JPH11245352A - Biaxially oriented polypropylene film for metallization and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the adhesion between a metal film and a film backing in metallization and to obtain a metallized film with a good gloss. SOLUTION: A surface layer of a polypropylene resin in which an endothermic main peak associated with crystal melting is in the range of 155-163 deg.C, and the quantity of heat of crystal melting is 20-90 J/g is laminated on one side of a base layer consisting of isotactic polypropylene, and the wet tension of the surface layer is 33-55 mN/m. All the endothermic peaks associated with the crystal melting of the polypropylene resin to be laminated on the base layer are in the range of 155-163 deg.C.

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 for metallization and a method for producing the same. More particularly, the present invention relates to a metallized biaxially oriented polypropylene film having excellent film-forming properties and high rigidity. The present invention relates to a biaxially oriented polypropylene film for metallization, which has excellent adhesiveness and easily provides a metallic luster, and a method for producing the same.

[0002]

2. Description of the Related Art Biaxially oriented polypropylene films are widely used as packaging films due to their excellent moisture-proof properties, strength, transparency, and surface gloss. They improve the appearance of metallic luster during display and improve gas barrier performance. Metals such as aluminum are deposited (metallization) for the purpose of suppressing deterioration of the contents due to external light such as ultraviolet rays
It is also widely practiced.

[0003] However, the surface of the biaxially oriented polypropylene film is inactive. In order to improve the adhesion between the metal film and the base film during metallization, the surface is treated by a treatment such as corona discharge treatment or flame treatment. Activation is commonly performed.

[0004] In order to improve the effect of corona discharge treatment, US Patent No. 4,297,187 discloses performing corona discharge treatment in a mixed gas of nitrogen and carbon dioxide. According to these corona discharge treatment methods,
By increasing the treatment strength, the surface is more activated and the adhesive strength between the metal film and the base film is improved, but at the same time, the base material is deteriorated, and the separation between the base film surface layer and the base film inside is prevented. It is known that this is likely to occur and the effect of improving the adhesive strength is limited. It is also known that if the processing strength is too high, blocking tends to occur.

US Pat. No. 4,345,005 discloses an ethylene-propylene copolymer containing from about 2% to about 4% ethylene formed by coextrusion on at least one side of a base layer of isotactic polypropylene resin. There is a disclosure of a metallized biaxially oriented polypropylene film in which a resin layer is subjected to corona discharge treatment and metal-deposited.

Further, US Pat. No. 4,357,383 discloses that a random copolymer layer of 0.25 to 15% by weight of ethylene and an α-olefin having 3 to 6 carbon atoms is formed on a base layer and a metal layer is further formed. There is a disclosure of a multi-layer metallized packaging film formed with. Similarly, a biaxially oriented polypropylene composite film for metal oxide deposition is disclosed in JP-A-9-94929.
Discloses that the polyolefin resin of the surface layer to be vapor-deposited has a heat of crystal fusion of 30 to 85 J / g. As a resin for this purpose, a polypropylene-based copolymer, a syndiotactic polypropylene resin, ethylene and α -Olefin copolymers and blended resins of these resins with isotactic homopolypropylene or polypropylene copolymers.

Further, Japanese Patent Application Laid-Open No. 6-67285,
JP-A-6-126281 discloses that the surface layer to be metallized is a syndiotactic polypropylene or a mixed resin layer of syndiotactic polypropylene and isotactic polypropylene.

[0008] By laminating a copolymer resin among these surface resins on the surface layer, the adhesion between the metal film and the surface layer resin is improved. However, since the copolymer resin generally has a low melting point, it is necessary to use a longitudinal stretching roll during film formation. There are great restrictions on film formation such as sticking, and a decrease in gloss due to sticking marks becomes a problem. In addition, when the metallization is performed due to the low melting point, the metal film is easily whitened due to heat of coagulation of the metal and radiation heat from the evaporation source, and it is difficult to obtain a metallic luster. Similarly, when the surface layer is made of syndiotactic polypropylene, the melting temperature is low as shown in JP-A-7-89022, and it is known that a problem relating to heat resistance occurs similarly to a copolymer resin.

Further, US Pat. No. 4,419,410 discloses that in an oriented polypropylene film, a high stereoregularity polypropylene and a relatively low stereoregularity polypropylene are laminated, and an organic lubricant and an antistatic agent are developed. There is a disclosure of a technology for promoting
As described in Japanese Patent Application Publication No. 005-005 and Japanese Patent Publication No. Hei 8-18404, it is known that the addition of an organic lubricant among these additives particularly deteriorates the adhesion to the deposited film. It could not be applied to polypropylene.

