JP2020175652A - Polypropylene-based composite film and laminate using the same - Google Patents

Abstract

To provide a polypropylene-based composite film which can be used without incorporating a powder material since it is excellent in heat sealability and low-temperature impact resistance as a sealant of a packaging bag and is also excellent in blocking resistance, can be suitably used for retort applications since it is excellent in anti-orange peel skin properties, and can prevent breakage of a packaging bag to scatter or leak contents by lowering a seal force and making the steam pass when the packaging bag filled with a retort food product is heated with a microwave oven, and a packaging material using the same.SOLUTION: There is provided a polypropylene-based composite film in which a seal layer (B) is layered on at least one surface of a base material layer (A), in which the base material layer (A) is a resin composition containing 75-90 wt.% of a propylene-ethylene block copolymer (a) and 10-25 wt.% of linear low-density polyethylene (a2), the seal layer (B) contains 30-40 wt.% of a propylene-ethylene block copolymer (b1), 30-50 wt.% of a propylene-ethylene block copolymer (b2), 15-25 wt.% of homopolypropylene (b3), 3-10 wt.% of linear low-density polyethylene (b4) and 50-5,000 ppm of a crystal nucleating agent (b5), and (b1), (b2) and (b5) satisfy specific conditions.SELECTED DRAWING: None

Description

The present invention relates to a polypropylene-based composite film that can be suitably used for retort applications and a laminate using the same.

Conventionally, as a sealant film for retort packaging that is retort-sterilized at a high temperature of 120 ° C to 135 ° C, a non-stretched film containing a propylene / ethylene block copolymer as a main component (hereinafter, may be referred to as CPP) is used. It has been. Its main usage is polyethylene terephthalate stretched film (hereinafter sometimes referred to as PET), nylon stretched film (hereinafter sometimes referred to as ON), aluminum foil (hereinafter sometimes referred to as Al foil), etc. It is used by laminating with a laminated base material layer to form a laminate having a composition of PET / ON / Al foil / CPP, PET / Al foil / ON / CPP, or PET / Al foil / CPP, and then bag-making. That is. Further, the CPP constituting the innermost surface is required to have physical properties such as low temperature impact resistance, heat sealability, and blocking resistance.

In addition, with the spread of retort pouch foods in recent years, the level of demand for the appearance of packaging bags has increased, and it is possible to minimize the occurrence of fine uneven appearance, so-called loose skin, that occurs on the surface of the laminate after retort sterilization. It is desired, and for convenience when using a retort food packaging bag, it has a function of preventing the packaging bag from breaking and the contents from scattering or leaking by passing steam from the seal part when heating in a microwave oven. There is a request.

However, CPP for retort has poor slipperiness due to the limitation of lubricant addition, wrinkles occur in the film forming process and slitting process, and it can be stored for a long time as a packaging material laminated with other base materials or in a high temperature state in summer. When stored, a so-called blocking phenomenon occurs in which the CPP of the laminated body and the laminated base material layer adhere to each other, which makes it difficult to unwind the laminated film, lowers the bag making workability, and significantly lowers the content filling workability. there were.

In order to solve the above problems, a method of sprinkling a blocking inhibitor, for example, a powder such as starch having a water resistant surface treatment on a sealant to prevent blocking, a method of avoiding blocking by a so-called powdering method has been conventionally adopted. .. However, the powdering method is a factor that reduces the commercial value of the bag, such as spoiling the appearance of the bag or mixing it with the food filled with powder, which adversely affects the taste, and does not require powdering. , So-called non-powder, and a polypropylene-based film that can be suitably used for retort applications as a sealant for packaging materials or packaging bags has been strongly desired.

As a method for solving the above problem, in Patent Document 1, it is a laminated film in which a base material layer and a sealant layer are laminated, and the base material layer is formed by a multi-layer co-extrusion film formation, and the multi-layer co-extrusion product is produced. It has been proposed as a laminate in which the outermost layer of the film is a slippery layer containing a lubricant and / or an antiblocking agent, and a packaging container using the same, but since it contains an organic lubricant, it is a sealant. Factors that reduce the commercial value, such as the transfer of organic lubricant to the roll in the extrusion process, slitting process, and bag making process, which reduces productivity, and mixes with the food filled with the organic lubricant, which adversely affects the taste. It was.

In Patent Document 2, (1) medium density by a metallocene catalyst or a single-site catalyst having a density of 0.930 g / cm ³ or more, a vicat softening point of 105 to 125 ° C., and a melt flow rate in the range of 2 to 25 g / 10 minutes. A polyethylene composition consisting of 40% to 90% by weight of polyethylene and (2) 10% to 60% by weight of linear low-density polyethylene using a metallocene catalyst or a single-site catalyst having a density of 0.929 g / cm ³ or less. When forming a laminate layer on a base material by extrusion coating, the surface roughness Rz can be adjusted to 5 to 12 μm, the hole diameter can be reduced, and the processing can be performed using a cooling roll with a reduced number of holes without sprinkling powder. However, it was not suitable for high-retort applications (125 ° C to 135 ° C sterilization), which is the mainstream of retorts.

Further, in Patent Document 3, as a formulation for the purpose of low temperature impact resistance, yuzu skin, slipperiness, and non-powder for retort pouch, the base material layer is made of propylene / ethylene block copolymer + linear low density polyethylene and sealed. A two-layer laminated film of propylene / ethylene block copolymer + propylene / ethylene random copolymer + propylene polymer + linear low-density polyethylene has been proposed, but it is slippery compared to the conventional powdering method. In addition, when the retort food is heated in a microwave oven or the like, there is a problem that the steaming from the seal portion is insufficient and the packaging bag is torn and the contents are scattered or leaked.

Further, Patent Document 4 proposes a packaging bag having a structure in which a tape having a reduced sealing force when heated in a microwave oven or the like is inserted into a part of a sealing layer, but a laminating or bag making process. However, there is a problem that the yield of bag-making products is low and the cost is high.

Japanese Unexamined Patent Publication No. 2004-284126 Japanese Unexamined Patent Publication No. 2004-338147 Japanese Unexamined Patent Publication No. 2015-168151 Japanese Unexamined Patent Publication No. 2005-178813

Therefore, as a result of diligent studies in view of the problems of the prior art, the present inventors provide a polypropylene-based composite film that solves the above-mentioned problems and a laminate using the polypropylene-based composite film.

That is, the present invention is a film in which the seal layer (B) is laminated on at least one side of the base material layer (A), and the base material layer (A) is a propylene / ethylene block copolymer (a1). It is a resin composition containing 75 to 90% by weight and 10 to 25% by weight of linear low density polyethylene (a2), and the seal layer (B) contains 30 to 40% by weight of propylene / ethylene block copolymer (b1). %, 30-50% by weight of propylene / ethylene block copolymer (b2), 15-25% by weight of homopolypropylene (b3), 3-10% by weight of linear low-density polyethylene (b4), crystal nucleating agent. A polypropine-based composite film containing 50 to 5000 ppm of (b5), wherein the above (b1), (b2), and (b5) are resin compositions satisfying the following conditions.
Propylene / ethylene block copolymer (b1): Melt flow rate is 1 to 3 g / 10 minutes, the ratio of xylene insoluble part at 20 ° C. is 75 to 90% by weight, and the ultimate viscosity ([η] _H ) of the insoluble part is 1. .7 to 2.2 dl / g, the ratio of the xylene soluble part at 20 ° C. is 10 to 25% by weight, and the ultimate viscosity ([η] _EP ) of the soluble part is 2.5 to 3.5 dl / g.
Propylene / ethylene block copolymer (b2): Melt flow rate is 4 to 10 g / 10 minutes, the proportion of xylene insoluble part at 20 ° C. is 80 to 95% by weight, and the ultimate viscosity ([η] _H ) of the insoluble part is. 1.4 to 1.8 dl / g, the ultimate viscosity ([η] _EP ) of the soluble part is 1.5 to 2.0 dl / g.
Crystal nucleating agent (b5): At least one crystal nucleating agent selected from the group consisting of metal phosphates and metal dicarboxylic acid salts.

Further, the present invention is a laminate in which a heat-resistant base material layer, a gas barrier layer, and the polypropylene-based composite film described above are laminated in this order so that the seal layer (B) is on the opposite side of the heat-resistant base material layer. The peel strength after heat-sealing the surfaces of the seal layer (B) at 230 ° C. and then retorting at 130 ° C. for 30 minutes is 30 N / 15 mm or more in an atmosphere of 23 ° C., and 80 ° C. It is a laminated body of 1 to 10 N / 15 mm under the atmosphere of.

INDUSTRIAL APPLICABILITY The present invention can be used as a sealant for packaging bags without powder because it has excellent heat-sealing properties, low-temperature impact resistance, and blocking resistance, and can also be suitably used for retort pouch applications due to its excellent surface resistance. Furthermore, when the packaging bag filled with retort food is heated in a microwave oven or the like, the sealing force is reduced and the packaging bag is passed through, so that the packaging bag can be prevented from breaking and the contents from being scattered or leaking out. A polypropylene-based composite film and a laminate using the same can be provided.

Hereinafter, the polypropylene-based composite film of the present invention and the laminate using the same will be specifically described.

