JPH0995532A - Plyamide resin excellent in gas barrier property and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a film having excellent oxygen barrier properties and reduced in the dependency of the properties on temperatures by performing a step of prepolymerizing a specified polyamide resin under conditions in which the reaction mixture is molten under pressure so that a specified conditions may be held between the product of the steam pressure and the polymerization time and the polymerization temperature, and starting the post- polymerization step. SOLUTION: In producing a polyamide resin containing 20mol % or above, based on the entire resin, amide repeating units such as meta-xyleneadipamide units by a polycondensation process comprising a prepolymerization step under conditions in which the reaction mixture is molten under pressure and a subsequent post-polymerization step at normal pressure or in a vacuum, the precondensation step is performed under conditions in which the polymerization temperature (T) is 170-220 deg.C, the steam pressure (P) is 3kgf/cm<2> G or above, and the relationship between Pt (t) is the polymerization time) and T is specified, the state is brought into one in which the temperature is 220 deg.C or below and the pressure is normal pressure or below, the water of condensation is removed, and the post-polymerization step is started. The water absorptivity of the amorphous part of the formed resin is 8wt.% or below (at an RH of 100% and 25 deg. and the activation energy for β relaxation is 18kJ/mol or below (at 100Hz and a strain of 0.05%).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyamide resin which comprises specific components and compositions and is suitable for a film material having excellent gas barrier properties, and a method for producing the same. More specifically, it shows an excellent oxygen gas barrier property both during drying and under high humidity, and is suitably used as a packaging material for foods, pharmaceuticals, cosmetics, etc., and a polyamide resin for a film excellent in gas barrier property and The manufacturing method is related.

[0002]

2. Description of the Related Art Gas barrier properties, particularly barrier properties against oxygen gas, are one of the most important and basic functions required of packaging materials in practical use. Current,
Polyamide resin (that is, nylon), polyacrylonitrile (PAN), polyvinylidene chloride (PVDC), ethylene-vinyl alcohol copolymer (EVOH), and the like are used as the base polymer of the material that meets this demand. All of these polymers have a highly polar functional group in the molecule and form a molecule with a strong cohesive force. PAN, PVDC and EVO, among others
H has a high gas barrier property.

However, each of these polymers has a poor thermal stability as compared with nylon, and therefore has a problem in melt moldability. In particular, PVDC and PAN are difficult to be melt-molded, and therefore they are copolymerized to improve the moldability while sacrificing the barrier property. Further, although PVDC has an excellent oxygen gas barrier property, it has a drawback that chlorine-based gas is generated during combustion.
In addition, EVOH has a property that the moisture content increases with the increase of relative humidity due to the influence of side chain hydroxyl groups, and the oxygen gas barrier property is significantly lowered accordingly, which is a major drawback when used in casings, retorts and the like. ing.

Nylon, on the other hand, has many aspects including physical properties such as toughness, impact resistance, pinhole resistance and transparency, molding processability such as melt moldability and stretchability, and price. It is the most balanced material for films, with polycaproamide (nylon 6) forming its core. However, when the nylon 6 film is used as a packaging material for foods, pharmaceuticals, cosmetics, etc., it is not possible to sufficiently meet the recent high demand for oxygen gas barrier property. For example, as a high barrier material using nylon, a multilayer film having PVDC as a barrier layer (for example, PVDC coated nylon 6)
However, there are various drawbacks such as whitening during hot water treatment, delamination between nylon layer and PVDC layer, and generation of chlorine-based gas during incineration disposal.

Therefore, as a substitute material for the barrier layer, polymethaxylylene adipate made from metaxylylenediamine (MXD) and adipic acid, which have the highest barrier properties among the industrially produced nylons, is used. Mido (nylon MXD6) can be mentioned first. Then, as the product, a multilayer stretched film with nylon 6 having nylon MXD6 as a barrier layer has been put on the market and is being evaluated by the market (for example, JP-A-5-19).
2995, JP-A-5-193081, etc.).

It is well known that various types of multilayer bottles, containers, etc. are manufactured and put into practical use for this nylon MXD6 by melt blending with nylon 6, polyethylene terephthalate, polycarbonate or polypropylene, coextrusion and lamination. (For example, JP-A-6-106615 and JP-A-6-106615)
JP 99486, JP 6-99487, JP 6-106691, JP 5-261874, JP 5-156155, JP 5-31.
No. 866, No. 4-103348, No. 2-198820, No. 2-135259, European Patent Application No. 540293 A1, European Patent Application No. 288972 A2, European Patent Application No. Three
18964 A2, etc.).

However, nylon MXD6 has an excellent gas barrier property in a dry state, but has a relative humidity of 90%.
Since the gas barrier property deteriorates in the above high humidity atmosphere, development of an excellent gas barrier nylon which covers this drawback is strongly desired. Further, nylon MXD6 has a 1,3-phenylene bond in the main chain and is rigid, so that it has a higher elastic modulus than aliphatic nylons such as nylon 6 and nylon 66, and has a disadvantage of poor pinhole resistance. Have.

Further, metaxylylene adipamide (MXD
6) As a method for producing a polyamide resin containing a repeating unit, for example, Japanese Patent Publication No. 52-9236 discloses a method of producing a polyamide resin at 190 to 280 ° C. under a naturally occurring pressure of water used in a closed container.
Is carried out for 2 to 5 hours to carry out initial polymerization, and then water is removed to the outside of the reaction system to further heat to 240 to 300 ° C. for 1 to 5 hours to complete the polymerization. There is. However, when the polymerization is carried out under the conditions described in the above publication, a side reaction may occur due to the high temperature in the initial polymerization process and the water removal process,
A yellow-colored polymer containing an insoluble and infusible gel is obtained, and a polyamide resin having good moldability and physical properties cannot be produced.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to comprise a polyamide resin containing a metaxylylene type polyamide such as nylon MXD6 as an essential component, which has an excellent barrier property against oxygen gas and the humidity dependency of the oxygen gas barrier property. (EN) It is intended to provide a novel polyamide resin excellent in gas barrier property, which is suitable for use as a packaging material for foods, pharmaceuticals, cosmetics and the like having a small size, and a method for producing the same.

[0010]

Means for Solving the Problems Accordingly, the present inventors have:
As a result of extensive studies on a polyamide resin having excellent barrier properties against oxygen gas and having little humidity dependence of the oxygen gas barrier property and a method for producing the same, a specific component was made an essential component, and the essential component was made to have a specific composition. In the production of the polyamide resin containing, by performing prepolymerization by specifying the temperature, pressure and time, it is possible to obtain a polyamide resin without gel or yellow coloring, which has characteristic physical properties. The film formed is
The inventors have found that the film has both an excellent oxygen gas barrier property and a small humidity dependency of the oxygen gas barrier property, which have not been known in the related art, and have completed the present invention.