In US Pat. No. 4,888,237, a flame treatment is applied to a surface layer containing at least 50% by weight of an isotactic homopolymer having a xylene dissolved content not exceeding 10% by weight, and a metallized layer is applied thereon. There is a disclosure of a film made. The isotactic homopolymer is a normal polypropylene homopolymer having an atacticity of substantially not more than 6%, and preferably up to 50% when containing a homopolymer having an atacticity of 6% to 15%. It is disclosed that the use of such a polymer greatly improves the adhesiveness in combination with a flame treatment. However, the effect of improving the adhesiveness was not recognized by the corona discharge treatment, and there was no surface resin that could improve the adhesiveness even by a simple corona discharge treatment.

[0011]

SUMMARY OF THE INVENTION The present invention maintains the excellent stiffness of biaxially oriented polypropylene and provides two contradictory properties that cannot be achieved with the above-mentioned conventional biaxially oriented polypropylene film for metallization, namely: An object of the present invention is to provide a biaxially oriented polypropylene film for metallization, which can provide a metallized film having excellent gloss while improving the adhesion between a metal film and a film substrate when metallized.

[0012]

Means for Solving the Problems That is, the present inventors,
Although the low heat of crystal fusion of the surface resin according to the prior art contributes to the adhesion, the poor heat resistance leads to various drawbacks, and the present invention has been accomplished.

The present invention has been made in order to solve such a problem.
On at least one surface of the base layer made of isotactic polypropylene, the main peak of endothermic accompanying crystal melting is 155 to
A biaxially oriented polypropylene film for metallization, wherein a surface layer made of a polypropylene resin having a heat of crystal fusion of 20 to 90 J / g at 163 ° C. is laminated, and the surface layer has a wet tension of 33 to 55 mN / m. Further, as a method for producing the same, at least one surface of a base layer made of isotactic polypropylene has a main endothermic peak due to crystal melting at 155 to 163 ° C. and a heat of crystal melting of 20 to 90 ° C.
Provided is a method for producing a biaxially oriented polypropylene film for metallization in which a surface layer made of a polypropylene resin having a J / g is laminated by co-extrusion, cooled and solidified, then biaxially oriented, and the surface layer is subjected to a surface activation treatment. .

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The resin forming the base layer of the present invention comprises:
It is a crystalline isotactic polypropylene resin.
The mesopentad fraction of the isotactic polypropylene resin is preferably at least 88%. The mesopentad fraction is the ratio of the isotactic tertiary structure to the whole, and is measured by ¹³ C-NMR. If the meso pentad fraction is less than 88%, the rigidity of the biaxially oriented polypropylene film will be low, resulting in poor workability. More preferably, the mesopentad fraction is 90% or more.

The isotactic polypropylene resin of the base layer preferably has an isotacticity of 85% or more. The isotacticity is the weight ratio of the undissolved portion when extracted with boiling n-heptane. If the isotacticity is less than 85%, the amount of eluted by a solvent such as xylene or n-hexane becomes too large, which may make the film unsuitable as a packaging film. The isotacticity of the isotactic polypropylene resin of the base layer is more preferably 88% or more, further preferably 90% or more. Further, the melt flow index (MFI) of the polypropylene resin is preferably from 1 to 10 g / 10 minutes from the viewpoint of film-forming properties, and more preferably from 2.5 to 6 g / 10 minutes.

The resin of the base layer is preferably an isotactic polypropylene resin alone, but a polypropylene-based copolymer resin or the like may be laminated on the base layer depending on the purpose. When reused, another copolymer resin may be contained within a range not to impair the object of the present invention.

The surface layer resin laminated on at least one surface of the base layer has a main endothermic peak of 155 to 16 due to crystal melting.
It is a polypropylene resin having a crystal melting heat of 20 to 90 J / g at 3 ° C.

An important point of the present invention is that the peak temperature of the endothermic accompanying the crystal melting of the polypropylene resin of the surface layer is relatively high. 155 peak
It is important to be at ~ 163 ° C.

In this case, the main peak is the single peak itself when only a single endothermic peak is observed, and 2/2 of the entire peak area when multiple endothermic peaks are observed.
Points to occupy 3 or more. The upper limit of the endothermic peak temperature due to crystal melting is defined as a characteristic value specific to polypropylene, but the lower limit of the peak temperature due to crystal melting is the film forming property of the biaxially oriented polypropylene film for metallization, If the peak temperature due to crystal melting is too low, there is a case where problems such as sticking to a roll at the time of film formation as in the prior art and lowering of metallic luster after metallization occur. The main endothermic peak due to crystal melting of the polypropylene resin of the surface layer of the present invention is preferably at 157 to 162 ° C, more preferably at 158 to 162 ° C. If a minor peak is observed below 155 ° C., it is preferred that the peak is above 140 ° C.

