imine, which is a tertiary nitrogen compound, by a deammonification reaction from the terminal amino group of two molecules to perform a reaction. It has been shown to promote. In view of this, increasing the salt concentration (conversely, decreasing the amount of the water solvent) means that the ion dissociation of the aminocarboxylate is less likely to occur, and as a result, the concentration of the hydrogen cation having a catalytic action is increased. And the production of imine is suppressed. Here, since the generated imine is a trifunctional compound, it becomes a tertiary amide in which a terminal carboxyl group reacts, and becomes three-dimensional, causing gelation. In the present invention, the salt concentration is preferably 80% by weight or more, and more preferably 85% by weight or more. If the salt concentration is less than 80% by weight, the amount of imine produced increases and gelation becomes easy. As one of the methods for reducing the content of tertiary nitrogen to 0.5 mol% or less, a method of adjusting the production time at the time of producing a polyamide resin as described below is preferably used. In the present invention, the production time during the production of the polyamide resin (hereinafter, may be abbreviated as the production time),
The time required for polyamide production, that is, after the raw materials (aqueous aminocarboxylate solution from diamine and dicarboxylic acid) are charged into the polymerization vessel (in the case of the batch method), or the supply of the raw materials to the amidation process is started (continuously). (In the case of the process-type manufacturing method) to the time required for taking out the polymer. In the present invention, the production time is preferably 210 minutes or less, more preferably 190 minutes or less, and particularly preferably 180 minutes or less. Production time 210
When the amount exceeds the limit, not only the content of tertiary nitrogen increases, but also coloration and molecular weight decrease due to deterioration of the polyamide resin are easily induced. Further, in the production of a polyamide resin,
It is preferable that the process from the start of the introduction of the raw materials to the removal of the polymer be a continuous process. Due to the continuous process, in the case of continuous batch production, a part of the previous batch remaining as a tank residue and the polymer adhering to the wall surface of the pot or the stirring blades are subject to heat history and cause an increase in the amount of tertiary nitrogen. Is prevented, the production time can be significantly shortened and the production process can be cleaned, and the tertiary nitrogen content can be reduced. In the production of a polyamide resin, the polymerization temperature is also involved in the production of imine. The imine production reaction also occurs at the initial stage of the reaction between diamine and dicarboxylic acid, and also depends on the melting point and melt viscosity depending on the structure and composition of the polyamide. Since the temperature involved in the production of imine changes, the polymerization temperature in the production of the polyamide resin of the present invention is appropriately set according to these various conditions, and is not particularly limited. In the production of the polyamide resin of the present invention, an alkali metal compound such as sodium hydroxide and sodium acetate and a phosphorus compound such as sodium hypophosphite may be used, if necessary, as long as the action of the present invention is not impaired. May be added for the purpose of suppressing thermal decomposition or as a polycondensation catalyst. The relative viscosity (R) of the polyamide resin of the present invention
v) is preferably 1.85 to 3.5 from the viewpoint of the mechanical properties of a molded article obtained from the polyamide resin of the present invention. If Rv is less than 1.85, the molecular weight is too small, and the mechanical properties are likely to deteriorate. When Rv exceeds 3.5, it takes a long time for polymerization, which is liable to cause deterioration of the polymer and undesired coloring, thereby lowering productivity and increasing costs. Further, even if the content of tertiary nitrogen is reduced, gelation easily occurs. The gelling time of the polyamide resin of the present invention is preferably longer from the viewpoint of production, but is preferably at least 7 hours or more, more preferably 8 hours or more. The oxygen permeability coefficient of the polyamide resin of the present invention is preferably 5 or less, more preferably 4 or less, from the viewpoint of its use. The oxygen permeability coefficient is
The smaller the value, the more difficult it is to transmit oxygen.Containers and packaging using materials with a low oxygen permeability coefficient are:
It will be excellent in long-term storage stability of foods, beverages, pharmaceuticals, cosmetics and the like. The polyamide resin of the present invention can be suitably used for films, sheets, containers, packaging bags, etc. having oxygen barrier properties. Further, by blending the polyamide resin of the present invention with another polymer having a low oxygen barrier property such as polyethylene terephthalate, the oxygen barrier property of the other polymer can be improved. Test Example Test Method (1) Gelation time 3 g of polyamide resin of Example and Comparative Example dried under reduced pressure at 100 ° C. for 24 hours in a branched test tube having an inner volume of about 20 ml.
