JPH1120103A - Easily-printable biaxially oriented polyamide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve adhesion and resistance to blocking of printed material by providing, on at least one film surface, a specified amount of a primer layer composed of resin and a surface-active agent. SOLUTION: On at least one surface of a biaxially oriented polyamide film composed of a linear high-molecular compound having amide bond in a molecule such as polycaprolactam, a polyamide film is applied so that a primer layer is 0.01-0.03 g/m<2> after orientation of the polyamide film. The primer layer may be a solvent type, however a layer composed of a nonionic surface active agent composed of water-dispersed polyurethane resin, and polyethylene glycol alkyl alcohol ether, etc., used, for easy controlling of the crosslinking degree of polyurethane resin, and in consideration of environmental problems in a manufacturing site.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to the present invention which has excellent performance in mechanical strength, impact resistance, pinhole resistance and heat resistance, as well as adhesion of dust in printing, laminating, bag making, etc. It is related to a biaxially stretched polyamide film which has no electrostatic interference, and has excellent adhesion to printed matter printed on the film surface and excellent blocking resistance.
The present invention relates to an easily printable biaxially stretched polyamide film suitable for packaging of liquid foods and oily foods and sterilizing packaging of boiled and retorted foods.

[0002]

2. Description of the Related Art Food packaging materials are required to have a function of protecting the contents, ease of handling, sales promotion function, suitability for packaging machines, etc., and at the same time, a role of displaying product information when used by consumers. I also carry. From this point of view, food packaging and pharmaceutical packaging are required to display the product name, raw material name, content, date of manufacture, expiration date, etc.
It must be printed on the surface of the packaging bag so that it can be easily seen by consumers. However, conventionally, the printed matter printed on the base film on the bag surface sometimes comes off during the distribution process until it reaches the consumer. For example, there is a case in which printed matter falls off due to the influence of impact, vibration, compression or the like in the boil / retort sterilization step, food filling step or distribution step. Usually, the surface of a packaging bag that uses a stretched film as the outermost layer is highly oriented and crystallized and has poor surface activity, so the adhesion of printed matter is weak, and problems such as partial peeling or falling off may occur. is there. In particular, the tendency is remarkable in packaging bags filled with liquid foods such as water and pickles, and oily foods such as liquid soups or packaging bags subjected to boiling and retort sterilization. Liquid food, oily food packaging and boil / retort sterilization packaging materials are required to have impact resistance, pinhole resistance, gas barrier properties, etc.Laminated using biaxially stretched polyamide film to satisfy such properties Film is widely used. However, although the biaxially stretched polyamide film has excellent suitability for multicolor printing and lamination, etc., a hot printer method in which a metal type plate heated through a printer tape with a colored surface is stamped on the film surface by heat and pressure. However, there is a disadvantage that the adhesion of the printed matter is poor due to the above-mentioned factors. A method of using a film subjected to a corona treatment or an easy-adhesion treatment on the surface of the bag to improve the adhesion of the printed matter is considered, but in the above-described printing method, the adhesion is insufficient, In particular, in the case of using a film which has been subjected to a conventional easy-adhesion treatment, there is a case where bags fuse with each other by blocking.

[0003]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned problems, and it is intended to provide an easily printable biaxially stretched polyamide film excellent in adhesion and blocking resistance of printed matter by a hot printer system or the like. It is intended to provide such a laminated film.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve such a problem and found that a biaxially stretched polyamide film has a specific thickness comprising a polyurethane resin and a nonionic surfactant. The present inventors have found that a biaxially stretched polyamide film excellent in adhesion, antistatic property and blocking resistance of a printed matter can be obtained by forming a primer layer of the present invention.

