JPH11322974A - Polyamide film excellent in pinhole resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyamide film which is excellent in resistances to pinhole and impact and, when used as a packaging material, can prevent the contamination or leak of the contents due to pinholes by monoaxially stretching a film obtd. from a blend of a polyamide polymer and an elastomer. SOLUTION: This film is formed from a blend of 85-99 wt.% polyamide polymer and 15-1 wt.% elastomer and has been stretched at least monoaxially. Examples of the polyamide polymer are nylon 6, nylon 6.6, nylon 12, and nylon 6.10. The elastomer is pref. a block copolymer comprising hard segments formed from a polyamide component selected from among lactams, ω-aminoaliph. carboxylic acids, combinations of aliph. diamines with aliphl. dicarboxylic acids, and combinations of aliph. diamines with arom. dicarboxylic acids and soft segments formed from a polyoxyalkylene glycol component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a polyamide film, and more particularly, to a film having excellent pinhole resistance and impact resistance, which is used in food packaging materials due to bending fatigue and impact during the processing step and transportation of the film. The present invention relates to a polyamide film which is effective in preventing bag breakage and is suitable for various packaging applications.

[0002]

2. Description of the Related Art Films made of a polyamide polymer, such as nylon 6 and nylon 66, are superior to films made of other plastics in film strength and impact resistance, and are used for various kinds of packaging mainly for food packaging. Widely used as a material.

[0003]

However, even in a packaging material using a film made of such a polyamide-based polymer, local destruction of the film due to bending fatigue in a processing step such as vacuum packaging or the like when transporting goods. There has been a problem that a pinhole is generated due to vibration or impact. The occurrence of pinholes in the packaging material causes contamination and leakage of the contents, which has caused problems in processing and transportation.

In order to solve the above problems, a method has been proposed in which another thermoplastic resin, for example, an ionomer resin is added to a polyamide-based polymer (Japanese Patent Application Laid-Open No. 56-147847). However, even in these methods, a polyamide film satisfying the pinhole resistance and the impact resistance and having sufficient film characteristics as a packaging material has not yet been obtained.

The present invention solves the problems of the conventional polyamide film, and is excellent in pinhole resistance and impact resistance, which are the film characteristics required as a packaging film.
An object of the present invention is to provide a polyamide film suitable for various packaging applications, by preventing contamination and leakage of contents caused by generation of pinholes when used as a packaging material.

[0006]

In order to achieve the above object, the polyamide film of the present invention comprises a mixed polymer of 85 to 99% by weight of a polyamide polymer and 15 to 1% by weight of an elastomer, It is characterized in that it is stretched in at least one axial direction. In this case, the elastomer is (a) lactam, ω-aminoaliphatic carboxylic acid, a hard segment composed of a polyamide component selected from the group of aliphatic diamine and aliphatic dicarboxylic acid or aliphatic diamine and aromatic dicarboxylic acid. And (b) a polyamide-based block copolymer comprising a soft segment composed of a polyoxyalkylene glycol component.

The polyamide film of the present invention has excellent pinhole resistance and impact resistance, and when used as various packaging materials, can prevent contamination and leakage of contents due to generation of pinholes. it can.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the polyamide film of the present invention will be described in detail.

The polyamide-based polymer used in the present invention is typically nylon 6, nylon 6.6, nylon 12, nylon 6.10, polymethaxylylene adipamide and the like. Nylon 6 / 6.6, Nylon 6 / 6.10, Nylon 6.6 /
6.10, a copolymer obtained by copolymerizing ε-caprolactam as a main component and a small amount of a nylon salt of hexamethylenediamine and isophthalic acid, a nylon salt of meta-xylylenediamine and adipic acid, and meta-xylylene /
It is also possible to use copolymers such as paraxylylene adipamide copolymer.

The elastomer used in the present invention is a polyamide block copolymer such as polyether amide, polyether ester amide, polyester amide, etc., and is constituted by a hard segment composed of a polyamide component and a polyoxyalkylene glycol component. Consisting of a soft segment, the polyamide component of the hard segment is selected from the group consisting of lactams, ω-amino aliphatic carboxylic acids, aliphatic diamines and aliphatic dicarboxylic acids, aliphatic diamines and aromatic dicarboxylic acids,
Examples include lactams such as ε-caprolactam, ω-amino aliphatic carboxylic acids such as aminoheptanoic acid, aliphatic diamines such as hexamethylene diamine, aliphatic carboxylic acids such as adipic acid, and aromatic dicarboxylic acids such as terephthalic acid. Can be. Examples of the polyoxyalkylene glycol constituting the soft segment of the polyamide-based block copolymer include polyoxytetramethylene glycol, polyoxyethylene glycol, polyoxy-1,2-propylene glycol, and the like.

The polyamide film of the present invention comprises 85 to 99% by weight of a polyamide polymer and 15 to 1% of an elastomer.
When the amount of the elastomer is less than 1% by weight, the effect of improving the bending fatigue resistance and impact resistance is small, and when the amount is more than 15% by weight, the transparency of the film deteriorates. A particularly preferred range in which the bending fatigue resistance and impact resistance and the transparency of the film are balanced is from 2 to 1.
0% by weight. By mixing the polyamide-based polymer with the elastomer, it is possible to provide an elastic recovery force under normal temperature or low temperature environment, and to impart excellent characteristics to flex fatigue resistance and impact resistance.

