JPH0571613B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a polypropylene film for deposition. More specifically, the present invention relates to a polypropylene film for deposition that has excellent barrier properties against gases such as water vapor and oxygen. [Prior Art] Conventionally, polypropylene films are surface-treated and metals such as aluminum are deposited on them for packaging purposes (for example, Japanese Patent Publication No. 18381/1981). [Problem to be solved by the invention] The vapor deposited film obtained by the conventional method is
If the vapor deposition adhesive strength is not sufficient, the vapor deposited film will be easily damaged and peeled off due to abrasion, and if the vapor deposition adhesive strength is not sufficient, the vapor deposited film will easily disappear under high temperature and high humidity, resulting in a deterioration of the gas barrier properties of the vapor deposited film. do. Also, since the film receives heat during metal deposition,
The gas barrier properties of the vapor-deposited film were poor, probably because the film underwent minute dimensional changes and the vapor-deposited film induced micro-cracks. The present invention improves these problems and provides a vapor-deposited film with strong adhesive strength and excellent gas barrier properties.
The purpose is to provide a polypropylene film for vapor deposition. [Means for Solving the Problems] The present invention provides one side of a polypropylene film (A
The atomic composition ratio (number of oxygen atoms/number of carbon atoms) of the surface layer (abbreviated as surface) is in the range of 0.10 to 0.34, (number of nitrogen atoms/number of carbon atoms) is in the range of 0.005 to 0.08,
and the temperature at which heat loss starts in the longitudinal direction of the film is
This is a polypropylene film for vapor deposition characterized by a temperature of 105°C or higher. The polymer of the polypropylene film in the present invention is preferably a propylene homopolymer, but propylene may also be a copolymer with other α-olefins (eg, ethylene, butene, pentene, etc.). When using a copolymer, the propylene component is preferably 95% by weight or more. The isotactic index (II) of the propylene polymer is preferably 90 or more, preferably 95 or more. The intrinsic viscosity [η] is preferably in the range of 1.2 to 2.5 dl/g. The _F5 value (stress at 5% elongation) of the polypropylene film of the present invention in the longitudinal direction is 4.0 Kg/mm ² or more,
Preferably, it is 4.5 Kg/mm ² or more because gas barrier properties can be improved. This is due to the effect of controlling cracks in the vapor-deposited film by preventing dimensional changes in the film due to tension during vapor deposition or post-processing of the vapor-deposited film. The polypropylene film of the present invention may also contain commonly used additives such as slip agents, heat and antioxidant agents, inorganic fine particles, antistatic agents, thickeners, and thinners. The ratio (number of oxygen atoms/number of carbon atoms) of the A-side surface layer in the present invention (hereinafter abbreviated as "O/C")
must be in the range 0.10 to 0.34,
More preferably, it is in the range of 0.20 to 0.30. If the value is smaller than this range, the vapor deposition adhesive strength will be poor. Conversely, if the value is larger than this range, the surface layer of the film tends to become brittle, resulting in a decrease in adhesive strength. Next, the ratio (number of nitrogen atoms/number of carbon atoms) (hereinafter abbreviated as "N/C")
must be in the range 0.005 to 0.08,
More preferably, it is in the range of 0.01 to 0.05. When the N/C value is smaller than this range, the vapor deposition adhesive strength becomes inferior.
