JPH08134242A - Packaging film - Google Patents

Abstract

PURPOSE: To obtain a packaging film improved in gas-barrier properties and moistureproofness and having good slipperiness, heat sealability, and clarity by coating a biaxially oriented polypropylene film with a specific topcoating agent. CONSTITUTION: A packaging film is obtd. by coating both sides of a biaxially oriented polypropylene film with a topcoating agent which contains 100 pts.wt. vinylidene chloride copolymer, 5-15 pts.wt. liq. paraffin, 5-15 -pts.wt. paraffin wax having a mol.wt. of 500-1,000 and an m.p. of 40-100 deg.C, 0.05-0.5 pt.wt. org. or inorg. powder having an average particle size of 1-6μm, and 0.2-1.5 pts.wt. antistatic agent. The liq. paraffin and/or the paraffin wax is present on the surface of and in the topcoating layer as a disperse phase having a lamellar structure with an average particle size of 0.1-0.7μm. The vinylidene chloride content of the copolymer is pref. 80-92wt.%.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a packaging film having improved gas barrier properties and moisture resistance. More specifically, the present invention relates to a packaging film having good slipperiness, heat sealability, and transparency, which is obtained by laminating a topcoat layer containing a vinylidene chloride polymer as a main component on both surfaces of biaxially oriented polypropylene.

[0002]

2. Description of the Related Art A packaging material in which a vinylidene chloride copolymer is laminated on a plastic film is widely used because of its excellent gas or water vapor barrier property. Especially 2
A packaging material in which a vinylidene chloride-based copolymer is laminated on an axially stretched polypropylene film is used as a film for packaging foods and luxury items.

In the production of these packaging films,
The vinylidene chloride copolymer is coated with a water dispersion or a solution of an organic solvent on a substrate and dried. In order to improve the gas barrier property and moisture resistance of the packaging film, it is necessary to increase the crystallinity of the vinylidene chloride-based copolymer, but in this case, the heat sealability decreases and the high-speed packaging property is impaired. there were. In addition, when a vinylidene chloride copolymer with low crystallinity is used to maintain heat sealability and ensure suitability for high-speed packaging, not only the gas barrier and moisture resistance of the packaging film but also blocking resistance. There was a problem that slipperiness was insufficient.

Therefore, as a method for improving gas barrier properties, moisture resistance, blocking resistance and slipperiness, a top coat layer containing a vinylidene chloride copolymer as a main component and containing wax and / or organic or inorganic powders. Is used. For example, JP-A-49-9607
No. 4 discloses a topcoat layer containing a microcrystalline wax, and JP-B No. 61-34391 and JP-B No. 3-63586 propose a topcoat layer containing a wax and an organic and / or inorganic powder. There is.

[0005]

However, although these methods can considerably improve the blocking resistance and the slipping property, in order to cope with the speeding up of the packaging machine due to the recent strong demand for the improvement of the packaging productivity, Still not enough. Nothing has been obtained that satisfies all of the most important properties as a packaging material, that is, gas barrier property, moisture proof property and heat seal property.

[0006]

Means for Solving the Problems That is, the present invention is a packaging film comprising a biaxially oriented polypropylene film and a topcoat agent laminated on both sides thereof, wherein the topcoat agent is a vinylidene chloride copolymer. As a main component, a) 5 to 15 parts by weight of liquid paraffin, and b) a molecular weight of 500 to 100 relative to 100 parts by weight of vinylidene chloride copolymer.
Paraffin wax 5 having a melting point of 40 to 100 ° C. 0
˜15 parts by weight, c) 0.05 to 0.5 parts by weight of organic or inorganic powder having an average particle size of 1 to 6 μ, d) 0.2 to 1.5 parts by weight of an antistatic agent, And a and / or b are present as a dispersion having a lamellar structure having an average particle diameter of 0.1 to 0.7 μm on the surface of the topcoat agent and in the topcoat agent.

The biaxially stretched polypropylene film referred to in the present invention is produced by melt extruding a polypropylene resin and then biaxially or sequentially biaxially stretching it, and has been conventionally used for packaging materials such as foods, pharmaceuticals and clothing. Say what has been used. In the present invention, although not particularly limited, the film thickness is generally 15 to 40 μm. Further, it is preferable that a surface treatment such as a corona discharge treatment is applied in order to maintain the adhesion when the topcoat agent is laminated directly or via an anchor agent.