Further, all of the endothermic peaks associated with the crystal melting of the polypropylene resin of the surface layer of the present invention are 155 to 155.
A temperature of 163 ° C. is preferred for film forming properties and heat resistance during metallization.

The heat of crystal fusion of the polypropylene resin of the surface layer of the present invention must be 20 to 90 J / g. The point is that the heat of crystal fusion of the normal isotactic polypropylene resin is 100 J / g or more, whereas the heat of crystal fusion of the polypropylene resin used as the surface resin of the present invention is small. If the heat of crystal fusion is too large, the adhesion to the metal film will be poor. If the heat of crystal fusion is too small, the heat resistance during metallization will be poor. The heat of crystal fusion of the polypropylene resin of the surface layer of the present invention is 30 to 8
5 J / g is preferred, and 40-85 J / g is more preferred.

The selection of the resin is important in order to make the main endothermic peak and the heat of crystal fusion accompanying the crystal melting of the polypropylene resin in the surface layer within the range of the present invention. In a conventional polypropylene-based copolymer resin alone, for example, ethylene
In the propylene / random copolymer, the heat of crystal fusion decreases with the amount of ethylene copolymerized. However, at the same time, the melting temperature sharply decreases, so that it is difficult to fall within the scope of the present invention. However, this can be achieved depending on the polymerization conditions, and a polypropylene-based copolymer resin alone is not excluded from the scope of the present invention.

In the present invention, a resin suitable as a surface layer resin is mainly an isotactic polypropylene resin having a mesopentad fraction of 60 to 88%. An isotactic polypropylene resin having a mesopentad fraction of 60 to 88%, and a polypropylene copolymer resin having an endothermic peak at 140 to 163 ° C. due to crystal melting mixed with an upper limit of 1/3 by weight. It can be used preferably. Further, a preferable surface layer resin in the present invention is a mixture of an isotactic polypropylene resin having a mesopentad fraction of 60 to 88% and a polypropylene copolymer resin having an endothermic peak at 155 to 163 ° C. due to crystal melting. Most preferred is isotactic polypropylene alone with a mesopentad fraction of 60-88%.

As a method for producing a surface resin in the present invention, it is important to select an external donor, reduce the amount of the external donor, and control a specific mesopentad fraction using a normal Ziegler-Natta catalyst. Become.

If the mesopentad fraction is less than 60%, whitening may occur due to an increase in the rubber component of the resin, lack of gloss of the surface layer, or poor heat resistance during metallization. If the meso pentad fraction exceeds 88%, the adhesion to the metal film may be poor. The mesopentad fraction of the isotactic polypropylene of the surface resin of the present invention is more preferably from 65 to 85%, most preferably from 68 to 83%. The mesopentad fraction can be set to such a value by selecting an isotactic polypropylene having a mesopentad fraction of the present invention or by mixing two or more isotactic polypropylene resins having different mesopentad fractions. .

The molecular weight distribution Mw / Mn of isotactic polypropylene is preferably in the range of 2 to 6 for film-forming properties and solvent resistance, more preferably 2.3 to 5, and more preferably 2.4 to 4.
Is most preferred.

The MFI of the polypropylene resin used as the surface resin of the present invention is preferably 1 to 20 g / 10 minutes for the lamination property with the base layer.

The thickness of the surface layer of the present invention is preferably not less than 0.25 μm and not more than half the thickness of the base layer. If the thickness of the surface layer is less than 0.25 μm, uniform lamination becomes difficult due to film breakage or the like, and the effect of improving adhesiveness may be reduced. If the thickness is too large, the contribution of the surface layer to the mechanical properties increases, causing a decrease in Young's modulus, and the biaxially oriented polypropylene film for metallization tends to be stretched with respect to tension, resulting in poor workability. The biaxially oriented polypropylene film for metallization of the present invention preferably has a Young's modulus in the longitudinal direction of 1.3 GPa or more, preferably 1.5 GPa.
a or more is more preferable.