That is, the first invention according to claim 1 is an amide repeating unit selected from the group consisting of a metaxylylene adipamide unit, a metaxylylene isophthalamide unit and a metaxylylene terephthalamide unit. Of a polyamide resin containing at least 20 mol% of at least one of the above, and at 25 ° C. and a relative humidity of 10
Activation of β relaxation in the temperature-dispersed spectrum of dynamic viscoelasticity measured in tensile mode under conditions of a water content of 8% or less by weight at 0% and a frequency of 10 Hz and a strain of 0.05%. Energy is 18kJ / mo
It can be achieved by providing a polyamide resin having an excellent gas barrier property, which is characterized by being 1 or less.

The second invention according to claim 2 is
In producing a polyamide resin having excellent gas barrier properties by a polycondensation method comprising a prepolymerization step under pressure melting and a subsequent postpolymerization step under normal pressure and / or reduced pressure, the prepolymerization step comprises Polymerization temperature is over 170 ℃ 22
Water vapor pressure in the polymerization system is below 0 ° C and 3kgf / c
m ² G or more and the polymerization time (t) represented by the steam pressure (P) and time represented by kgf / cm ² G
(Pt) and the polymerization temperature (T) expressed in ° C. are satisfied under the condition that the mathematical formula (I) and the mathematical formula (II) are simultaneously satisfied, and then at a temperature of 220 ° C. or lower at normal pressure. This can be achieved by providing the method for producing a polyamide resin according to the first invention, which is characterized in that the pressure is released to the following pressure to remove the condensation water, and then the post-polymerization step is performed.

The present invention will be described in detail below. The polyamide resin of the present invention has at least one amide repeating unit selected from the group consisting of a metaxylylene adipamide unit, a metaxylylene isophthalamide unit and a metaxylylene terephthalamide unit with respect to the entire resin. At least 20 mol% or more, preferably 25 mol% or more,
More preferably, it comprises a polyamide resin containing 30 mol% or more, and its physical properties are 25 ° C. and a relative humidity of 10
Activation of β relaxation in the temperature-dispersed spectrum of dynamic viscoelasticity measured in tensile mode under conditions of a water content of 8% or less by weight at 0% and a frequency of 10 Hz and a strain of 0.05%. Energy is 18kJ / mo
It is a polyamide resin having a l or less.

In the present invention, the water absorption of the amorphous portion means that water is adsorbed only on the amorphous portion of the polyamide resin, and literature data on crystallinity and moisture content of various polyamide resins (for example, Fukumoto Osamu, Polyamide Resin Handbook, Nikkan Kogyo Shimbun (1988) and R. J. Hernandez et al., J. Membrane.
Sci. , Vol. 65, pp. 187-199 (1992)
(See, etc.) is the value obtained based on. Further, in the present invention, the β relaxation activation energy corresponds to the size of the molecular gap, based on the molecular mobility of the weak hydrogen bonding force between amides in the amorphous portion of the polyamide resin, It can be obtained by the method described below. And
The polyamide resin excellent in gas barrier property in the present invention means, for example, the oxygen gas permeability when converted to a thickness of 30 μm is 30 cc / m ^{2 at} a relative humidity of 0%.
・ 24 hr ・ atm or less, preferably 26 cc / m ²・
24hr.atm or less and 98% relative humidity
Under high humidity, the polyamide resin shows a value which does not exceed the value at the relative humidity of 0%.

In the present invention, when the ratio of the metaxylylene adipamide repeating unit and / or the metaxylylene isophthalamide repeating unit and / or the metaxylylene terephthalamide repeating unit to the whole polyamide resin is less than 20 mol%. In addition, the obtained polyamide resin has a low barrier property against oxygen gas and cannot achieve the object of the present invention, which is not preferable. The ratio is 20
When the amount is more than 25 mol% and more than 25 mol%, the polyamide resin may have a low barrier property against oxygen gas. When the ratio is more than 25 mol% and less than 30 mol%, the ratio exceeds 20 mol% and 25 mol%.
The polyamide resin tends to have a low barrier property against oxygen gas, though not so much as in the range below. Further, in the polyamide resin of the present invention,
Water absorption rate of amorphous part is 8 at 25 ℃ and relative humidity 100%
When the content exceeds 50% by weight, the polyamide resin has a large humidity dependency of oxygen gas barrier property, and for example, has a thickness of 30 μm.
The oxygen gas permeability at a relative humidity of 98% when converted as m is larger than the oxygen gas permeability at a relative humidity of 0%, so that the oxygen gas barrier property in the high humidity region is deteriorated, which is not preferable. Furthermore, in the polyamide resin of the present invention, when the activation energy for β relaxation in the temperature dispersion spectrum measurement of dynamic viscoelasticity under the above-mentioned conditions exceeds 18 kJ / mol, for example, the thickness of 30
A polyamide resin film of μm is used at room temperature and relative humidity of 0.
% Oxygen gas permeability is 3 when measured by the isobaric method
Now more than ^{0cc / m 2 · 24hr · atm} ,
The polyamide resin is not preferable as a gas barrier material.

That is, in the present invention, at least one of amide repeating units selected from the group consisting of metaxylylene adipamide units, metaxylylene isophthalamide units and metaxylylene terephthalamide units is an essential component. , This is at least 20 based on the total polyamide resin
It is contained in an amount of more than mol% and has a physical property of 25
The water absorption rate of the amorphous part at 8 ° C and relative humidity of 100% is 8% by weight or less, and the frequency is 10 Hz and the strain is 0.
A film made of a polyamide resin having an activation energy of β relaxation of 18 kJ / mol or less in a temperature dispersion spectrum of dynamic viscoelasticity measured in a tensile mode under a condition of 05% has not been obtained by a conventional nylon film. It is possible to provide an excellent gas barrier film having both high barrier properties and low humidity dependency.

As a raw material for the polyamide-forming component constituting the essential component of the polyamide resin of the present invention, as for the metaxylylene adipamide repeating unit, adipic acid and metaxylylenediamine or equimolar salt or metaxylyl obtained from them. For renisophthalamide repeating units, isophthalic acid and metaxylylenediamine or equimolar salts obtained from them, and for metaxylyleneterephthalamide repeating units, terephthalic acid and metaxylylenediamine or equimolar salts obtained from them. Salts are preferably used.

As the raw materials for the polyamide-forming components other than those mentioned above which compose the polyamide resin of the present invention, diamine and dicarboxylic acid or salts obtained from these, ω-
Aminocarboxylic acid or a lactam having three or more membered rings is preferably used. Specifically, examples of the diamine include ethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, nonamethylenediamine, undecamethylenediamine, dodecamethylenediamine, 2,2,4-trimethylhexamethylenediamine and 2 Aliphatic diamines such as 4,4,4-trimethylhexamethylenediamine, 1,3
-Diaminocyclohexane, 1,4-diaminocyclohexane, 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, bis (4-aminocyclohexyl) methane and 2,2-
Examples thereof include alicyclic diamines such as bis- (4′-aminocyclohexyl) propane, and aromatic diamines such as metaxylylenediamine and paraxylylenediamine. As the dicarboxylic acid, for example,
Aliphatic dicarboxylic acids such as glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid and heptadecanedicarboxylic acid,
Alicyclic dicarboxylic acids such as 1,3-cyclohexyldicarboxylic acid and 1,4-cyclohexyldicarboxylic acid,
Further, aromatic dicarboxylic acids such as isophthalic acid, terephthalic acid, 1,4-naphthalenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid can be exemplified. And as a salt obtained from a diamine and a dicarboxylic acid, a salt obtained from the above diamine and the above dicarboxylic acid can be mentioned. On the other hand, as the ω-aminocarboxylic acid, for example, ε-aminocaproic acid, ω-aminoheptanoic acid, ω-aminononanoic acid, ω-aminoundecanoic acid, ω-aminododecanoic acid, and the like, as a lactam having a three-membered ring or more, , For example, ε-caprolactam, ω-
Examples thereof include enanthlactam, α-pyrrolidone, δ-methylpyrrolidone, α-piperidone, undecane lactam and dodecane lactam.