, And subjected to reduced pressure nitrogen replacement three times, and then immersed in an oil bath at a constant temperature of 260 ° C. while flowing nitrogen gas at 30 ml / min, and heated for a predetermined time. When 0.25 g of the heat-treated polyamide resin was dissolved in 25 ml of 96% sulfuric acid at room temperature for 16 hours, the time required for visually recognizing the insoluble component was defined as the gelation time. (2) Relative viscosity (Rv) A sample solution was prepared by dissolving 0.25 g of the polyamide resin of the example and the comparative example in 25 ml of 96% sulfuric acid as a solvent.
From 10 seconds of the sample solution measured at 20 ° C. using a Ostwald viscometer at 20 ° C., the following formula 1
Was used to determine the relative viscosity (Rv). t ₀ : second of falling of solvent t: second of falling of sample solution (3) Content of tertiary nitrogen The polyamide resins of Examples and Comparative Examples were dissolved in hexafluoroisopropanol (HFIP) and subjected to NMR spectroscopy. Using a unit (Unity-500, manufactured by Varian)
The spectrum of ₁₃ (C ¹³ ) was analyzed to determine the content of tertiary nitrogen. (4) Oxygen Permeability Coefficient The oxygen permeability coefficients of the polyamide resins of the examples and comparative examples are as follows:
It was measured under the conditions of 24 ° C. and 100% RH according to JIS K7126. (5) Carboxyl end group concentration (CEG) 10 ml of benzyl alcohol was added to 0.2 g of the polyamide resin of the example and the comparative example, and dissolved at 180 ± 5 ° C. for 5 minutes to obtain a solution. The solution was cooled in water for 15 seconds, and phenolphthalene was used as an indicator.
Titration was performed with normal ethanolic potassium hydroxide, and the carboxyl end group concentration (CEG) was determined using the following equation 2. A: titer (ml) B: blank titer of solution (ml) N: concentration of ethanolic potassium hydroxide (mol / L) f: factor of ethanolic potassium hydroxide W: weight of polyamide resin ) Amino end group concentration (AEG) 0.6 g of the polyamide resin of each of Examples and Comparative Examples was dissolved in 50 ml of phenol / ethanol (vol ratio: 4/1), and 20 ml of water / ethanol (vol ratio: 3/2) was added. The indicator methyl orange was added, and titration was performed with a 1/10 normal ethanolic hydrochloric acid aqueous solution, and the amino terminal group concentration (AEG) was determined using the following formula 3. A: titration (ml) B: blank titration of solvent (ml) N: concentration of ethanolic hydrochloric acid (mol / L) f: factor of ethanolic hydrochloric acid W: weight of polyamide resin Table 1 shows the test results. EXAMPLE 1 In a continuous production process of polyamide comprising a raw material preparation process, an amidation process, an initial polymerization process, and a late polymerization process, adipic acid (AA) melted at 170 ° C. was 3.03.
M-Xylylenediamine (MXD) heated to 60 ° C. was continuously supplied to the amidation step at a supply rate of 9 kg / hr and at a supply rate of 2.828 kg / hr. The raw material supplied in the amidation step is converted to an internal pressure of 0.4 MPa.
