JPH09239930A - Laminated polyamide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain sufficient water resisting adhesion which does not peel a sealant layer even at processing in hot water by providing an adhesion modified layer on one face of a polyamide base material film and specifying a refractive index of the film in the thickness direction. SOLUTION: A laminated polyamide film comprises an adhesion modified layer on one face of a polyamide base material film. The refractive index of the film it the thickness direction is set to 1.5050 or above. As an example of an adhesion modified resin, a polyester resin crosslinked by a crosslinking agent such as a multifunctional isocyanate, a melamine, an epoxy compound, a silane compound, or an acrylic resin, a polyurethane resin, and an acrylic graft polymer of a polyester resin and a polyurethane resin, or a resin which is crosslinked by a crosslinking agent can be named. Further, in the adhesion modified layer, an additive such as an antistatic agent, an inorganic lubricant, and an organic lubricant is added.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyamide film having excellent adhesiveness, and more particularly to a laminated polyamide film having improved adhesiveness with a sealant layer laminated by dry lamination, extrusion lamination or the like.

[0002]

2. Description of the Related Art Biaxially stretched polyamide film is tough
Since it has excellent pinhole resistance, bending resistance, and heat resistance, it is widely used in various applications. Among them, for example, when used for packaging applications, generally, an adhesive layer is provided on the surface of the biaxially stretched polyamide substrate film, and a sealant layer made of polyethylene, polypropylene or the like is formed thereon by dry lamination or extrusion lamination. The provided polyamide film laminate is used. Then
After optionally printing this polyamide film laminate, it is formed into a bag, and the contents (for example,
After filling with seasonings such as miso and soy sauce, water-containing foods such as soups and retort foods or chemicals, and heat-sealing the openings, the packaged product is provided to general consumers.

Generally, in such a polyamide film laminate, when moisture enters between the layers forming the laminate, the adhesive force between the layers is significantly reduced, and the sealant layer is peeled from the polyamide base film. There's a problem. Therefore, when this is used as a packaging bag containing, for example, a retort food, the packaging bag may be damaged during treatment in hot water such as boiling water treatment or retort treatment.

In order to solve this problem, there has been proposed a method for producing a laminated polyamide film in which an adhesion modifying layer obtained by crosslinking a polyester resin with polyisocyanate is provided on the surface of a polyamide substrate film. However, the laminated polyamide film having such an adhesion-modified layer does not sufficiently improve the water-resistant adhesion to the sealant layer in hot water, and cannot satisfy the higher requirements of the market.

[0005]

DISCLOSURE OF THE INVENTION The present invention is intended to solve the above problems. Specifically, it has good adhesiveness with a sealant layer, and the sealant layer can be formed even in hot water treatment. An object of the present invention is to provide a laminated polyamide film having sufficient water resistant adhesiveness without peeling.

[0006]

The present invention is a laminated polyamide film having a modified adhesion layer on at least one side of a polyamide substrate film, the refractive index (n _Z ) in the thickness direction of the film being 1.050. That is all. This solves the above object.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The laminated polyamide film of the present invention has a refractive index (n _Z ) in the thickness direction of the film of 1.550 or more, preferably 1.5055 or more, from the viewpoint of improving water-resistant adhesion. .

The following polyamide substrate film is used for the laminated polyamide film of the present invention.

The polyamide base film used in the present invention is a film containing a polyamide resin as a main component.
As such a polyamide resin, a polyamide resin obtained by polycondensation of lactams having three or more membered rings, a polyamide resin obtained by polycondensation of ω-amino acid, a polyamide resin obtained by polycondensation of dibasic acid and diamine Is mentioned. More specifically, examples of lactams having 3 or more membered rings include ε-caprolactam, enanthlactam, capryllactam, lauryllactam and the like. Examples of ω-amino acids include 6-aminocaproic acid, 7-aminoheptanoic acid, 9-aminononanoic acid, 11
-Amino undecanoic acid and the like. Examples of dibasic acids are adipic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecadioic acid, hexadecadioic acid, eicosandioic acid, eicosadiendioic acid, 2 , 2,4-trimethyladipic acid, terephthalic acid, isophthalic acid, 2,
6-naphthalenedicarboxylic acid, xylylenedicarboxylic acid and the like can be mentioned. Examples of diamines include ethylenediamine, trimethylenediamine, tetramethylenediamine, hexamethylenediamine, pentamethylenediamine, undecamethylenediamine, 2,2,4 (or 2,4,4) -trimethylhexamethylenediamine, cyclohexane. Examples thereof include diamine, bis- (4,4′-aminocyclohexyl) methane, and metaxylylenediamine. Examples of polymers obtained by polycondensation of these or copolymers thereof include nylon 6, nylon 7, nylon 11, nylon 12, nylon 6.6, nylon 6.9, nylon 6.11, nylon 6. 12,
Nylon 6T, Nylon 6I, Nylon MXD6, Nylon 6 / 6.6, Nylon 6/12, Nylon 6/6
T, and nylon 6/61, nylon 6 / MXD6. In particular, it is preferable to use nylon 6 or a blend system of nylon 6 and a nylon elastomer.

