JPH0613207B2 - Polyolefin laminated film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a polyolefin laminated film having excellent adhesion to water-based inks and water-based adhesives.

[Prior Art] Conventionally, as a polyolefin film for printing an aqueous ink or coating an aqueous adhesive, a film in which an ethylene vinyl acetate copolymer is laminated on polypropylene is known.

Further, in order to improve the adhesiveness of ink or the like, it is known that an antistatic agent is added to a polymer mainly composed of polypropylene (JP-A-53-66973).

[Problems to be Solved by the Invention] However, the film formed by laminating the above ethylene vinyl acetate copolymer is apt to cause blocking, and when printing with a water-based ink or application of a water-based adhesive is performed. However, there were problems such as weak scratching, partial peeling, and falling off.

In addition, the latter is mainly composed of polypropylene, so that it cannot be said that the adhesiveness is sufficient.

In view of such conventional drawbacks, the present invention has an object to provide a polyolefin film excellent in printability of a water-based ink, coating suitability of a water-based adhesive, and adhesiveness.

[Means for Solving Problems] The present invention contains an antistatic agent in an amount of 0.2 to 1.0% by weight,
In addition, a biaxially stretched film mainly composed of polypropylene is laminated on one surface with a coating layer mainly composed of an ethylene-propylene copolymer having an ethylene content of 0.5 to 25% by weight, and the surface of the coating layer has a wetting index of 34 dyne. A polyolefin laminated film having a surface resistivity of 9 × 10 ¹³ Ω or less and a surface resistivity of 9 × 10 ¹³ Ω or less.

The biaxially stretched film (base material layer) in the present invention may be any biaxially stretched film, either simultaneously or sequentially,
The polymer is mainly polypropylene, preferably 80% by weight or more, and even if a homopolymer or copolymer of α-olefin represented by ethylene or butene-1 is blended. good. in this case,
The propylene component is preferably 80% by weight or more, and the melting differential thermal curve (5 mg of the sample is heated at 280 ° C. at a heating rate of 20 ° C./min.
It is preferable that one or more of the melting point peaks referred to in the so-called second-run melting curve when the temperature is raised to 1, melted once, then cooled to 20 ° C. and then heated again) is 158 ° C. or higher.

As the antistatic agent contained in the base material layer, an anionic surfactant (eg, alkylbenzene sulfonate, higher alcohol sulfate ester, etc.), nonionic surfactant (eg, aliphatic glycerin ester, polyoxyalkylamine, etc.), Cationic surfactants (eg, aliphatic amine salts, quaternary ammonium salts, etc.), amphoteric surfactants (eg, imidazoline type, betaine type, etc.), silicone type surfactants (eg, siloxane / oxyethylene copolymers, etc.) ) Can be used. Particularly preferred are amphoteric surfactants.

The amount of the antistatic agent contained in the base material layer is 0.2 to 1.
Must be 0% by weight. If the content of the antistatic agent is less than 0.2% by weight, the adhesion of the water-based ink, the adhesion of the water-based adhesive, and the adhesive strength will be weak. Also, 1.0
When the content is more than 5% by weight, the film causes blocking, and the adhesiveness of the water-based ink and the water-based adhesiveness are deteriorated.

The coating layer containing ethylene propylene copolymer as the main component in the present invention contains ethylene propylene copolymer as the main component (preferably 85 wt% or more), and has an ethylene content of 0.5 to 25 wt%, preferably Is 1.0 to 10% by weight
Is a copolymer with propylene, more preferably an ethylene-propylene random copolymer having an ethylene content of 1.5 to 8.0% by weight. When the amount of ethylene is less than the above range, the adhesion of the water-based ink becomes weak, and the adhesion of the water-based adhesive becomes weaker, and when it exceeds the range, the film tends to be blocked, and the coating layer is scratched.
The adhesion and adhesion are weak.

The coating layer must have a wetting index of 34 dyne / cm or more on the surface (side not in contact with the base material layer). When the wetting index is less than 34 dyne / cm, the adhesion of the water-based ink and the adhesion of the water-based adhesive become poor. The upper limit of the wetting index is not particularly limited, but 72 dyne / cm or less is preferable from the viewpoint of film blocking, and 56 dyne / cm or less is more preferable.

The surface resistivity of the coating layer (the side not in contact with the base material layer) must be 9 × 10 ¹³ Ω or less. If the surface specific resistance exceeds 9 × 10 ¹³ Ω, the adhesion of the water-based ink, the adhesion of the water-based adhesive, and the adhesion strength will be weak. The lower limit value of resistance is not particularly limited, but is 9 × 1.
0 The at ⁸ Omega than or blocking of the film, adhesion of the water-based ink is preferable in terms of the adhesion strength of the aqueous adhesive. In order to reduce the surface resistivity to 9 × 10 ¹³ Ω or less, the wetting index must be 34 dyne / cm or more and the base material layer must contain an antistatic agent. The amount of the antistatic agent in the coating layer is not particularly limited, but may be 0.2 to 1.0% by weight.