That is, the polyamide-forming component other than the above-mentioned essential components constituting the polyamide resin of the present invention is obtained by polycondensing the diamine and the dicarboxylic acid, or a salt obtained from them, or the ω-aminocarboxylic acid. Alternatively, an amide repeating unit constituting a polyamide obtained by ring-opening polymerization of the lactam, for example, a tetramethylene adipamide unit, a caproamide unit, a hexamethylene adipamide unit, a hexamethylene sebacamide unit, an undecane amide. Units, aliphatic polyamide constitutional units such as dodecane amide units and hexamethylene dodecanoamide units, and hexamethylene isophthalamide units, hexamethylene terephthalamide units,
A xylylene group-containing polyamide structural unit such as a metaxylylene sebacamide unit, a metaxylylene beramide unit and a paraxylylene adipamide unit (however, a metaxylylene adipamide unit, a metaxylylene isophthalamide unit and a metaxylylene isophthalamide unit (Excluding xylylene terephthalamide unit)
And the like, such as an aromatic polyamide structural unit.

Next, in the polymerization for obtaining the polyamide resin of the present invention, for example, the powdery raw materials are dry blended or mixed in the form of an aqueous solution of a salt and / or a monomer. , These raw materials mixed in a predetermined ratio in advance, or a predetermined amount of the powdered raw material, or alternatively, these raw materials and a predetermined amount of water are charged into a pre-polymerization apparatus, and the following is described while stirring. It is necessary to obtain a prepolymer (oligomer) by polymerizing under the conditions. The polymerization temperature in the pre-polymerization step under pressure in the present invention is 170 ° C. or higher, 22
It is 0 ° C or lower, preferably 180 ° C or higher and 210 ° C or lower. When the polymerization temperature is lower than 170 ° C., the polymerization time becomes extremely long, and when it exceeds 220 ° C., a branched structure is formed due to a side reaction, coloring, gelation during post-polymerization and the like occur, which is not preferable. In addition, when the polymerization temperature is out of the preferable range described above, there is a tendency that these undesirable phenomena occur.

In the present invention, the pressure in the polymerization system in the pre-polymerization step is the pressure in the pre-polymerization apparatus at that time, and is mainly the vapor pressure at the time of polymerization equilibrium indicated by the lower-order polymer, that is, the mixture of the oligomer and water. Is. Therefore, the pressure in the polymerization system, that is, the water vapor pressure depends on the above-mentioned polymerization temperature and the amount of water described later, and is not less than 3 kgf / cm ² G (where G is a gauge pressure. Preferably, the pressure should be adjusted to 4 kgf / cm ² G or more and a saturated steam pressure or less. When the polymerization pressure is lower than 3 kgf / cm ² G, heterogeneous polymerization may occur in the solid state, which is not preferable. When the polymerization pressure is out of the above preferable range, the above-mentioned unfavorable phenomenon tends to occur. The pressure can be adjusted by a valve or the like provided in a steam discharge line directly connected to the prepolymerization apparatus.

The production method of the present invention, that is, the feature of the second invention is that the polymerization conditions of the prepolymerization step under pressure are within the above-mentioned polymerization temperature and polymerization pressure.
The relationship between the polymerization temperature (T) expressed in ° C and the product (Pt) of the steam pressure (P) in the polymerization system expressed in kgf / cm ² G and the polymerization time (t) expressed in hours is as follows. Formula (III)

[0023]

(Equation 3)

And the following equation (IV)

[0025]

[Equation 4]

It is within the range of simultaneously satisfying the above conditions. The condition that Pt does not satisfy the formula (III), that is, Pt> 2.29 × 10 ⁷ exp (−5.99 ×)
Under the condition of 10 ^-2 T), an ammonia odor due to a side reaction is recognized, which is not preferable because it causes coloring and gelation during the post-polymerization. On the other hand, the condition that Pt does not satisfy the formula (IV), that is, Pt <3.11 × 10 ⁷ exp (−
The condition of 6.79 × 10 ⁻² T) is not preferable because the polymerization is not sufficient and a large amount of unreacted monomer is present in the oligomer.

In the present invention, when a predetermined amount of the powdery raw material and a predetermined amount of water are charged into the prepolymerization apparatus during the prepolymerization,
The water supplied to the prepolymerization apparatus is not particularly limited, but pure water such as ion exchanged water or distilled water is preferable. The presence of water in the prepolymerizer is
It is based on water supplied to the prepolymerization device and water by-produced by the polycondensation reaction or the ring-opening polymerization reaction of the raw material, and the presence of this water is the pressure due to the steam pressure in the prepolymerization device. It is possible to hold
The molecular weight of the resulting oligomer is determined.

The amount of water existing in the prepolymerization apparatus is determined by the type, shape and size of the prepolymerization apparatus, the amount of the raw material or the raw material and water charged into the prepolymerization apparatus, and the temperature of the prepolymerization apparatus. It is determined depending on the pressure conditions and the like and cannot be generally stated, but based on the charging standard of the raw material to the prepolymerization apparatus, 100 parts by weight or less, preferably 50 parts by weight or less, per 100 parts by weight of the total amount of the raw materials. Is desirable. The amount of water is 1 per 100 parts by weight of the total amount of the raw materials
When it is more than 100 parts by weight, the polycondensation reaction of the above-mentioned raw material, diamine and dicarboxylic acid, or a salt thereof, or ω-aminocarboxylic acid, or the polycondensation reaction after ring-opening of the above-mentioned raw material lactam is sufficiently advanced. However, the degree of polymerization of the resulting oligomer becomes small, and therefore the degree of polymerization does not increase in the post-polymerization step, which is not preferable. When the amount of water is more than 50 parts by weight and less than 100 parts by weight per 100 parts by weight of the total amount of the raw materials, this unfavorable phenomenon may occur.

