WO2019065306A1

WO2019065306A1 - Polypropylene-based laminate film

Info

Publication number: WO2019065306A1
Application number: PCT/JP2018/034179
Authority: WO
Inventors: 理木下; 山田　浩司
Original assignee: 東洋紡株式会社
Priority date: 2017-09-26
Filing date: 2018-09-14
Publication date: 2019-04-04
Also published as: KR20200047733A; JP2023001143A; CN111132831A; JP7238779B2; TW201919900A; JP7409459B2; JPWO2019065306A1; KR102593205B1

Abstract

To provide a heat-sealable stretched polypropylene laminate film which has a low shrinkage rate at 150°C comparable to the shrinkage rate of PET and a high rigidity. A polypropylene-based laminate film which comprises a substrate layer (A), said substrate layer (A) being formed of a polypropylene resin satisfying requirements 1) to 4), and a heat seal layer (B) formed of a polyolefin-based resin, said heat seal layer (B) being laminated on one or both faces of the substrate layer, wherein the lower limit of the plane orientation coefficient of the film is 0.0125. 1) The lower limit of the mesopentad fraction is 96%. 2) The upper limit of the content of comonomer(s) other than propylene is 0.1 mol%. 3) The ratio [mass-average molecular weight (Mw)/number-average molecular ratio (Mn)] is 3.0-5.4 inclusive. 4) The melt flow rate (MFR) measured at 230°C and 2.16 kgf is 6.2-9.0 g/10 min inclusive.

Description

Polypropylene-based laminated film

The present invention relates to a polypropylene-based laminate film having heat sealability. More particularly, it relates to a polypropylene-based laminate film having excellent heat seal strength for use as a packaging application. In particular, the present invention relates to a polypropylene-based laminate film which can be suitably used in various fields where dimensional stability at high temperature and high rigidity are required, and which is excellent in heat resistance and mechanical properties and which is excellent in heat sealability.

In the past, polypropylene-based oriented films have been used for a wide range of applications such as packaging for food and various products, electrical insulation, surface protection films, etc., but applications that require heat sealability in one of them There is. Heretofore, as a polypropylene-based laminated film having heat sealability, a co-extrusion laminated polypropylene-based resin film in which a low melting point polyolefin-based resin is laminated on a polypropylene-based resin has been widely used.
As one of such heat sealable films, a stretched polypropylene laminated film which has a low shrinkage comparable to PET at 150 ° C. and can be heat-sealed at a high temperature has been proposed (see, for example, Patent Document 1). .
However, this film also has room for improvement in mechanical properties.

WO 2015/0126165 brochure

The present invention has been made on the background of the problems of the prior art. That is, an object of the present invention is to provide a polypropylene-based laminate film having excellent heat seal strength for use as a packaging application.

As a result of intensive investigations to achieve such an object, the present inventor has completed the present invention. That is, according to the present invention, a heat composed of a base material layer (A) in which the polypropylene resin constituting the layer satisfies the following conditions 1) to 4) and a polyolefin resin laminated on one side or both sides of this base layer It is a polypropylene-type laminated film which consists of a sealing layer (B) and the lower limit of the plane orientation coefficient of a film is 0.0125.
1) The lower limit of the mesopentad fraction is 96%.
2) The upper limit of the amount of copolymerized monomers other than propylene is 0.1 mol%.
3) Mass average molecular weight (Mw) / number average molecular weight (Mn) is 3.0 or more and 5.4 or less.
4) The melt flow rate (MFR) measured at 230 ° C. and 2.16 kgf is 6.2 g / 10 min or more and 9.0 g / 10 min or less.

In this case, it is preferable that the thermal shrinkage at 150 ° C. in the longitudinal direction and the transverse direction of the film is 8% or less.

In this case, it is preferable that the Young's modulus in the MD direction is 2.1 GPa or more, and the Young's modulus in the TD direction is 3.7 GPa or more.

Furthermore, the 180 ° peel strength of a 10 mm wide test piece obtained by overlapping the heat seal layer (B) surfaces and performing hot plate sealing at 140 ° C. for 1 second is 8.0 N / 15 mm or more Is preferred.

Furthermore, in this case, it is preferable that the polyolefin resin constituting the heat seal resin (B) is a propylene random copolymer and / or a propylene block copolymer.

According to the present invention, it was excellent for use as a packaging application and very suitable for heat seal processing.
Furthermore, for example, by setting the heat seal temperature high, it is possible to increase the line speed in bag-making processing and the like, and the productivity is improved. In addition, the heat seal strength can also be improved by increasing the heat seal temperature.
Furthermore, it can be suitably used in various fields where dimensional stability at high temperatures and high rigidity are required, and for example, when performing high temperature treatment such as retort, the amount of deformation of the bag can be suppressed. As a result, thinning can be achieved.

