JP6721269B2 - Polyamide film - Google Patents

Description

The biaxially stretched polyamide film of the present invention has excellent thermal stability during film production and can be manufactured stably with less appearance defects, and also has excellent toughness, mechanical properties, thermal properties, gas barrier properties, and high processability. It can be preferably used as a packaging material.

The biaxially stretched polyamide film has excellent toughness, mechanical properties, and thermal properties as well as a high gas barrier property, and is widely used for packaging applications. Films mainly used for packaging are required to have excellent workability during printing, vapor deposition, laminating, bag making and filling. There is a problem that slipperiness deteriorates underneath, especially because there was a problem in processing suitability in a high humidity environment such as the rainy season, various methods have been proposed as means for improving the slipperiness of the biaxially stretched polyamide film. ing.
For example, Patent Documents 1 to 3 describe a method of forming protrusions on the film surface by adding an inorganic filler. It is described in Patent Documents 4 to 8 that the surface of the inorganic filler is subjected to a hydrophobic treatment to prevent the inorganic filler from falling off due to voids in the filler interface during stretching and the film from being whitened to improve the slipperiness. Patent Documents 9 to 11 propose a method of adding a lubricant in addition to the inorganic filler for the purpose of further improving the slipperiness.

However, when the inorganic filler is silica, there is a case where a foreign substance whose core is a silica aggregate is generated by the kneading in the resin extruder, which is a factor that adheres to the film surface and hinders stretching, and it is difficult to stably form the film Therefore, there is a problem that productivity is reduced because the extruder is stopped and cleaned in order to remove foreign matter.

In order to suppress the generation of foreign matter in the polyolefin resin, blending a plasticizer (Patent Document 1), blending a phosphorus flame retardant plasticizer (Patent Document 2), a specific ethylene-ethyl acrylate copolymer , Blending an ethylene-α-olefin copolymer and an acid-modified ethylene-based polymer (Patent Document 3), and blending a phosphite and/or phosphonite antioxidant with a paraffin wax (Patent Document 4). ), blending a fluorine-based polymer having a molecular weight of 20,000 to 200,000 (Patent Document 5), and the like.
However, these foreign matter suppressing methods are carried out by combining a specific polymer with a specific inhibitor, are not versatile, and are not effective unless a considerably large amount of the inhibitor is used.

In addition, a method of adding a specific polyoxyalkylene borate ester (Patent Document 6) and a method of adding a higher fatty acid have been proposed (Patent Document 7).
Further, it has been proposed to mix a fatty acid metal salt in order to suppress the generation of foreign matter in a polyamide resin (Patent Document 8), to use a fibrous zonotolite+surface treated product as an alternative to silica (Patent Document 8). Reference 9)

Japanese Patent No. 3490132 Japanese Patent No. 3471066 Japanese Patent No. 3510314 JP 2001-59045 A JP-A-9-143318 Japanese Patent No. 3834582 JP-A-51-011833 JP, 6-179813, A JP-A-9-111117

The present inventors have overcome the drawbacks of such conventional polyamide resin films, have excellent transparency and slipperiness, and are unlikely to cause defective appearance even when continuous film formation is performed. The inventors have earnestly studied to provide a polyamide resin film containing an inorganic filler.

It has been found that the above problems can be solved by forming a film using a resin composition containing a polyamide, inorganic filler particles and an alkaline earth metal.
That is, the present invention is a polyamide resin 100 parts by weight of non-filler 0.0 2 to 0.60 parts by weight resin containing an oxide or hydroxide 0.01 to 0.50 parts by weight of an alkaline earth metal It is a biaxially stretched polyamide film composed of a composition and having a single film haze of 1.0 to 8.0%.

Specifically by blending the (1) oxides of the polyamide resin 100 parts by weight of an inorganic filler from 0.02 to 0.60 parts by weight and an alkaline earth metal or hydroxide 0.01 to 0.50 parts by weight , A biaxially stretched polyamide film having a single film haze of 1.0 to 8.0%.
(2) The biaxially stretched polyamide film according to (1), wherein the inorganic filler has a pore volume of 0.5 ml/g or less.
(3) The biaxially stretched polyamide film according to (1), wherein the inorganic filler is silica. (4) The biaxially stretched polyamide film according to (1), which has a static friction coefficient of 0.15 to 0.80 at 23°C x 50%.

According to the present invention, when the polyamide resin and the inorganic filler are mixed and melt-kneaded, by co-extruding the oxide or hydroxide of the alkaline earth metal, it is possible to suppress the aggregation of the inorganic filler and thus be stable for a long time. It is possible to produce a film having excellent transparency and slipperiness.