In the present invention, the molecular weight of the oligomer is determined by the terminal group concentration (amino group concentration ([NH
₂ ]) and the carboxyl group concentration ([COOH])), and the number average molecular weight (hereinafter abbreviated as “Mn”)
Is preferably 1000 or more. Therefore, pre-polymerization is performed under conditions (that is, polymerization temperature, polymerization pressure, and polymerization time) that simultaneously satisfy the above formulas (III) and (IV), and subsequently, pressure below atmospheric pressure at a temperature of 220 ° C. or less. It is necessary to release the pressure until the condensation water produced as a by-product is removed, and then to the post-polymerization step. M of the oligomer
When n is less than 1000, side reactions are likely to occur during post-polymerization. In the post-polymerization under normal pressure and / or reduced pressure, which is performed at a higher temperature than the pre-polymerization under pressure, the raw material monomer is pre-polymerized at an unfavorable temperature exceeding 220 ° C. described above. Substantially unchanged, side reactions become noticeable, the end group concentration balance is lost due to evaporation of diamine components, etc.
This has an unfavorable effect on the physical properties of the finally obtained polyamide resin. When the condensation water generated as a by-product is not removed by releasing the pressure to a pressure equal to or lower than the normal pressure, in the subsequent post-polymerization step under normal pressure and / or reduced pressure, the polycondensation reaction of the oligomer is It does not proceed sufficiently and the increase in the molecular weight of the polymer is not sufficient, which is not preferable. Further, when the pressure is released below the atmospheric pressure at a temperature of over 220 ° C. after the prepolymerization, a branched structure is formed by a side reaction, coloring and gelation in the postpolymerization step under the atmospheric pressure and / or the reduced pressure may occur. It is not preferable because it occurs.

In the present invention, the apparatus for prepolymerization (prepolymerization apparatus) is not particularly limited, and a batch reaction kettle, a one-to-many or multi-tank continuous reaction apparatus, a tubular continuous reaction apparatus, etc. are known. Things can be used. Among these, a batch reactor is preferably used in order to make the polymerization time of the oligomer uniform.

In the present invention, the oligomer thus obtained is obtained in the subsequent post-polymerization step to obtain a polyamide resin having a high molecular weight and film moldability, which is a characteristic of the present invention. Be done. In the post-polymerization step under normal pressure and / or reduced pressure in the present invention, a melt polycondensation method of polymerizing at a melting point of the finally obtained polyamide resin or a solid phase of polymerizing in a solid state below the melting point of the polyamide resin is used. Although various known polycondensation methods such as a polymerization method can be applied, the former melt polycondensation method is preferably used in view of shortening the polymerization time and interlocking with the prepolymerization.

Therefore, when the melt polycondensation method is applied in the post-polymerization step under normal pressure and / or reduced pressure in the present invention, the melting point of the polyamide resin finally obtained +
The final polyamide resin is obtained by melt polymerization at a temperature of 10 ° C. or higher and 300 ° C. or lower, preferably the melting point + 10 ° C. or higher and 280 ° C. or lower. If the polymerization temperature during melt polymerization is lower than the melting point of the finally obtained polyamide resin + 10 ° C, the polymer may not be completely melted, and the target polyamide resin is stabilized by partial solidification during production. It may not be possible to manufacture it. Further, if the polymerization temperature during the melt polymerization is higher than 300 ° C., it is not preferable since the polyamide resin finally obtained will be colored due to thermal deterioration and the mechanical properties will be deteriorated. In order to reliably suppress the occurrence of these unfavorable phenomena, it is necessary to set the polymerization temperature during melt polymerization within the above-mentioned preferable range.

Next, the pressure during the post-polymerization is, as described above, normal pressure and / or reduced pressure, and preferably 50 to 50.
760 mmHg, particularly preferably 100 to 760 mmHg
g. When the pressure exceeds 760 mmHg,
It is not preferable because water contained in the oligomer and water vapor generated by the polycondensation reaction of the oligomer are not actively exhausted to the outside of the system, and thus the polycondensation reaction of the oligomer does not proceed sufficiently. Also, the pressure is 50 mm
If it is less than Hg, not only the effect of further accelerating the polycondensation reaction of the oligomer cannot be expected, but also the depressurizing equipment for exhausting a large amount of cost is not preferable. The exhaust is performed by providing at least one vent port in the post-polymerization apparatus described below and opening the vent port to the atmosphere, or by using a known port such as a Nash pump, mechanical booster, or steam ejector for the vent port. It is performed by connecting to vacuum equipment and forcibly exhausting.

The polymerization time under the above normal pressure and / or reduced pressure should be selected so that the molecular weight is sufficiently increased and the polymer does not undergo thermal decomposition.
~ 3 hours. If the polymerization time is shorter than the above range, the increase in the molecular weight of the polymer is not sufficient, and if it is long, the polymer undergoes thermal deterioration, and in any case it is not possible to obtain a polyamide resin having the desired physical properties. Absent.

In the post-polymerization step under normal pressure and / or reduced pressure, the polyamide resin of the present invention can be obtained under the above conditions, but the process for producing the polyamide resin of the present invention is not particularly limited. However, it may be a batch process or a continuous process. In the case of a batch process, the pre-polymerization step and the post-polymerization step may be carried out in one reactor, or only the pre-polymerization step is carried out in a pressure reaction vessel, and the post-polymerization step has a short residence time, A kneading extruder having excellent surface renewal property (such as a single-screw kneading extruder, a twin-screw kneading extruder and a multi-screw kneading extruder) and a horizontal second polymerization tank disclosed in JP-B-4-32096 (two It is also possible to use a device such as a shaft mixing stirrer. In the case of a continuous process, a known one such as a one-tank type or multi-tank type continuous reaction apparatus or a tubular continuous reaction apparatus can be used.

The polyamide resin for gas barrier films of the present invention obtained as described above is a homopolyamide or copolyamide comprising the above-mentioned polyamide-forming components, or a mixture of these homopolyamides or copolyamides. Is 7000-3000
It is in the range of 0. When Mn is less than 7,000,
It is not preferable because a polyamide resin having desired film physical properties cannot be obtained. When it exceeds 30,000, the obtained polyamide resin has a high viscosity at the time of melting and is difficult to melt-mold, which is not preferable.

In the present invention, in the pre-polymerization or the post-polymerization, if necessary, an inorganic phosphorus compound or the like may be added as a polymerization accelerator without causing any problem. As the inorganic phosphorus compound, phosphoric acid, phosphorous acid, hypophosphorous acid, pyrophosphoric acid,
Polyphosphoric acid and alkali metal salts and alkaline earth metal salts thereof are preferably used. The addition amount of these inorganic phosphorus compounds is usually 100 to 5000 ppm based on the oligomer or polymer to be obtained. If the amount added is out of this range, 1
If it is less than 00 ppm, almost no addition effect is observed, and if it exceeds 5000 ppm, an unfavorable phenomenon occurs such that the molecular weight of the polymer is remarkably increased and the finally obtained polyamide resin becomes difficult to be melt-molded. The addition method is not particularly limited, and for example, a method of dry blending with a raw material monomer during prepolymerization, or supplying as an aqueous solution during prepolymerization or postpolymerization is suitable.

Further, in order to stabilize the melt viscosity of the obtained polyamide resin during molding, if necessary, amine or carboxylic acid may be added as a molecular weight modifier during prepolymerization or postpolymerization without any problem. There is no. The amine or carboxylic acid to be added is not particularly limited as long as it is monofunctional and / or difunctional, and examples thereof include monoamines such as laurylamine, stearylamine and benzylamine, pentamethylenediamine, hexamethylenediamine, and unamine. Decamethylenediamine, dodecamethylenediamine, metaxylylenediamine, paraxylylenediamine and other diamines, acetic acid, benzoic acid, lauric acid, stearic acid and other monocarboxylic acids and adipic acid, pimelic acid, suberic acid, azelaic acid, sebacin Suitable examples thereof include acids, dodecanedicarboxylic acid, terephthalic acid, and dicarboxylic acids such as isophthalic acid. The addition amount of these molecular weight modifiers is appropriately selected so that the molecular weight (Mn) of the polyamide resin to be finally obtained is in the range of 7,000 to 30,000 described above.

