JP2003011297A - Packaging polypropylene oriented film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a packaging film, which has a favorable productivity, can side-seal and satisfies both antifogging performance and side sealing strength. SOLUTION: In the packaging polypropylene oriented film, the surface layer of which is laminated on one side of both the sides of an intermediate layer and which is oriented at least unidirectionally or more two or more times as much, (1) the intermediate layer is made of a polypropylene resin composition including 0.5 to 2.0 pt.wt. of an antifogging agent to 100 pt.wt. of a polypropylene resin, (2) the melt flow rate (MFRB) of an intermediate layer polypropylene resin composition is 0.5 to 5.0 g/10 min, (3) the surface layer is made of a polypropylene having a peak fusing temperature (Tm) of 100 to 150 deg.C, (4) the total thickness of the surface layer is 2 to 40% of the total film thickness and (5) the relationship between the melt flow rate (MFRH) of a surface layer polypropylene satisfy the following equation: MFRB/ MFRH>=0.143×MFRB+0.01.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polypropylene-based stretched film for packaging, and more specifically, it is a multi-layered polypropylene-based film composed of a polypropylene resin having a specific composition and is excellent in sealing strength and antifogging property. The present invention relates to a stretched film.

[0002]

2. Description of the Related Art As a packaging material for vegetable packaging, fiber packaging, bread packaging, etc., a polypropylene bag processed by a fusion cutting method is generally used. From the viewpoint of improving the productivity of packaging bags, the advent of a film that can be fused and sealed at low temperature in a short time has been required. In order to meet the above-mentioned demand, for example, a film in which a heat-sealing layer having a low melting point as described in Japanese Patent Publication No. 7-17043 is laminated has been proposed. There is a problem that the strength of the applied portion is easily weakened and the bag is easily broken.

On the other hand, in the packaging of vegetables, antifogging performance is generally required for the purpose of keeping the freshness of the contents, and it is necessary to appropriately bleed out the antifogging agent on the film surface. However, when a low melting point polypropylene resin composition is laminated on the surface layer in order to improve the productivity at the time of fusing and sealing, the antifogging agent is likely to excessively bleed out, and the sealing strength of the fusing and heat sealing part is reduced. It will be easier. As described above, it was difficult to satisfy all of the productivity at the time of fusing and sealing processing, the antifogging performance, and the fusing and sealing strength.

In the technique disclosed in Japanese Examined Patent Publication No. 7-17043, it is necessary to control the thickness of the low melting point heat seal layer to 0.2 to 0.8 μm in order to satisfy this problem. Had. In addition, Japanese Patent Laid-Open No. 7-1
Japanese Patent No. 17193 also proposes a method for satisfying this problem, but the product of Young's modulus in the longitudinal direction and the width direction of the film is limited to 3.6 to 8.0 (kg / cm ² ) ^2. However, there is a limit to meet the demand of the market for a stronger film. As described above, there has been a demand for the development of a packaging film that satisfies all of the productivity at the time of fusing and sealing processing, the antifogging performance, and the fusing and sealing strength, and that eliminates the restrictions at the time of film molding as much as possible.

[0005]

[PROBLEMS TO BE SOLVED BY THE INVENTION] To obtain a polypropylene film for packaging which can be fused and sealed with good productivity and which satisfies both antifogging performance and fusion and sealing strength.

[0006]

The present inventors have conducted extensive studies to solve the above-mentioned problems, and as a result, have identified a polypropylene resin composition having a melt flow rate (MFR) in a specific range as an intermediate layer and a specific surface layer. Melting peak temperature (Tm)
It has been found that the bleed-out amount of the antifogging agent can be appropriately controlled by selecting and laminating polypropylene having a ratio of MFR of the intermediate layer polypropylene resin composition within a specific range. did.

That is, the present invention is a polypropylene-based stretched film in which a surface layer is laminated on one side or both sides of an intermediate layer and stretched at least two times in at least one axial direction,
(1) The intermediate layer is composed of a polypropylene resin composition containing 0.5 to 2.0 parts by weight of an antifogging agent with respect to 100 parts by weight of the polypropylene resin, and (2) the intermediate layer polypropylene resin composition. Melt flow rate (MF
R _B) is 0.5 to 5.0 g / 10 min, (3) the surface layer is composed of a melting peak temperature (Tm) 100 to 150 ° C. for polypropylene, the total thickness of (4) a surface layer film 2 to 40% of the total thickness, (5) a melt flow rate of the intermediate layer polypropylene resin composition (MFR _B) and the surface layer of polypropylene has a melt flow rate (MF
A polypropylene-based stretched film characterized in that the relationship with R _H ) satisfies the following formula. MFR _B / MFR _H ≧ 0.143 x MFR _B +0.01

