JP2985724B2 - Polyolefin laminated film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyolefin-based laminated film having excellent moisture-proof properties and gas barrier properties and suitable for packaging.

[0002]

2. Description of the Related Art Conventionally, polyolefins, for example,
It is known that the addition of petroleum resin and terpene resin to polypropylene can improve Young's modulus and moisture resistance (Japanese Patent Publication No. 1-25033, Japanese Patent Publication No.
No. 31347). It is also known that a metal vapor deposition and a polyvinylidene chloride-based resin are laminated on a film obtained by adding a petroleum resin and a terpene resin to polypropylene to further improve the moisture proof property (Japanese Patent Publication No. 2-27).
No. 940, Japanese Patent Publication No. 5-1138). Further, a film having a matte layer, that is, a so-called mat layer, for hiding the contents of a package or for giving a sense of quality, etc., is also known.

[0003]

However, simply adding a petroleum resin and a terpene resin to polypropylene improves the Young's modulus and moisture resistance, but the petroleum resin and the terpene resin have low softening points. The added film is inferior in dimensional stability, and when the film is wound into a roll, the film is tightened to deteriorate the flatness. In addition, there is a problem that the process stability during processing is inferior due to a large heat shrinkage.

Further, when a metal is vapor-deposited on the film to give it a further moisture-proof property, the film is shrunk by heat at the time of vapor deposition, cracks are formed on the metal-deposited surface, and the moisture-proof property is not improved. was there.

Further, when a resin such as polyethylene is laminated or coated on the vapor deposition surface, the adhesive strength between the vapor deposited film and the resin layer such as polyethylene becomes stronger than the adhesive strength between the vapor deposited film and the base film. There is also a problem that the vapor-deposited film may be inconveniently peeled from the base film.

The present invention has been made in view of the above circumstances of the prior art, and has as its object to provide a polyolefin-based laminated film having a mat layer, which can improve the moisture-proof property and gas barrier property without causing inconvenience. Aim.

[0007]

According to the present invention, there is provided a laminated polyolefin film according to the present invention, which comprises at least three laminated films, one of which is composed of a petroleum resin substantially free of a polar group and a polar group. Is a layer in which at least one kind of terpene resin substantially free of is mixed with 5 to 30% by weight, and the surface of the layer is subjected to a discharge treatment, and the other surface layer is subjected to a matte treatment. And a mat layer.

[0008] The discharge treatment applied to the surface of the one surface layer is substantially more CO ₂ than that performed in air.
And / or under N ₂ atmosphere, ie, CO ₂ and / or
Alternatively, the method is preferably performed in an atmosphere in which the concentration of N ₂ is equal to or higher than a predetermined concentration.

Further, in the polyolefin-based laminated film according to the present invention, in order to prevent blocking when the laminated film is wound into a roll and unwound, for example, in order to prevent blocking during vapor deposition processing, Preferably, the surface of the mat layer is also subjected to a discharge treatment. The discharge treatment is not particularly limited, and may be simply performed in the air, so-called ordinary corona discharge treatment.

In such a polyolefin-based laminated film, the main component is, for example, polypropylene. That is, it is a polypropylene-based laminated film. The stretching form of the film is not particularly limited, and may be unstretched (unoriented) or uniaxially stretched (uniaxially oriented).
Particularly preferred for packaging and the like is the form of a biaxially stretched film (biaxially oriented film).

In the present invention, as the base material of the film layer in which the petroleum resin and / or terpene resin is mixed, for example, crystalline polypropylene is preferable. Such a crystalline polypropylene has an isothermal crystallization time at 125 ° C. (hereinafter sometimes abbreviated as t- ／) of 6.5 minutes or less, and an isotactic index (hereinafter II).
May be abbreviated as ) Is preferably 94.5% or more. t-1 / 2 exceeded 6.5 minutes, II was 9
If it is less than 4.5%, the crystallinity of the film does not increase, and the heat shrinkage in the longitudinal direction increases, which is not preferable, and the resistance to organic solvents also deteriorates. When the melt flow index (MFI) is in the range of 1 to 4 g / 10 minutes, the dispersibility of the petroleum resin and / or the terpene resin is improved, and the film forming property and the moisture resistance are also improved. Also,
A second component other than propylene, for example, ethylene, butene,
A small amount of hexene or the like may be randomly copolymerized. In addition, known additives such as a crystal nucleating agent, an antioxidant, a heat stabilizer, a sliding agent, an antistatic agent, an antiblocking agent, a filler, a viscosity modifier, and a coloring inhibitor may be contained in appropriate amounts.