It is preferable that an organic lubricant such as a fatty acid amide is not added to the surface resin of the present invention for the adhesion of the metal film. However, in order to impart slipperiness and improve workability and winding property. It is permissible to add a small amount of organic crosslinkable particles or inorganic particles. Organic crosslinkable particles for this purpose include crosslinked silicone and crosslinked polymethyl methacrylate particles, and inorganic particles include zeolite, calcium carbonate, silicon oxide, calcium phosphate and the like.

The surface roughness of the surface layer of the biaxially oriented polypropylene film for metallization of the present invention is not particularly limited, but the center line surface roughness (Ra) is preferably from 0.03 to 0.3 μm, more preferably 0 to 0.3 μm. 0.05 to 0.2 μm.
If the Ra is too small, the lubricity may be poor, and the winding property may be poor. If the Ra is too large, the gloss after metallization may be poor.

The surface gloss of the biaxially oriented polypropylene film for metallization of the present invention is preferably 135% or more for the beautiful metal gloss after vapor deposition, more preferably 138% or more.

The surface resin of the present invention contains at least one resin selected from petroleum resins substantially free of polar groups and terpene resins substantially free of polar groups per 100 parts by weight of the surface resin. It is more preferable to add 20 parts by weight to the upper limit because the adhesion to the metal film can be further strengthened. If it is added in excess of 20 parts by weight, slipperiness may deteriorate and problems such as blocking may occur.

The petroleum resin substantially free of polar groups is
A hydroxyl group (-OH), a carboxyl group (-COOH), a sulfonic acid group (-SO ₃ Y, Y is H, Na, etc.) and a petroleum resin having no polar group made of their modified product, i.e. petroleum It is a resin mainly composed of a cyclopentadiene-based or higher olefin-based hydrocarbon using an unsaturated hydrocarbon directly as a raw material.

In the present invention, when these resins are added to the surface resin, the glass transition temperature of the resin to be added measured by a differential calorimeter is preferably 50 ° C. or higher, so as not to lower the heat resistance of the surface resin. More preferably 76
° C or higher. Hydrogenated petroleum resin is particularly preferable, in which hydrogen is added to the petroleum resin so that the degree of hydrogenation is 80% or more, preferably 95% or more. Further, the petroleum resin is preferably amorphous (ie, substantially no crystal melting is observed when the petroleum resin is measured by a differential scanning calorimeter) from the viewpoint of compatibility with the polypropylene resin of the surface layer, and The number average molecular weight is preferably 1,000 or less.

The terpene resin having substantially no polar group includes a hydroxyl group (—OH), an aldehyde group (—CHO), a ketone group (—CO—), a carboxyl group (—COOH),
Halogen group, sulfonic acid group (—SO ₃ Y, Y is H, Na
And terpene resins having no polar group, such as modified hydrocarbons having a composition of (C ₅ H ₈ ) _n and modified compounds derived therefrom. Note that n is a natural number of about 2 to 20. Terpene resins are sometimes referred to as terpenoids. Representative compound names include pinene, dipentene, kalen, myrcene, ocimene, limonene, terpinolene, terpinene, sabinene, tricyclene, bisabolene, zingiperene, santalen, camphorene, millen, totalene, and the like. %, Preferably 90% or more, particularly preferably hydrogenated β-pinene and hydrogenated dipentene.

In the biaxially oriented polypropylene film for metallization of the present invention, the surface layer is subjected to a surface activation treatment. As the surface activation treatment, known corona discharge treatment or flame treatment can be used, but corona discharge treatment is preferable as a simple method. In the case of corona discharge treatment, treatment in air, nitrogen gas, or a mixed gas of carbon dioxide and nitrogen gas can be employed. Is more preferable because the bonding strength with the metal film can be strengthened with low processing strength (power).

The surface tension after the surface activation treatment needs to be in the range of 33 to 55 mN / m, more preferably in the range of 35 to 50 mN / m. If the wetting tension is small, the adhesion to the metal film is poor. If the wetting tension is too large, the surface layer tends to peel off due to deterioration of the base material near the surface, and the bonding strength is rather reduced.

In the biaxially oriented polypropylene film for metallization of the present invention, the above surface layer resin is laminated on at least one side of the base layer. The surface layer is laminated on one side of the base layer resin, and the opposite side is optionally coated on the opposite side. , A third layer may be laminated.
As the resin of the third layer, for example, a polypropylene-based copolymer is laminated to impart heat sealing properties. Further, in order to impart a slipperiness, a polypropylene resin to which organic crosslinked particles or inorganic particles are added, an ethylene-propylene block copolymer, a mixture of an ethylene-propylene block copolymer and a high-density polyethylene, or the like. It is preferable that they are laminated. The third layer surface on the opposite side is activated by corona discharge treatment or the like as necessary.

