JPH0555299B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to an aluminum-deposited polypropylene multilayer film that is excellent in workability and low-temperature heat-sealing properties and exhibits little loss in gloss and gas barrier properties during heat-sealing. Technical background of the invention and its problems When packaging frozen foods, confectionery, retort foods, etc., packaging materials that are safe from a food hygiene perspective and have excellent water vapor barrier properties, gas barrier properties, and light reflectivity are used. It is preferable. Such water vapor barrier properties,
Aluminum foil has been widely used as a packaging material with excellent gas barrier properties, but this aluminum foil has the problems of being more expensive than polymer films and having poor bending resistance. Ta. To solve these problems, aluminum vapor-deposited films, in which an aluminum vapor-deposited layer is provided on a polymer film such as a polyester film or a polypropylene film, have begun to be used instead of aluminum foils. This aluminum vapor-deposited film has excellent water vapor barrier properties, gas barrier properties, and light reflection properties that are comparable to aluminum foil, and thanks to the development of large-scale, high-performance vapor deposition equipment, it has become cheaper than aluminum foil. It has the advantage of being manufacturable. By the way, at present, as mentioned above, the polymer films on which the aluminum vapor deposited layer is provided are:
Polyester films, polypropylene films, etc. are used, but specifically, biaxially oriented polyester films, biaxially oriented polypropylene films, coated films with special coatings on biaxially oriented polypropylene films,
Unstretched single-layer polypropylene films, unstretched single-layer polyethylene films, and the like are used for a variety of purposes, taking advantage of their respective characteristics. Among these, unstretched polypropylene films are excellent as food packaging materials because they can be heat-sealed and produce aluminum-deposited films with excellent heat resistance and workability. Although both propylene homopolymers and copolymers are used as the unstretched polypropylene film, propylene-based copolymers are mainly used. The reason for this is that heat sealing is used when manufacturing packaging bags from aluminum vapor-deposited film obtained by vapor-depositing aluminum on polypropylene film, or when sealing after filling food etc. It is preferable to use a film that melts at a low temperature in order to improve the heat seal processing efficiency per unit time, and in this respect, a propylene-based copolymer is preferable to a propylene homopolymer because it melts at a low temperature. It is from. By the way, propylene-based copolymers have a melting point (DSC melting peak temperature) of 135-145℃.
It is common that However, since this copolymer film has low rigidity, it is flexible and has the problem that various troubles tend to occur during unwinding and winding of the film in various steps such as film formation and vapor deposition. Furthermore, during production, such propylene-based copolymers contain many substances that impair film properties, such as oligomers and sticky low-melting polymers, and it is difficult to completely remove these substances even through the purification process. be. If these oligomers, such as low melting point polymers, are unevenly distributed on the surface of the film on which aluminum is deposited, there is a problem in that the aluminum is not deposited uniformly on the film, resulting in unevenness. On the other hand, when an aluminum vapor-deposited unstretched single-layer polypropylene film obtained by vapor-depositing aluminum on an unstretched propylene polymer is used to produce packaging bags or to seal foods, etc. by the heat-sealing method, the heat-sealed part In this case, the metallic luster of aluminum is significantly impaired. The inventors investigated the cause of this phenomenon and found that the polypropylene film melts during heat sealing, making it unable to support the aluminum thin film deposited on the heat sealing area, resulting in fine cracks in the aluminum thin film. It was found that this is due to the crazing phenomenon that occurs. When crazing occurs in an aluminum vapor-deposited film, it not only reduces its commercial value due to poor appearance, but also impairs the water vapor barrier properties and gas barrier properties that the aluminum vapor-deposited film is said to have. Purpose of the Invention The present invention aims to solve the problems associated with the prior art as described above. The purpose of the present invention is to provide an aluminum vapor-deposited film based on polypropylene, which can be sealed at a low sealing temperature and without uneven vapor deposition during aluminum vapor deposition. The present invention achieves the above objects by using a film having a multilayer structure in which a plurality of polypropylene-based films are laminated. Summary of the Invention The aluminum vapor deposited film of the first aspect of the present invention has a polypropylene-based first film on which:
