JPH0680873A - Polyamide resin composition for film - Google Patents

Abstract

PURPOSE:To obtain the subject composition having toughness and tensile characteristics, etc., excellent in oxygen gas barrier properties and useful as a film for food packaging by uniformly dispersing a phyllosilicate into a resin mixture of an aliphatic polyamic resin and an aromatic polyamide resin. CONSTITUTION:The objective composition is obtained by uniformly dispersing (C) 0.05-90wt.% phyllosilicate into a resin mixture consisting of (A) 95-50wt.% alphatic polyamide resin and (B) 52-50wt.% aromatic polyamide resin. Example of the component A include (co)polymer of epsilon-caprolactam and those of the component B include a resin, etc., obtained by polycondensing terephtharic acid and/or isophthalic acid with hexamethylene diamine. Examples of the component C includes preferably a phyllosiicate mineral having 6-20Angstrom thickness and 0.002-1mum length of one side, e.g. montmorillonite. This composition is preferably obtained by kneading the component C uniformly dispersed in a dispersing medium in a swollen state with the component A and then bending the kneaded product with the component B.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a resin composition suitable for a film having an aliphatic polyamide resin containing a uniformly dispersed layered silicate as a main component and having excellent gas barrier property, particularly oxygen gas barrier property. It is about things.

[0002]

2. Description of the Related Art The biggest problem in the field of food packaging is deterioration of quality and freshness due to oxidation of contents, and therefore, further improvement of gas barrier property has been demanded in recent years.

Films made of polyolefins, polystyrenes, polyvinyl chlorides, etc. have been conventionally used for daily products such as foods, but since they are poor in gas barrier properties, they are used for food packaging where quality maintenance is required. Not suitable.

On the other hand, polyamide films are often used in the food packaging field because of their excellent properties such as toughness, pinhole resistance, heat resistance and oil resistance.

However, the gas barrier property of the polyamide resin film is not fully satisfactory depending on the application. In particular, under high humidity, the gas barrier property of the polyamide film is significantly reduced. Therefore, the ethylene-vinyl alcohol copolymer (EV
OH) and a polyamide resin are co-extruded, or the surface of the polyamide film is coated with polyvinylidene chloride (PVDC) having a good gas barrier property.
However, EVOH or PVDC has poor molding stability, and in addition, the use of these EVOH or PVDC has a problem that the layer structure of the coextruded film is increased, or a coating line is required, and the work process is increased accordingly. is there. However, among the polyamide resins, a film containing an aromatic ring in the main chain, for example, a crystalline polyamide resin MXD-6 obtained by polycondensation of metaxylylenediamine and adipic acid has an oxygen gas barrier property of polyamide-6. It is known to be 10 to 20 times superior to such aliphatic polyamide resin films. Furthermore, it is known that the film made of an amorphous polyamide resin obtained by polycondensation of terephthalic acid and / or isophthalic acid and hexamethylenediamine is also very excellent in oxygen gas barrier property as compared with the aliphatic polyamide resin film. Has been.

[0006]

Films made of these aromatic polyamide resins are whitened due to moisture absorption under high humidity. In addition, there is a problem in flexibility, which is a drawback of the aromatic polyamide resin. Conventionally, a material excellent in high retort treatment resistance and oxygen gas barrier property (JP-A-53-6355) and a material for stretched film use excellent in oxygen gas barrier property (JP-A-52).
-136260, JP-A-62-41261, JP-A-62-131060, JP-A-62-1
In order to overcome the above-mentioned drawbacks, a method of mixing an aromatic polyamide resin with an aliphatic polyamide such as polyamide-6 has been proposed in the improvement of Japanese Patent No. 27346).
However, in this method, when the ratio of the aromatic polyamide resin is 50% by weight or more, the effect of improving the flexibility is poor, while when it is less than 50% by weight, the excellent gas barrier property of the aromatic polyamide resin is greatly impaired. There is such a problem.

It is an object of the present invention to provide a polyamide resin composition for a film which retains the various properties of the aliphatic polyamide and has good gas barrier properties.

[0008]

That is, the invention of the present application is
The layered silicate is uniformly dispersed in a resin composed of 95 to 50% by weight of the aliphatic polyamide resin (A) and 5 to 50% by weight of the aromatic polyamide resin (B). The present invention provides a characteristic polyamide resin composition for a film.