The biaxially oriented polypropylene film for metallization of the present invention has a main endothermic peak at 155 to 163 ° C. associated with crystal melting on at least one surface of the base layer made of isotactic polypropylene, and has a heat of crystal melting of 20 to 163 ° C. 9
It can be manufactured by laminating a surface layer made of a polypropylene-based resin of 0 J / g by co-extrusion, solidifying by cooling, biaxially orienting, and subjecting the surface layer to a surface activation treatment.

The co-extrusion means that the resin of the base layer and the resin of the surface layer are supplied to the respective extruders together with the resin of the opposite layer, if necessary, melted, and if necessary, passed through a filter and then into a short tube or a die. Merging and pushing out of the base. The shape of the die may be a slit die or a ring die.In the case of a slit die, the die is wound around a cooling drum and solidified by cooling, and then the ring die is successively biaxially or simultaneously biaxially formed. In this case, the biaxially oriented polypropylene film for metallization of the present invention is produced by simultaneous biaxial stretching after cooling by an air stream and further subjected to a surface activation treatment.

The biaxially oriented polypropylene film for metallization of the present invention has a metallized biaxial film having excellent adhesion to a metal film and excellent metallic luster by depositing a metal such as aluminum, silver, chromium or zinc. It can be an oriented polypropylene film. Above all, it is preferable to deposit aluminum for economy, hygiene, and gas barrier performance.

The adhesive strength between the biaxially oriented polypropylene film for metallization of the present invention and the metal film is preferably at least 80 g / cm, more preferably at least 100 g / cm.

The surface gloss after metallization is a 60 ° gloss value.
It is preferably at least 780%, more preferably at least 800%.

Hereinafter, an example of a method for producing the biaxially oriented polypropylene film for metallization of the present invention will be described, but the present invention is not limited by the following production method.

An isotactic polypropylene resin for the base layer and a polypropylene resin for the surface layer according to the present invention are prepared, and supplied to separate extruders to supply them at 230 to 290 ° C.
After passing through a filtration filter, it is merged in a short tube or a base, extruded from a slit base with the desired lamination thickness, wound around a metal drum, cooled and solidified into a sheet, and then unstretched laminated film And In this case, the temperature of the cooling drum is preferably set to 30 to 60 ° C. to crystallize the film. This unstretched laminated film is biaxially stretched and biaxially oriented. As the stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used. In the case of the sequential biaxial stretching method, the unstretched film is then heated to a temperature of 115 to 145 ° C.
The film is stretched 7 times, cooled, then introduced into a tenter type stretching machine, stretched 7 to 11 times in the width direction at 140 to 170 ° C., relaxed at 155 to 170 ° C., and cooled. Further, after a corona discharge treatment in air, nitrogen, or a mixed atmosphere of carbon dioxide and nitrogen, the film is wound up to obtain the biaxially oriented polypropylene film for metallization of the present invention.

{Method of Measuring Characteristic Values} The characteristic values of the present invention were measured by the following methods.

(1) Isotacticity (%) The resin is extracted with n-heptane at a temperature of 60 ° C. or less for 2 hours to remove additives to the polypropylene. Then 13
Vacuum dry at 0 ° C. for 2 hours. From this, a sample of weight W (mg) is taken, placed in a Soxhlet extractor and extracted with boiling n-heptane for 12 hours. Next, the sample was taken out, washed sufficiently with acetone, vacuum-dried at 130 ° C. for 6 hours, and then cooled to room temperature, the weight W ′ (mg) was measured, and the following equation: isotacticity = (W ′ / W) ) × 100 (%).

(2) Melt flow index (MF)
I: g / 10 min) 230 ° C., 2.16 k according to ASTM-D-1238
g.

(3) Crystal melting endothermic peak temperature (° C.) and crystal melting calorie (J / g) Thermal analyzer R manufactured by Seiko Instruments
A DC220 type was charged with 5 mg of the surface layer resin sealed in an aluminum pan and heated at a rate of 20 ° C./min to determine the peak temperature of the crystal melting endotherm. The heat of crystal fusion was calculated from the area of the endothermic peak by using a built-in program of the company's thermal analysis system SSC5200. When a mixture of two or more resins has a plurality of endothermic peaks, the sum of the respective heats of crystal fusion is defined as the heat of crystal fusion.