The top coat agent of the present invention contains a vinylidene chloride copolymer as a main component. The vinylidene chloride-based copolymer referred to in the present invention mainly comprises vinylidene chloride,
Methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, (meth) acrylic acid 2
(Meth) acrylic acid esters such as ethylhexyl,
A radical polymerizable monomer such as (meth) acrylonitrile, (meth) acrylic acid, 2-hydroxyethyl (meth) acrylate, glycidyl ester of (meth) acrylic acid, vinyl chloride, or styrene may be copolymerized if necessary.

In the present invention, the content of vinylidene chloride monomer unit in the vinylidene chloride copolymer is 80
It is preferably ˜92% by weight. When the content of the vinylidene chloride monomer unit is less than 80, the top coat agent has a low crystallinity, so that the blocking resistance, slipperiness, gas barrier property and moisture resistance are insufficient. The content of the vinylidene chloride monomer unit of the vinylidene chloride-based copolymer is a formula represented by 10 ≧ V1−V2 ≧ 1 in order to have both heat sealability and slipperiness after packaging of the contents. Is preferred.

However, V1 is the vinylidene chloride monomer unit content (% by weight) of the vinylidene chloride-based copolymer in the top coat agent on the surface (surface) that does not come into contact with the packaged object, and V2 is the contact with the packaged object. The content (% by weight) of the vinylidene chloride monomer unit of the vinylidene chloride-based copolymer in the top coating agent on the surface (back surface) to be coated. If the content difference of vinylidene chloride monomer units of the front and back vinylidene chloride copolymers is less than 1% by weight, the effect of improving the slipperiness of the surface is not sufficient, and if it exceeds 10% by weight, the blocking resistance and slipperiness of the back surface Is not sufficient, which is not preferable.

The vinylidene chloride copolymer according to the present invention preferably has a weight average molecular weight of 40,000 to 200,000. If the weight average molecular weight is less than 40,000, the flexibility of the film is poor, and if it is more than 200,000, the surface property of the film is poor. In the present invention, the top coat agent is
5-1 to 100 parts by weight of vinylidene chloride copolymer
It contains 5 parts by weight of liquid paraffin. If the content of liquid paraffin is less than 5 parts by weight, gas barrier properties, moisture resistance and slipperiness at low temperatures are insufficient, and if it exceeds 15 parts by weight, facilities such as packaging machines are contaminated. The liquid paraffin as used herein is a hydrocarbon wax that is liquid at room temperature.

In the present invention, the top coat agent has a molecular weight of 5 to 15 parts by weight and a melting point of 40 to 100 with respect to 100 parts by weight of the vinylidene chloride copolymer.
It contains paraffin wax which is at 0 ° C. When the content of paraffin wax is less than 5 parts by weight, gas barrier properties, moisture resistance and slipperiness at high temperatures are insufficient, and when it exceeds 15 parts by weight, the transparency of the packaging film is insufficient. If the molecular weight of paraffin wax is less than 500 or the melting point is less than 40 ° C, the equipment such as a packaging machine is contaminated and the molecular weight is 10
If the melting point exceeds 00 or the melting point exceeds 100 ° C, the slipperiness is insufficient.

Further, in the present invention, liquid paraffin and / or paraffin wax is present in the top coat agent as a dispersion having a lamellar structure having an average particle size of 0.1 to 0.7 μm. The dispersion having a lamellar structure of liquid paraffin and / or paraffin wax contributes to a dramatic improvement in gas barrier properties and moisture resistance. If the average particle size of the dispersion is less than 0.1 μ, the effect is insufficient, and if it exceeds 0.7 μ, the transparency of the packaging film is insufficient.

In the present invention, the top coating agent is used in an amount of 0.05 to 100 parts by weight of the vinylidene chloride copolymer.
0.5 parts by weight of an organic or inorganic powder having an average particle size of 1 to 6 μ is contained. If the content of the powder is less than 0.05 parts by weight, the blocking resistance is insufficient and there is a problem in slipperiness when unwinding the packaging film, and if it exceeds 0.5 parts by weight, the gas barrier property of the packaging film, Moisture resistance and transparency are insufficient. If the average particle size of the powder is less than 1 μ, the blocking resistance is insufficient, and if it exceeds 6 μ, the transparency of the packaging film is insufficient. The organic or inorganic powder referred to in the present invention may be any one that has been used for film coating of vinylidene chloride-based copolymer, but, for example, polyolefin such as polypropylene or polyethylene, polymethylmethacrylate, polyamide , Organic powder such as polyvinylidene chloride copolymer, and inorganic powder such as spherical silica and amorphous silica.