Polypropylene Resin Composition for Intermediate Layer The intermediate layer is composed of a composition containing a polypropylene resin as a main component and a predetermined amount of an antifogging agent. The content of the antifogging agent is 0.5 to 2.0 parts by weight, preferably 0.8 to 1.5 parts by weight, based on the composition. If it is less than the above range, sufficient antifogging performance cannot be exhibited, and if it is more than 2.0 parts by weight, the film becomes sticky or the fusion-cut seal strength is lowered. As the antifogging agent used in the present invention, known substances are used without particular limitation. In some cases, the antifogging agent is also called an antistatic agent, a surfactant, etc., and is a fatty acid ester of a polyhydric alcohol, an ethylene oxide adduct of an alkylamine, an ethylene oxide adduct of a fatty acid amide, and a fatty acid ester thereof. , Fatty acid amides, and the like. Specific examples thereof will be given below, but the present invention is not limited thereto. Fatty acid esters of polyhydric alcohols include glycerin fatty acid esters such as capric acid monoglyceride, lauric acid monoglyceride, myristic acid monoglyceride, palmitic acid monoglyceride, stearic acid monoglyceride; sorbitan monocaprate, sorbitan monolaurate, sorbitan monomyristate, sorbitan monoglyceride. There are sorbitan fatty acid esters such as palmitate and sorbitan monostearate.

Examples of the ethylene oxide adduct of alkylamine and the ethylene oxide adduct of fatty acid amide include higher aliphatic amines such as decylamine, laurylamine, myristylamine, palmitylamine, stearylamine and oleylamine, capric acid amide, and lauric acid. A variety of one or more ethylene oxide added between the nitrogen atom of a higher fatty acid amide such as amide, myristic acid amide, palmitic acid amide, stearic acid amide, oleic acid amide and the like and two hydrogen atoms bonded thereto. There is a compound of. Between the nitrogen atom and the two hydrogen atoms,
In general, alkyl diethanol amine, fatty acid diethanol amide to which ethylene oxide is added one by one, and polyoxyethylene alkyl amine and polyoxyethylene fatty acid amide to which a plurality of ethylene oxide are added are common. The fatty acid ester of the above ethylene oxide adducts is a monoester obtained by esterifying only one of the two alcoholic hydroxyl groups of the ethylene oxide adduct with an aliphatic carboxylic acid having 8 to 30 carbon atoms. And both are esterified diesters, but the use of monoesters is common. As the fatty acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, oleic acid amide, erucic acid amide, ethylenebispalmitic acid amide, ethylenebisstearic acid amide, hexamethylenebisstearic acid amide, ethylenebisoleic acid amide, Hexamethylenebisoleic acid amide and the like can be mentioned.

As the polypropylene resin constituting the intermediate layer, propylene homopolymer, propylene / α-olefin random copolymer and the like are used. Where α
-The olefin has 2 to 10 carbon atoms other than propylene.
Α-olefin is used, and the content thereof is usually 0.01 to 10% by weight with respect to propylene. The polypropylene resin is preferably a propylene homopolymer or a propylene / α-olefin copolymer having an α-olefin content of 0.02 to 5% by weight, and more preferably a propylene homopolymer. The density is 0.89
It is preferably from 0.91 g / cm ^{3 in view} of the balance between stretchability and film rigidity. Such polypropylene melt flow rate of the resin in the polypropylene resin composition obtained by incorporating an antifogging agent (MFR _B) is 0.5 to 5.
It is 0 g / 10 minutes, preferably 1 to 4.5 g / 10 minutes. When the melt flow rate is higher than the above range, unevenness in thickness is apt to occur during stretching and productivity is deteriorated. On the other hand, when it is less than the above range, the extrusion load becomes large and the productivity deteriorates.

To the polypropylene resin composition for the intermediate layer, in addition to the antifogging agent, additives such as antioxidants, antiblocking agents, slip agents, weathering agents, nucleating agents and pigments for general polypropylene resins are added. The agent can be added depending on the purpose within a range that does not impair the effects of the present invention.

