JP3318479B2 - Unstretched polypropylene film deposited with metal oxide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal oxide-deposited unstretched polypropylene film. More specifically, the present invention relates to a metal oxide-deposited unstretched polypropylene film obtained by subjecting an unstretched polypropylene film to metal oxide deposition and being transparent, having excellent gas barrier properties, and having excellent secondary workability.

[0002]

2. Description of the Related Art Conventionally, unstretched polypropylene films have been
Excellent in transparency, mechanical properties, moisture resistance and heat sealability, laminated with a heat resistant base such as biaxially oriented polypropylene film or polyethylene terephthalate film, widely used as a heat seal layer for packaging materials, such as packaging applications. I have. Further, in order to improve the gas barrier property of the film, vinylidene chloride is coated thereon, and the film is widely used as a gas barrier film. However, it has been pointed out that vinylidene chloride has an adverse effect on the environment because chlorine-based gas is generated during waste incineration, and it is said that a heavy burden is imposed on an incinerator for purifying exhaust gas. Therefore, as a packaging film for solving this environmental problem, a structure of a heat-resistant film / printed layer / adhesive layer / vapor-deposited film / heat-resistant film / adhesive layer / unstretched polypropylene film provided with a metal evaporated film is mainly used. . In recent years, there has been a high demand for simplification of the film configuration and cost reduction, and further, there has been a demand for a vapor deposition film that requires transparency and that is compatible with a microwave oven. Therefore, for the purpose of simplifying the configuration and reducing the cost, a configuration in which the unstretched polypropylene film is subjected to metal vapor deposition to eliminate the heat-resistant film has been studied. However, unstretched polypropylene film has low Young's modulus, low tensile strength at the time of vapor deposition, cracks in the vapor deposited layer, and has poor gas barrier performance as a packaging bag due to poor bag making processability. there were.
As a transparent gas barrier film, a film formed of silicon oxide or aluminum oxide on a film is disclosed in
-12953 and JP-A-62-179935. However, these techniques have not been able to impart high gas barrier properties to unstretched polypropylene films.

[0003]

The present invention provides a transparent and high gas barrier property by depositing a metal oxide on an unstretched polypropylene film, which has not been achieved by such a technique. Vapor deposition, lamination)
It is an object of the present invention to provide a metal oxide vapor-deposited unstretched polypropylene film excellent in the above.

[0004]

As a result of intensive studies, in order to solve the above problems, a lubricant was added to a mixed resin of 85 to 99% by weight of a polypropylene random copolymer and 15 to 1% by weight of a high-density polyethylene. A film prepared by adding a metal oxide to a film obtained by adding 0.05 to 0.5 parts by weight of at least one of the metal oxide-deposited films.
Direction Young's modulus is 0.7 GPa or more and light transmittance is 6
A metal oxide-deposited unstretched polypropylene film characterized by having a water 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 (hereinafter abbreviated as r-CPP) of the present invention 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-
Examples thereof include methylpentene-1, hexene-1, octene-1, and the like, with ethylene and butene-1 being particularly preferred. α-
3 to 15% by weight of olefin monomer
The range is preferably 2 to 6% by weight for ethylene monomer, and 3 to 10% by weight for butene-1 monomer. Specific implementation measures include ethylene-
Propylene copolymer (hereinafter abbreviated as EPC), ethylene-propylene-butene-1 copolymer (hereinafter abbreviated as EPBC), propylene-butene-1 copolymer (hereinafter abbreviated as B)
PC). Since the unstretched polypropylene film uses a non-evaporated surface as a heat seal layer during bag making, the melting point of r-CPP is preferably in the range of 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 min because of good extrusion film forming property, and more preferably 2 to 10 g / 10 min.