In the present invention, the top coat agent is 0.2 to 100 parts by weight of the vinylidene chloride copolymer.
It contains 1.5 parts by weight of antistatic agent. Content is 0.2
If it is less than 1.5 parts by weight, slippage due to static electricity may occur, and if it exceeds 1.5 parts by weight, the packaging film may be colored.
The antistatic agent referred to here is a cationic or zwitterionic agent, and, for example, an ammonium salt type,
It is a pyridium salt-type cationic, sulfate-type, and sulfonate-type zwitterionic antistatic agent.

In the packaging film of the present invention, the surface of the biaxially stretched polypropylene film may be activated by corona discharge treatment, flame treatment or the like in order to adhere the topcoat agent and the biaxially stretched polypropylene film. Further, if necessary, the top coat agent may be laminated after applying the anchor coat agent. As the anchor coating agent, an acrylic acid ester-based copolymer, an aqueous dispersion of an acrylic acid ester-styrene-based copolymer, a polyester resin,
It is possible to use a mixture of a thermoplastic resin such as a polyether resin and an adduct or burette compound of polyisocyanates such as tolylene diisocyanate and hexamethylene diisocyanate.

The packaging film of the present invention can be prepared by applying a water dispersion of the above-mentioned top coat agent to a biaxially oriented polypropylene film, followed by drying and winding. Furthermore, if necessary, it can be aged at room temperature to 60 ° C. for 1 day to several days.

[0018]

EXAMPLES In the examples, all parts are parts by weight.
The method of measuring the characteristics is as follows. (1) Gas barrier property (oxygen permeability) is JIS-K-
It was measured by the 7126B method (isobaric method).

(2) Moisture resistance (water vapor transmission rate) is JIS
-Z-0208 (cup method) was used for measurement. (3) The slipperiness was measured by a method according to ASTM 1984-63. (4) The heat-sealing property was measured at a temperature of 10 at the surface top coat surface and the back surface top coat surface of the packaging film.
Under conditions of 0 ° C., pressure of 1 Kg / cm ² and time of 0.5 seconds,
It was heat-sealed with a width of 15 mm. Using a Tensilon tensile tester, the heat sealing strength was measured as an average of 4 points at a tensile speed of 100 mm / min.

(5) For the transparency, the haze value of the packaging film was measured using a haze meter (manufactured by Suga Test Instruments). (6) The lamellar structure in the top coat agent was measured by observing the cross section of the packaging film with a scanning electron microscope.

[0021]

Example 1 Vinylidene chloride copolymer latex (Saran latex L533, vinylidene chloride monomer unit content = about 90%, weight average molecular weight = about 100,000, manufactured by Asahi Kasei) 100 parts (solid content = about 50%), Liquid paraffin 6 parts, paraffin wax (melting point = 45 ° C., molecular weight =
900) 6 parts, silica powder (Sylysia 320, grain system =
An aqueous dispersion of a topcoat agent was prepared with 0.01 parts of 2μ, manufactured by Nippon Silysia Chemical Ltd., 0.5 parts of an antistatic agent (Esocard C / 12, cationic, manufactured by Lion Akzo), and 12 parts of ion-exchanged water.

However, liquid paraffin and paraffin wax were blended in such a manner that they were melted by heating and then dispersed in ion-exchanged water to form an emulsion. Separately, use a Meyer bar to apply a urethane-based anchoring agent to both sides of a biaxially stretched polypropylene film that has been subjected to corona discharge treatment, at 0.3 g / m ²
It was applied and dried. On the surface of this anchor agent layer, the above-mentioned aqueous dispersion of the top coat agent was applied with a Mayer bar to one side of 2 g /
m ² (solid content) applied, dried at 100 ° C. for 30 seconds,
A packaging film was obtained. The evaluation results of the obtained packaging film are shown in Table 1.

Wax particles having a lamellar structure of 0.5 μ were dispersed.

[0024]

Example 2 An aqueous dispersion of a top coat agent was prepared in the same manner as in Example 1 except that the amount of liquid paraffin was changed to 3 parts. The evaluation results of the obtained packaging film are shown in Table 1.
Wax particles having a lamellar structure of 0.4 μm were dispersed.