A multilayer film in which a second polypropylene film and a third polypropylene film are laminated in this order, a thin aluminum film is deposited on the third film, and the first films are heat-sealed to each other. The melting point of the first polymer constituting the first film is 15° C. or more lower than the melting point of the second polymer constituting the second film, and the third film is composed of the second polymer constituting the second film. It is characterized by being composed of a polymer blended with 5 to 80% by weight of the first polymer. Further, in the aluminum vapor-deposited film of the second aspect of the present invention, a polypropylene-based third film is laminated on the polypropylene-based first film, and an aluminum thin film is vapor-deposited on the third film, and the first films are heated together. The third film is a multilayer film designed to be sealed, and the third film is made by blending the first polymer constituting the first film with a polypropylene second polymer having a melting point 15°C or more higher than that of the polymer in an amount of 5 to 80% by weight. It is characterized by being made of a polymer. In this multilayer film made of a polypropylene film, the film on which the aluminum thin film is deposited is made of a blend of a polypropylene second polymer with a high melting point and a polypropylene first polymer with a low melting point. Moreover, by forming the heat-sealing surface with the first polypropylene polymer having a low melting point, unevenness in aluminum vapor deposition will not occur during aluminum vapor deposition even if this film is wound and stored. Furthermore, fine cracks will not occur in the deposited aluminum thin film during heat sealing. DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below with reference to embodiments shown in the drawings. As shown in FIG. 1, the aluminum vapor-deposited film of the first aspect of the present invention includes a first polypropylene film 1, a second polypropylene film 2, and a third polypropylene film 3.
are laminated in this order, and an aluminum thin film 4 is deposited on this third film. The melting point of the first polypropylene polymer constituting the first film 1 is 15% higher than the melting point of the second polypropylene polymer constituting the second film.
The temperature is preferably lower than 15°C, preferably 15 to 30°C. In order to make the melting point of the first polypropylene polymer constituting the first film 1 15° C. or more lower than the melting point of the second polypropylene polymer constituting the second film, the first polypropylene polymer may be, for example, Copolymer of propylene and ethylene with a melting point of 135-145 ° C,
A copolymer of propylene, ethylene and butene with a melting point of 130 to 145°C or a copolymer of propylene, ethylene and hexene with a melting point of 130 to 145°C is used, and a homopolymer of propylene with a melting point of 163°C, for example, is used as the second polypropylene polymer. You can use The polypropylene-based third film 3 is prepared by blending the first polymer with the second polymer as described above such that the first polymer is present in an amount of 5 to 80% by weight, preferably 10 to 70% by weight of the whole. It is composed of a polymer. If the blend amount of the first polymer is less than 5% by weight, when the multilayer film is wound and stored in the manufacturing process of the aluminum vapor-deposited film, the orimago contained in the polypropylene-based first film has a low melting point and is sticky. This is not preferable because the surface of the third polypropylene film, which is the surface on which aluminum is deposited by polymer or the like, is contaminated, resulting in uneven deposition of the aluminum thin film. On the other hand, if the blending amount of the first polymer exceeds 80% by weight, this is undesirable because crazing of the deposited aluminum thin film occurs during heat sealing. In the aluminum vapor deposited film explained above,
The thickness of the polypropylene first film 1 is 1~
100μ, polypropylene second film 2
The thickness of the third polypropylene film 3 is 1 to 200 μ, and the thickness of the aluminum thin film 4 deposited on the third polypropylene film is 100 to 600 Å. is preferred. Next, an aluminum vapor-deposited film according to a second aspect of the present invention will be explained. As shown in FIG. An aluminum thin film 4 is deposited on this third film. In the aluminum vapor deposited film of the second embodiment, the first polypropylene film 1 and the third polypropylene film 3 have the same structure as the first film 1 and the third film 3, respectively, in the aluminum vapor deposited film of the first embodiment. Except for the thickness of each film, the aluminum vapor-deposited film of the second embodiment has the same structure as the aluminum vapor-deposited film of the first embodiment except for the second polypropylene film. Therefore, the third film 3 in the aluminum vapor-deposited film of the second embodiment is composed of a polymer obtained by blending the above-mentioned first polypropylene polymer and second polypropylene polymer in a specific ratio. . In the aluminum vapor-deposited film of this second embodiment, the film thickness of the polypropylene-based first film 1 is 1
The thickness of the third polypropylene film 3 is preferably 1 to 400 μ, and the thickness of the aluminum thin film 4 deposited on the third polypropylene film is preferably 100 to 600 Å. In the present invention, heat sealing of the aluminum vapor-deposited film is performed on the surface of the polypropylene-based first film made of the first polymer having a low melting point in both the first embodiment and the second embodiment. In the present invention, if necessary, contact or In order to reduce the effects of crimping, anti-blocking agents such as SiO ₂ .nH ₂ O can also be added. However, use of a large amount of this anti-blocking agent should be avoided since it will significantly impair the gloss of the deposited surface. In addition, care must be taken because uneven vapor deposition of the aluminum thin film may occur due to poor dispersion of polymer additives added to the polymer constituting the aluminum vapor-deposited film according to the present invention or adhesion of oily substances to the vapor deposition surface. be. Further, excessive addition of polymer additives such as fatty acid amide and metal soaps is not preferable because the vapor deposition of aluminum itself is suppressed. In the aluminum vapor deposited film according to the present invention,
