Biaxially stretched polypropylene film, food packaging body, and food packaging body

Abstract

A biaxially stretched polypropylene film (100) is provided with a biaxially stretched film layer (101) containing a propylene polymer, and has a crystal long period in the TD direction of 28.0 nm or less as determined by small angle X-ray scattering (SAXS) measurement.

Description

Technical Field

[0001] The present invention relates to a biaxially stretched polypropylene film, a food packaging body and a food packaging body. Background Art

[0002] Biaxially oriented polypropylene film (hereinafter also referred to as OPP film) has excellent balance in performance such as processability, water vapor barrier property, transparency, mechanical strength and rigidity, and is used as a packaging film for packaging food, for example.

[0003] Examples of the technology related to food packaging films using such OPP films include the technology described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2008-73926) and Patent Document 2 (Japanese Patent Application Laid-Open No. 2004-82499).

[0004] Patent document 1 describes a biaxially stretched multilayer polypropylene film, characterized in that on one side of a biaxially stretched film formed from a propylene polymer composition containing 75 to 90% by mass of a propylene homopolymer (A) and 25 to 10% by mass of a tackifier (D), there is a layer formed from a propylene·α-olefin random copolymer (C) having a melting point in the range of 125 to 145°C via a layer formed from a propylene-based polymer (B) having a melting point of 155°C or more, and on the other side of the above-mentioned biaxially stretched film there is a layer formed from a propylene-based polymer (E).

[0005] Patent Document 1 discloses that the biaxially stretched multilayer polypropylene film can suppress the bleeding of petroleum resin and the like to the film surface and is excellent in lamination strength and moisture resistance.

[0006] Patent document 2 describes a multilayer resin film, characterized in that it is a multilayer resin film having a polyvinyl alcohol resin layer on at least one side of a biaxially stretched polypropylene resin layer containing 10 to 40% by mass of a highly crystalline resin and 6 to 15% by mass of a petroleum resin via an adhesive layer, and the multilayer resin film has an oxygen permeability of 600 mL / m under the conditions of a relative humidity of 85% RH and a temperature of 23°C. 2 ·day·MPa or less, and the water vapor permeability under the conditions of relative humidity 90%RH and temperature 40℃ is 3.5g / m 2 ·day·20μm or less.

[0007] Patent Document 2 describes that the multilayer resin film has excellent oxygen barrier properties and moisture resistance.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Publication No. 2008-73926

[0011] Patent Document 2: Japanese Patent Application Publication No. 2004-82499 Summary of the invention

[0012] Problems to be solved by the invention

[0013] In recent years, from the viewpoint of environmental issues, there is a demand for packaging materials to be made of a single material.

[0014] However, from the viewpoint of suppressing heat wrinkles at the seal portion during bag making and suppressing heat elongation during evaporation and coating, the conventional conventional biaxially stretched polypropylene film sometimes has insufficient thermal dimensional stability. That is, for the biaxially stretched polypropylene film, from the viewpoint of suppressing heat wrinkles at the seal portion during bag making and suppressing heat elongation during evaporation and coating, it is required to further improve the thermal dimensional stability.

[0015] The present invention has been made in view of the above circumstances, and provides a biaxially stretched polypropylene film, a food packaging body, and a food packaging body having improved thermal dimensional stability.

[0016] Means for solving problems

[0017] The inventors of the present application conducted intensive studies to solve the above problems and found that the thermal dimensional stability of a biaxially stretched polypropylene film can be improved by adjusting the long crystal period in the TD direction determined by small angle X-ray scattering (SAXS) measurement to a specific range, thereby completing the present invention.

[0018] That is, according to the present invention, there are provided the following biaxially stretched polypropylene films, food packaging bodies, and food packaging bodies.

[0019] [1] A biaxially stretched polypropylene film comprising a biaxially stretched film layer containing a propylene-based polymer,

[0020] The long crystal period in the TD direction determined by small-angle X-ray scattering (SAXS) measurement was 28.0 nm or less.

[0021] [2] The biaxially stretched polypropylene film according to [1] above, wherein the amorphous thickness in the TD direction determined by SAXS measurement is 15.5 nm or less.

[0022] [3] The biaxially stretched polypropylene film according to [1] or [2], wherein the crystal thickness in the TD direction determined by SAXS measurement is 13.5 nm or less.

[0023] [4] The biaxially stretched polypropylene film according to any one of [1] to [3], wherein the crystallization ratio at 165° C. or lower determined by differential scanning calorimetry is 38% or more.

[0024] [5] The biaxially stretched polypropylene film according to any one of [1] to [4], wherein the main melting point of the biaxially stretched polypropylene film determined by differential scanning calorimetry is 165° C. or more and 180° C. or less.

[0025] [6] The biaxially stretched polypropylene film according to any one of [1] to [5], wherein the heat of fusion (ΔH) of the biaxially stretched polypropylene film as a whole, as determined by differential scanning calorimetry, is 100 J / g to 150 J / g.

[0026] [7] The biaxially stretched polypropylene film according to any one of [1] to [6], wherein the heat of fusion (ΔH) of the biaxially stretched polypropylene film at 165° C. or lower determined by differential scanning calorimetry is 40 J / g or more.

[0027] [8] The biaxially stretched polypropylene film according to any one of [1] to [7], wherein the biaxially stretched polypropylene film has a crystallization content of 20% or more at 165°C or less.

[0028] [9] The biaxially stretched polypropylene film according to any one of [1] to [8], wherein the amount of the structural units derived from α-olefins other than propylene contained in the biaxially stretched polypropylene film is 0.05 mol% or more, when the total amount of the structural units derived from monomers contained in the biaxially stretched polypropylene film is 100 mol%.

[0029]

[10] The biaxially stretched polypropylene film according to any one of [1] to [9], which expands in the TD direction when heat-treated at 120° C. for 15 minutes in accordance with JIS C2151:2019.

[0030]

[11] The biaxially stretched polypropylene film according to any one of [1] to

[10] , which expands in the TD direction and shrinks in the MD direction when heat-treated at 120° C. for 15 minutes in accordance with JIS C2151:2019.

[0031]

[12] The biaxially stretched polypropylene film according to any one of [1] to

[11] , wherein the coefficient of thermal expansion in the TD direction when heat treated at 120° C. for 15 minutes in accordance with JIS C2151:2019 is 0.1% to 2.0%.

[0032]

[13] The biaxially stretched polypropylene film according to any one of [1] to

[12] , wherein the heat shrinkage in the MD direction when heated at 120° C. for 15 minutes in accordance with JIS C2151:2019 is 5.0% or less.

[0033]

[14] The biaxially stretched polypropylene film according to any one of [1] to

[13] , wherein the heat shrinkage in the TD direction when heated at 150°C for 15 minutes in accordance with JIS C2151:2019 is 8.5% or less.

[0034]

[15] The biaxially stretched polypropylene film according to any one of [1] to

[14] , wherein the heat shrinkage in the MD direction when heated at 150° C. for 15 minutes in accordance with JIS C2151:2019 is 8.0% or less.

[0035]

[16] The biaxially stretched polypropylene film according to any one of [1] to

[15] , wherein the heat shrinkage in the TD direction and the heat shrinkage in the MD direction when heated at 150° C. for 15 minutes in accordance with JIS C 2151: 2019 are respectively denoted as X TD [%] and X MD [%], X TD +X MD Less than 6.0%.

[0036]

[17] The biaxially stretched polypropylene film according to any one of [1] to

[16] , wherein the heat fusion strength when the biaxially stretched polypropylene films are heat-sealed at 200°C is 4.0 N / 15 mm or less.

[0037]

[18] The biaxially stretched polypropylene film according to any one of [1] to

[17] , wherein the heat fusion strength when the biaxially stretched polypropylene films are heat-sealed at 170°C is 1.0 N / 15 mm or less.

[0038]

[19] The biaxially stretched polypropylene film according to any one of [1] to

[18] , wherein the propylene-based polymer comprises homopolypropylene (A) and at least one polymer (B) selected from the group consisting of random polypropylene (B1) and α-olefin copolymers (B2);

[0039] The MFR of the polymer (B), measured under the conditions of 230° C. and a load of 2.16 kg in accordance with ASTM D1238, is 0.01 g / 10 min or more and 30 g / 10 min or less.

[0040]

[20] The biaxially stretched polypropylene film according to

[19] , wherein the isotactic pentad fraction (mmmm) of the homopolypropylene (A) is 96.0% or more.

[0041]

[21] The biaxially stretched polypropylene film as described in

[19] or

[20] above, wherein the content of the polymer (B) is 1% by mass or more and 50% by mass or less, when the total amount of the biaxially stretched film layer is 100% by mass.

[0042]

[22] The biaxially stretched polypropylene film according to any one of

[19] to

[21] , wherein the melting point of the polymer (B) is 50°C or more and 155°C or less.

[0043]

[23] The biaxially stretched polypropylene film according to any one of

[19] to

[22] , wherein the weight average molecular weight (Mw) of the polymer (B) is 100,000 to 1,000,000.

[0044]

[24] The biaxially stretched polypropylene film according to any one of

[19] to

[23] , wherein the weight average molecular weight (Mw) / number average molecular weight (Mn) of the polymer (B) is 1.5 to 8.0.

[0045]

[25] A biaxially stretched polypropylene film as described in any one of

[19] to

[24] above, wherein the α-olefin copolymer (B2) comprises a random copolymer of propylene and one or more α-olefins selected from the group consisting of ethylene and α-olefins having a carbon number of 4 to 10.

[0046]

[26] The biaxially stretched polypropylene film according to any one of [1] to

[25] , further comprising a surface resin layer on at least one surface of the biaxially stretched film layer.

[0047]

[27] The biaxially stretched polypropylene film according to

[26] above, wherein the surface resin layer comprises homopolypropylene (A).

[0048]

[28] The biaxially stretched polypropylene film as described in

[27] above, wherein the content of the homopolypropylene (A) in the surface resin layer is 75% by mass or more and 100% by mass or less, when the entire surface resin layer is taken as 100% by mass.

[0049]

[29] The biaxially stretched polypropylene film according to any one of

[26] to

[28] , wherein the thickness of the surface resin layer is 0.1 μm to 10.0 μm.

[0050]

[30] The biaxially stretched polypropylene film according to any one of [1] to

[29] , wherein the thickness of the biaxially stretched film layer is 5 μm to 100 μm.

[0051]

[31] A biaxially stretched polypropylene film as described in any one of [1] to

[30] above, wherein the total value (T1+T2) of the tensile modulus T1 in the MD direction and the tensile modulus T2 in the TD direction of the biaxially stretched polypropylene film, measured in accordance with JIS K7127 (1999) using a tensile testing machine under the conditions of a measuring temperature of 23±2°C, 50±5%RH, and a tensile speed of 5 mm / min, is 3000 MPa or more and 10000 MPa or less.

[0052]

[32] The biaxially stretched polypropylene film according to any one of [1] to

[31] , which is a food packaging film.

[0053]

[33] A food packaging body using the biaxially stretched polypropylene film according to any one of [1] to

[32] .

[0054]

[34] A food packaging body, comprising:

[0055] The food packaging body described in

[33] above; and

[0056] The food in the aforementioned food packaging.

[0057] Effects of the Invention

[0058] According to the present invention, a biaxially stretched polypropylene film, a food package, and a food package having improved thermal dimensional stability can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] [ Figure 1 ] is a cross-sectional view schematically showing an example of the structure of the biaxially stretched polypropylene film of the present embodiment.

[0060] [ Figure 2 ] is a cross-sectional view schematically showing an example of the structure of the biaxially stretched polypropylene film of the present embodiment.

[0061] [ Figure 3 ] is a cross-sectional view schematically showing an example of the structure of the biaxially stretched polypropylene film of the present embodiment. DETAILED DESCRIPTION

[0062] Hereinafter, the embodiments of the present invention will be described using the accompanying drawings. It should be noted that the drawings are schematic diagrams and are not consistent with the actual dimensional ratios. It should be noted that, unless otherwise specified, "-" between numbers in the text means above to below.

[0063] <Biaxially stretched polypropylene film>

[0064] Figure 1 to Figure 3 It is a cross-sectional view schematically showing an example of the structure of the biaxially stretched polypropylene film 100 according to the present embodiment.

[0065] The biaxially stretched polypropylene film 100 of the present embodiment includes a biaxially stretched film layer 101 containing a propylene-based polymer, and has a long crystal period in the TD direction determined by small-angle X-ray scattering (SAXS) measurement of 28.0 nm or less.

[0066] As described above, from the viewpoint of suppressing heat wrinkles at the seal portion during bag making and suppressing thermal elongation during vapor deposition and coating processing, further improvement in thermal dimensional stability is required for the biaxially stretched polypropylene film.

[0067] Here, according to the research of the inventors of the present application, it was found that the thermal dimensional stability of the biaxially stretched polypropylene film 100 can be improved by setting the long crystal period in the TD direction determined by SAXS measurement to 28.0 nm or less, thereby completing the present invention.

[0068] That is, according to the biaxially stretched polypropylene film 100 of the present embodiment, thermal dimensional stability can be improved.

[0069] Furthermore, since the biaxially stretched polypropylene film 100 of the present embodiment has improved thermal dimensional stability, heat wrinkles at the seal portion during bag making can be suppressed, and as a result, bag making properties can be improved.

[0070] The crystal long period S2 in the TD direction of the biaxially stretched polypropylene film 100 determined by SAXS measurement is 28.0 nm or less, preferably 27.8 nm or less, more preferably 27.6 nm or less, further preferably 27.0 nm or less, further preferably 25.0 nm or less, further preferably 23.0 nm or less, further preferably 20.0 nm or less, further preferably 18.0 nm or less, further preferably 15.0 nm or less, and further preferably 5.0 nm or more, more preferably 8.0 nm or more, further preferably 10.0 nm or more, further preferably 12.0 nm or more, further preferably 15.0 nm or more, further preferably 18.0 nm or more, further preferably 20.0 nm or more, further preferably 23.0 nm or more, further preferably 25.0 nm or more, further preferably 27.0 nm or more, from the viewpoint of further improving the performance balance between the transparency and the water vapor barrier property of the biaxially stretched polypropylene film 100.

[0071] In addition, from the viewpoint of further improving the thermal dimensional stability of the biaxially stretched polypropylene film 100, the crystal long period S1 in the MD direction of the biaxially stretched polypropylene film 100 determined by SAXS measurement is preferably 16.5 nm or less, more preferably 16.0 nm or less, further preferably 15.8 nm or less, and further preferably 15.5 nm or less. Furthermore, from the viewpoint of further improving the performance balance between the transparency and the water vapor barrier property of the biaxially stretched polypropylene film 100, it is preferably 5.0 nm or more, more preferably 8.0 nm or more, further preferably 10.0 nm or more, further preferably 12.0 nm or more, and further preferably 14.0 nm or more.

[0072] From the viewpoint of further improving the thermal dimensional stability of the biaxially stretched polypropylene film 100, the total value (S1+S2) of the long crystal period S1 in the MD direction and the long crystal period S2 in the TD direction of the biaxially stretched polypropylene film 100 determined by SAXS measurement is preferably 44.5 nm or less, more preferably 44.0 nm or less, further preferably 43.5 nm or less, further preferably 43.0 nm or less, further preferably 40.0 nm or less, further preferably 35.0 nm or less, further preferably 32.0 nm or less, further preferably 30.0 nm or less , more preferably 28.0 nm or less. Furthermore, from the viewpoint of further improving the performance balance of the transparency and water vapor barrier properties of the biaxially stretched polypropylene film 100, it is preferably 15.0 nm or more, more preferably 20.0 nm or more, more preferably 25.0 nm or more, more preferably 28.0 nm or more, more preferably 30.0 nm or more, more preferably 32.0 nm or more, more preferably 35.0 nm or more, more preferably 38.0 nm or more, more preferably 40.0 nm or more, and more preferably 42.0 nm or more.

[0073] The long crystal period S1 in the MD direction and the long crystal period S2 in the TD direction of the biaxially stretched polypropylene film 100 obtained by SAXS measurement can be measured by the method described in Examples.

[0074] From the viewpoint of further improving the thermal dimensional stability of the biaxially stretched polypropylene film 100, the amorphous thickness S4 in the TD direction of the biaxially stretched polypropylene film 100 determined by SAXS measurement is preferably 15.5 nm or less, more preferably 15.2 nm or less, further preferably 15.0 nm or less, further preferably 14.5 nm or less, further preferably 13.0 nm or less, further preferably 11.0 nm or less, further preferably 10.0 nm or less, further preferably 8.0 nm or less, and from the viewpoint of further improving the performance balance between the moldability and transparency of the biaxially stretched polypropylene film 100, it is preferably 3.0 nm or more, more preferably 5.0 nm or more, further preferably 8.0 nm or more, further preferably 10.0 nm or more, further preferably 13.0 nm or more.

[0075] When the amorphous thickness S4 that is easily changed during heating is equal to or less than the above upper limit, the thermal dimensional stability of the biaxially stretched polypropylene film 100 can be further improved.

[0076] In addition, from the viewpoint of further improving the thermal dimensional stability of the biaxially stretched polypropylene film 100, the amorphous thickness S3 in the MD direction of the biaxially stretched polypropylene film 100 determined by SAXS measurement is preferably 9.5 nm or less, more preferably 9.0 nm or less, further preferably 8.8 nm or less, further preferably 8.6 nm or less, further preferably 8.0 nm or less. Furthermore, from the viewpoint of further improving the performance balance between the moldability and transparency of the biaxially stretched polypropylene film 100, it is preferably 3.0 nm or more, more preferably 5.0 nm or more, further preferably 7.0 nm or more, further preferably 7.5 nm or more, further preferably 8.0 nm or more.

[0077] From the viewpoint of further improving the thermal dimensional stability of the biaxially stretched polypropylene film 100, the total value (S3+S4) of the amorphous thickness S3 in the MD direction and the amorphous thickness S4 in the TD direction of the biaxially stretched polypropylene film 100 determined by SAXS measurement is preferably 24.5 nm or less, more preferably 24.0 nm or less, further preferably 23.5 nm or less, further preferably 23.0 nm or less, further preferably 20.0 nm or less, further preferably 18.0 nm or less, further preferably 16.0 nm or less, further preferably 15.0 nm or less, and from the viewpoint of further improving the performance balance between the moldability and transparency of the biaxially stretched polypropylene film 100, it is preferably 5.0 nm or more, more preferably 8.0 nm or more, further preferably 10.0 nm or more, further preferably 13.0 nm or more, further preferably 15.0 nm or more, further preferably 17.0 nm or more, further preferably 20.0 nm or more, further preferably 22.0 nm or more, further preferably 23.0 nm or more.

[0078] The amorphous thickness S3 in the MD direction and the amorphous thickness S4 in the TD direction of the biaxially stretched polypropylene film 100 obtained by SAXS measurement can be measured by the method described in Examples.

[0079] From the viewpoint of further improving the performance balance between the moldability and thermal dimensional stability of the biaxially stretched polypropylene film 100, the crystal thickness S6 in the TD direction of the biaxially stretched polypropylene film 100 determined by SAXS measurement is preferably 13.5 nm or less, more preferably 13.0 nm or less, further preferably 12.5 nm or less, further preferably 12.0 nm or less, further preferably 10.0 nm or less, further preferably 8.0 nm or less. Furthermore, from the viewpoint of further improving the performance balance between the transparency and water vapor barrier properties of the biaxially stretched polypropylene film 100, it is preferably 3.0 nm or more, more preferably 5.0 nm or more, further preferably 8.0 nm or more, further preferably 10.0 nm or more, further preferably 12.0 nm or more, further preferably 12.5 nm or more.

[0080] In addition, from the viewpoint of further improving the performance balance between the moldability and thermal dimensional stability of the biaxially stretched polypropylene film 100, the crystal thickness S5 in the MD direction of the biaxially stretched polypropylene film 100 determined by SAXS measurement is preferably 9.0 nm or less, more preferably 8.0 nm or less, and even more preferably 7.5 nm or less. Furthermore, from the viewpoint of further improving the performance balance between the transparency and water vapor barrier properties of the biaxially stretched polypropylene film 100, it is preferably 3.0 nm or more, more preferably 5.0 nm or more, and even more preferably 6.5 nm or more.

[0081] From the viewpoint of further improving the performance balance between the moldability and the thermal dimensional stability of the biaxially stretched polypropylene film 100, the total value (S5+S6) of the crystal thickness S5 in the MD direction and the crystal thickness S6 in the TD direction of the biaxially stretched polypropylene film 100 determined by SAXS measurement is preferably 21.0 nm or less, more preferably 20.5 nm or less, further preferably 20.0 nm or less, further preferably 19.0 nm or less, further preferably 18.0 nm or less, further preferably 17.0 nm or less, further preferably 16.0 nm or less, further preferably 15.5 nm or less. Furthermore, from the viewpoint of further improving the performance balance between the transparency and the water vapor barrier property of the biaxially stretched polypropylene film 100, it is preferably 5.0 nm or more, more preferably 8.0 nm or more, further preferably 10.0 nm or more, further preferably 13.0 nm or more, further preferably 15.0 nm or more, further preferably 16.0 nm or more, further preferably 18.0 nm or more, further preferably 19.0 nm or more.

[0082] The crystal thickness S5 in the MD direction and the crystal thickness S6 in the TD direction of the biaxially stretched polypropylene film 100 obtained by SAXS measurement can be measured by the method described in Examples.

[0083] The crystallization long period, amorphous thickness, and crystal thickness of the biaxially stretched polypropylene film 100 can be adjusted, for example, by adjusting the type and content ratio of the propylene polymer contained in the biaxially stretched film layer 101, the thickness of the biaxially stretched film layer 101, the stretching ratio, the constituent materials and thickness of the surface resin layer 103, etc.

[0084] From the viewpoint of further improving the thermal dimensional stability of the biaxially stretched polypropylene film 100 , the crystallization ratio at 165° C. or lower of the biaxially stretched polypropylene film 100 of the present embodiment determined by differential scanning calorimetry is preferably 38% or more.

[0085] As described above, from the viewpoint of suppressing heat wrinkles at the seal portion during bag making and suppressing thermal elongation during vapor deposition and coating processing, further improvement in thermal dimensional stability is required for the biaxially stretched polypropylene film.

[0086] Here, according to the research of the inventors of the present application, it was found that the amount of crystalline components below 165°C affects the thermal dimensional stability. Based on the above findings, the inventors of the present application conducted further research and found that the thermal dimensional stability of the biaxially stretched polypropylene film 100 can be improved by setting the crystallization ratio below 165°C to 38% or more.

[0087] That is, according to the biaxially stretched polypropylene film 10 of the present embodiment in which the crystallization ratio at 165° C. or lower is 38% or more, the thermal dimensional stability can be further improved.

[0088] In addition, since the thermal dimensional stability of such a biaxially stretched polypropylene film 100 is further improved, heat wrinkles at the seal portion during bag making can be further suppressed, and as a result, bag making properties can be further improved.

[0089] The crystallization ratio of the biaxially stretched polypropylene film 100 at 165° C. or lower determined by differential scanning calorimetry is preferably 38% or more. From the viewpoint of further improving the thermal dimensional stability of the biaxially stretched polypropylene film 100, it is more preferably 39% or more, more preferably 40% or more, more preferably 41% or more, more preferably 42% or more, and still more preferably 43% or more. Furthermore, from the viewpoint of further improving the performance balance between the moldability and the thermal dimensional stability of the biaxially stretched polypropylene film 100, it is preferably 70% or less, more preferably 65% ​​or less, more preferably 60% or less, more preferably 55% or less, and still more preferably 50% or less.

[0090] The crystallization ratio of the biaxially stretched polypropylene film 100 at 165° C. or lower can be measured by the method described in Examples.

[0091] From the viewpoint of further improving the thermal dimensional stability of the biaxially stretched polypropylene film 100, the main melting point of the biaxially stretched polypropylene film 100 determined by differential scanning calorimetry is preferably 165° C. or higher, more preferably 168° C. or higher, and further preferably 170° C. or higher. From the viewpoint of further improving the performance balance between the moldability and thermal dimensional stability of the biaxially stretched polypropylene film 100, the main melting point is preferably 180° C. or lower, more preferably 178° C. or lower, further preferably 175° C. or lower, and further preferably 173° C. or lower.

[0092] The main melting point of the biaxially stretched polypropylene film 100 can be measured by the method described in Examples. Here, in this specification, the peak temperature of the maximum melting peak of the DSC curve is taken as the main melting point.

[0093] From the viewpoint of further improving the thermal dimensional stability of the biaxially stretched polypropylene film 100, the heat of fusion (ΔH) of the entire biaxially stretched polypropylene film 100 determined by differential scanning calorimetry is preferably 100 J / g or more, more preferably 105 J / g or more, further preferably 110 J / g or more, further preferably 113 J / g or more, further preferably 115 J / g or more, further preferably 117 J / g or more, and from the viewpoint of further improving the performance balance between the formability and thermal dimensional stability of the biaxially stretched polypropylene film 100, it is preferably 150 J / g or less, more preferably 140 J / g or less, further preferably 130 J / g or less, further preferably 128 J / g or less.

[0094] The heat of fusion (ΔH) of the entire biaxially stretched polypropylene film 100 can be measured by the method described in Examples. In this specification, when a plurality of melting peaks appear in a DSC curve, the total area of ​​the plurality of melting peaks is taken as the heat of fusion (ΔH).

[0095] From the viewpoint of further improving the thermal dimensional stability of the biaxially stretched polypropylene film 100, the heat of fusion (ΔH) at 165° C. or lower of the biaxially stretched polypropylene film 100 determined by differential scanning calorimetry is preferably 40 J / g or higher, more preferably 42 J / g or higher, further preferably 43 J / g or higher, further preferably 45 J / g or higher, further preferably 48 J / g or higher, further preferably 50 J / g or higher. Furthermore, from the viewpoint of further improving the performance balance between the moldability and the thermal dimensional stability of the biaxially stretched polypropylene film 100, it is preferably 90 J / g or lower, more preferably 85 J / g or lower, further preferably 80 J / g or lower, further preferably 75 J / g or lower, further preferably 70 J / g or lower, further preferably 65 J / g or lower, further preferably 60 J / g or lower.

[0096] The heat of fusion (ΔH) of the biaxially stretched polypropylene film 100 at 165° C. or less can be measured by the method described in Examples.

[0097] From the viewpoint of further improving the thermal dimensional stability of the biaxially stretched polypropylene film 100, the crystallinity of the biaxially stretched polypropylene film 100 determined by differential scanning calorimetry is preferably 40% or more, more preferably 45% or more, more preferably 50% or more, more preferably 53% or more, and still more preferably 55% or more. Furthermore, from the viewpoint of further improving the performance balance between the moldability and the thermal dimensional stability of the biaxially stretched polypropylene film 100, it is preferably 80% or less, more preferably 75% or less, still more preferably 70% or less, still more preferably 65% ​​or less, still more preferably 62% or less, and still more preferably 60% or less.

[0098] The crystallinity of the biaxially stretched polypropylene film 100 can be measured by the method described in Examples.

[0099] From the viewpoint of further improving the thermal dimensional stability of the biaxially stretched polypropylene film 100, the crystallization amount at 165° C. or lower of the biaxially stretched polypropylene film 100 determined by differential scanning calorimetry is preferably 20% or more, more preferably 22% or more, further preferably 23% or more, and further preferably 24% or more. Furthermore, from the viewpoint of further improving the performance balance between the moldability and the thermal dimensional stability of the biaxially stretched polypropylene film 100, it is preferably 40% or less, more preferably 38% or less, further preferably 36% or less, preferably 35% or less, and further preferably 30% or less.

[0100] The amount of crystallinity at 165° C. or lower of the biaxially stretched polypropylene film 100 can be measured by the method described in Examples.

[0101] The above-mentioned properties of the biaxially stretched polypropylene film 100 obtained by differential scanning calorimetry can be adjusted by, for example, adjusting the type and content of the propylene-based polymer contained in the biaxially stretched film layer 101, the thickness and stretching ratio of the biaxially stretched film layer 101, the constituent material and thickness of the surface resin layer 103, etc.

[0102] The total value (T1+T2) of the tensile elastic modulus T1 in the MD direction and the tensile elastic modulus T2 in the TD direction of the biaxially stretched polypropylene film 100, measured in accordance with JIS K7127 (1999) using a tensile testing machine under the conditions of a measuring temperature of 23±2°C, 50±5%RH, and a tensile speed of 5 mm / min, is preferably 3000 MPa or more, more preferably 3500 MPa or more, further preferably 4000 MPa or more, further preferably 5000 MPa or more, further preferably 6000 MPa or more, further preferably 6500 MPa or more, and preferably 10000 MPa or less, more preferably 8000 MPa or less, further preferably 7500 MPa or less.

[0103] When the total value (T1+T2) of the tensile elastic modulus T1 in the MD direction and the tensile elastic modulus T2 in the TD direction is equal to or greater than the above lower limit, the performance balance of the biaxially stretched polypropylene film 100, such as thermal dimensional stability, formability, water vapor barrier properties, mechanical properties, transparency, bag making properties, and operability, can be further improved. In addition, the stiffness of the biaxially stretched polypropylene film 100 can be improved, and as a result, the positional deviation of the film during heat sealing can be suppressed, and the occurrence of poor sealing can be suppressed.

[0104] That is, when the total value (T1+T2) of the tensile elastic modulus T1 in the MD direction and the tensile elastic modulus T2 in the TD direction is greater than the above lower limit, the performance balance of the biaxially stretched polypropylene film 100 in terms of thermal dimensional stability, formability, water vapor barrier properties, mechanical properties, transparency, bag making properties, operability and packaging suitability can be further improved.

[0105] In addition, when the total value (T1+T2) of the tensile elastic modulus T1 in the MD direction and the tensile elastic modulus T2 in the TD direction is below the above upper limit value, it is less likely that failures such as cutting will occur during the molding of the biaxially stretched polypropylene film 100, and continuous stretching molding of the film becomes easy, which can further improve industrial continuous productivity.

[0106] Such tensile elastic modulus is a substitute value for quantitatively measuring the stiffness of the film, and can be adjusted by, for example, adjusting the type and content ratio of the propylene polymer contained in the biaxially stretched film layer 101, the thickness of the biaxially stretched film layer 101, the stretching ratio, the constituent materials and thickness of the surface resin layer 103, etc.

[0107] In addition, from the viewpoint of further improving the performance balance of the biaxially stretched polypropylene film 100 in terms of thermal dimensional stability, formability, water vapor barrier properties, mechanical properties, transparency, bag making properties, handleability, and packaging suitability, the tensile elastic modulus T1 in the MD direction of the biaxially stretched polypropylene film 100 is preferably 1000 MPa or more, more preferably 1200 MPa or more, further preferably 1300 MPa or more, further preferably 1400 MPa or more, further preferably 1500 MPa or more, further preferably 1800 MPa or more, further preferably 2000 MPa or more, further preferably 2300 MPa or more, and from the viewpoint of further improving the performance balance of the biaxially stretched polypropylene film 100 in terms of thermal dimensional stability, antistatic properties, bag making properties, and packaging suitability, it is preferably 4000 MPa or less, more preferably 3500 MPa or less, further preferably 3000 MPa or less, further preferably 2800 MPa or less, further preferably 2600 MPa or less.

[0108] From the viewpoint of further improving the thermal dimensional stability of the biaxially stretched polypropylene film 100, the biaxially stretched polypropylene film 100 of the present embodiment preferably has the following properties: when heat-treated at 120°C for 15 minutes in accordance with JIS C2151:2019, the film expands in the TD direction and shrinks in the MD direction.

[0109] As described above, from the viewpoint of suppressing heat wrinkles at the seal portion during bag making and suppressing thermal elongation during vapor deposition and coating processing, further improvement in thermal dimensional stability is required for the biaxially stretched polypropylene film.

[0110] Here, according to the research of the inventors of the present application, it was found that the thermal dimensional stability of the biaxially stretched polypropylene film 100 can be improved by having the property of expanding in the TD direction and shrinking in the MD direction when heated at 120° C. for 15 minutes.

[0111] Usually, the roll of biaxially stretched polypropylene film is unfolded in the MD direction, and a tension is applied while bag making, coating, vapor deposition, etc. are performed. That is, since no tension is applied in the TD direction, the biaxially stretched polypropylene film is easily affected by heat shrinkage when heated, and heat wrinkles are easily generated in the sealing portion. In addition, since tension is applied in the MD direction, when heated, if the heat resistance of the film is low, the film is easily thermally stretched in the MD direction.

[0112] On the other hand, it is considered that the biaxially stretched polypropylene film 100 of the present embodiment has the property that it expands in the TD direction and shrinks in the MD direction when heated at 120°C for 15 minutes, so that even if the biaxially stretched polypropylene film 100 is heated, thermal shrinkage in the TD direction and thermal elongation in the MD direction are unlikely to occur. Therefore, it is speculated that the biaxially stretched polypropylene film 100 of the present embodiment, which has the property that it expands in the TD direction and shrinks in the MD direction when heated at 120°C for 15 minutes according to JIS C2151:2019, improves thermal dimensional stability, and as a result, heat wrinkles in the seal portion can be further suppressed.

[0113] That is, the thermal dimensional stability can be further improved by the biaxially stretched polypropylene film 100 of the present embodiment having the characteristics of expanding in the TD direction and shrinking in the MD direction when heat-treated at 120° C. for 15 minutes in accordance with JIS C2151:2019.

[0114] In addition, since the thermal dimensional stability of such a biaxially stretched polypropylene film 100 is improved, heat wrinkles at the seal portion during bag making can be suppressed, and as a result, bag making properties can be further improved.

[0115] From the viewpoint of further improving the performance balance between thermal dimensional stability and bag-forming properties, the biaxially stretched polypropylene film 100 is preferably expanded in the TD direction when subjected to a heat treatment at 120° C. for 15 minutes in accordance with JIS C2151:2019.

[0116] More specifically, from the viewpoint of further improving the performance balance between thermal dimensional stability and bag making properties, and from the viewpoint of further suppressing heat wrinkles at the seal portion and obtaining a bag product with good heat wrinkles at the seal portion, the thermal expansion coefficient in the TD direction of the biaxially stretched polypropylene film 100 when heated at 120°C for 15 minutes is preferably 0.1% or more, more preferably 0.2% or more, further preferably 0.3% or more, further preferably 0.4% or more, further preferably 0.5% or more, and from the viewpoint of further improving the performance balance between thermal dimensional stability and bag making properties, it is preferably 2.0% or less, more preferably 1.5% or less, further preferably 1.2% or less, further preferably 1.0% or less, further preferably 0.8% or less.

[0117] Here, usually, the roll of the biaxially stretched polypropylene film is unrolled in the MD direction, and a bag-making process, coating, vapor deposition, etc. are performed while applying tension. That is, since no tension is applied in the TD direction, the biaxially stretched polypropylene film is easily affected by heat shrinkage when heated, and heat wrinkles are easily generated in the sealing portion. On the other hand, if the thermal expansion coefficient in the TD direction when heated at 120° C. for 15 minutes is within the above range, even if the biaxially stretched polypropylene film 100 is heated, heat shrinkage in the TD direction is not likely to occur, so that heat wrinkles in the sealing portion can be further suppressed.

[0118] The thermal expansion coefficient in the TD direction of the biaxially stretched polypropylene film 100 when subjected to a heat treatment at 120° C. for 15 minutes was calculated by the following method.

[0119] First, a 10 cm×10 cm test piece was cut out from the biaxially stretched polypropylene film 100, and the test piece was heat-treated at 120° C. for 15 minutes. Next, when the length of the test piece in the TD direction after the heat treatment is TD1 [cm], the thermal expansion coefficient [%] in the TD direction is calculated by 100×(TD1-10) / 10.

[0120] In addition, from the viewpoint of further improving the performance balance between thermal dimensional stability and bag-making properties, and from the viewpoint of further suppressing the thermal elongation of the film during processing, the heat shrinkage rate in the MD direction of the biaxially stretched polypropylene film 100 when heated at 120° C. for 15 minutes is preferably 5.0% or less, more preferably 4.0% or less, further preferably 3.0% or less, further preferably 2.5% or less, further preferably 2.2% or less, further preferably 2.0% or less, and may be 0.1% or more, 0.3% or more, or 0.5% or more.

[0121] Here, usually, the roll of the biaxially stretched polypropylene film is unrolled in the MD direction, and a bag-making process, coating, vapor deposition, etc. are performed while applying tension. That is, since tension is applied in the MD direction, when heated, if the heat resistance of the film is low, the film is likely to be thermally elongated in the MD direction. On the other hand, if the heat shrinkage rate in the MD direction when heated at 120° C. for 15 minutes is within the above range, the thermal elongation in the MD direction when the biaxially stretched polypropylene film 100 is heated can be further suppressed.

[0122] The heat shrinkage rate in the MD direction of the biaxially stretched polypropylene film 100 when subjected to a heat treatment at 120° C. for 15 minutes was calculated by the following method.

[0123] First, a 10 cm×10 cm test piece was cut out from the biaxially stretched polypropylene film 100, and the test piece was heat-treated at 120° C. for 15 minutes. Next, when the length of the test piece in the MD direction after the heat treatment is MD1 [cm], the heat shrinkage rate [%] in the MD direction is calculated by 100×(10-MD1) / 10.

[0124] In addition, from the viewpoint of further improving the performance balance between thermal dimensional stability and bag-making properties, the heat shrinkage X in the TD direction of the biaxially stretched polypropylene film 100 when heated at 150° C. for 15 minutes is TD It is preferably 8.5% or less, more preferably 7.0% or less, further preferably 5.0% or less, further preferably 3.0% or less, further preferably 2.0% or less, further preferably 1.0% or less, further preferably 0.8% or less, and may be 0.0% or more, 0.1% or more, or 0.2% or more.

[0125] In addition, from the viewpoint of further improving the performance balance between thermal dimensional stability and bag-making properties, the heat shrinkage X in the MD direction of the biaxially stretched polypropylene film 100 when heated at 150° C. for 15 minutes is MD It is preferably 8.0% or less, more preferably 7.0% or less, further preferably 6.0% or less, further preferably 5.5% or less, further preferably 5.0% or less, further preferably 4.8% or less, and may be more than 0.1%, more than 0.5%, more than 1.0%, more than 1.5%, more than 2.0%, or more than 2.5%.

[0126] In the biaxially stretched polypropylene film 100, the heat shrinkage in the TD direction and the heat shrinkage in the MD direction when heated at 150° C. for 15 minutes are denoted as X and denoted as TD [%] and X MD[%], from the viewpoint of further improving the performance balance between the thermal dimensional stability and bag-making properties of the biaxially stretched polypropylene film 100, X TD +X MD Preferably it is less than 6.0%, more preferably less than 5.0%.

[0127] In addition, the biaxially stretched polypropylene film 100 X TD [%] and X MD [%] was calculated using the following method.

[0128] First, a 10 cm × 10 cm test piece was cut out from the biaxially stretched polypropylene film 100, and the test piece was heat-treated at 150°C for 15 minutes. Next, when the length of the test piece in the TD direction after the heat treatment is denoted as TD1 [cm] and the length of the test piece in the MD direction after the heat treatment is denoted as MD1 [cm], X TD [%] Calculated by 100×(10-TD1) / 10, X MD [%] Calculated by 100×(10-MD1) / 10.

[0129] The thermal expansion coefficient and thermal shrinkage coefficient of the biaxially stretched polypropylene film 100 can be adjusted by, for example, adjusting the type and content ratio of the propylene polymer contained in the biaxially stretched film layer 101, the thickness and stretching ratio of the biaxially stretched film layer 101, the constituent material and thickness of the surface resin layer 103, etc.

[0130] In addition, the thermal expansion coefficient and thermal shrinkage coefficient of the biaxially stretched polypropylene film 100 can be measured in accordance with JIS C2151:2019.

[0131] From the viewpoint of further improving the performance balance between thermal dimensional stability and bag-making properties, the heat fusion strength when the biaxially stretched polypropylene films 100 are heat-sealed at 200° C. (hereinafter also referred to as “heat fusion strength at 200° C.”) is preferably 4.0 N / 15 mm or less.

[0132] In this specification, the heat fusion strength is used as an index of the heat fusion resistance of the biaxially stretched polypropylene film surface. The lower the heat fusion strength is, the better the heat fusion resistance of the biaxially stretched polypropylene film surface can be judged to be.

[0133] Here, the heat-sealed strength at 200°C can be measured by the following method. First, two biaxially stretched polypropylene films 100 are heat-sealed under the conditions of 200°C, 2.0 kgf pressure, and 1.0 second sealing time to obtain a laminated film. Next, the two biaxially stretched polypropylene films 100 are peeled off under the conditions of 15 mm width, 90 degree peeling, 300 mm / min peeling speed, and stretching in the TD direction, and the peeling strength at this time is defined as the heat-sealed strength.

[0134] As described above, from the viewpoint of suppressing heat wrinkles at the seal portion during bag making and suppressing thermal elongation during vapor deposition and coating processing, further improvement in thermal dimensional stability is required for the biaxially stretched polypropylene film.

[0135] Here, according to the research of the inventors of the present application, it was found that a biaxially stretched polypropylene film having a heat fusion strength of 4.0 N / 15 mm or less when heat-sealed at 200° C. can improve thermal dimensional stability.

[0136] That is, the thermal dimensional stability can be further improved by the biaxially stretched polypropylene film 100 of the present embodiment having a heat fusion strength of 4.0 N / 15 mm or less when heat-sealed at 200°C.

[0137] In addition, since the thermal dimensional stability of such a biaxially stretched polypropylene film 100 is improved, heat wrinkles at the seal portion during bag making can be suppressed, and as a result, bag making properties can be further improved.

[0138] In addition, from the perspective of environmental issues, packaging materials are required to be made of a single material. From the perspective of suppressing heat wrinkles at the seal portion during bag making and suppressing heat fusion between the film and the sealing strip, it is required to improve the heat resistance of the film surface compared to the conventional biaxially stretched polypropylene film.

[0139] The biaxially stretched polypropylene film 100 of this embodiment, which has a heat fusion strength of 4.0 N / 15 mm or less when heat-sealed at 200° C., has a further improved performance balance between thermal dimensional stability and heat resistance of the film surface, and can therefore further suppress heat wrinkles at the seal portion during bag making and heat fusion between the film and the seal strip.

[0140] In a package body made using the biaxially stretched polypropylene film 100, from the viewpoint of further improving the weld prevention property between the film and the sealing strip during bag making and the performance balance of the sealing appearance, the heat weld strength (TD stretching direction) of the portion where the biaxially stretched polypropylene film 100 is heat-welded under the conditions of 200° C., 2.0 kgf pressure, and 1.0 second sealing time (hereinafter also referred to as “heat weld strength at 200° C.”) is preferably 4.0 N / 15 mm or less, more preferably 3.5 N / 15 mm or less, further preferably 3.0 N / 15 mm or less, further preferably 2.5 N / 15 mm or less, further preferably 2.0 N / 15 mm or less, further preferably 1.5 N / 15 mm or less, and further preferably 1.3 N / 15 mm or less. The lower limit of the heat fusion strength of the biaxially stretched polypropylene film 100 at 200°C is not particularly limited and may be 0.01 N / 15 mm or more, 0.05 N / 15 mm or more, 0.1 N / 15 mm or more, 0.3 N / 15 mm or more, 0.5 N / 15 mm or more, or 0.8 N / 15 mm or more.

[0141] In this specification, the heat fusion strength is used as an index of the heat fusion resistance of the biaxially stretched polypropylene film surface. The lower the heat fusion strength is, the better the heat fusion resistance of the biaxially stretched polypropylene film surface can be judged to be.

[0142] Here, the heat-welding strength at 200°C can be measured by the following method. First, two biaxially stretched polypropylene films 100 are heat-welded under the conditions of 200°C, 2.0 kgf pressure, and 1.0 second sealing time to obtain a laminated film. Next, the two biaxially stretched polypropylene films 100 are peeled off under the conditions of 15 mm width, 90 degree peeling, 300 mm / min peeling speed, and stretching in the TD direction, and the peeling strength at this time is defined as the heat-welding strength.

[0143] The thermal fusion strength at 200°C can be adjusted, for example, by adjusting the type and content ratio of the homopolypropylene (A) and polymer (B) contained in the biaxially stretched film layer 101, the thickness and stretching ratio of the biaxially stretched film layer 101, the constituent materials and thickness of the surface resin layer 103, etc.

[0144] From the viewpoint of further improving the performance balance of thermal dimensional stability and bag making properties, the heat fusion strength when the biaxially stretched polypropylene films 100 are heat-sealed at 170°C (hereinafter, also referred to as "heat fusion strength at 170°C") is preferably 1.0N / 15mm or less, more preferably 0.8N / 15mm or less, further preferably 0.5N / 15mm or less, further preferably 0.3N / 15mm or less, and further preferably 0.2N / 15mm or less. The lower limit of the heat fusion strength at 170°C of the biaxially stretched polypropylene film 100 is not particularly limited, and may be 0.01N / 15mm or more, 0.03N / 15mm or more, or 0.05N / 15mm or more.

[0145] Here, the heat-sealed strength at 170°C can be measured by the following method. First, two biaxially stretched polypropylene films 100 are heat-sealed under the conditions of 170°C, 2.0 kgf pressure, and 1.0 second sealing time to obtain a laminated film. Next, the two biaxially stretched polypropylene films 100 are peeled off under the conditions of 15 mm width, 90 degree peeling, 300 mm / min peeling speed, and stretching in the TD direction, and the peeling strength at this time is defined as the heat-sealed strength.

[0146] The heat-sealing strength at 170°C can be adjusted by, for example, adjusting the type and content of the propylene polymer contained in the biaxially stretched film layer 101, the thickness and stretching ratio of the biaxially stretched film layer 101, the constituent material and thickness of the surface resin layer 103, etc.

[0147] From the viewpoint of further improving the transparency of the biaxially stretched polypropylene film 100, the haze of the biaxially stretched polypropylene film 100 measured using a haze meter in accordance with JIS K7136:2000 is preferably 5.0% or less, more preferably 3.0% or less, further preferably 2.5% or less, further preferably 2.0% or less, further preferably 1.5% or less, further preferably 1.0% or less.

[0148] Such haze can be adjusted by, for example, adjusting the type and content of the propylene-based polymer contained in the biaxially stretched film layer 101, the thickness and stretch ratio of the biaxially stretched film layer 101, the constituent material and thickness of the surface resin layer 103, etc.

[0149] Here, the food packaging body produced using the biaxially stretched polypropylene film 100 exhibits sufficient performance in terms of water vapor barrier properties. Therefore, the biaxially stretched polypropylene film 100 can be particularly suitably used as a food packaging film for packaging food requiring water vapor barrier properties.

[0150] From the viewpoint of stably obtaining a food packaging body having improved water vapor barrier properties, the water vapor permeability of the biaxially stretched polypropylene film 100 measured by the following method is preferably 20.0 g / (m 2 ·24h) or less, more preferably 15.0g / (m 2 ·24h) or less, more preferably 12.0g / (m 2 ·24h) or less, more preferably 10.0g / (m 2 ·24h) or less, more preferably 8.0g / (m 2 24h) or less.

[0151] (Measurement method)

[0152] The biaxially stretched polypropylene film 100 was folded in half and heat-sealed on both sides to form a bag. Then, calcium chloride was added as the content. Next, the other side was heat-sealed to a surface area of ​​0.01 m 2 The bags were then stored at 40°C and 90% RH for 72 hours. The mass of calcium chloride before and after storage was measured, and the water vapor permeability (g / (m 2 ·24h)).

[0153] Such water vapor permeability can be adjusted by, for example, adjusting the type and content of the propylene-based polymer contained in the biaxially stretched film layer 101, the thickness and stretching ratio of the biaxially stretched film layer 101, the constituent material and thickness of the surface resin layer 103, etc.

[0154] From the viewpoint of further improving the performance balance of the moldability, thermal dimensional stability, and bag-making property of the biaxially stretched polypropylene film 100, when the total amount of the structural units derived from the monomers contained in the biaxially stretched polypropylene film 100 is set to 100 mol%, the amount of the structural units derived from α-olefins other than propylene contained in the biaxially stretched polypropylene film 100 is preferably 0.05 mol% or more, more preferably 0.1 mol% or more, further preferably 0.3 mol% or more, further preferably 0.5 mol% or more, further preferably 1.0 mol% or more, further preferably 3.0 mol% or more, further preferably 5.0 mol% or more, further preferably 8.0 mol% or more, and further preferably 10. In addition, from the viewpoint of further improving the performance balance of the thermal dimensional stability, water vapor barrier properties, bag-making properties and transparency of the biaxially stretched polypropylene film 100, it is preferably 50.0 mol% or less, more preferably 30.0 mol% or less, further preferably 25.0 mol% or less, further preferably 20.0 mol% or less, further preferably 15.0 mol% or less, further preferably 12.0 mol% or less, further preferably 10.0 mol% or less, further preferably 8.0 mol% or less, further preferably 5.0 mol% or less, further preferably 2.0 mol% or less, further preferably 1.0 mol% or less.

[0155] When the amount of the structural units derived from α-olefins other than propylene contained in the biaxially stretched polypropylene film 100 is within the above range, the softening effect of the structural units derived from the α-olefins can be exerted to suppress the yield point stress at the start of stretching in the stretching process, thereby improving the moldability. In addition, the melting point lowering effect of the structural units derived from the α-olefins can more effectively relax the residual stress in the heat setting process during film molding, thereby improving the moldability and suppressing the thickness unevenness. As a result, the thermal dimensional stability of the biaxially stretched polypropylene film 100 can be further improved.

[0156] The amount of the structural unit derived from α-olefin other than propylene in the biaxially stretched polypropylene film 100 can be measured by the method described in Examples.

[0157] From the viewpoint of further improving the balance of performances such as thermal dimensional stability, formability, water vapor barrier properties, cost, mechanical properties, transparency, bag-making properties, handleability, appearance and lightness, the thickness of the biaxially stretched polypropylene film 100 is preferably 5 μm or more, more preferably 10 μm or more, further preferably 12 μm or more, further preferably 15 μm or more, and is preferably 100 μm or less, more preferably 50 μm or less, further preferably 40 μm or less, further preferably 30 μm or less, further preferably 25 μm or less.

[0158] Hereinafter, each layer constituting the biaxially stretched polypropylene film 100 will be described.

[0159] [Biaxially stretched film layer]

[0160] The biaxially stretched film layer 101 (also referred to as a biaxially stretched polypropylene film layer) contains a propylene polymer.

[0161] The biaxially stretched film layer 101 is formed by biaxially stretching a film made of a propylene polymer composition containing a propylene polymer, for example.

[0162] The biaxially stretched film layer 101 may be a single layer or a laminate of a plurality of layers composed of a propylene-based polymer composition, but must be biaxially stretched.

[0163] From the viewpoint of further improving the balance of performances such as thermal dimensional stability, formability, water vapor barrier properties, cost, mechanical properties, transparency, bag-making properties, operability, appearance and light weight of the biaxially stretched polypropylene film 100, the thickness of the biaxially stretched film layer 101 is preferably 5 μm or more, more preferably 10 μm or more, further preferably 12 μm or more, further preferably 15 μm or more, and is preferably 100 μm or less, more preferably 50 μm or less, further preferably 40 μm or less, further preferably 30 μm or less, further preferably 20 μm or less.

[0164] In the biaxially stretched polypropylene film 100, the ratio of the thickness of the biaxially stretched film layer 101 to the overall thickness of the biaxially stretched polypropylene film 100 is preferably 50% or more, more preferably 60% or more, further preferably 70% or more, further preferably 75% or more, and is preferably 100% or less, more preferably 99% or less, further preferably 95% or less, further preferably 90% or less.

[0165] (Propylene polymer composition)

[0166] The propylene-based polymer composition of the present embodiment contains a propylene-based polymer.

[0167] From the viewpoint of further improving the balance of performances such as thermal dimensional stability, environmental adaptability, heat resistance, water vapor barrier properties, transparency, cost, mechanical properties, rigidity, bag-making properties, fluidity, moldability, operability, appearance and lightness of the biaxially stretched polypropylene film 100, when the entire propylene polymer composition is set to 100 mass%, the content of the propylene polymer in the propylene polymer composition of the present embodiment, i.e., the biaxially stretched film layer 101, is preferably 60 mass% or more, more preferably 70 mass% or more, further preferably 80 mass% or more, further preferably 90 mass% or more, further preferably 95 mass% or more, further preferably 98 mass% or more, and, for example, is 100 mass% or less.

[0168] (Propylene polymer)

[0169] The propylene-based polymer of the present embodiment is a polymer containing a structural unit derived from propylene, and examples thereof include homopolypropylene (A); at least one polymer (B) selected from the group consisting of random polypropylene (B1) and α-olefin copolymers (B2); and the like.

[0170] From the viewpoint of further improving the performance balance between the thermal dimensional stability and the antistatic properties of the biaxially stretched polypropylene film 100, the propylene-based polymer of the present embodiment preferably comprises homopolypropylene (A) and at least one polymer (B) selected from the group consisting of random polypropylene (B1) and α-olefin copolymers (B2), and more preferably comprises homopolypropylene (A) and at least one polymer (B) selected from the group consisting of random polypropylene (B1) and α-olefin copolymers (B2), and the MFR of the polymer (B) measured under the conditions of 230° C. and 2.16 kg load in accordance with ASTM D1238 is 0.01 g / 10 min or more and 30.0 g / 10 min or less.

[0171] As described above, from the viewpoint of suppressing heat wrinkles at the seal portion during bag making and suppressing thermal elongation during vapor deposition and coating processing, further improvement in thermal dimensional stability is required for the biaxially stretched polypropylene film.

[0172] On the other hand, from the viewpoint of improving thermal dimensional stability, if highly crystalline homopolypropylene is used, the yield stress during molding is high due to its high crystallinity, and the stretching point is unstable, so the effect of improving thermal dimensional stability cannot be fully obtained.

[0173] Here, according to the research of the inventors of the present application, it was found that when homopolypropylene (A) and at least one polymer (B) selected from the group consisting of random polypropylene (B1) and α-olefin copolymer (B2) are used in combination as the propylene polymer constituting the OPP film, the residual stress of the film is effectively relaxed, thereby improving the thermal dimensional stability of the biaxially stretched polypropylene film.

[0174] That is, the biaxially stretched polypropylene film 100 of the present embodiment comprising homopolypropylene (A) and at least one polymer (B) selected from the group consisting of random polypropylene (B1) and α-olefin copolymer (B2) can further improve thermal dimensional stability.

[0175] In addition, since the thermal dimensional stability of such a biaxially stretched polypropylene film 100 is further improved, heat wrinkles at the seal portion during bag making can be further suppressed, and as a result, bag making properties can be further improved.

[0176] (Homopolypropylene (A))

[0177] Examples of the homopolypropylene (A) include propylene homopolymers and propylene-based copolymers containing 2.0 mol% or less of structural units derived from α-olefins other than propylene.

[0178] In the homopolypropylene (A), when the total content of the structural units constituting the homopolypropylene (A) is 100 mol%, the content of the structural units derived from propylene is 98.0 mol% or more, preferably 98.5 mol% or more, more preferably 98.7 mol% or more, further preferably 99.0 mol% or more, further preferably 99.5 mol% or more, further preferably 99.8 mol% or more, and for example, 100.0 mol% or less.

[0179] The α-olefin other than propylene includes, for example, one or more selected from the group consisting of ethylene and α-olefins having a carbon number of 4 to 20, preferably one or more selected from the group consisting of ethylene and α-olefins having a carbon number of 4 to 6, more preferably at least one selected from the group consisting of ethylene and 1-butene, and further preferably ethylene.

[0180] When the entire homopolypropylene (A) is taken as 100 mol%, the content of the structural unit derived from α-olefin other than propylene is preferably 2.0 mol% or less, more preferably 1.5 mol% or less, further preferably 1.3 mol% or less, further preferably 1.0 mol% or less, further preferably 0.5 mol% or less, further preferably 0.2 mol% or less.

[0181] The homopolypropylene (A) in the biaxially stretched film layer 101 may be used alone or in combination of two or more.

[0182] From the viewpoint of further improving the performance balance of the biaxially stretched polypropylene film 100, such as thermal dimensional stability, heat resistance, water vapor barrier properties, mechanical properties, rigidity and bag-making properties, the isotactic pentad fraction (mmmm) of the homopolypropylene (A) is preferably 96.0% or more, more preferably 96.5% or more, further preferably 97.0% or more, further preferably 97.3% or more, further preferably 97.5% or more, further preferably 97.8% or more, further preferably 98.0% or more. The upper limit of the isotactic pentad fraction (mmmm) of the homopolypropylene (A) is not particularly limited, but from the viewpoint of ease of production, it is 99.5% or less, more preferably 99.3% or less, further preferably 99.0% or less.

[0183] The isotactic pentad fraction (mmmm) is an indicator of stereoregularity and can be calculated based on 13 The C-nuclear magnetic resonance (NMR) spectrum was obtained by a known method.

[0184] When two or more homopolypropylenes are used as the homopolypropylene (A), the isotactic pentad fraction of the homopolypropylene (A) can be the isotactic pentad fraction of a mixture obtained by melt-blending the two or more homopolypropylenes (A) by a known method.

[0185] From the viewpoint of further improving the performance balance between fluidity and moldability, the melt flow rate (MFR) of the homopolypropylene (A) measured at 230°C and a load of 2.16 kg in accordance with ASTM D1238 is preferably 0.5 g / 10 min or more, more preferably 1.0 g / 10 min or more, even more preferably 2.0 g / 10 min or more, and from the viewpoint of further stabilizing the moldability, it is preferably 20.0 g / 10 min or less, more preferably 10.0 g / 10 min or less, even more preferably 7.0 g / 10 min or less.

[0186] When two or more homopolypropylenes are used as the homopolypropylene (A), the MFR of the homopolypropylene (A) can be the MFR of a mixture obtained by melt-blending the two or more homopolypropylenes (A) by a known method.

[0187] From the viewpoint of further improving the balance of properties such as thermal dimensional stability, heat resistance, water vapor barrier properties, mechanical properties, rigidity, bag-making properties, fluidity and moldability of the biaxially stretched polypropylene film 100, the melting point of the homopolypropylene (A) is preferably 150° C. or higher, more preferably 155° C. or higher, further preferably 160° C. or higher, further preferably 163° C. or higher, and is preferably 180° C. or lower, more preferably 175° C. or lower, further preferably 170° C. or lower, further preferably 168° C. or lower.

[0188] When two or more homopolypropylenes are used as the homopolypropylene (A), the melting point of the homopolypropylene (A) is the peak temperature of the maximum melting peak.

[0189] The homopolypropylene (A) can be produced by various methods, for example, using a known catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst.

[0190] (Polymer (B))

[0191] The polymer (B) comprises at least one selected from the group consisting of random polypropylene (B1) and α-olefin copolymers (B2), and preferably comprises random polypropylene (B1).

[0192] From the viewpoint of further improving the performance balance between the moldability and thermal dimensional stability of the biaxially stretched polypropylene film 100, the melt flow rate (MFR) of the polymer (B) measured under the conditions of 230° C. and a load of 2.16 kg in accordance with ASTM D1238 is preferably 0.01 g / 10 min or more, more preferably 0.1 g / 10 min or more, further preferably 0.5 g / 10 min or more, further preferably 1.0 g / 10 min or more, further preferably 2.0 g / 10 min or more, and preferably 30.0 g / 10 min or less, more preferably 20.0 g / 10 min or less, further preferably 15.0 g / 10 min or less, further preferably 12.0 g / 10 min or less, further preferably 10.0 g / 10 min or less.

[0193] When two or more polymers are used as the polymer (B), the MFR of a mixture obtained by melt-blending the two or more polymers (B) by a known method can be used.

[0194] From the viewpoint of further improving the balance of performances such as thermal dimensional stability, heat resistance, water vapor barrier properties, mechanical properties, rigidity, bag-making properties, fluidity and formability of the biaxially stretched polypropylene film 100, the melting point of the polymer (B) is preferably 50°C or higher, more preferably 60°C or higher, further preferably 70°C or higher, further preferably 80°C or higher, further preferably 90°C or higher, and is preferably 155°C or lower, more preferably 150°C or lower, further preferably 148°C or lower, further preferably 145°C or lower.

[0195] When two or more polymers are used as the polymer (B), the melting point of the polymer (B) is the peak temperature of the maximum melting peak.

[0196] From the viewpoint of further improving the performance balance of the formability, thermal dimensional stability, anti-blocking property and unfoldability of the biaxially stretched polypropylene film 100, the weight average molecular weight (Mw) of the polymer (B) is preferably 100,000 or more, more preferably 150,000 or more, further preferably 200,000 or more, further preferably 220,000 or more, and from the viewpoint of further improving the thermal dimensional stability, it is preferably 1,000,000 or less, more preferably 800,000 or less, more preferably 600,000 or less, further preferably 500,000 or less, further preferably 450,000 or less.

[0197] From the viewpoint of further improving the performance balance among the formability, thermal dimensional stability, anti-blocking property and sheet developability of the biaxially stretched polypropylene film 100, the weight average molecular weight (Mw) / number average molecular weight (Mn) of the polymer (B) is preferably 1.5 or more, more preferably 1.8 or more, and from the viewpoint of further improving the performance balance among the formability, thermal dimensional stability, anti-blocking property and sheet developability of the biaxially stretched polypropylene film 100, it is preferably 8.0 or less, more preferably 7.5 or less, further preferably 7.0 or less, and further preferably 6.8 or less.

[0198] When two or more polymers are used as polymer (B), the weight average molecular weight (Mw) and number average molecular weight (Mn) of polymer (B) can be the weight average molecular weight (Mw) and number average molecular weight (Mn) of a mixture obtained by melt blending two or more polymers (B) using a known method. The weight average molecular weight (Mw) and number average molecular weight (Mn) of polymer (B) can be measured using the method described in the Examples.

[0199] From the viewpoint of further improving the performance balance between the formability and thermal dimensional stability of the biaxially stretched polypropylene film 100, when the entire biaxially stretched film layer 101 is set to 100 mass%, the content of the polymer (B) is preferably 1 mass% or more, more preferably 2 mass% or more, and further preferably 3 mass% or more. Furthermore, from the viewpoint of further improving the performance balance of the thermal dimensional stability, water vapor barrier properties, transparency, mechanical properties, rigidity, bag-making properties, fluidity and formability of the biaxially stretched polypropylene film 100, it is preferably 50 mass% or less, more preferably 40 mass% or less, further preferably 30 mass% or less, further preferably 25 mass% or less, further preferably 22 mass% or less, and further preferably 20 mass% or less.

[0200] (Random polypropylene (B1))

[0201] The random polypropylene (B1) comprises a random copolymer of propylene and an α-olefin other than propylene, wherein the content of structural units derived from an α-olefin other than propylene is greater than 2.0 mol% and not more than 15.0 mol%.

[0202] The α-olefin other than propylene includes, for example, one or more selected from the group consisting of ethylene and α-olefins having a carbon number of 4 to 20, preferably one or more selected from the group consisting of ethylene and α-olefins having a carbon number of 4 to 6, more preferably at least one selected from ethylene and 1-butene, and even more preferably ethylene.

[0203] From the viewpoint of further improving the performance balance among the moldability, thermal dimensional stability and bag-forming property of the biaxially stretched polypropylene film 100, the content of the structural unit derived from α-olefin other than propylene in the random polypropylene (B1) is preferably greater than 2.0 mol%, more preferably 2.5 mol% or more, further preferably 3.0 mol% or more, further preferably 3.5 mol% or more, further preferably 4.0 mol% or more, and from the viewpoint of further improving the performance balance among the thermal dimensional stability, water vapor barrier property, bag-forming property and transparency of the biaxially stretched polypropylene film 100, it is preferably 15.0 mol% or less, more preferably 12.0 mol% or less, further preferably 10.0 mol% or less, further preferably 8.0 mol% or less, further preferably 6.5 mol% or less.

[0204] The amount of the structural unit derived from α-olefin other than propylene can be measured by the method described in Examples.

[0205] The random polypropylene (B1) preferably comprises one or more selected from the group consisting of a propylene·ethylene random copolymer, a propylene·ethylene·1-butene random copolymer and a propylene·1-butene random copolymer, more preferably comprises one or more selected from the group consisting of a propylene·ethylene random copolymer and a propylene·1-butene random copolymer, and further preferably comprises a propylene·ethylene random copolymer.

[0206] The random polypropylene (B1) in the biaxially stretched film layer 101 may be used alone or in combination of two or more.

[0207] (α-Olefin copolymer (B2))

[0208] The α-olefin copolymer (B2) is a copolymer of two or more α-olefins, for example, a copolymer of α-olefins containing more than 15.0 mol% of structural units derived from α-olefins other than propylene.

[0209] The α-olefin copolymer (B2) comprises a random copolymer of propylene and an α-olefin other than propylene, wherein the content of structural units derived from an α-olefin other than propylene is greater than 15.0 mol%.

[0210] The α-olefin other than propylene includes, for example, one or more selected from the group consisting of ethylene and α-olefins having carbon atoms of 4 to 10, preferably one or more selected from the group consisting of α-olefins having carbon atoms of 4 to 8, more preferably at least one selected from 1-butene and 1-octene, and further preferably 1-butene.

[0211] From the viewpoint of further improving the performance balance among moldability, thermal dimensional stability and bag-making property of the biaxially stretched polypropylene film 100, the content of the structural unit derived from α-olefin other than propylene in the α-olefin copolymer (B2) is preferably greater than 15.0 mol%, more preferably 20.0 mol% or more, further preferably 30.0 mol% or more, further preferably 50.0 mol% or more, further preferably 70.0 mol% or more, further preferably 80.0 mol% or more, and from the viewpoint of further improving the performance balance among thermal dimensional stability, water vapor barrier property, bag-making property and transparency of the biaxially stretched polypropylene film 100, it is preferably 99.0 mol% or less, more preferably 98.0 mol% or less, further preferably 95.0 mol% or less, further preferably 92.0 mol% or less, further preferably 90.0 mol% or less.

[0212] The amount of the structural unit derived from α-olefin other than propylene in the α-olefin copolymer (B2) can be measured by the method described in Examples.

[0213] The α-olefin copolymer (B2) preferably comprises a random copolymer of propylene and one or more α-olefins selected from the group consisting of ethylene and α-olefins having a carbon number of 4 to 10, more preferably comprises a random copolymer of propylene and one or two α-olefins selected from the group consisting of 1-butene and 1-octene, and further preferably comprises a random copolymer of propylene and 1-butene.

[0214] The α-olefin copolymer (B2) in the biaxially stretched film layer 101 may be used alone or in combination of two or more.

[0215] The polymer (B) can be produced by various methods, for example, using a known catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst.

[0216] (Other ingredients)

[0217] To the propylene polymer composition of the present embodiment, various additives such as tackifiers, heat stabilizers, weather stabilizers, antioxidants, ultraviolet absorbers, lubricants, slip agents, nucleating agents, antiblocking agents, antistatic agents, antifogging agents, pigments, dyes, and inorganic or organic fillers may be added as needed within a range that does not impair the purpose of the present embodiment.

[0218] (Method for preparing propylene polymer composition)

[0219] The propylene polymer composition of the present embodiment can be prepared by mixing or melt-kneading the components using dry blending, a tumble mixer, a Banbury mixer, a single-screw extruder, a twin-screw extruder, a high-speed twin-screw extruder, a heat roll, or the like.

[0220] [Surface resin layer]

[0221] Depending on the purpose, from the perspective of imparting functions such as heat resistance, heat sealing, antistatic properties, anti-blocking properties, printability, and slip properties to the film surface, the biaxially stretched polypropylene film 100 preferably also has a surface resin layer 103 on at least one surface of the biaxially stretched film layer 101.

[0222] The surface resin layer 103 may be provided on both surfaces of the biaxially stretched film layer 101. By providing the surface resin layer 103 on both surfaces of the biaxially stretched film layer 101, different functions can be imparted to each surface of the film.

[0223] In addition, depending on the purpose, from the viewpoint of further improving the functions of the biaxially stretched polypropylene film 100 such as heat resistance, heat sealing, antistatic properties, anti-blocking properties, printability, and slip properties, the surface resin layer 103 is preferably provided as the outermost layer of the biaxially stretched polypropylene film 100.

[0224] The surface resin layer 103 is preferably provided so as to be in direct contact with the surface of the biaxially stretched film layer 101. This can simplify the production process of the biaxially stretched polypropylene film 100.

[0225] In the biaxially stretched polypropylene film 100, from the viewpoint of further improving the functions of the biaxially stretched polypropylene film 100, such as heat fusion resistance, antistatic property, anti-blocking property, printability, and slippage, the thickness of the surface resin layer 103 is preferably 0.1 μm or more, more preferably 0.2 μm or more, more preferably 0.5 μm or more, more preferably 1.0 μm or more, and more preferably 1.5 μm or more. Furthermore, from the viewpoint of further improving the balance of performances such as heat fusion resistance, thermal dimensional stability, moldability, cost, mechanical properties, transparency, environmental adaptability, and lightness of the biaxially stretched polypropylene film 100, the thickness is preferably 10.0 μm or less, more preferably 8.0 μm or less, more preferably 6.0 μm or less, more preferably 5.0 μm or less, and more preferably 3.0 μm or less.

[0226] Here, the thickness of the surface resin layer 103 refers to the thickness of the surface resin layer 103 provided on one side of the biaxially stretched film layer 101. That is, in the present embodiment, when the surface resin layer 103 is provided on both sides of the biaxially stretched film layer 101, the above-mentioned thickness of the surface resin layer 103 represents the thickness of the surface resin layer 103 provided on one side of the biaxially stretched film layer 101.

[0227] In the biaxially stretched polypropylene film 100, the surface resin layer 103 is preferably a single layer. This can further simplify the production process of the biaxially stretched polypropylene film 100.

[0228] The surface resin layer 103 is preferably formed by biaxially stretching simultaneously with the film in a state before biaxial stretching of the biaxially stretched film layer 101. Thus, the biaxially stretched polypropylene film 100 can be produced using a laminated film produced by a molding method such as coextrusion molding, i.e., one-step molding, so that the manufacturing process of the biaxially stretched polypropylene film 100 can be further simplified. Therefore, the surface resin layer 103 is preferably biaxially stretched.

[0229] In order to further improve the performance balance between the printability and anti-blocking properties of the biaxially stretched polypropylene film 100, the surface resin layer 103 may be surface treated. Specifically, surface activation treatments such as corona treatment, flame treatment, plasma treatment, primer treatment, and ozone treatment may be performed.

[0230] The surface resin layer 103 is composed of, for example, a polyolefin-based resin composition (A) containing polyolefins. The polyolefins constituting the surface resin layer 103 include, for example, homopolymers or copolymers of α-olefins such as ethylene, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene; high-pressure low-density polyethylene; linear low-density polyethylene (LLDPE); high-density polyethylene; homopolypropylene; random copolymers of propylene and α-olefins having a carbon number of 2 to 10; ethylene-vinyl acetate copolymers (EVA); and ionomer resins, etc., One or more of the group consisting of the above.

[0231] Among these, as the polyolefin constituting the surface resin layer 103, homopolypropylene is preferably used from the viewpoint of further improving the performance balance of the heat-resistant fusion bonding, thermal dimensional stability, heat resistance, water vapor barrier, transparency, mechanical properties, rigidity, bag-making property, fluidity and formability of the biaxially stretched polypropylene film 100. Here, the preferred mode of the homopolypropylene constituting the surface resin layer 103 is the same as the aforementioned homopolypropylene (A). That is, the homopolypropylene constituting the surface resin layer 103 preferably includes the aforementioned homopolypropylene (A).

[0232] From the viewpoint of further improving the balance of performances such as heat-resistant welding property, thermal dimensional stability, heat resistance, water vapor barrier property, transparency, mechanical properties, rigidity, bag-making property, fluidity and moldability of the biaxially stretched polypropylene film 100, when the entire polyolefin-based resin composition (A), i.e., the entire surface resin layer 103, is set to 100% by mass, the content of polyolefin in the polyolefin-based resin composition (A), i.e., the surface resin layer 103, is preferably 75% by mass or more, more preferably 80% by mass or more, further preferably 90% by mass or more, further preferably 95% by mass or more, further preferably 98% by mass or more, further preferably 99% by mass or more, and preferably less than 100% by mass.

[0233] From the viewpoint of further improving the balance of performances such as heat-resistant fusion bonding, thermal dimensional stability, heat resistance, water vapor barrier properties, transparency, mechanical properties, rigidity, bag-making properties, fluidity and moldability of the biaxially stretched polypropylene film 100, when the entire polyolefin resin composition (A), i.e., the entire surface resin layer 103, is set to 100% by mass, the content of homopolypropylene (A) in the polyolefin resin composition (A), i.e., the surface resin layer 103, is preferably 75% by mass or more, more preferably 80% by mass or more, further preferably 90% by mass or more, further preferably 95% by mass or more, further preferably 98% by mass or more, further preferably 99% by mass or more, and preferably 100% by mass or less.

[0234] (Other ingredients)

[0235] To the polyolefin resin composition (A) constituting the surface resin layer 103, various additives such as tackifiers, heat stabilizers, weather stabilizers, antioxidants, ultraviolet absorbers, lubricants, slip agents, nucleating agents, anti-blocking agents, antistatic agents, anti-fogging agents, pigments, dyes, inorganic or organic fillers may be added as needed within the range that does not impair the purpose of the present embodiment.

[0236] (Method for preparing polyolefin resin composition (A))

[0237] The polyolefin resin composition (A) can be prepared by mixing or melt-kneading the components using, for example, dry blending, a tumble mixer, a Banbury mixer, a single-screw extruder, a twin-screw extruder, a high-speed twin-screw extruder, a heat roll or the like.

[0238] <Method for producing biaxially stretched polypropylene film>

[0239] The biaxially stretched polypropylene film 100 can be obtained, for example, by biaxially stretching the following film using a known biaxially stretched film manufacturing method such as a simultaneous biaxial stretching method, a sequential biaxial stretching method, and an inflation biaxial stretching method, wherein the film is obtained by co-extruding and molding a propylene polymer composition for forming a biaxially stretched film layer 101 and a polyolefin resin composition (A) for forming a surface resin layer 103 as required in a film form.

[0240] There are no particular limitations on the molding device and molding conditions, and the molding device and molding conditions known in the past can be used. As the molding device, a T-die extruder, a multilayer T-die extruder, an inflation molding machine or a multilayer inflation molding machine can be used. The conditions for biaxial stretching can, for example, adopt the manufacturing conditions of the known OPP film. More specifically, in the sequential biaxial stretching method, for example, the stretching temperature in the MD direction is 100°C to 145°C, the stretching ratio in the MD direction is in the range of 4.5 to 6 times, the stretching temperature in the TD direction is 130°C to 190°C, and the stretching ratio in the TD direction is in the range of 9 to 11 times.

[0241] Alternatively, the biaxially stretched polypropylene film 100 can be obtained by separately molding the biaxially stretched film layer 101 and the surface resin layer 103 used as required, laminating them, and heat-molding them.

[0242] <Application of biaxially stretched polypropylene film>

[0243] The biaxially stretched polypropylene film 100 can also be suitably used as a food packaging film constituting a food packaging body.

[0244] The food packaging body of the present embodiment is a packaging body using a biaxially stretched polypropylene film 100, for example, a packaging bag used for the purpose of storing food. In addition, the food packaging body involved in the present embodiment can use the biaxially stretched polypropylene film 100 in a part thereof or in the entire food packaging body according to the application.

[0245] The food package of the present embodiment includes the food package of the present embodiment and the food in the aforementioned food package. That is, the food package of the present embodiment is obtained by accommodating the food in the food package of the present embodiment.

[0246] As mentioned above, although embodiment of this invention was described with reference to drawings, these are examples of this invention, and various structures other than the above-mentioned can also be adopted.

[0247] The biaxially stretched polypropylene film 100 may further include one or two or more layers selected from the group consisting of a sealant layer and a coating layer.

[0248] In addition, the biaxially stretched polypropylene film 100 can also be used as a coating material.

[0249] Example

[0250] Hereinafter, the present embodiment will be described in detail with reference to Examples and Comparative Examples. It should be noted that the present embodiment is not limited at all by the description of these Examples.

[0251] 1. Raw materials

[0252] The raw materials used in Examples and Comparative Examples are shown below.

[0253] (1) Homopolymer (A)

[0254] h-PP1: homopolypropylene (MFR: 3.0 g / 10 min, melting point: 165°C, isotactic pentad fraction (mmmm): 98.0%, Mw: 370,000, Mn: 68,000, Mw / Mn: 5.4, content of structural units derived from propylene: 100 mol%)

[0255] (2) Polymer (B)

[0256] r-PP1: Random polypropylene (MFR: 7.0 g / 10 min, melting point: 139°C, Mw: 322,000, Mn: 50,700, Mw / Mn: 6.4, content of structural units derived from ethylene: 3.2 mol%, content of structural units derived from 1-butene: 2.9 mol%, content of structural units derived from propylene: 93.9 mol%)

[0257] BPR1: 1-butene·propylene copolymer (MFR: 9.0 g / 10 min, melting point: 100° C., Mw: 227,000, Mn: 114,000, Mw / Mn: 2.0, content of structural units derived from 1-butene: 88.9 mol%, content of structural units derived from propylene: 11.1 mol%)

[0258] 2. Measurement and evaluation methods

[0259] (1) Isotactic pentad fraction of homopolypropylene (A) (mmmm)

[0260] The isotactic pentad fraction (pentad fraction, (mmmm)) was measured using a nuclear magnetic resonance apparatus (manufactured by BrukerBiospin Corporation, AVANCE III cryo-500 model) using 13 The sample was dissolved in the following measurement solvent for measurement, and the measurement was performed, and the evaluation was performed based on the integrated intensity of each signal.

[0261] [Measurement conditions]

[0262] Measuring nucleus: 13C (125MHz)

[0263] Measurement mode: Single pulse proton broadband decoupling

[0264] Pulse width: 45°

[0265] Points: 64k

[0266] Repeat time: 5.5 seconds

[0267] Determination solvent: o-dichlorobenzene / deuterated benzene (4:1)

[0268] Sample concentration: 50mg / 0.6mL

[0269] Measuring temperature: 120℃

[0270] Window function: exponential (BF: 0.5Hz)

[0271] Chemical shift standard: mmmm (CH3): 21.59 ppm

[0272] (2) MFR of homopolypropylene (A) and polymer (B)

[0273] The test was conducted in accordance with ASTM D1238 at 230°C and a load of 2.16 kg.

[0274] (3) Melting points of homopolypropylene (A) and polymer (B)

[0275] For the homopolypropylene (A) and the polymer (B), a first differential scanning calorimetry (1st Run) and a second differential scanning calorimetry (2nd Run) were continuously performed under a nitrogen flow using a differential scanning calorimeter (product name: Q200DSC, manufactured by TA Instruments). The first differential scanning calorimetry (1st Run) included a process of heating from -30°C to 250°C at a heating rate of 10°C / min and a process of cooling from 250°C to -30°C at a cooling rate of 10°C / min, and the second differential scanning calorimetry (2nd Run) included a process of heating from -30°C to 250°C at a heating rate of 10°C / min.

[0276] The peak temperature of the maximum melting peak in the DSC curve in the 2nd Run was taken as the melting point.

[0277] (4) Weight average molecular weight (Mw) and number average molecular weight (Mn) of homopolypropylene (A) and polymer (B)

[0278] The weight average molecular weight (Mw) and number average molecular weight (Mn) of the homopolypropylene (A) and the polymer (B) were measured by gel permeation chromatography (GPC).

[0279] As for the GPC method, a gel permeation chromatograph (manufactured by Tosoh Corporation, HLC-8321GPC / HT type) was used for the following determination. The separation columns were 2 TSKgel GNH6-HT and 2 TSKgel GNH6-HTL, and the column dimensions were 7.5 mm in diameter and 300 mm in length. The column temperature was set to 145°C, and o-dichlorobenzene and BHT 0.025% by mass as an antioxidant were used in the mobile phase, and the flow was performed at 1.0 mL / min. The sample concentration was set to 0.1% (w / v), and the sample injection volume was set to 400 μL. A differential refractometer was used as a detector. The molecular weight converted to polypropylene was obtained based on monodisperse polystyrene.

[0280] (5) Determination of the Content of Structural Units Derived from α-Olefins Other Than Propylene in Homopolypropylene (A) and Polymer (B), and the Content of Structural Units Derived from α-Olefins Other Than Propylene in Biaxially Stretched Polypropylene Film

[0281] The content of the structural unit derived from α-olefin other than propylene in the homopolypropylene (A) and the polymer (B), and the content of the structural unit derived from α-olefin other than propylene contained in the biaxially stretched polypropylene film were measured by using a nuclear magnetic resonance apparatus (manufactured by Bruker Biospin Corporation, AVANCE III cryo-500 model). 13C-NMR was used for measurement. The sample was dissolved in the following measurement solvent for measurement, and the evaluation was performed based on the integrated intensity of each signal. The obtained 13C-NMR spectrum was used as a reference to Macromolecules (1982) Ethylene-1-Butene Copolymers.1.Comonomer Sequence Distribution and Macromolecules (1977) Carbon-13 Nuclear Magnetic Resonance Determination of Monomer Composition and Sequence Distributions in Ethylene-Propylene Copolymers Prepared with a Stereoregular Catalyst System, etc., to assign the signals and quantify the content (mol %) of the structural unit derived from ethylene, the content (mol %) of the structural unit derived from propylene, and the content (mol %) of the structural unit derived from 1-butene in each polymer.

[0282] [Measurement conditions]

[0283] Determination of the core: 13 C(125MHz)

[0284] Measurement mode: Single pulse proton broadband decoupling

[0285] Pulse width: 45°

[0286] Points: 64k

[0287] Repeat time: 5.5 seconds

[0288] Determination solvent: o-dichlorobenzene / deuterated benzene (4:1)

[0289] Sample concentration: 50mg / 0.6mL

[0290] Measuring temperature: 120℃

[0291] Window function: exponential (BF: 0.5Hz)

[0292] In addition, in the measurement of the content of the structural unit derived from α-olefin other than propylene contained in the biaxially stretched polypropylene film, the biaxially stretched polypropylene film is used as a sample.

[0293] (6) Tensile elastic modulus

[0294] A test piece of 15 mm × 15 cm was cut out from the biaxially stretched polypropylene film. Next, the tensile elastic modulus T1 in the MD direction and the tensile elastic modulus T2 in the TD direction of the test piece were measured using a tensile testing machine manufactured by Orientec in accordance with JIS K7127 (1999) at a measuring temperature of 23 ± 2°C, 50 ± 5% RH, and a tensile speed of 5 mm / min.

[0295] (7) Small angle X-ray scattering (SAXS) measurement of biaxially stretched polypropylene films

[0296] In the biaxially stretched polypropylene film of each example, for the measurement in the MD direction, the MD direction of the film was set as the up-down direction, and the TD direction was set as the left-right direction, and the film to be measured was set in the following apparatus in such a manner that the angle formed by the X-ray source direction and the film surface became perpendicular. For the measurement in the TD direction, the TD direction was set as the up-down direction, and the MD direction was set as the left-right direction, and the small-angle X-ray scattering (SAXS) measurement was performed using the following apparatus and conditions.

[0297] Device: Made by RIGAKU Co., Ltd., product name: Ultima IV (small angle scattering attachment system)

[0298] X-ray incident direction: film normal direction

[0299] X-ray wavelength: 0.15418nm

[0300] Optical unit specifications:

[0301] 1. Select slit for optical system; use 0.03mm (= 1st slit) for small angle scattering

[0302] 2.DS; anti-scatter slit 1.00mm (= 2nd slit)

[0303] 3. Incident side Soller slit; 5° using flexible optical system

[0304] 4.1st.~2nd.Slit distance: 70mm

[0305] 5.2nd.~ Distance between samples: 98mm

[0306] 6. Vacuum path length: 100mm (front surface of the light receiving slit box, set on a dedicated table)

[0307] 7.RS, SS; scattering slit 0.20mm, light receiving slit 0.10mm

[0308] 8. Camera length: 285mm

[0309] 9. Cable slit on the light receiving side; 5° using flexible optical system

[0310] 10. Monochromation: None (monochromatization on the incident side by multilayer mirror)

[0311] 11. Detector: RIGAKU scintillation detector (HV: 762V) (one-dimensional)

[0312] X-ray irradiation conditions:

[0313] A. Scan axis: 2theta

[0314] B. Determination method: Continuous

[0315] C. Scanning start angle: 0.1°

[0316] D. Scan end angle: 1.0°

[0317] E. Sampling width: 0.02°

[0318] F. Scanning speed: 0.5° / min

[0319] G. Voltage and current: 40kV-40mA

[0320] H. Number of sample stacks: To obtain sufficient scattering intensity, the samples were stacked to a thickness of about 0.5 mm while keeping their orientations aligned.

[0321] The X-ray scattering pattern obtained under the above measurement conditions is subjected to background correction and air scattering correction of the detector to obtain a SAXS spectrum I(q). The Bragg angle θ is calculated according to the following formula (1) using the magnitude of the scattering vector of the peak from the long crystal period of the SAXS spectrum, and the Bragg angle θ is substituted into the following Bragg formula (2) to calculate the long crystal period (d).

[0322] q=4πsinθ / λ (1)

[0323] θ: Bragg angle

[0324] q: the magnitude of the scattering vector

[0325] λ: X-ray wavelength

[0326] 2dsinθ=λ (2)

[0327] d: Long crystallization period

[0328] θ: Bragg angle

[0329] λ: X-ray wavelength

[0330] In addition, with reference to the structural analysis of crystalline polymer materials based on the scattering method in NICHIAS Technology Times (2014) No. 2 No. 365, the scattering intensity spectrum I (q) was Fourier transformed using the following formula (3), thereby calculating the electron density correlation function γ (r). γ (r) has a special property that can be directly used for structural characterization. As structural information, the amorphous thickness (da) of the obtained biaxially stretched polypropylene film is calculated. In addition, r represents the distance (nm).

[0331] [Mathematical formula 1]

[0332]

[0333] In addition, the value obtained by subtracting the amorphous thickness (da) from the crystal long period (d) was calculated as the crystal thickness (dc).

[0334] (8) Differential Scanning Calorimetry of Biaxially Stretched Polypropylene Film

[0335] A test piece of about 5.0 mg was cut out from the biaxially stretched polypropylene film. Next, the sample was subjected to a first differential scanning calorimetry (1st Run) using a differential scanning calorimeter (product name: Q200DSC, manufactured by TA Instruments) under a nitrogen flow, including a process of heating from -50°C to 250°C at a heating rate of 5°C / min and a process of cooling from 250°C to -50°C at a cooling rate of 5°C / min.

[0336] From the obtained DSC curve, the main melting point (°C), the heat of fusion ΔH (J / g) of the entire film, and the heat of fusion ΔH (J / g) below 165°C were determined. Here, the peak temperature of the maximum melting peak in the DSC curve was taken as the main melting point.

[0337] The heat of fusion ΔH (J / g) of the entire film is calculated from the melting peak area of ​​the DSC curve in accordance with JIS K 7122: 1987 (wherein the heating rate is 5°C / min.) It should be noted that when a plurality of melting peaks are present in the DSC curve, the total area of ​​the plurality of melting peaks is taken as the heat of fusion (ΔH) of the entire film.

[0338] The heat of fusion ΔH (J / g) of 165° C. or less is the heat of fusion in the range of 165° C. or less in the heat of fusion ΔH (J / g) of the entire film.

[0339] Next, the crystal ratio (%) below 165° C., the crystallinity (%), the amorphous amount (%), and the crystal amount below 165° C. were calculated according to the following formulae.

[0340] The heat of fusion of complete crystallization of polypropylene used in the calculation was 209 J / g as described in Macromolecular Chemie, Rapid Communication, Vol. 9, Item 75 (1988).

[0341] Crystallization ratio below 165°C (%) = 100 × heat of fusion below 165°C ΔH (J / g) / heat of fusion of the entire film ΔH (J / g)

[0342] Crystallinity (%) = 100 × heat of fusion of the entire film ΔH (J / g) / heat of fusion of complete crystallization of polypropylene (209 J / g)

[0343] Amorphous content (%) = 100 - crystallinity (%)

[0344] Amount of crystallization below 165°C (%) = degree of crystallization (%) × ratio of crystallization below 165°C (%) / 100

[0345] (9) Water vapor permeability

[0346] The biaxially stretched polypropylene film was folded in half so that the surface resin layer 1 became the inner surface, and the two sides were heat-sealed to form a bag. Then, calcium chloride was added as the content. Next, the other side was heat-sealed to a surface area of ​​0.01 m 2 The bags were then stored at 40°C and 90% RH for 72 hours. The mass of calcium chloride before and after storage was measured, and the water vapor permeability (g / (m 2 ·24h)).

[0347] (10) Thermal expansion and thermal shrinkage of biaxially stretched polypropylene films at 120°C

[0348] The thermal expansion coefficient and thermal shrinkage coefficient of the biaxially stretched polypropylene film at 120° C. were measured in accordance with JIS C2151:2019.

[0349] First, a 10 cm × 10 cm test piece was cut out from a biaxially stretched polypropylene film. Then, the test piece was heat treated at 120°C for 15 minutes. At this time, the test piece was hung in a hot air circulation thermostatic bath (manufactured by ADVANTEC, product name: DRM620DE) without applying force and heated. Then, after the test piece was cooled to room temperature, the length of the test piece was measured. Then, the length of the TD direction of the test piece after the heat treatment was set to TD1 [cm], and the thermal expansion coefficient in the TD direction was calculated by 100 × (TD1-10) / 10 [%]. In addition, the length of the MD direction of the test piece after the heat treatment was set to MD1 [cm], and the thermal shrinkage rate in the MD direction was calculated by 100 × (10-MD1) / 10 [%]. The above measurement was performed 3 times, and the average values ​​of the measured values ​​obtained were used as the thermal expansion coefficient and thermal shrinkage rate of the biaxially stretched polypropylene film at 120°C.

[0350] (11) Thermal shrinkage of biaxially stretched polypropylene film at 150°C

[0351] The heat shrinkage of the biaxially stretched polypropylene film at 150° C. is measured in accordance with JIS C2151:2019.

[0352] First, a 10 cm × 10 cm test piece was cut from a biaxially stretched polypropylene film. Next, the test piece was heated at 150°C for 15 minutes. At this time, the test piece was hung in a hot air circulation thermostatic bath (manufactured by ADVANTEC, product name: DRM620DE) without applying force and heated. Next, after the test piece was cooled to room temperature, the length of the test piece was measured. Next, when the length of the test piece in the TD direction after the heat treatment was set to TD1 [cm] and the length of the test piece in the MD direction after the heat treatment was set to MD1 [cm], X TD [%] Calculated by 100×(10-TD1) / 10, X MD [%] Calculated by 100×(10-MD1) / 10. The above measurement was performed three times, and the average value of the obtained measured values ​​was adopted as the heat shrinkage rate of the biaxially stretched polypropylene film at 150°C.

[0353] (12) Haze

[0354] The haze of the biaxially stretched polypropylene film was measured using a haze meter (NDH5000, manufactured by Nippon Denshoku Industries, Ltd.) in accordance with JIS K7136:2000.

[0355] (13) Thermal fusion strength at 170°C or 200°C

[0356] The surface resin layers 1 (heat-resistant fusion layer) of two biaxially stretched polypropylene films cut into 15 mm width were heat-fused to each other at 170°C or 200°C, a pressure of 2.0 kgf, and a sealing time of 1.0 second to obtain laminated films. Next, the two biaxially stretched polypropylene films were peeled off under the conditions of 15 mm width, 90 degree peeling, a peeling speed of 300 mm / min, and stretching in the TD direction, and the peeling strength at this time was respectively used as the heat fusion strength at 170°C or 200°C.

[0357] (14) Bag making properties (wrinkles when heat-sealed at 180°C)

[0358] The surface resin layers 1 (heat-resistant fusion layer) of two biaxially stretched polypropylene films cut to 15 mm width were heat-fused together at 180°C, 2.0 kgf pressure, and 1.0 second sealing time to obtain a laminated film. The seal portion was then visually observed for heat wrinkles.

[0359] (15) Thermal dimensional stability

[0360] The thermal dimensional stability of the biaxially stretched polypropylene film was evaluated according to the following criteria.

[0361] AA (very good): thermal shrinkage at 150°C (X MD +X TD ) is less than 5.0%

[0362] A (good): thermal shrinkage at 150°C (X MD +X TD ) is 5.0% or more and less than 6.0%

[0363] B (bad): thermal shrinkage at 150°C (X MD +X TD ) is 6.0% or more and less than 7.0%

[0364] C (very bad): thermal shrinkage at 150°C (X MD +X TD ) is 7.0% or more

[0365] [Examples 1 to 6 and Comparative Example 1]

[0366] The polypropylene films were extruded with the compositions shown in Table 1, and then biaxially stretched to prepare biaxially stretched polypropylene films, and each evaluation was performed. The extrusion molding conditions and biaxially stretched treatment conditions were as follows. In addition, the surface of the surface resin layer 2 side in Table 1 was corona treated.

[0367] Extrusion molding machine: Multilayer T-die extruder (screw: L / D=27, manufactured by Screw Engineering Co., Ltd.)

[0368] Extrusion setting temperature: 230-250°C, processing speed: 20m / min (winding speed)

[0369] Stretching temperature in MD direction [°C]: shown in Table 1

[0370] Stretching ratio in MD direction [times]: shown in Table 1

[0371] Stretching temperature in TD direction [°C]: shown in Table 1

[0372] Stretching ratio in TD direction [times]: shown in Table 1

[0373] Mitigation rate [%]: shown in Table 1

[0374] Here, the relaxation rate means the maximum stretching width in terms of device setting / the width at the tenter exit.

[0375] In addition, the expression "A / B / C" of the stretching temperature in Table 1 means "preheating temperature (temperature for heating the film blank before stretching) / stretching temperature (temperature during stretching) / heat setting temperature (temperature during heat setting (annealing) after stretching)".

[0376] [Table 1]

[0377] Table 1

[0378]

[0379] The biaxially stretched polypropylene film of the example had improved thermal dimensional stability compared to the biaxially stretched polypropylene film of the comparative example.

[0380] This application claims priority based on Japanese patent applications No. 2022-155360, No. 2022-155356, No. 2022-155359, No. 2022-155365, and No. 2022-155368, filed on September 28, 2022, the disclosures of which are incorporated herein in their entirety.

[0381] The present invention can also adopt the following aspects.

[0382] [1a] A biaxially stretched polypropylene film comprising a biaxially stretched film layer containing a propylene-based polymer,

[0383] The crystal ratio at 165° C. or lower determined by differential scanning calorimetry is 38% or more.

[0384] [2a] The biaxially stretched polypropylene film according to [1a] above, wherein the main melting point of the biaxially stretched polypropylene film determined by differential scanning calorimetry is 165° C. or more and 180° C. or less.

[0385] [3a] The biaxially stretched polypropylene film according to [1a] or [2a], wherein the heat of fusion (ΔH) of the biaxially stretched polypropylene film as a whole, as determined by differential scanning calorimetry, is 110 J / g to 150 J / g.

[0386] [4a] The biaxially stretched polypropylene film according to any one of [1a] to [3a], wherein the heat of fusion (ΔH) of the biaxially stretched polypropylene film at 165°C or below, as determined by differential scanning calorimetry, is 40 J / g or more.

[0387] [5a] The biaxially stretched polypropylene film according to any one of [1a] to [4a], wherein the amount of crystallinity at 165°C or below of the biaxially stretched polypropylene film determined by differential scanning calorimetry is 20% or more.

[0388] [6a] The biaxially stretched polypropylene film as described in any one of [1a] to [5a] above, wherein the amount of structural units derived from monomers contained in the biaxially stretched polypropylene film is 0.05 mol% or more when the total amount of structural units derived from monomers contained in the biaxially stretched polypropylene film is set to 100 mol%.

[0389] [7a] The biaxially stretched polypropylene film according to any one of [1a] to [6a], further comprising a surface resin layer on at least one surface of the biaxially stretched film layer.

[0390] [8a] The biaxially stretched polypropylene film according to [7a] above, wherein the surface resin layer comprises homopolypropylene (A).

[0391] [9a] The biaxially stretched polypropylene film according to [8a], wherein the content of the homopolypropylene (A) in the surface resin layer is 75% by mass or more and 100% by mass or less, when the entire surface resin layer is taken as 100% by mass.

[0392] [10a] The biaxially stretched polypropylene film according to any one of [7a] to [9a], wherein the thickness of the surface resin layer is 0.1 μm or more and 10.0 μm or less.

[0393] [11a] The biaxially stretched polypropylene film according to any one of [1a] to [10a] above, wherein the thickness of the biaxially stretched film layer is 5 μm to 100 μm.

[0394] [12a] A biaxially stretched polypropylene film as described in any one of [1a] to [11a] above, wherein the total value (T1+T2) of the tensile elastic modulus T1 in the MD direction and the tensile elastic modulus T2 in the TD direction of the biaxially stretched polypropylene film, measured in accordance with JIS K7127 (1999) using a tensile testing machine under the conditions of a measuring temperature of 23±2°C, 50±5%RH, and a tensile speed of 5 mm / min, is 3000 MPa or more and 10000 MPa or less.

[0395] [13a] The biaxially stretched polypropylene film according to any one of [1a] to [12a], which expands in the TD direction when heat-treated at 120°C for 15 minutes in accordance with JIS C2151:2019.

[0396] [14a] The biaxially stretched polypropylene film according to any one of [1a] to [13a], which is a food packaging film.

[0397] [15a] A food packaging body using the biaxially stretched polypropylene film according to any one of [1a] to [14a].

[0398] [16a] A food package, comprising:

[0399] The food packaging body described in [15a] above; and

[0400] The food in the aforementioned food packaging.

[0401] The present invention can also adopt the following aspects.

[0402] [1b] A biaxially stretched polypropylene film comprising a biaxially stretched film layer containing a propylene-based polymer,

[0403] When heated at 120°C for 15 minutes in accordance with JIS C2151:2019, the film expands in the TD direction and shrinks in the MD direction.

[0404] [2b] The biaxially stretched polypropylene film according to [1b] above, wherein the coefficient of thermal expansion in the TD direction when heated at 120° C. for 15 minutes in accordance with JIS C2151:2019 is 0.1% to 2.0%.

[0405] [3b] The biaxially stretched polypropylene film according to [1b] or [2b], wherein the heat shrinkage in the MD direction when heated at 120°C for 15 minutes in accordance with JIS C2151:2019 is 5.0% or less.

[0406] [4b] The biaxially stretched polypropylene film according to any one of [1b] to [3b], wherein the heat shrinkage in the TD direction when heated at 150°C for 15 minutes in accordance with JIS C2151:2019 is 8.5% or less.

[0407] [5b] The biaxially stretched polypropylene film according to any one of [1b] to [4b], wherein the heat shrinkage in the MD direction when heated at 150°C for 15 minutes in accordance with JIS C2151:2019 is 8.0% or less.

[0408] [6b] The biaxially stretched polypropylene film according to any one of [1b] to [5b], wherein the heat shrinkage in the TD direction and the heat shrinkage in the MD direction when heated at 150° C. for 15 minutes in accordance with JIS C 2151: 2019 are respectively denoted as X TD [%] and X MD [%], X TD +X MD Less than 16.0%.

[0409] [7b] The biaxially stretched polypropylene film as described in any one of [1b] to [6b] above, wherein the amount of structural units derived from monomers contained in the biaxially stretched polypropylene film is 0.05 mol% or more when the total amount of structural units derived from monomers contained in the biaxially stretched polypropylene film is set to 100 mol%.

[0410] [8b] The biaxially stretched polypropylene film according to any one of [1b] to [7b], further comprising a surface resin layer on at least one surface of the biaxially stretched film layer.

[0411] [9b] The biaxially stretched polypropylene film according to [8b] above, wherein the surface resin layer comprises homopolypropylene (A).

[0412] [10b] The biaxially stretched polypropylene film as described in [9b] ​​above, wherein the content of the homopolypropylene (A) in the surface resin layer is 75% by mass or more and 100% by mass or less, when the entire surface resin layer is taken as 100% by mass.

[0413] [11b] The biaxially stretched polypropylene film according to any one of [8b] to [10b], wherein the thickness of the surface resin layer is 0.1 μm to 10.0 μm.

[0414] [12b] The biaxially stretched polypropylene film according to any one of [1b] to [11b], wherein the thickness of the biaxially stretched film layer is 5 μm to 100 μm.

[0415] [13b] A biaxially stretched polypropylene film as described in any one of [1b] to [12b] above, wherein the total value (T1+T2) of the tensile elastic modulus T1 in the MD direction and the tensile elastic modulus T2 in the TD direction of the biaxially stretched polypropylene film, measured in accordance with JIS K7127 (1999) using a tensile testing machine under the conditions of a measuring temperature of 23±2°C, 50±5%RH, and a tensile speed of 5 mm / min, is 3000 MPa or more and 10000 MPa or less.

[0416] [14b] The biaxially stretched polypropylene film according to any one of [1b] to [13b], which is a food packaging film.

[0417] [15b] A food packaging body using the biaxially stretched polypropylene film according to any one of [1b] to [14b].

[0418] [16b] A food packaging body, comprising:

[0419] The food packaging body described in [15b] above; and

[0420] The food in the aforementioned food packaging.

[0421] The present invention can also adopt the following aspects.

[0422] [1c] a biaxially stretched polypropylene film comprising a biaxially stretched film layer containing a propylene-based polymer,

[0423] The heat fusion strength when the biaxially stretched polypropylene films are heat-sealed at 200° C. is 4.0 N / 15 mm or less.

[0424] [2c] The biaxially stretched polypropylene film according to [1c], wherein the heat fusion strength when the biaxially stretched polypropylene films are heat-sealed at 170°C is 1.0 N / 15 mm or less.

[0425] [3c] The biaxially stretched polypropylene film as described in [1c] or [2c] above, wherein the amount of structural units derived from α-olefins other than propylene contained in the biaxially stretched polypropylene film is 0.05 mol% or more when the total amount of structural units derived from monomers contained in the biaxially stretched polypropylene film is set to 100 mol%.

[0426] [4c] The biaxially stretched polypropylene film according to any one of [1c] to [3c], further comprising a surface resin layer on at least one surface of the biaxially stretched film layer.

[0427] [5c] The biaxially stretched polypropylene film according to [4c] above, wherein the surface resin layer comprises homopolypropylene (A).

[0428] [6c] The biaxially stretched polypropylene film as described in [5c] above, wherein the content of the homopolypropylene (A) in the surface resin layer is 75% by mass or more and 100% by mass or less, when the entire surface resin layer is taken as 100% by mass.

[0429] [7c] The biaxially stretched polypropylene film according to any one of [4c] to [6c], wherein the thickness of the surface resin layer is 0.1 μm or more and 10.0 μm or less.

[0430] [8c] The biaxially stretched polypropylene film according to any one of [1c] to [7c], wherein the thickness of the biaxially stretched film layer is 5 μm to 100 μm.

[0431] [9c] A biaxially stretched polypropylene film as described in any one of [1c] to [8c] above, wherein the total value (T1+T2) of the tensile elastic modulus T1 in the MD direction and the tensile elastic modulus T2 in the TD direction of the biaxially stretched polypropylene film, measured in accordance with JIS K7127 (1999) using a tensile testing machine under the conditions of a measuring temperature of 23±2°C, 50±5%RH, and a tensile speed of 5 mm / min, is 3000 MPa or more and 10000 MPa or less.

[0432] [10c] The biaxially stretched polypropylene film according to any one of [1c] to [9c], which is a food packaging film.

[0433] [11c] A food packaging body using the biaxially stretched polypropylene film according to any one of [1c] to [10c].

[0434] [12c] A food package comprising:

[0435] The food packaging body described in [11c] above; and

[0436] The food in the aforementioned food packaging.

[0437] The present invention can also adopt the following aspects.

[0438] [1d] A biaxially stretched polypropylene film comprising a biaxially stretched film layer, wherein the biaxially stretched film layer comprises homopolypropylene (A) and at least one polymer (B) selected from the group consisting of random polypropylene (B1) and α-olefin copolymer (B2),

[0439] The MFR of the polymer (B), measured under the conditions of 230° C. and a load of 2.16 kg in accordance with ASTM D1238, is 0.01 g / 10 min or more and 30 g / 10 min or less.

[0440] [2d] The biaxially stretched polypropylene film as described in [1d] above, wherein the amount of structural units derived from monomers contained in the biaxially stretched polypropylene film is 0.05 mol% or more when the total amount of structural units derived from monomers contained in the biaxially stretched polypropylene film is set to 100 mol%.

[0441] [3d] The biaxially stretched polypropylene film according to [1d] or [2d], wherein the isotactic pentad fraction (mmmm) of the homopolypropylene (A) is 96.0% or more.

[0442] [4d] The biaxially stretched polypropylene film as described in any one of [1d] to [3d] above, wherein the content of the polymer (B) is 1% by mass or more and 50% by mass or less, when the total weight of the biaxially stretched film layer is 100% by mass.

[0443] [5d] The biaxially stretched polypropylene film according to any one of [1d] to [4d], wherein the melting point of the polymer (B) is 50°C or more and 155°C or less.

[0444] [6d] The biaxially stretched polypropylene film according to any one of [1d] to [5d], wherein the weight average molecular weight (Mw) of the polymer (B) is 100,000 to 1,000,000.

[0445] [7d] The biaxially stretched polypropylene film according to any one of [1d] to [6d], wherein the weight average molecular weight (Mw) / number average molecular weight (Mn) of the polymer (B) is 1.5 to 8.0.

[0446] [8d] A biaxially stretched polypropylene film as described in any one of [1d] to [7d] above, wherein the α-olefin copolymer (B2) comprises a random copolymer of propylene and one or more α-olefins selected from the group consisting of ethylene and α-olefins having a carbon number of 4 to 10.

[0447] [9d] The biaxially stretched polypropylene film according to any one of [1d] to [8d], further comprising a surface resin layer on at least one surface of the biaxially stretched film layer.

[0448] [10d] The biaxially stretched polypropylene film according to [9d] above, wherein the surface resin layer contains homopolypropylene (A).

[0449] [11d] The biaxially stretched polypropylene film as described in [10d] above, wherein the content of the homopolypropylene (A) in the surface resin layer is 75% by mass or more and 100% by mass or less, when the entire surface resin layer is taken as 100% by mass.

[0450] [12d] The biaxially stretched polypropylene film according to any one of [9d] to [11d], wherein the thickness of the surface resin layer is 0.1 μm to 10.0 μm.

[0451] [13d] The biaxially stretched polypropylene film according to any one of [1d] to [12d] above, wherein the thickness of the biaxially stretched film layer is 5 μm to 100 μm.

[0452] [14d] A biaxially stretched polypropylene film as described in any one of [1d] to [13d] above, wherein the total value (T1+T2) of the tensile elastic modulus T1 in the MD direction and the tensile elastic modulus T2 in the TD direction of the biaxially stretched polypropylene film, measured in accordance with JIS K7127 (1999) using a tensile testing machine under the conditions of a measuring temperature of 23±2°C, 50±5%RH, and a tensile speed of 5 mm / min, is 3000 MPa or more and 10000 MPa or less.

[0453] [15d] The biaxially stretched polypropylene film according to any one of [1d] to [14d], which expands in the TD direction when heat-treated at 120°C for 15 minutes in accordance with JIS C2151:2019.

[0454] [16d] The biaxially stretched polypropylene film according to any one of [1d] to [15d], which is a food packaging film.

[0455] [17d] A food packaging body using the biaxially stretched polypropylene film according to any one of [1d] to [16d].

[0456] [18d] A food packaging body, comprising:

[0457] The food packaging body described in [17d] above; and

[0458] The food in the aforementioned food packaging.

[0459] Description of Reference Numerals

[0460] 100 Biaxially oriented polypropylene film

[0461] 101 Biaxially stretched film layer

[0462] 103 Surface resin layer

Claims

1. A biaxially stretched polypropylene film comprising a biaxially stretched film layer containing a propylene-based polymer, The long crystal period in the TD direction determined by small-angle X-ray scattering (SAXS) measurement was 28.0 nm or less.

2. The biaxially stretched polypropylene film according to claim 1, wherein The amorphous thickness in the TD direction determined by SAXS measurement was 15.5 nm or less.

3. The biaxially stretched polypropylene film according to claim 1 or 2, wherein The crystal thickness in the TD direction determined by SAXS measurement was 13.5 nm or less.

4. The biaxially stretched polypropylene film according to any one of claims 1 to 3, wherein The crystal ratio at 165° C. or lower determined by differential scanning calorimetry is 38% or more.

5. The biaxially stretched polypropylene film according to any one of claims 1 to 4, wherein The main melting point of the biaxially stretched polypropylene film determined by differential scanning calorimetry is 165° C. or higher and 180° C. or lower.

6. The biaxially stretched polypropylene film according to any one of claims 1 to 5, wherein The heat of fusion (ΔH) of the biaxially stretched polypropylene film as a whole, determined by differential scanning calorimetry, is 100 J / g or more and 150 J / g or less.

7. The biaxially stretched polypropylene film according to any one of claims 1 to 6, wherein The heat of fusion (ΔH) of the biaxially stretched polypropylene film at 165° C. or lower, determined by differential scanning calorimetry, is 40 J / g or more.

8. The biaxially stretched polypropylene film according to any one of claims 1 to 7, wherein The biaxially stretched polypropylene film has a crystallization content of 20% or more at 165°C or less.

9. The biaxially stretched polypropylene film according to any one of claims 1 to 8, wherein When the total amount of the structural units derived from monomers contained in the biaxially stretched polypropylene film is 100 mol %, the amount of the structural units derived from α-olefins other than propylene contained in the biaxially stretched polypropylene film is 0.05 mol % or more.

10. The biaxially stretched polypropylene film according to any one of claims 1 to 9, wherein When heated at 120°C for 15 minutes in accordance with JIS C2151:2019, it expands in the TD direction.

11. The biaxially stretched polypropylene film according to any one of claims 1 to 10, wherein When heated at 120°C for 15 minutes in accordance with JIS C2151:2019, the film expands in the TD direction and shrinks in the MD direction.

12. The biaxially stretched polypropylene film according to any one of claims 1 to 11, wherein The thermal expansion coefficient in the TD direction when subjected to a heat treatment at 120° C. for 15 minutes in accordance with JIS C2151:2019 is 0.1% to 2.0%.

13. The biaxially stretched polypropylene film according to any one of claims 1 to 12, wherein The heat shrinkage in the MD direction when heated at 120°C for 15 minutes in accordance with JIS C2151:2019 is 5.0% or less.

14. The biaxially stretched polypropylene film according to any one of claims 1 to 13, wherein The heat shrinkage in the TD direction when heated at 150°C for 15 minutes in accordance with JIS C2151:2019 is 8.5% or less.

15. The biaxially stretched polypropylene film according to any one of claims 1 to 14, wherein The heat shrinkage in the MD direction when heated at 150°C for 15 minutes in accordance with JIS C2151:2019 is 8.0% or less.

16. The biaxially stretched polypropylene film according to any one of claims 1 to 15, wherein The heat shrinkage in the TD direction and the heat shrinkage in the MD direction when heated at 150°C for 15 minutes according to JIS C2151:2019 are respectively designated as X TD [%] and X MD [%], X TD +X MD Less than 6.0%.

17. The biaxially stretched polypropylene film according to any one of claims 1 to 16, wherein The heat fusion strength when the biaxially stretched polypropylene films are heat-sealed at 200° C. is 4.0 N / 15 mm or less.

18. The biaxially stretched polypropylene film according to any one of claims 1 to 17, wherein The heat fusion strength when the biaxially stretched polypropylene films are heat-sealed at 170° C. is 1.0 N / 15 mm or less.

19. The biaxially stretched polypropylene film according to any one of claims 1 to 18, wherein The propylene-based polymer comprises homopolypropylene (A) and at least one polymer (B) selected from the group consisting of random polypropylene (B1) and α-olefin copolymers (B2), The MFR of the polymer (B), measured at 230° C. and a load of 2.16 kg in accordance with ASTM D1238, is 0.01 g / 10 min or more and 30 g / 10 min or less.

20. The biaxially stretched polypropylene film according to claim 19, wherein The isotactic pentad fraction (mmmm) of the homopolypropylene (A) is 96.0% or more.

21. The biaxially stretched polypropylene film according to claim 19 or 20, wherein When the entire biaxially stretched film layer is taken as 100 mass %, the content of the polymer (B) is 1 mass % or more and 50 mass % or less.

22. The biaxially stretched polypropylene film according to any one of claims 19 to 21, wherein The melting point of the polymer (B) is 50° C. or higher and 155° C. or lower.

23. The biaxially stretched polypropylene film according to any one of claims 19 to 22, wherein The weight average molecular weight (Mw) of the polymer (B) is 100,000 to 1,000,000.

24. The biaxially stretched polypropylene film according to any one of claims 19 to 23, wherein The weight average molecular weight (Mw) / number average molecular weight (Mn) of the polymer (B) is 1.5 to 8.

0.

25. The biaxially stretched polypropylene film according to any one of claims 19 to 24, wherein The α-olefin copolymer (B2) comprises a random copolymer of propylene and one or more α-olefins selected from the group consisting of ethylene and α-olefins having 4 to 10 carbon atoms. 26 . The biaxially stretched polypropylene film according to claim 1 , further comprising a surface resin layer on at least one surface of the biaxially stretched film layer.

27. The biaxially stretched polypropylene film according to claim 26, wherein The surface resin layer comprises homopolypropylene (A).

28. The biaxially stretched polypropylene film according to claim 27, wherein When the entire surface resin layer is taken as 100 mass %, the content of the homopolypropylene (A) in the surface resin layer is 75 mass % or more and 100 mass % or less.

29. The biaxially stretched polypropylene film according to any one of claims 26 to 28, wherein The surface resin layer has a thickness of 0.1 μm or more and 10.0 μm or less.

30. The biaxially stretched polypropylene film according to any one of claims 1 to 29, wherein The biaxially stretched film layer has a thickness of 5 μm to 100 μm.

31. The biaxially stretched polypropylene film according to any one of claims 1 to 30, wherein The total value (T1+T2) of the tensile elastic modulus T1 in the MD direction and the tensile elastic modulus T2 in the TD direction of the biaxially stretched polypropylene film, measured in accordance with JIS K7127 (1999) using a tensile testing machine under the conditions of a measuring temperature of 23±2°C, 50±5%RH, and a stretching speed of 5 mm / min, is 3000 MPa or more and 10000 MPa or less.

32. The biaxially stretched polypropylene film according to any one of claims 1 to 31, which is a food packaging film.

33. A food packaging body using the biaxially stretched polypropylene film according to any one of claims 1 to 32.

34. A food package, comprising: The food packaging body according to claim 33; and The food is contained in the food packaging body.

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