Next, the high-density polyethylene having a film composition of the present invention (hereinafter abbreviated as HDPE) has a density of 0.9.
The melting point is 3 or more, preferably 0.94 or more, and the melting point is 125 ° C. or more, preferably 130 ° C. or more.
The mixing amount of HDPE is 1 to 15% by weight, preferably 3 to 1%.
The range is 0% by weight. The purpose of the addition of HDPE is to increase the crystallinity of the film to increase the Young's modulus and improve the secondary workability. If the mixing amount is less than 1% by weight, the Young's modulus of the film does not increase, and the slit or lamination is not performed. Occasionally, wrinkles are formed, the film is stretched and cracks are formed in the vapor deposition layer, and the gas barrier properties are deteriorated, and the secondary workability is also deteriorated. On the other hand, if the content exceeds 15% by weight, the film is whitened, and the light transmittance is lowered and the heat sealing strength at the time of bag making is unfavorably deteriorated.

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 size 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 parts by weight.
% By weight. If the addition amount is less than 0.05 parts by weight, when the deposited film is unwound, slippage with the non-deposited surface is poor and blocking occurs, cracks are formed in the deposited layer, and gas barrier properties are deteriorated. On the other hand, if the addition amount exceeds 0.5 parts by weight, the film surface is too rough, so that the transparency and the heat sealing property are deteriorated, and the adhesion of the vapor deposited layer is deteriorated, so that the gas barrier property is unfavorably deteriorated.

[0008] 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 a heat stabilizer, 2,6-di-tert-butyl-4-methylphenol (BHT) or the like is 0.5% by weight or less, and as an antioxidant, tetrakis- (methylene-
(3,5-di-tert-butyl-4-hydroxy-hydrocinnamate)) pentane ("Irganox")
1010) is preferably added at 0.1% by weight or less.

The film of the present invention must have a Young's modulus in at least one direction of at least 0.7 GPa, and particularly preferably a film having a Young's modulus in the longitudinal direction of at least 0.7 GPa. If the Young's modulus is less than 0.7 GPa,
Due to poor tensile strength during vapor deposition and lamination
It is not preferable because cracks enter the vapor deposition layer to deteriorate gas barrier properties.

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

The corona discharge treatment is applied to the surface on which the unstretched polypropylene film of the present invention is deposited to increase the wet tension of the film surface to 35 mN / m or more, so that the adhesion of the deposited film is improved. . Atmosphere gas at the time of the corona discharge treatment at this time may be any of air, carbon dioxide gas or a mixed system of nitrogen / carbon dioxide gas.
Nitrogen / carbon dioxide gas mixture (volume ratio = 95/5 to 50 /
It is preferable to perform the corona treatment in step 50) because the wetting tension on the film surface increases to 35 mN / m or more.

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

Here, the imperfect aluminum oxide vapor-deposited layer means a small amount of aluminum metal (Al) and a complete aluminum oxide (Al ² ) as metal species constituting the vapor-deposited layer.
O ³ ). The means for changing the light transmittance is as follows: in a vacuum vapor deposition device equipped with a film traveling device, while heating and evaporating aluminum metal, supply oxygen gas to the evaporation vapor point, and oxidize the aluminum to agglomerate and deposit on the traveling film surface. Then, a deposition layer is provided. By changing the ratio between the amount of aluminum evaporated and the amount of supplied oxygen gas at this time, the light transmittance of the incomplete aluminum oxide deposited film can be changed. At this time, the thickness of the incomplete aluminum oxide deposited layer 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%. A completely metal oxide vapor-deposited film of the vapor-deposited layer has a light transmittance of more than 90% and is a transparent film, but is not preferable because the water vapor transmittance is increased. Further, if the light transmittance is less than 60%, the transparency is inferior, which is not preferable.

The film of the present invention preferably has a water vapor transmission rate of 2.5 g / m ² · d or less, and if the water vapor transmission rate exceeds 2.5 g / m ² · d, the film must have moisture proof properties. For example, when used as a packaging bag for potato chips or the like, the content is inferior in long-term storage properties, which is not preferable.

