JP2002079620A - Polyamide double-layered film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyamide double-layered film having excellent strength and dimensional stability, excellent oxygen barrier properties and aroma retention, and excellent pinhole resistance, and suitable as a packaging material for food, medicines or the like. SOLUTION: The double-layered film has at least two layers, that is, a layer comprising a polyamide resin and a layer comprising a saponfied ethylene/vinyl acetate copolymer. A polyester dispersion coating layer is formed on at least the single surface of this laminated film. Alternately, 5-15 mass % of talc is added to the layer comprising the saponified ethylene/vinyl acetate copolymer with respect to 95-85 mass % of the saponified ethylene/vinyl acetate copolymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyamide-based multilayer film, and more particularly to a polyamide resin (hereinafter referred to as "PA").
And a layer comprising a saponified ethylene-vinyl acetate copolymer (hereinafter referred to as "EVOH"). The present invention relates to a polyamide-based multilayer film having both excellent strength and dimensional stability and excellent gas barrier properties of an EVOH resin, and also having excellent fragrance retention properties and suitable for packaging of foods and pharmaceuticals.

[0002]

2. Description of the Related Art Plastic films are excellent in strength, dimensional stability, transparency and flexibility.
In particular, it is widely used in the food packaging field. In particular, when it is necessary to prevent decay or deterioration of the contents to be packaged, such as preserved foods, the plastic film is widely used by taking advantage of the gas barrier property and the water vapor barrier property of the plastic film.

Conventional gas barrier films include polyvinylidene chloride (PVDC) -based films, polyvinyl alcohol (PVA) films, nylon films (O
N), an EVOH film, or a multilayer film obtained by laminating these films. Also, polyester films such as polyethylene terephthalate, ON,
A film obtained by coating a base film such as a polypropylene film with PVA or PVDC having a barrier property is exemplified. Further, a vapor-deposited film in which silica, aluminum, aluminum oxide, or the like is vapor-deposited on a substrate film under vacuum conditions may be used.

Conventionally, among such gas barrier films, a gas barrier film coated with PVDC has been widely used. However, a polymer containing chlorine, such as PVDC, may generate harmful substances such as dioxin at the time of combustion, and therefore, the appearance of an alternative is strongly desired. For this reason, the above-mentioned vapor-deposited films and multilayer films are promising.

[0005] Among these gas barrier films, P
A multilayer film having a layer composed of A and a layer composed of EVOH has excellent strength, dimensional stability, pinhole resistance, transparency of the PA film, and excellent gas barrier properties of the EVOH film, In particular, attention has been paid to food packaging applications. As such a multilayer film, for example, a PA / EVOH multilayer film, a PA / EVOH / PA multilayer film, or a film obtained by laminating a polyester film or a polyolefin-based film on these multilayer films is used.

[0006] However, while the multilayer film comprising PA and EVOH has excellent oxygen barrier properties, its fragrance retention properties are not at a satisfactory level, resulting in a decrease in flavor or suspicion of breakage during unpacking. And may need to be improved. That is,
For example, when a substance having a strong odor such as miso, soy sauce or mustard is used as a content, there is a problem that the odor starts to leak in only a few days, and therefore the use is often limited.

Also, since the strength of the pinhole is lower than that of the PA monolayer film and the pinhole resistance against bending and impact at low temperature is insufficient, pinholes resulting from dropping, piercing from the outside or by the contents, and the like are obtained. As a result, troubles such as leakage of the contents may occur, and the functional materials cannot be sufficiently satisfied as a packaging material.

[0008]

An object of the present invention is to provide a polyamide which has excellent strength and dimensional stability, and has excellent oxygen gas barrier properties and fragrance retention properties, which is suitable as a packaging material for foods, pharmaceuticals and the like. Another object of the present invention is to provide a system multilayer film.

Another object of the present invention is to provide a polyamide-based multilayer film having more excellent pinhole resistance in addition to the above characteristics.

[0010]

Means for Solving the Problems In order to solve such problems, the polyamide-based multilayer film of the present invention is a multilayer film having at least two layers of a layer made of PA and a layer made of EVOH, It is characterized in that a polyester dispersion coat layer is formed on at least one side of the laminated film.