Furthermore, in the polyamide resin obtained as described above, during the production of the oligomer (that is, during prepolymerization) or during the melt polycondensation of the oligomer or during the solid phase polymerization (that is, during the postpolymerization). If necessary, a heat-resistant agent, an antioxidant, a weather-resistant agent, a lubricant, a crystal nucleating agent, an antistatic agent, a pigment, a dye, an anti-blocking agent and the like can be added within a range that does not impair the physical properties.

In the present invention, the polyamide resin obtained by the above method is molded to produce a gas barrier film suitable as a packaging material for foods, pharmaceuticals or cosmetics. There is no particular limitation on the molding method. For example, a known cast molding method or tubular molding method using an extruder can be applied. In the cast molding method, the polyamide resin of the present invention can be extruded into a film form in a molten state from a T-die head of an extruder, and then cooled and solidified on a casting drum to form the gas barrier film. Further, in the tubular molding method, the polyamide resin of the present invention is extruded into a tube form in a molten state from a ring-shaped die head of an extrusion molding machine, subsequently, air or the like is blown into the tubular body, and then air-cooled by an air ring. Alternatively, the gas barrier film can be formed by cooling and solidifying by water cooling by directly contacting with water.

[0041]

EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples. However, the present invention is not limited to these Examples and Comparative Examples as long as the gist thereof is not exceeded. Various properties of the polymer (oligomer and / or polymer) in each of the following Examples and Comparative Examples were measured by the following methods. (1) Relative Viscosity (ηr) According to JIS K6810, 98% by weight sulfuric acid was used as a solvent and measured at 25 ° C. at a polymer concentration of 1% by weight / volume.

(2) Terminal amino group concentration ([NH ₂ ]) About 1 g of a polymer was dissolved in 40 ml of a phenol / methanol mixed solvent (volume ratio: 9/1), and the obtained sample solution was used as an indicator. Using thymol blue, N /
Titrated with 20 hydrochloric acid.

(3) Terminal carboxyl group concentration ([COO
H]) 40 ml of benzyl alcohol was added to about 1 g of the polymer, and the mixture was heated and dissolved in a nitrogen gas atmosphere, and the obtained sample solution was prepared using phenolphthalein as an indicator.
It was titrated with a N / 20 potassium hydroxide-ethanol solution.

(4) β-relaxation activation energy Using a rheometrics RSA II (dynamic viscoelasticity measuring device), the temperature dispersion spectrum of the dynamic viscoelasticity of the sample film was measured under the following conditions. The size of the sample film is 5 mm (width) x 35 mm (length) x 0.0
It was 3 mm (thickness). Measurement mode: Tensile frequency: 62.7998 rad / sec (10 Hz) Temperature range: −150 to 250 ° C. Temperature rising step: 3 ° C. Strain: 0.05% β activation energy for relaxation is obtained by the above measurement. It was calculated by the figure integration method from the β relaxation peak of the loss elastic modulus.

(5) Oxygen Gas Permeability Oxygen Gas Permeability Measuring Device OX-TRAN manufactured by MOCON
2/20 was used and measured at 23 ° C. for each sample film under the conditions of relative humidity of 0%, 65%, 90% and 98%. When measuring under conditions other than 0% relative humidity, oxygen gas whose humidity was controlled under each set condition was used.

(6) Copolymer composition: JNM-EX400 type FT-NM manufactured by JEOL Ltd. at a polymer concentration of 5% by weight using 97% by weight bisulfate as a solvent.
The composition was determined from the proton NMR spectrum measured at room temperature using R.

Example 1 An equimolar salt of adipic acid and metaxylylenediamine was placed in a pressure vessel having a volume of 70 liters equipped with a stirrer, a thermometer, a pressure gauge, a nitrogen gas inlet, a pressure outlet and a polymer outlet. (MXD6 salt) From 10.82 kg (38.317 mol) and 11 kg of water, MXD6 salt aqueous solution, from equimolar salt (6T salt) of terephthalic acid and hexamethylenediamine 4.64 kg (16.432 mol) and from 13 kg of water 6T salt aqueous solution, adipic acid 0.133
kg (0.910 mol) and sodium hypophosphite 1
29 g (0.274 mol) of the hydrate was charged. Therefore,
After sufficiently replacing the inside of the pressure vessel with nitrogen, the temperature was raised in a sealed state with stirring, and prepolymerization was performed at 210 ° C. for 4 hours. Pressure is 8kg
It was f / cm ² G. This is the relationship between the polymerization temperature (T) expressed in ° C and the product (Pt) of the steam pressure (P) in the polymerization system expressed in kgf / cm ² G and the polymerization time (t) expressed in hours. Satisfy the above formulas (III) and (IV), that is, Pt ≦ 2.29 × 10 ^7.
exp (−5.99 × 10 ⁻² T) and Pt ≧ 3.11
It is a condition included in the range of × 10 ⁷ exp (−6.79 × 10 ⁻² T).

Next, the pressure in the pressure vessel is released to normal pressure at 210 ° C. over 1 hour, and then 2 seconds in the vessel.
260 while flowing nitrogen gas at a speed of 00 ml / min
The temperature was raised to ° C. When the temperature reached 260 ° C., the polycondensation reaction was allowed to proceed for 2 hours at that temperature and a pressure of 760 mmHg. After the completion of the reaction, stirring was stopped, and the produced polymer was taken out in the form of a string from the polymer outlet at the bottom of the pressure vessel, immediately cooled in a water tank, cut into cylindrical chips, and vacuum dried at 80 ° C. for 72 hours. The obtained polymer is colorless and transparent, and has ηr
= 2.48, [NH ₂ ] = 1.2 × 10 ⁻⁵ eq / g and [COOH] = 17 × 10 ⁻⁵ eq / g. The copolymer composition is MXD6 / MXDT / 6.
6 / 6T = 0.52 / 0.19 / 0.21 / 0.08
(Mole ratio) (however, MXD6, MXDT, 66 and 6T represent the polyamide-forming components in the polymer, and each represents a metaxylylene adipamide unit, a metaxylylene terephthalamide unit, a hexamethylene adipamide unit and a It represents a hexamethylene terephthalamide unit (the same applies below).

Then, an extruder equipped with a T-die [screw diameter (D): 25 mm, ratio of screw length (L) to D (L / D) = 28, barrel temperature: 270]
C.] to supply the above polymer to form a film having a thickness of 30 μm. Table 1 shows the physical properties of the film, such as water absorption, β relaxation activation energy, and oxygen gas permeability.