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

Next, a 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 shape, and put in a water bath. After cooling, the chip is cut by a chip cutter into a length of 3 to 5 mm to form a chip. Next, the chip is heated to 80 ° C.
And dried in a single screw extruder for 5 hours or more.
After melting at a temperature of ~ 280 ° C and passing through a filtration filter,
Formed into a sheet with a slit-shaped die,
It is wound around a metal drum kept at 80 ° C. to be cooled and solidified, and is wound up as a roll as an unstretched polypropylene film. It is preferable that the unstretched polypropylene film is allowed to stand for 5 hours or more and gradually cooled to crystallize the film. In order to increase the wetting tension of the surface of the obtained unstretched polypropylene film on which vapor deposition is performed, corona discharge treatment or plasma treatment in a rare gas under reduced pressure is performed. Here, the plasma treatment is performed while introducing a small amount of oxygen, argon, helium, carbon dioxide gas or the like into a container having a degree of vacuum of 133 Pa or less, and performing glow discharge from the electrode to which a high voltage is applied toward the film surface. The processing intensity is voltage × current × electrode width / film running speed (W · min /
m ² ), and the treatment intensity is preferably 3
２００200 W · min / m ² , more preferably 5-50 W
- is a min / m ^2. A preferred combination in the case where the surface is subjected to a surface treatment and the surface is subjected to metal oxide deposition is not particularly limited.For example, in the case of a metal oxide such as incomplete aluminum oxide or incomplete silicon oxide, in air or nitrogen. It is preferable to perform at least one of a corona discharge treatment and a plasma treatment in a mixed gas atmosphere of / carbon dioxide gas. Next, the unstretched polypropylene film is set in a vacuum evaporation apparatus equipped with a film traveling device, and is run through a cooling metal drum. At this time, while heating and evaporating the aluminum metal,
Oxygen gas is supplied to the evaporative vapor point, and aluminum is oxidized to cause agglomeration and deposition on the surface of the running film. By changing the ratio between the amount of aluminum evaporated and the amount of supplied oxygen gas at this time, the light transmittance of the incomplete aluminum oxide deposited film can be changed. After the vapor deposition, the inside of the vacuum vapor deposition apparatus is returned to normal pressure, the wound film is slit, and aging is performed at a temperature of 30 ° C. or more for 1 day or more, since the gas barrier property is stabilized, so that it is preferable.

[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 on the film surface Measured according to 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 and expressed in units of g / m ² · d.

(5) Thickness of Deposited Layer of Metal Oxide A cross section of the film was photographed with a transmission electron microscope (TEM) under the following conditions, and the thickness of the laminated layer was measured.

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

(6) Light transmittance Using a spectrophotometer type 324 manufactured by Hitachi, Ltd., a metal oxide-deposited unstretched polypropylene film was subjected to a wavelength of 550 nm.
The transmittance was determined by the following formula.

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

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

(9) Slipperiness According to ASTM D-1894, both surfaces of the film were overlapped and the coefficient of friction was measured. At this time, when the value of μs (static friction coefficient) was less than 1.0, the slipperiness was good and the result was evaluated as ○
1.5 or more was evaluated as poor due to poor slipperiness, and the middle was evaluated as Δ.

(10) Blocking property A sample having a width of 3 cm and a length of 10 cm is superimposed on both sides of the sample over a length of 4 cm, and a load of 500 g is applied.
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 30 μm-thick biaxially stretched polypropylene film is coated with a polyurethane adhesive manufactured by Takeda Pharmaceutical Co., Ltd.
-971 / curing agent “Takenate” A-3 = 9/1) using a coating bar to apply a thickness of about 4 μm, and after bonding to the vapor-deposited surface of a metal oxide vapor-deposited unstretched polypropylene film, Aging was carried out for 2 days at a temperature of 2 ° C. Thereafter, the non-deposited surfaces of the unstretched polypropylene film of the laminated film are overlapped with each other, and heat-sealed by a one-side heating method of a heat sealer at a sealing temperature of 115 ° C., a sealing pressure of 1 kg / cm ² , and a sealing time of 2 seconds. went. This heat-sealed sample is
m and cut using a tensile tester (manufactured by Toyo Sokki).
When the force required for peeling the sealing surface 90 degrees at a speed of 00 mm / min is 300 g / cm or more,
/ Cm or less was evaluated as x, and the middle one was evaluated as Δ.