Hereinafter, under the condition that the temperature in the apparatus rises from 170 ° C. to 245 ° C., the amidation reaction is carried out by retaining for about 50 minutes,
It was continuously fed to the initial polymerization step. In the initial polymerization step,
The mixture is kept for about 60 minutes under the condition of the temperature in the apparatus at 265 ° C. and the pressure in the apparatus at 0.4 MPa or less, and after the condensed water and the water used as the solvent are distilled off, it is continuously supplied at a supply rate of 5 kg / hr to the latter polymerization step. did. In the latter polymerization step, polycondensation was performed for about 6 minutes under the conditions of a resin temperature of 260 ° C., a screw rotation speed of 150 rpm, and a degree of vent vacuum of 1 hPa, and then the mixture was discharged into water in a strand form to obtain a polyamide resin. Examples 2 to 8 The composition, salt concentration and residence time (time required from the start of supply of the raw materials to the amidation step to the discharge of the polymer in a strand form) of the polyamide resin are shown in Table 1. A polyamide resin was obtained in the same manner as in Example 1 except for the above. Comparative Example 1 A reaction vessel was charged with 14614 parts by weight of adipic acid (AA), sufficiently purged with nitrogen, heated under a nitrogen atmosphere, and uniformly melted at 170 ° C. 13346.6 there
2 parts by weight of m-xylylenediamine (MXD) were continuously added dropwise with stirring. The time required for the addition was 330 minutes,
During this time, the temperature inside the apparatus rose to 245 ° C. After raising the temperature inside the device to 260 ° C for 180 minutes,
The remaining 272.38 parts by weight of MXD were continuously added dropwise over 50 minutes. After completion of the dropwise addition, the mixture was further reacted at the same temperature for 60 minutes, and then the content was discharged into water in a strand form to obtain a polyamide resin. The water generated by the reaction was distilled out of the system through a condenser. Comparative Examples 3 and 5 Except that the composition of the polyamide resin was changed to the composition shown in Table 1,
A polyamide resin was obtained in the same manner as in Comparative Example 1. Comparative Example 2 14614 parts by weight of adipic acid (A
A) 13619 parts by weight of m-xylylenediamine (M
XD) and 15200 parts by weight of water,
The jacket temperature was raised to 275 ° C. in minutes. The pressure in the kettle was adjusted to 1 MPa, and the reaction was carried out while draining water. The reaction temperature rose with the distilling of water, and reached 240 ° C. in 260 minutes from the start of the temperature rise. At this point, the pressure was released, and the pressure was reduced to normal pressure for 60 minutes. During this time, the reaction temperature was 260
° C. After continuing the reaction at the same temperature for another 60 minutes, the content was discharged into water in the form of a strand to obtain a polyamide resin. Comparative Examples 4, 6 to 8 Polyamide resins were obtained in the same manner as in Comparative Example 2, except that the composition, salt concentration and residence time of the polyamide resin were as shown in Table 1. The polyamide resin of the present invention suppresses gelling and has excellent oxygen barrier properties. Since the polyamide resin of the present invention has excellent oxygen barrier properties, it can be widely applied to containers and packaging bags containing foods, beverages, pharmaceuticals, cosmetics, and the like, or films and sheets. Long-term storage is possible by suppressing changes in efficacy. In addition, since the gelation is suppressed, it is possible to achieve an improvement in productivity during the production and an improvement in the quality of the obtained polyamide resin. [Table 1]

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Kenta Suzuki             10-24 Toyocho, Tsuruga-shi, Fukui Toyobo             Shikisha Polymer Development Center F term (reference) 4J001 DA01 DB01 DB02 DC14 EB05                       EB06 EB07 EB08 EB09 EB10                       EB14 EB34 EB35 EB36 EB37                       EB46 EB71 EC04 EC05 EC06                       EC07 EC08 EC09 EC14 EC16                       EC47 EC48 GB06 JB02 JB29                       JB50

Claims (1)

Claims: 1. Nitrogen based on secondary amide, which is the sum of nitrogen based on imino compound and nitrogen based on tertiary amide, wherein at least 70 mol% of the diamine component is m-xylylenediamine. A polyamide resin having a tertiary nitrogen content represented by a molar ratio (mol%) of 0.5 mol% or less.