That is, the present invention provides a film having a primer layer comprising a polyurethane resin and a nonionic surfactant provided on at least one side of a film so that the coating amount is 0.01 to 0.03 g / m ² , The gist of the present invention is an easily printable biaxially stretched polyamide film having excellent antistatic properties.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The biaxially stretched polyamide film in the present invention is a linear polymer compound having an amide bond in the molecule, and is composed of polycaprolactam (nylon 6), polyhexamethylene adipamide (nylon 66), and polyhexamethylene sebacamide. (Nylon 610), polyaminoundecanoic acid (nylon 11), polylaurinlactam (nylon 12) and copolymers thereof. Particularly preferred polyamides for the present invention are nylon 6, nylon 6
6 can be mentioned.

[0007] The polyurethane resin forming the primer layer is not particularly limited, and examples thereof include polyester polyurethane, polyether polyurethane, and polyurethane polyurea resin. The polyurethane resin used in the present invention may be any of a solvent type and a water dispersion type, but the degree of cross-linking of the polyurethane resin film is easily adjusted, and the water dispersion type polyurethane resin is preferably used due to environmental problems at the production site. desirable. As the water-dispersed polyurethane resin, a carboxylate (such as —COONa) or a sulfonate (—SO ₃
Self-emulsifiable polyurethane resin into which a hydrophilic group such as Na has been introduced.

In order to strengthen the primer layer, a polyurethane, melamine, epoxy or imine crosslinking agent may be added to the polyurethane resin in an amount of about 3 to 10% by weight based on the polyurethane resin.

In order to impart antistatic properties and blocking resistance to the film of the present invention, it is necessary to incorporate a nonionic surfactant into the primer layer. Examples of the nonionic surfactant include polyethylene glycol alkyl alcohol ether, polyethylene glycol fatty acid ester, polyethylene glycol phenyl ether, ethylene oxide adducts of fats and oils, etc., and polyethylene glycol alkyl alcohol ether and polyethylene glycol fatty acid ester are preferable. is there.

It is desirable that the solid content of the nonionic surfactant in the primer layer is 10 to 30% by weight, preferably 10 to 20% by weight. When the amount is less than 10% by weight, the antistatic effect is poor, and when the amount is more than 30% by weight, the adhesiveness of the film is hindered.

The coating amount of the primer layer is preferably 0.01 to 0.03 g / m ² after stretching the polyamide film, more preferably 0.015 g / m ² .
It is necessary that the ~0.03g / m ^2. The coating amount is 0.01g / m ²
When the amount is less than the above, the adhesion and antistatic properties are insufficient, and when the amount is more than 0.03 g / m ² , the film may cause blocking.

The ease of printing in the present invention means that the printed matter printed by a known hot printer system or hot roll printer system has excellent adhesion. The hot printer system is a system in which printing is performed by a hot printer, in which heat and pressure are applied to a printing object with a metal type printing plate through a colored printer tape. Printer tapes have a structure in which a release agent (hot-melt wax), a coloring material (carbon or pigment), and a thermoplastic adhesive are mainly coated on a polyester film base, depending on the material to be printed, the printing color, and the application. There are many types. The hot roll printer system is a method in which an ink roll impregnated with a mixture of a resin and carbon (coloring material) in urethane foam is heated, a printing plate is pressed against the hot roll, and then transferred to an object to be printed.

As a method for obtaining the biaxially stretched polyamide film of the present invention, for example, a polyamide resin is charged into an extruder, and is usually heated and melted at 240 to 280 ° C., then extruded from a T-die into a film, and adhered to a cooling drum. And quenched to form a film. Followed by the primer solution in an unstretched film obtained after the coating amount after stretching was applied so as to 0.01~0.03g / m ^2, it was stretched by sequential biaxial stretching method or a simultaneous biaxial stretching method It is a biaxially stretched film. The stretching temperature of the biaxially stretched film is set at 1 in terms of stability and strength.
It is appropriate that the stretching ratio is 50 to 220 ° C. and the stretching ratio is 2.5 to 3.5 times in the machine direction (MD) and the width direction (TD), respectively.
According to this method, since a large amount of heat is applied in the preheating, stretching, and heat setting steps, the base film and the primer layer are firmly adhered to each other. It is also advantageous in terms of cost. As a stretching method, besides the tenter method described above, a tubular method can also be used.

