JPH07233322A - Polyamide film - Google Patents

Abstract

PURPOSE:To obtain a polyamide film composed of a composition produced by compounding a polyamide resin with a specific flexibilizing agent, imparted with flexibility without deteriorating the gas-barrierness and transparency and suitable as a food packaging material, especially a packaging material for skin pack, etc. CONSTITUTION:This polyamide film is composed of a composition produced by compounding (A) 100 pts.wt. of a polyamide resin (preferably nylon 6 or nylon 6/nylon 6.6 copolymer resin) with (B) 0.05-1 pt.wt., preferably 0.5-1 pt.wt. of a flexibilizing agent consisting of a polyalkylene glycol having an average molecular weight of 200-2,000 (preferably polyethylene glycol or polypropylene glycol). The raw film for the drawn film is preferably formed by T-die process or water-cooled inflation process from the viewpoint of continuous drawing operation. The thickness of the film is preferably 30-70mum.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polyamide film having excellent flexibility. More specifically, the present invention relates to a polyamide film characterized in that, when a polyamide film is used as a packaging material, the adhesiveness with the contents, that is, the so-called skin pack property is improved to form a packaging form that looks good.

[0002]

2. Description of the Related Art Polyamide films have superior oxygen barrier properties, tough strength, flexibility, heat resistance, transparency, and can be used in a wide temperature range compared to biaxially oriented polypropylene films and biaxially oriented polyester films. Since it has characteristics such as sex, it is mainly used as a food packaging material by utilizing such characteristics.

Among the packaging forms of food, so-called skin packs which are often used for packaging processed meat foods and the like are important to have gas barrier properties and transparency. Therefore, a polyamide film is particularly suitable. It is used.

[0004]

However, since the polyamide film has a higher elastic modulus and is harder than polyethylene and polypropylene, it is difficult to follow the surface shape of the contents, and therefore, the voids generated after the packing are not covered by the polyamide film. It had a drawback that the meat juice and water generated from the processed meat food would be accumulated and the commercial value would be reduced.

[0005]

Therefore, as a result of intensive studies to solve the above problems, the present inventors have found that by adding a polyalkylene glycol having a specific molecular weight range as a flexibility-imparting agent to a polyamide resin, the polyamide It was found that the film has flexibility and follows the surface shape of the package contents well, and the present invention has been completed.

That is, the gist of the present invention is that the composition comprises 0.05 to 1 part by weight of a polyalkylene glycol having an average molecular weight of 200 to 2000 with respect to 100 parts by weight of a polyamide resin. Polyamide film. The present invention will be described in detail below. As the polyamide resin used in the present invention, a polyamide resin obtained by polycondensation of a lactam having 3 or more membered rings, a polymerizable ω-amino acid, a dibasic acid and a diamine, or the like can be used. Specifically, polymers such as ε-caprolactam, aminocaproic acid, enanthlactam, 7-aminoheptanoic acid, 11-aminoundecanoic acid, 9-aminononanoic acid, α-pyrrolidone and α-piperidone, hexamethylenediamine, nonamethylenediamine. , Undecamethylenediamine, dodecamethylenediamine, metaxylenediamine and other diamines and dicarboxylic acids such as terephthalic acid, isophthalic acid, adipic acid, sebacic acid, dodecane dibasic acid and glutaric acid. It is a coalesced product or a copolymer, for example, nylon 4, 6, 7, 8, 11, 12, 6,6, 6,10,
6/11, 6/12, 6T, 6/6/6, 6/12, 6
/ 6T, 6I / 6T, etc. can be raised.

The thermal of the film obtained among these,
In terms of mechanical properties, nylon 6 nylon 6/6 ・
The use of 6-copolymer resins is suitable. Regarding relative viscosity (ηrel) of polyamide resin, JIS-K-6810
A suitable range is 2 to 6, preferably 2 to 5 as specified at 98% sulfuric acid concentration 1% and temperature 25 ° C. If the relative viscosity is too low, the mechanical strength of the obtained film is low and it cannot be used. On the other hand, if the relative viscosity is too high, the extrusion pressure and torque are too high, and molding becomes impossible.