The present invention relates to a polypropylene-based laminate film having heat sealability. More particularly, it relates to a polypropylene-based laminate film having sufficient heat seal strength which is excellent for use as a packaging application.
The feature of the polypropylene-based laminate film of the present invention lies in the molecular weight distribution of the polypropylene resin used for the substrate layer (A).

The polypropylene-based laminate film of the present invention comprises a substrate layer (A) in which the polypropylene resin constituting the layer satisfies the following conditions 1) to 4), and a polyolefin-based resin laminated on one side or both sides of this substrate layer. It is a polypropylene-based laminated film comprising the heat seal layer (B) and the lower limit of the plane orientation coefficient of the film being 0.0125.
1) The lower limit of the mesopentad fraction is 96%.
2) The upper limit of the amount of copolymerized monomers other than propylene is 0.1 mol%.
3) Mass average molecular weight (Mw) / number average molecular weight (Mn) is 3.0 or more and 5.4 or less.
4) The melt flow rate (MFR) measured at 230 ° C. and 2.16 kgf is 6.2 g / 10 min or more and 9.0 g / 10 min or less.
Further details are described below.

(Base material layer (A))
The polypropylene resin used for the base material layer (A) of the present invention may be a polypropylene resin copolymerized with ethylene and / or an α-olefin having 4 or more carbon atoms at 0.5 mol% or less. Such copolymerized polypropylene resin is also included in the polypropylene resin of the present invention (hereinafter, polypropylene resin). 0.3 mol% or less is preferable, 0.1 mol% or less is more preferable, and the completely homopolypropylene resin which does not contain a copolymerization component is the most preferable.
When ethylene and / or an α-olefin having 4 or more carbon atoms are copolymerized in excess of 0.5 mol%, the crystallinity and rigidity may be excessively lowered, and the thermal shrinkage at high temperatures may be increased. You may blend and use such resin.

The mesopentad fraction ([mm mm]%) measured by ¹³ C-NMR, which is an index of stereoregularity of a polypropylene resin, is preferably 96 to 99.5%. More preferably, it is 97% or more, and more preferably 98% or more. When the mesopentad ratio of the polypropylene of the base material layer (A) is small, the melting point of the crystals is lowered, and the elastic modulus and the heat resistance at high temperature may be insufficient. 99.5% is a realistic upper limit.

In addition, Mw / Mn, which is an index of molecular weight distribution, is preferably 3.0 to 5.4 in the polypropylene resin. More preferably, it is 3.0 to 5.0, still more preferably 3.2 to 4.5, and particularly preferably 3.3 to 4.0.
When the Mw / Mn of the entire polypropylene resin constituting the base material layer (A) is 5.4 or less, although the high molecular weight component is present, the amount thereof tends to be small, and the heat shrinkage tends to be small. When a high molecular weight component is present, there is a surface that promotes crystallization of the low molecular weight component, but the entanglement between molecules becomes strong, and this is also a factor that increases the thermal contraction rate even if the crystallinity is high.
Moreover, when Mw / Mn of the whole polypropylene resin which comprises a base material layer (A) is 5.4 or less, there exists a tendency for the low molecular weight component with a considerably low molecular weight to increase, and an elastic modulus to become small. If a low molecular weight component having a considerably low molecular weight is present, the entanglement of the molecules becomes weak, stretching at a low stretching stress becomes possible, and the crystallinity becomes high, but it also becomes a factor to lower the elastic modulus.
Film formation becomes difficult for Mw / Mn of the whole polypropylene resin which comprises the base material layer (A) of this invention to be less than 3.0. Mw means mass average molecular weight, and Mn means number average molecular weight.

The mass average molecular weight (Mw) of the polypropylene resin is preferably 180,000 to 500,000. The lower limit of Mw is more preferably 190,000, further preferably 200,000, and the upper limit of Mw is more preferably 320,000, further preferably 300,000, particularly preferably 250,000.

The number average molecular weight (Mn) of the polypropylene resin is preferably 20,000 to 200,000. The lower limit of Mn is more preferably 30,000, more preferably 40,000, particularly preferably 50,000, and the upper limit of Mn is more preferably 80,000, still more preferably 70,000, particularly preferably 60,000. is there.

When the gel permeation chromatography (GPC) integration curve of the entire polypropylene resin constituting the substrate layer (A) is measured, the lower limit of the amount of the component having a molecular weight of 100,000 or less is preferably 35% by mass, more preferably It is 38% by mass, more preferably 40% by mass, particularly preferably 41% by mass, and most preferably 42% by mass.
On the other hand, the upper limit of the amount of the component having a molecular weight of 100,000 or less in the GPC integration curve is preferably 65% by mass, more preferably 60% by mass, still more preferably 58% by mass, particularly preferably 56% by mass Most preferably 55% by weight. Within the above range, stretching becomes easy, thickness unevenness becomes small, and the stretching temperature and the heat setting temperature are easily increased, and the heat shrinkage ratio can be suppressed to a lower level.