Furthermore, the coating layer has a ratio of the number of nitrogen atoms N and the number of carbon atoms C on the surface (the side not in contact with the base material layer), that is, N / C in the range of 0.005 to 0.10, and further 0. .01-0.
It is preferable to perform the electric discharge treatment so as to be in the range of 05 because the adhesion of the aqueous printing ink and the adhesive strength of the aqueous adhesive can be improved. When N / C is less than the above range, the adhesion of the water-based ink, the adhesion of the water-based adhesive, and the adhesive strength are insufficient. Further, if it exceeds the range, the production efficiency is not good.

The water-based ink in the present invention is an ink composed of a known water-based resin, a pigment, a solvent, and an additive.

Aqueous resins include acrylic copolymer resin (alkali soluble), rosin ester resin, styrene copolymer resin, polyester resin (including water-dilutable alkyd), vinyl resin, nitrified cotton emulsion resin, polyamide resin, polyurethane resin, Shellac resin or the like may be used alone or as a mixture.

The pigments are roughly classified into inorganic pigments and organic pigments. As the inorganic pigments, titanium oxide, carbon black and various extender pigments are used, and as the organic pigments, azo pigments, phthalocyanine pigments and the like are used.

As the solvent, in addition to water, lower alcohols such as ethanol, isopropyl alcohol and N-propyl alcohol, glycols and esters thereof are used.

Additives include waxes (wear resistance, scratch resistance), various activators, silicone oil (dispersant, defoamer)
Etc. are mentioned as an example.

The water-based adhesive in the present invention is classified into a water-soluble adhesive and an emulsion adhesive. As the resin component, starch, glue, gelatin, polyvinyl alcohol, polyacrylamide, polyethyleneimine, polyamide epichlorohydrin, polyvinyl acetate, polyacrylic ester,
Examples thereof include acid bi-acrylic acid ester copolymers, vinyl acetate / ethylene copolymers, rubber latex, etc., which may be used alone or as a mixture. The solvent is mainly water, and may be mixed with lower alcohols and glycols, and antifoaming agents and surfactants may be added.

The base layer and the coating layer to be laminated used in these inventions include a heat stabilizer, an antioxidant, an ultraviolet absorber, a nucleating agent,
An inorganic lubricant or the like may be added.

The laminated film of the present invention has a layer structure in which a coating layer is laminated on at least one surface of a base material layer.

In addition, the coating layer is laminated on both sides of the base material layer and printed on both sides with an aqueous ink, printed on one side, coated with an aqueous adhesive on the other side, or further coated with an adhesive on the print. You may do so.

The thickness of each layer of the film of the present invention is not particularly limited,
The base material layer preferably has a thickness of 5 to 100 μ, and is 10 to 30.
μ is more preferable. The coating layer preferably has a thickness of 0.5 to 10 μm, and more preferably 0.5 to 3 μm.

Next, an example of the method for producing the polyolefin laminated film of the present invention will be described.

Polypropylene containing 0.2 to 1.0% by weight of an antistatic agent added to one extruder and ethylene added to another extruder at 0.5
-25% by weight of ethylene / propylene copolymer is supplied, melted at 230 to 300 ° C, coextruded, and wound on a cooling drum (130 to 100 ° C) to form a sheet.

This unstretched sheet was introduced into a roll group and heated to 100 to 130 ° C. and stretched 3 to 7 times to obtain a uniaxially stretched film. In order to further stretch in the perpendicular direction, it is introduced into a tenter and stretched 5 to 15 times in an atmosphere of 150 to 180 ° C.
If necessary, relaxation and heat fixation were performed in an atmosphere of 140 to 170 ° C. to obtain a biaxially stretched polyolefin film.

In addition, without coextruding as described above, first, polypropylene with 0.2 to 1.0% by weight of an antistatic agent added was supplied to one extruder to prepare an unstretched sheet, It is also possible to use a method in which the uniaxially stretched polypropylene film is stretched in the direction of 1, the ethylene propylene copolymer extruded from another extruder is laminated, and the laminated product is stretched in the transverse direction.

The surface treatment (corona discharge treatment) is applied to the ethylene-propylene copolymer layer of the polyolefin laminated film thus obtained. To obtain a wetting index of 34 dyne / cm or more, the surface of the ethylene-propylene copolymer can be obtained by corona discharge treatment, but corona discharge treatment in a mixed gas of nitrogen and carbon dioxide is preferable.