Further, the packaging material of the present invention is characterized by having at least one layer of the above-mentioned polyamide-based multilayer film. Further, the polyamide-based multilayer film of the present invention has a PA
A multilayer film having at least two layers of a layer made of EVOH and a layer made of EVOH, wherein the layer made of EVOH contains talc of 5 to 15 with respect to 95 to 85% by mass of EVOH.
% By mass.

Further, the polyamide-based multilayer film of the present invention provides a film containing talc as described above,
Oxygen permeability in a 20 ° C, 85% RH atmosphere is 50 ml / (m ² · day · MPa) (/ one sheet thickness) or less. The number is 10 or less, and the haze after the repeated bending fatigue test is 6% or less.

According to the present invention, by adopting such a constitution, it is possible to obtain a suitable polyamide-based multilayer film having excellent oxygen gas barrier properties and fragrance retention properties. In addition, the present invention can provide a similarly excellent oxygen gas barrier property and a fragrance retention property by allowing talc to be contained in the layer made of EVOH in an amount of 5 to 15% by mass. In addition, the pinhole resistance can be improved.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION PA in the present invention is a thermoplastic resin having an amide bond (-CONH-) in its molecule and capable of being melt-molded, and specifically, nylon 6, nylon 66, nylon 610, and the like. Nylon 11, Nylon 1
2. Polyhexamethylene terephthalamide (nylon 6
T), polymethaxylylene adipamide (MXD) and the like, which are used alone, in the form of a mixture or in the form of a copolymer. In addition, in these PA,
Nylon 6 and nylon 66 are preferable in terms of productivity and performance.

[0015] PA includes talc, silica, alumina, magnesia, and the like as long as the performance of the film is not impaired.
Lubricants such as calcium carbonate, ethylenebisstearylamide, and calcium stearate, and pigments, heat stabilizers, antioxidants, weathering agents, flame retardants, plasticizers, and release agents can also be blended.

The EVOH in the present invention has an ethylene component content of 10 to 60 mol%, preferably 20 to 50 mol%, and more preferably 25 to 35 mol%. Further, those having a saponification degree of vinyl acetate of 96 mol% or more, preferably 99 mol% or more are preferable in that they have excellent gas barrier properties and strength.

If the content of the ethylene component is less than 10 mol%, a gel tends to be generated in the film-forming step, and if it exceeds 60 mol%, the gas barrier properties and strength of the obtained film are lowered.

EVOH includes silica, alumina, magnesia, and the like as long as the properties of the film are not impaired.
Lubricants such as calcium carbonate and calcium stearate,
Pigments, heat stabilizers, antioxidants, antistatic agents, plasticizers and the like can also be blended.

In the present invention, when the polyester dispersion coat layer is formed, the content of the polyester resin in the polyester dispersion is appropriately selected depending on the use of the film, the intended thickness of the coating, and the molding method. , 0.5 to 50% by mass.
0 mass% is more preferable. Further, an organic solvent, a stabilizer such as an alcohol or a basic compound, a curing agent, a pigment and the like may be contained as long as the properties of the polyester dispersion are not impaired. Examples of the curing agent include a phenol resin, an aminoplast resin, a polyfunctional epoxy resin, a polyfunctional isocyanate compound and various blocked isocyanate compounds thereof, and a functional aziridine compound. When the above-mentioned curing agent is used in combination, a heat treatment for further promoting the curing reaction is performed. In addition, repelling agents, leveling agents, antifoaming agents, anti-pecking agents, rheology control agents, pigment dispersions, and the like may be added as agents.

As the polyester dispersion, either an organic solvent dispersion or an aqueous dispersion may be used, but from the viewpoint of environmental suitability and odor due to residual solvent, an aqueous dispersion is desirably used. In addition, an antistatic agent, a filler, a curing agent, and the like may be added as long as the properties of the coating of the coat layer are not impaired.

In the present invention, when talc is contained in the EVOH layer, the talc having an average particle size of less than 1.3 μm is used. As the particle size increases, the transparency of the film deteriorates. As described above, the amount of talc added is 5 to 85 to 85% by mass of EVOH.
To 15% by mass, preferably EVOH 93 to 87.
It is 7 to 13% by mass relative to the mass%. When the amount is less than 5% by mass, the effect of improving gas barrier properties and fragrance retention is small. Conversely, when the amount is more than 15% by mass, the transparency of the film is reduced, or fisheye due to secondary aggregation of talc is caused. Or increase.