Further, the polyamide-based film is an additive such as an antioxidant, a light-proofing agent, an anti-gelling agent, a lubricant, an anti-blocking agent, a pigment, an antistatic agent, and a surfactant as long as the purpose is not impaired. Of at least one of

The polyamide substrate film used in the present invention may be a monolayer film or a multilayer film obtained by coextrusion or the like.

An unstretched film is formed by a known film forming method such as a T-die method and an inflation method, using the above polyamide resin and, if necessary, the above additives. As for this unstretched film, a continuous sheet of the unstretched film is roll-stretched in the longitudinal direction (longitudinal stretching) as required.
It may be formed into a uniaxially stretched polyamide film.
Further, the biaxially stretched polyamide film may be formed by tenter stretching (transverse stretching) in the width direction.

In such a method for producing a polyamide substrate film, in the longitudinal stretching step, the unstretched film can be stretched by using two or more rolls having different peripheral speeds. As the heating means at this time, a method using a heating roll, a method of performing non-contact heating, or a method of using them in combination can be used.

Thus, the polyamide base film used in the present invention is molded. The obtained polyamide substrate film is preferably 15 μm or more and 50 μm or less,
More preferably, it has a thickness of 20 μm or more and 30 μm or less.

The laminated polyamide film of the present invention has an adhesion modifying layer on at least one surface of the above polyamide base film. This adhesion modifying layer contains the following adhesion modifying resin.

The adhesion-modifying resin is not particularly limited as long as it has water-resistant adhesion, and conventionally known synthetic resins can be appropriately selected. Examples of such an adhesion-modifying resin include those obtained by crosslinking a polyester resin with a crosslinking agent such as a polyfunctional isocyanate, oxazoline, melamine, and an epoxy compound silane compound, or an acrylic resin, a polyurethane resin, and a polyester resin. Examples thereof include an acrylic graft polymer with a polyurethane resin, and those crosslinked with the crosslinking agent.

Further, the adhesion modifying layer may contain additives such as an antistatic agent, an inorganic lubricant and an organic lubricant within the range not impairing the object of the present invention.

The adhesion modifying resin is applied to at least one surface of the polyamide base film to form an adhesion modifying layer. As a method for laminating the adhesion modifying layer on such a polyamide substrate film, a usual coating method such as a gravure method, a reverse method, a die method, a bar method, a dip method can be used.

The coating amount of the adhesion modifying resin is not particularly limited,
Preferably, the solid content of the polyamide base film is 1 m.
Per ² 0.01 g to 1 g, more preferably 0.02
It is g or more and 0.5 g or less. The amount of the adhesion-modifying resin used can be appropriately selected depending on its type.

After applying the adhesion-modifying resin to the polyamide substrate film, the resulting film is dried. The temperature used in the drying step after coating is preferably 150 ° C.
That is all. Next, heat setting is performed at 200 ° C. or higher. This improves the adhesiveness between the adhesion modifying layer and the polyamide base film.

Alternatively, after coating the polyamide-based film with the adhesion-modifying resin, the resulting film may be dried and optionally uniaxially or biaxially stretched. In the drying step at this time, it is preferable to control the water content of the polyamide base film in the range of 0.1% to 2% so as not to impair the stretchability of the film in the subsequent stretching step.

Thus, the laminated polyamide film of the present invention is produced.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments. Parts in the examples represent parts by weight, and% means% by weight. Each measurement item followed the following method.

(1) Refractive Index Using an Abebe refractometer, the refractive index in the thickness direction of the laminated polyamide film obtained by NaD ray was measured.

(2) Peel strength during storage under normal conditions The obtained polyamide film laminate during storage under normal conditions (dry and wet), the sealant layer of the polyamide film laminate, the polyamide base film, and the adhesion-modifying layer The peel strength between and was measured by performing a 90 ° peel test at a pulling speed of 100 mm / min using a tensile tester.

(3) Peel strength upon immersion in hot water When the obtained polyamide film laminate is immersed in hot water at 90 ° C., the sealant layer of the polyamide film laminate, the polyamide base film and the adhesion-modifying layer are formed. The peel strength between the two was measured using a tensile tester at a tensile speed of 100 mm /
It was measured by performing a 90 ° peel test in minutes.