The polyolefin laminated film of the present invention is preferably used by laminating it to another substrate, and may be laminated by applying aqueous ink printing or applying an aqueous adhesive on the surface of the coating layer of the present invention.

In this case, on the opposite surface of the polyolefin laminated film of the present invention, that is, on the surface of the base material layer, ethylene propylene copolymer, ethylene butene copolymer, propylene butene copolymer, ethylene propylene butene terpolymer, etc. It is preferred that the olefin copolymers of and the blends thereof are laminated. It is more preferable that heat sealability or vapor deposition suitability is imparted. The laminated thickness is preferably 0.5 to 10 μm.

Other substrates to be laminated include unstretched or uniaxially or biaxially stretched films, and polypropylene, polyethylene, nylon, polyethylene, nylon, polyester, cellophane, K-coated cellophane, etc., and the stretched film is preferable. The thickness of this film is 3 to
100μ is good. It can also be used by subjecting other substrates to be laminated to vapor deposition or printing.

The method of measuring the characteristics and the evaluation criteria in the present invention are as follows.

(1) Wetting index Based on JIS K-6768.

(2) Surface resistivity The electrical resistance of the unit surface of the insulator measured according to the volume resistivity test of JIS C-2330, which is the resistance (Rs) between two electrodes in contact with a sample (film). Applied voltage (V) and current flowing on the film surface (Is)
, That is, Rs = V / Is, and a value obtained by converting this into a unit electrode distance is defined as the surface specific resistance, and the unit is represented by Ω.

The conversion formula when the annular electrode is used is as follows.

Surface specific resistance = π (D + d) Rs / (D−d) d: Outer diameter of inner electrode (main electrode) metal ring (cm) D: Outer electrode (counter electrode) inner diameter of metal ring (cm) Rs: Surface resistance (Ω) The measurement was carried out with a super insulation meter (R-503) room temperature measurement box (P-601) manufactured by Kawaguchi Denki Seisakusho.

(3) Printing Adhesiveness Cellotape was attached to the surface printed with the water-based printing ink (acrylic copolymerization type) and peeled off, and the adhesiveness of the ink was evaluated as follows.

Grade 5: Peeled area less than 5% 〃 4: Peeled area 5% to less than 10% 〃 3: Peeled area 10% to less than 25% 〃 2: Peeled area 25% to less than 50% 〃 1: Peeled The printed surface having an area of 50% or more was written with a pencil and evaluated by the hardness of the removed pencil. The harder the better.

(5) Adhesive Strength After bonding the evaluation surfaces with an aqueous adhesive (vinyl acetate-based), the mixture was left at room temperature and normal humidity for 3 days, and then the 180-degree peel strength was measured.

(6) Blocking shearing force (evaluation of blocking resistance) A sample film having a width of 3 cm and a length of 10 cm was superposed over a length of 4 cm, and 40 ° C. (40 g in an atmosphere of 80% RH).
After standing for 24 hours under a load of / cm ^2, the force required for shear peeling is measured with a tensile tester. The smaller the value, the better the blocking resistance.

(7) Quantitative determination of ethylene content The quantitative determination of ethylene content is usually carried out using infrared absorption spectrum, at 1170 cm ^-1 due to polypropylene and 715 to 725 cm ^-1 or 73 due to copolymerized ethylene.
It can be determined by the calibration curve method from the absorbance ratio of ⁰ to 735 cm ^-1 . The ethylene component referred to in the present invention can be identified by the presence or absence of absorption at 730 to 735 cm ^-1 in the infrared absorption spectrum.

(8) Ratio of Number of Nitrogen Atoms to Number of Carbon Atoms (N / C) The ratio N / C of the number of nitrogen atoms to the number of carbon atoms is a value determined by the following method.

Kokusai Denki Co., Ltd. ESCA spectrometer ES20
The film surface was measured under the following conditions using a 0 type.

Excitation X-ray: AlKα ray (1486.6 eV) X-ray output: 10 KV 20 mA Temperature: 20 ° C. Kinetic energy correction: Neutral carbon Was adjusted to 1202.0 eV.

From the obtained spectrum, the ratio of the area ratio of the C _1S peak and the N _1S peak (the number of nitrogen atoms / the number of carbon atoms), that is, the value of N / C was used.

[Examples] Hereinafter, the present invention will be described in more detail based on Examples.