When the gel permeation chromatography (GPC) integration curve of the entire polypropylene resin constituting the substrate layer (A) is measured, the lower limit of the amount of the component having a molecular weight of 10,000 or less is preferably 1% by mass, more preferably It is 1.5% by mass.
On the other hand, the upper limit of the amount of components having a molecular weight of 10,000 or less in the GPC integration curve is preferably 5% by mass, more preferably 4% by mass, still more preferably 3.5% by mass, particularly preferably 3 It is weight%.

The melt flow rate (MFR; 230 ° C., 2.16 kgf) of the polypropylene resin at this time is preferably 6.2 g / 10 minutes to 10.0 g / 10 minutes.
The lower limit of the MFR of the polypropylene resin is more preferably 6.5 g / 10 min, still more preferably 7 g / 10 min, and particularly preferably 7.5 g / 10 min. The upper limit of the MFR of the polypropylene resin is more preferably 9 g / 10 min, still more preferably 8.5 g / 10 min, and particularly preferably 8.2 g / 10 min.
When the melt flow rate (MFR; 230 ° C., 2.16 kgf) is 6.2 g / 10 min or more, the heat shrinkage at high temperatures can also be made smaller. Furthermore, since the degree of crystallization of the film generated by stretching becomes strong, the rigidity of the film, in particular, the tensile elastic modulus (Young's modulus) in the width (TD) direction becomes high. In addition, when the melt flow rate (MFR; 230 ° C., 2.16 kgf) is 9.0 g / 10 min or less, film formation can be easily performed without breakage.
The molecular weight distribution of the polypropylene resin can be obtained by polymerizing components of different molecular weights in multiple stages in a series of plants, blending components of different molecular weights offline with a kneader, or blending catalysts having different performances for polymerization. It is possible to adjust by using a catalyst that can realize a desired molecular weight distribution.

The polypropylene resin used in the present invention can be obtained by polymerizing propylene as a raw material using a known catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst. Among them, it is preferable to use a Ziegler-Natta catalyst and to use a catalyst capable of highly stereoregular polymerization in order to eliminate foreign bonds.
As a polymerization method of propylene, a known method may be adopted, for example, a method of polymerizing in an inert solvent such as hexane, heptane, toluene, xylene or the like, a method of polymerizing in a liquid monomer, a catalyst to a gas monomer And polymerizing in the gas phase, or a method of polymerizing these in combination, and the like.

The polypropylene resin may contain additives and other resins. Examples of the additive include an antioxidant, an ultraviolet light absorber, a nucleating agent, an adhesive, an antifogging agent, a flame retardant, an inorganic or organic filler, and the like. Other resins include polypropylene resins other than polypropylene resins used in the present invention, random copolymers which are copolymers of propylene and ethylene and / or α-olefins having 4 or more carbon atoms, and various elastomers. These may be sequentially polymerized using a multistage reactor, blended with a polypropylene resin and a Henschel mixer, or diluted with polypropylene so as to obtain a predetermined concentration of master pellets prepared beforehand using a melt kneader Alternatively, the whole may be melt-kneaded in advance and used.

(Heat seal layer (B))
In the present invention, the resin used for the heat seal layer (B) is preferably a low melting point propylene random copolymer having a melting point of 150 ° C. or less, or a propylene block copolymer in which an elastomer component containing a comonomer is dispersed, Moreover, these can be used individually or in mixture. As the comonomer, it is preferable to use ethylene or at least one selected from α-olefins having 3 to 10 carbon atoms such as butene, pentene, hexene, octene and decene.

Furthermore, the melting point of the propylene random copolymer forming the heat seal layer (B) is preferably 60 to 150 ° C. Thereby, sufficient heat seal strength can be given to an oriented polypropylene resin laminated film. When the melting point of the propylene random copolymer forming the heat seal layer (B) is less than 60 ° C., the heat resistance of the heat seal portion is poor, and when it exceeds 150 ° C., improvement in heat seal strength can not be expected. The melting point of the elastomer component contained in the propylene block copolymer is also preferably 150 ° C. or less.
The MFR may be in the range of 0.1 to 100 g / 10 min, preferably 0.5 to 20 g / 10 min, more preferably 1.0 to 10 g / 10 min.