(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 metal oxide vapor-deposited unstretched polypropylene film are superposed on each other. Then, through a nip roll cooled to 30 ° C, a low-density polyethylene (L-705 manufactured by Sumitomo Chemical Co., Ltd.) melted at 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 laminate were measured, and the laminate had no wrinkles and had a water vapor transmission rate of 2.0 g / m 2.
Those with less than ² · d were evaluated as ○, wrinkles were formed, and those with a water vapor transmission rate of 2.5 g / m ² · d or more were evaluated as ×, with no wrinkles and a water vapor transmission rate of 2.0 g / m ² · d or more, 2.5 g / m ² · d
Those less than were evaluated as △.

[0033]

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

Examples 1-4, Comparative Examples 1-4 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 the ratio shown in Table 1, supplied to a twin screw extruder, melt-extruded in a gut shape at a temperature of 240 ° C., cooled in a water bath, and then 3 to 5 mm in a tip cutter. To obtain chips of each composition. Next, the chip is supplied to a single screw extruder, melted at a temperature of 260 ° C., extruded into a sheet shape with a slit die through a filter, cooled around a metal drum heated to a temperature of 50 ° C. and cooled. As a result, an unstretched film having a thickness of 25 μm was obtained. The surface on which the film was to be deposited was subjected to a corona discharge treatment in air under a treatment condition of 40 W · min / m ² , and the film was wound into a roll with a wet tension of 45 mN / m. The film temperature at that time was 35 ° C,
After allowing to stand for 24 hours to increase the crystallinity, slitting was performed in a small width. The film quality at this time was evaluated and shown in Table 1.
Next, the slit film having the small width was set in a vacuum evaporation apparatus equipped with a film traveling device, and 1.33 × 10 ^−2.
After a high vacuum of Pa, the sample was run through a cooling metal drum at -20 ° C. At this time, while heating and evaporating the aluminum metal, oxygen gas was supplied to the evaporating vapor, and the aluminum was oxidized to be agglomerated and deposited on the surface of the running film. At this time, the light transmittance of the incomplete aluminum oxide deposited film was changed by changing the ratio of the amount of aluminum evaporated and the amount of supplied oxygen gas. After the evaporation, the inside of the vacuum evaporation apparatus is returned to normal pressure, and the wound evaporation film is slit into 4 pieces.
After aging for 3 days at a temperature of 0 ° C., the quality of each film was evaluated. The characteristics of the film are shown in Table 1. Next, the secondary workability of the obtained metal oxide unstretched polypropylene film was evaluated, and the properties are shown in Table 1. Example 1
The metal oxide-deposited unstretched polypropylene films according to the present invention are excellent in gas barrier properties, transparency, high Young's modulus, and excellent in slipperiness, so that they are excellent in secondary workability. Was. However, the films of Comparative Examples 1-4 deviating from the scope of the present invention have gas barrier properties, transparency,
The film was inferior in either heat sealability or secondary workability.

[0035]

[Table 1]

[0036]

The metal oxide-deposited unstretched polypropylene film of the present invention has an excellent gas barrier by 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 has excellent properties and transparency, and is excellent in secondary processing properties such as slitting and lamination, and can be used as a metal oxide-deposited unstretched polypropylene film suitable for various packaging applications.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification code FI C23C 16/40 C23C 16/40 // C23C 14/20 14/20 A (72) Inventor Itsuo Nagai 1-chome Sonoyama, Otsu City, Shiga Prefecture No. 1-1 Toray Industries, Inc. Shiga Plant (56) References JP-A-6-212404 (JP, A) JP-A-3-92344 (JP, A) JP-A-2-53847 (JP, A) (58) ) Field surveyed (Int.Cl. ⁷ , DB name) C08J ⁷ /04-7/06 B32B 27/00-27/32 C23C 16/40 C23C 14/20

Claims (2)

(57) [Claims] 1. A polypropylene random copolymer 85 to 85.
A film obtained by depositing a metal oxide on a film obtained by adding 0.05 to 0.5 part by weight of a lubricant to a mixed resin of 99% by weight and 15 to 1% by weight of a high-density polyethylene. The oxide-deposited 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.
% And a water vapor transmission rate of 2.5 g / m ² · d or less. 2. The unstretched polypropylene film deposited with metal oxide according to claim 1, wherein the polypropylene random copolymer is a copolymer of propylene and α-olefin.