JP2017209900A - Polyamide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a biaxially drawn polyamide film having excellent transparency, and practical strength in a polyamide film composed of MXD6 as a principal constituent, and capable of stably producing without being affected by a production condition such as an extrusion temperature, a retention time, and a shear velocity.SOLUTION: The film can be stably produced with a simple method by coextruding an oxide or hydroxide of an alkali earth metal when melt-kneading to suppress the copolymerization reaction of aliphatic polyamide with MXD6 without being affected by a production device of film, and a production condition.SELECTED DRAWING: None

Description

The present invention is a polyamide-based film mainly composed of a polyamide (hereinafter referred to as “MXD6”) composed of a structural unit formed by a polycondensation reaction of metaxylylenediamine and adipic acid, and has excellent transparency and practical use. The present invention relates to a biaxially stretched polyamide film that has strength and can be stably produced without being affected by production conditions such as extrusion temperature, residence time, and shear rate.

Conventionally, unstretched films or stretched films of polyamide-based polymers have been used as various packaging materials, either alone or laminated with other films. However, a film made of a commonly used aliphatic polyamide polymer alone is excellent in mechanical properties such as tensile strength and bending pinhole resistance, but has a drawback that it is not sufficient in oxygen gas barrier properties. . On the other hand, as a film having a good oxygen gas barrier property, an aromatic polyamide whose main component is a polyamide constituent unit composed of m- and / or p-xylylenediamine and an α, ω-aliphatic dicarboxylic acid having 6 to 12 carbon atoms. Those using polymers as raw materials have been proposed. Although this film is excellent in transparency and oil resistance, its use is limited because it is inferior in bending resistance.

  In order to obtain a film that combines the advantages of both the above-mentioned polyamide polymers, that is, the properties of excellent tensile strength, flex resistance, and oxygen gas barrier properties, the two polyamide polymers are melted separately. A method of producing a laminated biaxially stretched film by extrusion and an inflation method has been proposed (Patent Document 1). A multilayer film having a structure in which a layer mainly composed of an aromatic polyamide polymer is sandwiched between layers composed mainly of an aliphatic polyamide polymer has also been proposed (Patent Document 2).

On the other hand, there is a method of imparting easy tearability by mixing an aliphatic polyamide resin and MXD6. A mixed polyamide composition composed of aliphatic polyamide / MXD6 and aliphatic polyamide / MXD6 = 40 to 85 parts by weight / 15 to 60 parts by weight is melt-extruded, and the longitudinal direction (MD) and the width direction (TD) are obtained by using an inflation method. ) Both lannate films in which easily tearable films stretched by 2.8 times or more are formed as one layer (Patent Documents 3 and 4), aliphatic polyamide / MXD6 = 80 to 95 parts by weight / 20 A biaxially oriented polyamide film composed of ˜5 parts by weight of a mixture and having a straight tearing property in which the shape of dispersed particles of MXD6 is dispersed in a specific shape has been proposed (Patent Document 5).

However, in order to express easy tearability, MXD6 needs to be appropriately dispersed in the aliphatic polyamide. However, when the aliphatic polyamide and MXD6 are melt-mixed, if the temperature is high or the residence time is long, Alternatively, when shearing is large, the copolymerization reaction of aliphatic polyamide and MXD6 proceeds, and the dispersed particles of MXD6 disappear, and not only easy tearability but also physical properties such as tensile strength, impact strength, puncture strength and oxygen gas barrier properties There was a problem of lowering, and there were large restrictions in terms of extruder type, screw type, distance from the extruder hopper to the die, and extrusion conditions (temperature, speed, rotation speed, filter mesh, etc.) during film formation. .

As described above, when MXD6 and aliphatic polyamide are melt-mixed, the copolymerization reaction proceeds and affects the strength physical properties of the film. Therefore, when MXD6 and aliphatic polyamide are melt-extruded and a laminated biaxially stretched film is produced by an inflation method, The restrictions were large in terms of the type of extruder, screw type, distance from the extruder hopper to the die, and extrusion conditions (temperature, speed, rotation speed, filter mesh, etc.) during film formation.