The deposited film is easily damaged by abrasion, resulting in poor gas barrier properties. On the other hand, if the value is larger than this range, the adhesiveness will be poor and at the same time the film will start to block. In the present invention, the surface layer of the polypropylene film (usually an extremely thin layer from the surface to a depth of about 10 nm)
It is necessary to simultaneously contain oxygen atoms and nitrogen atoms within the above range. Note that if the surface layer only contains oxygen atoms or only nitrogen atoms, the adhesion with the metal vapor deposited film and abrasion resistance will be poor, so the gas barrier properties will be poor. It is extremely difficult to use it as a good vapor deposition film. Further, in the present invention, the temperature at which heat loss begins in the longitudinal direction of the polypropylene film must be 105°C or higher, preferably 110°C or higher. If the heat loss start temperature is less than 105°C, preferably less than 110°C, gas barrier properties will be significantly deteriorated. Although the cause of this is not clear, it is presumed that the amount of heat during metal vapor deposition causes minute dimensional changes in the film, causing distortion at the vapor deposition interface and causing cracks in the vapor deposited film. In the present invention, the side opposite to side A (hereinafter referred to as “side B”)
It is preferable to use a propylene/ethylene copolymer or/and an ethylene/propylene/butene copolymer laminated on the (abbreviated as). This is because the propylene/ethylene copolymer layer or ethylene/propylene/butene copolymer layer adheres closely to the cooling drum (cooling can) of the vapor deposition machine during metal deposition, preventing it from slipping on the cooling drum. As a result, the amount of thermal dimensional change in the film can be reduced, and gas barrier properties can be greatly improved. Here, the propylene/ethylene copolymer is preferably one in which 1 to 7% by weight of ethylene is randomly copolymerized with propylene, and the ethylene/propylene/butene copolymer is preferably one in which propylene is randomly copolymerized with 1 to 5% by weight of ethylene. , butene is preferably copolymerized in an amount of 3 to 20% by weight. Lamination thickness is not particularly limited, but may be 1 to 8 μm,
From the viewpoint of gas barrier properties and dimensional stability, the thickness is preferably 1 to 3.5 μm. Next, an example of the method for producing the polypropylene film of the present invention will be explained. The extruder temperature is 210-280℃, the isotactic index is more than 90%, the limit [η] 1.2-2.5
Melt dl/g of polypropylene resin and extrude it into a sheet through a T-die with slits.
It is cooled and solidified using a cooling roll at ℃ to form an unstretched sheet. At this time, if necessary, a propylene-ethylene copolymer or/and an ethylene-propylene-butene copolymer are melt-extruded from another extruder and laminated using a T-die to form a laminated unstretched sheet. This unstretched sheet is stretched 3 to 6 times in the length direction while heating in an oven heated to 133 to 144°C, and then stretched 7 to 12 times in the width direction at a temperature of 155 to 165°C.
It is stretched twice and heat treated at a temperature of 155 to 165°C while relaxing 8.5 to 12% in the width direction. Thereafter, the film is introduced into a mixed gas of nitrogen and carbon dioxide gas (volume ratio of carbon dioxide gas: 0.5 to 50%), and while maintaining the film temperature at 40 to 100°C, preferably 45 to 90°C, the film is heated at 20 to 120 W. The A ^side is subjected to corona discharge treatment at a rate of 100% of the film forming speed ratio. Further, the film thus obtained is slit to a predetermined width and length, and it is preferable that the longitudinal tension at the time of slitting is also low. The method of measuring the characteristic value and the method of evaluating the effect of the present invention are as follows. (1) Measuring method of atomic composition ratio of film surface layer Using ESCA750 manufactured by Shimadzu Corporation, the film surface was treated with excitation X-ray: MgK〓 _1,2 line, photoelectron escape angle was 90 degrees, C _1s main peak was Adjust the binding energy value to 284.6eV and adjust the 1s axial path.
From the spectrum obtained by ESCA measurement, C _1s
The area ratio between _{the peak} of The ratio of the number of nitrogen atoms/the number of carbon atoms, that is, the value of N/C. (2) Temperature at which heat loss begins in the longitudinal direction of the film (℃) Using a thermomechanical analyzer (TMA system) manufactured by Perkin-Elmer, a sample measuring 14 mm in the length direction and 5 mm in the width direction was taken from the film. After setting the film so that the sample length is 10 mm without wrinkles or tilting, 1 mm ² (cross-sectional area) of the film is set.
A load of 40 g was applied to each sample, and the temperature of this sample was raised from a heating start temperature of 25°C at a heating rate of 10°C/min.