The thickness of the multilayer film is not particularly limited, but is usually 5 when used as a flexible packaging material.
５０50 μm, preferably 10-30 μm. If the thickness is small, it is difficult to exhibit desired pinhole resistance, gas barrier properties, and fragrance retention properties. If the thickness is large, transparency and bending fatigue resistance deteriorate. If the thickness of the EVOH layer is less than 4 μm with respect to the total thickness of the multilayer film excluding the coat layer of 15 μm, it is not possible to maintain good gas barrier properties and fragrance retention, so care must be taken.

When this multilayer film is used as a packaging material such as a packaging bag or a lid material, polyethylene, polypropylene, polyvinyl, or the like is used to impart heat sealing properties, moisture proof properties, light shielding properties, and beautifulness. It can be used by laminating it with a plastic film such as alcohol, paper, aluminum foil or the like.

In producing a multilayer film composed of a layer composed of PA and a layer composed of EVOH, several kinds of resins forming each layer are melted by separate extruders, and superposed in a multilayer structure in a feed block. , A method of extruding from a die (mono-manifold type method) or a multi-manifold type method of extruding several kinds of molten resin by overlapping them in a multilayer structure in a die can be used, but from the high thickness accuracy of each layer A multi-manifold type method is preferred. As the shape of the die, any type of T type, coat hanger type and ring type may be used. Then, after co-extrusion from a die, the sheet is rapidly cooled on a cooling roll to obtain a laminated unstretched sheet.

The unstretched multilayer film composed of PA and EVOH obtained in this manner is stretched 2 to 4 times in the machine direction and the transverse direction, respectively, so that the gas barrier property, transparency and mechanical properties are extremely high. It becomes an excellent multilayer film.
As a stretching method for this purpose, after the molten sheet supplied from the die is brought into close contact with a casting roll and quenched and solidified, a tenter-type simultaneous biaxial stretching method, a tenter-type sequential biaxial stretching method, and a tubular simultaneous biaxial stretching method are used. Method is used. Usually, heat setting is performed after stretching. Specifically, for example, after the obtained unstretched sheet is subjected to a water-containing treatment in a hot water tank whose temperature is controlled, the end of the sheet is gripped with a clip, and the sheet is heated at a temperature of 80 to 200 ° C. and vertically and horizontally 2.5 to 4 times each.
Simultaneous biaxial stretching at a draw ratio of about 2 times and heat treatment at a temperature of 180 to 220 ° C. at a relaxation rate of 3 to 8% in the film width direction can obtain a stretched film having a desired thickness.

As a method for forming the polyester dispersion coat layer, there are a post-coat method and a pre-coat method. Of these, the post-coating method includes PA and EVO by a dip coating method, a brush coating method, a roll coating method, a spray coating method, a gravure coating method, a curtain flow coating method, or the like.
An organic solvent dispersion or an aqueous dispersion of polyester is applied to a multilayer film made of H. In the precoating method, coating is applied to a multilayer unstretched film composed of PA and EVOH or a multilayer film stretched uniaxially, and then stretched. The precoating method is superior to the postcoating method in adhesion to the coated substrate.

[0027]