The polypropylene resin used in the heat seal layer (B) is obtained by polymerizing propylene as a raw material using a known catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst. Among them, in order to eliminate foreign bonds, it is preferable to use a Ziegler-Natta catalyst and to use a catalyst capable of highly regular polymerization.
As a polymerization method of propylene, a known method may be used, a method of polymerizing in an inert solvent such as hexane, heptane, toluene, xylene or the like, a method of polymerizing in liquid propylene or ethylene, propylene in gas or propylene. The method of adding a catalyst and polymerizing in a gas phase state, or the method of combining and polymerizing these, etc. are mentioned.
The high molecular weight component and the low molecular weight component may be separately polymerized and then mixed, or may be produced in a series of plants in a multistage reactor. In particular, a method is preferable in which a high molecular weight component is first polymerized and then the low molecular weight component is polymerized in the presence thereof using a plant having a multistage reactor.

(Method for producing polypropylene film)
The polypropylene-based laminate film of the present invention may be a uniaxially stretched film in the longitudinal direction (MD direction) or the transverse direction (TD direction), but is preferably a biaxially stretched film. In the case of biaxial stretching, it may be sequential biaxial stretching or simultaneous biaxial stretching.
By setting it as a stretched film, it is possible to obtain a film having a low thermal shrinkage even at 150 ° C., which could not be predicted with a conventional polypropylene-based laminate film.

The following will describe a method of producing a longitudinally stretched-laterally stretched sequential biaxially stretched film which is the most preferable example.
First, the base material layer (A) is melt-extruded from one extruder, the heat seal layer (B) is melt-extruded using the other extruder, and heat is applied to the polypropylene resin layer (A) in the T die. It laminates | stacks so that it may become a sealing layer (B), it cools and solidifies with a cooling roll, and obtains an unstretched sheet. As the melt extrusion conditions, the resin temperature is set to 200 to 280 ° C., the sheet is extruded from a T-die, and it is cooled and solidified by a cooling roll at a temperature of 10 to 100 ° C. Then, the film is stretched 3 to 7 times in the length (MD) direction with a stretching roll at 120 to 165 ° C., and subsequently at a temperature of 155 ° C. to 175 ° C., preferably 158 ° C. to 170 ° C. in the width (TD) direction. Perform stretching 6 to 12 times.
Furthermore, heat treatment is performed while allowing 1 to 15% relaxation at an ambient temperature of 165 to 175 ° C., preferably 166 to 173 ° C.
If necessary, a roll sample can be obtained by applying corona discharge treatment to at least one side and winding with a winder.

The lower limit of the draw ratio of MD is preferably 3 times, more preferably 3.5 times. If it is less than the above, film thickness unevenness may occur.
The upper limit of the draw ratio of MD is preferably 8 times, more preferably 7 times. If the above is exceeded, it may be difficult to carry out the subsequent TD stretching.

The lower limit of the stretching temperature of MD is preferably 120 ° C., more preferably 122 ° C. If it is less than the above, mechanical load may increase, thickness unevenness may increase, or surface roughness of the film may occur.
The upper limit of the MD stretching temperature is preferably 150 ° C., more preferably 145 ° C., still more preferably 135 ° C., particularly preferably 130 ° C. A higher temperature is preferable for lowering the heat shrinkage, but it may stick to the roll and not be able to be stretched.

The lower limit of the draw ratio of TD is preferably 4 times, more preferably 5 times, and still more preferably 6 times. If it is less than the above, thickness unevenness may occur.
The upper limit of the TD stretch ratio is preferably 20 times, more preferably 17 times, and still more preferably 15 times. If the above is exceeded, the thermal contraction rate may be high, or the film may break during stretching.

The preheating temperature in TD stretching is preferably set 10 to 15 ° C. higher than the stretching temperature in order to rapidly raise the film temperature to around the stretching temperature.

TD stretching is performed at a higher temperature than conventional heat sealable polypropylene laminated stretched films.
The lower limit of the stretching temperature of TD is preferably 157 ° C., more preferably 158 ° C. If the amount is less than the above, breakage may occur without sufficient softening, or the heat shrinkage may increase.
The upper limit of the TD stretching temperature is preferably 170 ° C., more preferably 168 ° C. In order to lower the heat shrinkage rate, it is preferable that the temperature be higher, but if the temperature is higher than the above, the low molecular weight component may be melted and recrystallized to cause surface roughness and whitening of the film.

The stretched film is heat set. Heat setting can be done at higher temperatures than conventional polypropylene films. The lower limit of the heat setting temperature is preferably 165 ° C, more preferably 166 ° C. When it is less than the above, the heat shrinkage may be high. In addition, a long time may be required to lower the thermal contraction rate, and the productivity may be poor.
The upper limit of the heat setting temperature is preferably 175 ° C, more preferably 173 ° C. If the above is exceeded, low molecular weight components may melt and recrystallize to cause surface roughness and whitening of the film.

It is preferable to relax during heat setting. The lower limit of relaxation is preferably 2%, more preferably 3%. When it is less than the above, the heat shrinkage may be high.
The upper limit of relaxation is preferably 10%, more preferably 8%. When the above is exceeded, thickness unevenness may become large.