The polypropylene-based composite film of the present invention is a polypropylene-based composite film composed of a base material layer (A) and a seal layer (B), and the base material layer (A) is a propylene / ethylene block copolymer (a1) 75. It is composed of a resin composition in which ~ 90% by weight and 10 to 25% by weight of linear low-density polyethylene (a2) are mixed.

Here, in the propylene / ethylene block copolymer (a1) of the base material layer (A), the proportion of the 20 ° C. xylene-insoluble portion of the block copolymer is 75 to 90% by weight, and the proportion of the soluble portion is 10. It is ~ 25% by weight, the intrinsic viscosity of the insoluble portion (hereinafter referred to as [η] _H ) is 1.7 to 2.2 dl / g, and the ultimate viscosity of the soluble portion (hereinafter referred to as [η] _EP). ) Is preferably 2.5 to 3.5 dl / g. The 20 ° C. xylene insoluble part and the soluble part are the propylene / ethylene block copolymer pellets, which are completely dissolved in boiling xylene, then cooled to 20 ° C. and left to stand for 4 hours or more, and then this is used. When the precipitate and the solution are separated by filtration, the precipitate is referred to as a 20 ° C. xylene-insoluble portion, and the portion obtained by drying the solution portion (filtrate) at 70 ° C. under reduced pressure is the 20 ° C. xylene-soluble portion. Called a department.

The 20 ° C. xylene-insoluble portion corresponds to a sea component made of polypropylene in a propylene / ethylene block copolymer, and the xylene-soluble portion corresponds to an island component made of polyethylene and an ethylene / propylene copolymer rubber component. Regarding the ratio of the insoluble portion to the soluble portion, it is more preferable that the ratio of the insoluble portion is 80 to 85% by weight. If the insoluble portion is smaller than 75% by weight, the bending whitening resistance is lowered, and if the insoluble portion is larger than 90% by weight, the heat resistance is insufficient.

The ultimate viscosity ([η] _H ) of the xylene-insoluble portion is in the range of 1.7 to 2.2 dl / g, more preferably in the range of 1.8 to 2.0 dl / g. If the intrinsic viscosity ([η] _H ) is smaller than 1.7 dl / g, the molecular weight of polypropylene, which is a sea component, is small and the low temperature impact resistance becomes insufficient. If it is larger than 2.2 dl / g, polypropylene is conversely. The molecular weight of the material becomes too large, and the bending whitening resistance is lowered.

The ultimate viscosity ([η] _EP ) of the xylene-soluble portion is in the range of 2.5 to 3.5 dl / g, more preferably in the range of 2.7 to 3.3 dl / g. If the ultimate viscosity ([η] _EP ) of the xylene-soluble part is less than 2.5 dl / g, the blocking resistance deteriorates such as stickiness of the film, and if it is more than 3.5 dl / g, the polyethylene and ethylene / propylene copolymer rubber components There is a concern that gels, fish eyes, etc. may be generated due to the large dispersed particle size of the island component composed of the above, and when oil-based foods are packaged, the bending whitening resistance is lowered and the yuzu skin resistance is lowered.

The ethylene content of the xylene-soluble portion is preferably in the range of 20 to 50% by weight, more preferably in the range of 25 to 40% by weight. If the content is less than 20% by weight, the low temperature impact resistance at low temperature is lowered, and conversely, if it is more than 50% by weight, the blocking resistance tends to be insufficient.

Further, as the melt flow rate (unit: g / 10 minutes, hereinafter abbreviated as MFR) of the propylene / ethylene block copolymer (a1), from the viewpoint of cast moldability, deterioration of low temperature impact resistance, gel, and fish. From the viewpoint of concern about the occurrence of eye, the range of 1 to 3 g / 10 minutes is preferable, and the range of 1 to 2.5 g / 10 minutes is more preferable. If the MFR is less than 1 g / 10 minutes, the melt viscosity is too high and it is difficult to stably extrude from the base during film formation, and if the MFR exceeds 3 g / 10 minutes, the low temperature impact resistance is lowered.

Here, as a method for adjusting the extreme viscosity of the xylene insoluble and soluble components of the propylene / ethylene block copolymer (a1) and the MFR, hydrogen is used in each step during the polymerization of the propylene / ethylene block copolymer. A method of adding a molecular weight modifier such as gas or a metal compound, a method of adding an additive when melt-kneading and pelletizing a polymer obtained in the form of powder, and a method of melt-kneading and pelletizing a polymer obtained in powder form. A method of adjusting the kneading conditions of the above can be mentioned.

Examples of the method for producing a propylene / ethylene block copolymer used in the present invention include a method of polymerizing raw materials such as propylene and ethylene using a catalyst. Here, as the catalyst, a Ziegler-Natta type, a metallocene catalyst, or the like can be used, and for example, those listed in JP-A-07-216017 can be preferably 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 (in the formula, R is a hydrocarbon group having 1 to 20 carbon atoms). , X satisfies the halogen atom, 0 <a≤4, preferably 2≤a≤4, particularly preferably a = 4), and is obtained by reducing the titanium compound with an organomagnesium compound. A trivalent titanium compound-containing solid catalyst obtained by treating a product with an ester compound and then a mixture of an ether compound and titanium tetrachloride or a mixture of an ether compound and titanium tetrachloride and an ester compound, (2). Examples thereof include a catalytic system composed of an organoaluminum compound and (3) an electron-donating compound (dialkyldimethoxysilane and the like are preferably used).

As a method for producing the above propylene / ethylene block copolymer, from the viewpoint of productivity and low temperature impact resistance, a polymer portion mainly composed of propylene is polymerized in the first step in the absence of a substantially inactivator. Then, it is preferable to use a method of polymerizing the ethylene / propylene copolymer in the gas phase in the second step.

Here, the polymer portion mainly composed of propylene is preferably a propylene copolymer having a melting point of 160 ° C. or higher from the viewpoint of heat resistance, rigidity, etc., but if the polymer portion has a melting point of 160 ° C. or higher, propylene is used. It may be a copolymer with a small amount of α-olefin such as ethylene or 1-butene.

In the present invention, by mixing the propylene / ethylene block copolymer (a1) of the base material layer (A) with the linear low-density polyethylene (a2), the glass transition is lower than that of the propylene / ethylene block copolymer. By increasing the component of dots, low temperature impact resistance and bending whitening resistance can be improved, and when used as a packaging material for retort applications, unevenness (skin) due to film swelling due to oily foods in the contents Occurrence can be suppressed (improved useless skin resistance).

The linear low-density polyethylene (a2) is a copolymer of ethylene and an α-olefin having 3 or more carbon atoms, for example, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene and the like. Those manufactured and commercially available by commonly known methods can be used. The density of the linear low density polyethylene (a2) is preferably from .900 to 0.935 / cm ^3, more preferably in the range of from .915 to .930 / cm ^3. If the density of the linear low-density polyethylene (a2) is less than 0.900 g / cm ³ , the heat-sealing force may decrease, and if it is larger than 0.935 g / cm ³ , the dispersibility decreases and the use resistance is reduced. Skin resistance, bending whitening resistance, and low temperature impact resistance may decrease.

The MFR of the linear low-density polyethylene (a2) is in the range of 1 to 20 g / 10 minutes, more preferably in the range of 3 to 10 g / 10 minutes, that is, the propylene / ethylene block copolymer. It is preferable because it has good dispersibility in (a1) and improves resistance to shavings and bending and whitening.

The base material layer (A) needs to be mixed with the above-mentioned linear low-density polyethylene in an amount of 10 to 25% by weight. If it is less than 10% by weight, the yuzu skin resistance, bending whitening resistance, and low temperature impact resistance are lowered, and if it exceeds 25% by weight, the dispersibility is lowered and streaky defects are formed in the film formation. The interlayer adhesion between the base material layer (A) and the seal layer (B) is reduced, and the heat seal strength after the retort treatment is reduced.

Since the resin constituting the base material layer (A) is only the propylene / ethylene block copolymer (a1) and the linear low-density polyethylene (a2), low-temperature impact resistance and anti-skin resistance are exhibited. However, for environmental reasons, the thickness adjusting portion and the removed edge portion during film formation are recovered and reused as a raw material for the base material layer (A) together with the resin for the seal layer (B). Therefore, it is permissible to add other resins as long as these characteristics are not impaired. The proportion of the resin other than the propylene / ethylene block copolymer (a1) and the linear low-density polyethylene (a2) in the base material layer (A) is preferably less than 20% by weight, more preferably less than 10% by weight for the above reasons. Is.

Next, the seal layer (B) contains 30 to 40% by weight of the propylene / ethylene block copolymer (b1), 30 to 50% by weight of the propylene / ethylene block copolymer (b2), and homopolypropylene (b3) 15. It is composed of a resin composition obtained by mixing ~ 25% by weight, 3 to 10% by weight of linear low density polyethylene (b4), and 50 to 5000 ppm of a crystal nucleating agent (b5).

The functions of the seal layer (B) are low temperature impact resistance, heat sealability, blocking resistance between seal layers, and steamability when heated in a microwave oven. By blending these resins in the above proportions, these Can be expressed in a well-balanced manner.

The propylene / ethylene block copolymer (b1) used for the seal layer (B) in the present invention has a melt flow rate in the range of 1 to 3 g / 10 minutes and a proportion of the xylene-insoluble portion at 20 ° C. of 75 to 90% by weight. The ultimate viscosity ([η] _H ) of the insoluble portion is 1.7 to 2.2 dl / g, the proportion of the xylene-soluble portion at 20 ° C. is 10 to 25% by weight, and the ultimate viscosity of the soluble portion ([η] _H ). [Η] _EP ) is 2.5 to 3.5 dl / g.