The polyamide resin used in the present invention is not particularly limited, but it is a polyamide resin such as nylon 6, nylon 66, nylon 46, nylon 610, nylon 12, etc., and these thermoplastic resins may be homopolymers or copolymers. It may be a polymer. 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 more than 30,000, the entanglement of the molecular chains is remarkable and excessive strain is generated by the stretching process, so that breakage or puncture frequently occurs during the stretching process, and stable production cannot be achieved.

Examples of the inorganic filler used in the present invention include silica, talc, kaolin and zeolite. Silica is suitable in that the porosity such as particle shape, size, specific surface area and pore volume can be arbitrarily adjusted by changing synthesis conditions.

The pore volume of the inorganic filler used in the present invention is preferably 0.5 ml/g or less, more preferably 0.2 ml/g or less. Conventionally, silica fine particles having a large specific surface area and a large pore volume and high porosity have been used, but this is an anchor effect due to the polyamide resin entering into the pores, and the polyamide resin and silica during film stretching It is considered that this was for suppressing the voids at the interface. However, silica having a high degree of porosity is easily broken during extrusion and kneading of the resin, and is unlikely to undergo the aggregation preventing effect of the present invention.

The average particle size of the inorganic filler used in the present invention is 1 to 8 μm, more preferably 2 to 4 μm. If the average particle size is less than 1 μm, a large amount of addition is required to obtain good slipperiness, while if the average particle size exceeds 8 μm, the appearance of the film is deteriorated and film breakage easily occurs in the film production process. Become. When the average particle diameter of the inorganic filler is 2 to 4 μm, protrusions having a desired height are formed on the surface of the film after biaxial stretching, and a film having excellent slipperiness can be easily obtained.

The inorganic filler is preferably hydrophobized with a surface treatment agent before blending with the polyamide resin. The surface treatment makes the dispersion in the polyamide resin easy and uniform, and also suppresses the voids at the interface between the polyamide resin and the inorganic filler during stretching in the film-forming step, and the loss of the inorganic filler and the transparency of the film The decrease can be suppressed.

When the inorganic filler is silica, the specific surface area is preferably 200 m ² /g or less, more preferably 100 m ² /g or less, and particularly preferably 50 m ² /g or less.

The type and amount of the inorganic filler surface treatment agent vary depending on the type of the inorganic filler used, but, for example, when the inorganic fine particles are silica described above, a silane having an amino group or an epoxy group is generally used. Coupling agents are preferably used. Specifically, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltriethoxysilane, γ-aminodithiopropyltrihydroxysilane, γ-(polyethyleneamino)propyltrimethoxysilane, N-β-(aminopropyl)-γ-aminopropyl Amino-based silane coupling agents such as methyldimethoxysilane, N-(trimethoxysilylpropyl)-ethylenediamine, γ-dibutylaminopropyltrimethoxysilane and γ-ureidopropyltriethoxysilane, or γ-glycidoxypropyltrimethoxy Mention may be made of silane and epoxy-based silane coupling agents such as β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. Further, a mixture of two or more of these silane coupling agents can also be used.

Further, the addition amount of the surface treatment agent also varies depending on the porosity of the inorganic filler, but the addition amount of the silane coupling agent is generally 2 to 10% by weight, preferably 3 to 5% by weight with respect to these silicas. % By weight. If the addition amount is less than 2% by weight, the surface hydrophobicity of the silica fine particles will not be sufficient and the dispersibility in the polyamide resin will be insufficient. On the other hand, when the amount added exceeds 10% by weight, the dispersibility of the inorganic filler in the polyamide resin is not improved even if the amount added is increased, and the mechanical properties of the finally obtained polyamide film are impaired. Problems arise. The surface treatment method is not particularly limited, for example, a method of performing surface treatment by adding a predetermined amount of the surface treatment agent diluted with an appropriate amount of water to a predetermined amount of the above-mentioned silica under heating and stirring, and a predetermined amount of each. A commonly used method such as a method of mixing the surface treatment agent and the above-mentioned silica with an appropriate device such as a Henschel mixer and then heat-treating at a predetermined temperature can be applied.

The content of the inorganic filler in the polyamide resin is 0.20 to 0.60% by weight, more preferably 0.25 to 0.45% by weight. When the content is less than 0.20% by weight, the number of protrusions on the film surface is small, and the slipperiness of the film is particularly low under high humidity. On the other hand, if the content of the inorganic filler exceeds 0.60% by weight, the transparency of the obtained film may decrease, which is not preferable.

The method of adding the inorganic filler to the polyamide resin is not particularly limited. It may be added in the polymerization step for producing a polyamide resin, or the polyamide resin may be used by dry blending a masterbatch of an inorganic filler. The surface-treated inorganic filler of the present invention has no problem in dispersion in a polyamide resin. Furthermore, by using an inorganic filler having a low porosity, uniform dispersion in the polyamide resin can be achieved more easily.