(4) Mesopentad fraction (%) The base resin or the surface resin is o-dichlorobenzene-D
6, and ¹³ C-NMR was measured at a resonance frequency of 67.93 MHz using a JNM-GX270 apparatus manufactured by JEOL. For the assignment of the obtained spectrum and the calculation of the mesopentad fraction, see T.W. The method performed by Hayashi et al. (Polymer, 29, 138-143 (198)
8) Based on the spectrum derived from the methyl group,
Each peak was assigned with the mmmmmm peak being 21.855 ppm, the peak area was determined, and the ratio to the total peak area derived from the methyl group was expressed as a percentage. Detailed measurement conditions are as follows.

Measurement concentration: 15 to 20 wt% Measurement solvent: o-dichlorobenzene (90 wt%) / benzene-D6 (10 wt%) Measurement temperature: 120 to 130 ° C. Resonance frequency: 67.93 MHz Pulse width: 10 μsec (45 °) Pulse) Pulse repetition time: 7.091 seconds Data point: 32K Integration frequency: 8168 Measurement mode: Noise decoupling.

(5) Wetting tension (mN / m) Determined by JIS K6782 method.

(6) Young's modulus (GPa) Determined based on ASTM D882-64T.

(7) Surface Gloss of Film (%) Based on JIS Z8741 method, it was determined as 60 ° specular gloss using a digital variable angle gloss meter UGV-5D manufactured by Suga Test Instruments.

(8) Surface gloss (%) of vapor-deposited film A biaxially oriented polypropylene film for metallization was loaded into a continuous vacuum vapor-deposition apparatus, and aluminum was evaporated from an electron beam heating type evaporation source to continuously form the film. While running, the optical density (-log (light transmittance)) is 1.3 to
Aluminum was deposited in the range of 1.4. This metallized biaxially oriented polypropylene film was treated according to JIS Z874.
The surface gloss was determined based on 1.

(9) Adhesive strength (g / cm) Metallized biaxially oriented polypropylene film
A biaxially oriented polypropylene film having a thickness of 20 μm (S645 manufactured by Toray Industries Inc.) is bonded using a polyurethane-based adhesive, left at 40 ° C. for 48 hours, and 90 ° at a peeling speed of 10 cm / min. It was measured by peeling.

[0057]

EXAMPLES The present invention will be described with reference to examples.

Example 1 Isotactic polypropylene (isotacticity: 96%, MFI: 2.5) was used as the resin of the base layer of the present invention.
g / 10 min, mesopentad fraction: 92%), and isotactic polypropylene (isotacticity: 86%, MFI: 2.8 g /
10 minutes, mesopentad fraction: 74%, peak temperature of endotherm accompanying crystal melting: 161 ° C., heat of crystal fusion: 77 J /
g) Ethylene / propylene / random copolymer of 80% by weight and 4.8% by weight of ethylene copolymer (endothermic peak temperature due to crystal melting: 146 ° C., heat of crystal fusion: 73 J /
g) 20% by weight of a mixture, an ethylene / propylene / butene copolymer (ethylene copolymerization amount: 1.5% by weight, butene copolymerization amount: 15) as a heat seal resin on the surface opposite to the surface layer
(% By weight) of the crosslinked silicone particles having an average particle diameter of 3 μm as an organic crosslinked particle lubricant (average particle diameter was measured using a field emission scanning electron microscope (FE-SEM)). And 0.15% by weight) were supplied to separate extruders.
After being melt-extruded at ℃ and passing through a filtration filter, they were merged in a short tube so as to become a surface layer / base layer / heat seal layer, extruded from a slit die, wound around a metal drum heated to 40 ° C., and formed into a sheet.

This sheet was heated to a temperature of 135 ° C., stretched 5 times in the longitudinal direction, cooled and then guided to a tenter-type stretching machine, heated at 165 ° C. and stretched 9 times in the width direction.
Heat treatment was carried out at a temperature of 165 ° C. while giving 10% relaxation in the width direction, followed by cooling. In addition, corona discharge treatment was performed in air for 15 minutes.
The film was wound at a processing intensity of W minutes / m ² . The thickness of the film is: surface layer / base layer / heat seal layer: 1 μm / 19 μ
m / 2 μm. The surface wetting tension was 37 mN / m. The main peak temperature of endothermic accompanying the crystal melting of the surface resin was 161 ° C., and the heat of crystal fusion was 76 J / g.

Examples 2, 3, and 4 Example 1 was repeated except that the surface resin was an isotactic polypropylene having a mesopentad fraction, a peak temperature of endotherm accompanying crystal melting, and a heat of crystal melting as shown in Table 1. A film was formed under the same conditions as those described above and evaluated.