In the present invention, the base material of the above-mentioned film layer,
For example, a petroleum resin substantially free of a polar group, which is mixed with crystalline polypropylene, is a petroleum resin having no polar group consisting of a hydroxyl group, a carboxyl group, a halogen group, a sulfone group and a modified form thereof, that is, Cyclopentadiene-based resin directly derived from petroleum unsaturated hydrocarbons or resin derived from higher olefinic hydrocarbons as the main raw material.

The petroleum resin substantially free of such a polar group has a glass transition temperature (hereinafter abbreviated as Tg) of 60.
It is preferable that the temperature is not lower than ° C. When Tg is less than 60 ° C,
The effect of improving the moisture resistance is small.

A hydrogenated petroleum resin obtained by adding hydrogen to such a petroleum resin and having a hydrogenation rate of 90% or more, preferably 99% or more, is particularly desirable for the polyolefin-based laminated film of the present invention. Representative hydrogenated petroleum resins include, for example, high Tg completely hydrogenated alicyclic petroleum resins such as polydicyclopentadiene having a Tg of 70 ° C. or more and a hydrogenation ratio of 99% or more.

A terpene resin substantially free of a polar group is a terpene resin having no polar group, such as a hydroxyl group, an aldehyde group, a ketone group, a carboxyl group, a halogen group, a sulfone group, and a modified product thereof. , Ie (C
₅ H ₈₎ is a hydrocarbon and now modified compound derived composition of n. n is a natural number of about 2 to 20.

The terpene resin is sometimes called a terpenoid, and typical compounds include pinene, dipentene, kalen, myrcene, osimene, limonene, terpinolene, terpinene, sabinene, tricyclene, bisabolene, zingiperene, santalen, camphorene, There are millen and totalene, and in the case of the film of the present invention, hydrogen is added and the hydrogenation rate is 90% or more, preferably 9%.
9% or more, particularly β-pinene, hydrogen β
-Pinene, hydrogenated β-dipentene and the like are preferred.

Thus, the use of one or more petroleum resins substantially free of polar groups and terpene resins substantially free of polar groups is important in the present invention, and the bromine number is preferably 10 or less, more preferably 10 or less. Is preferably 5 or less, more preferably 1 or less.

The mixing amount of at least one of the petroleum resin substantially free of the polar group and the terpene resin substantially free of the polar group contained in the film of the present invention is 70 to 95% by weight of the film base resin. % To 5% by weight. In particular, it is preferably from 10 to 20% by weight. If the mixing amount of the resin is less than 5% by weight, the moisture-proof property is not improved, and if it exceeds 30% by weight, the heat resistance deteriorates, which is not preferable. Further, when the content is close to 40% by weight, film formation becomes impossible due to extrusion trouble.

A polyolefin-based film layer, for example, a polypropylene-based film layer, is laminated on such a film layer containing a petroleum resin and / or a terpene resin substantially free of a polar group. The polypropylene-based film layer is not particularly limited, and may be a layer containing polypropylene as a main component and a layer having general dimensional stability (for example, a heat shrinkage ratio equal to or less than a predetermined value).
Since the polypropylene film layer is used as a base material layer to provide thermal dimensional stability of the entire laminated film, the film layer containing the petroleum resin and / or the terpene resin according to the present invention and the heat seal layer are thin layers. , The desired dimensional stability of the entire laminated film can be ensured. Polypropylene film layer (hereinafter referred to as B
Sometimes called a layer. ) Is 10 to 20 μm
m is preferable, and the thickness of the petroleum resin and / or terpene resin-containing layer (hereinafter also referred to as C layer) is preferably about 0.1 to 5.0 μm.

