JP2000263723A - Biaxially oriented polypropylene film with superior mineral oil resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of swelling and wrinkles caused by mineral oil by having a petroleum resin-containing polypropylene resin layer blended with an aliphatic or aromatic petroleum resin in a polypropylene resin by a specific quantity, and allowing its thermal shrinkage in each longitudinal and lateral direction to be in a specific range at a specific temperature. SOLUTION: The biaxially oriented polypropylene film is composed of a matter having a petroleum resin-containing polypropylene resin layer comprising blending 0.5-5 wt.% aliphatic or aromatic petroleum resin in a polypropylene resin, and being biaxially oriented so as to be 0.02-0.4% in its thermal shrinkage in the longitudinal and lateral direction at a temperature of 50 deg.C. If the film is used as an outer packaging film for mineral oil-containing goods, packaging paper, or the like, it has never swelling or wrinkles generated by mineral oil, so that the value of goods can be maintained excellently for a long period of time. Also, since such biaxially oriented polypropylene film does not need of providing a vinylidene chloride layer on the surface of the film, there is no fear of having an environmental pollution due to chlorine gas during incineration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented polypropylene film which does not swell when it comes into contact with a mineral oil-containing material by packaging or the like.

[0002]

2. Description of the Related Art Biaxially stretched polypropylene films (hereinafter, also simply referred to as polypropylene films) are excellent in transparency, moisture resistance, light weight and mechanical strength.
Utilizing its features, it is widely used for packaging materials and industrial materials.

[0003] However, since polypropylene films are inherently poor in mineral oil resistance, products using mineral oils in the production process, catalogs printed with offset ink containing mineral oil, tobacco wrapping paper, or chocolate are not used. When wrapping is covered with a polypropylene film,
There has been a problem that the polypropylene film swells and wrinkles due to the mineral oil remaining in the product or the wrapping paper, thereby deteriorating the commercial value.

Conventionally, in order to prevent the above-mentioned problems, a polypropylene film having mineral oil resistance imparted by applying vinylidene chloride to both surfaces of a polypropylene resin layer has been used as an exterior polypropylene film for products and packaging paper containing mineral oils. Have been. However, since a polypropylene film coated with vinylidene chloride is liable to generate highly toxic dioxin due to chlorine gas at the time of incineration, there is an eager demand for a substitute product that does not use vinylidene chloride.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been proposed to solve the above-mentioned problems, and it has been proposed to use mineral oil when used as an exterior film for goods or wrapping paper containing mineral oil. It is an object of the present invention to provide a biaxially oriented polypropylene film which is excellent in mineral oil resistance and does not cause swelling and wrinkles due to chlorine gas and does not generate dioxin due to chlorine gas during incineration.

[0006]

According to the present invention, there is provided a petroleum resin-containing polypropylene resin layer obtained by mixing an aliphatic or aromatic petroleum resin with a polypropylene resin in an amount of 0.5 to 5% by weight. Vertical and horizontal thermal shrinkage of 0.0
The present invention relates to a biaxially oriented polypropylene film having excellent mineral oil resistance, which is 2 to 0.4%.

[0007] The biaxially oriented polypropylene film of the present invention having excellent mineral oil resistance has a petroleum resin-containing polypropylene resin layer provided with a heat seal layer on at least one surface, or an aliphatic or aromatic petroleum resin. It is sometimes referred to as hydrogenated.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The biaxially oriented polypropylene film excellent in mineral oil resistance of the present invention has a petroleum resin-containing polypropylene resin layer obtained by blending an aliphatic or aromatic petroleum resin with a polypropylene resin in an amount of 0.5 to 5% by weight. It is biaxially stretched so that the heat shrinkage in the vertical and horizontal directions at 0 ° C is 0.02 to 0.4%. The longitudinal direction refers to the direction of film flow (extrusion direction) during film production, and the transverse direction refers to the direction perpendicular to the direction of film flow (extrusion direction). Incidentally, the biaxially stretched polypropylene film of the present invention is a single-layer film consisting of only the petroleum resin-containing polypropylene resin layer, or the petroleum resin-containing polypropylene resin layer as a base layer, depending on its use, and one or both sides of the base layer And a composite film in which a resin layer different from the base layer is laminated.

The polypropylene resin in the present invention includes a polypropylene homopolymer, a copolymer of propylene with an α-olefin, or a mixture thereof.

