WO2024009724A1

WO2024009724A1 - Polypropylene-based film for retort packaging, and layered body

Info

Publication number: WO2024009724A1
Application number: PCT/JP2023/022266
Authority: WO
Inventors: 浩忠徳田; 和城中上; 裕豊島; 涼安岡
Original assignee: 東レフィルム加工株式会社
Priority date: 2022-07-08
Filing date: 2023-06-15
Publication date: 2024-01-11
Also published as: TW202411077A

Abstract

The present invention provides a polypropylene-based film that, as a sealant for packaging bag, has extremely excellent heat-sealing properties and low-temperature impact resistance and that can also be favorably used in retort applications due to excellent blocking resistance and peeling resistance.　The present invention is a polypropylene-based film for retort packaging for which: the limiting viscosity [η]CXS of a 20°C xylene-soluble portion CXS of the film is at least 2.5 dL/g and no more than 3.0 dL/g; the amount of the 20°C xylene-soluble portion CXS is no more than 15% by mass; the limiting viscosity [η]CXIS of a 20°C xylene-insoluble portion CXIS is at least 1.6 dL/g and no more than 2.2 dL/g; the limiting viscosity difference Δ[η]([η]CXS − [η]CXIS) of the 20°C xylene-soluble portion CXS and the 20°C xylene-insoluble portion CXIS is at least 0.7 and less than 1.2; and the mean value of the Young's modulus of the film in a vertical direction (MD) and a horizontal direction (TD) in a −10°C atmosphere is less than 1000 MPa.

Description

Polypropylene film and laminate for retort packaging

The present invention relates to a polypropylene film for retort packaging and a laminate.

Conventionally, as a sealant film for retort packaging that is retort sterilized at a high temperature of 120°C to 135°C, an unstretched polypropylene film (hereinafter sometimes referred to as CPP) whose main component is a propylene/ethylene block copolymer has been used. has been used. Its main uses are polyethylene terephthalate stretched film (hereinafter sometimes referred to as PET), biaxially stretched polyamide film (hereinafter sometimes referred to as ON), and aluminum foil (hereinafter sometimes referred to as Al foil). After laminating with a laminate base material layer such as PET/ON/Al foil/CPP, PET/Al foil/ON/CPP, PET/Al foil/CPP, PET/metal-deposited PET/CPP, It is used after being made into bags. In addition, physical properties such as low-temperature impact resistance, heat sealability, and blocking resistance have been required for the CPP constituting the innermost surface.

In recent years, laws related to environmentally friendly packaging have been enacted one after another, and it has become essential to design containers and packaging with consideration for the environment. A two-layer structure in which a sealant film is bonded to a base material with barrier properties is also being considered. For example, retort pouches made of vapor-deposited PET/CPP and vapor-deposited OPP (stretched polypropylene film)/CPP, which are mono-materials and have excellent recyclability, are being studied, and the sealant film has even higher low-temperature impact resistance. Sealing properties are required.

In addition, the level of requirements for the appearance of packaging bags has become higher, and it is desirable to minimize the appearance of minute irregularities that occur on the surface of the laminate after retort sterilization, so-called yuzu skin. For convenience in use, there is a demand for a function that prevents the packaging bag from tearing and the contents from scattering or leaking by passing steam through the sealed portion during heating in a microwave oven.

In order to solve the above problems, in Patent Document 1, the intrinsic viscosity and rubber content of a propylene-ethylene block copolymer are regulated, and linear low-density polyethylene with defined density and melt flow rate is used. A sealant film suitable for retort packaging, which has extremely high levels of low-temperature impact resistance and resistance to yuzu peeling, as well as excellent sealing strength, blocking resistance, and flex whitening resistance.A film for retort packaging. However, because the seal strength at high temperatures is very weak, there was a concern that when heated in a microwave oven, the pouch would peel off at the bag-forming seal area rather than at the steam passage area, causing the pouch to break. . Furthermore, the vapor-deposited PET/retort packaging film structure has poor low-temperature impact resistance.

International Publication No. 2017/038349

The present invention can be used as a sealant for packaging bags, and has excellent heat-sealability and low-temperature impact resistance.Furthermore, when a packaging bag filled with retort food is heated in a microwave oven, the sealing force decreases and the packaging bag breaks. The present invention provides a polypropylene film for retort packaging and a laminate that can prevent contents from scattering or leaking.

In view of the problems of the prior art, the present inventors conducted extensive studies on the amount of the olefin resin added to the polypropylene film and the rubber component of the polypropylene film and its viscosity, and as a result, they were able to solve the above problem.

That is, in the present invention, the intrinsic viscosity [η]CXS of the 20°C xylene soluble portion CXS of the film is 2.5 dl/g or more and 3.0 dl/g or less, and the amount of the 20° C. xylene soluble portion CXS is 15.0 dl/g or more and 3.0 dl/g or less. Mass% or less, the intrinsic viscosity [η] of the 20°C xylene insoluble part CXIS is 1.6 dl/g or more and 2.2 dl/g or less, the limiting viscosity of the 20°C xylene soluble part CXS and the 20°C xylene insoluble part CXIS The difference Δ[η] ([η]CXS - [η]CXIS) is 0.7 or more and less than 1.2, and the average Young's modulus of the film in the machine direction (MD) and transverse direction (TD) in a -10°C atmosphere This is a polypropylene film for retort packaging having a value of less than 1000 MPa. Further, the present invention is a polypropylene composite film for retort packaging comprising a base layer (A) and the polypropylene film for retort packaging (hereinafter sometimes referred to as a sealing layer (B)).

As a sealant for packaging bags, the present invention has excellent heat-sealability and low-temperature impact resistance, so in order to reduce the number of layers (volume reduction) of multilayer dry laminated laminated film, only a base material with barrier properties can be used. It is also possible to consider creating a two-layer structure with a sealant film laminated using it.It has excellent blocking resistance and yuzu skin resistance, making it suitable for retort applications.In addition, packaging bags filled with retort food can be electronically When heating in a microwave or the like, the sealing force is reduced and steam is passed through, thereby preventing the packaging bag from tearing and the contents from scattering or leaking.

Below, the polypropylene film for retort packaging and the laminate of the present invention will be specifically explained.

In the polypropylene film of the present invention, the intrinsic viscosity [η]CXS of the 20° C. xylene soluble portion CXS of the film is 2.5 dl/g or more and 3.0 dl/g or less, and the amount of the 20° C. xylene soluble portion CXS is 15 .0% by mass or less, the intrinsic viscosity [η]CXIS of the 20°C xylene insoluble part CXIS is 1.6 dl/g or more and 2.2 dl/g or less, the 20°C xylene soluble part CXS and the 20°C xylene insoluble part CXIS The intrinsic viscosity difference Δ[η] ([η]CXS−[η]CXIS) is 0.7 or more and less than 1.2.

Here, the 20°C xylene-insoluble part CXIS and the soluble part CXS refer to the above-mentioned propylene-based film completely dissolved in boiling xylene, cooled to 20°C, left to stand for 4 hours or more, and then precipitated. When the substance and the solution were separated by filtration, the precipitate was called the 20°C xylene insoluble part CXIS (sometimes referred to as the xylene insoluble part CXIS), and the solution part (filtrate) was dried at 70°C under reduced pressure. The obtained portion is referred to as the 20° C. xylene soluble portion CXS (sometimes referred to as xylene soluble portion CXS).

The 20° C. xylene insoluble portion CXIS corresponds to polypropylene or polyethylene, and the xylene soluble portion CXS corresponds to a rubber component.

The polypropylene composite film of the present invention is a composite film consisting of a base material layer (A) and the polypropylene film for retort packaging (hereinafter sometimes referred to as a sealing layer (B)), and the sealing layer (B) is , the intrinsic viscosity [η]CXS of the 20°C xylene soluble part CXS is 2.5 dl/g or more and 3.0 dl/g or less, the amount of the 20°C xylene soluble part CXS is 15.0% by mass or less, 20°C xylene The intrinsic viscosity [η] of the insoluble part CXIS is 1.6 dl/g or more and 2.2 dl/g or less, the intrinsic viscosity difference Δ[η] ([ η]CXS-[η]CXIS) is 0.7 or more and less than 1.2.

