JPH09143294A - Nonorientated polypropylene film metallized with metal oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare an unorientated polypropylene film metallized with a metal oxide, which is transparent, high in gas barrier properties, excellent in secondary processability such as slit or laminate, etc., and is useful for various packings. SOLUTION: The objective film is prepared by adding 0.05-0.5 pt.wt. of a lubricant to a mixed resin of 85-99wt.% of a polypropylene random copolymer and 15-1wt.% of a high-density polyethylene to give a film and metallizing the film with a metal oxide, which has >=0.7GPa Young's modulus at least in one direction of the film metallized with the metal oxide, 60-90% light transmittance and <=2.5g/m<2> /d water vapor transmission.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a metal oxide vapor-deposited unstretched polypropylene film. More specifically, the present invention relates to a metal oxide vapor-deposited unstretched polypropylene film which is transparent, has excellent gas barrier properties, and has excellent secondary processability by subjecting a non-stretched polypropylene film to vapor deposition of a metal oxide.

[0002]

2. Description of the Related Art Conventionally, unstretched polypropylene film is
It has excellent transparency, mechanical properties, moisture resistance, and heat sealability, and is laminated with a heat-resistant base material such as biaxially oriented polypropylene film or polyethylene terephthalate film, and widely used as a heat seal layer of packaging materials for packaging applications. There is. Further, in order to improve the gas barrier property of the film, it is widely used as a gas barrier film coated with vinylidene chloride. However, vinylidene chloride has been pointed out to have an adverse effect on the environment because chlorine-based gas is generated during waste incineration, and it is said that the burden on the incinerator for purifying exhaust gas is large. Therefore, as a packaging film for solving this environmental problem, a structure of a heat-resistant film / printing layer / adhesive layer / vapor-deposited film / heat-resistant film / adhesive layer / unstretched polypropylene film provided with a metal vapor-deposited film is mainly used. . In recent years, there has been a strong demand for simplification of the film structure and cost reduction. Further, a vapor deposition film is required to have transparency, and a vapor deposition film which can be used in a microwave oven is desired. Therefore, for the purpose of simplifying the structure and reducing the cost, a structure in which a heat-resistant film is omitted by subjecting an unstretched polypropylene film to metal vapor deposition has been studied. However, since the unstretched polypropylene film has a low Young's modulus, it has a low tensile strength during vapor deposition and cracks in the vapor deposition layer, and also has a problem that the gas barrier performance as a packaging bag is insufficient due to poor bag-making processability. there were.
Further, as a transparent gas barrier film, one having silicon oxide or aluminum oxide formed on the film is disclosed in JP-B-53.
No. 12953 and JP-A No. 62-179935. However, these techniques have not been able to impart a high gas barrier property to unstretched polypropylene films.

[0003]

DISCLOSURE OF THE INVENTION The present invention has a transparent and high gas barrier property obtained by subjecting an unstretched polypropylene film to metal oxide vapor deposition, which cannot be achieved by such a technique, and further has a secondary processability ( Vapor deposition processing, lamination processing)
The present invention provides a metal oxide-deposited unstretched polypropylene film excellent in

[0004]

As a result of careful examination, in order to solve the above-mentioned problems, a mixed resin of 85 to 99% by weight of a polypropylene random copolymer and 15 to 1% by weight of high-density polyethylene and a lubricant is added to the mixture resin. A film formed by vapor-depositing a metal oxide on a film formed by adding .05 to 0.5 part by weight, at least one of the metal oxide vapor-deposited films.
Young's modulus in the direction is 0.7 GPa or more, and light transmittance is 6
A metal oxide vapor-deposited unstretched polypropylene film having a moisture vapor transmission rate of 0 to 90% and a water vapor transmission rate of 2.5 g / m ² · d or less.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The polypropylene random copolymer of the present invention (hereinafter abbreviated as r-CPP) is a copolymer of propylene and α-olefin having a substantially isotactic structure. As the α-olefin monomer to be copolymerized, ethylene, butene-1, pentene-1, 4-
Methylpentene-1, hexene-1, octene-1, etc. are mentioned, and ethylene and butene-1 are particularly preferable. α-
Copolymerization amount of olefin monomer is 3 to 15% by weight
Is preferable, in the case of ethylene monomer, the range is 2 to 6% by weight, and in the case of butene-1 monomer, the range is preferably 3 to 10% by weight. As a concrete implementation response, ethylene-
Propylene copolymer (hereinafter abbreviated as EPC), ethylene-propylene-butene-1 copolymer (hereinafter abbreviated as EPBC), propylene-butene-1 copolymer (hereinafter B)
(Abbreviated as PC) and the like. Since the non-stretched polypropylene film uses the non-deposited surface as a heat seal layer during bag making, the melting point of r-CPP is preferably 125 to 145 ° C. from the viewpoint of heat seal strength. Further, the melt flow index (MFI) of r-CPP is preferably in the range of 1 to 15 g / 10 minutes because the extrusion film-forming property is good, and more preferably 2 to 10 g / 10 minutes.