Furthermore, in order to reduce the thermal contraction rate, the film produced in the above process may be once wound into a roll and then annealed off-line.
The lower limit of the off-line annealing temperature is preferably 160 ° C., more preferably 162 ° C., and still more preferably 163 ° C. If it is less than the above, the effect of annealing may not be obtained.
The upper limit of the off-line annealing temperature is preferably 175 ° C., more preferably 174 ° C., and still more preferably 173 ° C. If the above is exceeded, the transparency may be reduced, or the thickness unevenness may be significant.

The lower limit of the off-line annealing time is preferably 0.1 minutes, more preferably 0.5 minutes, and still more preferably 1 minute. If it is less than the above, the effect of annealing may not be obtained.
The upper limit of the off-line annealing time is preferably 30 minutes, more preferably 25 minutes, and still more preferably 20 minutes. If the above is exceeded, productivity may fall.

The thickness of the film is set according to each application, but the lower limit of the film thickness is preferably 2 μm, more preferably 3 μm, and still more preferably 4 μm. The upper limit of the film thickness is preferably 300 μm, more preferably 250 μm, still more preferably 200 μm, particularly preferably 100 μm, and most preferably 50 μm.

The polypropylene-based laminate film thus obtained is usually formed as a roll having a width of 2000 to 12000 mm and a length of about 1000 to 50000 m, and is wound into a roll.
Furthermore, it is slitted according to each use and provided as a slit roll having a width of about 300 to 2000 mm and a length of about 500 to 5000 m.

The polypropylene-based laminate film of the present invention has the above-mentioned excellent properties not heretofore available.
When it is used as a packaging film, it can be made thin because it has high rigidity, and cost and weight can be reduced.
In addition, since the heat resistance is high, high-temperature drying can be performed at the time of drying of the coating or printing, and it is possible to use a coating agent, an ink, a laminating adhesive, etc. Since there is no need for a lamination process using an organic solvent or the like, it is preferable from the viewpoints of both economic and global impact.

(Film characteristics)
The lower limit of the thermal shrinkage at 150 ° C. in the MD and TD directions of the polypropylene-based laminate film of the present invention is preferably 0.5%, more preferably 1%, still more preferably 1.5%, Preferably it is 2%, most preferably 2.5%. If it is in the above-mentioned range, realistic production may be facilitated in terms of cost and the like, or thickness unevenness may be reduced.

The upper limit of the heat shrinkage at 150 ° C. in the MD direction is preferably 7%, more preferably 6%, and still more preferably 5%. If it is in the above range, it becomes easier to use in applications that may be exposed to high temperatures of about 150 ° C. In addition, if the thermal contraction rate at 150 ° C. is up to about 2.5%, for example, it is possible by increasing the low molecular weight component, adjusting the stretching conditions and fixing conditions, but annealing below that may be performed offline. preferable.
In the conventional stretched polypropylene laminated film, the thermal contraction rate at 150 ° C. in the MD direction is 15% or more, and the thermal contraction rate at 120 ° C. is about 3%. By making heat contraction rate into said range, the polypropylene-type laminated film excellent in heat resistance can be obtained.

The upper limit of the heat shrinkage at 150 ° C. in the TD direction is preferably 8%, more preferably 7%, and still more preferably 7%. If it is in the above range, it becomes easier to use in applications that may be exposed to high temperatures of about 150 ° C. In addition, if the thermal contraction rate at 150 ° C. is up to about 2.5%, for example, it is possible by increasing the low molecular weight component, adjusting the stretching conditions and fixing conditions, but annealing below that may be performed offline. preferable.
In the conventional stretched polypropylene laminated film, the thermal contraction rate at 150 ° C. in the TD direction is 15% or more, and the thermal contraction rate at 120 ° C. is about 3%. By making heat contraction rate into said range, the polypropylene-type laminated film excellent in heat resistance can be obtained.

When the polypropylene-based laminate film of the present invention is a biaxially stretched film, the lower limit of Young's modulus (23 ° C.) in the MD direction is preferably 1.8 GPa, more preferably 1.9 GPa, and still more preferably 2. 0 GPa, particularly preferably 2.1 GPa, most preferably 2.2 GPa.
The upper limit of Young's modulus in the MD direction is preferably 3.7 GPa, more preferably 3.6 GPa, still more preferably 3.5 GPa, particularly preferably 3.4 GPa, and most preferably 3.3 GPa. is there. Within the above range, practical manufacture may be easy, or MD-TD balance may be improved.