When the biaxially stretched polyamide film of the present invention is used as a packaging bag, the primer layer is the outermost layer, and polyethylene, polypropylene, ethylene-vinyl ester copolymer, ethylene- A sealant material such as a (meth) acrylic acid copolymer is laminated. Further, in order to provide an oxygen gas barrier property, a multilayer structure in which a metal foil such as an ethylene-vinyl alcohol copolymer, a polyvinylidene chloride copolymer, or aluminum is disposed in an intermediate layer may be employed. The lamination method is not particularly limited, but a dry lamination method or an extrusion lamination method can be used.

By making such a laminated film such that the primer layer is on the front surface side of the bag, a packaging bag having excellent adhesion to printed matter printed on the bag surface can be obtained. Since the printed matter does not fall off even in scratching or hot water, it is useful as a packaging bag for liquid food packaging, oily food packaging, boiled and retort sterilized packaging, and the like.

[0016]

Next, the present invention will be described in detail with reference to examples. Each property of the film was evaluated by the following methods. (1) Adhesion of printed matter to substrate film Cellophane tape peeling A cellophane tape (18 mm width) is stuck on the printed part so that air bubbles do not enter, and it is rubbed lightly 20 times from above.
Next, peel off the cellophane tape to the film at an angle of 180 °
The printed matter was rapidly peeled off, and the degree of removal of the printed matter was visually observed, and evaluated in four steps according to the following criteria. The evaluation was performed on the film under normal conditions and after processing at 120 ° C. for 30 minutes. (Evaluation criteria) A: Very good (Printed matter cannot be obtained) B: Good (Printed matter is slightly removed) C: Somewhat poor (Printed matter is removed and printing is unclear) C: Bad (Most printed matter Oil resistance A cotton swab is rubbed with salad oil and lightly rubbed 50 times,
The degree of removal of the printed matter was visually observed, and evaluated on a four-point scale according to the above criteria. The evaluation was performed on the film under normal conditions and after processing at 120 ° C. for 1 minute. Scratch resistance Under a 70g load, the printed area is adjusted with a 0.5R metal pin.
It was rubbed repeatedly, and the degree of removal of the printed matter was visually observed, and evaluated according to the above criteria in four steps. Evaluation is normal and 120 ℃
× Performed on the film after 1 minute treatment.

(2) Blocking Resistance A few drops of water are dropped on the primer layers of the two films cut into A4 plates to form a thin water film, and the primer layers are overlaid. Apply a load of 10 g / cm ² from above to 40 ° C x
Leave at 90% RH for 24 hours. Then, the sheet was cut into a strip having a width of 15 mm, and the load (g) required for peeling the two sheets was measured with a tensile tester and used as an index of blocking resistance. The smaller the value, the better the blocking resistance. (3) Surface resistivity (Ohm) The ratio between the voltage (V) applied between two electrodes in contact with the film and the current (Is) flowing on the film surface according to the volume resistivity test of JIS C-2330. (V / Is). (4) Comprehensive evaluation The above-mentioned respective characteristic values were comprehensively evaluated according to the following criteria and evaluated in four steps. ◎… Very good ○… Good △… Some problem x… Problem

Example 1 Nylon 6 (A1030BRF manufactured by Unitika) having a relative viscosity of 3.0 measured at 25 ° C. in 96% concentrated sulfuric acid was melt-extruded from a T-die at 270 ° C., closely adhered on a cooling drum at 30 ° C., and rapidly cooled. , Thickness
An unstretched film of 160 μm was obtained. On one side of the obtained unstretched film, a nonionic surfactant containing 80% by weight of a self-emulsifying polyurethane polyurea resin (KU-400SF manufactured by Dainippon Ink and Chemicals, Inc.) and polyethylene glycol alkyl ether as main components. A solution prepared by adding 6 parts by weight of a melamine-based cross-linking agent to 100 parts by weight of a 20% by weight mixture and adjusting the concentration so that the thickness of a primer layer after stretched film formation is 0.01 g / m ² was measured by an air knife method. And then biaxially stretched at a stretching temperature of 180 ° C. at a magnification of 3.3 times in MD and 3.5 times in TD to obtain a biaxially stretched polyamide film having a thickness of 15 μm. Next, a polyurethane-based adhesive for dry lamination (main agent LX747A / hardening agent KX75 manufactured by Dainippon Ink and Chemicals, Inc.) is applied to the opposite side of the primer layer of the obtained biaxially stretched polyamide film, and a non-stretched polypropylene having a thickness of 60 μm is applied. The films were laminated by a dry lamination method to prepare a laminated film. On the primer layer surface of this laminated film, using a ribbon BY general-purpose type (manufactured by EDM) as a printer tape, print "Production date 97.5.23" with an intermittent hot printer HP-241B (manufactured by EDM). did. Table 1 shows the results of measuring the blocking resistance, the adhesion of the printed matter to the laminate film, and the surface resistivity of the laminate film.
Shown in