JP-A-57-51427 JP-A-56-155762 JP 2001-233958 A Japanese Patent No. 3808847 JP 49-45960 A

 Therefore, the problem of the present invention is that the polyamide-based film containing MXD6 as a main component has excellent transparency and practical strength, and is stable without being affected by production conditions such as extrusion temperature, residence time, and shear rate. It is an object of the present invention to obtain a biaxially stretched polyamide film that can be produced.

Co-extrusion of alkaline earth metal oxide or hydroxide during melt kneading can suppress the copolymerization reaction between aliphatic polyamide and MXD6, and is a simple method that is not affected by film production equipment or production conditions Thus, the present invention has been completed.

In particular,
(1) 0.01 to 0 alkaline earth metal oxide or hydroxide with respect to 100 parts by weight of a polyamide-based resin composed of 100 to 65 parts by weight of metaxylene adipamide and 0 to 35 parts by weight of an aliphatic polyamide Alkaline with respect to 100 parts by weight of a polyamide-based resin composed of an intermediate layer composed of a resin composition added with 50 parts by weight, 60 to 0 parts by weight of one or more metaxylene adipamides and 100 to 40 parts by weight of an aliphatic polyamide A biaxially stretched polyamide film having an outer layer made of a resin composition to which 0.01 to 0.50 parts by weight of an earth metal oxide or hydroxide is added.
(2) A biaxially stretched polyamide film is provided wherein the alkaline earth metal oxide or hydroxide according to claim 1 is magnesium hydroxide or magnesium oxide.

According to the present invention, a polyamide-based film containing MXD6 as a main component has excellent transparency and practical strength, and is stably produced without being affected by production conditions such as extrusion temperature, residence time, and shear rate. can do.

The aliphatic polyamide used in the present invention is not particularly limited, but is an aliphatic polyamide such as nylon 6, nylon 66, nylon 46, nylon 610, nylon 12, and these thermoplastic resins are homopolymers. May also be a copolymer. In the nylon 6 raw material, the number average molecular weight is preferably 10,000 to 30,000, particularly preferably 22,000 to 24,000. When the number average molecular weight is less than 10,000, the impact strength and tensile strength of the obtained ONy film are insufficient. When the number average molecular weight is larger than 30000, the molecular chain is entangled excessively and excessive strain is generated by the stretching process. Therefore, breakage and puncture frequently occur during the stretching process, and stable production cannot be achieved.

  MXD6 used in the present invention has a structural unit generated by a polycondensation reaction of metaxylylenediamine and adipic acid. This thermoplastic resin may be a homopolymer or a copolymer. There may be.

In the at least one intermediate layer, the mixing amount of MXD6 and aliphatic polyamide is such that MXD6 is 100 to 65 parts by weight and aliphatic polyamide is 0 to 35 parts by weight. The outer layer is composed of 60 to 0 parts by weight of MXD6 and 100 to 40 parts by weight of aliphatic polyamide.

In the present invention, if the mixing amount of MXD6 and aliphatic polyamide used for the intermediate layer and outer layer is the above mixing amount, even if the mixed raw material has a history of mixing and melt-kneading the aliphatic polyamide and MXD6. Good.

  Although there is no restriction | limiting in particular in the alkaline earth metal oxide or hydroxide used in this invention, The oxide or hydroxide of beryllium, magnesium, calcium, strontium, barium can be used. In particular, magnesium oxide and magnesium hydroxide are preferable. These oxides or hydroxides can be used alone or in combination of two or more, and a plurality of particles of the same type and different in average particle diameter and specific surface area may be used in combination.