The polyamide-based polymer 85 to 85 of the present invention
If necessary, the mixed polymer of 99% by weight and the elastomer of 15 to 1% by weight may contain other thermoplastic resins, for example, a polyester-based polymer such as polyethylene terephthalate, a polyolefin-based polymer such as polypropylene, and the like. You may. It is also possible to add various additives such as antistatic agents, inorganic lubricants, organic lubricants, antifogging agents, antiblocking agents, heat stabilizers, ultraviolet absorbers, dyes, pigments and the like.

The thickness of the polyamide film of the present invention is as follows:
Although not particularly limited, when used as a packaging material, a material having a thickness of 100 μm or less, usually 5 to 50 μm is used.

The polyamide film of the present invention can be produced by a known production method. That is, using a single-layer die, melt-extruding a mixed polymer of 85 to 99% by weight of a polyamide polymer and 15 to 1% by weight of an elastomer to form an unstretched sheet, and then stretching at least uniaxially, Alternatively, the main layer is a mixed polymer of 85 to 99% by weight of a polyamide polymer and 15 to 1% by weight of an elastomer, and if necessary, a polyamide polymer of 85 to 99%.
A layer in which various additives are added to a mixed polymer of 15% to 1% by weight of an elastomer and 15 to 1% by weight of an elastomer, and a layer of another thermoplastic resin is laminated by a coextrusion method or a lamination method. You can take the method.

The polyamide film of the present invention needs to be stretched at least uniaxially, and is preferably stretched biaxially in order to improve the workability and transparency of the film. As a biaxial stretching method,
Known methods such as a flat sequential biaxial stretching method, a flat simultaneous biaxial stretching method, and a tubular method can be used.

[0016]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples. The evaluation of the film was performed by the following measurement method.

Bending Fatigue Resistance (Number of Pinholes) A film is cut into a circular shape having a diameter of 150 mm, formed into a bag, and attached to the tip of a glass tube of a bending machine. The bending machine sends and exhausts compressed air (pressurized 0.7 kg / cm ² ) (decompressed 760 mmHg)
Are alternately performed to give bending fatigue to the bag-like film at a rate of 7.5 times / minute. Under the environment of a temperature of 23 ° C. and a relative humidity of 65%, the bag-shaped film was subjected to 5,000 bending fatigue, and the number of holes generated in the film was counted.

Haze A haze meter S type manufactured by Toyo Seiki Seisaku-sho, Ltd. was used and measured in accordance with JIS K-7105. Haze (%) = [Td (diffuse transmittance%) / Tt (total light transmittance%)] * 100

Impact Strength Using a film impact tester manufactured by Toyo Seiki Seisaku-sho, the impact strength was measured in an environment at a temperature of 23 ° C. and a relative humidity of 65%.

Relative viscosity (RV) The relative viscosity (RV) was measured using an Ubbelose viscometer at a concentration of 1 g / dl and a temperature of 20 ° C. using 96% sulfuric acid.

Example 1 A polymer composed of 98% by weight of nylon 6 (RV 2.80) and 2% by weight of a copolymer of polylaurin lactam and polyether (Daiamide, manufactured by Daicel Huls) was melt-extruded from a T-die. Cool on drum at 25 ° C.
An 8 μm unstretched sheet was obtained. The obtained unstretched sheet was stretched 3.3 times in the machine direction and then 3.6 times in the transverse direction to obtain a 15 μm biaxially stretched film. Table 1 shows the number of pinholes, haze, and impact strength of the obtained biaxially stretched film.

Example 2 A biaxially stretched film was obtained in the same manner as in Example 1 except that the description in Example 1 was changed as follows. A polymer consisting of 95% by weight of nylon 6 (RV 2.80) and 5% by weight of a copolymer of polylaurin lactam and polyether (Daiamide, manufactured by Daicel Huls) was used.
Table 1 shows the number of pinholes, haze, and impact strength of the obtained biaxially stretched film.

Comparative Example 1 A biaxially stretched film was obtained in the same manner as in Example 1 except that the description in Example 1 was changed as follows. A polymer consisting of 88% by weight of nylon 6 (RV 2.80) and 12% by weight of polymethaxylylene adipamide (RV 2.10) was used. Table 1 shows the number of pinholes, haze, and impact strength of the obtained biaxially stretched film.

Comparative Example 2 A biaxially stretched film was obtained in the same manner as in Example 1 except that the description in Example 1 was changed as follows. A polymer consisting of 100% by weight of nylon 6 (RV 2.80) was used. Table 1 shows the number of pinholes, haze, and impact strength of the obtained biaxially stretched film.

[0025]

[Table 1]

From Table 1, it can be seen that the polyamide film of the present invention is excellent in bending fatigue resistance and impact resistance, and is a practically useful film. The film of the comparative example has poor bending fatigue resistance, increases the number of pinholes generated in the film processing step and the transport step, and poses a practical problem as a packaging material.

【The invention's effect】

The polyamide film of the present invention has bending fatigue resistance and impact resistance required as a packaging material, and is suitable for various packaging applications such as foods and pharmaceuticals. The utility value is extremely high.

Claims (2)

[Claims] 1. A mixed polymer of 85 to 99% by weight of a polyamide polymer and 15 to 1% by weight of an elastomer,
A polyamide film having excellent pinhole resistance, which is stretched at least in a uniaxial direction. 2. A hard material wherein the elastomer is constituted by (a) a polyamide component selected from the group consisting of lactam, ω-aminoaliphatic carboxylic acid, aliphatic diamine and aliphatic dicarboxylic acid or aliphatic diamine and aromatic dicarboxylic acid. 2. The polyamide film according to claim 1, which is a polyamide block copolymer comprising a segment and (b) a soft segment constituted by a polyoxyalkylene glycol component.