JPS6315942B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a modified polypropylene film having excellent metal deposition properties and ink adhesion properties. More specifically, the present invention provides a method for producing a modified polypropylene film that has excellent adhesion to metal during metal vapor deposition and adhesion to printing ink. In recent years, metal-deposited polypropylene films, especially aluminium-deposited polypropylene films, have increased in price due to the soaring price of aluminum, as well as having a beautiful metallic luster, good gas barrier properties, and UV rays.
Due to its properties such as good visible light and infrared ray blocking effects, it is used in large quantities as food packaging materials, building materials, electrical component materials, etc. However, since the surface of polypropylene film is inert, its adhesion to metal is weak, and many methods have been tried to improve this problem. For example, methods of physically making the film surface rough, methods of roughening it with perchlorethylene or trichlorethylene, oxidation and polarization through treatments such as gas flame, heated air, corona discharge, ozone, ultraviolet irradiation, and radiation irradiation. Pretreatment methods such as a method of imparting a group or a method of anchor coating with a material that has good vapor deposition ability with aluminum have been carried out. However, with the various pretreatment methods mentioned above,
Even if metal is vapor-deposited, the strength of the vapor-deposition is insufficient;
Another disadvantage is that the vapor deposition process and operations are complicated due to the pretreatment. On the other hand, in order to improve these drawbacks, it has been proposed to use a film made of polypropylene modified with unsaturated carboxylic acids. As an improvement to this technique, it has been proposed in JP-A-53-30678 to use modified propylene having a random index of 0.5 or more. Similarly, it has been proposed to subject the surface of a polypropylene film to a corona discharge treatment in a nitrogen atmosphere for the purpose of improving printability and metal deposition properties. However, the surface of a film made of polypropylene simply modified with unsaturated carboxylic acids,
The metal deposition power is not sufficient. Also random digits
When using a modified copolymer in which an unsaturated carboxylic acid is grafted onto a copolymer having rubber elasticity such as a propylene-ethylene random copolymer of 0.5 or more, or when the film is further subjected to corona discharge treatment, Although further improvement was seen, it was still not completely satisfactory. As a result of intensive research into a method for manufacturing a polypropylene film with high metal deposition ability, the inventors of the present invention have developed a method of corona discharge treatment of a film made of a specific modified polypropylene grafted with unsaturated carboxylic acids and a finely powdered inorganic filler. They have discovered that it is possible to produce a polypropylene film that has good metal vapor deposition properties and also has good printing ink adhesion, and has arrived at the present invention. The present invention relates to a modified polypropylene containing 30% by weight or more of a propylene-ethylene block copolymer having an ethylene content of 1 to 30% by weight, and
A film of a modified polypropylene composition comprising a mixture with 4.8 to 50% by weight of a finely divided inorganic filler, the modified polypropylene composition comprising 0.005 to 50% by weight of a finely divided inorganic filler.
This is a modified polypropylene film characterized in that 5% by weight of unsaturated carboxylic acid is grafted thereon and the film is corona discharge treated. In the present invention, modified polypropylene is a general term for propylene polymers or copolymers in which at least some of the molecules are graft-bonded with unsaturated carboxylic acids. The modified polypropylene composition is a mixture of the modified polypropylene and a finely powdered inorganic filler. Furthermore, the propylene-ethylene block copolymer used in the present invention is obtained by polymerizing propylene to form a propylene polymer chain of sufficient length, and then adding ethylene or a mixture of ethylene and propylene to the remaining polymer chain. The propylene-ethylene block copolymer is obtained by polymerization, and the ethylene content in the propylene-ethylene block copolymer is 1 to 30% by weight. A feature of such a copolymer is that it has the rigidity of crystalline polypropylene and also has the characteristics of being partially amorphous. Furthermore, the film obtained by the present invention is