When a heating dimensional change curve is drawn with the dimensional change rate on the vertical axis and the temperature on the horizontal axis, the temperature at the intersection of the heating dimensional change curve with the dimensional change rate 0% axis (the dimensional change rate increases at the beginning as the temperature increases) The temperature at which the temperature increases, reaches a maximum value, then decreases to 0% again) is defined as the heat recovery start temperature. FIG. 1 is an example of a heating dimensional change curve,
1 is a heating dimensional change curve, and 2 is a heat loss start temperature. (3) Gas barrier properties (A) Water vapor permeability Measured according to JIS Z 208. At this time, it was set so that the evaporation surface was on the calcium chloride side. (B) Oxygen permeability After leaving the film at room temperature and humidity for one week,
Oxygen permeability was measured according to ASTM-D-1434 using an OX-TRAN100 oxygen permeability measuring device manufactured by Modern Controls. (4) Vapor deposition adhesive strength Evaluation was made by the remaining area of metal adhesion after laminating a commercially available cellophane adhesive tape (registered trademark "Cello Tape") to the metal vapor deposition surface and peeling it off at 90°. Remaining area Adhesion index 95% or more 5 90% or more and less than 95% 4 75% or more and less than 90% 3 50% or more and less than 75% 2 Less than 50% Judgment was made according to the criteria of 1. The higher the adhesion index, the better the adhesion. (5) Abrasion resistance of vapor-deposited surfaces Rub the vapor-deposited surfaces together 10 times under a load of 5 g/cm ² pressure.
Judgment was made as follows based on the difference in gloss before and after rubbing. Glossiness reduction rate (ΔG) = Glossiness before rubbing - Glossiness after 10 rubs / Glossiness before rubbing ○: ΔG≧0.95 △: 0.85≦ΔG＜0.95 ×: ΔG＜0.85 (6) _F5 value Using Tensilon, film width 10mm, sample length
A 100 mm sample was pulled at a tensile speed of 300 mm/min, and the strength (Kg) at 5% elongation of the film was divided by the cross-sectional area (mm ² ) of the film. [Function] By setting the surface of A side to a specific atomic composition ratio (O/C, N/C), the metal vapor deposition film is not damaged or peeled off due to wear, and the vapor deposition adhesion is strong. becomes. What should be noted here is that if the surface has a specific atomic composition ratio, it will ooze out from the polypropylene surface layer during metal vapor deposition and increase the intermolecular force between the metal microcrystals. The filling state becomes dense, and as a result, it is effective in suppressing gas permeation with extremely few crystal defects and voids. In addition, the temperature at which heat loss begins in the film length direction is set to 105
By setting the temperature above 0.degree. C., changes in shrinkage dimensions of the film due to heat generation during vapor deposition are suppressed, and metal vapor deposition cracks are prevented, thereby improving gas barrier properties. [Example] The present invention will be explained based on an example. Example 1 A propylene homopolymer with an [η] of 2.2 dl/g and an isotactic index of 96.5% was melt-extruded at an extruder temperature of 270°C, cooled and solidified in a cooling drum at 40°C, and an unstretched sheet was obtained. I made it. This sheet was passed through an oven heated to 141°C and stretched 5 times in the longitudinal direction while being heated. Next, this uniaxially stretched film was heated to 115°C and subjected to 3% relaxation. Next, while heating to 163℃,
Stretched 9 times in the width direction and heat treated at 160℃ with 9.5% relaxation in the width direction to a thickness of 20μ
A biaxially oriented polypropylene film of m was prepared.
Next, one side (Side A) of this film was heated to 80°C in a mixed gas of nitrogen and carbon dioxide gas (volume fraction of carbon dioxide gas: 10%), corona discharge treated at 26 W min/ ^m2 , and rolled. I took it. O/C, N/ of the film
C. The heat loss start temperature was calculated and shown in Table 1. Furthermore, this film was coated with a 1000mm width vapor deposition machine for 300mm
Aluminum was deposited to a thickness of 35 nm on the A side at a rate of m/min. Table 1 shows the properties of the deposited film. Example 2 A propylene homopolymer having an [η] of 1.85 dl/g and an isotactic index of 97.5% was melt-extruded at an extrusion temperature of 260° C. to produce a uniaxially stretched film in the same manner as in Example 1. Next, this uniaxially stretched film was subjected to 4.8% relaxation while being heated at 130°C. Subsequently, the film was stretched 9 times in the width direction while being heated to 164°C, and the rest was carried out in exactly the same manner as in Example 1 to produce a biaxially stretched polypropylene film.