Next, the high density polyethylene (hereinafter abbreviated as HDPE) of the film composition of the present invention has a density of 0.9.
The melting point is 3 or higher, preferably 0.94 or higher, and the melting point is 125 ° C. or higher, preferably 130 ° C. or higher.
The mixing amount of HDPE is 1 to 15% by weight, preferably 3 to 1
The range is 0% by weight. The purpose of adding HDPE is to increase the crystallinity of the film to increase the Young's modulus and improve the secondary workability. When the mixing amount is less than 1% by weight, the Young's modulus of the film does not increase, and the slits and the laminate are laminated. At times, wrinkles are formed, or the film stretches and cracks in the vapor deposition layer, which deteriorates the gas barrier property and also deteriorates the secondary workability. On the other hand, if it exceeds 15% by weight, the film is whitened, the light transmittance is lowered, and the heat seal strength during bag making is unfavorable.

The lubricant contained in the film of the present invention may be either inorganic particles and / or crosslinked organic particles, or a mixture thereof. The particle shape is preferably spherical, and the particle diameter is preferably 1 to 6 μm. The addition amount is 0.0
5 to 0.5 parts by weight, preferably 0.1 to 0.3
% By weight. If the added amount is less than 0.05 parts by weight, when the vapor-deposited film is rewound, slippage with the non-vapor-deposited surface is poor and blocking occurs, the vapor-deposited layer is cracked, and the gas barrier property deteriorates. On the other hand, if the addition amount exceeds 0.5 parts by weight, the film surface becomes too rough and the transparency and heat seal properties deteriorate, and the adhesiveness of the vapor deposition layer deteriorates and the gas barrier property deteriorates, which is not preferable.

The film of the present invention preferably contains a small amount of a heat stabilizer, an antioxidant and the like, if necessary. For example, as the heat stabilizer, 2,6-di-tert-butyl-4-methylphenol (BHT) or the like is 0.5 wt% or less, and as the antioxidant, tetrakis- (methylene-).
(3,5-di-tert-butyl-4-hydroxy-hydrocinnamate)) Butane ("Irganox")
1010) and the like are preferably added in an amount of 0.1% by weight or less.

The Young's modulus in at least one direction of the film of the present invention must be 0.7 GPa or more, and particularly, the Young's modulus in the longitudinal direction of the film is preferably 0.7 GPa or more. When Young's modulus is less than 0.7 GPa,
Inferior tensile strength during vapor deposition and laminating,
It is not preferable because cracks occur in the vapor deposition layer and the gas barrier property deteriorates.

The thickness of the film of the present invention is not particularly limited, but it is preferably 10 to 100 μm, more preferably 20 to 70 μm.

The surface of the unstretched polypropylene film of the present invention to be vapor-deposited is subjected to corona discharge treatment to increase the wetting tension of the film surface to 35 mN / m or more, so that the adhesion of the vapor-deposited film is improved, which is preferable. . The atmosphere gas at the time of the corona discharge treatment at this time may be air, carbon dioxide gas or a mixed system of nitrogen / carbon dioxide gas,
Mixed gas of nitrogen / carbon dioxide (volume ratio = 95/5 to 50 /
The corona treatment in 50) is preferable because the wetting tension of the film surface increases to 35 mN / m or more.

Next, the metal oxide deposited on the unstretched polypropylene film of the film of the present invention is a film of a metal oxide such as aluminum, zinc, magnesium or silicon. Among them, incomplete aluminum oxide is preferable in terms of adhesion to the film, gas barrier property, and workability.

