JP2001329168A - Method for producing polyamide composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a polyamide composite material having transparency, gas-barrierness and mechanical properties required for a packaging material at a low cost by uniformly and finely dispersing a lamellar silicate in a polyamide resin having a specific structure. SOLUTION: The objective polyamide composite material composed of (A) a polyamide resin and (B) a lamellar silicate is produced by carrying out the polycondensation reaction of a diamine containing >=70 mol% xylylenediamine or bis(aminomethyl)cyclohexane in the diamine component with a dicarboxylic acid containing >=70 mol% 4-20C α,ω-straight-chain aliphatic dicarboxylic acid in the dicarboxylic acid component and adding (B) lamellar silicate to the polycondensation product when the amount of water produced by the polycondensation reaction reaches >=70% of the theoretical production amount of water. The amount of the lamellar silicate is adjusted to give a polyamide composite material having a lamellar silicate content of 0.1-10 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyamide composite material having excellent transparency, gas barrier properties, mechanical properties, and the like as a packaging material for foods, beverages, medicines, electronic parts, and the like.

[0002]

2. Description of the Related Art Polyamides obtained from a polycondensation reaction between xylylenediamine and an aliphatic dicarboxylic acid, such as polyamides obtained from meta-xylylenediamine and adipic acid (hereinafter sometimes referred to as MX nylon), have high strength.
Because of its high elastic modulus and low permeability to gaseous substances such as oxygen and carbon dioxide, it is used as a film and bottle as a gas barrier material in the field of fiber-reinforced injection molding materials and packaging materials. However, in the field of packaging materials, in recent years, the necessity of gas barrier packaging for preserving foods and beverages for a long period of time without deteriorating freshness has been further increased, and further improvement in gas barrier properties has been demanded.

As one method for improving the gas barrier properties of a polyamide resin, Japanese Patent Application Laid-Open No. 2-69562 discloses a method in which a layered silicate is added to a polyamide resin. As the addition method, during the synthesis of the polyamide resin in the polymerization step of adding a layered silicate in advance,
An extrusion addition method in which melt kneading is performed using various commonly used extruders such as a single screw or twin screw extruder, and the like. In the case of the former addition method at the time of synthesis, the extrusion step is not required, so that the manufacturing process can be simplified. The viscosity is high, and water generated by the polycondensation reaction is less likely to volatilize from the surface of the reaction solution. As a result, the surface of the reaction solution rises, and it may be difficult to smoothly proceed with the reaction.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides excellent transparency, gas barrier properties and mechanical performance required for packaging materials by uniformly and finely dispersing a layered silicate in a polyamide resin having a specific structure. It is intended to provide a method for economically producing a polyamide composite material.

[0005]

Means for Solving the Problems The inventors of the present invention have made intensive studies to achieve the above object, and as a result, by adding a layered silicate during the polycondensation step of a polyamide resin having a specific structure, the above problem was solved. They have found that they can be solved and have completed the present invention.

That is, the present invention relates to a method for producing a polyamide composite material, comprising a diamine containing xylylenediamine or bis (aminomethyl) cyclohexane in a diamine component in an amount of 70 mol% or more, and a dicarboxylic acid component containing 4 carbon atoms. A polycondensation reaction with a dicarboxylic acid containing at least 70 mol% of α, ω-linear aliphatic dicarboxylic acid of at least about 20 at normal pressure or under pressure, and at least 70% of the theoretical amount of water generated by the polycondensation reaction. After the water is generated in the reaction system, the layered silicate (B) is added so that the compounding ratio in the polyamide composite material becomes 0.1 to 10% by mass, and a polycondensation reaction is further performed. The present invention relates to a method for producing a polyamide composite material comprising a polyamide resin (A) and a layered silicate (B).

In the present invention, the starting diamine of the polyamide resin (A) contains at least 70 mol% of xylylenediamine or bis (aminomethyl) cyclohexane. Examples of xylylenediamine include meta-xylylenediamine and para-xylylenediamine, and examples of bis (aminomethyl) cyclohexane include 1,3-bis (aminomethyl) cyclohexane and 1,4-bis (aminomethyl) cyclohexane.

In the present invention, the xylylenediamine or bis (aminomethyl) cyclohexane may contain other diamines such as tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, octamethylenediamine, and nonamethylenediamine. Diamines, paraphenylenediamines, metaxylylenediamines, aromatic diamines such as paraxylylenediamine,
1,3-bis (aminomethyl) cyclohexane and 1,4
-Alicyclic diamines such as bis (aminomethyl) cyclohexane can be used in an amount of less than 30 mol% in all diamine components.

In the present invention, α, ω having 4 to 20 carbon atoms, which is a dicarboxylic acid component as a raw material of the polyamide resin (A), is used.
-Examples of straight-chain aliphatic dicarboxylic acids include aliphatic dicarboxylic acids such as succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, adipic acid, sebacic acid, undecandioic acid, dodecandioic acid, and the like. Of these, adipic acid is preferred. Use of aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid in the above α, ω-linear aliphatic dicarboxylic acid in a range of less than 30 mol% in the total dicarboxylic acid component. Can be.