The petroleum resin added to the polypropylene-based resin is obtained by polymerizing monoolefins and diolefins contained in a cracked oil fraction by-produced when producing ethylene, propylene, etc. from a so-called ethylene plant in the petrochemical industry. It is roughly divided into the following three types. That is, cracked oil distillate fraction 5 carbon atoms is referred to as aliphatic or C ₅ petroleum resin obtained by the raw materials of an aromatic or C ₉ to those fractions of 9 carbon atoms in the raw material It is referred to as a petroleum-based resin, and the one made from both of them is referred to as a C ₅ C ₉ copolymerized petroleum resin.

The petroleum resin in the present invention may be hydrogenated. The hydrogenated petroleum resin is a resin in which the unsaturated bond of the petroleum resin is changed into a saturated bond by a chemical bond with hydrogen, thereby improving hue and stability.

The amount of petroleum resin added to the polypropylene resin must be 0.5 to 5% by weight. When the amount of the petroleum resin is less than 0.5% by weight, the effect of improving the mineral oil resistance is poor. Conversely, when the amount exceeds 5% by weight, the mineral oil resistance is not so improved, and the expensive petroleum resin is wasted. In addition to the use of a large amount of petroleum resin, the addition of a large amount of petroleum resin causes the blocking property of the polypropylene film to deteriorate, and when the products wrapped with the resulting polypropylene film are stacked, they adhere to each other and cause difficulties in handling. And the appearance of the package is impaired. A particularly preferred range is 1 to 3% by weight of petroleum resin based on the polypropylene resin.

When the biaxially oriented polypropylene film of the present invention is composed of a composite film, the resin laminated on the petroleum resin-containing polypropylene resin layer may be a polypropylene resin containing no petroleum resin, polyethylene, polybutene, or any of these. Can be used. In particular, when a composite film is formed for the purpose of imparting heat sealing properties, a resin having a melting point of 10 ° C. or more, preferably 15 ° C. or more lower than the melting point of the polypropylene resin in the petroleum resin-containing polypropylene resin layer is used as a heat-sealing laminated resin. , Stable heat sealing properties can be obtained.

Known resins such as a crystal nucleating agent, an antioxidant, a heat stabilizer, a lubricant, an antiblocking agent and an antistatic agent are added to the resin constituting the petroleum resin-containing polypropylene resin layer and the heat seal layer. Is also good. One or both surfaces of the petroleum resin-containing polypropylene resin layer and the heat seal layer may be subjected to a surface treatment represented by a corona discharge treatment.

The biaxial stretching in the present invention is carried out by a known method. Generally, after extruding a raw sheet and solidifying it by cooling, a film is generally formed by a simultaneous stretching method or a sequential stretching method. In the present invention, in the case of simultaneous stretching, the raw sheet is heated to 120 to 170 ° C. and simultaneously stretched 5 to 10 times in the machine direction and 5 to 10 times in the transverse direction, and heat set (annealed) at 130 to 150 ° C. After cooling, it is wound up. In the case of sequential stretching, the film is heated to 115 to 145 ° C. and stretched 4 to 7 times in the machine direction, then guided to a transverse stretching machine, heated to 140 to 170 ° C., and stretched 7 to 11 times in the transverse direction. It heat-sets at 130-150 degreeC, winds up after cooling. When the biaxially stretched polypropylene film of the present invention is used as a composite film, a petroleum resin-containing film and another film are laminated by a coextrusion method or a laminating method, and then biaxially stretched.

The conventional biaxially stretched polypropylene film has a heat shrinkage at 50 ° C. of about 0-0.01% in each of the longitudinal and transverse directions. It is prepared so that the heat shrinkage at 50 ° C. is in the range of 0.02 to 0.4% in each of the vertical and horizontal directions. When the heat shrinkage at 50 ° C. is less than 0.02%, the mineral oil resistance is poor.
If it exceeds 0.4%, dimensional stability will be poor, and wrinkles will be promoted and packaging problems will occur. In order to further improve the mineral oil resistance, the heat shrinkage rate at 50 ° C. is set to 0.0% in the longitudinal direction (the direction along the film flow direction).
It is preferable that the content be 2 to 0.03% and 0.2 to 0.3% in the lateral direction (the direction perpendicular to the film flow direction). In this case, the heat shrinkage in both the vertical and horizontal directions needs to be within the above range.

The heat shrinkage depends on the stretching ratio, the stretching temperature, the crystallinity of the polypropylene used, and the like at the time of forming the polypropylene film. The heat setting temperature most greatly depends on the heat setting temperature. In the biaxially stretched polypropylene film of the present invention, the heat set temperature during biaxial stretching of the raw sheet having the petroleum resin-containing polypropylene resin layer is lower than the normal temperature of 130 to 150.
By setting the temperature at 50 ° C., the heat shrinkage at 50 ° C. can be adjusted to 0.02 to 0.4% in each of the vertical and horizontal directions. Further, the heat shrinkage in the longitudinal direction at 50 ° C.
In order to set the heat shrinkage in the transverse direction to 0.03% and the heat shrinkage in the horizontal direction to 0.2 to 0.3%, the heat setting temperature is appropriately set to, for example, 130 to 1
The temperature may be set to 40 ° C.