When the MFR of the propylene / ethylene block copolymer (b1) is in the range of 2 to 3 g / 10 minutes, the film-forming property is stable and more preferable. If it is less than 1 g / 10 minutes, the melt viscosity is too high, the dispersibility of other resins is lowered, and the yuzu skin resistance and bending whitening resistance after the retort treatment are lowered. Further, when the MFR exceeds 3 g / 10 minutes, the low temperature impact resistance is lowered.

The proportion of the insoluble portion of (b1) is in the range of 75 to 90% by weight, more preferably in the range of 78 to 85% by weight. If the insoluble portion of (b1) is less than 75% by weight, the bending whitening resistance is lowered, and if the insoluble portion of (b1) is more than 90% by weight, the low temperature impact resistance is lowered.

The ultimate viscosity ([η] _H ) of the xylene-insoluble portion of (b1) is 1.7 to 2.2 dl / g, more preferably in the range of 1.8 to 2.0 dl / g. When the ultimate viscosity ([η] _H ) is smaller than 1.7 dl / g, the low temperature impact resistance is lowered, and when it is larger than 2.2 dl / g, the bending whitening resistance is lowered. Further, when the ultimate viscosity ([η] _EP ) of the xylene-soluble portion of (b1) is smaller than 2.5 dl / g, the blocking resistance is lowered, and when it is larger than 3.5 dl / g, the yuzu skin resistance is lowered. To do.

The role of the propylene / ethylene block copolymer (b2) in the composition of the seal layer (B) in the present invention is to roughen the surface of the seal layer (B) to improve blocking resistance, and to function as a non-powder. Is to be given.

The propylene / ethylene block copolymer (b2) has an xylene-insoluble portion at 20 ° C. of 80 to 95% by weight, and the insoluble portion of (b2) has an ultimate viscosity ([η] _H ) of 1.4 to 1. It is .8 dl / g, the proportion of the xylene-soluble portion at 20 ° C. is 5 to 20% by weight, and the ultimate viscosity ([η] _EP ) of the soluble portion of the (b2) is 1.5 to 2.0 dl / g. Must be met. The proportion of the 20 ° C. xylene insoluble portion of (b2) is more preferably 85 to 90% by weight. If the proportion of the xylene-insoluble portion at 20 ° C. is less than 80% by weight and the proportion of the soluble portion exceeds 20% by weight, the heat-sealing force after the retort treatment is lowered and the yuzu skin resistance is lowered. If the proportion of the xylene insoluble portion at 20 ° C. exceeds 95% by weight and the proportion of the soluble portion is less than 5% by weight, the surface of the seal layer is not sufficiently roughened, the blocking resistance is lowered, and the low temperature impact resistance is improved. It will be insufficient.

The ultimate viscosity ([η] _H ) of the xylene-insoluble portion of (b2) is preferably in the range of 1.5 to 1.7 dl / g. If the ultimate viscosity ([η] _H ) of the xylene-insoluble part is less than 1.4 dl / g, the heat seal strength and low-temperature impact resistance after the retort treatment become insufficient, and if it is larger than 1.8 dl / g, the yuzu-resistant skin The property and bending whitening resistance are reduced.

The ultimate viscosity ([η] _EP ) of the xylene-soluble portion of (b2) is preferably in the range of 1.6 to 1.8 dl / g. If the ultimate viscosity ([η] _EP ) of the xylene-soluble part is less than 1.5 dl / g, the blocking resistance such as stickiness of the film decreases, and if it is larger than 2.0 dl / g, the bending whitening resistance after retort treatment Is insufficient.

The MFR of the propylene / ethylene block copolymer (b2) is in the range of 4 to 10 g / 10 minutes, preferably 4 to 7 g / 10 in order to finely roughen the surface of the seal layer (B). It is a range of minutes. If the MFR is less than 4 g / 10 minutes, the surface roughness becomes small and the blocking resistance is lowered, and if the MFR exceeds 10 g / 10 minutes, the low temperature impact resistance is lowered.

The seal layer (B) needs to be mixed with the propylene / ethylene block copolymer (b2) in an amount of 30 to 50% by weight, preferably in the range of 35 to 45% by weight. If it is less than 30% by weight, the unevenness of the surface is insufficient and the surface roughness is small, the blocking resistance is lowered and the non-powdering is insufficient, and if it exceeds 50% by weight, the low temperature impact resistance is lowered.

The homopolypropylene (b3) of the seal layer (B) in the present invention is homopolypropylene which is a polymer of propylene alone. By mixing homopolypropylene (b3), the blocking resistance is further improved, and the heat seal strength is lowered at 80 ° C. or higher, so that the retort food packaging material can be steamed when heated in a microwave oven. ..

The MFR of the (b3) at 230 ° C. is preferably in the range of 1 to 20 g / 10 minutes, more preferably in the range of 1 to 10 g / 10 minutes, and further preferably in the range of 5 to 8 g / 10 minutes. If the MFR of the (b3) is less than 1 g / 10 minutes, the dispersibility in the propylene / ethylene block copolymers (b1) and (b2) may deteriorate, and the heat seal strength is high at 80 ° C. or higher. The steamability of retort food packaging materials when heated in a microwave oven may be reduced. If the MFR exceeds 20 g / 10 minutes, the low temperature impact resistance and the heat seal strength after the retort treatment may decrease.

The mixing amount of the homopolypropylene (b3) of the seal layer (B) needs to be 15 to 25% by weight. When the amount of homopolypropylene (b3) is less than 15% by weight, the blocking resistance is improved and the steamability when heated in a microwave oven is not sufficient, and when it exceeds 25% by weight, the low temperature impact resistance and the retort treatment are performed. The heat seal strength decreases.

The linear low-density polyethylene (b4) of the seal layer (B) in the present invention is mixed for the purpose of improving the yuzu skin resistance and the bending whitening resistance.

The linear low-density polyethylene (b4) contains ethylene and an α-olefin having 3 or more carbon atoms such as propylene and 1-butene, similarly to the linear low-density polyethylene (a2) of the base material layer (A). A copolymer of 1-pentene, 1-hexene, 1-octene, etc., which is manufactured by a generally known method and is commercially available can be used. Density of the (b4) is preferably from .900-0.935 / cm ^3, more preferably in the range of from 0.915 to 0.930 / cm ^3. If the density of (b4) is less than 0.900 g / cm ³ , the heat-sealing force after the retort treatment may decrease, and if it is greater than 0.935 g / cm ³ , the dispersibility decreases and the yuzu skin resistance And the bending whitening resistance may decrease.

The MFR of the linear low-density polyethylene (b4) is preferably in the range of 1 to 20 g / 10 minutes. If the MFR is less than 1 g / 10 minutes, the dispersibility in the propylene / ethylene block copolymer (a1) is deteriorated, and the yuzu skin resistance and the bending whitening resistance are lowered. If the MFR exceeds 20 g / 10 minutes, the retort The heat-sealing force after the treatment may decrease.

The amount of the linear low-density polyethylene (b4) mixed with the seal layer (B) needs to be 3 to 10% by weight. If the mixing amount is less than 3% by weight, the yuzu skin resistance and bending whitening resistance are lowered, and if it exceeds 10% by weight, the blocking resistance and the heat seal strength after the retort treatment are lowered.

Further, the seal layer (B) in the present invention is mixed with at least one crystal nucleating agent (b5) of a metal phosphate and a dicarboxylic acid metal salt at 50 to 5000 ppm, more preferably 100 to 3000 ppm. It is possible to increase the crystallinity of the surface to form fine irregularities to satisfy the surface roughness and blocking resistance, and further, the peel strength at 80 ° C. is 1 to 1 so that it can be steamed when heated in a microwave oven. It can be controlled to 10N / 15mm.

If the amount of the crystal nucleating agent (b5) is less than 50 ppm, the blocking resistance is lowered and the steamability during microwave heating is also insufficient. If the amount is more than 5000 ppm, no further improvement in blocking resistance is observed, and odor may be emitted by the retort treatment, which is not preferable.

Examples of the phosphoric acid metal salt in the present invention include phosphoric acid ester compounds, and among them, aromatic phosphoric acid ester metal salt is preferable for the purpose of the present invention.