Examples 5 and 6 Films were formed and evaluated under the same conditions as in Example 2 except that the mesopentad fraction of isotactic polypropylene as the base resin was changed as shown in Table 1.

Examples 7 and 8 Films were formed under the same film forming conditions as in Example 2, and the final corona discharge treatment was performed at 5 W min / m ^{2 in} Example 7, carbon dioxide (20% by volume) + nitrogen. 5 in gas (80% by volume) atmosphere
Example 8 was treated at 0 W min / m ² . The wetting tension of each was 34 mN / m and 52 mN / m.

Examples 9 and 10 The lamination structure was as follows: surface layer / base layer / heat seal layer: 0.5 μm
Example 9 was a film formed under the same conditions as in Example 2 except that the thickness was changed to /19.5 μm / 2 μm, and a film was formed under the same conditions except that the surface layer / base layer / heat seal layer was changed to 2 μm / 18 μm / 2 μm. Was set to Example 10.

Example 11 Example 1 was repeated except that 10 parts by weight of a petroleum resin (ESCOLETS 5320HC manufactured by Tonex) was added to 100 parts by weight of the isotactic polypropylene resin used in Example 2 to obtain a surface resin. A film formed in the same manner as in Example 11 was used as Example 11.

Examples 12 and 13 The laminated structure was changed to a surface layer / base layer / heat seal layer: 0.2 μm
Example 12 was formed under the same conditions as in Example 2 except that the thickness was changed to /19.8 μm / 2 μm, and the same conditions as in Example 2 were used except that the surface layer / base layer / heat seal layer was changed to 7 μm / 13 μm / 2 μm. Example 13 was formed.

Example 14 The resin of the surface layer was composed of 80% by weight of the isotactic polypropylene used in Example 2 and an ethylene / propylene / random copolymer having an ethylene copolymerization amount of 1.3% by weight (endothermic accompanying crystal melting). Peak temperature: 159 ° C., heat of crystal fusion 1
Example 14 was a film formed under the same conditions as in Example 1 except that a mixed resin of 20 J / g) was used. The endothermic peak temperature accompanying the crystal melting of the mixed resin is 160 ° C,
The heat of crystal fusion was 82 J / g.

Example 15 The resin of the surface layer was composed of 80% by weight of isotactic polypropylene used in Example 2 and syndiotactic polypropylene (endothermic peak temperature due to crystal melting: 132 ° C.
Example 1 was a film formed under the same conditions as in Example 1 except that the mixed resin was used in an amount of 20% by weight.
It was set to 5. The main peak temperature of the endotherm accompanying the crystal melting of the mixed resin was 161 ° C., and the heat of crystal fusion was 70 J / g.

Table 1 shows the constitutions of the above Examples, and Table 2 shows the characteristics of these films and metallized films.

As shown in Table 2, the biaxially oriented polypropylene film for metallization of the present invention has a high Young's modulus, a high surface gloss of the film, an excellent metallic luster after metallization, and an excellent adhesive strength. It has the feature of. Example 6
As apparent from the above, when the mesopentad fraction of the isotactic polypropylene of the base layer is low, the Young's modulus tends to be low. As is apparent from Example 11, when a petroleum resin is added to the surface resin, the adhesiveness is further improved, which is more preferable. As is apparent from Example 12, when the thickness of the surface layer is small, a decrease in glossiness or a decrease in adhesive strength, which may be caused by film breakage, may be observed. Further, as is apparent from Example 13, when the thickness of the surface layer is too large, the Young's modulus tends to decrease.

[0070]

[Table 1]

[0071]

[Table 2]

Comparative Example 1 The procedure of Example 1 was repeated except that the resin in the surface layer was a mixture of 30% by weight of the isotactic polypropylene of Example 1 and 70% by weight of an ethylene / propylene / random copolymer having an ethylene copolymerization amount of 4.8% by weight. A film formed under the same conditions as in Example 1 was used as Comparative Example 1. The main endothermic peak due to crystal melting is 146
C., heat of crystal fusion was 74 J / g.

Comparative Examples 2 and 3 Mesopentad fraction, melting temperature and crystal heat of fusion were measured as isotactic polypropylene of the surface layer, respectively.
%, 162 ° C., and 118 J / g, and Comparative Examples 2 and 58 were formed under the same conditions as in Example 1.
%, 154 ° C. and 18 J / g were used as Comparative Example 3.

Comparative Examples 4, 5, and 6 Films formed under the same conditions as in Example 1 except that the ethylene / propylene / random copolymer shown in Table 3 was used for the surface layer were compared with Comparative Examples 4, 5, and 6. did.