The film itself can be used as a packaging film or other general film, and the film of the present invention can also be used as a material for a composite film laminated on other films, such as polypropylene film, by known means. The present invention will be specifically explained below. One of the features of the present invention is that at least 30% by weight of modified polypropylene is composed of a propylene-ethylene block copolymer. That is, the entire modified polypropylene may be the same copolymer, or it may contain less than 70% by weight of other polymers, such as propylene homopolymers, random or blocked propylene and other α-olefins. It may also be a mixture with a copolymer (α-olefin contains ethylene). These modified polypropylenes are modified polypropylene compositions containing a finely powdered inorganic filler, which will be described later, and are grafted with unsaturated carboxylic acids in an amount of 0.005 to 5% by weight. The unsaturated carboxylic acids in the modified polypropylene may be graft-bonded to one or more of the polymers constituting the modified polypropylene. Propylene used in the present invention -
The ethylene block copolymer is not particularly limited, but has an MFI of 0.1 to 50 g/10 min, preferably 0.5 to 30
g/10 min, and an ethylene content of 1 to 30 parts by weight, preferably 2 to 15 parts by weight. The method for producing the propylene-ethylene block copolymer is not particularly limited;
For example, propylene is polymerized in the presence of a catalyst containing titanium trichloride and an organoaluminum compound, and then in the presence of a polymer containing the catalyst obtained in the first step,
There are two-step polymerization methods in which ethylene alone or a mixed monomer of ethylene and propylene are block copolymerized. Examples of the unsaturated carboxylic acids used in the present invention include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, and their acid anhydrides, esters, amides, imides, metal salts, etc. For example, maleic anhydride, citraconic anhydride, itaconic anhydride, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate,
Butyl methacrylate, glycidyl acrylate, glycidyl methacrylate, monoethyl maleate, diethyl maleate, monomethyl fumarate, dimethyl fumarate, monomethyl itaconate, diethyl itaconate, acrylamide, methacrylamide, maleic acid Monoamide, maleic acid diamide, maleic acid-N-monoethylamide, maleic acid-N,N-diethylamide, maleic acid-
N-monobutylamide, maleic acid-N,N-dibutylamide, fumaric acid monoamide, fumaric acid diamide, fumaric acid-N-monoethylamide, fumaric acid-N,N-diethylamide, fumaric acid-N-
Monobutyramide, fumaric acid-N,N-dibutyramide, maleimide, N-butylmaleimide, N
- phenylmaleimide, sodium acrylate,
Sodium methacrylate, potassium acrylate,
Examples include potassium methacrylate.
Among these, it is most preferable to use maleic anhydride. The method for grafting unsaturated carboxylic acids in modified polypropylene is not particularly limited. For example, a method of reacting in a molten state (e.g., Japanese Patent Publication No. 43-27421), a method of reacting in a solution state (e.g., Japanese Patent Publication No. 44-15422), a method of reacting in a slurry state (e.g., Japanese Patent Publication No. 43-18144).
(No.), a method of reacting in a gas phase (for example, JP-A-Sho
No. 50-77493), but among these methods, the melt-kneading method using an extruder is preferably used because it is easy to operate. The amount of unsaturated carboxylic acids to be used is not particularly limited, but in order to obtain a good modified polypropylene, it is generally 0.01 to 20 parts by weight, preferably 0.01 to 20 parts by weight, per 100 parts by weight of the base polymer (hereinafter referred to as polypropylene). It is necessary to add 0.1 to 5 parts by weight. Furthermore, organic peroxides are used to promote the reaction between polypropylene and unsaturated carboxylic acids. Examples of organic peroxides include benzoyl peroxide, lauroyl peroxide, azobisisobutyronitrile, dicumyl peroxide, α,α'-bis(t-butylperoxydiisopropyl)benzene, 2,5-dimethyl-2 ,5
-di(t-butylperoxy)hexane, 2,5
-dimethyl-2,5-di(t-butylperoxy)hexane-3, di-t-butyl peroxide, cumene hydroperoxide, t-butyl hydroperoxide and the like. The amount of organic peroxide added is not particularly limited, but is usually 0.005 to 5 parts by weight per 100 parts by weight of polypropylene.
Preferably it is 0.01 to 1 part by weight. A specific method for producing modified polypropylene is to thoroughly mix the polypropylene shown above, unsaturated carboxylic acids, and organic peroxide in a tumbler, Henschel mixer, etc., and then mix the polypropylene at a temperature above the melting point of polypropylene, generally above the melting point and below 280°C. The grafting reaction is carried out by melt-kneading at a certain temperature. The melt-kneading method is not particularly limited, and can be carried out using, for example, a screw extruder, a Banbury mixer, a mixing roll, etc., but a screw extruder is preferably used because of its ease of operation. The temperature and time of melt-kneading vary depending on the decomposition temperature of the organic peroxide used, but generally 160 to 280°C for 0.3 to 30 minutes, preferably 170 to 250°C for 1 to 10 minutes is appropriate. Note that the melt-kneading may be performed in an inert gas stream. However, in the modified polypropylene produced as described above, even if unsaturated carboxylic acids are used in a predetermined ratio as described above, unreacted monomers inevitably remain. Therefore, in order to obtain the desired purpose, the above modified polypropylene is further added.