Specifically, sodium-bis (4-t-butylphenyl) phosphate, sodium-bis (4-methylphenyl) phosphate, sodium-bis (4-ethylphenyl) phosphate, sodium-bis (4-i). -Propylphenyl) phosphate, sodium-bis (4-t-octylphenyl) phosphate, potassium-bis (4-t-butylphenyl) phosphate, calcium-bis (4-t-butylphenyl) phosphate, magnesium -Bis (4-t-butylphenyl) phosphate, lithium-bis (4-t-butylphenyl) phosphate, aluminum-bis (4-t-butylphenyl) phosphate, sodium-2,2'-methylene- Bis (4,6-di-t-butylphenyl) phosphate, sodium-2,2'-ethylidene-bis (4,6-di-t-butylphenyl) phosphate, lithium-2,2'-methylene- Bis (4,6-di-t-butylphenyl) phosphate, lithium-2,2'-ethylidene-bis (4,6-di-t-butylphenyl) phosphate, sodium-2,2'-ethylidene- Bis (4-i-propyl-6-t-butylphenyl) phosphate, lithium-2,2'-methylene-bis (4-methyl-6-t-butylphenyl) phosphate, lithium-2,2'- Methylene-bis (4-ethyl-6-t-butylphenyl) phosphate, calcium-bis [2,2'-thiobis (4-methyl-6-t-butylphenyl) phosphate], calcium-bis [2, 2'-thiobis (4-ethyl-6-t-butylphenyl) phosphate], calcium-bis [2,2'-thiobis- (4,6-di-t-butylphenyl) phosphate], magnesium-bis [2,2'-thiobis (4,6-di-t-butylphenyl) phosphate], magnesium-bis [2,2'-thiobis- (4-t-octylphenyl) phosphate], sodium-2, 2'-butylidene-bis (4,6-di-methylphenyl) phosphate, sodium-2,2'-butylidene-bis (4,6-di-t-butylphenyl) phosphate, sodium-2,2' -T-octylmethylene-bis (4,6-di-methylphenyl) phosphate, sodium-2,2'-t-octylmethylene-bis (4,6-di-t-butylphenyl) Le) Phosphate, calcium-bis [2,2'-methylene-bis (4,6-di-t-butylphenyl) phosphate], magnesium-bis [2,2'-methylene-bis (4,6-) Di-t-butylphenyl) phosphate], barium-bis [2,2'-methylene-bis (4,6-di-t-butylphenyl) phosphate], sodium-2,2'-methylene-bis (2,2'-methylene-bis (4,6-di-butylphenyl) phosphate] 4-Methyl-6-t-Butylphenyl) Phosphate, Sodium-2,2'-Methylene-bis (4-Ethyl-6-t-Butylphenyl) Phosphate, Sodium- (4,4'-Dimethyl-5) , 6'-di-t-butyl-2,2'-biphenyl) Phosphate, calcium-bis [(4,4-'dimethyl-6,6'-di-t-butyl-2,2'-biphenyl) Phosphate], sodium-2,2'-ethylidene-bis (4-m-butyl-6-t-butylphenyl) phosphate, sodium-2,2'-methylene-bis (4,6-di-methylphenyl) ) Phosphate, sodium-2,2'-methylene-bis (4,6-di-ethylphenyl) phosphate, potassium-2,2'-ethylidene-bis (4,6-di-t-butylphenyl) phos Fate, calcium-bis [2,2'-ethylidene-bis (4,6-di-t-butylphenyl) phosphate], magnesium-bis [2,2'-ethylidene-bis (4,6-di-t) -Butylphenyl) Phosphate], Barium-Bis [2,2-'Ethylden-Bis (4,6-di-t-Butylphenyl) Phosphate], Aluminum-Tris [2,2'-Methylene-Bis (4) , 6-di-t-butylfel) phosphate] and aluminum-tris [2,2'-ethylidene-bis (4,6-di-t-butylphenyl) phosphate] and mixtures of two or more of these are exemplified. can do.

In particular, sodium-2,2'-methylene-bis (4,6-di-t-butylphenyl) phosphate is preferable.

The dicarboxylic acid metal salt is a compound represented by the following structural formula (i) disclosed in Japanese Patent Application Laid-Open No. 2015-212078.

(In formula (i), M ₁ and M ₂ are sodium, hydrogen, calcium, strontium or lithium and may be the same or different. R ² , R ³ , R ⁴ , R. ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ and R ¹¹ are hydrogen atom, halogen atom, alkyl group having 1 to 9 carbon atoms, hydroxyl group, alkoxy group having 1 to 9 carbon atoms, and carbon number 1 ~ 9 alkyleneoxy group, amino group, alkylamino group having 1 to 9 carbon atoms, or phenyl group, which may be the same or different. R ² , R ³ , R ⁴ , R. Any two of ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ and R ¹¹ are bonded together with the cyclohexane ring carbon atom depicted in formula (i) to which they are bonded. In addition, a saturated hydrocarbon ring having 3 to 6 carbon atoms may be formed. R ² and R ³ may be in a trans configuration or a cis configuration.

Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom and the like. Examples of the alkyl group having 1 to 9 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group and the like. Examples of the alkoxy group having 1 to 9 carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group and the like. Examples of the alkylamino group having 1 to 9 carbon atoms include a methylamino group, an ethylamino group, a dimethylamino group and a diethylamino group. Examples of the alkyleneoxy group having 1 to 9 carbon atoms include a group represented by the following formula.

R (R'O) _n −
(In the formula, R represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, R'represents an alkylene group having 2 or 3 carbon atoms, and n represents an integer of 2 to 4. The total number of carbon atoms of R and R'is 9 or less.)
When the alkyleneoxy group having 1 to 9 carbon atoms is the group represented by the above formula, preferably H (CH ₂ CH ₂ O) _2- , H (CH ₂ CH ₂ O) _3- , H ( _{CH 2 CH 2 O) 4 -} , CH 3 (CH 2 CH 2 O) 2 -, CH 3 (CH 2 CH 2 O) 3 -, CH 3 (CH 2 CH 2 O) 4 -, CH 3 CH 2 ( CH ₂ CH ₂ O) ₂ −, CH ₃ CH ₂ (CH ₂ CH ₂ O) ₃ −, (CH ₃ ) ₂ CH (CH ₂ CH ₂ O) ₂ −, (CH ₃ ) ₂ CH (CH ₂ CH ₂₎ O) _3- , H ((CH ₃ ) CHCH ₂ O) _2- , H ((CH ₃ ) CHCH ₂ O) _3- , CH ₃ ((CH ₃ ) CHCH ₂ O) _2- , or CH ₃ CH ₂ ((CH ₃ ) CHCH ₂ O) _2- .

The dicarboxylic acid metal salt is preferably disodium-bicyclo (2,2,1) heptane-2,3-dicarboxylate represented by the following structural formula (ii) or represented by the following structural formula (iii). A calcium salt of 1,2-cyclohexanedicarboxylate is preferred.

The present invention may further contain 100 to 3000 ppm of a saccharide-based crystal nucleating agent. However, if the content is large, the odor of the film after retort may be deteriorated, so the content is preferably 200 to 2000 ppm. At that time, it is possible to satisfy the better steamability during microwave heating. The saccharide-based crystal nucleating agent includes sorbitol-based, nonitol-based, xylitol-based, and specifically, bis-1,3: 2,4- (3'-methyl-4'-fluoro-benzylidene) 1-. Propyl sorbitol, bis-1,3: 2,4- (3', 4'-dimethylbenzylidene) 1'-methyl-2'-propenyl sorbitol, bis-1,3,2,4-dibenzylidene 2', 3 ′ -Dibromopropyl sorbitol, bis-1,3,2,4-dibenzylidene 2'-bromo-3'-hydroxypropyl sorbitol, bis-1,3: 2,4- (3'-bromo-4'-ethyl Benzylidene) -1-allyl sorbitol, mono 2,4- (3'-bromo-4'-ethyl benzylidene) -1-allyl sorbitol, bis-1,3: 2,4- (4'-ethylbendylidene) 1- Allyl sorbitol, bis-1,3: 2,4- (3', 4'-dimethylbenzylidene) 1-methylsorbitol, 1,2,3-trideoxy-4,6: 5,7-bis-[(4-4-) Propylphenyl) methylene] -nonitol, bis-1,3: 2,4- (4'-ethylbenzylidene) 1-allyl sorbitol, bis-1,3: 2,4- (5', 6', 7', 8'-tetrahydro-2-naphthaldehyde benzylidene) 1-allylxylitol, bis-1,3: 2,4- (3', 4'-dimethylbenzidylene) 1-propylxylitol and the like can be mentioned.

The crystal nucleating agent (b5) used in the present invention is preferably used in a masterbatch because of the problem of dispersibility. The base resin of the masterbatch is, for example, any resin of the propylene / ethylene block copolymer (b1), the propylene / ethylene block copolymer (b2), and the homopolypropylene (b3) of the seal layer (B). Is preferable.

The center line average surface roughness (Ra) of the seal layer (B) in the present invention is preferably 0.15 μm or more, preferably 0.2 to 0.35 μm from the viewpoint of blocking resistance and heat seal strength.

Further, the blocking shear force between the seal layers (B) in the present invention is 10 N / 12 cm ² or less, more preferably 7 N / 12 cm ² or less. If the blocking shear force exceeds 10 N / 12 cm ² , the film will not be easily unwound after long-term storage or storage in a high temperature state in summer, resulting in deterioration of laminateability with other substrates and bag making workability, and the mouth of the packaging bag. May become difficult to open and the filling property of the contents may be significantly reduced.

The polypropylene-based composite film 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 is insufficient, and if it exceeds 150 μm, the laminating workability is lowered and the cost may be increased.

The thickness ratio of the base material layer (A) and the seal layer (B) is preferably 3: 1 to 15: 1 in consideration of the balance between low temperature impact resistance and heat seal strength.