The surface of the C layer is subjected to a discharge treatment. As described above, the discharge treatment may be a mere discharge treatment in the air. However, from the viewpoint of improving the adhesion to the metal deposition layer provided on the surface, the discharge treatment is performed in an atmosphere of CO ₂ and / or N ₂ . Discharge treatment is more preferred. Where CO ₂
And / or N ₂ atmosphere is, for example, an atmosphere containing CO ₂ or N ₂ singly or more at a certain concentration or more.
_An atmosphere containing a mixed gas of ₂ and N ₂ at a certain concentration or more, and a mixed gas of CO ₂ and Ar, a mixed gas of N ₂ and Ar, or a mixed gas of CO ₂ , N ₂ and Ar at a certain concentration This is the atmosphere that includes the above.

By subjecting the surface of the C layer to such a discharge treatment, the adhesive strength (deposition strength) with a metal vapor deposited layer, for example, an Al vapor deposited layer is significantly increased. Al deposition is performed in a usual manner, for example, in a vacuum vessel (for example, 10 ⁻⁴ to 10 ⁻⁵ T).
orr vacuum container) purity 99.9-99.999%
Al may be deposited.

This metal deposited layer (for example, an Al deposited layer)
By providing the film, the gas barrier properties of the laminated film are remarkably enhanced, and the film becomes suitable for packaging of dry matter, potato chips and the like in combination with the moisture-proof property. The gas barrier property is an oxygen permeability (hereinafter, also referred to as O ₂ TR).
O ₂ TR is 1.5cc / 100in ² / da
It is preferably y or less.

In the present invention, a mat layer is provided as a surface layer on the side opposite to the C layer of the laminated film. The mat layer (hereinafter, also referred to as an A layer) is made of, for example, a block copolymer of polypropylene and another polymer,
Basically, it is a layer whose surface is roughened in the process of film formation to give a matte effect. As the thickness of the mat layer,
About 0.1 to 5.0 μm is appropriate.

The surface of the mat layer is preferably subjected to a discharge treatment, for example, a corona discharge treatment. The atmosphere of the discharge treatment is not particularly limited, and the discharge treatment in air may be used. In this way, by subjecting this surface to the discharge treatment, printing on this surface and polyethylene extrusion lamination can be performed. The discharge treatment on the surface on the A layer side is preferably performed so that the film surface wetting tension after the treatment is 35 to 45 dyne.

The laminated form of the film of the present invention may have at least a three-layered constitution of A / B / C, as long as the A layer and the C layer form both surfaces. Alternatively, a laminated structure of four or more layers in which another layer is interposed between the layer B and the layer C may be used.

Next, an example of a method for producing a heat and moisture resistant film of the present invention will be described. For example, t-1 at 125C
/ 2 is 6.5 minutes or less, II is 94.5% or more, and
An extruder is used to extrude a C-layer resin comprising a mixture of a specific range of a petroleum resin substantially free of polar groups and a terpene resin substantially free of polar groups in crystalline polypropylene having a melt flow index of 1 to 4 g / 10 minutes. C, and the resin temperature is 200 ° C. or higher, preferably 220 ° C. to 29 ° C.
Melt extruding at a temperature of 0 ° C., supplying a B layer resin to an extruder B and extruding at a resin temperature of 240 ° C. to 320 ° C., supplying an A layer resin to an extruder A, extruding at a resin temperature of 240 ° C. to 300 ° C., Each is discharged as a three-layer laminated sheet of A / B / C layers using a three-layer composite die through a filter. This molten laminated sheet is cast on a cooling drum controlled to a surface temperature of 20 to 60 ° C. and solidified by cooling to produce an unstretched laminated film.