It is desirable to perform the heat treatment at a temperature of 60°C or higher, preferably 100°C or higher. If the heating temperature is below 60°C, the treatment will take a long time and is not practical. Although the upper limit of the heating temperature is not particularly limited, it is preferably below the melting point of the modified polypropylene in order to prevent fusion of the modified polypropylene. The heat treatment means may be a conventionally known method, such as an aeration band type dryer, a material agitation type dryer, a fluidized bed dryer, a flash dryer, a spray dryer, a rotary dryer, a drum type dryer, a vacuum dryer, Although the drying can be carried out using an infrared drying device, a far-infrared drying device, a microwave drying device, etc., a hot air drying device is preferably used. Note that if the heat treatment is performed under reduced pressure, the treatment effect will be further improved. The heat treatment time is not particularly limited, but if the heating temperature is low and the modified polypropylene contains a large amount of unreacted monomers of unsaturated carboxylic acids, it will take a long time, and if the heating temperature is high and the unreacted monomer is small. In some cases, a short period of time is sufficient. Generally, it is preferable to carry out the heat treatment so that the amount of unreacted monomer is 0.1% by weight or less. In the present invention, by mixing the modified polypropylene produced as described above with a finely powdered inorganic filler and, if necessary, unmodified polypropylene,
A modified polypropylene composition is obtained. In the present invention, the propylene-ethylene block copolymer does not necessarily have to be graft-modified with unsaturated carboxylic acids, but the modified polypropylene must contain at least 30% by weight of the propylene-ethylene block copolymer component. is important. That is, when the propylene-ethylene block copolymer component in the modified polypropylene is less than 30% by weight, the modified polypropylene film produced using the modified polypropylene composition containing the finely divided inorganic filler has good metal deposition properties and Does not exhibit ink adhesion. Another feature of the present invention is that a fine powder inorganic filler is also used. The fine powder inorganic filler used in the present invention is not particularly limited, but it is preferably one with an average particle diameter of 50 μm or less. Examples of fine powder inorganic fillers include calcium carbonate, talc, clay, silica, diatomaceous earth, alumina, zinc white, magnesium oxide, mica, calcium silicate, calcium sulfate, calcium sulfite,
Examples include magnesium carbonate, aluminum hydroxide, calcium hydroxide, glass powder, asbestos, and gypsum. Among these, calcium carbonate and talc are preferably used. If the amount of the fine powder inorganic filler added is less than 2 parts by weight per 100 parts by weight of modified polypropylene, the effect of improving vapor deposition properties will be small. Moreover, if the amount exceeds 200 parts by weight, the vapor deposition properties will deteriorate, so in general, 100 parts by weight or less is appropriate. Therefore, it is advisable to mix the modified polypropylene composition in an amount of 2 to 50% by weight, preferably 4.8 to 50% by weight. Incidentally, both the modification of polypropylene and the mixing of the inorganic filler may be performed first, or may be performed simultaneously. The mixture of modified polypropylene, finely divided inorganic filler and optionally unmodified polypropylene is
It can be carried out using a tumbler, Henschel mixer, etc., and melt-kneaded using a screw extruder, Banbury mixer, mixing roll, etc. The modified polypropylene composition produced as described above preferably contains 0.005 to 5% by weight of unsaturated carboxylic acids in a graft bond. Content of unsaturated carboxylic acids is 0.005% by weight
When the amount is less, the effect of improving vapor deposition properties is small, and when it exceeds 5% by weight, not only does the manufacturing cost increase, but the effect of improving vapor deposition properties becomes saturated. In addition, the modified polypropylene composition may include other polymeric substances other than polypropylene and commonly used heat stabilizers, weather stabilizers, lubricants, antistatic agents, nucleating agents, pigments, dyes, flame retardants, antiblocking agents, etc. May contain. The present invention is a film having the above-mentioned modified polypropylene composition on at least one side. Therefore, the film referred to in the present invention includes not only ordinary films and sheets but also laminates thereof. Examples of such a film include a single film made