By blending the inorganic filler in the polyamide resin, unevenness on the film surface is formed by the stretching step during film production, and this reduces the contact area between the films, so that good slipperiness can be exhibited.

There is no particular limitation on the oxide or hydroxide of the alkaline earth metal used in the present invention, but oxides or hydroxides of magnesium, calcium, strontium, barium can be used. A plurality of these oxides or hydroxides may be used in combination, and a plurality of particles of the same type but having different average particle diameters and specific surface areas may be used in combination.

The alkaline earth metal oxide or hydroxide used in the present invention is not particularly limited, but beryllium, magnesium, calcium, strontium, barium oxide or hydroxide is particularly preferable, and magnesium oxide and calcium hydroxide are particularly preferable. preferable.

The amount of the alkaline earth metal oxide or hydroxide used in the present invention is 0.01 to 0.50 part by weight, preferably 0.02 to 0.30 part by weight, based on 100 parts by weight of the polyamide resin. Is preferable, and the range of 0.04 to 0.25 parts by weight is more preferable. If it is less than 0.01 part by weight, the effect of preventing the aggregation of the inorganic filler is weak, and if it is more than 0.50 part by weight, transparency is lowered and extrusion trouble occurs, which is not preferable.

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, it is preferably 10~500μm ² / g, 20~300μm ² / g is more preferred. If it exceeds 300 μm ² /, moisture may be rapidly absorbed, and handling during manufacturing may be difficult.

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

The alkaline earth metal oxide or hydroxide used in the present invention can be used as a surface treatment without any treatment, but the transparency may be lowered. Therefore, surface treatment is better. The surface treatment agent and the surface treatment method are not particularly limited, and known methods may be used. For example, as the surface treatment agent, those surface-treated with silane, titanium and aluminum-based coupling agents, higher fatty acids and phosphoric acid esters, alkali metal salts thereof, esters of polyhydric alcohols and fatty acids, and the like can be preferably used. At this time, in the surface treatment method, the oxide or hydroxide of an alkaline earth metal is suspended in a solvent such as water or alcohol and heated to 20°C to 80°C. A surface treatment agent solution dissolved in a solvent such as water or alcohol is poured therein, followed by solid-liquid separation, washing and drying, or a powder of alkaline earth metal oxide or hydroxide. A dry method in which the surface treatment agent solution is added while stirring at a temperature of from 150 to 150°C is mentioned.

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

Additives and modifiers that are usually added can be added as necessary within a range that does not significantly reduce the laminating strength or significantly affect the film strength. For example, heat resistance stabilizer, ultraviolet absorber, light stabilizer, antioxidant, antistatic agent, tackifier, sealability improver, antifogging agent, crystal nucleating agent, release agent, plasticizer, crosslinking agent, difficult Examples include flammable agents and colorants (pigments, dyes, etc.).

To produce the film of the present invention, the biaxially stretched polyamide film of the present invention can be formed by a known film forming method. For example, a molten polymer is extruded from a T-die, cooled with a casting roll to prepare an unstretched sheet, which is simultaneously biaxially stretched or sequentially biaxially stretched. Further, as another method, there is a tubular film forming method in which a molten polymer is extruded into a cylindrical shape from a ring die, and once cooled, air is retained in front and rear nip rolls and continuous simultaneous biaxial stretching is performed while heating.

The stretching ratio in both MD and TD is 2 to 6 times, preferably 2.5 to 4 times. If it is less than 2 times, the required strength physical properties cannot be obtained. At a draw ratio of more than 6 times, the stability of the draw is lacking and problems such as cutting of the film increase.

The biaxially stretched film is heat-treated as necessary to improve the dimensional stability. Moreover, you may perform a corona discharge process as needed.

The biaxially stretched polyamide film of the present invention obtained by the above method has a thickness of 8 to 50 μm, preferably 10 to 30 μm. The biaxially stretched polyamide film of the present invention may be a single layer film, or may be used by laminating another film by coextrusion or lamination.

The polyamide film of the present invention has excellent toughness, pinhole resistance, dimensional stability, and is suitable for packaging bags. When the film of the present invention is used as a packaging bag, it is usually provided with heat sealability or polypropylene, polyethylene, an ethylene-vinyl acetate copolymer, a plastic film such as polyester in order to give gas barrier properties and design properties. It is used by laminating it with paper, metal foil such as aluminum. In this case, the film of the present invention is used for at least one layer, and the number of layers is not particularly limited. Since this packaging bag is excellent in toughness, mechanical properties, thermal properties, and gas barrier properties, it is useful as a packaging bag for foods such as soups, jams, and lept pouches, as well as pharmaceuticals, daily necessities, and toiletries.