Next, the present invention will be described more specifically with reference to examples. In the following examples and comparative examples, the raw materials used for the evaluation and the evaluation method are as follows. (1) Raw material Laminated film: Embron E nylon 6 manufactured by Unitika Ltd. A1030BRF EVOH manufactured by Unitika Ltd. EVAL EP-F101BZ manufactured by Kuraray Co., Ltd.
(Ethylene copolymerization ratio 32 mol%) Polyester dispersion: Elitel product number KZA-5023, KZA-0134 manufactured by Unitika Talc: Super Talc SG-200 manufactured by Nippon Talc
0 (average particle size 1.1 μm) (2) Evaluation method (i) Oxygen permeability (milliliter / (m ² · day · MP)
a) (/ Thickness of one sheet)) The method of measuring the oxygen permeability as an index of the gas barrier property of the film is as follows: (a) OX-TRA manufactured by Modern Control Co.
According to the method of measuring under conditions of 20 ° C./85% RH using N2 / 20 type and (b) ASTM D-3985,
A method of measuring under conditions of 20 ° C./65% using OX-TRAN100 model manufactured by Modern Control Co. was selectively adopted. (ii) Haze Fully automatic haze meter (TC-H3DP, manufactured by Tokyo Denshoku Co., Ltd.)
K) was measured in accordance with JIS K-6714. (iii) Flex pinhole resistance Fed. shown in MIL-B-131F. Test M
method Std. Method 201 of 101C
According to No. 7, a sample film of 12 inches × 8 inches is gripped in a cylindrical shape having a diameter of 3.5 inches, and an initial grip interval is 7 inches and a grip interval at the maximum bending is 1 inch, using a so-called gel botester (manufactured by Rigaku Corporation). Evaluation was made by the number of pinholes after bending 500 times at 5 ° C. (iv) Perfumery (a) Using a film, a bag measuring 50 mm x 50 mm is prepared, and miso and soy sauce are put into the bag and sealed, and the sealed bag is subjected to a temperature of 20 ° C and a humidity of 65% RH for 2 hours. Saved ~ 28 days. After the lapse of each storage day, those in which the fragrance retention of the content was maintained were evaluated as ○, and those in which the odor was leaked were evaluated as ×.

(B) An adhesive / L is applied to the obtained stretched film.
LDPE (50 μm) is laminated, and a sachet (outside dimensions 80 mm) filled with miso, soy sauce, and mustard using the laminated film
× 80 mm three-sided bag). The sachet was placed in a 100 ml reagent bottle and stored in an atmosphere of 20 ° C. and 65% RH, and the presence or absence of odor leakage was checked by a sensory test every time. The evaluation criteria were as follows.

After one week, confirmation of odor leakage ... × After two weeks, confirmation of odor leakage ... △ After 15 days, no odor leakage ... ○ (Examples 1 and 2) Multilayer film manufactured by Unitika Ltd. Embron E (PA 5 μm / EVOH 5 μm / PA
5 μm three-layer laminated stretched film, total thickness 15 μm)
Water-based polyester dispersion KZ manufactured by Unitika Ltd.
A-5023 was applied at the thicknesses shown in Table 1, respectively.
Thereafter, a heat treatment was performed at 150 ° C. for 30 seconds to obtain a stretched multilayer film. Next, a urethane adhesive A5 manufactured by Takeda Pharmaceutical Co., Ltd. was coated on the coated surface of the multilayer film.
15 / A50 was applied at 4 g / m ² , and a 50 μm-thick L-LDPE film T.C. U. X. FC
A laminated film having S bonded thereto was obtained. The oxygen permeability of this film was measured under the above condition (b). Using this laminated film, a sealed bag containing miso and soy sauce was prepared, and the fragrance retention test (a) was performed. Table 1 shows the results.

[0030]

[Table 1] (Examples 3 and 4) An aqueous polyester dispersion KZA-0134 manufactured by Unitika Ltd. was added to Embron E having a thickness of 15 μm which is the same multilayer film as those of Examples 1 and 2.
Each was applied with the thickness shown in Table 1, and then 150 ° C
By performing a heat treatment for 30 seconds, a stretched multilayer film was obtained. Next, 4 g / m ² of a urethane-based adhesive A515 / A50 manufactured by Takeda Pharmaceutical Co., Ltd. was applied to the coated surface of the multilayer film in the same manner as in Examples 1 and 2, and a thickness of 50 μm manufactured by Tosero Corporation was applied. L-LDPE film T. U.
X. A laminate film on which FCS was laminated was obtained.
Thereafter, using this laminate film, a sealed bag containing miso and soy sauce was prepared, and the above-mentioned fragrance retention test (a) was performed. Table 1 shows the results. (Comparative Example 1) Using the same multilayer film as in each of the above examples, Embron E having a thickness of 15 μm, the same adhesive, and the same L-LDPE film, but using a polyester dispersion. The other conditions were the same, and a laminated film was obtained. Then, the above-mentioned fragrance retention test (a) was similarly performed using this laminated film. Table 1 shows the results. (Comparative Example 2) A bag was prepared under the same conditions as in Comparative Example 1 except that Embron E having a thickness of 25 µm was used as a multilayer film, and the bag was used in the same manner as in the above (a). Was done. Table 1 shows the results. (Comparative Example 3) A emblem ON, which is a single-layer nylon film having a thickness of 25 µm manufactured by Unitika Ltd., was used as a multilayer film, and a bag was prepared under the same conditions as in Comparative Example 1 except for this. Similarly, the above-mentioned fragrance retention test (a) was performed. Table 1 shows the results.