The unstretched film is heated at 135 to 165 ° C.
Stretched 4.0 to 5.0 times in the longitudinal direction, and 15 to
It is cooled at 50 ° C. to obtain a uniaxially stretched laminated film. Subsequently, the uniaxially stretched film was guided to a tenter,
It is preheated to 180 ° C., stretched 7 to 12 times in the width direction, and heat-treated after stretching. The surface of the C layer of the obtained biaxially stretched laminated film is subjected to corona discharge treatment in an atmosphere of, for example, CO ₂ , N ₂ , or a mixed gas of CO ₂ and N ₂ , at the same time, or before or after the discharge treatment. The surface of the layer A is subjected to corona discharge treatment in air, for example, and is wound up after the treatment. After winding, an aging process is performed as necessary, and the product is slit into a product having a predetermined width. Then, metal evaporation, for example, aluminum evaporation is performed on the surface of the C layer as necessary.

[Method for measuring characteristics and evaluating effect]
The method for measuring the characteristic values and the method for evaluating the effects of the present invention are as follows. (1) Isotactic index (II) In the state of the raw material, it may be measured individually. In the case of a composite film, first, a sample is extracted with n-heptane at a temperature of 60 ° C. or less for 2 hours, and the additive to propylene is added. Is removed.
Thereafter, vacuum drying is performed 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, vacuum-dried at 130 ° C. for 6 hours, and then cooled to room temperature, the weight W ′ (mg) is measured, and it is determined by the following equation. II (%) = (W ′ / W) × 10
Regarding the composite layer, the surface layer may be scraped off and measured by the same method as described above.

(2) Glass transition temperature (Tg), isothermal crystallization time (t-1 / 2) In the state of the raw material, the measurement may be performed individually. In the case of the composite film, the sample is first heated to a temperature of 60 ° C. or less. For 2 hours to separate propylene from petroleum resin and terpene resin. Then, propylene is vacuum dried at 130 ° C. and petroleum resin and terpene resin are dried at 60 ° C. for 2 hours. Then, for each sample, a differential scanning calorimeter (DSC-
2 type, manufactured by PerkinElmer Co., Ltd.)
When the temperature was raised from room temperature at a rate of 20 ° C./min, the change in specific heat accompanying the second-order transition type was defined as the glass transition temperature (Tg), and then to the melting holding temperature of 280 ° C. After raising the temperature and holding for 5 minutes, the mixture was cooled at a cooling rate of 20 ° C./min. When the temperature was held at 125 ° C., the start time and end time of the peak of the latent heat accompanying crystallization were recorded. Half the time was taken as the isothermal crystallization time (t-1 / 2). In addition, about a composite layer, what is necessary is just to scrape a surface layer, and to measure by the same method as the above.

(3) Melt flow index (MF)
I) 230 ° C., 2.16 according to ASTM-D-1238
It was measured under the condition of kg.

(4) Bromine value Measured according to JIS-K2543-1979. It is represented by the number of g of bromine added to the unsaturated component in 100 g of the sample oil.

(5) Heat Shrinkage The heat shrinkage is sampled at a test length of 260 mm and a width of 10 mm, and a mark is placed at a position of 200 mm as the original size (L0). A load of 3 g was applied to the lower end of the sample, and 12
Heat treatment is performed in an oven at 0 ° C. for 15 minutes, after which the length (L1) marked on the sample is measured. This heat shrinkage (R) is obtained by the following equation. Heat shrinkage (R) (%) = [(L ₀ −L ₁ ) / L ₀ ] × 1
00

(6) Film thickness The film thickness was measured using a dial gauge type thickness meter (JIS-B7509).

(7) Lamination Thickness The film cross-sectional structure was observed using a field emission scanning electron microscope (FE-SEM), and the thickness was measured.

(8) Measurement of Al Deposition Strength Surlyn was heat-sealed on the Al-deposited film surface (1).
At 20 ° C. × 1 second), the vapor-deposited film and the Surlyn layer were pulled apart at a peeling speed of 300 m / min in the opposite direction by 180 ° using a tensile tester (Tensilon), and the peel strength at that time was measured. The unit is g / sample width 1 inch.

(9) Oxygen permeability O ₂ TR Measured using a commercially available oxygen permeability measuring device (unit: c)
c / 100m / day).