Example 2 6 kg of an equimolar salt (MXDI salt) of isophthalic acid and metaxylylenediamine was placed in the same pressure vessel as in Example 1.
(19.844 mol) and 11.14 kg of water in MXDI salt aqueous solution, 14 kg of equimolar salt (6I salt) consisting of isophthalic acid and hexamethylenediamine (49.57).
9 mol) and a 4.51 kg water solution of 6I salt,
0.192 kg (1.156 mol) of isophthalic acid and 15 g (0.142 mol) of sodium hypophosphite monohydrate were charged. Therefore, after thoroughly replacing the inside of the pressure vessel with nitrogen, the temperature was raised in a sealed state with stirring, and prepolymerization was carried out at 200 ° C. for 4 hours. The pressure was 10 kgf / cm ² G. This is the polymerization temperature (T) expressed in ° C and kgf / cm
The relationship between the product (Pt) of the water vapor pressure (P) in the polymerization system represented by ² G and the polymerization time (t) represented by time satisfies the above formulas (III) and (IV), that is, , Pt ≦ 2.29 × 10 ⁷ exp (−5.99 × 10
^-2 T) and Pt ≧ 3.11 × 10 ⁷ exp (−6.7)
It is a condition included in the range of 9 × 10 ⁻² T).

Next, the pressure in the pressure vessel is released to normal pressure at 200 ° C. over 1 hour, and then the pressure in the vessel is reduced to 2
260 while flowing nitrogen gas at a speed of 00 ml / min
The temperature was raised to ° C. When the temperature reached 260 ° C, the polycondensation reaction was allowed to proceed for 1 hour at that temperature and a pressure of 760 mmHg. After the completion of the reaction, stirring was stopped, and the produced polymer was taken out in the form of a string from the polymer outlet at the bottom of the pressure vessel, immediately cooled in a water tank, cut into cylindrical chips, and vacuum dried at 80 ° C. for 72 hours. The obtained polymer is colorless and transparent, and has ηr
= 2.02 was achieved, of [NH _2] = 3.5 × 10 ^-5 eq / g and [COOH] ^{= 17 × 10 -5 eq / g} . The copolymer composition is MXDI / 6I = 0.3.
0 / 0.70 (molar ratio) (however, MXDI and 6I
Represents a polyamide-forming component in the polymer and represents a metaxylylene isophthalamide unit and a hexamethylene isophthalamide unit, respectively. The same applies below).

Subsequently, an extruder equipped with a T-die (screw diameter: 25 mm, L / D = 28, barrel temperature: 2)
The above polymer was supplied to 70 ° C.) to form a film having a thickness of 30 μm. Table 1 shows the physical properties of the film, such as water absorption, β relaxation activation energy, and oxygen gas permeability.

Example 3 An equimolar salt (MXD6 salt) of adipic acid and metaxylylenediamine (15.5) was placed in the same pressure vessel as in Example 1.
MX consisting of kg (54.89 mol) and 24 kg of water
D6 salt aqueous solution, equimolar salt consisting of terephthalic acid and metaxylylenediamine (MXDT salt) 4.5 kg (14.8
MXDT salt aqueous solution consisting of 83 mol) and 10 kg of water, 0.204 kg (1.396 mol) of adipic acid and 37 g (0.349 mol) of sodium hypophosphite monohydrate were charged. Therefore, the inside of the pressure vessel was sufficiently replaced with nitrogen, the temperature was raised in a sealed state with stirring, and prepolymerization was performed at 190 ° C. for 8 hours. The pressure was 10 kgf / cm ² G. This is the polymerization temperature (T) expressed in ° C and kgf / cm
The relationship between the product (Pt) of the water vapor pressure (P) in the polymerization system represented by ² G and the polymerization time (t) represented by time satisfies the above formulas (III) and (IV), that is, , Pt ≦ 2.29 × 10 ⁷ exp (−5.99 × 10
^-2 T) and Pt ≧ 3.11 × 10 ⁷ exp (−6.7)
It is a condition included in the range of 9 × 10 ⁻² T).

Next, the temperature of the prepolymer in the pressure vessel was adjusted to 19
While raising the temperature from 0 ° C. to 220 ° C., the pressure was released at 220 ° C. to atmospheric pressure over 1 hour, and subsequently, nitrogen gas was flown into the container at a rate of 200 ml / min.
The temperature was raised to 0 ° C. When the temperature reached 260 ° C, the polycondensation reaction was allowed to proceed for 1 hour at that temperature and a pressure of 760 mmHg. After the completion of the reaction, stirring was stopped, and the produced polymer was taken out in the form of a string from the polymer outlet at the bottom of the pressure vessel, immediately cooled in a water tank, cut into cylindrical chips, and vacuum dried at 80 ° C. for 72 hours. The polymer obtained is white and ηr =
2.32, [NH ₂ ] = 1.8 × 10 ⁻⁵ eq / g and [COOH] = 18.1 × 10 ⁻⁵ eq / g. The copolymer composition is MXD6 / MXDT =
It was 0.79 / 0.21 (molar ratio).

Then, an extruder equipped with a T-die (screw diameter: 25 mm, L / D = 28, barrel temperature: 2)
The above polymer was supplied to 70 ° C.) to form a film having a thickness of 30 μm. Table 1 shows the physical properties of the film, such as water absorption, β relaxation activation energy, and oxygen gas permeability.

Example 4 In a pressure vessel similar to that of Example 1, equimolar salt (MXDI salt) 14k consisting of isophthalic acid and metaxylylenediamine was used.
MX consisting of g (46.302 mol) and 20 kg of water
6 kg of powder of an equimolar salt (MXDT salt) composed of an aqueous solution of DI salt and terephthalic acid and metaxylylenediamine (19.
844 mol), isophthalic acid 0.183 kg (1.10)
1 mol) and sodium hypophosphite monohydrate 34.5
g (0.325 mol) was charged. Therefore, after sufficiently replacing the inside of the pressure vessel with nitrogen, the temperature is raised in a sealed state with stirring,
Prepolymerization was carried out at 0 ° C. for 15 hours. Pressure is 8kgf / cm
Was ² G. This is the polymerization temperature (T) expressed in ° C.
And the product of the vapor pressure (P) in the polymerization system expressed in kgf / cm ² G and the polymerization time (t) expressed in hours (P
The relationship with t) satisfies the formulas (III) and (IV), that is, Pt ≦ 2.29 × 10 ⁷ exp.
(−5.99 × 10 ⁻² T) and Pt ≧ 3.11 × 10
It is a condition included in the range of ⁷ exp (−6.79 × 10 ⁻² T).

Next, the pressure in the pressure vessel is released to a normal pressure at 190 ° C. over 1 hour, and then the pressure in the vessel is increased to 2
250 while flowing nitrogen gas at a speed of 00 ml / min
The temperature was raised to ° C. When the temperature reached 250 ° C., the polycondensation reaction was allowed to proceed for 1 hour at that temperature and a pressure of 760 mmHg. After the completion of the reaction, stirring was stopped, and the produced polymer was taken out in the form of a string from the polymer outlet at the bottom of the pressure vessel, immediately cooled in a water tank, cut into cylindrical chips, and vacuum dried at 80 ° C. for 72 hours. The obtained polymer is colorless and transparent, and has ηr
= 2.20 was achieved, of [NH _2] = 1.7 × 10 ^-5 eq / g and [COOH] ^{= 18.3 × 10 -5 eq / g} . The copolymer composition is MXDI / MXDT =
It was 0.71 / 0.29 (molar ratio).