Polypropylene for surface layer As the polypropylene constituting the surface layer, propylene homopolymer, propylene.α-
Olefin random copolymers can be used, preferably propylene / ethylene random copolymers, propylene / butene random copolymers, propylene / hexene random copolymers, propylene / octene random copolymers, propylene / ethylene / It is a butene random terpolymer. Particularly preferred are propylene / ethylene random copolymers and propylene / ethylene / butene random terpolymers obtained by polymerization with a metallocene catalyst. As the metallocene catalyst, zirconium, hafnium, a metallocene complex in which a halogen atom or the like is coordinated with an organic compound having a cyclopentadienyl skeleton in a transition metal such as titanium, an alumoxane compound, an ion-exchange silicate, an organoaluminum compound, etc. Combined catalysts are effective.

The melting peak temperature (Tm) of polypropylene constituting the surface layer measured by a differential calorimeter (DSC) is 100.
~ 150 ° C. The temperature is preferably 110 to 140 ° C, more preferably 115 to 140 ° C. If it is less than the above range, the appearance tends to deteriorate due to stickiness in the roll stretching process. On the other hand, when the temperature exceeds 150 ° C, the antifogging performance deteriorates and the fusion-cut seal strength also decreases.

The melt flow rate (MFR _H ) of polypropylene constituting the surface layer is usually 1 to 8 g / 10 minutes,
It is preferably 2 to 6 g / 10 minutes. When the melt flow rate is higher than the above range, unevenness in thickness is apt to occur during stretching and productivity is deteriorated. On the other hand, when it is less than the above range, the extrusion load becomes large and the productivity deteriorates.

Further important in the present invention is that the melt flow rate (MFR _B ) of the polypropylene resin composition constituting the intermediate layer and the melt flow rate (MFR _H ) of the polypropylene constituting the surface layer are as follows. To satisfy the relational expression. MFR _B / MFR _H ≧ 0.143 × MFR _B +0.01 Further, MFR _B / MFR _H is preferably 0.4 or more, more preferably 0.5 or more. When MFR _B / MFR _H is less than the above, the fusion-cut seal strength is lowered. On the other hand, MF
R _B / MFR _H is preferably 1.5 or less. If it is larger than 1.5, appearance defects such as sharkskin are likely to occur during coextrusion.

For the purpose of preventing blocking, it is preferable to add an anti-blocking agent such as silica, cross-linked PMMA, magnesium carbonate and spherical silicone particles to the polypropylene for the surface layer. Further, general additives for polypropylene resins such as antioxidants, weather resistance agents, slip agents and antistatic agents can be added within a range that does not impair the effects of the present invention. In addition, when polypropylene for a surface layer is formulated with the above compounding agent, a polypropylene resin composition is obtained, but in the present specification, it is simply referred to as “polypropylene” regardless of the presence or absence of the compounding agent. On the other hand, the polypropylene resin for the intermediate layer must contain an antifogging agent, and thus was referred to as "polypropylene resin composition".

Production of Laminated Film A laminated film is produced using polypropylene for the surface layer and polypropylene resin composition for the intermediate layer as raw materials. The method for producing the laminated film is not particularly limited, and a usual processing method can be adopted. For example, a co-extrusion molding machine such as a T-die method, an inflation method and a calender roll method can be used. A more specific example will be described using a co-extrusion T-die molding machine. The resin material of the present invention is charged into each layer of the extruder, heated and melted and kneaded at a temperature of 190 to 270 ° C., and then a flow path adjusting machine of a feed block. In a laminated structure, extruded in a film form from the die lip of the T die, and sandwiching and cooling the laminated molten film sheet by an air knife method, an air chamber method, a polishing roll method, a swing roll method, a belt cast method, a water cooling method, etc. A desired laminated sheet can be manufactured by taking it with a take-up machine.

The unstretched laminated film (sheet) obtained by coextrusion molding is then uniaxially stretched in the film-drawing direction (longitudinal direction) at a stretching ratio of 2 to 7, preferably 4 to 6. If the stretching ratio is less than the above, insufficient rigidity and thickness unevenness are likely to occur, while if it exceeds the above range, breakage or stretching unevenness may occur. The stretching treatment is performed by heating the unstretched film as it is or by slitting it into a predetermined width and changing the peripheral speed of the stretching roll, for example. 1
Simultaneously with the axial stretching or after the uniaxial stretching, the transverse stretching may be further performed by a tenter or the like to perform the biaxial stretching at a stretching ratio of 5 to 12.