As shown in Table 1, Examples 1 to 4 of the present invention
The multilayer film and the bag made using the multilayer film have a low oxygen permeability and are coated with a polyester dispersion. The preservatives of miso and soy sauce were kept, showing excellent preservative properties.

In Comparative Example 1, the oxygen permeability was low because a multilayer film of PA and EVOH was used, but the polyester dispersion was not applied. The odor leakage occurred in the bag sealed in 7 days.

In Comparative Example 2, since the thickness of the multilayer film of PA and EVOH was larger than that of Comparative Example 1, the oxygen permeability was correspondingly reduced, but the polyester dispersion was similarly coated. As a result, the fragrance retention was low, and the fragrance retention was slightly improved as compared to Comparative Example 1 by increasing the thickness of the multilayer film, but was not at a satisfactory level.

In Comparative Example 3, since a single-layer nylon film having no EVOH layer was used, the oxygen permeability was high, which was not suitable for packaging bags for foods and the like. Also,
As in the case of the other comparative examples, the polyester dispersion was not applied, and only a single-layer nylon film was used. Therefore, the fragrance retention was extremely low. (Example 5) First, talc was added to 90% by mass of EVOH.
The mixture was added at a ratio of 0% by mass, melt-kneaded with a twin-screw extruder set at 210 ° C., and pelletized.

Next, using a co-extrusion T die for two and three layers, nylon 6 is melted and extruded at 250 ° C. from the first extruder (hereinafter, the obtained layer is referred to as “X”). The talc-containing EVOH was heated at a temperature of 2
A sheet which was melted and extruded at 15 ° C. (hereinafter, a layer obtained thereby is referred to as “Y”) and laminated in the order of X / Y / X with a multi-manifold type die was subjected to a surface temperature of 1
The layer was quenched by closely contacting it on a cooling drum adjusted to 8 ° C., and the thickness of each layer was X / Y / X = 50/50/50 μm and the total thickness was 15
An unstretched film of 0 μm was obtained.

The obtained unstretched film was guided to a hot water bath controlled at 60 ° C., and subjected to a water absorption treatment for 90 seconds.
Simultaneous biaxial stretching was performed to obtain a stretched film having a thickness of 15 μm. This stretching was performed at a temperature of 175 ° C. by a factor of 3 in the machine direction and a factor of 3.3 in the transverse direction. Then temperature 210 ° C, relaxation rate 5
%.

With respect to the multilayer film thus obtained, the oxygen permeability was measured under the above condition (a), and the haze and the pinhole resistance were measured. A bag was prepared using this multilayer film, and its fragrance retention was measured under the conditions described in (b) above. Table 2 shows the results.

[0038]

[Table 2] (Examples 6 and 7) Compared with Example 5, the amount of talc added was changed under the conditions shown in Table 2. Except for this, the film was extruded and stretched under the same conditions as in Example 5 to obtain a stretched film having a thickness of 15 μm. Example 5
Various properties were measured in the same manner as in the above. Table 2 shows the results. (Example 8) Compared with Example 5, the thickness of each layer of the film and the amount of talc added were changed under the conditions shown in Table 2. Except for this, the film was extruded and stretched under the same conditions as in Example 5 to obtain a stretched film in the same manner. Various characteristics of the obtained film were measured in the same manner as in Example 5. Table 2 shows the results. (Comparative Example 4) A thickness of 15 µm was prepared without adding talc to EVOH, except that the other conditions were the same as in Example 5.
Was obtained. Various characteristics of the obtained film were measured in the same manner as in Example 5. Table 2 shows the results. (Comparative Examples 5 and 6) Compared with Example 5, the amount of talc added was changed under conditions outside the range of the present invention shown in Table 2. Except for this, the film was extruded and stretched under the same conditions as in Example 5 to obtain a stretched film in the same manner. Various characteristics of the obtained film were measured in the same manner as in Example 5. Table 2 shows the results.