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. The physical properties of the film were determined by the methods described below.
(1) Haze: Haze value and gloss value were measured according to JIS K7105.
(2) Static friction coefficient, dynamic friction coefficient: The static friction coefficient and the dynamic friction coefficient between films/films not subjected to corona discharge treatment according to ASTM D1894 at a temperature of 23° C. and a relative humidity of 50% were measured.
(3) Aggregation of inorganic filler: Foreign matter generation time from the start of operation is visually observed for foreign matter with silica agglomerates adhering to the film as the core, and less than 12 hours, 12 to 24 hours, 24 to 48 hours , 48 hours or more.

The inorganic fine particles and the masterbatch thereof used for producing the film were prepared by the following method.
(1) Surface treatment method of inorganic fine particles 1 kg of inorganic fine particles and 50 g of γ-aminopropyltriethoxysilane were put in 200 ml of water and mixed with stirring at 80° C. to evaporate water, and then dried at 105° C. for surface treatment. Inorganic fine particles were obtained.

(2) Inorganic fine particles used A: gel type amorphous silica. Average particle diameter 2.5 μm, specific surface area 380 m ² /g, pore volume 1.9 ml/g
Fine particles B: Precipitation type amorphous silica. Average particle diameter 2.4 μm, specific surface area 40 m ² /g, pore volume 0.1 ml/g

(3) Preparation of fine particle masterbatch (method 1) 10 kg of powder resin having a relative viscosity of 2.5 and 600 g of inorganic fine particles are dry blended, extruded in a strand shape while kneading with a twin-screw extruder, cooled in a water tank, and then cut. Then, a polyamide resin masterbatch of inorganic fine particles was prepared.
(Method 2) 10 kg of ε-caprolactam, 1 kg of water, and 600 g of inorganic fine particles are charged into an autoclave with a stirrer having an internal volume of 50 liters, and heated to 100° C., and the reaction system becomes uniform at this temperature. So that it was stirred. Subsequently, the temperature was further raised to 260° C., and the mixture was stirred under a pressure of 15 kg/cm ² G for 1 hour. Then, the pressure was released and the water was volatilized from the reaction vessel to carry out a polymerization reaction under normal pressure at 260° C. for 2 hours, and further under a reduced pressure of 400 mmHg at a temperature of 260° C. for 1 hour. After completion of the reaction, the product was taken out in a strand form, cooled in a water tank, and then cut to prepare a polyamide resin masterbatch of inorganic fine particles.

Hereinafter, examples will be described in order to describe the present application in more detail. However, the present invention is not limited to the embodiments.

(Example 1)
A mixture of 100 parts by weight of nylon 6 resin (polyamide resin: Ube Industries, Ltd.) having a relative viscosity of 3.5, 800 ppm of fine particle masterbatch A to the resin component, and 400 ppm of magnesium hydroxide to the resin component was added. It was melt extruded from a ring die and cooled with an inner and outer water cooling mandrel to obtain a tubular film having a thickness of 150 μm. The tube film was biaxially stretched simultaneously in MD and TD by the speed difference between the low speed nip roll and the high speed nip roll and the air pressure existing therebetween. After that, fold the tube and cut it into two pieces at both ends, heat-treat at 210°C for 10 seconds in a tenter oven to obtain a film with a thickness of 15 μm, cut both ears and make a flat film, and wind it on two rolls. I took it.

Examples 2 to 7, Comparative Examples 1 to 5 and Reference Example 1
A stretched film was obtained in the same manner as in Example 1 except that the type of inorganic filler, the amount of inorganic filler added, and the amount of alkaline earth metal added were changed as shown in Table 1.
Table 1 shows the evaluation results of the obtained stretched film.

The polyamide resin film of the present invention is excellent in transparency and slipperiness, and is less likely to cause filler agglomeration during film formation, so that it is possible to perform stable production with less appearance defects during film production, and toughness and mechanical properties. It has excellent thermal properties and gas barrier properties, has high processability, and can be suitably used as a packaging material.

Claims (3)

And 100 parts by weight of the polyamide resin and the inorganic filler from 0.02 to 0.60 parts by weight by blending the 0.01 to 0.50 parts by weight of magnesium or magnesium oxide hydroxide, haze of the single film is 1.0 to 5. a 2% der Ru off Irumu,
A biaxially stretched polyamide film, wherein the inorganic filler has a pore volume of 0.5 ml/g or less . The biaxially stretched polyamide film according to claim 1, wherein the inorganic filler is silica. The biaxially stretched polyamide film according to claim 1, which has a static friction coefficient of 0.15 to 0.37 at 23°C x 50%.