The surface layer is laminated on one side or both sides of the intermediate layer. When the surface layers are laminated on both sides, the composition of the surface layer resin may be the same or different, but if they are different, the same composition is preferable because the film tends to curl. Further, since a film having the same heat-sealing property without distinction between the front and the back is easy to use in bag-making processing, a symmetrical three-layer structure film is preferable. The thickness of the surface layer is 2 to 40% of the total thickness of the laminated film, preferably 3
~ 30%. If it is less than the above, it is difficult to obtain good antifogging performance and fusing seal strength. On the other hand, when it is larger than the above, the rigidity of the film becomes weak and the workability is easily deteriorated in the processes such as printing and bag making.

[0020]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In addition, the measured value of each item in the examples was measured by the following method. (MFR) (unit: g / 10 minutes) JIS K-7210 (condition 230 ° C, load 2.16k)
It measured based on g). (Melting peak temperature) (unit: ° C) Using a DSC manufactured by Seiko, a sample amount of 5.0 mg was taken and held at 200 ° C for 5 minutes, and then 10 ° C / 40 ° C.
It was cooled at a cooling rate of a minute, and was further melted at a heating rate of 10 ° C./min to obtain a heat of fusion curve, and Tp was calculated from the maximum peak temperature of the obtained heat of fusion curve.

(Anti-fogging property) (unit: second) The charging half-life was measured as an index for measuring the bleed-out of the anti-fogging agent on the film surface. At 23 ℃ -50% HR Shishido Shokai Co., Ltd. Static Honest Meter TYP
Using ES-5109, the half-life of a film sample prepared at 40 ° C. for 24 hours after molding was measured. If it is 30 seconds or less, it is determined that there is no problem in the antifogging property. (Blend seal strength) (unit: g / 15 mm width) Using a bag making machine equipped with a 400 ° C. fusing seal bar, 120 bags were made per minute, and the sealing portion of the obtained bag had a width of 15 m.
The test piece was cut so that the length was 100 mm on both sides of the seal part in the direction perpendicular to the sealing direction, including m, and the force required for breaking the sample was measured at a speed of 200 mm / min with a tensile tester at n = 5. Then, the average value was obtained. 2000 g /
If the width is 15 mm or more, there is no practical problem.

The following were used as polypropylene resins used in the following examples and comparative examples. (PP1) MFR = 2.4 g / 10 min propylene homopolymer powder. Tm = 161.5 ° C, FL6CK ungranulated product manufactured by Nippon Polychem. (PP2) Propylene / ethylene random copolymer powder with MFR = 1.5 g / 10 min. Ethylene content 4.
2% by weight, Tm = 140 ° C., EX6 ungranulated product manufactured by Nippon Polychem. (PP3) Propylene homopolymer powder with MFR = 4.5 g / 10 min. Tm = 161.5 ° C., FY4 ungranulated product manufactured by Nippon Polychem. (PP4) MFR = 2.5 g / 10 min propylene / ethylene random copolymer powder. Tm = 123 ° C., ethylene content 3.4% by weight. It was prepared by the following method using a metallocene catalyst. (PP5) MFR = 7.2 g / 10 min propylene / ethylene random copolymer powder. Ethylene content 3.
7% by weight, Tm = 124 ° C. It was prepared by the following method using a metallocene catalyst. (PP6) MFR = 5.8 g / 10 min propylene / ethylene / butene-1 random copolymer. Ethylene content 1.8% by weight, butene content 12.5% by weight, Tm = 1
35 ° C. Novatec PP4400 manufactured by Nippon Polychem.