(10) Inspection of blocking The evaporation film was rewound from the evaporation reel around which the Al evaporation film was wound, and the size and number of pinholes on the evaporation surface were compared with a limited sample (visually), and the pass / fail was measured. The percentage of rejects in all products was expressed as the rejection rate (%) due to blocking.

[0038]

The present invention will be described below based on examples and comparative examples. Examples 1 and 2 Crystalline polypropylene (PP) (t
-1/2: 4.5 min, II: 95.5%, MFI: 1.
7g / 10min) 1 specific hydrogenated non-polar petroleum resin
Using a resin composition mixed in a ratio of 5% by weight (Example 1) and 10% by weight (Example 2), the resin composition was supplied to an extruder C and 255
C., and melted at 280 ° C. by supplying ordinary PP as a resin for the B layer to the extruder B, and a resin for the mat layer formed of a block copolymer of ethylene and propylene as the resin for the A layer. The mixture was supplied to extruder A and melted at 270 ° C.

Each molten resin is sent through a filter to a three-layer composite die, laminated and discharged in three layers of A / B / C layers,
It was cooled and molded and solidified on a cooling drum having a surface temperature of 30 ° C. The unstretched film (sheet) was preheated to 150 ° C, stretched 4.3 times in the longitudinal direction, and then cooled at 30 to 40 ° C. Subsequently, the obtained uniaxially stretched film was supplied to a tenter, preheated at 160 ° C., stretched 10 times in the width direction, and then heat treated (heat set). The surface of the layer C of the obtained biaxially stretched laminated film was subjected to a corona discharge treatment in a mixed gas atmosphere of CO ₂ and N ₂ , and the surface of the layer A was subjected to a corona discharge treatment in air and then wound up. The thickness configuration of each layer of the obtained three-layer laminated biaxially stretched film is as shown in Table 1. Table 1 shows the properties of the obtained film with respect to O ₂ TR, blocking rejection rate, and Al deposition strength.

As shown in Table 1, in Example 1, O ₂ T
The film was excellent in R, blocking rejection rate, and Al deposition strength. In Example 2, since the amount contained in the C layer of petroleum resin is lowered slightly compared with Example 1, O ₂
Although the TR and the blocking rejection rate slightly increased and the Al deposition strength slightly decreased, a sufficiently satisfactory effect was obtained.

Comparative Examples 1 and 2 In Comparative Example 1, a laminate film having a two-layer structure of A / B layers was used, and neither petroleum resin was contained. Since no petroleum resin was contained, the Al deposition strength was low and the O ₂ TR was high (1.5 cc / 100 in ² / day or more). In Comparative Example 2, the ratio of the petroleum resin in the C layer was 40% by weight.
, The extrusion trouble occurred and the film could not be formed.

[0042]

[Table 1]

[0043]

As described above, the polyolefin-based laminated film having a mat layer according to the present invention has a discharge treatment in which a specific amount of a petroleum resin and / or a terpene resin is added to a surface layer opposite to the mat layer and mixed. It is a laminated film that has been applied, has excellent moisture-proof properties, has excellent adhesive strength of a metal deposition film, can exhibit excellent gas barrier properties, and can extremely reduce the occurrence rate of rejected products due to blocking. .

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B32B 1/00-35/00

Claims (5)

(57) [Claims] 1. A laminated film having at least three layers, wherein one surface layer contains 5 to 30% by weight of at least one kind of a petroleum resin substantially free of a polar group and a terpene resin substantially free of a polar group. A polyolefin-based laminated film, characterized in that it is a layer in which the surface is subjected to a discharge treatment and the other surface layer is a mat layer subjected to a matting treatment. 2. The polyolefin-based laminated film according to claim 1, wherein the surface of the mat layer is subjected to a discharge treatment. 3. The polyolefin-based laminated film according to claim 1, wherein the discharge treatment performed on the surface of the one surface layer is a discharge treatment in a CO ₂ and / or N ₂ atmosphere. 4. The polyolefin-based laminated film according to claim 1, wherein the main component is polypropylene. 5. An aluminum vapor-deposited film, wherein aluminum is vapor-deposited on the surface of said one surface layer of the polyolefin-based laminated film according to claim 1.