Here, the incomplete aluminum oxide vapor deposition layer means a small amount of aluminum metal (Al) and complete aluminum oxide (Al ² ) as the metal species constituting the vapor deposition layer.
O ³ ). The means for changing the light transmittance is, in a vacuum vapor deposition device equipped with a film traveling device, while heating and evaporating aluminum metal, supplying oxygen gas to the vaporized vapor portion and oxidizing aluminum to agglomerate and deposit on the traveling film surface. Then, a vapor deposition layer is attached. At this time, the light transmittance of the incomplete aluminum oxide vapor deposition film can be changed by changing the ratio of the evaporation amount of aluminum and the supplied oxygen gas amount. The thickness of the incomplete aluminum oxide vapor deposition layer at this time is preferably 5 to 50 n.
m, more preferably 10 to 30 nm.

The light transmittance of the metal oxide-deposited unstretched polypropylene film of the present invention is preferably in the range of 60 to 90%. The complete metal oxide vapor deposition film of the vapor deposition layer has a light transmittance of more than 90% and becomes a transparent film, but it is not preferable because it has a high water vapor transmission rate. Further, if the light transmittance is less than 60%, the transparency is inferior, which is not preferable.

The water vapor transmission rate of the film of the present invention is preferably 2.5 g / m ² · d or less, and when the water vapor transmission rate exceeds 2.5 g / m ² · d, contents requiring moisture resistance, For example, when it is used as a packaging bag for potato chips or the like, the long-term storability of the contents is deteriorated, which is not preferable.

The metal oxide vapor-deposited unstretched polypropylene film of the present invention is used as a packaging material by laminating it with another substrate through an adhesive or an adhesive resin.

Next, the method for producing the film of the present invention will be described.

First, a mixed resin of r-CPP, HDPE and a lubricant is supplied to a twin-screw extruder, melt-kneaded at a temperature of 230 to 280 ° C., melt-extruded in a gut form, and the gut is passed through a water tank. After cooling, a chip is cut to a length of 3 to 5 mm to form a chip. Next, heat the chip to 80 ° C.
After drying for 5 hours or more, it is fed to a single-screw extruder and
After melting at a temperature of ~ 280 ° C and passing through a filtration filter,
A slit-shaped die is used to form a sheet, and the sheet is
It is wound around a metal drum kept at 80 ° C., cooled and solidified, and wound as a roll as an unstretched polypropylene film. The unstretched polypropylene film is preferably left standing for 5 hours or more and gradually cooled to crystallize the film. The unstretched polypropylene film thus obtained is subjected to corona discharge treatment or plasma treatment in a dilute gas under reduced pressure in order to increase the wetting tension of the surface on which vapor deposition is performed. Here, the plasma treatment is performed by introducing a small amount of oxygen, argon, helium, carbon dioxide gas or the like into a container having a vacuum degree of 133 Pa or less, and performing glow discharge from the electrode to which a high voltage is applied toward the film surface. Treatment intensity is voltage x current x electrode width / film running speed (W.min /
m ² ) but the treatment strength is preferably 3
~ 200 W · min / m ² , more preferably 5 to 50 W
・ It is min / m ² . The preferred combination when the surface is subjected to a surface treatment and the metal oxide is vapor-deposited on the surface is not particularly limited, but in the case of a metal oxide such as incomplete aluminum oxide or incomplete silicon oxide, in air or nitrogen. It is preferable to carry out at least one of corona discharge treatment and plasma treatment in a mixed gas atmosphere of carbon dioxide gas. Next, the unstretched polypropylene film is set in a vacuum vapor deposition device equipped with a film running device, and run through a cooling metal drum. At this time, while heating and evaporating the aluminum metal,
Oxygen gas is supplied to the vaporized vapor portion to oxidize aluminum and to cause cohesive deposition on the surface of the traveling film, and a vapor deposition layer is attached and wound. At this time, the light transmittance of the incomplete aluminum oxide vapor deposition film can be changed by changing the ratio of the evaporation amount of aluminum and the supplied oxygen gas amount. After vapor deposition, it is preferable to return the inside of the vacuum vapor deposition apparatus to normal pressure, slit the wound film, and aged at a temperature of 30 ° C. or more for 1 day or more because the gas barrier property is stable.

[0019]

[Method of measuring characteristic values] The characteristic values of the present invention are determined by the following measuring methods.

(1) Isotactic index (I
I) Vacuum dry the sample at 130 ° C for 2 hours. From now on weight W
Take (mg) sample, place in Soxhlet extractor and extract with boiling n-heptane for 12 hours. Next, the sample is taken out, sufficiently washed with acetone, dried at 130 ° C. for 6 hours, and thereafter, the weight W ′ (mg) is measured and obtained by the following equation.