Polypropylene type 1 which is heat sealed
By forming the film from a polypropylene-based first polymer having a low melting point, it becomes possible to heat-seal efficiently even at low temperatures. Furthermore, a polypropylene-based third film on which an aluminum thin film is deposited, a polypropylene-based second polymer having a melting point higher than that of the above-mentioned first polymer by 15°C or more, and the above-mentioned first polymer; 80% by weight, preferably 10-70% by weight of the film laminate when depositing an aluminum thin film on the film laminate. Even if the first film and the third film are brought into contact or pressed together after being rolled up and stored, the surface of the third film, which is the aluminum-deposited surface, will not be the same as the first film.
The uneven deposition of the aluminum thin film due to contamination with the film is less likely to occur. Furthermore, the crazing phenomenon in which fine cracks occur in the aluminum thin film deposited on the third film during heat sealing is less likely to occur. In this way, in the aluminum vapor-deposited film according to the present invention, the aluminum thin film 4 is attached to the third film 3.
The aluminum film can be evenly and uniformly deposited on the top, and the deposited aluminum thin film 4 will not be destroyed during heat sealing, so the packaging bag obtained from this aluminum vapor-deposited film has excellent water vapor barrier properties (moisture proof properties) and gas barrier properties. It has properties (such as fragrance retention) and light reflectivity. The aluminum vapor-deposited film according to the present invention is produced by first manufacturing a multilayer polypropylene film as a base by, for example, a T-die method or an inflation method, and then depositing an aluminum thin film on the obtained film laminate using, for example, a vacuum evaporator. Manufactured by laminating layers to a desired thickness. Effects of the Invention The aluminum vapor-deposited film according to the present invention is a laminate of a first film, a second film, and a third film, or a laminate of a first film and a third film, each of which is made of a specific polypropylene polymer. Therefore, the aluminum thin film can be evenly and uniformly deposited on the third film, and furthermore, it can be sealed at a low sealing temperature. Therefore, crazing is less likely to occur in the aluminum thin film at the heat-sealed portion. Therefore, the packaging bag obtained from this aluminum vapor-deposited film has excellent water vapor barrier properties (moisture proof properties), gas barrier properties (fragrance retention properties), and light reflectivity. The present invention will be explained below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. Example 1 First film constituting the first polypropylene film
The polymer used was a propylene-ethylene random copolymer with a melting point of 138°C to which 4500 ppm of SiO ₂ .nH ₂ O, an anti-blocking agent, was added. Using propylene homopolymer, polypropylene tertiary
The third polymer constituting the film is a blend of 95% by weight of propylene homopolymer, which is the second polymer, and 5% by weight of propylene-ethylene random copolymer, which is the first polymer, to which 4500 ppm of SiO ₂ .nH ₂ O is added. The polymer was used. 25μ thick and 1950mm wide from these polymers
A multilayer film was prepared using a T-die type film forming machine and wound into a roll. The thickness of each film is the first
The film was 2.5μ, the second film was 20μ, and the third film was 2.5μ. After aging the obtained film in an atmosphere at 30° C. for 2 days, aluminum vapor deposition was performed using a winding type vacuum device EW series manufactured by Japan Vacuum Technology Co., Ltd. under the following vapor deposition conditions. However, aluminum vapor deposition was performed on the third film. Deposition conditions Deposition chamber vacuum 1×10 ^-4 torr Film winding speed 250 m/min Deposited film thickness 350Å Deposited metal Aluminum heat sealing conditions Heat sealing temperature 130°C Heat sealing time 0.5 seconds Heat sealing pressure 1Kg/cm ² Obtained aluminum The unevenness of aluminum vapor deposition on the vapor-deposited film was observed, and after the vapor-deposited film was heat-sealed on the first film surface, it was observed whether crazing had occurred in the aluminum thin film. Furthermore, four films before aluminum vapor deposition were stacked and their haze (%) was examined. The results are shown in Table 1. Comparative Example 1 In Example 1, the second polymer, a propylene homopolymer with a melting point of 163°C, was used as it was without adding the first polymer, a propylene-ethylene copolymer, as the third polymer constituting the third polypropylene film. Except that there was
An aluminum vapor-deposited film was prepared in the same manner as in Example 1, and the unevenness of aluminum vapor deposition, the presence or absence of crazing, and the degree of haze were examined. The results are shown in Table 1. Comparative Example 2 In Comparative Example 1, the melting point of the polymer constituting the first polypropylene film was that SiO ₂ .nH ₂ O, which is an anti-blocking agent, was not added.