In the present invention, the heat-resistant base material layer, the gas barrier layer, and the polypropylene-based composite film of the present invention are laminated to form a laminate, and then the seal layers (B) of the polypropylene-based composite film are heat-sealed at 230 ° C. The peel strength after the retort treatment at 130 ° C. for 30 minutes is 30 N / 15 mm or more in an atmosphere of 23 ° C., more preferably in the range of 35 to 45 N / 15 mm, and 1 to 10 N in an atmosphere of 80 ° C. It is in the range of / 15 mm, more preferably 3 to 7 N / 15 mm. If the peeling strength in the atmosphere of 23 ° C. is less than 30 N / 15 mm, the low temperature impact resistance may be lowered in the retort food packaging and the content protection may be inferior, and the peeling strength in the atmosphere of 80 ° C. If the strength is less than 1N / 15mm, the contents may leak when the packaging bag containing the retort food is heated in the microwave, and if it exceeds 10N / 15mm, the air permeability is poor when the packaging bag is heated in the microwave. The bag may be torn and the contents may scatter or leak.

In the polypropylene-based composite film of the present invention, the above (a1) and (a2) are mixed as the base material layer (A) resin from one extruder using two single-screw or twin-screw melt extruders. The kneaded product thus obtained is filtered by a filter and extruded, and from another extruder, the above-mentioned (b1), (b2), (b3), (b4) and (b5) are used as the seal layer (B) resin. ) Is mixed by a usual method, and the kneaded product obtained is filtered by a filter and extruded, compounded by a feed block method, a pinol method, a multi-manifold method, etc., from a T-type die or an annular die. It can be manufactured by extruding into a film. The temperature of the molten polymer extruded from the melt extruder is usually 200 to 300 ° C., but 220 to 270 ° C. is preferable in order to prevent decomposition of the polymer and obtain a film of good quality. When extruded from a T-die, the extruded film is brought into contact with a cooling roll set at a constant temperature of 20 to 65 ° C., cooled and solidified, and then wound. When extruding from an annular die, bubbles are formed by a method generally called an inflation method, which is cooled and solidified, and then wound up in a non-stretched film state.

The polypropylene-based composite film of the present invention can be used alone as a packaging film, but can be preferably used as a retort food packaging material containing a general Al foil.

The polypropylene-based composite film of the present invention contains an antioxidant, a heat-resistant stabilizer, a neutralizing agent, an antistatic agent, a hydrochloric acid absorber, an antiblocking agent, a lubricant, etc. in each layer as long as the object of the present invention is not impaired. Can be done. One of these additives may be used, or two or more of these additives may be used in combination.

Here, specific examples of the antioxidant include 2,6-di-t-butylphenol (BHT) and n-octadecyl-3- (3', 5'-di-t-butyl-4) as hindered phenols. '-Hydroxyphenyl) propionate ("Irganox" 1076, "Sumilizer" BP-76), tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane (" Irganox" Examples thereof include "1010," Sumilizer "BP-101), tris (3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate ("Irganox "3114, Mark AO-20) and the like. In addition, as phosphite-based (phosphorus-based) antioxidants, tris (2,4-di-t-butylphenyl) phosphite ("Irgafos" 168, Mark 2112), tetrakis (2,4-di-t-butyl). Phenyl) -4-4'-biphenylene-diphosphonite ("Sandstab" P-EPQ), bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite ("Ultranox" 626, Mark PEP-24G), Examples thereof include distearyl pentaerythritol diphosphite (Mark PEP-8). Among them, 6- [3- (3-t-butyl-4-hydroxy-5-methyl) propoxy] -2,4,8,10-tetra-, which has both functions of hindered phenol and phosphite. 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 preferable, and in particular, the combined use of both is effective in suppressing the decomposition of the xylene-soluble portion at 20 ° C. in film formation. However, it is preferable because it greatly contributes to both low temperature impact resistance and blocking resistance. If the decomposition of the xylene-soluble portion is promoted, the blocking resistance deteriorates.

The amount of the antioxidant added depends on the type of antioxidant used, but may be appropriately set in the range of 100 to 10,000 ppm.

Further, as the neutralizing agent, hydrotalcite compounds, calcium hydroxide and the like are preferable for reducing smoke generation during film formation.

Further, in the polypropylene-based composite film of the present invention, the surface of the base material layer (A) is subjected to a corona discharge treatment that is usually industrially performed for laminating with another base material, and the corona in a nitrogen or carbon dioxide gas atmosphere. It is preferable to perform surface treatment such as discharge treatment, plasma treatment, and ozone treatment so that the wetting index is 37 mN / m or more.

Further, the laminate using the polypropylene-based composite film of the present invention is specifically a biaxially stretched polyamide film as a heat-resistant base material layer on the opposite side of the seal layer (B) of the polypropylene-based composite film of the present invention. Using at least one layer selected from (ON), biaxially stretched polyester film (PET) and printing paper, as a gas barrier layer, a metal foil (Al foil), metal vapor deposition biaxially stretched polyamide film (vapor deposition ON), metal vapor deposition It is a laminated body in which at least one layer selected from a biaxially stretched polyester film (deposited PET) is laminated. These typical laminate configurations are PET / Al foil / polypropylene composite film, PET / ON / Al foil / polypropylene composite film, PET / Al foil / ON / polypropylene composite film, ON / polypropylene composite film. , PET / vaporized ON / polypropylene composite film, ON / vaporized PET / polypropylene composite film.

As a method for producing such a laminate, a normal dry lamination method in which films constituting the laminate are bonded with an adhesive can be preferably adopted, but if necessary, the polypropylene-based resin composition of the present invention is directly extruded and laminated. The method can also be adopted.

These laminates are used by making a flat bag (flat pouch), a standing pouch, or the like with the sealing layer (B) of the polypropylene-based composite film as the inner surface of the bag.

In addition, the laminated structure of these laminates has the required characteristics of the packaging bag (for example, barrier performance for satisfying the quality retention period of the food to be packaged, size / low temperature impact resistance corresponding to the weight of the contents, visibility of the contents). Etc.), and it is appropriately selected.

Hereinafter, the present invention will be specifically described with reference to Examples, but the scope of the present invention is not limited thereto. In addition, the detailed description of the present invention and the measured values of each evaluation item in the examples were measured by the following methods.

(1) Content of xylene-insoluble part and soluble part at 20 ° C. After 5 g of polypropylene pellets were completely dissolved in 500 ml of boiling xylene (Kanto Chemical Co., Inc. first grade), the temperature was lowered to 20 ° C. and left for 4 hours or more. To do. Then, this was filtered into a precipitate and a solution, and separated into a soluble part and an insoluble part. The weight of the insoluble portion was determined by drying the precipitated portion at 70 ° C. under reduced pressure and then measuring the weight at 23 ° C. to determine the content (% by weight). The soluble portion was obtained by drying the filtrate to dryness at 70 ° C. under reduced pressure and then measuring the weight thereof to determine the content (% by weight).

(2) Extreme viscosity of polymer and composition Using a Ubbelohde viscometer. Measurements were taken in 135 ° C. tetralin.

(3) Melt flow rate (MFR)
According to JIS K-7210-1999, propylene / ethylene block copolymer and homopropylene were measured at a temperature of 230 ° C., and linear low-density polyethylene was measured at a temperature of 190 ° C. under a load of 21.18 N.

(4) Density Based on JIS K-7112-1999, the measurement was performed by a measurement method using a density gradient tube.

(5) Blocking shearing force Prepare a film sample with a width of 30 mm and a length of 100 mm, superimpose the seal layers in a range of 30 mm × 40 mm, apply a load of 500 g / 12 cm ² , and in an oven at 80 ° C. for 24 hours. After the heat treatment, the film was left to stand in an atmosphere of 23 ° C. and a humidity of 65% RH for 30 minutes or more, and then the shear peeling force was measured at a tensile speed of 300 mm / min using Tensilon manufactured by Orientec. If the shear peeling force is 10 N / 12 cm ² or less in this measurement method, it has excellent blocking resistance and can be used as a packaging material without powder.

(6) Film Thickness and Thickness Composition The film thickness was measured at any 10 points on the film according to the JIS K7130 (1992) A-2 method using a dial gauge. The average value was divided by 10 to obtain the film thickness.

In the case of a laminated film, the thickness of each layer is determined by embedding the laminated film in epoxy resin, cutting out the cross section of the film with a microtome, and observing the cross section with a scanning electron microscope at a magnification of 3,000 times. The thickness was calculated.

(7) Low temperature impact resistance A PET film with a thickness of 12 μm, an ON film with a thickness of 15 μm, and a polypropylene-based composite film evaluated as an Al foil with a thickness of 9 μm are used in this order by a normal dry laminating method using a urethane adhesive. They were laminated and aged at 40 ° C. for 3 days to prepare a laminate having the following constitution.
Laminate structure: PET / adhesive / ON / adhesive / Al foil / adhesive / film (adhesive surface = base material layer, outermost layer = seal layer).

A CA-450-10 type heat sealer manufactured by Fuji Impulse Co., Ltd. was used to heat the above two laminates so that the seal layer of the film to be evaluated was the inner surface of the bag, and the heating time was 1.4 seconds (seal temperature: A packaging bag having a bag making size of 150 mm × 285 mm was prepared with a cooling time of 3.0 seconds (about 230 ° C.). This packaging bag is filled with 1000 cm ³ of saline solution having a concentration of 0.1% by weight, sealed under the same conditions as above, sealed, and retorted at 130 ° C. for 30 minutes. Next, the bag after the retort treatment was stored in a refrigerator at 0 ° C. for 24 hours, then taken out from the refrigerator and dropped from a height of 55 cm to a flat floor surface within 10 seconds in an atmosphere of 23 ° C. (n number 20). ), Record the number of times until the bag is broken. In this evaluation method, the average value of 20 n-numbers was 15 times or more as good low-temperature impact resistance.