II = (W '/ W) * 100 (%) (2) Wetting tension of the film surface It was measured by the method of JIS K-6768.

(3) Melt flow index (MF
I) Polypropylene test method according to JIS K-6758 (23
0 ° C, 2.16 kgf).

(4) Water Vapor Transmission Rate (Moisture Proof) A value measured at 40 ° C. and 90% RH in accordance with JIS Z-0208, which is shown in units of g / m ² · d.

(5) Thickness of evaporated layer of metal oxide The cross section of the film was photographed with a transmission electron microscope (TEM) under the following conditions to measure the layer thickness.

Device: JEM-12OOEX manufactured by JEOL Ltd. Observation magnification: 400,000 times Accelerated electron: 100 kV

(6) Light transmittance A metal oxide vapor-deposited unstretched polypropylene film was used with a spectrophotometer type 324 manufactured by Hitachi, Ltd. to have a wavelength of 550 nm.
It was calculated by the transmittance.

(7) Young's modulus The sample is attached to a tensile tester (manufactured by Toyo Sokki Co., Ltd.) with a gripping interval of 50 mm in accordance with JIS-K-7127. Then pulling speed 20mm / min, chart speed 500mm
The strength-elongation curve was recorded on a chart paper under the conditions, and the strength-elongation curve was obtained from the slope obtained by drawing a tangent to the rising curve from the base point.

(8) Melting point Thermal analyzer S11 manufactured by Seiko Instrument Co.
When 5 mg of a sample was heated from room temperature at a heating rate of 20 ° C./min using a mold, the melting endothermic peak accompanying the melting of crystals was taken as the melting point.

(9) Sliding property According to ASTM D-1894, both sides of the film were superposed and the coefficient of friction was measured. At this time, when the value of μs (coefficient of static friction) is less than 1.0, the slip property is good, and the result is ○.
When the slipperiness was 1.5 or more, it was evaluated as ×, and the middle thereof was evaluated as Δ.

(10) Blocking property A sample having a width of 3 cm and a length of 10 cm was superposed on both sides of the sample over a length of 4 cm, and a load of 500 g was placed thereon.
After leaving in an atmosphere of a temperature of 40 ° C. and a humidity of 85% for 24 hours, a force required for shearing peeling was measured by a tensile tester. The smaller the value is, the more excellent the blocking resistance is. The peel strength is 1.0 kg / 12 cm ² or less.
/ 12 cm ² or more was evaluated as x, and the middle one was evaluated as Δ.

(11) Heat-sealing property A biaxially oriented polypropylene film having a thickness of 30 μm and a polyurethane adhesive (main ingredient "Takelac" A, manufactured by Takeda Pharmaceutical Co., Ltd.)
-971 / Curing agent "Takenate" A-3 = 9/1) was applied with a coating bar to a thickness of about 4 μm and bonded to the vapor-deposited surface of the metal oxide vapor-deposited unstretched polypropylene film. It was aged at ℃ × 2 days to cure. After that, the non-evaporated polypropylene films of the laminated films are superposed on each other on the non-deposited surfaces, and heat-sealed by a one-sided heating method of a heat sealer under the conditions of a sealing temperature of 115 ° C., a sealing pressure of 1 kg / cm ² , and a sealing time of 2 seconds. went. Width 2c of this heat-sealed sample
Cut to m and use a tensile tester (Toyo Sokki) to
If the force required to peel the sealing surface 90 degrees at a speed of 00 mm / min is 300 g / cm or more, ○, 200 g
The evaluation was made with x being a value equal to or less than / cm and Δ being an intermediate value.

(12) Secondary workability A biaxially stretched polypropylene film having a thickness of 30 μm (water vapor transmission rate = 5.0 g / m ² · d) and a vapor deposition surface of a metal oxide vapor-deposited unstretched polypropylene film are superposed. Then, through a nip roll cooled to 30 ° C., low density polyethylene (L-705 manufactured by Sumitomo Chemical Co., Ltd.) melted to 300 ° C. is extruded and laminated to a thickness of 20 μm to obtain a laminate. The appearance and water vapor transmission rate of this laminated body were measured, and the laminated body was free of wrinkles and had a water vapor transmission rate of 2.0 g / m 2.
Less than ² · d is ○, wrinkles are included, and water vapor permeability is 2.5 g / m ² · d or more is x, wrinkle-free water vapor permeability is 2.0 g / m ² · d or more, 2.5 g / m ² · d
Those less than were evaluated as Δ.