Comparative Example 7 Comparative Example 7 used a mixture of 20% by weight of the isotactic polypropylene used in Example 15 and 80% by weight of the syndiotactic polypropylene as the surface layer resin. The main peak temperature associated with the crystal melting of the surface resin was 132 ° C., and the heat of crystal fusion was 49 J / g.

COMPARATIVE EXAMPLES 8 AND 9 A film was formed in the same manner as in Example 2 and was not subjected to the final corona discharge treatment. Comparative Example 8, carbon dioxide (20% by volume)
+100 W min / m ^{2 in} an atmosphere of + nitrogen gas (80% by volume)
The sample treated with the above was designated as Comparative Example 9. The respective wetting tensions were 32 mN / m and 57 mN / m.

Table 3 shows the constitution of the comparative example, and Table 4 shows the characteristics of these films and metalized films.

As shown in Table 4, in these comparative examples, there arise problems such as insufficient Young's modulus, insufficient surface gloss and metallic gloss, and insufficient adhesive strength.
That is, in Comparative Examples 1 and 7, the main peak temperature of endothermic accompanying melting of the crystal was low, and the heat resistance was poor, so that the film surface was roughened, and it was difficult to obtain a metallic luster after metallization. Adhesive strength is low because the heat of fusion is too high,
In Comparative Example 3, since the heat of crystal fusion is too low, the surface of the film becomes rough, and a problem arises that metallic luster cannot be obtained even after metallization. Further, in the ethylene-propylene-random copolymer, the melting temperature of the present invention, the relationship between the heat of crystal fusion is difficult to be obtained, and the decrease in the melting temperature is remarkable with respect to the decrease in the heat of crystal fusion. It was impossible to achieve both adhesion and surface gloss. Comparative Examples 8 and 9 show that the wetting tension of the present invention is necessary for the development of the adhesive strength, and that even if the wetting tension is too large, it is estimated that peeling in the film substrate is a cause. Is reduced.

[0079]

[Table 3]

[0080]

[Table 4]

[0081]

The biaxially oriented polypropylene film for metallization of the present invention can be achieved by the prior art by setting the peak value of the melting temperature of the surface layer to be metallized, the heat of crystal fusion, and the wetting tension to specific values. It is possible to provide a film-forming process that has not been performed and has no fear of roll sticking at the time of film-forming.

Claims (8)

[Claims] An at least one surface of an isotactic polypropylene base layer has a main endothermic peak at 155 to 163 ° C. due to crystal melting and has a heat of crystal melting of 20 to 9 ° C.
A biaxially oriented polypropylene film for metallization, wherein a surface layer made of a polypropylene resin having a thickness of 0 J / g is laminated, and the surface layer has a wet tension of 33 to 55 mN / m. 2. The biaxially oriented polypropylene film for metallization according to claim 1, wherein all endothermic peaks accompanying the crystal melting of the polypropylene resin laminated on the base layer made of isotactic polypropylene are at 155 to 163 ° C. . 3. The biaxially oriented polypropylene film for metallization according to claim 1, wherein the polypropylene resin of the surface layer is a resin mainly composed of isotactic polypropylene having a mesopentad fraction of 60 to 88%. . 4. The biaxially oriented polypropylene film for metallization according to claim 3, wherein the polypropylene resin of the surface layer is isotactic polypropylene having a mesopentad fraction of 60 to 88%. 5. The biaxially oriented polypropylene film for metallization according to claim 1, wherein the isotactic polypropylene of the base layer has a mesopentad fraction of 88% or more. 6. A polypropylene resin comprising at least one resin selected from the group consisting of petroleum resins substantially free of polar groups and terpene resins substantially free of polar groups.
The biaxially oriented polypropylene film for metallization according to any one of claims 1 to 5, wherein 20 parts by weight is added to the upper limit with respect to 00 parts by weight. 7. The biaxially oriented polypropylene film for metallization according to claim 1, wherein the thickness of the surface layer is 0.25 μm or more and half or less of the thickness of the base layer. 8. A main layer of endothermic heat due to crystal melting at 155 to 163 ° C. on at least one surface of the base layer made of isotactic polypropylene, and a heat of crystal melting of 20 to 9 ° C.
A method for producing a biaxially oriented polypropylene film for metallization, comprising laminating a surface layer made of a polypropylene-based resin of 0 J / g by co-extrusion, cooling and solidifying, biaxially orienting, and subjecting the surface layer to a surface activation treatment.