(8) Yuzu skin resistance The packaging bag created in item (7) is filled with commercially available retort curry (retort curry "Kukure curry" from House Foods Co., Ltd., dry) and then sealed under the same conditions as above. Immediately after the seal was sealed and the retort treatment was performed at 130 ° C. for 30 minutes, the state of occurrence of unevenness on the surface of the laminate was visually determined. Rank l for those with no unevenness, rank 2 for those with slight unevenness, rank 3 for those with slight unevenness, rank 4 for those with clear unevenness, and those with severe unevenness. Was evaluated as rank 5. In this evaluation method, ranks 1 to 3 were practical and had good yuzu skin resistance.

(9) Peeling strength Two seal layers (B) of the same laminate as in item (7) are sealed using a flat plate heat sealer at a sealing temperature of 230 ° C. (without lower plate heating), a sealing pressure of 98 kPa, and a sealing time of 1. The heat-sealed sample under the condition of seconds was retorted at 130 ° C. for 30 minutes and then cooled to 23 ° C. Then, using Tensilon manufactured by Orientec, the peel strength of this sample was measured in an atmosphere of 23 ° C. and in an oven at 80 ° C. at a tensile speed of 300 mm / min. If the peel strength at 23 ° C is 30 N / 15 mm or more in this measurement method, it can be used satisfactorily for normal retort applications, and if it is in the range of 1 to 10 N / 15 mm in an oven at 80 ° C, the retort food packaging material. When the pouch is heated in a microwave oven, both content protection and steamability can be achieved, and it can be used well in a microwave oven.

(10) Surface Roughness Using a fully automatic fine shape measuring machine (SURFCORDER ET4000A) manufactured by Kosaka Laboratory Co., Ltd., the center line of the surface of the seal layer (B) by the measuring method specified in JIS-B-0601-1982. The average roughness (Ra) was determined. The measurement direction was a direction orthogonal to the film flow direction (TD direction).

(11) Bending and whitening resistance After retort-treating a polypropylene-based composite film at 130 ° C. for 30 minutes, a sample width of 10 mm and a bending angle of 135 degrees (left and right) using a MIT bending tester manufactured by Toyo Seiki Seisakusho Co., Ltd. After bending 100 times under the condition of a load of 5.04 N, the whitening state of the bent portion was visually determined (n number 5). Rank 1 for those that do not whiten at all, rank 2 for those that whiten slightly, rank 3 for those that whiten lightly, rank 4 for those that whiten clearly, and rank those that whiten and have a tight linear bend. It was evaluated as 5. In this evaluation method, ranks 1 and 2 were rated as good bending whitening resistance (◯), and ranks 4 and 5 were rated as poor bending whitening resistance (x).

The various raw material compositions and raw material formulations used in the present invention are summarized in Table 1. In addition, the film characteristics and the characteristics of the laminate according to the raw material formulation are summarized in Table 2.

(1) Propropylene / ethylene block copolymer The above-mentioned polymerization conditions are changed to change the content of the xylene-insoluble part and the soluble part at 20 ° C., and their ultimate viscosities [η] _H , [η] _EP , and MFR. -Ethylene block copolymers were prepared and their compositions are summarized in Table 1.

(2) Linear low-density polyethylene (a2), (b4)
As the linear low-density polyethylene, the following commercially available ones were used.

Linear low-density polyethylene with a density of 0.921 g / cm ³ and an MFR of 2.2 g / 10 minutes (FV205 of "Sumikasen E" manufactured by Sumitomo Chemical Co., Ltd.).

(3) Homopolypropylene (b3)
As the homopolypropylene, the following commercially available ones were used.

Homopolypropylene (“Nobren” FLX80E4 manufactured by Sumitomo Chemical Co., Ltd.) having an MFR of 7.5 g / 10 minutes at 230 ° C.

(4) Crystal nucleating agent (b5)
The following commercially available crystal nucleating agent was used.

Disodium-bicyclo (2,2,1) heptane-2,3-dicarboxylate (“HYPERFORM®” HPN-68L available from Milliken Chemical) was used as the dicarboxylic acid metal salt of the crystal nucleating agent. Was (nuclear agent-1).

As the metal phosphate of the crystal nucleating agent, sodium-2,2'-methylene-bis (4,6-di-t-butylphenyl) phosphate (ADEKA "ADEKA STAB" NA-11), which is a phosphate metal salt, is used. ) Was used (nuclear agent-2).

[Examples 1 to 3]
The polypropylene-based composite film of the present invention has a density of 0. As the resin of the base material layer (A), as the propylene / ethylene block copolymer (a1) shown in Table 1 and as the linear low-density polyethylene (a2). Linear low-density polyethylene (FV205 of "Sumikasen" E (registered trademark) manufactured by Sumitomo Chemical Co., Ltd.) at 921 g / cm ³ and MFR 2.0 g / 10 minutes was used. The mixed resin composition ratio was changed from the lower limit to the upper limit of the range of the present invention shown in Table 1, and the mixture was supplied to an extruder whose temperature was adjusted to 260 ° C. and melt-kneaded. Further, as the resin of the seal layer (B), the propylene / polyethylene block copolymer (b1) shown in Table 1, the propylene / polyethylene block copolymer (b2), and the homopolypropylene (b3) were used at 230 ° C. Homopolypropylene with an MFR of 7.5 g / 10 min (“Nobrene®” FLX80E4 manufactured by Sumitomo Chemical Co., Ltd.) and linear low-density polyethylene (b4) with a density of 0.921 g / cm ³ . Linear low-density polyethylene with MFR of 2.0 g / 10 minutes (FV205 of "Sumikasen" E manufactured by Sumitomo Chemical Co., Ltd.) and disodium-bicyclo (2,2) of dicarboxylic acid metal salt as a crystal nucleating agent (b5). , 1) Heptane-2,3-dicarboxylate (“HYPERFORM®” HPN-68L manufactured by Milliken Chemical Co., Ltd.) was used. The mixed resin composition shown in Table 1 is supplied to another twin-screw extruder whose temperature has been adjusted to 260 ° C., melt-kneaded, and laminated in two layers with a multi-manifold base for co-extrusion to form a film. The surface of the base material layer (A) was subjected to corona discharge treatment to obtain a polypropylene-based composite film having a thickness of 70 μm after extruding the film into contact with a cooling roll at 45 ° C. for cooling and solidification.

The thickness ratio of the base material layer (A) and the seal layer (B) was 5: 1. Table 1 shows the characteristics of the obtained polypropylene-based composite film and the characteristics of the laminate obtained by laminating the polypropylene-based composite film with another base material. The polypropylene-based composite films of Examples 1 to 3 have low blocking shearing force and can be used as non-powder, have excellent low temperature impact resistance and heat seal strength, and have excellent yuzu skin resistance and are sufficient for retort applications. It had performance.

Furthermore, in the evaluation of the yuzu skin resistance in (8) above, when the sample was heated in a microwave oven to confirm the steamability, the packaging bag broke due to steaming and the contents were scattered or leaked. There was never.

[Examples 4 and 5]
In Example 1, the thickness was the same as in Example 1 except that the mixing ratio of the propylene / ethylene block copolymers (b1) and (b2) in the seal layer (B) was changed within the scope of the present invention. A 70 μm polypropylene-based composite film was obtained. Table 1 shows the characteristics of the obtained polypropylene-based composite film and the characteristics of the laminate obtained by laminating the polypropylene-based composite film with another base material. The polypropylene-based composite films of Examples 4 and 5 have low blocking shearing force and can be used as non-powder, have excellent low temperature impact resistance and heat seal strength, and have excellent yuzu skin resistance and are sufficient for retort applications. It had performance.

Furthermore, in the evaluation of the yuzu skin resistance in (8) above, when the sample was heated in a microwave oven to confirm the steamability, the packaging bag broke due to steaming and the contents were scattered or leaked. There was never.

[Examples 6 and 7]
In Example 6, as the propylene / ethylene block copolymer (b1) of the seal layer (B), the MFR is 1.5 g / 10 minutes, and the ratio of the insoluble portion at 20 ° C. xylene elution is 75% by weight. A propylene / ethylene block copolymer having a melted portion ratio of 25% by weight was used, and in Example 7, the MFR was 2.8 g / 10 minutes as the propylene / ethylene block copolymer (b1) of the seal layer (B). The thickness was the same as in Example 1 except that a propylene / ethylene block copolymer having 90% by weight of the insoluble part and 10% by weight of the soluble part at 20 ° C. xylene elution was used. A 70 μm polypropylene-based composite film was obtained. Table 1 shows the characteristics of the obtained polypropylene-based composite film and the characteristics of the laminate obtained by laminating the polypropylene-based composite film with another base material. The polypropylene-based composite films of Examples 6 and 7 all have low blocking shearing force and can be used as non-powder, have excellent low temperature impact resistance and heat seal strength, and have excellent yuzu skin resistance and are also suitable for retort applications. It had sufficient performance.

Furthermore, in the evaluation of the yuzu skin resistance in (8) above, when the sample was heated in a microwave oven to confirm the steamability, the packaging bag broke due to steaming, and the contents were scattered or leaked. I didn't put it out.