[Production of PP4 and PP5 by metallocene catalyst] Preparation of chemically treated clay 200 g of commercially available montmorillonite (Kunipia F, Kunimine Industry) was added to an aqueous solution prepared by mixing 218 g of sulfuric acid (96%) and 130 g of magnesium sulfate with 910 ml of demineralized water. It was dispersed and stirred at 100 ° C. for 2 hours. This montmorillonite water slurry solution was prepared to a solid content concentration of 12%, and spray granulated by a spray dryer to obtain particles. Then, the particles were dried under reduced pressure at 200 ° C. for 2 hours to obtain a chemically treated clay. Preparation of catalyst component Heptane 23 dehydrated and deoxygenated after thoroughly replacing the inside of a stirring autoclave with an internal volume of 1 liter with propylene
0 ml was introduced and the system temperature was maintained at 40 ° C. To this, 10 g of chemically treated clay slurried with toluene was added. Furthermore, dimethylsilylene bis [1,1 ′-{2-methyl-4- (4
-Chlorophenyl) -4H-azurenyl}] zirconium dichloride 0.15 mmol and triisobutylaluminum 1.5 mmol were added. Here, propylene was introduced at a rate of 10 g / h for 120 minutes, and then the polymerization was continued for 120 minutes. Further, the solvent was removed and dried under nitrogen to obtain a solid catalyst component. This solid catalyst component is
It contained 1.9 g of polypropylene per gram of solid component. Polymerization 1 (Production of PP4) After thoroughly replacing the inside of a stirring autoclave having an internal volume of 200 liters with propylene, 45 kg of sufficiently dehydrated liquefied propylene was introduced. To this, 500 ml of triisobutylaluminum / n-heptane solution (0.12 mo
1), 2.0 kg of ethylene and 3.5 NL of hydrogen were introduced,
The internal temperature was maintained at 30 ° C. Then, 1.45 g of the above-mentioned solid catalyst component was press-fitted with argon to start polymerization, and 30
The temperature was raised to 70 ° C. over a period of time, and the temperature was maintained for 1 hour.
Here, 100 ml of ethanol was added to stop the reaction. The residual gas was purged to obtain 14 kg of a propylene / ethylene random copolymer having the following physical properties. Polymerization 2 (Production of PP5) The amount of ethylene and hydrogen introduced is 2.25k for ethylene.
g, hydrogen 8.0 NL, except that the solid catalyst component was 1.2 g, the same operation as in Polymerization 1 was carried out to obtain 21 kg of a propylene / ethylene random copolymer.

[Example 1] (Polypropylene resin composition for intermediate layer) 100 parts by weight of PP1 powder, 0.4 part by weight of stearic acid monoglyceride as an antifogging agent, 0.5 part by weight of stearyl diethanolamine fatty acid ester, lauryl diethanolamine 0.08 parts by weight, erucic acid amide 0.05 parts by weight, and Irganox 101 manufactured by Ciba-Geigy as an antioxidant
0.1 parts by weight of 0, Irgafos 16 manufactured by Ciba Geigy
0.1 parts by weight of 8 and 0.05 parts of calcium stearate
After mixing by weight, the mixture was stirred with a Henschel mixer, melt-extruded with an extruder, and pelletized.

(Polypropylene for surface layer) 100 parts by weight of PP4 powder, 0.15 parts by weight of silica having a particle size of 1.8 μm as an anti-blocking agent, and 0.1 part by weight of Irganox 1010 manufactured by Ciba-Geigy as an antioxidant. 0.1 parts by weight of Irbafos 168 manufactured by Ciba Geigy Co., Ltd. and 0.05 parts by weight of calcium stearate were mixed, stirred with a Henschel mixer, melt-extruded with an extruder and pelletized.

(Production of Biaxially Stretched Film) The polypropylene resin composition for the intermediate layer and the polypropylene for the surface layer are separately charged into three extruders to form a three-layer stretched film having a total thickness of 25 μm. By co-extruding from the T-die so that the thickness of the surface layer is 1 μm and rapidly cooling with a cooling roll, a sheet with a thickness of about 1 mm is obtained. This sheet is produced by a tenter type sequential biaxial stretching device at 120 ° C. 5 vertically
2 times, subsequently preheated to 160 ° C. in a tenter furnace, and then stretched at 158 ° C. in the transverse direction at a draw ratio of 9 times, and heat set at 158 ° C. while relaxing 5% to obtain a total film thickness of 25 μm. Two kinds of three-layer biaxially oriented polypropylene-based films each having a surface layer thickness of 1 μm were obtained. The total thickness of the surface layer is 2μ
Therefore, the ratio to the total film thickness is 8%. Both sides of the obtained film were subjected to corona discharge treatment so as to be 41 dyn / cm. The evaluation results of the obtained film are summarized in Table 1.

[Example 2] A biaxially stretched film was obtained in the same manner as in Example 1, except that PP1 in Example 1 was changed to PP2. The evaluation results of the obtained film are summarized in Table 1.

[Example 3] A biaxially stretched film was obtained in the same manner as in Example 1 except that PP4 in Example 1 was changed to PP6. The evaluation results of the obtained film are summarized in Table 1.

[Example 4] A biaxially stretched film was obtained in the same manner as in Example 3 except that PP1 in Example 3 was changed to PP3. The evaluation results of the obtained film are summarized in Table 1.