When the polypropylene-based laminate film of the present invention is a biaxially stretched film, the lower limit of Young's modulus (23 ° C.) in the TD direction is preferably 4.4 GPa, more preferably 4.5 GPa, and still more preferably 4. 6 GPa, particularly preferably 4.7 GPa.
The upper limit of the Young's modulus in the TD direction is preferably 8 GPa, more preferably 7.5 GPa, still more preferably 7 GPa, and particularly preferably 6.5 GPa. Within the above range, practical manufacture may be facilitated, or MD-TD balance may be improved.
The Young's modulus can be increased by increasing the draw ratio, and in the case of MD-TD stretching, the MD draw ratio is set to a lower value, and the TD draw ratio is increased to increase the Young's modulus in the TD direction. Can.

The lower limit of the plane orientation coefficient of the polypropylene film of the present invention is preferably 0.0125, more preferably 0.0126, still more preferably 0.0127, particularly preferably 0.0128. . The upper limit of the plane orientation coefficient is preferably 0.0155, more preferably 0.0150, still more preferably 0.0148, particularly preferably 0.0145, as a practical value. Preferably it is 0.0140. The plane orientation coefficient can be in the range by adjusting the draw ratio. When the plane orientation coefficient is in this range, the thickness unevenness of the film is also good.

The heat seal strength of the polypropylene-based laminate film of the present invention at 140 ° C. is preferably 8.0 N / 15 mm or more, more preferably 9.0 N / 15 mm or more, and further preferably 10 N / 15 mm or more preferable.
The heat seal strength of the polypropylene-based laminate film of the present invention is preferably 1.5 N / 15 mm or more at 110 ° C., more preferably 2.0 N / 15 mm or more, and 2.2 N / 15 mm or more. It is further preferred that

The lower limit of the impact resistance (23 ° C.) of the stretched polypropylene film of the present invention is preferably 0.6 J, more preferably 0.7 J. If it is in the above range, it has sufficient toughness as a film and does not break during handling.
The upper limit of the impact resistance is preferably 3 J, more preferably 2.5 J, still more preferably 2.2 J, and particularly preferably 2 J from the practical viewpoint. For example, when the low molecular weight component is large, the impact resistance tends to decrease when the total molecular weight is low, or when the high molecular weight component is low or when the molecular weight of the high molecular weight component is low. These components can be adjusted to be in the range.

The lower limit of the haze of the polypropylene-based laminate film of the present invention is preferably 0.1%, more preferably 0.2%, still more preferably 0.3%, particularly preferably 0. It is 4%, most preferably 0.5%.
The upper limit of the haze is preferably 6%, more preferably 5%, still more preferably 4.5%, particularly preferably 4%, most preferably 3.5%. Within the above range, it may be easy to use in applications where transparency is required. The haze tends to be worse, for example, when the stretching temperature and the heat setting temperature are too high, when the cooling roll (CR) temperature is high and the cooling rate is slow, and when the low molecular weight is too high. You can do it.

The lower limit of the thickness uniformity of the polypropylene-based laminate film of the present invention is preferably 0%, more preferably 0.1%, still more preferably 0.5%, particularly preferably 1%.
The upper limit of thickness uniformity is preferably 20%, more preferably 17%, still more preferably 15%, particularly preferably 12%, and most preferably 10%. Within the above range, defects are less likely to occur during post-processing such as coating and printing, and it is easy to use for applications requiring precision.

EXAMPLES The present invention will be described in detail based on examples given below, but the present invention is not limited to these examples. The measuring method of the physical property in an Example is as follows.

1) Melt flow rate (MFR, g / 10 min)
It was measured at a temperature of 230 ° C. in accordance with JIS K7210.

2) Molecular weight and molecular weight distribution Molecular weight and molecular weight distribution were determined by gel permeation chromatography (GPC) on the basis of monodispersed polystyrene.
The used column and solvent in GPC measurement are as follows.
Solvent: 1, 2, 4- trichlorobenzene column: TSKgel GMH _HR- H (20) HT x 3
Flow rate: 1.0 ml / min
Detector: RI
Measurement temperature: 140 ° C
The number average molecular weight (Mn), mass average molecular weight (Mw), and Z + 1 average molecular weight (Mz + 1) are respectively determined by the molecular number (Ni) of the molecular weight (Mi) at each elution position of the GPC curve obtained through the molecular weight calibration curve. It is defined by the following equation.
Number average molecular weight: Mn = ((Ni · Mi) / Ni Ni
Mass average molecular weight: Mw = Σ (Ni · Mi ² ) / Σ (Ni · Mi)
Z + 1 average molecular weight: Mz + 1 = Σ (Ni · Mi ⁴ ) / ⁴ (Ni · Mi ³ )
Molecular weight distribution: Mw / Mn, Mz + 1 / Mn
Moreover, the molecular weight of the peak position of a GPC curve was set to Mp.
When the baseline is not clear, the baseline is set in the range up to the lowest position on the high molecular weight side of the elution peak on the high molecular weight side closest to the elution peak of the standard substance.
For peak separation, peak separation was performed on two or more components having different molecular weights from the obtained GPC curve. The molecular weight distribution of each component assumes a Gaussian function, and Mw / Mn = 4 so as to be similar to the molecular weight distribution of normal polypropylene. Each average molecular weight was calculated from the obtained curve of each component.