[Examples 8 and 9]
In Example 8, as the propylene / ethylene block copolymer (b1) of the seal layer (B), the ultimate viscosity of the insoluble portion at 20 ° C. xylene elution is 1.7 dl / g, which is the lower limit, and the ultimate viscosity of the soluble portion. In Example 9, the limit viscosity of the insoluble portion at 20 ° C. xylene elution was 2.2 dl / g, which was the upper limit, and the limit of the soluble portion was used. A polypropylene-based composite film having a thickness of 70 μm was obtained in the same manner as in Example 1 except that a propylene / ethylene block copolymer having an upper limit viscosity of 3.5 dl / g was used. Table 1 shows the characteristics of the obtained polypropylene-based composite film and the characteristics of the laminate obtained by laminating the polypropylene-based composite film with another base material. The polypropylene-based composite films of Examples 8 and 9 have low blocking shearing force and can be used as non-powder, have excellent low temperature impact resistance and heat seal strength, and have excellent yuzu skin resistance and are sufficient for retort applications. It had performance.

Furthermore, in the evaluation of the yuzu skin resistance in (8) above, when the sample was heated in a microwave oven to confirm the steamability, the packaging bag broke due to steaming, and the contents were scattered or leaked. I didn't put it out.

[Examples 10 and 11]
In Examples 10 and 11, as the propylene / ethylene block copolymer (b2) of the seal layer (B), the ratio of the insoluble component and the soluble component dissolved at 20 ° C. is the lower limit and the upper limit within the scope of the present invention. A polypropylene-based composite film was obtained in the same manner as in Example 1 except that the propylene / ethylene block copolymer of the above was used. Table 1 shows the characteristics of the obtained polypropylene-based composite film and the characteristics of the laminate obtained by laminating the polypropylene-based composite film with another base material. The polypropylene-based composite films of Examples 10 and 11 have excellent blocking resistance, low temperature impact resistance, heat seal strength, and yuzu skin resistance even when used as non-powder, and are suitable for retort applications. Also had sufficient performance.

Further, in the evaluation of the yuzu skin resistance as in Example 1, when the sample was heated in a microwave oven to confirm the steamability, the packaging bag broke due to steaming and the contents were scattered or leaked. There was never.

[Examples 12 and 13]
In Example 12, as the propylene / ethylene block copolymer (b2) of the seal layer (B), a raw material having a lower limit viscosity of the insoluble component and the soluble component eluted with xylene at 20 ° C. was used within the scope of the present invention. In Example 13, as the propylene / ethylene block copolymer (b2) of the seal layer (B), a raw material having an MFR of 8 g / 10 minutes and having an upper limit viscosity of the insoluble component and the soluble component eluted with xylene at 20 ° C. was used. A polypropylene-based composite film was obtained in the same manner as in Example 1 except for the above. Table 1 shows the characteristics of the obtained polypropylene-based composite film and the characteristics of the laminate obtained by laminating the polypropylene-based composite film with another base material. The polypropylene-based composite films of Examples 12 and 13 have excellent blocking resistance, low temperature impact resistance, heat seal strength, and yuzu skin resistance even when used as non-powder, and are sufficient for retort applications. It had excellent performance.

Further, in the evaluation of the yuzu skin resistance as in Example 1, when the sample was heated in a microwave oven to confirm the steamability, the packaging bag broke due to steaming and the contents were scattered or leaked. There was never.

[Examples 14 and 15]
In Example 1, in Example 14, the mixed amount of the crystal nucleating agent (b5) in the seal layer (B) was 5000 ppm, and in Example 15, the phosphoric acid ester metal of the phosphoric acid metal salt was used as the crystal nucleating agent (b5). Other than using the salt sodium-2,2'-methylene-bis 4,6-di-t-butylphenyl) phosphate (ADEKA "ADEKA STAB" (registered trademark) NA-11) (nuclear agent-2) Obtained a polypropylene-based composite film having a thickness of 70 μm in the same manner as in Example 1. Table 1 shows the characteristics of the obtained polypropylene-based composite film and the characteristics of the laminate obtained by laminating the polypropylene-based composite film with another base material. The films of Examples 14 and 15 have excellent blocking resistance, low temperature impact resistance, and seal strength even when used as non-powder, and have excellent yuzu skin resistance and are sufficient for retort applications. It had excellent performance. Further, in the evaluation of the yuzu skin resistance as in Example 1, when the sample was heated in a microwave oven to confirm the steamability, the packaging bag broke due to steaming and the contents were scattered or leaked. There was never.

[Examples 16, 17, 18]
In Example 1, in Example 16, the thickness composition ratio of the base material layer (A) and the seal layer (B) was set to 15: 1, and in Example 17, the extrusion discharge amount was kept constant and the film forming speed was increased. , The thickness of the film was set to 30 μm, and in Example 18, the polypropylene-based composite film was the same as in Example 1 except that the extrusion discharge amount was kept constant and the film forming speed was lowered to set the film thickness to 120 μm. Got Table 1 shows the characteristics of the obtained polypropylene-based composite film and the characteristics of the laminate obtained by laminating the polypropylene-based composite film with another base material. The polypropylene-based composite films of Examples 16, 17, and 18 have low blocking shearing force and can be used as non-powder, have excellent low-temperature impact resistance and seal strength, and have excellent yuzu skin resistance. It was also excellent and had sufficient performance for retort applications. Further, in the evaluation of the yuzu skin resistance as in Example 1, when the sample was heated in a microwave oven to confirm the steamability, the packaging bag broke due to steaming and the contents were scattered or leaked. There was never.

[Comparative Examples 1 and 2]
In Comparative Examples 1 and 2, the mixing ratio of the propylene / ethylene block copolymer (a1) and the linear low-density polyethylene (a2) as the resin composition of the base material layer (A) is the upper limit of the present invention or A polypropylene-based composite film having a thickness of 70 μm was obtained in the same manner as in Example 1 except that the composition was out of the lower limit. Table 2 shows the characteristics of the obtained polypropylene-based composite film and the characteristics of the laminate obtained by laminating the polypropylene-based composite film with another base material. In the film of Comparative Example 1, since the mixing amount of the linear low-density polyethylene (a2) exceeds the upper limit of the present invention, the interlayer adhesion with the seal layer (B) is lowered, and the heat-sealing power is low. It became a thing.

Further, in the film of Comparative Example 2, since the mixing amount of the linear low-density polyethylene (a2) is less than the lower limit of the present invention, the film has low yuzu skin resistance, bending whitening resistance, and low temperature impact resistance. Met.
[Comparative Examples 3 and 4]
In Comparative Examples 3 and 4, except that the ratios of the 20 ° C. xylene-insoluble portion and the soluble portion of the propylene / ethylene block copolymer (b1) of the seal layer (B) are out of the upper and lower limit ranges, respectively. A polypropylene-based composite film having a thickness of 70 μm was obtained in the same manner as in Example 1. Table 2 shows the characteristics of the obtained polypropylene-based composite film and the characteristics of the laminate obtained by laminating the polypropylene-based composite film with another base material. In Comparative Example 3, the proportion of the 20 ° C. xylene insoluble portion was as low as 70% by weight, which was less than the lower limit of the present invention, and the proportion of the soluble portion was as high as 30% by weight, so that the bending whitening resistance was lowered, and Comparative Example 4 Then, since the proportion of the insoluble portion was as high as 95% by weight, the low temperature impact resistance was lowered.

[Comparative Examples 5 and 6]
In Comparative Example 5, as the propylene / ethylene block copolymer (b1) of the seal layer (B), the ultimate viscosity of the insoluble portion at 20 ° C. xylene elution was 1.6 dl / g, which is less than the lower limit of the range of the present invention. In Comparative Example 6, the limit viscosity of the insoluble part at 20 ° C. xylene elution was the present, using a 2.2 dl / g propylene / ethylene block copolymer whose soluble part has an ultimate viscosity less than the lower limit of the range of the present invention. Except for the use of propylene / ethylene block copolymers at 2.5 dl / g, which exceeds the upper limit of the range of the present invention, and the ultimate viscosity of the soluble part exceeds 4.0 dl / g, which is the upper limit of the range of the present invention. , A polypropylene-based composite film having a thickness of 70 μm was obtained in the same manner as in Example 1. Table 2 shows the characteristics of the obtained polypropylene-based composite film and the characteristics of the laminate obtained by laminating the polypropylene-based composite film with another base material. In Comparative Example 5, since the insoluble part and the soluble part of the propylene / ethylene block copolymer (b1) have low extreme viscosities, the blocking shear force is high and the opening property after bag making is inferior, and the low temperature impact resistance is low. It was also inferior in sex. In Comparative Example 6, since the insoluble portion and the soluble portion of the propylene / ethylene block copolymer (b1) had high extreme viscosities, they were inferior in yuzu skin resistance and bending whitening resistance.

[Comparative Examples 7 and 8]
In Comparative Example 7, as the propylene / ethylene block copolymer (b1) of the seal layer (B), a 0.7 g / 10 minute g propylene / ethylene block copolymer having an MFR less than the lower limit of the range of the present invention was used. In Comparative Example 8, polypropylene having a thickness of 70 μm was used in the same manner as in Example 1 except that 4.0 g / 10 ming of propylene / ethylene block copolymer was used, which exceeded the upper limit of the range of the present invention. A system composite film was obtained. Table 2 shows the characteristics of the obtained polypropylene-based composite film and the characteristics of the laminate obtained by laminating the polypropylene-based composite film with another base material. In Comparative Example 7, since the MFR of the propylene / ethylene block copolymer (b1) is low, it has good yuzu skin resistance and bending whitening resistance, and also has heat seal strength at 23 ° C and heat seal at 80 ° C. Due to its low strength, it was unusable for practical use. In Comparative Example 8, since the MFR of the propylene / ethylene block copolymer (b1) was high, the low temperature impact resistance was inferior.