In the present invention, JP-A-2-105856
The polyamide resin composition disclosed in Japanese Patent Laid-Open Publication No. 2004-242242 was used. That is, by using the aliphatic polyamide resin in which the layered silicate is uniformly dispersed, the mixing amount of the aromatic polyamide resin in the resin composition, which retains various excellent characteristics of the aliphatic polyamide resin, Even if it is less than 50% by weight, excellent gas barrier properties are exhibited.

Here, the polyamide film exhibiting an excellent gas barrier property refers to one having 50 ml / 24 hr · 30 μ or less under the conditions of 100% RH and 23 ° C.

The aliphatic polyamide resin which constitutes the polyamide film of the present invention has an acid amide bond (-CONH-) in the molecular chain, and is, for example, ε-.
Polymers or copolymers obtained from caprolactam, 6-aminocaproic acid, ε-enanthlactam, 7-aminoheptanoic acid, 11-aminoundecanoic acid, 9-aminononanoic acid, α-pyrrolidone, α-piperidone; hexamethylenediamine , Polymers obtained by polycondensing diamines such as nonamethylenediamine, undecamethylenediamine and dodecamethylenediamine with dicarboxylic acids such as adipic acid and sebacic acid, copolymers thereof or polymers or copolymers thereof. The blended product can be mentioned.

On the other hand, the aromatic polyamide resin in the present invention has an acid amide bond in the molecular chain formed by polycondensation of diamine and dicarboxylic acid, and in addition, constitutes the minimum unit of the polymer chain. A crystalline or non-crystalline resin made of at least one of the two components having an aromatic ring. Specifically, of the aromatic polyamide resins, the crystalline polyamide resin is a normal,
For example, it refers to a resin having a clear crystal structure by X-ray diffraction, such as an aliphatic polyamide resin such as polyamide-6. Specific examples thereof include polycondensates of metaxylylenediamine and adipic acid. On the other hand, an aromatic amorphous polyamide resin refers to an unclear crystal structure,
Specific examples thereof include resins formed by polycondensation of terephthalic acid and / or isophthalic acid and hexamethylenediamine.

The amount of the aliphatic polyamide resin mixed in the polyamide resin composition is preferably 95 to 50% by weight. When the amount of the aliphatic polyamide resin mixed is less than 50% by weight, the flexibility of the film is lowered and the pinhole resistance is deteriorated. If it exceeds 95% by weight, the effect of improving the gas barrier property becomes poor.

Crystalline aromatic polyamide resin ((C)
The weight mixing ratio of the component) and the amorphous aromatic polyamide resin (component (D)) is 100 to 0% by weight of the component (C) and 0 of the component (D) depending on the purpose and use of the polyamide film.
It can be arbitrarily changed within the range of up to 100% by weight.

The average molecular weight of the polyamide resin is 9,000.
-40,000 are preferable. The layered silicate which is a constituent component of the aliphatic polyamide resin is preferably a flat silicate having a thickness of 6 to 20 l and a side length of 0.002 to 1 m.

Further, the layered silicate needs to be uniformly dispersed in the aliphatic polyamide resin, but when dispersed, each layer maintains an interlayer distance of 20 Å or more on average and is uniformly dispersed. It is preferable. Here, the interlayer distance means the average distance between the centers of gravity of the flat sheets of the layered silicate, and the uniform distribution means that one sheet of the layered silicate or a multi-layered article having an average overlap of 5 layers or less is parallel. 5 or randomly, or in a mixture of parallel and random
It means that 0% by weight or more, preferably 70% by weight or more, is dispersed without forming local lumps. Therefore, the layered silicate means, for example, one unit of a substance having a side of 0.002 to 1 μm and a thickness of 6 to 20 Å.

As a raw material for such a layered silicate, a layered phyllosilicate mineral composed of a layer of magnesium silicate or aluminum silicate can be exemplified. Specifically, montmorillonite, saponite, piederite, nontronite, hectorite, smectite clay minerals such as stevensite and vermiculite, it is possible to exemplify, for example, virosite, even if these are natural, It may be synthesized. Of these, montmorillonite is preferred. The amount of the layered silicate compounded is 0.05 to the polyamide resin composition.
It is 15% by weight. If the amount of the layered silicate is less than 0.05% by weight, the effect of improving transparency is low, which is not preferable. On the other hand, if it exceeds 15% by weight, the tensile properties, pinhole resistance and other properties are deteriorated, which is not preferable.

As the constituent components of the polyamide resin composition of the present invention, if necessary, additives such as a lubricant, an antioxidant, a heat stabilizer, a weather resistance imparting agent and an antistatic agent may be added. Can be done.

Regarding the method for uniformly dispersing the layered silicate in the aliphatic polyamide resin, the layered silicate composite in which the layered silicate is swollen in the dispersion medium is uniformly dispersed and mixed or kneaded with the polyamide resin. Method (JP-A-2-
See Japanese Patent No. 305828. ) Can be applied.
In addition, it is possible to apply a method in which an aliphatic polyamide resin containing a layered silicate at a high concentration is prepared in advance by the above method, and the aliphatic polyamide resin and the aliphatic polyamide resin containing no layered silicate are mixed. it can.

As a method for mixing the aliphatic polyamide resin and the aromatic polyamide resin, a method of dry blending both resins or a method of melt-kneading with an extruder can be applied.

The film composed of the polyamide resin composition of the present invention can be made into a laminate from the polyamide film containing the layered silicate described above and a polymer film other than the polyamide film. Examples of the other polymer film include a low density polyethylene film, a high density polyethylene film, a polypropylene film, an ethylene-vinyl acetate copolymer film and an ionomer resin film.

The method of forming the polyamide film into a laminate is not particularly limited, and for example, a method of adhering the polyamide film and another one or more polymer films with an adhesive; or a polyamide resin and one or two kinds A method of melt-extruding the above-described polymer compound constituting the other polymer film from the multilayer spinneret via an adhesive resin can be applied.

The film composed of the polyamide resin composition of the present invention, in which the layered silicate is dispersed in the film, has excellent gas barrier properties without impairing the various properties of the aliphatic polyamide resin. It is something to demonstrate.

[0024]

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples. In addition, the measuring method of the physical property below is as follows.

Molecular Weight of Polyamide According to JIS K6810-1970, the relative viscosity was measured using 98% sulfuric acid to determine the molecular weight (Mn).

Transparency (cloudiness) ASTM by a direct reading type haze meter manufactured by Suga Test Instruments Co., Ltd.
The haze value (haze ratio) of the film was measured according to D-1003.

Surface Glossiness ASTM by a direct reading type haze meter manufactured by Suga Test Instruments Co., Ltd.
The surface glossiness of the film was measured according to D-523.

Tensile Properties Tensilon UTM-3 manufactured by Toyo Baldwin Co., Ltd.
Tensile properties were measured according to ASTM D-882.

Gelbo flex test (pinhole resistance) With a gelbo flex tester manufactured by Rigaku Kogyo Co., Ltd., MIL
The pinhole resistance of the film was evaluated according to -B-131C. 40 cycles / min. After adding 1000 cycles of flex, the number of pinholes was measured. The tensile properties and gelbo flex test were 23 ℃,
It was performed under an atmosphere of 65% RH.

Oxygen gas permeability MOCON OX-TRAN manufactured by Modern Control Co.
The gas permeability of the film was measured according to ASTM D-3985-81 with 100A. The measurement conditions are 23 ℃,
0% RH and 100% RH.

Example 1 100 g of montmorillonite, which is a raw material having an average thickness of one unit of layered silicate of 8 Å and a side length of about 0.1 μm, was dispersed in 2.3 liters of water, and hot water at 80 ° C. At 28.1
g of 12-aminododecanoic acid is evenly dispersed,
The dispersion liquid containing 1 l of concentrated hydrochloric acid was mixed and stirred at 80 ° C. for 60 minutes. Further, after thoroughly washing this, suction filtration is carried out using a Buchner funnel to obtain a water-containing complex (hereinafter referred to as 1
Abbreviated as 2MMT. ) Got. The water content of this composite is 88
%Met. As a result of X-ray analysis, the interlayer distance of the layered silicate in the composite of 12-aminododecanoic acid and montmorillonite (12MMT) was 18.0Å. Next, ε-caprolactam was added to this 12MMT so that the ratio of 12MMT of 12-aminododecanoic acid and montmorillonite to ε-caprolactam was 1: 1 and the mixture was stirred and mixed.

Next, using a twin-screw kneading extruder having a diameter of 40 mm,
Under the condition that the cylinder temperature is 250 ° C., an aliphatic polyamide resin having an average molecular weight of 30,000 consisting of 80% by weight of polyamide-6 component and 20% by weight of polyamide-66 component is melted, and ε-caprolactam is further added to the above 12MMT. Was melt-kneaded while feeding, and the kneaded product taken out in a strand form from the extruder nozzle was water-cooled and cut to obtain pellets composed of an aliphatic polyamide resin and a montmorillonite composite. The content of montmorillonite complex in this aliphatic polyamide resin was 3.0% by weight.

Subsequently, the pellets of the aliphatic polyamide resin containing the layered silicate and the crystalline aromatic polyamide resin MXD-6 obtained by polycondensation of metaxylylenediamine and adipic acid were dry blended. The mixture was melt-kneaded by a twin-screw kneading extruder, and the mixture taken out in a strand form from the extruder nozzle was water-cooled and cut to obtain a polyamide resin composition. Here, the weight mixing ratio of the aliphatic polyamide resin containing layered silicate and MXD-6 was set to 80/20.

The pellets thus obtained were melted in an extruder having a diameter of 30 mm under the conditions of a cylinder temperature of 250 ° C. and a die width of 3
Extruded into a film with a 00 mm coat hanger die,
Cooled on a casting roll at 50 ℃, thickness 30μ
I got a casting film. The physical properties of the film are shown in Table 1.

Example 2 The uniformly dispersed layered silicate in Example 1 was used in an amount of 3.0.
A casting film was prepared and physical properties were measured in the same manner as in Example 1 except that the weight mixing ratio of the aliphatic polyamide resin contained by weight% and MXD-6 was set to 60/40. The results are shown in Table 1.

Example 3 The weight mixing ratio of the aliphatic polyamide resin containing 3.0% by weight of the uniformly dispersed layered silicate and the aromatic polyamide resin was set to 60/40, and this aromatic polyamide resin was used. Resin composition in which the weight mixing ratio of the crystalline MXD-6 component to the amorphous terephthalic acid and / or isophthalic acid and hexamethylenediamine resin (6T · 6I) component is 75/25 A casting film was prepared and the physical properties were measured in the same manner as in Example 1 except that the product was used. The results are shown in Table 1.

Example 4 MX in the aromatic polyamide resin component of Example 3
The weight mixing ratio of D-6 component and 6T · 6I component is 25/75.
A casting film was prepared in the same manner as in Example 3 except that the above was used, and the physical properties were measured. The results are shown in Table 1.

Example 5 A casting film was prepared in the same manner as in Example 3 except that only 6T · 6I was used as the aromatic polyamide resin component, and its physical properties were measured. The results are shown in Table 1.

Example 6 The type of the aliphatic polyamide resin containing 3.0% by weight of the uniformly dispersed layered silicate was an average molecular weight of 24,000.
Polyamide-6 of No. 6 was used as the aromatic polyamide resin, and a casting film was prepared in the same manner as in Example 1 except that 6T · 6I was used, and the mixing ratio was 70/30, and the physical properties were measured. . The results are shown in Table 1.

Example 7 The content of the layered silicate uniformly dispersed in the aliphatic polyamide resin was 5.0% by weight, and the mixing ratio of the aliphatic polyamide resin component and the aromatic polyamide resin component was 80 /. 20
A casting film was prepared and physical properties were measured in the same manner as in Example 1 except for the above. The results are shown in Table 1.

Comparative Example 1 A casting film was prepared in the same manner as in Example 1 except that the constituent component of the polyamide resin composition was polyamide-6, which did not contain layered silicate and had an average molecular weight of 24,000. did. The results are shown in Table 2.

Comparative Example 2 Polyamide-6 / polyamide-66 and MXD-6 having an average molecular weight of 30,000 and containing no layered silicate were used as the components of the polyamide resin composition, and the weight mixing ratio was 80 /.
A casting film was prepared in the same manner as in Example 1 except that the value was 20, and the physical properties were measured. The results are shown in Table 2.

Comparative Example 3 The constituent components of the polyamide resin composition in Example 1 were 6
A casting film was prepared in the same manner as in Example 1 except that only T · 6I was used, and the physical properties were measured. The results are shown in Table 2.

Comparative Example 4 The mixing ratio of the aliphatic polyamide resin containing 3.0% by weight of the uniformly dispersed layered silicate and 6T · 6I was 40/6.
A film was prepared in the same manner as in Example 1 except that the value was 0, and the physical properties were measured. The results are shown in Table 2.

Comparative Example 5 The mixing ratio of MXD-6 to the aliphatic polyamide resin containing 3.0% by weight of uniformly dispersed layered silicate was 40/6.
A film was prepared and physical properties were measured in the same manner as in Example 1 except that the value was 0. The results are shown in Table 2.

Comparative Example 6 Polyamide resin composition was composed of polyamide-6 / polyamide-66 and 6T · 6I having an average molecular weight of 30,000 and containing no layered silicate, and the weight mixing ratio was 60 /.
A casting film was prepared in the same manner as in Example 1 except that the value was 40, and the physical properties were measured. The results are shown in Table 2.

Comparative Example 7 The composition ratio of the polyamide resin composition was set such that the weight ratio of the aliphatic polyamide resin containing no layered silicate and the aromatic polyamide resin was 60/40, and MXD-6 component which is crystalline and 6T which is amorphous
A casting film was prepared and physical properties were measured in the same manner as in Example 1 except that a resin composition having a weight mixing ratio of 6I component of 50/50 was used. The results are shown in Table 2.

Comparative Example 8 Polyamide resin composition comprising polyamide-6 / polyamide-66 and MXD-6 having an average molecular weight of 30,000 and containing no layered silicate was used, and the weight mixing ratio was 60 /.
A casting film was prepared in the same manner as in Example 1 except that the value was 40, and the physical properties were measured. The results are shown in Table 2.

Comparative Example 9 The mixing ratio of MXD-6 to the aliphatic polyamide resin containing 0.05% by weight of uniformly dispersed layered silicate was 60 /.
A casting film was prepared in the same manner as in Example 1 except that the value was 40, and the physical properties were measured. The results are shown in Table 2.

Example 8 A film was melted in an extruder having a diameter of 40 mm at a cylinder temperature of 260 ° C., and a water-cooled three-layer tubular film molding machine having a die diameter of 100 mm was used to form a polyamide (outer layer) / adhesive resin (intermediate layer). Layer) / LDPE (inner layer)
A film having a three-layer structure of (30 μm / 25 μm / 30 μm) was obtained. The polyamide resin composition used was a mixture of MXD-6 at 60/40 with an aliphatic polyamide resin containing 3.0% by weight of the layered silicate uniformly dispersed by the method of Example 1. Adhesive resin is UBE Bond
F1100 (Ube Industries, Ltd.), LDPE is UBE
Polyethylene F022 (manufactured by Ube Industries, Ltd.) was used. The molding conditions are as follows. Die diameter: Diameter 100 mm Film folding diameter: 200 mm Pulling speed: 10 m / min. Cooling water temperature: 20 ° C. Molding temperature (setting) PA: 260 ° C., adhesive resin: 200 ° C. LDPE: 200 ° C. Table 3 shows each physical property value of the obtained three-layer structure film.

Example 9 The weight mixing ratio of the aliphatic polyamide resin and the aromatic polyamide resin in Example 8 was set to 60/40, and the crystalline MXD-6 component and the amorphous MXD-6 component in this aromatic polyamide resin were used. Polymerization mixing ratio of 6T and 6I components is 50 /
A water-cooled three-layer tubular film was prepared in the same manner as in Example 8 except that the resin composition of 50 was used.
The physical properties were measured. The results are shown in Table 3.

Comparative Example 10 Three layers of water cooling were carried out in the same manner as in Example 8 except that the polyamide-6 / polyamide-66 resin having an average molecular weight of 30,000 and containing no layered silicate was the only constituent of the polyamide resin composition. A tubular film was prepared and the physical properties were measured. The results are shown in Table 3.

COMPARATIVE EXAMPLE 11 A layered silicate was used as a constituent of a polyamide resin composition in an amount of 3.0.
A water-cooled three-layer tubular film was prepared and physical properties were measured in the same manner as in Example 8 except that only the aliphatic polyamide resin contained in a weight percentage was used. The results are shown in Table 3.

Comparative Example 12 The constituent components of the polyamide resin composition in Example 8 were M
A water-cooled three-layer tubular film was prepared in the same manner as in Example 8 except that only XD-6 was used, and the physical properties were measured.
The results are shown in Table 3.

[0055]

[Table 1]

[0056]

[Table 2]

[0057]

[Table 3]

[0058]

When the polyamide resin composition of the present invention is formed into a film, it exhibits an excellent oxygen gas barrier property without impairing various properties of the polyamide film such as pinhole resistance, toughness and tensile properties. Therefore, it is extremely useful in practice, especially as a film for food packaging.

Claims (1)

[Claims] 1. (A) Aliphatic polyamide resin 95-50
A polyamide resin composition for a film, characterized in that 0.05 to 15% by weight of a layered silicate is uniformly dispersed in a resin comprising 5% by weight and (B) 5 to 50% by weight of an aromatic polyamide resin.