Example 2 Example 1 was repeated except that the thickness of the primer layer was 0.03 g / m ^2.
In the same manner as in the above, a biaxially stretched polyamide film having a thickness of 15 μm was produced. Table 1 shows the results of measuring the performances in the same manner as in Example 1.

Example 3 A biaxially stretched polyamide film having a thickness of 15 μm was produced in the same manner as in Example 2 except that no melamine-based crosslinking agent was added. Table 1 shows the results of measuring the performances in the same manner as in Example 1.

Comparative Example 1 A biaxially stretched polyamide film having a thickness of 15 μm was produced in the same manner as in Example 2 except that the nonionic surfactant and the melamine crosslinking agent were not added. Table 1 shows the results of measuring the performances in the same manner as in Example 1. The blocking resistance was poor, there was a problem in practical use as a packaging bag, and the surface specific resistance was high.

Comparative Example 2 Comparative Example 1 was conducted except that the thickness of the primer layer was changed to 0.06 g / m ^2.
In the same manner as in the above, a biaxially stretched polyamide film having a thickness of 15 μm was produced. Table 1 shows the results of measuring the performances in the same manner as in Example 1. The blocking resistance was poor, there was a problem in practical use as a packaging bag, and the surface specific resistance was high.

Comparative Example 3 One surface of a film was subjected to corona discharge treatment (surface tension: 54 dyne / c).
m) A laminated film was prepared in the same manner as in Example 1 except that the biaxially stretched polyamide film subjected to m) was used.
Table 1 shows the results of measuring each performance. The printability was very poor and the surface resistivity was high.

[0024]

[Table 1]

[0025]

According to the present invention, the biaxially stretched polyamide film has excellent mechanical strength, impact resistance, pinhole resistance and heat resistance, as well as printing, laminating, bag making and the like. It is possible to provide a biaxially stretched polyamide film which is free from static electricity in the next processing step and has excellent adhesiveness to printed matter by a hot printer method or the like.

Continued on the front page (51) Int.Cl. ⁶ Identification code FI B32B 27/00 B32B 27/00 H 27/40 27/40 B65D 30/02 B65D 30/02 C08J 7/04 C08J 7/04 H CFG CFGA / / C08J 5/18 CFG C08J 5/18 CFG B29K 75:00 77:00 B29L 7:00 9:00

Claims (5)

[Claims] 1. A biaxially stretched polyamide film having a primer layer comprising a polyurethane resin and a nonionic surfactant provided on at least one side thereof in a coating amount of 0.01 to 0.03 g / m ² . Easy-to-print biaxially stretched polyamide film with excellent antistatic properties. 2. The polyamide film according to claim 1, wherein the nonionic surfactant is a polyethylene glycol alkyl ether or a polyethylene glycol fatty acid ester. 3. The nonionic surfactant in the primer layer is 10 to 30% by weight as a resin solid content.
The polyamide film according to the above. 4. The polyamide film according to claim 1, wherein a melamine crosslinking agent or an epoxy crosslinking agent is added to the primer layer. 5. A laminated film in which a sealant layer is laminated on a surface opposite to a primer layer, and a packaging bag made by using the laminated film.