of a modified polypropylene composition and a laminated film in which a modified polypropylene composition film is laminated on at least one side. A single film can be formed by a known method such as an extrusion casting method or an inflation method. In addition, single films include those stretched in uniaxial or biaxial directions. As a method for producing a laminated film, for example, a modified polypropylene film composition can be laminated on at least one side of an unmodified polypropylene film by a known lamination method such as an in-die lamination method, an outside-die lamination method, or thermocompression bonding using a press. . In the laminated film of the present invention, each layer may be unstretched, uniaxially stretched or biaxially stretched, or uniaxially or biaxially stretched after lamination. Yet another feature of the present invention is that the film surface of the modified polypropylene composition molded as described above is subjected to a corona discharge treatment. The corona discharge treatment can be carried out by a known method using a common commercially available corona discharge treatment machine. Corona discharge treatment is usually carried out in air, but N ₂ , He, CO ₂
If the process is carried out under an inert gas atmosphere such as, a film with even better metal deposition properties can be obtained. Among these, it is preferable to carry out under an N ₂ atmosphere with an oxygen concentration of 5% by volume or less. There are no particular limitations on the equipment and method for performing corona discharge treatment, but for example, a closed tank equipped with a film unwinder, a discharge electrode, an electrode holder, a counter electrode roll, and a film winder is used, and the oxygen concentration inside the tank is adjusted to 5
A method of performing corona discharge treatment by maintaining a reduced pressure, normal pressure, or pressurized nitrogen atmosphere of less than vol. There is a method in which corona discharge treatment is carried out continuously while blowing out nitrogen with an oxygen concentration of 5% by volume or less from a slit or small hole. Further, it is possible to perform corona discharge treatment on both sides by installing two sets of the above-mentioned devices. As the corona discharge treatment machine, a normal commercially available machine can be used. Regarding the processing conditions,
The film traveling speed can be 10 to 200 m/min, the gap between the electrode tip and the film to be processed can be 0.5 to 3 mm, and it is preferable to use two or more electrodes.
As for the corona discharge treatment strength, the treated film 1
Can be carried out at 20W/min or more and 200W/min or less ^{per m2} ,
In particular, 30W/min or more and 150W/min or less are preferable, and 1
If the treatment intensity is less than 20 W/min per m ² , the effect of improving metal vapor deposition properties will not be sufficient, and if it exceeds 200 W/min per 1 m ² , the film will be damaged by discharge electric shock, which is undesirable. The modified polypropylene composition film produced as described above has good metal deposition properties on the surface where the modified polypropylene composition is present and which has been subjected to corona discharge treatment, and has excellent adhesion to printing ink. . Examples will be described below, but the present invention is not limited thereto. In order to evaluate the metal deposition power, a film was set in a Bergier deposition machine, and aluminum was deposited on the deposition surface of the film under a vacuum of 5×10 ^-5 Torr. After vapor deposition, leave it for 24 hours at a humidity of 95% and a temperature of 40°C, then apply commercially available cellophane tape (23 mm width x
After attaching a 65mm length) and peeling off the tape by hand 5 times, the area percentage of aluminum remaining attached to the film surface without being peeled off by the tape is shown in the table below. Displayed in rank.

[Table] Furthermore, the quality of ink printability can be predicted according to the evaluation of the aluminum vapor deposition ability of the above film. Reference example 1 MFI = 0.6 g/10 min, 100 parts by weight of propylene-ethylene random copolymer with ethylene content of 2.0% by weight, 2 parts by weight of maleic anhydride, 2,5-dimethyl-2,5-di(t-butyl) peroxy)hexane
0.3 parts by weight, 0.1 parts by weight of butylated hydroxytoluene, and 0.1 parts by weight of calcium stearate were mixed in a Henschel mixer for 5 minutes, and a 40 mm tube with L/D=24 was mixed.
Melt-kneading pelletization is performed at 220℃ using a φ extruder, and then heat treatment is performed at 145℃ for 4 hours using a constant temperature dryer to produce modified polypropylene (hereinafter referred to as modified polypropylene).