[0033]

EXAMPLES The present invention will be described with reference to examples.

Examples 1 to 4 and Comparative Examples 1 to 4 As the resin of the present invention, ethylene-propylene-butene-
1 random copolymer (EPBC) (ethylene copolymerization amount =
2% by weight, butene-1 copolymerization amount = 5% by weight, MFI =
3.6 g / 10 min, melting point = 141 ° C.), high density polyethylene (HDPE) (MFI = 4.5 g / 10 min, melting point = 130 ° C., density = 0.937), and silicon oxide (SiO ₂ ) as a lubricant. , Particle size = 2 μm), mixed in a ratio shown in Table 1 and supplied to a twin-screw extruder, melt-extruded into a gut shape at a temperature of 240 ° C., cooled in a water tank, and then 3-5 mm with a chip cutter. It was cut into chips to obtain chips of each composition. Next, the chips are fed to a uniaxial extruder, melted at a temperature of 260 ° C., extruded into a sheet shape with a slit-shaped die through a filter, and the sheet is wound around a metal drum heated to a temperature of 50 ° C. and cooled. To obtain an unstretched film having a thickness of 25 μm. The surface of the obtained film to be vapor-deposited was subjected to corona discharge treatment in the air under the treatment condition of 40 W · min / m ² , and the film was wound into a roll with a wetting tension of 45 mN / m. The film temperature at that time was 35 ° C,
After leaving it for 24 hours to increase the crystallinity, it was slit into a small width. The film quality at this time was evaluated and shown in Table 1.
Next, the slit film with a small width was set in a vacuum vapor deposition apparatus equipped with a film running device, and 1.33 × 10 ⁻²
After making a high vacuum of Pa, it was made to run through a -20 degreeC cooling metal drum. At this time, while heating and evaporating the aluminum metal, oxygen gas was supplied to the vaporized vapor portion, and aluminum was oxidized to be agglomerated and deposited on the running film surface, and a vapor deposition layer of incomplete aluminum oxide was attached and wound. At this time, the light transmittance of the incomplete aluminum oxide vapor deposition film was changed by changing the ratio of the evaporation amount of aluminum and the supplied oxygen gas amount. After vapor deposition, return the atmospheric pressure to the vacuum vapor deposition equipment and slit the wound vapor deposition film.
The quality of each film was evaluated after aging at a temperature of 0 ° C. for 3 days, and the characteristics of the film are shown in Table 1. Next, the secondary processability of the obtained metal oxide unstretched polypropylene film was evaluated, and the characteristics are shown in Table 1. Example 1
The metal oxide vapor-deposited unstretched polypropylene films of the present invention within the range of to 4 are excellent in gas barrier property, transparency, high Young's modulus, and excellent in slipperiness, and are excellent in secondary processability. It was However, the films of Comparative Examples 1 to 4 which are out of the scope of the present invention have gas barrier properties, transparency,
The film was inferior in heat sealability and secondary processability.

[0035]

[Table 1]

[0036]

The metal oxide vapor-deposited unstretched polypropylene film of the present invention has an excellent gas barrier by vapor-depositing a specific metal oxide on an unstretched polypropylene film in which a specific resin and an additive are mixed in a specific range. It is possible to obtain a metal oxide vapor-deposited unstretched polypropylene film that exhibits excellent properties and transparency, and has excellent secondary processability such as slits and laminates and is suitable for various packaging applications.

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Claims (2)

[Claims] 1. A polypropylene random copolymer 85-
A film obtained by vapor-depositing a metal oxide on a film obtained by adding 0.05 to 0.5 parts by weight of a lubricant to a mixed resin of 99% by weight and 15 to 1% by weight of high-density polyethylene. The oxide vapor deposition film has a Young's modulus in at least one direction of 0.7 GPa or more and a light transmittance of 60 to 90.
%, A water vapor transmission rate of 2.5 g / m ² · d or less, a metal oxide vapor-deposited unstretched polypropylene film. 2. The metal oxide-deposited unstretched polypropylene film according to claim 1, wherein the polypropylene random copolymer is a copolymer of propylene and α-olefin.