An aluminum vapor-deposited film was prepared in the same manner as in Comparative Example 1, except that a propylene-ethylene random polymer at 138°C was used, and the unevenness of aluminum vapor deposition was examined. The results are shown in Table 1. Comparative Example 3 An aluminum vapor-deposited film was created in the same manner as in Example 1, except that the first film, second film, and third film were all constructed using a propylene-ethylene random copolymer with a melting point of 138°C. The results are shown in Table 1, and the results are shown in Table 1.

[Table] Example 2 In Example 1, as the third polymer constituting the third polypropylene film, 80% by weight of the second polymer, propylene homopolymer, and the first
An aluminum vapor-deposited film was prepared in the same manner as in Example 1, except that a polymer blended with 20% by weight of a propylene-ethylene random copolymer was used. In the obtained aluminum vapor-deposited film, no uneven vapor deposition was observed, and no crazing was observed at the heat-sealed portion. Example 3 In Example 1, as the third polymer constituting the third polypropylene film, 50% by weight of the second polymer, propylene homopolymer, was used.
Propylene-ethylene random copolymer 50, which is the first polymer to which SiO ₂・nH ₂ O is not added
An aluminum vapor-deposited film was prepared in the same manner as in Example 1, except that a polymer blended with % by weight was used. In the obtained aluminum vapor-deposited film, no uneven vapor deposition was observed, and only slight crazing was observed at the heat-sealed portion. Example 4 First film constituting the first polypropylene film
A propylene-ethylene random copolymer with a melting point of 138°C to which 4500 ppm of SiO ₂ .nH ₂ O, an anti-blocking agent, was added was used as the polymer, and a polymer with a melting point of 163°C was used as the third polymer constituting the third polypropylene film. A blend of 50% by weight of propylene homopolymer and 50% by weight of propylene-ethylene random copolymer to which 4500 ppm of SiO ₂ .nH ₂ O was added was used. From this first polymer and third polymer, the thickness
A multilayer film of 25 μm and width of 1950 mm was prepared using a T-die type film forming machine and wound into a roll. The thickness of each film was 2.5μ for the first film and 22.5μ for the third film. An aluminum vapor-deposited film was prepared from the obtained film in the same manner as in Example 1. In the obtained aluminum vapor-deposited film, no uneven vapor deposition was observed, and only slight crazing was observed in the heat-sealed portion. Example 5 First film constituting the first polypropylene film
A propylene-ethylene random copolymer with a melting point of 138°C to which 4500 ppm of SiO ₂ .nH ₂ O, an anti-blocking agent, was added was used as the polymer, and a polymer with a melting point of 163°C was used as the third polymer constituting the third polypropylene film. A blend of 80% by weight of propylene homopolymer and 20% by weight of propylene-ethylene random copolymer to which 4500 ppm of SiO ₂ .nH ₂ O was added was used. From this first polymer and third polymer, the thickness
A multilayer film with a size of 25μ and a width of 1950 mm was wound into a roll made using a T-die type film forming machine. The thickness of each film is 22.5μ for the first film and 22.5μ for the third film.