3) Stereoregularity Measurement of mesopentad fraction ([mm mm]%) and meso average chain length was performed using ¹³ C-NMR. The mesopentad fraction is determined according to the method described by Zambelli et al., Macromolecules, 6: 925 (1973), and the meso average chain length is determined according to J. Am. C. Calculated according to the method described in Randall, "Polymer Sequence Distribution", Chapter 2 (1977) (Academic Press, New York).
^{The 13} C-NMR measurement was carried out at 110 ° C. by dissolving 200 mg of the sample in an 8: 2 mixture of o-dichlorobenzene and heavy benzene at 135 ° C. using AVANCE 500 manufactured by BRUKER.

4) Cold xylene soluble part (CXS, mass%)
1 g of a polypropylene sample is dissolved in 200 ml of boiling xylene and allowed to cool, then recrystallized in a constant temperature water bath at 20 ° C. for 1 hour, and the ratio of the mass dissolved in the filtrate to the original sample amount is CXS (mass%) And

5) Heat shrinkage rate (%)
It measured based on JIS Z 1712.
(The stretched film was cut in the MD and TD directions with a width of 20 mm and a length of 200 mm, respectively, suspended in a hot air oven at 150 ° C. and heated for 5 minutes. The length after heating was measured and the shrinkage relative to the original length The heat shrinkage rate was determined by the ratio of

6) Impact resistance It measured at 23 degreeC using the Toyo Seiki film impact tester.

7) Young's modulus (unit: GPa)
Young's modulus in the MD and TD directions was measured at 23 ° C. in accordance with JIS K 7127.

8) Haze (unit:%)
It measured according to JIS K7105.

9) Plane orientation coefficient (ΔP)
It was measured according to JIS K7142-1996 5.1 (Method A) using an Atago Abbe refractometer. The refractive indices along the MD and TD directions are Nx and Ny, respectively, and the refractive index in the thickness direction is Nz. The plane orientation coefficient (ΔP) was determined by (Nx + Ny) / 2-Nz.
When the sealing layer is single-sided: The surface opposite to the sealing layer was measured three times, and the average value thereof was taken.
In the case where the sealing layer is on both sides: the surface of the sealing layer was measured three times on both sides and the average value thereof was taken.

10) Heat seal strength Heat seal temperature is 140 ° C. and 110 ° C., pressure is 1 kg / cm ² , heat seal time is 1 second, heat seal layer (B) faces of laminated stretched films are superposed and heat plate seal is formed. It carried out and produced the test piece of 10 mm width. The 180 degree peel strength of this test piece was measured to obtain the heat seal strength (N / 15 mm).

11) Curl property The degree of curl of the laminated stretched film of the film obtained in the evaluation of 10) was measured by visual observation.
○: no curling △: slightly curled ×: significant curling

12) Thickness spots A square sample having a length of 1 m was cut out from the wound film roll, and divided into 10 equal parts in the MD direction and the TD direction to prepare 100 measurement samples. The thickness of the substantially central portion of the measurement sample was measured with a contact-type film thickness meter.
The average value of the obtained data of 100 points is determined, and the difference between the minimum value and the maximum value (absolute value) is determined, and the absolute value of the difference between the minimum value and the maximum value is divided by the average value And

13) Heat-sealed appearance Heat-sealed by holding the produced film and Pylen Film-CT P1128 manufactured by Toyobo Co., Ltd. and using a test sealer manufactured by Seibu Kikai Co., Ltd. at 170 ° C. and a 2 kg load for 1 second The The degree of appearance change due to shrinkage of the film after heat sealing was visually evaluated. The heat seal portion with a small deformation amount in a range not affecting use was marked with ○, and a heat seal with a large shrinkage and a large deformation amount with ×.