  The alkaline earth metal oxide or hydroxide used in the present invention is added to the outer layer and the intermediate layer in which MXD6 is mixed. The amount to be added is 0.01 to 0.50 parts by weight with respect to a total of 100 parts by weight of the aliphatic polyamide and MXD6, preferably 0.02 to 0.30 parts by weight, and 0.04 to 0. A range of .25 parts by weight is more preferred. When the amount is less than 0.01 part by weight, the effect of inhibiting the copolymerization cannot be obtained, and when the amount is more than 0.50 part by weight, the transparency may be lowered or an extrusion trouble may occur.

There is no particular limitation on the specific surface area of the oxide or hydroxide of an alkaline earth metal used in the present invention, with respect to the specific surface area determined by the BET method, is preferably 10~500μm ² / g, 20~300μm ² / g is more preferable. If it exceeds 300 μm ² /, rapid moisture absorption may occur, and handling during production may be difficult.

  The average particle size of the alkaline earth metal oxide or hydroxide used in the present invention is not particularly limited, but is preferably 5 μm or less, more preferably 1 μm or less.

Although it can be used without treatment as the surface treatment of the alkaline earth metal oxide or hydroxide used in the present invention, it is preferable to use a surface-treated one because the transparency may be lowered. The surface treatment agent and the surface treatment method are not particularly limited, and may be a known method.
For example, as the surface treatment agent, those surface-treated with silane, titanium and aluminum coupling agents, higher fatty acids and phosphate esters, alkali metal salts thereof, esters of polyhydric alcohols and fatty acids, and the like can be suitably used. In this case, the surface treatment method involves suspending an alkaline earth metal oxide or hydroxide in a solvent such as water or alcohol and heating the suspension to 20 ° C to 80 ° C. A wet treatment method in which a surface treating agent solution dissolved in a solvent such as water or alcohol is poured into the solution, followed by solid-liquid separation, washing and drying, or an alkaline earth metal oxide or hydroxide powder 50 Examples include a dry method in which the surface treatment agent solution is added while stirring at a temperature of from ℃ to 150 ℃.

  The alkaline earth metal oxide or hydroxide used in the present invention may be previously melt-kneaded with aliphatic polyamide or MXD6 for the purpose of improving dispersibility.

 The present application has at least a three-layer structure. In the case of the three-layer structure, the present application is composed of one intermediate layer and one outer layer having the structure up to the preceding stage, and the other one outer layer can be arbitrarily configured. In the case of a five-layer configuration, the configuration up to the previous stage can be arbitrarily configured. For example, the structure of the intermediate layer up to the previous stage in the outermost layer, the structure of the outer layer up to the previous stage of the intermediate layer and the outermost layer, or the structure of the outer layer up to the previous stage, the outermost layer as the intermediate layer up to the previous stage. It is also possible.

  Additives and modifiers that are usually blended can be blended as needed within a range that does not cause significant problems in terms of lowering the strength of the laminate or generating eyes when film is formed. For example, heat-resistant stabilizer, ultraviolet absorber, light stabilizer, antioxidant, antistatic agent, tackifier, sealability improver, antifogging agent, crystal nucleating agent, mold release agent, plasticizer, crosslinking agent, difficulty Examples include flame retardants and colorants (pigments, dyes, etc.), gelation inhibitors, pin resistance modifiers, and the like.

The polyamide-based multilayer biaxially stretched film of the present invention can be produced by a known method.
For example, the resin forming each layer is melted by 2 to 3 extruders, extruded from a flat die or an annular die, and then rapidly cooled to form a flat or annular unstretched film, which is sequentially biaxial by the tenter method. Examples thereof include stretching, simultaneous biaxial stretching, and simultaneous biaxial stretching by a tubular method.

The draw ratio is 2 to 6 times, preferably 2.5 to 4 times for both MD and TD. If it is less than 2 times, the required strength properties cannot be obtained. If the draw ratio is larger than 6 times, the stretching stability is insufficient, and troubles such as film cutting increase.

The film after biaxial stretching is subjected to heat treatment as necessary in order to improve dimensional stability. Moreover, you may perform a corona discharge process as needed.