The thickness of the biaxially stretched polypropylene film of the present invention is not particularly limited in both cases of a single layer and a multilayer, but it is 12 to 6 in terms of film forming stability.
0 μm is preferred. Outside this range, breakage or the like is likely to occur during film formation. Further, the thickness of each layer in the case of forming a composite film is not limited, but when the surface is constituted by a heat seal layer, the thickness of the heat seal layer is preferably 0.3 to 6 μm. If the thickness is less than 0.3 μm, spots tend to occur, and if the thickness is more than 6 μm, stickiness occurs.

[0019]

EXAMPLES Next, specific examples of the present invention and comparative examples for confirming the effects will be described. The physical properties of the examples and comparative examples were measured by the following methods, and the results are shown in Table 1.

(1) Thermal shrinkage: A vertically long test piece (a test piece that is long in the film flow direction at the time of film production) and a horizontally long test piece (a direction perpendicular to the film flow direction at the time of film production) having a width of 15 mm and a length of 150 mm. Long test specimens) were prepared, each with a spacing of 10 in the longitudinal direction.
After drawing a mark line at 0 mm, the mark is left in a thermostat controlled at 50 ° C., taken out after 30 minutes, and the length between the mark lines is measured. The measured value at this time was subtracted from the length of 100 mm, which is the distance between the marked lines before accommodation in the thermostatic bath, and the value obtained by the subtraction was divided by the interval between the marked lines before accommodation in the constant temperature bath, 100 mm, and the percentage was 100%. And the heat shrinkage.

(2) Mineral oil resistance Mineral oil (mineral oil manufactured by Nikko Petrochemical Co., Ltd .: AF Solvent 4)
No. 5, No. 5 and No. 6 were mixed at the center of a 50 mm square copy paper at a rate of 0.2 ml per sheet to prepare a mineral oil impregnated paper for each test. After a test piece of 100 mm square was sandwiched between them, the test piece was left for 72 hours in a thermostat controlled at 55 ° C., and the test piece was taken out and the appearance of the test piece (degree of swelling and whitening) was visually measured as follows.

<Swelling degree> A: The surface of the test piece is smooth and no abnormality is observed. Δ: Fine wrinkles or fine undulations on the surface of the test piece. ×: There are large wrinkles and large undulations on the surface of the test piece. <Whitening> A: The test piece surface is not whitened (the surface is not whitened). ×: The test piece surface is whitened (surface is whitened).

(Example 1) a. Base layer raw material The following first component, second component, and third component are combined at a weight ratio of first component: second component: third component of 65:25:10 (final concentration of petroleum resin is 5% by weight). What is mixed so that it becomes. -1st component: polypropylene homopolymer-2nd component: 20% by weight of a hydrogenated product of dicyclopentadiene as a hydrogenated product of a polypropylene homopolymer and 80% by weight of an aliphatic petroleum resin (trade name: Escolets, manufactured by Tonex Corporation) % By using a twin-screw kneading granulator. Third component A mixture obtained by adding and mixing 5% by weight of an antistatic agent (stearyldiethanolamine: glycerin monostearate = 2: 8) to 95% by weight of a polypropylene homopolymer and granulating the mixture.

B. Heat seal layer raw material A material obtained by kneading 0.2% by weight of silica as an antiblocking agent with 99.8% by weight of an ethylene-butene-propylene copolymer having a melting point lower by 25 ° C. than the polypropylene homopolymer of the first component in the base layer material.

C. Film forming method The base layer raw material is melt-extruded with one extruder and the heat seal layer raw material is melted and extruded with two extruders, and then extruded from a slit-shaped die and brought into close contact with a metal roll temperature-controlled at 40 ° C to form a sheet. After heating to 130 ° C, stretched 5 times in the machine direction, then heated to 165 ° C, stretched 10 times in the transverse direction, heat-set at 135 ° C, rolled up after cooling, heat-seal layer A biaxially-stretched polypropylene film consisting of / base layer / heat seal layer was obtained. This film has a heat seal layer / base layer / heat seal layer thickness of 1/20.
/ 1 µm.