[Comparative Examples 9 and 10]
In Comparative Examples 9 and 10, the raw materials in which the ratios of the 20 ° C. xylene-insoluble portion and the soluble portion of the propylene / ethylene block copolymer (b2) of the seal layer (B) were out of the upper and lower limit ranges, respectively. A polypropylene-based composite film having a thickness of 70 μm was obtained in the same manner as in Example 1 except that it was used. Table 2 shows the characteristics of the obtained polypropylene-based composite film and the characteristics of the laminate obtained by laminating the polypropylene-based composite film with another base material. In Comparative Example 9, the proportion of the 20 ° C. xylene-insoluble portion in (b2) was as low as 75% by weight, which was less than the lower limit of the present invention, and the proportion of the soluble portion was high. The decoy and the heat seal strength at 23 ° C. and the heat seal strength at 80 ° C. were low, so that it could not be put into practical use. In Comparative Example 10, since the proportion of the insoluble portion of (b2) is larger than 90% by weight, the surface roughness of the seal layer (B) is small and the blocking shear force is high, which is the object of use of the present invention. It was inferior in powder performance and inferior in low temperature impact resistance.

[Comparative Examples 11 and 12]
In Comparative Example 11, as the propylene / ethylene block copolymer (b2) of the seal layer (B), the ultimate viscosity of the insoluble portion at 20 ° C. xylene elution was 1.3 dl / g, which is less than the lower limit of the range of the present invention. In Comparative Example 12, the limit viscosity of the insoluble part at 20 ° C. xylene elution was the present, using a 1.4 dl / g propylene / ethylene block copolymer whose soluble part had an ultimate viscosity less than the lower limit of the range of the present invention. Example 1 except that a propylene / ethylene block copolymer of 2.0 dl / g, which exceeds the upper limit of the range of the present invention, and 2.2 dl / g, which is the upper limit of the range of the present invention, is used. In the same manner as above, a polypropylene-based composite film having a thickness of 70 μm was obtained. Table 2 shows the characteristics of the obtained polypropylene-based composite film and the characteristics of the laminate obtained by laminating the polypropylene-based composite film with another base material. In Comparative Example 11, since the insoluble part and the soluble part of the propylene / ethylene block copolymer (b2) have low extreme viscosities, the blocking shear force is high, the low temperature impact resistance is inferior, and the heat at 23 ° C. Since the seal strength and the heat seal strength at 80 ° C. are low, it cannot be put into practical use. In Comparative Example 12, since the insoluble portion and the soluble portion of the propylene / ethylene block copolymer (b1) had high extreme viscosities, they were inferior in yuzu skin resistance and bending whitening resistance.

[Comparative Examples 13 and 14]
In Comparative Example 13, as the propylene / ethylene block copolymer (b2) of the seal layer (B), a 3.0 g / 10 ming propylene / ethylene block copolymer having an MFR less than the lower limit of the range of the present invention was used. In Comparative Example 14, a polypropylene-based composite having a thickness of 70 μm was used in the same manner as in Example 1 except that a 12 g / 10 minute g propylene / ethylene block copolymer whose MFR exceeded the upper limit of the range of the present invention was used. I got a film. Table 2 shows the characteristics of the obtained polypropylene-based composite film and the characteristics of the laminate obtained by laminating the polypropylene-based composite film with another base material. In Comparative Example 13, since the MFR of the propylene / ethylene block copolymer (b2) is low, the surface roughness Ra of the seal layer is small, the blocking shear force is high, and the opening property after bag making is inferior. Met. In Comparative Example 14, since the MFR of the propylene / ethylene block copolymer (b2) was high, it was inferior in low temperature impact resistance.

[Comparative Examples 15 and 16]
In Comparative Example 15 and Comparative Example 16, the propylene / ethylene block copolymer (b1), the propylene / ethylene block copolymer (b2), the homopolypropylene (b3), and the linear low-density polyethylene (linear low density polyethylene) of the seal layer (B) were used. A polypropylene-based composite film having a thickness of 70 μm was obtained in the same manner as in Example 1 except that the mixing ratio of b4) was out of the range of the present invention. Table 2 shows the characteristics of the obtained polypropylene-based composite film and the characteristics of the laminate obtained by laminating the polypropylene-based composite film with another base material.

When the mixing ratio of (b1), (b2), (b3), and (b4) is out of the scope of the invention, the subject of the present invention is blocking shear resistance, citron skin resistance, bending whitening resistance, and low temperature impact resistance. Properties such as properties, heat seal strength, and steamability during microwave oven heating could not be satisfied, and it was not practical as a laminate for retort for microwave oven heating.

[Comparative Example 17]
In Comparative Example 17, a polypropylene-based film having a thickness of 70 μm was obtained in the same manner as in Example 1, except that in Example 1, the mixing ratio of the crystal nucleating agent in the seal layer (B) was less than the lower limit of the range of the present invention. A composite film was obtained. Table 2 shows the characteristics of the obtained polypropylene-based composite film and the characteristics of the laminate obtained by laminating the polypropylene-based composite film with another base material. In this film, the surface roughness of the seal layer (B) becomes small, the blocking shear force becomes high, the opening property after bag making is inferior, and the heat seal strength at 80 ° C. is high, so that when heated in a microwave oven It was inferior in steamability.

INDUSTRIAL APPLICABILITY The present invention can be used as a sealant for packaging bags without powder because it has excellent heat-sealing properties, low-temperature impact resistance, and blocking resistance, and can also be suitably used for retort pouches due to its excellent surface resistance. Furthermore, when a packaging bag filled with retort-packed food is heated in a microwave oven or the like, the sealing force is reduced and steam is passed, so that the packaging bag can be prevented from breaking and the contents from scattering or leaking. Therefore, it can be suitably used as a packaging material for retort pouch foods for heating in a microwave oven.

Claims (7)

A polypropine-based composite film in which a seal layer (B) is laminated on at least one side of a base material layer (A).
The base material layer (A) is a resin composition containing 75 to 90% by weight of the propylene / ethylene block copolymer (a1) and 10 to 25% by weight of the linear low-density polyethylene (a2).
The seal layer (B) contains 30 to 40% by weight of the propylene / polyethylene block copolymer (b1), 30 to 50% by weight of the propylene / polyethylene block copolymer (b2), and 15 to 25% of the homopolypropylene (b3). It contains 3 to 10% by weight of linear low-density polyethylene (b4) and 50 to 5000 ppm of crystal nucleating agent (b5), and the above (b1), (b2) and (b5) satisfy the following conditions. A polypropine-based composite film characterized by being a resin composition.
Propylene / ethylene block copolymer (b1): Melt flow rate is 1 to 3 g / 10 minutes, the ratio of xylene insoluble part at 20 ° C. is 75 to 90% by weight, and the ultimate viscosity ([η] _H ) of the insoluble part is 1. .7 to 2.2 dl / g, the ratio of the xylene soluble part at 20 ° C. is 10 to 25% by weight, and the ultimate viscosity ([η] _EP ) of the soluble part is 2.5 to 3.5 dl / g.
Propylene-ethylene block copolymer (b2): Melt flow rate is 4 to 10 g / 10, the ratio of xylene insoluble part at 20 ° C is 80 to 95% by weight, and the ultimate viscosity ([η] _H ) of the insoluble part is 1. .4 to 1.8 dl / g, the ultimate viscosity ([η] _EP ) of the soluble part is 1.5 to 2.0 dl / g.
Crystal nucleating agent (b5): At least one crystal nucleating agent selected from the group consisting of metal phosphates and metal dicarboxylic acid salts. The polypropylene-based composite film according to claim 1, wherein the film thickness is 20 to 150 μm, and the thickness ratio of the base material layer (A) and the seal layer (B) is 3: 1 to 15: 1. The polypropylene-based composite film according to claim 1 or 2, wherein the center line average surface roughness (Ra) of the seal layer (B) is 0.15 μm or more. The polypropylene-based composite film according to any one of claims 1 to 3, wherein the blocking shear force between the seal layers (B) is 10 N / 12 cm ² or less. A laminate in which the heat-resistant base material layer, the gas barrier layer, and the polypropylene-based composite film according to any one of claims 1 to 4 are laminated in this order so that the seal layer (B) is on the opposite side of the heat-resistant base material layer. The peel strength after heat-sealing the surfaces of the seal layer (B) at 230 ° C. and then retorting at 130 ° C. for 30 minutes is 30 N / 15 mm or more in an atmosphere of 23 ° C., which is 80. A laminate characterized by being 1 to 10 N / 15 mm in an atmosphere of ° C. The laminate according to claim 5, wherein the heat-resistant base material layer is one selected from the group consisting of a biaxially stretched polyamide film, a biaxially stretched polyester film, and printing paper. The laminate according to claim 5 or 6, wherein the gas barrier layer is one selected from the group consisting of a metal foil, a metal-deposited biaxially stretched polyamide film, and a metal-deposited biaxially stretched polyester film.