Example 1 (Production of Polyamide Substrate Film) A blend consisting of 98 parts of polycaproamide resin and 2 parts of polyamide elastomer resin was heated and melted at 260 ° C. using a screw type extruder, and T-die After further extruding, it was cooled by a cooling drum to obtain an unstretched film. This unstretched film
A longitudinal stretching of 3.1 times was performed at 0 ° C. to form a polyamide base film.

(Preparation of Adhesion Modifying Resin Coating Solution) Stirrer,
In a reactor equipped with a thermometer, a reflux device, and a constant amount dropping device, 75 parts of an acrylic graft polyester resin having the composition shown in Table 1, 56 parts of methyl ethyl ketone and 19 parts of isopropyl alcohol were put, and heated at 65 ° C. and stirred. The polyester resin was dissolved.

[0029]

[Table 1]

After the polyester resin was completely dissolved, a mixture of 17.5 parts of methacrylic acid and 7.5 parts of ethyl acrylate, and a solution of 1.2 parts of azobisdimethylvaleronitrile in 25 parts of methyl ethyl ketone was added. 0.2
It was added dropwise to the reactor at ml / min, and stirring was continued for another 2 hours. After sampling for analysis (5 g) from this reaction solution, 300 parts of water and 25 parts of triethylamine were added to the reaction solution, and the mixture was further stirred for 1 hour. Then, the temperature of this reaction solution was raised to 100 ° C., and methyl ethyl ketone, isopropyl alcohol, and excess triethylamine were distilled off by distillation. The resulting graft polymer was a white water dispersion having an average particle size of 300 nm and had a B type viscosity at 25 ° C. of 50 cps. Then, the copolymerized polyester portion of the solid content of this aqueous dispersion was hydrolyzed, and the molecular weight of the graft portion was measured by GPC. The weight average molecular weight was 10,000. Finally,
An aqueous dispersion of the graft polymer was added to give a solid content concentration of 20.
The coating liquid of the adhesion-modifying resin was prepared by diluting with water so as to become 10%.

(Preparation of Laminated Polyamide Film) On one surface of the obtained polyamide substrate film, the coating solution of the adhesion-modifying resin was applied by a gravure method so that the coating amount was 4 g / m ² . Then, the polyamide substrate film coated with this adhesion-modifying resin was dried. The moisture content of the obtained polyamide substrate film was 1%. Then, this film was transversely stretched 4 times at 120 ° C., and then 6 times in the transverse direction.
% By 15% relaxation and heat setting at 220 ℃
A laminated polyamide film having a thickness of m was obtained. The laminated polyamide film thus obtained had n _Z of 1.560.

(Preparation of Polyamide Film Laminate) An unstretched polypropylene film (Pyrene P1151 manufactured by Toyobo Co., Ltd.) having a thickness of 40 μm was used as a sealant layer on the adhesion-modified layer surface of the above laminated polyamide film, and Tg was -16 as a main agent. A polyester polyurethane adhesive containing an aromatic / aliphatic copolymerized polyester polyol at 0 ° C. and a hexamethylene diisocyanate trimer as a cross-linking agent was used for dry lamination by a conventional method. Thus, a polyamide film laminate was manufactured. Table 2 shows the evaluation results of the obtained polyamide film laminate.

<Comparative Example 1> A longitudinal stretching ratio at the time of molding a polyamide substrate film was 3.2 times, and a relaxation rate in the lateral direction after laminating an adhesion modifying layer was 3%, and heat setting was performed at 220 ° C. A laminated polyamide film and a film laminate were obtained in the same manner as in Example 1 except that the steps were performed. The laminated polyamide film thus obtained had n _Z of 1.5043. Table 2 shows the evaluation results of the obtained polyamide film laminate.

Comparative Example 2 A polyamide film and a film laminate were obtained in the same manner as in Example 1 except that the acrylic graft polyester resin coating solution was not applied as the adhesion modifying layer. The laminated polyamide film thus obtained had n _Z of 1.560. Furthermore, Table 2 shows the evaluation results of the obtained polyamide film laminate.

Example 2 A polyamide substrate film was molded in the same manner as in Example 1.

Then, a linear polyester resin (Vylon 300 manufactured by Toyobo Co., Ltd.) and polyisocyanate (Coronate L manufactured by Nippon Polyurethane Co.) were used in a solid content ratio of 10.
Mixed at 0: 100, diluted with ethyl acetate to a solid content concentration of 4%, and amorphous silica (Silysia 310 manufactured by Fuji Silysia Chemical Ltd.) for the purpose of preventing blocking and imparting lubricity.
Was added so that the solid content ratio was 0.5% to obtain a mixed solution. This mixed solution was applied to one surface of the above polyamide substrate film by a gravure method, dried and then aged at 40 ° C. for 2 days to form an adhesion-modified layer. The coating amount of the polyester resin in the adhesion-modified layer was 0.15 g / m ² in the dried state. The laminated polyamide film thus obtained had n _Z of 1.560.