Embodiments 2 and 3 In Embodiment 1, the first
The weight ratio of component: second component: third component is 75:15:10
So that the final concentration of the petroleum resin is 3% by weight (Example 2), the weight ratio of the first component: the second component: the third component is 85: 5: 10, and the final concentration of the petroleum resin is 1% by weight. % (Example 3), and the other conditions were the same as in Example 1.
In the same manner as in the above, a film having a heat seal layer / base layer / heat seal layer thickness of 1/20/1 μm was formed.

(Examples 4 and 5) Instead of the second component in Example 1, 80% by weight of the same polypropylene homopolymer as the first component and α as an aromatic hydrogenated petroleum resin
-Methylstyrene-vinyltoluene copolymer (trade name:
Alcon, Arakawa Chemical Industry Co., Ltd.) of 20% by weight was mixed and granulated using a twin-screw kneading granulator, and the resulting mixture was used as the 2A component. The 1st component: the 2A component: the weight of the 3rd component The final concentration of the aromatic hydrogenated petroleum resin was 3 wt% with a ratio of 75:15:10 (Example 4), and the first component: 2A component: third component was 65:25:10. The final concentration of the aromatic hydrogenated petroleum resin was adjusted to 5% by weight (Example 5), and the other conditions were the same as in Example 1, and the thickness of the heat seal layer / base layer / heat seal layer was
A 1/20/1 μm film was formed.

(Comparative Examples 1 and 2) The weight ratio of the first component: the second component: the third component was set to 90: 0: 10 so that the final concentration of the aliphatic hydrogenated petroleum resin became 0% by weight ( Comparative Example 1), the weight ratio of the first component: the second component: the third component was 0:
At 90:10, the final concentration of the aliphatic hydrogenated petroleum resin was adjusted to 18% by weight (Comparative Example 2), and the other conditions were the same as in Example 1, except that the heat seal layer / base layer / heat seal layer A film having a thickness of 1/20/1 μm was formed.

(Comparative Examples 3, 4, 5, 6, and 7) In Example 1, the heat setting temperature was set to 160 ° C., and
The final concentration of the aliphatic hydrogenated petroleum resin is 0% by weight (Comparative Example 3), 3% by weight (Comparative Example 4), 5% by weight (Comparative Example 5), 10% by weight (Comparative Example 6), 18% by weight. Each of the test pieces of Comparative Example 7 was formed into a film. The thickness of the heat seal layer / base layer / heat seal layer of each test piece in Comparative Examples 3 to 7 was a film of 1/20/1 μm. Comparative Example 3 is Comparative Example 1 except for the heat setting temperature.
Similarly, for Comparative Example 4, the same as Example 2 except for the heat setting temperature, for Comparative Example 5, the same as Example 5 except for the heat setting temperature, and for Comparative Example 6, the heat setting temperature 160 ° C., the weight ratio of the first component: the second component: the third component was 40:50:10, and the other conditions were the same as those in the example 1, and the comparative example 7 was the same as the comparative example 2 except for the heat setting temperature. To form a film.

[0030]

[Table 1]

[0031]

As described above, the biaxially oriented polypropylene film of the present invention is a petroleum resin-containing polypropylene resin obtained by blending an aliphatic or aromatic petroleum resin with a polypropylene resin in an amount of 0.5 to 5% by weight. With layers, 50 ° C
Heat shrinkage in the vertical and horizontal directions of 0.02 to 0.4%
Therefore, there is an effect that the mineral oil resistance is excellent. Therefore, if the biaxially stretched polypropylene film of the present invention is used as an exterior film for products or wrapping paper containing mineral oil, it does not cause swelling or wrinkles due to mineral oil, and maintains good commercial value over a long period of time. be able to.

In addition, the biaxially oriented polypropylene film of the present invention does not need to provide a vinylidene chloride layer on the film surface, which has been conventionally required to improve the mineral oil resistance, so that there is a concern about environmental pollution due to chlorine gas during incineration. There is no safety.

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Claims (3)

[Claims] 1. A petroleum resin-containing polypropylene resin layer obtained by mixing an aliphatic or aromatic petroleum resin with a polypropylene-based resin in an amount of 0.5 to 5% by weight. Is 0.02 to 0.4%. 2. A biaxially oriented polypropylene film having excellent mineral oil resistance. 2. The biaxially oriented polypropylene film having excellent mineral oil resistance according to claim 1, wherein a heat sealing layer is provided on at least one surface of the petroleum resin-containing polypropylene resin layer. 3. The method according to claim 1, wherein the aliphatic or aromatic petroleum resin is hydrogenated.
A biaxially oriented polypropylene film having excellent mineral oil resistance as described.