Regarding the polyamide resin of the present invention, the water extraction amount for measuring the content of low molecular weight substances is 1% or less, preferably 0.5% according to JIS-K-6810.
The following is recommended. When the amount of water extracted is large, the oligomer component is remarkably adhered to the vicinity of the die, and the die line and fish eyes are generated by these adhered substances, which deteriorates the industrial continuous productivity.

The polyalkylene glycol used in the present invention is a terminal O according to JIS-K-15576.4.
The average molecular weight calculated from the H quantitative method is 200 to 2000,
It is preferably from 300 to 1500. Further, those having a liquid state of 300 to 600 at room temperature are preferable because they are easy to handle. If the molecular weight is less than 200,
Although it has a great effect as a softening agent, it has a high bleed-out property to the surface after film formation, and has poor adhesiveness when it is formed into a multilayer film by coextrusion or lamination, and also has poor printability. Further, since the film bleeds out from the surface, there is a possibility that the hardness of the film may change over time or the contents may be contaminated. If the average molecular weight is more than 2000, the effect as a softening agent is not sufficient.

Preferable examples of the polyalkylene glycol include polymers of alkylene glycol having 2 to 6 carbon atoms. More preferably, polyethylene glycol or polypropylene glycol is used. Moreover, these can also be used in mixture of 2 or more types. For example, polyethylene glycol and polypropylene glycol can be used together.

The amount of polyalkylene glycol added is in the range of 0.05 to 1 part by weight, preferably 0.2 to 1 part by weight, more preferably 0.5 to 1 part by weight, based on 100 parts by weight of the polyamide resin. Parts by weight. If the added amount is less than 0.05 parts by weight, the effect as a flexibility-imparting agent is not sufficient, while if the added amount is more than 1 part by weight, the bleed-out amount to the surface is increased and the printability or laminating property is deteriorated or the content is deteriorated. It is not preferable because it may cause contamination of the product.

The polyalkylene glycol is blended with the polyamide resin in a high concentration in advance by kneading the polyamide resin with a uniaxial or biaxial extruder, and diluting this at the time of so-called masterbatch. Method, kneading method used by kneading in polyamide resin in advance at the additive concentration used for molding, dry blending method of adding a predetermined amount to polyamide resin used during molding, polyalkylene glycol in organic solvent such as alcohol Attach the dissolved solution to the polyamide raw material by spraying or dipping,
Then, a method of evaporating the organic solvent is possible.

Further, since the high molecular weight polyalkylene glycol may be solid at room temperature, the polyamide resin raw material is preheated to a temperature not lower than the melting point of the polyalkylene glycol, and the polyalkylene glycol in the raw material in this state remains solid. A method in which glycol is added, the raw material is melted by heat, and the raw material is evenly attached is also possible. Further, when two or more kinds are used together, for example, the addition method of polyethylene glycol and polypropylene glycol may be different.

In the polyamide resin composition containing these polyalkylene glycols, various lubricants such as bisamide compounds, hindered phenols, phosphoric acid esters, and phosphorous acid ester compounds are added to the extent that the properties of the film are not impaired. Antioxidant including the beginning, weather resistance improver, release agent, antistatic agent, antiblocking agent, dye,
You may mix and use additives, such as a pigment.

The polyamide film of the present invention can be formed by a known method. For example, a melt of the resin composition is continuously extruded from a T-die and is formed into a film by cooling with a casting roll, a T-die method, continuously extruded from an annular die, and cooled by contact with water. A water-cooled inflation method, an air-cooled inflation method of extruding from an annular die and cooling with air, and the like are used. Further, a multilayer film can be obtained by a coextrusion method in which other materials are simultaneously extruded by these molding methods. As a method for forming a raw material for a stretched film, a T-die method and a water-cooled inflation method are particularly excellent in continuous stretchability.