Comparative Example 1 A biaxially stretched film was obtained in the same manner as in Example 1 except that PP4 in Example 1 was changed to PP5. The evaluation results of the obtained film are summarized in Table 1.
Since the ratio of MFR _B to MFR _H (MFR _B / MFR _H ) was outside the range of the present invention, the fusing seal strength was lowered.

[Comparative Example 2] PP1 of Example 1 was replaced with PP2
Further, a biaxially stretched film was obtained in the same manner as in Example 1 except that PP4 was changed to PP5. The evaluation results of the obtained film are summarized in Table 1. Since the ratio of MFR _B to MFR _H was outside the range of the present invention, the fusing seal strength decreased.

[Comparative Example 3] A biaxially stretched film was obtained in the same manner as in Example 1 except that PP1 in Example 1 was changed to PP1. The evaluation results of the obtained film are summarized in Table 1.
Since Tm was out of the range of the present invention, the antifogging property was lowered.

[0033]

[Table 1]

[0034]

The antifogging agent blended in the polypropylene resin composition for the intermediate layer migrates to the surface layer and imparts antifogging property to the film, but the migration is appropriately controlled by the constitution of the present invention, and fusing Sufficient antifogging property can be achieved without impairing the sealing property. Therefore, it is possible to obtain a packaging film that can be fused and sealed with high productivity and that satisfies both the antifogging performance and the fused and sealed strength.

Continued front page    F-term (reference) 3E086 AD01 BA04 BA15 BA33 BA35                       BB90 CA01 CA17 CA40 DA03                 4F100 AH02B AH03B AK07A AK07B                       AK07C AK64A AK64C AL03A                       AL03C BA03 BA06 BA10A                       BA10C CA10B EH20 EJ37A                       EJ37C EJ38 EJ55 GB15                       JA04A JA04C JA06A JA06B                       JA06C JL00 YY00A YY00B                       YY00C

Claims (6)

[Claims] 1. A polypropylene stretched film having a surface layer laminated on one side or both sides of an intermediate layer and stretched at least uniaxially by a factor of 2 or more, wherein (1) the intermediate layer comprises:
A polypropylene resin composition containing 0.5 to 2.0 parts by weight of an antifogging agent with respect to 100 parts by weight of the polypropylene resin, and (2) the melt flow rate (MFR) of the intermediate layer polypropylene resin composition. _B ) is from 0.5
5.0 g / 10 minutes, (3) the surface layer is composed of polypropylene having a melting peak temperature (Tm) of 100 to 150 ° C., and (4) the total thickness of the surface layer is 2 to 4 of the total film thickness.
0%, and (5) for packaging, wherein the relationship between the melt flow rate (MFR _B ) of the polypropylene resin composition for the intermediate layer and the melt flow rate (MFR _H ) of the surface layer polypropylene satisfies the following formula: Polypropylene stretched film. MFR _B / MFR _H ≧ 0.143 × MFR _B
+0.01 2. The surface layer of polypropylene is propylene
The polypropylene-based stretched film for packaging according to claim 1, which comprises an α-olefin random copolymer. 3. The polypropylene-based stretched film for packaging according to claim 2, wherein the propylene / α-olefin random copolymer is a propylene / ethylene random copolymer. 4. The polypropylene-based stretched film for packaging according to claim 2 or 3, wherein the propylene / α-olefin random copolymer is polymerized by a metallocene catalyst. 5. The polypropylene-based stretched film for packaging according to claim 1, wherein the antifogging agent is one or more selected from glycerin fatty acid ester, alkyldiethanolamine and fatty acid amide. 6. A biaxially stretched polypropylene-based stretched film having surface layers laminated on both sides of an intermediate layer,
(1) The intermediate layer is composed of a polypropylene resin composition containing 0.5 to 2.0 parts by weight of an antifogging agent with respect to 100 parts by weight of the polypropylene resin, and (2) the polypropylene resin composition of the intermediate layer. Melt flow rate (MF
R _B) is 0.5 to 5.0 g / 10 min, (3) the surface layer is composed of a melting peak temperature (Tm) 100 to 150 ° C. for polypropylene, the total thickness of (4) a surface layer film 2 to 40% of the total thickness, (5) a melt flow rate of the intermediate layer polypropylene resin composition (MFR _B) and the surface layer of polypropylene has a melt flow rate (MF
A polypropylene-based stretched film for packaging, characterized in that the relationship with R _H ) satisfies the following formula. MFR _B / MFR _H ≧
0.143 x MFR _B +0.01