The film was 2.5μ. An aluminum vapor-deposited film was prepared from the obtained film in the same manner as in Example 1. In the obtained aluminum vapor-deposited film, no uneven vapor deposition was observed, and no crazing was observed in the heat-sealed portion. Comparative Example 4 First film constituting the first polypropylene film
A propylene-ethylene random copolymer with a melting point of 141°C is used as the polymer, and a propylene homopolymer with a melting point of 163°C is used as the second polymer constituting the second polypropylene film.
The film thickness ratio of the first film and the second film is 9:1
A multilayer film was produced using the T-die method. Four sheets of this film were stacked so that the front and back sides were in contact with each other alternately, and a pressure of 1 kg/10 cm ² was applied from above, and the film was left in an atmosphere at 50° C. for 5 days. Thereafter, aluminum was deposited on the surface of the second film by vacuum deposition. This vapor deposition was carried out using a Hitachi HVS-3B vacuum vapor deposition machine under the following conditions. Vacuum degree 1×10 ^-4 torr Vapor deposition temperature
Approximately 1400°C (dungsten heater) Vapor deposition distance: 10 cm Vapor deposition time: 2 seconds The resulting vapor-deposited film had an aluminum film thickness of approximately 350 Å. However, when the transmitted light was visually observed, there was a clear difference in intensity of transmitted light between the area on which the load was placed and the area on which no load was placed, and more light was transmitted through the area where the load was placed. As a result, there is unevenness in light transmittance within a single film, which not only significantly reduces commercial value but also impairs moisture resistance and gas barrier properties.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are cross-sectional views of an aluminum vapor-deposited film according to the present invention. 1...Polypropylene first film, 2...
Polypropylene second film, 3... Polypropylene third film, 4... Aluminum thin film.

Claims (1)

[Claims] 1. A multilayer film in which a third polypropylene film is laminated on a first polypropylene film, and a thin aluminum film is vapor-deposited on the third film, and the first films are heat-sealed to each other. In the third film, 5 to 80% by weight of the first polypropylene polymer constituting the first film is added to the second polypropylene polymer whose melting point is 15°C or more higher than that of this polymer.
An aluminum vapor-deposited film characterized in that it is composed of a polymer blended in an amount of . 2. The aluminum vapor-deposited aluminum according to claim 1, wherein the first polymer constituting the first polypropylene film is a propylene-ethylene copolymer having a melting point of 135 to 145°C. 3. The aluminum-deposited film according to claim 1, wherein the first polymer constituting the polypropylene-based first film is a propylene-ethylene-butene copolymer having a melting point of 130 to 145°C. 4. The aluminum-deposited film according to claim 1, wherein the first polymer constituting the polypropylene-based first film is a propylene-ethylene-hexene copolymer having a melting point of 130 to 145°C. 5. The third polymer constituting the third polypropylene film is a polymer obtained by blending the first polymer with a second polypropylene polymer whose melting point is 15°C or more higher than that of this polymer in an amount of 10 to 70% by weight. An aluminum vapor-deposited film according to claim 1. 6. A second polypropylene film and a third polypropylene film are laminated in this order on the first polypropylene film, and a thin aluminum film is deposited on the third film, and the first films are heat-sealed to each other. The melting point of the first polypropylene polymer constituting the first film is 15° C. or more lower than the melting point of the second polypropylene polymer constituting the second film, and the third film is lower than the melting point of the second polypropylene polymer constituting the second film. 5 to 80% of the first polymer constituting the first film to the second polymer constituting the first film.
An aluminum vapor-deposited film characterized by being composed of polymers blended in weight percent. 7. The aluminum-deposited film according to claim 6, wherein the first polymer constituting the polypropylene-based first film is a propylene-ethylene copolymer having a melting point of 135 to 145°C. 8. Claim 6, wherein the first polymer constituting the first polypropylene film is a propylene-ethylene-butene copolymer with a melting point of 130 to 145°C.
The aluminum vapor-deposited film described in . 9. The aluminum vapor-deposited film according to claim 6, wherein the first polymer constituting the polypropylene-based first film is a propylene-ethylene-hexene copolymer having a melting point of 130 to 145°C. 10. The aluminum-deposited film according to claim 6, wherein the second polymer constituting the polypropylene-based second film is a propylene homopolymer. 11. The aluminum according to claim 6, wherein the third polymer constituting the third polypropylene film is a polymer obtained by blending the first polymer into the second polymer in an amount of 10 to 70% by weight. Evaporated film.