Further, dry lamination was carried out in the same manner as in Example 1 to produce a film laminate. Table 2 shows the evaluation results of the obtained film laminate.

Comparative Example 3 Example 2 was repeated except that the polyamide base film molding conditions described in Comparative Example 1 were used.
A laminated polyamide film and a film laminate were obtained in the same manner as in. The laminated polyamide film thus obtained had n _Z of 1.5045. Furthermore, Table 2 shows the evaluation results of the obtained polyamide film laminate.

<Example 3> Instead of the acrylic graft polyester resin used in Example 1, a water dispersion type polyurethane resin (Hydran HW-manufactured by Dainippon Ink and Chemicals, Inc.) was used.
140) and methylol melanin (Beckamine PM-N manufactured by Dainippon Ink and Chemicals, Inc.) at a solid content ratio of 100: 20.
A laminated polyamide film and a polyamide film laminate were obtained in the same manner as in Example 1 except that the above was used.
The obtained laminated polyamide film had n _Z of 1.560.
Met. Furthermore, Table 2 shows the evaluation results of the obtained polyamide film laminate.

Comparative Example 4 Example 3 was repeated except that the molding conditions for the polyamide base film described in Comparative Example 1 were used.
A laminated polyamide film and a film laminate were obtained in the same manner as in. The laminated polyamide film thus obtained had n _Z of 1.5043. Furthermore, Table 2 shows the evaluation results of the obtained polyamide film laminate.

<Example 4> Instead of the acrylic graft polyester resin used in Example 1, a water dispersion type polyester resin (Vylonal MD19 manufactured by Toyobo Co., Ltd.) was used.
30) and blocked isocyanate (Daiichi Kogyo Yakuhin Co., Ltd.)
Elastron BN11) manufactured by the company, the solid content ratio of 10
A laminated polyamide film and a film laminate were obtained in the same manner as in Example 1 except that 0:43 was used. The laminated polyamide film thus obtained had n _Z of 1.5062.
Met. Furthermore, Table 2 shows the evaluation results of the obtained polyamide film laminate.

Comparative Example 5 Example 4 was repeated except that the polyamide base film molding conditions described in Comparative Example 1 were used.
A laminated polyamide film and a film laminate were obtained in the same manner as in. N of the obtained laminated polyamide film
_Z was 1.5045. Furthermore, Table 2 shows the evaluation results of the obtained polyamide film laminate.

<Example 5> Instead of the acrylic graft polyester resin used in Example 1, a water dispersion type polyester resin (Vylonal MD19 manufactured by Toyobo Co., Ltd.) was used.
30) and a water-dispersed oxazoline group-containing polymer (Epocros K2010E manufactured by Nippon Shokubai Co., Ltd.) were used in the same manner as in Example 1 except that the solid content ratio was 70:30. Got the body _NZ of the obtained laminated polyamide film was 1.5.
It was 060. Furthermore, Table 2 shows the evaluation results of the obtained polyamide film laminate.

Comparative Example 6 Example 5 was repeated except that the molding conditions for the polyamide substrate film described in Comparative Example 1 were used.
A laminated polyamide film and a film laminate were obtained in the same manner as in. N of the obtained laminated polyamide film
_Z was 1.5045. Furthermore, Table 2 shows the evaluation results of the obtained polyamide film laminate.

[0045]

[Table 2]

As shown in Table 2, the polyamide film laminates produced from the laminated polyamide films of Examples 1 to 5 have high peel strength in hot water at 90 ° C,
It had excellent water resistant adhesion.

[0047]

According to the present invention, a laminated polyamide film having good adhesiveness with a sealant layer and improved water-resistant adhesiveness can be obtained. A packaging bag manufactured using this laminated film is, for example, miso, seasoning such as soy sauce, soup,
It is useful as a packaging bag for water-containing foods such as retort foods or medicines.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location B29K 77:00 B29L 9:00 (72) Inventor Chikao Morishige 2-chome Katata, Otsu City, Shiga Prefecture No. Toyobo Co., Ltd. Research Institute (72) Inventor Tsutomu Isaka 2-8 Dojimahama, Kita-ku, Osaka-shi, Osaka Toyobo Co., Ltd.

Claims (1)

[Claims] 1. A laminated polyamide film having an adhesion modifying layer on at least one surface of a polyamide substrate film, the refractive index (n _Z ) in the thickness direction of the film being 1.50.
A laminated polyamide film of 50 or more.