If necessary, it can be used as a uniaxially or biaxially stretched film. A well-known method can also be applied to the stretching method. For example, for a film formed by the T-die method, a longitudinal method (uniaxial stretching) uses a roll method, and a lateral direction stretch method uses a tenter method. For the above-mentioned sequential biaxial stretching method, and for the tubular film formed from the annular die, a tubular stretching method capable of stretching simultaneously in the longitudinal and transverse directions is used in addition to the above sequential biaxial method. With respect to the coextruded film, each layer can be simultaneously stretched (costretched) by the same method.

The biaxially stretched film thus formed is
In some cases, one side or both sides are used after corona treatment for improving printability and laminating property. still,
The thickness of the polyamide film of the present invention is not particularly limited, but is usually 10 to 300 μm, preferably 20 to 100 μm.
m, and more preferably 30 to 70 μm. The polyamide film of the present invention thus obtained is preferably used as a so-called skin pack packaging for processed meat foods and the like. Preferably, by providing an adhesive layer of polyethylene or the like by laminating or coextrusion, a more suitable food package for a skin pack can be obtained.

[0018]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples as long as the gist thereof is not exceeded. The physical properties in the following examples were measured by using an automatic dynamic viscoelasticity measuring device manufactured by Orientec Co .: Rheovibron DDV-II-EP, and the hardness of the film was measured at an elastic modulus (E ′) near room temperature. The ease of deformation was evaluated at a temperature of tan δmax. still,
The lower the value of E ', the higher the flexibility. Also, t
The temperature of an δmax indicates the temperature at which deformation is most likely. Therefore, the lower this temperature is, the easier it is to deform at low temperature, which is suitable for food packaging. Regarding the bleed-out property of the softening agent (polyalkylene glycol) on the surface, the bleeding property when the character was written on the film surface with an oily felt pen and the character was wiped with gauze after 1 minute was visually judged.

<Examples 1 to 7, Comparative Examples 1 to 3> Poly-ε-caprolactam (Novamid 1030 manufactured by Mitsubishi Kasei) having a relative viscosity of 4.5 was dry blended with the softening agent shown in Table 1. And then extruded continuously at a resin temperature of 250 ° C. using a 40 mmφ single screw extruder and a T-die.
A film with a thickness of 50 μm is formed, and E ′, ta at room temperature is formed.
The nδmax temperature and the bleeding property were compared. Incidentally, in Example 6, P
Since EG-1000 is a solid at room temperature, it is inconvenient to handle.

[0020]

[Table 1] *) The softening agent used was manufactured by NOF CORPORATION. PEG-300: polyethylene glycol (molecular weight 30
0: normal temperature liquid) PEG-400: polyethylene glycol (molecular weight 40
0: normal temperature liquid) PEG-1000: polyethylene glycol (molecular weight 100
0: solid at room temperature PEG-4000: polyethylene glycol (molecular weight 400
0: normal temperature solid) PPG-400: polypropylene glycol (molecular weight 4
(00: normal temperature liquid)

[0021]

EFFECTS OF THE INVENTION According to the present invention, a polyamide film which is excellent in gas barrier properties against oxygen and the like, but has a high elastic modulus and is hard, does not impair gas barrier properties and transparency and does not cause bleeding out. It is possible to impart flexibility, and it is particularly useful because it becomes suitable for applications requiring adhesiveness to food packaging materials, especially skin packs and deep drawing films.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI technical display location // (C08L 77/00 71:02) (72) Inventor Tomoaki Kanema 370 Enzo, Chigasaki, Kanagawa Prefecture Address Mitsubishi Kasei Co., Ltd. Chigasaki Plant

Claims (4)

[Claims] 1. To 100 parts by weight of polyamide resin,
A polyamide film comprising a composition containing 0.05 to 1 part by weight of a polyalkylene glycol having an average molecular weight of 200 to 2000. 2. With respect to 100 parts by weight of the polyamide resin,
A polyamide film comprising a composition comprising 0.05 to 1 part by weight of polyethylene glycol having an average molecular weight of 200 to 2000. 3. To 100 parts by weight of polyamide resin,
A polyamide film comprising a composition containing 0.05 to 1 part by weight of polypropylene glycol having an average molecular weight of 200 to 2000. 4. A skin pack package comprising the polyamide film according to any one of claims 1 to 3.