Subsequently, an extruder equipped with a T-die (screw diameter: 25 mm, L / D = 28, barrel temperature: 2)
The above polymer was supplied to 70 ° C.) to form a film having a thickness of 30 μm. Table 1 shows the physical properties of the film, such as water absorption, β relaxation activation energy, and oxygen gas permeability.

Comparative Example 1 The same operation as in Example 2 was performed until the prepolymerization under pressure was completed. Next, the pressure (10 kgf / cm ² G)
After heating up to 260 ° C. over 1 hour while maintaining
The pressure was released to normal pressure over 1 hour. Then, while flowing nitrogen gas into the pressure vessel at a rate of 200 ml / min, 26
Post-polymerization was carried out at 0 ° C. and a pressure of 760 mmHg for 1 hour. After that, stirring was stopped, and the produced polymer was taken out in the form of a string from the polymer product outlet at the bottom of the pressure vessel, but it was a partially gelled polymer.

Comparative Example 2 231 g (0.818 mol) of powder of equimolar salt (MXD6 salt) consisting of adipic acid and metaxylylenediamine, 99 g of powder of equimolar salt (6T salt) consisting of terephthalic acid and hexamethylenediamine. (0.351 mol), adipic acid 3.416 g (0.023 mol) and sodium hypophosphite monohydrate 0.249 g (0.002 mol) were dry blended, and a stirrer, a thermometer, a pressure gauge, A pressure vessel having a capacity of 1 liter equipped with a nitrogen gas inlet, a pressure outlet and a polymer outlet was charged. Therefore, after thoroughly replacing the inside of the pressure vessel with nitrogen, the temperature was raised in a sealed state with stirring, and the temperature was raised to 240 ° C for 3 hours.
Pre-polymerization was carried out for an hour. The pressure was 25 kgf / cm ² G. Next, the pressure in the pressure vessel was released to normal pressure over 1 hour, and subsequently, the temperature was raised to 260 ° C. while flowing nitrogen gas into the vessel at a rate of 200 ml / min. 260
When the temperature reaches ℃, 1 at that temperature and pressure of 760 mmHg
The time polycondensation reaction proceeded. After completion of the reaction, stirring was stopped, and the produced polymer was taken out in the form of a string from the polymer product outlet at the bottom of the pressure vessel, but it was a partially gelled polymer.

Comparative Example 3 The same pressure vessel as in Comparative Example 2 was used, and the raw materials were charged in the same manner as in Comparative Example 2. Next, after thoroughly replacing the inside of the pressure vessel with nitrogen, the temperature was raised in a sealed state with stirring, and prepolymerization was performed at 210 ° C. for 4 hours. The pressure was 17.5 kgf / cm ² G. Therefore, the pressure inside the pressure vessel is set to 17.5 kgf / cm.
While maintaining at ² G, the temperature was raised to 260 ° C. over 1 hour, and then the pressure was released to normal pressure over 1 hour. continue,
While allowing nitrogen gas to flow in the pressure vessel at a rate of 200 ml / min, the polycondensation reaction was allowed to proceed at 260 ° C. and a pressure of 760 mmHg for 1 hour, stirring was stopped, and the produced polymer was discharged from the polymer outlet at the bottom of the pressure vessel. It was taken out as a string, but it was a partially gelled polymer.

Comparative Example 4 103.8 g (0.343 mol) of powder of an equimolar salt (MXDI salt) consisting of isophthalic acid and metaxylylenediamine, and an equimolar salt (6I salt) consisting of isophthalic acid and hexamethylenediamine. 226.2 g (0.801 mol) of powder, 2.373 g (0.014 mol) of isophthalic acid and 0.245 g (0.1% of sodium hypophosphite monohydrate).
(002 mol) was dry-blended and charged in the same pressure vessel as in Comparative Example 2. Therefore, after thoroughly replacing the inside of the pressure vessel with nitrogen, the temperature was raised in a sealed state with stirring, and prepolymerization was performed at 200 ° C. for 3 hours. The pressure was 8 kgf / cm ² G. This is the polymerization temperature (T) expressed in ° C and kgf / cm
The relationship between the product (Pt) of the water vapor pressure (P) in the polymerization system represented by ² G and the polymerization time (t) represented by time does not satisfy the above formula (IV), that is, Pt <3. 11
The condition is in the range represented by × 10 ⁷ exp (-6.79 × 10 ^-2 T). Next, the pressure in the pressure vessel is adjusted to 20
The pressure was released to atmospheric pressure over 1 hour at 0 ° C., and then the temperature was raised to 260 ° C. while flowing nitrogen gas at a rate of 200 ml / min in the container. When the temperature reached 260 ° C, the polycondensation reaction was allowed to proceed for 1 hour at that temperature and a pressure of 760 mmHg. After the completion of the reaction, stirring was stopped, and the produced polymer was taken out in the form of a string from the polymer outlet at the bottom of the pressure vessel. However, the polymer had a sufficiently high molecular weight and was not film-formable.

Comparative Example 5 The same pressure vessel as in Comparative Example 4 was used, and the raw materials were charged in the same manner as in Comparative Example 4. Next, the inside of the pressure vessel was sufficiently replaced with nitrogen, the temperature was raised in a sealed state with stirring, and prepolymerization was performed at 200 ° C. for 20 hours. The pressure was 15 kgf / cm ² G.
This is based on the polymerization temperature (T) expressed in ° C and kgf / c.
The relationship between the product (Pt) of the water vapor pressure (P) in the polymerization system represented by m ² G and the polymerization time (t) represented by time is
Does not satisfy the formula (III), that is, Pt> 2.
It is a condition in the range represented by 29 × 10 ⁷ exp (−5.99 × 10 ⁻² T). Next, the pressure inside the pressure vessel was released to normal pressure at 200 ° C. over 1 hour, but an ammonia odor was observed when the pressure was released. Then, while flowing nitrogen gas into the container at a rate of 200 ml / min, 26
The temperature was raised to 0 ° C. When the temperature reached 260 ° C, the polycondensation reaction was allowed to proceed for 1 hour at that temperature and a pressure of 760 mmHg. After completion of the reaction, stirring was stopped, and the produced polymer was taken out in the form of a string from the polymer product outlet at the bottom of the pressure vessel, but it was a partially gelled polymer.

Comparative Example 6 Extruder equipped with a T-die (screw diameter: 25 m
m, L / D = 28, barrel temperature: 270 ° C., and nylon 6 (manufactured by Ube Industries, Ltd., trade name: UBE nylon 102)
4FDX8) was supplied to form a film having a thickness of 30 μm, and the activation energy for β relaxation and the oxygen gas permeability were measured. Physical properties of the film such as water absorption, β relaxation activation energy and oxygen gas permeability were as shown in Table 1. That is, the water absorption rate and the β-relaxation activation energy of this film were 20% by weight and 21.49 kJ / mol, respectively, and the oxygen gas barrier properties in the dry state and the high humidity state were both low.