As shown in Table 2, Examples 5 to 8 of the present invention
The multi-layer film and the bag made from the multi-layer film contain a predetermined range of talc in the EVOH, so that the number of pinholes generated is small, the oxygen permeability is low, and the bag is maintained at a predetermined level or higher. It had fragrance.

On the other hand, in Comparative Example 4, EVOH did not contain talc, so that the number of pinholes was large, the oxygen permeability was high, and the fragrance retention was poor. In Comparative Example 5, since the content of talc was too small, the number of pinholes was increased as compared with Examples 6 and 8, in which the content of talc was the lower limit of the range of the present invention.

In Comparative Example 6, since the content of talc was too large, the transparency of the film was lowered.

[0042]

As described above, according to the present invention, in addition to the excellent strength and dimensional stability of the PA film and the excellent gas barrier properties of the EVOH, a food product having an excellent fragrance retention property by a polyester resin coat layer. A film suitable as a packaging material for pharmaceuticals and the like is provided. Also according to the present invention,
By making EVOH contain a predetermined amount of talc,
Without significantly impairing the transparency of the film or raising the raw material cost, it is possible to obtain a film with improved fragrance retention and gas barrier properties and pinhole resistance that are important for practical use, and it has been limited until now The range of use of the gas barrier laminate film is greatly expanded. Therefore, the industrial utility value of the laminated film of the present invention is extremely high.

Continued on the front page (72) Inventor Atsushi Tachikawa 31-3 Uji Hinojiri, Uji-city, Kyoto Unitika Unitika Co., Ltd. (72) Inventor Fukayuki Tatsui 31-3 Uji-Hinojiri Uji-shi, Kyoto Unitika Unitika Co., Ltd. Inside Uji Plastic Factory (72) Inventor Junichi Tanaka 31-3 Uji Hinojiri Uji City, Kyoto Prefecture Unitika Ltd. Inside Uji Plastic Factory (72) Inventor Shunichi Kawakita 31-3 Uji Hinojiri Uji City, Kyoto Unitika Unitika Co., Ltd. Inside Uji Plastic Factory (72) Inventor Kiyohide Kimura 31-3 Uji Hinojiri Uji City, Kyoto Prefecture Unitika Ltd. Inside Uji Plastic Factory (72) Inventor Kazuhiro Kawaguchi 31-3 Uji Hinojiri Uji City, Kyoto Unitika Unitika Co., Ltd. F term in Uji Plastic Factory (reference) 4F100 AC10A AC10H AK41C AK41D AK46A AK48 AK63 AK69B BA03 BA04 BA06 BA07 BA10A BA10B BA10C BA10D EH46 EH462 EJ42 EJ422 GB15 GB23 JD03 JM01C JM01D YY00A

Claims (4)

[Claims] 1. A layer comprising a polyamide resin and ethylene-
At least 2 with a layer comprising a saponified vinyl acetate copolymer
What is claimed is: 1. A polyamide-based multilayer film, comprising a multilayer film having a layer, wherein a polyester dispersion coat layer is formed on at least one surface of the laminated film. 2. A packaging material comprising at least one layer of the polyamide-based multilayer film according to claim 1. 3. A layer comprising a polyamide resin and ethylene-
At least 2 with a layer comprising a saponified vinyl acetate copolymer
A multilayer film comprising a saponified ethylene-vinyl acetate copolymer, wherein talc is added to 95 to 85% by mass of the saponified ethylene-vinyl acetate copolymer.
A polyamide-based multilayer film, which is contained in an amount of from 15 to 15% by mass. 4. An oxygen permeability under an atmosphere of 20 ° C. and 85% RH of 50 ml / (m ² · day · MPa).
(/ One sheet thickness) The number of pinholes generated in the bending fatigue test repeated 500 times in an atmosphere of 5 ° C. was 10 or less.
6% or less after repeated bending fatigue test
The polyamide-based multilayer film according to claim 3, wherein: