JPH11181278A - Oriented polyamide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject film having small oxygen gas permeability, excellent in orientating properties, transparency and glossiness, and useful for food wrapping by using a polyamide composition comprising a specific aliphatic polyamide resin and an aromatic polyamide resin in a specified proportion. SOLUTION: This oriented polyamide film is obtained by using a polyamide resin composition comprising of (A) 95-50 pts.wt. aliphatic polyamide resin (e.g. polyamide 6) containing 0.05-30 wt.%, preferably 1-5 wt.% homogeneously dispersed laminar silicate (e.g. montmorillonite), and (B) 5-50 pts.wt. aromatic polyamide resin. The component B is exemplified by a polymer comprising a polycondensate of terephthalic acid and/or isophthalic acid with hexamethylenediamine. The mixing ratio of the components A/B is preferably (90/10)-(60/40).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an oxygen gas permeation obtained by using a resin composition containing an aliphatic polyamide resin containing a layered silicate dispersed uniformly as a main component and an aromatic polyamide. The present invention relates to a stretched polyamide film having a small degree and excellent in stretchability, transparency and glossiness.

[0002]

2. Description of the Related Art Conventionally, polyamide films are often used for food packaging because of their excellent properties such as toughness, heat resistance and oil resistance. Above all, films for packaging fresh foods, etc. must have excellent transparency and glossiness to accurately grasp the contents,
In order to prevent deterioration of quality and freshness due to oxidation and the like, a material having particularly smaller oxygen gas permeability has been required.

[0003] As a material corresponding to this requirement, an unstretched polyamide film containing a layered silicate has been proposed.
However, this film has sufficient strength,
In order to obtain rigidity and low oxygen gas permeability, it is necessary to increase the thickness, and there are drawbacks such as difficulty in handling and being economically expensive.

Stretching has been studied as an improvement measure, but it has been pointed out that when a polyamide film containing a layered silicate is stretched, transparency and glossiness are reduced. Various studies have been conducted on solving this problem.
For example, Japanese Patent Application Laid-Open No. 4-110347 discloses a stretched polyamide film comprising a resin composition obtained by adding a hindered phenol compound to a polyamide resin and a layered silicate. Japanese Patent Application Laid-Open No. 4-178559 discloses a stretched polyamide film comprising a polyamide resin, a layered silicate and a hindered phenol compound, and further comprising a silane coupling agent and / or a titanate coupling agent. However, even with these methods, it cannot be said that the required transparency, glossiness, and oxygen gas permeability are sufficient.

On the other hand, Japanese Patent Application Laid-Open No. Hei 6-80873 discloses that a resin composed of 95 to 50 parts by weight of an aliphatic polyamide resin and 5 to 50 parts by weight of an aromatic polyamide resin is added with a layered silicate of 0.1 to 50 parts by weight.
There is disclosed a polyamide resin composition for a film, which is uniformly dispersed in a proportion of from 0.5 to 15% by weight. However, this publication only describes a non-stretched film and does not disclose any effect by stretching.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a stretched polyamide film which is excellent in transparency and glossiness, and has a small oxygen gas permeability and excellent stretchability.

[0007]

Means for Solving the Problems As a result of intensive studies, the present inventors have drawn a polyamide film obtained from a resin composition obtained by adding an aromatic polyamide resin to an aliphatic polyamide resin in which layered silicate is uniformly dispersed. Thus, the present inventors have found that the above object can be achieved, and have reached the present invention.

That is, the present invention provides: (A) 95 to 50 parts by weight of an aliphatic polyamide resin containing 0.05 to 30% by weight of a layered silicate uniformly dispersed; and (B) 5 to 50 parts of an aromatic polyamide resin. A stretched polyamide film characterized by using a polyamide resin composition consisting of parts by weight.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The aliphatic polyamide resin constituting the stretched polyamide film of the present invention is an acid amide bond (-CONH) in the molecular chain.
-), For example, ε-caprolactam, 6-aminocaproic acid, ε-enantholactam, 7
-Aminoheptanoic acid, 9-aminononanoic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid, laurolactam, α-pyrrolidone, α-piperidone, hexamethylenediamine, nonamethylenediamine, undecamethylenediamine, dodecamethylenediamine And the like, or a polymer consisting of a polycondensate of a diamine and a dicarboxylic acid such as adipic acid and sebacic acid, or a copolymer thereof, or a blend of these polymers or copolymers. Preferably, ε-caprolactam, 6-
Aminocaproic acid, 11-aminoundecanoic acid, 12-
It is a polymer comprising a polycondensate of aminododecanoic acid, laurolactam, hexamethylenediamine and adipic acid, a copolymer thereof, or a blend of these polymers or copolymers.

It is necessary that the layered silicate used in the present invention is uniformly dispersed in the aliphatic polyamide resin. It is preferred that Here, the interlayer distance refers to the average distance between the centers of gravity of the plate of the layered silicate.
Or, in a state where a multilayer having an average overlap of 5 or less layers is parallel or randomly, or a mixture of parallel and random, 50% by weight or more, preferably 70% by weight thereof
The above is a state in which the local mass is dispersed without forming. Therefore, the layered silicate is, for example, 0.002 pieces.
This indicates one unit of a substance having a thickness of 1 to 1 μm and a thickness of 6 to 20 °.

As a raw material of such a layered silicate, a layered phyllosilicate mineral composed of a layer of magnesium silicate or aluminum silicate can be exemplified. Specifically, montmorillonite, saponite, paiderite, nontronite, hectorite, smectite clay minerals such as stevensite and vermiculite, virosite and the like can be exemplified, even if these are natural, It may be synthesized. Of these, montmorillonite is preferred. The compounding amount of the layered silicate is 0.05 to
The content is 30% by weight, preferably 0.1 to 15% by weight, more preferably 0.5 to 10% by weight, particularly preferably 1 to 5% by weight. If the amount of the layered silicate is less than 0.05% by weight, the effect of improving the oxygen gas permeability is low, such being undesirable. On the other hand, if it exceeds 30% by weight, the drawability and the transparency are lowered, which is not preferable.

The method of uniformly dispersing the layered silicate in the aliphatic polyamide resin includes mixing or kneading the layered silicate composite in which the layered silicate is uniformly dispersed in a dispersion medium with the layered silicate swollen. (Japanese Unexamined Patent Publication No.
See Japanese Patent Publication No. 305828. ) Can be applied.
It is also possible to apply a method in which an aliphatic polyamide resin containing a layered silicate at a high concentration is adjusted in advance by the above method, and this aliphatic polyamide resin is mixed with an aliphatic polyamide resin containing no layered silicate. it can.

On the other hand, the aromatic polyamide resin in the present invention is a resin having an acid amide bond (-CONH-) in a molecular chain formed by polycondensation of a diamine and a dicarboxylic acid. Refers to a polyamide resin comprising at least one of the two components constituting the minimum unit having an aromatic ring. For example, a polycondensate of an aromatic diamine such as meta-xylene diamine and adipic acid, an aliphatic diamine such as sebacic acid, and terephthalic acid,
Polymers or copolymers comprising a polycondensate of an aromatic dicarboxylic acid such as isophthalic acid and an aliphatic diamine such as tetramethylenediamine, hexamethylenediamine, nonamethylenediamine, undecamethylenediamine, dodecamethylenediamine, or these And a blend of the above polymers or copolymers. Preferably, a polymer or copolymer comprising a polycondensate of metaxylene diamine and adipic acid, a polycondensate of terephthalic acid and / or isophthalic acid and hexamethylenediamine, or a blend of these polymers or copolymers It is.

Although the molecular weight of the aliphatic polyamide resin and the aromatic polyamide resin is not particularly limited, JIS K
The relative viscosity measured according to 6810 is 1.5-5.
0, preferably 2.0 to 4.5. If the relative viscosity is excessively high, the melt viscosity becomes too high, and it may be difficult to produce a molded product, a film, or the like. On the other hand, if it is excessively low, practical properties such as mechanical properties of the obtained polyamide resin may be reduced.

The mixing ratio of the aliphatic polyamide resin and the aromatic polyamide resin is from 95/5 to 50/50% by weight. Preferably, it is 90/10 to 60/40% by weight. If the amount of the aromatic polyamide resin exceeds 50% by weight, the tensile strength of the stretched film is undesirably reduced. If the content is less than 5% by weight, transparency is deteriorated and oxygen gas permeability is increased, which is not preferable.

The polyamide resin composition used in the stretched polyamide film of the present invention can be obtained by dry-blending both aliphatic polyamide resin and aromatic polyamide resin, or by melt-kneading with an extruder. Can be applied.

The polyamide resin composition used in the stretched polyamide film of the present invention may contain a lubricant, an antioxidant, a heat stabilizer, a weathering agent, an antistatic agent, if necessary, as long as the properties and moldability are not impaired. Agents, water repellents, anti-blocking agents, and the like.

Next, a method for producing the film of the present invention will be described. The stretched polyamide film of the present invention is prepared by first preparing an unstretched polyamide film from the above-mentioned mixed polyamide resin composition and stretching the unstretched polyamide film in one direction or two directions perpendicular to each other along the film surface. The unstretched polyamide film is obtained by heating and melting the above mixed polyamide resin composition using an extruder, extruding through a T-die or a circular die, and contacting with a cooled roll, liquid or gas to solidify. The cooling temperature in this case is 0 to
A range of 80 ° C. is preferred. The unstretched polyamide film thus obtained is gripped by a roll stretching machine or a clip and stretched in one direction in a tenter to obtain a uniaxially stretched polyamide film. To obtain a biaxially stretched polyamide film, either a simultaneous stretching method or a sequential stretching method is used. The former is simultaneously stretched in two directions perpendicular to each other by a tubular method or a tenter method. In the latter, the film is stretched in a longitudinal direction by a roll stretching machine, and then stretched in a transverse direction by a tenter, or vice versa.

The stretching temperature is usually from 30 to 200 ° C, preferably from 40 to 150 ° C. The uniaxial stretching ratio is usually 1.
It is 5 to 8 times, preferably 2 to 6 times, and the biaxial stretching ratio is usually 1.5 to 6 times, preferably 2 to 5 times in each direction.

The obtained stretched polyamide film is desirably heat-treated by heating to a temperature not lower than the lowering point of the melting point or softening point of the aliphatic polyamide resin or the aromatic polyamide resin at a temperature higher than the stretching temperature. .

The thickness of the stretched polyamide film of the present invention is usually 1 to 100 μm, preferably 5 to 50 μm, more preferably 10 to 30 μm.

[0022]

The present invention will be specifically described below with reference to examples and comparative examples. The measured values shown in the examples and comparative examples were measured by the following methods.

1) Transparency (Haze) The haze was measured using a direct-reading haze meter manufactured by Suga Test Instruments Co., Ltd. according to ASTM D-1003.

2) Gloss The gloss was measured using a digital variable gloss meter manufactured by Suga Test Instruments Co., Ltd. according to ASTM D-523.

3) Oxygen gas permeability Measured using MOCON-OX-TRAN 2/20 manufactured by Modern Control Co. according to ASTM D-3985-81. The measurement conditions are 23 ° C. and 65% RH.

Example 1 Polyamide produced according to Japanese Patent Publication No. 7-47644
Montmorillonite composite material (hereinafter referred to as NCH)
You. ) Was used. The mon in the aliphatic polyamide resin
The morillonite complex content was 2.0% by weight, η_r
Is 3.8. To this NCH pellet, terephthal
Acid and isophthalic acid (molar ratio 3: 7) and hexamethylene
Aromatic polyamide resin composed of diamine (6T · 6
I) Component (η _r= 2.1) at a weight mixing ratio of 80/20.
Live blended. Using the obtained polyamide resin composition
GT-40-A-400 manufactured by Institute of Plastics Engineering
Using a mold T-die film molding machine, a molding temperature of 260 ° C,
An unstretched film having a film thickness of 100 μm at a roll temperature of 30 ° C.
A film was made. Next, using this film, Iwamoto
Using a biaxial stretching machine with a stretching speed of 5
0 mm / sec, stretching temperature 90 ° C., stretching ratio 2.0 ×
After simultaneous biaxial stretching to 2.0 times, heated air at 230 ° C
Heat treated to produce a 25μm thick biaxially stretched film
Then, various physical properties were measured. The results are shown in Table 1. This
The film state and maximum stress at the time of stretching
The stretchability was evaluated according to the following criteria. When stretching
In the film state, uniform stretching is possible and the maximum stretching stress is
If less than 20kg ◎, uniform stretching is possible and maximum
When the stretching stress is less than 30 kg.
When stretch unevenness occurs △, when stretch is impossible, ×
Was.

Example 2 The same NCH pellets as in Example 1 were used, and the same aromatic polyamide resin (6T-6I) as in Example 1 was used for the pellets.
The components were dry blended at a weight mixing ratio of 90/10. A stretched film was prepared from the obtained resin composition under the same conditions as in Example 1, and stretchability and physical properties were evaluated. Table 1 shows the measurement results of the various physical properties and the results of the stretching state and the stretching stress during stretching.

Example 3 The same NCH pellets as in Example 1 were used, and the same aromatic polyamide resin (6T · 6I) as in Example 1 was used for the pellets.
The components were dry blended at a weight mixing ratio of 70/30. A stretched film was prepared from the obtained resin composition under the same conditions as in Example 1, and stretchability and physical properties were evaluated. Table 1 shows the measurement results of the various physical properties and the results of the stretching state and the stretching stress during stretching.

Example 4 NCH pellets of polyamide 6 were produced in the same manner as in Example 1. The content of the montmorillonite complex in this resin was 5.0% by weight, and η _r was 3.8. The same aromatic polyamide resin as in Example 1 (6T
6I) The components were dry blended at a weight mixing ratio of 80/20. A stretched film was prepared from the obtained resin composition under the same conditions as in Example 1, and stretchability and physical properties were evaluated.
Table 1 shows the measurement results of the various physical properties and the results of the stretching state and the stretching stress during stretching.

Example 5 The same NCH pellets as in Example 4 were used, and the same aromatic polyamide resin (6T · 6I) as in Example 1 was used for the pellets.
The components were dry blended at a weight mixing ratio of 70/30. A stretched film was prepared from the obtained resin composition under the same conditions as in Example 1, and stretchability and physical properties were evaluated. Table 1 shows the measurement results of the various physical properties and the results of the stretching state and the stretching stress during stretching.

Example 6 The same NCH pellets as in Example 4 were used, and the same aromatic polyamide resin (6T · 6I) as in Example 1 was used for the pellets.
The components were dry blended at a weight mixing ratio of 60/40. A stretched film was prepared from the obtained resin composition under the same conditions as in Example 1, and stretchability and physical properties were evaluated. Table 1 shows the measurement results of the various physical properties and the results of the stretching state and the stretching stress during stretching.

Example 7 Polyamide 6 / Polyamide 66 by the method of Example 1.
Copolymerized NCH pellets were produced. This aliphatic poly
The amide resin is a weight set of polyamide 6 and polyamide 66
The composition ratio is 80/20 and the montmorillonite complex content is
2.0% by weight, η _rIs 3.8. The pellets
Same aromatic polyamide resin (6T · 6I) as in Example 1
Were dry blended at a weight mixing ratio of 90/10. Get
Stretched film under the same conditions as in Example 1
Was prepared and stretchability and physical properties were evaluated. Table 1
Measurement results and the results of stretching state and stretching stress during stretching.
Show.

Comparative Example 1 The same NCH pellets as in Example 1 were used. A stretched film was prepared under the same conditions as in Example 1 except that only NCH was used, and stretchability and physical properties were evaluated. Table 2 shows the measurement results of each physical property and the results of stretching state and stretching stress during stretching.

Comparative Example 2 The same NCH pellets as in Example 1 were used, and the same aromatic polyamide resin (6T-6I) as in Example 1 was used for the pellets.
The components were dry blended at a weight mixing ratio of 99/1. A stretched film was prepared from the obtained resin composition under the same conditions as in Example 1, and stretchability and physical properties were evaluated. Table 2 shows the measurement results of each physical property and the results of stretching state and stretching stress during stretching.

Comparative Example 3 The same NCH pellets as in Example 4 were used. A stretched film was prepared under the same conditions as in Example 1 except that the constituent component of the polyamide resin was only NCH, and a stretch test was performed.
However, it was broken during stretching, and physical properties could not be evaluated.

Comparative Example 4 The same NCH pellets as in Example 4 were used, and the same aromatic polyamide resin (6T · 6I) as in Example 1 was used for the pellets.
The components were dry blended at a weight mixing ratio of 97/3. A stretched film was prepared from the obtained resin composition under the same conditions as in Example 1, and a stretch test was performed. However, it was broken during stretching, and physical properties could not be evaluated.

COMPARATIVE EXAMPLE 5 The constituent components of the polyamide resin composition were a polyamide 6 having η = 3.8 and containing no layered silicate, montmorillonite.
A stretched film was prepared under the same conditions as in Example 1 and evaluated for stretchability and physical properties. Table 2 shows the measurement results of each physical property and the results of stretching state and stretching stress during stretching.

Comparative Example 6 The same NCH pellets as in Example 7 were used. A stretched film was prepared under the same conditions as in Example 1 except that the constituent component of the polyamide resin was only NCH, and a stretch test was performed.
Table 2 shows the measurement results of each physical property and the results of stretching state and stretching stress during stretching.

Comparative Example 7 An unstretched film having a thickness of 25 μm was prepared using the same NCH pellets as in Comparative Example 1 under the same conditions as in Example 1, and was evaluated as it was. The results are shown in Table 2.

Comparative Example 8 An unstretched film having a thickness of 25 μm was produced using the same resin composition as in Example 1 under the same conditions as in Example 1, and was evaluated as it was. The results are shown in Table 2.

Comparative Example 9 Triethylene glycol bis [3- (3-t) was used as a hindered phenol in the same NCH pellets as in Example 1.
-Butyl-5-methyl-4-hydroxyphenyl) propionate] (IRGAN manufactured by Ciba-Geigy Japan)
OX 245) was obtained by blending 0.25% by weight and using a resin composition obtained by blending 25 μm
m, and various physical properties were evaluated. Table 3 shows the results.

Comparative Example 10 Tetrakis (2,4-di-t-butylphenyl) -4,4′-biphenylphosphonite (IRGAFOS manufactured by Ciba-Geigy Japan) was used as a hindered phenol on the same NCH pellets as in Example 1. 168) to 0.
25% by weight, and further mixed with isopropyl triisostearoyl titanate (Plenact KA manufactured by Ajinomoto Co., Inc.).
Using a resin composition obtained by blending 0.1% by weight of (TTS), a stretched film of 25 μm was produced under the same conditions as in Example 1, and various physical properties were evaluated. Table 3 shows the results.

[0043]

[Table 1]

[0044]

[Table 2]

[0045]

[Table 3]

[0046]

The stretched polyamide film obtained from the polyamide resin composition of the present invention is a film having excellent transparency and glossiness, a small oxygen gas permeability and excellent stretchability. It has good post-processing properties such as printing, laminating and bag making, and is extremely useful practically especially for food packaging.

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Claims (1)

[Claims] (A) 95 to 50 parts by weight of an aliphatic polyamide resin containing 0.05 to 30% by weight of a layered silicate uniformly dispersed; and (B) 5 to 50 parts by weight of an aromatic polyamide resin. A stretched polyamide film characterized by using a polyamide resin composition.