[0025]

Example 3 An aqueous dispersion of a topcoat agent was prepared in the same manner as in Example 1 except that the amount of paraffin wax having a melting point of 45 ° C. was changed to 3 parts. The evaluation results of the obtained packaging film are shown in Table 1. Wax particles having a lamellar structure of 0.6μ were dispersed.

[0026]

Example 4 An aqueous dispersion of a topcoat agent was prepared in the same manner as in Example 1 except that the amount of silica powder was changed to 0.03 part. The evaluation results of the obtained packaging film are shown in Table 1. Wax particles having a lamellar structure of 0.6μ were dispersed.

[0027]

Example 5 The top coat agent of Example 1 was applied and dried on one side of the biaxially oriented polypropylene film obtained by applying and drying the anchor agent in Example 1, and then the vinylidene chloride copolymer latex (Saran latex L502, Vinylidene chloride monomer unit content = about 85%, weight average molecular weight = about 100,000, manufactured by Asahi Kasei) (solid content = about 50)
%) 100 parts, liquid paraffin 3 parts, paraffin wax (melting point = 45 ° C., molecular weight = 900) 3 parts, silica powder (Sylysia 320, grain system = 2μ, manufactured by Nippon Silysia Chemical Ltd.) 0.01 part, antistatic agent (Esocard C / 12, cationic, manufactured by Lion Akzo) 0.5 parts and ion exchange water 12 parts were used to prepare an aqueous dispersion of the topcoat agent. Applied to the
It was dried to obtain a packaging film. Table 1 shows the evaluation results of the obtained packaging film.

[0028]

Comparative Example 1 The procedure of Example 1 was repeated except that the liquid paraffin was removed from the top coat agent. Table 1 shows the evaluation results of the obtained packaging film. The presence of wax particles having a lamellar structure was not recognized.

[0029]

Comparative Example 2 The procedure of Example 1 was repeated except that the paraffin wax as the top coat agent was omitted. Table 1 shows the evaluation results of the obtained packaging film. No wax particles having a lamellar structure were found.

[0030]

[Comparative Example 3] The same procedure as in Example 1 was carried out except that the silica powder as the top coat agent was omitted. Table 1 shows the evaluation results of the obtained packaging film.

[0031]

Comparative Example 4 The procedure of Example 1 was repeated except that the amount of liquid paraffin was changed to 10 parts. Table 1 shows the evaluation results of the obtained packaging film.

[0032]

Comparative Example 5 The procedure of Example 1 was repeated except that the amount of paraffin wax having a melting point of 45 ° C. was changed to 10 parts.
Table 1 shows the evaluation results of the obtained packaging film.

[0033]

[Table 1]

[0034]

The packaging film of the present invention has remarkably improved gas barrier property and moisture proof property as compared with the conventional one, and has both slipperiness and heat sealing property, for example, high speed of caramel and snacks It is particularly suitable for overlapping.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area C08L 91:00 91:06) B29K 23:00 B29L 9:00

Claims (3)

[Claims] 1. A packaging film comprising a biaxially oriented polypropylene film and a top coating agent laminated on both sides thereof, wherein the top coating agent comprises a vinylidene chloride copolymer as a main component and a vinylidene chloride copolymer. A) 5 to 15 parts by weight of liquid paraffin, b) 5 to 15 parts by weight of paraffin wax having a molecular weight of 500 to 1000 and a melting point of 40 to 100 ° C., and c) an average particle size of 1 to 100 parts by weight of
An organic or inorganic powder having a size of 6 μ, 0.05 to 0.5 parts by weight, d) 0.2 to 1.5 parts by weight of an antistatic agent, and a and / or b being a top coat surface and a top. A packaging film, which is present as a dispersion having a lamellar structure having an average particle diameter of 0.1 to 0.7 µ in a coating agent. 2. The vinylidene chloride copolymer has a vinylidene chloride monomer unit content of 80 to 92% by weight and a weight average molecular weight of 40,000 to 200,000.
The packaging film according to claim 1, wherein 3. A vinylidene chloride-based copolymer having a vinylidene chloride monomer unit content of 10 ≧ V1-V2 ≧ 1.
The packaging film according to claim 1 or 2, which has the formula: However, V1 is the surface (surface) that does not contact the packaged object
Content of vinylidene chloride monomer unit of the vinylidene chloride copolymer in the top coat agent of
Is the vinylidene chloride monomer unit content (% by weight) of the vinylidene chloride-based copolymer in the topcoat agent on the surface (back surface) that contacts the object to be packaged.