The amount of xylene soluble portion CXS in the polypropylene film for retort packaging of the present invention is preferably 15.0% by mass or less. If it is more than 15.0% by mass, the sealing force at 100° C. will be significantly reduced, and the packaging bag may burst when heated in a microwave oven or the like. The amount of CXS is preferably in the range of 5.0% by mass or more and 15.0% by mass.

The intrinsic viscosity ([η]CXIS) of the xylene-insoluble portion CXIS is in the range of 1.6 dl/g or more and 2.2 dl/g. If the limiting viscosity ([η]CXIS) is less than 1.6 dl/g, the low-temperature impact resistance will be insufficient, and if it is more than 2.2 dl/g, the flex whitening resistance will decrease.

If the intrinsic viscosity ([η]CXS) of the xylene-soluble part CXS is less than 2.5 dl/g, the blocking resistance will deteriorate, and if it is more than 3.0 dl/g, the resistance to flexing and whitening will occur when packaging oil-based foods. In addition, the skin resistance to citron also decreases.

The range of the intrinsic viscosity difference Δ[η] ([η]CXS - [η]CXIS) between the xylene soluble part CXS and the insoluble part CXIS at 20°C of the polypropylene film for retort packaging of the present invention is 0.7 or more 1 It is less than .2. If Δ[η] is less than 0.7, the surface roughness will be low and the blocking resistance will be poor. When Δ[η] exceeds 1.2, the citron skin resistance and the bending resistance to whitening deteriorate.

The average Young's modulus in the machine direction (MD) and transverse direction (TD) of the polypropylene film for retort packaging of the present invention in a -10°C atmosphere is less than 1000 MPa. If it exceeds 1000 MPa, low-temperature impact resistance will deteriorate.

A laminate in which the polypropylene film for retort packaging of the present invention is laminated with at least one heat-resistant base material layer.The two polypropylene films are sealed together and retorted at 130°C for 30 minutes, followed by a 100°C atmosphere. The seal strength is preferably 8 N/15 mm or more and less than 15 N/15 mm. If the sealing strength is less than 8N/15mm, the sealing force will decrease due to expansion of the packaging bag during microwave heating, and the bag may break.If the sealing strength is 15N/15mm or more, the sealing strength will be strong during microwave heating, so Steaming may occur from a place other than the steam opening, and the packaging bag may tear.

The sealing layers (B) of the two polypropylene composite films are sealed together and retorted for 30 minutes at 130°C. The sealing strength under a 100° C. atmosphere after treatment is preferably 8 N/15 mm or more and less than 15 N/15 mm. If the sealing strength is less than 8N/15mm, the sealing force will decrease due to expansion of the packaging bag during microwave heating, and the bag may break.If the sealing strength is 15N/15mm or more, the sealing strength will be strong during microwave heating, so Steaming may occur from a place other than the steam opening, and the packaging bag may tear.

The heat-resistant base material layer is preferably a base material made of a resin having a melting point of 160° C. or higher, such as biaxially stretched polyamide film, biaxially stretched polyester film (especially PET), biaxially stretched polybutylene terephthalate film, biaxially stretched polybutylene terephthalate film, etc. Axial oriented polypropylene film (OPP), metal foil, metal evaporated biaxially oriented polyamide film (vapor deposition ON), metal evaporated biaxially oriented polyester film (among them evaporated PET), metal evaporated biaxially oriented polybutylene terephthalate film, metal evaporated biaxially oriented polyamide film (vapor deposited ON) It is preferable that it is a laminate in which at least one layer selected from an axially oriented polypropylene film (deposited OPP) and a printing paper are laminated.

The polypropylene film for retort packaging of the present invention preferably contains a polypropylene resin as a main component. Examples of the polypropylene resin include homopolypropylene polymers, propylene/ethylene block copolymers, and copolymers of propylene and α-olefins such as ethylene and 1-butene. Preferably, since the polypropylene film for retort packaging of the present invention is used for retort packaging or heating in a microwave oven, the main component thereof is a propylene/ethylene block copolymer having a melting point of 145 to 165°C. is preferable, and it is preferable to contain a homopolypropylene polymer in order to adjust the amount of CXS in the xylene soluble portion of the film.

Here, the above-mentioned main component refers to 50% by mass or more of the total mass of the film.

It is preferable that the base layer (A) of the polypropylene composite film for retort packaging of the present invention is provided with low-temperature impact resistance and yuzu skin resistance, and the sealing layer (B) is provided with adjustment of seal strength and blocking resistance. It is preferable to let

The base layer (A) of the polypropylene composite film for retort packaging of the present invention preferably contains a polypropylene resin as a main component. It is preferable to include an ethylene polymer or a propylene α-olefin random copolymer as a subcomponent, and the content of the ethylene polymer is preferably 10% by mass to 45% by mass, and 30% by mass to 45% by mass. It is more preferable that the content is % by mass. If the ethylene polymer content is less than 10% by mass, it is difficult to obtain the effects of yuzu skin resistance and low-temperature impact resistance, and if it exceeds 45% by mass, the sealing force may decrease. Further, the content of the propylene-based random copolymer is preferably added in the range of 1% by mass to 20% by mass; if the content exceeds the content of the seal layer (B), the low-temperature impact resistance deteriorates.

Here, the main component refers to 50% by mass or more of the total mass of the base layer (A).　

It is preferable that the sealing layer (B) of the polypropylene composite film for retort packaging of the present invention has a polypropylene resin as a main component, like the base layer (A). It is preferable to include an ethylene polymer or a propylene α-olefin random copolymer as a subcomponent, and the content of the ethylene polymer may be added within a range that does not exceed the content of the base layer (A). Preferably, the content is from 10% by mass to 30% by mass to obtain the effects of sealing strength and blocking resistance. Further, the content of the propylene random copolymer is preferably in the range of 20% by mass to 30% by mass. If the content is less than 20% by mass, it is difficult to obtain the effect of increasing seal strength. If it exceeds 30% by mass, blocking resistance may deteriorate. When the seal layer (B) contains a propylene random copolymer, it is added to the base layer (A) in a range of 1% by mass to 20% by mass to increase the sealing strength with the sealing layer (B). If the content exceeds the content of the sealing layer (B), low-temperature impact resistance will deteriorate.

Here, the main component refers to 50% by mass or more of the total mass of the seal layer (B).　

Examples of the polypropylene resin include homopolypropylene polymers, propylene/ethylene block copolymers, and copolymers of propylene and α-olefins such as ethylene and 1-butene. Preferably, since the polypropylene composite film for retort packaging of the present invention is used for retort packaging or heating in a microwave oven, the main component is a propylene/ethylene block copolymer having a melting point of 145 to 165°C. It is preferable that the film contains a homopolypropylene polymer in order to adjust the amount of CXS in the xylene soluble portion of the film.

Examples of the propylene/ethylene block copolymer include those produced by polymerizing raw materials such as propylene and ethylene using a catalyst. Here, as the catalyst, a Ziegler-Natta type catalyst, a metallocene catalyst, or the like can be used, and for example, those listed in JP-A-07-216017 can be suitably used. Specifically, (1) In the presence of an organosilicon compound and an ester compound having a Si--O bond, the general formula Ti(OR) _a X _4-a (wherein, R is a hydrocarbon group having 1 to 20 carbon atoms) , X is a halogen atom, and a represents a number of 0<a≦4, preferably 2≦a≦4, particularly preferably a=4.) is reduced with an organomagnesium compound. A trivalent titanium compound-containing solid catalyst obtained by treating the obtained solid product with an ester compound and then with a mixture of an ether compound and titanium tetrachloride or a mixture of an ether compound, titanium tetrachloride, and an ester compound. , (2) an organoaluminium compound, and (3) an electron-donating compound (dialkyldimethoxysilane or the like is preferably used).

As a method for producing the above propylene/ethylene block copolymer, from the viewpoint of productivity and low-temperature impact resistance, in the first step, a polymer portion mainly composed of propylene is polymerized in the presence of an inert hydrocarbon solvent, and then It is preferable to use a method in which an ethylene-propylene copolymer is polymerized in a gas phase in the second step.

Here, the propylene-based polymer portion is preferably a propylene homopolymer with a melting point of 160°C or higher from the viewpoint of heat resistance, rigidity, etc. However, if the melting point is in the range of 160°C or higher, It may also be a copolymer with a small amount of α-olefin such as ethylene or 1-butene.

It may also contain an ethylene polymer as a subcomponent. Examples include high-density polyethylene, linear low-density polyethylene, and low-density polyethylene, and by including the above-mentioned ethylene polymer, the low-temperature impact resistance is improved by increasing the component with a glass transition point lower than that of polypropylene. By finely dispersing the polyethylene component more uniformly in the polypropylene, the yuzu skin resistance can be improved.

The content of the above ethylene polymer can be adjusted within the range of the xylene soluble CXS amount of the polypropylene film for retort packaging of the present invention, but if the above ethylene polymer is contained, the film becomes xylene soluble. The intrinsic viscosity ([η]CXS) of CXS tends to decrease, and when Δ[η] is less than 0.7, the surface roughness [Ra] decreases, blocking property deteriorates, and bag making becomes difficult. When doing so, the sealants may block each other, resulting in poor opening of the bag.

The content of the ethylene polymer is preferably 10% by mass to 40% by mass, more preferably 30% by mass to 40% by mass. If the ethylene polymer content is less than 10% by mass, it is difficult to obtain the effects of yuzu skin resistance and low-temperature impact resistance, and if it exceeds 40% by mass, the sealing force may decrease.

The ethylene polymer preferably has a density in the range of 0.92 to 0.97 g/cm ³ . If the density of the ethylene polymer is less than 0.92 g/cm ³ , blocking resistance and sealing strength may deteriorate, and if it exceeds 0.97 g/cm ³ , low-temperature impact resistance may deteriorate. There are cases.
The lower the melt flow rate (hereinafter sometimes referred to as MFR) of the polyethylene polymer at 190° C. and a load of 21.18 N, the smoother the film tends to be. If the MFR is less than 10 minutes, the smoothness may deteriorate. On the other hand, if the MFR exceeds 30 g/10 minutes, the low-temperature impact resistance tends to deteriorate. preferable. More preferably, it is in the range of 1 to 20 g/10 minutes.

Here, yuzu skin is a phenomenon in which unevenness occurs on the film surface after encapsulating oily foods such as curry and retort sterilization, which is considered a problem in terms of appearance. The main cause of yuzu skin is when the oil contained in retort food penetrates and diffuses into the innermost CPP film, especially when the dispersed particle size of the rubber component in the film's constituent resin is large. It is thought that uneven swelling of the rubber component tends to cause uneven swelling, and as a result of the fine unevenness of the film caused by the uneven swelling of the rubber component, the appearance looks like citron skin.

The polypropylene film for retort packaging of the present invention may contain a propylene random copolymer having an MFR of 2 to 10 g/10 minutes at 230°C and a melting point of 130 to 150°C. A propylene-based random copolymer is a copolymer of propylene and at least one α-olefin. α-olefins include ethylene, butene, octene, etc., but ethylene and A propylene/ethylene random copolymer of the copolymer is preferred. The content of the propylene random copolymer is preferably in the range of 20% by mass to 30% by mass. If the content is less than 20% by mass, it is difficult to obtain the effect of increasing seal strength. If it exceeds 30% by mass, low-temperature impact resistance may deteriorate.

The polypropylene film for retort packaging of the present invention may contain 1 to 10% by mass of an ethylene/α-olefin copolymer elastomer.

If the content of the ethylene/α-olefin copolymer elastomer is less than 1% by mass, it is difficult to obtain low-temperature impact resistance effects, and if it exceeds 10% by mass, the sealing strength may decrease and The packaging bag may break when the sealing force decreases during heating.

The base layer (A) and sealing layer (B) of the polypropylene composite film for retort packaging of the present invention include propylene random copolymer having an MFR of 2 to 10 g/10 minutes at 230°C and a melting point of 130 to 150°C. It may also contain a polymer.

The above-mentioned propylene-based random copolymer is a copolymer of propylene and at least one α-olefin. Examples of the α-olefin include ethylene, butene, and octene. A propylene/ethylene random copolymer copolymer is preferred. The polypropylene composite film for retort packaging of the present invention includes an ethylene/α-olefin copolymer elastomer in the base layer (A) and sealing layer (B). may be contained in an amount of 1 to 10% by mass. If the content of the ethylene/α-olefin copolymer elastomer is less than 1% by mass, it is difficult to obtain low-temperature impact resistance effects, and if it exceeds 10% by mass, the sealing strength may decrease and The packaging bag may break when the sealing force decreases during heating.

The Vicat softening point of the ethylene/α-olefin copolymer elastomer is preferably 50°C or more and 90°C or less. If the Vicat softening point is less than 50°C, the sealing strength at high temperatures will decrease and the packaging bag may break.If it exceeds 90°C, the sealing strength at high temperatures will become stronger, and in areas that are not ventilation ports. This may result in steaming.

The above ethylene/α-olefin elastomer is preferably a low-crystalline or amorphous copolymer elastomer, which is a random copolymer of 50 to 90% by mass of ethylene as the main component and α-olefin as a comonomer. Specifically, those produced using metallocene catalysts are preferred.
As the α-olefin, those having 3 to 10 carbon atoms such as propylene, 1-butene, 1-hexene, 1-octene, etc. can be used, and specific α-olefin elastomers include ethylene-propylene random copolymer. , ethylene/butene random copolymer, ethylene/octene random copolymer, etc. Among them, ethylene/propylene random copolymer or ethylene/butene random copolymer can be preferably used.

The MFR of the above ethylene/α-olefin elastomer is 0.3 to 6 g/10 at 190°C and under a load of 21.18N from the viewpoint of miscibility with the propylene/ethylene block copolymer and blocking resistance. A range of minutes is preferred.　

The polypropylene film for retort packaging of the present invention preferably has a thickness of 20 to 150 μm, more preferably 40 to 100 μm. If the film thickness is less than 20 μm, the heat sealing force may be insufficient, and if it exceeds 150 μm, lamination processability may deteriorate and costs may increase.

Other mechanical properties of the polypropylene film for retort packaging of the present disclosure, such as elongation at 23°C, yield stress, stress at break, and Young's modulus, based on JIS K 7127:1999, are also determined according to the present disclosure. Improvements can be made by using polypropylene compositions. For example, the elongation at break is preferably 400% or more and 900% or less. On the other hand, the yield point stress is preferably 10 MPa or more and 30 MPa or less, and the breaking point stress is preferably 10 MPa or more. Young's modulus is preferably 300 MPa or more.

The thickness ratio of the base layer (A) and the sealing layer (B) of the polypropylene composite film for retort packaging of the present invention is preferably 9:1 to 3:1, which allows for both sealing performance and low-temperature impact resistance. becomes. Other mechanical properties of the polypropylene composite film for retort packaging of the present invention, such as elongation at 23°C, yield stress, stress at break, and Young's modulus based on JIS K 7127:1999, are also disclosed in the present disclosure. can be improved by the use of polypropylene compositions. For example, the elongation at break is preferably 400% or more and 900% or less. On the other hand, the yield point stress is preferably 10 MPa or more and 30 MPa or less, and the breaking point stress is preferably 10 MPa or more. Young's modulus is preferably 300 MPa or more.

The center line average surface roughness (Ra) of the polypropylene film for retort packaging of the present invention is such that the center line average surface roughness (Ra) of the film surface in the direction perpendicular to the film flow direction (TD direction) is 0.15 μm or more. The thickness is preferably 0.35 μm or less. When Ra is less than 0.15 μm, blocking resistance may deteriorate, and when Ra exceeds 0.35 μm, sealing force may decrease.

The polypropylene film for retort packaging of the present invention may contain an antioxidant, a heat stabilizer, a neutralizing agent, an antistatic agent, a hydrochloric acid absorbent, an anti-blocking agent, a lubricant, etc., to the extent that the purpose of the present invention is not impaired. Can be done. These additives may be used alone or in combination of two or more.

Specific examples of antioxidants include 2,6-di-t-butylphenol (BHT), n-octadecyl-3-(3',5'-di-t-butyl-4 '-Hydroxyphenyl) propionate (“Irganox” 1076, “Sumilizer” BP-76), tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane (“Irganox” "1010," "Sumilizer" BP-101), tris(3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate ("Irganox" 3114, Mark AO-20), and the like.

As phosphite-based (phosphorus-based) antioxidants, tris(2,4-di-t-butylphenyl) phosphite (“Irgafos” 168, Mark 2112), tetrakis(2,4-di-t-butylphenyl) -4-4'-biphenylene-diphosphonite ("Sandstab" P-EPQ), bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite ("Ultranox" 626, Mark PEP-24G), distearyl Examples include pentaerythritol diphosphite (Mark PEP-8).

Among them, 6-[3-(3-t-butyl-4-hydroxy-5-methyl)propoxy]-2,4,8,10-tetra- has both hindered phenol and phosphite functions. t-Butyldibenz[d,f][1,3,2]-dioxaphosphepine (“Sumilizer” GP) and 2[1-2-hydroxy-3,5-di-t-pentylphenyl acrylate ] Ethyl]-4,6-di-t-pentylphenyl ("Sumilizer" GS) is preferred, and in particular, the combination of the two is particularly effective in suppressing the decomposition of CXS, which is soluble in xylene at 20°C, during film formation. It is preferable because it greatly contributes to achieving both low-temperature impact resistance and blocking resistance. If the decomposition of such xylene soluble portion CXS is promoted, blocking resistance may deteriorate.

The amount of antioxidant added may be set as appropriate in the range of 100 to 10,000 ppm, although it depends on the type of antioxidant used.

As the neutralizing agent, hydrotalcite compounds, calcium hydroxide, etc. are preferable for reducing smoke generation during film formation.

The polypropylene film for retort packaging of the present invention is produced by using a single-screw or twin-screw melt extruder. The kneaded product obtained by mixing the combined elastomer and the ethylene polymer is filtered through a filter and extruded, compounded by a feed block method, pinol method, multi-manifold method, etc., and then processed into a film from a T-shaped die or an annular die. It can be preferably manufactured by extrusion. The temperature of the molten polymer extruded from a melt extruder is usually 200 to 300°C, but to prevent the decomposition of the polymer, the intrinsic viscosity [η]CXS of the xylene-soluble part CXS of the polypropylene film at 20°C is 2.5 dl/ g to 3.0 dl/g, the intrinsic viscosity [η]CXIS of the xylene-insoluble part is 1.6 dl/g to 2.2 dl/g, and the difference in the intrinsic viscosity Δ[ between the xylene-soluble part CXS and the xylene-insoluble part CXIS] η] ([η]CXS - [η]CXIS) In order to obtain a film having a range of 0.7 or more and less than 1.2, the temperature is preferably 220 to 270°C.　

The polypropylene composite film for retort packaging of the present invention is produced by using a single-screw or twin-screw melt extruder to produce a raw material containing polypropylene resin as the main component from two extruders, and adding ethylene and ethylene as a subcomponent. A kneaded product obtained by mixing an α-olefin copolymer elastomer, an ethylene polymer, and a propylene α-olefin random copolymer is filtered and extruded as a base layer (A) and a sealing layer (B), and then fed. It can be preferably manufactured by compounding by a block method, pinol method, multi-manifold method, etc., and extruding it into a film form from a T-shaped die or an annular die. The temperature of the molten polymer extruded from a melt extruder is usually 200 to 300°C, but to prevent polymer decomposition, the intrinsic viscosity [η]CXS of the xylene-soluble part CXS at 20°C of the polypropylene composite film is 2.5 dl. /g or more and 3.0 dl/g or less, the intrinsic viscosity [η]CXIS of the xylene-insoluble part is 1.6 dl/g or more and 2.2 dl/g or less, and the intrinsic viscosity difference Δ between the xylene-soluble part CXS and the xylene-insoluble part CXIS In order to obtain a film in which the range of [η] ([η]CXS - [η]CXIS) is 0.7 or more and less than 1.2, the temperature is preferably 220 to 270°C.

A film extruded from a T-die by a method generally called the T-die method is brought into contact with a cooling roll set at a constant temperature of 20 to 65°C, cooled and solidified, and then wound up. When extruding from an annular die, bubbles are generally formed by a method called an inflation method, the bubbles are cooled and solidified, and then wound up in the form of a non-stretched film.

In order to laminate the polypropylene film for retort packaging of the present invention with other base materials that are heat-resistant base materials, one side is subjected to corona discharge treatment, which is usually carried out industrially, or corona discharge treatment under a nitrogen or carbon dioxide atmosphere. It is preferable to perform a surface treatment such as , plasma treatment, or ozone treatment to make the wettability index 37 mN/m or more.

In order to laminate the polypropylene composite film for retort packaging of the present invention with another base material that is a heat-resistant base material, the base layer (A) side is subjected to corona discharge treatment, nitrogen or carbon dioxide gas, which is usually carried out industrially. It is preferable to perform a surface treatment such as corona discharge treatment, plasma treatment, or ozone treatment in an atmosphere so that the wettability index is 37 mN/m or more.　

Specifically, the retort packaging material of the present invention includes a biaxially oriented polyamide film, a biaxially oriented polyester film (especially PET) as a heat-resistant base material layer on the corona-treated side of the polypropylene film for retort packaging of the present invention. , biaxially oriented polybutylene terephthalate film, biaxially oriented polypropylene film (OPP), metal foil (aluminum foil), metallized biaxially oriented polyamide film, metallized biaxially oriented polyester film (among them evaporated PET), metallized It is preferable that it is a laminate in which at least one layer selected from the group consisting of an axially oriented polybutylene terephthalate film, a metallized biaxially oriented polypropylene film (evaporated OPP), and a printing paper is laminated. Typical laminate configurations of these are PET/aluminum foil/polypropylene film, PET/ON/aluminum foil/polypropylene film, PET/aluminum foil/ON/polypropylene film, and laminates used for microwave ventilation. Examples include ON/polypropylene film, PET/vapor-deposited ON/polypropylene film, ON/vapor-deposited PET/polypropylene-based film, vapor-deposited PET/PET/polypropylene-based film, PET/vapor-deposited PET/polypropylene-based film, vapor-deposited PET/polypropylene-based film. The film is a vapor-deposited OPP/polypropylene film. As a manufacturing method for such a laminate, the usual dry lamination method in which the films constituting the laminate are laminated with an adhesive or the extrusion lamination method using an adhesive resin can be suitably employed, but if necessary, the polypropylene resin composition may be directly added to the polypropylene resin composition. A method of extruding and laminating can also be adopted.

These laminates are used by being made into flat bags, standing pouches, etc., using the non-corona-treated surface of the polypropylene film as the inner surface of the bag.

The laminated structure of these laminates has the characteristics required for packaging bags (e.g., barrier performance to meet the shelf life of the food to be packaged, size and low-temperature impact resistance that can accommodate the mass of the contents, visibility of the contents, etc.) be selected accordingly.

Hereinafter, the present invention will be specifically explained with reference to Examples, but the scope of the present invention is not limited thereto. Moreover, the measured values of each evaluation item in the detailed explanation of the present invention and the examples were measured by the following method.

(1) Content of 20° C. xylene soluble portion CXS After completely dissolving 5 g of the film and polymer in 500 ml of boiling xylene (grade 1 manufactured by Kanto Kagaku Co., Ltd.), the temperature is lowered to 20° C. and left for 4 hours or more. Thereafter, this was filtered into a precipitate and a solution, and separated into a xylene soluble part and a xylene insoluble part. The mass of the xylene-insoluble portion was determined by drying the precipitated portion at 70° C. under reduced pressure, and then measuring the mass at 23° C. to determine the content (% by mass). Moreover, the content (mass %) of the xylene soluble portion CXS was determined by drying the filtrate to dryness at 70° C. under reduced pressure, and then measuring its mass.

(2) Intrinsic viscosity of xylene-insoluble part CXIS and soluble part CXS of film and polymer Using the sample separated by the above method, measurement was performed in tetralin at 135°C using an Ubbelohde viscometer.

(3) Melt flow rate (MFR)
According to JIS K-7210-1999, the temperature of propylene resin is 230℃, the temperature of ethylene polymer, ethylene/α-olefin copolymer, and ethylene/α-olefin copolymer elastomer is 190℃, and the load is 21.18N. Measured at

(4) Density Measured using a density gradient tube measurement method based on JIS K-7112-1999.

(5) Blocking resistance Prepare a film sample with a width of 30 mm and a length of 100 mm, overlap the sealing layers in an area of 30 mm x 40 mm, apply a load of 500 g/12 cm ² , and store in an oven at 80°C for 24 hours. After the heat treatment, the film was left in an atmosphere of 23°C and 65% humidity for 30 minutes or more, and then the shear peeling force was measured at a tensile rate of 300 mm/min using Tensilon manufactured by Orientech. In this measurement method, if the shear peeling force was 20 N/12 cm ² or less, it was evaluated as good blocking resistance, and if it exceeded 20 N/12 cm ² , it was evaluated as poor blocking resistance.

(6) Center line average surface roughness (Ra)
Using a fully automatic micro-shape measuring machine (SURFCORDER ET4000A) manufactured by Kosaka Laboratory Co., Ltd., the measurement direction was perpendicular to the film flow direction (TD) according to the measurement method specified in JIS-B-0601-1982. The film surface was measured.

(7) Film Thickness and Thickness Structure The film thickness was measured at 10 arbitrary locations on the film using a dial gauge according to JIS K7130 (1992) A-2 method. The average value was taken as the film thickness.

The thickness of each layer of the composite film can be determined by embedding the composite film in epoxy resin, cutting out a cross section of the film with a microtome, and observing the cross section with a scanning electron microscope at 3,000x magnification. Calculated.

(8) Low-temperature impact resistance A transparent vapor-deposited PET film with a thickness of 12 μm and the film to be evaluated were laminated in the following order using an ordinary dry lamination method using a urethane adhesive, aged at 40°C for 3 days, and then A laminate of the following composition was created.
Laminate structure: Transparent vapor-deposited PET/adhesive/film The above two laminates were placed with the film to be evaluated on the inner surface of the bag using a Fuji Impulse OPL-450 electric heating temperature control sealer. The bag was sealed at a heating temperature of 180° C., a heating time of 1.0 seconds, and a cooling drop temperature of 180° C., and a packaging bag having a bag size of MD: 140 mm x TD: 205 mm was prepared. After filling this packaging bag with 400 mL of saline solution having a concentration of 0.1%, it is sealed and sealed under the same conditions as above, and retorted at 130° C. for 30 minutes. Next, after storing the retorted bag in a refrigerator at 0°C for 24 hours, it was taken out from the refrigerator and continuously dropped from a height of 1.2 m onto a flat floor in an atmosphere of 23°C (n 20 pieces), and record the number of times until the bag breaks. In this evaluation method, when the average value of n number of 20 samples is 5 times or more, the low-temperature impact resistance is considered to be good.

(9) Yuzu skin resistance After filling the packaging bag prepared in (8) with commercially available retort curry (retort curry "Kukure Curry", dry, manufactured by House Foods Co., Ltd.), seal it under the same conditions as above. Immediately after the laminate was sealed and retorted at 130° C. for 30 minutes, the occurrence of unevenness on the surface of the laminate was visually determined. Rank 1 for those with no unevenness, Rank 2 for those with slight unevenness, Rank 3 for mild unevenness, Rank 4 for those with obvious unevenness, and Rank 4 for those with severe unevenness. was evaluated as rank 5. According to this evaluation method, grades 1 to 3 indicate practicality and good yuzu skin resistance, and are rated as "○". Others were marked "×".

(10) Heat sealing strength Two films of the same laminate as in item (8) were sealed together using a flat plate heat sealer, with an upper plate sealing temperature of 230°C (lower plate: 80°C) and a sealing pressure of 2kg/cm ² . The sample heat-sealed for 1 second was retorted at 130°C for 30 minutes, and then cooled to 23°C. Thereafter, using Tensilon manufactured by Orientech Co., Ltd., the heat seal strength of this sample was measured in an atmosphere of 23° C. and in an oven at 100° C. at a tensile speed of 300 mm/min. According to this measurement method, if the heat seal strength at 23°C is 40N/15mm or more, it can be used well in normal retort applications, and if it is in the range of 8N/15mm or more and 15N/15mm or less in a 100°C oven, When heating a retort food packaging pouch in a microwave oven, it is possible to both protect the contents and allow vapor to pass through, and it can be used satisfactorily when heated in a microwave oven.

(11) Bending whitening resistance After retorting the film alone at 130°C for 30 minutes, using an MIT bending tester manufactured by Toyo Seiki Seisakusho, the sample width was 10 mm, the bending angle was 135 degrees (left and right), and the load was 5.04 N. After bending 100 times, the whitening condition of the bent portion was visually determined (n number of 5 pieces). Rank 1 for those that do not whiten at all, rank 2 for those that whiten slightly, rank 3 for those that whiten mildly, rank 4 for those that whiten clearly, and rank 4 for those that whiten and the curved part becomes white and tight linear. It was evaluated as 5. In this evaluation method, ranks 1, 2, and 3 were evaluated as having good flex whitening resistance, and were rated "○," and ranks 4 and 5 were rated as poor flex whitening resistance, and were rated "x."

(12) Young's modulus in a -10°C atmosphere Based on JIS K 7127:1999, this sample was measured in a -10°C atmosphere using Tensilon manufactured by Orientech. The Young's modulus was measured 5 times each in MD and TD, and the average value of the 10 measurements was taken as the "Young's modulus in a -10°C atmosphere."

The various raw material compositions and raw material formulations used in the present invention are described below. Further, the film properties and the properties of the laminate depending on the raw material formulation are summarized in Tables 1 and 2.

For the propylene/ethylene block copolymer, the polymerization conditions were changed to change the content of xylene insoluble part CXIS and xylene soluble part CXS at 20°C, its intrinsic viscosity [η]CXIS, [η]CXS, and melt flow rate. The following resin was used.

(1) Propylene/ethylene block copolymer (a1)
MFR: 1.1g/10min
CXS amount: 18.0% by mass
[η]CXIS: 1.9dl/g
[η]CXS: 3.2dl/g
Melting point (Tm): 162°C.

(2) Propylene/ethylene block copolymer (a2)
MFR: 2.0g/10min
CXS amount: 12.0% by mass
[η]CXIS: 1.9dl/g
[η]CXS: 2.4dl/g
Melting point (Tm): 162°C.

(3) Propylene/ethylene block copolymer (a3)
MFR: 1.0g/10min
CXS amount: 11.0% by mass
[η]CXIS: 2.4dl/g
[η]CXS: 3.0dl/g
Melting point (Tm): 162°C.

The following commercially available homopolypropylene polymer was used.

(1) Homopolypropylene polymer (a4)
“Wintec TM (registered trademark)” “WFX6” manufactured by Nippon Polypro Co., Ltd.
MFR: 2.0g/10min.

The following commercially available polypropylene α-olefin random copolymer was used.

(1) Polypropylene-ethylene random copolymer (b1)
“Prime Polypro (registered trademark)” “E222” manufactured by Prime Polymer Co., Ltd.
MFR: 1.5g/10min.

The following commercially available polyethylene polymer was used.

(1) PE (c1)
Linear low-density polyethylene “Sumikasen (registered trademark)” E “FV205” manufactured by Sumitomo Chemical Co., Ltd.
MFR: 2.2g/min
Density: 0.921g/cm ³ .

The following commercially available ethylene/α-olefin copolymer elastomer was used.

(1) Ethylene/α-olefin copolymer elastomer (d1)
“Tafmer (registered trademark)” “XM-7080” manufactured by Mitsui Chemicals, Inc.
MFR: 3.0g/10min
Vicat softening point: 86°C.

[Example 1]
50% by mass of polypropylene resin, 20% by mass of (b1), 30% by mass of (c1), and 300ppm of "Sumilizer" GP and 750ppm of "Sumilizer" GS as antioxidants were mixed, and the temperature of one unit was 260%. It is melt-kneaded by feeding into a twin-screw extruder temperature-controlled at ℃, then extruded from a T-die at 60 m/min at 250℃, cooled and solidified by contacting with a cooling roll at 45℃, and one side is coated with corona. A polypropylene film with a thickness of 70 μm was obtained by discharge treatment.

Table 1 shows the properties of the obtained polypropylene film and the properties of the laminate in which the polypropylene film was laminated with a heat-resistant base layer of transparent vapor-deposited PET having a thickness of 12 μm. The polypropylene film of Example 1 satisfies all the required properties of the present invention, and the Young's modulus in a -10°C atmosphere, the heat seal strength in a 23°C atmosphere, and the seal strength in a 100°C atmosphere meet the present invention. It met all the required properties, had excellent yuzu skin resistance, whitening resistance, and low-temperature impact resistance, and had sufficient performance for retort use. Furthermore, when we heated the sample used in the evaluation of yuzu skin resistance in (9) above in a microwave oven to check its vapor permeability, we found that the packaging bag broke due to the steaming and the contents were scattered and leaked. Never happened.

[Example 2]
A polypropylene film with a thickness of 70 μm was obtained in the same manner as in Example 1, except that the polypropylene resin was changed to 60% by mass for (a1), 10% by mass for (b1), and 30% by mass for (c1).

Table 1 shows the properties of the obtained polypropylene film and the properties of a laminate in which the polypropylene film was laminated with a heat-resistant base layer of transparent vapor-deposited PET having a thickness of 12 μm. The polypropylene film of Example 2 satisfies all the properties required by the present invention in terms of Young's modulus in a -10°C atmosphere, heat seal strength in a 23°C atmosphere, and seal strength in a 100°C atmosphere, and is resistant to yuzu skin. It had excellent hardness, whitening resistance, and impact resistance, and had sufficient performance for retort use. Furthermore, when we heated the sample used in the evaluation of yuzu skin resistance in (9) above in a microwave oven to check its vapor permeability, we found that the packaging bag broke due to the steaming and the contents were scattered and leaked. Never happened.

[Example 3]
Polypropylene with a thickness of 70 μm was prepared in the same manner as in Example 1, except that the polypropylene resin was changed to (a3) 40% by mass, (b1) 20% by mass, (c1) 30% by mass, and (a4) 10% by mass. A series film was obtained.

Table 1 shows the properties of the obtained polypropylene film and the properties of a laminate in which the polypropylene film was laminated with a heat-resistant base layer of transparent vapor-deposited PET having a thickness of 12 μm. The polypropylene film of Example 3 satisfies all the properties required by the present invention in Young's modulus in a -10°C atmosphere, heat seal strength in a 23°C atmosphere, and seal strength in a 100°C atmosphere, and has yuzu skin resistance. It had excellent hardness, whitening resistance, and impact resistance, and had sufficient performance for retort use. Furthermore, when we heated the sample used in the evaluation of yuzu skin resistance in (9) above in a microwave oven to check its vapor permeability, we found that the packaging bag broke due to the steaming and the contents were scattered and leaked. Never happened.

[Example 4]
Polypropylene with a thickness of 70 μm was prepared in the same manner as in Example 1, except that the polypropylene resin was changed to (a1) 45% by mass, (b1) 20% by mass, (c1) 30% by mass, and (d1) 5% by mass. A series film was obtained.

Table 1 shows the properties of the obtained polypropylene film and the properties of a laminate in which the polypropylene film was laminated with a heat-resistant base layer of transparent vapor-deposited PET having a thickness of 12 μm. The polypropylene film of Example 4 satisfies all the properties required by the present invention in Young's modulus in a -10°C atmosphere, heat seal strength in a 23°C atmosphere, and seal strength in a 100°C atmosphere, and has yuzu skin resistance. It had excellent hardness, whitening resistance, and impact resistance, and had sufficient performance for retort use. Furthermore, when we heated the sample used in the evaluation of yuzu skin resistance in (9) above in a microwave oven to check its vapor permeability, we found that the packaging bag broke due to the steaming and the contents were scattered and leaked. Never happened.

[Example 5]
A polypropylene film with a thickness of 70 μm was obtained in the same manner as in Example 1, except that the polypropylene resin was changed to 45% by mass of (a1), 20% by mass of (b1), and 35% by mass of (c1).

Table 1 shows the properties of the obtained polypropylene film and the properties of a laminate in which the polypropylene film was laminated with a heat-resistant base layer of transparent vapor-deposited PET having a thickness of 12 μm. The polypropylene film of Example 5 satisfies all the properties required by the present invention in Young's modulus in a -10°C atmosphere, heat seal strength in a 23°C atmosphere, and seal strength in a 100°C atmosphere, and has yuzu skin resistance. It had excellent hardness, whitening resistance, and impact resistance, and had sufficient performance for retort use. Furthermore, when we heated the sample used in the evaluation of yuzu skin resistance in (9) above in a microwave oven to check its vapor permeability, we found that the packaging bag broke due to the steaming and the contents were scattered and leaked. Never happened.　

[Example 6]
Base layer (A) polypropylene resin (a1) 60% by mass, (b1) 5% by mass, (c1) 35% by mass, and antioxidants "Sumilizer" GP 300ppm and "Sumilizer" GS 750ppm. , 55% by mass of (a1), 25% by mass of (b1), 20% by mass of (c1) as the polypropylene resin of the sealing layer (B), and 300 ppm of "Sumilizer" GP and 750 ppm of "Sumilizer" GS as antioxidants were mixed. Then, each layer was melted and kneaded by feeding it into a twin-screw extruder controlled at a temperature of 260°C, so that the thickness ratio of base material layer (A): sealing layer (B) = 4:1 was 250°C. After coextruding from a T-die at 60 m/min at 60 m/min at 45° C. and cooling and solidifying it by contacting it with a cooling roll at 45° C., one side was subjected to corona discharge treatment to form a base material layer (A) with a thickness of 56 μm and a sealing layer (B) with a thickness of 56 μm. A polypropylene composite film having a total thickness of 14 μm and 70 μm was obtained.

Table 1 shows the properties of the obtained polypropylene composite film and the properties of the laminate in which the polypropylene composite film was laminated with a heat-resistant base layer of transparent vapor-deposited PET having a thickness of 12 μm. The polypropylene composite film of Example 1 satisfies all the required properties of the present invention, and the Young's modulus in a -10°C atmosphere, the heat seal strength in a 23°C atmosphere, and the seal strength in a 100°C atmosphere are in accordance with the present invention. It met all of the required properties, had excellent yuzu skin resistance, whitening resistance, and low-temperature impact resistance, and had sufficient performance for retort use.

Furthermore, when we heated the sample used in the evaluation of yuzu skin resistance in (9) above in a microwave oven to check its vapor permeability, we found that the packaging bag broke due to the steaming and the contents were scattered and leaked. Never happened.

[Example 7]
(a1) 60% by mass, (b1) 5% by mass, (c1) 35% by mass as the polypropylene resin of the base layer (A), (a1) 60% by mass as the polypropylene resin of the sealing layer (B), ( A polypropylene composite film with a thickness of 70 μm was obtained in the same manner as in Example 1, except that b1) was changed to 15% by mass and (c1) was changed to 25% by mass.

Table 1 shows the properties of the obtained polypropylene composite film and the properties of the laminate in which the polypropylene composite film was laminated with a 12 μm thick transparent vapor-deposited PET heat-resistant base layer. The polypropylene composite film of Example 2 satisfies all the properties required by the present invention in terms of Young's modulus in a -10°C atmosphere, heat seal strength in a 23°C atmosphere, and seal strength in a 100°C atmosphere, and is resistant to yuzu. It had excellent skin properties, whitening resistance, and low-temperature impact resistance, and had sufficient performance for retort use.

[Example 8]
(a1) 45% by mass, (a4) 10% by mass, (b1) 5% by mass, (c1) 40% by mass as the polypropylene resin of the base layer (A), as the polypropylene resin of the sealing layer (B) ( A polypropylene composite film with a thickness of 70 μm was obtained in the same manner as in Example 1, except that a1) 45% by mass, (a4) 10% by mass, (b1) 20% by mass, and (c1) 25% by mass. Ta.

Table 1 shows the properties of the obtained polypropylene composite film and the properties of the laminate in which the polypropylene composite film was laminated with a 12 μm thick transparent vapor-deposited PET heat-resistant base layer. The polypropylene composite film of Example 3 satisfies all the properties required by the present invention in terms of Young's modulus in a -10°C atmosphere, heat seal strength in a 23°C atmosphere, and seal strength in a 100°C atmosphere, and is resistant to yuzu. It had excellent skin properties, whitening resistance, and low-temperature impact resistance, and had sufficient performance for retort use. Furthermore, when we heated the sample used in the evaluation of yuzu skin resistance in (9) above in a microwave oven to check its vapor permeability, we found that the packaging bag broke due to the steaming and the contents were scattered and leaked. Never happened.

[Example 9]
As the polypropylene resin of the base layer (A), (a1) 50% by mass, (b1) 5% by mass, (c1) 40% by mass, (d1) 5% by mass, as the polypropylene resin of the sealing layer (B) ( A polypropylene composite film with a thickness of 70 μm was obtained in the same manner as in Example 1, except that a1) 55% by mass, (b1) 20% by mass, (c1) 20% by mass, and (d1) 5% by mass. Ta.

Table 1 shows the properties of the obtained polypropylene composite film and the properties of the laminate in which the polypropylene composite film was laminated with a 12 μm thick transparent vapor-deposited PET heat-resistant base layer. The polypropylene composite film of Example 4 satisfies all the properties required by the present invention in terms of Young's modulus in a -10°C atmosphere, heat seal strength in a 23°C atmosphere, and seal strength in a 100°C atmosphere, and is resistant to yuzu. It had excellent skin properties, whitening resistance, and low-temperature impact resistance, and had sufficient performance for retort use.

[Example 10]
(a1) 50% by mass, (b1) 10% by mass, (c1) 40% by mass as the polypropylene resin of the base layer (A), (a1) 50% by mass as the polypropylene resin of the sealing layer (B), ( A polypropylene composite film with a thickness of 70 μm was obtained in the same manner as in Example 1 except that b1) was changed to 25% by mass and (c1) was changed to 25% by mass.

Table 1 shows the properties of the obtained polypropylene composite film and the properties of the laminate in which the polypropylene composite film was laminated with a 12 μm thick transparent vapor-deposited PET heat-resistant base layer. The polypropylene composite film of Example 5 satisfies all the properties required by the present invention in terms of Young's modulus in a -10°C atmosphere, heat seal strength in a 23°C atmosphere, and seal strength in a 100°C atmosphere, and is resistant to yuzu. It had excellent skin properties, whitening resistance, and low-temperature impact resistance, and had sufficient performance for retort use.

[Comparative example 1]
Polypropylene with a thickness of 70 μm was prepared in the same manner as in Example 1, except that the polypropylene resin was changed to (a1) 50% by mass, (b1) 20% by mass, (c1) 25% by mass, and (d1) 5% by mass. A series film was obtained.

Table 2 shows the properties of the obtained polypropylene film and the properties of the laminate in which the polypropylene film was laminated with transparent vapor-deposited PET having a thickness of 12 μm as a heat-resistant base layer. In terms of film properties, since the amount of xylene-soluble portion CXS exceeds the upper limit, the heat sealability in an atmosphere of 23°C and 100°C is low, and the sample used in the evaluation of yuzu skin resistance in (9) above is When we checked the vapor permeability by heating it in a microwave oven, we found that the packaging bag would tear and the contents would scatter or leak.

[Comparative example 2]
Same as Example 1 except that the polypropylene resin was changed to (a2) 60% by mass, (b1) 20% by mass, (c1) 20% by mass, and the antioxidants were changed to 750ppm of Irganox1010 and 300ppm of RIANOX168. A polypropylene film with a thickness of 70 μm was obtained.

Table 2 shows the properties of the obtained polypropylene film and the properties of the laminate in which the polypropylene film was laminated with transparent vapor-deposited PET having a thickness of 12 μm as a heat-resistant base layer. Regarding the film properties, [η]CXIS was less than the lower limit of the present invention, so the blocking shear force was high.

[Comparative example 3]
A polypropylene film having a thickness of 70 μm was obtained in the same manner as in Example 1, except that the polypropylene resin was changed to 50% by mass of (a1), 20% by mass of (b1), and 30% by mass of (c1).

Table 2 shows the properties of the obtained polypropylene film and the properties of the laminate in which the polypropylene film was laminated with transparent vapor-deposited PET having a thickness of 12 μm as a heat-resistant base layer. Regarding the film properties, [η]CXS exceeded the upper limit of the present invention, so the yuzu skin resistance and whitening resistance were very poor.

[Comparative example 4]
Same as Example 1 except that the polypropylene resin was changed to (a2) 50% by mass, (b1) 20% by mass, (c1) 30% by mass, and the antioxidants were changed to 750ppm of Irganox1010 and 300ppm of RIANOX168. A polypropylene film with a thickness of 70 μm was obtained.

Table 2 shows the properties of the obtained polypropylene film and the properties of the laminate in which the polypropylene film was laminated with transparent vapor-deposited PET having a thickness of 12 μm as a heat-resistant base layer. Regarding the film properties, [η]CXS is less than the lower limit of the present invention and Δ[η] is less than the lower limit, so the heat sealability at 23°C and 100°C atmosphere is too low. When we checked the vapor permeability of the samples used in the evaluation of yuzu skin resistance by heating them in a microwave oven, we found that the packaging bag was torn due to the vaporization, causing the contents to scatter or leak.

[Comparative example 5]
A polypropylene film with a thickness of 70 μm was obtained in the same manner as in Example 1, except that the polypropylene resins were changed to 70% by mass for (a1), 20% by mass for (b1), and 10% by mass for (c1).

Table 2 shows the properties of the obtained polypropylene film and the properties of the laminate in which the polypropylene film was laminated with transparent vapor-deposited PET having a thickness of 12 μm as a heat-resistant base layer. Regarding the film properties, [η]CXS exceeded the upper limit of the present invention, so the yuzu skin resistance and whitening resistance were very poor. In addition, since Δ[η] exceeded the upper limit, the heat sealability in 23℃ and 100℃ atmospheres became too high, so the sample used in the evaluation of yuzu skin resistance in (9) above was When we checked the vapor permeability by heating the bag, we found that it did not pass and the packaging bag tore, causing the contents to scatter or leak.

[Comparative example 6]
(a1) 50% by mass, (b1) 10% by mass, (c1) 30% by mass, (d1) 10% by mass as the polypropylene resin of the base layer (A), as the polypropylene resin of the sealing layer (B) ( A polypropylene composite film with a thickness of 70 μm was obtained in the same manner as in Example 1, except that a1) 50% by mass, (b1) 20% by mass, (c1) 25% by mass, and (d1) 5% by mass. Ta.

Table 2 shows the properties of the obtained polypropylene-based composite film and the properties of the laminate in which the polypropylene-based composite film was laminated with a transparent vapor-deposited PET having a thickness of 12 μm as a heat-resistant base layer. In terms of film properties, since the amount of xylene-soluble portion CXS exceeds the upper limit, the heat sealability in an atmosphere of 23°C and 100°C is low, and the sample used in the evaluation of yuzu skin resistance in (9) above is When we checked the vapor permeability by heating it in a microwave oven, we found that the packaging bag would tear and the contents would scatter or leak.

[Comparative Example 7]
Base layer (A) polypropylene resin (a2) 60% by mass, (b1) 10% by mass, (c1) 30% by mass, as antioxidants Irganox 1010 750ppm and RIANOX168 300ppm, sealing layer (B Example 1 except that the polypropylene resin (a1) was 55% by mass, (b1) 25% by mass, and (c1) 20% by mass, and the antioxidants were changed to 750ppm of Irganox1010 and 300ppm of RIANOX168. In the same manner as above, a polypropylene composite film having a thickness of 70 μm was obtained.

Table 2 shows the properties of the obtained polypropylene-based composite film and the properties of the laminate in which the polypropylene-based composite film was laminated with a transparent vapor-deposited PET having a thickness of 12 μm as a heat-resistant base layer. As for film properties, [η]CXIS was less than the lower limit of the present invention, so the blocking shear force was high and the low-temperature impact resistance was poor.

[Comparative example 8]
(a1) 65% by mass, (b1) 15% by mass, (c1) 20% by mass as the polypropylene resin of the base layer (A), (a1) 70% by mass as the polypropylene resin of the sealing layer (B), ( A polypropylene composite film with a thickness of 70 μm was obtained in the same manner as in Example 1, except that b1) was changed to 25% by mass and (c1) was changed to 5% by mass.

Table 2 shows the properties of the obtained polypropylene-based composite film and the properties of the laminate in which the polypropylene-based composite film was laminated with a transparent vapor-deposited PET having a thickness of 12 μm as a heat-resistant base layer. Regarding the film properties, [η]CXS exceeds the upper limit of the present invention, so the yuzu skin resistance and whitening resistance are very poor, and the sealing strength at 100°C is high, so it cannot be heated in a microwave oven. When we checked the vapor permeability, we found that the contents usually scattered or leaked in areas other than the vapor vents.

[Comparative Example 9]
Base layer (A) polypropylene resin (a2) 55% by mass, (b1) 5% by mass, (c1) 40% by mass, as antioxidants Irganox 1010 750ppm and RIANOX 168 300ppm, sealing layer (B Example 1 except that the polypropylene resin (a1) was changed to 50% by mass, (b1) was 25% by mass, and (c1) was 25% by mass, and the antioxidants were changed to 750ppm of Irganox1010 and 300ppm of RIANOX168. In the same manner as above, a polypropylene composite film having a thickness of 70 μm was obtained.

Table 2 shows the properties of the obtained polypropylene-based composite film and the properties of the laminate in which the polypropylene-based composite film was laminated with a transparent vapor-deposited PET having a thickness of 12 μm as a heat-resistant base layer. Regarding the film properties, since [η]CXS is less than the lower limit of the present invention and Δ[η] is less than the lower limit, the average surface roughness Ra of the sealing layer (B) is small and the blocking resistance is poor. ℃ and 100℃ atmosphere became too low, so the sample used in the evaluation of yuzu skin resistance in (9) above was heated in a microwave oven to check its vapor permeability. There were cases where the packaging bag broke and the contents were scattered or leaked.

[Comparative Example 10]
(a1) 85% by mass, (b1) 5% by mass, (c1) 10% by mass as the polypropylene resin of the base layer (A), (a1) 65% by mass as the polypropylene resin of the sealing layer (B), ( A polypropylene composite film with a thickness of 70 μm was obtained in the same manner as in Example 1, except that b1) was changed to 30% by mass and (c1) was changed to 5% by mass.

Table 2 shows the properties of the obtained polypropylene-based composite film and the properties of the laminate in which the polypropylene-based composite film was laminated with a transparent vapor-deposited PET having a thickness of 12 μm as a heat-resistant base layer. Regarding the film properties, [η]CXS exceeded the upper limit of the present invention, so the yuzu skin resistance and whitening resistance were very poor. In addition, since Δ[η] exceeded the upper limit, the heat sealability in 23℃ and 100℃ atmospheres became too high, so the sample used in the evaluation of yuzu skin resistance in (9) above was When we checked the vapor permeability by heating the bag, we found that it did not pass and the packaging bag tore, causing the contents to scatter or leak.

The present invention has excellent heat sealability and low-temperature impact resistance as a sealant for packaging bags, and can be used in a non-powder form due to its excellent blocking resistance.It can also be suitably used for retort applications due to its excellent resistance to yuzu skin. Furthermore, when a packaging bag filled with retort food is heated in a microwave oven or the like, the sealing force is reduced and steam is passed, thereby preventing the packaging bag from tearing and the contents from scattering or leaking. This makes it suitable for use in laminates for retort foods for heating in microwave ovens.

Claims

The intrinsic viscosity [η]CXS of the 20° C. xylene soluble portion CXS of the film is 2.5 dl/g or more and 3.0 dl/g or less, the amount of the 20° C. xylene soluble portion CXS is 15.0% by mass or less,
The intrinsic viscosity [η] of the xylene-insoluble part CXIS at 20°C is 1.6 dl/g or more and 2.2 dl/g or less,
The intrinsic viscosity difference Δ[η] ([η]CXS−[η]CXIS) between the 20°C xylene soluble part CXS and the 20°C xylene insoluble part CXIS is 0.7 or more and less than 1.2,
A polypropylene film for retort packaging, which has an average Young's modulus in the machine direction (MD) and transverse direction (TD) of less than 1000 MPa in a -10°C atmosphere.
The polypropylene film for retort packaging according to claim 1, wherein the centerline average surface roughness (Ra) on at least one surface is 0.15 μm or more and 0.35 μm or less.
The polypropylene film for retort packaging according to claim 1, which has a blocking shear force of 20 N/12 cm 2 or less at 80°C.
A laminate in which the polypropylene film for retort packaging according to claim 1 is laminated with at least one heat-resistant base material layer.
The heat-resistant base material layer is a biaxially oriented polyamide film, a biaxially oriented polyester film, a biaxially oriented polypropylene film, a metal foil, a metallized biaxially oriented polyamide film, a metallized biaxially oriented polyester film, a metallized biaxially oriented polypropylene. The laminate according to claim 4, comprising at least one layer selected from the group consisting of film and printed paper.
4. The polypropylene film for retort packaging of the laminate has a sealing strength of 8 N/15 mm or more and 15 N/15 mm or less in a 100° C. atmosphere after heat-sealing the surfaces of the polypropylene film for retort packaging and retorting at 130° C. for 30 minutes. 5. The laminate according to 5.
The surfaces of the polypropylene film for retort packaging of the laminate are heat-sealed at 190°C for the upper plate and 80°C for the lower plate, and the sealing strength in an atmosphere of 23°C after retort treatment at 130°C for 30 minutes is 40N/15mm or more. The laminate according to claim 4 or 5.
A polypropylene composite film for retort packaging comprising the polypropylene film for retort packaging according to claim 1 (hereinafter sometimes referred to as the seal layer (B)) and a base layer (A).
The polypropylene composite film for retort packaging according to claim 8, wherein the centerline average surface roughness (Ra) of the sealing layer (B) is 0.15 μm or more and 0.35 μm or less.
The polypropylene composite film for retort packaging according to claim 8, wherein the sealing layer (B) has a blocking shear force of 20 N/12 cm 2 or less at 80°C.
A laminate in which the polypropylene composite film for retort packaging according to claim 8 is laminated with at least one heat-resistant base material layer.
The heat-resistant base material layer is a biaxially oriented polyamide film, a biaxially oriented polyester film, a biaxially oriented polypropylene film, a metal foil, a metallized biaxially oriented polyamide film, a metallized biaxially oriented polyester film, a metallized biaxially oriented polypropylene. The laminate according to claim 11, comprising at least one layer selected from the group consisting of a film and a printing paper.
The sealing layers (B) of the polypropylene composite film for retort packaging of the laminate are heat-sealed together and the sealing strength in a 100°C atmosphere after being retorted at 130°C for 30 minutes is 8 N/15 mm or more and 15 N/15 mm or less. A laminate according to claim 11 or 12.
Seal strength in an atmosphere of 23°C after heat-sealing the sealing layers (B) of the polypropylene composite film for retort packaging of the laminate at 190°C on the upper plate and 80°C on the lower plate, and retorting at 130°C for 30 minutes. The laminate according to claim 11 or 12, wherein is 40 N/15 mm or more.