Example 1 Polypropylene containing 0.6% of an antistatic agent (betaine-type amphoteric surfactant) added to one extruder (MI2.
5), ethylene propyken copolymer (ethylene content 6%, MI 5.0) is supplied to another extruder, the former is used as a base layer and the latter is used as a coating layer, melted at 280 ° C. and coextruded at 40 ° C. It was wound around a cooling drum to form a sheet. This unstretched sheet is introduced into a roll group and stretched 5.5 times while being heated to 125 ° C., further introduced into a tenter, stretched 10 times in the transverse direction at 165 ° C., and heat set in a 160 ° C. atmosphere. ,
Biaxially stretched film (base layer 23μ, coating layer 2
μ). The surface of the coating layer of this film was subjected to corona discharge treatment in a mixed gas of nitrogen and carbon dioxide gas to have a wetting index of 40 dynes / cm. The surface was printed with aqueous ink. The evaluation results of the film are shown in Table 1.

In addition, a film was prepared by laminating the treated surfaces of the above laminated film via an aqueous adhesive. The evaluation results of the film are shown in Table 1.

Example 2 The procedure of Example 1 was repeated except that the ethylene content of the ethylene-propylene copolymer was 20% by weight and the surface treatment was adjusted to 35 dyne / cm. Table 1 shows the evaluation results of the film.
It was shown to.

Comparative Example 1 The procedure of Example 2 was repeated except that polypropylene containing no antistatic agent was used for the base material layer. The evaluation results of the film are shown in Table 1.

Comparative Example 2 The procedure of Example 1 was repeated except that the coating layer portion was made of polypropylene (MI2.5). The evaluation results of the film are shown in Table 1.

Comparative Example 3 The procedure of Example 1 was repeated except that the coating layer portion was a propyne butene copolymer (butene amount: 5% by weight MI70).
The evaluation results of the film are shown in Table 1.

Comparative Example 4 An ethylene vinyl acetate copolymer (vinyl acetate 10
The same as Example 1 except that the weight% MI10) was used. The evaluation results of the film are shown in Table 1.

Comparative Example 5 A biaxially stretched film was prepared in the same manner as in Example 1. The surface of the coating layer of this film was subjected to corona discharge treatment in the atmosphere. The evaluation results of the film are shown in Table 1.

The following can be seen from Table 1.

The films of Examples 1 and 2 of the present invention had a low blocking shearing force, and the printing of the aqueous ink had good adhesiveness and excellent scratch resistance. Further, the application with a water-based adhesive was also uniform and good, and the adhesive strength was strong.

In Comparative Example 1, although the surface resistivity was high and the blocking shearing force was low, the adhesiveness of the aqueous ink was poor and the adhesive strength of the aqueous adhesive was low.

In Comparative Examples 2 and 3, although the surface resistivity was low, the adhesion evaluation of the water-based ink and the adhesive was low.

Comparative Example 4 has low surface resistivity, adhesiveness of water-based ink,
The adhesive strength of the water-based adhesive was excellent, but the scratch resistance was extremely poor, and the film easily blocked.

In Comparative Example 5, since the N / C was below the range, the adhesion of the water-based ink, the adhesion of the water-based adhesive, and the adhesive strength were insufficient.

[Advantages of the Invention] As described above, the present invention uses an antistatic agent in an amount of 0.2 to 1.0.
A biaxially stretched film mainly containing polypropylene by weight and having a coating layer composed mainly of an ethylene-propylene copolymer having an ethylene content of 0.5 to 25% by weight is laminated on one side of the film. The ratio of the number of nitrogen atoms N to the number of carbon atoms C (N / C) is 0.005 to 0.10, the wetting index is 34 dyne / cm or more, and the surface resistivity is 9 × 10.
^Since it was a polyolefin laminated film having a resistance of ¹³ Ω or less, the following excellent effects were obtained.

(1) The adhesion of the water-based printing ink was excellent, and the printing ink was resistant to scratching.

(2) The adhesive strength was excellent when laminating with an aqueous adhesive.

(3) Since it has excellent blocking resistance and antistatic property, it has excellent processability.

(4) Since water-based printing inks and water-based adhesives can be used, environmental pollution due to organic solvents does not occur, and it is excellent in environmental hygiene.

Claims (1)

[Claims] 1. An ethylene-propylene copolymer containing 0.2 to 1.0% by weight of an antistatic agent and having 0.5 to 25% by weight of ethylene on one side of a biaxially stretched film mainly composed of polypropylene. And a ratio of the number of nitrogen atoms N to the number of carbon atoms C (N / C) on the surface of the coating layer is 0.005 to 0.10 and the wetting index is 34.
A polyolefin laminated film having a dyne / cm or more and a surface specific resistance of 9 × 10 ¹³ Ω or less.