The thickness of the biaxially stretched polyamide film of the present invention obtained by the above method is 8 to 50 μm, preferably 10 to 30 μm.

The biaxially stretched polyamide film of the present invention may be a single film, or may be used by laminating other films by coextrusion or lamination.

  Since the polyamide film of the present invention has excellent toughness, pinhole resistance and dimensional stability, it is suitable for packaging bags. When the film of the present invention is used for a packaging bag, a film such as polypropylene, polyethylene, ethylene-vinyl acetate copolymer, or polyester, paper, or the like, for imparting heat sealing properties, oxygen gas barrier properties, design properties, etc. It is common to laminate a metal foil such as aluminum. Even in such a case, the film of the present invention may have at least one layer, and the number of layers is not limited. Since this packaging bag has excellent toughness, pinhole resistance, and oxygen gas barrier properties, it is useful as a packaging bag for foods such as soups, jams, and relt pouches, as well as pharmaceuticals, daily necessities, toiletries and the like.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. For the impact strength measurement, an impact drilling strength test (JIS P8134) using an impact tester manufactured by Toyo Seiki Co., Ltd. was used for evaluation, and those that were 10 kgf · cm or more were ◎, and those that were 8-10 kgf · cm. Were evaluated as x, and those having 8 kgf · cm or less were evaluated as x.

In order to describe the present application in more detail below, examples will be described. However, the present invention is not limited to the examples.
Example 1
An aliphatic polyamide resin having a relative viscosity of 3.5 (aliphatic polyamide: manufactured by Ube Industries, Ltd.) and MXD6 having a relative viscosity of 2.7 (aromatic polyamide: manufactured by Mitsubishi Gas Chemical Co., Ltd.) at a ratio of 80/20. After mixing, a mixture obtained by adding 400 ppm of magnesium hydroxide (Kisuma 5B: manufactured by Kyowa Chemical Industry Co., Ltd.) to the resin component was melt-kneaded from a ring die at 300 ° C., and then divided into two and three-layer coextrusion dies Led to both outer layers. Further, MXD6, a mixture obtained by adding 400 ppm of magnesium hydroxide to 100 parts by weight is melt-kneaded from a ring die at 300 ° C., led to an intermediate layer of a three-layer coextrusion die, and an outer layer in the three-layer coextrusion die: intermediate layer : Laminated so that the thickness ratio of the outer layer was 1: 1: 1, and after cooling, a tubular film having a thickness of 150 μm was obtained.
The tube film was subjected to simultaneous biaxial stretching of 3 times in the MD direction and 3 times in the TD direction at a temperature equal to or higher than the Tx of MXD6 due to the speed difference between the low speed nip roll and the high speed nip roll and the air pressure existing therebetween, and then 200 ° C. The film was heat-treated to obtain a film having a thickness of 15 μm, and both ears were excised to form a flat film and wound around two rolls.

Examples 2-6 and Comparative Examples 1-6
A stretched film was obtained in the same manner as in Example 1, except that the mixing ratio, extrusion melting temperature, alkaline earth metal, and alkaline earth metal addition amount were changed as shown in Table 1.
The evaluation results of the obtained stretched film are shown in Table 1.

Claims (2)

0.01 to 0.50 of an alkaline earth metal oxide or hydroxide with respect to 100 parts by weight of a polyamide-based resin composed of 100 to 65 parts by weight of metaxylene adipamide and 0 to 35 parts by weight of an aliphatic polyamide. Alkaline earth with respect to 100 parts by weight of a polyamide-based resin composed of an intermediate layer composed of a resin composition with parts by weight added, 0 to 60 parts by weight of one or more layers of metaxylene adipamide and 40 to 100 parts by weight of an aliphatic polyamide A biaxially stretched polyamide film having an outer layer made of a resin composition added with 0.01 to 0.50 parts by weight of a metal oxide or hydroxide.
  The biaxially stretched polyamide film, wherein the alkaline earth metal oxide or hydroxide according to claim 1 is magnesium oxide or magnesium hydroxide.