Example 1
Using two melt extruders and using the first extruder as the polypropylene resin, the polypropylene homopolymer PP-1 shown in Table 1 is used as the substrate layer (A), and using the second extruder as propylene. 85% by weight of ethylene-butene random copolymer (PP-7: Pr-Et-Bu, density 0.89 g / cm ³ , MFR 4.6 g / 10 min, melting point 128 ° C.), propylene-butene random copolymer A mixed resin of 15 wt% (PP-8: Pr-Bu, density 0.89 g / cm ³ , MFR 9.0 g / 10 min, melting point 130 ° C.) is used as a heat seal layer (B) in a die. Material layer (A) / heat seal layer (B), after melt coextrusion into a sheet form from T die at 250 ° C by T die method in order of base material layer (A) and heat seal layer (B) It solidified by cooling with a 30 ° C cooling roll After that, it is stretched 4.5 times in the longitudinal direction at 125 ° C., then both ends are clipped, led into a hot air oven, and after being preheated at 175 ° C., stretched 8.2 times in the transverse direction at 160 ° C. Then, it was heat-treated at 170 ° C. with 6.7% relaxation. Thereafter, one side of the film was subjected to corona treatment and was wound by a winder. The thickness of the film thus obtained was 20 μm, and a laminated stretched film in which the thicknesses of the base material layer and the heat seal layer were 18 μm and 2 μm in this order, respectively, was obtained. As shown in Tables 1, 2 and 3, the resulting laminated stretched film satisfies the requirements of the present invention, has a low thermal shrinkage, high rigidity, and has heat seal strength, stiffness and curling properties. Was also excellent.

(Example 2)
A polypropylene-based laminate film was obtained in the same manner as Example 1, except that the raw material used for the base material layer (A) was changed to the polypropylene homopolymer PP-2 shown in Table 1. As shown in Tables 1, 2 and 3, the resulting laminated stretched film satisfies the requirements of the present invention, has a low thermal shrinkage, high rigidity, and has heat seal strength, stiffness and curling properties. Was also excellent.

(Comparative example 1)
A polypropylene-based laminate film was obtained in the same manner as Example 1, except that the raw material used for the base material layer (A) was changed to the polypropylene homopolymer PP-3 shown in Table 1. As shown in Table 1, Table 2 and Table 3, the resulting laminated stretched film was excellent in heat seal strength, waist feel and curlability, but had a large heat shrinkage.

(Comparative example 2)
An attempt was made to obtain a polypropylene-based laminate film in the same manner as in Example 1 except that the raw material used for the base material layer (A) was changed to the polypropylene homopolymer PP-4 shown in Table 1. Was broken and no sample was obtained.

(Comparative example 3)
A polypropylene-based laminate film was obtained in the same manner as in Example 1, except that the raw material used for the base material layer (A) was changed to the polypropylene homopolymer PP-5 shown in Table 1. As shown in Table 1, Table 2 and Table 3, the resulting laminated stretched film was excellent in heat seal strength, waist feel and curlability, but had a large heat shrinkage.

(Comparative example 4)
The raw material used for the base material layer (A) is changed to polypropylene homopolymer PP-6 shown in Table 1, and the width direction stretch preheating temperature is 170 ° C., the width direction stretch temperature is 158 ° C., and the heat setting temperature is 165. A polypropylene-based laminate film was obtained in the same manner as in Example 1 except that the temperature was changed to ° C. As shown in Table 1, Table 2 and Table 3, the resulting laminated stretched film was excellent in heat seal strength, waist feel and curlability, but the heat shrinkage rate was very large.

The polypropylene-based laminate film of the present invention was excellent for use as a packaging application, and was very suitable for heat sealing.
Furthermore, for example, by setting the heat seal temperature high, it is possible to increase the line speed in bag-making processing and the like, and the productivity is improved. In addition, the heat seal strength can also be improved by increasing the heat seal temperature.

Claims

A heat seal layer (B) comprising a base layer (A) in which a polypropylene resin constituting the layer satisfies the following conditions 1) to 4) and a polyolefin resin laminated on one side or both sides of the base layer And the lower limit of the plane orientation coefficient of the film is 0.0125.
1) The lower limit of the mesopentad fraction is 96%.
2) The upper limit of the amount of copolymerized monomers other than propylene is 0.1 mol%.
3) Mass average molecular weight (Mw) / number average molecular weight (Mn) is 3.0 or more and 5.4 or less.
4) The melt flow rate (MFR) measured at 230 ° C. and 2.16 kgf is 6.2 g / 10 min or more and 9.0 g / 10 min or less.
The polypropylene-based laminate film according to claim 1 or 2, wherein the heat shrinkage at 150 ° C in the longitudinal direction and the transverse direction of the film is 8% or less.
The polypropylene-based laminate film according to claim 1 or 2, wherein Young's modulus in the MD direction is 2.1 GPa or more, and Young's modulus in the TD direction is 3.7 GPa or more.
The 180 ° peel strength of a 10 mm wide test piece obtained by laminating heat seal layer (B) surfaces and performing hot plate sealing at 140 ° C. for 1 second is 8.0 N / 15 mm or more. The polypropylene-based laminate film according to any one of the above.
The polypropylene-based laminate film according to any one of claims 1 to 4, wherein the polyolefin resin constituting the heat seal resin (B) is a propylene random copolymer and / or a propylene block copolymer.