Comparative Example 7 An extruder equipped with a T-die (screw diameter: 25 m
m, L / D = 28, barrel temperature: 270 ° C.), nylon MXD6 (manufactured by Mitsubishi Gas Chemical Co., Inc., trade name: MX600)
7) was supplied to form a film having a thickness of 30 μm, and the activation energy for β relaxation and the oxygen gas permeability were measured. Physical properties of the film such as water absorption, β relaxation activation energy and oxygen gas permeability were as shown in Table 1. That is, the water absorption rate and the β-relaxation activation energy of this film were 8.8 wt% and 13.87 kJ / mol, respectively, and the oxygen gas barrier property in a dry state was good, but the high humidity was high. In the state, the oxygen gas barrier property was lowered.

Comparative Example 8 Extruder equipped with a T-die (screw diameter: 25 m
m, L / D = 28, barrel temperature: 270 ° C) and nylon 6T / 6I (manufactured by DuPont, trade name: SelarPA)
Was supplied to form a film having a thickness of 30 μm, and the activation energy for β relaxation and the oxygen gas permeability were measured. Physical properties of the film such as water absorption, β relaxation activation energy and oxygen gas permeability were as shown in Table 1. That is, the water absorption rate and β relaxation activation energy of this film were 7.3% by weight and 2%, respectively.
It was 1.55 kJ / mol. The oxygen gas barrier property of this film in the high humidity condition was good, but the oxygen gas barrier property in the dry condition was low.

Comparative Example 9 8 kg of an equimolar salt of adipic acid and metaxylylenediamine (MXD6 salt) was placed in the same pressure vessel as in Example 1.
MXD consisting of (28.331 mol) and 17 kg of water
6 salt aqueous solution, 18.25 kg of caprolactam (161.
248 mol), adipic acid 0.138 kg (0.948
Mol) and sodium hypophosphite monohydrate 40 g
(0.377 mol) was charged. Therefore, after sufficiently replacing the inside of the pressure vessel with nitrogen, the same procedure as in Example 1 was performed to carry out prepolymerization (temperature: 210 ° C., pressure: 8 kgf / cm ² G and polymerization time: 4 hours) and postpolymerization (temperature: 260 ° C., pressure: 760 mmHg, and polymerization time: 2 hours). After the completion of the post-polymerization reaction, the stirring was stopped, and the produced polymer was taken out in the form of a string from the polymer outlet at the bottom of the pressure vessel,
Immediately after cooling in a water bath, cut into cylindrical chips,
It was vacuum dried at 72 ° C for 72 hours. The obtained polymer is white and has ηr = 3.52 and [NH ₂ ] = 1.6 × 10 ^−5.
eq / g and [COOH] = 7.1 × 10 ⁻⁵ eq / g
It was. The copolymer composition is MXD6 /
6 = 0.14 / 0.86 (molar ratio) (wherein 6 represents a caproamide unit as a polyamide-forming component in the polymer). Subsequently, the above polymer was supplied to an extruder (screw diameter: 25 mm, L / D = 28, barrel temperature: 270 ° C.) equipped with a T-die, and the thickness was 30 μm.
m was formed. Physical properties of the film such as water absorption, β relaxation activation energy and oxygen gas permeability were as shown in Table 1. That is, the water absorption rate and β relaxation activation energy of this film were 18% by weight and 20.32 kJ / mol, respectively,
Further, the oxygen gas barrier property was low in both the dry state and the high humidity state.

[0068]

[Table 1]

[0069]

INDUSTRIAL APPLICABILITY As described in detail above, the present invention provides a diamine and a dicarboxylic acid or salts obtained from them,
A polyamide-forming raw material such as an aminocarboxylic acid and a lactam, or a polycondensation method comprising a prepolymerization under pressure melting and a subsequent postpolymerization step under normal pressure and / or reduced pressure, using the raw material and a raw material thereof In producing the polyamide resin, as prepolymerization conditions under pressure, a polymerization temperature, a water vapor pressure in the polymerization system, and the polymerization temperature,
By specifying the relationship between the product of water vapor pressure in the polymerization system and the polymerization time, and by releasing the pressure in the polymerization system to a pressure below atmospheric pressure prior to the post-polymerization step under atmospheric pressure and / or reduced pressure. , Containing a specific polyamide-forming component as an essential component, containing the essential component in a specific composition, and having characteristic physical properties with respect to water absorption rate, activation energy for β relaxation, etc., and gel or yellow coloring The present invention provides a polyamide resin free from the above and a method for producing the same. Therefore, the polyamide resin of the present invention, when formed into a film, provides a film having both excellent oxygen gas barrier properties and a small humidity dependency of the oxygen gas barrier properties, which have not been obtained by conventionally known techniques. The film can be suitably used as a packaging material for foods, pharmaceuticals, cosmetics and the like.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideki Fujimura 1-12-32 Nishihonmachi, Ube City, Yamaguchi Prefecture Ube Industries, Ltd. Polymer Research Laboratory (72) Inventor Takashi Amane 1-chome Nishimotocho, Ube City, Yamaguchi Prefecture 12th 32nd Ube Industries, Ltd.

Claims (2)

[Claims] 1. At least one amide repeating unit selected from the group consisting of a metaxylylene adipamide unit, a metaxylylene isophthalamide unit, and a metaxylylene terephthalamide unit is used in at least 2 to the entire resin.
Consisting of a polyamide resin containing 0 mol% or more, the water absorption of the amorphous part at 25 ° C. and 100% relative humidity is 8% by weight or less, and the frequency is 10 Hz and the strain is 0.05%.
The activation energy of β relaxation in the temperature-dispersion spectrum of dynamic viscoelasticity measured in tensile mode under
A polyamide resin having excellent gas barrier properties, which is characterized by being kJ / mol or less. 2. At least one amide repeating unit selected from the group consisting of a metaxylylene adipamide unit, a metaxylylene isophthalamide unit and a metaxylylene terephthalamide unit is used in at least 2 to the entire resin.
Consisting of a polyamide resin containing 0 mol% or more, the water absorption of the amorphous part at 25 ° C. and 100% relative humidity is 8% by weight or less, and the frequency is 10 Hz and the strain is 0.05%.
The activation energy of β relaxation in the temperature-dispersion spectrum of dynamic viscoelasticity measured in tensile mode under
In producing a polyamide resin having a kJ / mol or less by a polycondensation method consisting of a prepolymerization step under pressure melting and a subsequent postpolymerization step under normal pressure and / or reduced pressure, the prepolymerization step comprises Polymerization temperature is 170 ℃ or above 220
℃ or less, and the vapor pressure in the polymerization system is 3kgf / cm
It is a ² G or more and a kgf / cm ² water vapor pressure represented by G (P) and the time the polymerization time expressed (t) product of the polymerization temperature represented by (Pt) and ° C. (T) Is expressed by the following mathematical expression (I) And the following formula (II): 2. The gas barrier according to claim 1, wherein the post-polymerization step is carried out after the condensation water is removed by releasing the condensed water at a temperature of 220 ° C. or less to a pressure of atmospheric pressure or less at the same time. A method for producing a polyamide resin having excellent properties.