The polyamide resin (A) contains at least 70 mol% of xylylenediamine or bis (aminomethyl) cyclohexane in the starting diamine component, and has 4 to 20 carbon atoms of α, ω-straight chain in the starting dicarboxylic acid component. When the product is obtained by polycondensation from a raw material containing at least 70 mol% of an aliphatic dicarboxylic acid, mechanical properties such as strength and elasticity, and oxygen, carbon dioxide gas and the like when formed into a film, sheet, or hollow container are used. Excellent properties such as barrier properties against gaseous substances.

The layered silicate (B) used in the present invention includes a 1: 1 type layered silicate composed of one tetrahedral layer and one octahedral layer, that is, kaolinite, halloysite, chrysotile, etc. 2: 1 type layered silicate composed of two tetrahedral layers and one octahedral layer, ie, smectites such as montmorillonite, hectorite, beidellite, savonite, mica such as muscobite, phlogovite, talc, pyrophyllite Light, vermiculite, chlorite and the like. Among these, montmorillonite, mica and vermiculite are preferred, but montmorillonite is particularly preferred. As these layered silicates, those obtained by previously contacting a swelling agent such as a polymer compound, an organic compound or an inorganic compound to expand the interlayer may be used.

The addition amount of the layered silicate (B) in the present invention is preferably 0.1 to 10% by mass, and 0.2 to 5% by mass.
% By mass is more preferred. When the added amount of the layered silicate (B) is 0.1% by mass or more, the effect of improving gas barrier properties is exhibited, and when it is 10% by mass or less, transparency is not impaired.

In the present invention, the layered silicate (B) contained in the polyamide resin (A) needs to be finely dispersed uniformly without local aggregation. The term "fine dispersion" as used herein means that layered silicates are separated into a plate shape in a polyamide, and 50% or more of them have an interlayer distance of 50 angstroms or more. The interlayer distance refers to the distance between the centers of gravity of the flat objects. The longer this distance is, the better the dispersion state is, the better the appearance such as transparency when finally made into a film, sheet, or hollow container, and the better the barrier property against gaseous substances such as oxygen and carbon dioxide gas. Can be.

The conventional method of adding the layered silicate (B) includes a method of adding the layered silicate (B) during the melt polymerization of the polyamide resin (A) and stirring, and a conventional method such as a single screw or twin screw extruder. Examples of the method include melt kneading using various extruders used. In the case of the addition method at the time of synthesis, an extrusion step is not required as compared with the extrusion addition method, and the production process can be simplified, so that a polyamide composite material can be economically produced.

As a method of adding the layered silicate (B) in the present invention, for example, the condensation reaction of the polyamide resin (A) is carried out by gradually adding the diamine component to the molten dicarboxylic acid component under normal pressure. A method in which 70% or more of the theoretical amount of water generated by the polycondensation reaction is generated in the reaction system, and then the layered silicate (B) is added, or in the presence of a dicarboxylic acid component, a diamine component and water, A method is preferred in which a condensation reaction is performed under pressure, and 70% or more of the theoretical amount of water generated by the polycondensation reaction is generated in the reaction system, and then the layered silicate (B) is added.

The theoretical amount of water generated by the polycondensation reaction of the present invention can be easily determined from the amount of the diamine component and the amount of the dicarboxylic acid component added to the reaction system. Further, the amount of water generated in the polycondensation reaction of the present invention, the amount of water in the reaction solution,
It can be easily obtained from the amount of water vapor present in the space of the reaction tank and the space of the reaction product water condensing device, and the amount of water accumulated in the reaction product water condensing device. From the above, it is possible to easily confirm that 70% or more of the theoretical amount of water was generated in the polycondensation step of the present invention.

By adopting a method in which the layered silicate is added to the reaction system after 70% or more of the theoretical amount of water generated by the above-mentioned polycondensation reaction is generated in the reaction system,
When the layered silicate (B) is added before water of 70% or more of the theoretical amount of water is generated in the reaction system, or the layered silicate is added in advance to the molten dicarboxylic acid component, When the polyamide resin is polymerized under normal pressure by gradually adding a diamine component, or in the presence of a diamine component, a dicarboxylic acid component, a layered silicate (B) and water,
Compared with the case where a polyamide resin is polymerized under pressure, a polyamide composite material can be produced without an increase in the level of a reaction solution.

In the present invention, lubricants such as fatty acid amides, fatty acid metal salts, fatty acid amides, copper compounds, organic or inorganic halogen compounds, hindered phenols, hindered amines, etc.
It is also possible to mix additives such as antioxidants such as hydrazine-based compounds, sulfur-based compounds and phosphorus-based compounds, and ultraviolet absorbers such as benzotriazole-based compounds.

[0019]

The present invention will be specifically described below with reference to examples. In the examples and the like, the following method was used to evaluate a polyamide molded product. Relative Viscosity of Polyamide Resin A 1 g / dl 96% sulfuric acid solution was measured for relative viscosity at 25 ° C. using a Cannon-Fenske viscometer. Dispersion state A 0.1 μm-thick flake was cut out from the unstretched film with a microtome, and the dispersion state of the layered silicate plate was photographed with a transmission electron microscope (model: JEM-1200EX2) manufactured by JEOL Ltd. (magnification) 100,000 times). For 20 screens of the photographic image, the distance between the centers of gravity of adjacent flat plates was measured on a scale, and the percentage of flat plates having a distance between the centers of gravity of 50 Å or more with respect to all the flat plates in the image was obtained.

Transparency Unstretched film manufactured by Nippon Denshoku Industries Co., Ltd.
Using ZE-2000, the haze of the film was measured according to ASTM D1003. Oxygen permeability The unstretched film was measured according to ASTM D3985. Measurements are made by Modern Control, Model: OX
The test was performed in an atmosphere of 23 ° C. and a relative humidity of 60% using TRAN 10 / 50A.

Example 1 A well-weighed 769.2 g of adipic acid was placed in a 3 liter flask equipped with a stirrer, a decomposer, a thermometer, a dropping funnel and a nitrogen gas inlet tube, and sufficiently purged with nitrogen. Further, adipic acid was dissolved in a small amount of nitrogen gas at 170 ° C. to make a uniform fluid state. In addition, the internal temperature was continuously
C. while raising the temperature to 65.degree.
2 g was added dropwise over 40 minutes with stirring. Subsequently, 71.6 g of meta-xylylenediamine was continuously added dropwise with stirring for 11 minutes.

During this time, the internal temperature was continuously raised to 235 ° C. Water distilled off with the dropwise addition of meta-xylylenediamine was removed from the system through a condensing device and a cooler. The amount of water generated at the end of dropping of meta-xylylenediamine was 75% of the theoretical amount. Thereafter, while the internal temperature was raised to 250 ° C., 13.1 g of montmorillonite (trade name: Orben, manufactured by Shiraishi Industry Co., Ltd.) was continuously added with stirring for 5 minutes, and the reaction was continued for 30 minutes. The relative viscosity of the obtained polyamide was 2.1.

After the polyamide was pulverized into chips, it was supplied to a twin screw extruder having a cylinder diameter of 20 mm and a T-die with a weighing feeder at a rate of 1.2 kg / hour.
Cylinder temperature 270 ° C, screw rotation speed 100rpm
After melt-kneading under the conditions of m, the film was extruded through a T-die and solidified on a cooling roll at 70 ° C. while being drawn at a speed of 2.7 m / min to obtain an unstretched film having a thickness of 50 μm. . The layered silicate dispersion state in this unstretched film is 98%, and the haze of the unstretched film is 1.
The oxygen permeability was 3% and the oxygen permeability coefficient was 0.59 ml-mm- / m ² -day-MPa.

COMPARATIVE EXAMPLE 1 In the same reactor as in Example 1, adipic acid 76
9.2 g and 13.1 g of montmorillonite (trade name: Orben, manufactured by Shiraishi Industry Co., Ltd.) were added, and the mixture was sufficiently purged with nitrogen.
Further, adipic acid was dissolved in a small amount of nitrogen gas at 170 ° C. to make a uniform fluid state. In addition, the internal temperature is continuously
While raising the temperature to 20 ° C, meta-xylylenediamine 48
3.9 g was added dropwise over 30 minutes while stirring, but at this time the reaction liquid surface rose and the polymerization reaction could not be continued.

[0025]

According to the method for producing a polyamide composite material of the present invention, the polyamide polycondensation reaction can be smoothly carried out, and the extrusion process is not required as compared with the extrusion addition method, and the production process is simplified. , And a polyamide composite material having a small heat history can be obtained.

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Claims (5)

[Claims] 1. A method for producing a polyamide composite material, comprising:
A diamine containing xylylenediamine or bis (aminomethyl) cyclohexane in an amount of 70 mol% or more in a diamine component, and an α, ω- having 4 to 20 carbon atoms in a dicarboxylic acid component.
Polycondensation reaction with dicarboxylic acid containing linear aliphatic dicarboxylic acid of 70 mol% or more under normal pressure or pressure is performed, and 70% or more of the theoretical amount of water generated by the polycondensation reaction is generated in the reaction system. After that, the layered silicate (B) is added so that the compounding ratio in the polyamide composite material is 0.1 to 10% by mass, and a polycondensation reaction is further performed. A method for producing a polyamide composite material comprising a silicate (B). 2. The method for producing a polyamide composite material according to claim 1, wherein the diamine component is a diamine containing at least 70 mol% of metaxylylenediamine. 3. The method according to claim 1, wherein the layered silicate (B) is montmorillonite. 4. The method for producing a polyamide composite material according to claim 3, wherein the layered silicate (B) has been pre-contacted with a swelling agent to expand the interlayer. 5. The method for producing a polyamide composite material according to claim 1, wherein the layered silicate (B) is uniformly finely dispersed in the polyamide resin (A).