Next, it was heated to 80° C. in a mixed gas of nitrogen and carbon dioxide and subjected to corona discharge treatment at 29 W·min/m ² . Subsequently, aluminum vapor deposition was performed in the same manner as in Example 1. The film properties are shown in Table 1. Comparative Examples 1 to 3 Biaxially stretched films were made in the same manner as in Example 1, except that the corona discharge treatment strength was changed to provide O/C and N/C as shown in Table 1. Aluminum was deposited in the same way as Matsutaku. The characteristics are shown in Table 1. Comparative Example 4 A biaxially stretched film was prepared in the same manner as in Example 1, and then one side (side A) of this film was heated in air to 65°C and corona discharge treated at 24W min/ ^m2 . The film was wound up in the same manner as in Example 1, and aluminum was deposited on the A side of the film to a thickness of 35 nm in the same manner as in Example 1. The characteristics are shown in Table 1. Comparative Example 5 A propylene homopolymer with [η] of 2.2 dl/g and isotactic index of 96.5% was melt-extruded at an extrusion temperature of 270°C, cooled and solidified in a cooling drum at 40°C, and an unstretched sheet was produced. Ivy. This sheet was passed through an oven heated to 135°C and stretched 5 times in the longitudinal direction while being heated. Next, this uniaxially stretched film was subjected to 2% relaxation at 110°C, then stretched 9 times in the width direction while being heated to 162°C, and heat treated at 155°C while applying 9.5% relaxation in the width direction. A biaxially stretched polypropylene film with a thickness of 20 μm was produced. The film was subjected to surface treatment and aluminum vapor deposition in the same manner as in Example 1. The film properties are shown in Table 1. Example 3 A propylene homopolymer with [η] 1.85 dl/g and an isostatic index of 97.5% was melt-extruded from one extruder at an extrusion temperature of 260°C, while an ethylene homopolymer was melt-extruded from another extruder. A propylene random copolymer (ethylene content 3.7% by weight) was melt extruded and laminated with a die. The thickness of the biaxially stretched film at this time was 16.5 μm for the polypropylene layer and 3.5 μm for the propylene/ethylene copolymer layer. Then, in the same manner as in Example 1, biaxial stretching, surface corona treatment, and aluminum vapor deposition were performed. The properties of the obtained film are shown in Table 1. As is clear from Table 1, Examples 1, 2, and 3
It can be seen that the film of the present invention has strong metal deposition adhesion, wear resistance, and excellent gas barrier properties (water vapor permeability, oxygen permeability). On the other hand, in Comparative Examples 1 to 4, if the atomic ratio of the surface layer is not within a specific range, the vapor deposition adhesive strength and the abrasion resistance of the vapor deposited film are poor, and the gas barrier properties are also poor. Furthermore, in Comparative Example 5, the gas barrier properties became poor as the heat recovery start temperature became lower.

〔Effect of the invention〕

As described above, the present invention provides the following excellent effects by specifying the atomic composition ratio on the surface of the polypropylene film and specifying the temperature at which heat loss begins in the longitudinal direction of the film. (1) A film with excellent adhesion to metal vapor deposition could be obtained. (2) A film with excellent gas barrier properties after metal vapor deposition could be obtained.

[Brief explanation of drawings]

FIG. 1 is an example of a heating dimensional change curve obtained when measuring the heat loss start temperature.

Claims (1)

[Claims] 1. The atomic composition ratio (number of oxygen atoms/number of carbon atoms) of the surface layer on one side of the polypropylene film is 0.10 to 0.10.
0.34, (number of nitrogen atoms/number of carbon atoms) is 0.005~
0.08, and a heat loss onset temperature in the longitudinal direction of the film is 105° C. or higher. 2. The polypropylene film for vapor deposition according to claim 1, wherein a propylene/ethylene copolymer or an ethylene/propylene/butene copolymer is laminated on the opposite side of the one side.