(also abbreviated as PP) was obtained. This modified polypropylene contained 0.5% by weight of maleic anhydride grafted therein. Above modified polypropylene, unmodified polypropylene (PP) and calcium carbonate (average particle size 1.2μ)
are mixed in the prescribed proportions shown in Table 1, and
A modified polypropylene composition was obtained by melt-kneading at 200°C using a CCM extruder. In addition, Table 1 shows the properties of unmodified polypropylene (PP). (1) Block PP: MFI = 1.5 g/10 min, ethylene content 2.7 wt% (2) Homo PP: MFI = 1.5 g/10 min (3) Random PP: MFI = 1.7 g/10 min, ethylene content 2.5 wt. %

【table】

[Table] Reference Example 2 100 parts by weight of the propylene-ethylene block copolymer used in Reference Example 1, talc 20 with an average particle size of 0.3μ
Parts by weight, 0.5 parts by weight of maleic anhydride, 0.3 parts by weight of benzoyl peroxide, 0.1 parts by weight of butylated hydroxytoluene, 0.1 parts by weight of calcium stearate.
Parts by weight were mixed for 5 minutes using a Henschel mixer, melt-kneaded and pelletized using a vented CCM extruder at 200°C, and heat-treated at 145°C for 3 hours using a constant temperature dryer. The modified polypropylene composition thus obtained contains maleic anhydride units.
0.18% by weight was grafted. Composition of this stuff
(11). Reference Example 3 The same procedure as Reference Example 2 was carried out except that maleic anhydride was not added. The obtained polypropylene composition was designated as Composition (12). Reference Example 4 Except for not adding talc in Reference Example 2,
The same procedure as in Reference Example 2 was carried out. The resulting modified polypropylene composition contained 0.21% by weight of maleic anhydride.
It was grafted together. This composition was designated as Composition (13). Reference Example 5 The same procedure as in Reference Example 2 was carried out except that the homopolypropylene used in Reference Example 1 was used instead of the propylene-ethylene block copolymer. The resulting modified polypropylene composition was grafted with 0.15% by weight of maleic anhydride. This composition was designated as composition (14). Reference Example 6 The same procedure as in Reference Example 2 was carried out except that the propylene-ethylene random copolymer used in Reference Example 1 was used instead of the propylene-ethylene block copolymer. The resulting modified polypropylene composition contained 0.17 maleic anhydride.
% by weight was grafted. This composition was designated as Composition (15). Examples 1 to 5 and Comparative Examples 1 to 12 Compositions (1) to (15) were prepared using a 65 mmφ extruder equipped with a 450 mm wide T-die at a die temperature of 240°C.
A 40 μm casting film was formed from each. Next, these films were subjected to corona discharge treatment in air at a treatment density of 60 W·min/m ² . The vapor deposition strength of the corona discharge treated surface of these films was as shown in Table 2.

[Table] Examples 6-10, Comparative Examples 13-25 MFI=1.0g/10min homopolypropylene at 290
65mmφ with 450mm width T-die set at ℃
The mixture was put into an extruder to obtain a sheet with a thickness of 1.5 mm. Next, this sheet was stretched 5 times in the longitudinal direction using a roll-type stretching machine set at a roll surface temperature of 155°C, and the thickness was
A 0.3 mm uniaxially stretched polypropylene sheet was made.
Next, compositions (1) to (15) were placed in an extrusion laminator set at 280°C, and extrusion laminated onto the uniaxially stretched polypropylene sheet to a thickness of 20μ. This laminated sheet was stretched 10 times in the transverse direction using an oven-type stretching machine set at an air temperature of 155°C.
A 32μ laminated film was obtained. Next, the laminated surfaces of these laminated films were subjected to corona discharge treatment at a treatment density of 50 W·min/m ² in an N ₂ atmosphere with an oxygen concentration of 0.05% by volume. The vapor deposition strength of these films on the corona discharge treated surface was as shown in Table 3.

【table】

【table】

Claims (1)

[Claims] 1 Propylene with an ethylene content of 1 to 30% by weight
A film of a modified polypropylene composition comprising a mixture of a modified polypropylene containing 30% by weight or more of an ethylene block copolymer and a finely powdered inorganic filler of 2 to 50% by weight based on the total weight, the modified polypropylene composition comprising: 1. A modified polypropylene film having 0.005 to 5% by weight of unsaturated carboxylic acids graft-bonded thereon, the film being corona discharge treated.